JP2008274988A - 3-pump hydraulic circuit system for construction machinery and 3-pump hydraulic circuit system for hydraulic excavator - Google Patents

Abstract

In a three-pump hydraulic circuit system of a construction machine, a discharge oil of a third hydraulic pump provided for ensuring independence of another actuator different from a specific actuator is merged with discharge oils of a first and second hydraulic pump. The first actuator is supplied to increase the speed of the first actuator, and the combined discharge of the third hydraulic pump is canceled according to the type of combined operation related to the specific actuator, thereby improving the combined operability. .
A merging valve 20 is provided for merging the discharged oil of a third hydraulic pump 4 with the discharged oil of the first and second hydraulic pumps 1 and 2 and supplying it to the bottom side of an arm cylinder 7. Whether or not the operation is performed in the cloud direction is detected by the operation pilot pressure, and when the bucket cylinder 9 is operated in the bucket cloud direction, the merge of the discharge oil of the third hydraulic pump 4 by the merge valve 20 is released.
[Selection] Figure 1

Description

  The present invention relates to a hydraulic circuit system provided in a construction machine such as a hydraulic excavator, and in particular, a specific actuator that can be driven by the joining of pressure oil by two hydraulic pumps, another actuator different from the specific actuator, The present invention relates to a three-pump hydraulic circuit system for a construction machine and a three-pump hydraulic circuit system for a hydraulic excavator, each having a third hydraulic pump that supplies pressure oil that drives another actuator.

  As a hydraulic drive device for a construction machine such as a hydraulic excavator, as disclosed in Patent Document 1, an engine, a variable displacement first hydraulic pump and a second hydraulic pump driven by the engine, and the first hydraulic pumps thereof And a specific actuator (for example, an arm cylinder) that can be driven by the merging of pressure oil discharged from each of the second hydraulic pumps, another actuator (for example, a turning motor) different from the specific actuator, and the engine, A third hydraulic pump for supplying pressure oil for driving the other actuator, and the discharge oil of the third hydraulic pump is merged with the discharge oil of the first hydraulic pump and the second hydraulic pump to specify the specific A merging valve that can be selectively supplied to the actuator is provided, and a merging release mechanism that releases the merging function of the merging valve. 3 pump hydraulic circuit system having a known.

  In this three-pump hydraulic circuit system, the merging release means includes a merging release valve, which is operated by the load pressure of the specific actuator. As an example of a configuration in which the merge release valve is operated with a load pressure, the load pressure of the specific actuator is directly guided to the pressure receiving portion of the merge release valve to switch the merge release valve. As another example, a control that detects the load pressure of a specific actuator with a pressure sensor, inputs the detected value of this pressure sensor to the controller, outputs a control signal from the controller to the proportional solenoid valve, and generates the proportional solenoid valve. The pressure is guided to the pressure receiving portion of the merge release valve to switch the merge release valve.

  Further, as a hydraulic drive device for construction machines such as hydraulic excavators, as described in Patent Document 2, the capacities of the first and second hydraulic pumps are controlled based on the discharge pressures of the first and second hydraulic pumps. A first regulator for controlling the absorption torque of the first and second hydraulic pumps so that the maximum absorption torque of the first and second hydraulic pumps does not exceed the assigned maximum absorption torque of the first and second hydraulic pumps; and a third hydraulic pressure By controlling the capacity of the third hydraulic pump based on the discharge pressure of the pump, the absorption torque of the third hydraulic pump is controlled so that the maximum absorption torque of the third hydraulic pump does not exceed the allocated maximum absorption torque of the third hydraulic pump. The first regulator has a pressure receiving portion that acts in the capacity decreasing direction of the first and second hydraulic pumps, and the discharge pressure of the third hydraulic pump is supplied to the pressure receiving portion. When the discharge pressure of the third hydraulic pump rises by controlling so that the pressure guided to the pressure receiving portion by the pressure reducing valve does not exceed the predetermined pressure, the discharge pressure of the third hydraulic pump is increased to the predetermined pressure. Until the maximum torque is reached, the maximum absorption torque (assigned maximum absorption torque) of the first and second hydraulic pumps is adjusted to be reduced so that the absorption torque of the three hydraulic pumps does not exceed the engine output torque. There has been known one provided with a pump torque control device that makes it possible to effectively use the output torque.

JP 2000-337307 A JP 2002-242904 A

  In the three-pump hydraulic circuit system described in Patent Document 1, the independence of another actuator (for example, a swing motor, hereinafter referred to as “third actuator”) different from a specific actuator (for example, arm cylinder, hereinafter referred to as “first actuator”). By supplying the discharge oil of the third hydraulic pump provided for securing to the discharge oil of the first and second hydraulic pumps and supplying it to the first actuator, it is possible to perform single operation or another actuator (for example, a bucket cylinder, In the combined operation with a light load (hereinafter referred to as “second actuator”), the speed increase of the first actuator is realized.

  Further, the three-pump hydraulic circuit system described in Patent Document 1 does not always join the discharge flow rate of the third hydraulic pump to the first actuator when the third actuator is not operated, During the combined operation of the first actuator and the second actuator in which the load pressure of the actuator becomes high, the merging of the discharge oil of the third hydraulic pump is canceled, and thereby, for example, the pump torque control device as described in Patent Document 2 The composite operability is prevented from lowering when torque control is performed so that the sum of the pump input torques (pump absorption torques) for the first to third hydraulic pumps does not exceed the engine output torque.

  That is, in the three-pump hydraulic circuit system described in Patent Document 1, if the discharge flow rate of the third hydraulic pump is always merged with the first actuator when the third actuator is not operated, In the combined operation of the first actuator and the second actuator in which the load pressure of the first actuator becomes high, the discharge pressure of the third hydraulic pump increases and the absorption torque of the third hydraulic pump increases, so that the above torque The total value of the absorption torques of the first and second hydraulic pumps is greatly reduced by the control, and the discharge flow rates of the first and second hydraulic pumps are also greatly reduced accordingly. In the three-pump hydraulic circuit system described in Patent Document 1, when the combined operation of the first actuator and the second actuator is performed, only the discharge oil from the second hydraulic pump is passed through the flow control valve to the second actuator. It is a configuration to be supplied. As a result, during heavy excavation work or the like, during the combined operation of the first actuator and the second actuator in which the load pressure of the first actuator becomes high, the first actuator has a discharge oil (first oil) (2) When there is a remaining discharge from the hydraulic pump, the remaining discharge oil) is combined and supplied, whereas only the discharge oil from the second hydraulic pump reduced by the torque control is supplied to the second actuator. Therefore, the operating speed (for example, bucket cloud speed) of the second actuator is remarkably slower than the operating speed (for example, arm cloud speed) of the first actuator, and the first actuator and the second actuator during heavy excavation work, etc. Combined operability is reduced, and work such as heavy excavation work is hindered.

  In the three-pump hydraulic circuit system described in Patent Document 1, the oil discharged from the third hydraulic pump is used during a combined operation of the first actuator and the second actuator in which the load pressure of the first actuator becomes high, such as during heavy excavation work. Is released, the decrease in the absorption torque (discharge flow rate) of the second hydraulic pump due to the increase in the absorption torque of the third hydraulic pump is prevented, and the operation of the second actuator due to the decrease in the discharge flow rate of the second hydraulic pump is prevented. A decrease in speed (for example, bucket cloud speed) is avoided, and the combined operability of the first actuator and the second actuator is improved.

  However, in the three-pump hydraulic circuit system described in Patent Document 1, since the load pressure of the first actuator is detected as a signal for releasing the merging of the discharge oil of the third hydraulic pump, the load of the first actuator In the combined operation where the pressure increases, regardless of the type of combined operation, the merging of the discharge oil of the third hydraulic pump is always released, and depending on the type of combined operation, the operating speed of the second actuator becomes too fast, There was a problem that the operability was lowered. As such a composite operation, for example, there is a composite operation of arm cloud and boom lowering (described later).

  Further, in the three-pump hydraulic circuit system described in Patent Document 1, a high-pressure load pressure (load pressure of the first actuator) is used as a signal for canceling the merge of the discharge oil of the third hydraulic pump. In order to guide the load pressure from the first actuator to the merging release valve, it is necessary to route high-pressure piping from the front work machine where the first actuator is installed to the inside of the vehicle body where the control unit including the merging release valve is installed In addition, the merging release valve needs to have a high pressure (load pressure) specification, so that it is relatively large and expensive. As a result, the entire hydraulic circuit is complicated, which is disadvantageous from the viewpoint of vehicle body layout and cost saving.

  Furthermore, in the three-pump hydraulic circuit system described in Patent Document 1, a merging release valve is required to operate the merging valve to release the merging of the discharge oil of the third hydraulic pump. However, it was disadvantageous from the viewpoint of vehicle layout and cost saving.

  The first object of the present invention is to combine the discharge oil of the third hydraulic pump provided for ensuring the independence of another actuator different from the specific actuator with the discharge oil of the first and second hydraulic pumps. The speed of the first actuator can be increased by supplying to the actuator, and the merging of the discharge oil of the third hydraulic pump can be canceled according to the type of combined operation related to the specific actuator, thereby improving the combined operability. It is to provide a pump hydraulic circuit system.

  The second object of the present invention is to combine the discharge oil of the third hydraulic pump provided for ensuring the independence of another actuator different from the specific actuator with the discharge oil of the first and second hydraulic pumps. By supplying to the actuator, the speed of the first actuator can be increased, the combined operability of the specific actuator and other actuators can be improved, the entire hydraulic circuit can be made compact, the body layout can be simplified, and the cost can be saved. It is to provide a three-pump hydraulic circuit system and a three-pump hydraulic circuit system of a hydraulic excavator that can be realized.

  (1) In order to achieve the first object, the present invention provides an engine, variable displacement first and second hydraulic pumps driven by the engine, and a third hydraulic pump driven by the engine. A first actuator that is driven by the confluence of the pressure oil discharged from each of the first and second hydraulic pumps, and a first actuator that is driven by the pressure oil discharged from one of the first and second hydraulic pumps. Two actuators, a third actuator driven by pressure oil discharged from the third hydraulic pump, and the third hydraulic pressure when the first actuator is operated in a state where the third actuator is not operated. 3-pump oil for construction machinery, comprising a merging valve for merging the discharge oil of the pump with the discharge oil of the first and second hydraulic pumps and supplying the oil to the first actuator In the circuit system, the capacities of the first and second hydraulic pumps are controlled so that the absorption torque of the first and second hydraulic pumps does not exceed the maximum absorption torque based on the discharge pressures of the first and second hydraulic pumps. And a pump torque control means for reducing the maximum absorption torque as the discharge pressure of the third hydraulic pump increases, and whether the second actuator is operated, and when the second actuator is operated Comprises merging release means for releasing merging of the discharge oil of the third hydraulic pump by the merging valve.

