JP5033004B2 - Impact rotary tool - Google Patents

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 is a tool that is tightened by applying a hammering impact in the rotational direction to the output shaft (anvil) with a hammer rotated by motor output. Widely used in construction sites and assembly factories where screws are tightened, impact rotary tools such as these have high torque characteristics, so they are overtightened or damage the object to be fastened. Since there are many situations where the tightening torque is greatly insufficient when working with fear of this point, a shut-off function is provided that automatically stops when the desired tightening torque is reached. Have been provided (see, for example, Patent Document 1).

  Here, whether or not the tightening torque has been reached is determined by detecting the impact by the impact mechanism that applies impact impact to the output shaft by the motor output and calculating the tightening torque based on the detected impact. However, such a sensor is arranged in the vicinity of the portion where the impact occurs so that the impact (impact caused by) can be sensitively detected. In this case, the sensor itself is damaged by the impact. The signal line connected to the sensor is likely to break.

If a state where such a hit cannot be detected occurs, the hit cannot be stopped with a target torque, resulting in excessive tightening or damage to the fastening target.
JP 2000-354976 A

  The present invention has been invented in view of the above-described conventional problems, and provides an impact rotary tool capable of accurately detecting an abnormality of a hit detection unit and preventing an abnormality from occurring in tightening torque management. Is an issue.

In order to solve the above problems, an impact rotary tool according to the present invention is based on an impact mechanism that applies a impact to an output shaft by a motor output, a hit detection unit that detects a hit by the impact mechanism, and an output of the hit detection unit. The impact rotary tool including a control unit that estimates the tightening torque and stops the motor when the estimated tightening torque reaches a preset torque value, includes a current detection unit that detects the motor current, and the above control. The unit includes a determination unit that determines an abnormality of the hit detection unit when there is no hit detection signal from the hit detection unit within a predetermined time from when the current detected by the current detection unit exceeds a threshold value . It has a special feature.

  When it is determined from the motor current that an impact is being made but no impact is detected by the impact detection unit, it is determined that there is an abnormality.

  Even if the determination unit of the control unit determines abnormality of the hit detection unit from the average current value of the current detected by the current detection unit and the output of the hit detection unit, the peak detected by the current detection unit The abnormality of the hit detection unit may be determined from the current and the output of the hit detection unit.

In addition, it is preferable that the determination unit of the control unit changes the determination reference according to a preset torque value so that more accurate determination can be made . In this case, the determination unit is set in advance. It is preferable to increase the current threshold and lengthen the predetermined time as the torque value increases .

Further, the control unit is provided with a memory for storing the abnormality when it is determined to be abnormal, and it is not appropriate that it is determined to be abnormal if the next activation restriction is performed according to the determination result stored in the memory. It is possible to prevent the work from being repeated. Moreover, it is preferable that a switch for canceling the start restriction is arranged in the tool.

  Since the present invention can accurately determine the abnormality of the impact detection unit, it is possible to prevent work in a state where tightening with normal tightening torque cannot be performed, and to accurately control the screw tightening torque. can do.

  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 unit comprising a microcomputer, 11 is a motor control circuit, 12 is a rechargeable battery as a drive power supply, SW is an operation switch (trigger switch), and the operation of the motor 1 is controlled by operating the operation switch SW. The motor control circuit 11 adjusts the applied voltage of the motor 1 and adjusts the motor rotation speed according to the operation amount.

  Further, the impact rotary tool includes a hit detection unit 7 that detects when the anvil 5 is hit by the hammer 4 and a current detection unit 8 that detects a current flowing through the motor 1.

  The hit detection unit 7 includes an acceleration sensor for detecting a hit impact, a sensor 70 such as a microphone for picking up hit sounds, and an amplifier circuit for amplifying the sensor 70. An example of the circuit configuration is shown in FIG. As shown in FIG. As the impact force increases, the detected impact output IO also increases.

  The current detection unit 8 detects the current flowing through the motor from the voltage across the current detection resistor, and the amplified output is input to the control unit 10 together with the output of the hit detection unit 7. An example of a current waveform during hitting detected by the current detector 8 is shown in FIG. As the striking force increases, the peak current PA increases and the average current AA also increases.

  There are various methods for calculating the tightening torque based on the number of hits and the hitting interval detected by the hit detection unit 7 in addition to the method shown in Patent Document 1 and the like. Therefore, although explanation is omitted here, if the calculated tightening torque reaches the torque preset by the setting input unit 13, the control unit 10 stops the motor 1 and stops the tightening operation. A time chart at this time is shown in FIG. At the start of the work, as described above, the anvil 5 follows the rotation of the hammer 4 so that no hit occurs and the average current is at a low level. However, when the hit starts, the average current AA increases.

