JPS6337276B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable displacement hydraulic device, and more particularly to a hydraulic pump or motor whose output is variable by adjusting the amount of displacement of a variable control element.

Conventionally, as this type of hydraulic device, for example,
90203, etc., and as shown in FIG. 9, a swash plate E constituting a variable control element is linked with a control piston P that adjusts the amount of displacement of the swash plate E, and a spool chamber X and the spool chamber
A control valve A having a freely movable spool Y and a pressing body G that presses the spool Y in one direction is provided, and the high pressure side pressure of the discharge passage H is introduced into the primary side of the spool Y. When the pressure exceeds a predetermined pressure set by the extruder G, the spool Y is moved to open the secondary side of the spool Y to the primary side and open the control passage C leading to the back surface of the control piston P. A control pressure is introduced and this control piston P
The swash plate E is moved from the maximum inclination position shown in the figure toward the neutral position, and the internal Capacity control is performed under so-called pressure compensation (pressure compensator, hereinafter referred to as PC), which discharges only a small amount of oil equivalent to the amount of leakage and keeps the actual discharge amount almost zero. There is.

However, in the capacity control using the control valve A as described above, when the discharge pressure reaches a predetermined pressure set by the pressing body G, the spool Y is moved to change the control passage C on the secondary side to the discharge passage on the primary side. open to H,
Moreover, since the opening degree is increased one after another as the discharge pressure increases without closing, the control fluid is introduced into the back of the control piston P one after another, and the swash plate E is immediately controlled to the neutral position. , 1st
As shown in Fig. 0, it corresponds to the setting value of the pressing body G.
For PC cutting starting pressure P1, for example 190Kg/cm ² ,
If the PC cut end pressure P2 at which the discharge amount becomes zero is, for example, 200 Kg/cm ² , the difference in discharge pressure (ΔP) must be a small value of about 10 Kg/cm ² .

Here, the spring force of the pressing body G is increased to minimize the amount of movement of the spool Y with respect to the increase in the discharge pressure, and the opening area to the control passage C is gradually increased to increase the rate of increase in the control pressure with respect to the increase in the discharge pressure. If the pressure difference (ΔP) is made sufficiently small, it is possible to secure a relatively large pressure difference (ΔP), but in this case, it becomes difficult to operate the control valve A, and the pressing body G becomes large and occupies space. There are also increasing difficulties. Furthermore,
Among the moments that tend to tilt the swash plate E in the maximum inclination direction or the neutral direction (hereinafter referred to as the "tilt moment"), mainly due to the rotation of the cylinder block B, the plurality of cylinders interposed in the block B are The cylinder chamber M is moved forward and backward by the plunger D...
What is generated based on the reaction force (hereinafter referred to as pressure moment) is the discharge side high pressure port HP communicating with the cylinder chamber M and the suction side low pressure port (not shown).
Although it depends on the porting design of the cylinder block B, the rotation angle of the cylinder block B usually fluctuates from time to time, and the swash plate E tends to wobble to some extent due to fluctuation factors such as this pressure moment. However, the control valve A for performing the above-mentioned PC control has no way to deal with this fluctuation factor, and therefore, even if the spring force of the pressing body G is increased to control the inclination angle of the swash plate E, Its control characteristics inevitably become unstable.

In the end, in the control valve using the above control valve A, the control with the characteristics shown in Fig. 7 (the capacity decreases slowly with respect to the discharge pressure, and the pressure difference between the PC cut start pressure and the PC cut end pressure) 10 for valve A only
Since it is several times or one order of magnitude larger than Kg/ ^cm2 , it is hereinafter referred to as long lamp PC control),
Control of the characteristics shown in FIG. 6 (hereinafter referred to as constant horsepower control because the aim is to approximate a hyperbola and make pressure x capacity, ie, horsepower, almost constant) was not possible.

Conventionally, in order to realize this type of long lamp PC control without being affected by fluctuations in pressure moment, etc., it has been known, for example, from Japanese Patent Application Laid-Open No. 53-126501, and as shown in FIG. In place of the control valve A, a constant horsepower control valve AA that can form a variable orifice O that can increase or decrease the opening area to the secondary side, that is, the control passage, is used.
Generally, the opening degree of the orifice is mechanically feedback-controlled by the amount of displacement of the swash plate E.

