JP3051903B2 - Torque sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a torque sensor, and more particularly to a torque sensor suitable for a power steering device of an automobile.

[Conventional technology]

2. Description of the Related Art Electric power steering devices for assisting a force for operating a steering wheel of an automobile are being developed. This has a structure in which a torque applied to a steered wheel is detected, and an electric motor for assisting a steering force provided in a steering mechanism is rotated according to the detected torque.

By the way, the present applicant has proposed a torque sensor of this type in Japanese Patent Application No. 63-191843. FIG. 3 is a block diagram showing a main part of the torque sensor. Power stabilization unit
The output voltage of 112 is supplied to an oscillation circuit 113 of the torque sensor unit TS and an offset voltage output unit 114 including a resistance voltage dividing circuit. Temperature compensation circuit 115 oscillating voltage composed of a resistor R ₁ parallel circuit via a (R ₂₀₎ a temperature compensation coil L ₁₀ and (the torque detection coil L ₂₀₎ and the capacitor C ₁₀ (C ₂₀₎ of the oscillation circuit 113
(Torque detection circuit 116). The AC voltage, which is the resonance voltage of the temperature compensation circuit 115 (torque detection circuit 116), is supplied to the clamp circuit 117 (122), and the output voltage of the clamp circuit 117 (122) is supplied to the peak detection circuit 118 (123).
Is being entered. The output voltage of the peak detection circuit 118 is input to the comparison circuit 120 and the differential amplifier circuit 121. Further, the output voltage of the peak detection circuit 123 is input to the differential amplifier circuit 121. The reference voltage of the reference voltage circuit 119 is input to the comparison circuit 120, and the output voltage of the comparison circuit 120 is output to a controller (not shown) via the connector CN1. The offset voltage output from the offset voltage output unit 114 is input to the differential amplifier circuit 121 and the voltage-current exchange circuit 125, and the output voltage of the differential amplifier circuit 121 is input to the voltage-current conversion circuit 124. Have been. The output voltages of the voltage-current conversion circuits 124 and 125 are
Output to the controller section via N1. The voltage of a power supply provided in a controller unit (not shown) is supplied to the power supply stabilizing unit 112 via a connector CN1.

In this torque sensor, the output voltage of the power supply stabilizing unit 112 is supplied to the oscillation circuit 113 and the offset voltage output unit 114, and the oscillation circuit 113 performs an oscillating operation, and the offset voltage output unit 114 outputs an offset voltage. And the oscillation circuit 113
Is input to the temperature compensation circuit 115 and the torque detection circuit 116. Whereby the AC voltage generated in accordance with the inductance of the temperature compensation coil L ₁₀ of the temperature compensation circuit 115 is input obtained in relation to the ambient temperature to the clamp circuit 117. The AC voltage generated in accordance with the inductance of the torque detection coil L ₂₀ of the torque detection circuit 116 is input obtained in relation to torque and ambient temperature act by operation of the steering wheel to the clamp circuit 122. Each of the clamp circuits 117 and 122 applies a bias for changing the level of the waveform to the positive voltage side so that the negative maximum value of the input AC voltage becomes 0 V, and clamps them. The output voltages of the clamp circuits 117 and 122 are individually input to the peak detection circuits 118 and 123, and the peak detection circuits 118 and 123 sequentially detect the peak values of the input AC voltage. Each output voltage of these peak detection circuits 118 and 123 is input to the differential amplifier circuit 121 together with the offset voltage of the offset voltage output unit 114, and the differential amplifier circuit 121 obtains each output voltage of the peak detection circuits 118 and 123, and The offset voltage is added to the output voltage of the difference. As a result, the output voltage of the differential amplifier 121 becomes the output voltage related to the ambient temperature of the temperature compensation circuit 115 and the torque detection circuit 116, and only the output voltage related to the acting torque is obtained. Will be done.

If the torque is not detected, the differential amplifier circuit 12
The output voltage of 1 becomes an offset voltage, and when a torque is detected, the output voltage changes in a positive or negative direction based on the offset voltage depending on the rotation direction of the steered wheels, and the output voltage of the power supply stabilizing unit 112 is An appropriate detected torque can be obtained even when there is a difference between the specified input voltage of the oscillation circuit 113 and the specified input voltage.
Then, an electric motor (not shown) for assisting the steering force is controlled in association with the detected torque.

