Abstract:
A power tool includes a bit mounting unit, a motor, and a control unit. The bit mounting unit is configured to mount thereon a bit. The motor is configured to rotatingly drive the bit. The control unit is configured to control a drive of the motor. The control unit includes a storing unit configured to store a plurality of prescribed values affecting the drive of the motor and a division number by which a range of the plurality of prescribed values is divided. At least one of the range and the division number is arbitrarily settable.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priorities from Japanese Patent Application No. 2012-052457 filed Mar. 9, 2012. The entire content of this priority application is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The invention relates to a power tool and a power tool system, and particularly to a power tool system capable of changing an operation mode of a power tool. 
       BACKGROUND 
       [0003]    In a screw driving tool or the like that is used at an assembly site such as an automobile plant, specific setting of tightening torque is required, and adjustments of torque setting are required for each tightened part. Thus, a tool capable of setting driving torque as disclosed in Japanese Patent Application Publication No. 2011-31314 is used to set predetermined tightening torque suitable for a tightened part, so that a driving operation is performed. 
       SUMMARY 
       [0004]    In the above-described tool, a maximum value, a minimum value, and settable values between the maximum value and the minimum value of tightening torque are set preliminarily. Hence, when an operation requires tightening torque outside this preset range, a tool needs to be provided for each required tightening torque. In view of the foregoing, it is an object of the invention to provide a power tool capable of dealing with a wide range of tightening torque with a single power tool, and to provide a power tool system capable of setting a wide range of tightening torque. 
         [0005]    In order to attain the above and other objects, the present invention provides a power tool. The power tool includes a bit mounting unit, a motor, and a control unit. The bit mounting unit is configured to mount thereon a bit. The motor is configured to rotatingly drive the bit. The control unit is configured to control a drive of the motor. The control unit includes a storing unit configured to store a plurality of prescribed values affecting the drive of the motor and a division number by which a range of the plurality of prescribed values is divided. At least one of the range and the division number is arbitrarily settable. 
         [0006]    With this configuration, because a range of prescribed values affecting operations of a motor or a division number can be set arbitrarily, a wide range of operations can be performed with a single power tool. Further, because prescribed values affecting operations of the motor can be changed on the power tool itself, changes of the prescribed values or the like become easier. 
         [0007]    According to another aspect of the invention, the present invention provides a power tool. The power tool includes a bit mounting unit, a motor, a control unit, a selecting unit, and an external device connecting unit. The bit mounting unit is configured to mount thereon a bit. The motor is configured to rotatingly drive the bit mounting unit. The control unit is configured to control a drive of the motor. The control unit includes a storing unit and a torque determining unit. The torque determining unit is configured to determine the fastening torque. The storing unit is configured to store a plurality of prescribed values having a range for determining a fastening torque and a division number by which the range is divided. The selecting unit is configured to select one of the plurality of prescribed values. The torque determining unit determines the fastening torque based on the selection of the selecting unit. The external device connecting unit is configured to be connected to an external device. The external device includes a changing unit configured to change at least one of the range of the plurality of prescribed values and the division number. 
         [0008]    With this configuration, because a division number and a plurality of prescribed values can be changed, a wide range of tightening torque can be obtained with a single power tool. Further, because an external device is required to change the reference value and the like, inadvertent changes of the division number and the like can be suppressed. 
         [0009]    According to still another aspect of the invention, the present invention provides a power tool. The power tool includes a bit mounting unit, a motor, a control unit, and a selecting unit. The bit mounting unit is configured to mount thereon a bit. The motor is configured to rotatingly drive the bit mounting unit. The control unit is configured to control a drive of the motor. The control unit includes a storing unit and a torque determining unit . The torque determining unit is configured to determine a fastening torque. The storing unit is configured to store a plurality of prescribed values having a range for determining the fastening torque and a division number by which the range is divided. The selecting unit is configured to select one of a first operation mode and a second operation mode. The selecting unit selects one of the plurality of prescribed values in the first operation mode and the torque determining unit determines the fastening torque based on the selection of the selecting unit. The selecting unit changes at least one of the range of plurality of prescribed values and the division number in the second operation mode. 
         [0010]    With this configuration, too, because a division number and a plurality of prescribed values can be changed, a wide range of tightening torque can be obtained with a single power tool. Further, because the division number and the like can be changed on the power tool itself, changes of the reference value and the like become easier. 
