JP5201530B2 - Electric tool - Google Patents

Description

  The present invention relates to an electric tool that is rotationally driven by a motor and tightens a fastening member such as a bolt using an intermittent striking force generated by hydraulic pressure.

  As an impact type tool for tightening screws, bolts, etc., an impact type tool using an oil pulse unit that generates an impact force using hydraulic pressure is known. A tool using an oil pulse unit has a feature that operation noise is low because there is no collision between metals. For example, Patent Document 1 discloses an impact type tool using an oil pulse unit. An air motor is used as power for driving the oil pulse unit, and an output shaft of the air motor is directly connected to the oil pulse unit. When a trigger switch for operating the impact type tool is pulled, air is supplied to the air motor. Then, it is detected whether the tightening has been performed with the specified tightening torque by using the output from the torque sensor or the rotation detection unit, and when the specified tightening value is reached, the rotation of the air motor is stopped.

JP-A-6-91552

  In recent years, brushless DC motors have been used as motors for portable electric tools. A brushless DC motor has the advantages of being able to control rotation with high accuracy, maintenance-free, long life, low loss, and increased workload. In order to drive a brushless DC motor in a portable electric tool, a detachable secondary battery is often used, but the voltage of the secondary battery is at most about 24 V, and a bolt with a large diameter is tightened. In the case of work requiring a high tightening torque, the tightening torque may be insufficient when using a secondary battery. Therefore, it is conceivable to use a commercial power source such as AC100V instead of a secondary battery as the power source. In this case, a rectifier circuit that prepares a DC voltage of 24V or more and allows a large current to achieve a high tightening torque. It is difficult to arrange the rectifier circuit inside the impact type tool from the viewpoint of size. In addition, when using a commercial power source, it was necessary to consider electrical insulation.

  The present invention has been made in view of the above background, and an object of the present invention is to provide a power tool having a sufficient tightening torque, which is reduced in size and weight.

  Another object of the present invention is to provide a power tool using a commercial power source having good insulation.

  Still another object of the present invention is to provide an electric tool that detects a tightening torque and can determine in a tool body whether a specified tightening has been performed.

  Of the inventions disclosed in the present application, typical features will be described as follows.

According to one aspect of the present invention, a brushless DC motor, a rotation control circuit that controls rotation of the motor, a housing that houses the motor, an output shaft that is driven by the motor and on which a tip tool is mounted , and a housing An electric tool having a case attached to the front of the case and having a case for holding an output shaft , and a motor and a rotation control circuit including a sensor attached to the inside of the case and a microcomputer for controlling tightening of the tip tool using the output of the sensor The motor system power source used as the power source of the system is a non-insulated DC power source rectified from the commercial power source , the motor and the rotation control circuit are covered with a housing made of an insulating material, and the control system power source serving as the power source for the torque detection means and the microcomputer is characterized in that it is a DC power source that is isolated is rectified from a commercial power source. The motor system power supply is an uninsulated direct current rectified from, for example, a commercial power supply of AC 100V, and the voltage is 140V, for example. The control system power supply is, for example, a low-voltage direct current rectified from a commercial power supply of AC 100V, and the voltage is 12V. The electric tool has an impact unit driven by a motor, an output shaft is coupled to the shaft of the impact unit, and a sensor is torque detection means for detecting the generation of impact torque on the output shaft.

  According to another feature of the present invention, the rectifier circuit for the motor system power supply and the rectifier circuit for the control system power supply are arranged in a power supply box provided separately outside the housing of the electric tool.

  According to still another feature of the present invention, the motor system power supply is a direct current obtained by rectifying a commercial power supply by a full-wave rectifying and smoothing circuit. The control system power supply is a direct current rectified from a commercial power supply by an AC / DC converter. A trigger switch for starting rotation of the motor is connected to the rotation control circuit, and the trigger switch is connected to a motor system power supply.

  According to still another aspect of the present invention, the rotation control circuit includes a motor position detection circuit, an inverter circuit, and a motor control microcomputer that controls the motor position detection circuit, and the motor control microcomputer includes: a tightening control microcomputer; Communication is performed through an insulated communication path. Then, the tightening control microcomputer determines whether proper tightening has been performed using the output from the torque detection means. When the tightening is completed, a motor stop signal is sent to the motor control microcomputer via the communication path. Configured to send.

