JP4289087B2 - Impact rotary tool - Google Patents

Description

  The present invention relates to a screw tightening portable tool called an impact driver or an impact wrench, which relates to an impact rotating tool capable of firmly tightening a screw by striking and rotating in a rotating direction.

  Conventionally, an impact rotary tool has been used (see, for example, Patent Document 1). As shown in FIG. 9, the impact rotary tool has a drive shaft 1 connected to an output shaft 81 of a motor via a speed reduction mechanism 82, and a substantially annular hammer 2 is fitted to the drive shaft 1 so as to be able to rotate and move forward and backward. The cams 4 and 5 are provided on the outer surface 1a of the drive shaft 1 and the inner surface 2a of the hammer 2, respectively. As will be described later, the cams 4 and 5 are provided with a cam groove 40 in a substantially V shape on the outer surface 1a of the drive shaft 1, and a cam groove 50 having a substantially inverted V shape in the axial direction on the inner surface 2a of the hammer 2. Formed. Then, the steel ball 6 is sandwiched between the cam groove 40 provided in the drive shaft 1 and the cam groove 50 provided in the hammer 2 in a state where the hammer 2 is fitted to the drive shaft 1, and the rotational motion of the drive shaft 1 is made of steel. The ball 6 and the cam grooves 40 and 50 cause the hammer 2 to rotate and move forward and backward. The hammer 2 is biased forward by a spring 7.

  As shown in FIG. 10, the cam 4 of the drive shaft 1 has a cam groove 40 having a substantially V-shaped inner wall 41 in sliding contact with the steel ball 6 on the outer surface 1 a of the drive shaft 1. The cam 5 of the hammer 2 is formed by arranging a cam groove 50 having a substantially inverted V-shaped inner wall 51 in sliding contact with the steel ball 6 on the inner surface 2a of the hammer 2 in the circumferential direction. is there. Here, the substantially V-shape and the substantially inverted V-shape are the rear (direction of arrow B in FIG. 10) side up and the front (direction of arrow F in FIG. 10 in which the anvil 3 is arranged) side. It shall mean the shape of the side view when the is down.

  On the front side of the hammer 2, the anvil 3 is rotatably supported by a hammer case 83 by a sleeve 84. The anvil 3 is provided with an anvil claw 30 at the rear end, and the hammer 2 is provided with a hammer claw 20 at the front end of the hammer 2 so that the hammer claw 20 is engaged with the anvil claw 30 when the hammer 2 moves forward. At this time, the rotation of the hammer 2 gives an impact to the anvil 3 in the direction of rotation, and can be tightened by momentarily applying a strong torque to the screw via a socket or the like attached to the attachment portion 32 of the anvil 3.

  By the way, in this impact rotary tool, the hammer 2 rotates relative to the drive shaft 1 in the direction opposite to the rotation direction by the reaction force received when the hammer 2 strikes the anvil 3. At this time, the steel ball 6 moves toward the side end portion in the cam groove 40 of the drive shaft 1 and moves toward the side end portion in the cam groove 50 of the hammer 2. If it is excessive, the steel ball 6 may collide with the side end portion in the cam groove 40 of the drive shaft 1 and the end portion in the cam groove 50 of the hammer 2.

  Here, operation | movement of an impact rotary tool is demonstrated based on FIG. In FIG. 10, the solid line indicates a state in which the outer surface 1 a of the drive shaft 1 is expanded left and right, the two-dot chain line indicates the position of the cam groove 50 of the hammer 2, and the arrow A indicates the rotation of the drive shaft 1 when tightened. The arrow indicates the direction of rotation of the drive shaft 1 when the screw is loosened, and the broken arrow c and d indicate the relative movement direction of the hammer 1 and the steel ball 6 with respect to the drive shaft 1 (arrow c is the forward rotation direction, arrow D indicates reverse rotation direction). Of the two-dot chain cam groove 50, 50A indicates the position of the cam groove 50 when the hammer 2 is most advanced, and 50B indicates the position of the cam groove 50 when the hammer 2 is most retracted.

  When the hammer 2 strikes the anvil 3, the hammer 2 receives a reaction force from the anvil 3 and rotates relative to the drive shaft 1 in the reverse direction of the arrow D, and the steel ball 6 moves in the cam groove 50 of the hammer 2. Slidably contacts the inner wall 51a on the rotation direction arrow A side and moves from the valley 51c side toward the end 52 side, and in the cam groove 40 of the drive shaft 1, it moves to the inner wall 41a on the counter rotation direction arrow B side. Since it slides and moves from the valley side toward the end 42 side, the hammer 2 eventually rotates against the spring 7 while rotating in the reverse rotation direction (arrow D direction) as described above in the arrow B direction. Retreat to. Then, when the hammer 2 moves backward and the engagement between the hammer claw 20 and the anvil claw 30 is released and the reaction force from the anvil 3 disappears, the hammer 2 turns from the backward movement to the forward movement by the urging force of the spring 7. At this time, the steel ball 6 moves in the cam groove 50 of the hammer 2 slidably in contact with the inner wall 51a on the side indicated by the arrow A in the direction of rotation and moves from the end 52 side toward the trough 51c. In 40, it slides in contact with the inner wall 41a on the opposite side of the anti-rotation direction arrow B and moves from the end 42 side toward the valley side, and the hammer 2 rotates relative to the drive shaft 1 while moving forward. When the hammer claw 20 engages with the anvil claw 30 when the hammer claw 20 rotates in the direction (arrow c direction), the hammer 2 gives a striking force (impact force) to the anvil 3 in the rotation direction (arrow b direction). A strong screw tightening torque can be applied to a screw or the like to be screwed through a socket or the like attached to the third mounting portion 32.

  As for the operation at the time of screw loosening, in the above description of the operation at the time of screw tightening, that is, the direction of rotation of the drive shaft 1 is the arrow B direction, and the forward rotation and reverse rotation relative to the drive shaft 1 (ie The same explanation is obtained by replacing d), replacing the inner wall 41a and the inner wall 41b, replacing the inner wall 51a and the inner wall 51b of the inner wall 51, and reversing the left and right.

  When the reaction force received by the hammer 2 from the anvil 3 is below a certain level (for example, when fastening wood screws, machine screws, etc.), the steel balls 6 are the wall surfaces of the end portions of the inner walls 41, 51 of the cam grooves 40, 50. Will not collide. However, when fastening a large-diameter bolt or the like, if an attempt is made to further fasten the large-diameter bolt or the like, the anvil 3 is fixed, and the hammer 2 strikes the fixed anvil 3. As a result, the hammer 2 receives an unexpected excessive reaction force, and the steel ball 6 collides with the wall surfaces of the end portions of the inner side walls 41 and 54.

Here, as shown in FIG. 11, the cam grooves 40 and 50 have the semicircular cross-sectional grooves described above, and the outer surface 1 a of the drive shaft 1 so as to be substantially V-shaped (and substantially inverted V-shaped) when viewed from the side. And the inner surface 2a of the hammer 2 are respectively drilled. In this conventional example, the portion of the inter-groove wall portions 43 and 53 between the cam grooves 40 and 50 is not particularly processed. next flush with the outer surface 1a of the drive shaft 1 (i.e., the outer diameter d _s of the drive shaft 1 in the cross section shown in FIG. 11, 180 ° phase between the grooves between the wall portions 43 the tip of the two cam grooves 40 shifted distance d _sk are equal), the distal end surface of the groove between the wall 53 is the inner surface 2a is flush hammer 2 (i.e., the inner diameter d _h of the hammer 2, the grooves of the two cam grooves 50 180 ° out of phase The distance d _hk between the tips of the intermediate wall portion 53 is equal).

For this reason, as described above, when the steel ball 6 collides with the inter-groove wall portions 43 and 53, from the bottom of the cam grooves 40 and 50 of the inter-groove wall portions 43 and 53 located between the end portions of the cam grooves 40 and 50, respectively. When the collision force F acts on the front end portion P of the inter-groove wall portion 43, for example, as shown in FIG. 12, the distance r from the base portion to the front end portion of the inter-groove wall portion 43 acts on the collision force F. M applied with '= F × r' is applied to the groove wall 43 as a moment, and since the distance r 'is large, a large moment M' is applied and the groove wall 43 is damaged as shown in FIG. There was a problem that. Further, in the conventional example, the minimum wall thickness d ′ of the inter-groove wall portion 43 is small, so that the minimum thickness d for maintaining a predetermined strength cannot be ensured and is easily damaged. there were.
JP 2001-219383 A

  The present invention was invented in view of the above-described conventional problems, and the object of the present invention is to break the groove wall portion at the side end portion of the cam groove as a cam formed on the drive shaft and the hammer. It is an object of the present invention to provide an impact rotary tool that does not perform.

In order to solve the above-mentioned problem, in the invention according to claim 1, a drive shaft 1 rotated by a motor, a hammer 2 fitted to the outer periphery of the drive shaft 1 so as to be able to rotate and advance / retreat, A hammer claw 20 provided on the hammer 2, an anvil 3 having an anvil claw 30 engageable with the hammer claw 20, and a plurality of cams arranged in parallel on the outer surface 1 a of the drive shaft 1 and the inner surface 2 a of the hammer 2. The steel balls 6 sandwiched between the grooves 40, 50, the cam groove 40 formed on the outer surface 1 a of the drive shaft 1 and the cam groove 50 formed on the inner surface 2 a of the hammer 2 , In an impact rotary tool provided with a spring 7 that constantly biases the hammer 2 toward the anvil 3 side, a plurality of cam grooves 40 arranged in parallel on the outer surface 1a of the drive shaft 1 and between the ends 42 and the hammer 2 Multiple side by side on the inner surface 2a The height from the cam grooves 40, 50 bottom of the groove between the walls 43, 53 located between the end portion 52 of the cam groove 50 which is characterized by comprising forming lower than the cam groove 40, 50 the height that It is. With such a structure, doing, it suppressed small moment M exerted on the groove between the walls 43, 53, it is possible to prevent the groove between the walls 43, 53 may be damaged.

  In the present invention, by reducing the moment when the steel ball collides with the groove wall portion between the cam grooves formed on the drive shaft and the hammer, respectively, or by removing the groove wall portion itself, It is intended to prevent damage to the inter-groove wall during high load work such as tightening, improve the tool life and increase the power of the tool itself.

  Hereinafter, the present invention will be described based on embodiments shown in the accompanying drawings. As shown in FIG. 4, the impact rotary tool includes an electric motor (not shown) housed in a main casing (not shown) as a drive source and a planetary gear mechanism connected to an output shaft 81 of the electric motor. A speed reducing means 82, a drive shaft 1 rotated via the speed reducing means 82, a hammer 2 and an anvil 3 provided on the front end side of the drive shaft 1, and a spring 7 for biasing the hammer 2 forward The main body consists of The hammer 2 has a substantially annular shape, and is fitted to the outer surface 1a of the drive shaft 1 so as to be rotatable about the axis and to be movable forward and backward in the axial direction. The anvil 3 is rotatably supported by a hammer case 83 attached to the front end portion of the main body via a sleeve 84, and the front end portion is a protrusion portion 31 protruding from the hammer case 83. A mounting portion 32 to which a socket for screw tightening (and loosening) or the like is mounted is provided at the front end.

  A steel ball 6 is provided between the drive shaft 1 and the hammer 2 fitted to the drive shaft 1. As will be described later, the steel ball 6 is disposed between the cam 4 formed on the outer surface 1a of the drive shaft 1 and the cam 5 formed on the inner surface 2a of the annular hammer 2. The hammer 2 is provided with a hammer claw 20 at the front end, while the anvil 3 is provided with an anvil claw 30 at the rear end. When the hammer 2 moves forward, the hammer claw 20 and the anvil claw 30 are engaged. At the same time, the engagement is released when the hammer 2 is retracted. The hammer 2 is biased forward by a spring 7.

  By the way, as the reaction force received by the hammer 2 from the anvil 3 during screw tightening increases, the backward movement and reverse rotation amount of the hammer 2 with respect to the drive shaft 1 also increases, and if the degree is large, the rear end portions of the cam grooves 40 and 50 are increased. The steel balls 6 collide with each other. As a result, there is a risk that the inter-groove wall portions 43 and 53 located between the end portions of the cam grooves 40 and 50 arranged in parallel as the cam grooves 40 and 50 may be damaged. The heights of the wall portions 43 and 53 from the bottom of the cam grooves 40 and 50 are made lower than the heights of the cam grooves 40 and 50, respectively, and the moment M received by the inter-groove wall portions 43 and 53 in the event of a collision is kept small. .

The cam grooves 40, 50 are formed in the outer surface 1 a of the drive shaft 1 and the inner surface 2 a of the hammer 2 so that the above-described semicircular grooves have a substantially V shape (and a substantially inverted V shape) when viewed from the side. As described above, the tip of the inter-groove wall portions 43 and 53 is flush with the outer surface 1a of the drive shaft 1 and the inner surface 2a of the hammer 2 as described above (see FIG. 11). As shown in FIG. 1, the distance d _sk between the tips of the inter-groove wall portions 43 of the two cam grooves 40 that is 180 ° out of phase with the outer diameter d _s of the drive shaft 1 is reduced (d _sk <d _s) and was increasing the distance _{d hk} between the grooves between the wall 53 distal of the two cam grooves 50 180 ° out of phase than the inner diameter _{d h} of the hammer _{2 (d hk> d h)} . Incidentally, when the height of the inter-groove wall portion 43 is formed low, a method using machining interference as shown in FIG. 8 is often used. This is because the 6 ′ portion in the drawing is removed by machining or the like, but if the removal processing is performed from both sides as the 6 ′ portion, the machining interference portion K is removed and the inter-groove wall portion 43 is lowered. In this case, the tip of the inter-groove wall portion 43 becomes an edge, and at this time, the minimum thickness d cannot be ensured, and it is easy to break, which is not preferable. For this reason, the front-end | tip part of the groove part wall part 43 is removed so that minimum thickness d may be ensured.

  According to the above configuration, even if the steel ball 6 collides with the inter-groove wall portions 43 and 53, the cam groove 40 of the inter-groove wall portions 43 and 53 located between the end portions of the cam grooves 40 and 50. 50, the height from the bottom is lower than that of the conventional one (that is, the tip surfaces of the inter-groove walls 43, 53 are flush with the outer surface 1a of the drive shaft 1 and the inner surface 2a of the hammer 2). The walls 43 and 53 are less likely to be damaged. For example, the groove part 43 will be described. As shown in FIG. 2, when a collision force F acts on the tip part P of the groove part 43, the tip part from the base part of the groove wall part 43 acts on the collision force F. M = F × r multiplied by a distance r up to is applied to the inter-groove wall 43 as a moment, but since the distance r is smaller than the conventional distance r ′ (r <r ′), the moment M is also smaller than the conventional one. It becomes a thing (M <M '), and it is suppressed that the wall part 43 between grooves is damaged. 2 shows that the minimum thickness d ′ of the conventional one (that is, the groove wall portion located between the arc-shaped inner wall surface of the cam groove 40 having the same diameter as the steel ball 6). 43, and the strength of this portion is the same and is easily damaged. However, as shown in FIG. 3, the end portion of the inter-groove wall portion 43 is set to the center side of the drive shaft (that is, the groove). By reducing the height of the inter-wall portion 43), a portion where the thickness d on the center side is larger than the minimum thickness d ′ (d> d ′) becomes the minimum thickness, and the strength at this portion is improved. It is even more difficult to break, and it is possible to prevent the broken part from getting stuck in the tool and stopping the tool operation, improving the life of the impact rotary tool during high load work, Or the lifetime accompanying the output improvement of an impact rotary tool itself can be improved.

  Next, another embodiment will be described with reference to FIGS. In this embodiment, in the above embodiment, the portions where the inter-groove wall portions 43 and 53 are located are communication portions 44 and 54 through which the steel balls 6 can come and go. 5 shows that a communicating portion 44 having the same semicircular cross section as that of the cam groove 40 is formed between the cam grooves 40 so that the adjacent cam grooves 40 communicate with each other, and that shown in FIG. A communication portion 54 having a semicircular cross section similar to that of the cam groove 50 is formed between the adjacent cam grooves 50. As a result, since the groove wall portions 43 and 53 themselves do not exist, the collision between the steel ball 6 and the groove wall portions 43 and 53 can be eliminated, and the occurrence of vibration and noise due to the collision can be avoided. Pleasure can be eliminated. In addition, if the inter-groove wall portions 43 and 53 exist in both the cam grooves 40 and 50, there is a possibility that parts are damaged due to overload when the steel ball 6 collides. Damage due to overload can be avoided.

  Further, the above effect can be obtained by eliminating one of the inter-groove wall portions 43 and 53, but it is of course possible to eliminate both of them as shown in FIG.

It is principal part sectional drawing of one Embodiment of this invention. It is sectional drawing explaining the height of the wall part between grooves same as the above. It is sectional drawing of the other example of the wall part between grooves. It is principal part side sectional drawing of an impact rotary tool. It is a side view explaining operation | movement of the drive shaft of another example, the cam groove of a hammer, and a steel ball. Furthermore, it is a side view of another example. Furthermore, it is sectional drawing of another example. It is sectional drawing explaining the process of a cam groove. It is principal part side sectional drawing of the conventional impact rotary tool. It is a side view explaining operation | movement of the drive shaft same as the above, the cam groove of a hammer, and a steel ball. It is sectional drawing same as the above. It is sectional drawing explaining the height of the wall part between grooves same as the above. It is sectional drawing which shows the state which the wall part between groove | channels same as the above damaged.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive shaft 1a Outer surface 2 Hammer 2a Inner surface 20 Hammer claw 3 Anvil 30 Anvil claw 4 Cam 40 Cam groove 41 Inner side wall 5 Cam 50 Cam groove 51 Inner side wall 6 Steel ball 7 Spring

Claims (1)

A driving shaft that is rotated by a motor; a hammer that is fitted to the outer periphery of the driving shaft so as to be able to rotate and move forward and backward; a hammer pawl provided on the hammer; and an anvil pawl that can be engaged with the hammer pawl An anvil, a plurality of cam grooves arranged in parallel on the outer surface of the drive shaft and the inner surface of the hammer, and a cam groove formed on the outer surface of the drive shaft and a cam groove formed on the inner surface of the hammer In an impact rotary tool having a steel ball that is rarely accommodated and a spring that constantly biases the hammer toward the anvil side, between the ends of the cam grooves that are arranged in parallel on the outer surface of the drive shaft and the hammer An impact rotary tool characterized in that a height from a cam groove bottom of an inter-groove wall portion positioned between end portions of a plurality of cam grooves arranged in parallel on the inner surface is formed lower than the cam groove height .

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