         [0011]    According to further aspect of the invention, the present invention provides a power tool system. The power tool system includes a power tool and an external device. The power tool includes a bit mounting unit, a motor, a control unit, a selecting unit, and an external device connecting unit. The bit mounting unit is configured to mount thereon a bit. The motor is configured to rotatingly drive the bit mounting unit. The control unit is configured to control a drive of the motor. The control unit includes a storing unit and a torque determining unit. The torque determining unit is configured to determine a fastening torque. The storing unit is configured to store a plurality of prescribed values having a range for determining the fastening torque and a division number by which the range is divided. The selecting unit is configured to select one of the plurality of prescribed values. The torque determining unit determines the fastening torque based on the selection of the selecting unit. The external device is configured to connect to the external device connecting unit. The external device includes a changing unit configured to change at least one of the range of the plurality of prescribed values and the division number. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
           [0013]      FIG. 1  is a central cross-sectional view of an electronic pulse driver according to a first embodiment of the present invention; 
           [0014]      FIG. 2  is a block diagram of the electronic pulse driver according to the first embodiment of the present invention; 
           [0015]      FIG. 3A  is a schematic view showing a display section of the electronic pulse driver according to the first embodiment of the present invention; 
           [0016]      FIG. 3B  is an explanation view showing a transition of a display of the display section each time a switch  26  is pressed according to the first embodiment of the present invention; 
           [0017]      FIG. 4  is a schematic view showing a state where the electronic pulse driver is connected to a PC according to the first embodiment of the present invention; 
           [0018]      FIG. 5  is a flowchart explaining a process for determining setting values in the electronic pulse driver according to the first embodiment of the present invention; 
           [0019]      FIG. 6  is a window of the PC before the PC is connected to the electronic pulse driver according to the first embodiment of the present invention; 
           [0020]      FIG. 7  is a window of the PC after the PC is connected to the electronic pulse driver according to the first embodiment of the present invention; 
           [0021]      FIG. 8  is a window of the PC when an error message is displayed on the PC according to the first embodiment of the present invention; 
           [0022]      FIG. 9  is a window of the PC when an error message is displayed on the PC according to the first embodiment of the present invention; 
           [0023]      FIG. 10  is a window of the PC when the PC reads in the setting values therein according to the first embodiment of the present invention; 
           [0024]      FIG. 11  is a window of the PC when the setting of the setting values is completed in the PC according to the first embodiment of the present invention; 
           [0025]      FIG. 12  is a block diagram of an electronic pulse driver according to a second embodiment of the present invention; 
           [0026]      FIG. 13  is a flowchart explaining a process for determining setting values in the electronic pulse driver according to the second embodiment of the present invention; 
           [0027]      FIG. 14  is a schematic view showing a display section of the electronic pulse driver according to the second embodiment of the present invention; 
           [0028]      FIG. 15  is a schematic view showing the display section of the electronic pulse driver when a setting of the minimum value is started according to the second embodiment of the present invention; 
           [0029]      FIG. 16  is a schematic view showing the display section of the electronic pulse driver when the setting of the minimum value is completed according to the second embodiment of the present invention; 
           [0030]      FIG. 17  is a schematic view showing the display section of the electronic pulse driver when a setting of a maximum value is started according to the second embodiment of the present invention; 
           [0031]      FIG. 18  is a schematic view showing the display section of the electronic pulse driver when the setting of the maximum value is completed according to the second embodiment of the present invention; 
           [0032]      FIG. 19  is a schematic view showing the display section of the electronic pulse driver when a setting of the number of steps is started according to the second embodiment of the present invention; 
           [0033]      FIG. 20  is a schematic view showing the display section of the electronic pulse driver when a setting of the number of steps is completed according to the second embodiment of the present invention; and 
           [0034]      FIG. 21  is a schematic view showing the display section of the electronic pulse driver when reviewing the setting values according to the second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Hereinafter, an electronic pulse driver  1  as an example of a power tool according to a first embodiment of the invention and a configuration combined with a PC (personal computer)  10  as an example of an external device will be described while referring to  FIGS. 1 through 11 . The PC  10  changes tightening torque characteristics as an operation mode of the electronic pulse driver  1  (an operation-mode change system of the power tool). 
         [0036]    As shown in  FIG. 1 , the electronic pulse driver  1  includes a main body  1 A and a battery  24 . The main body  1 A mainly includes a housing  2 , a motor  3 , a hammer section  4 , an anvil section  5 , an inverter circuit board  6 , a control section  7 , and rotational-position detecting elements (Hall elements)  8 . The housing  2  is made of resin and constitutes an outer shell of the electronic pulse driver  1 . The housing  2  mainly includes a body section  21  having substantially a cylindrical shape and a handle section  22  extending from the body section  21 . 
         [0037]    The motor  3  is disposed within the body section  21  such that the longitudinal direction of the body section  21  matches the axial direction of the motor  3 . Also, within the body section  21 , the hammer section  4  and the anvil section  5  are arranged toward one end side in the axial direction of the motor  3 . In the following descriptions, the anvil section  5  side is defined as a front side, the motor  3  side is defined as a rear side, and a direction parallel to the axial direction of the motor  3  is defined as a front-rear direction. Additionally, the body section  21  side is defined as a top side, the handle section  22  side is defined as a bottom side, and a direction in which the handle section  22  extends from the body section  21  is defined as a top-bottom direction. Further, a direction perpendicular to the front-rear direction and to the top-bottom direction is defined as a left-right direction. 
