JPS582036B2 - electric screw driver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric screw tightening machine that uses an electric motor as a drive source to tighten screws with constant torque.

Recently, there has been an increase in demand for screw tightening for resin products that requires control of screw tightening torque, and electric screwdrivers with electrical control have been attracting attention.
Conventional electric screwdrivers only stop the motor electrically, so they are unable to absorb the recoil that the worker receives when the motor stops.

For this reason, when tightening screws with high torque, the reaction force experienced by the worker is large, causing fatigue in the hands and shoulders.

Furthermore, in order to perform high-torque tightening with an electric screwdriver, it was necessary to considerably slow down the rotation of the bit and increase the motor torque, resulting in poor work efficiency. On the other hand, it had many problems as mentioned above.

In addition, with conventional pneumatic screwdrivers equipped with a shut-off clutch, the difficulty of finely adjusting the shut-off valve causes the motor to restart when the reset operation is performed after tightening, and the motor torque increases or decreases due to a drop in air pressure. This affected the tightening torque.

Furthermore, even with exhaust hoses, there is still a lot of noise and vibration during tightening, and in today's world where improvements in the assembly work environment are desired, this problem has been highlighted as an important problem.

In order to eliminate the above-mentioned problems, the present invention uses an AC power source that can be obtained even at home as a drive source, makes the drive motor smaller and more powerful, increases the bit rotation speed, and provides a tool for workers to tighten screws or nuts. The motor is rotated by the pressing action of the screwdriver, and when the screw tightening torque reaches a certain value, the electric motor is stopped by the action of a positive torque cutoff mechanism. In addition to significantly reducing
It eliminates the reaction caused by the moment of inertia of the motor armature that occurs immediately after tightening, unlike conventional electric screwdrivers, and stabilizes the timing at which the electric motor stop switch means turns off when the screw tightening torque reaches a certain value, making it reliable. This makes it possible to obtain highly repeatable tightening operations.

An electric screw tightening machine according to an embodiment of the present invention will be described below with reference to the drawings.

First, in Fig. 1 which is an overall view, a is a power supply unit,
b is a drive unit, c is a reduction unit, and d is a clutch unit.

In the power supply unit a, 1 is a driver cord, and an AC power outlet cap (not shown) is fixed to the tip of the driver cord.

2 is a switch that turns on and off the power and switches between forward and reverse rotation, and 3 is a hanger, each of which is fixed to the ceiling cover 4.

A resin plate 5 is adhered to the outer top surface of the ceiling cover 4.

Reference numeral 6 denotes a printed circuit board into which circuit components corresponding to the core of the power supply unit a are inserted, and a limit switch 7 is fixed to this.

8 is a stepped pin that operates the limit switch 7; 9 is a spring biased between the ring 10 fitted in the stepped pin 8 and the partition plate 11; this spring 9 causes the flange portion 8a of the stepped pin 8 to is in contact with the partition plate 11, and the lever 7a of the limit switch 7 is in contact with the head of the flange portion 8a of the stepped pin 8.

12 is a screw for fixing the two-split body force bar 14 that covers the entire screw tightening machine by joining together the ceiling cover 4 and the tip cover 13; 14a is a rib of the body force bar 14 for fixing the bulkhead plate 11; 15 is a printed circuit board The limit switch 7 is soldered and fixed to 6, the bracket is attached to the bulkhead plate 11, and 16 is the protective bush 1 of the driver cord 1.
This is the retaining ring of a.

In drive unit b, reference numeral 11 denotes a motor shaft, which is fitted into ball bearings 21 and 22 fitted into a bracket 19 fitted to the motor case 18 and another bracket 20, respectively, and a fan is attached to the protruding part toward the power supply unit a side. A fan 24 fixed to the boss 23 is fixed by a set screw 25,
On the other hand, a first sun gear 26 is provided at the end protruding toward the reduction unit side.
is fixed with adhesive.

The motor shaft 17 is tubular with a through hole in the center, and the head of the motor shaft 17 contacts the end surface of the stepped pin 8 in the through hole, and a switch rod 2 extending to the clutch unit d is inserted into the through hole.
7 is inserted.

