JPH051660A - Axial piston device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of pressure pulsation, vibration, noise and the like by maintaining an increment and/or decrement in pressurization and/or decompression at a proper value under the condition of a constant operating pressure in a wide capacity range. CONSTITUTION:A cylinder bore is bored in parallel with a shaft 11 in a cylinder block 21 rotating integrally with the shaft 11, a plunger 231 is slidably provided within the cylinder bore, and a swash plate 34 with which the plunger 231 is slidably brought into contact, is provided. The swash plate 34 is rotated around the axial center intersected with the center line of the shaft 11, and the capacity is constituted to be adjusted with a slant angle of alpha changed. And furthermore, the aforesaid axial line is constituted to be inclined by an angle of beta to the direction perpendicular to the slant angle of alpha.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement type axial piston device such as an axial piston pump and an axial piston motor.

[0002]

2. Description of the Related Art In an axial piston device such as an axial piston pump, the plunger moves while the cylinder is shut off from the outside when the intake stroke and the discharge stroke of each plunger are switched, so that the pressure rises in the sealed cylinder. Or, there is a descending section. For this reason, a large pressure fluctuation occurs at the moment when the cylinder bore communicates with the suction port or the discharge port, which causes noise.

This pressure fluctuation can be reduced to some extent by providing a notch on the plunger entry side of the suction port and the discharge port to prevent rapid communication between the port and the cylinder, but when the pressure difference between the suction port and the discharge port is large. However, the reduction effect is insufficient. In addition, this pressure fluctuation is set appropriately for the plunger stroke (pre-compression amount or pre-decompression amount) when the cylinder bore is blocked from the outside so that a large pressure difference does not occur at the moment when the cylinder bore and port communicate. However, if the plunger stroke is changed by changing the swash plate angle in the variable displacement axial piston device, the precompression amount and predecompression amount also change with the plunger stroke. There is a problem that it deviates greatly from the optimum value.

[0004] In order to solve this problem, actual Kaihei 2-1447
The axial piston pump disclosed in Japanese Patent No. 5 is provided with a bypass port communicating with the discharge port in a section where the cylinder bore is blocked from the outside, and the pressure in the cylinder bore is controlled by opening and closing the bypass port according to the discharge port pressure. The amount of pre-compression is changed in the same manner.

[0005]

[Problems to be Solved by the Invention] However, the actual Kaihei 2-14
The axial piston device of Japanese Patent No. 475 requires a bypass valve, an accumulator, a bypass valve opening / closing mechanism, etc., which causes a problem that the configuration becomes complicated. Also, since the bypass valve is kept closed when the discharge port pressure is higher than the specified value, the precompression amount cannot be adjusted when the discharge pressure is high, and it seems that the pump capacity was changed under a constant high discharge pressure. In such a case, there is a problem that the pre-compression amount deviates from an appropriate value and noise is generated as in the conventional case.

In many cases, the axial piston device such as the axial piston pump and the motor is actually used by changing the capacity under a constant high pressure. In such a case, the noise reduction effect tends to be insufficient.

In view of the above problems, the present invention always provides an appropriate precompression amount (or predecompression amount) even when the pump (or motor) capacity is changed under the condition that the pump discharge pressure (or motor suction pressure) is constant. The purpose of the present invention is to provide a pre-compression / pre-decompression mechanism of a simple structure that can obtain the above, and to achieve noise reduction of the axial piston device.

[0008]

According to the present invention, a cylinder block integrally attached around a rotary shaft, and a plurality of cylinder bores bored in the cylinder block in parallel with the rotary shaft are provided. A plunger slidably arranged in the cylinder bore and a swash plate with which the plunger end is slidably engaged, and the cylinder block is rotated together with the rotary shaft to slide the plunger end on the swash plate. This causes the plunger to reciprocate to suck and discharge fluid in the cylinder bore, and the stroke of the plunger can be adjusted by rotating the swash plate around an axis intersecting the center line of the rotation axis. In the displacement type axial piston device, the rotation axis of the swash plate is set to have a constant inclination angle with respect to a plane orthogonal to the rotation axis center line. Axial piston device is provided to symptoms.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Although the following description is for the axial piston pump, the present invention can be similarly applied to the axial piston motor. FIG. 1 is a first axial piston pump to which the present invention is applied.
FIG. 2 is a longitudinal sectional view of the embodiment, and FIG. 2 and FIG.
A sectional view taken along the line III-III is shown. In FIG. 1, 11 indicates a pump shaft. Shaft 11 is a bearing
The housing 12 and the cover 13 are rotatably supported by 14 and 15, respectively.

