Rotational speed detection device, rotational speed detection system, rotational speed calculation device, and rotational speed detection method

Abstract

To reduce information to be referred to when calculating the number of rotations of a rotating body. [Solution] A rotation speed detection device is provided, comprising: a magnetic wire that is subjected to an axial alternating magnetic field with two or more cycles per rotation as a rotating body rotates, and that outputs a pulse with a polarity according to the change in the direction of the magnetic field; a magnet polarity discrimination unit that forms the alternating magnetic field and discriminates the polarity of a magnet contained in the rotating body at a predetermined relative position with respect to the magnetic wire; and a calculation unit that counts circumferential segments of the rotating body and calculates a count value, wherein the calculation unit calculates the count value based on the polarity of the magnet of the rotating body obtained last time, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse was generated, but without using the polarity of the previous pulse.

Description

[Technical field]

[0001] The present invention relates to a rotation speed detection device, a rotation speed detection system, a rotation speed calculation device, and a rotation speed detection method. [Background technology]

[0002] Conventionally, a multiple rotation angle detection device using a power generation sensor is known (see, for example, Patent Document 1). Patent Document 1: JP 2024-106245 A Summary of the Invention [Problem to be solved by the invention]

[0003] To reduce information to be referred to when calculating the number of rotations of a rotating body. [Means for solving the problem]

[0004] In order to solve the above problems, a first aspect of the present invention provides a rotation speed detection device including a magnetic wire that is provided with an alternating magnetic field in an axial direction at least two periods per rotation as a rotor rotates, and outputs a pulse with a polarity according to a change in the direction of the magnetic field. The rotation speed detection device may include a magnet polarity discrimination unit that forms the alternating magnetic field and discriminates the polarity of a magnet included in the rotor at a predetermined relative position with respect to the magnetic wire. Any of the rotation speed detection devices may include a calculation unit that counts circumferential segments of the rotor to calculate a count value. In any of the rotation speed detection devices, the calculation unit may calculate the count value based on the previously acquired polarity of the rotor's magnet, the current polarity of the pulse, and the polarity of the rotor's magnet when the current pulse is generated, without using the previous polarity of the pulse.

[0005] In any of the above rotation speed detection devices, when the calculation unit is driven by the pulse and starts calculating the count value, it may detect that the other segment adjacent to the segment that faced the magnetic wire when the previous pulse was generated has moved to a position facing the magnetic wire when the current pulse is generated, based on the previously acquired polarity of the magnet of the rotating body, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse is generated. Any of the above rotation speed detection devices may include a memory unit that accumulates the count values ​​calculated by the calculation unit and stores the accumulated value.

[0006] In any of the above rotation speed detection devices, the calculation unit may change the count value for at least one of the polarities of the current pulse depending on whether the polarity of the magnet of the rotating body from the previous time matches the polarity of the magnet of the rotating body this time.

[0007] In any of the above rotation speed detection devices, the calculation unit may output the count value that maintains the integrated value when the polarity of the magnet of the rotating body at a previous time and the polarity of the magnet of the rotating body at a current time are the same.In any of the above rotation speed detection devices, the calculation unit may output the count value that increases or decreases the integrated value when the polarity of the magnet of the rotating body at a previous time and the polarity of the magnet of the rotating body at a current time are different.

[0008] In any of the rotation speed detection devices described above, the calculation section may change the sign of the count value depending on whether or not the polarity of the magnet of the rotating body at this time matches the polarity of the pulse at this time.

[0009] In any of the rotation speed detection devices described above, the magnetic wire may be arranged so as to output the pulse when the boundary of magnetization of the rotating body is displaced from the opposing position.

[0010] In any of the rotation speed detection devices described above, the magnetic wire may extend in a direction intersecting a tangent to the rotating body.

[0011] In any of the above rotation speed detection devices, the magnet polarity determination unit may be a magnetic sensor. In any of the above rotation speed detection devices, the magnetic sensor may be arranged so as not to face any boundary of magnetization of the rotating body when the magnetic wire is arranged at a position where the magnetic sensor faces a boundary of magnetization of the rotating body.

[0012] In any of the above rotation speed detection devices, the magnetic sensor may be positioned so that the distance from the magnetization boundary of the rotating body is greatest when the magnetic wire is positioned opposite the magnetization boundary of the rotating body.

[0013] In any of the rotation speed detection devices described above, the rotating body may be magnetized with four poles.

[0014] In any of the rotation speed detection devices described above, the magnetic sensor may be disposed within a range of 45±10 degrees or 135±10 degrees from the magnetic wire around the rotation axis of the rotating body.

[0015] In any of the above rotation speed detection devices, the rotating body may be magnetized to an n-pole. In any of the above rotation speed detection devices, the magnetic sensor detects an angle θ m The angles may be within a range of ±40 / n degrees from the center. θ m = ±180 × m / n However, m may be any odd number less than n.

[0016] In order to solve the above problem, in a second aspect of the present invention, there is provided a rotation speed detection system including any one of the rotation speed detection devices described above and the rotating body.

[0017] In order to solve the above problems, a third aspect of the present invention provides a rotation speed calculation device that counts circumferential segments of a rotating body and calculates a count value based on the output of a magnetic wire and a magnet polarity discrimination unit. In the above rotation speed calculation device, the magnetic wire may be given an axial alternating magnetic field of two or more periods per rotation as the rotating body rotates, and may output a pulse of a polarity according to a change in the direction of the magnetic field. In any of the above rotation speed calculation devices, the magnet polarity discrimination unit may discriminate the polarity of a magnet that forms the alternating magnetic field and is included in the rotating body at a predetermined relative position with respect to the magnetic wire. Any of the above rotation speed calculation devices may calculate the count value based on the previously acquired polarity of the magnet of the rotating body, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse is generated, without using the polarity of the previous pulse.

[0018] In order to solve the above problem, a fourth aspect of the present invention provides a rotation speed detection method. In the rotation speed detection method, an alternating magnetic field having two or more cycles per rotation is applied in the axial direction as the rotor rotates, and the polarity of the pulse of the magnetic wire output in response to a change in the direction of the magnetic field is acquired. In any of the above rotation speed detection methods, the polarity of a magnet included in the rotor that forms the alternating magnetic field may be acquired at a predetermined relative position with respect to the magnetic wire. In any of the above rotation speed detection methods, a count value may be calculated by counting circumferential segments of the rotor based on the previously acquired polarity of the rotor's magnet, the current polarity of the pulse, and the polarity of the rotor's magnet when the current pulse is generated, without using the previous polarity of the pulse.

