US20080307956A1

US20080307956A1 - Web-less valve plate

Info

Publication number: US20080307956A1
Application number: US11/764,267
Authority: US
Inventors: Joseph Wright
Original assignee: Sauer Danfoss Inc
Current assignee: Danfoss Power Solutions Inc
Priority date: 2007-06-18
Filing date: 2007-06-18
Publication date: 2008-12-18
Also published as: DE102008020829A1; CN101328884A; JP2008309154A

Abstract

A hydraulic unit that uses first and second support structures to eliminate the use of webs within an arcuate inlet and outlet of a valve plate. Specifically, a valve plate body extends between an inner and outer diameter wherein the outer diameter in a first position is placed in close proximity to a first support structure and the inner diameter is placed in close proximity to a second support structure. Thus, stress of hydraulic fluid flowing through the arcuate inlet or outlet deflects the inner and outer diameters causing them to engage the first and second support structures such that stress is passed to the first and second support structures and the valve plate is stiffened.

Description

BACKGROUND OF THE INVENTION

This invention relates to hydraulic units. More specifically, this invention relates to a web-less valve plate for a hydraulic unit.
Hydraulic units such as axial piston hydraulic units or bent axis hydraulic units, including pumps and motors, are known in the art. Each of these types of hydraulic units use valve plates therein that have arcuate openings that represent inlet and outlet ports. Specifically, each of these openings as shown in FIG. 1 contains a web portion therebetween to enhance the strength of the valve plate to account for pressure variations known in current hydraulic unit technology.
When hydraulic units were originally designed, as shown in U.S. Pat. No. 2,915,985 valve plates included non restricted inlet and outlet passages that were arcuate in shape and did not contain the webs. As performance of hydraulic units increased with higher operating pressures valve plates of this design became susceptible to failure in the area of the pressurized outlet passage. To eliminate this failure the strength enforcing webs as shown in FIG. 1 were added. An illustration of this is also seen in U.S. Pat. No. 3,249,061.
Though the webs assist in preventing failure of the pressurized outlet passage of the valve plate the webs restrict flow thus creating operating inefficiencies within the hydraulic unit. Attempts have been made to overcome these operating inefficiencies including creating openings within the webs themselves and using special strength materials to make the valve plates themselves stronger in an attempt to minimize the effects of the webs on fluid flow.
Despite these improvements, problems still remain in the art. Specifically, hydraulic units that attempt to overcome the problems associated with the webs that merely add extra openings within the webs weaken the valve plate making the valve plate susceptible to failure. These valve plates also do not eliminate the web completely and thus hamper fluid flow causing inefficiencies within the hydraulic unit. In regard to valve plates that use specialized materials extra steps are added to the manufacturing process to accommodate the complexity of the manufacturing of the valve plate causing additional expense and time.
Therefore, a principal object of the present invention is to provide a hydraulic unit with a valve plate that maximizes efficiency of the hydraulic unit.
Yet another object of the present invention is to provide a hydraulic unit with a valve plate assembly that reinforces the ability of the valve plate to undergo stress.
These and other objects, features, or advantages of the present invention will become apparent from the specification and claims.

BRIEF SUMMARY OF THE INVENTION

A hydraulic unit having a first support structure with an opening therein. A valve plate is detachably disposed within the opening of the first support structure. Specifically, the valve plate has an inner and outer diameter with a body extending therebetween. The outer diameter in a first position is placed adjacent and in close proximity to the first support structure whereas the inner diameter surrounds a valve plate opening. Said valve plate body also has an arcuate inlet and outlet disposed therein. Additionally, in the first position a second support structure is detachably disposed within the valve plate opening. When fluid flows through the arcuate inlet and outlet the body of the valve plate deflects such that the inner diameter engages the second support structure and the outer diameter engages the first support structure to provide a second position. In this second position stress on the valve plate body is transferred from the body to the first and second support structures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art bottom plan view of a valve plate with webs;

FIG. 2 is a bottom sectional plan view of a valve plate within a hydraulic unit;

FIG. 3 is a bottom sectional plan view of a valve plate within a hydraulic unit in a second position; and

