JP7375298B2 - power tools - Google Patents

Description

The present invention relates to power tools.

BACKGROUND OF THE INVENTION Conventionally, board materials such as gypsum boards have been installed on ceilings and walls by screwing, and screw tighteners are widely used as power tools for screwing. For example, Patent Document 1 discloses that a plurality of first clutch plates and a plurality of A screwdriver is described that includes a multi-disc friction clutch having a second clutch plate. The multi-plate friction clutch is housed in a clutch drum having a cylindrical shape with a bottom, and is configured such that its rear end can come into contact with a rear wall of the clutch drum.

In the screw tightening machine described in Patent Document 1, while the first clutch plate is rotating under the driving force of the motor, an operator inserts a fastener (for example, a screw ), the tip tool mounting portion moves in a direction approaching the multi-disc friction clutch, and the rear end of the tip tool mounting portion comes into contact with the front end of the multi-disc friction clutch. In this state, the rear end of the multi-plate friction clutch is in contact with the rear wall of the clutch drum, and by further pressing the tip tool against the fastener, the tip tool mounting section presses the multi-plate friction clutch, and the first clutch plate and The surface pressure between the two clutch plates increases. With the surface pressure increased, the first clutch plate rotates relative to the second clutch plate in response to the driving force of the motor, causing friction between the first clutch plate and the second clutch plate. , the second clutch plate rotates due to the friction. The rotation of the second clutch plate causes the tip tool mounting portion (tip tool) to rotate.

Japanese Patent Application Publication No. 2009-101500

However, with the screw tightening machine described in Patent Document 1, for example, when screwing a board to a ceiling, the rear end of the multi-disc friction clutch comes into contact with the rear wall of the clutch drum due to its own weight. There was a possibility that the surface pressure between the first clutch plate and the second clutch plate would increase, and the output shaft portion (tip tool) would start rotating regardless of the operator's intention.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a power tool that can suppress rotation of an output shaft portion that is not intended by the operator.

In order to solve the above-mentioned problems, the present invention includes a drive source that generates a drive force, a drive section that is rotationally driven by the transmission of the drive force, and a tip tool that can be attached and detached, and that can be positioned at a position when no load is applied. an output shaft portion that is movable between a first position where the force is applied and a second position that is located when a force in a predetermined direction is applied, and that is rotatable in response to the driving force transmitted to the drive unit; is provided between the drive section and the output shaft section in the transmission path of the output shaft section, and is pressed when the force in the predetermined direction acts on the output shaft section, and receives the driving force transmitted to the drive section. A power tool comprising a transmission section that transmits a driving force according to a pressing force to the output shaft section, wherein the output shaft section has a first contact section that can come into contact with the transmission section in the predetermined direction. , the drive section has a second contact section that can come into contact with the transmission section in the predetermined direction, and when the output shaft section is located at the first position, the first contact section and the transmission section and the second contact part and the transmission part are spaced apart from each other, and when the output shaft part is located at the second position, the first contact part and the transmission part The present invention provides a power tool characterized in that the second contact portion and the transmission portion are configured to be separated from each other, and the second contact portion and the transmission portion are in contact with each other.

In the power tool having the above configuration, when the output shaft portion is in the first position and there is no load, the transmission portion and the first contact portion provided on the output shaft portion are in contact with each other, while the transmission portion and the first contact portion provided on the drive portion are in contact with each other. The second contact portion is configured to be spaced apart from the second contact portion. On the other hand, when a force in a predetermined direction acts on the output shaft section and the output shaft section is located at the second position, the transmission section and the first contact section are separated, while the transmission section and the second contact section are separated. It is configured to come into contact with the part. In other words, the transmission part is configured so that it comes into contact with different points when there is no load and when the operator presses the tip tool against a fastener, etc., so when there is no load, the output shaft may be unintended by the operator. It becomes possible to provide a power tool that can suppress the rotation of.

In the power tool configured as described above, the output shaft portion includes a tip tool mounting portion to which the tip tool can be attached and detached, and the tip tool mounting portion, the transmission portion, and the first contact portion are arranged in the predetermined direction. In this case, it is preferable that the tip tool attachment section, the transmission section, and the first contact section are arranged in this order.

According to such a configuration, for example, when working with the tip tool directed toward the ceiling (upward), the first contact portion is located below the transmission portion. For this reason, it is possible to suitably bring the transmission section and the first contact section into contact with each other during no-load conditions when the output shaft section is located at the first position.

Further, the tip tool mounting section, the transmission section, and the second contact section are arranged in the order of the tip tool mounting section, the transmission section, and the second contact section in the predetermined direction, and the output shaft When the part is located at the first position, it is preferable that at least a part of the first abutting part be located closer to the tip tool mounting part than the second abutting part.

According to such a configuration, for example, when working with the tip tool directed toward the ceiling (upward), at least a portion of the first contact portion is in an unloaded state when the output shaft portion is located at the first position. It is located above the second contact portion. Therefore, when the output shaft portion is in the first position and there is no load, the transmission portion and the first contact portion are suitably brought into contact with each other, and the transmission portion and the second contact portion are suitably separated from each other. becomes possible.

The apparatus further includes a housing that supports the output shaft, and a biasing member that biases the output shaft in a direction opposite to the predetermined direction is provided between the output shaft and the housing. is preferred.

According to such a configuration, when the output shaft portion is located at the first position, at least a portion of the first contact portion is preferably located at a position closer to the tip tool mounting portion than the second contact portion. It becomes possible to do so.

Further, the first contact portion may be configured to be able to come into contact with the transmission portion at a position inward in the radial direction of the output shaft portion from a position where the second contact portion contacts the transmission portion. preferable.

According to such a configuration, the output shaft portion is connected to the first output shaft portion where the driving force (transmission torque) transmitted by the transmission portion is proportional to the pressing force acting on the transmission portion and the distance from the rotation center of the point of application of the pressing force. It becomes possible to suppress the transmission of driving force when the vehicle is located at a certain position. This makes it possible to suppress rotation of the output shaft portion that is not intended by the operator.

Further, it is preferable that the output shaft section has a shaft extending in the predetermined direction, and that the first contact section is provided on the shaft and has an outer diameter larger than an outer diameter of the shaft.

According to such a configuration, it is possible to make the first contact part and the transmission part come into contact with each other inward in the radial direction of the output shaft part from the position where the second contact part and the transmission part come into contact with each other. becomes.

Further, the drive part has a cylindrical shape that extends in the predetermined direction and has a first engagement part extending in the predetermined direction formed on the inner peripheral surface, and the output shaft part is inserted through the drive part and has a cylindrical shape that extends in the predetermined direction. A second engaging portion extending in a predetermined direction is formed, and the transmitting portion includes a plurality of first plates formed in a disc shape and having a first engaged portion that engages with the first engaging portion. , a plurality of second plates formed in a disc shape and having second engaged parts that engage with the second engaging part, wherein the first plate and the second plate are arranged in the predetermined direction. The driving force is transmitted to the output shaft portion by a frictional force generated between the first plate and the second plate when the transmission portion is pressed. is preferred.

According to such a configuration, it becomes possible to transmit the driving force transmitted from the drive section to the output shaft section by the frictional force generated between the first plate and the second plate. In addition, since the driving force is transmitted only by the frictional force generated between the first plate and the second plate, the generation of impact is suppressed when the drive section and output shaft section switch from a non-transmission state to a transmission state. It becomes possible to do so.

Further, it is preferable that the area of the first plate when viewed in the predetermined direction is less than half the area of the second plate when viewed in the predetermined direction.

According to such a configuration, it is possible to reduce the weight of the power tool. Furthermore, compared to the conventional configuration, the center of gravity is located at the rear, that is, the center of gravity can be brought closer to the handle gripped by the operator, so it is possible to provide a power tool with good operability. Furthermore, the portion of the first plate that does not contribute to the transmission of the driving force can be reduced, thereby reducing the contact area with the second plate and reducing the generation of heat.