When the oscillation circuit 113 fails and its oscillation voltage disappears, the output voltages of the temperature compensation circuit 115 and the torque detection circuit 116 disappear. Then, only the reference voltage from reference voltage circuit 119 is applied to comparison circuit 120, and the output voltage of comparison circuit 120 changes significantly. An abnormal operation of the oscillation circuit 113 is detected based on the change in the output voltage.

[Problems to be solved by the invention]

As described above, the conventional torque sensor requires the oscillation operation monitoring circuit including the reference voltage circuit 119 and the comparison circuit 120 for monitoring the operation of the oscillation circuit 113, in addition to the circuit for detecting the torque. Therefore, the circuit of the torque sensor becomes complicated, and the reference voltage circuit 119 and the comparison circuit 120
Abnormal operation becomes a problem, and it is difficult to improve reliability.

In view of such a problem, the present invention does not need to monitor the operation of an oscillating circuit that oscillates an AC voltage for inducing a voltage related to a torque applied by a steering force, so that the circuit is simple and reliable. It is an object to provide a torque sensor.

[Means for solving the problem]

The torque sensor according to the present invention obtains a magnetic coupling state related to a torque applied by a steering force, and detects the torque by an AC voltage induced in relation to the magnetic coupling, wherein the AC voltage is induced. A torque detection circuit having a coil, an oscillation circuit that outputs a signal for inducing an alternating voltage to the coil of the torque detection circuit via a first buffer circuit, and a timing signal that is synchronized with the signal of the oscillation circuit A synchronous timing circuit, a reference voltage circuit connected to the oscillating circuit and the synchronous timing circuit via a second buffer circuit, and a synchronous detector for receiving the AC voltage and the timing signal and detecting the synchronous voltage in synchronization with the timing signal A circuit for detecting the torque based on the voltage output by the synchronous detection circuit, and stopping the operation of the oscillation circuit. The synchronous detection circuit is characterized in that it is constituted to stop the detection operation by the disappearance of the timing signal.

[Action]

The signal output by the oscillation circuit is input to the torque detection circuit and the synchronization timing circuit, and the synchronization timing circuit synchronizes the signal of the oscillation circuit with a timing signal that is electrically insulated from the signal applied to the torque detection circuit. Output and input to synchronous detection circuit. An AC voltage that is induced by the voltage of the oscillating circuit and is related to the acting torque is input to the synchronous detection circuit. The synchronous detection circuit detects the input AC voltage in synchronization with the timing signal and outputs the detected voltage.

Thus, when the operation of the oscillation circuit stops, the timing signal disappears and the synchronous detection circuit stops the detection operation.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments.

FIG. 1 is a block diagram of a main part of a torque sensor according to the present invention. The oscillating voltage of the oscillating circuit 1 that oscillates an AC voltage having a predetermined frequency is input to the buffer 2 and the synchronization timing circuit 15. The output of the buffer 2 is inputted to the temperature compensation circuit 3 consisting of an amplifier 3a for amplifying the parallel circuit and the terminal voltage thereof and the temperature compensation coil L ₁ and capacitor C _1. The amplifier 4a outputs of the buffer 2 is to amplify the parallel circuit and the terminal voltage thereof between the torque detection coil L ₂ and capacitor C ₂
And the like. That is, the signal is input to the temperature compensation circuit 3 and the torque detection circuit 4 while being electrically isolated from the input to the synchronization timing circuit 15 by the buffer 2. Temperature compensation circuit 3
The output voltage of the amplifier 3a is output as the output of the temperature compensation circuit 3, and the output voltage of the amplifier 4a of the torque detection circuit 4 is output as the output of the torque detection circuit 4. . Inductance of the temperature compensation coil L ₁ varies with the state change of the magnetic coupling portion (not shown) changes the magnetic coupling state with respect to the ambient temperature, whereas the inductance torque detection coil L _2, acts by the steering force The magnetic coupling state changes according to the torque and the ambient temperature. The temperature compensation circuit 3
The output voltage of the torque detection circuit 4 is input to the differential amplifier 5. The output voltage of the differential amplifier 5 is input to a synchronous detection circuit 6, and the synchronous detection circuit 6
Is supplied with a timing signal of the synchronous timing circuit 15. The output voltage of the synchronous detection circuit 6 is input to the voltage-current conversion circuit 8 via the smoothing circuit 7. The offset voltage of the offset circuit 9 is input to the voltage-current conversion circuit 8. Output serving detected torque signal TS ₁ of the voltage-current converting circuit 8 are outputted to the controller unit (not shown) via the connector 21.

