JP2012045679A - Automatic screw fastening machine - Google Patents

Abstract

The present invention provides an automatic screw tightening machine that realizes screw tightening by high speed low torque drive and low speed high torque drive with one motor, and that can fasten a screw with high speed and high accuracy.
A high-speed and low-torque transmission system that is directly connected to a rotary drive source and transmits high-speed and low-torque drive to an output shaft, and a low-speed and high-torque drive that is connected to the rotary drive source via a speed reducer. In the temporary fastening stage, the rotational drive is transmitted to the output shaft 9 by the high speed and low torque transmission system, while in the final fastening stage, the rotational drive is transmitted to the output shaft 9 by the low speed and high torque transmission system. The clutch means 7 and 11 for switching these transmission systems according to the rotational load acting on the output shaft 9 and the rotary drive source 3 rotate at a high speed in the temporary fastening stage, while the rotary drive source 3 is temporarily attached in the stage before the final fastening stage. And a control unit that controls to rotate at a lower speed and at a higher speed than the latter stage of the final tightening stage.
[Selection] Figure 1

Description

  The present invention relates to an automatic screw tightening machine that performs final tightening with low speed and high torque after temporarily tightening a screw component with high speed and low torque.

  Conventionally, as a screw tightening machine belonging to the above technical field, there is one shown in Patent Document 1. This screw tightening machine includes a high-speed low-torque motor and a low-speed high-torque motor. In the temporary tightening stage, the drive of the high-speed low-torque motor is transmitted to the driver bit. Then, when the screw component is seated and its impact torque is detected, the driving is switched to the driving of the low-speed high-torque motor, and the process proceeds to the final tightening stage to complete the screw tightening. According to this screw tightening machine, although the screw tightening time is shortened, the apparatus is provided with two motors, so that not only the apparatus becomes large but also there is a problem in terms of cost.

  Therefore, as a conventional screw tightening machine that solves the above problem, there is one disclosed in Patent Document 2. The motor used in this screw tightening machine can be driven at high speed and low torque and at low speed and high torque, and can be driven forward and reverse. Further, the drive transmission mechanism of the screw tightener is composed of two systems: a drive path in which an input is output via a speed reducer and a drive path in which an input is output without passing through a speed reducer. . By arranging a plurality of one-way clutches on the transmission path, high-speed and low-torque torque is output without the speed reducer during forward rotation of the motor, while output is routed through the speed reducer during reverse rotation of the motor. Low speed high torque drive is configured to be transmitted. With this configuration, it is possible to realize temporary fastening with high speed and low torque and permanent fastening with low speed and high torque, even though the motor has a single configuration.

JP 2008-006560 A JP 2008-114303 A

  However, in the screw tightening machine shown in Patent Document 2, high-speed low-torque driving and high-speed low-torque driving are switched using a one-way clutch and by forward / reverse driving of the motor. For this reason, when the screw tightening is completed, the output shaft cannot be reversed, and the biting between the driver bit and the screw component cannot be released. Further, in the final tightening stage, if the rotation speed is increased, the tightening accuracy is deteriorated, so that the rotation speed cannot be increased, and the time required to complete the tightening is long.

  The automatic screw tightening machine according to the present invention is configured in view of the above problems, and is a high-speed low-torque transmission system that is directly connected to a rotary drive source and transmits high-speed low-torque drive to an output shaft, and is decelerated to the rotary drive source. Low-speed high-torque transmission system that transmits low-speed, high-torque drive to the output shaft through the means, and low-speed high-torque transmission system in the final tightening stage, while the rotational drive is transmitted to the output shaft by the high-speed, low-torque transmission system Clutch means for switching the transmission system according to the rotational load acting on the output shaft so as to transmit the rotational drive to the output shaft, and the rotational drive source rotates at a high speed in the temporary fastening stage, while the rotational drive source in the stage before the final fastening stage. And a control unit that controls the motor to rotate at a lower speed than the temporary fastening stage and at a higher speed than the latter stage of the final fastening stage.

  In the automatic screw tightening machine of the present invention, the clutch means is operated according to the rotational load acting on the output shaft without using the one-way clutch, and the rotational drive by the high speed low torque transmission system and the low speed high torque transmission system is switched. Yes. As a result, the operation of reversing the output shaft at the completion of the final tightening can be performed, so that the biting of the screw can be released. In addition, the time required to complete the screw tightening can be shortened by controlling the rotation before the final tightening stage at a higher speed than after the final tightening stage.

