JPS59227371A - Clutch device for electric driver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a clutch structure for determining the tightening torque of an electric screwdriver for automatically tightening screws, bolts, or nuts.

Conventional Structure and Problems In the clutch structure of a conventional electric screwdriver, as shown in FIG.
As shown in FIG. 2, in an electric screwdriver in which the driving force is transmitted to the clutch 4 through the clutch 4 and a predetermined screw tightening is performed with a bit 6, the driving member 6 that directly receives the driving force of the motor 2 has a plurality of cam ridges 6a. , a plurality of steel balls 8 are held on the side facing the cam ridges 6a of the driving member 6 of the driven member 7 which can slide on the driving member 6, and the steel balls 8 are pushed onto the cam ridges 6a by the elastic force of the torque spring 90. It was a pressure contact.

When the torque applied to the screw (not shown) of the bit 6 reaches a certain value, the steel ball 8 climbs the cam ridge 6a against the biasing pressure of the torque spring 9 and performs an operation to cut off the driving force of the motor 6. It has a structure. However, it is impossible to accurately allocate the plurality of cam ridges 6a with respect to the axis of the drive member 6 and to make the ridge heights uniform due to machining, and it is common for some error to occur. For this reason, a plurality of steel balls 8 do not mesh with a plurality of cam ridges 6a at the same time, and the repeated torque applied to the screw when the driving force is cut off fluctuates.

OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks, the present invention provides a clutch structure that corrects the machining dimensional accuracy of clutch component parts and improves the repeatability l/lux accuracy when the clutch is disengaged.

Structure of the Invention The present invention has a drive section that directly receives torque from a drive source;
A torque-responsive clutch structure consists of a driven member facing oppositely to this, and cam means interposed between the two, and the cam means maintains a predetermined clearance with respect to the axis of either the driving part or the driven member. The cam ridges formed on the driving member or the driven member or the steel balls are rotatably connected to each other, and the deviation in the allocation angle and axial ridge height with respect to the axis of each cam crest or steel ball is corrected by the free-moving cam means, and the torque response is improved. This has the unique effect of equalizing the torque value when the clutch torque is cut off.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows an outline of an electric screwdriver including an embodiment of the present invention, in which when a bit 1 is pressed firmly against a clutch 4. Reducer 3. A limit switch 1 is operated by a switch rod 10 interposed in a center hole of a motor 2, and power supplied from a power cord 11 enters the motor 2, causing the motor 2 to rotate. 12 is a switch for changing the direction of rotation of the motor, and 13 is an exterior cover.

In FIG. 3 showing the first embodiment, 14 is a camshaft (driving member), and a ring cam 16 is fitted onto this. Ball 16 climbing up and down cam mountain 15a of ring cam 15
A non-marring (driven member) 17 having in its groove
is slidably fitted onto the camshaft 14. ring cam 1
5 and ball 16 are cam means for cutting off the torque applied to the bit 6, and the ring cam 15 is rotationally connected to the cam shaft 14, but meshes with the shaft portion 14a with a predetermined clearance. The ball 16 rotates integrally with the reed hammer ring 17 in the groove 17a of the hammer ring 17. Reference numeral 18 denotes a bit holder that fits into the center hole of the camshaft 14, and a return spring 1 is inserted between it and the camshaft 14.
9 is intervening.

The bit holder 18 has a pawl receiver 21 that slides in the axial direction but is regulated in the rotating direction by a steel ball 20, and the pawl 21a at one end is connected to the pawl 17b at one end of the hammer ring 1.
It is designed to interlock.

Retaining ring 2 near the center of the pawl receiver 21 and bit holder 18
A reset spring 23 is biased between the two.

The left end surface of the lock cam 24, which is inserted into the center hole of the cam shaft 14 and the bit holder 18, is pressed onto the cam shaft 14.

A lock spring 26 is enclosed between the inserted camshaft dish 25, and the switch rod 10 is inserted into the center of the lock spring 26.
It extends at limit switch 1-1: in the figure. A steel ball 27 interposed in a horizontal hole of the bit holder 18 partially peeks out from the neck 24a of the lock cam 24. Reference numeral 28 denotes a clutch case that covers the clutch 4, and a torque spring 32 is biased between the inner surface of the clutch case and the non-marring ring 17 via a thrust bearing 29 and spring seats 30 and 31.

Since the torque adjustment mechanism and the bit attachment/detachment mechanism are the same as those of the conventional example, they will be explained with reference to FIG. Several pins 35 in 28 push the spring seat 31 as the torque adjustment nut 33 moves. 36 fits into the clutch case 28, and the knob spring 3 is inserted between the clutch case 28 and the clutch case 28.
A ring 4o is fitted to prevent the sleeve 39 from being pulled out. 41 is a stopper that is stuck in the knob 36.

Returning to FIG. 3, reference numeral 42 is a ring fitted to the camshaft 14;
43 is a steel ball for stopping the bit 6 from being removed. When the bit 6 is pressed against the screw, the pawl 21a of the pawl receiver 21 and the pawl 1 of the hammer ring 17 engage with each other. At this time, the movement of the switch rod 10 causes the limit switch 1 to operate and the motor 2 to rotate.

In FIG. 4, when the screw (not shown) reaches a certain torque, the bit 6, bit holder 18, and pawl receiver 21 stop, but the motor 2 still tries to continue rotating, so the torque is transmitted through the reducer 3. The driving force transmitted to the camshaft 14 also rotates the ring cam 15, causing the ball 16 to move around the ring cam 15.
The hammer ring 17 moves in the direction of the arrow a as it climbs the cam peak 16a. The hammer ring 17 pushes back the pawl receiver 21 at its right end. At this time, the steel ball 27 is moved by the pressure of the lock spring 26 that presses the O-tsuk cam 24 and enters the hole in the pawl receiver 21. At this time, the switch rod 1o returns to its original position and the limit switch 1 is turned off and the motor 2
stops. As shown in FIG. 5, when the hammer ring 1 moves onto the cam ridge 1ea, it moves again in the direction indicated by the arrow, while the pawl receiver 21 cannot return to its original position due to the action of the steel ball 2γ, so the pawl 17b , 21a are disengaged. In this state, transmission of the driving force to the bit 5 is completely cut off.

