JP2016059978A - Screw fastening device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw fastening device that can add previously prepared thrust force to a driving bit, corresponding to a set fastening torque value, and calculate new thrust force in response to change in the set fastening torque value.SOLUTION: The screw fastening device comprises: a moving unit 2 that converts rotation of a servo motor 2d for movement into reciprocating movement, and moves a driving bit 3e, which is rotated by a screw fastening motor 3b, forward and backward; and a memorizing portion 9 that memorizes a plurality of reference thrust force Ds (B, Ts) to be added to the driving bit 3e for every reference torque value Ts, which is configured to calculate by linear interpolation thrust force Ft3 to a set final fastening torque value Tm, from two reference torque values Tsd2 and Tsu2 across the set final fastening torque value and reference thrust force Dsd2 and Dsu2 corresponding to the reference torque values respectively when the set final fastening torque value Tm is inputted. This configuration can prevent the driving bit 3e from separating from a driving hole 4a of the screw 4 and calculate optimal thrust force even if the set final fastening torque value Tm is changed.SELECTED DRAWING: Figure 1

Description

  The present invention adds a thrust prepared in advance corresponding to the set tightening torque value to the drive bit, and can calculate a new thrust according to the change even if the set tightening torque value is changed. The present invention relates to a fastening device.

  In general, when a member to be fastened is fastened to a mating member with a screw, a screw fastening device including a drive bit that is rotated by a screw fastening motor is used. In this screw tightening device, as shown in FIG. 12, when the head 54b of the screw 54 is seated on a member to be fastened (not shown), the rotational force Fr of the drive bit 53e is applied to the drive hole 54a of the screw 54. Acting on the inclined surface 54aa, a vertical component Fco (hereinafter, referred to as a cam-out force) of the upward force in the direction away from the drive hole 54a is generated in the drive bit 53e (particularly in the case of a cross hole). Therefore, in order to prevent the drive bit 53e from being detached from the drive hole 54a of the screw 54 by the camout force Fco, a screw tightening device described in Patent Document 1 in which a constant thrust is always applied to the drive bit 53e has been devised. ing.

  The screw tightening device includes a screw tightening unit including a drive bit, and a thrust applying unit that converts the rotation of the AC servo motor into a lifting operation and applies a thrust to the drive bit. According to this thrust applying means, an arbitrary thrust can be applied to the drive bit by adjusting the current value of the AC servo motor. Therefore, even if the set tightening torque value is changed, a new set tightening torque value is obtained. Accordingly, the thrust applied to the drive bit can be adjusted in advance. In such a screw tightening device, as shown in FIG. 13, it is also possible to apply high and low thrusts to the drive bit at the start of screw fitting at the temporary tightening process and the final tightening process. ing. The reason why the thrust is switched in this manner is that the camout force Fco is small when the torque Fr of the driving bit 53e, that is, the tightening torque value is low, and the camout force Fco is large when the tightening torque value is high. By switching the thrust, the drive bit can be prevented from being detached from the drive hole of the screw in all steps during tightening, and high-quality tightening can be performed.

Japanese Patent No. 3797598

  However, in this screw tightening device, since the camout force Fco generated in the drive bit in the temporary tightening process and the final tightening process is unknown at the start of screw fitting, it is applied to the drive bit according to the tightening torque value generated in each process. Although the thrust force to be set cannot be set and a difference in height is provided, a sufficiently large value obtained from each experience value is set. For this reason, the weight of products has been reduced as seen in recent electronic devices, and the mating member to which the component is attached has also been made thinner, so the deflection of the mating member due to the pressing of the drive bit has increased, leading to breakage. There is a risk that a problem such as an adverse effect on the operation of other parts attached to the mating member may occur.

  An object of the present invention is to solve the above-mentioned problem, by adding an optimal thrust to the drive bit corresponding to the set tightening torque value to prevent the drive bit from being detached from the screw drive hole and to set To provide a screw tightening device capable of calculating a new thrust corresponding to the changed set tightening torque value even if the tightening torque value is changed and the camout force is changed.

  In order to achieve the above object, the present invention provides a screw tightening unit having a drive bit that is rotated by a screw tightening motor and a rotation of the moving servo motor into a reciprocating movement. Screw tightening provided with a moving unit that moves forward and backward, a main control unit that controls the screw tightening motor and the moving servo motor, and a storage unit that stores a plurality of reference thrusts to be added to the drive bit for each reference torque value When a set tightening torque value at a predetermined tightening position is input to the main control unit, two reference torque values sandwiching the set tightening torque value and reference thrusts corresponding to each of these reference torque values And a thrust calculation unit that calculates the thrust for the set tightening torque value by linear interpolation.

  According to this configuration, an optimal thrust prepared in advance corresponding to the set tightening torque value can be applied to the drive bit in order to prevent the drive bit from being detached from the screw drive hole. Therefore, the mating member is not excessively pressed during tightening, and the mating member is not damaged, and the operation of other parts attached to the mating member is not adversely affected. Tightening work can be performed. Further, when the set tightening torque value at each tightening position is changed, the camout force generated in the drive bit changes, and it is necessary to change the thrust applied to the drive bit in order to cancel the camout force. Since the camout force is roughly proportional to the electromagnetic force generated in the screw tightening motor, that is, the current value flowing through the screw tightening motor, the thrust for suppressing the camout force is also the current value flowing through the screw tightening motor, in other words, the tightening torque value. It will be roughly proportional. Therefore, a reference torque value sandwiching the set tightening torque value and a reference thrust corresponding to these reference torque values are called, and a new thrust for the changed set tightening torque value is obtained from these reference torque values and the corresponding reference thrust. Can be calculated by linear interpolation. As a result, every time the set tightening torque value is changed at each tightening position, the optimum thrust corresponding to the set tightening torque value can be calculated, so that the operator can obtain the camout force generated in the drive bit prior to the tightening operation. Therefore, it is not necessary to measure troublesome and troublesome work at the work site, and an easy-to-use screw fastening device can be provided.