[0019] The above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions. [Brief description of the drawings]

[0020] [Figure 1]FIG. 1 is a diagram illustrating a rotation speed detection system 200 according to an embodiment. [Diagram 2] 2 is a diagram showing an example of the arrangement of a magnetic wire 10, a magnet polarity determination unit 14, and a magnet 20. FIG. [Figure 3A] 1 is a diagram for explaining the polarity of a pulse output by a magnetic wire 10 and the polarity of a magnet 20 discriminated by a magnet polarity discriminator 14. FIG. [Figure 3B] 10 is a diagram for explaining the relationship between the polarity of a pulse, the polarity of a magnet 20, and a count value. FIG. [Figure 4A] 1 is a diagram for explaining the polarity of a pulse outputted from a magnetic wire 10 of Patent Document 1 and the polarity of a magnet 20 discriminated by a magnet polarity discriminator 14. FIG. [Figure 4B] 1 is a diagram illustrating the relationship between the polarity of a pulse in Patent Document 1, the polarity of a magnet 20, and a count value. [Figure 5A] FIG. 4 is a diagram for explaining the polarity of a pulse and the polarity of a magnet 20 when the arrangement of the magnetic wire 10 and the magnet polarity discriminator 14 in Patent Document 1 is the same as that in FIG. 3A. [Figure 5B] 5B is a diagram for explaining the relationship between the polarity of the pulse in FIG. 5A, the polarity of the magnet 20, and the count value. FIG. [Figure 6A] 10 is a diagram for explaining the polarity of a pulse and the polarity of a magnet 20 when the arrangement of the magnetic wire 10 and the magnet polarity determination unit 14 in the embodiment is different. FIG. [Figure 6B] 6B is a diagram for explaining the relationship between the polarity of the pulse in FIG. 6A, the polarity of the magnet 20, and the count value. FIG. [Figure 7] 4 is a flowchart showing an example of a method for detecting the number of rotations of a rotating body 30. [Figure 8A] 2 is a diagram for explaining the relative position of a magnet polarity determination unit 14 with respect to a magnetic wire 10. FIG. [Figure 8B] 13 is another diagram for explaining the relative position of the magnet polarity determination unit 14 with respect to the magnetic wire 10. FIG. [Figure 9] 2 is a perspective view showing an example of the arrangement of a magnet 20, a magnet polarity determination unit 14, and a magnetic wire 10. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. In this specification, the same parts in each figure are given the same reference numerals, and the description may be omitted. In addition, some configurations may not be illustrated for convenience of explanation.

[0022] In this specification, technical matters may be explained using an orthogonal coordinate system of X, Y, and Z axes. The orthogonal coordinate system merely specifies the relative positions of components, and does not limit a specific direction. For example, the Z-axis direction does not limit the height direction relative to the ground. Note that the +Z-axis direction and the -Z-axis direction are opposite directions. When the Z-axis direction is described without indicating positive or negative, it means the direction parallel to the +Z-axis and -Z-axis.

[0023] In this specification, when terms such as "same", "equal", "parallel" or "perpendicular" are used, they may include cases in which there is an error due to manufacturing variations, etc. The error is, for example, within 10%.

[0024] FIG. 1 is a diagram showing a rotation speed detection system 200 in an embodiment. FIG. 1 shows a cross section of the rotation speed detection system 200. The rotation speed detection system 200 includes a rotating body 30, a rotation speed detection device 100, a support base 40, and a support member 42. The rotation speed detection device 100 detects the rotation of the rotating body 30. The rotation speed detection device 100 detects at least one of the rotation speed and the rotation direction of the rotating body 30. The rotation speed detection system 200 may further include a single-turn sensor that detects the rotation angle within one rotation period of the rotating body 30.

[0025] The rotating body 30 in this example has a rotating shaft 32 and a mounting part 34. As an example, the rotating shaft 32 is the rotating shaft of a motor or the axis of a stage. In Fig. 1, the rotating shaft 32 extends in the Z-axis direction. The mounting part 34 is attached to the rotating shaft 32. In Fig. 1, the rotating body 30 rotates in the XY plane with the Z-axis direction as the axial direction.

[0026] The mounting portion 34 has a magnet 20. The magnet 20 is a multi-pole magnet. The magnet 20 has two or more first polarity portions 21 and two or more second polarity portions 22. One of the first polarity portion 21 and the second polarity portion 22 is an N pole and the other is an S pole. In FIG. 1 and the following figures, the first polarity portion 21 is hatched.

[0027] The rotor 30 is magnetized with four or more poles along the rotation direction. The rotor 30 being magnetized may be magnetized itself, or may have a magnet 20 with four or more poles attached to the rotor 30 as in this example. The first polarity section 21 and the second polarity section 22 in this example are alternately arranged along the rotation direction of the rotor 30. The rotation direction is the direction in which the rotor 30 rotates when viewed from the axial direction (Z-axis direction) of the rotor 30, and is the circumferential direction of a circle centered on the rotation axis 32. For example, the first polarity section 21 is arranged next to the second polarity section 22 in the circumferential direction shown in FIG. 1, and the second polarity section 22 is arranged next to the first polarity section 21 in the circumferential direction. When viewed from the Z-axis direction, two or more first polarity sections 21 and two or more second polarity sections 22 may be arranged along the circumferential direction.

[0028] The magnet 20 may be cylindrical and may have a cavity in a direction perpendicular to the bottom surface of the cylinder. In other words, the magnet 20 may be a cylindrical ring magnet. The cylindrical cavity of the magnet 20 in this example overlaps with the rotation axis 32 in the Z-axis direction. The magnet 20 rotates together with the rotor 30.

[0029] The rotation speed detection device 100 includes a magnetic wire 10, a magnet polarity discrimination unit 14, and a calculation unit 16. The rotation speed detection device 100 may further include a memory unit 18. Fig. 1 shows an XZ cross section of the rotation speed detection device 100 and a rotor 30. However, some components may not exist on the same cross section, but for the sake of explanation, Fig. 1 shows each component on the same cross section.

[0030] The magnetic wire 10, magnet polarity discrimination unit 14, calculation unit 16 and memory unit 18 are attached to a support base 40. The support base 40 is attached to a support member 42 and is disposed facing the rotating body 30 in the Z-axis direction. The rotating body 30, magnet 20, support base 40 and support member 42 may have a circular shape in the XY plane centered on the rotation axis 32. In this example, the support base 40 does not rotate.

[0031] The magnetic wire 10 may be a laminated wire of layers of materials with different magnetic sensitivities, i.e. a Wiegand wire. The magnetic wire 10 has a first material 11 and a second material 12. The second material 12 wraps around the first material 11 to form a two-layered wire. A coil may be wound around the magnetic wire 10.

[0032] The first material 11 and the second material 12 have different magnetic sensitivities. In this example, the first material 11 is hard magnetic, and the second material 12 is soft magnetic. When the strength of the external magnetic field gradually changes, only the magnetization direction of the second material 12, which has a high magnetic sensitivity at a certain magnetic field strength, changes. At that time, a pulse is generated in the coil wound around the magnetic wire 10. The pulse may be a voltage pulse, a current pulse, or both. However, the magnetic sensitivity of the first material 11 of the magnetic wire 10 may be higher than that of the second material 12.

[0033] When the rotor 30 rotates, the magnet 20 rotates relative to the magnetic wire 10, and the strength and direction of the magnetic field that the magnetic wire 10 receives from the magnet 20 change. The magnetic wire 10 outputs a pulse with a polarity corresponding to the change in the direction of the magnetic field. The magnetic wire 10 may output a pulse with a polarity corresponding to the change in the strength and direction of the magnetic field. There are two types of pulse polarity depending on the direction in which the second material 12 is magnetized. In this specification, the polarity of the pulse is represented by positive (+) and negative (-). That is, the magnetic wire 10 generates a pulse by the rotation of the rotor 30. In other words, an alternating magnetic field is formed by the magnet 20 two or more times per rotation, and this alternating magnetic field is applied in the longitudinal direction of the magnetic wire 10, so that the magnetic wire 10 outputs a pulse according to the change in the direction of the magnetic field.

