JP2002038536A - Cutoff control apparatus for construction equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutoff control apparatus for construction equipment, which sufficiently reduces its energy loss while alleviating mental burden on the operator. SOLUTION: The cutoff control apparatus is installed in the construction equipment having a plurality of actuators 7a, 7b,..., and a relief valve 10. According to the cutoff control apparatus, an oil temperature in a relief circuit 11 having the relief valve arranged thereacross, is detected by temperature sensors 22a and 22b, and a commanding current value A of a command signal S to a proportional solenoid valve 30 is controlled by a controller 23 according to the detected oil temperature. Then, a pressure value of pressure oil introduced from a pilot hydraulic pump 31 via conduits 29a and 29b and a shuttle valve 21 to a regulator 13 is regulated, to thereby reduce a discharge flow rate Q of a hydraulic pump 9 to a predetermined cutoff flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cut-off control device for a construction machine which performs cut-off control for reducing a discharge flow rate of a hydraulic pump when a pressure of a discharge circuit of the hydraulic pump becomes a predetermined pressure near a relief pressure. More specifically, the present invention relates to a construction machine cutoff control device capable of sufficiently reducing energy loss while reducing a mental burden on an operator.

[0002]

2. Description of the Related Art For example, a hydraulic shovel, which is one of construction machines, includes a traveling body having crawler tracks or wheels as traveling means, and a turning device having a turning hydraulic motor above the traveling body. A revolving body is provided so as to be revolvable through the arm, and an articulated front device (boom, arm, and bucket) operably connected to a front portion of the revolving body.

[0003] The boom, the arm, the bucket,
The revolving unit and the traveling unit have corresponding hydraulic actuators for driving them, that is, hydraulic cylinders (boom hydraulic cylinder, arm hydraulic cylinder, bucket hydraulic cylinder) and hydraulic motors (swing hydraulic motor, Left and right traveling hydraulic motors) are provided. These hydraulic actuators include a control valve that controls hydraulic oil from a driven hydraulic pump disposed in an engine device disposed on the revolving superstructure in response to operation of an operation lever in the cab. It is supplied via a control valve device. When each hydraulic actuator is driven in this manner, the boom, the arm, the bucket, the revolving unit, and the traveling unit perform various operations (excavation,
(Turning, self-propelled, etc.).

At this time, the discharge pressure of the hydraulic pump is
It increases or decreases according to the load pressure of each hydraulic actuator,
From the viewpoint of ensuring the safety of the discharge circuit of a hydraulic pump,
A relief valve is provided in a relief circuit branched from the discharge circuit, and a maximum value of the discharge circuit is determined by a set relief pressure (generally determined by a spring force for urging a valve body of the relief valve). I have. Thereby, when the pressure of the discharge circuit increases according to the increase of the load pressure,
When the pressure exceeds the set relief pressure, the relief valve opens to release the pressure oil in the discharge circuit to the hydraulic tank,
The pressure in the discharge circuit is maintained at or below the set relief pressure.

When such a relief valve is operated (hereinafter, appropriately,
At the time of relief), a considerable part of the discharge flow rate of the hydraulic pump is guided to the hydraulic tank via the relief valve without being supplied to each hydraulic actuator. Therefore, at the time of such relief, cutoff control for reducing the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate is performed. That is, a discharge pressure detecting means (for example, a pressure sensor) for detecting the discharge pressure of the hydraulic pump and a discharge flow rate controlling means (for example, a controller and a regulator) for controlling the discharge flow rate of the hydraulic pump are provided. When the discharge pressure detected by the means becomes equal to the set relief pressure (for example, 35 MPa),
The discharge flow rate of the hydraulic pump is controlled to, for example, a minimum discharge flow rate uniquely determined from the structure of the hydraulic pump. Specifically, when the discharge circuit pressure detected by the pressure sensor becomes equal to or higher than a pressure preset in the controller corresponding to the relief pressure of the relief valve (hereinafter, appropriately referred to as a cutoff pressure), the controller sends the pressure to the regulator. A control signal for reducing the discharge flow rate of the hydraulic pump is output to
Cutoff control is performed. As described above, the surplus flow rate discharged to the hydraulic tank at the time of relief is reduced, and energy loss is reduced (energy saving).

Here, the cutoff pressure at which the cutoff control is started is preferably originally set to be equal to the relief pressure of the relief valve from the viewpoint of energy saving as described above. However, in general, the magnitude of the actual relief pressure of the relief valve varies to some extent from product to product, and due to this variation, the actual relief pressure may be lower than the designed relief pressure of the relief valve. In such a case, if the cut-off pressure is set equal to the designed relief pressure, the relief valve operates before the discharge circuit pressure reaches the designed relief pressure, and the discharge circuit pressure rises to the designed relief pressure. Therefore, there is a concern that cutoff control will not function. In addition, since the accuracy of the pressure sensor varies from product to product, similar concerns arise.

In order to avoid such adverse effects due to variations in the actual relief pressure and the detection accuracy of the pressure sensor, and to ensure that the cut-off control functions, the cut-off pressure set in the controller is usually set to a relief value in design. The pressure is set to a value lower than the pressure by an amount that allows for the maximum width of these variations. For example, if the designed relief pressure of the relief valve is 35 MPa, the total of the actual relief pressure and the maximum width of the variation of the detection accuracy of the pressure sensor is 1.5 MPa.
In this case, the cutoff pressure is set to 33 MPa in consideration of a margin of 0.5 MPa.

However, with the above setting, the cutoff control functions before the discharge circuit pressure reaches the set cutoff pressure and the relief valve operates, thereby reducing the discharge flow rate of the hydraulic pump. For example, during heavy excavation work of a hydraulic excavator, etc., even when it is desired to supply a normal flow rate to the hydraulic actuator under a very high load pressure to start the operation of the relief valve and make the front device operate strongly, The operation speed of the actuator suddenly decreases, and the workability decreases.

In such a case, the operator increases the operation amount of the operation lever in order to return the operation speed to the original speed. However, the discharge flow rate of the hydraulic pump is cut off as described above. In this case, even if such an operation is performed, the operation speed does not return unless the cutoff control state is canceled. Usually, since a predetermined construction period is set for the entire construction including the excavation work, the operator becomes mentally impatient at the slow operation speed, and the mental burden is significantly increased.

To cope with this, conventionally, as disclosed in Japanese Patent Application Laid-Open No. Hei 10-246204, for example, a variable displacement hydraulic pump and a plurality of hydraulic pumps driven by hydraulic oil discharged from the hydraulic pump have been proposed. In a cut-off control device for a construction machine provided in a construction machine having an actuator and a relief valve for determining a maximum pressure of a discharge circuit of the hydraulic pump, a throttle unit provided downstream of the relief valve; Cut-off control means for reducing the discharge flow rate of the hydraulic pump to a predetermined cut-off flow rate in accordance with the pressure on the upstream side of the means has been proposed.

[0011]

In the above prior art, cutoff control is performed by converting the flow of pressure oil downstream of the relief valve during relief into a pressure rise upstream of the throttle means and detecting it. This eliminates concerns based on the gap between the cutoff pressure and the relief pressure as described above,
The mental burden on the operator can be reduced.

However, in this prior art,
The following new issues arise. This will be described with reference to FIGS.

(1) Influence of opening area upon detection of flow rate through throttling means FIG. 13 shows the effect of the difference in the opening area of the throttling means in the above-mentioned prior art in which the flow rate through the throttling means is measured as the pressure on the upstream side of the throttling means. FIG. The horizontal axis indicates the flow rate Q, and the vertical axis indicates the upstream pressure P of the throttle means. The characteristic curves are shown for each of the opening areas A1, A2 and A3 (where A1 <A2 <A3). FIG.
As shown in the figure, in each case, the tendency to increase to the right on the parabola according to the increase of the passing flow rate Q, but the larger the opening area, the smaller the amount of change in pressure, and the smaller the opening area, Change amount becomes large.

Therefore, the smaller the opening area of the throttle means (the larger the degree of throttle), the more the passing flow rate Q
It can be seen that it is easy to measure by converting to (in other words, the detection accuracy can be improved).

