JPH0146720B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a variable displacement hydraulic device, specifically, an operating plunger that adjusts the amount of displacement of a variable control element;
and a bias plunger that urges the variable control element in a direction of maximum inclination in opposition to the operation of the plunger, applying control pressure to the operation plunger and applying high pressure side pressure of the hydraulic device to the bias plunger. The present invention relates to a variable displacement hydraulic device in which the amount of displacement of the variable control element is adjusted by the operation of the operating plunger.

(Prior art) Generally, this type of hydraulic device is
As described in Japanese Patent No. 90203 and as shown in FIG. 7, it includes a spool chamber R, a spool S that is freely movable inside the spool chamber R, and a pressing body V that presses the spool S in one direction. Using the control valve E,
The high-pressure side pressure of the high-pressure side pressure passage H is introduced into the primary side of the spool S, and when the pressure exceeds a predetermined pressure set by the pressing body V, the spool S is moved and the second side of the spool S is moved. The next side is opened to the primary side, control pressure is introduced into the control passage C leading to the back side of the operating plunger A, the operating plunger A is moved, and the variable control element X formed by the slope is thereby controlled as shown in the figure. It moves from the maximum inclination position toward the neutral position, and the high-pressure side pressure discharged to the high-pressure side pressure passage H, that is, the discharge pressure, is maintained almost at the predetermined pressure, and only a small amount of oil corresponding to the internal leakage is released. Capacity control is performed under so-called pressure compensation in which the actual discharge amount is maintained at approximately zero.

By the way, in the case of a hydraulic device that performs capacity control as described above, it is necessary to always maintain the variable control element X at the maximum displacement position by overcoming the pressure moment caused by the piston P interposed in the cylinder block G. . In this case, for example, the high pressure side pressure is 140
For medium-sized ones such as Kg/ ^cm2 , the variable control element
It is sufficient to insert only a spring that urges the
If the weight is as high as Kg/cm ² , the pressure moment caused by the piston P will increase accordingly, so if we rely only on the spring force, the spring will become large and space will be difficult, and the variable control element will become larger. It becomes difficult to maintain X in the maximum tilt position. Therefore, in such a case, as shown in the figure, in conjunction with the bias spring F, the variable control element A bias plunger B is installed to maintain the bias plunger B at the maximum inclination position, and the bias plunger B
As shown in the figure, the high pressure side pressure of the high pressure side pressure passage H is generally applied to the back surface of the variable control element X to create a force that maintains the variable control element X at the maximum inclination position.

On the other hand, when control pressure is introduced to the back surface of the operating plunger A and the plunger A attempts to move, it is necessary to overcome the force exerted by the bias spring F and the bias plunger B to maintain the variable control element X at the maximum tilt position. , the variable control element X must be moved towards the neutral position. Therefore, the force based on the control pressure introduced to the back surface of the operating plunger A is made larger than the force based on the high pressure side pressure introduced to the back surface of the bias plunger B (strictly speaking, at least the urging force of the bias spring F). (larger)
Furthermore, even without the bias spring F, the control pressure after passing through the control valve E is usually lower than the high pressure side pressure on the primary side, and the operating plunger A is biased by the control pressure lower than this high pressure side pressure. Since there is also a need to move it against the plunger B, the pressure receiving area of the operating plunger A is made larger than that of the bias plunger B.

(Problems to be Solved by the Invention) As described above, the force based on the control pressure introduced to the back surface of the operating plunger A is made larger than the force based on the high pressure side pressure introduced to the back surface of the bias plunger B. Because of the need to do so, a difference is provided between the pressure receiving areas of both plungers A and B. Here, if the degree of pressure reduction of the control pressure is relatively small and the control pressure is close to the discharge pressure, the bias plunger B
There is no need to make the pressure receiving area of the operating plunger A very large. However, if the control pressure is set to a large value close to the discharge pressure in this way, problems such as leakage in the control system from the spool chamber R to the control passage C and the operating plunger A will become noticeable, and as will be explained in detail below, Difficulties also arise in terms of responsiveness, so
For example, as shown in Figure 6, if the maximum discharge pressure is 350 kg/cm ² , the control pressure should be suppressed to about one-fifth, about 70 kg/cm ² (characteristic d). I have a request. If this were to be achieved by the pressure-receiving area of the operating plunger A, an area five times or more than that of the bias plunger B would be required, resulting in the problem that the operating plunger A would be large.

