Power tool having a hammer mechanism

A movable support at least partially supports a final output shaft and a driving mechanism, and is integrally movable relative to a housing in an axial direction of a driving axis. A biasing member biases the movable support toward a front side in the axial direction. A first guide shaft extends in the axial direction and slidably guides the movement of the movable support in the axial direction. At least one intermediate shaft rotates in response to rotation of a motor shaft and transmit power of the motor to the driving mechanism. At least one bearing supports an end portion of the at least one intermediate shaft is located in the front side in the axial direction. A single metal support is immovable relative to the housing and supports the at least one bearing. The single metal support has a first hole for partially receiving the first guide shaft.

TECHNICAL FIELD

The present disclosure generally relates to a power tool configured to linearly reciprocally drive a tool accessory.

BACKGROUND

A rotary hammer (hammer drill) is configured to linearly reciprocally drive a tool accessory coupled to a tool holder along a driving axis (i.e. perform a hammering operation) and to rotationally drive the tool accessory around the driving axis (i.e. perform a drilling operation). In typical rotary hammers, a motion converting mechanism for converting rotation of an intermediate shaft into linear motion is employed to perform the hammering operation, and a rotation-transmitting mechanism for transmitting rotation to the tool holder via the intermediate shaft is employed to perform the drilling operation. Such a rotary hammer is subjected to a reaction force from a workpiece against the striking force of the tool accessory during the hammering operation. The reaction force generates vibration in an extension direction of the driving axis (hereinafter also referred to as an axial direction). Vibration thus generated is transmitted to the housing of the rotary hammer and to its user.

Japanese Patent No. 6325360 discloses a structure for absorbing such vibration. Specifically, a driving mechanism for performing a hammering operation is held by a holding member configured to be slidably movable relative to the housing along a guide shaft. The holding member is biased forward (i.e. in a direction in which a striking force is applied to the workpiece) by a biasing member. When a tool accessory is subjected to a reaction force during the hammering operation, the force causes the driving mechanism and the holding member to move rearward together with the tool accessory relative to the housing. At this time, the biasing member elastically deforms and partially cushions the reaction force. This cushioning effect serves to reduce vibration to be transmitted to the housing due to the reaction force.

In typical rotary hammers including the one disclosed in the Japanese Patent No. 6325360, plastic is used to form its constituent members when possible in order to reduce the weight. For example, plastic is commonly used to form a housing defining an outer shell of a rotary hammer. Plastic is also commonly used to form a member supporting a bearing for an intermediate shaft.

SUMMARY

A power tool is disclosed in this specification. The power tool may include a final output shaft, a motor, a driving mechanism, a housing, a movable support, a biasing member, a first guide shaft, at least one intermediate shaft, at least one bearing, and a single (integral) support made of metal (hereinafter referred to as a metal support).

The final output shaft may be configured to removably hold a tool accessory. The final output shaft may also define a driving axis of the tool accessory. The motor may have a motor shaft. The driving mechanism may be configured to perform at least a hammering operation of linearly reciprocally driving the tool accessory along the driving axis by using power from the motor. The housing may accommodate the motor and the driving mechanism. The movable support may at least partially support the final output shaft and the driving mechanism. The movable support may also be configured to be integrally movable relative to the housing in an axial direction of the driving axis. When one side in the axial direction in which the final output shaft is disposed is defined as a front side and an opposite side in the axial direction in which the motor is disposed is defined as a rear side, the biasing member may bias the movable support toward the front side in the axial direction. The first guide shaft may extend in the axial direction and may be configured to slidably guide movement of the movable support in the axial direction. The at least one intermediate shaft may extend in the axial direction. The at least one intermediate shaft may also be configured to rotate in response to rotation of the motor shaft and transmit the power of the motor to the driving mechanism. The at least one bearing may support an end portion of the at least one intermediate shaft, that is located in the front side in the axial direction (hereinafter referred to as a front end portion). The single metal support may be disposed to be immovable relative to the housing and may support the at least one bearing. The single metal support may also have a first hole for partially receiving the first guide shaft.

The first guide shaft may also be configured to move together with the movable support in the axial direction. In this case, the first guide shaft may be received in the first hole of the metal support so as to be slidable within the first hole when the movable support moves in the axial direction. Alternatively, the first guide shaft may be immovably received in the first hole of the metal support. In this case, the first guide shaft held by the metal support may be slidably received in a hole formed in the movable support.

According to the above-described power tool, the at least one bearing for supporting the front end portion of the at least one intermediate shaft is supported by the metal support. This provides stronger support strength compared to the case in which a support made of plastic (hereinafter simply referred to as a plastic support) is used to support the at least one bearing. Therefore, even if high power operation of the power tool results in increased vibration generated due to a reaction force against the striking force, the positional accuracy for the at least one intermediate shaft can be maintained at the required level. Further, according to the power tool of this aspect, the first guide shaft is partially received in the first hole of the metal support. Therefore, even if high power operation of the power tool results in an increased amount of heat produced when the first guide shaft slidably guides movement of the movable support in the axial direction, the support can have reduced thermal expansion compared to the case in which a plastic support is used to receive the first guide shaft. Therefore, the positional accuracy for the first guide shaft partially received in the first hole of the metal support can be maintained at the required level. This in turn provides satisfactory sliding property related to the first guide shaft and also allows for satisfactory isolation of vibration. As such, the power tool of the present aspect can achieve both high power operation and reduced vibration. Moreover, the use of the single metal support for supporting the at least one bearing and also for receiving the first guide shaft enables simplified tool structure as well as reduced man-hours related to manufacturing.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In one or more of embodiments, the housing may be made of plastic. The metal support may be fixed to the housing. According to the present embodiment, the power tool can achieve both high power operation and reduced vibration while successfully having a reduced weight.

In one or more embodiments, the metal support may include a first positioning part in the front side. The first positioning part is disposed so as to circumferentially surround the final output shaft. The housing may include a second positioning support also disposed so as to circumferentially surround the final output shaft. The first positioning part and the second positioning part may be shaped to be fitted with each other in the axial direction. According to the present embodiment, the first and second positioning parts can be aligned and fitted with each other in the process of assembling the power tool. This enables easy positioning of the metal support relative to the housing in a direction orthogonal to the axial direction.

In one or more embodiments, the metal support may include an attachment surface in the front side. The attachment surface spreads in form of a single plane at a position radially outward of the first positioning part. The attachment surface may abut on the housing in the axial direction. According to the present embodiment, the attachment surface can be abutted on the housing in the axial direction in the process of assembling the power tool. This enables easy positioning of the metal support relative to the housing in the axial direction.

In one or more embodiments, the first guide shaft may be disposed so as to be at least partially in the front side of the movable support. The power tool may further include a second guide shaft that is disposed so as to be at least partially in the rear side of the movable support and coaxial with the first guide shaft. According to the present embodiment, the distance over which the guide shafts extend as a whole can be shortened compared to a case in which a single guide shaft extends from where the first guide shaft is to where the second guide shaft is. The rotary hammer can thus have a reduced weight. Moreover, since the guide shafts are respectively placed on both sides of the movable support in the axial direction, the movable support can be guided satisfactorily irrespective of the reduced weight.

In one or more embodiments, the first guide shaft may extend frontward from the movable support. The first guide shaft may be configured to move together with the movable support in the axial direction. According to the present embodiment, the sliding property related to the first guide shaft can be maintained satisfactory.

In one or more embodiments, the metal support may include a first sleeve within the first hole. The first sleeve is made of iron-based metal. The first guide shaft may be configured to slide on an inner peripheral surface of the first sleeve while the movable support moves in the axial direction. The metal support may be made of aluminum-based metal except for the first sleeve. Examples of the iron-based metal include iron and any alloy that contains iron as its main component. Examples of the aluminum-based metal include aluminum and any alloy that contains aluminum as its main component. According to the present embodiment, the metal support can have sufficient strength to withstand sliding movement relative to the guide shaft and can also have a reduced weight as a whole.