(2) Influence of Restrictor on Relief Characteristics FIG. 14 shows a relief characteristic (override characteristic) of a relief valve without a normal restrictor and the downstream side of the relief valve corresponding to the above-mentioned prior art. FIG. 4 is a diagram showing a comparison with relief characteristics when a diaphragm unit is provided.
The horizontal axis indicates the pressure of the relief circuit (= pump discharge pressure), and the vertical axis indicates the flow rate Qr of the relief valve. The above two cases are indicated by characteristic curves. The horizontal axis indicates the relief pressure Pr set by the spring provided in the relief valve.
Are also shown.

In FIG. 14, in a normal relief valve having no throttle means, as shown by a characteristic line a in the figure,
When the circuit pressure P rises and reaches a pressure Pr ″ slightly smaller than the set relief pressure Pr, the valve body of the relief valve starts to open gradually, and when the circuit pressure P further rises to Pr ′ which is larger than Pr ″, the valve body is opened. The passage flow rate Qr suddenly rises linearly and rises at a stretch to increase, and the set relief pressure Pr
Fully open at

If a restrictor is simply added downstream of the relief valve having such a characteristic, a back pressure is applied to the relief valve. When the main body opens rapidly, the flow rate Qr does not rise linearly at a stretch, and the characteristic line b in FIG.
As shown in the graph, the degree of the increase in the flow rate Qr with respect to the increase in the circuit pressure P becomes lower on the higher pressure side. As a result, the pressure becomes Pr '''which is larger than the set relief pressure Pr, and finally the valve is fully opened. Such a tendency becomes more conspicuous as the aperture area of the diaphragm means is smaller (the degree of the diaphragm is increased).

In this case, from the viewpoint of circuit protection, which is the original purpose of the relief valve, actually, the spring force is set and used so that the pressure Pr ′ ″ is equal to the set relief pressure Pr. . FIG. 15 is a diagram showing actual relief characteristics in the related art in which a throttle means is provided downstream of a relief valve.

In FIG. 15, as shown by a characteristic line c,
When the circuit pressure P reaches Pr2, the valve body of the relief valve starts to open gently. When the circuit pressure P rises and becomes Pr1 larger than Pr2, the valve body opens greatly and the passing flow rate Qr increases, and the set relief pressure Pr Fully open at

However, in this case, the circuit pressure P becomes P
Since the valve body of the relief valve is greatly opened from Pr1 which is considerably smaller than r, a leak flow rate from the relief valve occurs even in a state where the circuit pressure is still relatively low. The reduction of the energy loss due to the reduction of the surplus flow rate discharged to the hydraulic tank is impeded, and the energy saving cannot be sufficiently achieved.

An object of the present invention is to provide a cut-off control device for a construction machine capable of sufficiently reducing energy loss while reducing a mental burden on an operator.

[0022]

(1) In order to achieve the above object, the present invention provides a variable displacement hydraulic pump, a plurality of actuators driven by hydraulic oil discharged from the hydraulic pump, A construction machine cut-off control device provided in a construction machine having a relief valve for determining a maximum pressure of a discharge circuit of the hydraulic pump, wherein at least one oil temperature for detecting an oil temperature of a relief circuit including the relief valve. There is a detecting means, and a first cutoff control means for reducing a discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate according to the detected oil temperature.

When the pressure in the discharge circuit increases in response to the increase in the load pressure and the pressure exceeds a set relief pressure, the valve body opens to release the pressure oil in the discharge circuit to the hydraulic tank. Then, the pressure in the discharge circuit is maintained at or below the set relief pressure. That is, until just before the relief, the pressure oil does not flow to the downstream side (the hydraulic tank side) of the relief valve. Therefore, the temperature on the downstream side is a relatively low temperature that is considerably close to the temperature of the hydraulic tank, that is, the outside air temperature.

On the other hand, the upstream side (discharge circuit side) of the relief valve is in contact with the pressure oil discharged from the hydraulic pump and supplied to the hydraulic actuator through each control valve. High temperature.

Accordingly, immediately after the relief, the pressure oil from the upstream side of the relief valve, which has a relatively high temperature as described above, flows toward the downstream side of the relief valve, which has a relatively low temperature. Temperature behavior (temperature distribution) changes. That is, the temperature of the downstream side of the relief valve rapidly rises due to the inflow of the high-temperature pressure oil.
In addition, since heat is generated due to pressure loss when passing through the relief valve, the temperature of the downstream side of the relief valve becomes higher than that of the upstream side of the relief valve.

Therefore, in the present invention, utilizing such a change in the temperature behavior, the oil temperature of the relief circuit is detected by at least one oil temperature detecting means, and the first cutoff is determined according to the detected oil temperature. The control means performs cutoff control for reducing the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate. Specifically, for example, the first upstream side of the relief valve
The oil temperature (Ta) and the second oil temperature (Tb) on the downstream side
And the second detecting means detects the relief of the relief valve based on the difference between the first oil temperature and the second oil temperature and performs the cutoff control, or performs the detection of the second oil temperature. The relief is detected based on the rate of change, and the cutoff control is performed.

This prevents a decrease in operating speed during heavy excavation work, for example, based on a difference between the cutoff pressure and the relief pressure, as in the case of performing cutoff with a cutoff pressure preset and stored in the controller. The mental burden on the operator can be reduced.

Also, at this time, unlike the conventional structure in which the throttle means is provided upstream of the relief valve by performing cutoff control by detecting the relief by detecting the oil temperature as described above, the relief characteristic itself is not affected at all. Do not give. That is, similar to a normal relief valve, it is possible to secure good relief characteristics in which the flow rate rises linearly at a stretch after the circuit pressure rises to a pressure close to the set relief pressure. Therefore, it is possible to prevent a leakage flow from the relief valve to the hydraulic tank from occurring in a state where the circuit pressure is relatively low as in the above-described conventional structure, thereby reducing the excess discharge flow to the hydraulic tank, which is the original purpose of the cutoff control. Energy loss can be sufficiently reduced, and energy saving can be sufficiently achieved.

(2) In the above (1), preferably,
The oil temperature detecting means includes first detecting means for detecting a first oil temperature on the upstream side of the relief valve, and second detecting means for detecting a second oil temperature on the downstream side of the relief valve, First
The cutoff control means reduces the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate based on a difference between the first oil temperature and the second oil temperature.

(3) In the above (2), more preferably, the first cut-off control means is configured to determine whether a difference between the first oil temperature and the second oil temperature becomes smaller than a predetermined threshold value. The discharge flow rate of the hydraulic pump is reduced to a predetermined cutoff flow rate.

(4) In the above (1), preferably, the oil temperature detecting means includes a second detecting means for detecting a second oil temperature downstream of the relief valve, and the first cutoff control. The means reduces the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate based on the rate of change of the second oil temperature.

(5) In the above (4), more preferably, the first cut-off control means, when the rate of change of the second oil temperature becomes larger than a predetermined threshold, the discharge flow rate of the hydraulic pump. To a predetermined cutoff flow rate.

(6) In order to achieve the above object, the present invention provides a variable displacement hydraulic pump, a plurality of actuators driven by hydraulic oil discharged from the hydraulic pump, and a discharge of the hydraulic pump. In a construction machine cutoff control device provided in a construction machine having a relief valve for determining a maximum pressure of a circuit, a poppet valve provided downstream of the relief valve and a displacement of a valve body of the poppet valve are detected. There is provided first displacement detection means, and second cutoff control means for reducing the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate according to the detected displacement.

In general, when a poppet valve is arranged in a pressure oil pipeline and the valve body is opened and closed by its upstream pressure (self-pressure), its structural characteristic is that the opening degree of the valve body changes according to the flow rate. In addition, the valve body can be opened and closed with little pressure increase due to the throttle effect on the pressure oil pipeline.

In the present invention, utilizing such characteristics of the poppet valve, the displacement of the valve body of the poppet valve is detected by the first displacement detecting means, and the second cut-off control means is controlled by the second displacement control means in accordance with the detected displacement. The discharge flow rate of the hydraulic pump is reduced to a predetermined cutoff flow rate. By detecting the relief of the relief valve as the displacement of the valve body of the poppet valve disposed on the downstream side in this way, similar to the above (1), during heavy excavation work based on the deviation between the cutoff pressure and the relief pressure The reduction of the operating speed can prevent the mental burden on the operator, and the relief characteristics of the relief valve are not affected at all. Therefore, the energy loss can be reduced sufficiently and the energy can be saved sufficiently. Can be.

