JPH11294338A - Control device of hydraulic pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of hydraulic pump which can realize an adequate horsepower control without making a spring to energize a spool for control, in a large size, and without providing an electromagnetic proportional pressure reducing valve. SOLUTION: A regulator 16 including a first pressure chamber 21 in which a main pump 2 driven by a prime mover 1, and having the variable capacity, a sub-pump 14 having a fixed capacity, an actuator 5 to control the tilting amount of the main pump 2, a spool 25 to control the actuator 5, a piston 18 to switch the spool 25, the first pressure chamber 21 provided with a pressure receiving surface for main pump of the poston 18, and the second pressure chamber 22 in which a pressure receiving surface for horsepower reduction 22 to receive the pressure of the subpump 14 of the piston 18 is provided; a conduit 23 to connect the main conduit 15 of the subpump 14, and the second pressure chamber 24; and a conduit 102 to connect the second pressure chamber 24 and a tank 3; are provided, while a first throttle 100 and a second throttle 101 is provided to the conduit 23 and 102 respectively, so as to generate an intermediate pressure to the second pressure chamber 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a hydraulic pump provided in a construction machine such as a hydraulic shovel.

[0002]

2. Description of the Related Art FIG. 2 is a hydraulic circuit diagram showing an example of a conventional hydraulic pump control device. The prior art shown in FIG. 2 is applied to, for example, a hydraulic excavator, and includes a prime mover 1, three hydraulic pumps driven by the prime mover 1, that is, a main pump 2 composed of a variable displacement hydraulic pump, and a fixed displacement. Pump 14 composed of a hydraulic pump
And a pilot pump 12.

[0003] Of these three hydraulic pumps, the main pump 2 is involved in the main work of the hydraulic excavator, for example, the excavation work, and causes a boom cylinder, an arm cylinder, a swing motor, a traveling motor, etc., which fluctuate the load pressure. Is supplied via the main pipe line 4 to operate the operation actuator. Although the sub-pump 14 is involved in the work performed by the hydraulic excavator and causes the load pressure to fluctuate, it is rather provided with an additional operation actuator, for example, a pressure for operating an earth discharging plate cylinder or the like. Oil is supplied via main line 15. Further, the pilot pump 12 includes the main pump 2 and the sub pump 14 described above.
It outputs a pilot pressure that is much smaller than the pressure of the hydraulic oil discharged from the controller. The pilot pressure is supplied to an operation system that switches a directional control valve that controls the above-described operation actuator. It is supplied to a regulator 16 to be described later via a path 13.

The tilt control mechanism 11 for controlling the tilt amount of the main pump 2 is driven by a control actuator 5 via a link 10. The control actuator 5 includes a cylinder 6 and a piston 7 slidable in the cylinder 6. The piston 7 includes a large-diameter piston portion 7A slidable in a large-diameter hole 6A in the cylinder 6, and a small-diameter piston portion 7B slidable in a small-diameter hole 6B in the cylinder 6. Large diameter hole 6 of cylinder 6
A and a large-diameter piston portion 7A of the piston 7 form one pressure chamber, that is, a large-diameter chamber 8, and a small-diameter hole 6B of the cylinder 6 and a small-diameter piston portion 7B of the piston 7 form another pressure chamber, that is, a large-diameter chamber. A small diameter chamber 9 is formed.
The driving of the control actuator 5 is performed by operating the control spool 25.

The control spool 25 is urged by a spring 26 to the left in FIG. The small-diameter chamber 9 of the control actuator 5 is connected to the pilot pump 12 via the above-mentioned pipe 13, and the small-diameter chamber 9 is always supplied with the pilot pressure discharged from the pilot pump 12. In addition, the large-diameter chamber 8 of the control actuator 5 is connected to the above-described pilot line 13 through a control spool 25.
And one of the tanks 3.

