JPH0731149Y2 - Torque sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a torque sensor, and particularly proposes a torque sensor suitable for being applied to an electric power steering device of an automobile.

[Conventional technology]

An electric power steering device is being developed as a power steering device for assisting a force for operating a steering wheel of an automobile. This has a structure in which the torque applied by the steered wheels is detected, and the electric motor provided in the steering mechanism is rotated according to the detected torque. By the way, the conventional torque sensor for detecting the torque applied by the steered wheels has a structure using a potentiometer.

However, if a potentiometer is used, contact failure may occur due to long-term use thereof, and torque may be erroneously detected. Therefore, the applicant of the present application has proposed, for example, a torque sensor having a structure shown in a half cross-sectional view in FIG. 3 (for example, Japanese Patent Application No. 63-72269). The input shaft 1 includes an upper shaft 1a to which a steering wheel (not shown) is attached and a lower shaft 1c to which a pinion (not shown) of the steering mechanism is attached.
It is coaxially connected via 1b, is inserted through a cylindrical case 2, and is rotatably supported by the case 2 by a bearing 3.

A first sleeve 4a made of a non-magnetic material is externally fitted and fixed to the lower end portion (left side in the drawing) of the upper shaft 1a, and a first cylinder 5 and a second cylinder 6 made of a magnetic material are attached to the first sleeve 4a. It is externally fitted and fixed with a proper distance in the axial direction.

The second cylinder 6 has a large number of teeth 6a provided around the shaft end surface of the first cylinder 5 which is not opposed to the shaft end surface. On the other hand, the lower shaft
A second sleeve 4b made of a non-magnetic material is externally fitted and fixed to 1c, and a third cylinder 7 made of a magnetic material is externally fitted and fixed to the second sleeve 4b. The third cylinder 7 has a large number of tooth portions 7a on the shaft end face opposite to the shaft end face of the second cylinder 6. The shaft end faces of the second and third cylinders 6 and 7 on which the tooth portions 6a and 7a are formed face each other with a proper distance. A bobbin 8 having two circumferential grooves 8a, 8b formed on its inner peripheral surface is internally fitted and fixed in the case 2, and the bobbin 8 is located at a position facing the shaft end surfaces of the first and second cylinders 5, 6. A temperature compensating coil 9 for obtaining an induced voltage related to magnetic coupling between the first and second cylinders 5 and 6 is wound around the opposing circumferential groove 8a. In addition, in the circumferential groove 8b facing the axial end surface facing positions of the second and third cylinders 6 and 7, the second and third cylinders 6 and
Torque detection coil 10 to obtain induced voltage by magnetic coupling of 7
Is wound.

The oscillation output of a high-frequency oscillator (not shown) is used as the torque detection coil.
10 and the temperature compensation coil 9. Now, when a rotational torque is applied to the upper shaft 1a, the torsion bar 1b is twisted according to the torque, and the second cylinder 6 fixed to the upper shaft 1a is
It rotates relative to the third cylinder 7 fixed to the lower shaft 1c. As a result, the opposed areas of the shaft end surfaces of both cylinders 6 and 7 change, the magnetic coupling state of both cylinders 6 and 7 changes according to the torque, and the induced voltage of torque detection coil 10 changes.
On the other hand, the induced voltage of the temperature compensation coil 9 is the first, second cylinder 5,
It is obtained according to the magnetic coupling state of 6 and changes accordingly when the ambient temperature changes and the facing area of both cylinders 5 and 6 changes. Therefore, the temperature-compensated detection torque is obtained by obtaining the induced voltage difference between the torque detection coil 10 and the temperature compensation coil 9. Separately from this, Japanese Patent Laid-Open No. 59-46526 discloses a pair of high magnetic permeability materials in which a serrated edge is formed at the shaft end and the serrated edges are opposed to each other. An electromagnetic stress sensor including a tubular body and a torque detection coil surrounding the tubular body so as not to contact the tubular body is shown. Further, in Japanese Patent Laid-Open No. 58-73833, detection coils are arranged in parallel on both sides of an excitation coil, whereby two detection coils are provided, and a relative displacement angle in a rotating state. A non-contact measuring device is shown.

