Patent Publication Number: US-2018036870-A1

Title: Driving machine

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a driving machine that moves a driver blade by pressure of a gas such as air to strike a stopper. 
     Description of the Related Art 
     Conventionally, there is known a driving machine or nailing machine that strikes a stopper by force of compressed air, wherein the driving machine is described in Patent Document 1. The driving machine described in Patent Document 1 includes: a motor provided within a housing; a gear transmitting a rotational force of the motor to a cam; a cylinder provided within the housing; a piston reciprocally movably accommodated in the cylinder; a driver blade fixed to the piston; and a bellows provided in the cylinder. The bellows is extendable, wherein a first end portion of the bellows is connected to the piston, and a second end portion of the bellows is fixed to the housing. The compressed air is sealed in the bellows to form a pressure chamber (pneumatic chamber). 
     In the driving machine described in Patent Document 1, when the cam is rotated by the rotational force of the motor, the piston is moved from a bottom dead point toward a top dead point by a rotational force of the cam. During movement of the piston from the bottom dead point toward the top dead point, the bellows is compressed and pressure of the pressure chamber increases. When the piston reaches the top dead point, the rotational force of the cam is no longer transmitted to the piston, and the piston is moved from the top dead point toward the bottom dead point by a force of the compressed air in the pressure chamber. As a result, the driver blade strikes the stopper. Prior-Art Documents 
     PATENT DOCUMENTS 
     
         
         Patent Document 1: JP 2014-69289 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the driving machine described in Patent Document 1, since the air is kept sealed in the pressure chamber forming in the bellows at all times, even in cases where the stopper is not struck, it is necessary to seal the bellows. There is a fear that, as a number of times of use and duration of use of the bellows increase, the air in the bellows may gradually decrease, and a striking force is reduced. 
     An object of the present invention is to provide a driving machine capable of easily replenishing air in a pneumatic chamber used to strike a piston. Another object of the present invention is to provide a driving machine that perform is replenishment (pressure accumulation) of the air in the pneumatic chamber by moving the piston in an opposite direction by an electric motor. Still another object of the present invention is to provide a driving machine capable of easily discharging gases in the pneumatic chamber. 
     Means for Solving the Problems 
     In order to achieve the above objects, a driving machine of the present invention includes: a housing; a cylinder provided within the housing; a pneumatic chamber spatially connected to the cylinder; a piston reciprocally movably provided in the cylinder; a blade attached to the piston and striking a stopper; and a moving mechanism reducing an internal volume of either the air chamber or the cylinder by a motor, and the driving machine drives the stopper by a repulsive force of compressed air, wherein the driving machine is configured to have a pressure accumulating mode in which the pneumatic chamber is pressurized by the motor from a state where the air chamber communicates with the outside, and a striking mode in which the piston is moved by the motor from a bottom dead point to a top dead point in the cylinder and then from the top dead point toward the bottom dead point, thereby driving the stopper. 
     Effects of the Invention 
     According to the present invention, since an operator can easily increase pressure of a gas in the pneumatic chamber, a driving machine having long life and high performance can be realized without being bothered by pressure reduction in the pneumatic chamber due to longtime use. In addition, since the pressure in the pneumatic chamber can be reduced, maintainability during nail clogging or the like is considerably improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view showing a driving machine  201  according to a first example of the present invention. 
         FIG. 2  is an arrow view as viewed from a direction A in  FIG. 1  (when a piston  47  is at a bottom dead point). 
         FIG. 3  is an arrow view as viewed from the direction A in  FIG. 1  (when the piston  47  is at a top dead point). 
         FIG. 4  is an arrow view of a nose portion  254  as viewed from a side opposite the direction A in  FIG. 1 . 
         FIG. 5  is a block circuit diagram of the driving machine  201 . 
         FIG. 6  is a partial enlarged view (part  1 ) of the vicinity of an external air intake valve  260  provided in a pressure accumulation container  250  in  FIG. 1 . 
         FIG. 7  is a partial enlarged view (part  2 ) of the vicinity of the external air intake valve  260  provided in the pressure accumulation container  250  in  FIG. 1 . 
         FIG. 8  is a partial enlarged view (part  3 ) of the vicinity of the external air intake valve  260  provided in the pressure accumulation container  250  in  FIG. 1 . 
         FIG. 9  is a flowchart showing a procedure for pressurizing a pneumatic chamber  249  in a pressure accumulating mode according to examples of the present invention. 
         FIG. 10  is a longitudinal sectional view showing a driving machine  301  according to a second example of the present invention. 
         FIG. 11  is enlarged longitudinal sectional views of a leak valve  360  in  FIG. 10 . 
         FIG. 12  is a partial longitudinal sectional view showing a driving machine according to a modification of the second example of the present invention. 
         FIG. 13  is a front view showing a driving machine  10  according to a third example of the present invention. 
         FIG. 14  is a side sectional view of the driving machine  10  shown in  FIG. 13 . 
         FIG. 15  is a front sectional view (part  1 ) of the driving machine  10  shown in  FIG. 13 . 
         FIG. 16  is a front sectional view (part  2 ) of the driving machine  10  shown in  FIG. 13 . 
         FIG. 17  is a side sectional view showing a fourth example of the driving machine of the present invention. 
         FIG. 18  is a front sectional view of the driving machine shown in  FIG. 17 . 
         FIG. 19  is a front sectional view showing a fifth example of the driving machine of the present invention. 
         FIG. 20  is a side sectional view of the driving machine shown in  FIG. 19 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Example 1 
     The driving machine  201  includes: a striking mechanism (including a cylinder  245 , the pressure accumulation container  250 , the piston  47 , and a blade  48 ) striking a nail  11  being a driving object; an electric motor  13  generating power for driving the striking mechanism; a power transmission mechanism moving the blade  48  of the striking mechanism by the power of the electric motor  13 ; a storage battery  15  supplying electricity to the electric motor  13 ; and a magazine  16  supplying the nail  11  to a shooting path of the striking mechanism one at a time and holding a plurality of the shot nails  11 . The nail  11  is a stopper formed by sharpening a tip of a thin round bar or square bar and widening a rear end thereof into a flange shape, and the driving machine  201  is capable of striking nails of about 50 to 110 mm. The striking mechanism is accommodated within a main body housing  202  made of synthetic resin and having a cylindrical shape. A grip  203  for being held by an operator by one hand is provided on a lateral side of the main body housing  202 , and a mounting portion  204  of the storage battery  15  is provided on an end portion of the grip  203 . The storage battery  15  is attachable to and detachable from the mounting portion  204 . A control circuit substrate  81  for mounting a later-described controller (control portion) is accommodated in the mounting portion  204 . 
     A seal member  55  is attached to an outer peripheral surface of the piston  47 , and the piston  47  is reciprocally movable in the cylinder  245  in an axial direction along a center line B 1 . The blade  48  for driving the nail  11  and being axially elongated is fixed to a lower portion of the piston  47 , and the pressure accumulation container  250  for storing air is provided on an upper portion of a space where the piston  47  moves. The pressure accumulation container  250  is formed by a container main body portion  251  having a substantial cup shape with an opening facing downward, and a flange portion  255  blocking the opening part of the container main body portion  251  and having formed therein an attaching portion for attachment to the cylindrical cylinder  245 . An internal space (pneumatic chamber  249 ) of the pressure accumulation container  250  has the pneumatic chamber  249  that maintains the air introduced from the outside in a pressurized state, and is fluidly connected to a space (a later-described cylinder chamber  248  in  FIG. 2 ) in which the air is compressed by the piston  47 . In order to introduce the air from the outside into the pneumatic chamber  249 , the external air intake valve  260  is provided on an upper portion of the pressure accumulation container  250 . Details of the external air intake valve  260  are described later. 
     The storage battery  15  has an accommodation case and a plurality of battery cells (not illustrated) accommodated in the accommodation case. The battery cells are rechargeable and dischargeable DC secondary batteries, and may be lithium-ion batteries, nickel-hydrogen batteries, lithium-ion polymer batteries, nickel-cadmium batteries and so on. A part of the mounting portion  204  is connected to a motor housing  17  continuous with a casing  233 . Herein, the main body housing  202 , the grip  203 , the mounting portion  204 , the casing  233 , and the motor housing  17  are made of a molded article made of synthetic resin such as plastic, the nose portion  254  is made of aluminum alloy or iron-based metal, and these components constitute a case part (housing in a broad sense) of the driving machine  201 . 
     The electric motor  13  is a brushless DC motor, including a stator  18  unrotatably fixed to the motor housing  17 , and a rotor  19  rotatably axially supported on an inner peripheral side of the stator  18 . The stator  18  is formed by winding a coil  21  for energization around a stator core made of a laminated iron core. The rotor  19  includes an output shaft  24  supported by two bearings  82   a  and  82   b , and a rotor core and a permanent magnet that are fixed to the output shaft  24 . The output shaft  24  is rotatable about an axis line A 1 . A substantially annular inverter circuit substrate  83  is provided on an end portion side of the electric motor  13 , and a plurality of switching elements  84  such as field-effect transistors (FETs) or insulated-gate bipolar transistors (IGBTs) that form a later-described inverter circuit are mounted thereon. In addition, a magnetic detection element (not illustrated) such as a Hall integrated circuit (IC) for detecting a rotation position of the rotor  19  is provided on the inverter circuit substrate  83 . 
     A rotational force of the electric motor  13  is transmitted to a drive shaft  234  through a decelerator  27 . A well-known speed reduction mechanism may be used as the decelerator  27 . Herein, by providing a planetary gear mechanism in two-stage series, a rotational speed of the output shaft  24  is reduced to about one ten-oddth thereof, so as to rotate the drive shaft  234 . A rotating body  238  is fixed to an end portion of the drive shaft  234  and rotates in synchronization with the drive shaft  234 . The rotating body  238  constitutes a part of the power transmission mechanism that moves the blade  48  of the striking mechanism by the power of the electric motor  13 , and configuration or operation thereof is described later in  FIG. 2  to  FIG. 4 . 
