JP2008008699A - Rotation detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus which detects the angle and the number of rotation of a rotary shaft with high accuracy, while it is small-sized. <P>SOLUTION: A rotation detecting apparatus 10 comprises: a rotor mechanism 12 which is directly fitted to a rotary shaft 11 and integrally rotates with the rotary shaft 11; and a rotation detecting sensor 15 which detects the variation of magnetic field caused by rotation of the rotor mechanism 12, thus detecting rotational state of the rotary shaft 11. The rotor mechanism 12 is provided with first and second rotor portions 12 and 12B, and nonmagnetic spacer 14 which is disposed between rotor portions 12A and 12B. First and second teeth 13A and 13B are provided in the outer circumferential portions of the rotor 12A and 12B respectively. Each of the circumferential positions of a plurality of teeth 13A disposed in the outer circumferential portions of the rotor 12A is shifted by p/4 from each of the circumferential positions of the second teeth 13B disposed in the outer circumferential portions of the second rotor 12B. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rotation detection device, and more particularly to a rotation detection device suitable for detecting a rotation angle and a rotation speed of a rotation shaft with high accuracy.

As a rotation sensor that detects the rotation of the rotating shaft, a rotation detector that detects the rotation of the rotating shaft by attaching a rotor with a large number of teeth formed at a predetermined pitch to the rotating shaft and detecting the teeth by a magnetic detection element Sensors have been proposed. For example, Patent Document 1 proposes a method of providing a missing portion on a part of a rotor and detecting a reference position of a rotating shaft from the missing portion. Patent Document 2 proposes a rotation detection device including a rotor, a bias magnet, and a magnetic detection circuit including four spin valve GMR elements that form a Wheatstone bridge circuit.
JP-A-11-62681 JP-A-2005-98942 JP 11-38030 A

  In the conventional rotation detection device disclosed in Patent Document 1 or the like, for example, a rotor provided with teeth every 10 ° is used, the rotation angle is detected every 10 °, and the time for a fine rotation angle is estimated. It is determined by control. However, at a rotation angle of every 10 °, there is a problem that a predetermined control timing deviates from a target timing due to slight rotation fluctuations of the rotation shaft. Further, in the missing tooth portion, the rotation angle is obtained by time estimation. However, there is a problem that the rotation angle cannot be accurately calculated when there is a rotation fluctuation on the rotation shaft and the rotation angle is not constant.

  Further, in order to improve the resolution of the rotation angle detected by the rotation detection device by the actual angle count control without performing the time estimation control, it is necessary to narrow the tooth pitch and increase the number of teeth as much as possible. However, if the number of teeth is simply increased, there will be a plurality of teeth in the detection area of the magnetic detection element, and fine magnetic changes cannot be read accurately, and the rotation angle may not be detected. is there. If the rotor diameter is increased, a large number of teeth can be provided without widening the pitch of the teeth, but this method increases the rotor diameter, which causes a problem that the entire rotation detection device is increased in size. .

  Accordingly, an object of the present invention is to provide a rotation detection device that can detect a rotation angle and a rotation speed of a rotation shaft with high resolution while being small in size.

  The object of the present invention is to have a plurality of teeth provided at a predetermined pitch in the circumferential direction and spaced apart by a predetermined distance in the axial direction. A rotor mechanism that is displaced in a direction; a plurality of magnetic sensors; and a bias magnet that generates a magnetic field around the magnetic sensor, wherein the plurality of magnetic sensors are disposed apart from each other in the axial direction. This is achieved by a rotation detection device that is arranged so as to be able to detect changes in the magnetic field due to the teeth.

  In the present invention, the rotor mechanism preferably includes a plurality of adjacent rotor portions. According to this, a rotor mechanism can be configured only by preparing a plurality of rotor parts having the same shape and combining them, and a precise rotor mechanism can be manufactured at low cost.

  In the present invention, when the number of rotor parts is n (n is an integer of 2 or more) and the pitch of a plurality of teeth provided in each rotor part is p, the number of teeth different from the teeth provided in each rotor part It is preferable that the teeth provided in the rotor portion are shifted by p / 2n in the circumferential direction.

