JP7064966B2 - Magnetic encoder - Google Patents

Description

The present invention relates to a magnetic encoder capable of detecting the origin of a magnetic scale.

Magnetic encoders are described in Patent Documents 1 and 2. The magnetic encoder of Patent Document 1 includes a magnetic scale and a magnetic sensor that detects the movement of the magnetic scale. The magnetic scale consists of a first magnetic track extending in the relative movement direction between the magnetic scale and the magnetic sensor, and a second magnetic track extending in parallel with the first magnetic track in contact with the first magnetic track in a direction orthogonal to the relative movement direction. And a third magnetic track extending in parallel with the second magnetic track in contact with the second magnetic track in the orthogonal direction. The magnetic sensor has a first magnetoresistive pattern facing the boundary between the first magnetic track and the second magnetic track with the magnetic sensitivity direction facing the relative movement direction, and a second magnetic track with the magnetic sensitivity direction facing the relative movement direction. A second magnetic resistance pattern facing the boundary between the magnetic track and the third magnetic track is provided. The magnetic sensor detects the movement of the magnetic scale based on the signal from the first magnetoresistance pattern and the signal from the second magnetoresistive pattern. The first reluctance pattern and the second reluctance pattern detect a rotating magnetic field whose in-plane orientation changes on the surface of the magnetic scale.

The magnetic encoder described in Patent Document 2 includes an annular magnetic scale and a magnetic sensor that detects rotation of the magnetic scale. The magnetic scale includes magnetic tracks in which different magnetic poles are magnetized alternately in the circumferential direction, which is the relative moving direction between the magnetic scale and the magnetic sensor. Further, the magnetic scale includes a magnetized portion magnetized to the N pole or the S pole at a preset origin. The magnetic sensor includes a first sensor element facing the magnetic track and a second sensor element capable of facing the magnetizing pattern. The magnetic sensor detects the rotation of the magnetic scale based on the signal from the first sensor element. Further, the magnetic sensor detects the origin of the magnetic scale based on the signal from the second sensor element. The second sensor element detects the strong and weak magnetic fields of the magnetized portion provided on the magnetic scale.

Japanese Unexamined Patent Publication No. 2007-271608 Japanese Unexamined Patent Publication No. 2007-198847

Even in the magnetic encoder of Patent Document 1, it is conceivable to detect the origin set in the magnetic scale. However, when a magnetized portion is provided at the origin of the magnetic scale and the strong and weak magnetic fields of the magnetized portion are detected by a magnetic sensor to detect the origin, there is a problem that the detection accuracy of the origin is lowered by the external magnetic field. That is, when an external magnetic field is applied to the magnetic encoder, the amplitude of the signal from the magnetoresistive element fluctuates, and the origin may not be accurately detected based on the signal from the magnetoresistive element.

In view of the above problems, an object of the present invention is to provide a magnetic encoder capable of accurately detecting the origin of a magnetic scale even when an external magnetic field is applied.

In order to solve the above problems, the magnetic encoder of the present invention includes a magnetic scale and a magnetic sensor for detecting the movement of the magnetic scale, and the magnetic scale includes the magnetic scale and the magnetic sensor. The first magnetizing pattern in which the N pole and the S pole are lined up with a predetermined origin as a boundary in the relative movement direction and the first magnetizing pattern adjacent to the first magnetizing pattern in the orthogonal direction orthogonal to the relative movement direction are provided. The S pole and the N pole are lined up with the origin as a boundary in the relative movement direction, and the S pole is located next to the N pole of the first magnetism pattern in the orthogonal direction, and the S pole of the first magnetism pattern is located. The magnetic sensor includes a magnetic resistance element for detecting the origin for detecting the origin of the magnetic scale, and the magnetic resistance for detecting the origin. The element is characterized in that the magnetic sensing direction is directed in the relative movement direction and faces the magnetic scale across the boundary between the first magnetizing pattern and the second magnetizing pattern.

According to the present invention, a rotating magnetic field whose in-plane direction changes is generated on the surface of the magnetic scale by the first magnetizing pattern and the second magnetizing pattern provided around the origin set on the magnetic scale. .. Further, since the magnetoresistive element for detecting the origin of the magnetic sensor faces the magnetic scale across the boundary between the first magnetizing pattern and the second magnetizing pattern, the rotating magnetic field can be detected. Here, if the rotating magnetic field is detected, the influence of the external magnetic field can be suppressed as compared with the case where the strong and weak magnetic fields are detected. Therefore, even when an external magnetic field is applied to the magnetic encoder, it is easy to detect the origin.

In the present invention, the magnetic scale has a first magnetic track in which a plurality of N poles and S poles are alternately arranged along the relative movement direction, and the first magnetic track is the first magnetic track in the orthogonal direction. The first magnetizing pattern is provided on the opposite side of the second magnetizing pattern with a gap from the first magnetizing pattern, and the N-pole magnetizing region of the first magnetizing pattern is relative to the first magnetizing pattern. It is located on one side of the origin in the movement direction, extends the relative movement direction from the origin to the one end of the first magnetic track, and the magnetized region of the S pole of the first magnetizing pattern is , Located on the other side of the origin in the relative movement direction, extending the relative movement direction from the origin to the other end of the first magnetic track, and landing the S pole of the second magnetizing pattern. The magnetic region is located on one side of the origin in the relative movement direction, extends the relative movement direction from the origin to the one end of the first magnetic track, and is N of the second magnetic pattern. The magnetized region of the pole is located on the other side of the origin in the relative movement direction, and is characterized in that the relative movement direction extends from the origin to the other end of the first magnetic track.

By doing so, the movement of the scale can be detected by detecting the magnetic field of the first magnetic track. Further, the first magnetizing pattern and the second magnetizing pattern are provided over the entire length of the first magnetic track in the relative moving direction. Therefore, it is possible to prevent the generation of strong and weak magnetic fields due to the first magnetizing pattern and the second magnetizing pattern while detecting the movement of the scale by detecting the magnetic field of the first magnetic track. Therefore, it is possible to prevent the signal from the magnetoresistance pattern from including a signal caused by a strong and weak magnetic field and deteriorating the detection accuracy of the origin. That is, when the first magnetizing pattern is shorter than the first magnetic track, a non-magnetizing region is provided next to the first magnetizing pattern in the relative moving direction. As a result, a strong and weak magnetic field is generated at the boundary between the first magnetized pattern and the non-magnetized region, so that the signal from the magnetoresistance pattern contains a component due to the strong and weak magnetic field, and distortion occurs. Similarly, when the second magnetized pattern is shorter than the first magnetic track, a non-magnetized region is provided next to the second magnetized pattern in the relative moving direction. As a result, a strong and weak magnetic field is generated at the boundary between the second magnetized pattern and the non-magnetized region, so that the signal from the magnetoresistance pattern contains a component due to the strong and weak magnetic field, and distortion occurs. On the other hand, if the first magnetizing pattern is provided over the entire length of the first magnetic track, a non-magnetized region is not formed next to the first magnetizing pattern in the relative movement direction, so that a strong and weak magnetic field is not generated. .. Similarly, if the second magnetizing pattern is provided over the entire length of the first magnetic track, a non-magnetized region is not formed next to the second magnetizing pattern in the relative moving direction, so that a strong and weak magnetic field is not generated. As a result, the signal from the magnetoresistance pattern does not contain components due to the strong and weak magnetic fields, and the signal from the magnetoresistance pattern is not distorted. Therefore, it is possible to prevent the origin detection accuracy from being lowered.

Here, when a strong and weak magnetic field is generated at the end of the first magnetizing pattern and the second magnetizing pattern in the relative moving direction, if the magnetizing of the first magnetizing pattern and the second magnetizing pattern is strengthened, the strong and weak magnetic fields are generated. Becomes larger. As a result, the signal from the magnetoresistance pattern tends to contain components due to the strong and weak magnetic fields, and the distortion of the signal increases. Therefore, when a strong and weak magnetic field is generated, it is difficult to increase the magnetism of the first magnetizing pattern and the second magnetizing pattern to increase the residual magnetic flux density. On the other hand, if the first magnetizing pattern and the second magnetizing pattern are provided over the entire length of the first magnetic track, a strong and weak magnetic field is provided at the end of the first magnetizing pattern and the second magnetizing pattern in the relative moving direction. Does not occur. Therefore, even when the magnetism of the first magnetizing pattern or the second magnetizing pattern is strengthened, the signal from the magnetoresistance pattern is not distorted. Therefore, the magnetism of the first magnetizing pattern and the second magnetizing pattern can be relatively strong to increase the residual magnetic flux density. Here, if the residual magnetic flux densities of the first magnetizing pattern and the second magnetizing pattern are high, the amplitude of the signal from the magnetoresistance pattern can be relatively large. Therefore, even when the gap between the magnetic scale and the magnetic sensor is increased, it is possible to suppress the amplitude of the signal from the magnetoresistance pattern from becoming small. Therefore, the origin can be easily detected based on the signal from the magnetoresistance pattern regardless of the fluctuation of the gap between the magnetic scale and the magnetic sensor.

