Offset Output Shaft Cooling Structure for Power Transmission
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Solution Overview
Problem
The existing cooling structures for power transmission devices in electric vehicles suffer from power loss due to friction and viscosity resistance, and they require additional space for oil supply pipes, which limits their efficiency and compactness.
Innovation Solution
The cooling structure features a tubular input shaft with an offset output shaft and an oil supply pipe positioned in a wide axial space, eliminating the need for a sealing member and reducing the inner diameter of the input shaft, allowing efficient oil flow without friction or viscosity resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sealing member is used to section the oil chamber between input shaft and output shaft, then cooling function is achieved, but friction power loss occurs due to sliding contact
Solution Approach 1:
The invention removes the sealing member from the system entirely. Instead of using a sealing member to section the oil chamber, the patent uses the offset configuration of the output shaft relative to the input shaft centerline to naturally create separate oil flow paths, thereby eliminating friction power loss while maintaining the cooling function.
Solution Approach 2:
The invention employs asymmetric positioning of the output shaft, which is offset from the centerline of the input shaft. This asymmetric configuration creates unequal spacing between the shafts at different angular positions, allowing the oil supply pipe to be positioned in the wider gap and enabling natural oil flow without sealing members.
2Productivity
If oil supply pipe is disposed axially in the space between input shaft and output shaft, then cooling efficiency is improved, but inner diameter of input shaft must increase reducing space savings
Solution Approach 1:
The asymmetric offset configuration of the output shaft creates a non-uniform gap between the input shaft and output shaft. The oil supply pipe is positioned axially in the wider portion of this asymmetric gap, allowing efficient oil supply without requiring an increased input shaft inner diameter, thus maintaining compact design.
Solution Approach 2:
The invention utilizes the radial offset dimension to create additional axial space for the oil supply pipe. By positioning the output shaft offset from the input shaft centerline in the radial direction, a wide axial space is created on the opposite side of the offset, allowing the oil supply pipe to be disposed without increasing the input shaft's inner diameter.
3Device complexity
If output shaft is disposed coaxially with input shaft, then structural simplicity is maintained, but no wide space is available for oil supply pipe
Solution Approach 1:
The invention deliberately introduces asymmetry by offsetting the output shaft from the input shaft centerline. This simple asymmetric configuration creates a wide axial space in the gap between the shafts where the oil supply pipe can be positioned, without significantly increasing overall structural complexity.
Solution Approach 2:
The invention transitions from a coaxial (one-dimensional alignment) configuration to an offset (two-dimensional positioning) configuration. This dimensional change creates additional radial and axial space that accommodates the oil supply pipe while maintaining relatively simple structural implementation.
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 configuration effectively cools the rotor of the electric motor by minimizing power loss and saving space, enhancing the operational stability and durability of the power transmission device.
Implementation Method 1
oil that is fed from an oil pump, which is not illustrated in the drawing, in a compressed manner is ejected from a tip end of the oil supply pipe 212 and supplied to a rotor 202a of an electric motor as illustrated by the arrow in FIG. 7, and a magnet portion 202a1 that is a heat generation portion of the rotor 202a is cooled by the oil
Data Source
AI summary
There is provided a cooling structure of a power transmission device 1 that the power transmission device includes a tubular input shaft 3 and an output shaft 4R that is inserted into and disposed inside the input shaft 3, and that the power transmission device delivers power output from an electric motor (drive source) 2 to the input shaft 3 to the output shaft 4R via a deceleration mechanism T and a differential device D, wherein the output shaft 4R is disposed such that the output shaft 4R is offset relative to a shaft center of the input shaft 3 in a radial direction, and an oil supply pipe 12 is disposed in an axial direction in a wide space that is formed on a side opposite to an offset side of the output shaft 4R in a space S between the output shaft 4R and the input shaft 3.