Electric Power Steering Auxiliary Power Supply Discharge Circuit
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Solution Overview
Problem
Conventional electric power steering systems disable steering assist when the engine is turned off, requiring drivers to restart the engine to adjust the position of the front wheels, which is inconvenient.
Innovation Solution
An electric power steering apparatus with a motor drive circuit, battery, auxiliary power supply, charge-discharge circuit, and control circuit that enables steering assist by utilizing the auxiliary power supply's remaining energy after the ignition is turned off, allowing the system to provide assistance for a predetermined period and reducing battery power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor relay contact is controlled to open when the ignition key is turned off, then the engine can be deactivated, but steering assist becomes unavailable requiring the driver to restart the engine to adjust wheel position
Solution Approach 1:
The control circuit performs a power latch operation that maintains motor control capability for a predetermined period after ignition off. This preliminary action allows the driver to adjust steering wheel position without restarting the engine, resolving the contradiction by preparing the system in advance to handle post-shutdown steering needs
2Ease of operation
If the control circuit continues operation after ignition off, then steering assist is available, but battery power consumption increases
Solution Approach 1:
The control circuit operates in a time-limited periodic manner, providing power latch control only for a predetermined period after ignition off. This periodic action maintains steering assist availability when needed while automatically terminating to reduce battery power consumption, resolving the energy vs. functionality contradiction
3Use of energy by moving object
If the auxiliary power supply is continuously charged, then energy is available for steering assist, but the auxiliary power supply service life decreases
Solution Approach 1:
The charge-discharge circuit intentionally allows the auxiliary power supply to discharge during the power latch period, converting what would normally be considered waste (discharge cycles) into a beneficial function. This enables steering assist after ignition off while the discharge-preference circuit configuration helps manage the charge-discharge cycles to extend service life
4Ease of operation
If the motor relay contact remains closed after ignition off, then steering assist is available, but the engine cannot be properly deactivated
Solution Approach 1:
The power supply control is segmented into two independent circuits: the motor relay contact circuit for engine deactivation and the charge-discharge circuit for steering assist. This segmentation allows the motor relay to open for proper engine shutdown while the charge-discharge circuit independently maintains auxiliary power supply for steering assist, resolving the contradiction between deactivation reliability and steering availability
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 steering assist after the engine is disabled, effectively utilizing the auxiliary power supply's energy to reduce battery power consumption and extend the service life of the auxiliary power supply by maintaining it in a completely discharged state.
Implementation Method 1
an auxiliary power supply capable of supplying electric power to the motor; a charge-discharge circuit that configures a circuit for charging the auxiliary power supply and a circuit for discharging the auxiliary power supply
Data Source
Figure 1
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AI summary
An electric power steering apparatus 1 comprises a charge-discharge circuit 25 capable of configuring a circuit for charging an auxiliary power supply 7 and a circuit for discharging a battery 6 and the auxiliary power supply 7 as well as configuring a discharge-preference circuit which enables only the discharge of the auxiliary power supply 7 while avoiding the charge thereof. In the apparatus, a control circuit 20 performs a power latch operation of carrying on control till the end of a predetermined period of time following an operation of turning off an ignition key 23, and also causes the charge-discharge circuit 25 to configure the discharge-preference circuit thereby enabling steering assist accompanied by the discharge of the auxiliary power supply 7.