JPH0949487A - Variable displacement piston pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To forcedly supply oil between a bush and a cradle in a low load condition, while turnably supporting a support surface of a cradle type swash plate by the bush without using a half-split needle bearing or the like, for impeding seizure caused by insufficiency of supply oil to a bush surface generated in the case of supporting by the bush. SOLUTION: In a variable displacement piston pump constituting a cradle type swash plate for arbitrarily controlling a delivery flow rate in accordance with a pump delivery pressure, in balance of a piston part receiving a delivery pressure formed in an end part of a cradle 1 with a part of a tilt control spring 2, the second support point 5 is provided separately from the center of swiveling curvature of the cradle 1 in a side of the tilt control panel 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a variable displacement piston pump for supplying pressure oil to a hydraulic working machine in an axial piston pump, a construction machine, etc.

[0002]

2. Description of the Related Art Conventionally, an axial piston pump has been
For example, it is known from Japanese Utility Model Application Laid-Open No. 59-7279. In a construction machine such as a backhoe, a technique shown in FIG. 2 has been publicly known as a technique for directly fixing it to a crankshaft of an engine and providing it as a fixed displacement piston pump. However, in the conventional technique, since the fixed displacement pump is attached to the crankshaft of the engine, the length of the pump portion becomes long and it cannot be accommodated within the turning radius of the turning frame of the backhoe. . Also,
Since it is a fixed displacement pump, in order to obtain a sufficient pressure and discharge amount of pressure oil to be sent to various working machines in the backhoe, it is unavoidable to mount a large horsepower engine. This is the reason why the pump protrudes from the turning radius of the turning frame.

The present invention uses a variable displacement type pump to reduce the size of the pump itself, and in a high load range,
By reducing the discharge flow rate, the overload condition on the engine is eliminated and the discharge flow rate is controlled so that engine stall does not occur even with a low horsepower engine, and the mounted engine has a lower horsepower and a smaller engine than before Is.

Further, in the conventional cradle type variable displacement piston pump, the rotation support portion of the cradle is
It is difficult to assemble the half-split needle bearing because it is supported by the half-split needle bearing, or the trunnion shaft that protrudes on both sides of the swash plate is provided and the trunnion shaft is supported by the bearing. The problem is that the variable displacement piston pump has a large outer dimension. In the present invention, the supporting surface of the cradle type swash plate is rotatably supported by a bush without using a half needle bearing or the like.However, the burning due to insufficient oil supply to the bush surface, which occurs when the bush is supported, is burned. In order to prevent sticking, forced lubrication can be performed between the bush and the cradle 1 under a low load condition. Further, with this configuration, the rotation resistance is reduced when the cradle type swash plate is tilted.

[0005]

SUMMARY OF THE INVENTION The present invention, when a hydraulic pump is attached to an engine mounted on a construction machine such as a backhoe, so that the hydraulic pump portion does not protrude from the arc of the swing frame of the backhoe, The hydraulic pump is miniaturized by configuring it as a variable displacement piston pump. In addition, in order to prevent the hydraulic pump part from protruding from the swing frame, the conventional fixed displacement type piston pump was changed to a variable displacement type piston pump, and the discharge amount was reduced in the high load range to reduce the load. The engine is reduced in size so that engine stall does not occur even in a low horsepower engine so that the hydraulic pump does not protrude from the arc of the swing frame.

Further, in the cradle type variable displacement piston pump, a lubricating oil film is always formed between the cradle 1 and the bush 3 in order to prevent the oil film from running out on the surface of the cradle 1 and prevent seizure and wear. In order to be able to do so, the lubricating oil was forcibly supplied. In addition, by providing a gap between the cradle 1 and the bush 3, it is possible to eliminate the abnormal noise of the variable displacement piston pump that is generated, and to prevent problems such as bearing damage due to local high surface pressure. To prevent.

