JP5348009B2 - Angle sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angle sensor allowing high accuracy angle detection with detection resolution enhanced. <P>SOLUTION: The angle sensor 11 includes: a rotor 30 having a rolling groove 31 that spirally coils and rotating in conjunction with the rotation of a rotary shaft 20; a rolling element 40 that rolls in the rolling groove 31; a guide 60 guiding the moving direction of the rolling element 40 so that the position of the rolling element 40 and the rotation angle of the rotary shaft 20 are one-to-one related with each other; a magnetic sensor 50 for detecting a magnetic field changing according to the position of the rolling element 40 to output a detection signal corresponding to the position of the rolling element 40; and a signal processing circuit 80 for calculating the rotation angle of the rotary shaft 20 based on the detection signal. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an angle sensor that detects a rotation angle of a rotation shaft.

  As a magnetic sensor for detecting an external magnetic field, a magnetoresistive effect element such as a giant magnetoresistive effect element or a magnetic tunnel effect element is used. Magnetoresistive elements have a magnetization direction that is set to a specific direction and is configured so that the magnetization state (for example, the magnetization direction and the strength of magnetization) is not affected by the displacement of the external magnetic field. A layer (pinned magnetic layer) and a magnetization free layer (free magnetic layer) whose magnetization state is displaced by a change in an external magnetic field. When an external magnetic field acts on the magnetoresistive effect element, the magnetization state of the magnetization free layer changes, and the magnetization state between the magnetization state of the magnetization fixed layer in which the magnetization state is fixed and the magnetization free layer in which the magnetization state changes The displacement difference is generated. This displacement difference in the magnetized state appears as a change in magnetoresistance of the magnetoresistive effect element. As an application example of this type of magnetoresistive effect element, for example, Japanese Patent Application Laid-Open No. 2006-125938 discloses a displacement of a magnetic fluid guided so as to move in the radial direction of the steering shaft in conjunction with the rotation of the steering shaft. There has been proposed a rotation angle detection device that detects a rotation angle of a steering shaft by detecting with a magnetoresistive element.

JP 2006-125938 A

  However, since the rotation angle detection device disclosed in the publication requires a magnet for attracting the magnetic fluid in the radial direction of the steering shaft, the angle detection is performed by the influence of the magnetic field generated by the magnet on the magnetoresistive effect element. There is a risk that the accuracy may decrease.

  Therefore, an object of the present invention is to solve such a problem and provide a highly accurate angle sensor.

  In order to solve the above-described problems, an angle sensor according to the present invention has a rolling groove that is wound in a spiral shape, a rotor that rotates in conjunction with the rotation of a rotating shaft, and a rolling groove that rolls on the rolling groove. A moving member, a guide member that guides the moving direction of the rolling element so that the position of the rolling element and the rotation angle of the rotating shaft are in one-to-one correspondence, and a magnetic field that changes according to the position of the rolling element are detected. A magnetic sensor that outputs a detection signal corresponding to the position of the moving body; and a signal processing circuit that calculates a rotation angle of the rotary shaft based on the detection signal. Unlike the prior art, a magnet for attracting the magnetic fluid in the radial direction of the steering shaft is not required, so that highly accurate angle detection is possible.

  The rolling groove may be wound more than once. Thereby, the signal processing circuit can calculate the multi-rotation absolute angle of the rotating shaft.

  The magnetic sensor may include a magnetoresistive effect element including a magnetization fixed layer whose magnetization direction is fixed, and a magnetization free layer whose magnetization direction changes following the action of a magnetic field. The magnetization direction of the magnetization fixed layer is preferably substantially parallel to the moving direction of the rolling elements. Thereby, since the fluctuation width in the magnetic field direction can be increased, the detection resolution of the angle sensor can be improved.

  The moving direction of the rolling element is preferably a direction passing through a position shifted by a predetermined distance with respect to a radial direction passing through the rotation center of the rotation shaft, and a direction different from the rotation center direction. Thereby, since the moving distance of a rolling element can be increased, the detection resolution of an angle sensor can be improved. Further, the moving path of the rolling element guided by the guide groove is preferably a line segment connecting the start point and the end point of the rolling groove (may be a straight line, a curve, or a combination of a straight line and a curve). As a result, the angle detection resolution can be maximized. Note that if the magnetization direction of the magnetization fixed layer of the magnetoresistive element is orthogonal to the moving direction of the rolling element, the sensitivity of the magnetic sensor decreases, so the magnetization direction of the magnetization fixed layer is the moving direction of the rolling element and its moving direction. A direction within a plane including a direction orthogonal to the plane (however, excluding a direction orthogonal to the moving direction of the rolling element) is preferable. The direction of the magnetic field is preferably a direction substantially orthogonal to the moving direction of the rolling elements.

