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

Abstract

When calculating the rotational speed of a rotating body, reduce the amount of information referenced. [Solution] A rotation speed detection device is provided comprising: a magnetic wire that applies an alternating magnetic field of two or more periods per rotation in the axial direction in conjunction with the rotational movement of a rotating body and outputs pulses of polarity corresponding to the change in the direction of the magnetic field; a magnet polarity determination unit that determines the polarity of the magnets contained in the rotating body that form the alternating magnetic field at a predetermined relative position with respect to the magnetic wire; and a calculation unit that counts the 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 magnets of the rotating body acquired in the previous instance, the polarity of the current pulse, and the polarity of the magnets of the rotating body when the current pulse was generated, without using the polarity of the previous pulse.

Description

Technical Field

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

Background Art

[0002] Conventionally, a multi-rotation angle detection device using a power generation sensor has been known (see, for example, Patent Document 1). Patent Document 1 Japanese Unexamined Patent Application Publication No. 2024-106245

Summary of the Invention

Problems to be Solved by the Invention

[0003] When calculating the rotational speed of a rotating body, reduce the information to be referred to.

Means for Solving the Problems

[0004] In order to solve the above problems, in a first aspect of the present invention, a rotational speed detection device is provided that includes a magnetic wire that generates an alternating magnetic field of two or more cycles per rotation in the axial direction in accordance with the rotational operation of a rotating body and outputs pulses of a polarity corresponding to a change in the direction of the magnetic field. The rotational speed detection device may include a magnet polarity determination unit that forms the alternating magnetic field and determines the polarity of a magnet included in the rotating body at a predetermined relative position with respect to the magnetic wire. Any of the rotational speed detection devices may include an arithmetic unit that counts segments in the circumferential direction of the rotating body and calculates a count value. In any of the rotational speed detection devices, the arithmetic unit may calculate the count value based on the polarity of the magnet of the rotating body acquired last time, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse is generated, and without using the polarity of the previous pulse.

[0005] In any of the above-described rotational speed detection devices, when the calculation unit is driven by the pulse and the calculation of the count value begins, it may detect, based on the polarity of the magnet of the rotating body acquired in the previous instance, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse occurred, that another segment adjacent to the segment facing the magnetic wire when the previous pulse occurred has moved to a position facing the magnetic wire when the current pulse occurred. Any of the above-described rotational speed detection devices may include a storage unit that accumulates the count values ​​calculated by the calculation unit and stores them as an accumulated value.

[0006] In any of the rotation speed detection devices described above, the calculation unit may set the count value for at least one of the current pulses differently depending on whether the polarity of the magnet of the rotating body in the previous instance matches the polarity of the magnet of the rotating body in the current instance.

[0007] In any of the above-described rotational speed detection devices, the calculation unit may output the count value that maintains the accumulated value if the polarity of the magnet of the rotating body in the previous instance is the same as the polarity of the magnet of the rotating body in the current instance. In any of the above-described rotational speed detection devices, the calculation unit may output the count value that increases or decreases the accumulated value if the polarity of the magnet of the rotating body in the previous instance is different from the polarity of the magnet of the rotating body in the current instance.

[0008] In any of the rotation speed detection devices described above, the calculation unit may change the sign of the count value depending on whether the polarity of the magnet of the rotating body and the polarity of the pulse match.

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

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

[0011] In any of the above-described rotational speed detection devices, the magnet polarity determination unit may be a magnetic sensor. In any of the above-described rotational speed detection devices, the magnetic sensor may be positioned such that it does not face either boundary of the magnetization of the rotating body when the magnetic wire and the boundary of the magnetization of the rotating body are facing each other.

[0012] In any of the rotation speed detection devices described above, the magnetic sensor may be positioned such that the distance from the boundary of the magnetization of the rotating body is maximized when the magnetic wire and the boundary of the magnetization of the rotating body are facing each other.

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

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

[0015] In any of the above rotational speed detection devices, the rotating body may be magnetized to an n pole. In any of the above rotational speed detection devices, the magnetic sensor is set to an angle θ from the magnetic wire centered on the rotation axis of the rotating body. m They may be positioned within a range of ±40 / n degrees centered on one of the points. θ m = ±180 × m / n However, m can be any odd number less than n.

[0016] To solve the above problems, a second embodiment of the present invention provides a rotation speed detection system comprising any of the above-described rotation speed detection devices and the rotating body.

[0017] To solve the above problems, a third aspect of the present invention provides a rotational speed calculation device that calculates a count value by counting the circumferential segments of a rotating body based on a magnetic wire and the output of a magnet polarity discrimination unit. In the above rotational speed calculation device, the magnetic wire may be subjected to an alternating magnetic field of two or more periods per rotation in the axial direction in accordance with the rotational movement of the rotating body, and may output pulses of polarity corresponding to the change in the direction of the magnetic field. In any of the above rotational speed calculation devices, the magnet polarity discrimination unit may determine the polarity of the magnets included in the rotating body that form the alternating magnetic field at a predetermined relative position with respect to the magnetic wire. Any of the above rotational speed calculation devices may calculate the count value based on the polarity of the magnets of the rotating body acquired in the previous instance, the polarity of the current pulse, and the polarity of the magnets of the rotating body when the current pulse was generated, without using the polarity of the previous pulse.

