Rotation angle detection device

Abstract

A rotation angle detection device is disclosed. The rotation angle detection device includes a driving gear (11), two driven gears (12, 13), two sensors (17, 18) and an operation circuit (19). The two driven gears (12, 13) have different numbers of teeth and are respectively meshed with the driving gear (11). The operation circuit (19) is configured to calculate the rotation angle of the driving gear (11) based on the rotation angles of the two driven gears (12, 13) detected by the two sensors (17, 18). The operation circuit (19) is configured to detect abnormality of the rotation angle of the driving gear (11) calculated by the operation circuit (19) when the relationship between the rotation angles of the two driven gears (12, 13) detected by the two sensors (17, 18) is different from the relationship when the rotation angle of the driving gear (11) calculated by the operation circuit (19) is normal.

Description

Technical Field

[0001] The invention relates to a rotation angle detection device. Background Art

[0002] There is an electric power steering (EPS) device that applies the torque of a motor as an auxiliary force to the steering mechanism of a vehicle. The controller of the EPS controls the motor based on the steering torque, steering angle, etc. For example, from the perspective of ensuring the reliability of the operation of the EPS, the EPS of Japanese Unexamined Patent Application Publication No. 2015-058911 (JP 2015-058911 A) includes two steering torque sensors (i.e., a main steering torque sensor and a secondary steering torque sensor), two steering angle sensors (i.e., a main steering angle sensor and a secondary steering angle sensor), and two motor rotation angle sensors (i.e., a main motor rotation angle sensor and a secondary motor rotation angle sensor). The controller of the EPS has a function of detecting abnormalities of these sensors.

[0003] For example, the controller detects an abnormality in the steering angle sensor as follows. The controller calculates two steering angle calculation signals based on two motor rotation angle signals, and detects an abnormality in a steering angle detection signal generated by a primary steering angle sensor or a secondary steering angle sensor by comparing the two steering angle calculation signals with two steering angle detection signals generated by the two steering angle sensors. As with the steering angle sensor, the controller also detects an abnormality in these sensors by using detection signals of a steering torque sensor or a motor rotation angle sensor. Summary of the invention

[0004] The method of detecting an abnormality of a sensor described in JP 2015-058911A assumes that the EPS includes a plurality of sensors of the same type. Depending on product specifications or other factors, only the steering angle sensor may be required to detect an abnormality of a steering angle detection signal generated by the steering angle sensor, and by extension, detect an abnormality of a steering angle detected by the steering angle sensor.

[0005] The present invention provides a rotation angle detection device capable of detecting abnormality of a rotation angle.

[0006] A rotation angle detection device according to one aspect of the present invention includes a driving gear, two driven gears, two sensors, and an operation circuit. The driving gear is configured to rotate integrally with a component whose rotation is to be detected. The two driven gears have different numbers of teeth and are respectively meshed with the driving gear. The two sensors are respectively configured to detect the rotation angle of the associated driven gear of the two driven gears. The operation circuit is configured to calculate the rotation angle of the driving gear based on the rotation angles of the two driven gears detected by the two sensors. The operation circuit is configured to detect an abnormality in the rotation angle of the driving gear calculated by the operation circuit when the relationship between the rotation angles of the two driven gears detected by the two sensors is different from the relationship when the rotation angle of the driving gear calculated by the operation circuit is normal.

[0007] For example, when the rotation angles of the two driven gears detected by the two sensors are abnormal, the relationship between the rotation angles of the two driven gears is different from the relationship when the rotation angle of the driving gear calculated by the operation circuit is normal. When the rotation angles of the two driven gears detected by the two sensors are abnormal, the rotation angle of the driving gear calculated based on the rotation angles of the two driven gears is certainly different from the normal value. Therefore, using the rotation angle detection device of this aspect of the present invention, in the case where the relationship between the rotation angles of the two driven gears detected by the two sensors is different from the relationship when the rotation angle of the driving gear calculated by the operation circuit is normal, the abnormality of the rotation angle of the driving gear calculated by the operation circuit is detected.

[0008] In the rotation angle detection device according to this aspect of the invention, the operational circuit can be configured to detect an abnormality in the rotation angle of the driving gear based on the difference between the rotation angles of the two driven gears calculated as a value indicating the relationship between the rotation angles of the two driven gears and the ideal difference between the rotation angles of the two driven gears.

[0009] For example, when the rotation angles of the two driven gears detected by the two sensors are abnormal, the difference between the rotation angles of the two driven gears also indicates an abnormal value. Therefore, with the rotation angle detection device according to this aspect of the invention, the abnormality of the rotation angle of the driving gear is detected based on the difference between the rotation angles of the two driven gears detected by the two sensors and the ideal difference between the rotation angles of the two driven gears detected by the two sensors.

[0010] In the rotation angle detection device according to this aspect of the invention, the operational circuit can be configured to detect an abnormality in the rotation angle of the driving gear based on the difference between the rotation amounts of the two driven gears calculated as a value indicating the relationship between the rotation angles of the two driven gears and the ideal difference between the rotation amounts of the two driven gears.

[0011] For example, when the rotation angles of the two driven gears detected by the two sensors are abnormal, the difference between the rotation amounts of the two driven gears also indicates an abnormal value. Therefore, with the rotation angle detection device according to this aspect of the invention, the abnormality of the rotation angle of the driving gear is detected based on the difference between the rotation amounts of the two driven gears detected by the two sensors and the ideal difference between the rotation amounts of the two driven gears detected by the two sensors.

[0012] In the rotation angle detection device according to this aspect of the invention, the operational circuit can be configured to detect an abnormality in the rotation angle of the driving gear based on the difference between the integrated values ​​of the rotation amounts of the two driven gears calculated as values ​​indicating the relationship between the rotation angles of the two driven gears and the ideal difference between the integrated values ​​of the rotation amounts of the two driven gears.

[0013] For example, when the rotation angles of the two driven gears detected by the two sensors are abnormal, the difference between the integral values ​​of the rotation amounts of the two driven gears also indicates an abnormal value. Therefore, with the rotation angle detection device according to this aspect of the invention, the abnormality of the rotation angle of the driving gear is detected based on the difference between the integral values ​​of the rotation amounts of the two driven gears detected by the two sensors and the ideal difference between the integral values ​​of the rotation amounts of the two driven gears detected by the two sensors.

[0014] In the rotation angle detection device according to the aspect of the present invention, the operation circuit may be configured to detect abnormality in the rotation angle of the drive gear when the difference is outside an allowable range set based on an ideal difference.

[0015] With the rotation angle detection device according to this aspect of the present invention, abnormality in the rotation angle of the drive gear is not excessively detected. By setting the allowable range, abnormality in the rotation angle of the drive gear is further appropriately detected.

