JP5003691B2 - Screw tightening device - Google Patents

Description

  The present invention generally relates to a screw tightening device having a driver for tightening a screw.

Technical background

  In order to prevent forgetting screw tightening in manual screw tightening work, a counter for counting the number of screws with increased torque has been provided. The number of screws is input to the counter in advance, and the counter is counted down or up every time the screw tightening is completed. If the user determines that the screw tightening operation has been completed and the counter value is 0 or a predetermined number, the user will not forget to tighten the screws. Otherwise there will be screws that you forgot to tighten.

  For manual screw tightening, tighten the screws one by one. If there are a large number of screws for mounting parts, tightening the screws one after the other and fixing them (hereinafter referred to as “main tightening”) will cause the screw holes of the parts and the screw holes of the object to be fastened and the subsequent screws Tightening is difficult or impossible. Therefore, temporary tightening for lifting the screw from the seating position is performed so that the attachment position of the component can be adjusted. Tighten all screws after the temporary tightening. The contact of the seat surface of the screw with the surface around the screw hole is called “sitting”. In addition, tightening and fixing a seated screw with a predetermined torque is called “torque up”.

As conventional techniques, there are Patent Documents 1 to 4.
Japanese Patent No. 2894198 Japanese Patent No. 2953292 Japanese Patent No. 3281360 Japanese Patent No. 2697240

  Conventionally, the amount of temporary tightening is adjusted by quickly moving the start switch or lever of the driver, so that the amount of temporary tightening varies from person to person, and the screw may be seated during temporary tightening. In particular, adjustment is difficult when the screw portion of the screw is short. In this case, it is necessary to loosen the seated screw. When the seat is loosened from the seat, the counter is liable to malfunction, and the counter value is not correct enough to prevent forgetting to tighten the screw. Further, if the distance to the seat of the temporarily tightened screw is large, the impact at the time of seating in the final tightening becomes large.

  The present invention relates to a screw tightening device that accurately controls the amount of temporary tightening.

  A screw tightening device according to one aspect of the present invention is a mode for switching between an electric driver for tightening a screw, a main tightening mode for tightening the screw to a seat, and a temporary tightening mode for tightening a predetermined amount before seating without seating the screw. And a counter that operates when the mode switch is set to the final tightening mode, does not operate when the mode switch is set to the temporary tightening mode, and counts the number of screws that have been torqued up, An input unit for setting the rotation speed of the electric driver in the temporary tightening mode; and when the mode switch is set to the temporary tightening mode and the electric driver starts to rotate, the electric driver is rotated by the rotation speed. And a control unit that stops. In such a screw tightening device, the counter operates only in the final tightening mode and is not affected by the temporary tightening mode, so that the conventional malfunction due to the temporary tightening does not occur. As a result, it is possible to prevent forgetting to tighten the screw during the final tightening. In addition, the input unit sets a temporary fastening amount to prevent variation. In particular, since a screw having a short screw portion can be securely tightened with a single operation, temporary tightening when temporarily tightening is facilitated.

Control method according to another aspect of the present invention is a method for controlling the driving of the electric driver having a bit to tighten the screws, tightened by a predetermined amount before sitting without sitting in front Symbol screw the in temporary tightening mode When a rotation start operation of the electric driver is performed , a step of rotating and stopping the electric driver by a set number of rotations, and a final tightening in which torque is increased after seating the screw without counting in the temporary tightening mode. And counting the number of screws that have been torqued up in the mode . This control method also has the same effect as the above-described screw tightening device. In the temporary tightening mode, the step of reversing the bit before starting the tightening operation of the screw, and the bit is rotated at a first speed in the direction of tightening the screw immediately after starting the tightening operation of the screw. Preferably, the method includes a step of rotating the bit at a second speed that is faster than the first speed after the step of rotating at the first speed. Clashing can be prevented by the reverse rotation step and the first speed (low speed) rotation step, and the throughput can be increased by the second speed rotation step.

Control method according to another aspect of the present invention is a method for controlling the driving of the electric driver having a bit to tighten the screw, to seat the screw in the temporary tightening mode tightening the pre Symbol screw by a predetermined amount before the seating And then stopping the electric driver after reversing the bit by the set number of rotations corresponding to the predetermined amount, and a book for torque-up after seating the screw without counting in the temporary fastening mode. And counting the number of screws that have been torque-up in the tightening mode . In such a control method, the screw and the bit are reversely rotated by a predetermined amount after sitting, so that the temporary tightening amount becomes constant.

In the temporary tightening mode, the step of reversing the bit before starting the tightening operation of the screw, and the bit is rotated at a first speed in the direction of tightening the screw immediately after starting the tightening operation of the screw. A step of rotating the bit at a second speed faster than the first speed after the step of rotating at the first speed, and the step of rotating at the second speed after the step of rotating at the second speed. Preferably, the method further comprises the step of rotating the bit at a third speed slower than the speed of 2 and waiting for seating. Clashing can be prevented by the reverse rotation step and the first speed (low speed) rotation step, and the throughput can be increased by the second speed rotation step. Further, the impact at the time of sitting can be suppressed by the third speed rotation step. Preferably, the electric screwdriver tightens a plurality of screws, and the amount of reverse rotation of the bit is adjusted so that the recess directions of the plurality of screws are aligned . Since the direction of the recess is aligned, the final tightening work becomes easy.

  It is preferable to further include a step of performing a torque hold for holding the screw for a predetermined time after the torque is increased in the final tightening mode. Thereby, torque up can be stabilized.

Preferably, the electric driver tightens a plurality of screws, and reverses the bit so that the recess directions of the plurality of screws are aligned after the torque hold is completed and the torque is released in the final tightening mode. This facilitates the work of loosening and tightening the screws again after the final tightening.

  In the counting step, the final tightening of the screw after temporary tightening is determined by determining whether the screw after temporary tightening is final tightened or the final tightened screw is tightened again according to the amount of bit rotation at the time of final tightening. It is preferable to count the number of successful final fastenings only when the method succeeds. Thereby, counting mistakes can be prevented and the reliability of the count value can be increased.

  In the final tightening mode, immediately after starting the tightening operation of the screw, the step of rotating the bit at a fourth speed in the direction of tightening the screw and the step of rotating at the fourth speed after the fourth speed are performed. And rotating the bit at a fifth speed that is faster than the fifth speed, and rotating the bit at a sixth speed that is slower than the fifth speed after the step of rotating at the fifth speed and the fifth speed. Preferably, the method further includes a waiting step. The first speed (low speed) rotation step can prepare for the second final tightening, and the second speed rotation step can increase the throughput, and the third speed rotation step can suppress the impact at the time of sitting. Can do.

