JP4699316B2 - Impact type screw tightening device - Google Patents

Description

  The present invention relates to an impact-type screw fastening device, and more particularly to an impact-type screw fastening device with improved energy efficiency.

  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.

  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 this case, since it is desired that the screw fastening device can be operated with one hand from the viewpoint of portability and workability, a pistol-shaped device is often used. However, in the case of the pistol shape, the distance between the output shaft and the handle cannot be increased, so that it is not possible to receive a large torque reaction force. Further, since the reaction of screw tightening must be received with one hand, the reaction becomes a problem as a burden on the operator as the tightening torque increases. In order to cope with this problem, a screw tightening device using an impact mechanism or an oil pulse mechanism is used.

  In the impact mechanism, the rotor is rotated by a motor, and a hammer attached to the rotor turns the output shaft once or twice while the rotor rotates once, thereby converting the impact caused by the inertia of the motor rotor into torque. Is generated on the output shaft.

  Also, in the oil pulse mechanism, the rotor is rotated by a motor, and the blade attached to the output shaft is provided with a portion where the hydraulic pressure is suddenly compressed once or twice during one rotation, and the fluid resistance at that time Thus, the rotor inertia is converted into a pulsed torque, and the pulsed torque is generated on the output shaft.

Further, the present applicant has proposed an impact-type screw fastening device that improves various conventional drawbacks (Patent Documents 1 and 2).
JP2002-1676 JP 2004-322262 A

By the way, the conventional impact type screw fastening device has the following problems.
(1) The mechanism that strikes the shaft with a rotating hammer generates a very loud sound continuously, so there is a noise problem such as wearing earplugs for a long period of work.
(2) With a mechanism that hits the shaft with a rotating hammer, the output torque varies with each hit, and the torque accuracy is very poor. In addition, the hammer and the output shaft that are subjected to impacts are heavily worn, so the life is short and frequent maintenance is required.
(3) Since the oil pulse mechanism is repeatedly compressed and non-compressed due to its structure, the shock generating mechanism itself generates heat, so that there is a problem that it cannot be used unless it is cooled by exhausting the air motor. Further, since the generated torque changes depending on the oil temperature, there is a problem that the torque cannot be stably generated from the start of use to the end of use. Also, since blades, packing, and oil are exposed to high temperatures and high pressures, they are severely deteriorated, and therefore have a short life and require frequent maintenance.
(4) Also, the screw tightening devices of Patent Documents 1 and 2 have room for improvement, for example, by improving motor control and impact generation mechanism to further increase energy efficiency.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an impact-type screw fastening device that is more advantageous than the conventional ones in terms of a low reaction force, a simple structure, and energy efficiency. To do.

The screw tightening device according to the present invention is an impact-type screw tightening device that uses an electric motor as a rotational drive source and generates impact by causing a hammer to collide with an anvil to apply a rotational force to a load. Is in an initial position, which is a position away from the anvil, the current is passed through the motor to rotate the hammer in the forward direction to accelerate, the hammer collides with the anvil to generate an impact, and the hammer after There impacting the anvil, by reversing the motor by applying a current in the opposite direction before SL motor, returning the hammer to the initial position from the collision position of the anvil, the load by repeating this It is configured to give a continuous impact.

  In addition, after the hammer collides with the anvil, the current to be supplied to the motor is once reduced to zero, and then the current is supplied in the opposite direction to forcibly reverse the motor, thereby returning the hammer to the initial position. .

  In addition, when a preset first time has elapsed since it was detected that the hammer collided with the anvil, it is assumed that the hammer has returned to the initial position, and a current is passed through the motor to cause the hammer to move in the forward direction. Rotate to

  In addition, a current is passed through the motor in the reverse direction only for a preset second time period after the hammer is detected to have collided with the anvil until a preset first time period elapses.

In addition, a torque sensor that detects rotational torque applied to the load is provided,
When the detection signal of the torque sensor reaches a preset set torque, it is detected that the hammer has collided with the anvil.

  According to the present invention, there are advantages over the prior art in terms of a small reaction force, a simple structure, and energy efficiency.

