JP4158598B2 - Combustion power tool - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion-type power tool, and in particular, a liquefied gas sealed in a gas cylinder is injected into a combustion chamber, mixed with air, and ignited to generate power for driving a piston and hit a stopper such as a nail. The present invention relates to a combustion type driving tool.
[0002]
[Prior art]
Conventional combustion power tools include a housing, a handle, a trigger switch, a head cap, a combustion chamber frame, a push lever, a cylinder, a piston, a driver blade, a blade guide, a motor, and a fan. The gas cylinder, the spark plug, the exhaust check valve, the magazine, and the tail cover are mainly provided. The head cap closes one end of the housing, the handle is fixed to the housing, and a trigger switch is attached. The combustion chamber frame is provided in the housing so as to be movable in the longitudinal direction of the housing, and is urged by a spring in the direction opposite to the head cap, but is provided so that one end can be in contact with the head cap against the urging force of the spring. It is done.
[0003]
The push lever is movably provided at the other end of the housing and is connected to the combustion chamber frame. The cylinder is positioned so as to be communicable with the combustion chamber frame and is fixed to the housing, guides the movement of the combustion chamber frame, and has an exhaust hole formed at substantially the center in the axial direction thereof. The piston is slidable with respect to the cylinder, and the cylinder is defined by a piston lower chamber and a piston upper chamber in the cylinder. When one end of the combustion chamber frame comes into contact with the head cap, the combustion chamber is defined together with the head cap, the combustion chamber frame, and the piston upper chamber in the cylinder. The driver blade extends from the anti-combustion chamber side of the piston toward the other end of the housing. The blade guide is fixed to the lower end of the housing and is positioned on the outer peripheral surface side of the driver blade to guide the reciprocating motion of the driver blade. The motor is supported by the head cap, and the fan is fixed to the motor and located in the combustion chamber. The fan is driven by a motor to promote combustion by mixing combustion gas and air in the combustion chamber, and when the combustion chamber frame is separated from the head cap, the outside air is introduced into the housing to move the inside of the combustion chamber frame. It scavenges and plays a role of cooling the outer peripheral side of the cylinder. The gas cylinder is accommodated in the housing and includes liquefied gas that is injected as a combustible gas into the combustion chamber through the gas passage of the head cap. The spark plug faces the combustion chamber and ignites a mixture of combustible gas and air. The exhaust check valve selectively shields the exhaust hole.
[0004]
The magazine is provided on the other end side of the housing and accommodates a stopper such as a nail. The tail cover is provided between the magazine and the push lever in order to feed the magazine stopper to a position facing the driver blade. A guide gap that communicates between the piston lower chamber in the cylinder and the outside air is formed at the lower end of the cylinder and the housing and through which the driver blade passes.
[0005]
To seal the combustion chamber when the combustion chamber frame comes into contact with the head cap, a predetermined surface of the head cap that is in close contact with the upper portion of the combustion chamber frame, and a head cap side end portion of the cylinder that is in close contact with the lower portion of the combustion chamber frame Are provided with sealing materials (seal rings).
[0006]
When the push lever is pressed against the workpiece, liquefied gas is injected into the combustion chamber from the gas cylinder installed in the housing with the combustion chamber defined, and the air and combustible gas are stirred and mixed by the fan. When the switch is turned on, the air-fuel mixture explodes and burns by ignition by the spark plug, and the piston is driven to drive a nail into a workpiece such as wood through a driver blade. The combustion chamber frame is kept in contact with the head cap until a predetermined time has elapsed after the explosion combustion, and the combustion chamber is sealed by closing the exhaust check valve after exhausting the combustion gas, and the temperature decreases. Due to the pressure drop in the combustion chamber caused by the above, a thermal vacuum is obtained on the piston upper chamber side in the cylinder. On the other hand, since the lower chamber side of the piston in the cylinder is connected to the atmosphere through the guide gap, the pressure in the lower chamber of the piston in the cylinder is higher than the upper chamber of the piston in the cylinder, so that the piston returns to the initial top dead center position. After that, when the trigger switch is released and the push lever is released from the workpiece (not shown), the combustion chamber frame and the push lever are lowered by the bias of the spring, the combustion chamber is opened to the outside air, and the scavenging is performed by the rotation of the fan. Return to the initial position. (For example, refer to Patent Document 1).
[Patent Document 1]
Japanese Patent Publication No. 7-36985
[0007]
[Problems to be solved by the invention]
In the conventional combustion type driving tool described above, the air in the piston lower chamber flows out of the tool through the exhaust hole and the guide gap until the piston reaches the exhaust hole of the cylinder during the downward stroke of the piston. The pressure increase in the chamber is small. However, when the piston passes through the exhaust hole, the passage between the piston lower chamber and the tool outside air is only the guide gap. Here, the guide gap is a gap in the blade guide that forms a hole covering the lower end of the cylinder so that the piston lower chamber in the cylinder communicates with the outside air, and a driver in the guide portion that guides the driver blade of the blade guide. It refers to the blade gap between the blade and the guide.