  In the temporary tightening mode, the step of reversing the bit before starting the tightening operation of the screw, and the bit is rotated at a first speed in the direction of tightening the screw immediately after starting the tightening operation of the screw. A step of rotating the bit at a second speed faster than the first speed after the step of rotating at the first speed, and the step of rotating at the second speed after the step of rotating at the second speed. Rotating the bit at a third speed slower than the speed of 2 and waiting for seating, and in the final tightening mode, a fourth speed in a direction of tightening the screw immediately after starting the tightening operation of the screw. Rotating the bit at a fifth speed faster than the fourth speed after the rotating at the fourth speed; A step of rotating the bit at a sixth speed slower than the fifth speed and waiting for seating after the step of rotating at the fifth speed, wherein the sixth speed is the third speed. It is preferable to have a step of making the impact torque at the time of seating in the final tightening smaller than the impact torque at the time of temporary tightening. Thereby, the seating impact torque at the time of the final tightening can be reduced, and the screw tightening can be performed more precisely than the case of performing the screw tightening at once without temporary tightening.

  A manufacturing method as another aspect of the present invention is a method of manufacturing a product by screwing a part to an object to be fastened using an electric screwdriver that tightens a screw, and has the above-described control method. Features. This method can also exhibit the same effect as the above-described screw tightening device.

  According to another aspect of the present invention, there is provided a control method for controlling driving of an electric driver having a bit for tightening a screw, wherein the number of screws that have been torque-up in a final tightening mode in which the torque is increased after seating the screw is determined. A step of counting, a step of setting the number of rotations of the electric driver, and the bit by the number of rotations corresponding to the predetermined amount after seating the screw in a temporary tightening mode of tightening the screw by a predetermined amount before seating. The step of stopping the electric driver after reversing the motor, and when the bit rotation speed falls below a specified value, when the actual bit rotation speed with respect to the commanded bit rotation speed falls below a prescribed ratio, or the motor When an increase in current is detected, it is determined to be seated, and reverse rotation is performed for temporary tightening from bit rotation speed control. Characterized by a step of automatically switching to the angle control to float the screw. Thereby, the seating can be automatically detected and automatically switched from the rotational speed control to the angle control for temporary fastening.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

It is a block diagram of the screw fastening device as one side of the present invention. Fig.2 (a) is a fragmentary sectional view which shows the positional relationship of the screw of a temporary fastening state, components, and a to-be-fastened object. FIG. 2B is a partial cross-sectional view showing the positional relationship between the seated screw, the component, and the object to be fastened. It is a flowchart explaining operation | movement of the screw fastening apparatus shown in FIG. It is sectional drawing of the modification of the driver shown in FIG. FIGS. 5A to 5E are cross-sectional views comparing the rotational speed of the driver shown in FIG. 4 according to the tightening state of the screw between the conventional example and this example. FIG. 5 is a graph showing a change in torque state when the rotational speed of the driver shown in FIG. 4 is controlled based on the control method of this embodiment as shown in FIGS. 5A to 5E are graphs showing changes in the torque state when the rotational speed of the driver shown in FIG. 4 is maintained at a high speed as in the conventional example. It is a flowchart explaining operation | movement of the screw fastening apparatus shown in FIG. FIG. 9A and FIG. 9B are a front view and a side view of a modified example of the driver shown in FIG. It is a block diagram of the principal part of the screw fastening apparatus using the driver shown to Fig.9 (a) and FIG.9 (b). FIG. 10 is a timing chart of a control method using the driver shown in FIGS. 9 (a) and 9 (b). FIG. It is a flowchart of the control method shown in FIG. 10 is a timing chart of another control method using the driver shown in FIGS. 9A and 9B. FIG. It is a flowchart of the control method shown in FIG. It is a timing chart of the modification of the control method shown in FIG. It is a flowchart of the control method shown in FIG.

  Hereinafter, the screw fastening device 100 will be described with reference to the accompanying drawings. The screw tightening device 100 includes an electric driver 110, a temporary tightening control unit 120, and a final tightening control unit 130. The screw tightening device 100 is obtained by adding a temporary tightening control unit 120 to the combination of the conventional electric driver 110 and the final tightening control unit 130, and can be added as an option without significantly changing the conventional configuration. It has the feature.

  The electric driver 110 is manually operated by a user to tighten the screw 10. The driver 110 has a main body 112, a bit 114, a lever 116, and a cable 118.

  The main body 112 is a part that is gripped by the user. A servo motor is mounted inside the main body 112, and a motor shaft is connected to the bit 114 via a cam. The bit 114 is a portion that has one end connected to the main body 112 and the other end engaged with the recess 12 of the screw 10 and rotated by the main body 112.

  The lever 116 is a start switch that is operated by the user to turn the power of the main body 112 on and off, and turns on and off the energization of the servo motor. The lever 116 is in the off state as shown in FIG. 1 and rotates when the force is applied counterclockwise by the user to turn on the main body 112. When the user releases the hand, it rotates clockwise and returns to the state shown in FIG. In principle, the servo motor in the main body 112 rotates while the lever 116 is pulled and turned on. Conventionally, the user has adjusted the amount of temporary fastening by operating the lever 116 quickly.

  The temporary fastening control unit 120 controls the temporary fastening operation of the driver 110, and includes a control unit 121, a mode switch 122, a timer 124, a timer input unit 125, terminals 128, and 129.

  The control unit 121 is provided inside the temporary fastening control unit 120 and is schematically shown by a dotted line in FIG. The control unit 121 includes an MPU, a memory, and the like, and controls each unit. The mode switch 122 switches between a final tightening mode in which the screw is tightened to the seating and a temporary tightening mode in which the screw is not seated and is tightened by a predetermined amount before the seating. The timer 124 sets the driving time of the driver 110 in the temporary tightening mode. The timer input unit 125 is used when the user arbitrarily sets the driving time in the timer 124. One end of the cable C is connected to the terminal 128. A cable 118 of the driver 110 is connected to the terminal 129.

  The final tightening control unit 130 controls the final tightening operation of the driver 110, but the user can also operate the lever 116 quickly to perform temporary tightening as in the conventional case. The final tightening control unit 130 includes a control unit 131, a power switch 132, a forward / reverse switch 133, a counter 134, a counter setting unit 135, and a terminal 138.

  The control unit 131 is provided inside the final fastening control unit 130 and is schematically shown by a dotted line in FIG. The control unit 131 includes an MPU, a memory, and the like, and controls each unit. In another embodiment, the control units 121 and 131 are integrally formed.