  FIG. 1 is a front sectional view of a screw fastening device main body 3 used in the screw fastening device 1 according to the present invention, FIG. 2 is an enlarged sectional view of a main part of the screw fastening device main body 3, and FIG. 4 and 4 are cross-sectional views taken along the line AA of the gear mechanism in FIG. 1, and FIG. 5 is a diagram for explaining the generation of an impact by the gear mechanism.

  1 and 2, the screw tightening device main body 3 is a pistol-type handy type having a handle grip portion for an operator to hold with one hand. The screw tightening device main body 3 is configured by providing a main body casing 10 with a motor 11, a planetary gear mechanism 12, which is an impact generating device, a torque detecting device 13, an encoder 14, an output shaft 15, and the like. By operating a switch (not shown), power on / off is controlled.

  For example, a three-phase AC servomotor is used as the motor 11. However, as long as forward and reverse rotation is possible, a free state is obtained at the time of stopping, and the rotational speed can be controlled, various other types such as a single-phase AC servo motor, induction motor, DC motor, etc. A motor can be employed.

  The planetary gear mechanism 12 operates as a speed reducer that reduces the rotation of the motor 11 and also operates as a collision energy generation mechanism that converts the rotational force of the motor 11 and the like into intermittent impact force.

  The planetary gear mechanism 12 is configured by connecting a first planetary gear mechanism 61 and a second planetary gear mechanism 71. In the first planetary gear mechanism 61 and the second planetary gear mechanism 71, the outer gears 62 and 72 are coaxial with each other, and can rotate relative to each other only within a predetermined relative angle range α. Outside the angle range α, they are arranged so as to be engaged with each other in the circumferential direction so that relative rotation is impossible. The sun gear 73 of the second planetary gear mechanism 71 is connected so as to rotate on the same axis with the rotation output of the carrier 65 of the first planetary gear mechanism 61 as an input.

  The first planetary gear mechanism 61 has an output shaft 11a, a key 11b, and a sun gear 63 of the motor 11 such that the outer gear 62 is fixed to the main body casing 10 and the sun gear 63 is rotationally driven by the motor 11. Are connected via an input shaft 63a. The rotation of the sun gear 63 causes the three planet gears 64 to rotate and revolve around the sun gear 63. The carrier 65 is rotated by the revolution of the planet gear 64, and the sun gear 73 integrated therewith is rotated.

  By the way, the outer gear 62 of the first planetary gear mechanism 61 is fixed to the main body casing 10 through the torque detection device 13 so as not to rotate.

  That is, in FIG. 2, the members 81 and 83 are positioned and fixed to the main body casing 10 by the pins 82 and 84. A gear (internal gear) is provided on the inner peripheral surface of the member 83. The torque detector 13 is provided with gears (external gears) on the outer peripheral surfaces of the flange portions at both ends of the flange-shaped sensor main body 131, and one of the external gears meshes with the internal gear of the member 83. The other is in mesh with the internal gear of the outer gear 62. Therefore, the outer gear 62 is fixed so as not to rotate by the member 83 via the torque detection device 13, and the torque applied to the outer gear 62 distorts the sensor body 131, which is detected by the strain gauge 132. It becomes.

  A gear case 85 that covers the entire planetary gear mechanism 12 and holds the planetary gear mechanism 12 is fixed by a fixing ring 86 having a female screw that engages with a male screw on the outer peripheral surface of the member 81. The outer gear 62 and the outer gear 72 are fitted into the inner peripheral surface of the gear case 85, and the outer gear 72 is rotatable with respect to the inner peripheral surface of the gear case 85. The output shaft 15 is rotatably held by a bearing 76.

  An O-ring 67 is mounted in a circumferential groove provided on the outer peripheral surface of the outer gear 62, and the O-ring 67 is appropriately compressed between the inner peripheral surface of the gear case 85 so that the outer gear 62 is not rattled. Is held in. The outer gear 72 is also provided with a circumferential groove on its outer peripheral surface. Although not shown, an O-ring is attached to the circumferential groove so that the outer gear 72 is not rattled, and against rotation in the circumferential direction. Moderate resistance. However, the O-ring may not be provided depending on the degree of fitting with the members around the outer gear 72 and the degree of friction.

