Rotation angle sensor

Abstract

This rotation angle sensor (1) comprises a rotor (2) which is provided to an end part of a shaft (6) that rotates about a rotational axis and that extends in the axial direction of the rotational axis, and which has three or more protruding parts (2a) protruding in the radial direction, a non-rotating permanent magnet (3) which is provided so as to be spaced apart from the rotor (2), and a chip (4) which is adjacent to and spaced apart from the rotor (2) and the permanent magnet (3) and which has a bridge circuit comprising four or more magnetoresistive elements (5), wherein: the magnetoresistive elements (5) are all arranged side by side in the circumferential direction on one side of the rotor (2), the one side being reverse of the shaft (6) side, and on the inward side in the radial direction of the ends of the protruding parts (2a) in the radial direction; the chip (4) is provided in parallel with the rotor (2) at a portion on the one side of the rotor (2); the direction of the magnetic field vector applied to each of the magnetoresistive elements (5) by the permanent magnet (3) is the radial direction; and the size of the magnetic field vector is uniform.

Description

Rotation angle sensor

[0001] This disclosure relates to a rotation angle sensor.

[0002] Rotation angle detection devices and methods that utilize changes in magnetic field strength or magnetic field direction are known (see, for example, Patent Documents 1 to 4). Generally, changes in the magnetic field are provided by the rotation of a rotor made of a magnetic material or permanent magnet attached to a rotating shaft such as a motor shaft. Magnetoelectric conversion elements are often used to detect changes in the magnetic field. Magnetoelectric conversion elements include Hall elements, AMR (Anisotropic magnetoresistance) elements, GMR (Giant magnetoresistance) elements, and TMR (Tunnel magnetoresistance) elements. AMR elements, GMR elements, and TMR elements are magnetoresistive elements. A magnetoresistive element is an element whose resistance value changes according to the strength of the applied magnetic field. For example, the rotation angle of the rotor can be obtained by calculating based on the voltage value obtained by the resistance change of the magnetoresistive element.

[0003] Patent Document 1 describes a rotation detection device comprising a bias magnet that generates a bias magnetic field toward a rotating gear-shaped gear, and first and second magnetoresistive element bridges arranged on an IC chip that detect changes in the bias magnetic field. The rotation state of the gear is detected based on the output potential of the first and second magnetoresistive element bridges. Patent Document 2 describes a rotation angle detection device comprising a rotor made of a magnetic material, and a stator having one bias magnetic field generating unit and a plurality of magnetic detection elements. The configurations of Patent Document 1 and Patent Document 2 are basically the same.

[0004] Patent Document 3 describes a rotation angle detection device comprising: first and second magnetoelectric conversion elements provided on a sensor chip for detecting a magnetic field horizontal to the surface of the sensor chip; and a bipolar magnet having a magnetization direction parallel to the surface of the sensor chip and rotating around a rotation axis perpendicular to the surface of the sensor chip. The rotation angle of the magnet is calculated using sinusoidal signals with different phases output from the first and second magnetoelectric conversion elements.

[0005] Patent Document 4 describes a rotation angle detection device comprising: a disc vertically mounted concentrically on the rotation axis; n pairs of magnetic poles arranged concentrically and at equal intervals on the surface of the disc; more than n pairs of magnetic poles arranged at equal intervals on the circumferential surface of the disc; n magnetic detection elements that detect the magnetic poles such that the phases of the electric angles formed by the n pairs of magnetic poles are equal angles apart; and a plurality of magnetic detection elements that detect the magnetic poles such that the phases of the electric angles formed by the magnetic poles on the circumferential surface are predetermined to be different. The rotation angle of the rotation axis is detected based on the detection signals output by each of the plurality of magnetic detection elements and the n magnetic detection elements. Patent Document 4 improves the accuracy of rotation angle detection by using a multi-pole magnet.

[0006] Japanese Patent Publication No. 3506078, Japanese Patent Publication No. 6997098, Japanese Unexamined Patent Publication No. 2013-2835, Japanese Unexamined Patent Publication No. 2001-343206

[0007] In the above-mentioned Patent Documents 1 and 2, a magnetoresistive element is placed on the radially outer side of the rotor to detect rotation. However, when a magnetoresistive element is placed around the rotating shaft in this way, there is a problem in that the accuracy of rotation angle detection decreases due to interference between the magnetic field generated by the motor connected to the rotating shaft and the detected magnetic field. In addition, depending on the motor, other components may be placed around the rotating shaft, which can cause interference between the placement of the sensor and other components.

[0008] In the above-mentioned Patent Document 3, a bipolar magnet is placed at the end of a rotating shaft and rotated, and a direction-sensing magnetoresistive element is placed opposite the magnet to detect the rotation angle of the magnet. However, when the magnet is rotated in this way, the number of poles to be detected is limited to the number of poles of the magnet, which presents a problem in that the accuracy of rotation angle detection is limited with a typical bipolar magnet.

[0009] In the above-mentioned Patent Document 4, a multi-pole magnet is rotated to improve the accuracy of rotation angle detection. However, high-precision multi-pole magnets tend to be relatively expensive due to the difficulty of manufacturing them. Furthermore, attaching the magnet to the shaft with high positional accuracy is not easy because an attractive force acts between the magnet and the shaft. If there is an attachment error between the magnet and the shaft, the magnetic field applied to each magnetoresistive element becomes uneven, which reduces the effectiveness of the correction by the bridge circuit made up of magnetoresistive elements, resulting in a problem of reduced accuracy in detecting the rotation angle.

[0010] Furthermore, rotation angle sensors using magnetoresistive elements have the challenge of difficult high-precision angle detection because their output signals contain harmonics. The harmonics in the output signal are due to the magnetic field generated by the rotation of the rotor having harmonics, and the magnetoresistive characteristics of the magnetoresistive element having higher-order components. The harmonic components that reduce detection accuracy can be suppressed by using a bridge circuit consisting of multiple magnetoresistive elements. However, in order to obtain a sufficient suppression effect, each magnetoresistive element constituting the bridge circuit needs to output a uniform signal. As described in Patent Documents 1 and 2 above, when the magnetoresistive elements are arranged perpendicular to the rotor, the angle of the magnetic field vector applied to the magnetoresistive elements becomes relatively uniform, but as mentioned above, the arrangement of the sensor and other components interferes with each other.

[0011] Therefore, the purpose of this disclosure is to obtain a high-precision rotation angle sensor.

[0012] The rotation angle sensor of this disclosure comprises a rotor that rotates about a rotation axis and is provided at the end of a shaft extending in the axial direction of the rotation axis, and having three or more radially protruding protrusions; a non-rotating permanent magnet provided at a distance from the rotor; and a chip adjacent to the rotor and the permanent magnet at a distance from each other, having a bridge circuit consisting of four or more magnetoresistive elements, wherein each of the magnetoresistive elements is arranged circumferentially on one side of the rotor opposite to the side of the shaft, radially inward from the radial ends of the protrusions, and the chip is provided on the portion of the rotor on that one side parallel to the rotor, and the direction of the magnetic field vector applied to each of the magnetoresistive elements by the permanent magnet is radial, and the magnitude of the magnetic field vector is uniform.

