JP2002317771A - Hydraulic pump control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic pump control device offering simple and inexpensive construction permitting easy change into mechanical control even when an electric system is in trouble. SOLUTION: The hydraulic pump control device comprises a first pilot line 24 and a second pilot line 25 formed and a shuttle valve 26 provided therebetween. The shuttle valve 26 selects higher one of a pressure P1 in the first pilot line 24 and a pressure P2 in the second pilot line 25. The output of the shuttle valve 26 is guided to a flow control cylinder 28. The pressure P2 in the second pilot line 25 is guided to a horse power control cylinder 29. The pressure P1 is used as a pilot pressure in a normal condition, and the pressure P2 is used as the pilot pressure when the electric system is malfunctioned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling a discharge flow rate of a hydraulic pump employed in, for example, a construction machine.

[0002]

[Problems to be solved by the prior art and the invention] (1)
2. Description of the Related Art A hydraulic device is widely used as a drive source for driving a work attachment or traveling a construction machine or the like (hereinafter referred to as “the machine”) itself in a construction machine or the like. As such, a hydraulic pump driven by an engine mounted on the machine has been adopted.

[0003] Depending on the contents of work by the machine, it is necessary to adjust the discharge flow rate from the hydraulic pump, and therefore,
Generally, this machine is provided with a function of adjusting the flow rate of a hydraulic pump (this is called "flow rate control"). Also, the discharge pressure of the hydraulic pump varies according to the load. The power required to drive the hydraulic pump is proportional to the product of the discharge pressure and the discharge flow rate. Therefore, when the hydraulic pump is driven by the engine mounted on this machine,
It is necessary to control the discharge flow rate of the hydraulic pump so that the power required to drive the hydraulic pump does not exceed the maximum output of the engine of this machine (this is called "horsepower control").

Normally, this machine is equipped with a hydraulic pump control device for performing such flow control and horsepower control, whereby a required flow of hydraulic oil is supplied within the maximum output range of the engine. It has become.

[0005] Such control is generally performed electrically using an electromagnetic valve or the like, so that if a failure occurs in the electric system, the control becomes impossible. In order to cope with such an emergency, a means for switching from electrical control to mechanical control is taken (Japanese Patent Laid-Open No. 10-2810).
No. 73).

(2) FIG. 5 shows a configuration of a conventional hydraulic pump control device for performing such control.

As shown in FIG. 1, the hydraulic pump control device 1 controls the discharge flow rate by changing the tilt angle of a swash plate of a hydraulic pump (swash plate pump) 2 by a servo cylinder 3. ing. This servo cylinder 3
Is always the pilot pressure (secondary pressure of the electromagnetic proportional valve 4) supplied by the electromagnetic proportional valve 4 as described later.
When the electrical system that controls the electromagnetic proportional valve 4 fails, the redundant valve 5 can be operated to switch from electrical control to mechanical control (hydraulic control). .

More specifically, the redundant valve 5 is normally set to the mode shown in FIG. An external pressure Psv (constant pressure guided from the main unit side) is guided to the primary side of the electromagnetic proportional valve 4, and the external pressure Psv is output as a secondary pressure by operating a solenoid of the electromagnetic proportional valve 4. Is done. here,
The solenoid of the proportional solenoid valve 4 is operated by an electric signal output from a solenoid valve controller 6 provided in the control device 1. The solenoid valve controller 6 requires that the hydraulic pump 2 be operated within the maximum output range of the engine of the machine. An output signal is transmitted so that a high flow rate of pressure oil can be supplied. Then, the secondary pressure is guided to the flow control cylinder 7, whereby the servo switching valve 8 is driven. As a result, the servo cylinder 3 is driven and the discharge flow rate of the hydraulic pump 2 is adjusted.

Reference numeral 9 denotes a horsepower control cylinder, and a pump pressure is guided to the horsepower control cylinder 9 as shown in the figure. However, the horsepower control cylinder 9
Is provided with a spring 10 and a horsepower control cylinder 9
Are operated against the spring force of the spring 10. Since this spring force is set to be extremely large (set in advance so), the operation of the horsepower control cylinder 9 is restricted, and the horsepower control cylinder 9 cannot control the horsepower of the hydraulic pump 2. I have. However, even in this case, as described above, appropriate control of the discharge flow rate is performed by the flow rate control cylinder 7. That is, the hydraulic pump control device 1 performs the flow control and the horsepower control of the hydraulic pump 2 at the same time by the electromagnetic operation (electric control) of the electromagnetic proportional valve 4.

