JP2010261739A - Torque detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering sensor capable of detecting axial torque of a steering shaft with a simple structure. <P>SOLUTION: The steering shaft 60 includes an input shaft 61 and an output shaft 62 connected to each other via a torsion bar 63. The steering sensor 10 includes magnetic sensors 21A, 21B for detecting the absolute angle a rotor 71 fixed to the input shaft 61; magnetic sensors 41A, 41B for detecting the absolute angle of a rotor 72 fixed to the output shaft 62; and an arithmetic circuit for performing an operation on the axial torque on the steering shaft 60 on the basis of the difference between the absolute angle of the input shaft 61 and the absolute angle of the output shaft 62. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a torque detection device that detects an axial torque of a rotary shaft having an input shaft and an output shaft connected via an elastic member.

  The electric power steering device (EPS) drives an electric motor based on the steering torque applied to the steering shaft by the operation of the steering wheel and the vehicle speed at the time of the steering operation, and provides the steering assist force to the steering shaft via the worm gear reduction mechanism or the like. This is a control device to be assigned. Along with the enhancement of vehicle behavior stability control, vehicles have been developed that detect the steering angle and steering direction of the steering wheel and use the detected information as a control signal for the skid prevention device (ECS). Conventionally, the torque sensor for detecting the steering torque of the steering shaft and the sensor for detecting the steering angle and steering direction of the steering wheel have different applications despite being arranged close to each other on the same shaft. Are mounted separately for. With the recent intelligence of vehicles, it is required to realize space saving and high functionality by integrating a plurality of sensors. For example, Japanese Patent Laid-Open No. 2001-194251 proposes a power steering detection device in which a sensor for detecting a steering torque applied to a steering shaft and a sensor for detecting a steering angle of a steering wheel are integrated. This power steering detection device includes two resolvers for detecting a phase difference caused by twisting of the steering shaft, and an absolute resolver for detecting an absolute angle of the steering shaft.

JP 2001-194251 A

  However, in the power steering detection device disclosed in the publication, since two resolvers are used as means for detecting the steering torque of the steering shaft, the sensor structure becomes large and complicated, and the size and size of the sensor are reduced. It is not suitable for in-vehicle sensors that require cost reduction.

  Therefore, an object of the present invention is to propose a torque detection device that can detect the shaft torque of the rotating shaft with a simple structure.

  In order to solve the above problems, a torque detection device according to the present invention is a torque detection device for detecting the axial torque of a rotary shaft having an input shaft and an output shaft connected to each other via an elastic member. A first rotating body fixed to the input shaft, wherein a distance between two points where a straight line passing through the rotation center of the first rotating body intersects the outer periphery of the first rotating body is constant A first magnetic sensor disposed near the outer periphery of the rotating body and the first rotating body, the outer periphery of the first rotating body and the first magnetic sensor periodically changing with the rotation of the first rotating body; A first magnetic sensor for detecting a magnetic field change corresponding to a change in a first distance between the magnetic sensor and outputting a first detection signal; and a rotation center of the first magnetic sensor and the first rotating body. Is equal to the distance between the center of rotation of the first rotating body and the first magnetic sensor. A second magnetic sensor disposed only at a position away from the rotation center of the first rotating body, the outer circumference of the first rotating body and the second magnetic sensor periodically changing with the rotation of the first rotating body A second magnetic sensor that detects a change in the magnetic field corresponding to a change in the second distance from the magnetic sensor and outputs a second detection signal; a first detection signal; and a second detection signal. First differential calculation means for performing differential calculation, first angle calculation means for calculating the absolute angle of the input shaft based on the result of differential calculation by the first differential calculation means, and fixed to the output shaft A second rotating body having a constant distance between two points where a straight line passing through the rotation center of the second rotating body intersects the outer periphery of the second rotating body, A second magnetic sensor disposed near the outer periphery of the second rotating body, wherein the second rotation changes periodically with the rotation of the second rotating body; A third magnetic sensor for detecting a change in the magnetic field corresponding to a change in the third distance between the outer periphery of the third magnetic sensor and the third magnetic sensor and outputting a third detection signal; a third magnetic sensor; On the straight line connecting the rotation center of the rotating body of the second rotating body, it is arranged at a position separated from the rotation center of the second rotating body by a distance equal to the distance between the rotation center of the second rotating body and the third magnetic sensor. A magnetic field corresponding to a change in a fourth distance between the outer circumference of the second rotating body and the fourth magnetic sensor, which is a fourth magnetic sensor and periodically changes as the second rotating body rotates. A fourth magnetic sensor for detecting a change and outputting a fourth detection signal; a second differential operation means for performing a differential operation on the third detection signal and the fourth detection signal; and a second difference A second angle calculating means for calculating an absolute angle of the output shaft based on the result of the differential calculation by the dynamic calculating means; Computing means for computing shaft torque based on the difference between the diagonal and the absolute angle of the output shaft.

  According to the present invention, since the phase difference between the input shaft and the output shaft is detected using the magnetic sensor, the torque detector can be reduced in size and cost.

  ADVANTAGE OF THE INVENTION According to this invention, the torque detection apparatus which can detect the axial torque of a rotating shaft with a simple structure can be provided.

1 is an explanatory diagram illustrating a schematic configuration of an electric power steering device according to Embodiment 1. FIG. 1 is a cross-sectional view of a steering sensor according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a sectional view taken along line 4-4 in FIG. FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. It is explanatory drawing which shows the function structure of the steering sensor which concerns on Example 1. FIG. It is a graph which shows the output characteristic of a magnetoresistive effect element. It is a graph which shows the change of the magnetic flux density with respect to the rotation angle of a rotary body. It is a graph which shows two detection signals output from a pair of magnetic sensor arranged diagonally. It is a graph which shows the signal which carries out differential calculation of the two detection signals output from a pair of diagonally arranged magnetic sensor. It is map data which shows the correspondence of the absolute angle of a rotary body, and a voltage value. It is an output signal waveform of the magnetic sensor which detects the rotation speed of a steering shaft. It is a graph which shows the initial phase difference of the absolute angle of two rotary bodies, and the initial difference of a voltage value. It is map data for calculating | requiring steering torque from the phase difference of two rotary bodies. It is explanatory drawing which shows the calculation method of the planar shape of a rotary body. It is a graph of elliptic function H (X, Y) when a = 0.9. It is a graph of elliptic function H (X, Y) when a = 1.5. It is a graph of elliptic function H (X, Y) when a = 0.5. It is explanatory drawing which shows schematic structure of the electric power steering apparatus which concerns on Example 2. FIG. It is explanatory drawing which shows the arrangement | positioning relationship between a rotary body and a magnetic sensor. It is a graph which shows the cos signal and sin signal before calibration execution. It is explanatory drawing which shows the amplitude correction and offset correction of a cos signal. It is explanatory drawing which shows the amplitude correction and offset correction of a sin signal. It is explanatory drawing which shows the digital sampling of a cos signal. It is explanatory drawing which shows the digital sampling of a sin signal. It is explanatory drawing of a conversion table. It is explanatory drawing which shows the reading range of a cos signal and a sin signal. It is a graph of a linear output value.