On the other hand, at the expense of increasing the size of the operating plunger A to some extent, the degree of pressure reduction of the control pressure is reduced as shown in characteristics c and b, and the increase rate of the control pressure with respect to the discharge pressure, that is, the rate of change of the control pressure, is changed to the characteristic d. If the control pressure is increased compared to , and approaches the control pressure = discharge pressure (characteristic a), the problem of oil leakage in the control system will become noticeable, and the opening degree of the secondary side relative to the primary side of the spool S will be increased. to reduce the degree of decompression,
Furthermore, since it is necessary to largely change the opening degree of the secondary side in accordance with changes in the discharge pressure, a problem arises in that the responsiveness of the operating plunger A and, in turn, the responsiveness of the variable control element X deteriorates. That is,
For example, the response of variable control element X is 0.05 sec.
responds to frequent load fluctuations at moderate intervals, and
We would like to respond to a minute oil amount of about 0.1 liter/min, but if the opening degree change on the secondary side of spool S is large, a small displacement of spool S, in other words, a small control flow rate, will cause the variable control element to It is impossible to displace X, and it is extremely difficult to obtain the above-mentioned targeted response.

On the other hand, in this type of hydraulic device, when the hydraulic cylinder at the end connected to the high-pressure side pressure passage H of the hydraulic device is stopped, for example, the hydraulic device is operated with low power. It is desirable to keep it in an idling state. However, in the above-mentioned conventional device, below the predetermined pressure set by the pressing body V,
Since the variable control element X is held at the maximum tilt position and oil is constantly discharged, the discharge amount is reduced to zero at a low pressure below the predetermined pressure set by the pressing body V to create a so-called idling state. Feathering control cannot be performed, and there are also difficulties in reducing power.

In the present invention, we have focused on the fact that it is excessive to apply discharge pressure directly to the back surface of the bias plunger, and by applying high-pressure side pressure, that is, a reduced pressure of the discharge pressure, to the bias plunger,
The operating plunger that is moved against the biasing force in the neutral direction by the bias plunger can be made smaller, and the rate of change of the control pressure with respect to the discharge pressure can be reduced, that is, the control pressure can be reduced to a sufficiently small value, and the control pressure can be reduced to a sufficiently small value. The object of the present invention is to provide a hydraulic device that can reduce system leakage, improve the stability of the control system, and improve the responsiveness of variable control elements. It is an object of the present invention to provide a hydraulic device that allows feathering control while providing advantages.

(Means for Solving the Problem) Therefore, the invention described in claim 1 (hereinafter referred to as the first invention) includes an operating plunger 14 for adjusting the displacement amount of the variable control element 6, and a control plunger 14 for adjusting the displacement amount of the variable control element 6. A bias plunger 13 that urges the variable control element 6 in the direction of maximum inclination in opposition to the operation is provided, the control pressure is applied to the operation plunger 14, and the high pressure side pressure of the hydraulic device is applied to the bias plunger 13. In the variable displacement hydraulic device in which the amount of displacement of the variable control element 6 is adjusted by the operation of the operation plunger 14, the bias plunger 13 and the high pressure side pressure passage 17
The primary side passages 55, 69 are connected to the communication passage 18 connecting the
and secondary side passages 56, 68, and a pressure reducing valve is interposed therebetween to open the secondary side passages 56, 68 to the drain passages 59, 67 due to the pressure increase in the secondary side passages 56, 68. To the bias plunger 13,
This is characterized in that a reduced pressure on the high pressure side is applied.

Further, in the invention set forth in claim 2 (hereinafter referred to as the second invention), in addition to the configuration of the first invention, the communication passage 18 has a switching passage 71 that is open to the tank _T2. This device is characterized in that a valve 70 is provided, and the switching operation of the switching valve 70 opens the bias plunger 13 to the tank _T2 .