According to the invention of claim 1, in the electric tool using the brushless DC motor, the motor system power source serving as a power source for the motor and the rotation control circuit is covered with a housing made of an insulating material using a high voltage non-insulated power source , Since the control system power supply that serves as the power supply for the sensor and microcomputer uses an insulated low-voltage power supply, the output can be increased while the motor is relatively small, and an electric tool with sufficient tightening torque can be realized. . Further, since the motor and the rotation control circuit are housed in a housing made of an insulating material, there is no problem with insulation, and safety against electric leakage can be secured. Furthermore, since the motor system power supply is a non-insulated DC rectified from the commercial power supply and the control system power supply is an isolated DC rectified from the commercial power supply, two types of power supply can be easily created from one commercial power supply. Therefore, the electric tool having this configuration can be realized with a simple configuration at a low cost.

According to a second aspect of the present invention, there is provided an impact unit that is driven by a motor, the output shaft is connected to a shaft of the impact unit, and the sensor detects a generation of impact torque on the output shaft. Therefore, an impact tool that can be accurately tightened with a sufficient tightening torque can be realized .

  According to the invention of claim 3, the rectifier circuit for the motor system power supply and the rectifier circuit for the control system power supply are arranged in a power supply box separately provided outside the main body housing of the electric tool. The impact tool body can be made small, and a reduction in size and weight can be achieved.

  According to a fourth aspect of the present invention, the rotation control circuit includes a motor position detection circuit, an inverter circuit, and a motor control microcomputer for controlling them, and the motor control microcomputer is insulated from the tightening control microcomputer. Since the communication is performed through the communication path, it is possible to detect the tightening torque, determine in the tool body whether the tightening has been performed as specified, and stop the rotation of the motor.

  According to the invention of claim 5, since the motor system power supply is a direct current obtained by rectifying a commercial power supply by a full-wave rectifying and smoothing circuit, a rectifier circuit can be realized with a simple configuration, and a transformer is not used. Smaller and lighter can be realized.

  According to the invention of claim 6, since the control system power supply is a direct current rectified from a commercial power supply by an AC / DC converter, an insulated low voltage direct current voltage can be easily created using a known power supply circuit. can do.

  According to the seventh aspect of the present invention, the rotation control circuit is connected to the trigger switch for starting the rotation of the motor, and this trigger switch is connected to the motor system power supply. The insulation state of the system power supply can be maintained.

  According to the eighth aspect of the present invention, the tightening control microcomputer determines whether proper tightening has been performed using the output from the torque detection means, and when the tightening is completed, the microcomputer is connected to the motor control microcomputer. Since the stop signal of the motor is sent via the bolt, the bolt, nut, screw and the like can be tightened with high accuracy by the set appropriate tightening torque.

  The above and other objects and novel features of the present invention will become apparent from the following description and drawings.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the present specification, the impact type tool 1 is used as an example of the electric power tool, and the vertical and front / rear directions of the impact type tool 1 are described as the directions shown in FIG. FIG. 1 is a diagram showing an entire impact type tool and a power supply box 30 connected thereto according to an embodiment of the present invention, and the impact type tool 1 is a cross-sectional view.

  The impact type tool 1 drives the motor 3 using the electric power supplied from the power supply box 30 through the cable 2, drives the oil pulse unit 4 by the motor 3, and outputs to the output shaft 5 connected to the oil pulse unit 4. By applying the rotational force and the striking force, the rotational striking force is transmitted continuously or intermittently to a tip tool (not shown) such as a hexagon socket to perform operations such as nut tightening and bolt tightening.

  The power supplied by the cable 2 is, for example, DC 140V, and this DC power is generated from a commercial power supply 29 such as AC 100V in a power supply box 30 provided outside the tool body. In the power supply box 30, a DC 12 V power supply that is further insulated for the control system power supply is generated from the commercial power supply 29 and supplied to the impact tool 1 via the cable 2. Although not shown, the cable 2 includes a power cord for DC 140V and a power cord for DC 12V inside, and the power cord and the impact tool 1 and / or the power box 30 have connectors (not shown). It may be configured to be detachable by use, or may be configured to be detachable.

