JP2009262273A - Impact rotary tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect hammering without being affected by a variation in the vibration transmission properties of a housing due to a variation in temperature and humidity. <P>SOLUTION: This impact rotary tool comprises an impact mechanism for applying a hammering impact to an output shaft by the output of a motor 1, a hammering detection part for detecting the hammering by the impact mechanism, and a control unit 10 for estimating a tightening torque according to the output of the hammering detection part and stopping the motor when the estimated tightening torque reaches a preset torque value. The hammering detection part comprises a plurality of sensors S1, S2 positioned at different distances from the impact mechanism in the housing 7. The control unit switches the plurality of sensors for detecting the hammering. Even if the vibration transmission properties of the housing are varied, the hammering can be accurately detected using any sensor. <P>COPYRIGHT: (C)2010,JPO&INPIT

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 output shaft (anvil) by hitting the output shaft (anvil) with a hammer that is rotated by motor output, and has a particularly large nominal diameter due to its high workability of high-speed rotation and high torque. 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, the determination as to whether or not the tightening torque has been reached is performed by detecting the impact by the impact mechanism that applies the impact to the output shaft by the motor output and calculating the tightening torque based on the detected impact. However, such a sensor is generally arranged in the vicinity of the portion where the impact occurs so that the impact (impact caused by the impact) can be sensitively detected (see Patent Document 2).

  By the way, the housing of this type of tool is widely used with a glass fiber-added polyamide resin so that it can withstand drop impacts, etc., but this changes the elastic modulus considerably due to water absorption due to temperature and humidity. As a result, the propagation characteristics of vibration change. The temperature is affected not only by the environmental temperature but also by the heat generated by the motor, which is the power source, and by the heat generated in the impact generating section.

  Here, the sensor output for detecting the impact is amplified and used at an amplification factor determined by the sensitivity of the sensor and the magnitude of vibration propagating through the housing. At this time, when it is dry at low temperature, the vibration propagation characteristics of the housing are good and good results can be obtained in terms of hit detection even with a low gain, but in this case the housing temperature is high or the water absorption state If this is the case, the vibration propagation characteristics of the housing will be reduced, so that the output waveform after amplification will be minute and the impact detection accuracy will be reduced.

On the other hand, if the amplification factor is set high, assuming that the vibration propagation characteristic of the housing is low, the output waveform after amplification will be too large and the impact detection accuracy will be reduced if the vibration propagation characteristic of the housing is good. become.
JP 2000-354976 A Japanese Patent No. 3264157

  The present invention has been invented in view of the above-described conventional problems, and an impact rotary tool capable of accurately performing impact detection without being affected by changes in vibration propagation characteristics of the housing due to temperature, humidity, or the like. The issue is to provide.

  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. And a control unit for stopping the motor when the estimated tightening torque reaches a preset torque value, the impact mechanism in the housing containing the impact mechanism as the hit detection unit And a plurality of sensors at different positions, and the control unit switches the plurality of sensors to detect a hit. Even if the vibration propagation characteristic of the housing changes, the impact detection can be accurately performed using any one of the sensors.

  When the sensor arranged near the impact mechanism and the sensor arranged in the grip portion of the housing are used as the plurality of sensors, there is a large difference in vibration propagation up to the two sensors. It is possible to deal with when there is a large change.

  And if a control part switches a sensor based on the integrated average value of the output waveform obtained from a sensor, it can detect a hit based on the output waveform which can always perform an accurate hit detection.

  The control unit may switch the sensor according to the output of the temperature sensor. In this case, switching to an appropriate sensor can be easily performed.

  According to the present invention, even if the vibration propagation characteristic of the housing changes, the impact detection can be performed accurately by performing the impact detection using the output of any one of the sensors. The shut-off operation when the torque reaches the set torque can be performed accurately.

  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 is increased, the hammer 4 is pushed back against the spring 6 by the force acting on the engagement portion between the hammer 4 and the anvil 5, and the engagement between the anvil 5 and the hammer 4 is released by this retreat. Then, the hammer 4 advances and re-engages while rotating by the urging by the spring 6 and the guidance by the cam mechanism, and at this time, a striking impact (impact) in the rotational direction is applied to the anvil 5.

  In FIG. 2, 10 is a control unit comprising a microcomputer, 11 is an operation switch (trigger switch), 12 is a rechargeable battery as a driving power source, 13 is a setting input unit for setting a tightening torque, and 14 is a set tightening torque. Reference numeral 15 denotes a display unit for displaying a set tightening torque.

  When performing the tightening operation, the control unit 10 calculates the tightening torque based on the striking interval, the number of striking, the motor rotation number, etc., and if the calculated tightening torque reaches the torque preset by the setting input unit 13 For example, the control unit 10 stops the motor 1 and stops the tightening operation. FIG. 3 shows a flowchart for this operation.