  In this way, by providing a merging valve that joins the discharge oil of the third hydraulic pump to the discharge oil of the first and second hydraulic pumps and supplies it to the first actuator, other different from the first actuator (specific actuator) The discharge oil of the third hydraulic pump provided to ensure the independence of the third actuator, which is an actuator, is merged with the discharge oil of the first and second hydraulic pumps and supplied to the first actuator to increase the speed of the first actuator. Can be realized.

  Further, by detecting whether or not the second actuator has been operated and providing a merging release means for releasing the merging of the discharge oil of the third hydraulic pump by the merging valve when the second actuator is operated, the first actuator ( In the combined operation of the specific actuator) and the second actuator, the merged discharge oil of the third hydraulic pump with respect to the first actuator is released and driven by the pressure oil of the first and second hydraulic pumps other than the first actuator and the second actuator. In the combined operation with the actuator to be operated, the discharge oil of the third hydraulic pump can be merged and supplied to the first actuator without releasing the merge, so that the torque control by the pump torque control means can be performed. In consideration of the influence, the first actuator and the second actuator which are combined operations that want to release the merge of the discharge oil of the third hydraulic pump Only the combined operation with the actuator can be surely canceled, so that the combined discharge of the third hydraulic pump can be canceled according to the type of combined operation related to the specific actuator, and the combined operability can be improved. it can.

  (2) Further, in order to achieve the second object, the present invention further includes a plurality of hydraulic pilot type operating lever devices for operating the first to third actuators in the above (1). The merging release means detects whether or not the second actuator has been operated based on an operating pilot pressure output from an operating lever device of the second actuator, and based on the operating pilot pressure, a third valve by the merging valve The merge of the oil discharged from the hydraulic pump shall be released.

In this way, the control line is branched from the pilot line from which the operation pilot pressure of the second actuator is guided by releasing the merge of the discharge oil of the third hydraulic pump by the merge valve using the operation pilot pressure of the second actuator. The operation pilot pressure can be led to the junction valve. Here, since the maximum pressure of the operation pilot pressure is as low as, for example, about 40 Kg / cm ² , the control line piping has a low pressure specification, and when the operation pilot pressure is guided to the merging valve and the merging valve is switched, The valve is also low pressure. In addition, since the control line only has to be branched from the pilot line of the second actuator, the piping length of the control line can be shortened. As a result, the entire hydraulic circuit can be made compact, and the vehicle body layout can be simplified and the cost can be reduced.

  (3) In the above (1), the merging release means detects whether or not the second actuator has been operated based on the load pressure of the second actuator, and based on the load pressure, a third hydraulic pump using the merging valve The merging of the discharged oil may be canceled.

  (4) Further, in order to achieve the second object, in the above (1), the merging valve is operated by being guided by the first hydraulic pressure signal generated when the first actuator is operated. A switching valve that joins and guides the discharge oil of the third hydraulic pump to the first actuator, and the joining release means generates a second hydraulic signal when the second actuator is operated, A second hydraulic pressure signal is applied to the side opposite to the first hydraulic pressure signal with respect to the merging valve.

  In this way, by causing the second hydraulic pressure signal to act directly on the side facing the first hydraulic pressure signal with respect to the merging valve, the merging valve is operated, and the merging of the discharge oil of the third hydraulic pump is released. The conventionally used merging release valve is not required, the entire hydraulic circuit is made compact, and the vehicle body layout can be simplified and the cost can be reduced.

  (5) Further, in order to achieve the second object, the present invention further includes a plurality of hydraulic pilot type operating lever devices for operating the first to third actuators in the above (4). The merging valve is operated by the operation pilot pressure output from the operation lever device of the first actuator as the first hydraulic pressure signal, and the oil discharged from the third hydraulic pump is merged with the first actuator. The merging release means guides the operating pilot pressure output from the operating lever device of the second actuator to the merging valve as the second hydraulic pressure signal, and this operating pilot pressure is transmitted to the merging valve. In contrast, the first actuator is operated on the side facing the operation pilot pressure.

  As a result, as described in (2) above, the piping of the control line that guides the operation pilot pressure of the second actuator to the merging valve becomes the low pressure specification and the merging valve also becomes the low pressure specification, and the control line is the pilot of the second actuator. Since it suffices to diverge from the line, the length of the control line can be shortened. As a result, the entire hydraulic circuit can be made more compact, and the vehicle body layout can be simplified and the cost can be reduced.

  (6) In order to achieve the first object, the present invention provides an engine, first and second variable displacement hydraulic pumps driven by the engine, and a third driven by the engine. Pressure discharged from one of the first and second hydraulic pumps, driven by a merge of pressure oil discharged from the hydraulic pump and each of the first and second hydraulic pumps, and driving the arm A second actuator that is driven by oil and drives a bucket, a third actuator that is driven by pressure oil discharged from the third hydraulic pump and that drives a swivel, and the third actuator is not operated. When the first actuator is operated in the arm cloud direction, the discharge oil of the third hydraulic pump is combined with the discharge oil of the first and second hydraulic pumps. In the three-pump hydraulic circuit system of a hydraulic excavator provided with a merging valve that is supplied to the first actuator, the absorption torque of the first and second hydraulic pumps based on the discharge pressure of the first and second hydraulic pumps Pump torque control means for controlling the capacities of the first and second hydraulic pumps so that the maximum absorption torque does not exceed the maximum absorption torque, and decreasing the maximum absorption torque as the discharge pressure of the third hydraulic pump increases, Detecting whether or not the second actuator is operated in the bucket cloud direction, and when the second actuator is operated in the bucket cloud direction, the merging release means for releasing the merging of the discharge oil of the third hydraulic pump by the merging valve Shall be provided.

  As a result, as described in (1) above, the discharge oil of the third hydraulic pump provided to ensure the independence of the third actuator, which is another actuator different from the first actuator (specific actuator), The speed of the first actuator can be increased by merging with the oil discharged from the second hydraulic pump and supplying it to the first actuator.

  Further, in the combined operation of the operation of the first actuator (specific actuator) in the arm cloud direction and the operation of the second actuator in the bucket cloud direction, the merge of the discharge oil of the third hydraulic pump with respect to the first actuator is canceled, and the first actuator In the combined operation of the operation in the arm cloud direction and the operation of the actuator driven by the pressure oil of the first and second hydraulic pumps other than the second actuator (for example, the operation in the boom lowering direction of the actuator that drives the boom) Therefore, the oil discharged from the third hydraulic pump can be joined and supplied to the first actuator without releasing the control, so that the influence of the torque control by the pump torque control means is taken into consideration. In the arm cloud direction of the first actuator, which is a complex operation that wants to cancel the merge of discharged oil Only the combined operation of the operation of the second actuator and the operation of the second actuator in the bucket cloud direction can be reliably canceled, thereby releasing the combined flow of the discharge oil of the third hydraulic pump according to the type of combined operation related to the specific actuator. In addition, the composite operability can be improved.

  (7) Further, in order to achieve the second object, in the above (6), the merging valve may be configured such that the first hydraulic pressure signal generated when the first actuator is operated in the arm cloud direction is A switching valve that is guided to operate and joins and discharges the discharge oil of the third hydraulic pump to the first actuator, and the joining release means is configured to be operated when the second actuator is operated in a bucket cloud direction. Two hydraulic pressure signals are generated, and this second hydraulic pressure signal is applied to the side opposite to the first hydraulic pressure signal with respect to the merging valve.

  As a result, as described in (4) above, the conventional merging release valve is not required, the entire hydraulic circuit is made compact, and the vehicle body layout can be simplified and the cost can be reduced.

  (8) In the above (7), preferably, it further includes a plurality of hydraulic pilot type operation lever devices for respectively operating the first to third actuators, and the merging valve is used as the first hydraulic pressure signal. An operation pilot pressure output from an operation lever device of the first actuator is guided and operated, and is a switching valve that guides the discharge oil of the third hydraulic pump to the first actuator, and the confluence release means includes: An operation pilot pressure of the bucket cloud output from the operation lever device of the second actuator as the second hydraulic pressure signal is guided to the merging valve, and this operation pilot pressure is applied to the arm cloud of the first actuator with respect to the merging valve. Acts on the side opposite the operating pilot pressure.

  Thereby, as described in (2) above, the piping of the control line that guides the operation pilot pressure of the bucket cloud of the second actuator to the merging valve becomes the low pressure specification and the merging valve also becomes the low pressure specification, and the control line is the second Since it suffices to branch from the pilot line of the bucket bucket of the actuator, the piping length of the control line can be shortened. As a result, the entire hydraulic circuit is made more compact, and the body layout is simplified and the cost is reduced. be able to.

  According to the present invention, the discharge oil of the third hydraulic pump provided for ensuring the independence of another actuator different from the specific actuator is merged with the discharge oil of the first and second hydraulic pumps and supplied to the first actuator. In addition, the speed increase of the first actuator can be realized, and the merging of the discharge oil of the third hydraulic pump can be canceled according to the type of the composite operation related to the specific actuator, so that the composite operability can be improved.

  Further, according to the present invention, the discharge oil of the third hydraulic pump provided for ensuring the independence of another actuator different from the specific actuator is merged with the discharge oil of the first and second hydraulic pumps, so that the first actuator The speed of the first actuator can be increased by supplying to the actuator, the combined operability of the specific actuator and other actuators can be improved, the entire hydraulic circuit can be made compact, and the body layout can be simplified and saved. Cost can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an overall configuration of a three-pump hydraulic circuit system for a construction machine according to an embodiment (first embodiment) of the present invention. In this embodiment, the present invention is applied to a hydraulic excavator as a construction machine.
<Configuration>
In FIG. 1, a three-pump hydraulic circuit system for a construction machine according to the present embodiment includes a prime mover (diesel engine) 1, a variable displacement first hydraulic pump 2 and a second hydraulic pump 3 driven by the prime mover 1. , Three main pumps of the third hydraulic pump 4, a fixed displacement type pilot pump 5 driven by the prime mover 1, and a control valve unit connected to the first, second and third hydraulic pumps 2, 3, 4 6, a plurality of hydraulic actuators 7, 8, 9, 10... Including an arm cylinder 7, a boom cylinder 8, a bucket cylinder 9, a swing motor 10 connected to the control valve unit 6, and an arm cylinder 7 Arm operating lever device 12, bucket operating lever device 13 for operating bucket cylinder 9, boom cylinder .. Of a plurality of operating lever devices 12, 13, 14,... Including a boom operating lever device 14 for operating the first hydraulic pump 2, the second hydraulic pump 3, and the third hydraulic pump 4. A pump torque control device 30 that controls the absorption torque (total value) so as not to exceed the output torque of the engine 1 is provided.

  The control valve unit 6 has first, second and third valve groups 6a, 6b and 6c corresponding to the first, second and third hydraulic pumps 2, 3 and 4, and the first valve The group 6a has a plurality of flow control valves A1, B2, C, the second valve group 6b has a plurality of flow control valves BU, B1, A2, and the third valve group 6c has a flow control valve S and a merging valve 20.