  Now, the outer gear 62 of the first planetary gear mechanism 61 and the outer gear 72 of the second planetary gear mechanism 71 are projecting engagement portions 621, 622, 721, 722 that project in the axial direction from the respective one end surfaces. Are provided, and the projecting engagement portions 621 and 622 of the first planetary gear mechanism 61 and the projecting engagement portions 721 and 722 of the second planetary gear mechanism 71 are engaged in the circumferential direction. Outside the relative angle range α, the relative rotation is impossible.

  That is, since the outer gear 62 is fixedly provided with respect to the main body casing 10, it does not rotate, but the outer gear 72 can rotate only within the relative angle range α.

  The protruding engagement portions 621 and 622 and the protruding engagement portions 721 and 722 are provided at equal intervals in the circumferential direction in the respective outer gears 62 and 72.

  For example, as shown in FIG. 5C, when the outer gear 72 is in a position where it does not engage with the outer gear 62 (initial position, acceleration position), a current is passed through the motor 11 in the positive direction (M1 direction). , Thereby rotating the outer gear 72 in the reverse direction (M2 direction) to accelerate it, causing the outer gear 72 to collide with the outer gear 62 as shown in FIG.

  After the outer gear 72 of the second planetary gear mechanism 71 collides with the outer gear 62 of the first planetary gear mechanism 61, the current flowing through the motor 11 is reduced to zero or the motor 11 is caused to flow in the opposite direction. From the engagement position with the outer gear 62 of the first planetary gear mechanism 61 by rotating the outer gear 72 of the second planetary gear mechanism 71 in the forward direction (M1 direction). Release. As a result, the outer gear 72 returns to the position (initial position) shown in FIG.

  That is, while the sun gear 63 of the first planetary gear mechanism 61 on the high speed side rotates several times, the outer gear 72 of the second planetary gear mechanism 71 on the low speed side rotates within the relative angle range α, An impact is generated when the protruding engagement portions 721 and 722 of the outer gear 72 actually hit the protruding engagement portions 621 and 622 of the outer gear 62.

  Hereinafter, a mechanism for converting the rotational force of the motor 11 into an impact force will be described in more detail.

  That is, while the outer gear 72 is rotating within the relative angle range α as described above, the output shaft 15 is in a state in which it cannot be rotated by a screw as a load. Therefore, the carrier 75 is also in a state where it cannot rotate. Therefore, when the sun gear 73 rotates, the planet gear 74 rotates, but the carrier 75 cannot rotate. Therefore, the planet gear 74 rotates the outer gear 72 without revolving. When the outer gear 72 rotates and the projecting engagement portions 721 and 722 collide with the projecting engagement portions 621 and 622 of the outer gear 62, the outer gear 72 cannot be rotated any further, so that it stops. At that time, the inertia energy (inertia) due to the rotation stored in the motor 11, the input shaft 63a, the sun gear 63, the carrier 65, and the like is the moment when the projecting engagement portions 721 and 722 collide with the projecting engagement portions 621 and 622. This is transmitted as a rotational impact force to the output shaft 15 via the planet gear 74 and the carrier 75. As a result, a tightening torque TQ due to a rotational impact force is generated with respect to a screw as a load. The load is rotated by the tightening torque TQ. The rotation angle depends on the magnitude of the impact force.

  Thus, from the state where the outer gear 72 is stopped at the initial position ST, the outer gear 62 is rotated by the rotation of the motor 11 and collides with the outer gear 62 when the motor 11 rotates at a high speed. A large torque resulting from the conversion is obtained from the output shaft 15 as the tightening torque TQ.

  Therefore, the relative angle range α needs to be set so that the motor 11 can stand up and reach the maximum rotation speed or an appropriate rotation speed. The relative angle range α can be called a play angle in the planetary gear mechanism 12, and inertia energy is stored by the existence of the play angle. In the present embodiment, the relative angle range α is set to 60 degrees.