[0013] The rotation angle sensor of this disclosure comprises a rotor that rotates around a rotation axis and is provided at the end of a shaft extending in the axial direction of the rotation axis, having three or more radially protruding protrusions; a non-rotating permanent magnet provided at a distance from the rotor; and a chip adjacent to the rotor and permanent magnet at a distance from the rotor and permanent magnet, having a bridge circuit consisting of four or more magnetoresistive elements. Each of the magnetoresistive elements is arranged circumferentially on one side of the rotor opposite to the side of the shaft, radially inward from the radial ends of the protrusions. The chip is provided on one side of the rotor, parallel to the rotor. The direction of the magnetic field vector applied to each of the magnetoresistive elements by the permanent magnet is radial, and the magnitude of the magnetic field vector is uniform, so the magnetic field applied to the magnetoresistive elements becomes uniform, and the output from each magnetoresistive element can be made uniform. Because the output from the magnetoresistive elements becomes uniform, the harmonic cancellation effect of the bridge circuit can be maximized, and a high-precision rotation angle sensor can be obtained. Furthermore, since the magnetoresistive element is positioned on one side of the rotor opposite to the rotor shaft, the influence of the magnetic field from the motor or other components on the rotor shaft side on the magnetoresistive element is reduced, thus suppressing a decrease in the accuracy of rotation angle detection due to external magnetic fields from the motor or other components. In addition, since the permanent magnet is not directly attached to the shaft of the magnetic material that attracts the permanent magnet, the permanent magnet can be attached with high positional accuracy, and the magnetic field applied to each magnetoresistive element can be made uniform, resulting in a highly accurate rotation angle sensor.

[0014] This is a schematic perspective view of the rotation angle sensor according to Embodiment 1. This is a schematic plan view of the rotation angle sensor according to Embodiment 1. This is a schematic side view of the rotation angle sensor according to Embodiment 1. This is a schematic plan view of the main part of another rotation angle sensor according to Embodiment 1. This is a diagram showing an example of the magnetoresistance characteristics of a GMR element. This is a diagram showing an example of the magnetoresistance characteristics of a GMR element to which a central magnetic field is applied. This is a schematic diagram showing a magnetoresistance element provided on the tip of the rotation angle sensor according to Embodiment 1. This is a schematic perspective view of a rotation angle sensor of a comparative example. This is a diagram showing the magnetic field vector applied to the tip of the rotation angle sensor in Figure 8. This is a diagram showing the magnetic field strength applied to the tip of the rotation angle sensor in Figure 8 with respect to the rotor angle. This is a schematic perspective view of another rotation angle sensor of a comparative example. This is a schematic diagram showing a magnetoresistance element provided on the tip of the rotation angle sensor according to Embodiment 2. This is a schematic perspective view of the rotation angle sensor according to Embodiment 3. This is a schematic plan view of the rotation angle sensor according to Embodiment 3. This is a schematic side view of the rotation angle sensor according to Embodiment 3. This is a schematic plan view showing the main parts of another rotation angle sensor according to Embodiment 3. This is a schematic perspective view showing a rotation angle sensor according to Embodiment 4. This is a schematic plan view showing a rotation angle sensor according to Embodiment 4. This is a schematic side view showing a rotation angle sensor according to Embodiment 4. This is a schematic plan view showing the main parts of another rotation angle sensor according to Embodiment 4. This is a schematic side view showing the mounting error of the permanent magnet of the rotation angle sensor according to Embodiment 4. This is a diagram showing the central magnetic field with respect to the mounting error of the rotation angle sensor according to Embodiment 4. This is a diagram showing the amplitude of the magnetic field with respect to the mounting error of the rotation angle sensor according to Embodiment 4. This is a schematic perspective view showing a rotation angle sensor according to Embodiment 5. This is a schematic perspective view showing the rotor of the rotation angle sensor according to Embodiment 5. This is a schematic plan view showing a rotation angle sensor according to Embodiment 5. This is a schematic side view showing a rotation angle sensor according to Embodiment 5. This is a schematic diagram showing a magnetoresistive element provided on the chip of the rotation angle sensor according to Embodiment 6. This is a diagram showing the connection configuration of the magnetoresistive element provided on the chip of the rotation angle sensor according to Embodiment 6.This figure schematically shows the magnetoresistive element provided on the chip of the rotation angle sensor according to Embodiment 7. This figure shows the connection configuration of the magnetoresistive element provided on the chip of the rotation angle sensor according to Embodiment 7.

[0015] The rotation angle sensor according to the embodiments of this disclosure will be described below with reference to the figures. In each figure, the same or equivalent members and parts will be denoted by the same reference numerals.

[0016] Embodiment 1. Figure 1 is a schematic perspective view of the rotation angle sensor 1 according to Embodiment 1, Figure 2 is a schematic plan view of the rotation angle sensor 1, Figure 3 is a schematic side view of the rotation angle sensor 1 with the addition of a fixing body 7 for fixing the permanent magnet 3, Figure 4 is a schematic plan view of the main parts of another rotation angle sensor 1 according to Embodiment 1, showing the permanent magnet 3 and the chip 4, Figure 5 is a diagram showing an example of the magnetoresistance characteristics of a GMR element, Figure 6 is a diagram showing an example of the magnetoresistance characteristics of a GMR element with a central magnetic field applied, and Figure 7 is a diagram showing a schematic of the magnetoresistance element 5 provided on the chip 4 of the rotation angle sensor 1 according to Embodiment 1. The rotation angle sensor 1 is a sensor that is attached to a shaft of a motor or the like and detects the rotation angle of the rotating shaft. The following describes an example in which the rotation angle sensor 1 is attached to the shaft 6 of a motor, but the location where the rotation angle sensor 1 is attached is not limited to the shaft 6 of a motor. Hereinafter, the axial direction of a cylindrical shaft 6 that rotates around a rotation axis will be referred to as the axial direction, the circumferential direction of the shaft 6 as the circumferential direction, and the radial direction of the shaft 6 as the radial direction. In the figure, the radial direction is denoted by arrow X, with arrow X1 indicating the inside of the radial direction and arrow X2 indicating the outside of the radial direction. The axial direction is denoted by arrow Y, with arrow Y1 indicating one side of the axial direction and arrow Y2 indicating the other side of the axial direction.

[0017] <Rotation Angle Sensor 1> As shown in Figure 1, the rotation angle sensor 1 comprises a rotor 2, a permanent magnet 3, and a tip 4. The rotor 2 is mounted at the end of a shaft 6 that extends in the axial direction of the rotation axis and rotates around the rotation axis, and has three or more radially protruding protrusions 2a. The rotor 2 is made of a so-called soft magnetic material, not a magnet such as an electromagnetic steel sheet containing iron, cobalt, nickel, etc., and has magnetic collecting properties, influencing the surrounding magnetic field. The permanent magnet 3 is a non-rotating permanent magnet 3 mounted at a distance from the rotor 2. The tip 4 is adjacent to the rotor 2 and permanent magnet 3 at a distance from them and has a bridge circuit consisting of four or more magnetoresistive elements 5 (not shown in Figure 1). In this embodiment, the shaft 6 is cylindrical, and the central axis of the cylinder is the rotation axis. Since the rotor 2 is attached to the shaft 6, the rotor 2 rotates in conjunction with the rotation of the shaft 6. Since the rotor 2 has three or more protrusions 2a, it is composed of three or more poles. In this embodiment, since the application of the rotation angle sensor 1 to a 4-pole motor, which is one of the common motor configurations, an example in which the rotor 2 has four protrusions 2a will be described. In this embodiment, the permanent magnet 3 is positioned on one side in the axial direction of the chip 4, and a magnetic field is applied from the permanent magnet 3 to the magnetoresistive element 5.

