JP2001254681A - Input torque control circuit for variable displacement pump - Google Patents

Abstract

(57) [Summary] [Problem] To smoothly operate a hydraulic actuator. SOLUTION: Adjusting means 110, 120 for adjusting the discharge amount of variable displacement pumps 201, 301 for discharging pressure oil to hydraulic circuits 210, 310, and variable displacement pumps 201, 30.
1 constant torque control means 130 for maintaining the first input torque at a constant target input torque, first torque setting means 140 for specifying the target input torque by an external input, and a target input with an increase or decrease of the operation amount of the actuator. A second torque setting means for specifying the torque; a target input torque selecting means for selecting a smaller one of the target input torques specified by the first and second torque setting means;
When the target input torque specified by the second torque setting unit 20 increases with a change in the operation amount of each actuator, a torque fluctuation reducing unit 40 that reduces the increasing speed;
Having.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input torque control circuit for controlling an input torque of a variable displacement pump provided for driving an actuator in a working shovel device or the like.

[0002]

2. Description of the Related Art Generally, when an actuator is operated by pressurized oil, a variable displacement pump is used for driving the actuator in order to cope with fluctuations in the operating state of the actuator and the load applied to the actuator.

For example, when a large number of actuators such as hydraulic cylinders and hydraulic motors are driven by one variable displacement pump as in a working shovel device,
When the variable displacement pump is driven by an engine, the discharge flow rate of the pump is reduced with an increase in the discharge pressure of the pump when a load exceeding a certain level occurs in order to prevent an overload of the engine. In general, the control to make it occur is performed.

FIG. 10 shows two variable displacement pumps 20 for operating each actuator of a working shovel device.
1, a conventional input torque control circuit 100 is shown.

First, an input torque control circuit 100 is assumed.
The configuration around this will be described. The first and second variable displacement pumps 201, 301 are two equivalent axial plunger pumps driven simultaneously by one engine 200. In addition, the output shaft of the engine 200 includes:
A control pump 103 for outputting an operation signal having a smaller capacity than these pumps is also connected, and the control pump 103 is also driven at the same time.

The first and second variable displacement pumps 201 and 301 are connected to a plurality of hydraulically operated actuators (eg, hydraulic cylinders, hydraulic motors, etc.) and operate in response to external operation commands. The hydraulic oil is discharged to first and second hydraulic circuits 210 and 310, respectively, which supply the corresponding amount of hydraulic oil to each actuator.

Further, the first variable displacement pump 201
The second variable displacement pump 301 is connected to the first hydraulic circuit 210 via the first discharge line 101 of the input torque control circuit 100, and is connected to the first hydraulic circuit 210 via the second discharge line 102 of the input torque control circuit 100. Connected to the second hydraulic circuit 310.

The first (second) hydraulic circuit 210 (3)
10) is a passage pipe 211 (311) in which the downstream end of the first (second) discharge pipe 101 (102) is connected to the upstream end thereof, as shown in FIG. Road 211
A plurality of direction switching valves 212 (312) arranged in order from upstream to downstream in the middle of (311).
And a configuration including:

The direction switching valve 2 of the first hydraulic circuit 210
Taking one of the examples as an example, the direction switching valve 212 is a three-position six-port direction switching valve that is gradually switched by moving the spool. And
The direction switching valve 212 is provided by dividing the supply line 211, and the upstream end and the downstream end of the supply line 211 in which two of the six ports of the direction switching valve 212 are divided. Connected to each other. The other two ports of the direction switching valve 212 are connected to the actuator 2
15 is connected to the positive pressure oil supply side (reverse pressure oil discharge side) and the positive pressure oil discharge side (reverse pressure oil supply side), and another port is branched from the passage pipe 211. The other port is connected to the supply line 213 and the other port is connected to the return line 214 toward the tank T for the pressurized oil.

At the first position (neutral position) of the direction switching valve 212, the upstream side and the downstream side of the supply line 211 are electrically connected, and the remaining four ports are all closed. Become. In addition, at the second position of the direction switching valve 212, the upstream and downstream sides of the supply line 211 are closed, and the supply line 213 is closed.
And the positive pressure oil supply side of the actuator 215 is electrically connected, and the positive pressure oil discharge side of the actuator 215 and the return line 214 are electrically connected. Furthermore, at the third position of the direction switching valve 212, the upstream side and the downstream side of the passage pipe 211 are closed respectively, and the supply pipe 213 and the reverse pressure oil supply side of the actuator 215 are connected. As a result, the reverse pressure oil discharge side of the actuator 215 and the return pipe 214 are brought into conduction. That is, at the first position of the direction switching valve 212, the supply of the pressure oil to the actuator 215 is stopped and the actuator 215 is stopped.
The third position urges the actuator 215 in a forward direction, and the third position
5 is energized in the opposite direction.

The switching of each position of the direction switching valve 212 is performed by an operation lever 216 connected to the direction switching valve 212. The operation lever 216 supplies the pressure oil discharged from the control pump 103 to the direction switching valve 212 in an amount corresponding to the operation amount input by the operator of the work shovel device, and the amount of movement of the spool of the direction switching valve 212 Control. Therefore, the actuator 215
The operation is performed with the operation amount input from the operation lever 216.

The operation lever 216 and the direction switching valve 2
A throttle valve 219 is interposed between the directional control valve 12 and the pressure control valve 12 to improve the operability of the actuator 215 by slowing the flow of the pressure oil and smoothing the spool switching operation of the direction switching valve 212. I have.

In FIG. 11, except for one directional control valve 212, each of the other directional control valves 212, 31
The illustration of the configuration around 2 is omitted. Reference numerals 217 and 317 in the figure denote relief valves, and reference numerals 218 and 3
Reference numeral 18 denotes a throttle valve.

Next, the input torque control circuit 100 will be described again with reference to FIG. The input torque control circuit 100 includes first and second variable displacement pumps 201,
First and second adjusting means 110 and 120 for respectively adjusting the discharge amount of the pump 301, and the first variable displacement pump 20 via each of the first adjusting means 110 and the second adjusting means 120.
Constant torque control means 130 for maintaining the input torque of the first and second variable displacement pumps 301 at a substantially constant target input torque
A first torque setting unit 140 that variably adjusts a target input torque maintained by the constant torque control unit 130 in accordance with an input from a driver; and an increase or decrease in the operation amount of each actuator connected to the first hydraulic circuit 210. Together with a first flow control means 150 for increasing / decreasing the discharge flow rate of the first variable displacement pump 201 via the first adjusting means 110, and with an increase / decrease of the operation amount of each actuator connected to the second hydraulic circuit 310. A second flow rate control means for increasing or decreasing the discharge flow rate of the second variable displacement pump via the second adjustment means;

Each of the above components will be described. First, the first (second) adjusting means 110 (120) includes a piston 111 (tilting a tilting plate 202 (302) for adjusting the discharge amount of the first (second) variable displacement pump 201 (301). 12
1) and two hydraulic cylinders 112, 113 (12) engaged at both ends of the piston 111 (121), respectively.
2, 123). This piston 111 (1
21), the pressure receiving surface corresponding to one hydraulic cylinder 112 (122) is set larger than the pressure receiving surface corresponding to the other hydraulic cylinder 113 (123). Therefore, even if pressure oil is supplied to the two cylinders 112 and 113 (122 and 123) at the same pressure, the movement of the piston 111 (121) is biased toward the cylinder 113 (123) and the tilting disc 2
02 (302) is tilted in the direction of arrow E (F). Incidentally, the first (second) variable displacement pump 201
(301) shows the tilting plate 202 (302) with an arrow E (F).
When tilted in the direction, the flow decreases.