[0008]
In order to suppress the pressure increase in the piston lower chamber, it is necessary to increase the flow path cross-sectional area of the guide gap. However, from the viewpoint of maintaining the mechanical strength of the blade guide, there is a restriction on increasing the size of the hole. As an example, in the case of a combustion type driving tool having a general nail length of 90 mm, the guide gap is about 160 mm. ² Degree. Further, since it is necessary to guide the movement of the driver blade as accurately as possible, the cross-sectional area of the blade gap needs to be very small. Therefore, when nailing, when the piston descends at a high speed, the cross-sectional area of the guide gap is not sufficient to exhaust the air in the lower chamber of the piston, and an increase in back pressure occurs especially after the piston passes through the exhaust hole. As a result, the piston speed decreases. Here, the driving energy E of the tool is E = (1/2) × mv ² As represented by (m: piston mass, v: piston speed), it is proportional to the square of the speed, so a decrease in the piston speed significantly reduces the driving energy.
[0009]
Further, since the magazine is provided on the other end side of the housing, the guide gap cannot be opened on the magazine fixing side at the lower part of the housing, and the guide gap must be opened only on the side opposite to the magazine at the lower part of the housing. Thus, a sufficient flow path opening cross-sectional area could not be obtained.
[0010]
Therefore, an object of the present invention is to provide a combustion type power tool that can suppress an increase in back pressure in a cylinder lower piston chamber even after the piston passes through an exhaust hole and does not reduce driving energy.
[0011]
[Means for Solving the Problems]
In order to achieve such an object, the present invention provides a housing, a handle extending from the housing and provided with a trigger switch, a head portion closing one end of the housing and having a combustible gas passage formed therein, and a head portion. Motor, a push lever provided below the housing and movable when pressed against the workpiece, a cylinder fixedly provided in the housing and having an exhaust hole, and an axial direction of the cylinder The piston is reciprocally slidable with respect to the cylinder, the piston defining the cylinder into a piston lower chamber and a piston upper chamber in the cylinder, and movably guided in the housing, and interlocked with the movement of the push lever. And a combustion chamber frame that forms a combustion chamber together with the head portion and the piston upper chamber in the cylinder, and a direction from the piston to the anti-combustion chamber. A driver blade that extends and reciprocates with the piston, a blade guide that is positioned on the outer peripheral surface side of the driver blade to guide the reciprocating motion of the driver blade, and when the combustion chamber frame abuts against the head portion, the combustion A seal that seals between the chamber frame and the head and seals between the combustion chamber frame and the cylinder; a fan that is rotatably provided in the combustion chamber and is driven to rotate by the motor; and the combustion An ignition plug facing the combustion chamber for igniting a mixture of combustible gas and air in the room, an exhaust check valve provided to open and close the exhaust hole, and a stopper located below the housing A magazine for storing and holding, and a tail cover for feeding a stopper accommodated in the magazine to the lower side of the driver blade and into which a tip portion of the driver blade enters, the cylinder In a combustion power tool in which a guide gap for communicating the piston lower chamber in the cylinder and the outside air is formed at a lower end portion of the housing and through which the driver blade passes, in the cylinder or the housing Provides a combustion type power tool in which a back pressure prevention passage that communicates the piston lower chamber in the cylinder and the outside air is formed separately from the guide gap at a position below the exhaust hole.
[0012]
Here, it is preferable that the back pressure prevention passage is composed of at least one through hole formed through the peripheral surface of the cylinder. Moreover, it is preferable that the lower end part in the cylinder is provided with a bumper for the piston to thrust, and the back pressure prevention passage is located below the piston thrusting surface of the bumper.
[0013]
Alternatively, the bottom portion of the housing is formed of a double wall that is spaced apart from each other in the axial direction of the driver bit, and the center portion of the double wall passes through the guide gap through which the tip of the driver bit passes. None, the space between the double walls is used as the back pressure prevention passage, and the magazine is preferably positioned below the double walls. Here, an opening communicating with the guide gap is formed at the bottom of the cylinder, and a guide portion extending in a diametrical direction from an edge of the opening is provided integrally with the cylinder to form the blade guide. Preferably there is.
[0014]
Further, the volume V m of the piston lower chamber in the cylinder at the piston top dead center ^Three And the total cross-sectional area Sm of the cross-sectional area of the guide gap and the cross-sectional area of the back pressure prevention passage ² The ratio V / S is preferably 1.5 or less.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment in which a combustion-type power tool according to the present invention is applied to a combustion-type driving tool will be described with reference to FIGS. The combustion type driving tool 1 has a housing 2 constituting an outer frame, and the housing 2 is a main housing portion 2A and a cylinder chamber portion provided in parallel with the main housing portion 2A along the longitudinal direction of the main housing portion 2A. 2B. An exhaust port 2a is formed in the lower portion of the main housing portion 2A.