(7) In order to achieve the above object, the present invention further provides a variable displacement hydraulic pump, a plurality of actuators driven by hydraulic oil discharged from the hydraulic pump, and discharge of the hydraulic pump. In a construction machine cutoff control device provided in a construction machine having a relief valve that determines a maximum pressure of a circuit, a second displacement detection unit that detects a displacement of a valve body of the relief valve, and according to the detected displacement. And a third cutoff control means for reducing the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate.

As described above, when the pressure in the discharge circuit increases in response to the increase in the load pressure, and when the pressure exceeds the set relief pressure, the valve body opens to release the pressure oil in the discharge circuit. The pressure is released to the hydraulic tank, and the pressure in the discharge circuit is maintained at or below the set relief pressure.

In the present invention, the displacement of the valve body of the relief valve is detected by the second displacement detecting means by utilizing the opening operation of the valve body at the time of the relief.
The third cutoff control means reduces the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate. By detecting the relief of the relief valve as the displacement of the valve body in this manner, similarly to the above (1), the operation speed can be prevented from being lowered during the heavy excavation work based on the difference between the cutoff pressure and the relief pressure. Since the mental load on the user can be reduced and the relief characteristic itself is not affected at all, energy loss can be sufficiently reduced and energy saving can be sufficiently achieved.

(8) In the above (6) or (7), more preferably, the first or second displacement detecting means is configured to connect the valve body of the relief valve or the valve body of the poppet valve to a connecting member. This is a displacement sensor connected via a switch.

[0040]

Embodiments of the present invention will be described below with reference to the drawings. The embodiment described below is an embodiment in which the present invention is applied to a hydraulic shovel as an example of a construction machine.

FIG. 1 is a perspective view showing the overall external structure of a hydraulic shovel to which the present invention is applied. This hydraulic shovel is, in general terms, a traveling body 1 and is capable of turning on the traveling body 1. , A driver's cab 3 provided on the left side in front of the revolving body 2, an engine device 4 arranged horizontally on the revolving body 2, and a counterweight 5 provided on a rear portion of the revolving body 2. And a boom 6
a, an articulated front device 6 comprising an arm 6b and a bucket 6c.

The traveling body 1 has an endless track 1 on the left and right.
a. The crawler track 1a is driven by the driving force of the traveling hydraulic motor 1b.

The revolving unit 2 including the cab 3, the engine unit 4, the counterweight 5, the articulated front unit 6, and the like is provided with a hydraulic motor for rotation provided at the center of the revolving unit 2 (not shown). ), The vehicle is turned with respect to the traveling body 1.

The boom 6a, the arm 6b, and the bucket 6c that constitute the multi-joint type front device 6 are respectively provided with a boom hydraulic cylinder 7a, an arm hydraulic cylinder 7b, and a bucket hydraulic cylinder 7c.
Is driven.

Here, the traveling body 1, the revolving superstructure 2, the boom 6a, the arm 6b, and the bucket 6c constitute a driven member driven by a hydraulic drive device provided in the hydraulic excavator. That is, the hydraulic cylinder 7
Hydraulic actuators such as a, 7b, 7c, a turning hydraulic motor, and a traveling hydraulic motor 1b include an engine (not shown, see FIG. 2 described later) provided in an engine device 4 disposed on the revolving unit 2. A control valve (not shown, see FIG. 2) is driven in response to an operation of an operation lever (not shown, see FIG. 2) in the cab 3 by a control valve (not shown). It is supplied via a control valve device (not shown) provided with a not-shown, FIG. 2). By driving the hydraulic actuators 7a, 7b, 7c, 1b, etc. in this manner, the boom 6a, the arm 6b,
The bucket 6c, the revolving unit 2, and the traveling unit 1 can perform various operations (excavation, turning, self-propelling, etc.).

FIG. 2 shows the hydraulic actuators 7a, 7
FIG. 1 is a hydraulic circuit diagram illustrating a main configuration of a hydraulic drive device of a hydraulic shovel to which the present invention is applied, the hydraulic drive device including b, 7c, 1b, an engine, a hydraulic pump, an operation lever, and the like.

In FIG. 2, the hydraulic drive system comprises a variable displacement hydraulic pump 9 driven by the engine 8 as a prime mover and a relief valve 10 for determining the maximum pressure of the discharge circuit of the hydraulic pump 9. A plurality of hydraulic actuators including the boom hydraulic cylinder 7a and the arm hydraulic cylinder 7b, which are driven by the relief circuit 11 provided and the hydraulic oil discharged from the hydraulic pump 9, and operating the hydraulic cylinders 7a and 7b. Lever device 1
A plurality of operation means including 2a and 12b and a pump control means for controlling the displacement of the hydraulic pump 9, for example, a regulator 13 are provided.

The center bypass line 15 connected to the discharge circuit 14 of the hydraulic pump 9 supplies hydraulic oil from the hydraulic pump 9 to a plurality of hydraulic actuators including the boom hydraulic cylinder 7a and the arm hydraulic cylinder 7b. A corresponding center bypass type control valve including a boom control valve 16 and an arm control valve 17 for controlling the flow rate and direction when is supplied is provided.

The operation lever devices 12a and 12b are
Boom operation lever device 1 for switching the boom control valve 16 to operate the boom 7a
2a and an arm control lever device 12b for operating the arm 7b by switching the control valve 17 for the arm. These operating lever devices 12a, 1
Each of the plurality of operating means including 2b generates a pilot pressure and switches a corresponding control valve by the pilot pressure via a corresponding pilot line.

Taking the operating lever device 12a for boom as an example, the operating lever 12aa and the pressure reducing valve 12ab are provided. When the operating lever 12aa is operated in the boom raising direction (or lowering direction), a hydraulic source (not shown) The pilot pressure from the pilot hydraulic pump 31 may be reduced by the pressure reducing valve 12ab in accordance with the operation amount thereof, and the pilot pressure is transmitted to the drive unit 16a of the boom control valve 16 via the pilot line 18a (or 18b).
(Or 16b), the control valve 16 is switched to the right switching position 16A in FIG. 2 (or the left switching position 16B in FIG. 2). Thereby, the bottom-side oil chamber 7aa (or the rod-side oil chamber 7ab) of the boom cylinder 7a.
Is supplied to the boom 6a, and the boom 6a is rotated in an upward direction (or a downward direction).

Similarly, when the operation lever 12ba of the arm operation lever device 12b is operated in the arm cloud direction (or the dump direction), the pilot pressure from the pressure reducing valve 12bb is transmitted to the arm through the pilot line 19a (or 19b). The pressure oil is supplied to the bottom side oil chamber 7ba (or the rod side 7bb) of the arm cylinder 7b, and the arm 6b moves in the cloud direction (or the dump direction). It is designed to rotate. Similarly, the other control means are adapted to switch the corresponding control valve via the corresponding pilot line.

In FIG. 1, among the plurality of actuators, the boom / arm hydraulic cylinders 7a, 7b are used.
The actuators other than b, the operation means other than the boom / arm operation lever devices 12a and 12b among the plurality of operation means, and the boom / arm control valves 16 and 17 related thereto are prevented from being complicated. For simplicity, the illustration is omitted, and they are collectively displayed by a dashed-dotted box 24.

The relief circuit 11 includes a hydraulic pump 9
From the discharge circuit 14 to the hydraulic tank 20, and the relief valve 10 is provided in the middle thereof. The relief valve 10 includes a valve body (main valve) 10a,
And a spring 10b for urging the pressure.
When the pressure reaches the relief pressure Pr set by the spring force of b, the opening operation is performed to open the valve, and the hydraulic oil from the hydraulic pump 9 is released back to the hydraulic tank 20.