In one or more embodiments, the movable support may include a second hole for partially receiving the second guide shaft, and a second sleeve disposed within the second hole. The second guide shaft may be disposed so as to be immovable relative to the housing. An inner peripheral surface of the second sleeve may be configured to slide on the second guide shaft while the movable support moves in the axial direction. The biasing member may be disposed around the second guide shaft in the rear side of the movable support in the axial direction, and may be configured to bias the movable support including the second sleeve integrally frontward. According to the present embodiment, only the second sleeve, among all the parts constituting the movable support, slides on the second guide shaft. Therefore, making the second sleeve from a selected material of sufficient strength can lead to smooth sliding property. Also, since the second sleeve is biased frontward by the biasing member, the sleeve can be prevented from being left behind and off the second hole while the movable support moves frontward.

In one or more embodiments, the driving mechanism may further be configured to perform a drilling operation of rotationally driving the tool accessory around the driving axis by using power from the motor. The at least one intermediate shaft may include a first intermediate shaft configured to transmit power for the hammering operation to the driving mechanism, and a second intermediate shaft configured to transmit power for the drilling operation to the driving mechanism. The at least one bearing may include a first bearing for supporting the first intermediate shaft, and a second bearing for supporting the second intermediate shaft. The first intermediate shaft may be configured to transmit power for the hammering operation but not for the drilling operation; whereas the second intermediate shaft may be configured to transmit power for the drilling operation but not for the hammering operation. According to the present embodiment, the first intermediate shaft and the second intermediate shaft can be made shorter compared to the case in which one common intermediate shaft is used for both the hammering operation and the drilling operation. Thus, the overall length of the rotary hammer can be reduced in the driving-axis direction. Further, the first intermediate shaft and the second intermediate shaft are respectively dedicated for power transmission for the hammering operation and power transmission for the drilling operation. This optimizes power transmission via the first intermediate shaft and power transmission via the second intermediate shaft to the final output shaft, respectively.

In one or more embodiments, the first bearing and the second bearing may be disposed at positions different from each other in the axial direction. According to the present embodiment, the positions of the first and second bearings may be set without any constraints from the metal support. Therefore, the positions of the first and second bearings can be set so as not to damage the effect of having shorter first and second intermediate shafts. In other words, increase in length of the rotary hammer due to the use of the metal support is reduced or eliminated.

The embodiment of the present disclosure is now described in more detail with reference to the drawings.

In this embodiment, a rotary hammer (hammer drill)101is described as an example of a power tool according to the present teachings. The rotary hammer101is a hand-held power tool that may be used for processing operations such as chipping and drilling. The rotary hammer101is configured to be capable of performing the operation (hereinafter referred to as a hammering operation) of linearly reciprocally driving a tool accessory91along a driving axis A1and of performing the operation (hereinafter referred to as a drilling operation) of rotationally driving the tool accessory91around the driving axis A1.

First, the general structure of the rotary hammer101is described with reference toFIG.1. As shown inFIG.1, an outer shell of the rotary hammer101is mainly formed by a body housing10and a handle17connected to the body housing10.

The body housing10is a hollow body which may also be referred to as a tool body or an outer shell housing. The body housing10houses parts such as a spindle31, a motor2, a driving mechanism5, and the like. The spindle31is an elongate member having a hollow circular cylindrical shape. At its end portion in the axial direction, the spindle31has a tool holder32configured to removably hold the tool accessory91. A longitudinal axis of the spindle31defines a driving axis A1of the tool accessory91. The body housing10extends along the driving axis A1. The tool holder32is disposed within one end portion of the body housing10in an extension direction of the driving axis A1(hereinafter simply referred to as a driving-axis direction).

The handle17is an elongate hollow body configured to be held by a user. One axial end portion of the handle17is connected to the other end portion (an end portion located on the side opposite to the side in which the tool holder32is located) of the body housing10in the driving-axis direction. The handle17protrudes from the other end portion of the body housing10and extends in a direction crossing (more specifically, generally orthogonal to) the driving axis A1. Further, in this embodiment, the body housing10and the handle17are integrally formed by a plurality of components connected together with screws or the like. A power cable179extends from the protruding end of the handle17and can be connected to an external alternate current (AC) power source. The handle17has a trigger171to be depressed (pulled) by a user, and a switch172configured to be turned ON in response to a depressing operation of the trigger171.

In the rotary hammer101, when the switch172is turned ON, the motor2is energized and the driving mechanism5is driven so that the hammering operation and/or the drilling operation is performed.

The detailed structure of the rotary hammer101is now described. In the following description, for convenience sake, the extension direction of the driving axis A1(the longitudinal direction of the body housing10) is defined as a front-rear direction of the rotary hammer101. The side of one end of the rotary hammer101in the front-rear direction in which the tool holder32is disposed is defined as a front side of the rotary hammer101; whereas the opposite side (the side in which the motor2is disposed) is defined as a rear side of the rotary hammer101. The direction that is orthogonal to the driving axis A1and corresponds to an axial direction of the handle17is defined as an up-down direction of the rotary hammer101. In the up-down direction, the side of one end of the handle17that is connected to the body housing10is defined as an upper side and the side of the protruding end of the handle17is defined as a lower side. Further, the direction that is orthogonal to both the front-rear direction and the up-down direction is defined as a left-right direction of the rotary hammer101. In the left-right direction, the side to the right when viewed from the rear side to the front side is defined as a right side of the rotary hammer101and the opposite side is defined as a left side of the rotary hammer101.

First, the structure of the body housing10is described. As shown inFIG.1, the body housing10has a front end portion of a hollow circular cylindrical shape. The portion is referred to as a barrel part131. The remaining portion of the body housing10other than the barrel part131has a generally rectangular box-like shape. An auxiliary handle132is removably attachable to the barrel part131.

The internal space of the body housing10is partitioned into two volumes by a first support15that is disposed within the body housing10. The first support15is arranged to cross the driving axis A1, is fitted into an inner periphery of the body housing10, and is fixedly held by the body housing10(so as to be immovable relative to the body housing10). The volume in the rear of the first support15is a volume (space) for mainly housing the motor2. The volume in front of the bearing support15is a volume (space) for mainly housing the spindle31and the driving mechanism5. In the following description, the portion of the body housing10that corresponds to the region for housing the motor2is referred to as a rear housing11, and the portion (including the barrel part131) of the body housing10that corresponds to the region for housing the spindle31and the driving mechanism5is referred to as a front housing13.

The rear housing11and the front housing13are both formed of plastic. The rotary hammer101can thus have a reduced weight. The rear housing11and the front housing13, however, may at least partially be formed of a freely-selected material (e.g., metal). Each of the rear housing11and the front housing13is a single tubular member.

The first support15is a member for supporting bearings of various shafts. Details of the first support15will be described later. To provide a required level of positional accuracy for the bearings, the first support15is formed of metal. In this embodiment, the first support15is formed of aluminum-based metal. The rotary hammer101can thus have a reduced weight. As shown inFIG.1, the first support15is fitted into a rear end portion of the front housing13so that an outer peripheral surface of the first support15comes into contact with an inner peripheral surface of the front housing13.

As shown inFIG.1, an annular groove152is formed on the outer peripheral surface of the first support15that is in contact with the inner peripheral surface of the body housing11. A rubber O-ring151is fitted in this groove152. The O-ring151serves as a seal member for sealing a gap between the body housing10and the first support15, and prevents lubricant used within the front housing13from leaking into the rear housing11.

The internal structures of the body housing10are now described. First, the motor2is described. In this embodiment, an AC motor, which may be powered by an external AC power source, is employed as the motor2. As shown inFIG.1, the motor2is fixed to the rear housing11. The motor2has a body20including a stator and a rotor, and a motor shaft25configured to rotate together with the rotor. In this embodiment, a rotation axis A2of the motor shaft25extends below the driving axis A1and in parallel to the driving axis A1.