[0034] The magnet polarity discrimination unit 14 discriminates the polarity of the magnet 20 of the rotating body 30. The magnet polarity discrimination unit 14 may be a magnetic sensor. In this example, the magnet polarity discrimination unit 14 is a Hall element. However, the magnet polarity discrimination unit 14 is not limited to a magnetic sensor as long as it can discriminate the polarity of the magnet 20 of the rotating body 30. For example, a notch corresponding to the polarity of the magnet 20 may be formed in the rotating body 30, and the polarity of the magnet 20 may be discriminated by measuring the notch using an optical sensor.

[0035] The calculation unit 16 is a rotation number calculation device that calculates a count value indicating the rotation number of the rotating body 30. The calculation unit 16 calculates the count value based on the output of the magnetic wire 10 and the magnet polarity discrimination unit 14. A method for calculating the count value will be described later. The calculation unit 16 may read information from the memory unit 18 to calculate the count value. The calculation unit 16 outputs the calculated count value to the memory unit 18. The calculation unit 16 and the magnet polarity discrimination unit 14 in this example are configured by an IC with a built-in Hall sensor. However, the calculation unit 16 may be provided separately from the magnet polarity discrimination unit 14.

[0036] The memory unit 18 accumulates the count values ​​calculated by the calculation unit 16 and stores the accumulated value. The memory unit 18 may be a low-power non-volatile memory such as FRAM (registered trademark). Although not shown, the magnetic wire 10, the magnet polarity discrimination unit 14, the calculation unit 16, and the memory unit 18 may be connected by wiring.

[0037] The magnet polarity discrimination unit 14, the calculation unit 16, and the storage unit 18 may be operated by the power of the pulses output by the magnetic wire 10. This allows the number of rotations of the rotating body 30 to be calculated and stored even if power is not supplied from a battery or the like. The magnet polarity discrimination unit 14 may determine the polarity of the magnet 20 of the rotating body 30 every time a pulse is generated. The calculation unit 16 may read information from the storage unit 18 every time a pulse is generated and calculate a count value, and may write the calculated count value, etc., to the storage unit 18. The calculation unit 16 may be provided with an external capacitor and may charge the power of the pulses of the magnetic wire 10. In addition, the calculation unit 16 may rectify the pulses of the magnetic wire 10.

[0038] Fig. 2 is a diagram showing an example of the arrangement of the magnetic wire 10, the magnet polarity discrimination unit 14, and the magnet 20. Fig. 2 shows an example of the arrangement of the magnetic wire 10, the magnet polarity discrimination unit 14, and the magnet 20 when viewed from the negative side of the Z axis in Fig. 1. For the sake of explanation, other configurations are not shown in Fig. 2. In addition, the entire magnetic wire 10 is roughly hatched.

[0039] The magnet 20 of this example has two first polarity portions 21 and two second polarity portions 22 on a circumference in the XY plane. The magnet 20 of this example has the first polarity portions 21 and the second polarity portions 22 at 90 degree intervals in the circumferential direction.

[0040] The magnetic wire 10 of this example may extend in a predetermined direction. For example, the extension direction of the cylindrical magnetic wire 10 is a direction perpendicular to the circular cross section. In FIG. 2, the magnetic wire 10 extends in the X-axis direction. In this specification, the direction of the magnetic wire 10 may be the extension direction of the magnetic wire 10.

[0041] The magnetic wire 10 may be arranged so as to output a pulse when the magnetization boundary of the rotating body 30 is shifted from the opposing position. In this example, the magnetization boundary of the rotating body 30 is the boundary between the first polarity portion 21 and the second polarity portion 22 of the magnet 20. The magnetic wire 10 may extend in a direction intersecting the tangent of the rotating body 30. The tangent of the rotating body 30 and the tangent of the magnet 20 may be in the same direction. The magnetic wire 10 of this example is perpendicular to the tangent of the magnet 20. With this arrangement, as described later, the magnetic wire 10 outputs a pulse when the magnetization boundary of the rotating body 30 is shifted from the opposing position.

[0042] The magnet polarity discrimination unit 14 is disposed at a predetermined relative position to the magnetic wire 10. In this example, the magnet polarity discrimination unit 14 is disposed at a position 45 degrees from the magnetic wire 10, with the center of the circle of the magnet 20 as a reference. At this position, the magnetic wire 10 may be disposed so as to overlap the magnet 20 in the Z-axis direction. The magnet polarity discrimination unit 14 discriminates the polarity (N pole, S pole) of the magnet 20 at this position.

[0043] Fig. 3A is a diagram explaining the polarity of the pulse output by the magnetic wire 10 and the polarity of the magnet 20 discriminated by the magnet polarity discriminator 14. Fig. 3B is a diagram explaining the relationship between the polarity of the pulse, the polarity of the magnet 20, and the count value. In this example, the first polarity portion 21 of the magnet 20 is an N pole, and the second polarity portion 22 is an S pole.

[0044] In this example, the magnetic wire 10 is arranged in a direction intersecting with the tangent of the magnet 20, so that when the magnet 20 rotates and the boundary between the first polarity portion 21 and the second polarity portion 22 shifts from the position facing the magnetic wire 10, the magnetic wire 10 outputs a pulse. Points a to h indicated by black circles in the figure are points where the boundary shifts from the position facing the magnetic wire 10, and the magnetic wire 10 outputs a pulse when each point comes to a position facing the magnetic wire 10.

[0045] The arrows on the outside of each point indicate that a pulse is output when the magnet 20 rotates in the direction of the arrow. The triangles on the outside of the arrows indicate the polarity of the pulse. In this example, a pulse with positive polarity is represented by an inward-facing triangle, and a pulse with negative polarity is represented by an outward-facing triangle.

[0046] The circles displayed outside the triangle indicate the polarity of magnet 20 detected by magnet polarity discrimination unit 14 when a pulse is generated. The hatched circles represent first polarity portions 21, and the unhatched circles represent second polarity portions 22. In this example, magnet polarity discrimination unit 14 detects the polarity of the portion of magnet 20 that faces magnet polarity discrimination unit 14 when a pulse is generated.

[0047] As an example, a case where the magnet 20 rotates clockwise from the state of FIG. 3A will be described. Even if the rotation proceeds and the point d rotates to a position facing the magnetic wire 10, the point d is a counterclockwise arrow, so no pulse is output. If the rotation proceeds further and the point c rotates to a position facing the magnetic wire 10, the point c is a clockwise arrow, so a pulse is output. The polarity at that time is positive. This is a pulse that occurs as a result of the magnetic wire 10 being magnetized in the opposite direction by the magnetic field of the first polarity part 21, when the first material 11 and the second material 12 are both magnetized in the same direction by the magnetic field of the second polarity part 22. Also, the polarity of the magnet 20 detected by the magnet polarity discrimination part 14 at that time is the first polarity part 21 (N pole). In the table of FIG. 3B, the "Previous" column indicates that the polarity of the pulse at position c is positive, and the polarity (MS) of the magnet 20 is N (+). In this example, the N pole is treated as + in calculating the count value.