  Embodiments according to the present invention will be described below with reference to the drawings. About the same member, the same code | symbol shall be attached | subjected and the overlapping description is abbreviate | omitted.

  FIG. 1 is an explanatory diagram showing a schematic configuration of an electric power steering apparatus 200 according to the present embodiment. The electric power steering device 200 is a control mechanism for electrically controlling the steering assist force based on the steering torque applied to the steering shaft 60 and the vehicle speed during the steering operation. The steering shaft 60 includes a torsion bar 63 made of an elastic member having a predetermined torsion-torque characteristic, an input shaft 61 connected to the input side of the torsion bar 63, and an output shaft 62 connected to the output side of the torsion bar 63. And a rotating shaft. The input shaft 61 and the output shaft 62 are arranged coaxially with each other, but are not directly connected but are connected with a torsion bar 63 interposed therebetween. The input shaft 61 is connected to the steering wheel 270 and rotates in synchronization with the rotation of the steering wheel 270. On the other hand, the output shaft 62 is connected to the steering gear mechanism 240, and the rotational motion transmitted from the input shaft 61 to the output shaft 62 via the torsion bar 63 is converted into a linear motion of the rod 250 by the steering gear mechanism 240. Thus, the steering direction of the wheels 261 and 262 is controlled.

  Here, the rotational motion of the input shaft 61 is transmitted to the output shaft 62 via the torsion bar 63, but the output shaft 62 rotates due to the friction between the wheels 261 and 262 and the road surface. The torsion bar 63 is twisted because it starts to rotate with a delay. The steering sensor 10 is applied to the steering shaft 60 based on the rotational speed of the steering shaft 60, the absolute angle within one rotation of the input shaft 61, and the rotational angle difference (phase difference) between the input shaft 61 and the output shaft 62. The detected steering torque, steering angle, and steering direction are detected, the detected information of the steering torque is output to the controller (ECU) 210, and the detected information of the steering angle and the steering direction is output to the skid prevention device (ECS) 280. The controller 210 calculates a command value for the steering assist force based on the steering torque and the vehicle speed, and outputs this to the motor 220. The output torque of the motor 220 is transmitted to the output shaft 62 via the speed reduction mechanism 230.

  In the present specification, the position of the steering wheel 270 when the steering direction of the wheels 261 and 262 is at the center of the steering angle is referred to as a reference position. A case where the steering wheel 270 is steered clockwise with respect to the reference position is referred to as positive direction steering, and a case where the steering wheel 270 is steered counterclockwise is referred to as negative direction steering.

  Next, the internal structure of the steering sensor 10 will be described with reference to FIGS. 2 is a sectional view of the steering sensor 10, FIG. 3 is a sectional view taken along line 3-3 in FIG. 2, FIG. 4 is a sectional view taken along line 4-4 in FIG. 2, and FIG. FIG. A rotating body 71 is fixed to the input shaft 61. The rotating body 71 is a rotor made of a ferromagnetic material (for example, iron, cobalt, nickel, etc.). When the axial center direction of the input shaft 61 is the Z-axis direction, the rotating body 71 rotates in the XY plane perpendicular to the Z-axis. As shown in FIG. 3, the shape (hereinafter referred to as “planar shape”) in which the rotating body 71 is projected onto the rotating plane (XY plane) is “rotating body 71” with respect to any straight line passing through the rotation center P. Is formed in a shape that satisfies the condition that the distance between two points intersecting the outer periphery of the rotating body 71 is constant (excluding a circle). In this embodiment, as such a shape, a shape formed by combining two different semi-ellipses is illustrated, but the shape is not limited to this example. Near the outer periphery of the rotator 71, a pair of magnetic sensors 21A and 21B arranged diagonally on a straight line 401 passing through the rotation center P of the rotator 71, and on a straight line 402 orthogonal to the straight line 401 and passing through the rotation center P A pair of magnetic sensors 21C and 21D arranged diagonally are arranged. Each of the magnetic sensors 21A, 21B, 21C, and 21D is fixed at an interval of 90 degrees with respect to the rotation center P, and even if the rotating body 71 rotates, the rotation center P and the respective magnetic sensors 21A, 21B, and 21C. , 21D is always constant.

  As shown in FIG. 2, the magnetic sensor 21 </ b> A detects, as a voltage change, a change in the external magnetic field that changes in conjunction with the rotation of the magnet 101 that functions as a magnetic field generation unit for generating an external magnetic field and the rotating body 71. A magnetoresistive element 91 is provided as a main component. As a mounting form of the magnetic sensor 21A, the magnetoresistive effect element 91 is arranged on the surface of one printed wiring board 111 so that the magnetoresistive effect element 91 is positioned on a straight line in the Z direction passing through the center point of the magnet 101, It is preferable to arrange the magnet 101 on the back surface of the printed wiring board 111. In the example shown in FIG. 3, the printed wiring board 111 is formed in a hollow ring shape, but may be a C-shape having an end. By using one printed wiring board 111, the assembly of the steering sensor 10 is facilitated, and an improvement in mounting accuracy can be expected. In order to efficiently collect an external magnetic field generated from the magnet 101, it is preferable to arrange yokes (not shown) on both poles of the magnet 101. The configuration of the magnetic sensors 21B, 21C, and 21D is the same as the configuration of the magnetic sensor 21A.

  The magnetoresistive element 91 has a magnetization direction set to a specific direction and is configured so that the magnetization state (for example, the magnetization direction and the strength of magnetization) is not affected by the displacement of the external magnetic field. A magnetic layer (not shown) and a free magnetic layer (not shown) whose magnetization state is displaced by a change in the external magnetic field are provided. As shown in FIG. 2, when the rotating body 71 rotates in synchronization with the rotation of the input shaft 61, the gap G between the outer periphery of the rotating body 71 and the magnetoresistive effect element 91 changes periodically. . When the gap G changes, the magnetic flux density drawn from the magnet 101 disposed on the back surface of the magnetoresistive effect element 91 through the magnetoresistive effect element 91 to the rotating body 71 changes. Then, since the magnetization state of the free magnetic layer in the magnetoresistive effect element 91 changes, the displacement difference of the magnetization state between the magnetization state of the pinned magnetic layer where the magnetization state does not change and the free magnetic layer where the magnetization state changes. Will occur. This displacement difference in the magnetized state is a physical quantity that reflects the rotation angle of the rotating body 71, and specifically appears as a change in the resistance value of the magnetoresistive effect element 91. A bias current is supplied to the magnetoresistive effect element 91 from the printed wiring board 111, and a change in the resistance value of the magnetoresistive effect element 91 is detected as a change in the output voltage. The output voltage of the magnetoresistive effect element 91 is signal-processed as a detection signal indicating the rotation angle of the rotating body 71. As the magnetoresistive element 91, a GMR element, MR element, AMR element, TMR element, or the like can be applied.