On the other hand, it is connected to the voltage stabilizing circuit 16 the positive terminal T _P of the power supply is made of through a connector 21 for example, three-terminal regulator in the controller unit (not shown), the negative terminal T _N
Are grounded via a connector 21. Then, for example, a voltage of 8 V + 8 V applied to the voltage stabilizing circuit 16 is applied to an electronic circuit (not shown). The output voltage of, for example, +5 V of the voltage stabilizing circuit 16 is supplied to the offset circuit 9 and the reference voltage circuit 17. This reference voltage circuit 17 is, for example, 2
A voltage of about 3 V is output, and the voltage is supplied to the buffers 18 and 19, respectively. The output voltage of the buffer 18 is controlled by a voltage stabilization circuit.
A voltage monitoring circuit 20 composed of, for example, an open collector circuit for monitoring voltage fluctuations of the voltage generator 16, an oscillation circuit 1, a synchronization timing circuit 15, and driving ICs (not shown) of the differential amplifier 5 are provided. . The output side 20a of the voltage monitoring circuit 20 is connected to the output side of the voltage / current conversion circuit 8. This voltage monitoring circuit 20 has a problem that the voltage stabilizing circuit 16
When the output voltage of the voltage stabilizing circuit 16 falls below the predetermined value or rises above the predetermined value, the circuit is closed and the output side 20a is grounded.

Next, the torque detecting operation of the torque sensor thus configured will be described with reference to FIG. 1 and FIG. Figure 2 shows the first
It is a waveform diagram which shows the voltage waveform of each part of the torque sensor in a figure.

Voltage stabilization circuit from power supply of controller not shown
When a voltage is applied to 16, a voltage is also applied to an electronic circuit (not shown) for control, and an output voltage of voltage stabilizing circuit 16 is applied to offset circuit 9. The output voltage of the reference voltage circuit 17 is supplied to the voltage monitoring circuit 20, the oscillation circuit 1, the synchronization timing circuit 15 and the differential amplifier 5 via the buffers 18 and 19, respectively. This is supplied to a drive circuit (not shown). As a result, the oscillating circuit 1 oscillates, and the oscillating voltage shown in FIG.
And it outputs the V _0. Note that the voltage applied to the voltage stabilizing circuit 16 is an oscillating voltage around a voltage level higher than 0 V because it is a positive single power supply of a battery (not shown). Then, the torque sensor enters an operating state. The oscillating voltage V ₀ is supplied to the temperature compensating circuit 3 and the torque detecting circuit 4 via the buffer 2 and to the synchronous timing circuit 15. Synchronization timing circuit 15 will input the timing signal V _T of the pulse shown in FIG. 2 in synchronization with the oscillation voltage V ₀ input (b) to the synchronous detection circuit 6.

