Inductive sensor and brake pedal device
An inductive sensor detects a position of a detection object relative to a fixed body, in which the detection object is either provided as (i) a rotating body rotatable about a predetermined axis relative to the fixed body or (ii) a movable body movable in accordance with movement of the rotating body. The inductive sensor includes a circuit board and multiple targets. The circuit board has, implemented thereon, a transceiver coil including a transmitter coil and a receiver coil, and a transceiver circuit that supplies a high frequency wave to the transmitter coil and outputs a signal corresponding to a change in inductance of the receiver coil, and is fixed to the fixed body. The multiple target objects are configured to move in synchronization with movement of the detection object and to include a conductor.
1 . An inductive sensor for detecting a position of a detection object relative to a fixed body, the detection object either being (i) a rotating body rotatably provided about a predetermined axis relative to the fixed body or (ii) a movable body moving in accordance with a movement of the rotating body, the inductive sensor comprising:
a circuit board fixed to the fixed body, the circuit board being implemented with a transceiver coil including a transmitter coil and a receiver coil, and a transceiver circuit that supplies a high frequency wave to the transmitter coil and outputs a signal corresponding to a change in inductance of the receiver coil; and
multiple targets configured to include a conductor and to move in synchronization with a movement of the detection object, wherein
the multiple targets include at least a first target and a second target actually-axially separated from the first target,
the transceiver coil has at least (i) a first transceiver coil that outputs a detection value corresponding to a position of the first target, and (ii) a second transceiver coil that outputs a detection value corresponding to a position of the second target,
a surface of the first target facing the first transceiver coil and a surface of the second target facing the second transceiver coil are arranged on a same surface at positions separated from the predetermined axis, the same surface being a first virtual plane, and
the first transceiver coil and the second transceiver coil provided in the circuit board are arranged on a second virtual plane parallel to the first virtual plane.
2 . The inductive sensor according to claim 1 , wherein
the first target and the second target are fixed on the same rotating body.
3 . The inductive sensor according to claim 2 , wherein
the first target is fixed to the rotating body at a first position in an axial direction of the rotating body,
the second target is fixed to the rotating body at a second position in the axial direction of the rotating body, and
the second position is different from the first position in the axial direction of the rotating body.
4 . The inductive sensor according to claim 1 , wherein
at least one of the multiple targets has a facing portion facing the transceiver coil, and
the facing portion is provided with at least a conductor part of made of the conductor, and an insulator part that is the rest of the facing portion and is made of an insulator.
5 . The inductive sensor according to claim 4 , wherein
the insulator forming a part of the targets is made of a resin, and the resin is used at a fixing portion where the part of the targets is fixed to the detection object.
6 . The inductive sensor according to claim 1 , wherein
both the first target and the second target are fixed to the rotating body by a same bolt.
7 . The inductive sensor according to claim 6 , further comprising:
a shaft serving as the rotating body and being inserted into a first hole of the first target and a second hole of the second target; and
an anti-rotation structure configured to restrict a relative rotation between the first target and the shaft, and to restrict a relative rotation between the second target and the shaft.
8 . The inductive sensor according to claim 1 , wherein
both of the first target and the second target are fixed to the rotating body by a caulking.
9 . The inductive sensor according to claim 1 , wherein
a range in which the first transceiver coil is implemented on the circuit board is larger than a movable range of the first target movable in synchronization with the movement of the detection object on one and other sides of a moving direction, and
a range in which the second transceiver coil is implemented on the circuit board is larger than a movable range of the second target movable in synchronization with the movement of the detection object on one and other sides of a moving direction.
10 . The inductive sensor according to claim 1 , wherein
the first target is larger than a range in which the first transceiver coil is implemented in the circuit board on both of a radial outside and a radial inside of a virtual circle perpendicular to the axis and centered on the axis, and
the second target is larger than a range in which the second transceiver coil is implemented in the circuit board on both of the radial outside and the radial inside of the virtual circle.
11 . A brake pedal device used for a brake-by-wire system in which a brake mechanism brakes a vehicle in accordance with a drive control of an electronic control device mounted on the vehicle, the brake pedal device comprising:
the inductive sensor according to claim 1 ;
a housing as the fixed body that is directly or indirectly fixed to a vehicle body;
a shaft as the rotating body, the shaft being rotatable within a predetermined angular range relative to the housing;
a brake pedal as the movable body, the brake pedal being fixed to the shaft to be movable within a predetermined angular range about an axis of the shaft; and
a reaction force generating mechanism configured to generate a reaction force against a pedaling force of a driver applied to the brake pedal.
12 . The brake pedal device according to claim 11 , wherein
the brake pedal device is used for a complete brake-by-wire system in which components of the brake mechanism and the brake pedal are not mechanically connected, and the electronic control device drives and controls the brake mechanism based on an output signal of the inductive sensor to brake the vehicle.
13 . The brake pedal device according to claim 11 , wherein the multiple targets are fixed to the shaft, the brake pedal device further comprising
a torsion spring provided to apply a load in a circumferential direction about the axis of the targets, to at least one of the multiple targets, and
one end of the torsion spring is engaged with at least one of the multiple targets, and an another end of the torsion spring is engaged with the fixed body.
14 . The brake pedal device according to claim 11 , wherein
both of the first target and the second target are fixed to the shaft by using a same bolt.
15 . The brake pedal device according to claim 14 , wherein the shaft is inserted into a first hole of the first target and a second hole of the second target, the brake pedal device further comprising
an anti-rotation structure configured to restrict a relative rotation between the first target and the shaft and to restrict a relative rotation between the second target and the shaft.
16 . The brake pedal device according to claim 11 , wherein
both of the first target and the second target are fixed to the shaft by a caulking.
17 . The brake pedal device according to claim 11 , wherein
the transceiver coil includes at least a first transceiver coil that outputs a detection value corresponding to a position of the first target, and a second transceiver coil that outputs a detection value corresponding to a position of the second target,
a range in which the first transceiver coil is implemented on the circuit board is larger than a rotation range of the first target that rotates in synchronization with the shaft, on one and another sides in a rotation direction of the first target, and
a range in which the second transceiver coil is implemented on the circuit board is larger than a rotation range of the second target that rotates in synchronization with the shaft, on one and another sides in a rotation direction of the second target.
18 . The brake pedal device according to claim 11 , wherein
the transceiver coil includes at least a first transceiver coil that outputs a detection value corresponding to a position of the first target, and a second transceiver coil that outputs a detection value corresponding to a position of the second target,
the first target is larger than a range in which the first transceiver coil is implemented on the circuit board on both of a radial outside and a radial inside of a virtual circle perpendicular to the axis and centered on the axis, and
the second target is larger on both a radial outside and a radial inside of the imaginary circle than an area in which the second transceiver coil is implemented on the circuit board.
19 . The inductive sensor according to claim 1 , wherein
the rotating body is a shaft having a rod shape, and
the first target and the second target are arranged around the shaft to have the same surface as the first virtual plane.