JP2523200Y2 - Torque sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a torque sensor, and proposes a torque sensor suitable for, for example, a power steering device of an automobile.

[Conventional technology]

2. Description of the Related Art An electric power steering device has been developed as a power steering device for assisting a force for operating a steering wheel of an automobile. As shown in FIG. 5, this electric power steering apparatus uses a power steering control circuit for controlling the voltage of a DC power supply E to rotate an electric motor for assisting a steering force provided in a steering mechanism.
Give to CTR. When the torque sensor TS detects the torque applied to the steered wheels, the detected torque is applied to the power steering control circuit CTR, and the power steering control circuit C
The TR has a structure in which an electric motor for assisting the steering force is rotated according to the detected torque given to the TR.

FIG. 6 is a block diagram showing a main part of the torque sensor TS. The input voltage V _IN applied to the power supply terminal T _IN of the connector CN from the power supply stabilization circuit (not shown) is applied to the offset voltage generation circuits 111 and 112, and further to various parts of the electronic circuit. The oscillation voltage of the oscillation circuit 110 is input to the torque detection coil 114 and the temperature compensation coil 115 via the buffer circuit 113.

An AC voltage of a torque detection coil 114 provided on a steering shaft (not shown) and configured so that the impedance changes according to the torque acting on the steering shaft is input to the clamp circuits 116 and 117. On the other hand, the AC voltage of the temperature compensation coil 115 is input to the clamp circuits 118 and 119. The output voltages of the clamp circuits 116 and 118 are individually input to the peak detection circuits 120 and 121, and the respective output voltages are input to the differential amplifier circuit 124. The output voltages of the clamp circuits 117 and 119 are equal to the peak detection circuits 122 and 123.
To the differential amplifier circuit 125.
Has been entered. Offset voltage generation circuits 111 and 112 are connected to one input terminals of the differential amplifier circuits 124 and 125, respectively.
Are provided separately for each of the offset voltages.

The output voltage of the differential amplifier circuit 124 is input to the voltage-current conversion circuit 126, the first torque signal S _T1 serving its output voltage is outputted to the signal terminal T ₁ of the connector CN. The output voltage of the differential amplifier circuit 125 is input to the voltage-current conversion circuit 127, the signal terminal T ₂ of the its second torque signal serving output voltage S _T2 connector CN
Output to A ground terminal T ₃ of the connector CN is grounded with the ground part of the electronic circuit section.

In this torque sensor, when an input voltage V _IN is applied to a power supply terminal T _IN , an oscillation circuit 110 performs an oscillating operation, and offset voltage generation circuits 111 and 112 output an offset voltage.
The oscillating voltage of the oscillating circuit 110 is input to the torque detecting coil 114 and the temperature compensating coil 115 via the buffer circuit 113. It changes according to the ambient temperature and is input to the clamp circuits 116 and 117.

On the other hand, the AC voltage generated in the temperature compensation coil 115 changes according to the ambient temperature and is input to the clamp circuits 118 and 119. The clamp circuits 116, 117, 118, and 119 apply 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 OV, and clamp the voltage. The output voltages of the clamp circuits 116 and 118 are detected by a peak detection circuit.
Then, the output voltages of the clamp circuits 117 and 119 are input to the peak detection circuits 122 and 123.

The peak detection circuits 120, 121, 122, 123 detect the peak value of the input AC voltage. Then, the output voltages of these peak detection circuits 120 and 121 are input to the differential amplifier circuit 124. The output voltages of the peak detection circuits 122 and 123 are input to the differential amplifier circuit 125.

The differential amplifier circuit 124 calculates the difference between the output voltages of the peak detection circuits 120 and 121 and adds an offset voltage to the difference. The differential amplifier 125 is the peak detection circuit 1
The offset voltage is added to the difference between the output voltages 22,22 and 123. The differential amplifier circuit
The output voltages of 124 and 125 are obtained by canceling the voltages related to the ambient temperature of the coil 114 for torque detection and the coil 115 for temperature compensation, and two output voltages corresponding to the acting torque, that is, the first torque signal S _T1 and second torque signal S
_T2 will be obtained.

The offset voltage, when a torque is not applied, are provided to make the respective first torque signal S _T1 and the second torque signal S _T2 to the midpoint of the torque signal.