[Problems to be solved by the device]

By the way, since both the conventional torque sensor and the electromagnetic stress sensor disclosed in Japanese Patent Laid-Open No. 59-46526 are provided with a single torque detection coil 10, if the torque detection coil 10 is disconnected. The torque acting on the upper shaft 1a cannot be detected. The relative displacement angle non-contact measuring device in the rotating state disclosed in Japanese Patent Laid-Open No. 58-73833 obtains the relative output by obtaining the differential output of two detection coils arranged side by side on the excitation coil. Since the displacement angle is measured, there is a problem that the relative displacement angle cannot be detected when one of the detection coils is broken. Therefore, if a vehicle is equipped with such a torque sensor,
There is a problem that the driver is forced to operate the steered wheels with a strong force after the disconnection.

In view of such a problem, the present invention has an object to provide a torque sensor that continuously detects the torque even when the torque detection by one torque detection coil becomes impossible.

[Means for Solving the Problems]

The torque sensor according to the present invention is fixed to one of the two shafts connected via a torsion bar, and is made of a magnetic material having first and second magnetic members having toothed portions around the end surface of one shaft. And a shaft fixed to the other shaft, and a tooth portion is provided around the one side shaft end surface, and the tooth portion faces the one side shaft end surface of the first and second cylinders,
Third and fourth cylinders made of magnetic material, the end faces of the other side shafts of which face each other, and a first torque detection coil for obtaining an induced voltage related to magnetic coupling between the first cylinder and the third cylinder. , Second
A second torque detecting coil for obtaining an induced voltage related to the magnetic coupling between the cylinder and the fourth cylinder; a first temperature compensation coil arranged on the outer periphery of the third cylinder; The second temperature compensation coil disposed on the outer periphery and the differential output between the first torque detection coil and the first temperature compensation coil are used as the first output, and the second torque detection coil and the second temperature are detected. A differential output from the compensation coil is used as a second output, and the first output and the second output are input, and selection means for selectively outputting one of the two outputs is provided. And

[Action]

When a rotational torque is applied to one of the two shafts connected via the torsion bar, the torsion bar is twisted. The first and third cylinders and the second and fourth cylinders relatively rotate in equal amounts, respectively, and the facing areas of the shaft end faces facing each other change. An induced voltage corresponding to the magnetically coupled states of the first and third cylinders is generated in the first torque detection coil. Second
An induced voltage corresponding to the magnetically coupled states of the second and fourth cylinders is generated in the torque detection coil.

Each of the first and second temperature compensation coils has a third cylinder and a fourth cylinder.
An induced voltage is generated which is related to the magnetic coupling state of the shaft end face which faces the cylinder of. The voltage difference between the induced voltage of the first torque detection coil and the induced voltage of the first temperature compensation coil becomes the first output that is the temperature-compensated detected torque, and the induced voltage of the second torque detection coil and the second output. The voltage difference from the induced voltage of the temperature compensation coil of is the second output which is the temperature-compensated detected torque. When the first output or the second output disappears due to a failure, the selecting means selects and outputs the second output or the first output.

As a result, the rotational torque applied to one shaft is
Both torque detection coils detect. First due to failure
The torque cannot be detected even if any of the output of 1 and the output of 2 disappears.

As a result, the rotational torque applied to one shaft is detected by both the first and second torque detection coils.

〔Example〕

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

FIG. 1 is a half sectional view showing a structure of a torque sensor according to the present invention. The input shaft 100 includes an upper shaft 11a to which a steering wheel (not shown) is attached and a lower shaft 11c to which a pinion (not shown) of a steering mechanism is attached, and a torsion bar 11b.
Is connected coaxially via the upper shaft 11
a is a bearing 1 in a cylindrical case 12 fixed to the vehicle body, for example.
It is rotatably supported via 3.

