JP2001133336A - Magnetostrictive torque detector and magnetostrictive torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the detection error resulted from a temperature change in a signal processing unit for generating a DC detection signal from the AC output of each detecting coil. SOLUTION: A pair of detecting coils 20A and 20B of a magnetostrictive torque sensor 10 is serially connected with reverse polarities to use both ends thereof as output ends for outputting the differential output of the AC output induced in each of the detecting coils 20A and 20B. Both the detecting coils 20A and 20B are provided with a difference in number of turns so that the magnitude of the differential AC shows a linear output characteristic in the detecting range of load torque when a load torque is added in the detecting range within a maximum detected load torque set every rotating direction to a shaft S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque detecting device and a magnetostrictive torque sensor.

[0002]

2. Description of the Related Art A magnetostrictive torque sensor is applied to a shaft to which a load torque is applied from the outside, a cylindrical magnetostrictive material (bulk material) fixedly fitted to the shaft to be detected, or a shaft to be detected. There is provided a pair of cylindrical magnetostrictive portions provided on the outer peripheral surface of a cylindrical magnetostrictive material externally fitted to an intermediate sleeve fixed in an externally fitted state. Further, the magnetostrictive torque sensor includes, for each magnetostrictive section, an exciting coil for applying a high frequency to the magnetostrictive section, and a detecting coil for exciting induced electromotive force via the magnetostrictive section.

[0003] When a load torque is applied to the shaft to be detected in any rotational direction, the magnetic permeability of one of the magnetostrictive portions increases, and the magnetic permeability of the other decreases. Then, the induction inductance between the exciting coil and the detecting coil electrically connected via one of the magnetostrictive portions increases, and the exciting coil and the detecting coil electrically connected via the other magnetostrictive portion. Inductive inductance between them is reduced. As a result, the induced electromotive force (AC output) generated in each detection coil by the high-frequency AC applied to the excitation coil has a difference in magnitude corresponding to the magnitude of the load torque. Then, by converting this difference into a DC detection signal, a DC output corresponding to the magnitude of the load torque is obtained.

As described above, in the magnetostrictive torque sensor, a pair of induced electromotive forces generated through a pair of magnetostrictive portions which are the same except that the magnetic permeability increases or decreases due to the load torque applied to the detected shaft. The magnitude of the load torque is detected by the differential AC. This is for canceling an error based on a temperature change from the AC output output from each detection coil of the magnetostrictive torque sensor and linearizing the DC detection signal.

Conventionally, in order to generate a DC detection signal from an induced electromotive force generated in each detection coil, a magnetostrictive torque detector has been configured as shown in FIG. First, the magnetostrictive torque sensor 50 separately outputs an AC signal induced in each of the detection coils 52A, 52B by the excitation coils 51A, 51B from the magnetostrictive torque sensor 50 to an external signal processing device 53. The signal processing device 53 separately rectifies each AC signal with the two rectifiers 54A and 54B to obtain DC signals, respectively, and averages the respective DC signals with separate low-pass filters 55A and 55B. The DC signal is differentially amplified by the differential amplifier 56.
That is, in this signal processing method, each detection coil 52A,
After separately converting the AC output from the DC power supply 52B into DC, the difference between the two DC signals is calculated and used as a DC detection signal. According to this DC difference method, the DC detection signal for the load torque in the detection range extending in both rotation directions with respect to the detected shaft 57 is linear from the maximum detected load torque in the counterclockwise direction to the maximum detected load torque in the clockwise direction. The output characteristic is such that the output when the load torque is “0” is “0”. According to the DC difference method, a difference between the two is generated after the AC output output from each detection coil is rectified, so that a detection error based on a phase shift of each AC output is suppressed.

