JP5047737B2 - Screw driving machine - Google Patents

Description

  The present invention is a so-called air tool that uses compressed air as a power source, and a screwdriver that has a screw set at the tip is advanced in the axial direction while rotating, and this screw is driven (tightened) into a screw driving material. Related to the machine.

For example, when a gypsum board as an upper material is screwed to a wooden board as a base, a screw driving machine capable of continuously tightening a large number of screws is used. This screw driving machine is configured to move the driver bit in the axial direction by rotating the driver bit by the thrust (driving force) of the piston using compressed air as the power source and the rotational force (screw tightening force) of the air motor. According to the above, in the movement process of the driver bit, the tip of the driver bit is fitted to the screw head of the screw connection band in which a large number of screws are connected in parallel, and the screw is detached from the screw connection band. The upper material can be screwed to the ground by penetrating the upper material into the ground while being rotated.
As a technique related to this screw driving machine, for example, techniques disclosed in the following patent documents have been publicly known. In Patent Document 1, the piston that moves the driver bit in the axial direction is divided into a main piston and a sub-piston, and is driven firmly with a large thrust at the beginning, and then rotated while being pressed with a weak thrust to have high screw resistance In this case, the air motor and a speed reduction mechanism for decelerating the output of the air motor are integrally stroked in the driving direction as the piston moves.
When the air motor and the speed reduction mechanism are integrated with the piston and move in the driving direction, the weight of the moving member increases. As a result, the reaction at the time of driving increases and the driving operation may become unstable.
On the other hand, in Patent Document 2, the air motor and the speed reduction mechanism do not move in the driving direction, and only the piston and the driver bit are moved in the driving direction, so that the reaction at the time of driving is reduced and the rotation output of the air motor is output. A technique is disclosed in which an air motor is made compact by amplifying it through a speed reduction mechanism and transmitted to a driver bit, and thus the driving machine is reduced in size and weight.
Japanese Patent No. 3793272 JP-A-11-300639

As described above, various improvements have been made in the conventional screw driving machine. However, it is necessary to further improve the conventional screw driving machine. For example, the screw driving machine is further reduced by reducing the reaction during driving. It was necessary to improve the operability of the machine.
As described above, in the screw driving machine having a configuration in which the rotation output of the air motor is decelerated by the planetary gear train and transmitted to the screwdriver screw bit, the oval two-sided width hole provided in the carrier of the planetary gear train A configuration is adopted in which the rotational power of the air motor is transmitted to the driver bit by engaging the two-sided width shaft portion of the driver bit in the rotational direction with the portion being movable in the axial direction. An object of this invention is to further reduce the reaction at the time of screwing about the screwing machine provided with the power transmission mechanism with respect to such a driver bit.

Said subject is solved by each following invention.
A first invention is a screw driving machine including an air motor that rotates a screwdriver driving bit in a screw tightening direction, a piston that moves the driver bit in a screw driving direction, and a main body housing that houses them. A gear train is provided as a speed reduction mechanism in the rotational power transmission path between the air motor and the driver bit, and the rotational power transmission shaft portion of the driver bit is inserted into the rotational power transmission hole of the gear train so that the driver bit is connected to the gear train. Rotational power with the rotational power transmission shaft portion of the driver bit in contact with the rotational power transmission hole portion at least at three points in the rotational direction. This is a screw driving machine having a configuration having a cross-sectional shape for transmitting the above.
According to the first invention , when the piston moves, the driver bit moves in the driving direction and the screw is driven. Further, when the air motor is started, the driver bit rotates in the screw tightening direction and the screw is tightened. The rotational power of the air motor is transmitted to the driver bit by integrating (engaging) the rotational power transmission shaft portion of the driver bit with the rotational power transmission hole of the gear train in the screw tightening direction. .
In the screw driving machine having such a configuration, according to the first invention , the rotational power transmission shaft portion of the driver bit is in contact with the rotational power transmission hole portion at least at three points, and the rotational power is transmitted in a three-point state. Since transmission is performed, the sliding resistance in the axial direction of the rotational power transmission shaft portion with respect to the rotational power transmission hole portion is smaller than that of a conventional rotational power transmission structure in a two-point state with a two-sided width portion. growing. This increase in axial sliding resistance reduces reaction in the driving direction (driver bit axial direction) during screw driving (relative movement in the driver bit axial direction with respect to the rotational power transmission hole of the rotational power transmission shaft portion). .
A second invention is a screw driving machine according to the first invention, wherein the cross section of the rotational power transmission shaft portion of the driver bit has an asymmetrical shape with respect to the rotational center axis of the driver bit.
According to the second aspect of the present invention , the cross-sectional shape of the rotational power transmission shaft portion of the driver bit is formed in an asymmetrical shape (a shape that is not point-symmetrical, hereinafter the same) with respect to the rotational center axis of the driver bit. The rotational power transmission shaft portion is engaged with the rotational power transmission hole portion in the rotational direction in a state where at least three points are hit. For this reason, according to the second aspect of the present invention , the rotational power of the gear train can be compared with the conventional configuration in which the rotational power is transmitted with the two-plane width shaft portion having a point-symmetrical cross section being in a two-point state. The sliding resistance in the axial direction of the rotational power transmission shaft portion of the driver bit with respect to the transmission hole portion increases, and the reaction in the driving direction during screw driving is reduced correspondingly. This could be confirmed empirically and objectively by tests on prototypes conducted by the applicant.
By adopting the astigmatic shape for the cross-sectional shape of the rotational power transmission shaft portion according to the second invention, as a result, the reaction at the time of screw driving can be reduced sensibly. The sliding resistance in the axial direction (driving direction) of the driver bit with respect to the rotational power transmission hole of the shaft portion increases, and it is considered that the reaction received by the user is reduced by consuming the increased energy. It is done.
Here, for example, the rotational power transmission shaft portion of the driver bit is a two-sided width shaft portion formed by two flat surfaces parallel to each other, and the rotational power transmission hole portion corresponding to this is two When a so-called small hole-shaped two-sided width hole formed on a flat surface is used to transmit the rotational power of the air motor to the driver bit according to the engagement state in the screw tightening direction, for example, the two-sided width shaft portion By setting the distance between the two flat surfaces from the rotation center axis of the driver bit different from each other, the cross-sectional shape of the two-surface width shaft portion can be made asymmetry. When the cross-sectional shape of the two-sided width shaft portion of the driver bit is an asymmetrical shape, the two-sided width shaft portion can be brought into a state of three points in the rotational direction with respect to the two-sided width hole portion.
As described above, in order to realize the state of at least three points of the rotational power transmission shaft portion with respect to the rotational power transmission hole portion, it is necessary to make the cross-sectional shape of the two-sided width shaft portion an asymmetrical shape. This is the most advantageous. In this respect, the rotational power transmission shaft portion can have a cross-sectional shape of point symmetry such as a triangle, a quadrangle, etc., so that at least three points can be achieved with respect to the rotational power transmission hole portion. In this case, the production cost increases.
According to a third invention, in the second invention, the rotational power transmission hole portion is a two-sided width hole portion formed by two flat surfaces parallel to each other, and the rotational power transmission shaft portion is two flat surfaces parallel to each other. As the two-surface width shaft portion formed by the surface, the two-surface width shaft portion is axially movable and integrated with respect to the two-surface width hole portion, and the two flat surfaces of the two-surface width shaft portion are integrated. This is a screw driving machine that is provided at different intervals with respect to the rotation center axis of the driver bit and has a configuration in which the cross-sectional shape of the two-sided width shaft portion has an asymmetrical shape with respect to the rotation center axis.
According to the third invention , the rotational power is transmitted from the gear train to the driver bit by the two-sided width shaft portion as the rotational power transmission shaft portion. The two flat surfaces parallel to each other of the two-surface width shaft portions are provided at different intervals with respect to the rotation center axis, so that the cross-sectional shape of the two-surface width shaft portion is set to an astigmatic shape. In this way, the transverse cross-sectional shape of the two-plane width shaft portion is provided asymptotically about the rotation center axis, so that the rotational power is transmitted in a state of hitting at least three points in the rotation direction with respect to the insertion hole. The sliding resistance in the driver bit axial direction with respect to the insertion hole of the two-surface width shaft portion increases, and the reaction at the time of screw tightening is reduced.
In a fourth aspect based on the third aspect, one flat surface is set to 65% to 75% of the other flat surface with respect to the distance from the rotation center axis of the two flat surfaces of the two-surface width shaft portion. It is a screw driving machine.
According to the fourth aspect of the present invention , the state between at least three points between the two flat width shaft portions is realized by slightly increasing the distance between the flat surface of the double flat width portion and the flat surface of the double flat width portion. Thus, the above-described effects can be obtained without impairing the workability of the rotational power transmission shaft portion (double width shaft portion).
According to a fifth invention, in the second invention, the rotational power transmission hole is a two-surface width portion formed by two flat surfaces parallel to each other, and the rotational power transmission shaft portion is formed by two flat surfaces. The two-surface width shaft portion is integrated with respect to the two-surface width shaft portion so that the two-surface width shaft portion can move in the axial direction and rotate about the axis. This is a screw driving machine that is provided with an angle and has a configuration in which the cross-sectional shape of the two-surface width shaft portion has an asymmetrical shape with respect to the rotation center axis.
According to the fifth aspect, the rotational power is transmitted from the gear train to the driver bit by the two-sided width shaft portion as the rotational power transmission shaft portion. By providing the two flat surfaces of the two-surface width shaft portion in an angled state (not parallel to each other), the cross-sectional shape of the two-surface width shaft portion is set to an astigmatic shape. . In this way, the cross-sectional shape of the two-surface width shaft portion is provided in an astigmatic shape with the rotation center axis as the center, thereby realizing a state corresponding to at least three points of the two-surface width shaft portion with respect to the two-surface width hole portion. As a result, the sliding resistance in the driving direction between the two increases, and the reaction during screw tightening is reduced.
A sixth invention is a screw driving machine including an air motor that rotates a screwdriver driving bit in a screw tightening direction, a piston that moves the driver bit in a screw driving direction, and a main body housing that accommodates the piston. A gear train is provided as a speed reducing mechanism in the rotational power transmission path between the air motor and the driver bit, and the two-sided width shaft portion of the driver bit is inserted into the two-sided width hole provided in the gear train, so that the driver bit is It is axially movable with respect to the gear train and integrated with respect to rotation around the shaft, and is asymmetric with respect to the cross-sectional shape of one or both of the two-sided width shaft portion of the driver bit and the two-sided width hole portion of the gear train. The screw driving machine is configured to transmit the rotational power in a state where the shapes are in contact with each other at least at three points.
According to the sixth aspect of the present invention , the two-surface width shaft portion is axially movable with respect to the two-surface width hole portion and integrated with respect to the rotation around the shaft, so that the pressing force in the screw driving direction of the piston and the air motor Rotational power is transmitted to the driver bit. In such a configuration, one or both of the cross-sectional shape of the two-sided width hole portion and the cross-sectional shape of the two-sided width shaft portion are made astigmatic, so that at least three points in the rotational direction between the two. The sliding resistance in the axial direction is increased by abutting, and thereby the reaction at the time of screw driving can be reduced.

