JP5421198B2 - Rotation angle detector - Google Patents

Description

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

  In recent years, for example, in a power steering device or an air conditioner mounted on an automobile, a so-called brushless motor is often used as a motor serving as a driving source. This brushless motor generally has a rotor formed of permanent magnets and a stator made of a coil that can be energized, and an electromagnetic force corresponding to the electric power supplied to the stator is applied to the rotor to cause the motor to move. The rotating shaft is rotated. The brushless motor is usually provided with a rotation angle detection device that detects the rotation angle of the rotor, and controls power feeding to the stator based on the rotation angle of the rotor detected through the rotation angle detection device. Thus, the rotation mode of the rotation shaft of the motor is controlled.

  As such a rotation angle detection device for detecting the rotation angle of a rotor or a rotation body such as a rotation shaft, for example, the one described in Patent Document 1 is known. This rotation angle detection device has a pulse ring that rotates integrally with a rotating body, an excitation coil that is disposed to face the outer peripheral surface of the pulse ring, and a detection coil that is disposed inside the excitation coil. doing. Here, the pulse ring is a member made of a magnetic material, and grooves are formed at predetermined intervals in the rotation direction. In the rotation angle detection device configured as described above, an eddy current is generated in the pulse ring by the excitation coil, and the magnetic flux generated by the eddy current is detected by the detection coil. Since the pulse ring is formed with grooves at predetermined intervals, when the pulse ring rotates, the eddy current changes depending on the presence or absence of the groove. As the eddy current changes, the magnetic flux detected by the detection coil also changes. In this rotation angle detection device, the rotation angle of the rotating body is calculated based on the voltage induced in the detection coil that changes in accordance with the change in magnetic flux.

JP 2006-10366 A

  In the rotation angle detection device of Patent Document 1, when the pulse ring rotates, the rotation angle is detected by detecting a magnetic field that changes depending on the presence or absence of a groove formed in the pulse ring. In patent document 1, since this rotation angle detection apparatus is utilized for a bearing, the axis deviation of a rotary body is not assumed. However, when the rotational angle detection device of this configuration is applied to a device that may cause an axis deviation, for example, a motor, the distance between the excitation coil and the pulse ring or the distance between the detection coil and the pulse ring is assumed to change. Is done. The voltage induced in the detection coil also changes when the distance between the excitation coil and the pulse ring or the distance between the detection coil and the pulse ring changes. In such a situation, it may be unclear whether the change in the voltage induced in the detection coil is due to axial misalignment or due to detection of the presence or absence of a groove accompanying the rotation of the pulse ring. Therefore, there is a possibility that the calculation accuracy of the rotation angle is lowered. In addition, although what uses magnetic sensors, such as a Hall sensor, and a magnet is also known as a rotation angle detection apparatus, the same subject also exists in this case.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a rotation angle detection device that enables accurate angle detection.

  In order to solve the above-described problem, the invention of claim 1 is a rotation angle detection device that detects a rotation angle of a cylindrical rotating body that rotates integrally with a detection target as a rotation angle of the detection target. A groove rotator which is a portion where a plurality of marks are provided on the outer peripheral surface at intervals over the entire circumference in the rotation direction, and a reference rotator which is also a portion where the marks are not provided over the entire circumference in the rotation direction. And a sensor that generates a sine signal corresponding to a magnetic field emitted from the rotating body that changes depending on the presence or absence of a mark when the rotating body rotates, respectively, facing the outer peripheral surfaces of the groove rotating body and the reference rotating body. The rotation angle of the rotating body is obtained based on a sine signal generated by a sensor facing the groove rotating body, and the signal is generated based on a signal generated by a sensor facing the reference rotating body. The presence or absence of the axis deviation of the rolling element is detected, and when the axis deviation is detected, the sine signal generated by the sensor facing the groove rotating body is corrected, and the rotating body is rotated based on the corrected signal. The gist is to calculate the angle.

  In this rotation angle detection device, a change in the magnetic field caused by the rotation of the rotating body is used. In such a rotation angle detection device, even when the axis of the rotating body is displaced and the distance between the rotating body and the sensor changes, the magnetic field changes. Therefore, the rotating body rotates from the change in the magnetic field. There is a risk that the angle has been changed. Therefore, according to the same configuration, a reference rotating body whose outer peripheral surface is formed flush with each other is adopted. Even when the reference rotator is rotated, no mark is formed, so that the magnetic field does not change in the reference rotator. In other words, if a change in the magnetic field accompanying a change in the distance between the reference rotator and the sensor is detected, it is possible to detect that a positional deviation has occurred. Therefore, by adopting the reference rotator as the rotator, it is possible to detect whether the change in the magnetic field is caused by the presence or absence of a mark accompanying the rotation of the rotator or due to the axis deviation of the rotator. it can. When the change in the magnetic field is due to the axial displacement of the rotating body, the signal generated by the sensor facing the groove rotating body is generated based on the sine signal formed by the sensor facing the reference rotating body. By correcting the amount of change due to the axis deviation, the rotation angle of the rotating body can be detected with high accuracy by correcting the data for the axis deviation.

  According to a second aspect of the present invention, in the rotation angle detection device according to the first aspect, the groove rotator includes a first groove rotator including the plurality of marks at a predetermined interval, and the plurality of marks. The gist is to include a second groove rotating body provided at a predetermined interval different from the one groove rotating body.

