JPS6337277B2 - - 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 pressing body G, the spool Y is moved to open the secondary side of the spool Y to the primary side, and open the secondary side of the spool Y to 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 immediately returns to the neutral position. controlled, first
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 some 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 What is generated based on the reaction force of the cylinder chamber M due to the forward and backward movement of the plunger D (hereinafter referred to as a pressure moment) is generated between the discharge side high pressure port HP and the suction side low pressure port (not shown) that communicate with the cylinder chamber M. 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/cm ² , it is hereinafter referred to as long lamp PC control)
Also, it is not possible to control the characteristics shown in Figure 6 (hereinafter referred to as constant horsepower control because the aim is to approximate a hyperbola so that pressure x capacity, that is, horsepower becomes almost constant). Ta.

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.
forming a cam mechanism K for detecting the amount of displacement of
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 the slope into two modes, the discharge rate decreasing slope can be made into two polygonal lines and 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, in the device shown in FIG. 8, the displacement amount of the swash plate E is mechanically fed back using the cam mechanism K, which not only becomes mechanically complicated and increases the cost, but also the amount of displacement of the swash plate E is The space occupied by the cam mechanism K constituting the sleeve F is large, and the physical arrangement relationship between the cam mechanism K and the sleeve F is also restricted to be orthogonal as described above. ,
The disadvantage was that the entire device became large.

Moreover, since the sleeve F is disposed orthogonally to the cam mechanism K and its ends are in sliding contact, the durability is affected by the sliding wear and the unbalanced load. 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 includes a control mechanism that adjusts the amount of displacement of a variable control element, and a forming mechanism that generates a control pressure for operating this control mechanism, and the control mechanism is provided with a high pressure of a hydraulic pump or a motor. guiding the side pressure and controlling the high pressure side pressure to an operating pressure by a first variable orifice formed in the control mechanism, and applying this operating pressure to an operating spool held on a control piston of the control mechanism; The working pressure is guided to the forming mechanism, and the high pressure side pressure is controlled by a second variable orifice of the forming mechanism under the action of the working pressure to perform predetermined constant horsepower or long ramp Pc control. This control pressure is applied to the rear side of the control piston to adjust the amount of displacement of the variable control element.

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. It is supported.

This block 7 is provided with a large number of plungers 8 that 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, and is in contact with a swash plate 11 constituting a variable control element via the shoe 10.

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 a control pressure forming device 40 that forms a control pressure P _F 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 movable relative to the swash plate 11, an operating spool 22 having a land 22a movably held by the piston 21, and The control piston 21 includes a first pressing body 23 that opposes the movement of the spool 22 due to the operating pressure PT, and the control piston 21 has a spool hole 21a that holds the spool 22, and is open to the spool hole 21a and is connected to the pump discharge passage. A first variable orifice 24 is provided between the land 22a of the spool 22 and the introduction path 21b, the opening area of which changes as the spool 22 moves. The secondary side of this orifice 24 is communicated with the back chamber 25 of the spool 22, and the working pressure PT of the discharge pressure P _S controlled by the orifice 24 is applied to the working surface 22b of the spool 22. It is accomplished as it works.

A control pressure P _F generated by a control pressure forming mechanism 40, which will be described in detail later, is introduced into the rear chamber 26 of the control piston 21, and the control piston 21 is moved in the direction of the swash plate 11 by this control pressure P _F. Let it happen.

