JP2829977B2 - Axial piston device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an axial piston device such as an axial piston pump or a motor.

[Conventional technology]

In a conventional axial piston pump, when switching between a suction stroke and a discharge stroke, the plunger chamber expands and contracts in a state of being shut off from the outside, so that the pressure in the plunger chamber rises or falls, and the suction port or the discharge port The pressure pulsation occurs at the moment of communication with the device, and noise is generated. This pressure pulsation can be reduced to some extent by forming notches in the suction port and the discharge port, but when the pump discharge pressure changes greatly,
This reduction effect is insufficient. Therefore, Japanese Patent Laid-Open No.
The publication discloses a configuration in which a plurality of port communication holes are formed adjacent to a suction port and a discharge port, and a pre-compression angle and a pre-expansion angle are changed according to a pump discharge pressure to prevent pressure pulsation. ing.

[Problems to be solved by the invention]

However, the above configuration having the port communication holes is complicated because it requires a mechanism for opening and closing these communication holes in accordance with the pump discharge pressure, and also has the problem that the discharge capacity changes due to the communication holes. Have.

An object of the present invention is to provide an axial piston device that can prevent pressure pulsation with a simple configuration without changing a discharge capacity.

[Means for solving the problem]

The axial piston device according to the first aspect of the present invention includes a housing having a suction port and a discharge port provided on mutually opposite sides with respect to the center, a rotation shaft provided in the housing, and a housing. A swash plate that is provided to rotate with respect to a first rotation center axis orthogonal to the rotation axis and that has a surface inclined with respect to the rotation axis, and is provided rotatably coaxially with the rotation axis in a housing; A cylinder block having a plunger chamber that can communicate with the suction port and the discharge port; a cylinder block slidably accommodated in the cylinder block; a head slidingly engaging the swash plate; When the engagement position with the plate changes, the plunger chamber is displaced substantially in parallel with the rotation axis to expand and contract, and liquid is sucked into the plunger chamber from the suction port. The piston that pressurizes and discharges from the discharge port, the piston head at a position perpendicular to the rotation axis and the first rotation center axis and at which the plunger chamber ends communication with the suction port, and the plunger chamber ends communication with the discharge port. And a pre-compression pre-decompression control mechanism for rotating and displacing the swash plate around a second rotation center axis connecting the piston head at the position.

In the axial piston device according to the second aspect of the present invention, in addition to the above points, the swash plate includes an outer peripheral member and an inner member, and a first rotation center is provided between the outer peripheral member and the housing. A first bearing is provided for rotatably coupling the shaft and the second rotation center shaft on one of the axes, and between the outer peripheral component and the inner component, A second bearing that rotatably couples the first rotation center axis or the second rotation center axis on the axis of the rotation center axis that does not correspond to the first bearing is provided. Features.

Further, in the axial piston device according to the third aspect of the present invention, in addition to any of the above features, the servo of the position control in which the pre-compression pre-decompression control mechanism is displaced in accordance with the magnitude of the operating pressure. A mechanism is provided to increase or decrease the amount of rotational displacement of the swash plate.

In the axial piston device according to the fourth aspect of the present invention, the amount of liquid discharged from the discharge port is changed by rotating and displacing the surface of the swash plate around the first rotation center axis.

(Operation)

The pre-compression pre-decompression control mechanism tilts the straight line connecting the piston head at the position where the plunger chamber ends communication with the suction port and the piston head at the position where the plunger chamber ends communication with the discharge port as the rotation center. By rotating and displacing the plate, the phase of the reciprocating motion of the piston changes, and the stroke of the piston in the pre-decompression stroke and the pre-compression stroke is displaced. Is prevented.

〔Example〕

 Hereinafter, the present invention will be described with reference to illustrated embodiments.

1 to 5 show an axial piston pump according to a first embodiment of the present invention. 1 is a sectional view showing the axial piston cut along a horizontal plane, and FIG. 2 is a sectional view showing the axial piston cut along a plane perpendicular to the horizontal plane.

The housing 100 includes a cup-shaped body 101 and a cover fitted to an opening of the body 101 via an O-ring 102.
The cover 103 has a suction port 104 and a discharge port 105 provided on opposite sides of the center. The openings of the suction port 104 and the discharge port 105 have arc shapes facing each other when the cover 103 is viewed from the body 101 side, as shown in FIG. An annular valve seat 110 is attached to the surface of the cover 103 on the body 101 side, and the valve seat 110 is
2 integrally connects to the cover 103. This valve seat 110
An opening 111 corresponding to the opening of the suction port 104 and the opening of the discharge port 105, and a hydraulic balance groove are formed in the opening. As will be described later, with the rotation of the shaft 201, the piston 211 moves forward and backward, and the plunger chamber 212 expands and contracts, whereby the fluid is sucked into the plunger chamber 212 from the suction port 104 and compressed, and the fluid is discharged from the discharge port 105. Discharged.

