JPH062186U - Torque detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a compact and highly rigid torque detector suitable for measuring tightening torque of small diameter screws, etc., by using a wave gear device. [Structure] A torque detector 1 has a wave gear device 2 and a motor 3 as a driving means. A member 4 that can be connected to a small diameter screw or the like to be measured is connected to the output side of the wave gear device. Circular spline 2 of wave gear device
1, bulges 211 and 212 are formed, and on the housing 31 side of the wave gear device, these insertion grooves 311 and 312 are formed.
12 are formed. Piezoelectric elements 71, 72, 81, 82 are inserted between the overhang portion and the insertion groove, respectively. Since the piezoelectric element is distorted by the rotational force transmitted through the wave gear device, the rotational torque can be measured from this distortion amount.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a torque detector used for measuring screw tightening torque and the like, and more particularly to a torque detector suitable for measuring tightening torque of a screw having a small diameter.

[0002]

[Prior art]

 As a torque detector used to measure the tightening torque of a screw, a torque detector suitable for measuring the tightening torque of a screw having a small diameter of about 2 mm or 3 mm has been proposed. This torque detector uses a wave gear device, and inserts an elastic pressure-sensitive conductive material such as pressure-sensitive conductive rubber between the input side element and the output side element, This is crushed by the rotational force transmitted through the wave gear device. When the pressure-sensitive conductive rubber is crushed by the rotational force, the resistance value of the rubber changes according to the degree of its deformation. Therefore, the rotational torque is detected from the change in the resistance value.

[0003]

[Problems to be solved by the device]

 However, since the rubber, which is an elastic body, is inserted in the input / output member of the wave gear device as described above, there is a problem to be solved that the rotational rigidity on the output side of the detector is reduced.

An object of the present invention is to realize a high-rigidity torque detector focusing on this point.

[0005]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, in the torque detector of the present invention, a small-diameter screw is used by using a piezoelectric element made of a material that is a rigid body and has an extremely small deformation amount such as ceramic, instead of the conductive rubber. The tightening torque etc. is detected. That is, the input side of the wave gear device is connected to the drive means for driving the wave generator, and the output side thereof is connected to the member capable of connecting the object to be detected, and further, the rigid internal gear and the housing of the wave gear device are connected. A structure in which a piezoelectric element is inserted between the two is adopted.

[0006]

[Action]

 When a rotational force transmitted through the wave gear device acts on the piezoelectric element, the piezoelectric element deforms at most a few micrometers, but causes distortion. A voltage corresponding to the amount of strain can be obtained from the piezoelectric element. The rotation torque can be measured from this voltage value.

[0007]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings.

1 and 2, the torque detector 1 of this example includes a wave gear device 2. The wave gear device itself has been introduced in various documents, and its basic configuration is a circular spline 21, which is an annular rigid internal gear, and a flexex, which is a flexible external gear, arranged inside the circular spline 21. It is composed of a spline 22 and a wave generator 23 which is provided inside so as to bend the flex spline into a non-circular shape so as to partially mesh with the rigid internal teeth and rotate the meshing position.

The wave gear device 2 rotates a non-circular shape (for example, an elliptical shape) of a flexspline by rotating a wave generator connected to an input shaft, and external teeth of the flexspline are rotated to internal teeth of the circular spline. Orbiting above, which causes relative rotation between both splines with a large reduction ratio resulting from the total number of teeth and the difference in number of teeth. Therefore, since this wave gear device can obtain a large deceleration ratio with a small number of gears, it is widely used in precision machines and the like.

The torque detector 1 of the present embodiment includes the wave gear device 2, drive means such as a motor 3 which is connected to the input shaft (not shown) and drives the wave generator 23, and the wave gear device 2. Member 4 which is formed so as to be connected (of course, may be integrated) to an object to be detected (for example, a small-diameter screw), the circular spline 21 of the wave gear device 2, and the housing 31. And piezoelectric elements 71, 72 and 81, 82 interposed between and.