  According to the same configuration, the rotation angle detection device includes the first groove rotation body and the second groove rotation body having different arrangement intervals of the marks, so that the rotation angle can be detected from both of them. it can. From the data obtained from both the first groove rotator and the second groove rotator, the rotation angle detector can calculate an absolute angle in one rotation (360 °) of the rotator.

According to a third aspect of the present invention, in the rotation angle detection device according to the second aspect, the rotating body is configured such that a reference rotating body is provided between the first groove rotating body and the second groove rotating body. Is the gist.
According to this configuration, the rotation angle detection device suitably detects an axial deviation in which the rotating body is displaced in the radial direction by providing the reference rotating body between the first groove rotating body and the second groove rotating body. can do.

  According to a fourth aspect of the present invention, in the rotation angle detection device according to the second aspect, the rotating body is provided in such a manner that a reference rotating body sandwiches the first groove rotating body and the second groove rotating body. Is the gist.

  According to this configuration, the rotation angle detection device can detect the distance between the rotation body and the sensor due to the axial deviation of the rotation body because the reference rotation body is on both sides. As a result, the rotation angle detection device is configured such that the rotational body is tilted due to the change in the distance between the rotational body and the sensor, the axial displacement due to the rotational body being displaced in the radial direction, and the rotational body is further displaced in the axial direction. Axis deviation can be detected.

  According to a fifth aspect of the present invention, in the rotation angle detection device according to any one of the first to fourth aspects, the rotating body is made of a conductive material, the mark is made of a groove or a protrusion, The sensor includes an exciting coil that generates an eddy current on the outer peripheral surface of the rotating body by applying an alternating magnetic field to the outer peripheral surface of the rotating body, and a magnetic field change caused by the eddy current generated on the outer peripheral surface of the rotating body. The gist of the present invention is an eddy current flaw detection sensor that includes a detection coil for detection and detects the proximity of the groove or the protrusion based on a change in a magnetic field detected through the detection coil.

  According to this configuration, it is possible to easily configure a rotating body suitable for detection of a rotation angle only by forming a groove in a cylindrical conductive material.

  In the present invention, it is possible to provide a rotation angle detection device that enables accurate angle detection.

The schematic diagram showing one embodiment of the rotation angle detection device in the present invention. The perspective view which shows the mounting position of the eddy current flaw detection sensor in the same embodiment, and the structure of a rotary body. The expanded view which expanded the outer peripheral surface of the rotary body linearly in order to show the mounting position of the eddy current flaw detection sensor in the same embodiment. (A) is a perspective view schematically showing the structure of the eddy current flaw detection sensor and the flow mode of the eddy current, and (b) schematically shows the flow mode of the eddy current when there is a groove in the vicinity of the eddy current flaw detection sensor. FIG. (A) is a perspective view showing a state in which the rotating body is off-axis and the distance between the rotating body and the eddy current flaw detection sensor is larger than the reference distance, and (b) is the same rotation with the rotating body off-axis. The perspective view which shows the state where the distance of a body and an eddy current flaw detection sensor is nearer than a reference distance. (A) shows a case where the distance between the eddy current flaw sensor and the rotating body is standard, and (b) shows a case where the distance between the eddy current flaw sensor and the rotator is large or a groove is formed in the vicinity of the eddy current flaw detection sensor. FIG. 6C is a diagram showing a waveform of an alternating voltage induced in the detection coil in each case when the distance between the eddy current flaw detection sensor and the rotating body is short. (A) is a figure which shows the waveform of the alternating voltage output from an exciting coil, (b)-(h) is a figure which shows the waveform of the alternating voltage induced by a detection coil. The figure which shows the angle response | compatibility used for calculation of the absolute angle of a rotary body stored in a control apparatus. The flowchart which shows the process sequence of the rotor rotation angle detection process by the rotation angle detection apparatus of the embodiment. (A) is a perspective view which shows the modification in this invention, (b) is the schematic which shows the aspect | mode of the axial shift of the rotary body shown to (a).

Hereinafter, an embodiment in which the present invention is embodied in a rotation angle detection device provided in a brushless motor will be described with reference to the drawings.
As shown in FIG. 1, a rotating body 20 is provided on the motor shaft 11 of the brushless motor 10 so as to be integrally rotatable. The rotating body 20 is formed in a cylindrical shape from a conductive material.

  The rotator 20 includes three parts, that is, a reference rotator 21 and first and second groove rotators 23 and 24. The outer peripheral surface of the reference rotator 21 is formed flush. On the outer peripheral surface of the first groove rotating body 23, six grooves D (one for every 60 °) are formed at regular intervals in the rotation direction. On the outer peripheral surface of the second groove rotating body 24, five grooves D (one for every 72 °) are formed at regular intervals in the rotation direction. Each groove D extends along the axis of the motor shaft 11. The rotating body 20 is provided in the order of the first groove rotating body 23, the reference rotating body 21, and the second groove rotating body 24 from the motor 10 side (right side in the figure).

