JP7610935B2 - Hybrid type stepping motor - Google Patents

Description

The present invention relates to technology for a hybrid stepping motor system with multi-revolution counting function.

Magnetic elements that exhibit a large Barkhausen jump are described in Patent Document 1 and Patent Document 2. The magnetic element described in Patent Document 1 is in the form of a wire made of a crystalline metal and is known as a Wiegand wire. The magnetic element described in Patent Document 2 is in the form of a wire or ribbon made of an amorphous metal.

Patent documents 3 to 6 describe technologies that use magnetic elements that exhibit a large Barkhausen jump for rotation detection. In patent document 3, magnetic flux lines extending radially from the center of a single magnetic pole face of a magnet are detected by a single magnetic element. According to patent document 4, one magnetic element, one exciter magnet, and an additional sensor element (e.g., a Hall element) that identifies forward and reverse rotation are provided. According to patent document 5, the magnetic domain direction of the magnetic element is identified and corrected by an excitation function that passes a current through a coil wound around the magnetic element. According to patent document 6, three magnetic detection units consisting of magnetic elements and coils, and four magnetic generation units for applying two cycles of an alternating magnetic field per rotation are provided.

Japanese Unexamined Patent Publication No. 53-137641 Japanese Patent Application Publication No. 5-195170 JP 2000-161989 A Patent No. 4712390 JP 2012-225917 A Patent No. 5511748

Conventional technology may be able to detect the direction of rotation, but may not be able to accurately detect the number of rotations. Or, even if it is possible to detect the direction of rotation and the number of rotations, the number of parts tends to be relatively large, and the structure tends to be complex due to the need to supply power to the elements required for identification (Hall element, excitation function).

In view of the prior art, the present invention aims to provide a hybrid stepping motor that is capable of accurately detecting the direction and speed of rotation and has a relatively simple structure.

In order to achieve the above object, a hybrid type stepping motor according to the present invention includes a rotating shaft rotatable in both directions, and a rotor attached to the rotating shaft rotatable in both directions, the rotor including first and second rotor magnetic pole portions made of a soft magnetic material and spaced apart in the axial direction, and a permanent magnet sandwiched between the first and second rotor magnetic pole portions and magnetized in the axial direction , and one of both axial end faces of the rotor is provided with two protrusions made of a soft magnetic material that have the same shape and are spaced apart from each other in the circumferential direction of the rotor, the two protrusions being magnetized to the same magnetic pole by the permanent magnet to generate a magnetic field; an elongated magnetic element that exhibits a large Barkhausen jump; and and a coil wound around each of the protrusions, wherein when the rotor rotates, a circle is drawn by the two protrusions , and a magnetic field from single magnetic pole surfaces on the upper and side surfaces of the two protrusions is detected by the first magnetic sensor and the second magnetic sensor, the first magnetic sensor and the second magnetic sensor are arranged parallel to each tangent of a circle that is coaxial with the circle so that output signals of the first magnetic sensor and the second magnetic sensor have a phase relationship of 90 degrees, the first magnetic sensor and the second magnetic sensor face each of the contact points in the radial direction of the circle or the direction of the rotation axis, and rotation of the rotor is detected from the output signals of the first magnetic sensor and the second magnetic sensor .

The present invention provides a hybrid stepping motor that is capable of accurately detecting the direction and speed of rotation and has a relatively simple structure.

FIG. 1 is a perspective cross-sectional view of a hybrid type stepping motor. FIG. 1 is a perspective cross-sectional view of a hybrid type stepping motor. 1 is a perspective view of a hybrid stepping motor according to a first embodiment; FIG. 1 is a top view of a hybrid stepping motor according to a first embodiment. 1 is a front view of a hybrid stepping motor according to a first embodiment; FIG. 1 is a top view of a hybrid stepping motor according to a first embodiment. 5A and 5B are perspective views of a rotor based on a modified example of the first embodiment. FIG. 11 is a top view of a rotor based on a modified example of the first embodiment. FIG. 11 is a front view of a rotor based on a modified example of the first embodiment. FIG. 11 is a perspective view of a hybrid stepping motor based on a modified example of the first embodiment. FIG. 11 is a perspective view of a hybrid stepping motor according to a second embodiment. FIG. 11 is a plan view of a hybrid stepping motor according to a second embodiment. FIG. 11 is a perspective view of a hybrid stepping motor according to a third embodiment. FIG. 11 is a front view of a hybrid stepping motor according to a third embodiment. FIG. 11 is a top view of a hybrid stepping motor according to a third embodiment. 13A is a perspective view of a rotor according to a first modified example of the third embodiment, and FIG. 13B is a top view of the rotor according to the first modified example of the third embodiment. 13A is a perspective view of a rotor according to a second modified example of the third embodiment, and FIG. 13B is a top view of the rotor according to the second modified example of the third embodiment. 13A is a perspective view of a rotor according to a third modified example of the third embodiment, and FIG. 13B is a top view of the rotor according to the third modified example of the third embodiment. 13A is a perspective view of a rotor according to a fourth modified example of the third embodiment, and FIG. 13B is a top view of the rotor according to the fourth modified example of the third embodiment. 13A is a perspective view of a rotor according to a fifth modified example of the third embodiment, and FIG. 13B is a top view of the rotor according to the fifth modified example of the third embodiment. FIG. 13 is a perspective view of a hybrid stepping motor based on a fifth modified example of the third embodiment. FIG. 13 is a perspective view of a hybrid stepping motor according to a fourth embodiment. FIG. 13 is a top view of a hybrid stepping motor according to a fourth embodiment. 11A and 11B are explanatory diagrams showing another embodiment of the magnetic sensor. 5 is a graph showing the relationship between the rotational position and the detected magnetic field during normal rotation of the motor based on the first and second embodiments. 10 is a graph showing the relationship between the rotation position and the detected magnetic field when the motor is rotated in reverse based on the first and second embodiments. 13 is a graph showing the relationship between the rotational position and the detected magnetic field during normal rotation of the motor based on the third and fourth embodiments. 13 is a graph showing the relationship between the rotation position and the detected magnetic field when the motor is rotated in reverse based on the third and fourth embodiments.

