JPS6045314B2 - piston pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a piston pump, in particular, a piston pump that is equipped with a swash plate whose inclination angle can be changed, and a plurality of pistons held in a cylinder block are mounted on the swash plate. The present invention relates to a piston pump in which the piston is rotated in sliding contact with the piston and the reciprocating movement of the piston causes the pumping action to be performed.

This type of piston pump is also described in Japanese Unexamined Patent Publication No. 49-76104 and is already known.

To explain this based on FIG. 5, a cylinder block 52 having a large number of pistons 51 is spline-coupled to a drive shaft 50, and the head of the piston 51 is
A swash plate 53 with a variable inclination angle supported by the trunnion shaft A is brought into contact with the swash plate 53. On the other hand, on the back side of the swash plate 53 with respect to the cylinder tab head notch 52, the swash plate 53 is set to the maximum inclination angle. A bias spring 54 for biasing is brought into contact with the cylinder block 52 side of the swash plate 53 opposite to the spring 54, and an operating piston 55 for moving the swash plate 53 back to the neutral position is brought into contact with the cylinder block 52 side of the swash plate 53. There is. (Prior Art) However, in recent years, the above-mentioned piston pumps have been made smaller and have higher pressures in order to reduce costs.

However, when the pump is made smaller and has a higher pressure, a noise problem arises due to the collision between the high pressure fluid and the low pressure fluid, and especially in the above-mentioned variable displacement pump in which the swash plate 53 is variable, the swash plate 53 may rattle. Mechanical noise is also generated by pumps, and it is practically impossible to reduce the above-mentioned noise while maintaining pump characteristics such as efficiency, pressure compensation performance, and high response. It was hot. However, in the past, as a method for preventing the above-mentioned noise, for example, V-shaped grooves were provided in the valve plate (Japanese Utility Model Publication No. 40-31).
(Refer to No. 167), ball bearings and metal bearings are used as bearings.

(Problems to be Solved by the Invention) However, the above structure cannot fundamentally solve the above-mentioned noise problem.

In particular, when a ■-shaped groove is provided on the valve plate to prevent noise caused by fluid collision, the tilting moment of the swash plate 53 must be taken into consideration in the variable displacement pump, so if the design focuses on noise prevention, The rotation of the cylinder block 52 with respect to the top dead center and the bottom dead center determines the non-communicating position when the piston hole 56 into which the piston 51 is inserted transitions from the low pressure boat to the high pressure boat and from the high pressure boat to the low pressure boat. It becomes necessary to index toward the front in the direction, which increases internal leakage of liquid and causes cavitation. This results in a decrease in efficiency, and it is not possible to prevent noise without decreasing efficiency. The present invention was invented in view of the above-mentioned problems, and the purpose is to reduce the rattling of the trunnion shaft that supports the swash plate with a simple structure, and to reduce mechanical noise! It also reduces noise caused by fluid collision without reducing pump efficiency.
Another object of the present invention is to provide a piston pump that can be used without narrowing the rotational speed range, has improved pressure compensation characteristics, and is furthermore compact and inexpensive.

(Means for solving the problem) That is, the present invention rotates a cylinder block 14 equipped with a large number of pistons 18 in sliding contact with a valve plate 30 equipped with a high pressure boat 31 and a low pressure boat 32, The piston hole 17 of the block 14 is connected to the high pressure boat 3.
1 and a low-pressure boat 32, is in sliding contact with the head of the piston 18, and has a variable inclination angle. bias piston 40
and an operating piston 41 are provided facing each other around the trunnion shaft 27 and coupled to the swash plate 23, and the diameter of the bias piston 40 is made smaller than the diameter of the operating piston 41, so that the bias piston 40 is provided with a bias spring 44, while this bias piston 40
The rear chamber of the operating piston 41 is connected to the discharge passage 11a via a pilot spool 52 that operates at a predetermined discharge pressure. 14 pistons 18 form a V-shaped groove 33 between the boats 32 and 31 on the side facing from the low-pressure boat 32 to the high-pressure boat 31, which constantly communicates with the high-pressure boat 31, while the pistons 18 of the cylinder block 14 The boat 3 on the side facing the low pressure boat 32 from the boat 31
1 and 32, a communication hole 34 is provided adjacent to the low pressure boat 32 side and communicating with the suction passage 11b.

(Function) Since the bias piston 40, the bias spring 44, and the operating piston 41 apply their respective pressing forces to the swash plate 23 from the same direction, the trunnion supporting the swash plate 23 A pushing force always acts on the shaft 27 in a certain direction, and as a result, the trunnion shaft 27 is prevented from rattling and mechanical noise is eliminated.Furthermore, the bias piston 40 pushes the swash plate 23 to the maximum. Since the pressing force in the direction of the inclination angle is shared, the elasticity of the bias spring 44 can be made smaller than before.
As a result, the characteristics during pressure compensation can also be improved.