The shaft 201 is rotatably supported around its axis by a bearing 202 provided in the opening 106 of the body 101 and a bearing 203 fixed to the cover 103. One end of the shaft 201 protrudes from the opening 106 of the body 101 and is connected to a rotation drive source (not shown). Body 10 from shaft 202 bearing 202
An oil seal 205 is fitted to the inner part of 1 to prevent the fluid in the housing 100 from flowing out of the opening 106.

The cylinder block 213 is connected to the shaft 201 by a spline 204 in the housing 100, and rotates together with the shaft 201. Cylinder block 213
A plurality of cylinder bores 214 extending in parallel with the axis of the shaft 201 are formed therein. A piston 211 is slidably housed in these cylinder bores 214, and the plunger chamber 2 is formed therein.
12 is formed. The plunger chamber 212 can communicate with the suction port 104 and the discharge port 105 via a port 215 formed in the cylinder block 213 and an opening 111 formed in the valve seat 110.

A portion of the piston 211 opposite to the plunger chamber 212 projects from the cylinder block 213, and has a spherical head 2 at its tip.
16 are formed. The shoe 217 is fixed to the spherical head 216,
The swash plate 220 is slidably engaged with the annular flat surface 221. The swash plate 220 has a hemispherical central portion 222 and a fourth
As can be understood from the figure, the central portion 222 has arms 223, 224, and 225 that project in the radial direction.
226 is drilled. The spherical surface of the central portion 222 is supported by the concave spherical surface 232 of the holder 231 fixed to the body 101 and has a through hole.
226 is inserted through the shaft 201. The swash plate 220 includes a capacity control mechanism 300 and a pre-compression pre-decompression control mechanism 4 as described later.
00, thereby causing the concave spherical surface 232 of the holder 231 to be pressed.
And the inclination angle of the shaft 201 with respect to the axis is changed.

Two annular plates 241 and 242 are provided in an annular chamber 218 formed between the central portion of the cylinder block 213 and the shaft 201, and a spring 243 is provided between the annular plates 241 and 242. One annular plate 241 is fixed to the cylinder lock 213 by a circlip 244. The other annular plate 242,
A pin 246 extending through the cylinder block 213 is provided between the shaft holder 201 and a hemispherical plate holder 245 connected to the shaft 201 by a spline. Annular plate 247
Is slidably fitted on the spherical outer peripheral surface of the plate holder 245, and can be rotated and displaced against the spherical outer peripheral surface. Spring
The annular plate 242, the pin 246, and the plate holder 245 are pressed toward the swash plate 220 by the elastic force of the 243. Therefore, the shoe 217 is pressed by the spring 243, and is always in sliding contact with the annular flat surface 221 of the swash plate 220. In addition, the cylinder block 213 is always in sliding contact with the valve seat 110 by the elastic force of the spring 243.

The displacement control mechanism 300 rotationally displaces the swash plate 220 around a first straight line passing through the axis of the shaft 201 and perpendicular to the plane of FIG. 2 to change the stroke of the piston 211 to change the pump displacement. Things. The first straight line is represented by the XX axis in FIG. The capacity control mechanism 300
It comprises a front piston part 310 for pressing a spherical concave part 227 formed on the front surface of the 20 arm part 223 and a rear piston part 320 for pressing a spherical concave part 228 formed on the rear surface of the arm part 223. .

The front piston portion 310 includes a cylindrical support member 311 fitted in a hole formed in the body 101, a piston 312, and a spring 31.
With 3. The support member 311 is fixed to the body 101 by the circlip 314, and an O-ring 315 is inserted between the support member 311 and the body 101 to maintain liquid tightness. The piston 312 is slidably supported in the support member 311 and has a shaft
It can be displaced parallel to the axis of 201. A spring 313 is provided in a pressure chamber 316 formed between the rear end of the piston 312 and the bottom of the support member 311. The resilient force of the spring 313 supports the hemispherical tip of the piston 312. A spherical recess formed on the front surface of the arm 223 of the swash plate 220 protruding from the member 311
Always engages 227. A control pressure is introduced into the pressure chamber 316 by a control valve mechanism (not shown), and the piston 312 presses the arm 223 of the swash plate 220 to the left in the drawing by the control pressure.