  The motor 3 is a brushless DC motor including a rotor 3b having a permanent magnet on the inner peripheral side and a stator 3a having a winding wound around an iron core on the outer peripheral side, and includes two bearings 10a and 10b. Thus, the rotary shaft 20 is fixed and accommodated in the cylindrical body 6a of the housing. In the housing, the body portion 6a, the grip portion 6b, and the circuit board housing portion 6c are integrally manufactured from plastic or the like as an insulator. A drive circuit board 7b for driving the motor 3 is disposed on the rear side of the motor 3, and an inverter circuit composed of semiconductor elements such as FETs and a rotational position of the rotor 3b are detected on the circuit board. A rotational position detecting element 42 for mounting is mounted. As the rotational position detection element 42, for example, a Hall element or a Hall IC can be used. A cooling fan 17 for cooling the motor 3 and the oil pulse unit 4 is provided at the rearmost end inside the body portion 6a of the housing.

  A trigger switch 8 is disposed in the vicinity of the attachment portion of the grip portion 6b extending downward at a substantially right angle from the body portion 6a of the housing, and is proportional to the amount of the trigger switch 8 pulled by the switch circuit board 14 provided immediately therebelow. The signal is transmitted to the motor control board 7a. A motor control board 7a and a control board 9 are provided on the circuit board housing part 6c below the grip part 6b. The control substrate 9 is provided with a plurality of light emitting diodes (LEDs) 18, and the light from the light emitting diodes 18 is arranged so that it can be identified from the outside through a transmission window of a housing (not shown) or through a through hole.

  As the oil pulse unit 4 built in the body 6a of the housing, a known unit can be used. The oil pulse unit 4 is mainly synchronized with the drive portion that rotates in synchronization with the motor 3 and the output shaft 5 to which the tip tool is attached. Thus, the output part is composed of two parts that rotate. The drive portion that rotates in synchronization with the motor 3 includes a liner plate 23 that is directly connected to the rotary shaft 20 of the motor 3 and a liner 22 that has a substantially cylindrical outer diameter that is fixed so as to extend forward on the outer peripheral side thereof. . The output portion that rotates in synchronization with the output shaft 5 includes a main shaft 24 and a blade (not shown) that is attached to a groove formed 180 degrees apart on the outer peripheral side of the main shaft 24 via a spring. Is done. The main shaft 24 is penetrated by the integrally molded liner 22 and is held so as to be able to rotate in a closed space formed by the liner 22 and the liner plate 23, and oil for generating torque is generated in the closed space. (Hydraulic oil) is filled.

  When the trigger switch 8 is pulled to start the motor 3, the rotational force of the motor 3 is transmitted to the oil pulse unit 4. When the oil pulse unit 4 is filled with oil and no load is applied to the output shaft 5 or when the load is small, the output shaft 5 is nearly rotated by the motor 3 only by the resistance of the oil. Rotate synchronously. When a strong load is applied to the output shaft 5, the rotation of the output shaft 5 and the main shaft 24 stops, and only the liner 22 on the outer peripheral side of the oil pulse unit 4 continues to rotate. The oil pressure rapidly rises to generate a shock pulse, and the main shaft 24 is rotated by a strong spire-like torque, and a large tightening torque is transmitted to the output shaft 5. Thereafter, the same striking operation is repeated several times, and the fastening target is tightened with the set torque.

  The output shaft 5 is held at the rear end by a bearing 10 c and at the front by a metal bearing 16 in a case 15. The bearing 10c of the present embodiment is a ball bearing, but other bearings such as a needle bearing can be used.

On the inner peripheral side of the case 15 , the diameter of the output shaft 5 is thin, and a strain gauge 12 as a torque detection sensor is attached to the thinned portion. On the front side of the location where the strain gauge 12 is attached, the diameter of the output shaft 5 is thick, and the input transformer 11a for supplying voltage to the strain gauge 12 at that location and the output from the strain gauge 12 are transmitted. An output transformer 11b is provided. The input transformer 11a and the output transformer 11b include coils disposed on the inner peripheral side and the outer peripheral side, respectively. The inner peripheral side coil is fixed to the output shaft 5, and the outer peripheral side coil is fixed to the case 15. Input / output voltages to the input transformer 11a and the output transformer 11b are transmitted to the control board 9 through the connector 11c. Each part mentioned above attached to the output shaft 5 is integrated in the cylindrical case 15, and the case 15 is attached to the trunk | drum 6a of a housing. In addition, a wiring cover 19 for covering connection wiring and the like is provided at the lower portion of the case 15.

