Brake Pedal Position Sensing with Magnetic Shielded Redundancy
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Solution Overview
Problem
Existing position detection devices for rotating bodies are susceptible to reliability issues due to disturbance magnetic fields affecting the output signals of magnetoresistive elements, particularly in brake pedal devices.
Innovation Solution
The position detection device incorporates an inductive sensor and a magnet-type rotation angle sensor with a cylindrical magnetic circuit acting as a magnetic shield, preventing disturbance magnetic fields from interfering with the magnetic detection section, and includes redundancy through dual detection methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnet-type rotation angle sensor is used for position detection, then detection capability is provided, but disturbance magnetic fields affect the output signals reducing reliability
Solution Approach 1:
A magnetic shield (cylindrical structure made of magnetically conductive material) is introduced as an intermediary between the disturbance magnetic field source and the magnet-type rotation angle sensor. This shield intercepts and redirects disturbance magnetic field lines, preventing them from reaching the sensor's magnetic detection elements, thus protecting the output signal reliability while maintaining detection capability
Solution Approach 2:
The magnetic shield is positioned in advance around the magnetic detection section to preemptively block disturbance magnetic fields before they can interfere with the sensor operation. This proactive shielding approach cushions the sensor against magnetic interference, ensuring reliable output signals in environments with potential magnetic disturbance sources
2Reliability
If redundancy is introduced through dual detection methods, then reliability is improved, but device complexity increases
Solution Approach 1:
The inductive sensor and magnet-type rotation angle sensor are merged into a single integrated position detection device, sharing common structural elements such as the target member and housing. This combination provides redundant detection capabilities through two different sensing principles while minimizing the increase in device complexity through shared components and compact arrangement
3Reliability
If a magnetic shield is added to protect against disturbance fields, then output signal reliability is improved, but device complexity increases
Solution Approach 1:
The cylindrical magnetic shield structure serves multiple functions: it acts as a magnetic field shield protecting the detection section, provides structural support for the sensor assembly, and defines the geometric configuration of the magnetic circuit. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving reliable output signals
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 enhances the reliability of output signals by shielding against disturbance fields and providing redundant position detection, ensuring accurate and stable operation of brake pedal devices.
Implementation Method 1
The receiving and transmitting circuit detects a position of the target based on a change in an inductance of the inductive coil, which changes due to an eddy current flowing through the target when an alternating current is applied to the inductive coil
Implementation Method 2
The magnetic circuit section is cylindrically formed around an axis center and fixed to the rotating body to form a magnetic field in which magnetic flux flies in a direction intersecting the axis center
Implementation Method 3
The magnetic detection section is fixed to the fixed body and provided in a region radially inward from an inner peripheral surface of the magnetic circuit section, and outputs a signal corresponding to the magnetic field formed by the magnetic circuit section
Data Source
AI summary
A position detection device detects a position of a rotating body that is provided around a predetermined axis center with respect to a fixed body. A target is fixed to the rotating body. An inductive coil is fixed to the fixed body at a position facing the target in an axial center direction. The transmitting and receiving circuit applies an alternating current to the inductive coil and detects a position of the target. A magnetic circuit section is formed around the axis center and is fixed to the rotating body. A magnetic detection section is fixed to the fixed body and provided in region on a radially inner side than an inner circumferential surface of the magnetic circuit section. The target, the inductive coil, and the receiving and transmitting circuit constitute an inductive sensor, and the magnetic circuit section and the magnetic detection section constitute a magnet-type rotation angle sensor.