JPH11118628A - Torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detecting sensitivity by saving dissipation power necessary to detect torque or without increasing the dissipation power. SOLUTION: Magnetostrictive material 6 is externally engaged with a shaft 2 to be detected for its torque. AC current of a predetermined frequency converted from DC from a DC power source 12 by inverters 13, 14 is supplied to exciting coils 10, thereby generating a magnetic flux for passing the material 6. When torque 13 is applied on the shaft 2, magnetic characteristics of the material 6 are changed so that the magnetic flux is altered with the result that output values of detecting coils 11 are varied. A CPU 18 inputs detected voltages obtained by processing output values of the coils 11 by a processor 16 or the like. The CPU 18 calculates torque from detected voltage at each input of a sampling trigger signal, for example, at each several tens of milliseconds. The CPU 18 controls to switch switching elements 22, 23 contained in the inverters 13, 14 so that currents just flow to the coils 10 at the time of inputting the trigger signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor for detecting a torque of a shaft to be detected by using a magnetic material having a stress magnetic property such as a magnetostrictive property.

[0002]

2. Description of the Related Art Conventionally, in this type of torque sensor, a magnetic material having stress magnetic properties is fixed to a shaft, and a magnetic circuit through which a magnetic flux passes is formed by an exciting coil, and the torque of the shaft is reduced. A corresponding coil acts on the magnetic body to detect a change in inductance when the magnetic permeability changes (for example, JP-A-5-118938, JP-A-59-77326, etc.). . Torque sensors include a magnetostrictive type using strain-magnetic characteristics and an inductance type using stress-magnetic characteristics.

FIG. 5 is a schematic view of a magnetostrictive torque sensor. The torque sensor 51 includes a magnetostrictive material 53 externally fitted to the shaft 52, an exciting coil 54 for forming a magnetic circuit through which magnetic flux passes through the magnetostrictive material 53, and a detection sensor for detecting a change in magnetic flux passing through the magnetostrictive material 53. And a coil 55. Magnetostrictive material 5
On the outer peripheral surface of No. 3, two detection areas formed with a large number of cut grooves 53a extending in the circumferential direction at 45 ° and −45 ° with respect to the axial direction are formed separately in the axial direction. Two excitation coils 54 and two detection coils 55 are provided so as to face each of the two detection areas. When a current flows through the exciting coil 54 from the AC power supply 56, a magnetic circuit in which a magnetic flux passes through the coil 54 → the magnetostrictive material 53 → the coil 54 is formed.

When a torque acts on the shaft 52, a tensile force acts on one of the two detection areas of the magnetostrictive material 53 and a compressive force acts on the other, and the magnetostrictive material 53 has a magnetic permeability according to the positive or negative of the distortion at that time. Change. Therefore, one of the magnetic fluxes passing through the two detection areas of the magnetostrictive material 53 increases, and the other decreases.
An electromotive force is induced in the detection coil 55 in accordance with the strength of the magnetic flux.
Is input to In the processing circuit 57, the two input values are subtracted and then rectified, and the output signal is passed through an A / D conversion circuit 58 to a C (microcomputer) 59 in a computer (microcomputer) 59.
The detection voltage V is input to the PU 60. The CPU 60 calculates the direction and magnitude of the torque from the level of the input detection voltage V.

[0005]

By the way, usually, CP
The torque detection by U60 is performed at predetermined time intervals. That is, as shown in FIG. 6, when the CPU 60 receives, for example, a sampling trigger signal, the CPU 60 performs an arithmetic process for calculating the direction and magnitude of the torque from the detected voltage V corresponding to the axial distortion (strain of the magnetostrictive material) ε at that time. Do. Thus CP
The torque detection in U60 is only performed when a sampling trigger signal is input. However, in the prior art, as shown in FIG. 6 (v1 is an AC voltage and i1 is an AC current) during the operation of the torque sensor 51, the current continues to flow through the exciting coil 54.
Even when the torque is not detected, current flows through the exciting coil 54, and power is wasted. Further, if the current flowing through the exciting coil 54 is increased in order to increase the torque detection sensitivity, the power consumption of the torque sensor 51 increases.

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 reduce power consumption required for detecting torque or to detect power without increasing power consumption. An object of the present invention is to provide a torque sensor capable of improving sensitivity. A second object is to prevent the detection accuracy from lowering when the first object is achieved. A third object is that the time interval of detection is, for example, 10 to
An object of the present invention is to make it possible to save power consumption without deteriorating the detection accuracy even if it is as short as 1000 milliseconds.

