JPH0242631B2 - - Google Patents

Description

Detailed Description of the Invention "Industrial Application Field" The present invention prevents variations in the set torque, tightens screws with a constant torque, stops the motor when the set torque is reached, and simultaneously uses the reaction force of the motor to work. The present invention relates to an electric screwdriver equipped with a ball clutch portion that prevents the ball from being transmitted to other people.

``Prior Art'' A conventional electric screw tightening machine has a clutch mechanism that operates at a constant torque in order to transmit or not transmit the rotation of the motor to the screw tightening bit. The pawls on the engaging surface of this clutch mechanism are formed by milling, so it requires skill to manufacture.
In addition, because the processing is complicated, it is difficult to achieve a uniform finished surface.
As a result, there is a drawback that the set torque varies greatly depending on the machining accuracy of the meshing surfaces, and furthermore, the milling process is complicated and time consuming, which inevitably increases costs.

``Problems to be Solved by the Invention'' In view of these conventional drawbacks, the present invention eliminates the need for complicated claws for engagement in the clutch mechanism, eliminates the complicated milling process that requires skill, and The purpose is to prevent variations in the set torque by using balls with uniform machining accuracy in the clutch part, and to stop the motor at the same time as the clutch part is disengaged when the set torque is reached, thereby reducing the inertia of the motor and other parts. This reduces the amount of force transmitted to the worker's hands.

"Means for Solving the Problems" In order to achieve the above object, the present invention has a hollow motor shaft connected to a motor located on the axis center line, and provided at the lower part of a ball receiving shaft interlocked with the hollow motor shaft. A through hole is formed point-symmetrically in the cylindrical portion, a clutch ball having a diameter larger than the wall thickness of the cylindrical portion is accommodated in the through hole, and an upper portion is fitted into the cylindrical portion so as to be slidable in the axial direction. Ball accommodating grooves are formed point-symmetrically at the upper end of the cylindrical bit holder, and an engaging ball having a diameter larger than the wall thickness of the bit holder is accommodated in the ball accommodating groove. A pilot, which has a concave portion on the outer periphery of the lower part of the body connected to the small diameter portion having a head housed therein and biased by a spring from above, is fitted into the stopper attached to the bit holder so as to be slidable in the vertical direction. Then, a ball having a diameter larger than the wall thickness of the bit holder is accommodated in a small hole provided in the middle of the bit holder, and the ball that engages and disengages from the recess is pressed in the centripetal direction to reduce frictional resistance with the bit holder. A sleeve having a ring on the inner surface for increasing the torque is attached to the outer periphery of the bit holder so that it can be slidably pressed by a spring, and the sleeve is slidably inserted into the hollow motor shaft and biased downwardly by the spring to operate the motor. The lower end of the pilot pin is hooked to the head of the pilot in the stopper, and a spring is applied between the lower end of the cylinder of the ball receiving shaft and the locking ring fixed to the outer periphery of the bit holder, so that the bit holder is attached downward. The engaging ball and the clutch ball that engage in the circumferential direction are opposed to each other on the same plane, and a taper ring having a mortar-shaped taper opening is rotatably fitted to the outer periphery of the ball receiving shaft. The clutch ball is mounted by springing upward with a torque adjustment spring, and the engagement ball accommodated in the ball accommodation groove is opposed to the tapered opening via the clutch ball accommodated in the through hole of the cylindrical portion. .

``Operation'' A through hole is formed point-symmetrically in the cylindrical portion provided at the bottom of the ball receiving shaft, and the clutch ball accommodated in the through hole and the bit holder accommodated in the ball receiving shaft so as to be slidable in the axial direction. The driving force of the motor is transmitted or not transmitted to the bit holder by turning ON/OFF the ball clutch, which is made up of engaging balls housed in ball housing grooves provided point-symmetrically on the upper part.

