JPH04220539A - Torque sensor - Google Patents

Abstract

PURPOSE:To remove the effect of disturbance such as a temp. change in a torque sensor utilizing the inductance of a coil. CONSTITUTION:First coils 20A, 20B changing in inductance corresponding to torque and second coils 20C, 20D having no relation to torque are provided and the torque transmitted to first and second rotary shafts 2,3 is operated corresponding to the electromotive forces induced in the first and second coils 20A-20D.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a torque sensor that detects torque transmitted to a rotating shaft, and in particular, it is capable of accurately detecting torque by removing the effects of external disturbances such as temperature. .

0002

[Background Art] 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 due to twisting of the torsion bar. . Since the direction and amount of the relative rotation are determined by the direction and magnitude of the torque transmitted to the rotating shaft, the torque can be detected by measuring the relative rotation.

[0003] Sensors that measure the relative rotation between two rotating shafts include contact-type sensors that use potentiometers, etc., and non-contact-type sensors that use changes in coil inductance, etc. Contact-type sensors have a problem in that they have a sliding part and are therefore at high risk of disconnection due to wear or the like. Conversely, non-contact sensors have the advantage of having fewer such problems.

0004

[Problem to be Solved by the Invention] However, in non-contact sensors that utilize changes in coil inductance, the detected value fluctuates independently of torque due to the influence of external disturbances such as changes in ambient temperature. Therefore, unless the influence of that disturbance is removed from the measured torque, the reliability of the measurement results will be low, and if it is left unreliable in equipment that requires high accuracy (
For example, it could not be used in automobile power steering devices).

[0005]Although a method of adjusting the temperature around the torque sensor to eliminate disturbances caused by temperature changes is possible,
This results in an extremely large size of the device, and has the disadvantage that it cannot be installed especially around a steering shaft where installation space is limited. This invention was made with attention to the problems that need to be solved with the conventional technology, and it is an object of the present invention to develop a torque sensor that can eliminate the effects of external disturbances such as temperature changes without significantly increasing the size of the device. is intended to provide.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the torque sensor of the present invention includes first and second rotating shafts arranged coaxially, and a connecting elastic member; a variable magnetic resistance means for changing the magnetic resistance of the magnetic circuit according to the relative rotation between the first and second rotating shafts; and a first coil disposed within the magnetic circuit. , a second coil disposed outside the magnetic circuit, and torque transmitted to the first and second rotating shafts based on electromotive force induced in the first coil and the second coil. Torque calculating means for calculating.

[0007]

[Operation] When torque is transmitted to the first and second rotating shafts, the elastic member is twisted, and the tension between the first and second rotating shafts changes depending on the direction and magnitude of the torque. A relative rotation occurs. Then, since the magnetic resistance variable means changes the magnetic resistance of the magnetic circuit, the inductance of the first coil changes in accordance with the change in the magnetic resistance of the magnetic circuit.
An electromotive force corresponding to the torque is induced in the coil.

On the other hand, since the second coil is disposed outside the magnetic circuit, it is not affected by the variable magnetic resistance means, and the electromotive force induced therein is unrelated to torque. However, the influence of disturbances such as temperature is
Since both of the coils are affected by the disturbance, the first
The inductance of both the coil and the second coil varies.

In other words, the electromotive force induced in the first coil has a value that depends on the torque and the disturbance, but the electromotive force induced in the second coil has a value that depends only on the disturbance. , in the torque calculation means, the first and second coils are
The torque transmitted to the coil is calculated.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. 1 to 4 are diagrams showing a first embodiment of the present invention. First, to explain the configuration, FIG. 1 is a sectional view of a vehicle power steering device to which a torque sensor according to the present invention is applied. An input shaft 2 as a first rotation shaft and an output shaft 3 as a second rotation shaft are rotatably supported by bearings 5a, 5b, and 5c. However, the input shaft 2, output shaft 3, and torsion bar 4 are arranged coaxially.

