JP6628660B2 - Magnetic position detector - Google Patents

Description

  The present invention relates to a magnetic position detector that detects a rotational position of a rotating body.

  The following is known as a conventional technique for detecting the state of a rotating body using a magnetic sensor.

  Patent Document 1 discloses a rotation detection device. The rotation detecting device includes a magnetism generating unit, a magnetic sensor array, and an angle calculating unit. The magnetism generating means has circumferential anisotropy around the center of rotation. The magnetic sensor array includes magnetic sensor elements arranged in a matrix. The angle calculating means calculates a rotation angle from the output of the magnetic sensor array.

  Patent Literature 2 discloses an apparatus that measures a position and a tilt angle of a measured surface with respect to a reference surface. The device includes a permanent magnet, a magnetic sensor array, a feature extraction unit, and a calculation unit. The permanent magnet is installed on the end surface of the rotating body that is the surface to be measured. The magnetic sensor array is installed on the reference plane side and measures the distribution of magnetic flux generated by the permanent magnet. The feature extraction unit extracts the position of the center of gravity and the distortion of the magnetic flux distribution. The calculation unit calculates the position and the inclination angle of the permanent magnet based on the position of the center of gravity and the distortion.

JP-A-2003-148999 JP 2005-207746 A

  Due to aged deterioration, a “shift” of the rotation axis of the rotating body may occur. For example, when the bearing that supports the rotating body is degraded due to electrolytic corrosion, displacement of the rotating shaft occurs. The above prior art does not consider such a deviation of the rotation axis. Therefore, when the displacement of the rotation axis occurs, an error occurs in the calculation result.

  An object of the present invention is to provide a magnetic position detector capable of calculating a rotational position of a rotating body without being affected by a shift of a rotating shaft.

  In one aspect of the present invention, a magnetic position detector is provided. The magnetic position detector has (a) a magnetic field generator attached to a rotating body that rotates around a rotation axis and generates a magnetic field, and (b) a sensor surface facing the magnetic field generator. And (c) an arithmetic unit for calculating the rotational position of the rotating body based on the detected intensity distribution. The magnetic field detection region is a region on the sensor surface where the strength of the magnetic field is equal to or greater than a threshold. The magnetic field generator and the magnetic sensor are configured such that at least two magnetic field detection regions are generated separately from each other. The arithmetic device calculates a rotational position based on a relative positional relationship between the two magnetic field detection regions.

  According to the magnetic position detector of the present invention, it is possible to calculate the rotational position of the rotating body without being affected by the displacement of the rotating shaft.

FIG. 1 is a configuration diagram showing a configuration of a magnetic position detector according to an embodiment of the present invention. A conceptual diagram for explaining a principle of calculating a rotational position according to an embodiment of the present invention. Conceptual diagram for explaining the definition of the magnetic field detection area Conceptual diagram for explaining the definition of the magnetic field detection area A conceptual diagram for explaining a principle of calculating a rotational position according to an embodiment of the present invention. A conceptual diagram for explaining a principle of calculating a rotational position according to an embodiment of the present invention. Conceptual diagram for explaining the definition of the magnetic field center position Conceptual diagram for explaining the definition of the magnetic field center position Conceptual diagram for explaining a first example of calculation of a rotational position Conceptual diagram for explaining a first example of calculation of a rotational position Conceptual diagram for explaining a second example of calculation of a rotational position Conceptual diagram for explaining a third example of calculation of a rotational position Conceptual diagram for explaining a fourth example of calculation of a rotational position Conceptual diagram for explaining detection of displacement of a rotating shaft Configuration diagram showing an example of a magnetic field generator Configuration diagram showing another example of a magnetic field generator Configuration diagram showing an example of a magnetic sensor Conceptual diagram showing the relationship between the cell size of the magnetic sensor and the size of the magnetic field detection area Conceptual diagram showing the relationship between the cell size of the magnetic sensor and the size of the magnetic field detection area Conceptual diagram showing the relationship between the cell size of the magnetic sensor and the size of the magnetic field detection area Block diagram illustrating a configuration example of an arithmetic unit FIG. 1 is a configuration diagram showing a configuration of a motor system to which a magnetic position detector according to an embodiment of the present invention is applied.