[0018] As shown in Figure 2, each of the magnetoresistive elements 5 is arranged circumferentially on one side of the rotor 2 opposite to the shaft 6 side, radially inward from the radial end of the protrusion 2a. As shown in Figure 3, the tip 4 is provided on one side of the rotor 2, parallel to the rotor 2. If the magnetoresistive elements 5 are arranged around the shaft 6, the large magnetic field generated by the motor connected to the shaft 6 will interfere with the magnetic field detected by the magnetoresistive elements 5. When the magnetic field emitted by the motor and the detected magnetic field interfere, the accuracy of rotation angle detection will decrease due to the interference of the magnetic fields. In this embodiment, since the magnetoresistive elements 5 are arranged on one side of the rotor 2 opposite to the shaft 6 side, the influence of the magnetic field caused by the motor on the magnetoresistive elements 5 is reduced, so the decrease in rotation angle detection accuracy due to the external magnetic field caused by the motor can be suppressed. Also, depending on the motor, other components may be arranged around the shaft 6, so if the magnetoresistive elements 5 are arranged around the shaft 6, the arrangement of the magnetoresistive elements 5 and other components will interfere. In this embodiment, the magnetoresistive element 5 is positioned on one side of the rotor 2 opposite to the side with the shaft 6, thus avoiding interference between the magnetoresistive element 5 and other components.

[0019] <Magnetoresistive Element 5> The magnetoresistive element 5 is an element whose resistance value changes according to the strength of the magnetic field applied to it. In this embodiment, a GMR element with a meander shape formed on the magnetoresistive element 5 is used. The magnetoresistive element 5 is not limited to a GMR element, and other magnetoresistive elements may be used. By using a GMR element, it is possible to utilize magnetoresistive characteristics that are more sensitive than those of an AMR element. The magnetoresistive characteristics of a GMR element will be explained using Figure 5. As shown in Figure 5, a GMR element has magnetoresistive characteristics in which the resistance value decreases when a magnetic field is applied. In the region where the applied magnetic field is small, the change in resistance with respect to the change in magnetic field is small. Also, in the region where the applied magnetic field is small, the change in resistance with respect to the change in magnetic field is not linear. Therefore, when using a GMR element as a magnetic sensor, the GMR element is generally used with a constant magnetic field applied to it.

[0020] When a constant magnetic field is applied to a GMR element, for example, a permanent magnet is used to apply the magnetic field to the GMR element. The magnetic field applied to the GMR element by a permanent magnet is called the central magnetic field. The magnetoresistance characteristics of the GMR element when the central magnetic field is applied are explained using Figure 6. When the magnetic field applied to the GMR element fluctuates due to the application of a magnetic field to the GMR element from an external source other than the central magnetic field, or due to the approach of a magnetic material, the resistance of the GMR element changes by the amount of the difference in magnetic field from the central magnetic field. By incorporating the GMR element into an appropriate circuit, a magnetic sensor can be constructed that utilizes the magnetoresistance characteristics of this GMR element.

[0021] A bridge circuit consisting of four or more GMR elements is formed on chip 4. The rotation angle sensor 1 using magnetoresistive elements 5 contains harmonics in its output signal. The harmonics in the output signal are due to the magnetic field generated by the rotation of the rotor 2 having harmonics, and the magnetoresistive characteristics of the magnetoresistive elements 5 having higher-order components. The harmonic components that reduce detection accuracy can be suppressed by using a bridge circuit consisting of multiple magnetoresistive elements 5. In order to obtain a sufficient suppression effect, each magnetoresistive element 5 constituting the bridge circuit needs to output a uniform signal. In addition, external noise can be canceled by using a bridge circuit.

[0022] As the rotor 2 rotates, the magnetic field applied to the GMR element changes. The resistance of the GMR element changes according to the magnetoresistance characteristics shown in Figure 6. The change in the resistance of the GMR element can be read as a voltage signal using a processing circuit consisting of a fixed resistor and an operational amplifier. The rotation angle of the shaft 6 is calculated by performing calculations based on the read voltage signal.

[0023] <Comparative Examples> Before describing the magnetic field vector applied to the magnetoresistive element 5 by the permanent magnet 3, which is the main part of this disclosure, two comparative examples will be described using Figures 8 to 11. Figure 8 is a schematic perspective view of the rotation angle sensor 100 of the comparative example, Figure 9 is a diagram showing the magnetic field vector applied to the chip 4 of the rotation angle sensor 100 of Figure 8 with arrows, and the outline of the permanent magnet 3 superimposed on the chip 4 is shown with a dashed line, Figure 10 is a diagram showing the magnetic field strength applied to the chip 4 of the rotation angle sensor 100 of Figure 8 with respect to the angle of the rotor 2, and Figure 11 is a schematic perspective view of the rotation angle sensor 100 of another comparative example. The configuration of the comparative example shown in Figure 8 differs from that of Figure 1 in the configuration and arrangement of the permanent magnet 3. The configuration of the comparative example shown in Figure 11 differs from that of Figure 8 in the arrangement of the chip 4 and the magnetoresistive element 5.

[0024] In the comparative example in Figure 8, the permanent magnet 3 is a bipolar magnet with different magnetic poles perpendicular to the axial direction. The inner magnetic pole in the radial direction is designated as the south pole 3a, and the outer magnetic pole in the radial direction is designated as the north pole 3b. The permanent magnets 3 are placed at intervals, parallel to the chip 4, on the side of the chip 4 opposite to the rotor 2. In the axial direction, the rotor 2, chip 4, and permanent magnet 3 are arranged in that order. As shown in Figure 9, a magnetic field vector indicated by the arrow is applied to the chip 4. The dashed line shown on the chip 4 is a part of a circle centered on the rotation axis of the rotor 2 and runs along the circumferential direction. The magnetoresistive element 5 is positioned along this dashed line. The locations where the magnetoresistive element 5 is placed are, for example, locations A and B in Figure 9.

[0025] As can be seen from Figure 9, the direction of the magnetic field vector applied to the magnetoresistive element 5 and the direction of the rotation center at the position of the magnetoresistive element 5 are non-uniform. In Figure 10, the magnetic field strength at points A and B in Figure 9 is shown with respect to the angle of the rotor 2. Because the direction of the magnetic field vector and the direction of the rotation center at the position of the magnetoresistive element 5 are non-uniform, the magnetic field strength at points A and B is also non-uniform. Therefore, the output from the magnetoresistive elements 5 placed at points A and B becomes non-uniform, and the effect of the bridge circuit in suppressing harmonic components that reduce detection accuracy is reduced.

[0026] In the second comparative example shown in Figure 11, the chip 4 and magnetoresistive element 5 are positioned perpendicular to the rotor 2, and the surface of the chip 4 on which the magnetoresistive element 5 is mounted faces radially when viewed in the axial direction. This configuration makes it possible to make the direction of the magnetic field vector and the direction of the rotation center at the position of the magnetoresistive element 5 relatively uniform. Because the direction of the magnetic field vector and the direction of the rotation center at the position of the magnetoresistive element 5 are relatively uniform, the output from the magnetoresistive element 5 can be made uniform. However, because it is necessary to position the magnetoresistive element 5 perpendicular to the permanent magnet 3, the structure becomes complex, especially when multiple elements are required, which increases the cost of the rotation angle sensor 1 and reduces its productivity.

