JP2014184515A - Striking type fastening tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a striking type fastening tool capable of completing fastening in a short time, without causing over-fastening.SOLUTION: An impact wrench 10 comprises an electric motor 23 and a main spindle 24 for rotating by imparting pulse-like impact torque of converting rotational torque from the electric motor 23, and fastens a bolt 100 by rotation of the main spindle 24, and comprises a torque sensor 30 for detecting torque T and a controller 50 for controlling the fastening of the bolt 100, and a target torque curve Cv of determining partial target torque Tm with every impact is set in the controller 50, and the controller 50 controls impact strength D of the electric motor 23 (a rotating speed of the electric motor 23) so that the torque T detected by the torque sensor 30 becomes a value along the target torque curve Cv.

Description

  The present invention relates to a technique of an impact-type fastening tool for fastening a screw or the like, and more particularly to a technique for tightening control of an impact-type fastening tool.

  An impact-type tightening tool is well known as a tool for tightening screws such as bolts and nuts. The impact-type tightening tool is a tool that applies pulsed torque to a main shaft and tightens a screw by rotating the main shaft. For example, Patent Document 1 discloses three modes: section A in which a screw is tightened at a constant rotational speed, section B in which the rotational speed is set while performing a hit, and section C in which the rotational speed is set at a lower rotational speed than section B. A striking tightening tool is disclosed.

  However, in the impact-type tightening tool disclosed in Patent Document 1, when shifting from the section B to the section C, the rotational speed of the spindle is once lowered, so that it takes extra time to reach the final target torque. Will be. That is, the impact-type tightening tool disclosed in Patent Document 1 has a problem that the tightening time is long although the accuracy of reaching the final target torque is good.

  On the other hand, in the impact-type tightening tool disclosed in Patent Document 1, if the section C is abolished, it is considered that the tightening is completed in a short time. However, by eliminating section C, there is a risk of overtightening the screws.

JP 2011-031369 A

  The problem to be solved by the present invention is to provide an impact-type tightening tool that can complete tightening in a short time without causing excessive tightening.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, according to the first aspect of the present invention, there is provided a rotation drive source and a main shaft that is rotated by applying a pulsed impact torque obtained by converting the rotation torque from the rotation drive source. An impact-type tightening tool for tightening, comprising: torque detection means for detecting screw tightening torque; and control means for controlling screw tightening, wherein the control means includes a screw tightening torque for each impact. A target torque curve with a set target value is set, and the control means controls the rotational speed of the rotary drive source so that the torque detected by the torque detection means becomes a value along the target torque curve. To do.

  According to a second aspect of the present invention, in the impact-type tightening tool according to the first aspect, the target torque curve increases with an increase in the number of impacts, and a final target torque that is a target torque when the tightening is completed. In which the slope becomes smaller as the torque approaches the final target torque.

  According to a third aspect of the present invention, in the impact type tightening tool according to the first or second aspect, the target torque curve is a curve obtained by connecting a plurality of partial target torques that are target torques for each impact, and the partial target torque Is set so that the interval between the adjacent partial target torques becomes smaller as the final target torque is approached.

  According to the percussion type tightening tool of the present invention, the tightening can be completed in a short time without causing excessive tightening.

The schematic diagram which shows the structure of an impact wrench. The block diagram which similarly shows the control structure of an impact wrench. The flowchart which shows the flow of the tightening control by an impact wrench. The graph which shows a torque curve. The graph which shows the relationship between the number of hits, torque, and hitting strength.

The impact wrench 10 will be described with reference to FIG.
In FIG. 1, the impact wrench 10 is schematically shown in a side view.

  The impact wrench 10 is an embodiment according to the impact-type tightening tool of the present invention. The impact wrench 10 is a tool used for tightening the bolt 100 as a screw when the base material 101 and the base material 102 are fastened with the bolt 100 and the nut 105, for example.

  The impact wrench 10 includes a tool main body 20 and a controller 50 (see FIG. 2) as control means. The tool main body 20 includes an electric motor 23 as a rotational drive source, a main shaft 24, and an impact torque generating device 28 in a housing 22. The housing 22 is formed with a gripping portion 22a. The electric motor 23 may be an air motor.

  The electric motor 23 includes a rotor 25 that generates rotational torque. The main shaft 24 is an output shaft in the tool body 20 and is rotatably supported by the housing 22. The distal end portion 24 a of the main shaft 24 protrudes from the housing 22 and is a portion that engages with the bolt 100 via the attachment 60.

  The striking torque generator 28 is a device that converts continuous rotational torque from the electric motor 23 into pulsed striking torque. The pulsed impact torque converted by the impact torque generating device 28 is transmitted to the main shaft 24 to drive the main shaft 24 in rotation. In addition, the electric motor 23 of this embodiment is comprised by the inverter motor, and it shall assume that the rotation speed V can be changed freely.