In this example, the circular spline 21 of the wave gear device 2 is not fixed to a fixed one such as a machine frame. Instead of this, the following structure is adopted as the rotation stopping mechanism of the circular spline 21. That is, on the outer circumference of the circular spline 21, there are formed a pair of outwardly projecting protruding portions 211 and 212 having a rectangular cross section, which are located on the housing 31 side of the wave gear device. It is inserted into a pair of grooves 311 and 312 formed at corresponding positions. Further, the widths of the grooves 311 and 312 in the circumferential direction are set to be larger than those of the overhang portions 211 and 212, and the side surface of each groove and the side surface of the overhang portion inserted therein. Between them, a pair of piezoelectric elements 71, 72 and 81, 82 are fitted, respectively.

Here, each piezoelectric element is set such that the strain direction thereof is substantially the same as the tangential direction of the circular plane at the mounting position.

In the torque detector 1 having this configuration, for example, when the output side member 4 is connected to the screw to be measured and the motor 3 is driven, a pressure corresponding to the rotational force transmitted to the screw side is generated. , Acts on the piezoelectric elements 71, 72, 81, 82. As a result, the piezoelectric element is distorted. A voltage corresponding to this strain can be obtained from these piezoelectric elements. Therefore, the rotary torque acting on the screw can be measured based on the output voltage of each piezoelectric element.

Although the motor 3 is used as the driving means in this example, other rotation driving means may be used, or manual rotation driving means such as a torque wrench may be used. In addition, in this example, in order to suppress the eccentricity of the circular spline in the radial direction when torque is applied and improve the torque detection accuracy, two pairs of piezoelectric elements are used to simultaneously obtain the output voltage. The piezoelectric element of is used. In order to further improve the torque detection accuracy, three or more pairs of piezoelectric elements may be used. However, basically one piezoelectric element may be used.

Further, in order to prevent the rotation of the circular spline 21 from being locked by a part other than the rotation stopping mechanism having the above-mentioned configuration, a slipping member is provided between the annular side surfaces on both sides of the circular spline 21 and the adjacent member. It is preferable to interpose. For example, the sliding material can also be used as the shim plate. Alternatively, thrust bearings may be inserted.

[0016]

[Effect of device]

 As described above, in the torque detector of the present invention, the piezoelectric element is inserted between the circular spline of the wave gear device and the fixed member, and the piezoelectric element is generated by the rotational force transmitted through the wave gear device. A strain is generated in the shaft and the rotational torque is measured based on this strain amount. Since the amount of strain of the piezoelectric element is on the order of a few micrometers, the rotational rigidity on the output side can be remarkably increased as compared with the case of inserting elastic rubber having a large amount of deformation as in the conventional case.

[Brief description of drawings]

FIG. 1 is a front view of a torque detector according to an embodiment of the present invention.

2 is a schematic cross-sectional view of a portion of the torque detector of FIG. 1 taken along line II-II.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Torque detector 2 ... Wave gear device 21 ... Circular spline 211.212 ... Overhang part for rotation stop 22 ... Flex spline 23 ... Wave generator 3 ... -Motor 31 ... Housing of wave gear device 311, 312 ... Groove for stopping rotation 4 ... Member 71, 72, 81, 82 ... Piezoelectric element

Claims (1)

[Scope of utility model registration request] 1. A torque detector used for measuring tightening torque of a screw, comprising: an annular rigid internal gear, a flexible external gear inside thereof, and
A wave gear device including a wave generator that flexibly bends the flexible external gear in the radial direction and partially meshes with the rigid internal teeth, and rotates the meshing position, and an input shaft of the wave gear device. Drive means for driving the wave generator by being connected to the member, a member connected to the output shaft of the wave gear device to be connected to an object to be detected, and within the rigidity of the wave gear device. A member comprising a piezoelectric element interposed between a gear and a housing, and a torque detector.