JP5620772B2 - Driving tool - Google Patents

Description

  The present invention relates to a driving tool such as a screw driving machine that operates using compressed air as a power source.

For example, the above-described compressed air type screw driving machine performs screw tightening by rotating the head of one screw supplied to the driving guide portion with a driver bit while rotating in the screw tightening direction. As a power source, a tool main body portion having a reciprocating piston and a rotating air motor are provided. The driving guide portion is provided at the tip of the tool main body in the driving direction. The air motor reciprocates integrally with the piston, and a driver bit is attached to its output shaft. The tip portion of the driver bit reaches the driving guide portion. The driving guide section is provided with a screw supply section that operates in conjunction with the driving operation of the tool main body section and a magazine that stores a large number of screws.
A handle portion that is gripped by the user is provided on a side portion of the tool body portion, and a trigger type switch lever that is operated by the user with a fingertip is provided near the base portion of the handle portion. When the switch lever is pulled, compressed air is supplied to the piston upper chamber of the tool body, the piston moves downward, and the air motor rotates to make a screw. When the pulling operation of the switch lever is released, the compressed air supplied to the piston upper chamber side flows into the piston lower chamber side, and the piston and the air motor are integrally returned to the top dead center. A part of the compressed air (return air) that flows into the piston lower chamber side flows into the screw supply part and is used as a power source for screw feeding, and is released to the atmosphere mainly through the exhaust passage.
Such screw driving machines are provided with a function of switching between a wood driving mode for driving screws into wood and a steel plate driving mode for driving screws into steel plates. In the former wood hammering mode, it is relatively low in order to reduce the recoil when driving or to avoid screw driving (to drive the screw like a nail instead of rotating it with an air motor) While the driving force is output, the latter steel plate driving mode outputs a driving force larger than the wood driving mode. Conventionally, as a method for switching the driving force, a technique for switching the pressure of compressed air supplied to the piston upper chamber is known, and the following patent document describes switching of the output mode by switching the exhaust efficiency of the piston lower chamber. Techniques for performing are disclosed.
The output mode switching technology disclosed in the following patent document utilizes the principle that when the diameter of the exhaust passage leading to the piston lower chamber is changed, the exhaust efficiency changes and the piston lowering speed changes. Exhaust efficiency of the piston lower chamber can be increased by providing a rotating plate having two large and small discharge ports in the section and switching the position of the rotating plate to switch the diameter of the discharge port of the exhaust passage to a large diameter hole (steel plate driving mode). As a result, the downward movement speed of the piston is increased, and the striking force against the screw is larger than in the wood driving mode. Switching the position of the rotating plate to the small-diameter hole side (wood hammering mode) reduces the exhaust port diameter and lowers the exhaust efficiency of the piston lower chamber. It became the composition which becomes.
Further, in the driving tool disclosed in the following patent document, the compressed air for generating the impact force supplied to the piston upper chamber is used as return air for returning the piston from the bottom dead center to the top dead center after the driving is completed. The exhaust return method is adopted. In this exhaust return method, the compressed air in the upper chamber of the piston is not exhausted as it is after the completion of the driving, but once flows into the lower chamber of the piston and a part thereof is used as compressed air for returning the piston, and the remaining compressed air is exhausted. It is configured to exhaust through a passage.

Japanese Patent Laid-Open No. 2006-983

In the driving tool that adopts the exhaust return method and switches the output mode by switching the diameter of the exhaust passage as described above, there is a limit to further increasing the output in the conventional steel plate driving mode.
When the exhaust return method described above is adopted, if the exhaust passage is enlarged to increase the exhaust efficiency in order to increase the output, most of the compressed air that has flowed into the piston lower chamber from the piston upper chamber after the completion of driving is exhausted. As a result, there is a risk of malfunction such as the return air for returning the piston to the top dead center after the completion of driving and the piston not being returned to the top dead center. For this reason, there has been a limit to increase the output by increasing the diameter of the exhaust passage in the configuration employing the conventional exhaust return system.
Therefore, the present invention provides a higher driving force by increasing the exhaust efficiency by increasing the exhaust passage diameter while ensuring sufficient return air in the piston lower chamber, for example, in a driving tool employing an exhaust return method. The purpose is to be able to.

