JP5427619B2 - Rotation detector - Google Patents

Description

  The present invention relates to a rotation detection device that detects a rotation direction, a rotation speed, and a rotation angle of a rotating body.

  2. Description of the Related Art Conventionally, it is well known to use a magnetic sensor that detects a rotation angle of a rotating inspection object in a rotation detection device such as an encoder or a potentiometer. It is also known to use a magnetoresistive element for such a magnetic sensor. The magnetoresistive effect element has a characteristic that the resistance value changes according to a change in the external magnetic field, and a change in resistance value is output as a voltage change by forming a bridge circuit with a plurality of magnetoresistive effect elements. The rotation detection device provided with the magnetoresistive effect element is configured to detect the rotation direction, the rotation speed, and the rotation angle of the rotating body that is the object to be inspected by the change in the voltage output from the bridge circuit ( For example, see Patent Document 1).

  The magnetic sensor of this rotation detecting device is configured by a substrate on which four magnetoresistive elements are arranged facing a magnetic pole surface of a bias magnet. Each magnetoresistive element is arranged at a position along two axes orthogonal to each other at the center point of the substrate so that two magnetoresistive elements face each other with the center point interposed therebetween, and each set of magnetoresistive elements facing each other. The effect elements are connected so as to form a half-bridge circuit. Further, the substrate is disposed so as to face the bias magnet such that the center point of the substrate overlaps the magnetic center of the bias magnet. A rotation detecting device is configured by providing a two-pole rotating magnet at the tip of a rotating body that is an object to be inspected and arranging a magnetic sensor so as to face the rotating magnet.

  According to this rotation detection device, the accuracy of the magnetic sensor can be increased by using a bias magnet, and at the same time, sinusoidal signals having a phase difference with each other in the same period as the magnetic field cycle of the rotating magnet installed in the rotating body, and Since the cosine wave signal can be output to the magnetic sensor, the rotation direction, rotation speed, and rotation angle of the rotating body can be detected. That is, by applying a magnetic field in a certain direction as a bias magnetic field, the direction of the bias magnetic field becomes the magnetization axis, and the unstable and unstable magnetization axis disappears. A periodic output signal free from distortion due to a combined magnetic field of a stable bias magnetic field and an external magnetic field by a rotating magnet can be obtained. Further, by applying a bias magnetic field to the magnetoresistive effect element, an output signal having the same period as the magnetic field period of the external magnetic field from the dipole rotating magnet can be output to the magnetic sensor.

JP 2006-208025 A

  However, in the rotation detection device described above, in order to accurately obtain a sine wave and a cosine wave having the same amplitude as the output signal, it is necessary to arrange the magnetic sensor so as to face the magnetic pole surface of the rotating magnet. If the sensor is arranged in an inclined state with respect to the magnetic pole surface of the rotating magnet, there arises a problem that the detection accuracy is lowered.

  The present invention has been made to cope with such a problem, and an object of the present invention is to provide an outer peripheral surface or an inner peripheral surface of a rotating body with a rotating magnet provided on the rotating body while maintaining a good detection accuracy. An object of the present invention is to provide a rotation detecting device suitable for the rotary shaft penetrating structure arranged in the above. In addition, in the description of each constituent element of the present invention below, in order to facilitate understanding of the present invention, reference numerals of corresponding portions of the embodiment are described in parentheses, but each constituent element of the present invention is The present invention should not be construed as being limited to the configurations of the corresponding portions indicated by the reference numerals of the forms.

In order to achieve the above-described object, the configuration of the rotation detection device according to the present invention is characterized by a two-pole circular rotating magnet (12, 22, 32, 32) attached to a rotating body (11, 21, 31, 41). 42, 52, 62, 72, 82), two magnetic sensors (13A, 13B, 23A, 23B, 33A, 33B, 43A, 43B, 53, 63) for detecting a change in the magnetic field of the circular rotating magnet, A rotation detection device (10, 20, 30) including an arithmetic processing circuit (19, 49) for calculating a rotation angle of a circular rotary magnet from detection results of two magnetic sensors, wherein the magnetic sensor is a bias magnet. (14), the substrate (15, 45, 55, 65) facing the magnetic pole surface in a state where the center point is aligned with the magnetic center of the magnetic pole surface of the bias magnet, and perpendicular to the magnetic pole surface and parallel to the magnetic pole surface. Center point along two axes Magnetoresistance effect elements (a to d, a1 to d1, a2 to d2) formed in the same shape in four regions (15a to 15d, 45a to 45d, 65a to 65d) set at the same distance, respectively. , A3 to d3), and two magnetoresistive elements provided along each of the two axes are connected in series to form two bridge circuits, and the power supply voltage is applied to both ends of the two bridge circuits. To output an output waveform signal from the connection point of the two magnetoresistive elements, and the arithmetic processing circuit calculates the rotation angle of the circular rotating magnet using the output waveform signal. One of the two axes is parallel to a tangent of a circle formed by the outer peripheral surface of the circular rotating magnet, and the rotational center of the circular rotating magnet on the other of the two axes of each magnetic sensor Against the axis As the inclination angle becomes identical to each other, disposed two magnetic sensors, the position spaced 90 degrees from each other in the center and the circumferential direction central axis of rotation of the circular rotary magnet at outer side of the outer peripheral surface of the circular rotating magnet Furthermore, the arithmetic processing circuit outputs an output waveform corresponding to the X axis of one of the magnetic sensors (13B, 23B, 33B, 43B) when one of the two axes is the X axis and the other is the Y axis. The signal and the output waveform signal corresponding to the Y axis of the other magnetic sensor are calculated, the output waveform signal corresponding to the X axis of the other magnetic sensor (13A, 23A, 33A, 43A) and the Y of one magnetic sensor. An output waveform signal corresponding to the axis is calculated to extract a sine wave signal and a cosine wave signal having the same amplitude, and arc tangent calculation is performed using the extracted sine wave signal and cosine wave signal, thereby obtaining two magnetic fields. Sen While maintaining the position of the magnetic pole surface of one of the magnetic sensors, the X and Y axes of one magnetic sensor are rotated 90 degrees about the center point with respect to the X and Y axes of the other magnetic sensor. In this state, by outputting output waveform signals from the two magnetic sensors to the arithmetic processing circuit, respectively, a sine wave signal and a cosine wave signal having the same amplitude are taken out .

  In the rotation detection device according to the present invention, since the two magnetic sensors are arranged outside the outer peripheral surface of the circular rotating magnet, the circular rotating magnet is not located at the end of the rotating body but at the axially central portion of the rotating body. Even if the rotating shaft penetrating structure is provided on the outer peripheral surface or inside, the magnetic sensor can be easily arranged. In addition, since two magnetic sensors are used and the two magnetic sensors are installed at positions 90 degrees apart from each other in the circumferential direction, the output waveform signal of each magnetic sensor can be compensated by the arithmetic processing of the arithmetic processing circuit. Even if the sensor is not disposed facing the magnetic pole surface of the circular rotating magnet, the rotational direction, the rotational speed, and the position in the rotational direction of the rotating body can be accurately detected.

  Furthermore, since each magnetoresistive element is formed in the same shape, the shape of the magnetoresistive element is not uneven, and the detection accuracy of the magnetic sensor is improved. In the present invention, it is possible to arbitrarily set an inclination angle of the other axis of the two axes of each magnetic sensor with respect to the rotation center axis of the circular rotating magnet, but the other axis is a circular rotating magnet. More preferably, it is parallel to or perpendicular to the rotation center axis of the. When the other axis is made parallel to the rotation center axis of the circular rotating magnet, the rotation detecting device can be downsized relative to the radial direction of the rotating direction of the circular rotating magnet. When the other axis is orthogonal to the rotation center axis of the circular rotating magnet, the rotation detector can be downsized relative to the direction of the rotation center axis of the circular rotating magnet.

  Further, the two poles of the circular rotating magnet are preferably arranged with one S pole and one N pole at a portion along the rotation direction on the surface of the circular rotating magnet. In addition to this, a magnetic sensor By providing the bias magnet, the magnetic sensor can output a sine wave signal and a cosine wave signal having a phase difference with a waveform of one cycle when the circular rotating magnet makes one rotation. This increases the detection accuracy of the magnetic sensor. Further, it is preferable that the substrate is composed of a single substrate. According to this, the magnetoresistive effect element can be accurately arranged at the set position, so that the detection accuracy of the magnetic sensor is further improved. It should be noted that the positions 90 degrees apart from each other in the circumferential direction around the rotation center axis of the circular rotating magnet in which the two magnetic sensors are arranged are not limited to 90 degrees and may be approximately 90 degrees. Needless to say.

Further, in the rotation detecting equipment according to the present invention, the arithmetic processing circuit, when the other one of the two axes in the X-axis is assumed to be Y-axis, an output waveform corresponding to the X axis of one of the magnetic sensors thereby calculating an output waveform signal corresponding to the Y-axis of the signal and the other magnetic sensor, an output waveform signal corresponding to the Y axis of the output waveform signal and one of the magnetic sensors corresponding to the X-axis of the other magnetic sensor by calculating the taken out respectively a sine wave signal and a cosine wave signal having the same amplitude each other to the so that to arctangent calculation using a sine wave signal and a cosine wave signal extracted.

In this case, the X axis and Y axis of one magnetic sensor are centered with respect to the X axis and Y axis of the other magnetic sensor while maintaining the position of the magnetic pole surface of the other magnetic sensor of the two magnetic sensors. while rotating 90 degrees about a point, by outputting two output waveform signal to the arithmetic processing circuit from the magnetic sensor, respectively, to extract a sine-wave signal and a cosine wave signal having the same amplitude.

  Compensation of the waveform signals output from the two magnetic sensors in such a rotation detection device is performed by using the outputs of the two bridge circuits of one magnetic sensor and the output waveform signals of the two bridge circuits of the other magnetic sensor. For example, it can be passed through an arithmetic processing circuit having a differential amplifier. A sin signal (sine wave signal) and a cos signal (cosine wave signal) can be obtained by passing the waveform signals output from the two magnetic sensors through an arithmetic processing circuit. Then, the rotation angle of the circular rotating magnet can be obtained by performing an arctangent calculation (Arctan) using the sin signal and the cos signal.

  For example, when the X axis and Y axis of two magnetic sensors are set in the same direction, and the magnetic field waveform in the rotation center axis direction (Y direction) of the circular rotating magnet in the other magnetic sensor is α sin θ, the circular rotation The magnetic field waveform in the direction parallel to the tangent to the outer circumference of the magnet (X direction) is β cos θ, and the magnetic field waveform in the direction of the rotation center axis of the circular rotating magnet (Y direction) in one magnetic sensor is α sin (θ + π / 2) = α cos θ. Thus, the magnetic field waveform in the direction parallel to the tangent of the circular rotating magnet (X direction) is βcos (θ + π / 2) = − βsinθ. At this time, αsinθ and βcosθ or αcosθ and -βsinθ, that is, a sin signal and a cos signal can be obtained only by the other magnetic sensor, and thus a signal representing the rotation angle of the circular rotating magnet is obtained by performing an arctangent calculation. Can do. However, in this case, Arctan (α sin θ / β cos θ) is obtained, and α / β correction is required.