(Function) The bias plunger 13 has a primary passage 55,
69 and secondary side passages 56, 68, the high pressure side pressure is caused by opening the secondary side passages 56, 68 to the drain passages 59, 67 due to the pressure increase in the secondary side passages 56, 68. By applying a reduced pressure of , it is possible to relieve the urging force exerted by the bias plunger 13 to maintain the variable control element 6 in the maximum inclination direction. Therefore, the operating plunger 14 that opposes the urging force of the bias plunger 13 does not need to be very large, and the control pressure applied to the operating plunger 14 can be made sufficiently low to prevent leakage. It is also possible to improve the response of the reduction and control.

Moreover, in the second invention, in addition to this, the switching valve 70
Bias plunger 1
3 to the tank _T2 , the urging force of the bias plunger 13 can be reduced, and so-called feathering control can be performed in which the discharge amount is made zero at an arbitrary discharge pressure.

(Example) First, an example of the first invention will be described based on FIGS. 1 and 2.

The hydraulic device shown in FIG. 1 is a known swash plate type axial piston pump to which the present invention is applied.
A drive shaft for books is supported, and a pair of cylinder blocks 5, 5 are spline-coupled to this drive shaft 4, and swash plates 6, 6 constituting variable control elements are provided for each cylinder block 5, 5, respectively. The figure shows a two-barreled pump.

The device of the present invention can be applied to any variable displacement hydraulic machine including a single pump other than the dual pump shown in FIG.

To explain the pump shown in FIG. 1, the cylinder blocks 5, 5 are provided with a large number of pistons 7 that can freely reciprocate, and the head of each piston 7 is supported by a retainer 8. The shoes 9 are each attached, and these shoes 9
is in contact with the swash plates 6, 6.

The swash plates 6, 6 are supported via a trunnion shaft 10 so as to be able to slide freely within a certain range of inclination angle, and are connected to the swash plates 6, 6 via connecting rods 11, 12 which are pin-coupled at positions displaced by 180°. A bias plunger 13 that presses the plates 6, 6 in the direction of the maximum inclination angle.
and an operating plunger 14 for adjusting the inclination angle of the swash plates 6, 6, respectively.

The bias plunger 13 is movably supported by a cylinder 15 fixed to the end cap 1a of the housing 1, and a spring 16 is interposed between the cylinder 15 and the head of the plunger 13. Back chamber 13a of the plunger 13
As will be described in detail later, as shown in FIG. 2, a communication passage 18 branching from the high-pressure side pressure passage, ie, the discharge passage 17, is communicated via a pressure reducing valve (50 or 60).

The operation plunger 14 is movably supported by a cylindrical body 19 fixed to the end cap 1a, and the rear chamber 14a has a second
As shown, a control passage 24 extending from the control valve 20 is open so that control pressure acts on the back surface of the operating plunger 14.

Therefore, when the control pressure from the control passage 24 is not acting on the operation plunger 14, the swash plates 6, 6 have a maximum inclination angle,
When the maximum discharge amount can be obtained and control pressure is applied to the operating plunger 14, the inclination angle of the swash plates 6, 6 is adjusted, and the discharge amount commensurate with the inclination angle can be obtained. .

The control valve 20 is a constant horsepower control valve with a feedback mechanism. 21a, and a spool 22 which is freely movable inside the spool chamber 21a and has two lands 22a and 22b, and is connected to one end of the spool 22 from the discharge passage 17 in the pump via a piston 28, which will be described later. Branching first high pressure passage 2
3, pressure bodies 40 and 41 made of springs are provided on the other end side of the spool 22, and the sleeve 37 is
A communication port 24a having one end open to the spool chamber 21a and the other end leading to the control passage 24 leading to the rear chamber 14a of the operating plunger 14, and a second high pressure extending from the discharge passage 17 and opening to the spool chamber 21a. an open port 25a of the passage 25;
Moreover, the other end of the spool 22, that is, the spring chamber 26 in which the pressing bodies 40, 41 are housed, is communicated with the tank _T1 via a drain passage 27 shown in FIG.