  As shown in FIG. 7, the operation region of the magnetoresistive effect element 91 is a region A or a region B where the relationship between the magnetic flux density passing through the magnetoresistive effect element 91 and the output voltage of the magnetoresistive effect element 91 is linear. It is preferable to design the strength of the external magnetic field, the average interval of the gap G, and the like. In this case, according to the distance of the gap G, the output of the magnetic sensor 21A has linearity. Further, the positional relationship in the thrust direction between the rotating body 71 and the magnetic sensor 21 </ b> A is a positional relationship in which the rotating body 71 does not deviate from the magnetoresistive effect element 91, including misalignment due to the runout caused by the rotation of the rotating body 71. desirable. For example, if the mounting error is ± 0.5 mm, the runout is ± 0.5 mm, and the thickness of the magnetoresistive element 91 is 0.5 mm, the thickness of the rotating body 71 is preferably 3.0 mm or more.

  Now, when the rotating body 71 rotates once, as shown in FIG. 8, a change corresponding to one cycle appears in the waveform indicating the change in the magnetic flux density of the external magnetic field passing through the magnetic sensor 21A. Since the rotating body 71 is processed into a shape in which two different half ovals are combined, the magnetic flux density waveform shown in FIG. 8 is not a sine waveform in a strict sense, but is a waveform similar to a sine waveform. Since the relationship between the magnetic flux density passing through the magnetoresistive effect element 91 and the output voltage of the magnetoresistive effect element 91 is linear as described above (see FIG. 7), the detection signal output from the magnetoresistive effect element 91 is , Having a waveform similar to a sine wave. The rotating body 71 has a shape in which the distance between two points where the straight line passing through the rotation center P of the rotating body 71 intersects the outer periphery of the rotating body 71 is constant for any straight line passing through the rotation center P. Therefore, when the first distance between one magnetic sensor 21A of the pair of magnetic sensors 21A and 21B arranged diagonally and the outer periphery of the rotating body 71 changes, the other magnetic sensor 21B and the rotating body 71 are changed. The second distance between the outer circumference and the outer circumference changes in a complementary manner so as to follow the change in the first distance. That is, when the first distance is shortened, the second distance is increased by the shortened distance. This is because the pair of magnetic sensors 21A and 21B are diagonally arranged by 180 degrees. Therefore, the detection signals of the magnetic sensors 21A and 21B have a phase difference of 180 degrees as shown in FIG. In FIG. 9, reference numeral 501 indicates a detection signal of the magnetic sensor 21A, and reference numeral 502 indicates a detection signal of the magnetic sensor 21B. Note that the detection signals of the other pair of magnetic sensors 21C and 21D arranged diagonally also have a phase difference of 180 deg.

  Returning to the description of FIG. A rotating body 72 is fixed to the output shaft 62. The material and planar shape of the rotating body 72 are the same as the material and planar shape of the rotating body 71. As shown in FIG. 5, in the vicinity of the outer periphery of the rotator 72, a pair of magnetic sensors 41 </ b> A and 41 </ b> B diagonally arranged on a straight line 403 passing through the rotation center Q of the rotator 72, and orthogonal to the straight line 403 and rotating. A pair of magnetic sensors 41C and 41D arranged diagonally on a straight line 404 passing through the rotation center Q of the body 72 are arranged. Each of the magnetic sensors 41A, 41B, 41C, and 41D is fixed at an interval of 90 degrees with respect to the rotation center Q of the rotating body 72. Even if the rotating body 72 rotates, the rotation center Q and the respective magnetic sensors. The distances between 41A, 41B, 41C and 41D are always constant. As shown in FIG. 2, the magnetic sensor 41 </ b> A includes a magnetoresistive effect element 92 and a magnet 102, and one piece so that the magnetoresistive effect element 92 is positioned on a straight line in the Z direction passing through the center point of the magnet 102. Preferably, the magnetoresistive effect element 92 is disposed on the back surface of the printed wiring board 112, and the magnet 102 is disposed on the front surface of the printed wiring board 112.

  As shown in FIGS. 2 and 4, a worm 81 that meshes with a worm wheel 82 that is rotatably supported inside the housing 120 is connected to the input shaft 61. A magnet 103 that functions as a magnetic field generating means for generating an external magnetic field is attached to the worm wheel 82. When the input shaft 61 rotates, the worm 81 rotates in synchronization therewith. The rotation of the worm 81 is transmitted to the worm wheel 82 to rotate the magnet 103 in the XZ plane. For example, when the worm 81 rotates once, the worm wheel 82 rotates by one tooth. A magnetoresistive effect element 93 that detects a change in the external magnetic field that changes in conjunction with the rotation of the magnet 103 as a voltage change is mounted on the printed wiring board 113 at a position away from the magnet 103 by a predetermined gap interval in the Y direction. ing. The magnetoresistive effect element 93 and the magnet 103 function as the magnetic sensor 31 that outputs a magnetic signal that changes in conjunction with the rotation of the steering shaft 60. The worm 81 and the worm wheel 82 are made of a resin such as polyacetal.

  FIG. 6 is an explanatory diagram showing a functional configuration of the steering sensor 10. The steering sensor 10 has an input shaft angle for detecting an absolute angle within one rotation of the input shaft 61 within a range of 0 deg to 360 deg with reference to the position of the input shaft 61 when the steering wheel 270 is at the reference position. The detection unit 20, the rotation number detection unit 30 for detecting the rotation number of the steering shaft 60, and the absolute position within one rotation of the output shaft 62 with reference to the position of the output shaft 62 when the steering wheel 270 is at the reference position An output shaft angle detection unit 40 for detecting the angle within a range of 0 deg to 360 deg, and an arithmetic circuit 50 for calculating the multi-rotation absolute angle and steering torque of the steering shaft 60 are provided. The functions of these units are realized by IC chips (not shown) mounted on the printed wiring boards 111, 112, and 113. In this embodiment, it is assumed that the steering shaft 60 can rotate a maximum of 2.5 in each of the positive direction and the negative direction. The multi-rotation absolute angle of the steering shaft 60 is synonymous with the steering angle of the steering wheel 270 and is determined by the absolute angle within one rotation of the input shaft 61 and the rotation speed of the steering shaft 60.

