JP2009016202A - Non-contact switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-contact switch in which error operation can be prevented and detection precision can be improved. <P>SOLUTION: Two MR sensors 261a, 261b are arranged in regions A, B where projection parts 260b, 260c magnetized N-pole and magnetic vectors 262 generated by the N-pole of the base part 260a are aligned in one direction, and according to the output voltage of the MR sensors 261a, 261b based on changes in the magnetic vectors 262 caused by approach of the detecting part 20a, the ECU 100 controls lighting or light-out of a brake lamp 10a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-contact switch using a magnetic sensor.

  As a conventional technique, a concave portion is formed in a part of the N pole of the magnet, and three sides of the concave portion are surrounded by the N pole, and this concave portion is used as a detection region for detecting magnetic flux so that the magnetic member approaches the detection region. In addition, there is a non-contact switch in which a magnetic field sensitive element is disposed (for example, Patent Document 1).

According to this non-contact switch, when the magnetic member is displaced from a position away from the detection area to a position approaching the detection area, the N pole is detected in the detection area that is a magnetic flux-free space because the three sides are surrounded by the N pole. Magnetic flux is generated due to the magnetic flux flowing between the magnetic member and the magnetic member. The switch circuit can be turned on / off by detecting the generation of the magnetic flux by the magnetic field sensitive element.
Japanese Patent No. 2921603

  However, the conventional non-contact switch detects whether or not magnetic flux is generated in the detection region, so that malfunction occurs due to an external magnetic field, and there is a limit to increase detection accuracy.

  Therefore, an object of the present invention is to propose a non-contact switch that can suppress malfunctions and increase detection accuracy.

  In order to achieve the above object, the present invention has a substantially U-shape, a magnet for generating a magnetic flux directed in a predetermined direction in a detection region, and a plane orthogonal to a plane including a pair of extreme surfaces of the magnet. A magnetic sensor disposed in the detection region and configured to detect a change in the direction of the magnetic flux due to the approach of a magnetic member, and a determination unit configured to determine on / off based on a detection output of the magnetic sensor. Provide a non-contact switch.

  According to such a configuration, it is possible to provide a non-contact switch that can suppress malfunction and increase detection accuracy.

  Hereinafter, embodiments of the non-contact switch of the present invention will be described in detail with reference to the drawings.

[First embodiment]
(Configuration of vehicle 1)
FIG. 1A is a side view of a vehicle according to the first embodiment of the present invention, and FIG. 1B is a schematic view of the interior of the vehicle according to the first embodiment of the present invention. . The vehicle 1 decelerates the vehicle 1 by a brake device 2 as a non-contact switch that decelerates the vehicle 1 by a driver's operation, a brake lamp 10a that is lit (turned on) by a driver's brake operation, and a driver's brake operation. A hydraulic brake 10b, a panel 11 provided inside the vehicle 1 and provided with a brake device 2, an accelerator pedal 12 and the like, an accelerator pedal 12 capable of adjusting the acceleration of the vehicle 1 by a driver's operation, and the vehicle 1 And a shift lever 13 that can be operated such as traveling, stopping, and moving backward.

(Configuration of brake device 2)
FIG. 2A is a side view of the brake device according to the first embodiment of the present invention, and FIG. 2B is a front view of the brake device according to the first embodiment of the present invention. FIG. 3 is a block diagram of the brake device according to the first embodiment of the present invention.

  The brake device 2 includes a brake pedal 20 made of a ferromagnetic metal such as steel, a detected portion 20a that changes a magnetic flux generated from a magnet 260, which will be described later, by approaching or leaving the sensor 26, and a brake A pedal pad 21 provided on the pedal 20 and a side surface of the panel 11 of the vehicle 1, and a through hole at a position corresponding to the through hole provided at the tip of the brake pedal 20 as shown in FIG. 2, and a pedal bracket 22 that supports the brake pedal 20 so as to be able to rotate and move in the direction of arrow A shown in FIG. A brake pedal and a cylinder 24a connected to a piston (not shown) in the cylinder 24a and a joint 24d provided at the tip. 20 and a piston rod 24b that moves in conjunction with each other via a piston pin 24c, and between the panel 11 and the brake pedal 20, an elastic force is applied to the brake pedal 20 in the direction opposite to the arrow A, and the brake pedal is operated after the brake operation. 20 includes a return spring 25 for returning 20 to the initial position before the brake operation, and a sensor 26 that is provided on the attachment portion 22a of the pedal bracket 22 and detects the presence or absence of the brake operation based on the position of the detected portion 20a.