[0027] In this embodiment shown in Figure 1, the chip 4 is provided parallel to the rotor 2 on one side of the rotor 2, as described above. The arrangement of the chip 4 is the same as that of the comparative example shown in Figure 8. However, the configuration and arrangement of the permanent magnet 3 are different from those shown in Figure 8. Therefore, although the details will be described later, even with the same arrangement of the chip 4 as in Figure 8, the direction of the magnetic field vector and the direction of the rotation center at the position of the magnetoresistive element 5 become uniform, so the output from the magnetoresistive element 5 can be made uniform. Since the magnetoresistive element 5 is arranged parallel to the rotor 2 and does not become a complex arrangement like in Figure 11, multiple magnetoresistive elements 5 can be arranged on one side of the rotor 2 with a relatively simple structure.

[0028] <Permanent Magnet 3> The configuration and arrangement of the permanent magnet 3 in this embodiment will be described. In this embodiment, the shape of the permanent magnet 3 is a cylinder, or a cylindrical portion that is cut out from a cylinder with a sector formed at a predetermined central angle on the base of the cylinder. The permanent magnet 3 shown in Figures 1 to 3 is a cylinder, and the permanent magnet 3 shown in Figure 4 is a cylindrical portion. The cylinder and the cylindrical portion are bipolar magnets having different magnetic poles in the height direction of the cylinder and the cylindrical portion. In this embodiment, one side of the permanent magnet 3 in the axial direction is the south pole 3a and the other side in the axial direction is the north pole 3b, but it is not limited to this, and the permanent magnet 3 may have a configuration with opposite magnetic poles.

[0029] The cylinder and cylindrical portion are positioned on one side of the rotor 2 such that the direction of height at the center of the base of the cylinder and at the vertex of the central angle of the base of the cylindrical portion coincides with the axial direction of the rotation axis. In the rotation angle sensor 1 of this embodiment, the rotor 2, tip 4, and permanent magnet 3 are arranged in the axial direction in the order of rotor 2, tip 4, and permanent magnet 3.

[0030] The configuration of the magnetic field vector based on the arrangement of the parts described above will now be explained. For each of the GMR elements, which are magnetoresistive elements 5, the direction of the magnetic field vector applied by the permanent magnet 3 is radial, and the magnitude of the magnetic field vector is uniform. Because the direction of the magnetic field vector applied by the permanent magnet 3 to each of the GMR elements is radial, and the magnitude of the magnetic field vector is uniform, the direction of the magnetic field vector and the direction of the rotation center at the position of the GMR element become uniform, and the magnetic field applied to the GMR elements becomes uniform, so that the output from each GMR element can be made uniform. Because the output from the GMR elements becomes uniform, the harmonic cancellation effect by the bridge circuit can be maximized, so that a high-precision rotation angle sensor 1 can be obtained.

[0031] The configuration and arrangement of the permanent magnets 3 that direct the magnetic field vector radially and uniformly for each magnetoresistive element 5 are not limited to the configurations shown in Figure 1 or Figure 4. Configurations and arrangements of the permanent magnets 3 different from those in Figure 1 or Figure 4 will be described in other embodiments later. As in this embodiment, by making the permanent magnet 3 a cylinder or a cylindrical portion and arranging the cylinder or cylindrical portion as described above, it is possible to direct the magnetic field vector radially and uniformly for each magnetoresistive element 5 with a simple configuration. Furthermore, since a bipolar magnet is used for the permanent magnet 3, an expensive multipolar magnet is not required, thus reducing the cost of the rotation angle sensor 1. When the permanent magnet 3 is a cylindrical portion, the permanent magnet 3 can be miniaturized. Even when the permanent magnet 3 is a cylindrical portion, by making the circumferential length of the cylindrical portion larger than the length perpendicular to the radial direction of the chip 4 when viewed in the axial direction, it is possible to direct the magnetic field vector radially and uniformly for each magnetoresistive element 5.

[0032] In this embodiment, as shown in Figure 3, the permanent magnet 3 is housed inside the sensor housing 8 together with the chip 4. The sensor housing 8 is made of, for example, resin and is fixed to a fixed body 7 provided on the outside. The fixed body 7 is made of, for example, a non-magnetic material such as aluminum and is fixed to a motor housing (not shown) that houses a motor. The location where the sensor housing 8 is fixed is not limited to the fixed body 7; it may also be fixed directly to the motor housing that houses the motor. In this embodiment, the permanent magnet 3 is housed inside the sensor housing 8 and is modularized as a rotation angle sensor 1, and the permanent magnet 3 is not directly attached to the shaft 6 of the magnetic material that attracts the permanent magnet 3. Compared to a configuration in which the permanent magnet 3 is directly attached to the shaft 6, the attachment of the sensor housing 8 including the permanent magnet 3 to the fixed body 7 is relatively easy. Therefore, the permanent magnet 3 can be easily attached with higher positional accuracy than in a configuration in which the permanent magnet 3 is directly attached to the shaft 6, so that the magnetic field applied to each of the magnetoresistive elements 5 can be made more uniform. Since the magnetic field applied to each of the magnetoresistive elements 5 becomes more uniform, an even more accurate rotation angle sensor 1 can be obtained.

[0033] <Detection of Rotation Angle> The detection of the rotation angle will be explained below. The resistance value of the GMR element changes periodically as the four protrusions 2a move due to the rotation of the rotor 2. Therefore, one period of mechanical rotation of the four-pole rotor 2 corresponds to a change of four periods of the resistance value. The mechanical rotation angle of the shaft 6 is called the mechanical angle, and the angle where the angle of one period of the resistance value is 360° is called the electrical angle. When the rotor 2 has four poles, the electrical angle is four times the mechanical angle. Hereafter, the mechanical angle will be denoted as (m) and the electrical angle as (e). For example, if the electrical angle is 90°, it will be denoted as 90°(e).

[0034] In this embodiment, the rotor 2 is made multi-pole by providing multiple protrusions 2a. In a configuration where permanent magnets are placed on the shaft 6, a multi-pole permanent magnet is required to increase the number of poles. High-precision multi-pole permanent magnets are difficult to manufacture and are relatively expensive. Furthermore, attaching the permanent magnet to the shaft 6 with high positional accuracy is not easy because an attractive force acts between the permanent magnet and the shaft 6. In this embodiment, since the rotor is made multi-pole by multiple protrusions 2a, the number of poles depends on the number of poles of the rotor 2, so it can be made multi-pole relatively easily.

[0035] In this embodiment, the mechanical angle is not calculated directly, but the electrical angle is calculated. Generally, the electrical angle is calculated using the arctangent from two output signals with a phase difference of 90°. In this case, the two GMR elements are positioned relative to each other at a mechanical angle of 22.5° (m) around the axis of rotation. With this arrangement, when the rotor 2 rotates, the signals from the two GMR elements have a phase difference of 90° (e) in electrical angle. It is assumed that the output signals of each GMR element are ideal sine waves with equal amplitude. The two GMR elements are designated as S_R1 as the GMR element corresponding to sin and C_R1 as the GMR element corresponding to cos, and their respective phases are θ S_R1 , θ C_R1 Let's assume that the initial position of the GMR element S_R1 is the reference position, and the electrical angle θe of the rotor 2 is expressed by Equation 1. As shown in Equation 1, the electrical angle can be obtained based on the output signals from each of the two GMR elements.

