JPH0540848U - Magnetostrictive torque sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] In a torque sensor for automobiles, the detection sensitivity in the low torque region can be improved, and the shift timing control of the automatic transmission mechanism of the automobile can be accurately performed to improve the riding comfort and the fuel consumption. Surely. [Configuration] A function generation circuit 21 is connected between the integration circuit 15 and the control unit 16. The function generating circuit 21 uses a point of zero torque as an inflection point and changes in a logarithmic function, and steepens the gradient of the voltage E ′ in the low torque region to improve the detection sensitivity.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a magnetostrictive torque sensor which is preferably used for detecting a torque generated on an output shaft of an automobile engine, for example.

[0002]

[Prior Art]

 In an automatic vehicle or the like equipped with an automatic transmission, it has been proposed to attach a torque sensor to a propeller shaft or the like in order to optimize the shift timing by an automatic transmission mechanism.

Therefore, as a torque sensor according to this type of conventional technology, FIGS. 3 to 5 show a two-coil type magnetostrictive torque sensor as an example.

In the figure, reference numeral 1 denotes a magnetostrictive shaft formed of a magnetostrictive material such as chrome molybdenum steel, and the magnetostrictive shaft 1 is provided, for example, in the middle of a propeller shaft. It becomes the output side mounting portion 1B, and the slit groove forming portion 1C is formed in the middle thereof, and the slit groove forming portions 1C have slit grooves 2 and 3 engraved downward 45 ° and upward 45 ° on the outer periphery thereof. They are provided so as to face each other.

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. Reference numeral 4 is fixedly attached to the 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, and the core member 6 is provided with detection coils 7 and 8 at positions facing the slit grooves 2 and 3, respectively. The self-inductances of the detection coils 7 and 8 are L1 and L2.

Next, a detection circuit and a detection processing circuit are shown in FIG. 4 and will be described.

In FIG. 4, reference numeral 9 denotes a bridge circuit as a detection circuit. The bridge circuit 9 includes detection coils 7 and 8, iron losses r1 and r2 of the detection coils 7 and 8, and the detection coils 7 and 8. The oscillator 10 is connected between the connection point a of the detection coils 7 and 8 and the connection point b of the adjustment resistors R and R. The connection point c between the detection coil 7 and the adjustment resistor R and the connection point d between the detection coil 8 and the adjustment resistor R are output terminals for deriving the output voltages V1 and V2 from the detection coils 7 and 8, respectively. The connection points c and d are respectively connected to the input terminals of the differential amplifier 11.

Next, the detection processing circuit will be described. The detection processing circuit is roughly composed of an oscillator 10, a differential amplifier 11, a phase adjustment circuit 13, a detection processing circuit 14, an integration circuit 15 and the like which will be described later.

Reference numeral 10 denotes an oscillator, which generates an AC voltage V having a peak value V 0 and a frequency f (for example, 30 KHZ), the output side of which is connected to a connection point a of the bridge circuit 9. At the same time, it is connected to the phase adjustment circuit 13.

Reference numeral 11 denotes a differential amplifier, which is composed of an operational amplifier or the like, the input terminals thereof are connected to the connection points c and d of the bridge circuit 9, respectively, and the output voltages V1 and V2 are inputted thereto. The output terminal 12 is connected to the detection processing circuit 14 and outputs the detection voltage 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 the phase adjustment voltage VP to the detection processing circuit 14. ..

Reference numeral 14 denotes a detection processing circuit. The input side 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 to detect the detection voltage E0 and the phase adjustment voltage VP. Is entered. Then, the detection processing circuit 14 outputs the portion obtained by synchronizing the detection voltage E0 with the phase adjustment voltage VP to the integration circuit 15. Then, the integrating 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.

By adjusting each adjusting resistor R, the bridge circuit 9 is balanced so that the output voltages V1 and V2 from the connection points c and d have the same waveform when the torque acting on the magnetostrictive shaft 1 is zero. The offset adjustment circuit 17 is connected to the operational amplifier of the differential amplifier 11 so that the detection voltage E0 from the output terminal 12 of the differential amplifier 11 at this time is offset to the DC voltage VCO [V]. Has been done. Therefore, when the torque acting on the magnetostrictive shaft 1 is zero, the voltage E output to the control unit 16 via the integrating circuit 15 becomes VCO [V] (see FIG. 5).