  Further, it is preferable that the distance between the magnetic sensor and the rolling element becomes constant as the rolling element moves. By arranging in this way, the distance between the magnetic sensor and the rolling element becomes constant, so the possibility that the sensitivity of the magnetic sensor varies with the movement of the rolling element can be reduced. That is, the magnetic sensor may be arranged in accordance with the idea of the guide groove or rolling groove shape.

  For example, by using a magnet as the rolling element, the strength of the magnetic field attracted to the rolling element can be increased, so that the detection resolution of the angle sensor can be improved.

  An angle sensor according to another aspect of the present invention has a closed-curved rolling groove, which rotates in conjunction with rotation of a rotating shaft, and first and second rolling elements that roll in the rolling groove. A first guide member that guides the moving direction of the first rolling element so that the position of the first rolling element and the rotation angle of the rotation shaft are associated with each other in a one-to-two manner, and the position of the second rolling element And a first magnetic field that changes according to the position of the first rolling element, and a second guide member that guides the moving direction of the second rolling element so that the rotation angle of the rotating shaft is associated with one to two. A first magnetic sensor that outputs a first detection signal corresponding to the position of the first rolling element, and a second magnetic field that changes according to the position of the second rolling element, A second magnetic sensor for outputting a second detection signal corresponding to the position of the second rolling element, and rotation of the rotary shaft based on the first and second detection signals And a signal processing circuit for calculating a. Unlike the prior art, a magnet for attracting the magnetic fluid in the radial direction of the steering shaft is not required, so that highly accurate angle detection is possible.

  The closed curve forming the contour of the rolling groove is preferably a closed curve excluding a circle coaxial with the rotation center of the rotating shaft. For example, the first and second detection signals have a signal waveform of one cycle per rotation of the rotating shaft or It is preferable to adjust the signal so as to output an asymmetric two-cycle signal waveform.

  The first magnetic sensor includes a first magnetic pinned layer having a fixed magnetization direction and a first magnetic free layer having a first magnetization free layer in which the magnetization direction changes following the action of the first magnetic field. A resistance effect element may be included. In addition, the second magnetic sensor includes a second magnetization fixed layer whose magnetization direction is fixed, and a second magnetization free layer whose magnetization direction changes following the action of the second magnetic field. The magnetoresistive effect element may be included. The magnetization direction of the first magnetization fixed layer is preferably substantially parallel to the moving direction of the first rolling element, and the magnetization direction of the second magnetization fixed layer is approximately parallel to the moving direction of the second rolling element. It is preferable that Thereby, since the fluctuation width in the magnetic field direction can be increased, the detection resolution of the angle sensor can be improved.

  According to the present invention, a highly accurate angle sensor can be provided.

1 is a plan view of an angle sensor according to Embodiment 1. FIG. FIG. 2 is a partial cross-sectional view taken along line 2-2 in FIG. 1. It is a schematic diagram which shows the cross-sectional laminated structure of the magnetoresistive effect element concerning Example 1,2. 3 is a graph of a detection signal output from a magnetoresistive effect element according to Example 1. It is explanatory drawing which shows the modification of the angle sensor concerning Example 1. FIG. It is explanatory drawing which shows the modification of the angle sensor concerning Example 1. FIG. It is explanatory drawing which shows the modification of the angle sensor concerning Example 1. FIG. 7 is a plan view of an angle sensor according to Embodiment 2. FIG. FIG. 9 is a partial cross-sectional view taken along line 9-9 in FIG. 8. FIG. 10 is a partial cross-sectional view taken along line 10-10 in FIG. 6 is a graph of the output voltage of the magnetic sensor according to Example 2. It is explanatory drawing of the angle sensor concerning a reference example. It is a graph of the output voltage of the magnetic sensor concerning a reference example. It is explanatory drawing which shows the modification of the angle sensor concerning Example 2. FIG. 6 is a graph of the output voltage of the magnetic sensor according to Example 2. 1 is a configuration diagram of a magnetic sensor according to Embodiment 1. FIG. 6 is an explanatory diagram showing a magnetization direction of a magnetization fixed layer according to Example 1. FIG. 1 is a configuration diagram of a magnetic sensor according to Embodiment 1. FIG. 6 is an explanatory diagram showing a magnetization direction of a magnetization fixed layer according to Example 1. FIG.

  Embodiments according to the present invention will be described below with reference to the drawings. About the same member, the same code | symbol shall be attached | subjected and the overlapping description is abbreviate | omitted.

