JP2540865B2 - Torque detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetostrictive torque detection device which measures the axial torque of a passive shaft such as a rotary shaft in a non-contact manner and has excellent output accuracy.

[Prior art]

Conventionally, as a means for measuring the shaft torque of a passive shaft, a method of sticking a strain gauge on the rotating shaft and detecting the torque by changing the resistance value has a known Young's modulus between the drive side and the load side. There is a method in which an intermediate shaft is provided and the twist of the intermediate shaft is detected as a phase difference. However,
In the strain gauge method, the accuracy depends on whether the gauge is attached or not, and a telemeter or the like is required, and the device becomes large. In addition, the method of detecting the phase difference due to the twist of the intermediate shaft requires a specific intermediate shaft, which complicates the measuring device and the electric circuit, which is expensive.

On the other hand, it has been proposed to use an oscillating circuit in which a plurality of elongated magnetic layers are fixed to the outer circumference of a passive shaft, and a detection coil is arranged around the thin magnetic layer (apart from JP-A-60-19).
5430).

As shown in FIG. 6, a plurality of elongated magnetic layers 90 are fixed to the outer periphery of the passive shaft 1 at an angle of 45 degrees in the axial direction, and the magnetic layer 90 is surrounded by the predetermined axis 1 so as to surround the magnetic layer 90. The detection coils 91 and 92 are wound with a gap X therebetween. The detection coils 91 and 92 are used to form a self-excited oscillation circuit (FIG. 7) having the passive shaft 1 to which the magnetic layer 90 is fixed as a magnetic core, and the magnetic layer 90 when torque is applied.
By detecting the change in the oscillation frequency of the oscillation circuit caused by the change in magnetic permeability, the magnitude and direction of the applied torque are detected without contact.

Therefore, as shown in FIG. 7, the electric circuit for converting the applied torque into an electric signal is a magnetic excitation type, which is composed of the passive shaft 1 to which the magnetic layer 90 is fixed as a magnetic core and the detection coils 91 and 92. The oscillator circuit 9. What is shown in the figure is a resistance capacitor type inverter. The frequency change is detected by a known frequency-voltage converter or the like.

In the figure, VCC is the drive power supply and VO is the output voltage.

This conventional method is superior in that the magnitude and direction of the torque can be measured as described above by the oscillation circuit of the magnetic layer and the detection coil, and the device is simple.

However, the oscillation circuit 9 in this torque detection device has a gap X between the magnetic layer 90 fixed to the passive shaft 1 and the detection coils 91, 92 arranged so as to surround the magnetic layer 90. The gap X is an air layer, and when the passive shaft rotates, the gap may change due to slight eccentricity, vibration, or the like. Therefore, the presence of the gap X affects the oscillation frequency of the oscillation circuit that detects and outputs the change in permeability in the magnetic layer by the detection coil, and the accuracy and sensitivity of the output VO decrease.

[Problems to be solved]

According to the present invention, the change in magnetic permeability in the above conventional device is detected on both the rotating side (rotating shaft) and the fixed side (detecting coil), and since there is a gap between the two, the detection accuracy and sensitivity are low. It is to clarify and solve such problems.

That is, the present invention aims to provide a magnetostrictive torque detection device having excellent detection accuracy and sensitivity by forming the oscillation circuit in a specific configuration.

[Means for Solving Problems] According to the present invention, a magnetostrictive film that is fixed to the outer circumference of a passive shaft that receives a torque is provided, a solenoid coil that is wound on the magnetostrictive film, and a capacitor that is connected in series with the solenoid coil. A resonance circuit is constituted by the above, the resonance circuit is fixed to the passive shaft, and a detection unit having a set of an input coil and an output coil composed of a magnetic core and a coil wound around the magnetic core is provided, and an input of the detection unit is provided. A coil and an output coil are arranged on both sides of the passive shaft so as to face the solenoid coil with a gap therebetween, and the resonance circuit and the detection unit form an oscillation circuit that oscillates at the resonance frequency of the resonance circuit. A torque detection device is characterized by detecting a change in magnetic permeability of a magnetostrictive film as a change in oscillation frequency.

In the present invention, the magnetostrictive film corresponds to the magnetic layer in the conventional device. The most important thing in the present invention is that the solenoid coil is wound on the magnetostrictive film and the solenoid coil and the capacitor are connected in series to form a resonance circuit together with the magnetostrictive film. It is fixed to. In particular, the circuit corresponding to the above-mentioned oscillation circuit of the prior art is configured as a resonance circuit including a magnetostrictive film, a solenoid coil, and a capacitor, and the resonance circuit is provided on the passive axis without providing a gap between the magnetostrictive film and the solenoid coil. It has stuck to. Then, the resonance frequency in this resonance circuit is detected by the passive off-axis detector.