The present invention will be described below based on the illustrated embodiment. However, the present invention is not limited to the embodiment described below.

[Hybrid type stepping motor]
1A shows a hybrid stepping motor 10. The hybrid stepping motor 10 has a stator 11, a rotor 12, and a rotating shaft 12c. The rotor 12 is attached to the rotating shaft 12c and includes an A rotor 12a and a B rotor 12b made of a soft magnetic material, and a permanent magnet 12d. The A rotor 12a and the B rotor 12b are spaced apart in the axial direction, and the permanent magnet 12d is disposed so as to be sandwiched between the A rotor 12a and the B rotor 12b. The permanent magnet 12d is magnetized in the axial direction.

The A rotor 12a and the B rotor 12b are magnetized in the axial direction by a permanent magnet 12d, so that when the A rotor 12a has an N pole, the B rotor 12b has an S pole. A plurality of small teeth are formed on the outer circumferential surfaces of the A rotor 12a and the B rotor 12b at equal intervals in the circumferential direction, and the small teeth of the A rotor 12a and the small teeth of the B rotor 12b are mechanically offset by 1/2 pitch.
The A rotor 12a and the B rotor 12b can also be referred to as the first rotor magnetic pole portion 12a and the second rotor magnetic pole portion 12b, respectively.

The stator 11 is roughly cylindrical, and multiple magnetic poles that protrude radially inward are formed on the inner circumferential surface at equal intervals. Multiple small teeth are formed on the surface of each magnetic pole that faces the rotor 12. A winding (not shown) is wound around each magnetic pole. The same winding is wound around two magnetic poles that face each other in the radial direction, and when a current is passed through the winding, both magnetic poles are magnetized to the same polarity. In this way, one phase is formed by the two facing magnetic poles.

A type with five phases, from A to E, is called a five-phase stepping motor, and a type with two phases, A and B, is called a two-phase stepping motor.

A radial magnetic field is generated from the small teeth on the outer circumferential surfaces of the A rotor 12a and the B rotor 12b. Furthermore, a leakage magnetic field is generated in the direction of the arrows in the figure from both axial end surfaces of the rotor 12 (specifically, the upper surface of the A rotor 12a and the lower surface of the B rotor 12b). The embodiment described below utilizes the leakage magnetic field. Depending on the motor design, the "leaked" magnetic field may be too small to be detected, so in order to obtain a sufficient magnetic field, it is also effective to intentionally increase the leakage magnetic field by making the overall axial length of the A rotor and the B rotor longer or shorter than the overall axial length of the stator.

As shown in FIG. 1B, it is also possible to adopt a rotor stack in which multiple rotors 12 are arranged in the direction of the rotation axis.

[First embodiment]
2A to 2D show a hybrid stepping motor 10 according to a first embodiment.
In addition to the configuration shown in FIG. 1A, the hybrid type stepping motor 10 includes a first magnetic sensor 20, a second magnetic sensor 30, and two protrusions 40a and 40b provided on the axial upper end surface of the A rotor 12a.
The first magnetic sensor 20 includes an elongated magnetic element 21 that exhibits a large Barkhausen jump and a coil 22 wound around the magnetic element 21. Similarly, the second magnetic sensor 30 includes an elongated magnetic element 31 that exhibits a large Barkhausen jump and a coil 32 wound around the magnetic element 21.

The protrusions 40a, 40b are made of a soft magnetic material and have the same shape. These protrusions are arranged to form 180 degrees with respect to the rotation axis 12c. The protrusions 40a, 40b are cylindrical in shape and are fixed by press-fitting or the like into holes provided in the A rotor 12a. The axial direction of the protrusions 40a, 40b is parallel to the rotation axis. Since small teeth are formed on the outer periphery of the rotor, it is preferable to arrange the protrusions at a distance from the base of the small teeth of the A rotor to suppress the occurrence of iron loss.

By providing the protrusions 40a and 40b on the outer periphery of the end face of the magnetized A rotor 12a, both protrusions become magnetic field generating parts and are magnetized to the same single magnetic pole, the N pole (or S pole), as the A rotor 12a. Since the protrusions 40a and 40b are of the same shape and material, magnetic fields of the same magnitude and direction are generated from the upper surfaces of both protrusions. In FIG. 2B, the arrows indicate the direction of magnetic flux lines leaking from the upper surfaces of the protrusions 40a and 40b. The upper surfaces of the protrusions 40a and 40b each become a single magnetic pole surface, and the leaking magnetic flux lines extend radially from the center. The gradation of the arrows represents the magnetic flux density, and the darker the arrow, the higher the magnetic flux density. On the circle 50 described later, it can be seen that magnetic flux lines extend in opposite directions at the center of the single magnetic pole surface. The magnetic field strength on the circle 50 caused by the protrusions is at most equal to or greater than the stabilizing magnetic field. The stabilizing magnetic field will be described later.