The opening of the housing 1 on the input shaft 2 side is sealed by a seal ring 6, and the opening on the output shaft 3 side is sealed with a cap 7. A steering wheel is integrally attached to the right end side of the input shaft 2 in the rotation direction in FIG. 3a is integrally formed, and furthermore, the pinion shaft 3a is connected to the rack shaft 8 of the rack and pinion type steering device within the housing 1.
It meshes with the

Therefore, the steering force generated by the driver steering the steering wheel is transmitted to the steered wheels (not shown) via the input shaft 2, torsion bar 4, output shaft 3, pinion shaft 3a, and rack shaft 8. be done. on the other hand,
A protrusion 2a continuous in the axial direction is formed on the left end of the input shaft 2, and the protrusion 2a is a vertical groove formed on the right end of the output shaft 3 and slightly wider than the protrusion 2a. 3b, thereby preventing relative rotation between the input shaft 2 and the output shaft 3 beyond a predetermined range (approximately ±5 degrees).

Furthermore, a gear 3A for transmitting the output of an electric motor (not shown) to the output shaft 3 as a steering assist torque is integrally fitted onto the right end of the output shaft 3 in the rotation direction. Note that the inner peripheral surface of the left end of the input shaft 2 and the torsion bar 4
A bush 4a is interposed between the outer circumferential surface of the left end portion of the bush 4a. The input shaft 2 also has a boss 10 formed on the inner diameter side.
Disc 1 made of a conductor such as aluminum by fitting a onto the outside
The flange portion 11 is formed by being spaced apart from the disk 10 toward the output shaft 3 side in the axial direction and having a larger diameter than other portions.

Furthermore, a cylindrical member 12 is externally fitted between the disk 10 and the flange portion 11 of the input shaft 2 via a bush 13 so as to be rotatable relative to the input shaft 2. A boss 14a formed on the inner circumferential side is fitted onto the end of the cylindrical member 12 on the disk 10 side, so that the disk 14 made of a conductor such as aluminum is fixed adjacent to the disk 10. At the same time, a flange portion 15 is formed at the end portion on the flange portion 11 side by molding it to have a larger diameter than other portions.

The cylindrical member 12 also has a cylindrical shaft that passes through the flange portion 11 with a sufficient gap to prevent contact, has one end loosely inserted into the square hole 3c of the output shaft 3, and is parallel to the input shaft 2. The other end side of 16 is press-fitted. Here, the shaft 16 and the square hole 3c are integral in the rotational direction of the output shaft 3, but are inserted loosely in the axial direction of the shaft 16, so that a relative displacement in the axial direction can be caused by a relatively small force. is possible.

Further, a cylindrical coil holding member 17 is arranged between the disk 14 and the flange portion 15 so as to be rotatable relative to the cylindrical member 12. Coil holding member 1
7 has an outer circumferential surface close to the inner circumferential surface of the housing 1, and the inner end of a pin 18 press-fitted into the housing 1 is inserted into a groove 17a cut in the outer circumferential surface parallel to the axis. Therefore, it is integrated with the housing 1 in the rotational direction, but integrated with the cylindrical member 12 in the axial direction.

Furthermore, a bobbin 17b is embedded in the end surface of the coil holding member 17 on the disk 14 side.
7b, four coils 20A, 20B, 20C and 20D are arranged in two layers in both the axial direction and the radial direction.
It is wound coaxially with the input shaft 2. 2(a) is a plan view of the disk 14, FIG. 2(b) is a plan view of the disk 10, and FIG. 2(c) is a plan view of the disks 10 and 14 superimposed.

That is, as shown in FIG. 2(a), the disk 14
, a plurality of through holes 23, . . . , 23 and 24, .
4 is open. These through holes 23,..., 23 and 2
4, . . . , 24 are opened at intervals of half a pitch from each other such that the radially inner through holes 24 face between the radially outer through holes 23, 23.

On the other hand, as shown in FIG. 2(b), the disk 10
, there are elongated through holes 2 extending from the outside in the radial direction to the inside at the same pitch as the through holes 23,..., 23 and 24,..., 24.
5 is open. When there is no relative rotation between the input shaft 2 and the output shaft 3, that is, when the steering torque is zero, as shown in FIG. 2(c), the through holes 23, 2
4 and the through hole 25 is 50% (the most overlapping state is 100%).
0 and 14 are fixed.