The control spool 25 is switched by a control piston 18 slidable in the casing 1. The casing 17 includes a first pressure chamber 21 and a second pressure chamber 24. Of these, the first pressure chamber 2
1 is a main pump 2 through a main line 4 and a branch line 20.
The first pressure chamber 21 is connected to the main pump 2
Is supplied from the pressure oil. The second pressure chamber 24
The sub-pump 14 is connected to the sub-pump 14 via the main pipe 15 and the pipe 23, and pressure oil discharged from the sub-pump 14 is supplied to the second pressure chamber 24.

The above-described control piston 18 is formed of a single structure having a stepped portion. A pressure receiving surface 19 for the main pump that receives the discharge pressure of the main pump 2, that is, a self-pressure is formed in the stepped portion, and the pressure receiving surface 19 for the main pump is arranged in the first pressure chamber 21 of the casing 17. .

The end of the control piston 18 has a reduced horsepower receiving surface 22 which receives the discharge pressure of the sub-pump 14.
The pressure-reducing surface 22 for horsepower reduction is disposed in the second pressure chamber 24 of the casing 17.

The control spool 25 and the spring 26
The casing 16, the control piston 18, and the control actuator 5 including the piston 7 constitute a regulator 16 that controls the tilt amount of the main pump 2.

In the prior art shown in FIG. 2, the prime mover 1 is in a driving state, and an operating actuator such as a boom cylinder is driven by pressure oil discharged from a main pump 2, but is discharged from a sub-pump 14. FIG. 4 shows a state in which another operating actuator, such as a cylinder for the earthing plate driven by pressure oil, is stopped and held.
The discharge pressure P and the discharge flow rate Q of the main pump 2 are controlled so as to maintain the relationship of the characteristic line A1 shown in FIG.

For example, when the load pressure of the operation actuator driven by the pressure oil discharged from the main pump 2 is relatively low, the discharge pressure P of the main pump 2 is correspondingly low. Thus, the main line 4, the branch line 20
When the pressure supplied to the first pressure chamber 21 of the casing 17 of the regulator 16 via the
When the force due to the pressure applied to the main pump pressure receiving surface 19 of the control piston 18 is smaller than the force of No. 6,
The control spool 25 moves to the left in FIG. 2 by the force of the spring 26, whereby the large-diameter chamber 8 of the control actuator 5 and the tank 3 communicate with each other, and the large-diameter chamber 8 and the pilot line 1
3 is cut off. At this time, since the pressure oil discharged from the pilot pump 12 is supplied to the small-diameter chamber 9 of the control actuator 5, the piston 7 of the control actuator 5 moves in the left direction of FIG. Movement, tilt control mechanism 1 via link 10
1 moves in the direction of arrow D. As a result, the discharge flow rate Q of the main pump 2 is maintained at a large discharge flow rate Q, as exemplified by the characteristic line A1 in FIG. Accordingly, a relatively large flow rate is supplied to the operation actuator such as the boom cylinder via the main pipeline 4.

Conversely, when the load pressure of the operating actuator driven by the pressure oil discharged from the main pump 2 is high, the discharge pressure of the main pump 2 also increases accordingly. Accordingly, the force corresponding to the pressure applied to the main pump pressure receiving surface portion 19 of the control piston 18 becomes larger than the force of the spring 26, and the control spool 25 is moved in the right direction of FIG. The large-diameter chamber 8 of the cylinder 6 of the control actuator 5 moves and communicates with the pilot line 13, so that the large-diameter chamber 8 and the tank 3 are shut off. Thus, the pressure oil discharged from the pilot pump 12 is supplied to both the large-diameter chamber 8 and the small-diameter chamber 9 of the control actuator 5. At this time,
Due to the area difference between the large-diameter piston portion 7A and the small-diameter piston portion 7B of the piston 7 of the control actuator 5, the control actuator 5 moves to the right in FIG. 11 moves in the direction of arrow C, and the discharge flow rate Q of the main pump 2 decreases. The pump input torque T obtained during this time has a characteristic shown by a characteristic line A3 in FIG.