Therefore, as shown in FIG. 2, the discharge passage 1
The pressure of the discharge fluid flowing through the pressing body 40,
41 or less, the spool 22 is
It is stationary at the rest position shown in FIG. 1 or 2, and in this rest position, the second high pressure passage 25 is closed and the control passage 24 is connected to the tank T ₁ through the spring chamber 26. It communicates with
Moreover, the pressure of the discharged fluid is the pressure of the pressing body 40,
41, the spool 22 moves and the control passage 24 becomes the second high pressure passage 25.
and a communication port 24 to the control passage 24.
a and the land 22a of the spool 22, a part of the discharge fluid is introduced from the second high pressure passage 25 into the control passage 24 as a control pressure, and the operation The plunger 14 is operated to adjust the angle of inclination of the swash plates 6, 6.

In addition, what is shown in FIG. 1 is the spool chamber 2.
1a, in series with the spool 22, a piston 2
A cylinder 29 having a cylinder 8 inside is disposed, and the tip of the piston 28 is brought into contact with one end side of the spool 22, and the rear chamber 29 of the piston 28 is disposed.
b, an annular groove 29 communicating with the first high pressure passage 23;
A is communicated with the piston 28 so that the spool 22 is urged by high pressure side pressure.

Furthermore, the one shown in FIG. 1 is a constant horsepower control valve with a feedback mechanism using a link, in which one end of a link 30 is pivotally connected to the valve body 21 via a pin 31 for free swinging. A link 33 is swingably connected to the other end of the link 30 via a pin 32, and this link 33 is pivotally connected to the swash plate 6 via a pin 34.
A roller 36 is rotatably attached to the middle part of the cylinder 29 via a pin 35, and furthermore, this roller 36 is brought into contact with the end of the cylinder 29, so that the cylinder 29 can be moved following the movement of the swash plate 6. That's what I do.

Therefore, the pressure of the discharged fluid is reduced to the pressure of the pressing body 4.
0.41 and through the piston 28,
When the spool 22 moves, the operation plunger 14 operates as described above, and the swash plate 6 moves. At this time, the links 33 and 30 also operate following the movement of the swash plate 6, and the roller 3
6 moves the cylinder 29 in the direction of the pressing bodies 40 and 41, and the movement of the cylinder 29 moves the guide sleeve 37, which connects the land 22a of the spool 22 and the communication port 24a leading to the control passage 24. This reduces the opening area of the orifice formed in the opening.

Therefore, through this series of feedback operations, the inclination angle of the swash plate 6 is gradually adjusted toward the neutral position.

It goes without saying that the control valve 20 is not limited to such a constant horsepower control valve, but may be a valve of the type shown in the conventional example shown in FIG.

In the hydraulic device of the first invention, in which the hydraulic device is configured as described above, a high-pressure side pressure passage 1 as shown in FIG.
7 and the back chamber 13a of the bias plunger 13 is interposed with a constant secondary pressure reducing valve 50 as shown in FIG. As the pressure increases, the secondary passage 56 is opened to the drain passage, thereby applying a reduced pressure of the high pressure side pressure. Incidentally, instead of the constant secondary pressure type pressure reducing valve 50, a proportional pressure reducing valve 60 shown in FIG. 4 may be interposed.