Therefore, when the torque is not detected, the output voltages of the differential amplifier circuits 124 and 125 are in accordance with the offset voltage, and when the torque is detected, the output is based on the offset voltage in accordance with the direction of the torque. The voltage changes in the increasing or decreasing direction, and the torque acting together with the steering direction is detected. And the first torque signal S _T1 and the second torque signal S _T2 in accordance with the detected torque applied to the power steering control circuit CTR, power steering control circuit first CTR is given to the second one of the torque signal Accordingly, the rotation of the electric motor for assisting the steering force is controlled.
Further, when a voltage difference between the first torque signal _ST1 and the second torque signal _ST2 occurs, an abnormality occurs in the torque detecting circuit,
It is determined that the torque is erroneously detected, and the control of the electric motor for assisting the steering force is stopped.

FIG. 7 is a line diagram showing the relationship between the voltage of the torque signal (the midpoint voltage of the sensor) and the input voltage _VIN when no torque is applied. When the input voltage V _IN falls below the predetermined voltage V _D , the first torque signal S _T1 and the second torque signal S
Both _T2 decrease in proportion to the decrease rate of the input voltage _VIN , and the detection sensitivity of the torque sensor TS decreases. Therefore, a circuit for monitoring the input voltage V _IN supplied to the torque sensor is provided in the power steering control circuit CTR, and the input voltage V _IN
Is reduced to a predetermined value or less, the control of the electric motor by the power steering control circuit CTR is stopped.

[Problems to be solved by the invention]

By the way, when the contact resistance of the connector of the torque sensor increases and the voltage for generating the offset voltage decreases, a circuit for monitoring the input voltage supplied to the torque sensor is provided in the power steering control circuit. The first torque signal or the second torque signal in a state where the voltage drop is not detected and the torque detection sensitivity of the torque sensor is reduced thereby is given to the power steering control circuit,
There is a problem that the electric motor for assisting the steering force may be controlled.

The present invention has been made in view of the above problems, and has as its object to provide a torque sensor that can detect a decrease in input voltage from a difference voltage between first and second torque signals.

[Means for solving the problem]

The torque sensor according to the present invention adds a first torque signal and a second torque signal by adding an offset voltage output by each of the first offset voltage generation circuit and the second offset voltage generation circuit to a voltage related to the applied torque. In the torque sensor that outputs each of the constant voltage generating circuits, the first offset voltage generating circuit and the second offset voltage generating circuit each include a constant voltage generating circuit for obtaining an offset voltage, and the output voltages of the constant voltage generating circuits are different. It is characterized by having a configuration.

[Action]

The torque sensor outputs a first torque signal and a second torque signal obtained by adding an offset voltage to a voltage related to the applied torque. When the input voltage decreases, for example, the output voltage of the constant voltage generation circuit in the first offset voltage generation circuit decreases first, and the offset voltage decreases. Therefore the first
The voltage of the torque signal decreases first. When the input voltage further decreases, the output voltage of the constant voltage generation circuit in the second offset voltage generation circuit decreases, and the offset voltage decreases. Therefore, the voltage of the second torque signal decreases. An input voltage drop state is detected based on a voltage difference between a predetermined value at which the voltage of the first torque signal has dropped and a predetermined value of the voltage of the second torque signal at which the voltage has not dropped.

 As a result, a drop in the input voltage can be directly detected.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment thereof.
FIG. 1 is a block diagram showing a main part of the torque sensor according to the present invention. The input voltage V _IN given to the power supply terminal T _IN of the connector CN from a power supply stabilization circuit provided in a control circuit (not shown) is converted into first and second offset voltage generation circuits 111 and 112 provided with shunt regulators (not shown). And a buffer circuit 113 and clamp circuits 116, 117, 11
It is given to electronic circuits such as 8,119. The oscillation voltage of the oscillation circuit 110 is input to the torque detection coil 114 and the temperature compensation coil 115 via the buffer circuit 113. An AC voltage of a torque detecting coil 114 provided on a steering shaft (not shown) and configured so that impedance changes according to a torque acting on the steering shaft and an ambient temperature is input to clamp circuits 116 and 117. On the other hand, the AC voltage of the temperature compensation coil 115, whose impedance changes according to the ambient temperature, is input to the clamp circuits 118 and 119.

