JP2012107929A - Position detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost and compact position detecting device having a high level of measurement accuracy in spite of a broad detecting range.SOLUTION: A plurality of magnetic detectors 5 are arranged at intervals each shorter than the length of a magnet 3, and the detecting range is divided by the plurality of magnetic detectors 5 for measurement thereby; this configuration enables a position detecting device of any desired detecting range to be produced, the magnet 3 to be made compact even where the detecting range is long and, furthermore, the overall length of the position detecting device to be reduced; also, as the intensity of the lines of magnetic force is enabled to smoothly and gradually vary over the full length direction of the magnet by making the magnetizing direction of the magnet 3 hetero-polar to the moving direction and detecting the lines of magnetic force in a direction perpendicular to the moving direction, a position detecting device having a high level of measurement accuracy can be realized; furthermore, as measurement is accomplished in a state in which the detecting range is divided by the plurality of magnetic detectors 5, the resolution of positional measurement can be enhanced to make possible highly precise measurement.

Description

  The present invention relates to a position detection device, and more particularly to a position detection device used for detecting an operation position of a long linear motion device.

  In an automobile engine, a linear motion device may be used for various controls. For example, in an exhaust gas recirculation mechanism used as one of the measures to improve the fuel efficiency of an engine, a valve is provided in a path for recirculating a part of the exhaust gas to the intake side, and a diaphragm device, which is a kind of linear motion equipment, uses a valve. The amount of exhaust gas recirculation is controlled by adjusting the opening and closing amount.

  When adjusting the opening / closing amount of a valve with a diaphragm device, there are many methods for accurately adjusting the opening / closing amount of the valve by measuring the operating position of the diaphragm device with a position detection device.

  In a conventional position detection device, for example, as disclosed in Patent Document 1, a structure is known in which a magnet that moves together with a moving member and a magnetic detector are combined, and the surface of the magnet facing the magnetic detector is a curved surface. .

  Since the operation amount of the linear motion device used in the exhaust gas recirculation mechanism is relatively small, the detection range of the position detection device may be relatively small. However, depending on the application destination, the amount of movement of the linear motion device is large, and a wide detection range may be required for the position detection device.

  Although the conventional position detection device can detect with good linearity within the detection range, it is necessary to make the magnet long in order to widen the detection range, and there is a problem that the position detection device is also enlarged. .

  In addition, the minimum distance that can be detected by the magnetic detector is a value obtained by dividing the detection range by the resolution. However, when the resolution is the same and the detection range is widened, there is a problem that the minimum distance that can be detected increases and the measurement accuracy decreases. .

  For such a problem, for example, as disclosed in Patent Document 2, a magnet position is determined by a magnetic distribution obtained by combining a small magnet and a plurality of magnetic detectors and interpolating detection values of the plurality of magnetic detectors. A method of measuring is known.

JP 2010-60339 A JP-A-8-50004

In the method disclosed in Patent Document 2, a plurality of magnetic field detection sensors are arranged on a straight line, and the magnetic field value obtained by interpolating the magnetic field value detected by each magnetic field detection sensor with a straight line or a curve becomes zero. The position of the permanent magnet is measured by obtaining the point, and it is possible to downsize the magnet and the position detection device by this method.
However, if the magnet position is calculated by linear interpolation, there is a problem that the error in interpolation is large and high measurement accuracy cannot be obtained. Also, if the magnetic field values are calculated by curve interpolation of the magnetic field values detected by multiple magnetic field detection sensors and the magnet position is calculated, the error in interpolation is reduced, but the calculation process of curve interpolation becomes complicated and the calculation circuit becomes large There was a problem of doing.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small position detection device having high measurement accuracy while having a wide detection range.

To achieve the above object, the present invention provides a moving member that linearly reciprocates along a guide surface provided on a fixed member, a magnet that is held by the moving member and moves together with the moving member, and the movement A magnetic detector installed on the fixed member that detects the strength of the magnetic lines of force from the magnet in a direction perpendicular to the moving direction of the member and outputs an output signal that changes according to the strength of the magnetic lines of force, and receives the output signal In a position detection device having an electronic control unit,
The magnet is magnetized so as to have a different polarity in the moving direction of the moving member, and a plurality of the magnetic detectors are arranged in the moving direction of the moving member, and the plurality of magnetic detectors are arranged. The arrangement interval of the magnetic detectors is shorter than the length of the magnet in the moving direction of the moving member, and the electronic control unit determines from the output signal of an effective magnetic detector among the plurality of magnetic detectors. While calculating the position of the magnet, when the magnet moves out of the measurement range of the effective magnetic detector, the next adjacent magnetic detector in the direction in which the magnet has moved is selected as a new effective magnetic detector. It has a special feature.

  Thus, in the present invention, without changing the length of the magnet, a plurality of magnetic detectors are arranged in the moving direction of the magnet, and the position of the moving magnet is sequentially detected by the plurality of magnetic detectors. A position detection device having a detection range that is a multiple of the detection range of the magnetic detector can be manufactured.

  At this time, since it is not necessary to change the length of the magnet, the size of the magnet can be reduced, and the overall length of the position detection device can be shortened. Furthermore, since the magnetization direction of the magnet is different from the moving direction and the strength of the magnetic force lines in the direction perpendicular to the moving direction is detected, the strength of the magnetic force lines in the detecting direction is linear in a wide range in the full length direction of the magnet. The position of each magnetic detector can be detected with high accuracy, and the moving range is divided and measured by multiple magnetic detectors, so each magnetic detector is divided even if the detection range is widened. Since the narrow range can be measured with the resolution of each magnetic detector, high-precision and high-resolution measurement is possible over the entire length of the detection range.

  According to the present invention, the electronic control unit has a recording unit that holds a predetermined upper limit value and a predetermined lower limit value of the output signal, respectively, and the output signal of the effective magnetic detector when the magnet moves. When the value exceeds the range determined from the predetermined upper limit value and the lower limit value, it is determined that the magnet has moved out of the measurement range of the effective magnetic detector.

  Accordingly, in the present invention, the electronic control unit can switch the effective magnetic detector only by monitoring the output signal of the effective magnetic detector, and the position detection device having a wide detection range can be simply configured.

