Variable Displacement Pump Dynamic Spring Control
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Solution Overview
Problem
Existing variable displacement pumps experience excessive rise in discharge pressure at higher pump revolution speeds due to large spring constants, leading to inefficient energy consumption and deviation from required discharge pressure characteristics.
Innovation Solution
A variable displacement pump design featuring a cam ring with a biasing member and control oil chambers, where a switching mechanism and control mechanism regulate the eccentricity of the cam ring to maintain desired discharge pressure across varying speeds, utilizing a spool valve and electromagnetic switching valve to manage hydraulic pressure and prevent excessive pressure increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a large spring constant is used to bias the cam ring, then the discharge pressure can be maintained at desired levels, but the discharge pressure rises excessively at high pump revolution speeds
Solution Approach 1:
The patent applies dynamics by making the spring constant variable rather than fixed. The spring constant changes based on the pump revolution speed, being larger at lower speeds to maintain discharge pressure and smaller at high speeds to prevent excessive pressure rise. This is achieved through a switching mechanism that selects different springs or adjusts spring properties according to operating conditions.
Solution Approach 2:
The patent changes the parameter of spring constant dynamically. By selecting different spring constants based on pump revolution speed, the system optimizes discharge pressure control across different operating ranges. The switching mechanism enables parameter change from a large spring constant at low speeds to a small spring constant at high speeds.
2Stress or pressure
If a large spring constant is used to bias the cam ring, then the discharge pressure can be maintained, but the discharge pressure characteristic deviates from required characteristics
Solution Approach 1:
The system dynamically adjusts the spring constant to match different operating conditions. At low revolution speeds, a large spring constant maintains discharge pressure, while at high speeds, a small spring constant prevents deviation from required pressure characteristics. This dynamic adaptation ensures accurate pressure control across the entire speed range.
Solution Approach 2:
The spring constant parameter is changed based on pump revolution speed to maintain accurate discharge pressure characteristics. The switching mechanism enables selection of appropriate spring constants for different speed regions, ensuring the discharge pressure characteristic matches requirements without excessive deviation.
3Productivity
If the pump revolution speed is raised, then the discharge quantity increases, but the discharge pressure rises excessively causing energy wastage
Solution Approach 1:
The spring constant is made dynamic and speed-dependent. At high revolution speeds where discharge quantity is high, the system automatically selects a smaller spring constant to prevent excessive discharge pressure rise. This dynamic adjustment eliminates energy wastage by ensuring discharge pressure remains appropriate for the given discharge quantity and speed condition.
Solution Approach 2:
The spring constant parameter is changed at high speeds to prevent energy wastage. By switching to a smaller spring constant when revolution speed increases, the system allows discharge pressure to increase only as much as necessary for the given discharge quantity, preventing the excessive pressure rise that would cause energy wastage.
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
The design effectively suppresses excessive discharge pressure rises at higher speeds, maintaining desired discharge pressures and reducing energy wastage, while ensuring the pump operates efficiently and accurately matches required hydraulic pressure characteristics.
Implementation Method 1
a biasing member configured to bias the cam ring toward the one direction toward which the eccentricity of the cam ring with respect to the rotary center of the rotor becomes large
Implementation Method 2
a first control oil chamber configured to move the cam ring toward the other direction against a biasing force of the biasing member when a discharge pressure is introduced into the first control oil chamber
Data Source
AI summary
A variable displacement pump includes: a first control oil chamber which moves a cam ring toward a direction against a biasing force of a biasing member when a discharge pressure is introduced thereinto; a second control oil chamber which acts a hydraulic pressure upon the cam ring by cooperating with the biasing force of the biasing member when hydraulic oil is introduced thereinto; a switching mechanism which switches between one state in which hydraulic oil whose pressure is decreased than a discharge pressure is introduced to the second control oil chamber from the discharge section and another state in which hydraulic oil is discharged from the second control oil chamber; and a control mechanism operated before an eccentricity of the cam ring becomes a minimum and which discharges a greater amount of hydraulic oil within the second control oil chamber as the discharge pressure becomes larger.