When the operation actuator such as the cylinder for the discharge plate on the sub-pump 14 is driven in conjunction with the driving of the operation actuator on the main pump 2 side, the pressure oil discharged from the sub-pump 14 causes The discharge pressure of the sub-pump 14 increases according to the load pressure of the operating actuator to be driven, and the increased discharge pressure is supplied to the second pressure chamber 24 of the casing 17 via the main pipe 15 and the pipe 23. Therefore, sub pump 1
4 is applied to the pressure-reducing pressure receiving surface 22 of the control piston 18 and the control piston 18 only drives the operation actuator by the pressure oil of the main pump 2 as shown in FIG. The amount of movement in the right direction tends to increase, that is, the control spool 25 and the piston 7 of the control actuator 5 tend to move in the direction A in FIG. The control mechanism 11 tends to move in the C direction, and the discharge flow rate Q of the main pump 2 tends to decrease. FIG. 4 (a)
A characteristic line A2 indicates the characteristic at this time. Also,
As the discharge flow rate Q of the main pump 2 changes in this manner, the input torque T of the main pump 2 also decreases as shown by the characteristic line A4 in FIG.

As described above, the operation actuator (not shown) driven by the main pump 2 and the sub-pump 1
By changing the discharge pressure P-discharge flow rate Q characteristic of the main pump 2 and the discharge pressure P-pump input torque T characteristic of the main pump 2 according to a combined operation with an operation actuator (not shown) driven by the control unit 4, The total pump input torque of the main pump 2 and the sub pump 14 is
Horsepower control is performed so as not to exceed a value obtained by subtracting the input torque of the pilot pump 12 from the output torque T of the prime mover 1.

[0015]

In the prior art described above, when the horsepower of the sub-pump 14 is relatively large, it may be difficult to manufacture the control piston 18. Usually, the diameter of the control piston 18 utilized for the above-described horsepower reduction control is determined as follows.

The diameter of the piston 18 at the portion having the main pump pressure receiving surface 19 to which the self-pressure of the main pump 2 is applied is d0, and the portion of the piston 18 at the portion having the reduced horsepower pressure receiving surface 22 to which the sub-pump 14 is provided with the pressure oil horsepower ratio of the sub-pump 14 a diameter d, with respect to the horsepower of the main pump 2, i.e. the horsepower ratio and epsilon, d ² / = a relationship of ^{(d0 2 -d 2) = ε} / (1-ε).

Accordingly, for example, if d0 = 3 (mm) when the horsepower ratio ε is ε = (6.5 / 36) = 0.181, the control piston 18 having the reduced horsepower pressure receiving surface 22 is set. The diameter d of the part is
d = 1.276 (mm), which is extremely small.
For this reason, it is difficult to manufacture the control piston 18 with high accuracy. Along with this, it becomes difficult to accurately drill holes in the cylinder section through which the control piston 18 is inserted.

It should be noted that the diameter of the control piston 18 and the diameter of the
In addition, it is conceivable to increase the size of the hole in the cylinder portion through which the control piston 18 is inserted. However, in this case, the shape and size of the spring 26 for urging the control spool 25 must be set large. As a result, the size of the regulator 16 is increased. In addition, since the control spool 25 is slid against the force of the enlarged spring 26, it is difficult to control the position of the control spool 25, whereby the control accuracy of the tilt amount of the main pump 2 is reduced. Another problem is reduced reliability.

Therefore, in order to prevent the spring 26 from increasing in size as described above, as shown in FIG. 3, an electromagnetic proportional pressure reducing valve 50 is provided in a pipe 23 connecting the main pipe 15 of the sub-pump 14 and the second pressure chamber 24. Is provided, a pressure smaller than the discharge pressure of the sub-pump 14 is supplied to the second pressure chamber 24, and the small pressure is applied to the horsepower-reducing pressure receiving surface 22 of the control piston 18.

With such a construction, the spring 2 having the same shape and dimensions as those of the prior art shown in FIG.
6, the diameter of the control piston 18 can be set to be larger than that in the prior art shown in FIG. 2 in accordance with the decrease in the pressure applied to the horsepower reducing pressure receiving surface 22. Therefore, since the diameter of the control piston 18 can be increased in this manner, the manufacture of the control piston 18 becomes relatively easy, and accordingly, highly accurate manufacture can be realized.