The above problems are solved by the following invention.
A first invention is a driving tool for generating a driving force by lowering a piston with compressed air supplied to the piston upper chamber while exhausting the piston lower chamber through an exhaust passage. A driving tool provided with an exhaust valve that opens the passage and restricts the exhaust passage when the piston moves up.
According to the first aspect of the present invention, the exhaust passage can be increased in diameter to increase the exhaust efficiency of the piston lower chamber, whereby the driving force can be increased. The effective passage area of the exhaust passage changes depending on the operation of the exhaust valve. The exhaust passage is reduced in diameter by operating the exhaust valve toward the throttle side when the piston moves up, and the diameter is increased by operating the exhaust valve on the open side when moving down the piston.
For this reason, even if the exhaust passage is enlarged in diameter and the driving force is increased, the exhaust passage is throttled by operating the exhaust valve after the completion of driving, so that the exhaust efficiency of the piston lower chamber is appropriately suppressed. As a result, the return air can sufficiently flow into the lower chamber of the piston to reliably return the piston to the top dead center.
A second invention is a driving tool provided with an output mode switching mechanism that changes the driving force by manually changing the diameter of the exhaust port of the exhaust passage in the first invention.
According to the second invention, for example, by manually operating the output mode switching dial and changing the size of the exhaust port, the mode can be switched between a wood driving mode with a small driving force and a steel plate driving mode with a larger driving force. it can. Apart from the mode switching by this output mode switching mechanism, the exhaust passage is throttled at an appropriate timing by the exhaust valve during one driving operation, so that a large driving force can be obtained when the piston moves downward, while the piston moving upward Sometimes a sufficient amount of return air is secured in the piston lower chamber, and malfunction of the driving tool is avoided.
According to a third invention, in the first or second invention, the compressed air supplied to the piston upper chamber is caused to flow into the piston lower chamber via the return air passage, and a part of the compressed air is returned to the top dead center. This is a driving tool having an exhaust return structure that is used as return air and exhausts the remainder through an exhaust passage.
According to the third aspect of the present invention, in the driving tool having the so-called exhaust return structure, the exhaust passage is throttled by the exhaust valve when the piston is moved up, so that sufficient return air is secured in the piston lower chamber to operate the driving tool. Since it is possible to avoid defects, it is possible to eliminate the conventional limitations on increasing the diameter of the exhaust passage and increasing the output of the driving tool.
A fourth invention is a driving tool according to the third invention, wherein the exhaust valve is operated in the throttle direction by the return air in the return air passage.
According to the fourth invention, in the driving tool having the exhaust return structure, the exhaust valve is operated to the throttle side using the return air flowing from the piston upper chamber to the piston lower chamber through the return air passage after the completion of driving. Thus, the exhaust efficiency of the piston lower chamber is suppressed at an appropriate timing.
According to a fifth invention, in any one of the first to third inventions, a head valve for opening and closing the piston upper chamber with respect to the pressure accumulating chamber is provided. This is a driving tool configured to be actuated automatically.
According to the fifth invention, instead of the configuration in which the exhaust valve is operated to the throttle side using the return air in the return air passage in the exhaust return structure, the compressed air that operates the head valve to the closing side after the completion of driving. By operating the exhaust valve to the throttle side, the exhaust efficiency of the piston lower chamber can be appropriately suppressed, and the piston can be reliably returned to the top dead center by a sufficient amount of return air. Such a configuration can also be applied to a driving tool that does not include an exhaust return structure.
A sixth invention is a driving tool according to the third or fourth invention, wherein the exhaust passage and the return air passage are merged. According to the sixth aspect of the present invention, the passage configuration can be simplified as compared with the configuration in which the exhaust passage and the return air passage are provided independently of each other, and the exhaust passage can be easily increased in diameter.
A seventh aspect of the invention includes an air motor that operates with compressed air in any one of the first to sixth aspects of the invention. While the screw is hit by the downward movement of the piston, the air motor is rotated to rotate the screw. This is a so-called screwdriver. The configuration according to any one of the first to sixth inventions can be applied to a so-called screw driving machine. Therefore, the configuration according to any one of the first to sixth inventions is a driving tool that does not include such an air motor, and can be applied to, for example, a compressed air type nailing machine.

It is a side view of the internal structure of the driving tool which concerns on 1st Embodiment of this invention. This figure has shown the non-operation state. It is a side view of the internal structure of the driving tool of 1st Embodiment. This figure shows the state at the moment when the trigger valve is turned on by pulling the switch lever. It is a side view of the internal structure of the driving tool of 1st Embodiment. This figure shows a state at the time when the head valve is opened, compressed air is supplied to the piston upper chamber, the piston and the air motor move down integrally, and the piston reaches its bottom dead center. The air motor is moving downward. It is a side view of the internal structure of the driving tool of 1st Embodiment. This figure shows the state at the time when the screw has been tightened by reaching the bottom dead center while the air motor is rotating. It is a side view of the internal structure of the driving tool of 1st Embodiment. This figure shows the state at the moment when the pulling operation of the switch lever is released and the trigger valve is turned off, so that the head valve is closed. At this stage, the exhaust valve is operating to the throttle side. It is a side view of the internal structure of the driving tool of 1st Embodiment. This figure has shown the state in the middle of returning a piston and an air motor to a top dead center. At this stage, the exhaust valve is held in the throttle position. FIG. 4 is an enlarged view of a part of FIG. 3, and is an internal enlarged view around a head valve. In this figure, the exhaust valve is held in the open position. It is the figure which expanded and showed a part of FIG. 6, Comprising: It is an internal enlarged view around a head valve. In this figure, the exhaust valve is held at the throttle position. In the driving tool of 2nd Embodiment, it is the side view which expanded and showed the internal structure of a head valve periphery periphery. This figure shows a state where the exhaust valve is held in the open position when the piston is moving downward (when the screw is hit). In the driving tool of 2nd Embodiment, it is the side view which expanded and showed the internal structure of a head valve periphery periphery. This figure shows a state in which the exhaust valve is held at the throttle position when the piston moves up. It is a side view of the internal structure of the driving tool of 3rd Embodiment.