  Further, the sensor 26 of the brake device 2 controls the vehicle 1 and is connected to an ECU (Electronic Control Unit) 100 as a determination unit provided in a storage unit (not shown) with a threshold value 101 described later via a connector unit 26B. The ECU 100 constitutes a non-contact switch together with the detected portion 20a and the sensor 26, compares the output voltage from the sensor 26 with the threshold value 101, determines the presence or absence of a brake operation, and determines that the brake operation has been performed. The brake lamp 10a is turned on (turned on). In addition, when the driver performs a brake operation, the cylinder 24a that receives a force in the direction of the arrow A via the brake pedal 20, the piston pin 24c, the joint 24d, and the piston rod 24b generates hydraulic pressure and generates the hydraulic brake 10b. Is activated. In the present embodiment, the output voltage from the sensor 26 to the ECU 100 is output for each MR sensor 261a, 261b, the sum of the outputs of the two MR sensors, the average value of the two outputs, or any The presence or absence of the brake operation may be determined based on the output from the one MR sensor, but the present invention is not limited to this.

(Configuration of sensor 26)
FIG. 4A is a perspective view of the sensor according to the first embodiment of the present invention, and FIG. 4B is a front view of the sensor according to the first embodiment of the present invention. (C) is a side view of the sensor which concerns on the 1st Embodiment of this invention. The sensor 26 is accommodated in a housing (not shown) and is molded with a resin material. The MR sensors 261a and 261b may have a connected shape in order to be fixed at the positions shown in FIGS. 4 (a), (b) and (c).

  The sensor 26 includes a magnet 260 and MR sensors 261a and 261b as magnetic sensors. The magnet 260 is formed into a U shape by mixing Nd (neodymium) with resin, and includes a base portion 260a, convex portions 260b and 260c, and a concave portion 260d that forms a concave shape between the convex portions 260b and 260c. Yes.

  The magnet 260 has an S extreme surface 260e, an N extreme surface 260f that is an end surface of the convex portions 260b and 260c, and a base portion when a predetermined magnetic field is applied in the proximity of the magnetizing pieces from the facing direction. An N extreme surface 260g, which is a surface facing the S extreme surface 260e of 260a, is magnetized and formed. It should be noted that the S pole and the N pole can function in the same manner even if they are magnetized in the reverse combination of those shown above.

(Configuration of MR sensors 261a and 261b)
FIG. 5 (a) is a schematic configuration diagram of the MR sensor according to the first embodiment of the present invention, and FIG. 5 (b) configures the MR sensor according to the first embodiment of the present invention. FIG. 6A is a schematic diagram of a bridge circuit, and FIG. 6A is a schematic diagram illustrating the orientation of a magnetic vector on a plane on which an MR sensor is placed before the detected portion approaches according to the first embodiment of the present invention. FIG. 6B is a schematic diagram showing the orientation of the magnetic vector on the plane on which the MR sensor is arranged after the detected part approaches according to the first embodiment of the present invention. A magnetic vector 262 in the plane S1 shown in FIG. FIG. 6A shows, as an example, a magnetic vector 262 when the distance d between the detected portion 20a shown in FIG. 4A and the convex portions 260b and 260c of the magnet 260 is 8 mm. ) Represents, as an example, a magnetic vector 262 when the distance d is 1 mm. Although the length of the magnetic vector 262 is proportional to the strength of the magnetic field, the size of the arrow is not related to the strength of the magnetic field.

  The MR sensor 261a is a substrate 261A that is an insulator such as silicon, and a magnetoresistive element 261B that is provided on the substrate 261A and is manufactured using a ferromagnetic material such as Fe—Ni by a known method such as photolithography. ˜261E, an input terminal 261F connected to a power source (not shown) of the vehicle 1, an earth terminal 261G, an output terminal 261H from which the midpoint potential V1 of the magnetoresistive elements 261B and 261C is output, a magnetoresistive element 261D and And an output terminal 261I from which a midpoint potential V2 of 261E is output. The MR sensor 261b has a similar configuration. In addition, the output voltage V shall output the difference value of V1 and V2.

