JP4525416B2 - Rotation detector - Google Patents

Description

  The present invention relates to a rotation detection device that is disposed in the vicinity of a rotating rotor (detected object) and detects a rotation state of the rotor by a change in a bias magnetic field.

  For example, Japanese Patent Laid-Open No. 7-260813 (Patent Document 1) discloses a rotation detection device (magnetic detection device) that is arranged in the vicinity of a rotating rotor (detected body) and detects the rotation state of the rotor by a change in bias magnetic field. ).

  3A to 3C show a conventional rotation detection device (magnetic detection device) disclosed in Patent Document 1. FIG. FIG. 3A is an overall configuration diagram showing the gear-shaped magnetic rotor 1 to be detected and the rotation detection device 90. The rotation detection device 90 is arranged to face the magnetic rotor 1 at a predetermined interval as shown in the figure, and the rotation state of the magnetic rotor 1 connected to the rotation body (not shown) is represented by the rotation detection device 90 and the magnetic material. Detection is performed by a magnetic field change between the rotors 1.

  The rotation detection device 90 includes a cylindrical resin housing 3, and a columnar (permanent) magnet 4 is disposed on the front end surface of the housing 3. The magnet 4 generates a bias magnetic field toward the magnetic rotor 1. Further, a cap 5 having a covered cylindrical shape is attached to the housing 3 by caulking so as to cover the distal end surface and outer peripheral portion of the magnet 4 and the outer peripheral portion on the distal end side of the housing 3. The cap 5 is made of stainless steel (SUS304), which is a nonmagnetic material having a thickness of 0.25 mm. By this cap 5, the front end surface of the housing 3 and the magnet 4 are in contact.

  Further, a concave portion 6 is formed on the tip surface of the magnet 4 in FIG. 3A, and a through hole 7 linearly extending in the left and right directions in the drawing is formed in the central portion of the magnet 4. The right end of the through hole 7 opens at the bottom of the recess 6. Further, a tapered portion 8 that is wider toward the opening side is formed at the left end opening portion of the through hole 7 of the magnet 4.

  A magnetic detection sensor (mold IC) 9 in which a magnetic detection element (IC chip) 10 such as a magnetoresistive element (MRE) is molded is inserted into the through hole 7 of the magnet 4. Specifically, in the magnetic detection sensor 9, a magnetic detection element 10 is mounted on a copper lead frame 11. A part of the lead frame 11 and the magnetic detection element 10 are molded with a molding material 12 as an insulating resin material (an epoxy resin in this embodiment). That is, the magnetic detection element 10 is located in the recess 6 of the magnet 4, and the lead frame 11 is exposed from the left end surface of the mold material 12 that penetrates the through hole 7.

  Further, a partition 13 that divides the interior into left and right is formed in the cylindrical housing 3, and an external terminal (terminal) 14 made of brass is inserted through the partition 13. The external terminal 14 includes an output terminal, a ground (GND) terminal, a power supply terminal, and the like. And the front-end | tip part of the external terminal 14 and the front-end | tip part of the lead frame 11 are connected and fixed by welding.

  FIGS. 3B and 3C are a plan view and a side view showing a part of the magnetic detection sensor (mold IC) 9 with a part thereof broken.

The lead frame 11 shown in FIG. 3B includes a lead terminal 17, an island 15 made of a flat portion, and a tie bar 16 that holds the island 15. A magnetic detection element (IC chip) 10 is mounted on the island 15 and fixed by an epoxy-based conductive adhesive (Ag paste) containing Ag powder. Further, the lead terminal 17 of the lead frame 11 and the electrode on the chip are connected by wire bonding.
JP-A-7-260813

  The conventional rotation detection device 90 shown in FIG. 3A has a structure in which the magnet 4 is sandwiched between the housing 3 and the cap 5, and the detection sensitivity can be increased by bringing the magnet 4 and the magnetic rotor 11 closest to each other. it can. However, since the housing 3 and the cap 5 are fixed by caulking, the assembling positions of the magnet 4 and the mold IC 9 (and hence the IC chip 10) change due to variation of caulking stress and deterioration of the caulking portion with time, resulting in characteristic variation. It is easy to generate. In addition, in the structure of the rotation detection device 90 in FIG. 3A, the magnetic detection element (IC chip) 10 needs to be molded as shown in the figure for protection, but the molding material 12 improves sensitivity. It is an obstruction factor.

  Therefore, the present invention is a rotation detection device that detects a rotation state of a detected object by measuring a change in a bias magnetic field accompanying the rotation of the detected object by a magnetic detection element, and is a bare chip-state magnetism that is not resin-molded. An object of the present invention is to provide a high-sensitivity and high-accuracy rotation detection device in which the assembly position of a magnet and a magnetic detection element is difficult to change using the detection element.

