JPH10216963A - Friction welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly understand the softened condition of a work joining surface. SOLUTION: The load current value In of a motor to turn a work is increased from zero to I2 , and then, dropped to the prescribed value I1 when the speed reaches the prescribed value. When works are abutted on each other, the load current value is increased up to I4 to keep the speed of the motor to be constant against the frictional resistance. When the joined surface is softened, the frictional resistance of the work abutting surface is reduced, and the load current value is reduced to the prescribed value 13. The pressing force Pn to be applied between the works when the work feeding speed is the constant value of V1 is generated as soon as the works are abutted on each other, and increased to P2 . When the whole joined surface of the work is completely softened, and the pressing force is diffused due to the deformation of the joined surface, the pressing force is reduced to the prescribed value P1 . The softened condition of the work joined surface is judged taking into consideration the fluctuation of the load current value to indicate the trend and the fluctuation of the pressing force, and the upset force is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for welding a workpiece using frictional heat, and more particularly, to a method for facilitating management of dimensional accuracy after welding.

[0002]

2. Description of the Related Art Conventionally, a friction welding method has been used as a technique for joining works. In the work process, first, one of a pair of opposedly disposed works is rotationally driven and pressed against the other to generate frictional heat at a joint between the two works, and the frictional heat causes the joint between the two works to be generated. Soften. Next, softening is advanced to a desired state (the above process is referred to as an upsetting period). Finally, an upset force is applied while stopping the rotation of the work (this step is called an upset period). Then, the joints are integrated and welded to each other so as to dent each other.

[0003] In this friction welding apparatus for performing friction welding, one of a pair of works is clamped and fixed, and the other is fixed to a chuck provided in a rotary drive means, and is arranged coaxially. I have. Then, while rotating one of the workpieces, the workpiece can be moved in parallel so as to be brought into contact with the other workpiece. The rotation drive means and the parallel movement means can each use a servo motor or the like as a power source, and can accurately control the number of rotations of the work and the feed amount in the horizontal direction to set values. Then, in the upset period, the friction welding can be completed so that the portion (the shift margin) to be deformed by applying the upset force has a value set in advance.

Conventionally, the following method has been employed in order to correctly advance the friction welding process. An appropriate value of the friction torque to be applied to the contact portion of the work is set in advance during the upsetting period. During the actual upsetting period, the driving torque of the motor that rotationally drives the work is detected from a torque detector attached to the motor or a driving current value. A friction torque is calculated from the detected driving torque of the motor. The drive torque of the motor that translates the work is controlled so that the calculated value becomes an appropriate value of the friction torque obtained in the step. Processing proceeds for a predetermined time with the pressing force adjusted to the optimum value. After the lapse of the predetermined time, an upset force is applied to complete the friction welding. As a conventional example of the friction welding method having such a configuration, the details thereof are disclosed in Japanese Patent Application Laid-Open No. 3-124384.

[0005]

However, the above-mentioned prior art has the following problems. In the step, the friction torque calculated in the step is compared with an appropriate value set in advance in the step. In setting the appropriate value, a change from a solid generated in the contact portion of the workpiece to a molten state is made. It is necessary to know exactly. For this purpose, it was necessary to perform trial welding as much as possible. Further, every time the material, contact area (area where friction occurs), shape, etc. of the work are changed, it is necessary to grasp the state of the change of the contact portion, and a high-quality product can be obtained for various works. It took many preparation steps and time to obtain.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to easily obtain an optimum value of a friction torque and to simplify a friction welding process, thereby making the friction welding process easier. It is to perform pressure welding with high accuracy and at low cost.

[0007]

Means for solving the above-mentioned problems according to the present invention is to generate frictional heat at a joint of two works by rotating and driving a pair of works arranged opposite to each other and pressing the other against the other. A friction welding method for welding a joint portion of the two works softened by the frictional heat, wherein the work is rotationally driven when a relative rotation speed and a feed speed of the work are constant during an upsetting period. Based on the fluctuation of the load current of the motor and the fluctuation of the pressing force applied between the workpieces,
It is characterized in that a time for applying the upset force to the work is determined.

