JPH0957511A - Torque transmission mechanism of power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set stable torque limit even if low-priced belleville springs are adopted. SOLUTION: In a transmission mechanism of a hammer drill, a helical gear 52 engaged with a motor shaft 9a is loosely fitted coaxially to the step part of the disc part 47 of a sleeve 45, eight connecting recessed parts 47a, 47a... are radially provided on the disc part 47, similarly eight connecting recessed parts 52a, 52a... are provided on the inner circumference of the helical gear 52, hence both connecting recessd parts 47a, 52a are conformed to each other so as to form radial clutch grooves 53, 53..., and balls 54, 54... havrng a taper part 55a is loosely fitted to a cylindrical part 46 so that the upper end is locked with a clip 56, and it is energized downward by two opposite belleville springs 57, 58.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque transmission mechanism provided for transmitting rotation of a motor shaft to a bit side in an electric tool such as an electric hammer and a hammer drill.

[0002]

2. Description of the Related Art As a conventional torque transmission mechanism, an actual engine has been developed.
The one disclosed in 0-23319 is known. This is because a gear that is transmitted from the motor shaft is loosely fitted to a shaft that is axially supported between the motor shaft side and the bit side, and a holding plate that is slidable in the axial direction is provided so as to rotate integrally with the shaft. The pressing plate is biased toward the gear side by two disc springs, and the gear and the pressing plate are integrated by the engagement of the ball provided on one side and the engaging hole provided on the other side, and The rotation can be transmitted to the shaft. Here, the function of an overload clutch is provided in which when the load on the shaft increases, the engagement between the ball and the engagement hole is released and the gear idles. Further, in Japanese Patent Laid-Open No. 2-116405, between a clutch gear that meshes with a motor shaft to rotate and is loosely fitted to a shaft, and a cage integrated with the shaft, the cage is provided in the radial direction thereof. A locking member protruding in the radial direction by a compression spring is provided in the notch, and a locking groove in which the locking member is locked is provided in the clutch gear. An invention has been disclosed that functions as a load clutch.

[0003]

In the above-mentioned conventional torque transmission mechanism, the former one adopts an inexpensive disc spring and sets the pressing force as it is as the torque limit. Since the amount of deflection with respect to the load in the axial direction is large and the variation is large, it is necessary to provide an adjusting screw on the disc spring to adjust the pressing force for each tool, and the assembling work becomes very troublesome. In the latter case, the torque limit value can be set easily by using a compression spring with less variation in characteristics, but on the other hand, it is necessary to install a compression spring in each of the notches. The problem of labor and cost increase will occur.

[0004]

