JP2002115651A - Pressure oil feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure of a hydraulic circuit by feeding the pressure oil discharged from two pressure oil discharge ports to high pressure feed port and a low pressure feed port after sorting the discharged oil into high and low pressure oils so as to share components. SOLUTION: A pressure oil P1 discharged from a pressure oil discharge port 1b is assumed to be higher in pressure than a pressure oil P2 discharged from a pressure oil discharge port 1c. In this case, the outlet of a check valve 32 is shut out, and the outlet of a check valve 31 is opened. Accordingly, the pressure oil P1 on the high pressure side is output from the check valve 32 to a pipeline 55, and fed to a high pressure oil feed port 21e. Also, the pilot check valve 34 is opened, and the pilot check valve 33 is shut out. As a result, the pressure oil P2 on the low pressure side is output from the pilot check valve 34 to a pipeline 56, and fed to a low pressure oil feed port 21f.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for supplying a high-pressure side pressure oil out of two pressure oils discharged from two discharge ports of a pressure oil supply source to a high-pressure supply port of a pressure oil supply object. The present invention relates to a pressure oil supply device that supplies low pressure side pressure oil to a low pressure supply port of a pressure oil supply target.

[0002]

2. Description of the Related Art Self-pressure assist control is performed in a hydraulic pump used for construction machines and the like.

The self-pressure assist control is to control the displacement q (cc / rev) of its own hydraulic pump using the discharge pressure oil of the hydraulic pump as a drive source. Controlling the displacement volume q corresponds to controlling the tilt angle of the swash plate in the case of a swash plate type piston pump. According to the self-pressure assist control, there is an advantage that another hydraulic source is not required as a drive source for controlling the pump displacement volume q.

Here, there is a hydraulic pump called a double pump having two pressure oil discharge ports for one pump. The control of the tilt angle of the swash plate of the double pump is as follows.

FIG. 7 shows a hydraulic circuit used to control the tilt angle of the swash plate of the double pump.

In the hydraulic circuit shown in FIG. 7, a variable displacement hydraulic pump 1 is used as a pressure oil supply source for supplying pressure oil to a hydraulic actuator. The hydraulic pump 1 has two pressure oil discharge ports 1b and 1c, and the swash plate 1a has a pressure oil discharge port 1b,
1c.

[0007] The hydraulic pump 1 shown in FIG. 7 supplies hydraulic oil to hydraulic actuators such as a hydraulic cylinder for a boom and a hydraulic cylinder for an arm if the application object is a construction machine. The hydraulic pump 1 is driven by the engine 2.

The pressure reducing valve 5 reduces the pressure oils P1 and P2 discharged from the pressure oil discharge ports 1b and 1c to a pressure 1/2 (p1 + p2), which is the sum of the pressures p1 and p2. Further pressure reducing valve 5
Supplies the pressure oil PE after decompressing the pressure oils P1 and P2 to the PC valve 19 via the pipe 42.

The swash plate drive mechanism 16 includes a servo piston 17 for driving the swash plate 1a of the hydraulic pump 1 and a drive pressure oil (hereinafter simply referred to as a drive oil) for driving the servo piston 17 on the large diameter side (left side in the drawing) of the servo piston 17. "Drive pressure oil") PS
LS valve (load sensing valve) 18 that acts on the valve, and PC valve (power control valve) 1 that also acts on the large diameter side (left side in the drawing) of the servo piston 17 with the driving pressure oil PS.
9.

The LS valve 18 controls the tilt angle of the swash plate 1a of the hydraulic pump 1 according to the load pressure of the hydraulic actuator. This control is called LS control.

The PC valve 19 controls the tilt angle of the swash plate of the hydraulic pump 1 according to the discharge pressure of the hydraulic pump 1. If the rotation speed (rev / min) of the engine 2 is constant, control is performed so that the absorption horsepower of the hydraulic pump 1 does not exceed the maximum horsepower generated by the engine 2. This control is called P
It is called C control.

The PC valve 19 controls the tilt angle of the swash plate 1a of the hydraulic pump 1 as follows.

That is, the pressure oil discharge port 1b of the hydraulic pump 1
The pressure oils P1 and P2 discharged from the pressure control valve 1c are reduced in pressure by the pressure reducing valve 5 to be pressure oil PE, and then the PC valve 19 through the pipe 42.
Is supplied as driving pressure oil. On the other hand, the pressure oil PE reduced in pressure by the pressure reducing valve 5 is supplied to the PC via the pipe 42 and the pipe 42a.
The pilot pressure oil is supplied to a pilot port 19b on the right side of the valve 19 in the drawing. Pilot pressure oil is externally supplied to the pilot port 19c on the right side of the PC valve 19 in the drawing.

A spring force by a spring 19a is applied to the left side of the PC valve 19 in the drawing. The spring 19a is connected to a servo rod 17a that moves together with the servo piston 17. The set spring force of the spring 19a is the servo rod 1
It changes according to the position of 7a.

When the pressure of the pilot pressure oil applied to the pilot port 19b exceeds the set spring force of the spring 19a, the valve position of the PC valve 19 moves to the position 19g. Therefore, the driving pressure oil PS is supplied to the large-diameter side (left side in the drawing) of the servo piston 17 via the PC valve 19, the LS valve 18, and the pipe line 43. Then, the servo piston 17 is driven in a direction (MIN side in the drawing) in which the capacity of the hydraulic pump 1 is minimized. As the swash plate 1a of the hydraulic pump 1 changes to the MIN side, the servo rod 17a moves to the right in the drawing, and the set spring force of the spring 19a increases. Therefore, the valve position of the PC valve 19 is set to the position 1
Move to 9h side. Therefore, the pressure oil on the large-diameter side (left side in the drawing) of the servo piston 17 is discharged to the tank via the pipeline 43, the LS valve 18, and the PC valve 19. Then, the direction in which the servo piston 17 maximizes the capacity of the hydraulic pump 1 (see FIG.
AX side). Thus, the tilt angle of the swash plate 1a of the hydraulic pump 1 is controlled.