The most downstream part of the center bypass line 15 (the part downstream of the enclosing part 24) is a throttle for generating a control pressure for negative tilt control (so-called negative control) described later. And a conduit 26 for guiding a control pressure for negative tilt control described later to the regulator 13 so as to branch from the center bypass line 15 on the upstream side of the throttle unit 25. Is provided.

That is, as described above, the boom control valve 16 and the arm control valve 17
Each of the control valves (hereinafter, appropriately referred to as control valves 16, 17 and the like) is a center bypass type valve, and the flow rate flowing through the center bypass line 15 is controlled by the operation amount of the control valves 16 and 17 (that is, the spool valve). Switching stroke). When the control valves 16 and 17 are neutral, that is, when the control valves 16 and 17
(In other words, a plurality of hydraulic actuators including the corresponding boom hydraulic cylinder 7a and arm hydraulic cylinder 7b (hereinafter referred to as hydraulic actuators 7a,
7b), most of the pressure oil discharged from the hydraulic pump 9 flows through the center bypass line 15 as an excess flow rate,
Is relatively large. As a result, a relatively large pressure is generated on the upstream side of the throttle means 25, so that a relatively low control pressure (negative control pressure) is applied to the conduit 26.
Occurs.

This high control pressure is guided to the pressure receiving chamber 13a of the regulator 13 via the shuttle valve 27 and the line 28, and the operating piston (pump control actuator) 13c is moved in FIG. 2 against the urging force of the spring 13b. Move to the right. As a result, the tilt of the inclined shaft 9a of the hydraulic pump 9 is reduced, and the discharge flow rate of the hydraulic pump 9 is increased.

On the other hand, on the other hand, the control valves 16 and 1
When the valve 7 is operated to be in an open state, that is, when the required flow rate required for the hydraulic pump 9 is large, the surplus flow rate flowing to the center bypass line 15 is equal to the flow rate flowing to the hydraulic actuators 7a and 7b. Therefore, the flow rate passing through the throttle means 25 is relatively small,
The control pressure in line 26 decreases.

As a result, the pressure guided to the pressure receiving chamber 13a of the regulator 13 decreases, and the operating piston 13c moves leftward in FIG. 2 by the urging force of the spring 13b. To increase the discharge flow rate.

As described above, in the regulator 13, the discharge flow rate corresponding to the required flow rate of the control valves 16, 17 and the like is obtained, specifically, the flow rate passing through the throttle means 25 of the center bypass line 15 is minimized. Next, a negative tilt control for controlling the tilt (discharge flow rate) of the inclined shaft 9a of the hydraulic pump 9 is performed.

The cutoff control device for the hydraulic pump according to the present embodiment is provided in the above-described hydraulic drive device. This cut-off control device includes the relief circuit 11
Temperature sensors (oil temperature) which are provided in pipelines 21a and 21b branched from the upstream and downstream sides of the relief valve 10 and detect the oil temperatures Ta and Tb of the pressure oil upstream and downstream of the relief valve 10, respectively. Meter) 22a, 22b, a pilot hydraulic pressure source (for example, a pilot hydraulic pump) 31, and pipe lines 29a, 29b connecting the shuttle valve 27, and an electromagnetic proportional valve capable of cutting off and communicating with these pipe lines 29a, 29b. The valve 30 includes a controller 23 that receives detection signals Ta and Tb from the temperature sensors 22a and 22b and outputs a control signal S corresponding to the input signals to the electromagnetic proportional valve 30.

The solenoid proportional valve 30 includes a solenoid 30a.
The communication position 30 on the right side in FIG. 2 according to the command current value of the command signal S input to the solenoid 30a.
A, and the pilot pressure from the pilot pump 31 is applied to the pipelines 29a and 29b and the shuttle valve 2
7 to the oil chamber 13a of the regulator 13. As a result, the discharge flow rate of the hydraulic pump 9 decreases according to the command current value of the command signal S. On the other hand, the command signal S is OFF
When the command current value becomes 0, the electromagnetic proportional valve 30
0b with a restoring force of 0b, and returns to the shut-off position 30B shown in FIG.
A pipe 29b and a pipe 29a communicating with the shuttle valve 27;
And the pipe line 29b is communicated with the tank line 32 to the hydraulic tank 20, and the pressure in the pipe line 29b is used as the tank pressure. As a result, the oil chamber 1 of the regulator 13
The pressure of 3a decreases, and the discharge flow rate of the hydraulic pump 9 increases. FIG. 3 shows the current value A of the command signal S and the discharge of the hydraulic pump 9 which are realized as a result of the above-mentioned operation by the electromagnetic proportional valve and the controller which constitute one embodiment of the cut-off control device for the construction machine of the present invention. This shows the relationship with the flow rate Q (however, the influence of the control of the discharge flow rate Q by the negative tilt control described above is excluded). As described above, when the command current value A is 0, the discharge flow rate Q of the hydraulic pump 9 is the largest, and as the command current value A increases, the discharge flow rate Q decreases accordingly. After reaching the uniquely determined minimum discharge flow rate (minimum displacement), the discharge flow rate Q is maintained at the minimum discharge flow rate thereafter even if the command current value A increases.

FIG. 4 shows the controller 23 which is a main part of one embodiment of the cut-off control device for a construction machine according to the present invention.
5 is a flowchart illustrating a control procedure of a cutoff control function of FIG.

In FIG. 4, first, at step 101
Then, the detected temperature Ta from the temperature sensor 22a is input.
Then, in step 102, the detected temperature Tb from the temperature sensor 22b is input.

Then, in step 103, step 10
Based on the detected temperatures Ta and Tb input in step 1 and step 102, a temperature difference ΔT = Ta−Tb, which is the difference between them, is calculated.

Then, in step 104, step 10
In step 3, a command signal S having a command current value A having a magnitude corresponding to the temperature difference ΔT is output to the electromagnetic proportional valve 30, and the flow ends. FIG. 5 shows the relationship between the command current value A output in step 104 and the temperature difference ΔT in the control procedure of the cut-off control function of the controller 23 constituting one embodiment of the cut-off control device of the construction machine of the present invention. FIG.

In FIG. 5, the temperature difference ΔT (= Ta)
-Tb) ≧ 0, that is, if the temperature Ta upstream of the relief valve 10 in the relief circuit 11 is the same as the temperature Tb downstream or higher than Ta, the command current value A = Set to 0. Also, the temperature difference ΔT <0
In other words, when Ta becomes smaller than Tb, the command current value is linearly increased according to the absolute value of the temperature difference ΔT.

In the above, the temperature sensor 22a constitutes first detecting means for detecting the first oil temperature Ta on the upstream side of the relief valve, and the temperature sensor 22b detects the second oil temperature Tb on the downstream side of the relief valve. These two components constitute second detecting means for detecting, and these two constitute at least one oil temperature detecting means for detecting the oil temperature of the relief circuit provided with the relief valve.

The controller 23, the pilot hydraulic pump 31, the electromagnetic proportional valve 30, the pipes 29a and 29b, and the shuttle valve 27 determine the discharge flow rate of the hydraulic pump based on the difference between the first oil temperature and the second oil temperature. To a predetermined cutoff flow rate.

Next, the operation of the embodiment of the present invention configured as described above will be described.

When the operator operates at least one of the plurality of operation means including the operation lever devices 12a and 12b with the intention of performing excavation work, the corresponding control lever is set to the neutral position by the pilot pressure generated by the operation. And the hydraulic oil from the hydraulic pump 9 is supplied to the corresponding hydraulic actuator, and the hydraulic actuator is driven. At this time, the relief circuit 1
The temperature Ta on the upstream side and the temperature Tb on the downstream side of the relief valve 10 in 1 are detected by the corresponding temperature sensors 22a and 22b.

At the time of normal excavation other than heavy excavation, since the load pressure of each hydraulic actuator does not increase so much, the pressure (discharge pressure) of the discharge circuit of the hydraulic pump 9 is reduced.
Is smaller than the relief pressure set by the spring 10b of the relief valve 10, and the valve body 10a of the relief valve 10 does not open. Therefore, the pressure oil does not flow downstream of the relief valve 10 (on the side of the hydraulic tank 20), and the temperature Tb on the downstream side is a relatively low temperature that is considerably close to the temperature of the hydraulic tank 20, that is, the outside air temperature. On the other hand, the temperature Ta on the upstream side of the relief valve 10
, And comes into contact with the pressure oil supplied to the hydraulic actuator through each control valve, and usually has a relatively high temperature of, for example, about 50 ° C.

