JPS6274579A - Method and apparatus for clamping vibration screw by pneumatic pressure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method and device for fastening a vibrating screw using pneumatic pressure, and more specifically, a reversible screw fastening method and device that uses a pneumatic screw connected to a pressure source with a constant air pressure via a switching valve. During one cycle of vibration of a screw fastening tool using an air motor, screw tightening is performed in the direction of angle θ.
O rotation, loosening angle θ m rotation in the screw loosening direction (however, 1
The present invention relates to a screw fastening technique for fastening a screw member engaged with the screw fastening tool by applying an extremely low frequency vibration torque such that θo1>1θm1).

[Background of the invention]

A screw is one of the most basic mechanical elements.

It is used in a very wide range of industrial fields as a fastening element that can be assembled and disassembled, and as the requirements for reliability and economy of aircraft, automobiles, and other types of machinery that are subject to vibration are becoming increasingly strict. There is a growing demand for highly reliable screw tightening that meets the demands.

Generally speaking, among mechanical parts, it is said that the reliability of a screw fastened body made by connecting threaded parts such as bolts and nuts depends on the following three factors.

■ Reliability of threaded parts such as bolts and threaded parts themselves due to shape, material, and processing method ■ Reliability regarding setting of tightening force at the design stage ■ Tightening is determined by preset tightening force at the work stage (
Reliability of whether it is tightened with M bolt axial force) If any of the above factors (■ or ■) is insufficient, the function of the screw fastening body will not be fully demonstrated, and the screw may become loose or the bolt may be damaged. It can cause such things.

By the way, screws have traditionally been tightened using a screwdriver or Monkeys 1? In the past, screw tightening tools such as wrenches were used to tighten screws, but recently, with the advancement of automation technology for screw tightening work, in order to improve work efficiency, torque is used to tighten screws on-site, where a large number of screw parts are to be tightened. Screw fastening tools with electric motors or air motors have become obsolete. Therefore, to control screw tightening, the torque method, which controls tightening by torque and tightening by force, is carried out using relatively simple tools such as torque wrenches and torque drivers, so the current amount is also common. is being carried out.

However, even if the tightening torque is sufficiently controlled using the above torque method and the screw tightening operation is performed, the tightening process may vary depending on the accuracy of the tool, the machining accuracy of the screw, the surface treatment, the lubrication conditions, etc. The coefficient of solid friction that acts between the bolt head seating surface and the nut seating surface varies over a wide range, and the ultimate goal when tightening a large number of threaded members is to obtain uniform bolt axial force without variation. The thing is,
The situation was extremely difficult.

In order to obtain the above-mentioned uniform bolt axial force without variation during screw tightening, the present inventor first discovered the effect of reducing the solid friction of the bearing surface and threaded surface due to vibration, and the mutual relationship between them. We have developed a vibration screw fastening technology that utilizes the running-in effect caused by vibration (see Japanese Patent Publication No. 118θO0, 1983). This vibrating screw fastening technology applies superimposed direct current and alternating current to a constant-speed DC motor/motor to generate a superimposed motion of unidirectional rotational motion and torsional vibration on the motor shaft, and transfers the superimposed motion to the motor shaft. The signal is transmitted via the connected and fixed elastic rod for resonance to a screw fastening tool that is integrated with the elastic rod or connected and fixed thereto, and the screw member that engages with the screw fastening tool is fastened.

In vibrating screw fastening using the above-mentioned electric motor, compared to screw fastening using a conventional constant speed electric motor, the solid friction on the thread surface is reduced to an equal constraint due to screw υ vibration, and a conforming effect of the thread surface is produced. As a result, the torque coefficient decreases and its variation is reduced, making it possible to expect high-precision screw fastening.