  In the first valve group 6a, the flow control valves A1, B2, C are arranged in the order of the flow control valves A1, B2, C from the upstream side on the center bypass line 15 connected to the discharge line 2a of the first hydraulic pump 2. In the second valve group 6b, the flow control valves BU, B1 and A2 are on the center bypass line 16 connected to the discharge line 3a of the second hydraulic pump 3 from the upstream side. It is a center bypass type flow control valve arranged in the order of the flow control valves BU, B1, and A2. In the third valve group 6c, the flow control valve S is a center connected to the discharge line 4a of the third hydraulic pump 4. This is a center bypass type flow control valve disposed on the bypass line 17. In the first to third valve groups 6a, 6b, and 6c, the most downstream side of the center bypass lines 15 to 17 is connected to the tank T, and the flow control valves A1, A2, B1, B2, BU, and S are in the illustrated neutral positions. , The discharge lines 2a, 3a, 4a of the first, second and third hydraulic pumps 2, 3, 4 communicate with the tank T via the center bypass lines 15-17, and the first, second, The discharge pressure of the third hydraulic pumps 2, 3 and 4 is reduced to the tank pressure.

  In the first valve group 6a, the flow control valves B2 and C are downstream of the flow control valve A1, so that the pressure oil discharged from the first hydraulic pump 2 is preferentially supplied to the flow control valve A1. In the second valve group 6b, the flow control valves B1 and A2 are downstream of the flow control valve BU, and the pressure oil discharged from the second hydraulic pump 3 is preferentially supplied to the flow control valve BU. The flow rate control valve A2 is tandemly connected so that the pressure oil discharged from the second hydraulic pump 3 is preferentially supplied to the flow rate control valve B1 on the downstream side of the flow rate control valve B1. . In the third valve group 6 c, the merging valve 20 is tandemly connected so that the pressure oil discharged from the third hydraulic pump 4 is preferentially supplied to the flow control valve S on the downstream side of the flow control valve S. .

The flow control valves A1 and A2 are for the first and second arms, respectively, and one of the two actuator ports of the flow control valve A1 is connected to the bottom side of the arm cylinder 7 via the first actuator line 50a, and the other Is connected to the rod side of the arm cylinder 7 via the second actuator line 50b, and the two actuator ports of the flow control valve A2 are similarly connected to the bottom side of the arm cylinder 7 via the first actuator line 50a. The other is connected to the rod side of the arm cylinder 7 via the second actuator line 50b.
The flow control valves B1 and B2 are for the first and second booms, respectively, and one of the two actuator ports of the flow control valve B1 is connected to the bottom side of the boom cylinder 8 via the first actuator line 51a. Is connected to the rod side of the boom cylinder 8 via the second actuator line 51b, and the two actuator ports of the flow control valve B2 are similarly connected to the bottom side of the boom cylinder 8 via the first actuator line 51a. The other is connected to the rod side of the boom cylinder 8 via the second actuator line 51b.

  The flow control valve BU is for a bucket, and one of the two actuator ports is connected to the bottom side of the bucket cylinder 9 via the first actuator line 52a, and the other is connected to the bucket cylinder 9 via the second actuator line 52b. Connected to the rod side.

  The flow control valve A1 has a first pressure receiving portion 55a for arm cloud operation and a second pressure receiving portion 55b for arm dump operation. When the operation pilot pressure is guided to the first pressure receiving portion 55a, the flow control valve A1 switches to the right position in the figure. Then, when the discharge oil of the first hydraulic pump 2 is supplied to the bottom side of the arm cylinder 7 and the operation pilot pressure is guided to the second pressure receiving portion 55b, it switches to the left side in the figure, and the discharge oil of the first hydraulic pump 2 Is supplied to the rod side of the arm cylinder 7. The flow rate control valve A2 has a first pressure receiving portion 55c that is operated by an arm cloud. When the operation pilot pressure is guided to the first pressure receiving portion 55c, the flow control valve A2 is switched to the position on the left side in the drawing, and the discharge oil of the second hydraulic pump 3 is discharged. Supply to the bottom side of the arm cylinder 7.

  The flow rate control valve B1 has a first pressure receiving part 56a for boom raising operation and a second pressure receiving part 56b for boom lowering operation. When the operation pilot pressure is guided to the first pressure receiving part 56a, the flow control valve B1 is switched to the left position in the figure. Then, when the discharge oil of the second hydraulic pump 3 is supplied to the bottom side of the boom cylinder 8 and the operation pilot pressure is led to the second pressure receiving portion 56b, the operation is switched to the right position in the figure, and the discharge oil of the second hydraulic pump 3 Is supplied to the rod side of the boom cylinder 8. Similarly, the flow rate control valve B2 has a first pressure receiving portion 56c for boom raising operation and a second pressure receiving portion 56d for boom lowering operation. When the operation pilot pressure is guided to the first pressure receiving portion 56c, the flow control valve B2 is moved to the left position in the figure. When the pilot oil is supplied to the bottom side of the boom cylinder 8 and the operation pilot pressure is guided to the second pressure receiving part 56d, the first hydraulic pump 2 is switched to the position on the right side of the figure. Discharged oil is supplied to the rod side of the boom cylinder 8.

  The flow control valve BU has a first pressure receiving portion 57a for bucket cloud operation and a second pressure receiving portion 57b for bucket dump operation. When the operation pilot pressure is guided to the first pressure receiving portion 57a, the flow control valve BU switches to the left position in the figure. Then, when the discharge oil of the second hydraulic pump 3 is supplied to the bottom side of the bucket cylinder 9 and the operation pilot pressure is guided to the second pressure receiving portion 57b, the operation is switched to the right side in the figure, and the discharge oil of the second hydraulic pump 3 Is supplied to the rod side of the bucket cylinder 9.

  The flow rate control valve S is for swiveling, has pressure receiving portions 58a and 58b similar to the flow rate control valve, and is switched similarly. Each of the first to third valve groups 6a, 6b, and 6c includes a flow control valve (not shown), and the flow control valve C and the flow control valve (not shown) similarly have a pressure receiving portion. Is switched to.

  The merging valve 20 has two output ports, one of which is connected to the tank T, and the other is connected to the first actuator line 50 a of the arm cylinder 7 at the merging point 61 via the merging line 60. The merging line 60 is provided with a check valve (check valve) 62 that allows the flow of pressure oil from the merging valve 20 toward the first actuator line 50a and blocks the flow of pressure oil in the reverse direction.

  Further, the merging valve 20 includes a first pressure receiving portion 63a for merging release operation and a second pressure receiving portion 63b for merging operation, and a spring 63c that holds the merging valve 20 in the illustrated position (merging release position). When the operating pilot pressure is not guided to either the pressure receiving portion 63a or the second pressure receiving portion 63b, or when the operating pilot pressure is guided to the first pressure receiving portion 63a, the first pressure receiving portion 63a is in the position shown in the figure. When the operating pilot pressure is guided to the second pressure receiving portion 63b in a state where the operating pilot pressure is not guided to the second position, the position is switched from the illustrated position to the right side position (merging position). When the merging valve 20 is at the position shown in the drawing, the portion of the center bypass line 17 between the flow control valve S and the merging valve 20 is connected to the tank T, and the oil discharged from the third hydraulic pump 4 is transferred to the tank T. When recirculated and switched from the illustrated position to the right position in the figure, the portion of the center bypass line 17 between the flow control valve S and the merging valve 20 is connected to the merging line 60, and the discharged oil of the third hydraulic pump 4 Is supplied to the first actuator line 50a through the merge line 60. As a result, the oil discharged from the first and second hydraulic pumps 2 and 3 and the oil discharged from the third hydraulic pump 4 are merged in the first actuator line 50 a (3 pumps merged) and supplied to the bottom side of the arm cylinder 7.

  The operation lever devices 12, 13, and 14 are hydraulic pilot types having operation levers 12a, 13a, and 14a and a pair of pilot valves (reducing valves) 12b and 12c; 13b and 13c; 14b and 14c, respectively. A pair of pilot valves 12b, 12c; 13b, 13c; 14b, 14c are selectively operated according to the operation direction and operation amount of 12a, 13a, 14a, and the pilot valves 12b, 12c of the operation lever device 12 are respectively armed An operation pilot pressure is output as a cloud operation signal and an arm dump operation signal, and the pilot valves 13b and 13c of the operation lever device 13 output an operation pilot pressure as a bucket cloud operation signal and a bucket dump operation signal, respectively. 14 pilot valves 14b and 14c are And it outputs the operation pilot pressures as raising operation signal and the boom lowering operation signal. The operating pilot pressure output from the pilot valves 12b and 12c of the operating lever device 12 is guided to the corresponding pressure receiving portions 55a and 55b of the first flow control valve A1 for the arm via the pilot lines 65a and 65b, respectively. The operating pilot pressure output from the pilot valve 12b is guided to the corresponding pressure receiving portion 55c of the second flow control valve A2 for the arm via the pilot line 65c branched from the pilot line 65a. The operating pilot pressures output from the pilot valves 13b and 13c of the operating lever device 13 are guided to the corresponding pressure receiving portions 57a and 57b of the bucket flow control valve BU via the pilot lines 66a and 66b, respectively. The operation pilot pressures output from the pilot valves 14b and 14c of the operation lever device 14 are guided to the corresponding pressure receiving portions 56a and 56b of the first flow control valve B1 for the boom via the pilot lines 67a and 67b, respectively. The pilot lines 67c and 67d branched from the pilot lines 67a and 67b are led to the corresponding pressure receiving portions 55c and 56d of the second flow control valve B2 for the boom.

  Further, a first control line 71 branches from a pilot line 65a that guides an operation pilot pressure as an arm cloud operation signal, and the first control line 71 is connected to the second pressure receiving portion 63b of the merging valve 20 to perform arm cloud operation. The operation pilot pressure as a signal is also guided to the second pressure receiving portion 63b of the merging valve 20. A second control line 72 branches from a pilot line 66a that guides an operation pilot pressure as a bucket cloud operation signal. This second control line 72 is connected to the first pressure receiving portion 63a of the merging valve 20, and is used as a bucket cloud operation signal. The pilot pressure is also guided to the first pressure receiving portion 63a of the merging valve 20.