  A magnetic position detector according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1. Configuration and Principle FIG. 1 schematically shows a configuration of a magnetic position detector 10 according to an embodiment of the present invention. The magnetic position detector 10 is applied to the rotator 1 that rotates around the rotation axis RA, and calculates and outputs the rotational position of the rotator 1. The rotation position of the rotator 1 can also be called a rotation angle. The rotating body 1 is optional, but an example is a motor shaft.

  Typically, the rotating body 1 is supported by a bearing 2 and rotates around a rotation axis RA. Here, there is a possibility that a “displacement” of the rotation axis RA occurs due to aging. For example, when the bearing 2 deteriorates due to electrolytic corrosion, a shift of the rotation axis RA occurs. Such a deviation of the rotation axis RA is hereinafter referred to as “axis deviation”. When the axis shift occurs, an error may occur in the calculation result of the rotational position. The time scale of aging is sufficiently longer than the rotation period of the rotating body 1.

  The magnetic position detector 10 according to the present embodiment can calculate the rotational position of the rotating body 1 without being affected by the axis deviation. As shown in FIG. 1, the magnetic position detector 10 includes a magnetic field generator 20, a magnetic sensor 30, and an arithmetic device 40.

  The magnetic field generator 20 generates a magnetic field. The magnetic field generator 20 is typically formed using a permanent magnet. Such a magnetic field generator 20 is attached to the rotating body 1. When the rotating body 1 rotates, the spatial distribution of the magnetic field generated from the magnetic field generator 20 also changes.

  The magnetic sensor 30 is arranged to face the magnetic field generator 20 and detects the intensity distribution of the magnetic field generated from the magnetic field generator 20. More specifically, the magnetic sensor 30 has a sensor surface SS facing the magnetic field generator 20, and detects a magnetic field intensity distribution on the sensor surface SS. For example, the magnetic sensor 30 includes a plurality of magnetic sensor elements arranged in an array on the sensor surface SS. Examples of the magnetic sensor element include a Hall element and a magnetoresistive element. When the rotating body 1 rotates, the magnetic field intensity distribution detected by the magnetic sensor 30 also changes. The magnetic sensor 30 outputs detected magnetic field data DH indicating the detected magnetic field strength distribution to the arithmetic device 40.

  The arithmetic unit 40 is connected to the magnetic sensor 30 and receives the detected magnetic field data DH from the magnetic sensor 30. Then, the arithmetic unit 40 calculates the rotational position of the rotating body 1 based on the magnetic field intensity distribution indicated by the detected magnetic field data DH. The calculation of the rotational position by the arithmetic unit 40 will be described later in detail. The arithmetic device 40 outputs rotation position data DR indicating the calculated rotation position to the outside. As the arithmetic device 40, a microcomputer is exemplified.

  Next, the principle of calculating the rotational position in the present embodiment will be described with reference to FIGS.

  First, a portion of the magnetic field generator 20 that generates a magnetic field is the magnetic field generating portion 21. In the example shown in FIG. 2, the magnetic field generator 20 has at least two magnetic field generating portions 21, and the magnetic field generating portions 21 are separated from each other. That is, the magnetic field generator 20 separately generates a magnetic field from each of the at least two magnetic field generating portions 21. Therefore, the magnetic sensor 30 also detects at least two magnetic field strength distributions.

  A region facing the magnetic field generating portion 21 on the sensor surface SS is a magnetic field detection region 31. Here, the definition of the magnetic field detection region 31 will be described in more detail with reference to FIGS. FIGS. 3 and 4 show examples of the magnetic field intensity distribution along the line A-A 'in FIG. The horizontal axis represents the position on the sensor surface SS, and the vertical axis represents the magnetic field strength. In the example shown in FIGS. 3 and 4, there are two magnetic field strength distributions caused by each of the two magnetic field generating portions 21. In addition, as shown in FIG. 4, the polarity of the magnetic pole of the magnetic field generating portion 21 does not matter. The magnetic field detection region 31 in the present embodiment is a region on the sensor surface SS where the magnetic field intensity is equal to or larger than the threshold value Hth. When the magnetic field strength distribution is isotropic, the magnetic field detection region 31 has a circular shape. However, the shape of the magnetic field detection region 31 is not limited to a circle, but may be an ellipse, a substantially rectangle, an irregular shape, or the like.

