JPH0716835B2 - Shock absorber in screw tightener - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a shock absorber in a power screw tightening machine for tightening a screw with a predetermined torque by eliminating the influence of inertia of a rotating part in the final stage of screw tightening. Regarding

<< Prior Art >> When the screw reaches the bottom in the final stage of screw tightening, the motor suddenly stops, but the inertia of the rotating portion of the motor is large, and therefore excessive tightening torque is applied to the screw.

In order to eliminate such inconvenience, conventionally, for example, in JP-A-62-255028, by using a planet cone, when the rotation of the driver bit stops, the reduction ratio becomes infinite and A device is disclosed which is adapted to provide a constant torque.

<< Problems to be Solved by the Invention >> However, this structure has a complicated structure such as using a planet cone, and there is a limit to miniaturization.

It is an object of the present invention to obtain a dynamic torque absorbing device which has a simpler structure and can be made compact.

<< Means for Solving the Problems >> A shock absorber in a power screw fastener according to the present invention includes an input shaft that receives a rotational torque from a motor; a driver bit supported so as to be rotatable by a limited angle with respect to the input shaft. An output shaft transmitting rotational torque to the input shaft; a spring pushing the output shaft against the input shaft in the tightening direction; a friction joint and a one-way clutch placed between the input and output shafts; The joint frictionally connects the input shaft and the output shaft so that the input and output shafts will slip relative to each other when a torque greater than a certain value is applied; the one-way clutch has the output shaft with respect to the input shaft. It is configured to allow free rotation only in the tightening direction.

<Operation> When the input shaft is rotated in the tightening direction, the output shaft is rotated through the friction joint, and the screw is tightened by the driver bit attached to the output shaft. When the screw bottoms, the rotation of the driver bit, and thus of the output shaft, stops, with which the friction joint slips and the input shaft continues to rotate further against the force of the spring, Due to friction loss, the input shaft will gradually rotate. Thus, the input shaft is coupled with the output shaft with a sufficiently reduced rotation speed after rotating by a limited angle. The input shaft thus joins the output shaft after deceleration, so that no shock force is exerted on the output shaft and thus the bit. The screw is finally tightened with a torque corresponding to the starting torque of the motor.

When the driver bit is removed from the screw, the one-way clutch is disengaged, the output shaft spins idle with the force of the spring, and it returns to the initial state, waiting for the next work.

<< Embodiment >> As shown in FIG. 4, the shock absorber 1 is used by being mounted between an electric motor 2 and a driver bit 3.

FIG. 1 is a vertical sectional view of the shock absorber, in which reference numeral 4 is an input shaft, which is connected to the shaft of the motor 2.
Reference numeral 5 is an output shaft, and a driver bit 3 is provided at the tip thereof.
Is attached.

The output shaft 5 is formed to be hollow except for the tip portion, and the input shaft 4 is rotatably supported in the output shaft 5 via a bearing 6. As the bearing 6, one that can bear not only a radial load but also a thrust load is used. Reference numeral 7 is a cap screwed onto the output shaft 5 so that the input shaft 4 does not come off.

A sleeve 8 is placed between the input shaft 4 and the output shaft 5, and a pin 9 is fixed to this sleeve. Input shaft 4
A spiral groove 10 with which the inner end of the pin 9 engages is formed around the periphery of the, while a linear groove 11 with which the outer end of the pin 9 engages is formed on the inner wall of the output shaft 5. It is formed in the axial direction.

A friction coupling 12 and a one-way clutch 13 are placed between the input shaft 4 and the output shaft 5. As shown in FIG. 3, the one-way clutch 13 has a sleeve 13a fitted around the input shaft 4, a groove 13b on the inner surface thereof, and a steel ball 13c in the groove. The depth of the groove 13b is not uniform in the circumferential direction but is shallow in the tightening direction. Therefore, when the input shaft 4 rotates in the tightening direction, the balls 13c move to the shallower side of the groove 13b and are tightly sandwiched, so that the sleeve 13a rotates together with the input shaft 4. When the input shaft 4 rotates in the opposite direction to the front, the ball 13c moves deeper in the groove 13b.
The sleeve 13a does not rotate (in other words, the sleeve can freely rotate in the tightening direction even when the input shaft is stopped).