(3) If a failure occurs in the electric system of the hydraulic pump control device 1 and the operation of the electromagnetic proportional valve 4 becomes impossible, the engine of the machine is stopped or substantially stopped. The operation with this machine becomes impossible. The reason is as follows.

First, when the hydraulic pump control device 1 performs so-called negative control, no horsepower control can be performed at all because the operation of the horsepower control cylinder 9 is restricted. Restrictions do not work. Therefore, when the discharge flow rate increases, the required power for driving the hydraulic pump 2 exceeds the maximum output of the engine of the present invention, and as a result, the engine of the present engine stops.

On the other hand, when the hydraulic pump control device 1 performs so-called positive control, the operation of the horsepower control cylinder 9 is restricted, so that the maximum horsepower is limited and the discharge flow rate does not increase. as a result,
Work with the machine becomes practically impossible.

(4) In order to solve such a problem, the above-mentioned redundant valve 5 is provided, and by operating this,
The hydraulic pump control device 1 performs the following control.

First, the redundant valve 5 is switched, and the external pilot pressure Pn is led to this. As the external pilot pressure Pn, for example, an operating pressure of an actuator for driving the attachment is employed.

By doing so, the external pilot pressure Pn
Can drive the flow control cylinder 7, and the external pilot pressure Pn uses the operating pressure of the actuator that is actually driven.
Just guiding n to the flow control cylinder 7 as it is enables appropriate flow control.

Since the external pilot pressure Psv is guided to the horsepower control cylinder 9, the horsepower control cylinder 9
Driven by the pump pressure and the external pilot pressure Psv (the prerequisite for this is that the spring force of the spring 10 is set to be higher than the force generated by the pump pressure and lower than the force generated by the sum of the pump pressure and the external pilot pressure Psv). Keep it). As a result, appropriate horsepower control becomes possible.

That is, by switching the redundant valve 5, the electric control can be changed to the hydraulic control, and even if a failure occurs in the electric system, the operation by the machine can be continued.

(5) However, the redundant valve 5 is a kind of directional switching valve, and has a port and a spool for switching directions. Therefore, when the redundant valve 5 is incorporated in the hydraulic pump control device 1, the structure of the hydraulic pump control device 1 becomes extremely complicated, and the cost increases.

Therefore, an object of the present invention is to provide a simple and inexpensive structure that can easily switch to mechanical control to control the flow rate of a hydraulic pump even when a failure occurs in an electric system. It is to provide a hydraulic pump control device.

[0020]

Means for Solving the Problems (1) In order to achieve the above object, a hydraulic pump control device according to the present application comprises: a servo cylinder connected to a hydraulic pump for changing a tilt angle of the hydraulic pump; A servo switching valve having a servo spool connected to a cylinder and a drive cylinder for driving the same, and an electromagnetic proportional valve that guides a predetermined secondary pressure to the drive cylinder by using one external pilot pressure as a primary pressure, The drive cylinder includes a flow control cylinder that adjusts a discharge flow rate required for the hydraulic pump, and a horsepower control cylinder that adjusts a discharge flow rate of the hydraulic pump to suppress power for driving the hydraulic pump within a certain range. Provided, the flow control cylinder includes a high-pressure priority type shuttle valve that selects any one of the high pressure side of the secondary pressure of the electromagnetic proportional valve and another external pilot pressure. The horsepower control cylinder is connected to the secondary side of the electromagnetic proportional valve via the external pilot pressure and the discharge pressure of the hydraulic pump, and is set to operate against a predetermined spring force. It is characterized by having.