In the upsetting period in the workpiece pressing process, the load current of the motor for rotating and driving the workpiece first increases from zero to a certain value when starting from a stopped state, and decreases to a certain value when the speed becomes constant. It will be constant. next,
When the workpieces are brought into contact with each other, the load current increases in order to keep the motor speed constant against the frictional resistance. The increase in the load current at this time continues until signs of softening (solid solution) appear on the joint surface of the work. Then, when the softening of the joining surface starts, the frictional resistance of the work contact surface decreases, so that the load current decreases to a predetermined value and becomes almost constant. In the upsetting period, the pressing force applied between the works when the feed speed of the works is constant is generated and increased at the same time when the works are brought into contact with each other. Then, when the entire surface of the joining surface of the workpiece is completely softened and the pressing force is dispersed by the deformation of the joining surface, the pressing force decreases to a predetermined value and becomes substantially constant (slightly decreases). The softened state of the workpiece joint surface is determined in consideration of the variation of the load current of the motor and the variation of the pressing force, which indicate the above tendency, and the time for applying the upset force is determined to frictionally weld the workpiece.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 illustrates a friction welding apparatus used in the embodiment of the present invention. This friction welding apparatus has a spindle unit 2, a clamp 3 and a stopper 16 on an equipment base 1. Workpiece W ₁ and W ₂ are each adapted to support at the spindle unit 2 and the clamp 3.

The main shaft 4 is rotatably supported by the main shaft unit 2. The spindle 4 is located inside the spindle unit 2.
It is drivingly connected to a rotation servomotor 7 via gears 5 and 6. Further, a brake disk 8 is attached to the main shaft 4, and the brake can be applied to the main shaft 4 by operating the brake caliper 9. Furthermore, the tip of the main shaft 4 has a chuck 10 is mounted, it is possible to fix the workpiece W ₁ to the spindle 4.

The spindle unit 2 is attached to the equipment base 1 via a linear guide 11, and can be moved in the axial direction of the spindle 4 (the left-right direction in FIG. 4). The spindle unit 2 has an arm 12 projecting into the equipment base 1, and the arm 12 is inserted with a press-contact feed shaft 14 driven by a press-servo motor 13, and
By rotating 14, a propulsion force is generated between the shaft 12 and the arm 12 by a thread groove formed in the shaft. The driving force guides the main spindle unit 2 in the axial direction. Stroke sensor 1 between spindle unit 2 and equipment base 1
5 and 15a are provided, and the spindle unit 2 (that is, the work W ₁
) And the feed amount (or current position) can be measured. Furthermore, the arm 12 of the load sensor 17 is provided between the pressure-feed shaft 14, it is possible to measure the pressing force applied to the spindle unit 2 (i.e. workpiece W _1).

[0013] clamping 3 is composed of a clamp 3a for positioning a workpiece W ₂ in the axial direction of the main shaft 4, a clamp 3b for the positioning in the lateral direction with respect to said axis, the clamp 3c. Then, each axis clamp by appropriately adjusting, in the work W ₁ coaxially to the fixed to the main shaft 4, it is possible to arrange the workpiece W _2.

The stopper 16 can be provided with a drive structure capable of guiding the drive in the axial direction, similarly to the spindle unit 2. Then, the axial position can be set accurately. The stopper 16 is adjusted to an optimum position according to the size of the work to be subjected to friction welding.

FIG. 5 shows the structure of the control means used in the friction welding apparatus of FIG. As shown in the figure, the rotation servomotor 7 and the pressure servomotor 13 are respectively provided to the rotation servomotor 7 and the pressure servomotor 13.
And a friction welding controller 20 as these control means. In addition, the friction welding controller 20
It is in communication with a host controller (PLC) 21 that controls the entire equipment. In the figure, reference numerals 22 and 23 are encoders. Therefore,
The operation status of the rotation servomotor 7 and the press-contact servomotor 13 can be accurately grasped, and an accurate operation instruction can be issued. By the way, the control means of the stopper 16 can also have the same configuration, and the host controller (PLC) 21 can control the position of the stopper 16 and accurately grasp the current position.

Further, the host controller 21 is also in communication with the stroke sensor 15 and the load sensor 17, and the work W ₁
It can be the feed amount and detects the pressing force of the workpiece W ₁ and W _2. A load current detector 24 is connected to the rotation servomotor 7 and transmits a detection signal of the load current detector 24 to the host controller 21. Incidentally, if we also connect the load current detector to press servomotor 13, it is also possible to know the pressing force of the workpiece W ₁ and W ₂ from the detected value. Thus, the upper controller 21 grasps the operating condition of the entire device, by friction welding controller 20, to accurately control the speed of each motor 7,13 (ie revolution and the feed rate of the workpiece W ₁₎ to the desired value be able to. Further, the host controller 21, the dimension value L ₁ on the workpiece W _1, W ₂ drawings,
L ₂ and the sum thereof, product length L _M to be required for the work W _1, W ₂ after friction welding, when the dimensions of the workpiece W _1, W ₂ was L _1, L _2, after friction welding work bond dimensions may store the product length work feeding amount in (product dimension) period upsetting required for the L _M (approach margin) S, and the like.