[0006]

When the magnetostrictive torque sensor 50 is used in an electric power steering device, the load torque applied to the steering shaft, which is the detected shaft 57, from the steering wheel side is applied from the steering wheel. It reaches more than 20 times the maximum load torque. Therefore,
The signal processing circuit 53 including the rectifiers 54A and 54B is designed to receive an AC output that is output from each of the detection coils 52A and 52B in accordance with the maximum overload torque. For this reason, the magnitude of the AC output output from each of the detection coils 52A and 52B corresponding to the maximum load torque within the detection range (rated torque) of the load torque actually detected depends on the input signal range of the rectifiers 54A and 54B. 20 for
The range is as narrow as one-tenth or less. As a result, both rectifiers 54
The rectifiers 54A, 54A, 5B have different temperature characteristics depending on the rectifiers 54A, 54B.
Since the level of the DC signal output from 4B greatly fluctuates, the detection signal includes an error.

Since the AC signals output from the detection coils 52A and 52B contain electrical noise in the signal processing circuit 53 and the like, the lower the level of the AC signal, the higher the S / N ratio of the DC detection signal. The ratio decreases and the detection accuracy deteriorates. Therefore,
In the load torque detection region where the level of the AC signal is low, the detection accuracy is relatively deteriorated. In the magnetostrictive torque sensor 50 that performs the signal processing of the DC difference method, the output level near the load torque of “0” is low, so that the detection accuracy of the load torque near “0” relatively deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object of the present invention is to provide a signal processing circuit for converting each AC output into a DC detection signal. An object of the present invention is to provide a magnetostrictive torque detecting device having a small error.

A second object, in addition to the first object, is to provide a magnetostrictive torque detector having high output sensitivity over the entire range of load torque detection and excellent in linearity of output characteristics. It is in.

[0010]

In order to achieve the first object, the invention according to claim 1 is provided on an outer peripheral side of a shaft to be detected, and is provided by a load torque applied to the shaft to be detected. A pair of magnetostrictive portions that generate a magnetostrictive effect, a pair of exciting coils provided for each of the magnetostrictive portions and for applying an alternating magnetic field to each of the magnetostrictive portions, and an alternating magnetic field of the primary coil provided for each of the magnetostrictive portions; And a pair of detection coils for detecting through the magnetostrictive section, a magnetostrictive torque detecting device,
A magnetostrictive torque detection device that generates a differential AC by subtracting an AC output generated in each of the detection coils from a load torque applied to the detected shaft.

[0011] To achieve the second object, a second aspect of the present invention is provided.
The invention according to claim 1, wherein the differential AC when a load torque is applied within a detection range within each of the maximum detection load torques set for each rotation direction with respect to the detected shaft. There is a difference in the number of turns between the two detection coils so that the size of the detection coil has a linear output characteristic in the detection range.

According to a third aspect of the present invention, in the second aspect, the pair of detection coils are connected in series with opposite polarities, and the differential AC is output from both ends of the both detection coils. Is done.

According to a fourth aspect of the present invention, in the second aspect of the invention, the AC output of each of the detection coils is separately input to an AC difference circuit, and the AC difference circuit separates the AC output from each AC output by the AC difference circuit. An alternating current is generated.

According to a fifth aspect of the present invention, in the first aspect of the present invention, a direct current detection signal proportional to the magnitude of the load torque is generated from the differential alternating current. A signal conversion device is provided.

According to a sixth aspect of the present invention, there is provided a pair of magnetostrictive portions provided on an outer peripheral side of a shaft to be detected and generating reverse magnetostriction by a load torque applied to the shaft to be detected. A pair of excitation coils provided to apply an alternating magnetic field to each magnetostrictive section, and a pair of detection coils provided for each of the magnetostrictive sections and detecting the alternating magnetic field of the primary coil through the magnetostrictive section. In the magnetostrictive torque sensor provided, the two detection coils are connected in series with opposite polarities, and both ends thereof are output terminals for outputting a difference AC obtained by subtracting an AC output generated in each of the detection coils, and The magnitude of the differential AC when a load torque is applied in a detection range within each maximum detection load torque set for each rotation direction with respect to the detected shaft so that the output characteristic is linear in the detection range. , Both Difference in the number of turns of the output coil is magnetostrictive torque sensor provided.

(Operation) According to the first aspect of the present invention,
From the AC output induced in each excitation coil by the high-frequency AC applied to each excitation coil, a differential AC that is a difference between the two AC outputs is generated. When this differential AC is rectified, a DC detection signal having a magnitude corresponding to the magnitude of the load torque applied to the detected shaft is generated. Therefore, since each AC output is subtracted before being rectified, unlike the case where each AC output is rectified separately, an error based on a difference in temperature characteristics of the rectification unit is not included.