Further, the drive section has a cylindrical shape with an opening formed on the opposite side of the second contact section with respect to the transmission section, the transmission section is housed in the drive section, and the output shaft section has a cylindrical shape. , a pressing portion is provided which projects outward in the radial direction of the output shaft portion and presses the transmission portion through the opening as the output shaft portion moves in the predetermined direction; It is preferable that a groove that is concave toward the surface is formed.

According to such a configuration, it is possible to prevent water, oil, etc. from entering the drive section.
Further, the present invention includes a drive source that generates a driving force, and a drive unit that is rotatable around an axis extending in the front-rear direction, and that is rotationally driven by the transmission of the drive force. The power tool is equipped with an output shaft rotatable about the axis, and a tip tool for tightening a screw is configured to be removably attached to a front part of the output shaft, and the power tool a first position located when there is no load, in which the power tool is not pressed toward the screw; and a second position, located during work when the power tool is pressed toward the screw and a backward pressing force is acting on the output shaft portion. an output shaft portion that is movable between the output shaft portion and rotatable in response to the driving force transmitted to the driving portion while in the second position; and the driving portion and the output shaft portion in the transmission path of the driving force. The output shaft is provided between the output shaft and the output shaft, and is pressed when the rearward force acts on the output shaft, and receives the driving force transmitted to the drive unit, and the output shaft receives the driving force and the point of application of the pressing force. A power tool comprising: a transmission section that transmits a driving force proportional to a product of a distance from a center of rotation to the output shaft section; the driving part has a second contact part that can come into contact with the transmission part in the front-rear direction, and when the output shaft part is located at the first position, the first When the contact part and the transmission part are in contact with each other, and the second contact part and the transmission part are separated from each other, and the output shaft part is located at the second position, the first contact part and the transmission section are separated from each other, and the second contact section and the transmission section are configured to come into contact with each other.
Further, the output shaft portion includes a tip tool mounting portion to which the tip tool can be attached and detached, and the tip tool mounting portion, the transmission portion, and the first abutment portion are configured to support the tip tool in the front-rear direction. It is preferable that the mounting part, the transmission part, and the first contact part are arranged in this order.
The tip tool mounting portion, the transmission portion, and the second contact portion are arranged in the order of the tip tool mounting portion, the transmission portion, and the second contact portion in the front-rear direction, and the output shaft portion is arranged in the order of the tip tool mounting portion, the transmission portion, and the second contact portion. When located at the first position, it is preferable that at least a portion of the first abutting part be located closer to the tip tool mounting part than the second abutting part.
It is preferable that the apparatus further include a housing that supports the output shaft part, and that a biasing member that biases the output shaft part forward is provided between the output shaft part and the housing.
It is preferable that the first contact part is configured to be able to come into contact with the transmission part at a position inward in the radial direction of the output shaft part from a position where the second contact part contacts the transmission part.
It is preferable that the output shaft portion has a shaft extending in the front-rear direction, and that the first contact portion is provided on the shaft and has an outer diameter larger than an outer diameter of the shaft.
The drive part has a cylindrical shape in which a first engagement part extending in the front-rear direction is formed on an inner peripheral surface, and the output shaft part is inserted into the drive part and has a first engagement part extending in the front-rear direction on an outer peripheral surface. 2 engaging portions are formed, and the transmitting portion includes a plurality of first plates formed in a disc shape and having a first engaged portion that engages with the first engaging portion, and the second engaging portion. a plurality of second plates formed in a disc shape and having a second engaged part that engages with the first plate, and the first plate and the second plate are alternately stacked in the front-rear direction. It is preferable.
It is preferable that the driving force is transmitted to the output shaft part by a frictional force generated between the first plate and the second plate when the transmission part is pressed.
It is preferable that the area of the first plate in the front-rear direction is less than half the area of the second plate in the front-rear direction.
The drive section has a cylindrical shape with an opening formed on a side opposite to the second contact section with respect to the transmission section, the transmission section is accommodated in the drive section, and the output shaft section has the A pressing portion is provided that projects outward in the radial direction of the output shaft portion and presses the transmission portion through the opening as the output shaft portion moves in the front-rear direction, and the pressing portion has a pressing portion that presses the transmission portion toward the transmission portion. It is preferable that a recessed groove is formed.

According to the power tool of the present invention, it is possible to suppress rotation of the output shaft portion that is not intended by the operator.

1 is a cross-sectional side view showing the internal structure of a screw tightening machine according to an embodiment of the present invention. 1 is a cross-sectional side view showing the internal structure of a gear housing of a screw tightening machine according to an embodiment of the present invention. It is a figure which shows the outer plate and inner plate of the multi-plate friction clutch of the clutch part of the screw tightening machine based on embodiment of this invention, (a) is a front view of an outer plate, (b) is a front view of an inner plate. It is. 2A and 2B are diagrams illustrating the operation of the screw tightening machine according to the embodiment of the present invention during work, in which (a) shows no load, and (b) shows a state in which the operator is pressing the tip tool against the fastener. has been done. It is a figure explaining the operation|movement at the time of a conventional screw tightening machine's work, (a) shows a state in which there is no load, and (b) shows a state in which the operator is pressing the tip tool against the fastener. It is a figure which shows the outer plate and inner plate of the multi-plate friction clutch of the clutch part of the conventional screw tightening machine, (a) is a front view of an outer plate, (b) is a front view of an inner plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A screw tightening machine 1, which is an example of a power tool according to an embodiment of the present invention, will be described below with reference to FIGS. 1 to 6. The screw tightening machine 1 is an electric power tool for screwing plate materials such as gypsum boards to ceilings and walls, for example.

In the following description, "front" shown in the figures is defined as the front direction, "rear" as the rear direction, "top" as the upward direction, and "bottom" as the downward direction. Furthermore, when the screw tightening machine 1 is viewed from the rear, "right" is defined as the right direction, and "left" is defined as the left direction. Furthermore, regarding rotatable members, rotation in the clockwise direction when viewed from the rear of the screw tightening machine 1 is defined as "normal rotation", and rotation in the counterclockwise direction is defined as "reversal". Note that when referring to dimensions, numerical values, etc. in this specification, we do not mean only dimensions and numerical values that completely match the dimensions, numerical values, etc., but also dimensions and numerical values, etc. that almost match (for example, within the range of manufacturing error). ) shall be included. "Identical", "orthogonal", "parallel", "coinciding", "flush", "same diameter", etc. are also "substantially identical", "substantially orthogonal", "substantially parallel", "substantially coincident", etc. This includes "substantially flush", "substantially the same diameter", etc.

As shown in FIG. 1, the screw tightening machine 1 includes a housing 2, a motor 3, a control section 4, a clutch section 5, and a tip tool P that can be attached and detached and centered around an axis B that extends in the front-rear direction. It mainly includes a rotatable output shaft portion 6 and a coil spring 7.

The housing 2 forms the outer shell of the screw tightening machine 1 and mainly includes a motor housing 21, a handle housing 22, a gear housing 23, and a cover 24.

The motor housing 21 has a cylindrical shape extending in the front-rear direction, and houses the motor 3 and the control unit 4. A plurality of intake ports are formed at the rear of the motor housing 21 (not shown).

The handle housing 22 is formed into a substantially U-shape when viewed from the side, and includes a grip portion 221 , a first connection portion 222 , and a second connection portion 223 .

The grip portion 221 is a portion that is gripped by the operator during work. The grip portion 221 forms the rear portion of the handle housing 22 and extends in the vertical direction. A trigger switch 22A operated by an operator is provided at the upper front portion of the grip portion 221, and a switch mechanism 22B electrically connected to the control portion 4 is provided inside the grip portion 221. The switch mechanism 22B sends a tool start signal to the control unit 4 to start the motor 3 when the trigger switch 22A is pulled or started (for example, pushed into the grip part 221 by an operator's finger). When the pull operation on the trigger switch 22A is released, that is, the pull operation is stopped (for example, when the operator releases the pull operation by releasing his/her finger from the trigger switch 22A), a tool start signal is output to the control unit 4. is configured to stop.

