Choke Valve Delay Mechanism for Hydraulic Pump Flow and NVH Trade-off
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Solution Overview
Problem
Piston pumps in hydraulic brake systems face limitations in maximum volume flow due to the dynamic choke point closing rapidly, leading to pressure build-up performance losses, while maintaining NVH performance at low engine speeds.
Innovation Solution
Integration of targeted inertia in the closing body via direction-dependent friction or an elastomer spring delays the closing of the dynamic choke point, allowing the static choke point to be disabled after a few pump strokes, enabling a bypass and adjusting the dynamic choke point's opening cross section based on pressure differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the dynamic choke point closes rapidly after each pump stroke, then the NVH performance is improved, but the maximum volume flow rate decreases
Solution Approach 1:
A delay device is introduced as an intermediary between the pressure differential and the closing body. This delay device includes a friction element with a lip that creates direction-dependent friction, selectively delaying the closing movement of the closing body while allowing rapid opening. The friction element acts as a mediator that transforms the direct pressure-response mechanism into a controlled, delayed response, enabling the system to achieve both rapid opening for high flow rate and delayed closing for NVH performance
Solution Approach 2:
The friction element changes the effective response parameters of the closing body by introducing direction-dependent friction. When the closing body moves in the closing direction, the friction lip creates higher resistance, delaying closure. When moving in the opening direction, friction is minimized, allowing rapid response. This parameter change enables the system to achieve both rapid opening and delayed closing behaviors
2Object-affected harmful factors
If the static choke point remains active continuously, then the NVH performance is maintained, but the pressure build-up performance is reduced
Solution Approach 1:
The system transitions from a static choke configuration to a dynamic one where the static choke point can be selectively disabled. The closing body, when held in the closed position by the delay device, dynamically bypasses the static choke point. This dynamic behavior allows the system to switch between using the static choke for NVH control and bypassing it for high-pressure build-up scenarios
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 solution increases the maximum flow rate at high engine speeds while maintaining NVH performance at low engine speeds by delaying the dynamic choke point's closure, effectively bridging the static choke point with a bypass at high speeds and enabling pressure-independent choking at low speeds.
Implementation Method 1
The delay device (20) comprises a friction element (22) with a lip (22.1) which is arranged between the closing body (16) and an inner wall (14.2) of the pot-like base body (14) and creates a direction-dependent friction
Implementation Method 2
Integration of targeted inertia in the closing body via direction-dependent friction or an elastomer spring delays the closing of the dynamic choke point
Implementation Method 3
a closing body (16) guided axially moveably in the pot-like base body (14) against the spring force of a spring element (18)
Data Source
AI summary
A device for choking a fluid flow includes a pot-like base body, in the base of which a first passage opening is arranged, and a closing body guided axially moveably in the pot-like base body against a spring force of a spring element and having a second passage opening that forms a static choke point with a predefined fixed opening cross section. The closing body in combination with the spring element and the first passage opening forms a dynamic choke point with a dynamic opening cross section that is variably adjustable depending on a pressure difference.