The motor shaft25is supported via two bearings251and252so as to be rotatable around the rotation axis A2relative to the body housing10. The front bearing251is held on a rear surface side of the first support15, and the rear bearing252is held by the rear housing11.

A cooling fan27for cooling the motor2is fixed to a portion of the motor shaft25between the body20and the front bearing251. The cooling fan27is a centrifugal fan and is configured to suck air in the axial direction and discharge the air radially outward. Rotation of the motor shaft25and thus of the fooling fan17produces a flow of air inside the rotary hammer101. The air flows from outside the rotary hammer101through an inlet opening28into the rotary hammer101, goes through the motor2(more specifically, between the rotor and the stator) in the axial direction, and then is directed radially outward by the cooling fan27and discharged outside through a discharge opening29. The passage for the thus produced flow of air is shown by an arrow26inFIG.1.

In the example shown inFIG.1, the inlet opening28is formed on a side surface of the handle17, and the discharge opening29is formed on a bottom surface of the rear housing11. The inlet opening28and the discharge opening29may, however, be formed in freely-selected locations. For example, the inlet opening28may be formed on an upper surface of the handle17in addition to or instead of the side surface of the handle17. Also, the discharge opening29may be formed on one or both side surfaces or on an upper surface of the rear housing11in addition to or instead of the bottom surface of the rear housing11. The flow of air thus generated serves to cool the motor2.

The first support15is disposed adjacent to the cooling fan27in the front-rear direction. The space in the rear of the first support15is in communication with a space in which the cooling fan27is disposed. Moreover, in this embodiment, the first support15is formed of metal. Therefore, the flow of air going through the passage26also serves to cool the first support15. In other words, the first support15is arranged such that heat generated in the front side of the first support15and transmitted to the first support15can be dissipated. Details of this function will be described later.

A front end portion of the motor shaft25extends through a through hole153of the first support15and protrudes into the front housing13. A pinion gear255is fixed to this end portion of the motor shaft25that protrudes into the front housing13.

Next, power-transmission paths from the motor shaft25to the driving mechanism5are described. As shown inFIGS.2and3, in this embodiment, the rotary hammer101includes two intermediate shafts (i.e. a first intermediate shaft41and a second intermediate shaft42). The driving mechanism5is configured to perform the hammering operation using power transmitted from (via) the first intermediate shaft41and perform the drilling operation using power transmitted from (via) the second intermediate shaft42. In other words, the first intermediate shaft41is a shaft provided exclusively for (dedicated to) power transmission for hammering operations, and the second intermediate shaft42is a shaft provided exclusively for (dedicated to) power transmission for drilling operations.

Both the first intermediate shaft41and the second intermediate shaft42extend within the front housing13in parallel to the driving axis A1and the rotation axis A2. As shown inFIG.3, the first intermediate shaft41is supported via two bearings411and412so as to be rotatable around a rotation axis A3relative to the body housing10. Similarly, the second intermediate shaft42is supported via two bearings421and422so as to be rotatable around a rotation axis A4relative to the body housing10.

The bearing411that supports the first intermediate shaft41in the front side and the bearing421that supports the second intermediate shaft42in the front side are supported by a second support16. More specifically, the bearing411is supported by a portion of the second support16, namely a bearing-support part164, that is formed into an generally hollow circular cylindrical shape, and the bearing421is supported by another portion of the second support16, namely a bearing-support part165, that is formed into an generally hollow circular cylindrical shape (seeFIGS.3,13, and14). The bearing412that supports the first intermediate shaft41in the rear side and the bearing422that supports the second intermediate shaft42in the rear side are supported by the first support15. More specifically, the bearing412is supported by a portion of the first support15, namely a bearing-support part154, that is formed into a hollow circular cylindrical shape, and the bearing422is supported by another portion of the first support15, namely a bearing-support part155, that is formed into a hollow circular cylindrical shape (seeFIGS.3and11).

As shown inFIG.3, the bearing411for supporting the first intermediate shaft41in the front side and the bearing421for supporting the second intermediate shaft42in the front side are disposed at positions different from each other in the front-rear direction. This is because the bearings411and421are arranged at positions that allow the first intermediate shaft41and the second intermediate shaft42to have minimum lengths, respectively. That is, even though the bearings411and421are supported by a single (integral) member, namely the second support16, the positions of the bearings411and421in the front-rear direction are not constrained by the second support16. Therefore, the rotary hammer101can be prevented from getting longer due to the use of a single member to support both the bearings411and421.

As shown inFIGS.1and3, the second support16is fixed inside the front housing13. More specifically, as shown inFIGS.13and14, the second support16includes a first positioning part163, an attachment surface168, and two through holes162. The first positioning part163is a portion having a hollow circular cylindrical shape protruding frontwards. As shown inFIGS.7and8, this first positioning part163is disposed so as to circumferentially surround the spindle31(in other words, so that the spindle31extends through the first positioning part163in the front-rear direction). As shown inFIGS.13and14, the attachment surface168spreads, at a position radially outward of the first positioning part163, in the form of a single plane orthogonal to the front-rear direction. The two through holes162extend through the second support16in the front-rear direction, respectively.

On the other hand, the front housing13to which the second support16is fixed includes a second positioning part133and an attachment surface135, as shown inFIGS.7and8. The second positioning part133is a portion of the inside of the front housing13protruding rearward. The second positioning part133has a concave portion formed on its radially inward side and is disposed so as to circumferentially surround the spindle31. A rear end surface of the second positioning part133forms the attachment surface135orthogonal to the front-rear direction.

As shown inFIGS.7and8, the second support16is attached to the front housing13so that the first positioning part163is fitted with the concave portion of the second positioning part133in the front-rear direction. The fitting structure between the concave and convex shapes enables precise and easy positioning of the second support16relative to the front housing13in a direction orthogonal to the front-rear direction in the process of assembling the rotary hammer101. In an alternative embodiment, the first positioning part163and the second positioning part133may have reversed shapes. That is, the first positioning part163may be a concave portion formed in the second support16; whereas the second positioning part133may be a convex portion protruding from the front housing13and may be fitted with the concave portion of the second support16.

As shown inFIGS.7and8, the attachment surface168of the second support16abuts the attachment surface135of the front housing13in the front-rear direction when the first positioning part163is fitted with the second positioning part133in the front-rear direction. Each of the attachment surfaces168and135is a plane orthogonal to the front-rear direction. This enables precise and easy positioning of the second support16relative to the front housing13in the front-rear direction in the process of assembling the rotary hammer101.

The second support16thus positioned relative to the front housing13is then fixed to the front housing13by screws161respectively inserted into the through holes162of the second support16, as shown inFIG.4.

To provide a required level of positional accuracy for the bearings411and421, the second support16of such a structure is formed of metal. In this embodiment, the second support16is formed of aluminum-based metal. The rotary hammer101can thus have a reduced weight.

As shown inFIG.3, a first driven gear414is fixed to a rear end portion of the first intermediate shaft41adjacent to and in front of the bearing412. The first driven gear414meshes with a pinion gear255.

A gear member423having a second driven gear424is disposed adjacent to and in front of the bearing422on a rear end portion of the second intermediate shaft42. The second driven gear424meshes with the pinion gear255. The gear member423has a hollow circular cylindrical shape and is disposed on an outer peripheral side of the second intermediate shaft42(specifically, of a drive-side member74which will be described later). A spline part425is provided on an outer periphery of a hollow circular cylindrical front end portion of the gear member423. The spline part425includes a plurality of splines (external teeth) extending in a direction of the rotation axis A4(i.e. front-rear direction). Rotation of the second driven gear424(the gear member423) is transmitted to the second intermediate shaft42via a second transmitting member72and a torque limiter73. Details of the mechanism will be described in detail later.

As described above, in this embodiment, two power-transmission paths branch from the motor shaft25and respectively serve as a power-transmission path dedicated to hammering operations and another power-transmission path dedicated to drilling operations.