Therefore, according to the present invention, even if an inexpensive disc spring is adopted, a stable torque limit can be easily set, and a low-cost and highly reliable torque transmission mechanism is provided. The taper is configured such that the ball is provided so as to be able to move forward and backward from the center of rotation in the radial direction, while the biasing means abuts the ball and biases it in the locking direction with the recess. And a spring member such as a Belleville spring that presses the holding member toward the ball side.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of a hammer drill 1, which has a housing cap 4 inside an outer housing 2.
And an operating mechanism 3 supported by a crank housing 5 screwed to the housing cap 4, and supported by the crank housing 5 and a gear housing 6,
A transmission mechanism 40 that transmits rotation from the motor 9 to the actuation mechanism 3 is configured, respectively. Further, between the actuating mechanism 3 and the transmitting mechanism 40, a switching mechanism 6 capable of switching the operation between three modes of striking mode, neutral, and striking + rotating mode.
0 is interposed. First, the operating mechanism 3 will be described. In the present embodiment, the bit 7 side is the front, the handle 8 side is the rear, the upper side of FIG. 1 is the upper side, and the lower side is the lower side. A motor shaft 9a of a motor 9 arranged vertically in the rear of the hammer drill has a gear 11 integrated with a crankshaft 10 axially supported in the rear of the crank housing 5.
The piston 14 is connected to the connecting pin 12 which is engaged with the crankshaft 10 and is eccentrically provided above the crankshaft 10 via the connecting rod 13.
Is converted into reciprocating motion of the piston 14. It should be noted that the crankshaft 10 is a hollow member having an opening at the top as shown in cross section, so that the weight is reduced. The piston 14 is provided inside a cylindrical cylinder 15. The cylinder 15 is made of aluminum, and its rear portion is gripped and fixed to the crank housing 5 to extend forward,
A slide sleeve 16 and a tool holder 17 are coaxially fitted to the front half of the front half. Tool holder 17
Comprises a small-diameter portion 18 for attaching and detaching the bit 7, a medium-diameter portion 19 axially supported by a ball bearing 4a provided on the housing cap 4, and a large-diameter portion 20 externally fitted to the slide sleeve 16. The part 18 projects forward from the housing 2 and has a chuck sleeve 80.
The locking grooves 7a, 7a of the bit 7 are locked by the rollers 81, 81 pressed by, and the bit 7 is integrally rotatably gripped, and the rear large-diameter portion 20 has the engagement protrusion 2 formed on the outer periphery.
The latter half of 1, 21, ... Is the shaft 2 of the transmission mechanism 40.
The bevel gear 23, which meshes with the shaft 5 and is axially supported by the metal 22, meshes with the engaging teeth 24 at the front end of the bevel gear 23, and the tool holder 17 is rotatable from the motor 9 via the transmission mechanism 40. Next, the slide sleeve 16 is a cylindrical body made of synthetic resin that is loosely inserted between the large-diameter portion 20 of the tool holder 17 and the cylinder 15 so as to be slidable forward and backward. The front end is abutted to regulate the rear position, and the washer 26 and the rubber 27 are arranged on the front side so that the washer 26 and the rubber 27 can move back and forth between the middle diameter portion 19 and the washer 26. You can move forward until you touch them. On the other hand, a compression spring 29 is disposed behind the slide sleeve 16 and between the compression spring 29 and the bevel gear 23 to urge the slide sleeve 16 forward. A receiving ring 28 made of iron is interposed.

In the cylinder 15, the piston 14
A striker 31 is disposed in front of the air chamber 30 so as to be movable back and forth, and a second air chamber 32 is formed in front of the striker 31.
Is also arranged so that it can be moved back and forth. Cylinder 1
At the position of the air chamber 30 of No. 5, one replenishing hole 34 and six air holes 35, 35 ...
Six vent holes 36, 36 ... Are provided in the air chamber 32. First, the refill hole 34 on the side of the air chamber 30 is
The air hole 35 replenishes the air loss of the receiving ring 2 which is retracted at the same time only in the retracted position where the folded portion 16a of the slide sleeve 16 abuts on the tip of the cylinder 15.
It is blocked by 8 (Fig. 2). Slide sleeve 1
As shown in FIG. 3, large slits 37, 37 ..., And narrow slits 38, 38 ... Are respectively formed in the axial direction in the front part of the tool 6, and in addition to the large diameter part 2 of the tool holder 17.
At the outer peripheral position of the vent hole 36 of the cylinder 15 at 0,
.. and six auxiliary holes 39a, 39a whose axial positions are offset from the front of the six through holes 39, 39.
.. and are respectively provided, but slide sleeve 16
The slits 37, 38 of the tool holder 17 allow the slide sleeve 16 to communicate with the vent hole 36 regardless of whether the slide sleeve 16 is in the forward or backward position.
Is the slit 37, even if the tool holder 17 rotates.
38 are provided so that they can communicate with each other.

