Work tool

The disclosure provides a work tool having an electric motor, a power transmission means that receives motive power from the electric motor and transmits the motive power to a tip tool, a gear housing for accommodating at least a portion of the power transmission means, weights swingably supported on the gear housing, and coil springs that function as an urging means for urging the weights such that the weights are located at an initial neutral position, wherein the weights and the coil springs are provided respectively on the two sides of the gear housing so as to put the power transmission means therebetween, and a rotational support axle is provided that functions as a connecting means for connecting the weights provided on both sides of the gear housing so as to connect the weights such that the weights swing integrally.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 of international application of PCT application serial no. PCT/JP2015/063010, filed on Apr. 30, 2015, which claims priority benefits of Japan application no. 2014-093640, filed on Apr. 30, 2014, and Japan application no. 2014-093641, filed on Apr. 30, 2014. The entirety of each of the abovementioned patent applications is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to a work tool, and particularly relates to a work tool including a power transmission means that receives motive power from a motor and transmits the motive power to a tip tool.

Description of Related Art

In a work tool provided previously, the work tool includes a power transmission mechanism, such as a reciprocal movement conversion mechanism or a rotation transmission mechanism, in a housing, and includes a vibration-reducing mechanism that exerts control on vibration generated through the power transmission mechanism (see Patent Literature 1, for example). The vibration-reducing mechanism includes a weight portion that is swingably supported and an urging means. The urging means includes a plate spring, a spring, or the like that urges the weight portion to make the weight portion return to an initial neutral position.

PRIOR ART LITERATURE

Patent Literature

SUMMARY OF THE INVENTION

Problem to be Solved

However, in the conventional art, a vibration-reducing mechanism is located on a central axis of a tip tool, and disposed between a striking mechanism in a housing and a handle. Therefore, a total length becomes longer. Accordingly, Patent Literature 1 also proposes to dispose a vibration-reducing mechanism including a weight portion and an urging means on left and right sides or an upper surface of the housing. However, in correspondence with a direction where vibrations are generated, the weight portion disposed to the left and right sides or the upper surface may swing abruptly. Therefore, a vibration damping effect is reduced.

In view of the above, the invention is set to solve the issue and provides a work tool that ensures the vibration damping effect even if the vibration-reducing mechanism is disposed to the side surface of the housing to reduce the total length of the device. Besides, the invention is also set to provide a work tool capable of damping vibrations in a preferable efficiency regardless of strength of the vibrations.

Technical Means for Solving the Issue

To solve the issue, a work tool of the invention has: a motor; a power transmission means, receiving motive power of the motor and transmitting the motive power to a tip tool; a housing, accommodating at least a portion of the power transmission means; weights, swingably supported by the housing; and urging means, urging the weights such that the weights are located at an initial neutral position. For the work tool, the weight and the urging means are respectively disposed to two sides of the housing to put the power transmission means therebetween, and the work tool has a connection means connecting the weights respectively disposed to the two sides of the housing, so as to swing integrally.

Inventive Effect

According to the invention, even if the vibration-reducing mechanism is disposed to the side surface of the housing to reduce the total length of the device, the connection means is used to integrate the weights disposed to the two sides of the housing to swing. Therefore, the vibration damping effect is ensured.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the invention are described with reference to the figures. In the following description, the same or equivalent forming elements, components, processes shown in the respective figures are marked with the same reference symbols. In addition, repeated descriptions are appropriately omitted. Also, in the following descriptions, the vertical direction refers to the directions shown in the figure.

First Embodiment

A work tool1of the first embodiment is a striking tool that exerts powerful to-and-fro strikes on a tip tool while operating, or more specifically, a hammer drill as follows. Namely, a drill is mounted to function as a tip tool not shown herein, and the hammer drill exerts powerful to-and-fro strikes on the drill while drilling. Referring toFIGS. 1 and 2, the work tool1includes a main handle portion10, a motor housing20, a gear housing30, a strike housing40, an external housing50covering the motor housing20, the gear housing30, and the strike housing40, and a sub-handle portion60that are connected with respect to each other. In addition, the embodiment is described by defining the left side inFIGS. 1 and 2as a front end side mounted with the tip tool, and the right side as a rear end side of the work tool1.