The outer diameter of the lower end of the upper shaft 11a (on the left side in the drawing) is small for insertion into the hole of the upper end of the lower shaft 11c (on the right side in the drawing). Around the upper end of the lower shaft 11c, a circumferential recess 1 with an appropriate width
1d is provided. A first sleeve 14a made of a non-magnetic material having an inner diameter dimension slightly larger than the outer diameter dimension of the lower shaft 11c is loosely fitted and disposed at the position of the circumferential recessed portion 11d. Insert the pin 15 engaged in this into the lower shaft 11c
Is penetrated in the radial direction and is engaged with the small diameter portion of the upper shaft 11a, and is concentrically provided around the upper shaft 11a. A plurality of pins 15 are equally arranged in the circumferential direction of the first sleeve 14a, and the lower shaft 11c portion through which these pins penetrate is the lower shaft 11c.
A pin hole 11e having an appropriate length is provided in the circumferential direction so as not to hinder the rotation of the pin. As a result, the first sleeve 14a is linked with the upper shaft 11a.

The first sleeve 14a is provided with a first cylinder 61 made of a magnetic material and having a plurality of teeth 61a provided on one end of the shaft.
The upper shaft 11a is set to the upper end side (right side in the drawing) of the upper shaft 11a for external fitting.

A second sleeve 14b made of a non-magnetic material is externally fitted and fixed to the large-diameter portion at the lower end of the upper shaft 11a. The second sleeve 14b has the same pitch as the tooth portion 61a on the end face of one side of the shaft. The second cylinder 62 made of a magnetic material and surrounding a large number of tooth portions 62a is externally fitted and fixed with the tooth portion 62a facing the tooth portion 61a. The upper end of the lower shaft 11c has a third non-magnetic material
The sleeve 14c is externally fitted and fixed, and the third sleeve 14c
Includes a large number of teeth 63a at the same pitch as the teeth 61a on the end face of one shaft.
A third cylinder 63 made of a magnetic material and a fourth cylinder 64 made of a magnetic material having a large number of tooth portions 64a.
The other-side shaft end surfaces 63b, 64b having no tooth portions 63a, 64a are opposed to each other with a proper distance therebetween and are externally fitted and fixed. Then, the shaft end surface having the tooth portion 61a of the first cylinder 61 and the tooth portion 6 of the third cylinder 63.
3a and one side shaft end surface, and also the tooth portion 62 of the second cylinder 62.
The one-side shaft end surface having a and the one-side shaft end surface having the tooth portion 64a of the fourth cylinder 64 face each other at the same distance.
Further, the tooth portions 61a and 63a and the tooth portions 62a and 64a have the same facing state.

In addition, the opposed tooth portions are opposed to each other in the entire tooth width, but may be opposed to each other in a part of the tooth width.

Inside the case 12, there are four circumferential grooves 16a, 16b, 16 on the inner peripheral surface.
A bobbin 16 in which c and 16d are arranged side by side in the axial direction is internally fixed. When the bobbin 16 is fitted in a predetermined position of the case 12, the center of the circumferential groove 16a in the width direction is toothed portions 61a and 63a.
Circumferential grooves 16b and 16c are provided at positions facing a, and third and fourth cylinders 63 and 6 are provided.
Provided so that the center of the circumferential groove 16d in the width direction is located at the position facing the tooth portions 62a, 64a of the second and fourth cylinders 62, 64, respectively, near the positions facing the other shaft end surfaces 63b, 64b of the other 4 side. ing. And the circumferential groove 16a
The first torque detecting coil 17 in the
The torque detecting coils 18 are wound along the respective grooves, the wire diameters of the coils 17 and 18 are the same, and the number of windings is appropriately the same.