[0007]

According to the first aspect of the present invention, there is provided a torque sensor, comprising: a magnetic body having a stress magnetic property fixed to a shaft to be detected; A coil for generating a magnetic flux passing through the body, a power supply for passing a current to the coil, and a torque corresponding to a change in the magnetic flux passing through the magnetic body caused by receiving a stress corresponding to a torque acting on the detected shaft. Detecting means for detecting the detection value at a predetermined timing; and switching means for switching and controlling the supply of the current to the coil so that the current flows intermittently each time the torque is detected by the detecting means. And

In order to achieve the second object, according to the second aspect of the present invention, in the first aspect of the present invention, the switching means is configured to detect the torque at the time of detecting the torque rather than at the time of detecting the torque by the detecting means. The supply of the current to the coil is started before the predetermined time required for the current flowing through the coil to stabilize.

According to a third aspect of the present invention, in the first or second aspect, the power supply is a DC power supply, and converts DC to AC between the DC power supply and the coil. An inverter is provided, and the switching means switches and controls the output of the inverter.

According to a fourth aspect of the present invention, in order to achieve a third object, the switching means is provided on a circuit formed by the power supply and the exciting coil. And a switching control means for switching on / off of the switching circuit, wherein the switching circuit is provided on the coil side with respect to any capacitor built in the inverter.

(Operation) Therefore, according to the first aspect of the present invention, when a current flows through the coil, a magnetic circuit is formed in which the magnetic flux passes through the path from the coil to the magnetic body to the coil. When a torque acts on the shaft to be detected, a stress due to the torque acts on the magnetic body, so that the magnetic characteristics of the magnetic body change, and the magnetic flux passing through the magnetic body changes according to the torque. The detecting means detects this magnetic flux change at a predetermined timing as a torque detection value. The supply of current to the coil is performed intermittently every time torque is detected by switching control by the switching means, and the current just flows through the coil when torque is detected by the detecting means. Therefore, at times other than the time of torque detection, current does not flow through the coil, and power consumption is reduced as compared with a configuration in which current continues to flow. In addition, this means that the detection sensitivity is higher than the power consumption, and the detection sensitivity can be increased without increasing the power consumption.

According to the second aspect of the present invention, the current supply to the coil is started at least a predetermined time before the torque is detected by the switching means. Become. For this reason,
The torque is always detected under a constant condition in which the current flowing through the coil is stable and there is no unstable factor.

According to the third aspect of the present invention, the AC obtained by converting the DC from the DC power supply by the inverter flows through the coil. The switching of the supply of the alternating current to the coil is performed by the switching means switching and controlling the output of the inverter.

According to the fourth aspect of the present invention, since the switching circuit is provided on the coil side with respect to any of the capacitors built in the inverter, the capacitor is maintained even while the switching circuit is turned off by the switching control means. Charged. For this reason, when the switching circuit is switched to a state in which a current flows through the coil (on), the current in the coil rises at high speed without delay due to charging of the capacitor and immediately transitions to a stable state. Therefore, even if the periodic torque detection by the detecting means is performed by a computer or the like at very short time intervals in the range of, for example, 10 to 1000 milliseconds, it is possible to sufficiently cope with the situation. In other words, even if the detection time interval is very short due to the detection processing by the computer or the like, it becomes possible to intermittently switch the current flowing through the coil every time the torque is detected, while ensuring its stability.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 4 is a sectional view of a shaft structure in a portion where the torque sensor 1 is mounted. The shaft 2 as a shaft to be detected is rotatably supported via a bearing 4 while being inserted into a substantially cylindrical housing 3. A cylindrical magnetostrictive material 6 having a magnetostrictive property as a magnetic material is externally fitted to the shaft 2 via a sleeve 5. The magnetostrictive material 6 is welded to the shaft 2 via the sleeve 5 so as to be integrally rotatable.

The magnetostrictive material 6 has a magnetostrictive effect, and is made of permalloy, iron / nickel / chromium alloy, Ni
A high permeability soft magnetic material such as SpanC is used, and a magnetostrictive film is formed on a core material. On the surface (magnetostrictive film area) of the magnetostrictive material 8, two detection areas A and B are formed, each of which has a large number of cut grooves 6a that form 45 ° and −45 ° in the axial direction and are formed at equal intervals in the circumferential direction. ing. The magnetostrictive material 6 may be an iron-aluminum-based magnetostrictive material or an amorphous magnetostrictive material.