     The nose portion  254  is attached to a shooting direction side of the main body housing  202 , and forms the shooting path of the shot nail  11 . A pushrod  104  is provided on the nose portion  254  so as to cover a tip part thereof. The pushrod  104  is movable with respect to the nose portion  254  in a predetermined range in the same direction as and in an opposite direction to the shooting direction, and is a kind of safety device used in performing a driving operation. The driving machine  201  is controlled so that, during driving of the nail  11 , if the operator does not press the pushrod  104  against an object (driven material) into which the nail  11  is driven, the electric motor  13  does not rotate even if a trigger (trigger lever)  72  is pulled. When a tip side of the pushrod  104  in the shooting direction does not contact anything, the pushrod  104  is energized by a compression spring  105  and is located on the shooting direction side. When the operator presses the pushrod  104  against the object, the pushrod  104  moves in a direction opposite the shooting direction against a force of the compression spring  105  and then stops. When the pushrod  104  moves backward, a pressing detection switch (not illustrated) is switched on, and an output thereof is transmitted to a later-described controller. The controller allows activation of the electric motor  13  only when both states where the pushrod  104  is pressed and where the trigger  72  is pulled are realized. 
       FIG. 2  is an arrow view as viewed from the direction A in  FIG. 1 , showing a state where the piston  47  is at the bottom dead point. In the present example, a moving mechanism is provided moving the piston  47  in a cylinder  45  in a direction in which pressure of the pneumatic chamber  249  is increased. This moving mechanism mainly includes the rotating body  238  rotated by a driving force of the electric motor  13 , and the blade  48  having a rack  53 . Herein, by rotating the rotating body  238  that has a pinion (gear)  241  on a part of its outer peripheral edge and meshing the pinion  241  with the rack  53  formed on a longitudinal side surface of the blade  48 , the piston  47  is moved from the bottom dead point to the top dead point. The rotating body  238  and the pinion  241  are formed of an integral product made of metal, and the rotating body  238  is rotatable in a direction of arrow  242  or an opposite direction thereto by rotation of the drive shaft  234 . The pinion  241  is arranged on the outer edge part of the rotating body  238  corresponding to a rotational angle of about 270 degrees. Thus, when the rotating body  238  rotates, a tip tooth  241   a  of the pinion  241  starts meshing with an upper end tooth  53   a  of the rack  53 , and the blade  48  can thereby be moved upward. Accordingly, the piston  47  fixed to the blade  48  can also be moved toward the top dead point side. 
       FIG. 3  shows a state where the rotating body  238  is rotated about 300 degrees in the direction of arrow  242  from the state in  FIG. 2 , showing a state immediately before the meshing between the rack  53  and the whole pinion  241  ends and meshing between a lower end tooth  53   b  of the rack  53  and a rear end tooth  241   b  of the pinion  241  is just about to be released. When a tip  48   b  of the blade  48  moves upward in a shooting path  256 , the next nail  11  to be driven is fed from the magazine  16  into the shooting path  256 . Immediately after the state in  FIG. 3 , i.e., when the piston  47  reaches the top dead point, since the contact state between the rear end tooth  241   b  of the pinion  241  and the lower end tooth  53   b  of the rack  53  is released, a force that supports the piston  47  that has compressed the air in the pneumatic chamber  249  is gone, and the piston  47  rapidly starts moving toward the bottom dead point due to a repulsive force of the compressed air in the pneumatic chamber. At this time point, the nail  11  has been loaded by the magazine  16  so that a head portion  11   a  comes to directly under the tip  48   b  of the blade  48 . Thus, the blade  48  is capable of driving the nail  11  into an object. 
       FIG. 4  shows a state after  FIG. 3 , and is an arrow view of the nose portion  254  after driving of the nail  11  is completed, as viewed from the side opposite the direction A in  FIG. 1 . During striking of the nail  11 , since the electric motor  13  rotates, the drive shaft  234  also continues to rotate. However, in one place in a circumferential direction of the rotating body  238 , a columnar pin  235  is provided parallel to the drive shaft  234 , and the pin  235  acts on an off switch  236  at a timing at which the driving of the nail  11  ends. The off switch  236  is provided on a side surface of the nose portion  254 , an output thereof is connected to a controller and an output pulse is transmitted at a timing at which the nail  11  is shot. An operating lever  237  for operating a plunger  236   a  is provided in the vicinity of the off switch  236 . By rotation of the rotating body  238 , the position of the pin  235  also moves in the circumferential direction. The operating lever  237  is made of a metal thin plate having elasticity, such as a spring material, and has on its tip a part bent into a semi-cylindrical shape. When the rotating body  238  rotates in the direction of arrow  242 , the pin  235  provided parallel to the drive shaft  234  abuts against the semi-cylindrical portion of the operating lever  237 , and the operating lever  237  is deformed by being pressed by the pin  235 . Thus, the plunger  236   a  of the off switch  236  is pressed. Since the time point of pressing the plunger  236   a  is after completion of the driving of the nail  11 , when the later-described controller receives an output signal of the off switch  236 , the controller stops supplying driving power to the electric motor  13 . After the plunger  236   a  is pressed, since the state where the operating lever  237  abuts against the pin  235  is released, the drive shaft  234  also stops and the rotating body  238  stops in the position in  FIG. 4 . Moreover, at the time point when the nail  11  is driven, the rack  53  and the pinion  241  are in a non-contact state. 
     Whether the nail  11  is correctly struck and whether the blade  48  has stopped in a correct position can be detected using a magnetic sensor  257 . The magnetic sensor  257  is attached to the nose portion  254 , and is provided in a position between the lower end tooth  53   b  of the rack  53  and an adjacent tooth when the piston  47  has moved to the bottom dead point. Due to approaching of the teeth of the rack  53  that protrude toward the magnetic sensor  257 , the magnetic sensor  257  transmits a signal to the controller. Moreover, although the magnetic sensor  257  is large in  FIG. 4  since it is schematically illustrated, in fact, the magnetic sensor  257  is miniaturized so as to be built in the nose portion  254 , and a lead wire is also wired in an unnoticeable manner (thus, they are not illustrated in  FIG. 1  to  FIG. 3 ). When the piston  47  moves to the bottom dead point, since only the lower end tooth  53   b  of the blade  48  crosses in front of the magnetic sensor  257 , an output signal corresponding to one pulse is transmitted from the magnetic sensor  257  to the controller. Thus, the controller is capable of correctly identifying whether the blade  48  has moved to a shooting position according to presence or absence of this output signal. Since in this stopped state, the piston  47  is located at the bottom dead point, after the operator releases the pushrod  104  temporarily, by again pressing the pushrod  104  in a next striking position to pull the trigger  72 , the next striking operation can be started. When nail clogging occurs, the lower end tooth  53   b  of the blade  48  does not pass in front of the magnetic sensor  257 . Accordingly, when nail clogging is detected, pressure in a pressure accumulation chamber is released, and the operator performs an operation of removing the clogging nail after the release step. 
       FIG. 5  is a control block diagram of the driving machine  210  of the present example. An inverter circuit  65  is a circuit generating, from a DC current from the storage battery  15 , a three-phase AC current (excitation current) for driving the electric motor  13 , and is mounted on the inverter circuit substrate  83  (see  FIG. 1 ) provided on a rear end side of the electric motor  13 . The inverter circuit  65  includes six switching elements  84  (see  FIG. 1 ) connected to the coil of the stator  18  of the electric motor  13 , and on/off of the switching elements  84  is controlled by a controller  66 . The controller  66  controls rotation of the electric motor  13  during striking (second step) of the nail  11  and controls rotation during pressurization (first step) of the pneumatic chamber  249  using the electric motor  13 . The controller  66  is configured by including a microcomputer (hereinafter referred to as “micon”) (not illustrated). A phase detection sensor  67  detecting a phase of the rotor  19  in a rotational direction is provided in the electric motor  13 . The phase detection sensor  67  can be realized by including a plurality of Hall ICs that detect a magnetic field of the permanent magnet contained in the rotor  19  of the electric motor  13 . The controller  66  is capable of obtaining a position of the rotor  19  in the rotational direction and a rotational speed of the rotor  19  based on a signal of the phase detection sensor  67 . The controller  66  estimates a position of the rotating body  38  in the rotational direction, i.e., a rotational angle of the rotating body  38 , based on the signal of the phase detection sensor  67  and a gear ratio of the decelerator  27 . 
     A rotational direction switching switch  68  is provided switching the rotational direction of the rotor  19  of the electric motor  13 . The rotational direction switching switch  68  is operated by the operator. The rotational direction switching switch  68  has operation positions for normal rotation and reverse rotation. Furthermore, the signal of the off switch  236  that detects completion of the driving of the nail  11  and the signal of the magnetic sensor  257  that detects whether or not the blade  48  has reached the bottom dead point are inputted to the controller  66 . The controller  66  processes the signal inputted from the phase detection sensor  67  so as to estimate the position of the piston  47  in the direction of the center line B 1  of a cylinder  46 . A trigger switch  71  (see  FIG. 1 ) is a switch mechanism switched on and off by the operator operating the trigger  72  (see  FIG. 1 ). A signal of the trigger switch  71  is inputted to the controller  66 . Furthermore, a pressing detection sensor  121  is provided detecting whether or not the pushrod  104  is being pressed against the object, and a signal outputted from the pressing detection sensor  121  is inputted to the controller  66 . Based on the signals of these switches and sensors, the controller  66  controls the rotation, stopping, rotational speed and rotational direction of the electric motor  13 . 
