JP3114122B2 - Torque sensor for power steering device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor that is applied to a power steering device of a vehicle and detects a torque transmitted to a steering system.

[Conventional technology]

When torque is transmitted to two rotating shafts connected via an elastic member such as a torsion bar, relative rotation occurs between the two rotating shafts with the torsion of the torsion bar. And since the direction and amount of the relative rotation are determined by the direction and magnitude of the torque transmitted to the rotating shaft,
By measuring the relative rotation, the torque can be detected.

Here, the sensors for measuring the relative rotation between the two rotating shafts include a contact-type sensor using a potentiometer and the like and a non-contact sensor using a change in coil inductance. The sensor has a disadvantage that the risk of disconnection failure due to abrasion or the like is high because the sensor has a sliding portion. Conversely, a non-contact type sensor has an advantage that there are few such problems.

However, even a non-contact type sensor that uses a change in coil inductance does not have any danger of failure and requires some countermeasure. If the detection results do not match, it is determined that a failure has occurred in any of the torque sensors, and the subsequent processing is stopped.

[Problems to be solved by the invention]

Certainly, if two torque sensors are prepared, the overall reliability will be significantly improved, but the coil and its inductance will be changed in accordance with the torque as two systems.
There is a problem that the device becomes large, and failure of the coil itself or a mechanical configuration that changes the inductance of the coil in accordance with the torque is extremely unlikely to occur. The improvement in reliability is small compared to the increase in

Conversely, since the oscillation circuit that excites the coil is usually composed of an electronic circuit, it is relatively susceptible to disturbance, and the failure rate is higher than that of coils, etc., so it is advisable to use two parts for this part. It can be said that.

However, even if the oscillation circuit is simply divided into two systems and their outputs are compared, if there is an abnormality in the previous stage of the oscillation circuit, for example, if there is an abnormality in the power supply unit or the like, a failure is found even when comparing the outputs of the two oscillation circuits. There is a drawback that accurate judgment cannot be made.

Therefore, the present invention has been made in view of the problems to be solved by such conventional technology, and a non-contact type in which reliability is reliably improved without inviting a remarkable increase in size of the device. It is intended to provide a torque sensor.

[Means for solving the problem]

In order to achieve the above object, the invention according to claim (1) includes first and second rotating shafts arranged coaxially, an elastic member connecting the first and second rotating shafts, A coil in which an electromotive force caused by an output of the oscillation circuit is induced, an inductance changing unit that changes an inductance of the coil according to a relative rotation between the first and second rotation axes, and an inductance induced in the coil The first based on the electromotive force
And a torque calculating means for calculating a torque transmitted to the second rotating shaft, wherein the amplitude of the output of the oscillation circuit is defined by an upper limit value and a lower limit value in a torque sensor applied to a power steering device of a vehicle. And an amplitude upper / lower limit judging unit for judging whether or not the amplitude falls within the allowable range. If the amplitude of the output of the oscillation circuit is out of the allowable range, it is determined that an abnormality has occurred.

Further, in order to achieve the above object, the invention described in claim (2) is characterized in that the first and second rotating shafts arranged coaxially,
An elastic member for connecting the first and second rotating shafts, a coil for inducing an electromotive force resulting from the output of the oscillation circuit,
Inductance changing means for changing the inductance of the coil in accordance with the relative rotation between the first and second rotating shafts, and transmitting to the first and second rotating shafts based on an electromotive force induced in the coil Torque calculating means for calculating the applied torque, wherein the frequency of the output of the oscillation circuit is within an allowable range defined by an upper limit and a lower limit in the torque sensor applied to the power steering device of the vehicle. Frequency upper / lower limit determining means for determining whether or not an error has occurred is provided, and when the frequency of the output of the oscillation circuit is out of the allowable range, it is determined that an abnormality has occurred.

[Action]

When torque is transmitted to the first and second rotating shafts, relative rotation according to the direction and magnitude of the torque is caused between the first and second rotating shafts with the torsion of the elastic member. Occurs.

