JP2006231445A - Impact fastening tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impact fastening tool capable of stopping a motor by desired fastening torque at a low cost. <P>SOLUTION: This tool is provided with the motor 1 serving as a driving source and a hammering mechanism for transmitting rotary force of the motor 1 together with hammering by a hammer 5 up to an output shaft 7. The tool is provided with a hammering detection means 8 for detecting the hammering by the hammer 5 and a fastening deciding part 10 for stopping the motor 1 by judging that the fastening torque reaches set torque when a hammering interval detected by the hammering detection means 8 becomes a set value or below. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an impact tightening tool, such as an impact wrench or impact driver, used for tightening work such as screws and bolts and nuts.

  2. Description of the Related Art Conventionally, an impact tightening tool including a motor that is a driving source and a striking mechanism that transmits the rotational force of the motor to an output shaft along with striking with a hammer is known. Such an impact tightening tool has a function of automatically stopping the motor when a tightening torque reaches a predetermined value when tightening a member to be tightened such as a screw or a bolt and a nut. Preferably it is. In order to realize the above functions, it is most desirable in terms of accuracy to measure the actual tightening torque, but in this case, it is necessary to provide a torque measuring means on the output shaft, which increases the cost and the entire device. However, there is a problem that the size becomes larger and the usability becomes worse.

  On the other hand, control means has also been proposed in which the motor is stopped when the number of hits reaches a preset number (see Patent Document 1). In this case, however, there is an advantage that the motor control is simple. However, there is a problem in that the tightening torque when the motor is stopped varies greatly, resulting in insufficient tightening or excessive member tightening that causes member destruction.

In addition, the impact energy detected by the hammer and the rotation angle for each impact of the fastened member are detected, the tightening torque is estimated based on both detection values, and if the tightening torque exceeds the set value, Control means for stopping the motor has also been proposed (see Patent Document 2). According to this means, it is possible to stop the motor with an appropriate number of hits. However, since the hit energy is detected based on the rotational speed at the moment of hitting, high-resolution detection means and high speed There is a problem that the calculation means is essential, and therefore the cost increases and cannot be provided inexpensively.
Japanese Patent Laid-Open No. 5-162086 JP 2000-354976 A

  The present invention has been invented in view of the above problems, and can stop a motor with a desired tightening torque without using a high-resolution detection means or a high-speed calculation means, and can therefore be manufactured at a low cost. It is an object to provide a simple impact tightening tool.

  In order to solve the above-described problems, the hammer 5 is an impact tightening tool including the motor 1 as a driving source and a striking mechanism that transmits the rotational force of the motor 1 to the output shaft 7 together with striking with the hammer 5. The hit detection means 8 for detecting the hit by the hit, and the tightening for stopping the motor 1 by determining that the tightening torque T has reached the set torque Ts when the hit interval P detected by the hit detecting means 8 is less than the set value Ps. It is assumed that the determination unit 10 is provided.

  Between the tightening torque T and the striking interval P, there is a correlation characteristic that the striking interval P becomes shorter as the tightening torque T increases. Therefore, the striking interval P is detected in this way, and the set value Ps. By comparing, it can be determined whether or not the tightening torque T has reached a desired value (that is, the set torque Ts). That is, it is possible to realize a tightening operation with a desired tightening torque T by a simple and inexpensive means capable of detecting the hitting interval P without using a high-resolution detection means or a high-speed calculation means. is there.

  The impact tightening tool having the above-described configuration includes the information detection means 20 that can detect the rotational speed ω information of the hammer 5 and corrects the set value Ps based on the detection result of the information detection means 20. Is preferred. Since the correlation characteristic between the tightening torque T and the striking interval P changes according to the rotational speed ω of the hammer 5, high accuracy at a desired tightening torque T can be obtained by correcting the set value Ps in this way. Tightening work becomes possible.

  The information detection means 20 is preferably a rotation speed setting means 15 capable of setting the rotation speed of the motor 1. When the rotation speed setting means 15 is used, the user can easily set the optimum striking force for the work content, and when the rotation speed ω of the hammer 5 is changed by changing the setting of the rotation speed setting means 15 Even so, it is possible to perform a highly accurate tightening operation with a desired tightening torque T without any problem.

  It is also preferable that the information detection means 20 is the voltage detection means 14 that detects the voltage applied to the motor 1 or the current detection means 13 that detects the consumption current of the motor 1. In this way, even when the voltage variation is large because the battery is used as the power source, the desired tightening torque T can be obtained without being affected by the change in the rotational speed ω of the hammer 5 due to the voltage variation. High-precision tightening work is possible.

  The present invention can stop the motor with a desired tightening torque without using a high-resolution detection means or a high-speed calculation means, and thus can be an impact tightening tool that can be manufactured at a low cost.