There is also known a hydraulic circuit that performs the same control using a hydraulic pump called a tandem pump instead of a double pump.

A tandem pump is a hydraulic pump in which two pumps are connected to an engine with a common rotating shaft.

FIG. 8 shows a hydraulic circuit using a tandem pump.

In the hydraulic circuit shown in FIG. 8, a swash plate 20a and a swash plate 20a serve as pressure oil supply sources for supplying pressure oil to a hydraulic actuator.
A hydraulic pump 20 provided with a pressure oil discharge port 20b;
A swash plate 20'a and a hydraulic pump 20 'provided with a pressure oil discharge port 20'b are used. The hydraulic pump 20 and the hydraulic pump 20 ′ are connected to the engine 2 via a common rotating shaft 3. Hereinafter, control of the hydraulic pump 20 will be described as a representative. The same components as those of the hydraulic circuit of FIG. 7 are denoted by the same reference numerals, and description thereof will not be repeated.

That is, the hydraulic pump 20 is provided with the swash plate drive mechanism 16.

The swash plate drive mechanism 16 includes the servo piston 1
7, the LS valve 18 and the PC valve 21.

The PC valve 21 controls the tilt angle of the swash plate of the hydraulic pump 20 in accordance with the discharge output of the hydraulic pump 20, similarly to the PC valve 19 of FIG. If the rotation speed (rev / min) of the engine 2 is constant, control is performed so that the absorption horsepower of the hydraulic pump 20 does not exceed the maximum horsepower generated by the engine 2.

The PC valve 21 is provided with a pressure oil supply port 21e and a pressure oil supply port 21f. The pressure oil supply port 21e is P
It communicates with a pilot port 21b on the right side of the C valve 21. The pressure oil supply port 21f communicates with another pilot port 21c on the right side of the PC valve 21.

The PC valve 21 is a swash plate 20a of the hydraulic pump 20.
Is controlled as follows.

That is, the pressure oil discharge port 20 of the hydraulic pump 20
The pressure oil P3 discharged from b is supplied to the pressure oil supply port 21e of the PC valve 21 via the line 45. Pressure oil supply port 21
e is supplied to the PC valve 21 as drive pressure oil.
And supplied to the pilot port 21b of the PC valve 21 as pilot pressure oil. On the other hand, the pressure oil P4 discharged from the pressure oil discharge port 20'b of the hydraulic pump 20 'is supplied to the PC valve 21 via a pipe 45' and a pipe 46 '.
Is supplied to the pressure oil supply port 21f. The pressure oil P4 supplied to the pressure oil supply port 21f is supplied as pilot pressure oil to a pilot port 21c on the right side of the PC valve 21 in the drawing. The pilot port 21 on the right side of the drawing of the PC valve 21
d is supplied with pilot pressure oil from outside.

A spring force by a spring 21a is applied to the left side of the PC valve 21 in the drawing. The spring 21a is connected to a servo rod 17a that moves together with the servo piston 17. The set spring force of the spring 21a is the servo rod 17
It is changed according to the position of a.

When the pressure of the pilot pressure oil applied to the pilot ports 21b and 21c exceeds the set spring force of the spring 21a, the valve position of the PC valve 21 moves to the position 21g. For this reason, the driving pressure oil PS is supplied to the large-diameter side (left side in the drawing) of the servo piston 17 via the PC valve 21, the LS valve 18, and the pipeline 43. Then, the servo piston 17 is driven in a direction (MIN side in the drawing) that minimizes the capacity of the hydraulic pump 20. As the swash plate 20a of the hydraulic pump 20 changes to the MIN side, the servo rod 17a moves to the right in the drawing, and the set spring force of the spring 21a increases. Therefore, the PC valve 21
Moves to the position 21h side. For this reason, the pressure oil on the large-diameter side (left side in the drawing) of the servo piston 17 flows through the pipeline 43, L
It is discharged to the tank via the S valve 18 and the PC valve 21. Then, the servo piston 17 is driven in a direction (MAX side in the drawing) in which the capacity of the hydraulic pump 20 is maximized. Thus, the tilt angle of the swash plate 20a of the hydraulic pump 20 is controlled.

As described above, unlike the PC valve 19 shown in FIG.
In addition to the hydraulic oil P3 discharged from the hydraulic pump 20, a hydraulic oil P4 discharged from another hydraulic pump 20 'acts on the C valve 21 as a pilot hydraulic oil.

[0029]

As shown in FIGS. 7 and 8, a swash plate driving mechanism 1 is used regardless of whether a double pump or a tandem pump is used as a hydraulic pump.
6, a common servo piston 17 and LS valve 18 are used. On the other hand, a PC valve 19 is used for the swash plate drive mechanism 16 of the double pump, and a PC valve 21 having a different structure from the PC valve 19 is used for the swash plate drive mechanism 16 of the tandem pump.

Here, in order to share the components of the swash plate drive mechanism 16, a PC of the swash plate drive mechanism 16 shown in FIG.
Instead of the valve 19, the P of the swash plate drive mechanism 16 shown in FIG.
There is a request to use the C valve 21. But PC valve 2
If 1 is incorporated in the hydraulic circuit of FIG. 7, the following problem occurs.

That is, the PC valve 21 is provided with two pressure oil supply ports 21e and 21f through which pressure oil is supplied. In this case, the pressure oil on the high pressure side of the pressure oil discharged from the pressure oil discharge ports 1b and 1c of the hydraulic pump 1 is reliably supplied to the pressure oil supply port 21e.
It is necessary to use the hydraulic pressure for driving the servo piston 17. If the low-pressure side pressure oil of the pressure oil discharged from the pressure oil discharge ports 1b and 1c is supplied to the pressure oil supply port 21e, the drive pressure oil becomes low pressure and the servo piston 17 is operated to operate the hydraulic pump 1. This is because the swash plate 1a cannot be changed.

