JP2003343424A - Swash plate type fluid pump/motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a swash plate type fluid pump/motor capable of surely preventing a scratch and seizure of a slide surface of a cylinder to that of a piston, hardly causing leakage of a working fluid, and excellent in operation efficiency. <P>SOLUTION: This swash plate type fluid pump/motor is provided with: a swash plate 14 formed so as to make its tilt angle adjustable; and the piston 6 rotatable around a rotation axis along with the swash plate 14, and fitted into the cylinder 3 to reciprocate relatively to the cylinder 3. The fluid pump/ motor is characterized by forming, on the circumferential surface of a cylinder part 6a of the piston body 6, a groove part 20 for communicating the vicinity of a piston head part 6d on the swash plate side with a piston bottom part 6d positioned on the axially opposite side to the swash plate, and opened to a working fluid chamber 8 faced by the piston bottom part 6d. Preferably, the groove part 20 is spirally formed at an angle of around 50-80° with respect to the axis line of the piston body and at an interval or pitch of around 0.4-0.6 of the piston diameter. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device,
The present invention relates to a swash plate type fluid pump / motor which is applied to a fluid machine such as a steering gear for a ship, and is configured to be capable of reciprocating by a relative movement of a piston and a swash plate part, using a low viscosity fluid as a working fluid.

[0002]

2. Description of the Related Art Conventionally, swash plate type fluid pumps and motors have been widely used in fluid machines such as drive devices for construction machines and steering gears for ships. Such a swash plate type fluid pump / motor comprises a cylindrical cylinder block which is rotatably supported and fixed integrally with a pump shaft for transmitting drive or output, and the cylinder block is concentric with respect to its central axis and A plurality of parallel cylinders are bored, and a piston that can reciprocate in the axial direction is housed in each cylinder.

The piston is constructed so as to slide on a swash plate fixed to the pump shaft so that the tilt angle can be adjusted, through a spherical portion, and the piston can be adjusted according to the tilt angle of the swash plate. The amount of reciprocating movement is determined. A minute space, that is, a clearance is formed on the sliding surface between the piston and the cylinder, and the working fluid that has entered the clearance acts as a lubricant to smoothly reciprocate between the piston and the cylinder. That is, when the fluid machine is operated, hydraulic pressure is applied to the working fluid, which causes the working fluid to enter the clearance, so that the working fluid is always present on the reciprocating sliding surface of the piston-cylinder, and the liquid film is formed. Is formed.

However, during low-pressure operation, the liquid pressure becomes extremely low, so that it is difficult to form a liquid film, and the piston and cylinder come into metal contact with each other, causing galling and seizure reduction. In particular, when the slope angle is zero and the amount of movement of the piston is zero, the working fluid hardly flows, the hydraulic pressure is not generated, and the liquid film is formed due to the minute vibration generated by the rotation of the pump shaft. It disappears, and damage to the sliding portion due to galling, seizure, etc. is more likely to occur.

Therefore, in order to prevent the galling and the seizure which are caused in this way, JP-A-6-26447 is used.
No. 0, which is shallower than the gap between the piston 020 and the cylinder, on the outer peripheral surface of the piston 020, as shown in FIG.
20c is provided between the oil sumps 020a and on both sides thereof, and a plurality of hydraulic pumps / motors are provided in the axial direction of the piston 020. As a result, the pressure oil is guided to each groove 020c and a lubricating oil film is easily formed between the piston 020 and the cylinder, so that abrasion of these can be suppressed and seizure can be prevented.

Further, Japanese Patent Laid-Open No. 11-93829 discloses a hydraulic pump having a hydraulic piston as shown in FIG. According to the invention, a part of the outer periphery of the piston 05a, that is, a portion near the contact point a between the piston 05a and the hole 04a of the cylinder block 03a on the piston shoe 06 side is not orthogonal to the axis of the piston 05a and the pitch is b point. Oil groove with a clearance of 0.5 or less in
7 is provided. Further, in order to ensure the refueling, a porous metal such as sintered metal is used around the piston. As a result, even when the swash plate angle is zero, oil penetrates into the groove to form an oil film, and seizure or galling due to metal contact can be prevented.

