JP4166653B2 - Rotation angle detector - Google Patents

Description

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

  As a prior art, there is a rotation angle detection device (see Patent Document 1) filed earlier by the present applicant.

This rotational angle detection device is provided on the outer circumferential side of the magnet, which is connected to the rotating shaft and in which the N pole and the S pole are connected at an interval of about 180 degrees in the circumferential direction. A magnetic yoke in which a radial gap is formed at approximately every 90 degrees and two magnetic gaps that are continuous in the circumferential direction of the magnetic yoke are arranged one by one, and an electric signal is detected by detecting the magnetic flux density generated in the gap. And a rotation angle detector that calculates the rotation angle of the rotating shaft based on the electric signal converted by the magnetic sensor and determines a short circuit of the electric signal of the magnetic sensor.
Japanese Patent Application No. 2003-6349

  In the rotation angle detection device described in Patent Document 1 described above, the periodic waveform of the electrical signal converted by the two magnetic sensors becomes a substantially triangular waveform with a phase shift of approximately 90 degrees. In two degrees, there are two coincident portions where the electric signals converted by the two magnetic sensors coincide with each other.

In addition, when the two magnetic sensors have a short circuit failure, the electric signals converted by the two magnetic sensors match each other, so when the rotation angle calculation unit matches the electric signals converted by the two magnetic sensors A short-circuit failure between the two magnetic sensors can be determined.
However, even if no short-circuit failure has occurred in the two magnetic sensors, there are two coincident portions where the electric signals converted by the two magnetic sensors coincide as described above, so that there are two rotation angle calculation units. There is a problem in that it is erroneously determined that two magnetic sensors are short-circuited in spite of no short-circuit failure occurring in the magnetic sensor.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a rotation angle detection device that can reliably determine a short-circuit failure without erroneously determining a short-circuit failure between at least two magnetic sensors. And

  In order to solve the above-described problem, in claim 1, the rotating shaft, the first magnetic pole and the second magnetic pole having different magnetic polarities are alternately formed in the circumferential direction, and the hard magnetic body is formed. A magnetic circuit configured to change the magnetic flux density when the relative position of the magnetic circuit changes with the rotation of the rotating shaft to change the magnetic flux density. A plurality of magnetic flux density converters that convert each magnetic flux density generated in the body's magnetic circuit into an electrical signal, and a rotational angle calculation for computing the rotational angle of the rotating shaft based on the electrical signal converted by the magnetic flux density converter The plurality of electrical signals are electrical signals converted so as not to have the same potential with respect to the rotation angle of the rotating shaft, and when at least two electrical signals have the same potential, the magnetic flux If there is a short-circuit fault between the density converters It is characterized by a constant.

  With this configuration, the magnetic flux density converter converts the magnetic flux density into an electric signal so as not to have the same electric potential with respect to the rotation angle of the rotation shaft, so that a short circuit failure occurs between at least two magnetic flux density converters. Only occasionally, the plurality of electrical signals converted by the magnetic flux density converter have the same potential. From this, when the electric signals converted by at least two magnetic flux density converters have the same potential, it is determined that there is a short-circuit failure between the magnetic flux density converters. It is possible to reliably determine the short circuit failure without erroneously determining the short circuit failure.

  According to a second aspect of the present invention, the fact that the plurality of electrical signals are not at the same potential with respect to the rotation angle of the rotating shaft means that the electric potentials are not at the same potential within the range of the rotation angle of the rotating shaft of 360 degrees. It is said.

  With this configuration, when there is no short-circuit failure between the plurality of magnetic flux density converters, the plurality of electrical signals are not at the same potential in the range of the rotation angle of the rotation shaft of 360 degrees, so the rotation shaft rotates. A plurality of electrical signals converted by the magnetic flux density converter can be set to the same potential only when a short circuit failure occurs between at least two magnetic flux density converters in all possible angular regions.