  That is, in FIG. 5, the projecting engagement portions 621 and 622 of the outer gear 62 each have a center angle of 60 degrees, and the projecting engagement portions 721 and 722 of the outer gear 72 also have a center angle of 60 degrees. The central angle of the space in which the outer gear 72 can rotate is 60 degrees.

  Since the relative angle range α is 60 degrees, the corresponding rotation angle of the motor 11 is multiplied by a magnification based on the inner diameter of the outer gear 72, the outer diameter of the sun gear 73, the reduction ratio of the first planetary gear mechanism 61, and the like. It will be.

For example, when the reduction ratio of the first planetary gear mechanism 61 is “3.8”, the number of teeth of the outer gear 72 is “42”, and the number of teeth of the sun gear 73 is “12”,
60 degrees × 3.5 × 3.8 = 798 degrees, which is about 2.2 rotations. Therefore, the motor 11 only needs to rise up to a predetermined required rotational speed until it rotates 2.2 times.

  As described above, the planetary gear mechanism 12 of the present embodiment is a speed reducer that decelerates the rotation of the motor 11, and is also a collision energy generation mechanism that converts the rotational force into an impact force. Since the relative angle range α can be as large as 60 degrees, the motor 11 and the like can obtain a sufficient rotation angle for storing inertial energy by a synergistic action with the reduction gear ratio of the planetary gear mechanism 12, and a large impact force. That is, the tightening torque TQ can be generated.

  Moreover, by controlling the rotation speed of the motor 11, the impact force (torque) can be adjusted accurately, and the tightening torque TQ for screw tightening can be adjusted and managed with high accuracy. Further, there is no fluctuation in impact force due to temperature change or the like, and the tightening torque TQ does not fluctuate depending on the temperature.

  Further, the impact force is generated when the projecting engagement portions 721 and 722 collide with the projecting engagement portions 621 and 622, and the speed of the projecting engagement portions 721 and 722 at that time is not so great and stops due to the collision. Therefore, the impact sound is small and it does not become a loud noise. In addition, there are no parts that are greatly worn, the durability of each part is improved, the life is long, and maintenance is easy as in the case of ordinary gears. In addition, the structure is simple, and it can be configured compactly and compactly.

  Further, when the outer gear 72 collides with the projecting engagement portions 621 and 622, the current of the motor 11 is set to zero and the motor 11 is brought into a free state. By doing so, the outer gear 72 rotates to some extent in the forward direction (M1 direction), which is the opposite direction, by rebounding due to the reaction of the collision. Rotate to quickly return to the initial position (acceleration position) ST. Thereafter, a positive current is supplied to the motor 11 to accelerate the positive rotation.

  By rotating the motor 11 in the reverse direction in order to return the outer gear 72 to the initial position after the collision, it becomes possible to return to the initial position in a shorter time, and the cycle time is shortened and the impact force is applied to the fixed time. The number of occurrences can be increased.

  Various methods can be used to confirm whether or not the outer gear 72 has returned to the initial position. For example, it is assumed that the first time TF has elapsed since the outer gear 72 collided with the outer gear 62. Alternatively, a sensor for detecting the rotational angle position of the outer gear 72 is provided. Alternatively, the rotation angle of the motor 11 is detected by the encoder 14 and the rotation angle of the outer gear 62 is calculated. Note that the first time TF can be set using a timer or the like and can be adjusted by the user.

  In this way, by controlling the current flowing through the motor 11, the operation of causing the outer gear 72 to collide with the outer gear 62, returning to the initial position, and accelerating for the next collision can be easily realized. . By controlling the speed of the outer gear 72 at the time of collision, the magnitude of the impact force and the interval at which the impact force is generated can be easily controlled.

  In addition, since the initial position for each collision is stable and acceleration is started from the same position, the stability and reproducibility of the impact force are good.

  In the state in which the outer gear 72 is engaged with the outer gear 62, the planetary gear mechanism 12 operates as a two-stage normal planetary gear mechanism. 15 can be continuously rotated and the screw can be rotated at a high speed to be tightened. For example, the screw can be seated by high-speed rotation. Further, the screw can be loosened by rotating at high speed in the opposite direction. Thus, it can also be used as a normal nutrunner or drill.