However, in the case of vibrating screw fastening using an electric motor, the frequency of vibration is as low as 20 Hz to 30 Hz, and tightening requires tools and a servo. Since the vibration coupling is performed at the resonance frequency of the motor and the rotor, the angular displacement amplitude of the screw vibration is about 1° to 4°, which is not very large. Therefore, if the rotational speed (DC component) of unidirectional rotation is too high, the friction force cannot be switched between positive and negative, so the rotational speed (DC component) must be kept low, and as a result, the effect of conforming to the thread surface is reduced. It takes time to generate the fastening torque, and it takes time to complete the fastening with the specified fastening torque.Also, in order to obtain a large fastening torque, the motor and power supply used must be larger. However, the cost of the device as a whole was high.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned actual situation, and its purpose is to solve the problems in the vibrating screw fastening method and device using an electric motor without losing the characteristics of the screw fastening method using vibration. An object of the present invention is to provide a vibration screw fastening method and device using pneumatic pressure that solves the problems.

[Summary of the invention]

In order to achieve the above object, the vibrating screw fastening method according to the present invention uses a reversible rotary air motor connected to a pressure source of constant air pressure via a switching valve, and by controlling the switching valve, the motor shaft of the air motor is During one period of vibration, an extremely low frequency vibration torque is applied such that the tightening screw rotates by an angle θ0 in the tightening direction and the loosening angle θm rotates in the screw loosening direction (however, 1θo1>1θm1). The vibration screw fastening device according to the present invention is characterized in that a screw member engaged with a screw fastening tool connected and fixed to a motor shaft is fastened. a reversible air motor connected via a switching valve to the
An extremely low-frequency vibration torque is applied to the motor shaft of the air motor such that during one vibration period, the screw rotates by an angle θ0 in the tightening direction and rotates by the loosening angle θm in the screw loosening direction (however, 1θo1>1θAl). The present invention is characterized by comprising means for controlling the switching valve, and a screw fastening tool connected and fixed to the motor shaft.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic explanatory diagram of a vibrating screw fastening device according to the present invention, which is equipped with an axial force detector and a tool dynamometer for torque detection, especially for the purpose of experiment, in which 1 is a compressor and 2 is a pressure control unit. These constitute a pressure air source for supplying constant pressure air to the reversible rotary air motor 5.

Reference numeral 3 is a Dubshin reflex 423 position type switching valve that can be switched at an extremely low frequency of 0 to 10Hz by setting a timer 6, and by this switching, the air motor 5 is driven to rotate alternately in the screw tightening direction and the screw loosening direction. do. In this case, as shown in FIG. 2, the speed controllers 4 installed in the forward rotation side conduit 7 and the reverse rotation side conduit 8 between the switching valve 3 and the air motor 5 tighten the screws during one vibration cycle. The screw can be controlled so that it rotates by θO in the direction of screw loosening, and by a small amount of θm in the direction of loosening the screw. In FIG. 2, numeral 9 denotes a regulator for applying an electric signal generated by the timer 5 to the switching valve, and numeral 10 denotes an exhaust muffler.

In FIG. 1, reference numeral 11 denotes a motor shaft, and a screw fastening tool (hexagonal bar) 1 is attached to the motor shaft 11 by a scroll chuck 12.
3 are connected and fixed. The screw member to be screwed is
In the illustrated example, there is a bolt 14 with a hexagonal socket and a nut 15 that is screwed into the thread of the bolt 14. A flat washer 16 and an axial force detector 17 are interposed between the seat 14 and the nut 15, and the nut 15 is installed in a tool dynamometer 18 for torque detection. In the case of actual screw tightening work, the flat washer 16 and the axial force detector 17 are connected to the melt 14 and the nut 1.
5. This is a member to be fastened by 5.

Next, the operation of screw fastening according to the present invention will be explained with reference to FIGS. 2 to 4.

In Fig. 2, the air compressed by the compressor 1 is sent to the 1-TR air control unit 2, which includes a filter with a drain, an internal pressure reducing valve, a pressure gauge, and a lubricator. The compressed air whose pressure has been adjusted is supplied to the solenoid switching valve 3.