[0016] In the rotation angle detection device according to the aspect of the invention, the component whose rotation is to be detected may be one of a steering shaft and a pinion shaft in a steering system of a vehicle.

[0017] With the rotation angle detection device according to this aspect of the invention, abnormality in the rotation angle is detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals represent like elements, and in which:

[0019] Figure 1 is a block diagram showing a schematic configuration of a first embodiment of a rotation angle detection device;

[0020] Figure 2 is a block diagram of a microcomputer of the first embodiment;

[0021] Figure 3 is a diagram showing a relationship between a rotation angle of a first driven gear and a rotation angle of a drive gear and a relationship between a rotation angle of a second driven gear and a rotation angle of a drive gear in the first embodiment;

[0022] Figure 4 is a diagram showing a relationship between a rotation angle of a first driven gear after gradient adjustment and a rotation angle of a driving gear and a relationship between a rotation angle of a second driven gear after gradient adjustment and a rotation angle of a driving gear in the first embodiment;

[0023] Figure 5 is a diagram showing a relationship between a rotation angle of a drive gear and a difference between a gradient-adjusted rotation angle of a first driven gear and a gradient-adjusted rotation angle of a second driven gear in a first embodiment;

[0024] Figure 6 is a diagram showing the relationship between the actual rotation angle of the drive gear and the rotation angle (absolute value) of the drive gear in the first embodiment;

[0025] Figure 7 is a diagram showing an allowable range of a difference between a rotation angle of a first driven gear after gradient adjustment and a rotation angle of a second driven gear after gradient adjustment in the first embodiment;

[0026] Figure 8 is a table used when calculating the rotation angle of the drive gear in the first embodiment;

[0027] Fig. 9 is a block diagram of a microcomputer of a second embodiment; and

[0028] Fig.10 It is a block diagram of an abnormality detection unit according to the second embodiment. DETAILED DESCRIPTION

[0029] First embodiment

[0030] Hereinafter, a first embodiment of the rotation angle detection device will be described. Figure 1As shown, the rotation angle detection device 10 includes a driving gear 11, a first driven gear 12 and a second driven gear 13. The driving gear 11, the first driven gear 12 and the second driven gear 13 are made of synthetic resin material. The driving gear 11 is assembled to the shaft 14 so as to be able to rotate integrally with the shaft 14. The shaft 14 is a component to be detected. The first driven gear 12 and the second driven gear 13 are both engaged with the driving gear 11. The number of teeth of the first driven gear 12 and the number of teeth of the second driven gear 13 are different from each other. Therefore, when the driving gear 11 rotates with the rotation of the shaft 14, the rotation angle α of the first driven gear 12 and the rotation angle β of the second driven gear 13 are different from each other for the rotation angle θ of the driving gear 11. For example, when the number of teeth of the driving gear 11 is "z", the number of teeth of the first driven gear 12 is "m", and the number of teeth of the second driven gear 13 is "n", when the driving gear 11 rotates one circle, the first driven gear 12 rotates "z / m" circles, and the second driven gear 13 rotates "z / n" circles.

[0031] The rotation angle detection device 10 includes a first magnet 15, a second magnet 16, a first magnetic sensor 17, a second magnetic sensor 18, and a microcomputer 19 used as an operation circuit. The first magnet 15 is configured to rotate integrally with the first driven gear 12. The second magnet 16 is configured to rotate integrally with the second driven gear 13. The first magnetic sensor 17 is disposed near the first magnet 15 and detects a magnetic field emitted from the first magnet 15. The second magnetic sensor 18 is disposed near the second magnet 16 and detects a magnetic field emitted from the second magnet 16.

[0032] For example, an MR sensor composed of four bridge-connected magnetoresistive elements is used as each of the first magnetic sensor 17 and the second magnetic sensor 18. The resistance value of the magnetoresistive element changes according to the direction of the applied magnetic field. The first magnetic sensor 17 detects the rotation angle α of the first driven gear 12 based on the change in the direction of the magnetic flux emitted from the first magnet 15. The second magnetic sensor 18 detects the rotation angle β of the second driven gear 13 based on the change in the direction of the magnetic flux emitted from the second magnet 16. Specifically, the first magnetic sensor 17 and the second magnetic sensor 18 are configured as follows.

[0033] The first magnetic sensor 17 generates a first sine signal and a first cosine signal, which are two analog signals that continuously change with the rotation angle α of the first driven gear 12. When the first driven gear 12 rotates the detection range Ω of the first magnetic sensor 17, that is, when the driving gear 11 rotates "(m / z)Ω", one cycle of each of the first sine signal and the first cosine signal passes. The phase of the first cosine signal is offset by 1 / 4 cycle relative to the phase of the first sine signal. By calculating the inverse tangent based on the first sine signal and the first cosine signal, the first magnetic sensor 17 obtains the rotation angle α of the first driven gear 12 within the detection range (one cycle) Ω of the first magnetic sensor 17.

[0034] The second magnetic sensor 18 generates a second sine signal and a second cosine signal, which are two analog signals that continuously change with the rotation angle β of the second driven gear 13. When the second driven gear 13 rotates the detection range Ω of the second magnetic sensor 18, that is, when the driving gear 11 rotates "(n / z)Ω", one cycle of each of the second sine signal and the second cosine signal passes. The phase of the second cosine signal is offset by 1 / 4 cycle relative to the phase of the second sine signal. By calculating the inverse tangent based on the second sine signal and the second cosine signal, the second magnetic sensor 18 obtains the rotation angle β of the second driven gear 13 within the detection range (one cycle) Ω of the second magnetic sensor 18.

[0035] For the rotation angle θ of the driving gear 11, the rotation angle α of the first driven gear 12 and the rotation angle β of the second driving gear 13 change as shown in FIG. Figure 3 As shown in the figure. Figure 3 In the figure, the axis of abscissa represents the rotation angle θ of the driving gear 11. Figure 3 In the figure, the vertical axis represents the rotation angle α of the first driven gear 12 and the rotation angle β of the second driven gear 13 .

[0036] like Figure 3 As shown in the figure, as the rotation angle θ of the driving gear 11 changes, the rotation angle α of the first driven gear 12 changes in an alternating rising and falling manner according to the number of teeth m at a predetermined cycle. Specifically, each time the first driven gear 12 rotates the detection range Ω of the first magnetic sensor 17, in other words, each time the driving gear 11 rotates "mΩ / z", the rotation angle α changes in an alternating rising and falling manner. The rotation angle β of the second driven gear 13 changes in an alternating rising and falling manner according to the number of teeth n of the second driven gear 13 at a predetermined cycle. Specifically, each time the second driven gear 13 rotates the detection range Ω of the second magnetic sensor 18, in other words, each time the driving gear 11 rotates "nΩ / z", the rotation angle β changes in an alternating rising and falling manner.

