Rotor Core Shrink-Fit Assembly With a Heated Holding Jig
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Solution Overview
Problem
The existing rotor manufacturing methods for rotating electrical machines face challenges in productivity due to difficulties in inserting a transmission member into a rotor core with minimal gap, leading to reduced torque transmission capacity and distortion of the rotor core during the shrink-fitting process.
Innovation Solution
A rotor manufacturing method involving a holding jig that attaches to the rotor core, heating it to a temperature higher than the insertable temperature for the transmission member, and then cooling it to fix the transmission member in place, thereby reducing distortion and improving insertion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the transmission member is inserted into the heated rotor core to minimize gap, then the torque transmission capacity is improved, but the rotor core cools down causing distortion
Solution Approach 1:
A holding jig is introduced as an intermediary device between the transmission member and the rotor core. The holding jig is heated to a high temperature (equal to or higher than the insertable temperature) and used to hold the transmission member during insertion. This mediator transfers the heat to the transmission member and maintains the thermal environment during insertion, preventing the rotor core from cooling down and distorting while still enabling minimal gap insertion.
Solution Approach 2:
The holding jig is pre-heated to the insertable temperature or higher before the transmission member insertion process begins. This preliminary heating action ensures that when the transmission member is inserted, the thermal conditions are already optimal, preventing heat loss from the rotor core and avoiding subsequent distortion. The preparation is done in advance to maintain the thermal state required for precise insertion.
2Ease of operation
If the rotor core is heated for shrink fitting, then the transmission member can be inserted, but the manufacturing time increases
Solution Approach 1:
The heating processes for magnet fixing and shrink fitting are merged into a single heating step. The rotor core is heated to a temperature (equal to or higher than the insertable temperature) that satisfies both requirements simultaneously. This eliminates the need for separate heating cycles, reducing total manufacturing time while still enabling easy transmission member insertion through thermal expansion.
Solution Approach 2:
The heating temperature parameter is optimized to be equal to or higher than the insertable temperature, which is higher than the conventional curing temperature. By changing the temperature parameter to this higher value, the rotor core achieves both sufficient thermal expansion for easy insertion and maintains the heat needed for the subsequent cooling and shrink fitting process, eliminating the need for additional heating time.
3Strength
If the rotor core is cooled to fix the transmission member, then the fastening force increases, but the productivity decreases due to distortion
Solution Approach 1:
The holding jig serves as a thermal mediator that prevents excessive heat loss from the rotor core during transmission member insertion. By maintaining the rotor core temperature at the insertable temperature or higher during the critical insertion phase, the subsequent cooling process proceeds uniformly without thermal shock or distortion, ensuring both strong fastening force and high productivity.
Solution Approach 2:
The transmission member is pre-heated by contact with the heated holding jig before insertion into the rotor core. This preliminary heating of the transmission member reduces the thermal gradient between the transmission member and rotor core during insertion, preventing localized cooling and distortion of the rotor core. The uniform thermal state enables smooth insertion and subsequent uniform cooling, maintaining both fastening force and productivity.
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 method enhances productivity by ensuring the transmission member can be easily inserted and fixed within the rotor core without causing distortion, thereby improving torque transmission capacity and reducing manufacturing time.
Implementation Method 1
the rotor core is heated so that the rotor core has an increased inner diameter
Implementation Method 2
the transmission member is inserted and then cooled to shrink, so that the rotor core and the transmission member are fastened together
Data Source
AI summary
A rotor manufacturing method includes: a jig attachment step of attaching a holding jig to a rotor core, the holding jig being a member that holds the rotor core by sandwiching the rotor core in a stacking direction of laminated steel sheets and pressing the rotor core; a rotor hub insertion step of inserting a rotor hub into an inner peripheral surface of the rotor core with the rotor core and the holding jig heated to a temperature equal to or higher than an insertable temperature at which the rotor hub can be inserted into the inner peripheral surface of the rotor core; and a cooling step of cooling the rotor core to fix the rotor core and the rotor hub together. The rotor hub insertion step is performed with the holding jig kept attached to the rotor core.