JP2004045137A - Torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-resolution and high-precision torque sensor at low cost. <P>SOLUTION: The sensor outputs a first alternating signal whose phase changes according to changes in the rotation angle of a first shaft, and a second alternating signal whose phase changes according to changes in the rotation angle of a second shaft capable of rotating elastically with respect to the first shaft. A phase difference correspondence signal whose waveform changes according to changes in the phase difference between the first alternating signal and second alternating signal is output. A value corresponding to the torque transferred by the first and second shafts is derived from the phase difference correspondence signal. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a torque sensor used for detecting a steering torque in, for example, an electric power steering device.
[0002]
[Prior art]
A first shaft, a second shaft elastically rotatable relative to the first shaft, a first resolver detecting a rotation angle of the first shaft, and a second resolver detecting a rotation angle of the second shaft. A torque sensor including two resolvers is known. From the difference between the detected rotation angle of the first shaft by the first resolver and the detected rotation angle of the second shaft by the second resolver, the transmission torque by both shafts is determined.
[0003]
[Problems to be solved by the invention]
When a shaft rotation angle detected by the resolver is θ, when a sine wave signal is input to the rotor winding of the resolver, a signal proportional to sin θ and a signal proportional to cos θ are output from the two-phase stator winding. From tan ^-1 The rotation angle θ can be obtained by performing the calculation of (sin θ / cos θ) using a computer.
[0004]
However, there is a limit to the resolution when capturing the output values of the sine wave signal and the cosine wave signal by the computer, so the resolution of the torque sensor is limited, and as the resolution increases, the load for signal processing increases. Become. Further, since the output values of the sine wave signal and the cosine wave signal change non-linearly with respect to the rotation angle θ, improvement in torque detection accuracy is hindered.
An object of the present invention is to provide a torque sensor that can solve the above problems.
[0005]
[Means for Solving the Problems]
A torque sensor according to the present invention includes a first shaft, a second shaft elastically relatively rotatable with respect to the first shaft, and a first alternating shaft whose phase changes in response to a change in the rotation angle of the first shaft. First alternating signal output means for outputting a signal; second alternating signal output means for outputting a second alternating signal whose phase changes in response to a change in the rotation angle of the second shaft; An output signal processing section for outputting a phase difference corresponding signal whose waveform changes in accordance with a change in the phase difference between the two alternating signals, and corresponding to the transmission torque by the first and second shafts from the phase difference corresponding signal. Is determined.
According to the present invention, the phase change of the first alternating signal corresponds to a change in the rotation angle of the first shaft, and the phase change of the second alternating signal corresponds to a change in the rotation angle of the second shaft. The phase difference between the second alternating signal corresponds to the rotation angle difference between the first shaft and the second shaft. Since the waveform of the phase difference corresponding signal changes in accordance with the change in the rotation angle difference, it can be used as a signal corresponding to the torque transmitted by the first and second shafts. That is, the rotation angle difference corresponding to the transmission torque can be directly obtained without separately detecting the rotation angle of the first shaft and the rotation angle of the second shaft. Therefore, it is not necessary to take in the output values of the sine wave signal and the cosine wave signal in order to obtain the torque unlike the related art, so that the load for signal processing can be reduced and the non-linear element can be eliminated.
[0006]
The first alternating signal output means includes a first detector and a first signal processing unit. The first detector has a coefficient of KE, an angular frequency of the excitation signal of ω, a time of t, and θ of the first shaft. As a rotation angle, a first sine amplitude signal represented by KE sin (ωt) sin θ and a first cosine amplitude signal represented by KE sin (ωt) cos θ are output, and the first signal processing unit outputs the first sine amplitude signal. A first phase shift circuit that shifts the amplitude signal by π / 2 to obtain a first phase shift signal represented by KE sin (ωt + π / 2) sin θ, and converts the first phase shift signal and the first cosine amplitude signal. A first adding circuit for adding the first alternating signal represented by KEsin (ωt + θ), the second alternating signal output means including a second detector and a second signal processing unit; 2 The detector uses KE as a coefficient and ω as the angular circumference of the excitation signal. The second sine amplitude signal represented by KE sin (ωt) sin (θ + Δθ) and the second cosine represented by KE sin (ωt) cos (θ + Δθ), where the number and t are time and θ + Δθ is the rotation angle of the second shaft. An amplitude signal is output, and the second signal processing unit shifts the second sine amplitude signal by π / 2 to obtain a second phase shift signal represented by KE sin (ωt + π / 2) sin (θ + Δθ). It is preferable to have a second phase shift circuit and a second adder circuit that adds the second phase shift signal and the second cosine amplitude signal to obtain the second alternating signal represented by KE sin (ωt + θ + Δθ).