[0037] Here, as an example, a case will be discussed in which the number of teeth z of the driving gear 11 is "48", the number of teeth m of the first driven gear 12 is "26", the number of teeth n of the second driven gear 13 is "24", and the detection range Ω of each of the first magnetic sensor 17 and the second magnetic sensor 18 is 360°. In this case, whenever the driving gear 11 rotates 195°, the rotation angle α of the first driven gear 12 changes in an alternating manner of rising and falling. Whenever the driving gear 11 rotates 180°, the rotation angle β of the second driven gear 13 changes in an alternating manner of rising and falling.

[0038] When the rotation angle θ of the driving gear 11 reaches a predetermined value, the phase difference between the rotation angle α of the first driven gear 12 and the rotation angle β of the second driven gear 13 within the detection range Ω of each of the first magnetic sensor 17 and the second magnetic sensor 18 disappears. Therefore, the calculation range (calculatable range) of the rotation angle θ of the driving gear 11 for multiple turns exceeding 360 degrees is determined by the ratio between the number of teeth m of the first driven gear 12, the number of teeth n of the second driven gear 13, and the number of teeth z of the driving gear 11. For example, the calculation range Ra of the rotation angle θ of the driving gear 11 is expressed by the following mathematical expression (A).

[0039] Ra=mnΩ / z(mn)(A)

[0040] “m” is the number of teeth of the first driven gear 12, “n” is the number of teeth of the second driven gear 13, and “z” is the number of teeth of the driving gear 11. “Ω” is the detection range of each of the first magnetic sensor 17 and the second magnetic sensor 18.

[0041] Similar to the above case, when the number of teeth z of the driving gear 11 is "48", the number of teeth m of the first driven gear 12 is "26", the number of teeth n of the second driven gear 13 is "24", and the detection range Ω of each of the first magnetic sensor 17 and the second magnetic sensor 18 is 360°, the calculation range of the rotation angle θ of the driving gear 11 is 2340°.

[0042] exist Figure 3, the midpoint of the calculation range Ra of the rotation angle θ of the drive gear 11 is set as the origin (rotation angle θ=0°). Here, the calculation range Ra of the rotation angle θ of the drive gear 11 is 2340°, the upper limit of the calculation range Ra is +1170°, and the lower limit of the calculation range Ra is -1170°. In other words, in this example, the rotation angle θ of the drive gear 11 can be calculated in an absolute value within the range of -1170° to +1170°. The calculation range Ra corresponds to 6.5 turns (±3.25 turns) of the shaft 14. When the shaft 14 rotates in the positive direction relative to 0° as the origin, the rotation angle θ of the drive gear 11 increases in the positive direction; conversely, when the shaft 14 rotates in the reverse direction, the rotation angle θ increases in the negative direction.

[0043] The microcomputer 19 calculates the rotation angle θ of the drive gear 11 for multiple turns exceeding 360°, that is, the rotation angle θ of the shaft 14 for multiple turns exceeding 360°, in absolute value by using the rotation angle α of the first driven gear 12 detected by the first magnetic sensor 17 and the rotation angle β of the second driven gear 13 detected by the second magnetic sensor 18.

[0044] Next, the configuration of the microcomputer 19 will be described in detail. Figure 2 As shown, the microcomputer 19 includes a gradient adjustment unit 21 , a difference calculation unit 22 , a rotation calculation unit 23 , an absolute angle calculation unit 24 , and an abnormality detection unit 25 .

[0045] The gradient adjustment unit 21 adjusts the first gradient and the second gradient so that the first gradient and the second gradient become the same value. The first gradient is the ratio of the change in the rotation angle α of the first driven gear 12 to the change in the rotation angle θ of the driving gear 11. The second gradient is the ratio of the change in the rotation angle β of the second driven gear 13 to the change in the rotation angle θ of the driving gear 11.

[0046] For example, the gradient adjustment unit 21 multiplies the rotation angle α of the first driven gear 12 detected by the first magnetic sensor 17 by the weight W represented by the following mathematical expression (B1): α , and the rotation angle β of the second driven gear 13 detected by the second magnetic sensor 18 is multiplied by a weight W represented by the following mathematical expression (B2): β Therefore, the gradient of the rotation angle α of the first driven gear 12 and the rotation angle θ of the drive gear 11 and the gradient of the rotation angle β of the second driven gear 13 and the rotation angle θ of the drive gear 11 are made equal to each other.

[0047] W α =m / LCM mn (B1)

[0048] W β=n / LCM mn (B2)

[0049] "m" is the number of teeth of the first driven gear 12, and "n" is the number of teeth of the second driven gear 13. "LCM mn ” is the least common multiple of the number of teeth m of the first driven gear 12 and the number of teeth n of the second driven gear 13.

[0050] like Figure 4 As shown in the figure, the gradient of the first waveform representing the change in the rotation angle α′ of the first driven gear 12 after gradient adjustment and the change in the rotation angle θ of the driving gear 11 and the gradient of the second waveform representing the change in the rotation angle β′ of the second driven gear 13 after gradient adjustment and the change in the rotation angle θ of the driving gear 11 are parallel to each other.

[0051] The difference calculation unit 22 calculates the difference Δαβ between the rotation angle α′ of the first driven gear 12 and the rotation angle β′ of the second driven gear 13 after the gradient is adjusted by the gradient adjustment unit 21. The relationship between the rotation angle θ of the drive gear 11 and the difference Δαβ is as follows.

[0052] like Figure 5 As shown in the figure, for each cycle in which the rotation angle α of the first driven gear 12 or the rotation angle α′ of the first driven gear 12 after the gradient is adjusted by the gradient adjustment unit 21 changes in an alternately rising and falling manner, the value of the difference Δαβ is unique to the rotation angle θ of the driving gear 11. In other words, the value of the difference Δαβ is unique to the number of cycles of the rotation angle α of the first driven gear 12 or the rotation angle α′ of the first driven gear 12 after the gradient is adjusted by the gradient adjustment unit 21.

[0053] For each cycle in which the rotation angle β of the second driven gear 13 or the rotation angle β′ of the second driven gear 13 after the gradient is adjusted by the gradient adjustment unit 21 changes in an alternately increasing and decreasing manner, the value of the difference Δαβ is unique to the rotation angle θ of the driving gear 11. In other words, the value of the difference Δαβ is unique to the number of cycles of the rotation angle β of the second driven gear 13 or the rotation angle β′ of the second driven gear 13 after the gradient is adjusted by the gradient adjustment unit 21.