Therefore, step 103 in FIG.
Is equal to ΔT> 0, and accordingly, the command current value A of the command signal S output to the electromagnetic proportional valve 30 at step 104 becomes A = 0. Thereby, the electromagnetic proportional valve 30 returns to the shut-off position 30B by the restoring force of the spring 30b, and the pressure in the pipe line 29b is used as the tank pressure. As a result,
In the shuttle valve 27, the control pressure (negative control pressure) through the pipe 26 is always selected, so that the pressure in the oil chamber 13a of the regulator 13 is controlled only by the control pressure. That is, no cutoff control is performed,
Only the normal negative tilt control is performed.

On the other hand, when the discharge pressure of the hydraulic pump 9 becomes equal to or higher than the above-described relief pressure due to heavy excavation or the like, the valve body 10a of the relief valve 10 enters a relief state in which it is opened.
Relatively high-temperature pressure oil flows from the upstream side of the relief valve 10 to the downstream side. Thereby, the relief valve 1
The temperature Tb on the downstream side 0 rapidly rises due to the inflow of the high-temperature pressure oil. In addition, since heat is generated due to pressure loss when passing through the relief valve 10, the relief valve 10
The temperature Tb on the downstream side is the temperature T on the upstream side of the relief valve 10.
The temperature becomes higher than a.

As a result, the temperature difference ΔT calculated in step 103 becomes ΔT <0, and accordingly, the command current value A of the command signal S output to the electromagnetic proportional valve 30 in step 104 increases. . Thereby, the electromagnetic proportional valve 30 is switched to the communication position 30A, and the pressure in the pipe line 29b is increased. As a result, in the shuttle valve 27, a large pressure in the pipe line 29b is selected and the regulator 1
The cutoff control is performed to reduce the discharge flow rate Q of the hydraulic pump 9 guided to the third oil chamber 13a.

According to the embodiment of the present invention having the above-described structure and operation, the relief time of the relief valve 10 is accurately detected, and the cutoff control is performed after the relief, so that the operation of the relief valve 10 can be started. A normal flow rate (a flow rate only by the negative tilt control) can be supplied to the hydraulic actuators 7a and 7b without starting the cutoff to the last minute. Therefore, it is possible to prevent the operation speed from being reduced by starting the cutoff before the relief, as in the case of performing the cutoff with the cutoff pressure set and stored in advance in the controller, and to reduce the operator's psychology due to the reduced operation speed. As a result, the mental burden on the operator can be reduced.

At this time, as described above, the oil temperatures Ta, T
By detecting the relief of the relief valve 10 by detecting b and performing cutoff control, unlike the conventional structure in which a throttle means is provided upstream of the relief valve, the relief characteristics of the relief valve 10 itself are not affected at all. That is, similar to a normal relief valve, it is possible to secure good relief characteristics in which the flow rate rises linearly at a stretch after the circuit pressure rises to a pressure close to the set relief pressure.
Therefore, when the pressure of the discharge circuit 14 is relatively low as in the conventional structure described above, the hydraulic tank 20
Since it is possible to prevent the leakage flow rate from occurring, it is possible to sufficiently reduce the energy loss due to the reduction of the surplus discharge flow rate to the hydraulic tank 20, which is the original purpose of the cutoff control, and to sufficiently achieve the energy saving.

In the embodiment of the present invention, as described above with reference to FIG.
T (= Ta−Tb) = 0 as a threshold value, when ΔT ≧ 0, the command current value A = 0, and when the temperature difference ΔT <0, the command current value according to the absolute value of the temperature difference ΔT Is linearly increased, but is not limited to this.

That is, as shown by the two-dot chain line a in FIG. 5, ΔT = ΔT1 larger than 0 is set as a threshold value, and ΔT
When ≧ 0, the command current value A may be set to 0, and when the temperature difference ΔT <0, the command current value may be linearly increased according to the absolute value of the temperature difference ΔT. In this case, the relief valve 10
When the relief starts and the Tb rises and approaches the Ta to some extent, the cutoff control is started without waiting for it to become equal to the Ta. Therefore, the cutoff control is performed more than in the embodiment of the present invention. There is an effect that the response of the start is improved.

On the contrary, as shown by a two-dot chain line A in FIG. 5, ΔT = ΔT1 larger than 0 is set as a threshold value, and when ΔT ≧ 0, a command current value A = 0. , Temperature difference ΔT
When <0, the command current value may be linearly increased according to the absolute value of the temperature difference ΔT. In this case, the relief valve 10 starts relief and Tb rises to a sufficient degree T
Since the cut-off control is started after the pressure becomes higher than a, the cut-off is started before the relief and the operation speed can be more reliably prevented from being reduced. There is an effect that it can be reduced more reliably.

In the above embodiment of the present invention, the relief of the relief valve 10 is detected by taking the temperature difference ΔT between the upstream side temperature Ta and the downstream side Tb of the relief valve 10. However, the present invention is not limited to this, and other detection methods may be used. Hereinafter, such modified examples will be described step by step.

(1) When Only Tb or Ta is Used That is, the controller 23 sequentially takes in, for example, the downstream temperature Tb of the relief valve 10 at predetermined short intervals, and sequentially calculates the difference at that time, thereby obtaining the oil temperature change. Calculate the rate (temperature gradient). Then, the oil temperature change rate is appropriately set and inputted in advance and stored as a threshold value (for example, a sufficiently large value that can be regarded as an oil temperature change due to the inflow of high-temperature oil from the relief valve without being affected by a change in air temperature or the like). When the value becomes larger than the value, it is determined that relief of the relief valve 10 is started, and the command signal S is output to the electromagnetic proportional valve 30. The command current value A of the command signal S at this time may be increased or decreased according to, for example, the difference between the relief valve downstream temperature at the start of the command signal S output and the current relief valve downstream temperature. Alternatively, it may be increased or decreased according to the difference between the threshold value of the oil temperature change rate and the current oil temperature change rate, or may be a constant current value of a predetermined magnitude.

In this case, the temperature sensor 22b constitutes second detecting means for detecting the second oil temperature Tb downstream of the relief valve, and at least one of the temperature sensors 22b for detecting the oil temperature of the relief circuit provided with the relief valve. One oil temperature detecting means is constituted. The controller 23, the pilot hydraulic pump 31, the electromagnetic proportional valve 30, the pipes 29a and 29b, and the shuttle valve 27 reduce the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate based on the rate of change of the second oil temperature. The first cutoff control means is constituted.

Further, instead of using the downstream temperature Tb of the relief valve 10, only the upstream temperature Ta of the relief valve 10 is detected, and the same control as described above is performed using the oil temperature change rate (temperature gradient). good. Further, the relief valve 10 may be regarded as being relieved only when both the condition of the oil temperature change rate and the condition of the temperature difference ΔT of the embodiment of the present invention are satisfied.

(2) Case of Providing Poppet Valve Downstream of Relief Valve FIG. 6 shows a modified example in which a poppet valve is provided downstream of the relief valve in one embodiment of the cutoff control device for construction equipment of the present invention. FIG. 2 is a hydraulic circuit diagram illustrating a main configuration of a hydraulic drive device of the hydraulic excavator to be applied.

In FIG. 6, a known poppet valve 33 is provided downstream of the relief valve 10 of the relief circuit 11, and pressure oil that passes through the relief valve 10 and returns to the tank 20 passes through the poppet valve 33. It is supposed to go through.

The poppet valve 33 is provided with a casing 33
a, a poppet (valve body) 33b slidably disposed in the casing 33a in the axial direction, and a poppet 3
A spring 33c for biasing the relief valve 3b, an introduction port 33d provided at one axial end of the casing 33a and connected to a downstream pipe 11a of the relief valve 10 in the relief circuit 11, and an axial direction of the casing 33a. A discharge port 33e is provided on the intermediate side between the one end and the other end, and is connected to the pipeline 11b of the relief circuit 11 to the hydraulic tank 20.

