JPH02136725A - Torque measuring instrument - Google Patents

Abstract

PURPOSE:To surely maintain the linearity of a torque detecting voltage by providing a 1st and 2nd magnetic anisotropy parts wherein the magnetic anisotropy is imparted in the direction parallel with the center of a shaft for torque transmission and the direction of a main stress for compression based on the torque. CONSTITUTION:A magnetic permeability of the 2nd magnetic anisotropy part 13 is varied in accordance with a right torque 14 exerted to the shaft 11 for torque transmission, and the detected voltage V of a detecting coil 20 is decreased as the right torque 14 value is increased. In this anisotropic part 13, the magnetic anisotropy is imparted in the direction of the main stress 15 for compression and the saturation of a magnetizing circuit is late, thereby the linearity of the voltage V is less affected even by the large torque force. In the 1st magnetic anisotropy part 12, the magnetic anisotropy is imparted in the direction parallel with the center of the shaft 11 and the magnetic permeability is hardly varied with the torque force of the shaft 11, then the detected voltage V0 of the detecting coil 19 is almost constant without change for whichever torque forces exerted in right or left. So, linearity of the detected voltage for torque synthesized by the difference between both detected voltages V0-V is improved only for the right torque force, hence the accurate torque measurement can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a torque measuring device, and more particularly to a torque measuring device that can be used in agricultural machinery, automobiles, industrial machinery, and other devices having shafts for transmitting torque.

Prior Art A conventional torque measuring device of this type is disclosed in Japanese Patent No. 1693.
Some of these are disclosed in Specification No. 26 and the like. As shown in FIG. 9, magnetic fields are formed on the outer periphery of a shaft 1 having soft magnetism and magnetostriction that are inclined in opposite directions at an angle of about 45 degrees with the axis of the shaft 1. Anisotropic part 2, 3
is formed by a large number of grooves, etc., and an excitation coil 4.5 and a detection coil 6.7 are arranged around each magnetic anisotropy section.

According to such a configuration, the change in magnetic permeability in each magnetic anisotropic portion 2, 3 based on the transmitted torque is detected by the detection coil. At this time, since the magnetic anisotropic portions 2.3 are inclined in opposite directions, when a principal tensile stress acts in the direction of one magnetic anisotropic portion in the axial surface layer, the other magnetic anisotropic portion Compressive principal stress acts in the direction of . Therefore, as shown in FIG. 10, the detection voltage of one of the detection coils 6.7 increases as the torque increases, while the detection voltage of the other coil decreases. Therefore, if we take the difference in surface detection voltages - v2 and synthesize it.

As shown in FIG. 11, a torque detection voltage indicating only a change in torque is obtained.

Problems to be Solved by the Invention Let us now discuss the case where the shaft material has positive magnetostriction. In conventional torque measuring devices of this type, the voltages v0 and v2 generated from the detection coil are V1/, V2/ as indicated by the dotted lines in FIG. As shown in FIG.
Most of the results were published in such a way that they were almost on a straight line, such as V and l. However, if we look at these characteristics in detail, we find that in reality, the solid line V and v2 in Figure 10
As shown in the figure, the detection voltage gradually becomes saturated as the torque increases for both right-hand and left-hand torques, and moreover, the surface shear stress generated on the shaft surface by the torque begins to saturate at a level that is considerably lower than the elastic limit of the shaft material. Sometimes. As a result, the torque vs. detection voltage characteristic begins to become saturated at a fairly low torque as shown by the solid line V knee (2) in FIG. 11, posing a problem in manufacturing a torque sensor with good linearity.

Additionally, the magnetic permeability of the material that makes up the shaft 1 usually changes with changes in ambient temperature, but conventional torque measuring devices do not take measures to deal with such temperature changes. There is a problem in that torque cannot be detected with high accuracy when temperature changes are large.

SUMMARY OF THE INVENTION An object of the present invention is to simultaneously solve the above two problems and provide a torque measuring device that has a simple configuration, ensures linearity of torque detection voltage, and also has a temperature compensation function.