According to the invention described in claim 2, according to claim 1
In addition to the operation of the invention described in (1), the difference in the number of turns between the two detection coils causes the AC output generated in one detection coil to be larger than the AC output generated in the other detection coil Therefore, the value of the load torque when the magnitude of the differential AC becomes the minimum value is larger than the maximum load torque in the detection range in both rotation directions of the detected shaft. Therefore, the output characteristic of the difference AC with respect to the load torque within the detection range becomes a predetermined output value larger than the minimum value of the AC difference, and also increases linearly from this output value.

According to the invention described in claim 3, according to claim 2,
In addition to the operation of the invention described in (1), since a differential AC is output from both ends of the two detection coils connected in series, an AC differential circuit for performing the AC differential is not required.

According to the invention described in claim 4, according to claim 2,
In addition to the operation of the invention described in (1), a differential AC is generated by an AC difference circuit from the AC output separately output from each detection coil.

According to the invention described in claim 5, according to claim 1,
The DC detection signal corresponding to the magnitude of the load torque is generated from the difference AC having the magnitude corresponding to the magnitude of the load torque within the detection range. Therefore, the magnitude of the load torque is output as a DC detection signal.

According to the sixth aspect of the present invention, the output terminal of the magnetostrictive torque sensor including both ends of the two detection coils connected in series has a smaller value than the minimum value of the differential AC with respect to the load torque detection range. A difference AC having a linear output characteristic which is greater than or equal to a large predetermined output value and linearly increases from this output value is output. Therefore, a differential AC is directly output from a sensor having a simple configuration without a differential amplifier or the like that generates a differential output from each AC output.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, a magnetostrictive torque sensor 1 includes a magnetostrictive torque sensor 1.
0 and the signal processing device 30.

As shown in FIG. 2, the magnetostrictive torque sensor 1
Numeral 0 is provided on a shaft S as a shaft to be detected which is rotatably supported by a bearing B in a housing H.

The magnetostrictive torque sensor 10 is supported so as to be rotatable relative to the shaft S, and is integrally rotatable with respect to the housing H. And a detecting unit 12 connected thereto.

The detected part 11 is formed of a high-permeability soft magnetic material in a cylindrical shape, and is formed of a magnetic material 1 fitted externally to the shaft S.
Consists of three. Permalloy, as high permeability soft magnetic material,
There are Fe-Ni-Cr alloys and the like.

On the outer peripheral surface of the magnetostrictive member 13, a pair of magnetostrictive regions 14A and 14B are provided as magnetostrictive portions whose magnetic permeability increases and decreases alternately by a load torque applied to the shaft S. Each of the magnetostrictive regions 14A and 14B is formed in a cylindrical shape. A plurality of spiral grooves for generating a compressive stress in the magnetostrictive region 14A by twisting the shaft S clockwise in the magnetostrictive region 14A, and also generating a tensile stress in the magnetostrictive region 14A by twisting the shaft S counterclockwise. 15A are formed at equal intervals in the circumferential direction. Further, in the magnetostrictive region 14B, a plurality of strains for generating a tensile stress in the magnetostrictive region 14B by the twisting of the shaft S in the clockwise direction and generating a compressive stress in the magnetostrictive region 14B by the twisting in the counterclockwise direction are also used. The spiral grooves 15B are formed at equal intervals in the circumferential direction.

The detecting section 12 has a yoke 17 whose both ends are supported by a pair of bearings 16 so as to be rotatable relative to the shaft S. Further, the detection unit 12 includes a magnetostrictive region 14.
A excitation coil 19A and detection coil 20A housed in a circumferential groove 18A provided on the inner peripheral surface of the yoke 17 so as to face the coil A and the inner peripheral surface of the yoke 17 so as to face the magnetostrictive region 14B. An excitation coil 19B and a detection coil 20B are provided in the provided circumferential groove 18B.

