JP2013107165A - Impact rotary tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform fastening by more accurate torque.SOLUTION: The impact rotary tool includes an impact mechanism for adding striking shocks to an output shaft by a motor output, a striking detection means 21 for detecting striking by the impact mechanism, a rotational angle detection means 22 for detecting the revolution speed of a motor, a striking detection means 24 for calculating a striking speed from striking timing obtained by the striking detection means and a motor rotational angle obtained by the rotational angle detection means, and a control means 10 for counting the number of strikes detected by the striking detection means and stopping the motor when a prescribed number of strikes is reached. The control means corrects the number of strikes by a short amount when a striking speed detected by the striking speed detection means is equal to or lower than a prescribed striking speed. The tool further includes an adjustment part 15 for adjusting the correction amount of the short number of strikes.

Description

  The present invention relates to an impact rotary tool such as an impact wrench and an impact driver used for tightening (and loosening) screws such as bolts and nuts.

  The impact rotary tool tightens the hammer by rotating it with a motor output by giving impact to the output shaft (anvil) in the direction of rotation. In such an impact rotary tool, in order to provide a shut-off function that automatically stops when the desired tightening torque is reached, the number of hits described above is counted and the number of hits is set to the desired tightening torque. Japanese Patent Application Laid-Open No. H10-228707 discloses control based on whether or not the number of times corresponding to torque has been reached.

  By the way, the maximum tightening force of the impact rotary tool is determined by the rotation speed of the hammer (motor rotation speed) which depends on the voltage of the drive power supply. For this reason, when shut-off is performed using only the above-mentioned number of strikes, when the driving power source is a battery and the battery voltage gradually decreases due to continuous work, the tightening torque also gradually decreases. In a process that requires management of tightening torque of bolts, nuts, etc., such as factories, the management becomes impossible.

  For this reason, Patent Document 2 discloses a technique for detecting the hitting speed and correcting the hitting number when the hitting speed is reduced.

Japanese Patent Laid-Open No. 5-200677 JP 2009-083038 A

  However, since the relationship between the hit correction and the hitting speed changes depending on the working conditions, if the hitting correction amount accompanying the reduction of the hitting speed is uniform, the correct correction may not be possible depending on the working conditions. Therefore, further improvement in accuracy is desired.

  This invention is made | formed in view of the said problem, and makes it a subject to provide the impact rotary tool which can perform the clamp | tightening by more exact torque.

  An impact rotary tool according to the present invention includes an impact mechanism that applies impact impact to an output shaft by motor output, impact detection means that detects impact by the impact mechanism, rotation angle detection means that detects the rotational speed of the motor, and impact A hit detecting means for calculating the hitting speed from the timing of hitting obtained by the detecting means and a motor rotation angle by the rotation angle detecting means, and a motor when the hit number detected by the hit detecting means is counted to reach a predetermined hit number. And the control means for correcting the number of shortage hits when the hitting speed obtained by the hitting speed detecting means is equal to or lower than a predetermined hitting speed. It is characterized by having an adjustment unit for adjusting the amount.

  As the adjusting portion, a device that applies an adjustment amount set in advance according to the hardness of the tightening member to be struck and the counterpart member to which the tightening member is tightened can be suitably used.

  Moreover, it is preferable that the said adjustment part is provided as another apparatus different from a tool main body.

  As described above, in the present invention, since the impact energy and the impact speed of one impact are correlated, a stable tightening torque is detected in order to detect the impact speed and correct the number of impacts according to the impact speed. In addition, the presence of the adjustment part makes it possible to adjust the correction amount according to the fastening member such as a screw or bolt, or the mating member such as an iron plate or a molded product. Tightening torque can be realized, and it is effective in operations requiring tightening management at factories and the like.

It is a flowchart which shows operation | movement of an example of embodiment of this invention. It is a block diagram same as the above. It is explanatory drawing of the relationship between a fastening torque same as the above and a rotation angle. It is explanatory drawing of the relationship between the impact speed same as the above, and the correction | amendment impact number.