  The configuration of the angle sensor 11 according to this embodiment will be described with reference to FIGS. 1 is a plan view of the angle sensor 11, and FIG. 2 is a partial cross-sectional view taken along line 2-2 of FIG. However, for convenience of explanation, the magnetic sensor 50 is a perspective view in FIG. 1, and the guide member 60 is a perspective view in FIG. As shown in FIGS. 1 and 2, the angle sensor 11 includes a rotor 30 having a rolling groove 31 wound spirally, a rolling element 40 that rolls on the rolling groove 31, and a moving direction of the rolling element 40. , A magnetic sensor 50 that detects an external magnetic field 90 that changes according to the position of the rolling element 40, and outputs a detection signal according to the position of the rolling element 40, and a rotating shaft based on the detection signal And a signal processing circuit 80 that calculates 20 rotation angles. The rotor 30 is a rotating plate that rotates in conjunction with the rotation of the rotating shaft 20, and is disposed coaxially with the rotation center 21 of the rotating shaft 20. On the main surface of the rotor 30, a rolling groove 31 having a substantially constant groove depth and groove width is formed in a spiral shape with the rotation center 21 as a winding center. The number of turns of the rolling groove 31 is adjusted according to the angle detection range of the rotating shaft 20. For example, in order to measure the rotation angle of the rotating shaft 20 in the range of 0 to 900 deg in the clockwise direction and in the range of 0 to −900 deg in the counterclockwise direction, the number of turns of the rolling groove 31 is 5 You may adjust to. By adjusting the number of turns of the rolling groove 31 to 1 or more, the angle sensor 11 can detect a multi-rotation absolute angle of one rotation or more of the rotating shaft 20. The multi-rotation absolute angle means an absolute angle from the reference position of the rotation shaft 20 in consideration of the rotation number of the rotation shaft 20, for example, the rotation number of the rotation shaft 20 is N rotations from the reference position of the rotation shaft 20. The multi-rotation absolute angle φ having a relative angle α is φ = 360 × N + α [deg]. An example of the rotating shaft 20 is a steering shaft, but this embodiment is not limited to this.

  The guide member 60 has a guide groove 61 that guides the movement of the rolling element 40 in a linear direction (for example, the X direction or the Y direction). When the axial direction of the rotary shaft 20 is the Z direction, the rotor 30 rotates in the XY plane in conjunction with the rotation of the rotary shaft 20. The rotor 30 may be fixed to the rotating shaft 20 or may be serrated. The rolling element 40 linearly moves along the guide groove 61 while rolling the rolling groove 31 when the rotor 30 rotates. The material of the rolling element 40 is not particularly limited as long as it is a material having an action of attracting the external magnetic field 90. For example, a ferromagnetic material (iron, cobalt, nickel, etc.) or a magnet may be used. . The shape of the rolling element 40 is not particularly limited as long as it is easy to roll. For example, a sphere, a cylinder, or the like is suitable.

  The magnetic sensor 50 includes a magnet 53 for generating an external magnetic field 90, a magnetoresistive effect element 51 that detects a change in the external magnetic field 90 whose magnetic field direction changes following the movement of the rolling element 40, and a magnetic And a printed wiring board 52 for supplying a sense current to the resistance effect element 51. As shown in FIGS. 16 to 19, the arrangement relationship between the magnetoresistive effect element 51 and the printed wiring board 52 can be variously arranged according to the magnetization direction 73A of the magnetization fixed layer. For example, as shown in FIG. 16, when the magnetoresistive effect element 51, the printed wiring board 52, and the magnet 53 are stacked in the Z direction, as shown in FIG. The magnetization direction 73A faces an arbitrary direction in the XY plane. Assuming that the moving direction of the rolling element 40 is the X direction and the direction orthogonal to the moving direction is the Y direction, the sensitivity of the magnetic sensor 50 decreases when the magnetization direction 73A of the magnetization fixed layer faces the Y direction. For this reason, it is preferable that the magnetization direction 73A of the magnetization fixed layer is an arbitrary direction in the XY plane excluding the Y direction. Further, for example, as shown in FIG. 18, when the magnetoresistive effect element 51 and the printed wiring board 52 are stacked in the Y direction (the printed wiring board 52 is illustrated because it is disposed on the back surface of the magnetoresistive effect element 51. Note that, as shown in FIG. 19, the magnetization direction 73A of the magnetization fixed layer of the magnetoresistive effect element 51 faces an arbitrary direction in the XZ plane. If the moving direction of the rolling element 40 is the X direction and the direction orthogonal to the moving direction is the Z direction, the sensitivity of the magnetic sensor 50 is lowered when the magnetization direction 73A of the magnetization fixed layer faces the Z direction. For this reason, it is preferable that the magnetization direction 73A of the magnetization fixed layer is an arbitrary direction in the XZ plane excluding the Z direction. The direction of the magnetic field 90 is preferably a direction substantially orthogonal to the moving direction of the rolling element 40. As the magnetoresistive effect element 51, a known magnetoresistive effect element such as a giant magnetoresistive (GMR) type, a tunnel magnetoresistive (TMR) type, a ballistic magnetoresistive (BMR) type, an anisotropic magnetoresistive (AMR) type or the like is used. be able to.