  The power switch 132 is operated by the user to turn on and off the power supply of the final fastening control unit 130. The forward / reverse switch 133 switches between rotating the driver 110 in the forward direction in which the screw is tightened or rotating in the reverse direction in which the screw is loosened. The counter 134 operates when the mode switch 122 is set to the final tightening mode, and does not operate when the temporary tightening mode is set. The counter 134 counts the number of screws 10 whose torque has been increased. The counter setting unit 135 is used when the user arbitrarily sets the number of screws in the counter 134. The other end of the cable C is connected to the terminal 138, whereby the temporary fastening control unit 120 and the final fastening control unit 130 are electrically connected. In the present embodiment, the temporary tightening control unit 120 obtains power from the final tightening control unit 130 and supplies a part of the power to the driver 110. However, the temporary tightening control unit 120 has its own power cable and power supply. You may get

  Hereinafter, the operation of the screw tightening device 100 will be described with reference to FIGS. Here, FIG. 2A is a partial cross-sectional view showing a positional relationship among the screw 10 in the temporarily tightened state, the component 20, and the fastened object 30. FIG. 2B is a partial cross-sectional view showing the positional relationship between the seated screw 10, the component 20, and the fastened object 30. FIG. 3 is a flowchart for explaining the operation of the screw tightening device 100.

First, the user turns on the power switch 132 to turn on the temporary fastening control unit 120 and the final fastening control unit 130. Next, the user sets and starts temporary tightening (step 1002). That is, the mode switch 122 is set to temporary tightening, the forward / reverse rotation switch 133 is set to forward rotation, and the lever 116 is pulled. When the mode switch 122 sets the temporary fastening mode, the operation of the driver 110 is controlled only by the control unit 121 of the temporary fastening control unit 120. Next, the user sets the driving time to 0.2 seconds, for example, via the timer input unit 125 (step 1004). Then
Next, the user pulls the lever 116 by fitting the tip of the bit 114 into the recess 12 of the screw 10. In response to this, the controller 121 starts energizing the driver 110 and rotates the driver 110 (step 1006). At the same time, the timer 124 starts counting down. For the countdown, the internal clock of the temporary fastening control unit 120 can be used. If it is determined that the driving time set in the timer 124 has become zero (step 1008), the control unit 121 stops energization of the driver 110 (step 1010). As a result, since the bit 114 rotates only for the driving time set by the timer 124, a temporary fastening amount without variation can be given to the screw 10. The screw 10 given the temporary tightening amount is as shown in FIG.

  At this time, the control unit 121 sets the rotation speed of the driver 110 in the temporary tightening mode to be lower than that in the final tightening mode, for example, half. As a result, the driving time of the timer 124 can be lengthened and control is facilitated, so that the accuracy of the temporary fastening amount can be increased. The temporary tightening operation can prevent the screw hole 32 of the article 30 to be screwed and the screw hole 22 of the component 20 from being shifted in the final tightening operation, and the other screw 10 cannot be inserted.

  Next, the user sets and starts the final tightening (step 1012). That is, the mode switch 122 is set to the final tightening, the forward / reverse rotation switch 115 is set to the forward rotation, and the lever 116 is pulled. When the mode switch 122 sets the final tightening mode, the operation of the driver 110 is controlled only by the control unit 131 of the final tightening control unit 130. Next, the user operates the counter setting unit 135 to input the number of screws into the counter 134 (step 1014).

  Next, the user pulls the lever 116 by fitting the tip of the bit 114 into the recess 12 of the screw 10. In response to this, the controller 131 starts energizing the driver 110 and rotates the driver 110 (step 1016). Thereby, as shown in FIG.2 (b), the screw 10 is finally tightened. Until the screw 10 is seated, the motor shaft and the cam rotate integrally. However, when the torque of the screw increases, the motor shaft rides on the cam with the torque and stops rotating. In response to the rotation stop, the counter 134 counts down (step 1018).

  When the user determines that all the screws have been fully tightened, the user looks at the counter 134 (step 1020). If the value of the counter 134 is zero, the final fastening is finished. If the counter 134 is not zero, there is a screw that has been forgotten to be tightened, and this is tightened. As a result, forgetting to tighten can be prevented.

  In the final tightening mode, as described above, the control unit 131 sets the rotation speed larger than that in the temporary tightening mode and quickly performs the final tightening. Further, since the counter 134 does not operate at the time of temporary tightening, it is possible to prevent malfunction of the counter 134 due to temporary tightening and to prevent forgetting to tighten.

  The screw fastening device 100 of the present embodiment is particularly suitable for temporarily fastening a screw having a short threaded portion. As in the prior art, if temporary fastening is performed only by the final fastening control unit 130 and only the ON operation time of the lever 116, it is difficult to turn on the lever 116 for 0.2 seconds. If the screw is short, the screw will be seated after about 3 rotations. Therefore, when the user sits down, the user needs to reverse the forward / reverse switch 133 to loosen the screw. It is difficult to turn on only for seconds. Temporary fastening can be reliably performed by using the temporary fastening control unit 120 provided with the timer 124 as in this embodiment.

  Here, the impact (torque) at the time of sitting is considered. For example, the component 20 may be a spring member (for example, a clamp ring) or the component 20 may be fixed to the fastened object 30 via a spring member (for example, a spring washer). In this case, if the torque at the time of sitting is constant, the spring member applies the same elastic force. However, if the torque is too strong, for example, the spring member warps and an elastic force having a polarity opposite to the target elastic force is generated. Thus, control of torque at the time of sitting may be important. Since the screw tightening device 100 of this embodiment gives a certain amount of temporary tightening, the distance until the temporarily tightened screw is seated is equal. For this reason, the torque at the time of seating in the subsequent final tightening is also constant.

  FIG. 4 shows the internal structure of another driver 110A that reduces the torque at the time of sitting. The driver 110A includes a servo motor 140, a coupling (shaft joint) 141, a universal joint (universal joint) 142, a linear sliding shaft 143, a universal joint 144, a coupling 145, a bit 114A, and a detection unit. 150 and an encoder 158.

  The servo motor 140 rotates the motor shaft 140a. The coupling 141 couples the motor shaft and the shaft of the universal joint 142. The universal joint 142 transmits the rotation of the motor shaft 140a to the linear sliding shaft 143 at an angle. The linear sliding shaft 143 is a shaft that can slide in the arrow direction. The universal joint 144 transmits the rotation of the linear sliding shaft 143 to the bit 114A at an angle.

  In the driver 110A, the servo motor 140 is eccentric with respect to the bit 114A. Such eccentricity is not essential for the driver 110A. Therefore, the motor shaft 140a of the servo motor 140 may be arranged linearly or concentrically with the bit 114A.