  Hereinafter, the present invention will be described based on an embodiment shown in the accompanying drawings. Reference numeral 1 in FIG. 2 denotes a motor as a drive source, and the rotation output thereof is decelerated by the speed reducer 2 and transmitted to the drive shaft 3. A hammer 4 is connected to the drive shaft 3 via a cam mechanism (not shown). The hammer 4 is engaged with an anvil 5 having an output shaft, and is urged toward the anvil 5 by a spring 6. The hammer 4, the anvil 5, the spring 6, and the cam mechanism are used as an impact mechanism. Is configured.

  Since the hammer 4 and the anvil 5 are engaged with each other by the bias of the spring 6, when the load is not applied to the anvil 5 side, the rotation of the motor 1 is transmitted to the anvil 5 side as it is. However, if the load torque increases, the hammer 4 moves backward against the spring 6, and if the anvil 5 and the hammer 4 are disengaged due to the backward movement, the biasing by the spring 6 and the cam mechanism are performed. The hammer 4 moves forward while being guided and applies a striking impact (impact) in the rotational direction to the anvil 5.

  In FIG. 2, 10 is a control circuit, 11 is a motor drive circuit, 12 is a rechargeable battery as a drive power source, and 13 is a trigger switch. The operation of the trigger switch 13 turns the motor 1 on and off and the amount of operation thereof. Accordingly, the rotational speed of the motor 1 is adjusted.

  Further, in this impact rotary tool, a hit detection means 21 for detecting when the anvil 5 is hit by the hammer 4, a rotation angle detection means 22 for detecting the rotation angle of the motor 1, and a seating detection means 23. And a striking speed detecting means 24. In addition, the seating detection means 23 and the hitting speed detection means 24 are comprised by the calculating part in the control circuit 10 in this example.

  The hit detection means 21 is composed of a microphone that captures the hitting sound or an acceleration sensor that senses the hitting impact, and detects the timing at which the hitting impact is applied.

  The rotation angle detection means 22 detects the rotation angle of the motor 1. When the motor 1 is a brush motor, it is a rotation sensor (for example, a frequency generator) added to the motor 1. When the motor 1 is a brushless motor, the rotation angle of the rotor is detected. A position detection sensor (Hall element) for detecting the position is used.

  The seating detection means 23 is for detecting the seating of the head of the screw or bolt in contact with the member to be fastened, and estimates the tightening torque from the rotational speed of the motor 1 and the amount of motor rotation between impacts. The detection is based on whether the tightening torque has reached a predetermined value.

  In the present invention, the seating is determined based on the estimated tightening torque obtained by the above calculation, and the final tightening torque is determined by counting the number of hits after the seating. The reason will be described later.

The estimation of the tightening torque by the seating detection means 23 is based on the balance of kinetic energy for each hit, and the energy given to the anvil 5 by the hammer 4 hit is approximately equal to the energy consumed by the tightening. The relationship between the rotation angle θ of the screw near the seating determined by the member and the tightening torque T can be expressed by the function T = τ (θ) as shown in FIG. Is generated at each point of the anvil rotation angle θ1... ΘN, the value E1 obtained by integrating the function τ in the interval [θ1, θ2] is the energy consumed for the tightening work, and the hammer 4 at the θ1 point. Is equal to the energy given to the anvil 5 by hitting the anvil 5. Therefore, the average tightening torque T in the section [θN + 1, θN] is obtained from the energy En and the rotation angle between hits θn = (θN + 1−θN).
T = En / θn (1)
It can be asked.

The energy En is calculated from the hitting speed ωn obtained by the hitting speed detecting means 24 performing the calculation of dividing the anvil rotation angle between hits by the hitting interval, and the known inertia moment Ja of the anvil 5.
En = 1/2 × Ja × ωn ² (2)
It can be asked. Here, the anvil rotation angle θ is calculated from the relationship between the motor rotation angle between hits, the reduction ratio of the speed reducer 2, and how many times the anvil 5 is hit while the hammer 4 makes one rotation.

  Here, when it is determined whether or not the target tightening torque has been reached based on the number of strikes, the repetition accuracy is deteriorated due to a decrease in the power supply voltage as described above.