In the present invention, each of the plurality of magnetic detectors includes a first magnetic detector, a second magnetic detector, and a third magnetic detector each having a measurable range,
An end on the first magnetic detector side of the measurable range of the second magnetic detector is set as one end of the measurable range of the second magnetic detector, and the second magnetic detector has the end of the measurable range. When the end of the measurable range on the third magnetic detector side is the other end of the measurable range of the second magnetic detector, the first magnetic detector is the second magnetic detector. It is arranged at a position of one end of the measurable range or a position closer to the second magnetic detector than the one end, and the third magnetic detector is located in the measurable range of the second magnetic detector. Arranged at the other end position, or at a position closer to the second magnetic detector than the other end,
An end of the measurable range of the first magnetic detector opposite to the second magnetic detector is set as one end of the measurable range of the first magnetic detector, and the third magnetic detector When the end of the measurable range opposite to the second magnetic detector is the other end of the measurable range of the third magnetic detector, the movable range of the magnet is the first magnetic Narrower than the range from one end of the measurable range of the detector to the other end of the measurable range of the third magnetic detector,
The electronic control unit is characterized in that the effective magnetic detector is selected from the output signals of the first magnetic detector and the third magnetic detector.

  Thus, in the present invention, the first magnetic detector uses only half of the measurable range from the center of the measurable range to one end, and the third magnetic detector uses the other side from the measurable range to the other side. Only half of the measurable range up to the end is used, and the other measuring range is measured using the second magnetic detector.

  Therefore, when the output signal of the first magnetic detector is in the range from the median value to the minimum value (or maximum value) of the output value range, the first magnetic detector is selected as an effective magnetic detector, When the output signal of the third magnetic detector is in the range from the median value to the maximum value (or minimum value) of the output value range, the third magnetic detector is selected as an effective magnetic detector, and the first magnetism The output signal of the detector is in the range from the median value to the maximum value (or minimum value) of the output value range, and the output signal of the third magnetic detector is from the median value of the output value range to the minimum value (or maximum value). If the second magnetic detector is selected as an effective magnetic detector, the effective magnetic detector can be selected over the entire measurement range.

  Therefore, in the present invention, an effective magnetic detector can be selected only by confirming the output values of the output signals of the first magnetic detector and the third magnetic detector. Can be spread.

  As described above, in the position detection device of the present invention, by arranging a plurality of magnetic detectors, a position detection device having a detection range that is a multiple of the detection range of each magnetic detector can be manufactured, and the magnet can be reduced in size. The overall length of the detection device can be shortened.

  In addition, since the magnetizing direction is different from the moving direction and the strength of the magnetic force lines in the direction perpendicular to the moving direction is detected, the strength of the magnetic force lines in the detecting direction is gentle over a wide range in the full length direction of the magnet. Therefore, each magnetic detector can detect a position with high accuracy. In addition, since the moving range is divided and measured by multiple magnetic detectors, each magnetic detector can measure the divided narrow range with the resolution of each magnetic detector even if the detection range is wide. High-precision measurement is possible over the entire length of the range.

BRIEF DESCRIPTION OF THE DRAWINGS It is an external view of the position detection apparatus which concerns on the 1st Embodiment of this invention, (a) is a top view, (b) is a side view, (c) is a front view. It is a disassembled perspective view of the position detection apparatus in the 1st Embodiment of this invention. It is AA sectional drawing of (a) of FIG. 1 which shows the center cross section of the position detection apparatus in the 1st Embodiment of this invention. FIG. 5 is a graph for explaining a detection operation in the first embodiment of the present invention, where (a) is a graph showing the relationship between the distance from the center position of the magnet and the magnetic field intensity, and (b) is a magnet when the magnet moves. It is a graph which shows the relationship between the position of and the output signal of a sensor. It is a schematic diagram which shows the circuit structure of the position detection apparatus in the 1st Embodiment of this invention. It is a graph explaining the sensor switching operation | movement by the position of the magnet when the magnet in the 1st Embodiment of this invention moves. It is a center sectional view of a position detection device concerning a 2nd embodiment of the present invention. FIG. 6 is a graph illustrating sensor output processing according to the second embodiment of the present invention, where (a) is a graph showing the relationship between the position of the magnet and the output signal of the sensor when the magnet is moved, and (b) is the magnet moving. It is a graph explaining the output signal of a sensor and sensor switching operation | movement at the time of doing. Is a central sectional view of the position detecting device for explaining the difference in the overall length of the position detecting device of various configuration examples, (a) is a conventional product for the conventional detection range, (b) is a longer conventional product. In the case where the detection range is enlarged, (c) is a position detection device in which the detection range is enlarged according to the first embodiment of the present invention. It is a sensor output characteristic graph explaining the difference between the detection accuracy of the position detection device in the first embodiment of the present invention and the detection accuracy when the conventional product is elongated and the detection range is expanded.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. Note that the position detection device according to the first embodiment of the present invention is a linear scale used for controlling various devices of an automobile. However, the present invention is not limited to this, and an arbitrary range in which a wide detection range is required. The present invention can be applied to a small position detection apparatus.

  FIG. 1 is an external view of a linear scale according to an embodiment of the present invention. As shown in FIG. 1, in the linear scale, a slidable detection portion 2a protrudes from the center of the flange portion 1a of the case 1 (fixed portion), and the tip of the detection portion 2a is brought into contact with the measurement object. To measure the position of the object to be measured.

  FIG. 2 is an exploded perspective view showing the configuration of the linear scale. Hereinafter, the components of the linear scale will be described with reference to FIG.

  As shown in FIG. 2, the linear scale includes a case 1 constituting an outer shape, a substrate assembly 71 held inside the case 1, a slider 2 (moving member) held movably in the case 1, It comprises a magnet 3 held by the slider 2, a compression spring 9 that biases the slider 2 in the protruding direction, and a cover 4 that fits into the opening of the case 1.

  The case 1 is formed of a molding material or the like into a substantially box shape with one side opened, and has a substantially plate-like flange portion 1a on the opening side. A guide surface 1b extending in the moving direction of the slider 2 is formed on two opposing surfaces of the inner surface connected to the opening, and a substrate mounting surface 1c is formed on one surface parallel to the guide surface 1b. The flange portion 1a is provided with four round holes for attaching a linear scale, and the inner peripheral portion of the round hole is reinforced with a metal sleeve.