What is shown in FIG. 3 is the control piston 21
is freely movably mounted inside a cylinder 17 fixed to the cover 2 with bolts 16, and a mounting cylinder 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 27, which is different from the control piston 21, is movably supported on the outer periphery of this mounting cylinder 18. The operation piston 27 is disposed 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 28. 21, and the tilt angle of the swash plate 11 is adjusted via the operation piston 27. That is, a slidable push rod 28 supported by a first receiver 29 and a second receiver 31 (described later) is interposed between the control piston 21 and the operating piston 27, and the control piston is operated via the push rod 28. 21 is transmitted to the operating piston 27. This operation piston 27 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 receiving body 29 fixed to the mounting tube 18, that is, a stationary member, and a push rod 30 slidably supported by the operating spool 22 and the control piston 21. A second receptor 31 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 30 and the second receiving body 31. 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, 32 is a cover that is screwed onto the open side of the cylinder 17, and 33 is this cover 32.
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, 34 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. A second variable orifice 46 is formed between the servo spool 43 and the servo spool 43, and the secondary side of the orifice 46 is connected to the rear chamber of the control piston 21 in the control mechanism 20. A control pressure P _F of the discharge pressure P _S controlled by the opening of the orifice 46 is introduced into the rear chamber 26 of the control piston 21, and this control pressure P _F causes the control piston 21 to move toward the swash plate 11. The rear chamber 47 of the sleeve 41 is
The sleeve 41 is connected to the secondary side of the first variable orifice 24 formed in the control mechanism 20, and the operating pressure PT of the discharge pressure P _S controlled by the first variable orifice 24 is applied to the sleeve 41. The sleeve 41 is moved so as to be balanced with the pressing force of the second pressing body 42.

In the one shown in FIG. 4, the forming mechanism 40 is
The sleeve 41, the block 50 formed separately from the housing 1 and cover 2,
It is constructed by incorporating a servo spool 43, a second pressing body 42, and third pressing bodies 44, 45, and the block 50 is fixed to the housing 1 or cover 2 with a fixing means 80 such as a bolt, and the sleeve 41 The working pressure 51 extending from the rear chamber 47 of the cylinder 17 is communicated with a passage 35 formed in the cylinder 17, that is, a passage 35 communicating with the rear chamber 25 of the operation spool 21, and the secondary side of the second variable orifice 46. A control pressure passage 52 communicating with the passage 36 formed in the cylinder 17, that is, a passage 36 communicating with the rear chamber 26 of the control piston 21, further communicates with the working surface 4 of the servo spool 43.
A high pressure passage 53 communicating with the discharge passage 70 is configured to communicate with the discharge passage 70.

More specifically, the block 50 freely supports the sleeve 41 at its center, and has the operating pressure passage 51, the control pressure passage 5, and the high pressure passage 53.
a sleeve hole 54 with an opening, the pressing body 42,
44 and 45, and on the open side of this storage chamber 55, there is provided a cover 56 that supports one end of the second pressing body 42, and a cover 56 that is screwed into the center of the cover 56, and which is screwed into the center of the cover 56. A first adjusting body 57 that supports one of the three pressing bodies 44 and 45 and this adjusting body 5
7, and the third pressing body 44, 45
A second adjusting body 58 is provided to support the other side 45 of the second adjusting body 58 .

In the sleeve hole 54, the sleeve 41 having a servo spool 43 is movably housed, and in the housing chamber 55, the pressing body 41 is movably installed.
2, 44, 45, and the second pressing body 42
is interposed between a receiver 48 fixed to the sleeve 41 and the cover 56, and a receiver 49 that connects the third pressing bodies 44, 45 to the servo spool 43; Second adjustment body 5
7 and 58.

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 in contact with the adjustment body 57, the other body 45
is shorter than the length of the receiving body 49 and the supporting end surface of the second adjusting body 58, 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, by operating the first adjusting body 57 and adjusting the pressing force of one of the third pressing bodies 44, 45, 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 Figure 6, and the second
By adjusting the pressing force of the other 45 using the adjusting body 58, the characteristics of the latter half of the center bending point can be adjusted in the direction of arrow C in FIG.

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

The pressure compensator valve 60 for actuating the operation piston 27 includes a control spool _{61 having an operating surface 61a that moves according to the discharge output 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 27, that is, with the mounting tube 18 and the inner chamber a of the cylinder 17.

