JP4453425B2 - Magnetic encoder detection method - Google Patents

Description

  The present invention relates to a detection method of a magnetic encoder used in a detection device that detects the rotation of a rotating member provided in, for example, an automobile, a home appliance, or the like.

  2. Description of the Related Art Conventionally, as this type of magnetic encoder, one used for a detection device that detects a rotational speed, such as a vehicle speed sensor that detects the vehicle speed of an automobile, is known. Patent Document 1 discloses a sealing device in which a metal surface having a multi-pole shape in the circumferential direction is coated with an elastic body, and a rotation detection sensor is installed in proximity to the sealing device, and the number of rotations of the sealing device is set. Detected.

The rotation detection sensor can calculate the vehicle speed from the number of magnetic poles of the magnetic encoder and the circumference of the rotating body including the magnetic encoder. The rotation speed detection range is determined by the peripheral speed of the shaft rotation and the number of magnetized magnetic poles. When the high-speed rotation area is used regularly, the number of magnetic poles is reduced. When the low-speed rotation area is used regularly, the number of magnetic poles is increased. There is a need.
Japanese Utility Model Publication No. 5-69464

  However, in the prior art, when it is necessary to detect the rotational speed in a wide range from low speed rotation to high speed rotation, it is necessary to provide a magnetic encoder and a magnetic sensor for low speed and high speed respectively. For this reason, it has been impossible to avoid an increase in cost due to an increase in mounting space, an increase in the number of parts, and an increase in the number of mounting steps.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a magnetic encoder detection method capable of detecting a magnetic encoder applicable from low-speed rotation to high-speed rotation by one detection means. It is to provide.

  Another object of the present invention is to provide a magnetic encoder detection method capable of detecting a plurality of magnetic force waveforms.

  Another object of the present invention is to provide a detection method for a magnetic encoder capable of detecting two types of magnetic force waveforms with suppressed waveform loss due to interference.

In order to achieve the above object, the present invention provides:
Rotating relative to the detection means for detecting the strength of the magnetic field,
A first magnetic pole array that generates a magnetic field that varies repeatedly at a first wavelength in the circumferential direction; and a second magnetic pole array that generates a magnetic field that varies repeatedly at a second wavelength longer than the first wavelength in the circumferential direction; A magnetic encoder detection method comprising:
The detection means detects a magnetic field repeatedly changing at the second wavelength together with a magnetic field repeatedly changing at the first wavelength at a detection position for detecting the magnetic field repeatedly changing at the first wavelength. To do.

Alternatively, it rotates relative to the detection means for detecting the strength of the magnetic field,
A first magnetic pole array that generates a magnetic field that varies repeatedly at a first wavelength in the circumferential direction; and a second magnetic pole array that generates a magnetic field that varies repeatedly at a second wavelength longer than the first wavelength in the circumferential direction; Have
The first magnetic pole array and the second magnetic pole array are detection methods of a magnetic encoder arranged concentrically,
The detection means detects a magnetic field repeatedly changing at the second wavelength together with a magnetic field repeatedly changing at the first wavelength at a detection position for detecting the magnetic field repeatedly changing at the first wavelength. To do.

  In this way, a plurality of magnetic force waveforms with different intervals of repeatedly varying wavelengths can be obtained, so that a wide range from a low speed to a high speed rotation range can be detected using a single magnetic encoder.

  Further, it is preferable that the detection position is a position close to a region between the first magnetic pole row and the second magnetic pole row.

  Alternatively, the detection position is preferably an intermediate portion between the first magnetic pole row and the second magnetic pole row.

  In this way, a larger combined waveform can be detected in a state where the attenuation of the magnetic field from the two magnetic pole rows is small. For this reason, it is possible to detect the rotational speed with high accuracy.

  Further, it is preferable that the first magnetic pole array and the second magnetic pole array have S poles or N poles alternately arranged.

  In this way, it is possible to easily and stably generate a magnetic field that varies repeatedly at a predetermined wavelength in the circumferential direction.