Moreover, a high pressure boat 31 provided on the valve plate 30
The V-shaped groove 33, which is always in communication with the suction passage 11b, and the communication hole 34, which is in communication with the suction passage 11b, eliminate noise caused by fluid collision without reducing efficiency.

That is, since the swash plate 23 can be held at the maximum inclination angle by the pushing force of the bias piston 40, when designing the valve plate 30, the high pressure and low pressure boats 31
, 32 and the opening positions and shapes of the V-shaped groove 33 and the communication hole 34 can be determined by considering only pump efficiency and noise prevention without considering the tilting moment of the swash plate 23, and, Since a communication hole 34 communicating with the low pressure boat 32 is provided between the boats 31 and 32 going from the high pressure boat 31 to the low pressure boat 32, compared to a case where a V-shaped groove communicating with the low pressure boat 32 is provided. The low pressure boat 32 can be extended to the high pressure boat 31 side, and as a result, the opening area of the low pressure boat 32 can be increased, so cavitation can also be suppressed and fluid collisions can be prevented without reducing efficiency. This makes it possible to prevent noise caused by noise.

(Example) Embodiments of the present invention will be described in detail below based on the drawings.

What is shown in the drawings is an axial piston pump, and its outer shape is composed of a housing 10 and an end cap 11.

The housing 10 has a drain outlet 10a opened therein as shown in FIG. ) are provided, and these housing 10 and end cap 1 are provided.
1 through several bolts (not shown).

Further, a through hole 10b is bored in the housing 10, and a bearing 16 is attached to the through hole 10b.A blind hole 11d is bored in the end cap 11, and the bearing 16 is attached to the blind hole 11d. A bearing 15 facing the is attached. A drive shaft 12 equipped with a cylinder block 14 is rotatably supported by these two bearings 15 and 16, and driving force from a motor (not shown) is transmitted from the drive shaft 12 to the cylinder block 14. This is accomplished by rotating the cylinder block 14 to perform a pumping action.

The cylinder block 14 has a plurality of, specifically nine, piston holes 17 extending in its axial direction, and a piston 18 that is freely movable in the axial direction is inserted into each of these piston holes 17. . The end of the piston hole 17 is elongated and opens outward as shown in FIG. plate 2
It collides with the through hole 20a of No. 0.

Further, the piston 18 has a spherical head 18a, and a shoe 21 is attached to the head 18a, and the shoe 21 is in contact with a swash plate 23 installed inside the housing 10 via a retainer 22. Thus, the cylinder block 14 configured as described above has the end cap 11
It is positioned between a valve plate 30, which will be described later, and a swash plate 23, which are closely fixed to each other via pins 19, and is supported on the drive shaft 12 via a driving connection 13 made of a spline connection. The bearing plate 20 provided on the end face of the cylinder block 14 is brought into close contact with the valve plate 30 by the pressing force of a spring 24 inserted in the center hole of the block 14, and the shoe 21 is connected to the retainer guide 25 and the The retainer 22 is brought into close contact with the swash plate 23 by the pressing force of a spring 26 provided on the cylinder block 14.

The swash plate 23 is supported by a trunnion shaft 27 via a bearing 28 and is free to swing within a certain range of inclination angle.

In the end cap 11 of the piston pump constructed as described above, a bias piston 40 and an operating piston 41 are arranged opposite to each other about the axis of the trunnion shaft 27.
The swash plate 23 is connected to the swash plate 23 via connecting rods 42 and 43.
A bias spring 44 is provided between the end cap 11 and the bias piston 40.

The bias piston 40 is attached to the end cap 11
The piston 40 is slidably provided in a bias cylinder 45 formed in the piston 40, and the back chamber 45a of the piston 40 is communicated with the discharge passage 11a via a communication passage 46.
This bias piston 40 is connected to the bias spring 4
4 to the swash plate 23 side, and when the operation is stopped, the swash plate 23
is maintained at the maximum angle of inclination.

This bias piston 40 only needs to maintain the swash plate 23 at the maximum inclination angle when the operation is stopped, in other words, when the operation is started, and therefore, its elastic force may be weak.

In other words, a part of the fluid discharged at the same time as the operation is introduced from the discharge passage 11a to the back chamber 45a via the communication passage 46, and the bias piston 40 is caused by the discharge pressure (load pressure).
is pressed in the direction of the swash plate 23, and this pressing force is large, and the piston 18, which performs the pumping action,
The spring 44 can sufficiently overcome the tilting moment of the swash plate 23 caused by the
A weak elastic force is sufficient to maintain the swash plate 23 at the maximum inclination angle when the operation is stopped. Also, this bias piston 40
The pressing force of the swash plate 23 and the bias spring 4
4 act on the swash plate 23 from the same direction, so the bearing 28 on the trunnion shaft 27 that supports the swash plate 23
The swash plate 23 is also pressed in a fixed direction, and the swash plate 23 does not wobble.