However, in such a conceivable configuration,
An electromagnetic proportional pressure-reducing valve 50 having a high component cost and a control device for controlling the drive of the electromagnetic proportional pressure-reducing valve 50 are required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned situation in the prior art, and has as its object to prevent an increase in the size of a spring for urging a control spool included in a regulator, and to provide an electromagnetic proportional pressure reducing valve. It is an object of the present invention to provide a hydraulic pump control device capable of realizing appropriate horsepower control without providing a hydraulic pump.

[0023]

Means for Solving the Problems In order to achieve this object, an invention according to claim 1 of the present invention is provided in a construction machine, and is involved in a prime mover and driven by the prime mover to perform a predetermined operation. A main pump composed of a variable displacement hydraulic pump for supplying pressure oil for operating the operation actuator, and a sub pump composed of a fixed displacement hydraulic pump,
A control actuator for controlling the tilt amount of the main pump, a control spool for controlling the control actuator, pressure oil discharged from the main pump, and pressure oil discharged from the sub-pump, A first control piston for switching and driving the control spool, and a first pressure receiving surface for the main pump for receiving the pressure of the pressure oil discharged from the main pump of the control piston.
A control device for a hydraulic pump, comprising: a pressure chamber; and a regulator including a second pressure chamber in which a pressure-reducing pressure-receiving surface for receiving a pressure of hydraulic oil discharged from the sub-pump of the control piston is disposed. A first conduit connecting the main pressure line and the second pressure chamber, which guides the pressure oil discharged from the actuator to the operation actuator, and a first conduit provided separately from the first pressure line, the second pressure chamber and the tank. Second to contact
And a first throttle provided in the first pipe, and a second throttle provided in the second pipe.

According to the first aspect of the present invention, as described above, the first pipe connecting the main pipe of the sub-pump and the second pressure chamber is provided with the first throttle, and the second pressure chamber and the tank are provided. Since the second throttle is provided in the second conduit communicating with the sub-pump, when the corresponding operating actuator is driven by the pressure oil from the sub-pump, the pressure oil of the sub-pump passes through the first conduit and the first throttle described above. To the second pressure chamber, and the pressure oil in the second pressure chamber is released to the tank via the second pressure chamber and the second throttle. As a result, the second pressure chamber is maintained at a pressure lower than the discharge pressure of the sub-pump and higher than the tank pressure, that is, a so-called intermediate pressure. Even when a spring having the same shape and dimensions as those in the prior art shown in FIG. The diameter of the control piston for moving the control spool can be set to be larger than that of the prior art shown in FIG. Further, there is no need for an electromagnetic proportional pressure reducing valve or a control device for controlling the driving of such an electromagnetic proportional pressure reducing valve, and the electromagnetic pressure is generated by the above-described intermediate pressure generated by the first and second throttles having a relatively simple structure. Appropriate horsepower control can be realized in the same manner as when the proportional pressure reducing valve is provided.

In the invention according to the above-described claim 1, the control actuator includes a piston having a large-diameter piston portion forming a large-diameter chamber and a small-diameter piston portion forming a small-diameter chamber, and is driven by a prime mover. Alternatively, a pilot pump may be provided which constantly supplies pilot pressure to the small diameter chamber of the control actuator and selectively supplies pilot pressure to the large diameter chamber of the control actuator via the control spool.

Further, each of the above-described configurations may be applied to, for example, a hydraulic shovel.

[0027]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a hydraulic pump control apparatus according to an embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram showing one embodiment of the present invention. FIG. 1 is drawn corresponding to FIG. 2 described above. Therefore,
The same reference numerals as those shown in FIG. 2 indicate the same members and devices.