The yoke 7 is provided so as to be rotatable relative to the shaft 2 via two bearings 9 respectively fitted into two substantially cylindrical support members 8 fitted at both ends thereof. Two concave portions are formed on the inner peripheral surface of the yoke 7 at positions opposed to the detection areas A and B of the magnetostrictive material 6, and each of the concave portions has an exciting coil 10 as a coil inside and a detection coil outside. The coil 11 is assembled in a state of being wound in two layers. That is, the exciting coil 10 and the detecting coil 1
1 is provided two each so as to face the detection areas A and B, respectively. Since the yoke 7 is supported on the shaft 2 via the bearing 9, even if the shaft 2 is mounted eccentrically with respect to the housing 3, the yoke 7
And the magnetostrictive material 6 are aligned with each other, and the gap between the two is kept constant with high accuracy in the circumferential direction.

FIG. 1 shows an electrical configuration of the torque sensor 1. In this embodiment, a DC power supply 12 is used as a power supply for the torque sensor 1. The DC power supply 12 is connected to input terminals of inverters 13 and 14, and the two exciting coils 10 and 10 are connected to output terminals of inverters 13 and 14, respectively. The inverters 13 and 14 convert the DC input from the DC power supply 12 into an AC having a predetermined frequency (Hz) and output the AC to the exciting coils 10 and 10. The drive of the inverters 13 and 14 is controlled by a controller 15 as described later.

One of two terminals of the detecting coils 11 and 11 is grounded and the other is connected to the controller 15.
Is connected to the input terminal of the processing circuit 16 provided in the first stage. The processing circuit 16 includes a differential circuit and a rectifier circuit (both are not shown). The processing circuit 16 includes the detection coil 1
Each input voltage (high-frequency voltage) from 1 and 11 is subtracted by a differential circuit, and the output voltage from the differential circuit is rectified by a rectifier circuit and output from an output terminal. Because of the subtraction processing in the differential circuit, compensation for canceling disturbance noise due to temperature change or the like can be performed, and highly accurate torque detection can be performed.

The controller 15 has a built-in microcomputer 17. The microcomputer 17 has a central processing unit (hereinafter referred to as a CPU) 1 as a switching control means.
8, a read only memory (ROM) 19 and a read / write rewritable memory (RAM) 20 are provided. CPU
Reference numeral 18 denotes a drive control process for the inverters 13 and 14 based on the program data stored in the ROM 19, and a direction and a torque direction based on an input value (detection voltage V) input from the processing circuit 16 via the A / D conversion circuit 21. A torque calculation process for calculating the magnitude is performed. The detection coil 1
1, 11, the processing circuit 16 and the CPU 18 constitute detection means.

The inverters 13 and 14 have various elements incorporated therein, and include therein a capacitor (for example, a smoothing capacitor or a commutation capacitor depending on the type of the inverter) (not shown) and a switching circuit. There are switching elements 22 and 23. The CPU 18 is connected to the inverters 13 and 14 so as to be able to output on / off signals to the switching elements 22 and 23. The switching elements 22 and 23 are located downstream of any of the capacitors in the inverters 13 and 14, that is, the exciting coils 10 and 10.
Connected to the side. Switching means is constituted by the CPU 18 and the switching elements 22 and 23.

Next, a drive control process of the inverters 13 and 14 will be described. A sampling trigger signal Str is input to the CPU 18 at predetermined time intervals (for example, every 50 to 100 milliseconds) from an upper CPU (not shown) (FIG. 2).
reference). The sampling trigger signal Str is a detection command signal for setting a timing for performing torque calculation processing, which will be described later, which is executed by the CPU 18, that is, torque detection.

The CPU 18 generates a sampling trigger signal Str
The drive control is performed such that the outputs of the inverters 13 and 14 are turned on and off intermittently in synchronism with the cycle of the sampling trigger signal Str so that the current just flows through the exciting coils 11 and 11 at the time of input. In the present embodiment, since the input time interval of the sampling trigger signal Str is constant,
The sampling trigger signal Str is used as a timing signal for on / off control of the inverters 13 and 14.

The CPU 18 generates a sampling trigger signal Str
After a lapse of a predetermined time T1 from the input of the inverters 13 and 14,
To output a voltage from the output terminals of the inverters 13 and 14. Then, the CPU 18 stops the output of the ON signal after a lapse of a predetermined time T2 from the output of the ON signal, and stops the voltage output from the output terminals of the inverters 13 and 14.