  An operation lever 26 and a main valve 27 are provided on the grip portion 22 a of the housing 22. The operation lever 26 is interlocked with the main valve 27 and performs operations for supplying and stopping high-pressure air to the rotor 25. The main valve 27 supplies and stops high-pressure air to the rotor 25 by operating the operation lever 26.

  With such a configuration, the continuous rotational torque from the electric motor 23 is converted into a pulsed impact torque on the main shaft 24. Then, the hitting torque tightens the bolt 100 via the attachment 60. That is, the main shaft 24 is rotationally driven by the impact torque transmitted from the impact torque generator 28. Then, the bolt 100 connected to the main shaft 24 via the attachment 60 is tightened by the rotational driving force of the main shaft 24.

  The tool body 20 includes a torque sensor 30 as a tightening torque detection means. The torque sensor 30 is a sensor that detects the tightening torque of the bolt 100. The torque sensor 30 is configured as a magnetostrictive sensor that is provided in the housing 22 and includes an excitation coil 31 and a detection coil 32 that are arranged so as to go around a predetermined portion of the main shaft 24.

A control configuration of the impact wrench 10 will be described with reference to FIG.
In FIG. 2, the control configuration of the impact wrench 10 is shown in a block diagram.

  The controller 50 is connected to the electric motor 23, the torque sensor 30, and the display unit 51. The controller 50 controls the tightening operation of the impact wrench 10. The controller 50 has a function of setting the rotation speed V of the electric motor 23. The display unit 51 displays, for example, the torque T detected by the torque sensor 30 or the detection result of the tightening failure.

The tightening control S1000 will be described with reference to FIG.
In addition, in FIG. 3, the flow of fastening control S1000 is represented by the flowchart.

  The tightening control S1000 is an embodiment related to tightening control by the striking tightening tool of the present invention. The tightening control S1000 is control for tightening the bolt 100 as a screw with the impact wrench 10 when the base material 101 and the base material 102 are fastened with the bolt 100 and the nut 105, for example. The tightening control S1000 includes a first tightening control S100 and a second tightening control S200.

  The first tightening control S100 (steps S110 to S120) is control from the start of tightening until the bolt 100 is seated on the base material 101. The second tightening control S200 (steps S210 to S230) is control from when the bolt 100 is seated on the base material 101 to when the tightening is completed so that the torque T becomes the final target torque Tf.

  In step S110, the controller 50 rotates the spindle 24 with the impact strength D as the impact strength D1. The striking strength D represents the ratio of the rotational speed to the maximum rotational speed of the electric motor 23. Further, the impact strength D1 is set in the controller 50 in advance.

  In the first tightening control S100, a period from when the operation lever 26 is turned on until the bolt 100 is seated on the base material 101 is referred to as a free-run state. In the free-run state, the bolt 100 is screwed into the nut 105, so that no torque is generated in the impact wrench 10 yet.

  In step S120, the controller 50 confirms whether the torque T detected by the torque sensor 30 is greater than the reference torque T1. The reference torque T1 is a torque when the bolt 100 is seated on the base material 101, and is set in the controller 50 in advance.

  In step S120, if the torque T is greater than the reference torque T1, the controller 50 proceeds to step S210 of the second tightening control S200. On the other hand, when the torque T is equal to or less than the reference torque T1, the controller 50 continues the rotation of the main shaft 24 with the impact strength D being the impact strength D1.

  In step S210 performed after the bolt 100 is seated on the base material 101, the controller 50 calculates the impact strength Dn. Note that the impact strength Dn is calculated for each impact. Specifically, the controller 50 multiplies the difference between the torque T detected by the torque sensor 30 at the previous impact and the partial target torque Tm by the gain G with respect to the previous impact strength Dn−1. to add.

  In the second tightening control S200, the partial target torque Tm is a target tightening torque value of the bolt 100 set for each impact, and is set in the controller 50 in advance. The partial target torque Tm will be described later in detail. The gain G is a constant for converting the difference between the torque T and the partial target torque Tm into the impact strength D, and is set in the controller 50 in advance. The gain G may be changed depending on the work place or the tightening place.

  In step S220, the controller 50 rotates the spindle 24 with the impact strength D as the impact strength Dn.

  In step S230, the controller 50 confirms whether the torque T detected by the torque sensor 30 is greater than the final target torque Tf. The final target torque Tf is a target torque when the tightening of the bolt 100 is completed, and is set in the controller 50 in advance. The final target torque Tf is the final value of the partial target torque Tm described above.

  In step S230, when the torque T is greater than the final target torque Tf, the controller 50 completes the tightening control S1000 (second tightening control S200). On the other hand, when the torque T is equal to or lower than the final target torque Tf, the controller 50 proceeds to step S210 again.

The target torque curve Cv will be described with reference to FIG.
In FIG. 4, the horizontal axis represents the number of hits N, the vertical axis represents the torque T, and the target torque curve Cv is represented by a graph.

  The target torque curve Cv is represented by the correlation between the number of hits N and the tightening torque T. The target torque curve Cv is a torque curve set in advance so that the tightening can be completed in a short time without causing excessive tightening in consideration of the characteristics of the impact wrench 10.