[0054] The rotation calculation unit 23 calculates the number of cycles γ1 of the first driven gear 12 based on the value of the difference Δαβ calculated by the difference calculation unit 22. The cycle γ1 refers to an integer value indicating how many cycles the first sine signal or the first cosine signal generated by the first magnetic sensor 17 passes through, that is, how many times the detection range (one cycle) of the first magnetic sensor 17 is repeated.

[0055] The rotation calculation unit 23 calculates the period number γ1 of the first driven gear 12 by referring to a table stored in a storage device (not shown). Figure 8 As shown, Table TB defines the relationship between the following three items: the allowable range of the value of the difference Δαβ between the gradient-adjusted rotation angle α′ and the gradient-adjusted rotation angle β′ (described later), the ideal value of the difference Δαβ, and the period number γ1 of the first driven gear 12. Figure 8 In the example, as indicated by classification numbers TN1, TN2, TN3, TN4, TN5, TN6, TN7, TN8, TN9, TN10, TN11, TN12, TN13, TN14, TN15, TN16, TN17, TN18, TN19, TN20, TN21, TN22, TN23, TN24, TN25, TN26, TN27, the three items described above are limited every 360° (the detection range of the first magnetic sensor 17) in the entire calculation range of the rotation angle θ of the drive gear 11.

[0056] In fact, as Table TB, a table is used which is obtained by assigning the three items described above to each minimum detection angle (for example, 2°) of the rotation angle α of the first driven gear 12 determined according to the resolution of the first magnetic sensor 17, the number of teeth m of the first driven gear 12, etc., using classification numbers TN1, TN2, TN3, TN4, TN5, TN6, TN7, TN8, TN9, TN10, TN11, TN12, TN13, TN14, TN15, TN16, TN17, TN18, TN19, TN20, TN21, TN22, TN23, TN24, TN25, TN26, TN27.

[0057] The rotation calculation unit 23 determines which of the classification numbers TN1, TN2, TN3, TN4, TN5, TN6, TN7, TN8, TN9, TN10, TN11, TN12, TN13, TN14, TN15, TN16, TN17, TN18, TN19, TN20, TN21, TN22, TN23, TN24, TN25, TN26, TN27 the value of the difference Δαβ calculated by the difference calculation unit 22 belongs to, and detects the period number γ1 of the first driven gear 12 associated with the determined classification number. For example, when the value of the difference Δαβ calculated by the difference calculation unit 22 is "-2160°", the value of the difference Δαβ belongs to the classification number TN7, and therefore it is found that the period number γ1 of the first driven gear 12 is "-6".

[0058] The absolute angle calculation unit 24 calculates the rotation angle θ of the driving gear 11 in absolute angle based on the rotation angle α of the first driven gear 12 detected by the first magnetic sensor 17 and the period number γ1 of the first driven gear 12 calculated by the rotation calculation unit 23. For example, the rotation angle θ of the driving gear 11 for multiple turns exceeding 360° is obtained based on the following mathematical expression (C).

[0059] θ=mα / z+(m / z)Ωγ1 (C)

[0060] "m" is the number of teeth of the first driven gear 12, "n" is the number of teeth of the second driven gear 13, and "z" is the number of teeth of the driving gear 11. "Ω" is the detection range of each of the first magnetic sensor 17 and the second magnetic sensor 18. "α" is the rotation angle of the first driven gear 12 detected by the first magnetic sensor 17. "mα / z" indicates the rotation angle of the driving gear 11 relative to the rotation angle α of the first driven gear 12 within the detection range Ω of the first magnetic sensor 17.

[0061] The relationship between the actual rotation angle θ of the driving gear 11 and the rotation angle θ (absolute angle) of the driving gear 11 calculated by the absolute angle calculation unit 24 is as follows: Figure 6 As shown in the figure. Figure 6 In the figure, the horizontal axis represents the actual rotation angle θ of the drive gear 11, and the vertical axis represents the rotation angle θ (absolute angle) of the drive gear 11 calculated by the absolute angle calculation unit 24. Figure 6 As shown in the figure, the rotation angle θ (absolute angle) of the driving gear 11 changes linearly with the change of the actual rotation angle θ of the driving gear 11. Since the actual rotation angle θ of the driving gear 11 and the rotation angle θ (absolute angle) of the driving gear 11 have a linear relationship, the actual rotation angle θ of the driving gear 11 and the rotation angle θ (absolute angle) of the driving gear 11 correspond to each other one by one. In other words, the rotation angle θ (absolute angle) of the driving gear 11, that is, the absolute rotation angle of the shaft 14, is immediately detected.

[0062] The abnormality detection unit 25 detects an abnormality in the rotation angle θ (absolute angle) of the drive gear 11 calculated by the absolute angle calculation unit 24 based on the value of the difference Δαβ between the gradient-adjusted rotation angle α′ and the gradient-adjusted rotation angle β′ calculated by the differential calculation unit 22. This is based on the fact that when the value of the difference Δαβ is abnormal, the period number γ1 of the first driven gear 12 calculated based on the value of the difference Δαβ is likely to be abnormal, and by extension, the rotation angle θ of the drive gear 11 calculated based on the period number γ1 is also likely to be abnormal. When the value of the difference Δαβ is outside the allowable range determined based on the ideal value as the value of the ideal difference Δαβ, the abnormality detection unit 25 determines that the rotation angle θ (absolute angle) of the drive gear 11 calculated by the absolute angle calculation unit 24 is abnormal.

[0063] like Figure 7 As shown in the figure, the allowable range of the difference Δαβ is limited by an upper limit ε and a lower limit -ε. The upper limit ε is set to a positive value relative to "zero" which is an ideal value of the difference Δαβ. The lower limit -ε is set to a negative value relative to "zero" which is an ideal value of the difference Δαβ. The method of setting the upper limit ε and the lower limit -ε will be described in detail later.

[0064] When the value of the difference Δαβ between the gradient-adjusted rotation angle α′ of the first driven gear 12 and the gradient-adjusted rotation angle β′ of the second driven gear 13 falls within the range of “±ε” relative to the ideal value, the abnormality detection unit 25 determines that the rotation angle θ of the drive gear 11 calculated by the absolute angle calculation unit 24 is normal. When the value of the difference Δαβ between the gradient-adjusted rotation angle α′ of the first driven gear 12 and the gradient-adjusted rotation angle β′ of the second driven gear 13 falls outside the range of “±ε” relative to the ideal value, the abnormality detection unit 25 determines that the rotation angle θ of the drive gear 11 calculated by the absolute angle calculation unit 24 is abnormal.