  Then, by simply switching the control mode (speed control mode, impact mode) of the motor 11, the output from the output shaft 15 can be easily switched between normal high-speed rotation and high torque due to impact force.

  Further, since the torque applied to the outer gear 62 is detected by the torque detection device 13, the output torque at the time of normal high-speed rotation and the output torque as the ink trench can be easily obtained instantaneously by calculation, and the control of the motor 11 Therefore, the output torque (tightening torque) can be maintained with high accuracy. In addition, the necessary torque can be generated instantaneously.

  And according to this embodiment, the reaction force by impact force is small, the energy consumed is also reduced and the energy efficiency is increased. Next, these points will be described.

  That is, in the screw tightening device 1, the current of the motor 11 is made zero when the outer gear 72 collides with the outer gear 62 in the impact mode. That is, immediately after the impact force is generated, the current of the motor 11 is made zero and the supply of energy is stopped. Then, based on only the impact force due to the inertial energy of the part that has been rotating, the screw as a load is rotated and tightened, that is, a tightening torque TQ is obtained, and the body casing 10 is tightened. The reaction force due to the attached torque TQ does not appear at all. As a result, the reaction force due to the impact does not act on the operator who holds and operates the screw tightening device body 3 by hand, and the operator is not burdened even if the operation is performed with one hand.

  In addition, the impact force is generated by inertial energy, and the current of the motor 11 is zeroed when the impact force is generated. Therefore, wasteful current is not consumed and energy efficiency is high.

  Incidentally, in the prior art, the motor 11 is driven to rotate even after the impact force is generated, which causes wasteful consumption of current and causes heat generation.

  In other words, since the conventional device is a mechanism that intermittently generates impact torque based on the rotational force of the continuously rotating motor, it performs a push-off operation for the convenience of the mechanism against the reaction that occurs when the impact torque is generated. The motor continues to generate maximum torque during its push-off operation. However, the rotational output of the motor in the meantime is not used to generate or increase the impact torque, but merely receives a huge reaction force when the impact torque is generated. It was an energy loss, the energy efficiency was very poor, and the reaction force against the worker was large.

  According to the control method of the planetary gear mechanism 12 and the motor 11 according to the present embodiment, the motor 11 is rotated and accelerated only to accumulate inertia energy for generating the impact force, and at the moment when the impact force is generated, the motor is rotated. By stopping the driving of 11, the reaction force is not applied to the worker and wasteful energy is not consumed, so that about half of the power consumption is required compared to the conventional one, energy saving, cost saving, This was a significant improvement in terms of weight and size.

  Moreover, although the outer gear 72 rotates to the opposite side by the reaction force when it collides with the outer gear 62, the energy efficiency can be further enhanced by regenerating this rotational force and collecting it on the power source side.

  In the above embodiment, the protruding engagement portions 721 and 722 of the outer gear 72 correspond to the “hammer” of the present invention, and the protruding engagement portions 621 and 622 of the outer gear 62 correspond to the “anvil” of the present invention. To do. However, the impact force applied to the output shaft 15 is that the inertia energy stored so far is applied to the output shaft 15 due to the outer gear 72 colliding with the outer gear 62 as described above. Is obtained. That is, an impact force is generated when the outer gear 72 collides with the outer gear 62, but it is the inertia energy stored in the motor 11 and the planetary gear mechanism 12 that actually generates the impact force. In short, when an impact force is generated, the motor 11 can be freely rotated so that no reaction force is applied to the operator.

  Further, the rotational directions of the outer gear 72 and the hammer differ depending on the arrangement on the mechanism and the like, and therefore may be determined in consideration of the substantial meaning. For example, a direction that causes a specific function to be noticed may be considered as “positive”.

  Next, the entire screw tightening device 1 including the control device of the screw tightening device main body 3 will be described. Here, the control device will be mainly described.

  FIG. 6 is a block diagram showing the overall configuration of the screw fastening device 1.