28.28' is a nut that holds down the conductive ring 29.29'; 30. 30' is a lead wire from the switch 2 to the motor, which is connected to the conductive ring 29, 29'.

31, 31' are lead wire guide pins protruding from the main body cover 14.

14b is a hole provided in the main body cover 14 for discharging heat generated by the drive unit b by the fan 24, and the partition plate 11 also plays the role of blocking the hot air expelled by the fan 24 from affecting the power supply unit a.

In the reduction unit c, 32 is a first planetary gear made of a conductive material that meshes with the first sun gear 26 and the internal gear 33, and rotates around a pin 35 press-fitted into the first reduction shaft 34. Planetary movement centered on 26.

36 is a spacer made of a non-conductive material inserted between the bracket 20 and the internal gear 33, and 37 is a spacer made of a non-conductive material inserted between the first planetary gear 32 and the first reduction shaft.

A second planetary gear 38 meshes with a second sun gear 39 press-fitted into the first reduction shaft 34 and an internal gear 33 and rotates around a pin 41 press-fitted into the second reduction shaft 40 .

42 is a ball bearing that fits into the internal gear 33 and is fixed by a ring 43, and the second feed reduction shaft 40 is attached to the inner ring of the ball bearing 42.
is inserted.

The internal gear 33 is fitted into the bracket 20 so as not to rotate in the circumferential direction.

In FIGS. 1 and 2 showing the clutch unit d,
Reference numeral 44 denotes a clutch shaft, which is fitted into the second reduction shaft 40 and transmits driving force through a flat end portion of the clutch shaft 44.

45 is a lock spring biased between the lock cam 46 and the clutch shaft 44; 47 is a bit holder that fits onto the clutch shaft 44 and holds the bit 48 with a ball 49 and an elastic band 50; 51 is a lock spring that is applied to the clutch shaft 44; It is a hammer ring that is slidable in the axial direction and rotatably fitted through a large number of balls 52. One end has convex teeth 51a, and although it slides on the bit holder 47, it is It has a structure in which it meshes with a convex tooth 54a at one end of a clutch pawl receiver 54 that is fitted so as not to rotate.

A return spring 55 is biased between the bit holder 47 and the clutch shaft 44, and a reset spring 57 is biased between the clutch pawl receiver 54 and a ring 56 fitted into the bit holder 47.

A cap 60 into which a pusher 59 is press-fitted is also screwed into the clutch case 58 which is screwed onto the bracket 20 so as to fit with the internal gear 33 and also fit with the bracket 20 so that its axis is aligned with the clutch case 58. Several pins 61 are slidably fitted into the cap 60, with one end abutting a ring 62 and the other end abutting an adjustment nut 63.

A torque spring 64 is biased between the hammer ring 51 and the ring 62 via a ball 67 held by a spring seat 65 and a ball holding plate 66.

68 is a lock ball located between the lock cam 46 and the clutch pawl receiver 54, 69 is a stopper ball of the lock cam, and 70 is a presser ring for the stopper ball 69.

71 is a groove 51b between the clutch shaft 44 and the hammer ring 51
Ring 7 fitted into the clutch shaft with a ball interposed between
It is in contact with 2.

73 is a retainer for a large number of balls 52 interposed between the clutch shaft 44 and the hammer ring 51.

The relationship between the clutch shaft 44, the ball 11, and the hammer ring 51 is as shown in FIG. 71 to the outside, and this ball 71 pushes down the hammer ring 51 in the direction of arrow a as shown in FIG. 3b.

Reference numeral 14 denotes a ring fitted into the bit holder 41, which is in contact with the front end surface of the bush 59 when the bit holder 41 is stopped.

75 is a ring fitted into the clutch shaft 44, 76 is a screw that fixes the main body cover 14 and the tip cover 13, and 77 is a nut thereof.

Next, the effect will be explained.

In Fig. 1, the AC power supplied from the driver cord 1 is rectified by the circuit in the printed circuit board 6 in the power supply unit a, passes through the limit switch 7 and the switch 2, and is connected to the drive unit b by the lead wire 30, 30'. Supplied.

Then, the electric motor starts rotating, and the rotational force is transmitted to the deceleration unit c.