The rear piston section 320 includes a cylindrical support member 321 fitted in a hole formed in the cover 103, a piston 322, and a spring 32.
With 3. The support member 321 is fixed to the cover 103 by the circlip 324, and the space between the support member 321 and the cover 103 is kept liquid-tight by the O-ring 325. The piston 322 is slidably supported in the support member 321 and can move forward and backward in parallel with the axis of the shaft 201. In the pressure chamber 326 formed between the rear end of the piston 322 and the bottom of the support member 321,
A spring 323 is provided, and the hemispherical tip of the piston 322 projects from the support member 321 by the elastic force of the spring 323, and the swash plate is provided.
It always engages with the spherical concave portion 228 formed on the back surface of the arm portion 223 of 220. A control pressure is introduced into the pressure chamber 326 by a control valve mechanism (not shown), and the piston 322 presses the arm 223 rightward in the drawing by the control pressure.

The pre-compression pre-decompression control mechanism 400 controls the swash plate 220
Rotational displacement about a second straight line passing through the axis of 1 and perpendicular to the plane of FIG. 1 changes the phase of the reciprocation of the piston 211 to change the stroke of the piston in the pre-decompression stroke and the pre-compression stroke. Things. The second straight line is the fourth
In the figure, it is represented by the Y-Y axis and intersects at right angles to the first straight line. The pre-compression and pre-decompression control mechanism 400 presses the control piston 410 that presses the concave portion 229 formed on the front surface of the arm portion 224 of the swash plate 220, and presses the concave portion 230 formed on the front surface of the arm portion 225 of the swash plate 220. And a supporting portion 420.

The control piston section 410 has a cylindrical support member 411 fitted in a hole of the body 101, a piston 412, and a spring 413. The support member 411 includes a stopper 41 screwed to the body 101.
4 to the body 101, the support member 411 and the body 101
During this period, the liquid tightness is maintained by the O-ring 415. Piston 412
Is slidably supported in the support member 411 and is displaceable in parallel with the axis of the shaft 201. A spring 413 is provided in a pressure chamber 416 formed between the rear end of the piston 412 and the bottom of the support member 411.
The hemispherical tip of the piston 412 projects from the support member 411 and always engages with a recess 229 formed on the front surface of the arm 224 of the swash plate 220. The discharge pressure of the present pump is introduced into the pressure chamber 416 through a passage (not shown), and the piston 412 presses the arm portion 224 to the left in the drawing by the discharge pressure.

The support portion 420 is provided with the stopper 42 fitted in the hole of the body 101.
1, a pressing member 422, and a spring 423. Stopper 421
Is fixed to the body 101 by a circlip 424, and liquid-tightness is maintained between the stopper 421 and the body 101 by an O-ring 425. The spring 423 is provided between the pressing member 422 and the stopper 421, so that the pressing member 422 protrudes from the hole of the body 101, and the concave portion 230 formed in the arm portion 225 of the swash plate 220.
, And urges the arm portion 225 to the left in the drawing.

 The normal pump operation will be described with reference to FIG.

The swash plate 220 is inclined by an angle α around the first straight line (the XX axis in FIG. 4), that is, by an angle α with respect to a straight line CL extending vertically upward from the axis of the shaft 201. Assume that When the shaft 201 rotates, the cylinder block 213 and the plate holder 245 rotate integrally therewith. As a result, the shoe 217 rotates about the axis of the shaft 201 while sliding on the annular flat surface 221 of the swash plate 220, and the piston 2
11 also rotates around the axis of the shaft 201. Since the annular plane 221 of the swash plate 220 is inclined, the piston 211 reciprocates in the cylinder bore 214 along the axis of the shaft 201 in accordance with a change in the engagement position between the shoe 217 and the annular plane 221. That is, the volume of the plunger chamber 212 changes according to the rotation of the shaft 201. On the other hand, the cylinder block 213 is in rotational sliding contact with the valve seat 110, whereby the plunger chamber 2
3 rotates in the direction of the arrow while reaching the suction port 104 in FIG.
It rotates in the direction of the arrow while communicating with 5, and reaches the bottom dead center B.
While the plunger chamber 212 communicates with the suction port 104, the plunger chamber 212 expands due to the retraction of the piston 211, so that fluid is sucked into the plunger chamber 212. Next, while the plunger chamber 212 communicates with the discharge port 105, the plunger chamber 212 is compressed by the advance of the piston 211, whereby the fluid in the plunger chamber 212 is discharged from the discharge port 105 to the outside.

The pump displacement is determined by the stroke of the piston 211, and this stroke is determined by the inclination angle α of the swash plate 220. Here, the distance between the center of the piston 211 and the axis of the shaft 201 is R, the rotation angle of the cylinder block 213 is θ, the end rotation angle (top dead center T) of the suction stroke is θ ₃ (see FIG. 3), Assuming that the cross-sectional area of the piston 211 is A, the piston 211
The stroke S, is represented by S = Rcosθtanα, piston 211, the volume of the working fluid V = ARtanα in the suction stroke (cosθ ₃ -cosθ ₁₎ is sucked into the plunger chamber 212, also the working fluid in the discharge stroke It is discharged from the plunger chamber 212. Normally, since θ ₃ = 360 ° and θ ₁ = 180 °, each piston 211 sucks and discharges a working fluid having a volume of 2ARtanα while the cylinder block 213 rotates. Therefore, if N cylinders 211 are provided in the cylinder block 213, a working fluid having a volume of 2 ARNtanα per rotation is sucked and discharged.