Further, first (second) adjusting means 110
(120) corresponds to each hydraulic cylinder 112, 113 (12
2, 123) and a supply line 114 (124) for supplying pressure oil at the same pressure, and one hydraulic cylinder 112 (1).
22), a three-position directional switching valve 115 (1) for switching between a pressure oil supply state, a pressure oil discharge state, and a neutral state.
25).

The above-mentioned supply line 114 (124)
This is a pipeline separated from the (second) discharge pipeline 101 (102), and one hydraulic cylinder 11
2 (122) side and the other hydraulic cylinder 113 (123)
Separated to the side. Then, the supply line 114 (12
A direction switching valve 115 (125) is interposed in the middle of the separation end to the hydraulic cylinder 112 (122) side of 4).

The direction switching valve 115 (125)
This is a three-position three-port directional switching valve that is gradually switched by moving the spool. Then, the supply pipeline 114 (124) in which two ports are separated from each other.
Upstream side 114a (124a) and downstream side 114b (12
4b), and the other one port is connected to a return line toward the tank T for pressurized oil.

The direction switching valve 115 (12
In the first position (neutral position) of 5), all ports are closed. Further, at the second position, the upstream side 114a (124a) and the downstream side 114b (124b) of the supply pipe 114 (124) that have been separated communicate with each other, and only the port on the return pipe 116 (126) side is connected. It becomes a closed state. Further, the direction switching valve 115
In the third position (125), the supply line 114
(124) is closed on the upstream side 114a (124a), and the downstream side 114b of the supply pipeline 114 (124) is closed.
(124b) and the return line 116 (126) are brought into conduction.

That is, the direction switching valve 115 (12
In the first position of 5), since the movement of the pressure oil in the cylinder 112 (122) is not performed, the piston 111 (121) is not moved.
Is stopped, and in the second position, both cylinders 11
2, 113 (122, 123) are supplied with the same oil pressure, so that the piston 111 (121)
(123) side, and in the third position, the cylinder 11
3 (123) is supplied with pressure oil and cylinder 1
12 (122) is discharged, so that the piston 11
1 (121) moves to the cylinder 112 (122) side.

The above-described direction switching valve 115 (125)
Is switched by moving the spool as described above. That is, the spool is in the first position when it is located in the middle, and gradually shifts to the second position when biased to one side and to the third position when biased to the other. An elastic spring that presses the spool toward the third position is provided at one end of the spool, and a spring that presses the spool toward the second position against the elastic spring is provided at the other end. Two hydraulic piston mechanisms 131 (132) and 151 (161) are provided side by side.

The above-described constant torque control means 130 controls the first and second adjusting means 1 to maintain the input torque of each of the variable displacement pumps 201 and 301 at a substantially constant target input torque.
Activate 10,120. Each variable displacement pump 201,
The input torque of 301 is obtained from the product of the discharge flow rate and the discharge pressure. The constant torque control means 130 is connected to the hydraulic piston mechanisms 131 and 132 and each supply line 11.
Pressure detection lines 133,1 branched from the middle of 4,124
34, a pressure detection line 135 branched from the second discharge line 102, and a pressure detection line 136 branched from the first discharge line 101.

The hydraulic piston mechanism 131 (132) has a stepped piston 131a (132) having three pressure receiving surfaces.
a) and cylinders 131b, 131 corresponding to each pressure receiving surface.
c, 141 (132b, 132c, 142). More precisely, the hydraulic piston mechanism 13
1, 132, the stepped piston 131a, 1
32a and cylinders 131b, 13 corresponding to the respective pressure receiving surfaces.
1c, 132b and 132c correspond to the constant torque control means 13
0, the cylinders 141 and 142 are part of the configuration of the first torque setting means 140.

The above-mentioned pressure detection line 133 branches from the supply line 114 and is connected to the cylinder 131b, and urges the discharge pressure of the first variable displacement pump 201 to the cylinder 131b. The pressure detection pipe 134 is branched from the supply pipe 124 and connected to the cylinder 132b, and urges the discharge pressure of the second variable displacement pump 301 to the cylinder 132b. The pressure detection line 135 is
It branches off from the second discharge pipe line 102 and is connected to the cylinder 131c, and urges the discharge pressure of the second variable displacement pump 301 to the cylinder 131c. Pressure detection line 1
36 is a cylinder branching from the first discharge line 101
32c, the first variable displacement pump 201
Is urged to the cylinder 132c.

Next, the first torque setting means 140 will be described. The first torque setting means 140 is connected to the cylinder 14 of each of the hydraulic piston mechanisms 131 and 132 described above.
1, 142, communication conduits 143, 144 communicating with these cylinders 141, 142, and the control pump 103.
And a torque shift pressure transmission line 148 connected to each of the communication lines 143 and 144 from the discharge side of
And a proportional control valve 145 for power shift control, which is interposed in the middle and supplies pressure oil to each of the communication conduits 143 and 144 with a torque shift pressure according to an external signal.
Calculation unit 146 that outputs a signal for supplying pressure oil at any one of a plurality of stages of torque shift pressures set in advance at 45
And an input device 14 for the operator to input to the arithmetic unit 146 which of a plurality of stages of torque shift pressure to select.
7 is included.

The proportional control valve 145 is supplied with a constant discharge pressure from the control pump 103 via the torque shift pressure transmission line 148. And the control pump 10
With the discharge pressure from No. 3 as the upper limit, the pressure according to the input signal from the arithmetic unit 146 is urged to each of the communication conduits 143 and 144. Accordingly, the pumps 201, 132a are provided on the stepped pistons 131a, 132a of the hydraulic piston mechanisms 131, 132, respectively.
In addition to the discharge pressure of 301, the torque shift pressure selected by the input device 147 acts. That is, the first torque control means 140 can thereby perform a torque shift of the input torque of each of the variable displacement pumps 201 and 301.