When the rotor 12 rotates, a first circle is drawn by the single magnetic pole faces of the protrusions 40a and 40b. The second circle obtained by translating the first circle upward in the axial direction is indicated by the reference symbol 50 (FIGS. 2B and 2C). The second circle 50 is coaxial with the first circle. As shown in FIG. 2D, the first magnetic sensor 20 and the second magnetic sensor 30 are disposed at two positions 50a and 50b on the circle 50 based on the rotation axis 12c so that the output signals are in a phase relationship of 90° in electrical angle. When both magnetic sensors are viewed from above the rotation axis, the first magnetic sensor 20 is rotated 90° counterclockwise in mechanical angle based on the rotation axis 12c, and overlaps with the second magnetic sensor 30. The first magnetic sensor 20 and the second magnetic sensor 30 are disposed so that their longitudinal directions are parallel to the tangents 51 and 52 of the circle 50 passing through the positions 50a and 50b. Positions 50a and 50b can also be called contact points.

The magnetic element 21 may be, for example, wire-shaped, ribbon-shaped, or film-type, but is not limited thereto, and may be any magnetic material that exhibits a large Barkhausen jump. The longitudinal direction of the magnetic element 21 may be the magnetization easy direction of the magnetic anisotropy. The magnetic element 21 includes a core and a skin portion that is provided to surround the core. As an example, the core is a soft layer in which the magnetization direction is reversed even in a weak magnetic field, and the skin portion is a hard layer in which the magnetization direction is not reversed unless a strong magnetic field is applied. A pulse signal is induced in the coil 22 when the magnetic element 21 exhibits a large Barkhausen jump.
The magnetic element 31 is similar to the magnetic element 21. A pulse signal is induced in the coil 32 when a large Barkhausen jump occurs in the magnetic element 31.

Coils 22 and 32 are connected to a circuit (not shown) that processes the signals generated in both coils and is used to detect rotation.

The longitudinal direction of the magnetic element 21 is parallel to the vertical direction of the paper in Fig. 2D. With respect to the longitudinal direction of the magnetic element 21, the downward direction on the paper in Fig. 2D is called the positive direction, and the upward direction on the paper is called the negative direction.
The longitudinal direction of the magnetic element 31 is parallel to the left-right direction of the paper in Fig. 2D. With respect to the longitudinal direction of the magnetic element 31, the right direction of the paper in Fig. 2D is called the positive direction, and the left direction of the paper is called the negative direction.
When the magnetization directions of the hard layer and the soft layer are in the same direction (e.g., negative direction), if the external magnetic field strength in the opposite direction (e.g., positive direction) increases and reaches a magnetic field strength at which the magnetization direction of the soft layer is reversed, the magnetization direction of the soft layer is reversed. At this time, a large Barkhausen jump occurs, and a pulse signal is induced in the coil wound around the magnetic element. The magnetic field strength at which the magnetization direction of the soft layer is reversed is called the "operating magnetic field."

When the external magnetic field strength described above increases further and reaches a magnetic field strength at which the magnetization direction of the hard layer is reversed, the magnetization direction of the hard layer is also reversed. The magnetic field strength at which the magnetization direction of the hard layer is reversed is called the "stabilizing magnetic field."

For a large Barkhausen jump to occur, it is necessary that the magnetization direction of only the soft layer is reversed, assuming that the magnetization directions of the hard layer and soft layer are consistent. Even if the magnetization direction of only the soft layer is reversed when the magnetization directions of the hard layer and soft layer are mismatched and do not form a single magnetic domain, no pulse signal is generated, or if one is generated, it is very small, making it difficult to use the above circuit for rotation detection.

When one of the single pole faces of the protrusions 40a and 40b on the rotor 12a passes near the magnetic sensor, a stabilizing magnetic field is applied to the magnetic element in its extension direction, and the magnetic element is magnetized into a single magnetic domain. Then, as the rotation continues and the other single pole face of the protrusions 40a and 40b approaches the magnetic sensor, an operating magnetic field in the opposite direction to the magnetization direction of the single magnetic domain is applied in the extension direction of the magnetic element, and the Great Barkhausen phenomenon occurs. The relationship between the magnetic field applied from the single pole face of the protrusion and the output signals of the two magnetic sensors 20 and 30 when the rotor 12 rotates will be explained in detail.

Figure 10A shows the relationship between the rotation position during forward rotation and the magnetic field Ha applied to the first magnetic sensor 20 and the magnetic field Hb applied to the second magnetic sensor 30. Figure 10B also shows the relationship between the rotation position during reverse rotation and the magnetic fields Ha and Hb. Forward rotation and reverse rotation respectively refer to right rotation and left rotation when the hybrid stepping motor 10 is viewed from above in the axial direction. In both figures, the magnetic field Ha applied to the first magnetic sensor 20 from the protrusion 40a is shown by a solid line, and the magnetic field Ha applied to the first magnetic sensor 20 from the protrusion 40b is shown by a dashed line. Also, the magnetic field Hb applied to the second magnetic sensor 30 from the protrusion 40a is shown by a dashed line, and the magnetic field Hb applied to the second magnetic sensor 30 from the protrusion 40b is shown by a two-dot chain line. ±H1 is the operating magnetic field strength, and ±H2 is the stabilizing magnetic field strength.

