Electric tool, electric tool system, attachment, and replaceable tool system

Abstract

An object of the present disclosure is to provide an electric tool, an electric tool system, an attachment, and a replaceable tool system which are configured to suppress a task from being carried out in a state where a combination with the attachment is inappropriate. In an electric tool (1), a dimension (X11) in a predetermined direction (D1) between a connection surface (132) and a tool-side engagement part (131) is equal to a dimension (X31) in the predetermined direction (D1) between a tip end of at least one dedicated projection (321) and a dedicated engagement part (31) and equal to a dimension (X51) in the predetermined direction (D1) between a tip end of at least one dual-purpose projection (521) and a dual-purpose engagement part (51). A dimension (X12) in the predetermined direction (D1) between a tip end of at least one tool-side projection (133) and the tool-side engagement part (131) is equal to a dimension (X32) in the predetermined direction (D1) between an end surface (32) and the dedicated engagement part (31) of a dedicated attachment (3) and greater than a dimension (X52) in the predetermined direction (D1) between an end surface (52) and the dual-purpose engagement part (51) of a dual-purpose attachment (5).

Description

Technical Field

[0001] The present disclosure generally relates to electric tools, electric tool systems, attachments, and replaceable tool systems. More specifically, the present disclosure relates to an electric tool to which attachments are selectively attachable, an electric tool system, an attachment, and a replaceable tool system.Background Art

[0002] Patent Literature 1 discloses an impact rotary tool including an impact force generating unit, a shaft, a torque measuring unit, a rotation angle measuring unit, a calculator, and a controller. The impact force generating unit converts motive power of a drive source into pulse torque, thereby generating an impact force. The shaft transmits the pulse torque to a tip tool by using the impact force thus generated. The torque measuring unit measures measurement torque which is torque applied to the shaft. The rotation angle measuring unit measures the angle of rotation of the shaft. The calculator calculates an angular acceleration on the basis of the angle of rotation thus measured and calculates tightening torque on the basis of the angular acceleration and the measurement torque. The controller controls the drive source on the basis of the tightening torque.

[0003] To an electric tool, such as the impact rotary tool described above, are selectively attachable a plurality of types of attachments, including an attachment having a function of measuring torque. In this case, there is the possibility that an attachment in an inappropriate combination with the electric tool is attached to the electric tool. That is, there is the possibility that a task is carried out in a state where the combination with the attachment is inappropriate.Citation List Patent Literature

[0004] Patent Literature 1: WO 2017 / 154623 AlSummary of Invention

[0005] It is an object of the present disclosure to provide an electric tool, an electric tool system, an attachment, and a replaceable tool system which are configured to suppress a task from being carried out in a state where a combination with the attachment is inappropriate.

[0006] An electric tool (a first electric tool) according to an aspect of the present disclosure is an electric tool to which a dedicated attachment (a first dedicated attachment) and a dual-purpose attachment are selectively attachable. The dedicated attachment is attachable to only a predetermined type of electric tool. The dual-purpose attachment is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool includes a drive unit, an output shaft, and an attachment. The output shaft is configured to be rotated by the drive unit. The attachment is disposed around the output shaft. To the attachment, the dedicated attachment or the dual-purpose attachment is to be attached. The attachment has a tool-side engagement part and a connection surface. The tool-side engagement part is engageable with a dedicated engagement part which the dedicated attachment has and a dual-purpose engagement part which the dual-purpose attachment has. To the connection surface, an end surface of the dedicated attachment or an end surface of the dual-purpose attachment is connected respectively when the tool-side engagement part is engaged with the dedicated engagement part or when the tool-side engagement part is engaged with the dual-purpose engagement part. The electric tool is aligned with the dedicated attachment or the dual-purpose attachment in a predetermined direction respectively when the dedicated attachment is attached to the electric tool or when the dual-purpose attachment is attached to the electric tool. The connection surface has at least one tool-side projection which is a projection protruding in the predetermined direction. The end surface of the dedicated attachment is provided with at least one dedicated projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction. The end surface of the dual-purpose attachment is provided with at least one dual-purpose projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction. A dimension in the predetermined direction between the connection surface and the tool-side engagement part is equal to a dimension in the predetermined direction between a tip end of the at least one dedicated projection and the dedicated engagement part and equal to a dimension in the predetermined direction between a tip end of the at least one dual-purpose projection and the dual-purpose engagement part. A dimension in the predetermined direction between a tip end of the at least one tool-side projection and the tool-side engagement part is equal to a dimension in the predetermined direction between the end surface and the dedicated engagement part of the dedicated attachment and greater than a dimension in the predetermined direction between the end surface and the dual-purpose engagement part of the dual-purpose attachment.

[0007] An electric tool (a second electric tool) according to an aspect of the present disclosure is an electric tool to which a dedicated attachment (a second dedicated attachment) and a dual-purpose attachment are selectively attachable. The dedicated attachment is attachable to only a predetermined type of electric tool. The dual-purpose attachment is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool includes a drive unit, an output shaft, and an attachment. The output shaft is configured to be rotated by the drive unit. The attachment is disposed around the output shaft. To the attachment, the dedicated attachment or the dual-purpose attachment is to be attached. The attachment has a tool-side engagement part and a connection surface. The tool-side engagement part is engageable with a dedicated engagement part which the dedicated attachment has and a dual-purpose engagement part which the dual-purpose attachment has. To the connection surface, an end surface of the dedicated attachment or an end surface of the dual-purpose attachment is connected respectively when the tool-side engagement part is engaged with the dedicated engagement part or when the tool-side engagement part is engaged with the dual-purpose engagement part. The electric tool is aligned with the dedicated attachment or the dual-purpose attachment in a predetermined direction respectively when the dedicated attachment is attached to the electric tool or when the dual-purpose attachment is attached to the electric tool. The connection surface has at least one tool-side projection which is a projection protruding in the predetermined direction. The end surface of the dedicated attachment is provided with at least one dedicated projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction. The end surface of the dual-purpose attachment is provided with at least one dual-purpose projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction. A dimension in the predetermined direction between the connection surface and the tool-side engagement part is equal to a dimension in the predetermined direction between a tip end of the at least one dedicated projection and the dedicated engagement part and greater than a dimension in the predetermined direction between a tip end of the at least one dual-purpose projection and the dual-purpose engagement part. A dimension in the predetermined direction between a tip end of the at least one tool-side projection and the tool-side engagement part is equal to a dimension in the predetermined direction between the end surface and the dedicated engagement part of the dedicated attachment and equal to a dimension in the predetermined direction between the end surface and the dual-purpose engagement part of the dual-purpose attachment.

[0008] An electric tool system according to an aspect of the present disclosure is an electric tool system including the first electric tool and the second electric tool. The dimension in the predetermined direction between the connection surface and the tool-side engagement part of the first electric tool is smaller than a dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part of the second dedicated attachment. The dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part of the first electric tool is greater than the dimension in the predetermined direction between the end surface of the second dedicated attachment and the dedicated engagement part of the second dedicated attachment. The dimension between the connection surface and the tool-side engagement part of the second electric tool in the predetermined direction is greater than the dimension between the tip end of the at least one dedicated projection and the dedicated engagement part of the first dedicated attachment in the predetermined direction. The dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part of the second electric tool is smaller than the dimension in the predetermined direction between the end surface of the first dedicated attachment and the dedicated engagement part of the first dedicated attachment.

[0009] An attachment according to an aspect of the present disclosure is the dedicated attachment attachable to only the electric tool of the first aspect. The attachment includes the dedicated engagement part, the end surface, a holder, and a transmission mechanism. To the end surface, the connection surface is to be connected when the dedicated engagement part is engaged with the tool-side engagement part. The holder is configured to hold a tip tool. The transmission mechanism is configured to transmit rotation of the output shaft to the holder when the dedicated engagement part is engaged with the tool-side engagement part. The end surface is provided with the at least one dedicated projection. The dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part is equal to the dimension in the predetermined direction between the connection surface and the tool-side engagement part. The dimension in the predetermined direction between the end surface and the dedicated engagement part is equal to the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part.

[0010] An attachment according to an aspect of the present disclosure is the dedicated attachment attachable to only the electric tool of the second aspect. The attachment includes the dedicated engagement part, the end surface, a holder, and a transmission mechanism. To the end surface, the connection surface is to be connected when the dedicated engagement part is engaged with the tool-side engagement part. The holder is configured to hold a tip tool. The transmission mechanism is configured to transmit rotation of the output shaft to the holder when the dedicated engagement part is engaged with the tool-side engagement part. The end surface is provided with the at least one dedicated projection. The dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part is equal to the dimension in the predetermined direction between the connection surface and the tool-side engagement part. The dimension in the predetermined direction between the end surface and the dedicated engagement part is equal to the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part.

[0011] An attachment according to an aspect of the present disclosure is a dual-purpose attachment attachable to both the first electric tool and a second electric tool. The attachment includes the dual-purpose engagement part, the end surface, a holder, and a transmission mechanism. To the end surface, the connection surface of the first electric tool or the connection surface of the second electric tool is connected respectively when the dual-purpose engagement part is engaged with the tool-side engagement part of the first electric tool or when the dual-purpose engagement part is engaged with the tool-side engagement part of the second electric tool. The holder is configured to hold a tip tool. The transmission mechanism is configured to transmit rotation of the output shaft of the first electric tool or rotation of the output shaft of the second electric tool to the holder respectively when the dual-purpose engagement part is engaged with the tool-side engagement part of the first electric tool or when the dual-purpose engagement part is engaged with the tool-side engagement part of the second electric tool. The end surface is provided with the at least one dual-purpose projection. The dimension in the predetermined direction between the tip end of the at least one dual-purpose projection and the dual-purpose engagement part is equal to the dimension in the predetermined direction between the connection surface the tool-side engagement part of the first electric tool. The dimension in the predetermined direction between the end surface and the dual-purpose engagement part is equal to the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part of the second electric tool.

[0012] A replaceable tool system according to an aspect of the present disclosure includes: the electric tool system; the first dedicated attachment; the second dedicated attachment; and the dual-purpose attachment.Brief Description of Drawings

[0013] [FIG. 1] FIG. 1 is an exterior perspective view of a first electric tool according to the present embodiment, wherein a first dedicated attachment is attached to the first electric tool; [FIG. 2] FIG. 2 is a block diagram of a schematic configuration of a replaceable tool system of the present embodiment; [FIG. 3] FIG. 3 is an exterior perspective view of a main part of the first electric tool; [FIG. 4] FIG. 4 is an exterior perspective view of the first dedicated attachment; [FIG. 5] FIG. 5A is a schematic development view of a part of a cross section of a connection surface of the first electric tool, FIG. 5B is a schematic development view of a part of a cross section of a connection surface of a second electric tool of the present embodiment, FIG. 5C is a schematic development view of a part of a cross section of an end surface of the first dedicated attachment, FIG. 5D is a schematic development view of a part of a cross section of an end surface of the second dedicated attachment, and FIG. 5E is a schematic development view of a part of a cross section of an end surface of a dual-purpose attachment of the present invention; [FIG. 6] FIG. 6 is a sectional view of a main part of the first electric tool, wherein the first dedicated attachment is attached to the first electric tool; [FIG. 7] FIG. 7 is a schematic development view of a part of cross sections of the connection surface of the first electric tool and the end surface of the first dedicated attachment when the first electric tool and the first dedicated attachment are brought close to each other; [FIG. 8] FIG. 8 is a schematic development view of a part of cross sections of the connection surface of the first electric tool and the end surface of the second dedicated attachment when the first electric tool and the second dedicated attachment are brought close to each other; [FIG. 9] FIG. 9 is a schematic development view of a part of cross sections of the connection surface of the first electric tool and the end surface of the dual-purpose attachment when the first electric tool and the dual-purpose attachment are brought close to each other; [FIG. 10] FIG. 10 is a schematic development view of a part of cross sections of the connection surface of the second electric tool and the end surface of the first dedicated attachment when the second electric tool and the first dedicated attachment are brought close to each other; [FIG. 11] FIG. 11 is a schematic development view of a part of cross sections of the connection surface of the second electric tool and the end surface of the second dedicated attachment when the second electric tool and the second dedicated attachment are brought close to each other; and [FIG. 12] FIG. 12 is a schematic development view of a part of cross sections of the connection surface of the second electric tool and the end surface of the dual-purpose attachment when the second electric tool and the dual-purpose attachment are brought close to each other. Description of Embodiments

[0014] An electric tool and an attachment according to an embodiment will be described below with reference to the drawings. Note that the embodiment described below is a mere example of various embodiments of the present disclosure. Various modifications may be made to the embodiment described below as long as the object of the present disclosure is achieved. Moreover, figures described in the following embodiment are schematic views. The ratio of sizes and the ratio of thicknesses of components in the figures do not necessarily reflect actual dimensional ratios.(Present Embodiment)(1) Overview

[0015] The overview of an electric tool 1 according to the present embodiment will be described below with reference to FIGS. 1 to 5E.

[0016] The electric tool 1 according to the present embodiment is assumed to be an electrically driven screw driver used by a worker in a tightening task of tightening a tightening member (e.g., a screw, a bolt, or a nut) to a tightening target (e.g., an electric appliance or furniture). Note that the electric tool 1 may be an electrically driven screwdriver used by the worker in a detachment task of loosening the tightening member from the tightening target.

[0017] The electric tool 1 (see FIGS. 1 and 2) is an electric tool to which a dedicated attachment 3 (see FIGS. 1 and 2) and a dual-purpose attachment 5 (see FIG. 2) are selectively attachable. The dedicated attachment 3 is attachable to only a predetermined type of electric tool. The dual-purpose attachment 5 is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool 1 with the dedicated attachment 3 attached thereto is shown in FIG. 1. The dedicated attachment 3 is an attachment attachable to only the electric tool 1. In contrast, the dual-purpose attachment 5 is an attachment attachable to both the electric tool 1 (hereinafter referred to as a first electric tool 1) and a second electric tool 2 which is a different type of electric tool from the first electric tool 1.

[0018] To facilitate a tightening task at various angles, the dedicated attachment 3 and the dual-purpose attachment 5 have, for example, a structure that changes a position or an orientation at which a tip tool B1 for tightening a tightening target is held. Moreover, the dedicated attachment 3 and the dual-purpose attachment 5 may have a function of measuring torque or a function of counting the number of times of tightening.

[0019] As shown in FIG. 2, the first electric tool 1 includes a drive unit 11, an output shaft 12, and an attachment 13. The output shaft 12 is rotated by the drive unit 11. The attachment 13 is disposed around the output shaft 12. The dedicated attachment 3 or the dual-purpose attachment 5 is attached to the attachment 13.

[0020] As shown in FIG. 3, the attachment 13 has a tool-side engagement part 131 and a connection surface 132. The tool-side engagement part 131 is engageable with a dedicated engagement part 31 (see FIGS. 2 and 4) of the dedicated attachment 3 and a dual-purpose engagement part 51 (see FIG. 2) of the dual-purpose attachment 5. When the tool-side engagement part 131 is engaged with the dedicated engagement part 31 or the dual-purpose engagement part 51, an end surface 32 of the dedicated attachment 3 or an end surface 52 of the dual-purpose attachment 5 is connected to the connection surface 132, respectively.

[0021] As shown in FIG. 1, when the dedicated attachment 3 or the dual-purpose attachment 5 is attached to the first electric tool 1, the first electric tool 1 is in alignment with the dedicated attachment 3 or the dual-purpose attachment 5, respectively, in a predetermined direction D1.

[0022] FIG. 5A is a schematic development view of a part of a cross section of the connection surface 132 of the first electric tool 1 along a sectional line L1 shown in FIG. 3. A dotted line Y1 shown in FIG. 5A indicates a position where the tool-side engagement part 131 of the first electric tool 1 is disposed in the predetermined direction D1. Moreover, FIG. 5C is a schematic development view of a part of a cross section of the end surface 32 of the dedicated attachment 3 along a sectional line L2 shown in FIG. 4. A dotted line Y3 shown in FIG. 5C indicates a position where the dedicated engagement part 31 of the dedicated attachment 3 is disposed in the predetermined direction D1. In a similar manner to FIG. 5C, FIG. 5E is a schematic development view of a part of a cross section of the end surface 52 of the dual-purpose attachment 5. A dotted line Y5 shown in FIG. 5E indicates a position where the dual-purpose engagement part 51 of the dual-purpose attachment 5 is disposed in the predetermined direction D1. FIGS. 5A, 5C, and 5E are schematic diagrams and thus do not reflect the dimensional ratios of FIGS. 3 and 4.

[0023] As shown in FIGS. 3 and 5A, the connection surface 132 has at least one tool-side projection 133 which is a projection protruding in the predetermined direction D1. As shown in FIGS. 4 and 5C, the end surface 32 of the dedicated attachment 3 is provided with at least one dedicated projection 321 which is a projection arranged to be engaged with the tool-side projection 133 and protruding in the predetermined direction D1. Similarly, as shown in FIG. FIG. 5E, the end surface of the dual-purpose attachment 5 is provided with at least one dual-purpose projection 521 which is a projection arranged to be engaged with the tool-side projection 133 and protruding in the predetermined direction D1.

[0024] A dimension X11 (see FIG. 5A) in the predetermined direction D1 between the connection surface 132 and the tool-side engagement part 131 (i.e., the dotted line Y1) is equal to a dimension X31 (see FIG. 5C) in the predetermined direction D1 between a tip end of the at least one dedicated projection 321 and the dedicated engagement part 31 (i.e., the dotted line Y3) and equal to a dimension X51 (see FIG. 5E) in the predetermined direction D1 between a tip end of the at least one dual-purpose projection 521 and the dual-purpose engagement part 51 (i.e., the dotted line Y5). In contrast, a dimension X12 (see FIG. 5A) in the predetermined direction D1 between a tip end of the at least one tool-side projection 133 and the tool-side engagement part 131 is equal to a dimension X32 (see FIG. 5C) in the predetermined direction D1 between the end surface 32 and the dedicated engagement part 31 of the dedicated attachment 3 and is greater than a dimension X52 (see FIG. 5E) in the predetermined direction D1 between the end surface 52 and the dual-purpose engagement part 51 of the dual-purpose attachment 5. As used in the present disclosure, "equal" is not limited to being exactly equal but tolerates some errors.

[0025] Due to the configuration described above, an attachment which is in an inappropriate combination with the first electric tool 1 is not attachable to the first electric tool 1. That is, the first electric tool 1 of the present embodiment has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.(2) Detailed Configuration(2-1) Replaceable Tool System

[0026] With reference to FIG. 2, a detailed configuration of a replaceable tool system 200 of the present embodiment will be described below.

[0027] As shown in FIG. 2, the replaceable tool system 200 includes an electric tool system 100, the first dedicated attachment 3, a second dedicated attachment 4, and the dual-purpose attachment 5.(2-2) Electric Tool System

[0028] As shown in FIG. 2, the electric tool system 100 includes the first electric tool 1 and a second electric tool 2. The first electric tool 1 is an electric tool which is a different type of electric tool from the second electric tool. For example, the first electric tool 1 is an impact driver, and the second electric tool 2 is a drill driver.(2-2-1) First Electric Tool

[0029] With reference to FIGS. 1 to 6, a detailed structure of the first electric tool 1 of the present embodiment will be described below.

[0030] As shown in FIGS. 1 and 2, the first electric tool 1 includes the drive unit 11, the output shaft 12, the attachment 13, a housing 14, an operation unit 15, and a control unit 16.

[0031] In the following description, an axial direction of the output shaft 12 (see FIG. 1) is defined as a front / rear direction. A side on which the attachment 13 is disposed in a body 141 described later is defined as a front side, and a side on which the attachment 13 is not disposed is defined as a rear side. The predetermined direction D1 described above is a direction in alignment with the front / rear direction. Moreover, as shown in FIG. 1, a direction in which the body 141 and a grip 142 described later are aligned with each other is defined as an up / down direction, wherein the body 141 is upward of the grip 142, and the grip 142 is downward of the body 141. Moreover, a direction orthogonal to the front / rear direction and the up / down direction is defined as a left / right direction. Note that these definitions are not intended to define a direction in which the first electric tool 1 is used.(Housing)

[0032] The housing 14 houses the drive unit 11, at least part of the output shaft 12, and the control unit 16.

[0033] As shown in FIG. 1, the housing 14 includes the body 141, the grip 142, and a battery attachment 143.

[0034] The body 141 houses the drive unit 11 and at least part of the output shaft 12.

[0035] As shown in FIG. 3, the body 141 has a side part 1411 and a bottom part 1412. The side part 1411 has a cylindrical shape. More specifically, the side part 1411 has a circularly cylindrical shape. The bottom part 1412 is arranged to cover an opening formed at the rear of the side part 1411 having the cylindrical shape. That is, the body 141 is a bottomed cylindrical body having an opening 1413 formed at the front thereof. The bottom part 1412 has a disk shape. A thickness direction defined with respect to the bottom part 1412 is in alignment with the front / rear direction. At least part of the output shaft 12 protrudes frontward from the opening 1413. The attachment 13 is disposed around the output shaft 12 between the output shaft 12 and the side part 1411. More specifically, the attachment 13 is disposed between the output shaft 12 and the side part 1411 to surround the output shaft 12. That is, the opening 1413 is covered with the output shaft 12 and the attachment 13. A detailed structure of the attachment 13 will be described later.

[0036] As shown in FIG. 1, the grip 142 protrudes from the body 141. More specifically, the grip 142 protrudes downward from the body 141. A worker may hold the grip 142 to carry out a task of, for example, tightening a screw. A worker may hold the grip 142 to carry out a task of, for example, tightening a screw.