The poppet 33b is seated on a seating surface (not shown) provided on the casing 33a so as to normally shut off the introduction port 33d and the discharge port 33e by the urging force of the spring 33c. And
When the relief valve 10 is relieved and pressurized oil flows into the introduction port 33d at one end in the axial direction, the other end in the axial direction (see FIG. 6) against the urging force of the spring 33c according to the introduction flow rate. (In other words, the opening degree of the poppet 33b changes according to the introduction flow rate), whereby the introduction port 33d communicates with the discharge port 33e on the side of the casing 33a, and the pressure oil flows through the pipe. The air is discharged to the road 11b.

FIG. 7 shows a relief valve 1 according to a modification of the embodiment of the present invention, in which a poppet valve is provided downstream of the relief valve in the embodiment of the cut-off control device for construction machines.
FIG. 6 is a diagram illustrating a relationship between a passing flow rate Qr of 0 and a displacement X of the poppet 33b. As shown in FIG. 7, the poppet 33b is displaced substantially in proportion to the flow rate Qr of the relief valve 10 (in other words, the flow rate introduced from the introduction port 33d).

Returning to FIG. 6, at this time, the poppet 33b
Is connected to a shaft member 34, and a known (for example, so-called increment type) displacement sensor 35 is connected to a side of the shaft member 34 opposite to the poppet 33b. Thereby, the displacement X of the poppet 33b due to the inflow of the pressure oil from the relief valve 10 is detected by the displacement sensor 35 via the shaft member 34, and the displacement detection signal X is input to the controller 23, and the controller 23 The electromagnetic proportional valve 3 according to the displacement detection signal X
The command current value A of the command signal S to 0 is controlled.

FIG. 8 shows a cut-off control apparatus for a construction machine according to an embodiment of the present invention, in which a pop-up valve is provided downstream of a relief valve. FIG. 3 is a diagram showing a relationship between a command current value A to the electromagnetic proportional valve 30 and a command current value A; As shown in FIG. 8, the controller 23
A command current value A substantially proportional to the displacement X of the poppet 33b is output.

In the above, the displacement sensor 35 constitutes first displacement detecting means for detecting the displacement of the valve body (poppet) of the poppet valve, and includes the controller 23, the pilot hydraulic pump 31, the electromagnetic proportional valve 30, the pipes 29a and 29b. , And the shuttle valve 27 reduces the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate in accordance with the detected displacement.
The cutoff control means is constituted.

Next, the operation of the above modified example configured as described above will be described.

At the time of normal excavation other than heavy excavation, since the pressurized oil does not flow downstream of the relief valve 10 (the poppet valve 33 side), the poppet 33 detected by the displacement sensor 35
The displacement X of b becomes 0, and the command current value A of the command signal S output from the controller 23 to the electromagnetic proportional valve 30 based on the characteristic line of FIG. As a result, the electromagnetic proportional valve 30 returns to the shut-off position 30B due to the restoring force of the spring 30b, and the pressure in the oil chamber 13a of the regulator 13 is controlled only by the above-described control pressure (negative control pressure). Is performed.

On the other hand, when the discharge pressure of the hydraulic pump 9 becomes equal to or higher than the above-described relief pressure due to heavy excavation or the like, the valve body 10a of the relief valve 10 enters a relief state in which the valve is opened.
The pressure oil flows toward the poppet valve 33 further downstream than the relief valve 10. Thereby, poppet 3
3b is displaced to the other axial side (the right side in FIG. 6) of the poppet valve 33 by the inflow of the pressure oil, and the command current value A of the command signal S output from the controller 23 to the electromagnetic proportional valve 30.
Is increased, the electromagnetic proportional valve 30 is switched to the communication position 30A, and the pressure in the pipe line 29b is increased. As a result, in the shuttle valve 27, a large pressure in the pipe line 29b is selected and guided to the oil chamber 13a of the regulator 13,
Cutoff control for reducing the discharge flow rate Q of the hydraulic pump 9 is performed.

According to the modification of the configuration and the operation as described above, the relief valve 10 is provided similarly to the embodiment of the present invention.
Is accurately detected and cutoff control is performed after this relief, so that cutoff does not start until just before the operation of the relief valve 10 starts, and the hydraulic actuators 7a,
A normal flow rate (a flow rate only by negative tilt control) can be supplied to 7b and the like. Therefore, the mental burden on the operator can be reduced.

In this modification, the relief of the relief valve 10 is detected by detecting the displacement of the poppet 33b of the poppet valve 33 as described above, and cutoff control is performed.
At this time, in general, when a poppet valve is disposed in a pressure oil pipe and the valve body is opened and closed by an upstream pressure (self-pressure), a pressure increase due to a restricting effect on the pressure oil pipe due to its structural characteristics. The opening and closing operation of the valve body can be performed with almost no effect. That is, in the present modified example, the poppet 33b can be operated with almost no increase in pressure applied to the relief circuit 11. Thereby, unlike the conventional structure in which the throttle means is provided on the upstream side of the relief valve, the relief characteristic itself of the relief valve 10 can be prevented from being affected at all. Good relief characteristics that rise linearly can be secured. Therefore, similarly to the above-described embodiment of the present invention, it is possible to sufficiently reduce the energy loss due to the reduction of the surplus discharge flow rate to the hydraulic tank 20, which is the original purpose of the cutoff control, and to sufficiently save energy. .

(3) Case of Directly Detecting Displacement of Valve Body of Relief Valve That is, the idea of (2) detecting a relief state by poppet displacement of a poppet valve is further applied, and displacement of the valve body itself of a relief valve is further applied. Is directly detected to detect the relief state.

FIG. 9 shows an essential part of a hydraulic drive device of a hydraulic shovel to which a modification for detecting displacement of a valve body of a relief valve is applied in one embodiment of a cut-off control device for construction machines of the present invention. It is a hydraulic circuit diagram showing.

In FIG. 9, a shaft member 36 having the same function as the shaft member 34 shown in FIG. 6 is connected to the valve body 10a of the relief valve 10. A displacement sensor 37 having the same function as the displacement sensor 35 shown in FIG. 6 is connected to the side opposite to 10a. Accordingly, the displacement X 'of the valve body 10a due to the relief of the relief valve 10 is detected by the displacement sensor 37 via the shaft member 36, and the displacement detection signal X' is input to the controller 23, and the controller 23 According to the displacement detection signal X ', the electromagnetic proportional valve 3
The command current value A of the command signal S to 0 is controlled.

FIG. 10 shows a relief valve 10 applicable to this modification for detecting the displacement of the valve body of the relief valve in one embodiment of the cut-off control device for the construction machine of the present invention.
1 shows an example of the configuration. In FIG. 10, the relief valve 10 is provided in a casing 10c, the valve body (poppet) 10a slidably disposed in the casing 10c in the axial direction, and a spring chamber 10g in the casing 10c. One end (the left end in FIG. 10) contacts the valve body 10a and the other end (the right end in FIG. 10).
Is provided on one axial side (left side in FIG. 10) of the casing 10c in contact with the adjusting screw 10f to urge the valve body 10a, and is located upstream of the relief valve 10 in the relief circuit 11. An introduction port 10d connected to a conduit 11c (see FIG. 9);
Of the above, the other side in the axial direction from the introduction port 10d (FIG. 10)
And a discharge port 10e connected to a pipeline 11b to the hydraulic tank 20 in the relief circuit 11. The valve body 10a is seated in the casing 10c so as to normally shut off the introduction port 10d and the discharge port 10e by the urging force of the spring 10b (however, it can be adjusted by the adjustment screw 10f). It is seated on the part 10h. Then, when the pressure of the discharge circuit 14 increases and the pressure of the introduction port 10d increases through the upstream pipe 11c (see FIG. 9), the valve body 10a responds to the increase in the pressure by the spring 10
b moves in the axial direction on the other side (right side in FIG. 10) against the biasing force of b (in other words, the opening degree of the valve body 10a changes according to the pressure), whereby the introduction port 10d and the discharge port 10e are moved. And the pressure oil is discharged to the pipeline 11b.