Then, since the inductance changing means changes the inductance of the coil according to the relative rotation between the first and second rotating shafts, the electromotive force generated in the coil by the output of the oscillation circuit is equal to the first and second rotating shafts. Between the relative rotations, ie, the direction and magnitude of the transmitted torque.

Therefore, the torque transmitted to the first and second rotating shafts is calculated by the torque calculating means based on the electromotive force induced in the coil.

According to the invention described in claim (1), the amplitude upper / lower limit determining means determines whether or not the amplitude of the output of the oscillation circuit is within an allowable range defined by the upper limit value and the lower limit value. If the amplitude of the output of the circuit is larger than the upper limit of the allowable range, and if the amplitude of the output of the oscillation circuit is smaller than the lower limit of the allowable range, it is determined that an abnormality has occurred.

For this reason, an abnormality in which a value larger than the actual torque is detected (when the amplitude of the output of the oscillation circuit is larger than the upper limit of the allowable range), and a value smaller than the actual torque is detected. Abnormality (when the amplitude of the output of the oscillation circuit is smaller than the lower limit of the allowable range) can be detected.

In the invention described in claim (2), the frequency upper / lower limit determining means determines whether or not the output frequency of the oscillation circuit is within an allowable range defined by an upper limit value and a lower limit value. If the frequency of the output of the circuit is higher than the upper limit of the allowable range, and if the frequency of the output of the oscillation circuit is lower than the lower limit of the allowable range, it is determined that an abnormality has occurred.

For this reason, an abnormality in which a value larger than the actual torque is detected (when the output frequency of the oscillation circuit is higher than the upper limit of the allowable range), and a value smaller than the actual torque is detected. It is possible to detect both an abnormality (when the frequency of the output of the oscillation circuit is lower than the lower limit of the allowable range).

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 8 show a first embodiment of the present invention.

First, the configuration will be described. FIG. 1 is a cross-sectional view of a vehicle power steering device to which a torque sensor according to the present invention is applied, and is connected to a housing 1 via a torsion bar 4 as an elastic member. An input shaft 2 made of a magnetic material as a first rotating shaft and an output shaft 3 as a second rotating shaft are rotatably supported by bearings 5a, 5b and 5c. However, the input shaft 2, the output shaft 3 and the torsion bar 4 are arranged coaxially.

The opening on the input shaft 2 side of the housing 1 is sealed by a seal ring 6, and the opening on the output shaft 3 side is sealed by a cap 7.

A steering wheel is integrally attached to the right end of the input shaft 2 in FIG. 1 (not shown) in the rotational direction. A left end of the output shaft 3 is provided with a pinion constituting a known rack and pinion type steering device. The shaft 3a is formed integrally, and the pinion shaft 3a meshes with the rack shaft 8 of the rack and pinion type steering device in the housing 1.

Therefore, the steering force generated by the steering of the steering wheel by the driver is input shaft 2, torsion bar
4, transmitted to the steered wheels (not shown) via the output shaft 3, the pinion shaft 3a, and the rack shaft 8.

On the other hand, as shown in FIG. 1 and FIG. 2 which is a cross-sectional view taken along the line AA in FIG. 1, at the left end of the input shaft 2, there are formed ridges 2a, 2a which are continuous in the axial direction. The ridges 2a, 2a are formed at the right end of the output shaft 3 and are inserted into vertical grooves 3b, 3b slightly wider than the ridges 2a, 2a. The relative rotation of a predetermined range (about ± 5 degrees) or more is prevented.

FIG. 1 is a sectional view taken along the line BB of FIG.

Further, the input shaft 2 is formed with a flange portion 9 formed by molding to have a larger diameter than other portions, and is separated from the flange portion 9 in the axial direction and integrated with the input shaft 2 in the axial direction and the rotational direction. And a flange portion 10 made of a ring-shaped magnetic material which is fitted to the outside.
A cylindrical member 11 made of a non-magnetic material and rotatable relative to the input shaft 2 is disposed between the cylindrical member 11 and the input shaft 2.