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the overall internal structure of the driving tool 1 according to the first embodiment. The illustrated driving tool 1 is a so-called screw driving machine, and is an air tool having a function of rotating a screw B in the screw tightening direction while hitting a single screw B to tighten the screw B into the driving material W.
The driving tool 1 includes a tool body 2, a handle 3, a driving guide 4, and a driving tool supply device 5. The tool main body 2 has a configuration in which each mechanism such as an impact mechanism 10 and an air motor 30 described below is housed in a substantially cylindrical main body case 2a. A handle portion 3 for a user to grip from the side portion of the tool main body portion 2 is provided in a state of protruding sideways. Illustration of the distal end side of the handle portion 3 is omitted. Compressed air is stored inside the handle portion 3 through an air hose connected to the tip of the handle portion 3 via a coupler. Hereinafter, a section inside the handle portion 3 and storing compressed air as a power source is referred to as a reservoir 3a. The reservoir 3a is always in communication with the pressure accumulating chamber 2b that is divided inside the main body case 2a and around the striking mechanism 10 and the air motor 30.
A trigger-type switch lever 6 that is pulled by a fingertip of a hand held by the user and a trigger valve 40 that is operated by the operation are provided near the base of the handle portion 3. Compressed air is supplied to and exhausted from the tool main body 2 side by turning on and off the trigger valve 40 accompanying the operation of the switch lever 6.
The driving guide portion 4 has a function of guiding one screw B supplied into the driving passage 4a to the driving material W by being struck by the driver bit 7, from below the tool main body portion 2 (the driving material). (W side). A contact arm 8 is provided at the tip of the driving guide portion 4. Only when the contact arm 8 is pressed against the screw driving portion, the pulling operation of the switch lever 6 becomes effective, and the driving operation in the tool body 2 is performed, thereby preventing the inadvertent driving operation. ing. A detailed description of the erroneous operation prevention mechanism, which is conventionally known, is omitted.
In addition, the present embodiment has a feature in the exhaust structure in the tool main body 2, and basic configurations of the striking mechanism 10, the air motor 30, the trigger valve 40, and the like are conventionally known, and in this embodiment No change is required. Furthermore, since the driving guide 4 and the driving tool supply device 5 are also conventionally known, detailed description thereof is omitted.

Hereinafter, the configuration of each part will be described from the upstream side along the flow of the compressed air supplied to the reservoir 3a. First, the trigger valve 40 is accommodated in a valve case portion 3 b provided at the base portion of the handle portion 3. The trigger valve 40 includes a valve outer frame portion 41, a valve inner frame portion 42, and a valve stem 43. A valve outer frame portion 41 is attached to the inside of the valve case portion 3b so as not to move. A valve inner frame portion 42 is accommodated inside the valve outer frame portion 41 so as to be movable up and down. A valve stem 43 is accommodated inside the valve inner frame portion 42 so as to be movable up and down. The distal end side of the valve stem 43 protrudes downward from the lower surface of the valve outer frame portion 41 and abuts against the back surface of the switch lever 6. On the upper surface of the valve stem 43, the air pressure of the reservoir 3a is constantly acting.
In a non-operating state in which the switch lever 6 is not pulled, the trigger valve 40 is off. In the off state of the trigger valve 40, the valve case hole 3c of the valve case portion 3b and the first air hole 41a of the valve outer frame portion 41, the valve outer frame portion 41 and the valve inner frame portion 42, the valve outer frame portion 41, and the like. The working air passage 2c on the tool body 2 side is in communication with the reservoir 3a through the second air hole 41b, and compressed air is supplied to the head valve upper chamber 11a through the working air passage 2c. It has become.
The head valve 11 has a function of opening and closing the piston upper chamber 12 a with respect to the pressure accumulating chamber 2 b, and is biased to the closing side by the compression spring 13. For this reason, in a state where compressed air is supplied to the head valve upper chamber 11a via the working air passage 2c, the air pressure cancels out with the compressed air in the pressure accumulating chamber 2b acting on the opening side. 11 is held in a closed position by a compression spring 13. As a result of the head valve 11 being held in a closed state, compressed air is not supplied to the piston upper chamber 12a, and therefore the tool body 2 is held in an inoperative state.
As shown in FIG. 2, when the switch lever 6 is pulled upward, the valve stem 43 moves up against the air pressure of the compression spring 43a and the reservoir 3a. When the valve stem 43 moves upward, the air pressure of the reservoir 3a acts on the upper surface of the valve inner frame portion 42, so that the valve inner frame portion 42 moves downward. When the valve inner frame portion 42 moves downward, the operating air passage 2c is blocked from the reservoir 3a, while being released to the atmosphere through the atmosphere opening hole 41c of the valve outer frame portion 41. When the working air passage 2c is opened to the atmosphere, the head valve upper chamber 11a is opened to the atmosphere, so that the head valve 11 is opened upward against the compression spring 13 by the air pressure in the pressure accumulating chamber 2b. When the head valve 11 is opened, the compressed air in the pressure accumulating chamber 2b flows into the piston upper chamber 12a, which acts on the inner peripheral upper surface of the piston 12 and the compressed air acts on the piston 12 in the downward movement direction. . In FIG. 3, the flow of compressed air (supply / exhaust) is indicated by white arrows.