The two exciting coils 19A and 19B are connected in series with forward polarity (the winding direction is the same). The detection coils 20A and 20B are connected in series with opposite polarities (winding directions are opposite), and a difference AC obtained by subtracting an AC output induced in the detection coils 20A and 20B by the excitation coils 19A and 19B is obtained. Output from both ends.

A high-frequency power supply 21 is connected to both ends of both exciting coils 19A and 19B. The high frequency power supply 21 outputs a high frequency AC signal in a range of, for example, 10 to 30 kHz. A signal processing device 30 is connected to both ends of each detection coil 20A, 20B. The signal processing device 30 includes a rectifier 31, a low-pass filter 32, and an amplifier 33. In the present embodiment, the rectifier 31, the low-pass filter 32, and the amplifier 33 form a signal conversion circuit. The rectifier 31 performs full-wave rectification on the differential AC output from both ends of the detection coils 20A and 20B. Low-pass filter 32
Averages the output of the rectifier 31. The amplifier 33 amplifies the output of the low-pass filter 32 at a predetermined amplification rate,
A DC detection signal having a magnitude in a predetermined range is generated.

The magnetostrictive torque sensor 10 according to the present embodiment
Indicates that each of the detection coils 20A, 20A,
The difference AC obtained by differentiating the AC output output from the 20B is approximately 0 to
It is generated in the range of magnitude of about 1V.

The excitation coil and the detection coil, which are features of the present invention, will be described in detail. Excitation coils 19A, 19
B are formed with the same number of turns. On the other hand, the detection coils 20A and 20B are arranged such that the number of turns of the detection coil 20A is larger than the number of turns of the detection coil 20B.
There is a difference in the number of turns. Both detection coils 20A,
The difference in the number of turns of 20B is provided such that the magnitude of the differential AC when a load torque within the detection range is applied to the shaft S has a linear output characteristic in the detection range.
In the present embodiment, the number of turns of each of the excitation coils 19A and 19B is 36T, the number of turns of the detection coil 20A is 144T, and the number of turns of the detection coil 20B is 128 to 14.
0T.

More specifically, the differential AC of the AC output induced in each of the detection coils 20A, 20B by the high-frequency AC applied to the excitation coils 19A, 19B connected in series with forward polarity is equivalent to a predetermined load torque. The magnitude becomes the minimum value, and the output characteristic increases in accordance with the deviation from the load torque. Here, the detection coil 20
For the number of turns of A and 20B, the value of the load torque when the magnitude of the differential AC is minimum is greater than the maximum detected load torque (maximum rated load torque) that is the boundary of the detection range in both rotation directions of the shaft S. Are also provided so as to be larger. In the present embodiment, by increasing the number of turns of the detection coil 20A to be greater than the number of turns of the detection coil 20B, the coil is applied clockwise from the maximum detected load torque of −10 N · m in the counterclockwise direction applied to the shaft S. The value of the load torque when the magnitude of the differential AC output to the detection range up to the maximum load torque of 10 N · m is the minimum is the maximum detected load torque 10 N which is the clockwise boundary of the detection range.
-The difference is provided to be larger than m.

Next, the operation of the magnetostrictive torque sensor configured as described above will be described. When a high-frequency AC is supplied from the high-frequency power supply 21 to the excitation coils 19A and 19B, an induced electromotive force having a magnitude corresponding to the mutual inductance between the excitation coil 19A and the detection coil 20A is generated in the detection coil 20A. . Similarly, the detection coil 20
At B, an AC output having a magnitude corresponding to the mutual inductance between the exciting coil 19B and the detecting coil 20B is generated. Then, the two detection coils 20 connected in series
A differential AC, which is a difference between the two AC outputs, is output from an output terminal of the magnetostrictive torque sensor 10 including both ends of A and 20B.

The differential AC output from the magnetostrictive torque sensor 10 to the signal processing device 30 is subjected to full-wave rectification by the rectifier 31 of the signal processing device 30 and then to the low-pass filter 3.
Averaged by 2. The averaged DC output from the low-pass filter 32 is amplified by the amplifier 33,
It is output as a DC detection signal having a magnitude proportional to the magnitude of the load torque. Therefore, since each AC output is subtracted before being rectified, there is no error based on the difference in the temperature characteristics of the rectifier, unlike the conventional DC difference method in which each AC output is rectified separately.