The valve body 64 is attached to the side of the block 50 as shown in FIG. 1, and the branch passage 53a branching from the middle of the high pressure passage 53 formed in this block 50 is connected to the control valve as shown in FIG. It communicates with one end of the spool 61, and as shown in FIG. are formed respectively.

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 part of the high-pressure fluid flowing through the discharge passage 70 passes through the high-pressure passage 53 to the primary side of the first variable orifice 24 in the operation spool 22, that is, the introduction passage 21b, and to the servo spool 43.
is guided to the action surface 43a of the branch path 53a.
to the active surface 61a of the control spool 61 in the pressure compensator valve 60.

At the beginning of operation, the operating spool 22 moves to the left as much as possible due to the pressing action of the first pressing body 23, and the first variable orifice 24 opens to the maximum opening amount.

Therefore, the high pressure fluid introduced into the introduction path 21b is reduced in pressure by the first variable orifice 24 at the minimum pressure reduction ratio, and the working pressure PT is close to the discharge pressure P _S.
It is then guided to the rear chamber 25 of the operating spool 22. With this introduction, the operating spool 22 moves to the right in FIG. 3 against the pressing force of the first pressing body 23 under the action of the operating pressure PT, and adjusts the opening amount of the orifice 24. The operating pressure PT is controlled to balance with the pressing force.

On the other hand, the high pressure fluid is connected to the servo spool 4.
3, the pressure P _S acts on the working surface 43a, and the servo spool 4
3 to the right in FIG. 4, but if the discharge pressure P _S is less than the pressure set by the third pressing body 44,
3 does not move, so the second variable orifice 4
6 does not open, the control piston 21 also remains stationary, and the swash plate 11 maintains its maximum tilt angle.

In this state, when the discharge pressure P _S exceeds the set pressure described above, the servo spool 43
The second variable orifice 46 begins to move to the right against the third pressing body 44, and the second variable orifice 46 opens by a predetermined opening amount.
The discharge pressure P _S becomes the control pressure P _F.

The control fluid controlled to the control pressure P _F passes through the control pressure passage 52 and the passage 36 to the control piston 2.
The control pressure P _F causes the control piston 21 to move to the right in FIG. Tilt it in the direction of.

This control pressure P _F is the pressure necessary to tilt the swash plate 11 as described above, and the rightward movement of the control piston 21 moves in the direction of opening the orifice 24. The operation spool 22 moves accordingly and stops when the operating pressure PT reaches a value that balances the pressing force of the first pressing body 23.

Further, the operating pressure PT of the discharge pressure P _S controlled by the movement of the operation spool 22 is guided to the back chamber 47 of the sleeve 41 that holds the servo spool 43 and causes the sleeve 41 to be pressed by the second pressing body 42 . It acts against the pressure and moves it to the right in FIG. This rightward movement of the sleeve 41 is in the direction of closing the second variable orifice 46,
It moves in conjunction with the rightward movement of the front servo spool 43 until it is balanced with the second pressing body 42 .

Therefore, the sleeve 41 moves 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.
To follow this servo spool 43,
The control pressure P _F corresponds to the amount of movement of the servo spool 43 and is obtained under adjustment of the sleeve 41.

That is, 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 P _F obtained by this control is controlled by the control. It acts on the back chamber 26 of the piston 21. As a result, the opening amount of the first variable orifice 24 becomes larger, so that the operating spool 22 follows the control piston 21 and moves to a position where it balances with the first pressing body 23. Therefore, the control piston 21
is the amount of movement of the piston 21 by the push rod 2
8 and the operating spool 27 to the swash plate 11 to control the tilt 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 from the above state and the servo spool 43 moves to the right, the other pressing body 45 of the third pressing bodies 44 and 45 is applied, and the servo spool 43 moves to the right. counter movement. By adding the third pressing body 45, the rate of increase in the control pressure P _F with respect to the rate of increase in the discharge pressure P _S becomes low, and as shown in Fig. 6, the rate of decrease in the discharge amount Q with respect to the increase in the discharge pressure P _S is controlled to be small. be done.