  In the pump torque control device 30, the discharge pressures of the first and second hydraulic pumps 2 and 3 are introduced via the pilot lines 37 and 38, and the capacity (displacement volume or swash plate) of the first and second hydraulic pumps 2 and 3 is introduced. The first regulator 31 that controls the absorption torque (consumption torque) of the first and second hydraulic pumps 2 and 3 by controlling the tilt of the first hydraulic pump 2 and the discharge pressure of the third hydraulic pump 4 via the pilot line 40 A second regulator 32 that controls the absorption torque (consumption torque) of the third hydraulic pump 4 by controlling the capacity of the third hydraulic pump 4 (the displacement volume or the tilt of the swash plate), and the third hydraulic pressure pump. When the discharge pressure of the pump 4 is introduced through the pilot line 39a and the discharge pressure of the third hydraulic pump 4 is below a predetermined pressure (P2 in FIG. 4) set by the spring 33a, the third hydraulic pressure If the discharge pressure of the third hydraulic pump 4 exceeds the predetermined pressure (P2 in FIG. 3) set by the spring 33a, the discharge pressure of the third hydraulic pump 4 is set to the predetermined pressure. And a pressure reducing valve 33 for reducing the pressure and outputting. The pressure output from the pressure reducing valve 33 is guided to the first regulator 31 via the pilot line 39b. The first regulator 31 and the pressure reducing valve 33 are configured so that the absorption torque of the first and second hydraulic pumps 2 and 3 does not exceed the maximum absorption torque based on the discharge pressures of the first and second hydraulic pumps 2 and 3. Pump torque control means is configured to control the volume of the second hydraulic pump, and to reduce the maximum absorption torque as the discharge pressure of the third hydraulic pump increases.

  Details of the pump torque control device 30 will be described with reference to FIG.

  The first regulator 31 includes springs 31a and 31b that act in the direction of increasing the capacity of the first and second hydraulic pumps 2 and 3, and three pressure receiving portions that act in the direction of decreasing the capacity of the first and second hydraulic pumps 2 and 3. 31c, 31d, 31e. The discharge pressures of the first and second hydraulic pumps 2 and 3 are introduced into the pressure receiving parts 31c and 31d through the pilot lines 37 and 38, and the output pressure (control pressure) of the pressure reducing valve 33 is supplied to the pressure receiving part 31e in the oil passage. 39b is introduced. The springs 31 a and 31 b and the pressure receiving portion 31 e have a function of setting the maximum absorption torque of the first and second hydraulic pumps 2 and 3, and the first regulator 31 includes the first and second hydraulic pumps 2 and 3. The capacity of the first and second hydraulic pumps 2 and 3 is controlled so that the absorption torque does not exceed the maximum absorption torque (assigned maximum absorption torque) set by the springs 31a and 31b and the control pressure guided to the pressure receiving portion 31e. .

  The springs 31a and 31b have a function of setting torque control characteristics of the first and second hydraulic pumps 2 and 3, and the pressure reducing valve 33 and the pressure receiving portion 31e are configured so that the discharge pressure of the third hydraulic pump 4 is reduced by the pressure reducing valve 33. The maximum absorption torque (assigned maximum absorption torque) of the first and second hydraulic pumps 2 and 3 as the discharge pressure of the third hydraulic pump 4 rises when the pressure is below the predetermined pressure (P2 in FIG. 4) Has a function of controlling the first regulator 31 so as to reduce.

  The second regulator 32 includes a spring 32a that acts in the direction of increasing the capacity of the third hydraulic pump 4, and a pressure receiving portion 32b that acts in the direction of decreasing capacity of the third hydraulic pump 4, and the pressure receiving portion 31b includes a third hydraulic pressure. The discharge pressure of the pump 4 is introduced through the pilot line 40. The spring 32 a has a function of setting the maximum absorption torque (assigned maximum absorption torque) of the third hydraulic pump 4. With such a configuration, the second regulator 32 controls the capacity of the third hydraulic pump 4 so that the absorption torque of the third hydraulic pump 4 does not exceed the maximum absorption torque set by the spring 32a.

  Main relief valves 25, 26, 27 are provided in the discharge lines 2 a, 3 a, 4 a of the first, second and third hydraulic pumps 2, 3, 4, and a pilot relief valve 28 is provided in the discharge line 5 a of the pilot pump 5. Is provided. The main relief valves 25, 26, 27 regulate the maximum discharge pressure of the first, second and third hydraulic pumps 2, 3, 4 and set the maximum pressure of the main circuit. The pilot relief valve 28 regulates the maximum discharge pressure of the pilot pump 5 and sets the pressure of the pilot hydraulic source.

  FIG. 3 shows the discharge pressure (average value) of the first and second hydraulic pumps 2 and 3 by the first regulator 31 and the capacity (displacement volume or tilt of the swash plate) of the first and second hydraulic pumps 2 and 3. It is a figure which shows the relationship.

  In FIG. 3, broken lines A, B, and C are torque control characteristics set by the springs 31a and 31b and the pressure receiving portion 31e, and a broken line A is operated by a hydraulic actuator related to the third hydraulic pump 4, for example, the hydraulic actuator 12. When the discharge pressure of the third hydraulic pump 4 is reduced to the minimum pressure P0 (see FIG. 4), the broken line B indicates that the discharge pressure of the third hydraulic pump 4 is the minimum pressure P0 (FIG. 4). And a starting pressure of absorption torque control by the second regulator 32 (minimum discharge pressure of the third hydraulic pump 4 at which absorption torque control by the second regulator 32 is performed) P2 (see FIG. 4). The broken line C is when the discharge pressure of the third hydraulic pump 4 is at P2 (see FIG. 4).

  When the discharge pressure of the third hydraulic pump 4 is at the minimum pressure P0, the capacities of the first and second hydraulic pumps change as follows based on the torque control characteristic of the broken line A (hereinafter referred to as characteristic line A as appropriate). To do.

  When the average value of the discharge pressures of the first and second hydraulic pumps 2 and 3 is within the range of P0 to P1A, the absorption torque control is not performed, and the capacity of the first and second hydraulic pumps 2 and 3 is the maximum capacity. It is on the characteristic line L1 and is the maximum (constant). At this time, the absorption torque of the first and second hydraulic pumps 2 and 3 increases as their discharge pressures increase. When the average value of the discharge pressures of the first and second hydraulic pumps 2 and 3 exceeds P1A, the absorption torque control is performed, and the capacities of the first and second hydraulic pumps 2 and 3 decrease along the characteristic line A. As a result, the absorption torque of the first and second hydraulic pumps 2 and 3 is controlled so as not to exceed the prescribed torque Ta (the maximum absorption torque assigned to the first and second hydraulic pumps 2 and 3) represented by the constant torque curve TA. The In this case, the pressure P1A is the start pressure of the absorption torque control by the first regulator 31, and P1A to Pmax are the discharge pressure ranges of the first and second hydraulic pumps 2 and 3 in which the absorption torque control by the first regulator 31 is performed. It is. Pmax is the maximum value of the average value of the discharge pressures of the first and second hydraulic pumps 2 and 3, and is a value corresponding to the relief set pressure of the main relief valves 15 and 16. When the discharge pressures of the first and second hydraulic pumps 2 and 3 increase to Pmax, the main relief valves 15 and 16 are operated, and further increase in pump discharge pressure is limited.

  Here, the output pressure (control pressure) of the pressure reducing valve 33 is introduced into the pressure receiving portion 31e of the first regulator 31 through the oil passage 39b. The pressure reducing valve 33 outputs the discharge pressure of the third hydraulic pump 4 as it is as the control pressure until the discharge pressure of the third hydraulic pump 4 reaches a predetermined pressure set by the spring 33a, and the discharge of the third hydraulic pump 4 When the pressure exceeds the predetermined pressure, the discharge pressure of the third hydraulic pump 4 is reduced to the predetermined pressure, and the reduced pressure is output as the control pressure. The output pressure (control pressure) of the pressure reducing valve 33 is introduced in a direction to reduce the set value of the maximum absorption torque of the first and second hydraulic pumps 2 and 3 in the pressure receiving portion 31e. As a result, when the discharge pressure of the third hydraulic pump 4 increases, the absorption torque control characteristic line shifts in the horizontal axis direction as indicated by the broken lines A, B, and C, and the first regulator 31 starts the absorption torque control accordingly. The pressure changes (decreases) from P1A to P1B and P1C, and the discharge pressure range in which the absorption torque control by the first regulator 31 is performed changes from P1A to Pmax to P1A to Pmax and P1A to Pmax. Accordingly, the assigned maximum absorption torque of the first and second hydraulic pumps 2 and 3 decreases from Ta to Tb and Tc.

  In the pressure reducing valve 33, the predetermined pressure set by the spring 33a is set to coincide with P2, which is the minimum discharge pressure of the third hydraulic pump 4 for which the absorption torque control by the second regulator 32 is performed.

  FIG. 4 is a diagram showing the relationship between the discharge pressure of the third hydraulic pump 4 by the second regulator 32 and the capacity of the third hydraulic pump 4 (displacement volume or swash plate tilt). In FIG. 4, a solid line D is a torque control characteristic set by the spring 32a.

  When the discharge pressure of the third hydraulic pump 4 is within the range of P0 to P2, the absorption torque control is not performed, and the capacity of the third hydraulic pump 4 is on the maximum capacity characteristic line L2 and is maximum (constant). . At this time, the absorption torque of the third hydraulic pump 4 increases as the discharge pressure increases. When the discharge pressure of the third hydraulic pump 4 exceeds P2, absorption torque control is performed, and the capacity of the third hydraulic pump 4 decreases along the characteristic line of the solid line D. Thus, the absorption torque of the third hydraulic pump 4 is controlled so as not to exceed the specified torque Td (the maximum absorption torque assigned to the third hydraulic pump) represented by the constant torque curve TD. In this case, the pressure P2 is the starting pressure of the absorption torque control by the second regulator 32, and P2 to Pmax are the discharge pressure range of the third hydraulic pump 4 in which the absorption torque control by the second regulator 32 is performed. Pmax is the maximum value of the discharge pressure of the third hydraulic pump 4 and is a value corresponding to the relief set pressure of the main relief valve 17. When the discharge pressure of the third hydraulic pump 4 rises to Pmax, the main relief valve 17 is activated, and further increase in the pump discharge pressure is restricted.

  FIG. 5 shows an external appearance of a hydraulic excavator in which the three-pump hydraulic circuit system according to the present embodiment is mounted.

  The hydraulic excavator includes a lower traveling body 202, an upper swing body 203, and a front work machine 204. The upper swing body 203 is rotatably mounted on the upper part of the lower travel body 202. It is attached to the front part so that it can move up and down. The upper swing body 203 is provided with an engine room 205 and an operator cab 206. The front work machine 204 has an articulated structure having a boom 208, an arm 209, and a bucket 210. The lower traveling body 202, the upper revolving body 203, and the front work machine 204 are respectively left and right traveling motors 211a and 211b (only one shown) as hydraulic actuators, the aforementioned revolving motor 10, boom cylinder 8, arm cylinder 7, and bucket cylinder 9 respectively. The lower traveling body 202 travels by the rotation of the left and right traveling motors 211, the upper swing body 203 rotates by the rotation of the swing motor 10, and the boom 208 of the front work machine 204 moves in the vertical direction by the expansion and contraction of the boom cylinder 8. The arm cylinder 209 rotates up and down and back and forth by the expansion and contraction of the arm cylinder 7, and the bucket 210 rotates up and down and front and back by the expansion and contraction of the bucket cylinder 9.