Next, an embodiment of the present invention will be described with reference to FIGS. FIG.1 and FIG.2 has shown the non-operation state (initial state) of the screw driving machine 1 which concerns on this embodiment. The screw driving machine 1 includes a main body portion 2 having a substantially cylindrical body shape, and a handle portion 3 provided so as to protrude sideways from substantially the center in the longitudinal direction of the main body portion 2. A trigger valve 4 is disposed near the base of the handle portion 3. The trigger valve 4 is opened and closed by a trigger 5 that is pulled by a user with a fingertip. Since the trigger valve 4 itself is the same as that conventionally known and does not require any particular change in the present embodiment, a detailed description of its configuration and operation is omitted.
When the user pulls the trigger 5, one screw S is driven into the screw driving material W from the tip (lower end in FIG. 1) of the main body 2. The screw driving material W has a two-layer structure of an upper material W1 and a base W2. The upper material W1 is, for example, a gypsum board, and the base W2 is a wooden board or a steel plate.
An air hose 6 for supplying compressed air serving as a power source of the screw driving machine 1 is connected to the tip of the handle portion 3. Compressed air is supplied from the air hose 6 to the pressure accumulating chamber 7 inside the handle portion 3. Further, an exhaust pipe 8 is attached inside the handle portion 3 along the longitudinal direction thereof. One end side (exhaust port 8 a) of the exhaust pipe 8 is opened at the distal end portion of the handle portion 3. The other end of the exhaust pipe 8 communicates with an exhaust chamber 8 b provided in the main body 2.
Between the lower part of the main body part 2 and the tip part of the handle part 3, a magazine 11 for accommodating a screw connection band (not shown) holding a number of screws S to S in parallel, and a screw pulled out from the magazine 11 A screw connection band feed mechanism 12 for pitch-feeding the connection band to the main body 2 side is provided.

The main body 2 includes an impact mechanism 20, an air motor 50, and a speed reduction mechanism 70 in order from the upper side in FIG. 1. As shown in the drawing, the striking mechanism portion 20 is disposed on the upper side with respect to the handle portion 3, and the air motor 50 and the speed reducing mechanism portion 70 are disposed on the lower side.
The striking mechanism 20 includes a cylinder 21 and a piston 22 accommodated therein. The piston 22 is accommodated in the cylinder 21 so as to reciprocate up and down in the drawing. Hereinafter, an upper chamber that is an air chamber inside the cylinder 21 and is hermetically partitioned by the piston 22 is referred to as a cylinder upper chamber 24, and a lower chamber is referred to as a cylinder lower chamber 25.
The cylinder 22 is held immovably inside the holding sleeve 27. The holding sleeve 27 is fixed to the main body housing 2 a of the main body 2.
At the center of the lower surface of the piston 22, an upper end portion of the driver bit 23 is coupled so as to be rotatable around its axis and not movable in the axial direction. The driver bit 23 extends from the center of the lower surface of the piston 22 downward (in the screw driving direction) and reaches the vicinity of the tip of the main body 2.
A cylindrical head valve 30 is disposed on the outer periphery of the holding sleeve 27. Details of the head valve 30 and its surroundings are shown in FIG. FIG. 3 shows a state in which the trigger 5 is started to be pulled from the initial state shown in FIGS. 1 and 2, the head valve 30 starts to open, the air motor 50 starts to rotate, and the damper 26 is moved upward. Operations from these initial positions will be described later.
Compression springs 31 to 31 are interposed between the head valve 30 and the head housing 2b. The head valve 30 is always urged downward (closed side) by the compression springs 31-31. In addition, on the upper surface side (head valve upper chamber 30a) of the head valve 30, the state is switched between a state where the compressed air in the pressure accumulating chamber 7 acts via the trigger valve 4 and a state where the compressed air is released to the atmosphere and does not act. . The air pressure action state of the head valve upper chamber 30a is switched by the operation of the trigger 5 and the operation of the trigger valve 4.

On the other hand, an outer pressure receiving surface 30e and an inner pressure receiving surface 30f, which are inclined in the direction of decreasing the thickness, are respectively provided at the lower part of the head valve 30 over the entire circumference. The compressed air of the pressure accumulating chamber 7 always flows into the head valve lower chamber 30d defined below the pressure receiving surface 30e on the outer peripheral side. For this reason, the air pressure of the compressed air always acts on the pressure receiving surface 30e. The compressed air pressure acting on the pressure receiving surface 30e acts in a direction to move the head valve 30 upward.
When the trigger valve 4 is turned on by pulling the trigger 5, the compressed air in the head valve upper chamber 30a is exhausted and released to the atmosphere. The urging force of the compression springs 31 to 31 is set to be smaller than the pressure of the compressed air acting on the pressure receiving surface 30e of the head valve 30. For this reason, when the trigger valve 4 is turned on, the head valve 30 is moved up against the compression springs 31 to 31 by the compressed air pressure acting on the pressure receiving surface 30e.
When the head valve 30 is moved upward, the inner peripheral side vent chamber 30b is changed to the outer peripheral side head valve lower chamber 30d at an initial stage (half-open state) where the lower end of the head valve 30 starts to open between the upper surface of the valve seat portion 35. As a result, compressed air flows into the ventilation chamber 30b. The ventilation chamber 30 b communicates with the air motor 50 through the ventilation chamber 32. For this reason, at the initial stage when the head valve 30 starts to open, the air motor 50 starts to rotate first. Details of the air motor 50 will be described later.
The compressed air that has flowed into the ventilation chamber 30b acts on the pressure-receiving surface 30f on the inner peripheral side of the head valve 30, so that the head valve 30 moves up at once and is fully opened. FIG. 7 shows a state where the head valve 30 is fully opened. When the head valve 30 is fully opened, an air passage is opened with the seal ring 27a attached to the outer periphery of the upper portion of the holding sleeve 27, and the air chamber 30c on the inner peripheral side of the head valve 30 is communicated with the air chamber 30b. Compressed air flows into the ventilation chamber 30c. The compressed air that has flowed into the ventilation chamber 30 c flows into the cylinder upper chamber 24 through the flow rate switching valve 40 mounted on the upper portion of the cylinder 21. Thus, when compressed air flows into the cylinder upper chamber 24, the piston 22 moves downward. When the piston 22 moves downward, the driver bit 23 moves downward along its axial direction.
When the driver bit 23 moves downward, its tip is engaged with the head of one screw S of the screw connection band supplied from the magazine 11, and after removing the screw S from the screw connection band as it is, the screw driving material W is driven into. The driving force of the driver bit 23 (the thrust of the piston 22) can be switched between large and small by switching the intake flow rate to the cylinder upper chamber 24 by a flow rate switching valve 40 described below.