  According to a third aspect of the present invention, the electric signal is an electric signal after being converted by the magnetic flux density converter output to the rotation angle calculation unit, and the magnetic flux density converter converts the magnetic flux density into an electric signal before conversion. Then, the converted electric signal is offset and converted into a converted electric signal.

  With this configuration, the magnetic flux density converter offsets the electric signal before conversion, so that the plurality of converted electric signals can be prevented from having the same potential with respect to the rotation angle of the rotating shaft.

  According to a fourth aspect of the present invention, the plurality of electrical signals converted by the magnetic flux density converter are substantially triangular waves each having a predetermined angle phase shifted with respect to the rotation angle of the rotating shaft, and the plurality of magnetic flux density converters include: Offset values for offsetting the electrical signal before conversion are set in advance, and the rotation angle calculation unit stores each of the preset offset values, and performs a plurality of conversions based on the stored offset values. The subsequent electrical signal is converted into an electrical signal before conversion, and the electrical signals before conversion are connected to calculate the rotation angle of the rotating shaft.

  With this configuration, the rotation angle calculation unit stores a preset offset value, and based on the stored offset value, reverts to the electric signal before conversion when the converted electric signal is not offset. The rotation angle calculation unit rotates even if the electrical signal converted by the magnetic flux density converter is offset because it converts the multiple electrical signals before conversion and calculates the rotation angle of the rotating shaft. The rotation angle of the shaft can be calculated normally.

  According to a fifth aspect of the present invention, the magnetic flux density converter has an output signal line connected to the rotation angle calculation unit, and the short circuit failure means that output signal lines of at least two magnetic flux density converters are short-circuited. It is characterized by that.

  With this configuration, it is possible to reliably determine the short-circuit failure of the output signal line connected to the rotation angle calculation unit of the magnetic flux density converter, and thus it is possible to prevent the rotation angle calculation unit from continuing to erroneously calculate the rotation angle of the rotation shaft. .

1A is a side view of the rotation angle sensor, and FIG. 1B is a cross-sectional view taken along the line II of FIG. 1A and a rotation angle detection device including the rotation angle sensor. FIG. 2 is a perspective view showing a magnet. 3A shows the direction of the magnetic flux amount φ generated from the magnet, and FIG. 3B shows the periodic waveform of the magnetic flux amount φ generated from the magnet at the circumferential angle θ of FIG. It is a graph. 4A is a diagram showing a state in which the magnet is rotated in the circumferential direction, and FIG. 4B is a graph showing a periodic waveform of an electric signal converted by the magnetic sensor. FIG. 5 is a flowchart showing a calculation procedure in the rotation angle calculation unit. FIG. 6 is a graph showing an electrical signal calculated by the rotation angle calculation unit.

  As shown in FIGS. 1A and 1B, the rotation angle detection device 1 according to the present embodiment includes a rotation angle sensor provided on the outer peripheral side of the rotation shaft 2 and a rotation angle calculation unit 6, and rotates. Based on the signal detected by the angle sensor, the rotation angle calculation unit 6 calculates the rotation angle of the rotation shaft 2.

  The rotation angle sensor includes a magnet 3 that is a hard magnetic material, a yoke 4 that is a soft magnetic material, and a magnetic sensor 5 that is a magnetic flux density detector.

  The magnet 3 has a ring shape and is connected to the outer periphery of the rotary shaft 2 and includes an N pole 3a forming a first magnetic pole having a different magnetic polarity and an S pole 3b forming a second magnetic pole. The N pole 3a and the S pole 3b are connected at an interval of about 180 degrees in the circumferential direction. Further, as shown in FIG. 2, the thickness h in the axial direction of the magnet 3 extends from the boundary 3c between the N pole 3a and the S pole 3b in the circumferential direction to the circumferential center of the N pole 3a and the S pole 3b. Gradually decreasing.