The piston 12 starts to move downward by the compressed air flowing into the piston upper chamber 12a. When the piston 12 starts to move downward, the air motor 30 starts to move downward together with the piston 12. The lower side (end plate 34a described later) of the air motor 30 is airtightly accommodated in a cylinder 18 attached to the main body case 2a. A front cushion 19 is attached to the lower portion of the cylinder 18. The driver pit 7 is inserted into the inner peripheral side of the front cushion 19. The lower side of the air motor 30 on the inner peripheral side of the cylinder 18 corresponds to the piston lower chamber 25.
The piston lower chamber 25 communicates with the atmosphere side through the inner peripheral side of the front cushion 19 and the exhaust passage 26. The exhaust passage 26 reaches the upper part of the main body case 2a. In this embodiment, the exhaust passage 26 is formed to have a larger diameter than that of the conventional one, and its effective ventilation area is sufficiently large, thereby increasing the exhaust efficiency when the piston is moved downward (when the screw is driven). Great striking power that has never been obtained can be obtained.
A disc-shaped output mode switching dial 45 is attached to the upper part of the main body case 2a as an example of an output mode switching mechanism. The output mode switching dial 45 is provided with a large-diameter large exhaust port 45a and a small-diameter small exhaust port (not shown). When the user manually rotates the output mode switching dial 45, the large exhaust port 45a is positioned at the upper end of the exhaust passage 26 (steel plate driving mode) or the small exhaust hole is positioned (wood driving mode). ) Can be arbitrarily switched. These two positions are held by a detent 45b comprising a spring-biased steel ball.
As shown in the figure, when the output mode switching dial 45 is switched to the former steel plate driving mode, the effective ventilation area of the exhaust passage 26 is maintained as it is, and high discharge efficiency can be maintained. For this reason, in this steel plate punching mode, a large striking force can be output in a steel plate punching operation or the like. On the contrary, when the output mode switching dial 45 is switched to the latter wood-cutting mode, the exhaust passage 26 is throttled at its outlet, so that the effective ventilation area is narrowed and the exhaust efficiency is lowered. For this reason, in this wood hammering mode, the striking force can be reduced and the reaction during screw driving can be suppressed, and the handling of the driving tool 1 can be improved in this respect.
As shown in the figure, an exhaust valve 20 is interposed in the exhaust passage 26. The exhaust valve 20 has a function of reducing the exhaust efficiency by narrowing the effective ventilation area of the exhaust passage 26 at the time of return, and this is a major feature of this embodiment. Details of the exhaust valve 20 will be described later.

A stroke shaft portion 31 of the air motor 30 is inserted into the inner peripheral side of the piston 12 so as to be relatively movable up and down. A stopper flange portion 32 is provided at the upper end portion of the stroke shaft portion 31. Four motor air inlets 33 to 33 are provided below the stopper flange portion 32. The compressed air that has flowed into the piston upper chamber 12 a when the head valve 11 is opened also flows into the inner peripheral side of the stroke shaft portion 31 through the motor air inlets 33 to 33.
The air motor 30 starts to rotate due to the compressed air flowing into the inner peripheral side of the stroke shaft portion 31 through the motor air inlets 33 to 33. The air motor 30 includes a motor case portion 34 that is eccentric with respect to the stroke shaft portion 31, and an output base 36 and a plurality of fins 35 to 35 can be displaced radially on the inner peripheral side of the motor case portion 34. The well-known structure accommodated in is provided. The output base 36 is accommodated so as to be rotatable with respect to the motor case 34 via bearings 36a and 36b. When compressed air flows into the motor case portion 34 through the inner peripheral side of the stroke shaft portion 31, the fins 35 receive the compressed air, whereby the output base 36 rotates, whereby the fins 35 reciprocate in the radial direction. Air supply and exhaust are made. As shown in FIG. 3, the motor air is exhausted through an exhaust port 2d provided on the side of the main body case 2a.
An output gear 36 c is formed at the lower end of the output base 36 of the air motor 30. The output gear 36c is connected to a planetary gear train 37 for reduction. A driver bit 7 is attached to the carrier 37 a of the planetary gear train 37. The carrier 37a is rotatably held with respect to the end plate 34a of the motor case part 34 via a bearing 38.
While the piston 12 and the air motor 30 are moved downward integrally by the compressed air flowing into the piston upper chamber 12a, the air motor 30 is rotated so that the driver bit 7 is driven downward while rotating in the driving passage 4a in the screw tightening direction. Thus, one screw B supplied into the driving passage 4a is hit by the driver bit 7, and then rotated in the tightening direction and fastened to the driving material W.
As shown in FIG. 3, after the piston 12 and the air motor 30 are integrally moved downward, and the piston 12 reaches the lower moving end position, the air motor 30 is further lowered alone. A piston stopper portion 12b provided on the outer periphery of the upper portion of the piston 12 abuts against the upper surface of the intermediate base portion 2e of the main body case 2a, whereby the lower end position of the piston 12 is regulated.
As shown by the white arrows in FIG. 3, when the piston 12 reaches the lower moving end, a plurality of auxiliary vent holes 12c to 12c provided around the piston 12 and a plurality of auxiliary passages provided around the intermediate base portion 2e. Since the pores 2f to 2f coincide with each other, the supply amount of compressed air to the inner peripheral side of the head valve 11 and the piston 12 increases at a stretch, whereby the air motor 30 starts to rotate at a high torque while moving down alone.
As shown in FIG. 4, after the piston 12 stops moving downward, the air motor 30 moves downward alone, so that the stopper flange portion 32 provided at the upper end portion of the stroke shaft portion 31 contacts the upper surface on the inner peripheral side of the piston 12. The air motor 30 comes into contact with the lower moving end position. When the stopper flange portion 32 comes into contact with the upper surface on the inner peripheral side of the piston 12, the supply of compressed air from the piston upper chamber 12a to the air motor 30 is stopped, and the rotation of the air motor 30 is stopped. At this point, the fastening of the screw B to the fastening material W is completed.
As described above, when the trigger valve 40 is turned on by pulling the switch lever 6, the compressed air is supplied to the piston upper chamber 12a, the piston 12 moves downward, and the air motor 30 rotates and is integrated with the piston 12. Then, the screw B is struck by the driving material W and tightened by reaching the lower moving end position while rotating at a higher torque and then reaching the lower moving end position. Is included.