FIG. 3 shows a structure including coils 20A to 20D, and based on the electromotive force induced in these coils 20A to 20D, relative rotation between the input shaft 2 and the output shaft 3, that is, generated in the steering system. FIG. 2 is a block diagram of a circuit for detecting steering torque. As shown in the figure, four coils 20A
~ 20D, the coil 20A disposed on the radially outer side and on the disk 14 side, and the radially inner side and the flange portion 1
The coil 20D arranged on the 1 side is connected in series, the coil 20B arranged on the radially inner side and on the disk 14 side, and the coil 20C arranged on the radially outer side and on the flange part 11 side are connected in series. A bridge circuit 3 is formed by connecting these coils and two resistors R1 and R2 with equal resistance values.
0, the resistors R1 and R2 are connected to an oscillation circuit 31 that supplies an AC voltage v0 of a predetermined frequency, and the coils 20C and 20D are grounded.

[0021] Then, the voltage v1 between the resistor R1 and the coil 20A, and the voltage v between the resistor R2 and the coil 20B.
2 is supplied to the differential amplifier circuit 32, the output voltage v3 of this differential amplifier circuit 32 is supplied to the smoothing circuit 33,
The voltage V1 smoothed by this smoothing circuit 33 is supplied to an amplifier circuit 34. Note that by appropriately adjusting the amplification factor of the amplifier circuit 34 and supplying an offset voltage to the amplifier circuit 34, the output voltage VOUT is a value within a predetermined range (for example, 0 to 5 V), and the torque is It is standardized to have a neutral value (for example, 2.5V) when it is zero.

Furthermore, the output voltage VOUT of this detection circuit
is supplied to a controller (not shown), and the controller supplies an operating current to an electric motor (not shown) connected to the gear 3A in accordance with the supplied output voltage VOUT, that is, the steering torque generated in the steering system. do. Next, the operation of this embodiment will be explained.

Now, assuming that the steering system is moving straight and the steering torque is zero, there is no relative rotation between the input shaft 2 and the output shaft 3, so they are integral with the input shaft 2 in the direction of rotation. No relative rotation occurs between the circular plate 10 and the circular plate 14, which is integrated in the rotational direction with the cylindrical member 12 to which the rotational force of the output shaft 3 is transmitted via the shaft 16. Therefore, as shown in FIG. 2C, the overlap between the through holes 23 and 25 and the overlap between the through holes 24 and 25 are each 50%.

On the other hand, when a rotational force is generated on the input shaft 2 by steering the steering wheel, the rotational force is transmitted to the output shaft 3 via the torsion bar 4. At this time, a resistance force is generated in the output shaft 3 according to the frictional force between the steered wheels and the road surface, the frictional force of the rack and pinion type steering device, etc., so a torsion bar is generated between the input shaft 2 and the output shaft 3. 4
When the output shaft 3 side is twisted, relative rotation occurs with a delay on the output shaft 3 side.

[0025] Then, relative rotation also occurs between the discs 10 and 14, so that the overlap between the through holes 23 and 25 and the overlap between the through holes 24 and 25 change. That is, when the steering torque is zero, FIG. 2(c)
In such an overlapping state, when the steering torque in the clockwise direction increases, the overlapping between the through holes 23 and 25 increases, and the overlapping between the through holes 24 and 25 decreases. Conversely, when the steering torque in the counterclockwise rotation direction increases, the overlap between the through holes 23 and 25 decreases,
The overlap between the through holes 24 and 25 increases.

Here, when the excitation coil 22 is supplied with an alternating current v0 from the oscillation circuit 31, the coils 20A to 20
An electromotive force is induced in D, but the electromotive force induced in each coil 20A-20D differs depending on the self-inductance of each coil 20A-20D. Also, coil 2
Since 0A and 20B are arranged opposite to the disks 10 and 14, the disks 10 and 14 are connected to the coil 20.
It forms part of a magnetic circuit through which the magnetic fluxes generated by A and 20B communicate.