  In the present invention, it is desirable that the set tightening torque value is the final tightening torque value in order to prevent the drive bit from being detached from the drive hole of the screw during the tightening in the final tightening step.

  Further, in the present invention, it is desirable that the set tightening torque value is set to the set temporary tightening torque value in order to prevent the drive bit from being detached from the drive hole of the screw during the tightening in the temporary tightening step.

  According to the present invention described above, when tightening with a predetermined tightening torque value, a thrust prepared in advance corresponding to the set tightening torque value is added to the drive bit, and the drive bit is detached from the drive hole of the screw. Thus, it is possible to provide a screw tightening device that can calculate an optimum thrust for a new set tightening torque value at a predetermined tightening position.

The flowchart explaining operation | movement at the time of the setting mode of the main control part which comprises the control apparatus of the screw fastening apparatus which concerns on embodiment of this invention. Schematic explanatory drawing which shows the structure of the screw fastening apparatus which concerns on embodiment of this invention. The schematic diagram which shows the relationship between the rotational force Fr and the thrust Ft of the AC servomotor for a movement which concerns on embodiment of this invention. The flowchart explaining operation | movement at the time of the screw fastening mode of the main control part which comprises the control apparatus of the screw fastening apparatus which concerns on embodiment of this invention. The flowchart explaining the operation | movement at the time of the screw tightening mode of the AC servomotor drive part for a movement which concerns on embodiment of this invention. The flowchart explaining operation | movement of the motor drive part for screw fastening which concerns on embodiment of this invention. 4 is a reference torque value-reference thrust table according to the embodiment of the present invention. FIG. 4 is an explanatory diagram of signal transmission / reception among a main control unit, a moving AC servo motor driving unit, a screw tightening motor driving unit, and an operation unit according to the embodiment of the present invention. The signal waveform diagram explaining schematic operation | movement at the time of the screw tightening mode of the screw tightening apparatus which concerns on embodiment of this invention. Explanatory drawing of the linear interpolation which calculates the thrust with respect to the setting tightening torque value which concerns on embodiment of this invention. FIG. 10 is a signal waveform diagram illustrating a schematic operation in measuring thrust for canceling a cam-out force generated in a drive bit according to another embodiment of the present invention. Explanatory drawing explaining the state which the drive bit which concerns on a screw fastening apparatus acts on the inclined surface of the drive hole of a screw. Explanatory drawing explaining the addition state of the thrust in the conventional screw fastening process.

  Hereinafter, as an example of a screw tightening apparatus according to an embodiment of the present invention, a screw tightening apparatus used as a robot tip unit will be described with reference to the drawings. As shown in FIG. 2, the screw fastening device 1 includes a moving unit 2 having a base 2a fixed to a tip arm (not shown) of a robot. An upper bracket 2b and a lower bracket 2c are attached to the base 2a of the moving unit 2. A moving AC servomotor 2d (hereinafter referred to as a moving motor) is attached to the upper bracket 2b so that its drive shaft 2e is downward and penetrates the upper bracket 2b. The moving motor 2d is connected to a pulse encoder 2f so that the current position of the moving motor 2d can be detected. Further, a screw shaft 2h rotatably connected to the lower bracket 2c is connected to the drive shaft 2e of the moving motor 2d via a first connector 2g. The screw shaft 2h is screwed into a bearing base 2k slidably guided by a linear guide 2j extending over almost the entire length of the base 2a, and the rotation of the moving motor 2d is converted into a reciprocating movement of the bearing base 2k. It becomes the composition which is done.

  A driver base 3a is integrally attached to the bearing base 2k, and a screw tightening unit 3 is integrally fixed to the driver base 3a so as to be capable of moving forward and backward. The screw tightening unit 3 includes a screw tightening motor 3b attached to a driver base 3a, and a drive shaft 3c of the screw tightening motor 3b is configured to penetrate the driver base 3a. A drive bit 3e is connected to the drive shaft 3c of the screw tightening motor 3b via a second connector 3d so that the drive bit 3e rotates upon receiving the rotation of the screw tightening motor 3b. It is configured. Further, the drive bit 3e passes through a pair of chuck claws (not shown) that are releasably arranged on the moving path, and is fitted into the drive hole 4a of the screw 4 held by the drive bit 3e. Is screwed into a predetermined tightening position of the mating member 5 (see FIG. 9).

  When the position information and current value are supplied as command values, the moving motor 2d receives power supply so that the current position matches the position information and does not exceed the current value, and power supply is stopped later. When the command signal is received, the power supply is stopped and the brake is activated. The screw tightening motor 3b is analog-connected to the screw tightening motor drive unit 11 described later, and the load current of the screw tightening motor 3b is read by the screw tightening motor drive unit 11 as analog information and is AD. It is configured to be converted and memorized every moment.

  The screw tightening device 1 includes a control device 6 that controls operations of the moving unit 2 and the screw tightening unit 3. The control device 6 includes a main control unit 7 having a thrust calculation unit 12, an operation unit 8 that outputs various operation command signals, information necessary for screw tightening (hereinafter referred to as screw tightening information), and the screw tightening unit 3. And a storage unit 9 for storing information necessary for the movement (hereinafter referred to as movement information). The operation unit 8 has an operation screen having a screw tightening mode key 8a and a setting mode key 8b. When the screw tightening mode key 8a is touched, a screw tightening mode signal Sg1 (see FIG. 8) is sent to the main control unit. 7 is output.