Here, the procedure in the preparation period (before the upsetting period) when performing friction welding in the present embodiment will be described with reference to FIG. First, the chuck 10 attached to the distal end of the main shaft 4 as shown in the drawing, for fixing the workpiece W _1. Further, the workpiece W ₂ is fixed to the clamp 3, so that the workpiece W ₁ and coaxially clamp 3b, to adjust each clamp 3c. Further, the stopper 16 is connected to the workpiece W ₂
Is advanced towards and adjusted to the distance between the workpiece W ₂ is about several millimeters.

Next, (positioned in the axial direction) of the clamp 3 clamps 3b, loosen 3c only, and only displaceable workpiece W ₂ in the axial direction. Then, to advance towards the spindle unit 2 to the workpiece W _2. Then, the work W ₁ is brought into contact with the workpiece W _2. Here, the spindle unit 2
Is moved forward, the workpiece W ₂ is pushed by the workpiece W ₁ and contacts the stopper 16. The workpiece W ₂ is in contact with the stopper 16, the workpiece W ₁ spindle 4, through the spindle unit 2 and the arms 12 is detected by the load sensor 17. When a load of a predetermined magnitude (preferably a load corresponding to an upset force) is detected by the load sensor 17, the positions of the spindle unit 2 and the stopper 16 are determined by the stroke sensors 15, 15a (or the encoder 23). )
Is detected by

The detected spindle unit 2 and stopper
From the position of -16, the spindle unit 2 (ie, spindle 4)
The distance from the stopper 16 is determined. This distance moves the workpieces
All workpieces (work W₁ and
Work W_Two ) Is the sum of the lengths. That is, the work W₁ 
L is the length of₁', Work W_Two L is the length of_Two'Then L₁'+
L_Two'Value is obtained. Then, it is stored in the upper controller 21.
Work W₁ , W _Two L of the dimension values on the drawing₁ + L
_Two And L₁'+ L_Two'Value. The difference that arises here
But work W₁ And work W_Two Is the sum of the dimensional errors
You. Therefore, the length L required for the product_M To get
Assuming that the required work feed amount (deviation) is S ′, S ′ = S − ｛(L₁ + L_Two )-(L₁'+ L_Two')｝. Also, L₁'+ L_Two'Value of the product
Length L_M , The work feed amount S ′ is S ′ = (L₁'+ L_Two') -L_M Can be obtained by

Further, (L ₁ + L ₂ )-(L ₁ '+ L ₂ ')
(Hereinafter referred to as an error value) are provided with a maximum limit value and a minimum limit value (negative value). When the value of the error exceeds the maximum limit value, the desired product length L _M
Since the work feed amount S ′ required to obtain the workpiece becomes excessive and the burr generated at the joint between the works becomes huge,
To avoid this, the subsequent friction welding step is not performed.
Also, the error value, when below the minimum position, while obtaining required strength of the bonded portion of the workpiece between judges that it is impossible to obtain a desired product length L _M, perform friction welding process after this Absent.

After this, the clamps 3b, 3
c The tightening again, to prevent axial displacement of the workpiece W _2. Then, the spindle unit 2 is retracted once and the work W
₂ from is separated the workpiece W _1, do the work period upsetting later. At this time, the contact position between the workpiece W ₁ and the workpiece W ₂ is because it is recognized (the position was measured position of the spindle unit 2 and the stopper 16 are abutment position of the workpiece between) was determined work feeding The friction welding process proceeds according to the amount S ′. The details of the procedure during the preparation period are disclosed by the present inventors in Japanese Patent Application No. Hei 8-221043.

Next, the procedure after the upsetting period is as follows:
The description will be made mainly with reference to FIGS. FIG. 1 shows the rotational speed N _{n of} the work W ₁ , the feed speed V _{n of} the work W ₁ , which changes with the progress of the friction welding process (time t has elapsed).
Load current value I _n and the workpiece W in rotation servomotor 7
Displaying a graph the relationship between the pressing force P _n between ₁ and W _2.
FIGS. 2 and 3 show flowcharts corresponding to the friction welding step shown in FIG.