Details of the flow rate switching valve 40 are also shown in FIGS. The flow rate switching valve 40 includes a generally disc-shaped valve pedestal portion 41 that is fixed in a state where the upper end portion of the cylinder 21 is airtightly closed, a valve main body 42, and a switching lever 43 that changes the relative position of both. .
The valve pedestal portion 41 is fitted into the upper end portion of the cylinder 21 opened in a mortar shape, and is not movable in the axial direction and is pivoted around the shaft while being sandwiched between the upper end portion of the cylinder 21 and the head housing 2b. It is fixed in a non-rotatable state. The valve pedestal portion 41 has moderate elasticity and functions as a damper (cushion body) that regulates the upper moving end (top dead center) of the piston 22 and absorbs an impact when moving upward. Also have. The valve pedestal 41 is provided with reference vent holes 41a to 41a penetrating in the plate thickness direction. In the present embodiment, the three reference vent holes 41a to 41a are arranged at circumferentially equally divided positions (120 ° intervals). As shown in FIGS. 12 and 15, each reference vent hole 41a is opened in a fan shape, and the opening area thereof is relatively large.
The valve main body 42 has a substantially disk shape facing the upper surface of the valve pedestal portion 41, and a support shaft portion 42c is integrally provided at the center of the upper surface. The valve main body 42 is supported by the head housing 2b via the support shaft portion 42c so as to be rotatable about its axis and parallelly movable within a certain range in the axial direction. The support shaft portion 42c passes through the head housing 2b and protrudes into a recess 2c provided on the outer surface of the head housing 2b. A switching lever 43 is attached to the protruding portion. The switching lever 43 is fixed to the tip of the support shaft part 42c with a screw 45. The position of the valve body 42 around the support shaft portion 42 c can be easily switched from the outside by the turning operation of the switching lever 43. As shown in FIGS. 10 and 13, the recess 2 c of the head housing 2 b is formed in a fan shape that opens at about 60 ° in plan view. The switching lever 43 is accommodated so as not to protrude from the recess 2b. For this reason, the switching lever 43 is tilted within a range of about 60 °. The valve body 42 is rotated in a range of about 60 ° by tilting the switching lever 43 by about 60 °.

The valve main body 42 is provided with three large vent holes 42a to 42a and three small vent holes 42b to 42b penetrating in the plate thickness direction. The three large vent holes 42a to 42a are arranged at the three-way positions in the circumferential direction around the support shaft portion 42c. In the present embodiment, each large vent 42a is formed in a fan shape having the same size as the reference vent 41a on the valve seat 41 side. The three small ventilation holes 42b to 42b are also arranged at the three-way positions in the circumferential direction around the support shaft portion 42c. Each small vent 42b is arranged at the center between two large vents 42a, 42a adjacent in the circumferential direction. Accordingly, the three large vent holes 42a to 42a and the three small vent holes 42b to 42b are alternately arranged at intervals of 60 ° on substantially the same circumference. For this reason, when the switching lever 43 is tilted within a range of about 60 °, the large ventilation hole 42a is aligned with each of the three reference ventilation holes 41a to 41a of the valve seat 41 (shown in FIG. 12). State) and a state where the small vents 42b are aligned (state shown in FIG. 15).
In the state in which the large ventilation holes 42 a to 42 a are aligned with the reference ventilation holes 41 a to 41 a of the valve seat 41 and the state in which the small ventilation holes 42 b to 42 b are aligned, the inner circumference side of the head valve 30 is arranged. The flow path areas between the ventilation chamber 30c and the cylinder upper chamber 24 are greatly different. The flow path area is smaller in the latter case than in the former case. In the former case, the total area of the three large vent holes 42a to 42a (in this embodiment, approximately equal to the total area of the three reference vent holes 41a to 41a) is the flow path area, and in the latter case, the three small vent holes The total area of the pores 42b to 42b is the flow path area.
For this reason, in the former case, the amount of compressed air flowing into the cylinder upper chamber 24 per unit time increases, and the thrust of the piston 22 increases, so that the driving force of the screw S increases. As will be described later, this case is suitable when the base W2 is a steel plate (steel plate mode).

On the other hand, in the latter case, the flow passage area is reduced, and the amount of compressed air flowing into the cylinder upper chamber 24 per unit time becomes smaller, and as a result, the thrust of the piston 22 is smaller than in the former case. Therefore, the driving force of the screw S is reduced. This case is suitable when the base W2 is a wood board (wood board mode).
As described above, the screw driving machine 1 of the present embodiment includes the flow rate switching valve 40 for adjusting the driving force of the screw S. According to this flow rate switching valve 40, the amount of compressed air flowing into the cylinder upper chamber 24 can be switched in two stages, so that an optimum driving force can be achieved for both so-called steel plate driving and wood plate driving. It is possible to perform the driving work. FIG. 10 shows a state in which the switching lever 43 is switched to a steel plate mode suitable for steel plate driving, and FIG. 11 shows a state in which the switching lever 43 is switched to a wood board mode suitable for wood board driving.
Position holding convex portions 2d and 2e for holding the switching lever 43 at the steel plate mode position and the wood plate mode position are provided at the bottom of the concave portion 2c. On the other hand, the valve body 42 is urged in a direction (downward in the drawing) to be pressed against the valve pedestal portion 41 by a compression spring 44 interposed between the valve body 42 and the head housing 2b. For this reason, the lever 43 integrally attached to the support shaft part 42c of the valve body 42 is in a state of being urged in a direction to be pressed against the position holding convex parts 2d and 2e of the concave part 2c by the urging force of the compression spring 44. ing. Due to the urging force of the compression spring 44, the elastic engagement state of the lever 43 with respect to the position holding convex portions 2d and 2e is held, and an appropriate movement resistance is given. By giving this movement resistance, the switching lever 43 is elastically held at the respective positions to prevent inadvertent movement.