Thus, by inputting the sine wave signals to the first and second detectors, the first and second alternating signals whose phases change in response to the change in the rotation angles of the first and second shafts are converted to a resolver or the like. And output using general-purpose components such as a detector, a phase shift circuit, and an adder circuit.
[0007]
The first alternating signal output means outputs the first alternating signal represented by KE sin (ωt + θ), where KE is a coefficient, ω is the angular frequency of the excitation signal, t is time, and θ is the rotation angle of the first shaft. The second alternating signal output means is represented by KE sin (ωt + θ + Δθ), where KE is a coefficient, ω is the angular frequency of the excitation signal, t is time, θ + Δθ is the rotation angle of the second shaft. Preferably, a second detector for outputting the second alternating signal is provided.
By inputting the sine wave signal and the cosine wave signal to the first and second detectors, the first and second alternating signals whose phases change in response to changes in the rotation angles of the first and second shafts. Can be output using a detector such as a resolver, which is a general-purpose component.
[0008]
The first detector and the second detector are arranged such that a phase difference between the first alternating signal and the second alternating signal becomes π / 2 when the torque transmitted by the first and second shafts is zero. A first logic signal conversion circuit configured to convert the first alternating signal into a first logic signal; and a second logic signal conversion circuit configured to convert the second alternating signal into a second logic signal. It is preferable to include a circuit and a PWM processing circuit that outputs a PWM signal corresponding to an exclusive OR of the first logic signal and the second logic signal as the phase difference corresponding signal.
Thus, a PWM signal whose pulse width changes in accordance with a change in the phase difference between the first alternating signal and the second alternating signal can be output as a phase difference corresponding signal. In addition, the PWM signal can be output using general-purpose components such as a circuit that converts an alternating signal into a logic signal and a circuit that generates a signal corresponding to an exclusive OR of the logic signal.
[0009]
A first logic signal conversion circuit for converting the first alternating signal into a first logic signal; a second logic signal conversion circuit for converting the second alternating signal into a second logic signal; A detecting circuit for detecting a rising point of the first logic signal, a detecting circuit for detecting a falling point of the second logic signal, and determining whether one of the rising point of the first logic signal and the falling point of the second logic signal is the rising point And a PWM processing circuit that outputs a PWM signal corresponding to the falling point of the other as the phase difference corresponding signal.
Thus, a PWM signal whose pulse width changes in accordance with a change in the phase difference between the first alternating signal and the second alternating signal can be output as a phase difference corresponding signal. A circuit for converting the PWM signal from an alternating signal to a logic signal; a circuit for detecting a rising time and a falling time of the logic signal; a rising time and a falling time corresponding to the rising time and the falling time of the logic signal; The signal having the time point can be output using a general-purpose component such as an SR flip-flop.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The torque sensor 1 of the present embodiment shown in FIG. 1 is used for detecting a torque transmitted by a steering shaft of an electric power steering device, and comprises a first cylindrical shaft 3 and a second cylindrical tube constituting the steering shaft. It has a shaft 4. The rotation of the unillustrated steering wheel connected to the first shaft 3 is transmitted to the wheels via an unillustrated steering gear connected to the second shaft 4, so that the steering angle of the vehicle changes.
[0011]
A torsion bar (elastic member) 5 is inserted into the first shaft 3 and the second shaft 4. One end of the torsion bar 5 is connected to the first shaft 3 by pins or serrations, and the other end is connected to the second shaft 4 by pins or serrations, so that the first shaft 3 and the second shaft 4 are mutually opposed. It is relatively rotatable elastically around a coaxial center. The first shaft 3 is supported by a sensor housing 7 via a bearing 6, and the second shaft 4 is supported via a bearing 8 by an annular resolver retainer 9 press-fitted into the sensor housing 7. A first resolver (first detector) 21 and a second resolver (second detector) 22 are covered by the sensor housing 7.
