JPH0545240A - Over-load preventive device for magneto-strictive torque sensor - Google Patents

Abstract

PURPOSE:To prevent damage of a torque transmitting shaft of a magnetostrictive torque sensor, wherein the shaft is provided at the periphery with a magnetically anisotropic part and it is likely that an overload torque good larger than normal value is impressed on the shaft, and maintain the torque measuring accuracy at a good acceptable level. CONSTITUTION:A torque transmitting shaft 11 is divided in the axial direction to form a pair of shafting segments 13, 14, on which a hollow magnetostriction sensing shaft 15 is fitted over the range where they are stretching, and the two ends of this sensing shaft are secured to the shaft segments 13, 14. The sensing shaft 15 is provided with magnetically anisotropic parts 17, 17 for sensing of the torque. While the torque given to the torque transmitting shaft 11 remains small, torque transmission is borne by the sensing shaft 15 solely, but when the torque given exceeds a certain level, the shaft segments 13, 14 are coupled together mechanically to contribute to transmission of the torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetostrictive torque sensor overload prevention device, and more particularly to a magnetostrictive torque used in robots, automobiles, screw tighteners, etc., which can improve controllability by detecting torque. The present invention relates to a sensor overload prevention device.

[0002]

2. Description of the Related Art In a conventional magnetostrictive torque sensor, as shown in FIG. 4, a pair of magnetic anisotropic portions 2 and 2 are formed on the outer peripheral surface of a torque transmission shaft 1, and the magnetic anisotropic portions are surrounded by the magnetic anisotropic portions. By arranging the coils 3 and 3 in the coil 3 and detecting the change in the magnetic permeability of the magnetic anisotropic portions 2 and 2 when the torque is applied to the shaft 1, the magnitude of the torque can be determined. I try to ask. Then, as shown in the drawing, the coils 3 and 3 are housed in the shield yoke 4, and the cylindrical housing 5 in which the shield yoke 4 is inserted is mounted on the shaft 1 by the bearings 6 and 6.
Is supported around.

In such a magnetostrictive torque sensor,
If a very large overload torque exceeding the measurement range is applied to the shaft 1, the torque transmission shaft 1 may be damaged. By the way, in the conventionally known general non-magnetostrictive torque sensor, various measures are taken to prevent such overload.

For example, in Japanese Utility Model Publication No. 3-7797, a cylindrical overload preventing stopper is provided on the outer periphery of the torque transmission shaft. The overload prevention stopper fixes a pair of cylindrical members to the outer periphery of the torque transmission shaft, and the end portion of one of the cylindrical members is fixed until a torque of a predetermined magnitude is applied to the torque transmission shaft. The torque is transmitted only by the torque transmission shaft without mechanically coupling the end of the other cylindrical member, and when a torque of a predetermined magnitude or more is applied, the torque based on this torque is applied. By mechanically coupling the end portion of the one cylindrical member and the end portion of the other cylindrical member by twisting the transmission shaft, torque is transmitted also by this coupling portion,
The torque transmission shaft is configured so that no torque of a certain magnitude or more is applied thereto.

[0005]

However, such a known overload preventing device cannot be directly applied to the magnetostrictive torque sensor. This is because in the magnetostrictive torque sensor, it is necessary to dispose the magnetic anisotropic portions 2, 2 and the coils 3, 3 close to each other as shown in FIG. 4, and to accommodate the coils 3, 3. Since there is the shield yoke 4, the housing 5, the bearings 6, 6, etc., it is necessary to house them all inside the cylindrical member. However, with such a configuration, the device becomes very large. is there. Further, although it is necessary to draw out the signal line from the coils 3 and 3 to the outside, when the coil and the shield yoke are arranged inside the cylindrical member fixed to the torque transmission shaft, all of these coils and the like also rotate. This is because the signal line is wrapped around the shaft, making it practically impossible to rotate continuously.

Therefore, an object of the present invention is to solve such problems and provide a special overload prevention device suitable for a magnetostrictive torque sensor.

[0007]

In order to achieve the above object, the present invention provides a magnetic anisotropy portion on the surface of a magnetostriction detecting shaft,
In a magnetostrictive torque sensor configured to detect a magnetostriction change of the magnetic anisotropy portion caused by a transmission torque by a coil provided in the vicinity of the magnetic anisotropy portion, a magnetostriction detection in which the magnetic anisotropy portion is formed is detected. The shaft is formed in a hollow cylindrical shape, and the hollow cylindrical portion is provided with an overload preventing portion for preventing the torque of a predetermined magnitude or more from being applied to the magnetostriction detecting shaft.