  In the example illustrated in FIG. 2, two magnetic field detection regions 31 are generated on the sensor surface SS so as to face each of the two magnetic field generation portions 21. Further, the two magnetic field detection regions 31 are separated from each other on the sensor surface SS. When the rotating body 1 rotates around the rotation axis RA, each magnetic field generating portion 21 also rotates around the rotation axis RA, and accordingly, each magnetic field detection region 31 also rotates around the rotation center RC. It can be said that the rotation center RC is a position facing the rotation axis RA on the sensor surface SS.

  What is important in the present embodiment is that at least two magnetic field detection regions 31 are generated separately from each other on the sensor surface SS. For this purpose, the structure of the magnetic field generator 20, the arrangement relationship between the magnetic field generator 20 and the magnetic sensor 30, the threshold value Hth of the magnetic sensor 30, and the like are appropriately designed. That is, according to the present embodiment, the magnetic field generator 20 and the magnetic sensor 30 are configured such that at least two magnetic field detection regions 31 are generated separately from each other.

  The arithmetic unit 40 can extract a plurality of magnetic field detection regions 31 based on the magnetic field strength distribution indicated by the detected magnetic field data DH. Then, the arithmetic device 40 calculates the rotational position of the rotating body 1 based on the relative positional relationship between two of the extracted plurality of magnetic field detection regions 31.

  For example, FIG. 5 shows two magnetic field detection regions 31-1 and 31-2 on the sensor surface SS. When the rotating body 1 rotates, each of the magnetic field detection regions 31-1 and 31-2 rotates around the rotation center RC. At this time, the relative positional relationship between the magnetic field detection regions 31-1 and 31-2 on the sensor surface SS fluctuates with the rotation of the rotating body 1. That is, the relative positional relationship between the magnetic field detection regions 31-1 and 31-2 is uniquely determined depending on the rotational position of the rotating body 1. Therefore, the arithmetic unit 40 can calculate the rotational position of the rotating body 1 based on the relative positional relationship between the magnetic field detection regions 31-1 and 31-2.

  Here, with reference to FIG. 6, a case where an axis shift has occurred will be considered. In the example of FIG. 6, first, the magnetic field detection regions 31-1 and 31-2 rotate around the rotation center RCa along the rotation trajectory Ca. After that, it is assumed that the rotation center RC moves from RCa to RCb as a result of the rotation axis RA of the rotating body 1 being shifted. Then, the magnetic field detection regions 31-1 and 31-2 rotate around the rotation center RCb along the rotation locus Cb. However, if the rotation position of the rotating body 1 is the same, the relative positional relationship between the magnetic field detection regions 31-1 and 31-2 is the same regardless of the position of the rotation center RC. Therefore, by using the relative positional relationship between the magnetic field detection areas 31-1 and 31-2, the arithmetic device 40 can calculate the rotational position without being affected by the axis deviation.

  As described above, according to the present embodiment, the magnetic field generator 20 and the magnetic sensor 30 are configured such that at least two magnetic field detection regions 31 are generated separately from each other on the sensor surface SS. . Then, the arithmetic device 40 calculates the rotational position of the rotating body 1 based on the relative positional relationship between the two magnetic field detection regions 31. Thus, the rotational position can be calculated without being affected by the axis deviation.

  In the present embodiment, strict alignment is not required as long as at least two magnetic field detection regions 31 are generated separately from each other. Therefore, the assembly and installation of the magnetic position detector 10 are easy.