When no load torque is applied to the shaft S, the magnetic permeability of the magnetostrictive regions 14A and 14B is the same. Therefore, since the number of turns of the detection coil 20A is larger than the number of turns of the detection coil 20B, the mutual inductance between the excitation coil 19A and the detection coil 20A becomes larger than the mutual inductance between the excitation coil 19B and the detection coil 20B. It is larger than the inductance. As a result, the AC output generated in the detection coil 20A becomes larger than the AC output generated in the detection coil 20B. Then
The magnitude of the difference AC output from both ends of the two detection coils 20A and 20B becomes a predetermined value, and the DC detection signal output by the signal processing device 30 becomes a predetermined no-load output value.

When a load torque is applied to the shaft S in the clockwise direction, a compressive stress is applied to the magnetostrictive region 14A to decrease the magnetic permeability, and a tensile stress is applied to the magnetostrictive region 14B to increase the magnetic permeability. Therefore, the exciting coil 19A
And the mutual inductance between the detection coil 20A and the excitation coil 19B and the detection coil 20A are reduced.
Mutual inductance between B increases. As a result, the induced electromotive force generated in the detection coil 20A decreases, and the induced electromotive force generated in the detection coil 20B increases.
The magnitude of the differential AC output from both ends increases by the magnitude of the load torque. As a result, the DC detection signal output by the signal processing device 30 has an output value reduced from the no-load output value by the magnitude of the load torque.

Conversely, when a load torque is applied to the shaft S in a counterclockwise direction, a tensile stress is applied to the magnetostrictive region 14A to increase the magnetic permeability, and a compressive stress is applied to the magnetostrictive region 14B to decrease the magnetic permeability. Therefore, the mutual inductance between the excitation coil 19A and the detection coil 20A increases, and the mutual inductance between the excitation coil 19B and the detection coil 20B decreases. As a result, the induced electromotive force generated in the detection coil 20A increases and the induced electromotive force generated in the detection coil 20B decreases, and the magnitude of the differential AC output from both ends increases by the magnitude of the load torque. I do. As a result, the DC detection signal output by the signal processing device 30 has a value increased from the no-load output value by the magnitude of the load torque.

Therefore, -10 N · m added counterclockwise
10N ・ m added clockwise from the maximum detected load torque of
The output characteristic of the AC difference with respect to the load torque in the detection range up to the maximum detected load torque becomes equal to or more than a predetermined output value larger than the minimum value of the AC difference, and increases linearly from this output value.

The graph shown in FIG. 3 shows the detection coil 20A.
While the number of turns T1 of the coil is 144T.
AC difference output when the number of turns T2 of 0B is changed
This is data on load torque characteristics. When the winding number T2 of the detection coil 20B is set to 144T, the differential AC output becomes the minimum value (approximately 0.04 V) when a load torque of about 5 N · m is applied clockwise, and the load torque is “0”. Does not reach the minimum value when. This is because each of the magnetostrictive regions 14A, 14A
This is due to the imbalance of the magnetic permeability of B, the imbalance of mutual inductance between the exciting coil 19A and the detecting coil 20A, and the mutual inductance between the exciting coil 19B and the detecting coil 20B due to an assembly error. As described above, when the minimum value of the difference output is the output value for the load torque within the detection range,
The output level near the load torque is low, and the detection accuracy near the load torque is relatively low.

Further, the magnetostrictive torque sensor having such an output characteristic has the same output value with respect to the magnitude of the load torque regardless of the direction in which the load torque is applied, as shown by the broken line in FIG. There is a need to. This is to enable the signal processing device to generate a DC detection signal corresponding to the direction and magnitude of the load torque only from the magnitude and phase of the differential AC. For this purpose, on either output line of both detection coils 20A and 20B,
It is conceivable to provide a resistor for temperature compensation or to provide a voltage dividing circuit. However, in this case, the output level of the differential AC is further reduced, and the detection accuracy of the load torque near “0” is further reduced.

