JP2013160711A - Position detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a position detection device capable of improving the accuracy of position detection by detecting vertical deviation between a fixed part and a movable part to correct the output of a magnetic sensor.SOLUTION: The position detection device of the present invention includes a magnetic field generation part which is a magnetic field generation source in one of a fixed part and a movable part, and in the other of the fixed part and the movable part, a plurality of magnetic sensors for detecting the magnetic field of the magnetic field generation part and an arithmetic part for calculating the position of the movable part from the output of the magnetic sensor. An interval between the magnetic sensors arranged in the movable direction of the movable part is equal to the movable-direction length of the magnetic field generation part. The arithmetic part includes a deviation detection part for detecting the vertical deviation of the magnetic sensor and the magnetic field generation part from an output addition value obtained by adding together the outputs of magnetic sensors adjacent to each other in the movable direction, and an output correction part for correcting the output of the magnetic sensor on the basis of the vertical deviation.

Description

  The present invention relates to a position detection device using a magnetic sensor.

  As an example of a position detection device using a magnetic sensor, for example, inventions listed in Patent Documents 1 to 3 are known. In the invention described in Patent Document 1, the amount of movement of the movable part is detected using a magnet and two Hall elements. In the invention described in Patent Document 1, in the predetermined range Dx in which the movable part moves linearly, the outputs of the two Hall elements are approximated by a sin function or a cos function, and the magnet and the two pieces have a predetermined phase difference α. By disposing the Hall element, the amount of movement of the movable part can be detected from the phase difference α.

  In the invention described in Patent Document 2, the position of the magnetic sensor, which is a movable part, is detected using a magnet and a magnetic sensor including a GMR element. In the invention described in Patent Document 2, the overlapping area of the GMR element and the magnet is changed with the relative movement of the magnetic sensor, so that the output of the magnetic sensor can be changed to detect the position of the movable part.

  In the invention described in Patent Document 3, the position of the magnet, which is a movable part, is detected using a magnet having N and S poles magnetized in the same direction as the magnetic sensing direction of the magnetic sensor. In the invention described in Patent Document 3, it is possible to detect the position of the movable part by subtracting and adding the outputs of the two magnetic sensors to calculate a subtraction value and an addition value and dividing them.

JP 2010-139338 A JP 2010-133882 A JP 2010-96540 A

  However, in the invention described in Patent Document 1, the output of the two Hall elements is approximated by a sine function or a cos function, and the movement amount of the movable part is detected using a predetermined phase difference α. It is necessary to increase the predetermined range Dx that moves. Therefore, in the invention described in Patent Document 1, the detection device is increased in size. In the invention described in Patent Document 2, since the position of the movable part is detected using a change in the overlapping area between the GMR element and the magnet, it is necessary to increase the movable range of the movable part. Therefore, in the invention described in Patent Document 2, the detection device is increased in size.

  On the other hand, in the invention described in Patent Document 3, the output values of the two magnetic sensors are arithmetically calculated to detect the position of the movable part, so that the detection device is smaller than the inventions described in Patent Documents 1 and 2. Can be However, in the invention described in Patent Document 3, if a vertical deviation occurs between the magnet and the magnetic sensor, the output value of the magnetic sensor changes with the deviation, and the accuracy of position detection decreases.

  The present invention has been made in view of the above circumstances, and it is possible to improve the accuracy of position detection by detecting the deviation in the vertical direction between the fixed portion and the movable portion and correcting the output of the magnetic sensor. It is an object to provide a position detection device.

  The position detection apparatus according to claim 1 is a position detection apparatus that detects a position of a movable part that moves relative to a fixed part at a predetermined distance, and includes a magnetic field applied to one of the fixed part and the movable part. A magnetic field generation unit that is a generation source is provided, and a position of the movable unit is calculated from a plurality of magnetic sensors that detect the magnetic field of the magnetic field generation unit on the other of the fixed unit and the movable unit, and an output of the magnetic sensor. An interval between the magnetic sensors arranged in the movable direction of the movable portion is the same as the length of the magnetic field generating portion in the movable direction, and the arithmetic portion is adjacent to the movable direction. A deviation detection unit that detects a vertical deviation of the magnetic sensor and the magnetic field generation unit from an output addition value obtained by adding the outputs of the output, and an output correction unit that corrects the output of the magnetic sensor based on the vertical deviation. Have.