However, in the hydraulic pump 1, it is not defined which of the two pressure oil discharge ports 1b and 1c discharges high-pressure oil and which low-pressure oil is discharged. Therefore, of the pressure oil discharged from the two pressure oil discharge ports 1 b and 1 c of the hydraulic pump 1, the high pressure side pressure oil is supplied to the pressure oil supply port 21 e of the PC valve 21, and the low pressure side pressure oil is supplied to the PC valve 21. It is necessary to add a circuit that distributes and supplies the oil to the oil supply port 21f.

Japanese Patent Application Laid-Open No. 2000-74233 describes an invention in which a fluid having a desired pressure of either high pressure or low pressure is selected from fluids supplied from two pipes. However, the invention described in the above publication is an invention in which only one of high-pressure and low-pressure fluids is selected and output from the fluids supplied from the two conduits. This publication does not describe distributing high-pressure and low-pressure oil to the pressure oil supply port 21e and the pressure oil supply port 21f of the PC valve 21, respectively.

As described above, according to the prior art, the hydraulic pump 1
Of the pressure oil discharged from the two pressure oil discharge ports 1b and 1c, the high pressure side pressure oil is supplied to the pressure oil supply port 21e of the PC valve 21, and the low pressure side pressure oil is supplied to the pressure oil supply port 21f of the PC valve 21. Could not be distributed to each. Therefore, instead of the PC valve 19 of the swash plate drive mechanism 16 shown in FIG.
The use of the PC valve 21 of the swash plate drive mechanism 16 shown in FIG. 8 could not achieve commonality of parts.

The present invention has been made in view of such circumstances, and distributes the pressure oil discharged from the two pressure oil discharge ports into a high pressure and a low pressure to respectively supply a high pressure oil supply port and a low pressure hydraulic oil. It is an object of the present invention to provide a supply port so as to share components and simplify the structure of a hydraulic circuit.

[0036]

Accordingly, a first aspect of the present invention is to provide a pressure oil supply source (1) comprising a pressure oil discharged from two pressure oil discharge ports (1b, 1c). In the pressure oil supply device for supplying the first pressure oil supply port (21e) and the second pressure oil supply port (21f) of the supply object (21),
A high-pressure supply unit that selects a high-pressure side pressure oil from the two pressure oils discharged from the two pressure oil discharge ports (1b, 1c), and supplies the selected pressure oil to the first pressure oil supply port (21e); The pressure oil on the low pressure side is selected from the two pressure oils discharged from the two pressure oil discharge ports (1b, 1c), and the second pressure oil supply port (21f) is selected.
Low pressure supply means for supplying the high pressure supply means and the low pressure supply means to the two pressure oil discharge ports (1b, 1b,
c) and between the first pressure oil supply port (21e) and the second pressure oil supply port (21f).

In a second aspect based on the first aspect, the high-pressure supply means includes a first check valve (31) and a second check valve (32), and the first pressure oil discharge port (32) is provided. 1
b) and the first pressure oil supply port (21e) are connected via the first check valve (31), and the second pressure oil discharge port (1c) is connected to the first pressure oil Supply port (21
e) is connected via the second check valve (32), and the high-pressure side of the two pressure oil discharge ports (1b, 1c) is supplied to the first and second check valves (31). , 3
2) through a first pilot check valve (33) and a second pilot check valve (3).
4), the first pressure oil discharge port (1b) and the second pressure oil supply port (21f) are connected via the first pilot check valve (33), and 2
The pressure oil discharged from the pressure oil discharge port (1c) is supplied as pilot pressure oil of the first pilot check valve (33), and the second pressure oil discharge port (1c) is connected to the second pressure oil discharge port (1c). An oil supply port (21f) is connected through the second pilot check valve (34), and the pressure oil discharged from the first pressure oil discharge port (1b) is supplied to the second pilot check valve. (34), when the pressure oil discharged from the second pressure oil discharge port (1c) is at a high pressure, the first pilot check valve (33) is supplied by the pilot pressure oil. ) To supply low pressure oil discharged from the first pressure oil discharge port (1b) to the second pressure oil supply port (21f), and to supply the first pressure oil discharge port (1b). If the pressure oil discharged from the The second pilot check valve (34) is opened by the pressure oil and the low pressure oil discharged from the second pressure oil discharge port (1c) is supplied to the second pressure oil supply port (21f). It is characterized by supplying.

The first invention and the second invention will be described with reference to FIG.

The supply of pressure oil from the pressure oil discharge ports 1b and 1c to the high pressure oil supply port 21e is performed as follows.

It is assumed that the pressure oil P1 discharged from the pressure oil discharge port 1b is higher in pressure than the pressure oil P2 discharged from the pressure oil discharge port 1c. In this case, the pressure oil P1 on the high pressure side is
Is supplied to the inlet of the check valve 31 via On the other hand, the pressure oil P2 on the low pressure side is supplied to the inlet of the check valve 32 via the pipe 53. Here, the pressure oil P1 supplied to the inlet of the check valve 31 is changed to the pressure oil P2 supplied to the inlet of the check valve 32.
Since the pressure is higher, the outlet of the check valve 32 is shut off and the outlet of the check valve 31 is opened. For this reason, the high-pressure side pressure oil P1 is output from the check valve 31 to the pipeline 55, and is supplied to the high-pressure pressure oil supply port 21e.

Similarly, when the pressure oil P2 discharged from the pressure oil discharge port 1c is higher in pressure than the pressure oil P1 discharged from the pressure oil discharge port 1b, the pressure oil supplied to the inlet of the check valve 32 Since the pressure P2 is higher than the pressure oil P1 supplied to the inlet of the check valve 31, the outlet of the check valve 31 is shut off and the outlet of the check valve 32 is opened. For this reason, the high-pressure side pressure oil P2 is output from the check valve 32 to the pipeline 55, and is supplied to the high-pressure pressure oil supply port 21e.

