JP2009036663A - Noncontact torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noncontact torque sensor which can be divided and fitted onto a shaft. <P>SOLUTION: A torque is measured by magnetic flux-detecting elements where an exciting coil and a detection coil are wound around an amorphous lamina. The magnetic flux-detecting elements are fixed on a dividable external cylinder 2 (illustrated) in a direction of about 45° and a direction of about -45° to a center axis of a shaft 1 to be measured. The dividable external cylinder is placed near a surface of a steel shaft to be measured, then change of magnetic permeability caused by the torque of the steel shaft is measured by the magnetic flux-detecting elements, and the torque is calculated and displayed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  Amid the frequent occurrence of large truck accidents, raising the safety awareness of drivers and improving safety skills are issues, and efforts to strengthen maintenance of tires and heavy trucks are required. Therefore, it is necessary to strictly inspect the torque of each tightening portion of the truck, and there is currently no small-sized and highly sensitive non-contact torque sensor.

  Automotive sensors include engine control system sensors, chassis control system sensors, and safety / comfort control system sensors, and the annual market scale is about 1500 to 160 billion yen. In the future, the market for automotive sensors will expand against the backdrop of an increase in the number of vehicles used per vehicle. Torque sensors are used for driving automobiles, but non-contact torque sensors are expected to realize light and flexible driving control.

  If a non-contact torque sensor is used to measure the torque applied to the shaft in various rotating machines, the influence of the friction coefficient can be avoided, and high-precision and high-speed rotation control is possible.

  The present invention relates to a non-contact torque sensor that detects torque applied to a tightening tool having a magnetostrictive characteristic, a tire wrench, or a rotating shaft based on a change in inductance of a detection coil.

Patent application 2001-211302 is a magnetostrictive torque sensor. Such a conventional magnetostrictive torque sensor is provided with a magnetic anisotropy portion on the outer periphery of the shaft and a coil disposed so as to surround the magnetic anisotropy portion. Since this method requires machining on the shaft, it cannot be said to be non-contact in a strict sense.

In Japanese Patent Application Publication No. 2007-114088, the detection coil has a first coil inclined by + 45 ° with respect to the central axis and a second coil inclined by −45 ° with respect to the central axis. Then, in order to measure the magnetic permeability of the entire shaft surface, the coil becomes large and an extra excitation current is required.

  In many cases, it is necessary to measure the torque applied to the power transmission shaft and the like. However, as in the patent document, it cannot be said that the actual shaft torque is accurately measured by machining the shaft. There is a great demand for measuring torque literally in a non-contact manner, and an object of the present invention is to measure the torque completely in a non-contact manner.

  Moreover, although it can be said that the method like patent document 2 is non-contact, it is difficult to wind a coil later for a torque measurement in the part in which a mechanism exists previously. Therefore, torque cannot be measured if the entire mechanism including the measurement target shaft has already been completed.

  In order to solve the problems in the previous period, the magnetostrictive material attached to the shaft as in Patent Document 1 is used to measure the reverse effect of magnetostriction that occurs on the steel shaft itself. Torque by placing the magnetic flux detection element as shown in FIGS. 1 and 3 on the outer cylinder, forming a magnetic path between the magnetic flux detection element and the steel shaft surface to be measured, and measuring the magnetic flux change in the magnetic path Completely non-contact torque measurement by measuring However, as in Patent Documents 1 and 2, the coil wound outwardly on the shaft cannot be divided, so that the magnetic flux detection means in which the excitation and detection coils are wound around an amorphous thin plate (about 0.1 mm) as magnetic flux detection means. As shown in FIG. 4, the element is divided into halves and attached to an outer cylinder. The element is attached so as to wrap the test shaft in a divided state, and is fitted with screws or the like. It is fixed to the stationary part outside the shaft so that the outer cylinder and the shaft do not touch. The torque of the shaft is measured by the magnetic flux detecting element fixed to the inner side or the surface of the arm of the outer cylinder container or clip having such an easily assembled structure.

