JP2010185853A - Position detection sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To readily detect the accurate moving position of a detection object, without requiring a complicated work for detecting accurately the moving position of the detection object. <P>SOLUTION: A position detection sensor 1 includes a fixed magnet 71 fixed to a support; a movable magnet 72 provided to the detection object 4, and moving following movement of the detection object; and a sensor part 76, provided between the fixed magnet 71 and the movable magnet 72 for detecting the position of the movable magnet 71, based on the change in the magnetoresistance caused by a change of a magnetic field angle from the fixed magnet 71 to the movable magnet 72. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a position detection sensor that detects the position of a moving detection object.

  Conventionally, as this type of position detection sensor, a linear position detection sensor that detects the position of a detection target by changing the strength of a magnetic field is known (see Patent Document 1). In this linear type position detection sensor, a rectangular magnet, a magnetic plate provided on the magnet and formed so as to have different widths in the short direction of the magnet, and a hall element having a longitudinal direction on the magnetic plate are provided. A sensor assembly that can move in the direction, and the output of the Hall element that moves on the magnetic plate changes with the strength of the magnetic field, thereby detecting the moving position of the sensor assembly relative to the magnetic plate.

JP 05-264326 A

  However, in the conventional position detection sensor, since the Hall element has a structure for reading the magnetic flux density, if there is a mechanical dimensional error in the magnetic plate, the change in the magnetic flux density is affected, and the output of the Hall element fluctuates. Easy structure. Therefore, in order to accurately detect the movement position of the sensor assembly that is the detection target, the dimensional accuracy of the magnetic plate corresponding to the stable magnetic flux density for each position is required. There was a problem that could not be detected easily.

  The present invention has been made in view of such a point, and can easily detect an accurate movement position of a detection object without requiring a complicated operation for accurately detecting the movement position of the detection object. An object of the present invention is to provide a position detection sensor capable of

  The position detection sensor of the present invention is provided between a fixed magnet fixed to a support, a movable magnet that is provided on a detection target and moves with the movement of the detection target, and the fixed magnet and the movable magnet. And a sensor unit that detects a position of the movable magnet based on a change in magnetic resistance caused by a change in magnetic field angle from the fixed magnet to the movable magnet.

  According to this configuration, since the sensor unit detects the position of the movable magnet based on the change in magnetic resistance due to the change in the magnetic field angle from the fixed magnet to the movable magnet, the movable magnet is provided via the position of the movable magnet. The position of the detected object can be detected. For this reason, it is possible to easily detect the movement position of the detection object without requiring a complicated operation for accurately detecting the movement position of the detection object as in the prior art.

  The present invention is characterized in that, in the position detection sensor, the length of the movable magnet in the moving direction is relatively longer than the length of the fixed magnet in the moving direction.

  According to this configuration, in order to further ensure the linearity of position detection (linearity), the positional relationship between the fixed magnet and the movable magnet can be detected linearly at a longer distance as a change in the magnetic field angle. became.

  In the position detection sensor according to the present invention, the length of the movable magnet in the moving direction is approximately 3 to approximately 5 times the length of the fixed magnet.

  ADVANTAGE OF THE INVENTION According to this invention, the exact movement position of a detection target object can be detected easily, without requiring the complicated operation | work for detecting the movement position of a detection target object correctly.

It is a disassembled perspective view which shows the position detection sensor which concerns on the 1st Embodiment of this invention. It is a perspective view which shows the principal part of the position detection sensor which concerns on this Embodiment. It is sectional drawing which showed typically the position detection sensor which concerns on this Embodiment. It is the top view which showed typically the position detection sensor which concerns on this Embodiment. It is sectional drawing which showed typically the position detection sensor which concerns on this Embodiment. It is sectional drawing which showed typically the position detection sensor which concerns on the 2nd Embodiment of this invention. It is the figure which showed the simulation result of the output and stroke length of the position detection sensor which concerns on a comparative example and this Embodiment. It is the figure which showed the simulation result of the magnetic field rotation angle and stroke length of the position detection sensor which concerns on a comparative example and this Embodiment.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The position detection sensor according to the embodiment of the present invention is a sensor that detects the position of a moving detection object. For example, in an automobile engine, an intake and exhaust air flow rate is adjusted according to the moving speed of a piston and the flow rate of intake and exhaust air. This is used for a variable valve timing (VVT) mechanism for controlling the opening / closing timing of the exhaust valve. Hereinafter, a case where the position detection sensor according to the embodiment of the present invention is used in a variable valve mechanism will be described as an example.