 Next, control of the pump displacement will be described.

As described above, the pump displacement is determined by the inclination angle α of the swash plate 220, and the inclination angle α is determined by the degree of protrusion of the pistons 312 and 322 of the displacement control mechanism 300.

In the swash plate 220 shown in FIG. 4, when the piston slides on the annular plane 221 along arrow E, the piston is in the suction stroke, and the piston moves along the annular plane 221 along arrow F.
When sliding up, this piston is in the discharge stroke. The axis connecting the position corresponding to the end rotation angle of the suction stroke (top dead center T) and the position corresponding to the end rotation angle of the discharge stroke (bottom dead center B) is a Y-Y axis, and an axis perpendicular to this axis is XX axis.
In FIG. 6, by the action of a control valve mechanism (not shown),
When a high pressure is introduced into one pressure chamber 316 and the other pressure chamber 326 is communicated with the low pressure section, one piston 312 projects leftward and the other piston 322 retreats leftward. As a result, the swash plate 220 is rotationally displaced counterclockwise about the XX axis in FIG. 6, and the inclination angle α increases. Therefore, the stroke of the piston 211 increases, and the pump capacity, that is, the discharge flow rate increases. Conversely, by the action of the control valve mechanism, one of the pressure chambers 316 is communicated with the low pressure section, and when high pressure is guided to the other pressure chamber 326, one of the pistons 312 retreats to the right and the other piston 312 moves to the right. 322 projects to the right. As a result, the swash plate 220 is rotationally displaced clockwise in FIG. 6, the inclination angle α is reduced, the stroke of the piston 211 is reduced, and the pump capacity, that is, the discharge flow rate is reduced.

Referring to FIG. 6 to FIG.
Control of pre-decompression and pre-compression by 0 will be described.

The pre-decompression and pre-compression are performed as described below.
This angle β is determined by an angle β around the YY axis of 0.
The degree of protrusion of the pis 412 of the pre-compression pre-decompression control mechanism 400, that is, the magnitude of the pressure in the pressure chamber 416 and the spring 41
Determined by 3,423 elasticity.

While maintaining the state in which the swash plate 220 is inclined around the XX axis (FIG. 4) by the angle α as shown in FIG. 6, the swash plate 220 is moved in the Y direction as shown in FIG. 7 and FIG. Consider a state in which the lens is inclined around the Y axis by an angle β. 7 occurs when the pump discharge pressure decreases and the pressure in the pressure chamber 416 of the control piston unit 410 becomes lower than a predetermined value. The arm portion 225 of the swash plate 220 is always urged counterclockwise in the figure by a spring 423 and a pressing member 422, and therefore, the pressure chamber 41
When the pressure in 6 is reduced, the swash plate 220 is rotationally displaced counterclockwise by the angle β due to the elastic force of the spring 423. Conversely
The state shown in the figure occurs when the pump discharge pressure rises and the pressure in the pressure chamber 416 becomes higher than a predetermined value, that is, the pressure chamber 41
Due to the pressure of 6, the swash plate 220 is rotationally displaced clockwise by an angle β against the spring 423.

Now, since the pump discharge pressure P acts on the swash plate 220 via the piston 211, a moment My acts around the Y-Y axis as shown in FIG. This moment My increases almost linearly with respect to the pump discharge pressure P, and can be expressed as My = C ₁ P, where C ₁ is a constant. On the other hand, the cross-sectional area of the piston 412 is A
p, the vertical distance between the YY axis and the contact portion between the swash plate 220 and the piston 412 is R ₀ , the piston 412 is swash plate with the force of ApP.
220 and therefore the swash plate 220 has the above moment My
Moment R ₀ ApP acts in the opposite direction. Also swash plate 220
Is pressed by the spring 423 at the arm 225,
The spring constant of 423 is k, the compression amount of spring 423 is Xs,
When the vertical distance 2 and Y-Y axis and R _1, moments R ₁ KXS in the same direction as moment My is applied to the swash plate 220. Therefore, the equation for balancing the moment acting on the swash plate 220 is R ₀ ApP = My + R ₁ kXs. By substituting My = C ₁ P into this equation, P = R ₁ kXs / (R ₀ Ap−C ₁ ). Become.