First, the servo control from the friction welding controller 20 is performed.
Outputs a drive command for the motor 7 (step 1),
Predetermined times obtained from wearing work (one or several times)
Rolling speed N₁ Until the arc W₁ To increase the rotation speed.
At this time, the load current value of the motor 7 is I_n = I_Two (First
Peak). Rotation speed is N ₁ 
When accelerated to a constant speed N₁ Operation at
The load current is not required as fast as in the case of high speed. Therefore, I_n of
The value corresponds to the rolling resistance in the rotating part of the friction welding device.
Applicable load current value I₁ Down to a constant. Here
In the process of the above, the load current value I_n Indicates the first peak
It is detected whether or not it has been performed (step 2). Shows the first peak
Work W₁ Rotation speed of N₁ Constant
Time t₁ After the passage (after the rotation speed has stabilized),
Driving of the pressure servomotor 13 from the friction welding controller 20
Command SG₁ Is output (step 3).

Work W₁ Feed speed V_n = V₁ Up to
Faster and constant speed V₁ To send. And work
W₁ , W_Two Abuts at the abutment position recognized during the preparation period
(ST₁ ). Then, frictional resistance is generated on the contact surface of the workpiece.
The friction of the motor 7
Speed N₁ To maintain the load current value I of the motor 7 _n 
Increase. And I_n = I_Four (The second peak)
The load current value rises until (ST_Two ). After this, I_n of
The value gradually decreases to a substantially constant value I_Three Becomes This load power
The change in the flow value is caused by the frictional heat generated by the frictional resistance.
Softening starts, reducing the frictional resistance of the workpiece contact surface
Slightly increase the rotation speed to N₁ Of motor 7 necessary to maintain
This is because the load current decreases. Here, the second peak
Load current value I_Four And the load current at the first peak
Value I₁ Difference I_s The value of
It is determined whether or not it is (step 4). I_s Value of trial welding
I found in business_s Is abnormal compared to the value of
If it exceeds the threshold value, stop the friction welding work
You.

Also, ST₁ (Work W₁ , W_Two Contact)
Pressing force P that was previously zero_n Is the value of ST₁ Increases with
Then P_n = P_Two Rise until (first peak)
(ST _Three ). After this, P_n Value gradually decreases and is almost constant
Value P₁ Becomes By the way, ST _Three Is ST_Two Later than (send
Amount S₁ After). The reason for this is that
ST is the point where softening starts partially_Two Although it is
Work surface is completely softened, and the pressing force is reduced.
The state is dispersed by the deformation of the mating surface, and the pressing force P_n 
ST is the point where_Three By being. Yo
And pressing force P_n In which the first peak of is detected_Three time
In terms of point, all the joint surfaces of the workpiece are completely softened,
It is in a state suitable for applying a cutting force. From now on,
The friction welding process can be shifted to the upset period
You.

[0026] Then, after the ST ₃ the feed amount S _2, the friction welding controller 20 outputs a differential command SG ₂ of the stop command and a brake caliper 9 to the servo motor 7 (step 5). At about the same time, the friction welding controller 20 outputs an acceleration command SG ₃ of the servo motor 13 (st
ep 6), increasing the feed rate of the workpiece W ₁ from V ₁ to V _2. Thereby, upset forces P ₃ is the work W _1, W ₂ (second peak) is applied. At this time, the load current value of the servomotor 7 is the I _n = I ₅ (third peak). Finally, whether the work feed amount has reached S '
It is detected whether or not the rotation speed of the servo motor 7 of the work has become zero (step 7), and if any of the conditions is satisfied,
Judging that the friction welded product of the correct dimensions has been obtained, the friction welding work is completed (step 8). When the work feed amount does not reach S ', the product is rejected as a dimensional defect. If the rotation speed does not become zero, it is rejected as welding failure.