  The operation unit 8 is configured to output a setting mode signal Sg21 (see FIG. 8) to the main control unit 7 when the setting mode key 8b is touched. Further, the operation screen of the operation unit 8 is configured to be reduced by a setting screen display command signal described later and switched to a setting screen (not shown). This setting screen includes the above-described screw tightening information, movement information, various control parameters (hereinafter referred to as control parameters) necessary for precise control of the moving motor 2d and the screw tightening motor 3b, and a tightening point number B (see FIG. 7), each input unit (not shown). The tightening point number B is provided corresponding to the tightening position of the mating member 5, and includes position information of the tightening position, that is, position information of the movement destination position of the tip unit of the robot, screw tightening information, movement information, and It is an index for calling control parameters. Further, the setting screen includes a numeric keypad (not shown) for inputting a value to each input unit, a cancel selection signal Sg23 (see FIG. 8) for canceling the value of each input unit, and a storage selection signal Sg24 for storing the value. And a save / cancel selection key (not shown) for outputting any one of them (see FIG. 8).

  The screw tightening information includes a temporary tightening set current value Is1 (initial value = 0) corresponding to a set temporary tightening torque value Tn (see FIG. 10A) as an example of a set tightening torque value, a temporary tightening rotation speed N1 ( 9), final tightening set current value Is2 (initial value = 0) corresponding to final tightening torque value Tm (see FIG. 10B), which is another example of set tightening torque value, and final tightening rotation speed N2. (Refer to FIG. 9) and information such as the type of the screw 4 (refer to FIG. 7). Further, as shown in FIG. 9, the movement information includes a standby position P0, a screw fitting thrust Ft1, a screw tightening start position P1, a temporary fastening thrust (a value lower than the screw fitting thrust, initial value = 0). Ft2, final tightening position P4, final tightening thrust (a value higher than the temporary tightening thrust, initial value = 0) Ft3 and return thrust Ft4 (see FIGS. 4, 8, and 9). Each of the thrusts is defined by a current value supplied to the moving motor 2d. As shown in FIG. 3, the reaction force of the rotational force Fr generated in the rotor (not shown) of the moving motor 2d by the current value is shown. The force Fc acts on the female thread slope 2ka of the bearing base 2k from the thread slope 2ha of the screw shaft 2h to obtain a forward thrust Ft.

  The storage unit 9 stores information input from the input screen for each tightening point number B (numbers 1, 2, 3, 4... Shown in FIG. 7) corresponding to the tightening position of the counterpart member 5. ing. Further, the storage unit 9 calculates thrusts Ft2 and Ft3 with respect to the set temporary fastening torque value Tn or the set final fastening torque value Tm (see FIG. 10) input from the setting screen. Reference thrusts Ds (B, Ts) and Es (B, Ts) (see FIG. 7) with respect to the reference torque value Ts are stored as a table for each screw. The reference thrusts Ds (B, Ts) and Es (B, Ts) cancel the camout force Fco generated when the drive bit 3e is driven with the set temporary tightening torque value Tn or the set final tightening torque value Tm. Has an optimal value.

  Further, as shown in FIG. 2, the control device 6 includes a moving AC servo motor driving unit 10 (hereinafter referred to as a moving motor driving unit), a screw tightening motor driving unit 11, and a screw supply device (not shown). A screw supply device drive unit 13 for controlling the operation of the above and an input / output unit 14 to which the above-described moving motor 2d and pulse encoder 2f are connected.

When the screw tightening mode signal Sg1 is output from the operation unit 8, that is, in the screw tightening mode, the main control unit 7 performs the following operations in steps S1 to S15 as shown in FIGS. Do.
S1) It is determined whether or not the screw tightening mode signal Sg1 from the operation unit 8 is input. When the screw tightening mode signal Sg1 is not input, the input waits while the screw tightening mode signal Sg1 is input. Then go to step S2.
S2) Call the screw tightening information (temporary tightening set current value Is1, temporary tightening rotation speed N1, final tightening set current value Is2, final tightening rotation speed N2) from the storage unit 9, and supply these to the screw tightening motor drive unit 11 To do.
S3) Storage information (standby position P0, screw fitting thrust Ft1, screw tightening start position, that is, temporary tightening start position P1, temporary tightening thrust Ft2, final tightening position P4, final tightening thrust Ft3, return thrust Ft4) 9, and these are supplied to the moving motor drive unit 10.
S4) An operation command signal Sg2 is output to the screw supply device driving unit 13.
S5) An operation command signal Sg3 is output to the moving motor drive unit 10.
S6) An operation command signal Sg4 is output to the screw tightening motor drive unit 11.
S7) It is determined whether or not the temporary tightening completion signal Sg5 is input from the screw tightening motor drive unit 11, and when the temporary tightening completion signal Sg5 is not input, the process waits for the temporary tightening completion signal Sg5 to be input. When the temporary fastening completion signal Sg5 is input, the process proceeds to step S8.
S8) A temporary fastening completion signal Sg5 is output to the moving motor drive unit.
S9) It is determined whether or not the final tightening completion signal Sg6 is input from the screw tightening motor drive unit 11, and when the final tightening completion signal Sg6 is input, the process jumps to step S14, while the final tightening completion signal Sg6 is If not, the process proceeds to step S10.
S10) It is determined whether or not the tightening NG signal Sg7 is input from the screw tightening motor drive unit 11. When the tightening NG signal Sg7 is not input, the process returns to step S9, while the tightening NG signal Sg7 is input. If it is, the process proceeds to step S11.
S11) A stop command signal Sg8 is output to the moving motor drive unit 10.
S12) The tightening NG display command signal Sg9 is output to the operation unit 8.
S13) It is determined whether or not the standby position return signal Sg10 is input from the moving motor drive unit 10. When the standby position return signal Sg10 is not input, the standby position return signal Sg10 is awaited while the standby position return signal Sg10 is input. Return to step S1.
S14) When the final tightening completion signal Sg6 is input in step S9, the stop command signal Sg8 is output to the moving motor drive unit 10.
S15) A tightening completion display command signal Sg11 is output to the operation unit 8, and the process returns to step S13.