A magnetic shielding effect occurs due to the eddy current generated when the magnetic flux interlinks with the disks 10 and 14, and the magnetic resistance of the magnetic circuit changes due to the magnetic shielding effect. Since it is approximately proportional to the shield area, the self-inductance of the coil 20A is affected by the overlap between the through-holes 23 and 25, and the self-inductance of the coil 20B is affected by the overlap between the through-holes 24 and 25. It will be influenced and changed.

In other words, since the overlap between the through holes 23, 24 and the through hole 25 changes according to the steering torque as described above, the self-inductance of the coils 20A and 20B changes according to the direction and magnitude of the steering torque. However, they have characteristics that increase and decrease in opposite directions depending on the torque. On the other hand, the coils 20C and 20D are connected to the disk 10
and 14,
The overlapping of the through holes 23, 24 and the through hole 25 does not affect the self-inductance of the coils 20C and 20D, therefore, the steering torque is unrelated.

The output voltage v1 of one side of the bridge circuit 30 is determined by the self-inductance of the coils 20A and 20D, and the output voltage v2 of the other side is determined by the self-inductance of the coils 20A and 20D.
It is determined by the self-inductance of 0B and 20C,
If disturbances such as temperature changes around the coils 20A to 20D are ignored, the output voltages v1 and v2 will increase and decrease in opposite directions depending on the steering torque.

Therefore, those output voltages v1 and v2
If the difference between the two is obtained by the differential amplifier circuit 32, the output v3 is smoothed by the smoothing circuit 33, and the output V1 is normalized by the amplifier circuit 34, the output voltage VOUT is determined according to the steering torque. The value changes within a predetermined range, which means that the steering torque has been detected. Therefore, if the electric motor is operated according to the output voltage VOUT of the detection circuit shown in FIG. 3, a steering assist torque corresponding to the steering torque is applied to the steering system, so the steering torque decreases. , the burden on the operator is reduced.

Furthermore, the output voltage v1 of the bridge circuit 30
and v2 increase and decrease in opposite directions depending on the steering torque, and when the difference between them is calculated, the slope is twice that of the case when they are used alone, so minute changes in torque can be determined with high precision. . As a result, measurement accuracy can be improved without making the torsion bar 4 more susceptible to twisting, such as by lengthening the torsion bar 4 or reducing its torsional strength. This prevents an increase in the size of the device due to the lengthening of the torsion bar 4 and a decrease in torque transmission characteristics between the input shaft 2 and output shaft 3 due to a decrease in the torsional strength of the torsion bar 4. Furthermore, it is possible to achieve the same accuracy as the conventional device with a small device with a short torsion bar 4.

Furthermore, since the axial coupling force between the shaft 16 and the square hole 3c is eliminated or reduced, for example, an axial force is applied to the input shaft 2 and the torsion bar 4
Even if the cylindrical member 12 is deformed in the axial direction and the axial distance between the input shaft 2 and the output shaft 3 changes, the change in distance is absorbed by the shaft 16 moving back and forth within the square hole 3c. is not transmitted, and the cylindrical member 12 maintains an appropriate axial position between the disk 10 and the flange portion 11.

Further, the coil holding member 17 is integrated with the housing 1 in the rotational direction due to the groove 17a and the pin 18, but is integrated with the cylindrical member 12 in the axial direction, so that it can be attached to the rack shaft 8, for example. When the output shaft 3 and the input shaft 2 move slightly in the axial direction due to the axial support rigidity of the bearings 5a, 5b, and 5c in response to the axial component force generated from the meshing part with the pinion shaft 3a, the input shaft 2 and Even if the relative position in the axial direction with respect to the housing 1 changes, the coil holding member 17 is displaced in the axial direction together with the input shaft 2 and the cylindrical member 12.