The opposite side of the shaft member 36 connected and fixed to the valve body 10a, opposite to the valve body 10a, has a sealing member 10cb formed in a through hole 10ca provided at one axial end (left end in FIG. 10) of the casing 10c. Is arranged through through
It is connected to a displacement sensor 37 provided outside the casing 10c.

The relationship between the flow rate Qr of the relief valve 10 and the displacement X 'of the relief valve body 10a at this time is, for example, the flow rate Qr of the relief valve 10 and the poppet 33b shown in FIG. X ′ is substantially proportional to Qr, similarly to the relationship with the displacement X. The relationship between the displacement X 'and the command current value A of the command signal S from the controller 23 to the electromagnetic proportional valve 30 is, for example, the displacement X of the poppet 33b of the poppet valve 33 and the command current shown in FIG. Similar to the relationship with the value A, A is approximately proportional to X '.

In the above, the displacement sensor 37 constitutes the second displacement detecting means for detecting the displacement of the valve body of the relief valve, the controller 23, the pilot hydraulic pump 31, the electromagnetic proportional valve 30, the pipes 29a and 29b, and the shuttle Valve 2
7 constitutes a third cutoff control means for reducing the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate according to the detected displacement.

Next, the operation of the above modified example configured as described above will be described.

At the time of normal excavation other than heavy excavation, since the relief valve 10 does not relieve as described above, the displacement X '= 0 of the valve body 10a detected by the displacement sensor 37 becomes zero. The command current value A of the command signal S output to 30 is 0. As a result, the pressure in the oil chamber 13a of the regulator 13 is controlled only by the aforementioned control pressure (negative control pressure), and only normal negative tilt control is performed.

On the other hand, if the discharge pressure of the hydraulic pump 9 becomes equal to or higher than the above-described relief pressure due to heavy excavation or the like, the relief valve 10 enters the relief state and the displacement X of the valve body 10a increases. The command current value A of the command signal S output from 23 to the electromagnetic proportional valve 30 increases. As a result, in the shuttle valve 27, a large pressure in the pipe line 29b is selected and guided to the oil chamber 13a of the regulator 13, and cutoff control for reducing the discharge flow rate Q of the hydraulic pump 9 is performed.

According to the above-described modified example of the configuration and operation, the relief time of the relief valve 10 is accurately detected and the cutoff control is performed after this relief, as in the embodiment of the present invention. The mental burden on the operator can be reduced.

In this modification, the relief is detected by directly detecting the displacement of the valve body 10a of the relief valve 10 as described above, and cutoff control is performed. Thereby, unlike the conventional structure in which the throttle means is provided on the upstream side of the relief valve, the relief characteristic itself of the relief valve 10 can be prevented from being affected at all, so that good relief characteristics can be secured. Therefore, similarly to the above-described embodiment of the present invention, it is possible to sufficiently reduce energy loss and sufficiently save energy. Further, since there is no need to separately provide a poppet valve, there is also an effect that the hydraulic circuit can be simplified as compared with the modification of the above (2).

In this modification, as shown in FIG. 10, a so-called poppet type relief valve 10 is used.
Has been described as an example, but the present invention is not limited to this. That is, another type of relief valve may be used.

FIG. 11 shows another example of the configuration of a relief valve applicable to the above-described modified example in which the displacement of the valve body of the relief valve is detected in one embodiment of the cut-off control device for a construction machine of the present invention. The same reference numerals are given to the same parts as those in FIG. 10, and the description will be appropriately omitted. This FIG.
Shows a so-called ball type relief valve 10A. Instead of the valve body (poppet) 10a,
A ball 10a1 is seated on the seat 10h and a spring support 10a2 is provided which can be fixed or abutted on the ball 10a1. At this time, one end (the left end in FIG. 10) of the spring 10b is in contact with the spring support portion 10a2, and the shaft member 36 is connected and fixed to the ball 10a1. Ball type relief valve 1 shown in FIG.
Even when 0A is used, the same operation as the poppet-type relief valve 10 of FIG. 10 is performed, and the same effect is obtained. The relief valves 10A, 10A of FIGS.
In B, the displacement is detected by the displacement sensor 37 via the shaft member 36 on the left side (opposite to the adjustment screw 10f) of each of the poppet 10a or the ball 10a1 in the drawings, but is not limited thereto. It may be configured to connect to the displacement sensor 37 via some intermediate member on the side. In this case, a similar effect is obtained.

The poppet type relief valve 10 shown in FIG. 10 and the ball type relief valve 10A shown in FIG. 11 are both referred to as direct-acting type relief valves. It is not something that can be done. That is, a pilot-actuated relief valve may be used.

FIG. 12 shows still another example of the configuration of a relief valve applicable to the above-described modification for detecting the displacement of the valve body of the relief valve in one embodiment of the cut-off control device for construction machines of the present invention. FIG. 10 and FIG.
The same reference numerals are given to the same parts as those described above, and the description will be appropriately omitted.

FIG. 12 shows a so-called pilot-operated relief valve 10B.
0c, a main poppet 10a3 slidably disposed in an axial direction (vertical direction in FIG. 12) in a spring chamber 10g provided in the center of the casing 10c, and one end ( 12 is the main poppet 1
12a and the other end (upper end in FIG. 12) of the main poppet 1 abuts on the upper inner wall 10g1 of the spring chamber 10g.
The main spring 10b1 for urging the casing 10a
12 is provided on one side (the left side in FIG. 12) of the relief circuit 11, and is connected to an upstream pipe 11c (see FIG. 9) of the relief valve 10 in the relief circuit 10; 12 and a discharge port 10e of the relief circuit 11 connected to a pipeline 11b to the hydraulic tank 20, and a branch from the introduction port 10d, and the spring chamber 10g behind the main poppet 10a3. First pilot port 10 reaching (upper side in FIG. 12)
i, a constricted portion 10j provided in the middle of the first pilot port 10i, and an outlet port 10e of the spring chamber 10g from behind the main poppet 10a3 (upper side in FIG. 12). A second pilot port 10k, a spring chamber 10m provided in the middle of the second pilot port 10k, and the main poppet, which is slidably disposed in the spring chamber 10m in the axial direction (vertical direction in FIG. 12). An auxiliary poppet 10a4, which constitutes the valve body 10a together with 10a3, is disposed in the spring chamber 10m, and one end (upper end in FIG. 12) is the auxiliary poppet 10a4.
And the other end (the lower end in FIG. 12) is a spring chamber 10 m.
Abuts the lower inner wall 10m1 of the auxiliary poppet 10a4
And the main spring 10b1 and the spring 10b
And an auxiliary spring 10b2.

At this time, the opposite side of the main poppet 10a3 of the shaft member 36 connected and fixed to the main poppet 10a3 penetrates through the through hole 10ca provided in the upper part of the casing 10c in FIG. 12 through the sealing member 10cb. And is connected to a displacement sensor 37 provided outside the casing 10c.

The main poppet 10a3 and the auxiliary poppet 10a4 normally shut off the introduction port 10d and the discharge port 10e, and the spring chamber 10g and the spring chamber 10m by the urging force of the springs 10b1 and b2. As described above, they are seated on the seating portions 10h1 and 10h2 provided in the casing 10c.

Then, the pressure of the discharge circuit 14 increases and the introduction port 1 is connected via the upstream pipeline 11c (see FIG. 9).
When the pressure of 0d increases, the pressure is first transmitted to the introduction side of the second pilot port 10k via the introduction port 10d, the first pilot port 10i, and the spring chamber 10g. 12a4 moves downward in FIG. 12 against the urging force of the spring 10b2, whereby the introduction port 10d and the discharge port 1 are moved.
0e is the first pilot port 10i, the spring chamber 10g,
And the second pilot port 10k.

As a result, the pressure in the spring chamber 10g decreases, so that the main poppet 10a3 opens rapidly, and the introduction port 10d and the discharge port 10e communicate directly with each other, so that the pressure oil is discharged to the pipeline 11b. It has become. In addition,
The restricting portion 10j of the first pilot port 10i is provided with an unstable repetition (hunting) of the interlocking operation of the main poppet 10a4 by the operation of the auxiliary poppet 10a4 as described above.
And stabilization.