The first connecting part 222 connects the upper part of the grip part 221 and the rear upper part of the motor housing 21, and extends in the front-rear direction.

The second connecting part 223 connects the lower part of the grip part 221 and the rear lower part of the motor housing 21, and has a substantially cylindrical shape extending in the front-rear direction. The second connection section 223 is provided with a changeover switch 22C electrically connected to the control section 4. The changeover switch 22C is a lever switch for switching the rotation direction (normal rotation and reverse rotation) of the motor 3 during work, and is provided on the right side surface of the second connection portion 223. In this embodiment, when the selector switch 22C is turned clockwise on the paper in FIG. The direction is configured to be switched to "reverse".

Further, a power cord 2A that is connected to an external power source (for example, a commercial AC power source), which is not shown, extends from the rear lower part of the second connecting portion 223. In this embodiment, when the trigger switch 22A is pulled, power is supplied to the motor 3 from an external power source (not shown) via the power cord 2A.

The gear housing 23 is formed in a substantially funnel shape that extends in the front-rear direction and tapers forward from the rear end. The rear part of the gear housing 23 is connected to the front end of the motor housing 21 via a plurality of screws 2B (the fact that a plurality of screws 2B are provided is not shown). The gear housing 23 houses the front part of the motor 3, the clutch part 5, the rear part of the output shaft part 6, and the coil spring 7. Further, a plurality of exhaust ports (not shown) are formed at the rear portion of the gear housing 23.

The cover 24 is made of resin and has a substantially funnel shape that tapers forward from its rear end. The cover 24 is fitted into the gear housing 23 so as to cover the outer peripheral surface of the front portion of the gear housing 23.

Further, as shown in FIG. 2, a spring clutch 25 is fixed inside the gear housing 23. The spring clutch 25 has a substantially cylindrical shape extending in the front-rear direction, and the output shaft portion 6 is inserted therethrough. The spring clutch 25 is configured to be able to switch between regulating and allowing normal rotation of the output shaft portion 6 depending on the position of the output shaft portion 6 in the front-rear direction. The spring clutch 25 includes a first cylindrical portion 25A, a second cylindrical portion 25B, and a spring 25C.

The first cylindrical portion 25A has a substantially cylindrical shape extending in the front-rear direction. The first cylindrical portion 25A is fixed to the inside of the front portion of the gear housing 23 by press fitting. The output shaft portion 6 is inserted through the first cylindrical portion 25A.

The second cylindrical portion 25B is disposed immediately after the first cylindrical portion 25A, and has a substantially cylindrical shape extending in the front-rear direction. The second cylindrical portion 25B is rotatable relative to the first cylindrical portion 25A. The output shaft portion 6 is inserted through the second cylindrical portion 25B. Further, the second cylindrical portion 25B is provided with a plurality of claws 25D that protrude rearward from the rear end at predetermined intervals in the circumferential direction of the second cylindrical portion 25B. (not shown).

The spring 25C is wound so as to span the rear part of the first cylindrical part 25A and the front part of the second cylindrical part 25B, and when the second cylindrical part 25B is about to rotate forward relative to the first cylindrical part 25A, The diameter is reduced to restrict rotation (normal rotation) of the second cylindrical portion 25B relative to the first cylindrical portion 25A, and when the second cylindrical portion 25B is about to reverse relative to the first cylindrical portion 25A, the diameter is expanded and the second cylindrical portion 25B is It is configured to allow rotation (reversal) of the cylindrical portion 25B with respect to the first cylindrical portion 25A.

The motor 3 is a brushless motor configured to be able to switch the rotation direction (normal rotation and reverse rotation). The motor 3 includes a rotating shaft 31, a pinion 32, a rotor 33, a stator 34, a sensor board 35, and a fan 36. The motor 3 is an example of a "drive source" in the present invention. Note that the motor 3 may be a brushed motor.

The rotating shaft 31 extends in the front-rear direction. The rear end of the rotating shaft 31 is supported by the motor housing 21 via a bearing 31B, and the front end of the rotating shaft 31 is supported by the gear housing 23 via a bearing 31A. In other words, the rotating shaft 31 is rotatably supported by the housing 2 about the axis A, and is rotated by the drive of the motor 3 to generate rotational force. Here, the axis A is a line extending in the front-rear direction and passing through the axis of the rotating shaft 31. The rotational force is an example of the "driving force" in the present invention.

The pinion 32 is provided at the front end of the rotating shaft 31 so as to be rotatable together with the rotating shaft 31. Further, a fan 36 is fixed to the rear of the pinion 32 so as to be rotatable coaxially with the rotating shaft 31 . In this embodiment, as the fan 36 rotates, outside air is drawn into the housing 2 from an air intake port (not shown) formed in the motor housing 21, cooling the components of the motor 3, and cooling the gear housing. It is configured to exhaust air from an exhaust port (not shown) formed in 23.

The rotor 33 is a rotor having a plurality of permanent magnets, and is provided on the rotating shaft 31 so as to be rotatable integrally with the rotating shaft 31. Stator 34 is a stator having stator windings. Stator 34 is fixed to motor housing 21 .

The sensor board 35 is provided behind the rotor 33 and stator 34. Three magnetic sensors (not shown) are provided on the side surface of the sensor board 35 facing the rotor 33. The magnetic sensor is, for example, a Hall element. Wiring extends from the sensor board 35. The wiring is a connection line that electrically connects the sensor board 35 and the control unit 4.

As shown in FIG. 1, the control unit 4 includes a board case 40. A board (not shown) is arranged in the board case 40. Specifically, the board is arranged in the board case 40 so that both sides thereof are perpendicular to the front-rear direction, and an inverter circuit section 41, a smoothing capacitor 42, a rectifier circuit (not shown), etc. are mounted on the front surface of the board.

The inverter circuit section 41 has six switching members (not shown) for supplying power from an external power source (not shown) to the motor 3 and controlling the rotation of the motor 3. The smoothing capacitor 42 is a polar electrolytic capacitor that smoothes a full-wave rectified voltage (fluctuating DC voltage) output from a rectifier circuit (not shown).

Further, the control unit 4 selects drive signals for the six switching members of the inverter circuit unit 41 according to the operator's operations on the trigger switch 22A and the changeover switch 22C and the signals output from the magnetic sensor on the sensor board 35. It houses a control circuit that outputs signals and controls the rotational direction, rotational speed, etc. of the motor 3. The control circuit includes, for example, a microcomputer, a drive signal output circuit, and the like.

As shown in FIG. 2, the clutch section 5 includes a clutch drum 51 and a multi-disc friction clutch 52. The clutch drum 51 has a substantially cylindrical shape extending in the front-rear direction and having an opening formed at the front, and is rotatably supported about an axis B via a bearing 5A and a bearing metal 5D. Here, the axis B is a line extending in the front-rear direction and passing through the axis of the output shaft portion 6. The clutch drum 51 has a first cylindrical portion 51A, a second cylindrical portion 51B, a first connection wall 51C, a third cylindrical portion 51D, a second connection wall 51E, and a contact portion 51G. . Clutch drum 51 is an example of a "drive section" in the present invention.

The first cylindrical portion 51A has a substantially cylindrical shape extending in the front-rear direction. An inner ring portion of a bearing 5A is fixed to the outer peripheral surface of the first cylindrical portion 51A.

The second cylindrical portion 51B extends in the front-rear direction and has a substantially cylindrical shape having a larger diameter than the first cylindrical portion 51A. A one-way clutch 5B is provided on the inner peripheral surface of the second cylindrical portion 51B. The one-way clutch 5B has an outer ring portion that is fixed (press-fitted) to the inner circumferential surface of the second cylindrical portion 51B, and an inner ring portion that is restricted from normal rotation and allowed to rotate in reverse relative to the outer ring portion.