  In FIG. 1, illustration of other actuators such as the traveling motors 211a and 211b shown in FIG. 5 and the flow rate control valves corresponding to them is omitted.

The operation lever devices 12, 13, and 14 shown in FIG. 1 are disposed in the cab 206, and the engine 1 and the first to third hydraulic pumps 2 to 4 are disposed in the engine room 205. The hydraulic equipment such as the control valve unit 6 is disposed at an appropriate position on the upper swing body 203.
<Operation>
Next, the operation of the present embodiment configured as described above will be described.
<1. Single operation of arm cloud>
The arm cloud operation is an operation of extending the arm cylinder 7 and rotating the arm 209 in the forward direction (cloud direction) when viewed from the cab 206, for example, by lowering the bucket 210 in the air at the start of excavation work. This operation is used when the bucket tip is bitten into the ground. When the operator operates the arm lever 12a of the arm operation lever device 12 in the arm cloud direction with the intention of such an individual operation of the arm cloud, an operation pilot pressure as an arm cloud operation signal is output from the pilot valve 12b. The operation pilot pressure is guided to the pressure receiving portion 55a of the arm first flow control valve A1 and the pressure receiving portion 55c of the second flow control valve A2 via the pilot lines 65a and 65c, and the first and second flow control. The valves A1 and A2 are switched to the right and left positions in the drawing according to the magnitude of the operation pilot pressure (the operation amount of the operation lever 12a), respectively, and the discharge oil of the first and second hydraulic pumps 2 and 3 is the first and second Metering is performed by the meter-in opening throttling of the second flow control valves A1 and A2, and flows into the first actuator line 50a.

  At the same time, the operation pilot pressure as the arm cloud operation signal is also guided to the second pressure receiving portion 63b of the merging valve 20 via the control line 71, and the merging valve 20 is moved to the position shown in the figure according to the magnitude of the operation pilot pressure. The (merge release position) is switched to the merge position on the right side of the figure, and the oil discharged from the third hydraulic pump 4 is metered by the throttle of the merge valve 20 and flows into the first actuator line 50a via the merge line 60.

As a result, the discharge oil of the first to third hydraulic pumps 2 to 4 is supplied to the first actuator line 50a by being joined (three-pump join), and the discharge oil that is joined by the first to third hydraulic pumps 2 to 4 Is supplied to the bottom side of the arm cylinder 7. The arm cylinder 7 is extended by such supply of pressure oil, and rotates the arm 209 in the cloud direction (arm cloud operation). At this time, the extension operation of the arm cylinder 7 is accelerated by the merging of the pressure oils from the three main hydraulic pumps of the first hydraulic pumps 2 to 4, and the bucket 210 can be quickly pressed against the ground from the air.
<2. Combined operation of arm cloud and bucket cloud>
The bucket cloud is an operation of extending the bucket cylinder 9 and rotating the bucket 210 in the forward direction (cloud direction) when viewed from the cab 206. The combined operation of the arm cloud and the bucket cloud is the operation of the arm cloud and the bucket cloud. These operations are performed simultaneously. The combined operation of the arm cloud and the bucket cloud is performed, for example, by causing the tip of the bucket 210 to bite into the ground by an arm cloud single operation during excavation work, and then causing the tip of the bucket 210 to deepen into the ground further by the bucket cloud. Used when scraping earth and sand. In the state where the operator operates the operation lever 12a of the arm operation lever device 12 in the arm cloud direction for the combined operation of the arm cloud and the bucket cloud, the operation lever 13a of the bucket operation lever device 13 is further operated. Is operated in the bucket cloud direction, an operation pilot pressure as a bucket cloud operation signal is output from the pilot valve 13b, and this operation pilot pressure is guided to the pressure receiving portion 57a of the bucket flow control valve BU via the pilot line 66a. The flow control valve BU is switched to the right position in the drawing according to the magnitude of the operation pilot pressure (the operation amount of the operation lever 13a), and the discharged oil of the second hydraulic pump 3 is metered by the meter-in opening throttle of the flow control valve BU. The ring is bent through the first actuator line 52a. It is supplied to the bottom side of the Toshirinda 9. As a result, the bucket cylinder 9 extends and rotates the bucket 210 in the cloud direction (bucket cloud operation).

  At the same time, the operation pilot pressure as the operation pilot pressure as the bucket cloud operation signal is guided to the pressure receiving portion 63a of the merging valve 20 via the control line 72, and the merging valve 20 is released from the merging position on the right side in the figure. Switch to position. As a result, the oil discharged from the third hydraulic pump 5 is circulated to the tank T via the merging valve 20, and the merging of the oil discharged from the third hydraulic pump 4 to the first actuator line 50a is released.

  The second flow control valve A2 for the arm is connected in tandem so that the oil discharged from the second hydraulic pump 3 is preferentially supplied to the flow control valve BU on the downstream side of the first flow control valve BU for the bucket. Therefore, when the flow control valve BU is switched to the right position in the figure as described above and the entire amount of oil discharged from the second hydraulic pump 3 is supplied to the bucket cylinder 9 (for example, when the operation lever 13a is fully operated). ), The supply of the oil discharged from the second hydraulic pump 3 to the flow rate control valve A2 is eliminated. Further, when a part of the oil discharged from the second hydraulic pump 3 is supplied to the bucket cylinder 9 (for example, when the operation lever 13a is half-operated), the remainder is supplied to the bucket cylinder 9.

  As a result, the first actuator line 50a for the arm cylinder 7 has only the discharge oil of the first hydraulic pump 2 (when the entire discharge oil of the second hydraulic pump 3 is supplied to the bucket cylinder 9) or the first hydraulic pump. 2 and the remainder of the discharge oil of the second hydraulic pump 3 (when a part of the discharge oil of the second hydraulic pump 3 is supplied to the bucket cylinder 9) are supplied, and the pressure oil is the bottom of the arm cylinder 7 The arm cylinder 7 extends in accordance with the amount of pressure oil supplied, and rotates the arm 209 in the cloud direction (arm cloud operation).

As described above, in the combined operation of the arm cloud and the bucket cloud, the merge of the discharge oil of the third hydraulic pump with respect to the arm cylinder (3-pump merge) is canceled and the pressure flow of the second hydraulic pump is mainly supplied to the arm cylinder 7. Since the arm cloud operation is performed and the bucket cylinder 9 is supplied with the pressure flow of the third hydraulic pump to perform the bucket cloud operation, the load pressure is particularly high during heavy excavation work in which the load pressure of the arm cylinder 7 becomes high. Is avoided by the fact that the bucket cloud speed is reduced due to the reduction of the absorption torque (discharge flow rate) of the second hydraulic pump 3 by being guided to the first regulator 31 through the pressure reducing valve 33, and the combined use of the arm cloud and the bucket cloud Operability can be improved (described later).
<3. Combined operation of arm cloud and boom lowering>
The boom lowering is an operation of retracting the boom cylinder 8 to rotate the boom in the lowering direction, and the combined operation of the arm cloud and the boom lowering is an operation of simultaneously performing the arm cloud and the boom lowering. The combined operation of arm cloud and boom lowering is, for example, when leveling the surface of the ground by pulling the tip of the bucket 210 into the ground and pulling it horizontally toward the front of the cab 206 (cloud direction) in a horizontal pulling operation, for example. Used for. The operator intends for the combined operation of the arm cloud and the boom lowering, and the operation lever 12a of the arm operating lever device 12 and the operation lever 14a of the boom operating lever device 14 are moved in the arm cloud direction and the boom lowering direction, respectively. Are simultaneously operated, the pilot pilot pressure is output from the pilot valve 12b as an arm cloud operation signal, the pilot pilot pressure is output from the pilot valve 14b as a boom lowering operation signal, and the operation pilot pressure as an arm cloud operation signal is As described above, the pressure is also led to the pressure receiving portion 55a of the first flow control valve A1 for the arm, the pressure receiving portion 55c of the second flow control valve A2, and the second pressure receiving portion 63b of the merging valve 20. The flow control valves A1 and A2 are switched to the positions on the right and left sides in the figure, respectively, and the merging valve 20 is The operation pilot pressure as a boom lowering operation signal is switched from the position shown in the figure (confluence release position) to the right side of the figure, and the boom lowering operation signal is received by the pressure receiving portion 56b of the first flow control valve B1 for the boom via the pilot lines 67b and 67d. Then, the first and second flow rate control valves B1 and B2 are respectively switched to positions on the right side of the drawing, being guided to the pressure receiving portion 56d of the second flow rate control valve B2.

  Here, the second flow control valve A2 for the arm is tandem so that the oil discharged from the second hydraulic pump 3 is preferentially supplied to the flow control valve B1 on the downstream side of the first flow control valve B1 for the boom. The second flow control valve B2 for the boom is tandem so that the oil discharged from the first hydraulic pump 2 is preferentially supplied to the flow control valve A1 on the downstream side of the first flow control valve A1 for the arm. It is connected.

  Therefore, the first flow control valve A1 for the arm and the second flow control valve B2 for the boom are switched as described above on the first hydraulic pump 2 side, and the first flow control valve for the boom is switched on the second hydraulic pump side. When B1 and the second flow control valve A2 for the arm are switched as described above, and the merging valve 20 is switched as described above on the third hydraulic pump 3 side, the first actuator line 50a for the arm cylinder 7 has the first The discharge oil of the first hydraulic pump 2 and the discharge oil of the third hydraulic pump are supplied by merging (when the entire amount of discharge oil of the second hydraulic pump 3 is supplied to the boom cylinder 8), or the second hydraulic pump 3 is supplied to the boom cylinder 8 (when a part of the discharge oil of the second hydraulic pump 3 is supplied to the boom cylinder 8), and the pressure oil is supplied to the arm series. Is supplied to the bottom side of the die 7, the arm cylinder 7 is extended in accordance with the supply amount of the pressurized oil to rotate the arm 209 in the cloud direction (arm crowding operation). Further, only the discharge oil of the second hydraulic pump 3 is provided in the second actuator line 51b for the boom cylinder 8 (when the whole discharge oil of the first hydraulic pump 2 is supplied to the arm cylinder 9), or further, the first hydraulic pump. 2 is supplied to the arm cylinder 7 of the discharged oil (when a part of the discharged oil of the first hydraulic pump 2 is supplied to the arm cylinder 7), and the pressure oil is supplied to the rod side of the boom cylinder 8. Supplied, the boom cylinder 8 contracts according to the amount of pressure oil supplied, and rotates the boom 208 in the downward direction (boom lowering operation).