  In the present invention, it is preferable that a nonmagnetic spacer is provided between the plurality of rotor portions. When the nonmagnetic spacer is used, the rotor portions can be disposed sufficiently close to each other, thereby reducing the size of the rotation detecting device.

  In the present invention, it is preferable to detect the rotation angle when the output signal from each magnetic sensor has passed the reference level. According to this, the rotation angle of the rotor portion can be accurately detected.

  In the present invention, the rotor mechanism may have a missing tooth region in which at least one of a plurality of teeth is missing, and the rotor mechanism is a long tooth in which at least two teeth adjacent in the circumferential direction are integrated. You may have. When a missing tooth region or long teeth are provided on the rotor mechanism, the reference position of the rotating shaft becomes clear, so that the rotational speed can be easily detected.

  According to the present invention, it is possible to detect the rotation angle with high accuracy by using a plurality of rotor portions and sequentially shifting the circumferential positions of the teeth provided on the outer periphery thereof. In addition, since non-magnetic spacers are used as signal interference avoidance means when these rotor parts are arranged close to each other, accurate detection can be performed with a single device. The rotation detection accuracy can be improved without increasing the cost and without losing the layout.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic perspective view showing the structure of a rotation detection device according to a preferred embodiment of the present invention, and FIG. 2 is a schematic front view.

  As shown in FIGS. 1 and 2, the rotation detection device 10 detects a rotor mechanism 12 that rotates together with the rotating shaft 11, and changes in the magnetic field due to the rotation of the rotor mechanism 12, thereby detecting the rotation state of the rotating shaft 11. The rotation detection sensor 15 is provided. The rotor mechanism 12 includes first and second rotor portions 12A and 12B directly attached to the rotary shaft 11, and a nonmagnetic spacer 14 sandwiched between the first rotor portion 12A and the second rotor portion 12B. It has. The first and second rotor portions 12A and 12B are both substantially disk-shaped magnetic bodies having the same shape, and a large number of teeth 13A and 13B are provided on the outer periphery at predetermined pitches, respectively. These teeth 13 </ b> A and 13 </ b> B are used for detecting a rotation angle every several degrees of the rotating shaft 11. The number of teeth 13A and 13B is preferably as large as possible within a range that can be detected by the rotation detection sensor 15, and particularly preferably 90 to 180 teeth.

  The rotation detection sensor 15 includes first and second magnetic sensors 16A and 16B provided at the distal end corresponding to the first and second rotor portions 12A and 12B, and a magnetic sensor 16A, A bias magnet 17 for generating a magnetic field around 16B and a case 18 for holding them are provided. The first magnetic sensor 16A is provided directly below the first rotor portion 12A in order to detect the rotation of the first rotor portion 12A. The second magnetic sensor 16B is provided directly below the second rotor portion 12B in order to detect the rotation of the second rotor portion 12B. As the first and second magnetic sensors 16A and 16B, it is preferable to use a spin valve GMR (Giant Magnetic Resistance) circuit. With a spin valve GMR circuit, it is possible to detect a minute magnetic field change due to rotation of the rotor with high accuracy. The direction of the magnetic field by the bias magnet 17 is set in a direction substantially orthogonal to the tangent line of the first and second rotor portions 12A and 12B.

  The first and second rotor portions 12A and 12B are arranged adjacent to each other, and a nonmagnetic spacer 14 for suppressing magnetic interference between the rotor portions 12A and 12B is interposed therebetween. When the two rotors are brought close to each other without the nonmagnetic spacer 14, the magnetic field change by one rotor part affects the magnetic field change by the other rotor part, and the rotational state cannot be read correctly. Cannot be brought too close together. However, when the nonmagnetic spacer 14 is interposed, the influence of the magnetic field change by the other rotor is sufficiently suppressed, so that the two rotors can be sufficiently close to each other, and the rotor portions 12A and 12B It is possible to accurately detect the rotation state. That is, when such a nonmagnetic spacer 14 is interposed, the reference position signals from the first and second rotor portions 12A and 12B arranged close to each other can be obtained independently.

As shown in FIG. 2, the diameter d ₁ of the first and second rotor portions 12A and 12B is preferably as small as possible as long as detection by the rotation detection sensor 15 is possible in consideration of restrictions on the installation space. In this embodiment, it is set to about 70 to 160 mm. The first and second rotor portions 12A, the thickness _{W 1} of 12B is as thin as possible should preferably as long as possible is detected by the rotation detecting sensor 15, for example, on the order of 1.5 to 4 mm.