The constant secondary pressure type pressure reducing valve 50 shown in FIG. A spring 54 is disposed at the right end of 53. On the other hand, in the upper part of the valve body 51, there is a primary side passage 55 communicating with the communication passage 18 branched from the high pressure side pressure passage 17, and on the left side of the valve body 51, there is a secondary side passage 55 communicating with the back chamber 13a of the bias plunger 13. A passage 56 is bored in each, and the primary passage 55 and the secondary passage 56 are provided so as to communicate with each other through the communication hole 57 and the spool hollow chamber 58 when the pressure reducing valve 50 is in a normal state. . Therefore, when the pressure in the secondary passage 56 becomes higher than the spring 54 pressure, the spool 53 is moved to the right against the spring 54, an orifice is formed by the primary passage 55 and the communication hole 57, and the second The pump discharge pressure is reduced so that the pressure in the next passage 56 does not exceed the spring 54 pressure, that is, so that the secondary pressure does not rise above a certain value. It is more desirable to provide an adjustment mechanism such as a screw on the right side of the valve body 51 so that the spring 54 pressure can be changed freely. Furthermore, if the pressure on the secondary side passage 56 side rises above the pressure set by the spring 54 and the spool 53 moves further to the right, communication between the communication hole 57 and the primary side passage 55 is cut off.
A drain passage 5 that communicates the communication hole 57 with the tank T
9 to prevent an abnormal pressure rise in the secondary passage 56. The configuration in which the drain passage 59 is provided and the secondary passage 56 is made to communicate with the primary passage 55 after the drain passage 59 is provided is known in the art. It is no different from a so-called pilot-operated constant secondary pressure pressure reducing valve that opens the next side to the drain.

Further, the proportional pressure reducing valve 60 shown in FIG.
springs 64 and 65 are provided on both sides of the spool 63, and a primary passage 69 on the small diameter side of the spool 63 is provided.
The connecting side of the communicating passage 18 to the discharge passage 17, that is, the primary side is connected to the large diameter side of the spool 63, and the connecting side to the bias plunger 13, that is, the secondary side is connected to the large diameter side of the spool 63. The large-diameter spool chamber 62a of the spool chamber 62 includes a high-pressure passage 66 extending from the primary passage 69, and a tank.
By opening the drain passage 67 leading to T ₂ and moving the spool 63, the secondary passage 68 provided on the large diameter side of the spool 63 is communicated with one of the high pressure side passage 66 and the drain passage 67. The opening of the high-pressure side passage 66 to the secondary side passage 68 reduces the pressure of the high-pressure side pressure fluid flowing through the high-pressure side passage 66 at a constant pressure reduction ratio, so that the high-pressure side pressure fluid flowing through the high-pressure side passage 66 is It flows to the secondary side of the communication passage 18.

In addition, in addition to the constant secondary pressure type pressure reducing valve and the constant ratio pressure reducing valve, a constant difference pressure reducing valve may be used. All you have to do is make it happen.

Therefore, in the above configuration, the discharge passage 17
A part of the discharge fluid flowing through the bias plunger 1 is taken into the communication passage 18, and is reduced to a predetermined pressure by the constant secondary pressure pressure reducing valve 50, the proportional pressure reducing valve 60, or the constant difference pressure reducing valve.
It acts on the back chamber 13a at 3.

Therefore, compared to the conventional device in which the high-pressure side pressure, which is the discharge pressure, is applied, the urging force exerted by the bias plunger 13 to maintain the inclined slope 6 at the maximum inclined position can be reduced, and the bias force applied to the bias plunger 13 can be reduced. Even if the pressure receiving area of the operating plunger 14 is not increased relative to the area of the pressure receiving surface, the operating plunger 14 is equipped with the bias plunger 1.
3 can be generated, and the operating plunger 14 can be made smaller accordingly. Further, as the biasing force is reduced by the bias plunger 13, the force generated in the operating plunger 14 can also be reduced, so that the control pressure for the high pressure side pressure can be reduced and the rate of change of the control pressure can be reduced, that is, the characteristics shown in FIG. d can be selected, leakage from the control system including the operating plunger 14 and the control valve 20 can be reduced, and the slope 6 can be controlled stably by the operating plunger 14. Even when the inclined slope 6 is frequently slightly displaced, the responsiveness can be improved.

Further, in the hydraulic device of the second invention, similar to the first invention, in the hydraulic device shown in FIG. 1, as shown in FIG. Connecting passage 18 connecting
In addition to interposing the proportional pressure reducing valve 60 described above,
An electromagnetic switching valve 70 having an open passage 71 to the tank T ₂ is installed, and the bias plunger 13 is
By applying a reduced pressure on the high pressure side and switching the switching valve 70, the back chamber 13a of the bias plunger 13 is opened to the tank _T2 . In addition, the proportional pressure reducing valve 6
0, a constant secondary pressure type pressure reducing valve 50 shown in FIG. 3 may be installed.

