JPH0476426A - Torque sensor - Google Patents

Abstract

PURPOSE:To enhance the accuracy of measurement by providing two coils for obtaining two outputs in directions which are opposite to each other in accordance with a torque, and by computing the torque in accordance with an output from a differential amplifier for obtaining a difference between the above-mentioned two outputs. CONSTITUTION:A difference in inductance between two coils 16, 17 caused by an induced torque in a rotational direction causes a bridge circuit 20 to be out of balance so that a differential amplifier 22 detects the difference and delivers the same to analog switches 25, 26. The output of the amplifier 22 is turned into a sinusoidal wave in accordance with a frequency of an oscillator 21, and if the polarity of a non-inverted input to the amplifier is positive, the output of a comparator 23 is a logical '0' so that the output from an inverter 22 becomes '1'. Accordingly, the switch 25 is turned on but the switch 26 is turned off so that the output of the amplifier 22 is delivered to an non-inverted input terminal of a differential amplifier 24. Meanwhile, the polarity of the non-inverted input to the amplifier 22 is negative, the output of the amplifier 22 is delivered to an inverted input terminal of the amplifier 24 so that the output from the amplifier 24 becomes the absolute value of the output of the amplifier 22. Accordingly, the output of a smoothing circuit 28 is linearly changed to the value of a steering torque in the direction of the latter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a torque sensor that detects torque transmitted to a rotating shaft.

[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 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.

[Problems to be Solved by the Invention] However, in conventional torque sensors that utilize elastic members such as torsion bars, when an axial force is applied to the rotating shaft and the torsion bar is deformed in the axial direction, Another problem is that the means for measuring relative rotation is also affected, and the measurement results fluctuate independently of the torque.

In addition, increasing the amount of relative rotation between the two rotary axes that occurs in response to torque has the advantage of improving measurement accuracy because even minute changes in torque can be detected. Reduce the torsional strength of
Alternatively, the torsion bar may be made longer to make it easier to twist, but this would deteriorate the torque transmission characteristics between the two rotating shafts. In addition, when the torsion bar is made longer, there is also a drawback that the device becomes larger.

This invention was made by focusing on the unresolved problems of the conventional technology, and it is possible to prevent fluctuations in measurement results even when axial force is applied, and to improve transmission between rotating shafts. It is an object of the present invention to provide a torque sensor that can improve measurement accuracy without deteriorating characteristics.

[Means for Solving the Problems] In order to achieve the above object, the torque sensor of the present invention has the following features:
first and second rotating shafts arranged coaxially;
and an elastic member that connects the second rotating shaft, and first and second elastic members that rotate together with the first rotating shaft and are spaced apart in the axial direction.
a movable member arranged between the first and second flange parts and rotatably displaceable about the first rotation axis, and parallel to the first and second rotation axes. One end side is coupled to the second rotation shaft, and the other end side is coupled to the movable member, and the coupling force in the axial direction of at least one of these coupling portions is applied in the axial direction between the movable member and the first rotation shaft. a rotational force transmitting shaft smaller than the coupling force of the rotational force transmitting shaft, and a first magnetic field that changes the magnetic resistance between the first flange portion and the movable member according to the relative rotational displacement between the first rotary shaft and the movable member. a resistance variable means, and a magnetic resistance between the second flange portion and the movable member in a direction opposite to that of the first variable magnetic resistance means according to a relative rotational displacement between the first rotating shaft and the movable member. a second variable magnetic resistance means for changing the magnetic resistance; a first measuring means for measuring the magnetic resistance between the first flange portion and the movable member; and a first measuring means for measuring the magnetic resistance between the second flange portion and the movable member. a second measuring means for measuring the torque, and a torque calculating means for calculating the torque transmitted to the first and second rotating shafts based on the difference between the measurement results of the first and second measuring means. Prepared.

[Effect]

When torque is transmitted to the first and second rotating shafts, relative rotation occurs between the first and second rotating shafts depending on the direction and magnitude of the torque, accompanied by twisting of the elastic member. arise.

