Brake Hydraulic Unit Shaft Sealing Under Thermal Tolerance
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Solution Overview
Problem
Existing hydraulic units in electronically controllable brake systems face challenges in maintaining reliable sealing of the motor shaft bore to prevent pressure medium leaks, especially under varying environmental conditions and dimensional tolerances between different materials, which can affect the accuracy of brake pressure control and stability.
Innovation Solution
The use of an insert seal subjected to a preloading force by a mechanical pretensioning device, which is integrated with the device housing, ensures reliable sealing by accommodating thermal and dimensional tolerances and maintaining the sealing properties under changing conditions, allowing for easy installation and compensation of offsets between the electronic control unit and the pump housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional sealing device is used to seal the shaft bore, then sealing is provided, but the sealing reliability deteriorates under varying environmental conditions and dimensional tolerances
Solution Approach 1:
The insert seal is designed to change its physical parameters (elastic deformation) in response to thermal expansion and dimensional variations. The seal material's elasticity allows it to adapt its shape and sealing force dynamically, maintaining reliable sealing across varying environmental conditions and tolerance ranges.
Solution Approach 2:
The sealing solution transitions from a static sealing arrangement to a dynamic one where the insert seal can elastically deform and adjust its sealing characteristics. This dynamic adaptation enables the seal to maintain contact pressure and sealing effectiveness despite thermal expansion, contraction, and manufacturing tolerances.
2Reliability
If an insert seal with mechanical preloading is used, then sealing reliability improves, but device complexity increases
Solution Approach 1:
The sealing function is segmented into distinct components: the insert seal element and the preloading device. This segmentation allows each component to be optimized independently and facilitates easier assembly, inspection, and replacement, offsetting the increased complexity through modularity and standardization.
Solution Approach 2:
The insert seal acts as an intermediary element between the shaft bore and the preloading device. This intermediary component absorbs dimensional tolerances and thermal variations, simplifying the overall design by isolating the complexity of adaptation requirements to a single replaceable element rather than the entire sealing system.
3Ease of manufacture
If conventional sealing methods are used, then assembly is straightforward, but sealing quality cannot be easily checked during assembly
Solution Approach 1:
The insert seal incorporates visual indicators (such as color-coded features or marked surfaces) that change or become visible during assembly, providing immediate visual confirmation of correct installation and adequate preloading. This allows quality inspection to be performed easily during the assembly process without specialized equipment.
Solution Approach 2:
The insert seal design includes self-indicating features that automatically show whether the seal is properly installed and preloaded. The seal itself provides the inspection information through its physical state (position, deformation, visual markers), eliminating the need for complex external measurement systems and enabling operators to verify sealing quality through simple visual or mechanical checks.
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 provides enhanced sealing reliability, reduces the risk of malfunctions, and allows for easier assembly and maintenance by ensuring the insert seal maintains effective sealing properties, even under thermal and dimensional variations, thus ensuring stable brake pressure control and system reliability.
Implementation Method 1
A mechanically prestressed insert seal accommodates thermally induced expansion tolerances and dimensional tolerances between the housing of the electronic control unit, which is usually made of plastic, and the pump housing, which is usually made of an aluminum alloy.
Implementation Method 2
An insert seal can easily compensate for any misalignment of the electronic control unit relative to the pump housing during assembly. A mechanically prestressed insert seal accommodates thermally induced expansion tolerances and dimensional tolerances
Data Source
Figure 1
AI summary
The invention relates to a hydraulic unit (10), more particularly for the open-loop and closed-loop control of brake pressure in a brake circuit of an electronically slip-controllable braking system of a motor vehicle and to a method for assembling a hydraulic unit (10). Known hydraulic units (10) have a pump housing (12), a motor (17) for driving a brake pressure generator (19), and an electronic control device (20) for controlling the motor (17) in line with demand. The motor (17) and the control device (20) are disposed on opposite sides of the pump housing (12), and a shaft bore (14) extending all the way through is formed therebetween, in which shaft bore a motor shaft (18) which can be rotationally driven is disposed. A sealing apparatus seals the shaft bore (14) with respect to an interior of the electronic control device (20). A sealing apparatus which comprises an insertion seal (50) disposed on the pump housing (12) in a seal socket (52) and to which a mechanical preloading force is applied by a preloading apparatus (48) is proposed.