Here, the mounting structure of the strain gauge 12 will be described with reference to FIG. FIG. 2 is a cross-sectional view taken along a line AA in FIG. The space on the inner circumferential side of the rotating element 3 a is the output shaft 5 located. Here, as can be understood from FIG. 2, only the position where the strain gauge 12 is attached to the cylindrical output shaft 5 has a small diameter and a substantially square cross section. And the strain gauge 12 was provided in each of the four planes located in the outer periphery of a cross section. Thereby, the detection accuracy of torque can be improved.

  Next, the configuration and operation of the drive control system of the motor 3 will be described with reference to FIG. FIG. 3 is a block diagram showing a circuit configuration of the drive control system of the motor 3. In the present embodiment, the motor 3 is a three-phase brushless DC motor. This brushless DC motor is a so-called inner rotor type, and includes a rotor (rotor) 3b including a plurality of sets of permanent magnets (magnets) including N and S poles, and a star-connected three-phase motor. In order to detect the rotational position of the stator 3a (stator) composed of the stator windings U, V, W and the rotor 3b, three rotations arranged at predetermined intervals in the circumferential direction, for example, every 60 ° angle. A position detection element 42 is provided. Based on the position detection signals from these rotational position detection elements 42, the energization direction and time to the stator windings U, V, W are controlled, and the motor 3 rotates.

  The drive circuit board 7b is configured to include an inverter circuit including six switching elements Q1 to Q6 such as FET (Field Effect Transistor) connected in a three-phase bridge form. The gates of the six switching elements Q1 to Q6 that are bridge-connected are connected to the rotation control circuit 51, and the drains or sources of the six switching elements Q1 to Q6 are star-connected stator windings U. , V, W. As a result, the six switching elements Q1 to Q6 perform a switching operation according to the switching element drive signals (drive signals H1 to H6) input from the rotation control circuit 51, and the 140V DC applied to the inverter circuit is three-phased. (U phase, V phase and W phase) Electric power is supplied to the stator windings U, V and W as voltages Vu, Vv and Vw.

  Of the switching element drive signals (three-phase signals) for driving the gates of the six switching elements Q1 to Q6, the three negative power supply side switching elements Q4, Q5, Q6 are converted into pulse width modulation signals (PWM signals) H4, The operation amount (stroke) of the trigger switch 8 is detected by the applied voltage setting circuit 49 and a setting signal based on this operation amount is output to the first microcomputer 50 for motor control. The microcomputer 50 adjusts the amount of power supplied to the motor 3 by changing the pulse width (duty ratio) of a PWM (Pulse Width Modulation) signal, and controls the start / stop of the motor 3 and the rotation speed.

  Here, the PWM signal is supplied to any one of the positive power supply side switching elements Q1 to Q3 or the negative power supply side switching elements Q4 to Q6 of the inverter circuit, and the switching elements Q1 to Q3 or the switching elements Q4 to Q6 are switched at high speed. As a result, the power supplied to each stator winding U, V, W is controlled by 140V DC. In this embodiment, since the PWM signal is supplied to the negative power supply side switching elements Q4 to Q6, the electric power supplied to the stator windings U, V, W by controlling the pulse width of the PWM signal. Can be adjusted to control the rotation speed of the motor 3. As described above, in the present embodiment, the direct current supplied to the switching elements Q1 to Q6 is 140 V, which is 5 to 15 times higher than the case where the secondary battery is used. Can be made extremely high.

  Although not shown, the microcomputer 50 has a central processing unit (CPU) for outputting a drive signal based on the processing program and data, a ROM for storing the processing program and control data, and a temporary storage for data. It includes a RAM, a timer having a clock function, and the like. Although details will be described later, 140 V direct current that is not insulated is supplied directly or under reduced pressure to the circuit shown in FIG.