The moving motor drive unit 10 performs the operations of the following steps SS1 to SS16 as shown in FIGS. 5, 8, and 9 in the screw tightening mode.
SS1) It is determined whether or not the movement motor drive unit operation command signal Sg3 is input. When the operation command signal Sg3 is input, the process proceeds to step SS2.
SS2) Call the screw tightening start position P1 and the screw fitting thrust Ft1.
SS3) A current value at which the screw tightening start position P1 and the screw fitting thrust Ft1 are obtained is supplied as a command value to the moving motor 2d.
SS4) It is determined whether or not the current position of the moving motor 2d has reached the screw tightening start position P1, and when the current position of the moving motor 2d has not reached the screw tightening start position P1, the screw tightening start position P1 is reached. On the other hand, when the current position of the moving motor 2d has reached the screw tightening start position P1, the process proceeds to Step SS5.
SS5) Call the final fastening position P4 and the temporary fastening thrust Ft2.
SS6) A current value from which the final fastening position P4 and the temporary fastening thrust Ft2 are obtained is supplied to the moving motor 2d as a command value.
SS7) It is determined whether or not the temporary fastening completion signal Sg5 is input from the main control unit 7, and when the temporary fastening completion signal Sg5 is not input, the input waits for the temporary fastening completion signal Sg5. Then go to Step SS8.
SS8) Call final fastening position P4 and final fastening thrust Ft3.
SS9) A current value at which the final fastening position P4 and the final fastening thrust Ft3 are obtained is supplied as a command value to the moving motor 2d.
SS10) It is determined whether or not the moving motor drive unit stop command signal Sg8 is input. When the stop command signal Sg8 is not input, the input is waited for, while the stop command signal Sg8 is input. Control goes to step SS11.
SS11) A power supply stop command signal Sg12 is output to the moving motor 2d.
SS12) The standby position P0 of the moving motor 2d and the return thrust Ft4 when returning to the standby position P0 are called.
SS13) The standby position P0 and the return thrust P0 are supplied as command values to the moving motor 2d.
SS14) It is determined whether or not the current position of the movement motor 2d has returned to the standby position P0, and when the current position of the movement motor 2d has not returned to the standby position P0, the return motor waits for the return. When the current position of 2d has returned to the standby position P0, the process proceeds to step SS15.
SS15) A standby position return signal Sg10 is output to the main controller 7.
SS16) End.

In the screw tightening mode, the screw tightening motor drive unit 11 performs the operations of the following steps ST1 to ST14 constituting the tightening torque control unit 11a as shown in FIGS.
ST1) It is determined whether or not the operation command signal Sg4 of the screw tightening motor drive unit 11 is input, and when the operation command signal Sg4 is not input, the input is awaited while the operation command signal Sg4 is input. When it is, the process proceeds to step ST2.
ST2) Call the temporary fastening rotation speed N1 and the temporary fastening set current value Is1.
ST3) A voltage corresponding to the temporary tightening speed N1 is supplied to the screw tightening motor 3b. (Activates the first timer 11b and the second timer 11c)
ST4) It is determined whether or not the load current of the screw tightening motor 3b has reached the temporary tightening set current value Is1, and when this has reached the temporary tightening set current value Is1, the routine jumps to step ST6, while the screw tightening motor When the load current 3b has not reached the temporary fastening set current value Is1, the process proceeds to step ST5.
ST5) It is determined whether or not the first timer 11b has timed up. When the first timer 11b has not timed up, the process returns to step ST4, while when the first timer 11b has timed up, the process jumps to step ST10. .
ST6) When the load current of the screw tightening motor 3b reaches the temporary tightening set current value Is1 in step ST4, a temporary tightening completion signal Sg5 is output to the main control unit 7, and the final tightening rotation speed N2 and final tightening setting are set. Call the current value Is2.
ST7) A voltage corresponding to the final tightening rotation speed N2 is supplied to the screw tightening motor 3b.
ST8) It is determined whether or not the load current of the screw tightening motor 3b has reached the final tightening set current value Is2, and when this has reached the final tightening set current value Is2, the routine jumps to step ST12, while the screw tightening motor When the load current 3b has not reached the final fastening set current value Is2, the process proceeds to step ST9.
ST9) It is determined whether or not the second timer 11c has timed up. When the second timer 11c has not timed up, the process returns to step ST8, while when the second timer 11c has timed up, the process proceeds to step ST10.
ST10) The voltage supply to the screw tightening motor 3b is stopped. The first timer 11b and the second timer 11c are reset.
ST11) Output the tightening NG signal Sg7 to the main control unit 7 and jump to step ST14.
ST12) When the load current of the screw tightening motor 3b reaches the final tightening set current value Is2 in step ST8, the voltage supply to the screw tightening motor 3b is stopped. The first timer 11b and the second timer 11c are reset.
ST13) A final fastening completion signal Sg6 is output to the main control unit 7.
ST14) End.