The magnetic encoder is an annular member,
The first magnetic pole row is located on an inner peripheral portion of the annular member, and the second magnetic pole row is located on an outer peripheral portion of the annular member;
The direction of the magnetic pole is preferably substantially parallel to the rotation axis of the magnetic encoder.

Alternatively, the magnetic encoder is an annular member,
The first magnetic pole row is located on an outer peripheral portion of the annular member, and the second magnetic pole row is located on an inner peripheral portion of the annular member;
The direction of the magnetic pole is preferably substantially parallel to the rotation axis of the magnetic encoder.

  In this way, by providing the detection means at a position facing one plane of the annular member, it is possible to detect two magnetic force waveforms with high accuracy with a single detection means.

Alternatively, the magnetic encoder is an annular member,
The first magnetic pole row is located on one plane side of the annular member; the second magnetic pole row is located on the other plane side of the annular member;
The direction of the magnetic pole is preferably substantially perpendicular to the rotation axis of the magnetic encoder.

  In this way, by providing the detection means at a position facing the outer peripheral surface or the inner peripheral surface of the annular member, it is possible to detect two magnetic force waveforms with high accuracy.

  Further, it is preferable that the magnetic field generated by the first magnetic pole row is substantially zero in a phase corresponding to the surface of the magnetic encoder where the magnetic field generated by the second magnetic pole row is substantially zero. is there.

Here, the phase corresponding to the surface of the magnetic encoder is the angle formed by the position where the magnetic encoder detects the magnetic field around the rotation axis and the predetermined point when the predetermined point on the surface of the magnetic encoder is used as a reference. (0 to 2π).

  In this way, the magnetic force waveform formed by each of the two magnetic pole rows can be obtained while suppressing the loss of the waveform due to interference, so that the detection means can accurately detect the rotational speed.

  Further, the first magnetic pole constituting the first magnetic pole row adjacent to the surface of the magnetic encoder corresponding to the phase at which the magnetic field generated by the first magnetic pole row and the second magnetic pole row becomes substantially zero It is preferable that the second magnetic pole constituting the second magnetic pole array facing the first magnetic pole is the same pole.

  In this way, the magnetic force waveform formed by each of the two magnetic pole rows can be obtained while suppressing the loss of the waveform due to interference, so that the detection means can accurately detect the rotational speed.

  In addition, it is preferable that the number of magnetic poles of the first magnetic pole row is an odd multiple of the number of magnetic poles of the second magnetic pole row.

  In this way, the first magnetic pole row constituting the first magnetic pole row adjacent to the surface of the magnetic encoder corresponding to the phase at which the magnetic field generated by the first magnetic pole row and the second magnetic pole row becomes substantially zero. And the second magnetic pole constituting the second magnetic pole array opposite to the first magnetic pole can be made the same pole over the entire circumference of the magnetic encoder, and formed by two magnetic pole arrays, respectively. A magnetic force waveform can be obtained while suppressing waveform loss due to interference. Therefore, accurate detection of the rotational speed by the detection means is possible over the entire circumference.

  According to the present invention, a magnetic encoder applicable from low speed rotation to high speed rotation can be detected by one detection means.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the embodiments and the drawings. However, the functions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. . Further, the materials, shapes, etc. of the members once described in the following description are the same as those in the first description unless otherwise described.

  FIG. 1A is a top view of the magnetic encoder according to the first embodiment, and FIG. 1B is a cross-sectional view taken along the line AA in FIG.

  The magnetic encoder 1 according to the first embodiment is an annular member that rotates relative to a detection unit 2 that detects the strength of a magnetic field. The size of the annular member may be appropriately selected depending on the rotating member to be attached. In the first embodiment, a magnetic encoder having an outer diameter of 85 mm and an inner diameter of 68 mm will be described.

  A magnetic sensor is used as the detection means 2. A magnetic sensor is a sensor that detects magnetic energy. Specifically, a magnetic head using an electromagnetic induction action, a differential transformer, a Hall element using an action that converts magnetic force into electricity, an MR element ( A magnetoresistive effect element) or the like is preferable. In the present embodiment, the following description will be given using an ADA HGM-3000P Gauss meter as the detection means. However, the detection means that can actually be used are not limited to this.