Next, the valve main body 42 is urged by the compression spring 44 in a direction in which the valve main body 42 is pressed against the valve pedestal 41. In the case of the steel plate mode, since the large vent holes 42a to 42a having substantially the same opening area are aligned with the three reference vent holes 41a to 41a of the valve seat 41, the piston 22 is moved upward. The compressed air pressure in the cylinder upper chamber 24 hardly acts on the valve body 42. For this reason, when the piston moves up in the steel plate mode, the valve main body 42 is maintained in a state of being pressed against the upper surface of the valve pedestal 41, and accordingly, inflow of compressed air into the cylinder upper chamber 24 and exhaust from the cylinder upper chamber 24. In any case, the total area of the three reference vent holes 41a to 41a is used as the flow path area.
On the other hand, in the case of the wood board mode shown in FIGS. 13 to 16, the small vent holes 42 b to 42 b have a sufficiently smaller opening area than the three reference vent holes 41 a to 41 a of the valve seat 41. 42b is aligned. Therefore, as shown in FIG. 14, the lower surface of the valve main body 42 is exposed in the cylinder upper chamber 24 in each reference vent hole 41 a. This exposed portion acts as a pressure receiving surface 42d that receives the compressed air pressure in the cylinder upper chamber 24 when the piston moves up, so that the compressed air pressure in the cylinder upper chamber 24 acts on the valve body 42. In this case, the compressed air pressure in the cylinder upper chamber 24 acts in a direction in which the valve body 42 is moved up against the compression spring 44. The urging force of the compression spring 44 is appropriately set so that the valve main body 42 can move up by the compressed air pressure in the cylinder upper chamber 24 when the piston 22 moves up.
As shown in FIG. 16, when the valve main body 42 moves up against the compression spring 44, the valve main body 42 is separated from the upper surface of the valve pedestal 41 and a gap 42e is generated between them. Through this gap 42e, the piston upper chamber 24 communicates with three large vent holes 42a to 42a in addition to the three small vent holes 42b to 42b of the valve body 42.
Thus, in the case of the steel plate mode shown in FIGS. 10 to 12, the large vent hole 42 a of the valve body 42 is aligned with each of the reference vent holes 41 a to 41 a of the valve pedestal portion 41. The intake flow rate per unit time to the cylinder upper chamber 24 during operation increases and a large driving force is obtained, and a sufficient amount of exhaust per unit time from the cylinder upper chamber 24 during piston movement is ensured. Thus, high exhaust efficiency can be ensured and a smooth upward movement of the piston 22 can be obtained.
On the other hand, in the wood board mode shown in FIGS. 13 to 16, the intake flow rate per unit time to the cylinder upper chamber 24 when the piston moves downward is reduced to obtain a weak driving force suitable for wood board driving. On the other hand, when the piston moves up, the valve body 42 moves against the compression spring 44, so that the flow passage area is automatically expanded and high exhaust efficiency is ensured. Smooth upward movement is ensured.

Exhaust gas is returned to the ventilation chamber 30 c on the inner peripheral side of the head valve 30 through the flow rate switching valve 40. In this case, since the head valve 30 is moved downward and closed with respect to the holding sleeve 27, the ventilation chamber 30c is airtightly blocked from the ventilation chamber 30b and the head valve lower chamber 30d. Therefore, the exhaust is exhausted to the exhaust chamber 30 h on the outer peripheral side of the head valve 30 through the exhaust holes 30 g to 30 g provided in the head valve 30. The exhaust chamber 30 h communicates with the exhaust chamber 8 b through an exhaust path (not shown), and thus communicates with the exhaust pipe 8 in the handle portion 3. Exhaust gas (compressed air) flowing into the exhaust pipe 8 is exhausted to the atmosphere through the exhaust port 8a.
A plurality of exhaust holes 21 a to 21 a are provided on the peripheral surface of the upper side of the cylinder 21. The exhaust holes 21a to 21a are airtightly closed only in one direction (intake side) by a seal ring 28 mounted on the outer peripheral side (check valve). Therefore, the cylinder upper chamber 24 is exhausted by the exhaust holes 21a to 21a in addition to the flow rate switching valve 40 when the piston moves up. The compressed air exhausted from the exhaust holes 21a to 21a flows into the ventilation chamber 30c in the same manner as the exhaust gas having passed through the flow rate switching valve 40, and is then exhausted to the exhaust chamber 30h through the exhaust holes 30g to 30g.
When the piston moves downward, the cylinder lower chamber 25 is exhausted through a plurality of return holes 21 b to 21 b provided on the lower peripheral surface of the cylinder 21. The return holes 21 b to 21 b are opened in a return air chamber 29 that is airtightly partitioned between the cylinder 21 and the holding sleeve 27. As will be described later, compressed air flows into the return air chamber 29 from the vent chamber 33 through the return holes 21b to 21b when the piston 22 reaches the bottom dead center and the damper 26 is opened. The compressed air flowing into the return air chamber 29 is returned to the cylinder lower chamber 25 through the return hole 21b again when the piston 22 moves upward, and is used as an operating source for moving the piston 22 upward.

Next, the lower end position (bottom dead center) of the piston 22 is regulated by the damper 26. Details of the configuration of the damper 26 and its periphery are shown in FIGS. The damper 26 is an elastic body that hermetically closes the lower end portion of the cylinder 21 and is supported so as to be displaceable in the piston movement direction (vertical direction in FIG. 4) within a certain range in this embodiment. An insertion hole 26 a is provided through the center of the damper 26. The driver bit 23 is inserted into the insertion hole 26a so as to be movable in the axial direction and rotatable about the axis.
The damper 26 includes a substantially truncated cone-shaped main body portion 26b and a support shaft portion 26c extending downward from the center of the lower surface of the main body portion 26b. The upper part of the main body part 26b is formed in a truncated cone shape that is inclined in a direction of a smaller diameter as the peripheral surface thereof reaches the upper side. The cylinder lower chamber 25 is hermetically sealed from a later-described vent chamber 33 by pressing the peripheral surface of the main body 26b against the inclined surface 21c formed in the lower opening of the cylinder 21.
The support shaft portion 26c of the damper 26 passes through the insertion hole 61a of the first frame body 61 fixed to the main body housing 2a, and below the support hole 60a of the second frame body 60 fixed to the main body housing 2a. It is inserted and supported so that it can move in the direction. On the second frame 60, a rotary shaft 51 on the upper side of an air motor 50 described later is rotatably supported via a bearing 53.
As shown in FIG. 9, the damper 26 is displaced downward by the thrust of the piston 22 while absorbing the impact when the piston 22 reaches the lower moving end position. In the present embodiment, the position displaced downward is the initial position of the damper 26. As will be described later, when the piston 22 reaches the bottom dead center and the damper 26 is displaced downward, the cylinder lower chamber 25 communicates with the vent chamber 33, whereby compressed air is supplied to the cylinder lower chamber 25 from the vent chamber 33. This flows into the return air chamber 29 through the return hole 21b.
A convex portion 26d having a semicircular cross section is provided on the entire lower surface of the main body portion 26b and around the support shaft portion 26c. The upper surface of the first frame 61 is located below the convex portion 26d. As the trigger 5 is pulled, the damper 26 is displaced upward as shown in FIG. 4, so that the convex portion 26 d is separated from the upper surface of the first frame 61. In this state, the ventilation chamber 33 on the outer peripheral side of the convex portion 26d is in communication with the inside of the insertion hole 61a. As will be described later, the ventilation chamber 33 communicates with the ventilation chamber 30 b on the inner peripheral side of the head valve via the ventilation chamber 32. For this reason, when the head valve 30 is opened, compressed air is supplied to the ventilation chamber 33 at an initial stage when the head valve 30 is opened. Therefore, when the damper 26 is moved upward from the initial position, the pressure accumulation chamber 7 is moved to the air motor 50. Compressed air is supplied, whereby the air motor 50 begins to rotate.
On the other hand, as shown in FIG. 9, when the damper 26 is displaced downward, the convex portion 26 d is pressed against the upper surface of the first frame body 61. In this state, the vent chamber 33 and the cylinder lower chamber 25 are in communication with each other as described above, while the vent chamber 33 is hermetically sealed with respect to the insertion hole 61a, the vent chamber 34, and the motor vent 52. It becomes. As will be described later, in this sealed state, the supply of compressed air from the pressure accumulation chamber 7 to the air motor 50 is cut off, and the air motor 50 is stopped.