     Next, operation and control of the driving machine  10  are explained. When the trigger switch  71  is switched on, the controller  66  controls the inverter circuit  65  to supply a current to the coil  21 , and rotates the rotor  19  of the electric motor  13 . Based on a signal of the rotational direction switching switch  68 , the controller  66  controls a direction of the current flowing to the coil  21  and determines the rotational direction of the rotor  19 . In addition, based on the signal of the phase detection sensor  67 , the controller  66  detects the position of the rotor  19  in the rotational direction, and controls a timing of switching on and off the switching element of the inverter circuit  65  and an ON ratio, i.e., duty ratio, of the switching element. In this way, the rotational speed of the rotor  19  per unit time is controlled. The electric motor  13  is capable of switching the rotational direction of the rotor  19  between normal rotation and reverse rotation by switching the direction in which the current is supplied to the coil  21 . When the rotor  19  rotates, a rotational force of the output shaft  24  is transmitted to the drive shaft  234  via the decelerator  27 . 
     When striking is performed using the driving machine  10 , the first step of increasing the air pressure in the pneumatic chamber  249  is performed in advance if necessary. The first step is a preparation step before start of the striking operation, and may be performed only when the pressure of the pneumatic chamber  249  is reduced (e.g., every several weeks to every several months). Normally, the process can be suddenly executed from the second step (normal driving operation). In the second step, when the operator presses the pushrod  104  against the object and pulls the trigger  72 , the air pressure in the pneumatic chamber  249  further increases and the nail  11  is struck. 
     Next, a procedure for increasing the pressure of the pneumatic chamber  249  in the first step is explained using  FIG. 6  to  FIG. 8 .  FIG. 6  to  FIG. 8  are partial enlarged views of the vicinity of the external air intake valve  260  provided in the pressure accumulation container  250  in  FIG. 1 .  FIG. 6  shows a state where the external air intake valve  260  is closed, showing a state where intake of the external air to the pressure accumulation container  250  is inhibited. The external air intake valve  260  is an on-off valve mechanism provided to pass through a through hole  251   b  provided on an upper side of the pressure accumulation container  250 , wherein inflow of air from the external air toward the pneumatic chamber  249  is allowed in an opened state ( FIG. 7  and  FIG. 8 ), and flow of air between the external air and the inside of the pneumatic chamber  249  is completely blocked in a closed state ( FIG. 6 ). The pressure accumulation container  250  is accommodated within the main body housing  202  made of synthetic resin, and a cushion material  270  is provided on a lower side of the flange portion  255  so that the pressure accumulation container  250  is held without wobbling. The cylinder  245  and the cylindrical part of the flange portion  255  are screwed by a male thread  245   c  formed on a side of the cylinder  245  and a female thread  255   c  formed on an inner peripheral side of the flange portion  255 . Furthermore, two O-rings  256   a  and  256   b  are interposed on an upper side of the screw part to improve confidentiality. 
     The external air intake valve  260  is configured by including: a selector  265  being a main component of the valve mechanism; a cylindrical sleeve  262  for holding the selector  265  and moving the selector  265  in the axial direction (direction of the axis line B 1 ), a movable mechanism ( 264 , and  262   a  and  263   b  shown in  FIG. 7 ) converting a rotational force of the cylindrical sleeve  262  into a moving force of the selector  265  in the axial direction; and a switching lever  261  for rotating the cylindrical sleeve  262 . The switching lever  261  is a knob arranged inside a through hole  202   b  formed in an upper portion of the main body housing  202 , and fixes the hollow cylindrical sleeve  262  having an external air intake passage  262   a  formed in the center. A through hole  261   a  is also formed in the center of an upper portion of the switching lever  261  and communicates with the external air intake passage  262   a . A ring-shaped metal  266  is attached to a through hole formed in the container main body portion  251 , and the cylindrical sleeve  262  is held movable in the B 1  axial direction by the metal  266 . A washer  267  is interposed between the switching lever  261  and the cylindrical sleeve  262 . The selector  265  is provided on a lower side of the cylindrical sleeve  262 . The selector  265  is configured to be movable in the axial direction while rotating, and has a cup-shaped inner wall surface abutting against an outer peripheral side of the cylindrical sleeve  262 . A communicating path  265   a  for communicating the cup-shaped inner part with an outer part of the selector  265  is formed in the vicinity of a bottom (lower side surface) of the cup-shaped inner wall surface. The communicating path  265   a  is two or a plurality of through holes extending radially outward from an axial center of the selector  265 , wherein when a lower end portion of the cylindrical sleeve  262  is separated from a bottom surface portion of the selector  265 , the external air intake passage  262   a  and the pneumatic chamber  249  can communicate with each other by the communicating path  265   a . In an outer peripheral outlet of the communicating path  265   a , a groove portion is formed so as to be continuous in a circumferential direction, and an O-ring  273  made of rubber is arranged in the groove portion. The O-ring  273  functions as a check valve to block flow of air from the side of the pneumatic chamber  249  toward the communicating path  265   a , and, in contrast, to allow flow of the air from the side of the communicating path  265   a  toward the pneumatic chamber  249  when there is an air pressure difference. In the cylinder  245 , a cylindrical depression  265   b  having a cylindrical shape from bottom to top and two or a plurality of communicating paths  265   c  extending radially outward from the cylindrical depression  265   b  are further formed. In an outer peripheral outlet of the communicating path  265   c , a groove portion is formed so as to be continuous in the circumferential direction, and an O-ring  272  made of rubber and functioning as a check valve is arranged in the groove portion. 
     The movable mechanism that converts the rotational force of the cylindrical sleeve  262  into the moving force of the selector  265  in the axial direction includes a collar  263  and a steel ball  264  provided on an inner peripheral side of the selector  265 . A hemispherical depression  263   a  (see  FIG. 7 ) is formed on an inner peripheral surface of the collar  263 . A spline groove  262   b  formed over a rotational angle of 180 degrees while varying in the circumferential direction and axial direction is formed on an outer peripheral surface of the cylindrical sleeve  262 . The steel ball  264  is arranged between the spline groove  262   b  and the depression  263   a . When the operator rotates the switching lever  261  about 180 degrees in the circumferential direction, with this rotation, the cylindrical sleeve  262  also rotates. Thereupon, the steel ball  264  is guided by the obliquely arranged spline groove  262   b , and the collar  263  thereby moves axially downward. The state after movement is as shown by the state of the selector  265  in  FIG. 7 . 
     In  FIG. 7 , the selector  265  is moved downward by the movable mechanism. By a close contact between a stepped portion  265   e  formed on a lower side of the selector  265  and an opening portion  245   a  on an upper end of the cylinder  245 , space of the pneumatic chamber  249  is separated from space of the cylinder chamber  248 . On this occasion, since an O-ring  271  arranged in an upper outer peripheral groove  265   d  (see  FIG. 6 ) of the selector  265  abuts against an inner wall part of a cylindrical portion  252  formed on an inner peripheral side of the container main body portion  251 , the pneumatic chamber  249  is maintained in a state sealed from the external air or the cylinder chamber  248 . By the O-ring  272 , only flow of the air from the cylinder chamber  248  toward the pneumatic chamber  249  is allowed (only when there is a pressure difference). 
     As shown in  FIG. 7 , when the switching lever  261  is operated and the external air intake valve  260  is in the “opened” state, if the piston  47  is moved in a direction of arrow  277 , since the pressure in the cylinder chamber  248  becomes negative, the external air is introduced into the cylinder chamber  248  through the external air intake passage  262   a  and the communicating path  265   a , as shown by arrow  276 . On this occasion, since the O-ring  273  is deformed so as to extend to an outer peripheral side, flow of the air shown by arrow  276  is allowed. By moving the piston  47  from the state (state where the piston  47  is located slightly lower than the top dead point) in  FIG. 6  to the bottom dead point in this way, the external air can be introduced into the cylinder chamber  248 . When the piston  47  reaches the bottom dead point, the piston  47  is again moved to the vicinity of the top dead point (but the piston  47  does not reach the top dead point). This state is shown in  FIG. 8 . 
     In  FIG. 8 , when the piston  47  is moved in the direction of arrow  278 , since the pressure in the cylinder chamber  248  becomes sufficiently greater than the pressure in the pneumatic chamber  249 , the air flows from the cylindrical depression  265   b  toward the pneumatic chamber  249  through the communicating path  265   c  as shown by arrow  279 . Moreover, since the O-ring  273  is pressed by the air pressure from outside to inside and therefore closes the communicating path  265   a , the air in the cylinder chamber  248  is not released outside. On the other hand, the O-ring  272  moves radially outward due to the high pressure on the side of the communicating path  265   c , thereby allowing flow of the air in the direction of arrow  279 . As a result, an amount of air in the pneumatic chamber  249  can be increased to increase the air pressure. 
     In this way, the operation of increasing the air pressure of the pneumatic chamber  249  in the first step is executed by moving the piston  47  in the cylinder chamber  248 . A power source of the piston  47  may be anything as long as it is capable of moving the piston  47  or the blade  48 . Theoretically, the blade  48  can be moved in an up-down direction by hand or by using a specialized movable tool. However, in the present example, a driving source for moving the blade  48  during the striking operation is used. Herein, the pressurization in the pneumatic chamber  249  and the cylinder chamber  248  in the first step is performed using the electric motor  13 . Hence, in the present example, as the electric motor  13 , a brushless DC motor capable of detecting a rotation position with good accuracy by a micon and capable of performing control of normal rotation and reverse rotation with high accuracy is used. That is, in the first step, by reversely rotating the electric motor  13 , the piston  47  that has reached a position immediately before the top dead point is lowered to the bottom dead point; when the piston  47  reaches the bottom dead point, by again normally rotating the electric motor  13 , the piston  47  is moved to the position immediately before the top dead point. The reverse rotation and normal rotation of the electric motor  13  are performed within a range in which meshing between the rack  53  and the pinion  241  is not released, and are controlled with high accuracy by the micon contained in the controller  66 . By repeating the pressurization operation (one stroke) by the piston  47  in the piston chamber  248  a plurality of times in this way, the air pressure of the pneumatic chamber  249  can be increased to about 3 to 5 atmospheres. When the pneumatic chamber  249  is pressurized to a predetermined air pressure, since execution of the pressure accumulating mode is terminated by the micon, the operator returns the switching lever  261  of the external air intake valve  260  to the original position shown in  FIG. 6 . In this state, advance preparation (pressure accumulating mode) for driving of the nail  11  is completed. 