The input device 147 is an input panel for the operator to select a work to be performed from now on with the work shovel device. A torque shift pressure at which a torque shift suitable for the selected work is performed is selected. The torque shift pressure is urged to the stepped pistons 131a and 132 via the proportional control valve 145.

FIG. 3 shows each of the variable displacement pumps 201 and 301.
FIG. 3 is a diagram illustrating an example of a relationship between a discharge pressure and a discharge flow rate of the liquid.
As can be seen by taking one of the plurality of characteristic curves as an example, the operation of the constant torque shift control means 130 described above reduces the discharge flow rate against the increase in the discharge pressure and conversely reduces the discharge pressure. On the contrary, it can be seen that the discharge flow rate is controlled to be increased. The characteristics of this characteristic curve include, for example, the elastic coefficients of the springs provided on the spools of the switching valves 115 and 125 and the stepped pistons 131a and 131a.
The input torque control circuit 100 is set so that the product of the discharge flow rate and the discharge pressure (input torque) becomes a constant target input torque. Thus, the torque load of engine 200 can be made constant.

The value of the above-mentioned target input torque can be changed by the first torque setting means 140. That is, the characteristic curve can be shifted in a certain direction by selecting the stepwise torque shift pressure by the first torque setting means 140. Incidentally, the higher the pressure selected by the first torque setting means 140, the more the characteristic curve shifts to the left in FIG.

Therefore, the amount of torque output from the engine can be adjusted according to the amount of work of each actuator, and the operation state can be stabilized.

Next, the first (second) flow control means 150
(160) will be described. The first (second) flow control means 150 (160) is provided with the hydraulic piston mechanism 151 (161) and the passage pipe 211 (311) of the first (second) hydraulic circuit 210 (310). Control pressure line 152 connected to the downstream end of the
(162) [Hereinafter referred to as a negative control pipeline].

First (second) hydraulic circuit 210 (310)
In this case, pressure oil corresponding to the operation amounts of all connected actuators flows into the actuators. Therefore, the relationship between the internal pressure of the negative control line 152 (162) and the operation amount of each actuator decreases when one increases, and increases when one decreases. Using this pressure, the switching valve 115 (12) is operated by the hydraulic piston mechanism 151 (161).
5) is moved to the second or third position, and control is performed to increase or decrease the discharge flow rate of the first (second) variable displacement pump 201 (301).

Therefore, the first (second) flow control means 15
0 (160), if the operation amount of each actuator increases, the first (second) variable displacement pump 201 (30)
If the discharge flow rate of 1) is also increased and the operation amount of each actuator is reduced, the first (second) variable displacement pump 201
Control for reducing the discharge flow rate in (301) is also performed. The amount of operation of each actuator for operating the first (second) flow control means 150 (160) depends on the pressure receiving surface area of the piston of the hydraulic piston mechanism 151 (161) and the spring provided on the switching valve 115. Is set by the spring constant.

[0034]

However, in the conventional input torque control circuit 100, each hydraulic circuit 21
When any one of the actuators starting from the state where all the actuators connected to 0,310 are not operated,
The negative control pressure of the hydraulic circuit connected to the operating actuator may drop suddenly, in which case,
The corresponding flow rate control means performs control to increase the flow rate of the variable displacement pump that is performing the flow rate control. Therefore,
Since the supply flow rate of the pressure oil to the actuator fluctuates abruptly, the operation becomes awkward and there is an inconvenience that the operability of the driver deteriorates.

Each of the above-mentioned flow control means 150, 1
Even in the case of an input torque control circuit having no 60,
When any of the actuators starts operating from the non-operation state, the operation starts from the state where the flow rates of the respective variable displacement pumps are set high by the constant torque control means 130 during the non-operation. There is also a disadvantage that the operation feeling of the pilot is similarly deteriorated.

[0036]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an input torque control circuit for a variable displacement pump which can smoothly operate a hydraulic actuator.

[0037]

According to the first aspect of the present invention, there is provided a variable hydraulic pressure discharger for supplying hydraulic oil to one or more hydraulic actuators for supplying hydraulic oil in accordance with an operation amount input from the outside. Adjusting means for adjusting the discharge amount of the displacement pump; constant torque control means for maintaining the input torque obtained by multiplying the discharge amount of the variable displacement pump and the discharge pressure via the adjusting means at a substantially constant target input torque; First torque setting means for specifying a target input torque to be maintained by the constant torque control means in accordance with a condition externally input.

Then, the second torque setting means for specifying the target input torque to be maintained by the constant torque control means in accordance with the increase or decrease of the operation amounts of one or all actuators, and the target specified by the first torque setting means. A target input torque selecting means for selecting a smaller one of the input torque and a target input torque specified by the second torque setting means and determining the target input torque of the constant torque control means; and a second torque setting means. When the target input torque specified by (1) increases with a change in the operation amount of each actuator, a torque fluctuation reducing unit that reduces the increasing speed is adopted.

According to the second aspect of the present invention, the hydraulic oil is discharged to the first and second hydraulic circuits for supplying the hydraulic oil to one or more hydraulic actuators in accordance with the operation amount input from the outside. An input torque control circuit for the first and second variable displacement pumps sharing a drive source, the first and second adjusting means for adjusting the discharge amounts of the first and second variable displacement pumps, respectively; Constant torque control means for maintaining the total input torque of the first variable displacement pump and the second variable displacement pump at a substantially constant target input torque via each adjusting means;
First torque setting means for specifying a target input torque to be maintained by the constant torque control means in accordance with a condition externally input.

The constant torque control means keeps the operation amount of one or all actuators of the first hydraulic circuit or the operation amount of one or all actuators of the second hydraulic circuit, whichever is larger. A second torque setting means for specifying a target input torque to be performed, and a smaller one of the target input torque specified by the first torque setting means and the target input torque specified by the second torque setting means. hand,
A target input torque selecting means for determining the target input torque of the constant torque control means, and a decreasing rate when the target input torque specified by the second torque setting means increases with a change in the operation amount of each actuator. And a torque fluctuation reducing means.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. Note that among the components shown in the present embodiment, the same components as those shown in the above-described conventional example are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 shows first and second hydraulic pressures for supplying hydraulic oil to a plurality of actuators of a working shovel device including a plurality of hydraulic cylinders, a hydraulic motor and the like according to an operation amount input by a driver. Circuits 210 and 310, first and second variable displacement pumps 201 and 301 for discharging pressure oil to these hydraulic circuits 210 and 310, respectively, and an input torque for controlling the torque of these two variable displacement pumps 201 and 301 2 shows a control circuit 10.