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 26 of the spool 21 includes a storage chamber 55,
It communicates with the tank T via the tank relay passage 69, and the control pressure P _F drops.

As the control pressure P _F decreases, the control piston 21 also moves to the left in FIG. 3, and the swash plate 11 tilts 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 transferred to the back surface of the operating piston 27, that is, the cylinder 17 and the mounting tube 18.
This allows the swash plate 11 to be tilted to the neutral position, thereby controlling the sharp cut characteristic Pc.

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 generates an operating pressure PT via a first variable orifice 24 formed between the control piston 21 and the operating spool 22 and causes this operating pressure PT to act on the back side of the sleeve 41 and This is because the control pressure PF controlled by the second variable pressure orifice 46 formed between the servo spool 43 is applied to the rear chamber 26 of the control piston 21, and the pressure moment etc. fluctuate. For example, even if the swash plate 11 tries to wobble in the direction of maximum inclination, the movement of the swash plate 11 is prevented by the control piston 2 through the push rod 28.
1, the control piston 21 is moved to the left in FIG.
By reducing PT, the sleeve 41 in FIG.
This variation can be counteracted by adjusting the second variable orifice 46 between the control piston 21 and the servo spool 43 to the open side, increasing the control pressure PF, and increasing the biasing force of the control piston 21 in the neutral direction. It is.

Therefore, even if the pressure moment acting on the swash plate 11 fluctuates, the back pressure chamber 26
Since the control pressure PF of the swash plate 11 is automatically adjusted to counteract fluctuation factors such as the 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 is similarly applicable to variable displacement pane pumps or motors. In the case of a pan pump or motor, 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 operated by the control pressure generated by the control pressure forming mechanism formed separately from the control mechanism, so that the feedback of the cam etc. Compared to conventional hydraulic equipment that uses mechanisms, it has a simpler structure and is smaller in size, and eliminates the problems of being subject to positional restrictions, being affected by sliding friction, or being subjected to uneven loads.
Constant horsepower control and long ramp Pc control that are close to the theoretical values 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, 22a...
Land, 23... First pressing body, 24... First variable orifice, 25, 26... Back chamber, 40... Control pressure formation mechanism, 41... Sleeve, 42... Second pressing body, 43... Servo spool, 44, 45
...Third pressing body, 46...Second variable orifice,
47... Back chamber, 57, 58... Adjustment body, 60...
...pressure compensator valve, 27...operating 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 pressure forming mechanism for controlling the variable control element; the control mechanism includes a control piston that is freely movable relative to the variable control element; an operating spool that is movably held by the piston and has a land; and the control mechanism that controls the spool in one direction. the control piston includes a spool hole for holding the spool, and an opening in the spool hole;
A first variable orifice is formed by the introduction path and the land, and the operating pressure controlled by the variable orifice is applied to the back surface of the spool. The control pressure forming mechanism includes a freely movable sleeve, a second pushing body that opposes the movement of the sleeve, and a movably held member of the sleeve that controls the pressure of the hydraulic pump or motor. A servo spool with a high-pressure side pressure surface,
and at least one third pressing body that opposes movement of the spool due to the high-pressure side pressure, and a second variable orifice that opens when the servo spool is moved is provided between the sleeve and the servo spool, The orifice communicates with the back chamber of the control piston in the control mechanism, and is configured to introduce a control pressure controlled by the opening of the second variable orifice, and the back chamber of the sleeve communicates with the control piston back chamber of the control mechanism. A variable displacement hydraulic device, characterized in that it communicates with a back chamber and guides the operating pressure controlled by the opening of the first variable orifice. 2. The variable displacement hydraulic device according to claim 1, wherein the control 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 rear chamber of the operating piston communicates with the control passage of the pressure compensator valve, and the control mechanism is configured to have a control piston having a control spool and a control piston. 3. The variable displacement hydraulic device according to claim 1, wherein the variable control element is controlled to a neutral position when the change occurs. 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.