Oscillating rotary electric power tool

An oscillating rotary electric power tool, in which a spindle with a distal end tool attached thereto is projected downward from a front end portion of a housing accommodating a motor, and the housing also accommodates a coupling member rotatable integrally with an output shaft of the motor, a crankshaft fitted with the coupling member in a depression and projection fitting structure, and a link member to which the spindle is fixed and power is transmitted from the crankshaft to rotate clockwise and counterclockwise in an oscillating manner so that the link member will be driven by the motor to rotate the spindle clockwise and counterclockwise in the oscillating manner, wherein an elastic body is interposed between the coupling member and the crankshaft in the same axial direction as the output shaft.

BACKGROUND OF THE INVENTION

This application claims the benefit of Japanese Patent Application Number 2012-038864 filed on Feb. 24, 2012, the entirety of which is incorporated by reference.

1. Technical Field

This invention relates to an oscillating rotary electric power tool in which a spindle with a distal end tool attached thereto is projected downward from a front end portion of a housing accommodating a motor so that the spindle will be driven by the motor to rotate clockwise and counterclockwise in an oscillating manner.

2. Background Art

As shown inFIG. 4, there is known a conventional oscillating rotary electric power tool50, where a motor M is accommodated in a housing51extending in a longitudinal direction (horizontal direction ofFIG. 4) of the oscillating rotary electric power tool50, and a spindle53to which various kinds of distal end tools52are able to be attached is projected downward from a front end portion (right side inFIG. 4) of the housing51in an orthogonal direction with respect to the longitudinal axis of the housing51. In this oscillating rotary electric power tool50, a coupling member55is coupled in front of an output shaft54of the motor M in such a manner that a projected portion58of a crankshaft57is fitted in a depressed portion56provided on a front end face of this coupling member55to integrate the coupling member55and the crankshaft57in the rotational direction. Then, a link member59to which the spindle53is fixed is supported in front of the crankshaft57within the housing51. As viewed from the front side of the oscillating rotary electric power tool50, this link member59rotates clockwise and counterclockwise in an oscillating manner by the transmission of power from the crankshaft57.

In the above oscillating rotary electric power tool50, when the output shaft54of the motor M rotates, the link member59rotates clockwise and counterclockwise in a oscillating manner as a result of the transmission of the torque of the motor M to the link member59through the coupling member55and the crankshaft57. Along with this, the spindle53fixed to the link member59and a distal end tool52rotate clockwise and counterclockwise in the oscillating manner. However, since the projected portion58is fitted in the depressed portion56with an allowance in the rotational direction, the depressed portion56and the projected portion58hit each other when the coupling member55and the crankshaft57rotate integrally along with the rotation of the output shaft54, suffering from the disadvantage of generating abnormal noise in a hitting portion.

As a technique for preventing the generation of such abnormal noise, Japanese Utility Model Application Publication No. 49-111654 describes that projected portions and depressed portions are formed alternately in a circumferential direction on the end face of a cylindrical driving body and the end face of a cylindrical driven body facing each other, respectively. The projected portions of the driving body are fit into the depressed portions of the driven body and the projected portions of the driven body are fit into the depressed portions of the driving body, and an elastic body is inserted into a clearance gap between each projected portion and each depressed portion in the circumferential direction.

SUMMARY OF THE INVENTION

However, like in the technique described in Japanese Utility Model Application Publication No. 49-111654 to prevent the generation of abnormal noise, when an elastic body is inserted between the depressed portion56and the projected portion58in the circumferential direction of the coupling member55, a force to squash the elastic body is applied from the projected portion58in the rotational direction along with the rotation of the output shaft54. In such a case, since the elastic body can be torn off by this force, it is hard to say that the durability of the elastic body is sufficient.

This invention is proposed in view of such circumstances, and it is an object thereof to provide an oscillating rotary electric power tool for satisfying both improvement in durability and prevention of the generation of abnormal noise.