With the above configuration and operation, FIG.
When the ball-type relief valve 10B shown in FIG. 10 is used, the same effects as those of the poppet-type relief valve 10 of FIG. 10 and the ball-type relief valve 10A of FIG. 11 are obtained.

[0119]

According to the present invention, the oil temperature of the relief circuit is detected by at least one oil temperature detecting means, and the discharge flow rate of the hydraulic pump is determined by the first cutoff control means in accordance with the detected oil temperature. Cut-off control to reduce the flow rate to the cut-off flow rate. Thus, it is possible to prevent a decrease in operation speed during heavy excavation work based on a difference between the cutoff pressure and the relief pressure, for example, and reduce the mental burden on the operator.

At this time, unlike the conventional structure in which the throttle means is provided on the upstream side of the relief valve by performing cutoff control by detecting the relief by detecting the oil temperature as described above, the relief characteristic itself is not affected at all. And good relief characteristics can be ensured without giving any stress. Therefore, it is possible to sufficiently reduce the energy loss due to the reduction of the surplus discharge flow rate to the hydraulic tank, which is the original purpose of the cutoff control, and to sufficiently save energy.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an overall external structure of a hydraulic shovel to which the present invention is applied.

FIG. 2 is a hydraulic circuit diagram illustrating a main configuration of a hydraulic drive device of a hydraulic shovel to which the present invention is applied.

FIG. 3 is a graph showing the relationship between the current value of the command signal and the discharge flow rate of the hydraulic pump, which is realized as a result of the above-described operation by the electromagnetic proportional valve and the controller that constitute one embodiment of the cut-off control device for the construction machine of the present invention. It is a figure showing a relation.

FIG. 4 is a flowchart illustrating a control procedure of a cutoff control function of a controller which is a main part of the cutoff control device for a construction machine according to the embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a command current value output in a control procedure of a cutoff control function of a controller constituting a cutoff control device of a construction machine of the present invention and a temperature difference.

FIG. 6 is a hydraulic circuit showing a main configuration of a hydraulic drive device of a hydraulic shovel to which a modification in which a poppet valve is provided downstream of a relief valve in one embodiment of a cutoff control device for a construction machine according to the present invention; FIG.

FIG. 7 is a diagram illustrating a relationship between a flow rate of a relief valve and displacement of a poppet in a modification in which a poppet valve is provided downstream of a relief valve in one embodiment of a cutoff control device for a construction machine of the present invention. is there.

FIG. 8 is a diagram illustrating an embodiment of a cutoff control device for a construction machine according to the present invention, in which a poppet valve is provided downstream of a relief valve; It is a figure showing the relationship with a command current value.

FIG. 9 is a hydraulic circuit showing a configuration of a main part of a hydraulic drive device of a hydraulic shovel to which a modification for detecting a displacement of a valve body of a relief valve is applied in one embodiment of a cutoff control device for a construction machine of the present invention. FIG.

FIG. 10 is a diagram showing an example of a configuration of a relief valve applicable to a modification for detecting displacement of a valve body of a relief valve in one embodiment of a cutoff control device for a construction machine of the present invention.

FIG. 11 is a view showing another configuration example of a relief valve applicable to a modification for detecting displacement of a valve body of a relief valve in one embodiment of a cutoff control device for a construction machine of the present invention.

FIG. 12 is a diagram showing still another configuration example of a relief valve applicable to the above-described modification for detecting displacement of a valve body of a relief valve in one embodiment of a cutoff control device for a construction machine of the present invention. .

FIG. 13 is a diagram showing the influence of the difference in the opening area of the throttle means in the conventional technique of measuring the flow rate passing through the throttle means as the upstream pressure of the throttle means.

FIG. 14 shows a comparison between a relief characteristic (override characteristic) of a relief valve not provided with a normal throttle means and a relief characteristic corresponding to the above-described prior art when a throttle means is provided downstream of the relief valve. FIG.

FIG. 15 is a view showing actual relief characteristics in a conventional technique in which a throttle means is provided downstream of a relief valve.

[Explanation of symbols]

7a Hydraulic cylinder for boom (hydraulic actuator) 7b Hydraulic cylinder for arm (hydraulic actuator) 9 Hydraulic pump 10 Relief valve 10A, B Relief valve 11 Relief circuit 13 Regulator 14 Discharge circuit 22a Temperature sensor (first detecting means, oil temperature detecting means) 22b Temperature sensor (second detection means, oil temperature detection means) 23 Controller (first, second, third cutoff control means) 27 Shuttle valve (first, second, third cutoff control means) 29a, b Pipe line (first, second, third cutoff control means) 30 Electromagnetic proportional valve (first, second, third cutoff control means) 31 Pilot hydraulic pump (first, second, third cutoff control means)
Third cutoff control means) 35 Displacement sensor (first displacement detection means) 37 Displacement sensor (second displacement detection means)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2D003 AA01 AB05 BA05 BB03 CA03 DA03 DA04 DB05 DB06 3H089 AA02 AA21 BB15 CC01 CC08 DA03 DB03 DB13 DB47 DB49 DB73 EE14 EE22 EE35 EE36 FF01 FF05 FF12 GG02 JJ02

Claims (8)

[Claims] A construction machine having a variable displacement hydraulic pump, a plurality of actuators driven by pressure oil discharged from the hydraulic pump, and a relief valve for determining a maximum pressure of a discharge circuit of the hydraulic pump. In a cut-off control device for a construction machine provided in, at least one oil temperature detecting means for detecting an oil temperature of a relief circuit having the relief valve, and a discharge flow rate of the hydraulic pump according to the detected oil temperature. And a first cutoff control means for reducing the flow rate to a predetermined cutoff flow rate. 2. The cut-off control device for a construction machine according to claim 1, wherein said oil temperature detecting means detects first oil temperature upstream of said relief valve, and said oil temperature detecting means detects said first oil temperature upstream of said relief valve. A second detection means for detecting a second oil temperature on the downstream side, wherein the first cutoff control means determines a discharge flow rate of the hydraulic pump based on a difference between the first oil temperature and the second oil temperature. Cut-off control device for a construction machine, wherein the cut-off flow rate is reduced to a predetermined cut-off flow rate. 3. The cut-off control device for a construction machine according to claim 2, wherein said first cut-off control means determines that a difference between said first oil temperature and said second oil temperature is smaller than a predetermined threshold value. A cut-off control device for a construction machine, wherein the discharge flow rate of the hydraulic pump is reduced to a predetermined cut-off flow rate. 4. The cut-off control device for a construction machine according to claim 1, wherein said oil temperature detecting means includes a second detecting means for detecting a second oil temperature downstream of said relief valve, The cutoff control device for a construction machine, wherein the cutoff control means reduces the discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate based on the rate of change of the second oil temperature. 5. The cut-off control device for a construction machine according to claim 4, wherein said first cut-off control means is configured to: when a change rate of said second oil temperature becomes larger than a predetermined threshold value.
A cut-off control device for a construction machine, wherein a discharge flow rate of the hydraulic pump is reduced to a predetermined cut-off flow rate. 6. A construction machine having a variable displacement hydraulic pump, a plurality of actuators driven by pressure oil discharged from the hydraulic pump, and a relief valve for determining a maximum pressure of a discharge circuit of the hydraulic pump. In a cut-off control device for a construction machine provided in: a poppet valve provided downstream of the relief valve; first displacement detection means for detecting a displacement of a valve body of the poppet valve; And a second cutoff control means for reducing a discharge flow rate of the hydraulic pump to a predetermined cutoff flow rate. 7. A construction machine having a variable displacement hydraulic pump, a plurality of actuators driven by pressure oil discharged from the hydraulic pump, and a relief valve for determining a maximum pressure of a discharge circuit of the hydraulic pump. A second displacement detecting means for detecting a displacement of a valve body of the relief valve; and a discharge flow rate of the hydraulic pump is reduced to a predetermined cutoff flow rate in accordance with the detected displacement. And a third cutoff control means for reducing the cutoff. 8. The cut-off control device for a construction machine according to claim 6, wherein said first or second displacement detecting means is connected to said valve body of said relief valve or said valve body of said poppet valve. A cut-off control device for a construction machine, wherein the cut-off control device is a displacement sensor connected via a link.