     Next, a procedure for pressurizing the pneumatic chamber  249  in the first step using the electric motor  13  is explained using the flowchart in  FIG. 9 . The sequential procedure shown in  FIG. 9  can be executed by software by the micon contained in the controller  66  using a pre-stored program. The flowchart in  FIG. 9  is started from, as a state where the switching lever  261  is rotated from the state shown in  FIG. 6 , and the selector  265  is lowered and the stepped portion  265   e  abuts against the opening portion  245   a  of the cylinder  245  as shown in  FIG. 7 , a state where a switch (switching lever  261 ) of the pressure accumulating mode is switched on (“ON”) (step  281 ). Moreover, although not illustrated in  FIG. 6  to  FIG. 8 , a sensor may be provided detecting the position of the switching lever  261 , so that it can be detected by the controller  66  that the switching lever  261  is switched. 
     First of all, the micon detects whether the pressure accumulating mode has become ON after the switching lever  261  is rotated (step  281 ). If the pressure accumulating mode is not achieved, standby is performed until the operator switches to the pressure accumulating mode (step  289 ). When the pressure accumulating mode is achieved, the micon detects whether or not the nail  11  remains in the magazine  16  and a nail shooting path (step  282 ). For this detection, a well-known stopper sensor or the like that detects whether the nail  11  is mounted in the shooting path  256  and presence or absence of the nail  11  may be provided. If the nail  11  remains in the magazine  16  or the shooting path, a warning lamp indicating that the nail  11  remains blinks, and standby is performed until the operator removes the nail  11  (step  290 ). Herein, when the nail  11  in the magazine  16  and the shooting path  256  is gone, rotation of the electric motor  13  becomes possible. When the trigger  72  is pulled by the operator, the micon reversely rotates the electric motor  13  and reversely rotates a hoisting cam (rotating body  238 ), thereby moving the piston  47  to the bottom dead point side (step  283 ). Thereby, the external air is attracted into the piston chamber  248  as shown by arrow  276  in  FIG. 7 . Moreover, during the initial reverse rotation of the cam in the pressure accumulating mode, since the piston  47  is almost located at the bottom dead point, step  283  terminates in an instant. 
     Next, by detecting a current value I flowing to the motor during reverse rotation of the cam (rotating body  238 ), the micon detects whether the nail  11  is clogging in the shooting path, i.e., whether a nail clogging state is present. The determination can be performed according to whether or not the detected current value I exceeds a threshold I 0  of current indicating nail clogging (step  284 ). The micon monitors the current value I at all times through a current detection circuit contained in a control circuit for driving the electric motor  13 . Thus, by using a detected value thereof, there is no need to provide a new current detection means. Herein, the reason is that, when the piston  47  is lowered, if the piston  47  can be smoothly lowered by the electric motor  13 , the current value I flowing to the motor does not become very large. If the current value I exceeds the set current value (threshold I 0 ), movement of the piston  47  and the blade  48  is thereby hindered. Therefore, the warning lamp indicating that the nail  11  remains blinks, and standby is performed until the operator removes the nail  11  (step  291 ). 
     Next, the micon normally rotates the electric motor  13  (rotation in a direction of hoisting the piston  47  during striking and rotation in a direction shown by the arrow in  FIG. 2 ) to normally rotate the hoisting cam (rotating body  238 ), thereby moving the piston  47  from the bottom dead point to the vicinity of (before) the top dead point (step  285 ). By this movement, the air (air attracted from the outside) in the cylinder chamber  248  can be sent into the pneumatic chamber  249  as shown by arrow  249  in  FIG. 8 . Herein, when the piston  47  is moved to the top dead point, since an engaged state between the hoisting cam (rotating body  238 ) and the rack  53  of the blade  48  is released, and the piston  47  rapidly moves due to pressure of the accumulated air (similarly as in the striking mode), it is important to stop the rise of the piston  47  at the position immediately before the top dead point. By the lowering operation (step  283 ) and the rising operation (step  285 ) of the piston  47  in this way, as shown in  FIG. 7  and  FIG. 8 , the external air is attracted through the external air intake valve  260  to increase the amount of the air in the pneumatic chamber  249 , and the air pressure can be increased. 
     Next, the micon determines whether or not the pressure accumulation performed by the lowering and rising operations of the piston  47  is completed (step  286 ). Whether the pressure accumulation (pressurization operation) is completed can be carried out by, for example, any of the following methods. (1) The current value I flowing to the electric motor  13  when the piston  47  is moved from the bottom dead point side to the top dead point side is detected, so as to determine whether the current value I has become greater than a threshold I 1  at the time of completion of the pressure accumulation operation. The reason is that, when the pressure (assumed to be increased to about 3 to 5 atmospheres by the pressure accumulating mode) in the pneumatic chamber  249  increases, since a load during movement of the piston  47  from the bottom dead point side to the top dead point side increases, the current value I increases with the increase in the load. (2) A pressure sensor (not illustrated) measuring the pressure in the pneumatic chamber  249  is provided, and whether or not the pressure P exceeds a set pressure P 0  is detected. This method directly measures the air pressure and is therefore the most accurate method. However, since it is necessary to provide the pressure sensor, the cost will increase and devices will increase in size. (3) The micon counts how many times the one-stroke operation has been executed, wherein the one-stroke operation refers to that the piston  47  is returned from the position immediately before the top dead point to the bottom dead point and is again raised from the bottom dead point to the position immediately before the top dead point. When the number of times of this reciprocating movement of the piston is executed N times, wherein N is a threshold being a predetermined number of times, the pressure accumulation operation is terminated. The threshold can be set to, for example, three times. When it is determined that the pressure accumulation operation is completed by any of the above methods (step  286 ), the micon detects whether the pressure accumulating mode has become OFF after the switching lever  261  is rotated (step  287 ). If the pressure accumulating mode is maintained, standby is performed until the operator operates the switching lever  261  to switch off the pressure accumulating mode (step  292 ). When the pressure accumulating mode becomes OFF, i.e., when the switching lever  261  is returned to the state in  FIG. 6 , the micon returns the piston  47  to an initial position (the bottom dead point or a predetermined position near the bottom dead point) (step  288 ), and the pressure accumulation process of the pneumatic chamber  249  by the first step is terminated. After that, the operator can execute the actual nail driving operation (second step). 
     As described above, according to the first example, since pressure of a gas in the pneumatic chamber  249  can be increased by movement of the piston  47  driven by the electric motor  13 , a driving machine having long life and high performance can be realized without being bothered by pressure reduction in the pneumatic chamber due to longtime use. 
     Example 2 
     Next, the second example of the present invention is explained using  FIG. 10  and  FIG. 11 . In a driving machine  301  of the second example, a difference from the first example is that a manual leak mechanism, i.e., the leak valve  360 , for allowing internal air to escape to the outside when pressure of a pneumatic chamber  349  exceeds a predetermined value, is provided in a pressure accumulation container  350 . Hence, the shape of the pressure accumulation container  350  is extended in the radial direction, and the leak valve  360  is provided in a position adjacent to the external air intake valve  260  on an upper surface of the pressure accumulation container  350 . The structure or function of the external air intake valve  260  is the same as that explained in the first example. Similarly to the first example, the pressure accumulation container  350  is made in a two-piece form using a container main body portion  351  and a flange portion  355 . However, as a container storing compressed air, it may be of an integral type or of a divided type, or may have other structures. The shape of an upper part of a main body housing  302  of the driving machine  301  changes with the change in the shape of the pressure accumulation container  350 . However, except the shape of the part in the vicinity of the pressure accumulation container  350 , the other parts have the same structures as those in the driving machine  201  of the first example. 
       FIG. 11  is longitudinal sectional views showing a detailed structure of the leak valve  360 . In the leak valve  360 , in addition to the function as a “release valve” which allows the internal air to escape to the outside when the pressure of the pneumatic chamber  349  (see  FIG. 10 ) exceeds the predetermined value, a function as a “leak valve” which enables the operator to discharge the air in the pneumatic chamber  349  at arbitrary timing is provided. When the nail  11  clogs in the shooting path  256  (see  FIG. 2 ) formed in the nose portion  254 , the arbitrary exhaust function by the leak valve is convenient to use when removing the clogging nail  11 . The reason is that, while the pressure of the pneumatic chamber  349  remains high, even if trying to remove the nail  11 , it is sometimes difficult to move the blade  48 . On the other hand, if the air in the pneumatic chamber  349  is released during removal of the nail  11 , since atmospheric pressure is reached in the pneumatic chamber  349  and the cylinder chamber  248 , the operator can easily move the blade  48 . Furthermore, if the pneumatic chamber  349  is returned to atmospheric pressure, there is no longer force to move the piston  47 . Thus, there is no longer a fear that the striking operation may be performed by mistake, and safety is thus further improved. 
     In  FIGS. 11 ( 1 ) and ( 2 ), a through hole  353  being an outlet of the air in the pneumatic chamber  349  is formed in the container main body portion  351  of the pressure accumulation container  350 , and the leak valve  360  is provided allowing discharge of the air from the through hole  353  in a predetermined state. The leak valve  360  is configured by including: a large-diameter portion  351   c  and a small-diameter portion  351   d  in which the container main body portion  351  protrudes inward in a cup shape; a cylindrical plunger  370  movable in the large-diameter portion  351   c  and the small-diameter portion  351   d  in the axial direction; a plunger holder  361  for holding the plunger  370  on the container main body portion  351 ; a push button  385  for moving the plunger  370 ; a ball  381  arranged inside the cylindrical plunger  370 ; and a pusher  382  for energizing the ball  381  in a predetermined direction. 
