JPH0620121Y2 - Torque detector abnormality detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used in, for example, an electric power steering system.
The present invention relates to an improvement of a torque detector abnormality detecting device that detects an abnormal state such as a wire break or a short circuit of a torque detector that detects a steering torque applied to a steering wheel and converts the steering torque into an electric signal.

[Conventional technology]

Generally, in an electric power steering apparatus, for example, Japanese Patent Laid-Open No.
As described in Japanese Patent Application Laid-Open No. 9-77966, a steering torque applied to a steering wheel is detected by a steering torque detector, and an electric output signal corresponding to the steering torque is input to a motor control circuit to generate a steering gear. By driving and controlling an electric motor connected to the mechanism, a steering assist torque is generated with respect to the steering torque so that the steering wheel can be steered lightly.

In such a power steering apparatus, since the steering torque applied to the steering wheel is detected by the steering torque detector and the electric motor is driven based on the detected value, the steering torque detector is in an abnormal state. When a steering torque detection value that is different from the steering torque value actually applied to the steering wheel is output from the steering torque detector, the electric motor will generate unnecessary steering assist torque, which will result in stable steering. Sex cannot be secured.

For this reason, conventionally, the abnormality detection device detects whether the output of the steering torque detector is normal or abnormal. The abnormality detection device includes a normal state when the output value of the steering torque detector is within a normal range determined by preset upper and lower limits, and a normal state when the output value of the steering torque detector deviates from the normal range. Each is judged to be an abnormal state.

[Problems to be solved by the invention]

However, in the above-described conventional torque detector abnormality detection device, whether the torque detector is normal or not is simply determined by whether or not the output value of the torque detector is within the normal range set by the upper limit value and the lower limit value. Since the abnormal state is discriminated, it is necessary to widen the width of the normal range in order to cope with the variation in the output value due to the individual difference of the torque detector. However, if the applied voltage side of the torque detector is broken,
The output value will exceed the upper and lower limit output values in the normal state, but if a short circuit occurs inside the torque detector,
Since the change in the output value becomes relatively small, the range of the output value of the torque detector must be narrowed in order to detect both disconnection and short circuit, and the setting range of the normal range is inevitably narrow. I had to do it.

As described above, when the output value of the torque detector is used within a narrow range, the noise resistance is poor, and the mechanical parts constituting the torque detector need to be finished with high precision, resulting in increased manufacturing costs. was there.

Therefore, the present invention has been made in view of the problems of the above conventional example, without narrowing the range of the output value of the torque detector, therefore, in the state where the setting range of the normal range of the abnormality detection device is wide, An object of the present invention is to provide an abnormality detection device for a torque detector that can reliably detect disconnection and short circuit of the torque detector.

[Means for solving problems]

In order to achieve the above object, the present invention is directed to a torque detector that detects an abnormal state of a torque detector that detects a torque and outputs an output voltage corresponding to a detected torque value while a predetermined voltage is applied. In the abnormality detection device, it is determined whether or not the output voltage of the torque detector is within a predetermined set range, and when it is outside the predetermined set range, it is determined that the torque detector is disconnected and an abnormal state detection signal is output. An output voltage abnormality detection circuit that outputs, and an applied voltage abnormality detection circuit that outputs an abnormal state detection signal by determining that the torque detector is short-circuited when the applied voltage applied to the torque detector is lower than a certain reference value. It is characterized by having.

[Action]

In this invention, when a disconnection occurs inside the torque detector, the output value is out of the normal range, and this is detected by the output voltage abnormality detection circuit connected to the output side, and inside the steering torque detector. When a short circuit occurs, its internal resistance is apparently reduced, and the divided voltage of the applied voltage is reduced accordingly, and this is detected by the applied voltage abnormality detection circuit to detect disconnection and short circuit separately. By detecting, while maintaining a wide range of output values of the torque detector,
The setting range of the upper limit value and the lower limit value of the output voltage abnormality detection circuit can be widened.

〔Example〕

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to an electric power steering apparatus.

In the figure, reference numeral 1 denotes a steering torque applied to a steering wheel (not shown), for example, a torsion angle of a torsion bar inserted between an input shaft connected to the steering wheel and an output shaft connected to a steering gear mechanism. Is a steering torque detector composed of a potentiometer for detecting the voltage applied to the steering torque detector 1. Applied voltage terminals t _T1 and t
_T2 and an output terminal t _O connected to the movable contactor 1a are connected to the power steering control device 2.

