Pneumatic Brake Servo Force Boost Adjustment
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Solution Overview
Problem
Existing brake servos in the automobile industry fail to meet high demands for precise tolerances in the force boost ratio due to component tolerances, spring tolerances, and shore hardness of the reaction element, leading to inadequate precision in the brake servo characteristic curve.
Innovation Solution
The solution involves adjusting the output effective area of the brake servo by varying the chamber volume of the reaction element, using a threaded bore and adjusting element that can be screwed into the output member, allowing for precise adjustment of the force boost ratio without requiring component exchange, and incorporating features like rotational locking and cost-effective production methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional brake servo components are used with standard tolerances, then manufacturing cost and assembly simplicity are maintained, but the force boost ratio tolerances and brake servo characteristic curve precision are insufficient
Solution Approach 1:
The adjusting element is pre-integrated into the output member assembly, allowing the output effective area to be adjusted during assembly without requiring disassembly or complex calibration procedures. The threaded bore and adjusting element are designed to work together in a pre-planned manner that simplifies the adjustment process.
Solution Approach 2:
The output effective area is made adjustable by varying the chamber volume of the reaction element through the adjusting element. This allows continuous adjustment of the force boost ratio by changing the physical parameters of the reaction element's chamber volume, enabling precise control of the brake servo characteristic curve.
2Manufacturing precision
If component tolerances and spring tolerances are reduced to achieve precise force boost ratio, then manufacturing precision improves, but manufacturing cost increases
Solution Approach 1:
Instead of relying on tight component tolerances, the invention uses an adjusting element that allows post-assembly adjustment of the output effective area. This shifts the approach from precision manufacturing to precision adjustment, using standardized components with normal tolerances but adding a low-cost adjustment mechanism.
Solution Approach 2:
The system transitions from a static, fixed output effective area determined solely by component dimensions to a dynamic system where the output effective area can be adjusted and optimized after assembly. This allows compensation for normal manufacturing variations without requiring expensive tight tolerances.
3Manufacturing precision
If the reaction element shore hardness is controlled tightly to achieve consistent performance, then force boost ratio precision improves, but manufacturing complexity and cost increase
Solution Approach 1:
The invention compensates for variations in reaction element shore hardness by providing adjustability in the output effective area. The adjusting element allows the system to be tuned to achieve the correct force boost ratio regardless of the actual hardness of the reaction element, eliminating the need for tight hardness control.
4Manufacturing precision
If friction variations are minimized to achieve precise force boost ratio, then brake servo characteristic curve precision improves, but manufacturing cost and process complexity increase
Solution Approach 1:
The adjusting element compensates for friction variations by allowing adjustment of the output effective area. This enables the system to achieve the correct force boost ratio despite variations in friction, eliminating the need for expensive friction control measures.
Data Source
AI summary
A pneumatic brake servo which can be acted on by a pneumatic differential pressure is described. The brake servo includes an actuable input member comprising a valve piston, an output member for acting on a master brake cylinder, and a control valve which is arranged in a control housing and which can be actuated by the valve piston for controlling the differential pressure. An elastic reaction element is arranged in a control housing recess and against which the output member bears. The input member acts with an input effective area A1 on the reaction element, and the output member acts with an output effective area A2 on the reaction element. The ratio of output effective area A2 to input effective area A1 determines the force boost ratio of the brake servo.Means are provided for adjusting the output effective area A2 in the assembled brake servo.