JP4484447B2 - Method and apparatus for controlling impact type screw fastening device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control method and apparatus for a screw tightening device, and more particularly to a screw tightening device that reduces reaction force so as to be suitable for one-hand holding.
[0002]
[Prior art]
Conventionally, a power-type screw fastening device has been used to fasten bolts and screws with a predetermined torque. In the screw tightening device, generally, control is performed such that the shaft is continuously rotated to tighten the screw, and when the torque reaches a certain value, the power is turned off or the clutch is slid.
[0003]
By the way, in various assembly lines, an operator often performs screw tightening work on a work on a conveyor by holding a screw tightening device by hand.
In that case, it is desired that the screw fastening device can be operated with one hand from the viewpoint of workability. In a single hand-held screw tightening device, the reaction of screw tightening must be received with one hand, so that the recoil becomes a problem as an operator's load as the tightening torque increases.
[0004]
As described above, the method of rotating the shaft continuously receives the reaction force (reaction) of the tightening torque directly by the operator's hand, so the load on the operator is large. In order to reduce this reaction force, an impact method using an impulse of a rotor rotating rotor is used.
[0005]
However, in conventional impact-type screw tightening devices, the screws are tightened via the collision energy generating mechanism and the socket, so the accuracy of the tightening torque greatly increases and decreases due to variations in their transmission efficiency, and screws that require accuracy Not suitable for tightening. In order to improve accuracy, a method is used in which a clutch mechanism is provided at the tip of the shaft and the clutch slips to control torque when more torque than necessary is input.
[0006]
Under these circumstances, a screw tightening device called an oil pulse wrench, which has both of two functions (impact generation unit and clutch mechanism), has been popularized against the two problems of reducing reaction force and improving accuracy. ing.
[0007]
The oil pulse wrench usually has an oil pulse portion in which an air motor that is a drive source and a bypass valve that generates an impulse and can use the oil pressure as a clutch mechanism are integrated.
[0008]
However, the oil pulse wrench requires troublesome adjustment of the hydraulic pressure of the bypass valve that works as a clutch mechanism, and it is necessary to frequently perform readjustment and replacement of parts as the oil pulse generator deteriorates. There are various problems such as that the accuracy of the oil fluctuates and that the oil pulse part generates a large amount of heat, so that countermeasures are necessary.
[0009]
In order to solve these problems, the present applicant has previously proposed a screw tightening device using an electric motor and a control method thereof (Japanese Patent Laid-Open No. 2002-1676).
[0010]
[Patent Document 1]
JP 2002-1676
[0011]
[Problems to be solved by the invention]
According to the above-mentioned screw fastening device proposed by the present applicant, the accuracy is good even though the reaction force to the worker is small. Therefore, the operator can perform the screw tightening operation with one hand.
[0012]
However, the present inventors conducted intensive research on the fact that it was desired to further reduce the reaction force on the worker, and succeeded in further reducing the reaction force by improving the above screw fastening device. did.
[0013]
Accordingly, an object of the present invention is to further reduce the reaction force in an impact-type screw fastening device using an electric motor as a rotational drive source.
[0014]
[Means for Solving the Problems]
The control method of the present invention includes an electric motor as a rotational drive source. And a shock generating device that generates a shock by causing the rotating input side member to collide with the output side member and applies torque to the load. A control method for an impact-type screw fastening device, wherein electric power is intermittently supplied to the motor to drive the motor so that the rotational speed is pulsed on the time axis, and Due to the rotation of the motor. The shock There has occurred Detected Sometimes control is performed to reduce the supply of power to the motor.
[0015]
Preferably, in the control as described above, the rotation speed of the motor is maximized at each pulse-like time. Detected Sometimes, the power supply for each pulse-like time is stopped.
Further, the torque is detected by sampling at a cycle shorter than the width of the one pulse-like torque, and when the detected torque value does not exceed the maximum value of the detected torque value, the torque is maintained. The electric power is controlled, and when the detected torque value exceeds the maximum value of the detected torque value so far, the electric power is controlled so as to increase the torque by a predetermined amount.
[0016]
Preferably, in a cycle shorter than the width of one of the pulse-like rotational speeds Times Rolling speed sampling And S Ring did The value was smaller than the previous time Detected Sometimes, the power supply is stopped assuming that the rotation speed becomes maximum.
[0017]
The control device of the present invention Control device for impact-type screw tightening device provided with impact generating device for generating impact by causing impact by impacting an input-side member rotating with an electric motor as a rotational drive source against an output-side member Because Torque detecting means for detecting the tightening torque of the screw by the motor, setting means for setting a target value of the tightening torque, and supplying electric power to the motor in intermittent pulses, Each time, the rotation speed of the motor became maximum Detected A current control unit that performs current control so as to stop power supply from time to time, and a stop control unit that stops supply of the pulsed power when a torque detection value reaches the target value.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing the overall configuration of a screw fastening device 1 according to the present invention.
In FIG. 1, the screw tightening device 1 includes a screw tightening device main body 3 and a control device 4 having a servo driver 7 and a controller 8 for control.
[0019]
The screw tightening device body 3 includes a motor 11, an impact generating device 12, a torque sensor 13, an encoder 14, an output shaft 15, and a casing, a switch, and the like (not shown).
[0020]
As the motor 11, for example, a three-phase AC servo motor is used. The impact generator 12 is a collision energy generating mechanism that converts the rotational force of the motor 11 into intermittent impact force. Various mechanisms are used as the impact generator 12. For example, a reduction gear such as a planetary gear, a two-hammer mechanism, a swing hammer mechanism, other hammer mechanisms, an oil pulse mechanism, or the like can be used. When planetary gears are used, the backlash (play) of the planetary gears and the play of the joints, etc. are used, and while the high speed side rotates multiple times, the low speed side gear rotates by the amount of play, and the gears actually hit each other Generates an impact. When the two-hammer mechanism is used, the motor 11 makes two strokes with one rotation. In the case of using a swing hammer mechanism, one rotation is one hit and the output of one hit is large.
[0021]
The torque sensor 13 detects a screw tightening torque TQ by the motor 11 and outputs a detection signal S31. In the present embodiment, among the torques output from the motor 11, the torque generated in the output shaft 15, that is, the torque for tightening the screw as the load (tightening torque) can be directly detected. Are directly connected to the output shaft 15. Therefore, the detection signal S31 obtained from the torque sensor 13 represents the waveform of the actual tightening torque TQ applied to the screw due to the impact by the impact generating device 12.
[0022]
The encoder 14 is for detecting the rotational speed of the motor 11 and outputs a number of pulse signals proportional to the rotational speed of the motor 11.
The screw tightening device main body 3 has a handle grip portion for an operator to hold with one hand, and is covered with a casing having a shape that can be operated with one hand as a whole. By operating a switch (not shown), power on / off is controlled.
[0023]
The servo driver 7 includes a power supply unit 21, an inverter 22, an AD converter 23, an adder 24, a speed error amplifier 25, a switch 26, a limit circuit 27, a current control calculation unit 28, a PWM circuit 29, a gate drive 30, and an encoder signal. It comprises a processing unit 31, a speed detection unit 32, current detectors 33 and 34, AD converters 35 and 36, and the like.
[0024]
The control controller 8 includes a preamplifier 41, an AD converter 42, a parameter storage unit 43, a command control unit 44, and the like. The command control unit 44 is provided with a speed / current command calculation unit 51, an operation control mode switching unit 52, a speed / current limit unit 53, and the like.
[0025]
The power supply unit 21 rectifies AC power of AC 100 volts, for example, and converts it into DC power of appropriate various voltages. The DC power is supplied to the inverter 22 and other circuits and parts.
[0026]
The AD converter 23 receives a speed / current command (speed / torque command) S1 output from the speed / current command calculation unit 51, and outputs command data D1 having a digital value corresponding to the command. The command data D1 becomes speed command data D1S or current (torque) command data D1T depending on the operation mode.
[0027]
The adder 24 subtracts the speed data D21 output from the speed detector 32 from the command data D1 output from the AD converter 23.
The speed error amplifier 25 differentially amplifies the speed command data D2 output from the adder 24.
[0028]
The switch 26 switches between the speed command data D3 output from the speed error amplifier 25 and the current command data D1T output from the AD converter 23 according to the control switching command S2 from the operation control mode switching unit 52. That is, switching is performed so that the speed command data D3 output from the speed error amplifier 25 is connected when speed control is performed, and the current command data D1T output from the AD converter 23 is connected when current control (torque control) is performed.
[0029]
The limit circuit 27 controls based on the speed / current limit command (speed / torque limit command) S3 from the speed / current limit unit 53 to limit the rotation speed or the maximum value of the current of the motor 11.
[0030]
The current control calculation unit 28 applies the motor 11 based on the command data D4 output from the limit circuit 27, the data D5 output from the encoder signal processing unit 31, and the current data D6 and D7 output from the AD converters 35 and 36. The current value to be flown is calculated and output as current command data D8.
[0031]
The PWM circuit 29 performs PWM (pulse width modulation) based on the current command data D8 output from the current control calculation unit 28, and outputs a pulse signal D10 subjected to pulse width modulation.
[0032]
The gate drive 30 generates a pulse signal D11 for turning on and off the gate of each switching element of the inverter 22 based on the pulse signal D10.
The encoder signal processing unit 31 performs signal processing of the pulse signal output from the encoder 14.
[0033]
The speed detector 32 detects the speed based on the signal output from the encoder signal processor 31 and outputs speed data D21 indicating a value corresponding to the speed. Therefore, the speed data D21 represents the actual rotational speed of the motor 11.
[0034]
The current detectors 33 and 34 detect u-phase and w-phase currents (motor currents) i flowing through the motor 11. The AD converters 35 and 36 convert the motor current i detected by the current detectors 33 and 34 into current data D6 and D7 of digital values, respectively.
[0035]
The preamplifier 41 amplifies the detection signal S31 detected by the torque sensor 13. The AD converter 42 converts the signal S 32 output from the preamplifier 41 into digital torque data D 31 and outputs the torque data D 31 to the speed / current command calculation unit 51. As described above, the torque data D31 is data indicating the actual tightening torque TQ for the screw.
[0036]
The parameter storage unit 43 stores various parameters necessary for calculation by the speed / current command calculation unit 51 and the like. Examples of the parameters include a minimum current value, a measurement start torque, a seating torque TS, a target torque TQJ, a maximum value TQM of the tightening torque TQ, and a current slope θ. These parameters are set by the setting unit 45. As the setting device 45, a digital switch, a numeric keypad, a touch panel, a changeover switch, or the like is used.
[0037]
The speed / current command calculation unit 51 calculates a speed command value and a command current value based on the torque data D31 from the AD converter 42, the parameters from the parameter storage unit 43, and the like, and the speed / current (torque). Output as command S1.
[0038]
Note that the current command S1T of the speed / current (torque) command S1 outputs a command current value only when a later-described current pulse DP is on time TN, and during the off time TF, the current command S1T Is zero.
[0039]
The operation control mode switching unit 52 switches between the speed control mode and the current control (torque control) mode.
In the speed control mode, control is performed so that the rotation speed of the motor 11 becomes the speed set by the speed command data D1S. Even if the load fluctuates, the current flowing through the motor 11 is controlled so that the set speed is obtained. In the speed control mode, a current limit value can be provided. The current limit value limits the maximum current value. Therefore, the set speed may not be reached depending on the state of the load.
[0040]
In the current control mode, control is performed so that the current flowing through the motor 11 becomes the current value set by the current command data D1T. The rotation speed of the motor 11 varies depending on the set current value and the load state. In the current control mode, a rotational speed limit value can be provided. When the rotation speed of the motor 11 reaches the limit value, the current value is limited.
[0041]
The switch 26 selects speed command data D3 in the speed control mode and current command data D1T in the current control mode.
In the tightening operation during automatic operation, the operation is first performed in the speed control mode, and the output shaft 15 is rotated at a high speed. When the tightening torque TQ generated in the output shaft 15 reaches a preset seating torque TS, it is determined that a screw as a load is seated, and the mode is switched to the current control mode. In the current control mode, the current flowing through the motor 11 is controlled so that the output torque indicated by the current command data D1T is obtained.
[0042]
During manual operation, one of the modes is set according to the operation of a changeover switch (not shown).
The speed / current limit unit 53 sets maximum values of speed and current (torque), and gives the set values to the limit circuit 27.
[0043]
The controller 8 for control is comprised using CPU, ROM, RAM, another peripheral element, etc. The speed / current command calculation unit 51, the operation control mode switching unit 52, the speed / current limit unit 53, and the like described above are realized by executing a program stored in the ROM by the CPU.
[0044]
The control controller 8 includes an input device for inputting data or a command, a display device for displaying the result of the tightening or not, a communication device for communication with other data processing systems or control devices, and the like.
[0045]
Next, the principle of the control method in this embodiment will be described with reference to FIG.
First, control (no reaction force control) for reducing the reaction force of the tightening torque TQ will be described.
[0046]
The screw tightening device main body 3 is operated by a worker holding the handle grip portion with one hand. In order to reduce the reaction force to the worker, the operation of the motor 11 is not a continuous operation in which a current flows continuously, but an intermittent operation with a pulsed current.
[0047]
That is, as shown in FIG. 8, a pulsed current (current pulse DP) is intermittently supplied to the motor 11 by command data D1 (current command data D1T). The current pulse DP has an on time TN and an off time TF that can be variably set, and is repeated in a predetermined cycle, that is, a cycle of a total time of the on time TN and the off time TF. The height of the current pulse DP, that is, the value of the current flowing through the motor 11 is determined in relation to the tightening torque TQ.
[0048]
In FIG. 8, when the current pulse DP is turned on, the motor 11 starts to rotate, and the rotational speed gradually increases. When the motor 11 is rotated by a predetermined angle or a predetermined number of rotations, the rotating input side member collides with the output side member in the impact generating device 12, thereby generating an impact. That is, the inertial energy of the input-side member in the impact generator 12 is transmitted as an impact force to the output-side member due to the collision of the member, and a large torque is generated by the impact force. This torque acts as a tightening torque TQ on the screw as a load. Most of the inertial energy of the input side member is transmitted to the output side member and transmitted to the screw during a short period from the moment of impact timp, for example, about 0.01 to 0.005 sec. After that, the rotation of the motor 11 is restarted, and inertia energy for the next impact is stored.
[0049]
In the present embodiment, the current flowing through the motor 11 is stopped at the moment of impact timp or before and after the minute width, particularly after the minute width. That is, the supply of power to the motor 11 is stopped. As the timing for stopping the current, the timing at which the rotation speed of the motor 11 is maximized is used. For example, the timing at which the rotation speed of the motor 11 changes from rising to lowering is detected. As a detection method therefor, for example, the rotation speed is sampled at a constant short time interval ts, and the rotation speed becomes maximum when the sampling value becomes smaller than the previous sampling value. Actually, in order to prevent erroneous detection due to noise or the like, it is detected that the rotational speed has become maximum when the sampling value is continuously reduced a plurality of times (for example, three times) from the previous time. The current command data D1T is created so that the current pulse DP is turned off at the detected timing. The time interval ts is set to 0.5 msec, for example.
[0050]
Thus, by stopping the supply of electric power to the motor 11 when the rotational speed of the motor 11 reaches the maximum, no unnecessary tightening torque after the occurrence of an impact is generated, and this acts on the operator. The reaction force to be applied is generally only the instantaneous torque generated by the motor 11 at the moment of impact timp. Thereby, the reaction force to the worker is greatly reduced.
[0051]
That is, if a current is continuously supplied to the motor 11 after the on-time TN has passed even after the occurrence of an impact, torque is generated by the current, and this acts as a reaction force to the operator. Conventionally, this reaction force has acted on the worker. In addition, the reaction force, that is, the torque generated by the current is much smaller than the torque due to the impact, and therefore hardly contributes to the tightening of the screw. In other words, the current (electric power) supplied to the motor 11 after the occurrence of an impact is a wasteful current (power), and the torque generated by the current is a wasteful torque and an undesirable torque that acts on the operator. That's what it means.
[0052]
According to the control of the present embodiment described above, this useless tightening torque TQ can be made almost zero, whereby the reaction force to the worker can be greatly reduced. In addition, since unnecessary current is reduced, power is also saved.
[0053]
Next, the control of the current pulse DP will be further described.
The value of the generated tightening torque TQ is also detected by sampling. That is, regardless of whether the current pulse DP is on or off, the actual tightening torque TQ is detected at regular time intervals ts, and the tightening torque TQ (torque detection value) becomes the maximum value TQM of the tightening torque TQ so far. When not exceeding, the current value is maintained, and when the tightening torque exceeds the maximum tightening torque value TQM, the current value is increased by a predetermined amount.
[0054]
Therefore, while the tightening torque TQ is increasing, the maximum value TQM is updated every time interval ts. The maximum value TQM is stored in the parameter storage unit 43 of the control controller 8.
[0055]
The predetermined increment may be, for example, an increment of the current slope θ corresponding to the time interval ts for performing such processing. The value of the current slope θ (increase relative to the time interval ts) can be set and changed to various values.
[0056]
For example, the ON time TN of the current pulse is set to 0.02 sec, the OFF time TF is set to 0.02 sec, and the time interval ts is set to 0.5 msec. This is repeated until the target torque TQJ is reached. In this case, the determination and processing described above are repeated every 0.5 msec. This determination and processing is performed regardless of whether the current pulse is on or off. However, in the off time TF, the calculation value of the current may increase due to the processing, but the current that actually flows to the motor 11 is zero, and when the on time TN is reached next, the result of the processing A current value (calculated value) is given as an initial value.
[0057]
As described above, it is possible to switch whether or not to perform control (no reaction force control) to make the current pulse DP zero when the rotation speed of the motor 11 reaches the maximum. That is, it is possible to switch between the no-reaction force control mode in which the no-reaction force control is performed and the simple control mode in which the no-reaction force control is not performed. A switch (not shown) is provided so that the operator can perform the switching.
[0058]
In any mode, the tightening torque can be accurately controlled regardless of disturbances, workpieces, operating conditions, etc., and since the operation pattern does not affect the accuracy, a pulsed tightening torque TQ is applied. Thus, the reaction force can be reduced. In particular, in the no-reaction force control mode, the reaction force to the worker can be greatly reduced.
[0059]
Next, a control method of the screw tightening device 1 will be described with reference to a flowchart illustrating a procedure and operation of a tightening process and a diagram illustrating an operation state.
2 is a flowchart showing the procedure of the tightening operation of the screw tightening device 1, FIG. 3 is a flowchart showing a routine for current control, FIG. 4 is a flowchart showing a routine for maximum rotation detection processing, and FIG. 5 is a routine for torque increase control processing. FIG. 6 is a diagram showing the overall state of the screw tightening operation by the screw tightening device 1, FIG. 7 is a diagram showing the relationship between the rotational speed of the motor 11 and the current command data D1T, and FIG. 8 is a control of the current pulse DP. FIG.
[0060]
As shown in FIG. 6, the tightening operation includes an operation in the speed control mode and an operation in the current control mode.
In FIG. 2, first, speed control in the speed control mode is performed (# 11). In the speed control, the rotation speed of the motor 11 is set by the speed command data D1S. The speed command value is gradually increased, and the rotation speed of the motor 11 is also increased. When the rotation speed reaches a predetermined value, the constant value is maintained. As a result, the motor 11 rotates at high speed, and temporary tightening is performed until the screw is seated. In the meantime, if the tightening torque TQ exceeds the measurement start torque, the measurement is started.
[0061]
When the tightening torque TQ reaches the seating torque TS (Yes in # 12), it is determined that the screw is seated, and the motor 11 is stopped suddenly (# 13).
In order to stop the motor 11 suddenly, the speed command value of the motor 11 is set to zero, and a current is applied to lock the motor 11 for braking. Then, the mode is switched to the current control mode (# 14).
[0062]
In the current control mode, first, the minimum current value ST1 necessary for idling rotation is set as the current command data D1T for the motor 11 (# 15).
Then, current control is performed until the tightening torque TQ reaches the target torque TQJ (No in # 17) (# 16).
[0063]
When the tightening torque TQ reaches the target torque TQJ (Yes in # 17), the motor 11 is stopped (# 18). In order to stop the motor 11, the supply of the current pulse DP is stopped, and the current flowing through the motor 11 is made zero.
[0064]
Then, it is determined whether or not the final tightening torque TQ and the maximum value TQM that has appeared so far are within the set upper and lower limit values, and the determination result is displayed on the display surface (# 19). .
[0065]
In the current control, the current flowing through the motor 11 is set by the current command data D1T. The rise of the motor 11, that is, the rotational speed is determined according to the magnitude of the current flowing through the motor 11, and the magnitude of the tightening torque TQ due to the impact is determined accordingly.
[0066]
In FIG. 3, every time the time interval ts elapses (Yes in # 21), the processing from step # 22 is performed. That is, every time the time interval ts elapses, first, the tightening torque TQ and the rotational speed (speed data D21) are measured and the values are taken in (# 22, 23).
[0067]
Next, maximum rotation detection processing is performed (# 24), and torque increase control is performed (# 25).
If it is during the on-time TN (Yes in # 26) and the maximum rotation detection flag described later is not “1” (No in # 27), an appropriate current value to be given to the motor 11 is set as the current command data D1T. Output (# 28). If it is during the off time TF (No in # 26) or the maximum rotation detection flag is “1” (Yes in # 27), the current command data D1T is set to zero (# 29).
[0068]
Even when the current command data D1T is set to zero, the command current value is not cleared and the value at that time is stored as a parameter.
Therefore, for example, immediately after the current control mode is entered, the first one current pulse DP1 is output. In the current pulse DP1, the current starts from zero, and the current increases with the slope of the current slope θ. When the set minimum current value ST1 is reached, the increase in current is stopped and the value is maintained.
[0069]
During the off time TF thereafter, the current command data D1T is zero. As a result, the current flowing through the motor 11 becomes zero. Even during this time, the processes of steps # 21 to # 25 are performed. Note that the value of the current command data D1T does not match the value of the current that actually flows through the motor 11 due to the electromagnetic action and transient phenomenon of the motor 11.
[0070]
In FIG. 4, in the maximum rotation detection process, the timing at which the rotation speed of the motor 11 becomes maximum is detected. That is, when the sampling value becomes smaller than the previous sampling value (Yes in # 31), “1” is added to the count value of the counter (# 32). When the count value becomes “3” (Yes in # 33), the maximum rotation detection flag is set to “1” (# 34). If the sampling value is not smaller than the previous time in step # 31 (No in # 31), the count value is set to “0” (# 35).
[0071]
When the maximum rotation detection flag is “1” by this process, the answer is YES in step # 27 of FIG. 3, and the current command data D1T, that is, the current pulse DP is turned off.
[0072]
That is, as shown in FIG. 7, for each current pulse DP, control is performed to turn off the current pulse DP when the rotational speed of the motor 11 reaches the maximum.
As described above, since the maximum rotation speed is detected when the sampling value is continuously smaller than the previous time a plurality of times (here, three times), erroneous detection due to noise or the like is prevented. .
[0073]
In FIG. 5, in the torque increase control, the acquired tightening torque TQ is compared with the maximum value TQM of the tightening torque TQ so far. If the maximum value TQM is not exceeded (No in # 41), the process returns without doing anything. If the maximum value TQM is exceeded, the command current value is increased by a predetermined amount (# 42). The maximum value TQM is updated with the tightening torque TQ at that time (# 43).
[0074]
As a result, the current command data D1T increases as the tightening torque TQ increases (see FIG. 8), and a larger tightening torque TQ is generated. Thus, the actual tightening torque TQ detected by the torque sensor 13 is fed back to the current value of the current command data D1T.
[0075]
By performing the current control as described above, it is no longer necessary to generate useless tightening torque after the occurrence of an impact. As a result, the reaction force acting on the worker is greatly reduced. As a result, even when the tightening torque TQ is large, the screw tightening device main body 3 can be used with one hand and high tightening accuracy can be obtained.
[0076]
Furthermore, optimal control according to the workpiece is possible. It is possible to control the output torque of the motor 11 so as to match the actual torque increase rate according to the current value in response to a change in torque, etc., on the workpiece side, or on an operator's external force or on / off due to control.
[0077]
Further, by changing the parameters, it is possible to easily control the target torque TQJ, the tightening accuracy, the degree of reaction force, or the like. Further, since an oil pulse part and a clutch mechanism, which are consumable parts as in the prior art, are unnecessary, maintenance is easy and the stability of the system can be maintained over a long period of time.
[0078]
Since the control is performed using the electric motor 11, energy efficiency is high, and it is possible to achieve a significant energy saving and cleanness without dust mist compared to the conventional oil pulse wrench where an air motor is a necessary condition. It becomes.