On the other hand, the diameter d ₂ of the non-magnetic spacer 14 is not particularly limited, the first and second rotor portions 12A, it is preferable to slightly less than the diameter d ₁ of 12B. In this way, it is possible to suppress magnetic interference from the other rotor portion when reading one rotor portion without adversely affecting normal reading. The thickness _{W 2} of the non-magnetic spacer 14, as far as possible thinner is preferable as long as possible to suppress the magnetic interference between the rotor portion 12A, 12B, for example, on the order of 1.5 mm. Since the non-magnetic spacer 14 is interposed, the two rotor portions 12A and 12B can be disposed close to each other, so that the distance D between them can be set to about 3 to 9.5 mm.

  FIG. 3 is an enlarged view of the portion X in FIG. 1 and is a schematic perspective view showing in detail the relationship between the teeth 13A of the first rotor portion and the teeth 13B of the second rotor portion.

  As shown in FIG. 3, the teeth 13A and 13B provided on the first and second rotor portions 12A and 12B are provided at a predetermined pitch p, and the tooth width and the width between the teeth are the same. (P / 2) is set. In the present embodiment, the circumferential position of the first teeth 13A provided on the outer periphery of the first rotor portion 12A and the circumference of the second teeth 13B provided on the outer periphery of the second rotor portion 12B. The positions of the directions do not match and are shifted by p / 4 (half teeth). As described above, in order to improve the rotation detection accuracy, the tooth pitch is made as narrow as possible and the number of teeth is simply increased. Changes cannot be read accurately.

  However, as in the present embodiment, when many teeth 13A provided on the outer periphery of the first rotor portion 12A and many teeth 13B provided on the outer periphery of the second rotor portion 12B are shifted by p / 4 Because the intermediate angle that cannot be detected by one rotor part can be detected by the other rotor part, twice the number of teeth are provided on one rotor without increasing the rotor diameter. The same effect can be obtained. For example, when one rotor with 180 teeth is used, the rotation angle can be counted in increments of 1 degree, but the rotor diameter must be about 160 mm. On the other hand, when two rotor parts are prepared and they are combined while being shifted by a half tooth in the circumferential direction, the rotor can be read even if the rotor diameter is about 70 mm, and the actual angle in 0.5 degree increments. Count control is possible.

  FIG. 4 is an output signal waveform diagram of the magnetic sensor, where the signal S1 indicates the output of the magnetic sensor 16A and the signal S2 indicates the output of the magnetic sensor 16B.

  As shown in FIG. 4, substantially sinusoidal waveforms are obtained as the output signals of the magnetic sensors 16A and 16B. However, when the teeth 13A and 13B of the two rotor portions are shifted by half a tooth in the circumferential direction, the output signals are 1 Two sine wave signals shifted by / 4 period are obtained, and as shown in the figure, four cross points crossing the reference level Vth during one period of one sine waveform can be detected. Therefore, it can be known that the rotation shaft has rotated 0.5 degrees when these sensor outputs have passed the reference level Vth. Furthermore, the rotation direction of the rotating shaft can be known from the phase difference between the outputs of the magnetic sensors.

  Next, the spin valve GMR circuit will be described with reference to FIGS. The spin valve GMR circuit is a magnetic sensor circuit in which an IC including four spin valve GMR elements R1, R2, R3, and R4 is assembled as a bridge circuit.

  5A and 5B are schematic views showing the basic structure of a spin bubble GMR element.

  As shown in FIGS. 5A and 5B, the spin valve GMR element 20 has a structure in which a ferromagnetic pinned layer 21, a nonmagnetic layer 22, and a ferromagnetic free layer 23 are stacked in this order. ing. The magnetization direction of the pinned layer 21 is constant without being changed by the external magnetic field, but the magnetization direction of the free layer 23 is changed by the external magnetic field. Here, when the magnetization direction of the free layer 23 (that is, the direction of the external magnetic field) is orthogonal to the magnetization direction of the pinned layer 21, the resistance change rate (ΔR / R) of the spin valve GMR element 20 is zero. However, when the magnetization direction of the free layer 23 is parallel to the magnetization direction of the pinned layer 21 and the directions are opposite to each other (that is, antiparallel), the rate of change in resistance of the spin valve GMR element 20 becomes positive, and the high resistance state Become. When the magnetization direction of the free layer 23 is parallel to the magnetization direction of the pinned layer 21 and the directions thereof are the same (that is, forward parallel), the resistance change rate of the spin bubble GMR element 20 becomes negative, and the low resistance state Become. The spin valve GMR circuit has four spin valve GMR elements R1, R2, R3, R4 having the above magnetic characteristics arranged on the same plane.