  The input shaft angle detection unit 20 includes a differential operation circuit 22A that outputs a sin signal by performing a differential operation on two detection signals output from the pair of magnetic sensors 21A and 21B, and a pair of magnetic sensors 21C and 21D. A differential operation circuit 22B that outputs a cos signal by performing a differential operation on the two output detection signals, and an angle calculation circuit that calculates an absolute angle within one rotation of the input shaft 61 based on the sin signal and the cos signal 23. Here, reference numeral 503 in FIG. 10 indicates a sin signal obtained by performing a differential operation on the two detection signals 501 and 502 shown in FIG. 9 by the differential operation circuit 22A. This sin signal is a substantially sine wave signal having a waveform shape very similar to an ideal sine waveform. Similarly, the cos signal output from the differential arithmetic circuit 22B is a substantially sine wave signal having a waveform shape very similar to an ideal sine waveform, and has a phase difference of 90 deg relative to the sin signal. Yes. The angle calculation circuit 23 calculates an absolute angle within one rotation of the input shaft 61 based on the sin signal output from the differential operation circuit 22A and the cos signal output from the differential operation circuit 22B. The angle calculation circuit 23 outputs a voltage value corresponding to the absolute angle calculated based on the sin signal and the cos signal to the arithmetic circuit 50 as digital data. FIG. 11 shows map data 504 indicating the correspondence between absolute angles and voltage values. The map data 504 is set so that the voltage value increases or decreases as a digital value in the range of 0.5 V to 4.5 V in proportion to the absolute angle.

  The output shaft angle detection unit 40 includes a differential operation circuit 42A that outputs a sin signal by performing a differential operation on two detection signals output from the pair of magnetic sensors 41A and 41B, and a pair of magnetic sensors 41C and 41D. A differential operation circuit 42B that outputs a cos signal by performing a differential operation on the two output detection signals, and an angle calculation circuit that calculates an absolute angle within one rotation of the output shaft 62 based on the sin signal and the cos signal 43. The functions of the differential operation circuits 42A and 42B and the angle calculation circuit 43 are the same as those of the above-described differential operation circuits 22A and 22B and the angle calculation circuit 23, respectively.

  The rotation speed detection unit 30 is output from the magnetic sensor 31 that outputs a magnetic signal that changes in conjunction with the rotation of the steering shaft 60, the amplifier 32 that amplifies the output signal (analog signal) of the magnetic sensor 31, and the amplifier 32. An A / D converter 33 that converts an analog signal into a digital signal and outputs the digital signal to the arithmetic circuit 50 is provided. FIG. 12 shows the output signal waveform of the magnetic sensor 31. In the present embodiment, since the rotation speed of the steering shaft 60 is limited to a maximum of 2.5 rotations in each of the positive direction and the negative direction, the worm wheel 82 rotates only by a maximum of 2.5 teeth. Assuming that the worm wheel 82 makes one rotation, the magnetic sensor 31 theoretically outputs a substantially sine wave signal for one cycle. In the example shown in the figure, the phase of the signal output from the magnetic sensor 31 is adjusted to 180 deg when the steering wheel 270 is at the reference position. When the steering shaft 60 rotates from the reference position, the phase of the output signal waveform of the magnetic sensor 31 changes within a range of Δφ (= 22.5 deg) per rotation with reference to 180 deg, and the signal level (voltage value) also changes. Monotonically increases or decreases monotonically according to the phase change. Therefore, the signal level of the magnetic sensor 31 serves as an index for determining the rotation speed of the steering shaft 60.

  The arithmetic circuit 50 calculates the multi-rotation absolute angle of the steering shaft 60 based on the information received from the input shaft angle detection unit 20 and the rotation speed detection unit 30. For example, as shown in FIG. 12, if the digital signal output from the rotation speed detection unit 30 is in the range of 2.47V to 2.52V, the arithmetic circuit 50 is obtained by rotating the steering shaft 60 once in the negative direction. If it is in the range of 2.42V to 2.47V, it is determined that the rotation has been made in the positive direction. As a specific example, for example, when the information received from the input shaft angle detection unit 20 is “absolute angle 60 deg” and the information received from the rotation speed detection unit 30 is “second rotation”, multiple rotations of the steering shaft 60 are performed. The absolute angle is calculated as 360 deg + 60 deg = 420 deg. The multi-rotation absolute angle calculated in this way is output to the above-described controller 210 via the connector 130 shown in FIGS. 2 and 4 as information indicating the steering angle of the steering wheel 270.

  The arithmetic circuit 50 receives the voltage value indicating the absolute angle of the input shaft 61 from the input shaft angle detection unit 20, and also receives the voltage value indicating the absolute angle of the output shaft 62 from the output shaft angle detection unit 40. The steering torque of the steering shaft 60 is obtained from the phase difference between the output shaft 62 and the spring constant of the torsion bar 63. By the way, since it is difficult to attach the rotating bodies 71 and 72 to the steering shaft 60 without causing a phase shift, there is no phase difference between the input shaft 61 and the output shaft 62. The voltage value output from the input shaft angle detector 20 and the voltage value output from the output shaft angle detector 40 may be different. Therefore, in this embodiment, after the rotating bodies 71 and 72 are attached to the steering shaft 60, as shown in FIG. 13, the initial phase difference Δθ (= θ1−θ2) and the voltage value of the absolute angles of the rotating bodies 71 and 72 are obtained. The initial difference ΔVref is obtained. In this embodiment, the maximum value (for example, ± 5 deg) of the phase difference between the rotating bodies 71 and 72 generated due to the steering torque applied to the torsion bar 63 of the steering shaft 60 by the operation of the steering wheel 270 is obtained in advance. Keep it. FIG. 14 shows map data 505 for obtaining the steering torque from the phase difference between the rotating bodies 71 and 72, the horizontal axis indicates the phase difference between the rotating bodies 71 and 72, and the vertical axis indicates the voltage value. In this map data 505, when the difference between the voltage value output from the input shaft angle detection unit 20 and the voltage value output from the output shaft angle detection unit 40 is ΔVref, the phase difference is set to indicate 0 deg. Has been. When the phase difference between the rotators 71 and 72 increases in the positive direction, the value of the map data 505 increases linearly in proportion to the increase in the phase difference, and when the phase difference between the rotators 71 and 72 decreases in the negative direction. The value of the map data 505 is set to decrease linearly in proportion to the decrease in the phase difference. The arithmetic circuit 50 obtains the steering torque of the steering shaft 60 using the map data 505.

  The pair of magnetic sensors 21C and 21D is not essential for detecting the angle of the input shaft 61, and the angle detection can be performed only by the pair of magnetic sensors 21A and 21B. In addition, the pair of magnetic sensors It should be noted that 41C and 41D are not essential for the angle detection of the output shaft 62, and the angle detection can be performed only by the pair of magnetic sensors 41A and 41B. Furthermore, although the longitudinal direction of the free magnetic layer of the magnetoresistive effect element 91 is not particularly limited, according to the experiments by the present inventors, magnetization is performed in a direction toward the rotation center P of the rotating body 71 (rotation center direction). In particular, it has been confirmed that highly accurate angle detection can be obtained. For example, when the longitudinal direction of the free magnetic layer is set in a direction orthogonal to the direction toward the rotation center P, an average magnetic field depending on the rotation angle is magnetoresistive over the entire longitudinal direction of the free magnetic layer. It will be detected by the effect element 91, and the detection error is considered to be relatively larger than when the longitudinal direction of the free magnetic layer is directed to the rotation center P.