[0007]

However, in the above-mentioned prior art, it is possible to prevent the seizure and galling of the piston and the cylinder at the time when the relative movement amount of the piston is zero or at the low pressure driving, but in the above-mentioned JP-A-6-26447. Since the groove is formed in a straight line in the axial direction of the piston, the hydraulic oil is likely to leak during driving, resulting in a large pressure loss of the hydraulic oil in the cylinder, which deteriorates the operating efficiency. Further, in this invention, since the edge of the groove has a corner portion, there is a possibility that the device may be damaged due to abrasion and metal powder generation due to sliding with the cylinder.

Further, in the structure in which the oil groove is provided only on the piston shoe side as in Japanese Patent Laid-Open No. 11-93829, the working oil in the cylinder cannot be sufficiently spread, and the periphery of the piston is porous. If it is made of metal, not only the manufacturing cost but also the material cost increases, and it is difficult to provide it to general consumers. Therefore, in view of the above problems of the prior art, the present invention provides a swash plate type fluid pump / motor that reliably prevents galling and seizure of the sliding surface between the cylinder and the piston, and that the working fluid is less likely to leak and has good operating efficiency. For the purpose of provision.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a swash plate having an adjustable tilt angle, and the swash plate and the rotation axis. In a swash plate type fluid pump / motor equipped with a piston that is fitted in a relatively rotatable cylinder and that reciprocates relative to the cylinder by the inclination angle of the swash plate, an outer peripheral surface of a cylindrical portion of the piston is provided. A groove is provided which communicates from the vicinity of the piston head located on the swash plate side to the piston bottom located axially opposite to the swash plate and is opened to the working fluid chamber facing the piston bottom. To do.

According to the invention, by providing the groove portion on the outer peripheral surface of the cylindrical portion of the piston over substantially the entire surface, the liquid film formed by the working fluid can be held on the sliding surface of the piston and the cylinder. It is possible to prevent galling and seizure due to metal contact between the piston and the cylinder even during low-pressure operation or operation at zero slope angle. Further, since the groove portion is provided so as to open to the working fluid chamber on the piston bottom side, the working fluid existing in the cylinder space passes through the opening portion even when there is no working fluid flow or hydraulic pressure. Since it penetrates the outer peripheral surface of the piston, the liquid film can be always held. The working fluid chamber is
The space surrounded by the cylinder and the bottom of the piston.

The invention according to claim 2 is characterized in that the groove portion according to claim 1 is a spiral groove portion provided along the outer peripheral surface of the cylindrical portion of the piston. And preferably, as in the invention according to claim 3, the spiral groove is at an angle of about 50 ° to 80 ° with respect to the axial center line of the piston and about 0.4 to about the piston diameter. 0.6
It may be configured to be formed at equal intervals with the pitch.
Further, as in the invention according to claim 4, the spiral groove portion has an angle of about 50 ° to 80 ° with respect to the axis of the piston, and the pitch is sparse from the piston head toward the piston bottom. You may form so that it may become.

According to this invention, the working fluid passage can be elongated by forming the groove portion in a spiral shape, and the working fluid can be used even when the fluid machine is operating, that is, when the working fluid has a high fluid pressure and a large flow. The amount of leakage of
It is possible to prevent a decrease in operating efficiency. Further, as described in claim 3, the angle of the groove is about 50 ° to 80 ° with respect to the axis of the piston, and the pitch of the groove is about 0.4 to 0.6 with respect to the piston diameter. By doing so, it is possible to secure a flow path length suitable for each piston, form a liquid film at all times, and minimize the amount of leakage during operation. Further, as in the invention according to claim 4, the pitch of the spiral groove portion is dense on the piston head side,
Since the piston bottom side is sparsely formed, the working fluid easily enters the piston head side where the piston and cylinder are easily worn and the lubrication conditions are severe, and the working fluid is less likely to leak during operation of the device. .

