JP2010240759A - Hammer drill - Google Patents

Abstract

Even when a torque limiter is provided, it is possible to maintain a suitable durability of a gear and achieve compactness.
In a hammer drill, a torque limiter is mounted on a tool holder 6 adjacent to a gear 13 so as to be integrally rotatable, and a cam ring 14 having a cam projection 18 projecting from a surface facing the gear 13; And a roller 21 that can be engaged with the cam projection 18 in the rotational direction, and urge the roller 21 toward the cam ring 14 to engage the roller 21 with the cam projection 18. When the torque applied to the tool holder 6 exceeds the set torque, the roller 21 moves in the through hole 20 against the urging force of the urging means. By moving over the cam projection 18 and rolling on the cam ring 14, the gear 13 is idled to interrupt torque transmission to the cam ring 14.
[Selection] Figure 1

Description

  The present invention relates to a hammer drill capable of imparting rotation and / or hitting to a bit at a tip.

For example, as shown in Patent Document 1, a hammer drill supports a tool holder serving as a final output shaft that holds a bit at a front end in the front of a housing, and a bit that is inserted by a reciprocating hammer in the rear thereof. An impact mechanism for impacting indirectly is provided, and an intermediate shaft to which rotation of the output shaft of the motor is transmitted is supported in parallel with the tool holder, and a gear provided on the intermediate shaft is provided on the tool holder. The rotation of the intermediate shaft can be transmitted to the tool holder.
In addition, the tool holder is provided with a torque limiter that cuts off torque transmission from the intermediate shaft when a torque higher than the setting is applied to the tool holder. In this torque limiter, the gear on the tool holder side is externally mounted so as to be rotatable and movable in the axial direction, and is biased to the cam ring side fixed to the tool holder by a coil spring. The roller which engages across is provided. That is, in the range where the torque to the tool holder does not exceed the set torque, the rotation of the gear is restricted and the torque is transmitted to the cam ring and the tool holder, and when the torque to the tool holder exceeds the set torque due to the rotational load on the bit, The gear moves forward against the bias of the coil spring and idles to interrupt the torque transmission to the cam ring.

US Pat. No. 5,373,905

  In such a hammer drill, when the torque limiter is actuated, the gear on the tool holder side slides in the axial direction while meshing with the gear on the intermediate shaft side, so there is a possibility that the teeth may wear at the meshing portion of the gears, Endurance will be reduced. In addition, since it is necessary to determine the shape of the housing in consideration of the gear stroke, this leads to an obstacle to downsizing.

  Accordingly, an object of the present invention is to provide a hammer drill that can maintain a suitable durability of a gear even if it is equipped with a torque limiter, and can be made compact without any trouble. .

In order to achieve the above object, the invention according to claim 1 is the cam ring in which the torque limiter is externally mounted adjacent to the gear so as to rotate integrally with the final output shaft, and the cam projection protrudes on the surface facing the gear. And a rolling element that is accommodated in a through hole formed in the gear concentrically with the cam protrusion and that can be engaged with the cam protrusion in the rotational direction, and urging the rolling element toward the cam ring side to the final output shaft And a biasing means for engaging the rolling element with the cam projection within a range where the torque does not exceed the set torque, and when the torque exceeds the set torque, the biasing means resists the bias of the biasing means. Thus, the rolling element climbs over the cam projection in the through hole and rolls on the cam ring, so that the gear is idled and the torque transmission to the cam ring is interrupted.
According to a second aspect of the present invention, in the configuration of the first aspect, the rolling element is a roller whose axis is aligned with the radial direction of the gear.

According to the first aspect of the present invention, even if a torque limiter is provided, the preferred durability of the gear can be maintained. Further, since the gear does not move in the axial direction, there is no need to ensure a gear movement stroke in the housing, and compactness can be easily achieved.
According to the second aspect of the present invention, in addition to the effect of the first aspect, the use of the roller increases the contact area with the cam ring as compared with the ball. Therefore, the reliability of the engagement with the cam protrusion is increased, and the burden on the cam protrusion is suppressed, and the durability of the cam ring is increased.