  Further, if the point where the magnetic sensor is arranged changes in the direction of the rotation center axis of the circular rotating magnet, the magnetic field generated at both the position before and after the change changes. In this case, since the ratio α / β described above is different, it is detected that the circular rotating magnet is displaced along the rotation center axis and the distance between the circular rotating magnet and the magnetic sensor is changed during the operation of the rotation detecting device. It becomes a problem in accuracy. However, the above-described α sin θ of the other magnetic sensor, -β sin θ of one magnetic sensor, β cos θ of the other magnetic sensor, and α cos θ of one magnetic sensor are compensated for each other by passing through an arithmetic processing circuit, and the ratio α / β is You can prevent it from being different. In this case, (α + β) sin θ is obtained by α sin θ − (− β sin θ), but (α + β) cos θ cannot be obtained by β cos θ−α cos θ.

  For this reason, the potential level can be reversed by rotating the X axis and the Y axis by 90 degrees while maintaining the position of the magnetic pole surface of one of the magnetic sensors. As a result, αcosθ described above becomes −αcosθ, and (α + β) cosθ can be obtained, and the calculation formula of rotation angle detection becomes Arctan ((α + β) sinθ / (α + β) cosθ), and the ratio α / β No effect. As a result, even if the position of the two magnetic sensors with respect to the circular rotating magnet is changed in the direction of the rotation center axis of the circular rotating magnet, the detection value is not affected, and the circular rotating magnet is displaced in the axial direction of the rotating body during operation. However, the signal accuracy is not lowered. That is, the operation of inverting the potential level and passing the output waveform signals of the two magnetic sensors through the arithmetic processing circuit and then performing the arc tangent calculation result in the circular rotating magnet even if the circular rotating magnet is misaligned. The accurate rotation angle can be obtained. The present invention is effective when a pair of power supply terminals for supplying a power supply voltage to a pair of bridge circuits are provided in common.

  In addition, another structural feature of the rotation detection device according to the present invention is that the sine wave signal is applied to the output waveform signal corresponding to the X axis of one magnetic sensor and the Y axis of the other magnetic sensor that are in phase with each other. The sum of the corresponding output waveform signal and the cosine wave signal is an output waveform signal corresponding to the X axis of the other magnetic sensor that is in phase with each other and an output waveform signal corresponding to the Y axis of the one magnetic sensor. It is to be sum.

  In addition, another structural feature of the rotation detection device according to the present invention is that the bridge circuit rotates the magnetoresistive effect elements (a to d, a3 to d3) by 90 degrees around the center point. A half formed by connecting two magnetoresistive effect elements located on respective axes of two axes formed one by one in four regions (15a to 15d, 65a to 65d) so that their positions overlap each other. It is a bridge circuit. According to this, the input resistance value can be increased and the wiring can be simplified. In addition, since the positions of the magnetoresistive elements are arranged so that the positions of the magnetoresistive elements overlap each other when the magnetoresistive elements are rotated by 90 degrees about the center point of the substrate, unevenness due to the arrangement of the magnetoresistive elements does not occur. Furthermore, the detection accuracy of the magnetic sensor is improved.

  In addition, another structural feature of the rotation detection device according to the present invention is that the bridge circuit includes magnetoresistive effect elements (a1 to d1, a2 to d2) centered on the center point of each element located on each axis. Two points are formed in four regions (45a to 45d) so as to be symmetrical with respect to each other, or to be arranged symmetrically with respect to each other with respect to each axis. It is that it is a full bridge circuit comprised by connecting four magnetoresistive effect elements located in each. As a result, the stability of the midpoint potential is improved and the signal output is doubled as compared with the case where the half-bridge circuit described above is used.

  Further, another structural feature of the rotation detection device according to the present invention is that the magnetoresistive effect elements (ab, a1-d1, a2-d2) are inclined 45 degrees with respect to the two axes. is there. According to this, since a magnetic field along both directions of the two axes is applied to each magnetoresistive effect element, more accurate detection is possible when an AMR element is used as the magnetoresistive effect element.

  Still another structural feature of the rotation detecting device according to the present invention is that the magnetoresistive element is an AMR element or a GMR element.

  The direction of magnetization of the AMR element (anisotropic magnetoresistive effect element) is determined by the balance between the anisotropy of the soft magnetic material (for example, Ni-Fe, Ni-Co, Ni-Fe-Co) and the external magnetic field. Is done. Anisotropy is a combination of crystal anisotropy and shape anisotropy induced after formation of the magnetoresistive effect element. When no external magnetic field is applied, the direction of magnetization is one of two directions along the easy axis determined by the anisotropy of the AMR element. When an external magnetic field is applied, the magnetization direction approaches the external magnetic field. For this reason, in the case of a magnetic sensor using an AMR element, when an external magnetic field with a rotating magnetic field greater than the saturation magnetic field is applied, the direction of magnetization is dominated by the direction of the external magnetic field, and a periodic resistance change is obtained. However, when the external magnetic field is less than or equal to the saturation magnetic field, the magnetization direction is shifted from the direction of the external magnetic field due to unstable anisotropy, and distortion is induced in the output signal.

  In the rotation detection apparatus according to the present invention, a bias magnet is used to apply a magnetic field in a certain direction that aligns magnetization as a bias magnetic field, so that the direction of the bias magnetic field becomes a magnetization axis and is stabilized. Further, by applying a bias magnetic field, an output signal having the same period as that of the external magnetic field can be obtained. Even when a GMR element (giant magnetoresistive element) is used, good detection is possible based on the principle described above when a soft magnetic material is used.

  Still another structural feature of the rotation detection device according to the present invention is that the bias magnet is composed of a sintered magnet or a resin magnet. According to this, a magnetic field intensity that cannot be obtained by a magnetic sensor using a thin film magnet such as vapor deposition can be obtained, and resistance to external magnetic field intensity can be exhibited.

  In addition, another structural feature of the rotation detecting device according to the present invention is that the circular rotating magnet is polarized so as to be divided into two parallel to the rotation center axis of the circular rotating magnet, and is polarized in two radial directions. It is constituted by a ring-shaped magnet provided on the outer peripheral portion of the shaft-like rotating body. According to this, since the circular rotating magnet is polarized in parallel with the central axis of rotation and magnetized in the radial direction, a magnetic field without distortion is generated, and the accuracy of the rotation detecting device is further improved.

  In addition, another structural feature of the rotation detecting device according to the present invention is that the circular rotating magnet is polarized so as to be divided into two parallel to the rotation center axis of the circular rotating magnet, and is polarized in two radial directions. In other words, the disk-shaped or columnar magnet is provided inside the cylindrical shaft-shaped rotating body. According to this, since the circular rotating magnet is polarized in parallel with the central axis of rotation and magnetized in the radial direction, a magnetic field without distortion is generated, and the accuracy of the rotation detecting device is further improved. Moreover, a circular rotating magnet can be attached to the inside of a cylindrical shaft-shaped rotating body. When a circular rotating magnet is attached inside a cylindrical shaft-shaped rotating body, the magnetic sensor is installed outside the rotating body.

It is the perspective view which showed the rotation detection apparatus which concerns on 1st Embodiment of this invention. It is a top view of the rotation detection apparatus shown in FIG. It is a front view of the rotation detection apparatus shown in FIG. It is the perspective view which showed the magnetic sensor with which a rotation detection apparatus is provided. It is an external appearance perspective view of the magnetic sensor shown in FIG. FIG. 6 is a cross-sectional view taken along 6-6 in FIG. 5. 5 is a half-bridge circuit of the magnetic sensor shown in FIG. 4. It is the graph which showed the relationship between an external magnetic field and the output of a magnetic sensor. It is the graph which showed the relationship between the external magnetic field when an external magnetic field is a rotating magnetic field, and the output of a magnetic sensor. It is explanatory drawing which showed the position of the magnetic sensor arrange | positioned at the outer peripheral side of a circular rotating magnet, and the direction of a magnetic field. It is the graph which showed the relationship between the rotation angle of the circular rotating magnet in the position of one magnetic sensor, and the magnitude | size of the magnetic field which one magnetic sensor detects. It is the graph which showed the relationship between the rotation angle of the circular rotary magnet in the position of the other magnetic sensor, and the magnitude | size of the magnetic field which the other magnetic sensor detects. It is the graph which showed the relationship between the magnetic field of a rotating shaft direction when changing the height position of a magnetic sensor, and the magnetic field of the tangential direction of a virtual concentric circle. An arithmetic circuit that performs arithmetic processing on outputs from two magnetic sensors is shown, (a) is a diagram assumed for convenience of explanation, and (b) is a diagram showing an actual circuit. The method of reversing an electric potential level by rotating a magnetic sensor is shown, (a) is explanatory drawing of the magnetic sensor before rotation, (b) is explanatory drawing of the magnetic sensor after rotation. (A), (b) is a circuit diagram which shows the modification of the arithmetic circuit of FIG.14 (b). 1 is a perspective view showing a rotation detection device according to Embodiment 1. FIG. 3 is a graph showing a relationship between an external magnetic field and an output of a magnetic sensor in the rotation detection device of Example 1. The characteristics when the height of the magnetic sensor is the same as the upper surface of the circular rotating magnet in the rotation detecting device of Example 1 are shown. (A) shows the rotation angle of the circular rotating magnet and the outputs of the two magnetic sensors. (B) shows the relationship between the rotational angle of the circular rotating magnet and the output after differential of the two magnetic sensors, and (c) shows the relationship between the rotational angle of the circular rotating magnet and the angular error. Show. FIG. 3 shows characteristics when the height of the magnetic sensor is set to a position of 3 mm from the upper surface of the circular rotating magnet in the rotation detecting device of Example 1, and (a) shows the rotation angle of the circular rotating magnet and the two magnetic sensors. (B) shows the relationship between the rotation angle of the circular rotating magnet and the output after differential of the two magnetic sensors, and (c) shows the relationship between the rotation angle of the circular rotating magnet and the angle error. Showing the relationship. The characteristics when the height of the magnetic sensor is 3 mm from the upper surface of the circular rotating magnet in the rotation detecting device of Example 2 are shown. (A) shows the rotational angle of the circular rotating magnet and the two magnetic sensors. (B) shows the relationship between the rotation angle of the circular rotating magnet and the output after differential of the two magnetic sensors, and (c) shows the relationship between the rotation angle of the circular rotating magnet and the angle error. Showing the relationship. It is the perspective view which showed the rotation detection apparatus which concerns on 2nd Embodiment of this invention. It is a top view of the rotation detection apparatus shown in FIG. It is a front view of the rotation detection apparatus shown in FIG. It is the perspective view which showed the magnetic sensor with which the rotation detection apparatus which concerns on 3rd Embodiment is provided. It is the figure which showed the full bridge circuit of the magnetic sensor with which the rotation detection apparatus which concerns on 3rd Embodiment is provided. It is the figure which showed the arithmetic circuit for calculating the signal output from two magnetic sensors with which the rotation detection apparatus which concerns on 3rd Embodiment is provided. It is the perspective view which showed the magnetic sensor with which the rotation detection apparatus which concerns on the modification of 3rd Embodiment is provided. It is the perspective view which showed the magnetic sensor with which the rotation detection apparatus which concerns on 4th Embodiment is provided. It is the figure which showed the full bridge circuit of the magnetic sensor using the GMR element which consists of a soft-magnetic material. It is the perspective view which showed the state which attached the ring-shaped circular rotary magnet provided with the big insertion hole to the outer periphery of the rotating shaft. It is the perspective view which showed the disk-shaped circular rotating magnet which carried out 2 pole magnetization in radial direction. It is the perspective view which showed the ring-shaped circular rotary magnet which magnetized the outer peripheral side and the inner peripheral side by two poles in the radial direction so that the adjacent outer peripheral side and inner peripheral side are different poles. It is the perspective view which showed the disk-shaped circular rotating magnet which magnetized two poles in the surface direction on the upper side and the lower side so that the adjacent left-right part may become a different pole. It is the perspective view which showed the ring-shaped circular rotary magnet which magnetized two poles on the upper side and the lower side in the surface direction so that the adjacent left and right parts may become different poles. 32 shows the characteristics of the circular rotating magnet shown in FIG. 32, (a) is a diagram showing magnetic flux lines, and (b) is a rotation angle of the circular rotating magnet and a magnetic sensor provided with the circular rotating magnet. It is the graph which showed the relationship with the magnitude | size of the magnetic field to perform. 33 shows the characteristics of the circular rotating magnet shown in FIG. 33, (a) is a diagram showing magnetic flux lines, and (b) is a rotation angle of the circular rotating magnet and a magnetic sensor provided with the circular rotating magnet. It is the graph which showed the relationship with the magnitude | size of the magnetic field to perform. 34 shows the characteristics of the circular rotating magnet shown in FIG. 34, (a) is a diagram showing magnetic flux lines, and (b) is a rotation angle of the circular rotating magnet and a magnetic sensor provided with the circular rotating magnet. It is the graph which showed the relationship with the magnitude | size of the magnetic field to perform. 35 shows the characteristics of the circular rotating magnet shown in FIG. 35, (a) is a diagram showing magnetic flux lines, and (b) is a rotation angle of the circular rotating magnet and a magnetic sensor provided with the circular rotating magnet. It is the graph which showed the relationship with the magnitude | size of the magnetic field to perform.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. 1 to 3 show a rotation detection device 10 according to the embodiment, and the rotation detection device 10 detects a rotation direction, a rotation speed, and a rotation angle of a rotating shaft 11 as a rotating body according to the present invention. It is a device for doing. The rotation detecting device 10 includes a circular rotating magnet 12 attached to the outer peripheral surface of the rotating shaft 11 at a predetermined distance from both upper and lower ends of the rotating shaft 11, and an outer peripheral side of the circular rotating magnet 12 supported by a support device (not shown). Are provided with two magnetic sensors 13A and 13B. The rotating shaft 11 is an object to be inspected that includes, for example, a rotating shaft of a motor, a steering shaft of an automobile or a ship, a joint portion of a robot arm, or the like.