10A, the positive pulse signal generated in the first magnetic sensor 20 during forward rotation is indicated by symbol A, and the stabilizing magnetic field that is the premise for the output of signal A is indicated by symbol As. Furthermore, the positive pulse signal generated in the second magnetic sensor 30 is indicated by symbol B, and the stabilizing magnetic field that is the premise for the output of signal B is indicated by symbol Bs.
10B, the negative pulse signal generated in the first magnetic sensor 20 during reversal is indicated by symbol C, and the stabilizing magnetic field that is the premise for the output of signal C is indicated by symbol Cs. Furthermore, the negative pulse signal generated in the second magnetic sensor 30 is indicated by symbol D, and the stabilizing magnetic field that is the premise for the output of signal D is indicated by symbol Ds.

The magnetic field of the protrusions 40a and 40b, which are located at equal intervals of 180 degrees from each other, is applied to the first magnetic sensor 20 and the second magnetic sensor 30, and the signals of the first magnetic sensor 20 and the second magnetic sensor 30 have a phase relationship of 90 degrees due to the relationship of the installation positions of the electrical angle. Each magnetic sensor outputs a signal of the same sign twice in one forward rotation, and in one reverse rotation, the same signal is output twice with a different sign from that in the forward rotation. The two magnetic sensors output signals A and B twice each in one forward rotation, and signals C and D twice each in one reverse rotation. If the center of the magnetic element 21 of the magnetic sensor 20 is aligned with position 50a and the center of the magnetic element 31 of the magnetic sensor 30 is aligned with position 50b, the waveform quality (wave height and half-width) of the forward and reverse output signals will be the same.

In other words, by providing a protrusion as part of the rotor, which is a core component of a hybrid stepping motor, the magnetic field of the motor can be directly detected by a magnetic sensor that utilizes the large Barkhausen effect. Depending on the magnetization state of the magnetic element, a pulse signal that is small in magnitude and difficult to evaluate may be generated, but it is possible to count multiple rotations without relying on such pulse signals. Another advantage is that since there are no permanent magnets other than the permanent magnet 12d of the rotor 12, there is no need to take measures to reduce the effect of leakage magnetic fields from other than the rotor 12 on the magnetic sensor. This results in an inexpensive and stable configuration.

As such, this embodiment provides a hybrid stepping motor that is capable of accurately detecting the direction of rotation and the number of rotations and has a relatively simple structure.

[Modification of the first embodiment]
As long as the protrusions are of the same shape, are provided at equal intervals on the axial end face of the rotor, and are made of a soft magnetic material, their shape is not limited to cylindrical, and the fixing method is not limited to press fitting. Modified examples of the protrusions are shown in Figures 3A to 3D.
As shown in Fig. 3A (A), a plurality of thin plates made of a soft magnetic material may be stacked on the axial end surface of the rotor 12. Each thin plate has a ring portion having a hole through which the rotating shaft 12c passes, and two extension portions extending radially outward from the ring portion. The two extension portions are aligned in a straight line. The two extension portions can be called protrusions 40a and 40b, respectively.
As shown in FIG. 3A(B), the ring portion and the two extension portions may be formed from a single member, rather than being laminated.

As shown in FIG. 3B, a single magnetic pole surface is formed on the upper surface of the protrusions 40a and 40b, and the leaking magnetic flux lines extend outward from the protrusions 40a and 40b. When the A rotor and the B rotor are made of laminated thin plates, there is an advantage that they can be manufactured without labor because they can undergo the same lamination process. Furthermore, there is an advantage that the protrusions are integrated with the rotor, increasing the magnetic force of the single magnetic pole surface and expanding the allowable range for installation of the magnetic sensor.

Another advantage of this shape is that, as shown in FIG. 3C, a single magnetic pole surface is also formed on the side surface (surface parallel to the axial direction) of each protrusion, and the leaking magnetic flux lines extend outward from each protrusion. As shown in FIG. 3D, two magnetic sensors 20, 30 are radially opposed to the single magnetic pole surface on the side surface of protrusions 40a, 40b at a distance such that the magnetic field strength is at its maximum equal to or greater than the strength of the stabilizing magnetic field. The first magnetic sensor 20 and the second magnetic sensor 30 are positioned at two positions 50a and 50b on a circle 50 based on the rotation axis 12c so that the output signals of the first magnetic sensor 20 and the second magnetic sensor 30 are 90° out of phase with each other in electrical angle. This allows the magnetic sensors to be positioned on the outer periphery of the protrusions rather than above them, making the axial dimension (motor length) smaller.