On the other hand, when the number of turns T2 of the detection coil 20B is reduced, the mutual inductance between the excitation coil 19B and the detection coil 20B is reduced, and the AC output induced in the detection coil 20B is reduced. . For this reason,
The minimum value of the difference output moves so as to correspond to the larger value of the load torque applied in the clockwise direction, and becomes larger than 10 N · m, which is the maximum clockwise detected load torque in the detection range. As a result, the magnitude of the AC difference with respect to the clockwise maximum detected load torque 10 N · m in the load torque detection range (approximately 0.2 V when T2 is 136T)
Is a predetermined output value larger than the minimum value (about 0.04 V) of the AC difference, and has a characteristic that linearly increases from this output value.

Therefore, the number of turns T1 of the detection coil 20A
Is larger than the number of turns T2 of the detection coil 20B so that the load torque when the differential AC is at a minimum value is out of the detection range. The output value is equal to or greater than a predetermined output value larger than the minimum value of the difference, and the output value increases linearly.

According to the magnetostrictive torque detecting device and the magnetostrictive torque sensor of the present embodiment described in detail above, the following effects can be obtained. (1) Each detection coil 20A. A differential AC obtained by subtracting the AC output generated at 20B is generated. By rectifying the differential AC, a DC detection signal having a magnitude corresponding to the magnitude of the load torque applied to the shaft S is generated.

Therefore, it is possible to reduce a detection error due to a temperature change caused by a signal processing device that generates a DC detection signal from each AC output. (2) When a load torque is applied to the shaft S in a predetermined detection range, the differential AC of the AC output induced in each of the detection coils 20A and 20B has an output characteristic linear with respect to the detection range. The two detection coils 20A, 20
A difference is provided in the number of turns of B.

Accordingly, the output characteristic of the differential AC with respect to the load torque within the detection range becomes a predetermined output value larger than the minimum value of the differential AC with respect to the predetermined overload load torque, and linearly increases from this output value. Characteristics.
As a result, a differential AC having high output sensitivity and excellent linearity can be obtained over the entire load torque detection range, so that the detection accuracy can be increased.

(3) A pair of detection coils 20A, 20
B are connected in series with opposite polarities, and the differential AC is applied to both coils 20A,
Output from both ends of 20B. Therefore, the configuration of the magnetostrictive torque detecting device 1 is simplified because a differential amplifier for generating a differential AC from the AC output induced in each of the detection coils 20A and 20B is not required.

(4) The detection coils 20A and 20B are connected with opposite polarities, and both ends thereof are connected to the detection coils 20A and 20B.
The magnetostrictive torque sensor 10 was configured as an output terminal for outputting a difference AC of the AC output induced at 20B. And
An external signal processing device 30 generates a DC detection signal from the differential AC output from the torque sensor 10.

Accordingly, since a differential AC is directly output from a sensor having no differential amplifier or the like, a comparison is made with a configuration in which a signal processing device external to the sensor generates a differential AC from the AC output of each detection coil 20A, 20B of the sensor. Thus, the configuration of the signal processing device can be simplified without complicating the configuration of the sensor.

Hereinafter, embodiments other than the above-described embodiment embodying the present invention will be listed as other examples. In the above embodiment, the detection coils 20A, 20B
Are connected in series with opposite polarities, and a differential AC is output from both ends of both coils 20A and 20B. As shown in FIG. 4, each of the detection coils 20A,
Alternatively, a configuration may be adopted in which an AC output is separately output from 20B, and a difference AC is generated from the two AC outputs by a difference amplifier 40 or the like as an AC difference circuit. Also in this case, high output sensitivity and output characteristics with excellent linearity can be obtained over the entire detection range. Further, a DC detection signal can be generated from a differential AC by a signal processing device having the same configuration as a conventional signal processing device.

In the above-described embodiment, the magnetostrictive torque sensor 10 is configured such that both ends of the two detection coils 20A and 20B connected in series with opposite polarities are output terminals for outputting a differential AC of each AC output. As shown in FIG. 4, this constitutes a magnetostrictive torque sensor 41 that separately outputs the AC output of each of the detection coils 20A and 20B, and an external signal processing device 42 generates a differential AC from each AC output. You may do so. The magnetostrictive torque sensor 41 and the signal processing device 42 constitute a magnetostrictive torque detection device. With this configuration, high output sensitivity and excellent linearity output characteristics can be obtained over the entire load torque detection range, and a signal processing device having the same configuration as a conventional signal processing device can be used. .