The supply of pressure oil from the pressure oil discharge ports 1b and 1c to the low-pressure pressure oil supply port 21f is performed as follows.

It is assumed that the pressure oil P2 discharged from the pressure oil discharge port 1c is higher in pressure than the pressure oil P1 discharged from the pressure oil discharge port 1b, that is, the pressure oil P1 is lower in pressure than the pressure oil P2. . In this case, the low pressure side pressure oil P1 '(same pressure as the pressure oil P1) is supplied to the inlet of the pilot check valve 33 via the branch pipe line 52. On the other hand, a pilot pressure oil P2 ″ (same pressure as the pressure oil P2) on the high pressure side is supplied to the pilot port 33a of the pilot check valve 33 via the pilot line 58. Therefore, the pilot check valve 33 is opened. Further, the pilot check valve 3 is connected via the branch line 54.
The pressure oil P2 '(same pressure as the pressure oil P2) on the high pressure side is supplied to the inlet 4. On the other hand, the pilot pressure oil P1 ″ (same pressure as the pressure oil P1) on the low pressure side is supplied to the pilot port 34a of the pilot check valve 34 via the pilot line 57. Therefore, the pilot check valve 34 is shut off. As described above, since the pilot check valve 33 is opened and the pilot check valve 34 is shut off, the low-pressure side pressure oil P1 is output from the pilot check valve 33 to the pipeline 56 and supplied to the low-pressure pressure oil supply port 21f. Is done.

When the pressure oil P1 discharged from the pressure oil discharge port 1b is higher than the pressure oil P2 discharged from the pressure oil discharge port 1c, the pilot check valve 34 is opened and the pilot check valve 33 is similarly opened. Is shut off. Therefore, the pressure oil P2 on the low pressure side flows from the pilot check valve 34 to the line 5
6 and supplied to the low-pressure pressure oil supply port 21f.

As described above, according to the first invention and the second invention,
Of the pressure oil discharged from the two pressure oil discharge ports 1b and 1c of the hydraulic pump 1, the high pressure side pressure oil is supplied to the pressure oil supply port 21e of the PC valve 21, and the low pressure side pressure oil is supplied to the PC valve 21 pressure oil. Supply port 21
f and can be supplied separately. Therefore, in place of the PC valve 19 of the swash plate drive mechanism 16 shown in FIG. 7, the PC valve 21 of the swash plate drive mechanism 16 shown in FIG. The structure can be simplified.

According to a third invention, in the first invention, the high-pressure supply means and the low-pressure supply means are integrally formed.

According to the third aspect of the present invention, the high-pressure supply means and the low-pressure supply means are integrally formed, so that the pressure oil supply device can be made compact.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a pressure oil supply device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a hydraulic circuit diagram of the first embodiment.

The hydraulic circuit shown in FIG. 1 is mounted on a construction machine such as a bulldozer that drives a hydraulic actuator using a hydraulic pump as a drive source.

The hydraulic pump 1 is a variable displacement type swash plate type hydraulic pump, and has two pressure oil discharge ports 1b, 1c as in FIG.
Are provided, and the swash plate 1a is common to the two pressure oil discharge ports 1b and 1c.

The hydraulic pump 1 is connected to the engine 2 via a rotating shaft. When the engine 2 rotates, the rotating shaft 3 rotates and the hydraulic pump 1 is driven. The displacement (displacement volume) q (cc / rev) of the hydraulic pump 1 changes as the tilt angle of the swash plate 1a changes.

The swash plate drive mechanism 16 includes a servo piston 17 for driving the swash plate 1a of the hydraulic pump 1 and a drive pressure oil (hereinafter simply referred to as a drive oil) for driving the servo piston 17 on the large diameter side (left side in the drawing) of the servo piston 17. "Drive oil") PS
LS valve (load sensing valve) 18 and PC valve (power control valve) 2 for applying drive hydraulic oil PS to the large diameter side (left side in the drawing) of servo piston 17.
And 1.

The LS valve 18 controls the tilt angle of the swash plate 1a of the hydraulic pump 1 according to the load pressure of the hydraulic actuator. This control is called LS control.

The PC valve 21 performs control to change the tilt angle of the swash plate of the hydraulic pump 1 according to the discharge output of the hydraulic pump 1. If the rotation speed (rev / min) of the engine 2 is constant, control is performed so that the absorption horsepower of the hydraulic pump 1 does not exceed the maximum horsepower generated by the engine 2. This control is called P
It is called C control.

The PC valve 21 is provided with a high-pressure oil supply port 21e and a low-pressure oil supply port 21f as in FIG. The pressure oil supply port 21e communicates with the pilot port 21b of the PC valve 21. Pressure oil supply port 21f is PC valve 2
It communicates with one other pilot port 21c.

The pressure oil supply section 60 sends the high pressure oil out of the pressure oil discharge ports 1 b and 1 c of the hydraulic pump 1 to the high pressure oil supply port 21 e of the PC valve 21 and the low pressure side Is distributed to and supplied to the low pressure oil supply port 21f of the PC valve 21. The pressure oil supply unit 60 will be further described later.

The PC valve 21 controls the tilt angle of the swash plate 1a of the hydraulic pump 1 as follows.

That is, the pressure oil discharge port 1b of the hydraulic pump 1
The pressure oil P1, P2 discharged from 1c is supplied to the pressure oil supply unit 60. The pressure oil supply unit 60 includes a pressure oil P1,
The pressure oil Pa on the high pressure side is selected from P2 and output to the pipeline 55. Therefore, the pressure oil Pa on the high pressure side is supplied to the PC via the pipe 55.
It is supplied to the pressure oil supply port 21 e of the valve 21. Pressure oil supply port 2
1e is supplied to the PC valve 2 as drive pressure oil.
1 and to the pilot port 21b on the right side of the drawing of the PC valve 21 as pilot pressure oil.

