JPS61275630A - Magnetostrictive torque detector - Google Patents

Abstract

PURPOSE:To detect stably torque applied to a body to be measured by arranging plural magnetic disks in parallel at intervals by linking their outer peripheries by a magnetic member and providing a coils for torque detection between the magnetic disks. CONSTITUTION:A magnetostrictive torque detector is provided with a couple of an exciting coil 20a and a detection coil 21a and another couple of an exciting coil 20b and a detection coil 21b. Then, the exciting coils 20a and 20b are connected in parallel and arranged so that magnetic flux produced by those exciting coils flow from a center magnetic disk to right and left in the opposite directions. Consequently, a magnetic circuit operates around the exciting coils 20a and 20b independently. The detection coils 21a and 21b have amplifiers 22 and 23 and rectifying and smoothing circuits 24 and 25 independently of each other to obtain analog voltages corresponding to induced electromotive forces generated by the respective coils and then obtain a differential outputs by a differential amplifier 26. Consequently, the direction and value of torque are detected with high sensitivity without being affected by the magnetic irregularity nor eccentricity of a shaft to be measured.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention utilizes the inverse magnetostrictive effect to detect the torque applied to an object to be measured such as a shaft, particularly the shaft torque applied to the crankshaft of a vehicle. related to formula torque detectors.

(Prior art) Conventionally, a torque measurement method that measures the torque applied to an object to be measured, such as a shaft, using the inverse magnetostriction effect was developed in Japanese Patent Publication No. 31-9.
It is known from Publication No. 42.

FIG. 9 shows the principle of such a conventionally known torque measurement method, in which an excitation coil 2 and a detection coil 3 are arranged around the outer circumference of an object to be measured (shaft in the figure) 1, and The excitation coil 2 changes the magnetic permeability of the magnetic path due to the inverse magnetostriction effect due to the stress caused by the torque applied to the object to be measured.
The change in the magnetic flux generated by the sensor is detected by the induced power distribution of the detection coil 3, and the torque value applied to the object to be measured is measured. In addition, the excitation coil and the detection coil are connected to the object to be measured 1.
In addition to being wound around the object to be measured 1, it may also be provided as a magnetic head type close to the surface of the object to be measured 1.

In such conventional torque detectors, the magnitude of the induced electromotive force taken out from the detection coil corresponds to the torque applied to the object to be measured, and the detection coil detects magnetic changes over the entire outer circumference of the object to be measured. Although the output of this method is not affected by the accuracy of the arrangement of the detector and the object to be measured, it has the fatal drawback that the direction of torque cannot be detected.

To improve this, in order to create magnetic anisotropy on the side of the measured object, for example, in the case of a measured object such as a shaft, multiple slits with an inclination of 45° to the axis of the measured object are installed. However, it is not practical due to problems such as the difficulty of machining and the reduction in shaft rigidity due to the slits. On the other hand, a magnetic head type torque detector has the advantage of being able to detect not only the magnitude of the torque but also the direction in which the torque is applied. There is a problem in that stable detection is not possible due to the strong influence of magnetic non-uniformity, eccentricity, or deflection of the object to be measured.

In order to improve this problem, for example, US Patent No. 410
0791, a method of arranging a plurality of magnetic heads continuously along the outer periphery of the measured object is considered, but each core for excitation and detection requires a coil, and variations in the coils may cause problems. Including such problems, there were problems that it was impractical in terms of productivity and cost.

(Object and Structure of the Invention) The present invention has been made in view of the above points, and an object of the present invention is to detect the magnitude and direction of torque applied to a measured object using a detector with a simple structure. In order to achieve this purpose, a plurality of magnetic disks each having an opening for inserting the object to be measured and in which a plurality of protrusions are arranged at a predetermined pitch along the opening are used. The plurality of magnetic disks are connected by a magnetic member at the outer periphery and spaced apart in parallel, and a coil for torque detection is provided between the plurality of magnetic disks. The device is configured to detect the torque applied to the object to be measured.

(Example) Hereinafter, the present invention will be explained based on the drawings.

