JPH0641889B2 - Torque detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetostrictive torque detection device, and more particularly to a torque detection device capable of performing highly accurate torque detection even in an environment where the temperature changes drastically. is there.

[Conventional technology]

The torque is a basic amount for controlling the rotary drive system, and it is desirable that the torque is detected in the rotary drive system in a non-contact manner. Recently, there has been proposed a torque detection device that directly utilizes non-contact torque detection by utilizing the magnetostrictive characteristics of amorphous metal. This conventional torque detecting device will be described with reference to FIGS. 3, 4, and 5. It is generally known that the magnetic properties of magnetic materials change when stress is applied,
For example, in an amorphous metal, the tensile stress increases the magnetic permeability, and the compressive stress decreases the magnetic permeability. By the way, as shown in FIG. 3, when torque T is applied to the passive shaft (1), stress ± σ is generated in the direction of ± 45 ° with respect to the central shaft (2).
In other words, tensile stress σ is generated on the line with an angle of + 45 ° with respect to the central axis (2), and compressive stress − on the line with an angle of −45 °.
σ occurs. Therefore, the torque can be detected by fixing the magnetic layer made of high magnetostrictive material on the outer circumference of the passive shaft (1) and utilizing the magnetostrictive effect when the torque is applied. FIG. 4 is a structural diagram of a conventional torque detecting device using this principle. (3a) and (3b) are magnetic layers made of elongated magnetic material (for example, amorphous metal), which are fixed to the surface of the passive shaft (1) so as to form symmetric angles with respect to the central axis (2). ing. The figure shows the case where the stress sensitivity is the maximum ± 45 °. (4) is a coil bobbin provided at a position facing the magnetic layers (3a) and (3b) and separated from the passive shaft (1) by a predetermined gear, and (5) and (6) are wound around this coil bobbin. The rotated detection coil converts the change in magnetic permeability of the magnetic layers (3a) and (3b) that occurs when torque is applied into an electric signal as a change in inductance. FIG. 5 is an example of an electric circuit diagram of a conventional torque detection device. (7a) is the magnetic layer (3
This is a push-pull type self-excited oscillation circuit in which detection coils (5) and (6) with a) and (3b) as magnetic cores are used as collector windings, and transistors (71a), (72a), resistors (73a), (74
a), capacitors (75a) and (76a). Here, the conduction time of the transistors (71a), (72a) changes according to the change of the magnetic permeability because the inductance of the collector winding changes when the magnetic permeability of the magnetic core changes. Therefore, the duty ratio changes depending on the relative change in the magnetic permeability of the magnetic layers (3a) and (3b) that are the magnetic cores of the detection coils (5) and (6).

Reference numeral (8a) is a waveform shaping circuit for shaping each collector signal of the oscillation circuit (7a) into a rectangular wave, and resistors (81a), (82a), (83
a), (84a), operational amplifier (85a), (86a). (9a) is an integrator circuit that sets each rectangular wave signal whose waveform is shaped to a DC level corresponding to the duty ratio.
It consists of a), (92a), capacitors (93a), and (94a). (10a) is a differential amplifier circuit, which includes resistors (101a), (102a)
It is composed of a), (103a), (104a), and operational amplifier (105a). Note that Vcc in FIG. 5 is a drive power supply for driving the circuit. Now, in FIG. 5, when no torque is applied, since the magnetic permeability of the two magnetic layers (3a) and (3b) is equal, each collector signal of the oscillator circuit (7a) has a duty ratio of 50.
% Signal, which is input to the differential amplifier circuit (10a) 2
The two integrated DC levels are equal, and therefore the output is zero. When torque is applied, the magnetic permeability of one magnetic layer increases and the other decreases in proportion to the amount of torque as described above, so the duty ratio of the collector signal of the oscillator circuit (7a) changes (one The duty ratio of the collector signal is larger than 50% and the other is smaller than 50%), and a signal having a level proportional to the torque amount appears in the output of the differential amplifier (10a). If the direction of torque application changes, the magnetic permeability of the magnetic layers (3a) and (3b) changes in the opposite direction to the previous one, so the output signal of the differential amplifier (10a) has the opposite sign. The torque application direction can also be determined.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional device, when the ambient temperature changes, in the ideal case where the passive shaft (1) and the magnetic layers (3a) and (3b) have the same thermal expansion coefficient. In addition to the stress due to torque, bias-like tensile or compressive stress is applied due to the difference in thermal expansion coefficient between the passive shaft and the magnetic layer, which changes with temperature. As described above, since the torque output differentially detects the change in the magnetic permeability of the two magnetic layer portions, the change in the bias stress due to the difference in the coefficient of thermal expansion is similarly applied to the two magnetic layer portions, so that the zero point Although it does not fluctuate, it causes a change in the amount of bias stress, changes the sensitivity of stress-permeability change, and changes the torque output sensitivity. As a means for correcting this, a method of arranging a temperature sensor such as a thermistor near the torque detection device to detect the ambient temperature and correcting the torque output accordingly can be considered. However, in this method, there is a problem that a time delay or the like occurs between the ambient temperature change and the temperature change of the passive shaft to which the magnetic layer is fixed, so that they do not always match and proper correction cannot be performed.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a torque detection device that can obtain an accurate torque output even when the ambient temperature changes.

[Means for solving problems]

The torque detecting device according to the present invention has a magnetic layer for detecting the temperature of the shaft fixed to the passive shaft to detect the temperature of the shaft in a non-contact manner, and according to the detected temperature signal, the temperature is detected according to the temperature. The torque signal is corrected.