In other words, the discs 10, 14 have through holes 23, 24, 25 that change the magnetic resistance of the magnetic circuit;
Since the relative position with respect to the coil holding member 17 holding the coils 20A to 20D does not change due to an axial force, that is, a force unrelated to the steering torque, an output corresponding only to the steering torque can be obtained. . Further, if no relative displacement occurs in the axial direction between the input shaft 2, the cylindrical member 12, and the coil holding member 17, the frictional resistance between the discs 10 and 14, the flange part 11 and the flange part 15, Since the frictional resistance between the coil holding member 17 and the disk 10 and the flange portion 15 does not change from the initial state, high heat generation due to increased frictional force and frictional resistance between the shaft 16 and the coil holding member 17 do not change from the initial state. There are no problems such as an increase in the load applied to the device and a decrease in its durability.

Furthermore, since the coil holding member 17 is integrated with the housing 1 in the rotational direction, the coil 20A
20D and the detection circuit provided outside the housing 1 can be connected without using a slip ring or the like, so there is no risk of disconnection due to wear of the slip ring or the like. FIG. 4 is a graph showing that even if a disturbance such as a temperature change around the torque sensor occurs, it has almost no effect on the detection results, and when the steering torque is zero,
This shows a case where the waveforms of various parts of the detection circuit change from the solid line to the broken line due to a change in ambient temperature.

Note that FIG. 4(a) shows the waveform of the electromotive force induced in the coil 20A, FIG. 4(b) shows the waveform of the electromotive force induced in the coil 20B, and FIG. 4(c) shows the waveform of the electromotive force induced in the coil 20C. (d) is the waveform of the electromotive force induced in the coil 20D, and (e) is the waveform of one output voltage v1 of the bridge circuit 30 (i.e., the waveform of the electromotive force induced in the coil 20A). sum of electric power and electromotive force induced in coil 20D)
, the figure (f) shows the other output voltage v2 of the bridge circuit 30.
(i.e., the sum of the electromotive force induced in the coil 20B and the electromotive force induced in the coil 20C), and (g) in the figure shows the waveform of the output voltage v3 of the differential amplifier circuit 32, respectively.

That is, the disturbance due to temperature change is caused by each coil 2.
It affects the electromotive force induced from 0A to 20D (Figure 4
(a) to (d)) are coils 20A and 20C,
Coils 20B and 20D have different winding diameters, so even though they have the same number of turns, they are different standards as coils.
Therefore, the fluctuations caused by disturbances will also differ (Fig. 4
(see (a) and (b)).

If the coils 20C and 20D are not provided, even if the difference in electromotive force induced in the coils 20A and 20B is determined, the disturbance components contained in them are different, so the disturbance components cannot be canceled out. I can't. However, in this embodiment, since the coils 20A and 20D are connected in series and the coils 20B and 20C are connected in series, the output voltage v1 and Since v2 will eventually include disturbance components of the same magnitude (see Figures 4(e) and (f)), the disturbance components will be canceled out by finding the difference between the output voltages v1 and v2 (Figure 4). (g)) is removed from the output voltage VOUT.

Note that even if a disturbance other than a temperature change occurs, it is of course canceled out by a similar effect. In this way, with the configuration of this embodiment, even if a disturbance such as a temperature change occurs, the detection result is not affected by it, so accurate steering torque can be detected and highly accurate steering assist torque control can be performed. .

Furthermore, since the device does not become significantly larger, it can be easily installed even in areas where installation space is limited, such as around the steering shaft, and it does not require any special equipment. Therefore, there will be no significant cost increase. Here, in this embodiment, the coils 20A and 20B correspond to the first coil, and the coil 20A and 20B correspond to the first coil.
C and 20D correspond to the second coil, and the through holes 25 formed in the disk 10 and the through holes 23 and 2 formed in the disk 14
4 constitutes a variable magnetic resistance means, and the circuit shown in FIG. 3 constitutes a torque calculation means.

FIG. 5 and FIG. 6 are diagrams showing a second embodiment of the present invention, and this embodiment also has the same features as the first embodiment described above.
The torque sensor according to the present invention is applied to an electric power steering device for a vehicle. Note that the same reference numerals are given to the same members and parts as those in the first embodiment.
The redundant explanation will be omitted. That is, in this embodiment, a coaxial excitation coil 40 is disposed between coils 20A and 20B and coils 20C and 20D, and a detection circuit including these coils is configured as shown in FIG. It is.