In the present invention, when the magnetic scale is a linear scale, the first magnetic track extends linearly, and the residual magnetic flux density is constant in the N-pole magnetizing region of the first magnetizing pattern. Yes, the residual magnetic flux density is constant in the magnetizing region of the S pole of the first magnetizing pattern, and the residual magnetic flux density is constant in the magnetizing region of the S pole of the second magnetizing pattern. In the magnetized region of the N pole of the two magnetizing patterns, the residual magnetic flux density can be assumed to be constant.

In the present invention, in the magnetizing region of the N pole of the first magnetizing pattern, the residual magnetic flux density decreases as the distance from the origin moves in the relative movement direction, and the S pole of the first magnetizing pattern is magnetized. In the magnetic region, the residual magnetic flux density decreases as the distance from the origin moves in the relative movement direction, and in the magnetized region of the S pole of the second magnetizing pattern, the magnetic region moves away from the origin in the relative movement direction. Along with this, the residual magnetic flux density can be reduced, and in the magnetized region of the N pole of the second magnetizing pattern, the residual magnetic flux density can be reduced as the distance from the origin is in the relative movement direction.

In the present invention, in the magnetizing region of the N pole of the first magnetizing pattern, the residual magnetic flux density is zero at one end in the relative moving direction, and the magnetizing region of the S pole of the first magnetizing pattern. Then, the residual magnetic flux density is zero at the other end in the relative movement direction, and the residual magnetic flux density is zero at the one end in the relative movement direction in the magnetized region of the S pole of the second magnetizing pattern. In the magnetized region of the N pole of the second magnetizing pattern, the residual magnetic flux density can be set to zero at the other end in the relative moving direction.

In the present invention, when the magnetic scale is a rotary scale, the first magnetic track is an annular shape, and one end of the magnetized region of the N pole of the first magnetizing pattern in the relative movement direction. And the other end of the magnetizing region of the S pole of the first magnetizing pattern in the relative movement direction are continuous, and the relative moving direction of the magnetizing region of the S pole of the second magnetizing pattern. It can be assumed that one end and the other end in the relative movement direction of the magnetizing region of the N pole of the second magnetizing pattern are continuous.

In the present invention, it is desirable that the width of the first magnetizing pattern in the orthogonal direction and the width of the second magnetizing pattern in the orthogonal direction are the same. By doing so, the rotating magnetic field formed by the first magnetizing pattern and the second magnetizing pattern becomes uniform. Therefore, regardless of the direction in which the external magnetic field is applied, the influence of the external magnetic field on the surface rotating magnetic field of the first magnetizing pattern and the second magnetizing pattern can be reduced.

In the present invention, the magnetic scale is provided in contact with the first magnetic track on the side opposite to the first magnetizing pattern of the first magnetic track, and is a second magnetic track extending in parallel with the first magnetic track. Further, the second magnetic track is provided with a third magnetic track provided in contact with the second magnetic track on the opposite side of the second magnetic track from the first magnetic track and extending in parallel with the second magnetic track. A plurality of S poles and N poles are alternately arranged along the relative movement direction, and the S pole is located next to the N pole of the first magnetic track in the orthogonal direction, and the S pole of the first magnetic track is located. The N pole is located next to the N pole, and in the third magnetic track, a plurality of S poles and N poles are alternately arranged along the relative movement direction, and next to the N pole of the second magnetic track in the orthogonal direction. The south pole is located at the center of the second magnetic track, and the north pole is located next to the south pole of the second magnetic track. In this way, the first magnetic track, the second magnetic track, and the third magnetic track can generate a rotating magnetic field on the surface of the magnetic scale for detecting the movement of the magnetic scale.

In the present invention, the magnetic sensor includes a phase A magnetic resistance pattern and a phase B magnetic resistance pattern that detect the movement of the magnetic scale with a phase difference of 90 °, and the phase A magnetic resistance pattern is 180 °. It has a + a phase magnetic resistance pattern and a −a phase magnetic resistance pattern that detects the movement of the magnetic scale with a phase difference of, and the B phase magnetic resistance pattern has the magnetic resistance of 180 °. It has a + b-phase magnetic resistance pattern and a -b-phase magnetic resistance pattern that detect scale movement, and is one of the + a-phase magnetic resistance pattern, the + b-phase magnetic resistance pattern, and the -b-phase magnetic resistance pattern. Means that the magnetic resistance direction is directed in the relative movement direction, the magnetic scale is opposed to the magnetic scale across the boundary between the first magnetic track and the second magnetic track, and the magnetic resistance pattern of the −a phase and the + b The other of the phase magnetic resistance pattern and the −b phase magnetic resistance pattern is the magnetic scale that directs the magnetic sensitivity direction in the relative movement direction and straddles the boundary between the second magnetic track and the third magnetic track. Can be opposed to. In this way, the rotating magnetic field generated on the surface of the magnetic scale by the first magnetic track, the second magnetic track, and the third magnetic track can be detected, and the movement of the magnetic scale can be detected.

According to the present invention, the origin of the magnetic scale can be detected by detecting the rotating magnetic field on the surface of the magnetic scale. Since the rotating magnetic field is less affected by the external magnetic field than the strong and weak magnetic fields, according to the present invention, it is easy to detect the origin even when the external magnetic field is applied.

It is explanatory drawing of the magnetic encoder of Example 1 to which this invention was applied. It is explanatory drawing of the magnetic track of a magnetic scale and the sensor board of a magnetic sensor. It is a circuit diagram which each magnetic resistance pattern of the A phase magnetic resistance pattern constitutes, and the circuit diagram which each magnetic resistance pattern of the B phase magnetic resistance pattern constitutes. It is a circuit diagram which each magnetic resistance pattern of the magnetic resistance pattern of Z phase constitutes. It is a figure which shows the origin signal obtained by the magnetic encoder of Example 1. FIG. It is explanatory drawing of the magnetic scale of the magnetic encoder of the comparative example. It is a figure which shows the origin signal obtained by the magnetic encoder of the comparative example. It is a graph which shows the change of the amplitude of the origin signal when the applied external magnetic field is increased in this example and the comparative example. It is explanatory drawing of the magnetic scale of the magnetic encoder of the modification 1. FIG. It is a figure of the origin signal obtained by the magnetic encoder of the modification 1. FIG. 2 is an explanatory diagram of a magnetic encoder according to a second embodiment. Example 3 It is explanatory drawing of the magnetic encoder.

The magnetic encoder to which the present invention is applied will be described below with reference to the drawings.

(Example 1)
FIG. 1 is an explanatory diagram of a magnetic encoder to which the present invention is applied. FIG. 2A is an explanatory diagram of a magnetic scale, and FIG. 2B is an explanatory diagram of a sensor substrate of a magnetic sensor. FIG. 2B shows a case where the sensor substrate is viewed from the side of the magnetic scale.

The magnetic encoder 1 of this example is a linear encoder. As shown in FIG. 1, the magnetic encoder 1 includes a magnetic scale 2 extending linearly and a magnetic sensor 3 for reading the magnetic scale 2. The magnetic scale 2 includes a magnetic track 5 for an incremental signal extending in a relative moving direction between the magnetic scale 2 and the magnetic sensor 3. Further, the magnetic scale 2 includes a magnetizing pattern 6 for an origin signal provided next to a magnetic track 5 for an incremental signal in a direction orthogonal to a relative moving direction.

In the following description, the direction orthogonal to the relative movement direction is the X direction, the relative movement direction is the Y direction, and the X direction and the direction orthogonal to the Y direction are the Z direction. The Z direction is the direction in which the magnetic scale 2 and the magnetic sensor 3 face each other. In the X direction, the direction from the magnetizing pattern 6 for the origin signal toward the magnetic track 5 for the incremental signal is the + X direction, and the opposite direction is the −X direction. One side in the Y direction is the + Y direction, and the other side is the −Y direction. In the Z direction, the direction from the magnetic scale 2 to the magnetic sensor 3 is the + Z direction, and the opposite direction is the −Z direction.

