JPH0929654A - Constant axial force bolt fastening device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a strain generating part from breaking and improve the time of operation of a constant axial force bolt fastening device. SOLUTION: Planet gears 6 rolling around a center gear 4 mounted to a motor shaft 3 are mounted to a fastening shaft 5. A torque detecting body 11 is provided with an interlocking part 11c to fix an outer peripheral gear 7 meshing with the planet gears 6, while being provided with a fixing part 11e to fix the opposite side to the interlocking part 11c to a fastening device A of a non-rotary member through a thin thickness strain generating part mounting a strain gauge 14. Stopper pins 13 are erected on the interlocking part 11c to extend through the fixing part 11e so that clearance holes 11f forming a gap between themselves and the surrounding are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when tightening a tightening means such as a bolt, in order to make the tightening torque constant, when the tightening torque reaches a constant value, the tightening torque is fixed. The present invention relates to a constant axial force bolt fastening device for stopping the rotation of fastening means.

[0002]

2. Description of the Related Art An example of a conventional constant axial force bolt fastening device is shown in FIG. 3 and will be described below. A motor 2 as an output means is fixed to a case 1 mounted in the non-rotating fastening device A, and a center gear 4 is fixed to a motor shaft 3 which is an output shaft of the motor 2.

On the other hand, a fastening shaft 5 having a fastening jig for rotating fastening means such as bolts is axially supported in the fastening device A coaxially with the motor shaft 3, and the fastening shaft 5 The end surface on the motor 2 side is formed on an enlarged plane 5a, and a plurality of planet gears 6 having the same diameter and meshing with the central gear 4 are rotatably supported at positions on the same circumference.

On the outer periphery of the planetary gear 6, an outer peripheral gear 7 provided with a gear surface meshing with the inner periphery of the planetary gear 6 is an outer periphery of a torque detecting body 9 rotatably supported by a bearing 8 with respect to the motor shaft 3. The torque detector 9 is fixed to the case 1 via the thin strain element 9a. Therefore, the torque detector 9 has a fixed portion 9b.
b is non-rotating, and a strain gauge 10 is attached to the outer peripheral surface of the strain-flexing portion 9a.

In this fastening device A, when a fastening means such as a bolt is attached to a fastening jig and the motor 2 is rotated so as to be fastened to a fastened means such as a female screw or a nut, the motor shaft 3 is rotated. The rotation is transmitted to the planetary gear 6 to rotate it, but since the torque detecting body 9 is fixed to the case 1 by the fixing portion 9b, the outer peripheral gear 7 meshing with the planetary gear 6 becomes non-rotating, and therefore, The planetary gear 6 rolls around the central gear 4 while decelerating the rotation of the motor shaft 3 and transmitting the decelerated rotation to the fastening shaft 5.

However, when the rotation of the fastening means approaches the end of fastening and reaches a certain torque, it becomes difficult for the fastening shaft 5 to rotate and the planetary gear 6 cannot roll around the outer periphery of the center gear 5. , The planetary gear 6 tries to rotate the outer peripheral gear 7. Then, the torque detector 9 also tries to rotate together with the outer peripheral gear 7, but since the fixed portion 9b is not rotatable, the thin strain element 9a is twisted.

Therefore, the strain gauge 10 attached to the strain-flexing portion 9a generates a strain signal due to this twisting action, and the rotation of the motor 2 is stopped by the strain signal, and fastening with a constant torque is performed. It is a thing.

[0008]

Such a constant axial force bolt fastening device has the following features when tightening small diameter bolts and screws.
Since the tightening dynamic torque is small, the strain gauge 10
Has a small full-scale value, and its absolute overload capacity is also low. On the other hand, if many bolts are fastened in a short time, the motor speed will be increased and the time required for one fastening will be shortened.

At this time, if the fastening shaft 5 is not sufficiently decelerated when the fastening torque approaches a certain value, an excessive torque is transmitted to the fastening shaft 5 due to inertia of the rotor of the motor or the like. There is a risk of damage to the bolt. However, if the bolt is not damaged, the strain generating portion 9a of the torque detector 9 receives the excessive torque, and the strain generating portion 9a is twisted and damaged.

Thus, if the strain-flexing portion 9a is damaged, it is necessary to replace the constant axial force bolt fastening device as a whole, and not only the operating time is significantly lost but also the defective constant axial force bolt fastening device is repaired. Will also result in the drawback of losing time and effort.