         [0038]    The body section  21  has a front portion provided with a metal-made hammer case  23  in which the hammer section  4  and the anvil section  5  are provided. The hammer case  23  has substantially a funnel shape tapering toward the front side. The hammer case  23  has a front-end portion formed with an opening  23   a.  A metal  23 A is provided at an inner surface defining the opening  23   a.    
         [0039]    The body section  21  is formed with a plurality of inlet ports  21   a  and outlet ports  21   b  for introducing external air into the body section  21  and for discharging air to the outside, respectively, with a fan  32  described later. The motor  3  is cooled by the external air. 
         [0040]    The handle section  22  extends downward from approximately a center position of the body section  21  in the front-rear direction, and is formed integrally with the body section  21 . The battery  24  for supplying the motor  3  and the like with electric power is detachably mounted on the bottom end of the handle section  22 . The handle section  22  includes a trigger  25 , a switching lever  27 , a switch  26  ( FIG. 3A ), and a display section  26 A ( FIG. 3A ). The trigger  25  is provided at a front upper portion of the handle section  22 . The switching lever  27  for alternately selecting a rotational direction of the motor  3  is provided immediately above the trigger  25 . The switch  26  shown in  FIG. 3A  for determining a tightening torque described later is provided on a lower right-side surface of the handle section  22 . The switch  26  is disposed within the display section  26 A and is for selecting one of the plurality of prescribed values defined between a maximum value and a minimum value, in order to determine the tightening torque. Specifically, the switch  26  is so configured that the prescribed value increases by one step when the switch  26  is pressed once for a short time (“press short”: to keep for 500 msec or less a state where the switch  26  is being pressed) and that the prescribed value returns to the minimum value when the switch  26  is further pressed short after the prescribed value reaches the maximum value. The switch  26  serves as a selecting unit of the present invention. The display section  26 A includes two-sets of seven-segment display section  26 B that displays the prescribed value. The display section  26 A serves as a display unit of the present invention. 
         [0041]    The motor  3  is a brushless motor mainly including a rotor  3 A having an output shaft section  31  and a stator  3 B arranged in confrontation with the rotor  3 A. The rotor  3 A is provided with a permanent magnet  3 C ( FIG. 2 ). The motor  3  is disposed within the body section  21  such that the axial direction of the output shaft section  31  is coincident with the front-rear direction. The output shaft section  31  protrudes forward and rearward from the rotor  3 A, and is rotatably supported at the protruding portions by the body section  21  via bearings. The fan  32  rotatable coaxially and together with the output shaft section  31  is provided at the front protruding section of the output shaft section  31 . Further, a pinion gear  31 A rotatable coaxially and together with the output shaft section  31  is provided at the front-end position of the front protruding section of the output shaft section  31 . 
         [0042]    The hammer section  4  mainly includes a gear mechanism  41  and a hammer  42 , and is disposed at the front side of the motor  3  within the hammer case  23 . The gear mechanism  41  includes a planetary gear mechanism  41 B having an outer gear  41 A. The outer gear  41 A is disposed within the hammer case  23  and is fixed to the body section  21 . The planetary gear mechanism  41 B is disposed within the outer gear  41 A so as to meshingly engage the outer gear  41 A. 
         [0043]    The hammer  42  is defined at the front side of a planetary carrier of the planetary gear mechanism  41 B. The hammer  42  includes a first engaging protrusion  42 A that protrudes forward and that is disposed at a position shifted from a rotational center of the planetary carrier of the planetary gear mechanism  41 B, and a second engaging protrusion (not shown) that is located at a directly opposite position to the first engaging protrusion  42 A with respect to the rotational center of the planetary carrier of the planetary gear mechanism  41 B. 
         [0044]    The anvil section  5  is disposed at the front side of the hammer section  4 , and mainly includes an end-bit mounting section  51  and an anvil  52 . The end-bit mounting section  51  has a cylindrical shape, and is rotatably supported in opening  23   a  of the hammer case  23  via the metal  23 A. The end-bit mounting section  51  is formed with a bore  51   a  in the front-rear direction through which a bit (not shown) is detachably inserted. The end-bit mounting section  51  has a front end portion provided with a chuck  51 A for holding a bit (not shown). The end-bit mounting section  51  serves as a bit mounting unit of the present invention. 
         [0045]    The anvil  52  is provided integrally with the end-bit mounting section  51  at a position rearward of the end-bit mounting section  51  and within the hammer case  23 . The anvil  52  includes a first engaged protrusion  52 A and a second engaged protrusion  52 B that protrude rearward and that are located at directly opposite positions with respect to the rotational center of the end-bit mounting section  51 . When the hammer  42  rotates, the first engaging protrusion  42 A and the first engaged protrusion  52 A collide with each other and, at the same time, the second engaging protrusion (not shown) and the second engaged protrusion  52 B collide with each other, which causes rotational force of the hammer  42  to be transmitted to the anvil  52 . 