As shown in FIG. 1, the magnetic sensor 3 includes a holder 7 made of a non-magnetic material, a sensor substrate 8 housed in the holder 7, and a cable 9 extending from the holder 7 in the + Y direction. The cable 9 is connected to the sensor board 8. The holder 7 is provided with an opening 10 on the facing surface 7a facing the magnetic scale 2. The sensor substrate 8 faces the magnetic scale 2 through the opening 10. As shown in FIG. 2B, a magnetoresistive element 11 for acquiring an incremental signal and a magnetoresistive element 12 for detecting the origin are provided on the substrate surface 8a facing the magnetic scale 2 in the sensor substrate 8. There is.

In the magnetic encoder 1, one of the magnetic scale 2 and the magnetic sensor 3 is arranged on the side of the fixed body, and the other is arranged on the side of the moving body. In this example, the magnetic scale 2 is arranged on the side of the moving body, and the magnetic sensor 3 is arranged on the side of the fixed body. The magnetic scale 2 moves in the Y direction with a predetermined gap opened in the Z direction with the magnetic sensor 3.

(Magnetic scale)
As shown in FIG. 2A, the magnetic scale 2 is magnetized for an origin signal provided next to a magnetic track 5 for an incremental signal extending in the Y direction and a magnetic track 5 for an incremental signal in the X direction. The pattern 6 is provided. A gap 14 is provided between the magnetic track 5 for the incremental signal and the magnetizing pattern 6 for the origin signal. Therefore, the magnetic track 5 for the incremental signal is separated from the magnetizing pattern 6 for the origin signal in the X direction.

(Magnetic track for incremental signals)
The magnetic track 5 for the incremental signal includes a first magnetic track 15, a second magnetic track 16, and a third magnetic track 17 arranged in parallel. More specifically, the magnetic track 5 for the incremental signal is provided in contact with the first magnetic track 15 extending in the Y direction and the first magnetic track 15 in the + X direction of the first magnetic track 15. It includes a second magnetic track 16 extending in parallel with 15, and a third magnetic track 17 provided in contact with the second magnetic track 16 in the + X direction of the second magnetic track 16 and extending in parallel with the second track.

In the first magnetic track 15, a plurality of N poles and S poles are alternately arranged at a constant pitch P along the Y direction. In the second magnetic track 16, a plurality of S poles and N poles are alternately arranged at a constant pitch P along the Y direction. In the second magnetic track 16, the S pole is located next to the N pole of the first magnetic track 15 in the X direction, and the N pole is located next to the S pole of the first magnetic track 15. In the third magnetic track 17, a plurality of S poles and N poles are alternately arranged at a constant pitch P along the Y direction. In the third magnetic track 17, the S pole is located next to the N pole of the second magnetic track 16 in the X direction, and the N pole is located next to the S pole of the second magnetic track 16. In this example, the width of the second track in the X direction is wider than the width of the first magnetic track 15 in the X direction. Further, the width of the second track in the X direction is wider than the width of the third magnetic track 17 in the X direction.

(Magnetization pattern for origin signal)
The magnetizing pattern 6 for the origin signal includes a first magnetizing pattern 21 in which the N pole and the S pole are arranged with the origin O predetermined in the Y direction as a boundary. In this example, the origin O is set at the center of the magnetic track 5 for the incremental signal in the Y direction. The magnetizing polarization line between the N pole and the S pole in the first magnetizing pattern 21 is located at the origin O. Further, the magnetizing pattern 6 for the origin signal includes a second magnetizing pattern 22 provided adjacent to the first magnetizing pattern 21 in the −X direction. In the second magnetizing pattern 22, the S pole and the N pole are lined up with the origin O predetermined in the Y direction as a boundary. In the second magnetizing pattern 22, the S pole is located next to the N pole of the first magnetizing pattern 21 in the X direction, and the N pole is located next to the S pole of the first magnetizing pattern 21. The magnetizing polarization line between the N pole and the S pole in the second magnetizing pattern 22 is located at the origin O.

Here, the magnetic polarization line between the S pole and the N pole and the origin O in each magnetic track 5 (first magnetic track 15, second magnetic track 16, and third magnetic track 17) for the incremental signal are , Do not overlap when viewed from the X direction. In each magnetic track 5 for the incremental signal, the magnetic polarization line closest to the origin O is deviated by 1/2 pitch in the Y direction from the origin O.

The magnetized region of the S pole of the first magnetizing pattern 21 is located in the −Y direction of the origin O in the Y direction, and extends in the Y direction from the origin O to the end of the magnetic track 5 for the incremental signal in the −Y direction. The magnetizing region of the N pole of the first magnetizing pattern 21 is located in the + Y direction of the origin O in the Y direction, and extends in the Y direction from the origin O to the end of the magnetic track 5 for the incremental signal in the + Y direction. Therefore, the first magnetizing pattern 21 is formed over the entire detection stroke in which the magnetic sensor 3 detects the movement of the magnetic scale 2. The N-pole magnetizing region of the second magnetizing pattern 22 is located in the −Y direction of the origin O in the Y direction, and extends in the Y direction from the origin O to the end of the magnetic track 5 for the incremental signal in the −Y direction. The magnetizing region of the S pole of the second magnetizing pattern 22 is located in the + Y direction of the origin O in the Y direction, and extends in the Y direction from the origin O to the end of the magnetic track 5 for the incremental signal in the + Y direction. Therefore, the second magnetizing pattern 22 is formed over the entire detection stroke in which the magnetic sensor 3 detects the movement of the magnetic scale 2.

The width D1 in the X direction of the first magnetizing pattern 21 and the width D2 in the X direction of the second magnetizing pattern 22 are the same. Further, the width D1 of the first magnetizing pattern 21 in the X direction and the dimension E of the gap 14 between the first magnetizing pattern 21 and the first magnetizing track are the same.

(Magnetic sensor)
The sensor substrate 8 is made of glass or silicon. As shown in FIG. 2B, the sensor substrate 8 includes a magnetoresistive element 11 for acquiring an incremental signal and a magnetoresistive element 12 for detecting an origin on a substrate surface 8a facing the magnetic scale 2. The magnetoresistive element 11 for acquiring an incremental signal and the magnetoresistive element 12 for detecting the origin are arranged in the X direction. The magnetoresistive element 11 for acquiring an incremental signal is located in the + X direction of the magnetoresistive element 12 for detecting the origin.

(Magnetic resistance element for acquiring incremental signals)
The magnetoresistive element 11 for acquiring an incremental signal includes a phase A magnetic resistance pattern 31 and a phase B magnetic resistance pattern 32 that detect the movement of the magnetic scale 2 with a phase difference of 90 °. The A-phase reluctance pattern 31 includes a + a-phase reluctance pattern 31 (+ a) and a -a-phase reluctance pattern 31 (-a) that detect the movement of the magnetic scale 2 with a phase difference of 180 °. .. The B-phase reluctance pattern 32 includes a + b-phase reluctance pattern 32 (+ b) and a −b-phase reluctance pattern 32 (−b) that detect the movement of the magnetic scale 2 with a phase difference of 180 °. .. The + a phase reluctance pattern 31 (+ a), the + b phase reluctance pattern 32 (+ b), the -a phase reluctance pattern 31 (-a), and the -b phase reluctance pattern 32 (-b) are , Both are provided with the magnetic reluctance direction facing the Y direction. In this example, the + a phase reluctance pattern 31 (+ a) and the + b phase reluctance pattern 32 (+ b) are arranged in the X direction. Further, the reluctance pattern 31 (—a) of the −a phase and the magnetoresistance pattern 32 (−b) of the −b phase are arranged in the X direction. The + a phase reluctance pattern 31 (+ a) and the −b phase reluctance pattern 32 (−b) are adjacent to each other in the Y direction. The reluctance pattern 31 (−a) of the −a phase and the magnetoresistance pattern 32 (+ b) of the + b phase are adjacent to each other in the Y direction. The + a phase reluctance pattern 31 (+ a), the + b phase reluctance pattern 32 (+ b), the −b phase reluctance pattern 32 (−b), and the −a phase reluctance pattern 31 (−a) are , Is formed of a single layer in a region of the substrate surface 8a that does not overlap with each other.