  A position detection apparatus according to a second aspect is the position detection apparatus according to the first aspect, wherein the output correction unit corrects the output of the magnetic sensor using a relational expression expressed by the following formula 1.

  However, the output of the magnetic sensor is f, the vertical position is z, the output correction amount of the magnetic sensor is Δf, and the vertical deviation is Δz.

  According to a third aspect of the present invention, in the position detection device according to the first or second aspect, the output correction unit corrects the output of the magnetic sensor in accordance with the output characteristics of the magnetic sensor at the end in the movable direction.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the plurality of magnetic sensors are formed of the same magnetic sensor.

  According to the position detection device of the first aspect, since the interval between the magnetic sensors arranged in the movable direction of the movable part is the same as the length of the magnetic field generating part in the movable direction, The output addition value obtained by adding the outputs of the adjacent magnetic sensors can be made constant. And since a calculating part has a deviation detection part which detects a perpendicular direction deviation of a magnetic sensor and a magnetic field generating part from an output addition value, and an output correction part which corrects an output of a magnetic sensor based on a vertical direction deviation, The output of the magnetic sensor can be corrected according to the vertical deviation. For this reason, even if a vertical deviation occurs between the magnetic sensor and the magnetic field generator, it is possible to suppress a decrease in position detection accuracy.

  According to the position detection device of the second aspect, the output correction unit corrects the output of the magnetic sensor using the relational expression shown in Equation 1, and therefore, compared with a case where an operation including higher-order partial differentiation is performed. The calculation time required for position detection can be shortened. In addition, since the vertical deviation of the magnetic sensor and the magnetic field generator is sufficiently smaller than the amount of movement of the movable part, it is possible to ensure the accuracy of position detection even with the calculation based on the first partial differential.

  According to the position detection device of the third aspect, the output correction unit corrects the output of the magnetic sensor in accordance with the output characteristic of the magnetic sensor at the end in the movable direction. Even when the output characteristics of the magnetic sensor in the central portion in the movable direction are different from each other, it is possible to suppress a decrease in position detection accuracy.

  According to the position detection device of the fourth aspect, since the plurality of magnetic sensors are formed of the same magnetic sensor, the temperature dependence of each magnetic sensor can be canceled with each other, and the output characteristics due to temperature fluctuations can be reduced. Change can be suppressed. In addition, it is easy to set the interval between the magnetic sensors to be the same as the length of the magnetic field generating unit in the movable direction, and the mounting error of the magnetic sensor can be reduced.

It is a block diagram which shows an example of a structure of a position detection apparatus. It is explanatory drawing which shows an example of the positional relationship of a magnetic sensor and a magnetic field generation part. It is a figure which shows an example of the output characteristic of a magnetic sensor. It is a block diagram which shows an example of the control block of a calculating part. It is a flowchart which shows the procedure of a position detection. It is explanatory drawing which shows an example of the relationship between the output addition value of a magnetic sensor, and a vertical direction deviation. It is explanatory drawing which shows an example of the relationship between a vertical direction deviation and an output correction amount.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each figure is a conceptual diagram and does not define the dimensions of the detailed structure.

(1) Configuration of Position Detection Device FIG. 1 is a configuration diagram showing an example of the configuration of the position detection device. FIG. 2 is an explanatory diagram illustrating an example of a positional relationship between the magnetic sensors S1 to S4 and the magnetic field generation unit M1. In the position detection device of the present embodiment, the fixed unit 20 includes four magnetic sensors S1 to S4 and the calculation unit 10, and the movable unit 30 includes a magnetic field generation unit M1. In this specification, the center of the movable direction (arrow X direction) of the magnetic field generation unit M1 is described as the position of the movable unit 30, and the shape of the movable unit 30 and the like are omitted for convenience of description.