[0036] In this embodiment, in addition to the two GMR elements described above, further GMR elements are provided to form a bridge circuit. In a configuration where a half-bridge is formed for each GMR element, the total number of GMR elements becomes four. Figure 7 shows an example of a bridge circuit configuration in which four GMR elements are arranged on the chip 4. The four GMR elements are S_R1, S_R2, C_R1, and C_R2. The four GMR elements are positioned along a part of the circle centered on the rotation axis of the rotor 2, that is, along the circumferential direction, when viewed in the axial direction. By arranging the four GMR elements in this way, the magnetic field applied to each of the magnetoresistive elements 5 can be made uniform. Note that Figure 7 is a schematic diagram showing the arrangement of the four GMR elements. Since the chip 4 is smaller than the size relationship between the chip 4 and the rotor 2 shown schematicly in Figure 2, the vertical arrangement of each of the four GMR elements in Figure 7 does not change as much as shown in Figure 7.

[0037] In a typical bridge circuit configuration, GMR elements positioned 180° apart in phase are connected in series, and the midpoint potential is obtained as the signal output. In this configuration, the two GMR elements constituting the bridge circuit are positioned at a relative mechanical angle of 45° (m) around the axis of rotation. In the configuration shown in Figure 7, S_R1 and S_R2 are connected in series, and C_R1 and C_R2 are connected in series. In the figure, the connection between S_R1 and S_R2 is shown by a solid line, and the connection between C_R1 and C_R2 is shown by a dashed line. The midpoint potential of S_R1 and S_R2 is output, and the midpoint potential of C_R1 and C_R2 is output. In Figure 7, the top of the figure represents the midpoint potential. Note that the bridge circuit configuration is not limited to this, and other arrangements are also possible.

[0038] As described above, the rotation angle sensor 1 according to Embodiment 1 is provided at the end of a shaft 6 that rotates about a rotation axis and extends in the axial direction of the rotation axis, and has three or more protruding portions 2a that protrude in the radial direction. A rotor 2, a non-rotating permanent magnet 3 provided at a distance from the rotor 2, and a chip 4 that is adjacent to the rotor 2 and the permanent magnet 3 at a distance and has a bridge circuit composed of four or more magnetoresistive elements 5. Each of the magnetoresistive elements 5 is arranged in the circumferential direction on the inner side in the radial direction rather than at the radial end of the protruding portion 2a on one side opposite to the side of the shaft 6 of the rotor 2. The chip 4 is provided parallel to the rotor 2 on one side portion of the rotor 2. For each of the magnetoresistive elements 5, the direction of the magnetic field vector applied by the permanent magnet 3 is in the radial direction and the magnitude of the magnetic field vector is uniform. Therefore, the direction of the magnetic field vector is equal to the direction of the center of rotation at the position of the magnetoresistive element 5, and the magnetic field applied to the magnetoresistive element 5 becomes uniform. Thus, the output from each magnetoresistive element 5 can be made uniform. Since the output from each magnetoresistive element 5 is made uniform, the harmonic cancellation effect by the bridge circuit can be maximized, and a rotation angle sensor 1 with high precision can be obtained.

[0039] In addition, since the magnetoresistive element 5 is arranged on one side opposite to the side of the shaft 6 of the rotor 2, the influence of the magnetic field caused by a motor or the like on the side of the shaft 6 of the rotor 2 on the magnetoresistive element 5 is reduced. Therefore, it is possible to suppress a decrease in the detection accuracy of the rotation angle due to an external magnetic field caused by a motor or the like. Also, since the permanent magnet 3 is not directly attached to the shaft 6 of the magnetic material that attracts the permanent magnet 3, the permanent magnet 3 can be attached with high positional accuracy, and the magnetic field applied to each of the magnetoresistive elements 5 can be made more uniform. Thus, a rotation angle sensor 1 with even higher precision can be obtained. Further, since the rotor 2 is multi-polarized by providing a plurality of protruding portions 2a on the rotor 2, the number of poles depends on the number of poles provided on the rotor 2, so it can be multi-polarized relatively easily.

[0040] The shape of the permanent magnet 3 is a cylinder or a cylindrical portion obtained by cutting a cylinder with a sector formed at a predetermined central angle on the bottom surface of the cylinder as the bottom surface. The cylinder and the cylindrical portion are bipolar magnets having different magnetic poles in the height direction of the cylinder and the cylindrical portion. The height directions at the center of the bottom surface of the cylinder and at the apex of the central angle of the bottom surface of the cylindrical portion coincide with the axial direction of the rotation axis. When the cylinder and the cylindrical portion are arranged on one side of the rotor 2 and are arranged in the axial direction in the order of the rotor 2, the chip 4, and the permanent magnet 3, with a simple configuration, for each of the magnetoresistive elements 5, the direction of the magnetic field vector can be made radial and the magnitude of the magnetic field vector can be made uniform. Further, since a bipolar magnet is used for the permanent magnet 3, an expensive multipolar magnet is not required, so the rotation angle sensor 1 can be made less costly.

[0041] Embodiment 2. The rotation angle sensor 1 according to Embodiment 2 will be described. FIG. 12 is a diagram schematically showing the magnetoresistive element 5 provided on the chip 4 of the rotation angle sensor 1 according to Embodiment 2. The rotation angle sensor 1 according to Embodiment 2 has an arrangement of the magnetoresistive elements 5 provided on the chip 4 different from that in Embodiment 1. Since the configuration other than the arrangement of the magnetoresistive elements 5 is the same as that in Embodiment 1, the description other than the arrangement of the magnetoresistive elements 5 is omitted.

[0042] In Embodiment 1, as shown in FIG. 7, the four magnetoresistive elements 5 are arranged side by side in the circumferential direction, and each element is arranged in the same direction as each other. In the present embodiment, the magnetoresistive element 5 is a GMR element in which a meander shape is formed. In the meander shape, the angles formed by the extending directions of the portions that are arranged adjacent to each other and extend in one direction and the direction of the magnetic field vector applied to the center of the GMR element are the same for all the GMR elements. In FIG. 12, the extending direction of the portions that are arranged adjacent to each other and extend in one direction in the meander shape of the GMR element is indicated by an arrow M. The direction of the magnetic field vector applied to the center of the GMR element is indicated by an arrow B. In the present embodiment, the angle formed by the arrow M and the arrow B is 90°. The angle formed by the arrow M and the arrow B is not limited to 90° and may be other angles.

[0043] Generally, intensity-sensing GMR elements without a fixed layer have relatively little sensitivity dependence on the direction of the applied magnetic field, but due to the anisotropy of their shape, sensitivity does become dependent on the direction of the magnetic field. Therefore, by applying the direction of the magnetic field vector at a constant angle to the meander shape of the GMR element, the response of each GMR element to the applied magnetic field, i.e., the resistance change of each GMR element, can be made equal. Since the resistance change of each GMR element becomes equal and the output from each GMR element becomes uniform, the harmonic cancellation effect of the bridge circuit can be maximized. Because the harmonic cancellation effect of the bridge circuit is maximized, a high-precision rotation angle sensor 1 can be obtained.