In the operation mechanism 3 constructed as described above, when the bit 7 is inserted from the tip of the tool holder 17 during normal work and the contacting intermediate element 33 is pushed in, the intermediate element 33 causes the washer 26 and the rubber 27 to retract. Contact the folded portion 16a of the slide sleeve 16,
6 and the receiving ring 28 are retracted against the bias of the compression spring 29 (position in FIG. 1). At this time, since the air hole 35 is closed by the receiving ring 28, when the piston 14 advances and retreats here, the air chamber 30 acts as an air spring to interlock the striker 31 and project into the second air chamber 32. The rear end of the meson 33 is struck to transmit the striking action to the bit 7. Further, since the second air chamber 32 is communicated to the outside by the slits 37, 38 of the slide sleeve 16 and the through hole 39 or the auxiliary hole 39a of the large diameter portion 20 of the tool holder 17, the second movement of the slide sleeve 16 is prevented. Even if the tool holder 17 rotates, there is no repulsion of air here, and no loss of impact force occurs. Incidentally, the washer 26 and the rubber 27
Serves to buffer the rearward shock by cushioning the recoil from the bit 7 at this time. And when hitting blank,
With the first impact of the impact element 31, the bit 7 advances until the rear end of the locking groove 7a abuts the rollers 81, 81 as shown in FIG. 4, and at the same time, the washer 26 abuts until the intermediate element 33 abuts the small diameter portion 18. The rubber 27 is moved forward by the urging force of the compression spring 29 until it comes into contact with the intermediate diameter portion 19. At this time, the slide sleeve 16 and the receiving ring 28 also move forward to the position shown in the figure, but the air hole 35 that has been closed by this is opened, so that the action of the air spring of the air chamber 30 is lost, and the action with the piston 14 is lost. The interlocking of the hitting element 31 is cut off, the hitting element 31 stops at a position where it comes into contact with the rear end of the advanced intermediate element 33, and the subsequent blank hitting is prevented. Also at this time, since the second air chamber 32 communicates with the outside from the ventilation hole 36 through the longer slits 37, 38, the through hole 39 or the auxiliary hole 39a, the air here repels and hits the striker. There is no risk of pushing back 31 to the piston 14 side.

As described above, in the hammer drill 1, the cylinder 15 is moved to the tool holder 17 for transmitting the rotation.
The cylinder 15 is made of a lightweight material such as aluminum because it is provided with the actuating mechanism 3 that separates the air hole 35, which is fixed in the housing and prevents blank driving, by opening and closing the slide sleeve 16. It can be formed, and weight reduction and cost reduction can be achieved. Although the slide sleeve 16 and the receiving ring 28 are separately provided in the above-described embodiment, they may be integrated with each other, and a vent hole for exhausting the air in the second air chamber 32 to the outside of the tool holder 17. The numbers and shapes of the slits 36, the slits 37 and 38, the through holes 39, and the auxiliary holes 39a can be appropriately changed.

Next, the transmission mechanism 40 will be described. FIG.
Shaft 25 meshing with the bevel gear 23
Is the motor shaft 9a by the ball bearings 41, 42.
Is axially supported in parallel with the shaft portion 25, and axial movement thereof is restricted by washers 43, 44 integral with the shaft 25, and a cylindrical portion 46 and a disk portion 47 provided around the cylindrical portion 46 are provided.
A sleeve 45 composed of and is rotatably loosely fitted.
Also, as shown in FIG. 6, symmetrical slide grooves 25a, 25a are formed in the axial direction of the shaft 25, and change keys 48, 48 for freely penetrating the washer 44 are provided in the slide grooves 25a, 25a, respectively. The change keys 48, 48 are vertically slidably inserted, respectively, but the range of vertical movement of the change keys 48, 48 is restricted between the upper and lower washers 43, 44 by the protrusions 49, 49 protruding from the upper portion. Further sleeve 45
In the upper half of the inner peripheral surface of the tubular portion 46 in
., 50, ... are formed, and the change keys 48, 4
In the upper limit position of 8, the protrusions 49, 49 are engaged with the two symmetrical cut portions 50, 50 so that the sleeve 45 and the shaft 2 are not in contact with each other.
When the change keys 48 and 48 are rotated together, the protrusions 49 and 49 are separated from the cut portions 50 and 50 at the lower limit position of the change keys 48 and 48, and the rotation of the sleeve 45 is not transmitted to the shaft 25. , 48 are connected to the lower portions of the change keys 48, 48, and the connecting ring 51 is gripped in the groove 62a of the holder portion 62 of the change link 61 in the switching mechanism 60, which will be described later. It is supposed to move up and down accordingly.