Next, when the head valve 30 is opened by the pulling operation of the trigger 5, the air motor 50 starts to rotate at the initial stage of the opening. The ventilation chamber 30 b on the lower inner peripheral side of the head valve 30 is communicated with the intake port 52 of the air motor 50 through the ventilation chambers 32, 33, and 34. Therefore, in the state where the head valve 30 is closed with respect to the valve pedestal 35 as shown in FIG. 3, the compressed air is supplied to the motor intake 52 because the ventilation chamber 30 b is blocked from the pressure accumulation chamber 7. Therefore, the air motor 50 is stopped.
When the head valve upper chamber 30a is opened to the atmosphere by the pulling operation of the trigger 5, and the head valve 30 begins to open, the head valve lower chamber 30d on the outer peripheral side of the head valve 30 is communicated with the vent chamber 30b on the inner peripheral side. Compressed air is supplied to the ventilation chamber 30b. The supply of compressed air to the ventilation chamber 30b causes the head valve 30 to move upward to create a gap between the seal ring 27a and the inner peripheral surface of the head valve 30, whereby the ventilation chamber 30b is connected to the inner periphery of the head valve. It starts from the stage before communicating with the side ventilation chamber 30c, that is, before the piston 22 starts to move downward (the initial stage of opening) when compressed air is supplied to the ventilation chamber 30c. As described above, the ventilation chamber 30b communicates with the ventilation chamber 33 via the ventilation chamber 32. Therefore, when compressed air flows into the ventilation chamber 30b, the ventilation chamber 30b flows into the ventilation chamber 33. The compressed air that has flowed into the ventilation chamber 33 acts to move the damper 26 displaced downward. In other words, in the initial state, the compressed air in the ventilation chamber 33 acts on the lower surface of the main body portion 26b of the damper 26 positioned on the lower side and on the outer peripheral side of the convex portion 26d in the direction in which the compressed air is displaced upward. The damper 26 moves up from its initial position. When the damper 26 moves upward, the cylinder lower chamber 25 and the ventilation chamber 33 are hermetically blocked, and the ventilation chamber 33 communicates with the ventilation chamber 34. For this reason, the compressed air that has flowed into the ventilation chamber 30b is supplied to the air motor 50 through the ventilation chamber 34 and the motor intake port 52, whereby the air motor 50 starts to rotate. That is, the air motor 50 starts to rotate immediately after the head valve 30 starts to open.
The rotary shaft 51 of the air motor 50 is provided with a bit insertion hole 51a having a circular cross section through the entire length thereof. The driver bit 23 is inserted into the bit insertion hole 51a so as to be relatively rotatable about the axis and relatively movable in the axial direction.
Since the air motor 50 itself is a conventionally known so-called vane motor, detailed description of its configuration and the like is omitted.
The rotation shaft 53 on the lower side of the air motor 50 is rotatably supported by a third frame 63 attached to the tip of the main body housing 2a via a bearing 54. An air motor 50 is configured between the third frame 63 and the second frame 60.

The lower rotary shaft portion 55 of the air motor 50 is coupled to the speed reduction mechanism portion 70. In this embodiment, a planetary gear train is used for the reduction mechanism unit 70. A sun gear 71 is attached to the rotating shaft portion 55. Two planetary gears 72 and 72 are meshed with the sun gear 71. The two planetary gears 72 and 72 are meshed with an internal gear 75 fixed to the main body housing 2a. The two planetary gears 72 and 72 are supported by a carrier 73. The carrier 73 is rotatably supported at the tip of the main body housing 2a via a bearing 74.
At the center of the carrier 73, a two-sided width hole portion 73a for inserting the driver bit 23 is formed so as to penetrate along the central axis. The driver bit 23 can move in the axial direction relative to the two-sided width hole 73a, and the rotation around the axis is inserted in an integrated state. The driver bit 23 is integrated with the piston 22 in the axial direction (screw tightening). The air motor 50 is provided so as to be able to rotate in the screw tightening direction while moving in the insertion direction.
The two-sided width hole 73a of the carrier 73 corresponds to one embodiment of the rotational power transmission hole described in the claims, and is a cross-sectional oval formed by two flat surfaces 73b and 73b parallel to each other. It has a shape (so-called small hole). On the other hand, the width of the two sides of the two flat surfaces 23a and 23b parallel to each other corresponding to the cross-sectional oblong shape of the two-sided width hole portion 73a is in the range of approximately half on the lower side in the axial direction of the driver bit 23. The shaft portion 23f is provided in a long range along the axial direction. The two-surface width shaft portion 23f formed by both flat surfaces 23a and 23b corresponds to an embodiment of the rotational power transmission shaft portion described in the claims. In the entire range in which the driver bit 23 moves in the axial direction, both flat surfaces 23a and 23b of the two-surface width shaft portion 23f are always positioned in the two-surface width hole portion 73a. The flat surfaces 23a and 23b are provided in a long range in the axial direction. Thus, since the flat surfaces 23a, 23b of the two-sided width shaft portion 23f are always positioned in the two-sided width hole portion 73a of the carrier 73, the driver bit 23 rotates around the rotation axis J73 with respect to the carrier 73. As a result, the rotational torque (rotational power) of the air motor 50 output through the carrier 73 is transmitted to the driver bit 23.
In this way, the rotational output (rotational power) of the air motor 50 is decelerated by the speed reduction mechanism 70 and transmitted to the driver bit 23. The air motor 50 and the speed reduction mechanism 70 are the distal end of the main body 2 and are screwed. Since the rotational torque is transmitted to the driver bit 23 at a portion closest to the S driving portion, the rotational torque (screw tightening torque) is efficiently applied to the screw S without generating twisting of the driver bit 23 as much as possible. Can do.

Here, the present embodiment is characterized in the engagement state of the two-surface width shaft portion 23 f of the driver bit 23 with respect to the two-surface width hole portion 73 a of the carrier 73. As shown in FIG. 17, an oval two-sided width hole 73 a is formed at the center of the carrier 73. As described above, two flat surfaces 73b and 73b which are parallel to each other are provided in the two-surface wide hole portion 73a. Both flat surfaces 73b and 73b are provided in parallel to each other at the same interval K73 with respect to the rotation center axis J73 of the carrier 73, which is the center axis of the two-surface width hole portion 73a. The circumferential surfaces 73c and 73c between the end portions of the both flat surfaces 73b and 73b are provided with the same curvature along the same circumference around the rotation center axis J73 of the insertion hole 73.
In the case of the present embodiment, the two-sided width hole portion 73a is based on a circular hole having a diameter D73 = 5.1 mm, and the interval between both flat surfaces 73b and 73b is set to 4.1 mm (= 2 × K73). The distances K73 and K73 between the flat surfaces 73b and 73b from the rotation center axis J73 are the same as each other and set to K73 = 2.05 mm.
On the other hand, the two flat surfaces 23 a and 23 b of the two-surface width shaft portion 23 f of the driver bit 23 are provided at different distances K 23 a and K 23 b from the rotation center axis J 23 of the driver bit 23. The interval K23b is set to a dimension that is sufficiently smaller than the interval K23a (K23b <K23a). In this embodiment, the driver bit 23 is made of a round bar having a diameter D23 = 5.0 mm, and both flat surfaces 23a and 23b with respect to the rotation center axis J23 have K23a = 2.0 mm, K23b is provided at an interval of 1.5 mm. For this reason, the center of gravity (centroid G) of the cross section of the two-face width shaft portion 23f of the driver bit 23 is shifted from the rotation center axis J23 toward the flat surface 23a as shown in the drawing. For this reason, in the no-load state shown in FIG. 17 (a state in which rotational power is not transmitted), the distance between the flat surface 23a of the driver bit 23 and the flat surface 73b of the two-sided width hole portion 73a is set to 0.05 mm. Has been. On the other hand, the distance between the flat surface 23b of the driver bit 23 and the flat surface 73b of the two-sided width hole 73a is set to 0.55 mm.
Circumferential surfaces 23c, 23c between the ends of both flat surfaces 23a, 23b of the driver bit 23 are along the same circumference with a diameter D23 = 5.0 mm centered on the rotation center axis J23 of the driver bit 23. It is provided with the same curvature. For this reason, the space | interval (gap) between the both circumferential surfaces 23c and 23c in the two-surface width shaft part 23f of the driver bit 23 and both the circumferential surfaces 73c and 73c in the two-surface width hole portion 73a is 0.05 mm. Is set to