  Here, when the sensor 70 of the hit detection means 7 is broken or broken, as shown in FIG. 6, no hit detection signal is actually obtained even during hitting. For this reason, when the hit detection signal is based on the calculation of the tightening torque, the calculated tightening torque is very small even when the preset torque is reached, which may lead to a situation such as excessive tightening. Become.

  For this reason, as shown in the flow chart of FIG. 1, the average current AA of the current detected by the current detection unit 8 is within a predetermined time Ta from the time when it is determined that the hit is started by exceeding the threshold value La. If the hit detection signal from the hit detection unit 7 does not enter (if the level of the hit detection signal does not exceed a predetermined value), the control unit 10 detects a hit due to a failure in the sensor 70 or the like of the hit detection unit 7. The motor 1 is stopped and the fact that a failure has occurred is displayed on the display unit 14 shown in FIG.

The “current determination value switching” in FIG. 1 is to increase the accuracy of the determination by switching the threshold value La according to the torque setting input and set by the setting input unit 13, but at this time, the threshold value La In addition, the accuracy can be further improved by switching the predetermined time Ta and the threshold voltage at the time of determining that there is a hit from the output of the hit detection unit 7. Note that the higher the set torque, the larger the current threshold La, the longer the predetermined time Ta, and the higher the hit determination voltage.

  Incidentally, there is a case where no impact occurs at all depending on the work, but at this time, since the average current AA of the current detected by the current detector 8 does not exceed the threshold value La as shown in FIG. There is no end.

The determination as to whether or not an impact has occurred from the current detected by the current detection means 8 may be made with the peak current PA instead of the average current AA. Since no peak current PA is generated when no impact occurs, the determination may be made based on whether or not the peak current PA is generated.

  By the way, when a situation that is considered to be a failure of the sensor 70 occurs, the motor 1 is stopped and an abnormality determination flag is written in the memory 15 shown in FIG. 2, and when the operation switch SW is operated next, the memory 15 If the abnormality determination flag is set, if the motor 1 is prohibited from starting, the impact rotating tool having a failure will not be used, so that the operation is repeated in a state where tightening is not appropriate. Can be prevented. 8 and 9 illustrate this point.

  The abnormality determination flag written in the memory 15 is preferably set so that it can be released by a position where it can be operated only by a repairer, for example, by operating a release switch 16 disposed in the tool.

It is a flowchart which shows an example of operation | movement of an example of embodiment of this invention. It is a block diagram same as the above. (a) is a time chart of the output of the hit detection unit, and (b) is a time chart of current values. It is a circuit diagram of a hit detection part same as the above. It is a time chart at the time of normal same as the above. It is a flowchart at the time of abnormality same as the above. It is a time chart at the time of another operation | movement. It is a flowchart which shows operation | movement of another example. It is a time chart at the time of abnormality same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 7 Impact detection part 8 Current detection part 10 Control part

Claims (7)

An impact mechanism that applies impact impact to the output shaft by motor output, a hit detection unit that detects hits by the impact mechanism, and a tightening torque that is estimated based on the output of the hit detection unit and the estimated tightening torque are preset. An impact rotary tool including a control unit that stops the motor when the torque value is reached, includes a current detection unit that detects a motor current, and the control unit detects that the current detected by the current detection unit exceeds a threshold value. An impact rotary tool comprising: a determination unit that determines an abnormality of the hit detection unit when there is no hit detection signal from the hit detection unit within a predetermined time from a point in time .   2. The impact according to claim 1, wherein the determination unit of the control unit determines an abnormality of the hit detection unit from the average current value of the current detected by the current detection unit and the output of the hit detection unit. Rotary tool.   2. The impact rotary tool according to claim 1, wherein the determination unit of the control unit determines an abnormality of the hit detection unit from a peak current detected by the current detection unit and an output of the hit detection unit.   The impact rotary tool according to any one of claims 1 to 3, wherein the determination unit of the control unit changes a determination reference according to a preset torque value.   5. The control unit according to claim 1, further comprising a memory for storing an abnormality when it is determined to be abnormal, and performing a next activation restriction according to a determination result stored in the memory. The impact rotary tool according to item. 5. The impact rotary tool according to claim 4, wherein the determination unit of the control unit increases the current threshold and lengthens the predetermined time as the preset torque value is higher. 6. The impact rotary tool according to claim 5, wherein a switch for releasing the start restriction is arranged in the tool.

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