JP2009172734A - Screw parts fastening machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw part fastening machine for fastening a screw part by controlling a thrust applied to a driver bit.
The present invention relates to a driver base 6 that moves up and down by a lifting mechanism 2 that operates in response to the rotation of a lifting motor 5, and a driver bit 3a that rotates in response to the rotation of a tightening motor 8 held on the driver base 6. And a load detector 7 for detecting the load applied to the driver bit 3a, and the thrust applied to the driver bit is controlled by controlling the speed of the elevating motor 5 from the detected value of the load detector 7. ing. Therefore, the thrust applied to the driver bit 3a can be detected to control the speed of the elevating motor 5, and the descending speed of the driver bit 3a is controlled to set the thrust added to the driver bit 3a to an arbitrary value. be able to. Moreover, even if the mass of the driver bit or the like is changed, it is not necessary to change the set thrust value, and the screw fastening operation can be continued.

[Selection] Figure 1

Description

  The present invention relates to a screw part fastening machine that controls a thrust applied from a driver bit to a screw part when fastening a screw part such as a screw or a bolt to fasten the screw part.

  Recently, when tightening a screw to a workpiece, the strength of the female screw is reduced if the workpiece is made of resin or thin plate. Therefore, in order to prevent damage to the female screw, self-drilling screws, tapping screws, standard screws, etc. A screw component fastening machine has been developed that can obtain an appropriate thrust according to the type and each tightening stage in the tightening process. As shown in FIG. 3, the screw component fastening machine 1 has a driver tool 3 having a driver bit 3 a, and the driver tool 3 is lifted and lowered by a lift mechanism 2 that operates by receiving the rotation of a lift motor 5. The driver bit 3a is rotated at a set speed in response to a speed command value from the tool controller 4f. The screw component fastening machine 1 is configured to limit the output torque of the lifting motor 5 by sending a speed command value from the control unit 4d to the servo controller 4e at each tightening stage of a predetermined tightening pattern.

Japanese Patent No. 2894198

  In this screw component fastening machine 1, by restricting the output torque of the elevating motor 5, the descending speed of the driver bit 3a can be suppressed, and the thrust applied to the driver bit 3a can be suppressed. The damage is considerably eliminated. However, the operator cannot actually grasp the thrust value added to the driver bit 3a, and there are disadvantages such as hindering the investigation of the cause when the tightening failure occurs. Further, since the total mass of the driver tool 3 and the lifting / lowering unit 21 affects the thrust of the driver bit 3a, every time the driver bit 3a is replaced due to the damage of the driver bit 3a, etc. The output torque of the motor 5 has to be reset, resulting in a disadvantage that the device is unsuitable for field work.

  For the purpose of solving the above problems, the present invention provides a driver base that moves up and down by an elevating mechanism that operates in response to the rotation of a lifting motor, and a driver bit that rotates in response to the rotation of a tightening motor held by the driver base. In the provided screw parts fastening machine, a load detection unit that detects the load applied to the driver bit is provided on the driver stand, and the thrust of the driver bit is controlled by controlling the speed of the lifting motor from the detection value of this load detection unit Is configured to do.

  The tightening motor may have a torque control function.

  According to the present invention, since the thrust applied to the driver bit can be detected, it is possible to control the descending speed of the driver bit by controlling the speed of the lifting motor so that the thrust becomes a preset thrust value. Therefore, the operator can grasp the actual thrust value added to the driver bit, and there is an advantage that the cause can be easily determined when a tightening failure occurs. In addition, even if the mass of the driver base including the driver bit is changed by exchanging the driver bit or the like, it is not necessary to consider the weight of the driver base, so even if the thrust value is set at each tightening stage, it is changed Therefore, it is possible to continue the fastening operation of the threaded parts, and to provide an optimum device for the field work.