As shown in the figure, coils 20A and 20
D are connected in series and the voltage between their terminals is converted into a rectifier circuit 41.
and the differential amplifier circuit 32 via the filter 42, and the coils 20B and 20C are connected in series, and the voltage between their terminals is supplied to the differential amplifier circuit 32 via the rectifier circuit 43 and the filter 42, In addition, the excitation coil 40
The output of the oscillation circuit 31 is supplied to the oscillation circuit 31.

[0043] Since the coils 20A and 20B are disposed facing the disks 10 and 14, the first
Due to the same effect as in the embodiment, the mutual inductance between the coils 20A and 20B and the excitation coil 40 changes according to changes in the steering torque, and the coils 20C and 20D
Since it is spaced apart from the disks 10 and 14,
The mutual inductance between the coils 20C, 20D and the exciting coil 40 is independent of the steering torque.

Even with this configuration, when a disturbance such as temperature occurs, the disturbance component included in the voltage between the terminals of the coils 20A and 20D, and the disturbance component included in the voltage between the terminals of the coils 20C and 20C. are equal, these disturbance components are canceled out in the differential amplifier circuit 32 and the output voltage VO
It is removed from the UT, and the same effects as in the first embodiment can be obtained.

[0045] Other functions and effects are the same as those of the first embodiment, so their explanation will be omitted. In this embodiment, the coils 20A and 20B correspond to the first coil, the coils 20C and 20D correspond to the second coil, and the torque calculation means is configured by the circuit shown in FIG.

FIGS. 7 to 10 are diagrams showing a third embodiment of the present invention, and this embodiment also has the same features as the above-mentioned embodiments.
The torque sensor according to the present invention is applied to an electric power steering device for a vehicle. Note that the same reference numerals are given to the same members and parts as in the configuration of each of the above embodiments, and the redundant explanation thereof will be omitted. That is, in this embodiment, two coils 50A and 50B coaxial with the input shaft 2 are wound around the bobbin 17b in parallel in the axial direction. Also, Figure 8
As shown in (a), both discs 10 and 14 are connected to the first
It has the same shape as the disk 10 in the example, and is shown in FIG.
As shown in , when the steering torque is zero, both discs 1
The through holes 25, 25 of Nos. 0 and 14 are arranged so that the overlap is 50%.

As shown in FIG. 9, a bridge circuit 30 is constituted by resistors R1 and R2 and coils 50A and 50B, and one output voltage v1 of the bridge circuit 30, which is the voltage between resistor R1 and coil 50A, is and the bridge circuit 3, which is the voltage between the resistor R2 and the coil 50B.
0 is supplied to the differential amplifier circuit 32, the output voltage v3 of the differential amplifier circuit 32 is supplied to the rectifier circuit 51, and the output voltage V2 of the rectifier circuit 51 is smoothed. It is supplied to the circuit 33.

FIG. 10 is a graph showing the waveforms of each part in FIG. 9. FIG. 10(1) is the waveform of each part under normal conditions without any disturbance such as temperature change, and FIG. 10(2) is the waveform of each part in the temperature range. The waveforms of each part are shown when a disturbance occurs due to a change. In addition, the figure (a) shows the waveform of one output voltage v1 of the bridge circuit 30, and the figure (b) shows the waveform of the output voltage v1 of the bridge circuit 30.
(c) is the waveform of the output voltage v3 of the differential amplifier circuit 32, (d) is the waveform of the output voltage V2 of the rectifier circuit 51, and (e) is the waveform of the output voltage V2 of the rectifier circuit 51. The waveforms of the output voltage V1 of the smoothing circuit 33 are shown.

That is, even in this embodiment, the coil 50A
are arranged opposite to the discs 10 and 14,
Through hole 25 due to relative rotation of those discs 10 and 14,
The self-inductance of the coil 50B changes under the influence of the change in the magnetic resistance of the magnetic circuit due to the change in the overlap of the coils 25, but since the coil 50B is disposed at a distance from the disks 10 and 14, its self-inductance is , disk 1
The relative rotations of 0 and 14 are irrelevant.