The first connection wall 51C has a substantially annular shape when viewed from the front. The first connection wall 51C extends radially inwardly of the second cylindrical portion 51B so as to connect the outer circumferential surface of the front end of the first cylindrical portion 51A and the inner circumferential surface of the rear end of the second cylindrical portion 51B. It is extending.

The third cylindrical portion 51D extends in the front-rear direction and has a substantially cylindrical shape having a larger diameter than the second cylindrical portion 51B. The clutch drum 51 is formed so that the rear part of the third cylindrical part 51D overlaps substantially the entire area of the second cylindrical part 51B in the front-rear direction (as seen in the radial direction of the clutch drum). The front end portion of the third cylindrical portion 51D is inserted into the bearing metal 5D, and a gear portion 5C having a plurality of gear teeth is provided on the outer peripheral surface of the rear portion of the third cylindrical portion 51D. The gear portion 5C meshes with the pinion 32 of the motor 3. Thereby, the rotational force from the motor 3 is transmitted to the clutch drum 51, and the clutch drum 51 is rotationally driven.

Further, the third cylindrical portion 51D is provided with an engaging portion 51F extending in the front-rear direction. The engaging portion 51F has grooves that are recessed from the inner circumferential surface of the third cylindrical portion 51D radially outward of the third cylindrical portion 51D and extend in the front-rear direction at predetermined intervals throughout the circumferential direction of the third cylindrical portion 51D. It is formed. The engaging portion 51F is an example of a “first engaging portion” in the present invention.

The second connection wall 51E has a substantially annular shape when viewed from the front. The second connecting wall 51E is configured in the radial direction of the third cylindrical portion 51D to connect the outer circumferential surface of the front end of the second cylindrical portion 51B and the inner circumferential surface of the substantially central portion of the third cylindrical portion 51D in the front-rear direction. extends inward.

The contact portion 51G has a substantially annular shape when viewed from the front. The contact portion 51G projects forward from the front surface of the second connection wall 51E, and is formed such that its projecting end surface is perpendicular to the front-rear direction. The contact portion 51G can contact the rearmost end of the multi-plate friction clutch 52 in the front-rear direction. As shown in FIG. 2, the distance between the axis B and the center of the contact portion 51G in the radial direction of the clutch drum 51 is a distance R. The contact portion 51G is an example of a “second contact portion” in the present invention.

Note that in this embodiment, the first cylindrical portion 51A, the second cylindrical portion 51B, the first connection wall 51C, the third cylindrical portion 51D, the second connection wall 51E, and the contact portion 51G are integrally formed. There is.

The multi-plate friction clutch 52 is configured to be able to transmit the rotational force of the clutch drum 51, which rotates in response to the rotational force of the motor 3, to the output shaft portion 6 by being pressed in the front-rear direction. Specifically, the multi-disc friction clutch 52 is provided between the clutch drum 51 and the output shaft section 6 in the transmission path of the driving force (rotational force) of the motor 3, and when the output shaft section 6 is moved rearward. In response to the rotational force transmitted to the clutch drum 51, the rotational force corresponding to the pressing force is transmitted to the output shaft portion 6. The multi-plate friction clutch 52 is housed in a third cylindrical portion 51D of the clutch drum 51, and includes an outer plate 52A formed in a disk shape as shown in FIG. 3(a), and an outer plate 52A formed in a disk shape as shown in FIG. 3(b). The formed inner plates 52B are stacked alternately in the front-rear direction. In this embodiment, eight outer plates 52A are provided, and nine inner plates 52B are provided. Further, as shown in FIG. 2, in this embodiment, inner plates 52B are arranged at the frontmost and rearmost ends of the multi-plate friction clutch 52. The multi-disc friction clutch 52 is an example of a "transmission section" in the present invention.

As shown in FIG. 3(a), each of the plurality of outer plates 52A is a thin metal plate and has a substantially annular shape when viewed from the front. The outer plate 52A is provided with an engaged portion 52C, and a through hole 52a is formed approximately in the center when viewed from the front. The outer plate 52A is an example of a "first plate" in the present invention.

Eight engaged portions 52C are provided at predetermined intervals (every 45 degrees) on the outer periphery of the outer plate 52A. Each of the eight engaged portions 52C protrudes radially outward from the outer plate 52A and engages with the engaging portion 51F of the third cylindrical portion 51D of the clutch drum 51. Thereby, the outer plate 52A can rotate together with the clutch drum 51 about the axis B as the rotation axis. The engaged portion 52C is an example of a “first engaged portion” in the present invention.

Further, the outer plate 52A has a transmission surface 52D. The transmission surface 52D has a substantially annular shape when viewed in the front-rear direction, and is defined on both the front and rear surfaces of the outer plate 52A. The transmission surface 52D is defined at a position closer to the engaged portion 52C than the axis B in the radial direction of the outer plate 52A.

As shown in FIG. 3(b), each of the plurality of inner plates 52B is a thin metal plate and has a substantially annular shape when viewed from the front. The inner plate 52B is provided with an engaged portion 52C, and a through hole 52b is formed approximately in the center when viewed from the front. Inner plate 52B is an example of a "second plate" in the present invention.

Six engaged portions 52E are provided at predetermined intervals (every 60 degrees) on the inner peripheral portion of the inner plate 52B. Each of the six engaged portions 52E projects inward in the radial direction of the inner plate 52B. The engaged portion 52E is an example of a “second engaged portion” in the present invention.

Moreover, the inner plate 52B has a transmission surface 52F. The transmission surface 52F has a substantially annular shape when viewed in the front-rear direction, and is defined on both the front and rear surfaces of the inner plate 52B. The transmission surface 52F is defined at the radially outer end of the inner plate 52B.

Here, in the state accommodated in the third cylindrical portion 51D, the transmission surfaces 52D and 52F of the adjacent outer plate 52A and inner plate 52B face each other in the front-rear direction. The transmission surfaces 52D and 52F receive the rotational force from the motor 3 when the multi-plate friction clutch 52 is pressed from the front and rear directions while the outer plate 52A is rotating together with the clutch drum 51 around the axis B. Contribute to the transmission of information. Specifically, when the multi-plate friction clutch 52 is pressed from the front and rear directions, the surface pressure between the transmission surfaces 52D and 52F increases. At this time, due to the frictional force (static frictional force) generated between the transmission surface 52D and the transmission surface 52F, the rotational force from the motor 3 transmitted to the outer plate 52A is transmitted to the inner plate 52B. In this way, since the rotational force is transmitted only by the frictional force generated between the outer plate 52A and the inner plate 52B, the impact generated when the clutch drum 51 and the output shaft section 6 switch from the non-transmission state to the transmission state is reduced. It is possible to suppress the occurrence of

Further, in the present embodiment, the area of the outer plate 52A in the front-rear direction is less than half the area of the inner plate 52B in the front-rear direction. Specifically, the outer plate 52A does not have a component radially inward than the transmission surface 52D. Thereby, the contact area between the outer plate 52A and the inner plate 52B is configured to be relatively small.

As shown in FIG. 2, the output shaft portion 6 has its rear portion accommodated in the gear housing 23 and its front portion extending forward from the front portion of the gear housing 23. Further, the rear part of the output shaft section 6 is inserted into the clutch drum 51. The output shaft section 6 has a spline shaft 61 and a bit mounting section 62. The output shaft section 6 is an example of the "output shaft section" in the present invention.