[0007]

The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described. According to the first aspect, in the variable displacement piston pump having a cradle type swash plate for arbitrarily controlling the discharge flow rate according to the pump discharge pressure, a tilting piston 6 for receiving the discharge pressure at the end of the cradle 1 is provided.
6 constitutes a portion that receives a pressing force, and a portion that receives the biasing force of the tilt control spring 2 on the opposite side, and the rotation center of the cradle 1 for balancing the forces from both sides is set to the cradle 1. A second fulcrum 5 is provided on the tilt control spring 2 side in addition to the center of the oscillating curvature, and a lubricating oil film is formed between the cradle 1 and the bush 3.

In the second aspect of the present invention, the second fulcrum 5 of the axial piston pump is configured so that the cradle 1 contacts only when the load is light, so that the lubricating oil film can be satisfactorily obtained and the load on the fulcrum can be reduced. It is something that is done. In claim 3, an elastic body is provided so that the second fulcrum 5 of the axial piston pump comes into contact with the cradle 1 immediately before it comes into contact with the cradle 1 to absorb the impact force from the cradle 1 that is suddenly applied to the second fulcrum. It is something that is done. In the fourth aspect, the second fulcrum 5 itself is made of an elastic body so that the cradle 1 can be supported without the second fulcrum 5 itself receiving a shock of high surface pressure. In the fifth aspect, the reversible valve provided with a throttle is provided in the cylinder chamber of the piston 6 that presses the cradle 1 from the opposite side with respect to the tilt control spring 2 that presses the cradle 1. Depending on the pump discharge pressure configured to control pulsation,
A cradle type swash plate for arbitrarily controlling the discharge flow rate is configured to absorb the impact force from the cradle 1 loaded on the second fulcrum by gradually decreasing the hydraulic pressure.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described. FIG. 1 is a plan view of a construction machine in which a variable displacement piston pump of the present invention is attached to a backhoe mounted engine, and FIG. 2 is a plan view of a conventional fixed displacement piston pump mounted in a backhoe mounted engine. FIG. 3 is an overall plan view of the variable displacement piston pump of the present invention, and FIG.
Is a side view of the variable displacement piston pump of the present invention,
FIG. 5 is a front sectional view of an embodiment in which the second fulcrum 5 is composed of a tilting pin, and FIG. 6 is a front sectional view of another portion.
FIG. 7 is a side sectional view of the embodiment of the present invention.

FIG. 8 is a sectional view of a piston portion for pressing the cradle 1, and FIG. 9 is a cradle 1 and a second fulcrum 5 under high load.
FIG. 10 is a front sectional view showing the positional relationship between the cradle 1 and the second fulcrum 5 at the time of medium load, and FIG. 11 is a positional relationship between the cradle 1 and the second fulcrum 5 at the time of light load. 13 is a front cross-sectional view showing a change in discharge flow rate in a high load region, a medium load region and a light load region, FIG.
Is a front sectional view of an embodiment in which an elastic body is interposed between the second fulcrum 5 and the cradle 1, and FIG. 14 is also a front view in a state where an urging spring is interposed between the cradle 1 and the second fulcrum 5. A sectional view, FIG. 15 shows a cylinder 7 of a piston 6 for pressing the cradle 1.
16 is a cross-sectional front view of a throttle mechanism that throttles the amount of pressure oil to the engine, FIG. 16 is another sectional view of the throttle mechanism, FIG. 17 is a sectional view showing another embodiment of the throttle mechanism, and FIG. 18 is another embodiment of the throttle mechanism. FIG. 19 is a sectional view showing an example of the elastic supporting structure of the second fulcrum 5, FIG. 19 is a sectional view showing another example of the elastic supporting structure of the second fulcrum 5, and FIG.

FIG. 1 and FIG. 2 will be described. FIG. 1 shows a state in which a variable displacement piston pump of the present invention is attached to an engine E mounted on a backhoe in a construction machine. Since the backhoe often carries out work such as excavating a groove in a narrow alley, the swivel frame F is configured to have a circular shape in a plan view, and the circular shape of the swivel frame F allows the hydraulic pump portion for the working machine to be removed. , It is required not to project outside. Conventionally, as shown in FIG. 2, since a fixed displacement piston pump P'is attached to the engine E ',
The horsepower of the engine E ′ was inevitably increased, and the fixed displacement piston pump P ′ itself had a long structure, and the fixed displacement piston pump P ′ was projected to the outside of the circular shape of the revolving frame F.

