Knock Sensor Signal Compensation for Temperature and Voltage Variations
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Solution Overview
Problem
Existing knock sensor signal processing systems for internal combustion engines face accuracy issues due to variations in operating temperature and power supply voltage, affecting the accuracy of A/D conversion and subsequent knock judgement.
Innovation Solution
A knock sensor signal processing apparatus that includes A/D converter control means for periodic conversions, compensation value calculation means to derive a compensation coefficient using reference voltages, and compensation means to apply this coefficient to successive A/D values, ensuring accurate knock judgement by minimizing the impact of temperature and voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If A/D conversion is performed using a pulse phase difference encoder circuit to achieve high speed and high resolution, then conversion speed and resolution are improved, but A/D conversion accuracy deteriorates due to variations in operating temperature and power supply voltage
Solution Approach 1:
The patent performs A/D conversion of reference voltages before A/D conversion of knock sensor signals to obtain compensation values in advance. These compensation values are stored and applied when processing knock sensor signals, allowing the system to pre-compensate for temperature and voltage variations without affecting real-time knock detection accuracy
Solution Approach 2:
The patent introduces reference voltages as an intermediary element. By converting reference voltages to digital values and comparing them with expected values, the system generates compensation values that mediate between the unstable A/D converter output and the required accurate knock detection, effectively isolating the knock judgment from temperature and voltage variations
2Adaptability or versatility
If separate knock sensors are provided for each cylinder set with switching between input signals, then adaptability to multi-cylinder engines is improved, but device complexity increases
Solution Approach 1:
The patent makes the A/D converter and processing circuitry universal by designing them to handle multiple knock sensor inputs through a unified compensation mechanism. The same A/D conversion and compensation process is applied regardless of which cylinder's knock sensor is being measured, eliminating the need for separate processing paths and reducing overall system complexity
Solution Approach 2:
The patent performs A/D conversion of reference voltages in advance, before actual knock sensor signal processing. This preliminary compensation value generation is done once and can be applied to multiple cylinders, reducing the complexity of real-time switching and processing for each cylinder individually
Data Source
AI summary
A knock sensor signal processing apparatus for an engine, which performs a series of A/D conversions of a knock sensor signal during each of successive knock judgement intervals to obtain A/D converted values for use in judging if engine knocking is occurring in a cylinder, derives compensation coefficients during an interval between the end of a knock judgement interval corresponding to a cylinder and the start of deriving knock sensor signal A/D values in a succeeding knock judgement interval for a succeeding cylinder, and applies these coefficients to correct the A/D converted values derived in the second knock judgement interval.