According to this configuration, the discharge flow rate of the hydraulic pump is normally adjusted by the following electrical control.
First, a plug is always inserted into a port to which another external pilot pressure is supplied. That is, other external pilot pressures are not always required. Then, one external pilot pressure is supplied to the primary side of the electromagnetic proportional valve, and the secondary pressure is determined based on an electric signal input to the electromagnetic proportional valve. Since this secondary pressure and the other external pilot pressure (in this case, there is substantially no other external pilot pressure) are led to the high-pressure priority shuttle valve, the high-pressure secondary pressure is reduced. Guided to the flow control cylinder.

On the other hand, another external pilot pressure is guided to the horsepower control cylinder. The horsepower control cylinder is operated by another external pilot pressure and the discharge pressure of the hydraulic pump. , The horsepower control cylinder does not operate. However, the discharge flow rate of the hydraulic pump can be controlled by the flow control cylinder including the horsepower control by the electric signal input to the electromagnetic proportional valve.

Next, if a failure occurs in the electric system, an electric signal for operating the electromagnetic proportional valve cannot be output, and the above-described control cannot be performed.
In this case, another external pilot pressure is led to the port where the plug is inserted. At this time, the one external pilot pressure can be used as it is as the other external pilot pressure, or another external hydraulic pressure can be used. Then, the other external pilot pressure is guided to the horsepower control cylinder, and the horsepower control cylinder is operated by the other external pilot pressure and the discharge pressure of the hydraulic pump. That is, horsepower control can be performed by the other external pilot pressure and the discharge pressure of the hydraulic pump.

On the other hand, at this time, the secondary pressure of the electromagnetic proportional valve and the other external pilot pressure are led to the high-pressure priority type shuttle valve, but the function of the electromagnetic proportional valve is stopped due to a failure in the electric system. Therefore, the other external pilot pressure is preferentially guided to the flow control cylinder. Thus, the flow control cylinder operates to determine the discharge flow rate of the hydraulic pump. At this time, even if the maximum flow rate is set by the flow control cylinder, the horsepower control by the horsepower control cylinder is performed as described above. Therefore, no inconvenience occurs.

(2) A mode in which a required external oil pressure is guided to the primary side of the electromagnetic proportional valve as the one external pilot pressure, and a mode in which the required external oil pressure is guided to the shuttle valve as the other pilot pressure. And a switching valve for switching to the above. If this switching valve is provided, the switching valve is switched when a failure occurs in the electric system, so that the one external pilot pressure can be directly used as another pilot pressure. The switching valve can be easily operated by adopting an electromagnetic switching valve and providing a dedicated independent electric system for electromagnetically operating the switching valve.

Further, the other external pilot pressure may be supplied by a bypass line in which the one external pilot pressure is bypassed, and a stop valve may be provided in the bypass line. With this configuration, by opening and closing the stop valve, one external pilot pressure is always supplied to the primary side of the electromagnetic proportional valve, and when the electric system fails, the one external pilot pressure is bypassed and the other external pilot pressure is bypassed. Can be used as external pilot pressure.

(3) In order to achieve the above object, a hydraulic pump control device according to the present invention includes a servo cylinder connected to a hydraulic pump for changing a tilt angle of the hydraulic pump, and a servo cylinder connected to the servo cylinder. A servo switching valve having a servo spool and a drive cylinder for driving the same, and an electromagnetic proportional valve for setting a first external pilot pressure as a primary pressure and guiding a predetermined secondary pressure to the drive cylinder. Comprises a flow control cylinder that adjusts the discharge flow rate required for the hydraulic pump, and a horsepower control cylinder that adjusts the discharge flow rate of the hydraulic pump to suppress the power for driving the hydraulic pump within a certain range. The flow control cylinder is controlled via a high-pressure priority type shuttle valve that selects one of the secondary pressure of the electromagnetic proportional valve and the second external pilot pressure. The horsepower control cylinder is connected to the secondary side of the electromagnetic proportional valve, and is set to operate against a predetermined spring force by the third external pilot pressure and the discharge pressure of the hydraulic pump. It is characterized by the following.

According to this configuration, the discharge flow rate of the hydraulic pump is normally adjusted by the following electrical control.
First, a plug is always inserted into a port to which the second and third external pilot pressures are supplied. That is, these external pilot pressures are not always required. Then, the first external pilot pressure is supplied to the primary side of the electromagnetic proportional valve, and the secondary pressure is determined based on an electric signal input to the electromagnetic proportional valve. Since the secondary pressure and the second external pilot pressure (in this case, the second external pilot pressure does not substantially exist) are led to the high-pressure priority type shuttle valve, the high-pressure secondary Pressure is directed to the flow control cylinder.