  The circular rotary magnet 12 is formed in a substantially ring shape with a small insertion hole 12a formed at the center, and is attached to the outer peripheral surface of the rotation shaft 11 by inserting the rotation shaft 11 through the insertion hole 12a. The circular rotating magnet 12 is polarized with two poles in the radial direction by being polarized with a plane that bisects the circular rotating magnet 12 across the rotation center axis (in this case, the rotation axis 11), One is the S pole and the other is the N pole. The magnetic sensors 13A and 13B are composed of the same sensor, and as shown in FIG. 4, the bias magnet 14, the substrate 15, and the four magnetoresistive elements a, b, formed on the substrate 15, respectively. c and d.

  The bias magnet 14 is made of a disc-shaped magnet composed of a sintered magnet or a resin magnet. The bias magnet 14 is polarized with a plane that bisects the thickness direction as a boundary and is polarized in two directions perpendicular to the plane, one of which is an S pole and the other is an N pole. The substrate 15 is composed of a thin square plate made of an insulating material such as silicon, glass, or ceramic. The magnetoresistive elements a, b, c, and d are composed of AMR elements (anisotropic magnetoresistive elements) made of Ni-Fe, Ni-Co, or Ni-Fe-Co, and are formed by a photolithographic method. By being formed into a film, it is formed on the surface of the substrate 15.

  For convenience of explanation, the substrate 15 has an X axis (horizontal axis indicated by a one-dot chain line that divides the substrate 15 in the vertical direction in FIG. 4) and a Y axis orthogonal to the X axis (the substrate 15 in FIG. And a vertical axis indicated by an alternate long and short dash line). Then, square regions 15a and 15b are formed on both sides of the portion along the X axis centering on the center point O where the X axis and the Y axis intersect, and square regions 15c and 15d are formed on both sides of the portion along the Y axis. Each is provided so as to be the same distance from the center point O.

  The magnetoresistive elements a, b, c, and d are each formed into a long and narrow quadrilateral, and they are inclined by 45 degrees with respect to the X axis and the Y axis and located on the same axis of the X axis and the Y axis. Are arranged one by one in the regions 15a, 15b, 15c and 15d so as to be point-symmetric with respect to the center point O. That is, when each magnetoresistive effect element a, b, c, d is rotated 90 degrees around the center point O on the substrate 15 to change its position, the other magnetoresistive effect element before the change of position is changed. Each of a, b, c, and d is arranged so as to be located in the portion where it was located.

  The magnetic sensors 13A and 13B configured as described above are actually biased to the lower surface and the upper surface of the lead frame 16b in the mold package 16a as shown in the external perspective view of FIG. 5 and the schematic sectional view of FIG. The magnet 14 and the substrate 15 are bonded. The mold package 16a is made of an epoxy resin, and the lead frame 16b is made of a conductor, for example, copper. A pair of power supply terminals 18a and 18b and a pair of signal output terminals 18c and 18d are provided outside the mold package 16a. As shown in FIG. 7, the magnetoresistive effect elements a and b and the magnetoresistive effect elements c and d constitute a pair of half bridge circuits connected in series in the mold package 16a.

  Both ends of the magnetoresistive effect elements a and b and both ends of the magnetoresistive effect elements c and d are connected in common, and the power supply voltage Vcc is supplied from the power supply terminal 18a to the connection point of the magnetoresistive effect elements a and c. It is like that. The connection point of the magnetoresistive effect elements b and d is grounded via the power supply terminal 18b. The connection point of the magnetoresistive elements a and b is connected to the signal output terminal 18c, and the signal output OutX is taken out from the signal output terminal 18c. The connection point of the magnetoresistive elements c and d is connected to the signal output terminal 18d, and the signal output OutY is taken out from the signal output terminal 18d. The substrate 15 on which the magnetoresistive elements a, b, c, and d are formed is opposed to the N pole side of the bias magnet 14 with the center point O coincident with the magnetic center of the magnetic pole surface of the bias magnet 14. . In this case, the S pole side of the bias magnet 14 may be opposed to the substrate 15.

  As shown in FIGS. 2 and 3, the magnetic sensors 13A and 13B are coaxial with the circular rotating magnet 12 along the tangent line of the virtual concentric circle 17 having a diameter slightly larger than the diameter of the circular rotating magnet 12. At a position above the magnet 12, they are arranged at an angle of 90 degrees in the circumferential direction of the virtual concentric circle 17 with a mutual interval. In the magnetic sensor 13 </ b> A, the X axis is arranged along the tangent line of the virtual concentric circle 17, and the Y axis is arranged in parallel to the rotation axis 11. In the magnetic sensor 13 </ b> B, the Y axis is arranged along the tangent line of the virtual concentric circle 17, and the X axis is arranged in parallel to the rotation axis 11. The reason why the X-axis and Y-axis directions of the magnetic sensor 13B are made different from the X-axis and Y-axis directions of the magnetic sensor 13A will be described later. In FIG. 3, the rotating shaft 11 is indicated by a broken line in order to represent the magnetic sensor 13B.

  Next, the relationship between the external magnetic field from the circular rotating magnet 12 and the output of the magnetic sensor 13A in the rotation detection device 10 configured as described above will be described. FIG. 8 shows the external magnetic field H and the output Vo on the side where the output value of the pair of output signals changes when the external magnetic field H by the circular rotating magnet 12 is applied to the magnetic sensor 13A from the X-axis direction (FIG. 7). (OutY) of FIG. As shown in the figure, when the external magnetic field H is in the range of the magnetic field strength substantially equivalent to the bias magnetic field strength Hb from the bias magnetic field strength −Hb by the bias magnet 14, a linear shape close to a straight line is drawn. When the bias magnetic field intensity is -Hb or less or the bias magnetic field intensity Hb or more, the curve changes so as to draw a gentle curve.

  When a bias magnetic field stronger than the saturation magnetic field of the magnetoresistive effect elements a, b, c, d is applied to the magnetoresistive effect elements a, b, c, d, the magnetoresistive effect elements a, b, c, d. The saturation magnetic field becomes substantially the same as the bias magnetic field strength Hb. FIG. 9 shows the relationship between the external magnetic field H and the output Vo on the same side as the above case (OutY in FIG. 7) when the external magnetic field H from the circular rotating magnet 12 is a rotating magnetic field. In this case, when the direction of the external magnetic field H changes from the X-axis direction to the Y-axis direction, the slope (amplitude) of the output curve decreases accordingly. When the external magnetic field H is in the same direction as the Y axis (90 degrees with respect to the X axis), the output Vo becomes “0”.

  In a linear region where the external magnetic field H is greater than or equal to the bias magnetic field strength −Hb and less than or equal to the bias magnetic field strength Hb, the external magnetic field H is parallel to the X axis in a direction inclined 45 degrees from the X axis. In comparison with the case where the magnitude of the output Vo is 70.75% and the direction of the external magnetic field H is inclined by 60 degrees from the X axis, the output Vo is compared to when the external magnetic field H is parallel to the X axis. The relationship that the size of 50% is recognized. In this case, the external magnetic field H becomes an output signal having the same period, and the strength of the external magnetic field H appears as the strength of the output signal of the magnetic sensor 13A. The magnetic sensors 13A and 13B according to the present embodiment operate in this linear region, that is, in a region where the external magnetic field H by the circular rotating magnet 12 is smaller than the bias magnetic field strength Hb by the bias magnet 14, thereby improving stability and accuracy. Is intended.

  Next, in the rotation detection device 10 according to the present embodiment, the reason why the directions of the X axis and the Y axis of the magnetic sensor 13B are different from the directions of the X axis and the Y axis of the magnetic sensor 13A will be described. FIG. 10 is an explanatory diagram showing the positions of the magnetic sensors 13A and 13B arranged on the virtual concentric circle 17 positioned above the circular rotating magnet 12 on the outer peripheral side of the circular rotating magnet 12 by points A and B. First, the X-axis and Y-axis directions of the magnetic sensor 13A and the X-axis and Y-axis directions of the magnetic sensor 13B are the same (both the X-axis is the tangential direction of the virtual concentric circle 17 and the Y-axis is a circular rotation). Assume that the rotation center axis of the magnet 12 (the direction parallel to the rotation axis 11) is set.

  At point A, the direction parallel to the rotation axis 11 (direction along the Y axis) is A1, the direction along the tangent line of the virtual concentric circle 17 (direction along the X axis) is A2, and the normal line of the virtual concentric circle 17 is along. A direction (direction passing through the center point O of the magnetic sensor 13A) is defined as A3. At point B, the direction parallel to the rotation axis 11 (direction along the Y axis) is B1, the direction along the tangent line of the virtual concentric circle 17 (direction along the X axis) is B2, and the normal line of the virtual concentric circle 17 Is defined as B3 (direction passing through the center point O of the magnetic sensor 13B). In this case, the circular rotating magnet 12 was rotated 360 degrees about the rotating shaft 11, and the magnetic field applied in the respective directions of points A and B was analyzed using magnetic simulation software. The results are shown in FIGS.

