JP2024042793A - magnetostrictive torque sensor - Google Patents

Abstract

[Problem] To provide a magnetostrictive torque sensor capable of improving detection accuracy even when there is variation in the resistance component of the detection coil. [Solution] The magnetostrictive torque sensor 1 is a torque sensor that detects torque transmitted by a magnetostrictive material 2 having magnetostrictive properties, and is equipped with a sensor unit 10 having a bridge circuit 10a including a first detection coil 31 having a first linear portion 31a inclined at a predetermined angle with respect to the axial direction of the magnetostrictive material 2 and a second detection coil 32 having a second linear portion 32a inclined at a predetermined angle in the opposite direction to the first linear portion 31a with respect to the axial direction of the magnetostrictive material 2, a drive unit 8 that applies an AC drive voltage to the bridge circuit 10a, and a voltage measurement unit 9 that measures the voltage output from the bridge circuit 10a, and the voltage measurement unit 9 is configured to measure the voltage when the current flowing through the bridge circuit 10a becomes zero. [Selected Figure] Figure 4

Description

The present invention relates to a magnetostrictive torque sensor.

Conventionally, a magnetostrictive material with magnetostrictive properties whose magnetic permeability changes when torque (rotational torque) is applied is used, and the change in the magnetic permeability of the magnetostrictive material when torque is applied is detected as a change in the inductance of a detection coil. A magnetostrictive torque sensor is known that detects torque applied to a magnetostrictive material by doing so.

Conventional magnetostrictive torque sensors have a sensor section in which four detection coils are bridge-connected, and the torque applied to a shaft with magnetostrictive characteristics is detected based on the change in impedance of each detection coil due to the application of torque. detected (for example, see Patent Document 1).

JP2020-160088A

However, the detection coil includes a resistance component, and there are variations in this resistance component. Particularly, when a detection coil is configured by a wiring pattern formed on a substrate, it is inevitable that a certain amount of error will occur in the thickness and width of the wiring pattern, resulting in variations in the resistance component of the detection coil. When variations in resistance components occur in the detection coil, a phenomenon called offset occurs in which an output is generated even when no torque is applied. Furthermore, since the offset due to variations in the resistance component varies greatly depending on the temperature, there is a risk that detection accuracy may be reduced.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetostrictive torque sensor that can improve detection accuracy even when there is variation in the resistance component of a detection coil.

In order to solve the above problems, the present invention provides a torque sensor that detects torque transmitted by a magnetostrictive material having magnetostrictive characteristics, the present invention comprising a first straight line inclined at a predetermined angle with respect to the axial direction of the magnetostrictive material. a second detection coil having a second linear portion inclined at a predetermined angle in a direction opposite to the first linear portion with respect to the axial direction of the magnetostrictive material; a sensor section that has a drive section that applies an alternating current drive voltage to the bridge circuit, and a voltage measurement section that measures the voltage output from the bridge circuit, the voltage measurement section that is connected to the bridge circuit. A magnetostrictive torque sensor is provided that is configured to measure a voltage when a current flowing through a circuit becomes zero.

The present invention provides a magnetostrictive torque sensor that can improve detection accuracy even when there is variation in the resistance component of the detection coil.

1 is a perspective view showing the appearance of a magnetostrictive torque sensor according to an embodiment of the present invention. (a) is a perspective view with the resin molded part omitted in FIG. 1, and (b) is a cross-sectional view showing a laminated structure of a flexible substrate and a magnetic ring. It is a figure showing an example of the wiring pattern formed in each wiring layer of a flexible board. FIG. 3 is a diagram showing a circuit configuration of a sensor section and a voltage measurement section. 5 is a time chart showing changes in voltage and current of each part in FIG. 4. FIG. FIG. 13 is a diagram showing a circuit configuration of a sensor section and a voltage measuring section of a magnetostrictive torque sensor according to another embodiment of the present invention.

[Embodiment]
Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a perspective view showing the appearance of a magnetostrictive torque sensor according to this embodiment. FIG. 2(a) is a perspective view of FIG. 1 with the resin molded part omitted, and FIG. 2(b) is a cross-sectional view showing a laminated structure of a flexible substrate and a magnetic ring. FIG. 3 is a diagram showing an example of a wiring pattern formed in each wiring layer of a flexible substrate.