When the user releases the pulling operation of the switch lever 6 after the screw driving is completed as shown in FIG. 5, the valve stem 43 of the trigger valve 40 is moved to the lower off position by the urging force of the compression spring 43a and the air pressure in the reservoir 3a. Returned to When the valve stem 43 is returned to the off position, the switch lever 6 is pushed and returned to the off position.
When the valve stem 43 is returned to the OFF position, the reservoir 3a is blocked from the upper surface of the valve inner frame portion 42, so that the air pressure of the reservoir 3a does not act on the upper surface, and as a result, the valve inner frame portion 42 is compressed. The spring 43a is moved upward by the urging force of the spring 43a. When the valve inner frame part 42 moves upward, the valve inner frame part 42 and the valve outer frame part 41 are blocked from the atmosphere side (atmosphere release hole 41c) side, while the valve case hole 3c of the valve case part 3b is closed. The working air passage 2c communicates with the reservoir 3a through the first air hole 41a of the valve outer frame part 41, between the valve outer frame part 41 and the valve inner frame part 42, and through the second air hole 41b of the valve outer frame part 41. Is done.
When the working air passage 2c communicates with the reservoir 3a in this way, the compressed air flows into the head valve upper chamber 11a through the working air passage 2c, and the head valve 11 is moved downward by the compression spring 13, thereby causing the piston upper chamber to move downward. 12a is cut off from the pressure accumulation chamber 2b side, and the supply of compressed air to the piston upper chamber 12a is stopped.
When the head valve 11 is closed, the compressed air confined in the piston upper chamber 12a is used as return air for returning the piston 12 and the air motor 30 to the top dead center. Therefore, the driving tool 1 of the present embodiment is an exhaust return type driving tool.
A cylindrical upper base portion 2g is provided on the upper portion of the main body case 2a. The upper base portion 2g defines a head valve upper chamber 11a. On the inner peripheral side of the upper base portion 2g, a stroke shaft portion 11b provided on the upper portion of the head valve 11 is held so as to be vertically movable and airtight. A valve stopper 14 is attached above the stroke shaft portion 11b and above the upper base portion 2g. A plurality of exhaust holes 15 to 15 are provided below the valve stopper 14 and on the side of the upper base portion 2g. Ring-shaped check valves 16 are attached to the outer peripheral sides of all the exhaust holes 15 to 15. A return air passage 17 communicates with the upper base portion 2g. The check valve 16 allows the flow of compressed air from the inner peripheral side of the upper base portion 2g through the exhaust holes 15 to 15 to the return air passage 17, and blocks the flow of compressed air in the reverse direction.
As shown in FIGS. 2 to 4, when the head valve 11 is moved upward and the piston upper chamber 12a is opened with respect to the pressure accumulating chamber 2b, the stroke shaft portion 11b of the head valve 11 abuts against the valve stopper 14. As a result, the piston upper chamber 12a is airtightly blocked from the exhaust holes 15-15. On the other hand, as shown in FIGS. 1 and 5, in the state where the head valve 11 is moved downward and the piston upper chamber 12a is shut off from the pressure accumulating chamber 2b, the stroke shaft portion 11b of the head valve 11 is connected to the valve stopper 14. The piston upper chamber 12a is separated and communicated with the exhaust holes 15 to 15 side. For this reason, as shown in FIG. 5, the compressed air confined in the piston upper chamber 12 a as the head valve 11 moves downward flows into the return air passage 17 through the exhaust holes 15 to 15 and the check valve 16.

The return air passage 17 communicates with the piston lower chamber 25 through a return hole 18 a provided in the lower part of the cylinder 18 and on the outer peripheral side of the front cushion 19. Therefore, the compressed air that has flowed into the return air passage 17 from the piston upper chamber 12a through the exhaust holes 15 to 15 and the check valve 16 flows into the cylinder lower chamber 25 through the return air passage 17 and the return hole 18a. To do. Compressed air (return air) flowing into the piston lower chamber 25 from the piston upper chamber 12a through the return air passage 17 acts on the end plate 34a of the air motor 30, thereby finally causing the piston 12 and the air motor 30 to move from the bottom dead center. Returned to top dead center.
As shown in FIG. 6, immediately after the air motor 30 starts to move upward, a part of the return air flows into the exhaust passage 26 through the inner peripheral side of the front cushion 19 and is exhausted.
Here, the exhaust valve 20 is provided in the exhaust passage 26 as described above. Details of the exhaust valve 20 are shown in FIGS. In the first embodiment, the exhaust valve 20 is provided between the return air passage 17 and the exhaust passage 26. The exhaust valve 20 of the first embodiment includes an exhaust piston 21 and a compression spring 22. The exhaust piston 21 has a throttle position protruding into the exhaust passage 26 as shown in FIGS. 5, 6, and 8 and an open position retracted from the exhaust passage 26 as shown in FIGS. 1 to 4 and 7. It is supported so as to be movable in the left-right direction in the figure. When the exhaust piston 21 moves to the former throttle position, the effective ventilation area of the exhaust passage 26 is narrowed, and the exhaust efficiency decreases. When the exhaust piston 21 moves to the latter open position, the effective ventilation area of the exhaust passage 26 is increased, so that the exhaust efficiency is increased.
The exhaust piston 21 is urged toward the open position by which the exhaust passage 26 is opened by the compression spring 22. The air pressure of the return air passage 17 acts on the upper surface (left side surface in the figure) of the exhaust piston 21 through the operation hole 23. As shown in FIG. 7, in a state where compressed air does not flow into the return air passage 17, the exhaust valve 21 is held in the open position by the compression spring 22, so that high exhaust efficiency of the exhaust passage 26 is maintained. In contrast, as shown in FIG. 8, when the head valve 11 is closed and the compressed air confined in the piston upper chamber 12a flows into the return air passage 17 through the exhaust holes 15 to 15 and the check valve 16, The air pressure acts on the exhaust piston 21 through the operating hole 23, and thereby the exhaust piston 21 moves to the throttle position against the compression spring 22. Therefore, when return air is supplied from the piston upper chamber 12a through the return air passage 17 to the piston lower chamber 25, the exhaust valve 20 is operated to the throttle side at the same time, and the exhaust passage 26 is throttled, thereby improving the exhaust efficiency. It is in a suppressed state.
In this way, by forming the exhaust passage 26 with a larger diameter than before and increasing its exhaust efficiency, it is possible to output a large striking force that could not be obtained in the past. Therefore, most of the return air that has flowed into the piston lower chamber 25 is consumed to return the piston 12 and the air motor 30 to the top dead center. Returned to top dead center.