The main handle portion10is disposed at a rear end of the work tool1and extends along a direction substantially orthogonal to an axial direction of the tip tool mounted on the front end side of the work tool1. An electric cable11is installed to the main handle portion10and a switch mechanism12is disposed in the main handle portion10. Besides, a trigger13operable by the user is disposed to the main handle portion10. The trigger13and the switch mechanism12are mechanically connected. Accordingly, the work tool1is driven by connecting the electric cable11to an external electric power source not shown herein and operating the trigger13.

The motor housing20is disposed to a lower portion of a front end side of the main handle portion10and accommodates an electric motor21as a motive power source. The electric motor21includes an output axle22outputting a rotational driving force of the electric motor21. The output axle22extends inside the gear housing30, and a pinion gear23is disposed to a front end of the output axle22.

In the gear housing30, on a rear end side of the pinion gear23, a crank axle31extending in parallel with the output axle22is rotatably supported. A first gear32engaged with the pinion gear23is coaxially fixed proximate a lower end of the crank axle31. A movement conversion mechanism33is disposed to an upper end portion of the crank axle31. The movement conversion mechanism33includes a crank weight34, a crank pin35, and a conrod36. The crank weight34is fixed to an upper end of the crank axle31. At an end portion of the crank weight34, the crank pin35is disposed upright and centrifugally with respect to the crank axle31. Moreover, the crank pin35is inserted into a rear end of the conrod36. Therefore, when the crank axle31drives by rotation, the conrod36moves reciprocally along the axial direction of the tip tool mounted at the front end side of the work tool1. The crank axle31and the movement conversion mechanism33are power transmission means that receive motive power of the electric motor21, transmit the motive power to the tip tool, and convert the rotational driving force generated by the electric motor21into reciprocal movement.

Besides, in the gear housing30, on a front end side of the pinion gear23, a rotational transmission axle37extending in parallel with the output axle22is rotatably supported. A second gear38engaged with the pinion gear23is coaxially fixed to a lower end the rotational transmission axle37. A first bevel gear39is coaxially fixed to an upper end of the rotational transmission axle37.

The strike housing40is disposed to a front end side of the gear housing30, and is provided with a cylinder41extending in a direction substantially orthogonal to the output axle22and coplanar with the output axle22. In the cylinder41, a piston42is disposed to be slidable along an inner circumference of the cylinder41. A piston pin42ais disposed in the piston42, and the piston pin42ais inserted into a front end of the conrod36. On a front end side in the cylinder41, a striking piece43is disposed to be slidable along the inner circumference of the cylinder41. In the cylinder41, an air chamber44is defined between the piston42and the striking piece43.

Besides, in the strike housing40, a rotational cylinder45is rotatably supported, so as to cover an outer circumference of the cylinder41. The rotational cylinder45is more extended toward the front end side than the cylinder41, and a tool maintaining portion46allowing the tip tool to be detachably mounted is disposed to a front end portion of the rotational cylinder45. A second bevel gear47engaged with the first bevel gear39is disposed to a rear end portion of the rotational cylinder45. A central axis of the rotational cylinder45is coplanar with the output axle22. Besides, an intermediate piece48slidable along a to-and-fro direction is disposed to a front end side of the striking piece43in the rotational cylinder45. The piston42, the striking piece43, and the intermediate piece48are power transmission means that receive the motive power of the electric motor21and function as a striking mechanism that transmits a striking force to the tip tool mounted at the tool maintaining portion46. Moreover, the rotational transmission axle37and the rotational cylinder45are also power transmission means that receive the motive power of the electric motor21and transmit the motive power to the tip tool, and function as a rotational transmission mechanism that transmits the rotational driving force to the tip tool mounted at the tool maintaining portion46.

Referring toFIGS. 3 and 4, a vibration-reducing mechanism70reducing vibrations generated by driving of the work tool1is disposed between the gear housing30and the external housing50. The vibration-reducing mechanism70includes weights80and coil springs71. The weights80and the coil springs71are respectively disposed to opposite positions on two sides of the gear housing30to put an axle center of the cylinder41therebetween. Besides, inFIGS. 3 and 4, a portion where the external housing50is removed is shown to illustrate a state where the vibration-reducing mechanism70disposed to the gear housing30is exposed.