The spindle31is now described. The spindle31is a final output shaft of the rotary hammer101. As shown inFIG.1, the spindle31is arranged within the front housing13along the driving axis A1and is supported to be rotatable around the driving axis A1relative to the body housing10. The spindle31is configured as an elongate, stepped hollow circular cylindrical member.

A front half of the spindle31forms the tool holder32to or in which the tool accessory91can be removably attached. The tool accessory91is inserted into a bit-insertion hole330formed in a front end portion of the tool holder32such that a longitudinal axis of the tool accessory91coincides with the driving axis A1. The tool accessory91is held in the insertion hole330so as to be movable relative to the tool holder32in the axial direction while its rotation around the axis is restricted (blocked). A rear half of the spindle31forms a cylinder33configured to slidably hold a piston65described below. The spindle31is supported by a bearing316held within the barrel part131and a bearing317held by a movable support18described below.

The driving mechanism5is now described. As shown inFIGS.3,5, and6, in this embodiment, the driving mechanism5includes a striking mechanism6and a rotation-transmitting mechanism7. The striking mechanism6is a mechanism for performing hammering operations, and is configured to convert rotation of the first intermediate shaft41into linear motion and linearly reciprocally drive the tool accessory91along the driving axis A1. The rotation-transmitting mechanism7is a mechanism for performing drilling operations, and is configured to transmit rotation of the second intermediate shaft42to the spindle31and rotationally drive the tool accessory91around the driving axis A1. The structures of the striking mechanism6and the rotation-transmitting mechanism7are now described in detail in this order.

In this embodiment, as shown inFIGS.3and5, the striking mechanism6includes a motion-converting member61, a piston65, a striker67, and an impact bolt68.

The motion-converting member61is disposed around the first intermediate shaft41, and is configured to convert rotation of the first intermediate shaft41into linear reciprocating motion and transmit it to the piston65. More specifically, the motion-converting member61includes a rotary body611and an oscillating member616. The rotary body611is supported by a bearing614so as to be rotatable around the rotation axis A3relative to the body housing10. The oscillating member616is rotatably mounted on an outer periphery of the rotary body611, and is configured to oscillate (pivot or rock back and forth) in an extension direction of the rotation axis A3(i.e. front-rear direction) while the rotary body611is rotating. The oscillating member616has an arm617extending upward away from the rotary body611.

The piston65is a bottomed hollow circular cylindrical member, and is disposed within the cylinder33of the spindle31so as to be slidable along the driving axis A1. The piston65is connected to the arm617of the oscillating member616via a connecting pin and reciprocally moves in the front-rear direction while the oscillating member616is oscillating (pivoting or rocking back-and-forth in the front-rear direction).

The striker67is a striking element for applying a striking force to the tool accessory91. The striker67is disposed within the piston65so as to be slidable along the driving axis A1. An internal space of the piston65in the rear of the striker67is defined as an air chamber that serves as an air spring. The impact bolt68is an intermediate element for transmitting kinetic energy of the striker67to the tool accessory91. The impact bolt68is disposed within the tool holder32in front of the striker67so as to be movable along the driving axis A1.

When the piston65is moved in the front-rear direction along with oscillating movement of the oscillating member616, the air pressure within the air chamber fluctuates and the striker67slides in the front-rear direction within the piston65by the action of the air spring. More specifically, when the piston65is moved forward, the air within the air chamber is compressed and its internal pressure increases. Thus, the striker67is pushed forward at high speed by the action of the air spring and strikes the impact bolt68. The impact bolt68transmits the kinetic energy of the striker67to the tool accessory91. Thus, the tool accessory91is linearly driven along the driving axis A1. On the other hand, when the piston65is moved rearward, the air within the air chamber expands and its internal pressure decreases so that the striker67is retracted (moved) rearward. The tool accessory91moves rearward along with the impact bolt68by being pressed against a workpiece. In this manner, the striking mechanism6repetitively performs the hammering operation.

In this embodiment, rotation of the first intermediate shaft41is transmitted to the motion-converting member61(specifically, the rotary body611) via a first transmitting member64and an intervening member63. The intervening member63and the first transmitting member64are now described in this order.

As shown inFIG.5, the intervening member63is a hollow circular cylindrical member coaxially disposed around the first intermediate shaft41, between the first intermediate shaft41and the motion-converting member61(specifically, the rotary body611). The intervening member63is immovable in the front-rear direction relative to the first intermediate shaft41while being rotatable around the rotation axis A3relative to the first intermediate shaft41.

More specifically, a front end portion (a portion adjacent to the rear side of the front bearing411) of the first intermediate shaft41is configured as a maximum-diameter part having a maximum outer diameter. A spline part416is provided on an outer periphery of the maximum-diameter part. The spline part416includes a plurality of splines (external teeth) extending in the rotation axis A3direction (i.e. front-rear direction). The intervening member63is held to be immovable in the front-rear direction between the spline part416and the first driven gear414fixed to the rear end portion of the first intermediate shaft41.

A spline part631is provided on an outer periphery of the intervening member63and extends generally over the entire length of the intervening member63. The spline part631includes a plurality of splines (external teeth) extending in the rotation axis A3direction (i.e. front-rear direction).

On the other hand, a spline part612is formed on an inner periphery of the rotary body611. The spline part612includes splines (internal teeth) to be engaged (meshed) with the spline part631. The intervening member63is always spline-engaged with the rotary body611, and is held by the rotary body611. Such a structure allows the rotary body611to be movable in the rotation axis A3direction (i.e. front-rear direction) relative to the intervening member63and the first intermediate shaft41as well as to be rotatable together with the intervening member63.

The first transmitting member64is disposed on the first intermediate shaft41, and is configured to be rotatable together with the first intermediate shaft41as well as to be movable in the rotation axis A3direction (i.e. front-rear direction) relative to the first intermediate shaft41and the intervening member63.

More specifically, the first transmitting member64is a generally hollow circular cylindrical member disposed around the first intermediate shaft41. A first spline part641and a second spline part642are provided on an inner periphery of the first transmitting member64.

The first spline part641is provided on a rear end portion of the first transmitting member64. The first spline part641includes a plurality of splines (internal teeth) configured to be engaged (meshed) with the spline part631of the intervening member63. As described above, the spline part631of the intervening member63is also engaged (meshed) with the spline part612of the rotary body611. The second spline part642is provided on a front half of the first transmitting member64. The second spline part642includes a plurality of splines (internal teeth) configured to be always engaged (meshed) with the spline part416of the first intermediate shaft41.

With such a structure, when the first spline part641of the first transmitting member64that is movable in the front-rear direction is placed in a position (hereinafter referred to as an engagement position) to be engaged with the spline part631of the intervening member63, as shown inFIG.5, the first transmitting member64is rotatable together with the intervening member63, that is, first transmitting member64is capable of transmitting power (rotational force) from the first intermediate shaft41to the intervening member63.

On the other hand, when the first spline part641of the first transmitting member64moveable in the front-rear direction is placed in a position (not shown, hereinafter referred to as a spaced apart position) to be spaced apart from (incapable of being engaged with) the spline part631, the first transmitting member64disables (interrupts, disconnects) power transmission from the first intermediate shaft41to the intervening member63.

As shown inFIG.6, in this embodiment, the rotation-transmitting mechanism7includes a driving gear78and a driven gear79. The driving gear78is fixed to a front end portion (a portion adjacent to the rear side of the front bearing421) of the second intermediate shaft42. The driven gear79is fixed to an outer periphery of the cylinder33of the spindle31and meshes with the driving gear78. The driving gear78and the driven gear79form a speed-reducing (torque-increasing) gear mechanism. The spindle31is rotated together with the driven gear79in response to rotation of the driving gear78together with the second intermediate shaft42. The drilling operation is thus performed in which the tool accessory91held by the tool holder32is rotationally driven around the driving axis A1.

As described above, in this embodiment, rotation of the second driven gear42caused by rotation of the motor shaft25is transmitted to the second intermediate shaft42via the second transmitting member72and the torque limiter73. The torque limiter73and the second transmitting member72are now described in this order.