Further, the operation piston 41 is connected to the bias piston 40.
The diameter is larger than that of the end cap 11, and the rear chamber 47a of the operating piston 41 is connected to the discharge passage 11a via a pilot valve 50, which will be described next. It communicates with.

This operation piston 41 displaces the swash plate 23 from the maximum inclination angle to a neutral position (inclination angle 0), and the piston 41 is controlled by the pilot valve 50. This pilot valve 50 has a pilot spool 52 slidably installed inside a valve body 51, a pilot spring 54 whose pressing force can be arbitrarily adjusted by an adjusting screw 53 on the tip side of the spool 52, and a pilot spring 54 on the rear side. A high pressure passage 56 extending from the rear chamber 45a is connected to the center land 52a. of the sprawl 52 via a sensor pin 55. A branch path 57 branching from the high pressure passage 56 is connected between the center land 52b and the right land 52b, and is further closed by the center land 52a.
2 opens to form an opening that communicates with the branch passage 57, and this opening is connected to the control passage 58.
It communicates with the rear chamber 47a of the operating piston 41 through the.

However, when the drive shaft 12 is rotated in the above configuration, a part of the fluid discharged through the discharge passage 11a is introduced into the back chamber 45a of the bias piston 40, and the discharge pressure and the spring 44 cause the fluid to be slanted. The plate 23 is pressed to maintain the maximum inclination angle, and a portion of the discharged fluid is guided to the pilot valve 50 via the high pressure passage 56, and the discharge pressure is applied to the pilot spool 5 via the sensor pin 55.
It acts on 2.

When the discharge pressure overcomes the set pressure of the pilot spring 54, the sprawl 52 moves and opens with the opening, directing a portion of the discharge fluid flowing through the branch passage 57 from the control passage 58 to the operating piston. 41 back chamber 47
a, the operating piston 41 is moved to move the swash plate 23 in the neutral direction, and the discharge amount is made zero. At this time,
The pump is maintained at a pressure set by the adjusting screw 53, and by setting the diameter of the operating piston 41 to a predetermined diameter with respect to the diameter of the bias piston 40, the pressure width during pressure compensation can be reduced. , a sharp turn-off characteristic can be obtained. That is, in the above configuration, the bias spring 44 can be made weaker, and the ratio of the diameters of the bias piston 40 and the operating piston 41, that is, the cross-sectional area ratio can be set to a desired size, so that the tilting of the swash plate 23 can be made weaker. The rate of change of the moment with respect to the inclination angle can be made small, and therefore the pressure width can be made small, and the pressure can be maintained at a pressure close to the pressure set by the pilot spring 53. With the above configuration, the bearing 28 of the trunnion shaft 27 that supports the swash plate 23 is pressed in a certain direction, and the swash plate 23 can be reliably prevented from wobbling, and mechanical noise due to this wobbling can be prevented.

Therefore, a heavy-duty bearing such as a roller bearing can be used as the bearing 28, and its life can be extended, and low-speed operation is also possible. Furthermore, the above configuration allows for good responsiveness and improved pressure compensation characteristics.

Further, in the above configuration, by configuring the valve plate 30 as shown in FIG. 4, in conjunction with the above configuration, it is also possible to effectively prevent noise due to collision of fluids.

That is, the valve plate 30 shown in FIG. 4 includes a crescent-shaped high-pressure boat 31 that constantly communicates with the discharge passage 11a of the end cap 11, and a crescent-shaped low-pressure boat 32 that constantly communicates with the suction passage 11b. These two boats 3
1 and 32, through holes 20a communicating with the piston hole 17 are alternately communicated with each other by rotation of the cylinder block 14. And this high pressure boat 31
A V-shaped groove 33 that constantly communicates with the boat 31 is formed at the starting end in the rotational direction of the cylinder block 14, and a circular through hole 34 of a predetermined diameter is formed at the starting end of the low-pressure boat 32. It is something.

That is, by forming the V-shaped groove 33 at the starting end of the high-pressure boat 31, the through hole 20a and the high-pressure boat 31 are communicated with each other in stages in proportion to the opening area of the ■-shaped groove 33, thereby preventing sudden pressure changes. On the other hand, by forming the circular through hole 34 on the starting end side of the low pressure boat 32 close to the through hole 20a (may be in communication with it slightly), it is more effective than the case where a V-shaped groove is formed. The distance between the low pressure boat 32 and the circular through hole 34 becomes longer.

