JP2009204371A - Position sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce abrasion of a member for scratching off foreign matters adhering to a movable body more than before, and also reducing abrasion of the outer circumferential surface of the movable body associated with the adhesion of foreign matters. <P>SOLUTION: A sensor body 1 is provided with a detection coil 4 in a housing 12 formed in tubular shape. The movable body 2 is provided with a detection body 22 made of metal and inserted in the sensor body 1 in such a way as to move in the axial directions of the sensor body 1 and partially freely enter in and be extracted from the sensor body 1. The detection coil 4 constitutes a resonance circuit of an oscillation circuit and detects impedance changes of the detection coil, as an oscillation amplitude, corresponding to positional changes with the detection body 22 associated with the movement of the movable body 2. A blush 3 provided with hairs to be in contact with the overall circumference of the outer circumferential surface of the movable body 2 in its circumferential direction is arranged in the section of the housing 12 of the sensor body 1 in which the movable body 2 is inserted. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a position sensor that detects a positional relationship between a metal movable body that moves on a straight line and a detection coil by changing the impedance of the detection coil.

  Conventionally, as shown in FIG. 2, a detection coil 4 and a metal movable body 2 are provided, and the relative position of the movable body 2 along the axial direction of the detection coil 4 is detected by changing the impedance of the detection coil 4. A position sensor has been proposed. In this type of position sensor, a configuration in which an oscillation circuit including the detection coil 4 as a resonance circuit is configured to pass a high-frequency current through the detection coil 4 and the oscillation amplitude is detected as an impedance equivalent amount of the detection coil 4 is widely adopted. (For example, refer to Patent Document 1).

  The configuration described in Patent Document 1 employs a configuration in which a detection coil in which a coil winding is wound around a cylindrical coil bobbin is used, and a metal movable body is advanced and retracted relative to the coil bobbin.

  On the other hand, in the configuration shown in FIG. 2, the detection coil 4 in which the coil winding 43 is wound around the rod-shaped core 42, and the cylindrical movable body 2 having an inner diameter larger than the outer diameter of the detection coil 4 A configuration is adopted in which the movable coil 2 is placed in a nested manner with respect to the detection coil 4 so that the detection coil 4 is inserted into the movable body 2 so as to advance and retract. In the configuration shown in FIG. 2, the detection coil 4 is housed in the cylindrical sensor body 1, and a part of the movable body 2 is inserted in a space between the sensor body 1 and the detection coil 4 so as to be able to advance and retract.

  Incidentally, the position sensor shown in FIG. 2 is assumed to be attached to a shock absorber of an automobile, and a movable part 5 of the shock absorber is coupled to the movable body 2 as a position detection target.

In this type of application, there is a possibility that foreign matter such as mud adheres around the position sensor, so that the foreign matter attached to the outer peripheral surface of the movable body 2 is movable so as not to enter the inside of the sensor body 1. A dust seal 8 that is in close contact with the outer peripheral surface of the body 2 is disposed in the sensor body 1. The dust seal 8 is made of, for example, a material having rubber elasticity, and has a function of scraping off foreign matter adhering to the outer peripheral surface of the movable body 2 when the movable body 2 moves in the direction of insertion into the sensor body 1. is doing.
Japanese Patent Laid-Open No. 2003-83764

  However, since the dust seal 8 is made of a material having rubber elasticity and is in surface contact with the outer peripheral surface of the movable body 2, there is a problem that the dynamic friction is likely to be worn out easily. In addition, when the foreign object is pressed between the outer peripheral surface of the movable body 2 and the dust seal 8 without being scraped off by the dust seal 8, the foreign object is pressed against the outer peripheral surface of the movable body 2. There is also a possibility that the outer peripheral surface of the movable body 2 is worn by the foreign matter.

  The present invention has been made in view of the above reasons, and its purpose is to provide a member that scrapes off foreign matter adhering to the movable body so that the foreign matter does not enter the sensor body, but the member that scrapes off foreign matter. It is an object of the present invention to provide a position sensor in which wear is reduced more than before and wear on the outer peripheral surface of a movable body accompanying adhesion of foreign matter is also suppressed.

  The invention according to claim 1 is a sensor main body formed in a cylindrical shape and provided with a detection coil, a metal movable body that is movable in the axial direction of the sensor main body, and a part of which is inserted into the sensor main body so as to be movable forward and backward. A circuit unit that detects the position of the movable body by detecting the impedance change of the detection coil in response to the position change of the movable body, and a peripheral portion of the movable body that is disposed at a position where the movable body is inserted in the sensor body. And a brush with bristles that contact the entire circumference of the direction.