[0044] Embodiment 3. The rotation angle sensor 1 according to Embodiment 3 will be described. Figure 13 is a schematic perspective view showing the rotation angle sensor 1 according to Embodiment 3, Figure 14 is a schematic plan view showing the rotation angle sensor 1, Figure 15 is a schematic side view showing the rotation angle sensor 1, and Figure 16 is a schematic plan view showing the main parts of another rotation angle sensor 1 according to Embodiment 3, showing the permanent magnet 3 and the chip 4. The rotation angle sensor 1 according to Embodiment 3 differs from Embodiment 1 in the shape of the permanent magnet 3 and the configuration of the magnetic poles.

[0045] In this embodiment, the shape of the permanent magnet 3 is a ring with a circular outer and inner circumference and height in the axial direction, or a ring portion cut out from the ring at a predetermined central angle. The permanent magnet 3 shown in Figures 13 to 15 is a ring, and the permanent magnet 3 shown in Figure 16 is a ring portion. The ring and the ring portion are bipolar magnets having different magnetic poles in the radial direction. In this embodiment, the inner radial side of the permanent magnet 3 is the south pole 3a and the outer radial side is the north pole 3b, but this is not limited to this, and the permanent magnet 3 may have a configuration with opposite magnetic poles.

[0046] The ring and ring portion are positioned on one side of the rotor 2 such that the height direction at the center of the ring and the vertex of the central angle of the ring portion coincides with the axial direction of the rotation axis. As shown in Figure 14, the ring and ring portion overlap with the radially outward projection 2a when viewed in the axial direction. As shown in Figure 15, the rotor 2, tip 4, and permanent magnet 3 are arranged in the axial direction in that order.

[0047] Even if the permanent magnet 3 is composed of a ring and a ring portion, the direction of the magnetic field vector applied by the permanent magnet 3 to each of the GMR elements, which are magnetoresistive elements 5, is radial, and the magnitude of the magnetic field vector is uniform. Because the direction of the magnetic field vector applied by the permanent magnet 3 to each of the GMR elements is radial, and the magnitude of the magnetic field vector is uniform, the direction of the magnetic field vector and the direction of the rotation center at the position of the GMR element become uniform, and the magnetic field applied to the GMR element becomes uniform, so the output from each GMR element can be made uniform. Because the output from the GMR elements becomes uniform, the harmonic cancellation effect by the bridge circuit can be maximized, so a high-precision rotation angle sensor 1 can be obtained.

[0048] By using a ring and a portion of the ring for the permanent magnet 3, radial magnetization of the permanent magnet 3 is facilitated, and the component of the magnetic field applied in the in-plane direction of the chip can be increased. Furthermore, since a bipolar magnet is used for the permanent magnet 3, an expensive multipolar magnet is not required, thus reducing the cost of the rotation angle sensor 1. When the permanent magnet 3 is a portion of the ring, the permanent magnet 3 can be miniaturized. Even when the permanent magnet 3 is a portion of the ring, by making the circumferential length of the ring portion greater than the length perpendicular to the radial direction of the chip 4 when viewed in the axial direction, the direction of the magnetic field vector for each of the magnetoresistive elements 5 can be made radial, and the magnitude of the magnetic field vector can be made uniform.

[0049] Embodiment 4. The rotation angle sensor 1 according to Embodiment 4 will be described. Figure 17 is a schematic perspective view showing the rotation angle sensor 1 according to Embodiment 4, Figure 18 is a schematic plan view showing the rotation angle sensor 1, Figure 19 is a schematic side view showing the rotation angle sensor 1, Figure 20 is a schematic plan view showing the main parts of another rotation angle sensor 1 according to Embodiment 4, showing the permanent magnet 3 and the chip 4, Figures 21(a) and 21(b) are schematic side views showing the mounting error of the permanent magnet 3 of the rotation angle sensor 1, Figure 22 is a diagram showing the central magnetic field with respect to the mounting error of the rotor 2 and the permanent magnet 3 in the rotation angle sensor 1 according to Embodiment 4, and Figure 23 is a diagram showing the amplitude of the magnetic field with respect to the mounting error of the rotor 2 and the permanent magnet 3 in the rotation angle sensor 1 according to Embodiment 4. The rotation angle sensor 1 according to Embodiment 4 differs from Embodiment 1 in the shape and arrangement of the permanent magnet 3.

[0050] In this embodiment, the shape of the permanent magnet 3 is a ring with a circular outer and inner circumference and height in the axial direction, or a ring portion cut out from the ring at a predetermined central angle. The permanent magnet 3 shown in Figures 17 to 19 is a ring, and the permanent magnet 3 shown in Figure 20 is a ring portion. The ring and the ring portion are bipolar magnets having different magnetic poles in the axial direction. In this embodiment, one side of the permanent magnet 3 in the axial direction is the south pole 3a and the other side in the axial direction is the north pole 3b, but this is not limited to this, and the permanent magnet 3 may be configured to have opposite magnetic poles.

[0051] As shown in Figure 18, the ring and ring portion are positioned radially outward from the radial end of the protrusion 2a, such that the height direction at the center of the ring and the vertex of the central angle of the ring portion coincides with the axial direction of the rotation axis. Radially, the ring and ring portion overlap with the rotor 2 in at least part. In the configuration shown in Figure 19, the entire ring overlaps with the rotor 2.

[0052] Even if the permanent magnet 3 is composed of a ring and a portion of the ring, and the permanent magnet 3 is positioned radially outward from the radial end of the protruding portion 2a, the direction of the magnetic field vector applied by the permanent magnet 3 to each of the GMR elements, which are magnetoresistive elements 5, is radial, and the magnitude of the magnetic field vector is uniform. Because the direction of the magnetic field vector applied by the permanent magnet 3 to each of the GMR elements is radial, and the magnitude of the magnetic field vector is uniform, the direction of the magnetic field vector and the direction of the rotation center at the position of the GMR element become uniform, and the magnetic field applied to the GMR elements becomes uniform, so the output from each GMR element can be made uniform. Because the output from the GMR elements becomes uniform, the harmonic cancellation effect by the bridge circuit can be maximized, so a high-precision rotation angle sensor 1 can be obtained.

[0053] In the schematic side views of the mounting errors in Figures 21(a) and 21(b), Figure 21(a) shows the case where the permanent magnet 3 is mounted shifted to one side in the axial direction, or the rotor 2 is mounted shifted to the other side in the axial direction, while Figure 21(b) shows the case where the permanent magnet 3 is mounted shifted to the other side in the axial direction, or the rotor 2 is mounted shifted to one side in the axial direction. In Figure 21(a), the amount of shift Δ is a negative value, and in Figure 21(b), the amount of shift Δ is a positive value. Due to the mounting errors shown in Figures 21(a) and 21(b), a difference may occur between the relative position of the rotor 2 and the permanent magnet 3 in the axial direction and its design value.

[0054] In this embodiment, the permanent magnet 3 is a ring or a portion of a ring, and is positioned radially outward of the rotor 2. With this configuration, as shown in Figures 22 and 23, the central magnetic field and the amplitude of the magnetic field applied to the magnetoresistive element 5 increase or decrease with respect to changes in the relative position of the rotor 2 and the permanent magnet 3 in both positive and negative directions in the axial direction. Therefore, by positioning the permanent magnet 3 as a ring or a portion of a ring radially outward of the rotor 2, a design that is highly robust to mounting errors can be achieved.