(Magnetostrictive material 2)
As shown in FIGS. 1 to 3, a magnetostrictive torque sensor (hereinafter simply referred to as a torque sensor) 1 is a sensor that detects torque (rotational torque) applied to a magnetostrictive material 2, and is attached around the magnetostrictive material 2. It is being

The magnetostrictive material 2 is a cylindrical member to which torque is applied in the circumferential direction. The magnetostrictive material 2 in the torque sensor 1 is, for example, a shaft used for transmitting torque in a vehicle's power train system or a shaft used for transmitting torque in a vehicle's engine. As the magnetostrictive material 2, a base material made of chromium steel containing chromium, such as chromium steel, chromium molybdenum steel, or nickel chromium molybdenum steel, is subjected to carburizing, quenching and tempering treatment, and then shot peening is used. be able to.

(Sensor unit 10)
The torque sensor 1 includes a sensor section 10 provided to cover the periphery of a magnetostrictive material 2. The sensor section 10 includes a detection coil 3 provided around the magnetostrictive material 2, and a magnetic ring (magnetic ring, back yoke) 4 provided to cover the periphery of the detection coil 3. In this embodiment, the sensor section 10 includes first to fourth detection coils 31 to 34.

As shown in FIGS. 1 and 2(a), the sensor section 10 includes a cylindrical bobbin 5 that is spaced apart from and coaxially arranged with the magnetostrictive material 2, and a flexible substrate 6 that is wound around the outer surface of the bobbin 5. It has a resin mold part 7. In this embodiment, the detection coil 3 is composed of a wiring pattern (wiring layer 60 described later) formed on a flexible substrate 6. The bobbin 5 is made of a non-magnetic material such as resin, and has a radially outwardly projecting collar 51 integrally formed at one axial end thereof. The magnetic ring 4 is provided so as to cover the periphery of the flexible substrate 6.

(Resin mold part 7)
As shown in FIG. 1, the resin mold part 7 is for protecting the flexible substrate 6 and the magnetic ring 4, and is molded with resin so as to cover the bobbin 5, the flexible substrate 6, and the magnetic ring 4. It is formed by The resin molded part 7 integrally includes a main body part 71 that covers the bobbin 5, the flexible substrate 6, and the magnetic ring 4, and a flange part 72 formed to protrude outward from the main body part 71. There is. The main body portion 71 is formed with a through hole 71a through which the magnetostrictive material 2 is passed. A holding hole 74 is formed in the flange portion 72, passing through the flange portion 72 and holding a short cylindrical collar 73 made of metal. The flange portion 72 is fixed to surrounding members (members that do not rotate with rotation of the magnetostrictive material 2) using bolts or the like.

(Flexible substrate 6)
2B, the flexible substrate 6 has four wiring layers 60, including a first wiring layer 61, a second wiring layer 62, a third wiring layer 63, and a fourth wiring layer 64. However, the number of layers of the wiring layers 60 is not limited to this, and may be two or more.

The first wiring layer 61 is formed on the surface of a first base resin layer 65a made of polyimide, and the back surface of the first base resin layer 65a is adhesively fixed to the second wiring layer 62 via an adhesive layer 66b. A first coverlay layer 67a made of polyimide is provided on the surface of the first wiring layer 61 via an adhesive layer 66a, and is subjected to an insulating treatment. Double-sided tape 68a is attached to the surface of the first coverlay layer 67a, and the flexible substrate 6 is adhesively fixed to the bobbin 5 via this double-sided tape 68a.

The second wiring layer 62 is formed on the surface of a second base resin layer 65b made of polyimide, and the third wiring layer 63 is formed on the back surface of the second base resin layer 65b.

The fourth wiring layer 64 is formed on the back surface of a third base resin layer 65c made of polyimide, and the surface of the third base resin layer 65c is adhesively fixed to the third wiring layer 63 via an adhesive layer 66c. . A second coverlay layer 67b made of polyimide is provided on the surface of the fourth wiring layer 64 via an adhesive layer 66d, and is subjected to insulation treatment. A double-sided tape 68b is attached to the second coverlay layer 67b, and the flexible substrate 6 and the magnetic ring 4 are adhesively fixed via this double-sided tape 68b.

