JP2012237619A - Rotational angle detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotational angle detector by which it is possible to specify magnetic poles which are sensed by magnetic sensors at an early stage immediately after a rotor starts rotation.SOLUTION: A rotational angle arithmetic unit 20 detects peak values of output signals V1, V2 of the magnetic sensors 21, 22. The rotational angle arithmetic unit 20 calculates ratio between extreme values of a first or second output signal V1, V2 to each of magnetic pole for specifying arbitrary adjacent pole positions on the basis of the detected peak values. The rotational angle arithmetic unit 20 specifies magnetic poles which are sensed by the respective magnetic sensors 21, 22 on the basis of calculated extreme value ratio, and extreme value ratio data. The rotational angle arithmetic unit 20 corrects amplitude of the output signals V1, V2 according to the specified magnetic poles. The rotational angle arithmetic unit 20 calculates an electric angle θof a rotor 1 on the basis of the output signals V1, V2 after amplitude correction.

Description

  The present invention relates to a rotation angle detection device that detects a rotation angle of a rotating body such as a rotor of a brushless motor.

  In order to control a brushless motor used in an electric power steering device or the like, it is necessary to apply a current to the stator winding in accordance with the rotation angle of the rotor. Therefore, a rotation angle detection device that detects a rotation angle of a brushless motor rotor using a detection rotor that rotates in accordance with the rotation of the brushless motor is known. Specifically, as shown in FIG. 8, the detection rotor 101 (hereinafter referred to as “rotor 101”) has a cylindrical shape having a plurality of magnetic pole pairs corresponding to the magnetic pole pairs provided in the rotor of the brushless motor. A magnet 102 is provided. Around the rotor 101, two magnetic sensors 121 and 122 are arranged at a predetermined angular interval around the rotation center axis of the rotor 101. Each magnetic sensor 121, 122 outputs a sine wave signal having a predetermined phase difference. Based on these two sine wave signals, the rotation angle of the rotor 101 (rotation angle of the brushless motor rotor) is detected.

  In this example, the magnet 102 has four pairs of magnetic poles. That is, the magnet 102 has eight magnetic poles arranged at equal angular intervals. The magnetic poles are arranged at an angular interval of 45 ° (180 ° in electrical angle) about the rotation center axis of the rotor 101. The two magnetic sensors 121 and 122 are arranged at an angular interval of 22.5 ° (electrical angle 90 °) around the rotation center axis of the rotor 101.

  A direction indicated by an arrow in FIG. 8 is a positive rotation direction of the detection rotor 101. When the rotor 101 is rotated in the forward direction, the rotation angle of the rotor 101 is increased. When the rotor 101 is rotated in the reverse direction, the rotation angle of the rotor 101 is decreased. As shown in FIG. 9, each magnetic sensor 121, 122 has a sine wave signal having a period during which the rotor 101 rotates an angle corresponding to one magnetic pole pair (90 ° (360 ° in electrical angle)). V1 and V2 are output.

The angle range of one rotation of the rotor 101 is divided into four sections corresponding to the four magnetic pole pairs, and the angle of the rotor 101 is expressed by setting the start position of each section to 0 ° and the end position to 360 °. It is assumed that the electrical angle θ _E is.
Here, an output signal of V1 = A1 · sin θ _E is output from the first magnetic sensor 121, and an output signal of V2 = A2 · cos θ _E is output from the second magnetic sensor 122. . A1 and A2 are amplitudes. When viewed as an amplitude A1, A2 of the two output signals V1, V2 are equal to each other, the electrical angle theta _E of the rotor 101, using both output signals V1, V2, can be determined based on the following equation (1).

θ _E = tan ⁻¹ (sin θ _E / cos θ _E )
= Tan ^-1 (V1 / V2) (1)
In this way, by using the obtained electrical angle theta _E, controls the brushless motor.

JP 2003-32823 A JP 2002-257649 A

In the conventional rotation angle detection device as described above, the amplitudes of the output signals V1 and V2 of the magnetic sensors 121 and 122 vary from one magnetic pole to another due to variations in magnetic force among the magnetic poles. An error occurs in detection. Therefore, according to the mechanical angle of the rotor 101, the output signals V1, V2 of the magnetic sensors 121, 122 are corrected (amplitude correction) so that the amplitudes of the output signals V1, V2 of the magnetic sensors 121, 122 are equal. after, it is considered for calculating the electrical angle theta _E of the rotor 101.

  When the magnetic force varies for each magnetic pole, the amplitude correction value used for correcting the amplitude for each cycle or half cycle of the electrical angle is changed for the output signals V1 and V2 of the magnetic sensors 121 and 122. There must be. Therefore, in order to perform such amplitude correction, it is necessary to specify the magnetic pole sensed by each of the magnetic sensors 121 and 122. After the rotor 101 has made one revolution, the magnetic poles sensed by the magnetic sensors 121 and 122 can be identified from the difference in the peak values of the magnetic poles. Therefore, the magnetic poles sensed by the magnetic sensors 121 and 122 Amplitude correction according to can be performed. However, immediately after the start of the brush motor, the magnetic pole sensed by each of the magnetic sensors 121 and 122 cannot be specified. Therefore, amplitude correction corresponding to the magnetic pole sensed by each of the magnetic sensors 121 and 122 is performed. I can't do it.

  An object of the present invention is to provide a rotation angle detecting device that can identify a magnetic pole sensed by a magnetic sensor at an early stage immediately after the rotating body starts rotating.

  In order to achieve the above object, the invention according to claim 1 is a rotor for detection (1) having a plurality of magnetic poles rotated according to the rotation of the rotating body (10) and provided at equiangular intervals in the circumferential direction. And first and second magnetic sensors (21, 22) for outputting first and second sine wave signals (V1, V2) having a predetermined phase difference according to the rotation of the detection rotor, respectively. A rotation angle detecting device for detecting a rotation angle of the rotating body based on output signals of these magnetic sensors, wherein the detection rotor is either one of the magnetic poles, or N pole or S pole When each magnetic pole having one polarity is a pole position specifying magnetic pole, the ratio of the extreme value of each sine wave signal to at least one pair of adjacent pole position specifying magnetic poles is the other pole position specifying magnetic pole. Ratio of extreme value of each sine wave signal to magnetic pole Magnetic pole characteristics that are distinguishable from each other, and an extreme value detection means (20, S7) for detecting the extreme value of each sine wave signal, and an extreme value detected by the extreme value detection means Each magnetic sensor senses the calculated extreme value ratio of the first or second sine wave signal to any adjacent pole position specifying magnetic pole and the preset extreme value ratio data. A magnetic pole specifying means (20, S11) for specifying the magnetic pole, an amplitude correcting means (20, S14) for correcting the amplitude of each sine wave signal according to the magnetic pole specified by the magnetic pole specifying means, and amplitude correction A rotation angle detector including rotation angle calculation means (20, S15) for calculating the rotation angle of the rotating body based on each subsequent sine wave signal. In addition, although the alphanumeric character in parentheses represents a corresponding component in an embodiment described later, of course, the scope of the present invention is not limited to the embodiment. The same applies hereinafter.

  In the above-described configuration, the ratio of the extreme value of the first or second sine wave signal to any adjacent pole position specifying magnetic pole calculated from the extreme value detected by the extreme value detection means, and a preset pole Based on the value ratio data, the magnetic pole sensed by each magnetic sensor is identified. The amplitude of each sine wave signal is corrected according to the specified magnetic pole. Then, the rotation angle of the rotating body is calculated based on each sine wave signal after amplitude correction.