  FIG. 2 shows a structural example of the magnetic flux detecting element as a magnetic permeability measuring means placed near the surface of the steel shaft. Thus, a magnetic path between the shaft and the amorphous plate is formed, a change in magnetic flux in the magnetic path is detected, and a change in permeability due to the torque on the shaft surface is detected. The structure is shown in FIG. 6 is an amorphous thin plate, 7 is a detection coil, and 8 is an exciting coil. Two such detection elements, as shown in FIG. 1, are inclined by about 45 ° in the longitudinal direction of one detection element with respect to the shaft axis, and the other detection element (the other side in FIG. 2) is about It is fixed by bonding or the like to the front or back surface of the outer cylinder that is arranged in a non-contact manner with an air gap outside the shaft at an angle of −45. Further, a plurality of magnetic flux detection elements may be provided, and as shown in FIG. 3, the same number of magnetic flux detection elements in the direction of about 45 degrees and magnetic flux detection elements inclined by about −45 degrees may be arranged. At this time, all the detection coils having a direction of about 45 degrees are coupled in series. Similarly, the magnetic flux detection element having a direction of minus 45 degrees and all the coils detected by the elements in this direction are also coupled in series. As shown in FIGS. 5 and 19, if the combined inductances of the differently connected directions in series are L1 and L2, the torque of the shaft is obtained from the difference between L1 and L2. In that case, by taking the difference, it is possible to reduce magnetic common mode noise that similarly changes in L1 and L2. Further, the difference in output of each element due to the eccentricity of the shaft can be averaged by serial coupling, and the effect of the eccentricity of the shaft can be reduced.

  A conventional magnetostrictive torque sensor such as a magnetostrictive torque sensor embedded with a magnetostrictive material as in Patent Document 1 cannot be said to be non-contact in a strict sense, but the sensor has a magnetic flux detecting element arranged on an outer cylinder outside the shaft. Therefore, it is a completely non-contact torque sensor. In addition, since the magnetic flux detection element is attached to an outer cylinder or creep arm that can be divided, the sensor can be easily mounted and measured, and can be inserted in parts where you want to measure torque, such as the shaft of a machine that has already been completed. Such a sensor can be expected to perform a wide range of torque measurements such as an improvement test of transmission efficiency in an actual machine that has already been completed.

  FIG. 1 shows an embodiment of the sensor. Reference numeral 1 denotes a steel target shaft to be measured, and the outer cylinder 2 is fixed to a stationary part such as a machine so that the shaft and the corresponding central axis coincide with each other at a constant interval outside the shaft to be measured. . One of the magnetic flux detection elements has a longitudinal direction of about 45 degrees with respect to the central axis of the axis so that the directions are symmetrical with each other on both side surfaces of the outer cylinder, and the other magnetic flux detection element has about −45. It is fixed in the direction of the degree. The magnetic flux detection element is arranged near the surface of the steel shaft to be measured, and forms a magnetic path with a gap from the surface of the steel shaft under the element. Therefore, when conditions such as distance are matched, the permeability of the surface of the steel shaft that forms the magnetic path changes due to the torque and the inverse effect of magnetostriction based on the magnetic anisotropy of the shaft, and the maximum change in the permeability Are decomposed into 45 degrees and -45 degrees. Therefore, if the difference between the magnetic flux density in the 45 degree direction and the magnetic flux density in the -45 degree direction is measured, the change in permeability due to the torque can be obtained. In order to measure the magnetic flux, a magnetic flux detecting element as shown in FIG. 2 is used. Reference numeral 6 denotes an amorphous thin plate having a rectangular shape of about 10 × 3 × 0.1 mm, around which a detection coil 7 and an excitation coil 8 are wound. The sensor circuit is configured as shown in FIG. 5, and an alternating current is passed through the exciting coil from the oscillator. At that time, the excitation coil is transformer-coupled and an excitation voltage is output. Since amorphous is fixed to the outer cylinder, the output voltage depends on changes in the magnetic permeability of the steel shaft surface under the element. If the distance condition between the shaft and the magnetic flux detection element is the same, the change is due to the inverse effect of the magnetostriction of the shaft due to torque. Further, by making the cross-section and shape of the magnetic flux detection elements the same, the difference in inductance of the detection coils can be regarded as the magnetic flux density, and the magnetic flux density is measured for the permeability change caused by the inverse effect of magnetostriction. Torque is calculated from the voltage that has been differentially amplified by the A / D converter 21 and taken into the microcomputer 22, the value taken on the display 23 is displayed, and the torque data is also transferred to an external device.