In the present invention, the two-port type variable displacement piston pump P having two discharge ports is attached to the engine E. There is no need to attach a ', and this alone shortens the variable displacement piston pump P. Further, as shown in FIG. 12, in a high load region, in a situation where the discharge pressure becomes high and an engine stall is likely to occur, the engine E is not engine stalled by changing the discharge capacity to a small volume. The fixed displacement piston pump P ′ could be driven by an engine E having a horsepower lower than that required by the engine E ′.

Therefore, the engine E'can be changed from the engine E'and the engine E can be shortened by itself. Therefore, the variable displacement piston pump P attached to the engine E is located inside the circle of the revolving frame F. Therefore, even if the trench is excavated in a narrow alley and the revolving frame F is rotated by 180 degrees to convey the excavated soil, the backhoe does not come into contact with the fence or the obstacle surrounding the alley. .

Next, the overall structure of the variable displacement piston pump P of the present invention will be described with reference to FIGS. 3 to 8. The variable displacement piston pump P of the present invention has an exterior formed of a plunger case 19 and an oil passage plate 10. A pump shaft 4, a cradle receiver 7, a cradle 1, a cylinder block 9 and the like are arranged inside a case constituted by the plunger case 19 and the oil passage plate 10. The pump plungers 8 are fitted in a plurality of cylinders provided in the cylinder block 9.

The pump shaft 4 is driven from the engine E side. The pump shaft 4 is supported by a bearing 17 on the side of the plunger case 19 and a bearing metal 16 on the side of the oil passage plate 10. A cylinder block 9 is spline-fitted to the pump shaft 4,
The cylinder block 9 rotates as the pump shaft 4 rotates. However, the cradle 1, the bush 3, and the cradle receiver 7, which are loosely fitted to the outer circumference of the pump shaft 4, are
Does not rotate with.

The cylinder block 9 which rotates together with the pump shaft 4 is provided with a pressing biasing spring 18 between the pump shaft 4 and the surface of the cylinder block 9 on the oil passage plate 10 side. The valve plate 21 on the 10 side is pressed and biased so that pressure oil does not leak from between the cylinder block 9 and the valve plate 21. The valve plate 21 and the oil passage plate 10 are integrated by a pin 22. The pump plunger 8 fitted in the cylinder hole of the cylinder block 9 is in contact with the piston shoe slide surface 12 of the cradle 1 arranged on the flat surface of the cradle 1 on the cylinder block 9 side at the piston shoe 11. Being hit.

As described above, when the pump shaft 4 is forcibly driven, the cylinder block 9 rotates, and the pump plunger 8 fitted in the cylinder hole of the cylinder block 9 also rotates together with the cylinder block 9. With the rotation of the pump plunger 8, the piston shoe 11 rotates while sliding on the piston shoe slide surface 12 of the cradle 1,
The plurality of pump plungers 8 move in and out of the cylinder holes of the cylinder block 9, suck the working oil from the suction port, and discharge the working oil to the discharge ports 20, 20 of the two ports. The discharged oil is used for raising and lowering the drive motors for the left and right traveling crawlers and the main boom of the backhoe.

Since the angle of the cradle 1 is of a variable capacity type, the cradle 1 is rotated so that the discharge amount is reduced as the discharge pressure increases as the discharge pressure increases. The discharge amount control mechanism of the cradle 1 is performed by a tilt control spring 2 on the upper part of the cradle 1 and a tilt piston 6 on the lower part.
That is, the tilt control spring 2 is in contact with the upper portion of the cradle 1 via the ball 15 and the spring receiver 14 so as to bias the same. At the lower part of the cradle 1, pressure oil from the discharge ports 20, 20 is guided into the tilting piston cylinders 14, 14.

Since the two discharge ports 20 and 20 are provided, two tilting piston cylinders 14 and 14 are prepared, and two tilting pistons 6 and 6 are also provided. Then, as shown in FIG. 8, the two tilting pistons 6 and 6 are
Is configured to press the lower end portion of the cradle 1 and to stop the rotation of the cradle 1 at a position balanced with the upper tilt control spring 2.