  According to the first aspect of the present invention, the magnet for generating the bias magnetic field and the magnetic detection element mounted on the holding part are inserted and arranged in a cylindrical housing with one end closed, A rotation detection device for detecting a rotation state of the detected object by measuring a change in the bias magnetic field accompanying rotation with the magnetic detection element, wherein the magnetic detection element is mounted on the holding unit in a bare chip state. The holding portion is inserted into an opening at the other end of the housing and connected to a front end surface of a cylindrical cap portion that covers the opening, and the magnet is closed on the housing. An end portion and a tip of the cap portion are fixed in contact with each other, and a predetermined portion of a cylindrical inner peripheral surface of the housing and a columnar outer peripheral surface of the cap portion is laser-welded.

  In the above rotation detection device, since the magnetic detection element in a bare chip state is mounted on the holding portion, the rotation detection device has higher sensitivity than a rotation detection device using a conventional resin-molded magnetic detection sensor. it can. In addition, a holding unit on which the magnetic detection element is mounted is coupled to the front end surface of the cap unit, and a magnet for generating a bias magnetic field is fixed in contact with the front end of the same cap unit and the closed end of the housing. For this reason, the relative position of a magnetic detection element and a magnet does not change in an assembly. Further, since the housing and the cap portion are laser-welded, residual stress is unlikely to occur and change with time is unlikely to occur. As described above, the rotation detection device can be a rotation detection device with high sensitivity and high accuracy.

  According to a second aspect of the present invention, in the rotation detection device, a ring-shaped protrusion is formed on the outer periphery of the column of the cap, and the protrusion is press-fitted into the cylinder of the housing. It is preferable that the ring outer peripheral surface is laser-welded to the cylindrical inner peripheral surface of the housing.

  Providing the protrusions that are press-fitted into the housing on the outer circumference of the cylinder of the cap part eliminates the gap between the housing and the cap part during assembly and laser welding, and the fixing position accuracy between the housing and the cap part (therefore, the magnetic sensing element and the magnet (Fixed position accuracy) is improved. In addition, since there is no gap between the housing and the cap portion on the ring outer peripheral surface of the protruding portion which is a laser welded portion, the reliability of laser welding can be improved. In addition, since the vicinity of the ring outer peripheral surface of the protruding portion where residual stress is generated by press fitting is melted and relaxed during laser welding, deterioration over time can be suppressed as compared with conventional fixing by caulking.

  According to a third aspect of the present invention, in the rotation detection device, the vicinity of the opening at the other end of the housing is preferably formed in a bowl-like thickness.

  This makes it easy to obtain the roundness during processing of the housing, and when the cap portion is press-fitted, the thickness with respect to the direction of stress generation is increased, so that the occurrence of cracks can be suppressed.

  When the housing and the cap portion are made of a resin material, the laser transmittance of the resin material constituting the housing is larger than the laser transmittance of the resin material constituting the cap portion. preferable.

  Thereby, when laser welding the inner peripheral surface of the cylinder of the housing and the outer peripheral surface of the cylinder of the cap portion, the laser can be irradiated and welded from the outside of the cylinder of the housing, so that a uniform weld portion can be easily obtained. .

  The resin material is, for example, a resin material constituting the housing and a resin material constituting the cap portion made of PPS (polyphenylene sulfide) resin, and the resin material constituting the cap portion is, as described in claim 5, for example. As compared with the resin material constituting the housing, it can be constituted so as to contain more carbon.

  According to this, since the cap part contains a lot of carbon, the laser transmittance of the housing becomes larger than that of the cap part, and laser irradiation from the outside of the cylinder of the housing becomes possible. Further, since the housing and the cap part are made of the same PPS resin, it is possible to obtain a strong welded part. In addition, it is possible to optimize the thickness of a laser welding part etc. by setting suitably the carbon content rate of the housing and cap part which consist of PPS resins.

  Preferably, the holding portion and the cap portion are integrally formed. Thereby, the manufacturing cost is reduced, and an error factor associated with the connection between the holding portion and the cap portion is eliminated, and the relative positional accuracy of the magnetic detection element with respect to the magnet can be increased.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a rotation detection device 100 of the present invention.

  A rotation detection device 100 shown in FIG. 1 detects a rotation state of the rotor 1 by measuring a change in a bias magnetic field associated with rotation of a rotor (detected body) 1 made of a magnetic material with a magnetic detection element 30.

  Unlike the magnetic detection sensor (mold IC) 9 in the rotation detection device 90 in FIG. 3A, the magnetic detection element 30 in the rotation detection device 100 in FIG. 1 is mounted on the holding unit 50h in a bare chip state that is not resin-molded. Is done. In FIG. 1, for the sake of simplicity, illustration of lead wires and wiring boards around the magnetic detection element 30 is omitted.