According to a fifth aspect of the present invention, the groove portion has an annular groove portion formed in parallel with the circumference of the piston.
It is characterized by comprising linear groove portions alternately formed in the axial direction so as to connect the annular groove portions. In the invention, an annular groove portion parallel to the circumference of the piston and a plurality of linear groove portions provided in the longitudinal direction of the piston form a groove portion so as to cover substantially the entire outer circumference of the piston,
A continuous groove is formed by connecting the annular groove with a linear groove. Further, since the linear groove portions are formed so as to have a phase, the flow path of the working fluid becomes long, and the working fluid does not easily leak during operation.

Further, as described in claim 6, it is preferable that the groove has a smoothly curved cross section. In this way, by forming the groove cross section into a curved shape having no corners, it is possible to prevent generation of metal powder due to wear and maintain a good operating condition. The groove depth is about 1
It is preferable that the thickness is from 00 to 200 μm, which can reduce the leakage amount of the working fluid.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative positions, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto unless otherwise specified, and are merely illustrative examples. Not too much. 1 is a sectional view of a swash plate type hydraulic pump according to a first embodiment of the present invention, and FIG. 2 is a side view (a) of the piston according to the first embodiment of FIG. )
3 and 4 are side views of the in-cylinder pistons according to the second and third embodiments of the present invention, and FIG. 5 is an overall schematic configuration diagram of the swash plate hydraulic pump according to the embodiment of the present invention. 6
FIG. 3 is an enlarged view of a Z portion of the swash plate according to the embodiment of the present invention.

In the present embodiment, a hydraulic pump whose main working fluid is mineral oil has been described, but any device can be used as long as it is a fluid machine such as a pump or a motor which uses a low viscosity fluid containing water as a working fluid. It is also applicable in. First,
Referring to FIG. 5, the overall structure of the swash plate type hydraulic pump according to the present invention will be described. Reference numeral 1 denotes a pump shaft that is rotationally driven by being connected to a drive source (not shown) such as an engine and an electric motor.
Is a bearing for rotatably supporting the rotationally driven pump shaft, 3 is a cylinder, and 4 is a cylinder block fitted to the pump shaft 1 via a spline and rotationally driven in synchronization with the pump shaft 1.

A plurality of cylinders 3 are bored in the cylinder block 4 at equal intervals in the circumferential direction, and 6 is a piston body housed in the cylinder 3 so as to be reciprocally slidable. A bush (not shown) may be inserted into the cylinder 3 and the piston body 6 may be reciprocally slidably fitted in the bush. The piston body 6 includes a cylindrical body portion 6a and a spherical portion 6 formed at one end of the piston body.
b, and a central hole is bored from the cylindrical portion 6a to the spherical portion 6b along the axis of the piston body.

The operating portion including the pump shaft 1, the cylinder 3 and the piston body 6 is a casing 11 and a base plate 1 fixed to both ends of the casing 11.
3, housed in a housing formed by the end plate 12, and configured to operate in a closed space. 5
Is a valve plate arranged on the oil supply / drainage hole 7 side of each cylinder 3 and fixed to the end plate 12.
Eyebrow-shaped suction holes and discharge holes are formed in the valve plate 5 so as to face both sides of the pump shaft 1. The end plate 12 includes a suction passage 9 and a discharge passage 1.
0 is formed, the suction passage 9 communicates with the suction hole of the valve plate 5, and the discharge passage 10 communicates with the discharge hole.

Reference numeral 14 is a swash plate attached to the base plate 13, and the swash plate angle is adjustable by a swash plate angle adjusting device 80 shown in FIG. That is, as shown in FIG. 6, each swash plate adjusting device 80 has a cylinder 08b.
A lever 08a is rotated by a piston 08c that reciprocates inside, and a swash plate shaft 08 fixed to the end of the lever 08a.
The sloping angle is changed by rotating the arrow as indicated by the arrow U in the figure. Reference numeral 16 is a slipper having a recess, and the spherical portion 6b of each piston body 6 and the recess are slidably joined to each other, and the swash plate 14 and the slipper 16 are provided.
And form a swash plate. Reference numeral 15 is a thrust plate disposed on the surface of the swash plate 14 on the side of the slipper 16 through a roller bearing 25, and the slipper 16 is in contact with the thrust plate 15 so as to be relatively slidable.