The output voltages of the clamp circuits 116 and 118 are individually input to the peak detection circuits 120 and 121, and the respective output voltages are individually input to the negative and positive input terminals-and + of the differential amplifier circuit 124. The output voltages of the clamp circuits 117 and 119 are individually input to the peak detection circuits 122 and 123, and the respective output voltages are individually input to the negative and positive input terminals-and + of the differential amplifier circuit 125.

Offset voltages output from the first and second offset voltage generation circuits 111 and 112 are input to positive input terminals + of the differential amplifier circuits 124 and 125 via the resistors R25 and R41, respectively. The output voltage of the differential amplifier circuit 124 is
Is input to the first torque signal S _T1 serving its output voltage is outputted to the signal terminal T ₁ of the connector CN. Differential amplifier circuit 125
Is input to the voltage-current conversion circuit 127, and the output voltage of the second torque signal _ST2 is applied to the signal terminal T of the connector CN.
Output to ₂ . A ground terminal T ₃ of the connector CN is grounded with the ground part of the electronic circuit section.

FIG. 2 shows first and second offset voltage generating circuits 111 and 112.
FIG. Between the power supply terminal T _IN and the ground terminal T ₃
It connects the shunt regulator IC5 connected to the cathode from the power supply terminal T _IN through a resistor R48, a series circuit of a resistor R49 and R50 is connected in parallel to the shunt regulator IC5. The connection between the resistors R49 and R50 is connected to the reference Ref of the shunt regulator IC5. The shunt regulator IC5 and the resistors R49 and R50 constitute a first constant voltage generation circuit REG1. Also between the power supply terminal T _IN and the ground terminal T _3, the series circuit is connected between the resistors R53 and R55, the resistor R53 resistor R54 are connected in parallel. These first constant voltage generating circuit REG1 and resistor R53,
A first offset voltage generating circuit 111 is configured by R54 and R55, and a first offset voltage OS1 is output from a connection between the resistors R53, R54, and R55.

Also between the power supply terminal T _IN and the ground terminal T _3, resistors R57
And shunt regulator IC with cathode connected to it
6 and the series circuit are connected. The cathode of the shunt regulator IC6 is directly connected to the reference Ref, and the shunt regulator IC6 forms a second constant voltage generation circuit REG2. Shunt regulator IC
6, a series circuit of resistors R58, R59 and R60 is connected in parallel, and a variable resistor VR is connected in parallel to the resistor R59. These second constant voltage generating circuit REG2, resistors R57 and R58,
The R59 and R60 and a variable resistor VR constitute a second offset voltage generating circuit 112, and a resistor variable terminal VR _C of the variable resistor VR and outputs a second offset voltage OS2.

The shunt regulators IC5 and IC6 are commercially available, for example, a high-precision variable shunt-type stabilized power supply μPC10.
The same standard of 93 is used, and the output voltage of the reference Ref is 2.5V.

FIG. 3 is a line diagram showing a relationship between an input voltage and an output voltage of the first constant voltage generation circuit REG1 and the second constant voltage generation circuit REG2. In FIG. 2, when an input voltage V _IN of, for example, 8 V is applied between the power supply terminal T _IN and the ground terminal T ₃ , the output voltages of the reference Refs of the shunt regulators IC 5 and IC 6 both become 2.5 V. However, the first constant voltage generation circuit REG1
In, because it is connected to resistor R49 and R50 in the shunt regulator IC 5, the power supply terminal T _IN side of the terminal voltage of the resistor R49, that is, the output voltage of the first constant voltage generating circuit REG1 for example 5.
Held at 5V. On the other hand, in the second constant voltage generating circuit REG2, since the reference Ref of the shunt regulator IC6 is directly connected to its cathode, the resistor R57 and the reference Ref are used.
, That is, the output voltage of the second constant voltage generation circuit REG2 is maintained at 2.5V. In this way, the output voltages of the constant voltage generating circuits REG1 and REG2 are made different.