  The magnetic sensors S <b> 1 to S <b> 4 and the calculation unit 10 are arranged on a substrate that is the fixed unit 20. For example, a known Hall sensor can be used as the magnetic sensors S1 to S4. The Hall sensor is a magnetic sensor using the Hall effect, and can convert the magnetic field generated by the magnetic field generator M1 into an electrical signal. The Hall sensor can be formed as a semiconductor chip containing Si, Ge, GaAs, InAs or the like, and the magnetic sensors S1 to S4 are preferably formed of the same magnetic sensor. Thereby, the temperature dependence of each magnetic sensor S1-S4 can be mutually canceled, and the change of the output characteristic by a temperature fluctuation can be suppressed. In addition, it is easy to set an interval LS between magnetic sensors S1 to S4, which will be described later, to be the same as the movable direction length LM of the magnetic field generation unit M1, and the mounting error of the magnetic sensors S1 to S4 can be reduced.

  The Hall sensor driving method may be, for example, constant current driving in which a constant current is applied to the input terminal of the Hall sensor, or constant voltage driving in which a constant voltage is applied to the input terminal of the Hall sensor. The magnetic sensors S1 to S4 need to perform gain adjustment. In gain adjustment, the ratio (magnetic sensitivity) between the magnetic flux density Bk and the output voltages of the magnetic sensors S1 to S4 is adjusted. Specifically, the peak values of the outputs SO1 to SO4 of the magnetic sensors S1 to S4 coincide when the magnetic field generator M1 and the magnetic sensors S1 to S4 are arranged in parallel with the vertical direction (arrow Z direction). To do. In this specification, a position detection device using four magnetic sensors S1 to S4 will be described as an example. However, the number of magnetic sensors is not limited to four, and may be two or more.

  The magnetic field generation unit M1 is arranged so as to be relatively movable at a predetermined distance LZ0 from the magnetic sensors S1 to S4. In FIG. 2, the movable direction of the magnetic field generator M1 is indicated by the arrow X direction, and the origin 0 in the X direction is at the center between the magnetic sensor S2 and the magnetic sensor S3. The magnetic field generation unit M1 is a magnetic field generation source, and for example, a permanent magnet can be used. For example, a ferrite magnet or a neodymium magnet can be used as the permanent magnet. The permanent magnet is magnetized with N and S poles in the same direction as the magnetic sensing directions of the magnetic sensors S1 to S4. That is, the magnetic sensing directions of the magnetic sensors S1 to S4 are the same as the arrow Z direction as described above. Further, in the drawing, the manner in which the magnetic field generator M1 moves in the direction of the arrow X is schematically shown by using the broken-line magnetic field generators M10 and M12. The shape of the magnetic field generation unit M1 can be, for example, a rectangular column such as a rectangular parallelepiped or a cube. That is, the planar shape of the magnetic field generation unit M1 when viewed in the direction of the arrow Z is a square shape.

  FIG. 3 is a diagram illustrating an example of output characteristics of the magnetic sensors S1 to S4. The horizontal axis indicates the movable direction X of the magnetic field generator M1, and the vertical axis indicates the magnetic flux density Bk. The X-direction origin 0 shown in FIG. 3 coincides with the X-direction origin 0 shown in FIG. 2, and when the X-direction center of the magnetic field generator M1 is at the origin 0 position shown in FIG. The X-direction center of the magnetic field generator M1 is located at the origin 0 position shown. The magnetic flux density Bk can be expressed as a voltage value that is the outputs SO1 to SO4 of the magnetic sensors S1 to S4. In the figure, the output addition value obtained by adding the outputs SO1 and SO2 of the adjacent magnetic sensors S1 and S2 is O12, and the output addition value obtained by adding the outputs SO2 and SO3 of the adjacent magnetic sensors S2 and S3 is O23. An output addition value obtained by adding the outputs SO3 and SO4 of the magnetic sensors S3 and S4 is defined as O34. In the figure, a curve connecting the output addition values O12 to O34 is indicated by a curve Z0.

  In the present embodiment, as shown in FIG. 2, the interval LS between the magnetic sensors S1 to S4 arranged in the movable direction X of the magnetic field generator M1 is set to be the same as the movable direction length LM of the magnetic field generator M1. Yes. Thereby, in the movable range (circle numerals 1-3 shown in FIG. 3) of the magnetic field generation | occurrence | production part M1, output addition value O12-O34 can be made constant. Note that the interval LS between the magnetic sensors S1 to S4 is set to be the same as the movable direction length LM of the magnetic field generation unit M1, that the interval LS between the magnetic sensors S1 to S4 is the movable direction length LM of the magnetic field generation unit M1. The output added values O12 to O34 need only be constant within the movable range (circled numbers 1 to 3 shown in FIG. 3) of the magnetic field generator M1. The interval LS between the magnetic sensors S1 to S4 can include, for example, manufacturing errors, mounting errors, and the like.