As shown inFIG.6, the torque limiter73includes a drive-side member74, a driven-side member75, and a biasing spring77. The drive-side member74is a hollow circular cylindrical member and is supported by a rear half of the second intermediate shaft42so as to be rotatable relative to the second intermediate shaft42. The driven-side member75is a hollow circular cylindrical member and is disposed around the second intermediate shaft42in the front side of the drive-side member74. The driven-side member75is configured to be rotatable together with the second intermediate shaft42as well as to be movable in the rotation axis A4direction (i.e. front-rear direction) relative to the second intermediate shaft42. The biasing spring77always biases the driven-side member75in a direction toward the drive-side member74. Therefore, in normal times, a front end portion of the drive-side member74and a rear end portion of the driven-side member75are engaged with each other. This allows torque to be transmitted from the drive-side member74to the driven-side member75and in turn enables rotation of the second intermediate shaft42.

When the second intermediate shaft42is rotating and a load exceeding the threshold is applied to the second intermediate shaft42via the tool holder32(the spindle31), the driven-side member75moves in a direction away from the drive-side member74(i.e. forward) against the biasing force of the biasing spring77and thus becomes disengaged from the drive-side member74. This disconnects transmission of torque from the drive-side member74to the driven-side member75and interrupts rotation of the second intermediate shaft42.

The drive-side member74includes a spline part743. The spline part743is provided on an outer periphery of the drive-side member74and includes a plurality of splines (external teeth) extending in the rotation axis A4direction (i.e. front-rear direction).

As shown inFIG.6, the second transmitting member72is disposed around the second intermediate shaft42, and is configured to be rotatable together with the drive-side member74of the torque limiter73as well as to be movable in the rotation axis A4direction (i.e. front-rear direction) relative to the drive-side member74and the gear member423.

More specifically, the second transmitting member72is a generally hollow circular cylindrical member disposed around the drive-side member74. A first spline part721and a second spline part722are provided on an inner periphery of the second transmitting member72. The first spline part721is provided on a front half of the second transmitting member72. The first spline part721includes a plurality of splines (internal teeth) that are always engaged (meshed) with the spline part743of the drive-side member74. The second spline part722is provided on a rear end portion of the second transmitting member72and has a larger inner diameter than the first spline part721. The second spline part722includes a plurality of splines (internal teeth) configured to be engaged (meshed) with the spline part425of the gear member423.

With such a structure, when the second spline part722of the second transmitting member72movable in the front-rear direction is placed in a position (hereinafter referred to as an engagement position) to be engaged with the spline part425of the gear member423in the front-rear direction, as shown inFIG.6, the second transmitting member72is rotatable together with the gear member423. This allows the drive-side member74, which is spline-engaged with the second transmitting member72, and thus the second intermediate member42, to which torque is transmitted via the driven-side member75, also to be rotatable together with the gear member423.

On the other hand, when the second spline part722movable in the front-rear direction is placed in a position (not shown, hereinafter referred to as a spaced apart position) to be spaced apart (separated) from (incapable of being engaged with) the spline part425, the second transmitting member72disables (interrupts, disconnects) power transmission from the gear member423to the drive-side member74and thus to the second intermediate shaft42.

As described above, in this embodiment, the first transmitting member64and the intervening member63function as a first clutch mechanism that transmits power for the hammering operation or interrupts this power transmission; whereas the second transmitting member72and the gear member423function as a second clutch mechanism that transmits power for the drilling operation (tool holder rotation) or interrupts this power transmission. Each of the first clutch mechanism and the second clutch mechanism is switched between a power-transmission state and a power-interruption state in response to user manipulation of a mode-changing dial800(seeFIG.1). More specifically, an intermediate member (not shown) configured to operate in response to the mode-changing dial800changes the position of the first transmitting member64and/or the position of the second transmitting member72according to the dial position of the mode-changing dial800and thereby achieves mode-switching of the first clutch mechanism and the second clutch mechanism.

In this embodiment, the rotary hammer101is switched between three action modes, namely a hammer-drill mode (rotation with hammering), a hammer mode (hammering only), and a drill mode (rotation only), in response to the manipulation of the mode-changing dial800. The hammer-drill mode is a mode in which the striking mechanism6and the rotation-transmitting mechanism7are both driven, so that the hammering operation and the drilling operation are both performed, i.e. the tool accessory91is simultaneously rotated and axially hammered. The hammer mode is a mode in which power transmission for the drilling operation is interrupted by the second clutch mechanism and only the striking mechanism6is driven, so that only the hammering operation is performed, i.e. the tool accessory91is only hammered (without rotation). The drill mode is a mode in which power transmission for the hammering operation is interrupted by the first clutch mechanism and only the rotation-transmitting mechanism7is driven, so that only the drilling operation is performed, i.e. the tool accessory91is only rotated (without hammering).

As described above, the rotary hammer101of this embodiment includes two separate (discrete) intermediate shafts (i.e. the first intermediate shaft41and the second intermediate shaft42) that are configured to extend in parallel to the driving axis A1and transmit power for the hammering operation and the drilling operation, respectively. Therefore, the first intermediate shaft41and the second intermediate shaft42can be made shorter compared to a case in which one common intermediate shaft is used for power transmission for both the hammering operation and the drilling operation. Thus, the overall length of the rotary hammer101can be reduced in the driving-axis direction.

Further, the first intermediate shaft41and the second intermediate shaft42are respectively dedicated to power transmission for the hammering operation and power transmission for the drilling operation. This optimizes power transmission via the first intermediate shaft41and power transmission via the second intermediate shaft42, respectively.

In this embodiment, the rotary hammer101is configured to reduces vibration (in particular, vibration in the front-rear direction) to be transmitted to the body housing10and the handle17due to driving of the driving mechanism5. The vibration-isolating structure of the rotary hammer101is now described.

In this embodiment, as shown inFIG.1, the spindle31and the striking mechanism6(specifically, the motion-converting member61, the piston65, the striker67, and the impact bolt68) are disposed within the body housing10so as to be movable in the driving-axis direction (i.e. front-rear direction) relative to the body housing10. More specifically, a movable support18is disposed within the body housing10in a state in which the movable support18is biased forward relative to the body housing10, and is movable in the front-rear direction relative to the body housing10. The spindle31and the striking mechanism6are supported by the movable support18and are thus movable together with the movable support18relative to the body housing10.

As shown inFIGS.5,6, and12, the movable support18includes a spindle-support part185and a rotary-body-support part187. In this embodiment, the movable support18is formed as a single (integral) metal member.

The spindle-support part185has a generally circular cylindrical shape and is configured as a part for supporting the spindle31. As shown inFIGS.5and6, the bearing317is held inside the spindle-support part185. The spindle-support part185supports a rear portion of the cylinder33via the bearing317so that the cylinder33is rotatable around the driving axis A1. As described above, the spindle31is supported by the two bearings316and317so as to be rotatable around the driving axis A1relative to the body housing10. The other bearing316is held within the barrel part131and supports a rear portion of the tool holder32so that the tool holder32is rotatable around the driving axis A1and movable in the front-rear direction.

The rotary-body-support part187is a generally hollow circular cylindrical portion and is located in the lower right side of the spindle-support part185. As shown inFIG.5, the bearing614is fixed to the rotary-body-support part187by screws. The rotary-body-support part187supports the rotary body611via the bearing614so that the rotary body611is rotatable around the rotation axis A3.

As described above, the spindle31and the rotary body611are supported by the movable support18. Therefore, the oscillating member616, which is mounted on the rotary body611, and the piston65, the striker67, and the impact bolt68, which are disposed within the spindle31, are also supported by the movable support18. Thus, the movable support18, the spindle31, and the striking mechanism6form a movable unit180as an assembly that is integrally movable relative to the body housing10(or in other words, the motor2) in the front-rear direction.

Movement of the movable unit180including the movable support18in the front-rear direction is slidably guided by a pair of first guide shafts191and a pair of second guide shafts192. As shown inFIGS.7and8, the pair of first guide shafts191and the pair of second guide shafts192coaxially extend in the axial direction (i.e. front-rear direction).