In this way, in the combined operation of the cloud cloud and the boom lowering, the merged discharge oil of the third hydraulic pump with respect to the arm cylinder 7 is not released, and at least the discharge oil of the first hydraulic pump and the discharge of the third hydraulic pump are discharged to the arm cylinder 7. Since the oil is joined (2 pumps join) and supplied, the arm cloud operation is performed, and the boom cylinder 8 is mainly supplied with the discharge oil of the second hydraulic pump to perform the boom lowering operation. It is possible to avoid a situation where the lowering speed becomes too fast with respect to the arm cloud speed, and to improve the combined operability of the arm cloud and the boom lowering (described later).
<Details of effects 2 and 3>
Details of the effect of the combined operation of the arm cloud and bucket cloud of the above 2 (effect of canceling the combined pump of 3 pumps) and the effect of the combined operation of the arm cloud and boom lowering of the above 3 (effect of canceling the combined release of the third hydraulic pump) are explained in detail. To do.
<Effects of 2 above (Effects of 3 pump merge release)>
When excavation work is performed by a combined operation of arm cloud and bucket cloud, the operation speed (bucket cloud speed) of the bucket cylinder 9 is not significantly slower than the operation speed of the arm cylinder 7 (arm cloud speed). It is important to have a moderate balance. If the operation speed (bucket cloud speed) of the bucket cylinder 9 becomes too slow compared with the operation speed (arm cloud speed) of the arm cylinder 7, the combined operability of the arm cloud and bucket cloud in the excavation work is reduced, and the excavation work Cause trouble.

<When 3 pump merging is not canceled>
When heavy excavation work is performed by a combined operation of the arm cloud and bucket cloud without canceling the merge of the three pumps, the operation speed of the bucket cylinder 9 is higher than the operation speed of the arm cylinder 7 by the torque control of the pump torque control device 30. There is a concern that it will be remarkably slow and interfere with heavy excavation work.

  That is, in the heavy excavation work performed by the combined operation of the arm cloud and the bucket cloud, the load pressure of the arm cylinder 7 becomes high, so when the discharge oil of the third hydraulic pump is also supplied to the arm cylinder 7 without releasing the merge of the three pumps, Since the discharge pressure of the third hydraulic pump 4 (hereinafter referred to as Pp3) also increases and the value of the absorption torque of the third hydraulic pump 4 increases, the total value of the absorption torque of the first and second hydraulic pumps 2 and 3 is increased. The effect will increase.

  Specifically, when the discharge pressure Pp3 of the third hydraulic pump 4 becomes high and becomes equal to or higher than P2 in FIG. 4, the pressure reducing valve 33 reduces the discharge pressure Pp3 to the set pressure P2 and outputs the output pressure (control). Pressure) is introduced into the pressure receiving portion 31e of the first regulator 31, and the first regulator 31 decreases the set value of the maximum absorption torque according to the control pressure. At this time, the absorption torque control characteristic line of the first regulator 3 shifts from the broken line A to the broken line C in FIG. 3, and the absorption torque (maximum absorption torque) of the first and second hydraulic pumps 2 and 3 decreases accordingly. As a result, the capacities of the first and second hydraulic pumps 2 and 3 also decrease, and the discharge flow rates of the first and second hydraulic pumps 2 and 3 decrease.

  On the other hand, during the combined operation of the arm cloud and the bucket cloud, the discharge oil of the first hydraulic pump 2 is supplied to the bottom side of the arm cylinder 7 and the discharge oil of the second hydraulic pump 3 is supplied to the bucket cylinder 9 as described above. Since the oil is preferentially supplied to the bottom side, at least the discharge oil from the first and third hydraulic pumps 2 and 4 (if there is any remaining discharge from the second hydraulic pump 3) further on the bottom side of the arm cylinder 7 In contrast, only the discharge oil of the second hydraulic pump 3 reduced by the torque control is supplied to the bottom side of the bucket cylinder 9. As a result, the operating speed of the bucket cylinder 9 (bucket cloud speed) is significantly slower than the operating speed of the arm cylinder 7 (arm cloud speed), and the combined operability of the arm cloud and bucket cloud in excavation work is reduced, This will hinder excavation work.

<In the case of the present invention (when canceling the merge of three pumps)>
On the other hand, when releasing the 3 pump merging at the time of heavy excavation work by the combined operation of the arm cloud and the bucket cloud as in the present invention, even if the load pressure of the arm cylinder 7 becomes high, the absorption torque of the third hydraulic pump 4 Does not affect the total value of the absorption torques of the first and second hydraulic pumps 2 and 3, the absorption torque (discharge flow rate) of the second hydraulic pump 3 is affected by the absorption torque of the third hydraulic pump 4. The decrease in bucket cloud speed due to a decrease in the absorption torque (discharge flow rate) of the second hydraulic pump 3 can be avoided and the combined operability of the arm cloud and bucket cloud can be improved.

  That is, when the 3 pump merging is canceled during heavy excavation work by the combined operation of the arm cloud and the bucket cloud, the merging valve 20 is in the merging release position shown in the figure, so that the discharge oil of the third hydraulic pump 4 is circulated to the tank. The discharge pressure Pp3 of the third hydraulic pump is the minimum pressure P0 (see FIG. 4) close to the tank pressure. For this reason, the control pressure output from the pressure reducing valve 33 is also the minimum pressure P0 close to the tank pressure, the set value of the maximum absorption torque of the first regulator 31 hardly changes, and the absorption torque control characteristic line of the first regulator 3 is The broken line A in FIG. 3 remains. As a result, the absorption torque (maximum absorption torque) of the first and second hydraulic pumps 2 and 3 does not decrease, and the capacities of the first and second hydraulic pumps 2 and 3 are controlled according to the characteristics of the broken line A, Large values corresponding to the polygonal line A are secured as the discharge flow rates of the first and second hydraulic pumps 2 and 3.

Further, during the combined operation of the arm cloud and the bucket cloud, as described above, the discharge oil of the first hydraulic pump 2 is supplied to the bottom side of the arm cylinder 7 and the discharge oil of the second hydraulic pump 3 is supplied to the bucket cylinder 9. Since it is supplied preferentially to the bottom side, the discharge oil of the first hydraulic pump 2 (if there is a discharge remaining of the second hydraulic pump 3) is supplied to the bottom side of the arm cylinder 7. Since the discharge oil of the second hydraulic pump 3 is supplied to the bottom side of the bucket cylinder 9, the operating speed of the bucket cylinder 9 (bucket cloud speed) is significantly higher than the operating speed of the arm cylinder 7 (arm cloud speed). The combined operability of arm cloud and bucket cloud can be improved without slowing down.
<Effect of the above 3 (effect of non-release of the third hydraulic pump joining)>
In the horizontal pulling operation by the combined operation of the arm cloud and the boom lowering, the operating speed of the arm cylinder 7 (arm cloud speed) is made faster than the operating speed of the boom cylinder 8 (boom lowering speed), and the arm 209 is quickly brought forward. It is important to be able to draw. If the operating speed of the arm cylinder 7 does not become higher than the operating speed of the boom cylinder 8, the combined operability of the arm cloud and the boom lowering in the horizontal pulling work is deteriorated, and the horizontal pulling work is hindered.

<When canceling the merge of the third hydraulic pump>
When the merging of the third hydraulic pump 4 is canceled and the horizontal pulling operation is performed by the combined operation of the arm cloud and the boom lowering, the operating speed of the arm cylinder 7 is not increased compared to the operating speed of the boom cylinder 8, and There is a concern that the pulling work may be hindered.

  That is, when the joining of the third hydraulic pump 4 is canceled during the horizontal pulling operation by the combined operation of the arm cloud and the boom lowering, as described above, the discharge pressure Pp3 of the third hydraulic pump is the minimum pressure P0 close to the tank pressure (see FIG. 4), the set value of the maximum absorption torque of the first regulator 31 hardly changes, and the absorption torque control characteristic line of the first regulator 3 remains the broken line A in FIG. The absorption torque (maximum absorption torque) of the first and second hydraulic pumps 2 and 3 does not decrease, and the capacities of the first and second hydraulic pumps 2 and 3 are controlled according to the characteristics of the polygonal line A. Large values corresponding to the polygonal line A are secured as the discharge flow rates of the hydraulic pump 2 and 3.

  On the other hand, during the combined operation of the arm cloud and the boom lowering, as described above, the discharge oil of the first hydraulic pump 2 is preferentially supplied to the bottom side of the arm cylinder 7, and the discharge oil of the second hydraulic pump 3 is supplied to the boom. Since the oil is preferentially supplied to the rod side of the cylinder 8, the discharge oil of the first hydraulic pump 2 (if there is remaining discharge of the second hydraulic pump 3 on the bottom side of the arm cylinder 7 is further remaining discharge oil). ) Is supplied to the bottom side of the boom cylinder 8, and the discharge oil of the second hydraulic pump 3 (or the remaining discharge oil if there is discharge remaining from the first hydraulic pump 2) is supplied to the bottom side of the boom cylinder 8, and as a result, the arm The same flow rate is supplied to the bottom side of the cylinder 7 and the rod side of the boom cylinder 8. Thus, when the same flow rate is supplied to the bottom side of the arm cylinder 7 and the rod side of the boom cylinder 8, the operating speed (boom lowering speed) of the boom cylinder 8 is the operation of the arm cylinder 7 in the horizontal pulling operation. The speed is too high with respect to the speed (arm cloud speed), and the combined operability of the arm cloud and the boom lowering in the horizontal pulling work is deteriorated, and the horizontal pulling work is hindered.

<In the case of the present invention (when the merging of the third hydraulic pump is not released)>
On the other hand, when the merging of the third hydraulic pump is not canceled (the merging of the third hydraulic pump is performed) at the time of the horizontal pulling operation by the combined operation of the arm cloud and the boom lowering as in the present invention, the load pressure of the arm cylinder 7 And the discharge pressure Pp3 of the third hydraulic pump 4 increases accordingly (Pp3> P2 in FIG. 4), so that the first regulator 31 absorbs the maximum according to the control pressure from the pressure reducing valve 33 as described above. The characteristic value of the absorption torque control of the first regulator 3 is shifted from the broken line A to the broken line C in FIG. 3, and the absorption torque (maximum absorption torque) of the first and second hydraulic pumps 2 and 3 is reduced. ) Decreases accordingly, and accordingly, the capacities of the first and second hydraulic pumps 2 and 3 also decrease, and the discharge flow rates of the first and second hydraulic pumps 2 and 3 decrease.

Further, during the horizontal pulling operation by the combined operation of the arm cloud and the boom lowering, the discharge oil of the first hydraulic pump 2 is preferentially supplied to the bottom side of the arm cylinder 7 as described above, and the second hydraulic pump 3 Since the discharge oil is preferentially supplied to the rod side of the boom cylinder 8, at least the discharge oil of the first and third hydraulic pumps 2, 4 (remaining discharge of the second hydraulic pump 3 is provided on the bottom side of the arm cylinder 7. If there is, the remaining discharge oil) is joined and supplied, whereas only the discharge oil of the second hydraulic pump 3 reduced by torque control is supplied to the rod side of the boom cylinder 8. As a result, a larger amount of pressure oil is supplied to the bottom side of the arm cylinder 7 than the rod side of the boom cylinder 8, so that the arm cylinder 7 operates compared to the operating speed (boom lowering speed) of the boom cylinder 8. The speed (arm cloud speed) is increased, and the arm 209 can be quickly pulled toward the front, the combined operability of the arm cloud and the boom lowering is improved, and good horizontal pulling work can be performed.
<Summary of effects>
1. Effects on Operability According to the present embodiment, the following effects can be obtained.