FIG. 2 shows the first and second hydraulic circuits 2.
It is a circuit diagram which shows the details of 10,310. As shown in FIG. 2, the configuration differs from the conventional configuration only in that a throttle valve 219 is not interposed between each actuator 212 of the first hydraulic circuit 210 and the operation lever 216.

The input torque control circuit 10 first includes first and second adjusting means 110 and 120 for adjusting the discharge amounts of the first and second variable displacement pumps 201 and 301, respectively.
A constant torque control means 130 for maintaining the input torque of the first variable displacement pump 201 and the second variable displacement pump 301 at a substantially constant target input torque via the adjusting means 110 and 120; A first torque setting means for specifying a target input torque to be maintained by the control means in accordance with an externally input condition; and a first adjustment along with an increase or a decrease in the operation amount of each actuator connected to the first hydraulic circuit. First flow control means 1 for increasing or decreasing the discharge flow rate of first variable displacement pump 201 through means 110
50, and a second flow control means 160 for increasing and decreasing the operation amount of each actuator connected to the second hydraulic circuit 310 and increasing or decreasing the discharge flow rate of the second variable displacement pump 301 via the second adjusting means 120. And

Further, in addition to the above configuration, the input torque control circuit 10 controls the operation amount of all the actuators of the first hydraulic circuit 210 or the operation amount of all the actuators of the second hydraulic circuit 310, whichever is greater. The second torque setting means 20 for specifying the target input torque to be maintained by the constant torque control means 130 with the increase / decrease, and the target input torque specified by the first torque setting means 140 and the second torque setting means 20 The smaller of the specified target input torques is selected to determine the target input torque of the constant torque control means 130, and the target input torque specified by the second torque setting means 20 is selected. A torque fluctuation reducing means 40 is provided for reducing the increasing speed when increasing with the change in the operation amount of each actuator.

Hereinafter, each part will be described in detail. First, the second torque setting means 20 determines whether the internal pressure of the branch pipe 21 branched from the negative control pipe 152, the branch pipe 22 branched from the negative control pipe 162, or the internal pressure of the branch pipe 21 or the branch pipe 22. Low pressure priority type shuttle valve 23 that connects the lower side to the downstream side
And a negative control detection line 24 connected downstream of the shuttle valve 23. The negative control detection line 24 is connected to a target input torque selecting means 3 described later.
0 is connected to the high pressure priority type shuttle valve 31.

As described above, each negative control conduit 152,
The relationship between the internal pressure at 162 and the total operation amount of the plurality of actuators connected to each of the hydraulic circuits 210 and 310 is such that if one increases, the other decreases, and if one decreases, the other increases. There is. In the second torque setting means 20, the pressure in each of the negative control conduits 152 and 162 is guided to the low-pressure priority type shuttle valve 23, and the lower pressure (the downstream side in which the operation amount of each of the hydraulic circuits 210 and 310 is larger) Pressure) and has the function of conducting to the negative control detection line 24. And this negative control detection line 24
Are the cylinders 141, 132 of the hydraulic piston mechanisms 131, 132 via the target input torque selecting means 30 under certain conditions.
Communicate to 142 to energize the selected pressure. For this reason, it is possible to cause the fluctuation of the target input torque maintained by the constant torque control means 30.

Accordingly, the second torque setting means 20 increases or decreases the operation amount of all actuators of the first hydraulic circuit 210 or the operation amount of all actuators of the second hydraulic circuit 310, whichever is greater. Constant torque control means 13
It is possible to specify the target input torque to be maintained at 0.

Further, a torque fluctuation reducing means 40 is interposed in the negative control detection pipe 24. That is, the torque fluctuation reducing means 40 includes a check valve 41 provided in the middle of the negative control detection pipe 24, a return pipe 42 branched from the negative control detection pipe 24 downstream of the check valve 41, A variable adjusting throttle valve 43 provided in the middle of the return pipe 42 is provided. The check valve 41 allows the flow of the pressure oil only in the direction from the low pressure priority type shuttle valve 23 to the high pressure priority type shuttle valve 31. The return pipe 42 branches off from the negative control detection pipe 24 and is connected to a tank T for pressurized oil. Then, since the variable adjusting throttle valve 43 is provided in the middle, excess pressure oil is gradually returned to the tank T from here.

With this configuration, even if the pressure selected by the second torque setting means 20 decreases rapidly with an increase in the operation amount of each actuator, the check valve 41 prevents the backflow of the pressure oil. At the same time, the pressure oil downstream of the check valve 41 is gradually discharged to the tank T via the return pipe 42 having the throttle valve 43, so that each hydraulic piston mechanism 1
The pressure applied to 31, 31 will gradually decrease.

Therefore, in the torque fluctuation reducing means 40, the target input torque specified by the second torque setting means 20 is:
When the amount of operation of each actuator increases and the urging pressure on each of the hydraulic piston mechanisms 131 and 132 decreases, the rate of increase of the target input torque can be reduced.

Next, the target input torque selecting means 30 will be described. The target input torque selecting means 30 employs a configuration having a high-pressure selecting type shuttle valve 31 and a torque shift pressure transmission line 32 connected downstream of the shuttle valve 31. This high pressure selective shuttle valve 31
Is connected to the torque shift pressure transmission line 148 of the first torque setting means 140 and the negative control detection line 24, and the higher pressure is conducted to the torque shift pressure transmission line 32. The torque shift pressure transmission line 32 is connected to the communication line 1.
Hydraulic piston mechanisms 131, 132 via 43, 144
Are connected to the respective cylinders 141 and 142.

With this configuration, the target input torque selecting means 30 is capable of controlling the torque shift pressure set by the first torque setting means 140 and the pressure selected by the second torque setting means (hereinafter, the selected negative control pressure). ) Is selected, and each of the hydraulic piston mechanisms 13 is selected.
1,132. Therefore, the target input torque selecting means 30 selects the smaller one of the target input torque specified by the first torque setting means 140 and the target input torque specified by the second torque setting means 20, and It is possible to determine the target input torque of the torque control means 130.

The solenoid valve 11 is provided downstream of the torque fluctuation reducing means 40 and in the middle of the negative control detection line 24. This solenoid valve 11
Is a two-port, two-position directional switching valve that conducts through the negative control detection line 24 at one position and closes it at the other position. By switching to the closed position, the solenoid valve 11 blocks the flow of the pressure oil from each of the negative control conduits 152 and 162 to the second torque setting means 20. Therefore, in such a case, the target input torque selecting means 30
Then, the torque shift pressure from the first torque setting means 140 must be selected and each hydraulic piston mechanism 131, 132
Energize. That is, when the solenoid valve 11 is switched to the closed position, the input torque control circuit 10
It is possible to function exactly the same as the conventional input torque control circuit 100. In addition, this solenoid valve 11
Alternatively, a manual directional switching valve may be used.