The second wiring layer 62 and the third wiring layer 63, which are the inner layers of the flexible substrate 6, are made of rolled copper foil. The first wiring layer 61 and the fourth wiring layer 64, which are the outer layers of the flexible substrate 6, are made of electrolytic copper foil plated with copper. Although the details will be described later, in the torque sensor 1, since it is necessary to form vias (through holes) in the flexible substrate 6, the first and fourth wiring layers 61 and 64, which are the outer layers, have a plating structure. There is.

FIG. 3 is a diagram showing an example of a wiring pattern formed on each wiring layer 60 of the flexible substrate 6. FIG. 3 schematically shows the wiring pattern of each wiring layer 60 when the flexible substrate 6 is developed into a flat surface.

As shown in FIG. 3, the first to fourth detection coils 31 to 34 are formed on the wiring layer 60 of the flexible substrate 6. The first and third detection coils 31 and 33 have first straight portions 31a and 33a inclined at a predetermined angle with respect to the axial direction of the magnetostrictive material 2, and the second and fourth detection coils 32 and 34 have It has second straight parts 32a, 34a which are inclined at a predetermined angle in a direction opposite to the first straight parts 31a, 33a with respect to the axial direction of the magnetostrictive material 2.

In the torque sensor 1, the change in magnetic permeability when torque is applied to the magnetostrictive material 2 is greatest in the directions of ±45 degrees with respect to the axial direction. Therefore, by forming the first straight portions 31a, 33a so as to be inclined at +45 degrees with respect to the axial direction, and by forming the second straight portions 32a, 34a so as to be inclined at −45 degrees with respect to the axial direction, detection is possible. Sensitivity can be improved.

In this torque sensor 1, the wiring patterns of the wiring layer 60 forming the first detection coil 31 and the wiring layer 60 forming the fourth detection coil 34 are partially interchanged, so that the first and fourth detection coils 31, 34 are formed across two wiring layers 60 (first and second wiring layers 61, 62). Similarly, the wiring patterns of the wiring layer 60 forming the second detection coil 32 and the wiring layer 60 forming the third detection coil 33 are partially interchanged, so that the second and third detection coils 32, 33 are formed across two wiring layers 60 (third and fourth wiring layers 63, 64). The wiring layers 60 are electrically connected through vias.

By forming each detection coil 3 over two wiring layers 60, it is possible to suppress the influence of the difference in characteristics between the two wiring layers 60. As a result, it becomes possible to suppress measurement errors caused by differences in characteristics between the wiring layers 60 and improve measurement accuracy.

In this embodiment, the wiring patterns formed in the first wiring layer 61 and the third wiring layer 63 and in the second wiring layer 62 and the fourth wiring layer 64 are substantially the same pattern. Further, currents flowing through the wiring patterns formed in the first wiring layer 61 and the third wiring layer 63, and in the second wiring layer 62 and the fourth wiring layer 64 are made to flow in the same direction. In FIG. 3, the direction of the current is indicated by a white arrow. In addition, in FIG. 3, the input side electrodes of the first to fourth detection coils 31 to 34 are shown as 31b, 32b, 33b, and 34b, and the output side electrodes are shown as 31c, 32c, 33c, and 34c. Further, the symbols a to y and A to Y in FIG. 3 are used to conveniently represent connection relationships by vias, and the same symbols represent electrical connections via vias. Note that the wiring pattern of each wiring layer 60 shown in FIG. 3 is just an example, and the specific structure of the wiring pattern is not limited to this.

(Circuit configuration of sensor section 10 and voltage measurement section 9)
FIG. 4 is a diagram showing the circuit configuration of the sensor section 10 and the voltage measurement section 9. As shown in FIG. 4, the torque sensor 1 includes a sensor section 10 having a bridge circuit 10a, a drive section 8 that applies an AC drive voltage to the bridge circuit 10a, and a voltage output from the bridge circuit 10a. A voltage measuring section 9 for measuring the voltage is provided.

The sensor section 10 is constituted by a bridge circuit 10a in which first, second, third, and fourth detection coils 31 to 34 are sequentially connected in a ring shape. The drive unit 8 is configured to apply a driving voltage between the connection part a of the first and fourth detection coils 31 and 34 and the connection part b of the second and third detection coils 32 and 33. has been done.

The voltage measuring section 9 is configured to measure the voltage between the connection part c of the first and second detection coils 31 and 32 and the connection part d of the third and fourth detection coils 33 and 34. ing. In this embodiment, the voltage measuring section 9 is configured to measure the voltage when the current I _coil flowing through the bridge circuit 10a becomes zero.

More specifically, the voltage measurement section 9 includes a pulse generation circuit 93 that outputs a pulse at the timing when the current I _coil flowing through the bridge circuit 10a becomes zero, and a bridge circuit that outputs a pulse when the pulse from the pulse generation circuit 93 is input. A sample-and-hold circuit 96 that holds the output voltage of the circuit 10a is included.

In this embodiment, the voltage measurement unit 9 further includes a current detection resistor 91a connected in series to the bridge circuit 10a, and a comparator 91b that compares the voltage across the current detection resistor 91a. The output of the comparator 91b is an output (high or low) according to the direction of the current I _coil . That is, when the current I _coil flows in one direction, the output is high, and when the current I coil flows in the other direction, the output is low.

The pulse generating circuit 93 is configured to output pulses in response to the output from the comparator 91b. In this embodiment, two pulse generation circuits 93, a first pulse generation circuit 93a and a second pulse generation circuit 93b, are provided. The output of the comparator 91b is directly connected to the input of the first pulse generation circuit 93b. Further, the output of the comparator 91b is connected to the input of the second pulse generation circuit 93b via an inversion circuit (NOT circuit) 94. Both pulse generation circuits 93a and 93b have a function of outputting one pulse when a high signal is input (when the input changes from low to high). That is, in this embodiment, the pulse generation circuit 93 generates a pulse at the timing when the direction of the current I _coil flowing through the bridge circuit 10a changes and the output of the comparator 91b changes, that is, at the timing when the current I _coil becomes zero. It will be output. When the current I _coil changes from positive to negative, a pulse is output from the first pulse generating circuit 93a, and when the current I _coil changes from negative to positive, a pulse is output from the second pulse generating circuit 93b. be done. The output of the first pulse generation circuit 93a is connected to the clock input of the first sample and hold circuit 96a. Further, the output of the second pulse generation circuit 93b is connected to the clock input of the second sample and hold circuit 96b.

On the other hand, the voltage between connections c and d to be detected is amplified by a first differential amplifier circuit 95 and input to two sample-and-hold circuits 96, first and second sample-and-hold circuits 96a and 96b. be done. In the sample-and-hold circuit 96, the sampling switch is turned on when a high signal is input to the clock input, and the input signal (amplified voltage V _s between connections c and d) is output as is. Ru. When the clock input goes low, the sampling switch is turned off and the state immediately before the sampling switch was switched is maintained. Note that if the pulse width (the time during which the voltage is high) of the pulse outputted by the pulse generation circuit 93 is long, the timing of the current I _coil becomes zero will deviate, so the pulse width of the pulse outputted from the pulse generation circuit 93 will be delayed. Preferably, the width is sufficiently short.

Since the pulse from the first pulse generation circuit 93a is input to the clock input of the first sample-and-hold circuit 96a, in the first sample-and-hold circuit 96a, when the current I _coil changes from positive to negative, The voltage V _s at the timing when the current I _coil becomes zero is held. Since the pulse from the second pulse generation circuit 93b is input to the clock input of the second sample-and-hold circuit 96b, the second sample-and-hold circuit 96b receives the pulse when the current I _coil changes from negative to positive. , the voltage V _s at the timing when the current I _coil becomes zero is held.

The outputs of both sample-and-hold circuits 96a and 96b are output to a second differential amplifier circuit 97, and after the difference is amplified, high-frequency noise components are cut through a low-pass filter 98, and then input to a voltage detection section 99. voltage value is detected. That is, the voltage detection section 99 detects a voltage value obtained by amplifying the difference between the output voltages of the first and second sample-and-hold circuits 96a and 96b.

FIG. 5 is a time chart showing changes in voltage and current at various parts in FIG. In FIG. 5, the voltage V ₀ at the connection point a, the current I _coil flowing through the bridge circuit 10a, the output voltage V _tp of the first pulse generation circuit 93a, the output voltage V _tn of the second pulse generation circuit 93b, the first differential Each time chart of the output voltage _Vs of the amplifier circuit 95 is shown. The time chart of the output voltage V _s of the first differential amplifier circuit 95 also shows the output voltage V _hp of the first sample-and-hold circuit 96a and the output voltage V _hn of the second sample-and-hold circuit 96b. ing.