[0037] The grip 142 of the present embodiment houses the control unit 16.

[0038] The battery attachment 143 is in the shape of a substantially rectangular parallelepiped. As shown in FIG. 1, the battery attachment 143 is connected to a lower end of the grip 142. A rechargeable battery pack (not shown) is detachably attachable to the battery attachment 143. The first electric tool 1 operates by using the battery pack as a power supply. That is, the battery pack is a power supply that supplies electric power for driving the drive unit 11. The battery pack is not a component included in the first electric tool 1. Note that the first electric tool 1 may include the battery pack. The battery pack includes an assembled battery including a plurality of secondary batteries (e.g., lithium ion batteries) connected in series to each other and a case in which the assembled battery is housed.(Drive Unit)

[0039] The drive unit 11 performs rotation operation. More specifically, the drive unit 11 operates by using electric power supplied from the battery pack attached to the battery attachment 143 and performs the rotation operation. The drive unit 11 includes: a rotor having a drive shaft and a permanent magnet; and a stator having a coil. Electromagnetic interaction between the permanent magnet and the coil rotates the rotor with respect to the stator.

[0040] Moreover, the drive unit 11 is a servomotor. The torque and rotational velocity of the drive unit 11 change in accordance with control by the control unit 16 (servo driver). More specifically, the control unit 16 controls the operation of the drive unit 11 by feedback control of performing control to make the torque and rotational velocity of the drive unit 11 close to target values.(Output Shaft)

[0041] The output shaft 12 is directly or indirectly connected to the drive shaft of the drive unit 11. As a result, the output shaft 12 rotates together with the drive shaft of the drive unit 11. That is, the output shaft 12 is rotated by the drive unit 11.

[0042] The output shaft 12 is a columnar body. The output shaft 12 of the present embodiment is cylindrical. At least part of the output shaft 12 protrudes from the opening 1413 of the body 141. More specifically, a front portion of the output shaft 12 protrudes from the opening 1413 of the body 141.

[0043] To the output shaft 12 is connectable a transmission mechanism 33 (see FIGS. 2 and 4), described later, of the first dedicated attachment 3. When the transmission mechanism 33 of the first dedicated attachment 3 is connected to the output shaft 12, the transmission mechanism 33 is rotated together with the output shaft 12 by the drive unit 11.

[0044] Similarly, to the output shaft 12 is connectable a transmission mechanism 53 (see FIG. 2), described later, of the dual-purpose attachment 5. When the transmission mechanism 53 of the dual-purpose attachment 5 is connected to the output shaft 12, the transmission mechanism 53 is rotated together with the output shaft 12 by the drive unit 11.

[0045] Moreover, the output shaft 12 includes a holder 121 (see FIG. 3) which holds the tip tool B1 when the transmission mechanism 33 of the first dedicated attachment 3 or the transmission mechanism 53 of the dual-purpose attachment 5 is not connected to the output shaft 12. The holder 121 is disposed at a front end portion of the output shaft 12. In the first electric tool 1, the output shaft 12 is capable of indirectly holding the tip tool B1 via the first dedicated attachment 3 or the dual-purpose attachment 5 (which will be described in detail later), and the holder 121 of the output shaft 12 is also capable of directly holding the tip tool B1. The tip tool B1 is, for example, a driver bit. When the holder 121 holds the tip tool B1, rotation of the output shaft 12 in a state where the tip tool B1 is fit to a tightening member enables a task such as tightening or loosening the tightening member to be carried out.(Attachment)

[0046] The first dedicated attachment 3 or the dual-purpose attachment 5 is attached to the attachment 13. As shown in FIG. 3, the attachment 13 has the tool-side engagement part 131 and the connection surface 132. The tool-side engagement part 131 is engageable with the dedicated engagement part 31, described later, of the first dedicated attachment 3 and the dual-purpose engagement part 51, described later, of the dual-purpose attachment 5. The connection surface 132 is a surface to which the end surface 32, described later, of the first dedicated attachment 3 or the end surface 52 of the dual-purpose attachment 5 is connected respectively when the tool-side engagement part 131 is engaged with the dedicated engagement part 31 of the first dedicated attachment 3 or when the tool-side engagement part 131 is engaged with the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0047] The shape of the attachment 13 will be described in detail below. FIG. 6 is a sectional view of the first electric tool 1 to which, as an example, the first dedicated attachment 3 is attached.

[0048] As shown in FIG. 6, the attachment 13 of the present embodiment has a first portion 134 and a second portion 135.

[0049] The first portion 134 is a bottomed cylindrical body having a bottom surface at the front thereof. More specifically, the first portion 134 is a bottomed, circularly cylindrical body having a bottom surface at the front thereof. That is, the bottom surface of the first portion 134 has a disk shape. In the present embodiment, an outer diameter of the bottom surface of the first portion 134 is substantially equal to an inner diameter of the opening 1413 of the body 141. The first portion 134 is disposed to cover the opening 1413.

[0050] The bottom surface of the first portion 134 has a through hole 1341 formed in the front / rear direction. The output shaft 12 is inserted into the through hole 1341 formed in the first portion 134. That is, the first portion 134 is disposed between the output shaft 12 and the side part 1411 to surround the output shaft 12.

[0051] The second portion 135 has a circularly cylindrical shape. The second portion 135 has a radius substantially equal to a radius of the through hole 1341 formed in the first portion 134. An axial direction of the second portion 135 is in alignment with the front / rear direction, and the second portion 135 has a rear end connected to the through hole 1341 formed in the first portion 134. That is, the second portion 135 is a circularly cylindrical member protruding frontward from the through hole 1341 formed in the first portion 134. The output shaft 12 is inserted through the second portion 135. A dimension of the second portion 135 in the predetermined direction D1 is smaller than a dimension of the output shaft 12 in the predetermined direction D1. Therefore, the output shaft 12 has a front end protruding from a front end of the second portion 135.

[0052] As shown in FIG. 6, the tool-side engagement part 131 of the present embodiment is a projection protruding outward from the front end of the second portion 135. The tool-side engagement part 131 of the present embodiment extends over a circumference of the second portion 135. For example, when the first dedicated attachment 3 is attached to the first electric tool 1 as shown in FIG. 6, a rear surface of the tool-side engagement part 131 is engaged with the dedicated engagement part 31, described later, of the first dedicated attachment 3. In contrast, when the dual-purpose attachment 5 is attached to the first electric tool 1, a rear surface of the tool-side engagement part 131 is engaged with the dual-purpose engagement part 51, described later, of the dual-purpose attachment 5. That is, in the present embodiment, the rear surface of the tool-side engagement part 131 is the surface which is to be engaged with the dedicated engagement part 31 of the first dedicated attachment 3 or the dual-purpose engagement part 51 of the dual-purpose attachment 5. The tool-side engagement part 131 has the configuration described above and is thus engageable with the dedicated engagement part 31 of the first dedicated attachment 3 and the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0053] The connection surface 132 of the present embodiment is a front surface of the first portion 134. That is, in the present embodiment, the connection surface 132 has a circularly annular shape when viewed in the predetermined direction D1.

[0054] As shown in FIG. 3, the connection surface 132 has the tool-side projection 133 which is a projection protruding in the predetermined direction D1. In other words, the front surface of the first portion 134 has the tool-side projection 133 as shown in FIG. 6. On the connection surface 132 of the present embodiment are formed a plurality of tool-side projections 133 as shown in FIG. 3. In other words, the connection surface 132 of the present embodiment has the plurality of tool-side projections 133. The plurality of tool-side projections 133 are disposed in a circularly annular shape along a circumference of the connection surface 132. More specifically, the plurality of tool-side projections 133 are disposed in a circularly annular shape at equal intervals along the circumference of the connection surface 132. The shape of each of the plurality of tool-side projections 133 viewed in the predetermined direction D1 is a shape obtained by dividing a circular annulus. The configuration described above provides the effect that the first dedicated attachment 3 or the dual-purpose attachment 5 is more firmly attached. This consequently provides the advantage that a tightening task can be stably carried out.

[0055] FIG. 5A is a schematic development view of a part of a cross section of the connection surface 132 of the first electric tool 1 along the sectional line L1 shown in FIG. 3, wherein the tool-side projections 133 are disposed on the connection surface 132. The dotted line Y1 shown in FIG. 5A indicates the position where the tool-side engagement part 131 of the first electric tool 1 is disposed in the predetermined direction D1. More specifically, the dotted line Y1 shown in FIG. 5A indicates the position of the rear surface (i.e., a surface which is to be engaged with the dedicated engagement part 31 of the first dedicated attachment 3 or the dual-purpose engagement part 51 of the dual-purpose attachment 5) of the tool-side engagement part 131 of the first electric tool 1 in the predetermined direction D1 as shown in FIG. 6. FIG. 5A is a schematic diagram and thus does not reflect the dimensional ratios of FIGS. 3 and 6.

[0056] As shown in FIG. 5A, each of the plurality of tool-side projections 133 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the tool-side projections 133, the end being connected to the connection surface 132. As used herein, the "end being connected to the connection surface 132" is a rear end of each of the plurality of tool-side projections 133, and the "tip end of a corresponding one of the tool-side projections 133" is a front end of the corresponding one of the tool-side projections 133. This configuration provides the advantage that attaching the first dedicated attachment 3 or the dual-purpose attachment 5 is facilitated.

[0057] Note that the dimension of each of the tool-side projections 133 of the first electric tool 1 in the predetermined direction D1 will be described later in "(3) Dimensional Relationship".(Operation Unit)

[0058] As shown in FIG. 1, the operation unit 15 protrudes from the grip 144. The operation unit 15 receives an operation for controlling rotation of the drive shaft of the drive unit 11. An operation of pulling the operation unit 15 can switch the drive unit 11 between ON and OFF. Moreover, a rotational velocity of the drive shaft is adjustable by a pulled amount indicating how deep the operation unit 15 is pulled. As the pulled amount increases, the rotational velocity of the drive shaft of the drive unit 11 increases.(Control Unit)

[0059] The control unit 16 rotates or stops the drive shaft of the drive unit 11 and controls the rotational velocity of the drive shaft in accordance with the pulled amount indicating how deep the operation unit 15 is pulled.

[0060] The control unit 16 includes, for example, a microcontroller. The control unit 16 can change the rotational velocity of the drive shaft of the drive unit 11, thereby changing the rotational velocity of the output shaft 12. The control unit 16 changes, for example, electric power to be supplied to the drive unit 11, thereby changing the rotational velocity of the drive shaft of the drive unit 11.(2-2-2) Second Electric Tool

[0061] As shown in FIG. 2, the second electric tool 2 includes a drive unit 21, an output shaft 22, an attachment 23, a housing 24, an operation unit 25, and a control unit 26. The drive unit 21, the output shaft 22, the housing 24, the operation unit 25, and the control unit 26 of the second electric tool 2 have similar configurations respectively to the drive unit 11, the output shaft 12, the housing 14, the operation unit 15, and the control unit 16 of the first electric tool 1, and therefore, the description thereof will be omitted.(Attachment)

[0062] To the attachment 23, the second dedicated attachment 4 or dual-purpose attachment 5 is attached. As shown in FIG. 2, the attachment 23 has a tool-side engagement part 231 and a connection surface 232. The tool-side engagement part 231 is engageable with a dedicated engagement part 41, described later, of the second dedicated attachment 4 and the dual-purpose engagement part 51 of the dual-purpose attachment 5. The connection surface 232 is a surface to which an end surface 42, described later, of the second dedicated attachment 4 or the end surface 52 of the dual-purpose attachment 5 is connected respectively when the tool-side engagement part 231 is engaged with the dedicated engagement part 41 of the second dedicated attachment 4 or when the tool-side engagement part 231 is engaged with the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0063] Note that since the shape of the tool-side engagement part 231 of the attachment 23 of the second electric tool 2 is substantially similar to the shape of the tool-side engagement part 131 of the attachment 13 of the first electric tool 1, and therefore, the detailed description thereof will be omitted.

[0064] In the following description, since the shape of the attachment 23 of the second electric tool 2 except for the shape of a tool-side projection 233, described later, of the connection surface 232 of the attachment 23 is substantially similar to the shape of the attachment 13 of the first electric tool 1 except for the shape of the tool-side projections 133 on the connection surface 132 of the attachment 13, the detailed description of the shape except for the shape of the tool-side projection 233 will be omitted, and only the shape of the tool-side projection 233 will be described below.

[0065] Similarly to FIG. 5A, FIG. 5B is a schematic development view of a part of a cross section of the connection surface 132 of the second electric tool 2, wherein the tool-side projections 133 are disposed on the connection surface 132. A dotted line Y2 shown in FIG. 5B indicates a position where the tool-side engagement part 231 of the second electric tool 2 is disposed in the predetermined direction D1. That is, the dotted line Y2 shown in FIG. 5B indicates a position of a rear surface of the tool-side engagement part 231 of the second electric tool 2 in the predetermined direction D1 (i.e., a surface which is to be engaged with the dedicated engagement part 41 of the second dedicated attachment 4 or the dual-purpose engagement part 51 of the dual-purpose attachment 5).

[0066] As shown in FIG. 5B, the connection surface 232 has the tool-side projection 233 which is a projection protruding in the predetermined direction D1. On the connection surface 232 of the present embodiment are formed a plurality of tool-side projections 233. In other words, the connection surface 232 of the present embodiment has the plurality of tool-side projections 233. The plurality of tool-side projections 233 are disposed in a circularly annular shape along a circumference of the connection surface 232. More specifically, the plurality of tool-side projections 233 are disposed in a circularly annular shape at equal intervals along the circumference of the connection surface 232.

[0067] As shown in FIG. 5B, each of the plurality of tool-side projections 233 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the tool-side projections 233, the end being connected to the connection surface 232. As used herein, the "end being connected to the connection surface 232" is a rear end of each of the plurality of tool-side projections 233, and the "tip end of a corresponding one of the tool-side projections 233" is a front end of the corresponding one of the tool-side projections 233. This configuration has the advantage that attaching the second dedicated attachment 4 or the dual-purpose attachment 5 is facilitated.

[0068] As shown in FIGS. 5A and 5B, the tool-side projections 233 of the second electric tool 2 are different from the tool-side projections 133 of the first electric tool 1 in the dimension in the predetermined direction D1. More specifically, the dimension of each of the tool-side projections 233 of the second electric tool 2 in the predetermined direction D1 is greater than the dimension of each of the tool-side projections 133 of the first electric tool 1 in the predetermined direction D1. Note that the dimension of each of the tool-side projections 233 of the second electric tool 2 in the predetermined direction D1 will be later described in "(3) Dimensional Relationship".(2-3) First Dedicated Attachment

[0069] The first dedicated attachment 3 is an attachment attachable to only the first electric tool 1.

[0070] In the following description, the first dedicated attachment 3 is assumed to have a structure that changes, to facilitate a tightening task at various angles, a position at which the tip tool B1 for tightening a tightening target is held. Note that the first dedicated attachment 3 may have a structure that changes the orientation in which the tip tool B1 is held. Moreover, the first dedicated attachment 3 may have a function of measuring torque or a function of counting the number of times of tightening.

[0071] As shown in FIG. 2, the first dedicated attachment 3 includes the dedicated engagement part 31, the end surface 32, the transmission mechanism 33, a rotary shaft 34, and a housing 35.(Housing)

[0072] The housing 35 houses the dedicated engagement part 31, the transmission mechanism 33, and at least part of the rotary shaft 34.

[0073] As shown in FIGS. 1 and 6, the housing 35 has a side part 351 and a bottom part 352. The side part 351 has a substantially cylindrical shape. More specifically, the side part 351 has a substantially circularly cylindrical shape.

[0074] As shown in FIGS. 4 and 6, the side part 351 of the present embodiment has a first portion 3511 and a second portion 3512. The first portion 3511 and the second portion 3512 are circularly cylindrical, and an outer diameter of the first portion 3511 is substantially equal to an outer diameter of the second portion 3512. The first portion 3511 is located slightly higher than the second portion 3512. The first portion 3511 and the second portion 3512 are aligned in the front / rear direction, and a rear end of the first portion 3511 is connected to a front end of the second portion 3512. As shown in FIG. 6, the bottom part 352 is disposed to cover an opening formed at the front of the first portion 3511, which is cylindrical. That is, the housing 35 is a bottomed cylindrical body having an opening at the rear thereof. The bottom part 352 has a disk shape. A thickness direction as defined with respect to the bottom part 352 is in alignment with the front / rear direction. The bottom part 352 has a through hole 3521 formed in the front / rear direction. The through hole 3521 is disposed above the bottom part 352. The rotary shaft 34 is inserted through the through hole 3521.(Dedicated Engagement Part)

[0075] The dedicated engagement part 31 is engageable with the tool-side engagement part 131 of the first electric tool 1.

[0076] As shown in FIGS. 4 and 6, the first dedicated attachment 3 of the present embodiment includes two dedicated engagement parts 31. Each of the two dedicated engagement parts 31 has a plate piece 311 protruding inward. A thickness direction defined with respect to the two plate pieces 311 is in alignment with the predetermined direction D1. In the present embodiment, each of the two plate pieces 311 is an elongated plate piece-shaped member having a longitudinal direction curved along a circumferential direction of the second portion 3512 of the side part 351 as shown in FIG. 4. The two plate pieces 311 are aligned with each other in the up / down direction. The plate piece 311 on an upper side protrudes downward, and the plate piece 311 on a lower side protrudes upward. When the first dedicated attachment 3 is attached to the first electric tool 1 as shown in FIG. 6, front surfaces of the two plate pieces 311 are engaged with the rear surface of the tool-side engagement part 131. That is, in the present embodiment, the front surface of each plate piece 311 is a surface which is to be engaged with the tool-side engagement part 131 of the first electric tool 1. The two dedicated engagement parts 31 have the configuration described above and are thus engageable with the tool-side engagement part 131 of the first electric tool 1.

[0077] In the present embodiment, the two dedicated engagement parts 31 are configured such that sliding operation units 312 frontward disengage the plate pieces 311 from the tool-side engagement part 131.(End Surface)

[0078] As shown in FIGS. 4 and 6, the first dedicated attachment 3 of the present embodiment further includes an annular member 320 which is a member having a circularly annular shape. An outer diameter of the annular member 320 is substantially equal to an inner diameter of the second portion 3512 of the side part 351 of the housing 35, and an inner diameter of the annular member 320 is substantially equal to an outer diameter of the second portion 135 of the attachment 13 of the first electric tool 1. The annular member 320 is disposed in an opening formed in the housing 35 such that an outer end surface of the annular member 320 is in contact with the second portion 3512 of the side part 351 of the housing 35. When the first dedicated attachment 3 is attached to the first electric tool 1 as shown in FIG. 6, the annular member 320 has an inner end surface in contact with the second portion 135 of the attachment 13 of the first electric tool 1.

[0079] In the present embodiment, a rear surface of the annular member 320 is the end surface 32 to which the connection surface 132 is connected when the dedicated engagement part 31 is engaged with the tool-side engagement part 131. That is, in the present embodiment, the end surface 32 has a circularly annular shape when viewed in the predetermined direction D1.

[0080] As shown in FIG. 4, the end surface 32 has a dedicated projection 321 which is a projection arranged to be engaged with the tool-side projections 133 of the first electric tool 1 and protruding in the predetermined direction D1. On the end surface 32 of the present embodiment are formed a plurality of dedicated projections 321. In other words, the end surface 32 of the present embodiment has the plurality of dedicated projections 321. The plurality of dedicated projections 321 are disposed in a circularly annular shape along the circumference of the connection surface 132. More specifically, the plurality of dedicated projections 321 are disposed in a circularly annular shape at equal intervals along the circumference of the connection surface 132.

[0081] FIG. 5C is a schematic development view of a part of a cross section of the end surface 32 of the first dedicated attachment 3 along a sectional line L2 shown in FIG. 4, wherein the dedicated projections 321 are disposed on the end surface 32. The dotted line Y3 shown in FIG. 5C indicates the position where the dedicated engagement part 31 (see FIG. 6) of the first dedicated attachment 3 is disposed in the predetermined direction D1. More specifically, the dotted line Y3 shown in FIG. 5C indicates a position of a front surface of the plate piece 311 of the dedicated engagement part 31 of the first dedicated attachment 3 in the predetermined direction D1 (i.e., the surface which is to be engaged with the tool-side engagement part 131 of the first electric tool 1).

[0082] As shown in FIG. 5C, each of the plurality of dedicated projections 321 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the dedicated projections 321, the end being connected to the end surface 32. As used herein, the "end being connected to the end surface 32" is a front end of each of the plurality of dedicated projections 321, and the "tip end of a corresponding one of the dedicated projection 321" is a rear end of the corresponding one of the dedicated projections 321. This configuration has the advantage that attachment to the first electric tool 1 is facilitated.