  In the present embodiment, the relative positional relationship between the two magnetic field detection regions 31 only needs to be known, and it is not necessary to strictly determine the absolute position of each magnetic field detection region 31. Therefore, fine processing of the magnetic field generator 20 is unnecessary, and it is not necessary to increase the resolution of the magnetic sensor 30 unnecessarily. These contribute to cost reduction.

2. Examples of Calculation of Rotation Position Hereinafter, various examples of calculation of the rotation position will be described. In the description, the concept of “magnetic field center position 32” will be introduced. 7 and 8 are conceptual diagrams illustrating the definition of the magnetic field center position 32. FIG. The magnetic field center position 32 is the “center of gravity” of the magnetic field intensity distribution in the magnetic field detection region 31. It can be said that the magnetic field center position 32 is a “weighted average position” of the magnetic field detection region 31 when the magnetic field strength is weighted.

  In the example shown in FIG. 7, the magnetic field intensity distribution is isotropic, and the shape of the magnetic field detection region 31 is circular. In this case, the magnetic field center position 32 matches the peak position of the magnetic field strength distribution, and also matches the center position of the circular magnetic field detection region 31. On the other hand, in the example shown in FIG. 8, the magnetic field strength distribution is anisotropic, and the magnetic field center position 32 does not coincide with the peak position of the magnetic field strength distribution. However, in any case, the arithmetic device 40 can calculate the magnetic field center position 32 based on the magnetic field intensity distribution in the magnetic field detection region 31. In addition, from the viewpoint of calculation load and calculation speed, the circular magnetic field detection region 31 is optimal.

  As described above, in the present embodiment, at least two magnetic field detection regions 31 are generated. The arithmetic device 40 calculates two magnetic field center positions 32 for each of the two magnetic field detection regions 31 based on the magnetic field strength distribution indicated by the detected magnetic field data DH. It can be said that the two magnetic field center positions 32 are representative positions of the two magnetic field detection regions 31 respectively. Therefore, by using the relative positional relationship between the two magnetic field center positions 32, the arithmetic device 40 can calculate the rotational position without being affected by the axis deviation.

2-1. First Example FIGS. 9 and 10 are conceptual diagrams for explaining a first example. The sensor surface SS is represented by an XY plane defined by an X axis and a Y axis orthogonal to each other. Two magnetic field center positions 32-1 and 32-2 exist for each of the two magnetic field detection regions 31-1 and 31-2.

  Here, the “first line LA” and the “first angle α” used in the present example are defined. The first line LA is a line connecting between the two magnetic field center positions 32-1 and 32-2. The first angle α is an angle between the first line LA and the reference line LR on the sensor surface SS. For example, when the reference line LR is the X axis, the first angle α is an angle between the first line LA and the X axis. It can be said that the first angle α represents the relative positional relationship between the two magnetic field center positions 32.

  When the rotating body 1 rotates, each of the magnetic field center positions 32-1 and 32-2 also rotates around the rotation center RC. Here, the distances from the rotation center RC to the magnetic field center positions 32-1 and 32-2 are r1 and r2. In this example, the distance r1 and the distance r2 are equal. Therefore, both the magnetic field center positions 32-1 and 32-2 rotate along the same rotation locus C.

  Further, in this example, the magnetic field center positions 32-1 and 32-2 exist at diagonal positions across the rotation center RC. Therefore, the first line LA connecting the magnetic field center positions 32-1 and 32-2 passes through the rotation center RC. It can be said that the arrangement of the magnetic field generating portion 21 with respect to the rotation axis RA of the rotating body 1 is determined so that the first line LA passes through the rotation center RC. Since the first line LA passes through the rotation center RC, the first angle α between the first line LA and the reference line LR is equal to the magnetic field center position 32-1 around the rotation center RC as viewed from the reference line LR. Represents the rotation angle. That is, the first angle α reflects the rotational position of the rotating body 1.