Thus, in this embodiment, the two flat surfaces 23a and 23b in the two-plane width shaft portion 23f of the driver bit 23 are not provided in a point-symmetric relationship with respect to the rotation axis J23. According to the astigmatic two-plane width shaft portion 23f according to the present embodiment, the two-surface width shaft portion 23f is engaged with the two-surface width hole portion 73a at three positions in the rotational direction in the rotational power transmission state. (Three points A, B, C hit state). In this case, in the case of a normal point-symmetrical two-surface width shaft portion 23g in which both flat surfaces are provided in a point-symmetric relationship, the two-point state is obtained.
FIG. 19 shows a general rotational power transmission shaft portion P0 (a point-symmetric type two-surface width) having flat surfaces 23a and 23a provided in a point-symmetrical relationship with respect to the two-surface width shaft portion 23g of the driver bit 23. (Shaft) is shown. The rotational power transmission shaft portion P0 shown in FIG. 19 is provided at positions where the two flat surfaces 23a, 23a of the two-surface width shaft portion 23g are point-symmetric with respect to the rotation center axis J23 (the same interval from the rotation center axis J23). 17 is different from the rotational power transmission shaft portion P1 (asymmetrical two-sided width shaft portion 23f) according to the present embodiment shown in FIG. 17 in other respects, and is otherwise configured in the same manner. About the same structure and member, the code | symbol same as this embodiment is used. In FIG. 18 and FIG. 20, white arrows indicate the rotation directions of the carrier 73 and the driver bit 23 during screw tightening.
In the case of this point-symmetric type two-surface width shaft portion 23g, the distance between the two flat surfaces 23a, 23a of the driver bit 23 is 4.0 mm. Therefore, each flat surface 23a and the flat surface 73b of the two-surface width hole 73a. The distance K23a between the two is 0.05 mm. In this case, the center of gravity (centroid G) regarding the cross section of the two-plane width shaft portion 23g coincides with the rotation axis J23. As shown in FIG. 20, in the case of this point-symmetrical two-surface width shaft portion 23 g, the two-surface width shaft portion 23 g of the driver bit 23 is in relation to the two-surface width hole portion 73 a of the carrier 73 in the rotational power transmission state. Thus, the two points D and E are brought into contact with each other and engaged in the rotational direction.
In the case of this embodiment, the two-sided width shaft part 23f (rotational power transmission shaft part P1) of the driver bit 23 is engaged with the two-sided width hole part 73a of the carrier 73 at three points in the rotational direction (three points A, It becomes a state per 3 points which contacted with B and C). For this reason, the sliding resistance in the driving direction (driver bit axis direction) of the two-surface width shaft portion 23f with respect to the two-surface width hole portion 73a is larger than that in the two-point state shown in FIG. It is thought that the recoil transmitted to the hand of the person is reduced.

As exemplified above, the distance K23b of one flat surface 23b in the two-surface width shaft portion 23f of the driver bit 23 having a diameter of 5 mm is in the range of 1.3 mm to 1.5 mm, and the distance K23a (= 2. By setting it smaller than 0 mm), the most remarkable reaction reduction effect can be obtained while avoiding biting (twisting or biting) of the driver bit 23 into the two-sided width hole portion 73a.
When the interval K23b of the flat surface 23b having the shorter interval is smaller than 1.3 mm (for example, set to 1.2 mm), the two surfaces wide hole 73a is caught by the rotational power load from the carrier 73. It becomes easy. On the other hand, when the distance K23b is larger than 1.5 mm, the clearance θ in the rotational direction of the two-sided width shaft portion of the driver bit 23 with respect to the two-sided width hole portion is gradually reduced, resulting in a two-point state. A sufficient recoil reduction effect cannot be obtained.
Further, when the shorter interval K23b is set in a range of 1.3 mm to 1.5 mm, the two-sided width shaft portion 23f of the driver bit 23 is formed in the two-sided width hole portion 73a when the rotational power is transmitted as shown in FIG. Abutting on the inner peripheral surface at three locations A, B, and C, the three-point abutting state is engaged with the two-surface width hole portion 73a in the rotational direction. On the other hand, the point-symmetrical two-surface width shaft portion 23g shown in FIG. 20 is in contact with the inner peripheral surface of the two-surface width hole portion 73a at two locations D and E. Thus, the two-sided width hole portion 73a is engaged in the rotation direction.
Accordingly, with respect to the distance from the rotation center axis J23 of the driver bit 23, by setting one flat surface 23b of the two-surface width shaft portion 23f to about 65% to 75% of the other flat surface 23a, It seems that the same recoil reduction effect can be obtained.
Next, a cylindrical driving tube portion 13 is provided at the lower end of the main body portion 2. The driver bit 23 reciprocates while rotating on the inner peripheral side of the driving cylinder portion 13. The screw connection band feeding mechanism 12 is connected to a halfway position in the longitudinal direction of the driving cylinder portion 13. The screw connection band feed mechanism 12 feeds the screw connection bands one pitch at a time, and the screws S are supplied into the driving cylinder portion 13 one by one in conjunction with the driving operation on the main body portion 2 side.
A bracket 14 to which an elastic sheet 14a is attached is attached to the tip of the driving cylinder portion 13 in order to prevent the screw driving material W from being damaged. The driving cylinder portion 13 is abutted against the screw driving material W through the bracket 14, and the screw S is driven (tightened) into the screw driving material W in this state.

According to the screw driving machine 1 of the present embodiment configured as described above, when the trigger 5 is pulled while the compressed air is supplied to the pressure accumulating chamber 7, the head valve upper chamber 30a is opened to the atmosphere, and the head valve 30 is moved. Move up. When the head valve 30 moves up, compressed air is first supplied to the ventilation chamber 30b at the initial stage of opening thereof, and flows into the ventilation chamber 33 through the ventilation chamber 32. When compressed air is supplied to the ventilation chamber 33, the damper 26 moves upward from the initial position due to the pressure, thereby closing the cylinder lower chamber 25, and bringing the ventilation chamber 33 into communication with the ventilation chamber 34. . Thus, the pressure accumulating chamber 7 is communicated with the venting chambers 30b, 32, 33, and 34, whereby compressed air is supplied to the air motor 50, whereby the air motor 50 starts to rotate. As the air motor 50 rotates, the rotational power is reduced between the two-sided width hole portion 73a (rotational power transmission hole) of the speed reduction mechanism 70 and the two-sided width shaft portion 23f (rotational power transmission shaft portion P1) of the driver bit 23. Is transmitted to the driver bit 23 by the engagement between them, and the driver bit 23 rotates in the screwing direction.
When the head valve 30 is fully opened, compressed air is supplied to the ventilation chamber 30c via the ventilation chamber 30b, and is supplied to the cylinder upper chamber 24 via the flow rate switching valve 40, whereby the piston 22 moves downward. To do. When the piston 22 moves downward, the driver bit 23 moves downward. Therefore, the driver bit 23 is moved downward in the screw driving direction by the piston 22 while being rotated in the screw tightening direction by the air motor 50, whereby one screw S supplied into the driving cylinder portion 13 is screwed by the driver bit 23. It is tightened while being driven into the driving material W.
In the process in which the piston 22 moves downward, a part of the compressed air in the cylinder lower chamber 25 is released around the driver bit 23 through the insertion hole 26a of the damper 26, and the remaining part is returned to the return holes 21b to 21b. As a result, the piston 22 smoothly moves downward by flowing into the return air chamber 29 and accumulating pressure. As the piston 22 smoothly moves down, the screw S is driven into the screw driving material W by the driver bit 23.

As shown in FIG. 9, when the piston 22 comes into contact with the damper 26 and reaches the lower moving end (bottom dead center), the driving (tightening) of the screw S is completed. As shown in the drawing, the impact is absorbed by the piston 22 reaching the lower moving end and elastically contacting the damper 26. Further, the damper 26 is displaced downward by the contact of the piston 22 (the thrust of the piston 22).
When the damper 26 is displaced downward, the main body portion 26b is disengaged from the lower opening of the cylinder 21, and as a result, a gap 26e is generated over the entire circumference between the damper 26 and the inclined surface 21c. The cylinder lower chamber 25 is in communication with the ventilation chamber 33. In the state where the trigger 5 is kept pulled, the compressed air is maintained in the ventilation chamber 33, so that the return air chamber 29 is passed through the gap 26e, the cylinder lower chamber 25, and the return hole 21b. Sufficient compressed air for returning the piston is supplied from the ventilation chamber 33.
Further, when the damper 26 is displaced to the lower initial position by the thrust of the piston 22, the convex portion 26 d of the main body portion 26 b is pressed against the upper surface of the first frame body 61, and between the ventilation chamber 33 and the ventilation chamber 34. Since the communication state is cut off, the supply of compressed air to the motor intake port 52 is cut off, so that the rotation of the air motor 50 is automatically stopped. For this reason, even when the trigger 5 is kept pulled, the arrival timing of the piston 22 to the lower end of the piston 22 and the stop timing of the air motor 50 are synchronized (performed almost simultaneously), so that the screw S is driven in. Overtightening on the material W is prevented.
Thereafter, when the user stops the pulling operation of the trigger 5, the compressed air is supplied to the head valve upper chamber 30a via the trigger valve 4, and the head valve 30 is moved downward. When the head valve 30 is moved downward and its lower end is in an airtight contact with the valve pedestal 35, the ventilation chamber 30c is blocked from the ventilation chamber 30b by the seal ring 27a, and the ventilation chamber 30b is located under the head valve. It will be in the state interrupted | blocked from the chamber 30d. For this reason, the supply of compressed air to the cylinder upper chamber 24 is shut off. When the supply of the compressed air to the cylinder upper chamber 24 is shut off, the compressed air in the cylinder upper chamber 24 flows into the flow rate switching valve 40, the exhaust holes 21a to 21a, the exhaust holes 30g to 30g of the head valve 30, and the exhaust chamber. 30 h and the state through which the air can be released through the exhaust pipe 8 (a state in which no downward thrust is generated with respect to the piston 22).
Thus, when the head valve 30 is closed and the supply of compressed air to the cylinder upper chamber 24 is shut off, when the cylinder upper chamber 24 becomes open to the atmosphere, the compressed air accumulated in the return air chamber 29 The piston 22 is returned to the top dead center.
Further, when the head valve 30 is closed, the supply of compressed air to the ventilation chamber 33 is interrupted, so that the damper 26 is maintained in a state of being displaced downward (an initial position of the damper 26).