  Further, when the tightening motor has a torque control function, it is possible to perform tightening by controlling the tightening torque and thrust, and therefore, it is possible to perform the optimal tightening for the workpiece material and the tightening pattern.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a screw part fastening machine that fastens a screw of an example of a screw part, a lifting mechanism 2 fixed to a base (not shown), and a driver tool 3 that moves up and down by the operation of the lifting mechanism 2. And a control device 4 for controlling them. The elevating mechanism 2 has an upper plate 2a, a lower plate 2b, and an upright plate 2c, and an elevating AC servo motor (hereinafter referred to as elevating motor) 5 is attached to the upper plate 2a with its drive shaft 5a facing downward. It has been. A ball screw shaft 2e is connected to the drive shaft 5a via a coupling 2d, and the lower end thereof is rotatably held by the lower plate 2b. Further, the ball screw shaft 2e is guided with a nut member 2f that is screwed into the screw portion, and a driver base 6 is attached to the nut member 2f. Moreover, the nut member 2f is guided by a linear rail 2g attached to the upright plate 2c, and is configured such that the driver base 6 moves up and down as the ball screw shaft 2e rotates.

  The raising / lowering motor 5 is provided with a pulse encoder 5b for outputting a pulse signal corresponding to the rotation of the drive shaft 5a. The pulse signal is sent to a control unit 4d to be described later, and the raising / lowering motor 5 is rotated. The speed and the lifting / lowering amount of the nut member 2f are feedback-controlled.

  The driver tool 3 includes a tightening AC servo motor (hereinafter referred to as a tightening motor) 8 as an example of a rotational drive source attached to the driver base 6 via a load detection unit 7. The shaft 8a is configured to pass through a driver tube 6 through a strain tube (not shown), which will be described later, and project downward. The drive shaft 8a is directly connected to the driver bit 3a via the coupling 3b, and is configured such that a force accompanying the lowering of the driver base 6, that is, a thrust is transmitted to the tip of the driver bit 3a. The tightening motor 8 is provided with a pulse encoder 8b that outputs a pulse signal according to the rotation of the drive shaft 8a, as with the lifting motor 5, and the pulse signal is sent to the control unit 4d for tightening. The rotational speed of the motor 8 is controlled.

  The load detector includes a strain-generating tube that can hold the tightening motor 8, and a strain gauge (not shown) that detects strain generated in the strain-generating tube when the driver bit 3a receives an upward reaction force during tightening. It is made up of. The detected value of the strain gauge is sent to the control unit 4d, and the thrust added to the driver bit 3a is detected from the detected value. In addition, it replaces with the load detection part which consists of a strain tube and a strain gauge, and the load detection part of the structure provided with the piezoelectric element (not shown) can also be utilized.

  The tip of the driver bit 3a is formed in a cross-shaped cross section and is magnetized so that the metal screw 9 can be held. A chuck unit (not shown) for holding the screw 9 is arranged in the moving path of the driver bit 3a, and the screw 9 held on the chuck unit by the non-magnetized driver bit 3a is fastened to the workpiece 10. Also good. The tightening motor 8 may not be an AC servo motor, but may be a DC motor (not shown) having a torque control function.

  The control device 4 includes a control unit 4d to which a storage unit 4a, an operation unit 4b, and a display unit 4c are connected, a servo controller 4e that controls the lifting motor 5, and a tool controller 4f that controls the tightening motor 8. Each controller is configured to be driven by various information and command signals sent from the control unit 4d. The storage unit 4a stores various information such as a final tightening torque value, a speed command value of the tightening motor 8 at each tightening stage, and an initial speed command value and a thrust value of the lifting motor 5 at each tightening stage. It is configured. The operation unit 4b is configured to output various command signals such as a tightening pattern signal for selecting one from a tightening pattern such as a standard tightening pattern, a tapping tightening pattern, an additional tightening pattern, a self-drilling tightening pattern, and a tightening start signal. Has been. Further, the operation unit 4b is configured to be able to select a setting mode and a work mode, and is configured to be able to input and store various information in the setting mode. In addition, the display unit 4c displays the final tightening torque value in the setting mode, the speed command value of the tightening motor 8 at each tightening stage according to the selected tightening pattern, the initial speed command value, the thrust value of the lifting motor 5, and the like. In the work mode, various information such as a torque waveform obtained from the load current of the tightening motor is displayed.