[0018] To solve the above problems, a fourth aspect of the present invention provides a rotation speed detection method. In the above rotation speed detection method, an alternating magnetic field of two or more periods per rotation is applied axially in accordance with the rotational movement of the rotating body, and the polarity of the pulses of a magnetic wire output in accordance with the change in the direction of the magnetic field may be obtained. In any of the above rotation speed detection methods, the polarity of the magnet included in the rotating body is obtained by forming the alternating magnetic field 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 the circumferential segments of the rotating body based on the polarity of the magnet of the rotating body obtained in the previous instance, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse was generated, and without using the polarity of the previous pulse.

[0019] It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. Furthermore, subcombinations of these features may also constitute an invention. [Brief explanation of the drawing]

[0020] [Figure 1]It is a diagram showing the rotational speed detection system 200 in the embodiment. [Figure 2] It is a diagram showing an arrangement example of the magnetic wire 10, the magnet polarity discrimination unit 14, and the magnet 20. [Figure 3A] It 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 discrimination unit 14. [Figure 3B] It is a diagram explaining the relationship between the polarity of the pulse, the polarity of the magnet 20, and the count value. [Figure 4A] It is a diagram explaining the polarity of the pulse output by the magnetic wire 10 of Patent Document 1 and the polarity of the magnet 20 discriminated by the magnet polarity discrimination unit 14. [Figure 4B] It is a diagram explaining the relationship between the polarity of the pulse of Patent Document 1, the polarity of the magnet 20, and the count value. [Figure 5A] It is a diagram 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 Patent Document 1 is the same as that in FIG. 3A. [Figure 5B] It is a diagram explaining the relationship between the polarity of the pulse in FIG. 5A, the polarity of the magnet 20, and the count value. [Figure 6A] It is a diagram explaining the polarity of the pulse and the polarity of the magnet 20 when the arrangements of the magnetic wire 10 and the magnet polarity discrimination unit 14 in the embodiment are different. [Figure 6B] It is a diagram explaining the relationship between the polarity of the pulse in FIG. 6A, the polarity of the magnet 20, and the count value. [Figure 7] It is a flowchart showing an example of a method for detecting the rotational speed of the rotating body 30. [Figure 8A] It is a diagram explaining the relative position of the magnet polarity discrimination unit 14 with respect to the magnetic wire 10. [Figure 8B] It is another diagram explaining the relative position of the magnet polarity discrimination unit 14 with respect to the magnetic wire 10. [Figure 9] It is a perspective view showing an example of the arrangement of the magnet 20, the magnet polarity discrimination unit 14, and the magnetic wire 10.

Mode for Carrying Out the Invention

[0021] The present invention will be described below through embodiments of the invention, but these embodiments are not intended to limit the invention as defined in the claims. Furthermore, not all 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 denoted by the same reference numerals, and their descriptions may be omitted. Also, some components may not be shown for the sake of clarity.

[0022] This specification may use a Cartesian coordinate system with X, Y, and Z axes to describe technical matters. The Cartesian coordinate system merely specifies the relative positions of components and does not limit any particular direction. For example, the Z-axis direction does not limit it to the height direction relative to the ground. Note that the +Z-axis direction and the -Z-axis direction are opposite directions. When the sign is not specified and only the Z-axis direction is written, it means the direction parallel to the +Z-axis and -Z-axis.

[0023] In this specification, terms such as "identical," "equal," "parallel," or "perpendicular" may include cases with errors due to manufacturing variations, etc. Such errors are, for example, within 10%.

[0024] Figure 1 shows a rotation speed detection system 200 in an embodiment. Figure 1 shows a cross-section of the rotation speed detection system 200. The rotation speed detection system 200 comprises 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 or 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 portion 34. For example, the rotating shaft 32 is the rotating shaft of a motor or the axis of a stage. In Figure 1, the rotating shaft 32 extends in the Z-axis direction. The mounting portion 34 is attached to the rotating shaft 32. In Figure 1, the rotating body 30 rotates in the XY plane with the Z-axis direction as its axis.

[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 polar portions 21 and two or more second polar portions 22. One of the first polar portions 21 and the second polar portions 22 is a north pole and the other is a south pole. In Figure 1 and subsequent figures, the first polar portions 21 are hatched.

[0027] The rotating body 30 is magnetized with four or more poles along the direction of rotation. The magnetization of the rotating body 30 means that the rotating body 30 itself is magnetized, or, as in this example, that four or more magnets 20 are attached to the rotating body 30. In this example, the first polarity portion 21 and the second polarity portion 22 are arranged alternately along the direction of rotation of the rotating body 30. The direction of rotation is the direction in which the rotating body 30 rotates when viewed from the axial direction (Z-axis direction) of the rotating body 30, and is the circumferential direction of a circle centered on the rotation axis 32. For example, in Figure 1, the first polarity portion 21 is located next to the second polarity portion 22 in the circumferential direction, and the second polarity portion 22 is located next to the first polarity portion 21 in the circumferential direction. When viewed from the Z-axis direction, two or more first polarity portions 21 and two or more second polarity portions 22 may be arranged along the circumferential direction.

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

[0029] The rotational speed detection device 100 comprises a magnetic wire 10, a magnet polarity discrimination unit 14, and a calculation unit 16. The rotational speed detection device 100 may further include a storage unit 18. Figure 1 shows the XZ cross-section of the rotational speed detection device 100 and the rotating body 30. However, some components may not be located in the same cross-section, but for explanatory purposes, each component is shown in the same cross-section in Figure 1.

[0030] The magnetic wire 10, magnet polarity discrimination unit 14, calculation unit 16, and memory unit 18 are attached to the support base 40. The support base 40 is attached to the support member 42 and is positioned opposite the rotating body 30 in the Z-axis direction. The shapes of the rotating body 30, magnet 20, support base 40, and support member 42 may be circular in the XY plane with respect to the rotation axis 32. In this example, the support base 40 does not rotate.