Further, in the present embodiment, the output shaft portion 6 is located at the position shown in FIG. 4A (hereinafter referred to as FIG. The position of the output shaft portion 6 in the front-rear direction shown in (a) is referred to as the "first position"). Further, the output shaft portion 6 moves rearward due to the force exerted in the rearward direction when the operator presses the main body of the screw tightening machine 1 toward the screw, and is moved to the position shown in FIG. 4(b). (Hereinafter, the position of the output shaft portion 6 in the front-rear direction shown in FIG. 4(b) will be referred to as the "second position"). The backward direction is an example of a "predetermined direction" in the present invention.

The bit mounting portion 62 has a substantially cylindrical shape extending in the front-rear direction, and is supported by the spring clutch 25 so as to be rotatable about the axis B and movable in the front-rear direction. A through hole 62a extending in the front-rear direction is formed in the bit mounting portion 62. The tip tool P can be attached to and detached from the through hole 62a. The bit mounting portion 62 is an example of a “tip tool mounting portion” in the present invention.

As shown in FIG. 2, the spline shaft 61 has a shaft portion 61A and a shaft collar 61B.

The shaft portion 61A has a substantially cylindrical shape extending in the front-rear direction, and is inserted into the through hole 52a of the outer plate 52A and the through hole 52b of the inner plate 52B. The front end of the shaft portion 61A is press-fitted into the through hole 62a of the bit mounting portion 62. Furthermore, an engagement portion 61C extending in the front-rear direction is provided approximately in the center of the shaft portion 61A in the front-rear direction. The engaging portion 61C has protruding portions that protrude outward in the radial direction of the shaft portion 61A from the outer circumferential surface of the shaft portion 61A and extend in the front-back direction at predetermined intervals over the entire circumferential area of the shaft portion 61A. The protruding part of the engaging part 61C is engaged with the engaged part 52E of the inner plate 52B, and when the inner plate 52B rotates, the inner plate 52B, the spline shaft 61, and the bit mounting part 62 rotate together. . The shaft portion 61A is an example of a "shaft" in the present invention. The engaging portion 61C is an example of a “second engaging portion” in the present invention.

The shaft collar 61B has a substantially cylindrical shape extending in the front-rear direction, and its inner peripheral surface is fixed to the rear end of the shaft portion 61A by press fitting, and has an outer diameter larger than the outer diameter of the shaft portion 61A. There is. The outer peripheral surface of the shaft collar 61B is fixed to the inner ring portion of the one-way clutch 5B. That is, the rear end portion of the shaft portion 61A into which the shaft collar 61B is press-fitted is supported by the second cylindrical portion 51B of the clutch drum 51 so as to be movable in the front-rear direction via the one-way clutch 5B. Thereby, the shaft portion 61A (spline shaft 61) can rotate together with the bit mounting portion 62 about the axis B as a rotation axis, and can move in the front-rear direction. Note that, as shown in FIG. 2, the distance between the axis B and the center of the shaft collar 61B in the radial direction of the shaft collar 61B is a distance r. Here, the distance r is smaller than the distance R between the axis B and the center of the contact portion 51G of the clutch drum 51 in the radial direction. The shaft collar 61B is an example of a "first contact portion" in the present invention.

In this embodiment, as shown in FIG. 4(a), when the main body of the screw tightening machine 1 is not pressed against a fastener (such as a screw) and there is no load, the end of the multi-plate friction clutch 52 is The rear surface of the inner plate 52B located at the end is in contact with the front end of the shaft collar 61B, or is not in contact with any member constituting the screw tightening machine 1 (the rear surface of the inner plate 52B located at the rear end when no load is applied) The state in which the inner plate 52B is not in contact with any member constituting the screw tightening machine 1 is omitted from illustration). On the other hand, the contact portion 51G of the clutch drum 51 and the rear surface of the inner plate 52B located at the rearmost end of the multi-plate friction clutch 52 are always separated from each other.

In other words, in this embodiment, when the output shaft portion 6 is located at the first position, the shaft collar 61B and the inner plate 52B located at the rearmost end can be in contact with each other, and the contact portion 51G and the inner plate 52B located at the rearmost end can be in contact with each other. It is configured so that it is always separated from the inner plate 52B located at the end.

Further, as shown in FIG. 2, the output shaft portion 6 is provided with a pressing portion 63. The pressing portion 63 has a substantially cylindrical shape extending in the front-rear direction, and projects radially outward of the output shaft portion 6 . The pressing portion 63 is disposed immediately after the bit mounting portion 62, and the front portion of the shaft portion 61A of the spline shaft 61 is fixed to the center portion in the radial direction by press fitting. Thereby, the pressing part 63 is rotatable about the axis B as a rotation axis together with the spline shaft 61 and the bit mounting part 62, and is movable in the front-rear direction. The pressing portion 63 presses the multi-disc friction clutch 52 through the opening in the front portion of the clutch drum 51 as the output shaft portion 6 moves rearward. A groove portion 63a is formed in the front portion of the pressing portion 63, and a protrusion portion 63B is provided in the rear portion.

The groove portion 63a is formed in the front portion of the pressing portion 63 so as to be recessed rearward from the front surface of the pressing portion 63. In other words, the groove portion 63a is depressed toward the multi-disc friction clutch 52. The groove portion 63a extends in the circumferential direction of the pressing portion 63. Further, as shown in FIG. 2, the pressing portion 63 is provided with a plurality of claws 63A that protrude forward from the bottom surface defining the groove portion 63a. The plurality of claws 63A are provided at predetermined intervals in the circumferential direction of the pressing portion 63 (illustration of the plurality of claws 63A is omitted). The plurality of claws 63A are arranged so that the pressing portion 63 is in a state where no external force is acting on the screw tightening machine 1 (in a state where the operator has not started pressing the screw tightening machine 1 main body against a fastener (screw, etc.)). When rotated together with the spline shaft 61 and the bit mounting part 62, it can engage with the plurality of pawls 25D of the second cylindrical part 25B of the spring clutch 25 of the housing 2. In this embodiment, when the output shaft portion 6 is about to rotate forward, the spring 25C of the spring clutch 25 restricts the forward rotation of the second cylindrical portion 25B relative to the first cylindrical portion 25A. The normal rotation of the output shaft portion 6 is restricted by engagement between the claw 25D and the claw 25D. On the other hand, when the output shaft section 6 is about to reverse, the spring 25C allows the second cylindrical section 25B to reverse with respect to the first cylindrical section 25A. The shaft part 6 can be reversed.

The protruding portion 63B has a substantially annular shape when viewed from the rear. The protruding portion 63B protrudes rearward from the rear surface of the outer end portion of the pressing portion 63 in the radial direction. When the tip tool P attached to the bit attachment part 62 is pressed against a fastener (such as a screw) and the pressing part 63 moves rearward together with the spline shaft 61 and the bit attachment part 62, the protrusion part 63B is a multi-plate part. It can come into contact with the front surface of an inner plate 52B located at the frontmost end of the friction clutch 52. Note that the distance between the axis B and the center portion of the protruding portion 63B in the radial direction of the pressing portion 63 is a distance R.

As shown in FIGS. 1 and 2, the coil spring 7 extends in the front-rear direction. The coil spring 7 is inserted through the first cylindrical portion 51A of the clutch drum 51, and is arranged to be expandable and contractible in the front-rear direction. The rear end of the coil spring 7 contacts the gear housing 23, and the front end contacts the rear end of the spline shaft 61, urging the spline shaft 61 (output shaft portion 6) forward. That is, the coil spring 7 is provided between the output shaft section 6 and the housing 2, and urges the output shaft section 6 forward. Therefore, when the output shaft portion 6 is located at the first position, at least a portion (front end portion) of the shaft collar 61B is located at a position closer to the bit mounting portion 62 than the contact portion 51G of the clutch drum 51. are doing. The coil spring 7 is an example of a "biasing member" in the present invention.