In the present invention, the direction of magnetic anisotropy of the magnetostrictive film fixed to the passive axis affects the amount and direction of change in magnetic permeability.
When the direction of the magnetic anisotropy is set at an angle of 45 degrees with the axial direction of the passive axis, when the direction of torque application reverses, the direction of magnetic permeability changes (increases or decreases) and the amount of change also changes. It is preferable because it is symmetrical with respect to the application direction. Also, the magnetostrictive film is fixed on the entire circumference of the position on the passive shaft where the torque is to be measured.

Further, as shown in the second embodiment, the magnetostrictive film may be fixed to only a part of the outer circumference of the passive shaft, and a high magnetic permeability film such as a permalloy film may be provided on the other part.

As the magnetostrictive film, nickel foil, permalloy foil, amorphous magnetic alloy foil, or the like is used.

The solenoid coil is constructed by winding a conducting wire on the magnetostrictive film, and the conducting wire is connected in series with the capacitor. This constitutes a closed resonant circuit.

Further, the magnetostrictive film, solenoid coil and capacitor in the resonance circuit are fixedly mounted on the shaft.

Further, when the torque of the vehicle drive system, steering system, and other rotary systems is measured in a non-contact manner, the torque detection device of the present invention is further mounted on these rotary systems to detect the torque and control the rotary system. When it is performed, it exerts a particularly excellent effect.

[Work]

In the present invention, when torque is applied to the passive shaft, stress is applied to the magnetostrictive film and its magnetic permeability changes. As a result, the inductance of the solenoid coil changes. Therefore, the resonance frequency of the resonance circuit formed on the passive axis changes, and the oscillation frequency in the detection unit provided outside the passive axis changes. Since the amount of change in magnetic permeability corresponds to the amount of torque, the applied torque can be detected from the amount of change in oscillation frequency.

[Effect]

According to the present invention, since the resonance circuit is arranged on the passive shaft, the change in permeability of the magnetostrictive film is directly caught by the solenoid coil to change the resonance frequency. Therefore,
The detection accuracy and sensitivity are extremely excellent as compared with the above-mentioned conventional technique having a gap between the magnetostrictive film and the detection coil.

Further, in the above-mentioned conventional technique, since the detection coil is opposed to the magnetic layer (magnetostrictive film) via the gap, when there is nonuniformity of the magnetostrictive film or nonuniformity of fixation along the rotation direction,
The output varies with the rotation angle of the shaft. However, in the present invention, even if there is such non-uniformity, the oscillation frequency is determined by the change in the overall magnetic permeability, so that the output does not fluctuate with respect to the rotation.

In addition, the signal transmission to the detector provided outside the passive axis is transmitted as frequency by the solenoid coil provided separately from the magnetostrictive film, so the S / N ratio is high and the power of the exciting coil of the detector is small. good. For example, it can be directly driven by an operational amplifier of about 5 volts.

〔Example〕

First Embodiment A torque detection device according to this embodiment will be described with reference to FIGS.

FIG. 1 is a conceptual diagram showing a resonance circuit and a detection part of the torque detection device of this example, FIG. 2 is a view showing a cross section perpendicular to the passive axis, and FIG. 3 is a resonance circuit K, a detection part L and a waveform shaping. It is an oscillation circuit diagram which consists of circuit N.

As shown in FIG. 1, the detection circuit in this example includes a resonance circuit K fixed to the passive shaft 1 and a detection unit L provided outside the passive shaft 1 as one set, and the detection circuit detects torque. Is what you are trying to do.

That is, the resonance circuit K is composed of a magnetostrictive film 2 fixed to the entire circumference of the passive shaft 1 by an adhesive, a solenoid coil 3 wound around the magnetostrictive film 2, and a capacitor 4 connected in series with the solenoid coil 3. These are fixed on the passive shaft 1. Further, the detection unit L that detects the resonance frequency output from the resonance circuit K includes an input coil 5 connected to the driving power supply V and an output coil 6 that transmits the detected signal. The input coil 5 includes a magnetic core 51 and a coil 52 wound around the magnetic core 51, and the output coil 6 includes a magnetic core 61 and a coil 62 wound around the magnetic core 61.

The adhesion of the magnetostrictive film 2 is arranged so as to have a magnetic anisotropy of 45 degrees with respect to the axial direction of the passive shaft 1. As shown in FIG. 2, the input coil 5 and the output coil 6 are arranged so as to face the solenoid coil 3, and a gap M is provided between both coils and the solenoid coil 4. As can be seen in FIG. 1, both ends of the magnetic cores 51 and 61 of the input and output coils face the portions of the magnetostrictive film 2 protruding on both sides of the solenoid coil 3.

Next, FIG. 3 shows an oscillator circuit in which the resonance circuit K and the detecting section L are connected to a waveform shaping circuit N to generate an output fo. In the figure, 81 is a current limiting resistor, 82 is an oscillation excitation capacitor, 83 is a comparator, and V is a drive power supply.

Therefore, as is known from FIGS. 1 to 3, when a torque is applied to the passive shaft 1, a stress whose magnetic permeability changes is applied to the magnetostrictive film, and, for example, when a tensile stress is applied to the magnetostrictive film 2, the transmissivity is changed. Magnetic susceptibility increases. Therefore, the magnetostrictive film 2
The inductance of the solenoid coil 3 wound around the coil increases. Then, the resonance frequency in this resonance circuit decreases. On the contrary to the above, when torque is applied to the magnetostrictive film 2 in the direction in which the compressive stress acts, the resonance frequency becomes high contrary to the above. Then, this resonance component is transmitted to the detection unit.

In the detecting section L, the input coil 5 and the output coil 6 catch the output signal from the solenoid coil 3 and output it to the waveform shaping circuit N as described above.

The output fo from the waveform shaping circuit is output as a voltage signal by a well-known means such as a frequency-voltage converter as described in the above-mentioned prior art.

As described above, according to this example, since the resonance circuit is arranged on the passive shaft, the change in permeability of the magnetostrictive film 2 can be caught as the change in inductance by the solenoid coil 3 wound directly around the resonance circuit. The detection accuracy and sensitivity are extremely excellent as compared with the above-mentioned conventional technique having a gap between the magnetostrictive film and the detection coil.

Further, according to the present example, as described above, even when the magnetostrictive film has nonuniformity or nonuniformity in fixation along the rotational direction of the passive shaft, the oscillation frequency is determined by the change in the entire magnetic permeability. Therefore, the output does not fluctuate with respect to rotation. Also,
Since the signal transmission to the detection section is transmitted as frequency, the S / N ratio is high.

Second Embodiment In this embodiment, as shown in FIGS. 4 and 5, the magnetostrictive film 20 and the high-permeability film 7 are alternately wound around the passive shaft 1 every 1/4 turn and fixed. is there.

 Others are the same as those in the first embodiment.

An amorphous magnetic alloy foil was used as the magnetostrictive film 20, and a permalloy film was used as the high magnetic permeability film.

Also in this example, the method of detecting the torque amount based on the change in the magnetic permeability of the magnetostrictive film is the same as in the first example.

According to this example, since the magnetostrictive film 20 is divided and the high magnetic permeability film 7 is arranged between them, the inductance of the solenoid coil 3 can be increased. Therefore, the number of turns of the solenoid coil 3 can be reduced.
Further, since the magnetostrictive film 20 can be divided and fixed, the fixing to the passive shaft 1 is easy. Further, in the above-mentioned conventional device, since the change in permeability is directly transmitted from the magnetostrictive film to the detection coil outside the passive axis, when the magnetostrictive film is divided and arranged on the passive axis, the output is output depending on the position. However, the detection calculation processing on the fixed side (outside the passive axis) was complicated. On the contrary,
In the present invention, the change in the magnetic permeability of the magnetostrictive film is caught as the change in the inductance of the solenoid coil connected to the magnetostrictive film. Therefore, even if the magnetostrictive film is divided and arranged, the oscillation frequency is determined as a whole. Not complicated.

[Brief description of drawings]

1 to 3 show a first embodiment, and FIG. 1 is a conceptual diagram showing a positional relationship between a passive shaft, a resonance circuit, and a detection unit, and FIG.
FIG. 1 is a sectional view of the passive shaft in the diametrical direction of FIG. 1, FIG. 3 is an oscillation circuit diagram, FIGS. 4 and 5 are second embodiments, and FIG.
FIG. 5 is a conceptual diagram similar to that of FIG. 5, FIG. 5 is a sectional view of the passive shaft in the direct direction of FIG. 4, FIGS. 6 and 7 show a conventional device, FIG. 6 is a diagram showing the arrangement of an oscillating circuit, and FIG. The electric circuit. 1 ... Passive shaft, 2,20 ... Magnetostrictive film, 3 ... Solenoid coil, 4 ... Capacitor, 5 ... Input coil, 6 ... Output coil, 7 ... High permeability film, K ... Resonance circuit , L …… Detector,

Claims (2)

(57) [Claims] 1. A resonance circuit is constituted by a magnetostrictive film which is fixed to the outer periphery of a passive shaft which receives a torque by being wound, a solenoid coil which is wound on the magnetostrictive film, and a capacitor which is connected in series with the solenoid coil. The resonance circuit is fixed to the passive shaft, and a detection unit having a set of an input coil and an output coil composed of a magnetic core and a coil wound around the magnetic core is provided, and the input coil and the output coil of the detection unit are The passive circuit is arranged on both sides of the passive shaft so as to face the solenoid coil with a gap, and the resonance circuit and the detection unit form an oscillation circuit that oscillates at the resonance frequency of the resonance circuit. Is detected as a change in oscillation frequency. 2. A magnetostrictive film is fixed to a part of the outer circumference of a passive shaft, a high permeability film such as a permalloy film is provided in the other part, and a solenoid coil is provided on the magnetostrictive film and the high permeability film. The torque detection device according to claim 1, characterized in that