Gear Oil Temperature Estimation Without In-Circuit Sensors
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Solution Overview
Problem
Existing methods for determining the temperature of oil used to lubricate and cool vehicle transmissions require direct temperature sensors, which increase costs, installation space, and limit design flexibility.
Innovation Solution
A physical model is used to determine oil temperature based on input variables such as rotor temperature, rotational speed, torque, coolant temperature, and ambient temperature, eliminating the need for a temperature sensor and allowing for more flexible transmission design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is installed in the oil circuit to directly measure oil temperature, then measurement precision is improved, but device complexity and installation space requirements increase
Solution Approach 1:
The patent uses an intermediary approach by measuring temperatures at other locations (coolant temperature, stator temperature, ambient temperature) and using these as intermediate variables to calculate the oil temperature indirectly through a physical model, avoiding direct sensor installation in the oil circuit
Solution Approach 2:
The patent replaces the mechanical/physical temperature sensor system with a computational approach using a physical model that calculates oil temperature based on thermodynamic relationships between various temperature parameters, substituting direct measurement with indirect calculation
2Measurement precision
If a temperature sensor is installed in the oil circuit, then oil temperature can be determined, but costs and installation space requirements increase
Solution Approach 1:
The patent employs intermediary measurements of coolant temperature, stator temperature, and ambient temperature as proxy variables to infer oil temperature, eliminating the need for expensive and space-consuming direct oil temperature sensors
Solution Approach 2:
The patent creates a virtual model (physical model) that replicates the thermal behavior of the transmission system, allowing oil temperature to be determined through calculation rather than direct physical measurement, reducing hardware requirements
3Measurement precision
If a temperature sensor is installed in the oil circuit, then direct temperature measurement is achieved, but design flexibility of the transmission is reduced
Solution Approach 1:
By using intermediary temperature measurements from coolant and ambient environments combined with a physical model, the patent maintains temperature determination capability while avoiding constraints on transmission design that would result from integrating direct oil temperature sensors
Solution Approach 2:
The physical model serves as a universal solution that can be applied across different transmission designs and configurations, providing temperature determination capability without being tied to specific sensor installation requirements, thereby enhancing design flexibility
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 reduces costs and installation space while providing precise temperature determination, enabling component protection mechanisms and improved transmission operation.
Implementation Method 1
a physical model is configured to determine the temperature of the oil depending on input variables that characterize a temperature of a rotor driving the transmission of a vehicle drive embodied as an electric machine, a rotational speed of the rotor, a torque of the rotor, a temperature of a stator of the drive, a temperature of a coolant used to cool the vehicle and/or the stator of the drive
Data Source
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AI summary
The invention relates to a device and a method for determining a temperature of an oil by means of which a gear unit (108) of a vehicle (100) is lubricated and cooled. A physical model (120) is configured to determine the temperature of the oil depending on input variables which characterise a temperature of a rotor of a drive (102) of the vehicle, in particular an electric motor, a speed of the rotor (104), a torque of the rotor (104), a temperature of a stator (106) of the drive (102), a temperature of a coolant by means of which the vehicle (100) and/or the stator (106) of the drive (102) is cooled, a volumetric flow of the coolant and an ambient temperature of the vehicle (100), the input variables being detected and the temperature of the oil being determined using the physical model (120) depending on the input variables.