  Each of the magnetoresistive elements 261B to 261E includes a magnetic sensing part 261J whose electrical resistance value changes according to a change in the direction of the magnetic field, and a folded part 261K that connects the magnetic sensing parts 261J. When the direction of magnetic flux is θ = 0 ° shown in FIG. 5A, the magnetic resistance values of the magnetoresistive elements 261C and 261D are minimized, and when θ = 45 °, the magnetic resistances of the magnetoresistive elements 261B to 261E are The resistance values are equal, and when [theta] = 90 [deg.], The magnetoresistance values of the magnetoresistive elements 261B and 261E are minimized.

  Each of the magnetoresistive elements 261B to 261E forms a bridge circuit 261L shown in FIG. 5B, and the magnetoresistive elements 261B and 261E shown by vertical lines in FIG. The magnetic resistance element 261C or 261D indicated by the horizontal line in b) is rotated 90 degrees.

  In order to stably detect the change in the distance d with respect to the sensor 26 of the detected part 20a, the directions of the magnetic vectors 262 are substantially aligned, and the magnetic vector 262 aligned with the approach of the detected part 20a is substantially equal. The MR sensors 261a and 261b are preferably arranged at positions that change in the same direction. This is because the anisotropic magnetoresistive element detects a change in the direction of the magnetic vector 262 of the magnetic field applied to the anisotropic magnetoresistive element, and is used for detecting the presence or absence of magnetic flux and the change in magnetic field strength. It is not suitable. Therefore, in order to perform stable detection, it is necessary to apply a magnetic field at which the magnetoresistance value is saturated to the MR sensors 261a and 261b by the magnet 260. This is because the magnetic resistance value is maximized by applying a magnetic field at which the magnetic resistance value is saturated to the MR sensors 261a and 261b, and a change in the magnetic resistance value based on a change in the direction of the magnetic vector 262 is easily detected. . Further, reliability is improved by using the two MR sensors 261a and 261b.

  In regions A and B shown in FIG. 6A, the magnetic vectors 262 are aligned in a certain direction, and FIG. 6A shows a state where the distance d between the detected portion 20a and the sensor 26 is large. The direction of the magnetic vector 262 in the areas A and B shown in (a) is greatly changed in FIG. 6 (b). On the other hand, the magnetic vector 262 in the region C near the center near the magnetic flux has a large change in the direction of the magnetic vector 262, but the magnetic flux is weak and a sufficient output cannot be obtained. Is not suitable.

  From the above results, the MR sensors 261a and 261b are planes orthogonal to the plane including the N extreme surface 260f as shown in FIG. 4B, and are substantially intermediate portions of the convex portions 260b and 260c. As shown in FIG. 4C, magnetic vectors 262 in the vicinity of the tips of the convex portions 260b and 260c are arranged apart from each other in a region aligned in one direction. Moreover, since the presence or absence of the approach to the to-be-detected part 20a is performed by the two MR sensors 261a and 261b, erroneous detection can be suppressed. The arrangement positions of the MR sensors 261a and 261b are not limited to this. For example, as long as the magnetic vector 262 is aligned in one direction and the direction of the magnetic vector 262 changes due to the approach of the detected part 20a, for example, Even in a plane parallel to the plane S1, it can be freely arranged.

  Even if the arrangement position of the MR sensors 261a and 261b is shifted in the direction perpendicular to the moving direction of the detected portion 20a with respect to the sensor 26, the deviation of the angle of the magnetic vector 262 on the arranged plane is the same direction. Therefore, the ECU 100 can determine the presence or absence of the brake operation stably based on the output voltage.

  FIG. 7 is a schematic diagram related to the output voltage of the MR sensor according to the first embodiment of the present invention, and shows a case where a voltage is applied to the MR sensors 261a and 261b so that the detection output becomes 50 mV. The vertical axis represents the output voltage V, and the horizontal axis represents the distance d between the MR sensors 261a and 261b and the detected portion 20a. The curve T1 is common to the MR sensors 261a and 261b.

  The distance d between the detected portion 20a and the convex portions 260b and 260c of the magnet 260 is 1 mm when the driver does not perform the brake operation (initial position), and the driver performs the brake operation. The threshold value 101 is set to 0 mv so that the brake lamp 10a is turned on (on) when 20a moves 3 mm in the direction of arrow A. In addition, these values are not limited to this, For example, according to the attachment position of the sensor 26, the setting of the play of the brake device 2, etc., it can change freely.

(Operation)
Hereinafter, the operation of the present embodiment will be described in detail with reference to FIGS.

  When the driver performs a brake operation during the driving operation of the vehicle 1, the brake pedal 20 moves in the direction of the arrow A shown in FIG. 2 around the bolt 23 attached to the tip of the brake pedal 20. To do.

  As the brake pedal 20 moves in the direction of arrow A, the distance d shown in FIG. 4A is increased in the detected portion 20a, and the magnetic vector 262 is changed from the state shown in FIG. 5B to FIG. 5A. The state changes continuously.

  The ECU 100 compares the threshold 101 with at least one output voltage transmitted from the sensor 26, that is, the two MR sensors 261a and 261b. When the brake operation exceeds 3 mm in the direction of arrow A, the distance d shown in FIG. 7 is 3 mm or more, and the sensor 26 outputs an output voltage of 0 mV or more which is the threshold value 101, the ECU 100 performs the brake operation. The brake lamp 10a is turned on (on). At the same time, when the brake operation is performed, the piston rod 24b receives a force through the piston pin 24c and the joint 24d and moves in the arrow A direction along with the movement of the brake pedal 20 in the arrow A direction. The hydraulic pressure is generated by pushing, the hydraulic brake 10b is operated by the hydraulic pressure, and the vehicle 1 decelerates.

  When the driver's brake operation is finished and the distance d shown in FIG. 7 is 3 mm or less, the ECU 100 determines that the brake operation is finished, and turns off the brake lamp 10a. At this time, since the brake pedal 20 returns to the initial position by the elastic force of the return spring 25, the piston pin 24c, the joint 24d, and the piston rod 24b move in the direction opposite to the arrow A, and the inside of the cylinder 24a is not shown. The piston moves in the direction opposite to the arrow A, the hydraulic pressure applied to the hydraulic brake 10b is released, and the brake operation ends.

  The above operation is determined by the ECU 100 based on at least one output voltage of the two MR sensors 261a and 261b, and the lighting / extinguishing (on / off) of the brake lamp 10a is controlled. For example, the MR sensors 261a and 261b When one of the above malfunctions, the ECU 100 can determine whether the brake lamp 10a is turned on or off (on / off) based on the output voltage from the MR sensor that is not malfunctioning. Further, the addition value obtained by adding the output voltages of the two MR sensors 261a and 261b, and determining whether the brake lamp 10a is turned on / off (on / off) based on an average value obtained by adding the two output voltages and averaging them. Also good.

(effect)
According to the first embodiment described above, since the approach of the detected part 20a is detected in a stable region where the magnetic vectors 262 are aligned in one direction, malfunction can be suppressed, and the two MR sensors 261a, Since it detects by 261b, detection accuracy can be improved.

[Second Embodiment]
(Constitution)
FIG. 8A is a perspective view of a sensor according to the second embodiment of the present invention, and FIG. 8B is a front view of the sensor according to the second embodiment of the present invention. (C) is a side view of a sensor according to a second embodiment of the present invention. In the present embodiment, only parts different from the first embodiment will be described.

  This embodiment has one MR sensor as compared with the first embodiment. The MR sensor 261a is disposed at the position shown in FIGS. 8B and 8C, but is not limited to this, and the region B shown in FIGS. 6A and 6B or a magnetic vector 262 corresponding thereto. It suffices if it is in a region facing in a predetermined direction. The relationship between the output voltage V of the MR sensor 261a and the distance d is the same as that shown in FIG.

(Operation)
When the driver performs a brake operation during the driving operation of the vehicle 1, the brake pedal 20 moves in the direction of arrow A around the bolt 23 attached to the tip of the brake pedal 20.

  As the brake pedal 20 moves in the direction of arrow A, the distance d shown in FIG. 8A increases in the detected portion 20a, and the magnetic vector 262 changes from the state shown in FIG. 6B to FIG. 6A. The state changes continuously.

  The ECU 100 compares the output voltage transmitted from the MR sensor 261 a of the sensor 26 with the threshold value 101. When the brake operation exceeds 3 mm in the arrow A direction, the distance d shown in FIG. 8 is 3 mm or more, and the sensor 26, that is, the MR sensor 261a outputs an output voltage of 0 mV or more which is the threshold value 101, the ECU 100 Then, it is determined that the brake operation has been performed, and the brake lamp 10a is turned on (turned on). At the same time, when the brake operation is performed, the piston rod 24b receives a force through the piston pin 24c and the joint 24d and moves in the arrow A direction along with the movement of the brake pedal 20 in the arrow A direction. The hydraulic pressure is generated by pushing, the hydraulic brake 10b is operated by the hydraulic pressure, and the vehicle 1 decelerates.

  When the driver's brake operation is finished and the distance d shown in FIG. 8 is 3 mm or less, the ECU 100 determines that the brake operation is finished, and turns off the brake lamp 10a. At this time, since the brake pedal 20 returns to the initial position by the elastic force of the return spring 25, the piston pin 24c, the joint 24d, and the piston rod 24b move in the direction opposite to the arrow A, and the inside of the cylinder 24a is not shown. The piston moves in the direction opposite to the arrow A, the hydraulic pressure applied to the hydraulic brake 10b is released, and the brake operation ends.

(effect)
According to the second embodiment described above, since the approach of the detected part 20a is detected in a stable region where the magnetic vectors 262 are aligned in one direction, malfunction can be suppressed.

[Third embodiment]
(Constitution)
FIG. 9A is a perspective view of a sensor according to the third embodiment of the present invention, and FIG. 9B is a front view of the sensor according to the third embodiment of the present invention. (C) is a side view of a sensor according to a third embodiment of the present invention, FIG. 10 is a schematic diagram of a bridge circuit according to the third embodiment of the present invention, and FIG. It is the schematic regarding the output voltage of the MR sensor which concerns on the 3rd Embodiment of this invention. In the present embodiment, only parts different from the first embodiment will be described.

  The MR sensor 261a in the present embodiment is configured by the half bridges 261M and 261N shown in FIG. 10, and the half bridge 261M is configured by the magnetoresistive elements 261B and 261C, and the plane S1 shown in FIG. 9A. It is arranged in a region B shown in FIG. The half bridge 261N is configured by magnetoresistive elements 261D and 261E, and is arranged in the region A in the plane S1.

  For example, the half bridge 261M outputs the output voltage of the curve T3 shown in FIG. 11 according to the distance d between the detected portion 20a and the sensor 26, and the half bridge 261N, for example, outputs the output voltage of the curve T2 shown in FIG. Is output according to the distance d. The half bridges 261M and 261N may be separately molded and arranged, or as one MR sensor 261a, molded so that the half bridges 261M and 261N are included in the regions A and B. However, it is not limited to this.

(Operation)
In the present embodiment, ECU 100 inverts the output voltage of half bridge 261M using an operational amplifier (not shown), and adds the inverted output voltage and the output voltage represented by curve T2 of half bridge 261N. The output voltage represented by the curve T4 is compared with the threshold value 101, so that the presence or absence of a brake operation can be determined and the turning on and off of the brake lamp 10a can be controlled. Even when one of the half bridges 261M and 261N fails, the ECU 100 can determine the presence or absence of a brake operation based on either output voltage and the threshold value 101. Note that the ECU 100 may determine the presence or absence of a brake operation based on a difference between two output voltages or an average obtained by inverting and adding one output voltage.

  Further, even if the arrangement position of the MR sensor 261a is shifted in the direction perpendicular to the moving direction of the detected portion 20a with respect to the sensor 26, the angle deviation of the magnetic vector 262 on the arranged plane is the same direction. The ECU 100 can stably determine the presence or absence of a brake operation based on the output voltage.

(effect)
According to the third embodiment described above, since the half bridges 261M and 261N are arranged in the region A and the region B, it is possible to determine the presence or absence of the brake operation stably.

  The present invention is not limited by the first, second and third embodiments. For example, in the first, second, and third embodiments, the lighting / extinguishing of the brake lamp 10a has been described, but it goes without saying that the present invention can be applied to other controls such as lighting control in the instrument panel storage box. It can also be applied to uses other than vehicles. Moreover, you may arrange | position MR sensor in the vicinity of the area | region A and the area | region B shown to Fig.6 (a) and (b).