In the two-coil type magnetostrictive torque sensor configured as described above, when the AC voltage V of the oscillator 10 is applied to the detection coils 7 and 8, a magnetic path is formed on the surface of the magnetostrictive shaft 1. 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 along the slit grooves 2 and 3.

On the other hand, when a torque T in the arrow direction (counterclockwise direction) as shown in FIG. 3 is applied to the input side mounting portion 1A of the magnetostrictive shaft 1, tensile stress + σ is generated in the slit groove 2. A compressive stress −σ is generated in the slit groove 3. It is known that when a positive magnetostrictive material is used for the magnetostrictive shaft 1, the tensile stress + σ increases the magnetic permeability μ and the compressive stress −σ decreases the magnetic permeability μ.

However, in the detection coils 7 and 8, the respective self-inductances L 1 and L 2 are

[0017]

[Equation 1] Calculate as

In the bridge circuit 9, L1 and r1 of the detection coil 7 are connected in series to the adjustment resistor R, and L2 and r2 of the detection coil 8 are connected in series to the adjustment resistor R, so that the detection coils 7 and 8 are connected in series. The flowing currents i1 and i2 are

[0019]

[Equation 2] The output voltages V1 and V2 at the connection points c and d are calculated by

[0020]

[Equation 3] Is calculated by

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

[0022]

## EQU00004 ## E0 = A.times. (V1-V2) where A is the amplification factor.

Thus, when a negative torque T in the direction of the arrow (counterclockwise) is applied to the magnetostrictive shaft 1, the magnetic permeability μ increases on the slit groove 2 side due to the tensile stress + σ, so that the slit groove 2 The self-inductance L1 of the opposing detection coil 7 increases, the current i1 flowing through the detection coil 7 decreases, and the output voltage V1 decreases.

On the other hand, on the slit groove 3 side, the magnetic permeability μ decreases due to the compressive stress −σ, so that the self-inductance L 2 of the detection coil 8 facing the slit groove 3 decreases and flows through the detection coil 8. The current i2 increases and the output voltage V2 increases.

Then, the output voltages V1 and V2 generate phase angles α1 and α2 based on the change of the magnetic permeability μ according to the formulas 1 and 3, and change the amplitude (voltage value) as shown in the formula 3. Then, the detection signal proportional to the torque T in the direction of the arrow is output to the detection processing circuit 14 as the detection voltage E0, and the detection processing circuit 14 detects the detection voltage E0 by the phase adjustment voltage VP from the phase adjustment circuit 13. The parts obtained in synchronization are integrated by the integrating circuit 15 and output 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 direction (clockwise direction) 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. Therefore, the detected voltage E0 is output to the detection processing circuit 14 according to the equation 4 and the voltage E (> VCO) corresponding to the torque T is output to the control unit 16 via the integrating circuit 15.

The voltage E with respect to the torque T applied to the magnetostrictive shaft 1 has a linear characteristic as shown in FIG.

Since the difference between the phase angles α1 and α2 when the torque T is zero and the phase angles α1 and α2 when the torque T is added depends on the change in the inductances L1 and L2 as shown in Formula 3, the denominator is Since the inductances L1 and L2 are extremely smaller than the resistance value of, the difference between the phase angles α1 and α2 can be regarded as almost zero.

[0029]

[Problems to be solved by the device]

 By the way, in the above-mentioned conventional technique, the stress generated by the torque T applied to the magnetostrictive shaft 1 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 the oscillator 10, the differential amplifier 11, Since the detection processing circuit including the phase adjustment circuit 13, the detection processing circuit 14, and the integration circuit 15 detects the torque T as the voltage E, the detection processing circuit changes the voltage E with respect to the amount of change in the torque T. It has a linear characteristic. However, when this torque sensor is used in, for example, an automatic transmission mechanism of an automobile, the same accuracy can be obtained even in a low torque region that requires high-precision detection or in a high torque region that requires low-precision detection. Therefore, particularly in a low torque region where automatic gear shift is performed by accurate torque detection, high-precision detection cannot be performed, and appropriate gear shift timing control cannot be performed, which causes deterioration of riding comfort and fuel consumption. is there.