As shown inFIGS. 2 and 5(b), a through hole30apenetrating through two side surfaces in a direction substantially orthogonal with respect to an axle center of the rotational cylinder45is formed in the gear housing30. In addition,FIG. 5(a)is a top view illustrating the gear housing30, andFIG. 5 (b)is a side view illustrating the gear housing30. In this embodiment, the through hole30ais formed by extending in a direction that is also substantially orthogonal to the output axle22of the electric motor21and penetrating through left and right side surfaces of the gear housing30. In addition, as shown inFIG. 2, the through hole30ais formed above the electric motor21and in an area surrounded by the crank axle31as a portion of the movement conversion mechanism33, the rotational transmission axle37as a portion of the rotational transmission mechanism, and the axle center of the rotational cylinder45.

As shown inFIGS. 3 and 4, a rotational support axle72is rotatably inserted into the through hole30a. Two ends of the rotational support axle72respectively protrude from left and right sides of the gear housing30. As shown inFIG. 6, the weights80are respectively fixed to the two protruding ends of the rotational support axle72. Therefore, the weights80respectively disposed to the two sides of the gear housing30are connected and integrated by the rotational support axle72, and are rotatably supported with the rotational support axle72as the center. Besides,FIG. 6is a view observing the weights80respectively fixed at the two ends of the rotational support axle72from a top side.

Referring toFIG. 7, the weight80includes a support portion82and a weight portion83. An end portion of the support portion82is formed with a fixing hole81for the end portion of the rotational support axle72to be inserted and fixed. The weight portion83is disposed to another end side (a release end side) of the support portion82. The support portion82and the weight portion83are integrated. A key groove81aparallel to an axle center of the fixing hole81is formed at the fixing hole81. Key grooves72aparallel to an axle center of the rotational support axle72are respectively formed at the two end portions of the rotational support axle72. By inserting the end portion of the rotational support axle72into the fixing hole81and inserting a key73for engagement into the key groove81aof the fixing hole81and the key groove72aof the rotational support axle72, the rotational support axle72and the support portion82(the weight80) are integrated in terms of rotational direction. Thus, the rotational support axle72functions as a connection means, and is connected with the weights80disposed to positions of the two sides of the gear housing30and integrated in terms of rotational direction.

The weight portion83is a fan-shaped plate. The fixing hole81serves as a center (fan axle) of the weight portion83, and the weight portion83is substantially perpendicular to the axle center of the fixing hole81. In addition, in the weight portion83, rod-shaped weight locking portions84parallel to the axle center of the fixing hole81are respectively disposed to positions linearly symmetrical with respect to a line connecting a gravity center G of the weight80and the axle center of the fixing hole81. The weight locking portion84locks a bending portion formed at one end of the coil spring71. In the weight portion83, a thinner thickness portion85is formed at a part where the weight locking portion84is disposed upright. A thickness of the thinner thickness portion85is configured to be greater than a diameter of the coil spring71.

As shown inFIGS. 3 and 5, in the gear housing30, housing locking portions30bare formed by protruding from the side surfaces. The housing locking portions30bare respectively disposed in correspondence with the weight locking portions84of the weight80and lock bending portions formed at another ends of the coil springs71. The coil spring71is an extension spring and stretched between the weight locking portion84and the housing locking portion30b. In a state when an external force is not in effect, as shown inFIG. 3, the weight80is located at an initial neutral position where the line connecting the gravity center G of the weight80and the axle center of the fixing hole81is substantially orthogonal with respect to the axle center of the rotational cylinder45. In a state that the weight80is located at the initial neutral position, the case locking portion30band the weight locking portion84are disposed on a same normal line of the axle center of the fixing hole81, namely the rotational support axle72. Consequently, at the initial neutral position, the housing locking portions30bare respectively formed at the positions lineally symmetrical with respect to the line connecting the gravity center G of the weight80and the axle center of the fixing hole81. Thus, by utilizing a urging force in a contracting direction of the coil spring71, the weight80may be easily located at the initial neutral position. Besides, in the state that the weight80is located at the initial neutral position, as illustrated in the side observation shown inFIG. 3, the gravity center G of the weight80is disposed near the axle center of the piston42functioning as a portion of the striking mechanism. Therefore, the vibration generated by the striking mechanism is able to be effectively controlled.

In a state that the coil string71is stretched between the weight locking portion84and the housing locking portion30b, the weight locking portion84is disposed to the thinner thickness portion85. Thus, as shown inFIGS. 4 and 6, in an axial direction of the rotational support axle72serving as a swing axle of the weight80, the coil spring71is located within an area of the weight80, namely within a thickness of the weight80. Therefore, relative to the weight80, the coil spring71does not protrude toward the axial direction of the rotational support axle72. As a result, the vibration-reducing mechanism70may be more compact in the axial direction of the rotational support axle72, and may be disposed by simply utilizing a small space formed between the gear housing30and the external housing50.

In the following, an operation of the work tool1of the first embodiment is described in detail.

In a state that the main handle portion10and the sub-handle portion60are held by hands, the work tool1is pressed against a cutting material not shown herein, and the trigger13is pulled. Accordingly, an electric power provided to the electric motor21, so as to drive the electric motor21to rotate. The rotational driving force of the electric motor21is transmitted to the crank axle31through the output axle22, the pinion gear23, and the first gear32. Rotation of the crank axle31is converted into a reciprocal movement of the piston42in the cylinder41through the crank weight34, the crank pin35, and the conrod36constituting the movement conversion mechanism33. Moreover, the reciprocal movement of the piston42makes an air pressure in the air chamber44repetitively increase and decrease, thereby providing a striking force to the striking piece43. The striking piece43moves forward and collides with a rear end of the intermediate piece48. The striking force is transmitted to the tip tool mounted at the tool maintaining portion46by the intermediate piece48. In addition, a central axis of the tip tool mounted at the tool maintaining portion46is consistent with the axle center of the piston42functioning as a portion of the striking mechanism, so the striking force may be effectively transmitted from the striking mechanism to the tip tool.

Besides, the rotational driving force of the electric motor21is transmitted to the rotational transmission axle37through the output axle22, the pinion gear23, and the second gear38. In addition, rotation of the rotational transmission axle37is transmitted to the rotational cylinder45through the first bevel gear39and the second bevel gear47, so as to rotate the rotational cylinder45. Through rotation of the rotational cylinder45, a rotational force is provided to the tip tool mounted at the tool maintaining portion46. The rotational force and the striking force are used and provided to the tip tool mounted at the tool maintaining portion46, so as to crush the cutting material.

Besides, when the work tool1is in operation, the reciprocal movement of the striking piece43may result in vibrations with a substantially fixed cycle. In addition, the vibrations are transmitted to the gear housing30accommodating the striking piece43. The vibrations transmitted to the gear housing30are transmitted to the rotational support axle72rotatably supported by the gear housing30. When the vibrations are transmitted to the rotational support axle72, the weight80may swing with the rotational support axle72as the center.

FIGS. 8(a)˜8(d) illustrates an example described as follows. Namely, as shown inFIG. 8(a), at the initial neutral position, the housing locking portions30bon the front end side and the rear end side are disposed above the respective weight locking portions84on the front end side and the rear end side. In addition, the coil springs71that are extension springs are respectively stretched between the weight locking portions84and the housing locking portions30b. In this embodiment, at the initial neutral position when an external force is not in effect, the housing locking portion30band the weight locking portion84are on the same normal line of the rotational support axle72. Moreover, at the initial neutral position, the housing locking portions30band the weight locking portions84on the front end side and the rear end side are in a linearly symmetrical arrangement with respect to the line connecting the gravity center G and the axle center of the rotational support axle72. As shown inFIG. 8(b), when the weight80swings from the initial neutral position shown inFIG. 8(a)toward a front end direction, the coil springs71on the front end side and the rear end side extend. As a consequence, urging forces of the coil springs71on the front end side and the rear end side in the directions returning to the initial neutral position become effective to the weight80. Moreover, as shown inFIG. 8(c), the same situation applies when the weight80swings toward a rear end direction. According to the configuration, as shown inFIG. 8(d), a variation (stretching rate) of the coil spring71increases as the weight80becomes more distant from the initial neutral position. Besides, length variations of the coil springs71on the front end side and the rear end side that swing with the weight80are often the same within a swinging range. No matter the weight swings toward which of the front end side and the rear end side, expansion rates of the coil springs71per unit angle are the same. Thus, a difference (difference in length) between a maximum and a minimum of a load applied to the coil spring71is reduced, and a lifetime of the coil spring71may be extended. Besides, in this embodiment, two coil springs71are disposed to the right end side and the rear end side. However, there may be only one coil spring71or three or more coil springs71disposed. The number of the coil springs71may be appropriately determined based on an intensity or a frequency of the vibrations to be absorbed. Furthermore, in this embodiment, at the initial neutral position, the housing locking portions30band the weight locking portions84are configured by being disposed to the positions lineally symmetrical with respect to the line connecting the gravity center G and the axle center of the fixing hole81. The linearly symmetrical positions are not subject to limitation as long as the housing locking portions30band the weight locking portions84are disposed on the same normal lines of the rotational support axle72. Whichever positions the housing locking portions30band the weight locking portions84are disposed, the expansion rates per unit angle of the coil springs71may remain the same. Thus, a design flexibility may be ensured.

Besides, with respect toFIGS. 8(a) to 8(c), in a swing direction of the weight80, a structure where a portion of the coil spring71is located within the area of the weight80is formed. Accordingly, in the swing direction of the weight80, the vibration-reducing mechanism70may be more compact, and may be disposed by simply utilizing the small space formed between the gear housing30and the external housing50.

FIGS. 9(a)˜9(d) illustrates an example where the housing locking portion30bis disposed to a position different from that inFIGS. 8(a)˜8(d). The housing locking portion30band the weight locking portion84are not disposed on the same normal line of the rotational support axle72, and an interval between two housing locking portion30bis reduced. Under this circumstance, at the initial neutral position when an external force is not in effect, a direction of the line connecting a gravity center of a weight80dand the axle center of the rotational support axle72and an urging direction of the coil spring71are substantially the same. Based on the configuration, the example is the same as the example shown inFIGS. 8(a)˜8(d) in that, when swinging, the urging forces in the directions of making the weight80return to the initial neutral position by using the coil springs71on the front end side and the rear end side become effective, and that the variation of the coil spring71increases as the weight80becomes more distant from the initial neutral position. However, compared with the configuration ofFIGS. 8(a)˜8(d), the interval between the case locking portions30bbecomes more reduced, so the vibration-reducing mechanism70may be more compact. Besides, as shown inFIG. 9(b), when the weight80swings toward the front end direction, compared to the coil spring71on the rear end side, the coil spring71on the front end side71expands to a greater extent. As shown inFIG. 9(c), when the weight80swings toward the rear end direction, compared with the coil spring71on the front end side, the coil spring71on the rear end side expands to a greater extent. Thus, compared with the example shown inFIGS. 8(a)˜8(d), where the housing locking portion30band the weight locking portion84are disposed on the same normal line of the rotational support axle72, the difference (difference in length) between the maximum and the minimum of the load applied to the coil spring71becomes greater, as shown inFIG. 9(d), so the coil spring71becomes burdened. InFIG. 9(d), the initial neutral position is a position where a swing angle is 0 degrees. At the initial neutral position, the housing locking portions30band the weight locking portions84are respectively disposed at the positions linearly symmetrical to the line connecting the gravity center G and the axle center of the fixing hole81. Therefore, a total length of the coil springs71on the front end side and the rear end side is as shown by a dashed line shown inFIG. 10. No matter the weight swings toward which side of the front end side and the rear end side, the expansion rates per unit angle of the coil springs71may remain the same. InFIG. 10, the initial neutral position is a position where the swing angle is 0 degrees. Besides, a solid line shown inFIG. 10represents the total length of the coil springs71on the front end side and the rear end side in the embodiment shown inFIGS. 8(a)˜8(d). The lines are curved lines that are substantially the same.

FIG. 10illustrates a circumstance when the coil spring71as an extension spring is used, as in the embodiment. Regarding the variation of the coil spring71, the swing direction of the weight80and a stretching direction of the coil spring70as an urging means are different. Therefore, the more distant the weight80from the initial neutral position and the greater the swing angle, the larger the variation of the coil spring71becomes. Consequently, as shown in a solid line inFIG. 11(a), a moment [N·m] where the urging force using the coil spring71is applied to the weight80exhibits a non-linear relation with respect to the swing angle of the weight80. Also, as shown in a solid line inFIG. 11(b), a variation of the moment where the urging force using the coil spring71is applied to the weight80also exhibits a non-linear relation with respect to the swing angle of the weight80.

Broken lines inFIGS. 11(a) and 11(b)represent the moment [N·m] where a compression spring71ais used as an urging means urging a weight80a, as shown inFIG. 11(c), with respect to the swing angle and a variation thereof. When the compression spring71ais used, as shown in the broken line inFIG. 11(a)representing the moment where an urging force using the compression spring71ais applied to the weight80a, the moment exhibits a linear relation with respect to a swing angle of the weight80a. Also, as shown in the broken line inFIG. 11(b)representing a variation of the moment where the urging force using the compression spring71ais applied to the weight80a, the variation is constant and irrelevant of the swing angle of the weight80a. Thus, a resonance frequency determined by the compression spring71aalso becomes constant. Thus, as shown inFIG. 12(b), vibrations being subjected to vibration damping simply exhibit a frequency band having a fixed width and centering at the fixed resonance frequency determined by the compression spring71a. In a case when a rotation speed control is exerted but the frequencies of vibrations are different, a vibration damping effect is reduced. Comparatively, when the coil spring71as an expansion spring is used, the variation of the moment per unit angle is not constant. As the swing angle increases, the resonance frequency also increases. Thus, as shown inFIG. 12(a), vibrations being subjected to vibration damping may have respective frequency bands having fixed widths and centering at the variable resonance frequencies. Thus, a vibration damping effect corresponding to rotation speed control may be obtained.

Besides, in this embodiment, the weights80disposed to the two sides of the gear housing30are connected by the rotational support axle72to achieve an integral configuration. Therefore, even if the compression spring71a, in replacement of the coil spring71as an extension spring, is used as the urging means urging the weight80to return to the initial neutral position, a fixing effect still remains.FIG. 13(a)illustrates an example described in the following. In the example, the compression springs71aare used to press pins74having abutting ends on arcs respectively from the front end side and the rear end side to the support portion82of a weight80b. An urging direction of the compression spring71ais a direction of the axle center of the piston42functioning as a portion of the striking mechanism. As shown inFIG. 13(b), when the weight80bswings toward the front end direction, the compression spring71aon the front end side is pressed and contracted, and urges to make the weight80bto return to the initial neutral position. As shown inFIG. 13(c), when the weight80bswings toward the rear end direction, the compression spring71ais pressed and contracted, and urges to make the weight80bto return to the initial neutral position.FIG. 14(a)illustrates an example described in the following. In the example, the compression springs71aare used to press the pins74having the abutting ends on the arcs respectively from the front end side and the rear end side to the weight portion83of the weight80b. The urging direction of the compression spring71ais a direction substantially orthogonal to the axle center of the piston42functioning as a portion of the striking mechanism. As shown inFIG. 14(b), when the weight80bswings toward the front end direction, the compression spring71aon the front end side is pressed and contracted, and urges to make the weight80bto return to the initial neutral position. As shown inFIG. 14(c), when the weight80bswings toward the rear end direction, the compression spring71ais pressed and contracted, and urges to make the weight80bto return to the initial neutral position.

Second Embodiment

In a work tool1aof the second embodiment, as shown inFIG. 15, a rotational support hole30cis formed on an upper surface of the gear housing30, and, as shown inFIG. 16, the rotational support axle72is rotatably supported by the rotational support hole30cto be able to rotate. Rest of the configuration is the same as that of the first embodiment.

According to the second embodiment, no through hole30aneeds to be disposed in the gear housing30. The gear housing30accommodates the movement conversion mechanism33or the rotation transmission mechanism, so a position for forming the through hole30ais limited. Comparatively, in the second embodiment, the rotational support hole30cmay be formed on any position on the upper surface of the gear housing30. Therefore, the design flexibility may be ensured.

Third Embodiment

In a work tool1bof the third embodiment, as shown inFIGS. 17 and 18, one ends weights80crespectively disposed to the two sides of the gear housing30are rotatably supported by the gear housing30. In addition, another ends of the weights80cextend beyond and protrude from the upper surface of the gear housing30. The another ends of the weights80crespectively disposed to the two sides are connected by a connection stick75.

According to the third embodiment, no through hole30apenetrating through the gear housing30needs to be disposed. The gear housing30accommodates the movement conversion mechanism33or the rotation transmission mechanism, so the position for forming the through hole30ais limited. Comparatively, in the third embodiment, it only requires that a bearing or an indicator axle disposed to the side surface of the gear bearing30to support the weight80cto be rotatable. Therefore, the design flexibility may be ensured.

Fourth Embodiment

In a work tool1cof the fourth embodiment, as shown inFIG. 19, in the gear housing30, on the front end side of the pinion gear23, the crank axle31extending in parallel with the output axle22is rotatably supported. Moreover, in the gear housing30, on the front end side of the crank axle31, the rotational transmission axle37extending in parallel with the output axle22is rotatably supported, and the second gear38engaged with the first gear32of the crank axle31is coaxially fixed to the lower end of the rotational transmission axle37.

A vibration-reducing chamber90is formed on the rear end side of the pinion gear23in the gear housing30. The vibration-reducing chamber90accommodates a weight80dhaving an end portion rotatably supported by the rotational support axle72orthogonal to the axle center of the cylinder41. On another end side of the weight80d, the weight locking portion84is disposed. Moreover, in the vibration-reducing chamber90, the housing locking portion30bis disposed outside a range of rotation of the weight80dand vertically above the rotational support axle72. In addition, the coil spring71as an extension spring is stretched between the weight locking portion84and the housing locking portion30b. In a state when an external force is not in effect, as shown inFIG. 19, the weight80is located at the initial neutral position where the line connecting the gravity center of the weight80dand the axle center of the support axle72, and the initial neutral position is substantially orthogonal with respect to the axle center of the rotational cylinder45. In a state where the weight80dis located at the initial neutral position, the housing locking portion30band the weight locking portion84are disposed on the same normal line of the rotational support axle72.

As described above, according to the embodiments, the work tool1of the invention has the electric motor21; a power transmission means (the movement conversion mechanism33or the rotational transmission mechanism) receiving the motive power of the electric motor21and transmitting the motive power to the tip tool; the gear housing30, accommodating at least a portion of the power transmission means; the weights80, swingably supported by the gear housing30; and the coil springs71functioning as the urging means, wherein the urging means urge the weights80such that the weights80are located at the initial neutral position, the weights80and the coil springs71are respectively disposed to the two sides of the gear housing30to put the power transmission means therebetween, and the work tool1includes: the rotational support axle72functioning as the connection means that connects the weights80respectively disposed to the two sides of the gear housing30to swing integrally. According to the configuration, even if the vibration-reducing mechanism70is disposed to the side surface of the gear housing30to reduce the total length of the device, the weights80disposed to the two sides of the gear housing30may swing integrally through the rotational support axle72. Therefore, the vibration damping effect is ensured.

Furthermore, according to the embodiments, the rotational support axle72is an axle component that swingably supports the weights80respectively disposed to the two side surfaces of the gear housing30. According to the configuration, without additional configuration, the axle component swingably supporting the weights80may be used to integrate the weights80disposed to the two sides of the gear housing30.

Moreover, according to the embodiment, the rotational support axle72is rotatably supported by the through hole30aformed at the gear housing30. The rotational support axle72and the weights80are supported unrotatably in the swing direction. According to the configuration, a simple configuration may be used to integrate the weights80on the two sides of the gear housing30.

In addition, according to the embodiments, the power transmission means includes: the movement conversion mechanism33that transmits the reciprocal movement to the tip tool; and the rotational transmission mechanism that transmits the rotational driving force to the tip tool. When observed from the side surface, the rotational support axle72is disposed between the movement conversion mechanism33and the rotational transmission mechanism. According to the configuration, the rotational support axle72may penetrate through a space in the gear housing30.

Moreover, according to the embodiments, it is configured such that the variation of the urging means (the coil spring71) urging the weight80is greater as the weight80becomes more distant from the initial neutral position.

According to the configuration, when weaker vibrations are generated, the weights80may sufficiently swing to damp the vibrations. Also, when stronger vibrations are generated, the swinging of the weights80may also be kept up. Thus, regardless of the strength of the vibrations, the vibrations may be damped in a preferable efficiency. Besides, the variation of the moment per unit angle is not constant. As the swing angle increases, the resonance frequency also increases. Therefore, the vibrations being subjected to vibration damping may cope with the frequency bands having fixed widths and centering at the variable resonance frequencies. Since it is not a low vibration mechanism merely coping with one rotation speed of the motor, the vibration damping may still come into effect to cope with multiple rotation speeds even if the rotation speed control is exerted.

In addition, according to the embodiments, the coil spring71has the bending portions on the two sides. The bending portions are engaged with the housing locking portion30bdisposed to the gear housing30and the weight locking portion84disposed to the weight80.

Moreover, according to the embodiments, two of the coil springs71and two of the weight locking portions84are disposed to one side and another side of the weight80in the axial direction of the tip too. In addition, the two coil springs71are disposed to stretch when the weight80swings. Besides, when the weight80is at the initial neutral position, the two coil springs71and weight locking portions84are disposed to be linearly symmetrical by using the line connecting the rotational support axle72and the gravity center of the weight80as a symmetry axis.

Furthermore, according to the embodiments, regarding the weight80, the support portion82swingably supporting an end portion by using the connection means and the fan-shaped weight portion83disposed to another end side of the support portion82are integrated. Also, the weight locking portion84is disposed to the thinner thickness portion85. According to the configuration, the vibration damping mechanism70may be more compact, and the vibration damping mechanism70may be disposed by simply utilizing the small space formed between the gear housing30and the external housing50.

Moreover, according to the embodiments, two of the housing locking portions30are disposed to one side and another side of the weight80in the axial direction of the tip tool. When the weight80is located at the initial neutral position, the weight locking portions84and the house locking portions30bare located on the normal lines of the rotational support axle72.

In addition, according to the embodiments, in the axial direction of the rotational support axle72, the coil spring71is located within the thickness of the weight80. According to the configuration, compared with the weight80, the coil spring71does not protrude toward the axial direction the rotational support axle72. Therefore, the vibration damping mechanism70may be more compact in the axial direction of the rotational support axle72. Thus, the vibration damping mechanism70may be disposed by simply utilizing the small space formed between the gear housing30and the external housing50.

Furthermore, according to the embodiments, in the swing direction of the weight80, a portion of the coil spring71is located within the thickness of the weight80. According to the configuration, in the swing direction of the weight80, the damping mechanism70may be more compact, and the vibration damping mechanism70may be disposed by simply utilizing the small space formed between the gear housing30and the external housing50.

Also, according to the embodiments, the weight80and the coil spring71are disposed between the gear housing30and the external housing50. According to the configuration, the weights80and the coil springs71disposed to the two sides of the gear housing30are covered by the external housing50. Therefore, an external influence on an operation of the coil springs71may be reduced.

In view of the foregoing, the invention is described based on the foregoing embodiments. However, it should be understood that the invention is not limited to the foregoing embodiments, and various changes and modifications may be made without departing from the spirit of the invention.

For example, in the embodiments, an example where the work tool is applied to be the hammer drill as a striking tool is described. However, the invention may also be applied to be a tool having a configuration that makes the tip tool move reciprocally. An example of such tool includes a hammer, a knife saw, a jigsaw, or the like, for example. Moreover, in the embodiments, an example where the weights80are disposed to the left and right sides of the gear housing30is described. However, the weights80may also be respectively disposed to upper and lower sides of the gear housing30or be disposed inclinedly, so as to put the axle center of the cylinder41therebetween. Furthermore, in the embodiments, an example where the weights80are disposed to the left and right sides of the gear housing30is described. However, the weights80may be disposed to two sides of the strike housing40, so as to put the axle center of the cylinder41therebetween.

SYMBOL DESCRIPTIONS