Inhibitor Switch Disconnection Detection Circuit
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Solution Overview
Problem
Existing inhibitor switches for vehicular automatic transmissions cannot distinguish between failures in the switch itself and failures in the harness, leading to inaccurate abnormality detection.
Innovation Solution
The design incorporates a printed circuit board with a disconnection detection circuit enclosed in an insulating seal material, allowing for direct confirmation of switch abnormalities and preventing short-circuits from operating oil, with a movable board and contact points that change contact combinations based on displacement to output specific signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a harness is connected to the inhibitor switch for signal transmission, then the selection range of the shift lever can be detected, but it becomes impossible to distinguish between switch failures and harness failures
Solution Approach 1:
The patent applies feedback by having the control device send a test signal through the harness to the inhibitor switch and evaluate the returned signal. This feedback mechanism allows the system to determine whether a disconnection abnormality originates from the switch or the harness, resolving the inability to distinguish failure sources while maintaining accurate abnormality detection.
2Reliability
If the control device determines abnormality based on input signals, then shift lever position can be monitored, but false abnormality signals occur due to oil-induced short-circuits
Solution Approach 1:
The patent introduces an insulating seal material as an intermediary between the printed circuit board and the operating oil. This seal material prevents the operating oil from causing short-circuits on the circuit board while allowing the switch to continue functioning, thereby eliminating false abnormality signals and improving determination reliability.
3Volume of moving object
If the printed circuit board is exposed to operating oil for compact design, then device size is reduced, but short-circuits occur due to oil contact
Solution Approach 1:
The insulating seal material serves as a protective intermediary that allows the printed circuit board to be positioned in proximity to operating oil without direct contact. This enables compact switch housing design while preventing oil-induced short-circuits, as the seal material blocks electrical conduction paths through the oil.
Solution Approach 2:
The patent uses an insulating seal material in the form of a shell or film structure that encapsulates the printed circuit board. This flexible sealing approach provides effective electrical insulation against operating oil while maintaining a compact overall device volume.
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 enables accurate detection of switch failures while preventing false signals from oil-induced short-circuits, ensuring reliable abnormality determination and improved operational integrity.
Implementation Method 1
a printed circuit board with a disconnection detection circuit enclosed in an insulating seal material, allowing for direct confirmation of switch abnormalities and preventing short-circuits from operating oil
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An inhibitor switch has a movable board 3, a pole board 2 on a surface of which contact pieces of a fixed contact point 6 are exposed, the surface facing the movable board 3, a movable contact point 5 that is supported by the movable board 3 and its contact pieces making resilient contact with an inner surface of the surface of the pole board 2, and an output terminal 7 including terminal parts corresponding to the contact pieces of the fixed contact point 6 on a one-to-one basis. In the inhibitor switch, a combination of the contact pieces of the fixed contact point 6 to come in contact with each other through the movable contact point 5 is changed based upon the displacement of the movable board 3 in the axis line direction. The fixed contact point 6 and the output terminal 7 are connected through a printed circuit board 9 having a disconnection detection circuit. The printed circuit board 9 is enclosed in an insulating seal material 10.