[0016]
A head cover 4 having an intake port is attached to the upper portion of the main housing portion 2A, and a gas cylinder 5 containing combustible liquefied gas is detachably accommodated in the cylinder chamber portion 2B. A handle 7 is extended from the cylinder chamber 2B. The handle 7 includes a trigger switch 6. Built-in battery not shown. Below the main housing portion 2A and the cylinder chamber portion 2B, there are provided a magazine 8 loaded with nails (not shown), and a tail cover 9 for feeding and guiding the nails in the magazine 8 to a predetermined position. .
[0017]
A push lever 10 is movably supported at the lower end of the main housing portion 2A corresponding to the nail setting position of the tail cover 9 and is connected to a connecting member 12 fixed to a combustion chamber frame 11 described later. Above the connecting member 12, a spring seat 20 </ b> B protruding in a flange shape from an outer peripheral surface of a cylinder 20, which will be described later, is located, and between the upper end of the connecting member 12 and the spring seat 2 </ b> C, a compression coil spring 22. Is interposed to urge the combustion chamber frame 11 toward the anti-head cap 13. When the tip of the push lever 10 abuts on a workpiece (not shown) and presses the entire housing 2 in the workpiece direction against the urging force of the compression coil spring 22, the upper portion of the push lever 10 is retracted into the main housing portion 2A. Is possible.
[0018]
A head cap 13 serving as a head portion for closing the upper end opening is fixed to the upper end of the main housing portion 2A. The head cap 13 supports a motor 3 having a fan 14 fixed on a rotating shaft, and also includes a trigger switch 6. The spark plug 15 that is ignited by the operation is stored and held. A head switch (not shown) for detecting that the tool is pressed against the workpiece and the combustion chamber frame 11 is at the upper end of the stroke is provided in the main housing portion 2A. When the push lever 10 is raised to a predetermined position, the head switch is turned on so that the motor 3 starts rotating and the fan 14 starts rotating.
[0019]
An injection passage 17 that is a fuel passage is formed in the cylinder chamber 2B side of the head cap 13, one end of the injection passage 17 forms an injection port 18 that opens to the lower end surface of the head cap 13, and the other end side is connected to the gas cylinder 5. The gas cylinder connecting part is connected. Further, the head cap 13 includes a first seal member formed of an O-ring for sealing between the head cap 13 and the combustion chamber frame 11 when an upper portion of a combustion chamber frame 11 described later contacts the head cap 13. 19 is installed.
[0020]
A combustion chamber frame 11 that is movable in the longitudinal direction of the main housing portion 2A and whose upper end can come into contact with the lower end surface of the head cap 13 is provided in the main housing portion 2A. As described above, since the connecting member 12 described above is fixed to the lower end portion of the combustion chamber frame 11 and connected to the push lever 10, the combustion chamber frame 11 also moves as the push lever 10 moves. A cylinder 20 that contacts the inner peripheral surface of the combustion chamber frame 11 and guides the movement of the combustion chamber frame 11 is fixed to the main housing portion 2A. An exhaust hole 21 that can communicate with the exhaust port 2a of the main housing portion 2A described above is formed in the vicinity of the central portion of the cylinder 20 in the axial direction. A check valve (not shown) is provided so as to selectively close the exhaust hole 21. Further, a bumper 23 is provided at the bottom of the cylinder 20. Further, an upper portion of the cylinder 20 includes an O-ring that seals between the lower side inner peripheral surface of the combustion chamber frame 11 and the upper outer peripheral surface of the cylinder 20 when the combustion chamber frame 11 contacts the head cap 13. Two sealing materials 24 are mounted.
[0021]
In the cylinder 20, a piston 25 that can reciprocate with respect to the cylinder 20 is provided. The piston 25 defines the cylinder 20 into a cylinder upper piston chamber and a cylinder lower piston chamber. When the upper end of the combustion chamber frame 11 comes into contact with the head cap 13, the combustion chamber 26 is defined by the head cap 13, the combustion chamber frame 11, the piston upper chamber in the cylinder, and the first and second sealing materials 19 and 24. Is done. When the combustion chamber frame 11 is separated from the head cap 13, a first flow path communicating with the outside air is generated between the head cap 13 and the upper end of the combustion chamber frame 11, and the lower end portion of the combustion chamber frame 11 and the cylinder 20. A second flow path following the first flow path is formed between the upper end of the first flow path and the upper end of the first flow path. The second flow path allows combustion gas and new air to pass through the outer peripheral surface of the cylinder 20 and is discharged from a discharge port (not shown) of the main housing portion 2A.
[0022]
A plurality of ribs 27 extend in the axial direction of the combustion chamber frame 11 and project inward in the radial direction at a portion defining the combustion chamber 26 of the combustion chamber frame 11. This rib 27 is for accelerating the stirring and mixing of the air and the combustible gas in the combustion chamber 26 in combination with the rotation of the fan 14. The intake port described above is formed to supply air into the combustion chamber 26, and the combustion gas in the combustion chamber 26 is discharged from the exhaust hole 21 and the exhaust port 2a.
