Electric Motor Play-Reducing Control for Gear Backlash Noise
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Solution Overview
Problem
Electrically-driven vehicles experience play (looseness) in the motor transfer system during creeping-cut and normal acceleration, leading to shock and abnormal noise due to backlash in the gear system when switching between different running ranges.
Innovation Solution
A play-reducing control apparatus that detects the creeping-cut permitting condition and outputs a torque smaller than the creep torque in the direction of the selected running range for a limited period to reduce play in the motor transfer system, preventing shock and noise during restart or acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If creeping-cut is performed to reduce power consumption, then energy efficiency is improved, but play in the motor transfer system increases causing shock and abnormal noise
Solution Approach 1:
The control apparatus performs preliminary action by detecting when a running range is selected during creeping-cut execution and proactively outputting torque in the drive direction before creep running is restarted or normal acceleration begins. This advance torque application eliminates play in the motor transfer system beforehand, preventing shock and abnormal noise when torque transmission resumes.
Solution Approach 2:
The control apparatus applies preliminary anti-action by outputting torque in the drive direction opposite to what would cause play accumulation. During creeping-cut, when a running range is selected, the system outputs torque that counteracts the tendency for play to increase in the motor transfer system, thereby preventing the harmful effect of shock and noise before it occurs.
2Use of energy by moving object
If creep torque is reduced to zero during creeping-cut, then power consumption is suppressed, but play elimination is delayed causing abnormal noise during restart
Solution Approach 1:
The control apparatus performs preliminary action by detecting when a running range is selected during creeping-cut execution and proactively outputting torque in the drive direction before creep running is restarted or normal acceleration begins. This advance torque application eliminates play in the motor transfer system beforehand, preventing shock and abnormal noise when torque transmission resumes.
3Speed
If torque is transmitted immediately when changing running ranges, then response speed is improved, but play in the motor transfer system causes shock and noise
Solution Approach 1:
The control apparatus performs preliminary action by detecting when a running range is selected during creeping-cut execution and proactively outputting torque in the drive direction before creep running is restarted or normal acceleration begins. This advance torque application eliminates play in the motor transfer system beforehand, preventing shock and abnormal noise when torque transmission resumes.
Data Source
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AI summary
When a non-running range is changed into a running range at timing t2 during the execution of creeping-cut (t1 ∼ t4), a flag FLAG is set at 1 and a timer T is reset. Then, the timer T is incremented to measure a time elapsed from timing t2. If the running range is a forward range, an electric motor outputs a play-reducing torque in a forwardly rotational direction as shown by a solid line for a time period between timing t2 and timing t3 for which the timer T is smaller than a set time T1, because the flag FLAG indicates 1. If the running range is a reverse range, the electric motor outputs the play-reducing torque in a reversely rotational direction as shown by a dotted line, because the flag FLAG indicates 1. At timing t3 at which the timer T becomes equal to the set time T1, the flag FLAG is set at 0, and the timer T is set at the set time T1, in preparation for a next play-reducing control. Hence, after timing t3, the play-reducing torque is not outputted. However, the play-reduction for the motor transfer system has already completed by the play-reducing torque outputted for the set time T1 started from timing t2. Hence, after timing t4, abnormal noise is not caused at the time of restart of creep running or normal acceleration for vehicle start.