  FIG. 6 is a schematic diagram showing a layout of the spin valve GMR circuit.

  As shown in FIG. 6, the spin valve GMR circuit includes a pair of spin valve GMR elements R1 and R3 whose pinned layer magnetization direction is rightward, and further includes spin valve GMR elements R2 and R4 whose pinned layer magnetization direction is leftward. A pair of two spin valve GMR element pairs 24 and 25 are arranged side by side. That is, the magnetization directions of the pinned layers of the spin valve GMR elements R1 and R3 and the magnetization directions of the pinned layers of the spin valve GMR elements R2 and R4 are opposite to each other. These spin valve GMR element pairs 24 and 25 are arranged in parallel to the thickness direction (axial direction) of the rotor as shown in the figure, and the midpoint between the spin valve GMR element pairs 24 and 25 is at the center of the rotor thickness direction. It is positioned. In addition, the magnetosensitive surface of these spin valve GMR elements is arranged in parallel with a plane in contact with the outer peripheral surface of the rotor.

  7A and 7B are circuit diagrams of a spin valve GMR circuit.

  As shown in FIGS. 7A and 7B, in the spin valve GMR circuit, four spin valve GMR elements R1 to R4 are used, and a series circuit of the spin valve GMR elements R1 and R2 and the spin valve GMR element R4, The R3 series circuit is configured as a Wheatstone bridge circuit connected in parallel. A constant voltage Vcc is supplied to one end of the spin valve GMR elements R1 and R4, and one end of the spin valve GMR elements R2 and R3 is connected to the ground. ing.

  FIGS. 8A and 8B show the relationship between the position of the teeth (convex part) of the rotor and the direction of the magnetic field at the magnetosensitive point, and FIG. 8A shows the spin valve GMR. When approaching the element, FIG. 8B is an explanatory diagram when the convex part moves away from the spin valve GMR element.

As shown in FIG. 8A, when the rotor teeth (convex portions) magnetized by the magnetic field of the bias magnet approach the magnetic sensing surface of the spin valve GMR element, the magnetic flux near the magnetic sensing surface of the spin valve GMR element is Since the convex portion faces in the approaching direction, a magnetic field component is generated in the tangential direction with respect to the rotor. In the spin valve GMR element, the magnetization direction of the free layer changes in response to the magnetic field component in the tangential direction. For example, the free layers of the spin valve GMR elements R1 and R3 are magnetized in the same direction as the pinned layer, and the free layers of the spin valve GMR elements R2 and R4 are magnetized in the opposite direction to the pinned layer. For this reason, the resistance values of the spin valve GMR elements R1 and R3 are decreased, and the resistance values of the spin valve GMR elements R2 and R4 are increased, and the output potentials of the output terminals P1 and P2 of the bridge circuit are equal to the potential of the output terminal P2. Thus, a negative potential is output as the output potential _VOUT . Further, as the convex portion of the rotor approaches, the magnetic field component in the tangential direction of the rotor decreases, and the output potential _VOUT decreases. When the convex portion of the rotor comes closest to the magnetic sensing point of the spin valve GMR element, the magnetic field component in the tangential direction of the rotor becomes substantially zero, the resistance values of the spin valve GMR elements R1 to R4 become equal, and the output potential V _OUT becomes zero.