Located inside the housing 12 is the shaft
A cylinder block 21 is provided around 11. A spline groove is formed on the inner peripheral surface of the cylinder block 21, and the spline groove is fitted into the spline groove 11a formed on the outer periphery of the shaft 11 so that the cylinder block 21 is rotated integrally with the shaft 11. ing. In this spline groove 11a, a spherical seat 22 having an arcuate outer peripheral surface is further provided.
Is fitted so that the spherical seat 22 is also rotated integrally with the shaft 11.

The housing 12 and the cover 13 are fastened together by a bolt (not shown) via a packing 23 to form a liquid-tight compartment. A drain port (not shown) is provided in the housing 12 to keep the inside at a predetermined drain pressure. The cover 13 is formed with a suction port 31 for sucking hydraulic oil and a discharge port 32 for discharging oil. Although the suction port 31 and the discharge port 32 are shown in cross section in the drawing, they are each formed in a semicircular shape so as to surround the shaft 11 and are opened inside the housing 12.

A step portion 13a is formed on the surface of the cover 13 corresponding to the inside of the housing 12 so as to surround the outer circumference of the shaft 11. The step portion 13a has a disc shape as shown in FIG. A valve plate 33 is fitted and fixed to the cover 13 by a pin (not shown). The valve plate 33 is formed with arc-shaped suction holes 33a and discharge holes 33b which communicate with the suction port 31 and the discharge port 32, respectively, and a closed section (pre-compression) for pre-compression between them. A section) 33c and a closed section (pre-decompression section) 33d for pre-decompression are provided.

A plurality of plunger chambers 211, 212, ... Having an axis parallel to the shaft 11 centering on the shaft 11 are bored at equal intervals in the cylinder block 21, and the plunger chambers 211, 212 ,. By the rotation of 21, the fluid is alternately communicated with the suction port 31 or the discharge port 32 via the plunger ports 221, 222, .... Plunger chambers 231, 232 ... in each of the plurality of plunger chambers 211, 212 ...
Is inserted, and shoes 241, 2 are attached to the tip of the housing 12 side.
42 ... Are rotatably attached and slide on the surface of the swash plate 34.

The side of the swash plate 34 that does not slidably contact the shoes 241, 242 ... Is formed in a cylindrical shape centering on an axis having a predetermined inclination angle β with respect to the shaft 11, and the same cylindrical swash plate holder 35.
Is in sliding contact with. A lever 37 is attached to the swash plate 34 with a screw 36, and an increase piston 38 and a decrease piston 39 as shown in FIG. The increase piston 38 and the decrease piston 39 can move the lever 37 by changing the protrusion amount thereof, and can rotate the swash plate 34 about the pin 41, and the tilt angle α of the swash plate 34 (see FIG. 2) can be continuously changed to adjust the pump capacity.

The shoes 241, 242 ... are retainers, respectively.
The spring 51 is fitted in the cylinder block 21 and is biased by a spring 51 provided inside the cylinder block 21 against the swash plate 34 via the ring 52, the pin 53 and the spherical seat 22. According to the present invention, as described above, the rotation axis of the swash plate 34 passing through the pin 41 forms the inclination angle β (see FIG. 1) with respect to the shaft 11 in the direction orthogonal to the inclination angle α of the swash plate 34. It is characterized by that.

In the axial piston pump constructed as described above, when the shaft 11 is rotationally driven by an electric motor or the like (not shown), the cylinder block 21 rotates integrally with the shaft 11. At this time, the plungers 231, 232, ... Rotate together with the cylinder block 21 while slidingly contacting the swash plate 34 via the shoes 241, 242 ,. Therefore, plunger 231, 23
2, ... rotate with shaft 11 and shaft 11 at the same time
Reciprocates in the cylinder block 21 in parallel with
When the 231, 232 ... move from the bottom dead center to the top dead center, the volume of the plunger chambers 211, 212 ... increases, and the plunger chamber 21 passes through the inlet 54, the suction port 31, and the suction hole 33a of the valve plate 33.
1, 212… Inhale oil. Plunger 231, 232 ...
Is moving from top dead center to bottom dead center, plunger chamber 211,
The oil in 212 ... Is discharged to the outside through the discharge hole 33b of the valve plate 33 and the discharge port 32.