  In the above configuration, the detection rotor has at least one pair of adjacent pole position specifying poles, where each magnetic pole or each magnetic pole having one of the N or S poles is a pole position specifying magnetic pole. The ratio of the extreme value of each sine wave signal to the magnetic pole has a magnetic pole characteristic such that the ratio of the extreme value of each sine wave signal to another set of adjacent pole position specifying magnetic poles is distinguishable from each other. . For example, the ratio of the extreme value of each sine wave signal to a certain set of adjacent pole position specifying magnetic poles (hereinafter referred to as “reference adjacent magnetic poles”) If it is discriminably different from any of the extreme value ratios of the wave signal, the first or second sine wave signal corresponding to each of the reference adjacent magnetic poles after the rotating body starts rotating. When the extreme value is detected by the detection means, the magnetic pole sensed by the magnetic sensor that outputs the detected extreme value can be specified. Further, the magnetic pole sensed by the other magnetic sensor can be specified by the arrangement and angular interval of both magnetic sensors, the configuration of the detection rotor, and the like. Accordingly, there is a high possibility that the magnetic pole sensed by each magnetic sensor can be specified after the rotating body starts rotating and before the detection rotor makes one rotation. That is, the magnetic pole sensed by each magnetic sensor can be identified at an early stage immediately after the rotating body starts rotating.

Further, the magnetic pole sensed by each magnetic sensor based on the ratio of the extreme values of the first or second sine wave signal corresponding to each of the adjacent pole position specifying magnetic poles and preset extreme value ratio data Therefore, even when each sine wave signal fluctuates due to a change in ambient temperature, the magnetic pole sensed by each magnetic sensor can be accurately specified.
According to a second aspect of the present invention, in the detection rotor, for each combination of adjacent pole position specifying magnetic poles, the ratio of the extreme values of the sine wave signals to the adjacent pole position specifying magnetic poles is identifiable. The extreme value ratio data is the extreme value of the first sine wave signal with respect to adjacent pole position specifying magnetic poles set in advance for each combination of adjacent pole position specifying magnetic poles. And / or the ratio of the extreme values of the second sine wave signal, the magnetic pole specifying means is the extreme value of the first or second sine wave signal for each of the adjacent poles for specifying the pole position. Is detected by the extreme value detecting means, the magnetic pole sensed by each magnetic sensor is specified based on the ratio of the magnitudes of the two detected extreme values and the extreme value ratio data. The circuit according to claim 1, wherein It is the angle detection device.

In this configuration, each magnetic field is detected when the extreme value of the first or second sine wave signal for each of the adjacent pole position specifying magnetic poles is first detected after the rotating body starts rotating. It becomes possible to specify the magnetic pole sensed by the sensor. For this reason, the magnetic pole sensed by the magnetic sensor can be identified at an early stage immediately after the rotating body starts rotating.
A third aspect of the present invention is the rotation angle detection device according to the first or second aspect, wherein the predetermined phase difference is 90 ° in electrical angle.

It is a schematic diagram which shows the structure at the time of applying the rotation angle detection apparatus which concerns on one Embodiment of this invention to the rotation angle detection apparatus for detecting the rotation angle of the rotor of a brushless motor. It is a schematic diagram which shows the structure of the rotor for a detection. It is a schematic diagram which shows the output signal waveform of the 1st and 2nd magnetic sensor, and the magnetic pole which the 1st magnetic sensor is sensing. It is a schematic diagram which shows the content of the peak value table. It is a flowchart which shows the procedure of the rotation angle calculation process by a rotation angle calculating device. It is a flowchart which shows the procedure of the setting process of the relative pole number of step S3 of FIG. It is a schematic diagram for demonstrating the setting process of a relative pole number. It is a schematic diagram for demonstrating the rotation angle detection method by the conventional rotation angle detection apparatus. It is a schematic diagram which shows the output signal waveform of a 1st magnetic sensor, and the output signal waveform of a 2nd magnetic sensor.

Hereinafter, an embodiment in which the present invention is applied to a rotation angle detection device for detecting the rotation angle of a rotor of a brushless motor will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing a configuration when a rotation angle detection device according to an embodiment of the present invention is applied to a rotation angle detection device for detecting the rotation angle of a rotor of a brushless motor.
The rotation angle detection device 100 includes a detection rotor that rotates in accordance with the rotation of the brushless motor 10 (hereinafter simply referred to as “rotor 1”), magnetic sensors 21 and 22, and a rotation angle calculation device 20. . As shown in FIG. 2, the rotor 1 includes a cylindrical magnet (multipolar magnet) 2 having a plurality of magnetic pole pairs corresponding to the magnetic pole pairs provided in the rotor of the brushless motor 10.

  The magnet 2 has four pairs of magnetic poles (M1, M2) (M3, M4) (M5, M6) (M7, M8). That is, the magnet 2 has eight magnetic poles M1 to M8 arranged at equiangular intervals. The magnetic poles M <b> 1 to M <b> 8 are arranged at an angular interval of 45 ° (180 ° in electrical angle) around the rotation center axis of the rotor 1. The magnitude of the magnetic force of each of the magnetic poles M1 to M8 is not constant.

  Two magnetic sensors 21 and 22 are disposed around the rotor 1. These magnetic sensors 21 and 22 are arranged at an angle interval of a predetermined angle of 22.5 ° (90 ° in electrical angle) around the rotation center axis of the rotor 1. These two magnetic sensors 21 and 22 may be referred to as a first magnetic sensor 21 and a second magnetic sensor 22, respectively. As the magnetic sensor, for example, a sensor provided with an element having a characteristic in which an electrical characteristic is changed by the action of a magnetic field, such as a Hall element or a magnetoresistive element (MR element) can be used.

  A direction indicated by an arrow in FIG. 2 is a positive rotation direction of the rotor 1. When the rotor 1 is rotated in the forward direction, the rotation angle of the rotor 1 is increased. When the rotor 1 is rotated in the reverse direction, the rotation angle of the rotor 1 is decreased. As shown in FIG. 3, each of the magnetic sensors 21 and 22 has a sinusoidal signal V1 having a period during which the rotor 1 rotates at an angle of 90 ° (electrical angle of 360 °) corresponding to one magnetic pole pair. V2 is output.

  In this embodiment, the rotor 1 (magnet 2) is a combination of adjacent pole position specifying magnetic poles (M1, M3), assuming that each of the magnetic poles M1, M3, M5, M7 having the polarity of N poles is a pole position specifying magnetic pole. ), (M3, M5), (M5, M7), (M7, M1), the ratio of the peak values (extreme values) of the sine wave signals V1, V2 to the adjacent pole position specifying magnetic poles can be identified. It has different magnetic pole characteristics.

FIG. 3 shows the rotor angle (mechanical angle) when the rotation angle of the rotor 1 is 0 ° when the boundary between the magnetic pole M8 and the magnetic pole M1 of the rotor 1 faces the first magnetic sensor 21. Output signals V1 and V2 of the magnetic sensors 21 and 22 are shown. FIG. 3 shows magnetic poles M1 to M8 sensed by the first magnetic sensor 21 corresponding to the rotor angle.
An absolute rotation angle of the rotor 1 from a predetermined reference position is referred to as a mechanical angle θ _{M of} the rotor 1. The angle range for one rotation of the rotor 1 is divided into four sections corresponding to the five magnetic pole pairs, and the rotation angle of the rotor 1 expressed as the start position of each section is 0 ° and the end position is 360 ° It is assumed that the electrical angle θ _E is 1.