  First to third eddy current flaw detection sensors 30 </ b> A, 30 </ b> B, and 30 </ b> C are provided on the outer peripheral side of the rotating body 20. These eddy current flaw detection sensors 30A, 30B, and 30C are each connected to the control device 12. The control device 12 controls the motor 10 based on detection signals from the eddy current flaw detection sensors 30A, 30B, and 30C.

  As shown in FIG. 2, the first eddy current flaw detection sensor 30A includes an excitation coil 31A and three detection coils 32AK, 32A1, and 32A2. The exciting coil 31 </ b> A corresponds across the outer peripheral surfaces of the reference rotating body 21 and the first and second groove rotating bodies 23 and 24. The three detection coils 32AK, 32A1, and 32A2 correspond to the outer peripheral surfaces of the reference rotator 21 and the first and second groove rotators 23 and 24, respectively. The three detection coils 32AK, 32A1, and 32A2 are provided inside the excitation coil 31A. The excitation coil 31A and the three detection coils 32AK, 32A1, and 32A2 are integrally formed of a synthetic resin material. The exciting coil 31 </ b> A applies an alternating magnetic field to the outer peripheral surface of the rotating body 20 based on the supply of an alternating voltage, and the rotating body 20, that is, the reference rotating body 21, the first and second groove rotating bodies 23, 24. An eddy current is generated in such a way as to straddle each outer peripheral surface. The three detection coils 32AK, 32A1, and 32A2 detect alternating magnetic fields generated in the reference rotating body 21 and the first groove rotating bodies 23 and 24, respectively, based on the eddy current generated by the exciting coil 31A. An alternating voltage is induced in the three detection coils 32AK, 32A1, and 32A2 by receiving an alternating magnetic field generated by an eddy current. The AC voltage induced in the detection coils 32 </ b> A <b> 1 and 32 </ b> A <b> 2 varies depending on the presence or absence of the groove D accompanying the rotation of the rotating body 20. The AC voltage induced in the detection coil 32AK basically has a constant value even when the rotating body 20 rotates. This is because the outer peripheral surface of the reference rotator 21 to which the detection coil 32AK corresponds is configured to be flush.

  The second eddy current flaw detection sensor 30B includes an excitation coil 31B and two detection coils 32BK and 32B1. The excitation coil 31 </ b> B corresponds across the outer peripheral surfaces of the reference rotating body 21 and the first groove rotating body 23. The two detection coils 32BK and 32B1 correspond to the outer peripheral surfaces of the reference rotating body 21 and the first groove rotating body 23, respectively. The two detection coils 32BK and 32B1 are provided inside the excitation coil 31B. The excitation coil 31A and the two detection coils 32BK and 32B1 are integrally formed of a synthetic resin material. The exciting coil 31 </ b> B generates eddy currents on the outer peripheral surfaces of the reference rotating body 21 and the first groove rotating body 23. The two detection coils 32BK and 32B1 detect magnetic fluxes generated in the first groove rotating body 23 and the reference rotating body 21 based on the eddy current generated by the exciting coil 31B. An alternating voltage is induced in the two detection coils 32BK and 32B1 by receiving an alternating magnetic field generated by an eddy current. The change mode of the AC voltage induced in the detection coils 32BK and 32B1 accompanying the rotation of the rotating body 20 is the same as that of the detection coils 32AK and 32A1.

  The third eddy current flaw detection sensor 30C has the same configuration as the second eddy current flaw detection sensor 30B. The third eddy current flaw detection sensor 30C includes an excitation coil 31C and two detection coils 32CK and 32C2. The exciting coil 31 </ b> C corresponds across the outer peripheral surfaces of the reference rotating body 21 and the second groove rotating body 24. The two detection coils 32CK and 32C2 correspond to the outer peripheral surfaces of the reference rotating body 21 and the second groove rotating body 24, respectively. The exciting coil 31 </ b> C generates eddy currents on the outer peripheral surfaces of the reference rotating body 21 and the second groove rotating body 24. The two detection coils 32CK and 32C2 detect magnetic fluxes generated in the reference rotating body 21 and the second groove rotating body 24 based on the eddy current generated by the exciting coil 31C. An alternating voltage is induced in the two detection coils 32CK and 32C2 by receiving an alternating magnetic field generated by an eddy current. The change mode of the AC voltage induced in the detection coils 32CK and 32C2 accompanying the rotation of the rotating body 20 is the same as that of the detection coils 32AK and 32A2.

  The coils of the first to third eddy current flaw detection sensors 30 </ b> A, 30 </ b> B, and 30 </ b> C are provided such that their axial centers are orthogonal to the rotation center axis of the rotating body 20. For this reason, the direction of the alternating magnetic field that the first, second, and third exciting coils 31 </ b> A, 31 </ b> B, and 31 </ b> C excite the rotating body 20 is the direction along the radial direction of the rotating body 20. In FIG. 2, for convenience of explanation, the axial directions of the second and third eddy current flaw detection sensors 30B and 30C are the same as those of the first eddy current flaw detection sensor 30A. The axial direction of the current flaw detection sensors 30 </ b> B and 30 </ b> C is provided to be perpendicular to the outer peripheral surface of the rotating body 20.

