JP3114042B2 - Power tool brake mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power tool for transmitting torque from an output shaft of a motor to a spindle via a speed reduction mechanism, and more particularly to a brake mechanism which operates when a motor rotating at a constant speed is stopped. .

[0002]

2. Description of the Related Art As a conventional brake mechanism, for example, a brake / clutch device disclosed in Japanese Patent Application Laid-Open No. 58-71109 is known. According to the present invention, for example, when a sharp load is applied to the blade at the time of cutting, a problem occurs in which the circular saw rebounds toward the handler due to reaction (kickback). This is to stop the rotation. A coil spring is interposed between the drive cylinder to which the rotational force is transmitted from the motor shaft and the spindle that rotates the blade, and the drive is transmitted from the motor to the spindle. Above all, the rotation of the coil spring is stopped directly to cut the torque transmission from the drive cylinder to the spindle, and the drive shaft is stopped by friction with the coil spring forcibly stopped.

[0003]

In the above-mentioned conventional apparatus, the coil spring used for coupling between the drive cylinder and the spindle is used as an emergency brake that acts at the time of kickback. Even if the motor is stopped by an electric brake, there is no effective stopping means to the blade because the coil spring only connects the drive cylinder and the spindle, and the motor stops when the blade is particularly large in diameter. Even if the blade continues to idle due to the inertial force, the shift to the next operation is delayed by that amount, and the workability is reduced. Further, the brake mechanism itself is complicated and many components are added to the tool, which leads to an increase in cost.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a brake mechanism which has a simple structure and effectively stops a spindle. The brake mechanism comprises a coaxial cylinder through which a spindle penetrates in a main body housing. The spindle is provided integrally with a shaft portion adjacent to the cylinder portion in the axial direction, and a coil spring wound in the opposite direction to the rotation direction of the spindle is provided between the cylinder portion and the shaft portion. The coil spring is provided with an urging means capable of arbitrarily changing its diameter,
By changing the diameter of the coil spring by the urging means to increase or decrease the winding force of the coil spring applied to the cylindrical portion of the main body housing and the shaft portion of the spindle, more preferably the urging means A gear attached to the outer periphery of the coil spring, meshing with the output shaft of the motor, and engaging one end of the coil spring with a gear set to rotate faster than the speed reduction mechanism, is configured with the rotation of the output shaft of the motor. The rotation of the gear rotates the coil spring in the expanding direction, and increases or decreases the winding force of the coil spring applied to the cylindrical portion of the main body housing and the shaft portion of the spindle according to the difference in the number of rotations between the gear and the spindle. That is to say.

[0005]

When the diameter of the coil spring is enlarged by the urging means when the power is turned on, the winding force of the coil spring is not transmitted to the shaft portion of the spindle, and the spindle rotates at a constant speed via the speed reduction mechanism. When the diameter of the coil spring is reduced by the biasing means by turning off the power supply, a force is applied in a direction in which the coil spring is retracted due to friction between the coil spring and the shaft portion of the rotating spindle, and the winding force is increased. The cylinder and the spindle shaft are gradually grasped and the spindle stops.
If the biasing means is a gear locked to the coil spring, the rotation speed of the gear is faster than that of the spindle when the power is turned on due to a difference in rotation setting, and the coil spring is urged in the expanding direction by locking with the gear. Therefore, the winding force of the coil spring is not transmitted to the main body housing cylindrical portion and the spindle shaft portion. Then, when the power is turned off and the motor decelerates,
The gear and the coil spring also decelerate similarly, but when the rotation of this gear becomes the same speed as the spindle rotating by inertia and reverses,
A force is applied to the coil spring in the direction of winding and contracting due to friction between the coil spring and the spindle shaft, the winding force of the coil spring is increased, and the main body housing cylinder and the spindle shaft are gradually grasped and the spindle stops.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIGS. 1 to 3 show an embodiment in which the brake mechanism of the present invention is applied to a circular saw machine. In the circular saw machine 1, a motor shaft 4 of a motor 3 built in a motor housing 2 is a ball bearing. 5, and protrudes into the gear housing 6. On the side of the motor shaft 4, a spindle 9 is supported by ball bearings 7, 8.
The gear 10 is loosely fitted to the rear of the motor shaft 4 so that the teeth 10a mesh with the pinion 4a at the tip of the motor shaft 4. An inner flange 13 and an outer flange 12 holding the disc-shaped blade 11 in the blade cover 11a are inserted into the tip of the spindle 9, and both flanges 12, 13 are bolts screwed to the tip of the spindle 9. It is fixed to the spindle 9 by 14 and a washer 15. On the other hand, inside the gear housing 6, the gear 10 has an inner cylindrical portion 16.
However, a large-diameter portion 17 is provided substantially at the center of the spindle 9, and a ring-shaped groove 20 whose inner diameter portion 21 matches the diameter of the large-diameter portion 17 is formed in the inner cylindrical portion 16. The gear 10 is restricted from moving in the spindle axial direction between the large diameter portion 17 and the ring 18. The large diameter portion 17 and the groove 2
A coil spring 19 having a rectangular cross section is wound clockwise slightly larger than the large-diameter portion 17 around the inner cylindrical portion 21 between the outer periphery of the inner diameter portion 21 and the zero. The inner diameter of the coil spring 19 is set slightly smaller (−0.3 mm) than the diameter of the groove inner diameter portion 21 and the large diameter portion 17 of the spindle 9, and the coil spring 19 is integrated with the inner cylindrical portion 16 with the rotation of the gear 10. Although it is rotatable, the winding force on the spindle large-diameter portion 17 depends on the spindle large diameter of the coil spring 19 when the starting torque is transmitted from the gear 10 to the spindle large-diameter portion 17 via the coil spring 19. The winding portion of the portion 17 is set so as to slightly slide on the outer periphery thereof.