Here, it is assumed that an output signal of V1 = A1 · sin θ _E is output from the first magnetic sensor 21 for each section corresponding to four magnetic pole pairs. In this case, the second magnetic sensor 22 outputs an output signal of V2 = A2 · sin (θ _E + 90 °) = A2 · cos θ _E for each section corresponding to the four magnetic pole pairs. Therefore, the magnetic sensors 21 and 22 output sine wave signals having a predetermined phase difference of 90 ° (electrical angle). A1 and A2 each represent an amplitude. However, the amplitudes A1 and A2 vary depending on the magnitude of the magnetic force of the magnetic pole. The output signals V1 and V2 of the magnetic sensors 21 and 22 may be referred to as a first output signal V1 and a second output signal V2, respectively.

Returning to FIG. 1, the output signals V <b> 1 and V <b> 2 of the magnetic sensors 21 and 22 are input to the rotation angle calculation device 20. The rotation angle calculation device 20 is composed of, for example, a microcomputer, and includes a CPU (Central Processing Unit) and a memory (ROM, RAM, rewritable nonvolatile memory, etc.).
The rotation angle calculation device 20 detects the peak values (extreme values: maximum value and minimum value) of the output signals V1, V2 of the magnetic sensors 21, 22. Based on the detected peak value, the rotation angle calculation device 20 determines the peak of the first or second output signal V1, V2 for any adjacent pole position specifying magnetic pole (in this example, an N-pole magnetic pole). The ratio of the values (in this example, the maximum value) is calculated. The rotation angle computing device 20 detects the magnetic poles detected by the magnetic sensors 21 and 22 based on the calculated extreme value ratio and the extreme value ratio data set in advance for each combination of adjacent pole position specifying magnetic poles. Is identified. The rotation angle calculation device 20 corrects the amplitudes of the output signals V1 and V2 according to the specified magnetic pole. Rotation angle computing unit 20, the output signal after amplitude correction V1 ', V2' based on the calculated electrical angle theta _E of the rotor 1. Further, the rotation angle calculation unit 20, based on the obtained electrical angle theta _E, calculates the mechanical angle theta _M of the rotor 1.

The electrical angle θ _E and the mechanical angle θ _M calculated by the rotation angle calculation device 20 are given to the motor controller 30. The motor controller 30 controls the brushless motor 10 using the electrical angle θ _E or the like given from the rotation angle calculation device 20.
The non-volatile memory of the rotation angle computing device 20 stores a peak value table for each of the magnetic sensors 21 and 22, and stores extreme value ratio data set in advance for each combination of adjacent pole position specifying magnetic poles. It is remembered.

FIG. 4 is a schematic diagram showing the contents of the peak value table.
In the peak value table, for each pole number 1 to 8 of each magnetic pole M1 to M8, the peak value (maximum value or minimum value) P1 (1) to P1 (1) to P1 (1) of the output signal V1 of the first magnetic sensor 21 corresponding to the magnetic pole. P1 (8) (see FIG. 3) and the peak value (maximum value or minimum value) P2 (1) to P2 (8) of the output signal V2 of the second magnetic sensor 22 corresponding to the magnetic pole are stored. Yes. Since the magnetic sensors 21 and 22 having substantially the same characteristics are used, the peak values of the magnetic sensors 21 and 22 with respect to the same magnetic pole are almost the same value.

For example, the peak value is stored in the peak value table before the brushless motor 10 is shipped. The peak value stored in the amplitude correction peak value table may be obtained from data for one period or may be obtained from an average value of data for a plurality of periods.
In this embodiment, the extreme value ratio data includes the following four types of data D1 to D4.
(i) D1 = P1 (1) / P1 (3)
The ratio of the peak value (maximum value) P1 (1) for the magnetic pole M1 to the peak value (maximum value) P1 (3) for the magnetic pole M3, which is 0.6 in this embodiment. Note that D1 may be obtained by D1 = P2 (1) / P2 (3).
(ii) D2 = P1 (3) / P1 (5)
The ratio of the peak value (maximum value) P1 (3) for the magnetic pole M3 to the peak value (maximum value) P1 (5) for the magnetic pole M5 is 0.83 in this embodiment. Note that D2 may be obtained by D2 = P2 (3) / P2 (5).
(iii) D3 = P1 (5) / P1 (7)
The ratio of the peak value (maximum value) P1 (5) for the magnetic pole M5 to the peak value (maximum value) P1 (7) for the magnetic pole M7, which is 2.0 in this embodiment. Note that D3 may be obtained by D3 = P2 (5) / P2 (7).
(Vi) D4 = P1 (7) / P1 (1)
The ratio of the peak value (maximum value) P1 (7) for the magnetic pole M7 to the peak value (maximum value) P1 (1) for the magnetic pole M1, which is 1.0 in this embodiment. Note that D4 may be obtained by D4 = P2 (7) / P2 (1).

  The extreme value ratio data may be set for each of the output signals V1 and V2. Specifically, for the first output signal V1, DA1 = P1 (1) / P1 (3), DA2 = P1 (3) / P1 (5), DA3 = P1 (5) / P1 (7 ) And four extreme value ratio data of DA4 = P1 (7) / P1 (1). On the other hand, for the second output signal V2, DB1 = P2 (1) / P2 (3), DB2 = P2 (3) / P2 (5), DB3 = P2 (5) / P2 (7) and DB4. = Four extreme value ratio data of P2 (7) / P2 (1) are set.

FIG. 5 is a flowchart showing a procedure of rotation angle calculation processing by the rotation angle calculation device 20.
The rotation angle calculation process shown in FIG. 5 is repeatedly performed every predetermined calculation cycle.
Using the magnetic pole sensed by the first magnetic sensor 21 at the start of the rotation angle calculation process as a reference magnetic pole, the number of each magnetic pole when a relative number is assigned to each magnetic pole is defined as a relative pole number. The relative pole number of the magnetic pole sensed by the first magnetic sensor 21 (hereinafter referred to as “first relative pole number”) is represented by a variable r1, and the magnetic pole sensed by the second magnetic sensor 22 is represented by the variable r1. The relative pole number (hereinafter referred to as “second relative pole number”) is represented by a variable r2. Each of the relative pole numbers r1 and r2 takes an integer of 1 to 8, and a relative pole number that is 1 less than 1 is 8, and a relative pole number that is 1 greater than 8 is 1.

  In this embodiment, when the magnetic pole (reference magnetic pole) sensed by the first magnetic sensor 21 at the start of the rotation angle calculation process is an N-pole, the relative pole number “1” is assigned to the magnetic pole. Is assigned. On the other hand, when the magnetic pole (reference magnetic pole) sensed by the first magnetic sensor 21 at the start of the rotation angle calculation process is an S pole, a relative pole number of “2” is assigned to the magnetic pole. It is done.