Therefore, by appropriately selecting the spring constant k of the spring 423, the compression amount Xs of the spring 423, that is, the angle β of the swash plate 220 is appropriately controlled. As a result, as described below, the stroke S of the piston 211 in the pre-decompression and pre-compression strokes, that is, the pressure in the plunger chamber 212 during the pre-decompression and pre-compression strokes becomes an appropriate magnitude.

When the swash plate 220 is tilted about the XX axis by an angle α and tilted about the YY axis by an angle β,
The stroke S of the piston 211 is represented by S = Rcosθtanα−Rsinθtanβ. FIG. 9 shows a change in the stroke S of the piston 211 with respect to the pump rotation angle, that is, the rotation angle of the cylinder block 213, when the rotation angle β of the swash plate 220 around the YY axis is used as a parameter. In this figure,
As shown in FIG. 3, the pump rotation angles θ _{1 to} θ ₂ are located in front of the suction port 104 and correspond to the pre-decompression stroke of the pump. Similarly, the pump rotation angles θ _{3 to} θ ₄
It is located further forward and corresponds to the pre-compression stroke of the pump. The pump rotation angles θ _{2 to} θ ₃ are located at the suction port 104 and correspond to the suction stroke of the pump. Similarly, the pump rotation angles θ ₄
Through? ₁ corresponds to the discharge stroke of the pump.

As can be understood from FIG. 9, when the pump discharge pressure is medium and the angle β is 0 °, the strokes l ₂ and m ₂ of the piston 211 in the pre-decompression stroke and the pre-compression stroke are moderate, As shown by the solid line I in FIG. 10, the pressure decreases in the pre-decompression stroke and increases in the pre-compression stroke. On the other hand, the pump discharge pressure becomes high and the angle β
When 3 ゜ (FIG. 8), the strokes l ₃ and m ₃ of the piston 211 in the pre-decompression stroke and the pre-compression stroke are, as understood from FIG. 9, compared with the case where the pump discharge pressure is medium. It becomes bigger. As a result, as shown by the dashed line J in FIG. 10, the pressure decreases in the pre-decompression stroke with a steeper slope than in the case of the solid line I, and the pressure increases in the pre-compression stroke with a steeper slope. . On the other hand, when the pump discharge pressure becomes low and the angle β is −1 ° (FIG. 7), the strokes l ₁ and m of the piston 211 in the pre-decompression stroke and the pre-compression stroke are performed.
₁ becomes smaller as compared with the case where the pump discharge pressure is medium as understood from FIG. As a result, as shown by the one-dot chain line K in FIG. 10, as compared with the case of the solid line I, the pressure decreases with a gentler slope in the pre-decompression stroke, and the pressure decreases with a gentler slope in the pre-compression stroke. To increase.

Thus, by controlling the angle β of the swash plate 220 with respect to the Y-Y axis according to the pump discharge pressure, the rate of change in the rise and fall of the pressure in the plunger chamber 212 during the pre-decompression and pre-compression strokes is appropriate. The pressure pulsation of the pump discharge pressure is reduced, and the noise is reduced.

Here, finish rotational angle theta ₃ 360 ° of the suction stroke, when the end rotation angle theta ₁ of the discharge stroke to 180 °, the pump capacity q is, q = ARN {(cos360 ° tanα-sin360 ° tanβ) - (cos180 {Tanα-sin180 {tanβ)} = ARN {(tanα-0)-(-tanα-O)} = 2ARNtanα. That is, the pump displacement q does not change even if the inclination angle β of the swash plate 220 with respect to the YY axis is increased or decreased according to the pump discharge pressure. When this is explained by Fig. 9, the stroke L of the effective piston 211 to pumping action, the position change of the piston 211 in the end position theta ₁ of the discharge stroke to the end position theta ₃ of the suction stroke, the amount of change Is valve seat 1
Since 10 is integrally fixed to the housing 100 and does not rotate around the axis, it is always constant. That is,
The pump displacement q does not change with the inclination angle β of the swash plate 220 around the YY axis.

11 and 12 show a second embodiment of the present invention. No.
FIGS. 11 and 12 correspond to FIGS. 1 and 2, respectively, of the first embodiment.

In the first embodiment, the swash plate 220 is provided with a hemispherical central portion 222 in order to rotationally displace the swash plate 220 three-dimensionally, and this slidably contacts the concave spherical surface 232 of the holder 231. On the other hand, in the second embodiment, as described below, bearings (hereinafter referred to as trunnions) are provided on the axes of the XX axis and the YY axis, and the swash plate is rotatably supported by these trunnions. It has a configuration, and other configurations are basically the same as those of the first embodiment. The definitions of the XX axis and the YY axis are the same as in the first embodiment, that is, the XX axis extends in the horizontal direction,
The -Y axis extends vertically.