Further, as shown in FIG. 8B, when the rotor teeth (convex portions) magnetized by the magnetic field of the bias magnet move away from the magnetosensitive surface of the GMR element, the magnetic flux near the magnetosensitive surface of the GMR element is Since it faces in the direction of the convex portion going away, a magnetic field component is generated in the direction opposite to the previous direction in the tangential direction to the rotor. In this case, the free layers of the spin valve GMR elements R1 and R3 are magnetized in the opposite direction to the pinned layer, and the free layers of the spin valve GMR elements R2 and R4 are magnetized in the same direction as the pinned layer. Therefore, the resistance values of the spin valve GMR elements R1 and R3 are increased, and the resistance values of the spin valve GMR elements R2 and R4 are decreased. The output potentials of the output terminals P1 and P2 of the bridge circuit are equal to the potential of the output terminal P1. Thus, a positive potential is output as the output potential _VOUT . When the convex portion of the rotor moves further away, the magnetic field component in the tangential direction of the rotor increases and the output potential _VOUT also increases. However, as the distance further increases, the magnetic field change due to the convex portion of the rotor becomes smaller, so the magnetic field component in the tangential direction of the rotor becomes smaller and the output potential _VOUT also becomes smaller. When the midpoint between the two adjacent teeth is closest to the magnetosensitive point of the GMR element, the resistance values of the spin valve GMR element pairs R1 to R4 become equal, and the output potential _VOUT becomes zero again. Thereafter, this operation is repeated as the rotor rotates.

  As described above, when the convex portion of the rotor approaches the magnetic sensing point of the spin valve GMR element or moves away from the magnetic sensing point, the resistance value of one spin valve GMR element pair becomes the maximum, and the other spin valve GMR element Since the resistance value of the pair is minimized, when a Wheatstone bridge circuit is assembled using these spin-valve GMR elements, an output level that is about four times that obtained when a single spin-valve GMR element is used is obtained. It becomes possible.

  Thus, by detecting the change in the magnetic field due to the rotation of the first and second rotor portions 12A and 12B, the rotation angle signal can be output every several degrees from the first spin valve GMR circuit 16A. As a result, the rotation angle and the number of rotations of the rotating shaft can be determined based on the output pulses of these magnetic sensors. Here, when there is no nonmagnetic spacer 14, the magnetic field detected by the first spin valve GMR circuit 16A is affected by the second rotor portion 12B and is inclined in the direction of the second rotor portion 12B. Since the magnetic field detected by the second spin valve GMR circuit 16B is affected by the first rotor portion 12A and tilts in the direction of the first rotor portion 12A, the tangent lines of the first and second rotor portions 12A and 12B The magnetic field component in the direction decreases, and the sensitivity of the first and second spin valve GMR circuits 16A and 16B decreases. However, when the nonmagnetic spacer 14 is provided, the magnetic interference between the first and second rotor portions 12A and 12B, that is, the first and second spin valve GMR circuits 16A due to the gradient of the magnetic field described above, Since the sensitivity decrease of 16B is suppressed, the rotation of the first and second rotor portions 12A and 12B can be accurately detected.

  As described above, according to this embodiment, the circumferential position of the first tooth provided on the outer periphery of the first rotor and the circumference of the second tooth provided on the outer periphery of the second rotor. Since the position in the direction is shifted by p / 4, rotation detection with high resolution can be realized. The rotor can be made smaller and thinner,

  In addition, a non-magnetic spacer is provided between two small and thin rotor portions 12A and 12B, and two rotors having a large number of teeth are brought close to each other by using high-sensitivity spin valve GMR circuits 16A and 16B. Can be arranged. Therefore, more accurate rotation angle detection is possible without being affected by the rotation fluctuation of the rotation shaft, and real angle count control can be realized.

  FIGS. 9A and 9B are schematic partial enlarged views showing the configurations of the rotation detection devices according to the second and third embodiments of the present invention.

  As shown in FIG. 9A, the rotation detection device 40 according to the second embodiment of the present invention is configured by using three (n = 3) rotor portions 12A to 12C, It is characterized in that the circumferential positions of the teeth 13A to 13C provided on the outer periphery are sequentially shifted by p / 6. Further, nonmagnetic spacers 14A and 14B are provided between the rotors, thereby reducing mutual interference between the rotors. Since other configurations are the same as those of the first embodiment, description thereof is omitted here.