  FIG. 9 shows a case where no axis deviation has occurred. At this time, the rotation center RC coincides with the coordinate origin of the XY coordinates, and the first line LA passing through the rotation center RC also passes through the coordinate origin. On the other hand, FIG. 10 shows a case where an axis shift has occurred. When the axis shift occurs, the rotation center RC shifts from the coordinate origin, and the first line LA does not pass through the coordinate origin. However, the first angle α is not affected by the misalignment. That is, if the rotational position of the rotating body 1 is the same, the first angle α is constant regardless of the presence or absence of the axis deviation. Therefore, the first angle α can be used as the rotation position without being affected by the axis deviation.

  As a comparative example, a rotation angle φ of the magnetic field center position 32-1 around the coordinate origin is considered instead of the rotation center RC. When no axis deviation occurs, the rotation angle φ matches the first angle α. However, when the axis shift occurs as shown in FIG. 10, the rotation angle φ does not match the first angle α that is the correct rotation angle. That is, the rotation angle φ is affected by the axis deviation. Therefore, when the rotation angle φ is used as the rotation position, a calculation error occurs due to the axis deviation.

  As described above, according to this example, the first line LA passes through the rotation center RC. The arithmetic device 40 calculates the first angle α as a rotation position based on the two magnetic field center positions 32-1 and 32-2. The first angle α is not affected by the misalignment. That is, the arithmetic device 40 can calculate the rotational position without being affected by the axis deviation. Further, since the calculation method of this example is simple and simple, the calculation load on the calculation device 40 can be greatly reduced.

2-2. Second Example FIG. 11 is a conceptual diagram for explaining a second example. Compared to the first example, in this example, the distance r1 and the distance r2 are different. The magnetic field center position 32-1 rotates along the rotation trajectory C1, and the magnetic field center position 32-2 rotates along the rotation trajectory C2. Others are the same as the first example.

  Also in this example, the magnetic field center positions 32-1 and 32-2 exist at diagonal positions across the rotation center RC, and the first line LA passes through the rotation center RC. Therefore, the first angle α can be used as the rotation position. That is, the rotational position can be easily calculated without being affected by the axis deviation.

  Further, in this example, there is no need to make the distance r1 and the distance r2 coincide. This means that strict alignment is not required. Therefore, the production and installation of the magnetic field generator 20 are facilitated. This contributes to cost reduction.

2-3. Third Example FIG. 12 is a conceptual diagram for explaining a third example. In this example, the magnetic field center positions 32-1 and 32-2 do not exist at diagonal positions with respect to the rotation center RC, and therefore, the first line LA does not pass through the rotation center RC.

  Here, the “second line LB” and the “second angle β” used in the present example are defined. The second line LB is a line connecting one magnetic field center position 32-1 and the rotation center RC. The second angle β is an angle between the first line LA and the second line LB. The second angle β is a parameter that defines a triangular shape composed of the three points of the rotation center RC and the two magnetic field center positions 32-1 and 32-2. The triangular shape is determined when the magnetic field generator 20 is attached to the rotating body 1. That is, the second angle β is a fixed parameter. Even if the rotating body 1 rotates, the second angle β remains constant.

  Next, as in the case of the first example, the rotation angle of the magnetic field center position 32-1 around the rotation center RC viewed from the reference line LR will be considered. In the case of the first example, the rotation angle was the first angle α. On the other hand, in the case of this example, as can be seen from FIG. 12, the rotation angle is the difference (α−β) between the first angle α and the second angle β. Therefore, α-β can be used as the rotation position. Here, it should be noted that the first angle α is a parameter that is not affected by the axis deviation, and the second angle β is a fixed parameter. Therefore, α-β is also a parameter that is not affected by the axis deviation. That is, α-β can be used as the rotational position without being affected by the axis deviation.

  The arithmetic device 40 calculates the first angle α based on the two magnetic field center positions 32-1 and 32-2. Then, the arithmetic device 40 calculates a difference (α−β) between the first angle α and the second angle β as a rotation position. Various methods are available for obtaining the second angle β. For example, when the second angle β is accurately determined at the time when the magnetic field generator 20 is attached to the rotating body 1, the second angle β is input to the arithmetic unit 40 from the outside in advance. The arithmetic unit 40 stores the input second angle β in the memory. Alternatively, immediately after the rotating body 1 starts rotating, the arithmetic device 40 calculates the initial position of the rotation center RC from the rotation trajectory of the magnetic field center position 32, and further calculates the initial position using the initial position and the magnetic field center position 32. 2 may be calculated. The arithmetic device 40 stores the calculated second angle β in the memory. In any case, the arithmetic device 40 can calculate the rotational position using the second angle β stored in advance.