The swash plate 500 has basically the same configuration as the swash plate 220 of the first embodiment, except that it does not have a hemispherical central portion,
An inner swash plate 510 and an outer swash plate 520 are provided. Inner swash plate
510 has a dish shape, the shaft 201 is inserted through the through-hole 511, and the shoe 217 is in sliding contact with the annular flat surface 512. The outer swash plate 520 has an annular shape and is provided on the outer peripheral side of the inner swash plate 510.

The outer swash plate 520 is connected to the inner swash plate 510 by inner trunnions 531 and 532, as shown in FIG. The inner trunnions 531 and 532 are fixed to the outer swash plate 520 by circlips 533 and 534, and are supported by bearings 535 and 536 that are fitted to portions of the inner swash plate 510 on the Y-Y axis. That is, the inner swash plate 510 can be rotationally displaced around the YY axis with respect to the outer swash plate 520 via the inner trunnions 531 and 532. On the other hand, the outer swash plate 520 is connected to the housing body 101 by outer trunnions 541 and 542 as shown in FIG. Outer trunnions 541,542
Support holes 543,5 formed in the portion on the XX axis of body 101
44 is fitted through O-rings 545,546. That is, the outer swash plate 520 can be rotationally displaced around the XX axis.

The capacity control mechanism 300 for rotating and displacing the swash plate 500 about the XX axis is the same as that of the first embodiment,
And a rear piston section 320. The piston 312 of the front piston section 310 is the inner trunnion 531 of the outer swash plate 520.
And the piston 322 of the rear piston portion 320 engages with the other surface of the outer swash plate 520 at that portion. Front piston part 310
The amount of protrusion of the rear piston portion 320 from the support members 311 and 321 changes in accordance with the magnitude of the control pressure guided to the pressure chambers 316 and 326, whereby the outer swash plate 520 and the inner swash plate 5
10 is integrally rotationally displaced around the XX axis.

The pre-compression pre-decompression control mechanism 400 for rotating and displacing the inner swash plate 510 about the Y-Y axis is the same as that of the first embodiment, and includes a control piston 410 and a support 420. The piston 412 of the control piston portion 410 engages with one surface of a portion of the inner swash plate 510 adjacent to the outer trunnion 542, and the support portion 420
The pressing member 422 is engaged with a portion on the same side as that surface and close to the outer trunnion 541. Piston 412
The amount of protrusion from the support member 411 is determined by the balance between the pump discharge pressure guided to the pressure chamber 416, the resilient force of the spring 423 of the support portion 420, and the moment around the Y-Y axis due to the discharge pressure in the plunger chamber 212. Thus, the inner swash plate 510 is rotationally displaced around the Y-Y axis.

The operation of the second embodiment having such a configuration is also the same as that of the first embodiment, and the rotational displacement of the inner swash plate 510 around the Y-Y axis reduces discharge pressure pulsation and noise.

The support mechanism using a spherical surface used in the first embodiment described above has a large sliding area of the spherical surface and a radius of the spherical surface of r _1.
And when the sliding distance L ₁ in the sliding surface for rotating the swash plate 220 by the angle alpha is because the r ₁ · alpha, sliding distance L ₁ is also increased. As a result, it cannot be said that there is no possibility that the sliding portion of the spherical surface does not slide smoothly and sticks or slips occur, or that it becomes difficult to control the inclination angle of the swash plate with high accuracy. The embodiment is a further improvement of the first embodiment so that the above points can be made perfect.

That is, in the configuration using two bearings whose axes are orthogonal to each other used in the second embodiment, the sliding surface only occurs inside the bearing. Therefore, if the radius of the bearing is r ₂ , r ₂ << r ₁
And the sliding distance L _{2 of the} bearing is r ₂ · α, and L ₂ << L ₁
Becomes That is, it is possible to sliding area of the bearing in the second embodiment can be smaller than the sliding area of the spherical in the first embodiment, is smaller sliding distance L ₂ of the bearing. Therefore, the second embodiment has an advantage that the inclination angle of the swash plate can be controlled with higher accuracy than the first embodiment.

13 to 16 show a third embodiment of the present invention, and FIG. 13 corresponds to FIG. 1 of the first embodiment.

The pre-compression pre-decompression control mechanism 400 of the first embodiment controls the rotation angle of the swash plate about the Y-Y axis by balancing the moments acting on the swash plate 220 about the Y-Y axis. The pre-compression pre-decompression control mechanism 600 according to the third embodiment controls the amount of protrusion of the control piston 601 from the collar 602 according to the pump discharge pressure, thereby controlling the rotation angle of the swash plate 220 about the Y-Y axis. . Other configurations of the third embodiment are the same as those of the first embodiment.