The switching valve 3 is on the forward rotation side of the air motor 5 (screw tightening is in the direction)
Port connected to conduit 7) A, reverse side (screwing direction)
Boat B connected to pipe line 8, exhaust ports R, R2 connected to exhaust silencer 10, supply air, p-to-p, 5-point, 3-position solenoid pulp, and timer 6 turned ON.
Tighten the time in the direction, and also the OFF time.
The time for loosening is set in , and each relay is wired to the solenoid of the switching valve 3 via the Tx 9.

Now, when the electric signal for tightening from Radex 9 is applied to the solenoid, the switching valve 3 operates in the forward rotation side, and the air supply boat P and the port are connected, and the air supply boat P and the exhaust port R are connected.
2 are connected. In this way, the constant air pressure is supplied to the air motor 5 by opening the check valve of the speed controller 4 of the forward rotation side piping 7, and the screw tightening is performed according to the ON time set in the direction. For tightening, the air motor 5 is rotated by an angle θ0, and the exhaust from the air motor 5 passes through the variable throttle valve of the speed controller 4 in the reverse rotation side piping 8, and is discharged through the port B, the exhaust boat R2, and the exhaust silencer 10.

Next, when the loosening electric signal from Relay GEX 9 is applied to the solenoid, the switching valve 3 operates in the reverse direction, connecting the air supply boat P and port B, and connecting the boat A and exhaust port R4. be done. In this way, the constant air pressure is supplied to the air motor 5 by opening the check valve of the speed controller 4 in the reversing side pipe line 8, and the air motor 5 is moved in the direction of loosening the screw at a loosening angle θ according to the set OFF time. On the other hand, the exhaust from the air motor 5 passes through the variable throttle valve of the speed controller 4 in the normal rotation side piping 7, and is then connected to the boat A, the exhaust port R4, and the exhaust silencer 10.
It is then discharged.

The above tightening angle θ0 and loosening angle θm are normal rotation side g7
1θo1 by adjusting the variable throttle valve of each speed controller 4 disposed in the reversing side pipe 8.
>10A1, but it is preferable to set it according to the present invention in terms of screw fastening efficiency.

FIG. 3 shows the movement of the fastening tool when fastening the vibrating screw according to the present invention, and shows the motor shaft 11 of the air motor 5.
and a fastening tool (hexagonal bar) 1 connected and fixed to the shaft 11
3, as shown in the figure, the screw is tightened by rotating by θO in the direction, and then the screw is loosened by rotating by θhf? :The rotation motion is set to 0 (
It is repeated at an extremely low frequency of f≦10Hz. As a result, before the screw tightening starts, each vibration period is 1θo1
-1θA1 When tightening a screw, the rotation progresses in the direction, and when the screw starts tightening, the tightening angle θ0 and the loosening angle θ both become smaller one after another), and eventually become zero, and the screw tightens. is completed.

Figure 4 shows the tightening torque and melt axial force generated when tightening an M8 hexagon socket head bolt at a frequency of 4 Hz, an initial tightening angle of 40° and an initial loosening angle of 24°, using the torque detection tool dynamometer 18 and the melt axial force, respectively. This is a graph showing a waveform recorded on a recorder using an axial force detector. As can be understood from this figure, the fastening torque increases with an approximate sine wave as the axial force increases, but In the initial stage, the force increases on the tightening side and decreases slightly on the loosening side.

When the tightening torque increases, the bolt axial force increases on the side facing tightening, but stagnates on the side facing loosening, and when the tightening torque approaches the set atmospheric pressure, the opposing force on the threaded surface almost disappears. The value becomes zero, and the conclusion is finally completed. Therefore, in the region I shown in the figure, there are two phenomena, Fi "looseness of the stripe" and "only stripe", and the tightening is completed in the region (2).