Then, the first and second flange parts also rotate together with the first rotating shaft, but the movable member disposed between the first and second flange parts rotates through the rotational force transmission shaft. Since the first and second flange portions are connected to the second rotating shaft, relative rotation occurs between the first and second flange portions and the movable member according to the direction and magnitude of the torque.

Then, the first magnetoresistance variable means changes the first
The magnetic resistance between the flange portion and the movable member and the magnetic resistance between the second flange portion and the movable member, which is changed by the second variable magnetic resistance means, change in opposite directions according to relative rotation ( If one increases, the other decreases), so if you calculate the difference between the first measurement means and the second measurement means, you will get a measurement result with twice the slope compared to a single measurement result. If the torque calculation means calculates the torque based on the difference, even minute torques can be detected with high accuracy.

Additionally, even if fluctuations unrelated to torque occur in the first and second measuring means due to changes in ambient temperature or various noises, the fluctuations can be canceled out by taking the difference between the measurement results. and removed from the final measurement results.

Further, the rotational force transmission shaft that transmits the rotational force of the second rotational shaft to the movable member is parallel to the first and second rotational axes, and the coupling portion on the second rotational shaft side and the rotational force transmission shaft on the movable member side are parallel to the first and second rotational shafts. Since the axial coupling force of at least one of the coupling parts is smaller than the axial coupling force between the movable member and the first rotating shaft, an axial force is applied between the first and second rotating shafts. Even if a relative displacement occurs in the axial direction, the relative displacement is not transmitted to the movable member. In other words, there is no change in the relative positional relationship between the first and second flange portions and the movable member. Measurement results will not change due to force.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

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. The input shaft 2 made of a magnetic material as a first rotating shaft and the output shaft 3 as a second rotating shaft are bearings 5a.

It is rotatably supported by 5b and 5c.

However, input shaft 2. The output shaft 3 and torsion bar 4 are
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 human power shaft 2 in the rotational direction in FIG. A shaft 3a is integrally formed, and the pinion shaft 3a is connected to a rack shaft 8 of a rack and pinion steering device within the housing 1.
It meshes with the

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

On the other hand, as shown in FIG. 1 and FIG. 2, which is a cross-sectional view taken along line A-A in the same figure, protrusions 2a, 2a that are continuous in the axial direction are formed at the left end of the input shaft 2. Projections 2a, 2a
is formed on the right end portion of the output shaft 3, and is formed on the protruding portions 2a, 2a.
The input shaft 2 and the output shaft 3 are inserted into vertical grooves 3b, 3b that are slightly wider than the input shaft 2, thereby preventing relative rotation between the input shaft 2 and the output shaft 3 beyond a predetermined range (approximately ±5 degrees).

Incidentally, FIG. 1 is a sectional view taken along the line BB in FIG. 2.

The input shaft 2 also includes a flange portion 9 as a first flange portion formed by molding to have a larger diameter than other portions, and a flange portion 9 that is spaced apart from the flange portion 9 in the axial direction and connected to the input shaft 2. A flange portion I as a second flange portion made of a ring-shaped magnetic material that is integrally fitted externally in the axial direction and rotational direction.
A cylindrical member 11 made of a non-magnetic material and rotatable relative to the input shaft 2 is disposed between the flange portions 9 and 10.

The outer peripheral surfaces of the flange parts 9 and 10 are provided with a plurality of protrusions 9a and 10a scattered at equal intervals in the circumferential direction,
These protrusions 9a and IOa have the same dimensions, but as shown in FIG.
The protrusions 10a are arranged to be offset by half a pitch so that the protrusions 10a are opposed to each other between the protrusions 10a, and the protrusions 9a are opposed to each other between the protrusions 10a and 10a.

Note that the gap between the input shaft 2 and the cylindrical member J1 and the gap between the cylindrical member 11 and the flange portions 9 and 10 are relatively narrow, and are adjusted to about 20 μm to 30 μm.