That is, the constant horsepower control valve AA includes a sleeve F and a freely movable servo spool S within the sleeve F.
forms a cam mechanism K for detecting the amount of displacement,
The sleeve F is disposed in a direction perpendicular to the rod L, and its end is brought into contact with the sliding surface of the cam mechanism K, and one end of the servo spool S is connected to a constant horsepower spring V.
An action chamber N is provided at the other end of the servo spool S and the sleeve F, and the orifice O whose opening degree is adjusted by relative movement between the servo spool S and the sleeve F is provided. and the discharge passage H is connected to the back pressure chamber X of the rod L through the orifice O.
A control pressure is introduced from the

When the discharge pressure introduced into the action chamber N exceeds the set value of the pressing body V, the servo spool S
is moved upward in the figure to open the orifice O, introduce control fluid into the back pressure chamber R, move the control piston P to the right in the figure, and move the swash plate E toward the neutral direction. Following this movement of the swash plate E, the position of the swash plate E is transmitted to the sleeve F via the cam mechanism K, and the sleeve F is moved upward. This results in
The opening degree of the orifice O is adjusted to the contraction side to reduce the introduction of control pressure and to stop the rightward movement of the push rod L and the control piston P. As the discharge pressure continues to rise, the servo spool S is further moved upward and the above operations are repeated, and the swash plate E is gradually controlled toward the neutral position, and its movement begins from the cut start pressure to the neutral position, where the cut ends. This means that long ramp control (control of the slope portion in FIG. 7) can be performed in which a large difference from the pressure is ensured.
In addition, the pressing body V is constructed of two springs of different lengths as shown in FIG. By changing to two modes, the sixth
The constant horsepower control shown in the figure can be performed.

In the device shown in FIG. 8, even if the swash plate E wobbles, the positional fluctuation of the swash plate E is always fed back to the opening degree of the orifice O via the cam mechanism K and the sleeve F, and the orifice O Although it is expected that stable control characteristics will be obtained because the opening degree of the valve is adjusted, the following problem exists.

That is, what is shown in FIG. 8 is the swash plate E.
Since the amount of displacement is mechanically fed back using the cam mechanism K, not only is the mechanism complicated and the cost is high, but also the space occupied by the cam mechanism K that constitutes this feedback mechanism is increased. In addition, there is a restriction that the physical arrangement of the cam mechanism K and the sleeve F must be orthogonal as described above.
The disadvantage was that the entire device became large.

Moreover, since the sleeve F is disposed perpendicularly to the cam mechanism K and its ends are in sliding contact, the sleeve F is affected by sliding wear and unbalanced loads, resulting in poor durability. In addition, it was difficult to smoothly follow the sleeve F by the cam mechanism K, and it was difficult to obtain accurate constant horsepower characteristics or long ramp characteristics.

An object of the present invention is to enable predetermined constant horsepower or long ramp PC control without employing a feedback mechanism having mechanical contact parts such as a cam mechanism, and to realize the same. At the same time, it is possible to solve the problem of fluctuation of variable control elements caused by pressure moment etc. during constant horsepower or long ramp PC control, and as a whole, it is possible to achieve accurate constant horsepower and long ramp while maintaining a simple structure and miniaturization. An object of the present invention is to provide a variable displacement hydraulic device that can be controlled by a PC.

That is, the present invention provides a control mechanism consisting of a control piston that adjusts the displacement amount of the variable control element, an operating spool, and a pressing body that presses the spool, and an operating pressure for constant horsepower control and long ramp PC control. is formed separately from the forming mechanism, and the operating pressure formed by this forming mechanism is guided to the operating spool of the control mechanism to operate the control mechanism, and the operation of the control mechanism makes the operating pressure the control pressure,
The displacement amount of the variable control element is adjusted by the operating pressure applied to the control piston,
This makes it possible to achieve the desired constant horsepower or long lamp PC control.

Embodiments of the device of the present invention will be described below based on the drawings.