When the tightening force of the screw reaches the set torque, the ball clutch section is disconnected, and at the same time, a tapered ring having a tapered opening that the clutch ball comes into contact with is lowered via a torque adjustment spring, and the sleeve is lowered by the tapered ring. The ball provided on the bit holder is moved in the radial direction, and the pilot is lowered by the elastic force of the spring.

As the pilot descends, the pilot pin also descends, and the operating pin is pushed down by the spring, releasing the pressure on the switch lever and turning off the limit switch, stopping the rotation of the motor.

"Example" Examples of the present invention will be described below.

In FIG. 1, an electric screwdriver 1 is comprised of a power input section 3 (to be described later), a drive section 4, a deceleration mechanism section 5, and a ball clutch section 6, which are provided in a main body 2 of a housing.

The power input section 3 is explained with reference to FIG. 1.
is a cord that connects to an external power source (not shown), and is attached to the upper end of the main body 2 together with a switch 12 that also serves to switch ON/OFF the power input and to switch forward/reverse rotation.

13 is a limit switch attached to a board 14 located inside the main body 2; 15 is an operator for operating the switch 13; 16 is a switch lever that is always in contact with the operator 15 due to the action of a spring (not shown); 17 is a switch inside the main body 2; A downwardly biased spring 19 is housed in a recess 18 provided at the upper center of the mounting plate, and the upper end of the operating pin 21 is housed in a recess 18 with a slightly larger diameter head 20 at the bottom. The switch lever 18 protrudes outside and is hooked to one end of the switch lever 16.

To explain the drive unit 4 with reference to FIG. 1, a hollow motor shaft 25 connected to a motor (not shown) housed in a casing fixed in the main body 2 passes through the center of the casing on an axial line, and extends from the center of the casing. A fan 26 for cooling the motor is attached to the upper end, and a bearing 2 is located at the center of a holder 27 fixed to the lower part of the drive unit 4.
8 supports the lower part of the hollow motor shaft 25, and the hollow motor shaft projects from below the holder 27.

The deceleration mechanism section 5 is explained with reference to FIG.
is a pinion fixed to the lower end of the hollow motor shaft 25;
32 is a cylindrical body 32 that is fixed to the inner surface of the holder 27 and has an internal gear 31 on the inner peripheral surface.
The cylindrical body 32 and clutch case 33 are fixed together. A plurality of planetary gears 34 are individually attached with pins 35 to a disk 37 formed integrally with a pinion 36 loosely fitted to a pilot pin 42 inserted through the hollow motor shaft 25, and the planetary gears meshed with the internal gear 31 and pinion 30. The gear 34 rotates and revolves around the pinion 30.

38 is a plurality of planetary gears meshing with the internal gear 31 and pinion 36 to rotate and revolve around the pinion 36; 40 is a boss located around the pilot pin 42 so as to be able to rotate together with the ball receiving shaft 45; A bearing 41 is mounted between the boss part 39 and the clutch case 33 using a pin that individually supports the planetary gear 34 on the part 39. A ball receiving shaft 45 loosely fitted onto a pilot pin 42 is fixed to the center of the boss portion 39, and the lower end of the pilot pin 42 protrudes from the lower surface of the shaft 45.

Next, the ball clutch portion 6 will be explained based on FIGS. 1, 2, and 6.

A stopper 47 of a pilot 53, which will be described later, is installed in a recess 46 provided from below concentrically with the hole located at the center of the ball receiving shaft 45. A spring 48 is biased from above to accommodate the pilot's head 49 in the stopper 47, and a small diameter portion 50 connected to the head is projected from below the stopper 47.
A concave portion 52 is formed on the outer periphery of the lower part of a body portion 51 having a slightly larger diameter and having a longer length formed continuously at the lower portion of the small diameter portion 50.
The pilot 53 with the formed shape is fitted into the bit holder 58 in the axial direction. A clutch ball 57 having a diameter larger than the wall thickness of the cylinder part 55 is accommodated in a point-symmetrically formed through hole 56 in the upper part of the cylinder part 55 provided at the lower part of the ball receiving shaft 45 so as to be able to move forward and backward in the radial direction. do.