More specifically, as shown inFIGS.7,8, and12, the movable support18includes a pair of hollow circular cylindrical parts181radially outward of the spindle-support part185(only one hollow circular cylindrical part18is visible inFIG.12). As shown inFIGS.7and8, the pair of hollow circular cylindrical part181are arranged to be bilaterally symmetrical. In other words, the hollow circular cylindrical parts181are symmetrically arranged respectively on the right and left sides of an imaginary plane P1(seeFIG.2) including the driving axis A1and the rotation axis A2. A hole183is formed through each hollow circular cylindrical part181in the front-rear direction. Approximately a rear half of each first guide shaft191is press fitted into the corresponding hole183, while approximately a front half of each first guide shaft191extends frontward from the movable support18. Therefore, the first guide shafts191are fixed to the movable support18and are configured to move in the front-rear direction together with the movable support18.

The pair of first guide shafts191are respectively received in a pair of holes166(seeFIGS.13and14) formed in the second support16. More specifically, as shown inFIGS.7and8, each hole166extends through the second support16in the front-rear direction. The inner diameter of each hole166is larger in its front portion than in its rear portion. Therefore, the second support16has stepwise inner surfaces each forming the corresponding hole166. The second support16includes a sleeve167of a hollow circular cylindrical shape within each hole166. The sleeve167is press fitted into the front portion of the hole166having the larger-diameter so that a rear end of the sleeve167abuts the step on the inner surface of the hole166. Each first guide shaft191is always received within the corresponding sleeve167so that the first guide shaft191slides on an inner peripheral surface of the sleeve167while the movable support18is moving in the front-rear direction. Each first guide shaft191only slides on the corresponding sleeve167but not on the other parts of the second support16. In this embodiment, a front end portion of each sleeve167abuts the front housing13. Therefore, the sleeve167is prevented from coming out of the hole166even if the first guide shaft191slides on the inner peripheral surface of the sleeve167. In this embodiment, the sleeve167is formed of iron-based metal. Meanwhile, the remaining parts of the second support16are formed of aluminum-based metal, as described above. Therefore, the second support16including the sleeves167can have sufficient strength to withstand sliding movement relative to the first guide shafts191and can also have a reduced weight as a whole.

The pair of second guide shafts192are located more rearward than the pair of first guide shafts191and are held by the first support15. More specifically, as shown inFIGS.7,8, and11, the first support15includes a pair of shaft-support parts156. Each shaft-support part156has a hollow circular cylindrical shape and extends frontward from a plate-like base150that is orthogonal to the front-rear direction. Approximately a rear half of each second guide shaft192is press fitted into the corresponding shaft-support part156. Therefore, the pair of second guide shafts192are immovable relative to the first support15and thus to the body housing10. Approximately a front half of each second guide shaft192extends frontward from the first support15.

As shown inFIGS.7,8, and12, the movable support18includes a pair of hollow circular cylindrical parts182coaxially with the pair of cylindrical parts181. A hole184is formed through each hollow cylindrical part182in the front-rear direction. The inner diameter of each hole184is larger in its rear portion than in its front portion. Therefore, each hollow cylindrical part182has a stepwise inner surface forming the corresponding hole184. The movable support18includes a sleeve186of a hollow circular cylindrical shape within each hole184. The sleeve186is press fitted into the larger-diameter rear portion of the corresponding hole184so that a front end of the sleeve186abuts the step on the inner surface of the hole184. A front end portion of each second guide shaft192is always received within the corresponding sleeve186so that an inner peripheral surface of the sleeve186slides on the second guide shaft192while the movable support18is moving in the front-rear direction. Each second guide shaft192only slides on the corresponding sleeve186but not on the other parts of the movable support18. In this embodiment, each sleeve186is formed of iron-based metal. Meanwhile, the remaining parts of the movable support18are formed of aluminum-based metal, as described above. Therefore, the movable support18including the sleeves186can have sufficient strength to withstand sliding movement relative to the second guide shafts192and can also have a reduced weight as a whole. In this embodiment, both the first guide shafts191and the second guide shafts192are formed of iron-based metal.

The first guide shafts191and the second guide shafts192, which are spaced apart from each other in the front-rear direction, are used to guide movement of the movable support18in the front-rear direction. Therefore, the distance over which the guide shafts extend as a whole can be shortened compared to a case in which a single guide shaft extends from where the first guide shaft191is to where the second guide shaft192is. The rotary hammer101can thus have a reduced weight. Moreover, since the guide shafts are respectively placed on both sides of the movable support18in the front-rear direction, the movable support18can be guided satisfactorily irrespective of the reduced weight.

A pair of biasing springs193are disposed in the rear side of the movable support18. Each spring193is a compression coil spring and is disposed in a compressed state between the first support15and the movable support18. More specifically, each biasing spring193is disposed around the corresponding one of the pair of second guide shafts192. A rear end of each biasing spring193abuts a washer disposed on the base150of the first support15. Each biasing spring193is fitted around the shaft-support part156. The biasing spring193is thus restricted from moving on a plane orthogonal to the front-rear direction. A front end of the each biasing spring193abuts a washer195disposed between the biasing spring193and the movable support18.

The sleeve186disposed within the hole184of the hollow circular cylindrical part182is always biased forward by the biasing spring193via the washer195. This allows the sleeve186to move together with the movable support18whenever the movable support18moves frontward. That is, the sleeve186can be prevented from being left behind and off the hole184when the movable support18is moving frontward.

With such a structure, the pair of biasing springs193always bias the movable support18(the movable unit180) frontward. Therefore, when no rearward external force is being applied to the movable support18, the movable support18is held in (biased to) its foremost position (initial position) where the movable support18abuts the second support16, as shown inFIG.7. An elastic member may be attached on a rear surface of the second support16in order to prevent direct abutment (to dampen the force of collision) between the second support16and the movable support18.

On the other hand, when a rearward external force is being applied to the movable support18, the movable support18can move to its rearmost position shown inFIG.8. Structures for defining this rearmost position are described below.

As shown inFIGS.9to11, the first support15includes a pair of elastic-member-holding parts158each having a bottomed hollow circular cylindrical shape and extending frontward from the base150. The pair of elastic-member-holding parts158are arranged to be bilaterally symmetrical. A hole159is formed in each elastic-member-holding part158. As shown inFIG.11, each elastic-member-holding part158extends more forward than the shaft-support part156. An elastic member194having a hollow circular cylindrical shape is disposed in the hole159of each elastic-member-holding part158. A rear end of the elastic member194abuts the base150while a front end of the elastic member194protrudes more frontward than a front end of the elastic-member-holding part158. The elastic member194is held in a state fitted within the elastic-member-holding part158. More specifically, an outer diameter of the elastic member194is slightly larger than an inner diameter of the elastic-member-holding part158. The elastic member194is thus slightly pressed radially inward within the elastic-member-holding part158and therefore held within the hole159by the restorative force from the pressing. With such a structure, the elastic member194can be removably attached with ease. This in turn enables easy manufacturing and also allows easy replacement of an elastic member194when it is deteriorated or worn out.

As shown inFIGS.9,10, and12, the movable support18includes a pair of projections188and an abutment part189. Each projection188has a solid circular cylindrical shape and extends more rearward than the hollow circular cylindrical part182. Each projection188is always received within the corresponding elastic member194. An outer diameter of the projection188is slightly larger than an inner diameter of the elastic member194. The elastic member194is thus slightly pressed radially outward, and therefore, the projection188and the elastic member194are always held in a state fitted with each other by the restorative force from the pressing. As the movable support18moves in the front-rear direction, the projection188slides on the inner surface of the elastic member194while being kept in the state fitted with the elastic member194. The abutment part189is formed into an arch-shaped plane orthogonal to the front-rear direction, and is connected with base portions of the projections188at both ends of the arch.