  The control unit 4d is configured to store the information in the storage unit 4a when various types of information are input from the operation unit 4b in the setting mode. Further, when a tightening start signal is sent from the operation unit 4b in the work mode, the control unit 4d receives the initial speed command value of the lifting motor 5 at each tightening stage according to the tightening pattern instructed by the operation unit 4b. The set thrust value at each tightening stage, the final tightening torque value, and the speed command value of the tightening motor at each tightening stage are called from the storage unit 4a and temporarily stored, while each tightening stage is temporarily stored. The initial speed command value is configured to be sent to the servo controller 4e. Further, the control unit 4d is configured to calculate a speed command value from which the set thrust value is obtained at each tightening stage from the detection value of the load detection unit 7, and to send the calculated speed command value to the servo controller 4e. In addition, when the control unit receives a tightening completion signal from the tool controller 4f, it sends a reverse rotation command value after stopping the lifting motor 5 to the servo controller 4e. On the other hand, when the nut member 2f returns to its upper limit, Configured to send. At the same time, when receiving a tightening start signal, the control unit 4d is configured to send a final tightening torque value to the tool controller 4f, and to send a speed command value to the tool controller 4f at each tightening stage.

  When the servo controller 4e receives an initial speed command value or a calculated speed command value sent from the control unit 4d, the servo controller 4e is configured to perform feedback control so as to rotate the elevating motor 5 at a speed corresponding thereto. When the servo controller 4e receives a reverse rotation command value from the control unit 4d, the servo controller 4e temporarily stops the lifting motor 5 and then reverses it at a low speed. On the other hand, the servo controller 4e stops the lifting motor 5 when the stop command signal is received. It is configured.

  When the tool controller 4f receives the speed command value at each tightening stage, the tool controller 4f receives the pulse signal from the pulse encoder 8b and tightens at the final tightening torque value while controlling the rotational speed of the tightening motor 8, and reaches the final tightening torque. Thereafter, the tightening motor 8 is further rotated by a predetermined rotation angle to complete the tightening, and a tightening completion signal is output to the control unit. The tool controller 4f is configured to detect each tightening step of the tightening pattern from the load current of the tightening motor 8 and send a detection signal of these tightening steps to the control unit 4d.

  In the screw component fastening machine, in the setting mode, one tightening pattern is selected from the standard screw tightening pattern, the tapping tightening pattern, the additional tightening pattern, the self-drilling tightening pattern, and the like in the operation unit 4b, and the tightening pattern signal is transmitted to the control unit 4d. Sent to. In accordance with the tightening pattern signal, the final tightening torque, the speed command value of the tightening motor 8 at each tightening stage, the initial speed command value and the thrust value of the lifting motor 5 at each tightening stage are set by the operation unit 4b. Is stored in the storage unit 4a. For example, in the self-drilling tightening pattern, as shown in FIG. 2, in the stage before tightening until the tip of the screw 9 comes into contact with the workpiece 10, a high-speed speed command value corresponding to the lifting motor 5 is used. Is set to a low speed command value. In the drilling stage in which a pilot hole (not shown) is opened in the workpiece 10, a large speed command value and a large set thrust value are provided for the lifting motor 5, and a high speed command value is provided for the tightening motor 8. Is set. Further, in the tapping stage until the screw 9 is seated, the tightening motor 8 has a set thrust value that does not destroy the female screw to the lifting motor 5 and does not cause the driver bit 3a to come out of the head of the screw 9. On the other hand, a medium speed command value is set. In addition, at the completion of tightening after the screw 9 is seated, a sufficient thrust value is set so that the driver bit 3a does not come out due to impact at the time of seating, and an ultra-low speed command value is set for the tightening motor 8. At the same time, the rotation angle from the time when the final tightening torque value is reached is set.