A plurality of protrusions 9a and 10a scattered at equal intervals in the circumferential direction are provided on the outer peripheral surface of the flange portions 9 and 10, and these protrusions 9a and 10a have the same size, but a part of them is developed. As shown in FIG. 3, the projections 10a are located between the projections 9a, 9a.
Are opposed, and the projection 9a is opposed between the projections 10a, 10a,
They are arranged with a half pitch shift.

The gap between the input shaft 2 and the cylindrical member 11 and the gap between the cylindrical member 11 and the flange portions 9 and 10 are relatively small.
It is adjusted to about 30 μm.

The cylindrical member 11 is inserted loosely into the square groove 3c of the output shaft 3 through the flange portion 9 with a sufficient gap so that one end side does not come into contact with the cylindrical shaft 11. Is press-fitted.

Here, the shaft 12 and the square groove 3c are integral with each other in the rotation direction of the output shaft 3, but can be relatively displaced with a relatively small force because they are loosely inserted in the axial direction of the shaft 12. It has become.

A ring 13 made of a magnetic material is provided on the outer peripheral surface of the cylindrical member 11.
Are externally fitted integrally in the rotation direction and the axial direction.

A plurality of projections 13a are provided on an end face of the ring 13 facing the flange 9 side, and a plurality of projections 13b are provided on an end face facing the flange 10 side.
However, the projections 13a and 13b have the same dimensions and pitch as shown in FIG. 3, and are arranged between the input shaft 2 and the output shaft 3 as shown in FIG. When the relative rotation does not occur, the lap amount S ₁ between the protrusion 9a and the protrusion 13a
When the lapping amount S ₂ of the projection 10a and the projection 13b, respectively 50
%.

Incidentally, the gap G ₁ between the projections 9a and the protrusion 13a, a protrusion 10a projecting
The gap G ₂ with 13b is the same distance, is relatively wide,
It is adjusted to about 0.3mm to 0.6mm.

In addition, the inner peripheral surface of the housing 1 has a flange portion 9,
A cylindrical holder 15 made of a magnetic material is embedded in a portion surrounding the cylindrical member 10 and the cylindrical member 11.
The two circumferential grooves 15a which are input shaft 2 side to surround the open and gap G _1, G _2, 15b are formed, further, and the circumferential groove 15a
In each of the coils 15b, coils 16, 17 of the same standard are stored.

The coils 16 and 17 are connected to a relative rotation detection circuit that calculates a difference between electromotive forces induced in the coils 16 and 17 and obtains a relative rotation between the input shaft 2 and the output shaft 3 based on the calculation result. .

Then, the relative rotation detection circuit calculates the torque generated in the steering system based on the detected relative rotation, and, for example, from an electric motor or the like connected to the rack shaft 8 so that the calculated torque decreases. Connected to a controller that outputs a control signal to the steering assist force applying device.

FIG. 4 is a circuit diagram showing the overall configuration of the relative rotation detection circuit 20.

That is, the coils 16, 17 and two resistors R ₁ ,
Bridge circuit 21 by connecting R ₂ is configured, two outputs of the bridge circuit 21, two processing circuits having a parallel relationship
22 and 23.

The processing circuits 22 and 23 include a differential amplifier 25 that determines the difference between the two outputs of the bridge circuit 21, a peak hold circuit 26 that extracts the maximum value of the output of the differential amplifier 25, an impedance matching circuit 27, Respectively.

The output of an oscillation circuit 30 that supplies an alternating current of a predetermined amplitude and frequency is supplied to the power supply side of the bridge circuit 21 via an impedance matching circuit 28.

Furthermore, the oscillation circuit 30 via the impedance matching circuit 31 to generate a two reference voltages V ₁ and V ₂ from the power supply V _CC be connected to the constant voltage circuit 32, one of the reference voltages V ₁ of which Is supplied.

Then, the AC voltage v ₁ supplied to the bridge circuit 21 is
It is also supplied to the abnormality detection circuit 35 shown in FIG.