[0083] Note that the dimension of each of the dedicated projections 321 of the first dedicated attachment 3 in the predetermined direction D1 will be described later in "(3) Dimensional Relationship".(Transmission Mechanism)

[0084] When the dedicated engagement part 31 is engaged with the tool-side engagement part 131 of the first electric tool 1, the transmission mechanism 33 transmits rotation of the output shaft 12 of the first electric tool 1 to the rotary shaft 34. More specifically, when the dedicated engagement part 31 is engaged with the tool-side engagement part 131 of the first electric tool 1, the transmission mechanism 33 transmits the rotation of the output shaft 12 of the first electric tool 1 to the rotary shaft 34, thereby rotating the rotary shaft 34. As shown in FIG. 6, the rear end of the transmission mechanism 33 is connectable to the front end of the output shaft 12 of the first electric tool 1.(Rotary Shaft)

[0085] The rotary shaft 34 rotates together with the output shaft 12 of the first electric tool 1 when the dedicated engagement part 31 is engaged with the tool-side engagement part 131 of the first electric tool 1. More specifically, the rotary shaft 34 rotates due to transmission of the rotation of the output shaft 12 of the first electric tool 1 to the rotary shaft 34 by the transmission mechanism 33 when the dedicated engagement part 31 is engaged with the tool-side engagement part 131 of the first electric tool 1.

[0086] The rotary shaft 34 is a columnar body. The rotary shaft 34 of the present embodiment is circularly columnar. In the present embodiment, an axial direction of the rotary shaft 34 is in alignment with the front / rear direction and is the same as the axial direction of the output shaft 12. At least part of the rotary shaft 34 protrudes from the through hole 3521 formed in the bottom part 352. More specifically, a front portion of the rotary shaft 34 protrudes from the through hole 3521 formed in the bottom part 352. That is, the rotary shaft 34 of the present embodiment protrudes frontward from the bottom part 352 of the housing 35.

[0087] In the present embodiment, the rotary shaft 34 is disposed above the output shaft 12. That is, the rotary shaft 34 and the output shaft 12 do not overlap each other when viewed in the front / rear direction.

[0088] The rotary shaft 34 has a holder 341 (see FIG. 6) for holding the tip tool B1. The holder 341 is disposed at a front end portion of the output shaft 12. The tip tool B1 is, for example, a driver bit as described above. When the holder 341 holds the tip tool B1, rotation of the rotary shaft 34 in a state where the tip tool B1 is fit to a tightening member enables a task such as tightening or loosening the tightening member to be carried out.(2-4) Second Dedicated Attachment

[0089] The second dedicated attachment 4 is an attachment attachable to only the second electric tool 2.

[0090] In the following description, the second dedicated attachment 4 is, in a similar manner to the first dedicated attachment 3, assumed to have a structure that changes, to facilitate a tightening task at various angles, a position at which the tip tool B1 for tightening a tightening target is held. Note that the second dedicated attachment 4 may have a structure that changes the orientation in which the tip tool B1 is held. Moreover, the second dedicated attachment 4 may have a function of measuring torque or a function of counting the number of times of tightening.

[0091] As shown in FIG. 2, the second dedicated attachment 4 includes the dedicated engagement part 41, the end surface 42, a transmission mechanism 43, a rotary shaft 44, and a housing 45. The transmission mechanism 43, the rotary shaft 44, and the housing 45 of the second dedicated attachment 4 have similar configurations respectively to the transmission mechanism 33, the rotary shaft 34, and the housing 35 of the first dedicated attachment 3, and therefore, the description thereof will be omitted.(Dedicated Engagement Part)

[0092] The dedicated engagement part 41 is engageable with the tool-side engagement part 231 of the second electric tool 2.

[0093] Note that the shape of the dedicated engagement part 41 of the second dedicated attachment 4 is substantially similar to the shape of the dedicated engagement part 31 of the first dedicated attachment 3, and therefore, the detailed description thereof will be omitted.(End Surface)

[0094] The end surface 42 is a surface to which the connection surface 232 is connected when the dedicated engagement part 41 is engaged with the tool-side engagement part 231 of the second electric tool 2. Note that since the shape of the end surface 42 of the second dedicated attachment 4 except for the shape of a dedicated projection 421, described later, of the end surface 42 is substantially similar to the shape of the end surface 32 of the first dedicated attachment 3 except for the shape of the dedicated projections 321 of the end surface 32, the detailed description of the shape except for the shape of the dedicated projection 421 will be omitted, and only the shape of the dedicated projection 421 will be described below.

[0095] In a similar manner to the dedicated projections 321 on the end surface 32 of the first dedicated attachment 3, the end surface 42 of the second dedicated attachment 4 has a dedicated projection 421 which is a projection arranged to be engageable with the tool-side projections 233 of the second electric tool 2 and protruding in the predetermined direction D1. On the end surface 42 of the present embodiment are formed a plurality of dedicated projections 421. In other words, the end surface 42 of the present embodiment has the plurality of dedicated projections 421. The plurality of dedicated projections 421 are disposed in a circularly annular shape along a circumference of the end surface 42. More specifically, the plurality of dedicated projections 421 are disposed in a circularly annular shape at equal intervals along the circumference of the end surface 42.

[0096] Similarly to FIG. 5C, FIG. 5D is a schematic development view of a part of a cross section of the end surface 32 of the first dedicated attachment 3, wherein the dedicated projections 321 are disposed on the end surface 32. A dotted line Y4 shown in FIG. 5D indicates a position where the dedicated engagement part 41 of the second dedicated attachment 4 is disposed. More specifically, the dotted line Y4 shown in FIG. 5C indicates a position of a plane on which the dedicated engagement part 41 of the second dedicated attachment 4 is to be engaged with the tool-side engagement part 231 of the second electric tool 2 in the predetermined direction D1.

[0097] As shown in FIG. 5D, each of the plurality of dedicated projections 421 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the dedicated projections 421, the end being connected to the end surface 42. As used herein, the "end being connected to the end surface 42" is a front end of each of the plurality of dedicated projections 421, and the "tip end of a corresponding one of the dedicated projection 421" is a rear end of the corresponding one of the dedicated projections 421. This configuration has the advantage that attachment to the second electric tool 2 is facilitated.

[0098] As shown in FIGS. 5C and 5D, the dedicated projections 421 of the second dedicated attachment 4 are different from the dedicated projections 321 of the first dedicated attachment 3 in terms of the dimension in the predetermined direction D1. The dimension of each of the dedicated projections 421 of the second dedicated attachment 4 in the predetermined direction D1 is greater than the dimension of each of the dedicated projections 321 of the first dedicated attachment 3 in the predetermined direction D1. Note that the dimension of each of the dedicated projections 421 of the second dedicated attachment 4 in the predetermined direction D1 will be described later in "(3) Dimensional Relationship".(2-5) Dual-Purpose Attachment

[0099] The dual-purpose attachment 5 is an attachment attachable to both the first electric tool 1 and the second electric tool 2.

[0100] In a similar manner to the first dedicated attachment 3, the dual-purpose attachment 5 is, in the following description, assumed to have a structure that changes, to facilitate a tightening task at various angles, a position at which the tip tool B1 for tightening a tightening target is held. Note that the dual-purpose attachment 5 may have a structure that changes an orientation at which the tip tool B1 is held. Moreover, the dual-purpose attachment 5 may have a function of measuring torque or a function of counting the number of times of tightening.

[0101] As shown in FIG. 2, the dual-purpose attachment 5 includes the dual-purpose engagement part 51, the end surface 52, the transmission mechanism 53, a rotary shaft 54, and a housing 55. The transmission mechanism 53, the rotary shaft 54, and the housing 55 of the dual-purpose attachment 5 have similar configurations respectively to the transmission mechanism 33, the rotary shaft 34, and the housing 35 of the first dedicated attachment 3, and therefore, the description thereof will be omitted.(Dual-Purpose Engagement Part)

[0102] The dual-purpose engagement part 51 is engageable with the tool-side engagement part 131 of the first electric tool 1 and the tool-side engagement part 231 of the second electric tool 2.

[0103] Note that the shape of the dual-purpose engagement part 51 of the dual-purpose attachment 5 is substantially similar to the shape of the dedicated engagement part 31 of the first dedicated attachment 3, and therefore, the detailed description thereof will be omitted.(End Surface)

[0104] The end surface 52 is a surface to which the connection surface 132 is connected when the dual-purpose engagement part 51 is engaged with the tool-side engagement part 131 of the first electric tool 1 and the connection surface 232 is connected when the dual-purpose engagement part 51 is engaged with the tool-side engagement part 231 of the second electric tool 2. Note that since the shape of the end surface 52 of the dual-purpose attachment 5 except for the shape of a dual-purpose projection 521, described later, of the end surface 52 is substantially similar to the shape of the end surface 32 of the first dedicated attachment 3 except for the shape of the dedicated projections 321 of the end surface 32, the detailed description of the shape except for the shape of dual-purpose projection 521 will be omitted, and only the shape of the dual-purpose projection 521 will be described below.

[0105] In a similar manner to the dedicated projections 321 on the end surface 32 of the first dedicated attachment 3, the end surface 52 of the dual-purpose attachment 5 has a dual-purpose projection 521 which is a projection arranged to be engaged with the tool-side projections 133 of the first electric tool 1 and the tool-side projections 233 of the second electric tool 2 and protruding in the predetermined direction D1. On the end surface 52 of the present embodiment are formed a plurality of dual-purpose projections 521. In other words, the end surface 52 of the present embodiment has the plurality of dual-purpose projections 521. The plurality of dual-purpose projections 521 are disposed in a circularly annular shape along a circumference of the end surface 52. More specifically, the plurality of dual-purpose projections 521 are disposed in a circularly annular shape at equal intervals along the circumference of the end surface 52.

[0106] Similarly to FIG. 5C, FIG. 5E is a schematic development view of a part of a cross section of the end surface 52 of the dual-purpose attachment 5, wherein the dual-purpose projections 521 are disposed on the end surface 52. The dotted line Y5 shown in FIG. 5D indicates the position where the dual-purpose engagement part 51 of the dual-purpose attachment 5 is disposed. More specifically, the dotted line Y3 shown in FIG. 5D indicates a position of a plane on which the dual-purpose engagement part 51 of the dual-purpose attachment 5 is to be engaged with the tool-side engagement part 131 of the first electric tool 1 or the tool-side engagement part 231 of the second electric tool 2 in the predetermined direction D1.

[0107] As shown in FIG. 5E, each of the plurality of dual-purpose projections 521 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the dual-purpose projections 521, the end being connected to the end surface 52. As used herein, the "end being connected to the end surface 52" is a front end of each of the plurality of dual-purpose projections 521, and the "tip end of a corresponding one of the dual-purpose projections 521" is a rear end of the corresponding one of the dual-purpose projections 521. This configuration provides the advantage that attachment to the first electric tool 1 or the second electric tool 2 is facilitated.

[0108] As shown in FIGS. 5C to 5D, the dual-purpose projections 521 of the dual-purpose attachment 5 are different from the dedicated projections 321 of the first dedicated attachment 3 and the dedicated projections 421 of the second dedicated attachment 4 in terms of the dimension in the predetermined direction D1. The dimension of each of the dual-purpose projections 521 of the dual-purpose attachment 5 in the predetermined direction D1 is greater than the dimension of each of the dedicated projections 321 of the first dedicated attachment 3 in the predetermined direction D1 and smaller than the dimension of each of the dedicated projections 421 of the second dedicated attachment 4 in the predetermined direction D1. Note that the dimension of each of the dual-purpose projections 521 of the dual-purpose attachment 5 in the predetermined direction D1 will be described later in "(3) Dimensional Relationship".(3) Dimensional Relationship(3-1) First Electric Tool

[0109] Described below is a dimensional relationship of each tool-side projection 133 of the first electric tool 1 to each of the dedicated projections 321 of the first dedicated attachment 3, the dedicated projections 421 of the second dedicated attachment 4, and the dual-purpose projections 521 of the dual-purpose attachment 5.

[0110] First of all, the dimension X11 (see FIG. 5A) in the predetermined direction D1 between the connection surface 132 and the tool-side engagement part 131 (i.e., the dotted line Y1 shown in FIG. 5A) of the first electric tool 1 will be described.

[0111] The dimension X11 of the first electric tool 1 is equal to the dimension X31 (see FIG. 5C) in the predetermined direction D1 between the tip end of each of the plurality of dedicated projections 321 of the first dedicated attachment 3 and the dedicated engagement part 31 (i.e., the dotted line Y3 shown in FIG. 5C). In other words, the dimension X31 of the first dedicated attachment 3 is equal to the dimension X11 of the first electric tool 1. As used in the present disclosure, "equal" is not limited to being exactly equal but tolerates some errors as described above. Further, the dimension X11 of the first electric tool is smaller than a dimension X41 (see FIG. 5D) in the predetermined direction D1 between the tip end of each of the plurality of dedicated projections 421 of the second dedicated attachment 4 and the dedicated engagement part 41 (i.e., the dotted line Y4 shown in FIG. 5C). Furthermore, the dimension X11 of the first electric tool 1 is equal to the dimension X51 (see FIG. 5E) in the predetermined direction D1 between the tip end of each of the plurality of dual-purpose projections 521 of the dual-purpose attachment 5 and the dual-purpose engagement part 51 (i.e., the dotted line Y5). In other words, the dimension X51 of the dual-purpose attachment 5 is equal to the dimension X11 of the first electric tool 1.

[0112] Next, the dimension X12 (see FIG. 5A) in the predetermined direction D1 between the tip end of each of the plurality of tool-side projections 133 and the tool-side engagement part 131 of the first electric tool 1 will be described.

[0113] The dimension X12 of the first electric tool 1 is equal to the dimension X32 (see FIG. 5C) in the predetermined direction D1 between the end surface 32 and the dedicated engagement part 31 of the first dedicated attachment 3. In other words, the dimension X32 of the first dedicated attachment 3 is equal to the dimension X12 of the first electric tool 1. Moreover, the dimension X12 of the first electric tool 1 is greater than a dimension X42 (see FIG. 5D) in the predetermined direction D1 between the end surface 42 and the dedicated engagement part 41 of the second dedicated attachment 4. Similarly, the dimension X12 of the first electric tool 1 is greater than the dimension X52 (see FIG. 5E) in the predetermined direction D1 between the end surface 52 and the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0114] Due to the above-described dimensional relationship, the first dedicated attachment 3 and the dual-purpose attachment 5 are attachable to the first electric tool 1, and the second dedicated attachment 4 is not attachable to the first electric tool 1.

[0115] With reference to FIGS. 7 to 9, a more specific description will be given. FIG. 7 is a schematic development view of a part of cross sections of the connection surface 132 of the first electric tool 1 and the end surface 32 of the first dedicated attachment 3 when the first electric tool 1 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the first dedicated attachment 3 come into contact with each other. FIG. 8 is a schematic development view of a part of cross sections of the connection surface 132 of the first electric tool 1 and the end surface 42 of the second dedicated attachment 4 when the first electric tool 1 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the second dedicated attachment 4 come into contact with each other. FIG. 9 is a schematic development view of a part of cross sections of the connection surface 132 of the first electric tool 1 and the end surface 52 of the dual-purpose attachment 5 when the first electric tool 1 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the dual-purpose attachment 5 come into contact with each other.

[0116] When the first electric tool 1 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the first dedicated attachment 3 come into contact with each other, the dotted line Y1 and the dotted line Y3 are coincident with each other as shown in FIG. 7. In other words, when the first electric tool 1 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the first dedicated attachment 3 come into contact with each other, the dedicated engagement part 31 of the first dedicated attachment 3 comes into contact with the tool-side engagement part 131 of the first electric tool 1. Thus, bringing the first electric tool 1 and the first dedicated attachment 3 close to each other in the predetermined direction D1 until the first electric tool 1 and the first dedicated attachment 3 come into contact with each other engages the dedicated engagement part 31 of the first dedicated attachment 3 with the tool-side engagement part 131 of the first electric tool 1, thereby attaching the first dedicated attachment 3 to the first electric tool 1.

[0117] Meanwhile, when the first electric tool 1 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the second dedicated attachment 4 come into contact with each other, the dotted line Y1 and the dotted line Y4 are not coincident with each other as shown in FIG. 8. In other words, when the first electric tool 1 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the second dedicated attachment 4 come into contact with each other, the dedicated engagement part 41 of the second dedicated attachment 4 does not come into contact with the tool-side engagement part 131 of the first electric tool 1. Thus, even when the first electric tool 1 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the second dedicated attachment 4 come into contact with each other, the dedicated engagement part 41 of the second dedicated attachment 4 is not engaged with the tool-side engagement part 131 of the first electric tool 1, and therefore, the second dedicated attachment 4 is not attached to the first electric tool 1.

[0118] Moreover, when the first electric tool 1 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the dual-purpose attachment 5 come into contact with each other, the dotted line Y1 and the dotted line Y5 are coincident with each other as shown in FIG. 8. In other words, when the first electric tool 1 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the dual-purpose attachment 5 come into contact with each other, the dual-purpose engagement part 51 of the dual-purpose attachment 5 comes into contact with the tool-side engagement part 131 of the first electric tool 1. Thus, bringing the first electric tool 1 and the dual-purpose attachment 5 close to each other in the predetermined direction D1 until the first electric tool 1 and the dual-purpose attachment 5 come into contact with each other engages the dual-purpose engagement part 51 of the dual-purpose attachment 5 with the tool-side engagement part 131 of the first electric tool 1, thereby attaching the dual-purpose attachment 5 to the first electric tool 1.

[0119] Thus, in the present embodiment, an attachment (e.g., second dedicated attachment 4) which is in an inappropriate combination with the first electric tool 1 is unattachable to the first electric tool 1. That is, the first electric tool 1 of the present embodiment has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.(3-2) Second Electric Tool

[0120] Described below is a dimensional relationship of each of the tool-side projections 233 of the second electric tool 2 to each of the dedicated projections 321 of the first dedicated attachment 3, the dedicated projections 421 of the second dedicated attachment 4, and the dual-purpose projections 521 of the dual-purpose attachment 5.

[0121] First of all, the dimension X21 (see FIG. 5B) in the predetermined direction D1 between the connection surface 232 and the tool-side engagement part 231 (i.e., the dotted line Y2 shown in FIG. 5B) of the second electric tool 2 will be described.

[0122] The dimension X21 of the second electric tool 2 is greater than the dimension X31 (see FIG. 5C) in the predetermined direction D1 between the tip end of each of the plurality of dedicated projections 321 and the dedicated engagement part 31 (i.e., the dotted line Y3 shown in FIG. 5C) of the first dedicated attachment 3. Moreover, the dimension X21 of the second electric tool 2 is equal to the dimension X41 (see FIG. 5D) in the predetermined direction D1 between the tip end of each of the plurality of dedicated projections 421 and the dedicated engagement part 41 of the second dedicated attachment 4. In other words, the dimension X41 of the second dedicated attachment 4 is equal to the dimension X21 of the second electric tool 2. Moreover, the dimension X21 of the second electric tool 2 is greater than the dimension X51 (see FIG. 5E) in the predetermined direction D1 between the tip end of each of the plurality of dual-purpose projections 521 and the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0123] Next, the dimension X22 (see FIG. 5B) between in the predetermined direction D1 the tip end of each of the plurality of tool-side projections 233 and the tool-side engagement part 231 of the second electric tool 2 will be described.

[0124] The dimension X22 of the second electric tool 2 is smaller than the dimension X32 (see FIG. 5C) in the predetermined direction D1 between the end surface 32 and the dedicated engagement part 31 of the first dedicated attachment 3. Moreover, the dimension X22 of the second electric tool 2 is equal to the dimension X42 (see FIG. 5D) in the predetermined direction D1 between the end surface 42 and the dedicated engagement part 41 of the second dedicated attachment 4. In other words, the dimension X42 of the second dedicated attachment 4 is equal to the dimension X22 of the second electric tool 2. Moreover, the dimension X22 of the second electric tool 2 is equal to the dimension X52 (see FIG. 5E) in the predetermined direction D1 between the end surface 52 and the dual-purpose engagement part 51 of the dual-purpose attachment 5. In other words, the dimension X52 of the dual-purpose attachment 5 is equal to the dimension X22 of the second electric tool 2.

[0125] Due to the dimensional relationship described above, the second dedicated attachment 4 and the dual-purpose attachment 5 are attachable to the second electric tool 2, and the first dedicated attachment 3 is not attachable to the second electric tool 2.

[0126] With reference to FIGS. 10 to 12, a more specific description will be given. FIG. 10 is a schematic development view of a part of cross sections of the connection surface 232 of the second electric tool 2 and the end surface 32 of the first dedicated attachment 3 when the second electric tool 2 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the first dedicated attachment 3 come into contact with each other. FIG. 11 is a schematic development view of a part of cross sections of the connection surface 232 of the second electric tool 2 and the end surface 42 of the second dedicated attachment 4 when the second electric tool 2 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the second dedicated attachment 4 come into contact with each other. FIG. 12 is a schematic development view of a part of cross sections of the connection surface 232 of the second electric tool 2 and the end surface 52 of the dual-purpose attachment 5 when the second electric tool 2 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the dual-purpose attachment 5 come into contact with each other.

[0127] When the second electric tool 2 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the first dedicated attachment 3 come into contact with each other, the dotted line Y2 and the dotted line Y3 are not coincident with each other as shown in FIG. 10. In other words, when the second electric tool 2 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the first dedicated attachment 3 come into contact with each other, the dedicated engagement part 31 of the first dedicated attachment 3 does not come into contact with the tool-side engagement part 231 of the second electric tool 2. As a result, even when the second electric tool 2 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the first dedicated attachment 3 come into contact with each other, the dedicated engagement part 31 of the first dedicated attachment 3 is not engaged with the tool-side engagement part 231 of the second electric tool 2, and therefore, the first dedicated attachment 3 is not attached to the second electric tool 2.