  As shown in FIG. 3, when the position of the first eddy current flaw detection sensor 30A is 0 °, the second eddy current flaw detection sensor 30B is displaced by 75 ° (60 ° + 15 ° (1/4 of 60 °)). The third eddy current flaw detection sensor 30C is shifted by 90 ° (72 ° + 18 ° (1/4 of 72 °)) from the first eddy current flaw detection sensor 30A around the motor shaft 11, respectively. Be placed.

  The control device 12 performs power supply control to the excitation coils 31A, 31B, and 31C. Further, the control device 12 detects the rotation angle of the rotating body 20, that is, the motor shaft 11, based on the AC voltage induced in the detection coils 32A1, 32A2, 32B1, and 32C2. The control device 12 detects the rotation angle of the rotor (not shown) of the motor 10, that is, the magnetic pole position of the rotor, based on the rotation angle of the motor shaft 11.

  Next, the detection principle of the distance between the first to third eddy current flaw detection sensors 30A, 30B, 30C and the rotating body 20 and the detection principle of the groove D provided in the rotating body 20 will be described. Here, the first eddy current flaw detection sensor 30A will be described representatively.

  As shown in FIG. 4A, in this eddy current flaw detection sensor 30A, the excitation coil 31A applies an alternating magnetic field to the detection target body (here, the rotating body 20) through the supply of an AC voltage having a constant frequency. As a result, an eddy current Iw is generated on the outer peripheral surface of the rotating body 20. Three detection coils 32AK, 32A1, and 32A2 (here, only the detection coil 32A1 is illustrated) have an alternating magnetic field induced by an eddy current Iw and an alternating magnetic field induced by an alternating voltage supplied to the excitation coil 31A. An alternating voltage is induced by the combined magnetic field.

  As shown in FIG. 4A, when the groove D does not exist directly below or in the vicinity of the eddy current flaw detection sensor 30A, even if the rotator 20 rotates, the eddy current flaw detection sensor 30A and the rotator The distance from the outer peripheral surface 20 is constant (reference distance). At this time, an AC voltage shown in FIG. 6A is induced in the detection coil 32A1. That is, the AC voltage (amplitude) induced in the detection coil 32A1 is maintained at a constant value corresponding to the distance between the eddy current flaw detection sensor 30A and the outer peripheral surface of the rotating body 20. In this example, the AC voltage induced in the detection coil 32AK corresponding to the reference rotator 21 is always constant.

  As shown in FIG. 5A, when the rotating body 20 is misaligned and the distance between the outer peripheral surface of the rotating body 20 and the eddy current flaw detection sensor 30A becomes larger than the reference distance, FIG. ), The AC voltage (amplitude) induced in the detection coil 32A1 becomes small. On the other hand, as shown in FIG. 5B, when the distance between the outer peripheral surface of the rotating body 20 and the eddy current flaw detection sensor 30A is smaller than the reference distance, the detection is performed as shown in FIG. The AC voltage (amplitude) induced in the coil 32A1 increases.

  The control device 12 can detect the axial deviation of the rotating body 20 by detecting the distance between the outer peripheral surface of the rotating body 20 and the detecting coil 32A1 based on the magnitude of the AC voltage induced by the detecting coil 32A1.

  Further, the magnitude of the AC voltage induced in the detection coil 32A1 varies depending on the presence or absence of the groove D. As shown in FIG. 4B, when the rotating body 20 rotates and a groove D or the like is present directly below or in the vicinity of the eddy current flaw detection sensor 30A, the flow of the eddy current Iw changes. For example, as compared with the state shown in FIG. 4A, a part of the eddy current Iw is blocked by the groove D in the state shown in FIG. That is, the area where the eddy current Iw flows favorably decreases. The strength of the magnetic field generated by the eddy current Iw is proportional to the size of the area through which the eddy current Iw flows. Therefore, in the situation shown in FIG. 4B, the AC voltage (amplitude) induced in the detection coil 32A1 becomes small as shown in FIG. 6B.

Thus, in the eddy current flaw detection sensor 30A, the presence or absence of the groove D can be detected by a change in the alternating voltage induced in the detection coil 32A1.
It should be noted that the detection of the axis deviation of the rotating body 20 and the presence or absence of the groove D can be detected in the same way as the first eddy current flaw detection sensor 30A in both the second and third eddy current flaw detection sensors 30B and 30C. is there. In this example, the axis deviation of the rotating body 20 is performed using the detection coils 32AK, 32BK, and 32CK corresponding to the reference rotating body 21. The rotation angle of the rotating body 20 is detected using the detection coils 32A1, 32A2, 32B1, and 32C2. When the axial deviation of the rotating body 20 is detected based on the AC voltage induced in the detection coils 32AK, 32BK, and 32CK, the control device 12 converts the AC voltage induced in the detection coils 32AK, 32BK, and 32CK into the AC voltage. Based on this, the AC voltage induced in the detection coils 32A1, 32A2, 32B1, and 32C2 is corrected. The control device 12 calculates the rotation angle of the rotating body 20 based on the corrected AC voltage.