  Next, the overall configuration of the circuit of the impact tool 1 according to the embodiment of the present invention will be described with reference to FIG. In the impact type tool 1 according to the present embodiment, the motor system power source is a power source for the motor 3 and the motor control circuit, and the control system power source for other control devices is divided into two systems. The control system power supply is configured to be driven by an insulated power supply.

  Two direct currents are supplied from the power supply box 30 provided outside to the entire circuit 1A incorporated in the impact type tool via the cable 2. One is a 140 V DC that is not insulated from the AC power supply 29 and a 12 V DC that is insulated from the AC power supply 29. The 140 V direct current is generated by the full-wave rectifying / smoothing circuit 31 in the power supply box 30. The full-wave rectifying / smoothing circuit 31 is, for example, a combination of a rectifying circuit in which four rectifying elements are connected in a bridge shape and a smoothing circuit using a capacitor. In this embodiment, a transformer is not used. Insulated state. This is because a large current flows through the motor 3, so that a huge transformer is required if it is to be isolated from the AC power supply 29, and it is difficult to downsize the power supply box 30 to the extent that there is no practical problem. Because. Further, since the supply destination of 140V DC is only the circuit portion shown in FIG. 3, particularly the motor 3 and the motor control circuit, insulation measures are relatively easy, so a power supply that is not insulated as 140V DC is used. It was. The 12V direct current is generated by an AC / DC converter 32 arranged in the power supply box 30. In this embodiment, the AC / DC converter 32 uses a known device whose output is insulated.

  In the circuit 1A, 140V direct current is supplied to the drive circuit board 7b of the motor 3. This is the power supply to the inverter circuit of FIG. Drive power is supplied to a stator winding of a predetermined motor 3 by an inverter circuit mounted on the drive circuit board 7b. The 140V direct current is also supplied to the 18V constant voltage circuit 53. The 18V constant voltage circuit 53 is not insulated and generates a DC voltage of 18V from a DC power supply of 140V, and may be constituted by a known chopper circuit or a known constant voltage combining a Zener diode and a transistor. You may comprise with a circuit. Next, the non-insulated 18V direct current output from the 18V constant voltage circuit 53 is input to the second constant voltage circuit 52, and the second constant voltage circuit 52 operates the operation voltage Vcc for operating the microcomputer 50, for example, 5V DC and 3.3V DC are generated. Here, the two-stage configuration of the 18V constant voltage circuit 53 and the second constant voltage circuit 52 is for convenience of design, and if possible, an operating voltage for operating the microcomputer 50 directly from 140V DC. May be created. The reason why the signal for operating the microcomputer 50 is created not from the insulated 12V power supply but from the non-insulated 140V power supply is because the circuit connected to the microcomputer 50 is not insulated. This is because if the insulated 12V power supply is used here, the insulated state is lost. As is apparent from FIG. 4, the motor 3 and the motor control circuit are all driven using a non-insulated DC 140V.

  The insulated 12V DC power generated by the power supply box 30 is input to a portion other than the control circuit for the motor 3. First, the 12V DC power supply is input to the constant voltage circuit 64, where a voltage for operating the microcomputer 60, for example, 5V, 3.3V is generated and input to the microcomputer 60. Also. Input to ± 12 V power supply 71. The ± 12V power supply 71 generates a voltage of −12V in addition to + 12V. −12V is used for driving the strain gauge 12. Note that the power supply line from the ± 12 V power supply 71 to the strain gauge 12 is not shown.

  The 12 V direct current is also supplied to the cooling fan 17. The cooling fan 17 is ON / OFF controlled by the drive circuit 72 under the control of the microcomputer 60. Here, the reason why the cooling fan 17 is driven by the insulated 12 V direct current is that the microcomputer 60 for controlling the cooling fan 17 is driven by the insulated power source. In addition, if the cooling fan 17 is controlled by the microcomputer 50, the power source of the non-insulated constant voltage circuit 53 can be used. However, the cooling fan 17 is formed with an air inflow port, an air outflow port, and the like, and dust and dust may enter inside. In addition, since the mounting position of the cooling fan 17 is located at the rear end of the main body 6a of the housing 6, the cooling fan 17 is driven by an insulated power source in order to minimize the possibility of accidental touching. Is preferred.