At the same time, the fan 24 also rotates to move the atmosphere through arrows V, ,
Inhale through the V2 and V3 routes, and move inside the motor using the arrow V4.
, V5, and the hot air inside the drive unit b is discharged to the atmosphere again.

When the first sun gear 26 starts rotating, the first reduction shaft 34
The first planetary gear 32 made of a non-conductive material, which is rotatably attached with a pin 35 to The rotation is the rotation of the motor shaft 17 that is decelerated.

Furthermore, a second planetary gear 38 is press-fitted into the first reduction shaft 34 and is rotatably attached to the second reduction shaft 40 by a pin 41 around the second sun gear 39 whose axis is aligned with the first reduction shaft 34. The rotation of the second reduction shaft 40 is caused by the planetary movement while meshing with the internal teeth of the internal gear 33.
As a result, the rotation of the motor shaft 17 is decelerated in two stages and taken out by the second deceleration shaft 40.

Here, in order to insulate the reduction part from the drive unit b, the internal gear 33 is fitted into the bracket 20 made of a non-conductive material so that their axes coincide with each other, and the first sun gear 26 which is adhesively fixed to the motor shaft 17 is fitted. The first planetary gear 32 rotating around the periphery is also made of a non-conductive material, and a spacer 37 made of a non-conductive material is interposed between the end face of the first sun gear 26 and the first reduction shaft 34.

Further, the switch rod 27 is also made of a non-conductive material so as to insulate the speed reduction unit c and the clutch unit d.

The first reduction unit composed of the first planetary gear 32, the pin 35, the spacer 37, the first reduction shaft 34, and the second sun gear 39 has a spacer 36 interposed between it and the bracket 20, so that the relative speed of each In addition to reducing the sliding friction that occurs, the first reduction unit is floated.

The teeth of the first planetary gear 32, the first sun gear 26, the internal gear 33, and the teeth of the second planetary gear 38, the second sun gear 39, and the internal gear 33 are shifted or reversed so that they mesh appropriately. The rush is set to the optimum value.

Therefore, the first deceleration unit performs a rotational movement smoothly while playing a self-centering role.

When the motor shaft 17 is decelerated in two stages by the deceleration unit c, the rotational force of the drive unit b is transmitted from the second deceleration shaft 40 to the clutch unit d. In the unpressed state before the screws are screwed together, the limit switch 7 is not energized and the motor does not rotate.

However, when the bit 48 is pushed in the direction of the arrow b for screwing as shown in FIG. Contact, lock cam 46
moves back against the lock spring 45, and the switch rod 27
is pushed down, the stepped pin 8 moves back against the spring 9, and the limit switch 7 is activated.

As a result, the electric motor begins to rotate, and the rotational force decelerated and amplified by the action of the reduction unit c is applied to the clutch shaft 4.
4, and the hammer ring 51 begins to rotate via the ball 71.

At the same time, the clutch pawl holder 54 moves back together with the bit holder 47 due to the elastic force of the reset spring 57.
The teeth 54a of the hammer ring 51 mesh with the teeth 51a of the hammer ring 51, the bit holder 47 begins to rotate via the clutch pawl receiver 54 and the ball 53, and a screw (not shown) connected to the bit 48 is screwed together. start.

The bit holder 47 stops moving in the direction of arrow b when its rear end surface contacts the front end surface of the clutch shaft 44, but the thrust load in the direction of arrow b is applied by the clutch shaft 44 to the inner ring of the ball bearing 42, resulting in a second deceleration. The structure is such that it does not affect the shaft 40 at all.

As shown in Figure 3b, when the screw is tightened, the clutch shaft 44
The peak portion 44a pushes the ball 71 outward, and the hammer ring 51 is pushed down in the direction of arrow a against the torque spring 64.

At the same time, the clutch pawl receiver 54 also moves against the reset spring 57, and the hollow portion 54b of the clutch pawl receiver 54 is positioned above the lock ball 68.

In this state, the lock cam 46 biased by the lock spring 45 pushes up the lock ball 68 with its slope 46a, causing the ball to fit into the cavity 54b.