The thrust calculation unit 12 constitutes a main part of the present invention, and is configured as a part of the main control unit 7, that is, a part of the operation in the setting mode. In the setting mode, as shown in FIGS. 1, 8, and 10, the operations of the following steps SP1 to SP19 are performed.
SP1) It is determined whether or not the setting mode signal Sg21 is input. When the setting mode signal Sg21 is not input, the input is waited for. When the setting mode signal Sg21 is input, the process proceeds to step SP2.
SP2) The setting screen display command signal Sg22 is output to the operation unit 8.
SP3) It is determined whether or not the tightening point number B is input to the input portion of the tightening point number B on the setting screen, and when the tightening point number B is not input, the input is awaited while the tightening point number B is input. If so, the process proceeds to step SP4.
SP4) Call various information corresponding to the input tightening point number B from the storage unit 9.
SP5) The called information is set in the input unit of the setting screen of the operation unit 8.
SP6) In the called information, the temporary fastening set current value Is1 is temporarily stored as the temporary storage temporary fastening value Tn0, and the final fastening set current value Is2 is temporarily stored as the temporary storage final fastening value Tm0.
SP7) It is determined whether or not the save / cancel selection signal from the operation unit 8 is input, and when it is not input, the input is waited for, while when the cancel selection signal Sg23 is input, the process jumps to step SP18. When the save selection signal Sg24 is input, the process proceeds to step SP8.
SP8) Recall each information of the input part of the setting screen and store (overwrite) it in the storage part 9.
SP9) It is determined whether or not the set temporary tightening torque value Tn is equal to the temporary stored temporary tightening value Tn0. When these are equal, the process jumps to step SP18, while the set temporary tightening torque value Tn is equal to the temporary stored temporary tightening value Tn0. If not, the process moves to step SP10.
SP10) The reference torque value Ts sandwiching the set temporary tightening torque value Tn from the reference torque value-reference thrust table of the storage unit 9 is used as the boundary temporary tightening torque values Tsd1, Tsu1, and the reference thrust for these boundary temporary tightening torque values Tsd1, Tsu1. Ds (B, Ts) is called as reference temporary fastening thrusts Dsd1, Dsu1.
SP11) Based on the boundary temporary fastening torque values Tsd1 and Tsu1 and the reference temporary fastening thrusts Dsd1 and Dsu1 corresponding thereto, the temporary fastening thrust Ft2 with respect to the set temporary fastening torque value Tn is calculated by linear interpolation.
SP12) The calculated temporary fastening thrust Ft2 is stored (overwritten) as the temporary fastening thrust Ft2 for the new set temporary fastening torque value.
SP13) It is determined whether or not the set final tightening torque value Tm is equal to the temporary stored final tightening value Tm0. When these are equal, the process jumps to step SP18, while the set final tightening torque value Tm is equal to the temporary stored final tightening value Tm0. If not, the process proceeds to step SP14.
SP14) The reference torque value Ts sandwiching the set final tightening torque value Tm from the reference torque value-reference thrust table of the storage unit 9 is set as the boundary final tightening torque value Tsd2, Tsu2, and the reference thrust with respect to these boundary final tightening torque values Tsd2, Tsu2 Ds (B, Ts) is called as the standard final tightening thrust Dsd2, Dsu2.
SP15) Based on the boundary final tightening torque values Tsd2 and Tsu2 and the corresponding reference final tightening thrusts Dsd2 and Dsu2, the final tightening thrust Ft3 with respect to the set final tightening torque value Tm is calculated by linear interpolation.
SP16) The calculated final fastening thrust Ft3 is stored (overwritten) as the final fastening thrust Ft3 for the newly set final fastening torque value.
SP17) A thrust calculation completion display command signal Sg25 is output to the operation unit 8.
SP18) When the cancel selection signal Sg23 is input in step 7, when the set temporary tightening torque value Tn is equal to the temporary storage temporary tightening value Tn0 in step 9, or in step 13, the set final tightening torque value Tm is temporarily stored final tightening. When the value is equal to the value Tm0 or following step 17, the operation screen display command signal Sg26 is output to the operation unit 8.
SP19) End.

  In the screw tightening device 1, when performing a normal tightening operation as shown in FIGS. 2 and 8, the screw tightening mode key 8 a on the operation screen of the operation unit 8 is touched, and a screw tightening mode signal is sent to the main control unit 7. Sg1 is output. The screw tightening mode signal Sg1 causes the screw tightening motor drive unit 11 to receive the temporary tightening set current value Is1, the temporary tightening rotation speed N1, the final tightening set current value Is2, and the final tightening rotation speed N2, and the moving motor driving unit 10 Are supplied with a standby position P0, a screw fitting thrust Ft1, a screw tightening start position (temporary tightening start position) P1, a temporary tightening thrust Ft2, a final tightening position P4, a final tightening thrust Ft3, and a return thrust Ft4 (step). (See S1-S3). Subsequently, an operation command signal Sg2 is output to the screw supply device drive unit 13 (see step S4 and FIG. 8), the screw supply device is operated, and the pair of chucks in which the screw 4 is disposed on the moving path of the drive bit 3e. The nail is supplied and held by the chuck nail. Thereafter, operation command signals Sg3 and Sg4 are output to the moving motor driving unit 10 and the screw tightening motor driving unit 11, respectively (see steps S5 and S6 and FIG. 8).

  When the movement motor drive unit 10 receives the operation command signal Sg3, the screw fitting thrust Ft1 and the screw tightening start position P1 are called (see steps SS1 and SS2 and FIG. 8). Subsequently, the screw tightening start position P1 and the current value for obtaining the screw fitting thrust Ft1 are supplied as command values to the moving motor 2d (see step SS3), and the moving motor 2d sets the screw tightening starting position P1 as a target. As a position, it rotates by receiving power supply so that the current value can be obtained. In response to the rotation of the moving motor 2d, the screw shaft 2h rotates, and the bearing base 2k screwed to the screw shaft 2h advances to the screw tightening start position P1 while holding the current value, that is, the screw fitting thrust Ft1. (See signal waveform We1 in FIG. 9). With the advancement of the bearing stand 2k, the drive bit 3e of the screw tightening unit 3 held by the driver stand 3a integrated with the bearing stand 2k advances from the standby position P0, and the screw 4 held by the chuck claw starts to tighten. Extruded to position P1 (see FIG. 9).

  When receiving the operation command signal Sg4, the screw tightening motor drive unit 11 calls the temporary tightening rotation speed N1 and the temporary tightening set current value Is1 (see steps ST1 and ST2 and FIG. 8). Subsequently, a predetermined voltage corresponding to the temporary tightening rotation speed N1 is supplied to the screw tightening motor 3b (see step ST3), and the screw tightening motor 3b rotates at the temporary tightening rotation speed N1 (high speed low torque) (see FIG. 9 (see signal waveform Wd1), the drive bit 3e rotates in response to this rotation. At the same time, it is determined whether or not the load current of the screw tightening motor 3b has reached the temporary tightening set current value Is1 (see step ST4). At this time, the first timer 11b and the second timer 11c are operated, and the determination of the temporary fastening failure and the final fastening failure is started.