(First embodiment)
FIG. 1 is an exploded perspective view showing a position detection sensor according to an embodiment of the present invention. FIG. 2 is a perspective view showing the periphery of the sensor unit of the position detection sensor. FIG. 3 is a cross-sectional view showing the position detection sensor viewed from the front side. FIG. 4 is a view schematically showing a state in which the periphery of the sensor unit of the position detection sensor is viewed from the upper surface side. For convenience of explanation, FIG. 2 shows a part of the upper surface of the position detection sensor omitted. Hereinafter, description will be made assuming that front and rear, left and right, and top and bottom follow the directions shown in FIG.

  As shown in FIG. 1, the position detection sensor 1 according to the present embodiment includes a case 2 whose bottom surface is opened, and a lid 3 that is attached to the opening of the case 2 and forms a housing portion. And the lid 3 are combined to form a substantially cylindrical box-like body. A movable body 4, a sensor unit 7 and a sensor unit support body 8 which will be described later are housed in a housing portion formed by the case 2 and the lid 3.

  An opening 2a is formed at a substantially central position on the upper surface of the case 2, and the shaft 4a of the movable body 4 is inserted through the opening 2a. Further, a pair of spring holding portions 2b, 2b for holding a pair of springs 5 to be described later are provided on the inner peripheral surface of the case 2 so as to face each other (FIG. 2). A recess is formed on the upper surface of the lid 3, and a circuit board 6 for signal processing is accommodated in the recess. The signal processing circuit board 6 is connected to an engine control unit (ECU) (not shown).

  The movable body 4 is an object to be detected by the position detection sensor 1, and has a substantially cylindrical shaft 4a protruding upward, a shaft support portion 4b that supports the shaft 4a, and one end portion of the shaft support portion 4b. The housing case 4c is integrally formed with the housing case 4c.

  The shaft 4a is inserted into the opening 2a of the case 2 and is configured to reciprocate up and down by driving an intake or exhaust valve (not shown). The shaft support 4b is formed of a substantially rectangular plate-like member extending in the front-rear direction. A shaft 4a is provided at the center of the upper surface of the plate-like member, and a pair of protruding portions 4d protruding downward are formed at both ends of the back surface. One end of a pair of springs 5 that urge the movable body 4 and the sensor unit support body 8 is engaged with the pair of protrusions 4d.

  The housing case 4c is formed in a substantially rectangular box-like body in which the inner part and a part of the outer part of the case 2 are opened, and the movable side magnet (movable magnet) 72 is partially exposed to the outside. Is housed in. The housing case 4c is configured to be guided by a guide portion 8c provided on the sensor unit support 8. The housing case 4c is guided by the guide portion 8c as the shaft 4a reciprocates, and the movable magnet 72 is moved. It reciprocates in the case 2.

  The sensor unit 7 includes a fixed magnet 71 fixed to the sensor unit support 8, a movable magnet 72 that moves as the movable body 4 moves at a position facing the fixed magnet 71, and a magnetoresistive element (GMR sensor). And a protective plate 74 that protects the fixed magnet 71 and the movable magnet 72.

  The fixed magnet 71 is formed in a substantially rectangular parallelepiped shape, and is fixed to one end side of the sensor unit support 8 in a state where it is positioned vertically (FIG. 5). The movable magnet 72 is formed in a substantially rectangular shape, and is attached to a housing case 4 c provided on the other end side of the sensor unit support 8. The surface of the fixed magnet 71 facing the movable magnet 72 is magnetized to the N pole, and the surface of the movable magnet 72 facing the fixed magnet 71 is magnetized to the S pole. Therefore, a magnetic field is formed in the housing portion of the case 2 so that a magnetic flux flows from the fixed magnet 71 to the movable magnet 72 in the direction indicated by the arrow (FIG. 4).

  The magnetic detection member 73 is provided at a substantially intermediate position between the fixed magnet 71 and the movable magnet 72, and has a L-shaped substrate 75 in front view, a magnetoresistive effect element 76 attached to the substrate 75, and a plurality of connection terminals 77. , Is composed of.

  The substrate 75 is attached to the support portion main body 8 b of the sensor unit support 8 with both mounting portions of the magnetoresistive effect element 76 facing the front surface. The plurality of connection terminals 77 are attached below the substrate 75 and pass through the support plate portion 8a of the sensor unit support 8 and are connected to the circuit board 6 (FIG. 3).