On the other hand, the third external pilot pressure (the pressure does not substantially exist like the second external pilot pressure) is guided to the horsepower control cylinder. However, since the third external pilot pressure is substantially absent, the horsepower control cylinder does not operate. However, the discharge flow rate of the hydraulic pump can be controlled by the flow control cylinder including the horsepower control by the electric signal input to the electromagnetic proportional valve.

Next, if a failure occurs in the electric system, an electric signal for operating the proportional solenoid valve cannot be output, and the above-described control cannot be performed.
In this case, the second and third external pilot pressures are led to each port where the plug is inserted. At this time, the first external pilot pressure can be directly used as the third external pilot pressure, or another external hydraulic pressure can be used. The third external pilot pressure is guided to the horsepower control cylinder, and the horsepower control cylinder is operated by the third external pilot pressure and the discharge pressure of the hydraulic pump. That is, the horsepower control can be performed by the third external pilot pressure and the discharge pressure of the hydraulic pump.

On the other hand, at this time, the secondary pressure of the electromagnetic proportional valve and the second external pilot pressure are led to the high-pressure priority type shuttle valve, but the function of the electromagnetic proportional valve is stopped due to a failure in the electric system. Therefore, the second external pilot pressure is preferentially guided to the flow control cylinder. Thus, the flow control cylinder operates to determine the discharge flow rate of the hydraulic pump. At this time, even if the maximum flow rate is set by the flow control cylinder, the horsepower control by the horsepower control cylinder is performed as described above. For,
No inconvenience occurs.

[0032]

Embodiments of the present invention will be described below. <First Embodiment> FIG. 1 is a hydraulic system diagram showing a configuration of a hydraulic pump control device according to a first embodiment of the present invention.

The hydraulic pump control device 20 is mounted on a construction machine or the like (the machine) and controls the discharge flow rate of a hydraulic pump 21 driven by the engine of the machine. As described above, the discharge flow rate control includes the flow rate control (control of the discharge flow rate necessary for operating a work attachment attached to the machine) and the horsepower control (power required to drive the hydraulic pump 21). Control of the discharge flow rate to keep the engine output below the maximum output of the engine. A specific control method will be described later.

The hydraulic pump control device 20 includes the hydraulic pump 2
1; a servo switching valve 23 for driving the servo cylinder 22; a first pilot line 24 and a second pilot line 25 for supplying pilot pressure to the servo switching valve 23; A high-pressure priority type shuttle valve (hereinafter simply referred to as “shuttle valve”) connected to the first and second pilot lines 24 and 25.
26, and an electromagnetic proportional valve 27 provided in the first pilot line 24.

The feature of this embodiment is that the first pilot line 24 and the second pilot line 2
5 is connected, the secondary pressure of the electromagnetic proportional valve 27 supplied from the first pilot line and the second
Among the external pressures (other external pilot pressures) guided from the pilot line 25, a high pressure one is automatically selected and guided to the flow control cylinder 28 of the servo switching valve 23. That is, the servo control valve 23 is guided to the horsepower control cylinder 29 through the servo switching valve 23.

With this structure, the servo switching valve 23 is driven by the pressure selected by the shuttle valve 26, but the secondary pressure (the pressure of the first pilot line 24 ) Is electrically controlled, and the discharge flow rate of the hydraulic pump 21 is controlled by the controlled secondary pressure (flow rate control). If an abnormality occurs in the electric system, the second pilot line 25 can be easily controlled. The pressure can be selected and used for controlling the discharge flow rate of the hydraulic pump 21 (horsepower control).

The hydraulic pump 21 is a swash plate pump provided with a swash plate 30, and the discharge flow rate is changed by changing the tilt angle of the swash plate 30. As the hydraulic pump 21, a commonly used known pump can be employed.

The servo cylinder 22 includes a servo piston 31
The servo piston 31 is provided with the hydraulic pump 2
It is connected to one swash plate 30. Therefore, when the servo piston 31 is operated, the tilt angle of the swash plate 30 changes, and the discharge flow rate changes. The servo cylinder 23 may be a known one.