  During this time, as shown in FIG. 12, the force Fr in the rotational direction of the drive bit 3e acts on the inclined surface 4aa of the drive hole 4a of the screw 4, thereby causing the drive bit 3e to move away from the drive hole 4a of the screw 4. Although the cam-out force Fco acts, the cam-out force Fco is canceled out by the above-described screw-fitting thrust Ft1. Further, in the movement motor drive unit 10, whether or not the current position of the movement motor 2d has reached the screw tightening start position P1, that is, whether or not the drive bit 3e that has advanced from the standby position P0 has reached the screw tightening start position P1. Is determined (see step SS4), and when the current position reaches the screw tightening start position P1, the final tightening position P4 and the temporary tightening thrust Ft2 are called (see step SS5). Subsequently, a current value for obtaining the final fastening position P4 and the temporary fastening thrust Ft2 is supplied to the moving motor 2d (see step SS6 and FIG. 8), and the moving motor 2d rotates while holding the temporary fastening thrust Ft2. (See signal waveform We2 in FIG. 9). Under the rotation of the moving motor 2d, the bearing base 2k and the driving bit 3e integrated therewith advance, so that the screw 4 fitted to the driving bit 3e is until its head is seated on the fastened member 15. That is, it is screwed in while applying the temporary fastening thrust Ft2 to the position P2 at the time of completion of the temporary fastening (see FIG. 9).

  Thereafter, until the load current of the screw tightening motor 3b reaches the temporary tightening set current value Is1, it is determined whether or not the first timer 11b has expired (see step ST5), and the first timer 11b has expired. During the operation, the voltage supply to the screw tightening motor 3b is stopped, and the tightening NG signal Sg7 is output to the main controller 7 (see steps ST10 and ST11 and FIG. 8). At the same time, the first timer 11b and the second timer 11c are reset, and the temporary fastening failure determination and the final fastening failure determination are completed. Further, when the load current of the screw tightening motor 3b reaches the temporary tightening set current value Is1, the temporary tightening is completed, and a temporary tightening completion signal Sg5 is output from the screw tightening motor drive unit 11 to the main control unit 7 ( Step ST6 and FIG. 8). When this temporary tightening is completed, that is, when the driving bit 3e is located at the temporary tightening completion position P2, the final tightening rotation speed N2 and the final tightening set current Is2 are called, and the screw tightening motor 3b is rotated at a low tightening speed with high torque. A voltage is supplied so as to switch to N2 (see signal waveform Wd2 in steps ST6 and ST7 and FIG. 9). Since the temporary fastening completion signal Sg5 is output to the moving motor drive unit 10 by the temporary fastening completion signal Sg5, the final fastening position P4 and the final fastening thrust Ft3 are called by the moving motor drive unit 10 (step SS8 and (See FIG. 8). Subsequently, the final tightening position P4 and the current value for obtaining the final tightening thrust Ft3 are supplied as command values to the moving motor 2d (see step SS9 and FIG. 8), and the moving motor 2d holds the final tightening thrust Ft3. (See signal waveform We3 in FIG. 9). In response to the rotation of the moving motor 2d, the bearing base 2k and the drive bit 3e move forward with the final fastening position P4 as the target position while holding the final fastening thrust Ft3 (see FIG. 9).

  While the bearing stand 2k moves forward by receiving the rotation of the moving motor 2d, the screw tightening motor drive unit 11 determines whether or not the load current of the screw tightening motor 3b has reached the final tightening set current value Is2. When the load current has not reached the final fastening set current value Is2, it is determined whether or not the second timer 11c has timed up (see step ST9). In this determination, when the second timer 11c has not timed out, the determination in step ST8 described above is repeated. Further, when the second timer 11c has timed up in the determination of step ST9, the voltage supply to the screw tightening motor 3b is stopped and the tightening NG signal Sg7 is output to the main control unit 7 (step ST10). And ST11 and FIG. 8).

  When the load current of the screw tightening motor 3b reaches the final tightening set current value Is2 while the bearing stand 2k moves forward under the rotation of the moving motor 2d, that is, the drive bit 3e is positioned at the final tightening completion position P3. Then, the voltage supply to the screw tightening motor 3b is stopped, the screw tightening motor 3b is stopped, the final tightening is completed, and the final tightening completion signal Sg6 is output to the main control unit 7 (step ST12 and ST13 and FIG. 8). At the same time, the first timer 11b and the second timer 11c are reset, and the temporary tightening failure determination and the final tightening failure determination are ended.

  When the main tightening completion signal Sg6 is input, the main control unit 7 outputs a stop command signal Sg8 to the moving motor driving unit 10 and also outputs a tightening completion display command signal Sg11 to the operation unit 8 (step). S14 and S15 and FIG. 8). Therefore, the movement motor drive unit 10 receives this stop command signal Sg8, outputs a power supply stop command signal Sg12 to the movement motor 2d, and stops power supply to the movement motor 2d (steps SS10 and SS11). And FIG. 8). Subsequently, the movement motor drive unit 10 calls the standby position P0 and the return thrust Ft4 of the movement motor 2d, and supplies the standby position P0 and the return thrust Ft4 to the movement motor 2d as command values ( Steps SS12 and SS13 and FIG. 8). Therefore, since the moving motor 2d is rotated by receiving power supply so as to return to the standby position P0 and to obtain the return thrust Ft4, the bearing base 2k and the drive bit 3e of the screw tightening unit 3 return. Returning to the standby position P0 while holding the hourly thrust Ft4 (see signal waveform We4 in FIG. 9). Accordingly, the standby position return signal Sg10 is output to the main controller 7 (see steps SS14 and SS15 and FIG. 8), and the input of the standby position return signal Sg10 is confirmed by the main controller 7 (see step S13). A series of tightening operations are completed.