One end of the cylindrical member 11 passes through the flange portion 9 with a sufficient gap so as not to come into contact with it, is loosely inserted into the square groove 30 of the output shaft 3, and serves as a rotational force transmission shaft parallel to the input shaft 2. A cylindrical shirt (12) is press-fitted.

Here, the shaft 12 and the square groove 30 are integral in the rotational direction of the output shaft 3, but are loosely inserted in the axial direction of the shaft 12, so that relative displacement can be achieved with a relatively small force. It becomes.

Further, a ring 1 made of a magnetic material is provided on the outer peripheral surface of the cylindrical member 11.
3 is integrally fitted onto the outside in the rotational and axial directions.

The ring 13 has a plurality of protrusions 13a on the end face facing the flange 9 side, and a plurality of protrusions 13b on the end face facing the flange 10 side, which are scattered at equal intervals in the circumferential direction,
These protrusions 13a and 13b, as shown in FIG.
The input shaft 2 and the output shaft 3 have the same dimensions and the same pitch.
When there is no relative rotation between the protrusion 9a and the protrusion 13
The arrangement is such that the amount of overlap S1 between the projection 10a and the projection 13b is 50%, and the amount S2 of overlap between the projection 10a and the projection 13b is 50%.

Note that the gap G1 between the protrusion 9a and the protrusion 13a and the protrusion 10
The gap G2 between a and the protrusion 13b is the same distance,
It is relatively wide and adjusted to about 0.311I11 to 0.6 mm.

Further, the inner circumferential surface of the housing 1, the 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, and the holder 15 is open on the input shaft 2 side and has gaps c, , G,
Two circumferential grooves 15a and 15b are formed surrounding the circumferential grooves 15a and 15b, and coils 16 and 17 of the same standard are housed in each of the circumferential grooves 15a and 15b.

The coils 16 and 17 calculate the difference in inductance between the coils 16 and 17, calculate the torque to be transmitted to the input shaft 2 and the output shaft 3 based on the calculation result, and reduce the calculated torque. , for example, is connected to a controller that outputs a control signal to a steering assist force applying device comprising an electric motor or the like connected to the rack shaft 8.

FIG. 4 is a diagram showing an example of a circuit that is configured in the controller and measures the inductance of the coils 16 and 17 and calculates the difference between the inductances. and connect their other ends to two resistors R1 and R with equal resistance values.
2 and a bridge circuit 20 connected via coil 16.
The oscillator 21 is connected between the coil 17 and the resistor R+, and the resistor R2 is connected to the non-inverting input terminal, and the coil 17 and the resistor Rt is connected to the inverting input terminal. amplifier 22, coil 16 and resistor R
, are connected to the inverting input terminal and the ground is connected to the non-inverting input terminal, and the comparator 23 is interposed between the output terminal of the differential amplifier 22 and the inverting input terminal of the differential amplifier 24. An analog switch 25 is provided between the output terminal of the differential amplifier 22 and the non-inverting input terminal of the differential amplifier 24, and the analog switch 25 is turned on or off depending on the output. analog switch 26 that turns on or off
and a smoothing circuit 28 that smoothes the output of the differential amplifier 24.

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. 9, 10, and a cylindrical member 11 to which the rotational force of the output shaft 3 is transmitted via the shaft 12. No relative rotation occurs with the ring 13 either. Therefore, the protrusion 9a and the protrusion 13a
The overlap amount S1 between the projection 10a and the projection 13b and the overlap amount S2 between the projection 10a and the projection 13b each maintain a state of 50%.

Then, the inductance of coil 16 is
Since the inductance I2 of 7 is equal, in the circuit shown in FIG. 4, the bridge circuit 20 maintains a balanced state, and no difference occurs in the re-input of the differential amplifier 22.