  FIG. 3 shows a cross-sectional laminated structure of the magnetoresistive effect element 51. The magnetoresistive element 51 has a structure in which a base layer 71, an antiferromagnetic layer 72, a magnetization fixed layer 73, a nonmagnetic conductive layer 74, a magnetization free layer 75, and a protective layer 76 are laminated. The magnetization direction 73A of the magnetization fixed layer 73 is hardly affected by the external magnetic field 90 because it is strongly magnetically coupled with the magnetization direction 72A of the antiferromagnetic layer 72. On the other hand, the magnetization direction 75 </ b> A of the magnetization free layer 75 changes so as to follow the magnetic field direction of the external magnetic field 90. It is known that the magnetoresistance of the magnetoresistive effect element 51 changes depending on the magnetic field strength of the external magnetic field 90 detected by the magnetoresistive effect element 51 and the direction of the magnetic field. If the magnetic field strength of the external magnetic field 90 is constant, the magnetoresistance of the magnetoresistive element 51 depends on the angle difference ψ between the magnetization direction 73A of the magnetization fixed layer 73 and the magnetization direction 75A of the magnetization free layer 75. Change. More specifically, the magnetoresistance of the magnetoresistive element 51 has a characteristic that changes in proportion to (1-cos ψ), and the magnetization direction 73 A of the magnetization fixed layer 73 and the magnetization direction 75 A of the magnetization free layer 75. Are the same and parallel to each other, and the magnetoresistance is minimized. When the magnetization direction 73A of the magnetization fixed layer 73 and the magnetization direction 75A of the magnetization free layer 75 are opposite and parallel, the magnetoresistance is maximized. A sense current is supplied to the magnetoresistive element 51 from the printed wiring board 52, and a change in the magnetoresistance of the magnetoresistive element 51 is detected as a change in the output voltage. The magnetic field direction of the external magnetic field 90 attracted from the magnet 53 to the rolling element 40 changes according to the position of the rolling element 40 that moves linearly along the guide groove 61. Since the rolling element 40 moves in a linear direction along the guide groove 61 while rolling the spiral rolling groove 31 when the rotating shaft 20 rotates, the position of the rolling element 40 and the rotation angle of the rotating shaft 20 are different from each other. , One-to-one correspondence. The output voltage of the magnetoresistive effect element 51 is signal-processed as a detection signal including information on the rotation angle of the rotating shaft 20.

  FIG. 4 shows a graph of the detection signal 101 output from the magnetoresistive effect element 51. In the figure, the horizontal axis indicates the rotation angle of the rotary shaft 20, and the vertical axis indicates the output voltage of the magnetoresistive element 51. Further, -θmax indicates the lower limit of the angle detection range, and θmax indicates the upper limit of the angle detection range. The output voltage of the magnetoresistive element 51 increases and decreases linearly according to the rotation angle of the rotating shaft 20. The signal processing circuit 80 holds a data table (or function) indicating the correspondence between the rotation angle of the rotating shaft 20 and the output voltage of the magnetoresistive element 51 in a memory (not shown), and the magnetoresistive element The rotation angle of the rotating shaft 20 is calculated by comparing the output voltage 51 and the data table (or function).

