Eccentric Guide Surface Torque Measurement Unit
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Solution Overview
Problem
The existing torque measuring units for electric power steering devices face challenges in reducing size and weight while maintaining good assembly workability, particularly due to interference issues during the assembly of the torque detecting coil unit and the housing body, which complicates the fitting and fixing process.
Innovation Solution
The proposed solution involves a torque measuring unit with a housing that includes a housing body and a lid body, an input shaft and output shaft connected by a torsion bar, and a torque detecting coil unit with an eccentric guide surface portion that allows for eccentric insertion and fixation, enabling reduced size and weight while ensuring assembly workability through a specific assembly method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the torque detecting coil unit is inserted into the housing body from the front end opening, then the assembly process is simplified, but the connection terminal interferes with the housing body due to insufficient insertion distance
Solution Approach 1:
The patent introduces an eccentric guide surface portion that is offset from the central axis of the housing body. This asymmetric feature allows the torque detecting coil unit to be inserted eccentrically, creating sufficient clearance between the connection terminal and the housing body inner peripheral surface, thereby eliminating the interference issue while maintaining straightforward assembly from the front end opening.
Solution Approach 2:
The eccentric guide surface portion acts as an intermediary element that guides the torque detecting coil unit during insertion. It mediates the relationship between the coil unit and the housing body, ensuring proper positioning and preventing interference by maintaining appropriate spacing through its eccentric geometry.
2Ease of operation
If the distance from the center of the detection body to the end edge of the connection terminal is increased, then the connection to the circuit board is improved, but the connection terminal interferes with the inner peripheral surface of the housing body
Solution Approach 1:
By introducing the eccentric guide surface portion offset from the central axis, the patent creates an asymmetric insertion path that accommodates a longer connection terminal extending from the detection body center. This asymmetric geometry ensures the terminal can extend sufficiently for circuit board connection while maintaining clearance from the housing body inner peripheral surface.
3Volume of moving object
If the diameter of the second cylindrical surface portion is reduced to minimize housing size, then the overall device size is reduced, but the assembly of the torque detecting coil unit becomes more difficult
Solution Approach 1:
The eccentric guide surface portion enables the torque detecting coil unit to be inserted along an eccentric path rather than a concentric one. This allows the second cylindrical surface portion to have a smaller diameter while still accommodating the coil unit and its connection terminal, as the eccentric insertion creates additional clearance space that would not be available with concentric insertion.
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 design effectively reduces the size and weight of the electric power steering device while ensuring good assembly workability, allowing for the insertion of the torque detecting coil unit without interference and enabling automatic assembly, thus improving the overall efficiency and usability of the device.
Implementation Method 1
an input shaft and an output shaft that are coaxially connected to each other by a torsion bar
Implementation Method 2
a torque detecting coil unit that is fitted and fixed into a second cylindrical surface portion... and detects a direction and a magnitude of torque applied to the input shaft
Data Source
Figure 1
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AI summary
An eccentric guide surface portion (48), which has a shape of a partially cylindrical surface, is formed at a front end portion of a second cylindrical surface portion (32a), into which a torque detecting coil unit (31a) is fitted and fixed, of an inner peripheral surface of a housing body (16a) that is joined and fixed to a front end portion of a steering column. The center of curvature of the eccentric guide surface portion (48) is offset to a side opposite to a connection hole (39a), which is formed at the housing body (16a), in a radial direction so that a connection terminal (36a) of the torque detecting coil unit (31a) is connected to a circuit board (40a). Accordingly, a torque measuring unit for an electric power steering device, of which the size and weight are reduced while good assembly workability is ensured, is obtained.