Next, the operation of the input torque control circuit 10 having the above configuration will be described with reference to FIGS. Note that, as described above, FIG.
FIG. 3 is a diagram illustrating an example of a relationship between a discharge pressure and a discharge flow rate of a discharge 301;

One of the curves shown in FIG.
In the input torque control circuit 10, for example, the discharge pressure is set so that the integrated value (input torque) of the discharge flow rate and the discharge pressure of each of the variable displacement pumps 201 and 301 is approximately constant as shown in FIG. If it increases, the discharge flow rate will decrease,
When the discharge pressure decreases, the constant flow control means 130 controls to increase the discharge flow rate.

Then, the target input torque to be fixed by the constant torque control means 130 is equal to the first torque setting means 14.
It can be changed by the torque shift pressure urged from 0 or the negative control pressure urged by the second torque setting means 20. The plurality of PQ curves shown in FIG.
9 shows an example of a PQ curve when torque is shifted by a torque shift pressure or a negative control pressure. In FIG. 3, the PQ curve located on the rightmost side is a PQ curve in a state where no torque shift pressure or negative control pressure is applied, and the PQ curve becomes left as the applied pressure increases. Shift toward

The operation of the input torque control circuit 10 will be described with reference to each PQ curve in FIG. 3 in order from the right, taking various work operations of the work shovel device to which the input torque control circuit 10 is applied as an example. First, when each part of the work shovel device is not operated, each hydraulic circuit 210,
Since none of the actuators 310 is in operation, the negative control pressures of the hydraulic circuits 210 and 310 have substantially the same value at the maximum. Therefore, a slightly lower negative control pressure is selected by the second torque setting means 20.

On the other hand, in the first torque setting means 140,
Since it is customary to perform a torque shift in order to prevent engine stall due to insufficient output of the engine 200, the maximum value of the target input torque is generally selected when each actuator is not operating. Therefore, 0 is selected as the torque shift pressure. That is, if the first torque setting means 140 is applied, the operation of each of the variable displacement pumps 201 and 301 is controlled according to the PQ curve.

However, the target input torque selecting means 3
0 selects the higher pressure, so that the negative control pressure from the second torque selecting means 20 is applied to each hydraulic piston mechanism 13
1, 132, for example, each variable displacement pump 20
1, 301 is operation-controlled according to the PQ curve.

Then, for example, it is assumed that an operation of lowering the boom of the work shovel apparatus from such a state is performed. The hydraulic cylinder (actuator) of the boom is the first
Is connected to the hydraulic circuit 210, the pressure oil flowing into the first hydraulic circuit 210 is supplied to the hydraulic cylinder side, so that the negative control pressure rapidly decreases.

Accordingly, the second torque setting means 20 selects the negative control pressure of the first hydraulic circuit 210 and makes it conductive downstream. Accordingly, such a rapid pressure drop occurs in the negative control detection pipe 24, but the check valve 41 of the torque fluctuation reducing means 40 provided in the middle thereof suppresses the rapid pressure drop on the downstream side.

That is, the pressure oil on the downstream side of the check valve 41 in the negative control detection pipe 24 passes through the return pipe 42 and is gradually discharged to the tank T, and slowly flows upstream of the check valve 41. Transition to pressure. The negative control pressure at this time is P-
When a pressure change that causes a shift from the Q curve to the PQ curve occurs, the change is performed gradually.

At this time, if the first torque setting means 14
If the torque shift pressure for controlling each of the variable displacement pumps 201 and 301 according to the PQ curve is selected at 0, the target input torque selecting means 30 gradually changes the PQ curve to the PQ curve. Will be performed. In any case, the torque fluctuation mitigation means 40 prevents the target input torque from fluctuating rapidly.

Each variable displacement pump 201, 301 before the fluctuation
Is in the point B on the PQ curve, when a torque fluctuation that shifts to the PQ curve occurs, the operation state becomes a point A on the PQ curve. If this torque fluctuation occurs rapidly, each of the variable displacement pumps 201, 301
Will rapidly jump up, and the lowering operation of the boom will also start with a steep behavior. However, in the input torque control circuit 10, since the torque fluctuation is gradually performed by the action of the torque fluctuation mitigation means 40, the start of such an instantaneous operation can be effectively avoided. This effect is the same not only for the rotation of the boom but also for all the operations in each part of the work shovel device.

Next, the operation of the input torque control circuit 10 in the case of an operation requiring precision such as leveling work in the work shovel device will be described. In this leveling operation, an operation of simultaneously performing the boom raising operation and the arm excavating operation of the work shovel device is performed. However, the operation itself by the operation lever is shallow, and therefore, the negative control pressure of each of the hydraulic circuits 210 and 310 is large. Does not drop. Therefore, any one of the hydraulic circuits 210, 310 selected by the second torque setting means 20
The negative control pressure is also selected by the target input torque selecting means 30 and is energized by the hydraulic piston mechanisms 131 and 132.

At this time, since the negative control pressure is higher than the normal excavation operation, the target input torque can be set small. Therefore, the discharge flow rate of each variable displacement pump is set to be small, and the operation speed of each actuator can be reduced, so that work can be performed with high accuracy. Also in this case, even if a sudden decrease in the negative control pressure occurs, the torque fluctuation alleviating means 40 suppresses a sudden increase in the target input torque, which is suitable for performing a more precise operation.

Next, the excavation and work in the work shovel
The operation of the input torque control circuit 10 when the operation amount such as the loading operation is large will be described. In this case, since the operation amount is large, the negative control pressure of each of the hydraulic circuits 210 and 310 is greatly reduced. On the other hand, in the first torque setting means 140, the torque shift pressure is set low in preparation for work with a large operation amount. However, since the negative control pressure selected by the second torque setting means 20 is lower than the torque shift pressure set by the first torque setting means 140, the target input torque selecting means 30 uses the first torque setting means 140.
Is selected, and the torque shift pressure is urged to the hydraulic piston mechanisms 131 and 132. Thus, the work is performed in a state where the target input torque is set to be large, as in the related art.

In this excavation / loading operation, each actuator may be in a non-operating state for a short time. At this time, the negative control pressure rises, so that the negative control pressure is reduced by each hydraulic piston mechanism 131, 13
2 may be energized. However, even if the negative control pressure returns after returning to the operating state again, the rapid fluctuation is avoided by the torque fluctuation mitigation means 40 and the torque shift pressure is selected again by the target input torque selection means 30. The effect on each actuator is avoided.

As described above, in the input torque control circuit 10 of the present embodiment, when the operation of any one of the actuators is started from the non-operation state of all the actuators,
The second torque setting means 20 controls the constant torque control means 1
In addition to causing the target input torque to fluctuate, the torque fluctuation suppressing means 40 slows down the fluctuation speed of the target input torque, so that the instantaneous operation can be effectively avoided and the operation can be smoothly performed. It is possible to provide the driver with good operability. In addition, since instantaneous operation is prevented from occurring, it is also effective in preventing lever hunting of the operation lever caused thereby.