An oscillating rotary electric power tool according to a first aspect of the present invention includes a housing provided to extend in a longitudinal direction, a motor accommodated in the housing, a spindle projected downward from a front end portion of the housing, a distal end tool to be attached to the spindle, a coupling member accommodated in the housing and coupled to an output shaft of the motor on an identical axis to that of the output shaft to be rotatable integrally with the output shaft, a crankshaft accommodated in the housing, arranged to be rotatable on the identical axis, and fitted with the coupling member in a depression and projection fitting structure, and a link member accommodated in the housing, to which the spindle is fixed and power is transmitted from the crankshaft to rotate clockwise and counterclockwise in an oscillating manner. In the oscillating rotary electric power tool, the link member is driven by the motor through the coupling member and the crankshaft to rotate the spindle to clockwise and counterclockwise in the oscillating manner, and an elastic body is interposed between the coupling member and the crankshaft in a direction of the identical axis to fit the coupling member and the crankshaft together in the depression and projection fitting structure.

According to a second aspect of the present invention, in the first aspect, a depressed portion is formed in either an end face of the coupling member or an end face of the crankshaft facing each other in the identical axial direction, and a projected portion is formed on the other end to project from the end face in the identical axial direction to fit in the depressed portion in the depression and projection fitting structure, and the elastic body is interposed between the end face on an open side of the depressed portion and the end face on a base end side of the projected portion.

According to a third aspect of the present invention, in the second aspect, the depressed portion is formed in the end face of the coupling member and the projected portion is formed on the end face of the crankshaft.

According to a fourth aspect of the present invention, in the second aspect, the elastic body is an O-ring mounted on an outer circumference of a base end of the projected portion.

According to the oscillating rotary electric power tool according to the first aspect of the invention, the elastic body elastically deforms between the coupling member and the crankshaft in the direction of the identical axis to that of the output shaft of the motor so that the elastic body can adhere to the coupling member and the crankshaft. Therefore, as a result of increasing the resistance by the elastic body in the rotational direction of the coupling member or the rotational direction of the crankshaft, the unity between the coupling member and the crankshaft in the rotational direction is increased. Thus, it is possible to prevent the generation of abnormal noise caused by hitting of the coupling member and the crankshaft.

In addition, the elastic body just deforms elastically to adhere to the coupling member and the crankshaft, and no force to squash the elastic body is applied to the elastic body in the rotational direction during the rotation of the coupling member or the rotation of the crankshaft. Since the elastic body is not squashed and torn off, the durability of the elastic body can be improved.

According to the second aspect of the invention, the elastic body is sandwiched between the end face on the open side of the depressed portion and the end face on a base end side of the projected portion to so that both end faces can be easily adhered. Thus, the resistance between both end faces increases in the rotational direction of the coupling member or the rotational direction of the crankshaft.

According to the third aspect of the invention, the depressed portion is formed in the end face of the coupling member to provide two portions having projected cross-sections in the end portion of the coupling member. The weights of the two portions make the weight of the coupling member heavier than the weight of the crankshaft having one projected portion. Thus, it is possible to make the strength of the coupling member stronger than the strength of the crankshaft driven by the coupling member to move.

According to the fourth aspect of the present invention, there is no need to create an additional space for the elastic body between the coupling member and the crankshaft. Furthermore, if a commercially available O-ring is used for the elastic body, the elastic body can be formed at low cost.

DETAILED DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be described with reference toFIG. 1toFIG. 3. An oscillating rotary electric power tool1shown inFIG. 1andFIG. 2includes a housing2, which is molded with resin, has a round cross-section, and extends in the longitudinal direction (horizontal direction inFIG. 1andFIG. 2) of the oscillating rotary electric power tool1. A motor M is accommodated inside the housing2, and a slide lever3(seeFIG. 1) is provided on the outer circumference of the housing2to switch the motor M between an on-state and an off-state. Further, a battery attachment portion4is provided in a rear end portion of the housing2(left side ofFIG. 1andFIG. 2). A battery pack5is removably attached to the battery attachment portion4to feed power to the motor M when the slide lever3is switched to the on-state.

As shown inFIG. 1andFIG. 2, a cylindrical coupling member10is concentrically coupled to an output shaft9in front of the output shaft9of the motor M inside the housing2. Here, the output shaft9is pressed into the coupling member10. This allows the coupling member10to rotate integrally with the output shaft9. A depressed portion11having a bottom and extending in the axial direction of the output shaft9is opened up in the front end face of this coupling member10. Further, a crankshaft12is rotatably supported within the housing2through bearings13and14on the same axis as the output shaft9in front of the coupling member10. Thus, the front end face of the coupling member10faces a rear end face15(seeFIG. 3) of the crankshaft12in the same axial direction X as the axis of the output shaft9. Then, a projected portion16projecting toward the depressed portion11in the same axial direction X is formed integrally on this rear end face15. An O-ring17made of rubber is mounted on the outer circumference of a base end of this projected portion16as shown inFIG. 1andFIG. 3. It should be noted that the O-ring17is not shown inFIG. 2. This O-ring17is an example of an elastic body of the present invention.

The projected portion16and the depressed portion11are fitted together with an allowance in the rotational direction of the coupling member10to fit the crankshaft12and the coupling member10together in a depression and projection fitting structure. In this depression and projection fitting state, as shown inFIG. 1, the O-ring17is interposed between the front end face of the coupling member10and the rear end face15of the crankshaft12located on the base end side of the projected portion16in the same axial direction X. The O-ring17is sandwiched between the front end face and the rear end face15, elastically deforming in the same axial direction X. This makes the O-ring17adhere to the front end face and the rear end face15. It should be noted that the front end face of the coupling member10is an example of an end face on the open side of the depressed portion in the present invention. Further, the rear end face15of the crankshaft12is an example of an end face on the base end side of the projected portion in the present invention.

Further, as shown inFIG. 1andFIG. 3, an eccentric-shaft portion18extending in the axial direction X1from a position eccentric to the shaft center of the crankshaft12is formed in a substantially central portion of the crankshaft12in the axial direction X1. A bearing19(seeFIG. 1) with an arc-like outer ring is assembled externally around this eccentric-shaft portion18.

Further, as shown inFIG. 1, in the front end portion of the housing2, a spindle21is supported within the housing2through bearings22and23, and the distal end of the spindle21projects downward of the housing2. Any of various kinds of distal end tools different in shape and intended use, such as a cutting tool and a grinding tool, is fixable at the distal end of the spindle21with a bolt24.FIG. 1shows an example where a cutting tool25of which the planer view is fan-shaped is fixed to the spindle21.

In addition, as shown inFIG. 1andFIG. 2, a link member30is supported between the crankshaft12and the spindle21in the longitudinal direction within the housing2. The link member30includes a ring-shaped main body part31, a pair of engaging parts32,32, and an arm part33. The main body part31is placed face to face with the eccentric-shaft portion18, and the front end side of the crankshaft12is inserted through the main body part31as shown inFIG. 1. The pair of engaging parts32,32are provided to project from the main body part31into the eccentric-shaft portion18side and arranged to be parallel to each other on the outside of the crankshaft12as shown inFIG. 2. The bearing19is placed in a space between the engaging parts32,32as shown inFIG. 2. The arm part33is provided to project from the main body part31into the spindle21side, and a spindle positioning hole34(seeFIG. 1) is formed in the arm part33. The spindle21is pressed into the spindle positioning hole34.

Next, as an example, an action of using the oscillating rotary electric power tool1to cut a column material installed on the floor in a standing manner will be described. A user switches the slide lever3to the on-state while holding the housing2to drive the motor M. When the coupling member10rotates together with the output shaft9of the motor M, the rotation of the motor M is transmitted to the crankshaft12fitted with the coupling member10in the depression and projection fitting structure. Along with this, when the crankshaft12rotates integrally with the coupling member10, the bearing19assembled, around the eccentric-shaft portion18eccentrically rotates about the crankshaft12. During the eccentric rotation, the bearing19repeats motion to come into contact with the engaging parts32,32of the link member30only to right and left so that the link member30will rotate clockwise and counterclockwise in an oscillating manner as viewed from the front side of the oscillating rotary electric power tool1as indicated by the arrow inFIG. 2. As a result, the spindle21and the cutting tool25rotate clockwise and counterclockwise in an oscillating manner about the axis of the spindle21. Then, the cutting tool25rotating in the oscillating manner is pressed against the column material while the spindle21is kept perpendicular to the floor to cut the column material.

Conventionally, when the coupling member10and the crankshaft12rotate integrally, since the projected portion16of the crankshaft12moves in the rotational direction within the depressed portion11of the coupling member10, the depressed portion11and the projected portion16hit each other, suffering from the disadvantage of generating abnormal noise in the hitting portion. To prevent this, in the embodiment, the O-ring17(seeFIG. 1andFIG. 3) is interposed between the front end face of the coupling member10and the rear end face15(seeFIG. 3) of the crankshaft12. This O-ring17is sandwiched between the front end face and the rear end face15, elastically deforming in the same axial direction X (seeFIG. 1). This makes the O-ring17adhere to the front end face and the rear end face15, resulting in increases in resistance in the rotational direction of the coupling member10and the rotational direction of the crankshaft12. Therefore, the unity between the coupling member10and the crankshaft12in the rotational direction is increased to prevent the projected portion16from moving in the rotational direction within the depressed portion11, preventing the depressed portion11and the projected portion16from hitting each other. Thus, it is possible to prevent the generation of abnormal noise.

Further, when the output shaft9of the motor M accommodated in the housing2has a backlash in the axial direction, the output shaft9and the coupling member10shake during the operation of the oscillating rotary electric power tool1, and this is considered to be the cause of abnormal noise. In the embodiment, the front end face of the coupling member10coupled to the output shaft9is struck against the rear end face15of the crankshaft12in such a state that there is no clearance gap in the axial direction of the output shaft9through the O-ring17. Thus, the coupling member10and the output shaft9are prevented from moving in the axial direction during the operation of the oscillating rotary electric power tool1. As a result, it is possible to prevent the generation of abnormal noise due to a backlash.

Effect of the Embodiment

In the oscillating rotary electric power tool1of the embodiment, the O-ring17elastically defouns between the coupling member10and the crankshaft12in the same axial direction X as the axis of the output shaft9to allow the coupling member10and the crankshaft12to adhere to each other. Therefore, as a result of increasing the resistance by the O-ring17in the rotational direction of the coupling member10and the rotational direction of the crankshaft12, the unity between the coupling member10and the crankshaft12in the rotational direction is increased. Thus, it is possible to prevent the generation of abnormal noise caused by hitting of the coupling member10and the crankshaft12.

In addition, the O-ring17just deforms elastically to adhere to the coupling member10and the crankshaft12, and no force to squash the O-ring17is applied to the O-ring17in the rotational direction during the rotation of the coupling member10and the rotation of the crankshaft12. Thus, since the O-ring17is not squashed and torn off, the durability of the O-ring17can be improved.

Further, the O-ring17is interposed and sandwiched between the front end face of the coupling member10and the rear end face15of the crankshaft12so that the two end faces can be easily adhered. Thus, the resistance between the two end faces increases in the rotational direction of the coupling member10and the rotational direction of the crankshaft12.

Further, in the embodiment, the depressed portion11is opened up in the front end face of the coupling member10, and the projected portion16to be fitted in the depressed portion11is formed on the rear end face15of the crankshaft12. Therefore, two portions having projected cross-sections are provided in the front end portion of the coupling member10. The weights of the two portions make the weight of the coupling member10heavier than the weight of the crankshaft12having the one projected portion16. Thus, it is possible to make the strength of the coupling member10stronger than the strength of the crankshaft12driven by the coupling member10to move.

In addition, since the O-ring17is mounted on the outer circumference of the base end of the projected portion16formed on the crankshaft12, there is no need to create an additional space for the O-ring17between the coupling member10and the crankshaft12. Furthermore, since a commercially available O-ring is used for the O-ring, there is an advantage that the O-ring is cheap.

It should be noted that the present invention is not limited to the aforementioned embodiment, and part of the structure can be changed without departing from the spirit and scope of the invention. For example, unlike the aforementioned embodiment, the structure may be such that a depressed portion is opened up in the rear end face15of the crankshaft12and a projected portion to be fitted in the depressed portion is formed on the front end face of the coupling member10to fit the coupling member10and the crankshaft12together in a depression and projection fitting structure. The O-ring17may also be made of resin, rather than of rubber. Further, although the aforementioned embodiment illustrates an example of applying the present invention to a rechargeable oscillating rotary electric power tool, it is not limited thereto and the present invention may also be applied to an AC-driven oscillating rotary electric power tool.