Further, the pole number (absolute pole number) of the magnetic pole sensed by the first magnetic sensor 21 is q1, and the pole number (absolute pole number) of the magnetic pole sensed by the second magnetic sensor 22 is q2. I will represent it. Each of the absolute pole numbers q1 and q2 takes an integer of 1 to 8, and a pole number that is 1 less than 1 is 8, and a pole number that is 1 greater than 8 is 1.
When the rotation angle calculation process is started, the rotation angle calculation device 20 reads the output signals (sensor values) V1 and V2 of the magnetic sensors 21 and 22 (step S1). In the memory (for example, RAM) of the rotation angle calculation device 20, a plurality of times of sensors from the sensor value read a predetermined number of times to the latest read sensor value are output for each of the output signals V1 and V2. The value is stored.

  In this embodiment, in order to detect the peak value (maximum value and minimum value) of the sensor value V1, a sensor value having a larger absolute value among the read sensor values V1 is a peak value candidate of the sensor value V1. Is stored in memory. Similarly, in order to detect the peak value (maximum value and minimum value) of the sensor value V2, a sensor value having a larger absolute value among the read sensor values V2 is stored in the memory as a peak value candidate of the sensor value V2. Is done. However, these peak value candidates are reset to zero at a predetermined timing, which will be described later, when a zero cross of the corresponding output signal is detected.

When the sensor values V1 and V2 are read in step S1, the rotation angle calculation device 20 determines whether or not the current process is the first process after the start of the rotation angle calculation process (step S2). If the current process is the first process after the start of the rotation angle calculation process (step S2: YES), the rotation angle calculation device 20 performs a relative pole number setting process (step S3).
FIG. 6 shows the detailed procedure of the relative pole number setting process.

  First, the rotation angle calculation device 20 determines whether or not the first output signal V1 is greater than 0 (step S21). When the first output signal V1 is greater than 0 (step S21: YES), the rotation angle calculation device 20 has an N-pole magnetic pole (reference magnetic pole) sensed by the first magnetic sensor 21. And the first relative pole number r1 is set to 1 (step S24). Then, the process proceeds to step S26.

  On the other hand, when the first output signal V1 is 0 or less (step S21: NO), the rotation angle calculation device 20 determines whether or not the first output signal V1 is smaller than 0 (step S22). . If the first output signal V1 is smaller than 0 (step S22: YES), it is determined that the magnetic pole (reference magnetic pole) sensed by the first magnetic sensor 21 is the S magnetic pole, and the first The relative pole number r1 is set to 2 (step S25). Then, the process proceeds to step S26.

  If it is determined in step S22 that the first output signal V1 is equal to or greater than 0 (step S22: NO), that is, if the first output signal V1 is 0, the rotation angle calculation device. 20 determines whether the second output signal V2 is greater than 0 in order to determine whether the rotor rotation angle (electrical angle) is 0 ° or 180 ° (step S23). When the second output signal V2 is greater than 0 (step S23: YES), the rotation angle calculation device 20 determines that the rotor rotation angle (electrical angle) is 0 °, and the first relative pole number is determined. r1 is set to 1 (step S24). Then, the process proceeds to step S26.

On the other hand, when the second output signal V2 is 0 or less (step S23: NO), the rotation angle calculation device 20 determines that the rotor rotation angle (electrical angle) is 180 °, and the first relative The target pole number r1 is set to 2 (step S25). Then, the process proceeds to step S26.
In step S26, the rotation angle calculation device 20 determines whether or not the condition of “V1> 0 and V2 ≦ 0” or “V1 <0 and V2 ≧ 0” is satisfied. When this condition is satisfied (step S26: YES), the rotation angle calculation device 20 detects the pole number of the magnetic pole sensed by the second magnetic sensor 22 by the first magnetic sensor 21. It is determined that the number is 1 larger than the pole number of the existing magnetic pole, and a number (r2 = r1 + 1) larger by 1 than the first relative pole number r1 is set as the second relative pole number r2 (step S27). ). And it transfers to step S13 of FIG.

  On the other hand, when the condition of step S26 is not satisfied (step S26: NO), the rotation angle calculation device 20 indicates that the pole number of the magnetic pole sensed by the second magnetic sensor 22 is the first magnetic sensor. 21 is determined to be the same as the pole number of the magnetic pole sensed, and the same number (r2 = r1) as the first relative pole number r1 is set as the second relative pole number r2 (step S28). . And it transfers to step S13 of FIG.

When the condition of step S26 is satisfied, a number (r2 = r1 + 1) larger than the first relative pole number r1 by 1 is set for the second relative pole number r2, and the condition of step S26 is satisfied. The reason why the same number (r2 = r1) as the first relative pole number r1 is set in the second relative pole number r2 in the case where the second relative pole number r2 is not set will be described.
For example, the signal waveforms of the output signals V1, V2 of the first and second magnetic sensors 21, 22 when the magnetic pole pair composed of the magnetic pole M1 and the magnetic pole M2 in the rotor 1 passes through the first magnetic sensor 21 are schematically shown. If it represents, it will come to show to Fig.7 (a) (b).

  7A and 7B, a region indicated by S1 is a region where the first magnetic sensor 21 senses the magnetic pole M1 and the second magnetic sensor 22 senses the magnetic pole M1. The region indicated by S2 is a region where the first magnetic sensor 21 senses the magnetic pole M1 and the second magnetic sensor 22 senses the magnetic pole M2. The region indicated by S3 is a region where the first magnetic sensor 21 senses the magnetic pole M2 and the second magnetic sensor 22 senses the magnetic pole M2. The region indicated by S4 is a region where the first magnetic sensor 21 senses the magnetic pole M2 and the second magnetic sensor 22 senses the magnetic pole M3.

That is, in the areas S1 and S3, the pole number of the magnetic pole sensed by the second magnetic sensor 22 is the same as the pole number of the magnetic pole sensed by the first magnetic sensor 21. On the other hand, in the regions S2 and S4, the pole number of the magnetic pole sensed by the second magnetic sensor 22 is larger by 1 than the pole number of the magnetic pole sensed by the first magnetic sensor 21.
In the region S1, the sensor values V1 and V2 satisfy the first condition of V1 ≧ 0 and V2> 0. In the region S2, both sensor values V1 and V2 satisfy the second condition of V1> 0 and V2 ≦ 0. In the region S3, the sensor values V1 and V2 satisfy the third condition of V1 ≦ 0 and V2 <0. In the region S4, both sensor values V1 and V2 satisfy the fourth condition of V1 <0 and V2 ≧ 0.

  Therefore, when the rotation angle calculation device 20 satisfies the second condition (V1> 0 and V2 ≦ 0) or the fourth condition (V1 <0 and V2 ≧ 0), the second magnetic sensor 22 is provided. The pole number of the magnetic pole sensed by is determined to be 1 larger than the pole number of the magnetic pole sensed by the first magnetic sensor 21, and if the second condition or the fourth condition is not satisfied, The pole number of the magnetic pole sensed by the second magnetic sensor 22 is determined to be the same as the pole number of the magnetic pole sensed by the first magnetic sensor 21.

Returning to FIG. 5, if it is determined in step S2 that the current process is not the first process after the start of the rotation angle calculation process (step S2: NO), the process proceeds to step S4.
In step S4, the rotation angle calculation device 20 determines, based on the sensor values V1 and V2 stored in the memory, whether or not a zero cross where the sign of the sensor value is inverted is detected for each of the sensor values V1 and V2. To do. When the zero cross is not detected (step S4: NO), the rotation angle calculation device 20 proceeds to step S13.