  However, an eccentric configuration may be preferable. For example, six screw holes are provided in the clamp ring, there are cases where the six screws are tightened simultaneously, and there are cases where the six drivers 110A are used simultaneously. In this case, if the motor shaft 140a of the servo motor 140 is concentric with the bit 114A, the servo motors 140 of the six drivers 110A collide, and a plurality of drivers 110A cannot be disposed adjacent to each other. Such a problem can be solved if it is eccentric as in this embodiment.

  In the above example, the screwdriver 110A automatically performs screw tightening, but an eccentric configuration may be preferable even when one screwdriver 110A is used manually. For example, there is a case where there is a tall part or wall near the screw and the servo motor 140 collides with it.

  Coupling 145 couples detector 150 and bit 114A. The detection unit 150 detects a position immediately before insertion, which will be described later. The detection unit 150 includes a sensor mounting portion 151, a sensor 152, a connection plate 153, a sun dog 154, a rotation stopper 155, and a fixed block 156. The configuration of the detection unit 150 is merely an example.

  The sensor attachment portion 151 is a rod-like member that attaches the sensor 152 to the side wall 156a of the fixed block 156 perpendicularly. The sensor 152 is a photoelectric sensor. The connection plate 153 is a flat plate member having one end coupled to the coupling 145 and the sensor dog 154 attached to the other end. The sensor dog 154 is a light shielding plate. The rotation stopper 155 is a rod-like member that prevents the sensor dog 154 from rotating, and penetrates the connection plate 155. The fixed block 156 includes a side wall 156a and a bottom portion 156b, and has an L-shaped cross section. A detent 155 is vertically attached to the bottom 156b.

  The encoder 158 detects the rotation angle of the motor shaft 140a of the servo motor 140.

  When the bit 114A moves up and down, the sensor dog 154 moves up and down together with the connection plate 153 connected to the coupling 145. If the sensor dog 154 is arranged with the position where the light path of the sensor 152 at this time is shielded as the origin, the origin can be easily detected.

  The inserted state of the screw 10 into the component 20 is shown in FIGS. FIG. 5A is a cross-sectional view showing the positional relationship between the screw 10 at the start of insertion and the component 20. FIG. 4B is a cross-sectional view showing the positional relationship between the screw 10 and the component 20 immediately before insertion. FIG. 4C is a cross-sectional view showing the positional relationship between the screw 10 and the component 20 immediately before sitting. FIG. 4D is a cross-sectional view showing a state where the screw 10 is seated. FIG. 4E is a cross-sectional view showing the positional relationship between the screw 10 and the component 20 that are receiving a torque increase. FIG. 6 is a graph showing the relationship between time and torque when the screw tightening method of this embodiment is applied.

  In this embodiment, since temporary fastening is not performed, the driver 110A shown in FIG. 4 is attached to the final fastening control unit 130A. The final fastening control unit 130 </ b> A has a configuration in which the input unit 136 is provided in the control unit 130. The input unit 136 sets the rotation amount (four rotations in this embodiment) of the motor shaft 140a detected by the encoder 158. The final fastening control unit 130A acquires the outputs of the detection unit 150 and the encoder 158, and the control unit 131 controls the on / off of the energization of the servo motor 140 and the rotation speed based on these outputs. In this embodiment, the driver 110A may be manual or automatic. In the case of manual operation, the user can pull the lever 116 of the driver 110A, and in the case of automatic operation, the user can start driving the driver 110A via the switch of the final tightening control unit 130A or the switch of the device connected to the driver 110A. .

  In the present embodiment, the position of the screw 10 immediately before insertion shown in FIG. 5B is set as the origin. The length of the screw portion of the screw 10 and the pitch amount per rotation are acquired in advance. For example, if the length of the screw portion of the screw 10 is 5 mm and 1 mm is inserted per one rotation, it will be seated as shown in FIG. 5D when it is rotated five times from the state shown in FIG. Become.

  Therefore, in this embodiment, the screw 10 is rotated at a high speed until the state immediately before the seating shown in FIG. 5C, for example, a state where the screw 10 has rotated four times, and the last one rotation is rotated at a low speed. The high speed is, for example, 500 rotations, and the low speed is, for example, 10 rotations. The user may input 4 rotations via the input unit 136, or the controller 131 may calculate 4 rotations by inputting the length and pitch amount of the screw portion.

  Hereinafter, the operation of the screw fastening device 100A having the driver 110A will be described with reference to FIGS. FIG. 7 is a graph showing the relationship between time and torque in the conventional method of performing final fastening at a high speed compared with FIG. FIG. 8 is a flowchart for explaining the operation of the screw tightening apparatus 100A.

  First, the user turns on the power switch 132 of the final fastening control device 130A to set and start the final fastening (step 1102). Next, the user adjusts the detection unit 150 to set the origin position detected by the sensor 152 to the position immediately before insertion shown in FIG. 5B (step 1104). Next, the user inputs rotation information from the state shown in FIG. 5B to the state shown in FIG. 5D via the input unit 136 (step 1106). Further, the user operates the counter setting unit 135 to input the number of screws into the counter 134 (step 1108).

  Next, the user pulls the lever 116 by fitting the tip of the bit 114 into the recess 12 of the screw 10. In response to this, the control unit 131 starts energization of the driver 110 and rotates the driver 110 (step 1110). The control unit 131 rotates the servo motor 140 at a high speed from the insertion start state shown in FIG. 5A until the detection unit 150 detects the state just before the insertion shown in FIG. 5B.

  When the detection unit 150 detects the state immediately before insertion shown in FIG. 5B and receives a notification to that effect from the detection unit 150 (step 1112), the control unit 131 starts receiving the detection result by the encoder 158 (step 1112). Step 1114). The servo motor 140 is rotated at high speed until the encoder 158 detects the state just before the seating shown in FIG.

  Next, when the encoder 158 detects that the motor shaft 140a has rotated four times and receives a notification to that effect from the encoder 158, the control unit 131 determines that the screw 10 is in the position just before the seating shown in FIG. Then, the operation mode of the servo motor 140 is switched from the high speed mode to the low speed mode (step 1118). As a result, as shown in FIG. 6, the torque at the time of sitting shown in FIG. 5 (d) can be reduced.

  When detecting the seating of the screw 10 shown in FIG. 5D (step 1120), the control unit 131 changes to the high speed mode again (step 1122). As will be described later, the seating can be detected from a voltage value, an encoder value, a Hall element value, and the like. Next, the control unit 131 ends the screw tightening when the specified torque is reached. The screw tightening device 100 detects the specified torque using the cam in the driver 110, but the screw tightening device 100A detects the specified torque by monitoring the torque value. Thereafter, the control unit 131 causes the counter 134 to count down (step 1126).