[0031] The magnetic wire 10 may be a wire in which layers of materials with different magnetic sensitivities are laminated, i.e., a Wiegand wire. The magnetic wire 10 has a first material 11 and a second material 12. The second material 12 covers the first material 11, forming a two-layer 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 changes gradually, at a certain magnetic field strength, only the direction of magnetization of the second material 12, which has higher magnetic sensitivity, 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] As the rotating body 30 rotates, the magnet 20 rotates relative to the magnetic wire 10, causing the strength and direction of the magnetic field that the magnetic wire 10 receives from the magnet 20 to change. The magnetic wire 10 outputs pulses with a polarity corresponding to the change in the direction of the magnetic field. The magnetic wire 10 may output pulses 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 (-). In other words, the magnetic wire 10 generates pulses due to the rotation of the rotating body 30. To put it another way, 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 direction of the long axis of the magnetic wire 10, causing the magnetic wire 10 to output pulses corresponding to the change in the direction of the magnetic field.

[0034] The magnet polarity determination unit 14 determines the polarity of the magnet 20 of the rotating body 30. The magnet polarity determination unit 14 may be a magnetic sensor. In this example, the magnet polarity determination unit 14 is a Hall element. However, the magnet polarity determination unit 14 is not limited to a magnetic sensor as long as it can determine 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 determined by measuring the notch using an optical sensor.

[0035] The calculation unit 16 is a rotation speed calculation device that calculates a count value representing the rotation speed 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. The method for calculating the count value will be described later. The calculation unit 16 may read information from the storage unit 18 in order to calculate the count value. The calculation unit 16 outputs the calculated count value to the storage unit 18. In this example, the calculation unit 16 and the magnet polarity discrimination unit 14 are composed of ICs with built-in Hall sensors. 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 arithmetic unit 16 and stores them as the accumulated value. The memory unit 18 may be a low-power non-volatile memory such as FRAM (registered trademark). Although not shown in the figures, the magnetic wire 10, the magnet polarity discrimination unit 14, the arithmetic unit 16, and the memory unit 18 may be connected by wiring.

[0037] The magnet polarity determination unit 14, the calculation unit 16, and the storage unit 18 may operate using the power of the pulses output by the magnetic wire 10. This allows the rotation speed of the rotating body 30 to be calculated and maintained even without power supplied from a battery or the like. The magnet polarity determination unit 14 may determine the polarity of the magnet 20 of the rotating body 30 each time a pulse is generated. The calculation unit 16 may read information from the storage unit 18 each time a pulse is generated to calculate a count value, and may write the calculated count value to the storage unit 18. The calculation unit 16 may be provided with an external capacitor to charge the power of the pulses from the magnetic wire 10. The calculation unit 16 may also rectify the pulses from the magnetic wire 10.

[0038] Figure 2 shows an example of the arrangement of the magnetic wire 10, the magnet polarity discrimination unit 14, and the magnet 20. Figure 2 shows an example of the arrangement when viewed from the negative Z-axis side in Figure 1. In Figure 2, other components are not shown for illustrative purposes. Also, the entire surface of the magnetic wire 10 is covered with coarse hatching.

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

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

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

[0042] The magnet polarity determination unit 14 is positioned at a predetermined relative position with respect to the magnetic wire 10. In this example, the magnet polarity determination unit 14 is positioned at a 45-degree angle from the magnetic wire 10, with reference to the center of the circle of the magnet 20. At this position, the magnetic wire 10 may overlap with the magnet 20 in the Z-axis direction. The magnet polarity determination unit 14 determines the polarity (N pole, S pole) of the magnet 20 at this position.

[0043] Figure 3A illustrates the polarity of the pulse output by the magnetic wire 10 and the polarity of the magnet 20 as determined by the magnet polarity determination unit 14. Figure 3B illustrates the relationship between the pulse polarity, the polarity of the magnet 20, and the count value. In this example, the first polarity part 21 of the magnet 20 is the north pole, and the second polarity part 22 is the south pole.

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

[0045] The arrows displayed outside each point indicate that a pulse is output when magnet 20 is rotating in the direction of the arrow. The triangles displayed outside the arrows indicate the polarity of the pulse. In this example, positive polarity pulses are represented by inward-pointing triangles, and negative polarity pulses are represented by outward-pointing triangles.

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

[0047] As an example, let's explain the case where the magnet 20 rotates clockwise from the state shown in Figure 3A. As the rotation progresses, even when point d is facing the magnetic wire 10, no pulse is output because point d is a counterclockwise arrow. Then, as the rotation progresses further and point c is facing the magnetic wire 10, a pulse is output because point c is a clockwise arrow. The polarity at that time is positive. This pulse is caused by the magnetic wire 10 being magnetized in the same direction by the magnetic field of the second polarity part 22, where the first material 11 and the second material 12 are both magnetized in the same direction, and then the second material 12 is magnetized in the opposite direction by the magnetic field of the first polarity part 21. At that time, the polarity of the magnet 20 detected by the magnet polarity discrimination unit 14 is the first polarity part 21 (N pole). In the table in Figure 3B, the "Previous" column shows that the polarity of the pulse at position c was positive, and the polarity (MS) of the magnet 20 was N(+). In this example, the north pole is treated as positive when calculating the count value.