The above construction is similar to that of the conventional swash plate type hydraulic pump. In the present invention, the piston body 6 is improved. Cylinder of swash plate type hydraulic pump according to FIG.
The sectional view which expanded the piston part is shown. In FIG. 1, 8
Is a hydraulic oil chamber formed by the piston bottom portion 6c and the cylinder 3, and 18 is a clearance of a minute gap provided on the sliding surface between the piston cylinder portion 6a and the cylinder 3. The hydraulic oil chamber 8 and the clearance 18 are filled with hydraulic oil, and the piston body 6 and the cylinder 3 are smoothly reciprocally slid by the lubricating action of the hydraulic oil that has entered the clearance 18.

On the outer peripheral surface of the piston cylindrical portion 6a, the piston bottom portion 6 is opened toward the hydraulic oil chamber 8.
spiral groove 2 communicating from c to piston head 6d
0 is provided, and the working oil flows out from the working oil chamber 8 through the groove portion 20 to form an oil film on the outer peripheral surface of the cylindrical body portion 6a. Such grooves 20 are machined in a spiral at a pitch W _P with respect to the angle α a and the piston diameter D with respect to the axial line of the piston body 6, as shown in FIG. 2 (a). In this case, the angle α of about 50 ° to 80 °, preferably in a pitch W _P about 0.4-0.6, thereby independently of the type of piston without optimum groove portion can be formed.

Further, as shown in the sectional view taken along the line AA of the groove portion 20 of FIG. 2B, the sectional shape of the groove portion 20 is preferably a smooth curved concave portion having no corners, By forming in this way, it is possible to prevent metal powder from being generated due to sliding and abrasion with the cylinder 3, and to prevent damage to the device, and the working oil flowing into the groove 20 is evenly distributed on the outer peripheral surface of the piston. A spreading oil film is easily formed. Further, it is preferable that the width W _{Q of the} groove portion 20 is about 1 mm and the depth L of the groove is about 100 to 200 μm.
As a result, the hydraulic oil is unlikely to leak even when the hydraulic pump is operating, and the deterioration of operating efficiency can be prevented.

FIG. 3 is a side view of an in-cylinder piston according to a second embodiment of the present invention. The piston body 6 is provided with the spiral groove portion 20 as in the first embodiment. the groove portion 20 loosely is the angle α and the pitch W _P with respect to the axial center line of the piston body 6 in the piston bottom 6c side and the piston head 6d side is formed to be dense. The angle α is about 50 as in the first embodiment.
It is preferable to set the angle to 80 °. As a result, the hydraulic oil easily flows into the piston head 6d side where the piston main body 6 and the cylinder 3 are easily worn and the lubrication condition is severe, and the piston bottom 6c side pitch is sparse so that the hydraulic oil is It becomes difficult to leak.

In the hydraulic pump according to the third embodiment of the present invention, as shown in FIG. 4, a plurality of annular groove portions 21 formed in parallel with the circumference of the piston and a linear groove portion connecting the annular groove portions 21 are formed. It comprises a piston body 6 having a groove consisting of 22 and 22. A plurality of the linear groove portions 22 are linearly provided in the axial direction of the piston body 6, and each of them is formed with a phase, so that the flow path of the hydraulic oil becomes long,
The hydraulic oil does not easily leak during operation. In addition, by making the groove width of the linear groove portion 22 smaller than that of the annular groove portion 21, leakage during operation is minimized, and hydraulic oil is retained in the annular portion 21 during low pressure operation or zero slope angle operation. It is easy to form an oil film.

[0025]

As described above, according to the present invention, by providing a groove on the outer peripheral surface of the cylindrical portion of the piston over substantially the entire surface, the liquid formed by the working fluid on the sliding surface of the piston and the cylinder. It is possible to retain the film and prevent galling and seizure due to metal contact between the piston and the cylinder even during low pressure operation or operation at zero slope angle. Further, since the groove portion is provided so as to be opened to the working fluid chamber on the piston bottom side, the working fluid flows into the piston outer peripheral surface through the opening portion even when there is no working fluid flow or hydraulic pressure, The liquid film can be held at all times.

