JP2529980Y2 - Magnetostrictive torque sensor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque sensor suitably used for detecting a torque generated on an output shaft of an automobile engine, for example.

[0002]

2. Description of the Related Art In an automatic vehicle or the like having an automatic transmission, it has been proposed to mount a torque sensor on a propeller shaft or the like, for example, in order to optimize shift timing by an automatic transmission mechanism.

FIGS. 7 to 9 show a two-coil type magnetostrictive torque sensor as an example of such a conventional torque sensor.

In FIG. 1, reference numeral 1 denotes a magnetostrictive shaft formed of a magnetostrictive material such as chromium molybdenum steel. The magnetostrictive shaft 1 is provided, for example, in the middle of a propeller shaft. It becomes the side mounting portion 1B, the middle of which becomes the slit groove forming portion 1C, and the outer periphery of the slit groove forming portion 1C is opposed to the slit grooves 2 and 3 cut at 45 ° downward and 45 ° upward, respectively. It is provided in.

[0005] Reference numeral 4 denotes a coil fixing member provided so as to be rotatable relative to the magnetostrictive shaft 1 via a pair of bearings 5 and 5 so as to surround the outer periphery of the slit groove forming portion 1C. Is fixedly attached to a vehicle body (not shown). Reference numeral 6 denotes a ring-shaped core member fixed to the inner peripheral side of the coil fixing member 4.
Detection coils 7 and 8 are provided at positions facing the slit grooves 2 and 3, respectively, and the self-inductances of the detection coils 7 and 8 are L1 and L2.

Next, FIG. 8 shows and describes a detection circuit and a detection processing circuit.

In FIG. 8, reference numeral 9 denotes a bridge circuit serving as a detection circuit. The bridge circuit 9 includes detection coils 7, 8, the core losses r1, r2 of the detection coils 7, 8, and the detection coils 7, 8. The oscillator 10 described later is connected between a connection point a of the detection coils 7 and 8 and a connection point b of the adjustment resistors R and R. A connection point c between the detection coil 7 and the adjustment resistor R and a connection point d between the detection coil 8 and the adjustment resistor R serve as output terminals for deriving output voltages V1 and V2 from the detection coils 7 and 8, respectively. The connection points c and d are the differential amplifier 1
1 input terminals.

Next, the detection processing circuit will be described. The detection processing circuit includes an oscillator 10, a differential amplifier 11,
Phase adjustment circuit 13, detection processing circuit 14, and integration circuit 1
5 and so on.

Reference numeral 10 denotes an oscillator, which generates an AC voltage V having a peak value V0 and a frequency f (for example, 30 KHZ).
And to the phase adjustment circuit 13.

Reference numeral 11 denotes a differential amplifier.
Reference numeral 1 denotes an operational amplifier or the like. The connection terminals c and d of the bridge circuit 9 are respectively connected to the input terminals, the output voltages V1 and V2 are input, the output terminal 12 is connected to the detection processing circuit 14, and the output terminal Outputs E0.

Reference numeral 13 denotes a phase adjustment circuit connected to the output side of the oscillator 10. The phase adjustment circuit 13 adjusts the phase difference by the bridge circuit 9 and outputs a phase adjustment voltage VP to the detection processing circuit 14.

Reference numeral 14 denotes a detection processing circuit. The input terminal of the detection processing circuit 14 is connected to the output terminal 12 of the bridge circuit 9 and the output side of the phase adjustment circuit 13, and the output voltage E0
And the phase adjustment voltage VP. Then, the detection processing circuit 14 outputs only a synchronized portion to the integration circuit 15 based on the phase adjustment voltage VP of the output voltage E0.
Then, the integration circuit 15 integrates this voltage and outputs it as a DC voltage E to the control unit 16.
Further, the control unit 16 controls the shift timing of the automatic transmission mechanism based on the input voltage E.

When the torque acting on the magnetostrictive shaft 1 is zero, the connection points c and d are adjusted by adjusting the respective adjustment resistors R.
The balanced state of the bridge circuit 9 is maintained so that the output voltages V1 and V2 of the differential amplifier 11 have the same waveform, and the output voltage E0 from the output terminal 12 of the differential amplifier 11 at this time is the DC voltage VCO
An offset adjusting circuit 17 is connected to the differential amplifier 11 so as to be offset by [V]. Therefore,
When the torque acting on the magnetostrictive shaft 1 is zero, the voltage E output to the control unit 16 via the integration circuit 15 becomes VCO [V] (see FIG. 9).