The servo switching valve 23 includes a servo spool 32
And a flow control cylinder 28 and a horsepower control cylinder 29 for driving the same. The servo spool 32 is mechanically connected to the servo piston 31. When the servo spool 32 is driven, the angle of the swash plate 30 of the hydraulic pump 21 can be changed via the servo piston 31. I have. The servo spool 32 is driven by the flow control cylinder 28 and the horsepower control cylinder 29.

The flow control cylinder 28 and the horsepower control cylinder 29 are common in that they both control the discharge flow rate of the hydraulic pump 21, but have different standards for their control. That is, the flow control cylinder 28 controls the discharge flow rate of the hydraulic pump 21 in order to achieve the flow rate required for the operation by the machine, whereas the horsepower control cylinder 29 controls the power required for driving the hydraulic pump 21. Hydraulic pump 2 so that is within the maximum output range of the engine of this machine.
1 controls the discharge flow rate.

As described above, the pressure selected by the shuttle valve 26 is guided to the flow control cylinder 28, and the pressure of the second pilot line 25 and the pump pressure of the hydraulic pump 21 are guided to the horsepower control cylinder 29. Has been.

The flow control cylinder 28 and the horsepower control cylinder 29 are provided with springs 33 and 34, respectively. Each of the cylinders 28 and 29 operates against the spring force of the springs 33 and 34. It has become. Therefore, even if the pilot pressure is guided to each of the cylinders 28 and 29 as described above, if the force for operating each of the cylinders 28 and 29 is smaller than the spring force of each of the springs 33 and 34, 28 and 29 do not work. In the present embodiment, the spring force of the spring 34 is set to be very strong, and this spring force is greater than the force of the hydraulic pump 21 due to the pump pressure, and the pressure of the second pilot line 25 and the pump force of the hydraulic pump 21 It is set smaller than the pressure force.

Next, the electromagnetic proportional valve 27 and the shuttle valve 2
6 will be described. In this embodiment, the electromagnetic proportional valve 27 and the shuttle valve 26 are configured as one hydraulic unit 40 together with the piping of the first pilot line 24 and the second pilot line 25. That is, the first pilot line 24 and the second pilot line 25 are processed and piped on the single base block 35, and the electromagnetic proportional valve 27 is arranged in series with the first pilot line 24. The secondary side of the electromagnetic proportional valve 27 and the second pilot line 25 are connected to the shuttle valve 2.
6 is connected. This shuttle valve 26 is also incorporated in the base block 35.

In the base block 35, a first input port 36 and a second input port 37, and a first output port 38 and a second output port 39 are formed.
The first input port 36 forms an inlet of the first pilot line 24 and is connected to the primary side of the proportional solenoid valve 27.
In the present embodiment, a constant external pressure (one external pilot pressure) P <b> 1 is guided to the first input port 36. The secondary side of the electromagnetic proportional valve 27 is connected to the shuttle valve 26 via the first pilot line 24 as described above.

The second input port 37 constitutes the entrance of the second pilot line 25, and the second pilot line 25 is connected to the shuttle valve 26 as described above. In the present embodiment, a constant external pressure (other external pilot pressure) P2 is also guided to the second input port 37.

The first output port 38 communicates with the second pilot line 25 and is connected to the horsepower control cylinder 29. The second output port 39 communicates with the output side of the shuttle valve 26 and is connected to the flow control cylinder 28.

The solenoid proportional valve 27 is controlled by a solenoid valve controller (not shown) provided on the machine side, and the spool operates based on a signal output from the solenoid valve controller. It is supposed to.
Therefore, the external oil pressure P1 is input to the electromagnetic proportional valve 27 as a primary pressure, and is output from the secondary side as a secondary pressure subjected to predetermined control.

According to the hydraulic pump control device 20 configured as described above, the following operation and effect can be obtained.