  The slider 2 is formed of a molding material or the like, and is substantially parallel to the moving direction of the main body 2b, the substantially box-shaped main body 2b, the columnar detecting portion 2a projecting to one of the surfaces perpendicular to the moving direction of the main body 2b. The arm portion 2c protrudes on both side surfaces, and the magnet holding portion 2d is provided on the bottom surface. The arm 2c holds the end face of the compression spring 9.

  The magnet 3 is a magnet made of a neodymium magnet or the like formed into a substantially plate shape, sintered or molded with a small amount of plastic material, and the surface opposite to the surface held by the slider 2 is a curved surface. In addition, two end faces that are magnetized along the moving direction of the slider 2 and perpendicular to the moving direction have different polarities.

  The board assembly 71 is an assembly part in which three sensors 5 (magnetic detectors), a controller 6 (electronic control unit), and external connection terminals 8 are mounted on a rectangular board 7. The three sensors 5 face the curved surface of the magnet 3.

  The three sensors 5 are, for example, Hall ICs arranged at predetermined intervals, and output signals that linearly change from the minimum voltage to the maximum voltage in proportion to the direction and strength of the magnetic field lines perpendicular to the substrate surface.

  The controller 6 receives the outputs of the three sensors 5, calculates the position of the magnet 3 to be measured from the outputs of the effective sensors, and outputs position data.

  The external connection terminal 8 is formed in a plate shape with a metal such as a copper alloy, and is connected to an external power source and ground and outputs the output of the controller 6 to the outside.

  The compression spring 9 is made of a nonmagnetic spring steel wire or the like.

  The cover 4 is formed in a substantially plate shape with a molding material or the like, the outer shape is fitted to the opening of the case 1 to seal the opening, and the detection unit 2a protrudes through the central round hole 4a.

  Next, the configuration of the linear scale and the sensor switching operation of this embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view showing a state in which the slider 2 is moved to the most protruding side.

  The board 7 is held on the board mounting surface 1c of the case 1, and the board 7 has a total of three sensors 5, the first sensor 51, the second sensor 52, and the third sensor 53, the controller 6, and the outside. A connection terminal 8 is mounted.

  The slider 2 holding the magnet 3 is slidably held on the guide surface 1 b of the case 1, and the compression spring 9 biases the slider 2 in the protruding direction.

  When the slider 2 is urged in the protruding direction by the compression spring 9, the disk-shaped protrusion 2 e at one end of the main body 2 b comes into contact with the cover 4 and stops. Hereinafter, this stop position is described as a protruding end position.

  The columnar detector 2a protruding from one side surface of the slider 2 passes through the central circular hole 4a of the cover 4 and comes into contact with the measurement object outside.

  When the measurement object moves the detection unit 2a in the insertion direction, the magnet 3 held by the slider 2 faces the sensor 5 but does not come into contact with the third sensor from one side of the first sensor 51. Move to the other side of 53.

  When the slider 2 is moved in the insertion direction, the rear end protrusion 2f of the other end of the main body 2b comes into contact with the protrusion on the inner bottom surface of the case 1 and stops. This stop position is described as the insertion end position.

  In the linear scale of the present embodiment, the range from the protruding end position to the insertion end position is the detection range.

  When the slider 2 moves in the detection range, the magnet 3 held by the slider 2 also moves, and the first sensor 51, the second sensor 52, and the third sensor according to the direction and strength of the magnetic force lines generated by the magnet 3. 53 output signals change. By measuring the output signal of each sensor 5, the position of the magnet 3 is calculated, and the position of the slider 2 is obtained.

  Below, with reference to FIG. 4, the change of the output signal of each sensor 5 and the position of a magnet when the magnet 3 moves is demonstrated.

  First, with reference to FIG. 4A, the change characteristic of the magnetic field strength by the magnet 3 will be described.

  FIG. 4 (a) shows the distance from the center of the length in the magnetizing direction of the magnet, the magnetizing direction of the magnet, at a position away from the surface of the magnet 3 facing the sensor 5 by the distance between the magnet and the sensor. It is a graph which shows the simulation result which calculated | required the relationship of the magnetic field intensity of the component of the orthogonal direction. In addition, (+) of the perpendicular direction magnetic field intensity in a graph shows the direction which goes to a magnet, (-) shows the direction away from a magnet.

  First, for comparison, a simulation result of the magnetic field strength of a rectangular parallelepiped magnet whose surface facing the sensor 5 is a plane, which is not according to the first embodiment of the present invention, is indicated by a broken line L2.

  In a rectangular parallelepiped magnet whose surface facing the sensor 5 is a flat surface, one of the two end faces perpendicular to the moving direction is the N pole and the other is the S pole among the end faces of the rectangular parallelepiped magnet. At this time, the magnetic lines of force exit from the N pole of the magnet, pass through the outside of the magnet while curving, and finally return to the S pole, but at the central position of the magnet, the magnetic lines of force are parallel to the magnetizing direction of the magnet. Magnetic field lines are concentrated near the magnetic pole.

  Therefore, the magnetic field strength of the component in the direction perpendicular to the magnet magnetization direction becomes zero at the center position of the magnet magnetization direction length, and gradually changes to the plus or minus side when moving away from the center position. In the vicinity of the magnetic pole of the part, that is, at the full length position, the magnetic field strength rapidly changes due to the concentration of the magnetic field lines and becomes an extreme value, and thereafter gradually approaches zero.

  As described above, the magnetic field strength of the component in the direction orthogonal to the magnetization direction of the cuboid magnet whose surface facing the sensor 5 is a plane is zero at the center as shown by the broken line L2 in FIG. It changes gently in the vicinity of the central portion, changes greatly in the vicinity of the full length position, shows a change that gradually approaches zero when exceeding the end face, and shows an S-shaped change with undulation as a whole.

  A rectangular magnet whose surface facing the sensor 5 is a flat surface has a wavy change in magnetic field strength. Therefore, when this magnet is used for position measurement, the position cannot be accurately calculated from the output of the sensor 5.

  On the other hand, in the magnet 3 used in the first embodiment of the present invention, the surface facing the sensor 5 has a curved shape in a direction away from the sensor 5 at the full length position. The distance from the surface increases gradually, and the change in the magnetic field lines near the center position increases. Further, since the distance to the magnetic pole is large at the full length position, the influence of the concentration of the magnetic field lines on the magnetic pole is reduced, and the magnetic field intensity at the full length position does not change suddenly, and changes almost linearly to the vicinity of the full length position.