  The yoke 4 is an annular body disposed close to the outer periphery of the magnet 3, and is composed of first to fourth yokes 4a to 4d. The first to fourth yokes 4a to 4d are provided via gaps 41 at intervals of about 90 degrees in the circumferential direction. Further, as shown in FIG. 1A, the axial thickness of the yoke 4 is formed thicker than the axial thickness of the magnet 3, and the central position of the yoke 4 in the axial thickness direction is The center position of the magnet 3 in the thickness direction in the axial direction coincides with the axial direction over the entire circumference.

  The magnetic sensor 5 includes first and second magnetic sensors 5a and 5b. The first magnetic sensor 5a is in the gap 41 between the first and fourth yokes 4a and 4d in the circumferential direction, and the second magnetic sensor 5b is in contact with the first and second yokes 4a and 4b. It is inserted in the gap 41 between the circumferential directions, and the amount of magnetic flux generated in each inserted gap 41 is detected as the magnetic flux density. However, the first and second magnetic sensors 5 a and 5 b are provided in non-contact with the yoke 4. As the magnetic sensor 5, for example, a Hall element, a Hall IC, a magnetoresistive element, or the like can be used. The detected magnetic flux density is converted into an electric signal (for example, a voltage signal) and output to the rotation angle calculation unit 6. . Further, the magnetic sensor 5 has a parameter capable of freely offset the converted electric signal. The first and second magnetic sensors 5 a and 5 b have output signal lines 50 a and 50 b for outputting the converted electric signals to the rotation angle calculation unit 6.

  Output signal lines 50a and 50b of the first and second magnetic sensors 5a and 5b are connected to the rotation angle calculation unit 6, and electric signals converted by the first and second magnetic sensors 5a and 5b are connected to the rotation angle calculation unit 6. The signal is input through the output signal lines 50a and 50b (see FIG. 12). And the rotation angle calculating part 6 calculates the rotation angle (absolute angle) of the rotating shaft 2 based on the input electrical signal. Specifically, the two electrical signals converted by the first and second magnetic sensors 5a and 5b are connected to calculate the rotation angle of the continuous rotating shaft 2 of 90 degrees or more.

  Next, the basic operation of this embodiment will be described.

  First, the magnetic flux density of the magnetic flux generated from the magnet 3 will be described. As described above, the axial thickness h of the magnet 3 gradually decreases in the circumferential direction from the boundary portion 3c between the N pole 3a and the S pole 3b toward the circumferential central portion of the N pole 3a and the S pole 3b. For this reason, the thickness of the central portion in the circumferential direction of the N pole 3a and the S pole 3b is thinner than the thickness of the boundary portion 3c between the N pole 3a and the S pole 3b. Therefore, the surface line of the outer peripheral surface near the circumferential center of the N pole 3a and the S pole 3b becomes small, and the magnetic flux density of the magnetic flux generated in the radial direction from any portion near the circumferential center of the N pole 3a and S pole 3b. Is smaller than the magnetic flux density of the magnetic flux generated from any part of the magnet 3 near the center in the circumferential direction of the N pole 3a and the S pole 3b with the same thickness h over the entire circumference. Therefore, the amount of magnetic flux generated in the radial direction from any portion near the center in the circumferential direction of the N pole 3a and the S pole 3b is the N pole 3a and S pole 3b of the magnet 3 having the same thickness h over the entire circumference. This is less than the amount of magnetic flux generated from any part near the center in the circumferential direction. That is, the amount of magnetic flux generated from the portion where the amount of magnetic flux of the N pole 3a and the S pole 3b is large can be reduced. From this, the periodic waveform of the amount of magnetic flux generated from the magnet 3 of this embodiment is the waveform shown in FIG. 3B, and the range X (near the center in the circumferential direction of the N pole 3a) and the range Y (the S pole 3b). The amount of magnetic flux with the vicinity of the center in the circumferential direction can be set substantially constant.