[0065] When an abnormality in the rotation angle θ of the drive gear 11 is detected, the driver or the like is prompted to take some measures, such as repairing the rotation angle detection device 10, by notifying the abnormality. Alternatively, when an abnormality in the rotation angle θ of the drive gear 11 is detected, the detection reliability of the rotation angle detection device 10 can be ensured by stopping the calculation of the rotation angle θ of the drive gear 11 or not using the calculated rotation angle θ.

[0066] How to set upper and lower limits

[0067] Next, a method of setting an upper limit ε and a lower limit -ε will be described. The upper limit ε and the lower limit -ε are obtained based on an ideal value and an actual value of the difference Δαβ between the gradient-adjusted rotation angle α′ and the gradient-adjusted rotation angle β′. The ideal value Δαβ1 of the difference Δαβ is expressed by the following mathematical expression (D1). The actual value Δαβ2 of the difference Δαβ is expressed by the following mathematical expression (D2).

[0068] Δαβ1=α′·W α -β′·W β (D1)

[0069] Δαβ2=Δαβ1+δ αβ =(α′+δ α )·W α -(β′+δ β )·W β (D2)

[0070] “α′” is the rotation angle of the first driven gear 12 after the gradient adjustment, and “β′” is the rotation angle of the second driven gear 13 after the gradient adjustment. α " is a weight obtained by using the mathematical expression (B1) and assigned to the rotation angle α of the first driven gear 12, and "W β ” is a weight obtained using mathematical expression (B2) and assigned to the rotation angle β of the second driven gear 13.

[0071] “δ αβ ” is the maximum permissible tolerance of the ideal value Δαβ1 of the difference Δαβ. α " is the maximum allowable tolerance when calculating the gradient-adjusted rotation angle α' of the first driven gear 12 when the rotation angle detection device 10 is normal. "δ β ” is the maximum allowable tolerance when calculating the gradient-adjusted rotation angle β′ of the second driven gear 13 when the rotation angle detection device 10 is normal.

[0072] For example, the tolerance δ α The tolerance includes mechanical tolerances, for example, the clearance and assembly tolerance between the driving gear 11 and the first driven gear 12, and electrical tolerances due to the detection accuracy of the first magnetic sensor 17, temperature characteristics, etc. For example, the tolerance δ β Mechanical tolerances such as a clearance and assembly tolerance between the driving gear 11 and the second driven gear 13 and electrical tolerances due to the detection accuracy of the second magnetic sensor 18 , temperature characteristics, and the like are included.

[0073] Therefore, as shown in the following mathematical expression (D3), the maximum allowable tolerance δ of the ideal value Δαβ1 of the difference Δαβ can be obtained from mathematical expressions (D1) and (D2): αβ .

[0074] δ αβ =δ α ·W α -δ β ·W β (D3)

[0075] In this embodiment, as shown in the following mathematical expression (D4), the maximum allowable tolerance δ of the ideal value Δαβ1 of the difference Δαβ is αβ The absolute value of is set to the absolute value of each of the upper limit ε and the lower limit -ε.

[0076] |δ αβ |=|±ε| (D4)

[0077] Therefore, the allowable range R of the difference Δαβ is αβ It is represented by the following mathematical expression (D5).

[0078] R αβ =Δαβ1±ε (D5)

[0079] Advantageous Effects of the First Embodiment

[0080] According to the first embodiment, the following advantageous effects are obtained.

[0081] The abnormality of the rotation angle θ of the drive gear 11 calculated by the absolute angle calculation unit 24 is detected based on the value of the difference Δαβ between the gradient-adjusted rotation angle α′ of the first driven gear 12 and the gradient-adjusted rotation angle β′ of the second driven gear 13. This is based on the fact that when the value of the difference Δαβ is abnormal, the cycle number γ1 calculated based on the value of the difference Δαβ is likely to be abnormal, and by extension, the rotation angle θ of the drive gear 11 calculated based on the cycle number γ1 is also likely to be abnormal.

[0082] The abnormality detection unit 25 detects an abnormality in the rotation angle θ of the drive gear 11 calculated by the absolute angle calculation unit 24 when the value of the difference Δαβ calculated by the difference calculation unit 22 falls outside the allowable range determined based on the difference Δαβ. Therefore, the abnormality in the rotation angle θ of the drive gear 11 is not overdetermined.

[0083] For example, when determining whether the rotation angle θ of the drive gear 11 is abnormal based only on the comparison between the value of the difference Δαβ and the ideal value of the difference Δαβ, there is the following problem. In other words, the value of the difference Δαβ may be different from the ideal value due to the dimensional tolerance of the first driven gear 12 and the second driven gear 13, etc.; however, even in this case, there is a problem of determining the rotation angle θ of the drive gear 11 as abnormal. Therefore, ideally, whether the rotation angle θ of the drive gear 11 is abnormal is determined based on whether the value of the difference Δαβ falls within the allowable range determined based on the ideal value. In the present embodiment, the allowable range of the value of the difference Δαβ is set based on the maximum allowable tolerance according to product specifications, etc., and therefore, the abnormality of the rotation angle θ of the drive gear 11 can be further appropriately detected. In addition, the reliability of the operation of the rotation angle detection device 10 is ensured.

[0084] The driving gear 11, the first driven gear 12, and the second driven gear 13 are made of synthetic resin material. Therefore, the abnormal noise caused by the meshing of the gears is reduced, however, on the other hand, there is a problem that the first driven gear 12 and the second driven gear 13 may wear due to long-term use. When the meshing state of the driven gears 12, 13 with the driving gear 11 changes due to such wear, there is a problem that the rotation angles α, β of the driven gears detected by the magnetic sensors 17, 18 indicate abnormal values, and by extension, there is a problem that the rotation angle θ of the driving gear 11 calculated based on the rotation angles α, β indicates an abnormal value. Therefore, when the driving gear 11, the first driven gear 12, and the second driven gear 13 are made of synthetic resin material, it is particularly necessary to detect the abnormality of the rotation angle θ of the driving gear 11.

[0085] The rotation angle detection device 10 does not need to include a special component for detecting abnormality of the rotation angle θ of the drive gear 11. Therefore, the configuration of the rotation angle detection device 10 does not become complicated.