[0048] There are four positions where a pulse may occur after the previous pulse at point c: point c, point d, point f, and point a. In the "this time" column of FIG. 3B, the points are shown in this order in each row. First, a case where a current pulse occurs at point c will be described. In this case, after the previous pulse is generated at point c, the magnet 20 hardly rotates clockwise and starts to rotate in the reverse direction (counterclockwise). At this time, the first material 11 of the magnetic wire 10 is not magnetized by the magnetic field of the first polarity portion 21 of the magnet 20. Therefore, even if the magnet 20 rotates counterclockwise and the point d rotates to a position facing the magnetic wire 10, no pulse is generated. This phenomenon in which a pulse is not generated at a position where a pulse should be generated is called "pulse missing". After that, when the magnet 20 rotates clockwise again and the point c rotates to a position facing the magnetic wire 10, a pulse is generated. The polarity of the pulse at this time is positive, and the polarity (MS) of the magnet 20 is N(+), as shown in the row of point c in the "this time" column in Fig. 3B. Both the pulse polarity and the polarity of the magnet 20 are the same as in the previous case of point c. Note that in this specification, "previous time" may refer to the time when the previous pulse was generated, and "this time" may refer to the time when the current pulse is generated.

[0049] Next, a case where the current pulse occurs at point d will be described. In this case, after the previous pulse occurs at point c, the magnet 20 rotates clockwise until the first material 11 of the magnetic wire 10 is magnetized by the magnetic field of the first polarity portion 21. After that, it turns counterclockwise, and when it rotates to a position where point d faces the magnetic wire 10, a pulse is generated. At this time, the polarity of the pulse is negative, and the polarity (MS) of the magnet 20 is N(+).

[0050] Next, we will explain the case where the current pulse occurs at point f. In this case, the magnet 20 rotates counterclockwise, and a pulse is missed, so that no pulse occurs at point d, which is the same as the case of point c. After that, the magnet 20 continues to rotate counterclockwise until point f rotates to a position facing the magnetic wire 10, at which point a pulse is generated. The polarity of the pulse at this time is positive, and the polarity (MS) of the magnet 20 is S (-).

[0051] Next, we will explain the case where the current pulse occurs at point a. In this case, the magnet 20 continues to rotate clockwise after generating the previous pulse at point c. Then, when point a rotates to a position facing the magnetic wire 10, a pulse is generated. The polarity of the pulse at that time is negative, and the polarity (MS) of the magnet 20 is S (-).

[0052] Next, the calculation of the count value will be described. The count value is a value representing the number of rotations of the rotating body 30. In this example, a count value of 4 corresponds to one rotation. The count values ​​are shown in the rightmost column of the table in FIG. 3B. In this example, the count value is positive (+) for clockwise (CW) and negative (-) for counterclockwise (CCW). In other words, as shown in FIG. 3A, the rotating body 30 or the magnet 20 is defined as having four segments (quadrants) divided by two axes that pass through the rotation axis and are perpendicular to each other when a rotation coordinate system is set with the rotation axis as the center, and the count value increases or decreases according to the change in the segment facing the magnetic wire 10 due to rotation. The determination of whether the count value is increased or decreased is further determined by a combination with the detection result of the magnet polarity determination unit 14. In addition to the above definition, the segment may be defined as an area having a predetermined angle width in the rotation direction around the rotation axis. In other words, when four count values ​​are one rotation, an area equivalent to an angle width of 90 degrees in the rotation direction may be given as a segment. The segment facing the magnetic wire 10 is the one of the multiple segments included in the rotating body 30 that is closest to the installation position of the magnetic wire 10, and changes according to the rotation operation.

[0053] If the previous pulse generation position was point c and the current pulse generation position is point c, the count value will be 0. This corresponds to the previous and current pulses being generated in quadrant 2 in FIG. 3A. If the previous pulse generation position was point c and the current pulse generation position is point d, the count value will be 0. This also corresponds to the previous and current pulses being generated in quadrant 2 in FIG. 3A.

[0054] If the previous pulse was generated at point c and the current pulse is generated at point f, the count value will be -1. This corresponds to the previous pulse being generated in quadrant 2 and the current pulse being generated in quadrant 3 in FIG. 3A. If the previous pulse was generated at point c and the current pulse is generated at point a, the count value will be +1. This corresponds to the previous pulse being generated in quadrant 2 and the current pulse being generated in quadrant 1 in FIG. 3A.

[0055] The calculation of the count value shown in FIG. 3B is an example, and the method is summarized as follows. The calculation unit 16 calculates the count value based on the previous polarity of the magnet 20, the polarity of the current pulse, and the polarity of the current magnet 20. The calculation unit 16 also calculates the count value without using the polarity of the previous pulse. In other words, in response to the rotation of the rotating body 30 on which the magnet 20 is installed, the calculation unit 16 counts the circumferential segments (here, four segments) of the rotating body 30 to calculate the count value. More specifically, it is explained as follows. When an alternating magnetic field formed by the rotation of the magnet 20 included in the rotating body 30 is applied to the magnetic wire 10, a pulse is generated in response to the change in the direction of the magnetic field. Then, in response to the generation of the pulse, the magnet polarity discrimination unit 14 discriminates the polarity of the magnet 20 at a predetermined relative position with respect to the magnetic wire 10. This operation may be considered as counting the number of times that the segment facing the magnetic wire 10 changes to another adjacent segment due to the rotational movement of the rotor 30, with respect to multiple segments virtually defined as areas having a predetermined angular width around the circumference of the rotor 30.

[0056] The calculation unit 16 may change the count value for at least one of the polarities of the current pulse depending on whether the polarity of the magnet 20 from the previous time matches the polarity of the magnet 20 from the current time. In the example shown in Fig. 3B, when the polarity of the magnet 20 from the previous time matches the polarity of the magnet 20 from the current time (points c and d of "this time"), the count value is the same (count value 0) regardless of the polarity of the pulse. When the polarity of the magnet 20 from the previous time differs from the polarity of the magnet 20 from the current time (points f and a of "this time"), the count value is changed to +1 and -1 for the polarity of the pulse.

[0057] When the polarity of the magnet 20 at the previous time is the same as the polarity of the magnet 20 at this time (points c and d of "this time"), the calculation unit 16 may output a count value that maintains the integrated value. In FIG. 3B, the count value is 0. When the polarity of the magnet 20 at the previous time is different from the polarity of the magnet 20 at this time (points f and a of "this time"), the calculation unit 16 may output a count value that increases or decreases the integrated value. In FIG. 3B, the count value is +1 or -1.

[0058] The calculation unit 16 may change the sign of the count value depending on whether the polarity of the magnet 20 this time matches the polarity of the pulse this time. In FIG. 3B, when the polarity of the magnet 20 last time is different from the polarity of the magnet 20 this time (points f and a of "this time"), if the polarity of the magnet 20 this time matches the polarity of the pulse this time (point a), the sign is negative, and when the polarity of the magnet 20 this time is different from the polarity of the pulse this time (point f), the sign is positive. In this case, the absolute values ​​of the count values ​​may be the same. In FIG. 3B, when the current time is point a, the count value is +1, and when the current time is point f, the count value is -1. That is, the absolute value is 1.

[0059] As described above, the calculation unit 16 calculates the count value without using the polarity of the previous pulse. That is, in any of the above calculations of the count value, the count value is calculated without using the polarity of the previous pulse. This makes it possible to reduce the amount of information to be referred to when calculating the count value.