When the magnetic sensor 3 is opposed to the magnetic scale 2, the −a phase reluctance pattern 31 (—a) and the + b phase reluctance pattern 32 (+ b) are the first of the magnetic tracks 5 for the incremental signal. It faces the magnetic scale 2 across the boundary between the magnetic track 15 and the second magnetic track 16. As a result, the -a phase reluctance pattern 31 (-a) and the + b phase reluctance pattern 32 (+ b) of the first magnetic track 15 and the second magnetic track 16 adjacent to each other in the X direction on the magnetic scale 2. Detects the rotating magnetic field generated at the boundary. Further, when the magnetic sensor 3 is opposed to the magnetic scale 2, the + a phase reluctance pattern 31 (+ a) and the −b phase reluctance pattern 32 (−b) are the magnetic tracks 5 for the incremental signal. It faces the magnetic scale 2 across the boundary between the second magnetic track 16 and the third magnetic track 17. As a result, the + a phase magnetoresistance pattern 31 (+ a) and the −b phase magnetoresistance pattern 32 (−b) are generated at the boundary between the second magnetic track 16 and the third magnetic track 17 adjacent to each other in the X direction. Detects the rotating magnetic field.

Further, the magnetoresistive element 11 for acquiring an incremental signal detects a rotating magnetic field by utilizing the saturation sensitivity region thereof. That is, the reluctance element 11 for acquiring the incremental signal includes the + a phase reluctance pattern 31 (+ a), the + b phase reluctance pattern 32 (+ b), and the −b phase reluctance pattern 32 (−b) and −a. A current is passed through the phase magnetic reluctance pattern 31 (−a), and a magnetic field strength that saturates the resistance value is applied to detect a rotating magnetic field whose in-plane direction changes at the boundary portion.

FIG. 3A is a circuit diagram composed of each magnetoresistance pattern of the A-phase reluctance pattern 31, and FIG. 3B is a circuit diagram composed of each magnetoresistance pattern of the B-phase reluctance pattern 32. be. As shown in FIG. 3A, the + a-phase reluctance pattern 31 (+ a) and the -a-phase reluctance pattern 31 (-a) form a bridge circuit, both of which have a power supply terminal at one end. It is connected to (Vcc) and the other end is connected to the ground terminal (GND). Further, a terminal + a for outputting the + a phase is provided at the midpoint position of the + a phase magnetic resistance pattern 31 (+ a), and a terminal + a for outputting the + a phase is provided at the midpoint position of the −a phase magnetic resistance pattern 31 (−a). A terminal-a for outputting the -a phase is provided. Therefore, if the outputs from the terminals + a and the terminals −a are input to the subtractor, a differential output of a sine wave with less distortion can be obtained.

Similarly, the + b-phase reluctance pattern 32 (+ b) and the -b-phase reluctance pattern 32 (-b) constitute a bridge circuit as shown in FIG. 3 (b), and both of them form one end. Is connected to the power supply terminal (Vcc) and the other end is connected to the ground terminal (GND). A terminal + b for outputting the + b phase is provided at the midpoint position of the + b phase magnetoresistance pattern 32 (+ b), and −b is provided at the midpoint position of the −b phase magnetoresistance pattern 32 (−b). A terminal-b from which the phase is output is provided. Therefore, if the outputs from the terminal + b and the terminal −b are input to the subtractor, a differential output of a sine wave with less distortion can be obtained.

(Magnetic resistance element for origin detection)
The magnetoresistive element 12 for detecting the origin has a + z phase magnetoresistance pattern 35 (+ z) and a −z phase magnetoresistance pattern 35 (−z) for detecting the movement of the magnetic scale 2 with a phase difference of 180 °. Be prepared. Both the + z-phase reluctance pattern 35 (+ z) and the −z-phase reluctance pattern 35 (−z) are provided with the magnetic sensitivity direction facing the Y direction.

When the magnetic sensor 3 is opposed to the magnetic scale 2, the + z phase reluctance pattern 35 (+ z) and the −z phase reluctance pattern 35 (−z) are the first of the magnetic resistance patterns 6 for the origin signal. It faces the magnetic scale 2 across the boundary between the magnetizing pattern 21 and the second magnetizing pattern 22. The + z-phase reluctance pattern 35 (+ z) and the -z-phase reluctance pattern 35 (-z) are boundaries between the first magnetic field pattern 21 and the second magnetic field pattern 22 adjacent to each other in the X direction on the magnetic scale 2. Detects the rotating magnetic field generated in the part. Here, the magnetoresistive element 12 for detecting the origin detects the rotating magnetic field by utilizing the saturation sensitivity region thereof. That is, a current is passed through the + z phase magnetoresistance pattern 35 (+ z) and the −z phase magnetoresistance pattern 35 (−z), and a magnetic field strength that saturates the resistance value is applied to the in-plane direction at the boundary portion. Detects a rotating magnetic field whose direction changes.

FIG. 4 is a circuit diagram composed of a + z phase magnetoresistance pattern 35 (+ z) and an −z phase magnetoresistance pattern 35 (−z). As shown in FIG. 4, the + z-phase reluctance pattern 35 (+ z) and the -z-phase reluctance pattern 35 (-z) form a bridge circuit, both of which have a power supply terminal (Vcc) at one end. And the other end is connected to the ground terminal (GND). Further, a terminal + z for outputting the + z phase is provided at the midpoint position of the + z phase magnetoresistance pattern 35 (+ z), and a terminal + z for outputting the + z phase is provided at the midpoint position of the −z phase magnetoresistance pattern 35 (−z). A terminal -z for outputting the -z phase is provided. Therefore, if the outputs from the terminal + z and the terminal −z are input to the subtractor, the origin signal S having a large amplitude at the origin O can be obtained. FIG. 5 is a diagram showing an origin signal S.

(Action effect)
According to the magnetic encoder 1 of this example, the surface of the magnetic scale 2 is in the in-plane direction due to the first magnetic field pattern 21 and the second magnetic field pattern 22 provided with the origin O set in the magnetic scale 2 as a boundary. A rotating magnetic field that changes the direction of is generated. Further, since the magnetoresistive element for detecting the origin of the magnetic sensor 3 faces the magnetic scale 2 across the boundary between the first magnetizing pattern 21 and the second magnetizing pattern 22, the rotating magnetic field is detected. Here, if the rotating magnetic field is detected, the influence of the external magnetic field can be suppressed as compared with the case where the strong and weak magnetic fields are detected.

Further, in this example, the magnetizing pattern 6 for the origin signal (first magnetizing pattern 21 and second magnetizing pattern 22) is a magnetic track 5 (first magnetism) for an incremental signal in the Y direction (relative movement direction). The track 15, the second magnetic track 16 and the third magnetic track 17) are provided over the entire length. Therefore, strong and weak magnetic fields caused by the first magnetizing pattern 21 and the second magnetizing pattern 22 are generated in the entire detection stroke for detecting the movement of the magnetic scale 2 by detecting the magnetic field of the magnetic track 5 for the incremental signal. Can be prevented. Therefore, it is possible to prevent the signal from the magnetoresistance pattern from including a signal caused by a strong and weak magnetic field and deteriorating the detection accuracy of the origin O.

That is, when the first magnetizing pattern 21 is shorter than the magnetic track 5 for the incremental signal, a non-magnetizing region is provided next to the first magnetizing pattern 21 in the Y direction. As a result, a strong and weak magnetic field is generated at the boundary between the first magnetized pattern 21 and the non-magnetized region, so that the signal from the magnetoresistance pattern includes a signal caused by the strong and weak magnetic field, and distortion occurs. Similarly, when the second magnetized pattern 22 is shorter than the magnetic track 5 for the incremental signal, a non-magnetized region is provided next to the second magnetized pattern 22 in the Y direction. As a result, a strong and weak magnetic field is generated at the boundary between the second magnetized pattern 22 and the non-magnetized region, so that the signal from the magnetoresistance pattern includes a signal caused by the strong and weak magnetic field, and distortion occurs. On the other hand, if the first magnetizing pattern 21 is provided over the entire length of the magnetic track 5 for the incremental signal, an unmagnetized region is not formed next to the first magnetizing pattern 21 in the Y direction, so that the incremental is incremental. No strong or weak magnetic field is generated in the entire detection stroke for detecting the movement of the magnetic scale 2 by detecting the magnetic field of the magnetic track 5 for the signal. Similarly, if the second magnetizing pattern 22 is provided over the entire length of the magnetic track 5 for the incremental signal, a non-magnetized region is not formed next to the second magnetizing pattern 22 in the Y direction, so that it is used for the incremental signal. No strong or weak magnetic field is generated in the entire detection stroke for detecting the movement of the magnetic scale 2 by detecting the magnetic field of the magnetic track 5. As a result, it is possible to prevent the signal from the magnetoresistance pattern from being distorted due to the strong and weak magnetic fields, and thus it is possible to prevent the detection accuracy of the origin O from being lowered.