The collar 602 is fitted in a hole formed in the body 101 of the housing, and the open end 603 of the collar 602 is closed by a plug 604 screwed into the hole of the body 101. The fluid tightness between the collar 602 and the body 101 is maintained by O-rings 605 and 606, and the fluid tightness between the collar 602 and the plug 604 is maintained by the O-ring 607. The control piston 601 and the collar
An oil hole 608 for guiding the pump discharge pressure is formed in 602. The control piston 601 is slidably supported in the collar 602, and its tip projects from the collar 602 and abuts on the surface of the swash plate 220. The amount of protrusion of the piston 601 from the collar 602 is determined by the pump discharge pressure guided to the oil hole 608 and the spring force of the spring 609, as described later.

FIG. 14 shows only the pre-compression pre-decompression control mechanism 600. In this figure, the collar 602 has a large diameter hole 611 and a small diameter hole 612, and the control piston 601 has a large diameter hole 611.
A large-diameter portion 613 slidably supported by the small-diameter portion 612 and a small-diameter portion 614 slidably supported by the small-diameter portion 612 are provided. O-rings 615, 616, and 617 maintain the liquid tightness between the large diameter portion 613 and the small diameter portion 614 of the piston 601 and the inner peripheral wall surface of the collar 602. A support hole 621 extending along the axis of the piston 601 is formed in the piston 601, and a spool 630 is slidably supported in the support hole 621. One end of the support hole 621 has a collar 602 and a plug 604
Open in a pressure chamber 622 formed by Spool 630
Has a large-diameter portion 631 protruding into the pressure chamber 622, and a valve portion 632 slidably received in the support hole 621. Support hole 621
The inside and the right side of the valve portion 632 communicate with the pressure chamber 622. The spring 609 is disposed in the pressure chamber 622, and is provided between the large diameter portion 630 of the spool and the end face of the collar 602.
630 is constantly biased toward the plug 604 side.

In the control piston 601, a discharge pressure introducing furnace 623, a control pressure introducing passage 624, a drain passage 625, and a control port 626 are formed. 627 indicates an embedding plug. The discharge pressure introduction passage 623 communicates with the support hole 621 and extends radially outward of the piston 601, and communicates with the oil hole 608. The control port 626 opens to the support hole 621 and is controlled to open and close by a valve portion 632 of the spool 630. The control pressure introduction passage 624 communicates with the control port 626 and opens to a step 628 formed between the large diameter portion 613 and the small diameter portion 612 of the piston 601. One end of the drain passage 625 opens to the support hole 621, and the other end of the drain passage 625 opens to the outer peripheral surface near the tip of the piston 601. That is, the drain passage 625 communicates with the inside of the body 101 of the housing.

Referring to FIG. 14 to FIG. 16, the pre-compression and pre-decompression control mechanism 60
The operation of 0 will be described.

The pump discharge pressure guided to the oil hole 608 is equal to the discharge pressure port 623.
And through the support hole 621 to the pressure chamber 622. When the pump discharge pressure rises and the pressure in the pressure chamber 622 exceeds a predetermined value, the spool 630 is displaced leftward in the figure against the spring 609. Here, assuming that the discharge pressure is P and the cross-sectional area at a portion of the spool 630 that slides on the inner wall of the support hole 621 is As, the spool 630 is pressed to the left by the force of PAs by the pump discharge pressure and the spring 609 is pressed. And is displaced leftward with respect to the collar 602 and the piston 601 as shown in FIG. Assuming that the spring constant of the spring 609 is Ks and the compression amount of the spring 609 is Xs, the spring 609 is compressed by Xs = PAs / Ks.
Resilience KsXs and force PAs are balanced. At this time, since the control port 626 opens into the support hole 621, the control pressure introduction path 624 is formed.
Communicates with the discharge pressure introduction passage 623 through the control port 626 and the support hole 621, whereby the pump discharge pressure is guided to the step portion 628 of the piston 601. Therefore, piston 601 is
This discharge pressure moves leftward with respect to the collar 602, and the control port 626 is displaced to a position where it is closed by the valve seat 632 as shown in FIG. That is, the piston 601 is displaced leftward by an amount corresponding to the compression amount Xs of the spring 609.

When the pump discharge pressure decreases from this state, the pressure in the pressure chamber 622 decreases, and the spool 630 is released from the spring 609.
Displaces to the right in the figure. That is, the spring 609 expands, and the spool 630 moves from the state shown in FIG.
To the right. As a result, the control port 626 opens inside the support hole 621 on the left side of the valve portion 632, and communicates with the drain passage 625. Therefore, in the space 633 formed between the step portion 628 of the piston 601 and the collar 602, the control pressure introduction passage 624, the control port 626,
The interior of the body 101 is communicated via the support hole 621 and the drain passage 625, and the pressure in the space 633 decreases. Thus, the piston 601 is pressed by the swash plate 220 and displaces rightward, and stops at the position where the control port 626 is closed by the valve portion 632.

