Hybrid Vehicle Assist Power Control for Battery Temperature Limits
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Solution Overview
Problem
Hybrid electric vehicles experience sudden drops in driving force due to reduced electric power supply from the power storage device, leading to a feeling of strangeness and reduced drivability.
Innovation Solution
A vehicle control device that adjusts the upper-limit assist electric power supplied to the electric motor based on the power storage device's temperature, restricting it when the temperature reaches a certain threshold to maintain drivability and prevent battery degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If electric power from the power storage device is reduced to suppress degradation, then battery lifespan is improved, but driving force suddenly drops and drivability deteriorates
Solution Approach 1:
The upper-limit assist electric power is dynamically adjusted based on battery temperature conditions. When battery temperature is below the first threshold, full assist power is allowed. When temperature reaches the first threshold, the upper limit is restricted to maintain driving force within allowable range. When temperature reaches the second threshold, assist power is completely stopped. This dynamic adjustment resolves the contradiction between protecting battery lifespan and maintaining drivability.
Solution Approach 2:
The patent changes the parameter of upper-limit assist electric power based on battery temperature parameters. By monitoring battery temperature and adjusting the electric power parameter accordingly, the system prevents battery degradation while maintaining optimal drivability within safe operating conditions.
2Reliability
If maximum allowable power is changed according to battery temperature, then battery degradation is suppressed, but driving force may suddenly drop
Solution Approach 1:
The patent implements beforehand cushioning by preparing multiple upper-limit assist electric power values corresponding to different battery temperature conditions. When battery temperature approaches critical thresholds, the system has pre-determined restricted power levels ready to be applied, cushioning the transition and preventing sudden drops in driving force that would occur with abrupt power cuts.
3Reliability
If assist electric power is completely stopped when battery temperature reaches threshold, then battery degradation is prevented, but drivability significantly deteriorates
Solution Approach 1:
Instead of completely stopping assist electric power when battery temperature reaches the first threshold, the patent applies partial action by restricting the upper-limit assist electric power to a reduced but non-zero value. This partial restriction maintains sufficient driving force for normal operation while preventing battery degradation, avoiding the excessive action of complete power cutoff until the second threshold is reached.
Data Source
AI summary
A vehicle control device is configured to: execute motor assist when a vehicle is traveling by a drive wheel being driven by an internal combustion engine, in which electric power of a power storage device is supplied to an electric motor and the electric motor assists driving of the drive wheel; change upper-limit assist electric power, which is an upper-limit value of electric power supplied from the power storage device to the electric motor in order to perform the motor assist, in accordance with a temperature of the power storage device; and when the temperature of the power storage device reaches a first temperature, restrict the upper-limit assist electric power such that a reduction amount of a maximum driving force of the vehicle falls within an allowable range.