Vehicle Relay Switching Control for Durability
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Solution Overview
Problem
Existing electric power supply control systems for vehicles, which rely on relays with both positive-side and negative-side switches, fail to reduce the number of switching operations, thereby limiting the durability life of the relay.
Innovation Solution
An electric power supply control apparatus that includes a main relay with a relay control unit, which switches to a one-side off-state, reducing the number of operations for both the positive-side and negative-side switches, thereby prolonging the durability life of the relay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If both the positive-side switch and the negative-side switch are turned off at different timings when the relay is switched to off-state, then arc discharges are generated evenly at both switches, but the number of switching operations of each switch is not decreased and relay durability is not improved
Solution Approach 1:
The invention extracts the negative-side switch from the switching operation by maintaining it in the on-state when transitioning to single-battery mode. Only the positive-side switch is turned off, which removes the harmful arc discharge from the negative-side switch while keeping the relay functional. This selective extraction of the switching operation from one side resolves the contradiction by eliminating wear on the negative-side switch without affecting the relay's ability to control power flow.
Solution Approach 2:
Instead of turning off both switches symmetrically when transitioning to off-state, the invention inverts the approach by keeping the negative-side switch on and only turning off the positive-side switch. This asymmetric inversion changes the switching pattern from balanced (both switches operating) to unbalanced (only positive-side switch operating), thereby reducing the total number of switching operations and extending relay durability.
2Reliability
If both the positive-side switch and the negative-side switch are turned off when the relay is switched to off-state, then the relay is fully disconnected, but the number of operations of each switch increases and relay durability life is reduced
Solution Approach 1:
The invention extracts the switching operation from the negative-side switch by maintaining it in the on-state during mode transitions. This removes the negative-side switch from the counting of switching operations, thereby reducing the total number of operations that contribute to relay wear while maintaining adequate disconnection functionality through the positive-side switch alone.
Solution Approach 2:
The invention applies partial action by turning off only the positive-side switch instead of both switches when transitioning to single-battery mode. This partial switching action is sufficient to achieve the desired power isolation while avoiding the excessive wear that would result from operating both switches. The negative-side switch remains on, providing a stable reference potential without contributing to switching cycle wear.
Data Source
AI summary
In an electric power supply control apparatus for a motor in a hybrid vehicle or an electric vehicle, when a main relay is switched over from an on-state to an off-state, only one of its positive-side switch and negative-side switch is turned off to provide a one-side off-state. Thus the numbers of operations of its switches are reduced in comparison to a system, in which both switches are turned off. When a charging relay is switched over from an on-state to an off-state, only one of a positive-side switch and a negative-side switch is turned off to provide a one-side off-state. Thus the numbers of operations of its switches are also reduced.