[0060] When calculating the count value, the calculation unit 16 may read the previous polarity of the magnet 20 from the memory unit 18. When calculating the count value, the calculation unit 16 does not need to read the polarity of the previous pulse from the memory unit 18. The calculation unit 16 may calculate the count value based only on the previous polarity of the magnet 20, the polarity of the current pulse, and the polarity of the current magnet 20.

[0061] The calculation unit 16 may write the calculated count value to the memory unit 18. The calculation unit 16 may write information about the current polarity of the magnet 20 to the memory unit 18. This makes it possible to read out the polarity as the previous polarity of the magnet 20 when the next pulse is generated. The calculation unit 16 does not need to write information about the polarity of the current pulse to the memory unit 18. The memory unit 18 may store information about the polarity of the magnet 20. The memory unit 18 does not need to store information about the polarity of the pulse.

[0062] FIG. 4A is a diagram for explaining the polarity of the pulse output by the magnetic wire 10 of Patent Document 1 and the polarity of the magnet 20 that is discriminated by the magnet polarity discriminator 14. FIG. 4B is a diagram for explaining the relationship between the polarity of the pulse, the polarity of the magnet 20, and the count value of Patent Document 1. FIG. 1 and FIG. 2A-2C of Patent Document 1 show the power generation sensor 20 that is arranged in a direction parallel to the tangent of the magnetic field generating source 50, which is a four-pole magnetized magnet, and the sensor element MS that is "arranged so as to detect the polarity of the magnetic pole facing the center of the power generation sensor 20" (paragraph 0079). The arrangement of each component of Patent Document 1, the polarity of the generated pulse, and the polarity of the magnet 20 are shown in FIG. 4A using the notation of FIG. 3A of this specification.

[0063] In Fig. 4A, the magnetic wire 10 is arranged in a direction parallel to the tangent of the magnet 20, so the pulse generation position is different from that in Fig. 3A. In addition, the magnet polarity discrimination unit 14 detects the polarity of the magnet 20 at the portion facing the magnetic wire 10.

[0064] As in the case of FIG. 3A, a case will be described where the magnet 20 rotates clockwise from the state of FIG. 4A. As the rotation progresses and the point d rotates to a position facing the center of the magnetic wire 10, a pulse is output. The polarity at that time is negative. Also, the polarity of the magnet 20 detected by the magnet polarity discrimination unit 14 at that time is the second polarity section 22. In the table of FIG. 4B, the "Previous" column indicates that the polarity of the pulse at position d is negative, and the polarity (MS) of the magnet 20 is S (-).

[0065] There are four positions where a pulse may occur after the previous pulse at point d: point d, point e, point g, and point b. In the "this time" column of FIG. 4B, the points are shown in this order in each row. First, a case where a pulse occurs at point d this time will be described. In this case, the magnet 20 generates the previous pulse at point d and then starts rotating in the reverse direction (counterclockwise). Then, a pulse is missed at point e. After that, the magnet 20 rotates clockwise again, and when point d rotates to a position facing the center of the magnetic wire 10, a pulse is generated. The polarity of the pulse at that time is negative, and the polarity (MS) of the magnet 20 is S (-), which is shown in the row of point d in the "this time" column of FIG. 3B. Both the pulse polarity and the polarity of the magnet 20 are the same as in the previous case of point d.

[0066] Next, we will explain the case where the current pulse occurs at point e. In this case, after the previous pulse is generated at point c, the magnet 20 rotates clockwise until the first material 11 of the magnetic wire 10 is also magnetized. After that, it turns counterclockwise and when point e rotates to a position facing the center of the magnetic wire 10, a pulse is generated. The polarity of the pulse at this time is positive, and the polarity (MS) of the magnet 20 is S (-).

[0067] Next, we will explain the case where the current pulse occurs at point g. In this case, the magnet 20 rotates counterclockwise, and a pulse is missed, so that no pulse occurs at point e, which is the same as the case of point d. After that, the magnet 20 continues to rotate counterclockwise until point g rotates to a position facing the center of the magnetic wire 10, at which point a pulse is generated. The polarity of the pulse at this time is negative, and the polarity (MS) of the magnet 20 is N(+).

[0068] Next, we will explain the case where the current pulse occurs at point b. In this case, the magnet 20 continues to rotate clockwise after generating the previous pulse at point d. Then, when point b rotates to a position facing the center of the magnetic wire 10, a pulse is generated. The polarity of the pulse at that time is positive, and the polarity (MS) of the magnet 20 is N(+).

[0069] Next, the calculation of the count value will be explained. The method of calculating the count value is the same as in FIG. 3B. If the previous pulse generation position was point d and the current pulse generation position is point d, the count value will be 0. This corresponds to the fact that the previous and current pulses were generated in quadrant 2 in FIG. 4A. If the previous pulse generation position was point d and the current pulse generation position is point e, the count value will be -1. This corresponds to the fact that the previous pulse was generated in quadrant 2 and the current pulse is generated in quadrant 3 in FIG. 4A.

[0070] If the previous pulse was generated at point d and the current pulse is generated at point g, the count value will be -2. This corresponds to the previous pulse being generated in quadrant 2 and the current pulse being generated in quadrant 4 in FIG. 4A. If the previous pulse was generated at point d and the current pulse is generated at point b, the count value will be +1. This corresponds to the previous pulse being generated in quadrant 2 and the current pulse being generated in quadrant 1 in FIG. 4A.

[0071] In FIG. 4B, the count value is -2. When other points other than point d are considered, the count value is +2, so in the example of FIG. 4A, the absolute value of the count value is 2. FIG. 5 of Patent Document 1 shows the presence of +2 or -2. Also, in FIG. 4B, it is impossible to calculate the count value without using the polarity of the previous pulse, and it is necessary to use both the polarity of the previous magnet 20 and the polarity of the previous pulse. Paragraphs 0104 and 0105 of Patent Document 1 describe the use of the polarity of the previous pulse voltage and the previous sensor element state.

[0072] In the rotation speed detection device 100 of this embodiment, the count value is calculated without using the polarity of the previous pulse, so there is less information to refer to. Also, if the count value has an absolute value of 2, it may be necessary to write the count value twice to the storage unit 18. In the rotation speed detection device 100 of this embodiment, the absolute value of the count value is 1, so writing the count value to the storage unit 18 is always completed in one go.

[0073] Fig. 5A is a diagram for explaining the polarity of the pulse and the polarity of the magnet 20 when the arrangement of the magnetic wire 10 and the magnet polarity discrimination unit 14 in Patent Document 1 is the same as that in Fig. 3A. Fig. 5B is a diagram for explaining the relationship between the polarity of the pulse in Fig. 5A, the polarity of the magnet 20, and the count value.

[0074] In Fig. 5A, the magnetic wire 10 is arranged in a direction perpendicular to the tangent of the magnet 20, and the magnet polarity discrimination unit 14 is arranged at a position 45 degrees from the magnetic wire 10 with the rotation axis as the center. Detailed explanations of each point are omitted in Fig. 5A and Fig. 5B.