  Next, the operation of the thrust calculation unit of the main part of the present invention will be described. Prior to the aforementioned tightening operation, when setting screw tightening information, movement information, etc., as shown in FIGS. 1, 2, and 8, the setting mode key 8b on the operation screen of the operation unit 8 is touched. The setting mode signal Sg21 is output to the main control unit 7, that is, the thrust setting unit 12. Upon receiving the setting mode signal Sg21, the thrust setting unit 12 outputs a setting screen display command signal Sg22 to the operation unit 8, so that the operation screen is reduced and the setting screen is displayed (Steps SP1 and SP2 and (See FIG. 8). Wait until the tightening point number B corresponding to the tightening position is input to the input portion of the tightening point number B in this setting screen, and when this is input, the temporary setting point is set according to the tightening point number B from the storage unit 9. Screw tightening information, movement information and the like including the tightening torque value Tn and the set final tightening torque value Tm are called (see steps SP3 and SP4 and FIG. 8). These pieces of information are set and displayed on the input sections of the corresponding setting items on the setting screen, and the information setting temporary fastening torque value, that is, the temporary fastening set current value Is1 is stored as the temporary storage temporary fastening value Tn0. Similarly, the set final tightening torque value, that is, the final tightening set current value Is2, is temporarily stored as the temporary storage final tightening value Tm0 (see steps SP5 and SP6).

  After that, among the setting items on the setting screen, if an item that needs to be changed occurs and a new value is entered in the input field for that setting item, one of the selection items can be selected from the save / cancel selection key on the setting screen Wait for a signal to be output (see step SP7). At this time, when the cancel selection signal Sg23 is output, the setting mode ends immediately, the operation screen display command signal Sg26 is output to the operation unit 8, and the operation unit 8 closes the setting screen and returns to the operation screen (step). SP18 and FIG. 8). When the save selection signal Sg24 is output from the save / cancel selection key, the value of the input part of each setting item displayed on the setting screen is stored (overwritten and saved) in the storage part 9 (steps SP8 and SP8). (See FIG. 8).

Subsequently, the value of the input portion of the set temporary tightening torque value Tn is compared with the temporarily stored temporary tightening value Tn0. When these values are equal, that is, when the set temporary tightening torque value Tn is not changed, the cancel selection signal Sg23 described above is used. As in the case of, the setting mode ends, and the operation unit 8 returns to the operation screen (see steps SP9 and SP18). When the set temporary fastening torque value Tn and the temporarily stored temporary fastening torque value Tn0 are not equal, that is, when the set temporary fastening torque value Tn is changed to a new value, the reference torque value-reference thrust table in the storage unit 9 The reference torque value Ds (B, Ts) sandwiching the set temporary tightening torque value Tn from (see FIG. 7) is the boundary temporary tightening torque values Tsd1, Tsu1, and the reference thrust Ds corresponding to these boundary temporary tightening torque values Tsd1, Tsu1. (B, Ts) is called as the reference temporary fastening thrusts Dsd1, Dsu1 (see step SP10). From these boundary temporary tightening torque values Tsd1 and Tsu1 and the corresponding reference temporary tightening thrusts Dsd1 and Dsu1, the temporary tightening thrust Ft2 corresponding to the set temporary tightening torque value Tn is linearly interpolated, that is, the following equation (1):
Ft2 = Dsd1 + (Dsu1-Dsd1) * (Tn-Tsd1)
/ (Tsu1-Tsd1) ----- (1)
(See step SP11 and FIG. 10A). For example, when the tightening point number B is 1 and the set temporary tightening torque value Tn is 2.5 N · m, the boundary temporary tightening torque values Tsd1 and Tsu1 are 2 and 3, respectively, from FIG. Since the temporary fastening thrusts Dsd1 and Dsu1 are Ds (1, 2) and Ds (1, 3), respectively, when these values are substituted into the equation (1), the temporary fastening thrust Ft2 is
Ft2 = Ds (1,2) + ((Ds (1,3) -Ds (1,2)) * (2.5
-2) / (3-2)
Is calculated as The temporary fastening thrust Ft2 calculated by the above formula (1) is stored in the storage unit 9 as the temporary fastening thrust Ft2 for the set temporary fastening torque value Tn at the fastening point number 1 (see step SP12).

Thereafter, as in the case of the set temporary tightening torque value Tn, the value of the input portion of the set final tightening torque value Tm is compared with the temporarily stored final tightening value Tm0, and when these are equal, that is, to the set final tightening torque value Tm. When there is no change, the setting mode ends and the operation unit 8 returns to the operation screen (see step SP18). Further, when the set final tightening torque value Tm and the temporarily stored final tightening torque value Tm0 are not equal, that is, when the set final tightening torque value Tm is changed, the reference torque value Ds (B , Ts) is called as the boundary final tightening torque values Tsd2, Tsu2, and the reference thrust Ds (B, Ts) corresponding to these boundary final tightening torque values Tsd2, Tsu2 is called as the reference final tightening thrusts Dsd2, Dsu2 (step SP14). reference). From these, the final fastening thrust Ft3 with respect to the set final fastening torque value Tm is expressed by the following equation (2).
Ft3 = Dsd2 + (Dsu2-Dsd2) * (Tm-Tsd2) /
(Tsu2-Tsd2) ----- (2)
(See step SP15 and FIG. 10B). For example, when the tightening point number B is 1 and the set final tightening torque value Tm is 11.5 N · m, the boundary temporary tightening torque values Tsd2 and Tsu2 are 11 and 12 from FIG. Since the final fastening thrusts Dsd2 and Dsu2 are Ds (1, 11) and Ds (1, 12), respectively, when these values are substituted into the equation (2), the final fastening thrust Ft3 is
Ft3 = Ds (1,11) + (Ds (1,12) −Ds (1,11)) *
(11.5-11) / (12-11)
Is calculated as The final fastening thrust Ft3 calculated by the above equation (2) is stored in the storage unit 9 as the final fastening thrust Ft3 for the set final fastening torque value Tm at the fastening point number 1 (see step SP16). Subsequently, a thrust calculation completion display command signal Sg25 is output to the operation unit 8 and an operation screen display command signal Sg26 is output to the operation unit 8 to complete the setting operation (see steps 17 and 18 and FIG. 8). .

