JP2012152834A - Rotary tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fasten by a target fastening torque regardless of the difference in rigidity of a mating member or of an interposition such as a packing.SOLUTION: The rotary tool includes: a motor 2 as a rotary driving source; a torque application structure for applying torque generated by rotation of the motor to an output shaft 7; a sensor 10 for measuring the torque applied to the output shaft; and a controller C for stopping the torque application to the output shaft when the torque measured by the sensor reaches a set target torque. The controller corrects the target torque according to the rate of change of a torque value detected by the sensor and stops the torque application to the output shaft based on the corrected target torque.

Description

  The present invention relates to a rotary tool used for tightening and relaxing operations such as screws and bolts and nuts.

  As a rotary tool used for tightening and loosening screws, bolts and nuts with the motor as power, impact type torque generation that rotates the output part with a hammering impact by a rotationally driven hammer or a pulsed impact by hydraulic pressure Some are equipped with a device, while others transmit torque generated by a motor to an output unit only through a reduction gear.

  In such a rotary tool, in order to perform tightening with an appropriate tightening torque, a torque sensor is attached to the output shaft, and the motor is stopped when the torque detected by the torque sensor reaches a preset value. What is made to be proposed is proposed in Patent Document 1 and the like.

  In this case, it is easy to manage the tightening torque. However, when tightening the bolt or screw, when the mating member is a highly rigid member, a low rigidity member, or an elastic member such as packing or rubber. Even if tightening is performed at the same set value, there will be a difference in the actual tightening torque when the motor stops, assuming that the torque detected by the torque sensor reaches the set value. End up. Incidentally, when packing or rubber is interposed, the actual tightening torque is lower than the set value, and the target tightening torque may not be obtained.

JP-A-8-267368

  The present invention has been made in view of the above points, and provides a rotary tool capable of performing tightening with a target tightening torque regardless of the difference in rigidity of a mating member or the presence of packing or the like. Is an issue.

  The present invention provides a motor as a rotational drive source, torque applying means for applying torque generated by motor rotation to the output shaft, a sensor for measuring torque applied to the output shaft, and torque measured by the sensor being set And a control tool for stopping the application of torque to the output shaft when the target torque is reached. The control means is configured to control the target torque according to a rate of change of the torque value detected by the sensor. And the application of torque to the output shaft is stopped based on the corrected target torque.

  Preferably, the control means corrects the target torque so as to increase when the rate of change of the torque value detected by the sensor is small.

  Further, the control means may measure the time until the torque value detected by the sensor reaches a determination torque value set smaller than the target torque as a rate of change of the torque value detected by the sensor. Good.

  The control means may repeat calculating the change rate of the torque value every predetermined time and correcting the target torque according to the calculated change rate.

  The control means preferably includes a correction value corresponding to the detected change rate of the torque value as a table, and the table is more preferably set for each rotation speed of the motor.

  In the present invention, in order to correct the target torque for stopping the torque application from the rate of change in torque during tightening even when the rigidity of the counterpart member is low or packing is present, the difference in rigidity, the presence of an elastic body, etc. Therefore, it is possible to perform tightening with a target tightening torque without being affected by the above, and it is possible to always perform accurate tightening.

It is a flowchart which shows operation | movement of an example of embodiment of this invention. It is a schematic sectional drawing same as the above. It is a block diagram same as the above. It is operation | movement explanatory drawing same as the above. (a) and (b) are operation | movement explanatory drawings which show the difference in operation | movement by the length of judgment torque arrival time. It is explanatory drawing of an example of a correction table. It is explanatory drawing in case an elastic body interposes.

  The rotary tool 1 shown in FIG. 2 will be described in detail based on an example of the embodiment. The rotary tool 1 shown in FIG. 2 includes a motor 2 that is a drive source, a speed reducer 3 that decelerates rotation of the motor 2 at a predetermined reduction ratio, and an impact. The impact type torque generating device includes a hammer 4 to which the rotation of the motor 2 is transmitted through the speed reducer 3, an anvil 5 to be struck by the hammer 4, and a hammer 4 And a spring 6 that biases the shaft in the axial direction, and a rotational force is applied impactively to the output shaft 7 by striking the anvil 5. In the figure, 8 is a bit attached to the output shaft 7, and 9 is a battery pack. The hammer 4 is hit when the hammer 4 moves backward against the anvil 5 against the spring 6 and rotates more than a certain amount because a load torque greater than a predetermined value is applied between the hammer 4 and the anvil 5. Occurs.

  A torque sensor 10 is attached to the output shaft 7. The torque sensor 10 includes a magnetostrictive portion attached to the outer surface of the output shaft 7, a detection coil disposed on the outer periphery of the output shaft 7, a shield for external magnetism, and a yoke that covers the detection coil in order to improve the sensitivity of the detection coil. It consists of. The magnetostrictive portion is formed as a magnetostrictive amorphous foil provided with a slit pattern for torsional strain detection that is firmly bonded to the output shaft 7 with an epoxy adhesive. When the output shaft 7 is distorted by applying torque to the output shaft 7, the magnetic characteristics of the magnetostrictive portion 11 also change. At this time, a high-frequency voltage is applied to the detection coil from the control circuit C, and the output voltage changes due to the change in the magnetic characteristics of the magnetostrictive portion. Therefore, the magnitude of torque applied to the output shaft 7 can be obtained by measuring the output voltage.