In the above embodiment, the exciting coil 1
9A and 19B with the same number of turns, the detection coil 2
By providing a difference in the number of turns of 0A and 20B, the difference output has a linear output characteristic in the detection range of the load torque. This is because even if the number of turns of the detection coils 20A and 20B is the same and the number of turns of the excitation coils 20A and 20B is different, the difference output has a linear output characteristic in the load torque detection range. Good. Alternatively, the number of windings of the excitation coils 19A and 19B and the number of turns of the detection coil 20
By providing a difference in the number of turns of A and 20B, the difference output may have a linear output characteristic in the load torque detection range. In any case, it is possible to reduce a detection error caused by a temperature change in a signal processing circuit that generates a DC detection signal from a detection AC generated in each detection coil, and furthermore, in a whole range of a load torque detection range. High output sensitivity and output characteristics excellent in linearity can be obtained.

The present invention may be applied to a magnetostrictive torque detecting device or a magnetostrictive torque sensor in which the load torque detection range is set by different maximum load torques in the clockwise direction and the counterclockwise direction.

The magnetostrictive torque sensor is not limited to the magnetic material 13 having the magnetostrictive regions 14A and 14B formed on the outer peripheral surface of the magnetic material 13 which is fixed so as to be directly fitted on the shaft S. A magnetic material having an outer peripheral surface formed with a magnetostrictive region on the outer peripheral surface of a magnetic material fitted to the sleeve or a magnetic material having a magnetostrictive region formed on the outer peripheral surface of the shaft S may be used.

The magnetic material to be fitted onto the shaft S or the magnetic material made of the magnetic material is not limited to the outer peripheral surface of which has a magnetostrictive region. May be a magnetostrictive torque sensor in which a magnetostrictive portion is formed.

The detected shaft to which the load torque to be detected is applied is not limited to the steering shaft of the electric power steering device, but may be the output shaft of a rotary electric or hydraulic motor of various machines.

Hereinafter, in addition to the inventions described in the claims, the technical ideas grasped from the above-described embodiments and the respective examples will be described together with their effects. (1) A pair of magnetostrictive portions provided on the outer peripheral side of the detected shaft to generate a reverse magnetostrictive action by a load torque applied to the detected shaft, and an alternating magnetic field provided for each of the magnetostrictive portions, In a magnetostrictive torque sensor comprising: a pair of exciting coils that act on the coils; and a detecting coil provided for each of the magnetostrictive sections and detecting an alternating magnetic field of the primary coil through the magnetostrictive sections. The detection coils are each independently provided so as to output an AC output induced in each of the detection coils, and each of the detection coils does not exceed the maximum load torque set for each rotation direction with respect to the detected shaft. A difference is provided in the number of turns of the two detection coils so that the difference AC between the respective AC outputs when the load torque is applied in the detection range has a linear output characteristic in the detection range. Magnetostrictive torque sensor.

According to such a configuration, it is possible to reduce a detection error caused by a temperature change in a signal processing circuit that generates a DC detection signal from a detected AC generated in each detection coil, and furthermore, it is possible to reduce a load torque. In addition to obtaining high output sensitivity and output characteristics with excellent linearity over the entire detection range, a signal processing device having the same configuration as a conventional signal processing device can be used.

(2) In the first aspect of the present invention,
The magnitude of the differential AC when a load torque is applied in a detection range within each maximum detection load torque set for each rotation direction with respect to the detected shaft has a linear output characteristic in the detection range. There is a difference in the number of turns of at least one of the excitation coil and the detection coil.

According to such a configuration, it is possible to reduce a detection error caused by a temperature change in a signal processing circuit that generates a DC detection signal from a detected AC generated in each detection coil, and furthermore, it is possible to reduce a load torque. High output sensitivity and output characteristics with excellent linearity can be obtained over the entire detection range.

[0060]

According to the first to sixth aspects of the present invention, a detection error caused by a temperature change in a signal processing circuit for generating a DC detection signal from a detected AC generated in each detection coil is reduced. be able to.

