Variable Vane Pump Control via Segmented Hydraulic Chambers
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Solution Overview
Problem
Conventional variable displacement pumps face challenges in maintaining desired discharge pressure at high engine speeds due to the need for a large spring constant to counterbalance internal pressures, leading to increased discharge pressure and insufficient pressure characteristics.
Innovation Solution
A variable displacement pump design featuring a cam ring with a coil spring and control hydraulic chambers, where the cam ring's eccentricity is adjusted by hydraulic pressures, and a switching mechanism using a solenoid valve and spool valve to regulate hydraulic fluid flow, allowing for precise control of discharge pressure without relying on the spring constant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a spring with a relatively large spring constant is used to counterbalance internal pressures of the two control hydraulic chambers, then the cam ring can be held in position against high pressures, but the cam ring becomes difficult to move in accordance with the increase of discharge pressure
Solution Approach 1:
The control hydraulic chambers are segmented into multiple chambers (first, second, and third control hydraulic chambers) with different spring constants. This allows each chamber to contribute differently to the overall control force, enabling the system to maintain stability at high pressures while still allowing the cam ring to move in response to pressure changes. The segmented approach replaces a single high-stiffness spring with multiple lower-stiffness springs working in parallel.
Solution Approach 2:
The invention changes the parameter of spring constant by using multiple springs with different spring constants rather than one spring with a large spring constant. The first control hydraulic chamber has a first spring constant, the second control hydraulic chamber has a second spring constant smaller than the first, and the third control hydraulic chamber has a third spring constant smaller than the second. This parameter variation allows the cam ring to be more responsive to pressure changes while still maintaining positional stability.
2Stability of the object's composition
If the cam ring is difficult to move due to large spring constant, then stability is improved, but the discharge pressure increases largely in accordance with engine speed increase, failing to maintain desired pressure characteristics
Solution Approach 1:
The control system is segmented into multiple control hydraulic chambers that independently control different aspects of cam ring positioning. The first control hydraulic chamber provides primary stabilization with a larger spring constant, while the second and third chambers with smaller spring constants provide fine-tuned pressure control. This segmentation allows the system to maintain stability while preventing excessive discharge pressure increases.
Solution Approach 2:
The multiple control hydraulic chambers act as intermediaries between the engine pressure and the cam ring positioning. Instead of directly transmitting engine pressure to the cam ring, the system uses these intermediate chambers with different spring constants to modulate the control force, thereby preventing large pressure fluctuations while maintaining stable operation.
3Stress or pressure
If discharge pressure is introduced into control hydraulic chambers to control cam ring position, then pressure control is achieved, but the system requires complex two-stepped control with multiple chambers and pressure levels
Solution Approach 1:
The control system is divided into multiple control hydraulic chambers, each with distinct spring constants and pressure introduction mechanisms. The first control hydraulic chamber receives discharge pressure through a first introduction passage, the second chamber receives pressure through a second introduction passage with a pressure reducing valve, and the third chamber receives pressure through a third introduction passage. This segmentation enables sophisticated pressure control while maintaining clear functional separation.
Solution Approach 2:
Each control hydraulic chamber is designed with local quality - the first chamber has a larger spring constant for primary control, while the second and third chambers have smaller spring constants for fine control. The pressure introduction passages are also designed with different characteristics, including pressure reducing valves in specific passages. This local differentiation allows each part of the control system to perform its specific function optimally.
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 maintains desired discharge pressure across varying engine speeds, reducing power loss and preventing unnecessary increases in discharge pressure, thus ensuring optimal hydraulic pressure characteristics.
Implementation Method 1
a solenoid which is arranged to push the valve element toward the upstream side opening portion by being applied with an current
Implementation Method 2
a first control hydraulic chamber to which a hydraulic fluid discharged from the discharge portion is constantly introduced, and which is arranged to act an urging force to the cam ring in a direction in which the eccentric amount is decreased, by an internal pressure of the first control hydraulic chamber
Implementation Method 3
by a spring force of a spring arranged to urge the cam ring in a direction (hereinafter, referred to as an eccentric direction) in which the eccentric amount of the cam ring becomes large
Data Source
AI summary
A variable displacement pump includes: a control mechanism arranged to be actuated based on a hydraulic pressure introduced into the introduction passage before the eccentric amount is minimized, and arranged to introduce the hydraulic pressure through a throttling to the second control hydraulic chamber when the hydraulic pressure introduced from the introduction passage is equal to or smaller than a predetermined pressure, and to discharge the hydraulic fluid within the second control hydraulic chamber in accordance with the hydraulic pressure when the hydraulic pressure introduced from the introduction passage becomes greater than the predetermined pressure; and a switching mechanism arranged to switch between a state in which the hydraulic fluid introduced into the introduction passage is introduced to the control mechanism, and a state in which the hydraulic fluid introduced into the introduction passage is discharged from the control mechanism.