[0086] like Figure 5 As shown in the figure, for each cycle in which the gradient-adjusted α′, β′ changes in an alternating manner of rising and falling with the change of the rotation angle θ of the driving gear 11, the value of the difference Δαβ between the gradient-adjusted rotation angle α′ of the first driven gear 12 and the gradient-adjusted rotation angle β′ of the second driven gear 13 is unique to the rotation angle θ of the driving gear 11. Therefore, the value of the difference Δαβ is suitable for applications for detecting the period number γ1 of the first driven gear 12 or the period number γ2 of the second driven gear 13, and by extension, is suitable for applications for detecting the rotation angle θ of the driving gear 11. As shown in FIG. Figure 5As shown in the figure, the value of the difference Δαβ changes in a rectangular waveform as the rotation angle θ of the drive gear 11 changes. Therefore, the abnormality detection unit 25 can easily recognize the value of the difference Δαβ as a pattern, and by extension, can easily compare the value of the difference Δαβ with the ideal value. Therefore, the value of the difference Δαβ is suitable for applications for detecting abnormalities in the rotation angle θ of the drive gear 11. For example, the value of the difference between the rotation angles α and β before the gradient is adjusted changes linearly as the rotation angle θ of the drive gear 11 changes.

[0087] Second embodiment

[0088] Next, a second embodiment of the rotation angle detection device will be described. Figure 1 and Figure 2 The present embodiment differs from the first embodiment in the method of determining whether the rotation angle θ of the drive gear 11 is abnormal. Therefore, the same reference numerals denote the same members and components as those of the first embodiment, and detailed description thereof is omitted.

[0089] According to the first embodiment, the abnormality of the rotation angle θ of the driving gear 11 is detected based on whether the value of the difference Δαβ between the gradient-adjusted rotation angle α′ of the first driven gear 12 and the gradient-adjusted rotation angle β′ of the second driven gear 13 falls outside the allowable range.

[0090] However, there is a problem that the following events occur in the rotation angle detection device 10. For example, it is conceivable that a so-called tooth skip occurs in the meshing between the drive gear 11 and the first driven gear 12 or in the meshing between the drive gear 11 and the second driven gear 13. It is also conceivable that a so-called offset error occurs due to an abnormality of the magnetic sensors 17, 18, etc., that is, an abnormal value different from the actual value is calculated based on the rotation angles α, β of the driven gears 12, 13. Then, it can be considered that the value of the difference Δαβ significantly deviates from the allowable range associated with the original cycle number γ1, and therefore, falls within the allowable range associated with another cycle number γ1 different from the original cycle number.

[0091] For example, Figure 8 As shown, although the value of the difference Δαβ is originally "zero", when the value of the difference Δαβ is erroneously calculated as "360" due to an abnormality in the rotation angle detection device 10, the rotation calculation unit 23 erroneously identifies the cycle number γ1 as "-1" although the original cycle number γ1 is "zero". In this case, "360" as the erroneously identified value of the difference Δαβ falls within the allowable range of the difference Δαβ when the cycle number γ1 is "-1", so it is difficult for the abnormality detection unit 25 to detect the abnormality. In the present embodiment, the microcomputer 19 adopts the following components.

[0092] like Fig. 9 As shown, in addition to the abnormality detection unit 25, the microcomputer 19 includes another abnormality detection unit 26. The abnormality detection unit 26 detects abnormality of the rotation angle θ of the drive gear 11 calculated by the absolute angle calculation unit 24 based on the rotation amounts of the first driven gear 12 and the second driven gear 13.

[0093] like Fig.10 As shown, the abnormality detection unit 26 includes two final value holding units 31a, 31b, two subtractors 32a, 32b, two integrated value holding units 33a, 33b, two adders 34a, 34b, a conversion unit 35, a difference calculation unit 36 ​​and a determination unit 37.

[0094] The final value holding unit 31a acquires the rotation angle α of the first driven gear 12 calculated by the first magnetic sensor 17, and holds the acquired rotation angle α. While the first magnetic sensor 17 calculates the rotation angle α in a predetermined calculation cycle, the rotation angle α held in the final value holding unit 31a is updated each time the rotation angle α is calculated by the first magnetic sensor 17. In other words, the rotation angle α held in the final value holding unit 31a is the final value of the rotation angle α as the current value calculated by the first magnetic sensor 17 (the rotation angle α one calculation cycle ago).

[0095] The subtractor 32 a calculates the rotation amount Δα of the first driven gear 12 in one calculation cycle by subtracting the final value of the rotation angle α held in the final value holding unit 31 a from the current value of the rotation angle α calculated by the first magnetic sensor 17 .

[0096] The integrated value holding unit 33a acquires the integrated value Σ calculated by the adder 34a (described later). α , and keep the obtained integral value Σ α Whenever the adder 34a calculates the integral value Σ α When the integral value Σ is stored in the integral value holding unit 33a, α In other words, the integrated value Σ held in the integrated value holding unit 33a α is the integrated value Σ calculated by the adder 34a α The final value of the current value (the integral value Σ before one calculation cycle) α ).

[0097] The adder 34a adds the current value of the rotation amount Δα in one calculation cycle of the first driven gear 12 calculated by the subtractor 32a to the integrated value Σ of the rotation amount Δα held in the integrated value holding unit 33a. α The final value of is added to calculate the integral value Σ αThe current value of .

[0098] The final value holding unit 31b acquires the rotation angle β of the second driven gear 13 calculated by the second magnetic sensor 18, and holds the acquired rotation angle β. The rotation angle β held in the final value holding unit 31b is the final value of the current value of the rotation angle β calculated by the second magnetic sensor 18 (the rotation angle β one calculation cycle ago).

[0099] The subtractor 32 b calculates the rotation amount Δβ of the second driven gear 13 in one calculation cycle by subtracting the final value of the rotation angle β held in the final value holding unit 31 b from the current value of the rotation angle β calculated by the second magnetic sensor 18 .

[0100] The integrated value holding unit 33b acquires the integrated value Σ calculated by the adder 34b (described later). β , and keep the obtained integral value Σ β The integrated value Σ held in the integrated value holding unit 33b β is the integrated value Σ calculated by the adder 34b β The final value of the current value of .

[0101] The adder 34b adds the current value of the rotation amount Δβ in one calculation cycle of the second driven gear 13 calculated by the subtractor 32b to the integrated value Σ of the rotation amount Δβ held in the integrated value holding unit 33b. β The final value of is added to calculate the integral value Σ β The current value of .

[0102] The conversion unit 35 converts the integral value Σ of the rotation amount Δα calculated by the adder 34a into α Converted into the rotation angle θ of the driving gear 11 α The conversion unit 35 converts the integral value Σ of the rotation amount Δβ calculated by the adder 34b into β Converted into the rotation angle θ of the driving gear 11 β The rotation angle after conversion is θ α ,θ β Theoretically, they are the same value.

[0103] For example, the conversion unit 35 converts the integral value Σ of the rotation amount Δα calculated by the adder 34a into α The rotation angle θ of the driving gear 11 is calculated by multiplying the gear ratio (=z / m) between the driving gear 11 and the first driven gear 12. α The conversion unit 35 converts the integral value Σ of the rotation amount Δβ calculated by the adder 34b into β The rotation angle θ of the driving gear 11 is calculated by multiplying the gear ratio (=z / n) between the driving gear 11 and the second driven gear 13.β .