[0075] In FIG. 5B, the absolute value of the count value is 2. This is because Patent Document 1 calculates the count value based on the polarity of the pulse. In Patent Document 1, as described in paragraphs 0099 and 0100, if the polarity of the pulse is different, the count value is incremented by +1 or -1. A change in the count value means a change in the quadrant (segment). Therefore, in FIG. 5B, for example, a quadrant boundary exists between points c and d, which have different pulse polarities. As a result, if a pulse occurs at point c and then at point d, the count value is -1. Also, if a pulse is generated at point c and then at point d, and the next pulse occurs at point f, the count value is -2. For this reason, the variation of the count value increases to four types (0, -1, -2, +1), and it is necessary to use both the polarity of the previous pulse and the polarity of the previous magnet 20 to determine the count value.

[0076] In this embodiment, the count value is calculated based on the polarity of the magnet 20. That is, if the polarity of the magnet 20 changes, the absolute value of the count value is set to 1, and if the polarity of the magnet 20 does not change, the absolute value of the count value is set to 0. Therefore, if a pulse is generated at point c and then at point d, the count value will be 0 (see FIG. 3B). Even if a pulse is generated at point c, then a missing pulse occurs at point d, and the next pulse is generated at point f, the shift of the quadrant will be one in accordance with the change in polarity of the magnet 20, and the count value will be -1 (see FIG. 3B).

[0077] Fig. 6A is a diagram for explaining the polarity of the pulse and the polarity of the magnet 20 when the arrangement of the magnetic wire 10 and the magnet polarity discrimination unit 14 of the embodiment is different. Fig. 6B is a diagram for explaining the relationship between the polarity of the pulse in Fig. 6A, the polarity of the magnet 20, and the count value. Detailed explanations of each point are also omitted in Figs. 6A and 6B.

[0078] In Fig. 6A, the magnetic wire 10 is arranged in a direction parallel to the tangent of the magnet 20, so the pulse generation position is the same as in Fig. 4A. Also, the magnet polarity discrimination unit 14 detects the polarity of the magnet 20 at the portion facing the magnetic wire 10. However, in this example, the count value is calculated based on the polarity of the magnet 20. Therefore, the division into quadrants is different from that in Fig. 4A.

[0079] From Fig. 6B, it can be seen that in this example, as in Fig. 3B, the count value can be calculated without using the polarity of the previous pulse. Also, the absolute value of the count value in this example is 1. In other words, regardless of the arrangement of the magnetic wire 10 and the magnet polarity discrimination unit 14, the above-mentioned effect can be achieved by calculating the count value based on the polarity of the magnet 20.

[0080] Fig. 7 is a flow chart showing an example of a method for detecting the number of rotations of the rotor 30. In the method for detecting the number of rotations, the count value may be calculated as described in Figs. 1 to 3B, 6A or 6B. That is, in the method for detecting the number of rotations, the count value may be calculated based on the previous polarity of the magnet 20, the polarity of the current pulse, and the polarity of the current magnet 20. In addition, in the method for detecting the number of rotations, the count value may be calculated without using the polarity of the previous pulse. Fig. 7 is one example.

[0081] In Step 1, the polarity of the current pulse of the magnetic wire 10 is obtained. The pulse may be a pulse of the magnetic wire 10 that is output in response to a change in the direction of the magnetic field received from the rotating body 30 magnetized with four or more poles along the rotation direction. In Step 2, the polarity of the current magnet 20 is obtained. The polarity of the magnet 20 may be the polarity of the magnet 20 of the rotating body 30 at a predetermined relative position with respect to the magnetic wire 10. Steps 1 and 2 may be performed by the calculation unit 16 in FIG. 1.

[0082] In Step 3, the previous polarity of the magnet 20 is read out. In Step 3, the calculation unit 16 may read out the previous polarity of the magnet 20 from the storage unit 18. Note that the order of Steps 1-3 may be different from that in FIG.

[0083] In Step 4, it is determined whether the polarity of the magnet 20 this time matches the polarity of the magnet 20 last time. If the polarity of the magnet 20 this time matches the polarity of the magnet 20 last time (Yes), a count value at which the integrated value of the count value is maintained may be calculated. In this example, the process proceeds to Step 6, and a count value of 0 is calculated.

[0084] If the polarity of the magnet 20 this time does not match the polarity of the magnet 20 last time (No), a count value that increases or decreases the integrated value may be output. In this example, the process proceeds to Step 5, and it is determined whether the polarity of the current pulse matches the polarity of the magnet 20 this time. If the polarity of the current pulse matches the polarity of the magnet 20 this time (Yes), a count value of +1 is calculated in Step 6. If the polarity of the current pulse does not match the polarity of the magnet 20 this time (No), a count value of -1 is calculated in Step 6. Steps 4-6 may be performed by the calculation unit 16. In other words, when the calculation unit 16 is driven by a pulse and starts calculating the count value, it detects that another segment adjacent to the segment facing the magnetic wire 14 at the installation position of the magnetic wire 10 at the time of the previous pulse generation has moved to face the installation position of the magnetic wire 10 at the time of the current pulse generation, based on the polarity of the magnet 20 of the rotating body 30 acquired last time, the polarity of the current pulse, and the polarity of the magnet 20 of the rotating body 30 at the time of the current pulse generation. More specifically, the calculation unit 16 determines whether the segment facing the installation position of the magnetic wire 10 at the time of the current pulse generation has reached that position by a clockwise or counterclockwise rotation from the position it was in at the time of the previous pulse generation, and calculates a count value based on the result of this determination.

[0085] In Step 7, the calculated count values ​​are accumulated. The calculation unit 16 may output the calculated count values ​​to the storage unit 18, and the storage unit 18 may accumulate the count values. Also, in Step 7, the current polarity of the magnet 20 may be stored. The calculation unit 16 may write the current polarity of the magnet 20 to the storage unit 18. In Step 7, the polarity of the current pulse does not need to be stored.

[0086] Fig. 8A is a diagram for explaining the relative position of the magnet polarity discrimination unit 14 with respect to the magnetic wire 10. The rotating body 30 in this example is magnetized with four poles. However, Fig. 8A shows only the magnet 20 of the rotating body 30. The magnetic wire 10 in this example extends in a direction intersecting a tangent to the rotation direction of the rotating body 30.

[0087] The magnet polarity discrimination unit 14 in this example is a magnetic sensor. When the magnet polarity discrimination unit 14 in this example is arranged at a position where the boundaries of the magnetization of the magnetic wire 10 and the rotating body 30 face each other, the magnet polarity discrimination unit 14 is arranged so as not to face any boundaries of the magnetization of the rotating body 30. In this example, the boundaries of the magnetization of the rotating body 30 are the boundaries between the first polarity portion 21 and the second polarity portion 22 of the magnet 20. FIG. 8A shows a case where the boundaries of the magnetization of the magnetic wire 10 and the rotating body 30 are arranged at a position where they face each other. This can reduce erroneous detection of the magnet polarity discrimination unit 14. Not facing a boundary may mean that there is no boundary within a range of ±10 degrees in the rotational direction around the magnet polarity discrimination unit 14. The boundaries between the first polarity portion 21 and the second polarity portion 22 may be arranged at equal angular intervals in the rotational direction.