An intermediate cylinder 23 is provided between the large-diameter portion 17 and the ball bearing 7 on the blade 11 side so as to be integrally rotatable with the spindle by two chamfers.
The intermediate cylinder 23 is provided with an outer diameter portion 22 of the groove 20 of the gear 10.
A peripheral wall 24 having an inner diameter coinciding with the outer diameter portion 22, and an end portion of the peripheral wall 24 abutting against the outer periphery of the inner cylindrical portion 16 of the gear 10 to form a stepped portion 25.
Are connected. On the other hand, outside the intermediate cylinder 23,
A coil base 28 having a base portion 27 is fixedly mounted. The coil base 28 is provided with protrusions 27 a, 27 a. Are engaged with each other and pushed in, and are positioned in the gear housing 6, and are fixed at the positions by the retainer 6 b via the bearing box 7 a of the ball bearing 7. The intermediate tube 23 penetrating through the inside of the tube portion 26 is provided with a tube portion 2
6 comes into contact with each other, and the outer diameter of the cylindrical portion 26 is
Of the outer diameter of Further, an outer coil spring 29 having a rectangular cross section whose inner diameter is set slightly smaller (−0.3 mm) than the outer diameter of the cylindrical portion 26 and the band portion 25 is provided between the outer circumferences of the cylindrical portion 26 and the band portion 25. The winding is wound rightward with the winding amount of the band portion 25 slightly larger than that of the portion 26, and the terminal end on the coil base 28 side forms a bent portion 30 bent along the base portion 27. A brake gear 31 is fitted on the outer periphery of the outer coil spring 29. Brake gear 31
Are the tube portion 26 of the coil base 28 and the band portion 2 of the intermediate tube 23.
5 is a cylindrical gear whose inner periphery is loosely fitted to the outer periphery of the outer coil spring 29 wound around 5 and has a gear portion 32 formed at the motor-side end to mesh with the pinion 4 a of the motor shaft 4. On the other hand, the end on the coil base 28 side is in contact with the base 27, and the notch 31a locks the bent portion 30 of the outer coil spring 29. The number of gears formed in the gear portion 32 of the brake gear 31 is set smaller than the number of teeth 10 a of the gear 10, whereby the rotation speed associated with the rotation of the motor shaft 4 is higher in the brake gear 31. .