When the movable support18is located in its foremost position shown inFIG.7, the abutment part189of the movable support18is spaced apart from the front end portion of the elastic member194in the front-rear direction, as shown inFIG.9. On the other hand, when the movable support18is located in its rearmost position shown inFIG.8, the abutment part189of the movable support18abuts the front end portion of the elastic member194in the front-rear direction, as shown inFIG.10. That is, the elastic member194serves as a stopper for restricting further rearward movement of the movable support18. This structure thus defines the rearmost position of the movable support18shown inFIG.8.

In the rotary hammer101described above, when the tool accessory91is pressed against a workpiece and the processing operation is performed in the hammer-drill mode and the hammer mode in which the hammering operation is performed, vibration is caused mainly in the front-rear direction in the striking mechanism6due to the force of the striking mechanism6driving the tool accessory91and a reaction force from the workpiece against the striking force of the tool accessory91. Owing to this vibration, the movable unit180may move relative to the body housing10in the front-rear direction while being slidably guided by the first and second guide shafts191and192. At this time, the biasing springs193expand and contract (elastically deform). This elastic deformation absorbs (attenuates) vibration from the movable unit180and thereby reduces the amount of vibration transmitted to the body housing10and the handle17. Once the movable unit180has moved to its rearmost position, the abutment part189of the movable support18collides with and elastically deforms the elastic members194. This elastic deformation also serves to absorb (attenuate) vibration from the movable unit180.

According to the rotary hammer101described above, the bearings411and421for respectively supporting the front end portions of the first intermediate shaft41and the second intermediate shaft42are supported by the second support16formed of metal. This provides stronger support strength than in a case in which the bearings411and421are supported by a plastic support. Therefore, even if high power operation of the power tool results in increased vibration due to a reaction force produced against the striking force of the tool accessory91, the positional accuracy for the bearings411and421and thus for the first intermediate shaft41and the second intermediate shaft42can be maintained at the required level. The effects can be further reinforced by the use of the first support15formed of metal to support the bearings412and422for supporting the respective rear end portions of the first intermediate shaft41and the second intermediate shaft42.

Furthermore, according to the rotary hammer101, the first guide shafts191are respectively partially received within the holes166(more specifically, holes of the sleeves167) of the second support16formed of metal. Therefore, even if high power operation of the rotary hammer101results in an increased amount of heat produced as the first guide shafts191slidably guide movement of the movable support18in the front-rear direction, the second support16can have reduced thermal expansion compared to a case in which a plastic support is used to receive the first guide shafts191. Therefore, the positional accuracy required for the first guide shafts191partially received in the holes166of the second support16can be maintained at the required level. This in turn provides satisfactory sliding property related to the first guide shafts191and also allows for satisfactory isolation of vibration. The effects can be further reinforced by having the second guide shafts192respectively partially received within the holes184(more specifically, holes of the sleeves186) of the movable support18formed of metal.

As such, the rotary hammer101can achieve both high power operation and reduced vibration. Moreover, the use of the single member, namely the second support16, for both supporting the bearings411and421and also for receiving the first guide shafts191enables simplified tool structure as well as reduced man-hours related to manufacturing.

Furthermore, the use of the elastic members194each serving as a stopper in the rotary hammer101can improve dissipation of heat produced due to sliding movement of the movable support18in the front-rear direction. Structures therefor are now described. As described above with reference toFIGS.9and10, each elastic member194is disposed so as to be always in contact with the movable support18(more specifically, the projection188) and the first support15(more specifically, the elastic-member-holding part158) irrespective of where the movable support18is located in the front-rear direction.

An elastic material conductive of heat (e.g. conductive rubber) is used for the elastic members194. Heat conductivity may be achieved by forming the elastic member194from a filler-containing elastic material. Examples of the filler include metal, carbon nanotube, and the like. Being “conductive of heat” may be defined as having a heat conductivity of not less than 1.0 W/m*K.

As described above, the first support15is formed of metal, and is disposed adjacent to the passage16for flow of air generated by rotation of the cooling fan27. Therefore, the heat produced due to sliding movement of the movable support18in the front-rear direction can be transmitted via the heat conductive elastic member194to the first support15and then be dissipated efficiently by the flow of air generated by rotation of the cooling fan27.

In this embodiment, the elastic member194and the corresponding projection188of the movable support18are always kept in a state fitted with each other. Therefore, the elastic member194and the movable support18can have a larger contact area compared to a case in which the members makes a plane contact with each other. This enables enhanced heat transmission from the movable support18to the elastic member194and thus provides further improved heat dissipation. Also, the elastic member194and the corresponding elastic-member-holding part158of the first support15are always kept in a state fitted with each other. Therefore, the elastic member194and the first support15can have a larger contact area compared to a case in which the members makes a planar contact with each other. This enables enhanced heat transmission from the elastic member194to the first support15and thus provides further improved heat dissipation. Moreover, the fitted states are implemented as a hollow circular cylindrical shape fitted with another hollow circular cylindrical shape or with a solid circular cylindrical shape. This enables easy manufacturing while achieving a larger contact area.

Furthermore, as shown inFIG.11, the elastic members194are disposed adjacent to the second guide shafts192. Therefore, heat can be transmitted over a short distance from where heat is produced due to sliding movement, via the movable support18, and to the elastic member194. This enables further efficient heat dissipation.

Furthermore, as shown inFIG.11, in an imaginary plane orthogonal to the driving axis A1(in other words, a surface where the base150spreads), the distance between one of the pair of second guide shafts192(the one on the right side) and one of the pair of elastic members194(the one on the right side) that is disposed adjacent to the second guide shaft192is equal to the distance between the other one of the pair of second guide shafts192(the one on the left side) and the other one of the pair of elastic member194(the one on the left side). Therefore, the length of heat transmission path from the one of the second guide shafts192to the one of the elastic members194is equal to the length of heat transmission path from the other one of the second guide shafts192to the other one of the elastic members194(such an arrangement is also referred to as an equidistant arrangement). This reduces or minimizes unevenness of temperature in the movable support18and thus enables uniform heat dissipation.

FIG.11shows an example of equidistant arrangement in which one elastic member194is provided for one second guide shaft192. However, in alternative embodiments, multiple elastic members194may be provided for one second guide shaft192. For example, in an embodiment in which two elastic members194are provided for one second guide shaft192(in this case, there are four elastic members194in total), the equidistant arrangement may be implemented such that each distance between one of the second guide shafts192and each one of its corresponding two elastic members194is equal to each distance between the other one of the second guide shafts192and each one of its corresponding two elastic members194.

Correspondences between the features of the above-described embodiment and the features of the claims are as follows. The features of the above-described embodiment are, however, merely exemplary and do not limit the features of the present invention. The rotary hammer101is an example of the “power tool”. The spindle31is an example of the “final output shaft”. The driving axis A1is an example of the “driving axis”. The motor2and the motor shaft25are examples of the “motor” and the “motor shaft”, respectively. The driving mechanism5is an example of the “driving mechanism”. The body housing10is an example of the “housing”. The movable support18is an example of the “movable support”. The biasing spring193is an example of the “biasing member”. The first guide shaft191and the second guide shaft192are examples of the “first guide shaft” and the “second guide shaft”, respectively. The first intermediate shaft41and the second intermediate shaft42are examples of the “first intermediate shaft” and the “second intermediate shaft”, respectively. The bearing411and the bearing421are examples of the “first bearing” and the “second bearing”, respectively. The second support16is an example of the “metal support”. The hole166and the hole184are examples of the “first hole” and the “second hole”, respectively. The first positioning part163and the second positioning part133are examples of the “first positioning part” and the “second positioning part”, respectively. The sleeve167and the sleeve186are examples of the “first sleeve” and the “second sleeve”, respectively. The attachment surface168is an example of the “attachment surface”.

The above-described embodiment is merely an exemplary embodiment of the present disclosure, and power tools, such as rotary hammers and hammer drills, according to the present disclosure are not limited to the rotary hammer101of the illustrated structure. For example, the following modifications may be made. One or more of these modifications may be employed in combination with the rotary hammer101of the above-described embodiment or any one of the claimed aspects.