  The magnetoresistive effect element 76 is mounted on the mounting surface of the substrate 75 between the fixed magnet 71 and the movable magnet 72 and at a position affected by the flow of magnetic flux between the fixed magnet 71 and the movable magnet 72. (FIGS. 4 and 5). The magnetoresistive effect element 76 is configured such that the electric resistance value changes according to the influence of the acting magnetic flux direction.

  Here, the magnetoresistive effect element 76 will be briefly described. The magnetoresistive effect element 76 is a GMR element using a giant magnetoresistive effect (GMR effect), and is formed on the substrate from the bottom in an insulating layer, an underlayer, an antiferromagnetic layer, a fixed magnetic layer, a nonmagnetic intermediate layer, and a free magnetic layer. The layers and the protective layer are formed in this order using a thin film process. Since the antiferromagnetic layer and the pinned magnetic layer are formed in contact with each other, an exchange coupling magnetic field is generated at the interface between the two magnetic layers by heat treatment in a magnetic field, and the magnetization direction of the pinned magnetic layer is fixed in one direction. . On the other hand, unlike the pinned magnetic layer, the magnetization direction of the free magnetic layer is not fixed, and is configured to change in magnetization due to a change in the penetration direction of the external magnetic field.

  Therefore, when the magnetoresistive effect element 76 is affected by the magnetic flux that flows from the fixed magnet 71 to the movable magnet 72, the angle (magnetic field angle) of the magnetization direction of the free magnetic layer with respect to the magnetization direction of the fixed magnetic layer changes. The electric resistance value changes based on the change in the magnetic field angle. Based on the output signal based on the electric resistance value corresponding to the change in the magnetic field angle, the moving position of the movable magnet 72 that moves with the movement of the movable body 4 (that is, the movement position of the movable body 4) can be detected. The output signal detected by the magnetoresistive effect element 76 is output to the circuit board 6 via the connection terminal 77 of the board 75 and is output to an ECU (not shown).

  The protection plate 74 is formed in a substantially U shape in plan view, and is attached to the sensor unit support 8 so as to cover the outer surfaces of the fixed magnet 71 and the movable magnet 72 and the back side of the substrate 75. The protection plate 74 is made of a metal material and functions as a back yoke for returning the magnetic flux that flows from the fixed magnet 71 toward the movable magnet 72 to the fixed magnet 71 side again (FIG. 4). That is, the fixed magnet 71, the movable magnet 72, and the protection plate 74 function as a magnetic circuit. Therefore, the magnetic flux flowing from the movable magnet 72 is transmitted to the side plate portion 74b via the side plate portion 74a, and the magnetic field from the side plate portion 74b to the movable magnet 72 can be stabilized. The side plate portion 74a that covers the movable magnet 72 of the protection plate 74 is formed larger than the side plate portion 74b that covers the fixed magnet 71, and is configured to cover the outer portion of the guide portion 8c. Thereby, even when the storage case 4c to which the movable magnet 72 is attached is guided up and down by being guided by the guide portion 8c, the magnetic field received by the movable magnet 72 can be transmitted to the fixed magnet 71 via the side plate portions 74a and 74b. become. On the other hand, a protrusion 74c is formed on the inner surface of the side plate portion 74b covering the fixed magnet 71, and the upper surface side of the fixed magnet 71 is positioned by the protrusion 74c (FIG. 5).

  The sensor unit support 8 includes a support plate portion 8a formed in substantially the same shape as the lid 3 in a top view, a support portion main body 8b erected from the substantially center of the support plate portion 8a, and side portions of the support portion main body 8b. The guide part 8c provided in the.

  The support plate portion 8 a is accommodated in the case 2 so that the circuit board 6 is sandwiched between the support plate portion 8 a and the lid body 3. A pair of projecting portions 8d and 8d are formed on the upper surface of the support plate portion 8a so as to project upward with the support portion main body 8b interposed therebetween. The other ends of the pair of springs 5 are locked to the protrusions 8d. A protective plate holding portion 8e for holding the protective plate 74 is formed on the back surface side of the guide portion 8c and the support portion main body 8b and on the upper surface of the support plate portion 8a (FIG. 3).

  The support portion main body 8b is formed in a substantially box-like body that opens upward, and is provided with partition walls 8f and 8g that partition the inside of the box-like body in the left-right direction (FIG. 4). Both ends of the substrate 75 are attached to the partition walls 8f and 8g, respectively, and the substrate 75 is fixed to the support body 8b. A fixed magnet support portion 8i that supports the fixed magnet 71 from below is formed between the side wall of the support portion main body 8b facing the side where the guide portion 8c is provided and the partition wall 8f (see FIG. 5). The fixed magnet 71 is mounted on the fixed magnet support portion 8i and is fixed to the support portion main body 8b in a state where the fixed magnet 71 is positioned on the protrusion 74c formed on the side plate portion 74b of the protection plate 74. Further, a notch portion 8j for attaching the protection plate 74 is formed outside the fixed position of the fixed magnet 71 of the support portion main body 8b. The protection plate 74 is attached to the protection plate holding portion 8e and the cutout portion 8j, and is fixed to the sensor unit support 8 (FIG. 3).

  The guide portion 8c is formed of a pair of guide plates 8k and 8k that are erected on the upper surface of the support plate portion 8a. The housing case 4c is housed in a space formed by the inner side of the guide plates 8k, 8k, the side wall 8h of the support body 8b, and the side plate 74a of the protective plate 74, and the housing case 4c is guided to move up and down. ing.

  In the position detection sensor 1 configured as described above, the circuit board 6 is accommodated in the concave portion of the lid 3, the fixed magnet 71 is placed on the support body 8b, and the magnetoresistive effect element 76 is placed inside the support body 8b. Is mounted. At this time, the connection terminal 77 attached to the board 75 is connected to the circuit board 6 via the support plate portion 8a. When the fixed magnet 71 and the substrate 75 are attached to the support portion main body 8b, the protective plate 74 is attached to the guide portion 8c and the support portion main body 8b so as to cover the opening portion of the guide portion 8c and the fixed magnet 71. The movable body 4 having the movable magnet 72 attached to the housing case 4c is attached to the sensor unit support 8 while being urged by the pair of springs 5, and the case 2 is attached to the lid 3 to detect the position. 1 is assembled.

  Next, the effect | action of the position detection sensor 1 which concerns on this Embodiment is demonstrated using FIG.4 and FIG.5. FIG. 5 is a cross-sectional view schematically showing the position detection sensor 1 according to the present embodiment from the front side. Here, the position P1 of the movable magnet 72 in FIG. 5 will be described as the initial position. In FIG. 5, for convenience of explanation, some constituent members such as the spring 5 are omitted.

  At the initial position P1 shown in FIG. 5, the magnetic flux from the fixed magnet 71 to the movable magnet 72 flows in the direction indicated by the arrow A. When the shaft 4a moves upward in the case 2 by driving an intake or exhaust valve (not shown), the movable magnet 72 attached to the housing case 4c is also moved to the position P2. At this time, as the movable magnet 72 moves upward, the magnetic flux from the fixed magnet 71 to the movable magnet 72 changes in the direction indicated by the arrow B, and the magnetic field in the case 2 changes. When the magnetoresistive effect element 76 is affected by the change in the magnetic field, the magnetic field angle changes, the electric resistance value changes based on the change in the magnetic field angle, and an output signal based on the changed electric resistance value is output. Thereby, the movement position of the movable body 4 which is a detection target can be detected via the movement position P2 of the movable magnet 72. Similarly, when the shaft 4a moves downward in the case 2, the movable magnet 72 moves to the position P3 accordingly. At this time, as the movable magnet 72 moves downward, the magnetic flux from the fixed magnet 71 to the movable magnet 72 changes in the direction indicated by the arrow C, and the magnetic field in the case 2 changes. When the magnetoresistive effect element 76 is affected by the change of the magnetic field, the magnetic field angle changes, and an output signal based on the changed electric resistance value is output.

  As described above, according to the position detection sensor 1 of the present embodiment, the magnetoresistive element 76 detects the position of the movable magnet 72 based on the change in the magnetic resistance due to the change in the magnetic field angle from the fixed magnet 71 to the movable magnet 72. Therefore, the position of the movable body 4 that is the detection target can be detected via the position of the movable magnet 72. For this reason, it is possible to easily detect the movement position of the detection object without requiring a complicated operation for accurately detecting the movement position of the detection object as in the prior art.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The position detection sensor 1 according to the second embodiment of the present invention has a length of the fixed magnet and the movable magnet in the stroke direction of the movable body 4 as compared with the position detection sensor 1 according to the first embodiment described above. Only the difference. Therefore, only differences will be described in particular, and the same reference numerals are used for the same components, and repeated descriptions are omitted.