FIG. 4 is a graphical representation of pressure as it relates to stress on a valve plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2 shows a sectional view of a valve assembly 10 of a hydraulic unit in a first position. Though the hydraulic unit is not shown, the hydraulic unit could be of any type such as an axial piston hydraulic unit utilizing a swashplate as is shown U.S. Pat. No. 6,640,687 to Frantz et al. and U.S. Pat. No. 6,688,417 to Hansell, both of which are incorporated herein. Similarly, the hydraulic unit could be a bent axis unit as is shown in U.S. Pat. No. 6,203,283 to Fleming et al. and U.S. Pat. No. 1,137,283 to Pratt, both of which are also incorporated herein. Furthermore, the hydraulic unit could be either a pump or a motor and not fall outside of the scope of the disclosure.
The valve assembly 10 comprises a first support structure 12 that has an opening 14 disposed therein. The first support structure 12 in a bent axis unit is a yoke whereas in another embodiment the first support structure 12 is an end cap in an axial piston unit.
Disposed within the opening 14 of the first support structure 12 is a valve plate 16. The valve plate 16 has a body 18 that extends between an inner diameter 20 and an outer diameter 22. The inner diameter 20 surrounds a valve plate opening 24. The body 18 additionally has an arcuate inlet 26 and an arcuate outlet 28 both disposed between the inner diameter 20 and the outer diameter 22. When fluid passes through the arcuate inlet and outlet 26, 28 stresses are placed upon the perimeters of each.
Disposed within the valve plate opening 24 is a second support structure 30. In one embodiment, in a bent axis unit, the second support structure is a spindle. In another embodiment in an axial piston unit the second support structure is a bearing.
When manufactured the valve plate 16 is made of size and shape such that when placed in a first position disposed within the opening 14 (FIG. 2) of the first support structure 12 a first and second clearance 32, 34 are created between the valve plate 16 and the first support structure 12 and the second support structure 30 respectively. Specifically, in a first position as shown in FIG. 2, when minimal pressure is placed upon the arcuate inlet and outlet 26, 28 the outer diameter 22 is detachably placed adjacent the first support structure 12 within the opening 14. Thus, in the first position the outer diameter 22 of the body 18 is in close proximity to the first support structure 12. The distance between the outer diameter 22 and the first support structure 12 is considered the first clearance 32. In a preferred embodiment the first clearance is equal to or less than 0.1 mm.
Similarly, when in the first position as seen in FIG. 2 the valve plate 16 is placed such that the inner diameter 20 is detachably disposed adjacent and in close proximity to the second support structure 30. Specifically, the distance between the inner diameter 20 and the second support structure 30 is considered the second clearance 34. In a preferred embodiment the second clearance 34 is equal to or less than 0.1 mm.
During operation of the hydraulic unit when fluid flows through the arcuate inlet and outlet 26, 28 stresses are applied to the valve body 18. Upon reaching a threshold stress level the inner diameter 20 and outer diameter 22 deflect away from the inlet and outlet 26, 28 toward the first support structure and second support structure 12, 30. The inner diameter 20 deflects until engaging the second support structure whereas the outer diameter 22 deflects until engaging the first support structure 12. Once the inner diameter 20 or the outer diameter 22 engages the first support structure 12 or second support structure 30 or both the valve assembly 10 is considered in a second position.
In the second position because either the inner or outer diameters 20, 22 are engaged by either the first or second support structures 12, 30 added stiffness is provided to the valve plate body 18. Thus, when in a second position stress is transferred from the body 18 to either the first or second support structures or both 12, 30 to prevent failure of the valve plate 16 at the arcuate inlet and outlet 26, 28.
FIG. 4 shows a graph of the pressure 35 a versus the stress 35 b upon the valve plate body 18 during operation. In the first position as shown by line 36 the inner and outer diameters are not engaging the first or second support structures. Consequently, as pressure rises, stress rises at a rapid rate. Then at point 38 that represents placement in the second position of the valve plate 16 wherein the inner or outer diameter 20, 22 engage the first or second support members the rate at which the stress rises is greatly reduced as shown by line 40.
By providing first and second support structures 12, 30 in close proximity to the inner and outer diameters 20, 22 of the valve plate body 18 in a second position the valve plate body 18 is able to engage the first and second support structures 12, 30 for additional support to prevent failure. This occurs without the need of placing webs within the arcuate inlet or outlet 26, 28 and consequently maximum fluid flow is allowed through the inlet and outlet 26, 28 maximizing the efficiency of the hydraulic unit. Additionally, the amount of support provided can be customized for each design by optimizing clearance 32, 34 and stiffness of the valve plate and support members to provide support above a desired pressure level. Consequently, at the very least all of the stated objectives have been met.
It will be appreciated by those skilled in the art that other various modifications could be made to the device without the parting from the spirit in scope of this invention. All such modifications and changes fall within the scope of the claims and are intended to be covered thereby.

Claims

1. A hydraulic unit comprising:

a first support structure having an opening therein;

a valve plate detachably disposed within the opening and having an outer diameter adjacent the first support structure in a first position and an inner diameter surrounding a valve plate opening;

said valve plate having a body extending between the inner diameter and outer diameter, said body having an arcuate inlet and an arcuate outlet;

a second support structure detachably disposed within the valve plate opening adjacent the inner diameter in the first position;

wherein when above a threshold stress level the inner diameter deflects to engage the second support structure and the outer diameter deflects to engage the first support structure to provide a second position; and

wherein stress is transferred from the body to the first and second support structures in the second position.

2. The hydraulic unit of claim 1 wherein the first support structure is a yoke.

3. The hydraulic unit of claim 2 wherein the second support structure is a spindle.

4. The hydraulic unit of claim 1 wherein in the first position the outer diameter of the valve plate is positioned at or less than 0.1 mm from the first support structure to form a first clearance.

5. The hydraulic unit of claim 4 wherein in the first position the inner diameter of the valve plate is positioned at or less than 0.1 mm from the first support structure to form a second clearance.

6. The hydraulic unit of claim 1 wherein the first support structure is an end cap.

7. The hydraulic unit of claim 6 wherein the second support structure is a bearing.