  According to a second aspect of the invention, in the first aspect of the invention, the sensor main body includes a cylindrical housing and a detection coil disposed in the housing, and the movable body is a space between the housing and the detection coil. It is characterized in that it is formed in a cylindrical shape in which a part is inserted so as to be able to advance and retract.

  According to the configuration of the first aspect of the present invention, by providing a brush having hairs that come into contact with the outer peripheral surface of the movable body, the foreign matter adhering to the movable body is scraped off to prevent the foreign body from entering the sensor body. However, it is possible to disperse the force acting on the brush from the foreign matter by adopting a configuration in which each hair is point-contacted with the outer peripheral surface of the movable body instead of being in surface contact with the outer peripheral surface of the movable body. Thus, there is an advantage that wear of a member (brush) for scraping off foreign matter can be reduced as compared with the dust seal of the conventional configuration. In addition, when a brush is used, there is less possibility of foreign matter being caught between the outer peripheral surface of the movable body, and even when foreign matter is attached to the outer peripheral surface of the movable body, the foreign matter is pressed against the outer peripheral surface of the movable body. There is an advantage that wear of the movable body can be suppressed.

  According to the configuration of the invention of claim 2, the detection coil is disposed in the housing, and the foreign matter attached to the outer peripheral surface of the movable body is scraped off by the brush so that the foreign matter does not enter the housing. Even when used in an environment where foreign substances are not easily attached, it is possible to prevent a decrease in detection accuracy due to the foreign substances.

  As shown in FIG. 1, the position sensor described in the present embodiment includes a cylindrical sensor main body 1 in which a detection coil 4 is housed, and a metal movable body 2 formed in a cylindrical shape. A part of the movable body 2 is inserted into the sensor body 1 in such a manner that the sensor body 1 and the center line in the axial direction coincide with each other. In the following description, the cylinder is assumed to be a cylinder, but the cross-sectional shape of the cylinder may be a polygonal shape in addition to a circular shape.

  In the present embodiment, the case where the movable body 2 is coupled to the movable portion 5 in the shock absorber of the automobile will be described. The position sensor is attached, for example, between the chassis and the rear wheel or the front wheel axle so as to be exposed below, or in the vicinity of the shock absorber.

  The sensor body 1 includes a pedestal 11 to which the detection coil 4 is attached and a cylindrical housing 12 that is integrally fixed to the pedestal 11 so as to surround the detection coil 4. The housing 12 and the detection coil 4 are disposed on one surface (the lower surface in FIG. 1) of the base 11.

  The detection coil 4 is a synthetic resin molded product in which a cylindrical core 42 formed of a magnetic material is embedded in a cylindrical coil bobbin 41, and a winding 43 is wound around the outer periphery of the coil bobbin 41. It has a configuration. One end of the coil bobbin 41 in the axial direction is integrally formed with a mounting piece 41a that abuts against the one surface of the pedestal 11, and a plurality of pieces (illustrated example) to which the end of the winding 43 is connected are attached to the mounting piece 41a. The two terminal pins 44 are fixed so as to penetrate through the attachment piece 41a.

  The pedestal 11 has a storage recess 11a on the back surface (upper surface in FIG. 1) of the surface (the one surface) to which the detection coil 4 is fixed, and a cover plate 13 is fitted to the opening surface of the storage recess 11a. The The circuit board 6 is housed on the inner bottom surface of the housing recess 11a. On the circuit board 6, circuit components constituting a circuit unit such as an oscillation circuit using the detection coil 4 as a resonance circuit and a detection circuit for detecting the output amplitude of the oscillation circuit are mounted.

  A mounting hole 41b is formed through the mounting piece 41a provided on the coil bobbin 41, and the fixed projection 11b protruding from the one surface of the base 11 is inserted into the mounting hole 41b, and the fixed projection 11b is heat caulked. Thus, the detection coil 4 is fixed to the base 11. Here, the center line of the housing 12 and the detection coil 4 are matched. The pedestal 11 is formed with a plurality (two in the illustrated example) of terminal holes 11c penetrating between the one surface and the inner bottom surface of the storage recess 11a, and each terminal pin 44 is inserted through each terminal hole 11c. One end is connected to each circuit board 6.