On the other hand, a helical gear 52, which meshes with the motor shaft 9a, is coaxially and loosely fitted in the disk portion 47 of the sleeve 45, and eight connecting concave portions 4 are radially formed on the outer circumference of the disk portion 47.
7a, 47a .. .., and 8 coupling recesses 52a, 52a .. are also provided on the inner circumference of the helical gear 52, respectively, and both coupling recesses 47a, 52a are aligned and radial clutch grooves 53, 53. , And balls 54, 54, ... Are inserted in the clutch grooves 53, 53 ,. Further, a retaining ring 55 having a tapered portion 55a, which is thinned toward the outer periphery around the lower surface, is loosely fitted above the tubular portion 46, and the upper end of the retaining ring 55 is locked by a clip 56. The disc springs 57 and 58 are loosely fitted to the cylindrical portion 46 so as to be biased downward. Therefore, the tapered portion 55a of the restraining ring 55, which is normally urged downward, urges the balls 54 in the radial direction of the clutch groove 53, and the balls 54 at this position connect the connecting recesses 47a and 52a. As a result, the helical gear 52 and the sleeve 45 rotate integrally. In other words, the pressing force of the disc springs 57 and 58 that is converted in the radial direction of the ball 54 by the holding ring 55 limits the torque on the shaft 25.

In the transmission mechanism 40 configured as described above, the change link 61 is located above and the projections 49,
When the helical gear 52 is rotated by the rotation of the motor shaft 9a in a state in which 49 is locked to the cutouts 50, 50 of the sleeve 45, the pressing ring 55 pressed by the biasing of the disc springs 57, 58 at each time is rotated. Since the balls 54 in the clutch groove 53 are biased in the radial direction respectively to integrate the helical gear 52 and the disk portion 47 of the sleeve 45, the sleeve 45 also rotates together with the helical gear 52, and the cut portion 5 is formed.
The shafts 25 rotate via the change keys 48, 48 by the protrusions 49, 49 locked to 0, 50 to transmit the rotation to the bevel gear 23 and rotate the tool holder 17 as described above. During this rotation operation, rotation resistance is generated on the tool holder 17 side, and the disc spring 57,
When the set torque value due to the pressing of 58 is exceeded, each ball 54 in the clutch groove 53 moves toward the center of rotation while slidingly contacting the tapered portion 55a against the pressing of the holding ring 55 (FIG. 7). Then, the coupling recess 4 in each clutch groove 53
When the unification of 7a and 52a is released, the rotation from the helical gear 52 is no longer transmitted to the disk portion 47 of the sleeve 45, and it functions as an overload clutch. In particular, as a characteristic of the disc spring, the change in the deflection becomes smaller as the load approaches the elastic limit, but in the hammer drill 1 having the transmission mechanism 40, the disc springs 57 and 58 are provided.
The pressing force in the axial direction caused by the disc portion 47 is reduced by the tapered portion 55a of the restraining ring 55 and the ball 54 of the clutch groove 53.
By adopting a structure in which the disc spring is converted to the radial direction, the pressing force to the restraining ring 55 can be set within a range of a load in which the amount of deflection of the disc spring is small, and a stable set torque value can be obtained. Further, since there is no unevenness in each tool, it is not necessary to provide a screw member for adjusting the pressing force, and the assembling work is not required. The number and shape of the disc springs and the clutch grooves are not limited to the above-mentioned form, and can be increased / decreased or changed in shape as appropriate. Of course, the transmission mechanism can be applied to other electric tools other than the hammer drill.