  Hereinafter, the present invention will be described based on embodiments shown in the accompanying drawings. FIG. 1 shows a basic configuration of an impact driver which is an example impact tightening tool according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a motor as a drive source, and has a structure in which the rotational force of the motor 1 is transmitted to the drive shaft 3 via a speed reducer 2 having a predetermined reduction ratio. A hammer 5 is attached to the drive shaft 3 via a cam mechanism (not shown), and the hammer 5 is spring-biased to the output shaft 7 by a spring 4. The output shaft 7 has an anvil 6 that engages with the hammer 5 in the rotational direction. When the load applied to the output shaft 7 is small, the hammer 5, the anvil 6, and the output shaft 7 rotate together, and the output shaft When the load on 7 is large, the hammer 5 moves backward against the urging force of the spring 4 by the cam mechanism, and after the engagement with the anvil 6 is released, the hammer 5 moves forward and strikes the anvil 6. Accordingly, the output shaft 7 is re-engaged and the output shaft 7 is rotated by giving an impact in the rotational direction by the impact. That is, in this example, the above-described configuration forms a striking mechanism that transmits the rotational force of the motor 1 to the output shaft 7 together with striking with the hammer 5.

  In the figure, reference numeral 8 denotes a hit detection means for detecting a hit on the anvil 6 by the hammer 5 and is appropriately formed using a microphone or an acceleration sensor. The detection result of the hit detection means 8 is sent to the hit detection processing unit 9, and the hit detection processing unit 9 detects the hit interval P, which is the elapsed time between the current hit and the previous hit, based on the detection result. To do. The striking interval P detected by the striking detection processing unit 9 is sent to the tightening determination unit 10, and the tightening determination unit 10 compares the striking interval P with the set value Ps, and the time interval P becomes equal to or less than the set value Ps. At this point, it is determined that the current tightening torque T of the member to be tightened has reached the set torque Ts, and the tightening determination unit 10 outputs a motor 1 stop command. Upon receiving this stop command, the motor control unit 12 stops the motor 1 via the motor control circuit 11.

  The set value Ps is determined based on the correlation characteristics between the striking interval P and the current tightening torque T and the set torque Ts that is the desired tightening torque T input by the torque setting means 16. This correlation characteristic is a characteristic that the striking interval P becomes shorter as the current tightening torque T increases, and is clarified by the experimental results shown in FIGS. That is, the correlation characteristic between the hitting interval P and the tightening torque T is stored in the tightening determination unit 10, and the set torque Ts that is a desired tightening torque is transmitted via the torque setting means 16 during the tightening operation. 10, it can be determined that the tightening torque has reached the set torque Ts when the hit interval P detected via the hit detection means 8 and the hit detection processing unit 9 becomes equal to or less than the set value Ps. It is.

  Instead of comparing the striking interval P with the set value Ps as described above, the tightening determination unit 10 estimates the current tightening torque T based on the striking interval P and the correlation characteristic, and The determination procedure may be such that the tightening torque T is compared with the set torque Ts input by the torque setting means 16 and the motor 1 is stopped when the tightening torque T exceeds the set torque Ts. .

  As shown in FIG. 2, the correlation characteristic between the hitting interval P and the tightening torque T changes according to various combinations of the fastened member and the fastened member to be fastened. A condition input means 19 is provided. Depending on various conditions of a member to be fastened (screws, bolts and nuts, etc.) and a target member (plate material, etc.) input from the condition input means 19, the striking interval P and the tightening torque T Correlation characteristics are corrected, and as a result, the setting value Ps of the hitting interval P corresponding to the desired setting torque Ts is corrected.

  In the upper right frame in FIG. 2, the conditions (specifically, the diameter and length of the screw) of the member to be fastened corresponding to each mark such as ◆, ■, ▲, ×, *, and ● are shown. That is, the used screw has a diameter of 4.1 mm and a length of 75 mm in the ♦ mark, a diameter of 4.1 mm and a length of 25 mm in the ■ mark, and a diameter of 3.5 mm and a length of 20 mm in the ▲ mark. , The diameter is 3.8 mm and the length is 25 mm, the * mark is the diameter of 4.1 mm and the length is 25 mm, and the ● mark is the diameter of 3.5 mm and the length is 20 mm. In addition, although not shown, as a target member to which the screw is fastened, a wooden board is used for each of the marks ◆, ■, and ▲, a plaster board is used for the × mark, and a veneer board is used for the * mark. ● The steel plate is used for the mark.

  In the figure, reference numeral 15 denotes a rotation speed setting means for setting the rotation speed of the motor 1, reference numeral 14 denotes a voltage detection means for detecting the applied voltage of the motor 1, and reference numeral 13 in the figure denotes a current consumption of the motor 1. Current detection means. In the figure, 17 is a rechargeable battery used as a power source, and 18 is a trigger switch.