  The magnetic field waveform of A1 at the point A is α sin θ shown by a curve with a black square in FIG. 11, and the magnetic field waveform of A 2 is β cos θ shown by a curve with a black triangle in FIG. The magnetic field waveform of B1 at point B is α sin (θ + π / 2) shown by a curve with a white square in FIG. 12, and the magnetic field waveform of B2 is shown by a curve with a white triangle in FIG. βcos (θ + π / 2). The phase of the magnetic field waveform in the direction A2 is 90 degrees ahead of the phase of the magnetic field waveform in the direction A1. The phase of the magnetic field waveform in the direction B2 is 90 degrees ahead of the phase of the magnetic field waveform in the direction B1. The amplitude α of the magnetic field waveform in the directions A1 and B1 and the amplitude β of the magnetic field waveform in the directions A2 and B2 have a relationship of α ≧ β. Since the magnetic sensors 13A and 13B output by reflecting the change in the magnetic field, the magnetic field waveforms shown in FIGS. 11 and 12 can be replaced with output signals.

  In this case, when the rotation detection of the circular rotating magnet 12 is calculated by the calculation formula Arctan by the arctangent calculation using only the magnetic sensor 13A disposed at the point A, Arctan (αsinθ / βcosθ) is obtained, and α / β correction is necessary. Further, if the point where the magnetic sensor 13A is disposed changes from the point A shown in FIG. 10 to a point A 'above the point A, the magnetic field waveforms in the directions A1 and A2 change. The difference is shown in FIG. FIG. 13 shows the relationship between the magnetic field in the rotation axis direction and the magnetic field in the tangential direction, with the solid line indicating the magnetic field at point A and the broken line indicating the magnetic field at point A ′.

  In this case, when the amplitudes at the point A ′ corresponding to the amplitudes α and β at the point A are α ′ and β ′, the ratio α ′ / β ′ at the point A ′ is the ratio α / It is different from β. For this reason, when the rotation detecting device 10 is operated, the circular rotating magnet 12 is displaced along the rotating shaft 11 and the distance between the circular rotating magnet 12 and the magnetic sensors 13A and 13B changes, which is a problem in detection accuracy. . However, the output signals OutX and OutY of each pair from the magnetic sensors 13A and 13B are subjected to predetermined arithmetic processing to compensate each other for the output signals of the magnetic sensors 13A and 13B, and the ratio α ′ / at the point A ′. The problem resulting from the difference between β ′ and the ratio α / β at point A can be solved. In FIG. 10, it has been described that only the point A has shifted to the point A ′. However, since the circular rotating magnet 12 is displaced along the rotating shaft 11, the point B also has the same amount in the direction parallel to the point A. As for the point B, the ratio α / β changes as the ratio α ′ / β ′.

Before describing this arithmetic processing, the output signals OutX and OutY output from the output terminals 18c and 18d of the magnetic sensor 13A corresponding to the directions A1 and A2, and the output terminal 18c of the magnetic sensor 13B corresponding to the directions B1 and B2. , 18d, the output signals OutX and OutY will be described. These output signals are expressed by the following formulas 1 to 4.
A1 (18c of 13A, OutX): α sin θ + Vcc / 2 Equation 1
A2 (18d of 13A, OutY): βcos θ + Vcc / 2 Equation 2
B1 (18c of 13B, OutX): αsin (θ + π / 2) + Vcc / 2
= Αcos θ + Vcc / 2 (Formula 3)
B2 (18d of 13B, OutY): βcos (θ + π / 2) + Vcc / 2
= −βsin θ + Vcc / 2 (Formula 4)

  Next, the arithmetic processing will be described. For convenience of explanation, a virtual arithmetic circuit 19 is shown in FIG. The output signals OutX and OutY from the magnetic sensors 13A and 13B are input to the arithmetic circuit 19, respectively. The arithmetic circuit 19 includes differential amplifiers 19a and 19b, analog / digital converters (A / D converters) 19c and 19d, and an arctangent calculator 19e. The differential amplifier 19a subtracts the output signal OutY (corresponding to B2 in Expression 4) from the output terminal 18d of the magnetic sensor 13B from the output signal OutX (corresponding to A1 in Expression 1) from the output terminal 18c of the magnetic sensor 13A. Output to the A / D converter 19c. The differential amplifier 19b subtracts the output signal OutX (corresponding to B1 in Expression 3) from the output terminal 18c of the magnetic sensor 13B from the output signal OutY (corresponding to A2 in Expression 2) from the output terminal 18d of the magnetic sensor 13A. Output to the A / D converter 19d.

  The A / D converters 19c and 19d perform analog / digital conversion (A / D conversion) on the voltage signals (output signals) from the differential amplifiers 19a and 19b, respectively, and output them to the arctangent calculator 19e. The arc tangent calculator 19e is configured by, for example, a microcomputer, and performs an arc tangent calculation (Arctan) using program processing on the output signals from the A / D converters 19c and 19d, thereby obtaining an angle θ. That is, an angle signal corresponding to the rotation angle of the circular rotating magnet 12 can be obtained in the range of 0 degrees to 360 degrees.

  In this case, (α + β) sin θ is obtained by the operation of Equation 1 to Equation 4 by the differential amplifier 19a, but (β−α) cos θ is obtained by the operation of Equation 2 to Equation 3 by the differential amplifier 19b. I can't get it. For this reason, the influence which arises from the value of (alpha) and (beta) cannot be removed. Next, a method for obtaining (β + α) cos θ instead of (β−α) cos θ will be described. As shown in FIG. 15, the potential level of the half-bridge circuit on the Y-axis is set by rotating the magnetic sensor 13B 90 degrees to the left from the state of FIG. 15A to the state of FIG. 15B. Can be reversed. In FIG. 15, the Vcc level of the magnetic sensor 13B is shown as “+”. In FIG. 15A, the “+” of the half-bridge circuit along the X axis is located on the left side, and the half along the Y axis. The “+” of the bridge circuit is located on the upper side. From this state, when the magnetic sensor 13B is rotated 90 degrees counterclockwise to the state of FIG. 15B, the “+” of the half bridge circuit along the X axis is located on the left side, and the half bridge along the Y axis The “+” of the circuit is located on the lower side.

As described above, when the magnetic sensor 13B is rotated by 90 degrees, the output from the output terminals 18c and 18d of the magnetic sensors 13A and 13B corresponding to the directions A1, A2, B1, and B2 expressed by the expressions 1 to 4 is performed. The output signals to be output are as shown in the following equations 1 ′ to 4 ′.
A1 (18c of 13A, OutX): α sin θ + Vcc / 2 (1)
A2 (18d of 13A, OutY): βcos θ + Vcc / 2 (2)
B1 (18c of 13B, OutY): -αsin (θ + π / 2) + Vcc / 2
= −αcos θ + Vcc / 2 Equation 3 ′
B2 (18d of 13B, OutX): βcos (θ + π / 2) + Vcc / 2
= −βsin θ + Vcc / 2 (Formula 4 ′)

  According to this, (α + β) sin θ is obtained by the calculation of Expression 1′-Expression 4 ′, and (α + β) cos θ is obtained by the calculation of Expression 2′-Expression 3 ′. However, in this case, the output signal OutY in the B1 direction is output from the output terminal 18c of the magnetic sensor 13B, and the output signal OutX in the B2 direction is output from the output terminal 18d of the magnetic sensor 13B. Therefore, actually, the virtual arithmetic circuit 19 in FIG. 14A is changed as shown in FIG. That is, the output terminal 18c of the magnetic sensor 13B is connected to the negative input “−” of the differential amplifier 19a, and is connected to the output terminal 18d of the magnetic sensor 13B or the negative input “−” of the differential amplifier 19b. Will be changed as follows.

  In this way, by rotating the magnetic sensor 13B by 90 degrees, it is possible to invert only the potential level of the half bridge circuit along the Y axis while maintaining the potential level of the half bridge circuit along the X axis. For this reason, if the magnetic sensor 13B rotated 90 degrees is arranged at the point B in FIG. 10, α cos θ of B1 can be converted to −α cos θ, and Equations 2 and 3 become (α + β) cos θ. As a result, the calculation formula Arctan ((α + β) sin θ / (α + β) cos θ) for rotation detection can be obtained, and the influence of the ratio α ′ / β ′ and the ratio α / β does not occur. Note that this is the state before rotating the magnetic sensor 13B, and in the arithmetic circuit shown in FIG. 14A, Vcc of the half-bridge circuit composed of the magnetoresistive effect elements a and b of the magnetic sensor 13B. This is the same as when the terminal and the terminal of Gnd are interchanged.

  Since this point is also related to a modification of the present embodiment, further explanation will be added. In this modification, the magnetic sensors 13A and 13B are both arranged at the position of the above embodiment. Without rotating the magnetic sensor 13B by 90 degrees, the X axes of the magnetic sensors 13A and 13B are along the tangential direction of the virtual concentric circle 17, and the Y axes of the magnetic sensors 13A and 13B are both parallel to the rotation axis 11. (See FIG. 15A). Also in this modification, the magnetic sensors 13A and 13B have the same configuration. However, as shown in FIG. 16A, the power supply terminals 18a1 and 18b1 for the half bridge circuit including the magnetoresistive elements a and b are used. And power supply terminals 18a2 and 18b2 for the half-bridge circuit composed of the magnetoresistive elements c and d are provided independently of each other.

  In this case, in the magnetic sensor 13A, the voltage Vcc is supplied to the power supply terminals 18a1 and 18a2, and the power supply terminals 18b1 and 18b2 are grounded. In the magnetic sensor 13B, the voltage Vcc is supplied to the power supply terminals 18b1 and 18a2, and the power supply terminals 18a1 and 18b2 are grounded. The other circuit configuration is the same as that of FIG. 14A assumed for convenience of explanation. According to this, the application direction of the voltage to the half bridge circuit composed of the magnetoresistive effect elements a and b in the magnetic sensor 13B is opposite to that in the case of FIG. Accordingly, the output signals output from the output terminals 18c and 18d in the directions A1, A2, B1, and B2 expressed by the above formulas 1 to 4 are expressed by the following formulas 1 ″ to 4 ″.

A1 (18c of 13A, OutX): αsin θ + Vcc / 2 (1)
A2 (18d of 13A, OutY): βcos θ + Vcc / 2 (2)
B1 (18c of 13B, −OutX): −α sin (θ + π / 2) + Vcc / 2
= −αcos θ + Vcc / 2 Equation 3 ″
B2 (18d of 13B, OutY): βcos (θ + π / 2) + Vcc / 2
= −βsin θ + Vcc / 2 (4)

  Therefore, (α + β) sin θ is obtained in the calculation of Expression 1 ″ −Expression 4 ″ by the differential amplifier 19a. Further, (α + β) cos θ is obtained by the calculation of Expression 2 ″ −Expression 3 ″ by the differential amplifier 19b. As a result, even with this modification, the calculation formula Arctan ((α + β) sinθ / (α + β) cosθ) for rotation detection can be obtained, and the influence of the ratio α ′ / β ′ and the ratio α / β does not occur. . However, in this modification, the same sensors can be used as the magnetic sensors 13A and 13B, but four more power supply terminals are required than in the above embodiment.

  Furthermore, by using the magnetic sensor 13A, 13B of the above-described embodiment and using the arithmetic circuit 19 as shown in FIG. 16B, (β−α) cos θ by the calculation of Expression 2 to Expression 3 is set to (α + β). It is also possible to change to cos θ. The arithmetic circuit of FIG. 16B is provided with a conversion circuit 19f between the output terminal 18c and the negative input (−) of the operational amplifier 19b in the virtual arithmetic circuit 19 of FIG. The conversion circuit 19f converts the output signal αcos θ + Vcc / 2 (OutX) output from the output terminal 18c of the magnetic sensor 13B into −αcos θ + Vcc / 2 by a combination of a plurality of differential amplifiers (analog arithmetic circuits). For example, after the voltage Vcc / 2 is subtracted from the output signal αcos θ + Vcc / 2, the sign of the subtraction result αcos θ is inverted, and the voltage Vcc / 2 is added to the inverted signal −αcos θ.