When the discharge pressure is high, as the cylinder block 21 rotates, the plunger chambers 211, 212 ... From the suction hole 33a (low pressure) to the discharge hole 33b (high pressure) of the valve plate 33.
Or when the discharge hole 33b is switched to the suction hole 33a, the pressure in the plunger chambers 211, 212 ... Abruptly changes, which causes large vibration and noise.

On the other hand, in this embodiment, as shown in FIG. 4, the plunger 33 is provided with closing sections 33c and 33d for precompression and predecompression between the suction hole 33a and the discharge hole 33b of the valve plate 33. The pressure inside the chambers 211, 212 ... is gradually changed to reduce vibration and noise.

Using the inclination angles α and β of the swash plate 34, the volume V (θ) in the plunger chamber 211 when a certain plunger chamber 211 rotates from the plunger top dead center (FIG. 4) by an angle θ is obtained. V (θ) = V + A ・ R ・ (cosθ ・ tanα-sinθ
・ Tan β). However, V: Plunger chamber volume at neutral position (θ = 90 °) R: Distance between center of plunger and center of shaft A: Cross-sectional area of plunger. At this time, the pressure increase ΔP due to the closure in the pre-compression section 33c is ΔP = K ((V (0) −V (θ)) / V (0)) = K · A when the bulk elastic coefficient K of the hydraulic oil is used.・ R · {tanα (1-cosθ) + sinθ · tanβ} / (V + A · R · tanα) (1) The pressure in the plunger chamber depends on this precompression section 33c.
If the discharge pressure becomes equal to the discharge pressure due to the pressure increase ΔP at, the pressure fluctuation does not occur when the plunger chambers 211, 212, ... Communicate with the discharge port 32, so that noise can be prevented.

In the conventional pump, since the rotation axis of the swash plate 34 is set at a right angle (β = 0) to the center line of the shaft 11, the pressure increase ΔP 'in the precompression section 33c is β in the above equation (1). It is expressed as = 0. That is, ΔP ′ = K · A · R · tanα (1-coscos) / (V + A · R · tanα) (2)

As can be seen from the equation (2), in the conventional pump, when the swash plate angle α is changed to adjust the displacement, the pressure increase ΔP 'also greatly changes. For this reason, when the discharge pressure (pressure increase) is used at a constant value, an appropriate pressure increase ΔP can be obtained at the design point, but when the capacity is changed from the design point, the pressure increase ΔP changes significantly, and Noise and vibration will be generated. Therefore, in the conventional pump, the generation of noise and vibration could not be prevented in the usage of changing the pump capacity while keeping the discharge pressure constant.

On the other hand, in the present invention, as a result of inclining the rotation axis of the swash plate 34 by the angle β, the change in ΔP due to α is corrected by the amount of the sin θ · tan β term of the numerator as shown in the equation (1). Therefore, even if α changes, there is little change in ΔP.
In particular, as shown in FIG. 5, in the conventional pump, the swash plate angle α
Is smaller than the design point, that is, when the capacity is smaller than the design point, the precompression amount ΔP changes greatly, but in the case of the present invention, the precompression amount at the design point hardly changes. Therefore, by optimizing the precompression amount at the design point, it is possible to maintain an appropriate precompression amount in the entire capacity range and achieve low noise. It should be noted that the plunger rotation angle θ ₀ for obtaining the optimum precompression amount by inclining the rotation axis of the swash plate 34 by β (the precompression amount in FIG. The rotation angle corresponding to the section (hereinafter referred to as the precompression angle) has a different value from the case of β = 0.

Next, changes in the precompression amount ΔP will be described with reference to FIGS. 6 and 7. FIG. 6 shows the relationship between the rotation angle θ and the plunger stroke at the design point (α = α ₁ ). In the figure, the solid line shows the case of the present invention, and the broken line shows the conventional pump (β = 0).
Represents the case. Now, the pre-compression amount at the design point is Δ
When P ₁ is taken, the pump must be designed so that the precompression angle is θ ₀ in the present invention and θ ₀ ′ in the conventional example as shown in FIG. This pre-compression angle does not change depending on the swash plate angle α, and once set, it is kept the same. As a result, at the design point (α = α ₁ ), an appropriate amount of precompression can be obtained in both the present invention and the conventional example, and low noise operation of the pump becomes possible.