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 improving the detection accuracy in a low torque region that requires particularly high-precision torque detection. The purpose is to

[0031]

[Means for Solving the Problems] A feature of the configuration adopted by the present invention to solve the above-mentioned problems is that a function that changes logarithmically with a point of zero torque as an inflection point at the output side of a detection processing circuit. There is a generator circuit.

[0032]

[Action]

 With the above configuration, in the low torque region applied to the magnetostrictive shaft, the gradient of the low torque region can be made steep by changing the output signal logarithmically according to the change amount of the inductance of each detection coil.

[0033]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In the embodiments, the same components as those of the above-described conventional technique are designated by the same reference numerals, and the description thereof will be omitted.

Here, FIG. 1 shows a bridge circuit 9 as a detection circuit, an oscillator 10 as a detection processing circuit, a differential amplifier 11, a phase adjustment circuit 13, a detection processing circuit 14, an integration circuit 15 and a function generation circuit. A circuit 21 is shown.

In the figure, reference numeral 21 denotes a function generating circuit of the present embodiment, which is connected between the integrating circuit 15 and the control unit 16 and applies a non-linear voltage E having a linear characteristic line. The voltage is converted into a voltage E ′ having a characteristic line 22.

Then, the function generating circuit 21 generates a logarithmic function having the characteristic line 22A in FIG. 2 when the torque T is positive, with the voltage VCO when the torque T is zero as an inflection point, When the torque T is negative, the logarithmic function having the characteristic line 22B in FIG. 2 is generated.

As a result, the function generating circuit 21 according to the present embodiment can convert the voltage E having the linear characteristic line according to the related art shown in FIG. 5 into the voltage E ′ having the characteristic line 22 shown in FIG. You can

In FIG. 2, the characteristic line 22A corresponding to the positive torque T can be seen as a logarithmic function, and the characteristic line 22B corresponding to the negative torque T can be seen as a negative logarithmic function.

As a result, the voltage E ′ output from the detection processing circuit is the characteristic line 22 in which the amount of change in the voltage VCO when the torque T is zero has a steep gradient near the inflection point. ′ Is output to the control unit 16.

However, in the torque sensor including the detection processing circuit according to the present embodiment, the voltage E ′ can be greatly changed with a slight change in the torque T in the low torque region which is the high accuracy required region. This enables high-precision detection in the low torque region.

Thus, by using this torque sensor to detect the axial torque of a vehicle equipped with an automatic transmission mechanism, highly accurate detection can be performed in the low torque region, and accurate shift timing control can be reliably performed. Therefore, it is possible to surely improve the riding comfort and the fuel economy.

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

[0043]

[Effect of the device]

 As described above in detail, according to the present invention, the point of zero torque is set as an inflection point on the output side of the detection processing circuit, and a function generating circuit for changing logarithmically is provided, so that the torque applied to the magnetostrictive shaft is The detection at low torque can be performed with high accuracy, the shift timing of the automatic transmission mechanism of the automobile can be accurately controlled, and the riding comfort and the fuel consumption can be surely improved.

[Brief description of drawings]

FIG. 1 is a circuit configuration 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 characteristic diagram showing a relationship between torque and a voltage output from a function generating circuit according to an embodiment.

FIG. 3 is a configuration diagram of a magnetostrictive torque sensor according to a conventional technique.

FIG. 4 is a circuit configuration diagram showing a detection circuit and a detection processing circuit according to a conventional technique.

FIG. 5 is a characteristic diagram showing a relationship between torque and voltage output from a rectifier circuit according to a conventional technique.

[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 Function generation circuit

Claims (1)

[Scope of utility model registration request] 1. A magnetostrictive shaft, at least a pair of detection coils provided on the outer peripheral side of the magnetostrictive shaft, a detection circuit for detecting a torque applied to the magnetostrictive shaft by a change in inductance from each detection coil, In a magnetostrictive torque sensor consisting of a detection processing circuit that converts torque into an electric signal based on a signal from the detection circuit, a function that changes logarithmically with a point of zero torque at the output side of the detection processing circuit as an inflection point. A magnetostrictive torque sensor having a generating circuit.