  As shown in FIG. 3B, the thickness h of the magnet 3 is set to the N pole 3a so that the amount of magnetic flux generated from any part in the vicinity of the center in the circumferential direction of the N pole 3a and the S pole 3b becomes substantially constant. And gradually decreased from the boundary portion 3c of the S pole 3b toward the circumferential central portion of the N pole and the S pole.

  Next, as shown in FIG. 4, a change in magnetic flux density detected by the magnetic sensor 5 when the rotating shaft 2 rotates in the circumferential direction will be described.

In the case of the state (I) (0 deg) shown in FIG. 4A, the first yoke 4a and the fourth yoke 4
Magnetic flux does not flow in the gap 41 between the yoke 4d and the magnetic flux density is zero. In addition, a maximum value of negative polarity magnetic flux density is generated in the gap 41 between the first yoke 4a and the second yoke 4b. Therefore, the first and second magnetic sensors 5a and 5b convert the voltage signal shown by the dotted line (I) in FIG. 4B.
When the rotary shaft 2 is rotated 90 degrees clockwise in the circumferential direction from the state (I) shown in FIG. 4A, the first yoke 4a and the fourth yoke 4 In the gap 41 with the yoke 4d, the maximum value of the positive polarity magnetic flux density is generated. Further, no magnetic flux flows through the gap 41 between the first yoke 4a and the second yoke 4b, and the magnetic flux density is zero. Therefore, the first and second magnetic sensors 5a and 5b convert the voltage signal shown by the dotted line (II) in FIG. 4B.
Further, when the rotary shaft 2 is rotated 90 degrees clockwise in the circumferential direction from the state (II) shown in FIG. 4A, the state becomes the state (180) of the first yoke 4a and the fourth yoke. A magnetic flux does not flow through the gap 41 between the yoke 4d and the magnetic flux density is zero. In addition, the maximum value of the positive polarity magnetic flux density is generated in the gap 41 between the first yoke 4a and the second yoke 4b. Therefore, the first and second magnetic sensors 5a and 5b convert the voltage signal shown by the dotted line (III) in FIG. 4B.
Further, since the amount of magnetic flux generated from any part of the magnet 3 near the center in the circumferential direction of the N pole 3a and the S pole 3b is substantially constant, the first and second rotations when the rotating shaft 2 rotates in the circumferential direction are performed. The magnetic flux density of the magnetic flux generated in the fourth gap 41 and the first and second gaps 41 changes at a constant rate. From this, the first and second magnetic sensors 5a and 5b convert into voltage signals that change at a constant rate as indicated by the thick lines in FIG. 4B.

  The electric signals Va and Vb converted by the first and second magnetic sensors 5 described above are not offset because no parameters are set. Therefore, as shown in FIG. 4B, in the range of the rotation angle 360 degrees of the rotating shaft 2, the coincidence voltage (Equation) in which the electric signal Va converted by the magnetic sensor 5a matches the electric signal Vb converted by the magnetic sensor 5b ( There are two points (VH, VL).

  Next, the processing procedure of the rotation angle calculation unit 6 will be described based on the flowchart shown in FIG. The output voltage of the first magnetic sensor 5a is Va, the output voltage of the second magnetic sensor 5b is Vb, and the output voltage of the rotation angle calculation unit 6 is Vout.

  In S1, it is determined whether Va is larger than 3.0 [V]. When Va is larger than 3.0 [V], the process proceeds to S6, the following equation (1) is calculated, and the process returns to S1. When Va is smaller than 3.0 [V], the process proceeds to S2.

Vout = 1 + Vb (1)
In S2, it is determined whether Va is smaller than 2.0 [V]. When Va is smaller than 2.0 [V], the process proceeds to S7, the following equation (2) is calculated, and the process returns to S1. If Va is greater than 2.0 [V], the process proceeds to S3.

