Integrated Inverter Case Design for Compact Drive Devices
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Solution Overview
Problem
Existing drive devices with rotary electric machines and inverters are bulky and costly due to the use of dedicated inverter cases and expensive Hall element current sensors, which increase the number of components and overall size.
Innovation Solution
A drive device with an alternating-current rotary electric machine and an inverter connected directly to a case, using shunt resistors for current detection, reducing the number of components and size by eliminating dedicated inverter cases and incorporating shunt resistors to detect currents flowing in switching element units, thereby lowering costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated inverter cases are used to accommodate the inverter, then the inverter is protected and easily assembled, but the number of components increases and the overall size increases
Solution Approach 1:
The inverter case is merged with the rotary electric machine case to form an integrated housing structure. The inverter is mounted directly on the rotary electric machine case, eliminating the need for a separate dedicated inverter case. This merging reduces the number of components while maintaining the protective function through the integrated case structure.
2Measurement precision
If Hall element current sensors are used to detect current, then current detection accuracy is high and drive control is accurate, but the product cost increases
Solution Approach 1:
The patent replaces expensive Hall element current sensors with inexpensive shunt resistors for current detection. The shunt resistors are connected in series with the switching element units, and current is detected by measuring the voltage drop across them. This substitution significantly reduces product cost while maintaining sufficient current detection accuracy for drive control.
3Ease of manufacture
If shunt resistors are disposed outside the driving force source room, then installation is easier, but wiring length increases and wiring resistance increases
Solution Approach 1:
The shunt resistors are pre-installed inside the driving force source room on the rotary electric machine case, close to the switching element units. This preliminary placement minimizes the wiring length between the shunt resistors and switching elements, reducing wiring resistance and improving current detection accuracy while maintaining installation ease through integrated mounting structures.
4Ease of repair
If the inverter is fixed to a separate case, then the inverter is easily accessible for maintenance, but the overall device size increases
Solution Approach 1:
The integrated case structure is designed with modular sections that allow the inverter to be accessed separately for maintenance. The rotary electric machine case serves dual purposes as both structural housing and inverter mounting platform, with accessible panels or openings that enable inverter maintenance without requiring separation of the inverter from the case structure.
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 solution results in a more compact and cost-effective drive device with improved current detection accuracy and reduced wiring resistance, allowing for accurate control of the rotary electric machine while minimizing the influence on control accuracy and product cost.
Implementation Method 1
the inverter includes shunt resistors that detect currents flowing in the respective switching element units for the corresponding phases between the direct-current power supply and the switching element units for the respective phases
Data Source
AI summary
Both downsizing of an apparatus as a whole and reduction in a product cost are attained. The preferred embodiments relate to a drive device including an alternating-current rotary electric machine, an inverter, and a case. The inverter is fixed to the case. The case and the inverter are disposed in a driving force source room. The inverter includes shunt resistors to detect currents flowing in respective switching element units for corresponding phases.