This power steering control device 2 has a stabilizing power supply circuit 4 to which electric power from an external battery B is supplied via a key switch 3, and each of the power steering control device 2 is supplied from this stabilizing power supply circuit 4. Constant voltages of positive voltage + V and negative voltage -V are supplied to the internal circuit. Then, at the connection terminals t _C1 and t _C2 to which the applied voltage terminals t _T1 and t _T2 of the steering torque detector 1 of the power steering control device 2 are connected, positive voltage + V and negative voltage −V are applied to the resistors R ₁ and The input terminal t _I, which is applied via R ₂ and is connected to the output terminal t _O of the steering torque detector 1, is connected between the input terminal t _I and the ground, which forms a part of the output voltage abnormality detection circuit. Resistor R ₃ having a resistance value sufficiently larger than the resistance values of the resistors R ₁ and R ₂ inserted in the resistor R ₄ and the resistor R ₄ inserted at the connection point between the resistor R ₃ and the input terminal t _I. And an integrating circuit 5 composed of a charging / discharging capacitor C.

Then, the voltage V _{1 at} the connection point of the resistor R ₁ and the connection terminal t _C1 is input to the applied voltage abnormality detection circuit 6. In the applied voltage abnormality detection circuit 6, the voltage V ₁ is applied to the non-inverting input side,
A positive voltage + V is divided by resistors R ₅ and R ₆ and a divided voltage is input to the inverting input side as a lower limit value setting voltage VS _{1L. 1} is the lower limit value setting voltage VS
High level H, lower limit value setting voltage VS when _{exceeding 1L}
When it is _1L or less, the low level L abnormality detection signal AS ₁ is output. Here, the lower limit value setting voltage VS _1L is selected to be a value capable of detecting a decrease in the voltage V ₁ due to a decrease in internal resistance when a short circuit occurs inside the steering torque detector 1.

Further, the terminal voltage V _I of the charging / discharging capacitor C of the integrating circuit 5 is input to the output voltage abnormality detecting circuit 7. The output abnormality detection circuit 7 applies a positive voltage + V to the resistor R on the non-inverting input side.
_The divided voltage divided by ₇ and R ₈ is input as the upper limit setting voltage VS _2H , and the operational amplifier 7a to which the voltage V _I is input to the inverting input side and the voltage V _I to the non-inverting input side are input to the inverting input side. Is provided with a window comparator 7c configured with an operational amplifier 7b to which a voltage obtained by dividing the negative voltage -V by the resistors R ₉ and R ₁₀ is input as the lower limit value setting voltage VS _2L , and the output side of these window comparators 7c. To VS _2L <V
High level when _I <VS _2H , V _I ≤ VS _2L and V _I ≥
When VS _2H , the low-level L detection signal AS ₂ is output. Here, as shown in FIG. 3, the upper limit value setting voltage VS _2H and the lower limit value setting voltage VS _2L are the upper limit value V _H and the lower limit value of the output voltage output from the output terminal V ₀ of the steering torque detector 1. It is selected to be a value larger than V _L.

The output sides of the abnormality detection circuits 6 and 7 are connected to each other and to the input side of the latch circuit 8, and
It is connected to a positive voltage + V via a pull-up resistor R ₁₁ .

On the other hand, the inter-terminal voltage V _I of the charging / discharging capacitor C of the integrating circuit 5 is input to the motor control circuit 10 and the neutral state determination circuit 11.

The electric motor control circuit 10 compares the amplifier 10a to which the inter-terminal voltage V _I according to the steering torque detection voltage of the steering torque detector 1 is input, and a pulse width modulation by comparing the amplified output of the amplifier 10a with a sawtooth wave. From the pulse width modulation circuit 10b that outputs the pulse output Pa having the duty ratio corresponding to the output voltage and its inverted pulse output Pb, the output of the latch circuit 8, the pulse width modulation circuit 10b, and the neutral state determination circuit 11. AND circuit 10 to which the output of
c and 10d, and an electric motor drive circuit 10f for driving and controlling an electric motor 10e to which the outputs of the AND circuits 10c and 10d are supplied and which is connected to, for example, a rack and pinion type steering gear. Here, the pulse width modulation circuit 10b has a duty ratio of 5 when the pulse fundamental frequency is selected to be about 15 to 20 kHz, which is below the audible range, and the output voltage of the amplifier 10a is 0 (V).
When the voltage is 0:50, the duty ratio changes continuously from 50:50 to 100: 0 according to the voltage value, and when the voltage is negative, the duty ratio changes according to the voltage value. A pulse output Pa that continuously changes from 50:50 to 0: 100 and its inverted pulse output Pb are output.