  Also by this, (α + β) sin θ is obtained in the calculation by the differential amplifier 19a, as in the case of the modified example of FIG. Further, (α + β) cos θ is obtained by the calculation by the differential amplifier 19b. As a result, even with this modification, the calculation formula Arctan ((α + β) sinθ / (α + β) cosθ) for rotation detection can be obtained, and the influence of the ratio α ′ / β ′ and the ratio α / β does not occur. . However, in this modified example, the magnetic sensor 13 having the same number of power supply terminals as the above embodiment can be used as the magnetic sensors 13A and 13B, but the arithmetic circuit 19 becomes complicated.

  Further, in the embodiment of FIG. 14 (b) and the modified examples of FIGS. 16 (a) and 16 (b), only the arctangent calculator 19e of the arithmetic circuit 19 is constituted by a digital circuit, and the rest. The circuit was configured with an analog circuit. However, instead of these, analog signals from the output terminals 18c and 18d of the magnetic sensors 13A and 13B are converted into digital signals by the A / D converter, and the differential amplifiers 19a and 19b and the conversions of the above-described embodiment and the modification are converted. Analog computation by the circuit 19f may be realized by digital computation by program processing of a microcomputer, similarly to the arctangent computing unit 19e.

  In this case, the analog signals from the output terminals 18c and 18d of the magnetic sensors 13A and 13B are converted into digital signals by time division using an A / D converter and supplied to the microcomputer in time division. May be. Also in the above-described embodiment and modification, only one A / D converter 19c, 19d is provided, and the output signal from the differential amplifiers 19a, 19b is A / D converted in a time division manner, and an arctangent calculator. You may make it supply to 19e (microcomputer).

  The magnetic sensors 13A and 13B are each provided with a bias magnet 14 with the N pole side facing the rotating shaft 11, and the circular rotating magnet 12 is magnetized with one N pole and one S pole in the rotational direction. Has been. For this reason, in the rotation detection device 10 according to the present embodiment, when the rotation shaft 11 rotates during the operation of the rotation detection device 10, the output signals of the magnetic sensors 13 </ b> A and 13 </ b> B become one cycle for each rotation of the circular rotating magnet 12. In addition, it is possible to obtain sine wave and cosine wave waveforms that are shifted from each other by ¼ period. By using these two waveforms, the direction of rotation, the number of rotations, and the rotation angle of the rotating shaft 11 can be detected. In addition, since the two magnetic sensors 13A and 13B are used, even when the magnetic sensors 13A and 13B are installed on the outer peripheral side of the circular rotating magnet 12, a good magnetic field can be detected.

Example 1
Next, as an example product, the rotation detection device 20 shown in FIG. 17 was produced and the characteristics thereof were confirmed. In this rotation detecting device 20, a disk-shaped circular rotating magnet 22 is attached to the upper end portion of the rotating shaft 21, and the two magnetic sensors 23A and 23B are disposed slightly above the outer peripheral side of the circular rotating magnet 22 as described above. , 13B. As the magnetoresistive effect element of each of the magnetic sensors 23A and 23B, the resistance change rate is as low as 3% to 5%. Was used. And wiring which comprises two half-bridge circuits with the magnetoresistive effect element which consists of an AMR element on the board | substrate which is the same form as the magnetic sensors 13A and 13B and whose length and width are 1.8 mm each and thickness is 0.1 mm. In addition to these, wirings between these half-bridge circuits, power supply terminals (Vcc, Gnd) and output terminals were formed by a photolithographic process.

  As the bias magnet, a resin magnet having a diameter of 1.5 mm and a thickness of 0.25 mm obtained by magnetizing rare earth (SmFeN) having a holding force of about 7 k Oersted with 40 k Oersted was used. The substrate and the bias magnet are epoxy-sealed through general semiconductor manufacturing processes such as die bonding, wire bonding, and transfer molding, and the length is 2.5 mm, the width is 2.8 mm, and the thickness is 0.8. Magnetic sensors 23A and 23B set to 8 mm were manufactured. Further, as the circular rotating magnet 22, a ferrite sintered disc-shaped magnet having a diameter of 9 mm and a thickness of 3 mm and having two poles in the radial direction was used. FIG. 18 shows the relationship between the external magnetic field and the output measured by the magnetic sensors 23A and 23B. FIG. 18 shows the output of the half-bridge circuit in the Y-axis direction when an external magnetic field is applied to the magnetic sensor 23A in the X-axis direction.

  The output of the half-bridge circuit in the X-axis direction when an external magnetic field was applied to the magnetic sensor 23A in the Y-axis direction was the same result. It can be seen from the curve shown in FIG. 18 that the magnetic field strength of the bias magnet provided in the magnetic sensors 23A and 23B is about 25 kA / m. Further, on the virtual concentric circle 27 or the virtual concentric circle at a position where the gap r shown in FIG. 17 from the outer peripheral surface of the circular rotating magnet 22 is 1.5 mm and the height h from the upper surface of the circular rotating magnet 22 is 0 mm or 3 mm. Magnetic sensors 23A and 23B were arranged at positions 90 degrees apart from each other on 27a in the circumferential direction. FIG. 19 shows the characteristics of the magnetic sensors 23A and 23B at the position where the gap r is 1.5 mm and the height h is 0 mm. The magnetic sensor 23A at the position where the gap r is 1.5 mm and the height h is 3 mm. , 23B are shown in FIG.

  FIG. 19A shows the relationship between the rotation angle of the circular rotating magnet 22 and the outputs of the magnetic sensors 23A and 23B when the height h is 0 mm, and the curve C1 is the direction of the rotating shaft 21 in the magnetic sensor 23A. The output of the half bridge circuit, the curve C2 is the output of the half bridge circuit in the tangential direction of the virtual concentric circle 27 in the magnetic sensor 23A, the curve D1 is the output of the half bridge circuit in the direction of the rotating shaft 21 in the magnetic sensor 23B, and the curve D2 is the magnetic sensor 23B. Represents the output of the half bridge circuit in the tangential direction of the virtual concentric circle 27 in FIG.

  FIG. 20A shows the relationship between the rotation angle of the circular rotating magnet 22 and the outputs of the magnetic sensors 23A and 23B when the height h is 3 mm, and the curve C1 ′ indicates the direction of the rotating shaft 21 in the magnetic sensor 23A. Output of the half-bridge circuit, curve C2 ′ is the output of the half-bridge circuit in the tangential direction of the virtual concentric circle 27a in the magnetic sensor 23A, curve D1 ′ is the output of the half-bridge circuit in the direction of the rotation axis 21 in the magnetic sensor 23B, curve D2 ′ Represents the output of the half bridge circuit in the tangential direction of the virtual concentric circle 27a in the magnetic sensor 23B.

  FIG. 19B shows the output of the half-bridge circuit in the direction of the rotating shaft 21 in the magnetic sensor 23A and the equivalent circuit of the half-bridge in the tangential direction of the virtual concentric circle 27 in the magnetic sensor 23B when the height h is 0 mm. Is output through the differential amplifier, the output of the half bridge circuit in the direction of the rotating shaft 21 in the magnetic sensor 23B when the height h is 0 mm, and the half bridge in the tangential direction of the virtual concentric circle 27 in the magnetic sensor 23A. The output of the circuit is shown after being differentially passed through a differential amplifier.

  FIG. 20B shows a differential amplifier that outputs the output of the half-bridge circuit in the direction of the rotating shaft 21 in the magnetic sensor 23A and the output of the half-bridge circuit in the tangential direction of the virtual concentric circle 27a in the magnetic sensor 23B when the height h is 3 mm. , The output of the half bridge circuit in the direction of the rotating shaft 21 in the magnetic sensor 23B when the height h is 3 mm, and the output of the half bridge circuit in the tangential direction of the virtual concentric circle 27a in the magnetic sensor 23A. It shows the output after differential passing through the differential amplifier.

  Further, FIG. 19C obtains each output shown in FIG. 19A as an electrical angle by arc tangent calculation, and calculates the difference between the electrical angle and the mechanical angle that is the actual rotation angle of the circular rotating magnet 22. FIG. 20 (c) shows the angle error at the time of taking, and each output shown in FIG. 20 (a) is obtained as an electrical angle by arctangent calculation, and the electrical angle and the actual rotation of the circular rotating magnet 22 are obtained. The angle error is shown by taking the difference from the mechanical angle, which is an angle. These characteristics are shown in Table 1 below.

表１より、回転検出装置２０では、磁気センサ２３Ａ，２３Ｂの円形回転磁石２２の上面からの高さを変更しても、すなわち円形回転磁石２２に対する磁気センサ２３Ａ，２３Ｂの設置範囲を広くしても磁界の精度の高い検出が可能であることが分かる。

From Table 1, in the rotation detection device 20, even if the height of the magnetic sensors 23A and 23B from the upper surface of the circular rotating magnet 22 is changed, that is, the installation range of the magnetic sensors 23A and 23B with respect to the circular rotating magnet 22 is increased. It can also be seen that the magnetic field can be detected with high accuracy.

(Example 2)
Next, as a circular rotating magnet, a neodymium sintered ring-shaped magnet with an outer diameter of 15 mm, an inner diameter of 8 mm, a thickness of 3 mm, and two poles in the radial direction, a diameter of 25 mm, a thickness of 3 mm, and a radial direction of 2 The characteristics were confirmed with a rotation detection device using a pole magnetized neodymium sintered disc-shaped magnet. As a result, in the rotation detection device using a ring-shaped magnet, when the gap r is 6 mm and the height h is 0 mm, in the rotation detection device using a columnar magnet, the gap r is 8 mm, When the height h is 0 mm, the same characteristics as those shown in FIG. 19 can be obtained.

  Furthermore, as a circular rotating magnet, the characteristics were confirmed with a rotation detecting device using a ferrite sintered cylindrical magnet magnet having a diameter of 9 mm, a thickness of 3 mm, and two poles magnetized in the plane direction (thickness direction). As a result, when the gap r was 1.5 mm and the height h was 3 mm, the characteristics shown in FIG. 21 could be obtained. As shown in FIG. 21, when a circular rotating magnet magnetized in the surface direction was used, the individual output waveforms of both magnetic sensors became a waveform including distortion.

  In this case, the waveform distortion of one magnetic sensor has an odd harmonic component added to the fundamental wave, and the waveform distortion of the other magnetic sensor has an odd harmonic component minus the fundamental wave. Therefore, the output after passing through the subtracting circuit the output C3 of the half bridge circuit in the direction of the rotation axis of one magnetic sensor and the output D4 of the half bridge circuit in the tangential direction of the other magnetic sensor and the tangential direction of the one magnetic sensor. The output after passing the output C4 of the half bridge circuit and the output D3 of the half bridge circuit in the rotation axis direction of the other magnetic sensor through the subtracting circuit cancels each other's distortion, and the distortion decreases. As shown in FIG. 21 (c), the angle error based on the waveform after passing through the subtracting circuit is ± 2 degrees or less, and no significant deterioration in accuracy has occurred.