Next, a method for calculating the planar shape of the rotator 71 will be described with reference to FIG.
Here, it is assumed that the planar shape of the rotator 71 is formed by combining a semi-ellipse F (Y ≧ 0) and a semi-elliptic function H (Y ≦ 0) in the XY coordinate system, and one of the ellipses F is known. Consider the case where the other elliptic function H is calculated.
An ellipse F (x, y) is defined as follows.
(X, y) = (L cos θ, L sin θ) (1)
x ² + y ² / a ² = r ² (2)
y ≧ 0 (3)

Here, the origin of the XY coordinate system is assumed to coincide with the rotation center P, and the distance between the rotation center P and a point on the ellipse F is expressed by the following equation.
(R ² / (cos ² θ + sin ² θ / a ² )) ^1/2 = L (4)
Therefore, the coordinates of the ellipse F can be expressed by θ by substituting the equation (4) into the equation (1).

Now, the elliptic function H (X, Y) is “the distance between two points where the straight line passing through the rotation center P intersects the outer periphery of the rotating body 71 is constant for any straight line passing through the rotation center P”. Since the condition must be met, the following equation holds.
H (X) = X = 2r · cos θ−F (x) (5)
H (Y) = Y = 2r · sin θ−F (y) (6)
Here, F (x) and F (y) indicate the X coordinate and the Y coordinate of the point where the straight line passing through the rotation center P intersects the ellipse F. That is, H and F satisfying the expressions (5) and (6) have the same angle with the X axis starting from the rotation center. Further, if a function F (not limited to an ellipse) is defined from the expressions (5) and (6), the coordinates of the corresponding function H (not limited to an ellipse function) can be obtained.

Here, when Expressions (5) and (6) are expressed on the XY coordinates, when a = 0.9, the waveform is as shown in FIG. 16 (r = 1). However, depending on the value of a (for example, when a = 1.5), the waveform has a valley with X = 0 as shown in FIG. 17, and when a = 0.5, Y> as shown in FIG. When X is 0, X = r is obtained, and the inflection point for changing the sign of the rate is obtained. Here, in the cases as shown in FIGS. 17 and 18, it is considered that the magnetic field is disturbed at the troughs and inflection points, and the detection output may not be stable. Therefore, it is preferable that the rotating body does not have a valley point as shown in FIG. Therefore, a preferable rotating body is an ellipse (x ² + y ² / a ² = r ² ) and 0 <a <2 (conditions where the coordinate origin exists in the closed curve plane) (however, a = 1 is excluded). Tanibe is a combined elliptic function that does not have an inflection point that changes the sign of the ratio. As a result, it is possible to obtain a sine wave in which the ellipses F and H have one maximum and one minimum in one rotation. Of course, the rotator having a shape that does not have an inflection point that changes the sign of the valley and the ratio is not limited to an ellipse and an elliptic function, and various shapes are possible. The planar shape of the rotating body 72 can also be calculated by the same procedure.

This embodiment has the following advantages.
(1) Since the rotating body 71 having a constant distance between two points where the straight line passing through the rotation center P of the rotating body 71 intersects the outer periphery of the rotating body 71 is used, a pair of magnetic sensors 21A arranged diagonally. , 21B (or 21C, 21D) is obtained by performing a differential operation on the detection signal to be a substantially sine wave signal including rotation angle information of the rotating body 71, and an absolute angle within one rotation of the input shaft 61 is 0 deg. It can be detected with high accuracy over a range of ˜360 deg.

(2) Since the shape of the rotating body 71 projected on the plane of rotation has a shape in which two different semi-ellipses are combined, a pair of magnetic sensors 21A, 21B (or 21C, 21D) arranged diagonally. Since the signal obtained by performing the differential operation on the detection signal becomes a substantially sine wave signal including the rotation angle information of the rotating body 71, angle detection with a small detection error can be performed.

(3) Even when the absolute angle within one rotation of the output shaft 62 is detected over the range of 0 deg to 360 deg using the rotator 72, the above advantages (1) and (2) are obtained.

(4) Since the rotational speed of the steering shaft 60 can be determined based on the level of the detection signal output from the magnetic sensor 31, the steering speed can be determined without storing the rotational speed information of the steering shaft 60 in the nonvolatile memory when the power is turned off. The multi-turn absolute angle of the shaft 60 can be detected.

(5) Since the absolute angles of the rotating bodies 71 and 72 are detected using the magnetic sensors 21A, 21B, 21C, 21D, 41A, 41B, 41C, and 41D, the sensor structure is more than the method of detecting the absolute angle using a resolver. Can be simplified.

  The steering sensor 10 according to the second embodiment includes an arrangement relationship between the rotating body 72 and the pair of magnetic sensors 41A and 41B for detecting an absolute angle within one rotation of the output shaft 62, and detection from the magnetic sensors 41A and 41B. The signal processing method is different from that of the first embodiment, and is identical in other points. In the following description, the differences between the first and second embodiments will be referred to, and redundant description will be omitted.

  As shown in FIG. 20, the magnetic sensor 41A is located on a straight line 405 passing over the rotation center Q of the rotating body 72, and the magnetic sensor 41B is located on a straight line 406 passing over the rotation center Q. The angle at which the two straight lines 405 and 406 intersect is 90 deg. The distances from the rotation center Q to the magnetic sensors 21A and 21B are the same. The two magnetic sensors 41 </ b> A and 42 </ b> B are arranged equidistant from the rotation center Q with a phase difference (mechanical angle) of 90 deg with respect to the rotation center Q of the rotating body 72. The magnetic sensor 41A detects a magnetic field change corresponding to a change in the first distance between the outer circumference of the rotating body 72 and the magnetic sensor 41A that periodically changes as the rotating body 72 rotates, and is similar to a sine waveform. A first substantially sinusoidal signal having the waveform shape is output. The magnetic sensor 41B detects a magnetic field change corresponding to a change in the second distance between the outer circumference of the rotating body 72 and the magnetic sensor 41B that periodically changes as the rotating body 72 rotates, and is similar to a sine waveform. The second substantially sinusoidal signal having the waveform shape is output. The first and second substantially sinusoidal signals are detection signals having a phase difference (electrical angle) of 90 deg from each other. For convenience of explanation, the detection signal output from the magnetic sensor 41A is referred to as a cos signal, and the detection signal output from the magnetic sensor 41B is referred to as a sin signal.

  As shown in FIG. 19, the cos signal (analog signal) output from the magnetic sensor 41A is amplified by the amplifier 44A, converted to a digital signal by the A / D converter 45A, and output to the angle calculation circuit 43. The Similarly, a sin signal (analog signal) output from the magnetic sensor 41B is amplified by the amplifier 44B, converted into a digital signal by the A / D converter 45B, and output to the angle calculation circuit 43. The angle calculation circuit 43 calculates an absolute angle within one rotation of the input shaft 61 based on the sin signal output from the amplifier 44A and the cos signal output from the amplifier 44B. The angle calculation circuit 43 outputs a voltage value corresponding to the absolute angle calculated based on the sin signal and the cos signal to the arithmetic circuit 50. The conversion table 46 is held, the absolute angle of the rotating body 72 corresponding to the cos signal and sin signal output from the magnetic sensors 41A and 41B is read from the conversion table 46, and the read absolute angle is output. This conversion table 46 is created by, for example, calibration performed at the time of product shipment or when the steering shaft 60 is attached.