Further, the electric motor drive circuit 10f, as shown in FIG.
The transistor bridge circuit 10g is provided. This transistor bridge circuit 10g has four transistors
Have Tr ₁ to Tr _4, together with the transistor Tr ₁ and Tr ₂ are connected in series, the transistors Tr ₃ and Tr ₄ are connected in series, these series circuits are connected in parallel battery B The external relay 12 is connected via a relay contact 12a. Then, the motor 10e between the connection point of the connection point of the transistors Tr ₁ and Tr ₂ and the transistor Tr ₃ and Tr ₄ are connected, and the output of the AND circuit 10c to the base of the transistor Tr ₁ and Tr ₄ are transistors The outputs of the AND circuit 10d are supplied to the bases of Tr ₂ and Tr ₃ , respectively.

The neutral state determination circuit 11 is configured to include, for example, a window comparator, and has a logical value “0” when the voltage V _I corresponding to the output voltage of the steering torque detector 1 is within the dead band width near zero, and otherwise. At a certain time, the neutral state determination output Na of the logical value "1" is output, and this is output to AND circuits 10c and 1c.
Supply to 0d.

Also, the output of the latch circuit 8 is supplied to the relay controller 13 that controls the external relay 12, and when the output of the latch circuit 8 has the logical value "1", the relay coil 12b of the external relay 12 is energized and attached. Energize and relay contact 12a
When the output of the latch circuit 8 becomes the logical value "0", the relay coil 12b is de-energized to open the relay contact 12a and the electric motor 10e is de-energized.

Next, the operation of the above embodiment will be described. Now, assuming that the steering torque detector 1 is in a normal state, the steering torque detector 1 outputs a positive output voltage in response to right steering of the steering wheel and a negative output voltage in response to left steering as shown in FIG. As for the output voltage, zero output voltage is output during non-steering. Here, the output voltage of the steering torque detector 1 is proportional to the steering torque, but the mechanical stopper provided in the steering torque detector 1 does not exceed the upper limit value V _H and the lower limit value V _L. .

In this normal state, the output voltage of the steering torque detector 1 does not exceed the upper limit value V _H and the lower limit value _L as described above, so the charging / discharging capacitor C in the integrating circuit 5 of the power steering control device 2 is prevented. Since the inter-terminal voltage V _I of the output voltage of the steering torque detector 1 is also equal to the output voltage of the steering torque detector 1, the output voltage abnormality detection circuit 7 does not exceed the upper limit value V _H and the lower limit value V _L.
Detection signal A of high level from the window comparator 7c of
S ₂ is output.

Further, since the steering torque detector 1 is in a normal state, the voltage V ₁ of the connection point of the connecting terminals t _C1 and resistor R ₁ power steering device 2, the internal resistance of the steering torque detector 1 and the resistance R ₁ Since the steering torque detector 1 has a relatively large internal resistance, the lower limit value setting voltage VS _1L of the applied voltage abnormality detection circuit 6 is exceeded. Therefore, the applied voltage abnormality detection circuit 6 also outputs the high-level abnormality detection signal AS ₁ .

Therefore, the abnormality detection signal A of each abnormality detection circuit 6 and 7
The output of the latch circuit 8 to which S ₁ and AS ₂ are input maintains a logical value “1”, which is input to the AND circuits 10c and 10d, and the external relay controller 13 energizes the relay coil 12b of the external relay 12. Then, the relay contact 12a is closed and the electric power of the battery B can be supplied to the electric motor drive circuit 10f.

Therefore, in this state, when the steering wheel is not steered and the steering torque is at or near zero, the determination output Na of the neutral state determination circuit 11 becomes the logical value "0", so the AND circuits 10c and 10d. No pulse output is output from the motor drive circuit 10
Each of the transistors Tr _{1 to} Tr ₄ of f is turned off, and no electric power is supplied to the electric motor 10e.
As shown in the figure, the zero output is maintained and the steering assist torque is not generated.