That is, this embodiment shown in FIG. 1 is also provided in a hydraulic excavator such as a small turning hydraulic excavator, for example, and includes a motor 1 and three hydraulic pumps driven by the motor 1, that is, a variable displacement type hydraulic pump. The main pump 2 includes a hydraulic pump, a sub pump 14 including a fixed displacement hydraulic pump, and a pilot pump 12. Among these three hydraulic pumps, the main pump 2 and the sub-pump 14 supply pressure oil to an operation actuator (not shown) which is involved in the work performed by the hydraulic shovel and may cause a change in load pressure. The pilot pump 12 supplies a pilot pressure to an operation system that switches a directional control valve (not shown) that controls the above-described operation actuator, or supplies a pilot pressure to a regulator 16 via a pilot line 13. Therefore, the horsepower of pilot pump 12 is always constant. The horsepower reduction control targeted by the present embodiment is to prevent the sum of the horsepower of the main pump 2 and the horsepower of the sub pump 14 from exceeding a value obtained by subtracting the horsepower of the pilot pump 12 from the horsepower of the prime mover 1.

The main pump 2 supplies, via the main pipeline 4, pressure oil for operating an operation actuator such as a boom cylinder or an arm cylinder, which increases a load pressure involved in the main work of the hydraulic excavator, for example, the excavation work. I do. Although the sub-pump 14 is involved in the work performed by the hydraulic excavator, it is rather provided additionally, and the sub-pump 14 has a lower load pressure than the operation actuator such as the boom cylinder described above. Pressure oil for operating an actuator for operation such as
5 to be supplied. In addition, the pilot pump 12
(1/7) to (1) much smaller than the pressure of the pressure oil discharged from the main pump 2 and the sub pump 14 described above.
/ 10) is output.

The tilt control mechanism 11 for changing the tilt amount of the main pump 2 described above, a link 10 connected to the tilt control mechanism 11, and a control actuator 5 for moving the link 10 are provided. ing. The control actuator 5 includes a cylinder 6 and a piston 7 slidable in the cylinder 6. The piston 7 has a large-diameter piston portion 7 slidable in the large-diameter hole 6A of the cylinder 6.
A and a small-diameter piston portion 7B slidable in a small-diameter hole 6B of the cylinder 6. A large-diameter chamber 8 is formed by the large-diameter hole 6A of the cylinder 6 and the large-diameter piston portion 7A of the piston 7, and a small-diameter chamber 9 is formed by the small-diameter hole 6B of the cylinder 6 and the small-diameter piston portion 7B of the piston 7. It is.

The small-diameter chamber 9 of the control actuator 5
Is connected to a pilot pump 12 via a pipe 13, and the small-diameter chamber 9 is always supplied with a pilot pressure discharged from the pilot pump 12. The large-diameter chamber 8 of the control actuator 5 is selectively connected to one of the pilot line 13 and the tank 3 via a control spool 25.

The control spool 25 is urged leftward in FIG. 1 by a spring 26 and is switched by a control piston 18 slidable in the casing 17. The casing 17 includes a first pressure chamber 21 and a second pressure chamber 24.
And The first pressure chamber 21 is connected to the main pump 2 via the main pipe 4 and the branch pipe 20, and the first pressure chamber 21 is supplied with pressure oil discharged from the main pump 2. The second pressure chamber 24 is supplied with pressurized oil discharged from the sub-pump 14 via the main pipe 15 and the pipe 23.

The above-mentioned control piston 18 is formed of a single structure having a stepped portion, and a main pump pressure receiving surface 19 for receiving the discharge pressure of the main pump 2, that is, the self-pressure, is formed in the stepped portion. The main pump pressure receiving surface 19 is disposed in the first pressure chamber 21 of the casing 17. At the end of the control piston 18, a pressure-reducing surface 22 for reducing horsepower that receives the pressure of the sub-pump 14 is formed. The pressure-receiving surface 22 for reducing horsepower is disposed in the second pressure chamber 24 of the casing 17. It is.

The control spool 25 and the spring 26
The casing 16, the control piston 18, and the control actuator 5 including the piston 7 constitute a regulator 16 that controls the tilt amount of the main pump 2.