As shown in FIG. 5, when the polarity of the voltage V ₀ applied to the bridge circuit 10a is reversed, the polarity of the current I _coil is accordingly reversed after a predetermined time td. Then, when the direction of the current I _coil changes from positive to negative, a pulse is output from the first pulse generation circuit 93a (see the time chart of the output voltage V _tp ), and the output of the first differential amplifier circuit 95 at that point. The voltage V _s is held in the first sample-and-hold circuit 96a as the output voltage V _hp . Further, when the direction of the current I _coil changes from negative to positive, a pulse is output from the second pulse generation circuit 93b (see the time chart of the output voltage V _tn ), and the output of the first differential amplifier circuit 95 at that point is The voltage V _s is held as the output voltage V _hn in the second sample-and-hold circuit 96b. By extracting these differences using the second differential amplifier circuit 97, the amplitude of the output voltage _Vs can be extracted. Note that the amplitude (fluctuation width) of the output voltage V _s changes depending on the torque applied to the magnetostrictive material 2, so the amplitude (fluctuation width) of the output voltage V _s changes depending on the torque applied to the magnetostrictive material 2 based on the detected value of the amplitude (fluctuation width) of the output voltage V s. Torque can be determined.

At this time, the output voltages _Vhp , Vhn of both sample and hold circuits 96a, _96b are voltage values when the current _Icoil is zero, and are therefore not affected by the resistance components of the detection coils 31 to 34. This makes it possible to ignore the effects of variations in the resistance components of the detection coils 31 to 34 and fluctuations in the resistance components due to temperature changes, making it possible to accurately detect the torque applied to the magnetostrictive material 2.

(Modified example)
In this embodiment, two pulse generation circuits 93 and two sample-and-hold circuits 96 are used, but the present invention is not limited to this, and one pulse generation circuit 93 and one sample-and-hold circuit 96 may be used. That is, the second pulse generation circuit 93b and the second sample-and-hold circuit 96b can be omitted. In this case, the torque applied to the magnetostrictive material 2 may be determined based on the voltage value of the output voltage _Vhp of the first sample-and-hold circuit 96a.

Further, in this embodiment, four detection coils 31 to 34 are used, but the present invention is not limited to this, and for example, the third and fourth detection coils 33 and 34 may be replaced with resistive elements.

(Actions and effects of embodiments)
As described above, in the torque sensor 1 according to the present embodiment, the voltage measuring section 9 is configured to measure the voltage when the current flowing through the bridge circuit 10a becomes zero. This suppresses the influence of the resistance components of the detection coils 31 to 34, and makes it possible to substantially ignore the influence of variations in the resistance components of the detection coils 31 to 34 and the fluctuations in the resistance components due to temperature changes. As a result, it becomes possible to accurately detect the torque applied to the magnetostrictive material 2. That is, according to the present embodiment, even if there are variations in the resistance components of the detection coils 31 to 34, it is possible to reduce temperature fluctuations and improve detection accuracy. This embodiment is particularly effective when the detection coils 31 to 34 are constructed from wiring patterns whose widths and thicknesses tend to fluctuate.

(Other embodiments)
FIG. 6 is a diagram showing a circuit configuration of a sensor section and a voltage measuring section of a torque sensor 1 according to another embodiment of the present invention. The circuit configuration shown in FIG. 6 is basically the same as the circuit configuration shown in FIG. 4, but differs in the method of extracting the timing when the current I _coil becomes zero.

In the example of FIG. 6, the drive unit 8 has a clock generation circuit 81 that generates a clock signal of a predetermined period, and an amplifier circuit 82 that amplifies the clock signal output from the clock generation circuit 81 and outputs it as a drive voltage. The voltage measurement unit 9 has a delay circuit 92 that receives the clock signal from the clock generation circuit 81 and delays and outputs the input clock signal. The pulse generation circuit 93 is configured to output a pulse according to the output from the delay circuit 92.

As shown in FIG. 5, the polarity of the current I _coil changes as the polarity of the voltage V ₀ applied to the bridge circuit 10a changes, but the change in the polarity of the current I _coil depends on the material of the magnetostrictive material 2 and the Depending on the configuration of the detection coils 31 to 34, etc., a delay occurs with respect to a change in the polarity of the voltage V ₀ . Therefore, it is possible to determine by experiment or calculation how much the change in polarity of the current I _coil is delayed with respect to the clock signal generated by the clock generation circuit 81 (the time corresponding to time td in FIG. 5). By delaying the clock signal by the obtained delay time, it is possible to extract the timing at which the current I _coil becomes zero. In other words, the delay circuit 92 generates the clock signal generated by the clock generation circuit 81 so that the timing at which the clock signal switches between high and low levels corresponds to the timing at which the polarity of the current I _coil changes. It serves as a delay. The clock signal delayed by the delay circuit 92 has exactly the same waveform as the output of the comparator 91b in FIG. 4.