Next, the switching mechanism 60 will be described. FIG.
8 and 9, the change link 61 includes a holder portion 62 that holds the change keys 48 and 48, and a link portion 63 that is continuous to the holder portion 62 at a right angle.
To the long hole 63a provided in the front-rear direction at the tip of the link portion 63,
An eccentric pin 67 protruding from the switching knob 65 penetrates. The switching knob 65 is rotatable with a cylindrical penetrating portion 66 pivotally supported in an insertion hole 64 formed by the housing 2 and the crank housing 5.
A retaining portion 66a is formed on the peripheral edge of the tip of the. Further, the penetrating portion 66 integrally connects the ends of the rectangular tubular operation portion 68 having one end opened outside the housing 2 from the opening, and the stopper 69 is loosely inserted into the operation portion 68. This is urged in the projecting direction by the compression spring 71, but the pin 70 projecting orthogonally to the stopper 69 is inserted into the arc-shaped slit 72 provided in the housing 2 to come off from the operating portion 68. It has been stopped.
The slit 72 is provided with cuts 73a, 73b, 73c toward the center of the circular arc at the front and rear (0 degree and 180 degree) and the intermediate position (90 degree) between them, respectively.
While the pin 70 is guided by the slit 72 during the rotation of 5, the pin 70 is locked by the biasing force of the compression spring 71 at each cut position and can be stopped at that position (every 90 degrees). ing.

On the other hand, on the outer circumference of the large diameter portion 20 of the tool holder 17, the sliding teeth 5 formed on the inner circumference of the crank housing 5 are provided.
A pinion 74a that meshes with a is formed on the outer circumference, and a lock ring 74 that is movable back and forth is externally fitted. The lock ring 74 is biased rearward by a compression spring 78 arranged between the lock ring 74 and a bearing retainer 77 press-fitted into the housing cap 4, and a chamfered portion 75 on the side thereof has a square cutout portion 76. Then, here, the switching knob 65 that penetrates the long hole 63a of the change link 61
The eccentric pin 67 is locked. Further, on the inner circumference of the rear end portion of the lock ring 74, there are provided engagement teeth 79, 79 ... Engaging with the front half of the engagement projection 21 of the tool holder 17. Therefore, here, the eccentric pin 67 moves its position in FIG. 5 to 0 degrees (pin 70) as the switching knob 65 rotates every 90 degrees.
Is locked to the cut 73a), it moves to the lower left position at 90 degrees (the pin 70 is locked to the cut 73b) and to the lower right position at 180 degrees (the pin 70 is locked to the cut 73c). But
The change link 61 moves up and down according to the vertical movement of the eccentric pin 67 to move the change keys 48 held by the holder 62 up and down, and the lock ring 74 moves forward and backward according to the forward and backward movement. The engaging projection 21
Will be engaged and disengaged with.

In the switching mechanism 60 constructed as described above, three modes can be selected depending on the rotational position of the switching knob 65. That is, as shown in FIG. 10, first, in the same figure (A) at the 0 degree position, the eccentric pin 67 at the upper left restricts the lock ring 74 at the position away from the engaging projection 21 and the change link 61 at the upper limit position. Change key 48,
The protrusions 49, 49 of the forty-eight
Lock to 0. Therefore, here, as described above, in addition to the striking operation by the piston 14, the striking element 31, and the intermediate element 33, the rotation of the shaft 25 causes the bevel gear 2 to rotate.
3. Rotation + striking mode in which the tool holder 17 rotates. Next, when the switching knob 65 is rotated 90 degrees from here, the eccentric pin 67 maintains the separated position of the lock ring 74 only by moving to the lower left of the excision portion 76 as shown in FIG. The link 61 is moved to the lower limit position to disengage the projections 49, 49 of the change keys 48, 48 from the notches 50, 50 of the sleeve 45, so that the rotation of the sleeve 45 is not transmitted to the shaft 25 and the striking operation is obtained. However, the tool holder 17 is in a neutral state (idle state) in which it can freely rotate. Then, when the switching knob 65 is further rotated from this position to the 180 degree position, the eccentric pin 67 moves to the lower right and retracts the lock ring 74, as shown in FIG. 21 to lock the rotation of the tool holder 17. At this time, since the change link 61 remains at the lower limit position, the rotation transmission from the sleeve 45 to the shaft 25 is not performed, and the striking mode is achieved in which only the striking operation is obtained. Therefore, when it is necessary to determine the angle of the bit 7 with a chisel or the like, the tool holder 17 is freed with the neutral shown in FIG.
Is adjusted to a predetermined angle, and then the switching knob 65 is adjusted to the striking mode shown in FIG.
Since the angle of is fixed, it is very convenient for chipping work.