  As described above, in the rotation detection device 10 according to this embodiment, the magnetic sensors 13A and 13B are arranged outside the outer peripheral surface of the circular rotating magnet 12, so that the circular rotating magnet 12 is rotated instead of the end of the rotating shaft 11. The magnetic sensors 13 </ b> A and 13 </ b> B can be easily installed even with the rotary shaft penetrating structure provided on the outer peripheral surface of the central portion in the axial direction of the shaft 11. In addition, since the two magnetic sensors 13A and 13B are used and the two magnetic sensors 13A and 13B are installed at positions 90 degrees apart from each other in the circumferential direction, the output signals of the magnetic sensors 13A and 13B can be compensated for each other. It is possible to detect the rotation direction, the rotation speed, and the position of the rotation shaft 11 with high accuracy.

  Further, since the Y axis of the magnetic sensor 13 </ b> A and the X axis of the magnetic sensor 13 </ b> B are parallel to the rotary shaft 11 of the circular rotating magnet 12, the rotation detecting device 10 can be reduced in size relative to the radial direction of the circular rotating magnet 12. Furthermore, the circular rotating magnet 12 is polarized with the boundary of the surface that bisects the circular rotating magnet 12 across the rotating shaft 11 and is polarized as two poles, one of which is an S pole and the other is an N pole. When the circular rotary magnet 12 makes one rotation, the magnetic sensors 13A and 13B can output a sine wave and a cosine wave having a phase difference with a waveform of one cycle. In addition, since the magnetic sensors 13A and 13B are each provided with the bias magnet 14, an output signal having the same period as the magnetic field period of the external magnetic field by the bias magnet 14 can be obtained.

  Further, one magnetoresistive effect element a, b, c, d is formed in each of the four regions 15a, 15b, 15c, 15d, and the magnetoresistive effect element a, b located on the X axis (or Y axis). And magnetoresistive elements c and d located on the Y-axis (or X-axis) constitute a half-bridge equivalent circuit. Since a subtracting circuit (arithmetic circuit) that subtracts signals output from the magnetic sensors 13A and 13B to compensate each other is provided, the input resistance value can be increased and the wiring can be simplified. .

  The magnetic sensor 13A has the Y axis parallel to the rotational axis 11 of the circular rotating magnet 12, and the X axis is arranged along the tangent line of the virtual concentric circle 17, whereas the magnetic sensor 13B has the X axis. Is parallel to the rotation axis 11 of the circular rotating magnet 12 and the Y axis is arranged along the tangent line of the virtual concentric circle 17. As described above, by rotating the magnetic sensor 13B by 90 degrees with respect to the magnetic sensor 13A, the potential level of the half bridge circuit along the X axis of the magnetic sensor 13B is maintained, and the half bridge circuit along the Y axis is maintained. Only the potential level can be inverted. As a result, even if the position of the magnetic sensors 13A and 13B with respect to the circular rotating magnet 12 is changed as described above, the detection value is not affected.

  In addition, since the magnetoresistive elements a, b, c, and d are inclined by 45 degrees with respect to both the X axis and the Y axis, each magnetoresistive element a, b, c, d has directions of both axes. Therefore, a more accurate detection is possible. Furthermore, since the magnetoresistive elements a, b, c, and d are composed of AMR elements, good detection is possible. Since the bias magnet 14 is composed of a sintered magnet or a resin magnet, the magnetic sensors 13A and 13B can obtain good magnetic field strength and can exhibit resistance to external magnetic field strength. Furthermore, since the circular rotating magnet 12 is polarized in parallel with the rotating shaft 11 and magnetized in the radial direction, a magnetic field without distortion is generated, and the accuracy of the rotation detecting device 10 is further improved.

(Second Embodiment)
22 to 24 show a rotation detection device 30 according to the second embodiment of the present invention. In this rotation detection device 30, the magnetic sensors 33A and 33B are arranged so that the X axis and the Y axis are in the horizontal direction and the center points O are coaxial with the circular rotary magnet 32 and are circular as shown in FIGS. It is positioned on a virtual concentric circle 37 having a diameter slightly larger than the diameter of the rotating magnet 32, and is arranged at a position above the circular rotating magnet 32 with an interval of 90 degrees in the circumferential direction of the virtual concentric circle 37. Has been.

  In this case, the magnetic sensor 33A is arranged along the tangent line of the virtual concentric circle 37 with the X axis along the normal line of the virtual concentric circle 37, and the magnetic sensor 33B is arranged with the tangent line of the virtual concentric circle 37 along the Y axis. The X axis is arranged along the normal line of the virtual concentric circle 37. In FIG. 24, the rotating shaft 31 is indicated by a broken line in order to represent the magnetic sensor 33B. The rest of the configuration of the rotation detection device 30 is the same as that of the rotation detection device 10 described above. Accordingly, the same parts are denoted by the same reference numerals and the description thereof is omitted.

  Next, in the rotation detection device 30 according to the present embodiment, the direction of the X axis and the Y axis of the magnetic sensor 33B is different from the direction of the X axis and the Y axis of the magnetic sensor 33A, as in the above-described embodiment. The reason for this will be described with reference to FIG. Also in this case, the following is assumed in FIG. The positions of the magnetic sensors 33A and 33B are points A and B. The X-axis directions of the magnetic sensors 33A and 33B are both tangential to a virtual concentric circle 17 (37 in FIG. 23 but 17 here using the reference numeral in FIG. 10) and the magnetic sensors 33A and 33B. Both the Y-axis directions are normal directions of the virtual concentric circle 17.

  Then, the direction along the tangent line of the virtual concentric circle 17 at the point A is A2, the direction along the normal line of the virtual concentric circle 17 is A3, the direction along the tangent line of the virtual concentric circle 17 at the point B is B2, and the virtual concentric circle 17 The direction along the normal was B3. At this time, the circular rotating magnet 12 was rotated 360 degrees, and the magnetic field applied in each direction was analyzed using magnetic simulation software. As a result, in the magnetic sensor 33A, the magnetic field waveform indicated by a curve with a black triangle in FIG. 11 appears in the direction A2, and the magnetic field waveform indicated by a curve with a black rhombus appears in the direction A3. It was. In the magnetic sensor 33B, a magnetic field waveform indicated by a curve with a white triangle in FIG. 12 appears in the direction B2, and a magnetic field waveform indicated by a curve with a white rhombus appears in the direction B3. .

  That is, as in the case of the above embodiment, the magnetic field waveform in the direction A2 at the point A is βcos θ indicated by a curve with a black triangle in FIG. 11, and the magnetic field waveform in the direction A3 at the point A is Assuming that γ sin θ shown by a curve with a black diamond at 11, the magnetic field waveform in the direction B 2 at point B is βcos (θ + π / 2) shown by a curve with a white triangle in FIG. The magnetic field waveform in the direction B3 is γ sin (θ + π / 2) shown by a curve with diamond-shaped squares in FIG. Note that β is the amplitude of the magnetic field waveform in directions A2 and B2, and γ is the amplitude of the magnetic field waveform in directions A3 and B3, and the relationship between β and γ is γ ≧ β. That is, when the magnetic sensors 33A and 33B are oriented in the horizontal direction, the relationship between the directions A3 and A2 at the point A and the directions B3 and B2 at the point B is the same as the vertical direction of the magnetic sensors 13A and 13B of the above-described embodiment. Is substantially the same as the relationship between the directions A1 and A2 at the point A and the directions B1 and B2 at the point B.

  Therefore, even when the magnetic sensors 33A and 33B are arranged horizontally, the magnetic field waveforms in the directions A2 and A3 and in the directions B2 and B3 change when the position in the direction along the rotation axis 31 changes. For this reason, when the rotation detection device 30 is operated, the circular rotating magnet 32 is displaced along the rotating shaft 31 to prevent the occurrence of problems due to the change in the distance between the circular rotating magnet 32 and the magnetic sensors 33A and 33B. Therefore, it is necessary to compensate by performing arithmetic processing on the output signals of the magnetic field waveforms in the directions A3 and B2 and the directions A2 and B3 of the magnetic sensors 33A and 33B, and to remove the influence of the ratio γ / β.

  Also in this case, the magnetic sensors 33A and 33B may be connected to the arithmetic circuit 19 as shown in FIG. However, in this case, an output signal γ sin θ + Vcc / 2 of the magnetic field waveform in the direction A3 in the magnetic sensor 33A is supplied to the positive input “+” of the differential amplifier 19a, and an output of the magnetic field waveform in the direction B2 in the magnetic sensor 33B. The signal βcos (θ + π / 2) + Vcc / 2 is supplied to the negative input “−” of the differential amplifier 19a. Further, an output signal βcos (θ + π / 2) + Vcc / 2 of the magnetic field waveform in the direction A2 in the magnetic sensor 33A is supplied to the positive input “+” of the differential amplifier 19b, and the magnetic field waveform in the direction B3 in the magnetic sensor 33B. The output signal −γ sin θ + Vcc / 2 is supplied to the negative input “−” of the differential amplifier 19a.

  Also in this case, the potential level of the half-bridge circuit along the X axis of the magnetic sensor 33B is maintained by rotating the magnetic sensor 33B by 90 degrees with respect to the magnetic sensor 33A to the state shown in FIGS. Only the potential level of the half-bridge circuit along the Y axis can be reversed. This eliminates the influence of the ratio γ / β on the calculation formula Arctan (γsinθ / βcosθ) for detecting the rotation angle. Further, according to the rotation detection device 30, since the magnetic sensors 33 </ b> A and 33 </ b> B are arranged in the horizontal direction, the rotation detection device 30 can be reduced in size with respect to the rotation axis direction of the circular rotary magnet 32. The other effects of the rotation detection device 30 are the same as those of the rotation detection device 10 described above.

  Also in the second embodiment, the same modifications as in the first embodiment can be made. That is, without rotating the magnetic sensor 33B by 90 degrees, the X axis of the magnetic sensors 33A and 33B is along the tangential direction of the virtual concentric circle 37, and the Y axis of the magnetic sensors 33A and 33B is along the normal direction of the virtual concentric circle 37. I will let you. And what is necessary is just to connect magnetic sensor 33A, 33B to the arithmetic circuit 19 shown to Fig.16 (a), (b) similarly to the case of the modification of the said embodiment.

  When the pair of magnetic sensors are inclined at a predetermined angle between the magnetic sensors 13A and 13B arranged vertically in the rotation detecting device 10 and the magnetic sensors 33A and 33B arranged horizontally in the rotation detecting device 30. 11, the magnetic field waveform in the direction A1 or the direction A3 shown in FIG. 11 changes between the curve in the direction A1 and the curve in the direction A3, and the magnetic field waveform in the direction B1 or the direction B3 shown in FIG. It changes between the curve and the curve in direction B3. For this reason, even when a pair of magnetic sensors are arranged to be inclined with respect to the rotation axis, the influence of the ratio α / β and the like is eliminated by rotating one magnetic sensor by 90 degrees with respect to the other magnetic sensor. be able to.

(Third embodiment)
FIG. 25 shows a magnetic sensitive surface on the substrate 45 of the magnetic sensor 43 provided in the rotation detecting device according to the third embodiment of the present invention. The magnetic sensor 43 includes a bias magnet (not shown), a substrate 45, and eight magnetoresistive elements a1, a2, b1, b2, c1, c2, d1, and d2 formed on the substrate 45. Has been. For convenience, the substrate 45 is provided with regions 45a and 45b on both sides of the portion along the X axis with the center point O at which the X axis and the Y axis intersect, and regions on both sides of the portion along the Y axis. 45c and 45d are provided. The distances from these regions 45a, 45b, 45c, 45d to the center point O are set to be equal.