[Action]

The temperature detecting portion of the passive shaft according to the present invention has substantially the same structure as the torque detecting portion, but the magnetic layer for temperature detection fixed to the shaft has a sufficiently elongated shape so as not to be sensitive to torque. It is fixed in parallel with the longitudinal direction, a temperature correction signal is derived from the signal of this temperature detection unit, and the gain of the torque output sensitivity is adjusted according to the temperature.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a structural view showing an embodiment of the present invention, FIG. 2 is an electric circuit diagram thereof, and the same or corresponding parts as in FIG. 3, FIG. 4 and FIG. There is. In FIG. 1, (11) is a magnetic layer for detecting the temperature of the passive shaft (1),
It has an elongated shape and is fixed parallel to the direction of the central axis (2) of the axis (1). The material is preferably the same as the magnetic material used for the torque detection unit, but is not particularly limited thereto. (12) is a coil for temperature detection wound around a coil bobbin (13) facing the magnetic layer (11), and (14) is a coil bobbin (13) located off the magnetic layer (11). ) Is a coil for temperature detection which is wound around.

In FIG. 2, (7b) is a detection coil (12) having a magnetic layer (11) for temperature detection as a magnetic core and a detection coil (14) arranged without the magnetic layer (11) as a collector winding. This is a push-pull type self-excited oscillating circuit configured, and transistors (71b), (72b), resistors (73b), (74
b), capacitors (75b) and (76b). (8
Reference numerals b), (9b), and (10b) denote a waveform shaping circuit, an integrating circuit, and a differential amplifier circuit, respectively, which are similar to the torque detecting unit, and these constitute a temperature detecting unit for the shaft (1). (15) is an adder circuit, and (16) is a divider circuit for gain control.

When the ambient temperature changes, the temperature of the passive shaft (1) also changes accordingly, and the magnetic layer (11) fixed to the passive shaft (1) becomes
Due to the difference in the coefficient of thermal expansion with the shaft material, the magnetic permeability changes due to the stress proportional to the temperature change. Since the detection coil (12) is wound close to the magnetic layer (11), the inductance of the detection coil (12) changes according to the temperature change. On the other hand, since the detection coil (14) is wound without the magnetic layer (11), its inductance does not change even if the temperature changes. Therefore, when the temperature changes, only the inductance of one of the detection coils changes, so the duty ratio of the oscillation signal of the push-pull oscillator circuit (7b) changes and the temperature of the axis (1) is changed. An output signal V _b = k × ΔT is obtained (where k is a constant due to the material and circuit, ΔT is the amount of temperature change from the reference temperature). This temperature signal V _b is converted by the adder circuit (15) into a temperature correction signal V _d =
It is converted into (1 + ΔT) k and input to the gain control circuit composed of the division circuit (16). On the other hand, the torque signal V _{a that} is not temperature-corrected is the amount of temperature change from the reference temperature Δ
If the torque signal at T and the reference temperature is V _T , then V _a = (1 + △
T) V _T , which is the other input of the division circuit (16). Therefore, the output of the division circuit (16) is And an output signal independent of temperature is obtained. Needless to say, the magnetic layer (11) for temperature detection has a sufficiently elongated shape and is fixed in parallel with the longitudinal direction of the shaft.
It is almost insensitive to the stress in the ° direction, and only the signal due to the stress in the longitudinal direction of the shaft generated by the temperature change is obtained.

Although the detection coil (14) is wound around the outer circumference of the shaft without the magnetic layer (11) in the above embodiment, it may be arranged anywhere if a magnetic core insensitive to temperature is used. (1)
It may be provided on the circuit board instead of above. Further, in the above-described embodiment, both the torque detection unit and the temperature detection unit adopt the method of detecting the duty ratio change using the push-pull oscillation circuit for the torque detection and the temperature detection, but the magnetic permeability is determined by using the exciting coil and the detecting coil. It is also possible to adopt a method of detecting a change.

〔The invention's effect〕

As described above, according to the present invention, since the shaft temperature can be detected in a non-contact manner by the magnetic material fixed on the passive shaft and the temperature is corrected by this signal, the accurate torque can be obtained regardless of the ambient temperature change. You can get a signal.

[Brief description of drawings]

FIG. 1 is a structural diagram showing a torque detection device according to an embodiment of the present invention, FIG. 2 is an electric circuit diagram thereof, FIG. 3 is a diagram for explaining the principle of torque detection, and FIG. FIG. 5 is a structural diagram showing the torque detection device of FIG. 5, and FIG. 5 is an electric circuit diagram thereof. In the figure, (1) is a passive shaft, (3a) and (3b) are magnetic layers for torque detection, (5) and (6) are coils for torque detection, (7a) is a push-pull oscillation circuit for torque detection, (7b) is a push-pull oscillator for shaft temperature detection, (8a), (8b) is a waveform shaping circuit,
(9a) and (9b) are integration circuits, (10a) and (10b) are differential amplification circuits,
(11) is a magnetic layer for detecting the shaft temperature, (12) and (14) are coils for detecting the shaft temperature, (15) is an adding circuit, and (16) is a dividing circuit. The same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A detection coil having a magnetic layer fixed to the outer circumference of a passive shaft that receives a torque, and a change in magnetic permeability of the magnetic layer caused when torque is applied to the passive shaft is detected by a detection coil wound around the outer circumference of the magnetic layer. In a torque detection device for detecting a torque signal by detecting, a slender magnetic layer fixed on the passive shaft and parallel to the central axis of the passive shaft, and a detection coil wound around the outer circumference of the magnetic layer. A torque detection device comprising a passive shaft temperature detection circuit configured to output a signal according to the temperature of the passive shaft, and correcting the torque signal by an output signal of the detection circuit.