Here, a method of creating the conversion table 46 will be described. FIG. 21 shows the cos signal 701 and the sin signal 702 before calibration. Before the calibration is performed, the cos signal 701 and the sin signal 702 generally do not have the same amplitude and intermediate value. Therefore, the waveforms of one period of each of the cos signal 701 and the sin signal 702 are taken in, and the amplitude and intermediate value of each of the cos signal 701 and the sin signal 702 are calculated. Then, as shown in FIGS. 22 and 23, the upper limit value of the cos signal 701 and the sin signal 702 after calibration is V _T , the lower limit value is V _B , and the intermediate value is (V _T + V _B ) / 2. Thus, the gain and offset value of the amplifier 44A for amplifying the cos signal 701 output from the magnetic sensor 41A and the gain and offset value of the amplifier 44B for amplifying the sin signal 702 output from the magnetic sensor 41B are Each adjustment is performed, and amplitude adjustment and offset correction of the detection signal are performed. 22 and 23, the broken line indicates the signal waveform before calibration, the solid line indicates the signal waveform after calibration, the alternate long and short dash line indicates the intermediate value after offset correction, and the alternate long and two short dashes line indicates the offset Indicates the intermediate value before correction.

  The cos signal 701 and the sin signal 702 after the calibration are converted into digital data by the A / D converters 45A and 45B, respectively, and supplied to the angle calculation circuit 43. As shown in FIGS. 24 and 25, the angle calculation circuit 43 samples the digitized cosine signal 701 and sin signal 702 at a constant angular interval over one period, and the sampled read data is converted into a cosine signal value 802, And the sin signal value 803 is stored in the conversion table 46 (see FIG. 26). For example, in order to have a resolution of a rotation angle of 0.2 deg, an angle accuracy of 0.1 deg or less is necessary. Therefore, the cos signal 701 and the sin signal 702 are sampled with an angle accuracy of 0.1 deg or less and sampled. The read data is preferably stored in the conversion table 46. Note that the time of one cycle of the digitized cos signal 701 and sin signal 702 can be calculated as an upper limit interval (or lower limit interval). Further, when the cos signal 701 takes an upper limit value or when the sin signal 702 takes an intermediate value, the 0 deg determination criterion may be used.

  As shown in FIG. 26, the conversion table 46 associates a linear output value 801, a cos signal value 802, and a sin signal value 803 in an angle range of 0 deg to 360 deg. As shown in FIG. 28, the linear output value 801 is created in advance as map data that linearly increases monotonously in an angle range of 0 deg to 360 deg. For example, when it is desired to output the linear output value 801 in the range of 1.0 V to 4.0 V, the linear output value 801 is set to 1.0 V at 0 deg, and the linear output value 802 is set to 2.5 V at 180 deg. The linear output value 801 is set to 4.0 V at 359 degrees, and the relationship between the absolute angle of the rotating body 72 and the linear output value 801 may be linear. Note that the output range of the linear value 801 can be arbitrarily adjusted, and is not limited to the above numerical values. The linear output value 801 may be created as map data that monotonously decreases linearly in an angle range of 0 deg to 360 deg.

  Next, a method for obtaining the absolute angle of the rotating body 72 using the conversion table 46 created through the above-described procedure will be described. The cosine signal 701 and the sin signal 702 output from the magnetic sensors 41A and 41B are subjected to amplitude adjustment and offset correction by the amplifiers 44A and 44B, and further sampled at a constant angular interval by the A / D converters 45A and 45B. , And supplied to the angle calculation circuit 43. The angle calculation circuit 43 searches the conversion table 46 for a cos signal value 802 that matches the read sampling data of the cos signal 701, and reads a linear output value 801 corresponding to the searched cos signal value 802 from the conversion table 46. Further, the angle calculation circuit 43 searches the conversion table 46 for a sin signal value 803 that matches the sampling data of the read sin signal 702, and converts the linear output value 801 corresponding to the searched sin signal read value 803 to the conversion table 46. Read from. The linear output value 801 read out in this way is supplied to the arithmetic circuit 50 as a signal indicating the absolute angle of the rotating body 72.

  At this time, as shown in FIG. 27, the angle calculation circuit 43 obtains sampling data within an angle range of ± 45 deg with respect to the angle when the signal waveform of the cos signal 701 and the sin signal 702 takes an intermediate value. It is preferable to read. For example, in the angle range of 0 deg to 45 deg, since the amplitude change amount of the detection signal is larger in the sin signal 702 than in the cos signal 701, the sampling data of the sin signal 702 is read. In the angle range of 45eg to 135 deg, the cos signal 701 has a larger amplitude change amount of the detection signal than the sin signal 702. Therefore, the sampling data of the cos signal 701 is read. In the angle range of 135 eg to 225 deg, the sin signal 702 has a larger amplitude change amount of the detection signal than the cos signal 701. Therefore, the sampling data of the sin signal 702 is read. In this way, by reading the sampling data near the intermediate value with a large amplitude change amount rather than the sampling data near the peak of the signal waveform with a small amplitude change amount, it is possible to suppress variations in detection errors and to withstand noise. Can be increased.

  Note that the method of detecting the absolute angle using the conversion table 46 can also be applied to the input shaft angle detection unit 20, so the principle thereof will be briefly described (this method can also be applied to a modified example described later). ). For example, in FIG. 20, the difference signal between the sin signal obtained by differentially calculating the detection signals from the magnetic sensors 21A and 21B by the differential arithmetic circuit 22A and the detection signal from the magnetic sensors 21C and 21D by the differential arithmetic circuit 22B. The cos signal obtained by the dynamic calculation has a phase difference (electrical angle) of 90 deg. If the conversion table 46 is mounted in the angle calculation circuit 23 in advance, the angle calculation circuit 23 samples and reads the sin signal and the cosine signal output from the differential operation circuits 22A and 22B, and reads the read sampling. The absolute angle of the rotator 71 corresponding to the data can be searched from the conversion table, and the searched absolute angle can be output. Here, it is preferable to read sampling data in an angle range of ± 45 deg with respect to an angle when the signal waveform takes an intermediate value among the sine signal and the cosine signal output from the differential arithmetic circuits 22A and 22B.