  The calculation unit 10 can calculate the position of the magnetic field generation unit M1 from the outputs SO1 to SO4 of the magnetic sensors S1 to S4. The arithmetic unit 10 includes a microcomputer including a CPU and a memory (not shown), an amplifier, and an A / D converter. The microcomputer can also use a DSP (Digital Signal Processor) specialized for signal processing.

  Outputs SO1 to SO4 of the magnetic sensors S1 to S4 are transmitted to the amplifier, and the outputs SO1 to SO4 of the magnetic sensors S1 to S4 are amplified by the amplifier and transmitted to the A / D converter. The A / D converter converts the amplified outputs SO1 to SO4 (analog signals) of the magnetic sensors S1 to S4 into digital signals and transmits them to the memory. The memory can store outputs SO1 to SO4 from the magnetic sensors S1 to S4 as digital values. Moreover, the calculating part 10 can output a drive signal to each magnetic sensor S1-S4. When using the Hall sensor, the calculation unit 10 can supply the constant current or the constant voltage described above to the Hall sensor.

(2) Position detection method (Outline of position detection)
FIG. 4 is a block diagram illustrating an example of a control block of the calculation unit 10. FIG. 5 is a flowchart showing the procedure of position detection. As shown in FIG. 4, the calculation unit 10 includes a position calculation unit 11, a deviation detection unit 12, and an output correction unit 13 when viewed as a control block.

  The calculation unit 10 can calculate the position of the magnetic field generation unit M1 by executing a program stored in the memory. The program is repeatedly executed every elapse of a predetermined time according to the flowchart shown in FIG. That is, the provisional position of the magnetic field generation unit M1 is calculated in step S100, and the vertical deviation Δz of the magnetic sensors S1 to S4 and the magnetic field generation unit M1 is detected in step S101. In step S102, the output correction amount Δf of the magnetic sensors S1 to S4 is calculated using the relational expression shown in the following equation 1, and the final position of the magnetic field generation unit M1 is calculated in step S103. The position calculation unit 11 calculates the provisional position and the final position of the magnetic field generation unit M1, and the deviation detection unit 12 detects the vertical direction deviation Δz. The output correction unit 13 calculates the output correction amount Δf of the magnetic sensors S1 to S4.

  However, the output of the magnetic sensors S1 to S4 is f, the vertical position is z, the output correction amount of the magnetic sensors S1 to S4 is Δf, and the vertical deviation is Δz.

(Position calculation unit 11)
The position calculation unit 11 calculates a temporary position of the magnetic field generation unit M1. Assume that k is an integer of 1 to 3, and outputs of adjacent magnetic sensors S1 to S4 are represented by Vk and Vk + 1. Since Vk−Vk + 1 can be linearly approximated in the movable range of the magnetic field generation unit M1, the provisional position of the magnetic field generation unit M1 can be calculated using the following equation (2). The temperature dependence of the magnetic sensors S1 to S4 can be canceled by dividing the output subtraction value Vk−Vk + 1 of the magnetic sensors S1 to S4 by the output addition value Vk + Vk + 1.
(Equation 2)
(Vk−Vk + 1) / (Vk + Vk + 1)

  For example, when the magnetic field generation unit M1 is in the section indicated by the circled numeral 1 in FIG. 3, the outputs SO1 (= V1) and SO2 (= V2) of the adjacent magnetic sensors S1 and S2 are used to temporarily provision the magnetic field generation unit M1. The position can be calculated. That is, the provisional position of the magnetic field generation unit M1 in the section indicated by the circled number 1 can be calculated by substituting the outputs SO1 and SO2 of the magnetic sensors S1 and S2 into Equation 2. Similarly, when the magnetic field generation unit M1 is in the section indicated by the circled numeral 2, the temporary position of the magnetic field generation unit M1 is determined using the outputs SO2 (= V2) and SO3 (= V3) of the adjacent magnetic sensors S2 and S3. Can be calculated. When the magnetic field generation unit M1 is in the section indicated by the circled number 3, the temporary position of the magnetic field generation unit M1 is calculated using the outputs SO3 (= V3) and SO4 (= V4) of the adjacent magnetic sensors S3 and S4. Can do. As described above, the provisional position of the magnetic field generation unit M1 that does not consider the vertical deviation Δz of the magnetic sensors S1 to S4 and the magnetic field generation unit M1 can be calculated. If the change in the output characteristics due to temperature fluctuation is small, the temporary position of the magnetic field generation unit M1 can be calculated using only the output subtraction values Vk−Vk + 1 of the magnetic sensors S1 to S4.