〔Effect of the invention〕

The tightening torque generated when tightening the screw is T, and the +f silt force is F.
, when the nominal diameter of the screw is d, the tightening torque T is T
= K-F-d, and this comparison constant K is called a torque coefficient, but in order to increase gelt axial force with the same fastening torque, the torque coefficient should be made as small as possible. Furthermore, when performing screw fastening work on a large number of screw members of the same standard, it can be said that the smaller the standard deviation value of the torque coefficient, the higher the reliability of whether or not the set tightening is performed with the torque.

According to the pneumatic vibration screw fastening method of the present invention, as a result of the screw fastening tool performing the screw fastening work by the tool movement as explained in FIGS. 3 and 4, the thread surface is damaged by repeated friction of the thread surface. This results in an isometric reduction effect and a running-in effect on the friction coefficient at The bolt axial force can be increased with the same fastening torque, and highly accurate and reliable screw fastening can be achieved.

Furthermore, compared to the vibrating screw fastening method using an electric motor, which applies direct current and alternating current in a superimposed manner to the constant speed DC servo motor described above and utilizes the i-fold motion of unidirectional rotational motion and screw vibration, In the vibratory screw fastening method of the invention, since the angular displacement amplitude of the vibration can be much larger, the frictional force on the screw surface can easily be switched between positive and negative, and as a result, it takes a relatively long time to generate a conforming effect on the screw surface. The conclusion can be completed in a short time without having to do anything. Furthermore, since the present invention uses an air motor, it has the advantage that the main body of the screw fastening device can be made compact and compact even when a large fastening torque is required.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a schematic explanatory diagram showing an experimental apparatus including a vibrating screw fastening device according to the present invention, Fig. 2 is an explanatory diagram of a pneumatic speed control circuit in the apparatus shown in Fig. 1, and Fig. The figure is an explanatory diagram of the movement mode of the screw fastening tool due to vibration in the present invention, and FIG. 4 is a graph diagram showing the relationship between fastening torque and bolt axial force during vibration fastening according to the present invention. 1...Compressor 2...Pressure control unit 3...Switching valve 4...Speed controller 5...Air motor 6...Timer 7...
・Forward rotation side pipe 8...Reverse rotation side pipe 9...Relay box lO...Exhaust silencer 11...Motor shaft
12... Scroll chuck 13... Fastening tool (hexagon 141) 14... Melt with hexagonal hole 15... Oak) 16... Flat washer 17...
・Axial force detector 18...Tool dynamometer for torque detection Fig. 1 143 Yukane Keneki Kusao Air Tanabata - 16 External Luxury, Dust Exhaust Tool ψKaka Revision 4-
2.52'I"z2'- 77: 74 Nice roll 4I Nfu 75: Tightening tool (rJ, Haru) 74!: Water bolt with hole in Figure 3 Figure 4 Figure axial force

Claims (1)

[Claims] 1. Using a reversible air motor connected to a pressure source of constant air pressure via a switching valve, and controlling the switching valve,
Applying an extremely low frequency vibration torque to the motor shaft of the air motor such that the motor shaft rotates through a tightening angle θ_O in the direction of tightening the screw and rotates through the loosening angle θ_A in the direction of loosening the screw (where |θ_O|>|θ_A|) during one vibration cycle; A vibration screw fastening method using pneumatic pressure, characterized in that a screw member engaged with a screw fastening tool connected and fixed to the motor shaft is thereby fastened. 2. A pressure air source with constant air pressure, a reversible rotary air motor connected to the pressure air source via a switching valve, and a tightening angle θ_O in the screw tightening direction during one vibration cycle on the motor shaft of the air motor.
rotate, loosening angle θ_A rotation in the screw loosening direction (however, |
θ_O | > | θ_A |) The vibration caused by pneumatic pressure comprises means for controlling the switching valve so as to apply an extremely low frequency vibration torque such as θ_O | > | θ_A |), and a screw fastening tool connected and fixed to the motor shaft. Screw fastening device.