By using the circuit configuration of FIG. 6, it is possible to omit the current detection resistor 91a, simplifying the circuit configuration and reducing costs. However, the circuit configuration of FIG. 6 is based on the premise that the delay time is known. Therefore, if the delay time is unknown, it is preferable to use the more versatile circuit configuration of FIG. 4.

In the example of FIG. 6, the delay circuit 92 is used, but the operation of the delay circuit 92 may be configured to be performed by software. For example, the voltage measurement unit 9 may be provided with a control unit such as a microcomputer, and the control unit may perform the same operation as the delay circuit 92, i.e., the operation of delaying the clock signal. In this case, the clock generation circuit 81 of the drive unit 8 may be mounted collectively on the control unit such as a microcomputer.

(Summary of embodiments)
Next, technical ideas understood from the embodiments described above will be described using reference numerals and the like in the embodiments. However, each reference numeral in the following description does not limit the constituent elements in the claims to those specifically shown in the embodiments.

[1] A torque sensor that detects torque transmitted by a magnetostrictive material (2) having magnetostrictive characteristics, the first linear portion (31a) being inclined at a predetermined angle with respect to the axial direction of the magnetostrictive material (2). a first detection coil (31) having a first detection coil (31), and a second linear portion (32a) having a second linear portion (32a) inclined at the predetermined angle in a direction opposite to the first linear portion (31a) with respect to the axial direction of the magnetostrictive material (2). a sensor unit (10) having a bridge circuit (10a) including two detection coils (32); a drive unit (8) that applies an AC drive voltage to the bridge circuit (10a); a voltage measurement section (9) that measures the voltage output from the circuit (10a), the voltage measurement section (9) measures the voltage when the current flowing through the bridge circuit (10a) becomes zero. A magnetostrictive torque sensor (1) configured to.

[2] The voltage measurement unit (9) includes a pulse generation circuit (93) that outputs a pulse at a timing when the current flowing through the bridge circuit (10a) becomes zero, and a pulse generation circuit (93) that outputs a pulse at a timing when the current flowing through the bridge circuit (10a) becomes zero. The magnetostrictive torque sensor (1) according to [1], further comprising a sample-and-hold circuit (96) that holds the output voltage of the bridge circuit (10a) when input.

[3] The voltage measurement unit (9) includes a current detection resistor (91a) connected in series to the bridge circuit (10a) and a comparator ( 91b), and the pulse generation circuit (93) is configured to output a pulse according to the output from the comparator (91b). 1).

[4] The pulse generation circuit (93) includes a first pulse generation circuit (93a) into which the output from the comparator (91b) is directly input, and an inversion circuit (94) into which the output from the comparator (91b) is input. and a second pulse generation circuit (93b) inputted through the sample-and-hold circuit (96), the sample-and-hold circuit (96) has first and second sample-and-hold circuits to which the output voltage of the bridge circuit (10a) is inputted. circuit (96a, 96b), the first sample and hold circuit (96a) is configured to hold the output voltage when a pulse is input from the first pulse generation circuit (93a), The second sample-and-hold circuit (96b) is configured to hold the output voltage when a pulse is input from the second pulse generation circuit (93b), and the voltage measurement section (9) The magnetostrictive torque sensor (1) according to [3], further comprising a voltage detection section (99) that detects a difference between the outputs of the first and second sample-and-hold circuits (96a, 96b).

[5] The drive unit (8) includes a clock generation circuit (81) and an amplifier circuit (82) that amplifies the clock signal output from the clock generation circuit (81) and outputs it as the drive voltage. The voltage measurement unit (9) includes a delay circuit (92) to which a clock signal from the clock generation circuit (81) is input, delays the input clock signal, and outputs the delayed clock signal, The magnetostrictive torque sensor (1) according to [2], wherein the circuit (93) is configured to output a pulse according to the output from the delay circuit (92).