  By switching to the high-speed mode, the time required to give a predetermined elastic force to the spring member such as a spring washer between the screw and the component when the component is a spring member is shortened. As a result, the screw tightening shown in FIG. 5 (e) can be performed with a torque that is not too large. Comparing FIG. 6 and FIG. 7, it is understood that the torque at the time of sitting is drastically reduced according to the tightening control method of the present embodiment.

  When the user determines that all the screws have been fully tightened, the user looks at the counter 134 (step 1128). If the value of the counter 134 is zero, the final fastening is finished. If the counter 134 is not zero, there is a screw that has been forgotten to be tightened, and this is tightened. As a result, forgetting to tighten can be prevented.

  As described above, according to the present embodiment, the accuracy of keeping the seating torque within the standard value is improved, and a product (for example, a spindle motor hub) composed of parts (for example, a clamp ring) and a fastened object (for example, a hub of a spindle motor). The quality of the hard disk device) is stabilized. In addition, the life of the driver 110A can be extended without increasing the rigidity of the servo motor 140 and the mechanism compared to the conventional case where only the high speed is performed.

  As shown in FIG. 1, the electric screwdriver 110 has a temporary fastening control unit 120 as a separate body, but the present invention has a configuration in which the temporary fastening control unit 120 is integrated with the electric screwdriver 110 or the final fastening control unit 130. It does not prevent. FIG. 9A is a front view of the electric driver 110B integrated with the temporary fastening control unit 120, and FIG. 9B is a side view of the electric driver 110B.

  The electric driver 110B is different from the electric driver 110 in that a mode switch 113 and a forward / reverse switch 115 are attached to the surface of the main body 112A. The driver 110B also includes an encoder 158, but the driver 110 does not include an encoder. Furthermore, the electric driver 110B is attached to a final fastening control unit 130B similar to the final fastening control unit 130 shown in FIG. The final fastening control unit 130 </ b> B is different from the final fastening control unit 130 in that it does not have the forward / reverse rotation switch 115 but has an input unit 136. The operation of the driver 110B is different from both the drivers 110 and 110A.

  Table 1 shows the relationship among the mode switch 113, forward / reverse switch 115, and screw tightening operation.

  A necessary operation is set by the mode switch 113, and when the lever 116 is grasped, the operation is executed. If the lever 116 is released during the operation, the operation is interrupted on the spot. When the operation ends abnormally, for example, when the lever 116 is released during the final tightening operation, it is automatically returned by the screw loosening amount so that it can be visually confirmed that the final tightening is not correctly performed. Even in the temporary tightening operation, an abnormality may occur in the vicinity of the seating point.

  The counter 134 of the final fastening control unit 130B counts up (+1) when the final fastening is successful and it is confirmed from the bit rotation amount that the final fastening is after the temporary fastening. If the screw extraction or screw loosening operation is successful and the current return torque value measured from the current value is equal to or greater than the specified value, the final tightened screw is counted down (-1). The count value can be reset to 0 at any time by a push button switch. Note that if these count-up and count-down are changed to count-down and count-up, the result is the same as in the embodiment of FIG.

  Hereinafter, with reference to FIG. 10, the main structure of the screw fastening apparatus 100B which has the driver 110B is demonstrated. Here, FIG. 10 is a block diagram of a main configuration of the screw fastening device 100B.

  The switches 113 and 115 and the lever 116 transmit a user instruction to the MPU. The final tightening control unit 130B includes a control unit 131, a counter 134, an angle counter 160, a D / A converter 161, a power amplifier 162, and an A / D converter 163.

  The control unit 131 includes an MPU and is a microcontroller that controls the motor 140 in accordance with a user instruction. The control unit 131 is a small computer in which a ROM for storing a program, a temporary storage RAM, and the like are built in the same chip.

  The angle counter 160 is an up / down counter for measuring the rotation amount of the motor 140 and counts the output pulses of the incremental encoder 158. Further, the measured value of the rotation amount of the motor 140 is divided by the gear reduction ratio by the MPU and converted into the rotation amount of the bit 114. It is initialized to 0 when the operation is started by grasping the lever 116, and the amount of bit rotation during the subsequent operation is measured. The bit rotation speed is calculated by measuring the amount of increase / decrease in the bit rotation amount per unit time (about 1 msec) by the MPU and dividing by the time interval.

  The D / A converter 161 converts a digital operation amount to the motor 140 calculated for torque control, speed control, and angle control by the MPU into an analog voltage and outputs the analog voltage to the next power amplifier 162.

  The power amplifier 162 drives the motor 140 with a voltage proportional to the output of the D / A converter 161. It is also possible to drive the motor 140 by digital control by replacing the D / A converter 161 with a PWM (pulse width modulator) and the power amplifier with a switching circuit using an FET.

  The A / D converter 163 converts an analog value as a voltage across the resistor inserted in series with the motor winding into a digital value, divides the resistance value by the MPU, and measures the motor current value. Further, when the MPU multiplies the torque constant of the motor 140 and the gear reduction ratio, the bit output torque is obtained.

  The encoder 158 is an incremental rotary encoder for measuring the rotation amount of the motor 140. It is turned on / off for each micro rotation amount by detecting the brightness of light passing through the slit. In the type that can generate a rectangular wave signal and further generate a two-phase rectangular wave having a phase difference of 90 degrees from each other, the direction of rotation can be detected by analyzing the advance / delay of the signal. An absolute encoder that detects the absolute angle of the motor 140 may be used. In that case, the rotation angle is directly read into the MPU without using the counter 160, and instead of initialization, the rotation angle at the start of operation is stored in the MPU, and the stored rotation value is subtracted from the rotation amount during operation. Thus, the rotation amount of the motor 140 from the start of operation is set.

  The motor 140 is a brushed DC servo motor and generates a torque proportional to the motor current. A three-phase brushless motor may be used as the motor. In that case, it is necessary to replace the brush by adding a portion for performing sinusoidal commutation control using the motor rotation angle information of the encoder measurement. The operation amount (inlet) and the motor current (outlet) are equivalent to those of the DC servo motor, and the basic operation is the same as when the DC servo motor is used.

  The gear 146 rotates the bit 114 by increasing the output torque of the motor 140 to a reduction ratio of the gear. Instead, the bit rotation speed is reduced to 1 / reduction ratio. In FIG. 4, elements 141 to 145 correspond to the gear 146. When the torque is small, the rotation of the motor can be transmitted to the bit as it is without using a reduction gear such as a gear. In this case, the reduction ratio is set to 1.