In the case where the input voltage V _IN reaches a predetermined voltage V ₁₀ drops from 8V is lowered to an output voltage of 5.5V of the first constant voltage generating circuit REG1 is earlier, the input voltage V _IN is further lowered to a predetermined voltage If it reaches the V ₁₁ is the output voltage characteristic output voltage of 2.5V of the second voltage adjustment circuit REG2 is decreased.

FIG. 4 shows the first and the first in a state where no torque is applied.
FIG. 7 is a line diagram showing a relationship between input voltages V _{IN of} second constant voltage generation circuits REG1 and REG2 and voltages of first and second torque signals S _T1 and S _T2 output by a torque sensor.

When the input voltage _VIN decreases, the first constant voltage generation circuit REG1
And the output voltage of the second constant voltage generation circuit REG2 decreases as described above, and accordingly, the offset voltage generation circuits 111 and 11
It will be offset voltage 2 is output decreases and reaches the predetermined voltage V ₁₀ the voltage of the first torque signal S _T1 begins to decrease above. Then further decrease the input voltage V _IN, and reaches the predetermined voltage V ₁₁ is a second torque signal S _T2 has a voltage characteristic begins to decrease.

Next, the operation of the thus configured torque sensor will be described. When the input voltage V _IN is applied to the power supply terminal T _IN , the oscillation circuit 110 performs an oscillating operation, and the offset voltage generation circuit 111 and the
112 is a first and a second constant voltage generator REG1 provided respectively.
The first and second offset voltages OS1 and OS2 are output based on the output voltages of the REG2 and REG2, and are applied to the positive input terminals + of the differential amplifier circuits 124 and 125 via the resistors R25 and R41, respectively. Oscillation circuit 11
The oscillating voltage of 0 is applied to the torque detection coil via the buffer 113.
An AC voltage that is input to the coil 114 for temperature compensation and that is generated in accordance with the impedance of the coil 114 for torque detection is obtained according to the torque applied by operating the steered wheels and the ambient temperature. Is input to On the other hand, an AC voltage generated according to the impedance of the temperature compensation coil 115 is obtained according to the ambient temperature and input to the clamp circuits 118 and 119. Clamp circuit 116,
117, 118, and 119 apply 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 OV, and clamp them. The output voltages of the clamp circuits 116 and 118 are input to the peak detection circuits 120 and 121, respectively, and the output voltages of the clamp circuits 117 and 119 are input to the peak detection circuits 122 and 123, respectively. Peak detection circuit 120, 121, 12
2, 123 detects the peak value of the input AC voltage.
Then, the output voltages of these peak detection circuits 120 and 121 are added to the first offset voltage OS1 of the first offset voltage generation circuit 111 and input to the differential amplifier circuit 124. The output voltages of the peak detection circuits 122 and 123 are connected to the second offset voltage O of the second offset voltage generation circuit 112.
S2 is added and input to the differential amplifier circuit 125. The differential amplifier 124 outputs a voltage corresponding to the voltage difference input to its positive and negative input terminals + and-, while the differential amplifier 125 outputs its voltage to its positive and negative input terminals + and-. A voltage corresponding to the voltage difference is output. As a result, the output voltages of the differential amplifier circuits 124 and 125 are such that the output voltages corresponding to the ambient temperatures of the torque detecting coil 114 and the temperature compensating coil 115 are offset, and the output voltage of the differential amplifier circuits 124 and 125 The corresponding first torque signal _ST1 and second torque signal _ST2 are output.
The offset voltage is provided to form a respective first torque signal S _T1 and the second torque signal S _T2 when the torque is not applied to the midpoint of the torque signal.

Therefore, when the torque is not detected, the output voltages of the differential amplifier circuits 124 and 125 are in accordance with the offset voltage, and when the torque is detected, in accordance with the direction of the torque, based on the offset voltage. The output voltage changes in the increasing or decreasing direction, and the torque acting together with the steering direction is detected. Then, the first torque signal _ST1 and the second torque signal _ST2 are transmitted to the power steering control circuit CTR.
To control the electric motor that assists the steering force based on the second torque signal _ST2 .