[0012]
The first resolver 21 has a first resolver rotor 21a fitted around the outer periphery of the first shaft 3 so as to rotate together therewith, and an annular first resolver stator 21b that covers the first resolver rotor 21a. In the present embodiment, the first shaft 3 is press-fitted into the first resolver rotor 21a, so that the first resolver rotor 21a and the first shaft 3 rotate together. The second resolver 22 has a second resolver rotor 22a fitted around the outer periphery of the second shaft 4 so as to rotate together therewith, and an annular second resolver stator 22b that covers the second resolver rotor 22a. In the present embodiment, the second shaft 4 is press-fitted into the second resolver rotor 22a, so that the second resolver rotor 22a and the second shaft 4 rotate together. A cylindrical spacer 23 is arranged between the first resolver stator 21b and the second resolver stator 22b.
[0013]
The first resolver stator 21b, the second resolver stator 22b, and the spacer 23 are fitted to the inner periphery of the sensor housing 7 via the radial clearance of the first and second shafts 3, 4 from the shaft axis direction. The resolver stators 21b and 22b and the spacer 23 are fixed to the sensor housing 7 by being sandwiched between the resolver retainer 9 and a step 7a formed on the inner periphery of the sensor housing 7. An annular magnetic shielding portion 24 extending inward from the inner periphery of the spacer 23 is formed integrally with the spacer 23 by a magnetic shielding material. The magnetic shielding unit 24 performs magnetic shielding between the first resolver 21 and the second resolver 22.
[0014]
The first resolver 21 receives the excitation signal from a winding (not shown) provided on the first resolver rotor 21a, and thereby changes the two-phase winding (not shown) provided on the first resolver stator 21b from the first resolver. A sine amplitude signal and a first cosine amplitude signal are output. That is, assuming that the excitation signal is Esin (ωt) and θ is the rotation angle of the first shaft 3, the first sine amplitude signal is represented by KEsin (ωt) sinθ, and the first cosine amplitude signal is represented by KEsin (ωt) cosθ. Is done. Here, E is the signal amplitude, K is the transformation ratio, ω is the excitation angular frequency, and t is the time.
[0015]
The second resolver 22 receives the excitation signal from a winding (not shown) provided on the second resolver rotor 22a, and thereby the second resolver 22 receives a second phase signal from the two-phase winding (not shown) provided on the second resolver stator 22b. A sine amplitude signal and a second cosine amplitude signal are output. Assuming that the excitation signal is Esin (ωt) and θ + Δθ is the rotation angle of the second shaft 4, the second sine amplitude signal is represented by KEsin (ωt) sin (θ + Δθ), and the second cosine amplitude signal is KEsin (ωt) cos ( θ + Δθ).
[0016]
Output signals of both resolvers 21 and 22 are input via a signal cable 25 to a control device 20 provided outside the sensor housing 7 and shown in FIG. The control device 20 has a first signal processing unit 26, a second signal processing unit 27, and an output signal processing unit 28.
[0017]
The first signal processing unit 26 has a first phase shift circuit 26a and a first addition circuit 26b. The first phase shift circuit 26a shifts the phase of the first sine amplitude signal sent from the first resolver 21 via the input interface 20a by π / 2 to obtain the first sine amplitude signal represented by KE sin (ωt + π / 2) sin θ. This is a phase shift signal. The first adder circuit 26b adds the first phase shift signal and the first cosine amplitude signal sent from the first resolver 21 via the input interface 20b to obtain KE sin (ωt + π / 2) sin θ + KE sin (ωt ) Cos θ = KEcos (ωt) sin θ + KE sin (ωt) It is assumed that the first alternating signal is represented by cos θ = KE sin (ωt + θ). That is, the first resolver 21 and the first signal processing unit 26 constitute a first alternating signal output unit that outputs a first alternating signal whose phase changes in response to a change in the rotation angle θ of the first shaft 3.