The following configuration can be applied as a modification of the present embodiment.
(1) As a configuration of the input shaft angle detection unit 20, two magnetic sensors 21 </ b> A and 21 </ b> B are arranged equidistant from the rotation center P with a phase difference (mechanical angle) of 90 deg with respect to the rotation center P of the rotating body 71. In addition, the conversion table 46 is mounted in the angle calculation circuit 23, and the output shaft angle detection unit 40 is configured by arranging two magnetic sensors 41A and 41B diagonally at an equal distance with respect to the rotation center Q of the rotating body 72. The two magnetic sensors 41C and 41D are diagonally arranged at an equal distance with respect to the rotation center Q of the rotating body 72 (however, the straight line connecting the two magnetic sensors 41A and 41B and the two magnetic sensors 41C and 41D are connected). It shall be orthogonal to the straight line).
(2) As a configuration of the input shaft angle detection unit 20, the two magnetic sensors 21 </ b> A and 21 </ b> B are arranged equidistant from the rotation center P with a phase difference (mechanical angle) of 90 deg with respect to the rotation center P of the rotating body 71. In addition, the conversion table 46 is mounted in the angle calculation circuit 23, and the output shaft angle detection unit 40 is configured such that the two magnetic sensors 41A and 41B are provided with a phase difference (mechanical angle) of 90 deg from the rotation center Q of the rotating body 72 ) And equidistant from the rotation center Q, and the conversion table 46 is mounted in the angle calculation circuit 43.

  The present invention is not limited to the above-described first and second embodiments, and various modifications are possible. Even when the first and second embodiments are combined, the same effect can be obtained. .

  The torque detection device according to the present invention can be used for detection of steering torque of a steering shaft.

DESCRIPTION OF SYMBOLS 10 ... Steering sensor 20 ... Input shaft angle detection part 30 ... Rotation speed detection part 40 ... Output shaft angle detection part 60 ... Steering shaft 61 ... Input shaft 62 ... Output shaft 63 ... Torsion bar 71, 72 ... Rotating body 21A, 21B, 21C, 21D, 31, 41A, 41B, 41C, 41D ... magnetic sensors 22A, 22B, 42A, 42B ... differential operation circuits 23, 43 ... angle calculation circuits 50 ... operation circuits

Claims (9)