Further, when a strong and weak magnetic field is generated at the end of the first magnetizing pattern 21 and the second magnetizing pattern 22 in the Y direction, the magnetizing of the first magnetizing pattern 21 and the second magnetizing pattern 22 is strengthened. The strong and weak magnetic fields increase. As a result, the signal from the magnetoresistance pattern tends to contain components due to the strong and weak magnetic fields, and the distortion of the signal increases. Therefore, when a strong and weak magnetic field is generated, it is difficult to increase the magnetic flux of the first magnetizing pattern 21 and the second magnetizing pattern 22 to increase the residual magnetic flux density. On the other hand, if the first magnetic pattern 21 and the second magnetic pattern 22 are provided over the entire length of the magnetic track 5 for the incremental signal, the first magnetic pattern 21 and the second magnetic pattern 22 are provided. No strong or weak magnetic field is generated at the end of the Y direction. Therefore, even when the magnetism of the first magnetizing pattern 21 or the second magnetizing pattern 22 is strengthened, the signal from the magnetoresistance pattern is not distorted. Therefore, the magnetism of the first magnetizing pattern 21 and the second magnetizing pattern 22 can be relatively strong to increase the residual magnetic flux density.

Further, if the residual magnetic flux densities of the first magnetizing pattern 21 and the second magnetizing pattern 22 can be increased, the amplitude of the signal from the magnetoresistance pattern can be relatively increased. Therefore, even when the gap between the magnetic scale 2 and the magnetic sensor 3 is increased, it is possible to suppress the amplitude of the signal from the magnetoresistance pattern from becoming small. Therefore, regardless of the fluctuation of the gap between the magnetic scale 2 and the magnetic sensor 3, the origin O can be easily detected based on the signal from the magnetoresistance pattern.

Here, in FIG. 5A, the origin signal S (0 mT) when an external magnetic field is not applied to the magnetic encoder 1 and the case where an external magnetic field of 0.4 mT is applied in the + Y direction. The origin signal S (0.4 mTY) and the origin signal S (0.4 mT 45 °) and 0.4 mT when an external magnetic field of 0.4 mT is applied in a direction inclined by 45 ° with respect to the + Y direction. The origin signal S (0.4 mTX) when the external magnetic field of the above is applied in the + X direction is shown superimposed. Further, in FIG. 5B, the origin signal S (0 mT) when an external magnetic field is not applied to the magnetic encoder 1 and the origin signal when an external magnetic field of 2.0 mT is applied in the + Y direction. The signal S (2 mTY), the origin signal S (2 mT 45 °) when the external magnetic field of 2.0 mT is applied in the direction inclined by 45 ° with respect to the + Y direction, and the external magnetic field of 2.0 mT are + X. The origin signal S (2 mTX) when applied in the direction is superimposed and shown. The origin signal S is obtained by simulation. In the example shown in FIG. 5, the residual magnetic flux density of the magnetizing pattern 6 for the origin signal (first magnetizing pattern 21 and second magnetizing pattern 22) is 4 mT.

As shown in FIGS. 5A and 5B, the origin signal S () obtained by the output from the magnetoresistive element 12 for origin detection when an external magnetic field is not applied to the magnetic encoder 1. At 0 mT), one large peak appears at the origin O. Therefore, according to the magnetic encoder 1 of this example, the origin O can be accurately detected based on the peak of the origin signal S.

Here, as shown in FIG. 5A, the origin signal S (0.4 mT), which can be acquired by the output from the magnetic resistance element 12, when an external magnetic field of 0.4 mT is applied to the magnetic encoder 1. The origin signal S (0.4 mTY), the origin signal S (0.4 mT45 °), the origin signal S (0.4 mTX), and the output from the magnetic resistance element 12 when an external magnetic field is not applied to the magnetic encoder 1. It is almost the same as the origin signal S (0 mT) that can be obtained by. That is, in the magnetic encoder 1 of this example, even when an external magnetic field of 0.4 mT is applied, the amplitude of the origin signal S obtained by the output from the magnetoresistive element 12 for origin detection does not change, and the origin does not change. No distortion occurs in the waveform of the signal S. Therefore, according to the magnetic encoder 1, the origin O can be accurately acquired based on the origin signal S even when an external magnetic field of 0.4 mT is applied to the magnetic scale 2.

Further, as shown in FIG. 5 (b), the origin signal (2 mTY) and the origin signal S (2 mT45) that can be acquired by the output from the magnetoresistive element 12 when an external magnetic field of 2.0 mT is applied to the magnetic encoder 1. °), The origin signal S (2 mTX) has a reduced amplitude as compared with the origin signal S (0 mT) that can be acquired by the output from the magnetoresistive element 12 when an external magnetic field is not applied. However, as shown in FIG. 5 (b), the decrease in the amplitudes of the origin signal (2 mTY), the origin signal S (2 mT 45 °) and the origin signal S (2 mTX) with respect to the origin signal S (0 mT) is very small. Further, even when an external magnetic field is applied, the waveform of the origin signal S is not distorted. Therefore, according to the magnetic encoder 1 of this example, the origin O can be accurately acquired based on the origin signal S even when an external magnetic field of 2.0 mT is applied to the magnetic scale 2.

(Comparative example)
Here, as a comparative example, a magnetic encoder that detects the origin O by using a strong and weak magnetic field will be described. FIG. 6 is an explanatory diagram of the magnetic scale of the magnetic encoder of the comparative example. Since the magnetic encoder 50 of the comparative example has a configuration corresponding to the magnetic encoder 1, the corresponding configuration will be described with the same reference numerals.

As shown in FIG. 6, the magnetic scale 2 of the magnetic encoder 50 of the comparative example includes the same magnetic track 5 for the incremental signal as the magnetic scale 2 of this example. Further, a magnetizing pattern 51 for the origin signal is provided in the −X direction of the magnetic track 5 for the incremental signal. In the magnetizing pattern 51 for the origin signal, the north pole and the south pole are lined up with the origin O predetermined in the Y direction as a boundary. The magnetizing polarization line between the N pole and the S pole in the magnetizing pattern 51 is located at the origin O. The length of the magnetizing region of the N pole of the magnetizing pattern 51 for the origin signal in the Y direction is 1/2 of the pitch P of each pole in the magnetizing track for the incremental signal. The length of the magnetizing region of the S pole of the magnetizing pattern 51 for the origin signal in the Y direction is also ½ of the magnetizing pitch P of each pole in the magnetizing track for the incremental signal.

The magnetic sensor 3 is the same as the magnetic sensor 3. When the magnetic sensor 3 is opposed to the magnetic scale 2, the reluctance pattern 31 (-a) of the -a phase and the reluctance pattern 32 of the + b phase (-a)
+ B) means facing the magnetic scale 2 across the boundary between the first magnetic track 15 and the second magnetic track 16 of the magnetic track 5 for the incremental signal. The -a-phase reluctance pattern 31 (-a) and the + b-phase reluctance pattern 32 (+ b) are located at the boundary between the first magnetic track 15 and the second magnetic track 16 adjacent to each other in the X direction on the magnetic scale 2. Detects the generated rotating magnetic field. Further, when the magnetic sensor 3 is opposed to the magnetic scale 2, the + a phase reluctance pattern 31 (+ a) and the −b phase reluctance pattern 32 (−b) are the magnetic tracks 5 for the incremental signal. It faces the magnetic scale 2 across the boundary between the second magnetic track 16 and the third magnetic track 17. The + a phase magnetoresistance pattern 31 (+ a) and the −b phase magnetoresistance pattern 32 (−b) generate a rotating magnetic field at the boundary between the second magnetic track 16 and the third magnetic track 17 adjacent to each other in the X direction. To detect.

Further, the magnetoresistive element 11 for acquiring an incremental signal detects a rotating magnetic field by utilizing the saturation sensitivity region thereof. That is, the + a phase reluctance pattern 31 (+ a), the −b phase reluctance pattern 32 (−b), the + b phase reluctance pattern 32 (+ b), and the −a phase reluctance pattern 31 (−a). A rotating magnetic field whose direction changes in the in-plane direction at the boundary portion is detected by applying a magnetic field strength in which a current is passed and the resistance value is saturated.