When the output voltage of the steering torque detector 1 becomes equal to or higher than the dead band voltage set by the neutral state determination circuit 11, the determination output Na of the neutral voltage determination circuit 11 becomes the logical value "1", which is the AND circuits 10c and 10d. The output voltage of the steering torque detector 1 is amplified by the amplifier 10a from the AND circuits 10c and 10d, and the pulse width modulation circuit 10b outputs the pulse output Pa and Pb of the duty ratio according to the amplified voltage. Are output, and these are supplied to the transistor bridge circuit 10g of the electric motor drive circuit 10f. Therefore, since a current proportional to the output voltage of the steering torque detector 1 is supplied to the electric motor 10e, the electric motor 10e is rotationally driven in correspondence with the steering direction, and as shown in FIG. A steering assist torque corresponding to the generated steering assist torque is generated.

When the applied voltage terminal t _T1 (or t _T2 ) of the steering torque detector 1 is disconnected from the normal state of the steering torque detector 1, the steering torque detector 1 is connected between the output side and the ground. The resistance value of the connected resistor R ₃ is sufficiently compared with the resistance values of the resistors R ₁ and R ₂ connected between the positive voltage + V and the negative voltage −V applied to the steering torque detector 1. Since a large value is selected, the inter-terminal voltage V _I of the charging / discharging capacitor C of the integrating circuit 5 is a negative voltage −V (or a positive voltage +
V) and becomes lower than the lower limit value setting voltage VS _2L (or the upper limit value setting voltage VS _2H ) of the output voltage abnormality detection circuit 7, and the output of the operational amplifier 7b becomes low level,
In response to this, the output of the latch circuit 8 becomes the logical value "1". For this reason, the output of the pulse outputs Pa and Pb from the AND circuits 10c and 10d is stopped, the energization of the relay coil 12b of the external relay 12 by the external relay controller 13 is interrupted, and the relay contact opens to open the motor drive circuit. The power supply of the battery 3 to 10f is cut off. Therefore, the electric motor 10e is controlled to stop rotating, and the generation of the steering assist torque is stopped.

Further, when a wire breakage occurs between the movable slider 1a of the steering torque detector 1 and the output terminal t ₀ , the supply of the output voltage to the integrating circuit 5 is cut off. The electric charge that has been charged to is gradually discharged through the resistors R ₄ and R ₃ , and the inter-terminal voltage V _I of the charging / discharging capacitor C gradually decreases to zero at the end. in this way,
When the terminal voltage V _I becomes zero, the pulse width modulation circuit 10b
The duty ratios of the pulse outputs Pa and Pb of both are 50:
50, and the discrimination output N of the neutral state discrimination circuit 11
a becomes a logical value "0", and AND circuits 10c and 10d
Then, the output of the pulse outputs Pa and Pb is stopped, and the driving of the electric motor 10e is stopped.

Further, the applied voltage terminals t _T1 and t 1 of the steering torque detector 1
_{When the T2} side is disconnected at the same time, the supply of the applied voltage to the steering torque detector 1 is cut off, so that the output voltage from the output terminal t ₀ becomes zero, and the charging / discharging capacitor C of the integrating circuit 5 becomes similar to the above. After the electric discharge, the driving of the electric motor 10e is stopped.

Furthermore, when a short circuit occurs inside the steering torque detector 1, the internal resistance of the steering torque detector 1 is apparently reduced, and the input voltage V _{1 of the} applied voltage abnormality detection circuit 6 is reduced.
Is determined by the voltage division ratio between the internal resistance of the steering torque detector 1 and the resistance R ₁ , so that if the internal resistance becomes smaller, the voltage V
₁ drops below the lower limit value setting voltage VS _1L . For this reason,
Since the abnormality detection signal AS ₁ output from the comparator 6a of the applied voltage abnormality detection circuit 6 becomes low level and the latch output of the latch circuit 8 becomes a logical value “0” in response to this, the external relay controller 13 causes the external relay 1
The power supply to the second relay coil 12b is cut off, the relay contact 12a is opened, the power supply to the electric motor drive circuit 10f is cut off, and the AND circuits 10c and 10d.
The output of the pulse outputs Pa and Pb from is stopped. Therefore, the driving of the electric motor 10e is stopped.