  In the tightening control S1000, the impact strength D of the impact wrench 10 is controlled so that the tightening torque (torque T) of the bolt 100 by the impact wrench 10 becomes a value along the target torque curve Cv.

  The partial target torque Tm described above is a target value of the tightening torque of the bolt 100 determined for each impact (that is, a target torque for each impact), and is a torque for each impact in the target torque curve Cv. In other words, the partial target torque Tm is set so that the curve connecting the partial target torque Tm becomes the target torque curve Cv. In the present embodiment, up to the final target torque Tf is composed of seven partial target torques Tm.

  The target torque curve Cv is a curve that increases as the number of hits N increases and reaches the final target torque Tf when the horizontal axis is the number of hits N and the vertical axis is the torque T. Is set such that the gradient decreases as the torque T approaches the final target torque Tf from the reference torque T1.

  In other words, as the target torque curve Cv approaches the final target torque Tf, the target torque curve Cv is set so that the increase amount of the partial target torque Tm when the number of hits N increases by one. As the distance approaches, the interval between the adjacent partial target torques Tm decreases.

The operation of the tightening control S1000 will be described with reference to FIG.
In FIG. 5, the horizontal axis is the number of impacts N, the vertical axis is the torque T and the impact strength D, and the relationship between the impact number N and the torque T and the impact strength D detected by the torque sensor 30 is a graph. This is shown in the figure.

  In addition, in FIG. 5, in addition to the torque T (solid line in FIG. 5) and the impact strength D (dashed line in FIG. 5), a target torque curve Cv (dashed line in FIG. 5) is represented. The degree of proximity of the torque T to the target torque curve Cv (partial target torque Tm) can be found.

  In the first tightening control S100, the torque T is not generated until the bolt 100 is seated on the base material 101 after the operation lever 26 is turned on (in the free-run state). When the bolt 100 is seated on the base material 101, the torque T becomes larger than the reference torque T1 (1 hit).

  In the second tightening control S200, a value obtained by multiplying the difference between the torque T detected by the previous torque sensor 30 and the partial target torque Tm in the previous hit by the gain G with respect to the previous hit strength Dn−1. Addition is performed to calculate the impact strength Dn, and control is performed to set the impact strength Dn to a value such that the torque T approaches the partial target torque Tm.

  For example, in the number of hits 3, the torque T detected by the torque sensor 30 in the number of hits 2 is significantly smaller than the partial target torque Tm in the case of the number of hits 2, so the hitting strength D in the number of hits 3 is Control is performed to greatly increase the impact strength D when the number of impacts is 2.

  On the other hand, in the number of hits 4, the torque T at the number of hits 3 was close to the partial target torque Tm at the time of the number 3 hits. The striking strength D is slightly increased from the striking strength D when the number of hits is three so as to increase by the difference from the target torque Tm.

  In this way, by controlling the impact strength D so that the torque T approaches the partial target torque Tm for each impact, the bolt 100 is tightened by the impact wrench 10 so that the torque T follows the target torque curve Cv. It is supposed to be.

The effects of the impact wrench 10 and the tightening control S1000 will be described.
According to the impact wrench 10 and the tightening control S1000, the tightening can be completed in a short time without causing excessive tightening.

  That is, the main shaft 24 is rotated at a predetermined impact strength D1 until the bolt 100 is seated on the base material 101, and the torque T is applied for each impact number N from when the bolt 100 is seated on the base material 101 until the tightening is completed. Since the striking strength D is changed so as to approach the target torque curve Cv and the main shaft 24 is rotated, the tightening time can be reduced without causing excessive tightening.

10 Impact Wrench 23 Electric Motor 24 Spindle 30 Torque Sensor 50 Controller 100 Bolt 101 Base Material 102 Base Material 105 Nut D Impact Strength N Number of Strikes T Torque T1 Reference Torque Tm Partial Target Torque Tf Final Target Torque

Claims (3)

A striking-type tightening tool comprising: a rotational drive source; and a main shaft that is rotated by being applied with a pulsed striking torque converted from the rotational torque from the rotational drive source. There,
Torque detecting means for detecting the tightening torque of the screw;
Control means for controlling screw tightening;
Comprising
In the control means, a target torque curve in which a target value of the tightening torque of the screw is determined for each impact is set,
The control means controls the rotational speed of the rotary drive source so that the torque detected by the torque detection means becomes a value along the target torque curve;
Stroke type tightening tool. A striking tightening tool according to claim 1,
The target torque curve is a curve that increases as the number of hits increases and reaches a final target torque that is a target torque for completing tightening, and the slope decreases as the torque approaches the final target torque. Is set to be
Stroke type tightening tool. A striking tightening tool according to claim 1 or 2,
The target torque curve is a curve obtained by connecting a plurality of partial target torques, each of which is a target torque for each hit, and the partial target torque is set so that the interval between adjacent partial target torques becomes smaller as the final target torque is approached. Set,
Stroke type tightening tool.

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