Vout = 4-Vb (2)
In S3, it is determined whether Vb is smaller than 2.4 [V]. When Vb is smaller than 2.4 [V], the process proceeds to S8, the following equation (3) is calculated, and the process returns to S1. If Vb is greater than 2.4 [V], the process proceeds to S4.

Vout = Va (3)
In S4, it is determined whether Vb is larger than 2.6 [V] or Va is smaller than 2.5 [V]. When Vb is larger than 2.6 [V] and Va is smaller than 2.5 [V], the process proceeds to S9, the following equation (4) is calculated, and the process returns to S1. In other cases, the process proceeds to S5.

Vout = 3-Va (4)
In S5, it is determined whether Vb is larger than 2.6 [V] or Va is 2.5 [V] or more. When Vb is larger than 2.6 [V] and Va is 2.5 [V] or more, the process proceeds to S10, the following equation (5) is calculated, and the process returns to S1. In other cases, the process proceeds to S11, the following equation (6) is calculated, and the process returns to S1.

Vout = 7−Va (5)
Vout = 0 (6)
When the rotation angle calculation unit 6 calculates the above processing, Vout can be changed at a constant rate within a range of 360 degrees (−180 deg to 180 deg) of the rotation axis 2 as shown in FIG. 6. Therefore, an absolute angle of 360 degrees of the rotating shaft 2 can be detected.

  Here, a short-circuit fault detection method between the output signal line 50a of the first magnetic sensor 5a and the output signal line 50b of the second magnetic sensor 5b in the rotation angle calculation unit 6 which is a characteristic part of the present invention will be described. To do.

  Regarding the basic operation described above, the electric signals Va and Vb converted by the first and second magnetic sensors 5 are not offset because no parameters are set, but the first magnetic sensor here In 5a, a parameter (offset value) is set in advance so that the converted electric signal Va is offset by -1 [V]. Further, the second magnetic sensor 5b has parameters (offset values) set in advance so that the converted electric signal Vb is offset by 1 [V]. Therefore, the electrical signals Va and Vb after being offset by the first and second magnetic sensors 5a and 5b have the periodic waveforms shown in FIG. 7, and the coincidence voltage is within the range of the rotation angle 360 degrees of the rotating shaft 2. not exist.

  The electric signals Va and Vb converted by the first and second magnetic sensors 5a and 5b before the offset are the electric signals before the conversion in the claims, and the first and second after the offset The electric signals Va and Vb (electric signals Va and Vb output to the rotation angle calculation unit 6) converted by the magnetic sensors 5a and 5b are converted electric signals in the claims.

  And the rotation angle calculating part 6 performs the short circuit failure determination of the magnetic sensor 5 based on the flowchart shown in FIG.

  In step S100, the electric signals Va and Vb converted by the first and second magnetic sensors 5a and 5b are read, and the process proceeds to step S101. Here, the electric signals Va and Vb to be read are offset by −1 [V] for the electric signal Va and 1 [V] for the electric signal Vb as described above.

  In step S101, it is determined whether or not the electrical signals Va and Vb converted by the first and second magnetic sensors 5a and 5b match. If the electrical signals Va and Vb do not match, the process proceeds to step S102. When the electric signals Va and Vb match, the process proceeds to step S104.

  In step S102, since it is determined in step S101 that the electrical signals Va and Vb do not match, a short-circuit failure occurs between the output signal lines 50a and 50b of the first and second magnetic sensors 5a and 5b. Therefore, in order to return the offset electrical signals Va and Vb to the electrical signals Va and Vb before being offset, the following equations (7) and (8) are calculated, and the process proceeds to step S103.

Va = Va + 1 (offset value) (7)
Vb = Vb-1 (offset value) (8)
In step S103, the rotation angle of the rotating shaft 2 is calculated based on the flowchart of FIG. 5 described above, and the process returns to step S100.

  In step S104, since it is determined in step S101 that the electrical signals Va and Vb match, a short-circuit failure occurs between the output signal lines 50a and 50b of the first and second magnetic sensors 5a and 5b. Therefore, the following abnormality process is performed, and the process returns to step S100.