  Here, the correlation characteristic between the striking interval P and the tightening torque T changes according to the rotational speed ω of the hammer 5. Therefore, in this example, as the information detection means 20 capable of detecting the information on the rotation speed ω of the hammer 5, the above-described rotation speed setting means 15, voltage detection means 14, and current detection means 13 are used. , 14 and 13 is determined by the tightening determination unit 10 based on the correlation characteristic between the striking interval P and the tightening torque T, that is, based on the input set torque Ts. The set value Ps is provided so as to be corrected.

  The rotation speed setting means 15 sets the rotation speed of the motor 1, that is, the rotation speed ω of the hammer 5 to a high speed or a low speed according to the work in order to set the hammering force of the hammer 5 to a value according to the work. It is. Normally, if the rotation speed ω of the hammer 5 is set to a high speed, there is an advantage that the tightening work with a high torque becomes possible and the work becomes quick, but on the other hand, when a low torque work is performed at this high speed setting, There is also a risk of causing member destruction. Therefore, in the low torque operation, if the rotation speed ω of the hammer 5 is set so as to maintain a low speed by using the rotation speed setting means 15, a fine work can be performed. Then, according to the input of the rotational speed setting means 15, the tightening determination unit 10 appropriately corrects the set value Ps as described above, so that the desired set torque Ts is not affected by the change in the rotational speed ω of the hammer 5. The motor 1 can be surely stopped.

  Further, in this example, since the rechargeable battery 17 is used as a power source, the power supply voltage of the rechargeable battery 17 changes and the rotational speed of the motor 1, that is, the rotational speed ω of the hammer 5 changes. That is, the correlation characteristic between the striking interval P and the tightening torque T changes according to the change in the power supply voltage (see FIG. 3). On the other hand, as described above, the tightening determination unit 10 appropriately corrects the set value Ps in accordance with the detection result of the voltage detection unit 14, so that the desired value is not affected by the change in the rotational speed ω of the hammer 5 due to the voltage drop. The motor 1 can be reliably stopped with the set torque Ts.

  In addition, in this example, the tightening determination unit 10 is provided to correct the set value Ps as appropriate even in accordance with the detection result of the current detection means 13, so that the motor 1 is stopped more reliably at the desired set torque Ts. It is possible to make it.

  As the information detection means 20 for detecting the information on the rotational speed ω of the hammer 5, at least one of the above means 15, 14, 13 may be provided and used for correction, and other means may be used. It is also possible to have a configuration in which information on the rotational speed ω obtained from this is used for correction.

  When the tightening determination unit 10 uses a determination procedure that estimates the current tightening torque T based on the hitting interval P and the correlation characteristics and compares it with the set torque Ts as described above. For this, the estimated value of the tightening torque T may be corrected based on the information on the rotational speed ω, or the value of the set torque Ts may be corrected.

  In the impact tightening tool of this example having the above-described configuration, it is only necessary to measure the striking interval P, so there is no need to use a high-resolution detection means or a high-speed calculation means, and a standard and inexpensive one-tick. Torque control can be performed only with a microcomputer. That is, it can be manufactured at low cost.

It is a block diagram which shows the basic composition of an example impact fastening tool in embodiment of this invention. It is a graph of the correlation characteristic of the tightening torque and impact distance in the impact tightening tool same as the above, and shows a case where various conditions of the fastened member and the target member are changed. It is a graph of the correlation characteristic between the tightening torque and the hitting interval in the impact tightening tool same as above, and shows a case where the power supply voltage is changed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor 5 Hammer 7 Output shaft 8 Impact detection means 10 Tightening determination part 13 Current detection means 14 Voltage detection means 15 Rotation speed setting means 20 Information detection means P Impact interval Ps Set value T Tightening torque Ts Set torque ω Hammer rotation speed

Claims (5)

  In an impact tightening tool comprising a motor as a drive source and a striking mechanism for transmitting the rotational force of the motor to the output shaft along with striking with a hammer, a striking detection means for detecting striking with a hammer and a striking detection means An impact tightening tool comprising: a tightening determination unit that determines that the tightening torque has reached the set torque when the hitting interval is less than the set value and stops the motor.   2. The impact tightening tool according to claim 1, further comprising information detecting means capable of detecting hammer rotation speed information, and correcting the set value based on a detection result of the information detecting means.   2. The impact tightening tool according to claim 1, wherein the information detecting means is a rotational speed setting means capable of setting a rotational speed of the motor.   2. The impact tightening tool according to claim 1, wherein the information detection means is voltage detection means for detecting a voltage applied to the motor. 2. The impact tightening tool according to claim 1, wherein the information detecting means is a current detecting means for detecting a consumption current of the motor.

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