     A plurality of passages (communicating paths  371  and  374 ), and a narrowed part  372  for realizing a valve mechanism by the ball  381  are formed in the plunger  370 . O-rings  376  to  378  made of rubber and for maintaining airtightness between the plunger  370  and the plunger holder  361  are provided on an outer peripheral surface of the plunger  370 . The ball  381  is inserted from outside the container main body portion  351  into the plunger  370 , energized by the pusher  382  and a coil spring  383 , and held by a metal plate  384 . The metal plate  384  is retained by the push button  385  made of synthetic resin. Moreover, a retaining ring  386  is inserted into a lower side of the push button  385 . The plunger holder  361  holds the plunger  370  on the container main body portion  351 , and forms or closes a predetermined air passage along with a groove portion on an outer peripheral side of the plunger  370 . The plunger holder  361  passes through a through hole  302   c  of the main body housing  302 , and is pressed into the large-diameter portion  351   c  of the container main body portion  351 . An O-ring  363  is provided in order to maintain airtightness between the plunger holder  361  and the large-diameter portion  351   c . In addition, a discharge pipeline  365  extending the container main body portion  351  in a direction orthogonal to the axial direction. The discharge pipeline  365  is formed by drilling or the like into a part of the container main body portion  351 , and communicates outside the main body with a horizontal hole  361   c  formed in the plunger holder  361 . 
       FIG. 11 ( 1 ) shows a state where the driving machine  301  is not in use or where a normal striking operation is being performed. ( 2 ) shows a state where the push button  385  is pressed down in a direction of arrow  395  by the operator, wherein by moving the push button  385  axially downward, an air passage from the through hole  353  to the discharge pipeline  365  is delimited as shown by arrow  391 . Herein, the air passes through a gap between a lower end portion of the plunger holder  361  and an inside of the large-diameter portion  351   c  from the through hole  353 , passes through a gap formed between an inclined surface portion on an inner peripheral side of the plunger holder  361  and an O-ring  377  to flow upward, and flows to the part of a wide groove  375  continuous in the circumferential direction so as to continue from the axial lower side. The air is discharged outside from the discharge pipeline  365 , as shown by arrow  391 . During discharge of the air, a discharge sound of high pressure air occurs. However, when this sound stops and the operator releases the press-down of the push button  385 , the plunger  370  returns to the state in (1) due to a restoring force of a coil spring  379 . In this way, in cases where nail clogging occurs, decompression of the pressure accumulation container  350  performed by pressing down the push button  385  can be operated when removing the clogging nail. 
       FIG. 11 ( 3 ) shows a condition when the leak valve  360  acts as a release valve when pressurization of the pneumatic chamber  349  of the driving machine  301  is performed and a specified amount or more of air is taken in. It is assumed that the driving machine  301  of the present example drives a nail having a length of about 50 to 90 mm. In a preparation step (first step) before pressure accumulation, the pressure in the pneumatic chamber is set to about 5 to 8 atmospheres; in the striking step (second step) of performing actual driving, the pressure in the pneumatic chamber is increased up to about 10 to 14 atmospheres. If the striking step is performed after the pressure accumulation in the first step is performed in a specified amount or more, the pressure of the pneumatic chamber  349  may exceed the predetermined value. On that occasion, excess air is discharged outside by a path of arrow  393  shown in (3). In the state of (3), since the push button  385  is in the same normal position as in (1), the discharge path shown in (2) cannot be taken. Accordingly, the communicating path  371  is provided spatially connecting the narrowed part  372  closed by the ball  381  to the gap between the lower end portion of the plunger holder  361  and the inside of the large-diameter portion  351   c , and the pressure (arrow  392 ) of the pneumatic chamber  349  is applied to the ball  381 . Thus, when a predetermined amount or more of air pressure is applied to the ball  381 , the coil spring  383  is compressed through the pusher  382 . Thereby, the ball  381  is separated from the narrowed part  372 . Thereupon, the excess air flows around the ball  381  and is discharged outside through the communicating path  374 , as shown by arrow  393 . Moreover, although in (3), arrow  393  illustrates that the discharge is performed leftward, the discharge may also be performed rightward in the same way. On this occasion, when a predetermined amount of air is discharged and the pressure of the pneumatic chamber  349  becomes an appropriate air pressure, a spring force of the coil spring  383  becomes stronger than the pressure (arrow  392 ) of the pneumatic chamber  349 , and the ball  381  is again pressed against the narrowed part  372 . Thereby, the leak valve  360  returns to the state in  FIG. 11 ( 1 ), and the airtight state in the pneumatic chamber  349  is maintained. 
     As described above, according to the second example, when nail clogging occurs and removal of the nail is performed, since the operator can release the high pressure air in the pneumatic chamber  349 , the removal of the nail can be performed in a safe state. In addition, in cases such as where the driving machine is not in use over a long period of time, since the high pressure air in the pneumatic chamber  349  can be released if the operator wishes, a seal part of the pneumatic chamber or a seal portion of the piston can be prevented from aged deterioration at an early stage. Furthermore, when a high pressure equal to or higher than a specified value is reached in the pneumatic chamber  349 , since excess internal air can be automatically discharged, there is no fear of failure in the pressurization in the first step. 
       FIG. 12  shows a modification of the second example, obtained by replacing the leak valve  360  in  FIG. 11  with an electromagnetic valve  460 . The electromagnetic valve  460  is arranged so as to pass through a container main body portion  451 , wherein a discharge pipe  461  forming a communicating path  462  of discharged air, a valve  463  for opening or closing the communicating path  462 , and a solenoid actuator  464  moving the valve  463  are provided. The discharge pipe  461  is a substantially cylindrical member in which an axial center is closed. The discharge pipe  461  is mounted in a through hole portion  451   b  of the container main body portion  451 , and is attached by interposing an O-ring  468  made of rubber therebetween. In the closed part of the discharge pipe  461 , extremely thin communicating paths  462   a  and  462   b  are formed extending in the axial direction and radial direction. The parts of the communicating paths  462   a  and  462   b  extending in the radial direction are exposed in a depressed part formed on an outer peripheral side of the discharge pipe  461 , and the valve  463  is arranged so as to cover the depressed part. The solenoid actuator  464  moves an iron core  467  by magnetic force inside a coil  466  provided within a housing  465 . The iron core  467  is fixed to the valve  463 . By energizing the coil  466 , the valve  463  is moved so as to approach the side of the communicating path  462 ; by stopping energization to the coil  466 , the valve  463  is moved to the side away from the communicating path  462  due to action of a spring (not illustrated). By separation of the valve  463  from the communicating path  462 , a space is formed between the depressed part of the discharge pipe  461  and the valve  463 , and the paths  462   a  and  462   b  communicate with each other. Therefore, air pressurized in a pneumatic chamber  449  can be discharged outside through the discharge pipe  461 . By driving the solenoid actuator  464  by control of the micon in this way, it becomes possible to control opening or blocking of the communicating path  462 . 
     As described above, according to the second example, when an abnormality such as nail clogging occurs and the micon detects that it is necessary to remove the nail, by the micon operating the electromagnetic valve  460 , high pressure air in the pneumatic chamber  449  can be released. Thus, the operator can perform removal of the nail can be performed in a safe state. In addition, after the removal of the nail is completed, the operator operates the external air intake valve  260  and the pressure accumulating mode to increase the pressure of the pneumatic chamber  449  can be executed. Thus, a user-friendly driving machine can be realized. 
     Example 3 
     Next, the third example of the present invention is explained using  FIG. 13  to  FIG. 16 . The basic configuration of  FIG. 13  is almost the same as that of the driving machine  201  explained in the first example, particularly in terms of the nail feeding mechanism such as the magazine  16 , driving performed by the electric motor  13 , shape of a grip  101  or a mounting portion  1 , that the storage battery  15  is used as a power source, and that the storage battery  15  is attachable to and detachable from a mounting portion  102 . A main difference lies in a striking mechanism  12  that strikes the nail  11 , and the mechanism for pressurizing a pneumatic chamber is different. Herein, unlike the first example in which pressure accumulation is performed using the piston  47 , a pneumatic chamber is constituted by the movable second cylinder  46 , and the cylinder  46  is movable in the up-down direction by the driving force of the electric motor  13  (described later). In addition, a shape of a cover  100  also varies according to the form of the cylinder  46 . The electric motor  13  (not illustrated) is provided within the motor housing  17 , and its structure is a brushless DC motor of the same type as that explained in  FIG. 1 . The decelerator  27  of the same type as that explained in  FIG. 1  is accommodated in the casing  33  adjacent to the motor housing  17 , and the casing  33  is connected to a cylindrical nose portion  54 . 
       FIG. 14  is a side view as viewed from the direction A in  FIG. 13 , and a part thereof is shown in sectional view. A rotational driving force of the electric motor  13  is transmitted to a drive shaft  34  and a driven shaft  35  through an output of the decelerator  27 . Herein, two power transmission paths, i.e., a first power transmission path driven by rotation of the driven shaft  35  and a second power transmission path driven by rotation of the drive shaft  34 , are provided. The first power transmission path is movable in the up-down direction of the movable second cylinder  46  using a gear  44  rotated by the driven shaft  35 . The second power transmission path moves the blade  48  upward using a gear  41  rotated by the drive shaft  34 , thereby moving the piston  47  (see  FIG. 15 ) from the bottom dead point to the top dead point. While details thereof are described later, when the electric motor  13  is rotated in the normal direction, the power is only transmitted to the drive shaft  34  so that only the gear  41  rotates; when the electric motor  13  is rotated in the opposite direction, the power is only transmitted to the driven shaft  35  so that only the gear  44  rotates. Accordingly, by setting the rotational direction of the electric motor  13 , whether the power is transmitted toward the first power transmission path or toward the second power transmission path can be alternatively selected. 