Therefore, as shown by the dashed line, the low pressure boat 32 is inserted into the circular through hole 3.
4, the low pressure boat 32 can be extended by a distance b toward the lower end D. As a result, the opening area of the low-pressure boat 32 can be made larger than that of the ■-shaped groove, and cavitation caused by the suction stroke can be prevented. The formation positions of the V-shaped groove 33 and the through hole 34 can be designed by ignoring the tilting moment of the swash plate 23 due to the above-described configuration, and should be determined based on a balance between efficiency and noise. It's good.

Therefore, there is no need to index the position where the through hole 20a does not communicate with the boats 31, 32 with respect to the top dead center U and bottom dead center D of the piston 18, and indexing increases internal leakage and cavitation. There is no problem with the occurrence of , and therefore the decrease in efficiency can be avoided. This is because the bias piston 40 is provided as described above, and the bias piston 40 and the bias spring 44 are made to act in the same direction.
This is because the tilting moment of the swash plate 23 can be ignored in the above design.

Thus, by combining the above-described configuration and the configuration of the valve plate 30, it is possible to achieve
Furthermore, noise can be reduced without limiting the number of rotations used. As described above, according to the present invention, since the bias piston, the bias spring, and the operating cylinder are provided on the cylinder block side of the swash plate, the pushing force from these elements acts on the swash plate in the same direction. As a result, with a simple configuration, it is possible to eliminate rattling of the swash plate and eliminate mechanical noise.Therefore, it is possible to widen the range of low-speed operation where conventional products are noisy, and to extend the life of the bearing for the trunnion shaft. This makes it possible to use long roller bearings.

Moreover, the bias spring can be weakened by pressing the swash plate with the bias piston, and the rate of change of the tilting moment of the swash plate with respect to the inclination angle can be reduced, so that the pressure-knock compensation characteristic can be made into a sharp cutoff characteristic.

In addition, in the design of the valve plate, the tilting moment of the swash plate due to the rotation of the cylinder block can be ignored, which means that the swash plate can be maintained at the maximum tilt angle mostly by the pressing force of the bias piston, that is, by the discharge pressure. Since the tilting moment of the swash plate due to the rotation of the cylinder block can be ignored, there is no need for indexing as in conventional products, and therefore, noise caused by fluid collision can be prevented without reducing pump efficiency.

In addition, since there is no need for indexing, a through hole communicating with the suction passage can be formed on the low-pressure boat side of the valve plate, resulting in less cavitation and maximum high-speed operation without reducing pump efficiency. The number of revolutions can be increased, and the range of the number of revolutions used can be expanded as a whole, as well as the effect of expanding the range of low-speed operation. Furthermore, since the bias spring is installed together with the bias piston, compared to conventional products in which the bias spring is installed on the back side of the swash plate,
This allows for a smaller space and therefore a smaller housing, making it possible to provide an overall compact and lightweight piston pump.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a partially omitted longitudinal sectional front view, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1,
FIG. 3 is a longitudinal side view, FIG. 4 is a front view of only the valve plate, and FIG. 5 is a sectional view of a conventional example. 11a...Discharge passage, 11b...Suction passage, 14...Cylinder block, 17...
・Piston hole, 18... Zeston, 23...
・Swash plate, 27...Trunion shaft, 30...
... Valve plate, 31 ... High pressure boat, 3
2...Low pressure boat, 33...■shaped groove, 34
...Communication hole, 40...Bias piston, 41...Operation piston, 44...Bias spring, 50...Pilot valve, 52
...Pilot spool.

Claims (1)

[Claims] 1. A cylinder block 14 equipped with a large number of pistons 18 is rotated in sliding contact with a valve plate 30 equipped with a high pressure port 31 and a low pressure port 32, and the piston hole 17 of the cylinder block 14 is connected to the high pressure port 31 and the low pressure port 32. The piston 1 is alternately communicated with the ports 32.
In this piston pump, a bias piston 40 and an operating piston 41 are arranged on the cylinder block 14 side of the swash plate 23 with the trunnion shaft 27 as the center. The bias piston 40 is provided oppositely and interlocked with the swash plate 23, and has a diameter smaller than that of the operating piston 41, and a bias spring 44 is provided on the bias piston 40. The rear chamber of the operating piston 41 is connected to the discharge passage 11a via a pilot spool 52 that operates at a predetermined discharge pressure. The piston 18 of the block 14 is placed between the ports 32 and 31 on the side facing from the low pressure port 32 to the high pressure port 31.
1, the piston 18 of the cylinder block 14 is adjacent to the port 32 side between the ports 31 and 32 on the side facing from the high pressure port 31 to the low pressure port 32, and the piston 18 of the cylinder block 14 is adjacent to the port 32 side, A piston pump characterized in that a communication hole 34 communicating with the piston pump 11b is provided.