[0079]
By varying the on-time TN or / and the off-time TF according to the type or state of the load, the tightening accuracy and the reaction force state can be set to the optimum state.
[0080]
In the above embodiment, the timing at which the rotation speed of the motor 11 becomes maximum can be various timings according to the actual detection state or control state. That is, it is not necessarily the moment when the motor 11 actually reaches the maximum rotation speed, and may be a timing at which the motor 11 is substantially maximized, or a timing before and after the timing. Further, instead of stopping the supply of power to the motor 11 at that timing, the supply of power may be reduced. In short, what is necessary is to perform control so as to reduce the supply of electric power for each pulse when an impact due to the rotation of the motor 11 occurs.
[0081]
Further, various sensors, circuits, devices, calculation methods, programs, or the like other than those described above can be used to detect that the motor 11 has reached the maximum rotation speed.
[0082]
In the above embodiment, the torque sensor 13 is used to detect the tightening torque TQ, but the tightening torque TQ is calculated by calculation based on the rotational speed of the motor 11 without using the torque sensor 13. You may ask for it. That is, if the rotational speed of the motor 11 is known, the tightening torque TQ can be obtained by calculation from the mechanical structure of the screw tightening device body 3 or the like. Such a calculation formula or program may be stored in an appropriate memory, and the tightening torque TQ may be obtained in real time every time the rotational speed is detected. Also, instead of calculating it, the correspondence between the rotational speed and the tightening torque TQ is stored like a table, and the tightening torque TQ is read from the table every time the rotational speed is detected. Also good. In that case, a more accurate tightening torque TQ may be obtained by performing an appropriate interpolation operation on the read value. That is, in this case, the encoder 14, the speed detection unit 32, the command control unit 44, or the like can be a torque detection unit. In addition, for detecting the rotation speed of the motor 11, a sensor that outputs an analog signal proportional to the rotation speed or other sensors may be used.
[0083]
In the above embodiment, the structure, shape, number, processing content or order of the whole or each part of the screw tightening device main body 3, the control device 4, and the screw tightening device 1 are appropriately changed in accordance with the spirit of the present invention. Can do.
[0084]
【The invention's effect】
According to the present invention, the reaction force can be further reduced in an impact-type screw fastening device using an electric motor as a rotational drive source.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the overall configuration of a screw fastening device according to the present invention.
FIG. 2 is a flowchart showing a procedure of a tightening operation of the screw tightening device.
FIG. 3 is a flowchart showing a routine of current control.
FIG. 4 is a flowchart showing a routine of maximum rotation detection processing.
FIG. 5 is a flowchart showing a routine of torque increase control processing.
FIG. 6 is a diagram showing an overall state of a screw tightening operation by a screw tightening device.
FIG. 7 is a diagram showing the relationship between the rotational speed of a motor and current command data.
FIG. 8 is a diagram showing in detail the state of current pulse control.
[Explanation of symbols]
1 Screw tightening device
3 Screw tightening device
4 Control device
8 Controller for control
11 Motor
13 Torque sensor
14 Encoder
32 Speed detector
44 Command control unit (pulse drive means, pulse control means)
45 Setting device (setting means)
51 Speed / current command calculator
TQ Tightening torque
D1T current command data
DP current pulse

Claims (2)

Control method for impact type screw tightening device including impact generating device for generating impact by causing impact of input side member rotating using electric motor as rotation drive source and colliding with output side member Because
While intermittently supplying power to the motor and driving the motor so that the rotational speed is pulsed on the time axis,
Control is performed to reduce the supply of electric power to the motor when it is detected that the impact has occurred due to the rotation of the motor at each pulse-like time.
A control method for an impact-type screw tightening device. Control device for impact-type screw tightening device provided with impact generating device that generates impact by causing impact when input-side member rotating with electric motor as rotational drive source collides with output-side member Because
Pulse driving means for intermittently supplying power to the motor to drive and control the motor so that the rotational speed is pulsed on the time axis;
A pulse control means for controlling to reduce the supply of electric power to the motor when it is detected that the impact is generated by the rotation of the motor for each pulse-like time;
A control device for a screw tightening device.

Images