A torque detection device for detecting a shaft torque of a rotary shaft having an input shaft and an output shaft connected to each other via an elastic member,
A first rotating body fixed to the input shaft, wherein a distance between two points where a straight line passing through a rotation center of the first rotating body intersects an outer periphery of the first rotating body is constant; A rotating body,
A first magnetic sensor disposed near an outer periphery of the first rotating body, the outer periphery of the first rotating body periodically changing with the rotation of the first rotating body; A first magnetic sensor for detecting a magnetic field change corresponding to a change in the first distance between the magnetic sensor and outputting a first detection signal;
On the straight line connecting the first magnetic sensor and the rotation center of the first rotating body, the first magnetic sensor is a distance equal to the distance between the rotation center of the first rotating body and the first magnetic sensor. A second magnetic sensor disposed at a position away from the rotation center of the rotating body of the first rotating body, the outer periphery of the first rotating body periodically changing with the rotation of the first rotating body, and the first A second magnetic sensor that detects a magnetic field change corresponding to a change in a second distance between the two magnetic sensors and outputs a second detection signal;
First differential operation means for performing a differential operation between the first detection signal and the second detection signal;
First angle calculation means for calculating an absolute angle of the input shaft based on a result of the differential calculation by the first differential calculation means;
A second rotating body fixed to the output shaft, wherein a distance between two points where a straight line passing through a rotation center of the second rotating body intersects an outer periphery of the second rotating body is constant; Two rotating bodies,
A third magnetic sensor disposed near an outer periphery of the second rotating body, the outer periphery of the second rotating body periodically changing with the rotation of the second rotating body and the third magnetic sensor; A third magnetic sensor for detecting a magnetic field change corresponding to a change in the third distance between the magnetic sensor and outputting a third detection signal;
On the straight line connecting the third magnetic sensor and the rotation center of the second rotating body, the second magnetic body is equal to the distance between the rotation center of the second rotating body and the third magnetic sensor. A fourth magnetic sensor disposed at a position away from the rotation center of the rotating body of the second rotating body, the outer periphery of the second rotating body periodically changing with the rotation of the second rotating body, and the first A fourth magnetic sensor for detecting a magnetic field change corresponding to a change in the fourth distance between the four magnetic sensors and outputting a fourth detection signal;
Second differential operation means for performing a differential operation on the third detection signal and the fourth detection signal;
Second angle calculating means for calculating an absolute angle of the output shaft based on the result of the differential calculation by the second differential calculating means;
Computing means for computing the shaft torque based on the difference between the absolute angle of the input shaft and the absolute angle of the output shaft;
A torque detection device comprising: A torque detection device for detecting a shaft torque of a rotary shaft having an input shaft and an output shaft connected to each other via an elastic member,
A first rotating body fixed to the input shaft, wherein a distance between two points where a straight line passing through a rotation center of the first rotating body intersects an outer periphery of the first rotating body is constant; A rotating body,
A first magnetic sensor disposed near an outer periphery of the first rotating body, the outer periphery of the first rotating body periodically changing with the rotation of the first rotating body; A first magnetic sensor for detecting a magnetic field change corresponding to a change in the first distance between the magnetic sensor and outputting a first detection signal;
On the straight line connecting the first magnetic sensor and the rotation center of the first rotating body, the first magnetic sensor is a distance equal to the distance between the rotation center of the first rotating body and the first magnetic sensor. A second magnetic sensor disposed at a position away from the rotation center of the rotating body of the first rotating body, the outer periphery of the first rotating body periodically changing with the rotation of the first rotating body, and the first A second magnetic sensor that detects a magnetic field change corresponding to a change in a second distance between the two magnetic sensors and outputs a second detection signal;
First differential operation means for performing a differential operation between the first detection signal and the second detection signal;
First angle calculation means for calculating an absolute angle of the input shaft based on a result of the differential calculation by the first differential calculation means;
A second rotating body fixed to the output shaft, wherein a distance between two points where a straight line passing through a rotation center of the second rotating body intersects an outer periphery of the second rotating body is constant; Two rotating bodies,
A third magnetic sensor disposed near an outer periphery of the second rotating body, the outer periphery of the second rotating body periodically changing with the rotation of the second rotating body and the third magnetic sensor; A third magnetic sensor for detecting a magnetic field change corresponding to a change in the third distance between the magnetic sensor and outputting a third detection signal;
A distance equal to the distance between the rotation center of the second rotating body and the third magnetic sensor on a straight line orthogonal to the straight line connecting the third magnetic sensor and the rotation center of the second rotating body. A fourth magnetic sensor disposed only at a position away from the rotation center of the second rotating body, wherein the second rotating body periodically changes with the rotation of the second rotating body. A fourth magnetic sensor for detecting a magnetic field change corresponding to a change in a fourth distance between the outer circumference and the fourth magnetic sensor and outputting a fourth detection signal;
A conversion table for storing the absolute angle of the output shaft corresponding to the third and fourth detection signals;
A second angle calculating means for comparing the third and fourth detection signals output from the third and fourth magnetic sensors with the conversion table and outputting an absolute angle of the output shaft;
Computing means for computing the shaft torque based on the difference between the absolute angle of the input shaft and the absolute angle of the output shaft;
A torque detection device comprising: A torque detection device for detecting a shaft torque of a rotary shaft having an input shaft and an output shaft connected to each other via an elastic member,
A first rotating body fixed to the input shaft, wherein a distance between two points where a straight line passing through a rotation center of the first rotating body intersects an outer periphery of the first rotating body is constant; A rotating body,
A first magnetic sensor disposed near an outer periphery of the first rotating body, the outer periphery of the first rotating body periodically changing with the rotation of the first rotating body; A first magnetic sensor for detecting a magnetic field change corresponding to a change in the first distance between the magnetic sensor and outputting a first detection signal;
A distance equal to a distance between the rotation center of the first rotating body and the first magnetic sensor on a straight line orthogonal to a straight line connecting the first magnetic sensor and the rotation center of the first rotating body. A second magnetic sensor disposed at a position away from the center of rotation of the first rotating body, wherein the first rotating body periodically changes with the rotation of the first rotating body. A second magnetic sensor for detecting a magnetic field change corresponding to a change in a second distance between the outer periphery and the second magnetic sensor and outputting a second detection signal;
A conversion table for storing the absolute angle of the input shaft corresponding to the first and second detection signals;
A first angle calculation means for comparing the first and second detection signals output from the first and second magnetic sensors with the conversion table and outputting an absolute angle of the input shaft;
A second rotating body fixed to the output shaft, wherein a distance between two points where a straight line passing through a rotation center of the second rotating body intersects an outer periphery of the second rotating body is constant; Two rotating bodies,
A third magnetic sensor disposed near an outer periphery of the second rotating body, the outer periphery of the second rotating body periodically changing with the rotation of the second rotating body and the third magnetic sensor; A third magnetic sensor for detecting a magnetic field change corresponding to a change in the third distance between the magnetic sensor and outputting a third detection signal;
On the straight line connecting the third magnetic sensor and the rotation center of the second rotating body, the second magnetic body is equal to the distance between the rotation center of the second rotating body and the third magnetic sensor. A fourth magnetic sensor disposed at a position away from the rotation center of the rotating body of the second rotating body, the outer periphery of the second rotating body periodically changing with the rotation of the second rotating body, and the first A fourth magnetic sensor for detecting a magnetic field change corresponding to a change in the fourth distance between the four magnetic sensors and outputting a fourth detection signal;
A first differential operation means for performing a differential operation on the third detection signal and the fourth detection signal;
Second angle calculating means for calculating an absolute angle of the output shaft based on the result of the differential calculation by the first differential calculating means;
Computing means for computing the shaft torque based on the difference between the absolute angle of the input shaft and the absolute angle of the output shaft;
A torque detection device comprising: A torque detection device for detecting a shaft torque of a rotary shaft having an input shaft and an output shaft connected to each other via an elastic member,
A first rotating body fixed to the input shaft, wherein a distance between two points where a straight line passing through a rotation center of the first rotating body intersects an outer periphery of the first rotating body is constant; A rotating body,
A first magnetic sensor disposed near an outer periphery of the first rotating body, the outer periphery of the first rotating body periodically changing with the rotation of the first rotating body; A first magnetic sensor for detecting a magnetic field change corresponding to a change in the first distance between the magnetic sensor and outputting a first detection signal;
A distance equal to a distance between the rotation center of the first rotating body and the first magnetic sensor on a straight line orthogonal to a straight line connecting the first magnetic sensor and the rotation center of the first rotating body. A second magnetic sensor disposed at a position away from the center of rotation of the first rotating body, wherein the first rotating body periodically changes with the rotation of the first rotating body. A second magnetic sensor for detecting a magnetic field change corresponding to a change in a second distance between the outer periphery and the second magnetic sensor and outputting a second detection signal;
A first conversion table storing absolute angles of the input shafts corresponding to the first and second detection signals;
A first angle calculation that compares the first and second detection signals output from the first and second magnetic sensors with the first conversion table and outputs an absolute angle of the input shaft. Means,
A second rotating body fixed to the output shaft, wherein a distance between two points where a straight line passing through a rotation center of the second rotating body intersects an outer periphery of the second rotating body is constant; Two rotating bodies,
A third magnetic sensor disposed near an outer periphery of the second rotating body, the outer periphery of the second rotating body periodically changing with the rotation of the second rotating body and the third magnetic sensor; A third magnetic sensor for detecting a magnetic field change corresponding to a change in the third distance between the magnetic sensor and outputting a third detection signal;
A distance equal to the distance between the rotation center of the second rotating body and the third magnetic sensor on a straight line orthogonal to the straight line connecting the third magnetic sensor and the rotation center of the second rotating body. A fourth magnetic sensor disposed only at a position away from the rotation center of the second rotating body, wherein the second rotating body periodically changes with the rotation of the second rotating body. A fourth magnetic sensor for detecting a magnetic field change corresponding to a change in a fourth distance between the outer circumference and the fourth magnetic sensor and outputting a fourth detection signal;
A second conversion table for storing the absolute angle of the output shaft corresponding to the third and fourth detection signals;
A second angle calculation that compares the third and fourth detection signals output from the third and fourth magnetic sensors with the second conversion table and outputs an absolute angle of the output shaft. Means,
Computing means for computing the shaft torque based on the difference between the absolute angle of the input shaft and the absolute angle of the output shaft;
A torque detection device comprising: The torque detection device according to any one of claims 1 to 4,
The shape of the first rotating body projected onto the plane of rotation is a torque detection device having a shape in which two different semi-ellipses are combined. The torque detection device according to any one of claims 1 to 4,
The shape of the second rotating body projected on the plane of rotation has a shape in which two different semi-ellipses are combined. The torque detection device according to claim 2,
The third and fourth detection signals are substantially sinusoidal signals,
The second angle calculation means compares the conversion table with a detection signal in an angle range of ± 45 deg with respect to an angle at which the detection signal takes an intermediate value among the third and fourth detection signals. And a torque detector for outputting an absolute angle of the output shaft. The torque detection device according to claim 3,
The first and second detection signals are substantially sinusoidal signals,
The first angle calculation means compares the conversion table with a detection signal in an angle range of ± 45 deg with respect to an angle at which the detection signal takes an intermediate value among the first and second detection signals. And a torque detector for outputting an absolute angle of the input shaft. The torque detection device according to claim 3,
The first, second, third, and fourth detection signals are substantially sinusoidal signals,
The first angle calculation means includes a detection signal within an angle range of ± 45 deg with respect to an angle at which the detection signal takes an intermediate value among the first and second detection signals, and the first conversion table, And output the absolute angle of the input shaft,
The second angle calculation means includes a detection signal within an angle range of ± 45 deg with respect to an angle at which the detection signal takes an intermediate value among the third and fourth detection signals, and the second conversion table. And a torque detector that outputs an absolute angle of the output shaft.

Images