  On the other hand, the movable body 2 is fixed to a detection body 22 formed in a cylindrical shape with a metal such as aluminum, and one end of the detection body 22 (lower end in FIG. 1), and closes the one end of the detection body 22. And a coupling member 21. The detection body 22 is formed so that the outer diameter is smaller than the inner diameter of the housing 12 and the inner diameter is larger than the outer diameter of the portion where the winding 43 is wound in the detection coil 4. The other end of the detection body 22 is inserted into the housing 12 so as to freely advance and retract. That is, a part of the movable body 2 is inserted into the sensor body 1 so as to be able to advance and retract.

  As described above, the coupling member 21 is coupled to the movable part 5 of the shock absorber. In the illustrated example, the movable portion 5 is coupled to the movable body 2 by inserting the coupling protrusion 5 a provided on the movable portion 5 into the coupling hole 21 a provided on the coupling member 21. However, this coupling mode is an example.

  Therefore, if the movable part 5 moves in the vertical direction of FIG. 1, the amount of insertion of the movable body 2 into the housing 12 changes, so the amount of overlap between the detection body 22 and the detection coil 4 changes. Therefore, if the impedance equivalent amount of the detection coil 4 is detected by flowing a high-frequency current through the detection coil 4 by the oscillation circuit mounted on the circuit board 6 and detecting the oscillation amplitude of the oscillation circuit, the detection body 22 and the detection coil 4 Can be detected as a change in the impedance equivalent amount, and as a result, the displacement amount of the movable portion 5 can be detected.

  Incidentally, a brush having a bearing 7 that supports the detection body 22 and a flocked portion 31 that contacts the outer peripheral surface of the detection body 22 at an end portion (lower end portion in FIG. 1) of the housing 12 where the detection body 22 is inserted. 3 is attached.

  The bearing 7 is formed in an annular shape and is housed inside the end portion of the housing 12. A mounting notch 12 a for mounting the bearing 7 is formed on the inner peripheral surface of the end portion of the housing 12, and a portion where the mounting notch 12 a is formed is thinner than other portions of the housing 12. In a state where the bearing 7 is mounted in the mounting notch 12a, one end surface of the bearing 7 and one end surface of the housing 12 are flush with each other.

  The bearing 7 has a function of guiding the detection body 22 so as not to be shaken relative to the housing 12. Therefore, the cross-sectional shape of the inner peripheral surface of the bearing 7 matches the cross-sectional shape of the outer peripheral surface of the detection body 22. That is, the inner diameter of the bearing 7 is equal to the outer diameter of the detection body 22. In the present embodiment, the bearing 7 is made of a metal material such as brass, and a lubricant such as grease is applied to the inner peripheral surface so that the detection body 22 can move smoothly relative to the housing 12. It is desirable. However, the bearing 7 may be determined in consideration of the coefficient of friction with the housing 12, clearance, lubrication performance, hardness, compatibility with the material of the housing 12, and the like, and is not limited to a metal material.

  The brush 3 includes an attachment tube portion 32 attached to the outer peripheral surface of the housing 12 and a brush body 33 provided with a flocking portion 31 that are continuously integrated. The brush body 33 is formed in a shape in which a flocked portion 31 composed of a plurality of hairs is integrally provided on the inner peripheral surface of the cylindrical holding cylinder portion 34 over the entire circumference.

  The holding cylinder part 34 is composed of a pair of half holding cylinder parts made of a molded product having a shape obtained by dividing the holding cylinder part 34 by one plane including the central axis. The holding cylinder part 34 is formed by planting hair into a large number of flock holes formed in each half holding cylinder part and bonding the half holding cylinder parts with an adhesive or the like.

  The holding cylinder part 34 and the mounting cylinder part 32 have the same outer diameter, and the outer peripheral surfaces of both are continuous. The holding cylinder part 34 has an inner diameter smaller than that of the mounting cylinder part 32, and a step part 35 is formed on the inner peripheral surface of the holding cylinder part 34 and the mounting cylinder part 32. Further, the holding cylinder portion 34 is formed to have an inner diameter smaller than that of the housing 12. Therefore, when the brush 3 is attached to the housing 12, the stepped portion 35 abuts on one end surface (the lower end surface in FIG. 1) of the housing 12, and at this time, the bearing 7 is held by the mounting notch 12 a and the stepped portion 35. Will be.

  By the way, a retaining ring 23 is fixed to the outer peripheral surface of one end portion (upper end portion in FIG. 1) of the detection body 22 in a hook shape. The retaining ring 23 prevents the movable body 2 from falling off the sensor body 1. That is, since the outer diameter of the retaining ring 23 is larger than the inner diameter of the bearing 7 and the bearing 7 is held by the housing 12, the retaining ring 23 is moved to the bearing 7 when the detection body 22 moves downward with respect to the housing 12. The position in contact with is the lower limit position of the detection body 22.