It is a partial longitudinal cross-sectional view of a hammer drill (normal time). It is a partial longitudinal cross-sectional view of a hammer drill (at the time of a torque limiter action | operation).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a partial longitudinal sectional view showing an example of a hammer drill. The hammer drill 1 houses a gear housing 2 in which a rotation mechanism and a striking mechanism are provided, and a motor 4 behind the gear housing 2 (right side in FIG. 1). A tool holder 6 as a final output shaft having a motor housing 3 and having a bit mounted at the front end is rotatably supported in front of the gear housing 2.
The tool holder 6 is a cylindrical body that is rotatably supported by an intermediate portion 8 on a ball bearing 10 at the front end of the gear housing 2 and a rear portion 9 on an inner housing 11 assembled at the rear in the gear housing 2. An operation sleeve 12 for attaching / detaching a bit (not shown) inserted into the front end of the tool holder 6 is provided at the front end portion 7 protruding from the gear housing 2.

A gear 13 is rotatably mounted on the outer periphery of the rear portion 9 of the tool holder 6, and a cam ring 14 is integrally mounted on the front of the gear 13 with a stopper ball 15. On the other hand, a washer 16 and a coil spring 17 are externally provided behind the gear 13.
Six cam projections 18, 18... (Shown in FIG. 2) project at equal intervals in the circumferential direction near the periphery on the rear surface of the cam ring 14 (surface facing the gear 13). On the front surface of the gear 13 (the surface facing the cam ring 14), a protrusion 19 that contacts the rear surface of the cam ring 14 inside the cam protrusion 18 of the cam ring 14 is slightly higher than the cam protrusion 18. It is projecting at. Further, the gear 13 is provided with six through holes 20, 20... Which are concentric with the cam projection 18 and in phase with each other, a roller 21 is provided in each through hole 20, and an axis line is arranged in the radial direction of the gear 13. It is housed so that it can roll in the direction matched with.

The washer 16 has a diameter capable of closing the through hole 20 of the gear 13 from the rear, and is biased forward by the coil spring 17 to press the gear 13. The washer 16 and the coil spring 17 are the urging means of the present invention. A bearing 22 is supported by the inner housing 11 and pivotally supports the rear portion 9, and a spring receiver 23 is provided on the rear portion 9 between the bearing 22 and the coil spring 17 and receives the rear end of the coil spring 17.
By the washer 16 and the coil spring 17 being pressed, the movement of the gear 13 in the front-rear direction is restricted at a position where the protrusion 19 contacts the cam ring 14. In this state, each roller 21 penetrating the gear 13 is pressed by the washer 16 and protrudes forward from the through hole 20 and does not protrude from the rear surface of the gear 13.

  Therefore, within a range where the torque to the tool holder 6 does not exceed the set torque determined by the biasing force of the coil spring 17, when the gear 13 rotates, the roller 21 in the through hole 20 also rotates and rolls on the rear surface of the cam ring 14. In order to engage with the cam protrusion 18, the torque of the gear 13 is transmitted from the roller 21 to the tool holder 6 through the cam ring 14. On the other hand, when the torque to the tool holder 6 exceeds the set torque, the roller 21 pushes the washer 16 backward against the bias of the coil spring 17 and rolls over the cam projection 18, so that the gear 13 is idled. Thus, torque transmission to the tool holder 6 is interrupted. That is, a torque limiter is formed.

On the other hand, an impact bolt (meson) 30 is accommodated in the intermediate portion 8 of the tool holder 6 so as to be movable back and forth. The impact bolt 30 is regulated in a retracted position by an elastic ring 32 and a receiving ring 33 interposed between the impact bolt 30 and a cylindrical cap 31 assembled in the middle portion 8 at the rear. In normal use, the rear end of the impact bolt 30 is fitted, and when the tool holder 6 has no bit, the front end of a striker 37 (to be described later) is gripped to restrict its reciprocation. An O-ring 34 is accommodated.
A cylindrical piston cylinder 35 having an opening at the front is loosely inserted into the rear portion 9 of the tool holder 6, and a striker (batter) 37 is inserted in the piston cylinder 35 via an air chamber 36. It is housed movably.

  Further, an intermediate shaft 38 is supported in parallel with the tool holder 6 and the output shaft 5 below the output shaft 5 of the motor 4 in the gear housing 2, and a first gear 39 provided at the rear end is attached to the output shaft 5. Meshing. Spline teeth 40 are formed at an intermediate portion of the intermediate shaft 38, and a second gear 41 is externally mounted so as to be rotatable separately from the intermediate shaft 38 and meshed with the gear 13 of the tool holder 6. Yes. Further, a boss sleeve 42 is rotatably mounted on the rear side of the spline teeth 40 separately from the intermediate shaft 38, and a swash bearing 43 having an inclined axis is rotatably fitted on the outer periphery of the boss sleeve 42. Thus, the upper end of the connecting arm 44 protruding from the upper part of the swash bearing 43 is rotatably connected to the rear end of the piston cylinder 35.

The spline teeth 40 of the intermediate shaft 38 are spline-coupled with a sleeve-like clutch 45 having a V-shaped fitting groove 46 around its peripheral surface so as to be able to rotate integrally with the intermediate shaft 38 and slide back and forth. Yes. A mode switching knob 47 is rotatably fitted to the lower surface of the gear housing 2 below the clutch 45, and the upper end of the mode switching knob 47 is tapered so that the upper end is fitted into the fitting groove 46 of the clutch 45. The engaging pin 48 is held in a state where it can move up and down and is biased upward by a coil spring 49.
Therefore, when the mode switching knob 47 is rotated, the engaging pin 48 moves eccentrically while being fitted in the fitting groove 46, so that the clutch 45 also moves back and forth in accordance with the amount of movement of the engaging pin 48 in the front-rear direction. Thus, depending on the sliding position of the clutch 45 before and after, it is possible to engage and disengage with one or both of the second gear 41 and the boss sleeve 42.

  That is, in the forward position of the clutch 45, the clutch 45 is engaged only with the second gear 41 and integrated with the intermediate shaft 38 in the rotational direction (drill mode), and in the backward position of the clutch 45, the clutch 45 is in the boss sleeve 42. Only in the rotational direction and integrated with the intermediate shaft 38 (hammer mode). At the intermediate position of the clutch 45, the clutch 45 engages with both the second gear 41 and the boss sleeve 42 to engage with the intermediate shaft 38. Each operation mode can be selected by integrating them in the rotation direction (hammer drill mode).

  In the hammer drill 1 configured as described above, when the motor 4 is driven by selecting the drill mode by rotating the mode switching knob 47, the rotation of the output shaft 5 is transmitted from the first gear 39 to the intermediate shaft 38, It is transmitted to the second gear 41 and the gear 13 via the clutch 45. Here, as described above, if the torque applied to the tool holder 6 does not exceed the set torque, the torque limiter does not operate. Therefore, the rotation of the gear 13 is transmitted to the cam ring 14 via the roller 21, and the tool holder 6 Rotate. Therefore, the bit attached to the front end of the tool holder 6 also rotates. The mechanism from the output shaft 5 to the gear 13 is the rotation mechanism of the present invention.

  On the other hand, when the hammer mode is selected and the motor 4 is driven, the rotation of the output shaft 5 is transmitted from the first gear 39 to the intermediate shaft 38 and is transmitted to the boss sleeve 42 via the clutch 45. Therefore, the rotation of the boss sleeve 42 is converted to the swing of the connecting arm 44 forward and backward via the swash bearing 43, and the piston cylinder 35 is reciprocated. As a result, the striker 37 reciprocally moves in conjunction with the action of the air spring, and the bit is indirectly hit by hitting the impact bolt 30 that is pushed into the bit and in the retracted position. The mechanism from the output shaft 5 to the bit is the striking mechanism of the present invention.

  When the hammer drill mode is selected and the motor 4 is driven, the rotation of the output shaft 5 is transmitted from the first gear 39 to the intermediate shaft 38 and is transmitted to both the second gear 41 and the boss sleeve 42 via the clutch 45. . Therefore, the rotation of the tool holder 6 and the impact on the bit occur at the same time. Also in this case, if the torque to the tool holder 6 does not exceed the set torque, the torque limiter does not operate. Therefore, the rotation of the gear 13 is transmitted to the cam ring 14 via the roller 21 to rotate the tool holder 6.

  Among these operation modes, in the drill mode and the hammer drill mode, when the torque to the tool holder 6 increases due to the rotational resistance to the bit and exceeds the set torque of the torque limiter, as shown in FIG. The roller 21 is actuated to roll over the cam projection 18 of the cam ring 14 and roll on the cam ring 14, and the gear 13 idles to release the coupling with the cam ring 14. Torque transmission is interrupted. Regardless of whether the torque limiter is in operation or not, the gear 13 does not move in the axial direction but only rotates, so that the load on the meshing portion with the second gear 41 can be reduced.

  As described above, according to the hammer drill 1 of the above-described form, the torque limiter is mounted on the tool holder 6 so as to be integrally rotatable adjacent to the gear 13, and the cam ring 18 protrudes from the surface facing the gear 13. 14, a roller 21 that is accommodated in a through hole 20 formed in the gear 13 concentrically with the cam protrusion 18, and capable of engaging with the cam protrusion 18 in the rotational direction, and urges the roller 21 toward the cam ring 14. The biasing means (washer 16 and coil spring 17) for engaging the roller 21 with the cam projection 18 within a range in which the torque to the tool holder 6 does not exceed the set torque, the torque to the tool holder 6 is When the set torque is exceeded, the roller 21 moves over the cam projection 18 in the through hole 20 and rolls on the cam ring 14 against the urging force of the urging means, causing the gear 13 to idle. In the the possible to interrupt the transmission of torque to the cam ring 14, even those equipped with a torque limiter, it is possible to maintain a suitable durability of the gear 13 and second gear 41. Further, since the gear 13 does not move in the axial direction, it is not necessary to secure a moving stroke of the gear 13 in the gear housing 2, and compactness can be easily achieved.

  In particular, here, the rolling element is a roller 21 whose axis is aligned with the radial direction of the gear 13, so that the contact area with the cam ring 14 is increased as compared with the ball, and the reliability of the engagement with the cam protrusion 18 is increased. In addition, the burden on the cam protrusion 18 is suppressed and the durability of the cam ring 14 is also increased.

Note that the number of cam projections on the cam ring and the number of through holes in the gear can be increased or decreased as appropriate, and the rollers can be increased or decreased appropriately in accordance with the through holes. Of course, the rolling elements are not limited to rollers, and balls can also be used.
In addition, the biasing means may employ another elastic body such as a disc spring instead of the coil spring, and the direction of the torque limiter is not limited to the above form, and the cam ring is placed rearward, the washer and the elastic body are sandwiched between the gears. It is also possible to change the positions of them in front.

  In addition, the design of the hammer drill can be changed as appropriate. Other than the above-described forms, it is possible to appropriately change the form, such as the form of striking or the use of a crank mechanism for the reciprocating motion of the piston.

  1 .... hammer drill, 2 .... gear housing, 4 .... motor, 5 .... output shaft, 6 .... tool holder, 7 .... front end, 8 .... intermediate, 9 .... rear part, ... Gear, 14 ... Cam ring, 16 ... Washer, 17 ... Coil spring, 18 ... Cam projection, 20 .... Through hole, 21 ... Roller, 30 ... Impact bolt, 35 ... Piston cylinder, 37 ... Strike , 38 .. Intermediate shaft, 41 .. Second gear, 42 .. Boss sleeve, 45 .. Clutch, 47 .. Mode switching knob, 48.

Claims (2)

A rotation mechanism that transmits torque to a gear that is rotatably mounted on the final output shaft and a striking mechanism that strikes the bit are provided in a housing that rotatably supports the final output shaft on which the bit is mounted. On the other hand, in the range where the torque to the final output shaft does not exceed the set torque, the rotation of the gear is restricted and torque transmission to the final output shaft is permitted to the final output shaft. A hammer drill provided with a torque limiter that causes the gear to idle and exceed the torque transmission to the final output shaft,
The torque limiter is externally mounted adjacent to the gear so as to rotate integrally with the final output shaft, and a cam ring projecting a cam projection on a surface facing the gear, and the gear projecting on the gear concentrically with the cam projection. A rolling element that is accommodated in the formed through-hole and is capable of engaging with the cam protrusion in the rotation direction; and urging the rolling element toward the cam ring so that the torque does not exceed the set torque. An urging means for engaging the rolling element with the cam projection,
When the torque exceeds the set torque, the rolling element rolls over the cam projection in the through hole against the bias of the biasing means, and rolls on the cam ring. A hammer drill characterized in that a gear is idled to cut off torque transmission to the cam ring.   The hammer drill according to claim 1, wherein the rolling element is a roller having an axial line aligned with a radial direction of the gear.

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