The hydraulic device shown in FIG. 2 is a swash plate type axial piston pump, and in FIG. 2, reference numeral 1 denotes a hollow housing, and a cover 2 is fixed to one side of the housing. A main shaft 5 is rotatably supported inside the housing 1 via bearings 3 and 4, and a cylinder block 7 is rotatably supported on the main shaft 5 via a spline portion 6 formed at an intermediate portion thereof. is supported by

A large number of plungers 8 are provided on this block 7 and can freely reciprocate with a predetermined stroke. A shoe 10 supported by a retainer 9 is attached to the tip of each of these plungers 8. Swash plate 1 constituting a variable control element
It is in contact with 1.

This swash plate 11 can swing freely within a certain angle of inclination using the trunnion shaft 12 as a fulcrum.
A spring 13 is interposed between the rear surface of the housing 1 and the inner surface of the housing 1, which is in contact with the shoe 10, and acts to always maximize the inclination angle of the swash plate 11. Therefore, when the main shaft 5 is driven to rotate the cylinder block 7 in this state, each plunger 8 reciprocates, and this reciprocating movement provides the maximum discharge amount.Also, the inclination angle of the swash plate 11 can be adjusted. Therefore, an arbitrary discharge amount can be obtained.
In FIG. 2, 14 is a valve plate, and 15 is a spring receiver.

The pump shown in the drawings includes a control mechanism 20 that variably controls the discharge amount by adjusting the displacement amount, that is, the inclination angle, of the swash plate 11, and a control mechanism 20 that operates the control mechanism 20. By incorporating an operating pressure forming device 40 that forms an operating pressure PT for the engine, constant horsepower control shown in FIG. 6 or long ramp PC control shown in FIG. 7 can be performed.

As shown in detail in FIG. 3, the control mechanism 20 includes a control piston 21 that is movable relative to the swash plate 11, and is movably held by the piston 21,
An operating spool 22 having an operating surface 22a of the operating pressure PT, and the operating pressure PT of the spool 22.
It consists of a first pressing body 23 that opposes movement by the PT, and includes the control piston 21 and the operating spool 2.
2, a first variable orifice 24 is formed which opens when the spool 22 moves, and this orifice 24 is communicated with the back chamber 25 of the control piston 21, and is controlled by the opening of the orifice 24. The control piston 21 is moved toward the swash plate 11 by the control pressure PT' of the operating pressure PT.

What is shown in FIG. 3 is the control piston 21
is movably installed inside a cylinder 17 fixed to the cover 2 with bolts 16, and a mounting tube 18 is provided in the opposite direction to the mounting direction of the cylinder 17.
is supported by fixing means such as a snap spring, and an operating piston 26, which is different from the control piston 21, is movably supported on the outer periphery of this mounting cylinder 18. This operating piston 26 is
It is arranged in series with the control piston 21, its tip is in contact with the swash plate 11, and is operatively engaged with the control piston 21 by a push rod 27, so that it moves together with the movement of the control piston 21. and, via the operating piston 26,
The angle of inclination of the swash plate 11 is adjusted. That is, the control piston 21 and the operating piston 26
A slidable push rod 27 supported by a first receiver 28 and a second receiver 30 (to be described later) is interposed between the control piston 21 and the operating piston 26. I am trying to convey the message. This operation piston 26 communicates with a control passage 65 of a pressure compensator valve 60, which will be described later, to control the discharge pressure of the pump.
When P _S exceeds a predetermined pressure, it moves independently of the control piston 21 and adjusts the swash plate 11 to the neutral position, that is, performs Pc control.

The first pressing body 23 is mainly composed of a coil spring, and includes a first receiver 28 fixed to the mounting tube 18, that is, a stationary member, and a push rod 29 slidably supported by the operating spool 22 and the control piston 21. A second receptor 30 connected via
The spool 22 is interposed between
operates so as to be balanced with the first pressing body 23 regardless of changes in the fluctuation moment of the swash plate 11. In other words, the spool 22 is arranged to oppose the first pressing body 23 via the push rod 29 and the second receiver 30. The inner chamber a of the cylinder 17 and the mounting tube 18 communicates with the tank T via the tank passage 68 of the pressure compensator valve 60 except when Pc control is performed.