  For this purpose, when performing the control to perform the shut-off when the number of hits reaches a predetermined number of hits corresponding to the target tightening torque, the hitting speed ωn in the equation (2) is monitored, The predetermined number of hits is corrected according to the hit speed ωn.

  That is, in FIG. 1, step S104 indicates a seating determination, and steps S105 to S110 indicate a shut-off operation based on the number of hits. If the seating is determined, the control means 10 is an impact signal detected by the impact detection means 23. Count the number of hits.

  Then, when the hitting speed before stopping at the predetermined hitting number is equal to or higher than the first predetermined hitting speed (the hitting speed when the battery voltage is normally normal), the time when the hitting number reaches the predetermined hitting number (S112) The operation proceeds to the shut-off operation. If the hitting speed is lower than the first predetermined hitting speed, the predetermined hitting number is corrected.

In this correction, a value obtained by multiplying the hit energy calculated from the first predetermined hitting speed and the hit energy calculated from the hitting speed obtained by the detection calculation by the predetermined hit number is set as the insufficient hit energy. This is done by converting the energy into an insufficient number of hits, and adding the insufficient hit number to the predetermined hit number to obtain the corrected hit number. If the hit number reaches the corrected hit number (S109), the motor 1 is stopped. Let me shut off. By the way, the calculation of the above-mentioned insufficient energy (insufficient energy = ((first predetermined hitting speed) ² − (actual hitting speed) ² ) × predetermined set hitting number)) This is based on the fact that the square of the impact speed is considered to be proportional to the tightening torque.
Insufficient number of hits = Correction coefficient x Insufficient energy / (actual hitting speed) ²
Is going by. The lower the hitting speed, the greater the number of hits, so that more accurate correction can be performed. The correction coefficient is an arbitrary constant that varies depending on the impact rotary tool.

  By the way, the number of short hits is uniform depending on the type of fastening member such as a screw or bolt and whether the mating member to which the fastening member is fastened is a rigid body such as an iron plate or a soft body such as a molded product. Rather, the number of corrective hits will change accordingly.

  For this purpose, the correction amount according to the hitting speed can be adjusted by operating the adjusting unit 15 shown in FIG. 2 connected to the control circuit 10. For this adjustment, as shown in FIG. 4, assuming a typical member (iron plate, molded product), a curve of the hitting speed and the number of hits is set in advance for each assumed member, and this curve is selected. This adjusts the shortage hitting number (correction hitting number).

  Further, the adjusting unit 15 is detachable from the tool body, for example, so that it can be removed during work, or the adjusting unit 15 is configured by a personal computer or the like, and the tool body is connected to the adjusting unit 15 for adjustment. In other words, the adjustment unit 15 is configured as a separate device so that the operator cannot perform the adjustment operation without permission and is effective in on-site management. .

DESCRIPTION OF SYMBOLS 1 Motor 4 Hammer 5 Anvil 10 Control circuit 15 Adjustment part 21 Impact detection means 22 Rotation angle detection means 24 Impact speed detection means

Claims (3)

  An impact mechanism that applies impact impact to the output shaft by the motor output, impact detection means for detecting impact by the impact mechanism, rotation angle detection means for detecting the rotational speed of the motor, and timing of impact obtained by the impact detection means; A hit detection means for calculating the hitting speed from the motor rotation angle by the rotation angle detection means, and a control means for counting the hit number detected by the hit detection means and stopping the motor when the hit number is reached. The control means corrects the shortage hitting number when the hitting speed obtained by the hitting speed detection means is equal to or lower than a predetermined hitting speed, and further includes an adjustment unit for adjusting the correction amount of the shortage hitting number. An impact rotary tool characterized by comprising.   2. The impact rotation according to claim 1, wherein the adjusting portion applies an adjustment amount set in advance according to the hardness of the tightening member to be struck and the mating member to which the tightening member is tightened. tool.   The impact rotary tool according to claim 1, wherein the adjusting unit is provided as a device separate from the tool main body.

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