Next, with reference to FIGS. 1 to 4, we will explain the operation of tightening screws on a workpiece (not shown, such as a plate) using the screw tightening machine 1, and the operation of the screw tightening machine 1 during the tightening operation. explain. In addition, in FIG. 4, the position of the screw head of the screw is virtually shown by the chain line W. In the following description, unless otherwise specified, it is assumed that the direction in which the tip tool P is pressed against the screw (that is, the direction in which the screw tightening machine 1 is pushed toward the screw) is the same as the forward direction.

When tightening a screw, the operator first attaches the tip tool P to the through hole 62a of the bit attachment part 62 of the output shaft part 6, and then flips the changeover switch 22C clockwise in the paper (see Fig. 1). , performs a pull operation on the trigger switch 22A. Then, power is supplied to the motor 3 from an external power source (not shown) via the power cord 2A, and the motor 3 starts driving. When the motor 3 starts driving, the rotating shaft 31 and the pinion 32 rotate about the axis A as the center of rotation. As the pinion 32 is reversed, the clutch drum 51 rotates normally around the axis B via the gear portion 5C that meshes with the pinion 32. As the clutch drum 51 rotates in the normal direction, the plurality of outer plates 52A that are engaged (meshed) with the engaging portion 51F of the third cylindrical portion 51D of the clutch drum 51 rotate in the normal direction about the axis B as the rotation axis.

In this state, the operator engages the tip of the tip tool P with a groove (for example, a cross groove) formed in the screw head of the screw. Thereafter, the operator pushes the main body of the screw tightening machine 1 toward the screw, and presses the tip tool P against the screw. At this time, as shown in FIG. 4(b), the output shaft portion 6 (spline shaft 61, bit mounting portion 62, and pressing portion 63) moves rearward against the biasing force of the coil spring 7. When the output shaft portion 6 moves rearward, the protruding portion 63B of the pressing portion 63 and the inner plate 52B located at the frontmost end of the multi-plate friction clutch 52 come into contact. In addition, in this state, by moving the shaft collar 61B backward, the contact between the shaft collar 61B and the inner plate 52B located at the rearmost end of the multi-disc friction clutch 52 is released, and the inner plate 52B is located at the rearmost end. The inner plate 52B contacts the contact portion 51G of the clutch drum 51. That is, as the output shaft portion 6 moves rearward, the multi-plate friction clutch 52 is sandwiched between the protruding portion 63B of the pressing portion 63 and the contact portion 51G of the clutch drum 51 from the front and rear directions. At this time, the adjacent outer plate 52A and inner plate 52B of the multi-plate friction clutch 52 come into contact.

In this state, as the screw tightening machine 1 main body is further pushed into the screw, the output shaft portion 6 further moves rearward and is located at the second position, and the outer plate 52A and inner plate 52B, which are adjacent to each other in the front-rear direction, The surface pressure at the contact surfaces (transmission surfaces 52D, 52F) between the two increases. At this time, due to the frictional force generated between the outer plate 52A and the inner plate 52B as the outer plate 52A rotates forward, the rotational force of the motor 3 transmitted to the outer plate 52A is transmitted to the inner plate 52B, and the rotational force of the motor 3 is transmitted to the inner plate 52B. The output shaft portion 6 rotates together with the output shaft portion 6. Then, the rotational force from the motor 3 is transmitted to the tip tool P via the bit mounting portion 62 of the output shaft portion 6, and it is possible to tighten the screw against a workpiece (not shown). Note that as the output shaft portion 6 moves rearward, the plurality of pawls 25D of the second cylinder portion 25B of the spring clutch 25 and the pressing portion 63 of the output shaft portion 6 move as shown in FIG. 4(b). Since the plurality of pawls 63A are spaced apart in the front-rear direction, the output shaft portion 6 can rotate normally.

In this state (when the output shaft portion 6 is located at the second position), the shaft collar 61B and the inner plate 52B located at the rearmost end are separated, and the contact portion 51G of the clutch drum 51 and the rearmost end are separated from each other. It is in contact with the located inner plate 52B.

Further, when the operator finishes the screw tightening work and releases the tip tool P from the screw head of the screw, the output shaft portion 6 moves forward due to the biasing force of the coil spring 7. As a result, the pressure on the multi-plate friction clutch 52 in the front-rear direction is released, and the surface pressure on the contact surfaces (transmission surfaces 52D, 52F) between the outer plate 52A and the inner plate 52B that are adjacent in the front-rear direction is reduced, so that the Friction generated between the plate 52A and the inner plate 52B is reduced. In this state, the multi-plate friction clutch 52 moves forward entirely within the third cylindrical portion 51D of the clutch drum 51, thereby causing the contact portion 51G between the inner plate 52B located at the rearmost end and the clutch drum 51 to move forward. The contact with the

Even if the contact between the inner plate 52B located at the rearmost end and the contact portion 51G is not released, the entire end of the shaft collar 61B will be moved forward by the urging force of the coil spring 7, and the output shaft portion 6 will be moved forward by the urging force of the coil spring 7. The inner plate 52B comes into contact with the rear surface of the inner plate 52B located at the rearmost end and pushes the inner plate 52B forward. Thereby, the contact between the contact portion 51G and the inner plate 52B located at the rearmost end is suitably eliminated, and it becomes possible to suppress rotation of the output shaft portion 6 that is not intended by the operator.

Furthermore, when loosening a screw, the changeover switch 22C is turned counterclockwise on the paper (see FIG. 1), and the trigger switch 22A is pulled. At this time, if the operator can sufficiently press the tip tool P against the screw, the output shaft portion 6 moves rearward due to the press of the tip tool P against the screw. As the pressing portion 63 of the output shaft portion 6 presses the multi-plate friction clutch 52 rearward, the surface pressure between the outer plate 52A and the inner plate 52B adjacent to each other in the front-rear direction increases. As the outer plate 52A is reversed, friction occurs between the adjacent outer plate 52A and inner plate 52B. This friction causes the inner plate 52B to reverse, and the engagement between the engaged portion 52E of the inner plate 52B and the engaging portion 61C of the spline shaft 61 causes the output shaft portion 6 to also reverse. Therefore, the rotational force from the motor 3 is transmitted to the tip tool P via the bit mounting portion 62 of the output shaft portion 6, making it possible to loosen the screw.

When loosening a screw, the screw head of the screw does not protrude from the workpiece (not shown) (for example, when the screw is buried in the workpiece), and the operator does not fully insert the tip tool P into the screw. If it cannot be pressed, the bit mounting portion 62 cannot be moved sufficiently rearward, and sufficient friction will not occur between the outer plate 52A and the inner plate 52B. In this case, the rotational force of the motor 3 cannot be transmitted from the clutch drum 51 to the output shaft section 6 via the outer plate 52A and the inner plate 52B, but since the clutch drum 51 is reversed, the rotational force of the spline shaft 61 is Rotational force is transmitted from the clutch drum 51 to the spline shaft 61 via the one-way clutch 5B that allows reversal, and the screw can be loosened. Note that since the spring 25C of the spring clutch 25 allows the second cylindrical portion 25B to be reversed with respect to the first cylindrical portion 25A, the output is not generated even though the plurality of pawls 63A and the plurality of pawls 25D of the pressing portion 63 are engaged. The shaft part 6 can be reversed.

Next, with reference to FIGS. 4 to 6, the effects of this embodiment will be described in comparison with the conventional screw tightening machine 900 shown in FIG. 5.

First, the configuration of a conventional screw tightening machine 900 shown in FIGS. 5 and 6 will be described.

As shown in FIG. 5, a conventional screw tightening machine 900 includes a housing 92, a motor 93, a clutch section 95, an output shaft section 96, and a coil spring 97.

The housing 92 has a spring clutch 925 having the same configuration as the spring clutch 25 provided in the housing 2 of the screw tightening machine 1 in this embodiment. Further, the motor 93 has the same configuration as the motor 3 of the screw tightening machine 1 in this embodiment, and includes a pinion 932.