Therefore, the output of the differential amplifier 22 becomes zero, and even if it is amplified by the differential amplifier 24 and smoothed by the smoothing circuit 28, the output becomes zero and the torque is determined to be zero.

Therefore, the steering assist force applying device that applies a steering assist torque to the rack shaft 8 according to the torque determined by the controller does not operate, so no steering assist torque is generated, and the steering system maintains the straight-ahead state.

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 corresponding to the frictional force between the steered shaft and the road surface, the frictional force of the rack and pinion type steering device, etc. is generated on the output shaft 3, so between the input shaft 2 and the output shaft 3,
When the torsion bar 4 is twisted, a relative rotation occurs with a delay on the output shaft 3 side.

Then, the flange portion 9.10 that rotates together with the input shaft 2
During this period, 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, so the ring 13 is also displaced in the rotational direction, and the wrap amounts S1 and S2 change.

At this time, as shown in FIG. 3, since the protrusions 9a and 10a are arranged half a pitch apart, when the ring 13 is displaced in the rotational direction between them, the amount of overlap SI and S2
One increases and the other decreases, and the inductances I and I2 of the coils 16 and 17 change accordingly.

Here, for example, when torque in the clockwise rotation direction is generated, the wrap amount S1 increases and the wrap amount S! Assuming that the configuration is such that the wrap amount S decreases and the wrap amount Sz increases when torque in the counterclockwise direction is generated, the inductances 11 and I2 are
As shown in the figure, the characteristics are exactly opposite and intersect when the torque is zero.

Then, since a difference occurs in the inductance of the coils 16 and 17, the balanced state of the bridge circuit 20 is disrupted, and a difference occurs in the power of both the differential amplifiers 22.
and is supplied to analog switches 25 and 26.

Here, the output of the differential amplifier 22 becomes a sine wave depending on the frequency of the oscillator 21, but in this embodiment, the output of the differential amplifier 22
If the polarity of the non-inverting input of the comparator 23 is positive, the comparator 23
Since the output of the inverter 27 has a logical value of "0°" and the output of the inverter 27 has a logical value of "111", the analog switch 25 is off and the analog switch 26 is on, and the differential amplifier 2
The output of the comparator 23 is supplied to the non-inverting input terminal of the differential amplifier 24, and when the polarity of the non-inverting input of the differential amplifier 22 is negative, the output of the comparator 23 is a logical value "1 ++" and the output of the inverter 27 is Since the output becomes the logical value "0", the analog switch 25 is on and the analog switch 26 is off, and the output of the differential amplifier 22 is supplied to the inverting input terminal of the differential amplifier 24, so the differential amplifier The output of 24 is the absolute value of the output of differential amplifier 22.

Therefore, the output of the smoothing circuit 28 has a value that changes linearly according to the direction and magnitude of the steering torque.

Then, the controller multiplies the output of the smoothing circuit 28 by, for example, a predetermined gain to obtain the steering 1-rook, and outputs a control signal to the steering assist 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.
The burden on the operator is reduced.

In this embodiment, since the coils 16 and 17 are provided to obtain outputs in opposite directions depending on the torque, and the torque is calculated based on the output of the differential amplifier 22 which calculates the difference between the coils 16 and 17, the differential As shown in FIG. 6, the output of the amplifier 22 has a larger slope (see FIG. 5) than the individual measurement values of the coils 16 or 17, so it is possible to determine minute changes in torque with high precision. can.

As a result, measurement accuracy can be improved without making the torsion bar 4 easy to twist, that is, without increasing the size of the device or deteriorating the torque transmission characteristics between the input shaft 2 and the output shaft 3. This also means that accuracy equivalent to that of conventional devices can be achieved with a small device with a short torsion bar 4.

In addition, since the inductance I and the difference in one are calculated, for example, the temperature around the coils 16 and 17 may fluctuate, or various noises may occur, and the inductances (I) and (II) may be unrelated to the torque. Even if such fluctuations occur, they appear in the same direction in the inductances 1 and I2, so when their difference is determined, they are canceled out and removed from the final measured value. In other words, the device is not only temperature compensated but also resistant to noise.