[0088] The magnet polarity discriminator 14 may be arranged so that the distance from the magnetization boundary of the rotating body 30 is the largest when the magnet polarity discriminator 14 is arranged at a position where the magnet wire 10 and the magnetization boundary of the rotating body 30 face each other. The distance from the boundary may be the distance from the boundary closest to the magnet polarity discriminator 14. If the boundaries are arranged at equal angular intervals, there are two boundaries that are the same distance from the magnet polarity discriminator 14. In this example, the magnet polarity discriminator 14 is arranged at a position 45 degrees or 135 degrees from the magnetic wire 10 around the rotation axis 32 of the rotating body 30, and the distance from the boundary is the largest at that position. This can reduce false detection of the magnet polarity discriminator 14. However, the above arrangement or angle may have a width. The width may be ±10 degrees, ±5 degrees, or ±2 degrees.

[0089] FIG. 8B is another diagram for explaining the relative position of the magnet polarity discrimination unit 14 with respect to the magnetic wire 10. The rotating body 30 in this example is magnetized with six poles. However, in FIG. 8B as well, only the magnet 20 of the rotating body 30 is shown. The boundaries between the first polarity portion 21 and the second polarity portion 22 in this example are also arranged at equal angular intervals in the rotational direction. The magnetic wire 10 in this example also extends in a direction intersecting with the tangent to the rotational direction of the rotating body 30. The magnet polarity discrimination unit 14 in this example is also a magnetic sensor.

[0090] In this example, when the magnetic wire 10 and the magnetization boundary of the rotating body 30 are disposed in a position facing each other, the position of the magnet polarity discrimination unit 14 at which the distance from the magnetization boundary of the rotating body 30 is the largest is a position 30 degrees, 90 degrees, or 150 degrees from the magnetic wire 10, centered on the rotation axis 32 of the rotating body 30. By disposing the magnet polarity discrimination unit 14 at the above position, it is possible to reduce false detections of the magnet polarity discrimination unit 14. The above angle may have a width of ±5 degrees or ±2 degrees.

[0091] The above arrangement can be generalized as follows. In other words, when the magnetic wire 10 extends in a direction intersecting a tangent to the rotation direction of the rotating body 30, the arrangement of the magnet polarity discrimination unit 14 will be described so that the distance between the magnetic wire 10 and the magnetization boundary of the rotating body 30 is maximized when the magnetic wire 10 is arranged in a position facing the magnetization boundary of the rotating body 30. The rotating body is magnetized with n poles. n is an even number. n may be an even number of 4 or more, an even number of 6 or more, or an even number of 8 or more. In addition, the magnetization boundaries of the rotating body 30 are arranged at equal angular intervals in the rotation direction.

[0092] The magnet polarity determination unit 14 determines the angle θ from the magnetic wire 10 around the axis of rotation of the rotor 30 as follows: m If the object is located at the position, the distance to the boundary will be the greatest. θ m = 180 × m / n Here, m is an odd number less than n. Angle θ m The maximum value of is 180 degrees. In other words, the above formula may be used symmetrically in the clockwise and counterclockwise directions with the magnetic wire 10 as the reference.

[0093] For example, when n=4, the angle θ m is 45 degrees (m=1) and 135 degrees (m=3), which matches the example in FIG. 8A. m may have a width. The width may be ±40 / n degrees, ±20 / n degrees, or ±8 / n degrees. In addition, the boundary position of the magnetization of the rotor 30 may also be the angle θ m It may have a width similar to that of The magnetic wire 10 and the magnet polarity discrimination unit 14 are thus installed, and the segment allocation to the rotating body 30 is set so that each segment includes the boundary of magnetization, thereby enabling the above-mentioned detection of segment movement. This arrangement and segment allocation makes it possible to detect both the case where a segment change occurs in response to the generation of a pulse and the case where a segment change does not occur. More specifically, when a pulse occurs when the boundary of magnetization passes the opposing position with the magnetic wire 10 due to the rotation of the rotating body 30, it is detected that one of the segments is at that position. Furthermore, the magnet polarity discrimination unit 14 provided at the above-mentioned relative position identifies the polarity of the magnet 20 opposing at that position. Then, if the polarity of the magnet 20 and the polarity of the magnet 20 at the previous measurement match, it can be determined that the segment opposing the magnetic wire 10 is the same as the previous one. Also, if the polarity of the magnet 20 and the polarity of the magnet 20 at the previous measurement are different, it can be detected that a segment change has occurred. Then, based on a combination of this information and the polarity of the pulse, it is possible to determine whether the segment change is caused by a clockwise or counterclockwise rotation.

[0094] 9 is a perspective view showing an example of the arrangement of the magnet 20, magnet polarity discriminator 14, and magnetic wire 10. In the rotation speed detection system 200 described above, the arrangement of the magnet 20, magnet polarity discriminator 14, and magnetic wire 10 can be generalized, for example, as follows. That is, the rotation speed detection system 200 has, as a rotating magnet, the magnet 20 magnetized with four or more poles along the direction of rotation. In response to the rotation of the magnet 20, the magnetic wire 10 outputs a pulse (voltage) of a polarity according to the change in the magnetic field direction caused by this rotation. The magnet polarity discriminator 14 is provided at a predetermined relative position to the magnetic wire 10, and detects the polarity of the magnet 20 at that installation position.

[0095] In FIG. 9, the direction parallel to the rotation axis of the magnet 20 (the direction of the rotation axis) is the Z axis, and the long axis direction of the magnetic wire 10 is the X axis. The magnetic wire 10 may be arranged as follows. When viewed from the direction of the rotation axis of the magnet 20, one end 51 of the long axis of the magnetic wire 10 may be arranged in the outer edge region 24 of the magnet 20. FIG. 9 shows a dotted line extending in the Z axis direction from one end 51 of the magnetic wire 10 to the outer edge region 24 of the magnet 20. The magnetic wire 10 may be arranged such that a center point 52 of the long axis of the magnetic wire 10 is located outside the outer edge 25 of the magnet 20 in a direction perpendicular to the rotation axis of the magnet 20 (the X axis direction in FIG. 9). FIG. 9 shows a dotted line extending in the Z axis direction from the center point 52 of the magnetic wire 10 to outside the outer edge 25 of the magnet 20. Also, with respect to the ring-shaped magnet 20, the end of the magnetic wire 10 (one end 51 in FIG. 9) may be arranged so as to overlap the area occupied by the magnet 20 when viewed from the direction of the rotation axis of the magnet 20. In other words, when viewed from the direction of the rotation axis of the magnet 20, the end of the magnetic wire 10 may be arranged so as to be located in the area between the inner diameter and the outer diameter of the magnet 20. Also, the other end 53 in the long axis direction of the magnetic wire 10 may be arranged so as to be located on a straight line passing through the rotation axis of the magnet 20 and extending in the opposite direction to the rotation axis. In other words, when viewed from the direction of the rotation axis of the magnet 20, the rotation axis of the magnet 20, one end 51 of the magnetic wire 10, and the other end 53 of the magnetic wire 10 may be arranged on a straight line. Also, in the direction of the rotation axis of the magnet 20, the magnetic wire 10 may be installed in a space above the upper surface of the magnet 20 or below the lower surface of the magnet 20. The one end 51 and the other end 53 of the magnetic wire 10 may be central points of the ends of the magnetic wire 10 in a direction perpendicular to the long axis direction of the magnetic wire 10 (the Y-axis direction in FIG. 9).