     The drive shaft  34  is arranged concentrically with the output shaft  24  (see  FIG. 1 ) of the electric motor  13  and is rotatable about the axis line A 1 . A rotating body  37  and the rotating body  38  are attached to the drive shaft  34 . A gear  40  is provided on an outer peripheral surface of the rotating body  37 , and a rotational force is transmitted toward the driven shaft  35  by the gear  40 . The gear  40  is provided on the outer peripheral surface of the rotating body  37 . A one-way clutch  39  (see  FIG. 15 ) is provided connecting or blocking the power transmission path between the rotating body  37  and the drive shaft  34 . When the drive shaft  34  rotates in the counterclockwise direction in  FIG. 14 , a rotational force of the drive shaft  34  is transmitted to the rotating body  37 . Even if the drive shaft  34  rotates in the clockwise direction in  FIG. 14 , the one-way clutch  39  does not transmit the rotational force of the drive shaft  34  to the rotating body  37 . That is, the one-way clutch  39  connects or blocks the power transmission path between the drive shaft  34  and the driven shaft  35  according to the rotational direction of the drive shaft  34 . 
     The gear  41  is provided within a predetermined angle range on the outer peripheral surface of the rotating body  38 . In addition, in the rotational direction of the rotating body  38 , a roller  42  is provided at a part where the gear  41  is not provided. A part of an outer peripheral surface of the roller  42  is arranged outside the outer peripheral surface of the rotating body  38 . The roller  42  is rotatably supported. 
     The gear  44  is provided on the driven shaft  35 . The gear  44  meshes with the gear  40 . The blade  48  is arranged along the center line B 1  and is movable within a shaft hole  52  (see  FIG. 15 ). A rotation stopper  73  being a holding member that restricts rotation of a rotating body  60  is provided on the casing  33 . The rotation stopper  73  is swingable about a support shaft  74 . By meshing with a gear  61 , the rotation stopper  73  prevents the rotating body  60  from rotating in the counterclockwise direction in  FIG. 14  and allows the rotating body  60  to rotate in the clockwise direction. That is, the gear  61  and the rotation stopper  73  constitute a ratchet mechanism. The rack  53  is provided on the blade  48  in the length direction. The gear  41  is capable of meshing with or being detached from the rack  53 . The casing  33  has the cylindrical nose portion  54 , and the blade  48  is movable in the nose portion  54 . 
     The nose portion  54  is exposed outside the cover  100  (see  FIG. 13 ). The pushrod  104  is provided on the nose portion  54 . The pushrod  104  is movable with respect to the nose portion  54  in a predetermined range in the direction along the center line B 1 . The pushrod  104  is pressed and stopped in the direction along the center line B 1  by the force of the compression spring  105  (see  FIG. 15 ). When the pushrod  104  is pressed against the object, the pushrod  104  moves in the direction of the center line B 1  against the force of the compression spring  105  (see  FIG. 15 ) and then stops. 
       FIG. 15  is a front sectional view of the driving machine shown in  FIG. 13 . As shown in  FIG. 15 , the striking mechanism  12  includes the first cylinder  45 , the second cylinder  46 , the piston  47  and the blade  48 . The cylinders  45  and  46  are arranged within the cover  100  (see  FIG. 13 ). The cylinder  45  includes a cylindrical portion  49 , and an outward-facing flange  50  continuous with the cylindrical portion  49 . The center line B 1  of the cylindrical portion  49  intersects with the axis line A 1  at a substantially right angle, and a first end portion (lower end portion) of the cylindrical portion  49  in the direction along the center line B 1  is fixed to the casing  33 . A part of a power transmission mechanism  14  is provided in the casing  33 . The power transmission mechanism  14  includes the drive shaft  34  and the driven shaft  35  arranged parallel to each other. The drive shaft  34  is rotatably supported by the casing  33  through a bearing  36 . The drive shaft  34  is arranged concentrically with the output shaft  24  and is rotatable about an axis line D 1 . In addition, the rotating bodies  37  and  38  are attached to the drive shaft  34 . The rotating body  37  is arranged between the rotating body  38  and the decelerator  27  in a direction along the axis line A 1 . The rotational direction of the drive shaft  34  is the same as the rotational direction of the rotor  19  of the electric motor  13 . A one-way clutch  43  is provided between the rotating body  38  and the drive shaft  34 . When the drive shaft  34  rotates in the clockwise direction in  FIG. 14 , the one-way clutch  43  transmits the rotational force of the drive shaft  34  to the rotating body  38 ; when the drive shaft  34  rotates in the counterclockwise direction, the one-way clutch  43  does not transmit the rotational force of the drive shaft  34  to the rotating body  38 . 
     The gear  40  is provided on the outer peripheral surface of the rotating body  37 . The one-way clutch  39  is provided connecting or blocking the power transmission path between the rotating body  37  and the drive shaft  34 . When the drive shaft  34  rotates in the counterclockwise direction in.  FIG. 2 , the one-way clutch  39  transmits the rotational force of the drive shaft  34  to the rotating body  37 . Even if the drive shaft  34  rotates in the clockwise direction in  FIG. 14 , the one-way clutch  39  does not transmit the rotational force of the drive shaft  34  to the rotating body  37 . That is, the one-way clutch  39  connects or blocks the power transmission path between the drive shaft  34  and the driven shaft  35  according to the rotational direction of the drive shaft  34 . 
     The flange  50  is provided on a second end portion (upper end portion) of the cylindrical portion  49  in the direction along the center line B 1  being an axis line of the cylinder  45 . In addition, an annular damper  51  integrally formed of a rubber-like elastic body is provided between the cylindrical portion  49  and the casing  33 . The damper  51  includes the shaft hole  52 . 
     The piston  47  is reciprocally movable in the cylindrical portion  49  in the direction along the center line B 1 , and the seal member  55  is attached to the outer peripheral surface of the piston  47 . In addition, the shaft-shaped blade  48  is connected to or fixed to the piston  47 . The cylinder  46  includes a cylindrical portion  56  and a circular plate portion  57  continuous with the cylindrical portion  56 . The flange  50  is arranged in the cylindrical portion  56 , and the cylinder  46  is movable with respect to the cylinder  45  in the direction along the center line B 1 . A seal member  103  is attached to an outer peripheral surface of the flange  50 , and a pneumatic chamber  58  is formed in the cylinder  46 . The pneumatic chamber  58  communicates with the inside of the cylinder  45 . A breathing hole  59  is provided penetrating the cylindrical portion  56  in the radial direction. The breathing hole  59  connects the inside and outside of the pneumatic chamber  58 . The seal members  55  and  103  airtightly seal the pneumatic chamber  58 . The air being a compressible fluid goes into and out of the pneumatic chamber  58  through the breathing hole  59 . 
     The rotating body  60  having the gear  61  provided on its outer peripheral surface is attached to a part of the driven shaft  35  that is exposed outside the casing  33 . The rotating body  60  is rotatable about the axis line D 1  along with the driven shaft  35 . On the rotating body  60 , a support shaft  62  is provided in a position eccentric from the axis line D 1 . In addition, a support shaft  63  is provided on the cylinder  46 . A conrod  64  is provided connecting the rotating body  60  and the cylinder  46 . The conrod  64  is rotatably attached to the support shafts  62  and  63 , and constitutes, along with the rotating body  60 , an opening and closing mechanism that opens a ventilation passage. 
     When the trigger  72  is not being operated, the electric motor  13  is stopped. In addition, the cylinder  46  is stopped in the initial position in  FIG. 14  and  FIG. 15 . When the cylinder  46  is stopped in the initial position, the pneumatic chamber  58  is connected to outside of the pneumatic chamber  58  through the breathing hole  59 . That is, the initial pressure in the pneumatic chamber  58  and the cylinder  45  is the same as atmospheric pressure. In addition, the piston  47  contacts the damper  51  and then stops, and the gear  41  does not mesh with the rack  53  (see  FIG. 14 ). 
     In the preparation step (first step) before performing striking, the operator operates the rotational direction switching switch  68  (see  FIG. 5 ), so as to set the rotational direction of the drive shaft  34  to the counterclockwise direction in  FIG. 14 , and to apply an operating force to the trigger  72 . Moreover, in the first step, the pushrod  104  may not be pressed against the object, but may not move unless being pressed. Thereupon, when the trigger switch  71  is switched on, the electric motor  13  rotates. Herein, the drive shaft  34  is rotated in the counterclockwise direction in  FIG. 14  by the rotational force of the electric motor  13 . The rotational force of the drive shaft  34  is transmitted to the driven shaft  35  through the one-way clutch  39 , and the driven shaft  35  and the rotating body  60  integrally rotate in the clockwise direction in  FIG. 14 . 
     When the rotating body  60  rotates in the clockwise direction in  FIG. 14 , a rotational force of the rotating body  60  is transmitted to the cylinder  46  through the conrod  64 , and the cylinder  46  operates in a direction (shooting direction) of arrow B along the center line B 1 , and lowers in a direction approaching the casing  33  from the initial position shown in  FIG. 14  and  FIG. 15 . When the cylinder  46  lowers and the breathing hole  59  reaches between the seal member  103  and the casing  33  in the direction along the center line B 1 , the flange  50  blocks the breathing hole  59  and the pneumatic chamber  58 . That is, the breathing hole  59  is closed, and the pneumatic chamber  58  and the cylinder  45  become airtight. Hence, the pressure in the pneumatic chamber  58  and the cylinder  45  increases in the lowering stroke of the cylinder  46 . As a result, the pressure in the pneumatic chamber  58  and the cylinder  45  becomes a first pressure higher than atmospheric pressure. 