On the other hand, the pressure oil supply section 60 selects the pressure oil Pb on the low pressure side of the pressure oils P1 and P2 as will be described later, and
Output to Therefore, the low-pressure side pressure oil Pb is supplied to the pressure oil supply port 21f of the PC valve 21 via the pipe 56. The pressure oil Pb supplied to the pressure oil supply port 21f is supplied as pilot pressure oil to a pilot port 21c on the right side of the PC valve 21 in the drawing. Pilot pressure oil is externally supplied to the pilot port 21d on the right side of the PC valve 21 in the drawing.

A spring force by a spring 21a is applied to the left side of the PC valve 21 in the drawing. The spring 21a is connected to a servo rod 17a that moves together with the servo piston 17. The set spring force of the spring 21a is the servo rod 17
It is changed according to the position of a.

When the pressure of the pilot pressure oil applied to the pilot ports 21b and 21c exceeds the set spring force of the spring 21a, the valve position of the PC valve 21 moves to the position 21g. For this reason, the driving pressure oil PS is supplied to the large-diameter side (left side in the drawing) of the servo piston 17 via the PC valve 21, the LS valve 18, and the pipeline 43. Then, the servo piston 17 is driven in a direction (MIN side in the drawing) in which the capacity of the hydraulic pump 1 is minimized. As the swash plate 1a of the hydraulic pump 1 changes to the MIN side, the servo rod 17a moves to the right in the drawing and the spring 21
The set spring force of “a” increases. Therefore, the valve position of the PC valve 21 moves to the position 21h. For this reason, the pressure oil on the large-diameter side (left side in the drawing) of the servo piston 17 flows through the pipeline 43 and the LS valve 1
8. Discharged to the tank via the PC valve 21. Then, the servo piston 17 is driven in a direction (MAX side in the drawing) in which the capacity of the hydraulic pump 1 is maximized. Thus, the tilt angle of the swash plate 1a of the hydraulic pump 1 is controlled.

Next, the pressure oil supply section 60 will be described in detail.

The pressure oil supply unit 60 is roughly
1, 32, pilot check valves 33, 34 and line 5
1, 53, 55, and 56, branch pipelines 52 and 54, and pilot pipelines 57 and 58. The conduit 51 branches into a conduit 52. The pipe 53 branches into a pipe 54. The pipe 51 branches into a pilot pipe 57.
The pipe 53 branches into a pilot pipe 58.

The pressure oil discharge port 1 b of the hydraulic pump 1 communicates with the inlet of the check valve 31 via a pipe 51. The outlet of the check valve 31 and the pressure oil supply port 21 e of the PC valve 21 communicate with each other via a pipe 55. Check valve 31 allows the flow of pressure oil from line 51 to line 55.

Similarly, the pressure oil discharge port 1 c of the hydraulic pump 1 communicates with the inlet of the check valve 32 via a pipe 53. Outlet of check valve 32 and pressure oil supply port 2 of PC valve 21
1e is communicated via a conduit 55. Check valve 3
2 allows the flow of the pressure oil from the pipe 53 to the pipe 55.

The pressure oil discharge port 1b of the hydraulic pump 1 and the inlet of the pilot check valve 33 are connected through a pipe 51 and a branch pipe 52. Pilot check valve 33
Is communicated with the pressure oil supply port 21f of the PC valve 21 through a conduit 56. The pilot port 33a of the pilot check valve 33 communicates with the pressure oil discharge port 1c of the hydraulic pump 1 via the pilot line 58 and the line 53.
When the pressure of the pilot pressure oil P2 ″ in the pilot line 58 is higher than the pressure of the pressure oil P1 in the line 52, the pilot check valve 33 controls the pressure oil from the line 52 to the line 56. Allow flow.

Similarly, the pressure oil discharge port 1 c of the hydraulic pump 1 and the inlet of the pilot check valve 34 communicate with each other via a pipe 53 and a branch pipe 54. Pilot check valve 3
4 and the pressure oil supply port 21f of the PC valve 21
Is communicated through. The pilot port 34a of the pilot check valve 34 is connected to the pilot line 57,
Through the pressure oil discharge port 1b of the hydraulic pump 1. The pilot check valve 34 is connected to a pilot line 57
When the pressure of the pilot pressure oil P1 ″ is higher than the pressure of the pressure oil P2 in the pipe 54, the flow of the pressure oil from the pipe 54 to the pipe 56 is permitted.

Next, the operation of the pressure oil supply unit 60 will be described.

The supply of pressure oil from the pressure oil discharge ports 1b and 1c to the pressure oil supply port 21e for high pressure is performed as follows.

Assume that the pressure oil P1 discharged from the pressure oil discharge port 1b is higher in pressure than the pressure oil P2 discharged from the pressure oil discharge port 1c. In this case, the pressure oil P1 on the high pressure side is
Is supplied to the inlet of the check valve 31 via On the other hand, the pressure oil P2 on the low pressure side is supplied to the inlet of the check valve 32 via the pipe 53. Here, the pressure oil P1 supplied to the inlet of the check valve 31 is changed to the pressure oil P2 supplied to the inlet of the check valve 32.
Since the pressure is higher, the outlet of the check valve 32 is shut off and the outlet of the check valve 31 is opened. For this reason, the high-pressure side pressure oil P1 is output from the check valve 32 to the pipeline 55, and is supplied to the high-pressure pressure oil supply port 21e.

Similarly, when the pressure oil P2 discharged from the pressure oil discharge port 1c is higher in pressure than the pressure oil P1 discharged from the pressure oil discharge port 1b, the pressure oil supplied to the inlet of the check valve 32 Since the pressure P2 is higher than the pressure oil P1 supplied to the inlet of the check valve 31, the outlet of the check valve 31 is shut off and the outlet of the check valve 32 is opened. For this reason, the high-pressure side pressure oil P2 is output from the check valve 32 to the pipeline 55, and is supplied to the high-pressure pressure oil supply port 21e.