In FIG. 3, 31 is a cover that is screwed onto the open side of the cylinder 17, and 32 is this cover 31.
an adjusting body screwed into the swash plate 11 for adjusting the position of the control piston 21 in the cylinder 17;
The maximum inclination angle, that is, the maximum discharge amount is adjusted in the direction of arrow A in FIG. Further, 33 is a lock nut of the adjustment body.

Further, as shown in FIG. 4, the working pressure forming mechanism 40 includes a freely movable sleeve 41, a second pressing body 42 that opposes the movement of the sleeve 41, and is freely movably held by the sleeve 41, and controls the discharge of the pump. It consists of a servo spool 43 having a pressure P _S acting surface 43a and two third pressing bodies 44 and 45 that oppose the discharge pressure P _S of this spool 43, and between the sleeve 41 and the servo spool 43. forms a second variable orifice 46 that opens when the servo spool 43 moves, communicates this orifice 46 with the back chamber 47 of the sleeve 41, and controls the discharge pressure P _S controlled by the opening of the orifice 46. Reduced pressure, i.e. the working pressure PT
The rear chamber 47 of the sleeve 41 is connected to the operating surface 22a of the operating piston 22 in the control mechanism 20, and the orifice 46 is moved by the operating pressure PT. Working pressure formed by
PT is made to act on the action surface 22.

What is shown in FIG. 4 is a block 50 in which the forming mechanism 40 is formed separately from the housing 1 and the cover 2, and includes the sleeve 41, the servo spool 43, the second pressing body 42, and the third pressing body. The block 50 is constructed by incorporating bodies 44 and 45, and
is fixed to the housing 1 or the cover 2 with a fixing means 80 such as a bolt, and the sleeve 41
A communication passage 51 extending from the rear chamber 47 is formed in the cover 2 and the cylinder 17, and communicates with the passage 34 communicating with the working surface 22a of the operating spool 22, and also communicating with the working surface 43a of the servo spool 43. The high pressure passage 52 is connected to the discharge passage 70
It is made as if it is connected to.

More specifically, the block 50 freely supports the sleeve 41 at its center and has a sleeve hole 53 communicating with the communication passage 51 and the high pressure passage 52, and the press bodies 42, 44, 45. A housing chamber 54 is provided on the open side of the housing chamber 54 to support one end of the second pressing body 42 , and a cover 55 is screwed into the center of the cover 55 to support one end of the second pressing body 42 . , 45 supporting one side 44 of
An adjustment body 56 and a second adjustment body 57 that is screwed into the center of the adjustment body 56 and supports the other 45 of the third pressing bodies 44 and 45 are provided.

In the sleeve hole 53, the sleeve 41 having a servo spool 43 is movably housed, and in the accommodation chamber 54, the pressing body 41 is housed.
2, 44, 45, and the second pressing body 42
is interposed between a receiver 48 fixed to the sleeve 41 and the cover 55, and a receiver 49 that connects the third pressing bodies 44, 45 to the servo spool 43; Second adjustment body 5
6 and 57, respectively.

The second and third pressing bodies 42, 44, 45 are made of coil springs, and the third pressing bodies 44, 45
One side 44 has both ends connected to the receiver 49 and the first
while the other body 45 is in contact with the adjustment body 56.
is shorter than the length of the receiving body 49 and the supporting end surface of the second adjusting body 57, and one end thereof is separated from the supporting end surface by a predetermined distance.
The two third pressing bodies 44 and 45 are used in the sixth
This is for performing the constant horsepower control shown in the figure, and only one is required when performing the long ramp Pc control shown in FIG. 7. Furthermore, the length of one of the third pressing bodies 44, 45 is shortened and a distance is placed between it and the supporting end surface so that the servo spool 43 is not operated at the beginning of its operation, and the servo spool 43 is not activated. This is to operate when the spool 43 strokes beyond the above-mentioned interval, and to make the discharge pressure-discharge rate characteristic curved in the middle as shown in FIG. 6, thereby approximating the theoretical constant horsepower characteristic.