The clutch section 95 includes a clutch drum 951 and a multi-disc friction clutch 952. The clutch drum 951 has the same configuration as the clutch drum 51 of the clutch unit 5 of the screw tightening machine 1 in this embodiment, and includes a contact portion 951A. As shown in FIG. 5, the distance between the axis B' and the contact portion 951A of the clutch drum 51 in the radial direction is a distance R'. Here, the axis B' is a line extending in the front-rear direction and passing through the axis of the output shaft portion 96. Note that the distance R' is approximately equal to the distance R in this embodiment.

The multi-plate friction clutch 952 is constructed by laminating an outer plate 952A shown in FIG. 6(a) and an inner plate 952B shown in FIG. 6(b) in the front-rear direction. Twelve outer plates 952A and twelve inner plates 952B are provided each. In the conventional screw tightening machine 900, an inner plate 952B is arranged at the front end of the multi-plate friction clutch 952, and an outer plate 952A is arranged at the rear end.

As shown in FIG. 6A, the outer plate 952A has a surface 952E in addition to a transmission surface 952C that contributes to transmitting the rotational force from the motor 3. As shown in FIG. Further, as shown in FIG. 6(b), the inner plate 952B has a surface 952F in addition to a transmission surface 952D that contributes to transmitting the rotational force from the outer plate 952A. When the multi-disc friction clutch 952 is accommodated in the clutch drum 951, the transmission surface 952C and the transmission surface 952D are opposed to each other. Furthermore, when the multi-plate friction clutch 952 is housed in the clutch drum 951, the surfaces 952E and 952F are opposed to each other.

The output shaft section 96 includes a spline shaft 961, a bit mounting section 962 to which the tip tool P' can be attached and detached, and a pressing section 963 that is provided on the bit mounting section 962 and presses the multi-disc friction clutch 952. The spline shaft 961 is provided with a shaft collar 961A.

Generally, when screwing a plate material such as a gypsum board to a ceiling, it is necessary to perform the work with the tip of the tip tool facing upward. In this case, in the conventional screw tightening machine 900, as the tip tool P' is directed upward, the outer plate 952A located at the lowest end of the multi-plate friction clutch 952, which falls under its own weight, comes into contact with the clutch drum 951. The contact portion 951A comes into contact with the portion 951A. In other words, when performing ceiling work using the conventional screw tightening machine 900, even when the screw tightening machine 900 is not pressed against the screws and there is no load, the worker does not press the main body of the screw tightening machine 900 toward the screws. Even during the pressing operation, the contact portion 951A of the clutch drum 951 is in contact with the outer plate 952A located at the lowest end. In addition, the shaft collar 961A and the outer plate 952A located at the lowermost end are separated from each other even when there is no load and when working. In this way, in the conventional screw tightening machine 900, even when there is no load, the contact portion 951A of the clutch drum 951 comes into contact with the contact portion 951A of the clutch drum 951, so when the tip tool P' is turned upward, the gap between the outer plate 952A and the inner plate 952B is removed. There was a possibility that the output shaft portion 96 would start rotating regardless of the operator's intention. Note that the following description will be made on the assumption that the work is performed with the tip tool facing upward.

On the other hand, in the screw tightening machine 1 according to the present embodiment, as shown in FIG. The front end of the clutch drum 51 and the rear surface of the inner plate 52B located at the rearmost end of the multi-plate friction clutch 52 come into contact with each other (or do not come into contact with any member constituting the screw tightening machine 1). The contact portion 51G and the rear surface of the inner plate 52B located at the rearmost end of the multi-plate friction clutch 52 are always separated from each other. Further, as shown in FIG. 4(b), when the screw tightening machine 1 is pressed against the screw, the front end of the shaft collar 61B and the rearmost end of the multi-plate friction clutch 52 While being separated from the rear end of the inner plate 52B, the contact portion 51G of the clutch drum 51 and the rear surface of the inner plate 52B located at the rearmost end of the multi-plate friction clutch 52 are in contact with each other. In other words, since the multi-disc friction clutch 52 is configured to abut different locations during no-load and during work, it is possible to suppress rotation of the output shaft portion 6 that is not intended by the operator during no-load. It is possible.

More specifically, in a configuration in which the driving force of the motor is transmitted via the frictional force generated between the clutches, such as the multi-disc friction clutch 52 in this embodiment, the transmitted torque is equal to the pressing force (frictional force). , is known to be proportional to the product of the point of application of the pressing force and the distance from the center of rotation. Here, as shown in FIG. 5, in the conventional screw tightening machine 900, the outer plate 952A is located near the position where the distance from the axis B' becomes the distance R' both in the no-load state and during operation. and the contact portion 951A of the clutch drum 951 come into contact with each other. On the other hand, in the screw tightening machine 1 according to the present embodiment, when there is no load, the inner plate 52B and the shaft collar 61B come into contact near the position where the distance from the axis B is the distance r, and during operation The inner plate 52B and the contact portion 51G of the clutch drum 51 contact each other near the position where the distance from the axis B is a distance R greater than the distance r. That is, according to the screw tightening machine 1 according to the present embodiment, when the output shaft portion 6 is in the first position and there is no load, the multi-disc friction clutch 52 is activated near the position at the short distance r from the axis B. Since it is pressed, it becomes possible to suppress rotation of the output shaft portion 6 that is not intended by the operator. On the other hand, when the output shaft portion 6 is in the second position, the multi-disc friction clutch 52 is pressed near the position R, which is a long distance from the axis B. Through this, it becomes possible to suitably transmit the rotational force of the motor 3 to the output shaft portion 6.

Further, in the present embodiment, the bit mounting portion 62, the multi-disc friction clutch 52, and the shaft collar 61B are arranged in the order of the bit mounting portion 62, the multi-disc friction clutch 52, and the shaft collar 61B in the front-rear direction. That is, when working with the tip tool P facing the ceiling (upward), the shaft collar 61B is located below the multi-plate friction clutch 52. Therefore, during no-load conditions when the output shaft portion 6 is located at the first position, it is possible to suitably bring the multi-disc friction clutch 52 into contact with the shaft collar 61B.

Further, in this embodiment, the bit mounting section 62, the multi-disc friction clutch 52, and the contact section 51G are arranged in the order of the bit mounting section 62, the multi-disc friction clutch 52, and the contact section 51G in the front-rear direction. There is. Further, when the output shaft portion 6 is located at the first position, at least a portion of the shaft collar 61B is located closer to the bit mounting portion 62 than the contact portion 51G. Therefore, in the unloaded state when the output shaft portion 6 is located at the first position, the multi-disc friction clutch 52 and the shaft collar 61B are preferably brought into contact with each other, and the multi-disc friction clutch 52 and the clutch drum 51 are brought into contact with each other in a suitable manner. It becomes possible to suitably separate the portion 51G.

Further, in this embodiment, a coil spring 7 is provided that biases the output shaft portion 6 forward. Therefore, when the output shaft portion 6 is located at the first position, it is possible to suitably position at least a portion of the shaft collar 61B at a position closer to the bit mounting portion 62 than the contact portion 51G of the clutch drum 51. It becomes possible. This allows the multi-disc friction clutch 52 and the shaft collar 61B to contact each other in a suitable manner, and the multi-disc friction clutch 52 and the clutch drum 51 to contact each other in an unloaded state when the output shaft portion 6 is in the first position. It becomes possible to suitably separate the portion 51G.

Furthermore, as described above, the transmitted torque is proportional to the product of the pressing force (frictional force) on the multi-plate friction clutch and the distance from the center of rotation of the point of application of the pressing force. In the multi-disc friction clutch 952, transmission surfaces 952C and 952D located away from the axis B' mainly contribute to the transmission of rotational force (FIG. 6). In the multi-disc friction clutch 952, a surface 952E and a surface 952F defined radially inward of the multi-disc friction clutch 952 from the transmission surface 952C and the transmission surface 952D do not contribute to the transmission of rotational force; When the outer plate 952A rotates relative to the inner plate 952B while the outer plate 952A and the inner plate 952B are in contact with each other, the outer plate 952A becomes a heat source.