[0023]
The fan 14, spark plug 15, and injection port 18 are all arranged or opened in the combustion chamber 26. The rotation of the fan 14 causes the air and the combustible gas to be agitated and mixed when the combustion chamber frame 11 is in contact with the head cap 13, thereby causing turbulent combustion after ignition to promote combustion. When the frame 11 is separated from the head cap 13 and the first and second flow paths are generated, the three functions of scavenging the combustion gas in the combustion chamber 26 and cooling the cylinder 20 are performed.
[0024]
A driver blade 28 is provided extending from the surface of the piston 25 on the piston lower chamber side toward the lower end of the main housing portion 2A. The driver blade 28 is in a coaxial position where it can come into contact with the nail in the tail cover 9, and when the piston 25 descends, the nail is driven into the workpiece at the tip of the driver blade 28, and the piston 25 hits the bumper 23 described above. Surplus energy is absorbed and stopped.
[0025]
A through hole 30 through which the driver blade 28 is passed is formed in the bottom of the cylinder 20 and the main housing 2A, and a left blade guide 31 and a right blade guide having an L-shaped cross section are formed in the bottom of the main housing 2A. 32 is fixed. The left blade guide 31 has a fixed portion fixed to the bottom of the main housing portion 2A and a guide portion for guiding the driver blade 28. The fixed portion is formed with a through-hole 31a communicating with the through hole 30. The part has a slight blade gap with respect to the driver blade 28. Similarly, the right blade guide 32 has a fixed portion fixed to the bottom of the main housing portion 2 </ b> A and a guide portion for guiding the driver blade 28, and the guide portion has a slight blade gap with respect to the driver blade 28. The blade gap and the through hole 30 provide a guide gap 29 that allows the in-cylinder piston lower chamber and the outside air to communicate with each other via the exhaust port 2a. The guide gap 29 functions to introduce outside air into the cylinder lower piston chamber when the piston 25 returns to the initial position. The magazine 8 is installed below the right blade guide 32. Note that the top of the tail cover 9 is provided away from the left blade guide 31 so that the through-hole 31a communicates with the piston lower chamber in the cylinder and the outside air.
[0026]
In addition, a plurality of through-holes 20a serving as back pressure prevention passages are formed on the circumference of the same cross section on the peripheral wall surface below the cylinder 20 and below the top surface (piston contact surface) of the bumper 23. The through-hole 20a allows the piston lower chamber in the cylinder and the outside air to communicate with each other via the exhaust port 2a of the main housing part 2. The through hole 20a is opened not only on the anti-magazine 8 side but also on the magazine 8 side. The through-hole 20a serving as a back pressure prevention passage allows the air in the piston lower chamber in the cylinder to be actively discharged to the outside air after the piston 25 passes through the exhaust hole 21 while the piston 25 is descending. Has a function of preventing back pressure from being generated. Although it is considered that such a function can be achieved at a glance by the guide gap 29 described above, the size of the through-hole 31a of the fixing portion of the left blade guide 31 is to be increased from the viewpoint of maintaining the mounting strength of the blade guide. There are limitations. Further, since it is necessary to guide the movement of the driver blade as accurately as possible, the cross-sectional area of the blade gap needs to be very small. Therefore, by separately forming the through-hole 20a serving as a back pressure prevention passage, it is possible to positively prevent an increase in back pressure in the piston lower chamber.
[0027]
Next, operation | movement of the combustion type power tool 1 by this Embodiment is demonstrated. In the non-actuated state, the push lever 10 is urged downward by the urging force of the compression coil spring 22 and protrudes from the lower end of the tail cover 9. At this time, since the combustion chamber frame 11 is connected to the push lever 10 via the connecting member 12, the upper end of the combustion chamber frame 11 is separated from the head cap 13 and defines the combustion chamber 26 of the combustion chamber frame 11. A part and the upper end part of the cylinder 20 are separated, and a 1st flow path and a 2nd flow path are provided. At this time, the piston 25 is stopped at the top dead center position in the cylinder 20.
[0028]
When the handle 7 is gripped in this state and the push lever 10 is pressed against a workpiece such as wood, the push lever 10 moves up against the urging force of the compression coil spring 22 and similarly burns in conjunction with the push lever 10. The chamber frame 11 also rises, the above-described flow path is closed, and the combustion chamber 26 is sealed by the sealing materials 19 and 24.
[0029]
Further, as the push lever 10 moves, the entire gas cylinder 5 is inclined toward the head cap 13 by a cam (not shown), and an unillustrated injection rod of the gas cylinder 5 is pressed against the gas cylinder connecting portion of the head cap 13 so as to be within the combustion chamber 26. The liquefied gas in the gas cylinder 5 is injected from the injection port 18 only once.
[0030]
Further, when the combustion chamber frame 11 rises to the stroke end as the push lever 10 moves, the head switch is turned on, and as a result, the fan 14 starts rotating. As the fan 14 rotates in the combustion chamber 26 which is a sealed space, the injected combustible gas is mixed with the air in the combustion chamber 26 in combination with the ribs 27 protruding into the combustion chamber 26.