Means for Solving the Problems In order to achieve the above objects, the present invention provides a first magnetic anisotropy in which magnetic anisotropy is imparted in a direction parallel to the direction of the axis in a surface layer on the outer periphery of a shaft that transmits torque. A magnetic anisotropy is formed on the outer periphery of the axis in the anisotropic part and the surface layer in the vicinity of the first magnetic anisotropic part, and imparts magnetic anisotropy in the direction of the compressive principal stress acting on the surface layer based on the torque. and a second magnetic anisotropic portion arranged around each magnetic anisotropic portion,
The structure includes a detection coil that can detect the torque acting on the shaft from a change in detection voltage based on a change in magnetic permeability of the magnetic anisotropic portion when torque is applied to the shaft.

Further, according to the present invention, the excitation current of the excitation coil is controlled so that the detection voltage of the excitation coil for exciting each detection coil and the detection coil corresponding to the first magnetic anisotropy portion becomes a constant value. The configuration may include means for:

Further, according to the present invention, the difference between the detection voltage of the second detection coil corresponding to the second magnetic anisotropy section and the detection voltage of the first detection coil corresponding to the first magnetic anisotropy section is determined. It can be configured to include means for calculating and means for dividing the obtained difference value by the detected voltage value of the first detection coil.

EffectThe first magnetically anisotropic part has magnetic anisotropy in the direction parallel to the direction of the axis, so even if torque is applied to the axis,
The change in magnetic permeability caused by this is very small and can be said to be almost unchanged.

Regarding the second magnetic anisotropic part, there has been no detailed description of the relationship between the direction of stress applied to this anisotropic part and the detected voltage detected from this, and the present invention focuses on this point. I learned about the result method. In other words, when the principal tensile stress that occurs when torque is applied to the shaft material is processed in the same direction as the magnetic anisotropy direction (for example, the direction of the groove or the direction of the rectangle of the amorphous ribbon). The detected voltage starts to become saturated from a relatively low value of torque. The degree of saturation varies depending on the shaft material, the degree of anisotropy, the shape and depth of the groove, etc., but saturation begins at a relatively low torque level. This is thought to be due to the fact that the magnetization rotation generated within the magnetostrictive material is easily saturated when the tensile principal stress is applied. Conversely, if the direction of magnetic anisotropy is processed in the direction in which compressive principal stress acts.

The saturation phenomenon of the detected voltage due to the addition of torque is much slower than that described above, and the linearity of the detected voltage is not impaired even if a considerably large torque is applied. This is thought to be because the saturation of magnetization rotation is slow depending on the compressive stress.

Focusing on these points, in the present invention, the second magnetically anisotropic portion 1 has magnetic anisotropy in the direction in which compressive principal stress acts on the surface layer of the shaft in response to the torque applied during normal actual use. Therefore, even if a large torque is applied, the magnetization rotation is almost never saturated. Therefore, the detection voltage (Vo-V) of the detection coil provided corresponding to each magnetic anisotropic part is As shown in Figure 3, the torque applied during normal actual use (
For right-hand torque (in FIG. 3), a significantly improved linearity is obtained.

Incidentally, in a case where the direction of rotation of the shaft is reversed and the direction of the torque is reversed, the direction of the second magnetic anisotropic portion becomes the same direction as the direction of the principal tensile stress. However, 1. Normally, torque transmission shafts in many cases such as agricultural machinery, automobiles, and industrial machinery are required to improve accuracy in one direction, so if linearity is ensured only in this one direction, then In most practical applications, this does not pose any problem.

As mentioned above, since the first magnetic anisotropic part is hardly affected by the torque acting on the shaft, the detection voltage of the first detection coil corresponding to this first magnetic anisotropic part is: It changes primarily based solely on changes in ambient temperature. therefore,
The detection voltage of this first detection coil can be used for temperature compensation.

According to the present invention, the torque detection voltage, that is, the first
Temperature changes in the difference (Vo-V) between the detected voltage vO of the second coil and the detected voltage V of the second coil can be automatically compensated for at all times (even when torque is applied). or,
Temperature compensation can also be performed by having a configuration that includes means for calculating the difference in the detection voltages of the rain detection coils, and means for dividing the obtained difference value by the detection voltage value of the first detection coil.

Embodiment FIG. 1 shows a torque measuring device according to a first embodiment of the present invention. Here, 11 is a shaft for torque transmission, and a pair of first and second magnetic anisotropic parts 1 are formed on the outer periphery of the surface layer.
2.13 is formed. The first magnetic anisotropic portion 12 is constituted by a large number of machined grooves parallel to the direction of the axis of the shaft 11. However, this first magnetically anisotropic part and the second magnetically anisotropic part can be formed not only by machining but also by rolling, laser processing, carburizing, amorphous ribbon bonding, and other various methods. It is possible.