[0018]
The second signal processing unit 27 has a second phase shift circuit 27a and a second addition circuit 27b. The second phase shift circuit 27a shifts the second sine amplitude signal sent from the second resolver 22 via the input interface 20c by π / 2, and is represented by KE sin (ωt + π / 2) sin (θ + Δθ). As a second phase shift signal. The second adder circuit 27b adds the second phase shift signal and the second cosine amplitude signal sent from the second resolver 22 via the input interface 20d to obtain KE sin (ωt + π / 2) sin (θ + Δθ). ) + KEsin (ωt) cos (θ + Δθ) = KEcos (ωt) sin (θ + Δθ) + KEsin (ωt) cos (θ + Δθ) = KEsin (ωt + θ + Δθ). That is, the second resolver 22 and the second signal processing unit 27 constitute a second alternating signal output unit that outputs a second alternating signal whose phase changes according to the change of the rotation angle θ + Δθ of the second shaft 4.
[0019]
When the transmission torque by the first and second shafts 3 and 4 is zero, the phase difference between the first and second alternating signals is π / 2, that is, Δθ = 0. The first resolver 21 and the second resolver 22 are disposed relative to each other.
[0020]
The output signal processing unit 28 has a first logic signal conversion circuit 28a, a second logic signal conversion circuit 28b, and a PWM processing circuit 28c.
[0021]
The first logic signal conversion circuit 28a converts the first alternating signal into a first logic signal. The first logic signal is represented by a binary square wave of H and L having the same frequency as the first alternating signal. The second logic signal conversion circuit 28b converts the second alternating signal into a second logic signal. The second logic signal is represented by a binary square wave of H and L having the same frequency as the second alternating signal. The phase difference between the first alternating signal and the second alternating signal is made equal to the phase difference between the first logic signal and the second logic signal.
[0022]
The PWM processing circuit 28c outputs a PWM signal corresponding to an exclusive OR (EXOR) of the first logic signal and the second logic signal. In the present embodiment, the PWM duty obtained from the PWM signal is used as a value corresponding to the torque transmitted by the first and second shafts 3, 4. That is, FIG. 3A shows the first logic signal S1, the second logic signal S2, and the PWM signal S3 output from the PWM processing circuit 28c when the transmission torque is zero. In this case, the phase difference between the first logic signal S1 and the second logic signal S2 is π / 2, and the PWM duty is 50%. FIG. 3B shows the first logic signal S1, the second logic signal S2, and the PWM signal S3 when torque in one direction is transmitted by the first and second shafts 3, 4. In this case, the phase difference between the first logic signal S1 and the second logic signal S2 is π / 2 + Δθ (Δθ> 0), and the PWM duty becomes larger than 50% as the transmission torque increases. FIG. 3 (3) shows the first logic signal S1, the second logic signal S2, and the PWM signal S3 when torque in the other direction is transmitted by the first and second shafts 3, 4. In this case, the phase difference between the first logic signal S1 and the second logic signal S2 is π / 2 + Δθ (Δθ <0), and as the transmission torque increases, the PWM duty becomes smaller than 50%.
[0023]
Since the phase change of the first alternation signal corresponds to the change in the rotation angle of the first shaft 3 and the phase change of the second alternation signal corresponds to the change in the rotation angle of the second shaft 4, the first change signal and the second change signal Corresponds to the transmission torque corresponding to the rotation angle difference between the first shaft 3 and the second shaft 4. Since the phase difference between the first alternating signal and the second alternating signal is equal to the phase difference between the first logic signal S1 and the second logic signal S2, an exclusive OR of the first logic signal S1 and the second logic signal S2 is obtained. The corresponding PWM signal S3 is a phase difference corresponding signal whose waveform changes by changing the pulse width according to the change of the phase difference between the first alternating signal and the second alternating signal. The PWM signal S3 is used as a signal corresponding to the torque transmitted by the first and second shafts 3, 4. In the present embodiment, a steering assist force corresponding to the transmission torque of the first and second shafts 3 and 4 is calculated from a predetermined relationship between the PWM duty and the steering assist force, and the calculated steering assist force is calculated. Is controlled to generate the steering assist force (not shown). As the steering assist force generating electric actuator, a known actuator can be used. For example, an actuator that transmits a steering assist force generated by an electric motor to a steering shaft via a reduction gear mechanism can be used.
