Patent Publication Number: US-2023137720-A1

Title: Working tool

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The disclosure of Japanese Patent Application No. 2021-177856 filed on Oct. 29, 2021 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a working tool. 
     BACKGROUND ART 
     Patent Document 1 (International Patent Publication No. 2018/198672) discloses an electric driving tool which includes a magazine unit in which a plurality of rolled fasteners are stored and drives a feeder to feed the fasteners by an actuator. 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, since the actuator uses electric power, there is a fear that the power shortage occurs if the feeding operation of the feeder is to be carried out during driving of the drive unit that performs the driving operation. For this reason, there is a possibility that the feeding operation of the feeder is not carried out at an appropriate timing, resulting in the misfire. Although it is possible to set the timing of the feeding operation of the feeder in advance while avoiding the time zone in which the power shortage occurs in order to suppress the misfire, since the amount of required power varies depending on drive conditions such as the temperature of the working tool and the power supply situation, the timing of the feeding operation is unnecessarily delayed when there is power to spare. Therefore, it has been desired to improve the performance by improving the response from the operation by a worker to the driving operation. 
     Means for Solving the Problems 
     A working tool according to a first aspect includes a magazine unit in which a plurality of connected fasteners are stored in a rolled shape, an ejection unit to which the fastener is fed, a striking unit configured to strike the fastener held in the ejection unit to one side in a first direction, a first drive unit configured to drive the striking unit by receiving an electric power, a feeder unit capable of moving in a second direction crossing the first direction and configured to feed the fastener stored in the magazine unit to the ejection unit by moving to one side in the second direction, a second drive unit configured to drive the feeder unit by receiving an electric power, and a control unit configured to allow the second drive unit to drive when a load of the first drive unit satisfies a first condition. 
     Effects of the Invention 
     According to the present invention, it is possible to provide a working tool capable of suppressing the occurrence of misfire. Also, it is possible to provide a working tool with improved performance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a cross-sectional view of a working tool according to the first embodiment; 
         FIG.  2    is an external view of a speed reducing mechanism and a striking unit in the working tool; 
         FIG.  3    is a block diagram for describing a main configuration of the working tool; 
         FIG.  4 A  to  FIG.  4 F  are diagrams for describing an operation of a feeding mechanism in the first embodiment; 
         FIG.  5 A  to  FIG.  5 G  are timing charts for describing an operation of the working tool according to the first embodiment; 
         FIG.  6 A  to  FIG.  6 H  are timing charts for describing an operation of the working tool according to the first embodiment; 
         FIG.  7 A  to  FIG.  7 G  are timing charts for describing an operation of the working tool which changes depending on a temperature inside a housing; 
         FIG.  8 A  to  FIG.  8 G  are timing charts for describing an operation of a working tool according to the first modification; 
         FIG.  9 A  to  FIG.  9 F  are diagrams for describing an operation of a feeding mechanism in the second embodiment; 
         FIG.  10 A  to  FIG.  10 G  are timing charts for describing an operation of a working tool according to the second embodiment; 
         FIG.  11 A  to  FIG.  11 F  are diagrams for describing an operation of a feeding mechanism in the third embodiment; 
         FIG.  12 A  to  FIG.  12 G  are timing charts for describing an operation of a working tool according to the third embodiment; 
         FIG.  13 A  to  FIG.  13 F  are diagrams for describing an operation of a feeding mechanism in the fourth embodiment;  FIG.  14 A  to  FIG.  14 G  are timing charts for describing an operation of a working tool according to the fourth embodiment; and 
         FIG.  15 A  to  FIG.  15 G  are timing charts for describing an operation of a working tool according to the second modification. 
     
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
     A working tool according to the first embodiment will be described with reference to drawings. 
       FIG.  1    is a cross-sectional view of a working tool  10 . The working tool  10  includes a housing  11 , a striking mechanism  12 , a nose unit  13 , a power supply unit  14 , an electric motor  15 , a speed reducing mechanism  16 , a conversion mechanism  17 , a pressure accumulation container  18 , a feeding mechanism  19 , and a magazine unit  54 . 
     In the following description, an upper portion of the page of  FIG.  1    is referred to as an upper side, a lower portion of the page is referred to as a lower side, a right side of the page is referred to as a front side, and a left side of the page is referred to as a rear side in some cases. Also, the direction along a longitudinal direction of the page of  FIG.  1    is referred to as a first direction AR 1  in some cases. 
     Housing  11   
     The housing  11  is an outer shell element of the working tool  10 . The housing  11  has a cylinder case  20 , a handle  21  connected to the cylinder case  20 , a motor case  22  connected to the cylinder case  20 , and a mounting unit  23  connected to the handle  21  and the motor case  22 . A cylinder  28  is supported in the cylinder case  20 . The cylinder  28  is made of metal. The cylinder  28  is located with respect to the cylinder case  20  in a direction of a first center line X 1  parallel to the first direction AR 1  and in a radial direction (direction orthogonal to the first center line X 1 ). 
     Striking Mechanism  12   
     The striking mechanism  12  has a piston  29  and a driver blade  30 . The piston  29  is provided on the lower side in the first direction AR 1  with respect to the pressure accumulation container  18  which will be detailed later in detail, and is always biased downward in the first direction AR 1  by the pressure of a pressure chamber  27  provided in the pressure accumulation container  18 . The piston  29  is movable inside the cylinder  28  along the first direction AR 1 . A sealing member  119  is attached to an outer peripheral surface of the piston  29 . The sealing member  119  comes into contact with an inner peripheral surface of the cylinder  28  to form a sealing surface. 
     The driver blade  30  is made of, for example, metal. The driver blade  30  is connected to the piston  29  on the lower side of the piston  29  in the first direction AR 1  and extends along the first center line X 1 . Since the piston  29  is movable in the first direction AR 1  as described above, the driver blade  30  is also movable in the first direction AR 1 . A plurality of racks  47  (see  FIG.  2   ) are arranged on the driver blade  30  at predetermined intervals along the first direction AR 1  which is the moving direction. Note that the movement of the driver blade  30  to one side (downward) in the first direction AR 1  in  FIG.  1    is referred to as the descent. The movement of the driver blade  30  to the other side (upward) in the first direction AR 1  in  FIG.  1    is referred to as the ascent. 
     Nose Unit  13   
     The nose unit  13  is located and arranged with respect to the cylinder case  20  in the direction of the first center line X 1  and in the radial direction of the cylinder  28 . The nose unit  13  has a bumper support portion  31 , an ejection unit  32 , and a tubular portion  33 . The bumper support portion  31  has a tubular shape and has a guide hole  34 . The guide hole  34  is arranged about the first center line X 1 . 
     A bumper  35  is arranged inside the bumper support portion  31 . The bumper  35  is integrally formed of synthetic rubber such as elastomer. The bumper  35  is provided with a guide hole  36  centered on the first center line X 1 . The driver blade  30  is movable within the guide hole  36  in the first direction AR 1 . 
     The ejection unit  32  is connected to the bumper support portion  31  and the tubular portion  33  and protrudes downward from the bumper support portion  31  in the first direction AR 1 . The ejection unit  32  has an ejection path  37 , and the ejection path  37  is provided concentrically about the first center line X 1 . The driver blade  30  can move along the first direction AR 1  in the ejection path  37 . Nails which are fasteners stored in the magazine unit  54  to be described later are fed to the ejection path  37  of the ejection unit  32 . 
     A push lever  72  is attached to a lower end portion of the ejection unit  32  in the first direction AR 1 . The push lever  72  is movable with respect to the ejection unit  32  within a predetermined range in the first direction AR 1 . 
     Power Supply Unit  14   
     The power supply unit  14  is detachably attached to the mounting unit  23  and is a DC power supply that supplies electric power to the electric motor  15  and the feeding mechanism  19 . The power supply unit  14  has a storage case  53  and a plurality of battery cells stored in the storage case  53 . The battery cell is a secondary battery that can be charged and discharged, and any one of a lithium ion battery, a nickel hydrogen battery, a lithium ion polymer battery, and a nickel cadmium battery can be used. 
     Electric Motor  15   
     The electric motor  15  functions as a first drive unit that rotates by receiving power supplied from the power supply unit  14  and drives the striking mechanism  12 . The electric motor  15  is arranged in the motor case  22 . The electric motor  15  is a brushless motor having a rotor and a stator. A second center line X 2  which is the center of rotation of a rotation shaft  40  of the electric motor  15  is orthogonal to the first center line X 1 . 