  The control circuit C that controls the driving of the motor 2 performs control such as changing the rotation speed of the motor 2 according to the pulling amount of the trigger switch 15 when the operator operates the trigger switch 15. Further, the motor 2 is provided with a motor speed detector 16 for detecting the rotational speed. As the motor speed detection unit 16, a frequency generator that generates a frequency signal proportional to the number of rotations of the motor can be preferably used. However, an encoder or the like may be used. Speed detection may be performed by an electromotive force.

  FIG. 3 shows a block diagram of a control circuit C that performs control for stopping the tightening operation with the target torque and changing the rotation speed of the motor 2 in accordance with the magnitude of the target torque. In the figure, C1 is a motor speed measuring unit for A / D converting and taking in the signal from the speed detecting unit 16, and C3 is a torque measuring unit for taking in the signal from the torque sensor 10 by A / D converting. The rotation speed is feedback controlled under the control of the motor control unit C6.

  Now, if a target torque for tightening is set by a torque setting means (not shown) such as a volume, this target torque is set as the torque setting value C2, and the operator pulls the trigger switch 15 to pull the trigger switch 15. The motor control unit C6 controls and drives the motor 2 so that the motor 2 rotates at a speed corresponding to the amount.

  Then, the torque measurement value (for example, peak value) captured by the torque sensor 10 and the torque measurement unit C3 reaches the target torque (within ± 10% of the range) set to the torque setting value C2 as shown in FIG. For example, since the stop determination unit C4 sends a stop command to the motor control unit C6, the motor 2 stops and the tightening operation ends.

  Here, when the target torque set to the torque setting value C2 is large, the motor 2 is driven at the maximum speed if the trigger switch 15 is pulled to the maximum. In this case, the impact generated by hitting the anvil 5 with the hammer 4 is large, and the torque increase value per impact is also large. The torque increase value per impact decreases as the tightening progresses. However, when the torque increases within a range of ± 10% of the target torque, the stop determination unit C4 issues a motor stop command to stop the motor 2.

  However, even when the target torque set to the torque setting value C2 is small, if the motor 2 is driven at the maximum speed when the trigger switch 15 is pulled to the maximum, the torque increase value per impact However, the motor 2 may not be stopped at the target torque, resulting in excessive tightening.

  For this reason, here, the rotational speed of the motor 2 when the speed limit calculation unit C5 pulls the trigger switch 15 is regulated according to the magnitude of the target torque set to the torque setting value C2. That is, when the target torque is small, the motor 2 is limited to a speed that does not reach the maximum speed even when the trigger switch 15 is pulled to the maximum, and when the pulling amount of the trigger switch 15 is small, the speed is further suppressed. Accordingly, when the target torque set to the torque setting value C2 is small, the torque increase value per impact is small, the number of impacts until reaching the target torque is increased, and within a range of, for example, ± 10% of the target torque. The number of stays also increases. For this reason, when the stop determination unit C4 issues a stop signal and the motor 2 is stopped, the tightening torque falls within the target torque range.

  When the error range with respect to the target torque is ± x%, it is preferable that an impact of 50 / x times or more is required before reaching the lower limit of the target torque range. If the error range is ± 10% as described above, the torque increase value per impact is limited so that the target torque is reached over 50/10 = 5 over 5 pulses. In this case, two or more impacts occur within the error range of the target torque ± x%. Therefore, even if the motor 2 does not stop at the first impact, it can be stopped at the next impact. Thus, the tightening torque can be more reliably kept within the target torque range.

  In this rotary tool, in addition to the restriction of the motor rotation speed according to the magnitude of the torque setting value C2, a determination torque value smaller than the torque setting value C2 by a predetermined value is set in the determination torque setting unit C7. The impact time (determination torque arrival time) T from the start of tightening due to impact impact until the tightening torque reaches the determination torque value is measured by the impact time measuring unit C8, and the correction value corresponding to the time T is a correction value. The calculation unit C9 calculates and corrects the torque setting value C2.

  Here, when the counterpart member has high rigidity, the determination torque arrival time T is short as shown in FIG. 5A, and the elastic member 32 is interposed between the screw 31 to be tightened and the counterpart member 30 as shown in FIG. When the axial force transmission is delayed, such as when there is intervening, as shown in FIG. 5 (b), the determination torque arrival time T becomes longer. In order to solve the problem that the final tightening torque becomes smaller than the target torque, such as when the elastic member 32 is interposed, with this rotary tool, if the time T is long, the target torque is increased. The direction is corrected, and torque application to the output shaft 7 is stopped based on the corrected target torque.