Figure 1 (A) is a cross-sectional view showing the torque detector according to the present invention attached to a shaft that is a measured object (hereinafter referred to as the "measured shaft"), and (B) is a torque detection diagram shown in (A). FIG. 3 is an axial end view of the vessel. As shown in FIG. 2, the torque detector 5 has an opening 5a in the center for inserting the shaft to be measured.
, 7a, 8a are arranged in parallel with a predetermined distance apart, and the outer periphery is made of ferrite,
They are joined by a cylindrical case 9 made of a magnetic material such as permalloy, silicon steel, or magnetic soft iron, and coils 10 and 11 wound around a bobbin made of plastic or the like are arranged in an annular space formed between each magnetic disc. It consists of A plurality of protrusions are arranged at a predetermined pitch on the inner peripheral surface of each magnetic disk 6, 7.8 facing the shaft 1 to be measured. For example, the second
As shown in the figure, the magnetic disk 6 has a protrusion (6-1>
, (6-2>, (6-3), (6-4>, (6-5>), but for the magnetic disk 7, the protrusions (7-1), (7-2>,
(7-3>, (7-4>, (7-5)), and for the magnetic disk 8, the protrusions (8-1>, (8-2), (8-3
), (8-4), and (8-5) are arranged at equal pitches in the circumferential direction.

The coils 10 and 11 are connected in series, and when the coils are energized, two magnetic circuits are formed by the cylindrical case 9 and the shaft 1 to be measured, enclosing each coil. The wires are connected so that the directions of the generated magnetic flux are opposite to each other. Both ends of the connected coil are connected to the lead wire 1 through the hole 9a made in the cylindrical case 9.
2. The hole 9a is filled with adhesive 13 and the lead wire 12 is fixed.

FIG. 3 shows the positional relationship of the protrusions formed on each magnetic disk 6, 7, 8 as a developed view of the outer surface of the shaft to be measured. A-A in the figure indicates the axial direction of the shaft 1 to be measured. Protrusions of the magnetic disk 7 located in the center (7-1>, (7-2), (7-3)
, (7-4>.

For <7-5>, the protrusions of the left and right magnetic disks 6 and 8 are as shown in the figure, that is, when the pitch of the protrusions is L, L1 x L2 and Ll<1/2L, and the left and right protrusions The triangle formed by connecting the central protrusion is a right triangle (for example, the protrusion (6-2>
The straight line connecting the protrusion (7-2> of the magnetic disk 7a and the straight line connecting the protrusion (8-2) of the magnetic disk 8 and the protrusion (7-2>) of the magnetic disk 7 are at right angles to each other. ) to be placed.

In other words, if the straight line connecting the protrusion (6-2> and the protrusion (7-2>) has an inclination of 45° with respect to the axis A-A, then the protrusion (8-2> and the protrusion (7-2>) The connecting straight line is axis A-A
The arrangement shall be such that it has an inclination of -45° to the

By arranging the protrusions of the magnetic discs 6, 7.8 in this way, the magnetic flux generated in the coil 10, for example, is distributed between adjacent protrusions, that is, (6-1>
-(7-1>, (6-2>-(7-2>, (6-3>-
(7-3>, (6-4)-(7-4>, (6-5>-(
7-5), and in other words,
Similarly, the coil 11 will have a strong sensitivity to magnetic changes at 45° to the axis A-A.
-A has strong sensitivity in the -45° direction.

FIG. 4 shows the change in impedance (equivalent to inductance) of each coil 10.degree. 11 of the torque detector with respect to the torque acting on the shaft 1 to be measured.

When torque is applied to the shaft to be measured, stress is generated on the surface of the shaft to be measured in a direction of ±45° with respect to the axis, as shown in FIG. For example, if tensile stress is generated in the +45° direction with respect to rightward torque, compressive stress will be generated in the −45° direction.

The opposite is true for leftward torque. The relationship between the stress generated on the axis to be measured and magnetic permeability differs depending on the magnetic material used, but for example, in the case of iron-based materials, the permeability increases in the direction where tensile stress is applied, and the permeability increases in the direction where compressive stress is applied. Magnetic property decreases.

Therefore, with the above-described configuration, the coil 10 has sensitivity in the +45° direction with respect to the axis, so an increase in magnetic permeability on the surface of the shaft to be measured due to rightward torque causes an increase in inductance, that is, impedance, and conversely, in the leftward direction In response to torque, there is a decrease in impedance that corresponds to a decrease in magnetic permeability. On the contrary, since the coil 11 has sensitivity in the 1-45° direction, the characteristics are opposite to this, and the characteristics shown in FIG. 4 are obtained.

FIG. 5 shows the configuration of a torque detection circuit using a torque detector according to the present invention. Coils 10 and 11 are connected to resistor 14
and 15 form an AC bridge, and a differential amplifier 16 amplifies the unbalanced voltage generated in response to the change in impedance of the coils 10 and 11 with respect to the torque.

The unbalanced voltage changes in level corresponding to the magnitude of the torque, and at the same time detects the phase change of the unbalanced voltage using the excitation voltage of the bridge as a reference. In other words, the unbalanced voltage is detected by the phase detection circuit 17 using the excitation voltage as a reference signal. By detecting the phase and roughly smoothing it by the smoothing circuit 18, the sixth
As shown in the figure, an output corresponding to the torque is obtained, and the direction and magnitude of the torque can be detected. The excitation voltage of the bridge is determined by the material of the shaft 1 to be measured and the magnetic disk 6°7.
．． 8 and the material of the cylindrical case 9, it is set to an appropriate value and is about 200H2 to 5QKH2.