  In FIG. 6, 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.

  The torque detector 13 detects a screw tightening torque TQ by the motor 11 and outputs a detection signal S31.

  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 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.

  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.

  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.

  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.

  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.

  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.

  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.

  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.

  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.

  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.

  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.

  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.

  The preamplifier 41 amplifies the detection signal S31 detected by the torque detection device 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.

  The parameter storage unit 43 stores various parameters necessary for calculation by the speed / current command calculation unit 51 and the like. As the parameters, for example, the minimum current value, the measurement start torque, the seating torque TS, the target approach torque TQN, the target torque TQJ, the maximum value TQM of the tightening torque TQ, the current slope θ, the first slope θ1, and the second slope θ2. and so on. 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.

  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.

  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.

  The operation control mode switching unit 52 switches between the speed control mode and the impact mode (current control mode, 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.

  In the impact mode, the direction and magnitude of the current flowing through the motor 11 is controlled, and the planetary gear mechanism 12 is controlled to generate an impact torque. In the impact mode, a current designated by the current command data D1T flows through the motor 11. The rotation speed of the motor 11 changes according to the set current value.

  The switch 26 selects speed command data D3 in the speed control mode and current command data D1T in the impact 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 impact mode. In the impact mode, the current indicated by the current command data D1T flows or the current becomes zero, and the motor 11 repeats rotation in the forward direction and the reverse direction.

  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.

  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. Some of them can be realized by hardware circuits.

  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.

  Next, a control method of the screw tightening device 1 will be described with reference to a diagram showing an operation state.

  FIG. 7 is a diagram illustrating the overall state of the screw tightening operation by the screw tightening device 1, FIG. 8 is a diagram illustrating the relationship between the current command data D1T in the impact mode and the rotation speed of the motor 11, and FIG. It is a figure which expands and shows a part.

  As shown in FIG. 7, the operation is initially performed in the speed control mode, and the output shaft 15 is rotated at a high speed. During this time, the planetary gear mechanism 12 operates as a speed reducer. 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 impact mode. In the impact mode, the current indicated by the current command data D1T flows or the current becomes zero, and the motor 11 repeats rotation in the forward direction and the reverse direction.

  As shown in FIG. 8 and FIG. 9, in the impact mode, the current command data D1T continues to have a positive constant value at time T1, becomes zero at the next time T2, and has a negative constant value at the next time T3. Subsequently, it becomes zero at the next time T4. This is repeated.

  Then, a current i having a response delay flows with respect to the current command data D1T.

  At time T1, the motor 11 is accelerated in the positive rotation direction, and at time t2, the outer gear 72 collides with the outer gear 62, and an impact force is generated. The occurrence of the impact force is detected by the torque detection device 13 when the tightening torque TQ has become a certain value or more. The screw is rotated by this impact force, and the screw is tightened according to the magnitude of the inertial energy that is the source of the impact force.

  At time t2, the current command data D1T of the motor 11 becomes zero. Immediately after the current command data D1T of the motor 11 becomes zero, the actual current i is still flowing. Therefore, the rotational speed n of the motor 11 slightly increases, and then the rotational speed n decreases, and the rotational speed at time t3. n becomes zero. The period from time t2 to time t3 substantially coincides with time T2. Since the motor 11 does not generate torque at time T2, the reaction force of the tightening torque TQ is not transmitted to the operator.

  When the rotational speed n of the motor 11 becomes zero, the negative current command data D1T is sent, and a reverse current i is supplied to the motor 11 to rotate it in the reverse direction. The motor 11 rotates and accelerates in the reverse direction at time T3, and then rotates at a constant rotational speed n due to inertia at time T4 thereafter. During this time, the outer gear 72 rotates in the opposite direction and returns to the initial position.

  The sum of the times T2, T3, and T4 corresponds to the first time TF described above. Therefore, the first time TF can be adjusted by adjusting these times T2, T3, and T4.