58 is a cylindrical bit holder whose upper portion is slidably fitted into the cylindrical portion 55 of the ball receiving shaft;
A ball accommodation groove 59 is provided at the upper end of the bit holder 58.
are provided symmetrically with respect to the through hole 56. An engagement ball 60 having a diameter larger than the wall thickness of the bit holder is accommodated in the ball accommodation groove 59 so as to be movable forward and backward in the radial direction.
When the clutch ball 57 meets the small diameter portion 50 of
and the engagement ball 60 are aligned in the radial direction (FIG. 6), and the two are disengaged from each other in the circumferential direction.

A ball 62 having a diameter larger than the wall thickness of the bit holder 58 is accommodated in a small hole 61 provided in the middle of the bit holder 58, and is movable forward and backward in the radial direction. A accommodating portion 63 for accommodating a bit 95 is formed.
64 is a holding ball for holding the bit 95 in the bit holder 58, and is pressed in the centripetal direction by the leaf spring 65. A snap spring 66 fixed slightly above the leaf spring 65 of the bit holder 58
This prevents the bit holder from escaping from the clutch case 33.

In FIGS. 2 and 3, 70 is a tapered ring attached to the outside of the ball receiving shaft 45 so as to be vertically movable and rotatable. It comes into contact with a clutch ball 57 housed in a through hole 56 in the hole 55 . 73 is a through hole 75 provided vertically in a locking step 74 provided at the bottom of the clutch case 33.
The adjustment pin inserted therein rotates the adjuster string 76 screwed to the lower part of the clutch case 33 to move it up and down, and the lower locking ring 77 that engages with the adjustment pin 73 and the ball receiver shaft 45 are connected to each other. The set torque can be arbitrarily adjusted by adjusting the amount of compression of a torque adjustment spring 81 installed between a stepped portion 44 provided on the outer periphery of the section and an upper locking ring 80 fixed by a stop ring 79 via a ball 78. can.

A spring 83 is applied between the lower end of the cylindrical portion 55 of the ball receiving shaft and a locking ring 82 fixed slightly above the small hole 61 of the bit holder to urge it downward. A sleeve 84 for pressing the ball 62 accommodated in the hole 61 in the centripetal direction is attached so as to be slidable in the vertical direction, and a bit holder 58 is mounted on the inner surface of the sleeve 84.
A ring 85 is attached to increase the frictional resistance between the two.

Next, the operation of this embodiment will be explained.

When the bit 95 is inserted from below into the bit holder 58 shown in FIG.
The holding ball 64 is pushed out in the radial direction against the elastic force of the plate spring 65, and then the holding ball 64 is engaged with the circumferential groove formed on the outer periphery of the shaft rod by the elastic force of the leaf spring 65, and the bit 95 is attached to the bit holder 58. Hold.

In this case, the operating pin 21 and the pilot 53 are pressed down by the springs 19, 48, and the engagement ball 60 matches the small diameter portion 50 of the pilot 53 and does not protrude outward from the outer peripheral surface of the bit holder. Therefore, the engagement ball 60 and the clutch ball 57 are located on a straight line as shown in FIG. 6, and the clutch portion 6 remains in the OFF state.

Next, when the cord 11 is connected to an external power source and the switch 12 is turned on, the operating pin 21 and the pilot pin 42 are pushed down by the springs 19 and 48.
The switch lever 16 is also lowered, and the limit switch 13 is in the OFF state.