  The magnetic encoder 1 includes a first magnetic pole row 4 that generates a magnetic field that repeatedly fluctuates at a first wavelength L1 in the circumferential direction, and a magnetic field that fluctuates repeatedly at a second wavelength L2 that is longer than the first wavelength L1 in the circumferential direction. And a second magnetic pole row 5 for generating Therefore, two types of waveforms (magnetic force waveforms) having different magnetic field fluctuation periods (wavelengths) can be generated by one magnetic encoder 1, and the number of parts and the mounting space can be reduced. In addition, a single magnetic encoder applicable from low speed rotation to high speed rotation can be provided.

  The first magnetic pole row 4 and the second magnetic pole row 5 are arranged concentrically around the rotating shaft 6 of the magnetic encoder. Further, both the first magnetic pole row 4 and the second magnetic pole row 5 are alternately arranged with magnetic poles that are S poles or N poles.

  In the first embodiment, the detection means 2 is disposed above or below one of the two planes 3a and 3b of the magnetic encoder 1 and is located at a detection position that detects a magnetic field that fluctuates repeatedly at the first wavelength L1. A magnetic field that repeatedly fluctuates at the second wavelength L2 in the circumferential direction is detected together with a magnetic field that fluctuates repeatedly at the first wavelength L1 in the circumferential direction. For this reason, it is possible to easily detect a waveform in which two types of waveforms (magnetic force waveforms) having different magnetic field fluctuation periods (wavelengths) are combined by a single detection means, thereby reducing the number of components and the work process. Can be achieved.

  Here, the detection position at which the detecting means 2 detects the magnetic field can simultaneously detect a magnetic field that repeatedly fluctuates at the first wavelength L1 in the circumferential direction and a magnetic field that fluctuates repeatedly at the second wavelength L2 in the circumferential direction as a combined waveform. It does not matter if it is a position. For example, the position may be shifted from directly above the plane 3a of the magnetic encoder 1.

  More preferably, the position is close to the region between the first magnetic pole row 4 and the second magnetic pole row 5. Here, in the first embodiment, the region between the first magnetic pole row 4 and the second magnetic pole row 5 is the first in the plane 3a of the magnetic encoder 1 as shown in FIG. The circumferential R1 connecting the positions where the magnetic fields generated by the magnetic poles constituting the magnetic pole row 4 are maximized in the circumferential direction, and the positions where the magnetic fields generated by the magnetic poles constituting the second magnetic pole row 5 are maximized. This is an annular region X between the circumference R2 continuously connected in the circumferential direction. In the first embodiment, the circumference R1 and the circumference R2 are located at the center of the first magnetic pole row 4 and the second magnetic pole row 5, respectively.

  More preferably, the detection means 2 may be arranged in the vicinity of the circumference R3, which is an intermediate portion between the circumference R1 and the circumference R2, or an intermediate portion between the first magnetic pole row 4 and the second magnetic pole row 5.

  In this way, by detecting at a position close to the region X between the first magnetic pole row 4 and the second magnetic pole row 5, a larger composition is obtained in a state where both the magnetic field attenuation from the two magnetic pole rows is small. Waveform can be detected. For this reason, it is possible to detect the rotational speed with high accuracy.

  In the first embodiment, the first magnetic pole row 4 has 80 poles and the second magnetic pole row 5 has 16 poles. The number of magnetic poles of the first magnetic pole row 14 is 5 that is the number of magnetic poles of the second magnetic pole row 15. Double (odd multiple).

  The magnetization method was performed with an electromagnet having 80-pole and 16-pole metal yokes corresponding to the shape of the outer diameter and inner diameter. However, the production of the magnetic encoder according to the present invention is not limited to this method, and any method can be used as long as it can produce magnetic pole arrays having different numbers of poles.

FIG. 3 shows the phase of the magnetic encoder and the magnetic field strength at that position (the strength of the magnetic force and the magnitude of the magnetic flux density) when the magnetic field is detected from above the plane 3a of the magnetic encoder 1 by the detection means 2. It is a graph. The detected waveform is shown up to the phase θ6 shown in FIG. In FIG. 3, the detected magnetic flux density is shown so that the S pole side is positive and the N pole side is negative, and so on.