While the variable displacement piston pump P is rotating in the high load region and the medium load region, the cradle 1
Rotates about O in FIG. 5, which is the center of the curvature, but in the light load region, the pressing force of the tilting pistons 6 and 6 decreases, and the pressing force of the tilting control spring 2 increases. Due to the increase, the cradle 1 is largely rotated so that the back surface of the cradle 1 contacts the second fulcrum 5 of the present invention, and the cradle 1
The gap between the bush 3 and the bush 3 opens.

The opening of the gap between the cradle 1 and the bush 3 makes it possible to forcibly supply the lubricating oil between the bush 3 and the cradle 1.
Next, with reference to FIGS. 9 to 12, changes in the discharge capacity in the light load region, the medium load region, and the high load region will be described. The high load range shown in FIG. 9 will be described. In the high load range, the tilt control spring 2 presses the cradle 1 with the biasing force of Fs2. On the contrary, from the tilting piston 6 side, Fp = A *
It is biased by the biasing forces of P1 and P2. Further, the pressing force from the pump plunger 8 is pressed against the piston shoe slide surface 12 side of the cradle 1 by the pressures P1 and P2. The center of tilt in the high load region is the first fulcrum O which is the center of the radius of curvature. And in this case,
Pressing the cradle 1 from the tilting piston 6 ・ 6 side F
Since the pressing force of p is large, the cradle 1 is rotated clockwise, and the upper back surface of the cradle 1 and the second fulcrum 5 are not in contact with each other.

Next, description will be given in the medium load range shown in FIG. In this case, the biasing force of the tilt control spring 2 is Fs1, and the biasing force on the tilt piston 6 6 side is Fp = A * P.
There are 0 to P1. Then, on the piston shoe slide surface 12 of the cradle 1, the pump plunger 8 is P0 to P1.
Pressed with. In this case, the tilting pistons 6 ・ 6
The biasing force of the tilt control spring 2 increases,
The back surface of the cradle 1 is in contact with the second fulcrum 5 just before the contact. First fulcrum O in medium load range
Is the center of rotation of the cradle 1.

Next, in the light load region, the tilt control spring 2
Is pushed by the pressure of Fs0, and the tilting pistons 6 and 6 are pushed to Fp.
= A * 0 to P0. The piston shoe slide surface 12 of the cradle 1 is pressed from 0 to P0.
In this case, the discharge pressure of the discharge ports 20 and 20 is extremely low, and the cradle 1 is largely rotated in the counterclockwise direction by the pressing force of the tilt control spring 2 and the cradle 1
The back surface above the first fulcrum O contacts the second fulcrum 5. Then, when the cradle 1 further rotates counterclockwise, a state in which the fulcrum is changed from the first fulcrum O to the second fulcrum 5 occurs, the cradle 1 is separated from the surface of the bush 3, and the cradle 1 and the bush 3 are separated. A gap for forced lubrication occurs between and.

Next, referring to FIG. 12, the structure of the variable discharge amount control will be described. Variable displacement piston pump P of the present invention
Is a large discharge flow rate caused by a large difference in stroke of the pump plunger 8 in the light load region when the pressure in the discharge circuit gradually rises from the light load region to the high load region through the medium load region. However, the medium discharge amount and the low discharge amount gradually change. This is because the rotational state of the cradle 1 gradually changes due to the balance relationship between the tilt pistons 6 and 6 and the tilt control spring 2.

Then, in the high load region, as shown in FIG. 12, the discharge flow rate is suddenly decreased, so that the discharge flow rate is low although the pressure is high.
Since the load applied to the engine E does not increase so much, the engine is no longer in an stalled state without using a high horsepower engine as in the past. In this embodiment, the conventional fixed displacement piston pump P ′ shown in FIG. 2 is used.
The engine E'of 16 horsepower was mounted when the engine was used, but by equipping the variable displacement piston pump P as in the present invention, the engine E of 11 horsepower was installed in the backhoe of the same size. It is now possible to mount things.