     Then, when a rotational angle of the driven shaft  35  changes from the position in  FIG. 14  in which the rotation starts to the position in which a predetermined angle of less than 180 has been rotated, the controller  66  stops the electric motor  13 . That is, the cylinder  46  stops in the vicinity of (the bottom dead point) where the circular plate portion  57  is about to contact the flange  50  of the cylinder  45 . The circular plate portion  57  of the cylinder  46  receives the pressure of the pneumatic chamber  58 , and the cylinder  46  is energized in a rising direction along the center line B 1 . The energizing force received by the cylinder  46  is transmitted to the rotating body  60  through the conrod  64 . That is, the rotating body  60  receives a rotational force in the counterclockwise direction in  FIG. 14 . 
     Next, the operator operates the rotational direction switching switch  68  in order to perform the striking step (second step), so as to set the rotational direction of the electric motor  13  opposite that set in the first step. The electric motor  13  is stopped at a time point when the rotational direction is set. Then, in the state where the pushrod  104  is pressed against the object, the electric motor  13  rotates when the trigger  72  is operated, and the drive shaft  34  rotates in the clockwise direction in  FIG. 14 . When the drive shaft  34  rotates in the clockwise direction in  FIG. 8 , the one-way clutch  39  does not transmit the rotational force of the drive shaft  34  to the driven shaft  35 . 
     When the drive shaft  34  rotates in the clockwise direction in  FIG. 14 , the gear  41  meshes with the rack  53 , and the rotational force of the drive shaft  34  is converted to a force causing the piston  47  to rise. Accordingly, the pressure in the pneumatic chamber  58  and the cylinder  45  further increases. That is, the pressure in the pneumatic chamber  58  and the cylinder  45  becomes a second pressure higher than the first pressure. Then, when the piston  47  reaches the top dead point closest to the circular plate portion  57 , the gear  41  is separated from the rack  53 . 
     Thereupon, the piston  47  is rapidly lowered toward the damper  51  by the air pressure in the pneumatic chamber  58  and the cylinder  45 , and the blade  48  strikes the nail  11  to drive the nail  11  into the object. Then, the piston  47  collides with the damper  51  and then stops. The electric motor  13  rotates even after the gear  41  has been separated from the rack  53 . When the gear  41  reaches a predetermined position, i.e., before the gear  41  meshes with the rack  53 , the electric motor  13  stops. After that, by the operator separating the pushrod  104  from the object, the driving operation of the nail  11  terminates. 
     When the operator presses the pushrod  104  against the object to pull the trigger  72  in a next driving position, the electric motor  13  rotates to rotate the rotating body  38  in the clockwise direction in  FIG. 14 , the gear  41  meshes with the rack  53 , and the piston  47  rises. Thereby, the nail  11  is driven by the same action as above. 
     Moreover, in a state where the nail  11  is not set in the magazine  16  in the driving machine  10 , when the piston  47  is stopped, the operator grips the rotation stopper  73  by hand and rotates the rotation stopper  73  in the clockwise direction in  FIG. 14 , and the rotation stopper  73  is separated from the gear  61 . Thereby, the pressure in the pneumatic chamber  58  and the cylinder  45  can be reduced. 
     As described above, by connecting the pneumatic chamber  58  to the breathing hole  59 , the pressure in the pneumatic chamber  58  and the cylinder  45  can be reduced. Thus, in cases where the nail  11  clogs, the nail  11  can be easily removed. In addition, during storage of the driving machine  10 , since the air pressure of the pneumatic chamber  58  can be released, there is no need to provide a seal member for maintaining high pressure of the air chamber. 
     Example 4 
     A driving machine corresponding to the fourth example is shown in  FIG. 17  to  FIG. 18 . The driving machine  10  in  FIG. 17  includes the same structure and the same elements as those of the driving machine  10  shown in the third example. The cylinder  45  has a cylindrical shape. The flange  50  explained in Example 3 is not provided, and instead a partition  75  attached to the cylinder  45  is provided. The partition  75  includes a cylindrical portion  76  movable along an outer peripheral surface of the cylindrical portion  49  of the cylinder  45 , and an outward-facing flange  77  continued from the cylindrical portion  76 . An outer diameter of the flange  77  is less than an inner diameter of the cylindrical portion  56 . The partition  75  is movable with respect to the cylinder  45  and the cylinder  46  in the direction along the center line B 1 . 
     A seal member  78  is attached to an inner peripheral surface of the cylindrical portion  76 , and the seal member  78  airtightly seals between the outer peripheral surface of the cylindrical portion  49  and the partition  75 . In addition, a seal member  79  is attached to an outer peripheral surface of the flange  77 . The seal member  79  airtightly seals between an inner peripheral surface of the cylindrical portion  56  and the flange  77 . Furthermore, a support shaft  80  is provided on an outer peripheral surface of the cylindrical portion  76 , and the conrod  64  is rotatably connected to the support shaft  80 . That is, the rotating body  60  and the partition  75  are connected to each other in a manner capable of transmitting power through the conrod  64 . The arrangement range of the support shaft  80  and the conrod  64  in the radial direction of the center line B 1  is less than the inner diameter of the cylindrical portion  56 . 
     First of all, the first step of increasing the air pressure of the pneumatic chamber  58  is performed. In the second step, the air pressure of the pneumatic chamber  58  is further increased and the nail  11  is struck. The operator operates the rotational direction switching switch  68  to switch the rotational direction of the electric motor  13 , and sets the rotational direction of the drive shaft  34  in the first step to the counterclockwise direction in  FIG. 17 . 
     The partition  75  is stopped in an initial position in  FIG. 17  before the drive shaft  34  starts rotating. When the partition  75  is stopped in the initial position, the pneumatic chamber  58  is connected to outside of the pneumatic chamber  58  through the breathing hole  59 . That is, the pressure in the pneumatic chamber  58  and the cylinder  45  is the same as atmospheric pressure. In addition, the piston  47  contacts the damper  51  and is then stopped. 
     Then, when the operating force is applied to the trigger  72  in a state where the pushrod  104  is not being pressed against the object, the electric motor  13  rotates, and the drive shaft  34  rotates in the counterclockwise direction in  FIG. 17 . Thereupon, the rotating body  60  rotates in the clockwise direction in  FIG. 17  on the same principle as that of the driving machine  10  of Example 3. The rotational force of the rotating body  60  is converted into an operation force in the direction along the center line B 1  by the conrod  64 . Hence, the partition  75  rises along the center line B 1 . When the partition  75  rises and the seal member  79  reaches between the breathing hole  59  and the circular plate portion  57  in the direction along the center line B 1 , the pneumatic chamber  58  and the cylinder  45  become airtight. Hence, with the rise of the partition  75 , the pressure in the pneumatic chamber  58  and the cylinder  45  increases. That is, the pressure in the pneumatic chamber  58  and the cylinder  45  becomes the first pressure higher than atmospheric pressure. 
     Then, when the rotational angle of the driven shaft  35  changes from the position in  FIG. 17  in which the rotation starts to the position in  FIG. 18  in which a predetermined angle of less than 180 has been rotated, the electric motor  13  is stopped. That is, the partition  75  stops before reaching the top dead point. The flange  77  of the partition  75  receives the pressure of the pneumatic chamber  58 , and the partition  75  is energized in the direction approaching the casing  33  along the center line B 1 . The energizing force received by the partition  75  is transmitted to the rotating body  60  through the conrod  64 . That is, the rotating body  60  receives a rotational force in the counterclockwise direction in  FIG. 17 . 
     Next, the operator operates the rotational direction switching switch  68  in order to perform the second step, and switches the rotational direction of the electric motor  13 . The operation in the second step hereafter is the same as that in the third example. 
     In the driving machine  10  of the fourth example, even if the partition  75  rises and lowers in the direction along the center line B 1 , the whole length of the driving machine  10  in the direction along the center line B 1  does not change. The whole length of the driving machine  10  is a height from the tip of the pushrod  104  to the upper end of the cylinder  45 . 
     Example 5 
     A driving machine corresponding to the fifth example of the present invention is shown in  FIG. 19  and  FIG. 20 . The driving machine  10  shown in  FIG. 19  can use the electric motor  13 , the decelerator  27 , the rotating body  38 , the piston  47 , the roller  42 , the blade  48  and the cylinder  45  having the same structures as those in the driving machine  10  of the fourth example. However, the driving machine  10  in  FIG. 19  does not include the first power transmission path part (the driven shaft  35 , the rotating body  37 , the one-way clutch  43  and the conrod  64 ) of the fourth example. The driving machine  10  instead includes an outer cylinder  106  fixed to the casing  33 , and the cylinder  45  is arranged in the outer cylinder  106 . An inner cylinder  107  is provided in the outer cylinder  106 . The cylinder  45  is arranged between the inner cylinder  107  and the casing  33  in the direction along the center line B 1 . 
     The inner cylinder  107  includes a large-diameter portion  108  and a small-diameter portion  109 . The small-diameter portion  109  is arranged between the large-diameter portion  108  and the casing  33  in the direction along the center line B 1 . An inner diameter of the large-diameter portion  108  is larger than an inner diameter of the small-diameter portion  109 . Furthermore, the inner cylinder  107  has a connecting portion  117  connecting the large-diameter portion  108  and the small-diameter portion  109 . The connecting portion  117  has an annular shape. A breathing hole  111  is provided penetrating the large-diameter portion  108  in the radial direction. An end portion of the cylinder  45  in the length direction is fixed to the small-diameter portion  109 . A seal member  110  is provided sealing between an outer peripheral surface of the cylinder  45  and an inner peripheral surface of the small-diameter portion  109 . 