[0048] Previously, there are four possible locations where a pulse may occur after the pulse generated at point c: points c, d, f, and a. The "Current" column in Figure 3B shows the points in this order in each row. First, let's explain the case where the current pulse occurs at point c. In this case, after generating the previous pulse at point c, the magnet 20 does not rotate almost clockwise but begins to rotate in the opposite direction (counterclockwise). At this time, the first material 11 of the magnetic wire 10 is not magnetized by the magnetic field of the first polar part 21 of the magnet 20. Therefore, even when the magnet 20 rotates counterclockwise and points d rotate to a position opposite the magnetic wire 10, no pulse is generated. This phenomenon, where a pulse does not occur at a position where a pulse should occur, is called "pulse drop." Subsequently, when the magnet 20 rotates clockwise again and points c rotate to a position opposite the magnetic wire 10, a pulse is generated. The polarity of the pulse at that time was positive, and the polarity (MS) of the magnet 20 was N(+), as shown in the row of point c in the "This Time" column of Figure 3B. Both the pulse polarity and the polarity of the magnet 20 are the same as in the previous case at point c. In this specification, "previous time" refers to the time when the previous pulse occurred, and "this time" refers to the time when the current pulse occurred.

[0049] Next, we will explain the case where the current pulse occurs at point d. In this case, after generating the previous pulse 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 polar portion 21. Then, it turns counterclockwise, and when it rotates to a position where point d is opposite the magnetic wire 10, a pulse is generated. The polarity of this pulse is negative, and the polarity (MS) of the magnet 20 is N(+).

[0050] Next, we will explain the case where the pulse occurs at point f. In this case, the magnet 20 rotates counterclockwise, and the pulse is not generated at point d, which is the same as in the case of point c. After that, the magnet 20 continues to rotate counterclockwise, and when it rotates to a position where point f is opposite 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 S(-).

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

[0052] Next, the calculation of the count value will be explained. The count value represents 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 Figure 3B. In this example, clockwise (CW) is positive (+) and counterclockwise (CCW) is negative (-). In other words, as shown in Figure 3A, the rotating body 30 or magnet 20 is defined as having four segments (quadrants) divided by two orthogonal axes passing through the axis of rotation when a rotational coordinate system is set with respect to its axis of rotation, and the count value increases or decreases as the segment facing the magnetic wire 10 changes due to rotation. The distinction between an increase and a decrease in the count value is further determined by combining it with the detection result of the magnet polarity discrimination unit 14. In addition to the definition above, a segment may also be defined as, for example, a region having a predetermined angular width in the direction of rotation with respect to the axis of rotation. In other words, if four count values ​​represent one rotation, for example, a region corresponding to an angular width of 90 degrees in the direction of rotation may be given as a segment. The segment facing the magnetic wire 10 is the one among the multiple segments included in the rotating body 30 that is closest to the installation position of the magnetic wire 10, and it changes according to the rotational movement.

[0053] If the previous pulse originated at point c and the current pulse originates at point c, the count value is 0. This corresponds to the fact that both the previous and current pulses originated in quadrant 2 in Figure 3A. If the previous pulse originated at point c and the current pulse originates at point d, the count value is 0. This also corresponds to the fact that both the previous and current pulses originated in quadrant 2 in Figure 3A.

[0054] If the previous pulse originated at point c and the current pulse originates at point f, the count value is -1. This corresponds to the previous pulse originating in quadrant 2 and the current pulse originating in quadrant 3 in Figure 3A. If the previous pulse originated at point c and the current pulse originates at point a, the count value is +1. This corresponds to the previous pulse originating in quadrant 2 and the current pulse originating in quadrant 1 in Figure 3A.

[0055] The calculation of the count value shown in Figure 3B is just one example, and the method can be summarized as follows. The calculation unit 16 calculates the count value based on the polarity of the previous magnet 20, the polarity of the current pulse, and the polarity of the current magnet 20. Alternatively, the calculation unit 16 can calculate the count value without using the polarity of the previous pulse. In other words, in accordance with the rotation of the rotating body 30 on which the magnet 20 is installed, the calculation unit 16 counts the circumferential segments (in this case, a 4-segment configuration) of the rotating body 30 and calculates the count value. More specifically, it can be explained as follows. When the alternating magnetic field formed by the rotation of the magnet 20 contained in the rotating body 30 is applied to the magnetic wire 10, pulses are generated in accordance with the change in the direction of the magnetic field. Then, in response to the generation of pulses, the magnet polarity determination unit 14 determines the polarity of the magnet 20 at a predetermined relative position with respect to the magnetic wire 10. This operation can be considered as counting the number of times the segment that the magnetic wire 10 is facing changes to another adjacent segment due to the rotation of the rotating body 30, with respect to a plurality of segments that are virtually defined as regions with predetermined angular widths along the circumferential direction of the rotating body 30.

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

[0057] The calculation unit 16 may output a count value that maintains the cumulative value if the polarity of the magnet 20 in the previous measurement is the same as the polarity of the magnet 20 in the current measurement (points c and d in "this time"). In Figure 3B, this count value is 0. The calculation unit 16 may output a count value that increases or decreases the cumulative value if the polarity of the magnet 20 in the previous measurement is different from the polarity of the magnet 20 in the current measurement (points f and a in "this time"). In Figure 3B, this 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 in the current instance matches the polarity of the pulse in the current instance. In Figure 3B, when the polarity of the magnet 20 in the previous instance and the polarity of the magnet 20 in the current instance are different (points f and a of "this instance"), the sign is negative when the polarity of the magnet 20 in the current instance matches the polarity of the pulse in the current instance (point a), and the sign is positive when the polarity of the magnet 20 in the current instance differs from the polarity of the pulse in the current instance (point f). In this case, the absolute values ​​of the count values ​​may be the same. In Figure 3B, when this instance is point a, the count value is +1, and when this instance 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. In other words, in all of the above count value calculations, the count value is calculated without using the polarity of the previous pulse. This reduces the amount of information that needs to be referenced when calculating the count value.