(Deviation detector 12)
The deviation detector 12 detects the vertical deviation Δz of the magnetic sensors S1 to S4 and the magnetic field generator M1. The magnetic field generator M1 moves relative to the magnetic sensors S1 to S4 in the vertical direction (arrow Z direction) by a predetermined distance LZ0 and moves in the arrow X direction. However, for example, when the magnetic field generation unit M1 or the fixed unit 20 is vibrated, the vertical distances of the magnetic sensors S1 to S4 and the magnetic field generation unit M1 change. In addition, there is a possibility that the vertical distances of the magnetic sensors S1 to S4 and the magnetic field generator M1 may change gradually due to secular change, for example.

  When the vertical distance between the magnetic sensors S1 to S4 and the magnetic field generation unit M1 becomes smaller, the outputs SO1 to SO4 of the magnetic sensors S1 to S4 become larger than when the predetermined distance LZ0 is held. On the other hand, when the vertical distance between the magnetic sensors S1 to S4 and the magnetic field generator M1 increases, the outputs SO1 to SO4 of the magnetic sensors S1 to S4 become smaller than when the predetermined distance LZ0 is held. Therefore, in the present embodiment, the vertical direction deviation Δz of the magnetic sensors S1 to S4 and the magnetic field generator M1 is detected, and the outputs SO1 to SO4 of the magnetic sensors S1 to S4 are corrected.

  FIG. 6 is an explanatory diagram illustrating an example of the relationship between the output addition values O12 to O34 of the magnetic sensors S1 to S4 and the vertical deviation Δz. The horizontal axis indicates the movable direction X of the magnetic field generator M1, and the vertical axis indicates the magnetic flux density Bk. The magnetic flux density Bk can be expressed as a voltage value that is the output addition values O12 to O34 of the magnetic sensors S1 to S4. A curve Z0 indicates the output addition values O12 to O34 of the magnetic sensors S1 to S4 when the vertical distance between the magnetic sensors S1 to S4 and the magnetic field generator M1 is the predetermined distance LZ0, and is the same as the curve illustrated in FIG. It is. In the present specification, the output addition values O12 to O34 of the magnetic sensors S1 to S4 when the vertical distance is the predetermined distance LZ0 are referred to as “reference values indicating the predetermined distance LZ0”.

  Curves Z1 and Z2 indicate output addition values O12 to O34 of the magnetic sensors S1 to S4 when the vertical distance between the magnetic sensors S1 to S4 and the magnetic field generator M1 is smaller than the predetermined distance LZ0. The curve Z1 has a smaller vertical distance between the magnetic sensors S1 to S4 and the magnetic field generator M1 than the curve Z2. On the other hand, the curves Z3 and Z4 indicate the output addition values O12 to O34 of the magnetic sensors S1 to S4 when the vertical distance between the magnetic sensors S1 to S4 and the magnetic field generator M1 is larger than the predetermined distance LZ0. The curve Z4 has a larger vertical distance between the magnetic sensors S1 to S4 and the magnetic field generator M1 than the curve Z3.

  Since the output addition values O12 to O34 of the magnetic sensors S1 to S4 are constant in the movable range of the magnetic field generator M1 (circled numbers 1 to 3 shown in FIG. 3), the output addition values O12 to O34 of the magnetic sensors S1 to S4. And the deviation from the reference value indicating the predetermined distance LZ0 can detect the vertical deviation Δz of the magnetic sensors S1 to S4 and the magnetic field generator M1. That is, the vertical direction deviation Δz indicates a deviation amount from the predetermined distance LZ0.