As described above, according to the switching mechanism 60, the switching of the rotation transmission to the shaft 25 and the switching of the rotation lock of the tool holder 17 are performed by separate members, and also at different locations. It is possible to perform a design suitable for different loads applied to the lock ring 45 and the lock ring 74, and it is possible to maintain durability. Further, even if one of the parts is damaged, only the replacement is required, which leads to the suppression of cost increase. In particular, even with separate members, the rotation of the eccentric pin 67 due to the operation of the switching knob 65 is linked to the lock ring 74, the change link 61, and the change key 48 so that the mode can be switched rationally. Therefore, good operability can be obtained. In the above embodiment, the lock ring 74 as a lock member is moved in the axial direction of the tool holder 17 and the change key 48 as a key member is moved in the intersecting direction to perform rotation transmission and lock switching. Depending on the form of the transmission mechanism 40, it is also possible to adopt a form in which both are moved in the axial direction and switched.

[0016]

As described above, according to the present invention, the biasing force of the spring member generated in the axial direction of the rotary shaft is converted into the pressing force in the radial direction of the ball by the restraining member, so that the stable pressing force is obtained. The ball and recess can be locked with
The torque limit can be set easily and evenly.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a hammer drill.

FIG. 2 is a cross-sectional explanatory view of a cylinder and a receiving ring at a position of an air chamber.

FIG. 3 is a cross-sectional explanatory view of a cylinder, a slide sleeve, and a tool holder at a position of a second air chamber.

FIG. 4 is an operation explanatory view at the time of idle driving.

FIG. 5 is an explanatory diagram of a transmission mechanism.

FIG. 6 is an explanatory diagram of a transmission mechanism.

FIG. 7 is an explanatory diagram of a transmission mechanism.

FIG. 8 is an explanatory diagram of a switching mechanism.

FIG. 9 is an explanatory diagram of a switching mechanism.

FIG. 10 (A) is an operation explanatory view of the switching mechanism. (B) It is an operation explanatory view of a switching mechanism. (C) It is an operation explanatory view of a switching mechanism.

[Explanation of symbols]

1 ... Hammer drill, 2 ... Housing, 3 ... Operating mechanism, 5 ... Crank housing, 6 ... Gear housing, 7 ... Bit, 9 ... Motor, 10 ... Crank shaft, 14 ... Piston, 15 ・ ・ Cylinder, 16 ・
・ Slide sleeve, 17 ・ ・ Tool holder, 21 ・ ・
Engaging projections, 23 ... Bevel gears, 24 ... Engaging teeth, 25
..Shafts, 30..Air chambers, 31..Hiters, 32
..Second air chamber, 33..Meson, 40..Transmission mechanism,
45 ・ ・ Sleeve, 48 ・ ・ Change key, 51 ・ ・ Connecting ring, 52 ・ ・ Helical gear, 53 ・ ・ Clutch groove, 54 ・ ・ Ball, 55 ・ ・ Holding ring, 57, 58
..Disc springs, 60..Switching mechanism, 61..Change links, 65..Switching knobs, 67..Eccentric pins, 74 ..
Rock ring.

Claims (1)

[Claims] 1. A gear that rotates by rotation transmission from a motor side, and a rotation shaft that loosely inserts the gear coaxially and transmits rotation to the bit side. One side of the gear side and the rotation shaft side. A torque transmission mechanism for an electric tool, comprising a ball on the other side, a concave portion for locking the ball, and an urging means for pressing the ball toward the concave portion. A restraining member that is provided so as to be movable back and forth in a radial direction, has a taper portion that biases the biasing means in a direction of engaging with the ball and in a locking direction with the recess, and is movable in the axial direction of the rotating shaft. A torque transmission mechanism for an electric tool, characterized in that the restraining member is constituted by a spring member that presses the ball toward the ball.