Next, a detection mode of the rotation angle when the rotating body 20 rotates will be described. First, the description will be made on the assumption that no axis deviation of the rotating body 20 occurs.
Each excitation coil 31A, 31B, 31C to which the alternating voltage having the waveform shown in FIG. 7A is applied from the control device 12 generates eddy currents on the surface (outer peripheral surface) of the corresponding rotating body 20. In this case, waveforms of voltages induced in the detection coils 32AK, 32A1, and 32A2 in the first eddy current flaw detection sensor 30A are shown in FIGS. 7B, 7C, and 7D, respectively. Since no groove is formed in the reference rotating body 21, as shown in FIG. 7B, the waveform of the voltage induced in the detection coil 32AK is applied to the exciting coil 31A shown in FIG. It matches the waveform of the AC voltage that is generated. Since the groove D is formed in the first groove rotating body 23 every 60 °, the waveform of the voltage induced in the detection coil 32A1 has an amplitude every 60 ° as shown in FIG. Significantly smaller (approximate to 0). Since the groove D is formed in the second groove rotating body 24 every 72 °, the waveform of the voltage induced in the detection coil 32A2 has an amplitude every 72 ° as shown in FIG. Remarkably smaller.

  Next, waveforms of voltages induced in the detection coils 32BK and 32B1 in the second eddy current flaw detection sensor 30B are shown in FIGS. 7 (e) and 7 (f). Since no groove D is formed in the reference rotator 21, the waveform of the voltage induced in the detection coil 32BK is applied to the excitation coil 31A shown in FIG. 7 (a) as shown in FIG. 7 (e). It matches the waveform of the AC voltage that is generated. Since the groove is formed in the first groove rotating body 23 every 60 °, the waveform of the voltage induced in the detection coil 32B1 has a significant amplitude every 60 ° as shown in FIG. Get smaller. Here, the position where the detection coil 32B1 (second eddy current flaw detection sensor 30B) is provided is shifted by 75 ° from the position where the detection coil 32A1 (first eddy current flaw detection sensor 30A) is provided. In other words, the waveform of the voltage induced in the detection coil 32B1 is out of phase by 75 ° from the waveform of the voltage induced in the detection coil 32A1. Note that the waveform output from the detection coil 32B1 is a phase shifted by a quarter period (15 °) with respect to the waveform output from the detection coil 32A1.

  Next, waveforms of voltages induced in the detection coils 32CK and 32C2 in the third eddy current flaw detection sensor 30C are shown in FIGS. 7 (g) and 7 (h). Since no groove D is formed in the reference rotator 21, as shown in FIG. 7G, the waveform output from the detection coil 32CK is an alternating current applied to the excitation coil 31A shown in FIG. Matches the voltage waveform. On the other hand, since the groove is formed in the second groove rotating body 24 every 72 °, the waveform of the voltage induced in the detection coil 32C2 has an amplitude every 72 ° as shown in FIG. Becomes significantly smaller. Here, the position where the detection coil 32C2 (third eddy current flaw detection sensor 30C) is provided is shifted by 90 ° from the position where the detection coil 32A2 (first eddy current flaw detection sensor 30A) is provided. That is, the phase of the voltage waveform induced in the detection coil 32C2 is shifted by 90 ° from the waveform of the voltage induced in the detection coil 32A2. The waveform output from the detection coil 32C2 is a phase that is shifted by a quarter period (18 °) from the waveform output from the detection coil 32A2.

  Next, the control device 12 calculates the rotation angle of the rotating body 20 based on the voltages induced in the detection coils 32A1 and 32B1 and the detection coils 32A2 and 32C2. First, for the first groove rotating body 23 and the second groove rotating body 24, the control device 12 sets the rotating body 20 in the angle range (60 °, 72 °) between two adjacent grooves D in the rotation direction. The rotation angles θ1 and θ2 are calculated.

  In this example, the detection coils 32A1 and 32B1 output an alternating voltage (sine wave, cosine wave) shifted by a quarter cycle. The control device 12 applies the voltage value V obtained from these to the equation (1), so that the rotation in the angular range (60 °) between the two adjacent grooves D in the rotation direction of the first groove rotating body 23 is achieved. The rotation angle θ1 of the body 20 is specified.

θ = arctanV (1)
Since the waveform of the voltage induced in the detection coils 32A1 and 32B1 is shifted by a quarter period, the angle θ1 can be accurately specified from the shift of the period. Similarly, from the voltages induced in the detection coils 32A2 and 32C2, the rotation angle θ2 of the rotating body 20 in the angle range (72 °) of two adjacent grooves D in the rotation direction of the second groove rotating body 24 is obtained.

  The storage device of the control device 12 stores an angle correspondence table as shown in FIG. The control device 12 determines the angles θ1 and θ2 indicated by the first and second groove rotating bodies 23 and 24 based on the voltages induced in the detection coils 32A1, 32A2, 32B1, and 32C2, and the angle correspondence table shown in FIG. Thus, the rotation angle θ in one rotation (360 °) of the rotating body 20, that is, the motor shaft 11, is detected as an absolute value. For example, when the angle θ1 indicated by the first groove rotating body 23 is 36 ° and the angle θ2 indicated by the second groove rotating body 24 is 24 °, the rotation angle of the motor shaft 11 is 96 °. Thus, by adopting the two types of first and second groove rotating bodies 23 and 24 having different groove intervals, the rotation angle (absolute value) of the motor shaft 11 can be accurately calculated.

  Next, the case where the shaft deviation of the motor shaft 11 (positional deviation of the rotating body 20) occurs will be described. In this example, the reference | standard rotary body 21 in which a groove | channel is not formed over the perimeter is provided between the 1st and 2nd groove | channel rotary bodies 24. FIG. When the rotational body 20 is not misaligned, when an alternating voltage is applied to the exciting coils 31A, 31B, 31C, detection is performed based on the waveform of the applied alternating voltage and the eddy current generated on the surface of the reference rotating body 21. As described above, the waveforms of the voltages induced in the coils 32AK, 32BK, and 32CK coincide with each other. At this time, for example, when the rotating body 20 is displaced due to the displacement of the motor shaft 11, it is assumed that the distance between the rotating body 20 and the eddy current flaw detection sensor 30A changes. When the rotating body 20 and the eddy current flaw detection sensor 30A are separated from each other, the AC voltage (amplitude) induced in the detection coil 32AK is remarkably reduced as shown in FIG. On the other hand, when the rotating body 20 and the eddy current flaw detection sensor 30A approach each other, the AC voltage (amplitude) induced in the detection coil 32AK increases as shown in FIG. The control device 12 can detect the shaft deviation of the motor shaft 11 by monitoring the voltage induced in the detection coil 32AK. As a result, the control device 12 accurately determines whether the change in the AC voltage output from each of the detection coils 32A1 and 32A2 is due to the axis deviation of the rotating body 20 or the rotation of the rotating body 20. Can be detected.

  When the motor shaft 11 is misaligned, the control device 12 corrects the waveform of the AC voltage induced in the detection coils 32A1 and 32A2 based on the waveform of the AC voltage induced in the detection coil 32AK. Note that this is not limited to the case where the distance between the rotating body 20 and the eddy current flaw detection sensor 30A changes, and the same applies even when the distance between the rotation body 20 and the eddy current flaw detection sensors 30B and 30C changes. is there. Therefore, the control device 12 accurately detects the rotation angle of the motor shaft 11 from the corrected AC voltage of the detection coils 32A1, 32A2, 32B1, and 32C2 even when the shaft deviation of the motor shaft 11 occurs. can do.

  Next, a series of processing procedures related to motor control in the control device 12 will be described based on the flowchart shown in FIG. This flow is executed when a power supply voltage (not shown) is supplied and the control device 12 is driven.

  As shown in FIG. 9, the control device 12 supplies a power supply voltage to the motor 10 to rotate the motor shaft 11 (step S1). Next, the control device 12 supplies high-frequency AC voltage to the eddy current flaw detection sensors 30A, 30B, and 30C (excitation coils 31A, 31B, and 31C) to generate eddy currents on the surface of the rotating body 20 (step S2). ). The control device 12 detects the voltages of the detection coils 32AK, 32A1, 32A2, 32BK, 32B1, 32CK, and 32C2 induced by the eddy current (step S3).

  The control device 12 determines whether or not an axis deviation has occurred based on the alternating voltage induced in the detection coils 32AK, 32BK, and 32CK (step S4). If it is determined that no shaft misalignment has occurred (NO in step S4), the control device 12 calculates the rotation angle of the motor shaft 11 from the AC voltage induced in the detection coils 32A1, 32A2, 32B1, and 32C2. (Step S5). The control device 12 controls energization to the stator (not shown) based on the calculation result obtained in step S5, that is, the rotor position. (Step S6). Then, this series of processing ends.

  If it is determined in step S4 that a positional deviation has occurred (YES in step S4), the control device 12 corrects the value of the AC voltage induced in the detection coils 32A1, 32A2, 32B1, and 32C2. Then, the rotational angle of the motor shaft 11 is calculated using the corrected AC voltage (step S7). And the control apparatus 12 transfers the process to step S6. The series of processing in the control device 12 is repeatedly executed while the control device 12 is driven.

As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) Since the reference rotator 21 is not formed with the groove D, even if the rotator 20 rotates, the magnitude of the AC voltage induced in the detection coils 32AK, 32BK, and 32CK corresponding to the reference rotator 21 is increased. There is no change. In other words, if a change in the distance between the reference rotator 21 and the eddy current flaw detection sensors 30A, 30B, 30C, that is, a change in the magnitude of the AC voltage induced in the detection coils 32AK, 32BK, 32CK is detected, the rotation It is possible to detect that a position shift (axis shift) of the body 20 has occurred. Therefore, by providing the rotating body 20 with the reference rotating body 21, it is possible to detect the axial deviation of the rotating body 20. As a result, the control device 12 determines whether the change in the AC voltage output from each of the detection coils 32A1, 32A2, 32B1, and 32C2 is due to the axis deviation of the rotating body 20 or the rotation of the rotating body 20. Therefore, the rotation angle of the rotator 20 can be detected with high accuracy.

  (2) The rotator 20 includes a first groove rotator 23 and a second groove rotator 24 having different arrangement intervals of the grooves D. The control device 12 determines the angle corresponding to the interval between the grooves D from both the detection coils 32A1 and 32B1 corresponding to the first groove rotating body 23 and the detection coils 32A2 and 32C2 corresponding to the second groove rotating body 24. Within the range, the rotation angle of the rotating body 20 can be detected. As a result, the control device 12 calculates the rotation angle of the rotating body 20 in one rotation (360 °) as an absolute value from the waveform of the AC voltage obtained from both the first groove rotating body 23 and the second groove rotating body 24. can do.