In FIG. 3, when the tip of the bit 95 is aligned with a slot (not shown) in the screw head and the main body 2 is pushed down, the bit holder 58 rises while compressing the spring 83. When the sleeve 84 rises due to the frictional resistance between the bit holder 58 and the sleeve 84, the ball 62 attached to the bit holder 58
is pushed out in the centripetal direction by the sleeve 84 and engages with the recess 52 of the pilot, and the pilot pin 42 rises against the force of the spring 48. Therefore, the head 49 of the pilot pin pushes up the operating pin 21 via the pilot pin 42 and against the spring 19 shown in FIG.
Push up to turn on the limit switch 13 and start driving the motor (not shown). The rotation of the motor is transmitted from the hollow motor shaft 25 to the reduction mechanism section 5, and then to the ball receiving shaft 45 via a group of gears forming the mechanism section 5.

3, 4, and 7, when the pilot 53 rises, the engaging ball 60 accommodated in the ball receiving groove 59 of the bit holder 58 is pushed out in the radial direction by the body 51 of the pilot which is connected to the small diameter portion 50. The clutch ball 57 has a torque adjustment spring 81
The tapered opening 71 of the tapered ring is pushed upward to the maximum extent by the elastic force of the tapered ring, which protrudes in the centripetal direction. The clutch ball 57 is engaged in the circumferential direction with an engagement ball 60 protruding in the radial direction of the bit holder 58, and the clutch ball 57 is engaged with the engagement ball 60 protruding in the radial direction of the bit holder 58.
Tighten the screw (not shown) by rotating the bit 95 fixed to the screw clockwise (Fig. 7).

In FIG. 4, when the screw tightened by the rotation of the bit 95 reaches the torque set by the torque adjustment spring 81, the clutch ball 57 that engages the engagement ball 60 in the circumferential direction is pushed out to the maximum in the radial direction. The clutch ball 57, which rotates together with the ball receiving shaft 45, moves to the outside of the engagement ball 60. The rotation of the ball receiving shaft 45 is not transmitted to the bit holder 58. Therefore, even if the ball receiving shaft 45 continues to rotate, no reaction is transmitted to the operator's hands.

The sleeve 84 is pushed down by the tapered ring 70, the centripetal pressure on the ball 62 is released, and the ball 62 is released from the recess 52 at the lower end of the pilot.
When released, the pilot 53 is pushed down by the elastic force of the spring 48 until the head 49 is latched to the stopper 47, the pilot pin 42 is also lowered, and the operating pin 21 is pushed down by the spring 19. , release the pressure on the switch lever 16, and release the limit switch 1.
Turn 3 OFF to stop the motor.

In this case, in FIG. 5, the engagement ball 60 again aligns with the small diameter portion 50 of the pilot and moves in the centripetal direction within the ball accommodation groove 59, and the clutch ball 56 within the through hole 56 is also pushed out in the radial direction. As a result, the torque adjustment spring 81 causes the tapered ring 70 to rise and the tapered opening 71 to move the clutch ball 57 in the centripetal direction.

In FIG. 9, the engagement ball 60 and clutch ball 57 are disengaged (the clutch is in a disengaged state);
When you lift the main body 2 and release the bit 95 from the screw,
The bit holder 58 is pushed down by the spring 83, and at this time, the sleeve 84 descends together with the bit holder 58 due to the frictional resistance between the ring 85 and the bit holder 58. When the sleeve 84 descends to a certain position, the sleeve 84 moves to the engagement step of the clutch case 33. 7
4 and stops descending. Further, only the bit holder 58 is successively lowered by the action of the spring 83, causing the ball 62 to protrude in the centripetal direction of the bit holder 58, and to fit into the recess 52 of the pilot to hold the pilot 53. Snap spring 6 fixed to the outer periphery of the lower part
6 is engaged with the upper end of a bush 67 interposed between the clutch case 33 and the bit holder 58, and the bit holder 58 is stopped from descending.

"Effect of the invention" The present invention has the following effects.

The ball clutch part that switches between transmitting or not transmitting the torque generated in the ball receiving shaft due to the rotation of the motor to the bit holder has a clutch ball engaged in a through hole provided in the cylindrical part of the ball receiving shaft, and the upper part of the bit holder. Since the balls are made of highly uniform balls with high machining accuracy, it is extremely easy to maintain a constant torque.