  Also in this example, it is possible to easily calculate the rotational position without being affected by the axis deviation. Furthermore, in this example, the magnetic field center positions 32-1 and 32-2 do not need to be at diagonal positions across the rotation center RC. This means that strict alignment is not required. Therefore, the production and installation of the magnetic field generator 20 are facilitated. This contributes to cost reduction.

2-4. Fourth Example The number of magnetic field detection regions 31 is not limited to two, and may be three or more. For example, FIG. 13 illustrates a case where three magnetic field detection regions 31-1 to 31-3 exist. The arithmetic device 40 can calculate the rotational position using the two magnetic field detection regions 31, and the two magnetic field detection regions 31 are hereinafter referred to as a "magnetic field detection region pair". In the example of FIG. 13, a plurality of different magnetic field detection region pairs (31-1, 31-2), (31-2, 31-3), and (31-3, 31-1) exist.

  The arithmetic device 40 calculates the rotational position using at least one of the plurality of different magnetic field detection region pairs. For example, the arithmetic device 40 calculates a rotational position using one magnetic field detection region pair, and outputs the calculated rotational position. Alternatively, the arithmetic device 40 may calculate a plurality of rotation positions in parallel based on each of the plurality of magnetic field detection region pairs, and output one of the plurality of rotation positions. In any case, when the used magnetic field detection region pair changes to the unusable state, the arithmetic device 40 calculates the rotational position by using another of the plurality of magnetic field detection region pairs.

  As described above, according to this example, even when an abnormality occurs in the magnetic field generator 20, the calculation of the rotational position can be continued. In addition, as an example of the abnormality of the magnetic field generator 20, it is conceivable that some magnets fall from the rotating body 1.

3. Detection of Abnormality of Rotation Axis RA The arithmetic device 40 can also detect an abnormality of the rotation axis RA such as an axis shift. For example, consider an allowable range RNG of the rotation center RC as shown in FIG. Arithmetic unit 40 previously stores an allowable parameter indicating the allowable range RNG in a memory.

  During the rotation of the rotating body 1, the arithmetic device 40 periodically calculates the rotation center RC based on the rotation trajectory of the magnetic field detection area 31. Then, the arithmetic unit 40 detects an abnormality of the rotation axis RA by comparing the calculated position of the rotation center RC with the allowable range RNG. Specifically, when the calculated rotation center RC deviates from the allowable range RNG, the arithmetic device 40 determines that an abnormality has occurred in the rotation axis RA. When detecting an abnormality, the arithmetic unit 40 outputs an error to the outside.

  Detection of an abnormality of the rotation axis RA is preferable from the viewpoint of preventive maintenance. For example, it is possible to detect the abnormality before the bearing 2 completely fails.

4. Example of magnetic field generator 20 FIG. 15 shows an example of the magnetic field generator 20. In this example, the magnetic field generator 20 has at least two magnets 23 separated from each other. Each magnet 23 corresponds to the magnetic field generating portion 21 shown in FIG.

  FIG. 16 shows another example of the magnetic field generator 20. In this example, the magnetic field generator 20 includes a magnet 24 and a magnetic shield 25 formed on the magnet 24. Here, the magnet 24 is arranged on the rotating body 1 side, and the magnetic shield 25 is arranged on the magnetic sensor 30 side. The magnetic shield 25 is formed of a shield member that shields a magnetic field from the magnet 24. The magnetic shield 25 has at least two openings 26 separated from each other. No shield member is formed in the opening 26, and the magnetic field from the magnet 24 can pass through the opening 26. That is, each opening 26 corresponds to the magnetic field generating portion 21 shown in FIG.