  In the sensor configuration described above, the magnetization direction 73A of the magnetization fixed layer 73 is preferably substantially parallel to the moving direction 62 (see FIG. 1) of the rolling element 40. Thereby, the fluctuation width in the magnetic field direction of the external magnetic field 90 accompanying the movement of the rolling element 40 (the angle of the external magnetic field 90 corresponding to the minimum angle of the rotating shaft 20 and the angle of the external magnetic field 90 corresponding to the maximum angle of the rotating shaft 20) The detection resolution of the angle sensor 11 can be improved. Further, as shown in FIG. 1, the moving direction 62 of the rolling element 40 is a direction passing through a position shifted by a predetermined distance ΔX with respect to the radial direction 32 passing through the rotation center 21 of the rotation shaft 20, and the rotation center 21. It is preferable to adjust in a direction different from the direction toward the center (rotation center direction). In other words, the moving direction 62 of the rolling element 40 corresponds to the moving distance L of the rolling element 40 when the rotating shaft 20 rotates (the position of the rolling element 40 corresponding to the minimum angle of the rotating shaft 20 and the maximum angle of the rotating shaft 20). It is preferable to adjust in a direction passing through two points on the rotor 30 so that the difference between the rolling element 40 and the position of the rolling element 40 is longer than the radius of the rotor 30. Thereby, since the moving distance L of the rolling element 40 can be increased, the detection resolution of the angle sensor 11 can be improved.

  In the above description, the moving path of the rolling element 40 guided by the guide groove 61 is exemplified as a straight line. However, for example, as illustrated in FIG. 7, the moving path of the rolling element 40 guided by the guide groove 61. The guide groove 61 may be formed so that 63 is a line segment connecting the start point 31A and the end point 31B of the rolling groove 31 (which may be a straight line, a curve, or a combination of a straight line and a curve). As a result, the angle detection resolution can be maximized. Further, when the magnetization direction 73A of the magnetization fixed layer 73 of the magnetoresistive effect element 51 is orthogonal to the moving direction 41 of the rolling element 40, the sensitivity of the magnetic sensor 50 is reduced, so that the magnetization direction 73A of the magnetization fixed layer 73 is the rolling element. A direction in a plane including 40 moving directions 41 and a direction orthogonal to the moving direction 41 (except for a direction orthogonal to the moving direction 41) is preferable. The magnetic field direction 91 of the magnetic field 90 is preferably a direction substantially orthogonal to the moving direction of the rolling element 40. Note that, for convenience of explanation, FIG. 7 omits the illustration of the groove width of the rolling groove 31 and is illustrated as a spiral curve.

  Further, as shown in FIGS. 5 and 6, a plurality of rolling elements 40 may be moved along the guide groove 61 of the guide member 60. For example, FIG. 5 shows a case where one rolling element 40 rolls in each of two adjacent grooves 31 and a total of two rolling elements 40 move along the guide groove 61. FIG. 6 shows a case where two moving bodies 40 roll in two adjacent grooves 31 respectively, and a total of four rolling bodies 40 move along the guide grooves 61. With such a configuration, the strength of the external magnetic field 90 attracted by the plurality of rolling elements 40 increases, so that the detection resolution of the angle sensor 11 is improved.

  According to the angle sensor 11 according to the present embodiment, since the multi-rotation absolute angle of the rotation shaft 20 can be detected by one magnetic sensor 50, the rotation shaft 20 of the rotation shaft 20 is separated from the sensor for detecting the rotation angle of the rotation shaft 20. There is no need to provide a sensor for detecting the number of rotations, which is excellent in convenience. Further, unlike the prior art, a magnet for attracting the magnetic fluid in the radial direction of the steering shaft is not required, so that highly accurate angle detection is possible.

  In addition, by attaching the angle sensor 11 to each of the input shaft and the output shaft of the torsion bar, the shaft torque of the torsion bar can be obtained from the phase difference between the rotation angle of the input shaft and the rotation angle of the output shaft.

  Next, the configuration of the angle sensor 12 according to the present embodiment will be described with reference to FIGS. 8 is a plan view of the angle sensor 12, FIG. 9 is a partial cross-sectional view taken along line 9-9 in FIG. 8, and FIG. 10 is a partial cross-sectional view taken along line 10-10 in FIG. However, for convenience of explanation, in FIG. 8, the magnetic sensors 50A and 50B are perspective views, the guide member 60A is perspective view in FIG. 9, and the guide member 60B is perspective view in FIG. As shown in FIGS. 8 to 10, the angle sensor 12 includes a rotor 30 having a closed curved rolling groove 33, rolling elements 40 </ b> A and 40 </ b> B that roll in the rolling groove 33, and a linear relationship between the rolling elements 40 </ b> A. A guide member 60A having a guide groove 61A for guiding the moving direction, a guide member 60B having a guide groove 61B for guiding the linear moving direction of the rolling element 40B, and a magnetic field 90A that changes according to the position of the rolling element 40A. A magnetic sensor 50A that detects and outputs a detection signal corresponding to the position of the rolling element 40A and a magnetic field 90B that changes according to the position of the rolling element 40B are detected, and a detection signal that corresponds to the position of the rolling element 40B is output. A magnetic sensor 50B and a signal processing circuit 80 that calculates the rotation angle of the rotary shaft 20 based on detection signals output from the magnetic sensors 50A and 50B, respectively. The rotor 30 is a rotating plate that rotates in conjunction with the rotation of the rotary shaft 20, and a rolling groove 33 having a substantially constant groove depth and groove width is formed in a closed curve on its main surface. The guide grooves 61A and 61B do not necessarily have to be straight lines but may be curved lines. By making the guide grooves 61A and 61B curved, it is possible to earn a moving distance and improve the accuracy of rotation angle detection. In the present embodiment, the closed groove forming the contour of the rolling groove 33 is exemplified by a circle centered on the point 21 eccentric from the point 34, but is not limited thereto. The closed curve condition will be described later. In addition, when the planar shape of the rotor 30 is a circle or a point-symmetric shape with the point 34 as the center, the center of the rotor 30 is preferably arranged coaxially with the rotation center 21.