[Second embodiment]
In the first embodiment, two protrusions are provided, but in the second embodiment, four protrusions are provided. The following description will be given with reference to FIGS. 4A and 4B. As shown in FIG. 4A, four protrusions 40a, 40b, 40c, and 40d of the same shape are provided on the upper surface of the A rotor 12a, and these four protrusions are arranged at 90-degree intervals in the circumferential direction with respect to the rotating shaft 12c. Accordingly, when both magnetic sensors are viewed from above the rotating shaft as shown in FIG. 4B, the second magnetic sensor 30 is at a position where the first magnetic sensor 20 is rotated counterclockwise by 45° or (45°+180°=225°) in mechanical angle with respect to the rotating shaft 12c. In FIG. 4B, it is 225°. As a result, the output signals of the first magnetic sensor 20 and the second magnetic sensor 30 are out of phase with each other by 90° in electrical angle.

Since four protrusions are provided and the 360° of the output signal in Figures 10A and 10B corresponds to 180° in this embodiment, the magnetic sensor outputs a signal of the same sign four times in one forward rotation, and outputs the same signal four times with a different sign from the forward rotation in one reverse rotation. The two magnetic sensors output four types of signals, A and B, four times in one forward rotation, and C and D, four times in one reverse rotation. Compared to the first embodiment, the resolution of the output signal is doubled, improving the accuracy of rotation detection.

The number of protrusions can be further increased as long as they are spaced circumferentially at intervals such that the magnetic fields from the protrusions do not interfere with each other. In addition, the modified example of the protrusions in the first embodiment can also be applied to the second embodiment.

[Third embodiment]
As shown in FIG. 5A to FIG. 5C, the hybrid stepping motor 10 includes a first magnetic sensor 20, a second magnetic sensor 30, and protrusions 40a and 40a' provided on the axial upper end surface of the A rotor 12a. The protrusions 40a and 40a' are made of soft magnetic material and are arranged at 180 degree intervals with respect to the rotating shaft 12c. The protrusions 40a and 40a' are both cylindrical, but as shown in FIG. 5B, the height h' of the protrusion 40a' is smaller than the height h of the protrusion 40a. By providing the protrusions 40a and 40a' on the outer periphery of the end surface of the magnetized A rotor 12a, the protrusions become magnetic field generating parts and are magnetized to a single magnetic pole, the N pole (or S pole), the same as the A rotor 12a. Since the protrusions 40a and 40a' have different heights (h>h'), the maximum values of the magnetic field strength applied to the magnetic sensors are different.

Circle 50 is a circle coaxial with the orbit of the single magnetic pole face of protrusion 40a. As shown in FIG. 5C, the first magnetic sensor 20 and the second magnetic sensor 30 are arranged at two positions 50a and 50b on circle 50 based on the rotation axis 12c so that the output signals have a phase relationship of 180° in electrical angle. When both magnetic sensors are viewed from above the rotation axis, the second magnetic sensor 30 is at a position rotated 180° in mechanical angle counterclockwise from the first magnetic sensor 20 based on the rotation axis 12c. In addition, both magnetic sensors are arranged so that they are parallel to the tangent directions of tangents 51 and 52 that pass through those positions.

The magnetic flux lines leaking from the single pole surface, which is the upper surface of the protrusions 40a, 40a', extend in opposite directions from the center. However, due to the difference in height of the protrusions, the minimum distance between the protrusion 40a and the magnetic sensor is smaller than the minimum distance between the protrusion 40a' and the magnetic sensor. This difference in minimum distance adjusts the magnetic field applied to the magnetic sensor. The protrusion 40a is configured so that a magnetic field greater than or equal to the stabilizing magnetic field is applied from the protrusion 40a to the magnetic sensor at maximum. The protrusion 40a' is configured so that a magnetic field greater than or equal to the operating magnetic field and less than the stabilizing magnetic field is applied from the protrusion 40a' to the magnetic sensor at maximum.

When the rotor 12 rotates and one of the pair of protrusions, 40a, passes the magnetic sensor, the magnetic element of the magnetic sensor is magnetized into a single magnetic domain by the stabilizing magnetic field. After that, when the other protrusion, 40a', approaches the magnetic sensor, an operating magnetic field in the opposite direction to the magnetization direction of the single magnetic domain is applied, and the Great Barkhausen phenomenon occurs. At this time, the stabilizing magnetic field is not applied, so the magnetic element does not become a single magnetic domain. Therefore, even if one of the protrusions, 40a, approaches the magnetic sensor again and an operating magnetic field is applied, the Great Barkhausen phenomenon does not occur. Below, the relationship between the magnetic field applied from the protrusions and the output signals of the two magnetic sensors 20, 30 when the rotor rotates is explained.

Figure 11A shows the relationship between the rotation position and the magnetic fields Ha and Hb during forward rotation, and Figure 11B shows the relationship between the rotation position and the magnetic fields Ha and Hb during reverse rotation. In both figures, the magnetic field Ha applied to the first magnetic sensor 20 from the protrusion 40a is shown by a solid line, and the magnetic field Ha applied to the protrusion 40a' is shown by a dashed line. Furthermore, the magnetic field Hb applied to the second magnetic sensor 30 from the protrusion 40a is shown by a dashed line, and the magnetic field Hb applied to the protrusion 40a' is shown by a two-dot chain line. ±H1 is the operating magnetic field strength, and ±H2 is the stabilizing magnetic field strength.