5. Example of Magnetic Sensor 30 FIG. 17 shows an example of the magnetic sensor 30. The magnetic sensor 30 includes a cell array 33. The cell array 33 includes a plurality of cells 34 arranged in an array. One cell 34 (i, j) detects the intensity of the magnetic field and outputs the detected intensity as one output H (i, j). Therefore, a magnetic field strength distribution can be obtained by combining the outputs H (i, j) from each of the plurality of cells.

  FIG. 18 is a conceptual diagram showing the relationship between the size of the cell 34 and the size of the magnetic field detection region 31. Here, the length of one side of one cell 34 is a. The shape of the magnetic field detection region 31 is circular, and its diameter is d.

  It is desirable that the diameter d is not less than the length a (d ≧ a). As a comparative example, consider the case of d <a shown in FIG. When d <a, there is a possibility that one magnetic field detection region 31 is not distributed over a plurality of cells 34 and is completely contained in one cell 34. In this case, the output H (i, j) from the cell 34 is the same regardless of the position of the magnetic field detection region 31 in the cell 34. That is, the magnetic field center position 32 cannot be accurately calculated from the output H (i, j). From the viewpoint of the calculation accuracy of the magnetic field center position 32, it is desirable that the condition of d ≧ a is satisfied.

  In the case of d = a, the magnetic field center position 32 can be calculated with high accuracy based on the output H (i, j) from one cell 34 at a minimum and 2 × 2 cells at a maximum.

  When d = 2a, the magnetic field center position 32 can be calculated with high accuracy based on the output H (i, j) from the minimum 2 × 2 cells 34 and the maximum 3 × 3 cells 34. is there.

  In the case of d> 2a, as shown in FIG. 20, there is a possibility that 3 × 3 cells 34 are insufficient. However, as the number of cells 34 increases, the calculation load increases accordingly. From the viewpoint of reducing the calculation load, it is desirable that the 3 × 3 cells 34, that is, the condition of d ≦ 2a be satisfied. For example, when the 3 × 3 cells 34 are used, the calculation amount is 9/4096 compared with the case where the 64 × 64 cells 34 are used. This means that the time resolution of position calculation can be improved to 4096/9 times.

6. Example of Operation Device 40 FIG. 21 is a block diagram illustrating a configuration example of the operation device 40. The arithmetic device 40 includes a processor 41, a memory 42, an input / output interface 43, and a bus 44. The processor 41, the memory 42, and the input / output interface 43 are connected to each other via a bus 44.

  The detected magnetic field data DH output from the magnetic sensor 30 is input via the input / output interface 43. The input detected magnetic field data DH is stored in the memory 42. Various parameters may be stored in advance in the memory 42 as necessary. Examples of the various parameters include the above-described second angle β and the allowable range RNG. The processor 41 reads necessary data from the memory 42 and calculates a rotational position. Then, the processor 41 outputs rotation position data DR indicating the calculated rotation position to the outside via the input / output interface 43.

7. Application to Motor System The magnetic position detector 10 according to the present embodiment is applied to, for example, a motor system 100 as shown in FIG. The motor system 100 includes a rotating body 1, a magnetic position detector 10, a motor 110, and a motor control device 120.

  The motor 110 rotates the rotating body 1. The magnetic position detector 10 calculates the rotational position of the rotating body 1 and outputs rotational position data DR indicating the calculated rotational position to the motor control device 120. The motor control device 120 controls the operation of the motor 110 with reference to the rotation position data DR.

  The embodiments of the present invention have been described with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiment, and can be appropriately modified by those skilled in the art without departing from the gist.

  REFERENCE SIGNS LIST 1 rotating body, 2 bearing, 10 magnetic position detector, 20 magnetic field generator, 21 magnetic field generating part, 23 magnet, 24 magnet, 25 magnetic shield, 26 opening, 30 magnetic sensor, 31 magnetic field detection area, 32 magnetic field center Position, 33 cell array, 34 cells, 40 arithmetic unit, 41 processor, 42 memory, 43 input / output interface, 44 bus, 100 motor system, 110 motor, 120 motor controller, DH detected magnetic field data, DR rotation position data, LA 1 line, LB 2nd line, LR reference line, RA rotation axis, RC rotation center, RNG tolerance, SS sensor surface.