In the thus configured two-coil type magnetostrictive torque sensor, the detection coils 7 and 8 are provided with an oscillator 1.
When an AC voltage V of 0 is applied, a magnetic path is formed on the surface of the magnetostrictive shaft 1. However, since the slit grooves 2 and 3 are provided on the surface of the slit groove forming portion 1C, the magnetic path due to the surface magnetic field is formed by a slit. It is formed along the grooves 2 and 3.

On the other hand, the input side mounting portion 1A of the magnetostrictive shaft 1
7, a tensile stress + .sigma. Is generated in the slit groove 2, and a compressive stress -.sigma. Is generated in the slit groove 3. As shown in FIG. When a positive magnetostrictive material is used for the magnetostrictive shaft 1, it is known that the magnetic permeability μ increases due to the tensile stress + σ and decreases with the compressive stress −σ.

However, in the detection coils 7 and 8, respective self-inductances L1 and L2 are represented by:

[0017]

(Equation 1) It is calculated as follows.

In the bridge circuit 9, L1 and r1 of the detecting coil 7 are connected to the adjusting resistor R and L2 and
, R2 are connected in series to the adjustment resistor R, respectively, so that the currents i1, i2 flowing through the detection coils 7, 8 are:

[0019]

(Equation 2) And the output voltages V1 and V2 at the connection points c and d.
Is

[0020]

(Equation 3) Here, α1, α2 are calculated by the phase angles.

Further, the output voltage E0 output from the output terminal 12 of the differential amplifier 11 is

[0022]

E0 = A0 × (V1−V2) where A0: amplification factor.

Thus, when a negative torque T in the direction indicated by the arrow (counterclockwise) is applied to the magnetostrictive shaft 1, the slit groove 2
On the side, the magnetic permeability μ increases due to the tensile stress + σ,
The self-inductance L1 of the detection coil 7 facing the slit groove 2 increases, and the current i flowing through the detection coil 7 increases.
1 decreases, and the output voltage V1 decreases. On the other hand, since the magnetic permeability μ decreases on the slit groove 3 side due to the compressive stress −σ, the self inductance L2 of the detection coil 8 facing the slit groove 3 decreases, and the current i2 flowing through the detection coil 8 increases. , The output voltage V2 increases. The output voltages V1 and V2 are determined by the magnetic permeability μ according to the above-described equations (1) and (3).
, The amplitudes (voltage values) are changed as shown in Equation 3, and a detection signal proportional to the torque T in the direction of the arrow is output as an output voltage E0. The detection processing circuit 14 synchronizes the output voltage E0 with the phase adjustment voltage VP from the phase adjustment circuit 13, and integrates the output voltage E0 by the integration circuit 15. Then, it outputs to the control unit 16 as a voltage E (<VCO) corresponding to the torque T.

On the other hand, when a positive torque T in the direction opposite to the arrow (clockwise) is applied to the magnetostrictive shaft 1, the current i1 flowing through the detection coil 7 increases, and the current i2 flowing through the detection coil 8 increases. Since it decreases, it is output to the detection processing circuit 14 as the output voltage E0 according to the above equation 4, and the voltage E (> VCO) corresponding to the torque T is output to the control unit 16 via the integration circuit 15.

Then, the torque T applied to the magnetostrictive shaft 1
Has a linear characteristic as shown in FIG.

The phase angles α1, α when the torque T is zero are
2 and the torque T, the difference between the phase angles α1 and α2 is
Since the self-inductances L1 and L2 are very small as compared with the resistance value of the denominator as shown in Expression 3, the difference between the phase angles α1 and α2 can be regarded as almost zero.

[0027]

In the prior art described above, the torque T applied to the magnetostrictive shaft 1 causes
The generated stress is detected by the bridge circuit 9 as a change in the self-inductances L1 and L2 of the detection coils 7 and 8, and is detected by an oscillator 10, a differential amplifier 11, a phase adjustment circuit 13, a detection processing circuit 14, and an integration circuit 15. Since the circuit detects the torque T as the voltage E, the change in the voltage E with respect to the change in the torque T has a linear characteristic in the detection processing circuit. However, in practice, the magnetostrictive shaft 1
, The self-inductance of the detection coils 7 and 8 differs between when the torque T is applied in the positive direction (clockwise) and when the torque T is applied in the negative direction (counterclockwise). Variations occur in the amount of change, resulting in a characteristic that bends at a point where the torque is zero, as indicated by a characteristic line 18 shown by a dotted line in FIG. This causes a problem that accurate torque detection cannot be performed.