In the circular saw 1 having the above-described configuration, first, torque transmission by the coil spring 19 will be described. When the motor 3 is started, the motor shaft 4 rotates clockwise from the motor side toward the blade 11 ( Hereinafter, the left and right rotation directions are all directions viewed from the motor side), and the gear 10 meshing with the pinion 4a at the tip is rotated counterclockwise. At the same time as the rotation of the gear 10, the coil spring 19 wound around the inner cylinder 16 of the gear 10 also rotates counterclockwise integrally with the inner cylinder 16, and attempts to transmit rotation to the large-diameter portion 17 of the spindle 9. However, although the spindle 9 having the blade 11 starts rotating at the same time, since the winding force of the coil spring 19 is not sufficient, the winding portion of the coil spring 19 around the large diameter portion 17 first slides on the outer periphery of the large diameter portion 17. It will rotate at a slow speed. Then, as the rotation of the inner cylindrical portion 16 of the gear 10 increases, the coil spring 19 is wound and narrowed by the frictional force between the inner periphery thereof and the large-diameter portion 17. 19 firmly tightens the large diameter portion 17. Therefore, when the motor 3 rotates at a constant speed, the gear 1
The inner cylinder part 16 of 0 and the large diameter part 17 of the spindle 9 are firmly connected via a coil spring 19, and both rotate integrally. As described above, in this embodiment, although the rising speed of the spindle 9 is reduced due to the sliding of the coil spring 19, the constant rotation is reached at the same time as the gear 10, and there is no loss of torque from the motor 3. This rising slip is gear 10
The transmission of torque from the shaft to the spindle 9 is prevented from being performed suddenly, and the coil spring 19 serves as a cushion and
Absorbing the shock from zero, the generation of noise between the motor shaft 4 and the gear 10 and the wear of the pinion are reduced. Further, in addition to the cushion effect at the time of starting, even in a case where cutting resistance is applied to the blade due to, for example, a knot of the work material during the cutting operation, the coil spring connecting the gear and the spindle has a slight slip in the present embodiment. Since the setting is made, there is no fluttering of the blade at the time of cutting, and there is also an effect that the cut surface becomes good.

On the other hand, during the period from the start of the motor to the constant rotation, the brake gear 31 first rotates leftward at the same time due to the rotation of the motor shaft 4, but the brake gear 31 is faster than the gear 10 due to the difference in the number of teeth from the gear 10. Spin at speed. As the brake gear 31 rotates, an external force is applied to the outer coil spring 29 in the counterclockwise direction via the bent portion 30 due to the engagement between the notch 31a and the bent portion 30, but the outer coil spring 29 expands due to this rotation. A force is applied in the direction, so that the brake gear 31 rotates simultaneously with the outer coil spring 29. At this time, although a slight frictional force remains between the inner peripheral surface of the outer coil spring 29 to be expanded and the outer peripheral surface of the cylindrical portion 26 of the coil base 28, the brake gear 31 and the outer coil spring 29 Since the rotation is performed in the same direction as the spindle 9 at a higher speed, the rotational drive of the gear 10 and the spindle 9 by the torque transmission of the inner coil spring 19 is not affected. And turn on the power
When the motor 3 that rotates at a constant speed in the FF mode decelerates, the deceleration of the spindle 9 is reduced as compared with the deceleration of the motor shaft 4.
Due to the inertia of the motor, and a difference occurs between the two rotational speeds. Then, the brake gear 31 decelerated at the same time as the motor shaft 4 does not affect the intermediate cylinder 23 (spindle 9) from the time of constant rotation where the rotation speed is higher than the spindle 9 until the speed is reduced and becomes equal to the spindle. At the moment when the rotational speed is reversed and the brake gear 31 is slower than the spindle 9 which is going to continue rotating, the inner peripheral surface of the outer coil spring 29, which is also decelerating, becomes the band 25 of the intermediate cylinder 23. Of the outer coil spring 2
A force is applied in the direction in which 9 is wound and the winding force increases,
The outer coil spring 29 gradually grips the band 25 of the intermediate cylinder 23. At the same time, the winding force of the winding portion of the outer coil spring 29 on the coil base 28 is also increased, so that the outer coil spring 29 firmly grips the cylindrical portion 26, and as a result, the intermediate cylinder 23, the brake gear 31 are integrated into the coil base 28 (gear housing 6), and the spindle 9 and the blade 11 stop in a short idle time by these actions.