  As described above, the screw tightening device 1 according to the present embodiment converts the rotation of the screw tightening unit 3 including the drive bit 3e rotated by the screw tightening motor 3b and the moving motor 2d into a reciprocating movement, and this reciprocating movement. The moving unit 2 for moving the screw tightening unit 3 forward and backward, the main control unit 7 for controlling the screw tightening motor 3b and the moving motor 2d, and the reference thrust Ds (added to the drive bit 3e for each reference torque Ts value B, Ts), and a storage section 9 for storing a plurality of storages, wherein the main control section 7 is set tightening with a set temporary tightening torque value Tn or a set final tightening torque value Tm at a predetermined tightening position. When a torque value is input, two reference torque values Tsd1, Tsu1, Tsd2, Tsu2 sandwiching the torque value and these reference torque values Tsd1, Tsu1, Tsd2, su2 call reference thrust Dsd1, Dsu1, Dsd2, Dsu2 corresponding to each, and a thrust calculation section for calculating by linear interpolation thrust Ft2, Ft3 for setting initial tightening torque Tn or set the tightening torque value Tm.

  According to this configuration, in order to prevent the drive bit 3e from being detached from the drive hole 4a of the screw 4, an optimum thrust Ft2 prepared in advance according to the set temporary tightening torque value Tn or the set final tightening torque value Tm. , Ft3 can be added. Therefore, the mating member 5 is not excessively pressed at the time of tightening, the mating member 5 is not damaged, or the operation of other parts attached to the mating member 5 is not adversely affected. High-quality fastening work can be performed in either the temporary fastening process or the final fastening process. Further, when the set tightening torque value is changed at each tightening position, the camout force Fco generated in the drive bit 3e is changed, and it is necessary to change the thrust applied to the drive bit 3e in order to cancel the camout force Fco. Arise. Since the camout force Fco is roughly proportional to the electromagnetic force generated in the screw tightening motor 3b, that is, the current value flowing through the screw tightening motor 3b, the thrust for suppressing the camout force Fco is also the current value flowing through the screw tightening motor 3b, in other words, If this is the case, it will be roughly proportional to the tightening torque value. Therefore, a reference torque value sandwiching the set tightening torque value and a reference thrust corresponding to these reference torque values are called, and a new thrust for the changed set tightening torque value is obtained from these reference torque values and the corresponding reference thrust. Can be calculated by linear interpolation. As a result, the optimum thrust for the set tightening torque value can be calculated every time the set tightening torque value is changed at each tightening position, so that the operator can obtain the camout force Fco generated in the drive bit 3e prior to the tightening operation. Therefore, it is not necessary to measure complicated and troublesome work at the work site, and the screw tightening device 1 that is easy to use can be provided.

  In the embodiment of the present invention, the reference torque value-reference thrust table having an optimum value for canceling the camout force Fco generated in the drive bit 3e is stored in advance as a characteristic characteristic of the screw tightening device. Prior to the tightening operation, the reference thrust Ds (B, Ts) with respect to the reference torque value Ts may be measured for each counterpart member 5 and stored. When measuring the reference thrust Ds (B, Ts), the above-described screw tightening device 1 can be used. In this case, as shown in FIG. 11, the screw tightening device 1 moves the drive bit 3e in a state where the temporary thrust Ft5 is applied by the moving motor 2d (see the signal waveform We5 in FIG. 11) from the standby position P0 to the screw tightening start position. The configuration of moving through P1 to the position P2 at the time of completion of temporary tightening, and rotating the screw tightening motor 3b at a temporary tightening rotational speed N3 (medium speed medium torque) lower than the rotational speed N1 in the above-described screw tightening mode. The screw 4 that has been tightened in advance is tightened, and the screw tightening motor 3b is switched to the final tightening rotation speed N2 lower than the temporary tightening rotation speed N3 when the temporary tightening is completed (see signal waveforms Wd3 and Wd4 in FIG. 11). ). In addition, the feedback current value We6 of the moving motor 2d while the position of the drive bit 3e is held at the position P2 at the time of completion of temporary fastening, when the drive bit 3e reaches the position P3 at the time of completion of final fastening. The feedback current value We6 (Imf) is measured, and the thrust may be calculated from the feedback current value We6 (Imf).

  In addition, the specific configuration of each unit is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Screw fastening apparatus 2 ... Movement unit 2d ... Movement servo motor 3 ... Screw fastening unit 3b ... Screw fastening motor 3e ... Drive bit 7 ... Main control part 9 ... Memory | storage part 12 ... Thrust calculation part Ts ... Reference torque value Ds (B, T) ... Standard thrust

Claims (3)

  A screw tightening unit having a drive bit that is rotated by a screw tightening motor; a moving unit that converts the rotation of the moving servo motor into a reciprocating movement and moves the screw tightening unit forward and backward by the reciprocating movement; and the screw tightening motor. And a main control unit that controls the moving servo motor and a storage unit that stores a plurality of reference thrusts to be added to the drive bits for each reference torque value. When the set tightening torque value at the attachment position is input, the two reference torque values sandwiching the set tightening torque value and the reference thrust corresponding to each of these reference torque values are called to linearize the thrust against the set tightening torque value. A screw tightening device comprising a thrust calculation unit that calculates by interpolation.   The screw tightening device according to claim 1, wherein the set tightening torque value is a set final tightening torque value.   The screw tightening device according to claim 1, wherein the set tightening torque value is a set temporary tightening torque value.

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