The supply of pressure oil from the pressure oil discharge ports 1b and 1c to the low-pressure pressure oil supply port 21f is performed as follows.

It is assumed that the pressure oil P2 discharged from the pressure oil discharge port 1c is higher in pressure than the pressure oil P1 discharged from the pressure oil discharge port 1b, that is, the pressure oil P1 is lower in pressure than the pressure oil P2. . In this case, the low pressure side pressure oil P1 '(same pressure as the pressure oil P1) is supplied to the inlet of the pilot check valve 33 via the branch pipe line 52. On the other hand, a pilot pressure oil P2 ″ (same pressure as the pressure oil P2) on the high pressure side is supplied to the pilot port 33a of the pilot check valve 33 via the pilot line 58. Therefore, the pilot check valve 33 is opened. Further, the pilot check valve 3 is connected via the branch line 54.
The pressure oil P2 '(same pressure as the pressure oil P2) on the high pressure side is supplied to the inlet 4. On the other hand, the pilot pressure oil P1 ″ (same pressure as the pressure oil P1) on the low pressure side is supplied to the pilot port 34a of the pilot check valve 34 via the pilot line 57. Therefore, the pilot check valve 34 is shut off. As described above, since the pilot check valve 33 is opened and the pilot check valve 34 is shut off, the low-pressure side pressure oil P1 is output from the pilot check valve 33 to the pipeline 56 and supplied to the low-pressure pressure oil supply port 21f. Is done.

When the pressure oil P1 discharged from the pressure oil discharge port 1b is higher than the pressure oil P2 discharged from the pressure oil discharge port 1c, the pilot check valve 34 is opened and the pilot check valve 33 is similarly opened. Is shut off. Therefore, the pressure oil P2 on the low pressure side is supplied from the pilot check valve 34 to the line 56.
And supplied to the low-pressure pressure oil supply port 21f.

As described above, according to the first embodiment, the pressure oil on the high pressure side of the pressure oil discharged from the two pressure oil discharge ports 1 b and 1 c of the hydraulic pump 1 is changed to the pressure oil supply port of the PC valve 21. 21
e, the pressure oil on the low pressure side can be distributed and supplied to the pressure oil supply port 21f of the PC valve 21. Therefore, in place of the PC valve 19 of the swash plate drive mechanism 16 shown in FIG. 7, the PC valve 21 of the swash plate drive mechanism 16 shown in FIG. The structure can be simplified.

FIG. 2 is a hydraulic circuit diagram showing a deformed pressure oil supply section 60 'of the pressure oil supply section 60 shown in FIG.

The hydraulic oil supply section 60 ′ is mainly composed of a shuttle valve 70, a pilot operation valve 71, and lines 51, 53, 55,
56, branch lines 52, 54 and pilot lines 72, 73
It is composed of The branch line 52 branches into a pilot line 72. The branch line 54 is the pilot line 7
It branches to 3. The check valves 31 and 32 for selecting the high-pressure side hydraulic oil in FIG. 1 correspond to the shuttle valve 70 in FIG. 2, and the pilot check valve 3 for selecting the low-pressure side hydraulic oil in FIG.
Reference numerals 3 and 34 correspond to the pilot operation valve 71 in FIG.

The hydraulic oil discharge port 1 b of the hydraulic pump 1 and one inlet of the shuttle valve 70 communicate with each other via a pipe 51. In addition, the hydraulic oil discharge port 1c of the hydraulic pump 1 and the shuttle valve 7
0 communicates with the other inlet via a conduit 53. The outlet of the shuttle valve 70 and the pressure oil supply port 21 e of the PC valve 21 communicate with each other via a pipe 55.

The pressure oil discharge port 1 b of the hydraulic pump 1 and the inlet of the pilot operation valve 71 communicate with each other through a pipe 51 and a branch pipe 52. Also, the pressure oil discharge port 1c of the hydraulic pump 1
The other inlet of the pilot operation valve 71 communicates with the other via a pipe 53 and a branch pipe 54. Pilot operated valve 7
1 and the pressure oil supply port 21f of the PC valve 21
Is communicated through. Pressure oil discharge port 1b of hydraulic pump 1
And one pilot port 71 of the pilot operation valve 71
c is communicated via a pipeline 51, a branch pipeline 52, and a pilot pipeline 72. The pressure oil discharge port 1c of the hydraulic pump 1 and the other pilot port 71d of the pilot operation valve 71
Communicate with each other via a pipe 53, a branch pipe 54, and a pilot pipe 73. The pilot operation valve 71 is located at the valve position 71.
a, 71b. When the pressure of the pilot pressure oil Pd applied to the pilot port 71d (the same pressure as the pressure oil P2) becomes higher than the pressure of the pilot pressure oil Pc applied to the pilot port 71c (the same pressure as the pressure oil P1), the pilot operation valve 71 becomes a valve. It moves to the position 71a side and the branch pipeline 52 and the pipeline 5
6 communicates. When the pilot pressure P1 applied to the pilot port 71c becomes higher than the pilot pressure P2 applied to the pilot port 71d, the pilot operation valve 71
Moves to the valve position 71b side, and the branch conduit 54 and the conduit 56 communicate with each other.

Next, the operation of the pressure oil supply section 60 'will be described.

The supply of pressure oil from the pressure oil discharge ports 1b and 1c to the high pressure oil supply port 21e is performed as follows.