When the set torque is reached, the ball clutch consisting of the clutch ball and engagement ball is disengaged and the motor is stopped via the pilot pin, so the inertial force of the motor receiving shaft is not transmitted to the operator's hands, preventing fatigue. Work efficiency can be improved.

Ball machining is simple and highly accurate, making it possible to achieve mass production.Furthermore, the structure of this device makes it easy to replace the balls, making maintenance and inspection simple, increasing durability, and contributing to cost reduction.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention.
The figure is a longitudinal cross-sectional view of the whole, Figures 2, 3, 4, and 5 are cross-sectional views of main parts showing operating states in order, and Figure 6 is Figure 2A.
-A sectional view, Figure 7 is a BB sectional view in Figure 3,
Figure 8 is a sectional view taken along the line C-C in Figure 4, and Figure 9 is a cross-sectional view taken along the line C-C in Figure 4.
-D line sectional view. 2...Main body, 6...Ball clutch portion, 25...
...Hollow motor shaft, 42...Pilot pin, 45
... Ball receiving shaft, 48 ... Spring, 50 ...
Small diameter portion, 52... Recessed portion, 53... Pilot, 5
5... Cylindrical portion, 56... Through hole, 57... Clutch ball, 58... Bit holder, 59... Ball accommodation groove, 60... Engagement ball, 62... Ball, 7
0...Tapered ring, 71...Tapered opening,
81...torque adjustment spring, 82...locking ring,
83...Spring.

Claims (1)

[Claims] 1. A hollow motor shaft connected to a motor is located on the axial center line, and a through hole is formed point-symmetrically in a cylindrical portion provided at the bottom of a ball receiving shaft linked to the hollow motor shaft, and the cylinder is inserted into the through hole. a ball-accommodating groove is formed point-symmetrically at the upper end of a cylindrical bit holder that accommodates a clutch ball having a diameter larger than the wall thickness of the bit holder, and whose upper portion is fitted into the cylindrical portion so as to be slidable in the axial direction; An engaging ball having a diameter larger than the wall thickness of the bit holder is accommodated in the ball accommodating groove, and the head is biased from above by a spring and accommodated in a stopper attached to the upper part of the inside of the cylindrical portion of the ball receiving shaft. A pilot having a concave portion on the lower outer periphery of the body connected to a small diameter portion having a diameter is fitted into the bit holder so as to be able to slide vertically, and a ball having a diameter larger than the wall thickness of the bit holder is inserted into the middle of the bit holder. A sleeve is housed in a small hole provided in the recess and has a ring on the inner surface that presses the ball in the centripetal direction to increase the frictional resistance with the bit holder, and is slidable around the outer periphery of the bit holder. The lower end of the pilot pin for motor operation, which is attached by a spring and is slidably inserted into the hollow motor shaft and is biased downward by the spring, is hooked onto the head of the pilot in the stopper, and the ball is inserted into the hollow motor shaft. A spring is applied between the lower end of the cylinder of the receiving shaft and a locking ring fixed to the outer periphery of the bit holder to urge the bit holder downward, and the engaging ball and the clutch ball that engages in the circumferential direction are aligned. Tapered rings with mortar-shaped tapered openings facing each other on a plane are rotatably fitted onto the outer periphery of the ball receiving shaft, and are pushed upward by a torque adjustment spring to attach the rings, and the through holes in the cylindrical portion are fitted. The engagement ball housed in the ball housing groove and the taper opening are opposed to each other via the clutch ball housed in the bit holder, and when the torque of the bit holder reaches the set torque, the taper ring is lowered against the torque adjustment spring. The engagement ball is disengaged from the clutch ball that was pushed out in the radial direction, and the descending tapered ring lowers the sleeve and retreats the ball that is caught in the recess of the pilot in the radial direction, causing the spring to release. An electric screwdriver that uses force to lower the pilot pin along with the pilot and stop the motor.