The abnormality detecting circuit 35, by which the amplitude of the AC voltage v ₁ is to determine whether is within the upper limit value and within a predetermined allowable range defined by a lower limit value, the bridge circuit 21 and processing circuitry 22, 23 Is a circuit for determining whether or not is in a state in which it can operate normally, and comprises a smoothing circuit 36 and a window comparator 37 with hysteresis.

That is, if the AC voltage v ₁ is smoothed by the smoothing circuit 36 and the smoothed value falls within the allowable range defined by the window comparator 37, the abnormality detection circuit 35
Detection signal D ₁ whereas a high level of, or the smoothed value is greater than the upper limit defined by the window comparator 37, or than the lower limit value of the smoothed values is determined by the window comparator 37 if small, if any is satisfied, the output signal D ₁ becomes low level.

FIG. 6 is a circuit diagram showing a connection relationship between the processing circuits 22 and 23 and a controller 39 that outputs a control signal to the steering assist force applying device. As shown in FIG. The output voltage V _{OUT1 of} 22 is directly supplied, and the output voltage V _OUT2 of the processing circuit 23 is turned on when a high-level signal is supplied and cut off when a low-level signal is supplied. It is supplied via a switch 40.

Then, the controller 39 calculates the steering torque generated in the steering system based on the two output voltages V _OUT1 and V _OUT2 supplied, so that the steering assist torque is applied in a direction in which the steering torque decreases. A control signal is output to the steering assist force applying device, but if the output voltages V _OUT1 and V _OUT2 do not match, it is determined that an abnormality has occurred in the steering torque sensor, and the steering assist force applying device is stopped. .

Further, the analog switch 40, is supplied with the output signal D ₁ of the abnormality detection circuit 35, the controller 39 side of the analog switch 40, and outputs the processing circuits 22 and 23 when the steering torque is zero neutral Voltage (output voltage V _OUT1 , V
Assuming that _OUT2 changes between 0 and 5 V according to the steering torque, a constant voltage generation circuit 41 that generates 2.5 V) is connected.

 Next, the operation of this embodiment will be described.

Now, assuming that the steering system is in a straight running state and the steering torque is zero, there is no relative rotation between the input shaft 2 and the output shaft 3, so that the flange portion integrated with the input shaft 2 in the rotation direction. No relative rotation occurs between the cylindrical member 11 and the ring 13 to which the rotational force of the output shaft 3 is transmitted via the shaft 12. Therefore, the wrap amount S between the projection 9a and the projection 13a
₁ and the amount of wrap S ₂ between the projections 10a and 13b are 5
Since maintaining a 0% state, the self-inductance L ₁ of the coil 16 is equal to the self-inductance L ₂ of the coil 17.

On the other hand, when the steering wheel is steered to generate a torque on the input shaft 2, the torque is transmitted to the output shaft 3 via the torsion bar 4.

At this time, since a frictional force is generated on the output shaft 3 according to the frictional force between the steered wheels and the road surface and the frictional force of the rack and pinion type steering device, the torsion bar is provided between the input shaft 2 and the output shaft 3. Due to the twisting of the output shaft 4, a relative rotation occurs in which the output shaft 3 is delayed.

Then, the cylindrical member 11 to which the rotational force of the output shaft 3 is transmitted via the shaft 12 is displaced in the rotational direction between the flange portions 9 and 10 which rotate integrally with the input shaft 2.
Also displaced in the direction of rotation, the wrap amount S ₁ and S ₂ are changed.

At this time, as shown in FIG. 3, since the projections 9a and 10a are displaced by a half pitch, a ring is formed between them.
When 13 is displaced in the direction of rotation, while the increase of the lap amount S ₁ and S _2, the other is decreased, the coil 16 and in accordance with the increase or decrease
Self-inductance L ₁ and L ₂ of 17 is increased or decreased in opposite directions.