  From the above, the magnetic field strength of the component in the direction orthogonal to the magnetizing direction of the magnet 3 having a curved surface facing the sensor 5 is indicated by the solid line L1 in FIG. Becomes zero at the center position of the magnet 3, changes almost linearly to the vicinity of the full length position of the magnet 3, reaches an extreme value near the full length position of the magnet 3, and then gradually approaches zero.

  From the above-described change characteristics of the magnetic field strength of the magnet 3 having a curved surface facing the sensor 5 and the simulation results, the magnet 3 used in the first embodiment of the present invention has a total length of about 3 A characteristic that the magnetic field strength changes linearly in the range of / 4 can be obtained.

  Since the range in which the magnetic field intensity changes linearly can be a usable range in which the magnet 3 can be used for position measurement, the surface of the magnet 3 that faces the sensor 5 has a curved surface, thereby having a wide usable range. A magnet having characteristics suitable for position measurement can be obtained.

  Note that the optimal dimensions of the curved surface of the magnet that changes linearly over a wide range of the magnetic field strength depend on the outer dimensions of the magnet, the distance between the magnet and the sensor 5, the accuracy of the required linearity, etc. It is necessary to obtain an optimum value while using a simulation individually based on the dimensions.

  The above is the description of the relationship between the distance from the center of the magnet 3 and the magnetic field strength with reference to the center of the length in the moving direction of the magnet 3, but the hole used as the sensor 5 in the first embodiment of the present invention. Since the output signal of the IC changes in linear proportion to the magnetic field intensity in the detection direction of the sensor, the change in the output signal of the sensor 5 when the magnet 3 moves immediately above the plurality of sensors 5 is from the center of the magnet 3. This is the same as the change in the magnetic field lines depending on the distance, and the usable range of the magnet 3 is the measurable range of each sensor 5.

  Hereinafter, referring to FIG. 4B, the change in the output signal of the plurality of sensors 5 when the magnet 3 moves the detection range from the projecting end position to the insertion end position, and the number of sensors is three. An example will be described.

  The three sensors 5 are arranged at intervals shorter than the length of the magnet 3 in the moving direction, and can be the same distance as the measurable range of each sensor at the maximum. However, in the first embodiment of the present invention, each sensor 5 is slightly less than the measurable range as shown in FIG. Are arranged at short intervals. Further, both ends of the detection range of the linear scale, that is, the protruding end position and the insertion end position are set to positions that do not exceed the measurable range of the sensor 5 at both ends.

  Note that the Hall IC used as the sensor 5 in the first embodiment of the present invention is driven by the power supply voltage Vdd, and the output signal varies from near 0 V to near Vdd due to the magnetic field strength in the direction orthogonal to the magnet magnetization direction. When the magnetic field strength is zero, the intermediate voltage Vdd / 2 is output.

  Hereinafter, the state of the output signal of each sensor 5 when the position of the magnet 3 sequentially changes from the protruding end position to the insertion end position will be described with reference to FIG.

<Change in output status of each sensor>
(1) When the magnet 3 is at the protruding end position (one end of the detection range).
The output signal S1 of the first sensor 51 is around 0V.
The output signal S2 of the second sensor 52 is slightly lower than the intermediate voltage.
The output signal S3 of the third sensor 53 is near the intermediate voltage.

(2) When the magnet 3 moves to just above the first sensor 51.
The output signal S1 of the first sensor 51 rises linearly up to the intermediate voltage.
The output signal S2 of the second sensor 52 gradually decreases.
The output signal S3 of the third sensor 53 remains in the vicinity of the intermediate voltage and does not change.

(3) When the magnet 3 moves to an intermediate position between the first sensor 51 and the second sensor 52.
The output signal S1 of the first sensor 51 rises linearly from the intermediate voltage to near Vdd.
The output signal S2 of the second sensor 52 decreases to near 0V and then increases slightly.
The output signal S3 of the third sensor 53 slightly decreases from around the intermediate voltage.

(4) When the magnet 3 moves to just above the second sensor 52.
The output signal S1 of the first sensor 51 increases to the maximum value and then decreases.
The output signal S2 of the second sensor 52 rises linearly to the intermediate voltage.
The output signal S3 of the third sensor 53 gradually decreases from around the intermediate voltage.

(5) When the magnet 3 moves to an intermediate position between the second sensor 52 and the third sensor 53.
The output signal S1 of the first sensor 51 further decreases and approaches the intermediate voltage.
The output signal S2 of the second sensor 52 rises linearly from the intermediate voltage to near Vdd.
The output signal S3 of the third sensor 53 decreases to near 0V and then increases slightly.

(6) When the magnet 3 moves to just above the third sensor 53.
The output signal S1 of the first sensor 51 is almost an intermediate voltage.
The output signal S2 of the second sensor 52 rises to the maximum value and then decreases.
The output signal S3 of the third sensor 53 rises linearly to the intermediate voltage.

(7) When the magnet 3 moves to the insertion end position (the other end of the detection range).
The output signal S1 of the first sensor 51 remains unchanged at the intermediate voltage.
The output signal S2 of the second sensor 52 further decreases and approaches the intermediate voltage.
The output signal S3 of the third sensor 53 rises linearly from the intermediate voltage to near Vdd.

  Since the output signals S1, S2, and S3 of each sensor 5 change as described above due to the movement of the magnet 3, the sensor in which the output signal changes linearly in each of the movement ranges (1) to (7) is effective. By selecting the correct sensor and calculating the position of the magnet 3 from the output signal of the effective sensor, the position of the magnet 3 in the entire movement range can be calculated with high accuracy. That is, an effective sensor is selected under the following conditions.

(A) When the magnet 3 is in the range of the intermediate position between the first sensor 51 and the second sensor 52 from the protruding end position, the first sensor 51 is selected as an effective sensor.
(B) When the magnet 3 is in the range of the intermediate position between the second sensor 52 and the third sensor 53 from the intermediate position between the first sensor 51 and the second sensor 52, the second sensor 52 is effective. Select as sensor.
(C) When the magnet 3 is in the range from the intermediate position between the second sensor 52 and the third sensor 53 to the insertion end position, the third sensor 53 is selected as an effective sensor.

