EV Gearbox Temperature Control to Prevent Gear Jamming
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Solution Overview
Problem
The existing electric or hybrid vehicle propulsion systems face issues with gear wheel jamming due to temperature differences, leading to efficiency losses and noise, which are exacerbated by the need for increased tolerances to account for expansion, resulting in clearance between meshing teeth.
Innovation Solution
The system monitors temperature differences within the gearbox and adapts its control to maintain a predefined temperature threshold by heating the liquid and gearbox housing using resistors or selectively powering phases of the electrical stator winding to reduce temperature disparities, thereby minimizing jamming and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tolerances are increased in the dimensioning of reducer parts to avoid jamming, then reliability is improved, but manufacturing precision deteriorates and play between teeth increases
Solution Approach 1:
The invention changes the physical state of the housing material by heating it to reduce thermal contraction at low temperatures. This parameter change (temperature) allows the housing to maintain its dimensional stability and avoid jamming without requiring increased manufacturing tolerances, thus resolving the contradiction between reliability and manufacturing precision
Solution Approach 2:
The invention performs preliminary heating of the housing before the vehicle operation begins. This preliminary action ensures that the housing is already at the correct temperature to prevent jamming during operation, eliminating the need for excessive tolerances and maintaining manufacturing precision while ensuring reliability
2Reliability
If tolerances are increased to account for thermal expansion, then reliability is improved, but energy efficiency deteriorates due to play between teeth
Solution Approach 1:
By changing the temperature parameter of the housing through active heating, the invention maintains the housing at a temperature where thermal expansion is minimized. This allows tight tolerances to be maintained without risk of jamming, thereby eliminating tooth play and preventing energy efficiency losses while ensuring reliability
3Reliability
If tolerances are increased to prevent jamming at low temperatures, then reliability is improved, but noise increases when teeth come into contact
Solution Approach 1:
The invention changes the temperature parameter of the housing to reduce thermal contraction. By maintaining the housing at a higher temperature, the clearances between gear teeth are kept optimal, preventing both jamming and excessive tooth contact that would generate noise, thus improving reliability while reducing harmful noise
4Temperature
If heating resistors are used to increase liquid temperature, then temperature difference is reduced, but energy consumption increases
Solution Approach 1:
The invention uses the electric machine's own stator winding to generate heat through Joule effect during normal operation. This self-service approach utilizes the existing operational energy to simultaneously drive the motor and heat the housing, reducing temperature differences without requiring additional energy input specifically for heating
5Temperature
If selective phase powering is used to heat the liquid, then temperature difference is reduced, but torque production is affected
Solution Approach 1:
The invention uses periodic or intermittent powering of specific stator phases to generate heat in the housing. By controlling the duration and timing of these heating cycles, the system reduces temperature differences during periods when full torque is not required, while maintaining full power capability when needed, thus balancing temperature management with power production
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
This approach maintains efficient operation and reduces wear by maintaining optimal temperature differences between gear wheels and housing, preventing jamming and noise, while allowing for maximum torque transmission across varying temperature conditions.
Implementation Method 1
the control device is then configured to control the activation of these heating resistors so as to heat the liquid to reduce the temperature difference
Implementation Method 2
the control device can be configured to control the power supply of only certain phases of this stator electrical winding so as to heat the liquid to reduce the temperature difference
Implementation Method 3
the heat being exchanged between the latter by convection
Implementation Method 4
the heating in the electric machine can be transmitted to the casing of this electric machine then to the reducer housing by convection and conduction
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Control device (11) of a propulsion system (1) of an electric or hybrid vehicle, this propulsion system (1) comprising: - a rotating electrical machine (2) including a stator winding, - control electronics (3) for the rotating electrical machine (2), and - a gearbox (5) transmitting the torque output of the rotating electrical machine (2) to one or more external wheels (7) in contact with the ground, the gearbox (5) comprising a housing (10) inside which wheels (12) are arranged cooperating with each other by meshing to transmit the torque, this housing (10) receiving liquid which comes into contact with the wheels (12) of the gearbox (5), the control device being configured to: - compare: - the difference between two temperatures chosen from: the temperature of the housing (10) of the gearbox (5), the temperature of the wheels (12) of the gearbox (5), and the temperature of the liquid, and - a threshold value,and - adapt the propulsion system control (1) so that this temperature difference remains below the threshold value.