The present invention has been made in view of the above-mentioned problems of the prior art, and the present invention provides a magnetostrictive torque sensor capable of detecting a torque with high accuracy regardless of a positive torque or a negative torque. It is intended to be.

[0029]

To solve the above-mentioned problem, the present invention adopts a feature that the output side of the detection processing circuit receives an electric signal corresponding to a positive torque with a zero torque point as a boundary. A positive torque correction circuit and a negative torque correction circuit for separately correcting the electric signal corresponding to the negative torque so as to have a linear characteristic passing through the point of zero torque are provided.

[0030]

According to the above arrangement, the output signal due to the torque applied to the magnetostrictive shaft can be separately corrected for a positive torque and a negative torque.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the embodiments, the same components as those of the above-described conventional technology are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 shows a bridge circuit 9 as a detection circuit, an oscillator 10, a differential amplifier 11, a phase adjustment circuit 13, a detection processing circuit 14, an integration circuit 15 as a detection processing circuit, and a positive torque correction described later. 2 shows a circuit 21, a negative torque correction circuit 22, and an addition circuit 23. The positive torque correction circuit 21 and the negative torque correction circuit 22 are connected in parallel to the output side of the integration circuit 15, and the addition circuit 23 adds the outputs from the correction circuits 21 and 22 and adds a correction voltage E to the control unit 16. 'Is output.

Here, a specific example of the circuit configuration of the positive torque correction circuit 21, the negative torque correction circuit 22, and the addition circuit 23 will be described with reference to FIG.

In FIG. 2, reference numeral 21 denotes a positive torque correction circuit.
The positive torque correction circuit 21 is connected to an operational amplifier 24, an inverting terminal of the operational amplifier 24, and an input resistor 25 having a resistance value R1, and connected between an output side of the input resistor 25 and an output terminal of the operational amplifier 24. A feedback resistor 26 having the same resistance value R2, a first diode 27 having a cathode connected to the inverting terminal side of the operational amplifier 24 in parallel with the feedback resistor 26, an anode of the first diode 27 and the feedback resistor. 26 is the first diode 2 on the cathode side.
7 is constituted by an inverting ideal diode circuit comprising a second diode 28 facing the anode side. A voltage VCO at zero torque is input to a non-inverting terminal of the operational amplifier 24. A connection point 29 between the feedback resistor 26 and the feedback resistor 26 becomes an output terminal.

Then, in the positive torque correction circuit 21 configured as described above, the following voltage EA is output from the connection point 29 according to the magnitude of the voltage E input through the input side buffer circuit 30. .

That is, when E ≧ VCO,

[0037]

(Equation 5)

When E <VCO,

[0039]

EA = VCO and the voltage EA as shown in FIG.
Is output from the connection point 29.

Reference numeral 22 denotes a negative torque correction circuit. The negative torque correction circuit 22 includes an operational amplifier 31 and the operational amplifier 3.
1, an input resistor 32 having a resistance value R3, a feedback resistor 33 having a resistance value R4 connected between the output side of the input resistor 32 and the output terminal of the operational amplifier 31, and A first diode 34 whose anode side is connected to the inverting terminal side of the operational amplifier 31 in parallel with the resistor 33
And an inverting ideal diode circuit comprising a second diode 35 whose anode side faces the cathode side of the first diode 34 between the cathode of the first diode 34 and the feedback resistor 33. 31
The voltage VCO at the time when the torque is zero is input to the non-inverting terminal, and the connection point 36 between the cathode of the second diode 35 and the feedback resistor 33 becomes the output terminal.

In the negative torque correction circuit 22 configured as described above, the following voltage EB is output from the connection point 36 according to the magnitude of the voltage E input via the input buffer circuit 30. .

That is, when E ≧ VCO,

[0043]

[Equation 7] EB = VCO

When E <VCO,

[0045]

(Equation 8) Then, a voltage EB as shown in FIG.

Reference numeral 23 denotes each connection point 2 of the correction circuits 21 and 22.
Reference numerals 9 and 36 denote adder circuits connected via the respective output side buffer circuits 30 '. The adder circuits include an operational amplifier 37 and
Each buffer circuit 30 is connected to an inverting terminal of the operational amplifier 37.
'And an input resistor 3 having a resistance R5.
8, 38, and a feedback resistor 39 connected between the output terminal and the inverting terminal of the operational amplifier 37 and having a resistance value R6. The non-inverting terminal of the operational amplifier 37 receives the voltage VCO at zero torque. Has been entered.