Further, the second torque setting means 20 sets the first torque
And the negative control pressure having the larger total operation amount of each actuator of the second hydraulic circuit is selected, that is, the operation of the actuator is reliably detected, and the torque setting means 20 is operated despite the operation. Can be avoided.

Further, the target input torque selecting means 30 selects the smaller one of the target input torques specified by the first and second torque setting means 140 and 20, so that the occurrence of the output torque shortage of the drive source is effective. Can be avoided.

In this embodiment, as the first torque setting means, a configuration has been shown in which the target input torque is set by the operator's arbitrary selection or selection according to the work. A configuration may be adopted in which the number of revolutions at the time of output is detected (engine sensing), the target input torque is increased by increasing the number of revolutions due to excessive output, and the target input torque is decreased by decreasing the number of revolutions due to insufficient output.

Further, as shown in FIG. 4, the torque fluctuation reducing means 40 may be provided with an accumulator 44 in the middle of the return pipe 42 and upstream of the variable adjustment throttle valve 43. In such a configuration, when the inside of the negative control detection line 24 holds a certain pressure or more, the pressure oil is accumulated in the accumulator 44, the operation amount of each actuator increases, and the pressure in the negative control detection line 24 decreases. Occurs, the pressure oil in the accumulator 44 is discharged downstream of the check valve 41, and the pressure is reduced slowly. Therefore, in the case of such a configuration, since the torque fluctuation is performed more slowly, the instantaneous operation of the work shovel device can be more effectively prevented from starting.

FIG. 5 shows another torque fluctuation reducing means 4.
Indicates 0A. The torque fluctuation reducing means 40A is provided with a check valve 4 provided in the middle of the negative control detection line 24 as described above.
1 and the check valve 41 so as to avoid the check valve 41.
Upstream from the negative control detection line 24, the check valve 41
Pipe 42A that returns to the downstream side of the
The configuration has a variable adjustment throttle valve 43A provided in the middle of 2A and an accumulator 44A provided in the negative control detection pipe 24 and downstream of the avoidance pipe 42A.

In the case of such a configuration, when the pressure inside the negative control detection line 24 is maintained at a certain pressure or higher, the accumulator 4
When the pressure oil accumulates in the 4A and the operation amount of each actuator increases and the pressure in the negative control detection pipe 24 decreases, the pressure oil in the avoidance pipe 42A is variably adjusted by the variable throttle valve 43A.
A backflow occurs while the flow is restricted by the
On the downstream side of 2A, the pressure oil in the accumulator 44A is discharged, and the pressure drops slowly.
Therefore, in the case of such a configuration, since the torque fluctuation is performed slowly, it is possible to effectively avoid the instantaneous start of the operation of the work shovel device.

(Second Embodiment) Next, the second embodiment of the present invention will be described.
The embodiment will be described with reference to FIG. In addition, among the components shown in the present embodiment, the same components as those shown in the above-described input torque control circuit 10 are denoted by the same reference numerals, and redundant description will be omitted.

In the second embodiment, a part of the function of the first torque setting means 140, the function of the target input torque selecting means 30, and the function of the torque fluctuation reducing means 40 are described by using a CPU, ROM, 9 shows an input torque control circuit 10B performed by a calculation unit 146B configured by an electronic circuit including an A / D converter and the like.

That is, the operation unit 146B is provided with the pressure sensor 149 provided at the end of the negative control detection line 24 described above.
The target input torque selecting means 30B which compares the detected pressure of B with the torque shift pressure input from the input device 147, selects a large pressure, and outputs a signal corresponding thereto, and the target input torque selecting means 30B which selects the large pressure. Torque fluctuation reducing means for reducing the fluctuation speed when the pressure fluctuation speed exceeds a certain value, and outputting a drive signal for determining the pressure of the power shift control proportional control valve 145 at the reduced fluctuation speed. 40B.

In such a configuration, the pressure in the negative control detection line 24 is constantly detected by the pressure sensor 149B, and is compared with the torque shift pressure set by the input device 147.
When the amount of operation of each actuator changes and a rapid pressure change occurs in the negative control detection pipe 24, the pressure before and after the change is equal to or greater than the torque shift pressure set by the input device 147. , The power shift control proportional control valve 14
The fluctuation speed of the pressure adjusted in step 5 is reduced and transmitted to the hydraulic piston mechanisms 131 and 132. Therefore, also in the case of such a configuration, since the torque fluctuation is performed slowly, it is possible to effectively avoid the instantaneous start of the operation of the work shovel device.

Although the above-described torque fluctuation mitigation means 40 avoids only a rapid increase in the target input torque, the torque fluctuation mitigation means 40B may be set so as to suppress both a rapid increase and a rapid decrease. good. Further, in the input torque control circuit 10B, since the configuration of the hydraulic circuit is simplified and the number of parts is reduced as compared with the input torque control circuit 10, it is possible to improve productivity and reduce production costs. And

(Third Embodiment) Next, a third embodiment of the present invention will be described.
Will be described with reference to FIGS. 7 and 8. FIG.
FIG. 7 shows a circuit diagram of an input torque control circuit 10C according to the third embodiment. FIG. 8 shows this input torque control circuit 1
A first hydraulic circuit 210C and a second hydraulic circuit 310C connected to 0C are shown. In addition, among the components shown in the present embodiment, the same components as those shown in the above-described input torque control circuit 10 are denoted by the same reference numerals, and redundant description will be omitted.

In the input torque control circuit 10 described above, the negative control pressure is detected from the downstream side of each of the hydraulic circuits 210 and 310, and the lower one of them is set by the first torque setting means 140. In this case, the target input torque is shifted based on the negative control pressure when the target input torque is higher than the negative control pressure. However, the target input torque is determined based on the so-called positive control pressure (hereinafter referred to as the positive control pressure). It is also possible to perform a shift.

For this reason, in the present embodiment, the first and second hydraulic circuits 210C and 310C
The configuration is slightly different as compared with the configuration No. 0,310.
First, this point will be described. As shown in FIG. 8, since the input torque control circuit 10C does not detect the negative control pressure, the negative control lines 152 and 162 do not exist. Therefore, each passage pipe 211, 311 is connected to each switching valve 212,
Supply pressure oil to the 312 group, and supply each negative control line 152, 1
It is connected to the tank T without branching to 62.

On the other hand, the input torque control circuit 10C is different from the input torque control circuit 10 in that the input torque control circuit 10C includes a second torque setting means 20C for specifying the target input torque based on the positive control pressure.