  In the abnormal process, the system that receives the signal from the rotation angle calculation unit 6 is informed that the rotation angle calculation unit 6 cannot calculate the rotation angle of the rotary shaft 2.

[Effect of Example 1]
As described above, when the electrical signals Va and Vb converted by the first and second magnetic sensors 5a and 5b are not offset, the coincidence voltages (VH and VL) at which the electrical signals Va and Vb match each other. There are two points. In addition, when a short circuit failure occurs between the output signal lines 50a and 50b of the first and second magnetic sensors 5a and 5b, the electric signals Va and Vb input to the rotation angle calculation unit 6 match. Therefore, the output angle between the output signal lines 50a and 50b is the same when the rotation angle calculation unit 6 has the same voltage (VH, VL) even though the short-circuit failure has not occurred between the output signal lines 50a and 50b. It is erroneously determined as a short circuit failure. However, in this configuration, parameters (offset values) are set in advance so that the electric signals Va and Vb converted by the first and second magnetic sensors 5a and 5b are offset so that there is no coincidence voltage. In addition, when the offset electrical signals Va and Vb match, it is determined that a short-circuit fault has occurred between the output signal lines 50a and 50b of the first and second magnetic sensors 5a and 5b. Thus, the rotation angle calculation unit 6 can reliably detect the short circuit failure without erroneously determining the short circuit failure between the output signal lines 50a and 50b of the first and second magnetic sensors 5a and 5b.

  Further, since the electrical signals Va and Vb converted by the first and second magnetic sensors 5a and 5b are offset, respectively, there is no coincidence voltage that matches the electrical signals Va and Vb.

  Further, when no short-circuit failure has occurred between the output signal lines 50a and 50b of the first and second magnetic sensors 5a and 5b, the electric signals Va and Vb offset by the rotation angle calculation unit 6 are offset. By returning to the electrical signals Va and Vb again, the rotation angle of the rotating shaft 2 can be calculated by the basic algorithm.

  In order to offset the electrical signals Va and Vb converted by the first and second magnetic sensors 5a and 5b, parameters (offset values) preset in the first and second magnetic sensors 5a and 5b are as follows. By setting the electric signals Va and Vb to be offset, it is sufficient to set the parameters so that no coincidence voltage exists.

  9A is a diagram showing a state in which the magnet is rotated in the circumferential direction, and FIG. 9B is a graph showing a periodic waveform of an electric signal converted by the magnetic sensor. FIG. 10 is a graph showing a periodic waveform obtained by offsetting the electrical signal shown in FIG. FIG. 11 is a flowchart illustrating a processing procedure for determining a short-circuit fault of the magnetic sensor in the rotation angle calculation unit.

  In the first embodiment, the case where two magnetic sensors 5 are provided has been described, but in this embodiment, the case where three magnetic sensors 5 are provided will be described.

  As shown in FIG. 9A, a radial gap 41 is also formed at the circumferential center of the third yoke 4c. A third magnetic sensor 5c is newly added to the magnetic sensor 5. The third magnetic sensors 5c are inserted into gaps 41 formed at the circumferential center of the yoke 4c. The third magnetic sensor 5c is provided to detect an abnormality in each of the first and second magnetic sensors 5a and 5b.

  Further, when the electrical signals Va, Vb, and Vc converted by the first to third magnetic sensors 5a to 5c are not offset, the periodic waveform of the electrical signal Vc converted by the third magnetic sensor 5c is as shown in FIG. As shown in (b), the phase is shifted approximately 45 degrees from the periodic waveforms of the electrical signals Va and Vb converted by the first and second magnetic sensors 5a and 5b. The linear portion of the electric signal Vc converted by the third magnetic sensor 5c has a magnetic flux density detected more than the linear portion of the electric signals Va and Vb converted by the first and second magnetic sensors 5a and 5b. Slight disturbance occurs and changes at a substantially constant rate.