As described above, according to the screw driving machine 1 of this embodiment, the air motor 50 is disposed at a position that is closer to the front end side in the driving direction than the cylinder 21. According to this, since the rotational output of the air motor is transmitted (torque transmission) to the driver bit at a position closer to the screw driving portion, the substantial length contributing to the torsional deformation of the driver bit is shortened, and accordingly It is possible to transmit the rotational power efficiently while suppressing the deformation. Further, since the air motor 50 is fixed to the main body housing 2a (fixed so as not to move in the driving direction), the reaction at the time of driving can be suppressed as compared with the case where the air motor 50 moves together with the piston 22.
In addition, in the case of the present embodiment, the speed reduction mechanism portion 70 for reducing the rotation output of the air motor 50 is closer to the tip side than the air motor 50 and closest to the screw driving portion (tip portion of the driver bit 23). Has been placed. The speed reduction mechanism 70 is fixed so as not to move in the screw driving direction at a position on the distal end side of the main body housing 2a. The rotational output of the speed reduction mechanism 70 is a state in which the rotational power transmission shaft portion P1 of the driver bit 23 (the flat surfaces 23a and 23b of the two-sided width shaft portion 23f) is always inserted into the two-sided width hole portion 73a having an oval cross section. Thus, the driver bit 23 is integrated with respect to the rotation about the axis thereof, and is transmitted to the driver bit 23 (rotational power transmission unit).
For this reason, the distance between the speed reduction mechanism portion 70 which is a portion (rotational power transmission portion) for transmitting the screw tightening torque to the driver bit 23 and the tip end portion of the driver bit 23 is always kept shorter than before. Therefore, the rotation output of the air motor 50 output through the speed reduction mechanism unit 70 can be efficiently transmitted to the screw with almost no torsional deformation of the driver bit 23.
Further, since the speed reduction mechanism unit 70, the air motor 50 and the cylinder 21 are fixed so as not to move in the driving direction with respect to the main body housing 2a, the main members moving in the direction are only the piston 22 and the driver bit 23. It is possible to minimize the upward reaction of the main body 2 at the time of screw driving, and as a result, reliable screw driving can be performed.
Furthermore, since the air motor 50 is disposed in a portion relatively close to the exhaust pipe 8 in the handle portion 3, the exhaust path from the air motor 50 is easily shortened and simplified, thereby improving the responsiveness of the air motor 50. be able to.
Further, since the air motor 50 and the speed reduction mechanism portion 70 are arranged at the front end side in the driving direction with respect to the handle portion 3 provided in the vicinity of the center of the main body housing 2a in the driving direction, the center of gravity of the screw driving machine 1 is set to the handle portion. It becomes easier to set the tip in the driving direction than 3. By setting the center of gravity of the screw driving machine 1 to the front end side relative to the handle part 3, when the user grips the handle part 3, the front side in the driving direction (the driving cylinder part 13) of the screw driving machine 1 is set. Since it becomes easy to hold it down and in an easy posture, its operability and usability can be improved.

Various modifications can be made to the embodiment described above. For example, for the rotational power transmission shaft portion P1 of the driver bit 23, two flat surfaces 23a and 23b parallel to each other are illustrated, but as shown in FIG. 21, two flat surfaces 23a having an angle with each other (not parallel to each other). , 23d may be a two-sided width shaft portion 23h (rotational power transmission shaft portion P2). Also in this case, the cross-sectional shape of the two-plane width shaft portion 23h is asymmetric with respect to the rotation center axis J23, and the center of gravity G is eccentric with respect to the rotation center axis J23 of the driver bit 23. Such a configuration corresponds to an embodiment of the invention described in claim 5. Even with such a configuration, it is possible to set the engagement position in the rotation direction of the two-surface width shaft portion 23h with respect to the two-surface width hole portion 73a at three positions, and the center of gravity of the cross section is deviated from the rotation center axis J23. Because of this, the reaction at the time of driving in the screw can be reduced as described above.
In addition, as shown in FIG. 22, the two flat surfaces 23b and 23e of the two-surface width shaft portion 23i are parallel to each other, but as a result of the difference in the distance from the rotation center axis J23, the configuration becomes an asymmetrical shape. The same effect can be obtained. In such a configuration, the flat surface 23e has a distance from the rotation center axis J23 larger than the flat surface 23b indicated by a two-dot chain line in the drawing and smaller than the flat surface 23a. Also in this case, the center of gravity G of the cross section of the two-plane width shaft portion 23i is in an eccentric state with respect to the rotation center axis J23.
From the above, the following conditions can be considered as a configuration related to the cross-sectional shape necessary for obtaining the same reaction reduction effect as that of the exemplified rotational power transmission shaft portion P1.
(Condition 1) In the configuration in which the two-sided width shaft part (rotational power transmission shaft part) of the driver bit is inserted into the two-sided width hole part (rotational power transmission hole part) of the carrier and the rotation is integrated with each other. The cross section of the two-sided width shaft portion of the driver bit has an astigmatic shape with respect to the rotation center of the driver bit.
(Condition 2) The center of gravity (centroid G) regarding the cross section of the two-sided width shaft portion of the driver bit is eccentric with respect to the rotation center axis J23 of the driver bit.
(Condition 3) The gap between the flat surface of the two-sided width shaft portion of the driver bit and the flat surface of the two-sided width hole portion of the carrier is larger than the gap between the circumferential surfaces of the two.
(Condition 4) Contrary to condition 1, the two-sided wide hole portion of the carrier is astigmatized because the distance from the rotation center axis J73 is different between one flat surface and the other flat surface. It must be configured symmetrically.
(Condition 5) Regardless of whether or not the cross-sectional shape of the rotational power transmission shaft portion of the driver bit is an asymmetrical shape, by contacting the rotational power transmission hole portion in at least three locations in the rotational direction, The sliding resistance in the direction of the driver bit axis is greater than the two-point state due to the general width across flats.
By adopting a configuration that satisfies any of the above conditions, the reaction at the time of screwing is reduced as compared with the case where a normal point-symmetric rotational power transmission shaft portion P0 (two-sided width shaft portion 23g) is employed. It is thought that it can be further reduced.

Further, although the planetary gear train is exemplified as the speed reduction mechanism portion 70, for example, a speed reduction mechanism composed of a spur gear train or a worm gear and a worm wheel may be used as the speed reduction mechanism portion as long as the speed reduction output of the air motor 50 is reduced. it can.
In addition, a configuration is illustrated in which the rotational power is transmitted from the speed reduction mechanism 70 to the driver bit 23 by inserting the two-sided width portions 23a and 23b of the driver bit 23 into the oval two-sided width hole portion 73a. However, the shape of the insertion hole on the speed reduction mechanism side and the cross-sectional shape of the corresponding driver bit are arbitrary, and the shape may be oval, hexagonal, square, etc. Various forms such as a structure or the like that allow relative movement in the axial direction and integrate with respect to rotation can be used.
Furthermore, if at least the speed reduction mechanism 70 is fixed to the tip of the main body 2 (main body housing 2a), the air motor is configured to reciprocate integrally with the piston, or the air motor is disposed rearward of the cylinder. Even if it exists, compared with the past, the twisting deformation | transformation of the driver bit 23 can be suppressed and the efficient rotational power transmission can be performed, suppressing the reaction at the time of driving.