  The selection of the sensor 5 is switched by the controller 6 according to a predetermined condition while monitoring the output signal of each sensor 5. Further, the controller 6 performs correction according to the arrangement position of the selected sensor, and calculates the position of the magnet 3 from the output signal of the selected sensor 5.

<Sensor switching conditions>
In the first embodiment of the present invention, as shown in FIG. 5, the first sensor 51, the second sensor 52, and the third sensor 53 are respectively connected to the A / D port of the one-chip microcomputer that is the controller 6. Connected.

  The controller 6 includes a CPU, an A / D port, a memory, an output port, and the like, which are connected by an internal bus. The A / D port receives an external signal and converts it into digital data. The converted digital data is processed by the CPU and output from the output port to the outside. The memory holds data as needed. As a result, the output signal of each sensor 5 can be constantly monitored by the controller 6.

  Note that an upper limit value Vmax and a lower limit value Vmin, which are reference values when the controller 6 switches an effective sensor, are held in a part of the memory of the controller 6.

  As an example, the effective sensor switching operation when the first sensor 51 is selected as an effective sensor and the magnet 3 moves from the protruding end position will be described with reference to FIG.

  When the magnet 3 is at the protruding end position P1, the output signal S1 of the first sensor 51 is a voltage V1 that is slightly higher than the lower limit value Vmin.

  When the magnet 3 moves in the direction of the insertion end, the output signal S1 of the first sensor 51 increases linearly and eventually reaches the upper limit value Vmax. When the output signal S1 of the first sensor 51 reaches the upper limit value Vmax, the controller 6 switches the effective sensor to an adjacent sensor in the moving direction of the magnet 3, that is, the second sensor 52.

  When the magnet 3 further moves in the insertion direction and the output signal S2 of the second sensor 52 reaches the upper limit value Vmax, the controller 6 switches the effective sensor to the third sensor 53. When the magnet 3 further moves to the insertion end position P4, the output signal S3 of the third sensor 53 becomes a voltage V4 slightly lower than the upper limit value Vmax.

  Next, when the magnet 3 moves in the reverse direction, that is, in the protruding end direction, the output signal S3 of the third sensor 53 decreases linearly. However, when the output signal S3 reaches the lower limit value Vmin, the controller 6 determines that the effective sensor Is switched to a sensor adjacent to the moving direction of the magnet 3, that is, the second sensor 52.

  Thereafter, when the magnet 3 further moves in the protruding end direction and the output signal S2 of the second sensor 52 similarly reaches the lower limit value Vmin, the controller 6 switches the effective sensor to the first sensor 51.

  As described above, the controller 6 compares the output signals S1, S2, and S3 of each sensor 5 with the set upper limit value Vmax and lower limit value Vmin, and sequentially selects an effective sensor. The position can be calculated.

  The above explanation is a case where the magnet 3 moves in the entire detection range from the protruding end position to the insertion end position, but even when the magnet 3 changes the moving direction at an intermediate position from the protruding end position to the insertion end position, If the output signal of the effective sensor reaches the lower limit value Vmin or the upper limit value Vmax, the controller 6 selects the next effective sensor.

  In the linear scale according to the embodiment of the present invention, the sensors are arranged at slightly shorter intervals than the measurable range so that the measurement ranges of adjacent sensors partially overlap. As a result, in the linear scale according to the embodiment of the present invention, for the reasons described below, there are inconveniences when the characteristics are changed over a long period of time and when the magnet is in the vicinity of the sensor switching position. The chattering phenomenon that is frequently switched can be avoided.

  In the linear scale according to the embodiment of the present invention, when an upper limit value Vmax and a lower limit value Vmin that define the use range of the output signal of each sensor are set, depending on the magnetic characteristics of the magnet used and the magnetic detection characteristics of the sensor. The measurement range of each sensor is determined.

  Therefore, when the linear scale is used for a long time and the magnetic characteristics of the magnet deteriorates or the magnetic detection characteristics of the sensor fluctuate, the measurement range of each sensor may change and the measurement range of the sensor may decrease. possible.

  However, in the linear scale according to the embodiment of the present invention, each sensor is arranged at a slightly shorter interval than the measurable range so that the measurement ranges of adjacent sensors partially overlap, so that the sensor measurement Even when the range is reduced, it is possible to avoid the inconvenience that the measurement range of the adjacent sensor becomes discontinuous and the measurement becomes impossible or the measurement accuracy is lowered.

  Further, for example, the position of the magnet when the magnet 3 moves in the insertion direction, the output signal S1 of the first sensor 51 reaches the upper limit value Vmax, and the effective sensor is switched to the second sensor 52 is P2, When the magnet moves in the reverse direction, that is, the protruding direction, the output signal S2 of the second sensor 52 reaches the lower limit value Vmin, and the effective sensor is switched to the first sensor 51, the position of the magnet is P6. Since each sensor is arranged at a slightly shorter interval than the measurable range, the position P2 when the effective sensor is switched from the first sensor 51 to the second sensor 52, and the effective sensor is the second. There is a difference in the position P6 when the sensor 52 is switched to the first sensor 51.

  At this time, the voltage V2 of the output signal S2 of the second sensor 52 when the effective sensor is switched from the first sensor 51 to the second sensor 52 is slightly larger than the lower limit value Vmin. When the second sensor 52 is switched to the first sensor 51, the voltage V6 of the output signal S1 of the first sensor 51 is slightly smaller than the upper limit value Vmax.

  For this reason, even when the magnet is moved and the effective sensor is switched from the first sensor 51 to the second sensor 52, the magnet stops, and even when the magnet vibrates slightly at the stop position, the position of the magnet is The effective sensor does not exceed the position P6 when the second sensor 52 is switched to the first sensor 51, and the voltage V2 of the output signal S2 of the second sensor 52 does not exceed the lower limit value Vmin. The sensor is not switched from the second sensor 52 to the first sensor 51.

  Therefore, by placing each sensor at a slightly shorter interval than the measurable range so that the measurement ranges of adjacent sensors partially overlap, chattering where effective sensors are frequently switched between adjacent sensors is avoided. it can.

  As described above, when the magnet 3 moves in the insertion direction and the effective sensor is switched from the first sensor 51 to the second sensor 52, each sensor is set so that the measurement ranges of adjacent sensors partially overlap. Although it is a description of the effect by arranging at intervals slightly shorter than the measurable range, the same applies even when the magnet 3 moves in the discharge direction and the effective sensor is switched from the second sensor 52 to the first sensor 51. The effect is obtained.

  The upper limit value Vmax and the lower limit value Vmin of the output signal set in the controller 6 may be the same for each sensor 5. However, in order to eliminate the variation of each sensor 5, it is set individually for each sensor. Is also possible.

<First selection method of valid sensors>
In the above description regarding the switching of the sensor 5, the description has been made on the assumption that an effective sensor has already been selected. However, when power supply is started from a state where power is not supplied to the linear scale, for example, when a stopped automobile is started, an effective sensor is not selected at the time of start-up, and each sensor 5 Even if the output is monitored, a valid sensor may not be determined.
In such a case, an effective sensor is determined by the following method.

(1) From the application of the linear scale, the position of the linear scale at startup is specified.

  For example, when the present invention is applied to turbocharger control, the turbocharger is not working when the engine starts for the first time. Therefore, in the case of turbocharger control, for example, the position of the linear scale at the start-up can be specified according to the application such that the valve is closed at the start-up and the linear scale is in the most protruding state.

  In such a case, an effective sensor can be specified corresponding to the specified position of the linear scale at the time of activation.

(2) The measurement object is slightly operated at the time of activation, and an effective sensor is selected from the change in the output signal.

  In an application where the position of the linear scale at startup cannot be specified, the measurement object is intentionally slightly operated at startup, and the output signal of the sensor 5 at this time is within the range of the upper limit value Vmax and the lower limit value Vmin. The sensor 5 that matches the increase / decrease direction in which the change of the output signal is structurally determined is selected as an effective sensor.

  By using the methods (1) and (2) above, it is possible to select an effective sensor at startup. Once an effective sensor is selected, the output signal of each sensor 5 is monitored thereafter. It is possible to switch the effective sensor appropriately.

  In the first embodiment of the present invention, effective sensor switching is performed by comparing the output signals S1, S2 and S3 of each sensor 5 with the set upper limit value Vmax and lower limit value Vmin. It is also possible to perform effective sensor switching based on other signals that have been generated, for example, position data of the magnet 3 calculated from the output signal.

  In the above description of the first embodiment, the number of sensors 5 to be used has been described as three. However, the number of sensors 5 to be used is not limited to three, and can be arbitrarily increased or decreased as necessary. .

<Second Embodiment>
Next, the configuration of the linear scale and the sensor switching operation according to the second embodiment of the present invention will be described with reference to FIG. In addition, about the structure same as 1st Embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  FIG. 7 is a cross-sectional view showing a state where the slider 2 of the linear scale according to the second embodiment of the present invention is in the protruding end position.

  The configuration of the linear scale according to the second embodiment of the present invention is the same as the configuration of the linear scale according to the first embodiment of the present invention, but the arrangement interval of the sensors 5 is different, and the number of sensors 5 is three. Limited to pieces.

  A substrate 7 is held on the substrate mounting surface 1c of the case 1, and the substrate 7 has a total of three sensors, a first sensor 51, a second sensor 52, and a third sensor 53, a controller 6, and an external connection. Terminal 8 is mounted.

  The three sensors are arranged at intervals. As shown in FIG. 8A, the first sensor 51 is arranged at the end position on one side of the measurable range of the second sensor 52. The sensor 53 is disposed at the end position on the other side of the measurable range of the second sensor 52. Further, both ends of the detection range of the linear scale, that is, the protruding end position and the insertion end position are set to positions that do not exceed the measurable range of the sensor 5 at both ends.

  Hereinafter, the state of the output signals of the three sensors 5 when the position of the magnet 3 changes from the protruding end position to the insertion end position will be described with reference to FIG.

<Change in output state of each sensor in the second embodiment>
(1) When the magnet 3 is in the range from the protruding end position (one end of the detection range) to the position immediately above the first sensor 51 described as the first sensor placement position in FIG.
The output signal S1 of the first sensor 51 rises linearly from around 0V to the intermediate voltage.
The output signal S3 of the third sensor 53 is equal to or lower than the intermediate voltage.
(2) From the position immediately above the first sensor 51, in which the magnet 3 is described as the first sensor arrangement position in FIG. 8A, the third sensor is described as the third sensor arrangement position in FIG. When it is in the range up to just above the third sensor 53.
The output signal S1 of the first sensor 51 is equal to or higher than the intermediate voltage.
The output signal S2 of the second sensor 52 rises linearly from near 0V to near Vdd.
The output signal S3 of the third sensor 53 is equal to or lower than the intermediate voltage.
(3) When the magnet 3 is in the range from the position immediately above the third sensor 53 to the insertion end position (the other end of the detection range) described as the third sensor arrangement position in FIG.
The output signal S1 of the first sensor 51 is equal to or higher than the intermediate voltage.
The output signal S2 of the third sensor 53 rises linearly from the intermediate voltage to near Vdd.

  As the magnet 3 moves, the output signals S1, S2, and S3 of the sensors 5 change as described above. However, in the second embodiment of the present invention, the first sensor 51 and the third sensor 3 An effective sensor can be selected by comparing the output signals S1 and S3 of the sensor 53 with the intermediate voltage.

<Sensor switching method in the second embodiment>
(A) When the output signal S1 of the first sensor 51 is lower than the intermediate voltage, the first sensor 51 is selected as an effective sensor (the range described as the measurement range of the first sensor in FIG. 8B). ).
(B) When the output signal S3 of the third sensor 53 is higher than the intermediate voltage, the third sensor 53 is selected as an effective sensor (the range described as the measurement range of the third sensor in FIG. 8B). ).
(C) In cases other than the above (A) and (B), that is, when the output signal S1 of the first sensor 51 is higher than the intermediate voltage and the output signal S3 of the third sensor 53 is lower than the intermediate voltage, the second Sensor 52 is selected as an effective sensor (the range described as the measurement range of the second sensor in FIG. 8B).

  As described above, in the second embodiment of the present invention in which the number of sensors 5 is limited to three, the output signal range when each of the first sensor 51 and the second sensor 52 is effective is limited. Therefore, an effective sensor can be selected only by comparing the output signals S1 and S3 of the first sensor 51 and the third sensor 53 with the intermediate voltage.

  Further, even when the magnet 3 is at the protruding end position or the insertion end position, the magnet 3 is within the measurable range of the first sensor 51 or the third sensor 53, and therefore, the linear from the protruding end position to the insertion end position. It is possible to detect the magnet position with good linearity in the entire range within the detection range of the scale.

  The first sensor 51 and the third sensor 53 are each second from the end position of the measurable range of the second sensor 52 in consideration of the variation of the three sensors, the temporal change of the magnet 3, and the like. You may arrange | position in the position close | similar to the sensor 52. FIG.

<Calculation method of magnet position>
In the linear scale according to the first embodiment and the second embodiment of the present invention, the position of the magnet 3 is detected by the plurality of sensors 5, but the output signals S 1, S 2, output from each sensor 5. S3 is a signal proportional to the distance from each sensor 5 to the magnet 3, and is not a value proportional to the magnet position. Therefore, the actual position of the magnet 3 is calculated by adding the valid sensor position to the distance to the magnet 3 calculated from the output signal.

  However, since each sensor 5 is mounted on the substrate 7 by soldering or the like, it is difficult to accurately manage the mounting position of each sensor 5. For this reason, the measurement accuracy cannot be maintained even if the position of the magnet 3 is calculated by simply adding the effective sensor mounting position to the distance to the magnet 3 calculated from the output signal of the sensor 5. Therefore, in the embodiment of the present invention, the actual position of the magnet 3 is calculated by the following method (see FIG. 6).

  In the linear scale according to the first embodiment and the second embodiment of the present invention, when the effective sensor is switched, the magnet position at the sensor switching position obtained from the output signal of the sensor that was effective before switching is changed. The measurement reference value of the magnet position of the sensor enabled by switching the value, and the reference output signal value of the sensor enabled by switching the output signal value of the sensor switching position of the sensor enabled by switching The position of the magnet is calculated from the position measurement reference value and the sensor output signal that is activated by switching between the sensor reference output signal value and the sensor output signal.

  A specific calculation method of the position of the magnet 3 when an effective sensor is switched in the linear scale according to the first and second embodiments of the present invention will be described below with reference to FIG. To do.

For example, when the effective sensor is switched from the first sensor 51 to the second sensor 52, the position when the magnet 3 is at the protruding end position P1 is used as a reference.
(1) The position data of the position P2 of the magnet 3 when the output signal S1 of the first sensor 51 reaches the upper limit value Vmax is stored in the controller 6.
(2) The voltage V2 of the output signal of the second sensor 52 when the effective sensor is switched to the second sensor 52 is stored in the controller 6.
(3) While the effective sensor is the second sensor 52, that is, while the output signal S2 of the second sensor 52 does not exceed the upper limit value Vmax and does not fall below the lower limit value Vmin, the magnet 3 moves to the second sensor 52. When the output signal S2 of the sensor 52 changes, the temporary data of the position of the magnet 3 is calculated from the difference between the output signal S2 of the second sensor 52 and the voltage V2 of the stored output signal, The true position of the magnet 3 is calculated by adding the position data.

  Similarly, when the effective sensor is switched from the second sensor 52 to the third sensor 53, the position P3 of the magnet 3 when the output signal S2 of the second sensor 52 reaches the upper limit value Vmax is set. The position data and the voltage V3 of the output signal of the third sensor 53 when the valid sensor is switched to the third sensor 53 are stored in the controller 6, and thereafter the output signal S3 of the third sensor 53 is stored. The position of the magnet 3 is obtained from the output signal voltage V3 and the position data of the position P3.

  Further, when the moving direction of the magnet 3 is reversed and the output signal of the effective sensor reaches the lower limit value Vmin, the position of the magnet 3 is calculated by the same method.

  By calculating the position of the magnet 3 by the above method, even when the arrangement intervals of the sensors 5 vary, accurate position measurement can be performed without taking measures such as measuring the arrangement intervals individually. .

  Further, by holding the position data and output signal value stored in the controller 6 in, for example, the nonvolatile memory of the controller 6, the positions P1, P2, P3 and the position when the moving direction is reversed once during product manufacture. The data of P4, P5, and P6, the output signal voltages V1, V2, and V3, and the output signal voltages V4, V5, and V6 when the moving direction is reversed are merely stored, and subsequent data acquisition is unnecessary. .

  As described above, the method for switching the plurality of sensors 5 arranged at predetermined intervals by the controller 6 and the method for the controller 6 calculating the magnet position from the output signal of the sensor 5 have been described. However, the controller 6 is mounted in the linear scale. Is not essential, and the output signals S1, S2, and S3 of each sensor 5 are directly output from the linear scale, and the effects of the present invention can be achieved even when a plurality of sensors 5 are switched by an externally provided controller 6. It is.

<Comparative example>
When expanding the detection range of the linear scale, the simplest method is to lengthen the linear scale. However, in this case, there is a problem that the outer dimension of the linear scale is longer than that of the embodiment of the present invention, the magnet is enlarged, and the measurement accuracy is further lowered.

  The reasons why the above problems occur will be sequentially described below.

<Reason why the linear dimension becomes longer if the linear scale is simply made longer>
FIG. 9 is a cross-sectional view showing the structure of various linear scales. 9A is a conventional linear scale for a conventional detection range, FIG. 9B is a linear scale in which the detection range is tripled by elongating the magnet, and FIG. According to the first embodiment, the detection range is, for example, a linear scale that is tripled.

If the length of the magnet 3 in the conventional linear scale of FIG. 9A is W and the detection range is L, the total length of the linear scale is the length of the bottom of the case, the thickness of the cover, and the length of the portion longer than the magnet of the slider. (W + L) + Z
It is.

In the linear scale in which the detection range is tripled by elongating the magnet of FIG. 9B, the detection range is expanded to 3L, and the length of the elongated magnet 10 is approximately 3W. Therefore, the length of the linear scale is 3L + 3W + Z = 3 (L + W) + Z
Thus, it is approximately three times the conventional linear scale for the conventional detection range.

On the other hand, in the linear scale of FIG. 9C in which the detection range is tripled according to the first embodiment of the present invention, the detection range is 3L, but the length of the magnet 3 remains W. So, the total length of the linear scale is W + 3L + Z
It becomes.

By the way, the length W of the magnet 3 is always larger than the detection range L of the conventional linear scale.
W + 3L = W + L + 2L <W + W + 2L = 2W + 2L = 2 (W + L)
It is. Therefore, the total length of the linear scale in which the detection range is tripled according to the embodiment of the present invention is as follows.
W + 3L + Z <2 (W + L) + Z
Thus, it is approximately twice or less than the conventional linear scale for the detection range.

  Thereby, in the linear scale according to the first embodiment of the present invention, for example, even if the detection range is tripled, the total length of the linear scale is only doubled or less.

  As described above, the linear scale according to the first embodiment of the present invention can reduce the overall length while having a wide detection range.

<Reasons to increase the size of the magnet by simply lengthening the linear scale>
FIG. 10 is a graph showing the sensor output of a linear scale in which the detection range is tripled by elongating the magnet.

  In order to triple the detection range of the linear scale, the length of the magnet 3 may be increased by a factor of 3, but if the thickness of the magnet is made the same as in the normal detection range, the central portion of the magnet 10 There is a region where the change in magnetic field strength is small in the vicinity, and the output of the sensor 5 has a range where the change is small near the central portion of the elongated magnet 10 as shown by the broken line S12 in FIG. For this reason, as shown by the solid line S11 in FIG. 10, in order to maintain the output characteristics of the sensor 5 with good linearity in the detection range three times that of the conventional detection range, the thickness of the magnet needs to be substantially three times. .

  Therefore, if the detection range is increased by, for example, 3 times by increasing the length of the magnet, the volume of the magnet to be used becomes approximately 9 times, and the magnet becomes larger and heavier.

  <Reasons for measuring accuracy decrease when the linear scale is simply lengthened>

  For example, when the sensor output of the conventional linear scale for the conventional detection range is converted to digital data by a 10-bit AD converter with the detection range as L, the minimum distance that can be detected is L / 1024.

  In the system of the first embodiment of the present invention, the output signals of the plurality of sensors 5 divide the detection range in which the plurality of sensors 5 are expanded, such as the output signals S1, S2, and S3 indicated by the one-dot chain line in FIG. The output signal of each sensor 5 changes within the normal detection range L from near 0 V to near Vdd. For this reason, when the output of each sensor 5 is converted into digital data by, for example, a 10-bit AD converter, the minimum distance that can be detected is L / 1024, and the detection accuracy is the detection accuracy of the conventional linear scale for the conventional detection range. Are the same.

  On the other hand, the sensor output of a linear scale in which the detection range is increased to 3 times by elongating the magnet while maintaining the linearity, for example, is expanded as shown by the solid line S11 in FIG. Within 3L, the sensor output changes linearly from near 0V to near Vdd.

  For this reason, if the sensor output is converted into digital data by a 10-bit AD converter, for example, the minimum distance that can be detected is 3L / 1024, and the measurement accuracy is reduced as compared with the conventional linear scale for the conventional detection range.

  As described above, in a linear scale that is not according to the present invention and whose detection range is expanded by increasing the length, it is difficult to reduce the size of the linear scale, and the increase in size of the magnet is unavoidable, and the measurement accuracy also decreases.

1 Case (fixed part)
1a Flange 1b Guide surface 1c Substrate mounting surface 2 Slider (moving member)
2a detector 2b main body 2c arm 2d magnet holder 2e disc-like projection 2f rear end projection 3 magnet 4 cover 4a round hole 5 sensor (magnetic detector)
51 1st sensor 52 2nd sensor 53 3rd sensor 6 Controller (electronic control part)
7 Board 71 Board Assembly 8 External Connection Terminal 9 Compression Spring 10 Lengthened Magnet Vmax Upper Limit Vmin Lower Limit

Claims (3)

A moving member that linearly reciprocates along a guide surface provided on the fixed member;
A magnet that is held by the moving member and moves together with the moving member;
A magnetic detector installed on the fixed member that detects the strength of magnetic lines of force from the magnet in a direction perpendicular to the moving direction of the moving member and outputs an output signal that varies depending on the strength of the magnetic lines of force;
In an electronic control unit that receives the output signal,
The magnet is magnetized so as to have a different polarity in the moving direction of the moving member;
A plurality of the magnetic detectors are arranged in the moving direction of the moving member,
The arrangement interval of the plurality of magnetic detectors arranged is shorter than the length of the magnet in the moving direction of the moving member,
The electronic control unit calculates the position of the magnet from the output signal of an effective magnetic detector among a plurality of the magnetic detectors, and when the magnet moves outside the measurement range of the effective magnetic detector. A position detection device, wherein the next next magnetic detector in the direction in which the magnet has moved is selected as a new effective magnetic detector.   The electronic control unit has a recording unit that holds a predetermined upper limit value and a predetermined lower limit value of the output signal, respectively, and the magnet moves and the output signal of the effective magnetic detector is the predetermined upper limit value. The position detection device according to claim 1, wherein when the value exceeds a range determined from a value and the lower limit value, it is determined that the magnet has moved out of a measurement range of the effective magnetic detector. The plurality of magnetic detectors each include a first magnetic detector, a second magnetic detector, and a third magnetic detector each having a measurable range,
An end on the first magnetic detector side of the measurable range of the second magnetic detector is set as one end of the measurable range of the second magnetic detector, and the second magnetic detector has the end of the measurable range. When the end of the measurable range on the third magnetic detector side is the other end of the measurable range of the second magnetic detector, the first magnetic detector is the second magnetic detector. It is arranged at a position of one end of the measurable range or a position closer to the second magnetic detector than the one end, and the third magnetic detector is located in the measurable range of the second magnetic detector. Arranged at the other end position, or at a position closer to the second magnetic detector than the other end,
An end of the measurable range of the first magnetic detector opposite to the second magnetic detector is set as one end of the measurable range of the first magnetic detector, and the third magnetic detector When the end of the measurable range opposite to the second magnetic detector is the other end of the measurable range of the third magnetic detector, the movable range of the magnet is the first magnetic Narrower than the range from one end of the measurable range of the detector to the other end of the measurable range of the third magnetic detector,
The position detection device according to claim 1, wherein the electronic control unit selects the effective magnetic detector from the output signals of the first magnetic detector and the third magnetic detector.

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