The strain gauge 12, the oscillation signal from the oscillation circuit 70a of the torque detection circuit 70 is supplied through an input transformer 11a. Reference amplitude from oscillation circuit 70a at the same time is also sent to the microcomputer 60. This is because the microcomputer 60 cannot detect distortion from the torque waveform without inputting the reference amplitude. When tightening torque is generated by the oil pulse unit 4 on the output shaft 5, the resistance value of the strain gauge 12 changes, and the reference amplitude signal changed by the change in resistance value is transmitted to the detection circuit 70b via the output transformer 11b. It is detected. Since a signal for offset adjustment is sent from the microcomputer 60 to the detection circuit 70b, the detection signal corrected for offset is output to the microcomputer 60. The microcomputer 60 uses the output value of the strain gauge 12 to calculate how much torque value has been tightened (tightening torque).

  The first microcomputer 50 and the second microcomputer 60 are connected via a signal line to exchange data between them, but the signal line is connected via a photocoupler 65 in order to maintain the insulation relationship between the two. . Signals sent from the second microcomputer 60 to the first microcomputer 50 are a signal 68 for setting the rotational driving force of the motor 3 and an ON / OFF control signal 69 for turning off the rotation of the motor 3. The data sent from the first microcomputer 50 to the second microcomputer 60 is a signal 66 indicating whether or not the trigger 8 is turned on and an Acknowledge signal 67 for the signal 68 for setting the rotational driving force of the motor 3. Of course, the type of signal is not limited to this, and the exchange of other signals is arbitrary.

  Next, the operation at the time of bolt tightening using the impact type tool 1 of the present embodiment will be described. First, the operator operates an operation button (not shown) on the tool body to set a tightening torque value. The tightening torque setting means 62 recognizes the input torque value and outputs it to the microcomputer 60. When an operator pulls the trigger switch 8 after setting a bolt or the like on the tip tool and positioning it on the material to be fastened, the microcomputer 50 controls the motor 3 to rotate according to the drawn stroke. At this time, the microcomputer 60 may limit the rotation speed of the motor 3 according to the set tightening torque. For example, when the tightening torque is low, the microcomputer 60 corresponds to the microcomputer 50 with a low tightening torque. The maximum rotation number of the motor 3 is instructed. When the rotational speed of the motor 3 is limited as described above, the microcomputer 50 is instructed to rotate the motor 3 even if the stroke of the trigger switch 8 corresponds to a higher rotational speed. Control to be kept at.

  Next, the microcomputer 60 monitors the output of the strain gauge 12 to monitor whether the tightening has been performed with a predetermined tightening torque. If the microcomputer 60 determines that the tightening has been normally completed with the set tightening torque value, the microcomputer 60 sends a signal for turning off the motor 3 to the microcomputer 50 via the signal line 69. When the microcomputer 50 receives the instruction to turn off the motor, the microcomputer 50 stops the rotation of the motor 3 even though the trigger switch is turned on. The operator can recognize that the work is completed by the automatic stop of the motor 3.

  Although detailed description is omitted, the microcomputer 60 can exchange various data with an external device such as a host device via the transceiver 61. In this case, the transceiver 61 and the host device are connected using a cable (not shown). Moreover, you may use a well-known wireless communication system, without using a wired system.

FIG. 5 shows an electric circuit portion to which a non-insulated power supply is supplied in this embodiment, and 140 V direct current is supplied to a portion surrounded by a thick line. 140V DC is supplied to the motor 3, but in the case of a brushless DC motor, the stator 3a on which the coil is arranged and the rotor 3b attached to the rotary shaft 20 are separated from each other and are not in contact with each other. The insulation with respect to the shaft 20 can be kept good. Although 140V direct current is supplied also to the switch circuit board 14, since the trigger switch 8 is made of an insulating material such as plastic, there is no problem with the insulation at this portion. Further, since the motor control board 7a is housed in the housing 6 made of an insulating material, there is no problem with the insulation at this portion.

Note that the voltage of the non- insulated power supply is not limited to 140 V, and any voltage can be set as long as it is a high voltage that can be directly rectified from the commercial power supply, for example, a voltage that is ½ or more of the commercial power supply. The insulated power supply can be set to any number of voltages as long as it is a voltage that is significantly lower than the commercial power supply and has a low risk of electric shock, for example, a voltage of 24 V or less.

