Knock Sensor Stopper Ring Press-Fit Design
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Solution Overview
Problem
Conventional knock sensors experience unstable preload and irregularities in output characteristics and detecting precision due to inconsistent clamping force caused by axial misalignment and irregularities in equipment during the mounting process.
Innovation Solution
A knock sensor design featuring a stopper ring with a recess portion longer than the groove on the tube portion, where the stopper ring is radially deformed and pressed into the groove using a pressing jig, ensuring a stable preload on the piezoelectric element by absorbing misalignment irregularities and increasing the reliability of the clamping force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a nut is used to clamp the sensor main body, then the clamping force can be adjusted, but the preload becomes unstable due to irregularities in mounting torque and friction coefficients
Solution Approach 1:
The patent replaces the nut-based mechanical fastening system with a press-fit system using a pressing jig. The sensor main body is pressed directly into the base with a predetermined pressing force, eliminating the need for threads, nuts, and associated friction coefficients. This substitution of the mechanical fastening mechanism resolves the instability caused by variable mounting torque and friction irregularities.
2Reliability
If a punch is driven to form a protruding portion for fixing the stopper ring, then the stopper ring can be secured, but axial misalignment of the punch causes irregularities in clamping force
Solution Approach 1:
The patent incorporates a recess portion in advance on the outer peripheral surface of the stopper ring, positioned axially beyond the groove depth. This preliminary structural feature allows the pressing jig to automatically compensate for axial misalignment during the pressing operation. The recess acts as a buffer zone that absorbs positioning errors, ensuring that the pressing force is consistently applied regardless of minor axial variations in the punching process.
3Strength
If the stopper ring is crimped to fix the sensor main body, then the assembly is secured, but insufficient press-fit due to misalignment makes preload unstable
Solution Approach 1:
The patent designs the recess portion to extend axially beyond the groove depth, creating a built-in cushioning zone before the crimping operation. This recess absorbs axial misalignment and positioning errors that would otherwise prevent sufficient press-fit of the protruding portion into the groove. By providing this preliminary cushioning structure, the system ensures consistent clamping force even when alignment is not perfect.
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 design stabilizes output characteristics and detecting precision by providing a consistent clamping force to the piezoelectric element, improving the reliability of the knock sensor and reducing manufacturing costs through enhanced alignment and deformation characteristics.
Implementation Method 1
a piezoelectric element that is fitted over an outer peripheral portion of the tube portion
Implementation Method 2
fixed by driving a pressing jig radially inward toward an outer peripheral surface of the stopper ring to plastically deform the stopper ring and press a protruding portion into the groove
Data Source
AI summary
A knock sensor includes: a base made up of a flange portion, and a tube portion; a sensor main body including a piezoelectric element that is fitted over an outer peripheral portion of the tube portion; and a stopper ring that is fitted over the outer peripheral portion of the tube portion and cooperates with the flange portion to clamp the sensor main body, a groove being formed on the outer peripheral surface of the tube portion, and the knock sensor being fixed by driving a pressing jig into an outer peripheral surface of the stopper ring to plastically deform the stopper ring and press a protruding portion into the groove, wherein: an axial length of a recess portion that is formed simultaneously on the outer peripheral surface of the stopper ring when the protruding portion is formed is longer than an axial length of the groove.