Here, when a torque is applied to the steering shaft by rotating a steering wheel (not shown) to the right, for example, the magnetic coupling state of the magnetic coupling unit (not shown) changes according to the torque. However inductance of the temperature compensation coil L ₁ of the temperature compensation circuit 3 is a one corresponding to the ambient temperature, the output voltage V ₁ of the temperature compensation circuit 3 becomes an AC waveform shown by a broken line in FIG. 2 (c). On the other hand, the inductance of the torque detection coil L ₂ of the torque detection circuit becomes one corresponding to the torque,
Its inductance output voltage V ₂ is the second torque detecting circuit 4 becomes larger than the inductance of the temperature compensation coil L ₁
The alternating waveform shown by the solid line in FIG. These output voltages V ₁ and V ₂ are respectively input to the differential amplifier 5, and the differential amplifier 5 amplifies the difference voltage between the output voltages V ₁ and V ₂ and outputs the output voltage.
V ₃ becomes an AC waveform shown in FIG. 2 (d). Then, the output voltage V ₃ is input to the synchronous detection circuit 6. Synchronous detection circuit 6 outputs a voltage of the positive period of the output voltage V ₃ performs detection when the timing signal V _T is positive, the output voltage V ₄
Is a pulsating waveform shown in FIG. 2 (e). The output voltage V ₄ of the pulsating waveform is smoothed is inputted to the smoothing circuit 7, as an output voltage mean value equal to the voltage level V _H of the V _4, than the voltage level V _N to be described later when no give detected torque High second
Output voltage V ₅ shown in FIG. (F) is output from the smoothing circuit 7,
It is input to the voltage-current conversion circuit 8. Voltage-current conversion circuit 8
In addition the offset voltage to the output voltage V ₅ input, converts the DC voltage into a direct current, converted detected torque signal
TS ₁ is output to a controller (not shown). Thus the controller unit drives the electric motor for assisting a steering force by the detected torque signal TS ₁ that is input, rotated to the right steered wheel.

By the way, when a torque is applied to the steering shaft by rotating the steered wheels to the left, the magnetic coupling state of the magnetic coupling unit (not shown) changes according to the torque. In this case, the magnetic coupling state becomes smaller if the coupling amount in the case of clockwise rotation is large as described above. Inductance of the temperature compensation coil L ₁ as described above have become a thing according to the ambient temperature, the output voltage V ₁ of the temperature compensation circuit 3 unless the ambient temperature is changed by a broken line in FIG. 2 (c) The AC waveform shown by the broken line in FIG. 2 (g) is the same as the AC waveform shown. On the other hand, the inductance of the torque detection coil L ₂ are taken as corresponding to the torque, because the inductance is smaller than when rotated clockwise steering wheel, torque detection circuit 4
The output voltage V ₂ becomes an AC waveform shown by the solid line in FIG. 2 (g). These output voltages V ₁ and V ₂ are respectively input to the differential amplifier 5, and the differential amplifier 5 amplifies the difference voltage between the output voltages V ₁ and V _2, and the output voltage V ₃ is shown in FIG. Output voltage shown in d)
The signal has an opposite phase to V ₃ and is input to the synchronous detection circuit 6. Synchronous detection circuit 6 performs detection when the timing signal V _T is positive, and outputs a voltage of a negative period of the output voltage V _3, the pulsating waveform shown in FIG. 2 (i). Output voltage of this pulsating waveform
V ₄ is input to the smoothing circuit 7 and smoothed, and the output voltage V ₄
The voltage level V _L shown in FIG. 2 (j) equal to the average value is output as the output voltage V ₅ of the smoothing circuit 7 and input to the voltage-current conversion circuit 8. The voltage level V _L is in a significantly lower voltage level than the voltage level V _H shown in FIG. 2 (f). Then, after the voltage-current conversion circuit 8 by adding the offset voltage to the output voltage V ₅ input, converts the DC voltage into a direct current, it outputs to the controller unit (not shown) converts the detected torque signal TS ₁ was . The detected torque signal TS ₁ to thereby input to the controller unit drives the electric motor for assisting steering force, to the steering wheel is rotated counterclockwise. The detected torque obtained in this manner becomes positive and negative voltage levels with respect to the non-steering voltage level when the steered wheels rotate clockwise and counterclockwise. The operation direction of the steered wheels can be determined by comparing the voltage level with the voltage level.

Next, when the steered wheels are not operated, the torque does not act. Therefore, the output voltages V ₁ and V ₂ of the temperature compensation circuit 3 and the torque detection circuit 4 are the same voltage and the AC voltage shown in FIG. It becomes a waveform. Then, no difference voltage of the AC voltage is generated at the output of the differential amplifier 5 to which both the output voltages V ₁ and V ₂ are inputted,
The result is as shown in FIG. Accordingly, as shown in Figure 2 does not change the output voltage V ₄ also synchronous detection circuit 6 performs synchronous detection by the timing signal V _T (m), also the not also not change the output voltage of the smoothing circuit 7 2 As shown in FIG. That is, lower than the voltage level V _H of the smoothing circuit when the right rotary steering described above, a high voltage level V _N becomes than the voltage level V _L when the left rotation steering voltage when not detected torque a level V _N. That is,
The torque sensor does not output the detected torque when the steering wheel is not operated and no torque is applied.