11A, the positive pulse signal generated in the first magnetic sensor 20 during forward rotation is indicated by symbol A, and the stabilizing magnetic field that is the premise for the output of signal A is indicated by symbol As. Furthermore, the positive pulse signal generated in the second magnetic sensor 30 is indicated by symbol B, and the stabilizing magnetic field that is the premise for the output of signal B is indicated by symbol Bs.
11B, the negative pulse signal generated in the first magnetic sensor 20 during reversal is indicated by symbol C, and the stabilizing magnetic field that is the premise for the output of signal C is indicated by symbol Cs. Furthermore, the negative pulse signal generated in the second magnetic sensor 30 is indicated by symbol D, and the stabilizing magnetic field that is the premise for the output of signal D is indicated by symbol Ds.

The magnetic field of the protrusions 40a and 40a' arranged at 180 degree intervals is applied to the first magnetic sensor 20 and the second magnetic sensor 30, and the signals of the first magnetic sensor 20 and the second magnetic sensor 30 have a phase relationship of 180 degrees in electrical angle due to the relationship of the installation positions. Each magnetic sensor outputs a signal of the same sign once per forward rotation, and outputs the same signal once with a different sign from the forward rotation once per reverse rotation. The two magnetic sensors output four types of signals, A and B, once per forward rotation, and C and D, once per reverse rotation. As in the first embodiment, the waveform quality (wave height and half-width) of the forward and reverse output signals can be made the same by aligning the center of the magnetic element 21 of the magnetic sensor 20 with position 50a and the center of the magnetic element 31 of the magnetic sensor 30 with position 50b.

In other words, by providing a protrusion as part of the rotor, which is a core component of a hybrid stepping motor, the magnetic field of the rotor can be directly detected by a magnetic sensor that utilizes the large Barkhausen effect. Depending on the magnetization state of the magnetic element, a pulse signal that is small in magnitude and difficult to evaluate may be generated, but it is possible to count multiple rotations without relying on such pulse signals. Another advantage is that since there are no permanent magnets other than the permanent magnet 12d of the rotor 12, there is no need to take measures to reduce the effect of leakage magnetic fields from other than the rotor 12 on the magnetic sensor. This results in an inexpensive and stable configuration.

[Modification of the third embodiment]
The pair of protrusions may have shapes other than those described above, as long as they are made of soft magnetic material and have different shapes that can apply different magnetic fields to the magnetic sensor. Modified examples of protrusions 40a and 40a' are shown below. As shown in FIG. 6A, both protrusions are cylindrical and have the same height but different diameters. The diameter r' of protrusion 40a' is smaller than the diameter r of protrusion 40a. Since the magnetic flux density leaking from the single pole face of protrusion 40a' is smaller than that of protrusion 40a, the magnetic field strength applied to the magnetic sensor is different even if the distance between the magnetic sensor and protrusion 40a' is the same.
As shown in Fig. 6B, both protrusions 40a and 40a' have the same cylindrical shape, but the distance l' of protrusion 40a' from the rotation shaft 12c is smaller than the distance l of protrusion 40a from the rotation shaft 12c. The minimum distance between protrusion 40a and the magnetic sensor is smaller than the minimum distance between protrusion 40a' and the magnetic sensor. The difference in the minimum distance adjusts the magnetic field applied to the magnetic sensor.
7A to 7C show a ring portion and two extension portions similar to those in FIG. 3A. The two extension portions can be called protrusions 40a and 40a'. As shown in FIG. 7A, the height H' of the protrusion 40a' is smaller than the height H of the protrusion 40a. As shown in FIG. 7B, the width (dimension in the tangential direction) R' of the protrusion 40a' is smaller than the width R of the protrusion 40a. As shown in FIG. 7C, the distance L' of the protrusion 40a' from the rotation axis 12c is smaller than the distance L of the protrusion 40a from the rotation axis 12c. In this structure, the protrusions 40a and 40a' can also be made of soft magnetic laminated thin plates.

Another advantage of the shape of the protrusions shown in FIG. 7C is that a single magnetic pole surface is also formed on the side of each protrusion, and the leaking magnetic flux lines extend outward from each protrusion. As shown in FIG. 7D, the two magnetic sensors 20, 30 are arranged to face each other radially with respect to the circle described by the single magnetic pole surfaces on the side of the protrusions 40a, 40a'. The first magnetic sensor 20 and the second magnetic sensor 30 are arranged at two positions 50a and 50b on a circle 50 based on the rotation axis 12c so that the output signals of the first magnetic sensor 20 and the second magnetic sensor 30 have a phase relationship of 180° in electrical angle. This allows the magnetic sensors to be arranged on the outer periphery of the protrusions rather than above them, making it possible to reduce the axial dimension (motor length).

[Fourth embodiment]
As shown in FIG. 8A, a first set of protrusions 40a, 40a' and a second set of protrusions 40b, 40b' are provided on the axial upper end surface of the A rotor 12a. When the rotor 12 is viewed from above, the protrusions 40a, 40a', 40b, 40b' are arranged counterclockwise in order at equal intervals in the circumferential direction. The protrusions 40a and 40b are cylindrical and have the same height, and the protrusions 40a' and 40b' are also cylindrical and have the same height, but the height of the protrusions 40a' and 40b' is smaller than the height of the protrusions 40a and 40b. All four protrusions are made of soft magnetic material and serve as magnetic field generating parts, and are magnetized to a single magnetic pole, the N pole (or S pole), the same as the A rotor 12a. Since the protrusions 40a and 40a' and the protrusions 40b and 40b' have different heights, different magnetic field strengths are applied to the magnetic sensor.