Therefore, if the influence of disturbances such as temperature changes is ignored, the voltage between the terminals of the coil 50A varies depending on the steering torque, but the voltage between the terminals of the coil 50B, that is, the output voltage v2 is constant. Therefore, the output voltages v1 and v
The difference between 2 and 2 also varies depending on the steering torque, so in the end,
The output voltage VOUT of the circuit shown in FIG. 9 has a value corresponding to the steering torque, which means that the steering torque has been detected.

On the other hand, when a disturbance such as a temperature change occurs, the change affects the self-inductance of both coils 50A and 50B, so that the output voltages v1 and v2
A disturbance component is included in both (see FIGS. 10(a) and (b)). However, in this embodiment, as shown in FIG. 7, since the coils 50A and 50B are arranged side by side in the axial direction, coils of the same standard can be used for the coils 50A and 50B.

Therefore, since the disturbance components contained in the output voltages v1 and v2 are equal, the disturbance components are canceled out in the differential amplifier circuit 32, and the subsequent output voltages become equal in the normal state and in the disturbance occurrence ( Figures 10(c) to (e)
)reference. ), even if a disturbance such as a temperature change occurs, the output voltage VOUT is not affected by it, and accurate steering torque is detected. Other effects are the same as those of the first embodiment, so their explanation will be omitted.

In this embodiment, the coil 50A corresponds to the first coil, the coil 50B corresponds to the second coil, and the circuit shown in FIG. 9 corresponds to the torque calculation means. 11 to 13 are diagrams showing a fourth embodiment of the present invention, and in this embodiment, the torque sensor according to the present invention is applied to an electric power steering device for a vehicle, similar to the above embodiments. It is something. Note that the same reference numerals are given to the same members and parts as in the configuration of each of the above embodiments, and the redundant explanation thereof will be omitted.

That is, in this embodiment, three coils 50A, 50B coaxial with the input shaft 2 and an excitation coil 60 are wound around the bobbin 17b in parallel in the axial direction. Further, as shown in FIG. 12, a coil 50 disposed on the disk 10 side
The voltage across the terminals of A is supplied to the differential amplifier circuit 32 via the rectifier circuit 41 and the smoothing circuit 33, and the voltage across the terminals of the coil 50B disposed on the flange portion 11 side is supplied via the rectifier circuit 43 and the smoothing circuit 33. The output voltage of the oscillation circuit 31 is supplied to the differential amplifier circuit 32, and the output voltage of the oscillation circuit 31 is supplied to the exciting coil 60 located at the center.

FIG. 13 is a graph showing the waveforms of each part in FIG. 12, and FIG.
2) shows the waveforms of each part when a disturbance due to temperature change occurs. In addition, the same figure (a) shows the coil 50A.
(b) shows the waveform of the voltage between the terminals of the coil 50B, (c) shows the waveform of the output voltage of the rectifier circuit 41, and (d) shows the waveform of the output voltage of the rectifier circuit 43. The waveform, (e) is the waveform after the output voltage of the rectifier circuit 41 has passed through the smoothing circuit 33, (f) is the waveform after the output voltage of the rectifier circuit 43 has passed through the smoothing circuit 33, (g) ) indicate the waveform of the output voltage of the differential amplifier circuit 32, respectively.

[0056] The coil 50A is connected to the disks 10 and 1.
4, the mutual inductance between the coil 50A and the excitation coil 60 varies according to changes in the steering torque due to the same effect as in the first embodiment, and the coil 50B Since the coil 50B and the excitation coil 60 are arranged apart from the disks 10 and 14,
The mutual inductance with is independent of the steering torque.

Therefore, if the influence of disturbances such as temperature changes is ignored, the voltage between the terminals of the coil 50A varies depending on the steering torque, but the voltage between the terminals of the coil 50B is constant. Therefore, since the difference in voltage between these terminals also varies according to the steering torque, the output voltage VOU of the circuit shown in FIG.
T has a value corresponding to the steering torque, which means that the steering torque has been detected.