Next, a configuration for reducing noise will be described with reference to FIGS. 13 to 17. As in the present invention, in the light load region, the upper portion of the cradle 1 abuts on the second fulcrum 5 and rotates, whereby the lubricating oil is forcibly injected between the cradle 1 and the bush 3 to form an oil film. The lubrication performance is improved, and the durability performance can be improved despite the compact variable displacement piston pump P using the bush 3 instead of the needle bearing.

However, in the light load region, when the work is rapidly performed in the vicinity of the middle load region from the state where the oil sliding performance is increased, the cradle 1 and the bush 3 are not in close contact with each other. Cradle 1
The vibration sound caused by the pulsation of the discharge pressure is generated between and the second fulcrum 5. This sound is generated only when the load is suddenly changed from the light load region to the medium load region, but it is still a tactile sound, so it is necessary to mute it. In the present invention, as shown in FIG. 13, the cradle 1 and the second fulcrum 5
The elastic body 25 is interposed between the cradle 1 and the cradle 1, and the cradle 1 does not directly contact the second fulcrum 5 but always contacts the elastic body 25. Of. Further, the buffer spring 2 is provided in parallel with the elastic body 25.
It is also possible to improve the sound deadening effect by interposing 4 and by using the buffer spring 24.

Further, in FIG. 14, instead of interposing the elastic body 25, the second fulcrum 5 itself is replaced by the elastic C-shaped pin 2
6, the rattling sound between the cradle 1 and the second fulcrum 5 is eliminated by the elastic deformation force of the elastic C-shaped pin 26. It is also possible to dispose the buffer spring 24 in parallel with the elastic C-shaped pin 26.

The rattling sound caused between the cradle 1 and the second fulcrum 5 due to the pulsation of the discharge pressure is transmitted when the cradle 1 is pressed by the tilting pistons 6 and 6. It is caused by being done. Therefore, in the middle part where the pressure oil is supplied to the tilting piston cylinders 14, 14, the throttling mechanism that generates the throttling effect only on the pressure oil supplying side is provided with the tilting piston cylinders 14.
It is also possible to eliminate it by providing it between 14 and the oil passage plate 10.

In the embodiment shown in FIG. 15, the throttle body 27 is fitted between the tilting piston cylinders 14 and 14 and the oil passage plate 10, and the projection of the throttle body 27 and the tilting piston cylinders 14 and 14 are fitted. A gap 27a is formed between the inner diameter and the inner diameter of the variable displacement piston pump P, and a throttle operation is performed when the discharge pressure of the variable displacement piston pump P enters the tilting piston cylinder 14/14 side.
In the embodiment shown in FIG. 16, when the discharged oil flows from the oil passage plate 10 side to the tilting piston cylinders 14 and 14 side, the throttle acts, but the tilting piston cylinders 14 and 14
The throttle body 28 is interposed so as not to act when flowing from the side of the discharge port 20 to the side of the discharge port 20.

In the structure of FIG. 16, the throttle body 28 is normally urged toward the oil passage plate 10 by the urging spring 29, and the pressure oil is tilted from the discharge ports 20 and 20 side. When trying to flow into the side of 14 · 14, the throttle body 28 is moved to the left side against the biasing spring 29, and the large gap 28b on the side surface of the throttle body 28 is closed, and the throttle hole is closed. By connecting only 28a, it is configured to exert a throttling action. Conversely, the tilting piston cylinder 14
When the pressure oil is returned from the side 14 to the side of the discharge ports 20 and 20, both the large gap 28b and the throttle hole 28a are opened, so that the throttle action does not work and the control converges quickly. Of.

In FIG. 17, the diaphragm body 30 is provided with two stages of diaphragm portions n and m. The overall configuration is the same as that of FIG. 15, but by using a two-stage throttle, it is possible to eliminate clogging of the throttle hole, and also to use two stages for the pulsation of the discharge pressure. By this, the pulsation can be completely eliminated. FIG. 18 shows an embodiment of the throttle body 32 having the check valve 31 interposed therebetween. The throttle body 32 has a hole with a diameter v through which a check valve is inserted and a hole with a diameter w that is always open. The discharge pressure to the cradle 1 side pushes the check valve 31 and the diameter v Although the pressure passing through both the holes of w and w is applied, the return oil from the cradle 1 side returns only from the hole of diameter w because the check valve 31 is closed, thereby eliminating the pulsation.