It is assumed that the pressure oil P1 discharged from the pressure oil discharge port 1b is higher in pressure than the pressure oil P2 discharged from the pressure oil discharge port 1c. In this case, the pressure oil P1 on the high pressure side is
Is supplied to one inlet of a shuttle valve 70 via On the other hand, the pressure oil P2 on the low pressure side is supplied to the shuttle valve 70
To the other inlet. For this reason, the high-pressure side pressure oil P1 is output from the shuttle valve 70 to the pipeline 55, and is supplied to the high-pressure pressure oil supply port 21e.

Similarly, when the pressure oil P2 discharged from the pressure oil discharge port 1c is higher in pressure than the pressure oil P1 discharged from the pressure oil discharge port 1b, it is supplied to one inlet of the shuttle valve 70. Since the pressure oil P2 is higher in pressure than the pressure oil P1 supplied to the other inlet of the shuttle valve 70, the high-pressure side pressure oil P2 is output from the shuttle valve 70 to the pipeline 55, and the high-pressure pressure oil supply port 21e Supplied to

The supply of pressure oil from the pressure oil discharge ports 1b and 1c to the low-pressure pressure oil supply port 21f is performed as follows.

It is assumed that the pressure oil P2 discharged from the pressure oil discharge port 1c is higher in pressure than the pressure oil P1 discharged from the pressure oil discharge port 1b, that is, the pressure oil P1 is lower in pressure than the pressure oil P2. . In this case, the pressure of the pilot pressure oil Pd applied to the pilot port 71d (the same pressure as the pressure oil P2) becomes higher than the pressure of the pilot pressure oil Pc applied to the pilot port 71c (the same pressure as the pressure oil P1). Therefore, the pilot operation valve 71 moves to the valve position 71a side, and the branch pipe 52 and the pipe 5
6 communicates. For this reason, the pressure oil P1 on the low pressure side is
Branch line 52, line 56 via pilot operated valve 71
And supplied to the pressure oil supply port 21f for low pressure. The pressure oil P2 on the high pressure side is shut off by the pilot operation valve 71.

Similarly, when the pressure oil P1 discharged from the pressure oil discharge port 1b is higher in pressure than the pressure oil P2 discharged from the pressure oil discharge port 1c, that is, when the pressure oil P2 is lower in pressure than the pressure oil P1. Suppose. In this case, the pressure of the pilot pressure oil Pc applied to the pilot port 71c (the same pressure as the pressure oil P1) becomes higher than the pressure of the pilot pressure oil Pd applied to the pilot port 71d (the same pressure as the pressure oil P2). Therefore, the pilot operation valve 71 moves to the valve position 71b side, and the branch pipe 54 and the pipe 56 communicate with each other. Therefore, the low-pressure side pressure oil P2 is output to the line 56 via the line 53, the branch line 54, and the pilot operation valve 71, and is supplied to the low-pressure pressure oil supply port 21f. The pressure oil P1 on the high pressure side is shut off by the pilot operation valve 71.

FIG. 3 shows a valve element 90 in which the pressure oil supply section 60 shown in FIG. 1 is integrally formed.

FIG. 3 is a sectional view of the valve body 90, and FIG.
4A shows a state in which the check valves 31 and 32 and the pilot check valves 33 and 34 constituting the valve body 90 are open, and FIG. 4B shows the check valve 3 constituting the valve body 90.
1 and 32 and the state where the pilot check valves 33 and 34 are shut off.

The check valve 31 has a ball 31 b having a larger diameter than a pipe formed in the valve body 90. Ball 31
b is provided movably between the stoppers 31c and 31d. Other check valve 32, pilot check valve 3
The same applies to 3 and 34.

A rod 35 is provided between the balls 33b and 34b of the pilot check valves 33 and 34 to push the other ball as one ball moves to the other ball side.

Next, the check valves 31 and 32 and the pilot check valves 33 and 3 shown in FIGS. 3, 4A and 4B will be described.
4 will be described.

It is assumed that the pressure oil P1 discharged from the pressure oil discharge port 1b is higher in pressure than the pressure oil P2 discharged from the pressure oil discharge port 1c. In this case, the check valve 31 is shown in FIG.
An open state shown in FIG. On the other hand, the check valve 32 is in the shut-off state shown in FIG.

For this reason, the pipeline 51 and the pipeline 55 communicate with each other,
The pipe 53 and the pipe 55 are shut off. Therefore, the high-pressure side pressure oil P1 of the pressure oil discharged from the pressure oil discharge ports 1b and 1c is supplied to the pressure oil supply port 21e through the pipe 51, the side surface of the ball 31b of the check valve 31, and the pipe 55. Is done.

Similarly, when the pressure oil P2 discharged from the pressure oil discharge port 1c is higher in pressure than the pressure oil P1 discharged from the pressure oil discharge port 1b, the check valve 32 is shown in FIG. The valve is opened and the check valve 31 is shut off as shown in FIG.

For this reason, the pipe 53 and the pipe 55 communicate with each other,
The pipeline 51 and the pipeline 55 are shut off. Accordingly, the high-pressure side pressure oil P2 of the pressure oil discharged from the pressure oil discharge ports 1b and 1c is supplied to the pressure oil supply port 21e through the pipe 53, the side surface of the ball 32b of the check valve 32, and the pipe 55. Is done.

When the pressure oil P2 discharged from the pressure oil discharge port 1c is higher in pressure than the pressure oil P1 discharged from the pressure oil discharge port 1b, that is, when the pressure oil P1 is lower in pressure than the pressure oil P2. Suppose. In this case, the pilot check valve 34 is shut off as shown in FIG. That is, the ball 34b
Is on the stopper 34d side by high pressure oil P2 (left side in FIG. 3)
And is stopped by the stopper 34d. Thereby, the pipeline 53 and the pipeline 56 are shut off.