  The configuration of the magnetic sensors 50A and 50B is the same as the configuration of the magnetic sensor 50 of the first embodiment, and detailed description thereof is omitted. The material of the rolling elements 40A and 40B is not particularly limited as long as it is a material having an action of attracting the external magnetic fields 90A and 90B. For example, a ferromagnetic material (iron, cobalt, nickel, etc.) may be used. Or it may be a magnet. The shape of the rolling elements 40A and 90B is not particularly limited as long as it is easy to roll, and for example, a sphere, a cylinder, or the like is suitable.

  The rotor 30 is a rotating plate that rotates in conjunction with the rotation of the rotating shaft 20, and is disposed coaxially with the rotation center 21 of the rotating shaft 20. The guide members 60 </ b> A and 60 </ b> B are arranged with an angle difference ψ with respect to the rotation center 21 of the rotation shaft 20, and the guide grooves 61 </ b> A and 61 </ b> B face the radial direction of the rotation shaft 20. The guide grooves 61A and 61B do not necessarily have to face the radial direction. When the closed curve forming the contour of the rolling groove 33 is an eccentric circle, the rolling elements 40A and 40B periodically repeat repetitive linear motion close to simple vibration along the guide grooves 61A and 61B, respectively, when the rotor 30 rotates. Thereby, the magnetic field directions of the magnetic fields 90A and 90B acting on the magnetic sensors 50A and 50B change periodically in conjunction with the repetitive linear motion of the rolling elements 40A and 40B. The magnetic sensors 50A and 50B have the magnetoresistive effect element 51 shown in FIG. 3, and the change in the magnetic field direction of the magnetic fields 90A and 90B is the magnetoresistive effect element 51 of the magnetic sensors 50A and 50B, respectively. Appears as a change. A sense current is supplied from the printed wiring board 52 to the magnetoresistive effect element 51 of the magnetic sensors 50A and 50B, and the change in the magnetoresistance of the magnetoresistive effect element 51 is detected as a change in the output voltage. The positions of the rolling elements 40A and 40B and the magnetic field directions of the magnetic fields 90A and 90B acting on the magnetic sensors 50A and 50B are associated one-to-one, and the positions of the rolling elements 40A and 40B and the rotation angle of the rotating shaft 20 are a pair. Therefore, the output voltage of the magnetoresistive effect element 51 included in the magnetic sensors 50A and 50B is signal-processed as a detection signal including information on the rotation angle of the rotating shaft 20. Reference numerals 102A and 102B in FIG. 11 indicate output voltages of the magnetic sensors 50A and 50B, respectively. As shown in the figure, since the output voltages 102A and 102B are sinusoidal signals, there are a maximum of two rotation angles of the rotary shaft 20 corresponding to the same voltage value. This is because the position of the rolling element 40A and the rotation angle of the rotating shaft 20 are associated with each other in a one-to-two manner, and the position of the rolling element 40B and the rotation angle of the rotating shaft 20 are associated with each other in a one-to-two manner. Yes. As shown in FIG. 11, when the output voltages 102A and 102B of one cycle are output per rotation of the rotary shaft 20, the output voltages 102A and 102B are adjusted by adjusting the angle difference ψ shown in FIG. 8 to 90 degrees. Can be adjusted to 90 deg. The signal processing circuit 80 stores a data table (or function) indicating the correspondence between the output voltages 102A and 102B of the magnetoresistive effect element 51 of the magnetic sensors 50A and 50B and the rotation angle of the rotary shaft 20 (not shown). And the output voltage 102A, 102B and the data table (or function) are compared, and the rotation angle of the rotating shaft 20 is calculated.