However, in the above configuration, if the first adjustment body 56 is operated and the pressing force of one of the third pressing bodies 44, 45 is adjusted, the characteristics of the first half leading to the center bending point can be changed.
It can be adjusted in the direction of arrow B in FIG. 6, and if the pressing force of the other 45 is adjusted by the second adjustment body 57, the characteristics in the latter half of the center bending point can be adjusted in the direction of arrow C in FIG.

In FIG. 4, 58 is a lock nut of the first adjusting body 56, and 59 is a lock nut of the second adjusting body 57.

The pressure compensator valve 60 for operating the operation piston 26 includes a control spool _{61 having an operating surface 61a that moves in response to the discharge pressure P S as} shown in FIG. A valve body 64 that accommodates the spool 61 and the pressing body 62, and a regulating body 63 that adjusts the pressing force of the pressing body 62 and adjusts the Pc control pressure in the direction of arrow D in FIG.
is formed by the movement of the spool 61.
A control passage 65 for guiding the Pc control pressure is provided, and this passage 65 is communicated with the back surface of the operating piston 26, that is, with the mounting tube 18 and the inner chamber a of the cylinder 17.

The valve body 64 is attached to the block 50 as shown in FIG.
As shown in FIG. 2, a branch passage 52a branching from the middle of the high pressure passage 52 formed at 0 is connected to the side opposite to the pressing body 62 of the control spool 61,
Further, as shown in FIG. 2, the block 50 is provided with a relay passage 67 communicating with the control passage 65 and a tank relay passage 69 communicating with a tank passage 68 provided in the valve body 64.

Next, the operation of the hydraulic device (swash plate type axial piston pump) constructed as described above will be explained based on the block diagram shown in FIG.

When the swash plate 11 is at its maximum inclination angle as shown in FIG.
, a portion of the high pressure fluid flowing through the discharge passage 70 passes through the high pressure passage 52 and the branch passage 52a to the working surface 43a of the servo spool 43 and the working surface 61a of the control spool 61 in the pressure compensator valve 60. be guided by.

When the pressure of the high-pressure fluid, that is, the discharge pressure P _S is lower than the pressure set by the third pressing body 44, the servo spool 43 does not move and the swash plate 11 maintains the maximum inclination angle, but the discharge pressure P When _S exceeds the pressure, the servo spool 43 moves to the right in FIG. 4 against one of the third pressing bodies 44, 45. This movement opens the second variable orifice 46, which controls the discharge pressure P _S to the operating pressure PT.
The working fluid controlled to this working pressure PT is led to the back chamber 47 of the sleeve 41, and moves the sleeve 41 to the right in FIG. 4 against the second pressing body 42, and at the same time aisle 5
1. It leads to the working surface 22a of the operating spool 22 through the passage 34.

The rightward movement of the sleeve 41 is in the direction of closing the orifice 46 and the second pressing body 4
2, the servo spool 43
It moves in conjunction with the rightward movement of.

Therefore, when the servo spool 43 moves to maintain balance with the third pressing body 44 due to an increase in the discharge pressure P _S , the sleeve 41 moves by the same amount as the servo spool 43. Therefore, an operating pressure PT corresponding to the amount of movement of the servo spool 43 can be obtained.

Further, the working fluid controlled to the working pressure PT is
When the operating pressure PT is applied to the operating surface 22a of the operating spool 22, the operating spool 22 opposes the first pressing body 23 until it is balanced with the pressing force of the pressing body 23, as shown in FIG. It moves to the right at . This rightward movement opens the first variable orifice 24, and the operating pressure PT is controlled by this orifice 24 to become the control pressure PT', and the control fluid controlled to this control pressure PT' is applied to the back surface of the control piston 21. The control piston 21 guided into the chamber 25 is moved to the right in FIG. 3, and the angle of inclination of the swash plate 11 is tilted toward the neutral position. That is, the control pressure
PT' is the pressure necessary to tilt the swash plate 11, and the rightward movement of the control piston 21 is in the direction of closing the orifice 24, following the movement of the operating spool 22. In other words, the second variable orifice 46 is controlled so that the pressing force acting on the left end of the sleeve 41 and the pressing force of the second pressing body 42 are balanced, and the control pressure PT obtained by this control is It acts on the operating surface 22a of the operating spool 22. As a result, the first
Since the opening amount of the variable orifice 24 becomes larger,
The operation spool 22 moves to a position where it balances with the first pressing body 23. This movement causes the control piston 21 to move following the operating spool 22, and the amount of movement is transmitted to the swash plate 11 via the push rod 27 and the operating piston 26, thereby controlling the inclination angle of the swash plate 11. As a result, the flow rate is controlled to a value corresponding to the discharge pressure P _S.