[0031]
When the trigger switch 6 of the handle 7 is turned on in this state, the spark plug 15 sparks and ignites the mixed gas. At this time, since the fan 14 keeps rotating, the turbulent combustion of the air-fuel mixture is promoted, and the output of the power tool can be improved. The burned / expanded gas moves the piston 25 downward, and the nail in the tail cover 9 is driven into the workpiece through the driver blade 28 until the piston 25 abuts against the bumper 23.
[0032]
Until the piston 25 passes through the exhaust hole 21 of the cylinder 20, the air in the cylinder lower chamber energizes a check valve (not shown) to open the exhaust hole 21. Since the air is discharged to the outside air through the through hole 20a, the back pressure does not increase in the piston lower chamber. When the piston 25 passes through the exhaust hole 21 of the cylinder 20, a check valve (not shown) is urged by the pressure of the combustion gas in the piston upper chamber in the cylinder to open the exhaust hole 21. It is discharged to the outside and discharged to the outside from the exhaust port 2a of the main housing part 2A. Further, as indicated by arrows A1, A2, and B, the air in the cylinder lower piston chamber is discharged to the outside air through the guide gap 29 and the through hole 20a. At this time, since the through-hole 20a has a flow passage cross-sectional area that compensates for the flow passage cross-sectional area of the guide gap 29, an extreme back pressure rise in the piston lower chamber does not occur. Therefore, the lowering speed of the piston can be maintained until the piston 25 reaches the bottom dead center, and a decrease in driving energy can be prevented.
[0033]
When the combustion gas is released to the outside of the cylinder 20 and the inside of the cylinder 20 and the combustion chamber 26 becomes atmospheric pressure, the check valve is closed. The combustion gas remaining in the cylinder 20 and the combustion chamber 26 is at a high temperature because it is after combustion, and the heat is absorbed from the inner wall of the cylinder 20 and the inner wall of the combustion chamber frame 11, so that the combustion gas is rapidly cooled. The pressure in the closed space above the piston 25 is reduced to atmospheric pressure or lower (called thermal vacuum). At this time, since air is introduced into the piston lower chamber in the cylinder through the guide gap 29, the piston 25 is in an initial state due to the pressure difference between the pressure (atmospheric pressure) of the piston lower chamber in the cylinder and the internal pressure on the piston upper chamber side. It is pulled back to the top dead center position.
[0034]
When the trigger switch 6 is turned off, the entire tool 1 is lifted from the workpiece, and the push lever 10 is released from the workpiece, the push lever 10 and the combustion chamber frame 11 return downward due to the urging force of the compression coil spring 22. As the combustion chamber frame 11 descends, the first and second flow paths can be provided, the remaining combustion gas in the combustion chamber 26 is scavenged and replaced with fresh air, and the state returns to the initial state where the next nail can be driven.
[0035]
Thus, according to the combustion type driving tool 1 according to the first embodiment, the air in the piston lower chamber in the cylinder 20 remains in the guide gap even after the piston 25 passes through the exhaust hole 21 while the piston 25 is descending. 29, the piston 25 can be discharged to the outside through the through-hole 20a serving as a back pressure prevention passage, so that the piston 25 can be smoothly lowered without being obstructed by the air in the piston lower chamber in the cylinder 20, and the lowering speed of the piston 25 can be reduced. It is possible to prevent the driving energy from being lowered. Further, the through hole 20a can provide a back pressure prevention passage by a simple process of forming a through hole on the peripheral surface of the cylinder 20. Further, a bumper 23 with which the piston 25 is disposed is provided at the lower end portion of the cylinder 20, and the through hole 20 a is positioned below the piston 25 engagement surface of the bumper 23, so that the piston 25 collides with the bumper 23. After that, the air in the lower chamber of the piston in the cylinder 20 can be discharged not only through the guide gap 29 but also through the through hole 20a, and the driving energy can be improved.
[0036]
Next, a combustion type driving tool 101 according to a second embodiment of the present invention will be described with reference to FIGS. In these drawings, the same members as those in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted.
[0037]
In the second embodiment, the through hole 20a as in the first embodiment is not formed in the lower portion of the cylinder 120, but the bottom of the main housing portion 102A is separated from each other in the axial direction of the driver bit 128. The rectangular first bottom portion 102C and the second bottom portion 102D are arranged in a double wall, and a central portion of the double wall forms a guide gap 129 through which the tip of the driver bit 128 passes. The four corners of the first bottom portion 102C and the second bottom portion 102D are separated from each other via the rib 102E and are integrally molded. The space between the first bottom portion 102C and the second bottom portion 102D functions as the back pressure prevention passage 102b. Due to the double bottom structure described above, the magazine 8 is positioned lower than the first embodiment by a length L, and the driver bit 128 is accordingly longer than the first embodiment.