         [0046]    As shown in  FIG. 2 , the inverter circuit board  6  includes six (6) switching elements Q 1 -Q 6  such as FETs that are connected in three-phase bridge connection. The switching elements Q 1 -Q 6  are attached to the inverter circuit board  6 . The inverter circuit board  6  is fixed to the motor  3  at the rear end of the motor  3  such that the inverter circuit board  6  is substantially perpendicular to the output shaft section  31 . Note that, as shown in  FIG. 1 , the switching elements Q 1 -Q 6  are attached to the inverter circuit board  6  such that the longitudinal direction of the switching elements Q 1 -Q 6  is substantially parallel to the output shaft section  31 . The plurality of inlet ports  21   a  is formed in the body section  21  at positions radially outwardly from the inverter circuit board  6 . On the other hand, the outlet port  21   b  is formed in the body section  21  at a position radially outwardly from the fan  32 . 
         [0047]    The control section  7  is mounted on a board that is disposed at a position adjacent to the battery  24  in the handle section  22 . The control section  7  is connected to the battery  24 , the trigger  25 , the switch  26 , the switching lever  27 , the inverter circuit board  6 , and the display section  26 A as shown in  FIG. 2 . Further, the control section  7  includes a current detecting circuit  71 , a switch-operation detecting circuit  72 , an application-voltage setting circuit  73 , a rotational-direction setting circuit  74 , a rotor-position detecting circuit  75 , a rotational-angle detecting circuit  76 , an arithmetic section  78 , a control-signal outputting circuit  79 , a display circuit section  80  (display control unit), and an external connection terminal  81 . The external connection terminal  81  is a terminal for connecting the PC  10  ( FIG. 4 ), which is an external device, to the main body  1 A. The external connection terminal  81  is provided at a bottom end portion of the handle section  22  opposing the battery  24  in top-bottom direction as shown in  FIG. 1 . The external connection terminal  81  serves as an external device connecting unit of the present invention. The PC  10  can be connected to the main body  1 A only in a state where the battery  24  is detached from the main body  1 A, so that settings of the electronic pulse driver  1  cannot be changed during a use thereof 
         [0048]    The rotational-position detecting elements  8  are provided at positions opposing permanent magnets  3 C of the rotor  3 A in the axial direction of the output shaft section  31 , and are arranged in a circumferential direction of the rotor  3 A with a predetermined interval (for example, an angle of 60 degrees) therebetween. 
         [0049]    Next, the configuration of drive control system of the motor  3  will be described while referring to  FIG. 2 . In the present embodiment, the motor  3  is a three-phase brushless DC motor. The permanent magnet  3 C includes a plurality of sets (two sets in the present embodiment) of N pole and S pole. The stator  3 B is three-phase stator windings U, V, and W in star connection. 
         [0050]    A gate of each of the switching elements Q 1 -Q 6  of the inverter circuit board  6  is connected to the control-signal outputting circuit  79  of the control section  7 , and a drain or a source of each of the switching elements Q 1 -Q 6  is connected to the stator windings U, V, and W of the stator  3 B. The six switching elements Q 1 -Q 6  performs switching operations based on switching-element driving signals inputted from the control-signal outputting circuit  79 , and supplies to the stator windings U, V, and W the direct-current voltage of the battery  24  applied to the inverter circuit  6  as three-phase (U phase, V phase, and W phase) voltages Vu, Vv, Vw. Specifically, one of the stator windings U, V, and W to be energized, that is, the rotational direction of the rotor  3 A is controlled based on output switching signals H 1 , H 2 , and H 3  inputted to the positive side switching elements Q 1 , Q 2 , and Q 3  from the control-signal outputting circuit  79 . Further, an amount of supplying the stator windings U, V, and W with electric power, that is, the rotational speed of the rotor  3 A is controlled based on pulse-width modulation signals (PWM signals) H 4 , H 5 , and H 6  inputted to the negative side switching elements Q 4 , Q 5 , and Q 6  from the control-signal outputting circuit  79 . 
         [0051]    The current detecting circuit  71  detects a value of current supplied to the motor  3  and outputs the detected value to the arithmetic section  78 . The switch-operation detecting circuit  72  and the application voltage setting circuit  73  are electrically connected to the trigger  25 . The switch-operation detecting circuit  72  detects whether the trigger  25  has been operated and outputs the detection result to the arithmetic section  78 . The application-voltage setting circuit  73  outputs a signal based on an operation amount of the trigger  25  to the arithmetic section  78 . 
         [0052]    The rotational-direction setting circuit  74  is electrically connected to the switching lever  27 . Upon detecting a switching operation of the switching lever  27 , the rotational-direction setting circuit  74  outputs a signal for switching the rotational direction of the motor  3  to the arithmetic section  78 . 
         [0053]    The rotor-position detecting circuit  75  is electrically connected to the rotational-position detecting elements  8 . The rotor-position detecting circuit  75  detects a rotational position of the rotor  3 A based on signals from the rotational-position detecting elements  8 , and outputs the detection result to the arithmetic section  78 . 
         [0054]    The rotational-angle detecting circuit  76  is for detecting an angle of the rotor  3  and for using the detected value when a control based on the rotations A based on a signal from the rotor-position detecting circuit  75  l angle is performed. 