  The magnetic flux detection elements of the first embodiment are arranged at 45 degrees and −45 degrees with respect to the axial center axis, but a plurality of magnetic flux detection elements may be arranged as shown in FIG. 3 and 9 are outer cylinders placed on the outer side of the shaft, 10 is the magnetic flux detecting element arranged on the outer cylinder so that the longitudinal direction is about 45 degrees, and 11 is arranged at -45 degrees. Is. 10 and 11 are arranged in the same number in the outer cylinder, the excitation coils are connected in parallel as shown in FIGS. 5 and 17, and the detection coils are connected in series on their respective sides. did. This is to average the variation in the distance between the element and the shaft surface due to eccentricity by connecting them in series. Each element has almost the same shape, such as a cross-sectional area, excitation, and number of turns of the detection coil.

  Since the coil of the sensor is not wound around the axis but around the magnetic flux detection element, the magnetic flux detection means of the sensor can have a structure in which the outer cylinder portion is divided as shown in FIG. Reference numeral 12 denotes an outer cylinder having a shape obtained by dividing the outer cylinder in half. Reference numeral 13 denotes a plate portion for fitting the outer cylinders divided in half, 14 is a bolt hole, and 15 is the magnetic flux detecting element. In the outer cylinder divided in half, the magnetic flux detecting element is paired with another divided outer cylinder that is mounted in the direction of -45 degrees with respect to the central axis of the shaft, and is a bolt opened in the plate At hole 14, the bolt is threaded and aligned. Therefore, in the conventional torque measurement, the shaft needs to be removed, but the non-contact torque sensor that can be divided can be assembled after being divided and inserted around the shaft. Even if the magnetic flux detection element is an outer cylinder, the torque can be easily measured without disassembling the device by arranging it on the arm of a clip such as a clothespin.

Mounting example of the magnetic flux detection element on a steel shaft Magnetic flux detection element Installation example of multiple magnetic flux detection elements Examples of structures that can be divided Implementation circuit example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel shaft 2 Outer cylinder 3 Amorphous thin plate 4 Detection coil 5 Excitation coil 6 Amorphous thin plate 7 Detection coil 8 Excitation coil 9 Outer cylinder 10 Magnetic flux detection element of 45 degree direction 11 -45 direction magnetic flux detection element 12 Outer cylinder 13 Bonding plate 14 Stop hole 15 Magnetic flux detection element 16 Oscillation circuit 17 Excitation coil 18 Detection coil combined inductor (45 degree direction)
19 Detection coil composite inductor (-45 degrees direction)
20 Differential amplifier 21 Microcomputer 22 Display

Claims (4)

  As shown in FIG. 1, the detection element of the sensor is an amorphous thin plate having a thickness of about 0.1 mm, which is formed into a substantially rectangular shape, and an excitation coil and a detection coil are wound thereon. For the steel shaft as shown in FIGS. 2 and 23 to detect the torque, the length of the detection element is placed on the front or back surface of the outer cylinder arranged in a non-contact manner with a gap between the shaft of the steel shaft and a gap. The magnetic flux of the outer cylinder portion that is attached so that one of the angles formed with the central axis of the shaft is about 45 degrees and the other attachment angle of the detection element is about -45 degrees. A non-contact torque sensor that measures the torque of a steel shaft from the change in magnetic flux near the shaft surface using a detection element.   The number of the detection elements may be plural, and the number of the detection elements attached to the front or back surface of the outer cylinder in the direction of about 45 degrees is the same as the number of the detection elements attached in the direction of about -45 degrees. The non-contact torque sensor according to claim 1.   3. The torque sensor according to claim 2, wherein all of the detection elements of the outer tube portion in the 45 degree direction are connected in series, and all the detection coils in the -45 degree direction are also connected in series.   The detection element set to 45 degrees and the detection element set to -45 degrees are fixed to the inner side of the arm of the outer cylinder container or the clip that can be divided by the same number, and divided and inserted in the vicinity of the surface of the steel shaft for assembly. The non-contact torque sensor according to any one of claims 1 to 3.