Electric Motor Vehicle Relay Off-State Detection
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Solution Overview
Problem
Existing electric motor vehicles lack a reliable method to confirm the off state of the system main relay during a collision, which is crucial for discharging accumulated electric charges from the smoothing capacitor.
Innovation Solution
An electric motor vehicle system that includes a voltage conversion circuit, smoothing capacitors, an inverter circuit, an electric motor, voltage sensors, a rotational speed sensor, and a controller to detect the off state of the system main relay by monitoring voltage changes and rotational speed, allowing for independent confirmation of the relay's off state without relying on a signal for turning it off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system main relay is turned off to cut off the connection between the battery and the smoothing capacitor during a collision, then the electric charges can be discharged through the auxiliary machine drive circuit, but there is no reliable method to confirm that the relay is actually turned off
Solution Approach 1:
The patent applies feedback by using the voltage sensor to continuously monitor the voltage across the smoothing capacitor and provide this information back to the controller. The controller uses this feedback to determine whether the relay is actually off, creating a closed-loop verification system that confirms the relay's off-state without requiring additional complex detection hardware.
Solution Approach 2:
The patent replaces potential mechanical or direct electrical contact detection methods with a non-contact voltage sensing approach. By using the voltage sensor to detect voltage changes across the capacitor, the system substitutes direct mechanical verification with an electrical field-based detection method, simplifying the overall detection mechanism while maintaining reliability.
2Loss of energy
If voltage of the smoothing capacitor is stepped up by a DC/DC converter and supplied to an auxiliary machine drive circuit, then the electric charges can be discharged, but this requires the system main relay to be turned off first
Solution Approach 1:
The patent applies preliminary action by having the controller turn off the system main relay before initiating the voltage stepping operation of the DC/DC converter. This sequential approach ensures that the relay is already off and the connection between the battery and smoothing capacitor is cut before the capacitor voltage is stepped up to power the auxiliary machine drive circuit, preventing any potential short circuits or improper operation.
Solution Approach 2:
The patent implements a dynamic operational sequence where the controller adjusts the system state in two distinct phases: first turning off the relay to isolate the battery, then subsequently stepping up the capacitor voltage to power the auxiliary machines. This dynamic, staged approach allows the system to safely discharge accumulated charges while maintaining operational control and preventing energy loss through improper connections.
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
Enables reliable detection of the system main relay's off state, ensuring safe discharge of electric charges during a collision, thereby enhancing the safety and operational efficiency of electric motor vehicles.
Implementation Method 1
a voltage conversion circuit (20A), which converts the primary-side voltage (VL) to a higher voltage and outputs the converted voltage from a secondary side
Implementation Method 2
a high-capacity smoothing capacitor is used for the step-up converter, the inverter, and the like. While the step-up converter and the inverter are in operation, electric charges that correspond to applied voltage are accumulated in this smoothing capacitor
Implementation Method 3
a collision sensor (64) that detects a collision of the electric motor vehicle (100)
Data Source
AI summary
The electric motor vehicle includes a voltage conversion circuit, a primary-side smoothing capacitor, a battery, a system main relay, an inverter circuit, a secondary-side smoothing capacitor, an electric motor, a first voltage sensor, a collision sensor, and a controller. The controller is configured to adjust an operation of the voltage conversion circuit, detect primary-side voltage by using the first voltage sensor in a state that the voltage conversion circuit is operated in a case where a collision is detected by the collision sensor, and detect a state that the system main relay is off based on a change in the detected primary-side voltage.