As shown in FIG. 5, when return air flows into the piston lower chamber 25, this acts on the end plate 34 a of the air motor 30. Due to the area difference between the end plate 34 a and the upper surface of the stroke shaft portion 31, the air motor 30 first moves up by the air pressure on the return air chamber 25 side. As shown in FIG. 6, when the air motor 30 moves upward with respect to the piston 12, the stopper flange portion 32 is separated from the upper surface on the inner peripheral side of the piston 12, so that the piston upper chamber 12 a strokes through the motor air inlets 33 to 33. The piston upper chamber 12a is communicated with the inner peripheral side of the shaft portion 31, thereby opening the piston upper chamber 12a to the atmosphere via the motor air supply path and the exhaust port 2d. On the other hand, the return air flowing into the piston lower chamber 25 through the return air passage 17 is prevented from flowing back into the piston upper chamber 12a by the check valve 16. In this way, the piston upper chamber 12a is opened to the atmosphere, and the return air flows into the piston lower chamber 25, whereby the air motor 30 further moves up.
In addition, since a part of the compressed air (motor exhaust) flowing into the motor air supply path from the piston upper chamber 12a through the motor air inlets 33 to 33 acts on the lower surface of the piston 12, the piston 12 also starts to move up at this time. .
Through the state shown in FIG. 6, the stopper washer 39 provided around the stroke shaft portion 31 of the air motor 30 comes into contact with the lower surface of the intermediate base portion 2e, and the air motor 30 reaches the top dead center. Thus, the air motor 30 is returned to the top dead center, and the piston 12 is moved upward by exhausting the motor. Finally, the piston 12 is pushed by the air motor 30 that moves upward while the stopper washer 39 of the air motor 30 is in contact with the lower surface. Returned to dead point.
The return air flowing into the piston lower chamber 25 is discharged to the atmosphere from the large exhaust port 45a of the output mode switching dial 45 through the exhaust passage 26, and also from the inside of the driving passage 4a through the inner peripheral side of the front cushion 19. To be discharged. As a result of the return air in the piston lower chamber 25 being discharged to the atmosphere, when the air pressure in the return air passage 17 decreases, the exhaust piston 21 is returned to the open position by the compression spring 22 and the exhaust valve 20 is brought to the initial position. Returned.
Further, the air passage 5 a of the driving tool supply device 5 is communicated with the return air passage 17. For this reason, as shown in FIG. 5, after the completion of driving, a part of the compressed air flowing into the return air passage 17 from the piston upper chamber 12a is supplied to the driving tool supply device 5 through the air passage 5a. The feed piston 5b moves backward against the compression spring 5c by the compressed air supplied through the air passage 5a. When the return air in the piston lower chamber 25 is exhausted, the feed piston 5b moves forward by the compression spring 5c. The feed piston 5b is provided with feed claws 5d and 5d. When the feed piston 5b moves forward, one screw B is supplied into the driving passage 4a by the feed claws 5d and 5d.

According to the driving tool 1 of the first embodiment configured as described above, the exhaust passage 26 is formed to have a larger diameter than the conventional one and the exhaust efficiency of the piston lower chamber 25 is enhanced. Screw B can be driven into the steel plate with high output.
Moreover, an exhaust valve 20 is interposed in the exhaust passage 26. The exhaust valve 20 has a function of changing the effective ventilation area of the exhaust passage 26. According to the exhaust valve 20, when the piston is moved downward and when a screw is hit (tightened), the exhaust valve 20 moves to the open position, and the effective ventilation area of the exhaust passage 26 is expanded, whereby the exhaust of the piston lower chamber 25 is exhausted. While higher efficiency is achieved and higher output is performed, when the piston moves up after completion of the impact, the exhaust efficiency of the piston lower chamber 25 is suppressed by moving to the throttle position and narrowing the effective ventilation area of the exhaust passage 26. Thus, it is possible to sufficiently secure return air for returning the piston 12 and the air motor 30 to the top dead center, and to prevent malfunction of the driving tool 1.
As described above, in order to avoid the shortage of return air after completion of the conventional hitting, there is a limit to increasing the exhaust passage to increase the exhaust efficiency of the piston lower chamber, but the driving tool 1 of the present embodiment. According to the present invention, the exhaust passage 26 can be made larger in diameter while ensuring sufficient return air, so that it is possible to increase the driving force that has been difficult in the prior art. it can.
In addition, according to the driving tool 1 of the present embodiment, the effective full-time area of the exhaust passage can be fixedly switched by rotating the output mode switching dial 45 separately from the exhaust valve 20. A high output steel plate driving mode and a low output wood punching mode can be arbitrarily selected. In any case, since the exhaust valve 20 operates at a fixed timing (when the piston moves up after the completion of striking), the return air is sufficiently secured and the piston 12 and the air motor 30 are reliably returned to the top dead center. This prevents malfunctions.