When the discharge pressure P _S further increases and the rightward movement of the servo spool 43 progresses, another third pressing body 45 is applied and corresponds to the servo spool 43. Therefore, the rate of increase in the controlled operating pressure PT becomes smaller with respect to the rate of increase in the discharge pressure P _S , and the discharge pressure P _S decreases as shown in Fig. 6.
The rate of decrease in the discharge amount Q with respect to the increase in the amount Q also becomes smaller.

Although the above description has been made regarding the case where the discharge pressure P _S increases, the same applies to the case where the discharge pressure P _S decreases. In other words, when the discharge pressure P _S decreases, the servo spool 43
is moved to the left to the balance position in FIG. 4, and the second variable orifice 46 is in the closed state.
The back chamber 47 of the sleeve 41 includes a storage chamber 54,
communicates with the tank T via a tank relay passage 69;
The working pressure PT drops. And this working pressure PT
Due to the lowering of the sleeve 41, the orifice 4
6 to the left in the direction of opening, and comes to rest at a balanced position with the second pressing body 42.

Due to the drop in the operating pressure PT, the operating spool 22 also moves to the left to the balance position with the first pressing body 23 in FIG. The swash plate 11 is connected to the tank T via the inner chamber a of the cylinder 17 and the tank passage 68 of the pressure compensator valve 60, and the swash plate 11 is tilted in the direction of increasing the angle of inclination.

Also, when performing constant horsepower control as described above,
The discharge pressure P _S is set by the pressing body 62.
When the Pc pressure is reached, the control spool 61 of the pressure compensator valve 60 moves against the pressing body 62 to open the control passage 65,
The Pc control fluid controlled to the control pressure Pc is passed through the control passage 6.
5 to the back surface of the operating piston 26, that is, the inner chamber a of the cylinder 17 and the mounting tube 18, and the swash plate 1
1 to the neutral position, Pc control of the sharp cut characteristic can be performed.

After this Pc control, if the discharge pressure P _S decreases,
The control spool 61 is returned to its original position by the action of the pressing body 62, and the inner chamber a is connected to the tank T via the tank passage 68 of the pressure compensator valve 60.
Therefore, the constant horsepower control described above can be performed again.

In the embodiment described above, even if there is a fluctuation in the pressure moment or the like among the tilting moments acting on the swash plate 11, constant horsepower or long ramp PC control can be performed without being affected by the fluctuation.

This is because the control pressure PT' is applied to the rear chamber 25 of the control piston 21 via the first variable orifice 24 formed between the control piston 21 and the operation spool 22. For example, when the pressure moment etc. fluctuates, the swash plate 1
1 tries to wobble in the direction of maximum inclination, this fluctuation of the swash plate 11 is transmitted to the control piston 21 via the push rod 27, and the control piston 21
This is because it is possible to counteract this fluctuation by moving the variable orifice 24 to the left in FIG. .

Therefore, even if the pressure moment acting on the swash plate 11 fluctuates, the rear chamber 25
Since the control pressure PT' of the swash plate 11 is automatically adjusted to counteract fluctuation factors such as this pressure moment, it is possible to prevent the swash plate 11 from wobbling.

In other words, constant horsepower or long ramp PC control close to the theoretical value can be performed without changing the characteristics of constant horsepower or long ramp PC control due to fluctuation factors such as pressure moment.

