JPS6051999B2 - Electric screwdriver torque adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a torque adjustment mechanism for an electric screwdriver.

As shown in FIGS. 9 and 10, the conventional torque adjusting device includes a flange 74 that holds a plurality of steel balls 73 at an end 72 of a transmission shaft 71, and a chevron-shaped protrusion facing the steel balls 73. A ratchet 7 having a spline groove 76 on its inner diameter is fitted onto the output shaft 78.

On the other hand, a disc 83 is provided at the end 82 of the frame 81 held by the split housings 79, 80, and a stepped guide cam 8 is provided on the inner end surface between the disc 83 and the housings 79, 80.
An adjustment cylinder 85 having a diameter of 4 is disposed adjacent to the adjustment cylinder 85, and the chevron-shaped protrusion 75 of the ratchet 77 is held by the flange 74 through a spring receiver 86, a clutch spring 87, and a thrust needle bearing 88. The steel ball 73 is pressed against the steel ball 73. In operation of this mechanism, the transmission shaft 71 is rotated by the rotational force of the motor, and the steel ball 73 is engaged with the chevron-shaped protrusion 75 under the support of the clutch spring 87 to rotate the output shaft 78.

When a constant torque is applied to the output shaft 78, the rotational force of the transmission shaft 71 causes the steel ball 73 to push the chevron protrusion 75 over the pressing force of the clutch spring 87, and moves the ratchet 77 in the axial direction. The power transmission between the output shaft 78 and the output shaft 78 is cut off. The set torque can be adjusted by rotating the adjustment tube 85, and the spring receiver 86 is guided by the stepped guide cam 84 of the adjustment tube 85 and moves in the axial direction, changing the amount of compression of the clutch spring 87. pressure changes,
Torque adjustment is performed. Further, the adjusting cylinder 85 is rotated to the maximum, the clutch spring 87 is fully compressed, the chevron-shaped protrusion 75 of the ratchet 77 comes into contact with the steel ball 73, and the axial movement of the ratchet 77 is blocked, resulting in the maximum rotational force of the motor. is transmitted to the output shaft 78.

In the above-described mechanism, when an impact load is applied to the output shaft 78, the steel ball 73 held by the flange 74 may fall off.

Further, when the adjustment cylinder 85 is rotated to the maximum and the axial movement of the ratchet 77 is blocked, the spring receiver 86 and the disk 83 are elastically deformed, and the fully compressed clutch spring 87 causes a buckling phenomenon. It may become impossible to prevent the ratchet 77 from moving in the axial direction, and the transmission shaft 71 and output shaft 78 may become disconnected. On the other hand, since the chevron-shaped protrusion 75 of the ratchet 77 is bent and stands up against the side surface of the ratchet 77, it comes into point contact with the copper ball 73, causing impact when engaging or crossing over, making the operation unstable. There is a problem that wear resistance decreases. SUMMARY OF THE INVENTION An object of the present invention is to provide a torque adjusting device that eliminates the above-mentioned drawbacks of the prior art, and also stabilizes the operation and increases reliability.

That is, in the present invention, an engaging part in the form of a chevron-shaped protrusion is provided at the intermittent part of the transmission shaft and the output shaft, so that the power is interrupted by the frictional force of the slope of the chevron-shaped protrusion, and the maximum torque is transmitted. The boss of the spring receiver is brought into contact with the boss of the ratchet in order to ensure a secure connection during operation.

In addition, the involute spline joint was used to connect the output side flange of the differential planetary gear reduction section and the output shaft, paying attention to the fact that self-alignment improves when a transmission shaft is added. An electric screwdriver to which an embodiment of the present invention is applied is shown in FIGS. 1 to 8 below.