  Here, the periodic waveforms of the electric signals converted by the first to third magnetic sensors 5a to 5c shown in FIG. 9B are the electric signals Va and Vb converted by the first and second magnetic sensors 5a and 5b. However, as in the first embodiment, the first magnetic sensor 5a has parameters (offset values) set in advance so that the converted electric signal Va is offset by -1 [V]. Further, the second magnetic sensor 5b has parameters (offset values) set in advance so that the converted electric signal Vb is offset by 1 [V]. Note that no parameters are set for the third magnetic sensor 5c so that the converted electric signal Vc is not offset. Therefore, the electric signals Va, Vb, Vc converted by the first to third magnetic sensors 5a to 5c have a coincidence voltage in the range of the rotation angle 360 degrees of the rotating shaft 2 as shown in FIG. do not do.

  And the rotation angle calculating part 6 performs the short circuit fault determination of the output signal wire | line of the 1st-3rd magnetic sensors 5a-5c based on the flowchart shown in FIG.

  In step S200, the electric signals Va, Vb and Vc converted by the first to third magnetic sensors 5a to 5c are read, and the process proceeds to step S101. Here, in the electric signals Va, Vb and Vc to be read, Va is offset by −1 [V] and Vb is offset by 1 [V], respectively, and Vc is not offset.

  In step S201, it is determined whether or not the electrical signals Va, Vb, and Vc converted by the first to third magnetic sensors 5a to 5c satisfy any one of the following formulas (9) to (11). If any of the conditions is not satisfied, the process proceeds to step S202. If any one of the conditions is satisfied, the process proceeds to step S204.

Va = Vb (9)
Vb = Vc (10)
Vc = Va (11)
In step S202, since it is determined in step S201 that any one of the above formulas (9) to (11) is not satisfied, at least two output signals of the first to third magnetic sensors 5a to 5c are determined. Since no short-circuit failure has occurred between the lines, in order to return the offset electrical signals Va and Vb back to the non-offset electrical signals Va and Vb, as in the first embodiment, the above formula (7) and Expression (8) is calculated, and the process proceeds to step S203.

  In step S203, the rotation angle of the rotating shaft 2 is calculated based on the flowchart of FIG. 5 described in the first embodiment, and the process returns to step S200.

  In step S204, since it is determined in step S201 that any one of the above formulas (9) to (11) is satisfied, at least two outputs of the first to third magnetic sensors 5a to 5c are obtained. Since a short-circuit failure has occurred between the signal lines, the following abnormality process is performed, and the process returns to step S200.

  In the abnormality processing, since a short circuit failure has occurred between at least two output signal lines of the first to third magnetic sensors 5a to 5c, the rotation angle calculation unit 6 calculates the rotation angle of the rotary shaft 2. As in the first embodiment, it is impossible for the rotation angle calculation unit 6 to calculate the rotation angle of the rotation shaft 2 in the system receiving the signal from the rotation angle calculation unit 6. Inform.

  As described above, even when three magnetic sensors 5 are provided, as in the first embodiment, the rotation angle calculation unit 6 outputs at least two output signals of the first to third magnetic sensors 5a to 5c. A short-circuit fault can be reliably detected without erroneously determining a short-circuit fault between lines.

  Although not shown, the output signal line of the third magnetic sensor 5c is connected to the rotation angle calculation unit 6 in the same manner as the output signal lines 50a and 50b of the first and second magnetic sensors 5a and 5b. ing.

  In addition, in order to offset the electric signals Va, Vb, Vc converted by the first to third magnetic sensors 5a to 5c, parameters (offsets) set in advance in the first to third magnetic sensors 5a to 5c, respectively. The value may be set to a parameter that does not have a matching voltage by offsetting the electric signals Va, Vb, and Vc.