As soon as this ball has been fitted, Fig. 3C
The switch spring 9 pushes back the switch rod 27 to cut off the current to the motor.

At the same time, the torque spring 64 causes the hammer ring 51 to drop the ball 71 onto the flat portion 44b of the clutch shaft 44 and return to its original position.

Therefore, the teeth 51a and 54a are disengaged and the driving force is completely cut off.

Therefore, when the motor is stopped, that is, when the screw is tightened, there is no reaction at all due to the moment of inertia of the motor armature that is applied to the operator's hand, and the noise is also extremely small.

When the bit is pushed back in the direction of arrow d by the elastic force of the return spring 55 from the state shown in FIG. 3C, the lock ball 68
is located above the trough 46b of the lock cam 46, and in this state, the lock ball 68 is easily depressed by the elastic force of the reset spring 57, returning to the state before screw tightening, that is, the state shown in FIG. 2a.

The ball 67 functions to reduce the friction caused by the relative motion between the hammer ring 51 and the torque spring 64.

To adjust the tightening torque, tighten the adjustment nut 63.
This can be done by moving the ring 62 with the pin 61 to compress the torque spring 64 and increase its elastic force.

In addition, in the above configuration, the power supply unit a1, the drive unit b, the deceleration unit c, and the clutch unit d are each unitized, so several types of units are prepared for each unit, and the types of screws to be tightened and when Each unit a depends on the size of the tightening torque.
By changing the combination of -d, screw tightening work can be performed efficiently and appropriately.

Moreover, if this electric screw tightening machine is used together with an automatic screw feeding device, its efficiency will be even higher.

As described above, the electric screw tightening machine according to the present invention rotates the motor by the pressing action of the tool when the operator tightens a screw or nut, and has a torque cutoff mechanism that is activated when the screw tightening torque reaches a certain value. By stopping the electric motor by the function of Eliminates recoil caused by moment,
Moreover, by keeping the bit rotational speed constant even when tightening with high torque, the efficiency of screw tightening work can be improved.

Furthermore, the above-mentioned shut-off clutch having the torque cut-off mechanism realizes a highly accurate tightening torque, and can fully meet expectations in terms of torque management, which is required in recent years.

Furthermore, in the electric screw tightening machine according to the present invention, the switch rod that slides through the hollow motor shaft operates the switch means to control the rotation of the electric motor.
The movement of the switch rod does not adversely affect the electric motor, etc., and stable on/off operation of the switch means can be obtained.
Because it provides reliable and reliable repeating motion, there is no need to worry about occupational diseases such as health flu, which has recently become a problem, and because the electric motor rotates only when necessary for tightening screws, there is no noise. Above all, the life of the electric motor, such as the brush portion, can be extended.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an electric screw tightening machine showing one embodiment of the present invention, FIG. 2 a is a sectional view showing a clutch unit and a limit switch in the same electric screw tightening machine, and FIG. Cross-sectional view taken along line A-A shown in Figure 2a, Figure 2C
is a sectional view taken along line B-B shown in Figure 2a, Figure 3a, b,
c is a cross-sectional view of main parts showing the operating state of the clutch unit and limit switch. 7......Limit switch, 13...
...Tip cover, 14...Body cover, 18...Motor case, 20...
......Bracket, 32...First planetary gear, 44...Clutch shaft, 45
......Lock spring, 46...
・Lock cam, 47...Bit holder, 51...Hammer ring, 51a...
......Teeth, 53...Ball, 5
4......Crunch pawl holder, 54a...
...Teeth, 55...Return spring, 57
......Reset spring, 58...
・・crunch case, 60・・・・・・・cap, 61・・・・・・・pin, 63・・・・・・・・・
・Adjust nut, 64...Torque spring, 68...Lock ball, 69...
・・・・・・Stopper ball, 71・・・・・・・・・
·ball.