If the output voltage of the voltage stabilizing circuit 16 decreases or increases by a predetermined value or more due to a circuit failure or the like, the voltage monitoring circuit
The output side of the 20 is closed at the ground state, the detected torque signal TS ₁ is zero. Therefore, the detected torque signal TS ₁ given to the controller unit, the detected torque signal TS ₁ in the normal
0V, which is outside the output range, and abnormal operation of the voltage stabilizing circuit 16 is detected. In this case, the control of the electric motor for assisting the steering force is prohibited from being controlled by the detected torque.

When the oscillation circuit 1 fails and the oscillation operation stops, the timing signal V _T output from the synchronization timing circuit 15 is output.
Disappears. As a result, the synchronous detection circuit 6 does not perform the detection operation, and no output voltage is generated. That is, the detected torque cannot be obtained in the same manner as when the torque is not acting, and the malfunction of the oscillation circuit 1 prevents the electric motor assisting the steering force from being erroneously controlled and maintains the safety of the electric power steering. Will do. Further, since it is not necessary to provide a circuit for monitoring the operation of the oscillation circuit as in the related art, the circuit of the torque sensor is simplified and safety is not impaired. Further, when an oscillation operation monitoring circuit is provided as in the conventional case, the reliability may be impaired due to the malfunction, but high reliability can be maintained without such a risk.

〔The invention's effect〕

As described in detail above, in the torque sensor of the present invention, the voltage signal for obtaining the synchronization timing and the voltage signal applied to the torque detection circuit are electrically insulated from each other. In this case, the output of the synchronous detection circuit shifts and becomes an abnormal output. Therefore, the occurrence of the abnormality can be accurately detected by comparing with the output range in the normal state. The signal of the reference voltage circuit is supplied to the oscillation circuit and the synchronization timing circuit via the second buffer circuit, and the synchronization timing circuit outputs the output of the second buffer circuit and the output of the oscillation circuit that outputs a signal based on this output. , An extremely stable synchronization timing signal can be obtained. Further, when the operation of the oscillation circuit is stopped, the detection operation of the synchronous detection circuit is stopped, and the erroneous detection torque is not output. Thus, there is no need to provide a circuit for monitoring the operation of the oscillation circuit, and the reliability does not decrease due to the abnormal operation of the monitoring circuit. Therefore, there is an excellent effect that a torque sensor having a simple circuit, excellent safety, and high reliability can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a main part of a torque sensor according to the present invention,
FIG. 2 is a waveform diagram of a voltage waveform of each part, and FIG. 3 is a block diagram of a main part of a conventional torque sensor. 1 ... oscillation circuit, 3 ... temperature compensation circuit, 4 ... torque detection circuit, 5 ... differential amplifier, 6 ... synchronous detection circuit, 8 ...
… Voltage-to-current conversion circuit, 16 …… Voltage stabilization circuit, 20 …… Voltage monitoring circuit

Claims (1)

(57) [Claims] 1. A torque sensor for obtaining a magnetic coupling state related to a torque applied by a steering force and detecting a torque by an AC voltage induced in relation to the magnetic coupling, comprising a coil in which the AC voltage is induced. A torque detection circuit, an oscillation circuit for outputting a signal for inducing an alternating voltage to a coil of the torque detection circuit via a first buffer circuit, and a synchronization timing circuit for outputting a timing signal synchronized with the signal of the oscillation circuit A reference voltage circuit connected to the oscillation circuit and the synchronization timing circuit via a second buffer circuit, and a synchronization detection circuit that receives the AC voltage and the timing signal and detects the synchronization in synchronization with the timing signal. Detecting the torque based on the voltage output by the synchronous detection circuit, and stopping the operation of the oscillation circuit; A torque sensor, wherein the synchronous detection circuit stops detecting operation when a signal disappears.