The second magnetic anisotropic portion 13 is formed on the surface layer of the outer periphery of the shaft 11 at a position a short distance away from the first magnetic anisotropic portion 12 in the axial direction. The direction is such that compressive principal stress is generated when torque applied to the shaft 11 during normal use is applied. For example, if the torque during normal use is right-hand torque as shown in Figure 1, shaft 1
The anisotropic direction formed in 1 is formed in the 15 direction. This compressive principal stress 15 acts on the surface layer of the shaft 11 at an angle of 45 degrees with the axis of the shaft 11. A tensile principal stress 16 acts in a direction perpendicular to the compressive principal stress 15. Excitation coils 17.1 are arranged around each magnetic anisotropic portion 12.13.
8 and detection coils 19,20 are provided, respectively.

The torque measuring device having such a configuration is suitable for measuring the right torque 14. In other words, a right torque of 1 is applied to the shaft 11.
4 acts, the magnetic permeability of the magnetic anisotropic portion I3 changes accordingly, and the detection voltage V of the detection coil 20 decreases as the right torque value increases, as shown in the graph of FIG. . At this time, since magnetic anisotropy is imparted to the magnetically anisotropic portion 13 in the direction of the compressive principal stress 15, the saturation of magnetization rotation is slow even when a large torque is applied, and therefore, a large torque does not act. However, the linearity of the detected voltage V is less likely to be impaired.

The magnetic anisotropy portion 12 has magnetic anisotropy in a direction parallel to the axis of the shaft 11, so even if torque is applied to the shaft 11, the magnetic permeability will not change accordingly. Therefore, even when the right torque 14 as shown in FIG. 1 acts, or even when the left torque acts, the detection coil 19 as shown in FIG. Detection voltage V.

remains almost constant and does not change.

Therefore, as shown in FIG. 3, the linearity of the torque detection voltage obtained by taking and synthesizing the difference Vo-V between the two detection voltages is improved as long as the right torque acts. This enables highly accurate torque measurement.

When a left torque acts on the torque measuring device shown in FIG. 1, a tensile principal stress acts in the direction in which magnetic anisotropy is imparted in the magnetically anisotropic portion 13, contrary to the illustrated arrow. Therefore, in this case, the detection voltage V and the torque detection voltage V o -V undergo a saturation phenomenon from a small torque level, as in the case of the prior art described above. However, as mentioned above, since it is customary for a general torque transmission shaft to mainly rotate with emphasis on one direction, the torque measuring device shown in FIG. 1 focuses on measuring the right torque 14. If used, there will be no practical problems.

FIG. 4 shows a torque measuring device according to a second embodiment of the present invention. In this embodiment, the second magnetic anisotropic portion 13
is formed in the direction of the compressive principal stress 15 that is generated when the left torque 21 is applied to the shaft 11.

According to such a configuration, the opposite effect as explained in the embodiment of FIG. 1 works, and as is clear from FIGS. 5 and 6, excellent linearity is achieved when the left torque 21 is applied. can be obtained.

In the torque measuring device shown in FIGS. 1 and 4, since the magnetic permeability of the first magnetic anisotropic portion 12 hardly changes depending on the torque acting on the shaft 11, the detection coil 19 hardly detects the magnetic permeability. Changes in voltage vO are primarily due to changes in ambient temperature. Therefore, this detected voltage Vo can be used for temperature compensation.

FIG. 7 shows an example of a device for such temperature compensation. That is, both detection coils 19 and 20 are connected to the input side of the comparator 22, so that the difference V o -V between the two detection voltages appears on the output side of the comparator 22. The detection coil 19 is also connected to a comparison amplifier 24, which is further connected to a reference power source 25. In the comparison amplifier 24, the set voltage E of the reference power supply 25
and the output voltage of the detection coil 19 are compared, and the difference is amplified and output as an excitation current to the excitation coil 17, 18, and the output voltage vO of the detection coil 19 is automatically set to the reference voltage gf.
It is controlled to maintain the fi pressure E.