The above configuration is almost the same as the prior art shown in FIG. In the present embodiment, the diameter of the shaft forming the pressure-reducing surface 22 for reducing horsepower of the control piston 18 is set to be larger than the diameter of the shaft shown in FIG. I have. Accordingly, for example, the diameter of the shaft portion forming the main pump pressure receiving surface 19 of the control piston 18 is also set to be larger than the diameter of the corresponding shaft portion shown in FIG. 2 described above.

In this embodiment, the sub-pump 1
A pipe 15 for guiding the pressure oil discharged from the cylinder 4 to an operation actuator such as a cylinder for the earth-discharge plate;
A pipe 102 connecting the second pressure chamber 24 and the tank 3 separately from a pipe 23 (first pipe) connecting the pressure chamber 24.
That is, a second conduit is provided. And the above-mentioned pipeline 2
3 is provided with a first throttle 100, and the above-mentioned conduit 102 is provided with a second throttle 101.

The operation of the present embodiment configured as described above is as follows. The control by driving only the main pump 2 is the same as that described with reference to FIG. 2, but will be described once again. That is, although the prime mover 1 is in the driving state and the operating actuator such as the boom cylinder is driven by the pressure oil discharged from the main pump 2, the sub pump 14
In a state in which another operating actuator such as a cylinder for the earth discharging plate driven by the pressure oil discharged from the cylinder is stopped and held, the main line is maintained so as to maintain the relationship of the characteristic line A1 in FIG. The discharge pressure P and the discharge flow rate Q of the pump 2 are controlled.

For example, when the load pressure of the operating actuator driven by the pressure oil discharged from the main pump 2 is relatively low, the discharge pressure P of the main pump 2 is correspondingly low. Thus, the main line 4, the branch line 20
When the pressure supplied to the first pressure chamber 21 of the casing 17 of the regulator 16 via the
When the force due to the pressure applied to the main pump pressure receiving surface 19 of the control piston 18 is smaller than the force of No. 6,
The control spool 25 moves to the left in FIG. 1 by the force of the spring 26, whereby the large-diameter chamber 8 of the control actuator 5 and the tank 3 communicate with each other, and the large-diameter chamber 8 and the pilot line 1
3 is cut off. At this time, since the pressure oil discharged from the pilot pump 12 is supplied to the small-diameter chamber 9 of the control actuator 5, the piston 7 of the control actuator 5 moves in the left direction of FIG. Movement, tilt control mechanism 1 via link 10
1 moves in the direction of arrow D. As a result, the discharge flow rate Q of the main pump 2 is maintained at a large discharge flow rate Q, as exemplified by the characteristic line A1 in FIG. Accordingly, a relatively large flow rate is supplied to the operation actuator such as the boom cylinder via the main pipeline 4.

On the contrary, when the load pressure of the operating actuator driven by the pressure oil discharged from the main pump 2 is high, the discharge pressure of the main pump 2 also increases accordingly. Accordingly, the force corresponding to the pressure applied to the main pump pressure receiving surface portion 19 of the control piston 18 becomes larger than the force of the spring 26, and the control spool 25 is moved in the right direction of FIG. The large-diameter chamber 8 of the cylinder 6 of the control actuator 5 moves and communicates with the pilot line 13, so that the large-diameter chamber 8 and the tank 3 are shut off. Thus, the pressure oil discharged from the pilot pump 12 is supplied to both the large-diameter chamber 8 and the small-diameter chamber 9 of the control actuator 5. At this time,
Due to the area difference between the large-diameter piston portion 7A and the small-diameter piston portion 7B of the piston 7 of the control actuator 5, the control actuator 5 moves rightward in FIG. 11 moves in the direction of arrow C, and the discharge flow rate Q of the main pump 2 decreases. The pump input torque T obtained during this period is the same as that of FIG.
The characteristic is indicated by the characteristic line A3. The operation described above is the same as that described with reference to FIG.