     Speed Reducing Mechanism  16   
     The speed reducing mechanism  16  is provided in a gear case  41  in the motor case  22 . The gear case  41  has a tubular shape and does not rotate with respect to the tubular portion  33  of the nose unit  13 . The speed reducing mechanism  16  has an input element  42 , an output element  43 , and multiple sets of planetary gear mechanisms. The input element  42  of the speed reducing mechanism  16  is coupled to the rotation shaft  40  and is rotatably supported by a bearing  44 . 
     Conversion Mechanism  17   
     The conversion mechanism  17  will be described with reference to  FIG.  2    in addition to  FIG.  1   .  FIG.  2    is an external view of the conversion mechanism  17 , the piston  29 , and the driver blade  30  seen from the front side. 
     The conversion mechanism  17  is arranged in the tubular portion  33  of the nose unit  13 , and converts the rotational force of the output element  43  of the speed reducing mechanism  16  into a moving force of the driver blade  30  along the first direction 
     AR 1 . The conversion mechanism  17  has a drive shaft  45 , a pinwheel  46 , and pinion pins  48  as shown in  FIG.  1    and  FIG.  2   . The drive shaft  45  is rotatably supported by a bearing  110  about the second center line X 2 . The pinwheel  46  is fixed to the drive shaft  45 . The pinwheel  46  has a plurality of pinion pins  48 . 
     The plurality of pinion pins  48  are arranged at intervals in the rotation direction of the pinwheel  46  as shown in  FIG.  2   . The plurality of pinion pins  48  are arranged within a predetermined angular range in the rotation direction of the pinwheel  46 . The plurality of pinion pins  48  can be independently engaged and disengaged with the plurality of racks  47  provided on the driver blade  30  described above. When the pinwheel  46  rotates counterclockwise in  FIG.  2    and at least one pinion pin  48  and at least one rack  47  are engaged with each other, the rotational force of the pinwheel  46  is transmitted to the driver blade  30  of the striking mechanism  12 . By the transmitted rotational force, the driver blade  30  moves upward in the first direction AR 1  against the pressure of the pressure chamber  27 . Namely, the conversion mechanism  17  functions as a lifting unit that lifts the driver blade  30  upward in the first direction AR 1  by being rotated by the driving force of the electric motor  15  in a state of being engaged with the driver blade  30 . 
     When all the pinion pins  48  are released from the racks  47 , the rotational force of the pinwheel  46  is not transmitted to the driver blade  30 . 
     As shown in  FIG.  1   , a rotation regulating mechanism  49  is provided in the gear case  41 . The rotation regulating mechanism  49  is arranged between the elements constituting the planetary gear (for example, a carrier  50  and a ring fixed to the gear case  41 ). The rotation regulating mechanism  49  includes, for example, a roller and a ball. The rotation regulating mechanism  49  prevents the pinwheel  46  from rotating clockwise in  FIG.  2    in the state where the pinion pin  48  and the rack  47  are engaged. Specifically, when the driver blade  30  is biased downward in the first direction AR 1  in the state where the pinion pin  48  and the rack  47  are engaged, the pinwheel  46  receives clockwise torque in  FIG.  2   . At this time, the rotation regulating mechanism  49  bites between the carrier  50  and the ring to prevent the pinwheel  46  from rotating due to its wedging action. On the other hand, when the torque of the electric motor  15  is transmitted by the speed reducing mechanism  16 , the rotation regulating mechanism  49  does not bite between the carrier  50  and the ring. Namely, the rotation regulating mechanism  49  allows the pinwheel  46  to rotate counterclockwise in  FIG.  2   . 
     Further, as shown in  FIG.  2   , the working tool  10  has a magnet holder  56 , a magnet  57 , and a pinwheel position detection sensor  58 . The magnet holder  56  is provided on the pinwheel  46  and rotates together with the rotation of the pinwheel  46 . The magnet  57  is provided on the magnet holder  56 . The pinwheel position detection sensor  58  is, for example, a Hall sensor, and detects the magnetic field generated by the magnet  57  and outputs a first detection signal. Since the magnet  57  rotates together with the rotation of the pinwheel  46 , the relative positional relationship with the pinwheel position detection sensor  58  changes. When the magnet  57  approaches the pinwheel position detection sensor  58  with the rotation, the pinwheel position detection sensor  58  outputs the first detection signal. Namely, the first detection signal is a signal indicating the rotation position of the pinwheel  46 . The first detection signal is output to a control unit  73  which will be described later. 
     Pressure Accumulation Container  18   
     The pressure accumulation container  18  shown in  FIG.  1    has a cap  24  and a holder  25  to which the cap  24  is attached. A head cover  26  is attached to the upper side of the cylinder case  20  in the first direction AR 1 , and the pressure accumulation container  18  is arranged in the cylinder case  20  and in the head cover  26 . The pressure chamber  27  is provided in the pressure accumulation container  18 . The pressure chamber  27  is filled with gas. The gas may be any compressible gas. As the gas, for example, an inert gas such as nitrogen gas or rare gas is used in addition to air. As described above, the striking mechanism  12  is always biased downward in the first direction AR 1  by the pressure of the pressure chamber  27  provided in the pressure accumulation container  18 . Namely, the pressure chamber  27  functions as a biasing unit that biases the striking mechanism  12  downward in the first direction AR 1 . Note that the description will be given on the assumption that the pressure chamber  27  is filled with air. 
     Magazine Unit  54   
     The magazine unit  54  is supported by the ejection unit  32  and the mounting unit  23 . The magazine unit  54  stores a plurality of connected nails in a rolled shape. Specifically, the magazine unit  54  has a hollow drum portion  63  and the nails are stored in the drum portion  63 . A plurality of nails are connected to each other by a connecting element such as an adhesive, a wire, or the like. The plurality of connected nails are arranged in the drum portion  63  in a spiral or rolled state. 
     Feeding Mechanism  19   
     The feeding mechanism  19  feeds the nails stored in the drum portion  63  of the magazine unit  54  into the ejection unit  32  along a second direction AR 2 . Note that the second direction AR 2  is a direction which crosses the first direction AR 1  and is not parallel to the second center line X 2 . Further, in the following description, the front side in the second direction AR 2  is referred to also as one side, and the rear side in the second direction AR 2  is referred to also as the other side. 
     The feeding mechanism  19  has a spring  59 , a solenoid  60 , an iron core  61 , and a feeder unit  62 . The feeder unit  62  can reciprocate together with the iron core  61  along the second direction AR 2 . In the feeder unit  62 , a plurality of feed pawls (not shown) are provided at predetermined intervals along the second direction AR 2 . 
     The solenoid  60  has a bobbin, a coil provided in the bobbin, and the like. The iron core  61  can reciprocate with respect to the bobbin of the solenoid  60  along the second direction AR 2 . The iron core  61  is made of a magnetic material such as iron. The spring  59  is a biasing member that biases the iron core  61  toward the other side (rear side) in the second direction AR 2 , and locates the feeder unit  62  at the initial position. The coil of the solenoid  60  is connected to the power supply unit  14  and generates magnetic attractive force when current is supplied from the power supply unit  14 . By this magnetic attractive force, the iron core  61  moves to one side (front side) in the second direction AR 2  against the biasing force of the spring  59 . Along with this movement of the iron core  61 , the feeder unit  62  also moves to one side in the second direction AR 2 . 
     When the current supply by the power supply unit  14  ends, the coil cancels the magnetic attractive force. As a result, the iron core  61  moves to the other side in the second direction AR 2  by the biasing force of the spring  59 . Along with this movement of the iron core  61 , the feeder unit  62  also moves to the other side in the second direction AR 2  and returns to the initial position. 
     Regarding Control System of Working Tool  10   
     As shown in the block diagram of  FIG.  3   , the working tool  10  includes a control unit  73 , an inverter circuit  75 , a trigger switch  52 , a push lever switch  76 , a blade position detection sensor  77 , and a motor position detection sensor  78  in addition to the configuration shown in  FIG.  1    and  FIG.  2   . The control unit  73  is provided in the mounting unit  23  (see  FIG.  1   ). The control unit  73  is a microcomputer having an input/output interface, an arithmetic processing unit, and a storage unit. The control unit  73  controls the inverter circuit  75 . The control unit  73  controls the timing of power supply to the electric motor  15  and the solenoid  60  as will be described later in detail. Although details will be described later, the control unit  73  performs control to allow the solenoid  60  to drive when the load of the electric motor  15  satisfies a first condition. 
     The inverter circuit  75  is controlled by the control unit  73  to connect and disconnect the electric circuit between the power supply unit  14  and the electric motor  15 . The inverter circuit  75  includes a plurality of switching elements, and the plurality of switching elements can be turned on/off individually. 
     A trigger  51  is provided on the handle  21  as shown in  FIG.  1   . A worker, that is, a user can operate the trigger  51  while gripping the handle  21 . The trigger switch  52  shown in  FIG.  3    is provided in the handle  21 . The trigger switch  52  outputs a first operation signal to the control unit  73  when an operation force is applied to the trigger  51 . When the operation force on the trigger  51  is released, the trigger switch  52  stops the output of the first operation signal. 
     The push lever switch  76  is provided in the ejection unit  32 . The push lever switch  76  outputs a second operation signal to the control unit  73  when the push lever  72  is pressed to a workpiece W 1  by the operation of the user. When the push lever  72  is separated from the workpiece W 1 , the push lever switch  76  stops the output of the second operation signal. 
     The blade position detection sensor  77  shown in  FIG.  3    is provided in the housing  11 . The blade position detection sensor  77  is, for example, a Hall sensor, and detects a magnetic field generated by a magnet provided at a tip  115  (see  FIG.  1   ) of the driver blade  30 , thereby detecting the position of the driver blade  30  in the first direction AR 1 . Specifically, when the tip  115  of the driver blade  30  is located on the upper side in the first direction AR 1  than the head of the nail fed to the ejection unit  32  which will be described later in detail, the blade position detection sensor  77  outputs a second detection signal to the control unit  73 . Namely, the control unit  73  functions as a striking detection unit which detects that the position of the driver blade  30  in the first direction AR 1  is located on the other side (upper side) in the first direction AR 1  than a predetermined position, by using the second detection signal from the blade position detection sensor  77 . 
     The first detection signal output from the pinwheel position detection sensor  58  described above is input to the control unit  73 . As described above, since the first detection signal is a signal indicating the rotation position of the pinwheel  46 , the control unit  73  functions as a lifting detection unit which detects the rotation position of the pinwheel  46  based on the first detection signal. 
     Further, as described above, the driver blade  30  moves along the first direction AR 1  along with the rotation of the pinwheel  46 . Accordingly, the control unit  73  estimates the position of the driver blade  30  in the first direction AR 1  from the detected rotation position of the pinwheel  46 . In this case, the data indicating the relationship between the rotation position of the pinwheel  46  and the position of the driver blade  30  in the first direction AR 1  is acquired by conducting tests, simulations, etc., and the acquired data is stored in the storage unit in the control unit  73 . The control unit  73  refers to this data to estimate the position of the driver blade  30  in the first direction AR 1 . 
     The motor position detection sensor  78  is, for example, a Hall sensor, and is provided in the electric motor  15  described above. The motor position detection sensor  78  outputs a rotation position signal to the control unit  73  based on the change in the magnetic field caused by rotation of the rotor of the electric motor  15 . Since the rotation position signal is based on the change in the magnetic field caused by the rotation of the electric motor  15 , it indicates the rotation position (rotation angle) of the rotation shaft  40  of the electric motor  15 . Therefore, the control unit  73  functions as a motor position detection unit that calculates (detects) the rotation position (rotation angle) of the rotation shaft  40  of the electric motor  15  by using the rotation position signal. 
     As described above, the driver blade  30  is moved along the first direction AR 1  by the pinwheel  46  rotated by the rotation shaft  40  of the electric motor  15 . Accordingly, the control unit  73  estimates the position of the driver blade  30  in the first direction AR 1  from the detected rotation position of the electric motor  15 . In this case as well, the data indicating the relationship between the rotation position of the electric motor  15  and the position of the driver blade  30  in the first direction AR 1  is acquired by conducting tests, simulations, etc., and the acquired data is stored in the storage unit in the control unit  73 . The control unit  73  refers to this data to estimate the position of the driver blade  30  in the first direction AR 1 . 
     Fastener Feeding Operation 
     Next, the fastener feeding operation of a nail  55  to the ejection unit  32  by the feeding mechanism  19  will be described. 
     The operation of the feeding mechanism  19  will be described with reference to  FIG.  4 A  to  FIG.  4 F .  FIG.  4 A  to  FIG.  4 F  are diagrams each showing the feeding mechanism  19 , the piston  29 , and the driver blade  30  in the cross-sectional view shown in  FIG.  1   . 
       FIG.  4 A  shows the state where the driver blade  30  is stopped at the standby position, which is a position on the upper side in the first direction AR 1  than the head of the nail  55  fed to the ejection unit  32 , and the feeder unit  62  of the feeding mechanism  19  is stopped at the initial position. When the driver blade  30  is stopped at the standby position, the tip  115  of the driver blade  30  (the end portion on the lower side in the first direction AR 1 ) is located on the upper side in the first direction AR 1  than the head of the nail  55  located closest to the ejection path  37 . 
     When the current output from the power supply unit  14  is supplied, the solenoid  60  generates a magnetic attractive force. By this magnetic attractive force, the iron core  61  moves to one side (front side) in the second direction against the biasing force of the spring  59 . Along with the movement of the iron core  61 , the feeder unit  62  is driven toward the ejection unit  32 . Namely, the solenoid  60  functions as a second drive unit that drives the feeder unit  62 . 
     The feed pawl provided in the feeder unit  62  enters between the nails  55  that are connected by the connecting element. When the feeder unit  62  is moved to one side in the second direction AR 2  by the solenoid  60 , the nail  55  is sent to the ejection unit  32  on one side in the second direction AR 2  by the feed pawl that moves together with the feeder unit  62 . In this way, the feeder unit  62  moves to one side in the second direction AR 2 , thereby feeding the nail  55  located at the head (on one side in the second direction AR 2 ) among the nails  55  stored in the magazine unit  54  to the ejection unit  32 . 
       FIG.  4 B  shows the state where the nail  55  is moved to the position below the tip  115  of the driver blade  30  (hereinafter, referred to as a fastener feeding position) by the movement of the feeder unit  62  to one side in the second direction AR 2 . Current supply to the solenoid  60  continues even when the nail  55  is located at the fastener feeding position. 
     When the electric power output from the power supply unit  14  is supplied to the electric motor  15  in the state where the nail  55  is located at the fastener feeding position, the conversion mechanism  17  is rotated by the driving force of the electric motor  15  in the state of being engaged with the driver blade  30  as described above, thereby lifting the driver blade  30  upward in the first direction AR 1 . In the following description, the state where the tip  115  of the driver blade  30  is located on the other side (upper side) in the first direction AR 1  with respect to the fastener feeding position, that is, the state where the first detection signal and the second detection signal are output is referred to also as a second condition. 
       FIG.  4 C  shows the state where the driver blade  30  is lifted and reaches the top dead center on the upper side in the first direction AR 1  compared to the cases shown in  FIG.  4 A  and  FIG.  4 B . The top dead center of the driver blade  30  is the position where the piston  29  is farthest from the bumper  35  in the first direction AR 1 . When the pinwheel  46  rotates further from this state and all the pinion pins  48  are released from the racks  47 , the rotational force of the pinwheel  46  ceases to be transmitted to the driver blade  30 . As a result, the driver blade  30  descends due to the pressure of the pressure chamber  27  and strikes the nail  55  located at the fastener feeding position. Namely, the driver blade  30  functions as a striking unit that strikes the nail  55 , which is a fastener held by the feeder unit  62  of the feeding mechanism  19 , toward one side (lower side in the drawing) in the first direction AR 1 . The nail  55  is struck by the driver blade  30  and is driven into the workpiece W 1 . 
     After the driver blade  30  strikes the nail  55 , the piston  29  shown in  FIG.  1    collides with the bumper  35 . The bumper  35  with which the piston  29  collides absorbs the kinetic energy of the driver blade  30 . As a result, as shown in  FIG.  4 D , the driver blade  30  reaches the bottom dead center on the lower side in the first direction AR 1  compared to the cases shown in  FIG.  4 A  to  FIG.  4 C  and stops descending. Namely, the bottom dead center of the driver blade  30  is the position where the piston  29  is in contact with the bumper  35 . 
     When the driver blade  30  reaches the bottom dead center and stops descending, the current supply from the power supply unit  14  to the solenoid  60  is stopped. As described above, when the current supply by the power supply unit  14  is stopped, the iron core  61  is moved to the other side in the second direction AR 2  by the biasing force of the spring  59 . As a result, as shown in  FIG.  4 E , the feeder unit  62  is returned to the initial position. When the feeder unit  62  returns to the initial position, the feed pawl provided in the feeder unit  62  enters between the nails  55  connected by the connecting element. 
     The pinwheel  46  is rotated by the rotation of the electric motor  15  and the pinion pin  48  and the rack  47  are engaged again. Then, the driver blade  30  moves upward in the first direction AR 1  against the pressure of the pressure chamber  27 . As a result, as shown in  FIG.  4 F , the driver blade  30  moves to the standby position on the upper side in the first direction AR 1  compared to the states shown in  FIG.  4 D  and  FIG.  4 F . 
     Operation Timing 
     The operation timing of the working tool  10  will be described with reference to the drawings.  FIG.  5 A  to  FIG.  5 G  are timing charts in the case where the single nail  55  is driven into the workpiece W 1 .  FIG.  5 A  shows the relationship between the position of the driver blade  30  in the first direction AR 1  and the time, and  FIG.  5 B  shows the relationship between the position of the feeder unit  62  in the second direction AR 2  and the time.  FIG.  5 C  shows the relationship between the load current of the electric motor  15  and the time, and  FIG.  5 D  shows the relationship between the current value supplied to the solenoid  60  and the time.  FIG.  5 E  shows the relationship between the rotation angle of the electric motor  15  and the time,  FIG.  5 F  shows the relationship between the first detection signal output from the pinwheel position detection sensor  58  and the time, and  FIG.  5 G  shows the relationship between the second detection signal output from the blade position detection sensor  77  and the time. 
     At time t 0 , when the control unit  73  detects at least one of the off of the trigger switch  52  and the off of the push lever switch  76  (that is, when at least one of the first operation signal and the second operation signal is not output), the control unit  73  stops the electric motor  15  (see  FIG.  5 C  and  FIG.  5 D ). On the other hand, the driver blade  30  is biased downward in the first direction AR 1  by the pressure of the pressure chamber  27  and is stopped at the standby position (see  FIG.  5 A ). The standby position of the driver blade  30  is located between the top dead center and the bottom dead center. 
     At time t 1 , when the control unit  73  detects that the first operation signal is output from the trigger switch  52  and the second operation signal is output from the push lever switch  76 , the control unit  73  causes the power supply unit  14  to start the power supply to the electric motor  15  (see  FIG.  5 C ). Namely, the trigger  51  and the push lever  72  function as operation units that switch the driving state of the electric motor  15  by being operated by the user. 
     Since the torque increases when the electric motor  15  starts rotating, the load current of the electric motor  15  becomes a large value at time t 1  and starts decreasing after a predetermined time elapses (after time t 2 ) as shown in  FIG.  5 C . The electric motor  15  starts to rotate by the electric power whose supply is started at time t 1 , and the rotation angle increases as time elapses as shown in  FIG.  5 E . 
     When the rotational force of the electric motor  15  is transmitted to the pinwheel  46  and the pinwheel  46  is rotated, the driver blade  30  ascends to the upper side in the first direction AR 1  at time t 1  as shown in  FIG.  5 A . Along with the ascent of the driver blade  30 , the pressure of the pressure chamber  27  also rises. 
     At time t 2 , since the pinwheel  46  is rotated and the magnet  57  approaches the pinwheel position detection sensor  58 , the first detection signal is output (see  FIG.  5 F ). Further, at time t 2 , the blade position detection sensor  77  detects that the driver blade  30  has moved to the upper side in the first direction AR 1  than the predetermined position, and outputs the second detection signal (see  FIG.  5 G ). Based on the first detection signal and the second detection signal, the control unit  73  can estimate that the value of the load current of the electric motor  15  has decreased and the timing when it falls below a current threshold described later is approaching. 
     After time t 2 , the load current of the electric motor  15  gradually decreases as described above. After time t 3 , the value of the load current falls below a preset current threshold as shown in  FIG.  5 C . The current threshold is set to the value smaller than the load current flowing through the electric motor  15  when the driver blade  30  moves from the standby position to the top dead center and larger than the load current flowing through the electric motor  15  when the driver blade  30  moves from the bottom dead center to the standby position as described later (from time t 6  to time t 11  in  FIG.  5 C ). 
     Since both the first condition that the load current of the electric motor  15  falls below the current threshold and the second condition that the first detection signal and the second detection signal are output are satisfied at time t 3 , the control unit  73  causes the power supply unit  14  to start supplying current to the solenoid  60  at time t 4  (see  FIG.  5 D ). Consequently, at time t 5 , the feeder unit  62  moves to one side (front side) in the second direction AR 2 , and is located at the fastener feeding position where the nail  55  is fed to the ejection unit  32  at time t 5  (see  FIG.  5 B ). Namely, the nail  55  is located on the lower side with respect to the driver blade  30  as shown in  FIG.  4 B . 
     At time t 6 , the driver blade  30  reaches the top dead center by the rotation of the pinwheel  46  as shown in  FIG.  4 C  (see  FIG.  5 A ). Thereafter, all the pinion pins  48  are released from the racks  47  and the driver blade  30  descends by the pressure of the pressure chamber  27 . At this time, as shown in  FIG.  5 G , the blade position detection sensor  77  stops outputting the second detection signal. 
     When the driver blade  30  descends and strikes the nail  55  at the fastener feeding position, the driver blade  30  reaches the bottom dead center (see  FIG.  4 D ) and stops there at time t 7  as shown in  FIG.  5 A . Even after the driver blade  30  reaches the bottom dead center, the electric motor  15  continues to rotate. Namely, supply of electric power from the power supply unit  14  to the electric motor  15  is continued. 
     At time t 8 , the control unit  73  causes the power supply unit  14  to stop supplying current to the solenoid  60  as shown in  FIG.  5 D . Consequently, as shown in  FIG.  5 B , the feeder unit  62  starts moving to the other side (rear side) in the second direction at time t 8 . 
     Since the electric motor  15  continues to rotate as described above, the pinwheel  46  also continues to rotate. Consequently, the pinion pins  48  and the racks  47  are engaged again. As a result, as shown in  FIG.  5 A , the driver blade  30  ascends again toward the upper side in the first direction AR 1  from the bottom dead center to the standby position at time t 9 . 
     Thereafter, as the driver blade  30  ascends, the first detection signal is output from the pinwheel position detection sensor  58  at time t 10  as shown in  FIG.  5 F . Based on this first detection signal, the control unit  73  can estimate that the driver blade  30  ascends and is approaching the standby position. As shown in  FIG.  5 A , when the driver blade  30  reaches the standby position at time t 11 , the control unit  73  causes the power supply unit  14  to stop supplying electric power to the electric motor  15 . As a result, as shown in  FIG.  5 C  and  FIG.  5 E , both the load current and the rotation angle of the electric motor  15  become the same values as those at time t 0 . 
     Next, with reference to  FIG.  6 A  to  FIG.  6 H , the power supply operation of the working tool  10  when continuously driving the nails  55  into the workpiece W 1  will be described.  FIG.  6 A  to  FIG.  6 G  show the relationship between the position of the driver blade  30  and the time, the relationship between the position of the feeder unit  62  and the time, the relationship between the load current of the electric motor  15  and the time, the relationship between the current value supplied to the solenoid  60  and the time, the relationship between the rotation angle of the electric motor  15  and the time, the relationship between the output of the first detection signal and the time, and the relationship between the output of the second detection signal and the time, respectively.  FIG.  6 H  shows the relationship between the first and second operation signals output from the trigger switch  52  and the push lever switch  76  and the time. 
     Times t 1 , t 2 , t 3 , and t 4  in  FIG.  6 A  to  FIG.  6 H  correspond to times t 1 , t 3 , t 4 , and t 7  in  FIG.  5 A  to  FIG.  5 G , respectively. Namely, when the first operation signal and the second operation signal are output at time t 1  as shown in  FIG.  6 H , the control unit  73  causes the power supply unit  14  to start supplying electric power to the electric motor  15  as shown in  FIG.  6 C . Then, as shown in  FIG.  6 A , the driver blade  30  starts to ascend from the standby position. 
     When the load current of the electric motor  15  falls below the current threshold at time t 2  as shown in  FIG.  6 C , the control unit  73  starts supplying current to the solenoid  60  at time t 3  as shown in  FIG.  6 B . After reaching the top dead center, the driver blade  30  descends and reaches the bottom dead center at time t 4  as shown in  FIG.  6 A . Namely, the first nail  55  can be driven during time period T 1  (=t 4 -t 1 ) from time t 1  to time t 4 . Thereafter, the position of the driver blade  30 , the position of the feeder unit  62 , the load current of the electric motor  15 , the current supplied to the solenoid  60 , the rotation angle of the electric motor  15 , the first detection signal of the pinwheel position detection sensor  58 , and the second detection signal of the blade position detection sensor  77  transition in the same manner as those after time t 7  in  FIG.  5 A  to  FIG.  5 G . 
     When the first operation signal and the second operation signal are output at time t 5  as shown in  FIG.  6 H , the driver blade  30  reaches the standby position at time t 6  as shown in  FIG.  6 A , the first detection signal is output from the pinwheel position detection sensor  58  as shown in  FIG.  6 F , and the second detection signal is output from the blade position detection sensor  77  as shown in  FIG.  6 G , so that both the first condition and the second condition are satisfied. At time t 7 , the control unit  73  starts supplying current to the solenoid  60  as shown in  FIG.  6 D , and the feeder unit  62  starts moving from the initial position as shown in  FIG.  6 B . Namely, in the case where the operation for driving the second nail  55  is performed before the driver blade  30  reaches the standby position, the feeder unit  62  can be moved when the driver blade  30  reaches a predetermined position on the upper side than the head of the nail  55 . Therefore, the response from when the operation for driving the second nail  55  is performed to when the nail  55  is fed can be shortened. 
     After reaching the top dead center, the driver blade  30  starts to descend, and reaches the bottom dead center after driving the second nail  55  at time t 8  as shown in  FIG.  6 A . Namely, the second nail  55  can be driven during time period T 2  (=t 8 -t 5 ) from time t 5  to time t 8 . 
     Since the electric motor  15  continues to rotate even after driving the first nail  55 , the load current of the electric motor  15  does not become a large value as in the period from time t 1  to time t 2  due to inertia and does not exceed the current threshold, so that the first condition is always satisfied. In this case, since the driving of the feeder unit  62  can be started immediately when the first detection signal and the second detection signal are output and the second condition is satisfied, the time period from time t 5  to time t 6  becomes shorter than the time period (t 2 -t 1 ) required until the load current falls below the current threshold when driving the first nail  55 . Therefore, the time period from when the first operation signal and the second operation signal are output at time t 5  to when the feeder unit  62  starts moving at time t 7  becomes shorter than the time period (t 3 -t 1 ) until the feeder unit  62  starts to move when driving the first nail  55 . 
     Further, in order to ensure the time required for the movement of the feeder unit  62  so that the driver blade  30  does not start to descend from the top dead center before the nail  55  is fed to the fastener feeding position, the rotation speed of the electric motor  15  is restricted until the load current of the electric motor  15  falls below the current threshold, when driving the first nail  55 . On the other hand, when driving the second and subsequent nails  55 , since the load current of the electric motor  15  does not exceed the current threshold, the rotation speed of the electric motor  15  does not need to be restricted. Namely, when driving the second and subsequent nails  55 , the electric motor  15  can be driven at a higher speed than that when driving the first nail  55 . As a result, the time period T 2  (=t 8 -t 5 ) required for driving the second nail  55  becomes shorter than the time period T 1  (=t 4 -t 1 ) required for driving the first nail  55 . 
     Thereafter, when the driver blade  30  reaches the standby position at time t 9 , the control unit  73  causes the power supply unit  14  to stop supplying electric power to the electric motor  15  as shown in  FIG.  6 C . 
     According to the first embodiment described above, the following effects can be obtained. 
     (1) The working tool  10  includes the magazine unit  54 , the ejection unit  32 , the driver blade  30 , the electric motor  15 , the feeder unit  62 , the solenoid  60 , and the control unit  73 . The magazine unit  54  stores a plurality of connected nails  55  in a rolled shape. The nail  55  is fed to the ejection unit  32 . The driver blade  30  strikes the nail  55  held by the ejection unit  32  to one side in the first direction AR 1 . The electric motor  15  receives electric power to drive the driver blade  30 . The feeder unit  62  is movable in the second direction AR 2  that crosses the first direction AR 1 , and feeds the nails  55  stored in the magazine unit  54  to the ejection unit  32  by moving toward one side (front side) in the second direction AR 2 . The solenoid  60  receives electric power to drive the feeder unit  62 . The control unit  73  allows the solenoid  60  to drive when the load of the electric motor  15  satisfies the first condition. Specifically, the first condition is that the load current of the electric motor  15  falls below the current threshold. Consequently, since electric power is not supplied to the solenoid  60  in the state where the load current of the electric motor  15  exceeds the current threshold, the feeder unit  62  is not driven in the state where the power supplied from the power supply unit  14  is insufficient and the misfire of the nail  55  can be suppressed. 
     (2) The current threshold is set so as to be smaller than the load current flowing through the electric motor  15  when the driver blade  30  moves from the standby position to the top dead center and to be larger than the load current flowing through the electric motor  15  when the driver blade  30  moves from the bottom dead center to the standby position. Consequently, since current supply to the solenoid  60  is started when a large load current ceases to flow through the electric motor  15 , the time period from when the operation to drive the nail  55  is performed to when the nail  55  is fed to the fastener feeding position can be shortened, and performance and operability can be improved. 
     (3) The control unit  73  allows the solenoid  60  to drive when the driver blade  30  is located on the other side in the first direction AR 1  with respect to the fastener feeding position. Consequently, the nail  55  can be supplied to the fastener feeding position without colliding with the driver blade  30 , so that it is possible to suppress the occurrence of improper loading of the nail  55 . 
     (4) With the working tool  10  according to the first embodiment described above, it is possible to control the timing of starting the current supply to the solenoid  60  in accordance with the temperature inside the housing  11 . 
       FIG.  7 A  to  FIG.  7 G  are timing charts in the case where the working tool  10  drives the single nail  55  into the workpiece W 1 , in which the solid line indicates the case where the temperature inside the housing  11  is low and the dashed line indicates the case where the temperature inside the housing  11  is high. Further, similarly to  FIG.  4 A  to  FIG.  4 G ,  FIG.  7 A  to  FIG.  7 G  show the relationship between the position of the driver blade  30  and the time, the relationship between the position of the feeder unit  62  in the second direction and the time, the relationship between the load current of the electric motor  15  and the time, the relationship between the current value supplied to the solenoid  60  and the time, the relationship between the rotation angle of the electric motor  15  and the time, the relationship between the output of the first detection signal and the time, and the relationship between the output of the second detection signal and the time, respectively. 
     When the temperature in the housing  11  rises, the internal pressure of the housing  11  increases and the load for lifting the driver blade  30  increases. Therefore, the time period after the first operation signal and the second operation signal are output until the driver blade  30  moves along the first direction AR 1  to drive the nail  55  and reaches the bottom dead center to stop there increases. As shown in  FIG.  7 A , it takes only the time period until time t 6  for the driver blade  30  to reach the bottom dead center when the temperature is low, but it takes the time period until time t 7  when the temperature is high. Namely, the response from the operation for driving the nail  55  to the completion of the driving of the nail  55  is delayed. 
     As shown in  FIG.  7 C , the time when the load current of the electric motor  15  falls below the current threshold after power supply to the electric motor  15  is started at time t 1  is time t 2  when the temperature is low, while it is time t 4  when the temperature is high. Therefore, when the temperature is low, the control unit  73  causes the power supply unit  14  to start supplying current to the solenoid  60  at time t 3  (see  FIG.  7 D ), and the feeder unit  62  starts to move from the initial position (see  FIG.  7 B ). On the other hand, when the temperature is high, the control unit  73  causes the power supply unit  14  to start supplying current to the solenoid  60  at time t 5  (see  FIG.  7 D ), and the feeder unit  62  starts to move from the initial position (see  FIG.  7 B ). After the nail  55  is driven, the control unit  73  can stop the power supply to the electric motor  15  at time t 8  when the temperature is low, but it stops the power supply to the electric motor  15  at time t 9  when the temperature is high (see  FIG.  7 C ). 
     As described above, the driving of the solenoid  60  is allowed when the load current of the electric motor  15  affected by the internal temperature of the housing  11  falls below the current threshold. Namely, the timing of the current supply to the solenoid  60  can be controlled in accordance with the internal temperature of the housing  11 . Therefore, when the internal temperature of the housing  11  is low, it is possible to speed up the response from the operation for driving the nail  55  to the completion of the driving of the nail  55 . 
     The first embodiment described above can be modified as follows. 
     First Modification 
     The working tool  10  according to the first modification has the same configuration as the working tool  10  according to the first embodiment described above. The working tool  10  according to the first modification is different from the working tool  10  according to the first embodiment in that different current threshold is set for the load current of the electric motor  15  in accordance with the power capacity (remaining battery level) of the power supply unit  14  and the timing of supplying the current to the solenoid  60  is changed. 
       FIG.  8 A  to  FIG.  8 G  are timing charts in the case where the working tool  10  according to the first modification drives the single nail  55  into the workpiece W 1 .  FIG.  8 A  to  FIG.  8 G  show the relationship between the position of the driver blade  30  and the time, the relationship between the position of the feeder unit  62  in the second direction and the time, the relationship between the load current of the electric motor  15  and the time, the relationship between the current value supplied to the solenoid  60  and the time, the relationship between the rotation angle of the electric motor  15  and the time, the relationship between the output of the first detection signal and the time, and the relationship between the output of the second detection signal and the time, respectively. In addition, in  FIG.  8 A  to  FIG.  8 G , the solid line indicates the case where the remaining battery level is high, and the dashed line indicates the case where the remaining battery level is low. 
     When the remaining battery level decreases, the electric power supplied to the electric motor  15  decreases. Since the electric power itself supplied to the electric motor  15  decreases when the remaining battery level is low, the load current falls below the current threshold in the first embodiment (hereinafter, referred to as the first current threshold) even if the electromotive force becomes large like when the electric motor  15  starts rotating. Therefore, when the remaining battery level is low, the control unit  73  sets a second current threshold smaller than the first current threshold. 
     As shown in  FIG.  8 C , after power supply to the electric motor  15  is started at time t 1 , the load current of the electric motor  15  falls below the first current threshold at time t 2  when the remaining battery level is high, but it falls below the second current threshold at time t 4  when the remaining battery charge is low. Therefore, when the remaining battery level is high, the control unit  73  causes the power supply unit  14  to start supplying current to the solenoid  60  at time t 3  (see  FIG.  8 D ), and the feeder unit  62  starts to move from the initial position (see  FIG.  8 B ). On the other hand, when the remaining battery level is low, the control unit  73  causes the power supply unit  14  to start supplying current to the solenoid  60  at time t 5  (see  FIG.  8 D ), and the feeder unit  62  starts to move from the initial position (see  FIG.  8 B ). 
     As described above, since the time period required until the feeder unit  62  starts to move from the initial position is long when the remaining battery level is low, the time period required after the first operation signal and the second operation signal are output until the driver blade  30  ascends to the top dead center, descends to strike the nail  55 , and reaches the bottom dead center to stop there increases. As shown in  FIG.  8 A , the driver blade  30  reaches the bottom dead center at time t 6  when the remaining battery level is high, but it reaches the bottom dead center at time t 7  when the remaining battery level is low. Namely, when the remaining battery level is low, the response from the operation for driving the nail  55  to the completion of the driving of the nail  55  is delayed. 
     After the nail  55  is driven, the control unit  73  can stop the power supply to the electric motor  15  at time t 8  when the remaining battery level is high, but it stops the power supply to the electric motor  15  at time t 9  when the remaining battery level is low (see  FIG.  8 C ). 
     As described above, the driving of the solenoid  60  is allowed when the load current of the electric motor  15  affected by the remaining battery level falls below the current threshold. Therefore, when the remaining battery level of the power supply unit  14  is high, it is possible to speed up the response from the operation for driving the nail  55  to the completion of the driving of the nail  55 . 
     Second Embodiment 
     A working tool according to the second embodiment will be described with reference to  FIG.  9 A  to  FIG.  9 F . In the following description, the same components as those of the first embodiment are denoted by the same reference characters and differences are mainly described. Points that are not particularly described are the same as those in the first embodiment. The working tool  10  according to the second embodiment includes a feeding mechanism  19 A having a configuration different from that of the first embodiment, so that the timing of supplying current to the feeding mechanism  19 A is different from that of the first embodiment. 
       FIG.  9 A  to  FIG.  9 F  are diagrams each showing the feeding mechanism  19 A, the piston  29 , and the driver blade  30 , similarly to  FIG.  4 A  to  FIG.  4 F  described above, and the driver blade  30  is located at the standby position in  FIG.  9 A . The feeding mechanism  19 A has the spring  59 , the solenoid  60 , the iron core  61 , and the feeder unit  62 . In the feeding mechanism  19 A, unlike the first embodiment, the spring  59  biases the iron core  61  to the initial position on one side (front side) in the second direction. 
     Fastener Feeding Operation 
     When current is supplied to the coil of the solenoid  60  from the power supply unit  14 , the iron core  61  moves from the initial position to the other side (rear side) in the second direction AR 2  by the generated magnetic attractive force against the biasing force of the spring  59 . Along with the movement of the iron core  61 , the feeder unit  62  also moves from the initial position to a predetermined position on the other side in the second direction AR 2  (hereinafter referred to as a nail mounting position) (see  FIG.  9 B ). At the time of starting this movement, the feed pawl (not shown) provided in the feeder unit  62  does not enter between the plurality of nails  55  connected by the connecting element. Therefore, the plurality of nails  55  are not moved to the other side in the second direction AR 2 . When the feeder unit  62  reaches the nail mounting position, the feed pawl provided in the feeder unit  62  enters between the nails  55  connected by the connecting element. 
     Thereafter, when the current supply to the solenoid  60  by the power supply unit  14  is terminated, the coil cancels the magnetic attractive force. Consequently, the iron core  61  is returned from the nail mounting position to the initial position on one side in the second direction AR 2  by the biasing force of the spring  59 . Along with this movement of the iron core  61 , the feeder unit  62  also moves from the nail mounting position to the initial position on one side in the second direction AR 2 . When the feeder unit  62  moves to one side in the second direction AR 2 , the nail  55  is sent to the ejection unit  32  on one side in the second direction AR 2  by the feed pawl that moves together with the feeder unit  62 . In this way, the feeder unit  62  locates the nail  55  located at the head of the connecting element among the nails  55  stored in the magazine unit  54  at the fastener feeding position on the lower side of the driver blade  30  (see  FIG.  9 C ). 
     When the electric power output from the power supply unit  14  is supplied to the electric motor  15  in the state where the nail  55  is located at the fastener feeding position, the conversion mechanism  17  is rotated by the driving force of the electric motor  15  in the state of being engaged with the driver blade  30 , thereby lifting the driver blade  30  upward in the first direction AR 1 . As a result, as shown in  FIG.  9 D , the driver blade  30  reaches the top dead center on the upper side in the first direction AR 1  compared to the states in  FIG.  9 A  to  FIG.  9 C . When the pinwheel  46  rotates further from this state and all the pinion pins  48  are released from the racks  47 , the driver blade  30  descends by the pressure of the pressure chamber  27  and strikes the nail  55  located at the fastener feeding position. As a result, the nail  55  is driven into the workpiece W 1 , and the driver blade  30  reaches the bottom dead center on the lower side in the first direction AR 1  compared to the states of  FIG.  9 A  to  FIG.  9 D  and stops descending (see  FIG.  9 E ). 
     Thereafter, the pin wheel  46  is rotated by the rotation of the electric motor  15 , and the pinion pin  48  and the rack  47  are engaged again. Then, the driver blade  30  moves to the standby position on the upper side in the first direction AR 1  (see  FIG.  9 F ). 
     Operation Timing 
     The operation timing of the working tool  10  will be described with reference to  FIG.  10 A  to  FIG.  10 G .  FIG.  10 A  to  FIG.  10 G  are timing charts in the case where the single nail  55  is driven into the workpiece W 1 .  FIG.  10 A  to  FIG.  10 G  show the relationship between the position of the driver blade  30  and the time, the relationship between the position of the feeder unit  62  and the time, the relationship between the load current of the electric motor  15  and the time, the relationship between the current value supplied to the solenoid  60  and the time, the relationship between the rotation angle of the electric motor  15  and the time, the relationship between the output of the first detection signal and the time, and the relationship between the output of the second detection signal and the time, respectively. 
     The operation of each unit from time t 1  to time t 3  shown in  FIG.  10 A  to  FIG.  10 G  is the same as the operation from time t 1  to time t 3  shown in  FIG.  5 A  to  FIG.  5 G  described in the first embodiment. After time t 3  shown in  FIG.  10 C , the value of the load current falls below a preset current threshold. Then, as shown in  FIG.  10 D , the control unit  73  causes the power supply unit  14  to start supplying current to the solenoid  60  at time t 4 . Consequently, the feeder unit  62  moves to the nail mounting position on the other side (rear side) in the second direction 
     AR 2 , and the feed pawl of the feeder unit  62  enters between the nails  55 . 
     As shown in  FIG.  10 D , the control unit  73  causes the power supply unit  14  to stop supplying current to the solenoid  60  at time t 5 . Consequently, as shown in  FIG.  10 B , the feeder unit  62  moves to one side in the second direction AR 2  and the nail  55  is located at the fastener feeding position at time t 6 . The operation of each unit after time t 7  is the same as the operation after time t 6  in  FIG.  5 A  to  FIG.  5 G  described in the first embodiment. 
     According to the second embodiment described above, the same effects as those obtained by the first embodiment can be obtained. 
     Third Embodiment 
     A working tool according to the third embodiment will be described with reference to  FIG.  11 A  to  FIG.  11 F . In the following description, the same components as those of the first embodiment are denoted by the same reference characters and differences are mainly described. Points that are not particularly described are the same as those in the first embodiment. The working tool  10  according to the third embodiment includes a feeding mechanism  19 B having a configuration different from that of the first embodiment, so that the timing of supplying current to the feeding mechanism  19 B is different from that of the first embodiment. 
     Feeding Mechanism  19 B 
       FIG.  11 A  to  FIG.  11 F  are diagrams each showing the feeding mechanism  19 B, the piston  29 , and the driver blade  30 , similarly to  FIG.  4 A  to  FIG.  4 F  shown in the first embodiment.  FIG.  11 A  shows the case where the driver blade  30  is located at the standby position. The feeding mechanism  19 B includes a rotary solenoid  60 B, the feeder unit  62 , a feeder rod  64 , a rack  65 , and a pinion  66 . The rotary solenoid  60 B has a rotation shaft, a coil, and a permanent magnet. The rotation shaft of the rotary solenoid  60 B extends in a direction orthogonal to the second direction, and the coil is arranged around this rotation shaft. When current is supplied to the coil from the power supply unit  14 , the coil generates magnetic force. By the attractive and repulsive action between this magnetic force and the permanent magnet, the rotation shaft rotates clockwise or counterclockwise on the page of  FIG.  11    within a predetermined angular range. 
     The feeder rod  64  is a plate-like member extending along the second direction AR 2 . In a part of the feeder rod  64  on the other side (rear side) in the second direction AR 2 , the rack (gear)  65  is formed along the extending direction of the feeder rod  64  on one side (lower side) of the feeder rod  64  in the first direction AR 1 . 
     The pinion (gear)  66  is provided on the rotation shaft of the rotary solenoid  60 B and meshes with the rack  65  of the feeder rod  64 . When a current is supplied to the rotary solenoid  60 B and the rotation shaft is rotated, the pinion  66  is also rotated together. Along with the rotation of the pinion  66 , the rack  65  meshing with the pinion  66  moves to one side or the other side along the second direction AR 2 . As a result, the feeder rod  64  moves along the second direction AR 2  by the current supply to the rotary solenoid  60 B. The feeder unit  62  is attached to the feeder rod  64  on one side (front side) in the second direction AR 2 , and the feeder unit  62  moves along with the movement of the feeder rod  64 . 
     Fastener Feeding Operation 
     When current is supplied from the power supply unit  14  to the coil of the rotary solenoid  60 B, the pinion  66  rotates clockwise (hereinafter referred to also as forward rotation) on the page of the drawing as shown in  FIG.  11 B . The rotational force of the pinion  66  is transmitted to the feeder rod  64  via the rack  65 , and the feeder rod  64  moves to one side (front side) in the second direction AR 2 . Consequently, the feeder unit  62  moves from the initial position shown in  FIG.  11 A  to one side in the second direction AR 2 , and the nail  55  moves to the fastener feeding position on the lower side of the driver blade  30  as shown in  FIG.  11 B . 
     When the electric power output from the power supply unit  14  is supplied to the electric motor  15  in the state where the nail  55  is located at the fastener feeding position, the driver blade  30  ascends upward in the first direction AR 1  and reaches the top dead center as shown in  FIG.  11 C  as in the case of the first and second embodiments. 
     Thereafter, the driver blade  30  descends and strikes the nail  55  located at the fastener feeding position as in the case of the first and second embodiments. As shown in  FIG.  11 D , after striking the nail  55 , the driver blade  30  reaches the bottom dead center and stops descending. 
     When the driver blade  30  stops at the bottom dead center, the power supply unit  14  supplies current to the rotary solenoid  60 B to rotate the pinion  66  shown in  FIG.  11 E  counterclockwise (hereinafter referred to also as backward rotation) on the page of the drawing. The rotational force of the pinion  66  is transmitted to the feeder rod  64  via the rack  65 , and the feeder rod  64  moves to the other side (rear side) in the second direction AR 2 . Consequently, the feeder unit  62  moves to the initial position. When the feeder unit  62  moves to the initial position, the feed pawl (not shown) that moves together with the feeder unit  62  enters between the nails  55  connected by the connecting element. Thereafter, as in the case of the first and second embodiments, the driver blade  30  is moved to the standby position on the upper side in the first direction AR 1  by the rotation of the electric motor  15  as shown in  FIG.  11 F . 
     Operation Timing 
     The operation timing of the working tool  10  will be described with reference to  FIG.  12 A  to  FIG.  12 G .  FIG.  12 A  to  FIG.  12 G  are timing charts in the case where the single nail  55  is driven into the workpiece W 1 .  FIG.  12 A  to  FIG.  12 G  show the relationship between the position of the driver blade  30  and the time, the relationship between the position of the feeder unit  62  and the time, the relationship between the load current of the electric motor  15  and the time, the relationship between the current value supplied to the rotary solenoid  60 B and the time, the relationship between the rotation angle of the electric motor  15  and the time, the relationship between the output of the first detection signal and the time, and the relationship between the output of the second detection signal and the time, respectively. 
     The operation of each unit from time t 1  to time t 3  shown in  FIG.  12 A  to  FIG.  12 G  is the same as the operation from time t 1  to time t 3  shown in  FIG.  5 A  to  FIG.  5 G  described in the first embodiment. After time t 3 , the value of the load current of the electric motor  15  falls below a preset current threshold as shown in  FIG.  12 C . Then, as shown in  FIG.  12 D , the control unit  73  causes the power supply unit  14  to start supplying current to the rotary solenoid  60 B at time t 4 . Consequently, as shown in  FIG.  12 B , the feeder unit  62  starts to move to one side (front side) in the second direction AR 2  by the rotary solenoid  60 B rotating forward. At time t 5 , the nail  55  is moved to the fastener feeding position shown in  FIG.  11 B  by the feeder unit  62  that has moved to one side in the second direction AR 2  as shown in  FIG.  12 B . 
     Thereafter, as shown in  FIG.  12 A , the driver blade  30  that has reached the top dead center at time t 6  descends, and reaches the bottom dead center to stop there at time t 7 . As shown in  FIG.  12 D , at time t 8  after the driver blade  30  stops at the bottom dead center, the control unit  73  causes the power supply unit  14  to stop supplying current to the rotary solenoid  60 B. 
     Along with the rotation of the electric motor  15 , the driver blade  30  starts to ascend at time t 9  as shown in  FIG.  12 A . Thereafter, as shown in  FIG.  12 D , the control unit  73  causes the power supply unit  14  to start supplying current to the rotary solenoid  60 B at time t 10 . Consequently, as shown in  FIG.  12 B , the feeder unit  62  starts to move to the other side (rear side) in the second direction AR 2  by the rotary solenoid  60 B rotating backward. Then, the feeder unit  62  reaches the initial position at time t 11 . At time t 12  after the feeder unit  62  has moved to the initial position, the control unit  73  causes the power supply unit  14  to stop supplying current to the rotary solenoid  60 B. The operation of each unit after time t 11  is the same as the operation after time t 6  in  FIG.  5 A  to  FIG.  5 G  described in the first embodiment. 
     According to the third embodiment described above, the same effects as those obtained by the first embodiment can be obtained. 
     Fourth Embodiment 
     A working tool according to the fourth embodiment will be described with reference to  FIG.  13 A  to  FIG.  13 F . In the following description, the same components as those of the second embodiment are denoted by the same reference characters and differences are mainly described. Points that are not particularly described are the same as those in the second embodiment. The working tool  10  according to the fourth embodiment includes the feeding mechanism  19 A similar to that of the second embodiment, but the timing of moving the nail to the fastener feeding position is different from that of the second embodiment. 
     As the fourth embodiment, the working tool  10  having the feeding mechanism  19 A similar to that of the second embodiment will be described, but the working tool  10  having the feeding mechanism  19  of the first embodiment or the feeding mechanism  19 B of the third embodiment may perform the operations described below. 
     Fastener Feeding Operation 
       FIG.  13 A  is a diagram showing the feeding mechanism  19 A, the piston  29 , and the driver blade  30  similarly to  FIG.  9 A  described above, and the driver blade  30  is located at the standby position. However, unlike the case of  FIG.  9 A , the nail  55  has already been located at the fastener feeding position. 
     When the electric power output from the power supply unit  14  is supplied to the electric motor  15  in the state where the nail  55  is located at the fastener feeding position, the driver blade  30  ascends and reaches the top dead center as shown in  FIG.  13 B . When the pinwheel  46  rotates further from this state, the driver blade  30  descends to strike the nail  55  located at the fastener feeding position, and then reaches the bottom dead center to stop descending as shown in  FIG.  13 C . 
     Thereafter, the driver blade  30  moves upward in the first direction AR 1  again. As shown in  FIG.  13 D , when the tip  115  of the driver blade  30  reaches a position on the upper side than the upper portion (head) of the nail  55 , current is supplied to the coil of the solenoid  60  by the power supply unit  14 . Consequently, as described with reference to  FIG.  9 B  in the second embodiment, the feeder unit  62  moves from the initial position to the nail mounting position on the other side (rear side) in the second direction AR 2  against the biasing force of the spring  59 . 
     At the nail mounting position, as in the case of the second embodiment, the feed pawl provided in the feeder unit  62  enters between the nails  55  connected by the connecting element. Thereafter, when the current supply to the solenoid  60  by the power supply unit  14  is terminated, the feeder unit  62  is returned from the nail mounting position to the initial position on one side in the second direction AR 2  by the biasing force of the spring  59  as described with reference to  FIG.  9 C  in the second embodiment. When the feeder unit  62  moves to one side in the second direction AR 2 , the nail  55  located at the head of the connecting element among the nails  55  stored in the magazine unit  54  is located at the fastener feeding position as shown in  FIG.  13 E . Thereafter, the driver blade  30  moves to the standby position on the upper side in the first direction AR 1  by the rotation of the electric motor  15  as shown in  FIG.  13 F . 
     Operation Timing 
     The operation timing of the working tool  10  will be described with reference to the drawings.  FIG.  14 A  to  FIG.  14 G  are timing charts in the case where the single nail  55  is driven into the workpiece W 1 .  FIG.  14 A  to  FIG.  14 G  show the relationship between the position of the driver blade  30  and the time, the relationship between the position of the feeder unit  62  and the time, the relationship between the load current of the electric motor  15  and the time, the relationship between the current value supplied to the solenoid  60  and the time, the relationship between the rotation angle of the electric motor  15  and the time, the relationship between the output of the first detection signal and the time, and the relationship between the output of the second detection signal and the time, respectively. 
     In the fourth embodiment, unlike  FIG.  10 B , the nail  55  has already been located at the fastener feeding position by the feeder unit  62  at time t 0  (that is, before the first and second operation signals are output) as shown in  FIG.  14 B . When the first operation signal and the second operation signal are output in this state, the control unit  73  causes the power supply unit  14  to start supplying current to the electric motor  15  at time t 1  as shown in  FIG.  14 C . Thereafter, the load current of the electric motor  15  changes in the same manner as in the case of the second embodiment shown in  FIG.  10 C . 
     Thereafter, as shown in  FIG.  14 A , the driver blade  30  that has reached the top dead center at time t 2  descends, and reaches the bottom dead center to stop there at time t 3 . After reaching the bottom dead center, the driver blade  30  starts to ascend at time t 4 , and reaches a position on the upper side than the head of the nail  55  (nail head position) at time t 5 . As shown in  FIG.  14 F  and  FIG.  14 G , the first detection signal is output from the pinwheel position detection sensor  58  and the second detection signal is output from the blade position detection sensor  77  at time t 6 . 
     Thereafter, at time t 7 , the control unit  73  causes the power supply unit  14  to start supplying current to the solenoid  60 , thereby moving the feeder unit  62  to the nail mounting position as shown in  FIG.  14 D . At time t 8  after the feed pawl of the feeder unit  62  enters between the nails  55 , the control unit  73  causes the power supply unit  14  to stop supplying current to the solenoid  60  as shown in  FIG.  14 D . Consequently, as shown in  FIG.  14 B , the feeder unit  62  starts to move to one side (front side) in the second direction AR 2  from the nail mounting position at time t 8 , and the nail  55  is located at the fastener feeding position at time t 9 . 
     As shown in  FIG.  14 A , the driver blade  30  reaches the standby position at time t 9 . Thereafter, at time t 10 , the control unit  73  causes the power supply unit  14  to stop supplying electric power to the electric motor  15  as shown in  FIG.  14 C . Namely, after the nail  55  is struck, the working tool  10  locates the next nail  55  at the fastener feeding position, and stops the power supply to the electric motor  15  after the driver blade  30  reaches the standby position. 
     According to the fourth embodiment described above, the following effect can be obtained. 
     The feeder unit  62  feeds the nail  55  to the ejection unit  32  while the driver blade  30  moves from the bottom dead center to the standby position, specifically, before the driver blade  30  reaches the standby position. Consequently, since the next nail  55  can be fed in advance, the time period from when the operation of driving the next nail  55  is performed to when the nail  55  is actually driven into the workpiece W 1  can be shortened. 
     Second Modification 
     The working tool  10  according to the second modification has the same configuration as that of the working tool  10  according to the fourth embodiment. The working tool  10  according to the second modification is different from the working tool  10  according to the fourth embodiment in that the next nail  55  is moved to the fastener feeding position after stopping the power supply to the electric motor  15 . The power supply operation of the working tool  10  in this case will be described with reference to  FIG.  15 A  to  FIG.  15 G . 
       FIG.  15 A  to  FIG.  15 G  are timing charts in the case where the single nail  55  is driven into the workpiece W 1 .  FIG.  15 A  to  FIG.  15 G  show the relationship between the position of the driver blade  30  and the time, the relationship between the position of the feeder unit  62  and the time, the relationship between the load current of the electric motor  15  and the time, the relationship between the current value supplied to the solenoid  60  and the time, the relationship between the rotation angle of the electric motor  15  and the time, the relationship between the output of the first detection signal and the time, and the relationship between the output of the second detection signal and the time, respectively. 
     The operation of each unit from time t 1  to time t 5  shown in  FIG.  15 A  to  FIG.  15 G  is the same as the operation from time t 1  to time t 6  shown in  FIG.  14 A  to  FIG.  14 G . When the driver blade  30  reaches the standby position at time t 6  shown in  FIG.  15 A , the control unit  73  shown in  FIG.  15 C  causes the power supply unit  14  to stop supplying electric power to the electric motor  15 . The operation of each unit from time t 7  to time t 9  is the same as the operation from time t 7  to time t 9  shown in  FIG.  14 A  to  FIG.  14 G . Namely, the current supply to the solenoid  60  is started after the power supply to the electric motor  15  is stopped. 
     The control unit  73  of the second modification drives the solenoid  60  while the driving of the electric motor  15  is stopped. Since the next nail  55  can be fed in advance, the time period from when the operation of driving the next nail  55  is performed to when the nail  55  is actually driven into the workpiece W 1  can be shortened. 
     Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. 
     In the above embodiments, the control unit  73  determines the load of the electric motor  15  based on the load current of the electric motor  15 , but the present invention is not limited to this. The control unit  73  may determine whether the load satisfies the first condition (that is, whether the difference between the set value and the actual measured value of the rotation speed is equal to or less than the threshold) by monitoring the rotation speed of the electric motor  15  calculated from the detection value of the motor position detection sensor  78  and estimating the load torque of the electric motor  15  from the difference between the set value and the actual measured value of the rotation speed. Also, the control unit  73  may determine whether the load satisfies the first condition (that is, whether the load torque falls below the threshold) by directly measuring the load torque of the electric motor  15  by using a torque sensor such as a strain gauge. Further, the control unit  73  may determine whether the load satisfies the first condition (that is, whether the difference between the set value and the actual measured value of the moving speed is equal to or less than the threshold or whether the acceleration is equal to or less than the threshold) by providing a sensor that detects the moving speed or the acceleration of the driver blade  30  or the pinwheel  46  in the working tool  10  and estimating the load torque from the motion state of the driver blade  30 . As the load of the electric motor  15  decreases, the control unit  73  may cause the power supply unit  14  to gradually increase the current of the solenoid  60 .