[0096] The magnet polarity discrimination unit 14 may be disposed as shown below. The magnet polarity discrimination unit 14 may be disposed so as to overlap the outer edge region 24 of the magnet 20 when viewed from the direction of the rotation axis of the magnet 20. FIG. 9 shows a dotted line extending in the Z-axis direction from the center of the magnet polarity discrimination unit 14 to the outer edge region 24 of the magnet 20. Furthermore, for a ring-shaped magnet 20, the magnet polarity discrimination unit 14 may be disposed so as to overlap the region occupied by the magnet 20 when viewed from the direction of the rotation axis of the magnet 20. In other words, when viewed from the direction of the rotation axis of the magnet 20, the end of the magnet polarity discrimination unit 14 may be disposed so as to be located in the region between the inner diameter and the outer diameter of the magnet 20. Furthermore, the magnet polarity discrimination unit 14 may be integrated together with the calculation unit 16 into a single integrated circuit (IC chip). The magnet polarity discrimination unit 14 may be disposed at a position of 45 degrees or 135 degrees (including adjustment of about ±10 degrees) from a line segment (corresponding to the reference line of the angle in FIG. 8A) connecting the rotation axis and the center of the magnetic wire 10, as viewed from the direction of the rotation axis of the magnet 20. The magnet polarity discrimination unit 14 may be installed in a space above the upper surface of the magnet 20 or below the lower surface of the magnet 20, in the direction of the rotation axis of the magnet 20. In this case, the magnet polarity discrimination unit 14 may be disposed in a space on the same side of the magnet 20 as the center in the direction of the rotation axis of the magnet 20 (a space on the positive side of the Z axis from the magnet 20 in FIG. 9) or in a space on the opposite side (a space on the negative side of the Z axis from the magnet 20 in FIG. 9).

[0097] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the description of the claims that such modifications and improvements can also be included in the technical scope of the present invention.

[0098] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, flowcharts, and methods shown in the claims, specifications, and drawings is not specifically indicated as "before," "prior to," etc., and may be realized in any order unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, it does not mean that it is essential to perform the process in this order. [Explanation of symbols]

[0099] REFERENCE SIGNS LIST 10 magnetic wire, 11 first material, 12 second material, 14 magnet polarity discrimination unit, 16 calculation unit, 18 memory unit, 20 magnet, 21 first polarity unit, 22 second polarity unit, 24 outer edge region, 25 outer edge end, 30 rotating body, 32 rotating shaft, 34 mounting unit, 40 support base, 42 support member, 51 one end, 52 central point, 53 other end, 100 rotation speed detection device, 200 rotation speed detection system

Claims

1. a magnetic wire that outputs a pulse of a polarity corresponding to a change in the direction of the magnetic field when an alternating magnetic field having two or more periods per rotation is applied in the axial direction as the rotor rotates; a magnet polarity determination unit that forms the alternating magnetic field and determines the polarity of a magnet included in the rotor at a predetermined relative position with respect to the magnetic wire; a calculation unit that counts the circumferential segments of the rotating body and calculates a count value; Equipped with The calculation unit calculates the count value based on the previously acquired polarity of the magnet of the rotating body, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse is generated, without using the polarity of the previous pulse. Rotation speed detection device.

2. When the calculation unit is driven by the pulse and starts calculating the count value, it detects, based on the previously acquired polarity of the magnet of the rotating body, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse is generated, that another segment adjacent to the segment that faced the magnetic wire when the previous pulse was generated has moved to a position facing the magnetic wire when the current pulse is generated. The rotation speed detection device according to claim 1.

3. A storage unit is provided for integrating the count value calculated by the calculation unit and storing the integrated value. The rotation speed detection device according to claim 2.

4. The calculation unit changes the count value for at least one of the current polarities of the pulses depending on whether the previous polarity of the magnet of the rotating body and the current polarity of the magnet of the rotating body match. The rotation speed detection device according to claim 3.

5. the calculation unit outputs the count value at which the integrated value is maintained when the polarity of the magnet of the rotating body at a previous time and the polarity of the magnet of the rotating body at a current time are the same; When the polarity of the magnet of the rotating body in the previous time is different from the polarity of the magnet of the rotating body in the current time, the count value for increasing or decreasing the integrated value is output. The rotation speed detection device according to claim 4.

6. The calculation unit changes the sign of the count value depending on whether or not the polarity of the magnet of the rotating body at this time matches the polarity of the pulse at this time. The rotation speed detection device according to claim 5.

7. The magnetic wire is arranged to output the pulse when the boundary of magnetization of the rotor is displaced from the opposing position. The rotation speed detection device according to any one of claims 1 to 6.

8. The magnetic wire extends in a direction intersecting a tangent line of the rotor. The rotation speed detection device according to claim 7.

9. the magnet polarity determination unit is a magnetic sensor, The magnetic sensor is disposed so as not to face any boundary of magnetization of the rotating body when the magnetic wire is disposed at a position where the magnetic sensor faces a boundary of magnetization of the rotating body. The rotation speed detection device according to any one of claims 1 to 6.

10. The magnetic sensor is disposed so that the distance between the magnetic wire and the magnetization boundary of the rotating body is maximized when the magnetic wire is disposed in a position facing the magnetization boundary of the rotating body. The rotation speed detection device according to claim 9.

11. The rotor is magnetized with four poles. The rotation speed detection device according to claim 10.

12. The magnetic sensor is disposed within a range of 45±10 degrees or 135±10 degrees from the magnetic wire around the rotation axis of the rotating body. The rotation speed detection device according to claim 11.

13. The rotor is magnetized to an n-pole, The magnetic sensor detects an angle θ from the magnetic wire centered on the axis of rotation of the rotor. ｍ are arranged within a range of ±40 / n degrees from the center i ｍ =±180×m / n where m is any odd number less than n. The rotation speed detection device according to claim 10.

14. A rotation speed detection device according to any one of claims 1 to 6, The rotor and A rotation speed detection system comprising:

15. A rotation speed calculation device that counts circumferential segments of a rotating body and calculates a count value based on an output of a magnetic wire and a magnet polarity discrimination unit, The magnetic wire is applied with an alternating magnetic field in an axial direction with two or more periods per rotation in accordance with the rotational movement of the rotor, and outputs a pulse of a polarity according to the change in the direction of the magnetic field; the magnet polarity determination unit determines the polarity of a magnet that forms the alternating magnetic field and is included in the rotor at a predetermined relative position with respect to the magnetic wire; The rotation speed calculation device is The count value is calculated based on the previously acquired polarity of the magnet of the rotating body, the current polarity of the pulse, and the polarity of the magnet of the rotating body when the current pulse is generated, without using the previous polarity of the pulse. Rotation speed calculation device.

16. As the rotor rotates, an alternating magnetic field having two or more cycles per rotation is applied in the axial direction, and the polarity of the pulse of the magnetic wire output in response to the change in the direction of the magnetic field is obtained; At a predetermined relative position with respect to the magnetic wire, the alternating magnetic field is generated and the polarity of the magnet included in the rotor is obtained; Based on the previously acquired polarity of the magnet of the rotating body, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse was generated, but without using the polarity of the previous pulse, the number of circumferential segments of the rotating body is counted to calculate a count value. Rotation speed detection method.

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