  In the rotation detection device 100 of FIG. 1, a (permanent) magnet 20 that generates a bias magnetic field and a magnetic detection element 30 mounted on a holding portion 50h are inserted into a cylindrical housing 40 having one end closed. Has been placed. The opening at the other end of the housing 40 is covered with a cap portion 50c formed in a columnar shape, and the magnet 20 is fixed in contact with one closed end of the housing 40 and the tip of the cap portion 50c. Yes. 3A, the container in which the magnet 4 is inserted is used as the cap 5. In the rotation detection apparatus 100 in FIG. 1, the container in which the magnet 20 is inserted is used as the housing 40. For example, a PPS (polyphenylene sulfide) resin material can be used for the housing 40 and the cap portion 50c in the rotation detection device 100 of FIG. Predetermined portions of the cylindrical inner peripheral surface of the housing 40 and the cylindrical outer peripheral surface of the cap portion 50c are laser welded to form a weld portion 60.

  In the rotation detection device 100 of FIG. 1, since the magnetic detection element 30 in a bare chip state is mounted on the holding portion 50h, compared to the rotation detection device 90 using the conventional resin-molded magnetic detection sensor 9 of FIG. Thus, a rotation detection device having high sensitivity can be obtained. 1 is mounted on the holding portion 50h in a bare chip state, the rotation detection device 100 of FIG. 1 is compared with the rotation detection device 90 using the resin-detected magnetic detection sensor 9 of FIG. Thus, the overall diameter can be reduced, and a small rotation detection device can be obtained.

  In the rotation detection device 100 of FIG. 1, the holding portion 50 h on which the magnetic detection element 30 is mounted is connected to the tip surface of the cap portion 50 c, and the magnet 20 that generates a bias magnetic field is connected to the tip of the same cap portion 50 c and the housing 40. Fixed in contact with the closed end. For this reason, the relative positional relationship between the magnetic detection element 30 and the magnet 20 is determined by the mounting position of the magnetic detection element 30 on the holding portion 50h, and does not change during assembly. Further, since the housing 40 and the cap portion 50c are laser-welded, residual stress is unlikely to occur and change with time is unlikely to occur. Accordingly, the rotation detection device 100 of FIG. 1 can be a rotation detection device having high sensitivity and high accuracy.

  FIG. 2 is a cross-sectional view for each process showing the method of manufacturing the rotation detecting device 100 of FIG.

  FIG. 2A is a diagram illustrating a state before assembling of each component constituting the rotation detection device 100.

  The holding part 50h on which the magnetic detection element 30 is mounted is formed integrally with the cap part 50c. The holding part 50h and the cap part 50c may be formed as separate bodies, and the holding part 50h may be connected to the distal end surface of the cap part 50c, but it is preferable to form them integrally. As a result, the manufacturing cost is reduced, and an error factor associated with the connection between the holding portion 50 h and the cap portion 50 c is eliminated, and the relative positional accuracy of the magnetic detection element 30 with respect to the magnet 20 can be increased.

  Further, a ring-shaped protrusion 50t is formed on the outer periphery of the cylinder of the cap 50c. The protrusion 50t is press-fitted into the cylinder of the housing 40 at the time of assembly.

  The cylindrical housing 40 with one end closed is formed with a flange 40t near the opening at the other end, and the vicinity of the opening of the cylinder is thicker than that near the center. As a result, the roundness during the processing of the housing 40 can be easily obtained, and when the cap portion 50c shown below is press-fitted, the thickness with respect to the stress generation direction is increased, so that the occurrence of cracks is suppressed.

  When the housing 40 and the cap portion 50c are made of a resin material, it is preferable that the laser transmittance of the resin material constituting the housing 40 is larger than the laser transmittance of the resin material constituting the cap portion 50c. 2C, which will be described later, when laser welding is performed on the cylindrical inner peripheral surface of the housing 40 and the cylindrical outer peripheral surface of the cap portion 50c, the laser is irradiated from the outside of the cylinder of the housing 40 to be welded. And a uniform weld 60 can be obtained easily.

  For example, the resin material constituting the housing 40 and the resin material constituting the cap portion 50 c are the same PPS (polyphenylene sulfide) resin, and the PPS resin resin constituting the cap portion 50 c is compared with the PPS resin constituting the housing 40. It is configured to contain a lot of carbon. Thereby, since the cap part 50c contains much carbon and it is easy to absorb a laser, the laser transmittance of the housing 40 becomes larger than the cap part 50c, and the laser irradiation from the cylinder outside of the housing 40 described above becomes possible. Moreover, since the housing 40 and the cap part 50c consist of the same PPS resin, it is possible to obtain the strong weld part 60. In addition, it is possible to optimize the thickness etc. of the laser welding part 60 by setting the carbon content rate of the housing 40 and the cap part 50c which consist of PPS resin suitably.