[0128] In contrast, when the second electric tool 2 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the second dedicated attachment 4 come into contact with each other, the dotted line Y2 and the dotted line Y4 are coincident with each other as shown in FIG. 11. In other words, when the second electric tool 2 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the second dedicated attachment 4 come into contact with each other, the dedicated engagement part 41 of the second dedicated attachment 4 comes into contact with the tool-side engagement part 231 of the second electric tool 2. Thus, bringing the second electric tool 2 and the second dedicated attachment 4 close to each other in the predetermined direction D1 until the second electric tool 2 and the second dedicated attachment 4 come into contact with each other engages the dedicated engagement part 41 of the second dedicated attachment 4 with the tool-side engagement part 231 of the second electric tool 2, thereby attaching the second dedicated attachment 4 to the second electric tool 2.

[0129] Similarly, when the second electric tool 2 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the dual-purpose attachment 5 come into contact with each other, the dotted line Y2 and the dotted line Y5 are coincident with each other as shown in FIG. 12. In other words, when the second electric tool 2 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the dual-purpose attachment 5 come into contact with each other, the dual-purpose engagement part 51 of the dual-purpose attachment 5 comes into contact with the tool-side engagement part 231 of the second electric tool 2. Thus, bringing the second electric tool 2 and the dual-purpose attachment 5 close to each other in the predetermined direction D1 until the second electric tool 2 and the dual-purpose attachment 5 come into contact with each other engages the dual-purpose engagement part 51 of the dual-purpose attachment 5 with the tool-side engagement part 231 of the second electric tool 2, thereby attaching the dual-purpose attachment 5 to the second electric tool 2.

[0130] As described above, in the present embodiment, an attachment (e.g., the first dedicated attachment 3) which is not in an appropriate combination with the second electric tool 2 is unattachable to the second electric tool 2. That is, the second electric tool 2 of the present embodiment has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.(4) Variations

[0131] The embodiment described above is a mere example of various embodiments of the present disclosure. The embodiment described above may be variously modified depending on design or the like as long as the object of the present disclosure is achieved. Variations described below may accordingly be embodied in combination.

[0132] In the embodiment described above, the first electric tool 1 is an impact driver but is not limited to only the impact driver. Examples of the type of the electric tool 1 include an impact wrench, a hammer drill, a band saw, a power cutter, a sander, and a disk grinder.

[0133] Similarly, in the embodiment described above, the second electric tool 2 is a drill driver but is not limited to only the drill driver. Examples of the type of the electric tool 1 include an impact wrench, a hammer drill, a band saw, a power cutter, a sander, and a disk grinder.

[0134] In the embodiment described above, axial directions of the rotary shaft 34 of the first dedicated attachment 3 and the rotary shaft 54 of the dual-purpose attachment 5 are in alignment with the front / rear direction and are the same as the axial direction of the output shaft 12 of the first electric tool 1. However, the axial directions of the rotary shaft 34 of the first dedicated attachment 3 and the rotary shaft 54 of the dual-purpose attachment 5 may be a direction intersecting the axial direction of the output shaft 12.

[0135] Similarly, in the embodiment described above, axial directions of the rotary shaft 44 of the second dedicated attachment 4 and the rotary shaft 54 of the dual-purpose attachment 5 are in alignment with the front / rear direction and are the same as the axial direction of the output shaft 22 of the second electric tool 2. However, the axial directions of the rotary shaft 44 of the second dedicated attachment 4 and the rotary shaft 54 of the dual-purpose attachment 5 may be a direction intersecting the output shaft 22 of the second electric tool 2.

[0136] More specifically, in the embodiment described above, the rotary shaft 34 of the first dedicated attachment 3 protrudes frontward from the bottom part 352 of the housing 35 but may protrude upward, downward, leftward, or rightward from the housing 35. Similarly, the rotary shaft 44 of the second dedicated attachment 4 may protrude upward, downward, leftward, or rightward from the housing 45. Moreover, the rotary shaft 54 of the dual-purpose attachment 5 may protrude upward, downward, leftward, or rightward from the housing 55.(Summary)

[0137] An electric tool (1) of a first aspect of the embodiment is an electric tool to which a dedicated attachment (3) and a dual-purpose attachment (5) are selectively attachable. The dedicated attachment (3) is attachable to only a predetermined type of electric tool. The dual-purpose attachment (5) is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool (1) of the first aspect includes a drive unit (11), an output shaft (12), and an attachment (13). The output shaft (12) is configured to be rotated by the drive unit (11). The attachment (13) is disposed around the output shaft (12). To the attachment (13), the dedicated attachment (3) or the dual-purpose attachment (5) is to be attached. The attachment (13) has a tool-side engagement part (131) and a connection surface (132). The tool-side engagement part (131) is engageable with a dedicated engagement part (31) which the dedicated attachment (3) has and a dual-purpose engagement part (51) which the dual-purpose attachment (5) has. To the connection surface (132), an end surface (32) of the dedicated attachment (3) or an end surface (52) of the dual-purpose attachment (5) is connected respectively when the tool-side engagement part (131) is engaged with the dedicated engagement part (31) or when the tool-side engagement part (131) is engaged with the dual-purpose engagement part (51). The electric tool (1) is aligned with the dedicated attachment (3) or the dual-purpose attachment (5) in a predetermined direction (D1) respectively when the dedicated attachment (3) is attached to the electric tool (1) or when the dual-purpose attachment (5) is attached to the electric tool (1). The connection surface (132) has at least one tool-side projection (133) which is a projection protruding in the predetermined direction (D1). The end surface (32) of the dedicated attachment (3) is provided with at least one dedicated projection (321) which is a projection arranged to be engaged with the tool-side projection (133) and protruding in the predetermined direction (D1). The end surface (52) of the dual-purpose attachment (5) is provided with at least one dual-purpose projection (521) which is a projection arranged to be engaged with the tool-side projection (133) and protruding in the predetermined direction (D1). A dimension (X11) in the predetermined direction (D1) between the connection surface (132) and the tool-side engagement part (131) is equal to a dimension (X31) in the predetermined direction (D1) between a tip end of the at least one dedicated projection (321) and the dedicated engagement part (31) and equal to a dimension (X51) in the predetermined direction (D1) between a tip end of the at least one dual-purpose projection (521) and the dual-purpose engagement part (51). A dimension (X12) in the predetermined direction (D1) between a tip end of the at least one tool-side projection (133) and the tool-side engagement part (131) is equal to a dimension (X32) in the predetermined direction (D1) between the end surface (32) and the dedicated engagement part (31) of the dedicated attachment (3) and greater than a dimension (X52) in the predetermined direction (D1) between the end surface (52) and the dual-purpose engagement part (51) of the dual-purpose attachment (5).

[0138] This aspect has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.

[0139] An electric tool (2) of a second aspect of the embodiment is an electric tool to which a dedicated attachment (4) and a dual-purpose attachment (5) are selectively attachable. The dedicated attachment (4) is attachable to only a predetermined type of electric tool. The dual-purpose attachment (5) is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool (2) of the second aspect includes a drive unit (21), an output shaft (22), and an attachment (23). The output shaft (22) is configured to be rotated by the drive unit (21). The attachment (23) is disposed around the output shaft (22). To the attachment (23), the dedicated attachment (4) or the dual-purpose attachment (5) is to be attached. The attachment (23) has a tool-side engagement part (231) and a connection surface (232). The tool-side engagement part (231) is engageable with a dedicated engagement part (41) which the dedicated attachment (4) has and a dual-purpose engagement part (51) which the dual-purpose attachment (5) has. To the connection surface (232), an end surface (42) of the dedicated attachment (4) or an end surface (52) of the dual-purpose attachment (5) is connected respectively when the tool-side engagement part (231) is engaged with the dedicated engagement part (41) or when the tool-side engagement part (231) is engaged with the dual-purpose engagement part (51). The electric tool (2) is aligned with the dedicated attachment (4) or the dual-purpose attachment (5) in a predetermined direction (D1) respectively when the dedicated attachment (4) is attached to the electric tool (2) or when the dual-purpose attachment (5) is attached to the electric tool (2). The connection surface (232) has at least one tool-side projection (233) which is a projection protruding in the predetermined direction (D1). The end surface of the dedicated attachment (4) is provided with at least one dedicated projection (421) which is a projection arranged to be engaged with the tool-side projection (233) and protruding in the predetermined direction (D1). The end surface (52) of the dual-purpose attachment (5) is provided with at least one dual-purpose projection (521) which is a projection arranged to be engaged with the tool-side projection (233) and protruding in the predetermined direction (D1). A dimension (X21) in the predetermined direction (D1) between the connection surface (232) and the tool-side engagement part (231) is equal to a dimension (X41) in the predetermined direction (D1) between a tip end of the at least one dedicated projection (421) and the dedicated engagement part (41) and greater than a dimension (X51) in the predetermined direction (D1) between a tip end of the at least one dual-purpose projection (521) and the dual-purpose engagement part (51). A dimension (X22) in the predetermined direction (D1) between a tip end of the at least one tool-side projection (233) and the tool-side engagement part (231) is equal to a dimension (X42) in the predetermined direction (D1) between the end surface (42) and the dedicated engagement part (41) of the dedicated attachment (4) and equal to a dimension (X52) in the predetermined direction (D1) between the end surface (52) and the dual-purpose engagement part (51) of the dual-purpose attachment (5).

[0140] This aspect has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.

[0141] In an electric tool of a third aspect according to the embodiment referring to the first or second aspect, the connection surface (132, 232) has the at least one tool-side projection (133, 233) including a plurality of tool-side projections (133, 233). The plurality of tool-side projections (133, 233) are arranged in a circularly annular shape on the attachment (13, 23).

[0142] This aspect has the advantage that a tightening task can be stably carried out.

[0143] In an electric tool of a fourth aspect of the embodiment referring to any one of the first to third aspects, the at least one tool-side projection (133, 233) is tapered to have a decreasing width from an end toward a tip end of the tool-side projection (133, 233), the end being connected to the connection surface (132, 232).

[0144] This aspect has the advantage that attaching the attachment can be facilitated.

[0145] An electric tool system (100) of a fifth aspect of the embodiment is an electric tool system including: a first electric tool (1) which is the electric tool of the first aspect; and a second electric tool (2) which is the electric tool of the second aspect. The dedicated attachment (3) in the first aspect is a first dedicated attachment. The dedicated attachment (4) in the second aspect is a second dedicated attachment. The dimension (X11) in the predetermined direction (D1) between the connection surface (132) and the tool-side engagement part (131) of the first electric tool (1) is smaller than a dimension (X41) in the predetermined direction (D1) between the tip end of the at least one dedicated projection (421) and the dedicated engagement part (41) of the second dedicated attachment (4). The dimension (X12) in the predetermined direction (D1) between a tip end of the at least one tool-side projection (133) and the tool-side engagement part (131) of the first electric tool (1) is greater than the dimension (X42) in the predetermined direction (D1) between the end surface (42) of the second dedicated attachment (4) and the dedicated engagement part (41) of the second dedicated attachment (4). The dimension (X21) in the predetermined direction (D1) between the connection surface (232) and the tool-side engagement part (231) of the second electric tool (2) is greater than the dimension (X31) in the predetermined direction (D1) between the tip end of the at least one dedicated projection (321) and the dedicated engagement part (31) of the first dedicated attachment (3). The dimension (X22) in the predetermined direction (D1) between the tip end of the at least one tool-side projection (233) and the tool-side engagement part (231) of the second electric tool (2) is smaller than the dimension (X32) in the predetermined direction (D1) between the end surface (32) of the first dedicated attachment (3) and the dedicated engagement part (31) of the first dedicated attachment (3).

[0146] This aspect has the advantage that the electric tool system (100) configured to suppress a task from being carried out in a state where a combination with the attachment is inappropriate can be provided.

[0147] An attachment of a sixth aspect of the embodiment is the dedicated attachment (3) attachable to only the electric tool of the first aspect. The attachment of the sixth aspect includes the dedicated engagement part (31), the end surface (32), a holder (341), and a transmission mechanism (33). To the end surface (32), the connection surface (132) is connected when the dedicated engagement part (31) is engaged with the tool-side engagement part (131) The holder (341) is configured to hold a tip tool (B1). The transmission mechanism (33) is configured to transmit rotation of the output shaft (12) to the holder (341) when the dedicated engagement part (31) is engaged with the tool-side engagement part (131). The end surface (32) is provided with the at least one dedicated projection (321). The dimension (X31) in the predetermined direction (D1) between the tip end of the at least one dedicated projection (321) and the dedicated engagement part (31) is equal to the dimension (X11) in the predetermined direction (D1) between the connection surface (132) and the tool-side engagement part (131). The dimension (X32) in the predetermined direction (D1) between the end surface (32) and the dedicated engagement part (31) is equal to the dimension (X12) in the predetermined direction (D1) between the tip end of the at least one tool-side projection (133) and the tool-side engagement part (131).

[0148] This aspect has the advantage that the attachment configured to suppress a task from being carried out in a state where a combination with the electric tool is inappropriate can be provided.

[0149] An attachment of a seventh aspect of the embodiment is the dedicated attachment (4) attachable to only the electric tool of the second aspect. The attachment of the seventh aspect includes the dedicated engagement part (41), the end surface (42), a holder (441), and a transmission mechanism (43). To the end surface (42), the connection surface (232) is connected when the dedicated engagement part (41) is engaged with the tool-side engagement part (231). The holder (441) is configured to hold a tip tool (B1). The transmission mechanism (43) is configured to transmit rotation of the output shaft (22) to the holder (441) when the dedicated engagement part (41) is engaged with the tool-side engagement part (231). The end surface (42) is provided with the at least one dedicated projection (421). The dimension (X41) in the predetermined direction (D1) between the tip end of the at least one dedicated projection (421) and the dedicated engagement part (41) is equal to the dimension (X21) in the predetermined direction (D1) between the connection surface (232) and the tool-side engagement part (231). The dimension (X42) in the predetermined direction (D1) between the end surface (42) and the dedicated engagement part (41) is equal to the dimension (X22) in the predetermined direction (D1) between the tip end of the at least one tool-side projection (233) and the tool-side engagement part (231).

[0150] This aspect has the advantage that the attachment configured to suppress a task from being carried out in a state where a combination with the electric tool is inappropriate can be provided.

[0151] An attachment of an eighth aspect of the embodiment is a dual-purpose attachment (5) attachable to both a first electric tool (1) which is the electric tool of the first aspect and a second electric tool (2) which is the electric tool of the second aspect. The attachment of the eighth aspect includes the dual-purpose engagement part (51), the end surface (52), a holder (541), and a transmission mechanism (53). To the end surface (52), the connection surface (132) of the first electric tool (1) or the connection surface (232) of the second electric tool (2) is connected respectively when the dual-purpose engagement part (51) is engaged with the tool-side engagement part (131) of the first electric tool (1) or when the dual-purpose engagement part (51) is engaged with the tool-side engagement part (231) of the second electric tool (2). The holder (541) is configured to hold a tip tool (B1). The transmission mechanism (53) is configured to transmit rotation of the output shaft (12) of the first electric tool (1) or rotation of the output shaft (22) of the second electric tool (2) to the holder (541) respectively when the dual-purpose engagement part (51) is engaged with the tool-side engagement part (131) of the first electric tool (1) or when the dual-purpose engagement part (51) is engaged with the tool-side engagement part (231) of the second electric tool (2). The end surface (52) is provided with the at least one dual-purpose projection (521). The dimension (X51) in the predetermined direction (D1) between the tip end of the at least one dual-purpose projection (521) and the dual-purpose engagement part (51) is equal to the dimension (X11) in the predetermined direction (D1) between the connection surface (132) the tool-side engagement part (131) of the first electric tool (1). The dimension (X52) in the predetermined direction (D1) between the end surface (52) and the dual-purpose engagement part (51) is equal to the dimension (X22) in the predetermined direction (D1) between the tip end of the at least one tool-side projection (233) and the tool-side engagement part (231) of the second electric tool (2).

[0152] This aspect has the advantage that the attachment configured to suppress a task from being carried out in a state where a combination with the electric tool is inappropriate can be provided.

[0153] A replaceable tool system (200) of a ninth aspect of the embodiment includes: the electric tool system (100) of the fifth aspect; the first dedicated attachment (3); the second dedicated attachment (4); and the dual-purpose attachment (5).

[0154] This aspect has the advantage that the replaceable tool system (200) configured to suppress a task from being carried out in a state where a combination of the electric tool and the attachment is inappropriate can be provided.Reference Signs List

[0155] 1First Electric Tool (Electric Tool) 11Drive Unit 12Output Shaft 13Attachment 131Tool-Side Engagement Part 132Connection Surface 133Tool-Side Projection 2Second Electric Tool (Electric Tool) 21Drive Unit 22Output Shaft 23Attachment 231Tool-Side Engagement Part 232Connection Surface 233Tool-Side Projection 3First Dedicated Attachment (Dedicated Attachment) 31Dedicated Engagement Part 32End Surface 321Dedicated Projection 33Transmission Mechanism 4Second Dedicated Attachment (Dedicated Attachment) 41Dedicated Engagement Part 42End Surface 421Dedicated Projection 43Transmission Mechanism 5Dual-Purpose Attachment 51Dual-Purpose Engagement Part 52End Surface 521Dual-Purpose Projection 53Transmission Mechanism 100Electric Tool System 200Replaceable Tool System

Examples

embodiment

(Present Embodiment)

(1) Overview

[0015]The overview of an electric tool 1 according to the present embodiment will be described below with reference to FIGS. 1 to 5E.

[0016]The electric tool 1 according to the present embodiment is assumed to be an electrically driven screw driver used by a worker in a tightening task of tightening a tightening member (e.g., a screw, a bolt, or a nut) to a tightening target (e.g., an electric appliance or furniture). Note that the electric tool 1 may be an electrically driven screwdriver used by the worker in a detachment task of loosening the tightening member from the tightening target.

[0017]The electric tool 1 (see FIGS. 1 and 2) is an electric tool to which a dedicated attachment 3 (see FIGS. 1 and 2) and a dual-purpose attachment 5 (see FIG. 2) are selectively attachable. The dedicated attachment 3 is attachable to only a predetermined type of electric tool. The dual-purpose attachment 5 is attachable to both the predetermined type of electric to...

Technical Field

[0001] The present disclosure generally relates to electric tools, electric tool systems, attachments, and replaceable tool systems. More specifically, the present disclosure relates to an electric tool to which attachments are selectively attachable, an electric tool system, an attachment, and a replaceable tool system.Background Art

[0002] Patent Literature 1 discloses an impact rotary tool including an impact force generating unit, a shaft, a torque measuring unit, a rotation angle measuring unit, a calculator, and a controller. The impact force generating unit converts motive power of a drive source into pulse torque, thereby generating an impact force. The shaft transmits the pulse torque to a tip tool by using the impact force thus generated. The torque measuring unit measures measurement torque which is torque applied to the shaft. The rotation angle measuring unit measures the angle of rotation of the shaft. The calculator calculates an angular acceleration on the basis of the angle of rotation thus measured and calculates tightening torque on the basis of the angular acceleration and the measurement torque. The controller controls the drive source on the basis of the tightening torque.

[0003] To an electric tool, such as the impact rotary tool described above, are selectively attachable a plurality of types of attachments, including an attachment having a function of measuring torque. In this case, there is the possibility that an attachment in an inappropriate combination with the electric tool is attached to the electric tool. That is, there is the possibility that a task is carried out in a state where the combination with the attachment is inappropriate.Citation List Patent Literature

[0004] Patent Literature 1: WO 2017 / 154623 AlSummary of Invention

[0005] It is an object of the present disclosure to provide an electric tool, an electric tool system, an attachment, and a replaceable tool system which are configured to suppress a task from being carried out in a state where a combination with the attachment is inappropriate.

[0006] An electric tool (a first electric tool) according to an aspect of the present disclosure is an electric tool to which a dedicated attachment (a first dedicated attachment) and a dual-purpose attachment are selectively attachable. The dedicated attachment is attachable to only a predetermined type of electric tool. The dual-purpose attachment is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool includes a drive unit, an output shaft, and an attachment. The output shaft is configured to be rotated by the drive unit. The attachment is disposed around the output shaft. To the attachment, the dedicated attachment or the dual-purpose attachment is to be attached. The attachment has a tool-side engagement part and a connection surface. The tool-side engagement part is engageable with a dedicated engagement part which the dedicated attachment has and a dual-purpose engagement part which the dual-purpose attachment has. To the connection surface, an end surface of the dedicated attachment or an end surface of the dual-purpose attachment is connected respectively when the tool-side engagement part is engaged with the dedicated engagement part or when the tool-side engagement part is engaged with the dual-purpose engagement part. The electric tool is aligned with the dedicated attachment or the dual-purpose attachment in a predetermined direction respectively when the dedicated attachment is attached to the electric tool or when the dual-purpose attachment is attached to the electric tool. The connection surface has at least one tool-side projection which is a projection protruding in the predetermined direction. The end surface of the dedicated attachment is provided with at least one dedicated projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction. The end surface of the dual-purpose attachment is provided with at least one dual-purpose projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction. A dimension in the predetermined direction between the connection surface and the tool-side engagement part is equal to a dimension in the predetermined direction between a tip end of the at least one dedicated projection and the dedicated engagement part and equal to a dimension in the predetermined direction between a tip end of the at least one dual-purpose projection and the dual-purpose engagement part. A dimension in the predetermined direction between a tip end of the at least one tool-side projection and the tool-side engagement part is equal to a dimension in the predetermined direction between the end surface and the dedicated engagement part of the dedicated attachment and greater than a dimension in the predetermined direction between the end surface and the dual-purpose engagement part of the dual-purpose attachment.