The present invention is intended to solve the above-mentioned problems. An object of the present invention is to provide a means for preventing breakage of a strain-flexing portion in advance so that the operating time of a constant axial force bolt fastening device can be increased. In addition, the strain-flexing part is radially configured to prevent the strain-flexing part, and the tightening torque is changed and processed, and the gauge process is simplified.Furthermore, the circuit board is installed concentrically to further reduce the size. The purpose of the present invention is to provide a constant axial force bolt tightening device that can process the strain gauge wiring together with the board.

[0012]

SUMMARY OF THE INVENTION The constant axial force bolt fastening device of the present invention is intended to achieve the above-mentioned object. The means is a member fixed to a non-rotating member of a torque detector.
A gap between the stopper pin provided on either one of the member fixed to the reduction gear and the play hole in which the other is inserted, between the non-rotating member and the member to which the reduction gear is fixed. The maximum allowable strain is allowed, but if it exceeds the maximum allowable strain, the two will contact each other, and no further relative movement will take place. Damage to the strained portion is prevented.

Further, since the strain-flexing portion is provided in the radial direction, the strain generated therein bends the strain-generating portion, and this bending is the amount of strain allowable for the tensile strength that causes breakage. Is large, therefore, the difference from the allowable strain value to the fracture can be increased, and the risk of fracture of the strain-flexing portion can be reduced, and the length and thickness of the strain-flexing portion, the length,
Since the number of installations etc. can be set arbitrarily, changing the set torque,
Other processing can be simplified.

Further, since the circuit board connected to the strain gauge is attached so as to face the strain generating portion of the torque detector, signal amplification and other circuits can be incorporated therein, further downsizing and wiring It is possible to simplify.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, one embodiment of the present invention will be described below with reference to FIGS. 1 and 2, and the same parts as those in the conventional example of FIG. In this embodiment as well, the non-rotating fastening device A is provided with the motor 2 fixed to the case 1, and the motor shaft 3 of the motor 2 is provided with the central gear 4.

In the torque detector 11 having the fixing portion 11e fixed to the tip end of the fastening device A, the fastening shaft 5 for mounting the fastening jig is connected to the motor shaft 3 by the bearing 12 attached to the fixing portion 11e. The end surface of the fastening shaft 5 on the motor 2 side is coaxially supported, and the end surface on the motor 2 side is formed as an enlarged surface 5a. A plurality of planet gears 6 coaxially supported by the enlarged surface 5a mesh with the central gear 4. .

Outside the plurality of planetary gears 6, a plurality of protrusions 7a are formed on the inner peripheral surface of an outer peripheral gear 7 provided with gears meshing with these planetary gears on the inner periphery, and the protrusions 7a are formed on the torque detector 11. The interlocking portion 11c having a plurality of recesses 11a fitted to the outer periphery is formed, and the interlocking portion 1 of the torque detector 11 is formed.
1c is allowed to rotate in conjunction with the outer peripheral gear 7, and the torque detector 11 has a loose fitting portion 11b loosely fitted on the fastening shaft 5.

A stopper pin 13 is provided upright on the interlocking portion 11c of the torque detector 11 which is provided with the recess 11a and interlocks with the outer peripheral gear 7, and the loose fitting portion 11b and the interlocking portion 1 are provided.
Between 1c, there are a plurality of thin strain generating portions 11d in the radial direction.
Are formed, and strain gauges 14 are attached to both sides thereof. Further, the tip of the stopper pin 13 is bored in the fixing portion 11e, so that the stopper pin 1
3 is inserted into a play hole 11f having a size capable of forming a void around the circumference.

Further, a circuit board 15 which is connected to the strain gauge 14 and mounts a circuit for amplifying a signal output from the strain gauge 14 is attached to the loose fitting portion 11b so as to face the torque detector 11, and the strain gauge The rotation of the motor 2 is stopped by the output signal from 14.

In this constant axial force bolt fastening device, fastening means such as bolts are attached to the fastening jig of the fastening shaft 5, and the central gear 4 of the motor shaft 3 is rotated by the rotation of the motor 2. Then, in the torque detector 11 fixed to the non-rotating fastening device A1, since the concave portion 11a locks the protrusion 7a of the outer peripheral gear 7, the outer peripheral gear 7 also becomes non-rotating,
Therefore, the planetary gear 5 rolls around the center gear 4, and the fastening shaft 5 is decelerated and rotated to be fastened by the fastening jig.