Thus, the control piston 601 is displaced in accordance with the magnitude of the pump discharge pressure, whereby the swash plate 220 moves in the Y-Y axis (fourth axis).
(See Fig.) That is, also in the third embodiment, similarly to the first and second embodiments, the pressure pulsation of the discharge pressure is suppressed, and the generation of noise is reduced.

Although the first, second, and third embodiments all apply the present invention to a variable displacement pump and a motor, the present invention has the same effect on a fixed displacement pump and a motor. Play.

(Effect)

As described above, according to the present invention, with a simple configuration, it is possible to prevent pressure pulsation of the discharge pressure without changing the discharge capacity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of the first embodiment cut along a horizontal plane passing through a shaft, FIG. 2 is a cross-sectional view of the first embodiment cut along a vertical plane passing through a shaft, and FIG. 1 is an arrow view taken along the line III-III of FIG. 1; FIG. 4 is an arrow view of the swash plate taken along the line IV-IV of FIG. 2; FIG. 6 is a cross-sectional view showing a state where the swash plate is rotationally displaced around the XX axis in the first embodiment. FIG. 7 is a sectional view showing a state where the swash plate is rotationally displaced around the YY axis in the first embodiment. FIG. 8 is a cross-sectional view showing a state in which the swash plate is rotationally displaced around the YY axis in a direction opposite to that of FIG. 7, FIG. 9 is a graph showing a change in piston stroke with respect to a pump rotation angle, FIG. 10 is a graph showing a change in the pressure in the plunger chamber with respect to the pump rotation angle. FIG. 11 is a sectional view of the second embodiment cut along a horizontal plane passing through a shaft. FIG. 12 is a cross-sectional view showing the second embodiment cut along a vertical plane passing through the shaft, FIG. 13 is a cross-sectional view showing the third embodiment cut along a horizontal plane passing through the shaft, FIG. 14 is a cross-sectional view showing a pre-compression pre-decompression control mechanism of the third embodiment, FIG. 15 is a cross-sectional view showing a state where the spool is displaced to the left in the pre-compression pre-decompression control mechanism of the third embodiment, The figure is a cross-sectional view showing a state in which the control piston is displaced leftward in the pre-compression and pre-decompression control mechanism of the third embodiment. 100 ... housing, 104 ... suction port, 105 ... discharge port, 211 ... piston, 212 ... plunger chamber, 213 ... cylinder block, 220 ... swash plate, 300 ... capacity control mechanism, 400 ... Pre-compression and pre-pressure control mechanism.

────────────────────────────────────────────────── (5) References JP-A-49-81904 (JP, A) JP-A-60-147579 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F04B 1/00-7/06

Claims (4)

(57) [Claims] 1. A housing having a suction port and a discharge port provided on mutually opposite sides with respect to a center; a rotation shaft provided in the housing; and a second shaft orthogonal to the rotation shaft in the housing. 1
A swash plate that is provided to rotate with respect to the rotation center axis and has a surface that is inclined with respect to the rotation axis; and in the housing, the swash plate is provided to be rotatable coaxially with the rotation shaft, A cylinder block having a plunger chamber communicable with the discharge port, and slidably housed in the cylinder block, a head slidably engaged with the swash plate, and with rotation of the cylinder block, When the position of engagement with the swash plate changes, the plunger chamber is expanded and contracted by being displaced substantially in parallel with the rotation axis, and liquid is sucked into the plunger chamber from the suction port and pressurized to discharge the liquid. A piston discharged from a port, and the piston head at a position orthogonal to the first rotation center axis and at which the plunger chamber ends communicating with the suction port; A pre-compression pre-decompression control mechanism for rotating and displacing the swash plate around a second rotation center axis connecting the plunger chamber and the piston head at a position where communication with the discharge port ends. A characteristic axial piston device. 2. The swash plate according to claim 1, wherein said swash plate is composed of an outer peripheral member and an inner member, and between said outer peripheral member and said housing, one of said first rotation center axis and said second rotation center axis is provided. A first bearing is provided for rotatably connecting them on one of the axes, and the first rotation center axis or the first rotation center is provided between the outer peripheral component and the inner component. The first of the two rotation center axes;
2. The axial piston device according to claim 1, further comprising a second bearing that rotatably couples the rotation center shafts that do not correspond to the bearings described above. 3. The pre-compression pre-decompression control mechanism has a position control servo mechanism that is displaced in accordance with the magnitude of the operating pressure, thereby increasing or decreasing the rotational displacement of the swash plate. The axial piston device according to claim 1 or 2, wherein: 4. The discharge amount of a liquid discharged from the discharge port is changed by rotating and displacing the surface of the swash plate around the first rotation center axis. Or the axial piston device according to 2.