JPS6243734Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the structure of a clutch of a clutch-type tightening tool.

Many clutch-type tightening tools have been commercially available in the past, but they are: 1) When a predetermined tightening torque is reached, the clutch disengages, but the motor continues to rotate, and the clutch engages and disengages repeatedly; 2) The clutch disengages when a predetermined tightening torque is reached; When the torque reaches the specified tightening torque, the clutch disengages and the power supply to the motor is cut off, but the motor rotates due to inertia, and the clutch engages and disengages repeatedly for a while.3 When the specified tightening torque is reached, the clutch disengages. Although the power supply to the motor is cut off, since the motor continues to rotate due to inertia, a device other than the above-mentioned clutch is provided to cut off power transmission to the motor. etc. However, when the clutch repeatedly engages and disengages, the tightening tools 1 and 2 above cause the impact on the fastened object (e.g. screw).
The tightening force increases, making accurate torque management impossible. 3 required a power shearing device for the motor in addition to the clutch, and had the disadvantage that the structure was complicated.

An object of the present invention is to eliminate the drawbacks of the prior art described above and to enable simple and reliable control of tightening torque. An object of the present invention is to provide a clutch type tightening tool.

This invention focuses on the fact that the increase in tightening torque due to the inertia of the motor can be removed by stopping the rotation of the motor after the dog clutch is disengaged and before it is re-engaged. The structure of the nail is devised.

An embodiment of the present invention is shown in FIGS. 1 to 4.

In FIGS. 1 to 3, 1 is a motor, and 2 is a speed reduction device of a planetary gear mechanism. 3 is a fixed cam, which is the second idle gear 2a of the planetary gear mechanism 2.
is supported. The fixed cam 3 is provided with engaging pawls 3a and 3b having different rotation radii on the center line. 4 is a shaft, at one end of which a socket 6 for holding a driver bit 5 is connected and supported by a pink set screw 8, and at the other end a rotary plate 9 and 2 are connected.
A movable cam 11 consisting of two steel balls 10 is attached to a steel ball 12 so as to be slidable in the axial direction and to rotate together with the steel balls 12. The steel balls 10 are embedded on the center line of the rotary plate 9 with different rotation radii, and are pressed against the fixed cam 3 through the sleeve 14 and the rod 15 by the pressing force of the spring 13 for adjusting the tightening force, and are engaged with the fixed cam 3. has been done. 16 is a gear cover that houses each of the above-mentioned parts. 17 is a limit switch,
It is fixed to the gear cover 16, and is switched on and off by the sleeve 14 in response to the displacement of the movable cam 11.

The configuration of the electric circuit will be explained with reference to FIG. 20
21 is an operation switch for starting the motor 1, and 22 is a forward/reverse changeover switch for switching the direction of rotation of the motor 1. 23 is an NPN transistor, and when the operation switch 21 is turned on, the resistor 2
Since the base is energized by 4, it becomes conductive and supplies power to the motor 1. 25 is a thyristor, and when the limit switch 17 is turned on, the gate is heated through the resistor 26 and becomes conductive.
The base of the NPN transistor 27 is connected to the resistor 28,2
9 to turn on the NPN transistor 27 and energize the gate of the thyristor 30 to turn the thyristor 30 off.

When the NPN transistor 27 becomes conductive,
The base and emitter of the NPN transistor 23 are short-circuited, and the NPN transistor 23 is brought into a shut-off state, and power supply to the motor 1 is stopped. On the other hand, the thyristor 30 rolls and short-circuits the motor 1 via the resistor 31, so that dynamic braking is applied to the motor 1.