Here, for example, with the lap amount S ₁ is decreased wraps amount S ₂ increases when clockwise torque is generated, lapping amount when the torque of the left rotation direction is generated
If it is assumed that the configured such overlap amount S ₂ S ₁ is decreased to increase the self-inductance L ₁ and L ₂ are opposite characteristics as shown in FIG. 7, the torque intersect at the point of zero Becomes

Here, assuming that the steering torque is zero, as described above, the self-inductances L ₁ and L ₁ of the coils 16 and 17 are determined.
Since L ₂ are equal, the AC voltage v ₁ from the oscillation circuit 30 is also supplied to the bridge circuit 21, the electromotive force induced in the coils 16 and 17 are equal, therefore, the two outputs of the bridge circuit 21 are equal.

Therefore, since the output voltages of the differential amplifiers 25 and 25 become neutral voltages corresponding to the steering torque of zero, it is determined that the steering torque is zero based on the output voltages V _OUT1 and V _OUT2 of the processing circuits 22 and 23, Since the controller 39 does not operate the steering assist force applying device that applies the steering assist torque to the rack shaft 8, no steering assist torque is generated, and the steering system maintains the straight running state.

On the other hand, assuming that a steering torque is generated in the steering system, as described above, the coil according to the characteristic shown in FIG.
16 self-inductance L ₁ of increased or decreased, and, since self-inductance L ₂ of the coil 17 decreases or increases, the difference between the electromotive force is generated which is induced in coil 16 and coil 17, as a result, the differential amplifier At 25, 25, the output voltage increases or decreases from the neutral voltage.

Therefore, the controller 39 outputs the output voltages V _OUT and V _OUT
A steering torque is calculated based on _OUT2 , and a control signal is output to the steering assisting force applying device so that the steering torque decreases.

Then, since a steering assist torque corresponding to the steering torque is applied to the steering system, the steering torque decreases, and the burden on the driver is reduced.

Here, and self-inductance L ₁ of the coil 16 and 17
As shown in FIG. 8, the difference between L ₂ is twice as large as the slope of the self-inductances L ₁ and L ₂ of the coil 16 or 17 (see FIG. 7). , Coil 16 and
If the torque is calculated based on the outputs of the differential amplifiers 25, 25 which determine the difference between the two outputs of the bridge circuit 21 determined by the electromotive force induced by the 17, a minute change in torque can be obtained with high accuracy.

As a result, it is possible to improve the measurement accuracy without making the torsion bar 4 easy to twist, that is, without increasing the size of the device or reducing the torque transmission characteristics between the input shaft 2 and the output shaft 3. In other words, the same accuracy as that of the conventional device can be realized by a small device having a short torsion bar 4.

Further, since the determining a difference self-inductance L ₁ and L _2, for example, or the temperature fluctuates around the coil 16 and 17, or various noise occurs, their self-inductance L ₁ and L ₂ Even if torque-related fluctuations occur,
Because they appear in the same direction with self-inductance L ₁ and L _2, are offset by determining the difference between them, it will be removed from the final measurement value. That is, the temperature compensation is performed, and the device is resistant to noise.

Further, since the axial coupling force between the shaft 12 and the square groove 3c is eliminated or reduced, and the cylindrical member 11 is fitted to the input shaft 2 with a small gap, for example, Even if a force is applied, the force is absorbed by the shaft 12 moving back and forth in the angular groove 3c, so that the effect of the axial force is not transmitted to the cylindrical member 11, and the cylindrical member 11
11 maintains the proper axial position between the flanges 9 and 10.

That is, according to the configuration of the present embodiment, even if an axial force is applied and the relative position in the axial direction between the input shaft 2 and the output shaft 3 changes, the measurement result is not affected, and only the torque is applied. Is obtained.

Further, if the cylindrical member 11 is not displaced in the axial direction, the frictional resistance between the cylindrical member 11 and the flange portions 9 and 10 does not fluctuate from the initial state. There is no problem that the load applied to the shaft 12 is increased and its durability is reduced.

Furthermore, in the present embodiment, since the two processing circuits 22 and 23 are provided, even if a failure occurs in the processing circuit 22 or 23, if the output voltages V _OUT1 and V _OUT2 do not match, the controller 39 Since it is determined that a failure has occurred, there is no problem that an inappropriate steering assist force is applied to the steering system when the processing circuit 22 or 23 fails.