  By the way, the inner diameter of the mounting cylinder portion 32 is equal to the outer diameter of the housing 12, and a plurality of engagement holes 32 a penetrating in the radial direction are provided in a part of the mounting cylinder portion 32. On the other hand, a plurality of engaging protrusions 12b that engage with the engaging holes 32a are provided on the outer peripheral surface of the housing 12, and the brush 3 is attached to the housing 12 from below in FIG. The brush 3 is attached to the housing 12 by engaging the engaging protrusion 12b with the housing 12.

  In a state where the brush 3 is mounted on the housing 12, the tip of the hair forming the flocked portion 31 contacts the outer peripheral surface of the detection body 22 over the entire circumference. The flocked portion 31 has a hardness capable of scraping off foreign matters such as mud adhering to the outer peripheral surface of the detection body 22 when the detection body 22 advances and retreats with respect to the housing 12.

  As apparent from the above description, when the movable body 2 moves relative to the sensor body 1, the flocked portion 31 comes into sliding contact with the outer peripheral surface of the detection body 22, so that the outer peripheral surface of the detection body 22 looks like mud. Even if extraneous foreign matter is adhered, it can be scraped off by the flocked portion 31, and the bearing 7 is prevented from being worn by the foreign matter adhered to the outer peripheral surface of the detection body 22. Moreover, since the flocked portion 31 is formed by a large number of hairs, even if a foreign matter is sandwiched between the flocked portion 31 and the outer surface of the detection body 22, the foreign matter from the gap between the hairs as the detection body 22 moves. Is often discharged.

  Furthermore, when the vertical positions of the sensor body 1 and the movable body 2 are in the relationship shown in FIG. 1, even if water enters the housing 12, the water is discharged through the bearing 7 and the flocked portion 31. It is possible to prevent water from staying inside the housing 12.

  By the way, when the dust seal 8 is used as in the conventional configuration, the inner space of the housing 12 is sealed with the dust seal 8, and it is difficult for water to be discharged once the housing 12 enters. In some cases, the position sensor is disassembled and water is discharged. On the other hand, in the configuration of the present embodiment, the possibility of water remaining in the housing 12 can be reduced.

  As described above, in the configuration of the present embodiment, the mud adhering to the outer peripheral surface of the detection body 22 is brought into sliding contact with the outer peripheral surface of the detection body 22 of the movable body 2 with the brush 3 having the hair transplanted portion 31 made of hair. Such a foreign matter is scraped off by the flocked portion 31, so that it is difficult to bite the foreign matter between the bearing 7 or the flocked portion 31 and the detection body 22. In addition, even if a foreign object enters between the flocked portion 31 and the detection body 22, it is swept out from the gap between the hairs, so that the possibility that the foreign object stays and damages the outer peripheral surface of the detection body 22 is reduced. Can do.

  In the present embodiment, the position sensor coupled to the shock absorber is exemplified, but the present invention is not limited to this.

  Moreover, in this embodiment, although the flocked part 31 is formed in the inner surface of the holding | maintenance cylinder part 34, it is not restricted to this, You may form the flocked part 31 separately. Specifically, a plate made of synthetic resin material or aluminum is formed with a large number of flocking holes to plant hair, a member is formed by bending the plate into a cylindrical shape with the bristles inside, and the member is held by a holding cylinder It may be mounted on the portion 34 and fixed in the end portion of the housing 12 together with the bearing 7.

It is a longitudinal cross-sectional view which shows embodiment. It is a longitudinal cross-sectional view which shows a conventional structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor main body 2 Movable body 3 Brush 4 Detection coil 5 Movable part (of shock absorber) 6 Circuit board 12 Housing

Claims (2)

  A sensor body that is formed in a cylindrical shape and includes a detection coil, a metal movable body that is movable in the axial direction of the sensor body and that is partially inserted into the sensor body, and a position change of the movable body A circuit unit for detecting the position of the movable body by detecting the impedance change of the corresponding detection coil, and the outer peripheral surface of the movable body, which is disposed at the site where the movable body is inserted in the sensor body, over the entire circumference. A position sensor comprising: a brush having hairs that come into contact therewith.   The sensor body includes a cylindrical housing and a detection coil disposed in the housing, and the movable body is formed in a cylindrical shape in which a part of the movable body is inserted into a space between the housing and the detection coil so as to freely advance and retract. The position sensor according to claim 1, wherein the position sensor is provided.

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