  There are various methods for calculating the tightening torque in addition to the method shown in Patent Document 1 and the like, and the present invention is not limited to this method, and is described here. Is omitted.

  However, in the above calculation, it is essential to detect the impact generated by the impact mechanism. For this reason, a sensor (acceleration sensor) that can detect the impact for impact detection is provided. Two sensors S1 and S2 are used, and the sensors S1 and S2 are arranged at different vibration propagation distances from the impact mechanism. Specifically, one sensor S1 is disposed in the body 71 of the housing 7 that houses the impact mechanism, and the other sensor 72 extends from the body 71 so that the battery pack 8 is detachable at the tip. It is arranged on the front end side in the grip portion 72 to be mounted on.

  Of the two sensors S1 and S2, the sensor S1 disposed in the vicinity of the impact mechanism is used for detecting a hit when the vibration propagation characteristic is deteriorated due to the housing 7 being hot or absorbing moisture. The sensor S2 located away from the impact mechanism is used for detecting the impact when the vibration propagation characteristic of the housing 7 is good because the housing 1 is low temperature or dry. Here, whether to calculate the tightening torque based on the output of S2 is switched using the integrated average value A within the predetermined time of the output of the sensor S1.

  That is, the output of the sensor S1 is amplified at an amplification factor that assumes that the vibration propagation characteristic of the housing 7 is degraded. For this reason, when the vibration propagation characteristic of the housing 7 is degraded, As shown in FIG. 4 (a), the output waveform is a waveform that can accurately detect the impact, and the integrated average value A obtained by integrating and averaging the output waveform by the integrating circuit is shown in FIG. As shown in (b), it is at a low level.

  However, when the vibration propagation characteristic of the housing 7 is good, the amplified output waveform becomes large as shown in FIG. 5 (a), making it difficult to accurately detect the impact. Becomes a high level as shown in FIG. When the integrated average value A is higher than the preset threshold value TH, the control unit 10 performs the hit detection based on the output of the sensor S2, not based on the output of the sensor S1.

  Since the sensor S2 is disposed at a position farthest from the impact mechanism in the housing 7 and is in a portion that is gripped by the user when the tool is used, even when the vibration propagation characteristic of the housing 7 is good, the propagation is possible. The vibration that is generated is not so great, and for this reason, an output waveform at a level that enables accurate hit detection can be obtained. FIG. 1 shows a flowchart for switching the sensors S1 and S2.

  Switching between the sensors S1 and S2 may be performed based on the output of the temperature sensor T by disposing a temperature sensor (for example, a thermistor) T in the housing 7. When the temperature is low, the impact detection is performed using the sensor S2 located away from the impact mechanism, and when the temperature is high, the sensor S1 located near the impact mechanism is used.

  Although an example in which an impact sensor (acceleration sensor) is used as the sensors S1 and S2 for detecting the impact is shown, the sensors S1 and S2 may be microphones that pick up the impact sound. The propagation of the impact sound is also affected by temperature, humidity, and a change in the elastic coefficient of the housing 7 associated therewith.

It is a flowchart which shows the operation | movement in an example of embodiment of this invention. It is a schematic block diagram same as the above. It is a flowchart of a basic operation same as the above. FIG. 2 shows a case where a preferable output waveform of a sensor for detecting a hit is obtained, (a) is a time chart showing a waveform, and (b) is a graph showing an integrated average value. FIG. 5 shows a case where the output waveform of the sensor for detecting impact is too large, (a) is a time chart showing the waveform, and (b) is a graph showing the integrated average value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 2 Reduction gear 3 Drive shaft 4 Hammer 5 Anvil 6 Spring 10 Control part S1 sensor S2 sensor

Claims (4)

  The impact mechanism that applies a impact to the output shaft by the motor output, the impact detection unit that detects impact by the impact mechanism, the tightening torque is estimated based on the output of the impact detection unit, and the estimated tightening torque is preset. In the impact rotary tool provided with a control unit that stops the motor when the torque value is reached, the impact detection tool includes a plurality of sensors at different positions from the impact mechanism in the housing that houses the impact mechanism as the impact detection unit, The impact rotary tool according to claim 1, wherein the control unit switches the plurality of sensors to detect a hit.   2. The impact rotary tool according to claim 1, further comprising a sensor disposed in the vicinity of the impact mechanism and a sensor disposed in a grip portion of the housing as the plurality of sensors.   3. The impact rotary tool according to claim 1, wherein the controller switches the sensor based on an integrated average value of output waveforms obtained from the sensor.   3. The impact rotary tool according to claim 1, wherein the controller switches the sensor according to the output of the temperature sensor.

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