  The closed curve that forms the contour of the rolling groove 33 can include a closed curve excluding a circle that is coaxial with the rotation center 21 of the rotating shaft 20, but the following conditions must be satisfied. First, as a first condition, when the center point of the closed curve is eccentric with respect to the rotation center 21 of the rotating shaft 20, the output voltages 102A and 102B have two maximum and minimum values for each rotation of the rotating shaft 20, respectively. The signal waveform must be less than one and the sign of curvature does not change. For example, when the closed curve forming the contour of the rolling groove 33 has a shape as shown in FIG. 12, the output voltage output from the magnetic sensor 50A has a signal waveform as shown in FIG. The signal waveform as shown in FIG. 13 does not satisfy the first condition described above, and the maximum two voltage values correspond to the same rotation angle, so the rotation angle of the rotating shaft 20 cannot be obtained. Although not shown, the output voltages 102A and 102B output from the magnetic sensors 50A and 50B are constant values over a predetermined angle range (for example, the phase difference between the output voltages 102A and 102B corresponding to the angle difference ψ). Is not preferable because accurate angle detection cannot be performed. Next, as a second condition, the center point of the closed curve is eccentric with respect to the rotation center 21 of the rotating shaft 20, and the output voltages 102 </ b> A and 102 </ b> B are two-cycle signal waveforms per one rotation of the rotating shaft 20. In this case, the closed curve that forms the contour of the rolling groove 33 must be a signal in which the output voltages 102A and 102B output a two-period signal waveform that is asymmetric per rotation of the rotary shaft 20. If the output voltages 102A and 102B output a two-cycle signal waveform that is symmetric with respect to one rotation of the rotating shaft 20, there will be a maximum of four rotation angles of the rotating shaft 20 corresponding to the same voltage value. This is because the rotation angle of the rotary shaft 20 cannot be obtained by the two magnetic sensors 50A and 50B. However, when the output voltages 102A and 102B are signals that output a signal waveform of one cycle per rotation of the rotating shaft 20, the signal waveforms of the output voltages 102A and 102B do not need to be asymmetric.

  As shown in FIG. 14, when the closed curve forming the contour of the rolling groove 33 is point-symmetric with respect to the rotation center 21 of the rotating shaft 20, the output output from the magnetic sensor 50A is shown in FIG. Since the same signal waveform of a plurality of cycles is output for one rotation of the rotating shaft 20, the voltage when the rotation angle of the rotating shaft 20 becomes the reference angle θ0 is set as a threshold voltage, and the output voltage exceeds the threshold voltage Alternatively, the rotation angle of the rotating shaft 20 can be obtained by counting up the rotation angle as θ1, θ2, θ3,. As an example of a point-symmetric closed curve, FIG. 14 shows a hexagon, but it is not limited to this example, and may be an ellipse, a rhombus, or the like.

  The magnetization direction 73A of the magnetization fixed layer 73 included in the magnetoresistive effect element 51 of the magnetic sensor 50A is preferably substantially parallel to the moving direction of the rolling element 40A. Thereby, the fluctuation width in the magnetic field direction of the external magnetic field 90A accompanying the movement of the rolling element 40A can be increased, so that the detection resolution of the angle sensor 12 can be improved. For the same reason, the magnetization direction 73A of the magnetization fixed layer 73 included in the magnetoresistive element 51 of the magnetic sensor 50B is preferably substantially parallel to the moving direction of the rolling element 40B.

  In the first and second embodiments, it is preferable that the distance between the magnetic sensor and the rolling element becomes constant as the rolling element moves. By arranging in this way, the distance between the magnetic sensor and the rolling element becomes constant, so the possibility that the sensitivity of the magnetic sensor varies with the movement of the rolling element can be reduced. That is, the magnetic sensor is arranged according to the device of the guide groove or rolling groove shape.

  In the first and second embodiments, it is preferable that the longitudinal direction of the magnetization free layer 75 of the magnetoresistive effect element 51 and the moving direction of the rolling elements 40, 40A, 40B are orthogonal to each other. Thereby, since the magnetization free layer 75 does not invert in the longitudinal direction and there is no hysteresis, an improvement in angle detection accuracy can be expected.

  In addition, by attaching the angle sensor 12 to each of the input shaft and the output shaft of the torsion bar, the shaft torque of the torsion bar can be obtained from the phase difference between the rotation angle of the input shaft and the rotation angle of the output shaft.

  The angle sensor according to the present invention can be used for detecting the rotation angle of the rotation shaft, detecting the torque based on the rotation angle difference, and the like.