(A) is a side view of the rotation angle sensor, (b) is a cross-sectional view taken along the line I-I of (a), and a rotation angle detection device including the rotation angle sensor. Example 1 It is the perspective view which showed the magnet. Example 1 (A) is the figure which showed the direction of the magnetic flux amount (phi) generated from a magnet, (b) is the graph which showed the periodic waveform of the magnetic flux amount (phi) generated from the magnet in the angle (theta) of the circumferential direction of (a). . Example 1 (A) is the figure which showed the state which the magnet rotated in the circumferential direction, (b) is the graph which showed the periodic waveform of the electrical signal which the magnetic sensor converted. Example 1 It is the flowchart which showed the calculation procedure in a rotation angle calculating part. Example 1 It is the graph which showed the electric signal calculated in the rotation angle calculating part. Example 1 It is the graph which showed the periodic waveform which offset the electric signal shown in FIG.4 (b). Example 1 It is the flowchart which showed the process sequence of the short circuit fault determination of the magnetic sensor in a rotation angle calculating part. Example 1 (A) is the figure which showed the state which the magnet rotated in the circumferential direction, (b) is the graph which showed the periodic waveform of the electrical signal which the magnetic sensor converted. (Example 2) It is the graph which showed the periodic waveform which offset the electric signal shown in FIG.9 (b). (Example 2) It is the flowchart which showed the process sequence of the short circuit fault determination of the magnetic sensor in a rotation angle calculating part. (Example 2) FIG. 4 is a diagram showing a connection relationship between a magnetic sensor 5 and a rotation angle calculation unit 6.

Explanation of symbols

1 ... Rotation angle detection device,
2 ... Rotation axis,
3 ... Magnet,
4 ... York,
5 ... Magnetic sensor,
6 ... Rotation angle calculator

Claims (5)

A rotation axis;
A hard magnetic body in which first and second magnetic poles having different magnetic polarities are alternately provided in the circumferential direction;
A magnetic circuit is formed in a magnetic field formed by the hard magnetic material, and the magnetic circuit is configured to change the magnetic flux density when the relative position of the magnetic circuit changes with the rotation of the rotating shaft. Soft magnetic material,
A plurality of magnetic flux density converters each converting magnetic flux density generated in the magnetic circuit of the soft magnetic material into an electrical signal;
A rotation angle calculation unit for calculating a rotation angle of the rotation shaft based on the electric signal converted by the magnetic flux density converter;
The plurality of electrical signals are electrical signals converted so as not to have the same potential with respect to the rotation angle of the rotation shaft,
A rotation angle detecting device, wherein when at least two of the electric signals have the same potential, it is determined that a short circuit failure occurs between the magnetic flux density converters. The plurality of electric signals do not have the same potential with respect to the rotation angle of the rotating shaft, respectively, in the range of the rotation angle of the rotating shaft of 360 degrees, respectively. The rotation angle detection device according to 1. The electrical signal is an electrical signal after being converted by the magnetic flux density converter output to the rotation angle calculation unit,
The magnetic flux density converter converts the magnetic flux density into the electric signal before conversion, and offsets the converted electric signal to convert it into the electric signal after conversion. The rotation angle detection device described. A plurality of the electrical signals converted by the magnetic flux density converter are substantially triangular waves each having a predetermined angle phase shifted with respect to the rotation angle of the rotating shaft,
Each of the plurality of magnetic flux density converters is preset with an offset value for offsetting the electric signal before the conversion,
The rotation angle calculation unit stores the preset offset value, respectively.
Based on the stored offset value, a plurality of the converted electric signals are converted into the electric signals before the conversion,
The rotation angle detection device according to claim 3, wherein the rotation angle of the rotation shaft is calculated by connecting the electric signals before conversion. The magnetic flux density converter has an output signal line connected to the rotation angle calculation unit,
5. The rotation angle detection device according to claim 1, wherein the short circuit failure is a short circuit of the output signal lines of at least two of the magnetic flux density converters.

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