It is sectional drawing which shows the automatic screwing machine of this invention. It is the figure which gave thin coating to the high-speed low torque transmission system. It is the figure which gave thin coating to the low-speed high torque transmission system. It is a graph which shows drive control of the automatic screwing machine of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes an automatic screw tightener, which has a servo motor 3 (hereinafter simply referred to as a motor) that is an example of a rotational drive source fixed to a housing 2. A drive pulley 4 is attached to the drive shaft 3a of the motor 3 so as to be integrally rotatable. The rotation of the motor 3 is transmitted to the driven pulley 5 by the endless belt 6 wound around the drive pulley 4.

  The thinly coated portion shown in FIG. 2 shows a high-speed low-torque transmission system that forms a torque transmission system in a temporary fastening stage until the screw is seated, and the configuration will be described. A tooth clutch 7, which is an example of a clutch means, is attached to the driven pulley 5 so as to rotate as the driven pulley 5 rotates. The tooth clutch 7 transmits torque by meshing teeth, and is configured to switch connection / disconnection based on a command from a control unit, which will be described in detail later. The tooth clutch 7 supports the first transmission shaft 8 so as to be rotatable integrally therewith. For this reason, the transmission of the rotational drive to the first transmission shaft is switched according to the connection / disconnection by the tooth clutch 7. Further, an output shaft 9 having a driver bit (not shown) at the tip is connected to the tip of the first transmission shaft 8. The drive pulley 4, the driven pulley 5, the tooth clutch 7, the first transmission shaft 8, and the output shaft 9 form a high-speed and low-torque transmission system, and the output shaft 9 is directly connected to the motor 3 to output low torque. It is comprised so that.

  3 shows a low-speed high-torque transmission system that forms a torque transmission system in the final tightening stage from the screw seating to the completion of screw tightening, and its configuration will be described. A second transmission shaft 10 is rotatably supported by the driven pulley 5 integrally therewith. A wave gear device 11 is connected to the peripheral surface of the distal end portion of the second transmission shaft 10. The wave gear device 11 is an example of a speed reduction unit, and decelerates the rotation of the second transmission shaft 10 to output a high torque. The wave gear device 11 is configured to rotate in reverse on the output side due to its characteristics, and takes out the motion of the flex spline 11a that rotates in reverse as an output. An electromagnetic clutch 12, which is an example of clutch means, is attached to the flexspline 11a so as to be integrally rotatable. The electromagnetic clutch 12 is connected / disconnected by an electromagnetic force generated by energizing the coil, and is configured to switch connection / disconnection based on a command from a control unit described later in detail. Further, the output shaft 9 is rotatably supported on the output side of the electromagnetic clutch 12. With this configuration, transmission of rotational drive to the output shaft 9 is switched according to connection / disconnection by the electromagnetic clutch 12. The drive pulley 3, the driven pulley 4, the second transmission shaft 10, the wave gear device 11, the electromagnetic clutch 12, and the output shaft 9 form a low-speed high-torque transmission system. Is output.

  By the way, as described above, the wave gear device 11 outputs torque that is reversely rotated from the time of input. Therefore, at the time of tightening by the low speed and high torque transmission system, the output shaft 9 is controlled to rotate in the forward direction by driving the motor 3 in the reverse direction.

  The tooth clutch 7 and the electromagnetic clutch 12 are connected and disconnected based on a command signal issued from a control unit (not shown). First, in the temporary fastening stage (stage until the screw seat surface is seated), the screw is fastened by the high-speed low torque transmission system. At this time, a connection signal is issued to the tooth clutch 7, while a disconnection signal is issued to the electromagnetic clutch 12. For this reason, the second transmission shaft 10 rotates as the driven clutch 5 rotates and the wave gear device 11 is driven, but since it is disconnected by the electromagnetic clutch 12, it is configured to drive at a low torque when the motor is directly connected. ing.