Instead of the first intermediate shaft41and the second intermediate shaft42, a single intermediate shaft may be used for both power transmission for hammering operations and power transmission for drilling operations. Such a structure is disclosed in, for example, US Patent Application NO. 2017/106517, the disclosed contents of all of which are hereby fully incorporated herein by reference.

The first guide shaft191may be fixedly received within the hole166of the second support16, instead of being fixedly held to the movable support18. In this modification, the first guide shaft191held by the second support16may be slidably received within a hole formed in the movable support18.

The movable support18, the elastic member194, and the first support15may always be in contact with each other in an alternative manner. For example, the elastic-member-holding part158may have a solid circular cylindrical shape, the elastic member194may have a hollow circular cylindrical shape surrounding the elastic-member-holding part158, and the projection188may have a hollow circular cylindrical shape surrounding the elastic member194. Alternatively, the movable support18, the elastic member194, and the first support15may make a plane contact with each other.

The elastic member conductive of heat (the elastic member194in the above-described embodiment) may be disposed to be always in contact with the movable support18as well as a freely selected metal member disposed to be heat dissipative. In this modification, the metal member may extend from the front side of and through the first support15all the way until it reaches above the air flow passage26. Alternatively, the metal member may be a freely selected member disposed to be at least partially exposed to outside the rotary hammer101. For example, at least a portion of the body housing10exposed to the outside may be formed of metal, and this metal portion and the elastic member may be configured to be always in contact with each other.

In the above-described embodiments, the rotary hammer101capable of performing hammering operations and drilling operations is illustrated as an example of a power tool. However, the power tool may alternatively be an electric hammer (scraper, demolition hammer) capable of performing hammering operations only.

Further, to enhance dissipation of heat produced due to between-parts sliding movement, the following aspects1to10can be provided. Any one of the following aspects1to10can be employed on its own or in combination with any one or more others of the following aspects1to10. Alternatively, at least one of the following aspects1to10may be employed in combination with the rotary hammer101of the above-described embodiment, its modifications described above, and the claimed features.

A power tool comprising:

a final output shaft configured to removably hold a tool accessory and defining a driving axis of the tool accessory;

a motor including a motor shaft;

a driving mechanism configured to linearly reciprocally drive the tool accessory along the driving axis by using power from the motor;

a movable support at least partially supporting the final output shaft and the driving mechanism, the movable support being configured to be integrally movable relative to the motor in an axial direction of the driving axis;

a biasing member configured to bias the movable support toward a front side in the axial direction, the front side being defined as one side in the axial direction in which the final output shaft is disposed and a rear side being defined as an opposite side in the axial direction in which the motor is disposed;

at least one guide shaft extending in the axial direction and configured to slidably guide movement of the movable support in the axial direction;

a metal member disposed to be capable of dissipating heat;

at least one elastic member conductive of heat, the at least one elastic member being disposed to be always in contact with the movable support and the metal member irrespective of where the movable support is located in the axial direction.

According to the power tool of this Aspect, the at least one elastic member conductive of heat is always in contact with the movable support and also with the metal member disposed to be capable of dissipating heat. Therefore, heat produced due to sliding movement for guiding the movement of the movable support can be transmitted from the movable support to the metal member via the at least one elastic member and then be dissipated therefrom. This enhances dissipation of heat produced due to sliding movement for guiding the movement of the movable support.

The power tool according to Aspect 1, wherein

the metal member is disposed to be at least partially exposed to outside of the power tool.

According to this Aspect, heat transmitted from the movable support to the metal member can be dissipated with a simple structure. In this Aspect, the metal member may be a portion of a housing that defines an outer shell of the power tool.

The power tool according to Aspect 1 or 2, further comprising

a fan fixed to the motor shaft,

wherein the metal member is disposed on a passage for flow of air generated by rotation of the fan or is disposed adjacent to the passage.

According to this Aspect, heat transmitted from the movable support to the metal member can be dissipated efficiently by flow of air generated by rotation of the fan.

The power tool according to any one of Aspects 1 to 3, wherein:

the at least one elastic member is held by the metal support; and

the movable support is configured to slide on the at least one elastic member while the movable support moves in the axial direction.

According to this Aspect, the at least one elastic member can always be in contact with the movable support and the metal support in an easily implemented manner.

The power tool according to any one of Aspects 1 to 4, wherein

the at least one elastic member and the movable support are always kept in a state fitted with each other.

According to this Aspect, the at least one elastic member and the movable support can have a larger contact area compared to a case in which the at least one elastic member and the movable support makes a plane contact with each other. This enables enhanced heat transmission from the movable support to the at least one elastic member and thus provides further improved heat dissipation.

The power tool according to Aspect 5, wherein

the at least one elastic member and the movable support are shaped such that the state in which the at least one elastic member and the movable support are fitted with each other is implemented as a hollow circular cylindrical shape fitted with another hollow circular cylindrical shape or a solid circular cylindrical shape.

This Aspect enables easy manufacturing while achieving a larger contact area between the at least one elastic member and the movable support.

The power tool according to any one of Aspects 1 to 6, wherein

the at least one elastic member is disposed adjacent to the at least one guide shaft.

According to this Aspect, heat can be transmitted over a short distance from a portion of the movable support where heat is produced due to sliding movement to the at least one elastic member. This enables efficient heat dissipation.

The power tool according to any one of Aspects 1 to 7, wherein

when the movable support moves rearwards in the axial direction, the at least one elastic member serves as a stopper by abutting the movable support in the axial direction and restricting further rearward movement of the movable support.

According to this Aspect, elastic deformation of the at least one elastic member when serving as a stopper functions to cushion a part of a reaction force from a workpiece due to the hammering operation of the tool accessory. This enhances isolation of vibration in the power tool. The tool can also achieve improved durability.

The power tool according to any one of Aspects 1 to 8, wherein:

the at least one guide shaft includes a plurality of guide shafts;

the at least one elastic member includes a plurality of elastic members corresponding to the plurality of guide shafts; and

the at least one guide shaft and the at least one elastic member are arranged such that each one of the plurality of guide shafts and its corresponding elastic member (which may be one or more) are separated by an equal distance on an imaginary plane orthogonal to the driving axis.

According to this Aspect, each one of the plurality of guide shafts and its corresponding elastic member(s) are separated by an equal distance (i.e. heat is transmitted over a path of equal distance). This reduces or minimizes unevenness of temperature in the movable support and thus enables uniform heat dissipation.

The power tool according to any one of Aspects 1 to 9, wherein:

the metal support includes at least one hole; and the at least one elastic member is held in a state fitted within the at least one hole.

According to this Aspect, the at least one elastic member and the metal support can have a larger contact area compared to a case in which the at least one elastic member and the metal support makes a plane contact with each other. This enables enhanced heat transmission from the at least one elastic member to the metal support and thus provides improved heat dissipation. Furthermore, the at least one elastic member can be removably attached to the metal member with ease. This enables easy manufacturing and also allows for easy replacement of the at least one elastic member when it is deteriorated or worn out.

Correspondences between the features of the above-described embodiment and the features of Aspects 1 to 10 are as follows. The features of the above-described embodiment are, however, merely exemplary and do not limit the features of the present invention.

The rotary hammer101is an example of the “power tool”. The spindle31is an example of the “final output shaft”. The driving axis A1is an example of the “driving axis”. The motor2and the motor shaft25are examples of the “motor” and the “motor shaft”, respectively. The driving mechanism5is an example of the “driving mechanism”. The movable support18is an example of the “movable support”. The biasing spring193is an example of the “biasing member”. The second guide shaft192(or the second guide shaft192and the first guide shaft191) is an example of the “at least one guide shaft”. The first support15is an example of the “metal support”. The elastic member194is an example of the “at least one elastic member”. The cooling fan27is an example of the “fan”.

DESCRIPTION OF THE REFERENCE NUMERALS