  For example, as shown in FIG. 6, when the rotational speed N is 10,000 rpm, when the target torque is 20 N · m set to the torque setting value C2, if the determination torque arrival time T is 500 ms, no correction is made. If the determination torque arrival time T is 550 ms, the target torque is corrected to 20.5 N · m. If the determination torque arrival time T is 600 ms, the target torque is corrected to 21 N · m. When the tightening torque reaches the target torque corrected as described above, the stop determination unit C4 stops the motor 2 as described above.

  For the above correction, a correction table as shown in FIG. 6 is prepared for each rotational speed, and when the maximum rotational speed restriction is made according to the target torque set in the torque setting value C2, the control circuit C This is performed by reading a correction value corresponding to the determination torque arrival time T at the rotational speed from the correction table and correcting the target torque. By using the correction table, it becomes easy to perform appropriate correction for various tightening targets.

  Note that changing the correction value for each rotation speed (rotation speed) reduces the power supply voltage of the battery pack 9 and increases the maximum rotation speed even when the maximum rotation speed is not regulated according to the target torque. This is effective when the voltage drops or when the user performs work while suppressing the motor rotation speed.

  By the way, the time T is changed because the torque change rate (dT / dt) is changed, and the correction is performed according to the measurement result of the determination torque arrival time T without directly using the torque change rate. In order to facilitate the correction process, the torque change rate (dT / dt) may be calculated, and the correction may be performed based on the calculation result. A correction table in which correction values are set in advance may be used.

  When the torque change rate is used directly, correction is performed based on the torque change rate at the time when the tightening torque reaches the determination torque, and the torque change rate is calculated and calculated while the impact is being made. You may make it repeat correcting target torque according to a torque change rate for every predetermined time. In the latter case, the target torque is corrected according to the changes in the situation during the tightening operation, so appropriate tightening should be performed even when the torque change during the tightening operation is large, such as tightening a tapping screw or wood screw. In addition, since the feedback to the target value control is accelerated, it is effective when it is desired to detect and stop the torque with less impact, such as when the screw that has already been tightened is tightened.

  In addition, since the judgment torque arrival time T also changes depending on the output voltage of the battery pack 9 that affects the motor performance and the motor temperature, correcting the correction table based on the output voltage and temperature makes it possible to perform more accurate correction. It can be carried out.

  Further, when the rotary tool product is completed, the determination torque arrival time T and the value to be corrected are measured, and the correction table is created based on the measured value and stored in a non-volatile memory or the like. It is possible to obtain one that can perform high-precision tightening corresponding to individual differences in performance and motor performance.

  In each of the above examples, the correction table set in advance has been described. However, it is needless to say that the torque setting value C2 may be corrected using a correction coefficient corresponding to the arrival time T.

  After the tightening is completed, displaying the torque measurement result or displaying the determination of whether the tightening operation is good or not allows the operator to work more safely. If the torque measurement value and the determination result of pass / fail are notified to the management means by communication, the tightening torque can be managed.

  Although the rotary tool provided with the impact type torque generator by the hammer 4 and the anvil 5 is shown, it may be one that generates an impact with a hydraulic pulse, or outputs the torque generated by the motor without using the impact. It may be provided with a torque generating device of a type that transmits the shaft 7 directly or at a reduced speed. Even in a case where no impact is used, the occurrence of insufficient tightening force such as when the elastic member 32 is interposed can be suppressed by employing a correction value corresponding to the rate of change in torque. When the time until reaching the determination torque is used as the rate of change in torque, the time from when the bolt or screw is seated or when the torque value detected by the torque sensor 10 exceeds the predetermined value until the determination torque is reached. Use it.

DESCRIPTION OF SYMBOLS 1 Rotating tool 2 Motor 3 Reducer 4 Hammer 5 Anvil 7 Output shaft 10 Torque sensor C Control circuit

Claims (6)

A motor as a rotational drive source; torque applying means for applying torque generated by motor rotation to the output shaft; a sensor for measuring torque applied to the output shaft; and a target torque in which the torque measured by the sensor is set In the rotary tool provided with a control means for stopping the torque application to the output shaft when reaching
The control means corrects the target torque in accordance with the rate of change of the torque value detected by the sensor and stops applying torque to the output shaft based on the corrected target torque. Rotating tool.   2. The rotary tool according to claim 1, wherein the control means corrects the target torque in a direction to increase when the rate of change of the torque value detected by the sensor is small.   The control means measures the time until the torque value detected by the sensor reaches the determination torque value set smaller than the target torque as the rate of change of the torque value detected by the sensor. The rotary tool according to claim 1 or 2, characterized in that:   The rotary tool according to claim 1 or 2, wherein the control means repeatedly calculates a change rate of the torque value every predetermined time and corrects the target torque according to the calculated change rate. .   The rotary tool according to any one of claims 1 to 4, wherein the control means includes a correction value corresponding to the detected change rate of the torque value as a table.   6. The rotary tool according to claim 5, wherein the table is set for each rotation speed of the motor.

Images