(A) is a side view of the vehicle which concerns on the 1st Embodiment of this invention, (b) is the schematic inside the vehicle which concerns on the 1st Embodiment of this invention. (A) is a side view of the brake device which concerns on the 1st Embodiment of this invention, (b) is a front view of the brake device which concerns on the 1st Embodiment of this invention. 1 is a block diagram of a brake device according to a first embodiment of the present invention. (A) is a perspective view of the sensor which concerns on the 1st Embodiment of this invention, (b) is a front view of the sensor which concerns on the 1st Embodiment of this invention, (c) is this 1 is a side view of a sensor according to a first embodiment of the invention. (A) is a schematic block diagram of MR sensor which concerns on the 1st Embodiment of this invention, (b) is the outline of the bridge circuit which comprises MR sensor which concerns on the 1st Embodiment of this invention. FIG. (A) is the schematic showing the direction of the magnetic vector of the plane where the MR sensor before the to-be-detected part which approaches the 1st Embodiment of this invention approaches is arranged, (b) is this It is the schematic showing the direction of the magnetic vector of the plane where the MR sensor after the to-be-detected part which approached the 1st Embodiment of the invention approached is arrange | positioned. It is the schematic regarding the output voltage of MR sensor which concerns on the 1st Embodiment of this invention. (A) is a perspective view of the sensor which concerns on the 2nd Embodiment of this invention, (b) is a front view of the sensor which concerns on the 2nd Embodiment of this invention, (c) is this It is a side view of the sensor which concerns on the 2nd Embodiment of invention. (A) is a perspective view of the sensor which concerns on the 3rd Embodiment of this invention, (b) is a front view of the sensor which concerns on the 3rd Embodiment of this invention, (c) is this It is a side view of the sensor which concerns on the 3rd Embodiment of invention. It is the schematic of the bridge circuit which concerns on the 3rd Embodiment of this invention. It is the schematic regarding the output voltage of the MR sensor which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Brake device, 10a ... Brake lamp, 10b ... Hydraulic brake, 11 ... Panel, 12 ... Accelerator pedal, 13 ... Shift lever, 20 ... Brake pedal, 20a ... Detected part, 21 ... Pedal pad, 22 ... Pedal bracket, 22a ... Mounting part, 23 ... Bolt, 24a ... Cylinder, 24b ... Piston rod, 24c ... Piston pin, 24d ... Joint, 25 ... Return spring, 26A ... Sensor part, 26B ... Connector part, 26 ... Sensor, 101 ... threshold value, 260 ... magnet, 260a ... base portion, 260b, 260c ... convex portion, 260d ... concave portion, 260e ... S extreme surface, 260f, 260g ... N extreme surface, 261a, 261b ... MR sensor, 261A ... substrate 261B to 261E, magnetoresistive element, 261F, input terminal, 261G, arm. Terminal, 261H, 261I ... Output terminal, 261J ... Magnetic sensing part, 261K ... Folding part, 261L ... Bridge circuit, 261M, 261N ... Half bridge, 262 ... Magnetic vector, A, B, C ... Area, d ... Distance, S1 ... Plane, T1, T2, T3, T4 ... Curve, V ... Voltage, V1, V2 ... Output voltage

Claims (3)

A magnet having a substantially U-shape and generating a magnetic flux in a predetermined direction in a detection region;
A magnetic sensor disposed in the detection region in a plane orthogonal to a plane including a pair of extreme surfaces of the magnet, and detecting a change in the direction of the magnetic flux due to the approach of a magnetic member;
A determination unit for determining on or off based on an output signal of the magnetic sensor;
A non-contact switch comprising:   2. The magnetic sensor includes a bridge circuit formed by a plurality of magnetoresistive elements, and the bridge circuit is disposed in the detection region as a half bridge circuit divided into two. Non-contact switch as described in.   The magnetic sensor comprises a plurality of magnetoresistive sensors in which bridge circuits are formed by a plurality of magnetoresistive elements, and the plurality of magnetoresistive sensors are arranged in the detection region. Non-contact switch.

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