If a zero cross is detected for any one of the sensor values V1 and V2 in step S4 (step S4: YES), the rotation angle calculation device 20 performs each pole number specifying process in step S11, which will be described later. It is determined whether or not the magnetic pole detected by the magnetic pole sensors 21 and 22 has already been specified (step S5).
When the magnetic pole detected by each of the magnetic pole sensors 21 and 22 is not specified (step S5: NO), the rotation angle calculation device 20 performs a relative pole number update process (step S6). Specifically, the rotation angle calculation device 20 sets the relative pole number r1 or r2 currently set for the magnetic sensor in which the zero cross is detected in step S4 to 1 according to the rotation direction of the rotor 1. Change the number to a larger number or a smaller number by one.

  When the rotation direction of the rotor 1 is the positive direction (the direction indicated by the arrow in FIG. 2), the rotation angle calculation device 20 is set to the current set relative to the magnetic sensor in which the zero cross is detected in step S4. The target pole number r1 or r2 is updated to a number larger by one. On the other hand, when the rotation direction of the rotor 1 is the reverse direction, the rotation angle calculation device 20 decreases the relative pole number r1 or r2 currently set for the magnetic sensor in which the zero cross is detected by one. Update to a number. However, as described above, the relative pole number that is smaller by 1 than the relative pole number of “1” is “8”. Further, the relative pole number that is larger by 1 than the relative pole number of “8” is “1”.

  Note that the rotation direction of the rotor 1 can be determined based on, for example, the previous value and the current value of the output signal in which the zero cross is detected, and the current value of the other output signal. Specifically, when the output signal in which the zero cross is detected is the first output signal V1, “the previous value of the first output signal V1 is greater than 0 and its current value is less than or equal to 0, The condition that the output signal V2 of 2 is smaller than 0, or that the previous value of the first output signal V1 is less than 0 and its current value is 0 or more, and the second output signal V2 is greater than 0. If the condition is satisfied, the rotation direction is determined to be the positive direction (the direction indicated by the arrow in FIG. 2).

On the other hand, the condition that “the previous value of the first output signal V1 is greater than or equal to 0 and the current value is less than 0 and the second output signal V2 is greater than 0” or “the previous time of the first output signal V1. When the condition that the value is 0 or less and the current value is greater than 0 and the second output signal V2 is less than 0 is satisfied, the rotation direction is determined to be the reverse direction.
When the output signal in which the zero cross is detected is the second output signal V2, “the previous value of the second output signal V2 is greater than 0 and the current value is less than or equal to 0, and the first output signal V1 Or the condition that the previous value of the second output signal V2 is less than 0 and the current value is 0 or more and the first output signal V1 is less than 0 is satisfied. In this case, the rotation direction is determined to be the positive direction (the direction indicated by the arrow in FIG. 2). On the other hand, the condition that “the previous value of the second output signal V2 is 0 or more and the current value is less than 0 and the first output signal V1 is less than 0” or “the previous time of the second output signal V2” When the condition that the value is 0 or less and the current value is greater than 0 and the first output signal V1 is greater than 0 is satisfied, the rotation direction is determined to be the reverse direction.

  When the update process of the relative pole number in step S6 is completed, the rotation angle calculation device 20 performs a peak value detection process (step S7). The peak value detection process will be specifically described. The magnetic sensor corresponding to the output signal in which the zero cross is detected in step S4 will be referred to as a peak value detection target magnetic sensor. First, the rotation angle calculation device 20 determines whether or not the magnetic pole sensed by the magnetic sensor that is the peak value detection target has changed. In other words, the rotation angle calculation device 20 differs in the magnetic pole position sensed by the peak value detection target magnetic sensor between the time when the zero cross of the output signal of the magnetic sensor was detected last time and the time when it was detected this time. Or whether they are the same. When the rotation direction of the rotor 1 is reversed, the magnetic pole positions at both time points may be the same.

  This determination is made, for example, by the rotation direction of the rotor 1 at the time when the zero crossing of the output signal of the magnetic sensor that is the peak value detection target was previously detected and the rotation of the rotor 1 at the time when the zero crossing of the output signal was detected this time. This can be done based on whether the directions are the same. That is, if the rotation direction of the rotor 1 at the two time points is the same, the rotation angle calculation device 20 determines that the magnetic pole sensed by the magnetic sensor that is the peak value detection target has changed. On the other hand, if the rotation directions of the rotor 1 at the two time points are different, the rotation angle calculation device 20 determines that the magnetic pole sensed by the magnetic sensor that is the peak value detection target has not changed.

  When it is determined that the magnetic pole sensed by the magnetic sensor targeted for peak value detection has changed, the rotation angle calculation device 20 determines that the peak value has been detected, and the peak value candidate corresponding to the magnetic sensor. Is specified as the peak value. On the other hand, when it is determined that the magnetic pole sensed by the peak value detection target magnetic sensor has not changed, the rotation angle calculation device 20 determines that the peak value has not been detected.

  The peak value has a maximum value larger than 0 and a minimum value smaller than 0. In this embodiment, since the pole position specifying magnetic pole is an N-pole magnetic pole, the magnetic pole pair sensed by the first magnetic sensor 21 is specified based on the maximum value among the peak values. In the following, the maximum values of the first output signal V1 and the second output signal V2 detected in the peak value detection process may be represented by P1 and P2, respectively.

  When the maximum value is not detected in the peak value detection process (step S8: NO), the rotation angle calculation device 20 resets the peak value candidate corresponding to the output signal in which the zero cross is detected in step S4 to 0. Then, the process proceeds to step S13. Even when the peak value is detected in the peak value detection process, if the detected peak value is a minimum value, it is determined that the maximum value is not detected in the peak value detection process.

  When the maximum value is detected in the peak value detection process (step S8: YES), the maximum value is stored in the memory as the maximum value P1 or P2 with respect to the output signal in which the zero cross is detected in step S4 (step S9). . The memory stores, for each local maximum value P1 and P2, the local maximum value for two times of the local maximum value detected last time and the local maximum value detected this time. Thereafter, the rotation angle calculation device 20 resets the peak value candidate corresponding to the output signal in which the zero cross is detected in step S4 to 0, and then proceeds to step S10.

  In step S10, it is determined whether or not the maximum value of the output signal in which the zero cross is detected in step S4 is detected twice or more. When the maximum value of the output signal in which the zero cross is detected in step S4 is not detected twice or more (step S10: NO), the rotation angle calculation device 20 proceeds to step S13. On the other hand, when the maximum value of the output signal in which the zero cross is detected in step S4 is detected twice or more (step S10: YES), the rotation angle calculation device 20 performs a pole number specifying process (step S11). ).

  The concept of the pole number identification process will be described. As described above, for each combination (M1, M3), (M3, M5), (M5, M7), (M7, M1) of adjacent pole position specifying magnetic poles, each output for the adjacent pole position specifying magnetic poles. The ratio of the peak values (maximum values in this example) of the signals V1 and V2 is different. Therefore, at the time when the maximum value of the first output signal V1 is detected for each of the adjacent poles for specifying the local position (zero cross detection time), the ratio of these maximum values and the extreme value ratio data D1 to D4, Based on the rotation direction of the rotor 1, the pole number q1 of the magnetic pole currently sensed by the first magnetic sensor 21 can be specified. When the extreme value ratio data is set for each of the output signals V1 and V2, the extreme value ratio data DA1 set for the first output signal V1 instead of the extreme value ratio data D1 to D4. ~ DA4 is used.