Further, by making the groove portion spiral, the working fluid passage can be lengthened, and the leakage amount of the working fluid can be obtained even when the apparatus is operating at high pressure, that is, when the working fluid has a high fluid pressure and a large flow. Can be suppressed to a minimum, and a decrease in operating efficiency can be prevented. Further, the pitch of the spiral groove portion is such that the piston head side is dense and the piston bottom side is sparse, so that the piston and the cylinder are easily worn and the lubricating condition is severe. Easily enters, and the working fluid does not easily leak during operation.

Further, since the groove portion is formed by the annular groove portion and the linear groove portion that communicates with each other, and the linear groove portions are formed so as to have respective phases, the flow path of the working fluid becomes long, and the operation is performed. It is difficult for the working fluid to leak. Furthermore, by setting the groove depth to about 100 to 200 μm, it is possible to reduce the amount of leakage of the working fluid, and by making the groove cross section into a curved shape having no corners, it is possible to reduce wear. It is possible to prevent the generation of metal powder and maintain a good operating state, and the working fluid flowing into the groove is evenly spread on the outer peripheral surface of the piston to easily form a liquid film.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a swash plate hydraulic pump according to a first embodiment of the present invention.

2A is a side view of the piston according to the first embodiment of FIG. 1, and FIG. 2B is a sectional view taken along line AA of FIG.

FIG. 3 is a side view of an in-cylinder piston according to a second embodiment of the present invention.

FIG. 4 is a side view of an in-cylinder piston according to a third embodiment of the present invention.

FIG. 5 is an overall schematic configuration diagram of a swash plate type hydraulic pump according to an embodiment of the present invention.

FIG. 6 is an enlarged view of a Z portion of the swash plate according to the embodiment of the present invention.

FIG. 7 is an example of a piston of a conventional hydraulic pump / motor.

FIG. 8 is an example of a piston of a conventional hydraulic pump.

[Explanation of symbols]

1 pump shaft 3 cylinders 4 cylinder block 6 Piston body 6a cylindrical part 6b spherical part 7 Oil supply / drain hole 8 hydraulic oil chamber 9 Inhalation passage 10 Discharge passage 11 casing 14 Swash plate 16 slippers 20 spiral groove 21 annular groove 22 Linear groove

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3H070 AA01 BB04 BB06 CC07 CC21                       CC27 DD28                 3H071 AA03 BB01 CC11 CC26 CC27                       DD01                 3H084 AA08 AA16 AA43 AA45 AA51                       BB01 BB06 BB09 BB23 CC12                       CC17 CC41

Claims (6)

[Claims] 1. A swash plate having an adjustable tilt angle,
A swash plate-type fluid pump / motor comprising: a swash plate and a piston that is fitted in a cylinder that is relatively rotatable about a rotation axis and that reciprocates relative to the cylinder according to an inclination angle of the swash plate. A groove portion that communicates from the vicinity of the piston head located on the swash plate side to the piston bottom portion located axially opposite to the swash plate on the outer peripheral surface of the cylindrical portion of the piston, and is opened to the working fluid chamber facing the piston bottom portion. A swash plate type fluid pump / motor characterized by being provided with. 2. The swash plate type fluid pump / motor according to claim 1, wherein the groove portion is a spiral groove portion provided along an outer peripheral surface of a cylindrical portion of the piston. 3. The spiral grooves are equally spaced at an angle of about 50 ° to 80 ° with respect to the axis of the piston and at a pitch of about 0.4 to 0.6 with respect to the piston diameter. The swash plate type fluid pump / motor according to claim 2, wherein the swash plate type fluid pump / motor is formed. 4. The spiral groove portion is formed at an angle of about 50 ° to 80 ° with respect to the axial center line of the piston, and the pitch is sparse from the piston head portion to the piston bottom portion. The swash plate type fluid pump / motor according to claim 2, wherein 5. The groove portion comprises an annular groove portion formed parallel to the circumference of the piston and linear groove portions alternately formed in the axial direction so as to connect the annular groove portions to each other. The swash plate type fluid pump / motor according to claim 1. 6. The swash plate type fluid pump / motor according to claim 1, wherein a cross-sectional shape of the groove is a smooth curved line.