[0055] Furthermore, since a bipolar magnet is used for the permanent magnet 3, an expensive multipolar magnet is unnecessary, thus reducing the cost of the rotation angle sensor 1. If the permanent magnet 3 is made into a ring, the permanent magnet 3 can be miniaturized. Even when the permanent magnet 3 is made into a ring, by making the circumferential length of the ring portion larger than the length perpendicular to the radial direction of the chip 4 when viewed in the axial direction, the direction of the magnetic field vector for each of the magnetoresistive elements 5 can be made radial, and the magnitude of the magnetic field vector can be made uniform.

[0056] Embodiment 5. The rotation angle sensor 1 according to Embodiment 5 will be described. Figure 24 is a schematic perspective view showing the rotation angle sensor 1 according to Embodiment 5, Figure 25 is a schematic perspective view showing the rotor 2 of the rotation angle sensor 1 according to Embodiment 5, Figure 26 is a schematic plan view showing the rotation angle sensor 1, and Figure 27 is a schematic side view showing the rotation angle sensor 1. The rotation angle sensor 1 according to Embodiment 5 has a different shape of rotor 2 compared to Embodiment 4.

[0057] In this embodiment, as shown in Figure 25, the rotor 2 further has a disc-shaped stepped portion 2b on the opposite side from the other side, with a side surface 2b1 radially outward from the radial end of the protruding portion 2a. The shape of the permanent magnet 3 in this embodiment is the same as the permanent magnet 3 shown in Embodiment 4, and when viewed in the axial direction, it is a ring with a circular outer circumference and inner circumference and height in the axial direction, or a portion of a ring that is cut out from the ring at a predetermined central angle. The ring and the portion of the ring are bipolar magnets having different magnetic poles in the axial direction.

[0058] As shown in Figure 26, the ring and ring portion are positioned radially outward from the radial end of the protrusion 2a, such that the height direction at the vertex of the central angle of the ring's center and the ring portion coincides with the axial direction of the axis of rotation. As shown in Figure 27, the ring and ring portion overlap with the protrusion 2a in the radial direction, at least in part, and as shown in Figure 26, they overlap with the stepped portion 2b in the axial direction.

[0059] In all embodiments, the magnetoresistive element 5 is positioned on one side of the rotor 2 opposite to the side of the shaft 6. Therefore, the influence of the magnetic field caused by the motor on the shaft 6 side of the rotor 2 on the magnetoresistive element 5 is reduced, and the decrease in the accuracy of rotation angle detection due to the external magnetic field caused by the motor can be suppressed. However, when the rotor 2 rotates, a magnetic field caused by the motor on the shaft 6 side of the rotor 2 may be applied to the magnetoresistive element 5 from the portion between the protrusions 2a. When a magnetic field caused by the motor is applied to the magnetoresistive element 5, the accuracy of rotation angle detection decreases.

[0060] The rotor 2 further has a disc-shaped stepped portion 2b on the opposite side from the other side, with a side surface 2b1 radially outward from the radial end of the protrusion 2a. This prevents the magnetic field caused by the motor on the shaft 6 side of the rotor 2 from being applied to the magnetoresistive element 5 from the portion between the protrusions 2a. Because the magnetic field caused by the motor is prevented from being applied to the magnetoresistive element 5, the accuracy of rotation angle detection can be suppressed.

[0061] Embodiment 6. The rotation angle sensor 1 according to Embodiment 6 will be described. Figure 28 is a schematic diagram showing the magnetoresistive element 5 provided on the chip 4 of the rotation angle sensor 1 according to Embodiment 6, and Figure 29 is a diagram showing the connection configuration of the magnetoresistive element 5 provided on the chip 4 of the rotation angle sensor 1. In the rotation angle sensor 1 according to Embodiment 6, the arrangement of the magnetoresistive element 5 in the bridge circuit is defined. The configuration other than the arrangement of the magnetoresistive element 5 is the same as in Embodiment 1, so the explanation other than the arrangement of the magnetoresistive element 5 will be omitted.

[0062] The bridge circuit has a pair of magnetoresistive elements 5 connected in series, each positioned at a location where the phase difference in electrical angle is 180°. In this embodiment, assuming the application of the rotation angle sensor 1 to a 4-pole motor, the rotor 2 has four protrusions 2a. When using a rotor 2 for 4 poles in this way, the pair of magnetoresistive elements 5 constituting the bridge are positioned at a relative position of 45° (m) mechanical angle with respect to the rotation axis. In Figure 28, S_R1 and S_R2 are connected to the rotation axis by a dashed line, and C_R1 and C_R2 are connected to the rotation axis by a dashed line.

[0063] As shown in Figure 29, S_R1 and S_R2 are a pair of magnetoresistive elements 5 connected in series. One end of the series-connected magnetoresistive elements 5 is connected to the power supply, and the other end is connected to ground. The potential V at the midpoint of the series-connected magnetoresistive elements 5 SOUT This becomes the signal output. S_R1 and S_R2 are positioned relative to each other at a mechanical angle of 45° (m) (electrical angle is 180° (e)), as shown in Figure 28, at an angle φ S12(m) However, the mechanical angle becomes 45° (m). Similarly, as shown in Figure 29, C_R1 and C_R2 are a pair of magnetoresistive elements 5 connected in series. C_R1 and C_R2 are positioned relative to each other at a mechanical angle of 45° (m) (electrical angle is 180° (e)), and as shown in Figure 28, the angle φ C12(m) However, the mechanical angle becomes 45° (m).

[0064] By connecting two magnetoresistive elements 5 with a phase difference of 180°(e) in electrical angle in series, and obtaining the potential at the midpoint as a signal output, the bridge circuit can cancel out disturbance noise and second harmonics. Because disturbance noise and second harmonics are canceled out, the accuracy of the detected angle can be improved. As the accuracy of the detected angle is improved, a high-precision rotation angle sensor 1 can be obtained.

[0065] Embodiment 7. The rotation angle sensor 1 according to Embodiment 7 will be described. Figure 30 is a schematic diagram showing the magnetoresistive element 5 provided on the chip 4 of the rotation angle sensor 1 according to Embodiment 7, and Figure 31 is a diagram showing the connection configuration of the magnetoresistive element 5 provided on the chip 4 of the rotation angle sensor 1. In the rotation angle sensor 1 according to Embodiment 7, the arrangement of the magnetoresistive element 5 in the bridge circuit is defined. The configuration other than the arrangement of the magnetoresistive element 5 is the same as in Embodiment 1, so the explanation other than the arrangement of the magnetoresistive element 5 will be omitted.

[0066] The bridge circuit has two pairs of magnetoresistive elements 5, each positioned at a location where the phase difference in electrical angle is 180°, and connected in series. One end of each pair of magnetoresistive elements 5 is connected to ground, and the phase difference in electrical angle between the two magnetoresistive elements 5 on the ground side is 120 × n° (where n is an integer). In this embodiment, assuming the application of the rotation angle sensor 1 to a 4-pole motor, the rotor 2 has four protrusions 2a. When using a rotor 2 for 4 poles in this way, the pair of magnetoresistive elements 5 constituting the bridge are positioned at a relative position of 45° (m) mechanical angle with respect to the rotation axis. In Figure 30, S_R1, S_R2, S_R3, and S_R4 are connected to the rotation axis by dashed lines, and C_R1, C_R2, C_R3, and C_R4 are connected to the rotation axis by dashed lines.