  The time T1 is about 10 to 20 ms, the time T2 is about 4 to 10 ms, the time T3 is about 3 to 10 ms, and the time T4 is about 8 to 20 ms, for example. The total of the times T1 to T4, that is, one cycle is, for example, about 30 to 50 ms. The total time of the times T2 to T4 is the time from the collision of the outer gear 72 to the return to the initial position.

  Further, a current i having a magnitude corresponding to the height (amplitude) of the current command data D1T at time T1 flows, and the rotation of the motor 11 is accelerated accordingly. The current command data D1T is normally a maximum value. However, in order to adjust the magnitude of the tightening torque TQ in the impact mode, the magnitude (amplitude) of the current command data D1T may be adjusted, and the time T1 may be adjusted.

  Further, the time until the outer gear 72 returns to the initial position is adjusted by adjusting the magnitude of the current command data D1T at the time T3.

  Note that the outer gear 72 may return to the initial position only by the reaction force after the collision. In that case, it is not necessary to flow a current for reversing the motor 11. Alternatively, immediately after the outer gear 72 collides with the outer gear 62, the motor 11 may be reversely rotated by passing a current in the opposite direction to return the outer gear 72 to the initial position.

  Next, the flow of the screw tightening operation in the screw tightening device 1 will be described with reference to a flowchart.

  FIG. 10 is a flowchart showing the flow of the screw tightening operation in the screw tightening device 1, and FIG. 11 is a flowchart showing the operation in the impact mode.

  In FIG. 10, 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.

  That is, before the screw is seated, an electric current is passed through the motor 11 to rotate the outer gear 72 as a hammer, and the output shaft 15 is rotated in a state where the outer gear 72 is in contact with the outer gear 62 as an anvil. Rotate continuously.

  As a result, the motor 11 rotates at high speed, and temporary tightening is performed until the screw is seated.

  When the tightening torque TQ reaches the seating torque TS (Yes in # 12), it is determined that the screw is seated, and the mode is switched to the impact mode (# 13, 14). Note that the current flowing through the motor 11 may be once set to zero before switching to the impact mode.

  In the impact mode, current control is performed until the tightening torque TQ reaches the target torque TQJ (No in # 15).

  When the tightening torque TQ reaches the target torque TQJ (Yes in # 15), the motor 11 is stopped (# 16). 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.

  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 range of the set upper and lower limit values, and the determination result is displayed on the display surface of the display device ( # 17).

  In FIG. 11, in the impact mode, a current is passed through the motor 11 to rotate in the forward direction (M1 direction) (# 21). As a result, the sun gears 63 and 73 rotate in the forward direction, and the outer gear 72 rotates in the reverse direction (M2 direction) (# 22). When the outer gear 72 collides with the outer gear 62 (Yes in # 23), the current of the motor 11 is stopped (# 24). A tightening torque TQ due to the impact force is generated, thereby tightening the screw (# 25). The outer gear 72 rotates in the opposite direction, that is, the forward direction (M1 direction) due to the reaction of the collision (# 26). A reverse current is supplied to the motor 11 for reverse rotation (# 27), and the outer gear 72 is returned to the initial position (# 28).

  Steps # 21 to 27 are repeated until the target torque TQJ is reached (# 14, 15).

  According to the present embodiment, the screw tightening device 1 can be made lightweight and compact with a simple configuration because the planetary gear mechanism 12 serves both as a speed reducer and a collision energy generation mechanism. Control of the motor 11 can easily switch between direct operation (continuous operation) such as the speed control mode and impact operation in the impact mode, so that not only the screw tightening operation can be performed with high speed and high accuracy in screw tightening. Thus, the drilling operation and the screw tightening operation can be easily performed by the single screw tightening device 1.

  In the above-described embodiment, two protrusion engaging portions 621, 622, 721, and 722 of the outer gears 62 and 72 are provided, but three or more may be provided at equal intervals. In the case of one by one, a force in the radial direction is generated by an impact, so it is possible to take measures against this. Moreover, although the relative angle range α is 60 degrees, it may be more or less. The sizes of the projecting engagement portions of the two outer gears 62 and 72 are the same, but they may be different from each other.