Normally (when there is no abnormality in the electric system), for example, a plug is inserted without using the second input port 37. The external hydraulic pressure P1 is applied to the electromagnetic proportional valve 1
7, and a predetermined secondary pressure is output. The shuttle valve 26 has the secondary pressure and the external hydraulic pressure P
2, the secondary pressure is selected and guided to the flow control cylinder 28 because the external oil pressure P2 does not exist in this case. On the other hand, the external oil pressure P2 is guided to the horsepower control cylinder 29. In this case, the external oil pressure P2 does not exist, and the horsepower control cylinder 29 does not operate only with the pump pressure of the hydraulic pump 21 as described above.

However, the secondary pressure of the electromagnetic proportional valve 27 is
By operating the flow control cylinder 28 including the horsepower control, the discharge flow rate of the hydraulic pump 21 can be appropriately controlled.

Next, if a failure occurs in the electric system, the above-described control cannot be performed. In this case, the plug of the second input port 37 is removed and the external hydraulic pressure P2
Lead. As the external oil pressure P2, a constant pressure piloted from the machine can be used, but the external oil pressure P1 can be used as it is. That is, the external hydraulic pressure P1
The connection between the external hydraulic pressure P1 and the first input port 36 may be disconnected, and the external hydraulic pressure P1 may be connected to the second input port 37.

This external hydraulic pressure P 2 is guided to the horsepower control cylinder 29 via the second pilot line 25. As a result, the horsepower control cylinder 29 is operated by the external oil pressure P2 and the pump pressure of the hydraulic pump 21 to enable horsepower control.

The external hydraulic pressure P2 is guided to the shuttle valve 26, but the function of the electromagnetic proportional valve 27 is stopped due to the failure of the electric system. Therefore, the external hydraulic pressure P2 is guided to the flow control cylinder 28. Thereby, the flow control cylinder 28 operates to perform flow control. At this time, the external oil pressure P2
Is too large, and even if the hydraulic pump 21 is set to the maximum flow rate by the flow control cylinder 28, the horsepower control by the horsepower control cylinder 29 is performed as described above.
Control is performed appropriately.

As described above, in the present embodiment, the discharge flow rate of the hydraulic pump 21 is normally controlled by the electric control by the electromagnetic proportional valve 27. However, in the case where the electric system fails, the electric control becomes impossible. Even if there is, it is possible to control the hydraulically (mechanically) appropriate discharge flow rate using the external hydraulic pressure P2. In addition, since the switching from the electric control to the mechanical control is not performed by using a switching valve (redundant valve) as in the related art, but by the shuttle valve 26, the structure of the hydraulic unit 40 is simplified and the hydraulic pump control device is simplified. 20 can be simplified and the cost can be reduced.

Next, a modified example of this embodiment will be described.

FIG. 2 shows a first modification of the present embodiment, in which an electromagnetic switching valve 41 is provided in the hydraulic pump control device 20. Although not shown, the electromagnetic switching valve 41 has a dedicated electric system for switching the electromagnetic switching valve 41.

In this modification, the first port 36 and the second port 37 are connected to the output port of the electromagnetic switching valve 41. The electromagnetic switching valve 41 switches the mode to output the input external hydraulic pressure P1 to the first input port 36 or the second input port 37. If such an electromagnetic switching valve 41 is employed, even if a failure occurs in the electric system of the hydraulic pump control device 20, switching from the electric control to the hydraulic control can be performed very easily by switching the electromagnetic switching valve 41, so that the hydraulic pump 2
1 can control the discharge flow rate.

Although the electromagnetic switching valve 41 is employed in this modification, a manual switching valve may be employed.

FIG. 3 shows a second modified example of the present embodiment, in which a bypass line 42 is provided in the hydraulic pump control device 20 and is connected to a second pilot line 2.
5 and a bypass valve 42 is provided with a stop valve 43. That is, in the present modification, in order to guide the external oil pressure P2, the external oil pressure P1 is bypassed by the bypass line 42, and the bypass is used as the external oil pressure P2.

According to this modification, the stop valve 4 is always
3 is closed to supply the external hydraulic pressure P1 to the electromagnetic proportional valve 27, and when a failure occurs in the electric system, the stop valve 43 is opened and the external hydraulic pressure P1 is directly guided to the horsepower control cylinder 29 to enable horsepower control. . <Second Embodiment> FIG. 4 shows a configuration of a hydraulic pump control device according to a second embodiment of the present invention as a hydraulic system diagram.