  The waveform shown in FIG. 3 is a waveform obtained by combining a waveform that repeatedly fluctuates at the first wavelength L1 and a waveform that fluctuates repeatedly at the second wavelength L2. The detection means 2 detects this composite waveform by, for example, counting the number of times the waveform has shown a certain threshold value of magnetic force (threshold value S = approximately ± 6 and 0 shown in FIG. 3 in this embodiment). The composite waveform signal is output to a computing device such as a computer or IC.

  The arithmetic unit calculates the rotational speed of the magnetic encoder 1 from the time t1 (s) required from detecting a signal corresponding to one magnetic pole of the first magnetic pole row 4 to detecting a signal corresponding to the adjacent magnetic pole. Is calculated. Further, the arithmetic device detects the signal of the magnetic encoder 1 from the time t2 (s) required from detecting a signal corresponding to one magnetic pole of the second magnetic pole row 5 to detecting a signal corresponding to the adjacent magnetic pole. The rotation speed can also be calculated.

Specifically, since the first magnetic pole row has 80 poles, the rotation speed calculated from the magnetic field generated by the first magnetic pole row 4 is
60 / (80 × t1) (rpm) (Formula 1)
It is.

Since the second magnetic pole row has 16 poles, the rotation speed calculated from the magnetic field generated by the second magnetic pole row 5 is
60 / (16 × t2) (rpm) (Expression 2)
It is.

  Here, the arithmetic unit may be provided in the detection unit 2 or may be provided separately from the detection unit 2 and can be appropriately selected depending on the installation space and cost.

  In this way, the rotation speed is detected from the magnetic field generated by the first magnetic pole row 4 during low-speed rotation, and the rotation speed is detected from the magnetic field generated by the second magnetic pole row 5 during high-speed rotation. In a wide rotation speed range from high speed to high speed rotation, the rotation speed of the magnetic encoder can be detected with high accuracy by one detection means.

  The first magnetic pole row 4 may be inside or outside the second magnetic pole row 5, but more preferably, the first magnetic pole row 4 is located on the outer peripheral portion of the annular member, and the second magnetic pole row 4 5 is good to be located in the inner peripheral part of an annular member. This is because the number of magnetic poles of the first magnetic pole row 4 is large, so that the volume per one magnetic pole is increased by arranging the first magnetic pole row 4 on the outer diameter side with a long circumference, and magnetization at the time of manufacturing the magnetic encoder becomes easy. . Moreover, in Example 1, the direction of the magnetic pole is substantially parallel to the rotating shaft 6 of the magnetic encoder. Here, the direction of the magnetic pole is the direction of the lines of magnetic force on the surface of the magnetic pole, and is the direction shown in FIG.

  Furthermore, in the first embodiment, the phases corresponding to the outer peripheral position 7 and the inner peripheral position 8 on the surface of the magnetic encoder where the magnetic field generated in the second magnetic pole row 5 is substantially zero (for example, the phase θ1 shown in FIG. In θ2, θ3), the magnetic field generated by the first magnetic pole row 4 is arranged to be substantially zero. By arranging in this way, the combined waveform (magnetic force waveform) of the magnetic fields respectively formed by the two magnetic pole rows can be obtained while suppressing the loss of the waveform due to interference, so that the detection means 2 can accurately detect the rotational speed. It becomes.

In addition to the above-described configuration, the magnetic field corresponding to the phase where the magnetic fields generated by the first magnetic pole row 4 and the second magnetic pole row 5 are substantially zero (for example, the phases θ1, θ2, and θ3 shown in FIG. 1). A magnetic pole 4a (magnetic pole 4b), which is a first magnetic pole constituting the first magnetic pole row 4 and adjacent to the outer peripheral position 7 of the encoder, is opposed to the magnetic pole 4a (magnetic pole 4b) and adjacent to the inner peripheral position 8. The magnetic pole 5a (magnetic pole 5b), which is the second magnetic pole constituting the second magnetic pole row 5, may be the same pole.

  Specifically, in the first embodiment, the magnetic pole 4a and the magnetic pole 5a are S poles, and the magnetic pole 4b and the magnetic pole 5b are N poles, so that a combined waveform (magnetic force waveform) of the magnetic fields formed by the two magnetic pole rows is obtained. The waveform can be obtained without any loss due to interference, and the detection means 2 can accurately detect the rotational speed.

  In the second embodiment, the first magnetic pole row has 112 poles and the second magnetic pole row has 16, and the number of magnetic poles of the first magnetic pole row is 7 times (odd multiple) the number of magnetic poles of the second magnetic pole row. The point is greatly different. A description of the same configuration as that of the first embodiment is omitted.

  FIG. 4 shows the phase of the magnetic encoder when the magnetic field is detected from the upper side of the plane 3a of the magnetic encoder 1 by the detecting means 2 and the magnetic field strength at that position (the strength of the magnetic force and the magnitude of the magnetic flux density). It is a graph. The detected waveform is shown up to the phase θ6 shown in FIG.

  The waveform shown in FIG. 4 is a waveform obtained by combining a waveform that repeatedly fluctuates at the first wavelength L′ 1 and a waveform that fluctuates repeatedly at the second wavelength L2. The detection means 2 detects this combined waveform and outputs a signal of the total waveform to a computing device such as a computer or IC.

  As described above, also in the second embodiment, it is possible to obtain a combined waveform (magnetic force waveform) of the magnetic fields respectively formed by the two magnetic pole rows without any waveform loss due to interference, and the detection means 2 can accurately detect the rotational speed. It becomes possible.

  As in the configurations of the first and second embodiments, in the present invention, the number of magnetic poles of the first magnetic pole row 4 may be an odd multiple of the number of magnetic poles of the second magnetic pole row 5. . With such a configuration, the first magnetic pole adjacent to the position of the surface of the magnetic encoder corresponding to the phase where the magnetic fields generated by the first magnetic pole row 4 and the second magnetic pole row 5 are substantially zero. It is possible to make the first magnetic pole constituting the row and the second magnetic pole constituting the second magnetic pole row 5 facing the first magnetic pole the same pole over the entire circumference of the magnetic encoder.

(Comparative Example 1)
In the magnetic encoder 11 used in Comparative Example 1, the first magnetic pole row 14 has 80 poles and the second magnetic pole row 15 has 16 poles as in the first embodiment (see FIG. 7). However, at the outer peripheral position 17 of the magnetic encoder corresponding to the phase where the magnetic fields generated by the first magnetic pole row 14 and the second magnetic pole row 15 are substantially zero (for example, θ1, θ2, θ3 shown in FIG. 7). A magnetic pole 14a (magnetic pole 14b), which is a first magnetic pole constituting the adjacent first magnetic pole array 14, and a second magnetic pole array 15 facing the magnetic pole 14a (magnetic pole 14b) and adjacent to the inner peripheral position 18 are arranged. It is a pole different from the magnetic pole 15a (magnetic pole 15b) which is the second magnetic pole to be constructed.

When the magnetic encoder 11 is rotated and detected by the detecting means 12, as shown in FIG. 5, a waveform that fluctuates repeatedly at the first wavelength L11 and a waveform that fluctuates repeatedly at the second wavelength L12 are synthesized. A waveform is detected. In the waveform due to the magnetic field considered to be generated by the second magnetic pole row 15, 16 poles were detected as in the first embodiment. However, unlike the first embodiment, only 48 poles were detected in the waveform due to the magnetic field considered to be generated by the first magnetic pole row 14. This is because the first magnetic pole and the second magnetic pole are different from each other, the first magnetic pole and the second magnetic pole both weaken their strengths, and the magnetic field generated by the magnetic poles 14a and 14b having a particularly small volume. This is thought to be due to the decrease in strength. For this reason, in the configuration shown in Comparative Example 1, there are magnetic poles that cannot be detected by the detection means 12, so that a data loss portion occurs. For this reason, the waveform due to the magnetic field that is considered to be generated by the first magnetic pole row 14 lacks a peak corresponding to one wavelength for the rotation angle θ1, so an accurate continuous waveform cannot be obtained, and the rotational speed is accurately set. It cannot be detected.

(Comparative Example 2)
The magnetic encoder used in Comparative Example 2 has 112 poles for the first magnetic pole row and 16 poles for the second magnetic pole row, as in the second embodiment. However, the first magnetic pole constituting the first magnetic pole row adjacent to the surface of the magnetic encoder corresponding to the phase where the magnetic field generated by the first magnetic pole row and the second magnetic pole row is substantially zero, and The second magnetic pole is different from the second magnetic pole constituting the second magnetic pole row and facing the first magnetic pole.

  When the above magnetic encoder is rotated and detected by the detection means, as shown in FIG. 6, a waveform that repeatedly fluctuates at the first wavelength L′ 11 and a waveform that fluctuates repeatedly at the second wavelength L12 are synthesized. A waveform is detected. In the waveform due to the magnetic field considered to be generated by the second magnetic pole row, 16 poles were detected as in Example 2. However, unlike the second embodiment, only 80 poles were detected in the waveform due to the magnetic field considered to be generated by the first magnetic pole row. This is because the first magnetic pole and the second magnetic pole are different poles, so the first magnetic pole and the second magnetic pole both weaken their strength. This is thought to be due to a decline. For this reason, in the configuration shown in Comparative Example 2, there is a magnetic missing portion that cannot be detected by the detecting means, so that a data loss portion occurs. For this reason, the waveform due to the magnetic field that is thought to be generated by the first magnetic pole array lacks a peak for one wavelength per rotation angle θ1, so an accurate continuous waveform cannot be obtained, and the rotation speed is accurately detected. Can not do it.

  FIG. 2A is a side view of the magnetic encoder according to the third embodiment. 2B is a top view of the magnetic encoder of FIG. 2A viewed from the B direction, and FIG. 2C is a top view of the magnetic encoder of FIG. 2A viewed from the C direction.

  The magnetic encoder 21 used in the third embodiment is characterized in that the first magnetic pole row 24 is located on the one plane 29 side of the annular member, and the second magnetic pole row 25 is located on the other plane 30 side of the annular member. It is. In the third embodiment, the direction of the magnetic pole is substantially perpendicular to the rotating shaft 26 of the magnetic encoder. Here, the direction of the magnetic pole is the direction of the lines of magnetic force on the surface of the magnetic pole, and is the direction shown in FIGS. 2 (a) to 2 (c).

  The magnetic encoder 21 is an annular member that rotates relative to the detection means 22 that detects the strength of the magnetic field.

  The magnetic encoder 21 includes a first magnetic pole row 24 that generates a magnetic field that repeatedly fluctuates at a first wavelength L3 in the circumferential direction, and a magnetic field that fluctuates repeatedly at a second wavelength L4 that is longer than the first wavelength L3 in the circumferential direction. And a second magnetic pole row 25 for generating Therefore, two types of waveforms (magnetic force waveforms) having different magnetic field fluctuation periods (wavelengths) can be generated by one magnetic encoder 21, and the number of parts and the mounting space can be reduced. In addition, a single magnetic encoder applicable from low speed rotation to high speed rotation can be provided.

  The first magnetic pole row 24 and the second magnetic pole row 25 are arranged concentrically around the rotating shaft 26 of the magnetic encoder. Further, both the first magnetic pole array 24 and the second magnetic pole array 25 are alternately arranged with S or N poles.

In the third embodiment, the outer circumference 31 or the inner circumference 32 of the magnetic encoder 21 is located outside or inside the outer circumference 31 or the detection means 22 disposed at a detection position for detecting a magnetic field that repeatedly fluctuates at the first wavelength L3. A magnetic field that repeatedly fluctuates in the direction at the second wavelength L4 is detected together with a magnetic field that fluctuates in the circumferential direction at the first wavelength L3. For this reason, it is possible to easily detect a waveform in which two types of waveforms (magnetic force waveforms) having different magnetic field fluctuation periods (wavelengths) are combined by a single detection means, thereby reducing the number of components and the work process. Can be achieved.

  Here, the detection position at which the detecting means 22 detects the magnetic field can simultaneously detect a magnetic field that repeatedly varies in the circumferential direction at the first wavelength L3 and a magnetic field that repeatedly varies in the circumferential direction at the second wavelength L4 as a combined waveform. It does not matter if it is a position. For example, the position may be shifted from the inside or the outside of the peripheral surface of the magnetic encoder 1.

  More preferably, the position is close to the region between the first magnetic pole row 24 and the second magnetic pole row 25. Here, the region between the first magnetic pole row 24 and the second magnetic pole row 25 is, as shown in FIG. 8B, in the third embodiment, on the outer peripheral surface 31 of the magnetic encoder 1. A position at which the magnetic field generated by each of the magnetic poles constituting the second magnetic pole array 25 and the circumference R11 connecting the positions where the magnetic fields generated by the magnetic poles constituting the one magnetic pole array 24 are maximized in the circumferential direction are maximized. Is a ring-shaped region Y between the circumference R12 that is continuously connected in the circumferential direction. In the third embodiment, the circumference R11 and the circumference R12 are located at the center of the first magnetic pole row 24 and the second magnetic pole row 25, respectively.

  More preferably, the detection means 22 may be disposed in the vicinity of the circumference R13, which is an intermediate portion between the circumference R11 and the circumference R12, or an intermediate portion between the first magnetic pole row and the second magnetic pole row.

  In this way, by detecting at a position close to the region Y between the first magnetic pole row 24 and the second magnetic pole row 25, a larger composition can be achieved with less attenuation of the magnetic fields from the two magnetic pole rows. Waveform can be detected. For this reason, it is possible to detect the rotational speed with high accuracy.

  In Example 3, the first magnetic pole row 24 has 80 poles and the second magnetic pole row 25 has 16 poles. The number of magnetic poles of the first magnetic pole row 24 is 5 that is the number of magnetic poles of the second magnetic pole row 25. Double (odd multiple).

  In the third embodiment, the magnetic field generated by the first magnetic pole row 24 has a phase corresponding to the positions 27 and 28 on the surface of the magnetic encoder where the magnetic field generated by the second magnetic pole row 25 is substantially zero ( For example, the phase θ11, θ12, θ13) shown in FIG. 2 is arranged to be substantially zero. By arranging in this way, a combined waveform (magnetic force waveform) of magnetic fields respectively formed by the two magnetic pole rows can be obtained while suppressing loss of the waveform due to interference, so that the detection means 22 can accurately detect the rotational speed. It becomes.

  In addition to the above-described configuration, the magnetic encoder corresponding to the phase (for example, θ11, θ12, θ13 shown in FIG. 2) in which the magnetic fields generated by the first magnetic pole row 24 and the second magnetic pole row 25 are substantially zero. A magnetic pole 24a (magnetic pole 24b) constituting the first magnetic pole row 24 adjacent to the position 27 on the surface of the magnetic pole 24 and a second magnetic pole row 25 adjacent to the surface position 28 opposite to the magnetic pole 24a (magnetic pole 24b) are formed. The magnetic pole 25a (magnetic pole 25b) to be made is preferably the same pole.

  Specifically, in the third embodiment, the magnetic pole 24a and the magnetic pole 25a are S poles, and the magnetic pole 24b and the magnetic pole 25b are N poles. Therefore, the detection means 22 can accurately detect the rotational speed.