[0038]
With this configuration, as is clear from FIG. 4, the guide gap 129 can be set wider than the first embodiment by the cross-sectional integral surrounded by the broken line C and the arc on the right side of the driver blade 128, and The back pressure prevention passage 102b can also be provided on the entire circumference of the driver bit 128 as shown by the arrow D except for the portion where the rib 102E exists, in other words, on the right side of the driver blade 128. As a result, the cross-sectional area of the back pressure prevention passage can be set large, and the driving energy can be improved. The left blade guide 131 and the right blade guide 32 are attached to the second bottom portion 102D with screws 133 or the like.
[0039]
Since the cross-sectional area of the back pressure prevention passage 102b can be set large and the back pressure prevention passage 102b does not cross the left blade guide 131, the fixing portion fixed to the second bottom portion 102D of the left blade guide 131 includes The through hole 31a as in the first embodiment is not necessary, so that the tail cover 9 can be disposed in contact with the fixed portion of the left blade guide 131, and the overall length of the tool 101 is long despite the double wall structure. Never become.
[0040]
A combustion type driving tool 201 according to a third embodiment of the present invention will be described with reference to FIGS. In the third embodiment, the bottom portion of the main housing portion 202A is configured by a double wall of a rectangular first bottom portion 202C and a second bottom portion 202D that are spaced apart from each other in the axial direction of the driver bit 228. The central portion of the heavy wall forms a guide gap 229 through which the tip of the driver blade 228 passes, and the four corners of the first bottom portion 202C and the second bottom portion 202D are separated from each other via the rib 202E and are integrally molded. That the space between the first bottom portion 202C and the second bottom portion 202D functions as the back pressure prevention passage 202b is the same as in the second embodiment. However, the left blade guide 131 and the right blade guide 132 according to the second embodiment are omitted, and instead, a guide portion 220 </ b> A extending in the diametrical direction is provided at an opening leading to the guide gap 229 at the bottom of the cylinder 220. The guide portion 220A is formed with a guide hole 220a through which the driver blade 228 is inserted and guides the reciprocating movement of the driver blade. A slight gap between the guide hole 220a and the driver blade 228 also forms the guide gap 229. .
[0041]
As described above, the combustion type driving tool 201 according to the third embodiment not only exhibits the same function and effect as the combustion type driving tool 101 according to the second embodiment, but also has the trouble of separately preparing a blade guide component. This eliminates the need for fixing this part to the bottom of the housing, and can reduce the number of parts and the number of assembly steps.
[0042]
Next, the piston displacement of the combustion type driving tool 1 according to the first embodiment and the conventional combustion type driving tool, that is, the histone of the combustion type driving tool in which the through hole 20a of the cylinder 20 is not formed in the first embodiment. A comparative experiment was conducted for displacement and piston speed change.
[0043]
9A and 9B show data in the first embodiment, where FIG. 9A shows changes in pressure over time in the piston upper chamber, FIG. 9B shows changes in pressure in the lower chamber of the piston, and FIG. 9C shows piston displacement. The change with time is shown. In the graph (A), the air-fuel mixture is combusted and expanded by the discharge of the spark plug 15, and the pressure in the piston upper chamber rises. As is apparent from the graph (C), the piston 25 begins to descend with a delay of about 0.001 second. At this time, as is apparent from the graph (B), no extreme increase is observed in the pressure in the lower chamber of the piston, and as is apparent from the graph (C), the piston 25 reaches the bottom dead center in 0.005 seconds. The area of the guide gap 29 formed in the left blade guide 31 is a passage for introducing outside air so that the piston lower chamber does not become negative pressure when the piston 25 returns to the initial position. In the case of a combustion type driving tool having a general nail length of 90 mm, the guide gap 29 is about 160 mm. ² However, since the initial position return speed of the piston 25 is much slower than that when nailing, such an area is sufficient. When the piston 25 descends, air is discharged from the through hole 20a in addition to the guide gap 29, so that there is no extreme pressure rise in the piston lower chamber, and the piston 25 is not prevented from descending.
[0044]
FIG. 10 shows data of a conventional tool. The air-fuel mixture burns and expands due to the discharge of the spark plug, and the pressure in the piston upper chamber rises. As in FIG. 9, the piston begins to descend with a delay of about 0.001 second. At this time, as is apparent from the graph (B), the pressure in the piston lower chamber rapidly increases immediately before the piston reaches the bottom dead center. This phenomenon is due to the fact that the air in the piston lower chamber is compressed by the lowering of the piston, and only the guide gap 30 means that the air in the piston lower chamber is not sufficiently discharged. Therefore, as apparent from the graph (C), the piston 25 reaches the bottom dead center after 0.0052 seconds. Compared with FIG. 9C, a delay of 0.0002 seconds means a decrease in the piston lowering speed, and the driving energy of the combustion type driving tool is proportional to the square of the piston speed as described above. Lowering the speed significantly reduces the driving energy.