DESCRIPTION OF SYMBOLS 11, 12 ... Angle sensor 20 ... Rotary shaft 30 ... Rotor 31, 33 ... Rolling groove 40, 40A, 40B ... Rolling body 50, 50A, 50B ... Magnetic sensor 51 ... Magnetoresistive effect element 52 ... Printed wiring board 53 ... Magnet 60, 60A, 60B ... guide member 71 ... underlayer 72 ... antiferromagnetic layer 73 ... magnetization fixed layer 74 ... nonmagnetic conductive layer 75 ... magnetization free layer 76 ... protective layer 80 ... signal processing circuits 90, 90A, 90B ... external magnetic field

Claims (13)

A rotor having a rolling groove wound spirally and rotating in conjunction with rotation of the rotation shaft;
A rolling element that rolls in the rolling groove;
A guide member for guiding the moving direction of the rolling element so that the position of the rolling element and the rotation angle of the rotating shaft are associated one-to-one;
A magnetic sensor that detects a magnetic field that changes according to a position of the rolling element, and outputs a detection signal according to the position of the rolling element;
A signal processing circuit for calculating a rotation angle of the rotation shaft based on the detection signal;
An angle sensor comprising: The angle sensor according to claim 1,
The rolling groove is wound more than one turn,
The signal processing circuit is an angle sensor that calculates a multi-rotation absolute angle of the rotation shaft. The angle sensor according to claim 1 or 2,
The magnetic sensor includes a magnetoresistive element including a magnetization fixed layer whose magnetization direction is fixed, and a magnetization free layer whose magnetization direction changes following the action of the magnetic field,
The angle sensor, wherein a magnetization direction of the magnetization fixed layer is substantially parallel to a moving direction of the rolling elements. The angle sensor according to any one of claims 1 to 3,
An angle sensor in which the moving direction of the rolling element is a direction passing through a position shifted by a predetermined distance with respect to a radial direction passing through the rotation center of the rotation shaft and is different from the rotation center direction. The angle sensor according to any one of claims 1 to 4,
An angle sensor in which a distance between the rolling element and the magnetic sensor is constant. The angle sensor according to any one of claims 1 to 5,
The angle sensor, wherein the rolling element is a magnet. A rotor having a closed-curved rolling groove and rotating in conjunction with the rotation of the rotating shaft;
First and second rolling elements that roll in the rolling groove;
A first guide member for guiding the moving direction of the first rolling element so that the position of the first rolling element and the rotation angle of the rotating shaft are associated with each other in a one-to-two manner;
A second guide member for guiding the moving direction of the second rolling element such that the position of the second rolling element and the rotation angle of the rotating shaft are associated with each other in a one-to-two manner;
A first magnetic sensor that detects a first magnetic field that changes according to a position of the first rolling element and outputs a first detection signal according to the position of the first rolling element;
A second magnetic sensor that detects a second magnetic field that changes according to the position of the second rolling element and outputs a second detection signal according to the position of the second rolling element;
A signal processing circuit for calculating a rotation angle of the rotating shaft based on the first and second detection signals;
An angle sensor comprising: The angle sensor according to claim 7,
The angle sensor, wherein the closed curve is a closed curve excluding a circle coaxial with the rotation center of the rotation axis. The angle sensor according to claim 7 or 8,
An angle sensor in which the moving direction of the rolling element is a direction passing through a position shifted by a predetermined distance with respect to a radial direction passing through the rotation center of the rotation shaft and is different from the rotation center direction. An angle sensor according to any one of claims 7 to 9,
An angle sensor in which a distance between the rolling element and the magnetic sensor is constant. The angle sensor according to claim 7,
The angle sensor, wherein the closed curve is adjusted so that the first and second detection signals are signals that output a signal waveform of one cycle or an asymmetric two-cycle signal waveform for one rotation of the rotating shaft. The angle sensor according to any one of claims 7 to 11,
The first magnetic sensor includes a first magnetization fixed layer whose magnetization direction is fixed, and a first magnetization free layer whose magnetization direction changes following the action of the first magnetic field. Including a magnetoresistive effect element,
The magnetization direction of the first magnetization fixed layer is substantially parallel to the moving direction of the first rolling element,
The second magnetic sensor includes a second magnetization fixed layer in which a magnetization direction is fixed, and a second magnetization free layer in which the magnetization direction changes following the action of the second magnetic field. Including a magnetoresistive effect element,
The angle sensor, wherein a magnetization direction of the second magnetization fixed layer is substantially parallel to a moving direction of the second rolling element. An angle sensor according to any one of claims 7 to 12,
The angle sensor, wherein the first and second rolling elements are magnets.

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