Moreover, when a failure occurs in the oscillation circuit 30 or the constant voltage circuit 32, even if the output voltages V _OUT1 and V _OUT2 of the processing circuits 22 and 23 are not accurate, they may be matched, It is not possible to detect all failures only by monitoring the output voltages V _OUT1 and V _OUT2 , but in this embodiment, since the abnormality detection circuit 35 shown in FIG. And a failure occurring in the constant voltage circuit 32 can be detected, and a dangerous state is avoided.

That is, when abnormality occurs in the oscillation circuit 30 and constant-voltage circuit 32, the amplitude of the AC voltage v ₁ also becomes abnormal, deviates from the allowable range whose amplitude is determined by the window comparator 37 of the abnormality detection circuit 35, the abnormality detecting circuit detection signal D ₁ of the 35 analog switches 40 are cut off in the low level.

Here, the abnormality of the amplitude of the AC voltage v _1, and if the amplitude is greater than the normal, is considered and when smaller reversed. When the former abnormality occurs, an erroneous state is detected in which a value larger than the actual torque is detected, an excessive steering assist torque is generated, and the driver's steering feeling becomes too light. On the other hand, when the latter abnormality occurs, an incorrect state is detected in which a value smaller than the actual torque is detected, and an excessively small steering assist torque or no steering assist torque is generated. Becomes heavy.

However, according to the configuration of the present embodiment, if any one of these abnormalities occurs, the analog switch 40 is turned off as described above.

Then, the output voltage V _OUT2 of the processing circuit 23 is stopped by the analog switch 40, and the neutral voltage generated by the constant voltage generation circuit 41 is supplied to the controller 39 instead.

As a result, if the steering torque is actually zero, both inputs to the controller 39 indicate that the steering torque is zero, and if the steering torque is not zero, the two inputs to the controller 39 are In this case, it is determined that the torque sensor has failed. Therefore, no steering assist force is generated in any case, and there is no danger of generating an inappropriate steering assist force. Performance, that is, the safety of the power steering device is improved.

In addition, according to the configuration of the present embodiment, it is not necessary to provide a new signal line between the abnormality detection circuit 35 and the controller 39, and the determination processing in the controller 39 is simply performed by the processing circuit 22.
And 23 only need to determine whether or not the output voltages V _OUT1 and V _OUT2 match, thus providing the advantage of a simple configuration.

The voltage generated by the constant voltage generation circuit 41 is, for example,
An extremely large voltage that does not occur with normal steering torque may be used.

Here, in the present embodiment, the flange portions 9, 10, the projections 9a, 10a,
13a, the cylindrical member 11, the shaft 12, and the ring 13 constitute an inductance varying unit, the processing circuits 22, 23 and the controller 39 constitute a torque calculating unit, and the abnormality detecting circuit 35 constitutes an amplitude upper / lower limit judging unit.

FIGS. 9 to 12 show a second embodiment of the present invention.

That is, the circuit Fig. 9 is a circuit diagram of the abnormality detection circuit 45 in the present embodiment, this is based on the frequency of the AC voltage v _1, to detect an abnormality such as the oscillation circuit 30 or the constant voltage circuit 32 It comprises a frequency-voltage conversion circuit 46, a smoothing circuit 47, and a window comparator 48 with hysteresis.

10 to 12 are waveform diagrams at each point (a to d) of the abnormality detection circuit 45. FIG.
v If the frequency of ₁ is lower than the lower limit of the allowable range, Fig. 11 shows the case where the frequency is within the allowable range, and Fig. 12 shows the case where the frequency is higher than the upper limit of the allowable range. I have.

Then, as shown in FIG. 11, if the frequency of the AC voltage v ₁ is if falls within the allowable range, the detection signal D ₁ becomes high level, as shown in Figure 10 or Figure 12, the AC voltage v if the _first frequency is out of the allowable range, the detection signal D ₁ is from a low level, even in the present embodiment, the first embodiment and the same effect can be obtained.

Here, in the present embodiment, the abnormality detection circuit 45 corresponds to the frequency upper / lower limit determining means.