[0060] The calculation unit 16 may read the polarity of the previous magnet 20 from the storage unit 18 when calculating the count value. The calculation unit 16 does not need to read the polarity of the previous pulse from the storage unit 18 when calculating the count value. The calculation unit 16 may calculate the count value based only on the polarity of the previous 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 storage unit 18. The calculation unit 16 may write the polarity information of the magnet 20 for the current pulse to the storage unit 18. This allows the system to read out the current polarity as the previous polarity of the magnet 20 when the next pulse is generated. The calculation unit 16 does not need to write the polarity information of the current pulse to the storage unit 18. The storage unit 18 may store the polarity information of the magnet 20. The storage unit 18 does not need to store the polarity information of the pulse.

[0062] Figure 4A is a diagram illustrating the polarity of the pulse output by the magnetic wire 10 of Patent Document 1 and the polarity of the magnet 20 as determined by the magnet polarity determination unit 14. Figure 4B is a diagram illustrating the relationship between the pulse polarity of Patent Document 1, the polarity of the magnet 20, and the count value. Figures 1 and 2A-2C of Patent Document 1 show a power generation sensor 20 arranged in a direction parallel to the tangent of a magnetic field source 50, which is a four-pole magnetized magnet, and a sensor element MS "arranged to detect the polarity of opposing magnetic poles in the central part 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 Figure 4A using the representation in Figure 3A of this specification.

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

[0064] Similar to the case in Figure 3A, we will now explain the case where the magnet 20 rotates clockwise from the state shown in Figure 4A. As the rotation progresses, a pulse is output when point d is positioned opposite the center of the magnetic wire 10. The polarity at that time is negative. At that time, the polarity of the magnet 20 detected by the magnet polarity discrimination unit 14 is the second polarity unit 22. In the table in Figure 4B, the "Previous" column shows that the polarity of the pulse at position d was negative, and the polarity of the magnet 20 (MS) is indicated as S(-).

[0065] Previously, there are four possible locations where a pulse may occur after the pulse generated at point d: points d, e, g, and b. In Figure 4B, the "Current" column shows the points in this order in each row. First, let's explain the case where the current pulse occurs at point d. In this case, after generating the previous pulse at point d, the magnet 20 begins to rotate in the opposite direction (counterclockwise). Then, a pulse is missed at point e. After that, the magnet 20 rotates clockwise again, and when it rotates to a position where point d is opposite 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(-), as shown in the row for point d in the "Current" column of Figure 3B. Both the pulse polarity and the polarity of the magnet 20 are the same as in the previous case at point d.

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

[0067] Next, let's explain the case where the pulse occurs at point g. In this case, the magnet 20 rotates counterclockwise, and the pulse is not generated at point e, similar to the case at point d. After that, the magnet 20 continues to rotate counterclockwise, and when point g rotates to a position opposite 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 N(+).

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

[0069] Next, we will explain how to calculate the count value. The method for obtaining the count value is the same as in the case of Figure 3B. If the location of the previous pulse generation was point d and the location of the current pulse generation is point d, the count value will be 0. This corresponds to the fact that in Figure 4A, both the previous and current pulses were generated in quadrant 2. If the location of the previous pulse generation was point d and the location of the current pulse generation is point e, the count value will be -1. This corresponds to the fact that in Figure 4A, the previous pulse was generated in quadrant 2 and the current pulse was generated in quadrant 3.

[0070] If the previous pulse originated at point d and the current pulse originates at point g, the count value is -2. This corresponds to the previous pulse originating in quadrant 2 and the current pulse originating in quadrant 4 in Figure 4A. If the previous pulse originated at point d and the current pulse originates at point b, the count value is +1. This corresponds to the previous pulse originating in quadrant 2 and the current pulse originating in quadrant 1 in Figure 4A.

[0071] In Figure 4B, a count value of -2 exists. Considering the other points besides point d, a count value of +2 exists, so in the example of Figure 4A, an absolute value of 2 exists for the count value. Figure 5 of Patent Document 1 shows the existence of +2 or -2. Also, in Figure 4B, it is impossible to calculate the count value without using the polarity of the previous pulse, and it is always 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 using the polarity of the previous pulse voltage and the state of the previous sensor element.

[0072] In the rotational 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 there is an absolute value of 2 in the count value, it may be necessary to write to the storage unit 18 twice. In the rotational speed detection device 100 of this embodiment, the absolute value of the count value is 1, so writing to the storage unit 18 is always completed in one step.

[0073] Figure 5A is a diagram illustrating 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 described in Patent Document 1 is the same as in Figure 3A. Figure 5B is a diagram illustrating the relationship between the polarity of the pulse in Figure 5A, the polarity of the magnet 20, and the count value.

[0074] In Figure 5A, the magnetic wire 10 is positioned perpendicular to the tangent to the magnet 20, and the magnet polarity discrimination unit 14 is positioned at a 45-degree angle from the magnetic wire 10 with respect to the axis of rotation. Detailed explanations of each point in Figures 5A and 5B are omitted.

[0075] In Figure 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, the count value is increased by +1 or decreased by -1 if the polarity of the pulse is different. A change in the count value means a change in the quadrant (segment). Therefore, in Figure 5B, for example, there is a quadrant boundary between point c and point d, where the pulse polarities are different. As a result, if a pulse occurs at point c and then at point d, the count value becomes -1. Also, if a pulse occurs at point c, then there is a pulse dropout at point d, and then the next pulse occurs at point f, the count value becomes -2. Therefore, the number of count value variations increases to four (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 occurs at point c and then at point d, the count value becomes 0 (see Figure 3B). Also, even if a pulse occurs at point c, then there is a pulse gap at point d, and the next pulse occurs at point f, the quadrant shift is only one step according to the change in the polarity of the magnet 20, and the count value becomes -1 (see Figure 3B).

[0077] Figure 6A illustrates 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 differs from that of the embodiment. Figure 6B illustrates the relationship between the polarity of the pulse in Figure 6A, the polarity of the magnet 20, and the count value. Detailed explanations of each point in Figures 6A and 6B are omitted.

[0078] In Figure 6A, the magnetic wire 10 is positioned parallel to the tangent to the magnet 20, so the pulse generation position is the same as in Figure 4A. The magnet polarity discrimination unit 14 detects the polarity of the magnet 20 in 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 quadrant division differs from that in Figure 4A.

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

[0080] Figure 7 is a flowchart illustrating an example of a method for detecting the rotational speed of the rotating body 30. In the rotational speed detection method, the count value may be calculated as described in Figures 1 to 3B, Figure 6A, or Figure 6B. That is, in the rotational speed detection method, the count value may be calculated based on the polarity of the previous magnet 20, the polarity of the current pulse, and the polarity of the current magnet 20. Alternatively, the rotational speed detection method may calculate the count value without using the polarity of the previous pulse. Figure 7 is an example of this.

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

[0082] In Step 3, the polarity of the previous magnet 20 is read. In Step 3, the arithmetic unit 16 may read the polarity of the previous magnet 20 from the memory unit 18. Note that the order of Steps 1-3 may differ from that shown in Figure 7.

[0083] Step 4 determines whether the polarity of the current magnet 20 matches the polarity of the previous magnet 20. If the polarity of the current magnet 20 matches the polarity of the previous magnet 20 (Yes), a count value that maintains the cumulative value of the count can be calculated. In this example, we proceed to Step 6 and calculate a count value of 0.

[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 cumulative value may be output. In this example, proceed to Step 5 to determine whether the polarity of the pulse this time matches the polarity of the magnet 20 this time. If the polarity of the pulse this time matches the polarity of the magnet 20 this time (Yes), calculate a count value of +1 in Step 6. If the polarity of the pulse this time does not match the polarity of the magnet 20 this time (No), calculate a count value of -1 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, based on the polarity of the magnet 20 of the rotating body 30 acquired last time, the polarity of the pulse this time, and the polarity of the magnet 20 of the rotating body 30 when the pulse this time was generated, that other segments 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 have moved to face the installation position of the magnetic wire 10 at the time of the current pulse generation. More specifically, the calculation unit 16 determines whether the segment opposite the installation position of the magnetic wire 10 reached that position through a clockwise or counterclockwise rotation from its position during the previous pulse generation, and calculates a count value according to the determination result.

[0085] In Step 7, the calculated count values ​​are accumulated. The calculation unit 16 outputs the calculated count values ​​to the storage unit 18, and the storage unit 18 may perform the accumulation of the count values. Also, in Step 7, the polarity of the magnet 20 in this case may be saved. The calculation unit 16 may write the polarity of the magnet 20 in this case to the storage unit 18. In Step 7, the polarity of the pulse in this case does not need to be saved.

[0086] Figure 8A illustrates the relative position of the magnet polarity discrimination unit 14 with respect to the magnetic wire 10. In this example, the rotating body 30 is magnetized with four poles. However, in Figure 8A, only the magnet 20 of the rotating body 30 is shown. In this example, the magnetic wire 10 extends in a direction intersecting the tangent to the rotational direction of the rotating body 30.

[0087] The magnet polarity discrimination unit 14 in this example is a magnetic sensor. In this example, the magnet polarity discrimination unit 14 is positioned so as not to face either boundary of the magnetization of the rotating body 30 when the boundary of the magnetization of the magnetic wire 10 and the rotating body 30 are opposite each other. In this example as well, the boundary of the magnetization of the rotating body 30 is the boundary between the first polarity portion 21 and the second polarity portion 22 of the magnet 20. Figure 8A shows the case where the magnet polarity discrimination unit 14 is positioned so as to face the boundary of the magnetization of the magnetic wire 10 and the rotating body 30. This reduces false detections by the magnet polarity discrimination unit 14. Not facing a boundary means that there is no boundary within ±10 degrees in the rotational direction centered on the magnet polarity discrimination unit 14. The boundary 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 discrimination unit 14 may be positioned such that the distance from the magnetization boundary of the rotating body 30 is maximized when the magnetic wire 10 and the magnetization boundary of the rotating body 30 are positioned opposite each other. The distance from the boundary may be the distance to the boundary closest to the magnet polarity discrimination unit 14. If the boundaries are arranged at equal angular intervals, there will be two boundaries that are equally far from the magnet polarity discrimination unit 14. In this example, the magnet polarity discrimination unit 14 is positioned at 45 degrees or 135 degrees from the magnetic wire 10 with respect to the rotation axis 32 of the rotating body 30, and the distance from the boundary is maximized at that position. This reduces false detection by the magnet polarity discrimination unit 14. However, the above arrangement or angle may have a range. This range may be ±10 degrees, ±5 degrees, or ±2 degrees.

[0089] Figure 8B is another diagram illustrating 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 to 6 poles. However, in Figure 8B, 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 direction of rotation. The magnetic wire 10 in this example also extends in a direction intersecting the tangent to the rotation 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 positioned opposite each other, the position of the magnet polarity discrimination unit 14 that maximizes the distance from the magnetization boundary of the rotating body 30 is at a position of 30 degrees, 90 degrees, or 150 degrees from the magnetic wire 10, with respect to the rotation axis 32 of the rotating body 30. By positioning the magnet polarity discrimination unit 14 at the above position, false detections by the magnet polarity discrimination unit 14 can be reduced. The above angle may have a range of ±5 degrees or ±2 degrees.

[0091] The above arrangement can be generalized as follows. That is, when the magnetic wire 10 extends in a direction intersecting the tangent to the rotational direction of the rotating body 30, and the magnetic wire 10 and the magnetization boundary of the rotating body 30 are positioned opposite each other, we will describe the arrangement of the magnet polarity discrimination unit 14 such that the distance to the magnetization boundary of the rotating body 30 is maximized. Assume that the rotating body is magnetized to n poles. n is an even number. n may be an even number greater than or equal to 4, an even number greater than or equal to 6, or an even number greater than or equal to 8. Assume that the magnetization boundaries of the rotating body 30 are arranged at equal angular intervals in the rotational direction.

[0092] The magnetic polarity discrimination unit 14 is located at the angle θ from the magnetic wire 10 centered on the rotation axis of the rotating body 30, as shown below. m If it is positioned at this location, the distance from the boundary will be greatest. θ m = 180 × m / n However, m is any odd number less than n. Angle θ m The maximum value is 180 degrees. In other words, the above formula can be used symmetrically in clockwise and counterclockwise directions with respect to the magnetic wire 10.

[0093] For example, when n=4, the angle θ m The angles are 45 degrees (m=1) and 135 degrees (m=3), which matches the example in Figure 8A. m It may have a width. This width may be ±40 / n degrees, ±20 / n degrees, or ±8 / n degrees. Also, the boundary position of the magnetization of the rotating body 30 is an angle θ m It may have a similar width. With the magnetic wire 10 and magnet polarity discrimination unit 14 installed in this manner, and with each segment assigned to the rotating body 30 such that it includes the magnetization boundary, the detection of segment movement as described above becomes possible. This arrangement and segment assignment allows for the detection of both cases where a segment change occurs in response to pulse generation and cases where no segment change occurs. More specifically, when a pulse is generated as the magnetization boundary passes the position opposite 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 relative position described above, identifies the polarity of the opposing magnet 20 at that position. If the polarity of magnet 20 matches the polarity of magnet 20 in the previous measurement, it can be determined that the segment opposite the magnetic wire 10 is the same as in the previous measurement. If the polarity of magnet 20 differs from the polarity of magnet 20 in the previous measurement, it can be detected that a segment change has occurred. Based on the combination of this information and the polarity of the pulse, it is possible to determine whether the segment change is caused by clockwise or counterclockwise rotation.

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

[0095] In Figure 9, the direction parallel to the rotation axis of the magnet 20 (the direction of rotation axis) is defined as the Z-axis, and the direction of the long axis of the magnetic wire 10 is defined as 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 magnetic wire 10 in the direction of its long axis may be positioned in the outer edge region 24 of the magnet 20. Figure 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 also be arranged such that the midpoint 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 Figure 9). Figure 9 shows a dotted line extending in the Z-axis direction from the midpoint 52 of the magnetic wire 10 to outside the outer edge 25 of the magnet 20. Furthermore, with respect to the ring-shaped magnet 20, the end of the magnetic wire 10 (one end 51 in Figure 9) may be positioned 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 positioned so as to be located in the area between the inner and outer diameters of the magnet 20. The other end 53 of the magnetic wire 10 in the direction of its long axis may be positioned so as to be located on a straight line that passes through the rotation axis of the magnet 20 and extends in the opposite direction of 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 positioned on a straight line. Furthermore, in the direction of the rotation axis of the magnet 20, the magnetic wire 10 may be installed in a space above the top surface of the magnet 20 or below the bottom surface of the magnet 20. Furthermore, one end 51 and the other end 53 of the magnetic wire 10 may be the center point 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 Figure 9).

[0096] The magnet polarity discrimination unit 14 may be arranged as follows. The magnet polarity discrimination unit 14 may be arranged 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. Figure 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. For a ring-shaped magnet 20, the magnet polarity discrimination unit 14 may be arranged 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 ends of the magnet polarity discrimination unit 14 may be positioned in the region between the inner diameter and outer diameter of the magnet 20. The magnet polarity discrimination unit 14 may also be integrated together with the calculation unit 16 into a single integrated circuit (IC chip). The magnet polarity discrimination unit 14 may be positioned at a position of 45 degrees or 135 degrees (including adjustments of approximately ±10 degrees in each case) from the line segment connecting the rotation axis and the center of the magnetic wire 10 (corresponding to the angle reference line in Figure 8A), when viewed from the rotation axis direction of the magnet 20. The magnet polarity discrimination unit 14 may also be installed in the space above the top surface of the magnet 20 or below the bottom surface of the magnet 20, in the rotation axis direction of the magnet 20. In this case, the magnet polarity discrimination unit 14 may be positioned in the space on the same side of the magnet 20 as the magnet 20 in the rotation axis direction of the magnet 20 (the space on the positive Z-axis side of the magnet 20 in Figure 9), or on the opposite side (the space on the negative Z-axis side of the magnet 20 in Figure 9), with respect to the magnetic wire 10.