As described above, according to the above-described embodiment, the applied voltage abnormality detection circuit 6 detects the short-circuit state of the steering torque detector 1, and the output voltage abnormality detection circuit 7 detects the disconnection of the steering torque detector 1. When the abnormality detection circuits 6 and 7 detect an abnormal state of short circuit and disconnection, the drive of the electric motor 10e that generates the steering assist torque is stopped, so that when the abnormal state occurs in the steering torque detector 1. To
It is possible to reliably prevent the electric motor from generating the steering assist torque different from the actual steering state, and it is possible to improve the steering stability. Further, the output voltage abnormality detection circuit 7 detects only the disconnection abnormality of the steering torque detector 1, and the upper limit value setting voltage VS _2H and the lower limit value setting voltage VS _2L of the steering torque detector 1 are detected in the normal state.
It is possible to select a set voltage that exceeds the upper limit value and the lower limit value of the output voltage of, and thus it is possible to take a wide variable range of the output voltage of the steering torque detector 1 and improve noise resistance and durability. Further, it is possible to increase the dimensional tolerance of the mechanical parts that configure the steering torque detector 1, and prevent malfunction of the abnormality detection circuit due to individual differences of the steering torque detector.

In the above embodiment, the case where the pulse width modulation circuit 10b of the motor control circuit 10 outputs the two pulse outputs Pa and Pb having the duty ratios corresponding to the positive and negative input voltages has been described, but the present invention is not limited to this. However, a steering direction determination circuit and an absolute value circuit for determining the steering direction are provided on the output side of the amplifier 10a, and the absolute value output of the absolute value circuit is converted into a pulse output by the pulse width modulation circuit,
This pulse output is passed through an AND circuit to the motor drive circuit 1
0f, and the drive direction of the electric motor 10e may be controlled based on the determination result of the steering direction determination circuit by the electric motor drive circuit 10f. The configuration of the electric motor control circuit 10 is not limited to the configuration of the above embodiment. Not something.

Further, in the above embodiment, the applied voltage abnormality detection circuit 6
Although the case where the output voltage abnormality detection circuit 7 and the output voltage abnormality detection circuit 7 are each configured by a comparator has been described, the present invention is not limited to this and can detect a change in the input voltage of another comparator, a Schmitt circuit, or the like. If so, any detection circuit can be applied.

Further, in the above embodiment, the case where the present invention is applied to the electric power steering apparatus has been described, but it is needless to say that the present invention can be applied to other torque detectors.

Further, in the above embodiment, the case where the present invention is applied to the electric power steering apparatus has been described, but the present invention is not limited to this, and the present invention can of course be applied to other torque detectors.

[Effect of device]

As described above, according to the present invention, the applied voltage abnormality detection circuit for detecting an abnormal state of the applied voltage of the steering torque detector, and the output voltage abnormality detection circuit for detecting an abnormal output voltage of the steering torque detector are provided. Is provided, the applied voltage abnormality detection circuit detects an abnormality due to a short circuit of the steering torque detector, and the output voltage abnormality detection circuit detects an abnormality due to a disconnection of the steering torque detector. The upper limit value setting voltage and the lower limit value setting voltage can be set to large voltage values, and accordingly, the upper limit value and the lower limit value of the output voltage in the normal state of the steering torque detector can be set in a wide range, and noise resistance can be improved. Of the steering torque detector, the dimensional tolerance of the mechanical components that make up the steering torque detector can be increased, and the manufacturing cost can be reduced. Effects such can reliably prevent malfunction of the abnormality detecting circuit according to individual difference of the torque detector can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an electric power steering apparatus to which the present invention is applied, FIG. 2 is a block diagram showing a concrete configuration of the electric motor drive circuit of FIG. 1, and FIG. 3 is a steering torque. Is a characteristic diagram showing the relationship between the output voltage of the steering torque detector and FIG. 4, and FIG. 4 is a characteristic diagram showing the relationship between the output voltage of the steering torque detector and the motor output. In the figure, 1 is a steering torque detector, 2 is a power steering control device,
5 is an integrating circuit, 6 is an applied voltage abnormality detection circuit, 7 is an output voltage abnormality detection circuit, 8 is a latch circuit, 10 is a motor control circuit, 10a is an amplifier, 10b is a pulse width modulation circuit, 10
c and 10d are AND circuits, 10e is an electric motor, and 10f is an electric motor drive circuit.

Claims (1)

[Scope of utility model registration request] 1. A torque detector abnormality detecting device for detecting an abnormal state of a torque detector which detects a torque and outputs an output voltage corresponding to a detected torque value while a predetermined voltage is applied. An output voltage abnormality detection circuit that determines whether or not the output voltage of the detector is within a predetermined setting range, and determines that the torque detector is disconnected when the output voltage is outside the predetermined setting range and outputs an abnormal state detection signal. And an applied voltage abnormality detection circuit that outputs an abnormal state detection signal by determining that the torque detector is short-circuited when the applied voltage applied to the torque detector is lower than a certain reference value. Torque detector abnormality detection device.