On the other hand, in the magnetic encoder 50 of the comparative example, when the magnetic sensor 3 is opposed to the magnetic scale 2, the + z phase reluctance pattern 35 (+ z) and the −z phase reluctance pattern 35 (−z) are displayed. It faces the magnetized portion of the magnetizing pattern 51 for the origin signal. The + z phase reluctance pattern 35 (+ z) and the −z phase reluctance pattern 35 (−z) detect the strong and weak magnetic fields generated by the magnetic field pattern 51 for the origin signal. The configuration for acquiring the origin signal S based on the + z phase reluctance pattern 35 (+ z) and the −z phase reluctance pattern 35 (−z) is the same as that of the magnetic encoder 1.

FIG. 7 is an explanatory diagram of the origin signal S1 obtained by the output from the magnetoresistive element 12 for detecting the origin in the magnetic encoder 50 of the comparative example. In FIG. 7, the origin signal S1 (0 mT) when an external magnetic field is not applied to the magnetic encoder 50 and the origin signal S1 (0.) when an external magnetic field of 0.4 mT is applied in the + Y direction. 4mTY +), the origin signal S1 (0.4mTY-) when an external magnetic field of 0.4mT is applied in the −Y direction, and the origin signal when an external magnetic field of 0.4mT is applied in the + X direction. S1 (0.4 mTX) and S1 (0.4 mTX) are shown superimposed. The graph of each origin signal S1 is acquired by simulation. The residual magnetic flux density of the magnetizing pattern 51 for the origin signal is 2 mT.

As shown in FIG. 7, in the comparative example, the origin signal S1 (0 mT) obtained by the output from the magnetoresistive element 12 for origin detection when an external magnetic field is not applied to the magnetic encoder 50 is the origin. A peak appears at O. Therefore, the origin O can be obtained based on such a peak.

However, when an external magnetic field of 0.4 mT is applied to the magnetic encoder 50, the origin signal S1 (0.4 mTY +), the origin signal S1 (0.4 mTY−), which can be acquired by the output from the magnetic resistance element 12, And the amplitude of the origin signal S1 (0.4 mTX) fluctuates as compared with the origin signal S obtained by the output from the magnetic resistance element 12 for detecting the origin when no external magnetic field is applied. Further, the origin signal S1 (0.4 mTY +) and the origin signal S1 (0.4 mTY-) obtained by the output from the magnetic resistance element 12 for detecting the origin when an external magnetic field of 0.4 mT is applied to the magnetic scale 2. , And the waveform of the origin signal S1 (0.4 mTX) is distorted as compared with the waveform of the origin signal S1 (0 mT) obtained by the output from the magnetic resistance element 12 for detecting the origin when no external magnetic field is applied. I'm out. Here, if the origin signal S of the magnetic encoder 1 of this example shown in FIG. 5 is compared with the origin signal S1 of the magnetic encoder 50 of the comparative example shown in FIG. 7, the magnetic encoder 1 of this example is obtained. It is clear that the origin O can be detected accurately without being affected by the external magnetic field.

In the magnetic encoder 50 of the comparative example, it is difficult to obtain the origin signal S1 when an external magnetic field of 2 mT is applied by simulation. In other words, in the magnetic encoder 50 of the comparative example, it is difficult to detect the origin when an external magnetic field of 2 mT is applied.

Next, FIG. 8 shows a change in the amplitude of the origin signal S when the external magnetic field applied to the magnetic encoder 50 of this example is increased, and an increase of the external magnetic field applied to the magnetic encoder 50 of the comparative example. It is a graph which shows the change of the amplitude of the origin signal S1 in the case. FIG. 8 shows changes in amplitude when an external magnetic field is applied in the + X direction, the + Y direction, the −Y direction, and the + Z direction, respectively.

As shown in FIG. 8, in this example, there is almost no decrease in the amplitude of the origin signal S even when the applied external magnetic field is increased. Further, there is almost no decrease in the amplitude of the origin signal S regardless of the direction in which the external magnetic field is applied. On the other hand, in the comparative example, the amplitude of the origin signal S1 significantly decreases as the applied external magnetic field is increased regardless of the direction in which the external magnetic field is applied. Therefore, according to the magnetic encoder 50 of this example, it can be seen that the origin O can be detected accurately without being affected by the external magnetic field.

Here, in this example, the width dimension D1 of the first magnetizing pattern 21 and the width of the second magnetizing pattern 22 in the orthogonal direction are the same. As a result, the rotating magnetic field formed by the first magnetizing pattern 21 and the second magnetizing pattern 22 becomes uniform. Therefore, regardless of the direction in which the external magnetic field is applied, the influence of the external magnetic field on the rotating magnetic fields on the surfaces of the first magnetizing pattern 21 and the second magnetizing pattern 22 can be reduced.

Further, in this example, the magnetic track 5 for the incremental signal includes a first magnetic track 15, a second magnetic track 16, and a third magnetic track 17 extending in parallel, and the magnetic scale 2 is mounted on the surface of the magnetic scale 2. Generates a rotating magnetic field to detect movement. On the other hand, the magnetoresistive element for detecting the incremental signal detects the rotating magnetic field generated on the surface of the magnetic scale 2 by the first magnetic track 15, the second magnetic track 16, and the third magnetic track 17. Further, the magnetoresistive element 11 for acquiring an incremental signal detects a rotating magnetic field by utilizing the saturation sensitivity region thereof. Therefore, the incremental signal can also be acquired without being affected by the external magnetic field.

(Modification 1)
FIG. 9 is an explanatory diagram of the magnetic scale 2 of the magnetic encoder 1A of the modification 1. In FIG. 9, the strength and weakness of the residual magnetic flux density in the first magnetizing pattern 21 and the second magnetizing pattern 22 are shown by shading. The magnetic encoder 1A of the first modification has a method of magnetizing the N pole magnetizing region and a method of magnetizing the S pole magnetizing region of the first magnetizing pattern 21 on the magnetic scale 2, and a second magnetizing method. The method of magnetizing the N-pole magnetizing region and the method of magnetizing the S-pole magnetizing region of the magnetic pattern 22 are different from the above-mentioned magnetic encoder 1A. However, other configurations are the same as the magnetic encoder 1A. Therefore, the N-pole magnetizing region and the S-pole magnetizing region of the first magnetizing pattern 21 and the N-pole magnetizing region and the S-pole magnetizing region of the second magnetizing pattern 22 will be described. Other explanations will be omitted.

In this example, in the magnetized region of the N pole of the first magnetizing pattern 21, the residual magnetic flux density decreases as the distance from the origin O increases in the + Y direction. Further, in the magnetized region of the S pole of the first magnetizing pattern 21, the residual magnetic flux density decreases as the distance from the origin O in the −Y direction increases. Similarly, in the magnetized region of the S pole of the second magnetizing pattern 22, the residual magnetic flux density decreases as the distance from the origin O increases in the + Y direction. Further, in the magnetized region of the N pole of the second magnetizing pattern 22, the residual magnetic flux density decreases as the distance from the origin O in the −Y direction increases.

Further, in this example, in the magnetized region of the N pole of the first magnetizing pattern 21, the residual magnetic flux density is zero at the end in the + Y direction. Further, in the magnetized region of the S pole of the first magnetizing pattern 21, the residual magnetic flux density is zero at the other end in the −Y direction. Similarly, in the magnetized region of the S pole of the second magnetizing pattern 22, the residual magnetic flux density is zero at the end in the + Y direction. In the N-pole magnetizing region of the second magnetizing pattern 22, the residual magnetic flux density is zero at the end in the −Y direction.

FIG. 10 is an explanatory diagram of the origin signal S obtained by the magnetic encoder 1A of the modification 1. In FIG. 10A, the origin signal S (0 mT) when an external magnetic field is not applied to the magnetic encoder 1A and the origin signal S when an external magnetic field of 0.4 mT is applied in the + Y direction. (0.4mTY), the origin signal S (0.4mT45 °) when an external magnetic field of 0.4mT is applied in a direction inclined by 45 ° with respect to the + Y direction, and an external magnetic field of 0.4mT. Is superimposed on the origin signal S (0.4 mTX) when is applied in the + X direction. Further, in FIG. 10B, the origin signal S (0 mT) when an external magnetic field is not applied to the magnetic encoder 1A and the origin signal when an external magnetic field of 2.0 mT is applied in the + Y direction. The signal S (2 mTY), the origin signal S (2 mT 45 °) when the external magnetic field of 2.0 mT is applied in the direction inclined by 45 ° with respect to the + Y direction, and the external magnetic field of 2.0 mT are + X. The origin signal S (2 mTX) when applied in the direction is superimposed and shown. The waveform of the origin signal S was acquired by simulation. In the example shown in FIG. 10, the residual magnetic flux density of the magnetizing pattern 6 for the origin signal (first magnetizing pattern 21 and second magnetizing pattern 22) is 4 mT.