It is a longitudinal section of the whole screw driving machine concerning this embodiment. This figure shows the initial state. It is a longitudinal cross-sectional view of the main-body part of the driving machine which concerns on this embodiment. This figure shows the initial state of the main body. FIG. 3 is a partially enlarged view of FIG. 2, and is a longitudinal sectional view of the vicinity of a head valve and an upper part of a cylinder. This figure shows the fully closed state of the head valve in the initial state of the main body as in FIG. It is a longitudinal cross-sectional view of a cylinder lower part and a damper periphery. This figure shows the stage where the damper has moved up from the lower initial position and the air motor has started to rotate. It is a longitudinal cross-sectional view of the main-body part of the screw driving machine which concerns on this embodiment. This figure shows a stage where the air motor starts to rotate with the head valve half open. At this stage, the piston is still at top dead center. It is a longitudinal cross-sectional view of the main-body part of the screw driving machine which concerns on this embodiment. This figure shows a state in which the head valve is fully opened, the air motor rotates, and the piston starts to move downward. FIG. 7 is a partially enlarged view of FIG. 6, which is a longitudinal sectional view of a fully opened head valve and a cylinder upper portion periphery. In this figure, the piston is shown in which the head valve is fully opened and begins to move downward. It is a longitudinal cross-sectional view of the main-body part of the screw driving machine which concerns on this embodiment. This figure shows a stage where the piston reaches bottom dead center, and as a result, the air motor stops and the screw driving is completed. FIG. 9 is a partially enlarged view of FIG. 8, and is an enlarged view of the periphery of a piston and a damper that have reached bottom dead center. This figure shows a state where the air motor air passage is closed as a result of the damper being pushed down by the piston and moving downward. It is the rear view which looked at the main-body part from the arrow (10) direction in FIG. This figure shows a state in which the lever is switched to the steel plate mode position for steel plate driving. It is the (11)-(11) sectional view taken on the line in FIG. This figure shows the internal structure around the head valve in a longitudinal section. FIG. 12 is a sectional view taken along line (12)-(12) in FIG. 11. In this figure, the valve pedestal and the head valve of the switching valve are shown in cross section. It is a rear view of a main-body part. This figure shows a state in which the lever is switched to the wood board mode position for wood board driving. FIG. 14 is a sectional view taken along the line (14)-(14) in FIG. 13. In this figure, the valve pedestal and the head valve of the switching valve are shown in cross section. It is the (15)-(15) sectional view taken on the line in FIG. In this figure, the valve pedestal and the head valve of the switching valve are shown in cross section. FIG. 4 is a longitudinal sectional view around the flow rate switching valve at the top of the main body. This figure shows the flow rate switching valve when the piston moves up. The valve body moves up against the valve seat against the compression spring, and as a result, it is generated between the valve seat and the valve body. A state in which exhaust is performed through a gap is shown. FIG. 9 is a cross-sectional view taken along line (17)-(17) in FIG. 8 and is a cross-sectional view of the rotational power transmission shaft portion according to the present embodiment. It is a cross-sectional view of the rotational power transmission shaft portion according to the present embodiment. This figure shows a state where the air motor is activated and rotational power is transmitted from the carrier to the driver bit, and the driver bit is rotating. It is a cross-sectional view of a rotational power transmission shaft portion having a general point-symmetric two-sided width shaft portion. It is a cross-sectional view in the rotational power transmission state of a general point-symmetrical two-plane width shaft portion. It is a cross-sectional view of the rotational power transmission shaft part of another form. This figure shows a two-sided width shaft portion formed of two flat surfaces having an asymmetrical cross-sectional shape and having an angle with each other. It is a cross-sectional view of the rotary power transmission shaft part of another form. This figure shows a two-plane width shaft portion formed of two flat surfaces having an asymmetrical cross-sectional shape and having different distances from the center of rotation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Screw driving machine 2 ... Main-body part S ... Screw W ... Screw driving material 12 ... Screw connection band feed mechanism 13 ... Driving cylinder part 20 ... Impacting mechanism part 21 ... Cylinder 22 ... Piston 23 ... Driver bits 23a, 23b ... Flat surface (Dihedral width axis part), 23c ... circumferential surfaces 23d, 23e ... flat face 23f ... dihedral width axis part (astigmatic), 23g ... dihedral width axis part (point symmetry)
23h: Two-sided width axis (astigmatic), 23i ... Two-sided width axis (astigmatic)
26 ... Damper (bottom dead center side)
29 ... Return air chamber 30 ... Head valve 32 ... Ventilation chamber 33 ... Ventilation chamber 34 ... Ventilation chamber 35 ... Valve seat 40 ... Flow rate switching valve 43 ... Switching lever 50 ... Air motor 51 ... Rotating shaft 51a ... Bit insertion hole 55 ... Rotary shaft 60 ... Second frame 61 ... First frame 63 ... Third frame 70 ... Speed reduction mechanism (planetary gear train)
71 ... Sun gear 72 ... Planetary gear 73 ... Carrier, 73a ... Two-sided width hole portion, 73b ... Flat surface, 73c ... Circumferential surface 75 ... Internal gear J23 ... Driver bit rotation center axis J73 ... Carrier rotation center axis G: Center of gravity (centroid) of the cross section of the rotational power transmission shaft of the driver bit
K23a, K23b... Distance between the flat surface rotation center axis of the two-surface width shaft portion K73... Space between the flat surface rotation center shaft of the two-surface width hole portion P0 to P3.

Claims (5)

A screw driving machine including an air motor that rotates a screwdriver driving bit in a screw tightening direction, a piston that moves the driver bit in a screw driving direction, and a main body housing that accommodates them.
A gear train is provided as a speed reduction mechanism in the rotational power transmission path between the air motor and the driver bit, and the rotational power transmission shaft portion of the driver bit is inserted into the rotational power transmission hole portion of the gear train. Are integrated with respect to the gear train, and are capable of axial movement and rotation about the axis.
A cross section of the rotational power transmission shaft portion of the driver bit has an asymmetrical shape with respect to the rotational center axis of the driver bit, and at least three points in the rotational direction with respect to the rotational power transmission hole portion. screw driving tool with a row cormorants configure the transmission of rotational power while contacting. The screw driving machine according to claim 1 ,
The rotational power transmission hole is a two-sided width hole formed by two flat surfaces parallel to each other, and the rotational power transmission shaft is a two-sided width shaft formed by two flat surfaces parallel to each other. As described above, the two-surface width shaft portion is axially movable and integrated with respect to the two-surface width hole portion, and the two flat surfaces of the two-surface width shaft portion are the rotation center shafts of the driver bits. The screw driving machine is configured such that the cross-sectional shape of the two-plane width shaft portion has an asymmetrical shape with respect to the rotation center axis. The screw driving machine according to claim 2 , wherein
The screw driving machine in which one flat surface is set to 65% to 75% of the other flat surface with respect to a distance from the rotation central axis of the two flat surfaces of the two-surface width shaft portion. The screw driving machine according to claim 1 ,
The rotational power transmission hole is a two-sided width hole formed by two flat surfaces parallel to each other, and the rotational power transmission shaft is a two-sided width shaft formed by two flat surfaces. The two-surface width shaft portion is axially movable and integrated with respect to rotation about the axis with respect to the surface width hole portion, and the two flat surfaces of the two-surface width shaft portion are provided with an angle to each other A screw driving machine configured such that the cross-sectional shape of the two-sided width shaft portion has an asymmetrical shape with respect to the rotation center axis. A screw driving machine including an air motor that rotates a screwdriver driving bit in a screw tightening direction, a piston that moves the driver bit in a screw driving direction, and a main body housing that accommodates them.
A gear train is provided as a speed reduction mechanism in the rotational power transmission path between the air motor and the driver bit, and a two-sided width shaft portion of the driver bit is inserted into a two-sided width hole provided in the gear train. A driver bit is axially movable with respect to the gear train and integrated with respect to rotation about the axis,
The cross-sectional shape of one or both of the two-sided width shaft portion of the driver bit or the two-sided width hole portion of the gear train is asymmetric with respect to the cross-sectional shape, and rotational power is transmitted in a state where they are in contact with each other at least at three points. Screw driving machine configured to perform.

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