JP3771004B2 - Axial piston motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of an axial piston motor.
[0002]
[Prior art]
In the conventional axial piston motor, the pressing force of the sliding surface between the cylinder block and the valve plate is received only by the land portion around the port. The pressing force has a great influence on the sealing performance of the sliding surface. If the pressing force is reduced, the sealing performance around the port is lowered, and problems such as defective volume efficiency occur.
[0003]
On the other hand, if the pressing force is increased, the sealing performance is improved. On the other hand, thermal cracks (thermal cracks) are likely to occur due to the frictional heat of the sliding surface, and the durability is lowered. In particular, in recent years, if an attempt is made to satisfy the demand for higher rotation of the axial piston motor, the occurrence of thermal cracks accompanying the increase in the speed of the sliding surface is unavoidable.
[0004]
[Problems to be solved by the invention]
Therefore, it is possible to provide an auxiliary pad on the sliding surface near the outer periphery of the cylinder block and valve plate to reduce the actual surface pressure while keeping the pressing ratio (ratio of cylinder pressure and pressing force) at an effective value. It is done. However, in this case, when the smoothness of the sliding surface is low, the entire sliding surface is not evenly contacted. Especially when only the auxiliary pad portion is in sliding contact, the surface pressure of the auxiliary pad portion increases excessively and the land A gap is generated in the portion, and the sealing performance around the port cannot be maintained, causing problems such as a decrease in volumetric efficiency and a drain peak.
[0005]
The present invention aims to solve such problems.
[0006]
[Means for Solving the Problems]
The present invention provides an axial piston motor in which a cylinder block rotates while being in sliding contact with a valve plate. A land portion serving as a seal region is provided on a sliding surface between the cylinder block and the valve plate, and an escape groove is provided outside the land portion. An annular auxiliary pad portion is provided, and a gap is formed at a portion corresponding to the auxiliary pad portion on the joint surface with the motor housing on the opposite side of the sliding surface of the valve plate. It is getting bigger.
[0009]
[Action]
In the present invention , an auxiliary pad portion is interposed between the cylinder block and the valve plate in addition to the land portion. For this reason, the pressing force of the cylinder block is received by the land portion and the auxiliary pad portion, and the actual surface pressure of the land portion can be lowered. Since there is a gap on the opposite surface of the valve plate corresponding to the auxiliary pad portion, when excessive surface pressure is applied to the auxiliary pad portion, the valve plate is deformed to the opposite side, which causes the auxiliary pad portion to The surface pressure can be kept substantially the same as the surface pressure applied to the land portion. Therefore, it is possible to prevent the surface pressure from being excessively increased as the entire sliding surface while maintaining good sealability of the land portion, to prevent the occurrence of heat cracks, and to improve the durability. Further, since the gap becomes larger toward the outer peripheral side of the valve plate, a good follow-up deformation performance can be imparted to the valve plate with the minimum necessary gap.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The best embodiment of the present invention will be described with reference to the drawings.
[0013]
1 and 2, 1 is a motor housing, 2 is a motor shaft, 3 is a cylinder block, and 4 is a swash plate. In the cylinder block 3, a plurality of cylinders 7 are formed concentrically with the motor shaft 2, and a piston 5 is slidably disposed therein. The end face of the cylinder block 3 is in contact with the valve plate 6, and pressure oil is supplied to and discharged from the cylinder holes 7 through valve holes (supply holes and discharge holes) formed in the valve plate 6. In other words, the supply of pressure oil to the cylinder 7 from the supply hole of the valve plate 6 causes the piston 5 to extend. At this time, the rotational force applied to the cylinder block 3 by the circumferential force generated by the inclination angle of the swash plate 4. Occurs and the motor shaft 2 is rotated. After the piston 5 is stroked to the maximum, the piston 5 contracts while discharging the hydraulic oil in the cylinder 7 from the discharge hole of the valve plate 6, and thus the cylinder block 3 is 1 while the piston 5 is reciprocated once. Rotate.
[0014]
A land portion 10 is formed on the sliding contact surface between the cylinder block 3 and the valve plate 6 to seal the periphery of the port 8 of each cylinder 7. The land portion 10 prevents pressure oil from leaking from the sliding contact surface. Yes. An annular escape groove 11 is formed on the outer periphery of the land portion 10, and oil leaked through the plurality of grooves 11 a extending in the radial direction connected to the escape groove 11 is released to the housing inner space 9. An auxiliary pad portion 12 is formed outside the escape groove 11, and the auxiliary pad portion 12 also receives a pressing force applied to the cylinder block 3.
[0015]
The surface opposite to the sliding contact surface of the valve plate 6 is in close contact with the motor housing 1 and is fixed by pins 13 so as not to rotate. A pressure oil supply / exhaust passage (not shown) provided in the motor housing 1 and a valve hole of the valve plate 6 are connected to each other, but a seal region 15 for preventing leakage of pressure oil is provided on the contact surface 6b. An annular escape groove 14 is provided outside the seal region 15, and the leakage is released to the internal space 9 through the escape groove 14 as described above.
[0016]
The escape groove 11 and the escape groove 14 are provided at substantially corresponding positions, and between the valve plate 6 and the motor housing 1, a sliding contact surface of the valve plate 6 is provided outside the escape groove 14. A gap 16 is provided that allows deformation in the opposite direction. The gap 16 has a tapered cross section, and the gap becomes larger toward the outer periphery.
[0017]
The land portion 10 and the auxiliary pad portion 12 are slidable with good sliding characteristics by, for example, integrally forming a sliding layer 17 made of a bearing material of a predetermined thickness on the bottom surface of the cylinder block 3. Form a surface.
[0018]
It is comprised as mentioned above, Next, an effect | action is demonstrated.
[0019]
For each cylinder 7 of the cylinder block 3, the piston 5 strokes toward the top dead center by supplying the pressure oil in the extension region from the bottom dead center to the top dead center through the valve hole of the valve plate 6. At this time, a rotational force is generated in the cylinder block 3 by a circumferential component force generated according to the inclination angle of the swash plate 4 with which the tip of the piston 5 contacts. After the piston 5 reaches the top dead center, the piston 5 contracts toward the bottom dead center while discharging the hydraulic oil from the cylinder 7 as the cylinder block 3 rotates in the same direction. The piston 5 reciprocates, the cylinder block 3 rotates in response to this, and the motor shaft 2 rotates.
[0020]
On the sliding contact surface between the cylinder block 3 and the valve plate 6, the reaction force of the hydraulic pressure that pushes out the piston 5 and the pressing force of the valve plate 6 from the cylinder block 3 act in opposite directions, which corresponds to the differential force between them. The sealing property of the sliding contact surface is maintained according to the pressing ratio.
[0021]
The slidable contact surface is composed of a land portion 10 and an auxiliary pad portion 12 as a seal region, and has an effective pressure receiving area larger than that of the land portion 10 alone. Therefore, when the pressing ratio is set to a predetermined value, The surface pressure applied to the land portion 10 is relatively lowered.
[0022]
At this time, even if excessive surface pressure acts on the auxiliary pad portion 12 due to the accuracy of the sliding contact surface, the valve plate 6 is deformed to the opposite side because the gap 16 exists on the back surface side of the valve plate 6, and the surface pressure is reduced. Reduce. For this reason, an excessive pressure does not act only on the auxiliary pad portion 12, and a uniform contact pressure is maintained over the entire sliding contact surface. In addition, if the thickness of the auxiliary pad portion 12 is set larger than that of the land portion 10 in advance and the contact with the auxiliary pad portion 12 is absorbed by deformation to the opposite side, the surface pressure of the land portion 10 is surely increased. It can be smaller than 12.
[0023]
As a result, the substantial surface pressure of the sliding contact surface between the cylinder block 3 and the valve plate 6 is reduced, the frictional heat associated with the sliding is prevented from increasing, the occurrence of thermal cracks is avoided, and the motor rotation speed is increased. High durability can be maintained. On the other hand, even if the surface pressure of the slidable contact surface is lowered, the sealing performance of the land portion 10 is not deteriorated, so that it is possible to prevent the deterioration of volumetric efficiency and the occurrence of a drain peak, and the good pump performance. Can be maintained.
[0024]
Further, since the gap 16 becomes larger toward the outer periphery of the valve plate 6, the deformation of the valve plate 6 is easily and appropriately performed.
[0025]
Next, a reference example of FIG. 3 will be described. This is a gap between the cylinder block 3 and the valve plate 6 provided with a uniform gap 16a having the same interval over the entire area. This facilitates the formation of the gap 16a and improves the workability of the valve plate 6.
[0026]
In the above embodiment, the slidable contact surface between the cylinder block 3 and the valve plate 6 is formed in a spherical shape. However, the present invention is not limited to this, and it is obvious that the slidable contact surface may be a plane contact. .
[Brief description of the drawings]
FIG. 1 is an overall cross-sectional view showing an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view showing the main part.
FIG. 3 is an enlarged sectional view showing a reference example of the present invention .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor housing 2 Motor shaft 3 Cylinder block 5 Piston 6 Valve plate 7 Cylinder 10 Land part 11 Relief groove 12 Auxiliary pad part 14 Relief groove 16 Gap

Claims (1)

In an axial piston motor in which the cylinder block rotates while slidingly contacting the valve plate, a land portion serving as a seal region is provided on the sliding surface between the cylinder block and the valve plate, and an annular auxiliary member is provided outside the land portion via a relief groove. A pad portion is provided, and a gap is formed in a portion corresponding to the auxiliary pad portion on the joint surface with the motor housing on the opposite side of the sliding surface of the valve plate, and the gap becomes larger as it goes to the outer periphery of the valve plate. axial piston motor, characterized in that there.

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