Claims (12)

A magnetic field generator that is attached to a rotating body that rotates around a rotation axis and generates a magnetic field;
A magnetic sensor having a sensor surface facing the magnetic field generator and detecting an intensity distribution of the magnetic field on the sensor surface;
An arithmetic unit that calculates a rotational position of the rotating body based on the detected intensity distribution,
The magnetic field detection region is a region where the strength of the magnetic field is equal to or greater than a threshold on the sensor surface,
The magnetic field generator and the magnetic sensor are configured such that at least two of the magnetic field detection regions are generated separately from each other,
The arithmetic device calculates the rotational position based on a relative positional relationship between the two magnetic field detection regions ,
The magnetic sensor has a plurality of cells arranged in an array,
Each of the plurality of cells detects the intensity of the magnetic field, outputs the detected intensity as one output,
A magnetic position detector in which a combination of outputs from each of the plurality of cells is the intensity distribution . The magnetic position detector according to claim 1, wherein:
The magnetic field center position is the position of the center of gravity of the intensity distribution in the magnetic field detection region,
The arithmetic unit calculates two magnetic field center positions with respect to each of the two magnetic field detection regions, and calculates the rotational position based on a relative positional relationship between the two magnetic field center positions. . The magnetic position detector according to claim 2, wherein
The first line is a line connecting between the two magnetic field center positions,
The first angle is an angle between the first line and a reference line on the sensor surface,
The magnetic position detector, wherein the arithmetic device calculates the rotational position based on the first angle. The magnetic position detector according to claim 3, wherein
The magnetic field detection region rotates around a rotation center on the sensor surface,
The first line passes through the center of rotation,
The magnetic position detector, wherein the arithmetic device calculates the first angle as the rotation position. The magnetic position detector according to claim 4, wherein
A magnetic position detector, wherein a distance from each of the two magnetic field center positions to the rotation center is different. The magnetic position detector according to claim 3, wherein
The magnetic field detection region rotates around a rotation center on the sensor surface,
The second line is a line connecting between one of the two magnetic field center positions and the rotation center,
The second angle is an angle between the first line and the second line,
The magnetic position detector, wherein the arithmetic device calculates the rotational position based on a difference between the first angle and the second angle. The magnetic position detector according to claim 6,
The magnetic position detector, wherein the arithmetic device stores the second angle in advance, and calculates the rotational position using the stored second angle. The magnetic position detector according to claim 1, wherein:
The two magnetic field detection regions are a magnetic field detection region pair,
When three or more magnetic field detection regions occur separately, there are a plurality of different magnetic field detection region pairs,
The computing device calculates the rotational position using one of the plurality of different magnetic field detection region pairs, and when the one magnetic field detection region pair becomes unusable, the plurality of different magnetic field detection regions A magnetic position detector for calculating the rotational position using another of the pair. A magnetic position detector according to claim 1, wherein:
The magnetic field detection region rotates around a rotation center on the sensor surface,
The magnetic position detector, wherein the arithmetic unit stores an allowable range of the rotation center and detects an abnormality of the rotation axis by comparing the position of the rotation center with the allowable range. The magnetic position detector according to claim 1, wherein:
A magnetic position detector, wherein the magnetic field generator has at least two magnets separated from each other. The magnetic position detector according to claim 1, wherein:
The magnetic field generator,
A magnet,
And a magnetic shield formed of a shield member for shielding a magnetic field from the magnet,
The magnetic shield has at least two openings separated from each other;
The at least two openings allow a magnetic field from the magnet to pass therethrough. The magnetic position detector according to claim 1 , wherein:
The length of one side of each of the plurality of cells is a,
The shape of the magnetic field detection region is a circle having a diameter d,
A magnetic position detector that satisfies a ≦ d ≦ 2a.

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