The first embodiment described above can be implemented with various modifications. For example, the exhaust valve 20 is operated to the throttle side by using return air in the return air passage 17 in the exhaust return structure, but instead, the head valve 11 is operated to the closing side after the completion of driving. The exhaust valve 50 may be operated to the throttle side by compressed air. The driving tool of the second embodiment is shown in FIGS. The driving tool according to the second embodiment is different from the first embodiment in the configuration of the exhaust valve 50, and the other configurations are the same as those in the first embodiment. To do.
In the case of the second embodiment, as shown in FIGS. 9 and 10, the working air passage 2 c is branched in front of the head valve upper chamber 11 a to provide an exhaust valve working passage 53. An exhaust valve 50 according to the second embodiment is provided between the exhaust valve operating passage 53 and the exhaust passage 26. Similarly to the first embodiment, the exhaust valve 50 of the second embodiment includes an exhaust piston 51 and a compression spring 52 that biases the exhaust piston 51 to the open side. The upper surface (lower surface in the figure) of the exhaust piston 51 faces the exhaust valve operating passage 53.
As shown in FIG. 9, in a state where compressed air does not flow into the exhaust valve working passage 53 (atmospheric release state), the exhaust piston 51 opens the exhaust passage 26 by the urging force of the compression spring 52 (exhaust state). The position retracted from the passage 26). On the other hand, as shown in FIG. 10, when compressed air flows into the exhaust valve working passage 53 through the working air passage 2c, the exhaust piston 51 enters the exhaust passage 26 against the compression spring 52 by the air pressure. It moves to the aperture position (upward in the figure). When the exhaust piston 51 reaches the throttle position, the effective ventilation area of the exhaust passage 26 is reduced and the exhaust efficiency of the piston lower chamber 25 is suppressed.
According to the exhaust valve 50 according to the second embodiment, the pulling operation of the switch lever 6 is released after the screw tightening is completed, and the trigger valve 40 is turned off. Compressed air is supplied. Thus, when the inside of the working air passage 2c is switched from the open state to the compressed air supply state, the compressed air flows into the head valve upper chamber 11a and the head valve 11 is closed. As a result, the compressed air flows into the piston upper chamber 12a. While the supply is stopped, the compressed air also flows into the exhaust valve operating passage 53 that is branched from the operating air passage 2c. As a result, the exhaust piston 51 is operated to the throttle side and the exhaust passage 26 is throttled. It becomes a state.
When the head valve 11 is moved down and closed, the stroke shaft portion 11b is separated from the valve stopper 14, so that the exhaust holes 15 to 15 are communicated with the piston upper chamber 12a. The compressed air confined in the air flows into the return air passage 17 through the exhaust holes 15 to 15 and the check valve 16. The compressed air that has flowed into the return air passage 17 flows into the piston lower chamber 25 and moves the piston 12 and the air motor 30 upward, while part of the compressed air is exhausted to the atmosphere via the exhaust passage 26. At this stage, since the exhaust passage 26 is throttled by the exhaust valve 50, the exhaust efficiency is appropriately suppressed. Therefore, a sufficient amount of the return air flowing into the piston lower chamber 25 through the return air passage 17 is consumed to return the piston 12 and the air motor 30 to the top dead center, and the piston 12 and the air motor 30 are surely dead. Returned to the point.
As described above, by operating the exhaust valve 50 to the throttle side using the compressed air for closing the piston upper chamber 12a after the screw tightening is completed, the operation of the driving tool 1 while securing a sufficient amount of return air is ensured. Since the defect (defective return of the piston 12 or the like) can be surely prevented, the effective ventilation area of the exhaust passage 26 can be made sufficiently larger than before, and the high output that has been difficult in the past can be realized.