The operation and effect obtained by the embodiment of the present invention having the above configuration are as follows. Wherein as the at upsetting period, the load current value I _n of the servo motor 7 for rotating the workpiece W ₁ is (a first peak) increases from zero during acceleration from a stop condition to I _2, the motor When the rotation speed of 7 becomes constant at N _n = N ₁ , the load current value decreases to I _n = I ₁ and becomes almost constant. Here to begin feeding of the workpiece W _1, it is kept constant at a feed rate V _n = V _1. Then, when the workpieces W ₁ and W ₂ are brought into contact with each other (ST
_1), in opposition to the frictional resistance increases in order to keep the speed of the motor constant to the load current value I _n = I _4, showing the second peak of the load current (ST _2). Thereafter, the load current value I _n = I ₃
And becomes almost constant. The decrease in the load current value at this time is caused by the fact that the frictional resistance of the contact surface of the work decreases due to the softening (solid solution) of the joint surface of the work.

Further, the pressing force P _n applied between the workpiece generates simultaneously abut the workpiece together (ST _1), P _n
= A first peak increased to P ₂ (ST _3). Then, when the work joining surface is completely softened over the entire surface and the pressing force is dispersed by the deformation of the joining surface, the pressing force decreases to P _n = P ₁ and becomes almost constant (slightly decreases). Become. That is, at the time of the ST _3, all of the bonding surface of the workpiece is completely softened, it can be determined that a state suitable for applying the upset force.

That is, in the embodiment of the present invention,
In the incorporation period, the motor for rotating the work
Between the second peak in the variation of the load current and the workpiece
When the first peak in the fluctuation of the pressing force is detected
Point (ST_Three ), When to apply upset force to the work
To determine. ST_Three To give upset power after
Enables high-quality friction welding of workpieces.
You. The above load current value I _n And pressing force P_n The value of
W₁ Rotation speed N_n And feed speed V_n Always constant
By keeping it, you can get the exact value
Can determine exactly when to give upset power.
it can.

Therefore, it is easy to accurately grasp the state where the contact portion of the work changes from a solid state to a molten state, and it is not necessary to perform a lot of trial welding operations as in the prior art. Therefore, even when the material, contact area (area where friction occurs), shape, and the like of the work are changed, it is easy to cope with the change, and a high-quality product can be obtained in a short time.

By the way, since the ST ₃ and later can impart at any upset force, by further shortening the feed amount S ₂ of FIG. 1, eliminate wasteful softening of the workpiece joint surface, to suppress the occurrence of burrs Can be. Further, since the amount of heat applied to the material is reduced, the influence of heat on the material structure can be suppressed. Further, if the workpiece material such as foreign matter is mixed, so changes the value of I _s, the value of S ₁ is, a clue to this change, it is possible to discover the defective workpiece material. Also, by looking at the change in the value of I _1, it can be determined that the magnitude of the resistance of the rotating part of the friction welding device, the easier to detect the abnormality of the device.

[0032]

According to the present invention, the following effects are obtained. That is, during the upsetting period, when the relative rotational speed and the feed speed of the work are kept constant, based on the fluctuation of the load current of the motor that rotationally drives the work, and the fluctuation of the pressing force applied between the works, It is possible to accurately grasp the state of change from the solid state to the molten state at the contact portion of the work, and determine the time to apply the upset force to the work. Therefore, the friction welding of the work can be performed with high quality without performing much trial welding work as in the related art. Further, even when the material, contact area (area where friction is generated), shape, and the like of the work are changed, it is easy to cope with the change, and friction welding can be performed on various works with high accuracy and low cost.

[Brief description of the drawings]

FIG. 1 is a graph showing how various parameters change with the progress of a friction welding process according to an embodiment of the present invention.

FIG. 2 is a flowchart corresponding to the friction welding step shown in FIG.

FIG. 3 is a flowchart following FIG. 2;

FIG. 4 is a schematic diagram showing a friction welding device that can be used in the embodiment of the present invention.

5 is a block diagram showing control means used in the friction welding device shown in FIG.

[Explanation of symbols]

Feed rate of I _n pushing force V _n workpiece rotational speed P _n workpieces between the load current value N _n workpiece rotation servomotor of the workpiece rotating servo motor

Claims (1)

[Claims] 1. A friction welding method in which a pair of works arranged opposite to each other is rotationally driven and pressed against the other to generate frictional heat at a joint between the two works, and to weld the joint between the two works softened by the frictional heat. The method, during the upsetting period,
When the relative rotational speed and the feed speed of the work are constant, an upset force is applied to the work based on a change in a load current of a motor that rotationally drives the work and a change in a pressing force applied between the works. A friction welding method characterized by determining a timing.