Variable Stroke Piston Pump for Hydraulic Braking Systems
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Solution Overview
Problem
Existing piston pumps in hydraulic braking systems have a fixed stroke, making them inefficient in handling varying brake fluid viscosity, particularly at low temperatures where high viscosity requires more power, and at high temperatures where viscosity decreases, leading to increased energy consumption and production costs.
Innovation Solution
A piston pump assembly with a variable stroke, featuring a cam with multiple portions of different non-circular cross sections and eccentricities, allowing the cam to be selectively positioned to adjust the piston stroke based on temperature, enabling the piston pump to adapt to changing fluid viscosity by varying the stroke and volume of hydraulic fluid displaced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high power motor is used to drive the piston pump during cold-start phase when brake fluid viscosity is high, then the piston pump can overcome the high viscosity, but energy consumption and production costs increase
Solution Approach 1:
The cam's position relative to the piston axis is made variable rather than fixed. The cam can be selectively positioned in different locations along the drive shaft axis, each position corresponding to a different eccentricity value and thus a different piston stroke. This dynamic adjustability allows the system to optimize motor power requirements based on operating conditions.
Solution Approach 2:
The invention changes the geometric parameter of the cam (its axial position) to vary the piston stroke. By selecting different cam positions, the eccentricity parameter changes, which directly affects the piston stroke length and the volume of fluid displaced per revolution. This parameter change allows adaptation to different brake fluid viscosity conditions without changing the motor itself.
2Device complexity
If a fixed stroke piston pump is used, then the structure is simple, but the pump cannot adapt to changing brake fluid viscosity at different temperatures
Solution Approach 1:
The cam's axial position is made adjustable, transforming the fixed-stroke design into a variable-stroke design. The cam can be positioned at different locations along the drive shaft, and each position creates a different piston stroke when the drive shaft rotates. This simple dynamic mechanism provides adaptability to varying operating conditions without complex control systems.
Solution Approach 2:
The cam is designed with multiple discrete positioning locations along the drive shaft axis, each corresponding to a specific eccentricity value. This segmentation allows the system to offer multiple fixed stroke options rather than a continuous range, simplifying the adjustment mechanism while still providing adaptability to different temperature and viscosity conditions.
3Productivity
If the piston stroke is increased to handle high viscosity brake fluid, then pumping effectiveness improves, but energy consumption increases
Solution Approach 1:
The piston stroke is made dynamically adjustable through the variable cam position. During cold-start conditions with high viscosity brake fluid, the cam can be positioned to provide a larger piston stroke for maximum pumping effectiveness. Once the brake fluid warms up and viscosity decreases, the cam position can be changed to reduce the piston stroke, thereby reducing energy consumption while maintaining adequate pumping performance.
Solution Approach 2:
The piston stroke parameter is changed by varying the cam's axial position. This allows the system to optimize the stroke length according to the actual operating conditions - using longer strokes when needed for high viscosity fluid, and shorter strokes when the fluid has warmed up, thus balancing pumping effectiveness with energy efficiency.
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 variable stroke piston pump assembly provides stability and adaptability to changing brake fluid viscosity, reducing energy consumption and production costs by allowing the use of lower power motors and optimizing piston movement based on temperature, while being cost-effective and simple to manufacture.
Implementation Method 1
a cam disposed on the drive shaft; wherein the cam is configured to transform a rotating movement of the drive shaft into a linear movement of the piston
Implementation Method 2
a piston biased toward the cam and configured to reciprocate along a piston axis
Data Source
AI summary
The present disclosure relates to a piston pump assembly comprising a piston with a variable stroke and to a hydraulic braking system comprising the same. The piston pump assembly comprises at least: a rotatable drive shaft defining an axis of rotation of the rotatable drive shaft; a cam disposed on the drive shaft; and the piston biased toward the cam and configured to reciprocate along a piston axis for displacing a hydraulic fluid. The cam is movable relative to the piston axis and is selectively placed in one of a first position at a first distance from the piston axis and a second position at a second distance from the piston axis; and wherein the cam comprises at least two portions each of which has, at a given position of the cam relative to the piston axis, a different non-circular cross section in a plane perpendicular to the axis of rotation and/or a different eccentricity with respect to the axis of rotation, the at least two portions of the cam comprising at least a first cam portion having a first non-circular cross section and/or a first eccentricity, and a second cam portion having a second non-circular cross section and/or a second eccentricity.