The predetermined time T1 is set a predetermined time earlier than the input of the exciting coil 10, 10 so that the current flowing through the exciting coil 10, 10 is in a stable state when the next sampling trigger signal Str is input. It is set so that current supply to 10 is started. Also, a predetermined time T2
Are the excitation coils 10 and 10 until the CPU 18 finishes acquiring the input value (detection voltage V) for the torque calculation process that starts when the next sampling trigger signal Str is input.
The current is set to flow. The first sampling trigger signal Str at the start of the operation of the torque sensor 1
Is used only to determine the first output start timing of the inverters 13 and 14, and the second and subsequent sampling trigger signals Str are also used for torque calculation processing.

Next, the torque calculation processing will be described. When an alternating current of a predetermined frequency flows through the exciting coil 10,
A magnetic circuit through which a magnetic flux passes through the path of the yoke 7 → the magnetostrictive material 6 → the yoke 7 is formed. At this time, the magnetostrictive member 6 has two types of magnetic circuits in which magnetic flux passes through the two detection regions A and B along the respective regions between the cut grooves 6a in the direction of 45 ° or −45 ° with respect to the axial direction. It is formed.

When a torque acts on the shaft 2, a compressive force acts on one of the two detection areas A and B and a tensile force acts on the other in the two detection areas A and B according to the rotation direction at that time. The magnetic permeability of the magnetostrictive material 6 is large in the detection region that has received the positive strain ε (during tension), and small in the detection region that has received the negative strain ε (during compression). For this reason, the inductance L of each of the detection coils 11 and 11 is large on the side facing the detection area that has received the tensile force, and is small on the side facing the detection area that has received the compressive force. The electromotive force induced in the detection coils 11, 11 is larger on one side and smaller on the other side in accordance with the direction of the torque with respect to the electromotive force when no torque acts on the shaft 2. Then, the processing circuit 16 subtracts each input value from the two detection coils 11, 11 and further rectifies the voltage, and inputs the voltage as a detection voltage V to the CPU 18 via the A / D converter 21.

The ROM 19 stores a zero level Vo at a torque "0" corresponding to a case where the magnetostrictive material 6 has no distortion (see FIG. 2).
Is set in advance, and the CPU 18 calculates the direction and magnitude of the torque by checking the value of the input detection voltage V on the positive or negative side with respect to the zero level Vo.

According to the torque sensor 1, the following operation can be obtained. The CPU 18 generates a sampling trigger signal S
When tr is input, output of an ON signal to each of the inverters 13 and 14 is started after a lapse of a predetermined time T1 from the input of tr.
After a lapse of a predetermined time T2 from the start of the output, the output of the ON signal is stopped. As a result, during the predetermined time when the ON signal is output, that is, for a predetermined time T2 from a predetermined time slightly earlier than the input of the next sampling trigger signal Str as shown in FIG. And a current i1 flows. At this time, the exciting coil 1
The current i1 flowing through 0 and 10 is at least in a stable state before the next sampling trigger signal Str is input. Thus, current flows intermittently through the exciting coils 10 and 10 only for a predetermined period including the time when the sampling trigger signal Str is input.

Here, when the switching elements 22 and 23 in the inverters 13 and 14 are off and their voltage output is stopped, any capacitors in the inverters 13 and 14 can be charged. Therefore, when the switching elements 22 and 23 are turned on, the capacitor is already in the charged state, so that the rising of the output current does not occur, and the current flowing through the exciting coils 10 and 10 immediately becomes stable. Accordingly, the time during which the current flows through the exciting coils 10 and 10 is short (for example, 50 times).
The current flowing through the exciting coils 10, 10 can reach a stable state even if the detection time interval is as short as a fraction of the detection time interval.

The CPU 18 generates a sampling trigger signal Str
Is input, a torque calculation process is performed. In other words, the direction and magnitude of the torque are calculated by observing which value the detection voltage V input from the processing circuit 16 has on the positive or negative side with respect to the preset zero level Vo. Since the detection voltage V used in the torque calculation processing is a value when the current flowing through the exciting coils 10 and 10 is stable, the detection accuracy of the torque is the same as that of the conventional configuration in which the current continues to flow through the exciting coil. There is no inferior compared.