  (3) A reference rotator 21 having no groove D formed on its outer peripheral surface is provided between the first groove rotator 23 and the second groove rotator 24. With a simple configuration in which the corresponding detection coils 32AK, 32BK, and 32CK are disposed, it is possible to suitably detect the axial deviation of the rotating body 20 in the radial direction.

  (4) The reference rotator 21 is provided between the first groove rotator 23 and the second groove rotator 24, and a detection coil 32AK (32BK, 32CK) corresponding thereto is provided on the outer peripheral surface of the reference rotator 21. Is disposed. Further, detection coils 32A1, 32A2 (32B1, 32C2) corresponding to the first groove rotating body 23 and the second groove rotating body 24 are disposed on the outer peripheral surface of the first groove rotating body 23 and the second groove rotating body 24. When the waveform of the AC voltage output from the detection coil 32AK has a tendency similar to the waveform of the AC voltage output from the detection coil 32A1, the rotating body 20 moves to the right side in FIG. 2 and the AC output from the detection coil 32AK. When the voltage waveform shows a tendency similar to the waveform of the AC voltage output from the detection coil 32A2, it can be seen that the axis of rotation of the rotating body 20 to the left in FIG. 2 has occurred. That is, the axial deviation of the rotating body 20 in the axial direction can also be detected.

In addition, you may change the said embodiment as follows.
-In above-mentioned embodiment, although the reference | standard rotary body 21 was provided in one place between the 1st groove | channel rotary body 23 and the 2nd groove | channel rotary body 24, the position and number to provide are not restricted to this. For example, as shown in FIG. 10A, the rotating body 40 may be formed in such a manner that the first groove rotating body 23 and the second groove rotating body 24 are sandwiched between two reference rotating bodies 21A and 21B. In this case, instead of the eddy current flaw detection sensor 30A in the above embodiment, two eddy current flaw detection sensors 41A and 41B having the same configuration as the eddy current flaw detection sensor 30B and 30C in the above embodiment are employed. That is, the eddy current flaw detection sensor 41A includes an excitation coil 42A and two detection coils 43AK and 43A1, and the eddy current flaw detection sensor 41B includes an excitation coil 42B and two detection coils 43BK and 43B2. The eddy current flaw detection sensors 41A and 41B are arranged side by side in the axial direction of the rotating body 40 at the same position as the eddy current flaw detection sensor 30A in the above embodiment. The eddy current flaw detection sensor 41A corresponds to the outer peripheral surfaces of the reference rotator 21A and the first groove rotator 23, and the eddy current flaw detection sensor 41B corresponds to the outer peripheral surfaces of the reference rotator 21B and the second groove rotator 24, respectively.

  Even if comprised in this way, the control apparatus 12 is the same as the said embodiment, but the axial deviation from which the distance of the eddy current flaw detection sensor 30B, 30C, 41A, 41B and the outer peripheral surface of the rotary body 40 changes, and a rotary body Both axial deviations in which 40 is displaced in the axial direction can be suitably detected. Further, the control device 12 can detect this even when the rotating body 40 is tilted. For example, assume a situation as shown in FIG. In this case, since the right reference rotator 21A is separated from the eddy current flaw detection sensor 41A, the waveform of the AC voltage induced in the detection coil 43AK becomes a waveform with a small voltage as shown in FIG. On the other hand, since the left reference rotator 21B approaches the eddy current flaw detection sensor 41B, the waveform of the AC voltage induced in the detection coil 43BK becomes a waveform having a large voltage as shown in FIG. The control device 12 can detect the inclination of the rotating body 40 by detecting the voltage difference between the waveforms of the alternating voltage induced in the detection coils 43AK and 43BK on the right side and the left side.

  As described above, the control device 12 detects the axial displacement (proximity, separation, inclination) of the rotating body 40 from the change in the induced voltage based on the change in the distance between the eddy current flaw sensors 30B, 30C, 41A, 41B and the rotating body 40. And the waveform of the AC voltage induced in each of the detection coils 32B1, 32C2, 43A1, and 43B2 is corrected based on the detection result.

  In the above embodiment, a plurality of grooves D as marks are provided on the outer peripheral surface of the rotating body 20 (the first groove rotating body 23 and the second groove rotating body 24), and the presence / absence of the groove D is detected. A plurality of eddy current flaw detection sensors 30A, 30B, and 30C serving as rotation angle detecting means capable of performing the above are configured. However, instead of these, a magnet may be used instead of the groove D, and a magnetic sensor such as a Hall sensor or an MR sensor may be used instead of the eddy current flaw sensors 30A, 30B, and 30C. Even if it does in this way, the fall of the detection accuracy resulting from the axial shift of the rotary body 20 can be suppressed.

In the above embodiment, the groove D formed in the rotating body 20 may be replaced with a protrusion.
In the above embodiment, the interval between the grooves D formed in the first groove rotating body 23 and the second groove rotating body 24 is a constant interval, but it is not necessarily constant.

  In the above embodiment, six grooves D are formed on the outer periphery of the first groove rotating body 23 and five grooves D are formed on the outer periphery of the second groove rotating body 24. However, the number of the grooves D is not limited thereto. For example, as the number of the grooves D is increased, the resolution at which the rotation angle can be detected increases, so that the rotation angle of the rotating body 20 can be detected more finely.