FIG. 6 is a cross-sectional view of the clutch portion showing a state in which the camshaft 14 and the ring cam 15 are engaged. Width B of camshaft 14
A concave portion having a width B2 of the ring cam 15 engages with the convex portion of the ring cam 1 to regulate the rotation direction. Also, the diameter D of the camshaft body 14a
1, the inner diameter D2 of the ring cam 15 has a predetermined clearance because of the relationship D2>Dl.

FIG. 7 also shows the positional relationship between the cam shaft 14 and the ring cam 15.
This shows a case where the opening angles of the two cam ridges 15a are shifted by θ1. The parts that make up the clutch have undergone, for example, NC milling or quenching and tempering processes, so there will always be some errors in the dimensions, and even if the parts are the same shape, the dimensions of each part will be slightly different. It is. In particular, the ring cam 15 having two cam ridges 15a tends to cause angular deviation and dimensional errors in the height of the cam ridges. In such a case, the ring cam 16 is eccentric to the camshaft 14 as shown in FIGS. 4 and 7, and the clearance with the body 14a of the camshaft 14 is adjusted so that the balls 16 hit the two cam ridges 15a evenly. It is designed to cause movement within the range.

Next, a second embodiment will be explained. In FIG. 8, 44 is a camshaft (driving member) that directly receives the driving force of the motor 2.
Ball 45 and ball 4 climbing up and down this cam mountain 44a
5, and a hammer ring 46 (driven member) and a ball guide 47 rotatably coupled constitute a cam means. Other components are completely the same as in the first embodiment. 8th
The figure shows a state in which the ball 45 has climbed the cam peak 44a, and FIG. 9 shows a state in which the hammer ring 46 has returned to its original position and the torque has been cut off. FIG. 1o is a cross-sectional view of the clutch portion showing the engaged state of the clutch nog 46 and the ball guide 47. A ball guide 47 having a width B4 is engaged with a concave portion having a width B3 of the /S summer ring 46 to regulate the rotational direction.

It has no clearance. Although FIG. 11 shows the relationship between the re-camshaft 44 and the ball guide 47, it shows the case where the opening angles of the two cam ridges 44a of the camshaft 44 are deviated by 02.Such a case As shown in FIGS. 8 and 11, the ball guide 47 is eccentric with respect to the camshaft 44, and the ball guide 47 is placed within the clearance range with the body 44b of the camshaft 44 so that the balls 45 evenly hit the two cam ridges 44a. The system is designed to cause movement.

Effects of the Invention As described above, the present invention is a ring cam in which the cam means between the camshaft (driving member) and the hammer ring (driven member) is separated from the camshaft, and the direction of rotation is regulated, but the shaft center is free to move. It consists of a ball fixed to the thermosetting ring, or it is separated from the thermosetting ring and the direction of rotation is regulated, but the axis can be freely moved! - Torque value C) that arises from machining errors in the allocation angle and height of multiple cam mounts.
Fluctuation.

In particular, as shown in Figure 12, the latch's blocking movement ('p
Torque T1 that occurs every time. It is possible to prevent the height of T2 by using the idle motion of the cam means and to stabilize the repetitive torque T as shown in Fig. 13. By widely applying it to the clutch mechanism of electric screwdrivers, it is possible to prevent Tightening nuts improves torque reliability and has significant industrial effects.

[Brief explanation of the drawing]

Fig. 1 is an overall view of an electric screwdriver showing an embodiment of the present invention, Fig. 2 is a sectional view showing a conventional clutch structure, and Fig. 3 is a clutch in a reset state showing the first embodiment of Fig. 1. 4 is a cross-sectional view showing the structure immediately before the torque cutoff in FIG. 3, FIG. 6 is a cross-sectional view showing the torque cutoff in FIG. 3, and FIGS. 6 and 7 are the same as in FIG. 3 and FIG. FIG. 4 is a cross-sectional view showing the cam means, FIG. 8 is a cross-sectional view of the clutch structure immediately before torque cutoff, showing the second embodiment shown in FIG. 1, and FIG. 9 is a cross-sectional view showing the second embodiment when torque is cut off. 10 is a cross-sectional view showing the steady state of the cam means of the second embodiment, and FIG. 11 is a cross-sectional view showing the cam means of FIG. 8 in a floating state. 14.44...Cam shaft, 16...Ring cam, 1θ, 45...Ho) v, 17, 4
6.../% merging, 47...ball guide. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 4
Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 also Figure 11

Claims (3)

[Claims] (1) In an electric screwdriver having a clutch that cuts off torque transmission from the drive source when the torque reaches a certain value, tightening is performed by connecting the drive member directly connected to the drive source, the driven member directly connected to the screw tightening tool, and the 1. A clutch device for an electric screwdriver, characterized by having a cam means interposed between both members and fitted so as to be freely movable with respect to the axis of at least one member. (2) The clutch device for an electric screwdriver according to claim 1, wherein the cam means is rotatably coupled to the drive member and has a ring shape having a cam ridge whose axis is movable with respect to the drive member. (3) A clutch device for an electric screwdriver according to claim 1, wherein the cam means is rotatably coupled to a driven member and has a steel ball holding structure whose axis is movable with respect to the driven member.