     A holder  112  is fixed to the outer cylinder  106 . A screw member  113  is provided fixing the holder  112  to the outer cylinder  106 . By the holder  112 , the inner cylinder  107  is positioned and fixed to the outer cylinder  106  in the direction along the center line B 1 . The breathing hole  111  is connected to outside of the outer cylinder  106  through inside of the outer cylinder  106 . 
     In addition, a plunger  114  is attached to the holder  112 . The plunger  114  is a mechanism using a screw member, and a male thread of a shaft portion  115  of the plunger  114  is formed. A female screw hole  116  is provided in the holder  112 , and the shaft portion  115  is inserted into the female screw hole  116 . The operator can manually rotate the plunger  114  in normal and reverse directions, and the plunger  114  is movable in the direction along the center line B 1  when rotated in either direction. When the rotational direction of the plunger  114  differs, the direction in which the plunger  114  moves along the center line B 1  differs. 
     A movable partition  118  is attached to a tip of the shaft portion  115 . The movable partition  118  is arranged in the large-diameter portion  108 . The movable partition  118  is a circular plate rotatable about the center line B 1  with respect to the shaft portion  115 . An outer diameter of the movable partition  118  is less than the inner diameter of the large-diameter portion  108 , and an annular seal member  119  is attached to an outer peripheral surface of the movable partition  118 . In the large-diameter portion  108 , a pneumatic chamber  120  is formed from a space between the movable partition  118  and the connecting portion  117  and across in the cylinder  45 . The seal members  55 ,  110  and  119  airtightly seal the pneumatic chamber  120 . The breathing hole  111  connects the inside and outside of the pneumatic chamber  120 . 
     In  FIG. 20 , the configuration and operation of the second power transmission path part including the rotating body  38  are the same as those in the third to fourth examples. However, the rotational direction switching switch  68  for switching the rotational direction of the electric motor  13  is not provided since it is unneeded. 
     When using the driving machine  10 , before pressing the pushrod  104  against the object, the operator performs the first step of increasing air pressure of the pneumatic chamber  120 . In the second step, the operator further increases the air pressure of the pneumatic chamber  120 , and presses the pushrod  104  against the object to strike the nail  11 . The drive shaft  34  is stopped before the operator performs the first step. In addition, as shown on the right side of the center line B 1  in  FIG. 14 , the piston  47  contacts the damper  51 . Furthermore, the movable partition  118  is stopped in a position shown in chain double-dashed lines in  FIG. 14 . That is, the pneumatic chamber  120  is connected to outside of the outer cylinder  106  through the breathing hole  111 , and pressure of the pneumatic chamber  120  is the same as atmospheric pressure. 
     In the first step, the operator rotates the plunger  114  in a predetermined direction using a spanner or the like, so as to move the plunger  114  in the direction along the center line B 1 . In the first step, the plunger  114  lowers in a direction approaching the cylinder  45 . Thereupon, the movable partition  118  blocks the pneumatic chamber  120  and the breathing hole  111 , and the pressure of the pneumatic chamber  120  increases with movement of the movable partition  118 . The operator stops the movable partition  118  in a predetermined position in the direction along the center line B 1 . Hence, the pressure of the pneumatic chamber  120  is maintained at the first pressure higher than atmospheric pressure. 
     The operation in the second step is the same as that in the third and the fourth examples. In the driving machine  10  in the fifth example, by rotating the plunger  114  in a direction opposite that mentioned above and moving the plunger  114  in the direction of the center line B 1  in a direction away from the cylinder  45 , the pressure of the pneumatic chamber  120  can be reduced. When the movable partition  118  rises in the direction away from the cylinder  45  along with the plunger  114 , the seal member  119  reaches between the breathing hole  111  and the holder  112  in the direction of the center line B 1 , and the breathing hole  111  is connected to the pneumatic chamber  120 . Hence, the air pressure of the pneumatic chamber  120  is reduced to become the same as atmospheric pressure. Accordingly, the driving machine  10  of the fifth example obtains the same effects as those obtained by the driving machine  10  of Example 4. 
     The driving machine of the present invention is not limited to the above embodiments but can be modified in various ways without departing from the gist thereof. For example, the motor that transmits power to the drive shaft may be, in addition to an electric motor, an engine, a hydraulic motor, or a pneumatic motor. The electric motor may be either a brushed motor or a brushless motor. A power supply for the electric motor may be either a DC power supply or an AC power supply. Furthermore, compressed air having an initial pressure higher than atmospheric pressure and equal to or lower than the first pressure may be filled into the pneumatic chamber  58  and the cylinder  45 . 
     In addition, in the driving machine  10  in each drawing for explaining each example, the center line B 1  is shown as an up-down direction, i.e., vertical direction. However, the driving machine  10  can be used with the center line B 1  being inclined with respect to the vertical direction. Furthermore, the object to be driven by the driving machine includes, in addition to a shaft-shaped nail, a lateral U-shaped nail. In addition, the shaft-shaped nail includes a nail having a head or a nail having no head. Furthermore, the first pressure and the second pressure in the present invention are not fixed values but vary depending on conditions such as an operation amount of a movable member, pressure receiving area and so on. 
     In the third and fourth driving machine  10 , the rotational direction of the rotor  19  of the electric motor  13  is switched to switch the rotational direction of the drive shaft  34 . In contrast, by providing a rotational direction switching mechanism in the power transmission path between the electric motor  13  and the drive shaft  34  and controlling the rotational direction switching mechanism, it is possible to switch the rotational direction of the drive shaft  34  without switching the rotational direction of the electric motor  13 . 
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
         
           
               10 : driving machine;  11 : nail (stopper);  11   a : head portion;  12 : striking mechanism;  13 : electric motor;  14 : power transmission mechanism;  15 : storage battery;  16 : magazine;  17 : motor housing;  18 : stator;  19 : rotor;  21 : coil;  24 : output shaft;  27 : decelerator;  33 : casing;  34 : drive shaft;  35 : driven shaft;  36 : bearing;  37 : rotating body;  38 : rotating body;  39 : one-way clutch;  40 : gear;  41 : gear;  42 : roller;  43 : one-way clutch;  44 : gear;  45 : cylinder;  46 : cylinder;  47 : piston;  48 : blade;  48   b : tip;  49 : cylindrical portion;  50 : flange;  51 : damper;  52 : shaft hole;  53 : rack;  53   a : upper end tooth;  53   b : lower end tooth;  54 : nose portion;  55 : seal member;  56 : cylindrical portion;  57 : circular plate portion;  58 : pneumatic chamber;  59 : breathing hole;  60 : rotating body;  61 : gear;  62 : support shaft;  63 : support shaft;  64 : conrod;  65 : inverter circuit;  66 : controller;  67 : phase detection sensor;  68 : rotational direction switching switch;  71 : trigger switch;  72 : trigger (trigger lever);  73 : rotation stopper;  74 : support shaft;  75 : partition;  76 : cylindrical portion;  77 : flange;  78 ,  79 : seal member;  80 : support shaft;  81 : control circuit substrate;  82   a ,  82   b : bearing;  83 : inverter circuit substrate;  84 : switching element;  100 : cover;  101 : grip;  103 : seal member;  104 : pushrod;  105 : compression spring;  106 : outer cylinder;  107 : inner cylinder;  108 : large-diameter portion;  109 : small-diameter portion;  110 : seal member;  111 : breathing hole;  112 : holder;  113 : member;  114 : plunger;  115 : shaft portion;  116 : hole;  117 : connecting portion;  118 : movable partition;  119 : seal member;  120 : pneumatic chamber;  121 : detection sensor;  201 : driving machine;  202 : main body housing;  202   b : through hole;  203 : grip;  204 : mounting portion;  233 : casing;  234 : drive shaft;  235 : pin;  236 : off switch;  236   a : plunger;  237 : operating lever;  238 : rotating body;  241 : pinion;  241   a : tip tooth;  241   b : rear end tooth;  245 : cylinder;  245   a : opening portion;  245   c : male thread;  267 : washer;  248 : cylinder chamber;  249 : pneumatic chamber;  250 : pressure accumulation container;  251 : container main body portion;  251   b : through hole;  252 : cylindrical portion;  254 : nose portion;  255 : flange portion;  255   c : female thread;  256 : shooting path;  257 : magnetic sensor;  260 : external air intake valve;  261 : switching lever;  261   a : through hole;  262 : cylindrical sleeve;  262   a : external air intake passage;  262   b : spline groove;  263 : collar;  264 : steel ball;  265 : selector;  265   a : communicating path;  265   b : cylindrical depression;  265   c : communicating path;  265   d : outer peripheral groove;  265   e : stepped portion;  266 : metal;  270 : cushion material;  271  to  273 : O-ring;  301 : driving machine;  302 : main body housing;  302   c : through hole;  303 : grip portion;  349 : pneumatic chamber;  350 : pressure accumulation container  350 ;  351 : container main body portion;  351   c : large-diameter portion;  351   d : small-diameter portion;  353 : through hole;  355 : flange portion;  360 : leak valve;  361 : (leak) plunger holder;  361   c : horizontal hole;  363 : ring;  365 : discharge pipeline;  365   a : tip part;  370 : (leak) plunger;  371 : communicating path;  372 : narrowed part;  374 : communicating path;  375 : wide groove;  376  to  377 : O-ring;  379 : coil spring;  381 : ball;  382 : pusher;  383 : coil spring;  384 : metal plate;  385 : push button;  386 : retaining ring;  449 : pneumatic chamber;  450 : pressure accumulation container;  451 : container main body portion;  451   b : through hole portion;  455 : flange portion;  460 : electromagnetic valve;  461 : discharge pipe;  462 : communicating path;  463 : valve;  464 : solenoid actuator;  465 : housing;  466 : coil;  467 : iron core;  468 : O-ring