  In the above embodiment, the planetary gear mechanism 12, the screw tightening device main body 3, the control device 4, the structure of the whole or each part of the screw tightening device 1, the shape, the number, the processing contents or the order, etc. are in accordance with the spirit of the present invention. Can be changed as appropriate.

  In the above-described embodiment, the example in which the planetary gear mechanism 12 is used as the impact generating device has been described. However, the present invention can also be applied to an impact generating device having a structure other than the planetary gear mechanism 12.

It is front sectional drawing of the screw fastening apparatus main body which concerns on this invention. It is an expanded sectional view of the principal part of a screw fastening device main part. It is a front view which shows the external appearance of a gear mechanism. FIG. 2 is a cross-sectional view taken along line AA of the gear mechanism in FIG. 1. It is a figure for demonstrating generation | occurrence | production of the impact by a gear mechanism. It is a block diagram which shows the whole structure of a screw fastening apparatus. It is a figure which shows the whole state of the screw fastening operation | movement by a screw fastening apparatus. It is a figure which shows the operation state of each part in impact mode. It is a figure which expands and shows a part of FIG. It is a flowchart which shows the flow of the screw fastening operation | movement in a screw fastening apparatus. It is a flowchart which shows the operation | movement in impact mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw fastening apparatus 3 Screw fastening apparatus main body 10 Main body casing 11 Motor 12 Planetary gear mechanism 13 Torque detection apparatus 15 Output shaft 61 1st planetary gear mechanism 62 Outer gear (anvil)
71 Second planetary gear mechanism 72 Outer gear (hammer)
621, 622 Protruding engagement portion 721, 722 Protruding engagement portion ST Initial position

Claims (8)

An impact-type screw fastening device that uses an electric motor as a rotational drive source and generates impact by causing a hammer to collide with an anvil to give a rotational force to a load,
When the hammer is in an initial position, which is a position away from the anvil, an electric current is passed through the motor to accelerate the hammer by rotating it in the forward direction, causing the hammer to collide with the anvil to generate an impact,
After the hammer hits the anvil, by reversing the motor by applying a current in the opposite direction before SL motor, returning the hammer to the initial position from the collision position between the anvil,
Configured to continuously impact the load by repeating this,
This is an impact-type screw tightening device. After the hammer collides with the anvil, the current flowing through the motor is once reduced to zero, and then the motor is forced to reverse by flowing a current in the opposite direction, thereby returning the hammer to the initial position.
The impact-type screw fastening device according to claim 1. When a first preset time has elapsed since it was detected that the hammer collided with the anvil, it is assumed that the hammer has returned to the initial position and a current is passed through the motor to rotate the hammer in the forward direction. Let
The impact type screw fastening device according to claim 2 . In the period from when it is detected that the hammer has collided with the anvil until a preset first time elapses, a current is supplied to the motor in the reverse direction for a preset second time.
The impact type screw fastening device according to claim 3 . A torque sensor for detecting the rotational torque applied to the load is provided,
Detecting that the hammer has collided with the anvil when the detection signal of the torque sensor reaches a preset torque.
The impact-type screw fastening device according to any one of claims 1 to 4 . An impact-type screw fastening device that uses an electric motor as a rotational drive source and generates impact by causing a hammer to collide with an anvil to give a rotational force to a load,
When the hammer is in an initial position away from the anvil, the motor is accelerated by rotating the hammer in the positive direction by outputting current command data to flow current to the motor, and the hammer collides with the anvil. Let the impact occur,
After the hammer collides with the anvil, the current command data is once reset to zero, and then the negative current command data is output, thereby returning the hammer from the collision position with the anvil to the initial position,
Configured to continuously impact the load by repeating this,
This is an impact-type screw tightening device. When the preset first time has elapsed since it was detected that the hammer collided with the anvil, the current command data is output as positive by assuming that the hammer has returned to the initial position. Rotate in the positive direction,
The impact type screw fastening device according to claim 6 . The current command data that is negative for a preset second time is output during a period from when it is detected that the hammer has collided with the anvil until a preset first time elapses.
The impact type screw fastening device according to claim 7 .