The first magnetic sensor 20 and the second magnetic sensor 30 are arranged so as to be parallel to the tangents 51 and 52 at two positions 50a and 50b on the circle 50, respectively. The two positions 50a and 50b are positions where the output signals of the first magnetic sensor 20 and the second magnetic sensor 30 have a phase relationship of 180° in electrical angle. When both magnetic sensors are viewed from above the rotation axis as shown in FIG. 8B, when the first magnetic sensor 20 is rotated 90° in mechanical angle counterclockwise with the rotation axis 12c as the reference, it overlaps with the second magnetic sensor 30.

All four protrusions are made of the same material. However, due to differences in the heights of the protrusions, the protrusions 40a and 40b are spaced closer to the magnetic sensor, while the protrusions 40a' and 40b' are spaced farther from the magnetic sensor. This difference in space adjusts the magnetic field applied to the magnetic sensor. The protrusions 40a and 40b apply a magnetic field to the magnetic sensor that is at most equal to or greater than the stabilizing magnetic field. The protrusions 40a' and 40b' apply a magnetic field to the magnetic sensor that is at most equal to or greater than the operating magnetic field and less than the stabilizing magnetic field.
When the rotor 12 rotates and the protrusion 40a passes near the magnetic sensor, the magnetic element is magnetized into a single magnetic domain by the stabilizing magnetic field. After that, when the protrusion 40a' approaches the magnetic sensor, an operating magnetic field in the opposite direction to the magnetization direction of the single magnetic domain is applied, and the Large Barkhausen phenomenon occurs. Even when the protrusion 40a' passes the magnetic sensor, the stabilizing magnetic field is not applied, and the magnetic element does not become a single magnetic domain. Therefore, even if the protrusion 40b approaches the magnetic sensor and a stabilizing magnetic field exceeding the operating magnetic field is applied, the Large Barkhausen phenomenon does not occur. The magnetic element is magnetized into a single magnetic domain by this stabilizing magnetic field. After that, when the protrusion 40b' approaches the magnetic sensor, an operating magnetic field in the opposite direction to the magnetization direction of the single magnetic domain is applied, and the Large Barkhausen phenomenon occurs.
That is, since this embodiment has four protrusions, 360° of the output signal in Figures 11A and 11B corresponds to 180° in this embodiment. Therefore, the magnetic sensor outputs a signal of the same sign twice in one forward rotation, and in one reverse rotation, the same signal is output twice with a sign different from that of the forward rotation. The two magnetic sensors output four types of signals, A, B, C, and D, twice in one forward and reverse rotation. The resolution of the output signal is doubled compared to the third embodiment, improving the accuracy of rotation detection.

The number of protrusions can be further increased as long as they are spaced circumferentially at intervals such that the magnetic fields from the protrusions do not interfere with each other. In addition, the modified example of the third embodiment can also be applied to the fourth embodiment.

[Another embodiment of the magnetic sensor]
9 shows another embodiment of the first magnetic sensor 20. A coil 22 is wound around an elongated magnetic element 21 that exhibits a large Barkhausen jump. Furthermore, parts 23a and 23b made of soft magnetic material are attached to both ends of the magnetic element 21 so as not to come into contact with the magnetic element 21. It is preferable that both ends of the magnetic element are exposed from the parts 23a and 23b by the same length. It is also preferable that the parts 23a and 23b are equivalent in terms of material, shape, and position. As an example of a part, a ferrite core for EMS (electromagnetic susceptibility) countermeasures that is generally available on the market can be used.
Similarly, for the second magnetic sensor 30, a coil 32 is wound around a magnetic element 31, and parts 33a and 33b made of a soft magnetic material are attached to both ends of the magnetic element.
The magnetic flux collecting function of the soft magnetic member suppresses the demagnetizing field generated at the end of the magnetic element, and the output signal (amount of electric power) can be increased. In other words, the wire length of the magnetic element can be shortened, which has the advantage of making the magnetic sensor smaller.

Regarding the embodiments described above, the following supplementary notes are disclosed.
[Appendix 1]
A rotation axis;
a rotor attached to the rotating shaft, the rotor including first and second rotor pole portions made of a soft magnetic material and spaced apart in the axial direction, and a permanent magnet sandwiched between the first and second rotor pole portions, the rotor having a plurality of protrusions made of a soft magnetic material on one of both axial end faces of the rotor;
A hybrid stepping motor comprising: an elongated magnetic element exhibiting a large Barkhausen jump; a coil wound around the magnetic element; and two magnetic sensors disposed in the vicinity of a circle drawn by the protrusion when the rotor rotates.
[Appendix 2]
the plurality of protrusions have the same shape and are arranged at equal intervals along the circumferential direction of the rotor;
the two magnetic sensors are arranged parallel to a tangent to a circle coaxial with the circle such that output signals of the two magnetic sensors have a 90 degree phase relationship;
2. The hybrid stepping motor according to claim 1.
[Appendix 3]
the plurality of protrusions have different shapes and are arranged at equal intervals along a circumferential direction of the rotor;
the two magnetic sensors are arranged parallel to a tangent to a circle coaxial with the circle such that output signals of the two magnetic sensors have a phase relationship of 180 degrees;
2. The hybrid stepping motor according to claim 1.
[Appendix 4]
4. The hybrid stepping motor according to claim 2 or 3, wherein the longitudinal center of the magnetic element and the contact point on the tangential line are aligned.
[Appendix 5]
5. The hybrid stepping motor according to claim 1, wherein each of the two magnetic sensors further includes a soft magnetic member provided at both ends of the magnetic element.

Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment described above, and various modifications and changes are possible based on the technical concept of the present invention.

10 Hybrid type stepping motor 11 Stator 12 Rotor 12a A rotor 12b B rotor 12c Rotating shaft 12d Magnet 20, 30 Magnetic sensor 21, 31 Magnetic element 22, 32 Coil 23a, 23b, 33a, 33b Soft magnetic member 40a, 40a', 40b, 40b', 40c, 40d Projection 50 Circle 50a, 50b Contact point 51, 52 Tangent line

Claims (5)

A rotating shaft capable of rotating in both directions;
a rotor attached to the rotating shaft and rotatable in both directions, the rotor comprising first and second rotor magnetic pole portions made of a soft magnetic material and spaced apart in the axial direction, and a permanent magnet sandwiched between the first and second rotor magnetic pole portions and magnetized in the axial direction , two projections made of a soft magnetic material and having the same shape are provided on one of both axial end faces of the rotor, the two projections being spaced apart by 180 degrees along the circumferential direction of the rotor , the two projections being magnetized to the same magnetic pole by the permanent magnet to generate a magnetic field ;
a first magnetic sensor and a second magnetic sensor having an elongated magnetic element exhibiting a large Barkhausen jump and a coil wound around the magnetic element, wherein when the rotor rotates, a circle is drawn by the two protrusions , and a magnetic field from single magnetic pole surfaces on the upper and side surfaces of the two protrusions is detected by the first magnetic sensor and the second magnetic sensor, the first magnetic sensor and the second magnetic sensor are arranged parallel to each tangent of a circle that is coaxial with the circle so that output signals of the first magnetic sensor and the second magnetic sensor have a phase relationship of 90 degrees, the first magnetic sensor and the second magnetic sensor face each of the contact points in a radial direction of the circle or in the direction of the rotation axis, and the rotation of the rotor is detected from the output signals of the first magnetic sensor and the second magnetic sensor . A rotating shaft capable of rotating in both directions;
a rotor attached to the rotating shaft and rotatable in both directions, the rotor comprising first and second rotor magnetic pole portions made of a soft magnetic material and spaced apart in the axial direction, and a permanent magnet sandwiched between the first and second rotor magnetic pole portions and magnetized in the axial direction, two protrusions made of a soft magnetic material having the same shape and spaced apart from each other along the circumferential direction of the rotor by 180 degrees and arranged at different distances from the rotating shaft, the two protrusions being magnetized to the same magnetic pole by the permanent magnet to generate a magnetic field;
a first magnetic sensor and a second magnetic sensor having an elongated magnetic element exhibiting a large Barkhausen jump and a coil wound around the magnetic element, wherein a magnetic field from single pole faces on upper and side surfaces of the two protrusions is detected by the first magnetic sensor and the second magnetic sensor, the first magnetic sensor and the second magnetic sensor are arranged parallel to respective tangents of a circle that is coaxial with a circle drawn by one of the two protrusions that is farther from the rotation axis when the rotor rotates so that output signals of the first magnetic sensor and the second magnetic sensor have a phase relationship of 180 degrees, the first magnetic sensor and the second magnetic sensor face each of the contact points in a radial direction of the circle or in the direction of the rotation axis, and the rotation of the rotor is detected from the output signals of the first magnetic sensor and the second magnetic sensor;
A hybrid stepping motor comprising: A rotating shaft capable of rotating in both directions;
a rotor attached to the rotating shaft and rotatable in both directions, the rotor comprising first and second rotor magnetic pole portions made of a soft magnetic material and spaced apart in the axial direction, and a permanent magnet sandwiched between the first and second rotor magnetic pole portions and magnetized in the axial direction, two protrusions made of a soft magnetic material and having different shapes are provided on one of both axial end faces of the rotor, the two protrusions being spaced apart by 180 degrees along the circumferential direction of the rotor, the two protrusions being magnetized to the same magnetic pole by the permanent magnet to generate a magnetic field;
a first magnetic sensor and a second magnetic sensor having an elongated magnetic element exhibiting a large Barkhausen jump and a coil wound around the magnetic element, wherein when the rotor rotates, a circle is described by the two protrusions, and a magnetic field from single magnetic pole faces on the upper and side surfaces of the two protrusions is detected by the first magnetic sensor and the second magnetic sensor, the first magnetic sensor and the second magnetic sensor are arranged parallel to respective tangents of a circle coaxial with the circle such that output signals of the first magnetic sensor and the second magnetic sensor have a phase relationship of 180 degrees, the first magnetic sensor and the second magnetic sensor face each of the contact points in a radial direction of the circle or in the direction of the rotation axis, and the rotation of the rotor is detected from the output signals of the first magnetic sensor and the second magnetic sensor;
A hybrid stepping motor comprising: 4. The hybrid stepping motor according to claim 1, wherein a center of the magnetic element in the longitudinal direction and a contact point on the tangential line are aligned. The hybrid stepping motor according to any one of claims 1 to 4, wherein each of the two magnetic sensors further comprises a soft magnetic member provided at both ends of the magnetic element.