  (A) In the single operation of the arm cloud, the discharge oil of the first to third hydraulic pumps 2 to 4 is joined and supplied to the bottom side of the arm cylinder 7 (3-pump joining). The operation is accelerated and the bucket 210 can be quickly pressed against the ground from the air.

  (B) When excavation work is performed by the combined operation of the arm cloud and the bucket cloud, which is a combined operation for releasing the merging of the discharge oil of the third hydraulic pump 4 in consideration of the influence of the torque control by the pump torque control device 30 Since the load pressure is led to the first regulator 31 through the pressure reducing valve 33 and the absorption torque (discharge flow rate) of the second hydraulic pump 3 is suppressed from decreasing, the decrease in bucket cloud speed is avoided. The combined operability of arm cloud and bucket cloud can be improved.

  (C) On the other hand, when performing the horizontal pulling operation by the combined operation of the arm cloud and the boom lowering, the boom lowering speed becomes too high with respect to the arm cloud speed because the joining of the discharge oil of the third hydraulic pump is not released. , Speeding up the arm cloud speed and slowing down the boom lowering speed can improve the combined operability of arm cloud and boom lowering.

2. Other Effects According to the present embodiment, the following effects can be obtained.

(A) In the present embodiment, the discharge oil of the third hydraulic pump 4 by the merging valve 20 using the operation pilot pressure as the bucket cloud operation signal output from the pilot valve 13b of the bucket operation lever device 13 is used. In order to release the merging and guide the operation pilot pressure to the pressure receiving portion 63a of the merging valve 20, the control line 72 may be branched from the pilot line 66a and the control line 72 may be routed to the merging valve 20. . Here, since the maximum pressure of the operation pilot pressure is as low as, for example, about 40 kg / cm ² , the piping of the control line 72 that guides the operation pilot pressure has a low pressure specification, and the junction valve 20 that guides the operation pilot pressure is also low in pressure. It becomes a specification. Further, since the control line 72 may be branched from the pilot line 66a, the piping length of the control line 72 can be shortened. As a result, the entire hydraulic circuit can be made compact, and the vehicle body layout can be simplified and the cost can be reduced.

  (B) Further, the operation pilot pressure as the bucket cloud operation signal is directly applied to the side (pressure receiving portion 63a) opposite to the operation pilot pressure as the arm cloud operation signal with respect to the merge valve 20, and the merge valve 20 is operated. In order to cancel the merging of the oil discharged from the third hydraulic pump 4, the conventionally used merging release valve becomes unnecessary. In this respect as well, the entire hydraulic circuit can be made compact, the vehicle body layout can be simplified and the cost can be reduced. it can.

  A second embodiment of the present invention will be described with reference to FIG. In the figure, the same components as those shown in FIG.

  In the present embodiment, the merging valve 20 is switched to the merging release position using the load pressure instead of the operation pilot pressure.

  That is, in FIG. 6, the second control line 72 branches from the first actuator line 52 a that guides the discharge oil of the second hydraulic pump 3 of the third hydraulic pump to the bottom side of the bucket cylinder 9. Connected to the first pressure receiving portion 63Aa of the merging valve 20, the load pressure on the bottom side of the bucket cylinder 9 (load pressure of the bucket cloud) is guided to the first pressure receiving portion 63Aa of the merging valve 20. The first pressure receiving portion 63Aa has a smaller pressure receiving area than the second pressure receiving portion 63b in consideration of the relatively high load pressure.

  Also in the present embodiment configured as described above, whether or not the bucket cylinder 9 has been extended and the bucket cloud operation has been performed is detected by the load pressure on the bottom side of the bucket cylinder 9, and based on the load pressure, In order to cancel the merging of the discharge oil of the third hydraulic pump 4, similarly to the first embodiment, the merging of the discharge oil of the third hydraulic pump 4 is canceled in consideration of the influence of the torque control by the pump torque control device 30. The effects 1 (a) to (c) described above can be obtained, for example, only the combined operation of the arm cloud and the bucket cloud, which is the combined operation to be performed, can be reliably released.

  Further, the load pressure of the bucket cloud is made to act directly on the side (pressure receiving portion 63a) opposite to the operation pilot pressure as the arm cloud operation signal with respect to the merging valve 20 to operate the merging valve 20, and the third hydraulic pump 4 Since the joining of the discharge oil is released, the conventionally used joining release valve is not required, the entire hydraulic circuit is made compact, and the vehicle body layout can be simplified and the cost can be reduced (the effect of 2 (b) above).

  The first and second embodiments can be variously modified within the spirit of the present invention.

  For example, in the first and second embodiments, the operation pilot pressure or the load pressure, which is a signal generated when the arm cloud operation is performed by the bucket cylinder 9, is led to the pressure receiving portion 58 a or 58 Aa of the merging valve 20. As shown in Document 1, an operation pilot pressure as an arm cloud operation signal is guided to the pressure receiving portion 58a of the merging valve 20, a merging release valve is interposed in the path, and the merging release valve is operated during arm cloud operation by the bucket cylinder 9. Even if the operation pilot pressure or load pressure, which is a generated signal, is derived and the transmission of the operation pilot pressure as an arm cloud operation signal to the pressure receiving portion 58a of the merging valve 20 is switched, the operation of the merging valve 20 is controlled. Good.

  Further, an operation pilot pressure or a load pressure, which is a signal generated when the arm cloud is operated by the bucket cylinder 9, is detected by a pressure sensor, and a detected value of the pressure sensor is input to the controller, and a control signal is sent from the controller to the proportional solenoid valve. The merging valve 20 may be switched by outputting the control pressure generated by the proportional solenoid valve to the pressure receiving part 63a of the merging valve 20 or the pressure receiving part of the merging release valve.

  Even in these cases, it is detected whether or not the bucket cylinder 9 (second actuator) is operated in the extending direction based on the operation pilot pressure or the load pressure that is a signal generated when the arm cloud operation is performed by the bucket cylinder 9. The operability such as the improvement of the combined operability described in the above 1 (a) to (c) by releasing the merging of the oil discharged from the third hydraulic pump 4 by the merging valve 20 when operated in the extending direction. The effect regarding can be acquired.

  A third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a diagram showing a pump torque control device portion according to the third embodiment. In the figure, the same components as those shown in FIG. In the present embodiment, the first regulator and the second regulator are provided with a function of controlling the capacity (discharge flow rate) of the first to third hydraulic pumps according to the required flow rate.

  In FIG. 7, the first and second hydraulic pumps 2 and 3 include a first regulator 131, and the third hydraulic pump 4 includes a second regulator 132. The first and second hydraulic pumps 2 and 3 adjust the displacement volume (capacity) by adjusting the tilt angle of the swash plates 2b and 3b, which are displacement displacement variable members, by the first regulator 131, and according to the required flow rate. While controlling the pump discharge flow rate, the pump absorption torque is adjusted. The third hydraulic pump 4 adjusts the displacement volume (capacity) by adjusting the tilt angle of the swash plate 4b, which is a displacement displacement variable member, by the second regulator 131, and controls the pump discharge flow rate according to the required flow rate. Adjust pump absorption torque.

  The first regulator 131 includes a tilt control actuator 112 that operates the swash plates 2 b and 3 b, a torque control servo valve 113 that controls the actuator 112, and a position control valve 114. The tilt control actuator 112 is linked to the swash plates 2b and 3b and has a pump tilt control spool 112a having different pressure receiving areas at the pressure receiving portions provided at both ends, and a small area pressure receiving portion side of the pump tilt control spool 112a. A tilt control increasing torque receiving chamber 112b is provided, and a tilt control decreasing torque receiving chamber 112c is provided on the large area pressure receiving portion side. The tilt control increasing torque receiving chamber 112b is connected to the discharge line 5a of the pilot pump 5 via an oil passage 135, and the tilt control decreasing torque receiving chamber 112c is connected to the discharge passage 5a of the pilot pump 5 with an oil passage 135 and torque control. The servo valve 113 and the position control valve 114 are connected.

  The torque control servo valve 113 includes a torque control spool 113a, springs 113b1 and 113b2 positioned on one end side of the torque control spool 113a, a first PQ control pressure receiving chamber 113c and a second PQ control positioned on the other end side of the torque control spool 113a. A pressure receiving chamber 113d and a reduced torque control pressure receiving chamber 113e are provided. The first PQ control pressure receiving chamber 113c is connected to the discharge line 2a of the first hydraulic pump 2 via the signal line 115a, and the second PQ control pressure receiving chamber 113d is connected to the discharge line 3a of the second hydraulic pump 3 via the signal line 115b. The reduced torque control pressure receiving chamber 113e is connected to the output port of the pressure reducing valve 33 via the control oil passage 39b.

  The position control valve 114 includes a position control spool 114a, a weak spring 114b for position holding located on one end side of the position control spool 114a, and a control pressure receiving chamber 114c located on the other end side of the position control spool 114a. Yes. A hydraulic signal 116 corresponding to the operation amount (required flow rate) of the operation system related to the first and second hydraulic pumps 2 and 3 is guided to the control pressure receiving chamber 114c. The hydraulic signal 116 can be generated by various known methods. For example, the highest operating pilot pressure among the operating pilot pressures generated by the operating lever device may be selected and used as the hydraulic signal 116. Further, when the flow control valve is a center bypass type valve, a throttle is provided on the downstream side of the center bypass line, the pressure upstream of the throttle is taken out as a negative control pressure, and the negative control pressure is inverted as a hydraulic signal 116. Also good.

  The pump tilt control spool 112a controls the tilt angle (capacity) of the swash plate of the first and second hydraulic pumps 2 and 3 by the pressure balance of the pressure oil in the pressure receiving chambers 112b and 112c. The discharge pressure on the high pressure side of the first and second hydraulic pumps 2 and 3 is guided to the PQ control pressure receiving chamber 113c of the torque control servo valve 113, and the torque control spool 113a moves to the left in the drawing as the pressure increases. . As a result, the discharge oil of the pilot pump 5 flows into the pressure receiving chamber 112c, the pump tilt control spool 112a is moved to the right in the figure, and the swash plates 2b, 3b of the first and second hydraulic pumps 2, 3 are reduced in volume by pushing the pump. Drive in the direction to reduce the pump absorption torque by reducing the pump capacity. As the discharge pressures of the first and second hydraulic pumps 2 and 3 become lower, the reverse operation is performed, and the swash plates 2b and 3b of the first and second hydraulic pumps 2 and 3 are driven in the direction of increasing the displacement of the pump. Then, the pump absorption volume is increased to increase the pump absorption torque.