[0008]

According to this structure, since the magnetostriction detecting shaft has a hollow cylindrical shape and the overload preventing portion is provided therein, the enlargement of the portion is prevented. Further, since the coil is arranged outside the rotating part, the signal line can be taken out to the outside without any problem.

On the other hand, when the torque applied to the magnetostriction detecting shaft is up to a predetermined value, the overload preventing portion does not act, and the torque is transmitted only by the hollow magnetostriction detecting shaft having the magnetic anisotropic portion. .. Therefore, sufficient stress acts on the magnetostriction detection shaft due to normal torque, and the magnetic permeability of the magnetic anisotropy portion changes favorably, which enables accurate torque measurement. When an excessive torque exceeding the predetermined magnitude is applied to the shaft, the overload prevention portion acts, and the mechanical connection between the end portion of one shaft portion and the end portion of the other shaft portion is performed. Also transmits torque. Therefore, the torque transmission of the overload is shared by the joints between the end portions of the shaft portion, and an excessive torque does not act on the magnetostriction detection shaft. Damage is prevented from occurring.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 to 3, reference numeral 11 denotes a torque transmission shaft, which has a thickness that is not damaged even if a predicted maximum overload torque is applied. The torque transmission shaft 11 is divided into two in the axial direction. Reference numeral 12 is the divided portion, and 13 and 14 are a pair of shaft portions forming the divided portion 12. A hollow magnetostriction detecting shaft 15 is externally fitted over the one shaft portion 13 and the other shaft portion 14, and the magnetostriction detecting shaft 15 is fitted.
Both ends of 15 are fixed to both shaft portions 13 and 14 by fastening elements 16 such as bolts and pins. Also, the magnetostriction detection axis
The reference numeral 15 is formed with a wall thickness that can withstand the maximum applied torque under normal conditions without overload.

On the outer circumference of the magnetostriction detecting shaft 15, the magnetostriction detecting shaft is
A pair of magnetic anisotropy parts 17 and 17 which are inclined in directions opposite to each other at an angle of ± 45 degrees with respect to the direction of the axis of 15 are formed by a large number of grooves or the like. A cylindrical housing 18 is concentrically supported by bearings 19 and 19 around the magnetostriction detection shaft 15. A shield yoke 20 is concentrically housed inside the housing 18, and the shield yoke 20 has a coil 2 corresponding to each of the magnetic anisotropic portions 17, 17.
1, 21 are also housed concentrically. 22 is a coil 21
Signal line from.

An overload prevention portion 23 is formed by the ends of the shaft portions 13 and 14. That is, FIG. 2 and FIG.
As shown in detail, a concave portion 24 is formed on the end surface of one shaft portion 13, and a convex portion 25 that fits into the concave portion 24 is formed on the end surface of the other shaft portion 14. Torque transmitting surfaces 26, 27 facing each other are formed in the concave portion 24 and the convex portion 25. A gap 28 is provided between the two torque transmitting surfaces 26, 27 when no torque is applied to the shaft 11. In addition to the gap 28, a gap 29 is formed between the end of the shaft portion 13 and the end of the shaft portion 14 to prevent the shaft portions 13 and 14 from contacting each other.

In such a structure, when a relatively small torque in a normal state is applied to the shaft 11, the torque causes torsional deformation of the magnetostriction detecting shaft 15. But,
The deformation of the magnetostrictive detection shaft 15 due to this normal torque causes a gap 28
Since it is within the range of, the concave portion 24 of the shaft portion 13 and the convex portion 26 of the shaft portion 14
Is not mechanically coupled to, and torque is transmitted only by the magnetostriction detecting shaft 15. Therefore, the magnetic permeability of the magnetic anisotropic portions 17, 17 changes based on this torque, and by detecting the change in the magnetic permeability with the coil 21, the magnitude of the torque acting on the shaft 11 can be obtained. By making the wall thickness of the hollow magnetostrictive detection shaft 15 compatible with the applied torque,
The magnetic permeability of 17, 17 can be changed appropriately, and the applied torque can be detected with high sensitivity.

When excessive torque acts on the shaft 11,
A large twist occurs in the magnetostriction detection shaft 15 and the gap 28 is clogged,
The torque transmitting surface 26 of the concave portion 24 and the torque transmitting surface 27 of the convex portion 25 contact each other. Then, the shaft portions 13 and 14 are mechanically coupled to each other, and the torque is transmitted between the shaft portions 13 and 14. That is, the magnetostriction detection shaft 15 acts only torque enough to cause torsional deformation of the magnetostriction detection shaft 15 until the two torque transmission surfaces 26, 27 come into contact with each other. 14 will be communicated between them. As a result, overload torque does not act on the magnetostrictive detection shaft 15 and damage to it is prevented.