In this embodiment, in particular, when the operating actuator such as the earthing plate cylinder on the sub-pump 14 is also driven together with the driving of the operating actuator on the main pump 2 side, the discharge from the sub-pump 14 is performed. The discharge pressure of the sub-pump 14 increases according to the load pressure of the operating actuator driven by the pressurized oil, and the increased discharge pressure causes the main line 15, the line 23 (the first line), and the first throttle 100 to move. The pressure is supplied to the second pressure chamber 24 of the casing 17 via the second pressure chamber 24. Further, the pressure oil in the second pressure chamber 24 is released to the tank 3 via the pipe 102 (second pipe) and the second throttle 101. Therefore, in the second pressure chamber 24,
A pressure created by the first throttle 100 and the second throttle 101, that is, a pressure between the discharge pressure of the sub-pump 14 and the tank pressure, a so-called intermediate pressure, is generated. The amount of movement provided to the pressure receiving surface 22 to move the control piston 18 to the right in FIG. The spool 25 for control and the piston 7 of the control actuator 5 tend to move in the direction A in FIG. 1, and accordingly, the tilt control mechanism 11 tends to move in the direction C via the link 10, and the main pump 2, the discharge flow rate Q tends to decrease. The characteristic line A of FIG.
2 shows the characteristic at this time. Further, as the discharge flow rate Q of the main pump 2 changes in this manner, the input torque T of the main pump 2 also decreases as indicated by the characteristic line A4 in FIG. 4B.

As described above, the operation actuator (not shown) driven by the main pump 2 and the sub-pump 1
By changing the discharge pressure P-discharge flow rate Q characteristic of the main pump 2 and the discharge pressure P-pump input torque T characteristic of the main pump 2 according to a combined operation with an operation actuator (not shown) driven by the control unit 4, The total pump input torque of the main pump 2 and the sub pump 14 is
Horsepower control is performed so as not to exceed a value obtained by subtracting the input torque of the pilot pump 12 from the output torque T of the prime mover 1.

In the present embodiment configured as described above, the first throttle 100 is provided in the conduit 23 as described above,
Since the second restrictor 101 is provided in the pipe 102, when the corresponding operating actuator is driven by the pressure oil from the sub-pump 14, the pressure generated in the second pressure chamber 24 of the casing 17 is lower than the discharge pressure of the sub-pump 14. It is small and is maintained at an intermediate pressure greater than the tank pressure. Therefore, even when a spring having the same shape and size as that of the prior art shown in FIG. 2 is provided, the horsepower control can be properly performed by setting the diameter of the control piston 18 to be relatively large. In addition, although the first throttle 100 and the second throttle 101 are provided, it is not necessary to provide the electromagnetic proportional pressure reducing valve as described with reference to FIG. 3 and a control device for controlling such an electromagnetic proportional pressure reducing valve.

As described above, according to the present embodiment, since the diameter of the control piston 18 can be made relatively large, the manufacture of the control piston 18 becomes easy, and the control piston 18 is inserted. Drilling of the casing 17 to be performed is facilitated, and accordingly, high-precision manufacturing can be realized. In addition, the first structure has a simple structure and relatively low unit cost.
It suffices to provide the diaphragm 100 and the second diaphragm 101, that is, it is not necessary to provide an expensive electromagnetic proportional pressure reducing valve and its control device as described with reference to FIG. 3 described above, thereby reducing the manufacturing cost. Can be.

Although FIG. 1 shows the first diaphragm 100 and the second diaphragm 101 as fixed diaphragms, the present invention is not limited to the first diaphragm 100 and the second diaphragm 101 being fixed diaphragms. Instead, a variable aperture may be used.
In the case where the variable throttle is set as described above, the pump control reduced horsepower change amount of the characteristic line A1-A2 in FIG.
The pump input torque change amount on the characteristic line A3-A4 in FIG. 4B can be changed as appropriate.

Although only one main pump 2 is shown in FIG. 1, a plurality of, for example, two main pumps 2 may be provided. When two main pumps 2 are provided in this manner, a configuration may be employed in which separate operating actuators are operated by the respective pressure oils of the main pumps 2, and the two main pumps 2 are joined by combining the pressure oils. The configuration may be such that one operation actuator is operated.