(Output correction unit 13)
The output correction unit 13 calculates the output correction amount Δf of the magnetic sensors S1 to S4 based on the vertical deviation Δz. FIG. 7 is an explanatory diagram showing an example of the relationship between the vertical deviation Δz and the output correction amount Δf. The horizontal axis indicates the vertical direction Z, and the vertical axis indicates the magnetic flux density Bk. The magnetic flux density Bk can be expressed as a voltage value that is the output addition values O12 to O34 of the magnetic sensors S1 to S4. A straight line L10 indicates a characteristic at the central portion (X = 0 shown in FIG. 3) of the movable direction X of the magnetic field generator M1, and a straight line L20 is near both ends of the movable direction X (X = ± PXE shown in FIG. 3). The characteristic in is shown. The straight lines L10 and L20 represent the characteristics shown in FIG. 6 with the vertical direction Z as the horizontal axis. That is, the straight lines L10 and L20 indicate the relationship between the vertical distances of the magnetic sensors S1 to S4 and the magnetic field generator M1 and the output addition values O12 to O34 of the magnetic sensors S1 to S4.

  The output addition values O12 to O34 of the magnetic sensors S1 to S4 are constant in the movable range of the magnetic field generator M1 except for the vicinity of both end portions (X = ± PXE) in the movable direction X. Therefore, the straight line L10 can use characteristics at a predetermined position other than the central portion (X = 0) in the movable direction X, and can also use characteristics at a plurality of predetermined positions in accordance with the movable position of the magnetic field generation unit M1. . For example, the characteristics in the central portion of each section can be used for each section shown by circled numeral 1, section shown by round numeral 2, and section shown by round numeral 3 shown in FIG. 3.

  The characteristics indicated by the straight lines L10 and L20 can be acquired in advance by computer simulation or measurement by an actual machine. The characteristics indicated by the straight lines L10 and L20 can be stored in the memory using, for example, a map, a table, or the relational expression shown in Equation 1. Equation 1 represents the relationship between the vertical distances of the magnetic sensors S1 to S4 and the magnetic field generation unit M1 and the output addition values O12 to O34 of the magnetic sensors S1 to S4 as a function f (z), and is expanded by Taylor to perform a first-order approximation. It is a thing. Thereby, the output correction amount Δf of the magnetic sensors S1 to S4 can be easily calculated from the proportionality coefficient (∂f / ∂z) and the vertical deviation Δz. For example, in FIG. 7, the reference value indicating the predetermined distance LZ0 is BZ0. When the output addition values O12 to O34 of the magnetic sensors S1 to S4 are BZ1, the vertical direction deviation Δz is LZ1 to LZ0.

  The output correction unit 13 multiplies the proportionality coefficient (∂f / ∂z), which is the gradient of the straight line L10, and the vertical deviation Δz (= LZ1−LZ0) to obtain the output correction amount Δf of the magnetic sensors S1 to S4. Can be calculated. In this case, the output correction amount Δf of the magnetic sensors S1 to S4 is BZ0-BZ1. The output correction unit 13 adds the outputs SO1 to SO4 of the magnetic sensors S1 to S4 by an output correction amount Δf (= BZ0−BZ1). Then, the position calculation unit 11 calculates the final position of the magnetic field generation unit M1 using the corrected outputs SO1 to SO4 of the magnetic sensors S1 to S4. The method for calculating the final position of the magnetic field generator M1 is the same as the method for calculating the provisional position of the magnetic field generator M1 described above.

  In the present embodiment, since the output correction unit 13 corrects the outputs SO1 to SO4 of the magnetic sensors S1 to S4 using the relational expression shown in Equation 1, compared with the case of performing a calculation including higher-order partial differentiation, The calculation time required for position detection can be shortened. Note that the vertical deviation Δz of the magnetic sensors S1 to S4 and the magnetic field generator M1 is sufficiently small compared to the amount of movement of the movable part 30, so that the accuracy of position detection is ensured even by calculation based on the first-order partial differentiation. can do. In addition, the calculation by the secondary differential or higher can be performed as necessary.