The friction joint 12 is a friction shoe 12 attached to the output shaft 5.
The inner surface of the shoe is pressed against the sleeve 13a of the one-way clutch. Therefore, when the input shaft 4 rotates in the tightening direction, the sleeve 13a rotates, and the rotational force thereof is transmitted to the output shaft 5 via friction with the friction shoe 12a. When the rotation of the output shaft 5 is suppressed, the friction shoe 12a and the sleeve 13a slip,
The input shaft 4 idles. Reference numeral 12b is a screw for adjusting the pressure contact force of the shoe.

Reference numeral 14 is a torsion spring, the ends of which are fixed to screws 15 which are respectively set up in the caps 7 of the input shaft 4 and the output shaft 5, and bias the output shaft 5 against the input shaft 4 in the tightening direction. is doing.

When tightening the screw, the tightening torque is set by adjusting the voltage to be applied to the motor 2, and the tip of the bit 3 is engaged with the head groove of the screw to start the motor 2. Then, the input shaft 4 rotates, and the one-way clutch 13 and the friction joint are
The output shaft 5 turns through 12 and the screw is turned by the bit 3.

At the final stage of screw tightening (that is, when the screw reaches the bottom), the rotation of the driver bit 3 and thus the output shaft 5 is stopped, and the friction coupling 12 slips accordingly.
The input shaft 4 rotates while winding the spring 14 around it. During this, the input shaft 4 is braked by the friction shoe 12a, and the rotation speed of the input shaft 4, and thus the motor, gradually decreases. On the other hand, when the input shaft 4 idles in this way, the pin 9 fixed to the sleeve 8 moves along the spiral groove 10 of the input shaft 4, and eventually reaches the end of the groove 10, and the input shaft 4 stops. The output shaft 5 is connected to the input shaft 4, and the input shaft 4 also stops rotating.
It should be noted that when the input and output shafts are coupled in this manner, the input shaft is sufficiently decelerated so that no shocking torque is applied to the screw.

After the connection of the input / output shafts, the rotation speed of the motor is zero, so that the starting torque of the motor acts on the output shaft 4, whereby the screw is finally tightened. After tightening the screws, the power source of the motor 2 may be manually turned off, or it may be detected that the rotation of the output shaft of the motor has stopped and the current has become excessive and the power may be automatically shut off.

One-way clutch when driver bit 3 is removed from the screw
When 13 is cut off, the output shaft 5 idles due to the force of the spring 14 and returns to the initial state, waiting for the next work.

<Effect> According to the present invention, since the input and output shafts are connected by the friction joint and both shafts can be relatively rotated by a limited angle, at the final stage of screw tightening, Since the friction clutch slips to disconnect the input / output shaft, the input shaft is braked, and the input / output shaft is re-engaged after the rotation of the motor is sufficiently reduced, excessive torque is not applied to the screw. Further, unlike the conventional case, a complicated structure such as a planetary cone is not required, and the structure is simple, so that it can be provided at a low cost.

Furthermore, since it has a one-way clutch and a spring, when the bit is removed from the screw after tightening the screw, the output shaft returns to the original position and is ready for the next use.

[Brief description of drawings]

1 is a longitudinal sectional view of the shock absorber, FIG. 2 is a sectional view taken along line I-I of FIG. 1, FIG. 3 is a sectional view taken along line II-II of FIG. 1, and FIG. [Fig. 6] is an explanatory view of a usage state of the shock absorber. 1 ... shock absorber, 2 ... motor, 3 ... driver bit,
4 …… input shaft, 5 …… output shaft, 12 …… friction joint, 13 ……
One-way clutch, 14 ... Spring

Claims (1)

[Claims] 1. An input shaft (4) for receiving a rotational torque from a motor (2); an output shaft for transmitting the rotational torque to a driver bit (3) supported so as to be rotatable by a limited angle with respect to the input shaft. (5) ;; a spring (14) that pushes the output shaft against the input shaft in the tightening direction; and a direction that allows the output shaft to freely rotate with respect to the input shaft only in the tightening direction. Clutch (13); Power screw tightening consisting of a friction joint (12) placed between one of the input / output shafts and the one-way clutch, and slips when torque greater than a certain value is applied to stop transmitting torque. Shock absorber in the machine.