On the other hand, when a disturbance such as a temperature change occurs, the change affects the mutual inductance between the coil 50A and the excitation coil 60, and the mutual inductance between the coil 50B and the excitation coil 60, so that the voltage between both terminals changes. The disturbance component ε is included (see FIGS. 13(a) and (b)), and the outputs of the rectifier circuits 41 and 43 and the smoothing circuit 33 also fluctuate compared to the normal state (see FIGS. 13(c) and 13(d)). , (e) and (f)).

However, the disturbance component ε is
2, and the subsequent output voltage is the same under normal conditions and when a disturbance occurs (see (g) in the same figure). Therefore, even if a disturbance such as a temperature change occurs, the output voltage VOUT is not affected by it. , accurate steering torque is detected. Other effects are the same as those of the first embodiment, so their explanation will be omitted.

In this embodiment, the coil 50A corresponds to the first coil, the coil 50B corresponds to the second coil, and the circuit shown in FIG. 12 constitutes the torque calculation means. In addition, although the above-mentioned each Example demonstrated the case where the torque sensor based on this invention was applied to the power steering apparatus for vehicles, the object of application of this invention is not limited to this.

Furthermore, in each of the above embodiments, the magnetic resistance of the magnetic circuit is changed by utilizing the magnetic shielding effect caused by the change in the overlapping of the through holes, but the configuration for changing the magnetic resistance is limited to this. However, other configurations may be used instead.

[0062]

[Effects of the Invention] As explained above, according to the present invention,
A first coil whose inductance changes according to torque and a second coil unrelated to torque are provided, and the torque is determined based on the electromotive force induced in these coils, which significantly increases the size of the device. The effect of this method is that the influence of disturbances such as temperature changes can be removed from the detection results without causing an increase in costs or increase in costs, and accurate torque can be determined.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of a first embodiment of the present invention.

FIG. 2 is a plan view of a configuration for changing the magnetic resistance of a magnetic circuit in the first embodiment.

FIG. 3 is a circuit diagram of a circuit for determining steering torque in the first embodiment.

FIG. 4 is a graph showing waveforms of various parts of a circuit for determining steering torque in the first embodiment.

FIG. 5 is a sectional view showing the configuration of a second embodiment of the present invention.

FIG. 6 is a circuit diagram of a circuit for determining steering torque in a second embodiment.

FIG. 7 is a sectional view showing the configuration of a third embodiment of the present invention.

FIG. 8 is a plan view of a configuration for changing the magnetic resistance of a magnetic circuit in a third embodiment.

FIG. 9 is a circuit diagram of a circuit for determining steering torque in a third embodiment.

FIG. 10 is a graph showing waveforms of various parts of a circuit for determining steering torque in the third embodiment.

FIG. 11 is a sectional view showing the configuration of a fourth embodiment of the present invention.

FIG. 12 is a circuit diagram of a circuit for determining steering torque in a fourth embodiment.

FIG. 13 is a graph showing waveforms of various parts of a circuit for determining steering torque in the fourth embodiment.

[Explanation of symbols]

2 Input shaft (first rotating shaft) 3 Output shaft (second rotating shaft) 4 Torsion bar (elastic member) 10, 14
Discs 20A, 20B, 50A Coil (first coil) 20C, 20D, 50B Coil (second coil) 23, 24, 25 Through hole 30 Bridge circuit 31 Oscillator circuit 32 Differential amplifier circuit 33 Smoothing circuit 34 Amplifier circuit 40,60 Excitation coil

Claims (1)

[Claims] 1. First and second rotating shafts disposed coaxially, an elastic member connecting the first and second rotating shafts, and relative rotation between the first and second rotating shafts. a magnetic resistance variable means for changing the magnetic resistance of the magnetic circuit according to the magnetic circuit; a first coil disposed within the magnetic circuit; a second coil disposed outside the magnetic circuit; A torque sensor comprising: torque calculation means for calculating torques transmitted to the first and second rotating shafts based on electromotive force induced in the coil and the second coil.