Next, the operation of each part during tightening work will be explained. In FIG. 1, the rotational force of the motor 1 is reduced by the planetary gear mechanism 2, and the engagement of the two steel balls 10 of the movable cam 11 with the engagement pawls 3a, 3b of the fixed cam 3 causes the rotating plate 9, shaft 4, and socket to be rotated. The signal is transmitted to the driver bit 5 via the screwdriver bit 6 and tightens a screw or the like (not shown). As the screw continues to be tightened and reaches a predetermined tightening torque determined by the pressing force of the spring 13, the angle of the engaging claws 3a, 3b, the radius of rotation, and the friction angle, the steel ball 10 tightens the engaging claws 3a, 3b.
The clutch is pushed out, and the dog clutch is disengaged, and the rotational force transmission of the motor 1 is sheared off. On the other hand, the sleeve 14 also connects the spring 13 through the rod 15.
Since the motor 1 is pushed out to the side, the limit switch 17 is activated, the thyristor 25 is turned off, and the power supply to the motor 1 is cut off.The motor 1 is stopped by dynamic braking, and the tightening of the screws, etc. is completed. This state is maintained until the operating switch 21 is turned off. (See Figure 4) Here, the engaging claws 3a and 3 of the fixed cam 3
b. Similarly, since the two steel balls 10 of the movable cam 11 have different rotation radii, they do not engage again until the fixed cam 3 has rotated about one rotation (360 degrees) after disengagement. The braking time of the motor 1, that is, the rotation angle of the fixed cam 3 after disengagement, is determined by the moment of inertia of the motor 1, the reduction ratio of the reduction gear, and the resistance value of the dynamic braking circuit. If the resistor 31 is selected so as to stop within one rotation, the screw can be tightened without re-engaging after the clutch is disengaged.

As shown in FIG. 5, when the clutch is disengaged, the rotation radii of the two steel balls 10 of the movable cam 11 are R ₁ and R ₂ (R ₁ > R ₂ ), the pawl 3a of the fixed cam,
If the angles of 3b are α and β, then the axial displacement X with respect to the relative rotation angle θ between the movable cam 11 and the fixed cam
The values of are X=R ₁・θtanα and R ₂・θ・tanβ, respectively.
Fixed cam pawl 3 so that R ₁ tan α = R ₂ tan β
By determining the angles of a and 3b and the rotation radius of the steel ball 10, the balance between the two pairs of meshing parts is maintained, the sliding of the movable cam 11 in the axial direction becomes smooth, and the repeatability of tightening torque control is improved. do.

As described above, according to the present invention, since the rotation of the motor can be stopped after the dog clutch is disengaged and before the clutch is re-engaged, the tightening torque can be reliably controlled.

[Brief explanation of the drawing]

FIG. 1 shows a longitudinal sectional side view of the essential parts of an embodiment of the clutch-type tightening tool according to the present invention. FIG. 2 is a sectional view taken along the line -- in FIG. 1. FIG. 3 shows the tightening tool of the embodiment shown in FIG.
FIG. 3 is a longitudinal side view showing a state in which the fixed cam and the movable cam are disengaged from each other. FIG. 4 shows an embodiment of the electric circuit of the clutch type tightening tool according to the present invention. FIG. 5 shows a developed view of a clutch portion according to an applied modification. 1... Motor, 3... Fixed cam, 3a, 3b
...Interlocking pawl, 4...Shaft (output shaft), 5...
...Driver bit (tip tool), 11...Movable cam, 13...Spring.

Claims (1)

[Scope of utility model registration request] It has a meshing clutch consisting of a fixed cam and a movable cam, and the fixed cam is attached to the motor output shaft so that it rotates integrally with the output shaft, and the rear end of the shaft that connects and supports the tip tool slides along the shaft axis direction. A movable cam is attached so as to rotate freely and integrally with the shaft, and the movable cam is crimped and engaged with the fixed cam by a spring whose pressing force can be adjusted, and a load greater than the set pressing force of the spring is applied to the tip tool. When the clutch is released, the dog clutch is disengaged, and a stop signal generating switch is provided that operates upon detecting the disengagement of the clutch, and the stop signal is used to cut off the power supply to the motor and apply braking to the motor. A clutch-type tightening tool characterized in that the meshing clutch has a plurality of meshing pawls having different rotational orbits.