According to the second to sixth aspects of the present invention, high output sensitivity and output characteristics with excellent linearity can be obtained over the entire range of the load torque detection range. According to the third or fifth aspect of the present invention, since an AC difference circuit for generating a differential AC is not required, the configuration can be simplified.

According to the fifth aspect of the invention, it is possible to output a DC detection signal corresponding to the magnitude of the load torque. According to the sixth aspect of the present invention, the signal processing is performed without complicating the configuration of the sensor as compared with a configuration in which a differential AC is generated by a signal processing device outside the sensor from the AC output of each detection coil of the sensor. The configuration of the device can be simplified.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a magnetostrictive torque detector.

FIG. 2 is a sectional view of a magnetostrictive torque sensor.

FIG. 3 is a graph showing an AC difference output-load torque characteristic.

FIG. 4 is an electric circuit diagram of another example of a magnetostrictive torque detector.

FIG. 5 is an electric circuit diagram of a conventional DC difference type magnetostrictive torque detector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetostrictive torque detector, 10 ... Magnetostrictive torque sensor which comprises a magnetostrictive torque detector, 14A, 14B ... Magnetostrictive area | region as a magnetostrictive part, 19A, 19B ... Exciting coil, 20A, 20B ... Detection coil, Reference numeral 30 denotes a signal processing device that constitutes a magnetostrictive torque detector, 31 denotes a rectifier that constitutes a signal conversion circuit, 32 denotes a filter, 33 denotes an amplifier, and 40 denotes a difference amplifier as an AC difference circuit.
41 ... Magnetostrictive torque sensor constituting a magnetostrictive torque detecting device, 42 ... Similar signal processing device, S ... Shaft as shaft to be detected.

Claims (6)

[Claims] A pair of magnetostrictive portions provided on an outer peripheral side of a detected shaft to generate an inverse magnetostrictive action by a load torque applied to the detected shaft; provided for each of the magnetostrictive portions; A magnetostrictive torque detecting device comprising: a pair of exciting coils for applying an alternating magnetic field; and a pair of detecting coils provided for each of the magnetostrictive portions and detecting the alternating magnetic field of the primary coil through the magnetostrictive portions. 5. The magnetostrictive torque detecting device according to claim 1, wherein a differential AC is generated by subtracting an AC output generated in each of the detection coils from a load torque applied to the detected shaft. 2. The magnitude of the differential AC when a load torque is applied in a detection range within each maximum detection load torque set for each rotation direction with respect to the detected shaft is linear in the detection range. 2. The magnetostrictive torque detecting device according to claim 1, wherein a difference is provided in the number of windings of the two detection coils so as to obtain an output characteristic. 3. The magnetostrictive torque detecting device according to claim 2, wherein the pair of detection coils are connected in series with opposite polarities, and the differential AC is output from both ends of the both detection coils. 4. The magnetostrictive torque detection according to claim 2, wherein the AC output of each of the detection coils is separately input to an AC difference circuit, and the AC difference circuit generates the differential AC from each of the AC outputs. apparatus. 5. The magnetostrictive torque according to claim 1, further comprising a signal converter that generates a DC detection signal proportional to the magnitude of the load torque from the differential AC. Detection device. 6. A pair of magnetostrictive portions provided on an outer peripheral side of a detected shaft and generating an inverse magnetostrictive action by a load torque applied to the detected shaft; and a pair of magnetostrictive portions provided for each of the magnetostrictive portions. A magnetostrictive torque sensor comprising: a pair of exciting coils for applying an alternating magnetic field; and a pair of detecting coils provided for each of the magnetostrictive portions and detecting an alternating magnetic field of the primary coil through the magnetostrictive portions. The two detection coils are connected in series with opposite polarities, and both ends thereof are output terminals for outputting a differential AC obtained by subtracting an AC output generated in each of the detection coils, and are rotated with respect to the detected shaft. The magnitude of the differential AC when a load torque is applied in a detection range within each maximum detection load torque set for each direction is a linear output characteristic in the detection range, so that the two detection coils are Number of turns Magnetostrictive torque sensor difference is provided.