As shown in Fig. 2, a battery section 4 is disposed at the rear end of the housings 1, 2 inside the housings 1, 2, which are split-type outer frames in which a handle section 3 is provided in the middle of the body. A switch 5 is arranged at 3, and a chuck handle 6 is housed at the bottom. A motor 7 is disposed in the intermediate portion, and a torque adjustment device 8 of the present invention and a differential planetary gear reduction portion 9 are provided at the front end. The split-type housings 1 and 2 are screwed together at two places, and furthermore, the rear end is tightened with a band 11 which also serves as an attachment for a hanger 10. In the differential planetary gear reduction section, as shown in FIGS. 3 and 4, the rotational force of the motor 7 is transmitted to the output shaft 14 by a two-stage planetary gear reduction mechanism. Motor 7 with pinion 15 press-fitted onto motor shaft 16
The front end surface 18 of the motor 7 is fixed to the motor bracket 17 with screws 19. On the other hand, the motor bracket 17 is fixed to the gear case 20 with screws 21. A sun gear 23 having an internal gear portion 21 and a chevron-shaped protrusion 22 is rotatably disposed inside the gear case 20.
A first planetary gear part 25 having a transmission gear 24 therein meshes with a second planetary gear part 27 having an output flange 26, and an involute spline joint 28 formed on the inner diameter of the output flange 26 connects the output shaft 14. are connected to each other, and a drill chuck 12 is attached to the front end of the output shaft 14.

The pinion 15 press-fitted onto the motor shaft 16 is connected to the first
The transmission gear 24 of the second planetary gear 25 meshes with the second planetary gear 27 at the center to transmit power. Incidentally, thrust plates 30 and 31 are interposed between the motor bracket 17 and the first planetary gear 25 and between the transmission gear flange 29 of the first planetary gear 25 and the second planetary gear 27, respectively. Supports directional loads. The front end of the output shaft 14 is held by the adjustment tube 33 via a ball bearing 32, and the rear end is supported by a metal 34 press-fitted into the front end of the sun gear 23. At the periphery of the front end surface of the sun gear 23,
A plurality of chevron-shaped protrusions 22 are formed in the axial direction, and the chevron-shaped protrusions 2
A ratchet 36 having a chevron-shaped protrusion 35 of the same shape formed on the periphery of the surface is disposed opposite to the chevron-shaped protrusion 35, and the pressing force of a clutch spring 37 presses the surface formed by the chevron-shaped protrusion.

A front end portion of the clutch spring 37 is supported by a spring receiver 38 . In addition, the front end of the gear case 20 has a plurality of recesses 39 formed on its inner circumferential surface, and a ratchet 36 and a spring receiver 38 having protrusions 40 formed on the outer circumferential edge corresponding to the recesses 39 are arranged in the axial direction. They are fitted so that they are movable but not rotatable. On the other hand, J
forms a step-like guide cam 41, and since both are in contact with each other, by rotating the adjustment tube 33, the step-like guide cam 41 can be set out of phase with respect to the spring receiver 38. The offset spring receiver 38 is moved in the axial direction.

The two gear case 20 is fixed to the housings 1 and 2 with screws 42, and the adjustment cylinder 33 is fitted on the front outer peripheral surface of the gear case 20.
The rear end portions of the housings 1 and 2 are clamped and fitted. Note that the rotation of the adjustment cylinder 33 is inhibited by the engagement with the locking portion 60 with the gear case 20, thereby restricting the rotation range. In the above mechanism, the torque adjustment operation is as follows.

That is, the rotational force of the pinion 15 press-fitted onto the motor shaft is transmitted to the first planetary gear 25 and the second planetary gear 27.
is transmitted to rotate the output shaft 14. In this case, output shaft 1
4, when a certain torque is applied, the sun gear 23 receives a reaction force and tries to rotate, but the sun gear 23 engages with the chevron-shaped protrusion 22 formed on its front end surface and the chevron-shaped protrusion 35 of the ratchet 36. Can't rotate. deer. and output shaft 14
As the torque of increases, when a constant torque is reached,
The locking portion formed by the chevron-shaped protrusions 22 and 35 is connected to the clutch spring 37.
Overcoming the pressing force, the ratchet 36 is moved in the axial direction and removed, and the output shaft 14 stops rotating while being subjected to a constant torque. This torque adjustment is achieved by moving the spring receiver 38 in the axial direction by rotating the adjustment cylinder 33, and then moving the clutch spring 37.
The pressing force is changed and adjusted by changing the amount of compression. Next, the effects of the present invention will be explained.