As shown in FIG. 7, the second torque setting means 20C is connected to the switching valve 2 of the first hydraulic circuit 210C.
Twelve bidirectional positive control pressures (operation lever 216 in FIG. 7)
The two-way positive control pressure (the pressure output in two directions) and the high-pressure priority type shuttle valve 21C for selecting the higher one of these positive control pressures and the switching valve 312 of the second hydraulic circuit 310C. The high-pressure priority shuttle valve 22C, the high-pressure priority shuttle valve 21C, and the high-pressure priority shuttle 21C, which detect the pressure output in two directions from the operation lever 316 in FIG. 7 and select the higher of these positive control pressures. The high pressure priority type shuttle valve 23C for selecting the higher one of the positive control pressures selected by the valve 22C and the positive control pressure Po selected by the high pressure priority type shuttle valve 23C are input to the corresponding pressure P. , And an output line 25C connected to the output stage side of the reverse valve 24C.

The reversing valve 24C is set so that the input pressure Po and the output pressure P satisfy the formula P = Pi-Po. Here, the pressure Pi is a constant pressure supplied from the control pump 103 to the reversing valve 24C.

The output line 25C is connected to the reversing valve 24C and the high pressure priority type shuttle valve 3 of the target input torque selecting means 30.
1 connected. The torque fluctuation reducing means 40 and the solenoid valve 11 are provided in the output line 25C in place of the negative control pressure detecting line 24.

In the above configuration, the two positive control pressures input to the high-pressure priority type shuttle valve 21C are pressures for moving the spool of the switching valve 212. Therefore, when either positive control pressure is high, First
The actuator connected to the hydraulic circuit 210C has a large operation amount. Since the two positive control pressures are pressures for instructing the actuator to perform a forward operation and a reverse operation, respectively, the operation amount of the actuator is large even when either positive control pressure is high. Therefore, by selecting the higher positive control pressure using the high-pressure priority type shuttle valve 21C, it is possible to detect an increase or decrease in the operation amount of the actuator. The same can be said for the high-pressure shuttle valve 22C.

Then, each high-pressure priority type shuttle valve 21C,
By selecting the higher positive control pressure of the positive control pressure selected in 22C, the first hydraulic circuit 210C
Of the actuator of the second hydraulic pressure 310C and the actuator of the second hydraulic pressure 310C, whichever is greater. Furthermore, it decreases in response to the increase in the identified positive control pressure,
The positive control pressure is reversed by the reversing valve 24C that outputs a pressure that increases in response to the decrease, and the reversed pressure is output to the target input torque selecting means 30 via the torque fluctuation reducing means 40. Therefore, the pressure output to the target input torque selecting means 30 changes substantially in the same manner as the negative control pressure in the input torque control circuit 10, and the input torque control circuit 10C also has the same change as the input torque control circuit 10. It works, and it is possible to obtain the same effect.

In the above description, as shown in FIG.
Although only one switching valve 212 (312) is shown for the first (second) hydraulic circuit 210C (310C), in practice, as shown in FIG.
(312) is provided. Therefore, each switching valve 2
An operation lever 216 (316) is provided for each 12 (312), and a bidirectional positive control pressure is detected for each switching valve 212 (312). Furthermore, a high-pressure priority type shuttle valve (not shown) for comparing the positive control pressure of each switching valve 212 (312) is provided, and finally the first (second) hydraulic circuit 210C (31)
0C), the highest positive control pressure among the switching valves 212 (312) is guided to the high pressure priority type shuttle valve 23C. That is, the high-pressure priority type shuttle valve 2
In 3C, the highest positive control pressure in the first hydraulic circuit 210C is compared with the highest positive control pressure in the second hydraulic circuit 310C.

Further, in the input torque control circuit 10C, since the torque is shifted by the positive control pressure, the first and second flow control means 150 and 160 which are controlled based on the negative control pressure are replaced by: First and second flow control means 1 controlled based on positive control pressure
50C and 160C are provided.

The first (second) flow control means 150C
(160C) is a hydraulic piston mechanism 151 (161)
And the first (second) hydraulic circuit 210C (310)
C), the highest positive control pressure is detected among the switching valves 212 (312), and the hydraulic piston mechanism 151 (16) is detected.
Positive control pressure line (hereinafter abbreviated as positive control line) 152C (162C) for energizing 1)
And a lever mechanism 153C (163C) provided between the hydraulic piston mechanism 151 (161) and the spool of the direction switching valve 115 (125).

One end of the lever mechanism 153C (163C) is in pressure contact with the hydraulic piston mechanism 151 (161) across the fulcrum, and the other end is in pressure contact with the spool of the direction switching valve 115 (125). Therefore, when the pressure is applied to the hydraulic piston mechanism 151 (161), the first
The spool is pressed in the direction opposite to the (second) flow control means 150 (160).

That is, the first (second) flow control means 1
At 50C (160C), when the positive control pressure increases (the operation amount increases), the variable displacement pump 202 (302)
Since the discharge flow rate is increased, it functions almost in the same manner as the first (second) flow control means 150 (160) described above.

(Fourth Embodiment) Next, the fourth embodiment of the present invention will be described.
The embodiment will be described with reference to FIG. In addition, among the components shown in the present embodiment, the same components as those shown in the above-described input torque control circuit 10C are denoted by the same reference numerals, and redundant description will be omitted.

In the fourth embodiment, a part of the configuration of the first torque setting means 140, the function of the target input torque selection means 30 and the function of the torque fluctuation mitigation means 40 are described by using a CPU, ROM, 10 shows an input torque control circuit 10 </ b> D performed by a calculation unit 146 </ b> D configured by an electronic circuit including an A / D converter and the like.

That is, the operation unit 146D calculates the pressure P corresponding to the pressure Po detected by the pressure sensor 149D provided downstream of the output stage of the high-pressure priority type shuttle valve 23C.
And a target input torque selecting unit 30D that compares the output pressure P with the torque shift pressure input from the input device 147, selects a higher pressure, and outputs a signal corresponding to the higher pressure. When the speed of the pressure change selected by the target input torque selecting means 30D exceeds a certain value, the speed of the change is reduced, and the pressure of the power shift control proportional control valve 145 is reduced at the reduced speed. And a torque fluctuation mitigation means 40D for outputting a drive signal for determining

The pressure value converter 12D is set so that the input pressure Po and the output pressure P satisfy the formula P = Pi-Po. Here, the numerical value Pi is a value set so that the value of the pressure P becomes a value suitable for the torque shift of the target input torque.