Further, the first temperature compensation coil 19 is provided in the circumferential groove 16b and the first temperature compensation coil 19 is provided in the circumferential groove 1b.
The second temperature compensating coil 20 is wound around the groove 6c along the groove. The coils 19 and 20 have the same wire diameter and the same number of turns. Furthermore, the winding directions of the torque detection coils 17 and 18 are the same, and the temperature compensation coil 1
The winding direction of 9,20 is the same direction.

FIG. 2 is a circuit diagram of an essential part of an electric circuit of the torque sensor of the present invention. One ends of the first and second torque detection coils 17 and 18 and the first and second temperature compensation coils 19 and 20 are grounded.

First torque detection coil 17 and first temperature compensation coil 19
To the positive and negative input terminals + and − of the first differential amplifier 21.
And each is connected. The other ends of the second torque detection coil 18 and the second temperature compensation coil 20 are connected to the second differential amplifier 22.
Each of the positive and negative input terminals of + and-is connected. The outputs of the first and second differential amplifiers 21 and 22 are input to the amplifier circuits 23 and 24, respectively. The multiplexer 2 outputs the outputs of the amplifier circuits 23 and 24, respectively.
Input to each of the 5 input terminals 25a and 25b
The output signal TS selected by 25 is given to the control circuit (not shown) of the power steering motor. Further, a selection command signal SS is given to the multiplexer 25 from a selection control unit (not shown).

Next, the operation of the torque sensor of the present invention will be described with reference to FIG. When operating this torque sensor, for example, 5
A high-frequency oscillator (not shown) that oscillates at ˜10 kHz is oscillated, and its oscillation output is given to each of the first and second torque detection coils 17 and 18 and the first and second temperature compensation coils 19 and 20. Then, an induced voltage related to the magnetic coupling state of the one-side shaft end faces of the cylinders 61 and 63 is applied to the torque detection coil 17, and a magnetic coupling state of the one-side shaft end face of the cylinders 62 and 64 is applied to the torque detection coil 18. A related induced voltage is generated in the temperature compensation coils 19 and 20 related to the magnetic coupling state of the other shaft end faces of the cylinders 63 and 64.

Now, when operating the steered wheels (not shown in FIG. 1) to rotate the upper shaft 11a in the clockwise direction (solid arrow direction), the torsion bar 11b is twisted, and the first and second cylinders 61, 62 move to the third position. ,
By rotating relative to the fourth cylinders 63 and 64 in the clockwise direction, the facing areas of the tooth portions 61a and 63a and 62a and 64a are reduced, and the magnetic coupling becomes small. The induced voltage of the second torque detection coils 17 and 18 becomes low. On the other hand, the magnetic coupling of the portions where the other shaft end surfaces 63b and 64b of the third and fourth cylinders 63 and 64 face each other does not change. Therefore, the first and second temperature compensation coils 1
The induced voltage of 9,20 does not change. Thereby the differential amplifier 2
The outputs of 1, 22 are related to the relative rotation difference described above. The respective outputs of the two differential amplifiers 21 and 22 are the amplification circuit 2
The signals are input to 3, 24, amplified, and then input to the multiplexer 25. The multiplexer 25 selects one of the outputs of the amplifier circuits 23 and 24 by the selection command signal SS and outputs it to the control circuit (not shown) to drive the electric motor according to the detected torque.

Even when the steered wheels are operated in the counterclockwise direction (the direction of the broken arrow), the electromagnetic coupling state becomes small and the induced voltages of the first and second torque detection coils 17 and 18 become the same as in the case described above. It becomes low, and the output is performed in the same manner as described above.

Since the relative rotation amount is determined by the rotation torque applied to the input shaft 11 by the steered wheels, the differential amplifier is eventually used.
The output of 21 or 22 means that the torque can be detected.

Then, for example, when the torque detection coil 17 is broken, its induced voltage disappears and torque detection due to it disappears, but when a selection control unit (not shown) controls it, a new selection command signal SS is given to the multiplexer 25. Then, the multiplexer 25 selects the output of the amplifier circuit 24 and outputs the output signal TS, so that the output of the multiplexer 25 does not disappear instantaneously and the torque detection by the torque sensor does not become impossible.

