Torque Sensor Housing Segmentation for Molding Precision
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Solution Overview
Problem
Existing torque sensors face precision issues due to deformation of holders during injection molding, which affects the positional relationship of magnetism collection portions and the sensor element, leading to fluctuations in detection accuracy.
Innovation Solution
The sensor device employs insert molding to form a housing that integrally surrounds magnetism collection rings, with a sensor cover portion housing the sensor element between the collection portions, preventing molding pressure from altering their positional relationship and using a projection portion for precise assembly of the sensor element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If holders are formed by injection molding to surround magnetism collection rings, then manufacturing efficiency and integration are improved, but molding pressure causes holder deformation that affects positional precision
Solution Approach 1:
The housing is divided into two separately formed parts: a ring portion cover portion that surrounds the magnetism collection rings, and a sensor cover portion that houses the sensor element. These parts are then assembled together, which prevents the molding pressure from causing deformation that would affect the positional relationship between the sensor element and magnetism collection portions.
Solution Approach 2:
The ring portion cover portion and sensor cover portion are formed separately in advance through injection molding, allowing each part to be manufactured with optimal precision without the negative effects of molding pressure on the other part. The parts are then assembled with precise positioning features to achieve the required overall precision.
2Ease of manufacture
If holders are deformed by molding pressure, then housing formation is simplified, but positional relationship between sensor element and magnetism collection portions fluctuates
Solution Approach 1:
The housing is segmented into two parts that are formed separately and then assembled. This segmentation prevents the molding pressure from causing deformation that would affect the positional relationship between the sensor element and magnetism collection portions, while still maintaining ease of manufacture through the injection molding process.
Solution Approach 2:
The ring portion cover portion acts as an intermediary structure that is formed separately from the sensor cover portion. This intermediary structure allows the sensor element to be positioned with high precision relative to the magnetism collection rings without being affected by molding pressure deformations.
3Device complexity
If sensor element is housed during injection molding, then assembly is simplified, but molding pressure alters positional relationship and reduces detection accuracy
Solution Approach 1:
The housing is segmented into two parts that are formed separately and then assembled. The sensor element is housed in the sensor cover portion after both parts are formed, which avoids exposing it to molding pressure. This segmentation maintains relatively simple assembly while preserving detection accuracy.
Solution Approach 2:
The ring portion cover portion and sensor cover portion are formed separately in advance through injection molding, allowing each part to be manufactured with optimal precision without the negative effects of molding pressure on the other part. The parts are then assembled with precise positioning features to achieve the required overall precision.
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 configuration stabilizes the positional relationship of the sensor element with respect to the magnetism collection portions, enhancing detection precision and preventing deformation-induced inaccuracies, thus improving the sensor's ability to accurately measure torque.
Implementation Method 1
a permanent magnet attached to a first shaft and magnetized such that N poles and S poles appear alternately in a circumferential direction on an outer peripheral surface of the permanent magnet
Implementation Method 2
a magnetic yoke that is fixed to a second shaft coupled to the first shaft and is disposed in a magnetic field formed by the permanent magnet; a first magnetism collection ring that has an annular first ring portion that surrounds the magnetic yoke and a first magnetism collection portion that includes a portion disposed on a radially outer side of the first ring portion
Implementation Method 3
a sensor element that detects magnetism of a magnetic circuit formed by the permanent magnet, the magnetic yoke, the first magnetism collection ring, and the second magnetism collection ring
Implementation Method 4
a housing formed by insert molding so as to integrally surround the first ring portion and the second ring portion
Data Source
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AI summary
A sensor device that can suppress fluctuations in the positional relationship of a sensor element with a first magnetism collection portion and with a second magnetism collection portion due to a molding pressure applied to form a housing by injection molding is provided. A housing of a torque sensor has a ring portion cover portion (60) that surrounds and holds a first ring portion (41a) of a first magnetism collection ring (41) and a second ring portion (42a) of a second magnetism collection ring (42), and a sensor cover portion (70) that houses a first magnetism collection portion (41b), a second magnetism collection portion, and a sensor unit (110). The sensor cover portion (70) extends toward the radially outer side from the ring portion cover portion (60). The sensor cover portion (70) has a sensor housing portion (71) that houses the sensor unit (110) as interposed between the first magnetism collection portion (41b) and the second magnetism collection portion, an opening portion (72) that opens in the axial direction (X), and a lid portion (73) that closes the opening portion (72).