Motor Busbar Welding for High-Temperature Reliability
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Solution Overview
Problem
Brushless motors used in high-temperature environments, such as vehicle gear shift devices, face reliability issues due to solder melting at elevated temperatures, causing poor connections between conductor wires and busbars.
Innovation Solution
The use of TIG welding or resistance welding to connect conductor wires to busbar connection portions, reducing the contact area and preventing poor connections, with busbar holder designs that facilitate efficient welding by exposing connection portions on both axial sides, allowing for stable operation under high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If solder is used to connect conductor wires to busbars, then the connection process is simple, but the connection becomes poor under high temperature environments causing motor failure
Solution Approach 1:
The patent changes the connection method from soldering to welding, fundamentally altering the physical and chemical parameters of the connection process. Welding creates a metallurgical bond that maintains structural integrity at high temperatures, whereas soldering relies on eutectic alloys that melt at relatively low temperatures. This parameter change resolves the contradiction by achieving both manufacturing feasibility and high-temperature reliability.
Solution Approach 2:
The patent replaces the chemical bonding mechanism of soldering with the metallurgical bonding mechanism of welding. This substitution eliminates the temperature limitation inherent in solder joints, as welding creates a fusion bond similar to the base metals themselves, thereby maintaining connection reliability under high-temperature operating conditions.
2Strength
If large contact area is used between conductor wire and busbar, then connection strength is improved, but welding efficiency is reduced
Solution Approach 1:
The patent applies local quality by concentrating the welding current and heat input at specific localized points on the conductor wire and busbar interface, rather than distributing energy across a large area. This localized energy concentration creates strong metallurgical bonds at critical contact points while maintaining overall connection strength, thereby achieving both high strength and welding efficiency.
Solution Approach 2:
The patent segments the contact interface into discrete welding zones, creating multiple localized bond points along the conductor wire-busbar interface. This segmentation allows the welding process to achieve comprehensive connection strength through distributed focal points while maintaining high welding speed, as each segment can be welded independently and rapidly.
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
Ensures stable motor operation in high-temperature environments by maintaining effective connections between conductor wires and busbars, reducing the risk of connection failure and simplifying the welding process.
Implementation Method 1
end portions of conductor wires defining coils are connected with coil connection busbars by welding
Data Source
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AI summary
A motor(1), which is used to select a gear of a transmission installed in a vehicle, or to drive a clutch, includes a rotor(15) arranged to rotate about a rotation axis(J1); a stator core(12) including a plurality of teeth(12b); a plurality of coils(13), each defined by a conductor wire(130) wound around a separate one of the teeth(12b); and a busbar unit(20) arranged to supply a drive current to each coil(13). The busbar unit(20) includes a plurality of coil connection busbars(31,32,33), each including a conductor wire connection portion(313,323,333) connected with an end portion of the conductor wire; and a busbar holder(21) made of an insulating material and arranged to support the plurality of coil connection busbars(31,32,33). Each conductor wire connection portion(313,323,333) and the corresponding end portion of the conductor wire(130) is welded to each other. The busbar holder (21) includes a plurality of sensor holders (244), each holding a separate one of a plurality of sensors arranged to detect a rotational position of the rotor (15). The busbar unit (20) further includes a plurality of sensor connection busbars (41, 42, 43, 44, 45, 46, 51, 52, 53) arranged to supply a drive current to the sensors held in the respective sensor holders (244), or to output an output signal from the sensors. The busbar holder (21) is arranged to support the plurality of sensor connection busbars (41, 42, 43, 44, 45, 46, 51, 52, 53). At least one of the plurality of sensor connection busbars (41, 42, 43, 44, 45, 46, 51, 52, 53) includes a plurality of sensor connection portions (446, 447, 448) each directly connected with a terminal of a separate one of the sensors. Each sensor connection portion (446, 447, 448) and the terminal of the corresponding sensor are welded to each other.