[0104] The difference calculation unit 36 ​​calculates the two rotation angles θ calculated by the conversion unit 35 α ,θ β The difference Δθ αβ . Due to the rotation angle θ α and the rotation angle θ β Theoretically, they are the same value, so the difference Δθ αβ The value of is theoretically "zero".

[0105] When the two rotation angles θ calculated by the difference calculation unit 36 α ,θ β The difference Δθ αβ The value falls on the basis of the ideal difference Δθ αβ When the rotation angle θ of the drive gear 11 calculated by the absolute angle calculation unit 24 is outside the allowable range determined by the ideal value, the determination unit 37 determines that the rotation angle θ of the drive gear 11 calculated by the absolute angle calculation unit 24 is abnormal.

[0106] Difference Δθ αβ The permissible range of is defined by an upper limit κ and a lower limit -κ. The upper limit κ is relative to the difference Δθ αβ The ideal value of "zero" is set to a positive value. The lower limit -κ is relative to the difference Δθ αβ The method of setting the upper limit κ and the lower limit -κ will be described in detail later.

[0107] When the two rotation angles θ calculated by the difference calculation unit 36 α ,θ β The difference Δθ αβ When the value of falls within the range of "±κ" relative to the ideal value (here "zero"), the determination unit 37 determines that the rotation angle θ of the drive gear 11 calculated by the absolute angle calculation unit 24 is normal. α ,θ β The difference Δθ αβ When the value of falls outside the range of “±κ” with respect to the ideal value, the determination unit 37 determines that the rotation angle θ of the drive gear 11 calculated by the absolute angle calculation unit 24 is abnormal.

[0108] Next, a method of setting the upper limit κ and the lower limit −κ will be described. Based on the two rotation angles θ calculated by the difference calculation unit 36 α ,θ β The difference Δθ αβ The ideal value and actual value are used to obtain the upper limit κ and lower limit -κ. αβ The ideal value of Δθ αβ1 It is represented by the following mathematical expression (E1). Difference Δθαβ The actual value of Δθ αβ2 It is represented by the following mathematical expression (E2).

[0109] Δθ αβ1 =θ α ·λ1-θ β ·λ2=0 (E1)

[0110] Δθ αβ2 =(θ α +δ1)·λ1-(θ β +δ2)·λ2=0 (E2)

[0111] "λ1" is the gear ratio (=z / m) between the driving gear 11 and the first driven gear 12, and "λ2" is the gear ratio (=z / n) between the driving gear 11 and the second driven gear 13. "δ1" is the rotation angle θ calculated by the difference operation unit 36 ​​when the rotation angle detection device 10 is normal. α "δ2" is the rotation angle θ calculated by the difference operation unit 36 ​​when the rotation angle detection device 10 is normal. β The maximum permissible tolerance.

[0112] For example, the tolerance δ1 includes mechanical tolerances, such as a clearance and assembly tolerance between the driving gear 11 and the first driven gear 12, and electrical tolerances due to the detection accuracy, temperature characteristics, etc. of the first magnetic sensor 17. For example, the tolerance δ2 includes mechanical tolerances, such as a clearance and assembly tolerance between the driving gear 11 and the second driven gear 13, and electrical tolerances due to the detection accuracy, temperature characteristics, etc. of the second magnetic sensor 18.

[0113] Therefore, as shown in the following mathematical expression (E3), the difference Δθ can be obtained from mathematical expressions (E1) and (E2): αβ The ideal value of Δθ αβ1 The maximum permissible tolerance δ 12 .

[0114] δ 12 =δ1·λ1-δ2·λ2 (E3)

[0115] In this embodiment, as shown in the following mathematical formula (E4), the difference Δθ αβ The ideal value of Δθ αβ1 The maximum permissible tolerance δ 12 The absolute value of is set to the absolute value of each of the upper limit κ and the lower limit -κ.

[0116] |δ 12 |=|±κ| (E4)

[0117] Therefore, the difference Δθαβ The allowable range R Δαβ It is represented by the following mathematical expression (E5).

[0118] R Δαβ =Δθ αβ1 ±κ (E5)

[0119] According to the second embodiment, the following advantageous effects are obtained.

[0120] When at least one of the two driven gears 12 and 13 does not rotate appropriately with respect to the rotation angle θ of the drive gear 11, the two rotation angles θ calculated by the difference calculation unit 36 ​​are α ,θ β The difference Δθ αβ The value falls within the allowable range R Δαβ Therefore, it is possible to calculate the rotation angles θ based on the two rotation angles θ calculated by the difference calculation unit 36. α ,θ β The difference Δθ αβ Whether the value falls within the allowed range R Δαβ It is determined whether the driven gears 12, 13 rotate appropriately with respect to the rotation angle θ of the driving gear 11. By extension, it can be determined whether the rotation angle θ of the driving gear 11 calculated by the absolute angle calculation unit 24 is normal.

[0121] The integral value Σ of the rotation amounts Δα and Δβ of the driven gears 12 and 13 α ,Σ β is converted into the rotation angle θ of the driving gear 11 α ,θ β , and based on the transformed rotation angle θ α ,θ β For example, when the meshing between the driving gear 11 and any one of the two driven gears 12 and 13 causes so-called tooth skipping, the integral value Σ of the rotation amount Δα of the first driven gear 12 is α and the integral value Σ of the rotation amount Δβ of the second driven gear 13 β deviate significantly from each other. Therefore, the two rotation angles θ α ,θ β The difference Δθ αβ Falls within the allowable range R Δαβ Therefore, the difference Δθ αβ The value of is clearly outside the allowed range associated with the original period number γ1, for example, the difference Δθ αβ In the case where the value of falls within the allowable range associated with another cycle number γ1 different from the initial cycle number, the abnormality is appropriately detected.

[0122] Other Implementations

[0123] The first embodiment and the second embodiment may be modified as follows.

[0124] In the first embodiment, a configuration other than the gradient adjustment unit 21 may be used as the microcomputer 19. An abnormality in the rotation angle θ of the drive gear 11 is detected by comparing a value of a difference between a rotation angle α of the first driven gear 12 detected by the first magnetic sensor 17 and a rotation angle β of the second driven gear 13 detected by the second magnetic sensor 18 with an ideal value of the difference.