In contrast, in this embodiment, the outer plate 52A is not provided with a structure corresponding to the surface 952E of the outer plate 952A. Therefore, it is possible to suppress heat generation when the outer plate 52A rotates relative to the inner plate 52B while the outer plate 52A and the inner plate 52B are in contact with each other. Furthermore, it is possible to reduce the weight of the screw tightening machine 1 body. In addition, compared to the conventional configuration, the center of gravity is located at the rear, that is, the center of gravity can be brought closer to the grip part 221 that is gripped by the operator, so it is possible to provide the screw tightening machine 1 with good operability. Become.

Further, as shown in FIGS. 4 and 5, the thickness in the front-rear direction of the outer plate 52A of the multi-plate friction clutch 52 of the screw tightening machine 1 in this embodiment is the same as that of the outer plate of the conventional screw tightening machine 900. It is thinner than the thickness of 952A in the front-rear direction. Further, the thickness of the inner plate 52B of the multi-plate friction clutch 52 in the front-rear direction is thinner than the thickness of the inner plate 952B of the conventional screw tightening machine 900 in the front-rear direction. Thereby, it becomes possible to suppress an increase in the size of the screw tightening machine 1 in the front-rear direction. Furthermore, it is possible to reduce the weight of the screw tightening machine 1 body. In addition, compared to the conventional configuration, the center of gravity is located at the rear, that is, the center of gravity can be brought closer to the grip part 221 that is gripped by the operator, so it is possible to provide the screw tightening machine 1 with good operability. Become.

Further, in the multi-plate friction clutch 952 of the conventional screw tightening machine 900, a total of 24 clutch plates are provided, including the outer plate 952A and the inner plate 952B, but in the screw tightening machine 1 according to the present embodiment, a total of 24 clutch plates are provided. A total of 17 clutch plates are provided, including an outer plate 52A and an inner plate 52B. In other words, the screw tightening machine 1 according to the present embodiment has fewer clutch plates than the conventional screw tightening machine 900. Thereby, it becomes possible to suppress an increase in the size of the screw tightening machine 1 in the front-rear direction. Furthermore, it is possible to suppress heat generation when the outer plate 52A rotates relative to the inner plate 52B while the outer plate 52A and the inner plate 52B are in contact with each other. Furthermore, it is possible to reduce the weight of the screw tightening machine 1 body. In addition, compared to the conventional configuration, the center of gravity is located further back, that is, the center of gravity can be brought closer to the grip part 221 that is gripped by the operator, so it is possible to provide the screw tightening machine 1 with good operability. becomes.

Further, in the screw tightening machine 1 according to the present embodiment, a groove portion 63a that is depressed toward the multi-disc friction clutch 52 is formed in the pressing portion 63 of the output shaft portion 6. This makes it possible to prevent water, oil, etc. from entering the clutch drum 51.

The present invention has been described above based on the embodiments. It will be understood by those skilled in the art that this embodiment is merely an example, and that various modifications can be made to the combinations of the constituent elements, and that such modifications are also within the scope of the present invention.

For example, the spring clutch 25 may not be provided in the housing 2. In the conventional screw tightening machine 900, it is necessary to provide a spring clutch 925 in order to suppress the rotation of the output shaft portion 96 during no load as described above. On the other hand, in the screw tightening machine 1 according to the present embodiment, even if the spring clutch 25 is not provided, the shaft collar 61B and the inner plate 52B are in contact with each other in the no-load state, so that the rotation of the output shaft portion 6 is prevented. This can be suitably suppressed. Further, by not providing the spring clutch 25, it is possible to reduce costs, and it is also possible to suppress the front portion of the gear housing 23 from increasing in size.

Although the present embodiment has been described using the screw tightening machine 1 as an example of a power tool, the present invention is also applicable to power tools driven by motors other than screw tightening machines.

1... Screw tightening machine 2... Housing 3... Motor 4... Control part 5... Clutch part 6... Output shaft part 7... Coil spring

Claims (9)

a driving source that generates driving force;
a drive unit rotatable around an axis extending in the front-rear direction, the drive unit being rotationally driven by the transmission of the driving force;
A power tool comprising:
The output shaft is rotatable about the axis, and is configured such that a tip tool for tightening the screw can be attached to and removed from the front of the output shaft, and the power tool is not pressed against the screw. The power tool is movable between a first position at the time of operation and a second position at the time of work in which the power tool is pressed toward the screw and a backward pressing force is applied to the output shaft portion, and an output shaft portion rotatable in response to the driving force transmitted to the driving portion while in the second position;
The drive unit is provided between the drive part and the output shaft part in the drive force transmission path, and is pressed when the rearward force acts on the output shaft part, and transmits the drive force transmitted to the drive part. A power tool comprising: a transmission unit that receives the pressing force and transmits a driving force proportional to the product of the distance from the rotation center of the point of application of the pressing force to the output shaft portion,
The output shaft section has a first contact section that can come into contact with the transmission section in the front-rear direction, and the drive section has a second contact section that can come into contact with the transmission section in the front-rear direction. ,
When the output shaft portion is located at the first position, the first contact portion and the transmission portion are in contact with each other, and the second contact portion and the transmission portion are spaced apart,
When the output shaft portion is located at the second position, the first contact portion and the transmission portion are configured to be separated from each other, and the second contact portion and the transmission portion are configured to contact each other. A power tool characterized by: The output shaft portion includes a tip tool mounting portion to which the tip tool can be attached and detached,
The tip tool attachment section, the transmission section, and the first abutment section are arranged in the order of the tip tool attachment section, the transmission section, and the first abutment section in the front-rear direction. The power tool according to item 1. The tip tool attachment section, the transmission section, and the second abutment section are arranged in the order of the tip tool attachment section, the transmission section, and the second abutment section in the front-rear direction,
When the output shaft portion is located at the first position, at least a portion of the first contact portion is located closer to the tip tool mounting portion than the second contact portion. The power tool according to claim 2. further comprising a housing that supports the output shaft portion,
4. A biasing member according to claim 1, further comprising a biasing member provided between the output shaft and the housing to bias the output shaft in a forward direction. Power tools. The first contact portion is configured to be able to come into contact with the transmission portion at a position inward in the radial direction of the output shaft portion from a position where the second contact portion contacts the transmission portion. The power tool according to any one of claims 1 to 4. The output shaft portion has a shaft extending in the front-rear direction,
The power tool according to any one of claims 1 to 5, wherein the first contact portion is provided on the shaft and has an outer diameter larger than an outer diameter of the shaft. The driving portion has a cylindrical shape in which a first engaging portion extending in the front-rear direction is formed on an inner circumferential surface,
The output shaft portion is inserted into the drive portion, and a second engagement portion extending in the front-rear direction is formed on an outer peripheral surface of the output shaft portion.
The transmission section includes a plurality of first plates formed in a disc shape and having a first engaged section that engages with the first engagement section, and a second cover that engages with the second engagement section. a plurality of second plates each having an engaging portion and formed in a disc shape, and the first plate and the second plate are alternately stacked in the front-rear direction;
7. The driving force is transmitted to the output shaft portion by a frictional force generated between the first plate and the second plate when the transmission portion is pressed. The power tool described in item (1) above. The power tool according to claim 7, wherein an area of the first plate in the front-rear direction is less than half an area of the second plate in the front-rear direction. The drive section has a cylindrical shape with an opening formed on a side opposite to the second contact section with respect to the transmission section,
The transmission section is housed in the drive section,
The output shaft portion is provided with a pressing portion that protrudes outward in the radial direction of the output shaft portion and presses the transmission portion through the opening as the output shaft portion moves in the back and forth direction,
The power tool according to any one of claims 1 to 8, wherein the pressing portion is formed with a groove that is recessed toward the transmission portion.

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