  Thereafter, when a tightening start signal is output from the operation unit 4b with the operation mode selected by the operation unit 4b, a tightening pattern signal corresponding to the tightening pattern instructed by the operation unit 4b is sent to the control unit 4d. . Various information is called according to the tightening pattern signal, and these are temporarily stored. At the same time, a high-speed initial speed command value corresponding to the pre-tightening stage is sent to the servo controller 4e, and the lifting motor 5 rotates at high speed. Begin to. Therefore, the ball screw shaft 2e also rotates integrally, and the nut member 2f descends along the linear rail 2g. As the nut member 2f is lowered, the driver tool 3 is lowered, and at the same time, the final tightening torque value and the speed command value at the stage before tightening are also sent to the tool controller 4f, and the tightening motor 8 rotates at a predetermined speed. In the meantime, any tightening stage is detected from the load current of the tightening motor 8, and the detection signal is sent to the control unit 4d. When the drilling stage is detected from the load current of the tightening motor, the initial speed command value of the lifting motor 5 corresponding to this is sent to the servo controller 4e. At the same time, the reaction force generated in the driver bit 3 a when the screw 9 at the tip of the driver bit 3 a is screwed into the prepared hole of the work 10 is taken out as a detection value of the load detection unit 7. The speed command value of the lifting motor 5 is calculated as the calculated speed command value so that the detected value matches the set thrust value in the drilling stage, and feedback control is performed. Therefore, the thrust applied to the driver bit 3a that descends with the rotation of the elevating motor 5 is held at an optimum value in the drilling stage. Further, when the tapping stage and the tightening completion stage are detected from the load current of the tightening motor 8, the lifting motor 5 and the tightening motor 8 are similarly driven, and the optimum thrust is obtained at the optimum rotational speed at the fastening stage. In addition to the driver bit 3a, the screw 9 at the tip can be fastened to the workpiece 10.

  Therefore, at each tightening stage in the tightening process, the lifting motor 5 can always rotate at a speed at which the thrust applied to the driver bit 3a becomes the set thrust value, and the set thrust value corresponding to the tightening pattern is added to the screw 9 As a result, the optimum thrust is applied at each tightening stage. In addition, since the load detecting unit 7 detects the thrust applied at each tightening stage, the operator can grasp the actual thrust value added to the driver bit 3a, and when the tightening failure occurs, the cause can be easily investigated. Become. In addition, since it is not necessary to consider the influence of the driver tool 3 and the weight of the nut member 2f, even if the mass of the elevating part including the driver bit 3a is changed by replacing the driver bit 3a or the like, it is set at each tightening stage The screw 9 can be continuously tightened without changing the thrust. Further, when the tightening is performed with a thrust smaller than the weight of the elevating unit, the speed command value can be dealt with by only sending the speed command value in the reverse direction.

  In this embodiment, the self-drilling tightening pattern has been described. However, in any other tightening pattern, the same effect can be obtained by omitting a part of the self-drilling tightening pattern tightening step. The tool controller 4f is tightened by the torque-angle method, but can be tightened only by the torque method. Further, although each tightening stage is detected from the load current of the tightening motor, the drilling stage and the tightening completion stage can also be detected by a position detection sensor (not shown).

It is a block diagram which shows the structure of this invention. FIG. 6 is a waveform diagram for explaining a set thrust value, a speed command value of a tightening motor, and a load current characteristic at each tightening stage of the self-drilling tightening pattern according to the present invention. It is a block diagram which shows the structure of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw component fastening machine 2 Elevating mechanism 2a Upper board 2b Lower board 2c Upright board
2d Coupling 2e Ball screw shaft 2f Nut member 2g Linear rail 3 Driver tool 3a Driver bit 3b Coupling 4 Controller 4a Storage unit 4b Operation unit 4c Display unit 4d Control unit 4e Servo controller 4f Tool controller 5 Elevating AC servo motor 5a Drive shaft 5b Pulse encoder 6 Driver stand
7 Load detector 8 AC servomotor for tightening 8a Drive shaft 8b Pulse encoder 9 Screw 10 Workpiece

21 Elevator

Claims (2)

In a screw component fastening machine comprising a driver base that moves up and down by a lifting mechanism that operates in response to the rotation of a lifting motor, and a driver bit that rotates in response to the rotation of a tightening motor held by the driver base.
A load detector that detects the load applied to the driver bit is provided on the driver base, and the thrust applied to the driver bit is controlled by controlling the speed of the lifting motor from the detected value of the load detector. A screw part fastening machine that is characterized.   The screw component fastening machine according to claim 1, wherein the tightening motor has a torque control function.

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