[0007] An electric tool (a second electric tool) according to an aspect of the present disclosure is an electric tool to which a dedicated attachment (a second dedicated attachment) and a dual-purpose attachment are selectively attachable. The dedicated attachment is attachable to only a predetermined type of electric tool. The dual-purpose attachment is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool includes a drive unit, an output shaft, and an attachment. The output shaft is configured to be rotated by the drive unit. The attachment is disposed around the output shaft. To the attachment, the dedicated attachment or the dual-purpose attachment is to be attached. The attachment has a tool-side engagement part and a connection surface. The tool-side engagement part is engageable with a dedicated engagement part which the dedicated attachment has and a dual-purpose engagement part which the dual-purpose attachment has. To the connection surface, an end surface of the dedicated attachment or an end surface of the dual-purpose attachment is connected respectively when the tool-side engagement part is engaged with the dedicated engagement part or when the tool-side engagement part is engaged with the dual-purpose engagement part. The electric tool is aligned with the dedicated attachment or the dual-purpose attachment in a predetermined direction respectively when the dedicated attachment is attached to the electric tool or when the dual-purpose attachment is attached to the electric tool. The connection surface has at least one tool-side projection which is a projection protruding in the predetermined direction. The end surface of the dedicated attachment is provided with at least one dedicated projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction. The end surface of the dual-purpose attachment is provided with at least one dual-purpose projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction. A dimension in the predetermined direction between the connection surface and the tool-side engagement part is equal to a dimension in the predetermined direction between a tip end of the at least one dedicated projection and the dedicated engagement part and greater than a dimension in the predetermined direction between a tip end of the at least one dual-purpose projection and the dual-purpose engagement part. A dimension in the predetermined direction between a tip end of the at least one tool-side projection and the tool-side engagement part is equal to a dimension in the predetermined direction between the end surface and the dedicated engagement part of the dedicated attachment and equal to a dimension in the predetermined direction between the end surface and the dual-purpose engagement part of the dual-purpose attachment.

[0008] An electric tool system according to an aspect of the present disclosure is an electric tool system including the first electric tool and the second electric tool. The dimension in the predetermined direction between the connection surface and the tool-side engagement part of the first electric tool is smaller than a dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part of the second dedicated attachment. The dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part of the first electric tool is greater than the dimension in the predetermined direction between the end surface of the second dedicated attachment and the dedicated engagement part of the second dedicated attachment. The dimension between the connection surface and the tool-side engagement part of the second electric tool in the predetermined direction is greater than the dimension between the tip end of the at least one dedicated projection and the dedicated engagement part of the first dedicated attachment in the predetermined direction. The dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part of the second electric tool is smaller than the dimension in the predetermined direction between the end surface of the first dedicated attachment and the dedicated engagement part of the first dedicated attachment.

[0009] An attachment according to an aspect of the present disclosure is the dedicated attachment attachable to only the electric tool of the first aspect. The attachment includes the dedicated engagement part, the end surface, a holder, and a transmission mechanism. To the end surface, the connection surface is to be connected when the dedicated engagement part is engaged with the tool-side engagement part. The holder is configured to hold a tip tool. The transmission mechanism is configured to transmit rotation of the output shaft to the holder when the dedicated engagement part is engaged with the tool-side engagement part. The end surface is provided with the at least one dedicated projection. The dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part is equal to the dimension in the predetermined direction between the connection surface and the tool-side engagement part. The dimension in the predetermined direction between the end surface and the dedicated engagement part is equal to the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part.

[0010] An attachment according to an aspect of the present disclosure is the dedicated attachment attachable to only the electric tool of the second aspect. The attachment includes the dedicated engagement part, the end surface, a holder, and a transmission mechanism. To the end surface, the connection surface is to be connected when the dedicated engagement part is engaged with the tool-side engagement part. The holder is configured to hold a tip tool. The transmission mechanism is configured to transmit rotation of the output shaft to the holder when the dedicated engagement part is engaged with the tool-side engagement part. The end surface is provided with the at least one dedicated projection. The dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part is equal to the dimension in the predetermined direction between the connection surface and the tool-side engagement part. The dimension in the predetermined direction between the end surface and the dedicated engagement part is equal to the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part.

[0011] An attachment according to an aspect of the present disclosure is a dual-purpose attachment attachable to both the first electric tool and a second electric tool. The attachment includes the dual-purpose engagement part, the end surface, a holder, and a transmission mechanism. To the end surface, the connection surface of the first electric tool or the connection surface of the second electric tool is connected respectively when the dual-purpose engagement part is engaged with the tool-side engagement part of the first electric tool or when the dual-purpose engagement part is engaged with the tool-side engagement part of the second electric tool. The holder is configured to hold a tip tool. The transmission mechanism is configured to transmit rotation of the output shaft of the first electric tool or rotation of the output shaft of the second electric tool to the holder respectively when the dual-purpose engagement part is engaged with the tool-side engagement part of the first electric tool or when the dual-purpose engagement part is engaged with the tool-side engagement part of the second electric tool. The end surface is provided with the at least one dual-purpose projection. The dimension in the predetermined direction between the tip end of the at least one dual-purpose projection and the dual-purpose engagement part is equal to the dimension in the predetermined direction between the connection surface the tool-side engagement part of the first electric tool. The dimension in the predetermined direction between the end surface and the dual-purpose engagement part is equal to the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part of the second electric tool.

[0012] A replaceable tool system according to an aspect of the present disclosure includes: the electric tool system; the first dedicated attachment; the second dedicated attachment; and the dual-purpose attachment.Brief Description of Drawings

[0013] [FIG. 1] FIG. 1 is an exterior perspective view of a first electric tool according to the present embodiment, wherein a first dedicated attachment is attached to the first electric tool; [FIG. 2] FIG. 2 is a block diagram of a schematic configuration of a replaceable tool system of the present embodiment; [FIG. 3] FIG. 3 is an exterior perspective view of a main part of the first electric tool; [FIG. 4] FIG. 4 is an exterior perspective view of the first dedicated attachment; [FIG. 5] FIG. 5A is a schematic development view of a part of a cross section of a connection surface of the first electric tool, FIG. 5B is a schematic development view of a part of a cross section of a connection surface of a second electric tool of the present embodiment, FIG. 5C is a schematic development view of a part of a cross section of an end surface of the first dedicated attachment, FIG. 5D is a schematic development view of a part of a cross section of an end surface of the second dedicated attachment, and FIG. 5E is a schematic development view of a part of a cross section of an end surface of a dual-purpose attachment of the present invention; [FIG. 6] FIG. 6 is a sectional view of a main part of the first electric tool, wherein the first dedicated attachment is attached to the first electric tool; [FIG. 7] FIG. 7 is a schematic development view of a part of cross sections of the connection surface of the first electric tool and the end surface of the first dedicated attachment when the first electric tool and the first dedicated attachment are brought close to each other; [FIG. 8] FIG. 8 is a schematic development view of a part of cross sections of the connection surface of the first electric tool and the end surface of the second dedicated attachment when the first electric tool and the second dedicated attachment are brought close to each other; [FIG. 9] FIG. 9 is a schematic development view of a part of cross sections of the connection surface of the first electric tool and the end surface of the dual-purpose attachment when the first electric tool and the dual-purpose attachment are brought close to each other; [FIG. 10] FIG. 10 is a schematic development view of a part of cross sections of the connection surface of the second electric tool and the end surface of the first dedicated attachment when the second electric tool and the first dedicated attachment are brought close to each other; [FIG. 11] FIG. 11 is a schematic development view of a part of cross sections of the connection surface of the second electric tool and the end surface of the second dedicated attachment when the second electric tool and the second dedicated attachment are brought close to each other; and [FIG. 12] FIG. 12 is a schematic development view of a part of cross sections of the connection surface of the second electric tool and the end surface of the dual-purpose attachment when the second electric tool and the dual-purpose attachment are brought close to each other. Description of Embodiments

[0014] An electric tool and an attachment according to an embodiment will be described below with reference to the drawings. Note that the embodiment described below is a mere example of various embodiments of the present disclosure. Various modifications may be made to the embodiment described below as long as the object of the present disclosure is achieved. Moreover, figures described in the following embodiment are schematic views. The ratio of sizes and the ratio of thicknesses of components in the figures do not necessarily reflect actual dimensional ratios.(Present Embodiment)(1) Overview

[0015] The overview of an electric tool 1 according to the present embodiment will be described below with reference to FIGS. 1 to 5E.

[0016] The electric tool 1 according to the present embodiment is assumed to be an electrically driven screw driver used by a worker in a tightening task of tightening a tightening member (e.g., a screw, a bolt, or a nut) to a tightening target (e.g., an electric appliance or furniture). Note that the electric tool 1 may be an electrically driven screwdriver used by the worker in a detachment task of loosening the tightening member from the tightening target.

[0017] The electric tool 1 (see FIGS. 1 and 2) is an electric tool to which a dedicated attachment 3 (see FIGS. 1 and 2) and a dual-purpose attachment 5 (see FIG. 2) are selectively attachable. The dedicated attachment 3 is attachable to only a predetermined type of electric tool. The dual-purpose attachment 5 is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool 1 with the dedicated attachment 3 attached thereto is shown in FIG. 1. The dedicated attachment 3 is an attachment attachable to only the electric tool 1. In contrast, the dual-purpose attachment 5 is an attachment attachable to both the electric tool 1 (hereinafter referred to as a first electric tool 1) and a second electric tool 2 which is a different type of electric tool from the first electric tool 1.

[0018] To facilitate a tightening task at various angles, the dedicated attachment 3 and the dual-purpose attachment 5 have, for example, a structure that changes a position or an orientation at which a tip tool B1 for tightening a tightening target is held. Moreover, the dedicated attachment 3 and the dual-purpose attachment 5 may have a function of measuring torque or a function of counting the number of times of tightening.

[0019] As shown in FIG. 2, the first electric tool 1 includes a drive unit 11, an output shaft 12, and an attachment 13. The output shaft 12 is rotated by the drive unit 11. The attachment 13 is disposed around the output shaft 12. The dedicated attachment 3 or the dual-purpose attachment 5 is attached to the attachment 13.

[0020] As shown in FIG. 3, the attachment 13 has a tool-side engagement part 131 and a connection surface 132. The tool-side engagement part 131 is engageable with a dedicated engagement part 31 (see FIGS. 2 and 4) of the dedicated attachment 3 and a dual-purpose engagement part 51 (see FIG. 2) of the dual-purpose attachment 5. When the tool-side engagement part 131 is engaged with the dedicated engagement part 31 or the dual-purpose engagement part 51, an end surface 32 of the dedicated attachment 3 or an end surface 52 of the dual-purpose attachment 5 is connected to the connection surface 132, respectively.

[0021] As shown in FIG. 1, when the dedicated attachment 3 or the dual-purpose attachment 5 is attached to the first electric tool 1, the first electric tool 1 is in alignment with the dedicated attachment 3 or the dual-purpose attachment 5, respectively, in a predetermined direction D1.

[0022] FIG. 5A is a schematic development view of a part of a cross section of the connection surface 132 of the first electric tool 1 along a sectional line L1 shown in FIG. 3. A dotted line Y1 shown in FIG. 5A indicates a position where the tool-side engagement part 131 of the first electric tool 1 is disposed in the predetermined direction D1. Moreover, FIG. 5C is a schematic development view of a part of a cross section of the end surface 32 of the dedicated attachment 3 along a sectional line L2 shown in FIG. 4. A dotted line Y3 shown in FIG. 5C indicates a position where the dedicated engagement part 31 of the dedicated attachment 3 is disposed in the predetermined direction D1. In a similar manner to FIG. 5C, FIG. 5E is a schematic development view of a part of a cross section of the end surface 52 of the dual-purpose attachment 5. A dotted line Y5 shown in FIG. 5E indicates a position where the dual-purpose engagement part 51 of the dual-purpose attachment 5 is disposed in the predetermined direction D1. FIGS. 5A, 5C, and 5E are schematic diagrams and thus do not reflect the dimensional ratios of FIGS. 3 and 4.

[0023] As shown in FIGS. 3 and 5A, the connection surface 132 has at least one tool-side projection 133 which is a projection protruding in the predetermined direction D1. As shown in FIGS. 4 and 5C, the end surface 32 of the dedicated attachment 3 is provided with at least one dedicated projection 321 which is a projection arranged to be engaged with the tool-side projection 133 and protruding in the predetermined direction D1. Similarly, as shown in FIG. FIG. 5E, the end surface of the dual-purpose attachment 5 is provided with at least one dual-purpose projection 521 which is a projection arranged to be engaged with the tool-side projection 133 and protruding in the predetermined direction D1.

[0024] A dimension X11 (see FIG. 5A) in the predetermined direction D1 between the connection surface 132 and the tool-side engagement part 131 (i.e., the dotted line Y1) is equal to a dimension X31 (see FIG. 5C) in the predetermined direction D1 between a tip end of the at least one dedicated projection 321 and the dedicated engagement part 31 (i.e., the dotted line Y3) and equal to a dimension X51 (see FIG. 5E) in the predetermined direction D1 between a tip end of the at least one dual-purpose projection 521 and the dual-purpose engagement part 51 (i.e., the dotted line Y5). In contrast, a dimension X12 (see FIG. 5A) in the predetermined direction D1 between a tip end of the at least one tool-side projection 133 and the tool-side engagement part 131 is equal to a dimension X32 (see FIG. 5C) in the predetermined direction D1 between the end surface 32 and the dedicated engagement part 31 of the dedicated attachment 3 and is greater than a dimension X52 (see FIG. 5E) in the predetermined direction D1 between the end surface 52 and the dual-purpose engagement part 51 of the dual-purpose attachment 5. As used in the present disclosure, "equal" is not limited to being exactly equal but tolerates some errors.

[0025] Due to the configuration described above, an attachment which is in an inappropriate combination with the first electric tool 1 is not attachable to the first electric tool 1. That is, the first electric tool 1 of the present embodiment has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.(2) Detailed Configuration(2-1) Replaceable Tool System

[0026] With reference to FIG. 2, a detailed configuration of a replaceable tool system 200 of the present embodiment will be described below.

[0027] As shown in FIG. 2, the replaceable tool system 200 includes an electric tool system 100, the first dedicated attachment 3, a second dedicated attachment 4, and the dual-purpose attachment 5.(2-2) Electric Tool System

[0028] As shown in FIG. 2, the electric tool system 100 includes the first electric tool 1 and a second electric tool 2. The first electric tool 1 is an electric tool which is a different type of electric tool from the second electric tool. For example, the first electric tool 1 is an impact driver, and the second electric tool 2 is a drill driver.(2-2-1) First Electric Tool

[0029] With reference to FIGS. 1 to 6, a detailed structure of the first electric tool 1 of the present embodiment will be described below.

[0030] As shown in FIGS. 1 and 2, the first electric tool 1 includes the drive unit 11, the output shaft 12, the attachment 13, a housing 14, an operation unit 15, and a control unit 16.

[0031] In the following description, an axial direction of the output shaft 12 (see FIG. 1) is defined as a front / rear direction. A side on which the attachment 13 is disposed in a body 141 described later is defined as a front side, and a side on which the attachment 13 is not disposed is defined as a rear side. The predetermined direction D1 described above is a direction in alignment with the front / rear direction. Moreover, as shown in FIG. 1, a direction in which the body 141 and a grip 142 described later are aligned with each other is defined as an up / down direction, wherein the body 141 is upward of the grip 142, and the grip 142 is downward of the body 141. Moreover, a direction orthogonal to the front / rear direction and the up / down direction is defined as a left / right direction. Note that these definitions are not intended to define a direction in which the first electric tool 1 is used.(Housing)

[0032] The housing 14 houses the drive unit 11, at least part of the output shaft 12, and the control unit 16.

[0033] As shown in FIG. 1, the housing 14 includes the body 141, the grip 142, and a battery attachment 143.

[0034] The body 141 houses the drive unit 11 and at least part of the output shaft 12.

[0035] As shown in FIG. 3, the body 141 has a side part 1411 and a bottom part 1412. The side part 1411 has a cylindrical shape. More specifically, the side part 1411 has a circularly cylindrical shape. The bottom part 1412 is arranged to cover an opening formed at the rear of the side part 1411 having the cylindrical shape. That is, the body 141 is a bottomed cylindrical body having an opening 1413 formed at the front thereof. The bottom part 1412 has a disk shape. A thickness direction defined with respect to the bottom part 1412 is in alignment with the front / rear direction. At least part of the output shaft 12 protrudes frontward from the opening 1413. The attachment 13 is disposed around the output shaft 12 between the output shaft 12 and the side part 1411. More specifically, the attachment 13 is disposed between the output shaft 12 and the side part 1411 to surround the output shaft 12. That is, the opening 1413 is covered with the output shaft 12 and the attachment 13. A detailed structure of the attachment 13 will be described later.

[0036] As shown in FIG. 1, the grip 142 protrudes from the body 141. More specifically, the grip 142 protrudes downward from the body 141. A worker may hold the grip 142 to carry out a task of, for example, tightening a screw. A worker may hold the grip 142 to carry out a task of, for example, tightening a screw.

[0037] The grip 142 of the present embodiment houses the control unit 16.

[0038] The battery attachment 143 is in the shape of a substantially rectangular parallelepiped. As shown in FIG. 1, the battery attachment 143 is connected to a lower end of the grip 142. A rechargeable battery pack (not shown) is detachably attachable to the battery attachment 143. The first electric tool 1 operates by using the battery pack as a power supply. That is, the battery pack is a power supply that supplies electric power for driving the drive unit 11. The battery pack is not a component included in the first electric tool 1. Note that the first electric tool 1 may include the battery pack. The battery pack includes an assembled battery including a plurality of secondary batteries (e.g., lithium ion batteries) connected in series to each other and a case in which the assembled battery is housed.(Drive Unit)

[0039] The drive unit 11 performs rotation operation. More specifically, the drive unit 11 operates by using electric power supplied from the battery pack attached to the battery attachment 143 and performs the rotation operation. The drive unit 11 includes: a rotor having a drive shaft and a permanent magnet; and a stator having a coil. Electromagnetic interaction between the permanent magnet and the coil rotates the rotor with respect to the stator.

[0040] Moreover, the drive unit 11 is a servomotor. The torque and rotational velocity of the drive unit 11 change in accordance with control by the control unit 16 (servo driver). More specifically, the control unit 16 controls the operation of the drive unit 11 by feedback control of performing control to make the torque and rotational velocity of the drive unit 11 close to target values.(Output Shaft)

[0041] The output shaft 12 is directly or indirectly connected to the drive shaft of the drive unit 11. As a result, the output shaft 12 rotates together with the drive shaft of the drive unit 11. That is, the output shaft 12 is rotated by the drive unit 11.

[0042] The output shaft 12 is a columnar body. The output shaft 12 of the present embodiment is cylindrical. At least part of the output shaft 12 protrudes from the opening 1413 of the body 141. More specifically, a front portion of the output shaft 12 protrudes from the opening 1413 of the body 141.

[0043] To the output shaft 12 is connectable a transmission mechanism 33 (see FIGS. 2 and 4), described later, of the first dedicated attachment 3. When the transmission mechanism 33 of the first dedicated attachment 3 is connected to the output shaft 12, the transmission mechanism 33 is rotated together with the output shaft 12 by the drive unit 11.

[0044] Similarly, to the output shaft 12 is connectable a transmission mechanism 53 (see FIG. 2), described later, of the dual-purpose attachment 5. When the transmission mechanism 53 of the dual-purpose attachment 5 is connected to the output shaft 12, the transmission mechanism 53 is rotated together with the output shaft 12 by the drive unit 11.

[0045] Moreover, the output shaft 12 includes a holder 121 (see FIG. 3) which holds the tip tool B1 when the transmission mechanism 33 of the first dedicated attachment 3 or the transmission mechanism 53 of the dual-purpose attachment 5 is not connected to the output shaft 12. The holder 121 is disposed at a front end portion of the output shaft 12. In the first electric tool 1, the output shaft 12 is capable of indirectly holding the tip tool B1 via the first dedicated attachment 3 or the dual-purpose attachment 5 (which will be described in detail later), and the holder 121 of the output shaft 12 is also capable of directly holding the tip tool B1. The tip tool B1 is, for example, a driver bit. When the holder 121 holds the tip tool B1, rotation of the output shaft 12 in a state where the tip tool B1 is fit to a tightening member enables a task such as tightening or loosening the tightening member to be carried out.(Attachment)

[0046] The first dedicated attachment 3 or the dual-purpose attachment 5 is attached to the attachment 13. As shown in FIG. 3, the attachment 13 has the tool-side engagement part 131 and the connection surface 132. The tool-side engagement part 131 is engageable with the dedicated engagement part 31, described later, of the first dedicated attachment 3 and the dual-purpose engagement part 51, described later, of the dual-purpose attachment 5. The connection surface 132 is a surface to which the end surface 32, described later, of the first dedicated attachment 3 or the end surface 52 of the dual-purpose attachment 5 is connected respectively when the tool-side engagement part 131 is engaged with the dedicated engagement part 31 of the first dedicated attachment 3 or when the tool-side engagement part 131 is engaged with the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0047] The shape of the attachment 13 will be described in detail below. FIG. 6 is a sectional view of the first electric tool 1 to which, as an example, the first dedicated attachment 3 is attached.

[0048] As shown in FIG. 6, the attachment 13 of the present embodiment has a first portion 134 and a second portion 135.

[0049] The first portion 134 is a bottomed cylindrical body having a bottom surface at the front thereof. More specifically, the first portion 134 is a bottomed, circularly cylindrical body having a bottom surface at the front thereof. That is, the bottom surface of the first portion 134 has a disk shape. In the present embodiment, an outer diameter of the bottom surface of the first portion 134 is substantially equal to an inner diameter of the opening 1413 of the body 141. The first portion 134 is disposed to cover the opening 1413.

[0050] The bottom surface of the first portion 134 has a through hole 1341 formed in the front / rear direction. The output shaft 12 is inserted into the through hole 1341 formed in the first portion 134. That is, the first portion 134 is disposed between the output shaft 12 and the side part 1411 to surround the output shaft 12.

[0051] The second portion 135 has a circularly cylindrical shape. The second portion 135 has a radius substantially equal to a radius of the through hole 1341 formed in the first portion 134. An axial direction of the second portion 135 is in alignment with the front / rear direction, and the second portion 135 has a rear end connected to the through hole 1341 formed in the first portion 134. That is, the second portion 135 is a circularly cylindrical member protruding frontward from the through hole 1341 formed in the first portion 134. The output shaft 12 is inserted through the second portion 135. A dimension of the second portion 135 in the predetermined direction D1 is smaller than a dimension of the output shaft 12 in the predetermined direction D1. Therefore, the output shaft 12 has a front end protruding from a front end of the second portion 135.

[0052] As shown in FIG. 6, the tool-side engagement part 131 of the present embodiment is a projection protruding outward from the front end of the second portion 135. The tool-side engagement part 131 of the present embodiment extends over a circumference of the second portion 135. For example, when the first dedicated attachment 3 is attached to the first electric tool 1 as shown in FIG. 6, a rear surface of the tool-side engagement part 131 is engaged with the dedicated engagement part 31, described later, of the first dedicated attachment 3. In contrast, when the dual-purpose attachment 5 is attached to the first electric tool 1, a rear surface of the tool-side engagement part 131 is engaged with the dual-purpose engagement part 51, described later, of the dual-purpose attachment 5. That is, in the present embodiment, the rear surface of the tool-side engagement part 131 is the surface which is to be engaged with the dedicated engagement part 31 of the first dedicated attachment 3 or the dual-purpose engagement part 51 of the dual-purpose attachment 5. The tool-side engagement part 131 has the configuration described above and is thus engageable with the dedicated engagement part 31 of the first dedicated attachment 3 and the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0053] The connection surface 132 of the present embodiment is a front surface of the first portion 134. That is, in the present embodiment, the connection surface 132 has a circularly annular shape when viewed in the predetermined direction D1.

[0054] As shown in FIG. 3, the connection surface 132 has the tool-side projection 133 which is a projection protruding in the predetermined direction D1. In other words, the front surface of the first portion 134 has the tool-side projection 133 as shown in FIG. 6. On the connection surface 132 of the present embodiment are formed a plurality of tool-side projections 133 as shown in FIG. 3. In other words, the connection surface 132 of the present embodiment has the plurality of tool-side projections 133. The plurality of tool-side projections 133 are disposed in a circularly annular shape along a circumference of the connection surface 132. More specifically, the plurality of tool-side projections 133 are disposed in a circularly annular shape at equal intervals along the circumference of the connection surface 132. The shape of each of the plurality of tool-side projections 133 viewed in the predetermined direction D1 is a shape obtained by dividing a circular annulus. The configuration described above provides the effect that the first dedicated attachment 3 or the dual-purpose attachment 5 is more firmly attached. This consequently provides the advantage that a tightening task can be stably carried out.

[0055] FIG. 5A is a schematic development view of a part of a cross section of the connection surface 132 of the first electric tool 1 along the sectional line L1 shown in FIG. 3, wherein the tool-side projections 133 are disposed on the connection surface 132. The dotted line Y1 shown in FIG. 5A indicates the position where the tool-side engagement part 131 of the first electric tool 1 is disposed in the predetermined direction D1. More specifically, the dotted line Y1 shown in FIG. 5A indicates the position of the rear surface (i.e., a surface which is to be engaged with the dedicated engagement part 31 of the first dedicated attachment 3 or the dual-purpose engagement part 51 of the dual-purpose attachment 5) of the tool-side engagement part 131 of the first electric tool 1 in the predetermined direction D1 as shown in FIG. 6. FIG. 5A is a schematic diagram and thus does not reflect the dimensional ratios of FIGS. 3 and 6.

[0056] As shown in FIG. 5A, each of the plurality of tool-side projections 133 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the tool-side projections 133, the end being connected to the connection surface 132. As used herein, the "end being connected to the connection surface 132" is a rear end of each of the plurality of tool-side projections 133, and the "tip end of a corresponding one of the tool-side projections 133" is a front end of the corresponding one of the tool-side projections 133. This configuration provides the advantage that attaching the first dedicated attachment 3 or the dual-purpose attachment 5 is facilitated.

[0057] Note that the dimension of each of the tool-side projections 133 of the first electric tool 1 in the predetermined direction D1 will be described later in "(3) Dimensional Relationship".(Operation Unit)

[0058] As shown in FIG. 1, the operation unit 15 protrudes from the grip 144. The operation unit 15 receives an operation for controlling rotation of the drive shaft of the drive unit 11. An operation of pulling the operation unit 15 can switch the drive unit 11 between ON and OFF. Moreover, a rotational velocity of the drive shaft is adjustable by a pulled amount indicating how deep the operation unit 15 is pulled. As the pulled amount increases, the rotational velocity of the drive shaft of the drive unit 11 increases.(Control Unit)

[0059] The control unit 16 rotates or stops the drive shaft of the drive unit 11 and controls the rotational velocity of the drive shaft in accordance with the pulled amount indicating how deep the operation unit 15 is pulled.

[0060] The control unit 16 includes, for example, a microcontroller. The control unit 16 can change the rotational velocity of the drive shaft of the drive unit 11, thereby changing the rotational velocity of the output shaft 12. The control unit 16 changes, for example, electric power to be supplied to the drive unit 11, thereby changing the rotational velocity of the drive shaft of the drive unit 11.(2-2-2) Second Electric Tool

[0061] As shown in FIG. 2, the second electric tool 2 includes a drive unit 21, an output shaft 22, an attachment 23, a housing 24, an operation unit 25, and a control unit 26. The drive unit 21, the output shaft 22, the housing 24, the operation unit 25, and the control unit 26 of the second electric tool 2 have similar configurations respectively to the drive unit 11, the output shaft 12, the housing 14, the operation unit 15, and the control unit 16 of the first electric tool 1, and therefore, the description thereof will be omitted.(Attachment)

[0062] To the attachment 23, the second dedicated attachment 4 or dual-purpose attachment 5 is attached. As shown in FIG. 2, the attachment 23 has a tool-side engagement part 231 and a connection surface 232. The tool-side engagement part 231 is engageable with a dedicated engagement part 41, described later, of the second dedicated attachment 4 and the dual-purpose engagement part 51 of the dual-purpose attachment 5. The connection surface 232 is a surface to which an end surface 42, described later, of the second dedicated attachment 4 or the end surface 52 of the dual-purpose attachment 5 is connected respectively when the tool-side engagement part 231 is engaged with the dedicated engagement part 41 of the second dedicated attachment 4 or when the tool-side engagement part 231 is engaged with the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0063] Note that since the shape of the tool-side engagement part 231 of the attachment 23 of the second electric tool 2 is substantially similar to the shape of the tool-side engagement part 131 of the attachment 13 of the first electric tool 1, and therefore, the detailed description thereof will be omitted.

[0064] In the following description, since the shape of the attachment 23 of the second electric tool 2 except for the shape of a tool-side projection 233, described later, of the connection surface 232 of the attachment 23 is substantially similar to the shape of the attachment 13 of the first electric tool 1 except for the shape of the tool-side projections 133 on the connection surface 132 of the attachment 13, the detailed description of the shape except for the shape of the tool-side projection 233 will be omitted, and only the shape of the tool-side projection 233 will be described below.

[0065] Similarly to FIG. 5A, FIG. 5B is a schematic development view of a part of a cross section of the connection surface 132 of the second electric tool 2, wherein the tool-side projections 133 are disposed on the connection surface 132. A dotted line Y2 shown in FIG. 5B indicates a position where the tool-side engagement part 231 of the second electric tool 2 is disposed in the predetermined direction D1. That is, the dotted line Y2 shown in FIG. 5B indicates a position of a rear surface of the tool-side engagement part 231 of the second electric tool 2 in the predetermined direction D1 (i.e., a surface which is to be engaged with the dedicated engagement part 41 of the second dedicated attachment 4 or the dual-purpose engagement part 51 of the dual-purpose attachment 5).

[0066] As shown in FIG. 5B, the connection surface 232 has the tool-side projection 233 which is a projection protruding in the predetermined direction D1. On the connection surface 232 of the present embodiment are formed a plurality of tool-side projections 233. In other words, the connection surface 232 of the present embodiment has the plurality of tool-side projections 233. The plurality of tool-side projections 233 are disposed in a circularly annular shape along a circumference of the connection surface 232. More specifically, the plurality of tool-side projections 233 are disposed in a circularly annular shape at equal intervals along the circumference of the connection surface 232.

[0067] As shown in FIG. 5B, each of the plurality of tool-side projections 233 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the tool-side projections 233, the end being connected to the connection surface 232. As used herein, the "end being connected to the connection surface 232" is a rear end of each of the plurality of tool-side projections 233, and the "tip end of a corresponding one of the tool-side projections 233" is a front end of the corresponding one of the tool-side projections 233. This configuration has the advantage that attaching the second dedicated attachment 4 or the dual-purpose attachment 5 is facilitated.

[0068] As shown in FIGS. 5A and 5B, the tool-side projections 233 of the second electric tool 2 are different from the tool-side projections 133 of the first electric tool 1 in the dimension in the predetermined direction D1. More specifically, the dimension of each of the tool-side projections 233 of the second electric tool 2 in the predetermined direction D1 is greater than the dimension of each of the tool-side projections 133 of the first electric tool 1 in the predetermined direction D1. Note that the dimension of each of the tool-side projections 233 of the second electric tool 2 in the predetermined direction D1 will be later described in "(3) Dimensional Relationship".(2-3) First Dedicated Attachment

[0069] The first dedicated attachment 3 is an attachment attachable to only the first electric tool 1.

[0070] In the following description, the first dedicated attachment 3 is assumed to have a structure that changes, to facilitate a tightening task at various angles, a position at which the tip tool B1 for tightening a tightening target is held. Note that the first dedicated attachment 3 may have a structure that changes the orientation in which the tip tool B1 is held. Moreover, the first dedicated attachment 3 may have a function of measuring torque or a function of counting the number of times of tightening.

[0071] As shown in FIG. 2, the first dedicated attachment 3 includes the dedicated engagement part 31, the end surface 32, the transmission mechanism 33, a rotary shaft 34, and a housing 35.(Housing)

[0072] The housing 35 houses the dedicated engagement part 31, the transmission mechanism 33, and at least part of the rotary shaft 34.

[0073] As shown in FIGS. 1 and 6, the housing 35 has a side part 351 and a bottom part 352. The side part 351 has a substantially cylindrical shape. More specifically, the side part 351 has a substantially circularly cylindrical shape.

[0074] As shown in FIGS. 4 and 6, the side part 351 of the present embodiment has a first portion 3511 and a second portion 3512. The first portion 3511 and the second portion 3512 are circularly cylindrical, and an outer diameter of the first portion 3511 is substantially equal to an outer diameter of the second portion 3512. The first portion 3511 is located slightly higher than the second portion 3512. The first portion 3511 and the second portion 3512 are aligned in the front / rear direction, and a rear end of the first portion 3511 is connected to a front end of the second portion 3512. As shown in FIG. 6, the bottom part 352 is disposed to cover an opening formed at the front of the first portion 3511, which is cylindrical. That is, the housing 35 is a bottomed cylindrical body having an opening at the rear thereof. The bottom part 352 has a disk shape. A thickness direction as defined with respect to the bottom part 352 is in alignment with the front / rear direction. The bottom part 352 has a through hole 3521 formed in the front / rear direction. The through hole 3521 is disposed above the bottom part 352. The rotary shaft 34 is inserted through the through hole 3521.(Dedicated Engagement Part)

[0075] The dedicated engagement part 31 is engageable with the tool-side engagement part 131 of the first electric tool 1.

[0076] As shown in FIGS. 4 and 6, the first dedicated attachment 3 of the present embodiment includes two dedicated engagement parts 31. Each of the two dedicated engagement parts 31 has a plate piece 311 protruding inward. A thickness direction defined with respect to the two plate pieces 311 is in alignment with the predetermined direction D1. In the present embodiment, each of the two plate pieces 311 is an elongated plate piece-shaped member having a longitudinal direction curved along a circumferential direction of the second portion 3512 of the side part 351 as shown in FIG. 4. The two plate pieces 311 are aligned with each other in the up / down direction. The plate piece 311 on an upper side protrudes downward, and the plate piece 311 on a lower side protrudes upward. When the first dedicated attachment 3 is attached to the first electric tool 1 as shown in FIG. 6, front surfaces of the two plate pieces 311 are engaged with the rear surface of the tool-side engagement part 131. That is, in the present embodiment, the front surface of each plate piece 311 is a surface which is to be engaged with the tool-side engagement part 131 of the first electric tool 1. The two dedicated engagement parts 31 have the configuration described above and are thus engageable with the tool-side engagement part 131 of the first electric tool 1.

[0077] In the present embodiment, the two dedicated engagement parts 31 are configured such that sliding operation units 312 frontward disengage the plate pieces 311 from the tool-side engagement part 131.(End Surface)

[0078] As shown in FIGS. 4 and 6, the first dedicated attachment 3 of the present embodiment further includes an annular member 320 which is a member having a circularly annular shape. An outer diameter of the annular member 320 is substantially equal to an inner diameter of the second portion 3512 of the side part 351 of the housing 35, and an inner diameter of the annular member 320 is substantially equal to an outer diameter of the second portion 135 of the attachment 13 of the first electric tool 1. The annular member 320 is disposed in an opening formed in the housing 35 such that an outer end surface of the annular member 320 is in contact with the second portion 3512 of the side part 351 of the housing 35. When the first dedicated attachment 3 is attached to the first electric tool 1 as shown in FIG. 6, the annular member 320 has an inner end surface in contact with the second portion 135 of the attachment 13 of the first electric tool 1.

[0079] In the present embodiment, a rear surface of the annular member 320 is the end surface 32 to which the connection surface 132 is connected when the dedicated engagement part 31 is engaged with the tool-side engagement part 131. That is, in the present embodiment, the end surface 32 has a circularly annular shape when viewed in the predetermined direction D1.

[0080] As shown in FIG. 4, the end surface 32 has a dedicated projection 321 which is a projection arranged to be engaged with the tool-side projections 133 of the first electric tool 1 and protruding in the predetermined direction D1. On the end surface 32 of the present embodiment are formed a plurality of dedicated projections 321. In other words, the end surface 32 of the present embodiment has the plurality of dedicated projections 321. The plurality of dedicated projections 321 are disposed in a circularly annular shape along the circumference of the connection surface 132. More specifically, the plurality of dedicated projections 321 are disposed in a circularly annular shape at equal intervals along the circumference of the connection surface 132.

[0081] FIG. 5C is a schematic development view of a part of a cross section of the end surface 32 of the first dedicated attachment 3 along a sectional line L2 shown in FIG. 4, wherein the dedicated projections 321 are disposed on the end surface 32. The dotted line Y3 shown in FIG. 5C indicates the position where the dedicated engagement part 31 (see FIG. 6) of the first dedicated attachment 3 is disposed in the predetermined direction D1. More specifically, the dotted line Y3 shown in FIG. 5C indicates a position of a front surface of the plate piece 311 of the dedicated engagement part 31 of the first dedicated attachment 3 in the predetermined direction D1 (i.e., the surface which is to be engaged with the tool-side engagement part 131 of the first electric tool 1).

[0082] As shown in FIG. 5C, each of the plurality of dedicated projections 321 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the dedicated projections 321, the end being connected to the end surface 32. As used herein, the "end being connected to the end surface 32" is a front end of each of the plurality of dedicated projections 321, and the "tip end of a corresponding one of the dedicated projection 321" is a rear end of the corresponding one of the dedicated projections 321. This configuration has the advantage that attachment to the first electric tool 1 is facilitated.

[0083] Note that the dimension of each of the dedicated projections 321 of the first dedicated attachment 3 in the predetermined direction D1 will be described later in "(3) Dimensional Relationship".(Transmission Mechanism)

[0084] When the dedicated engagement part 31 is engaged with the tool-side engagement part 131 of the first electric tool 1, the transmission mechanism 33 transmits rotation of the output shaft 12 of the first electric tool 1 to the rotary shaft 34. More specifically, when the dedicated engagement part 31 is engaged with the tool-side engagement part 131 of the first electric tool 1, the transmission mechanism 33 transmits the rotation of the output shaft 12 of the first electric tool 1 to the rotary shaft 34, thereby rotating the rotary shaft 34. As shown in FIG. 6, the rear end of the transmission mechanism 33 is connectable to the front end of the output shaft 12 of the first electric tool 1.(Rotary Shaft)

[0085] The rotary shaft 34 rotates together with the output shaft 12 of the first electric tool 1 when the dedicated engagement part 31 is engaged with the tool-side engagement part 131 of the first electric tool 1. More specifically, the rotary shaft 34 rotates due to transmission of the rotation of the output shaft 12 of the first electric tool 1 to the rotary shaft 34 by the transmission mechanism 33 when the dedicated engagement part 31 is engaged with the tool-side engagement part 131 of the first electric tool 1.

[0086] The rotary shaft 34 is a columnar body. The rotary shaft 34 of the present embodiment is circularly columnar. In the present embodiment, an axial direction of the rotary shaft 34 is in alignment with the front / rear direction and is the same as the axial direction of the output shaft 12. At least part of the rotary shaft 34 protrudes from the through hole 3521 formed in the bottom part 352. More specifically, a front portion of the rotary shaft 34 protrudes from the through hole 3521 formed in the bottom part 352. That is, the rotary shaft 34 of the present embodiment protrudes frontward from the bottom part 352 of the housing 35.

[0087] In the present embodiment, the rotary shaft 34 is disposed above the output shaft 12. That is, the rotary shaft 34 and the output shaft 12 do not overlap each other when viewed in the front / rear direction.

[0088] The rotary shaft 34 has a holder 341 (see FIG. 6) for holding the tip tool B1. The holder 341 is disposed at a front end portion of the output shaft 12. The tip tool B1 is, for example, a driver bit as described above. When the holder 341 holds the tip tool B1, rotation of the rotary shaft 34 in a state where the tip tool B1 is fit to a tightening member enables a task such as tightening or loosening the tightening member to be carried out.(2-4) Second Dedicated Attachment

[0089] The second dedicated attachment 4 is an attachment attachable to only the second electric tool 2.

[0090] In the following description, the second dedicated attachment 4 is, in a similar manner to the first dedicated attachment 3, assumed to have a structure that changes, to facilitate a tightening task at various angles, a position at which the tip tool B1 for tightening a tightening target is held. Note that the second dedicated attachment 4 may have a structure that changes the orientation in which the tip tool B1 is held. Moreover, the second dedicated attachment 4 may have a function of measuring torque or a function of counting the number of times of tightening.

[0091] As shown in FIG. 2, the second dedicated attachment 4 includes the dedicated engagement part 41, the end surface 42, a transmission mechanism 43, a rotary shaft 44, and a housing 45. The transmission mechanism 43, the rotary shaft 44, and the housing 45 of the second dedicated attachment 4 have similar configurations respectively to the transmission mechanism 33, the rotary shaft 34, and the housing 35 of the first dedicated attachment 3, and therefore, the description thereof will be omitted.(Dedicated Engagement Part)

[0092] The dedicated engagement part 41 is engageable with the tool-side engagement part 231 of the second electric tool 2.

[0093] Note that the shape of the dedicated engagement part 41 of the second dedicated attachment 4 is substantially similar to the shape of the dedicated engagement part 31 of the first dedicated attachment 3, and therefore, the detailed description thereof will be omitted.(End Surface)

[0094] The end surface 42 is a surface to which the connection surface 232 is connected when the dedicated engagement part 41 is engaged with the tool-side engagement part 231 of the second electric tool 2. Note that since the shape of the end surface 42 of the second dedicated attachment 4 except for the shape of a dedicated projection 421, described later, of the end surface 42 is substantially similar to the shape of the end surface 32 of the first dedicated attachment 3 except for the shape of the dedicated projections 321 of the end surface 32, the detailed description of the shape except for the shape of the dedicated projection 421 will be omitted, and only the shape of the dedicated projection 421 will be described below.

[0095] In a similar manner to the dedicated projections 321 on the end surface 32 of the first dedicated attachment 3, the end surface 42 of the second dedicated attachment 4 has a dedicated projection 421 which is a projection arranged to be engageable with the tool-side projections 233 of the second electric tool 2 and protruding in the predetermined direction D1. On the end surface 42 of the present embodiment are formed a plurality of dedicated projections 421. In other words, the end surface 42 of the present embodiment has the plurality of dedicated projections 421. The plurality of dedicated projections 421 are disposed in a circularly annular shape along a circumference of the end surface 42. More specifically, the plurality of dedicated projections 421 are disposed in a circularly annular shape at equal intervals along the circumference of the end surface 42.

[0096] Similarly to FIG. 5C, FIG. 5D is a schematic development view of a part of a cross section of the end surface 32 of the first dedicated attachment 3, wherein the dedicated projections 321 are disposed on the end surface 32. A dotted line Y4 shown in FIG. 5D indicates a position where the dedicated engagement part 41 of the second dedicated attachment 4 is disposed. More specifically, the dotted line Y4 shown in FIG. 5C indicates a position of a plane on which the dedicated engagement part 41 of the second dedicated attachment 4 is to be engaged with the tool-side engagement part 231 of the second electric tool 2 in the predetermined direction D1.

[0097] As shown in FIG. 5D, each of the plurality of dedicated projections 421 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the dedicated projections 421, the end being connected to the end surface 42. As used herein, the "end being connected to the end surface 42" is a front end of each of the plurality of dedicated projections 421, and the "tip end of a corresponding one of the dedicated projection 421" is a rear end of the corresponding one of the dedicated projections 421. This configuration has the advantage that attachment to the second electric tool 2 is facilitated.

[0098] As shown in FIGS. 5C and 5D, the dedicated projections 421 of the second dedicated attachment 4 are different from the dedicated projections 321 of the first dedicated attachment 3 in terms of the dimension in the predetermined direction D1. The dimension of each of the dedicated projections 421 of the second dedicated attachment 4 in the predetermined direction D1 is greater than the dimension of each of the dedicated projections 321 of the first dedicated attachment 3 in the predetermined direction D1. Note that the dimension of each of the dedicated projections 421 of the second dedicated attachment 4 in the predetermined direction D1 will be described later in "(3) Dimensional Relationship".(2-5) Dual-Purpose Attachment

[0099] The dual-purpose attachment 5 is an attachment attachable to both the first electric tool 1 and the second electric tool 2.

[0100] In a similar manner to the first dedicated attachment 3, the dual-purpose attachment 5 is, in the following description, assumed to have a structure that changes, to facilitate a tightening task at various angles, a position at which the tip tool B1 for tightening a tightening target is held. Note that the dual-purpose attachment 5 may have a structure that changes an orientation at which the tip tool B1 is held. Moreover, the dual-purpose attachment 5 may have a function of measuring torque or a function of counting the number of times of tightening.

[0101] As shown in FIG. 2, the dual-purpose attachment 5 includes the dual-purpose engagement part 51, the end surface 52, the transmission mechanism 53, a rotary shaft 54, and a housing 55. The transmission mechanism 53, the rotary shaft 54, and the housing 55 of the dual-purpose attachment 5 have similar configurations respectively to the transmission mechanism 33, the rotary shaft 34, and the housing 35 of the first dedicated attachment 3, and therefore, the description thereof will be omitted.(Dual-Purpose Engagement Part)

[0102] The dual-purpose engagement part 51 is engageable with the tool-side engagement part 131 of the first electric tool 1 and the tool-side engagement part 231 of the second electric tool 2.

[0103] Note that the shape of the dual-purpose engagement part 51 of the dual-purpose attachment 5 is substantially similar to the shape of the dedicated engagement part 31 of the first dedicated attachment 3, and therefore, the detailed description thereof will be omitted.(End Surface)

[0104] The end surface 52 is a surface to which the connection surface 132 is connected when the dual-purpose engagement part 51 is engaged with the tool-side engagement part 131 of the first electric tool 1 and the connection surface 232 is connected when the dual-purpose engagement part 51 is engaged with the tool-side engagement part 231 of the second electric tool 2. Note that since the shape of the end surface 52 of the dual-purpose attachment 5 except for the shape of a dual-purpose projection 521, described later, of the end surface 52 is substantially similar to the shape of the end surface 32 of the first dedicated attachment 3 except for the shape of the dedicated projections 321 of the end surface 32, the detailed description of the shape except for the shape of dual-purpose projection 521 will be omitted, and only the shape of the dual-purpose projection 521 will be described below.

[0105] In a similar manner to the dedicated projections 321 on the end surface 32 of the first dedicated attachment 3, the end surface 52 of the dual-purpose attachment 5 has a dual-purpose projection 521 which is a projection arranged to be engaged with the tool-side projections 133 of the first electric tool 1 and the tool-side projections 233 of the second electric tool 2 and protruding in the predetermined direction D1. On the end surface 52 of the present embodiment are formed a plurality of dual-purpose projections 521. In other words, the end surface 52 of the present embodiment has the plurality of dual-purpose projections 521. The plurality of dual-purpose projections 521 are disposed in a circularly annular shape along a circumference of the end surface 52. More specifically, the plurality of dual-purpose projections 521 are disposed in a circularly annular shape at equal intervals along the circumference of the end surface 52.

[0106] Similarly to FIG. 5C, FIG. 5E is a schematic development view of a part of a cross section of the end surface 52 of the dual-purpose attachment 5, wherein the dual-purpose projections 521 are disposed on the end surface 52. The dotted line Y5 shown in FIG. 5D indicates the position where the dual-purpose engagement part 51 of the dual-purpose attachment 5 is disposed. More specifically, the dotted line Y3 shown in FIG. 5D indicates a position of a plane on which the dual-purpose engagement part 51 of the dual-purpose attachment 5 is to be engaged with the tool-side engagement part 131 of the first electric tool 1 or the tool-side engagement part 231 of the second electric tool 2 in the predetermined direction D1.

[0107] As shown in FIG. 5E, each of the plurality of dual-purpose projections 521 is tapered to have a decreasing width from an end toward a tip end of a corresponding one of the dual-purpose projections 521, the end being connected to the end surface 52. As used herein, the "end being connected to the end surface 52" is a front end of each of the plurality of dual-purpose projections 521, and the "tip end of a corresponding one of the dual-purpose projections 521" is a rear end of the corresponding one of the dual-purpose projections 521. This configuration provides the advantage that attachment to the first electric tool 1 or the second electric tool 2 is facilitated.

[0108] As shown in FIGS. 5C to 5D, the dual-purpose projections 521 of the dual-purpose attachment 5 are different from the dedicated projections 321 of the first dedicated attachment 3 and the dedicated projections 421 of the second dedicated attachment 4 in terms of the dimension in the predetermined direction D1. The dimension of each of the dual-purpose projections 521 of the dual-purpose attachment 5 in the predetermined direction D1 is greater than the dimension of each of the dedicated projections 321 of the first dedicated attachment 3 in the predetermined direction D1 and smaller than the dimension of each of the dedicated projections 421 of the second dedicated attachment 4 in the predetermined direction D1. Note that the dimension of each of the dual-purpose projections 521 of the dual-purpose attachment 5 in the predetermined direction D1 will be described later in "(3) Dimensional Relationship".(3) Dimensional Relationship(3-1) First Electric Tool

[0109] Described below is a dimensional relationship of each tool-side projection 133 of the first electric tool 1 to each of the dedicated projections 321 of the first dedicated attachment 3, the dedicated projections 421 of the second dedicated attachment 4, and the dual-purpose projections 521 of the dual-purpose attachment 5.

[0110] First of all, the dimension X11 (see FIG. 5A) in the predetermined direction D1 between the connection surface 132 and the tool-side engagement part 131 (i.e., the dotted line Y1 shown in FIG. 5A) of the first electric tool 1 will be described.

[0111] The dimension X11 of the first electric tool 1 is equal to the dimension X31 (see FIG. 5C) in the predetermined direction D1 between the tip end of each of the plurality of dedicated projections 321 of the first dedicated attachment 3 and the dedicated engagement part 31 (i.e., the dotted line Y3 shown in FIG. 5C). In other words, the dimension X31 of the first dedicated attachment 3 is equal to the dimension X11 of the first electric tool 1. As used in the present disclosure, "equal" is not limited to being exactly equal but tolerates some errors as described above. Further, the dimension X11 of the first electric tool is smaller than a dimension X41 (see FIG. 5D) in the predetermined direction D1 between the tip end of each of the plurality of dedicated projections 421 of the second dedicated attachment 4 and the dedicated engagement part 41 (i.e., the dotted line Y4 shown in FIG. 5C). Furthermore, the dimension X11 of the first electric tool 1 is equal to the dimension X51 (see FIG. 5E) in the predetermined direction D1 between the tip end of each of the plurality of dual-purpose projections 521 of the dual-purpose attachment 5 and the dual-purpose engagement part 51 (i.e., the dotted line Y5). In other words, the dimension X51 of the dual-purpose attachment 5 is equal to the dimension X11 of the first electric tool 1.

[0112] Next, the dimension X12 (see FIG. 5A) in the predetermined direction D1 between the tip end of each of the plurality of tool-side projections 133 and the tool-side engagement part 131 of the first electric tool 1 will be described.

[0113] The dimension X12 of the first electric tool 1 is equal to the dimension X32 (see FIG. 5C) in the predetermined direction D1 between the end surface 32 and the dedicated engagement part 31 of the first dedicated attachment 3. In other words, the dimension X32 of the first dedicated attachment 3 is equal to the dimension X12 of the first electric tool 1. Moreover, the dimension X12 of the first electric tool 1 is greater than a dimension X42 (see FIG. 5D) in the predetermined direction D1 between the end surface 42 and the dedicated engagement part 41 of the second dedicated attachment 4. Similarly, the dimension X12 of the first electric tool 1 is greater than the dimension X52 (see FIG. 5E) in the predetermined direction D1 between the end surface 52 and the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0114] Due to the above-described dimensional relationship, the first dedicated attachment 3 and the dual-purpose attachment 5 are attachable to the first electric tool 1, and the second dedicated attachment 4 is not attachable to the first electric tool 1.

[0115] With reference to FIGS. 7 to 9, a more specific description will be given. FIG. 7 is a schematic development view of a part of cross sections of the connection surface 132 of the first electric tool 1 and the end surface 32 of the first dedicated attachment 3 when the first electric tool 1 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the first dedicated attachment 3 come into contact with each other. FIG. 8 is a schematic development view of a part of cross sections of the connection surface 132 of the first electric tool 1 and the end surface 42 of the second dedicated attachment 4 when the first electric tool 1 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the second dedicated attachment 4 come into contact with each other. FIG. 9 is a schematic development view of a part of cross sections of the connection surface 132 of the first electric tool 1 and the end surface 52 of the dual-purpose attachment 5 when the first electric tool 1 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the dual-purpose attachment 5 come into contact with each other.

[0116] When the first electric tool 1 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the first dedicated attachment 3 come into contact with each other, the dotted line Y1 and the dotted line Y3 are coincident with each other as shown in FIG. 7. In other words, when the first electric tool 1 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the first dedicated attachment 3 come into contact with each other, the dedicated engagement part 31 of the first dedicated attachment 3 comes into contact with the tool-side engagement part 131 of the first electric tool 1. Thus, bringing the first electric tool 1 and the first dedicated attachment 3 close to each other in the predetermined direction D1 until the first electric tool 1 and the first dedicated attachment 3 come into contact with each other engages the dedicated engagement part 31 of the first dedicated attachment 3 with the tool-side engagement part 131 of the first electric tool 1, thereby attaching the first dedicated attachment 3 to the first electric tool 1.

[0117] Meanwhile, when the first electric tool 1 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the second dedicated attachment 4 come into contact with each other, the dotted line Y1 and the dotted line Y4 are not coincident with each other as shown in FIG. 8. In other words, when the first electric tool 1 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the second dedicated attachment 4 come into contact with each other, the dedicated engagement part 41 of the second dedicated attachment 4 does not come into contact with the tool-side engagement part 131 of the first electric tool 1. Thus, even when the first electric tool 1 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the second dedicated attachment 4 come into contact with each other, the dedicated engagement part 41 of the second dedicated attachment 4 is not engaged with the tool-side engagement part 131 of the first electric tool 1, and therefore, the second dedicated attachment 4 is not attached to the first electric tool 1.

[0118] Moreover, when the first electric tool 1 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the dual-purpose attachment 5 come into contact with each other, the dotted line Y1 and the dotted line Y5 are coincident with each other as shown in FIG. 8. In other words, when the first electric tool 1 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the first electric tool 1 and the dual-purpose attachment 5 come into contact with each other, the dual-purpose engagement part 51 of the dual-purpose attachment 5 comes into contact with the tool-side engagement part 131 of the first electric tool 1. Thus, bringing the first electric tool 1 and the dual-purpose attachment 5 close to each other in the predetermined direction D1 until the first electric tool 1 and the dual-purpose attachment 5 come into contact with each other engages the dual-purpose engagement part 51 of the dual-purpose attachment 5 with the tool-side engagement part 131 of the first electric tool 1, thereby attaching the dual-purpose attachment 5 to the first electric tool 1.

[0119] Thus, in the present embodiment, an attachment (e.g., second dedicated attachment 4) which is in an inappropriate combination with the first electric tool 1 is unattachable to the first electric tool 1. That is, the first electric tool 1 of the present embodiment has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.(3-2) Second Electric Tool

[0120] Described below is a dimensional relationship of each of the tool-side projections 233 of the second electric tool 2 to each of the dedicated projections 321 of the first dedicated attachment 3, the dedicated projections 421 of the second dedicated attachment 4, and the dual-purpose projections 521 of the dual-purpose attachment 5.

[0121] First of all, the dimension X21 (see FIG. 5B) in the predetermined direction D1 between the connection surface 232 and the tool-side engagement part 231 (i.e., the dotted line Y2 shown in FIG. 5B) of the second electric tool 2 will be described.

[0122] The dimension X21 of the second electric tool 2 is greater than the dimension X31 (see FIG. 5C) in the predetermined direction D1 between the tip end of each of the plurality of dedicated projections 321 and the dedicated engagement part 31 (i.e., the dotted line Y3 shown in FIG. 5C) of the first dedicated attachment 3. Moreover, the dimension X21 of the second electric tool 2 is equal to the dimension X41 (see FIG. 5D) in the predetermined direction D1 between the tip end of each of the plurality of dedicated projections 421 and the dedicated engagement part 41 of the second dedicated attachment 4. In other words, the dimension X41 of the second dedicated attachment 4 is equal to the dimension X21 of the second electric tool 2. Moreover, the dimension X21 of the second electric tool 2 is greater than the dimension X51 (see FIG. 5E) in the predetermined direction D1 between the tip end of each of the plurality of dual-purpose projections 521 and the dual-purpose engagement part 51 of the dual-purpose attachment 5.

[0123] Next, the dimension X22 (see FIG. 5B) between in the predetermined direction D1 the tip end of each of the plurality of tool-side projections 233 and the tool-side engagement part 231 of the second electric tool 2 will be described.

[0124] The dimension X22 of the second electric tool 2 is smaller than the dimension X32 (see FIG. 5C) in the predetermined direction D1 between the end surface 32 and the dedicated engagement part 31 of the first dedicated attachment 3. Moreover, the dimension X22 of the second electric tool 2 is equal to the dimension X42 (see FIG. 5D) in the predetermined direction D1 between the end surface 42 and the dedicated engagement part 41 of the second dedicated attachment 4. In other words, the dimension X42 of the second dedicated attachment 4 is equal to the dimension X22 of the second electric tool 2. Moreover, the dimension X22 of the second electric tool 2 is equal to the dimension X52 (see FIG. 5E) in the predetermined direction D1 between the end surface 52 and the dual-purpose engagement part 51 of the dual-purpose attachment 5. In other words, the dimension X52 of the dual-purpose attachment 5 is equal to the dimension X22 of the second electric tool 2.

[0125] Due to the dimensional relationship described above, the second dedicated attachment 4 and the dual-purpose attachment 5 are attachable to the second electric tool 2, and the first dedicated attachment 3 is not attachable to the second electric tool 2.

[0126] With reference to FIGS. 10 to 12, a more specific description will be given. FIG. 10 is a schematic development view of a part of cross sections of the connection surface 232 of the second electric tool 2 and the end surface 32 of the first dedicated attachment 3 when the second electric tool 2 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the first dedicated attachment 3 come into contact with each other. FIG. 11 is a schematic development view of a part of cross sections of the connection surface 232 of the second electric tool 2 and the end surface 42 of the second dedicated attachment 4 when the second electric tool 2 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the second dedicated attachment 4 come into contact with each other. FIG. 12 is a schematic development view of a part of cross sections of the connection surface 232 of the second electric tool 2 and the end surface 52 of the dual-purpose attachment 5 when the second electric tool 2 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the dual-purpose attachment 5 come into contact with each other.

[0127] When the second electric tool 2 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the first dedicated attachment 3 come into contact with each other, the dotted line Y2 and the dotted line Y3 are not coincident with each other as shown in FIG. 10. In other words, when the second electric tool 2 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the first dedicated attachment 3 come into contact with each other, the dedicated engagement part 31 of the first dedicated attachment 3 does not come into contact with the tool-side engagement part 231 of the second electric tool 2. As a result, even when the second electric tool 2 and the first dedicated attachment 3 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the first dedicated attachment 3 come into contact with each other, the dedicated engagement part 31 of the first dedicated attachment 3 is not engaged with the tool-side engagement part 231 of the second electric tool 2, and therefore, the first dedicated attachment 3 is not attached to the second electric tool 2.

[0128] In contrast, when the second electric tool 2 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the second dedicated attachment 4 come into contact with each other, the dotted line Y2 and the dotted line Y4 are coincident with each other as shown in FIG. 11. In other words, when the second electric tool 2 and the second dedicated attachment 4 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the second dedicated attachment 4 come into contact with each other, the dedicated engagement part 41 of the second dedicated attachment 4 comes into contact with the tool-side engagement part 231 of the second electric tool 2. Thus, bringing the second electric tool 2 and the second dedicated attachment 4 close to each other in the predetermined direction D1 until the second electric tool 2 and the second dedicated attachment 4 come into contact with each other engages the dedicated engagement part 41 of the second dedicated attachment 4 with the tool-side engagement part 231 of the second electric tool 2, thereby attaching the second dedicated attachment 4 to the second electric tool 2.

[0129] Similarly, when the second electric tool 2 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the dual-purpose attachment 5 come into contact with each other, the dotted line Y2 and the dotted line Y5 are coincident with each other as shown in FIG. 12. In other words, when the second electric tool 2 and the dual-purpose attachment 5 are brought close to each other in the predetermined direction D1 until the second electric tool 2 and the dual-purpose attachment 5 come into contact with each other, the dual-purpose engagement part 51 of the dual-purpose attachment 5 comes into contact with the tool-side engagement part 231 of the second electric tool 2. Thus, bringing the second electric tool 2 and the dual-purpose attachment 5 close to each other in the predetermined direction D1 until the second electric tool 2 and the dual-purpose attachment 5 come into contact with each other engages the dual-purpose engagement part 51 of the dual-purpose attachment 5 with the tool-side engagement part 231 of the second electric tool 2, thereby attaching the dual-purpose attachment 5 to the second electric tool 2.

[0130] As described above, in the present embodiment, an attachment (e.g., the first dedicated attachment 3) which is not in an appropriate combination with the second electric tool 2 is unattachable to the second electric tool 2. That is, the second electric tool 2 of the present embodiment has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.(4) Variations

[0131] The embodiment described above is a mere example of various embodiments of the present disclosure. The embodiment described above may be variously modified depending on design or the like as long as the object of the present disclosure is achieved. Variations described below may accordingly be embodied in combination.

[0132] In the embodiment described above, the first electric tool 1 is an impact driver but is not limited to only the impact driver. Examples of the type of the electric tool 1 include an impact wrench, a hammer drill, a band saw, a power cutter, a sander, and a disk grinder.

[0133] Similarly, in the embodiment described above, the second electric tool 2 is a drill driver but is not limited to only the drill driver. Examples of the type of the electric tool 1 include an impact wrench, a hammer drill, a band saw, a power cutter, a sander, and a disk grinder.

[0134] In the embodiment described above, axial directions of the rotary shaft 34 of the first dedicated attachment 3 and the rotary shaft 54 of the dual-purpose attachment 5 are in alignment with the front / rear direction and are the same as the axial direction of the output shaft 12 of the first electric tool 1. However, the axial directions of the rotary shaft 34 of the first dedicated attachment 3 and the rotary shaft 54 of the dual-purpose attachment 5 may be a direction intersecting the axial direction of the output shaft 12.

[0135] Similarly, in the embodiment described above, axial directions of the rotary shaft 44 of the second dedicated attachment 4 and the rotary shaft 54 of the dual-purpose attachment 5 are in alignment with the front / rear direction and are the same as the axial direction of the output shaft 22 of the second electric tool 2. However, the axial directions of the rotary shaft 44 of the second dedicated attachment 4 and the rotary shaft 54 of the dual-purpose attachment 5 may be a direction intersecting the output shaft 22 of the second electric tool 2.

[0136] More specifically, in the embodiment described above, the rotary shaft 34 of the first dedicated attachment 3 protrudes frontward from the bottom part 352 of the housing 35 but may protrude upward, downward, leftward, or rightward from the housing 35. Similarly, the rotary shaft 44 of the second dedicated attachment 4 may protrude upward, downward, leftward, or rightward from the housing 45. Moreover, the rotary shaft 54 of the dual-purpose attachment 5 may protrude upward, downward, leftward, or rightward from the housing 55.(Summary)

[0137] An electric tool (1) of a first aspect of the embodiment is an electric tool to which a dedicated attachment (3) and a dual-purpose attachment (5) are selectively attachable. The dedicated attachment (3) is attachable to only a predetermined type of electric tool. The dual-purpose attachment (5) is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool (1) of the first aspect includes a drive unit (11), an output shaft (12), and an attachment (13). The output shaft (12) is configured to be rotated by the drive unit (11). The attachment (13) is disposed around the output shaft (12). To the attachment (13), the dedicated attachment (3) or the dual-purpose attachment (5) is to be attached. The attachment (13) has a tool-side engagement part (131) and a connection surface (132). The tool-side engagement part (131) is engageable with a dedicated engagement part (31) which the dedicated attachment (3) has and a dual-purpose engagement part (51) which the dual-purpose attachment (5) has. To the connection surface (132), an end surface (32) of the dedicated attachment (3) or an end surface (52) of the dual-purpose attachment (5) is connected respectively when the tool-side engagement part (131) is engaged with the dedicated engagement part (31) or when the tool-side engagement part (131) is engaged with the dual-purpose engagement part (51). The electric tool (1) is aligned with the dedicated attachment (3) or the dual-purpose attachment (5) in a predetermined direction (D1) respectively when the dedicated attachment (3) is attached to the electric tool (1) or when the dual-purpose attachment (5) is attached to the electric tool (1). The connection surface (132) has at least one tool-side projection (133) which is a projection protruding in the predetermined direction (D1). The end surface (32) of the dedicated attachment (3) is provided with at least one dedicated projection (321) which is a projection arranged to be engaged with the tool-side projection (133) and protruding in the predetermined direction (D1). The end surface (52) of the dual-purpose attachment (5) is provided with at least one dual-purpose projection (521) which is a projection arranged to be engaged with the tool-side projection (133) and protruding in the predetermined direction (D1). A dimension (X11) in the predetermined direction (D1) between the connection surface (132) and the tool-side engagement part (131) is equal to a dimension (X31) in the predetermined direction (D1) between a tip end of the at least one dedicated projection (321) and the dedicated engagement part (31) and equal to a dimension (X51) in the predetermined direction (D1) between a tip end of the at least one dual-purpose projection (521) and the dual-purpose engagement part (51). A dimension (X12) in the predetermined direction (D1) between a tip end of the at least one tool-side projection (133) and the tool-side engagement part (131) is equal to a dimension (X32) in the predetermined direction (D1) between the end surface (32) and the dedicated engagement part (31) of the dedicated attachment (3) and greater than a dimension (X52) in the predetermined direction (D1) between the end surface (52) and the dual-purpose engagement part (51) of the dual-purpose attachment (5).

[0138] This aspect has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.

[0139] An electric tool (2) of a second aspect of the embodiment is an electric tool to which a dedicated attachment (4) and a dual-purpose attachment (5) are selectively attachable. The dedicated attachment (4) is attachable to only a predetermined type of electric tool. The dual-purpose attachment (5) is attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool. The electric tool (2) of the second aspect includes a drive unit (21), an output shaft (22), and an attachment (23). The output shaft (22) is configured to be rotated by the drive unit (21). The attachment (23) is disposed around the output shaft (22). To the attachment (23), the dedicated attachment (4) or the dual-purpose attachment (5) is to be attached. The attachment (23) has a tool-side engagement part (231) and a connection surface (232). The tool-side engagement part (231) is engageable with a dedicated engagement part (41) which the dedicated attachment (4) has and a dual-purpose engagement part (51) which the dual-purpose attachment (5) has. To the connection surface (232), an end surface (42) of the dedicated attachment (4) or an end surface (52) of the dual-purpose attachment (5) is connected respectively when the tool-side engagement part (231) is engaged with the dedicated engagement part (41) or when the tool-side engagement part (231) is engaged with the dual-purpose engagement part (51). The electric tool (2) is aligned with the dedicated attachment (4) or the dual-purpose attachment (5) in a predetermined direction (D1) respectively when the dedicated attachment (4) is attached to the electric tool (2) or when the dual-purpose attachment (5) is attached to the electric tool (2). The connection surface (232) has at least one tool-side projection (233) which is a projection protruding in the predetermined direction (D1). The end surface of the dedicated attachment (4) is provided with at least one dedicated projection (421) which is a projection arranged to be engaged with the tool-side projection (233) and protruding in the predetermined direction (D1). The end surface (52) of the dual-purpose attachment (5) is provided with at least one dual-purpose projection (521) which is a projection arranged to be engaged with the tool-side projection (233) and protruding in the predetermined direction (D1). A dimension (X21) in the predetermined direction (D1) between the connection surface (232) and the tool-side engagement part (231) is equal to a dimension (X41) in the predetermined direction (D1) between a tip end of the at least one dedicated projection (421) and the dedicated engagement part (41) and greater than a dimension (X51) in the predetermined direction (D1) between a tip end of the at least one dual-purpose projection (521) and the dual-purpose engagement part (51). A dimension (X22) in the predetermined direction (D1) between a tip end of the at least one tool-side projection (233) and the tool-side engagement part (231) is equal to a dimension (X42) in the predetermined direction (D1) between the end surface (42) and the dedicated engagement part (41) of the dedicated attachment (4) and equal to a dimension (X52) in the predetermined direction (D1) between the end surface (52) and the dual-purpose engagement part (51) of the dual-purpose attachment (5).

[0140] This aspect has the advantage that a task can be suppressed from being carried out in a state where a combination with the attachment is inappropriate.

[0141] In an electric tool of a third aspect according to the embodiment referring to the first or second aspect, the connection surface (132, 232) has the at least one tool-side projection (133, 233) including a plurality of tool-side projections (133, 233). The plurality of tool-side projections (133, 233) are arranged in a circularly annular shape on the attachment (13, 23).

[0142] This aspect has the advantage that a tightening task can be stably carried out.

[0143] In an electric tool of a fourth aspect of the embodiment referring to any one of the first to third aspects, the at least one tool-side projection (133, 233) is tapered to have a decreasing width from an end toward a tip end of the tool-side projection (133, 233), the end being connected to the connection surface (132, 232).

[0144] This aspect has the advantage that attaching the attachment can be facilitated.

[0145] An electric tool system (100) of a fifth aspect of the embodiment is an electric tool system including: a first electric tool (1) which is the electric tool of the first aspect; and a second electric tool (2) which is the electric tool of the second aspect. The dedicated attachment (3) in the first aspect is a first dedicated attachment. The dedicated attachment (4) in the second aspect is a second dedicated attachment. The dimension (X11) in the predetermined direction (D1) between the connection surface (132) and the tool-side engagement part (131) of the first electric tool (1) is smaller than a dimension (X41) in the predetermined direction (D1) between the tip end of the at least one dedicated projection (421) and the dedicated engagement part (41) of the second dedicated attachment (4). The dimension (X12) in the predetermined direction (D1) between a tip end of the at least one tool-side projection (133) and the tool-side engagement part (131) of the first electric tool (1) is greater than the dimension (X42) in the predetermined direction (D1) between the end surface (42) of the second dedicated attachment (4) and the dedicated engagement part (41) of the second dedicated attachment (4). The dimension (X21) in the predetermined direction (D1) between the connection surface (232) and the tool-side engagement part (231) of the second electric tool (2) is greater than the dimension (X31) in the predetermined direction (D1) between the tip end of the at least one dedicated projection (321) and the dedicated engagement part (31) of the first dedicated attachment (3). The dimension (X22) in the predetermined direction (D1) between the tip end of the at least one tool-side projection (233) and the tool-side engagement part (231) of the second electric tool (2) is smaller than the dimension (X32) in the predetermined direction (D1) between the end surface (32) of the first dedicated attachment (3) and the dedicated engagement part (31) of the first dedicated attachment (3).

[0146] This aspect has the advantage that the electric tool system (100) configured to suppress a task from being carried out in a state where a combination with the attachment is inappropriate can be provided.

[0147] An attachment of a sixth aspect of the embodiment is the dedicated attachment (3) attachable to only the electric tool of the first aspect. The attachment of the sixth aspect includes the dedicated engagement part (31), the end surface (32), a holder (341), and a transmission mechanism (33). To the end surface (32), the connection surface (132) is connected when the dedicated engagement part (31) is engaged with the tool-side engagement part (131) The holder (341) is configured to hold a tip tool (B1). The transmission mechanism (33) is configured to transmit rotation of the output shaft (12) to the holder (341) when the dedicated engagement part (31) is engaged with the tool-side engagement part (131). The end surface (32) is provided with the at least one dedicated projection (321). The dimension (X31) in the predetermined direction (D1) between the tip end of the at least one dedicated projection (321) and the dedicated engagement part (31) is equal to the dimension (X11) in the predetermined direction (D1) between the connection surface (132) and the tool-side engagement part (131). The dimension (X32) in the predetermined direction (D1) between the end surface (32) and the dedicated engagement part (31) is equal to the dimension (X12) in the predetermined direction (D1) between the tip end of the at least one tool-side projection (133) and the tool-side engagement part (131).

[0148] This aspect has the advantage that the attachment configured to suppress a task from being carried out in a state where a combination with the electric tool is inappropriate can be provided.

[0149] An attachment of a seventh aspect of the embodiment is the dedicated attachment (4) attachable to only the electric tool of the second aspect. The attachment of the seventh aspect includes the dedicated engagement part (41), the end surface (42), a holder (441), and a transmission mechanism (43). To the end surface (42), the connection surface (232) is connected when the dedicated engagement part (41) is engaged with the tool-side engagement part (231). The holder (441) is configured to hold a tip tool (B1). The transmission mechanism (43) is configured to transmit rotation of the output shaft (22) to the holder (441) when the dedicated engagement part (41) is engaged with the tool-side engagement part (231). The end surface (42) is provided with the at least one dedicated projection (421). The dimension (X41) in the predetermined direction (D1) between the tip end of the at least one dedicated projection (421) and the dedicated engagement part (41) is equal to the dimension (X21) in the predetermined direction (D1) between the connection surface (232) and the tool-side engagement part (231). The dimension (X42) in the predetermined direction (D1) between the end surface (42) and the dedicated engagement part (41) is equal to the dimension (X22) in the predetermined direction (D1) between the tip end of the at least one tool-side projection (233) and the tool-side engagement part (231).

[0150] This aspect has the advantage that the attachment configured to suppress a task from being carried out in a state where a combination with the electric tool is inappropriate can be provided.

[0151] An attachment of an eighth aspect of the embodiment is a dual-purpose attachment (5) attachable to both a first electric tool (1) which is the electric tool of the first aspect and a second electric tool (2) which is the electric tool of the second aspect. The attachment of the eighth aspect includes the dual-purpose engagement part (51), the end surface (52), a holder (541), and a transmission mechanism (53). To the end surface (52), the connection surface (132) of the first electric tool (1) or the connection surface (232) of the second electric tool (2) is connected respectively when the dual-purpose engagement part (51) is engaged with the tool-side engagement part (131) of the first electric tool (1) or when the dual-purpose engagement part (51) is engaged with the tool-side engagement part (231) of the second electric tool (2). The holder (541) is configured to hold a tip tool (B1). The transmission mechanism (53) is configured to transmit rotation of the output shaft (12) of the first electric tool (1) or rotation of the output shaft (22) of the second electric tool (2) to the holder (541) respectively when the dual-purpose engagement part (51) is engaged with the tool-side engagement part (131) of the first electric tool (1) or when the dual-purpose engagement part (51) is engaged with the tool-side engagement part (231) of the second electric tool (2). The end surface (52) is provided with the at least one dual-purpose projection (521). The dimension (X51) in the predetermined direction (D1) between the tip end of the at least one dual-purpose projection (521) and the dual-purpose engagement part (51) is equal to the dimension (X11) in the predetermined direction (D1) between the connection surface (132) the tool-side engagement part (131) of the first electric tool (1). The dimension (X52) in the predetermined direction (D1) between the end surface (52) and the dual-purpose engagement part (51) is equal to the dimension (X22) in the predetermined direction (D1) between the tip end of the at least one tool-side projection (233) and the tool-side engagement part (231) of the second electric tool (2).

[0152] This aspect has the advantage that the attachment configured to suppress a task from being carried out in a state where a combination with the electric tool is inappropriate can be provided.

[0153] A replaceable tool system (200) of a ninth aspect of the embodiment includes: the electric tool system (100) of the fifth aspect; the first dedicated attachment (3); the second dedicated attachment (4); and the dual-purpose attachment (5).

[0154] This aspect has the advantage that the replaceable tool system (200) configured to suppress a task from being carried out in a state where a combination of the electric tool and the attachment is inappropriate can be provided.Reference Signs List

[0155] 1First Electric Tool (Electric Tool) 11Drive Unit 12Output Shaft 13Attachment 131Tool-Side Engagement Part 132Connection Surface 133Tool-Side Projection 2Second Electric Tool (Electric Tool) 21Drive Unit 22Output Shaft 23Attachment 231Tool-Side Engagement Part 232Connection Surface 233Tool-Side Projection 3First Dedicated Attachment (Dedicated Attachment) 31Dedicated Engagement Part 32End Surface 321Dedicated Projection 33Transmission Mechanism 4Second Dedicated Attachment (Dedicated Attachment) 41Dedicated Engagement Part 42End Surface 421Dedicated Projection 43Transmission Mechanism 5Dual-Purpose Attachment 51Dual-Purpose Engagement Part 52End Surface 521Dual-Purpose Projection 53Transmission Mechanism 100Electric Tool System 200Replaceable Tool System

Examples

embodiment

(Present Embodiment)

(1) Overview

[0015]The overview of an electric tool 1 according to the present embodiment will be described below with reference to FIGS. 1 to 5E.

[0016]The electric tool 1 according to the present embodiment is assumed to be an electrically driven screw driver used by a worker in a tightening task of tightening a tightening member (e.g., a screw, a bolt, or a nut) to a tightening target (e.g., an electric appliance or furniture). Note that the electric tool 1 may be an electrically driven screwdriver used by the worker in a detachment task of loosening the tightening member from the tightening target.

[0017]The electric tool 1 (see FIGS. 1 and 2) is an electric tool to which a dedicated attachment 3 (see FIGS. 1 and 2) and a dual-purpose attachment 5 (see FIG. 2) are selectively attachable. The dedicated attachment 3 is attachable to only a predetermined type of electric tool. The dual-purpose attachment 5 is attachable to both the predetermined type of electric to...

Claims

1. An electric tool to which a dedicated attachment and a dual-purpose attachment are selectively attachable, the dedicated attachment being attachable to only a predetermined type of electric tool, the dual-purpose attachment being attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool, the electric tool comprising: a drive unit; an output shaft configured to be rotated by the drive unit; and an attachment which is disposed around the output shaft and to which the dedicated attachment or the dual-purpose attachment is to be attached, The attachment having a tool-side engagement part engageable with a dedicated engagement part which the dedicated attachment has and a dual-purpose engagement part which the dual-purpose attachment has and a connection surface to which an end surface of the dedicated attachment or an end surface of the dual-purpose attachment is connected respectively when the tool-side engagement part is engaged with the dedicated engagement part or when the tool-side engagement part is engaged with the dual-purpose engagement part, the electric tool being aligned with the dedicated attachment or the dual-purpose attachment in a predetermined direction respectively when the dedicated attachment is attached to the electric tool or when the dual-purpose attachment is attached to the electric tool, the connection surface having at least one tool-side projection which is a projection protruding in the predetermined direction, the end surface of the dedicated attachment being provided with at least one dedicated projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction, the end surface of the dual-purpose attachment being provided with at least one dual-purpose projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction, a dimension in the predetermined direction between the connection surface and the tool-side engagement part being equal to a dimension in the predetermined direction between a tip end of the at least one dedicated projection and the dedicated engagement part and equal to a dimension in the predetermined direction between a tip end of the at least one dual-purpose projection and the dual-purpose engagement part, a dimension in the predetermined direction between a tip end of the at least one tool-side projection and the tool-side engagement part being equal to a dimension in the predetermined direction between the end surface and the dedicated engagement part of the dedicated attachment and greater than a dimension in the predetermined direction between the end surface and the dual-purpose engagement part of the dual-purpose attachment.

2. An electric tool to which a dedicated attachment and a dual-purpose attachment are selectively attachable, the dedicated attachment being attachable to only a predetermined type of electric tool, the dual-purpose attachment being attachable to both the predetermined type of electric tool and an electric tool which is a different type of electric tool from the predetermined type of electric tool, the electric tool comprising: a drive unit; an output shaft configured to be rotated by the drive unit; and an attachment which is disposed around the output shaft and to which the dedicated attachment or the dual-purpose attachment is to be attached, the attachment having a tool-side engagement part engageable with a dedicated engagement part which the dedicated attachment has and a dual-purpose engagement part which the dual-purpose attachment has and a connection surface to which an end surface of the dedicated attachment or an end surface of the dual-purpose attachment is connected respectively when the tool-side engagement part is engaged with the dedicated engagement part or when the tool-side engagement part is engaged with the dual-purpose engagement part, the electric tool being aligned with the dedicated attachment or the dual-purpose attachment in a predetermined direction respectively when the dedicated attachment is attached to the electric tool or when the dual-purpose attachment is attached to the electric tool, the connection surface having at least one tool-side projection which is a projection protruding in the predetermined direction, the end surface of the dedicated attachment being provided with at least one dedicated projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction, the end surface of the dual-purpose attachment being provided with at least one dual-purpose projection which is a projection arranged to be engaged with the tool-side projection and protruding in the predetermined direction, a dimension in the predetermined direction between the connection surface and the tool-side engagement part being equal to a dimension in the predetermined direction between a tip end of the at least one dedicated projection and the dedicated engagement part and greater than a dimension in the predetermined direction between a tip end of the at least one dual-purpose projection and the dual-purpose engagement part, a dimension in the predetermined direction between a tip end of the at least one tool-side projection and the tool-side engagement part being equal to a dimension in the predetermined direction between the end surface and the dedicated engagement part of the dedicated attachment and equal to a dimension in the predetermined direction between the end surface and the dual-purpose engagement part of the dual-purpose attachment.

3. The electric tool (1, 2) of claims 1 or 2, wherein the connection surface has the at least one tool-side projection including a plurality of tool-side projections, and the plurality of tool-side projections are arranged in a circularly annular shape on the attachment (13, 23).

4. The electric tool (1, 2) of any one of claims 1 to 3, wherein the at least one tool-side projection is tapered to have a decreasing width from an end toward a tip end of the tool-side projection, the end being connected to the connection surface.

5. An electric tool system comprising: a first electric tool which is the electric tool of claim 1; and a second electric tool which is the electric tool of claim 2, the dedicated attachment in claim 1 being a first dedicated attachment, the dedicated attachment in claim 2 being a second dedicated attachment, the dimension in the predetermined direction between the connection surface and the tool-side engagement part of the first electric tool being smaller than a dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part of the second dedicated attachment, the dimension in the predetermined direction between a tip end of the at least one tool-side projection and the tool-side engagement part of the first electric tool being greater than the dimension in the predetermined direction between the end surface of the second dedicated attachment and the dedicated engagement part of the second dedicated attachment, the dimension in the predetermined direction between the connection surface and the tool-side engagement part of the second electric tool being greater than the dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part of the first dedicated attachment, the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part of the second electric tool being smaller than the dimension in the predetermined direction between the end surface of the first dedicated attachment and the dedicated engagement part of the first dedicated attachment.

6. An attachment which is the dedicated attachment attachable to only the electric tool of claim 1, the attachment comprising: the dedicated engagement part; the end surface to which the connection surface is connected when the dedicated engagement part is engaged with the tool-side engagement part; a holder configured to hold a tip tool; and a transmission mechanism configured to transmit rotation of the output shaft to the holder when the dedicated engagement part is engaged with the tool-side engagement part, the end surface being provided with the at least one dedicated projection, the dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part being equal to the dimension in the predetermined direction between the connection surface and the tool-side engagement part, the dimension in the predetermined direction between the end surface and the dedicated engagement part being equal to the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part.

7. An attachment which is the dedicated attachment attachable to only the electric tool of claim 2, the attachment comprising: the dedicated engagement part; the end surface to which the connection surface is connected when the dedicated engagement part is engaged with the tool-side engagement part; a holder configured to hold a tip tool; and a transmission mechanism configured to transmit rotation of the output shaft to the holder when the dedicated engagement part is engaged with the tool-side engagement part, the end surface being provided with the at least one dedicated projection, the dimension in the predetermined direction between the tip end of the at least one dedicated projection and the dedicated engagement part being equal to the dimension in the predetermined direction between the connection surface and the tool-side engagement part, the dimension in the predetermined direction between the end surface and the dedicated engagement part being equal to the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part.

8. An attachment which is a dual-purpose attachment attachable to both a first electric tool which is the electric tool of claim 1 and a second electric tool which is the electric tool of claim 2, the attachment comprising: the dual-purpose engagement part; the end surface to which the connection surface of the first electric tool or the connection surface of the second electric tool is connected respectively when the dual-purpose engagement part is engaged with the tool-side engagement part of the first electric tool or when the dual-purpose engagement part is engaged with the tool-side engagement part of the second electric tool; a holder configured to hold a tip tool; and a transmission mechanism configured to transmit rotation of the output shaft of the first electric tool or rotation of the output shaft of the second electric tool to the holder respectively when the dual-purpose engagement part is engaged with the tool-side engagement part of the first electric tool or when the dual-purpose engagement part is engaged with the tool-side engagement part of the second electric tool, the end surface being provided with the at least one dual-purpose projection, The dimension in the predetermined direction between the tip end of the at least one dual-purpose projection and the dual-purpose engagement part being equal to the dimension in the predetermined direction between the connection surface the tool-side engagement part of the first electric tool, the dimension in the predetermined direction between the end surface and the dual-purpose engagement part being equal to the dimension in the predetermined direction between the tip end of the at least one tool-side projection and the tool-side engagement part of the second electric tool.

9. A replaceable tool system comprising: the electric tool system of claim 5; the first dedicated attachment; the second dedicated attachment; and the dual-purpose attachment.

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