However, when the fastening torque of the fastening shaft 5 reaches a predetermined value due to this fastening, the rotation of the fastening shaft 5 becomes heavy, and the planet gear 6 rolls around the center gear 4 due to the load. Therefore, the planetary gear 6 to which the rotation of the center gear 4 is transmitted tries to rotate the outer peripheral gear 7 by bending the strain-flexing portion 11d of the torque detector 11.

Then, the strain-generating part 1 caused by this action
The bending of 1d is detected by the strain gauge 14, and the control circuit of the motor 2 is controlled by, for example, amplifying the generation of a signal associated with this detection by the amplification circuit of the circuit board 15 to stop the motor 2 and tighten the bolts and the like. To finish.

In the bending of the strain-flexing portion 11d at this time, the bending-generation degree is large with respect to the tensile strength leading to breakage.
Not only is the risk of damage to d reduced, but due to the relative displacement of the stopper pin 13 and the play hole 11f due to the curvature, the stopper pin 13 comes into contact with the hole surface of the play hole 11e, and the strain-flexing portion 11d receives the tensile strength. Therefore, it is possible to prevent breakage of the strain-flexing portion 9a that has occurred in the related art, without giving a large curvature to the extent of breakage.

In the above-described embodiment, the strain gauge 14 is mounted on the wide surface of the strain-flexing portion 11d as the mounting surface, but it is mounted on the narrow surface of the strain-flexing portion 11d as the mounting surface. Alternatively, the strain-flexing portion 11d may be formed as a thin and wide surface in the circumferential direction, and the strain gauge 14 may be attached to this wide surface.

[0025]

As described above, according to the present invention, when the stopper pin provided between the fixing member formed before and after the strain-flexing portion and the member fixed to the reduction gear and the play hole come into contact with each other, the strain-generating force is generated. Since the strain applied to the part is prevented from increasing above a certain level and the breakage of the strain-flexing part is prevented, various problems due to the breakage of the strain-flexing part can be solved.

Further, since the overload protection mechanism is formed by the dimensions of the stopper pin and the play hole, it is easy to determine at what level the protection against overload should be operated. The strength of this mechanism depends on the stopper pin. It can be adjusted by the number.

Moreover, since the strain-inducing portion is provided radially from the center, the strain caused by the tightening torque appears as a curve in the thickness direction, and this curvature in the thickness direction causes the tensile strength to break it. In comparison, the degree of bending deformation that appears as strain is large, and since the strain gauge outputs at this degree of deformation, the strain-flexing part does not break, and even from this point, the constant axial force bolt tightening device fails. The cause of is removed.

Since the strain-flexing portion is formed in a radial shape, the processing and the strain gauge mounting process are simplified,
It is convenient to change the rated load for fastening by changing the thickness of the strain-flexing part, the length by changing the diameter, and the length in the axial direction.

Further, since the circuit board connected to the strain gauge is attached so as to face the strain generating section, wiring from the strain generating section to the circuit board is easy and batch processing is possible, and the constant axial force bolt is used. As compared with the case where the board is provided outside the fastening device, the size and cost can be reduced.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is a vertical sectional view of a conventional constant axial force bolt fastening device.

[Explanation of symbols]

 2 motor 3 motor shaft 4 center gear 5 fastening shaft 6 planetary gear 7 outer peripheral gear 7a protrusion 11 torque detector 11a recess 11b loose fitting portion 11c interlocking portion 11d straining portion 11e fixing portion 11f play hole 13 stopper pin 14 strain gauge 15 Circuit board

Claims (3)

[Claims] 1. An output shaft of an output means such as a motor, a reduction shaft means for attaching the reduction gear means to the output shaft and a fastening means such as a bolt, and a gear meshing with the reduction gear means. In a constant axial force bolt tightening device that has a thin strain element that is fixed and has a strain gauge attached, and a torque detector fixed to a non-rotating member, the torque detector is not rotated. A stopper pin is erected on either one of the non-rotating member attached to the member and the member to which the gear that meshes with the reduction gear means is fixed, and on the other one of them,
A constant axial force bolt fastening device, wherein the stopper pin penetrates and a play hole around which a void is formed is provided. 2. The torque detecting body, wherein one of a member fixed with a gear meshing with a transmission gear means and a non-rotating member attached to a non-rotating member is an outer peripheral side and the other is an inner peripheral side, and both of them are provided. Providing a thin strain element in the radial direction between
3. A strain gauge is attached to the strain gauge.
Constant axial force bolt fastening device described. 3. The constant axial force bolt fastening device according to claim 2, wherein a circuit board connected to a strain gauge is attached to the torque detecting body so as to face the strain generating portion of the torque detecting body.