The switching valve 70 is a 3-port, 2-position electromagnetic switching valve, and when the solenoid is energized, the spool is moved to the right in FIG. , to the tank T ₂ , and by this opening, the urging force of the bias plunger 13 is reduced to that of the spring 16 alone, and the inclined slope 6 is reduced to the pressing body 4 of the control valve 20.
It is possible to restore the neutral position at a low pressure below the set pressure of 0.41, and perform capacity control under pressure compensation, that is, feathering control, which makes the discharge amount zero at the low pressure.

This feather ring is used when the load is idle, and pressure compensation can be performed at low pressure, so power loss during idling can be reduced.

Although the embodiment described above uses a feedback mechanism consisting of a link, it is also possible to use a control valve 20 that performs only pressure compensation control without using this feedback mechanism, as described above. be. Further, the present invention can be applied to motors other than axial piston pumps, and can also be applied to vane pumps or motors using other cam rings.

(Effect of the invention) As described above, in the first invention, the operation plunger 1
4 can be designed compactly, and the rate of change of control pressure with respect to the high pressure side pressure can be reduced, so leakage from the operating plunger 14 and its control system can be reduced, and control performance can be improved.
In addition, even if the load frequently changes minutely, the response can be improved.Also, in the second invention, while the above-mentioned effects are obtained, the switching operation of the switching valve 70 reduces the pressure. The so-called idling state is created by reducing the discharge amount to zero.
Feathering control can also be performed.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the device of the present invention;
Figure 2 is a schematic explanatory diagram showing the main parts of the first invention;
The figure is a cross-sectional view showing an example of a constant secondary pressure type pressure reducing valve, FIG. 4 is a cross-sectional view showing an example of a proportional pressure reducing valve, FIG. 7th diagram showing how control pressure changes with respect to discharge pressure
The figure is a longitudinal sectional view of a conventional example. 6... Swash plate, 13... Bias plunger, 1
4... Operation plunger, 17... High pressure side pressure passage, 18... Communication passage, 50... Secondary pressure constant pressure reducing valve, 55... Primary side passage, 56... Secondary side passage, 59... Drain Passage, 60...proportional pressure reducing valve,
67...Drain passage, 68...Secondary side passage, 69
...Primary side passage, 70...Switching valve, 71...Open passage, T, _T1 , _T2 ...Tank.

Claims (1)

[Scope of Claims] 1. An operating plunger 14 that adjusts the amount of displacement of the variable control element 6, and a bias plunger 13 that biases the variable control element 6 in the direction of maximum inclination in opposition to the operation of the plunger 14. A control pressure is applied to the operating plunger 14 and a high pressure side pressure of a hydraulic device is applied to the bias plunger 13, so that the displacement amount of the variable control element 6 is adjusted by the operation of the operating plunger 14. In the variable displacement hydraulic device, the communication passage 18 connecting the bias plunger 13 and the high pressure passage 17 includes primary passages 55 and 69 and a secondary passage 5.
6, 68, and a pressure reducing valve is installed to open the secondary side passage to the drain passages 59, 67 due to a pressure increase in the secondary side passage, and the bias plunger 13 is provided with a pressure reducing valve of the high pressure side pressure. A variable displacement hydraulic device characterized in that it acts as if it were made to act. 2 comprises an operating plunger 14 that adjusts the amount of displacement of the variable control element 6; and a bias plunger 13 that urges the variable control element 6 in the direction of maximum inclination in opposition to the operation of the plunger 14; A variable displacement hydraulic device in which a control pressure is applied to the bias plunger 13, and a high pressure side pressure of the hydraulic device is applied to the bias plunger 13, and the displacement amount of the variable control element 6 is adjusted by the operation of the operating plunger 14. A pressure reducing valve is interposed in the communication passage 18 connecting the bias plunger 13 and the high pressure side pressure passage 17, and a switching valve 70 having an open passage 71 to the tank _T2 is interposed. 70, the bias plunger 13 is opened to the tank _T2 .