In FIG. 19, the elastic support of the second fulcrum 5 is carried out by fitting the elastic support ring 35 around the second fulcrum 5. Further, in FIG. 20, the disc springs 36, 36 are provided on the rear surface of the second fulcrum 5 so as to be configured.

[0034]

Since the present invention is constructed as described above, it has the following effects. With the configuration according to claim 1, when the discharge pressure becomes a light load, the cradle 1
Since the lubricating oil is supplied from the gap between the bush 3 and the bush 3, the lubrication of the surface between the cradle 1 and the bush 3 is improved. Further, since the oil film is easily formed on the surface of the bush 3, the wear of the surface of the bush 3 can be minimized and the life of the bush 3 can be extended. Also, when the discharge pressure becomes a light load, the cradle 1
Since a part of the load of B is supported by the second fulcrum 5, which is another fulcrum of the swing center, it is possible to reduce the surface pressure of the bush 3 and reduce the wear of the bush 3. . Further, by constructing according to the present invention, the cost can be reduced, the assembling work can be facilitated, and the number of parts can be reduced.

Since the cradle 1 is rotated about the second fulcrum 5 as a fulcrum only in the light load range, the normal construction in the medium load range and the high load range is realized. Since it functions as the cradle type variable displacement piston pump P, noise and vibration are less likely to occur.

According to the third and fourth aspects,
With the cradle 1 and the second fulcrum 5 in contact with each other in the light load region, the pulsation of the discharge pressure oil is transmitted to the cradle 1 via the tilting pistons 6 and 6, and the vibration and noise caused by this are transmitted. The problem that occurs between the cradle 1 and the second fulcrum 5 is caused by the buffer spring 24, the elastic body 25, and the elasticity C.
The mold pin 26 was able to eliminate it.

According to the fifth aspect of the present invention, the pulsation of the discharge pressure oil that causes the vibration and noise is reduced by the throttle bodies 27, 28.
Thus, the vibration and noise between the cradle 1 and the second fulcrum 5 could be reduced by reducing the pulsation.

[Brief description of drawings]

FIG. 1 is a plan view of a construction machine in which a variable displacement piston pump of the present invention is attached to an engine mounted on a backhoe.

FIG. 2 is a plan view showing a state where a conventional fixed displacement piston pump is attached to an engine mounted on a backhoe.

FIG. 3 is an overall plan view of a variable displacement piston pump of the present invention.

FIG. 4 is a side view of the variable displacement piston pump of the present invention.

FIG. 5 is a front cross-sectional view of an embodiment in which a second fulcrum 5 is composed of a tilt pin.

FIG. 6 is a front sectional view of another portion of the same.

FIG. 7 is a side sectional view of the embodiment of the present invention.

FIG. 8 is a sectional view of a piston portion that presses the cradle 1.

FIG. 9 is a front sectional view showing the positional relationship between the cradle 1 and the second fulcrum 5 under high load.

FIG. 10: Cradle 1 and second fulcrum 5 under the same medium load
FIG.

FIG. 11 is a front sectional view showing the positional relationship between the cradle 1 and the second fulcrum 5 at the time of light load.

FIG. 12 is a drawing showing changes in discharge flow rate in a high load range, a medium load range, and a light load range.

13 is a front sectional view of an embodiment in which an elastic body is interposed between the second fulcrum 5 and the cradle 1. FIG.

FIG. 14 is a front cross-sectional view of a state in which a biasing spring is interposed between the cradle 1 and the second fulcrum 5.

FIG. 15 is a front cross-sectional view of a throttle mechanism that throttles the amount of pressure oil to the cylinder 7 of the piston 6 that presses the cradle 1.

FIG. 16 is another sectional view of the diaphragm mechanism.

FIG. 17 is a sectional view showing another embodiment of the diaphragm mechanism.

FIG. 18 is a sectional view showing another embodiment of the diaphragm mechanism.

FIG. 19 is a sectional view showing another embodiment of the elastic support structure of the second fulcrum 5.

FIG. 20 is a sectional view showing another embodiment of the elastic support structure of the second fulcrum 5.