[0045]
FIG. 11 is a diagram showing a change in piston speed over time, (A) is a graph showing a change in piston speed in the combustion type driving tool according to the first embodiment, and (B) is a graph showing a back pressure prevention passage. It is a graph showing the piston speed change in the conventional combustion type driving tool which is not. The piston lowering speed increases as the piston approaches the bottom dead center. In the conventional example, the maximum value of the piston speed is 42.4 m / sec. However, in the first embodiment of the present invention, since the back pressure is reduced, the maximum value is 45 m / sec, which is higher than the conventional example. . Here, the implantation energy E is E = (1/2) × mv ² (M: piston mass, v: piston speed) is proportional to the square of the speed, so the improvement in speed is very effective for improving the driving power. In FIG. 11, the second speed rising from 0.006 seconds (A) or 0.007 seconds (B) means that the piston has moved again due to reaction.
[0046]
Next, FIG. 12 and FIG. 13 show the relationship between the sum S of the cross-sectional area of the back pressure prevention passage and the cross-sectional area of the guide gap, the ratio V / S of the piston lower chamber volume V at the piston top dead center, and the driving energy. The description will be given with reference. Data was obtained based on the first embodiment. FIG. 12 shows the results of the relationship between the sum S of the back pressure prevention passage cross-sectional area, the guide gap cross-sectional area, and the driving energy J in the combustion type driving tools having nail lengths of 90 mm, 75 mm, 65 mm, and 50 mm. As is clear from the graph, the driving energy increases as the total sectional area S increases. Here, since the back pressure is generated by the resistance when the air in the piston lower chamber is discharged out of the main body, it is clear that the total cross-sectional area S is correlated with the volume V of the piston lower chamber. .
[0047]
FIG. 13 shows the relationship between V / S, which is the ratio between the total cross-sectional area S and the volume V of the piston lower chamber at the piston top dead center, and the driving energy in the first embodiment. From FIG. 12, in any combustion type driving tool having a nail length of 90 mm class to 50 mm class, when V / S increases, the driving energy decreases, and by setting V / S to 1.5 or less, the driving energy is reduced. It can be seen that it can be improved.
[0048]
The combustion power tool according to the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made within the scope described in the claims.
[0049]
【The invention's effect】
According to the combustion type power tool of the first aspect, even after the piston passes through the exhaust hole during the lowering of the piston, the air in the lower chamber of the piston in the cylinder is not only exposed to the outside through the back pressure prevention passage. Since the piston can be discharged, the piston can be smoothly lowered without being obstructed by the air in the piston lower chamber in the cylinder, the piston lowering speed is not lowered, and the driving energy can be prevented from being lowered. In other words, it is possible to efficiently use the driving energy that has conventionally been lost due to the increase in the back pressure in the piston lower chamber, and to improve the driving energy.
[0050]
According to the combustion type power tool of claim 2, since the back pressure prevention passage is composed of at least one through hole formed through the peripheral surface of the cylinder, simple machining by simply forming a hole through the cylinder. Thus, a back pressure prevention passage can be provided.
[0051]
According to the combustion type power tool of the third aspect, the lower end portion in the cylinder is provided with a bumper that is provided with a piston, and the back pressure prevention passage is located below the piston installation surface of the bumper. Therefore, even after the piston collides with the bumper, the air in the cylinder lower piston chamber can be discharged not only through the guide gap but also through the back pressure prevention passage, and the driving energy can be improved.
[0052]
According to the combustion type power tool of claim 4, the bottom part of the housing is constituted by a double wall arranged apart from each other in the axial direction of the driver bit, and the center part of the double wall is a tip part of the driver bit. The gap between the double walls is used as a back pressure prevention passage, and the magazine is positioned below the double wall. Therefore, the guide gap itself can be formed on the magazine side as well. The back pressure preventing passage communicating with the gap can be opened not only on the side opposite to the magazine but also on the magazine side, and the passage sectional area and passage opening area can be increased.
[0053]
According to the combustion type power tool of claim 5, an opening communicating with the guide gap is formed at the bottom of the cylinder, and a guide portion extending in a diametrical direction from the edge of the opening is provided integrally with the cylinder, and the blade Since the guide is configured, it is not necessary to prepare a separate blade guide and fix it to the bottom of the housing, and the number of parts and the number of assembly steps can be reduced.
[0054]
According to the combustion type power tool of claim 6, the volume V (m of the piston lower chamber in the cylinder at the piston top dead center. ^Three ) And the cross-sectional area S (m) of the cross-sectional area of the guide gap and the cross-sectional area of the back pressure prevention passage ² ) Is 1.5 or less, the amount of air discharged from the back pressure prevention passage can be increased, and the driving energy can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first embodiment in which a combustion type power tool of the present invention is applied to a combustion type driving tool, and shows a state in which the tool presses a workpiece.
2 is a cross-sectional view taken along line II-II in FIG.
FIG. 3 is a sectional view showing a combustion type driving tool according to a second embodiment of the present invention.
4 is a cross-sectional view taken along the line IV-IV in FIG. 3;
FIG. 5 is a partial cross-sectional perspective view showing a main part of a combustion type driving tool according to a second embodiment of the present invention.
FIG. 6 is a sectional view showing a combustion type driving tool according to a third embodiment of the present invention.
7 is a cross-sectional view taken along line VII-VII in FIG.