         [0055]    The arithmetic section  78  includes a central processing unit (CPU) (not shown) for outputting driving signals based on processing programs and data, an EEPROM  82  (storing unit) that is rewritable for storing data, and a timer (not shown). The CPU serves as a torque determining unit of the present invention. The EEPROM  82  stores the maximum value of tightening torque, the minimum value of tightening torque, the number of steps (division number), and a plurality of prescribed values that is obtained by equally dividing an interval between the maximum value and the minimum value by the number of steps. The number of steps is an integer value. Note that a minimum prescribed value of the prescribed values is the same as the minimum value, and that a maximum prescribed value of the prescribed values is the same as the maximum value. The above-mentioned maximum value, the minimum value, the number of steps, and the plurality of prescribed values are defined collectively as setting values. That is, the EEPROM  82  stores the maximum value of the tightening torque, the minimum value of the tightening torque, the number of steps, and the plurality of prescribed values as torque values calculated by dividing a torque range between the maximum value and the minimum value by the predetermined number. As will be described in greater detail, an operator can calculate the plurality of prescribed values by setting the maximum value and the minimum value each of the tightening torque and subsequently dividing the torque range into the number of steps. For example, assume that the maximum value of the torque is 5 Nm, the minimum value of the torque is 1 Nm, and the number of steps is 5. In this case, the torque range is 1 to 5, the predetermined number is 5, and hence the plurality of prescribed values (Nm) is 1, 2, 3, 4, and 5. 
         [0056]    The arithmetic section  78  generates the output switching signals H 1 , H 2 , and H 3  based on signals from the rotational-direction setting circuit  74  and the rotor-position detecting circuit  75 , and generates the pulse-width modulation signals (PWM signals) H 4 , H 5 , and H 6  based on signals from the application-voltage setting circuit  73 , and outputs the generated signals to the control-signal outputting circuit  79 . Note that the PWM signals may be outputted to the positive side switching elements Q 1 , Q 2 , and Q 3 , and the output switching signals may be outputted to the negative side switching elements Q 4 , Q 5 , and Q 6 . 
         [0057]    The arithmetic section  78  is connected to the above-described switch  26 . Based on an operation of the switch  26 , one of the plurality of prescribed values stored in the EEPROM  82  is determined The arithmetic section  78  is connected to the display circuit section  80  receiving the signal therefrom. The display circuit section  80  is electrically connected to the display section  26 A. The display circuit section  80  controls the display section  26 A (the seven-segment display section  26 B) based on the signal from the arithmetic section  78 . 
         [0058]    The PC  10  is a known personal computer and, as shown in  FIG. 4 , is connectable with the electronic pulse driver  1  via a cable  10 A. As shown in  FIG. 6 , upon running an application software for controlling the electronic pulse driver  1 , an operation-mode setting window  11  is displayed on a screen of the PC  10 . The operation-mode setting window  11  may be automatically displayed on the screen in a state where the PC  10  is connected to the electronic pulse driver  1 . The operation-mode setting window  11  serves as a changing unit of the present invention. 
         [0059]    The operation-mode setting window  11  includes a connect button  11 A, a set-value display area  11 B, a setting-value input area  11 C, a setting-value display area  11 D, a read-in button  11 E, a message display area  11 F, a transmit button  11 G, and an exit button  11 H. The operation-mode setting window  11  is for setting the setting values such as the maximum value, the minimum value, and the number of steps, and for calculating the plurality of the prescribed values. The connect button  11 A is clicked after the PC  10  is connected to the electronic pulse driver  1  via the cable  10 A, and then the electronic pulse driver  1  is recognized on the PC  10 . The set-value display area  11 B displays setting values that are currently stored in the EEPROM  82  in the electronic pulse driver  1 . The setting-value input area  11 C is an area for inputting setting values that are newly rewritten. The setting-value display area  11 D is an area for displaying step numbers and newly set setting values corresponding to the step numbers. The read-in button  11 E is clicked after new setting values are inputted in the setting-value input area  11 C, and then the inputted values are recognized as setting values. The message display area  11 F displays a request to an operator or the like with respect to various conditions of the operation-mode setting window  11 . When the transmit button  11 G is clicked, values displayed in the setting-value display area  11 D are transmitted to the electronic pulse driver  1  and then are stored in the EEPROM  82 . When the exit button  11 H is clicked, the operation-mode setting window  11  is closed and then the application software is ended. 
         [0060]    A process of setting an operation mode in the electronic pulse driver  1  and the PC  10  will be described while referring to the flowchart in  FIG. 5  (selecting unit) and the operation-mode setting window  11 . First, the process begins with S 01  in a state where the electronic pulse driver  1  is connected to the PC  10 . In S 01 , the connect button  11 A is clicked to read in setting values stored in the EEPROM  82 . If no setting value is returned from the electronic pulse driver  1  in S 02  (S 02 : No), more specifically, if the electronic pulse driver  1  is not recognized within a predetermined time (within one sec), then the routine proceeds to S 03 . In S 03 , the PC  10  displays an error message such as “Check connection of the device” in the message display area  11 F as a malfunction, and then returns to S 01 . If setting values are returned in S 02  (S 02 : Yes), the PC  10  displays values read out from the EEPROM  82  in the set-value display area  11 B and, as shown in  FIG. 7 , displays that “Please input setting value” in the message display area  11 F while proceeding to S 04 . 