[0024]
According to the torque sensor 1 of the above embodiment, the rotation angle difference corresponding to the transmission torque can be directly obtained without separately detecting the rotation angle of the first shaft 3 and the rotation angle of the second shaft 4. it can. Therefore, it is not necessary to take in the output values of the sine wave signal and the cosine wave signal in order to obtain the torque unlike the related art, so that the load for signal processing can be reduced and the non-linear element can be eliminated. The first and second alternating signals can be output using general-purpose components such as resolvers 21 and 22, phase shift circuits 26a and 27a, and adding circuits 26b and 27b. Further, the first alternating signal and the second alternating signal can be output. Logic signal conversion circuits 28a and 28b for converting an alternating signal into a logic signal from a PWM signal whose pulse width changes in accordance with a change in phase difference between the PWM signal and a signal corresponding to an exclusive OR of the logic signal It can be output using a general-purpose component called a PWM processing circuit 28c.
[0025]
(1), (2), and (3) of FIGS. 4 and 5 show modified examples of the control device 20. The difference from the above-described embodiment is that the first resolver 21 is configured such that the phase difference between the first alternating signal and the second alternating signal becomes zero when the torque transmitted by the first and second shafts 3 and 4 is zero. And the second resolver 22 are disposed relative to each other. The output signal processing unit 28 detects a rising point detection circuit 28d of the first logic signal output from the first logic signal conversion circuit 28a and a falling point detection of the second logic signal output from the second logic signal conversion circuit 28b. It has a circuit 28e. As the PWM processing circuit 28c ', an SR (set / reset) flip-flop is provided instead of a circuit that outputs a PWM signal corresponding to the exclusive OR of the first logic signal and the second logic signal. The detection signal at the rising point of the first logic signal is input to the S terminal of the flip-flop constituting the PWM processing circuit 28c ', and the detection signal at the falling point of the second logic signal is input to the R terminal. As a result, a PWM signal is output from the PWM processing circuit 28c '. The PWM duty of the PWM signal corresponds to the torque transmitted by the first and second shafts 3, 4.
[0026]
That is, FIG. 5A shows the first logic signal S1, the second logic signal S2, the PWM signal S3 output from the PWM processing circuit 28c ', the rising time detection signal S4, and the falling time detection when the transmission torque is zero. The signal S5 is shown. In this case, Δθ = 0, the phase difference between the first logic signal and the second logic signal becomes zero, and the time t1 from the rising point of the first logic signal to the falling point of the second logic signal is the second logic signal. Is equal to the time t2 from the falling point of the first logic signal to the rising point of the first logic signal, so that the PWM duty becomes 50%. FIG. 5B shows the first logic signal S1, the second logic signal S2, and the PWM signal S3 when torque in one direction is transmitted by the first and second shafts 3, 4. In this case, the phase difference between the first logic signal and the second logic signal is Δθ (> 0), and the time t1 from the rising point of the first logic signal to the falling point of the second logic signal is equal to the time t1 of the second logic signal. Since it is longer than the time t2 from the falling point to the rising point of the first logic signal, the PWM duty increases from 50% as the transmission torque increases. FIG. 5 (3) shows the first logic signal S1, the second logic signal S2, and the PWM signal S3 when torque in the other direction is transmitted by the first and second shafts 3, 4. In this case, the phase difference between the first logic signal and the second logic signal is Δθ (<0), and the time t1 from the rising point of the first logic signal to the falling point of the second logic signal is the time t1 of the second logic signal. Since the time is shorter than the time t2 from the falling point to the rising point of the first logic signal, the PWM duty decreases from 50% as the transmission torque increases. Accordingly, logic signal conversion circuits 28a and 28b for converting a PWM signal whose pulse width changes according to a change in phase difference between the first alternating signal and the second alternating signal into an alternating signal into a logic signal; General-purpose parts such as circuits 28d and 28e for detecting a rising point and a falling point of a signal, and SR flip-flops for generating a signal having a rising point and a falling point according to the rising point and the falling point of a logic signal. Can be used for output. Other parts are the same as those of the above embodiment, and the same parts are denoted by the same reference numerals. It should be noted that even if the detection signal at the falling point of the second logic signal is input to the S terminal of the SR flip-flop constituting the PWM processing circuit 28c 'and the detection signal at the rising point of the first logic signal is input to the R terminal, Good. As a result, the PWM processing circuit 28c 'converts the PWM signal corresponding to the rising time and the other of the falling time of the first logic signal and the falling time of the second logic signal into the PWM signal corresponding to the phase difference. Output as a signal.