1) A chevron-shaped engagement portion is provided at the intermittent portion of the sun gear 23 and the ratchet 36, and the engagement portion is locked and operated by the slope 43 of the projection, thereby stabilizing the operation and improving wear resistance.

In addition, by making the rising angle of the chevron-shaped protruding surface different in the forward rotation direction and the reverse rotation direction, the transmitted torque during turning and reverse rotation can be changed. 2) When the spring receiver 38 is moved to the ratchet 36 side by the maximum amount by rotating the adjustment cylinder 33, the gap 46 between the boss end face 44 of the spring receiver 38 and the boss end face 45 of the ratchet 35 is almost eliminated. Since the boss portions 47 and 48 are projected, the ratchet 36 cannot be moved in the axial direction even if the torque of the output shaft 14 increases.

Therefore, the sun gear 23 also cannot rotate and a state in which torque cannot be adjusted can be achieved. 3) Portion 4 that pivotally supports the sun gear 23
A planetary gear reduction part 9 is installed inside a gear case 20 which is integrally molded and has a recess 39 formed on the inner peripheral surface so that the ratchet 36 and spring receiver 38 fit together and cannot rotate.
and torque adjustment mechanism 8 are provided, and the shaft support of the rear end portion 50 of the drive shaft is supported by the metal 34 press-fitted into the small inner diameter portion 51 of the front end of the sun gear, so that the holding accuracy of the drive shaft 14 is improved. Since the deflection of the drill chuck 12 is reduced and the outer diameter of the torque adjustment mechanism section 8 can be made small, the bit 13 held at the tip of the drill chuck 12 during work can be reduced.
The tip has the effect of being easy to recognize and easy to use. 4) Since the output flange 26 of the planetary gear reduction section 9 and the output shaft 14 are connected by an involute spline joint, the planetary gear reduction section 9 and the torque adjustment mechanism section 8 are connected.
Since it can be divided into parts, each part can be assembled at the time of assembly, making assembly easier.

Furthermore, assembly costs can be reduced because partial assembly is possible. A similar effect can be expected in disassembly and repair. Furthermore, by adopting an involute spline joint, self-aligning properties work, and the second planetary gear 27 meshes smoothly with the sun gear 23, preventing uneven contact between the tooth surfaces, resulting in longer life and lower meshing noise. It has the effect of becoming. (5)
A portion that pivots to the front end portion 53 of the housings 1 and 2 is provided on the outer diameter portion 52 of the rear end of the adjustment tube 33, and is supported so as to be sandwiched between the housings 1 and 2, thereby reducing the number of parts to be attached to the adjustment tube 33 and reducing costs. You can measure the reduction.

Furthermore, since the fitting portion 54 between the inner diameter of the adjustment cylinder 33 and the outer diameter of the front side of the gear case 20 can be made longer in the axial direction, the holding accuracy of the adjustment cylinder 33 is improved, and play is reduced, so that the output shaft 14 It can prevent rattling. Further, since the entire torque adjustment section 8 is covered with the adjustment tube 33, there is an effect that the dust resistance of the torque adjustment section 8 is improved.

