Compressor Pressure Measurement via Motor Current
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Solution Overview
Problem
Existing portable air compressors for vehicle tire breakdown assistance devices face challenges in simplicity of operation and cost-effectiveness due to the need for electronic pressure sensors, which are expensive and prone to high temperature issues, limiting the widespread adoption of electronically supported systems.
Innovation Solution
The method determines the change in average motor current of the electric motor driving the compressor, which is proportional to the pressure at the compressor outlet, eliminating the need for separate pressure sensors and using a shunt resistor integrated into the motor control unit to provide a pressure-proportional input variable for the control device, allowing for pressure measurement and control without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electronic pressure sensors are used to enable electronically supported operation and pressure measurement, then measurement precision and control capability are improved, but device complexity and production costs increase significantly
Solution Approach 1:
The patent introduces an intermediary approach by using the motor's current consumption as a mediator to indirectly measure compressor outlet pressure. Instead of directly measuring pressure with a sensor, the system measures the electrical current drawn by the motor, which varies with the compression load, and uses this current signal as a proxy for pressure measurement and control.
Solution Approach 2:
The patent replaces the mechanical/electronic pressure sensing system with an electrical measurement system. By substituting the physical pressure sensor with an electrical current measurement of the motor, the system eliminates the need for separate pressure sensing hardware while maintaining control capability through electrical signal processing.
2Measurement precision
If electronic pressure sensors are installed at the compressor outlet to measure high pressure, then measurement precision is improved, but reliability deteriorates due to high temperature exposure
Solution Approach 1:
The patent uses the motor current as an intermediary measurement that indirectly reflects compressor outlet pressure without being exposed to the harsh high-temperature environment. The current measurement occurs in the electrical circuit away from the hot compressor outlet, providing a reliable proxy signal that avoids thermal degradation.
Solution Approach 2:
The patent replaces the physical pressure sensor exposed to high temperatures with an electrical current measurement system. The motor current measurement occurs in the electrical domain away from the thermal environment, eliminating the reliability issues associated with high-temperature sensor exposure while maintaining pressure measurement capability.
3Measurement precision
If separate pressure sensors are added to enable electronic pressure measurement, then measurement precision is improved, but manufacturing costs increase
Solution Approach 1:
The patent makes the motor serve multiple functions: it not only drives the compressor but also acts as a pressure sensing element through its current consumption characteristics. This multi-functionality eliminates the need for separate pressure sensor components, reducing part counts and manufacturing costs while maintaining electronic pressure measurement capability.
Solution Approach 2:
The patent enables the motor to self-report pressure information through its electrical characteristics. The motor's current consumption naturally varies with compression load, providing self-contained pressure measurement capability without requiring external sensing components, thereby reducing manufacturing complexity and cost.
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 approach reduces production costs, enhances reliability, and simplifies integration, enabling cost-effective, electronically supported operation of small compressors in breakdown assistance devices without the need for additional sensors, while accurately limiting maximum pressure.
Implementation Method 1
the change in the average motor current of an electric motor (2) driving the compressor (3), which is proportional to the pressure at the compressor outlet (3a), is determined
Data Source
Figure 1~2
AI summary
Method for measuring the pressure generated by a compressor driven by an electric motor, preferably a reciprocating compressor driven by an electric motor via a slider crank mechanism; in said method, the the mean motor current of the electric motor driving the compressor is determined, and said mean motor current, which is dependent on the pressure variation at the compressor outlet, is supplied to a control device or displayed as a pressure-proportionate input variable for operating the compressor.