  The torque control characteristics of the torque control servo valve 113 with respect to the first and second hydraulic pumps 2 and 3 are determined by the pressures guided to the springs 113b1 and 113b2 and the reduced torque control pressure receiving chamber 113e, and according to the output pressure of the pressure reducing valve 33. As described above, the torque control characteristic shifts (see FIG. 3). As a result, the maximum absorption torque (assigned maximum absorption torque) of the first and second hydraulic pumps 2 and 3 is controlled to decrease as the discharge pressure of the third hydraulic pump 4 increases, thereby preventing the engine 1 from being overloaded. In addition, when the third hydraulic pump 4 is not used, or when the discharge pressure of the third hydraulic pump 4 is lower than P2 in FIG. The output torque of the engine 1 can be effectively utilized by that amount.

  The second regulator 131 includes a tilt control actuator 212 that operates the swash plate 4 b, a torque control servo valve 213 that controls the actuator 212, and a position control valve 214. The tilt control actuator 212, the torque control servo valve 213, and the position control valve 214 are configured similarly to the tilt control actuator 112, the torque control servo valve 113, and the position control valve 114 of the first regulator 131. Equivalent parts are shown with reference numerals in which numbers in the 10s are changed to numbers in the 200s. However, since the torque control servo valve 113 does not require adjustment of the set torque, there is no equivalent to the first and second reduced torque control pressure receiving chambers 113d and 113e.

  The operation of the second regulator 132 is substantially the same as the operation of the first regulator 131. However, the absorption torque control characteristic is determined by the spring 213b of the torque control servo valve 213 and is constant (see FIG. 4).

  In the present embodiment configured as described above, the first regulator 131 and the second regulator 132 have a function of controlling the capacity (discharge flow rate) of the first to third hydraulic pumps 2 to 4 according to the required flow rate. The same effects as those of the first and second embodiments can be obtained.

  In the embodiment described above, the third hydraulic pump 4 is a variable displacement type, but may be a fixed displacement type.

1 is a diagram illustrating an overall configuration of a three-pump hydraulic circuit system for a construction machine according to a first embodiment of the present invention. It is a figure which shows the detail of the pump torque control apparatus with which the 3 pump hydraulic circuit system of FIG. 1 is equipped. It is a figure which shows the relationship between the discharge pressure (average value) of the 1st and 2nd hydraulic pump by a 1st regulator, and the capacity | capacitance (displacement volume or inclination of a swash plate) of a 1st and 2nd hydraulic pump. It is a figure which shows the relationship between the discharge pressure of the 3rd hydraulic pump by a 2nd regulator, and the capacity | capacitance (a displacement or inclination of a swash plate) of a 3rd hydraulic pump. It is a figure which shows the external appearance of the hydraulic excavator by which the 3 pump hydraulic circuit system concerning 1st Embodiment is mounted. It is a figure which shows the whole structure of the 3 pump hydraulic circuit system of the construction machine concerning the 2nd Embodiment of this invention. It is a figure which shows the pump torque control part of the 3 pump hydraulic circuit system concerning the 3rd Embodiment of this invention.

Explanation of symbols

1 prime mover (engine)
2 1st hydraulic pump 3 2nd hydraulic pump 4 3rd hydraulic pump 5 Pilot pump 6 Control valve units 6a, 6b, 6c Valve groups 7 to 10 Multiple hydraulic actuators 7 Arm cylinder (first actuator)
8 Boom cylinder 9 Bucket cylinder (second actuator)
10 Swing motor (third actuator)
12-14 Operation lever devices 15, 16, 17 Center bypass line 20 Merge valve 25-27 Main relief valve 30 Pump torque control device 31 First regulator 31a, 31b Spring 31c, 31d, 31e Pressure receiving portion 32 Second regulator 32a Spring 32b Pressure receiving portion 33 Pressure reducing valve 33a Spring 37, 38 Pilot line 39a, 39b Pilot line 40 Pilot line 50a First actuator line 50b Second actuator line 51a First actuator line 51b Second actuator line 52a First actuator line 52b Second actuator line 55a 1st pressure receiving part 55b 2nd pressure receiving part 55c 1st pressure receiving part 56a 1st pressure receiving part 56b 2nd pressure receiving part 56c 1st pressure receiving part 56d 2nd pressure receiving part 57b 1st pressure receiving part 57b 2nd receiving Pressure part 58a First pressure receiving part 58b Second pressure receiving part 60 Junction line 61 Junction point 62 Check valve 63a First pressure receiving part 63b Second pressure receiving part 63c Spring 65a, 65b Pilot line 66a, 66b Pilot line 67a, 67b Pilot line 67c , 67d Pilot line 71 First control line 72 Second control line 202 Lower traveling body 203 Upper turning body 204 Front work machine 205 Engine room 206 Operator's cab 208 Boom 209 Arm 210 Bucket 211a, 211b Traveling motor 131 First regulator 132 Second Regulator 112, 212 Tilt control actuator 113, 213 Torque control servo valve 113
113b1, 113b2 Spring 113c First PQ control pressure receiving chamber 113d Second PQ control pressure receiving chamber 113e Decrease torque control pressure receiving chamber 114, 214 Position control valve A1 Flow control valve (for arm)
A2 Flow control valve (for arm)
B1 Flow control valve (for boom)
B2 Flow control valve (for boom)
BU flow control valve (for bucket)
S Flow control valve (for turning)
T tank

Claims (8)

Engine,
Variable displacement first and second hydraulic pumps driven by the engine;
A third hydraulic pump driven by the engine;
A first actuator driven by a merge of pressure oil discharged from each of the first and second hydraulic pumps;
A second actuator driven by pressure oil discharged from one of the first and second hydraulic pumps;
A third actuator driven by pressure oil discharged from the third hydraulic pump;
When the first actuator is operated in a state where the third actuator is not operated, the discharge oil of the third hydraulic pump is merged with the discharge oil of the first and second hydraulic pumps, and the first actuator In a three-pump hydraulic circuit system of a construction machine having a merging valve to supply
Based on the discharge pressures of the first and second hydraulic pumps, the capacities of the first and second hydraulic pumps are controlled so that the absorption torque of the first and second hydraulic pumps does not exceed the maximum absorption torque, and the first A pump torque control means for reducing the maximum absorption torque as the discharge pressure of the three hydraulic pumps increases;
Detecting whether or not the second actuator has been operated, and when the second actuator has been operated, provided with a merging release means for releasing the merging of the discharge oil of the third hydraulic pump by the merging valve. 3-pump hydraulic circuit system for construction machinery. The three-pump hydraulic circuit system for the construction machine according to claim 1,
A plurality of hydraulic pilot operating lever devices for operating the first to third actuators;
The merging release means detects whether or not the second actuator has been operated based on an operating pilot pressure output from the operating lever device of the second actuator, and based on the operating pilot pressure, a third hydraulic pump by the merging valve A three-pump hydraulic circuit system for construction machinery, characterized by canceling the merging of the discharged oil. The three-pump hydraulic circuit system for the construction machine according to claim 1,
The merging release means detects whether or not the second actuator has been operated based on the load pressure of the second actuator, and releases the merging of the discharge oil of the third hydraulic pump by the merging valve based on the load pressure. A three-pump hydraulic circuit system for construction machinery. The three-pump hydraulic circuit system for the construction machine according to claim 1,
The merging valve is a switching valve that operates by being guided by a first hydraulic pressure signal generated when the first actuator is operated, and that guides the discharged oil of the third hydraulic pump to the first actuator.
The merging release means generates a second hydraulic pressure signal when the second actuator is operated, and causes the second hydraulic pressure signal to act on the side opposite the first hydraulic pressure signal with respect to the merging valve. A three-pump hydraulic circuit system for construction machinery. The three-pump hydraulic circuit system for a construction machine according to claim 4,
A plurality of hydraulic pilot operating lever devices for operating the first to third actuators;
The merging valve operates by receiving an operation pilot pressure output from the operation lever device of the first actuator as the first hydraulic signal, and merges the discharge oil of the third hydraulic pump to the first actuator. A switching valve that leads,
The merging release means guides an operation pilot pressure output from the operation lever device of the second actuator as the second hydraulic pressure signal to the merging valve, and this operation pilot pressure is transmitted to the merging valve from the first actuator. A three-pump hydraulic circuit system for a construction machine, characterized by acting on an operating pilot pressure. Engine,
Variable displacement first and second hydraulic pumps driven by the engine;
A third hydraulic pump driven by the engine;
A first actuator that is driven by a merge of pressure oil discharged from each of the first and second hydraulic pumps to drive an arm;
A second actuator that is driven by pressure oil discharged from one of the first and second hydraulic pumps to drive the bucket;
A third actuator that is driven by pressure oil discharged from the third hydraulic pump and drives the swivel;
When the first actuator is operated in the arm cloud direction when the third actuator is not operated, the discharge oil of the third hydraulic pump is merged with the discharge oil of the first and second hydraulic pumps. A three-pump hydraulic circuit system of a hydraulic excavator provided with a merging valve that supplies the first actuator;
Based on the discharge pressures of the first and second hydraulic pumps, the capacities of the first and second hydraulic pumps are controlled so that the absorption torque of the first and second hydraulic pumps does not exceed the maximum absorption torque, and the first A pump torque control means for reducing the maximum absorption torque as the discharge pressure of the three hydraulic pumps increases;
Detecting whether or not the second actuator is operated in the bucket cloud direction, and when the second actuator is operated in the bucket cloud direction, the merging cancel that releases the merging of the discharge oil of the third hydraulic pump by the merging valve A three-pump hydraulic circuit system for a hydraulic excavator, characterized by comprising: The three-pump hydraulic circuit system for a hydraulic excavator according to claim 6,
The merging valve is operated by being guided by a first hydraulic signal generated when the first actuator is operated in the arm cloud direction, and the switching valve is configured to merge and guide the discharged oil of the third hydraulic pump to the first actuator. And
The merging release means generates a second hydraulic pressure signal when the second actuator is operated in a bucket cloud direction, and this second hydraulic pressure signal is placed on the side facing the first hydraulic pressure signal with respect to the merging valve. A three-pump hydraulic circuit system for a hydraulic excavator, characterized by acting. The three-pump hydraulic circuit system for a hydraulic excavator according to claim 7,
A plurality of hydraulic pilot operating lever devices for operating the first to third actuators;
The merging valve operates by receiving an operation pilot pressure output from the operation lever device of the first actuator as the first hydraulic signal, and merges the discharge oil of the third hydraulic pump to the first actuator. A switching valve that leads,
The merging release means guides an operation pilot pressure of the bucket cloud output from the operation lever device of the second actuator as the second hydraulic pressure signal to the merging valve, and this operation pilot pressure is transmitted to the merging valve with respect to the first pressure. A three-pump hydraulic circuit system for a hydraulic excavator, wherein the actuator is operated on a side opposite to an operation pilot pressure of an arm cloud of an actuator.

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