[0027]
The present invention is not limited to the above-described embodiments and modified examples.
For example, in the above-described embodiment and the modified example, the first and second phase shift signals obtained by phase-shifting the first and second sine amplitude signals output from the first and second resolvers 21 and 22 are respectively converted into first and second phase shift signals. Although the first and second alternating signals are output by adding to the cosine amplitude signal, the first and second alternating signals may be directly output from the first and second resolvers 21 and 22. That is, by inputting the excitation signal represented by Esin (ωt) and Ecos (ωt) to the two-phase winding of the first resolver stator 21b, the excitation signal is represented by KEsin (ωt + θ) from the winding of the first resolver rotor 21a. By outputting the first alternating signal and inputting the excitation signal represented by Esin (ωt) and Ecos (ωt) to the two-phase winding of the second resolver stator 22b, KE sin ( (ωt + θ + Δθ) may be output. In this case, the first signal processing unit 26 and the second signal processing unit 27 in the above-described embodiment are not required as the alternating signal output units. As a result, the first and second alternating signals can be output using the resolvers 21 and 22, which are general-purpose components, and the configuration can be further simplified.
[0028]
Further, as shown in FIG. 6, the first phase shift circuit 26a and the second phase shift circuit 27a may be provided with phase shift amount adjusting means. That is, in each of the phase shift circuits 26a and 27a, the sine amplitude signal is input to the inverting input terminal of the operational amplifier OP via the resistor R1, and is input to the non-inverting input terminal of the operational amplifier OP via the capacitor C. The output terminal of the amplifier OP is grounded via a resistor R2, the phase shift signal output from the operational amplifier OP is negatively fed back via a resistor R3, and the capacitor C and the operational amplifier OP are connected via a variable resistor R4. Grounded. By changing the resistance value of the variable resistor R4, the amount of phase shift of the sine amplitude signal can be adjusted. This makes it possible to eliminate an error in the amount of phase shift when the first or second sine amplitude signal is phase-shifted by π / 2.
[0029]
Further, in the above embodiment, the PWM duty of the PWM signal output from the output signal processing unit 28 is used as a value corresponding to the transmission torque, but the time integral value of the PWM signal may be used as a value corresponding to the transmission torque. Good.
[0030]
【The invention's effect】
According to the present invention, a high-precision torque sensor with high resolution can be provided at low cost.
[Brief description of the drawings]
FIG. 1 is a sectional view of a torque sensor according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a signal processing unit in the torque sensor according to the embodiment of the present invention.
3A and 3B are diagrams illustrating a first logic signal, a second logic signal, and a PWM signal when the transmission torque is zero in the torque sensor according to the embodiment of the present invention, and FIG. And FIG. 3C is a diagram showing the first logic signal, the second logic signal, and the PWM signal when torque is transmitted in the other direction.
FIG. 4 is a diagram showing a configuration of a signal processing unit in a torque sensor according to a modification of the present invention.
FIG. 5 is a diagram showing a first logic signal, a second logic signal, a PWM signal, a rising point detection signal, and a falling point detection signal when the transmission torque is zero in the torque sensor according to the modified example of the present invention. (2) is a diagram showing a first logic signal, a second logic signal and a PWM signal when torque is transmitted in one direction, and (3) is a diagram showing a first logic signal and torque when torque is transmitted in the other direction. The figure which shows a 2nd logic signal and a PWM signal
FIG. 6 is a diagram showing a configuration of a phase shift circuit in a torque sensor according to a modification of the present invention.
