Rotating Electric Machine Cooling Unit for Coil Ends
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Solution Overview
Problem
Conventional rotary electric machines face inefficiencies in cooling coil ends due to limited reach and layout constraints of annular oil pipes, leading to partial cooling and increased size, which complicates processing and reduces cooling efficiency.
Innovation Solution
A rotary electric machine with a cooling unit featuring an outer periphery cooling portion, end surface cooling portion, and inner periphery cooling portion, each with injection holes to cover the entire coil end surface, allowing for effective cooling from multiple directions and shared cooling medium supply paths to simplify the structure and reduce size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If annular oil pipes are simply disposed on outer and inner peripheral sides of the coil end, then the cooling device structure is simple, but the cooling oil cannot be supplied to the axial end surface of the coil end, resulting in partial cooling
Solution Approach 1:
The cooling device is segmented into three distinct cooling portions: outer periphery cooling portion, end surface cooling portion, and inner periphery cooling portion. Each portion is responsible for cooling a specific region of the coil end, ensuring comprehensive coverage. The outer periphery cooling portion cools the outer peripheral surface, the end surface cooling portion cools the axial end surface, and the inner periphery cooling portion cools the inner peripheral surface, thereby resolving the partial cooling issue while maintaining structural clarity through functional segmentation.
Solution Approach 2:
The cooling approach transitions from a two-dimensional annular pipe configuration to a three-dimensional multi-directional cooling system. By adding the end surface cooling portion that extends axially and the inner periphery cooling portion that reaches the inner peripheral surface, the cooling coverage expands from a simple annular path to a comprehensive three-dimensional structure that addresses all surfaces of the coil end including the previously unreachable axial end surface.
2Ease of manufacture
If the outer peripheral annular oil pipe and inner peripheral annular oil pipe are used, then the cooling device can be constructed, but the oil pipe structure has a small surface area, making it difficult to provide a large number of discharge holes, hence cooling efficiency deteriorates
Solution Approach 1:
The cooling device is divided into three separate cooling portions, each with its own discharge holes optimized for its specific cooling target. The outer periphery cooling portion has discharge holes arranged for optimal outer surface cooling, the end surface cooling portion has discharge holes positioned for axial end surface coverage, and the inner periphery cooling portion has discharge holes configured for inner peripheral surface cooling. This segmentation allows each portion to have sufficient surface area and appropriately positioned discharge holes, thereby improving overall cooling efficiency.
Solution Approach 2:
Each cooling portion is designed with local quality optimization, where the discharge holes are strategically positioned and sized according to the specific cooling requirements of each region. The outer periphery cooling portion features discharge holes optimized for radial cooling, the end surface cooling portion has discharge holes arranged for axial cooling patterns, and the inner periphery cooling portion has discharge holes configured for inner surface cooling. This localized optimization ensures high cooling efficiency in each region rather than using a uniform design.
3Ease of manufacture
If the annular oil pipe is connected to the case side wall by columnar oil pipes, then the cooling liquid can be supplied to the oil pipes, but the processing applied to the case side wall becomes complicated and the cooling device increases in size
Solution Approach 1:
The three cooling portions are merged into a single integrated cooling device structure that is disposed within the insulating space between the case and the coil end. By combining the outer periphery cooling portion, end surface cooling portion, and inner periphery cooling portion into one unified structure, the need for multiple separate connections to the case side wall is eliminated. The integrated structure can be supplied with cooling liquid through a single or reduced number of connection points, thereby simplifying the case side wall processing while maintaining full cooling functionality.
Solution Approach 2:
The integrated cooling device structure serves multiple cooling functions simultaneously through its three cooling portions, making it a universal cooling solution. The single structure performs the functions of outer periphery cooling, end surface cooling, and inner periphery cooling, replacing what would otherwise require three separate cooling systems with three separate case side wall connections. This multi-functionality reduces the overall complexity of case side wall processing while achieving comprehensive cooling coverage.
4Ease of manufacture
If conventional cooling devices are used, then the cooling structure can be implemented, but the cooling device increases in size, leading to an increase in the size of the rotary electric machine
Solution Approach 1:
The cooling device is nested within the existing insulating space between the case and the coil end, utilizing the available space efficiently without requiring additional external volume. The outer periphery cooling portion, end surface cooling portion, and inner periphery cooling portion are arranged in a nested configuration that fits within the confined insulating space, thereby achieving comprehensive cooling coverage without increasing the overall size of the rotary electric machine.
Solution Approach 2:
The cooling device transitions from an external or side-wall connected configuration to an integrated three-dimensional structure disposed within the insulating space. By utilizing the axial and radial dimensions within the available space, the cooling portions are arranged to maximize cooling coverage while minimizing the device's external footprint. The end surface cooling portion extends axially, the outer periphery cooling portion extends radially outward, and the inner periphery cooling portion extends radially inward, creating an efficient three-dimensional cooling architecture that fits within the existing machine envelope.
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
The enhanced cooling unit effectively cools the coil end from all surfaces, improving cooling efficiency while minimizing the machine's size and manufacturing complexity, and reduces the number of components, thus lowering costs.
Implementation Method 1
a cooling unit (1) for cooling a coil end (CE) of the coil (C), which projects in an axial direction of the stator (S). The outer periphery cooling portion (20) includes a plurality of injection holes (ih) for injecting the cooling liquid onto the outer peripheral surface (3a). The end surface cooling portion (30) includes a plurality of injection holes (ih) for injecting the cooling liquid onto the axial end surface (3b).
Implementation Method 2
These losses are emitted in the form of thermal energy, in other words, Joule heat, leading to heat generation in the coil and the permanent magnet of the rotary electric machine.
Data Source
Figure 1
Figure 2
Figure 3~4B
AI summary
A rotary electric machine capable of cooling a coil end effectively without increasing the size of the rotary electric machine is provided. In a rotary electric machine M having a stator S including a coil C and a cooling unit I for cooling a coil end CE of the coil C, which projects in an axial direction of the stator S, the cooling unit I includes: an outer periphery cooling portion 20 that is disposed along an outer peripheral surface 3a of the coil end CE and includes a plurality of injection holes ih for injecting a cooling medium onto the outer peripheral surface 3a; and an end surface cooling portion 30 that is disposed along an axial end surface 3b of the coil end CE and includes a plurality of injection holes ih for injecting the cooling medium onto the axial end surface 3b.