[0125] In a first embodiment, if Figure 2 As shown by the alternating long and two short dash lines in the figure, when the abnormality detection unit 25 detects the abnormality of the rotation angle θ of the driving gear 11, the abnormality detection unit 25 can obtain the cycle number γ1 calculated by the rotation calculation unit 23, and refer to the Figure 8 Table TB shown. With this configuration, the abnormality detection unit 25 learns the cycle number γ1, so the abnormality detection unit 25 can further quickly identify the allowable range of the current value of the difference Δαβ between the gradient-adjusted rotation angle α′ and the gradient-adjusted rotation angle β′ calculated by the difference calculation unit 22. Therefore, the abnormality detection unit 25 can further quickly detect the abnormality of the rotation angle θ of the drive gear 11.

[0126] In the second embodiment, a configuration including only the abnormality detection unit 26 as a unit detecting abnormality of the rotation angle θ of the drive gear 11 may be used as the microcomputer 19. With this configuration, abnormality of the rotation angle θ of the drive gear 11 can also be detected.

[0127] In the second embodiment, when it is not necessary to detect an abnormality in the rotation angle θ of the drive gear 11 due to so-called tooth skipping or the like according to product specifications or the like, a configuration other than the adders 34a, 34b and the integrated value holding units 33a, 33b may be used as Fig.10 In this case, the conversion unit 35 converts the rotation amounts Δα and Δβ of the two driven gears 12 and 13 into the rotation angle θ of the driving gear 11. α ,θ β The difference calculation unit 36 ​​calculates the rotation angle θ converted by the conversion unit 35. α ,θ β The difference Δθ αβ The determination unit 37 determines the difference Δθ based on the αβ The abnormality of the rotation angle θ of the drive gear 11 is detected by determining whether the value of θ falls within the allowable range set based on the ideal value. The upper limit κ and the lower limit -κ that define the allowable range are set as follows.

[0128] In this case the difference Δθ αβ The ideal value of Δθ αβ1 It is represented by the following mathematical expression (F1). In this case, the difference Δθ αβ The actual value of Δθ αβ2 It is represented by the following mathematical expression (F2).

[0129] Δθ αβ1 =Δα·λ1-Δβ·λ2=0 (F1)

[0130] Δθ αβ2 =(Δα+δ1)·λ1-(Δβ+δ2)·λ2=0 (F2)

[0131] Therefore, as shown in the following mathematical formula (F3), the difference Δθ can be obtained from mathematical expressions (F1) and (F2): αβ The ideal value of Δθ αβ1 The maximum permissible tolerance δ 12 .

[0132] δ 12 =δ1·λ1-δ2·λ2 (F3)

[0133] As shown in the following mathematical expression (F4), the difference Δθ αβ The ideal value of Δθ αβ1 The maximum permissible tolerance δ 12 The absolute value of is set to the absolute value of each of the upper limit κ and the lower limit -κ.

[0134] |δ 12 |=|±κ| (F4)

[0135] In the first and second embodiments, the driving gear 11 , the first driven gear 12 , and the second driven gear 13 may be made of a metal material.

[0136] In the first and second embodiments, the rotation calculation unit 23 can calculate the period number γ2 of the second driven gear 13 based on the value of the difference Δαβ calculated by the differential calculation unit 22. In this case, for the table TB, a table TB that defines the relationship between the difference Δαβ and the period number γ2 of the second drive gear 13 is adopted. When a configuration in which the period number γ2 of the second driven gear 13 is calculated by the rotation calculation unit 23, the absolute angle calculation unit 24 calculates the rotation angle θ of the drive gear 11 for multiple turns exceeding 360° in absolute value based on the rotation angle β of the second driven gear 13 detected by the second magnetic sensor 18 and the period number γ2 of the second driven gear 13 calculated by the rotation calculation unit 23. Therefore, with this configuration, it is also possible to immediately detect the rotation angle θ of the drive gear 11, that is, the absolute rotation angle of the shaft 14.

[0137] In the first and second embodiments, a Hall sensor, a resolver, or the like may be used as each of the magnetic sensors 17, 18 for detecting the rotation angles α, β of the two driven gears 12, 13. Alternatively, an optical sensor may be used as each of the sensors for detecting the rotation angles α, β of the two driven gears 12, 13.

[0138] In the first and second embodiments, the rotation angle α of the first driven gear 12 and the rotation angle β of the second driven gear 13 can be calculated by the microcomputer 19 (specifically, by the absolute angle calculation unit 24 ).

[0139] In the first and second embodiments, examples of the shaft 14 include a steering shaft that rotates synchronously with the operation of a steering wheel and a pinion shaft constituting a rack and pinion mechanism in a steering system of a vehicle. The rotation angle detection device 10 is suitable for applications for detecting the rotation angle of shafts of various machines other than a steering system of a vehicle.

Claims

1. A rotation angle detection device, characterized in that: include: a driving gear (11) configured to rotate integrally with a member whose rotation is to be detected; Two driven gears (12, 13) having different numbers of teeth, each of the driven gears (12, 13) being meshed with the driving gear (11); two sensors (17, 18), each sensor being configured to detect a rotation angle of an associated driven gear of the two driven gears (12, 13); as well as an operation circuit (19) configured to calculate the rotation angle of the drive gear (11) based on the rotation angles of the two driven gears (12, 13) detected by the two sensors (17, 18), the operation circuit (19) being configured to detect an abnormality in the rotation angle of the drive gear (11) calculated by the operation circuit (19) when the relationship between the rotation angles of the two driven gears (12, 13) detected by the two sensors (17, 18) is different from the relationship when the rotation angle of the drive gear (11) calculated by the operation circuit (19) is normal, The two driven gears (12, 13) include a first driven gear (12) and a second driven gear (13), The operation circuit (19) is configured to detect an abnormality in the rotation angle of the driving gear (11) based on the difference between the rotation angle of the first driven gear (12) and the rotation angle of the second driven gear (13), after the gradient is adjusted to be equal to the gradient of the rotation angle of the first driven gear (12) and the rotation angle of the driving gear (11) and the gradient of the rotation angle of the second driven gear (13) and the rotation angle of the driving gear (11).

2. The rotation angle detection device according to claim 1, characterized in that: The operation circuit (19) is configured to detect an abnormality in the rotation angle of the driving gear (11) based on a difference between integral values ​​of the rotation amounts of the two driven gears (12, 13) and an ideal difference between integral values ​​of the rotation amounts of the two driven gears (12, 13), which is calculated as a value indicating the relationship between the rotation angles of the two driven gears (12, 13).

3. The rotation angle detection device according to claim 2, characterized in that: The operation circuit (19) is configured to detect an abnormality in the rotation angle of the drive gear (11) when the difference is outside an allowable range set based on the ideal difference.

4. The rotation angle detection device according to claim 1 or 2, characterized in that: The component whose rotation is to be detected is one of a steering shaft and a pinion shaft in a steering system of a vehicle.

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