  Further, as shown in FIG. 9B, the rotation detection device 50 according to the third embodiment of the present invention includes four (n = 4) rotor portions 12A to 12D, and each rotor portion. It is characterized in that the circumferential positions of the teeth provided on the outer circumference of the teeth are sequentially shifted by p / 8. Further, nonmagnetic spacers 14A to 14C are provided between the rotors, thereby reducing mutual interference between the rotors. Since other configurations are the same as those of the first embodiment, description thereof is omitted here.

  The above can be generalized as follows. That is, when the number of rotor parts is n (n is an integer of 2 or more) and the pitch of a plurality of teeth provided in each rotor part is p, the teeth provided in each rotor part are separated from the rotor parts. It is only necessary that the provided teeth are shifted by p / 2n in the circumferential direction. With such a configuration, it is possible to realize normal detection accuracy that is n times.

  FIGS. 10A and 10B are schematic enlarged views showing the configuration of the rotation detection device according to the fourth and fifth embodiments of the present invention.

  As shown in FIG. 10A, the rotation detection device 60 according to the fourth embodiment is characterized in that one of a plurality of teeth provided on the outer periphery of each rotor portion is missing. is doing. On the outer periphery of the first rotor, a large number of teeth 13A are provided at a constant pitch p, but one of them is removed to form a missing tooth region 28A. Similarly, a large number of teeth 13B are provided on the outer periphery of the second rotor portion 12B at a constant pitch, but one of them is removed to form a second missing tooth region 28B. Yes. The widths of the first and second missing tooth regions 28A and 28B are both 1.5p. The positional relationship between the teeth removed on the first rotor part and the teeth removed on the second rotor part is preferably teeth that partially overlap in the circumferential direction. Since other configurations are the same as those of the first embodiment, description thereof is omitted here.

  According to the present embodiment, the first and second missing tooth regions 28A and 28B provided on the outer periphery of each rotor serve as reference positions for rotation detection, and therefore the rotation speed can be easily detected. In addition, since many normal teeth 13A and 13B are provided in the other regions, the reading accuracy of the rotation angle can be further improved as in the first embodiment. In the present embodiment, both the first and second rotor portions 12A and 12B are provided with the missing tooth region, but the missing tooth region may be provided only for one of the rotors.

  As shown in FIG. 10B, the rotation detection device 70 according to the fifth embodiment is such that two of a plurality of teeth provided on the outer periphery of the rotor portion are integrated as one tooth. It has characteristics. A large number of teeth 13A are provided at a constant pitch p on the outer periphery of the first rotor portion 12A, and two of them are integrated to form a first long tooth 29A. Similarly, a large number of teeth 13B are provided on the outer periphery of the second rotor portion 12B at a constant pitch, but two of them are integrated to form a second long tooth 29B. Yes. The tooth widths of the first and second long teeth 29A and 29B are both 1.5P. The long teeth 29A on the first rotor portion 12A and the long teeth 29B on the second rotor portion 12B are shifted by P / 4 in the circumferential direction, like the normal teeth 13A and 13B. Since other configurations are the same as those of the first embodiment, description thereof is omitted here.

  According to the present embodiment, the first and second long teeth 29A and 29B provided on the outer periphery of each rotor serve as reference positions for rotation detection, so that the number of rotations can be easily detected. In addition, since many normal teeth 13A and 13B are provided in the other regions, the reading accuracy of the rotation angle can be further improved as in the first embodiment. In the present embodiment, long teeth are provided in both the first and second rotor portions 12A and 12B, but long teeth may be provided in only one of the rotors.

  The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention, and these are also included in the scope of the present invention. Needless to say.

  For example, in the above embodiment, two rotors having the same number of teeth having the same number of teeth are prepared and bonded together. However, the present invention is not limited to such a configuration, and two rotors are provided. It is also possible to integrally mold the rotor portions 12A and 12B in a state of being bonded together. That is, two tracks are provided in the circumferential direction of one rotor, a plurality of teeth 13A and 13B are formed on each track, and the teeth 13A and 13B between adjacent tracks are p / 2n in the circumferential direction. The structure may be shifted. In this case, a non-magnetic spacer cannot be interposed between the rotor portions. However, in the present invention, the non-magnetic spacer 14 is not essential, and the non-magnetic spacer 14 can be omitted if the distance between the two rotor portions is separated to some extent. Is possible. In such a configuration, the thickness of the entire rotor mechanism is increased and the rotation detection device is slightly enlarged. However, accurate rotation detection is possible as in the case where a nonmagnetic spacer is provided.