For example, as shown in FIG.
If the time during which the current flows through 0, 10 is one third of that of the conventional torque sensor, the power consumption becomes one third under the same strength of the current. FIG. 3 is a graph comparing the current intensity of the exciting coil obtained when the power consumption of the conventional torque sensor and the torque sensor of the present embodiment are made equal. The left side of the figure is a graph of the conventional current intensity, and the right side is a graph of the current intensity of the present embodiment. When the time for flowing the current to the exciting coils 10 and 10 is reduced to one third as shown in the graph on the right side of the figure, as shown in FIG. It is possible to secure a current value 3Io that is three times the current value Io. That is, the S / N ratio of the torque sensor 1 is improved without increasing the power consumption of the torque sensor 1, and the torque detection sensitivity can be increased.

As described in detail above, according to this embodiment, the following effects can be obtained. (1) Since the current is intermittently supplied to the exciting coils 10 and 10 so that the current just flows to the exciting coils 10 and 10 when the CPU 18 performs the torque detection, the power consumption of the torque sensor 1 is reduced. It can be kept low. Even if the intensity of the current flowing through the exciting coils 10 and 10 is increased, the detection sensitivity of the torque sensor 1 can be increased without increasing the power consumption.

(2) The start timing of the voltage output in the inverters 13 and 14 is set to be longer than that in the input of the signal Str so that the current flowing through the exciting coils 10 and 10 becomes stable when the sampling trigger signal Str is input. Since the predetermined time is set earlier, it is possible to improve the detection sensitivity of the torque sensor 1 with respect to the power consumption without lowering the detection accuracy.

(3) Built-in switching elements 22 and 23 for switching the outputs of inverters 13 and 14
Is connected to the exciting coils 10 and 10 more than any of the capacitors built in the inverters 13 and 14, and immediately after the switching elements 22 and 23 are turned on, the current flowing through the exciting coils 10 and 10 shifts to a stable state. Can be done. For this reason, even if the torque detection by the CPU 18 is performed in a high-speed process at a very short time interval of, for example, 50 to 100 milliseconds, power consumption can be reduced without lowering the detection accuracy.

(4) Since the sampling trigger signal Str for determining the torque detection timing is used to determine the timing of supplying the current to the exciting coils 10 and 10, a trigger signal for determining the current supply timing is newly provided. No need to prepare.

The embodiment is not limited to the above, and may be carried out as follows. ○ A dedicated trigger signal for timing the flow of current to the exciting coils 10 and 10 is sent from the upper CPU to the CPU.
18 and drive control of the inverters 13 and 14 based on this trigger signal. According to this configuration, although the number of trigger signals increases, the timing of flowing a current in synchronization with the sampling trigger signal Str can be made more accurate, and the reliability of torque detection accuracy can be increased. Further, the time interval of the torque detection by the CPU 18 does not need to be a fixed time. Even in such a case, the timing of the current supply timing can be accurately set by preparing a dedicated trigger signal.

The output values from the two detection coils 11, 11 are directly input to the CPU via the A / D converter,
The PU may perform a subtraction and rectification process (averaging process) to obtain a detection value corresponding to the torque. According to this configuration, the number of processing circuits 16 can be reduced.

The switching circuit such as a switching element for switching the current supply to the exciting coil is not limited to being provided in the inverter. For example, the switching circuit is provided between the inverter and the exciting coil, and
The switching control may be performed by the PU.

The time interval for torque detection by the CPU is not limited to 50 to 100 milliseconds. The range may be outside the range of 10 to 1000 milliseconds, or may be outside this range as necessary for the device employing the torque sensor. For example, when torque is detected by a CPU having an extremely short detection time interval of 10 to 1000 milliseconds or less, a switching circuit such as a switching element for switching the current supply to the exciting coil is formed by a power supply and the exciting coil. By providing the capacitor closer to the coil than any of the capacitors on the circuit, it is possible to cope with high-speed processing by a CPU (computer).

The present invention can also be implemented in a torque sensor that does not have a detecting coil, which detects torque from a change in power of a circuit formed by a power supply and an exciting coil. The invention is not limited to the magnetostrictive torque sensor. It can also be implemented in an inductance type torque sensor.

The power supply for the exciting coil may be an AC power supply as described in the related art. The alternating current flowing through the exciting coil may be a rectangular wave, a sine wave, or a variable frequency.