In the case of such a configuration, the high pressure priority type shuttle valve 2
Positive control pressure Po selected in 3C is always pressure sensor 14
9D, the converted pressure P based on the detected pressure is compared with the torque shift pressure set by the input device 147. Then, the amount of operation of each actuator changes, causing a rapid pressure change in the positive control pressure Po, and the conversion pressure P also causes a rapid change. Accordingly, the pressure before and after the change is input. When the pressure is equal to or higher than the torque shift pressure set by the device 147, the fluctuation speed of the pressure adjusted by the power shift control proportional control valve 145 is reduced by the torque fluctuation mitigation means 40D and transmitted to the hydraulic piston mechanisms 131 and 132. Therefore, also in the case of such a configuration, since the torque fluctuation is performed slowly, it is possible to effectively prevent the instantaneous operation of the work shovel device from starting.

Although the above-described torque fluctuation mitigation means 40C avoids only a rapid increase in the target input torque, the torque fluctuation mitigation means 40D may be set to suppress both a rapid increase and a rapid decrease. good. The input torque control circuit 10D includes an input torque control circuit 10D.
Compared with C, the configuration of the hydraulic circuit is simplified and the number of parts is reduced, so that it is possible to improve productivity and reduce production costs.

[0102]

According to the present invention, when the operation of any one of the actuators is started from the inoperative state of all the actuators, the second torque setting means causes a change in the target input torque of the constant torque control means. At the same time, the torque fluctuation suppressing means slows down the fluctuation speed of the target input torque, thereby effectively avoiding the start of instantaneous operation,
It can be operated smoothly, and it is possible to provide the driver with good operability. In addition, since instantaneous operation is prevented from occurring, it is also effective in preventing lever hunting of the operation lever caused thereby.

In the invention of the present application, when performing a work with a small amount of operation that requires high accuracy by each actuator of the hydraulic circuit, the second torque setting means has a function of specifying a small value of the target input torque. On the other hand, since the target input torque selecting means selects a smaller value of the target input torque, even if the target input torque specified by the first torque setting means is small or large, the constant The target input torque maintained by the control means can always be a small target input torque.

Accordingly, the discharge flow rate of each variable displacement pump is set to be small, and the operating speed of each actuator can be reduced. Therefore, according to the configuration of the present invention, it is possible to perform the operation with high accuracy. Also in this case, since the sudden fluctuation of the target input torque is suppressed by the torque fluctuation mitigation means, it is preferable to perform a more accurate operation.

Since the target input torque selecting means selects the smaller of the target input torque specified by the first and second torque setting means, it is possible to effectively avoid occurrence of insufficient output torque of the drive source. Can be.

Further, in the case of the configuration in which the input torque control of the two variable displacement pumps is performed, the second torque setting means may perform the operation when the total operation amount of each actuator of the first and second hydraulic circuits is large. Since the target input torque based on the amount is selected, that is, the operation of the actuator is reliably detected.
The inconvenience that the target input torque by the torque setting means does not fluctuate can be avoided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a hydraulic circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing details of each hydraulic circuit disclosed in FIG. 1;

FIG. 3 is a diagram showing an example of a relationship between a discharge pressure and a discharge flow rate of each variable displacement pump.

FIG. 4 is a circuit diagram of a hydraulic circuit showing an example in which an accumulator is added to the configuration of the torque fluctuation reducing means disclosed in FIG.

FIG. 5 is a circuit diagram of a hydraulic circuit showing an example of another torque fluctuation reducing means different from the torque fluctuation reducing means disclosed in FIG. 1;

FIG. 6 is a circuit diagram of a hydraulic circuit according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram of a hydraulic circuit according to a third embodiment of the present invention.

FIG. 8 is a circuit diagram showing details of each hydraulic circuit disclosed in FIG. 7;

FIG. 9 is a circuit diagram of a hydraulic circuit according to a fourth embodiment of the present invention.

FIG. 10 is a circuit diagram showing a hydraulic circuit according to a conventional example.

FIG. 11 is a circuit diagram showing details of each hydraulic circuit disclosed in FIG. 10;

[Explanation of symbols]

 10, 10B, 10C, 10D Input torque control circuit 20, 20C Second torque setting means 30, 30B, 30D Target input torque selecting means 40, 40A, 40B, 40D Torque fluctuation alleviating means 110 First adjusting means 120 Second Adjustment means 130 constant torque control means 140 first torque setting means 201 first variable displacement pump 210, 210C first hydraulic circuit 301 second variable displacement pump 310, 310C second hydraulic circuit

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2D003 AA01 AB05 AC06 AC08 BA01 CA04 DA03 DA04 DB02 DB03 3H045 AA04 AA10 AA16 AA24 AA33 BA15 CA03 CA28 DA25 EA33 3H089 AA01 AA16 BB05 DA03 DA06 DA13 DA17 EE02 EE02 GG02

Claims (2)

[Claims] An adjusting means for adjusting a discharge amount of a variable displacement pump for discharging a pressure oil to a hydraulic circuit for supplying a pressure oil according to an operation amount inputted from outside to one or more hydraulic actuators; A constant torque control means for maintaining an input torque obtained by multiplying the discharge amount of the variable displacement pump and a discharge pressure via the adjustment means at a substantially constant target input torque; and a target input maintained by the constant torque control means. First torque setting means for specifying a torque in accordance with an externally input condition, and specifying a target input torque to be maintained by the constant torque control means in accordance with an increase or a decrease in the operation amount of one or all of the actuators. A second torque setting unit; and a target input torque specified by the first torque setting unit or a target input torque specified by the second torque setting unit. And a target input torque selecting means for determining the target input torque of the constant torque control means, and a target input torque specified by the second torque setting means, in accordance with a change in the operation amount of each actuator. And a torque fluctuation mitigation means for reducing the increasing speed when increasing. The input torque control circuit of the variable displacement pump. 2. A method of supplying a hydraulic oil to one or a plurality of hydraulic actuators in accordance with an operation amount input from the outside.
An input torque control circuit for the first and second variable displacement pumps, which share the drive source and discharge the pressure oil to the first and second hydraulic pumps respectively. First and second adjusting means for adjusting the amount respectively, and a constant for maintaining the input torque of the first variable displacement pump and the second variable displacement pump at a substantially constant target input torque via the respective adjusting means. Torque control means, and first torque setting means for specifying a target input torque to be maintained by the constant torque control means in accordance with an externally input condition. A second torque setting means for specifying a target input torque to be maintained by the constant torque control means in accordance with an increase or a decrease in a larger one of an operation amount and an operation amount of one or all actuators of the second hydraulic circuit; Selecting the smaller of the target input torque specified by the first torque setting means and the target input torque specified by the second torque setting means, and selecting the target input torque of the constant torque control means. Target input torque selecting means, and torque fluctuation reducing means for reducing the increasing speed when the target input torque specified by the second torque setting means increases with a change in the operation amount of each actuator. An input torque control circuit for a variable displacement pump, comprising: