JP2005299645A - Axial-flow piston hydraulic power unit with false slipper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial-flow piston pump having longer life, toughness, durability and small contact stress without using a slipper. <P>SOLUTION: The axial-flow piston pump with a false slipper has a bull nose type axial-flow piston pump and a slipper type axial-flow piston pump combined and a slender piston body. A bore is formed in the piston body in the state of passing through the piston body. The bore includes a structure for functioning a hold-down mechanism. The false slipper is turnably connected to the piston body. The false slipper engages with a less frictional thrust bearing having a first race element and a second race element. The first race element and the second race element have a parallel relationship to a bearing element arranged therebetween. The less frictional thrust bearing controls the angle of a swash plate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an axial piston hydraulic power unit having a pseudo slipper.

  Conventionally, several different types of axial piston hydraulic pumps are known. For example, a slipper type axial piston pump is known. This type of axial piston pump has a piston body with a generally spherical ball at one end that engages a slipper bearing. The advantage of this slipper type axial piston pump is that the pump has a long life, is robust and extremely durable. Also, the contact stress inside the piston is small.

  This type of axial piston pump is advantageous in these respects, but has the disadvantage that it has a slipper holddown mechanism composed of a large number of complicated parts and has a large number of parts. Furthermore, to maintain the hydrostatic pressure balance, orifices must be opened in the piston and slipper, which is very expensive to operate. This orifice also loses oil in the pump, reducing efficiency. A slipper type piston has a relatively large mass, and this mass must reciprocate within the cylinder bore each time the pump rotates.

  Another type of axial piston pump is a bull nose type axial piston pump. This bull nose type piston pump has a hollow piston body, and a spring for holding the piston downward is arranged inside the hollow piston body, and the end of the piston engages with a race element. A ball thrust bearing is provided between the race elements.

  The bull nose type structure does not have a slipper, so it is easy to manufacture and is very inexpensive. However, the bull nose end portion of the piston makes point contact with the race of the thrust bearing, and a large load is transmitted to the point contact portion, so that the contact stress increases. This large contact stress limits the use of bull nose pistons to low power units that have a relatively short life.

  Currently, the slipper-type axial flow piston pump has a problem that not only is it machined precisely and the manufacturing cost of the slipper is high, but also the manufacturing cost of the piston body is high.

  When forming a hydrostatic oil film on which the slipper travels, there is a problem that fluid loss occurs and the slipper mass is large, so that the rotational speed is limited and the efficiency is low. On the other hand, bull nose type piston pumps have limited pressure, displacement and life. These practical limitations prevent the widespread use of bull nose piston pumps.

  Therefore, regardless of what type of piston is used, manufacturers suffer from shortcomings in either pump life or pump cost.

  Therefore, in this technical field, a slipper type axial piston pump element and a bull nose type axial piston pump element are combined so as to provide an axial piston pump that overcomes the disadvantages of the prior art. There is a need for an axial piston pump.

  There is also a need in the art to improve the rotary device of an axial piston pump that improves pump performance and reduces costs.

  Therefore, the main object of the present invention is to achieve a performance and lifetime that approximates or exceeds the performance or life of a slipper type axial piston pump at a low cost close to that of a bull nose type piston pump. It is an object of the present invention to provide an axial-flow piston rotating device.

  Yet another object of the present invention is to provide an axial piston pump that has a long life, is rugged, durable and has low contact stress without the use of slippers.

  Still another object of the present invention is to provide an axial piston pump that can be manufactured at a lower cost than a slipper type axial piston pump.

  It is yet another object of the present invention to provide a reduced friction bearing that engages a race member to improve contact stress in an axial piston pump.

  Still another object of the present invention is to manufacture a piston pump that improves the efficiency by eliminating the need to use pressurized fluid to form a hydrostatic pressure film on the slipper.

  Another object of the present invention is to provide a pump having characteristics similar to a slipper with a smaller reciprocating mass.

  These and other objects, features or advantages of the present invention will become apparent from the present specification and claims.

  The present invention relates to an axial flow piston pump combining a slipper type axial flow piston pump and a bull nose type axial flow piston pump. This axial piston pump has at least one elongated hollow piston, and a spring that generates a spring force applied to the pseudo slipper is disposed inside the hollow piston body. Alternatively, a spring may be provided outside the piston to generate a spring force in the same manner.

  The pseudo-slipper is in pivot contact with the piston body, but optionally has a first race element and a second race element in parallel relation to each other, and may be in contact with a reduced friction thrust bearing having a bearing. .

  When a variable displacement piston unit is desired, a friction reducing thrust bearing may be operably connected to the swash plate to control the angle of the swash plate.

  The figure shows an axial piston pump 10 according to the present invention. The axial flow piston pump 10 includes a cylinder block 12, and a piston main body 14 is disposed inside the cylinder block 12. The piston body 14 has an elongated bore 16 that extends through the piston body so that a spring element 18 can be fitted into the bore 16. Accordingly, the spring element 18 has one end engaged with the inner wall of the piston body 14 and the other end engaged with the wall of the cylinder block 12.

  A ball 20 is provided at the first end of the piston body 14, and this ball 20 is pivotally connected to a slipper element 22 which can be regarded as a pseudo slipper. The pseudo-slipper 22 engages with a friction-reducing thrust bearing 24. The thrust bearing 24 includes a first race element 26 and a second race element 28, and a bearing element 30 is interposed between the race elements. It is pinched. A swash plate (not shown) is operably connected to the friction reducing thrust bearing 24.

  FIG. 2 shows another embodiment of FIG. 1 in which the slipper element 22 is male. In this embodiment, the piston body 14 has a female groove 32 into which an arcuate male slipper element 22 can fit.

  In operation, the spring 18 generates a holding force on the piston body 14, so no additional parts are required. As the piston body 14 moves, the slipper element 22 pivots or rotates about the ball portion 20 of the piston body 14 so that the piston force on the reduced friction thrust bearing 24 is distributed.

  As the cylinder block 12 continues to rotate, the piston 14 continues to reciprocate inside and outside the cylinder bores. In this way, the hydraulic fluid is displaced and the hydraulic power unit operates as a hydraulic pump or hydraulic motor.

  The use of the spring 18 in the cylinder bore 16 eliminates the need for a slipper holding mechanism, thereby eliminating the need for complicated and expensive parts. Further, the pseudo-slipper structure can reduce the contact stress as compared with the bull nose axial piston, and can extend the life of the piston as compared with the bull nose axial piston. Thus, the present invention seeks to approximate the high performance of a slipper type device at a low cost that is closer to the cost range of a bull nose piston device.

  The present invention does not require a hydrostatic balance membrane as found in slipper type axial piston devices, so no oil is lost through the piston and the efficiency of the piston is not reduced. Furthermore, those skilled in the art will appreciate that the piston element can perform the holding function even if a piston element 18 is provided inside the bore 16 or, optionally, outside the bore 16.

  The friction-reducing thrust bearing 24 can further reduce the contact stress compared to a bull nose type axial piston pump. The friction reducing thrust bearing may be any one of the group consisting of a ball bearing, a roller bearing, a tapered roller bearing, or another suitable bearing.

  Further, by eliminating the hydrostatic pressure membrane and eliminating the leakage of oil used to form the membrane, losses are reduced and efficiency is improved.

  Finally, the reciprocating mass can be reduced by replacing a relatively large, high mass slipper of standard construction with the pseudo-slipper of the present invention. In this way, all of the objects of the present invention can be achieved.

  Those skilled in the art will appreciate that various modifications can be made to the apparatus without departing from the spirit of the invention. All such variations and modifications are intended to be within the scope of the claims and are covered by the claims.

It is sectional drawing of the axial flow piston pump of this invention. It is sectional drawing of the axial-flow piston pump of this invention in which a slipper element is a male type slipper element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Axial flow piston pump 12 Cylinder block 14 Piston body 16 Bore 18 Spring element 20 Ball 22 Pseudo slipper 24 Friction reduction thrust bearing 26 First race element 28 Second race element 30 Bearing element 32 Female groove

Claims (3)

Comprising at least one elongate piston disposed inside the pump, which is fitted with a spring for generating pressure on the pseudo-slipper;
The pseudo slipper is pivotally connected to the piston,
And a friction reducing thrust having a first race element and a second race element,
An axial piston pump comprising a pseudo slipper, wherein the first and second race elements are in between and in parallel relation to a bearing element that directly engages the slipper.   The axial piston pump of claim 1, wherein the piston has a first end forming a ball portion that pivotably engages the pseudo-slipper. An elongated piston body having a bore disposed in the cylinder block;
A spring firmly connected to the piston;
A slipper element pivotally connected to the piston body such that the spring generates a holding force on the slipper element;
An axial piston pump having a cylinder block, comprising: a friction reducing thrust bearing that directly engages the slipper element.

Images