         [0061]    In S 04 , the operator inputs a maximum value in the setting-value input area  11 C. Next, in S 05 , the operator inputs a minimum value in the setting-value input area  11 C. Next, in S 06 , the operator inputs the number of steps for obtaining prescribed values in the setting-value input area  11 C. The maximum value and the minimum value can be set between 10 to 1 Nm and be set at one decimal place. The number of steps is 10 steps at maximum. In S 07 , when the read-in button  11 E is clicked, the PC  10  determines whether the setting values inputted in the setting-value input area  11 C can be displayed in the setting-value display area  11 D (that is, whether the setting values inputted in the setting-value input area  11 C can be set). Specifically, if a maximum value larger than the settable maximum value, i.e., 10, is inputted as shown in  FIG. 8 , the PC  10  determines that the setting values cannot be displayed (set) (S 07 : No) and displays an error message such as “Inputted value is out of settable range” in the message display area  11 F (S 08 ). If a maximum value is smaller than a minimum value as shown in  FIG. 9 , the PC  10  determines that the setting values cannot be displayed (set) (S 07 : No) and displays an error message such as “Check setting value” in the message display area  11 F (S 08 ). If a number larger than a maximum number of steps, i.e., 10, is inputted, the PC  10  determines that the setting values cannot be displayed (set) (S 07 : No) and displays an error message “Inputted value is out of settable range” in the message display area  11 F (S 08 ). Then the routine returns to S 06 . Further, if the maximum value is the same as the minimum value and if a value other than “1” is inputted as the number of steps, then the PC  10  displays that “The number of steps cannot be changed in this case” in the message display area  11 F, and a display of the number of steps is returned to “1”. Conversely, if the maximum value is different from the minimum value and if a value of “1” is inputted as the number of steps, then the PC  10  displays an error message such as “The setting value needs to be larger than or equal to 2” in the message display area  11 F, and the inputted value of “1” is not reflected. 
         [0062]    If it is determined that the values can be displayed (the values can be set) (S 07 : Yes), the routine proceeds to S 09  and the PC  10  displays, in the setting-value display area  11 D, the step number (1, 2, . . . , 5 in the present embodiment) and torque values (prescribe values) corresponding to each of the step number. In  FIG. 10 , the PC  10  displays in the setting-value display area  11 D a maximum value of 3.0 Nm, a minimum value of 1.0 Nm, and torque values obtained by dividing by 5 the range between the minimum value and the maximum value. In S 10 , if the transmit button  11 G is clicked, as shown in  FIG. 11 , the PC  10  transmits newly set setting values to the EEPROM  82  and then the setting values are stored in the EEPROM  82 . The PC  10  also displays the setting values in the set-value display area  11 B and displays that “Setting is completed” in the message display area  11 F. Then, the process ends. 
         [0063]    An operation of changing set torque values (a maximum value of 3.0 Nm, a minimum value of 1.0 Nm, the number of steps of 5) using the electronic pulse driver  1  will be described below. Note that, as shown in  FIG. 11 , torque values for the respective numbers of steps are allocated in five steps between 1.0 Nm and 3.0 Nm, such that the torque value is 1.0 Nm at the step number of 1 and that the torque value is 3.0 Nm at the step number of 5. At an initial state, the user operates the switch  26 . When the switch  26  is pressed short once, the step number of 1 is displayed as shown in the left uppermost portion of  FIG. 3B . When the switch  26  is pressed long in this state, the torque value of 1.0 Nm corresponding to the step number of 1 is displayed as shown in the right uppermost portion of  FIG. 3B . Then, as shown in  FIG. 2 , the arithmetic section  78  receives the signal from the switch  26  upon the press thereof and outputs the signal to the display circuit section  80  to control the display section  26 A to display a certain prescribed value. 
         [0064]    Every time the switch  26  is pressed short, the step number increases by one, and can be changed from the minimum number of 1 to the maximum number of 5 as shown in the left side of  FIG. 3B . The switch  26  is pressed long in a state where a certain step number is displayed, the torque value allocated based on each step number is displayed as shown in the right side of  FIG. 3B . When a predetermined time (for example, 2 seconds) elapses after the torque value is displayed, a display is switched to the step number. 
         [0065]    Accordingly, the operator presses the switch  26  short until a desired step number (torque value) is displayed. A desired setting value is displayed, and the setting value is stored in the EEPROM  82 . As a method of storing the setting value, the setting value can be stored automatically if the switch  26  is not operated for a predetermined time or longer after the desired value is displayed, or the setting value can be stored by performing a predetermined operation with the switch  26 . With the above-described operations, the operator can set a desired torque value. Note that, when the tightening operation is completed and the battery  24  is detached temporarily, and the like, the setting values may be reset, or the existing setting values may be retained. 
         [0066]    With this configuration, because setting values can be changed, a wide range of tightening torque can be obtained with the electronic pulse driver  1 . Further, because PC  10  is required to change the setting values and the like, inadvertent changes of the setting values and the like can be suppressed. 
         [0067]    Next, a second embodiment of the invention will be described while referring to  FIGS. 12 through 21 . In the second embodiment, a power tool that can change an operation mode in a standalone manner without using an external device will be described. An electronic pulse driver  101  as the power tool according to the second embodiment is the same as the electronic pulse driver  1  according to the first embodiment, except that the power tool does not have an external connection terminal as shown in  FIG. 12 , and that the power tool has a different display section  125  as shown in  FIGS. 14 and 21 . Hence, duplicating descriptions will be omitted. Further, in the first embodiment, the switch  26  is used only for selection and determination of a prescribed value. In the second embodiment, however, the switch  26  is also used for changing setting values including a maximum value, a minimum value, and the number of steps. As shown in  FIG. 14 , the display section  125  includes two sets of seven-segment display section  125 A and a lighting display section  125 B having MIN, MAX, and CLT indications. 
         [0068]    Steps of setting an operation mode with the electronic pulse driver  101  will be described while referring to the flowchart of the arithmetic section  78  in  FIG. 13  and the display section  125 . The electronic pulse driver  101  has a “setting mode” and a “manipulation mode”. First, at the beginning, the switch  26  is pressed long for a predetermined time or longer (for example, 3 seconds or longer), so that an operation mode of the switch  26  is switched from the manipulation mode to the setting mode. Then, the flowchart shown in  FIG. 13  is started. Here, the “manipulation mode” is a mode of switching and determining a set plurality of prescribed values as described in the first embodiment, and the “setting mode” is a mode of changing the plurality of prescribed values (tightening torque). The “manipulation mode” serves as a first operation mode of the present invention, and the “setting mode” serves as a second operation mode of the present invention. 
         [0069]    In this state, the CPU proceeds to S 101 , and first starts the setting of a minimum value. The above-described long press for 3 seconds or longer starts the setting mode and, at the same time, as shown in  FIG. 15 , “MIN” lights up in the lighting display section  125 B and “1.0” blinks in the seven-segment display section  125 A. The CPU determines whether the switch  26  is pressed in S 102 . If not (S 102 : No), then the CPU waits for a press of the switch  26 . If so (S 102 : Yes), then the CPU determines whether the switch  26  has been pressed long for a period longer than or equal to 1 second and shorter than 3 seconds (S 103 ). If the switch  26  is pressed short in this state in S 102  (S 103 : No), then in S 104  the indication of the seven-segment display section  125 A increases by 0.1 Nm (torque increment process). Then the routine returns to S 102 . That is, each time the switch  26  is pressed short, the displayed value increases by 0.1 Nm. As shown in  FIG. 16 , after the indication of the seven-segment display section  125 A reaches a predetermined minimum value, for example, 2.0 Nm, the operator presses long the switch  26  for the period. If it is determined that the switch  26  has been pressed long for the period (S 103 : Yes), the CPU temporarily stores the minimum value in the EEPROM  82  and ends setting of the minimum value (S 105 ). That is, a torque value is changed with a short press of the switch  26 , and the torque value is determined (set) with a long press. 
         [0070]    Subsequently, the CPU proceeds to S 106  and starts the setting of a maximum value. After the switch  26  is pressed long for 1 second or longer at the step of determining the minimum value (S 103 ), as shown in  FIG. 17 , “MAX” lights up in the lighting display section  125 B in a state where the minimum value is displayed, and the minimum value (for example, 2.0 Nm) displayed in the seven-segment display section  125 A blinks. The CPU determines whether the switch  26  is pressed in S 107 . If not (S 107 : No), then the CPU waits for a press of the switch  26 . If so (S 107 : Yes), then the CPU determines whether the switch  26  has been pressed long for the period longer than or equal to 1 second and shorter than 3 seconds (S 108 ). If the switch  26  is pressed short in this state in S 107  (S 108 : No), then in S 109  the indication of the seven-segment display section  125 A increases by 0.1 Nm (torque increment process) from 2.0 Nm which has been displayed as the minimum value. Then the routine returns to S 107 . That is, each time the switch  26  is pressed short, the displayed value increases by 0.1 Nm. After an indication of the seven-segment display section  125 A reaches a predetermined maximum value (for example, 3.0 Nm) as shown in  FIG. 18 , the operator presses long the switch  26  for the period. If it is determined that the switch  26  has been pressed long for the period (S 108 : Yes), then in S 110  the CPU temporarily stores the maximum value in the EEPROM  82  and ends setting of the maximum value. Here, because the maximum value is larger than the minimum value, an operation of setting the maximum value can be performed smoothly by displaying the minimum value in the seven-segment display section  125 A as an initial value at the time of setting the maximum value. 
         [0071]    Subsequently, the CPU proceeds to S 111  and starts the setting of the number of steps. After the switch  26  is pressed long for 1 second or longer at the step of determining the maximum value (S 108 ), as shown in  FIG. 19 , “CLT” lights up in the lighting display section  125 B, and “1” blinks in the seven-segment display section  125 A. The CPU determines whether the switch  26  is pressed in S 112 . If not (S 112 : No), then the CPU waits for a press of the switch  26 . If so (S 112 : Yes), then the CPU determines whether the switch  26  has been pressed long for the period longer than or equal to 1 second and shorter than 3 seconds (S 113 ). If the switch  26  is pressed short in this state in S 112  (S 113 : No), then in S 114  the number of steps displayed in the seven-segment display section  125 A increases by one (step increment process). Then the routine returns to S 112 . That is, each time the switch  26  is pressed short, the displayed step increases by one. After an indication of the seven-segment display section  125 A reaches a predetermined number of steps (for example, 5) as shown in  FIG. 20 , the operator presses long the switch  26  for the period. If it is determined that the switch  26  has been pressed long for the period (S 113 : Yes), then in S 115  the CPU temporarily stores the number of steps in the EEPROM  82  and ends setting of the number of steps. 
         [0072]    Next, the CPU proceeds to S 116  and performs a review of the setting values. After the switch  26  is pressed long for 1 second or longer at the step of determining the number of steps (S 113 ), a setting-value review mode is started. Specifically, as shown in  FIG. 21 , “MIN”, “MAX”, and “CLT” light up repeatedly in this order at a predetermined time interval (for example, 0.5 second) in the lighting display section  125 B, and the seven-segment display section  125 A displays a setting value corresponding to an indication that lights up in the lighting display section  125 B. In this state, the CPU proceeds to S 117  and determines whether the switch  26  has been pressed. If so (S 117 : Yes), the CPU proceeds to S 118 . If not (S 117 : No), the CPU waits until the switch  26  is pressed. In S 118 , it is determined whether the switch  26  has been pressed long. If the switch  26  has been pressed for a period of shorter than 1 second (S 118 : Yes), the CPU proceeds to S 119  and stores in the EEPROM  82  the minimum value (2.0 Nm), the maximum value (3.0 Nm), and the number of steps (5), and ends the setting mode. On the other hand, if the switch  26  has been pressed long for a period of longer than or equal to 1 second (S 118 : No), the CPU returns to S 101  and redoes the settings. Note that, at the time when the number of steps is set in S 115 , each value may be fixed and end the setting mode. Anytime the switch  26  has been pressed 3 seconds or longer, the routine may be return to S 101 . 
         [0073]    Because the setting range of tightening torque can be changed in both of the first embodiment and the second embodiment, a wide range of tightening torque can be dealt with by a single power tool. In particular, in the first embodiment, setting of an electronic pulse driver which is an example of a power tool is performed with a PC which is an example of an external device. Thus, an unintentional change of the setting values by an operator can be suppressed. Further, because an external device is not required in the second embodiment, the setting values can be changed easily and, when necessary, the setting values can be changed easily. 
         [0074]    With this configuration, because a range of prescribed values affecting operations of the motor or the number of steps can be set arbitrarily, a wide range of operations can be performed with a single power tool. Further, prescribed values affecting operations of the motor can be changed on the power tool itself, facilitating changes of the prescribed values or the like. 
         [0075]    With this configuration, because a maximum value, a minimum value and a plurality of prescribed values can be changed, a wide range of tightening torque can be obtained with a single power tool. Further, because the setting values and the like can be changed on the power tool itself, changes of the setting values and the like become easier. 
         [0076]    While the power tool and the operation-mode change system of the power tool according to the invention have been described in detail with reference to the above aspects thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the claims. 
         [0077]    For example, in the second embodiment, because settings are performed only with the power tool, there is a possibility that settings cannot be performed well when the remaining amount of the battery is low. Thus, it may be so configured that a battery remaining-amount detecting circuit is provided in the control section for detecting the remaining amount of the battery, and that settings are prohibited based on a detection result of the battery remaining-amount detecting circuit 
         [0078]    Further, in the above-described embodiment, a PC which is a general-purpose product is described as an example of an external device. However, the external device is not limited to a PC, but may be a special device for changing the operation mode and the setting values. Further, in the second embodiment, both of the manipulation mode and the change mode are implemented with the switch  26 . However, the method is not limited to this, but a special operating section may be provided for each of the manipulation mode and the change mode. 
         [0079]    Further, in the above-described embodiment, an electronic pulse driver is described as an example of a power tool. However, the power tool is not limited to this, but may be a tool that rotates an end bit with a motor, for example, a driver drill. 
         [0080]    Further, the use is applicable for various works such as tightening of distribution boards, assembling of electronic appliances, assembling of automobiles, and the like. 
         [0081]    Further, the power tool of the second embodiment may be configured to be connectable to an external device like the first embodiment. With this configuration, an operation mode can be changed with each of the power tool itself and the external device.