[0046]

As described above, according to the present invention, the spring for biasing the control spool included in the regulator is not enlarged, and the electromagnetic proportionality is reduced. Appropriate horsepower control can be realized without providing a pressure reducing valve, that is, a pressure smaller than the discharge pressure of the sub-pump is generated by the first and second throttles, and this small pressure is reduced by the control piston for moving the control spool. Because it is applied to the horsepower pressure receiving surface, proper horsepower control can be realized even if the diameter of the control piston is set to a relatively large size. The drilling of the casing into which the piston is inserted is facilitated, and high-precision manufacturing can be realized.In addition, an expensive electromagnetic proportional pressure reducing valve and its control device must be provided. Without first diaphragm cheap comparatively component unit cost structure is simple, it is possible to reduce the manufacturing cost as compared with the conventional so need by providing the second aperture.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing one embodiment of a control device for a hydraulic pump of the present invention.

FIG. 2 is a hydraulic circuit diagram showing an example of a conventional hydraulic pump control device.

3 is a main part circuit diagram showing a configuration conceivable for preventing an increase in the size of a spring, which is a problem in the conventional hydraulic pump control device shown in FIG.

4 is a diagram showing a discharge pressure-discharge flow rate characteristic and a discharge pressure-pump input torque characteristic of a main pump composed of a variable displacement hydraulic pump obtained by the conventional hydraulic pump control device shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 prime mover 2 main pump (variable displacement hydraulic pump) 3 tank 4 main pipeline 5 control actuator 6 cylinder 6A large diameter hole 6B small diameter hole 7 piston 7A large diameter piston part 7B small diameter piston part 8 large diameter chamber 9 small diameter chamber 10 link DESCRIPTION OF SYMBOLS 11 Tilt control mechanism 12 Pilot pump 13 Pilot line 14 Sub pump (fixed displacement hydraulic pump) 15 Main line 16 Regulator 17 Casing 18 Control piston 19 Main pump receiving surface 20 Branch line 21 First pressure chamber 22 Reduced horsepower Pressure receiving surface 23 pipeline (first pipeline) 24 second pressure chamber 25 control spool 26 spring 100 first throttle 101 second throttle 102 pipeline (second pipeline)

Continued on the front page (72) Inventor Yukihiro Motozawa 650, Kandate-cho, Tsuchiura-shi, Ibaraki Prefecture Inside the Tsuchiura Plant of Hitachi Construction Machinery Co., Ltd. in the factory

Claims (3)

[Claims] 1. A main pump comprising a prime mover and a variable displacement hydraulic pump which is provided in a construction machine, and which is driven by the prime mover and supplies pressure oil for operating an operation actuator involved in performing a predetermined operation. A sub-pump comprising a fixed displacement hydraulic pump; a control actuator for controlling the tilt amount of the main pump; a control spool for controlling the control actuator; pressure oil discharged from the main pump; and discharge from the sub-pump. A control piston for switching and driving the control spool in accordance with each of the pressure oils to be supplied, and a main pump pressure receiving surface for receiving the pressure of the pressure oil discharged from the main pump of the control piston.
A hydraulic pump control device comprising: a pressure chamber; and a regulator including a second pressure chamber in which a pressure-reducing surface for reducing horsepower that receives the pressure of pressure oil discharged from the sub-pump of the control piston is disposed. A first conduit for connecting the main conduit for guiding the pressure oil discharged from the actuator to the operating actuator and the second pressure chamber; provided separately from the first conduit, the second pressure chamber and the tank; A control device for a hydraulic pump, comprising: a second conduit that communicates with the first conduit; a first restrictor provided in the first conduit; and a second restrictor disposed in the second conduit. 2. The control actuator according to claim 1, further comprising a piston including a large-diameter piston portion forming a large-diameter chamber and a small-diameter piston portion forming a small-diameter chamber, and driven by the prime mover. 2. The pilot pump according to claim 1, further comprising a pilot pump that supplies a pilot pressure to the small diameter chamber and selectively supplies a pilot pressure to the large diameter chamber of the control actuator via the control spool. Control device for hydraulic pump. 3. The hydraulic pump control device according to claim 1, wherein the construction machine is a hydraulic shovel.