[6] The sensor section (10) includes a third detection coil (33) having the first linear portion (33a) and a fourth detection coil (34) having the second linear portion (34a). The bridge circuit (10a) is configured by sequentially connecting the first, second, third, and fourth detection coils (31 to 34) in an annular manner, and the drive unit (8) has a , a drive voltage is applied between the connection part (a) of the first and fourth detection coils (31, 34) and the connection part (b) of the second and third detection coils (32, 33). The voltage measurement unit (9) is configured to apply a The magnetostrictive torque sensor (1) according to [1], wherein the magnetostrictive torque sensor (1) is configured to measure the voltage between the connecting portion (d) of the magnetostrictive torque sensor (33, 34).

(Additional note)
Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are essential for solving the problems of the invention. Moreover, the present invention can be implemented with appropriate modifications within a range that does not depart from the spirit thereof.

1...Magnetostrictive torque sensor (torque sensor)
2...Magnetostrictive material 3...Detection coil 31...First detection coil 32...Second detection coil 33...Third detection coil 34...Fourth detection coil 31a, 33a...First straight portion 32a, 34a...Second Straight line section 8... Drive section 81... Clock generating circuit 82... Amplifying circuit 9... Voltage measuring section 91a... Current detection resistor 91b... Comparator 92... Delay circuit 93... Pulse generating circuit 93a... First pulse generating circuit 93b... Second pulse Generation circuit 95...First differential amplifier circuit 96...Sample and hold circuit 96a...First sample and hold circuit 96b...Second sample and hold circuit 97...Second differential amplifier circuit 98...Low pass filter 99...Voltage detection section 10 ...Sensor section 10a...Bridge circuit

Claims (6)

A torque sensor that detects torque transmitted by a magnetostrictive material having magnetostrictive characteristics,
a first detection coil having a first linear portion inclined at a predetermined angle with respect to the axial direction of the magnetostrictive material; a sensor unit having a bridge circuit including a second detection coil having two linear parts;
a drive unit that applies an AC drive voltage to the bridge circuit;
A voltage measurement unit that measures the voltage output from the bridge circuit,
The voltage measurement unit is configured to measure the voltage when the current flowing through the bridge circuit becomes zero.
Magnetostrictive torque sensor. The voltage measuring section includes:
a pulse generating circuit that outputs a pulse at a timing when the current flowing through the bridge circuit becomes zero;
a sample-and-hold circuit that holds the output voltage of the bridge circuit when a pulse from the pulse generation circuit is input;
The magnetostrictive torque sensor according to claim 1. The voltage measuring section includes:
a current detection resistor connected in series to the bridge circuit;
a comparator that compares voltages across the current detection resistor;
The pulse generation circuit is configured to output a pulse according to the output from the comparator.
The magnetostrictive torque sensor according to claim 2. The pulse generating circuit includes a first pulse generating circuit to which the output from the comparator is directly input, and a second pulse generating circuit to which the output from the comparator is input via an inverting circuit,
The sample-and-hold circuit includes first and second sample-and-hold circuits into which the output voltage of the bridge circuit is input,
The first sample and hold circuit is configured to hold the output voltage when a pulse is input from the first pulse generation circuit,
The second sample and hold circuit is configured to hold the output voltage when a pulse is input from the second pulse generation circuit,
The voltage measurement section includes a voltage detection section that detects a difference between the outputs of the first and second sample-and-hold circuits.
The magnetostrictive torque sensor according to claim 3. the driving section includes a clock generating circuit and an amplifier circuit that amplifies a clock signal output from the clock generating circuit and outputs the amplified clock signal as the driving voltage;
the voltage measurement unit includes a delay circuit that receives a clock signal from the clock generation circuit and delays and outputs the input clock signal;
The pulse generating circuit is configured to output a pulse in response to an output from the delay circuit.
3. The magnetostrictive torque sensor according to claim 2. the sensor unit includes a third detection coil having the first straight portion and a fourth detection coil having the second straight portion;
the bridge circuit is configured by sequentially connecting the first, second, third, and fourth detection coils in a circular manner,
the driving unit is configured to apply a driving voltage between a connection portion of the first and fourth detection coils and a connection portion of the second and third detection coils;
The voltage measurement unit is configured to measure a voltage between a connection portion of the first and second detection coils and a connection portion of the third and fourth detection coils.
2. The magnetostrictive torque sensor according to claim 1.

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