  Subsequently, in the final tightening stage (after the screw seating until the screw tightening is completed), the screw is tightened by the low speed and high torque transmission system. Switching from the temporary fastening stage to the final fastening stage is performed based on an increase in the load current value due to the impact torque generated in the screw seating. When this impact torque is detected, the control unit issues a disconnection signal to the tooth clutch 7, while issuing a connection signal to the electromagnetic clutch 12 to switch to the low speed high torque transmission system. For this reason, it is decelerated by the wave gear device 11 and is configured to drive at a high torque.

  A strain-generating tube 13 is disposed around the output shaft 9 and is fixed to the housing 2 so as to be twisted according to the rotational resistance acting on the output shaft 9. Further, a strain gauge is affixed to the circumferential surface of the strain generating tube 13, thereby constituting a torque sensor. Therefore, the reference value for completion of screw tightening may be a value detected by the torque sensor instead of the load current value described above.

  As shown in FIG. 4, in the temporary fastening stage, the control unit issues a drive command signal to the motor 3 with a higher rotational speed than in the final fastening stage. On the other hand, at the final tightening stage, the rotational speed is different between the preceding stage and the subsequent stage, and a drive trial signal having a higher rotational speed than the latter stage of the final tightening stage is issued to the motor 3 at the previous stage. That is, the middle speed rotation is performed before the final tightening, and the low speed rotation is performed after the final tightening. Thereby, in the stage before the final tightening stage, it is possible to reduce the backlash inside the main body after switching between the tooth clutch 7 and the electromagnetic clutch 12, or the time until the clutches 7 and 12 are normally engaged. In addition, since the medium-speed rotation is switched to the low-speed rotation before the completion of the screw tightening, the high-precision tightening can be performed at the low-speed rotation without deteriorating the tightening accuracy when the screw tightening is completed.

  According to the automatic screw tightening machine 1 of the present invention, when screw tightening is completed, the motor 3 is temporarily reversely driven as necessary to reverse the driver bit so as to release the biting between the driver bit and the screw drive hole. Rotate. Thereby, the biting is released and the driver bit can be removed from the screw driving hole.

  Further, the high speed torque low torque transmission system and the low speed high torque transmission system are switched by the tooth clutch 7 or the electromagnetic clutch 12. Therefore, it is possible to provide the automatic screw tightening machine 1 that has a small number of parts and is compact and economical.

Furthermore, in the conventional configuration in which the switching from the high-speed torque low-torque driving to the low-speed high-torque driving is performed by rotating the motor 3 in the reverse direction and engaging the one-way clutch, the one-way clutch is changed at the time of switching due to the influence of the rotational inertia. There is a possibility that the load applied to is large and deteriorates. On the other hand, according to the screw tightening machine 1 of the present invention, the configuration without using the one-way clutch is excellent in durability. Therefore, in the temporary fastening stage, it is not necessary to reduce the rotational speed before the completion of temporary fastening in order to reduce the influence of the rotational inertia. Accordingly, even in the temporary tightening stage, it is possible to fasten the screw at a high rotational speed without considering the rotational inertia of the motor 3 from the start to the completion of the temporary tightening, so that high-speed screw tightening can be realized.

DESCRIPTION OF SYMBOLS 1 Automatic screwing machine 2 Housing 3 Motor 3a Drive shaft 4 Drive pulley 5 Driven pulley 6 Endless belt 7 Tooth clutch 8 First transmission shaft 9 Output shaft 10 Second transmission shaft 11 Wave gear device 11a Flex spline 12 Electromagnetic clutch 13 Strain tube

Claims (1)

A high-speed, low-torque transmission system that is directly connected to the rotary drive source and transmits high-speed, low-torque drive to the output shaft;
A low-speed high-torque transmission system that transmits low-speed high-torque drive to the output shaft via a speed reduction means to the rotational drive source;
In the temporary tightening stage, the rotational drive is transmitted to the output shaft by the high speed and low torque transmission system, while in the final tightening stage, the rotational load acts on the output shaft so that the rotational drive is transmitted to the output shaft by the low speed and high torque transmission system. Clutch means for switching according to
A control unit that controls the rotational drive source to rotate at a high speed in the temporary tightening stage, and to rotate the rotational drive source at a lower speed than the temporary tightening stage and at a higher speed than the subsequent stage of the final tightening stage. Automatic screw tightening machine.