  The counter 134 is an up / down counter that counts the number of screws 10 that have been successfully tightened to prevent forgetting to tighten the screws 10. The user operates the counter setting unit 135 to set the counter to zero. In this embodiment, when the final tightening of the screw that has been temporarily tightened is successful, the MPU instructs +1, and when the final tightened screw is loosened or pulled out, the value is -1. In that case, the return torque when the bit 114 is reversed is measured by a current value, and the final tightening success count value is counted down (-1) as if the screw 10 that had been tightened was loosened only when the bit torque was more than the specified value. To do.

  In this embodiment, two control methods are used in order to control the amount of temporary fastening to be constant. In the first control method, instead of measuring the temporary fastening time by the timer 124, the bit rotation amount (temporary fastening rotational amount) is measured by the encoder 158 to obtain the temporary fastening amount without being seated. In the second control method, once the screw is seated and the seating is detected, the forward rotation is stopped simultaneously and the temporary tightening amount is reversed by obtaining the temporary tightening amount. That is, in the second control method, the bit 114 is rotated until the screw 10 is once seated without stopping the tightening in the middle. In the present embodiment, the driver 110B is manually operated, but these two control methods can also be applied to an automatic clamping device.

  Hereinafter, the first control method will be described with reference to FIGS. 11 and 12. Here, FIG. 11 is a timing chart of the first control method. FIG. 12 is a flowchart of the first control method.

First, the user sets and starts a provisional fastening _{(P 1,} step 1202). That is, the mode switch 113 is set to temporary tightening, the forward / reverse rotation switch 115 is set to forward rotation, and the lever 116 is pulled. The magnetized bit 114 is fitted into the recess 12 of the iron cross-recessed screw 10 and set at the inlets of the female screw holes 22 and 32, and the temporary fastening sequence is started.

First, the screw holes 22 and 32 inlet at galling (seizure) of finely amount reversed for prevention _{(P 2,} step 1204). This is because galling is likely to occur when the screw is suddenly rotated in a state where the screw is tilted, so that the screw 10 is reversely rotated by a minute amount (about 90 ° to 360 °) and aligned straight with the screw 10 screw holes 22 and 32. Note that galling means that the screw has a low thermal conductivity and a high coefficient of thermal expansion, and therefore, when tightened with an electric tool or the like, the screw part expands due to frictional heat and the male screw and the female screw come into close contact and do not move.

Then, first for galling prevention at the inlet of the screw holes 22 and 32 to rotate the bit 114 at low speed _{(P 3,} Step 1206). During the low speed period, the user registers in advance in the final tightening control unit 130B via the input unit 136 as the rotation amount. The control unit 131 determines whether the rotation amount has been reached using the encoder 158. The low speed is, for example, two rotations.

Next, in order to shorten the tightening time, the bit 114 is rotated at high speed until just before sitting (P ₄ , step 1208). An encoder 158 is used to determine whether or not it is just before sitting. For example, if the length of the screw portion of the screw 10 is 5 mm and 1 mm is inserted per rotation, the screw 10 is seated in 5 rotations. Therefore, step 1208 rotates the bit 114 at a high speed until the encoder 158 detects a state where the screw 10 has rotated four times. The point that the user registers in advance the amount of rotation immediately before sitting in the final tightening control unit 130B via the input unit 136 is the same as in the final tightening control unit 130A. The control unit 131 determines whether the rotation amount has been reached using the encoder 158. The low speed mode is, for example, 10 rotations, and the high speed mode is, for example, 500 rotations.

Next, the control unit 131 to decelerate and stop the bit 114 when the screw 10 in a seated position immediately before is determined to have reached _{(P 5,} step 1210). Because it stops before seating is floating screws 10 (P _6). However, since the amount of rotation is determined using the encoder 158, the amount of temporary tightening varies depending on the length of the screw portion of the screw 10. In this state, since the screw 10 is not yet seated, there is almost no impact (torque) (P ₁₂ ).

Next, the user sets and starts the tightening _{(P 7,} step 1212). That is, the mode switch 113 is set to the final tightening, the forward / reverse rotation switch 115 is set to the forward rotation, and the lever 116 is pulled. The bit 114 is fitted into the recess 12 of the screw 10 to start the final tightening sequence. First, assuming double tightening, the bit 114 is initially rotated at a low speed (P ₈ , step 1214). That is, since the screw 10 may be tightened after the final tightening, the bit 114 is rotated at a low speed while this is detected from the rotation amount. When the low speed is commanded and the amount of rotation does not increase, it is determined that the screw 10 has been fully tightened after the final tightening, the seating is completed, the speed control is terminated, and the torque is increased. (At this time, the final tightening is normally completed, but as described later, the screw that has already been fully tightened is tightened again at 1226, so the count is not increased.)
Next, in order to shorten the tightening time, the bit 114 is rotated at a high speed until just before the seating (P ₉ , step 1216).

Next, rotate the bit 114 at a low speed in order to suppress the impact (torque) at the time of seating _{(P 10,} step 1218). As a result, the screw 10 is seated (P ₁₁ , step 1220). Since the rotational speed of the bit 114 decreases when the screw 10 is seated, it is detected that the rotational speed is less than the specified value (or the actual rotation speed decrease rate is less than the specified value with respect to the instructed rotational speed). And judge it to be seated. The rotation speed of the bit 114 can be measured as the rotation amount per minute time from the rotation amount measurement value by the encoder 158. Alternatively, it may be detected that the motor current value has increased beyond a specified value and determined to be seated, and switching from speed control to torque-up control may be performed.

Since the rotational speed at the time of seating is low, the torque can be reduced in both current and inertial force due to seating detection delay (P ₁₃ ). Thereby, the control part 131 complete | finishes the rotational speed control of the bit 114. FIG.

Next, the control unit 131 starts the torque-up control according to the torque curve of the designated _{(P 14,} step 1222). Next, the control unit 131 maintains the torque for a specified time at the maximum tightening torque and stabilizes the tightening (P ₁₅ , step 1224). Next, the controller 131 confirms that the temporarily tightened screw has been finally tightened from the rotation amount from the start of the final tightening to the seating (or until the torque is increased), and that torque up and torque hold are normally performed. If it is determined that it has been, one pulse (+1) for counting the number of screws 10 that have been successfully tightened is output (P ₁₆ , step 1226). If the screw that has been tightened is tightened again, it will rotate only a small amount equivalent to the looseness of the bit and recess fitting, so the amount of rotation is less than the amount of rotation that was floated for temporary tightening. In this case, it can be easily determined that the final tightened screw has been finally tightened again, and in this case, the successful tightening is not counted up. Furthermore, it is not only possible to count up, but it is also possible to explicitly output an alarm output when the final tightened screws are tightened again if necessary. (It is not necessary to treat it as an anomaly even if the final tightening is performed twice, but at least the final tightening success pulse is not output.)
If any abnormality is detected during the final tightening and the torque cannot be increased to the final tightening torque, the bit 114 is reversed to return the screw 10 to the temporary tightening position. This makes it easy to find forgetting to tighten. Also, after removing the cause of the abnormality, the final tightening can be performed again using the same procedure.

  Hereinafter, the second control method will be described with reference to FIGS. 13 and 14. Here, FIG. 13 is a timing chart of the second control method. FIG. 14 is a flowchart of the second control method. 14, the same steps as those in FIG. 12 are denoted by the same reference numerals, and the description thereof is omitted. Steps 1202 to 1208 are the same as those in FIG.

When the control unit 131 determines that the screw 10 has reached the position immediately before sitting, the control unit 131 rotates the bit 114 at a low speed (P ₂₁ , step 1302). The number of rotations in the low speed mode is, for example, 10 rotations.

Next, seating is detected when the rotational speed of the bit 114 is decreased, and the rotational speed control of the bit 114 is terminated and switched to angle control for reverse rotation (P ₂₂ , step 1304). Due to the seating detection delay, a momentary torque is generated by the current in the last part of the speed control (P ₂₅ ). This is because when the impact of the seating is instantaneous, such as when there is no spring washer, the detection of seating is delayed, so that a momentary torque may be generated by the motor current just before the speed control is finished. If the motor current value at this time is measured and becomes equal to or greater than a specified value, it can be determined that the user is seated. If the seating can be automatically detected by these methods, the control unit 131 can automatically switch to the angle control for temporary fastening and reverse the rotation. Moreover, the impact at the time of sitting appears in torque during the reverse rotation (P _26). This is because, due to the reverse rotation, the magnitude of the return torque of the screw tightened by the impact at the time of sitting appears in the current. If the current value of the P ₂₆ is greater than the current value of the P ₂₅ is proportional to the inertia of the rotating portion and the bit rotational speed, so that the inertial force that is inversely proportional to the shock-absorbing time is added.

Next, the control unit 131, reversed by the specified rotation amount for temporarily tightened (temporarily tightened weight) floating the screw 10 from the seating position _{(P 23,} step 1306). The temporary fastening amount is registered in advance in the final fastening control unit 130 </ b> B by the user via the input unit 136. The control unit 131 determines whether the rotation amount has been reached using the encoder 158. In this way, after detecting the seating, the torque is not increased and the rotation is reversed by a predetermined rotation amount, so that a gap corresponding to the temporary tightening amount is formed between the screw head and the component 20. The temporary tightening amount can be accurately controlled even for the screw 10 in which the frictional resistance when screwing is greatly varied. Thereby, the component 20 can be moved minutely and the other screws 10 can be easily tightened. When all the screws 10 are temporarily tightened, the component 20 is finely moved and fixed to a correct position as necessary.

Next, the user sets and starts the tightening _{(P 7,} step 1212). Through steps 1214 and 1216, the bit 114 is rotated at a low speed in order to suppress the impact (torque) at the time of sitting (P ₂₄ , step 1308). When approaching seating, the vehicle decelerates to suppress the impact when seated. Since it is known that if the seat is rotated by the amount of temporary tightening, it is known that the seating is performed, so the deceleration time can be set immediately before the seating. Since the period of this low-speed rotation can be sufficiently shortened, the bit rotation speed just before the seating can be lowered compared to the temporary tightening, and precise final tightening is possible. Thereafter, steps 1220 to 1228 are performed.

  Hereinafter, a modified example of the second control method will be described with reference to FIGS. 15 and 16. Here, FIG. 13 is a timing chart of a modified example of the second control method. FIG. 16 is a flowchart of a modification of the second control method. In FIG. 16, the same steps as those in FIG. 14 are denoted by the same reference numerals, and the description thereof is omitted. Steps 1202 to 1304 are the same as those in FIG.

The controller 131 reverses by a specified rotation amount (temporary tightening amount) for temporary tightening and lifts the screw 10 from the seating position, but the temporary tightening amount is finely adjusted so that the direction of the recess 12 or the direction of the bit 114 is aligned ( P _27, step 1310). Thereby, the bit 114 and the recess 12 can be fitted at the same angle during the final tightening. Moreover, even if the length of the screw part of the screw 10 changes, the amount of temporary fastening can always be controlled to the same amount. Further, since the return angle is very small, the direction of the recess 12 can be aligned while securing a necessary amount of temporary fastening.

  In order to align the direction of the recess 12, an origin sensor of the bit 114 may be provided. However, it does not have to be so strict. For example, the finely corrected final positioning angle is 90 degrees (or ± 45 degrees) when the recess 12 is a cross hole, 60 degrees (or ± 30 degrees) when the recess 12 is a hexagonal hole, and 180 when both are mixed. What is necessary is just to set the jump value in degrees (or ± 90 degrees) steps. This method is inexpensive because it is only a method of devising a calculation method that does not require special hardware. A state in which the recesses 12 of the cross holes are aligned beside FIG.

Thereafter, steps 1212 to 1224 are performed. Next, the operator is informed that the torque hold has been completed and the torque has been released, and when the operator knows that the final tightening has been completed, the driver is lifted, so the bit is uncoupled from the screw recess, Furthermore, release the lever that was gripping. When this lever is released by the control unit 131 when the opening operation is P _{7 ′} , the lever is reversed by a small amount to align the direction of the bit 114 (P ₂₈ , step 1312). As a result, the bit 114 and the recess 12 can be fitted at the same angle when the next screw is finally tightened. For this reason, the bit 114 is reversed after the torque is released from the torque hold. In this case, it is conceivable to perform forward rotation, but if the lever 116 is released before the coupling between the recess 12 and the bit 114 is released, the forward rotation will be overtightened in the case of normal rotation, so reverse rotation is safer. . At this time, the current is monitored to confirm that no torque is applied. If the torque is applied, the process is terminated abnormally. In order to align the direction of the recess 12, the final positioning angle is set to a value with the smallest amount of rotation with a jump value of 90 degrees when the recess 12 is a cross hole and 60 degrees when the recess 12 is a hexagonal hole.

Thereafter, steps 1226 to 1228 are performed. Incidentally, to measure the current value of the reverse rotation, if a large current above defined flows and an abnormal end as loosening the screw 10 is reversed before departing the coupling recess 12 and the bit 114, pulse P ₁₆ is output do not do.

  Even if the screw 10 is loosened by a specified amount of rotation due to an abnormality that occurs during final tightening or temporary tightening, the angle at which the screw 10 is finally reversely rotated and positioned is 90 ° step or 60 ° step depending on the shape of the recess. If the return angle is selected so as to stop only at, the direction of the bits 114 can be aligned and the operation can be terminated. Even during loosening and unscrewing operations, if the rotation amount is set to 90 degrees and 60 degrees so that the direction of the recess 12 is the same after completion, the direction of the bit 114 is always aligned even after these operations. . Also, when the lever 116 is released during these operations and the operation is interrupted, the operation is stopped at this jump angle.

  Also, the method of aligning the direction of the bit and the recess has been described as a modified example of the second control method. However, the angle at which the bit rotation is stopped before seating for temporary tightening also depends on the shape of the recess in the first control method. In the same manner, it is possible to control to a jump value such as 90 degree step and 60 degree step.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made.

Industrial applicability

  According to the present invention, it is possible to provide a screw tightening device that accurately controls the amount of temporary tightening.

Claims (13)

An electric screwdriver to tighten the screws,
A mode switch for switching between a final tightening mode in which the torque is increased after the screw is seated, and a temporary tightening mode in which the screw is not seated and is tightened by a predetermined amount before the seating;
A counter that operates when the mode switch is set to the final tightening mode, does not operate when the mode switch is set to the temporary tightening mode, and counts the number of screws that have been torqued up;
An input unit for setting the rotation speed of the electric driver in the temporary fastening mode;
A screw fastening device comprising: a control unit configured to rotate and stop the electric driver by the number of rotations when the mode switch is set to the temporary fastening mode and the electric driver starts to rotate. A method of controlling the driving of an electric driver having a bit for tightening a screw ,
When the rotation start operation of the electric driver in temporary tightening mode tightened by a predetermined amount before sitting without sitting in front Symbol screw is made, a step of stopping rotated by rotation speed set the electric driver,
Counting the number of screws that have been torqued up in the final tightening mode in which torque is increased after seating the screw without counting in the temporary tightening mode . In the temporary fastening mode,
Reversing the bit before starting the screw tightening operation;
Rotating the bit at a first speed in a direction to tighten the screw immediately after starting the tightening operation of the screw;
The method of claim 2, further comprising the step of rotating the bit at a second speed that is faster than the first speed after the step of rotating at the first speed. A method of controlling the driving of an electric driver having a bit for tightening a screw ,
A step of stopping the electric driver from by reversing the bits by the rotation speed set corresponding to the predetermined amount after being seated the screw in the temporary tightening mode tightening the pre Symbol screw by a predetermined amount before the seating,
Counting the number of screws that have been torqued up in the final tightening mode in which torque is increased after seating the screw without counting in the temporary tightening mode . In the temporary fastening mode,
Reversing the bit before starting the screw tightening operation;
Rotating the bit at a first speed in a direction to tighten the screw immediately after starting the tightening operation of the screw;
Rotating the bit at a second speed faster than the first speed after the step of rotating at the first speed;
5. The method of claim 4, further comprising the step of rotating the bit at a third speed slower than the second speed and waiting for seating after the step of rotating at the second speed. The electric screwdriver tightens a plurality of screws,
6. The method according to claim 4, wherein the amount of reversal of the bit is adjusted so that the recess directions of the plurality of screws are aligned.   The method according to any one of claims 2 to 6, further comprising a step of performing a torque hold for holding the screw for a predetermined time after torque-up in the final tightening mode. The electric screwdriver tightens a plurality of screws,
In the final tightening mode, after the torque hold is completed and the torque is released , it is detected that the lever is released, and the bit is rotated so that the recess directions of the plurality of screws are aligned. The method of claim 7 .   In the counting step, the final tightening of the screw after temporary tightening is determined by determining whether the screw after temporary tightening is final tightened or the final tightened screw is tightened again according to the amount of bit rotation at the time of final tightening. 5. The method according to claim 2 or 4, wherein the number of successful final fastenings is counted only when is successful. In the final tightening mode,
Rotating the bit at a fourth speed in a direction to tighten the screw immediately after starting the screw tightening operation;
Rotating the bit at a fifth speed faster than the fourth speed after the step of rotating at the fourth speed;
5. The method according to claim 2, further comprising the step of rotating the bit at a sixth speed slower than the fifth speed and waiting for seating after the step of rotating at the fifth speed. . In the temporary fastening mode,
Reversing the bit before starting the screw tightening operation;
Rotating the bit at a first speed in a direction to tighten the screw immediately after starting the tightening operation of the screw;
Rotating the bit at a second speed faster than the first speed after the step of rotating at the first speed;
After the step of rotating at the second speed, rotating the bit at a third speed slower than the second speed and waiting for seating;
In the final tightening mode,
Rotating the bit at a fourth speed in a direction to tighten the screw immediately after starting the screw tightening operation;
Rotating the bit at a fifth speed faster than the fourth speed after the step of rotating at the fourth speed;
Rotating the bit at a sixth speed slower than the fifth speed after the step of rotating at the fifth speed and waiting for seating;
5. The step of making the sixth speed slower than the third speed and suppressing the impact torque at the time of seating of final fastening to be smaller than the impact torque at the time of temporary fastening. Screw tightening method. A method of manufacturing a product by screwing a part to an object to be fastened using an electric screwdriver that tightens a screw .
When the rotation start operation of the electric driver in temporary tightening mode tightened by a predetermined amount before sitting without sitting in front Symbol screw is made, a step of stopping rotated by rotation speed set the electric driver,
And counting the number of screws that have been torque-up in the final tightening mode in which the screws are tightened to the seat without counting in the temporary tightening mode . A method of controlling the driving of an electric driver having a bit for tightening a screw,
Counting the number of screws that have been torqued up in a final tightening mode in which torque is increased after seating the screws;
Setting the rotational speed of the electric driver;
Stopping the electric driver after reversing the bit by the number of rotations corresponding to the predetermined amount after seating the screw in a temporary tightening mode in which the screw is tightened by a predetermined amount before sitting;
A step of determining seating when the bit rotation speed falls below a specified value, when the actual bit rotation speed with respect to the commanded bit rotation speed falls below a specified ratio, or when an increase in motor current is detected; ,
And automatically switching from bit rotation speed control to angle control for reverse rotation for temporary tightening and floating of the screw.