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

[0098] It should be noted that the execution order of operations, procedures, steps, and stages in the apparatus, systems, flowcharts, and methods shown in the claims, specification, and drawings is not explicitly stated as "before" or "prior to," and that these can be implemented in any order unless the output of a previous process is used in a later process. Even if the operation flows in the claims, specification, and drawings are described using phrases such as "first," "next," etc., for convenience, this does not mean that they must be performed in that order. [Explanation of symbols]

[0099] 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 part, 22...Second polarity part, 24...Outer edge region, 25...Outer edge end, 30...Rotating body, 32...Rotation axis, 34...Mounting part, 40...Support base, 42...Support member, 51...One end, 52...Center point, 53...Other end, 100...Rotation speed detection device, 200...Rotation speed detection system

Claims

1. A magnetic wire that, as a rotating body rotates, is subjected to an alternating magnetic field with two or more periods per rotation in the axial direction, and outputs pulses of polarity corresponding to the change in the direction of the magnetic field, A magnet polarity determination unit that determines the polarity of the magnets contained in the rotating body that form the alternating magnetic field 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 polarity of the rotating body's magnet acquired in the previous instance, the polarity of the current pulse, and the polarity of the rotating body's magnet when the current pulse was generated, without using the polarity of the previous pulse. Rotation speed detection device.

2. When the calculation unit is driven by the pulse and the calculation of the count value begins, it detects, based on the polarity of the magnet of the rotating body acquired in the previous instance, the polarity of the current pulse, and the polarity of the magnet of the rotating body when the current pulse occurred, that another segment adjacent to the segment facing the magnetic wire when the previous pulse occurred has moved to a position facing the magnetic wire when the current pulse occurred. The rotational speed detection device according to claim 1.

3. The system includes a storage unit that accumulates the count values ​​calculated by the calculation unit and stores them as an accumulated value. The rotational speed detection device according to claim 2.

4. The calculation unit causes the count value for at least one of the current pulses to differ depending on whether the polarity of the magnet of the rotating body in the previous instance matches the polarity of the magnet of the rotating body in the current instance. The rotational speed detection device according to claim 3.

5. The calculation unit outputs the count value that maintains the accumulated value if the polarity of the magnet of the rotating body is the same as the polarity of the magnet of the rotating body in the previous instance. If the polarity of the magnet on the rotating body in the previous instance is different from the polarity of the magnet on the rotating body in the current instance, the count value that increases or decreases the cumulative value is output. The rotational speed detection device according to claim 4.

6. The calculation unit changes the sign of the count value depending on whether the polarity of the magnet of the rotating body matches the polarity of the pulse. The rotational speed detection device according to claim 5.

7. The magnetic wire is arranged to output the pulse when the magnetization boundary of the rotating body shifts from its opposing position. A rotational speed detection device according to any one of claims 1 to 6.

8. The magnetic wire extends in a direction that intersects with the tangent to the rotating body. The rotational speed detection device according to claim 7.

9. The aforementioned magnet polarity discrimination unit is a magnetic sensor, When the magnetic sensor is positioned so as not to face either boundary of the magnetization of the rotating body when the magnetic wire and the boundary of the magnetization of the rotating body are facing each other, it is positioned so as not to face either boundary of the magnetization of the rotating body. A rotational speed detection device according to any one of claims 1 to 6.

10. The magnetic sensor is positioned such that, when the magnetic wire and the boundary of the magnetization of the rotating body are facing each other, the distance between the magnetic sensor and the boundary of the magnetization of the rotating body is maximized. The rotational speed detection device according to claim 9.

11. The rotating body is magnetized with four poles. The rotational speed detection device according to claim 10.

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

13. The rotating body is magnetized to an n pole, The angle θ of the magnetic sensor from the magnetic wire, centered on the rotation axis of the rotating body. ｍ It is positioned within a range of ±40 / n degrees centered on one of the following points. i ｍ =±180×m / n However, m is any odd number less than n. The rotational speed detection device according to claim 10.

14. A rotation speed detection device according to any one of claims 1 to 6, The rotating body and A rotational speed detection system equipped with the following features.

15. A rotational speed calculation device that calculates a count value by counting the circumferential segments of a rotating body based on the output of a magnetic wire and a magnet polarity discrimination unit, The magnetic wire is subjected to an alternating magnetic field with two or more periods per rotation in the axial direction as the rotating body rotates, and outputs pulses of polarity corresponding to the change in the direction of the magnetic field. The magnet polarity determination unit determines the polarity of the magnets included in the rotating body that form the alternating magnetic field at a predetermined relative position with respect to the magnetic wire. The rotational speed calculation device is The count value is calculated based on the polarity of the rotating body's magnet obtained in the previous instance, the polarity of the current pulse, and the polarity of the rotating body's magnet when the current pulse occurred, without using the polarity of the previous pulse. Rotation speed calculation device.

16. As the rotating body rotates, an alternating magnetic field with two or more periods per rotation is applied axially, and the polarity of the pulses output by the magnetic wire is obtained in response to the change in the direction of the magnetic field. At a predetermined relative position with respect to the magnetic wire, the alternating magnetic field is formed and the polarity of the magnet contained in the rotating body is obtained. Based on the polarity of the rotating body's magnet acquired in the previous instance, the polarity of the current pulse, and the polarity of the rotating body's magnet when the current pulse occurred, and without using the polarity of the previous pulse, the circumferential segments of the rotating body are counted to calculate the count value. Method for detecting rotational speed.

Images