The number of turns of the outer coil spring and the diameter difference between the cylindrical portion and the band portion of the coil base are not limited to those in the above-described embodiment, and an appropriate one can be selected according to the diameter of the blade to be applied, the type of tool, and the like. . Also, the outer diameter of the cylinder portion and the band portion of the coil base are the same, but it is acceptable to make the diameters of both smaller by, for example, setting one of the diameters smaller depending on the required winding force of the coil spring. Instead, in this case, the outer coil spring may be formed in a mortar shape having different diameters at both ends instead of a cylindrical shape at both ends. Although the shaft portion on the spindle side is an integral intermediate cylinder in the above-described embodiment, a larger diameter portion having a larger diameter may be provided so as to be adjacent to the cylinder portion of the coil base. Furthermore, the cross-sectional shape of the outer coil spring may be round, or the contact area of the cylindrical portion and the band portion may be further deviated, or conversely, may be wound evenly. In addition, the transmission of torque from the speed reduction mechanism to the spindle when the power is turned on has been described using a coil spring. However, the brake mechanism of the present invention can be applied to other mechanisms such as a meshing clutch or a ratchet as long as transmission is one-way.

[0011] Note that as the urging means outside the coil spring in the above embodiment, the brake gear having a small gear portion of teeth than the gear to the exterior outside the coil spring, the outer coil spring by rotation of the brake gear interlocked with the motor shaft Although the diameter is changed, a means for changing the diameter of the outer coil spring is provided independently even without interlocking with the motor shaft, and the spring is urged in accordance with power ON / OFF by operation from outside the housing. The object of the present invention can be achieved even if it is performed. Thus, the present invention can be applied to many types of tools,
As long as it is an electric tool that transmits torque to the spindle by rotation in one direction without being limited to the circular saw machine, the present invention can be applied to other tools such as a cutting machine.

[0012]

According to the present invention, when the power is turned off, the main body and the spindle can be gradually integrated and connected by using the winding force of the coil spring, and the spindle can be stopped. Even with a blade having a diameter, the idling time can be reduced and workability can be improved. Further, the brake mechanism can be constituted by simple components such as a coil spring and gears, so that the entire tool does not become complicated and the cost can be suppressed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a circular saw machine to which the present invention is applied.

FIG. 2 is a perspective view of components of a brake mechanism.

FIG. 3 is an end view taken along line AA of FIG . 1;

[Explanation of symbols]

1. Circular saw machine, 2. Motor housing, 3. Motor, 4. Motor shaft, 5. Ball bearing, 6.
Gear housing, 7, 8, ball bearing, 9,
Spindle, 10 ・ gear, 11 ・ blade, 12 ・
・Outer flange, 13 ・ ・Inner flange, 14
..Bolt, 15 .. washer, 16 .. inner cylinder part, 1
7, large diameter part, 18 ring, 19 coil spring,
20 ・ ・ groove 、 21 ・ ・ inner diameter part 、 22 ・ ・ outer diameter part 、 23 ・
・ Intermediate cylinder, 24 ・ ・ ・ Peripheral wall, 25 ・ ・ Band, 26 ・ ・ ・ ・ Cylinder, 27 ・ ・ Base, 28 ・ ・ Coil base, 29 ・
・ Outer coil spring, 30 ・ ・ Bending part, 31 ・ ・ Brake gear, 32 ・ ・ Gear part.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23D 47/12 B27G 19/04 F16D 41/20

Claims (2)

(57) [Claims] 1. A power tool for transmitting rotation from an output shaft of a motor to a spindle via a speed reduction mechanism, wherein a coaxial cylindrical portion through which the spindle penetrates is provided in a main body housing, and the cylindrical portion is provided on the spindle in an axial direction with the cylindrical portion. Adjacent shaft portions are provided integrally, and between the cylindrical portion and the shaft portion, a coil spring wound in the opposite direction to the rotation direction of the spindle is wound over the both, and the diameter of the coil spring is An arbitrarily changeable biasing means is provided, and the diameter of the coil spring is changed by the biasing means to increase or decrease the winding force of the coil spring applied to the cylindrical portion of the main body housing and the shaft portion of the spindle. Brake mechanism for electric tools. 2. The apparatus according to claim 1, wherein said urging means is attached to an outer periphery of said coil spring, and engages one end of said coil spring with a gear which meshes with an output shaft of a motor and is set to rotate faster than said speed reduction mechanism. The rotation of the gears accompanying the rotation of the output shaft of the motor causes the coil spring to rotate in the expanding direction, and according to the difference in the number of rotations between the gears and the spindle, the rotation of the gear and the spindle of the main body housing. 2. The brake mechanism for an electric tool according to claim 1, wherein the applied winding force of the coil spring is increased or decreased.