  In the above embodiment, a plurality of rotors having the same shape are prepared, and the rotors are bonded so that the teeth on each rotor portion are sequentially shifted by p / 2n. In addition to the pasting, a rotor portion having another shape may be pasted. For example, a rotor portion in which only one tooth is provided on the outer periphery may be further added to provide a reference position for rotation detection. According to this configuration, as in the fourth and fifth embodiments, it is possible to easily detect the rotation speed while improving the accuracy of reading the rotation angle.

FIG. 1 is a schematic perspective view showing a configuration of a rotation detection device according to a preferred embodiment of the present invention. FIG. 2 is a schematic front view showing the configuration of the rotation detection device 10 according to a preferred embodiment of the present invention. FIG. 3 is an enlarged view of a portion X in FIG. 1 and is a schematic perspective view showing in detail the relationship between the teeth 13A of the first rotor and the teeth 13B of the second rotor. FIG. 4 is an output signal waveform diagram of the magnetic sensor, where the signal S1 indicates the output of the magnetic sensor 16A and the signal S2 indicates the output of the magnetic sensor 16B. 5A and 5B are schematic views showing the basic structure of a spin bubble GMR element. FIG. 6 is a schematic diagram showing a layout of the spin valve GMR circuit. 7A and 7B are circuit diagrams of a spin valve GMR circuit. FIGS. 8A and 8B show the relationship between the position of the teeth (convex part) of the rotor and the direction of the magnetic field at the magnetosensitive point, and FIG. 8A shows the spin valve GMR. When approaching the element, FIG. 8B is an explanatory diagram when the convex part moves away from the spin valve GMR element. FIGS. 9A and 9B are schematic partial enlarged views showing the configurations of the rotation detection devices according to the second and third embodiments of the present invention. FIGS. 10A and 10B are schematic enlarged views showing the configuration of the rotation detection device according to the fourth and fifth embodiments of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rotation detection apparatus 11 Rotating shaft 12 Rotor 12A-12D Rotor 13 Teeth 13A-13D Teeth 14 Nonmagnetic spacer 14A-14C Nonmagnetic spacer 15 Rotation detection sensor 16A 1st magnetic sensor (spin bubble GMR circuit)
16B Second magnetic sensor (spin bubble GMR circuit)
17 Bias magnet 18 Case 20 Spin valve GMR element 21 Pinned layer 22 Nonmagnetic layer 23 Free layer 24 First spin valve GMR element pair 25 Second spin valve GMR element pair 28A First missing tooth region 28B Second missing part Tooth region 29A First long tooth 29B Second long tooth 40 Rotation detection device 70 Rotation detection device 80 Rotation detection device 90 Rotation detection device

Claims (7)

A plurality of teeth provided at a predetermined pitch in the circumferential direction and spaced apart by a predetermined distance in the axial direction, the adjacent teeth spaced apart in the axial direction being arranged offset from each other in the circumferential direction A rotor mechanism,
A plurality of magnetic sensors;
A bias magnet for generating a magnetic field around the magnetic sensor,
The rotation detecting device, wherein the plurality of magnetic sensors are arranged so as to be able to detect changes in the magnetic field due to the teeth arranged apart in the axial direction.   The rotation detection device according to claim 1, wherein the rotor mechanism includes a plurality of rotor portions arranged adjacent to each other.   When the number of the rotor parts is n (n is an integer of 2 or more), and the pitch of the plurality of teeth provided in each rotor part is p, the teeth provided in each rotor part are provided in a different rotor part. The rotation detection device according to claim 2, wherein the teeth are shifted by p / 2n in the circumferential direction.   The rotation detection device according to claim 2, wherein a nonmagnetic spacer is provided between the plurality of rotor portions.   5. The rotation detection device according to claim 1, wherein the rotation angle is detected when an output signal from each magnetic sensor passes a reference level. 6.   The rotation detection device according to claim 1, wherein the rotor mechanism has a missing tooth region in which at least one of the plurality of teeth is missing.   The rotation detection device according to any one of claims 1 to 6, wherein the rotor mechanism has long teeth in which at least two teeth adjacent in the circumferential direction are integrated.

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