Claims (1)

[Claims] 1. Electric motor having a hollow motor shaft 17;
, a switch means 7 for turning on and off the electric motor b, a drive clutch member 44 that receives the driving force of the electric motor b, a driven clutch member 51 that is slidable on the drive clutch member 44 in the axial direction, and both of the above. A torque-responsive clutch consisting of cam means 44b, 51b, 71 located between the clutch members, which performs a cam action and separates from each other when a set torque is reached, and the drive clutch member 4.
a bit holder 47 which is fitted into the bit holder 4 and is rotatable and slidable by urging a spring 55 between the bit holder 47 and the driven clutch member 5;
a second clutch member 54 having teeth 54a that mesh with teeth 51a provided in the second clutch member 54 and capable of sliding on the bit holder 47; a means 53 for rotationally coupling the bit holder 47 and the second clutch member 54; and the bit. A spring 57 biased in the axial direction between the holder 47 and the second clutch member 54
and the drive clutch member 4.
4 and the bit holder 47, a lock cam 46 which is slidable in the axial direction and has a spring 45 interposed between it and the drive clutch member 44, and a means 69 for regulating the forward movement of the lock cam 46 with respect to the drive clutch member. and a locking means consisting of a ball 68 interposed in the bit holder 47 between the lock cam 46 and the second clutch member 54; motor shaft 17
a switch rod 27 that is movable independently of the switch rod 27 and communicates with the switch means 7; a clutch case 60 that includes a bearing means 59 for the bit holder 47; the torque spring 64 and the enclosing case means 13;
．． 14, the electric motor b is started by the backward movement of the bit holder, and when the set torque is reached, the torque-responsive clutch is activated, the locking means is activated, and the electric motor is stopped by the movement of the switch rod 27. 2. According to claim 1, the two balls 68 interposed between the lock cam 46 and the second clutch member 54 make rolling contact with each other to smooth the locking operation. Electric screw tightening machine. 3. A driving clutch member 44 having a plurality of flat portions, a driven clutch member 51 having the same number of grooves 51b as the flat portions 44b of the driving clutch member 44 on its conical surface, and a groove 51b between the flat portions 44b and the grooves 51b. An electric screwdriver according to claim 1, which has a torque-responsive clutch comprising an intervening ball 71. 4. A patent characterized in that the front bearing means 59 of the electric motor b and the switch rod 27 are made of a non-conductive material, and the exposed parts are insulated by covering the whole with an exterior case 13, 14 made of a non-conductive material. An electric screw tightening machine according to claim 1. 5. The electric screw tightening machine according to claim 1, characterized in that a tilted body with a thick tip is provided between the electric motor covering part of the exterior case 13 and 14 and the clutch case part. 6. The electric screw tightening machine according to claim 1, wherein the outer shape of the outer case 13 and 14 is formed by two different symmetrical curved surfaces. 7 an electric motor b having a hollow motor shaft 17; a switch means 7 for turning on and off the drive motor b;
A driving clutch member 44 that receives the driving force of the electric motor b, a driven clutch member 51 that is slidable in the axial direction on the driving clutch member 44, and cam means 44b, 51b located between the two clutch members. 71, and a torque-responsive clutch that performs a cam action and separates from each other when a set torque is reached; and a bit holder that fits into the drive clutch member 44 and is rotatably slidable by biasing a spring 55 between them. 47, a second clutch member 54 which has teeth 54a that mesh with teeth 51a provided on the driven clutch member 51 and is slidable on the bit holder 47, and the bot holder 47 and the second clutch member 54. A dog clutch consisting of means 53 for rotational coupling, a spring 57 biased in the axial direction between the bit holder 47 and the second clutch member 54, and a lock cam 46 which is slidable in the direction of the drive clutch member and has a spring 45 interposed between it and the drive clutch member 44; a means 69 for regulating the forward movement of the lock cam 46 with respect to the drive clutch member; the lock cam 46 and the second clutch member; A locking means consisting of a ball 68 interposed in the bit holder 47 between 54 and 54; a switch rod 21 communicating with the switch means 7; and a bearing means 59 for the bit holder 47.
a torque spring 64 biased between the driven clutch member 51 and the clutch case 60, an adjustment nut 63 screwed into the clutch case 60, and a torque spring disposed within the clutch case 60. 64, and a case means 13.14 that surrounds the entire case means 13.14, and when the adjustment nut 63 is moved, the front end of the pin 61 presses the torque spring 64 to adjust the torque. Electric screw tightening machine.