By the way, when the torque sensor TS is detecting torque, the first and second constant voltage generating circuits REG1 and REG2 are reduced due to a decrease in the power supply voltage _VIN or an increase in the contact resistance of the connector CN, for example.
When the input voltage V _IN of reaches a predetermined voltage V ₁₀ decreases, the third
As shown in the figure, the output voltage of the first constant voltage generation circuit REG1 decreases first, and the first offset voltage OS1 decreases. Accordingly, the voltage of the first torque signal S _T1 is lowered input voltage V _IN is, as shown in FIG. 4 reaches a predetermined voltage V _10. However, the output voltage of the second constant voltage generation circuit REG2 is the input voltage V
Since _IN does not decrease until the predetermined voltage V _11, a voltage of the second torque signal S _T2 remains held, a predetermined voltage V ₁₁
The torque is correctly detected by the voltage of the second torque signal _ST2 until the torque decreases to That is, when the input voltage V _IN reaches the predetermined voltage V ₁₁
, The torque can be detected with high sensitivity by the second torque signal _ST2 . As is apparent from FIG. 4, when the first torque signal S _T1 starts to decrease and a voltage difference occurs between the first torque signal S _T1 and the second torque signal S _T2 , the voltage difference is equal to the input voltage V T. detecting a drop in the input voltage V _iN occurs in proportion to the _iN. Then, the input voltage V _IN is lower than the predetermined voltage V _11, when the voltage difference between the first torque signal S _T1 and the second torque signal S _T2 has reached a predetermined value, the power steering control circuit CT
By R, the control of the electric motor for assisting the steering force is stopped.

In this embodiment, the shunt regulators IC5 and IC6 are used for the constant voltage generation circuits REG1 and REG2, but a three-terminal regulator may be used. Also, the offset voltage generation circuit 11
Needless to say, the configurations of 1,112 are merely examples.
Further, the same effect can be obtained even when a potentiometer is used instead of a torque detecting coil for torque detection.

[Effect of the invention]

As described above in detail, according to the present invention, the output voltage of the constant voltage generation circuit in the first offset voltage generation circuit and the output voltage of the second
A predetermined voltage at which the output voltage of the constant voltage generating circuit in the offset voltage generating circuit is made different from the output voltage of the constant voltage generating circuit and the voltage of the first torque signal and the voltage of the second torque signal start to decrease when the input voltage of the constant voltage generating circuit decreases Since the voltages are made different, it is possible to detect a drop in the input voltage of the voltage adjustment circuit from the voltage difference between the torque signals.

When the voltage difference between the first torque signal and the second torque signal reaches a predetermined value, the control of the electric motor for assisting the steering force is stopped, and the torque detection sensitivity is reduced due to a decrease in the input voltage. To control the motor. In addition, if the motor is controlled using one of the torque signals, the voltage of the torque signal decreases with a delay, and even if the input voltage of the constant voltage generating circuit is further reduced, the motor can be controlled in accordance with the torque detected with high sensitivity. And so on.

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 circuit diagram of an offset voltage generating circuit thereof, and FIG. 3 is an input voltage and an output of a constant voltage generating circuit. FIG. 4 is a line diagram showing a relationship between a voltage and a voltage, and FIG. 4 is a line diagram showing a relationship between a voltage of a torque signal and an input voltage of a constant voltage generating circuit; FIG. FIG. 6 is a block diagram of a main part of a conventional torque sensor, and FIG. 7 is a line diagram showing the relationship between the voltage of the torque signal and the input voltage. 110: oscillation circuit, 111, 112: offset voltage generation circuit, 11
4… Torque detection coil, 115… Temperature compensation coil, 116,
117,118,119… Clamp circuit, 120,121,122,123… Peak detection circuit, 124,125… Differential amplifier circuit, CN… Connector, T _IN
… Power supply terminal, T ₁ , T ₂ … Signal terminal, T ₃ … Ground terminal

Claims (1)

(57) [Scope of request for utility model registration] 1. A first torque signal and a second torque signal are respectively output by adding an offset voltage output by each of a first offset voltage generation circuit and a second offset voltage generation circuit to a voltage related to an applied torque. In the torque sensor, the first offset voltage generation circuit and the second offset voltage generation circuit each include a constant voltage generation circuit for obtaining an offset voltage, and output voltages of the constant voltage generation circuits are different from each other. A torque sensor characterized in that: