Screw fastening tool

Abstract

A screw fastening tool is provided. The screw fastening tool has a housing, a motor, a spindle, a first clutch, and a second clutch. The first clutch is configured to be operatively connected to an output shaft and the spindle, and is capable of transmitting power from the output shaft to the spindle only when the output shaft is driven to rotate in a first direction. The second clutch is configured to be operatively connected to the output shaft and the spindle, and is capable of transmitting power from the output shaft to the spindle only when the output shaft is driven to rotate in a second direction. An output rotational speed of the spindle relative to a rotational speed of the same output shaft is different between when power is transmitted via the first clutch and when power is transmitted via the second clutch. Accordingly, a technology that contributes to improving the work efficiency of the screw fastening tool can be provided.

Description

Technical Field

[0001] This invention relates to a screw fastening tool. Background Technology

[0002] A screw-fastening tool drives its spindle to rotate in opposite directions during screw-fastening and screw-loosening operations. Patent Document 1 discloses a screw-fastening tool configured to initiate spindle rotation in response to spindle pressing. The pressing force on the screw can be less during screw-loosening operations compared to screw-fastening operations. Therefore, during screw-loosening operations, the screw-fastening tool initiates spindle rotation in response to a smaller spindle pressing force than during screw-fastening operations.

[0003] [Existing technical documents] [Patent Literature]

[0004] Patent Document 1: Japanese Patent Publication No. 2019-141945 Summary of the Invention

[0005] [The technical problem that the invention aims to solve]

[0006] The screw tightening tool described in Patent Document 1 can reduce the amount of spindle pressing during screw loosening operations. However, there is room for further improvement of this screw tightening tool.

[0007] In view of the above, a non-limiting object of this disclosure is to provide a technique that helps improve the operational efficiency of screw fastening tools.

[0008] [Technical solutions used to solve technical problems]

[0009] In one aspect of this disclosure, the screw fastening tool has a housing, a motor, a spindle, a first clutch, and a second clutch.

[0010] The motor is housed within a housing. The motor has an output shaft configured to be selectively driven to rotate in a first direction and a second direction opposite to the first direction. The first direction corresponds to the direction of fastening the screw. The second direction corresponds to the direction of loosening the screw. The spindle is supported in the housing in a manner that allows it to move along and rotate about the drive axis. The drive axis defines the front-to-back direction of the screw-fastening tool. The front end of the spindle is configured to allow for the attachment and removal of a tip tool.

[0011] The first clutch is operably connected to both the output shaft and the main shaft. The first clutch is configured to transmit power from the output shaft to the main shaft only when the output shaft is driven to rotate in a first direction. The second clutch is operably connected to both the output shaft and the main shaft. The second clutch is configured to transmit power from the output shaft to the main shaft only when the output shaft is driven to rotate in a second direction. Furthermore, the screw-fastening tool is configured such that the output rotational speeds of the main shaft relative to the same output shaft are different when power is transmitted via the first clutch and when power is transmitted via the second clutch.

[0012] In this screw-fastening tool, during screw tightening, power is transmitted from the motor to the spindle via a first clutch; conversely, during screw loosening, power is transmitted from the motor to the spindle via a second clutch. That is, power is transmitted via different paths during screw tightening and loosening. Furthermore, even if the motor's output shaft rotates at the same speed, the output speed when power is transmitted via the first clutch differs from the output speed when power is transmitted via the second clutch. In other words, even if the motor's output shaft rotates at the same speed, the spindle (and thus the screw) can be rotated at a speed suitable for each operation during screw tightening and loosening. This optimizes the efficiency of each operation. Attached Figure Description

[0013] Figure 1 This is a cross-sectional view of a screwdriver according to an embodiment of the present disclosure, showing the spindle in its initial position.

[0014] Figure 2 yes Figure 1 A magnified view of a portion of the image.

[0015] Figure 3 yes Figure 2 Section III-III.

[0016] Figure 4 It is a 3D exploded view of the main shaft, the first clutch, and the second clutch.

[0017] Figure 5 This is a three-dimensional view of the central shell as seen from the front.

[0018] Figure 6 This is a perspective view of the central shell with the base and felt embedded, viewed from the front.

[0019] Figure 7 yes Figure 3 Sectional view VII-VII (where the front housing and retaining components are omitted), showing the disengaged state of the first clutch.

[0020] Figure 8 Is with Figure 7The corresponding partial sectional view shows the state of the spindle in the working position.

[0021] Figure 9 Is with Figure 3 The corresponding sectional view shows the transmission state of the first clutch.

[0022] Figure 10 This is a three-dimensional view of the structure inside the front shell.

[0023] Figure 11 It is a three-dimensional view of the main shaft, the first clutch, and the limiting mechanism, showing the main shaft in its initial position.

[0024] Figure 12 This is a three-dimensional view of the front shell as seen from the rear.

[0025] Figure 13 It is a three-dimensional view of the main spindle, the first clutch, and the limiting mechanism, showing the main spindle in the working position.

[0026] Figure 14 yes Figure 2 It is a magnified view of a portion of the lubricant, and is an explanatory diagram used to illustrate the circulation path of the lubricant.

[0027] Figure 15 yes Figure 3 It is a magnified view of a portion of the lubricant, and is an explanatory diagram used to illustrate the circulation path of the lubricant.

[0028] Figure 16 This is a three-dimensional view of the retainer when viewed from the rear.

[0029] Figure 17 This is a three-dimensional view of the base as seen from the rear.

[0030] Explanation of reference numerals in the attached figures 1: Screwdriver; 11: Main housing; 12: Rear housing; 13: Front housing; 131: Stop; 133: Groove; 14: Central housing; 141: Partition wall; 142: Cylindrical part; 143: Bearing housing; 144: Groove; 15: Positioner; 17: Handle; 171: Grip; 173: Trigger; 174: Main switch; 175: Forward / reverse operating lever; 176: Forward / reverse switch; 178: Controller; 179: Power cord; 2: Motor; 23: Output shaft; 231: Bearing; 233: Bearing; 24: Pinion; 301: Bearing; 302: Bearing; 3: Spindle; 31: Shaft; 311: Tool insertion hole; 32: Shaft; 321: Groove; 34: Flange; 35: Thrust bearing; 36: Ball bearing; 4: First clutch; 40: Base; 401: Annular part; 405: Recess; 406: Groove; 407: Leg; 41: Tapered sleeve; 411: Tapered surface; 412: Protrusion; 414: Recess; 419: Recess; 43: Holder Holding part; 431: Annular portion; 432: Recess; 433: Groove; 434: Holding arm; 45: Roller; 47: Gear sleeve; 470: Gear tooth; 471: Small diameter portion; 472: Shoulder; 473: Retaining ring; 474: Large diameter portion; 475: Tapered surface; 478: Connecting hole; 48: Bearing; 49: Force spring; 5: Second clutch; 51: One-way clutch; 6: Restricting mechanism; 61: Rotating sleeve; 611: Cylinder wall; 613: Protrusion; 614: Inclined surface; 62 620: Restriction frame; 621: Cylinder wall; 622: Restriction part; 623: First surface; 625: Protrusion; 627: Protrusion; 66: Holding part; 661: Arm; 8: Circulation path; 80: Recess; 801: Felt; 81: Path; 811: First hole; 812: Second hole; 82: Path; 83: Path; 84: Path; 85: Path; 86: Path; 9: Screwdriver head; 90: Screw; 91: Workpiece; A1: Drive shaft. Detailed Implementation

[0031] In a non-limiting embodiment of this disclosure, the first clutch may be configured to selectively transmit power in response to the position of the spindle in the longitudinal direction. The second clutch may be configured to transmit power regardless of the position of the spindle in the longitudinal direction. According to this embodiment, during screw tightening operations, the spindle can be selectively rotated in response to the position of the spindle in the longitudinal direction, i.e., whether or not the screw is pressed against the workpiece. On the other hand, during screw loosening operations, since the spindle rotates even if the screw is not pressed against the workpiece, the operation can be started quickly.

[0032] Based on, or instead of, the screw fastening tool may further include a limiting mechanism configured to restrict the movement of the spindle in the longitudinal direction only when the output shaft is driven to rotate in the second direction. According to this embodiment, the limiting mechanism reliably hinders the operation of the first clutch when the output shaft is driven to rotate in the second direction.

[0033] Based on, or instead of, the above-described embodiment, the limiting mechanism may also include a first limiting part and a second limiting part. The first limiting part may be rotatable in the circumferential direction about the drive axis between a first position and a second position. The first limiting part may also be configured to be positioned in the first position in response to rotation of the output axis in a first direction, and in the second position in response to rotation of the output axis in a second direction. The second limiting part may also be configured to allow movement of the main shaft in the longitudinal direction when the first limiting part is in the first position, and to restrict movement of the main shaft in the longitudinal direction when the first limiting part is in the second position. According to this embodiment, the simple limiting mechanism can appropriately allow or restrict movement of the main shaft in the longitudinal direction in response to the rotation direction of the motor's output shaft.

[0034] Based on, or instead of, the screw fastening tool may further include a rotating member configured to be disposed between the output shaft and the main shaft in the power transmission path and to rotate via the output shaft. The first limiting part may also be configured to be disposed around the rotating member in a manner that allows selective rotation relative to the rotating member, and to rotate with the rotating member only between the first and second positions. Furthermore, "co-rotation" means that the second part, which is in contact with the first part, rotates with the first part in response to the rotation of the first part due to the friction between their respective contact surfaces. The second limiting part may also be substantially immobile relative to the housing. Furthermore, the second limiting part may be a component independent of the housing, and may be directly or indirectly fixed to the housing, or may be part of the housing. According to this embodiment, by utilizing the rotating member, a first limiting part capable of circumferential rotation between the first and second positions can be easily achieved.

[0035] Based on, or instead of, the above-described embodiment, the second limiting portion may also include a wall portion disposed behind the first limiting portion and extending circumferentially. The front end face of the wall portion may also include: a first surface extending in a direction orthogonal to the drive axis; and a second surface extending obliquely rearward from one end of the first surface in the circumferential direction. The first surface may also be configured to abut against the first limiting portion disposed in the second position from the rear. The second surface may also be configured to allow the main shaft to move in the front-rear direction. According to this embodiment, when the output shaft is driven to rotate in the second direction, the structurally simple second limiting portion can reliably impede the operation of the first clutch.

[0036] Based on, or instead of, the above-described embodiments, the first clutch may also be configured to serve as a speed reduction mechanism. According to this embodiment, since a separate speed reduction mechanism is not required outside the first clutch, a compact screw-fastening tool can be achieved.

[0037] Based on, or instead of, the above-described embodiments, the reduction mechanism may also include: a sun component, a ring component, and a planetary carrier arranged coaxially with the drive shaft, and a plurality of planetary rollers held on the planetary carrier in a rotatable manner. The ring component may be configured to rotate via an output shaft. The planetary carrier may be configured to rotate integrally with the main shaft. The plurality of planetary rollers may also be arranged at least partially in the radial direction between the conical outer peripheral surface of the sun component and the conical inner peripheral surface of the ring component. Alternatively, the ring component may be able to move integrally with the main shaft relative to the sun component in the longitudinal direction. The first clutch may also be configured such that, in response to the main shaft moving rearward from an initial position, the plurality of planetary rollers selectively engage with the outer peripheral surface of the sun component and the inner peripheral surface of the ring component, thereby transmitting power. According to this embodiment, by employing a so-called planetary roller type reduction mechanism that operates in response to the movement of the main shaft in the longitudinal direction as the first clutch, a reasonably structured screw fastening tool can be realized.

[0038] Based on, or instead of, the above-described embodiments, the spindle may also have: a first hole extending forward from the rear end of the spindle; and a second hole communicating with the first hole, extending in a direction intersecting the first hole and opening on the outer circumferential surface of the spindle. The screw-fastening tool may also have a circulation path within the housing, which allows lubricant discharged from the spindle through the first and second holes to return to the rear end of the spindle. According to this embodiment, lubricant discharged from the second hole by the centrifugal force during spindle rotation can flow back into the first hole of the spindle, thereby circulating within the housing. This allows for effective lubrication of the components within the housing.

[0039] Based on, or instead of, the above embodiments, a storage section for storing lubricant can be provided in the circulation path. According to this embodiment, lubricant can be stored in the storage section and circulated effectively. Furthermore, a component (e.g., felt) capable of absorbing and retaining lubricant can be provided in the storage section.

[0040] Hereinafter, a representative and non-limiting embodiment of the screwdriver 1 according to the present disclosure will be specifically described with reference to the accompanying drawings. The screwdriver 1 is an example of a screw fastening tool, which can selectively perform screw fastening and screw loosening operations by driving the rotation of a tip tool (specifically, screwdriver head 9) that is detachably mounted on the spindle 3.

[0041] First, the general structure of screwdriver 1 will be explained.

[0042] like Figure 1 As shown, the outer contour of the screwdriver 1 is formed by an elongated body shell (also called the tool body) 11 and a handle 17.

[0043] The main housing 11 houses the motor 2, the elongated spindle 3, and other components. The spindle 3 is arranged such that its rotation axis (i.e., the drive axis A1 of the screwdriver head 9) extends along the long axis of the main housing 11. One end of the spindle 3 is disposed within one end of the main housing 11 along its long axis. This end of the spindle 3 is configured to allow for the attachment and removal of the screwdriver head 9.

[0044] The handle 17 is shaped like the capital letter C and is looped to the other end of the main body housing 11 along its long axis. The handle 17 includes a grip portion 171 for the user to hold. The grip portion 171 extends linearly away from the main body housing 11 in a direction substantially orthogonal to the drive axis A1. One end of the grip portion 171 along its long axis is positioned on the drive axis A1, and a trigger 173 is provided at this end. Furthermore, a power cord 179 for connecting to an external AC power source is connected to the other end of the grip portion 171.

[0045] When the user presses trigger 173, motor 2 is driven, and spindle 3 and screwdriver head 9 are driven to rotate as a unit. Accordingly, screw 90, which is engaged with screwdriver head 9, rotates.

[0046] In the following description, for ease of explanation, the extension direction of the drive shaft A1 is defined as the front-rear direction of the screwdriver 1. In the front-rear direction, the side where the screwdriver head 9 is mounted is defined as the front side, and the side where the handle 171 is located is defined as the rear side. Furthermore, the direction orthogonal to the drive shaft A1 and roughly corresponding to the extension direction of the handle 171 is defined as the up-down direction of the screwdriver 1. In the up-down direction, the side where the trigger 173 is located is defined as the upper side, and the side where the power cord 179 is connected is defined as the lower side. Additionally, the direction orthogonal to both the front-rear and up-down directions is defined as the left-right direction of the screwdriver 1.

[0047] The detailed structure of screwdriver 1 will be explained below.

[0048] First, the detailed structure of the main body shell 11 and the internal structure of the main body shell 11 will be described.

[0049] like Figure 1 As shown, the main housing 11 includes a rear housing 12, a front housing 13, and a central housing 14. The rear housing 12 is cylindrical and primarily houses the motor 2; the front housing 13 is cylindrical and primarily houses the main shaft 3; the central housing 14 is disposed between the rear housing 12 and the front housing 13. Furthermore, the front end of the central housing 14 has a partition wall 141 arranged intersecting the drive axis A1. The central housing 14 and the front housing 13 are fixed to the rear housing 12 by screws, thereby integrating the three housings to form the main housing 11.

[0050] The rear housing 12 primarily houses the motor 2. The output shaft 23 of the motor 2 extends parallel to the main shaft 3 at a position lower than the main shaft 3. That is, the rotation axis of the output shaft 23 is parallel to the drive axis A1. The output shaft 23 is rotatably supported at its front and rear ends by bearings 231 and 233. Furthermore, the front bearing 231 is supported by the partition wall 141, and the rear bearing 233 is supported at the rear end of the rear housing 12. Additionally, the front end of the output shaft 23 protrudes forward through a through-hole in the partition wall 141 (inside the front housing 13). A pinion 24 is fixed to the front end of the output shaft 23.

[0051] like Figure 2 and Figure 3 As shown, the front housing 13 mainly houses the main shaft 3, the first clutch 4, and the second clutch 5.

[0052] The main shaft 3 is an elongated cylindrical (bar-shaped) component (shaft). The main shaft 3 extends along the drive axis A1 in the front-to-back direction. In this embodiment, the main shaft 3 is formed by connecting and fixing two separate components (two shafts 31, 32) together in the front-to-back direction. However, the main shaft 3 may also be a single component. A flange 34 is provided at the center of the main shaft 3 in the front-to-back direction.

[0053] The main shaft 3 is supported at its front and rear ends by bearings 301 and 302, enabling it to rotate relative to the main housing 11 about the drive axis A1 and to move (slide) along the drive axis A1 in the front-rear direction. The front bearing 301 is a ball bearing, supported at the front end of the front housing 13. The rear bearing 302 is a sliding bearing (also called a flat bearing or bushing bearing). The bearing 302 is pressed into and supported in a recess (hereinafter referred to as the bearing receiving portion 143), defined by the front surface of the partition wall 141 and a cylindrical portion 142 protruding forward from the front surface of the partition wall 141 (see reference). Figure 5 ).

[0054] The main shaft 3 is always subjected to a forward force, as will be described in detail later. Therefore, in the initial state where no external force is applied to the main shaft 3 in the rearward direction, the main shaft 3 is held in a position where the front end face of the flange 34 abuts against the stop 131 provided in the front housing 13. At this time, the position of the main shaft 3 is the foremost position in the movable range of the main shaft 3 (hereinafter also referred to as the initial position).

[0055] A cylindrical locator 15 is detachably connected to the front end of the front housing 13, covering the front end. The front end of the spindle 3 protrudes from the front housing 13 into the locator 15. A screwdriver tip insertion hole 311 is formed at the front end of the spindle 3. The screwdriver tip 9 is held in the screwdriver tip insertion hole 311 with its rear end inserted into it. Furthermore, the user can move the locator 15 relative to the front housing 13 in the front-rear direction and fix it in any position. Accordingly, the amount of protrusion of the screwdriver tip 9 from the locator 15 is set, that is, the tightening depth of the screw 90 is set.

[0056] Both the first clutch 4 and the second clutch 5 are configured to selectively transmit power from the output shaft 23 of the motor 2 to the main shaft 3. Details regarding the first clutch 4 and the second clutch 5 will be described later.

[0057] The structure inside handle 17 will be described below.

[0058] like Figure 1 As shown, the handle 17 houses the main switch 174, the forward / reverse switch 176, and the controller 178.

[0059] The main switch 174 is used to start the motor 2 and is located inside the upper end of the grip 171 and behind the trigger 173. The main switch 174 is normally in the off state and switches to the on state in response to pressing the trigger 173. The main switch 174 is connected to the controller 178 via a wire (not shown) and outputs a signal to the controller 178 indicating the on / off state.

[0060] A forward / reverse operating lever 175 is provided at the lower end of the connecting grip 171 in the handle 17 and at the lower rear end of the main housing 11 (rear housing 12). The forward / reverse operating lever 175 is an operating component for switching the rotation direction of the motor 2 (the rotation direction of the output shaft 23) and is connected to the forward / reverse switch 176 in an operable manner. The user can set the rotation direction of the motor 2 to either the direction in which the screwdriver head 9 tightens the screw 90 (hereinafter referred to as the forward direction, screw tightening direction) or the direction in which the screwdriver head 9 loosens the screw 90 (hereinafter referred to as the reverse direction, screw loosening direction) by operating the forward / reverse operating lever 175. The forward / reverse switch 176 is connected to the controller 178 via a wire (not shown). The forward / reverse switch 176 outputs a predetermined signal to the controller 178 according to the rotation direction set by the forward / reverse operating lever 175.

[0061] The controller 178 is disposed within the grip 171 below the main switch 174. The controller 178 includes a control circuit configured to control the drive of the motor 2. The controller 178 is configured to drive the motor 2 to rotate in the forward or reverse direction according to a signal from the forward / reverse switch 176 when the main switch 174 is in the on state.

[0062] The detailed structure of the first clutch 4 will be described below.

[0063] like Figure 2 and Figure 3 As shown, the first clutch 4 is operably connected to the output shaft 23 and the main shaft 3. That is, the first clutch 4 is positioned on the power transmission path from the output shaft 23 to the main shaft 3. The first clutch 4 is configured to selectively transmit power from the output shaft 23 to the main shaft 3 in response to the position of the main shaft 3 in the longitudinal direction.

[0064] In addition, the first clutch 4 in this embodiment also functions as a speed reduction mechanism. Specifically, the first clutch 4 is configured as a planetary speed reduction mechanism including a conical sleeve 41, a retainer 43, a plurality of rollers 45 and a gear sleeve 47.

[0065] The tapered sleeve 41, retainer 43, and gear sleeve 47 are coaxially arranged with the main shaft 3 (along the drive axis A1). The tapered sleeve 41, retainer 43, roller 45, and gear sleeve 47 correspond to the sun component, planet carrier, planet component, and ring component in the planetary reduction mechanism, respectively. In the first clutch 4, the tapered sleeve 41, gear sleeve 47, and retainer 43 function as a fixed structural element, an input structural element, and an output structural element, respectively. Therefore, the gear sleeve 47 and retainer 43 (main shaft 3) rotate in the same direction.

[0066] Furthermore, the rotation direction of the gear sleeve 47, retainer 43, and main shaft 3 when the motor 2 (output shaft 23) is driven to rotate in the positive direction (screw tightening direction) is referred to as the positive direction (screw tightening direction) of the gear sleeve 47, retainer 43, and main shaft 3. The rotation direction of the gear sleeve 47, retainer 43, and main shaft 3 when the motor 2 is driven to rotate in the opposite direction (screw loosening direction) is referred to as the reverse direction (screw loosening direction) of the gear sleeve 47, retainer 43, and main shaft 3. However, the rotation direction of the output shaft 23 is always opposite to the rotation direction of the gear sleeve 47, retainer 43, and main shaft 3.

[0067] like Figures 2-4 As shown, the tapered sleeve 41 is a cylindrical component. The tapered sleeve 41 is held in place of the main housing 11 via the base 40.

[0068] The base 40 is formed as a component independent of the main housing 11 and is coaxially connected to the main housing 11 (specifically, the partition wall 141) with respect to the drive shaft A1. More specifically, the base 40 includes an annular portion 401 and four legs 407 projecting rearward from the periphery of the annular portion 401. On the other hand, as... Figure 5 As shown, a plurality of recesses 80, divided by a plurality of ribs, are formed around the cylindrical portion 142 surrounding the bearing housing portion 143. Figure 6 As shown, the legs 407 of the base 40 are respectively inserted into the recesses 80. Accordingly, the base 40 is held in the main body housing 11 (partition wall 141) with its rotation about the drive axis A1 restricted.

[0069] Furthermore, in this embodiment, the recess 80 is also used as a reservoir (oil tank) for lubricant (e.g., grease, lubricating oil), and a felt 801 for absorbing and retaining the lubricant is embedded in the recess 80. Additionally, gaps exist within the recess 80 between the rear end (protruding end) of the leg 407 and the bottom surface of the recess 80, and between the radially inner surface of the leg 407 and the outer peripheral surface of the cylindrical portion 142 (see reference). Figure 15 Felt 801 is arranged in these gaps.

[0070] like Figures 2-4As shown, a plurality of protrusions 412 are provided at the rear end of the tapered sleeve 41, and these protrusions 412 are embedded in the recesses 405 formed in the inner periphery of the base 40. Accordingly, the tapered sleeve 41 is held in the main body housing 11 (partition wall 141) via the base 40 while its rotation about the drive axis A1 is restricted. The outer peripheral surface of the tapered sleeve 41 is configured as a tapered surface 411 inclined at a predetermined angle relative to the drive axis A1. More specifically, the tapered sleeve 41 is shaped like a frustum of a cone that tapers forward (the diameter decreases), and the tapered surface 411 is configured as a tapered surface that is inclined in the forward direction toward the drive axis A1.

[0071] The retainer 43 is configured to hold the roller 45 in a rotatable manner. In this embodiment, the retainer 43 includes an annular portion 431 and a plurality of retaining arms 434.

[0072] The annular portion 431 is a wall portion with a through hole in the center. A plurality of retaining arms 434 are arranged separately from each other in the circumferential direction and protrude generally rearward from the rear surface of the peripheral portion of the annular portion 431. Furthermore, each retaining arm 434 extends at the same angle relative to the drive axis A1 as the tapered surface 411 of the tapered sleeve 41 (i.e., parallel to the tapered surface 411). The space formed between adjacent retaining arms 434 in the circumferential direction functions as a retaining space for the retaining roller 45. The front end of this space is closed by the peripheral portion of the annular portion 431.

[0073] In this embodiment, with the retaining arm 434 positioned radially outward of the tapered sleeve 41, the retaining member 43 is supported on the main shaft 3 in a manner that prevents rotation relative to the main shaft 3 but allows movement in the front-rear direction. More specifically, as Figure 3 and Figure 4 As shown, two grooves 321 are formed at the rear end of the main shaft 3 (shaft 32) across the drive axis A1. Each groove 321 extends linearly in the front-rear direction. A ball 36 is arranged in each groove 321 in a rotatable manner. In addition, two recesses 432 are formed on the inner circumferential surface of the annular portion 431 of the retainer 43 across the drive axis A1. A portion of the ball 36 disposed in the groove 321 engages with the recess 432. Furthermore, an annular recess 414 is formed at the center of the front surface of the tapered sleeve 41. The retainer 43 is forced rearward by the force spring 49, and the ball 36 is disposed within the space defined by the recesses 414 and 432. The rear surface of the annular portion 431 is held in a state of contact with the front surface of the tapered sleeve 41. Details will be described later.

[0074] With this structure, the retainer 43 engages with the spindle 3 via the ball bearing 36, thereby enabling it to rotate integrally with the spindle 3. Furthermore, the ball bearing 36 can roll within the annular recess 419 of the tapered sleeve 41, allowing the retainer 43 to rotate together with the spindle 3 relative to the tapered sleeve 41 about the drive axis A1. On the other hand, within the range where the ball bearing 36 can roll within the groove 321, the spindle 3 can move relative to the retainer 43 and the tapered sleeve 41 in the back-and-forth direction.

[0075] like Figures 2-4 As shown, roller 45 is a cylindrical component. Each roller 45 has a certain diameter and is held between adjacent retaining arms 434 in a rollable manner. Additionally, as... Figure 7 As shown, the outer peripheral surface of the roller 45 protrudes slightly from the inner and outer surfaces of the retainer 434 in the radial direction of the retainer 43.

[0076] like Figures 2-4 As shown, the gear sleeve 47 is integrally constructed as a stepped cylindrical component. More specifically, the front end of the gear sleeve 47 has an inner diameter and an outer diameter smaller than the portion extending rearward from the front end. Hereinafter, the front end of the gear sleeve 47 will be referred to as the small diameter portion 471, and the portion extending rearward from the front end will be referred to as the large diameter portion 474. Furthermore, the stepped portion connecting the small diameter portion 471 and the large diameter portion 474 will be referred to as the shoulder portion 472. Both the small diameter portion 471 and the large diameter portion 474 have cylindrical walls and an inner diameter larger than the diameter of the main shaft 3.

[0077] The outer ring of a bearing (specifically, a ball bearing) 48 is fixed to the inner circumferential surface of the front end of the large diameter portion 474 (the portion adjacent to the shoulder 472). A main shaft 3 is inserted through the inner ring of the bearing 48. Accordingly, the gear sleeve 47 is supported by the main shaft 3 so that it can rotate relative to the main shaft 3 about the drive axis A1.

[0078] On the rear side of the bearing 48, a space is formed radially between the main shaft 3 and the large-diameter portion 474 (cylinder wall). A tapered sleeve 41, a retainer 43, and a portion of the roller 45 are disposed within this space. Furthermore, gear teeth 470 are integrally formed on the outer circumference of the rear end of the gear sleeve 47 (specifically, the large-diameter portion 474). The gear teeth 470 always mesh with the pinion 24. Therefore, the gear sleeve 47 is driven to rotate in the opposite direction to the output shaft 23 in response to its rotation.

[0079] like Figure 2 and Figure 3As shown, the inner circumferential surface of the rear end portion of the large-diameter portion 474 of the gear sleeve 47 is formed as a tapered surface 475. The tapered surface 475 is inclined relative to the drive axis A1 at the same angle as the tapered surface 411 of the tapered sleeve 41 (parallel to the tapered surface 411). That is, the tapered surface 475 is formed as a conical surface inclined rearward (towards the open end of the gear sleeve 47) away from the drive axis A1. The front portion of the roller 45 held in the retainer 43 is located between the tapered surface 411 and the tapered surface 475 in the radial direction of the main shaft 3 (orthogonal to the drive axis A1).

[0080] Additionally, the first clutch 4 includes a force-applying spring 49 disposed in the longitudinal direction between the gear sleeve 47 and the retainer 43 (more specifically, between the bearing 48 and the retainer 43). Furthermore, in this embodiment, a conical helical spring is used for the force-applying spring 49, but other types of springs may also be used. The force-applying spring 49 always applies force to the retainer 43 and the gear sleeve 47 in the direction of separation from each other, i.e., rearward and forward, respectively. Therefore, the movement of the conical sleeve 41, the retainer 43, and the roller 45 in the longitudinal direction is restricted, and they are held in predetermined positions relative to the main housing 11 in the longitudinal direction.

[0081] Furthermore, in the longitudinal direction, a thrust bearing 35 is disposed between the front surface of the gear sleeve 47 (small diameter portion 471) and the flange 34 of the main shaft 3. By the force of the force-applying spring 49, the gear sleeve 47 is forced forward, thereby, via the thrust bearing 35, the main shaft 3 is also forced forward. Accordingly, in the initial state, the main shaft 3 is held in the foremost position (initial position). Additionally, in response to the main shaft 3 moving in the longitudinal direction, the gear sleeve 47 also moves in the longitudinal direction. That is, the gear sleeve 47 and the main shaft 3 are configured to move integrally with respect to the main housing 11 in the longitudinal direction.

[0082] The first clutch 4, having the above structure, transmits power through the friction between the roller 45 and the tapered sleeve 41 (tapered surface 411), and the friction between the roller 45 and the gear sleeve 47 (tapered surface 475). That is, the first clutch 4 in this embodiment is a so-called planetary roller friction clutch.

[0083] The following describes the position of the main shaft 3 and gear sleeve 47 in the front-rear direction, and the operation of the first clutch 4.

[0084] First, such as Figure 2 and Figure 7As shown, when the main shaft 3 is positioned in the initial position, the roller 45 is held between the tapered surface 411 of the tapered sleeve 41 and the tapered surface 475 of the gear sleeve 47, allowing for slight movement. Therefore, the first clutch 4 is in a state where it cannot transmit power from the motor 2 to the main shaft 3 (hereinafter referred to as the disengaged state). Thus, even if the gear sleeve 47 rotates, this rotation will not be transmitted to the retainer 43.

[0085] On the other hand, such as Figure 8 As shown, when the user presses the screw 90, which engages with the screwdriver head 9, onto the workpiece 91, the spindle 3 overcomes the force of the force-applying spring 49 and is pressed rearward relative to the main housing 11. The gear sleeve 47 moves rearward integrally with the spindle 3 relative to the main housing 11, the tapered sleeve 41, the retainer 43, and the roller 45. As the gear sleeve 47 moves rearward, it approaches the tapered sleeve 41, and the radial distance between the tapered surface 411 of the tapered sleeve 41 and the tapered surface 475 of the gear sleeve 47 gradually narrows.

[0086] like Figure 8 and Figure 9 As shown, in response to the rearward movement of the main shaft 3 and gear sleeve 47, the roller 45 comes into frictional contact with the conical surfaces 411 and 475. When the frictional force increases and reaches a predetermined threshold, the roller 45 rotates on its own axis and revolves around the center in response to the rotation of the gear sleeve 47, causing the retainer 43 and the main shaft 3 to rotate in the same direction as the gear sleeve 47. That is, the first clutch 4 transitions from the disengaged state to a state in which power can be transmitted to the main shaft 3 (hereinafter referred to as the transmission state). Hereinafter, the position of the main shaft 3 and gear sleeve 47 in the front-rear direction at this time is referred to as the working position. Furthermore, since the first clutch 4 is a reduction mechanism, the rotational speed of the main shaft 3 is slower than the rotational speed of the gear sleeve 47.

[0087] Furthermore, in this embodiment, the first clutch 4 can transmit power from the output shaft 23 to the main shaft 3 only when the motor 2 is driven to rotate in the forward direction (screw tightening direction). In other words, when the motor 2 is driven to rotate in the reverse direction (screw loosening direction), the first clutch 4 cannot transition from the disengaged state to the transmission state. This will be described in detail later.

[0088] The detailed structure of the second clutch 5 will be described below.

[0089] like Figures 2-4As shown, the second clutch 5 is operably connected to the output shaft 23 and the main shaft 3. That is, the second clutch 5 is positioned on the power transmission path from the output shaft 23 to the main shaft 3. Unlike the first clutch 4, the second clutch 5 is configured to transmit power from the output shaft 23 to the main shaft 3 regardless of the position of the main shaft 3 in the longitudinal direction. Furthermore, in this embodiment, the second clutch 5 is configured to transmit power from the output shaft 23 to the main shaft 3 only when the rotation direction of the motor 2 (output shaft 23) is in the opposite direction (the direction of screw loosening).

[0090] The second clutch 5 in this embodiment is composed of a one-way clutch 51. The one-way clutch 51 is a clutch configured to transmit rotation only in one direction and to idle in the opposite direction. The one-way clutch 51 in this embodiment is a general one-way clutch and has a cylindrical outer ring and a plurality of rolling elements (clutch components) disposed inside the outer ring. The rolling elements are rollers (more specifically, needle rollers).

[0091] A one-way clutch 51 is radially positioned between the small-diameter portion 471 of the gear sleeve 47 and the main shaft 3. More specifically, the outer ring of the one-way clutch 51 is pressed into and fixed to the inner circumferential surface of the small-diameter portion 471 of the gear sleeve 47. The main shaft 3 is inserted through the one-way clutch 51.

[0092] When the motor 2 (output shaft 23) is driven to rotate in the forward direction (screw tightening direction), the one-way clutch 51 rotates together with the gear sleeve 47, but idles relative to the main shaft 3. That is, when the motor 2 is driven to rotate in the forward direction, the one-way clutch 51 does not transmit the rotation of the gear sleeve 47 to the main shaft 3. On the other hand, when the motor 2 is driven to rotate in the reverse direction (screw loosening direction), the one-way clutch 51 is locked to the main shaft 3 and rotates integrally with the gear sleeve 47 and the main shaft 3. That is, when the motor 2 is driven to rotate in the reverse direction, the one-way clutch 51 transmits the rotation of the gear sleeve 47 to the main shaft 3. The rotational speed of the gear sleeve 47 is the same as the rotational speed of the main shaft 3.

[0093] Furthermore, the screwdriver 1 has a limiting mechanism 6, which is configured to selectively restrict the movement of the spindle 3 and the gear sleeve 47 in the longitudinal direction. More specifically, when the motor 2 is driven to rotate in the forward direction (screw tightening direction), the limiting mechanism 6 allows the spindle 3 and the gear sleeve 47 to move in the longitudinal direction, thereby making the first clutch 4 operable. Conversely, when the motor 2 is driven to rotate in the reverse direction (screw loosening direction), the limiting mechanism 6 restricts (impedes) the movement of the spindle 3 and the gear sleeve 47 in the longitudinal direction, thereby making the first clutch 4 inoperable. That is, the limiting mechanism 6 is configured to switch the state of the first clutch 4 between an operable state and an inoperable state in response to the rotation direction of the motor 2. The detailed structure of the limiting mechanism 6 will be described below.

[0094] like Figures 2-4 , Figure 10 , Figure 11 As shown, the limiting mechanism 6 includes a rotating sleeve 61 and a limiting frame 62.

[0095] The rotating sleeve 61 is an integral cylindrical (annular) component (sleeve, ring). More specifically, the rotating sleeve 61 includes a cylindrical wall 611 and two protrusions 613 that protrude radially outward from the outer circumferential surface of the wall 611. The wall 611 is disposed around the small-diameter portion 471 of the gear sleeve 47 (nested around the outer circumference of the small-diameter portion 471). The outer diameter of the wall 611 is set such that its outer circumferential surface does not protrude radially from the outer circumferential surface of the large-diameter portion 474 of the gear sleeve 47. The two protrusions 613 are symmetrically arranged across the axis (drive axis A1) of the rotating sleeve 61. The protrusions 613 protrude radially outward from the outer circumferential surface of the large-diameter portion 474. Furthermore, the rear end face of each protrusion 613 includes a slightly circumferentially inclined inclined surface 614 (see reference). Figure 11 ).

[0096] The rotating sleeve 61 is configured such that, when no external force is applied to the rotating sleeve 61, or when the external force is relatively small, the rotating sleeve 61 rotates in response to the rotation of the gear sleeve 47. In this embodiment, the rotating sleeve 61 can rotate together with the gear sleeve 47 about the drive axis A1 relative to the main housing 11 through the frictional force between the inner circumferential surface of the rotating sleeve 61 (cylinder wall 611) and the outer circumferential surface of the gear sleeve 47 (small diameter portion 471). On the other hand, if an external force acts on the rotating sleeve 61 exceeding the frictional force that generates co-rotation, the rotating sleeve 61 and the gear sleeve 47 can rotate relative to each other about the drive axis A1.

[0097] A rotating sleeve 61 is positioned in the front-rear direction between the shoulder 472 of the gear sleeve 47 and the retaining ring 473 (and washer), wherein the retaining ring 473 is fixed to the outer periphery of the gear sleeve 47 (small diameter portion 471). Therefore, the movement of the rotating sleeve 61 relative to the gear sleeve 47 in the front-rear direction is restricted. Thus, the rotating sleeve 61, the gear sleeve 47, and consequently the main shaft 3 move integrally with respect to the main housing 11 in the front-rear direction.

[0098] The limiting frame 62 is a component that is substantially immovable relative to the main housing 11. The limiting frame 62 is configured to selectively restrict (impede) the movement of the rotating sleeve 61 (and consequently the main shaft 3 and gear sleeve 47) relative to the main housing 11 in the front-rear direction in response to the rotational position of the rotating sleeve 61 relative to the main housing 11 (the position of the protrusion 613 in the circumferential direction).

[0099] More specifically, the limiting frame 62 is a cylindrical component with a diameter larger than that of the rotating sleeve 61. More specifically, the limiting frame 62 has a cylindrical wall 620, two protrusions 625, and two protrusions 627. The cylindrical wall 620 is cylindrical and coaxially arranged around the gear sleeve 47. The two protrusions 625 protrude forward from the front end of the cylindrical wall 620. The two protrusions 627 protrude radially outward from the outer circumference of the cylindrical wall 620.

[0100] like Figure 3 and Figure 12 As shown, two grooves 133 corresponding to the protrusions 627 of the limiting frame 62 are formed inside the front housing 13. Each groove 133 is a groove extending in the front-rear direction and has a cross-sectional shape that matches the protrusions 627. The protrusions 627 are respectively embedded in the grooves 133. In addition, each protrusion 627 is defined in the front-rear direction by the front end face of the groove 133 and the arm portion 661 of the retaining member 66 (see reference). Figure 10 The arm 661 is clamped and held at the front end of the partition wall 141. With this structure, the limiting frame 62 is held in a manner that makes it substantially immobile relative to the main body housing 11. However, the limiting frame 62 can also be directly connected to and fixed to the main body housing 11 (front housing 13) without using the retaining member 66.

[0101] Two protrusions 625 project forward from the front end of the cylinder wall 620 at a position symmetrical with respect to the drive axis A1. That is, in the limiting frame 62, the two protrusions 625 and the two portions of the cylinder wall 620 without protrusions 625 are alternately arranged in the circumferential direction. When the main shaft 3 and the gear sleeve are in the initial position, the portion of the cylinder wall 620 without protrusions 625 (hereinafter referred to as the limiting portion 621) is located rearward in the front-rear direction than the rear end of the protrusion 613 of the rotating sleeve 61. On the other hand, each protrusion 625 of the limiting frame 62 projects forward from the rear end of the protrusion 613 of the rotating sleeve 61.

[0102] The position of the front end face of the limiting part 621 in the front-rear direction is configured to vary circumferentially along the cylinder wall 620. More specifically, the front end face of each limiting part 621 includes: a first surface 622 (planar), which is substantially orthogonal to the drive axis A1; and a second surface 623 (inclined surface), which extends obliquely rearward in the circumferential direction from one end of the first surface 622. More specifically, the second surface 623 is perpendicular to the positive direction of the first surface 622 in the rotational direction of the gear sleeve 47. Figure 11 The end of the arrow (in the direction of D1) is connected and tilts backward as it moves in the positive direction. Each protrusion 625 is arranged in the circumferential direction of the limiting frame 62 between the first surface 622 of one limiting part 621 and the second surface 623 of the other limiting part 621.

[0103] Furthermore, the inner diameter of the cylindrical wall 620 of the limiting frame 62 is set to be larger than the outer diameter of the large diameter portion 474 of the gear sleeve 47. Therefore, the inner circumferential surface of the cylindrical wall 620 is always far away from the large diameter portion 474, and the gear sleeve 47 will not interfere with the cylindrical wall 620, thereby allowing it to rotate about the drive axis A1 relative to the main housing 11 and the limiting frame 62. On the other hand, the inner diameter of the cylindrical wall 620 is smaller than the distance between the protruding ends of the two protrusions 613 of the rotating sleeve 61 (the maximum diameter of the rotating sleeve 61). Therefore, when the rotating sleeve 61 rotates relative to the limiting frame 62 by co-rotation, the protrusion 625 will interfere with the protrusion 613 of the rotating sleeve 61. In addition, when the main shaft 3 and the gear sleeve move rearward from the initial position, the limiting portion 621 will interfere with the protrusion 613 of the rotating sleeve 61.

[0104] Specifically, such as Figure 11 As shown, when the gear sleeve 47 rotates in the positive direction (direction of arrow D1), the rotating sleeve 61 rotates in the same direction as the gear sleeve 47 relative to the main housing 11 and the limiting frame 62 through co-rotation. Figure 11 As shown by the dashed line, the rotating sleeve 61 can be rotated to the position where the protrusion 613 abuts against the protrusion 625 on the positive side. This position of rotation of the rotating sleeve 61 (the position in the circumferential direction) is called the first position.

[0105] When the rotating sleeve 61 is positioned in the first position, the protrusion 613 is located directly in front of the end of the second surface 623 of the limiting portion 621 in the positive direction (arrow D1 direction). When the main shaft 3 is in the initial position, the protrusion 613 is away from the second surface 623. Therefore, as Figure 13 As shown, the rotating sleeve 61 can move rearward relative to the limiting frame 62. That is, when the rotating sleeve 61 is in the first position, the limiting portion 621 (specifically, the second surface 623) of the limiting frame 62 allows the spindle 3 to move rearward from the initial position. Furthermore, the limiting portion 621 (the second surface 623) is configured to allow the spindle 3 to move from the initial position to at least the working position (making the first clutch 4 actuated).

[0106] On the other hand, with the main shaft 3 in its initial position, when the gear sleeve 47 rotates in the opposite direction (in the direction of arrow D2), the rotating sleeve 61 rotates together, as... Figure 11 As shown by the solid line, the sleeve 61 can be rotated to a position where protrusion 613 abuts against protrusion 625 on the opposite side. This position (circumferential position) of the rotating sleeve 61 is called the second position.

[0107] When the rotating sleeve 61 is positioned in the second position, the protrusion 613 is located directly in front of the first surface 622 of the limiting portion 621. At this time, there is only a small gap between the protrusion 613 and the first surface 622 in the front-rear direction. Therefore, even if the spindle 3 wants to move rearward from the initial position, the first surface 622 will abut against the protrusion 613 from the rear, thereby preventing the rotating sleeve 61 from moving further rearward. That is, when the rotating sleeve 61 is in the second position, the limiting portion 621 (specifically, the first surface 622) restricts (obstructs) the spindle 3 from moving rearward from the initial position (making the first clutch 4 in an inoperable state).

[0108] The following is a detailed description of the operation of the limiting mechanism 6, the first clutch 4, and the second clutch 5 during screw tightening and loosening operations.

[0109] First, the screw tightening operation (i.e., the case where motor 2 is driven to rotate in the positive direction (screw tightening direction)) will be explained.

[0110] like Figure 2 As shown, when the spindle 3 is in its initial position, the first clutch 4 is disengaged. In this state, when the user presses the trigger 173, the main switch 174 is activated, and the controller 178 begins to drive the motor 2. The gear sleeve 47 is driven to rotate in the positive direction (screw tightening direction). As described above, the second clutch 5 (one-way clutch 51) is not engaged at this time, and the gear sleeve 47 idles relative to the spindle 3.

[0111] As described above, the rotating sleeve 61 of the limiting mechanism 6 is positioned in the first position by co-rotation. Figure 11 As shown by the dashed line, because the protrusion 613 of the rotating sleeve 61 abuts against the protrusion 625 of the limiting frame 62, the rotating sleeve 61 is prevented from rotating further in the positive direction, and the rotating sleeve 61 is held in the first position. The gear sleeve 47 rotates relative to the rotating sleeve 61 while continuing to rotate freely in the positive direction relative to the main shaft 3.

[0112] Since the rotating sleeve 61 is in the first position, the limiting part 621 (the second surface 623) does not interfere with the protrusion 613 of the rotating sleeve 61, thereby allowing the main shaft 3 to move rearward. That is, the first clutch 4 is in an actuated state. Thus, as Figure 8 and Figure 13 As shown, in response to the user pressing the screw 90 onto the workpiece 91, the spindle 3, gear sleeve 47, and rotating sleeve 61 move rearward relative to the main housing 11 and the limiting frame 62. When the spindle 3 moves rearward to the working position, the first clutch 4 shifts from the disengaged state to the transmission state, and the screw 90 is screwed into the workpiece 91.

[0113] When screw 90 is screwed into workpiece 91, and the top of locator 15 abuts against workpiece 91, the pressure point shifts from spindle 3 to locator 15, thus gradually decreasing the pressure applied to spindle 3. Consequently, the force exerted on roller 45 by the tapered surface 411 of tapered sleeve 41 and the tapered surface 475 of gear sleeve 47 gradually decreases, and consequently, the torque transmitted from gear sleeve 47 to spindle 3 also gradually decreases. If the torque transmitted from gear sleeve 47 to spindle 3 is lower than the torque required to tighten screw 90, the rotation of spindle 3 stops. The screw tightening operation thus ends.

[0114] Next, the screw loosening operation (i.e., the case where motor 2 is driven to rotate in the opposite direction (screw loosening direction)) will be explained.

[0115] With the spindle 3 in its initial position, when the user presses trigger 173, the main switch 174 is activated, and the controller 178 begins to drive the motor 2. The gear sleeve 47 is driven to rotate in the opposite direction (the screw loosening direction). As described above, due to the activation of the second clutch 5 (one-way clutch 51), the spindle 3 rotates integrally with the gear sleeve 47 as it begins to rotate, thus loosening the screw 90. That is, even when the motor 2 is driven to rotate in the opposite direction, the screw 90 can be loosened without the user pressing it against the workpiece 91. Therefore, the user can quickly begin the screw loosening operation.

[0116] Furthermore, as described above, the rotating sleeve 61 of the limiting mechanism 6 is positioned in the second position through co-rotation. Moreover, before the rotating sleeve 61 reaches the front of the first surface 622, the main shaft 3 is pressed rearward, and with the protrusion 613 abutting against the second surface 623, the rotating sleeve 61 can be guided to the second position by the action of the second surface 623 (which is an inclined surface) (and the inclined surface 614 of the protrusion 613). Figure 11 As shown by the solid line, when the rotating sleeve 61 is positioned in the second position, the protrusion 613 of the rotating sleeve 61 abuts against the protrusion 625 of the limiting frame 62, thus preventing further rotation of the rotating sleeve 61 in the opposite direction, and the rotating sleeve 61 is held in the second position. The gear sleeve 47 rotates relative to the rotating sleeve 61 while continuing to rotate in the opposite direction integrally with the main shaft 3.

[0117] As the screw 90 is loosened, it moves rearward. Therefore, the spindle 3 is pressed rearward. However, since the rotating sleeve 61 is in the second position, the limiting part 621 (first surface 622) abuts against the protrusion 613, limiting (impeding) the rearward movement of the spindle 3. That is, the first clutch 4 remains in an inoperable state, thereby preventing the first clutch 4 from operating during the operation of the second clutch 5. Thus, the power of the output shaft 23 is transmitted to the spindle 3 only via the second clutch 5, and the screw 90 is loosened and disengaged from the workpiece 91. Furthermore, as described above, since the first clutch 4 is a reduction mechanism, if the first clutch 4 and the second clutch 5 operate simultaneously, slippage of either one could be a cause of problems. In this embodiment, such problems can be appropriately avoided.

[0118] As described above, in the screwdriver 1 of this embodiment, during screw tightening, power is transmitted from the motor 2 to the spindle 3 via the first clutch 4; conversely, during screw loosening, power is transmitted from the motor 2 to the spindle 3 via the second clutch 5. That is, power is transmitted via different paths during screw tightening and screw loosening. Furthermore, since the first clutch 4 is also a reduction mechanism, even if the output shaft 23 of the motor 2 rotates at the same speed, the rotational speed of the spindle 3 when power is transmitted via the first clutch 4 is different from the rotational speed of the spindle 3 when power is transmitted via the second clutch 5. Specifically, when the motor 2 is driven to rotate at the same speed, the screw 90 can rotate at a higher speed during screw loosening compared to screw tightening. The torque required for screw loosening is less than that required for screw tightening. Therefore, as in this embodiment, by making the output speed of the spindle 3 different relative to the rotational speed of the same motor 2 according to the rotation direction of the motor 2, the efficiency of each operation can be optimized.

[0119] Furthermore, since the first clutch 4, which operates only when the motor 2 is driven to rotate in the forward direction (screw tightening direction), also serves as a reduction mechanism, there is no need to provide a separate reduction mechanism outside of the first clutch 4. Therefore, a compact screwdriver 1 can be achieved. On the other hand, when the motor 2 is driven to rotate in the reverse direction (screw loosening direction), the required torque is smaller. Therefore, the second clutch 5 only utilizes the one-way clutch 51 for transmitting rotation and does not perform reduction. Accordingly, a compact and relatively inexpensive second clutch 5 can be achieved.

[0120] Furthermore, the first clutch 4 begins to transmit power in response to the rearward pressing of the main shaft 3. The limiting mechanism 6 restricts the movement of the main shaft 3 in the forward and backward directions only when the motor 2 (output shaft 23) is driven to rotate in the reverse direction. Accordingly, when the motor 2 (output shaft 23) is driven to rotate in the reverse direction, the limiting mechanism 6 can reliably prevent the first clutch 4 from operating.

[0121] In particular, in this embodiment, the limiting mechanism 6 consists of a rotating sleeve 61 and a limiting frame 62. The rotating sleeve 61 is rotatable between a first position and a second position, and the limiting frame 62 is fixed to the main housing 11, limiting the movement of the main shaft 3 in the front-rear direction only when the rotating sleeve 61 is in the second position. The rotating sleeve 61 can rotate between the first and second positions by co-rotating with the gear sleeve 47 that rotates through the output shaft 23, thus simplifying the structure. Furthermore, the limiting frame 62 (limiting part 621) has only a simple structure with a first surface 622 that abuts against the rotating sleeve 61 from the rear, which reliably prevents the rearward movement of the main shaft 3.

[0122] Furthermore, in this embodiment, a protrusion 625 is provided on the limiting frame 62, which can abut against the protrusion 613 of the rotating sleeve 61 in the circumferential direction. Accordingly, without hindering the rotation of the gear sleeve 47, the rotating sleeve 61 can be prevented from passing through the first position and the second position and rotating together with the gear sleeve 47, thereby keeping the rotating sleeve 61 in the first position and the second position.

[0123] However, in the screwdriver 1, since various mechanisms and components requiring lubrication are housed within the front housing 13, a lubricant (e.g., grease, lubricating oil) is introduced into the front housing 13. In this embodiment, a circulation path 8 for effectively circulating the lubricant is provided within the front housing 13. The circulation path 8 will be described in detail below.

[0124] like Figure 14 and Figure 15 As shown, the circulation path 8 mainly includes: path 81, which passes through the interior of the spindle 3; and various paths 82 to 86, which guide the lubricant to the rear end of the spindle 3 from the outside of the spindle 3.

[0125] The path 81 inside the spindle 3 is defined by a first hole 811 and a second hole 812. The first hole 811 extends forward from the rear end of the spindle 3 along the axis of the spindle 3 (drive axis A1). The first hole 811 is a bottomed hole that is closed at the front end and open at the rear end of the spindle 3. The second hole 812 penetrates the spindle 3 in the diametrical direction. Furthermore, both ends of the second hole 812 are open on the outer circumferential surface of the spindle 3 (specifically, within the groove 321). Regardless of the position of the spindle 3 in the front-rear direction, both ends of the second hole 812 are located radially inside the first clutch 4 (surrounded by the first clutch 4). In addition, the central portion of the second hole 812 communicates with the front end of the first hole 811. That is, the first hole 811 and the second hole 812 are configured as a capital letter T.

[0126] Lubricant flowing from the rear end of the main shaft 3 into the first hole 811 can flow out of the main shaft 3 through the openings at both ends of the second hole 812. More specifically, under the centrifugal force of the main shaft 3 during rotation, the lubricant is discharged radially outward through path 81. Accordingly, lubrication can be achieved for components (especially the first clutch 4) arranged around the main shaft 3.

[0127] Path 82 is a path that allows the lubricant flowing out of the main shaft 3 via path 81 to flow radially outward to the gear sleeve 47. Specifically, as... Figure 15 As shown, two connecting holes 478 are provided in the large-diameter portion 474 of the gear sleeve 47. The connecting holes 478 penetrate the large-diameter portion 474 (cylinder wall), connecting the radially inner space (internal space of the gear sleeve 47) and the radially outer space (external space of the gear sleeve 47) of the large-diameter portion 474. Thus, lubricant flowing into the internal space of the gear sleeve 47 through path 81 can flow out radially outward through the connecting holes 478. In particular, when the gear sleeve 47 rotates, airflow is generated through the connecting holes 478 due to centrifugal force, thus effectively discharging lubricant to the outer side of the gear sleeve 47.

[0128] Path 83 is a path for guiding the lubricant flowing out of the main shaft 3 via path 81 to the periphery of the roller 45 through the space between the tapered sleeve 41 and the retainer 43. Specifically, as Figure 16 As shown, a plurality of shallow grooves 433 are formed on the rear surface of the annular portion 431 of the retainer 43. The grooves 433 extend radially from the inner edge to the outer edge of the annular portion 431 between the retaining arms 434. Figure 14As shown, path 83 is defined by the front surface of the tapered sleeve 41 and the groove 433. As described above, the retainer 43 is held in a state where the rear surface of the annular portion 431 abuts against the front surface of the tapered sleeve 41. However, the lubricant flowing out of the main shaft 3 through path 81 moves to the periphery of the roller 45 through path 83, which can lubricate the roller 45 and the tapered surfaces 411, 475.

[0129] Furthermore, the roller 45 rotates on its own axis and revolves around a central axis while in frictional contact with the tapered surface 411 of the tapered sleeve 41 and the tapered surface 475 of the gear sleeve 47. Therefore, slippage occurs due to the difference in rotation between the front and rear parts of the roller 45. Consequently, the lubricant supplied via path 81 effectively reduces wear on the roller 45 and the tapered surfaces 411 and 475, contributing to improved durability of the first clutch 4.

[0130] When the lubricant moves through paths 82, 83, etc. to the recess 80 (oil groove) of the partition wall 141 (see reference) Figure 15 When the lubricant is absorbed and retained by the felt 801 disposed within the recess 80, the lubricant is effectively circulated by utilizing the felt 801 to store the lubricant in the recess 80.

[0131] Path 84 is a path for guiding lubricant from the recess 80 to the opening in the bearing housing 143. Specifically, as... Figure 17 As shown, two shallow grooves 406 are formed on the rear surface of the annular portion 401 of the base 40. The two grooves 406 intersect the center of the annular portion 401 in a cross-shaped arrangement and extend along the diametrical direction. Figure 14 and Figure 15 As shown, path 84 is defined by the front surface of cylindrical portion 142 and groove 406. As described above, base 40 is held in a state where the rear surface of annular portion 401 abuts against the front surface of cylindrical portion 142, but lubricant absorbed and held in recess 80 by felt 801 can reach the opening of bearing housing portion 143 through path 84.

[0132] Paths 85 and 86 are paths for guiding lubricant from the opening of the bearing housing 143 inward (more specifically, around the rear end of the spindle 3).

[0133] Specifically, such as Figure 5 As shown, a shallow groove 144 is formed on the surface of the bearing housing 143. The groove 144 extends from the front end (protruding end) of the cylindrical portion 142 to the center of the bottom surface of the bearing housing 143. Figure 14As shown, path 85 is defined by the outer surface of bearing 302 and groove 144. Lubricant that reaches the opening of bearing housing 143 via path 84 enters bearing housing 143 via path 85, and then enters the interior of bearing 302, thereby reaching the periphery of the rear end of spindle 3. Thus, lubricant can re-enter path 81 inside spindle 3.

[0134] In addition, such as Figure 14 and Figure 15 As shown, the front end of bearing 302 (sliding bearing) is located slightly rearward than the front end of the cylindrical portion 142 of partition wall 141. Path 86 is formed by the gap between the front end of bearing 302 and the rear ends of base 40 and tapered sleeve 41. Lubricant reaching the opening of bearing housing 143 via path 84 can move towards the outer peripheral surface of spindle 3 via path 86, and reach the rear peripheral area of ​​spindle 3 via the space between bearing 302 and spindle 3. Therefore, lubricant can re-enter path 81 inside spindle 3.

[0135] In this embodiment, due to the rotation of the spindle 3, the pressure inside the bearing 302 is lower than the external pressure. In this embodiment, since lubricant can be accumulated in the recess 80 using the felt 801, the pressure difference can be used to guide the lubricant from the recess 80 to the bearing 302 by providing paths 84, 85, and 86. Furthermore, since the spindle 3 reciprocates relative to the bearing 302 in the front-rear direction, the lubricant can also be guided from the recess 80 to the bearing 302 through a pumping effect.

[0136] As explained above, in this embodiment, the components (especially the first clutch 4) within the front housing 13 can be effectively lubricated via the circulation path 8, which includes a path 81 passing through the interior of the main shaft 3 and paths 82-86 passing through the exterior of the main shaft 3. Furthermore, the circulation path 8 may include paths different from this example, and oil grooves may be configured at locations different from this example.

[0137] The correspondence between the structural elements (features) of the above embodiments and the structural elements (features) of this disclosure or invention is shown below. However, the structural elements of the embodiments are merely examples and do not limit the structural elements of this disclosure or invention.

[0138] Screwdriver 1 is an example of a "screw tightening tool". Main housing 11 is an example of a "housing". Motor 2 and output shaft 23 are examples of "motor" and "output shaft", respectively. The forward direction (screw tightening direction) is an example of "first direction". The reverse direction (screw loosening direction) is an example of "second direction". Spindle 3 is an example of a "spindle". Drive shaft A1 is an example of a "drive shaft". First clutch 4 is an example of a "first clutch". Second clutch 5 is an example of a "second clutch".

[0139] The limiting mechanism 6 is an example of a "limiting mechanism". The rotating sleeve 61 (protrusion 613) is an example of a "first limiting part". The limiting frame 62 (limiting part 621) is an example of a "second limiting part". The gear sleeve 47 is an example of a "rotating component". The limiting part 621 is an example of a "wall part". The first surface 622 and the second surface 623 are examples of "first surface" and "second surface", respectively. The conical sleeve 41 is an example of a "solar component". The gear sleeve 47 is an example of a "ring component". The retainer 43 is an example of a "planet carrier". The roller 45 is an example of a "planetary roller". The conical surface 411 is an example of a "conical outer peripheral surface of a solar component". The conical surface 475 is an example of a "conical inner peripheral surface of a ring component". The first hole 811 and the second hole 812 are examples of "first hole" and "second hole", respectively. The circulating flow path 8 is an example of a "circulating flow path". Recess 80 is an example of a "storage section".

[0140] Furthermore, the above embodiments are merely illustrative, and the screw-fastening tools involved in this disclosure are not limited to the illustrative screwdriver 1. For example, the following illustrative modifications can be added. In addition, at least one of these modifications can be combined with at least any one of the features described in the embodiments and the technical solutions.

[0141] For example, in the above embodiment, the first clutch 4 is a so-called planetary roller friction clutch. Alternatively, other types of clutches can be used, wherein the clutch is in an disengaged state when the main shaft 3 is in the initial position, and the clutch is switched to a transmission state by moving the main shaft 3 backward from the initial position. For example, a single-plate or multi-plate friction clutch, or a conical friction clutch, can also be used. Alternatively, an engaging clutch can also be used. Furthermore, when using a so-called planetary roller friction clutch, the structure (shape, size, number, etc.) and arrangement of the sun component, ring component, planet carrier, and planetary rollers can be appropriately modified.

[0142] Similarly, the second clutch 5 can also be a different type of clutch than the example of the above embodiment (e.g., a bracing one-way clutch). sprag type one-way clutch Furthermore, the configuration of the second clutch 5 can be appropriately modified in response to changes in the first clutch 4, or appropriately modified regardless of changes in the first clutch 4.

[0143] Furthermore, the limiting mechanism 6 can be of any structure as long as it can limit the movement of the main shaft 3 in the front-back direction only when the motor 2 (output shaft 23) is driven to rotate in the positive direction.

[0144] For example, the rotating sleeve 61 may not be connected to the gear sleeve 47, but may be movably connected to other components that rotate via the output shaft 23. Furthermore, the rotating sleeve 61 may have one or more protrusions 613. Alternatively, the portion of the rotating sleeve 61 other than the protrusions 613 may be able to abut against the limiting frame 62 (limiting portion 621). Corresponding to the change in the rotating sleeve 61, the number of limiting portions 621 and protrusions 625 of the limiting frame 62 may also be changed.

[0145] Furthermore, when the rotating sleeve 61 is positioned in the second position, the structure that abuts against a portion of the rotating sleeve 61 from the rear to restrict (obstruct) the rearward movement of the main shaft 3 is not limited to the limiting frame 62 (limiting part 621). For example, such a structure may be integrally provided inside the main body housing 11 (front housing 13). For example, a protrusion protruding toward the rotating sleeve 61 may be provided on the inner surface of the main body housing 11. Moreover, this protrusion may be configured such that it is positioned directly behind the protrusion 613 of the rotating sleeve 61 only when the rotating sleeve 61 is positioned in the second position, thereby abutting against the protrusion 613 from the rear and thus restricting the rearward movement of the main shaft 3.

[0146] Furthermore, the structure that restricts (obstructs) the rotation of the rotating sleeve 61 beyond the first and second positions by co-rotation is not limited to the protrusion 625 of the restricting frame 62. For example, similar to the variation of the restricting part 621 described above, at least one protrusion may be provided on the inner surface of the main body housing 11 (front housing 13), which abuts against a portion of the rotating sleeve 61 when the rotating sleeve 61 is positioned in the first and second positions, thereby preventing further rotation of the rotating sleeve 61.

[0147] Alternatively, the screwdriver 1 can be configured to operate without an external AC power source, but rather powered by a DC power supply. In this case, a battery mounting portion is provided on the main housing 11, which removably accepts a rechargeable battery. The shape and connection structure of the main housing 11 and the handle 17, as well as the type and configuration of the motor 2, can also be appropriately modified. For example, the motor 2 can also be a DC motor (e.g., a brushless DC motor). Furthermore, the motor 2 can also be configured such that the rotation axis of the output shaft 23 intersects the drive axis A1.

[0148] Furthermore, in view of the spirit of the present invention and the above embodiments, the following methods are constructed. Any one or more of the following methods can be used in combination with the screwdriver 1 of the embodiments and its modifications or the invention described in the various technical solutions.

[0149] [Method 1] The output speed when power is transmitted via the second clutch is higher than the output speed when power is transmitted via the first clutch.

[0150] According to this method, the screw rotation speed can be higher during screw loosening than during screw tightening, thereby achieving high efficiency in screw loosening.

[0151] [Method 2] The spindle is configured to typically remain in an initial position and move to a working position further rearward than the initial position in response to a rearward push. The first clutch is configured to cut off power transmission when the main shaft is in a position forward of the working position, and to transmit power in response to the main shaft being positioned in the working position.

[0152] [Method 3] The first limiting part is configured to move integrally with the main shaft along the front-rear direction. The second limiting part is configured to abut against the first limiting part disposed at the second position from the rear, thereby preventing the main shaft from moving rearward.

[0153] According to this method, by abutting the first limiting part against the second limiting part, the rearward movement of the main shaft can be reliably prevented.

[0154] [Method 4] The screw fastening tool further comprises: a first abutment portion configured to abut against the first limiting portion disposed in the first position in response to rotation of the output axis in the first direction, thereby limiting rotation of the first limiting portion in the first direction; and The second abutting portion is configured to abut against the first restricting portion, which is disposed at the second position in response to rotation of the output axis in the second direction, thereby restricting the rotation of the first restricting portion in the second direction.

[0155] The protrusion 625 in the embodiment is an example of the "first contact portion" and "second contact portion" of this method.

[0156] According to this method, it is possible to reliably prevent the first limiting part from rotating past the first position and the second position by co-rotation.

[0157] [Method 5] The second surface, relative to the first surface, is located on the rotation direction side of the first limiting part when the output shaft is driven to rotate in the first direction in the circumferential direction, and tilts backward toward the rotation direction of the first limiting part when the output shaft is driven to rotate in the first direction.

[0158] [Method 6] The second clutch is a one-way clutch configured to transmit rotation only in one direction and idle in the opposite direction.

[0159] [Method 7] The one-way clutch is configured to be located radially inside the ring component and radially outside the main shaft, and to transmit the rotation of the ring component to the main shaft only when the output shaft is driven to rotate in the second direction.

[0160] [Method 8] The second hole opens on the outer circumferential surface of the main shaft within the first clutch.

[0161] [Method 9] The rear end of the spindle is supported by a bearing fixed to the housing in a manner that allows it to slide along the drive axis and rotate about the drive axis. The storage section is located on the radial outer side of the bearing.

[0162] [Method 10] The circulation path includes at least one first path between the second hole and the storage section, and at least one second path between the storage section and the interior of the bearing.

Claims

1. A screw fastening tool, characterized in that, It has a housing, a motor, a main shaft, a first clutch, and a second clutch, wherein, The motor is housed in the housing and has an output shaft configured to be selectively driven to rotate in a first direction or a second direction, wherein the first direction corresponds to the direction of fastening the screw and the second direction corresponds to the direction of loosening the screw and is opposite to the first direction; The spindle is supported on the housing in a manner that allows it to move along and rotate about the drive axis, wherein the drive axis defines the front-to-back direction of the screw fastening tool, and the spindle has a front end configured to allow for the attachment and removal of a top tool. The first clutch is configured to be operatively connected to the output shaft and the main shaft, and to transmit power from the output shaft to the main shaft only when the output shaft is driven to rotate in the first direction; The second clutch is configured to be operatively connected to both the output shaft and the main shaft, and to transmit power from the output shaft to the main shaft only when the output shaft is driven to rotate in the second direction. When power is transmitted via the first clutch and when power is transmitted via the second clutch, the output speeds of the main shaft relative to the same output shaft are different. The first clutch is configured to selectively transmit power according to the position of the main shaft in the longitudinal direction. The second clutch is configured to transmit the power regardless of the position of the main shaft in the longitudinal direction. It also has a limiting mechanism configured to limit the movement of the main shaft in the front-rear direction only when the output shaft is driven to rotate in the second direction.

2. The screw fastening tool according to claim 1, characterized in that, The limiting mechanism includes a first limiting part and a second limiting part, wherein, The first limiting part is rotatable in the circumferential direction about the drive axis between the first position and the second position. The first limiting part is configured to be disposed in the first position in response to rotation of the output axis in the first direction, and disposed in the second position in response to rotation of the output axis in the second direction. The second limiting part is configured such that when the first limiting part is in the first position, the spindle is allowed to move in the front-rear direction, and when the first limiting part is in the second position, the spindle is restricted to move in the front-rear direction.

3. The screw fastening tool according to claim 2, characterized in that, It also includes a rotating component configured to be positioned between the output shaft and the main shaft along the power transmission path, and to rotate via the output shaft. The first limiting part is configured to be selectively rotatable relative to the rotating member, and to rotate with the rotating member only between the first position and the second position. The second limiting part is substantially immovable relative to the housing.

4. The screw fastening tool according to claim 2 or 3, characterized in that, The second limiting portion includes a wall portion disposed behind the first limiting portion and extending along the circumferential direction. The front end face of the wall includes: a first surface which is configured to extend in a direction orthogonal to the drive axis and abut against the first limiting portion disposed at the second position from the rear; and The second surface is configured to extend obliquely rearward from one end of the first surface in the circumferential direction, and allows the main shaft to move in the front-rear direction.

5. The screw fastening tool according to claim 2 or 3, characterized in that, The first clutch is configured to also function as a speed reduction mechanism.

6. The screw fastening tool according to claim 5, characterized in that, The deceleration mechanism includes a sun component, a ring component, and a planetary carrier arranged coaxially with the drive axis, and multiple planetary rollers held in a rotatable manner on the planetary carrier. The ring component is configured to rotate via the output shaft. The planetary structure rotates integrally with the main axis. The plurality of planetary rollers are at least partially disposed radially between the conical outer peripheral surface of the solar component and the conical inner peripheral surface of the ring component. The ring component is movable integrally with the main shaft relative to the sun component in the front-rear direction. The first clutch is configured such that, in response to the rearward movement of the main shaft from an initial position, the plurality of planetary rollers selectively engage with the outer peripheral surface of the solar component and the inner peripheral surface of the ring component, thereby transmitting power.

7. The screw fastening tool according to claim 2 or 3, characterized in that, The spindle has: a first hole extending forward from the rear end of the spindle; and a second hole communicating with the first hole, extending in a direction intersecting the first hole and opening on the outer circumferential surface of the spindle. The screw fastening tool also has a circulation path within the housing, which allows lubricant discharged from the spindle through the first and second holes to return to the rear end of the spindle.

8. The screw fastening tool according to claim 7, characterized in that, The circulation path is provided with a storage section for storing the lubricant.

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