For example, as described above, the magnetostriction detection shaft 15 has ±
If the shaft 11 is made thick enough to accurately measure a torque of 1 kgf ・ m and the shaft 11 receives an overload torque of 30 kgf ・ m, the magnetostriction detection shaft 15 will have a maximum of 2 kgf ・ m. Only the torque of m 2 acts, and the remaining torque can be configured to be transmitted between the shaft portions 13 and 14.

The construction of the overload preventing portion 23 is not limited to the above-mentioned one, and the shaft portions 13 and 14 are mechanically connected to each other until torque of a predetermined magnitude is applied to the shaft 11. Torque is transmitted only by the magnetostrictive detection shaft 15 without being mechanically coupled, and when a torque larger than a predetermined magnitude is applied, the magnetostrictive detection shaft 15 based on this torque is transmitted.
Any configuration may be used as long as the shaft portions 13 and 14 are mechanically coupled to each other by the twisting and the torque transmission by the shaft portions 13 and 14 is also performed.

[0017]

As described above, according to the present invention, the magnetic anisotropy portion is formed on the surface of the magnetostriction detecting shaft, and the magnetostriction change of the magnetic anisotropy portion caused by the transmission torque is detected by the magnetic anisotropy. In a magnetostrictive torque sensor configured to detect by a coil provided in the vicinity of the magnetostrictive portion, the magnetostrictive detection shaft in which the magnetic anisotropic portion is formed is formed in a hollow cylindrical shape, and the magnetostrictive detection shaft is formed in the hollow cylindrical portion. Since it is provided with an overload prevention part for preventing a torque of a predetermined magnitude or more from being loaded, not only can the structure be downsized, but the coil can be placed outside the rotating part. As it can be arranged, the signal line can be taken out without any problem,
In addition, sufficient torque is generated in the magnetostriction detection shaft due to the torque during normal operation, and the torque can be measured with high accuracy. Moreover, excessive torque does not act on the magnetostriction detection shaft. It is possible to prevent damage to the shaft.

[Brief description of drawings]

FIG. 1 is a sectional view of an overload prevention device for a magnetostrictive torque sensor according to an embodiment of the present invention.

FIG. 2 is a perspective view of an overload prevention unit in FIG.

3 is a cross-sectional view of the overload prevention unit in FIG.

FIG. 4 is a sectional view of a conventional magnetostrictive torque sensor.

[Explanation of symbols]

 11 Torque transmission shaft 12 Split part 13 Shaft part 14 Shaft part 15 Magnetostriction detection shaft 17 Magnetic anisotropy part 23 Overload prevention part 24 Recessed part 25 Convex part 28 Gap

Claims (3)

[Claims] 1. A magnetic anisotropy portion is formed on the surface of a magnetostriction detecting shaft, and a magnetostriction change of the magnetic anisotropy portion caused by a transmission torque is detected by a coil provided near the magnetic anisotropy portion. In the magnetostrictive torque sensor configured as described above, the magnetostriction detection shaft having the magnetic anisotropy portion is formed in a hollow cylindrical shape, and a torque of a predetermined magnitude or more is applied to the magnetostriction detection shaft in the hollow cylindrical portion. An overload prevention device for a magnetostrictive torque sensor, which is provided with an overload prevention unit for preventing the occurrence of a load. 2. The overload prevention portion has a pair of shaft portions fixed in the magnetostriction detection shaft in the axial direction, and a torque of the predetermined magnitude is applied to the magnetostriction detection shaft. Up to the torque of not less than the predetermined magnitude, while the torque is transmitted only by the magnetostriction detection shaft without mechanically connecting the end of one of these shafts and the end of the other shaft. When applied, the end of one of the shafts is mechanically connected to the end of the other shaft by twisting the magnetostriction detection shaft based on this torque, and torque is also transmitted by this connecting part. The overload prevention device for a magnetostrictive torque sensor according to claim 1, wherein the overload prevention device is configured so as to allow it. 3. A pair of magnetic anisotropy portions are formed on the surface of a hollow cylindrical magnetostriction detecting shaft, and the pair of magnetic anisotropy portions form a large number of grooves forming an angle of about ± 45 degrees with the axis. 3. The overload prevention device for a magnetostrictive torque sensor according to claim 1, wherein the overload prevention devices are formed so as to be inclined in mutually opposite directions.