The magnetostrictive member 6 may be formed as a smooth sleeve having no kerf 6a on its surface, and may be implemented in a torque sensor configured to detect the smooth sleeve with a crosshead type pickup.

The technical ideas other than the claimed invention grasped from the above embodiments are described below together with their effects. (A) In the invention according to claim 4, the detecting means includes a computer, and the computer detects the torque by 10 times.
High-speed processing is performed at time intervals within a range of up to 1000 milliseconds. According to this configuration, even if the torque detection is executed by the computer at high-speed processing at time intervals within the range of 10 to 1000 milliseconds, the current flowing through the coil is intermittently determined every time the torque is detected, while ensuring its stability. Can be switched.

(B) In the invention according to any one of claims 1 to 3, the switching means applies a current to the coil using a trigger signal for determining a torque detection timing by the detection means. The timing of the flow is planned. According to this configuration, the timing of supplying the current to the coil and the timing of detecting the torque by the detecting means can be determined by one trigger signal.

(C) In the invention according to any one of claims 1 to 4, the magnetic material has a region where the magnetic flux increases when a torque acts on the detected shaft and a region where the magnetic flux decreases. Are formed, and two coils are provided so that the magnetic flux passes through each of the detected areas. The detecting means detects the magnetic flux in the two detected areas of the magnetic body. There are provided two detection coils for detecting changes, and processing means for subtracting and rectifying the output value of each detection coil to obtain a torque detection value. According to this configuration, the reliability of torque detection sensitivity and detection accuracy can be increased. The processing circuit 16 constitutes processing means.

[0047]

As described in detail above, according to the first and third aspects of the present invention, the current flows through the coil only when the torque is detected by the detecting means. Power consumption can be reduced, or torque detection sensitivity can be improved without increasing power consumption.

According to the second and third aspects of the present invention, the current supply to the coil is started in advance at least a predetermined time required for the current flowing through the coil to stabilize before the torque is detected. So, without lowering the detection accuracy,
The power consumption of the torque sensor can be reduced and the detection sensitivity to the power consumption can be improved.

According to the fourth aspect of the present invention, since the switching circuit is provided on the coil side with respect to any of the capacitors built in the inverter, the capacitor is charged when the switching circuit is switched to a state in which current flows through the coil. , The current flowing through the coil can be immediately brought into a stable state. Therefore, even if torque detection is performed by a computer or the like in a high-speed process in which the detection time interval is very short,
It is possible to sufficiently cope with saving power consumption without lowering the detection accuracy.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram of a torque sensor according to an embodiment.

FIG. 2 is a timing chart in torque detection.

FIG. 3 is a graph for comparing a current flowing through an exciting coil.

FIG. 4 is a side sectional view showing a torque sensor assembled to a shaft.

FIG. 5 is an electrical configuration diagram of a torque sensor according to the related art.

FIG. 6 is a timing chart for torque detection.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Torque sensor, 2 ... Shaft as shaft to be detected, 6
... Magnetostrictive material as magnetic material, 7 ... Yoke, 10 ... Exciting coil as coil, 11 ... Detection coil constituting detection means, 12 ... DC power supply as power supply, 13, 14 ... Inverter, 16 ... Detection means , 18 ...
CPUs as detection means and switching means and switching control means, 22 and 23... Switching elements as switching means and switching circuits.

Claims (4)

[Claims] 1. A magnetic body having a stress magnetic property fixed to a detected shaft, a coil for generating a magnetic flux passing through the magnetic body, a power supply for flowing a current through the coil, and the detected shaft Detecting means for detecting, at a predetermined timing, a change in the magnetic flux passing through the magnetic body due to receiving a stress corresponding to a torque acting on the magnetic body at a predetermined timing as a torque detection value; Switching means for controlling the supply of current to the coil so that the current flows through the coil. 2. The switching unit starts the supply of the current to the coil in advance at least a predetermined time required before the current flowing in the coil is stabilized at the time of detecting the torque, at the time of detecting the torque by the detecting unit. The torque sensor according to claim 1. 3. The power supply is a DC power supply, further comprising an inverter for converting DC to AC between the DC power supply and the coil, and wherein the switching means switches and controls the output of the inverter. The torque sensor according to claim 2. 4. The switching means includes: a switching circuit provided on a circuit formed by the power supply and the exciting coil; and switching control means for switching on / off of the switching circuit. 4. The torque sensor according to claim 3, wherein the switching circuit is provided on the coil side with respect to any of the capacitors built in the inverter.