  In the above embodiment, the rotation angle detection device is not limited to that provided on the motor shaft 11. For example, the present invention can be applied to any rotating shaft or bearing that rotates.

  In the embodiment, either the first groove rotating body 23 or the second groove rotating body 24 may be omitted from the rotating body 20. For example, when the second groove rotating body 24 is omitted, the control device 12 determines the rotation angle of the rotating body 20 in the angle range (60 °) corresponding to the interval between two adjacent grooves D of the first groove rotating body 23. In addition to being able to calculate, it is possible to detect the axial deviation of the rotating body 20.

  In the above embodiment, the eddy current flaw detection sensor 30B is arranged at a position shifted by 72 ° with respect to the eddy current flaw detection sensor 30A, and the eddy current flaw detection sensor 30C at 90 ° with respect to the eddy current flaw detection sensor 30A. The position where the eddy current flaw detection sensors 30B and 30C are arranged is not limited to this. There is no problem if it is arranged so that a phase difference appears in the waveforms output from the detection coils 32A1, 32A2 and the detection coils 32B1, 32C2. As described in the above embodiment, the waveform of the AC voltage induced in the detection coils 32B1 and 32C2 and the waveform of the AC voltage induced in the detection coils 32A1 and 32A2 are shifted by a quarter period. The detection coil 32B1 is arranged at a position of 12 ° ± 60 ° × X (X is an integer) from the detection coil 32A1, and the detection coil 32C2 is arranged at a position of 15 ° ± 75 ° × X (X is an integer) from the detection coil 32A2. That's fine.

  In the above embodiment, the eddy current flaw detection sensors 30B and 30C are not necessarily provided. Even in this case, the control device 12 determines the rotation angle in the angle range corresponding to the interval between the two adjacent grooves D of the rotating body 20 and the absolute value in one rotation from the waveform of the AC voltage induced in the detection coils 32A1 and 32A2. It is possible to detect the angle. Further, it is possible to detect the axial deviation of the rotating body 20 based on the AC voltage induced in the detection coil 32AK.

θ, θ1, θ2 ... rotation angle, D ... groove, V ... voltage value, Iw ... eddy current, 10 ... brushless motor, 11 ... motor shaft, 12 ... control device, 20, 40 ... rotating body, 21, 21A, 21B Reference rotating body, 23 ... 1st groove rotating body, 24 ... 2nd groove rotating body, 30A ... 1st eddy current flaw detection sensor, 30B ... 2nd eddy current flaw detection sensor, 30C ... 3rd eddy current flaw detection sensor, 31A, 31B, 31C, 42A, 42B ... excitation coil, 32A1, 32A2, 32AK, 32B1, 32BK, 32C2, 32CK, 43A1, 43AK, 43B2, 43BK ... detection coil, 41A, 41B ... eddy current flaw sensor.

Claims (5)

In the rotation angle detection device that detects the rotation angle of the cylindrical rotating body that rotates integrally with the detection target as the rotation angle of the detection target,
The rotating body is a groove rotating body, which is a portion in which a plurality of marks are provided at intervals on the outer peripheral surface of the rotating body over the entire circumference in the rotation direction, and the mark is not provided over the entire circumference in the rotation direction. A reference rotating body that is a part,
When the rotating body rotates, a sensor that generates a sine signal corresponding to a magnetic field emitted from the rotating body that changes depending on the presence or absence of a mark is provided facing the outer peripheral surfaces of the groove rotating body and the reference rotating body,
A rotation angle of the rotating body is obtained based on a sine signal generated by a sensor facing the groove rotating body, and whether or not the rotating body is misaligned based on a signal generated by a sensor facing the reference rotating body. Detect
A rotation angle detecting device that corrects a sine signal generated by a sensor facing the groove rotating body and calculates a rotation angle of the rotating body based on the corrected signal when the axial deviation is detected. The rotation angle detection device according to claim 1,
The groove rotating body is
A first groove rotating body provided with the plurality of marks at a predetermined interval;
A rotation angle detecting device comprising: a second groove rotating body provided with the plurality of marks at a predetermined interval different from that of the first groove rotating body. In the rotation angle detection device according to claim 2,
The rotation angle detection device according to claim 1, wherein the rotation body is provided with a reference rotation body between the first groove rotation body and the second groove rotation body. In the rotation angle detection device according to claim 2,
The rotation angle detection device according to claim 1, wherein the rotation body is provided in such a manner that a reference rotation body sandwiches the first groove rotation body and the second groove rotation body. In the rotation angle detection apparatus as described in any one of Claims 1-4,
The rotating body is made of a conductive material, and the mark is made of a groove or a protrusion.
The sensor includes an exciting coil that generates an eddy current on the outer peripheral surface of the rotating body by applying an alternating magnetic field to the outer peripheral surface of the rotating body, and a magnetic field change caused by the eddy current generated on the outer peripheral surface of the rotating body. And a detection coil for detecting
A rotation angle detection device, wherein the rotation angle detection device is an eddy current flaw detection sensor that detects the proximity of the groove or the protrusion based on a change in a magnetic field detected through the detection coil.

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