  As described above, according to the present embodiment, an impact type tool having a sufficient tightening torque can be realized while the output can be increased while the motor is relatively small.

  In addition, this invention is not limited to the above-mentioned form, A various change is possible within the range which does not deviate from the meaning. For example, although a non-insulated DC power supply is used as the motor system power supply, the present invention is not limited to non-insulation, and the present invention can be similarly applied by using an insulating DC power supply. Further, although an impact type tool is used as an example of the electric tool, the electric tool is not limited to the impact tool, and can be similarly applied to an electric tool using a brushless DC motor.

It is sectional drawing which shows the whole impact type tool which concerns on embodiment of this invention. It is sectional drawing of the AA part of FIG. 3 is a block diagram showing a circuit configuration of a drive control system of a motor 3. FIG. It is a figure showing the whole circuit composition of impact type tool 1 concerning the present invention. It is a figure which shows the electric circuit part to which a non-insulated power supply is supplied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Impact type tool 1A Overall circuit 2 (incorporated inside) 2 Cable 3 Motor 3a Motor stator 3b Motor rotor 4 Oil pulse unit 5 Output shaft 6a (Housing) Body part 6b (Housing) grip part
6c (Housing) Circuit board housing part 7 Motor system board 7a Motor control board 7b Drive circuit board 8 Trigger switch 9 Control board
10a, 10b, 10c Bearing
11a Input transformer 11b Output transformer 11c Connector 12 Strain gauge 14 Switch circuit board 15 Case 16 Metal bearing 17 Cooling fan 18 Light emitting diode 19 Wiring cover 20 Rotating shaft 22 Liner 23 Liner plate 24 Main shaft 29 Commercial power supply
30 Power supply box 31 Full wave rectification smoothing circuit 32 AC / DC converter
DESCRIPTION OF SYMBOLS 41 Operation part 42 Rotation position detection element 47 Inverter circuit 49 Applied voltage setting circuit 50 Microcomputer 51 Rotation control circuit 52 Constant voltage circuit 53 18V constant voltage circuit 60 Microcomputer 61 Transceiver 63 Angle detection circuit 64 Constant voltage circuit 65 Photocouplers 66, 67 , 68, 69 Signal line 70 Torque detection circuit 71 ± 12V power supply

Claims (8)

Brushless DC system motor, rotation control circuit for controlling rotation of the motor , housing for housing the motor , output shaft driven by the motor and mounted with a tip tool, and attached to the front of the housing In the electric tool having a case for holding the output shaft ,
A sensor attached to the inside of the case, and a microcomputer for controlling the tightening of the tip tool using the output of the sensor ,
The motor system power source serving as the power source for the motor and the rotation control circuit is a non-insulated DC power source rectified from a commercial power source, and the motor and the rotation control circuit are covered with the housing made of an insulating material,
Control system power supply as a power supply of the sensor and before Symbol microcomputer, power tool, which comprises using a DC power source that is isolated is rectified from a commercial power source. Having an impact unit driven by the motor , the output shaft being connected to a shaft of the impact unit;
The electric power tool according to claim 1, wherein the sensor is a torque detection unit that detects generation of an impact torque in the output shaft . A rectifier circuit for the motor system power supply, a rectifier circuit for the control system power supply according to claim 2, characterized in that arranged in front KIHA Ujingu outside the provided power supply box of Electric tool. The rotation control circuit includes a position detection circuit for the motor, an inverter circuit, and a motor control microcomputer that controls these,
4. The electric tool according to claim 3, wherein the motor control microcomputer communicates with the tightening control microcomputer through an insulated communication path.   The electric power tool according to claim 2, wherein the motor system power supply is a direct current obtained by rectifying a commercial power supply by a full-wave rectifying and smoothing circuit.   The power tool according to claim 2, wherein the control system power supply is a direct current rectified from a commercial power supply by an AC / DC converter.   The electric power tool according to claim 2, wherein a trigger switch for starting rotation of the motor is connected to the rotation control circuit, and the trigger switch is connected to the motor system power source. The tightening control microcomputer determines whether proper tightening has been performed using the output from the torque detection means. When the tightening is completed, the motor control microcomputer is connected to the motor control microcomputer via the communication path. The power tool according to claim 4 , wherein a stop signal is sent.

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