However, when the swash plate angle is changed to α ₂ (α ₁ > α ₂ ) in order to reduce the pump capacity, there is a difference between the two. FIG. 7 shows a stroke when the swash plate angle of the pump of FIG. 6 is changed to α = α ₂ . As described above, since the pre-compression angles θ ₀ and θ ₀ ′ do not change, the pre-compression amount is greatly reduced to ΔP ₂ ′ in the conventional example, and the pre-compression amount becomes insufficient. On the other hand, in the present invention, the amount of compression in the precompression section appropriately increases as the plunger stroke decreases, so the amount of precompression ΔP ₂ substantially equal to the amount of precompression ΔP _{1 at the} design point.
Can be maintained. Therefore, in the present invention, the swash plate angle α
The required pre-compression amount can be obtained regardless of the (pump capacity), and noise reduction can be achieved over the entire range of use.

Although the above description relates to the precompression amount, the same description holds for the predecompression amount. Further, as described above, the noise reduction of the axial piston motor can be achieved with the same configuration as that of the present embodiment. Also, the inclination angle β
It is necessary to set an optimal value for the size of the pump depending on the specifications of the pump, but the desired effect can be achieved if approximately β = 3 to 5 °.

FIG. 8 shows a second embodiment of the present invention. FIG. 8 is a sectional view corresponding to FIG. 1 of the first embodiment. In this embodiment, the swash plate 34 'and the sliding surface (cylindrical surface) of the swash plate holder 35' are formed around an axis perpendicular to the axis of the shaft 11 '.
The surface of the 34 'that contacts the shoes 241', 242 '... Has an inclination angle β. In this case, the pin that becomes the center of rotation of the lever 37 '
The hole for 41 'can be made vertical to the surface of the housing 12', which facilitates the processing. Also, since the lever 37 'is parallel to the axis of the shaft 11', the lever 37 'and the cylinder block 2
Since the gap between 1'and the lever 37 'and the cover 13' can be reduced, the entire pump can be made smaller. With regard to noise reduction, the same effect as in the first embodiment can be obtained.

FIG. 9 is a sectional view corresponding to FIG. 1 showing a third embodiment of the present invention. This embodiment is an example in which the present invention is applied to a trunnion type swash plate, and a trunnion shaft 341 that supports the swash plate 34 ″ is provided so as to be inclined with respect to the axis of the shaft 11 ″,
The same effect can be obtained by inclining the surface of the swash plate 34 ″ which is in sliding contact with the shoe 241 ″ by the angle β. In this embodiment, the swash plate inclination angle α is changed by using a drive mechanism such as a hydraulic cylinder (not shown). Further, in the first and second embodiments described above, the levers 37 and 37 'are pushed in both directions by using the increase piston and the decrease piston, but if either of them is replaced by a coil spring. good.

[0028]

INDUSTRIAL APPLICABILITY The present invention has a wide range when the swash plate rotating shaft of the axial piston device is set to have a constant inclination angle with respect to the shaft so that the capacity is changed by constant discharge and suction pressure. It is possible to prevent the generation of noise and vibration by maintaining the precompression and predecompression amounts at appropriate values within the capacity range.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a first embodiment of an axial piston device of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a side view showing the valve plate shape of the embodiment of FIG.

FIG. 5 is a diagram showing changes in the amount of precompression with respect to the swash plate inclination angle in the present invention and the conventional axial piston pump.

FIG. 6 is a diagram showing a relationship between a plunger stroke and a rotation angle in the present invention and a conventional axial piston pump.

FIG. 7 is a view similar to FIG. 6 when the swash plate inclination angle is changed.

FIG. 8 is a sectional view showing a second embodiment of the axial piston device of the present invention.

FIG. 9 is a sectional view showing a third embodiment of the axial piston device of the present invention.

[Explanation of symbols]

 11 ... Shaft 21 ... Cylinder block 31 ... Suction port 32 ... Discharge port 33 ... Valve plate 34 ... Swash plate 35 ... Swash plate holder 211… Plunger chamber 221… Plunger port 231… Plunger 241… Shoe

Claims (1)

Claim: What is claimed is: 1. A cylinder block integrally attached to the periphery of a rotary shaft, a plurality of cylinder bores bored in the cylinder block in parallel with the rotary shaft, and respective cylinder bores. A plunger slidably disposed on the swash plate, and a swash plate with which the plunger end is slidably engaged, and the plunger end is slid on the swash plate by rotating the cylinder block together with the rotating shaft. A variable displacement axial type in which the fluid is sucked into and discharged from the cylinder bore by rotating the swash plate around the axis intersecting the center line of the rotary shaft to adjust the stroke of the plunger. In the piston device, the rotation axis of the swash plate is set to have a constant inclination angle with respect to a plane orthogonal to the rotation axis center line. · The Shall piston device.