The embodiment described above is a swash plate type axial piston pump, but the same applies to a motor.
Although not shown, the present invention can be similarly applied to a variable displacement vane pump or a motor. In the case of vane pumps or motors, the cam ring is the variable control element.

Further, although only constant horsepower control has been described, the same applies to long ramp Pc control.

As described above, according to the present invention, the control mechanism that adjusts the displacement amount of the variable control element is actuated by the working pressure generated by the working pressure forming mechanism formed separately from the control mechanism, so that the control mechanism that adjusts the displacement amount of the variable control element is actuated by the working pressure generated by the working pressure forming mechanism formed separately from the control mechanism. Compared to conventional hydraulic devices that use Constant horsepower control or long ramp Pc control that is close to the theoretical value can be performed without changing the characteristics of constant horsepower control or long ramp Pc control due to fluctuation factors such as pressure moment acting on the variable control element.

[Brief explanation of the drawing]

Fig. 1 is a schematic side view showing an embodiment of the device of the present invention, Fig. 2 is a schematic sectional view thereof, Fig. 3 is an enlarged sectional view of only the control mechanism, and Fig. 4 is an enlarged sectional view of only the operating pressure generation mechanism. , Figure 5 is a block diagram explaining the operation, Figures 6 and 7 are output characteristic diagrams, Figure 8 is a sectional view of the main part of a conventional device with a mechanical feedback mechanism, and Figure 9 is a sharp cut. A sectional view of a conventional device that performs PC control with characteristics, and FIG. 10 is a diagram of its output characteristics. DESCRIPTION OF SYMBOLS 11... Swash plate, 20... Control mechanism, 21... Control piston, 22... Operation spool, 23... First pressing body, 24... First variable orifice, 25...
...Back chamber, 40... Working pressure formation mechanism, 41...
Sleeve, 42... second pressing body, 43... servo spool, 44, 45... third pressing body, 46...
Second variable orifice, 47... Rear chamber, 56,5
7... Adjustment body, 60... Pressure convencator valve, 26... Operation piston.

Claims (1)

[Scope of Claims] 1. A hydraulic pump or motor whose output is variable by adjusting the amount of displacement of a variable control element, comprising a control mechanism that adjusts the amount of displacement of the variable control element, and a control mechanism that operates the control mechanism. a control piston that is freely movable relative to the variable control element;
an operating spool movably held by the piston and having a surface on which the operating pressure acts; and a first pushing body that opposes movement of the spool due to the operating pressure, and between the control piston and the spool. , a first variable orifice opened by movement of the spool, the orifice communicating with a back chamber of the control piston, the control piston being controlled by the control pressure of the operating pressure controlled by the opening of the orifice. The working pressure generating mechanism is configured to move in the direction of the variable control element, and the working pressure generating mechanism includes a freely movable sleeve, a second pressing body that opposes the movement of the sleeve, and is movably held by the sleeve, and a servo spool having a surface on which the high-pressure side pressure of the hydraulic pump or motor acts, and at least one third pressing body that opposes movement of the spool due to the high-pressure side pressure, and between the sleeve and the servo spool; , comprising a second variable orifice opened by movement of the servo spool, the orifice communicating with the back chamber of the sleeve and guiding the operating pressure of the high pressure side pressure controlled by the opening of the orifice;
A variable displacement hydraulic device, characterized in that the sleeve is moved by the operating pressure, and a rear chamber of the sleeve communicates with an operating surface of an operating spool in the control mechanism. 2. The variable displacement hydraulic device according to claim 1, wherein the working pressure forming mechanism includes an adjusting means for adjusting the pressing force of the third pressing body. 3. The control mechanism includes a control piston having an operating spool and an operating piston, and the back chamber of the operating piston communicates with the control passage of the pressure convencator valve, so that the high pressure side pressure exceeds a predetermined pressure. 3. The variable displacement hydraulic device according to claim 1 or 2, wherein the variable control element is controlled to a neutral position when the pressure is reduced. 4. A patent claim characterized in that a control piston and an operating piston are arranged in series, the operating piston is in contact with a variable control element, and the control piston and operating piston are operatively engaged with each other. The variable displacement hydraulic device according to item 3.