The hydraulic pump control device 50 according to the present embodiment
Is different from the hydraulic pump control device 20 according to the first embodiment in that the hydraulic pump control device 20 uses the external hydraulic pressure P2 to control the flow control cylinder 28 when the electric system fails.
And the horsepower control cylinder 29 are driven, whereas in the present embodiment, two external hydraulic pressures P3
The point is that the flow control cylinder 28 and the horsepower control cylinder 29 are separately driven using (second external pilot pressure) and P4 (third external pilot pressure). Note that other configurations are the same as those in the first embodiment, and thus detailed description thereof is omitted.

The hydraulic pump control device 50 according to the present embodiment
Has a base block 35, in which the electromagnetic proportional valve 2
7. A shuttle valve 26 is provided. The base block 35 is provided with a first input port 36, a second input port 44, and a third input port 45. External hydraulic pressure P1 (first external pilot pressure) is applied to first input port 36.
The external hydraulic pressure P3 is guided to the second input port 44, and the external hydraulic pressure P4 is guided to the third input port 45.

A first pilot line 46 leading from the third input port 45 to the first output port 38, a second pilot line 47 connecting the second input port 44 and the shuttle valve 26, and an electromagnetic force from the first input port 36. A third pilot line 48 connected to the shuttle valve 26 via the proportional valve 27 is formed.

The third pilot line 48 and the second pilot line 47 are connected to the shuttle valve 26, and the higher one of the external pressure P 3 and the secondary pressure of the electromagnetic proportional valve 27 is guided to the flow control cylinder 28. It has become.

According to the present embodiment, the discharge flow rate of the hydraulic pump 21 is normally adjusted by the following electrical control. First, plugs are always inserted into the second input port 44 and the third input port 45.

The external oil pressure P1 is supplied to the primary side of the proportional solenoid valve 27 to output a predetermined secondary pressure. This secondary pressure is
It is guided to a flow control cylinder 28 via a shuttle valve 26. On the other hand, the hydraulic pump 21 is
, The horsepower control cylinder does not operate. However, similarly to the first embodiment, the flow rate control cylinder 28 can appropriately control the discharge flow rate of the hydraulic pump 21.

Next, when a failure occurs in the electric system,
Unplug the second input port 44 and the third input port 45, supply the external hydraulic pressure P3 to the second input port 44,
An external oil pressure P4 is supplied to the third input port 45. At this time, as the external hydraulic pressure P4, as in the first embodiment,
The external oil pressure P1 may be used as it is. Also,
As the external oil pressure P3, for example, the operating pressure of an actuator that drives a work attachment mounted on the machine can be adopted.

In this manner, the external hydraulic pressure P4 is guided to the horsepower control cylinder 29, thereby enabling horsepower control. Further, the external hydraulic pressure P3 is guided to the flow control cylinder 28 via the shuttle valve 26, thereby enabling the flow control. Moreover, in the present embodiment, since the operating pressure of the actuator for driving the work attachment is employed as the external oil pressure P3, appropriate flow control according to the operating pressure can be performed.

That is, in this embodiment, the flow control by the flow control cylinder 28 and the horsepower control by the horsepower control cylinder 29 can be performed simultaneously.

As described above, in the present embodiment, similarly to the first embodiment, the discharge flow rate of the hydraulic pump 21 is normally controlled by electric control by the electromagnetic proportional valve 27, but a failure occurs in the electric system. Even if the electrical control becomes impossible due to this, it is possible to control the hydraulically (mechanically) appropriate discharge flow rate using the external hydraulic pressures P3 and P4. In addition, since the switching from the electric control to the mechanical control is not performed by using a switching valve (redundant valve) as in the related art, but by the shuttle valve 26, the structure of the hydraulic unit 40 is simplified and the hydraulic pump control device is simplified. The structure of the whole 50 can be simplified and the cost can be reduced.