[0067] As shown in the upper part of Figure 31, S_R1 and S_R2 form the first pair of magnetoresistive elements 5 connected in series, and S_R3 and S_R4 form the second pair of magnetoresistive elements 5 connected in series. One end of the series-connected magnetoresistive elements 5 is connected to the power supply, and the other end is connected to ground. The output V is obtained by combining the potentials of the midpoints of the two series-connected magnetoresistive elements 5. SOUT This becomes the signal output. S_R1 and S_R2 are positioned relative to each other at a mechanical angle of 45° (m) (electrical angle is 180° (e)), as shown in Figure 28, at an angle φ S12(m)becomes a mechanical angle of 45° (m). S_R3 and S_R4 are arranged at a relative position with a mechanical angle of 45° (m) (electrical angle is 180° (e)). S_R1 and S_R4 are arranged at a relative position with a mechanical angle of 30° (m) (electrical angle is 120° (e)), and the angle φ S14(m) becomes a mechanical angle of 30° (m). S_R1 and S_R4 may be arranged at a relative position with a mechanical angle of 60° (m) (electrical angle is 240° (e)).

[0068] Similarly, as shown in the lower part of FIG. 31, a first pair of magnetoresistive elements 5 in which C_R1 and C_R2 are connected in series, and a second pair of magnetoresistive elements 5 in which C_R3 and C_R4 are connected in series. One end of the magnetoresistive element 5 connected in series is connected to a power supply, and the other end is connected to ground. The output V obtained by synthesizing the potentials at the midpoints of the two sets of magnetoresistive elements 5 connected in series COUT becomes a signal output. C_R1 and C_R2 are arranged at a relative position with a mechanical angle of 45° (m) (electrical angle is 180° (e)), and as shown in FIG. 30, the angle φ C12(m) becomes a mechanical angle of 45° (m). C_R3 and C_R4 are arranged at a relative position with a mechanical angle of 45° (m) (electrical angle is 180° (e)). C_R1 and C_R4 are arranged at a relative position with a mechanical angle of 30° (m) (electrical angle is 120° (e)), and the angle φ C14(m) becomes a mechanical angle of 30° (m). C_R1 and C_R4 may be arranged at a relative position with a mechanical angle of 60° (m) (electrical angle is 240° (e)).

[0069] Thus, one side of each end in each of the two pairs of magnetoresistive elements 5 is connected to ground, and the phase difference in the electrical angle between the two magnetoresistive elements 5 on the side connected to ground is set to 120×n°. In addition to external disturbance noise, the second and third harmonics are canceled by the bridge circuit, so the accuracy of the detected angle can be improved. Since the accuracy of the detected angle is improved, a highly accurate rotation angle sensor 1 can be obtained.

[0070] Furthermore, while this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are envisioned within the scope of the art disclosed in this specification. For example, these include modifying, adding or omitting at least one component, or even extracting at least one component and combining it with a component from another embodiment.

[0071] 1. Rotation angle sensor, 2. Rotor, 2a. Protrusion, 2b. Step, 2b1. Side, 3. Permanent magnet, 3a. South pole, 3b. North pole, 4. Chip, 5. Magnetoresistive element, 6. Shaft, 7. Fixed body, 8. Sensor housing, 100. Rotation angle sensor

Claims

1. A rotation angle sensor comprising: a rotor that rotates around a rotation axis and is provided at the end of a shaft extending in the axial direction of the rotation axis, having three or more radially protruding protrusions; a non-rotating permanent magnet provided at a distance from the rotor; and a chip adjacent to the rotor and the permanent magnet at a distance from each other, having a bridge circuit consisting of four or more magnetoresistive elements, wherein each of the magnetoresistive elements is arranged circumferentially on one side of the rotor opposite to the side of the shaft, radially inward from the radial ends of the protrusions; the chip is provided on the portion of the rotor on that one side, parallel to the rotor; and the direction of the magnetic field vector applied to each of the magnetoresistive elements by the permanent magnet is radial, and the magnitude of the magnetic field vector is uniform.

2. The rotation angle sensor according to claim 1, wherein the magnetoresistive element is a GMR element with a meander shape, and the angle formed by the extension direction of the portions of the meander shape that are arranged adjacent to each other and each extends in one direction, and the direction of the magnetic field vector applied to the center of the GMR element is the same for all of the GMR elements.

3. The permanent magnet is a cylinder, or a cylindrical portion that is a sector formed at a predetermined central angle on the base of the cylinder and cut out from the cylinder, the cylinder and the cylindrical portion are bipolar magnets having different magnetic poles in the height direction of the cylinder and the cylindrical portion, the cylinder and the cylindrical portion are arranged on one side of the rotor such that the height direction at the center of the base of the cylinder and the vertex of the central angle of the base of the cylindrical portion coincide with the axial direction of the rotation axis, and the rotor, the tip and the permanent magnet are arranged in that order in the axial direction, according to claim 1 or 2.

4. The shape of the permanent magnet is a ring with a circular outer circumference and inner circumference and a height in the axial direction when viewed in the axial direction, or a ring portion that is a shape cut out from the ring at a predetermined central angle, the ring and the ring portion are bipolar magnets having different magnetic poles in the radial direction, the ring and the ring portion are arranged on one side of the rotor such that the direction of height at the center of the ring and the vertex of the central angle of the ring portion coincides with the axial direction of the rotation axis, the ring and the ring portion overlap with the radially outer protruding portion when viewed in the axial direction, and the rotor, the tip, and the permanent magnet are arranged in that order in the axial direction, according to claim 1 or 2.

5. The permanent magnet is a ring with a circular outer and inner circumference and height in the axial direction, or a ring portion cut from the ring at a predetermined central angle, as viewed in the axial direction, the ring and the ring portion are bipolar magnets having different magnetic poles in the axial direction, the ring and the ring portion are arranged radially outward from the radial end of the protrusion such that the height direction at the center of the ring and the vertex of the central angle of the ring portion coincides with the axial direction of the rotation axis, and the ring and the ring portion overlap with the rotor in at least a portion of the radial direction, as described in claim 1 or 2.

6. The rotor further has a disc-shaped stepped portion on the other side opposite to the one side, with the side surface provided radially outward from the radial end of the protrusion; the shape of the permanent magnet is, when viewed in the axial direction, a ring with a circular outer circumference and inner circumference and height in the axial direction, or a portion of a ring that is cut out from the ring at a predetermined central angle; the ring and the portion of the ring are bipolar magnets having different magnetic poles in the axial direction; the ring and the portion of the ring are arranged radially outward from the radial end of the protrusion such that the direction of height at the center of the ring and the vertex of the central angle of the portion of the ring coincides with the axial direction of the rotation axis; and the ring and the portion of the ring overlap at least a part with the protrusion when viewed radially and overlap with the stepped portion when viewed axially, the rotation angle sensor according to claim 1 or 2.

7. The rotation angle sensor according to claim 1 or 2, wherein the bridge circuit has a pair of magnetoresistive elements connected in series, each positioned at a location where the phase difference in electrical angle is 180°.

8. The rotation angle sensor according to claim 1 or 2, wherein the bridge circuit has two pairs of magnetoresistive elements connected in series, each positioned at a location where the phase difference in electrical angle is 180°, one end of each of the two pairs of magnetoresistive elements is connected to ground, and the phase difference in electrical angle between the two magnetoresistive elements on the ground side is 120 × n° (where n is an integer).

Images