[Explanation of symbols]
3 First shaft
4 Second shaft
21 1st resolver (1st detector)
22 1st resolver (2nd detector)
26 first signal processing unit
26a first phase shift circuit
26b first adder circuit
27 Second signal processing unit
27a Second phase shift circuit
27b Second adder circuit
28 Output signal processing unit
28a first logic signal conversion circuit
28b Second logic signal conversion circuit
28c, 28c 'PWM processing circuit
28d rising point detection circuit
28e Fall time detection circuit

Claims (5)

A first shaft;
A second shaft elastically rotatable relative to the first shaft;
First alternating signal output means for outputting a first alternating signal whose phase changes in accordance with the rotation angle change of the first shaft;
Second alternating signal output means for outputting a second alternating signal whose phase changes in accordance with the rotation angle change of the second shaft;
An output signal processing unit that outputs a phase difference corresponding signal whose waveform changes according to a change in a phase difference between the first alternating signal and the second alternating signal,
A torque sensor for obtaining a value corresponding to the torque transmitted by the first and second shafts from the phase difference corresponding signal. The first alternating signal output means includes a first detector and a first signal processing unit. The first detector has a coefficient of KE, an angular frequency of the excitation signal of ω, a time of t, and θ of the first shaft. A first sine amplitude signal represented by KEsin (ωt) sin θ and a first cosine amplitude signal represented by KEsin (ωt) cosθ are output as rotation angles,
The first signal processing unit shifts the first sine amplitude signal by π / 2 to obtain a first phase shift signal represented by KE sin (ωt + π / 2) sin θ, and a first phase shift circuit. A first adder circuit that adds the one phase shift signal and the first cosine amplitude signal to the first alternating signal represented by KEsin (ωt + θ),
The second alternating signal output means includes a second detector and a second signal processing unit,
The second detector is a second sine amplitude signal represented by KE sin (ωt) sin (θ + Δθ), where KE is a coefficient, ω is the angular frequency of the excitation signal, t is time, and θ + Δθ is the rotation angle of the second shaft. And outputs a second cosine amplitude signal represented by KE sin (ωt) cos (θ + Δθ),
A second phase shift circuit that shifts the second sine amplitude signal by π / 2 to obtain a second phase shift signal represented by KE sin (ωt + π / 2) sin (θ + Δθ); The torque sensor according to claim 1, further comprising a second addition circuit that adds the second phase shift signal and the second cosine amplitude signal to obtain the second alternating signal represented by KEsin (ωt + θ + Δθ). The first alternating signal output means outputs the first alternating signal represented by KE sin (ωt + θ), where KE is a coefficient, ω is the angular frequency of the excitation signal, t is time, and θ is the rotation angle of the first shaft. Comprising a first detector,
The second alternating signal output means outputs the second alternating signal represented by KE sin (ωt + θ + Δθ), where KE is a coefficient, ω is the angular frequency of the excitation signal, t is time, and θ + Δθ is the rotation angle of the second shaft. The torque sensor according to claim 1, further comprising a second detector that performs the operation. The first detector and the second detector are arranged such that a phase difference between the first alternating signal and the second alternating signal becomes π / 2 when the torque transmitted by the first and second shafts is zero. Relative to each other,
A first logic signal conversion circuit for converting the first alternating signal into a first logic signal; a second logic signal conversion circuit for converting the second alternating signal into a second logic signal; 4. The torque sensor according to claim 2, further comprising: a PWM processing circuit that outputs a PWM signal corresponding to an exclusive OR of the first logic signal and the second logic signal as the phase difference corresponding signal. A first logic signal conversion circuit that converts the first alternating signal into a first logic signal; a second logic signal conversion circuit that converts the second alternating signal into a second logic signal; A detecting circuit for detecting a rising point of the first logic signal, a detecting circuit for detecting a falling point of the second logic signal, and detecting one of the rising point of the first logic signal and the falling point of the second logic signal as a rising point 4. The torque sensor according to claim 2, further comprising: a PWM processing circuit that outputs a PWM signal corresponding to the falling point and the other as a phase difference corresponding signal.

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