  The magnetoresistive effect elements a1, a2, b1, b2, c1, c2, d1, and d2 are each formed in an elongated rectangular shape, and the magnetoresistive effect elements a1 and a2 are formed in the region 45a. b2 is formed in the region 45b, the magnetoresistive elements c1 and c2 are formed in the region 45c, and the magnetoresistive elements d1 and d2 are formed in the region 45d. The magnetoresistive effect elements a1, a2, b1, b2, c1, c2, d1, and d2 are formed to be inclined by 45 degrees with respect to the X axis and the Y axis, respectively. The magnetoresistive effect element a1 and the magnetoresistive effect element b1, magnetoresistive effect element a2 and magnetoresistive effect element b2, magnetoresistive effect element c1 and magnetoresistive effect element d1, and magnetoresistive effect element c2 and magnetoresistive effect element d2 are point-symmetric with respect to center point O. It is arranged to be.

  In addition, each set of magnetoresistive elements a1 and a2, magnetoresistive elements b1 and b2, magnetoresistive elements c1 and c2, and magnetoresistive elements d1 and d2 has a V shape with the top facing the center point O side. Arranged like drawing. That is, when the positions of the magnetoresistive elements a1, d2, b1, and c2 are changed by 90 degrees around the center point O on the substrate 45, the other magnetoresistive elements a1, d2, and so on before the position is changed. It arrange | positions so that either of b1 and c2 may be located in the part which was located. Then, when the positions of the magnetoresistive elements a2, d1, b2, c1 are changed by 90 degrees around the center point O on the substrate 45, the other magnetoresistive elements a2, d1, before the position change are performed. It arrange | positions so that either of b2 and c1 may be located in the part which was located.

  As shown in FIG. 26, the magnetoresistive elements a1, a2, b1, and b2 and the magnetoresistive elements c1, c2, d1, and d2 are connected to form a full bridge circuit. In one full bridge circuit, the signal output from the connection point of the magnetoresistance effect elements a1 and a2 is extracted as + OutX, and the signal output from the connection point of the magnetoresistance effect elements b1 and b2 is extracted as -OutX. In the other full bridge circuit, the signal output from the connection point of the magnetoresistive effect elements c1 and c2 is taken out as + OutY, and the signal output from the connection point of the magnetoresistive effect elements d1 and d2 is taken out as -OutY. The magnetic sensor 43 configured in this manner is housed in a mold package similar to the mold package 16a shown in FIG. 6, and in this case, the magnetic sensor 43 includes two pairs of power supply terminals and two pairs of power terminals. A signal output terminal is provided.

  In addition, this rotation detection device includes an arithmetic circuit shown in FIG. 27 instead of the arithmetic circuit shown in FIG. 14B as an arithmetic processing circuit according to the present invention. Other configurations of the rotation detection device according to the present embodiment are the same as those of the rotation detection device 10 described above. That is, also in this rotation detection device, a pair of magnetic sensors 43A and 43B are provided, along a tangent line of a predetermined virtual concentric circle, and at a position above the circular rotating magnet and spaced apart from each other by 90 degrees in the circumferential direction. It is arranged at an angle. As shown in FIGS. 1 to 3 of the first embodiment, in one magnetic sensor 43A, the X axis is arranged along the tangent line of the virtual concentric circle, and the Y axis is arranged in parallel with the rotation axis of the circular rotating magnet. ing. In the other magnetic sensor 43B, the Y axis is arranged along a tangent line of a virtual concentric circle, and the X axis is arranged in parallel with the rotation axis of the circular rotating magnet.

  Further, as shown in FIGS. 22 to 24 of the third embodiment, in one magnetic sensor 43A, the X axis is along the tangent of the virtual concentric circle, the Y axis is along the normal of the virtual concentric circle, and the other magnetic sensor In 43B, the X axis may be along the normal line of the virtual concentric circle and the Y axis may be along the tangent line of the virtual concentric circle. In this case, an arithmetic circuit 49 shown in FIG. 27 is used to compensate the signals output from the two magnetic sensors 43A and 43B.

  The arithmetic circuit 49 includes four differential amplifiers 49a, 49b, 49c, and 49d. The differential amplifier 49a subtracts the output signal −OutX (= −αsin θ + Vcc / 2) of the magnetic sensor 43A from the output signal OutX (= αsin θ + Vcc / 2) of the magnetic sensor 43A, and outputs the result. This subtraction substantially performs an addition function, and the waveform signal 2αsinθ is output from the differential amplifier 49a. Similarly, the differential amplifier 49b outputs the output signal OutY (= βcos (θ + π / 2) + Vcc / 2) of the magnetic sensor 43B to the output signal −OutY (= −βcos (θ + π / 2) + Vcc / 2) of the magnetic sensor 43B. Is subtracted to output the waveform signal 2βcos (θ + π / 2) (= −2βsinθ).

  Similarly, the differential amplifier 49c subtracts the output signal −OutY (= −βcos θ + Vcc / 2) of the magnetic sensor 43A from the output signal OutY (= βcos θ + Vcc / 2) of the magnetic sensor 43A, and outputs the waveform signal 2βcos θ. Similarly, the differential amplifier 49b outputs the output signal OutX (= αsin (θ + π / 2) + Vcc / 2) of the magnetic sensor 43B to the output signal −OutX (= −αsin (θ + π / 2) + Vcc / 2) of the magnetic sensor 43B. Is subtracted to output the waveform signal 2αsin (θ + π / 2) (= −2αcos θ).

  The output of the differential amplifier 49a is supplied to the positive input “+” of the differential amplifier 49e, and the output of the differential amplifier 49b is supplied to the negative input “−” of the differential amplifier 49e. The output of the differential amplifier 49c is supplied to the positive input “+” of the differential amplifier 49f, and the output of the differential amplifier 49d is supplied to the negative input “−” of the differential amplifier 49f. These differential amplifiers 49e and 49f correspond to the differential amplifiers 19a and 19b (see FIG. 14B) of the first embodiment, respectively. The waveform signal 2 (α + β) sin θ is output from the differential amplifier 49e. A waveform signal 2 (α + β) cos θ is output from the differential amplifier 49f. On the output side of the differential amplifiers 49e and 49f, A / D converters 49g and 49h and an arctangent calculator 49i similar to the A / D converters 19c and 19d and the arctangent calculator 19e of the first embodiment are provided. It is connected.

  Therefore, the angle signal is finally output also in the third embodiment. According to the rotation detection device according to the third embodiment, an output waveform signal having twice the amplitude is obtained as compared with the rotation detection device 10 including the half-bridge circuit described above, and the stability of the midpoint potential is improved. Improvement and output are doubled. About the other effect of this rotation detection apparatus, it is the same as that of the rotation detection apparatus 10 mentioned above. Also in the third embodiment, by providing a power supply terminal for each full bridge circuit of the magnetic sensors 43A and 43B, it is not necessary to rotate the magnetic sensor 43B by 90 degrees as in the modification of the above embodiment. . Similar to the above embodiment, instead of the analog calculation by the differential amplifiers 49a to 29f shown in FIG. 27, calculation processing using a microcomputer similar to the arctangent calculator 49i may be performed.

(Modification)
FIG. 28 shows a magnetic sensitive surface on the substrate 55 of the magnetic sensor 53 provided in the rotation detection device according to the modification of the third embodiment. The magnetic sensor 53 includes the magnetoresistive elements a1 and a2, the magnetoresistive elements b1 and b2, the magnetoresistive elements c1 and c2, and the magnetoresistive effect arranged so as to draw a V shape in the magnetic sensor 43 described above. The elements d1 and d2 are placed in the counterclockwise direction (counterclockwise direction in the state of FIGS. 25 and 28) around the center point of each of the regions 45a, 45b, 45c and 45d in the regions 45a, 45b, 45c and 45d, respectively. It is formed in a state rotated 90 degrees.

  About the structure of the other part of the rotation detection apparatus provided with this magnetic sensor 53, it is the same as that of the rotation detection apparatus which concerns on 3rd Embodiment mentioned above. The operational effects of the rotation detection device according to this modification are the same as the operational effects of the rotation detection device according to the third embodiment described above. Note that the rotation detecting device shown in FIGS. 25 and 28 may be configured by using a magnetoresistive effect element made of a GMR element using a ferromagnetic material, and this also allows the third embodiment and its modifications. A rotation detection device equivalent to the rotation detection device according to the example can be obtained.

(Fourth embodiment)
FIG. 29 shows the magnetic sensitive surface on the substrate 65 of the magnetic sensor 63 provided in the rotation detection device according to the fourth embodiment of the present invention. The magnetic sensor 63 includes a bias magnet (not shown), a substrate 65, and four magnetoresistive elements a3, b3, c3, and d3 formed on the substrate 65. For convenience, the substrate 65 has regions 65a and 65b on both sides of the portion along the X axis centered on the center point O where the X axis and the Y axis intersect, and virtual regions 65c and 65c on both sides of the portion along the Y axis. 65d is set to be the same distance from the center point O.

  The magnetoresistive effect elements a3, b3, c3, and d3 are composed of GMR elements using a soft magnetic material, and each is formed in an elongated rectangular shape. The magnetoresistive element a3 is formed in the region 65a, the magnetoresistive element b3 is formed in the region 65b, the magnetoresistive element c3 is formed in the region 65c, and the magnetoresistive element d3 is formed in the region 65d. ing. The magnetoresistive elements a3 and b3 are formed on the X axis with the longitudinal direction along the X axis, and the magnetoresistive elements c3 and d3 are formed on the Y axis with the longitudinal direction along the Y axis. The distances from the center point O of the magnetoresistive elements a3, b3, c3, and d3 are set to be the same. The magnetoresistive elements a3, b3, c3, and d3 are connected so as to form two half-bridge circuits as shown in FIG. In this case, a3 in FIG. 5 corresponds to a3, b3 to b3, c3 to c, and d3 to d.

  When the magnetoresistive effect elements a, b, c, and d constituted by AMR elements are used like the magnetic sensors 13A and 13B shown in FIG. 4, two directions of the X-axis direction and the Y-axis direction are used. Good detection is possible when there is a vector magnetic field. However, in the magnetic sensor 63 using the magnetoresistive effect elements a3, b3, c3, and d3 composed of GMR elements using a soft magnetic material, only the strength of the magnetic field is detected. Therefore, the magnetoresistive elements a3, b3, c3, and d3 can be formed along the X and Y axes in the longitudinal direction. The magnetoresistive elements a3, b3, c3, and d3 may be inclined by 45 degrees with respect to the X axis and the Y axis as in the magnetoresistive elements a, b, c, and d described above. The other configuration of the rotation detection device according to the present embodiment is the same as that of the rotation detection device 10 described above. The operational effects of the rotation detection device according to the present embodiment are the same as the operational effects of the rotation detection device 10 described above.

  In addition, the magnetoresistive elements a3, b3, c3, and d3 formed of GMR elements using soft magnetic materials are replaced with the magnetoresistive elements a1, a2, b1, b2, c1, c2, and FIGS. The magnetic sensor may be configured by arranging like d1 and d2. In this case, as shown in FIG. 30, the magnetoresistive elements a1, b1, a2, and b2 and the magnetoresistive elements c1, d1, c2, and d2 are connected to form a full bridge circuit, respectively. In one full bridge circuit, the signal output from the midpoint of the magnetoresistive effect elements a1 and b1 is taken out as + OutX, the signal output from the midpoint of the magnetoresistive effect elements b2 and a2 is taken out as -OutX, and the other In the full bridge circuit, the signal output from the midpoint of the magnetoresistive effect elements c1 and d1 is taken out as + OutY, and the signal output from the midpoint of the magnetoresistive effect elements d2 and c2 is taken out as -OutY.