Therefore, even if one torque detection coil is broken, the power steering control can be continued.

Apart from this, when the ambient temperature of the torque sensor changes, due to the coefficient of thermal expansion, the opposing gaps of the shaft end faces of the first and third cylinders 61 and 63 and the shafts of the second and fourth cylinders 62 and 64 are different. The facing gap of the end faces changes, but the third and fourth other shaft end faces are correspondingly changed.
Since the opposing gap between 63b and 64b also changes, the torque detection coil 1
7, 18 and temperature compensation coils 19 and 20 have the same effect on the induced voltage changes, and differential amplifiers 21 and 22 calculate the induced voltage difference between torque detection coils 17 and 18 and temperature compensation coils 19 and 20, respectively. This allows temperature compensation for torque detection.

The shape of the teeth of the cylinders 61, 62, 63, 64 made of a magnetic material is not limited to this embodiment, and the shape of the magnetic coupling between the opposite shaft end faces is changed by the relative rotation thereof. Good. Alternatively, the multiplexer 25 may be replaced with an OR circuit so that when the output of one amplifier circuit disappears, the output of the other amplifier circuit is output.

The torque sensor of the present invention can be applied not only to the power steering device of an automobile but also to the measurement of the rotation amount itself.

[Effect of device]

As described in detail above, the torque sensor of the present invention is
The torque detection coil and the first and second temperature compensation coils, and the differential output between the output of the first torque detection coil and the output of the first temperature compensation coil, and the output of the second torque detection coil. Since both the differential output of the second temperature compensation coil and the differential output of the second temperature compensation coil are obtained and the differential output is selected and output by the selection means, when one of the differential outputs cannot be obtained due to a failure. , The other differential output is selected and output by the selection means, there is no risk that the torque cannot be detected, temperature compensation for torque detection is performed, and the fail-safe function is provided and the torque detection accuracy is provided. Can be increased.

Therefore, the present invention has an excellent effect of providing a torque sensor having excellent reliability and safety.

[Brief description of drawings]

FIG. 1 is a half sectional view showing a structure of a torque sensor according to the present invention, FIG. 2 is a circuit diagram of an electric circuit main part of a torque sensor of the present invention, and FIG. 3 is a half sectional view showing a structure of a conventional torque sensor. It is a figure. 11a ... upper shaft, 11b ... torsion bar, 11c ... lower shaft, 12
... Case, 17 ... First torque detection coil, 18 ... Second torque detection coil, 19, 20 ... Temperature compensation coil, 61 ... First cylinder 61a ... Tooth portion, 62 ... Second cylinder, 62a ... Tooth Part 63 ... Third cylinder, 63a ... Tooth part, 64 ... Fourth cylinder 64a ... Tooth part, 100 ... Input shaft

Claims (1)

[Scope of utility model registration request] 1. A first and a second cylinder made of a magnetic material, which is fixed to one of two shafts connected via a torsion bar and has teeth on one end of one shaft. , Is fixed to the other shaft, and a tooth portion is provided around the end face of the one side shaft, and the tooth portion has the first and second teeth.
Magnetic coupling between the first and third cylinders, and third and fourth cylinders made of magnetic material, which face the one side shaft end surface of the second cylinder and the other side shaft end surfaces thereof face each other. A first torque detecting coil for obtaining an induced voltage related to the first cylinder, a second torque detecting coil for obtaining an induced voltage related to magnetic coupling between the second cylinder and the fourth cylinder, and an outer circumference of the third cylinder. The first temperature compensation coil arranged and the second temperature compensation coil arranged on the outer circumference of the fourth cylinder.
Of the temperature compensating coil and the differential output of the first torque detecting coil and the first temperature compensating coil as the first output, and the differential output of the second torque detecting coil and the second temperature compensating coil A torque sensor comprising: a second output, the first output and the second output being input, and selection means for selectively outputting one of the two outputs.