  Next, the vicinity of both end portions (X = ± PXE) in the movable direction X is considered. As shown in FIG. 6, in the vicinity of both end portions (X = ± PXE) in the movable direction X, when the vertical direction deviation Δz is the same, the output addition values O12 to O34 of the magnetic sensors S1 to S4 are the central portions in the movable direction X. It becomes larger than (X = 0). Therefore, in the vicinity of both ends (X = ± PXE) in the movable direction X, the output correction amount Δf of the magnetic sensors S1 to S4 is calculated by subtracting the increment ΔBk of the output addition values O12 to O34. The increment ΔBk can be expressed as an offset amount in the vertical axis direction of the straight lines L10 and L20. For example, in FIG. 7, when the output addition values O12 to O34 of the magnetic sensors S1 to S4 are BZ2, the output correction unit 13 uses BZ1 (= BZ2−ΔBk) as the output addition values O12 to O34. Therefore, the output correction amount Δf of the magnetic sensors S1 to S4 is BZ0−BZ1.

  In the present embodiment, the output correction unit 13 corrects the outputs SO1 to SO4 of the magnetic sensors S1 to S4 in accordance with the output characteristics of the magnetic sensors S1 to S4 at the movable direction end, so that the magnetic sensor S1 at the movable direction end. Even when the output characteristics of .about.S4 are different from the output characteristics of the magnetic sensors S1 to S4 in the central portion in the movable direction, it is possible to suppress a decrease in accuracy of position detection.

  In the present embodiment, the interval LS between the magnetic sensors S1 to S4 arranged in the movable direction of the movable unit 30 is the same as the movable direction length LM of the magnetic field generating unit M1, and therefore in a predetermined range in which the movable unit 30 moves relatively. The output addition values O12 to O34 obtained by adding the outputs SO1 to SO4 of the adjacent magnetic sensors S1 to S4 can be made constant. Then, the calculation unit 10 detects the vertical deviation Δz of the magnetic sensors S1 to S4 and the magnetic field generation unit M1 from the output addition values O12 to O34, and the magnetic sensors S1 to S4 based on the vertical deviation Δz. Output corrector 13 that corrects the outputs SO1 to SO4, so that the outputs SO1 to SO4 of the magnetic sensors S1 to S4 can be corrected according to the vertical deviation Δz. Therefore, even if a deviation in the vertical direction Z occurs between the magnetic sensors S1 to S4 and the magnetic field generator M1, it is possible to suppress a decrease in position detection accuracy.

(3) Others The present invention is not limited to the embodiment described above and shown in the drawings, and can be implemented with appropriate modifications within a range not departing from the gist. For example, the magnetic field generation unit M1 may be fixed and the magnetic sensors S1 to S4 may be moved relative to the magnetic field generation unit M1.

  The position detection device of the present invention can be used for position detection of a movable part that moves linearly (slides) within a predetermined range. For example, it can be used for a drive device for a power window or a drive device for an electric seat. Further, the position detection device of the present invention can further include a plurality of magnetic sensors in the Y direction orthogonal to the X direction and the Z direction. Thereby, the movable position in the X direction and the Y direction can be detected, and can also be used as an XY pointer.

S1 to S4: Magnetic sensor M1: Magnetic field generation unit 10: Calculation unit 12: Deviation detection unit 13: Output correction unit 20: Fixed unit 30: Movable unit

Claims (4)

A position detection device that detects the position of a movable part that moves relative to a fixed part at a predetermined distance,
One of the fixed part and the movable part is provided with a magnetic field generation part that is a magnetic field generation source, and the other of the fixed part and the movable part is a plurality of magnetic sensors that detect the magnetic field of the magnetic field generation part; A calculation unit that calculates the position of the movable unit from the output of the magnetic sensor,
The interval between the magnetic sensors arranged in the movable direction of the movable part is the same as the movable direction length of the magnetic field generating part,
The arithmetic unit detects a deviation in the vertical direction of the magnetic sensor and the magnetic field generation unit from an output addition value obtained by adding the outputs of the magnetic sensors adjacent in the movable direction; and
An output correction unit that corrects the output of the magnetic sensor based on the vertical deviation;
A position detecting device. The position detection device according to claim 1, wherein the output correction unit corrects the output of the magnetic sensor using a relational expression expressed by the following formula 1.

However, the output of the magnetic sensor is f, the vertical position is z, the output correction amount of the magnetic sensor is Δf, and the vertical deviation is Δz.   The position detection device according to claim 1, wherein the output correction unit corrects an output of the magnetic sensor in accordance with an output characteristic of the magnetic sensor at a movable direction end.   The position detection device according to claim 1, wherein the plurality of magnetic sensors are formed of the same magnetic sensor.

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