FIG. 8 is a partial cross-sectional perspective view showing a main part of a combustion type driving tool according to a third embodiment of the present invention.
FIG. 9 is a measurement result of pressure and piston displacement in the combustion type driving tool according to the first embodiment shown in FIG. 1, (A) shows changes in pressure over time in the piston upper chamber, and (B) shows The pressure change of the piston lower chamber with time is shown, and (C) shows the change of piston displacement with time.
FIGS. 10A and 10B are graphs showing measurement results of pressure and piston displacement in a conventional combustion type driving tool without a back pressure prevention passage. FIG. 10A shows changes in pressure over time in the piston upper chamber, and FIG. The pressure change with time is shown, and (C) shows the change with time of piston displacement.
FIGS. 11A and 11B are graphs showing changes in piston speed over time, FIG. 11A is a graph showing changes in piston speed with time in the combustion type driving tool according to the first embodiment, and FIG. 11B is back pressure prevention; The graph showing the time change of the piston speed in the conventional combustion type driving tool without a passage.
FIG. 12 shows driving energy, total cross-sectional area of back pressure prevention passage and guide gap (Sm ² ).
FIG. 13 is a graph showing the relationship between implantation energy and (V / S).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 101, 201: Combustion type driving tool, 2, 102 ,: Housing, 2A, 102A, 202A: Main housing part, 2B: Cylinder chamber part, 3: Motor, 6: Trigger switch, 9: Tail cover, 10: Push lever, 11: Combustion chamber frame, 12: Connecting member, 13: Head cap, 14: Fan, 15: Spark plug, 19: First sealing material, 20, 120, 220: Cylinder, 21: Exhaust hole, 22: Compression coil spring, 23: Bumper, 24: Second seal material, 25: Piston, 26: Combustion chamber, 28, 128, 228: Driver blade, 29, 129, 229: Guide gap, 31, 131: Left blade guide, 32: Right blade guide, 102C, 202C: First bottom, 102D, 202D: Second bottom, 102E, 202E: Bed, 120a: through hole, 202b: back pressure passage

Claims (6)

A housing;
A handle extending from the housing and provided with a trigger switch;
A head portion that plugs one end of the housing and in which a combustible gas passage is formed;
A motor provided in the head portion;
A push lever provided below the housing and movable when pressed against a workpiece;
A cylinder fixedly provided in the housing and having an exhaust hole;
A piston capable of reciprocating relative to the cylinder in the axial direction of the cylinder, and defining the cylinder into a piston lower chamber and a piston upper chamber in the cylinder;
A combustion chamber frame guided in a movable manner in the housing, contacting and separating from the head portion in conjunction with the movement of the push lever, and defining a combustion chamber together with the head portion and the piston upper chamber in the cylinder; ,
A driver blade extending from the piston toward the anti-combustion chamber and reciprocating with the piston;
A blade guide positioned on the outer peripheral surface side of the driver blade to guide the reciprocating motion of the driver blade;
A seal portion that seals between the combustion chamber frame and the head portion when the combustion chamber frame contacts the head portion, and seals between the combustion chamber frame and the cylinder;
A fan rotatably provided in the combustion chamber and driven to rotate by the motor;
A spark plug facing the combustion chamber for igniting a mixture of combustible gas and air in the combustion chamber;
An exhaust check valve provided to open and close the exhaust hole;
A magazine located below the housing for receiving and holding a stopper;
And a tail cover into which a front end portion of the driver blade enters, and a stopper that is accommodated in the magazine is fed to the lower side of the driver blade. In the combustion power tool in which a guide gap that communicates between the piston lower chamber in the cylinder and the outside air is formed in a portion through which the blade passes,
A combustion is characterized in that a back pressure prevention passage that communicates the lower chamber of the piston in the cylinder and outside air is formed in the cylinder or the housing at a position below the exhaust hole, separately from the guide gap. Power tool. 2. The combustion type power tool according to claim 1, wherein the back pressure prevention passage includes at least one through hole formed through the peripheral surface of the cylinder. 2. The lower end portion in the cylinder is provided with a bumper that the piston impinges on, and the back pressure prevention passage is located below the piston impinging surface of the bumper. Or the combustion type power tool of 2. The bottom portion of the housing is composed of double walls arranged apart from each other in the axial direction of the driver bit, and the central portion of the double wall forms the guide gap through which the tip of the driver bit passes, The combustion type power tool according to claim 1, wherein a space between the double walls is used as the back pressure prevention passage, and the magazine is located below the double walls. An opening communicating with the guide gap is formed at the bottom of the cylinder, and a guide portion extending in a diametrical direction from an edge of the opening is provided integrally with the cylinder to form the blade guide. The combustion type power tool according to claim 4. Ratio V / S of the volume V m ³ of the piston lower chamber in the cylinder at the piston top dead center and the total cross-sectional area Sm ² of the flow path cross-sectional area of the guide gap and the flow path cross-sectional area of the back pressure prevention passage The combustion type power tool according to any one of claims 1 to 5, wherein the power is 1.5 or less.

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