In such a configuration, when the temperature condition changes, the detection voltage 0 of the detection coil 19 changes accordingly. Then, the difference voltage between the detected voltage vO and the reference power supply voltage E is amplified by the comparison amplifier 24, and the output current adjusts the excitation current of the excitation coil 17, thereby increasing the detection voltage. This is to compensate for the change in vO and control the detected voltage Vo to a constant value regardless of temperature changes.

As a result, since the excitation current of the excitation coil 18 is also adjusted at the same time, the detection voltage V of the detection coil 20 is also temperature compensated. Therefore, the values of the temperature-compensated detection voltages Vo and V are inputted to the comparator 22, and a difference V o -V based on these values appears on its output side.

Fig. 8 shows another example of a device for temperature compensation. The output side of is connected to the 1 divider 27.

The divider 27 is configured to receive the detected voltage Vo as well, and outputs the value (V o -V)/V o obtained by dividing the value of the difference Vo - V by the value of the detected voltage vO. It is considered possible. In addition, 28 is an AC power supply, and both excitation coils 1
7.18 is connected.

According to such a configuration, unlike the device shown in FIG. 7 described above, the detection voltages Vo and V themselves are not temperature-compensated, and these detection voltages Vo and V vary according to temperature changes. By dividing the value of the difference vO-V by the value of the detection voltage Vo in the divider 27, the temperature change is canceled out and compensated.

Effects of the Invention As described above, the present invention focuses on actively utilizing only the region where the magnetization rotation of the magnetically anisotropic portion of the shaft material is slow to saturate even when a large torque is applied. With this structure, the linearity of the detection voltage of the detection coil is improved, and along with this, the linearity of the torque detection value can be improved. Furthermore, since the detection voltage of the first detection coil is not affected by the torque acting on the shaft, it can be used to perform temperature compensation.

Specifically, according to the present invention, by having a configuration having means for controlling the excitation current of the excitation coil so that the detection voltage of the first detection coil becomes a constant value, or by The measurement data can be temperature-compensated by having a configuration including means for calculating a voltage difference and means for dividing the obtained difference value by the detected voltage value of the first detection coil.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a torque measuring device in the first embodiment of the present invention, FIG. 2 is a diagram showing the detection voltage of the detection coil in the device in FIG. 1, and FIG. 3 is a diagram showing torque detection in the device in FIG. 1. 4 is a schematic diagram of the torque measuring device in the second embodiment of the present invention, FIG. 5 is a diagram showing the detected voltage of the detection coil in the device of FIG. 4, and FIG. 7 and 8 are diagrams showing the circuit for temperature compensation, respectively, FIG. 9 is a schematic diagram of a conventional torque measuring device, and FIG. 10 is a diagram showing the torque detection voltage in the device shown in FIG. FIG. 11 is a diagram showing the detection voltage of the detection coil in the device, and FIG. 11 is a diagram showing the torque detection voltage in the device of FIG. DESCRIPTION OF SYMBOLS 11... Axis, 12... First magnetic anisotropy part, 13.
...Second magnetic anisotropy part, 15゛...Compressive principal stress,
19.20...Detection coil, V, Vo...Detection voltage. Agent Yoshihiro MorimotoFigure 1Figure 2Figure 3Figure 4Figure 4Figure 1Figure 11

Claims (3)

[Claims] 1. a first magnetic anisotropy portion in which magnetic anisotropy is imparted in a direction parallel to the direction of the axis in a surface layer on the outer periphery of the shaft that transmits torque; a second magnetic anisotropy portion formed on the outer periphery of the axis in the surface layer and imparted with magnetic anisotropy in the direction of the compressive principal stress acting on the surface layer based on the torque; and each magnetic anisotropy portion. a detection coil that is disposed around the shaft and is capable of detecting the torque acting on the shaft from a change in detection voltage based on a change in permeability of the magnetically anisotropic portion when torque is applied to the shaft; A torque measuring device comprising: 2. An excitation coil for exciting each detection coil; and means for controlling an excitation current of the excitation coil so that the detection voltage of the detection coil corresponding to the first magnetic anisotropy portion becomes a constant value. The torque measuring device according to claim 1, characterized in that: 3. means for calculating the difference between the detection voltage of the second detection coil corresponding to the second magnetic anisotropy section and the detection voltage of the first detection coil corresponding to the first magnetic anisotropy section; 2. The torque measuring device according to claim 1, further comprising means for dividing the difference value by the detected voltage value of the first detection coil.