As shown in FIG. 10A, the origin signal S (0 mT) obtained by the output from the magnetoresistive element 12 for origin detection when an external magnetic field is not applied to the magnetic encoder 1A is the origin O. One big peak appears in. Therefore, according to the magnetic encoder 1A of this example, the origin O can be accurately detected based on the peak of the origin signal S.

Further, as shown in FIG. 10A, the origin signal S (0.4 mTY) obtained by the output from the magnetoresistive element 12 for detecting the origin when an external magnetic field of 0.4 mT is applied to the magnetic encoder 1A. ), The origin signal S (0.4 mT45 °), and the origin signal S (0.4 mTX) are the origin signal S (0 mT) obtained by the output from the magnetoresistive element 12 for detecting the origin when an external magnetic field is not applied. ) Is almost the same. That is, even when an external magnetic field of 0.4 mT is applied to the magnetic scale 2, the amplitude of the origin signal S obtained by the output from the magnetoresistive element 12 for origin detection does not change, and becomes the waveform of the origin signal S. No distortion has occurred. Therefore, according to the magnetic encoder 1A of this example, the origin O can be accurately acquired based on the origin signal S even when an external magnetic field of 0.4 mT is applied to the magnetic scale 2.

Further, as shown in FIG. 10B, the origin signal S (2mT45) obtained by the output from the magnetoresistive element 12 for detecting the origin when an external magnetic field of 2.0 mT is applied to the magnetic encoder 1A. °), The origin signal S (2 mTX) has a reduced amplitude as compared with the origin signal S obtained by the output from the magnetoresistive element 12 for detecting the origin when no external magnetic field is applied. However, as shown in FIG. 10B, the decrease in the amplitude of the origin signal S is negligible. Further, even when an external magnetic field is applied, the waveform of the origin signal S is not distorted. Therefore, according to the magnetic encoder 1A of this example, the origin O can be accurately acquired based on the origin signal S even when an external magnetic field of 2.0 mT is applied to the magnetic scale 2.

As described above, even in the magnetic encoder 1A of the modification 1, the same operation and effect as the above magnetic encoder 1 can be obtained.

(Example 2)
FIG. 11 is an explanatory diagram of the magnetic encoder of the second embodiment. In FIG. 11, the strength and weakness of the residual magnetic flux density in the first magnetizing pattern 21 and the second magnetizing pattern 22 in the magnetic scale 2 are shown by shading. The magnetic encoder 1B of the second embodiment is a rotary encoder. Since the magnetic encoder 1B of this example has a configuration corresponding to the magnetic encoder 1 of the first embodiment, the same reference numerals are given to the corresponding configurations, and the description thereof will be omitted.

The magnetic scale 2 of the magnetic encoder 1B has a cylindrical shape. On the outer peripheral surface of the magnetic scale 2, a magnetic track 5 for an incremental signal and a magnetizing pattern 6 for an origin signal are provided. The magnetic sensor 3 faces the magnetic scale 2 from the radial outside of the magnetic scale 2. The magnetic scale 2 and the magnetic sensor 3 rotate relative to each other in the circumferential direction around the axis L of the magnetic scale 2. Here, the magnetic sensor 3 is the same as that of the first embodiment.

In this example, the magnetic track 5 for the incremental signal is annular. Further, the magnetizing pattern 6 for the origin signal is also annular. In the magnetizing region of the N pole of the first magnetizing pattern 21 in the magnetizing pattern 6 for the origin signal, the residual magnetic flux density decreases as the distance from the origin O becomes one side in the relative rotation direction. In the magnetized region of the S pole of the first magnetizing pattern 21, the residual magnetic flux density decreases as the origin O moves away from the other side in the relative rotation direction. Similarly, in the magnetized region of the S pole of the second magnetizing pattern 22 in the magnetizing pattern 6 for the origin signal, the residual magnetic flux density decreases as the distance from the origin O becomes one side in the relative rotation direction. .. In the magnetized region of the N pole of the second magnetizing pattern 22, the residual magnetic flux density decreases as the origin O moves away from the other side in the relative rotation direction.

Further, in the magnetized region of the N pole of the first magnetizing pattern 21, the residual magnetic flux density is zero at one end in the relative rotation direction. In the magnetized region of the S pole of the first magnetizing pattern 21, the residual magnetic flux density is zero at the other end on the other side in the relative rotation direction. Then, one end of the magnetizing region of the N pole of the first magnetizing pattern 21 and the other end of the magnetizing region of the S pole of the first magnetizing pattern 21 are continuous. Similarly, in the magnetized region of the S pole of the second magnetizing pattern 22, the residual magnetic flux density is zero at one end in the relative rotation direction. In the N-pole magnetizing region of the second magnetizing pattern 22, the residual magnetic flux density is zero at the other end in the relative rotation direction. Then, one end of the magnetizing region of the S pole of the second magnetizing pattern 22 and the other end of the magnetizing region of the N pole of the second magnetizing pattern 22 are continuous.

Also in the magnetic encoder 1B of this example, the same effect as that of the magnetic encoder 1B of the first embodiment can be obtained.

(Example 3)
FIG. 12 is an explanatory diagram of the magnetic encoder of the third embodiment. In FIG. 12, the strength and weakness of the residual magnetic flux density in the first magnetizing pattern 21 and the second magnetizing pattern 22 are shown by shading. The magnetic encoder 1C of the third embodiment is a rotary encoder. Since the magnetic encoder 1C of this example has a configuration corresponding to the magnetic encoder 1 of the second embodiment, the same reference numerals are given to the corresponding configurations, and the description thereof will be omitted.

In this example, the magnetic scale 2 has a disk shape, and an annular magnetic track 5 for an incremental signal is provided on one surface in the L direction of the axis. Further, on the outer peripheral side or the inner peripheral side of the magnetic track 5 for the incremental signal, a magnetic track 5 for the incremental signal and a gap 14 are opened to provide a magnetizing pattern 6 for the annular origin signal. The magnetic sensor 3 faces the magnetic scale 2 from the L direction of the axis.

Also in the magnetic encoder 1C of this example, the same effect as that of the magnetic encoder 1B of the first embodiment can be obtained.

(Other embodiments)
In the above example, in the relative movement direction between the magnetic scale 2 and the magnetic sensor 3, the magnetizing pattern 6 for the origin signal is provided in the entire area of the magnetic track 5 for the incremental signal, but the magnetizing pattern for the origin signal is provided. 6 may be shorter than the total length of the magnetic track 5 for the incremental signal. Even in this case, if the magnetic sensor 3 detects the rotating magnetic field of the magnetizing pattern 6 for the origin signal and acquires the origin, the strong and weak magnetic fields are detected and the origin is acquired as in the magnetic encoder 50 of the comparative example. Compared to, the influence of the external magnetic field is small.

Here, when the magnetizing pattern 6 for the origin signal is shorter than the total length of the magnetic track 5 for the incremental signal, the magnetizing for the origin signal is similar to the magnetic scale of the magnetic encoder 1A of the second embodiment. In the magnetizing region of the N pole of the first magnetizing pattern 21 in the magnetic pattern 6, the residual magnetic flux density decreases as the magnetism pattern 6 moves away from the origin O on one side in the relative rotation direction. In the magnetized region of the S pole of the first magnetizing pattern 21, the residual magnetic flux density is lowered as the origin O moves away from the other side in the relative rotation direction. Similarly, in the magnetizing region of the S pole of the second magnetizing pattern 22 in the magnetizing pattern 6 for the origin signal, the residual magnetic flux density is lowered as the distance from the origin O to one side in the relative rotation direction. In the magnetized region of the N pole of the second magnetizing pattern 22, the residual magnetic flux density is lowered as the origin O moves away from the other side in the relative rotation direction. By doing so, it is possible to prevent or suppress the occurrence of strength and weakness times at both ends in the relative movement direction in the magnetizing pattern 6Y for the origin signal.

Further, when the magnetizing pattern 6 for the origin signal is made shorter than the total length of the magnetic track 5 for the incremental signal, a plurality of origins 0 are set in the magnetic scale 2 in the relative movement direction, and the origins are set at each origin 0. A magnetizing pattern 6 for a signal can be provided. In this way, a plurality of origins can be detected by the magnetic encoder.

In the above example, the rotating magnetic field is used for acquiring the incremental signal, but a strong or weak magnetic field may be used for acquiring the incremental signal. In this case, the magnetic track 5 for the incremental signal provided on the magnetic scale 2 may be only the first magnetic track 15.

Further, on the substrate surface 8a of the sensor substrate 8, the + a phase magnetic resistance pattern, the −a phase magnetic resistance pattern, the + b phase magnetic resistance pattern, and the −b phase magnetic resistance of the magnetic resistance element for detecting the incremental signal. The patterns may be laminated and provided. In this case, there may be two magnetic tracks 5 for the incremental signal, for example, a first magnetic track 15 and a second magnetic track 16. Further, in this case, the magnetoresistive element for detecting the incremental signal laminated on the sensor substrate 8 is assumed to face the magnetic scale 2 across the boundary between the first magnetic track 15 and the second magnetic track 16. ..

1.1A, 1B, 1C ... Magnetic encoder, 2 ... Magnetic scale, 3 ... Magnetic sensor, 5 ... Magnetic track for incremental signal, 6 ... Magnetic pattern for origin signal, 7 ... Holder, 7a ... Facing surface, 8 ... Sensor board, 8a ... Board surface, 9 ... Cable, 10 ... Opening, 11 ... Magnetic resistance element for acquiring incremental signal, 12 ... Magnetic resistance element for origin detection, 14 ... Gap, 15 ... First magnetic track, 16 ... 2nd magnetic track, 17 ... 3rd magnetic track, 21 ... 1st magnetizing pattern, 22 ... 2nd magnetizing pattern, 31 ... A phase magnetic resistance pattern, 31 (+ a) ... + a phase magnetic resistance pattern , 31 (-a) ...- a phase magnetic resistance pattern, 32 ... B phase magnetic resistance pattern, 32 (+ b) ... + b phase magnetic resistance pattern, 32 (-b) ...- b phase magnetic resistance pattern, 35 ... Z-phase magnetic resistance pattern, 35 (+ z) ... + z-phase magnetic resistance pattern, 35 (-z) ...- z-phase magnetic resistance pattern, 50 ... magnetic encoder of comparative example, 51 ... origin in comparative example Magnetization pattern for signal, S / S1 ... Origin signal

Claims (9)

With a magnetic scale,
It has a magnetic sensor that detects the movement of the magnetic scale, and has.
The magnetic scale has a first magnetizing pattern in which N poles and S poles are lined up with a predetermined origin as a boundary in the relative movement direction between the magnetic scale and the magnetic sensor, and a direction orthogonal to the relative movement direction. It is provided adjacent to the first magnetizing pattern, and the S pole and the N pole are lined up with the origin as the boundary in the relative moving direction, and S next to the N pole of the first magnetizing pattern in the orthogonal direction. A second magnetizing pattern in which a pole is located and an N pole is located next to the S pole of the first magnetizing pattern is provided.
The magnetic sensor includes a magnetoresistive element for detecting the origin for detecting the origin of the magnetic scale.
The magnetoresistive element for detecting the origin is characterized in that the magnetic resistance element is directed in the relative movement direction and faces the magnetic scale across the boundary between the first magnetizing pattern and the second magnetizing pattern. Magnetic encoder. The magnetic scale has a first magnetic track in which a plurality of N poles and S poles are alternately arranged along the relative moving direction.
The first magnetic track is provided in the orthogonal direction on the side opposite to the second magnetizing pattern of the first magnetizing pattern with a gap from the first magnetizing pattern.
The N-pole magnetizing region of the first magnetizing pattern is located on one side of the origin in the relative movement direction, and extends the relative movement direction from the origin to the one end of the first magnetic track. And
The magnetized region of the S pole of the first magnetizing pattern is located on the other side of the origin in the relative moving direction, and the relative moving direction extends from the origin to the other end of the first magnetic track. And
The magnetized region of the S pole of the second magnetizing pattern is located on one side of the origin in the relative moving direction, and the relative moving direction extends from the origin to the one end of the first magnetic track. And
The N-pole magnetizing region of the second magnetizing pattern is located on the other side of the origin in the relative movement direction, and extends the relative movement direction from the origin to the other end of the first magnetic track. The magnetic encoder according to claim 1, wherein the magnetic encoder is characterized by the above. The first magnetic track extends linearly and
In the N-pole magnetizing region of the first magnetizing pattern, the residual magnetic flux density is constant.
In the magnetized region of the S pole of the first magnetizing pattern, the residual magnetic flux density is constant.
In the magnetized region of the S pole of the second magnetizing pattern, the residual magnetic flux density is constant.
The magnetic encoder according to claim 2, wherein the residual magnetic flux density is constant in the N-pole magnetizing region of the second magnetizing pattern. In the N-pole magnetizing region of the first magnetizing pattern, the residual magnetic flux density decreases as the distance from the origin moves in the relative moving direction.
In the magnetized region of the S pole of the first magnetizing pattern, the residual magnetic flux density decreases as the distance from the origin moves in the relative moving direction.
In the magnetized region of the S pole of the second magnetizing pattern, the residual magnetic flux density decreases as the distance from the origin moves in the relative moving direction.
The magnetic encoder according to claim 2, wherein in the magnetized region of the N pole of the second magnetizing pattern, the residual magnetic flux density decreases as the distance from the origin moves in the relative moving direction. In the N-pole magnetizing region of the first magnetizing pattern, the residual magnetic flux density is zero at one end in the relative moving direction.
In the magnetized region of the S pole of the first magnetizing pattern, the residual magnetic flux density is zero at the other end in the relative moving direction.
In the magnetized region of the S pole of the second magnetizing pattern, the residual magnetic flux density is zero at one end in the relative moving direction.
The magnetic encoder according to claim 4, wherein in the magnetized region of the N pole of the second magnetizing pattern, the residual magnetic flux density is zero at the other end in the relative moving direction. The first magnetic track is annular and has an annular shape.
One end of the N pole magnetizing region of the first magnetizing pattern in the relative moving direction and the other end of the S pole magnetizing region of the first magnetizing pattern in the relative moving direction are It is continuous and
One end of the magnetized region of the S pole of the second magnetizing pattern in the relative moving direction and the other end of the magnetized region of the N pole of the second magnetizing pattern in the relative moving direction are The magnetic encoder according to claim 5, which is continuous. The invention according to any one of claims 2 to 6, wherein the width of the first magnetizing pattern in the orthogonal direction and the width of the second magnetizing pattern in the orthogonal direction are the same. Magnetic encoder. The magnetic scale is provided in contact with the first magnetic track on the side opposite to the first magnetizing pattern of the first magnetic track, and extends in parallel with the first magnetic track, and the first magnetic scale. A third magnetic track, which is provided in contact with the second magnetic track and extends in parallel with the second magnetic track, is provided on the side of the magnetic track opposite to the first magnetic track.
In the second magnetic track, a plurality of S poles and N poles are alternately arranged along the relative movement direction, and the S pole is located next to the N pole of the first magnetic track in the orthogonal direction, and the second pole is located. 1 The north pole is located next to the south pole of the magnetic track,
In the third magnetic track, a plurality of S poles and N poles are alternately arranged along the relative movement direction, and the S pole is located next to the N pole of the second magnetic track in the orthogonal direction. 2. The magnetic encoder according to any one of claims 2 to 7, wherein the N pole is located next to the S pole of the magnetic track. The magnetic sensor includes a phase A magnetoresistance pattern and a phase B magnetoresistance pattern that detect the movement of the magnetic scale with a phase difference of 90 °.
The A-phase reluctance pattern includes a + a-phase reluctance pattern and a -a-phase reluctance pattern that detect the movement of the magnetic scale with a phase difference of 180 °.
The B-phase reluctance pattern includes a + b-phase reluctance pattern and a −b-phase reluctance pattern that detect the movement of the magnetic scale with a phase difference of 180 °.
One of the + a phase magnetic resistance pattern, the + b phase magnetic resistance pattern, and the −b phase magnetic resistance pattern directs the magnetic sensitivity direction in the relative movement direction, and the first magnetic track and the second magnetic resistance pattern. Facing the magnetic scale across the boundary with the magnetic track,
The other of the −a phase magnetic resistance pattern, the + b phase magnetic resistance pattern, and the −b phase magnetic resistance pattern is directed to the magnetic sensitivity direction in the relative movement direction, and the second magnetic track and the second magnetic track. 3. The magnetic encoder according to claim 8, wherein the magnetic encoder straddles the boundary with the magnetic track and faces the magnetic scale.

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