In each of the above embodiments, the case where one abnormality detection circuit 35, 45 is provided is described.However, the present invention is not limited to this, and both are provided, and one of the abnormality detection circuits detects an abnormality. Occasionally, the configuration may be such that the analog switch 40 is turned off.

The output of the abnormality detection circuits 35 and 45 is directly
It is good also as composition supplied to 9.

Further, in the above embodiment, the coil is controlled according to the steering torque.
The case where the present invention is applied to a torque sensor having a configuration in which the self inductances L ₁ and L ₂ of 16 and 17 are changed has been described. May be changed.

〔The invention's effect〕

As described above, according to the inventions described in claims (1) and (2), it is monitored whether the amplitude or frequency of the output of the oscillation circuit is within an allowable range, and thus the coil is excited. It is possible to detect an abnormality in the oscillation circuit and the power supply part, and there is an effect that the reliability of the torque sensor for the power steering device is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a first embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view taken along line AA of FIG. 1, FIG. 3 is a development view of a portion that changes the inductance of the coil, FIG. 4 is a circuit diagram of a relative rotation detection circuit, and FIG. , FIG. 6 is a circuit diagram of a configuration for transmitting the detection result of the abnormality detection circuit to the controller, FIG. 7 is a graph showing the relationship between the torque and the self-inductance of the coil, and FIG. FIG. 9 is a circuit diagram of the abnormality detection circuit according to the second embodiment of the present invention, FIG. 10 is a waveform diagram of the abnormality detection circuit when the frequency deviates to a lower frequency, and FIG. FIG. 12 is a waveform diagram of the abnormality detection circuit when the frequency is normal, and FIG. 12 is a waveform diagram of the abnormality detection circuit when the frequency is shifted to the higher frequency. 2 ... input shaft (first rotating shaft), 3 ... output shaft (second rotating shaft), 4 ... torsion bar (elastic member), 9,10 ...
… Flange part, 9a, 10a, 13a …… Protrusion, 11 …… Cylindrical member,
12… Shaft, 13… Ring, 16,17 …… Coil, 21
…… Bridge circuit, 22,23 …… Processing circuit, 30 …… Oscillation circuit, 35 …… Abnormality detection circuit (amplitude upper / lower limit judgment means), 45…
... Abnormality detection circuit (frequency upper / lower limit judgment means)

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-40517 (JP, A) JP-A-46-7393 (JP, A) JP-A-57-178427 (JP, A) 130807 (JP, U) Actually open 62-17422 (JP, U)

Claims (2)

(57) [Claims] A first coaxially disposed first and second rotating shaft, an elastic member for connecting the first and second rotating shafts, and an electromotive force induced by an output of an oscillation circuit are induced. A coil, an inductance changing unit that changes an inductance of the coil according to a relative rotation between the first and second rotation axes, and the first and second rotations based on an electromotive force induced in the coil. A torque calculating means for calculating the torque transmitted to the shaft, wherein the amplitude of the output of the oscillation circuit is within an allowable range defined by an upper limit and a lower limit. And an amplitude upper / lower limit determining means for determining whether or not there is an error, wherein when the amplitude of the output of the oscillation circuit is out of the allowable range, it is determined that an abnormality has occurred. Torque sensor for word steering device. 2. An electromotive force induced by an output of an oscillation circuit, wherein first and second rotation shafts coaxially arranged, an elastic member connecting the first and second rotation shafts, and an output of an oscillation circuit are induced. A coil, an inductance changing unit that changes an inductance of the coil according to a relative rotation between the first and second rotation axes, and the first and second rotations based on an electromotive force induced in the coil. A torque calculating means for calculating the torque transmitted to the shaft, wherein the frequency of the output of the oscillation circuit is within an allowable range defined by an upper limit and a lower limit. Frequency upper / lower limit determining means for determining whether or not there is an error, wherein when the frequency of the output of the oscillation circuit is out of the allowable range, it is determined that an abnormality has occurred. Power steering apparatus for a torque sensor.