Variable Displacement Pump Cam Ring Seal Width Optimization
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Solution Overview
Problem
In variable displacement pumps, the sealing performance at high pressure areas is inadequate due to side clearance, leading to oil leaks and increased control pressure, which can be mitigated by thickening the cam ring, but this increases pump weight.
Innovation Solution
The design incorporates a variable displacement pump with a cam ring having a larger radial width for the second and third seal surfaces, enhancing sealing performance without increasing the overall pump weight by maintaining a thinner first seal surface, and includes a low pressure chamber to manage leaks and contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radial width of the cam ring is thickened to widen the seal width of the side clearance, then the sealing performance is improved, but the weight of the whole pump is increased
Solution Approach 1:
The invention applies different radial widths to different seal surfaces of the cam ring. Specifically, the first seal surface has a first radial width while the second seal surface has a second radial width that is greater than the first radial width. This local differentiation allows the seal surface subjected to high pressure (second seal surface) to have enhanced sealing capability without unnecessarily increasing the radial width of all seal surfaces, thereby improving sealing performance while controlling pump weight.
2Stress or pressure
If the radial width of the cam ring is thickened to suppress oil leaks through side clearance, then the control pressure stability is improved, but the pump weight increases
Solution Approach 1:
The invention differentiates the radial widths of seal surfaces based on their specific functional requirements. The second seal surface, which is subjected to high pressure from the pump discharge, is given a greater radial width to prevent oil leaks that would otherwise cause control pressure instability. This localized thickening at critical seal surfaces suppresses oil leaks and stabilizes control pressure without requiring a uniform increase in the entire cam ring thickness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively suppresses oil leaks and maintains stable control pressure across varying engine conditions, preventing unintended cam ring movement and ensuring durable pump operation.
Implementation Method 1
a coil spring forces the cam ring so as to increase the eccentric amount in the eccentric direction by a spring force of the coil spring
Implementation Method 2
by a pump discharge pressure being supplied to the first control hydraulic chamber, the cam ring is forced in a direction (hereinafter, called a concentric direction) in which an eccentric amount of the cam ring becomes small, while by the pump discharge pressure being supplied to the second control hydraulic chamber, the cam ring is forced in a direction (hereinafter, called an eccentric direction) in which the eccentric amount of the cam ring becomes large
Implementation Method 3
the plurality of pump chambers and the first and second control hydraulic chambers are sealed by so-called side clearance between opposing inside surfaces of the pump housing and both axial direction end surfaces, which are in sliding-contact with the respective opposing inside surfaces of the pump housing, of the cam ring
Data Source
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AI summary
Variable displacement pump has first control hydraulic chamber 21 giving force to cam ring 5 in direction that decreases volume variation of each pump chamber 13 by internal pressure, second control hydraulic chamber 22 giving force to cam ring in direction that increases volume variation of each pump chamber by internal pressure, first seal surface 44 formed on both end surfaces of cam ring, which are in sliding-contact with both opposing inside surfaces of pump body 1 and cover member 2, and sealing gap between each pump chamber and first control hydraulic chamber, and second seal surface 45 sealing gap between each pump chamber and second control hydraulic chamber at outlet section side. Radial direction width W2 of second seal surface is greater than that W1 of first seal surface. Increase in weight of the pump can be suppressed while suppressing increase in pump control pressure against intention of control.