  FIG. 2B is a view showing a state after the cap portion 50 c formed with the protrusion 50 t is press-fitted into the cylinder of the housing 40 and the magnet 20 and the magnetic detection element 30 are assembled.

  As described above, the protrusion 50t that is press-fitted into the housing 40 is provided on the outer periphery of the cylinder of the cap 50c, so that there is no gap between the housing 40 and the cap 50c during assembly. For this reason, the fixed position accuracy of the housing 40 and the cap portion 50c (therefore, the fixed position accuracy of the magnetic detection element 30 and the magnet 20) is improved.

  FIG. 2C is a view showing a state in which the ring outer peripheral surface of the protrusion 50t and the cylindrical inner peripheral surface of the housing 40 are laser-welded.

  When laser welding PPS resins together, in order to ensure the reliability of the welded portion, it is necessary to perform laser welding with at least the gap between both being within several tens of μm. With the above-described press-fitting, the gap between the housing 40 and the cap portion 50c is eliminated on the ring outer peripheral surface of the projection 50t, which is the laser welding portion, in the state after assembly in FIG. Can be increased. Further, in the welded portion 60, the vicinity of the ring outer peripheral surface of the protrusion 50t where residual stress is generated by press-fitting is melted and relaxed during laser irradiation, and thus is adopted in the rotation detection device 90 of FIG. As compared with the conventional fixing by caulking, deterioration with time can be suppressed.

  As described above, the rotation detection device 100 in FIG. 1 measures the change in the bias magnetic field associated with the rotation of the rotor 1 that is the object to be detected by the magnetic detection element 30 and detects the rotation state of the rotor 1. This is a device that uses a bare chip state magnetic detection element 30 that is not resin-molded, and is a highly sensitive and highly accurate rotation detection apparatus in which the assembly position of the magnet 20 and the magnetic detection element 30 is unlikely to change. .

It is typical sectional drawing of the rotation detection apparatus 100 of this invention. FIGS. 2A and 2B are cross-sectional views showing the manufacturing method of the rotation detection device 100 in FIG. 1, in which FIG. 1A is a view showing a state before assembling each component constituting the rotation detection device 100, and FIG. (C) is a figure which shows the mode at the time of laser welding. It is a figure which shows the conventional rotation detection apparatus, (a) is a whole block diagram which shows the magnetic body rotor 1 and the rotation detection apparatus 90 which are to-be-detected objects, (b), (c) is a magnetic detection sensor ( The mold IC) is a plan view and a side view showing a part by breaking a part thereof.

Explanation of symbols

90,100 Rotation detection device 1 Rotor (Detected object)
20 (permanent) magnet 30 magnetic detection element 40 housing 40t hook-shaped part 50c cap part 50h holding part 50t projection part 60 welding part

Claims (6)

A magnet that generates a bias magnetic field and a magnetic detection element mounted on the holding unit are inserted and disposed in a cylindrical housing with one end closed,
A rotation detecting device that detects a rotation state of the detected object by measuring a change in the bias magnetic field accompanying the rotation of the detected object with the magnetic detection element,
The magnetic detection element is mounted on the holding unit in a bare chip state,
The holding portion is inserted into an opening at the other end of the housing, and is connected to a front end surface of a cap portion formed in a column shape covering the opening,
The magnet is fixed in contact with the closed end of the housing and the tip of the cap;
A rotation detecting device, wherein predetermined portions of a cylindrical inner peripheral surface of the housing and a cylindrical outer peripheral surface of the cap portion are laser-welded. A ring-shaped protrusion is formed on the outer periphery of the cylinder of the cap,
The protrusion is press-fitted into the cylinder of the housing;
The rotation detection device according to claim 1, wherein a ring outer peripheral surface of the protrusion is laser welded to a cylindrical inner peripheral surface of the housing.   The rotation detection device according to claim 1, wherein the vicinity of the opening at the other end of the housing is formed in a bowl shape and is thick.   The housing and the cap portion are made of a resin material, and the laser transmittance of the resin material constituting the housing is larger than the laser transmittance of the resin material constituting the cap portion. The rotation detection device according to item. The resin material constituting the housing and the resin material constituting the cap portion are made of PPS (polyphenylene sulfide) resin,
The rotation detection device according to claim 4, wherein the resin material constituting the cap portion contains more carbon than the resin material constituting the housing.   The rotation detecting device according to any one of claims 1 to 5, wherein the holding portion and the cap portion are integrally formed.

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