Furthermore, since the axial coupling force between the shaft 12 and the square groove 30 is eliminated or reduced, and the cylindrical member 11 is externally fitted onto the input shaft 2 with a minute gap, for example, the input shaft 2 can be Even if a force is applied, the force is absorbed by the shaft 12 moving back and forth within the square groove 30, so the influence of the force in the axial direction is not transmitted to the cylindrical member 11, and the cylindrical member 11 Maintain proper axial position between parts 9 and 10.

In other words, with the configuration of this embodiment, even if an axial force is applied and the relative axial position between the input shaft 2 and the output shaft 3 changes, the measurement results are not affected, and only the torque is applied. You can get output according to the

Further, if the cylindrical member 11 is not displaced in the axial direction, the cylindrical member 11 and the flange portion 9. Since the frictional resistance between the shaft 12 and the shaft 12 does not change from its initial state, there are no problems such as high heat generation due to increased frictional force or increased load on the shaft 12 that reduces its durability. .

Here, in this embodiment, the cylindrical member 11 and the ring 13 correspond to the movable member, and the plurality of protrusions 9a and the plurality of protrusions 13
a corresponds to the first variable magnetic resistance means, and a plurality of protrusions 10
a and the plurality of protrusions 13b correspond to the second variable magnetic resistance means, the coil 16 and the holder 15 surrounding it correspond to the first measuring means, and the coil 17 and the holder 15 surrounding it correspond to the second measuring means. The controller corresponds to the torque calculation means.

In addition, in the above embodiment, the torque sensor according to the present invention is
Although the case where the present invention is applied to a power steering device for a vehicle has been described, the present invention is not limited to this.

〔Effect of the invention〕

As explained above, according to the present invention, measurement accuracy can be improved without increasing the size of the device or deteriorating the torque transmission characteristics between rotating shafts, and the measurement results can be improved by the axial force. This has the effect that there are no defects that would cause fluctuations.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the configuration of an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along the line A-A in Fig. 1, Fig. 3 is a developed view of the part that changes magnetic resistance, and Fig. 4 is a cross-sectional view showing the configuration of an embodiment of the present invention. FIG. 5 is a circuit diagram showing an example of a circuit for measuring coil inductance, FIG. 5 is a graph showing the relationship between torque and coil inductance, and FIG. 6 is a graph showing the relationship between torque and inductance difference. 2... Input shaft (first rotating shaft), 3... Output shaft (second rotating shaft), 4... Torsion bar (elastic member),
9... flange part (first flange part), 10...
Flange portion (second flange portion), 9a, 10a.

Claims (1)

[Claims] (1) First and second rotating shafts disposed coaxially, an elastic member connecting the first and second rotating shafts, and an elastic member that rotates integrally with the first rotating shaft and axially extends. first and second flange portions separated from each other; a movable member disposed between the first and second flange portions and rotatable about the first rotation axis; It is parallel to the rotation axis, one end side is connected to the second rotation axis, and the other end side is connected to the movable member, and the axial coupling force of at least one of these coupling parts connects the movable member and the first magnetic resistance between the first flange portion and the movable member according to the relative rotational displacement between the rotational force transmission shaft and the first rotation shaft and the movable member, which is smaller than the axial coupling force with the rotation shaft of the a first variable magnetic resistance means for changing the magnetic resistance; and a second flange portion that moves in a direction opposite to the first variable magnetic resistance means in accordance with a relative rotational displacement between the first rotating shaft and the movable member. and a second variable magnetic resistance means for changing the magnetic resistance between the movable members, a first measuring means for measuring the magnetic resistance between the first flange portion and the movable member, the second flange portion, and a second measuring magnetic resistance between the movable members;
and torque calculating means for calculating the torques transmitted to the first and second rotating shafts based on the difference between the measurement results of the first and second measuring means. torque sensor.