FIG. 7 shows another embodiment of the torque detector according to the present invention mounted on an object to be measured. The basic structure of this embodiment is exactly the same as that of the embodiment shown in FIG. 1, and the same components are designated by the same reference numerals.

This embodiment is characterized by providing one set of excitation coil 20a and detection coil 21a and another set of excitation coil 20b and detection coil 21b.

The detection circuit is shown in FIG. 8, and the excitation coils 20a and 20
b are connected in parallel and arranged so that the magnetic flux generated by these excitation coils flows in opposite directions from the central magnetic disk 7 to the left and right as shown by solid lines and broken lines in FIG. As in the embodiment of FIG. 1, the magnetic circuits around each of coils 20a and 20b operate independently. The detection coils 21a and 21b are each independently connected to an amplifier 22, 23 and a rectifying and smoothing circuit 24.
25, and after obtaining an analog voltage corresponding to the induced electromotive force generated in each coil, a differential amplifier 26 obtains a differential output.

The torque detection operation is the same as that in the embodiment shown in FIG. By taking the difference, the direction and magnitude of the torque can be detected with high sensitivity without being affected by magnetic non-uniformity or eccentricity of the axis to be measured.

In the above two embodiments, the line connecting the protrusion of the central magnetic disk among the three magnetic disks and the protrusions of the two left and right magnetic disks shifted in the circumferential direction of the opening is the axis to be measured. Although the angle between the axis and the axis is set to ±45°, although the highest detection sensitivity can be obtained at this angle, the present invention is not limited to this angle, and the detection sensitivity is slightly lowered at other angles as well. Nonuniformity and eccentricity are averaged out, and the direction and magnitude of torque can be detected.

(Effects of the Invention) As explained above, in the present invention, a coil with a simple structure that is wound around the object to be measured is used without any modification to the object to be measured. By simply shifting the positions of the protrusions provided on the magnetic disks by a predetermined distance between magnetic disks, detection sensitivity can be given directionality. Since detection is carried out at multiple positions along the measurement target, magnetic non-uniformity and eccentricity of the object to be measured are averaged out and the effects are eliminated, allowing for stable and accurate mounting. Torque can be detected without being affected. Furthermore, structurally, if the yoke is composed of three magnetic disks and a cylinder, detection sensitivity can be further improved. The torque detector according to the present invention has a simple structure regardless of whether the number of magnetic discs is 2, 3, or more, so it is extremely easy to manufacture and process, and can be integrated as a detector. It is also easy to convert and can be manufactured at low cost.

By taking advantage of the above-mentioned advantages, it is possible to realize a torque detector of the present invention suitable for implementation as a sensor for detecting the steering torque of a steering wheel, the output torque of an engine, or a transmission, etc., in an automobile, for example. is obtained.

[Brief explanation of drawings]

FIG. 1(A) is a sectional view showing an embodiment of the torque detector according to the present invention, FIG. 1(B) is an axial end view of the torque detector shown in FIG. 1, and FIG. FIG. 3 is a diagram showing the arrangement of protrusions on the magnetic disk of the torque detector according to the present invention, and FIG. 4 is a characteristic showing the relationship between the direction of torque and the change in impedance. 5 shows an example of a torque detection circuit using the torque detector according to the present invention, and FIG. 6 shows the output characteristics of the torque detector shown in FIG.
FIG. 7 is a sectional view showing another embodiment of the torque detector according to the present invention, FIG. 8 is an example of a torque detection circuit using the torque detector shown in FIG. 7, and FIG. 9 is a conventional magnetostrictive type FIG. 3 is a cross-sectional view of an example of a torque detector. 1... Axis to be measured, 5... Torque detector, 6, 7.8
... Disk, 6a, 7a, 8a... Opening, protrusion...
(6-1) ~ (6-5>, (7-1) ~ (7-5), (
8-1) ~ (8-5>, 9... Cylindrical case, 10°1
1...Coil.

Claims (1)

[Claims] A plurality of magnetic disks each having an opening for inserting the object to be measured and having a plurality of protrusions arranged at a predetermined pitch along the opening. The plurality of magnetic disks are connected at the outer periphery by a magnetic member and spaced apart in parallel, and a torque detection coil is provided between the plurality of magnetic disks to apply torque to the object to be measured. A magnetostrictive torque detector characterized by detecting torque.