For example, referring to FIG. 3, when the rotor 1 is rotating in the positive direction (the direction indicated by the arrow in FIG. 2), the first of the magnetic pole M3 is detected at the timing when the zero cross indicated by Z1 in FIG. 3 is detected. the detection of the local maximum value P1 _n-1 of the output signal V1, thereafter, at the timing when the zero-crossing is detected shown in Figure 3 Z2, the maximum value P1 _n of the first output signal V1 for pole M5 is detected To do. In this case, the ratio P1 _n-1 / P1 _n of both maximum values is substantially equal to D2 (= P1 (3) / P1 (5)) of the extreme value ratio data D1 to D4. It can be determined that the first magnetic sensor 21 senses the magnetic pole M6 at the timing when the zero cross indicated by Z2 is detected.

Referring to FIG. 3, when the rotor 1 rotates in the reverse direction, the maximum value P1 _n of the first output signal V1 with respect to the magnetic pole M5 at the timing when the zero cross indicated by Z3 in FIG. 3 is detected. It is assumed that the maximum value P1 _n of the first output signal V1 with respect to the magnetic pole M5 is detected at the timing when ₋₁ is detected and then the zero cross indicated by Z4 in FIG. 3 is detected. In this case, the ratio P1 _n / P1 _n−1 of the maximum values is almost equal to D2 (= P1 (3) / P1 (5)) of the extreme value ratio data D1 to D4. It can be determined that the first magnetic sensor 21 senses the magnetic pole M2 at the timing when the zero cross indicated by Z4 is detected. Thus, if the pole number q1 of the magnetic pole currently sensed can be identified, the pole number q2 of the magnetic pole currently sensed by the second magnetic sensor 22 is identified based on the relative pole numbers r1 and r2. Can do.

  Similarly, at the time when the maximum value of the second output signal V2 is detected for each of the adjacent poles for specifying the local position (zero cross detection time), the ratio between these maximum values and the extreme value ratio data D1 to D4. Based on the rotation direction of the rotor 1, the pole number q2 of the magnetic pole currently sensed by the second magnetic sensor 22 can be specified. When the extreme value ratio data is set for each of the output signals V1 and V2, the extreme value ratio data DB1 set for the second output signal V2 instead of the extreme value ratio data D1 to D4. ~ DB4 is used. If the pole number q2 of the magnetic pole currently detected by the second magnetic sensor 22 can be specified, the pole number q1 of the magnetic pole currently detected by the first magnetic sensor 23 is specified based on the relative pole numbers r1 and r2. can do.

More specific description will be given below. First, the pole number specifying process that is performed when the output signal in which the zero cross is detected in step S4 is the first output signal V1 will be described. In this case, the rotation angle calculation unit 20, the ratio of the maximum value P1 _n of the first output signal V1 which is detected this time the maximum value P1 _n-1 of the first output signal V1 which is previously detected, Based on the extreme value ratio data D1 to D4 and the rotation direction of the rotor 1, the pole number (absolute pole number) q1 of the magnetic pole sensed by the first magnetic sensor 21 is specified. The extreme value ratio data D1 to D4 may be represented by D _i (i = 1, 2, 3, 4), where i is the extreme value ratio data number.

When the rotation direction of the rotor 1 is the positive direction (the direction indicated by the arrow in FIG. 2), the rotation angle calculation device 20 calculates P1 _n−1 / P1 _n as the extreme value ratio X and rotates the rotor 1. When the direction is the reverse direction, P1 _n / P1 _n-1 is calculated as the extreme value ratio X. Next, the rotation angle calculation device 20 calculates the extreme value ratio data number i of the extreme value ratio data D _i closest to the extreme value ratio X based on the calculated extreme value ratio X and the extreme value ratio data D1 to D4. Is identified. The rotation angle calculation device 20 then detects the magnetic pole that the first magnetic sensor 21 currently senses based on the specified extreme value ratio data number i, the rotation direction of the rotor 1, and the contents of the following table 1. The pole number q1 is specified.

Table 1 shows the combinations of the extreme value ratio data number _i of the extreme value ratio data D _i closest to the extreme value ratio X and the rotation direction of the rotor 1, and the poles of the magnetic pole currently sensed by the first magnetic sensor 21. The relationship with the number q1 is shown.

  Specifically, when the rotation direction of the rotor 1 is the positive direction, the rotation angle calculation device 20 determines the pole of the magnetic pole currently sensed by the first magnetic sensor 21 based on q1 = 2 · i + 2. The number q1 is calculated. However, when the value of (2 · i + 2) exceeds 8, the rotation angle calculation device 20 calculates q1 based on q1 = 2 · i + 2-8. On the other hand, when the rotation direction of the rotor 1 is the reverse direction, the rotation angle calculation device 20 determines the pole number of the magnetic pole currently sensed by the first magnetic sensor 21 based on q1 = 2 · i−2. q1 is calculated. However, when the value of (2 · i−2) is 0 or less, the rotation angle calculation device 20 calculates q1 based on q1 = 2 · i−2 + 8.

  After that, the rotation angle calculation device 20 uses the second magnetic field based on the pole number q1 of the magnetic pole sensed by the first magnetic sensor 21 and the first and second relative pole numbers r1 and r2. The pole number q2 of the magnetic pole sensed by the sensor 22 is specified. Specifically, the rotation angle calculation device 20 specifies the pole number q2 of the magnetic pole sensed by the second magnetic sensor 22 based on q2 = (q1-r1) + r2.

Next, the pole number specifying process that is performed when the output signal in which the zero cross is detected in step S4 is the second output signal V2 will be described. In this case, the rotation angle calculation unit 20, the ratio of the maximum value P2 _n of the second output signal V2 detected this second local maximum value P2 _n-1 of the output signal V2 which is previously detected, Based on the extreme value ratio data D1 to D4 and the rotational direction of the rotor 1, the pole number (absolute pole number) q2 of the magnetic pole sensed by the second magnetic sensor 22 is specified.

When the rotation direction of the rotor 1 is the positive direction (the direction indicated by the arrow in FIG. 2), the rotation angle calculation device 20 calculates P2 _n−1 / P2 _n as the extreme value ratio Y and rotates the rotor 1. When the direction is the reverse direction, P2 _n / P2 _n-1 is calculated as the extreme value ratio Y. Next, the rotation angle calculation device 20 uses the extreme value ratio Y of the extreme value ratio data D _i closest to the extreme value ratio Y based on the calculated extreme value ratio Y and the extreme value ratio data D1 to D4. Is identified. The rotation angle calculation device 20 then detects the magnetic pole that the second magnetic sensor 22 currently senses based on the specified extreme value ratio data number i, the rotation direction of the rotor 1, and the contents of the following table 2. Specifies the pole number q2.

Table 2 shows a combination of the extreme value ratio data number _i of the extreme value ratio data D _i closest to the extreme value ratio Y and the rotation direction of the rotor 1, and the pole of the magnetic pole currently sensed by the second magnetic sensor 22. The relationship with the number q2 is shown.