FIG. 11 shows the driving tool 1 according to the third embodiment, in which the driving tool 1 of the second embodiment is further modified. The driving tool 1 according to the third embodiment is different from the second embodiment in that the driving tool 1 according to the third embodiment has a configuration in which the return air passage 17 and the exhaust passage 26 are joined together. Since the exhaust valve 50 and other configurations are not changed, description thereof is omitted using the same reference numerals.
As in the second embodiment, the working air passage 2 c is branched before the head valve upper chamber 11 a to provide an exhaust valve working passage 53, and the exhaust valve working passage 53 reaches the exhaust valve 50. For this reason, when the compressed air is supplied into the working air passage 2c after the screw tightening is completed and the head valve 11 is closed, the exhaust piston 51 of the exhaust valve 50 is operated toward the throttle side at the same time, and the exhaust passage 55 is activated. The ventilation area is reduced.
In the case of the third embodiment, the return air passage 56 provided around the upper base portion 2g communicates with the exhaust passage 55. The compressed air confined in the piston upper chamber 12 a by closing the head valve 11 flows into the return air passage 56 through the exhaust holes 15 to 15 and the check valve 16, and then into the piston lower chamber 25 through the exhaust passage 55. It acts as return air for returning the piston 12 and the air motor 30 to the top dead center.
As in the second embodiment, since the exhaust passage 55 is throttled by the exhaust valve 50 at this time, the exhaust efficiency of the piston lower chamber 25 is appropriate until the piston 12 and the air motor 30 are returned to the top dead center. It is in a state suppressed to. After the piston 12 and the air motor 30 are returned to the top dead center, the compressed air in the piston lower chamber 25 is exhausted mainly from the large exhaust port 45a to the atmosphere via the exhaust passage 55, and finally the piston lower chamber 25, return The air passage 56 and the exhaust passage 55 are opened to the atmosphere.
As long as the working air passage 2c is in the compressed air supply state, the exhaust valve 50 is in a state of being operated toward the throttle side. Therefore, the exhaust valve 50 is returned to the open side when the trigger lever 40 is turned on by pulling the switch lever 6 next time.
As described above, the configuration of the third embodiment in which the return air passage 56 is joined to the exhaust passage 55 as described above, as in the second embodiment, the exhaust valve 50 is operated to the throttle side after the screw tightening is completed, and the exhaust efficiency is appropriately set. By restraining to a sufficient value, a sufficient amount of return air can be secured, thereby preventing a malfunction of the driving tool 1 and obtaining a high output during screw driving. In the case of the third embodiment, the return air passage 56 can be joined to the exhaust passage 55 to function as a combined air passage having a larger ventilation area, so that the exhaust passage can be made wider while simplifying the passage arrangement. Thus, higher output can be achieved.
Further modifications can be made to the first to third embodiments described above. For example, the screw driving machine having the air motor 30 incorporated therein is exemplified as the driving tool 1, but this is a driving tool only for a hammering action that does not include this type of air motor, and can be similarly applied to a nailing machine. Moreover, although the driving tool provided with the exhaust return structure which utilizes the compressed air of the piston upper chamber as return air for returning the piston to the top dead center is illustrated, the piston upper chamber is moved when the piston moves downward (when the driving tool is hit). By applying the exhaust valves 20 and 50 exemplified for the driving tool having the air supply return structure that stores the compressed air supplied to the return air chamber and uses the compressed air as the return air when the piston moves up, the same effect can be obtained. An effect can be obtained.

B ... Screw W ... Fastening material 1 ... Driving tool 2 ... Tool main body 2a ... Main body case, 2b ... Accumulation chamber, 2c ... Working air passage, 2d ... Exhaust port 2e ... Intermediate base part, 2f ... Auxiliary vent hole, 2g ... Upper base part 3 ... Handle part 3a ... Reservoir, 3b ... Valve case part, 3c ... Valve case hole 4 ... Driving guide part, 4a ... Driving tool supply unit 5a ... Driving tool supply device 5a ... Air path, 5b ... Feeding piston, 5c ... compression spring, 5d ... feed claw 6 ... switch lever 7 ... driver bit 8 ... contact arm 10 ... impact mechanism 11 ... head valve, 11a ... head valve upper chamber 12 ... piston 12a ... piston upper chamber, 12b ... piston stopper , 12c ... auxiliary vent hole 13 ... compression spring 14 ... valve stopper 15 ... exhaust hole 16 ... check valve 17 ... return air passage 18 ... cylinder 19 ... Lont cushion 20 ... exhaust valve 21 ... exhaust piston 22 ... compression spring 23 ... operating hole 25 ... piston lower chamber 26 ... exhaust passage 30 ... air motor 31 ... stroke shaft part 32 ... stopper flange part 33 ... motor air inlet 34 ... motor case part 34a ... End plate 35 ... Fin 36 ... Output base 36a, 36b ... Bearing 36c ... Output gear 37 ... Planetary gear 37a ... Carrier 38 ... Bearing 39 ... Stopper washer 40 ... Trigger valve 41 ... Valve outer frame part 41a ... 1st air hole, 41b ... 2nd air hole, 41c ... Air release hole 42 ... Valve inner frame part 43 ... Valve stem, 43a ... Compression spring 45 ... Output mode switching dial, 45a ... Large exhaust port, 45b ... Detent 50 ... Exhaust valve (second embodiment)
51 ... Exhaust piston 52 ... Compression spring 53 ... Exhaust valve working passage 55 ... Exhaust passage (third embodiment)
56. Return air passage (third embodiment)

Claims (7)

While the piston lower chamber is exhausted through the exhaust passage, the piston is moved downward by the compressed air supplied to the piston upper chamber to generate a driving force, and the compressed air supplied to the piston upper chamber is used as return air as the return air. A driving tool that flows into the chamber and returns the piston to top dead center ,
A driving tool comprising an exhaust valve that opens the exhaust passage when the piston moves downward and throttles the exhaust passage when the piston moves upward. 2. The driving tool according to claim 1, further comprising an output mode switching mechanism that changes the driving force by manually changing an aperture of the exhaust port of the exhaust passage. The driving tool according to claim 1 or 2, wherein compressed air supplied to the piston upper chamber flows into the piston lower chamber through a return air passage, and part of the compressed air is returned to the top dead center. A driving tool having an exhaust return structure that is used as return air and exhausts the remainder through the exhaust passage. 4. The driving tool according to claim 3, wherein the exhaust valve is operated in a throttle direction by return air in the return air passage. The driving tool according to any one of claims 1 to 3, further comprising a head valve that opens and closes the piston upper chamber with respect to the pressure accumulating chamber, and the exhaust valve is throttled by compressed air that closes the head valve. Driving tool configured to operate in the direction. 5. The driving tool according to claim 3, wherein the exhaust passage and the return air passage are merged. It is a driving tool given in any 1 paragraph of Claims 1-6, Comprising: The air motor which operates with the compressed air is built in, and the air motor is rotated while hitting a screw by the downward movement of the piston. A driving tool which is a screw driving machine for tightening the screw.

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