Variable Displacement Pump Cam Ring Pressure Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing variable displacement pumps with two springs of different spring constants exhibit variability in hydraulic pressure characteristics, making it challenging to stepwisely increase hydraulic pressure consistently.
Innovation Solution
A variable displacement pump design featuring a cam ring with a first and second pressure control chamber, a hydraulic pressure supply valve, and a relief circuit that connects the second pressure control chamber to a low-pressure side, allowing the cam ring to be swung by a predetermined amount to control hydraulic pressure without relying on springs with different spring constants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two springs with different spring constants are used to control cam ring position, then hydraulic pressure can be increased, but hydraulic pressure characteristics become variable and inconsistent
Solution Approach 1:
The control chamber is divided into a first control chamber and a second control chamber with different pressure receiving surfaces. This segmentation allows each chamber to contribute differently to cam ring positioning, enabling stepwise pressure increase while maintaining consistent hydraulic pressure characteristics without relying on variable spring constants.
Solution Approach 2:
The invention changes the geometric parameter of the control chambers by providing different pressure receiving surface areas on the cam ring for the first and second control chambers. This parameter change enables differential pressure control that achieves stepwise pressure increase while maintaining reliability and consistency of hydraulic pressure characteristics.
2Ease of operation
If two springs with different spring constants are used, then cam ring swing control is achieved, but device complexity increases
Solution Approach 1:
The invention extracts and eliminates the need for one of the two springs by using a single spring combined with a divided control chamber system. The first and second control chambers with different pressure receiving surfaces replace the function of two different springs, simplifying the device while maintaining cam ring swing control capability.
Solution Approach 2:
The divided control chamber system acts as an intermediary mechanism that translates single spring force into differential pressure control. The different pressure receiving surfaces mediate between the single spring and the cam ring, achieving swing control without requiring two different springs.
3Device complexity
If a single spring is used with divided control chambers, then device complexity is reduced, but stepwise pressure increase control becomes difficult
Solution Approach 1:
The invention applies local quality by creating non-uniform pressure distribution through different pressure receiving surface areas in the first and second control chambers. This local difference in chamber characteristics enables stepwise pressure increase control while using only a single spring, maintaining both simplicity and functionality.
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 design stabilizes hydraulic pressure characteristics, enabling stepwise increases in hydraulic pressure while minimizing variations, thus maintaining consistent pump capacity across varying engine speeds.
Implementation Method 1
a first pressure control chamber which is defined between an inner circumference surface of the housing and an outer circumference surface of the cam ring, and which is arranged to urge the cam ring in a first swing direction; a second pressure control chamber which is defined between the inner circumference surface of the housing and the outer circumference surface of the cam ring to confront the first pressure control chamber, and which is arranged to urge the cam ring in a second swing direction
Implementation Method 2
a spring arranged to urge the cam ring in the second swing direction
Implementation Method 3
a hydraulic pressure supply valve arranged to be opened by a predetermined hydraulic pressure, and thereby to introduce a control hydraulic pressure to the first control chamber
Implementation Method 4
a relief circuit which is arranged to connect the second pressure control chamber and a low pressure side, to be opened or closed in accordance with a swing position of the cam ring, and to be closed when the cam ring is swung by a predetermined amount in the first direction
Data Source
AI summary
A variable displacement pump includes: a first pressure control chamber; a second pressure control chamber; a spring arranged to urge the cam ring in a second swing direction; a hydraulic pressure supply valve arranged to be opened by a predetermined hydraulic pressure, and thereby to introduce a control hydraulic pressure to the first control chamber; a connection passage formed in the housing or the cam ring, and arranged to connect the first pressure control chamber and the second pressure control chamber; and a relief circuit arranged to connect the second pressure control chamber and a low pressure side, to be opened or closed in accordance with a swing position of the cam ring, and to be closed when the cam ring is swung by a predetermined amount in the first direction.