1A is a top view of a magnetic encoder according to Embodiment 1. FIG. (B) It is AA sectional drawing of (a). (A) It is a side view of the magnetic encoder which concerns on Example 3. FIG. (B) It is the top view which looked at the magnetic encoder of (a) from the B direction. (C) It is the top view which looked at the magnetic encoder of (a) from the C direction. 3 is a graph showing a part of a detected waveform according to Example 1. 6 is a graph showing a part of a detected waveform according to Example 2. 10 is a graph showing a part of a detected waveform according to Comparative Example 1. 10 is a graph showing a part of a detected waveform according to Comparative Example 2. 6 is a top view of a magnetic encoder according to Comparative Example 1. FIG. (A) It is a top view for demonstrating the detection position of the magnetic encoder which concerns on Example 1. FIG. (B) It is a side view for demonstrating the detection position of the magnetic encoder which concerns on Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic encoder 2 Detection means 4 1st magnetic pole row 4a, 4b Magnetic pole (1st magnetic pole)
5 Second magnetic pole array 5a, 5b Magnetic pole (second magnetic pole)
6 Rotating axis 7 Plane L1 First wavelength L2 Second wavelength

Claims (11)

Rotating relative to the detection means for detecting the strength of the magnetic field,
A first magnetic pole array that generates a magnetic field that varies repeatedly at a first wavelength in the circumferential direction; and a second magnetic pole array that generates a magnetic field that varies repeatedly at a second wavelength longer than the first wavelength in the circumferential direction; A magnetic encoder detection method comprising:
The detection means detects a magnetic field repeatedly changing at the second wavelength together with a magnetic field repeatedly changing at the first wavelength at a detection position for detecting the magnetic field repeatedly changing at the first wavelength. Method for detecting magnetic encoder. Rotating relative to the detection means for detecting the strength of the magnetic field,
A first magnetic pole array that generates a magnetic field that varies repeatedly at a first wavelength in the circumferential direction; and a second magnetic pole array that generates a magnetic field that varies repeatedly at a second wavelength longer than the first wavelength in the circumferential direction; Have
The first magnetic pole array and the second magnetic pole array are detection methods of a magnetic encoder arranged concentrically,
The detection means detects a magnetic field repeatedly changing at the second wavelength together with a magnetic field repeatedly changing at the first wavelength at a detection position for detecting the magnetic field repeatedly changing at the first wavelength. Method for detecting magnetic encoder.   3. The method of detecting a magnetic encoder according to claim 1, wherein the detection position is a position close to a region between the first magnetic pole row and the second magnetic pole row.   The method of detecting a magnetic encoder according to claim 1, wherein the detection position is an intermediate portion between the first magnetic pole row and the second magnetic pole row.   5. The magnetic encoder detection method according to claim 1, wherein the first magnetic pole array and the second magnetic pole array have S poles or N poles alternately arranged. 6. . The magnetic encoder is an annular member;
The first magnetic pole row is located on an inner peripheral portion of the annular member, and the second magnetic pole row is located on an outer peripheral portion of the annular member;
The magnetic encoder detection method according to claim 1, wherein the direction of the magnetic pole is substantially parallel to a rotation axis of the magnetic encoder. The magnetic encoder is an annular member;
The first magnetic pole row is located on an outer peripheral portion of the annular member, and the second magnetic pole row is located on an inner peripheral portion of the annular member;
The magnetic encoder detection method according to claim 1, wherein the direction of the magnetic pole is substantially parallel to a rotation axis of the magnetic encoder. The magnetic encoder is an annular member;
The first magnetic pole row is located on one plane side of the annular member; the second magnetic pole row is located on the other plane side of the annular member;
6. The magnetic encoder detection method according to claim 1, wherein the direction of the magnetic pole is substantially perpendicular to a rotation axis of the magnetic encoder.   The magnetic field generated by the first magnetic pole row is substantially zero in a phase corresponding to the surface of the magnetic encoder where the magnetic field generated by the second magnetic pole row is substantially zero. Item 9. A method for detecting a magnetic encoder according to any one of Items 6 to 8.   A first magnetic pole constituting the first magnetic pole row adjacent to the surface of the magnetic encoder corresponding to the phase at which the magnetic field generated by the first magnetic pole row and the second magnetic pole row is substantially zero; The method of detecting a magnetic encoder according to claim 9, wherein the second magnetic pole constituting the second magnetic pole array facing the first magnetic pole is the same pole.   The method of detecting a magnetic encoder according to claim 1, wherein the number of magnetic poles of the first magnetic pole row is an odd multiple of the number of magnetic poles of the second magnetic pole row.

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