[Brief explanation of the drawing]

Fig. 1 is an external side view of an electric screwdriver to which an embodiment of the present invention is applied, Fig. 2 is a partially vertical side view thereof, and Fig. 3 is a second
The detailed longitudinal side view of the torque adjustment section and the differential planetary gear reduction section shown in the figure shows a state where the tightening torque is at its lowest. Fig. 4 is a detailed vertical side view of the torque adjustment section and differential planetary gear reduction section shown in Fig. 3, showing a state where torque adjustment is not possible. Fig. 5 is an exploded perspective view of the torque adjustment section and differential planetary gear reduction section. Fig. 6 ψIn is a sectional view taken along the line A-A in Figs. 3 and 4, Fig. 7 is an enlarged side view showing the engaged state of the chevron-shaped protrusions of the sun gear and ratchet, and Fig. 8 is the output flange. FIG. 9 is a longitudinal sectional side view of a conventional torque adjusting section, and FIG. 10 is an exploded perspective view of FIG. 9. In the figure, 1 and 2 are housings (outer frames), 7 is a motor, 8 is a torque adjustment section, 9 is a differential planetary gear reduction section, 1
4 is the output shaft, 20 is the gear case, 22 is the chevron-shaped protrusion, 2
3 is a sun gear, 26 is an output flange, 28 is an involute spline joint, 32 is a ball bearing, 33 is an adjustment tube, 34 is a metal, 35 is a chevron projection, 36 is a ratchet, 37 is a clutch spring, 38 is a spring receiver, 39 40 is a concave portion, 41 is a guide cam, 46 is a gap, 47
48 is the boss of the spring holder, 49 is the boss of the ratchet, and 49 is the boss of the ratchet.
55 is the outer diameter portion of the sun gear; 55 is the peripheral edge of the front end surface of the sun gear;
Reference numeral 56 represents a peripheral edge of the rear end surface of the ratchet, and reference numeral 57 represents a fitting portion between the adjustment cylinder and the spring receiver.

Claims (1)

[Scope of Claims] 1. A clutch mechanism that suppresses the rotational force of a motor housed in an outer frame from the sun gear of a differential planetary gear reduction device and applies a constant torque to an output shaft attached to the output side of the reduction device. In the electric screwdriver with an attached electric screwdriver, a plurality of chevron-shaped protrusions 22, 22, .
The rear end surface peripheral edge part 56 is provided with protrusions 35, 35, .
A clutch spring 37 is provided adjacent to the ratchet 36 for pressing the projections 22, 35 into contact with each other, and a clutch spring 37 is provided adjacent to the ratchet 36. , an adjustment tube 33 for adjusting the biasing force of the clutch spring 37 is pivotally connected via a spring receiver 38 that supports the clutch spring 37, and the spring receiver 38 and the adjustment tube 3
Step-shaped guide cams 41, 41 are molded on the engagement portion 57 with the spring receiver 38, and a plurality of radial convex portions 40, 40, . . . are molded on the outer peripheral portion of the spring receiver 38. Adjustment tube 33
A torque adjusting device characterized in that the biasing force of the clutch spring 37 can be adjusted by a rotational operation. 2 pivotally supports the outer peripheral portion 49 of the sun gear 23, and
A gear case 20 whose inner diameter is integrally formed with a recess 39 that fits into the radial convex portion 40 of the ratchet 36 and spring receiver 38.
The sun gear 23, ratchet 36, clutch spring 3
7.Claim 1, which is formed by gripping the spring receiver 38
Torque adjustment device as described in section. 3 The front end of the output shaft 14 is connected to a ball bearing 32.
The rear end portion is supported by a metal 34 that is press-fitted into the inner circumferential surface of the sun gear 23.
2. The torque adjusting device according to claim 1, wherein the output flange 26 of the differential planetary gear reduction device is fitted with an involute spline joint 28. 4 When adjusting the pressing force of the clutch spring 37 by moving the spring receiver 38 in the axial direction using the adjustment cylinder 33 and the stepped guide cam 41 of the spring receiver 38, the maximum rotational force of the motor 7 is adjusted to the output. In order to transmit to the shaft 14,
The boss portion 48 of the ratchet 36 facing the boss portion 47 of the spring receiver 38 is pressed so that the sun gear 23 and the chevron-shaped protrusions 22, 35 of the ratchet 36 cannot be separated when the maximum rotational force is applied. A torque adjusting device according to claim 1, which is in contact with the torque adjusting device of claim 1.