Variable Displacement Pump Contact Point Alignment
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Solution Overview
Problem
In variable displacement pumps, the displacement of the contact point between the piston portion and the roll or similar components leads to a tilting force that causes excessive wear of the piston accommodation portion and housing due to misalignment of the swash plate's inclination angle.
Innovation Solution
A variable displacement pump design where the contact point between the piston portion and the pressed portion is positioned at the axis center or near it when the swash plate is at an intermediate inclination angle, reducing the tilting force and wear by maintaining the contact point's alignment with the axis center, and incorporating a recessed portion for lubrication to minimize friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the contact point between the piston portion and the roll is allowed to displace in response to swash plate inclination angle changes, then the pump can achieve variable displacement control, but the piston portion becomes tilted relative to the piston accommodation portion axis, causing excessive wear
Solution Approach 1:
The patent introduces a pressed portion as an intermediary element between the piston portion and the swash plate. This pressed portion is pressed toward the swash plate by the piston portion and maintains a contact point that stays at the center portion of the piston portion's end surface even when the swash plate inclination angle changes. This intermediary structure allows the piston portion to remain axially aligned with the piston accommodation portion while still achieving variable displacement control through swash plate inclination changes, thereby preventing tilting forces and excessive wear.
2Adaptability or versatility
If the piston portion slides inside the piston accommodation portion while a tilting force is applied, then the pump can accommodate swash plate inclination changes, but the piston portion is easily caught by the piston accommodation portion
Solution Approach 1:
The pressed portion serves as a mediator that decouples the tilting motion of the swash plate from the piston portion. By maintaining the contact point at the center portion of the piston portion's end surface, the pressed portion ensures that the piston portion slides smoothly inside the piston accommodation portion without tilting forces, preventing the piston portion from being caught by the accommodation portion walls.
3Reliability
If the contact point is positioned at the center portion of the piston portion end surface, then tilting force is minimized, but the structure becomes more complex with the addition of the pressed portion
Solution Approach 1:
The pressed portion is a relatively simple intermediary component that can be integrated into the existing pump structure. It is pressed toward the swash plate by the piston portion and maintains the contact point at the center portion of the piston portion's end surface. This simple intermediary structure effectively minimizes tilting forces and wear without significantly increasing overall device complexity.
Data Source
AI summary
Provided is a variable displacement pump which sucks and discharges a working fluid by moving a piston with a stroke in response to an inclination angle of a swash plate, the variable displacement pump including: a control piston which includes a columnar piston portion pressing the swash plate and adjusts the inclination angle of the swash plate between a maximal inclination angle in which a discharge capacity of the working fluid becomes maximal and a minimal inclination angle in which the discharge capacity of the working fluid becomes minimal; a piston accommodation portion which is formed in the housing and accommodates the piston portion; and a pressed portion which is disposed between the swash plate and the piston portion and is pressed toward the swash plate by the piston portion, in which when the inclination angle of the swash plate is an intermediate inclination angle in which the discharge capacity of the working fluid becomes an intermediate amount between the maximal amount and the minimal amount, a contact point between the piston portion and the pressed portion is located at a center portion including an axis center of the piston portion in an end surface on the side of the swash plate in the piston portion.