Ball 34b of pilot check valve 34
Moves to the ball 33b side of the other pilot check valve 33, so that the rod 35 pushes the ball 33b. Therefore, the pilot check valve 33 is opened as shown in FIG. That is, the ball 33b is
Side (FIG. 3 left side). As a result, the pipe 51 and the pipe 56 communicate with each other. Therefore, the pressure oil discharge ports 1b, 1c
Of the low pressure side of the pressure oil discharged from the
1. The oil is supplied to the pressure oil supply port 21f through the branch pipe 52, the side surface of the ball 33b, and the pipe 56.

Similarly, when the pressure oil P1 discharged from the pressure oil discharge port 1b is higher in pressure than the pressure oil P2 discharged from the pressure oil discharge port 1c, that is, when the pressure oil P2 is lower in pressure than the pressure oil P1. In some cases, the pilot check valve 33 is turned off as shown in FIG.
An open state shown in FIG. Therefore, the pressure oil discharge port 1
Among the pressure oils discharged from b and 1c, the pressure oil P2 on the low pressure side is the pipe 53, the branch pipe 54, the side surface of the ball 34b, the pipe 5
6 and is supplied to the pressure oil supply port 21f.

The check valves 31, 32 and the pilot check valves 33, 34 using the balls 31b to 34b are
It is desirable to use it when the discharge flow rate of the hydraulic pump 1 is small.

FIG. 5 shows a modification of FIG.

FIG. 5 is a sectional view of the valve element 90 ', and FIG.
6A shows the open state of the check valves 31 and 32 and the pilot check valves 33 and 34, and FIG. 6B shows the closed state of the check valves 31 and 32 and the pilot check valves 33 and 34.

Check valve 3 shown in FIGS. 5, 6 (a) and 6 (b)
1 and 32 and the pilot check valves 33 and 34 are configured by replacing the balls 31b to 34b shown in FIG. 3 with poppets 31e to 34e.

The poppets 31e to 34e operate with the ball 3
The operation is the same as 1b to 34b. However, poppet 31
When e to 34e are used, the pressure oil passes through the inside of the poppets 31e to 34e as shown in FIG.

The check valves 31, 32 using the poppets 31e to 34e, and the pilot check valves 33, 34
Is used when the discharge flow rate of the hydraulic pump 1 is large.

According to the embodiment shown in FIGS. 3 and 5, since the pressure oil supply section 60 is a valve body integrally formed, the pressure oil supply device can be made compact.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing a modified example of a pressure oil supply unit.

FIG. 3 is a sectional view of a valve body in which a pressure oil supply unit is integrally formed.

FIG. 4A is a diagram showing a state where the check valve and the pilot check valve are opened, and FIG. 4B is a diagram showing a state where the check valve and the pilot check valve are shut off.

FIG. 5 is a sectional view of a valve body in which a pressure oil supply unit is integrally formed.

FIG. 6A is a view showing a state where the check valve and the pilot check valve are opened, and FIG. 6B is a view showing a state where the check valve and the pilot check valve are shut off.

FIG. 7 is a hydraulic circuit diagram showing a conventional technique.

FIG. 8 is a hydraulic circuit diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 1b, 1c Pressure oil discharge port 21 PC valve 21e, 21f Pressure oil supply port Check valve 31, 32 Pilot check valve 33, 34

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H071 AA03 BB01 BB13 CC34 DD11 DD31 3H089 AA27 AA83 CC11 DA03 DA13 DB34 GG02 JJ01

Claims (3)

[Claims] A pressure oil discharged from two pressure oil discharge ports (1b, 1c) of a pressure oil supply source (1) is supplied to a first pressure oil supply port (21e) of a pressure oil supply target (21). And a second pressure oil supply port (21f), wherein a high pressure side pressure oil is selected from both pressure oils discharged from the two pressure oil discharge ports (1b, 1c). A high-pressure supply means for supplying the first pressure oil supply port (21e); and a low-pressure side pressure oil selected from the two pressure oils discharged from the two pressure oil discharge ports (1b, 1c). Low pressure supply means for supplying to the second pressure oil supply port (21f), these high pressure supply means and low pressure supply means being connected to the two pressure oil discharge ports (1b, 1c) and the first pressure oil supply Mouth (21
e) and the second oil pressure supply port (21f). 2. The high pressure supply means comprises: a first check valve (31) and a second check valve (32).
The first pressure oil discharge port (1b) and the first pressure oil supply port (21e) are connected via the first check valve (31), and the second pressure oil discharge port (1b) is connected to the second pressure oil discharge port (1b). An oil discharge port (1c) and the first pressure oil supply port (21e) are connected via the second check valve (32), and a high pressure of the two pressure oil discharge ports (1b, 1c) is provided. Side pressure oil is supplied to the first pressure oil supply port (21e) via the first and second check valves (31, 32), and the low pressure supply means is provided with a first pilot A check valve (33) and a second pilot check valve (34) are provided, and the first pressure oil discharge port (1b) and the second pressure oil supply port (21f) are connected to the first pilot check valve. Valve (3
3), and pressurized oil discharged from the second pressure oil discharge port (1c) is supplied as pilot pressure oil of the first pilot check valve (33); The oil discharge port (1c) and the second pressure oil supply port (21f) are connected to the second pilot check valve (3
4), and supplies the pressure oil discharged from the first pressure oil discharge port (1b) as pilot pressure oil of the second pilot check valve (34); When the pressure oil discharged from the oil discharge port (1c) is at a high pressure, the first pilot check valve (33) is opened by the pilot pressure oil to release the first oil.
The low pressure oil discharged from the pressure oil discharge port (1b) is supplied to the second pressure oil supply port (21f), and the pressure oil discharged from the first pressure oil discharge port (1b) When the pressure is high, the pilot pressure oil opens the second pilot check valve (34) to release the second pilot check valve (34).
The pressure oil supply device according to claim 1, wherein the low pressure oil discharged from the pressure oil discharge port (1c) is supplied to the second pressure oil supply port (21f). 3. The pressure oil supply device according to claim 1, wherein said high pressure supply means and said low pressure supply means are integrally formed.