  The other configuration of this rotation detection device is the same as that of the rotation detection device including the magnetic sensors 43 and 53 shown in FIGS. The operational effects of this rotation detection device are also the same as the operational effects of the rotation detection device provided with the magnetic sensors 43 and 53 shown in FIGS. Magnetoresistive elements composed of GMR elements using a soft magnetic material are arranged as magnetoresistive elements a1, a2, b1, b2, c1, c2, d1, and d2 in FIGS. When configuring the magnetic sensor, it is preferable to connect the magnetoresistive elements a1, a2, b1, b2, c1, c2, d1, d2 as shown in FIG. 30 as described above. The connection can also be made as shown in FIG. Similarly, magnetoresistive effect elements composed of AMR elements can be connected as shown in FIG.

  In each of the embodiments described above, a small insertion hole 12a is formed at the center of the circular rotary magnet 12, and the rotation shaft 11 is inserted through the insertion hole 12a. Instead, as shown in FIG. A ring-shaped circular rotating magnet 42 having a large insertion hole 42a formed at the center may be used, and a cylindrical rotating shaft 41 having a large outer diameter and inner diameter may be inserted into the insertion hole 42a of the circular rotating magnet 42. According to this, it becomes possible to let wiring pass inside the rotating shaft 41. As the circular rotating magnet, various magnets such as those magnetized in the radial direction and those magnetized in the surface direction can be used. Among these, the disk-shaped circular rotating magnet 52 magnetized in the radial direction shown in FIG. 32, the ring-shaped circular rotating magnet 62 magnetized in the radial direction shown in FIG. 33, and the structure shown in FIG. There are a disk-like circular rotating magnet 72 magnetized in the surface direction and a ring-shaped circular rotating magnet 82 magnetized in the surface direction shown in FIG.

  The circular rotating magnet 52 is polarized with a boundary passing through the center axis of rotation and dividing the circular rotating magnet 52 into two equal parts, and is polarized in the radial direction. One is an S pole and the other is an N pole. Yes. The circular rotating magnet 62 is polarized with the surface that bisects the circular rotating magnet 62 in the axial direction along the diameter as a boundary and is polarized so that the outer peripheral side and the inner peripheral side are different poles. And the inner peripheral side are magnetized in two radial directions, one on the outer peripheral side is the S pole, the other is the N pole, one on the inner peripheral side is the N pole, and the other is the S pole.

  The circular rotating magnet 72 is polarized with the plane that bisects the circular rotating magnet 72 passing through the center axis of rotation as the boundary and the upper side and the lower side so as to bisect in the direction of the rotation axis with the plane orthogonal to the rotation axis as the boundary. One side on the upper side is an S pole, the other is an N pole, one on the lower side is an N pole, and the other is an S pole. The circular rotating magnet 82 is polarized with a plane that bisects the circular rotating magnet 82 in the axial direction along the diameter as a boundary, and is polarized so that the upper side and the lower side have different poles. One is an S pole, the other is an N pole, one on the lower side is an N pole, and the other is an S pole.

  The circular rotary magnets 62 and 82 are attached to the outer peripheral surface of the rotary shaft 41 and the like described above, but the circular rotary magnets 52 and 72 are installed inside the cylindrical rotary shaft. A virtual concentric circle similar to the virtual concentric circle 17 described above is set for the circular rotating magnets 52, 62, 72, and 82, and a predetermined magnetic sensor is disposed on the virtual concentric circle. In such a state, attention was paid to the magnetic field detected by the magnetic sensor when each of the circular rotating magnets 52, 62, 72, and 82 was rotated 360 degrees together with the rotation axis, and the magnetic simulation software analyzed. The results are shown in FIGS. 36 shows the result of the circular rotating magnet 52, FIG. 37 shows the result of the circular rotating magnet 62, FIG. 38 shows the result of the circular rotating magnet 72, and FIG. 39 shows the result of the circular rotating magnet 82.

  36 (a), FIG. 37 (a), FIG. 38 (a), and FIG. 39 (a), the positions of the circular rotary magnets 52, 62, 72, and 82 are shown at the respective lower end central portions. Black dots indicate positions analyzed by magnetic simulation software. Also, the square ranges indicated by broken lines in FIGS. 36 (a), 37 (a), 38 (a), and 39 (a) indicate the range of positions where the magnetic sensor is installed. The curves with black squares in FIGS. 36 (b), 37 (b), 38 (b), and 39 (b) indicate magnetic flux lines parallel to the tangent lines of the virtual concentric circles. The curve with triangles indicates the magnetic flux lines in the direction parallel to the normal of the virtual concentric circles, and the curve with black diamonds indicates the magnetic flux lines in the direction parallel to the rotation axis.

  It can be seen from FIGS. 36 (b) and 37 (b) that the circular rotating magnets 52 and 62 magnetized in the radial direction have a sinusoidal period, and the surface from FIGS. 38 (b) and 39 (b). It can be seen that the circular rotating magnets 72 and 82 magnetized in the direction have a period including distortion. Therefore, it is more preferable that the circular rotating magnet has a disk shape or a ring shape that is polarized in parallel with the rotation center axis and is magnetized in two directions in the radial direction, which leads to improvement in detection accuracy. Further, in the circular rotating magnets 52 and 62 magnetized in the radial direction from FIGS. 36 (a) and 37 (a), the outer peripheral side of the circular rotating magnets 32 and 42 even when the position is displaced along the rotation axis. It can also be seen that the magnetic flux lines do not change significantly at positions other than.

  The rotation detection device according to the present invention is not limited to the above-described embodiments, and can be implemented with appropriate modifications within the technical scope of the present invention. For example, in each of the embodiments described above, when all the arrangements of the magnetoresistive elements a to d, a1 to d1, a2 to d2, and a3 to d3 are rotated 90 degrees around the center point O, the positions of each other However, the arrangement of the magnetoresistive elements a1 to d1 and a2 to d2 constituting the full bridge circuit can be appropriately changed. That is, not only the magnetoresistive elements a1 to d1 and a2 to d2 that are located on the respective axes are symmetric with respect to the center point O, but also those that are arranged across the respective axes. May be axisymmetric. Further, the one located on one axis may be made point-symmetric with respect to the center point O, and the one located on the other axis may be made line-symmetric with respect to one axis.

  10, 20, 30 ... rotation detection device, 11, 21, 31, 41 ... rotating shaft, 12, 22, 32, 42, 52, 62, 72, 82 ... circular rotating magnet, 13A, 13B, 23A, 23B, 33A , 33B, 43, 43A, 43B, 53, 63 ... magnetic sensor, 14 ... bias magnet, 15, 45, 55, 65 ... substrate, 15a, 15b, 15c, 15d, 45a, 45b, 45c, 45d, 65a, 65b , 65c, 65d ... area, 17, 27, 27a, 37 ... virtual concentric circles, 19, 49 ... arithmetic processing circuit, a, b, c, d, a1, b1, c1, d1, a2, b2, c2, d2, a3, b3, c3, d3... magnetoresistive effect element.

Claims (9)

A two-pole circular rotating magnet attached to the rotating body, two magnetic sensors for detecting a change in the magnetic field of the circular rotating magnet, and the rotation angle of the circular rotating magnet from the detection results of the two magnetic sensors. A rotation detection device comprising an arithmetic processing circuit for calculating,
The magnetic sensor includes a bias magnet, a substrate opposed to the magnetic pole surface in a state where the center point is aligned with the magnetic center of the magnetic pole surface of the bias magnet, and orthogonal to the central point of the substrate and parallel to the magnetic pole surface. Four regions set at the same distance from the center point along two extending axes, respectively, and magnetoresistive elements formed in the same shape,
Two bridge circuits are formed by connecting two magnetoresistive elements provided along each of the two axes in series, and a power supply voltage is applied to both ends of the two bridge circuits. The output waveform signal is taken out from the connection point of two magnetoresistive elements,
The arithmetic processing circuit calculates the rotation angle of the circular rotating magnet using the output waveform signal,
One of the two axes of each magnetic sensor is parallel to a tangent of a circle formed by the outer peripheral surface of the circular rotating magnet, and the other axis of the two axes of each magnetic sensor The two magnetic sensors are arranged outside the outer peripheral surface of the circular rotating magnet and centered on the rotating central axis of the circular rotating magnet so that the inclination angles with respect to the rotating central axis of the circular rotating magnet are the same. Installed at positions 90 degrees apart from each other in the circumferential direction ,
When one of the two axes is the X axis and the other is the Y axis, the arithmetic processing circuit outputs an output waveform signal corresponding to the X axis of the one magnetic sensor and the Y axis of the other magnetic sensor. And an output waveform signal corresponding to the X axis of the other magnetic sensor and an output waveform signal corresponding to the Y axis of the one magnetic sensor to calculate the same amplitude. Sine wave signal and cosine wave signal having respectively, arc tangent calculation using the extracted sine wave signal and cosine wave signal,
While maintaining the position of the magnetic pole surface of one of the two magnetic sensors, the X and Y axes of the one magnetic sensor are centered with respect to the X and Y axes of the other magnetic sensor. By outputting output waveform signals from the two magnetic sensors to the arithmetic processing circuit in a state of being rotated 90 degrees around the point, the sine wave signal and cosine wave signal having the same amplitude are extracted. A rotation detection device characterized by that. The sine wave signal is a sum of an output waveform signal corresponding to the X axis of the one magnetic sensor and the output waveform signal corresponding to the Y axis of the other magnetic sensor that are in phase with each other, and the cosine wave signal The rotation detection device according to claim 1, which is a sum of an output waveform signal corresponding to the X axis of the other magnetic sensor and the output waveform signal corresponding to the Y axis of the one magnetic sensor that are in phase with each other. The bridge circuit forms the magnetoresistive effect elements one by one in the four regions so that the respective positions overlap each other when the magnetoresistive effect elements are rotated by 90 degrees about the center point. The rotation detection device according to claim 1, wherein the rotation detection device is a half-bridge circuit configured by connecting two magnetoresistive effect elements located on an axis. In the bridge circuit, the magnetoresistive effect element is arranged so that the elements located on each axis are point-symmetrical with respect to the center point, or the elements arranged across the axes are line-symmetrical. way to form two by two the four regions, the two four magnetoresistive elements located in each of the axes of the claims 1 or 2 is a full-bridge circuit formed by connecting each The rotation detection device described. Rotation detecting device according to any one of the magnetoresistive claims 1 was inclined 45 degrees with respect to the two axes of element 4. The rotation detection apparatus according to claim 1, wherein the magnetoresistive element is an AMR element or a GMR element. The rotation detection device according to any one of claims 1 to 6, wherein the bias magnet is formed of a sintered magnet or a resin magnet. The circular rotating magnet is a ring-shaped magnet that is polarized in two so as to divide into two in parallel to the rotation center axis of the circular rotating magnet, is magnetized in two radial directions, and is provided on the outer periphery of the shaft-shaped rotating body. The rotation detection device according to any one of claims 1 to 7, wherein the rotation detection device is configured. The circular rotating magnet is polarized so as to be bisected in parallel with the rotation center axis of the circular rotating magnet, and is polarized in two radial directions, and is provided in the shape of a disk or circle provided inside a cylindrical shaft-shaped rotating body. The rotation detection device according to any one of claims 1 to 7, wherein the rotation detection device is configured by a columnar magnet.

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