  FIG. 6 is a cross-sectional view schematically showing the configuration of the position detection sensor 1a according to the second embodiment of the present invention. In FIG. 6, for convenience of explanation, some constituent members such as the spring 5 are omitted.

  The position detection sensor 1a shown in FIG. 6 is configured such that the length of the movable magnet 72a in the moving direction is relatively longer than the length of the fixed magnet 71a in the moving direction. The length of the movable magnet 72a in the moving direction is preferably about 3 to about 5 times the length of the fixed magnet 71a. In the position detection sensor 1a of the present embodiment, the length L1 of the fixed magnet 71a is 2 mm, the length L2 of the movable magnet 72a is 8 mm, and the length of the movable magnet 72a is four times the length of the fixed magnet 71a. It is configured as. Thereby, in order to further secure the linearity of position detection, the magnetic field between the fixed magnet 71a and the movable magnet 72a can be changed. In FIG. 6, L3 indicates the moving distance (stroke length) of the center position of the movable magnet 72a in the moving direction.

  Next, using FIG. 7 and FIG. 8, the output of the position detection sensor 1a and the magnetic field rotation angle (magnetic field angle) and the moving (stroke) distance of the movable magnet are compared with the comparative example. The simulation result will be described. FIG. 7 is a diagram showing a simulation result of the output and the stroke length of the position detection sensor according to the comparative example and the present embodiment. FIG. 8 is a diagram illustrating a simulation result of the magnetic field rotation angle and the stroke length of the position detection sensor according to the comparative example and the present embodiment. 7 and 8, (a) shows the simulation result according to the comparative example, and (b) shows the simulation result according to the present embodiment. Here, a comparative example in which the length dimension of the fixed magnet 71a and the movable magnet 72a in the moving direction is the same dimension (4 mm) is used.

  As shown in FIGS. 7A and 8A, when the length dimensions in the moving direction of the fixed magnet 71a and the movable magnet 72a are the same, the linear output area of the position detection is narrow, and the service area is about It is about 4 mm. On the other hand, as shown in FIGS. 7B and 8B, when the length of the movable magnet 72a in the moving direction is four times that of the fixed magnet 71a, the linear output region for position detection is wide. Thus, it was confirmed that the service area was about 10 mm, which was about 2.5 times that of the comparative example. 7 and 8 show an example of a simulation result when the length of the movable magnet 72a in the moving direction is four times that of the fixed magnet 71a, the present inventors have shown that the movable magnet 72a in the moving direction It has been confirmed that the linear output region for position detection expands from about 2 to 3 times when the length of is increased from about 3 to 5 times that of the fixed magnet 71a. Thus, the magnetic field between the fixed magnet 71a and the movable magnet 72a is changed by configuring the length of the movable magnet 72a in the moving direction to be relatively longer than the length of the fixed magnet 71a in the same direction. Thus, the linearity of the position detection can be further ensured, and the service area (position detection range) of the position detection sensor 1a can be further expanded.

  The embodiment disclosed this time is illustrative in all respects and is not limited to this embodiment. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

  INDUSTRIAL APPLICABILITY The present invention can be applied to detection of a linear position of a relatively short distance of about 30 mm or less, such as a variable valve mechanism for controlling the opening / closing timing of an intake / exhaust valve of an automobile engine, detection of a vehicle body height, detection of a seat position, It is. The present invention can also be applied to position detection at a very minute distance such as a keyboard instrument such as a piano.

DESCRIPTION OF SYMBOLS 1, 1a Position detection sensor 4 Movable body 4a Shaft 4b Shaft support part 4c Storage case 7 Sensor unit 71, 71a Fixed magnet 72, 72a Movable magnet 73 Magnetic detection member 74 Protection board 75 Substrate 76 Magnetoresistance effect element (sensor part)
8 Sensor unit support (support)
8a Support plate part 8b Support part body 8c Guide part

Claims (3)

A fixed magnet fixed to the support;
A movable magnet provided on the detection object and moving with the movement of the detection object;
A sensor unit that is provided between the fixed magnet and the movable magnet and detects a position of the movable magnet based on a change in magnetic resistance due to a change in magnetic field angle from the fixed magnet to the movable magnet. A position detection sensor.   The position detection sensor according to claim 1, wherein a length of the movable magnet in the moving direction is relatively longer than a length of the fixed magnet in the moving direction.   The position detection sensor according to claim 2, wherein the length of the movable magnet in the moving direction is approximately 3 to approximately 5 times the length of the fixed magnet.

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