JP2010260136A - Automatic screwing machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic screwing machine preventing the breakage of a workpiece such as an electronic component caused by a leakage current from a motor and static electricity. <P>SOLUTION: The automatic screwing machine 1 includes a housing 2; the motor 3 supported by the housing 2; a transmission shaft 6 which is connected to a drive shaft 3a of the motor 3 and rotatively transmits the drive of the motor 3, and accommodated in the housing 2; and a bit 7 connected to the transmission shaft 6. The motor 3 is ground connected. Insulation members 4 and 5 insulate the motor 3 and the housing 2, and the drive shaft 3a of the motor 3 and the transmission shaft 6, respectively. The housing 2 and the motor 3 are made to electrically communicate with each other through a resistor 8. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a leakage current generated by driving a motor and an automatic screw tightening machine for preventing electrical destruction of a workpiece due to static electricity generated as a negative effect of taking measures against the leakage current.

  Conventionally, in an inverter-driven automatic screw tightening machine, a harmonic current is generated from an installed motor. When a screw is tightened to a workpiece such as an electronic component that handles a weak electrical signal using such an automatic screw tightening machine, harmonic current flows to the workpiece through the motor drive shaft and screw, and the electronic circuit or There was a problem of destroying electronic components. In view of such a problem, a noise filter shown in Patent Document 1 (Japanese Patent Laid-Open No. 2005-130575) is attached to an inverter-driven automatic screw tightening machine. According to this noise filter, the harmonic current is suppressed, so that the above-described problems can be reduced.

  However, the noise filter is expensive, and the automatic screwing machine including the noise filter has a problem in cost. Therefore, as an automatic screw tightening machine that realizes a countermeasure for electric leakage into the screw tightening machine main body at a low cost, there is one disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2004-249424). In this automatic screwing machine, the motor and the screwing machine main body are separated, and the screwing machine main body is covered with an insulating member. Therefore, the harmonic current or the like never flows into the screw tightener main body, and the above-described problem does not occur.

JP 2005-130575 A JP 2004-249424 A

  However, in the configuration in which the screw tightener main body is covered with an insulator, static electricity is generated by the rotation of the transmission shaft and the like housed in the main body. If this static electricity is charged around the transmission shaft and the screw is attracted to the tip of the bit and then tightened, the static electricity will flow to the object to be fastened through the driver bit and the screw. Will cause.

  The present invention was created in view of the above problems, and provides an automatic screw tightening machine that prevents the destruction of a workpiece such as an electronic component due to leakage current from a motor and static electricity without a noise filter. Objective.

  The present invention has been created in view of the above problems, and is connected to a housing, a motor supported by the housing, and a drive shaft of the motor to transmit rotation of the motor, and to the housing. In an automatic screw tightening machine including a transmission shaft to be accommodated and a bit connected to the transmission shaft, the motor is grounded, and the motor and the housing, and the motor drive shaft and the transmission shaft are insulated by an insulating member. In addition, the housing and the motor are electrically connected through a resistor.

  According to the present invention, since the motor and the housing, and the drive shaft and the transmission shaft of the motor are insulated, the leakage current from the motor does not flow to the workpiece through the transmission shaft, thereby preventing electrical destruction of the workpiece. it can. Moreover, as an adverse effect of electrically insulating the motor, static electricity is generated inside the housing due to the rotation of the transmission shaft. However, since the motor and the housing are electrically connected via a resistor, Static electricity is discharged to ground through an earth connected to the motor. Therefore, since static electricity does not flow into the fastened object, it is possible to prevent electrical destruction of the fastened object. On the other hand, static electricity is generated by the rotation of the drive shaft of the motor, and this may flow to the transmission shaft side depending on the state of the potential on the housing side. However, since the static electricity flows through the resistor, it becomes an appropriate value, and does not flow in a state where the workpiece is electrically destroyed, and the workpiece is not electrically destroyed.

It is a figure which shows the structure of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes an automatic screw tightening machine, which has a housing 2 and an inverter motor 3 supported by the housing 2. The housing 2 and the inverter motor 2 are insulated by a resin-made first insulating member 4 so that a leakage current (harmonic current) generated by driving the inverter motor 3 does not flow into the housing 2.

  The inverter 3 has a drive shaft 3a, and a transmission shaft 6 is connected to the drive shaft 3a via a second insulating member 5 so as to be integrally rotatable. The transmission shaft 6 is housed in the housing 2 and is supported by a bearing 9 attached to the housing 2. Further, a bit 7 having a tip shape that can be connected to the cross drive hole of the screw is connected to the tip of the transmission shaft 6 so as to be rotatable integrally with the transmission shaft 6. As described above, the configuration in which the drive shaft 3a and the rotary shaft 6 are connected via the resin insulating member 5 prevents the leakage current generated by driving the inverter motor 3 from flowing into the transmission shaft 6 and the bit 7. ing.

  The inverter motor 3 has a power cord (not shown) with a built-in ground wire and is grounded to a ground (GND). The inverter motor 3 and the housing 2 are electrically connected via a resistor 8. The resistance value of the resistor 8 is preferably set from 1 KΩ to 5 MΩ.

  In the automatic screw tightening machine 1 configured as described above, since the inverter motor 3 is electrically insulated by the first insulating member 4 and the second insulating member 5, the leakage current generated from the inverter motor 3 is not affected by the housing 2. Alternatively, it does not flow to the bit 7 through the transmission shaft 6. Therefore, even if a screw is tightened to a work such as an electronic component, the leakage current does not flow to the work but is discharged to the outside through the ground wire, thus preventing the work from being electrically destroyed.

  Further, as an adverse effect of the configuration in which the inverter motor 3 is electrically insulated, before the screw held by the tip of the bit 7 is engaged with the work, that is, in the state where the automatic screw tightener 1 is lifted, the inverter Static electricity generated by these rotations is accumulated in the drive shaft 3 a or the transmission shaft 6 of the motor 3. However, due to the configuration in which the housing 2 and the inverter motor 3 are electrically connected, static electricity accumulated around the transmission shaft 6 is discharged to the outside through the inverter motor 3 and the ground wire.

  On the other hand, static electricity accumulated around the drive shaft 3a of the inverter motor 3 is often discharged to the outside through a ground wire. However, depending on the situation of the potential on the housing 2 side, static electricity accumulated around the inverter motor 3 may flow into the housing 2 and flow to the work through the bit 7. However, since the inverter motor 3 and the housing 2 are electrically connected via the resistor 8, the static electricity becomes an appropriate value due to the action of the resistor 8 and stably flows to the housing 2. It is designed not to flow in a state where it is electrically destroyed.

As described above, in the automatic screw tightening machine 1 of the present invention, it is possible to prevent the leakage current generated from the inverter motor 3, the static electricity generated as a detrimental effect of this leakage current countermeasure, and the electrical breakdown of the workpiece due to both of them. is there.

DESCRIPTION OF SYMBOLS 1 Automatic screwing machine 2 Housing 3 Inverter motor 3a Drive shaft 4 First insulating member 5 Second insulating member 6 Transmission shaft 7 Bit 8 Resistor 9 Bearing

Claims (1)

A housing, a motor supported by the housing, a rotation shaft that is coupled to the drive shaft of the motor to transmit rotation of the motor, a transmission shaft that is housed in the housing, and a bit that is coupled to the transmission shaft In the automatic screw tightening machine provided,
The motor is grounded, the motor and the housing, and the drive shaft and transmission shaft of the motor are insulated by an insulating member, and the housing and the motor are electrically connected through a resistor. Automatic screw tightening machine.

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