[0071]

As described above, in the present invention, the discharge flow rate of the hydraulic pump is normally controlled by the electric control. However, even if the electric system fails and the electric control becomes impossible, The discharge flow rate of the hydraulic pump can be hydraulically (mechanically) appropriately controlled using the pilot pressure from the outside. In addition, the switching from the electric control to the mechanical control is not performed by using a switching valve (redundant valve) as in the related art, but by a high-pressure priority type shuttle valve.
The structure of the entire hydraulic pump control device can be simplified, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 shows a configuration of a hydraulic pump control device according to a first embodiment of the present invention as a hydraulic system diagram.

FIG. 2 is a hydraulic system diagram showing a configuration of a hydraulic pump control device according to a first modification of the first embodiment of the present invention.

FIG. 3 is a hydraulic system diagram showing a configuration of a hydraulic pump control device according to a second modification of the first embodiment of the present invention.

FIG. 4 is a hydraulic system diagram showing a configuration of a hydraulic pump control device according to a second embodiment of the present invention.

FIG. 5 shows a configuration of a conventional hydraulic pump control device as a hydraulic system diagram.

[Explanation of symbols]

 Reference Signs List 20 hydraulic pump control device 21 hydraulic pump 22 servo cylinder 23 servo switching valve 26 shuttle valve 27 electromagnetic proportional valve 28 flow control cylinder 29 horsepower control cylinder 30 swash plate 31 servo piston 32 servo spool 34 spring 42 bypass line 43 stop valve P1 to P4 External hydraulic

Continued on front page F term (reference) 2D003 AB05 BA01 BA07 BB02 CA02 DA03 DB02 3H002 BB06 BC01 BD04 BE08 3H045 AA04 AA10 AA24 AA33 BA41 CA03 DA25 EA33 3H070 AA01 BB04 CC12 CC37 DD52 DD60

Claims (4)

[Claims] A servo cylinder connected to the hydraulic pump for changing a tilt angle of the hydraulic pump; a servo switching valve having a servo spool connected to the servo cylinder and a driving cylinder for driving the servo spool; An electromagnetic proportional valve that guides a predetermined secondary pressure to the drive cylinder using an external pilot pressure as a primary pressure; the drive cylinder includes a flow control cylinder that adjusts a discharge flow rate required for the hydraulic pump; and a hydraulic pump. A horsepower control cylinder that adjusts the discharge flow rate of the hydraulic pump in order to keep the power for driving the hydraulic pump within a certain range, wherein the flow control cylinder has a secondary pressure of the electromagnetic proportional valve and another external pilot pressure. Connected to the secondary side of the solenoid proportional valve via a high-pressure priority type shuttle valve that selects one of the high pressure sides, and the horsepower control cylinder is Other by the discharge pressure of the external pilot pressure and the hydraulic pump, the hydraulic pump control apparatus characterized by being configured to operate against a predetermined spring force. 2. The hydraulic pump control device according to claim 1, wherein a mode in which a required external oil pressure is introduced as the one external pilot pressure to a primary side of the electromagnetic proportional valve, and a required external oil pressure is applied to the other pilot pressure. And a switching valve for switching to a mode leading to the shuttle valve. 3. The hydraulic pump control device according to claim 1, wherein the other external pilot pressure is supplied by a bypass line through which the one external pilot pressure is bypassed, and a stop valve is provided in the bypass line. A hydraulic pump control device. A servo cylinder connected to the hydraulic pump for changing a tilt angle of the hydraulic pump; a servo switching valve having a servo spool connected to the servo cylinder and a driving cylinder for driving the servo spool; An external proportional pilot pressure as a primary pressure, and an electromagnetic proportional valve for guiding a predetermined secondary pressure to the drive cylinder. The drive cylinder includes a flow control cylinder for adjusting a discharge flow rate required for a hydraulic pump, and a hydraulic pressure control cylinder. A horsepower control cylinder that adjusts the discharge flow rate of the hydraulic pump so as to suppress the power for driving the pump within a certain range, wherein the flow control cylinder is configured to control the secondary pressure of the electromagnetic proportional valve and a second external pilot. Connected to the secondary side of the proportional solenoid valve through a high-pressure priority type shuttle valve that selects any high pressure side of the pressure, The discharge pressure of the third external pilot pressure and the hydraulic pump, the hydraulic pump control apparatus characterized by being configured to operate against a predetermined spring force.