Here, the input voltage E 1 input from each of the torque correction circuits 21 and 22 to the inverting terminal of the operational amplifier 37 via each input resistor 38 is

[0048]

(Equation 9) And the characteristics as shown in FIG.

The correction voltage E 'output from the output terminal of the operational amplifier 37 inverts and amplifies the input voltage E1.

[0050]

(Equation 10) However, A1 is an amplification factor set from the resistance values R5 and R7, and has a characteristic obtained by inverting FIG. 5 as shown in FIG.

However, in the torque sensor provided with the detection processing circuit according to the present embodiment, when the torque T is positive (clockwise opposite to the direction of the torque T in FIG. 7), the positive torque correction circuit 21 By adjusting the resistance value R2 of the feedback resistor 26, fine adjustment in the direction indicated by the arrow A can be performed as shown in FIGS. 5 and 6, and the inclination in the positive direction can be corrected.

On the other hand, when the torque T is negative (counterclockwise as in the direction of the torque T in FIG. 7), the resistance value R4 of the feedback resistor 33 of the negative torque correction circuit 22 is adjusted. As shown in FIG. 5 and FIG. 6, fine adjustment in the direction of arrow B can be performed to correct the inclination in the negative direction.

Thus, even when the magnetic characteristics of the magnetostrictive shaft 1 vary, the torque T is applied in the positive direction (clockwise) and the torque T is applied in the negative direction (counterclockwise). And the change in the correction voltage E 'can be made a linear characteristic, the error due to the variation in the magnetic characteristics of the magnetostrictive shaft 1 can be reliably corrected, and the accurate torque can be corrected. Detection can be performed.

In the above embodiment, a two-coil type torque sensor has been described as an example. However, the present invention is not limited to this, and may be used for a four-coil type torque sensor.

In the above embodiment, the positive torque correction circuit 21 and the negative torque correction circuit 22 have been described by taking an inversion type ideal diode circuit as a specific example. However, the present invention is not limited to this. A voltage discriminating circuit, an amplifying circuit, and the like may be configured to correct the output voltage while distinguishing between the positive torque portion and the negative torque portion with the zero time as a boundary.

[0056]

As described in detail above, according to the present invention, a positive torque correction circuit and a negative torque correction circuit for separately correcting a positive torque and a negative torque with a zero torque point as a boundary of the detection processing circuit. Therefore, even if the magnetostrictive shaft has a variation in magnetic characteristics, high-precision torque detection can be always performed regardless of the torque in the positive direction and the torque in the negative direction.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a detection circuit and a detection processing circuit of a magnetostrictive torque sensor according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific example of a positive torque correction circuit, a negative torque correction circuit, and an addition circuit according to the embodiment.

FIG. 3 is a characteristic diagram showing a relationship between positive and negative torque and a voltage output from a positive torque correction circuit.

FIG. 4 is a characteristic diagram showing a relationship between positive and negative torque and a voltage output from a negative torque correction circuit.

FIG. 5 is a characteristic diagram showing a relationship between positive and negative torque and an input voltage input to an adding circuit.

FIG. 6 is a characteristic diagram illustrating a relationship between positive and negative torques and a voltage output from an adding circuit.

FIG. 7 is a configuration diagram of a conventional magnetostrictive torque sensor.

FIG. 8 is a circuit configuration diagram showing a detection circuit and a detection processing circuit according to the related art.

FIG. 9 is a characteristic diagram showing a relationship between positive and negative torques and a voltage output from an integration circuit according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetostrictive shaft 7, 8 Detection coil 9 Bridge circuit 10 Oscillator 11 Differential amplifier 13 Phase adjustment circuit 14 Detection processing circuit 15 Integration circuit 21 Positive torque correction circuit 22 Negative torque correction circuit 23 Addition circuit

Claims (1)

(57) [Scope of request for utility model registration] 1. A magnetostrictive shaft, at least one pair of detection coils provided on an outer peripheral side of the magnetostriction shaft, a detection circuit for detecting a torque applied to the magnetostriction shaft by a change in inductance from each detection coil, and In a magnetostrictive torque sensor comprising a detection processing circuit that converts torque into an electric signal based on a signal from the detection circuit, the output side of the detection processing circuit has an electric signal for positive torque with a zero torque point as a boundary. A magnetostrictive torque sensor comprising a positive torque correction circuit and a negative torque correction circuit for separately correcting an electric signal for negative torque so as to have a linear characteristic passing through the point of zero torque.