  Specifically, when the rotation direction of the rotor 1 is the positive direction, the rotation angle calculation device 20 determines the pole of the magnetic pole currently detected by the second magnetic sensor 22 based on q2 = 2 · i + 2. The number q2 is calculated. However, when the value of (2 · i + 2) exceeds 8, the rotation angle calculation device 20 calculates q2 based on q2 = 2 · i + 2-8. On the other hand, when the rotation direction of the rotor 1 is the reverse direction, the rotation angle calculation device 20 determines the pole number of the magnetic pole currently sensed by the second magnetic sensor 22 based on q2 = 2 · i−2. q2 is calculated. However, when the value of (2 · i−2) is 0 or less, the rotation angle calculation device 20 calculates q2 based on q2 = 2 · i−2 + 8.

  Thereafter, the rotation angle calculation device 20 performs the first magnetism based on the pole number q2 of the magnetic pole sensed by the second magnetic sensor 22 and the first and second relative pole numbers r1 and r2. The pole number q1 of the magnetic pole sensed by the sensor 21 is specified. Specifically, the rotation angle calculation device 20 specifies the pole number q1 of the magnetic pole sensed by the first magnetic sensor 21 based on q1 = (q2-r2) + r1. When the pole number specifying process in step S11 ends, the rotation angle calculation device 20 proceeds to step S14.

  If it is determined in step S5 that the magnetic poles sensed by the magnetic sensors 21 and 22 have already been identified (step S5: YES), the rotation angle calculation device 20 performs a pole number update process. This is performed (step S12). Specifically, the rotation angle calculation device 20 increases the pole number q1 or q2 already specified for the magnetic sensor in which the zero cross is detected in step S4 by one according to the rotation direction of the rotor 1. Change to a pole number or a pole number that is smaller by one.

  When the rotation direction of the rotor 1 is the positive direction, the rotation angle calculation device 20 sets the pole number q1 or q2 already specified for the magnetic sensor in which the zero cross is detected to a pole number that is larger by one. Update. On the other hand, when the rotation direction of the rotor 1 is the reverse direction, the rotation angle calculation device 20 sets the pole number q1 or q2 already specified for the magnetic sensor in which the zero cross is detected to a pole smaller by one. Update to a number. However, the pole number that is smaller by 1 than the pole number of “1” is “8”. In addition, the pole number that is larger by 1 than the pole number of “8” is “1”. The rotation angle computing device 20 proceeds to step S14 when the pole number update process in step S12 is completed.

In step S14, the rotation angle calculation device 20 performs an amplitude correction process. That is, the rotation angle calculation device 20 corrects the amplitudes of the output signals V1 and V2 of the magnetic sensors 21 and 22.
Specifically, in the rotation angle calculation device 20, the peak value of the first output signal V1 corresponding to the pole number q1 of the magnetic pole sensed by the first magnetic sensor 21 and the second magnetic sensor 22 sense. The peak value of the second output signal V2 corresponding to the pole number q2 of the magnetic pole being obtained is acquired from the peak value table (see FIG. 4). The peak values of the first and second output signals V1 and V2 acquired from the peak value table are represented by P1x and P2x, respectively. Then, the amplitudes of the output signals V1 and V2 are corrected based on the acquired peak values (amplitude correction values) P1x and P2x and a preset reference amplitude φ.

Specifically, assuming that the amplitude-corrected signals of the first and second output signals V1 and V2 are V1 ′ and V2 ′, respectively, the corrected first and second output signals V1 ′ and V2 ′ are Each is calculated based on the following equations (2) and (3).
V1 ′ = (V1 / P1x) × φ (2)
V2 ′ = (V2 / P2x) × φ (3)
The amplitude correction process is completed, the rotation angle calculation unit 20, the output signal after amplitude correction V1 ', V2' based on, it calculates the electrical angle theta _E (step S15). Specifically, based on the following equation (4), it computes the rotation angle of the rotor 1 (electrical angle) theta _E.

θ _E = tan ⁻¹ (V1 ′ / V2 ′) (4)
When the electrical angle θ _E is calculated, the rotation angle calculation device 20 calculates the mechanical angle (absolute angle) θ _M of the rotor 1. Specifically, the rotation angle calculation unit 20, using the pole number q1 of electrical angle theta _E and the first magnetic sensor 21 calculated in the step S15 is sensed, based on the following equation (5) Then, the mechanical angle θ _M is calculated (step S16).

θ _M = {θ _E + m × 360 °} / 4 (5)
However, when q1 = 1 or 2, m = 0,
If q1 = 3 or 4, m = 1,
If q1 = 5 or 6, m = 2,
When q1 = 7 or 8, m = 3.

Rotation angle computing unit 20, and the electrical angle theta _E calculated in the step S15, calculated in step S16, providing a mechanical angle theta _M to the motor controller 30. Then, the processing in the current calculation cycle is finished.
In step S13, since the magnetic pole sensed by each of the magnetic sensors 21 and 22 is not specified, the rotation angle calculation device 20 determines the electrical angle θ _E based on the sensor values V1 and V2 read in step S1. Is calculated. Specifically, on the basis of the following equation (6), computes the rotation angle of the rotor 1 (electrical angle) theta _E.

θ _E = tan ⁻¹ (V1 / V2) (6)
When the electrical angle theta _E is calculated in the step S13, the rotation angle calculation unit 20 provides the electrical angle theta _E to the motor controller 30. Then, the processing in the current calculation cycle is finished.
According to the embodiment, the extreme values P1 _n−1 and P1 _n of the first output signal V1 or the maximum value P2 _{n− of} the second output signal V2 for any pair of adjacent pole position specifying magnetic poles. ₁ and P2 _n are detected for the first time, it becomes possible to specify the magnetic pole sensed by each of the magnetic sensors 21 and 22. For this reason, the magnetic pole sensed by the magnetic sensors 21 and 22 can be identified at an early stage immediately after the rotating body starts rotating. As a result, the amplitude of the output signals V1, V2 of the magnetic sensors 21, 22 can be corrected at an early stage immediately after the rotation of the rotor 1 starts after the rotation angle calculation process starts. The rotational angle calculation accuracy of (brushless motor) is improved.

Further, based on the ratio of the extreme values P1 _n−1 and P1 _n of the first output signal V1 or the ratio of the maximum values P2 _n−1 and P2 _n of the second output signal V2 to the adjacent poles for specifying the pole position. Thus, the magnetic poles sensed by the magnetic sensors 21 and 22 are specified, so that the magnetic poles sensed by the magnetic sensors 21 and 22 even when the output signals V1 and V2 fluctuate due to changes in the ambient temperature. Can be accurately identified.

  As mentioned above, although embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the rotor 1 has adjacent poles for each combination (M1, M3), (M3, M5), (M5, M7), (M7, M1) of the adjacent pole position specifying magnetic poles. Although the magnetic pole characteristics have such that the ratio of the peak values of the sine wave signals V1 and V2 with respect to the positioning magnetic poles are identifiable, the rotor 1 has at least one pair of adjacent pole positioning magnetic poles. The ratio of the extreme values of the output signals V1 and V2 has a magnetic pole characteristic such that the ratio of the extreme values of each of the output signals V1 and V2 with respect to the other pole position specifying magnetic poles in another set is distinguishable. Just do it. For example, the ratio of the extreme values of the output signals V1 and V2 to a certain set of adjacent pole position specifying magnetic poles (hereinafter referred to as “reference adjacent magnetic poles”) is the same as that of another set of adjacent pole position specifying magnetic poles. If the ratio of the extreme values of the output signals V1 and V2 is identifiable, the first output signal V1 corresponding to each of the reference adjacent magnetic poles after the rotating body starts rotating. Alternatively, when the extreme value of the second output signal V2 is first detected by the detection means, it is possible to specify the magnetic pole sensed by the magnetic sensor that outputs the detected extreme value. Accordingly, there is a high possibility that the magnetic pole sensed by each of the magnetic sensors 21 and 22 can be specified before the rotor 1 makes one rotation after the brushless motor 30 is activated. That is, the magnetic pole sensed by each of the magnetic sensors 21 and 22 can be identified at an early stage immediately after the brushless motor is started.

  In the above-described embodiment, the magnetic poles M1, M3, M5, and M7 having the polarity of the N pole are the pole position specifying magnetic poles, but the magnetic poles M2, M4, M6, and M8 having the polarity of the S pole are used. A pole for specifying the pole position may be used. Also in this case, the rotor 1 has a ratio of the extreme values of the output signals V1 and V2 with respect to at least one pair of adjacent pole position specifying magnetic poles. , V2 as long as it has a magnetic pole characteristic that is distinguishable from any of the extreme value ratios of V2. The rotor 1 (magnet 2) includes adjacent pole position specifying magnetic poles for each combination (M2, M4), (M4, M6), (M6, M8), and (M8, M2) of the adjacent pole position specifying magnetic poles. It is preferable to have magnetic pole characteristics such that the ratios of the peak values of the sine wave signals V1 and V2 to each other are identifiable. In this case, the rotation angle calculation device 20 uses each magnetic sensor based on the ratio of the minimum value of the first or second output signal V1, V2 to any adjacent pole position specifying magnetic pole and the extreme value ratio data. The magnetic pole which 21 and 22 are sensing is specified. In this case, the extreme value ratio data is, for example, D1 = P1 (2) / P1 (4), D2 = P1 (4) / P1 (6), D3 = P1 (6) / P1 (8) and D4. = P1 (8) / P1 (2).

  The magnetic poles M1 to M8 may be pole position specifying magnetic poles. Also in this case, the rotor 1 has a ratio of the extreme values of the output signals V1 and V2 with respect to at least one pair of adjacent pole position specifying magnetic poles. , V2 as long as it has a magnetic pole characteristic that is distinguishable from any of the extreme value ratios of V2. The rotor 1 (magnet 2) is a combination of adjacent pole position specifying magnetic poles (M1, M2), (M2, M3), (M3, M4), (M4, M5), (M5, M6), (M6, Magnetic pole characteristics such that the ratio of the peak values (extreme values) of the sine wave signals V1 and V2 with respect to the adjacent magnetic poles for specifying the pole position differs for each of M7), (M7, M8), and (M8, M1). It is preferable to have. In this case, the rotation angle calculation device 20 is based on the absolute value of the ratio of the peak values of the first or second output signals V1 and V2 with respect to any adjacent pole position specifying magnetic pole and the extreme value ratio data. The magnetic pole sensed by each of the magnetic sensors 21 and 22 is specified. In this case, the extreme value ratio data is, for example, D1 = | P1 (1) / P1 (2) |, D2 = | P1 (2) / P1 (3) |, D3 = | P1 (3) / P1 (4) |, D4 = | P1 (4) / P1 (5) |, D5 = | P1 (5) / P1 (6) |, D6 = | P1 (6) / P1 (7) |, D7 = | P1 (7) / P1 (8) | and D8 = | P1 (8) / P1 (1) |

In the above embodiment, the phase difference between the first output signal V1 and the second output signal V2 is 90 ° in electrical angle, but the phase difference between the signals V1 and V2 is an arbitrary angle. May be. For example, the first output signal V1 of the phase difference between the second output signal V2 and alpha, the first output signal V1 and V1 = A1 · sin [theta _E, the second output signal V2 V2 = A2 · sin Assuming that (θ _E + α), the first output signal V1 ′ after amplitude correction is expressed by V1 ′ = φ · sin θ _E , and the second output signal V2 ′ after amplitude correction is V2 ′ = φ · sin ( θ _E + α). In this case, for example, the rotation angle calculation device 20 has a phase difference of 90 from the first and second output signals V1 ′ and V2 ′ after amplitude correction to the first output signal V1 ′ after amplitude correction. A signal V ₁₂ ′ (= φ · sin (θ _E + 90 °) = φ · cos θ _E ) to be ° is generated. Specifically, the rotation angle calculation device 20 generates the signal V ₁₂ ′ based on V ₁₂ ′ = (V 2 ′ −V 1 ′ · cos α) / sin α. Then, the rotation angle calculation device 20 calculates the electrical angle θ _{E of the} rotor based on θ _E = tan ⁻¹ (V1 ′ / V ₁₂ ′).

The present invention can also be applied when detecting the rotation angle of a rotating body other than the rotor of a brushless motor.
In addition, various design changes can be made within the scope of matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Detection rotor, 2 ... Magnet, 21, 22 ... Magnetic sensor, 10 ... Brushless motor, 20 ... Rotation angle arithmetic unit, M1-M8 ... Magnetic pole

Claims (3)

A detection rotor having a plurality of magnetic poles rotated according to the rotation of the rotating body and provided at equal angular intervals in the circumferential direction, and first and second having a predetermined phase difference according to the rotation of the detection rotor A rotation angle detection device that detects the rotation angle of the rotating body based on the output signals of these magnetic sensors, the first and second magnetic sensors each outputting a sine wave signal of
The detection rotor has at least one pair of adjacent pole position specifying magnetic poles, where each magnetic pole or each magnetic pole having one of the N and S poles is a pole position specifying magnetic pole. The ratio of the extreme values of each sine wave signal has a magnetic pole characteristic such that the ratio of the extreme value of each sine wave signal with respect to another set of adjacent pole position specifying magnetic poles is distinguishably different from each other.
Extreme value detection means for detecting an extreme value of each sine wave signal;
The ratio of the extreme value of the first or second sine wave signal to an arbitrary adjacent pole position specifying magnetic pole calculated from the extreme value detected by the extreme value detection means, and a preset extreme value ratio Magnetic pole identification means for identifying the magnetic pole sensed by each magnetic sensor based on the data;
Amplitude correction means for correcting the amplitude of each sine wave signal in accordance with the magnetic pole specified by the magnetic pole specifying means;
Based on each sine wave signal after amplitude correction, rotation angle calculation means for calculating the rotation angle of the rotating body,
Rotation angle detection device. The detection rotor has a magnetic pole characteristic such that for each combination of adjacent pole position specifying magnetic poles, the ratio of the extreme values of the sine wave signals to the adjacent pole position specifying magnetic poles is identifiable. ,
The extreme value ratio data is a ratio of the extreme value of the first sine wave signal to the adjacent pole position specifying magnetic pole and / or the second value set in advance for each combination of adjacent pole position specifying magnetic poles. Including the ratio of the extreme values of the sinusoidal signal
The magnetic pole specifying means detects the two poles detected when the extreme value of the first or second sine wave signal for each adjacent pole position specifying magnetic pole is detected by the extreme value detecting means. The rotation angle detection device according to claim 1, configured to specify a magnetic pole sensed by each magnetic sensor based on a ratio of magnitudes of values and the extreme value ratio data. The rotation angle detection device according to claim 1 or 2, wherein the predetermined phase difference is an electrical angle of 90 °.

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