[Explanation of symbols]

 E Engine P Variable displacement piston pump F Revolving frame O First fulcrum (center of curvature) 1 Cradle 2 Tilt control spring 3 Bush (concave receiving surface member) 4 Pump shaft 5 Second fulcrum 6 Tilt piston 7 Cradle receiver 8 Pump Plunger 9 Cylinder block 10 Oil passage plate 11 Piston shoe 12 Piston shoe slide surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Hori 1-32 Chayacho, Kita-ku, Osaka-shi, Osaka Yanmar Diesel Co., Ltd.

Claims (5)

[Claims] 1. A variable displacement piston pump comprising a cradle type swash plate for arbitrarily controlling the discharge flow rate according to the pump discharge pressure, wherein a tilting piston 6.6 receives the discharge pressure at the end of the cradle 1. Part of the cradle 1 that receives the biasing force of the tilt control spring 2 on the opposite side and the center of rotation of the cradle 1 for balancing the forces from both sides. A variable displacement type piston pump characterized in that a second fulcrum 5 is provided on the tilt control spring 2 side in addition to the center of swing curvature. 2. A variable displacement piston pump in which a cradle type swash plate for arbitrarily controlling a discharge flow rate according to a pump discharge pressure is pivotally supported by a concave receiving surface member so that the cradle can be rotated. The end of the tilting piston 6, which receives the discharge pressure, receives the pressing force of the tilting piston 6, and the opposite side receives the biasing force of the tilting control spring 2 to balance the force from both sides. The center of rotation of the cradle 1 for removing the cradle is set to be the center of swing curvature of the cradle 1, and further, a second fulcrum 5 is provided on the tilt control spring 2 side. Tilt control spring 2 due to lowering
The variable displacement piston is configured so that the cradle 1 tilts and abuts against the concave receiving surface member so as to cause a small clearance when the light load for pushing back the tilting pistons 6 and 6 is returned. pump. 3. A variable displacement piston pump configured to support a cradle type swash plate, which controls the discharge flow rate arbitrarily according to fluctuations in pump discharge pressure, at the center of rotation of the cradle 1. The end portion constitutes a portion that receives the pressing force of the tilting pistons 6 and 6 that receives the discharge pressure, and the opposite side portion that receives the urging force of the tilting control spring 2 to balance the force from both sides. Cradle 1 to take
The center of rotation of the cradle 1 and the center of swinging curvature of the cradle 1 are further provided with a second fulcrum 5 on the tilt control spring 2 side, and the second fulcrum 5 responds to the decrease in the pump discharge pressure by the cradle. 1. A variable displacement piston pump, characterized in that an elastic body is provided which is in contact immediately before contacting with 1. 4. A variable displacement piston pump comprising a cradle type swash plate for arbitrarily controlling the increase / decrease of the discharge flow rate according to the fluctuation of the discharge pressure of the pump, wherein the end portion of the cradle 1 has a tilt for receiving the discharge pressure. The rotation center of the cradle 1 for balancing the force from both sides, which constitutes the portion that receives the pressing force of the rolling pistons 6 and the portion that receives the biasing force of the tilt control spring 2 on the opposite side. In the configuration in which the second fulcrum 5 is provided on the tilt control spring 2 side in addition to the center of swing of the cradle 1, the second fulcrum 5 itself is made of an elastic body. Displacement type piston pump. 5. A variable displacement piston pump comprising a cradle type swash plate for arbitrarily controlling the discharge flow rate according to the pump discharge pressure, wherein the tilting piston 6 receives the discharge pressure at the end of the cradle 1.・ The portion that receives the pressing force of 6 is formed, and the portion that receives the biasing force of the tilt control spring 2 is formed on the opposite side, and the rotation center of the cradle 1 for balancing the forces from both sides is A second fulcrum 5 is provided on the tilt control spring 2 side in addition to the rocking curvature center of 1, and the cradle 1 is pressed from the opposite side with respect to the tilt control spring 2 pressing the cradle 1. In the cylinder chamber of the piston 6,
A variable displacement piston pump characterized in that a reversible valve provided with a throttle is interposed to control pulsation of discharge pressure.