JP3780636B2 - Ultrasonic welding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic welding method in which a plurality of workpieces are joined using ultrasonic vibration.
[0002]
[Prior art]
An ultrasonic welding apparatus for carrying out an example of a conventional ultrasonic welding method is shown in FIG.
[0003]
The ultrasonic welding apparatus shown in FIG. 6 sets workpieces (also referred to as joining members) 6 and 7 between an anvil (also referred to as a work table) 5 and a horn (also referred to as an ultrasonic tool) 4. The workpieces 6 and 7 are joined by ultrasonically vibrating the horn 4 while applying pressure P to the workpieces 6 and 7 by a pressurizing means (not shown).
[0004]
The ultrasonic welding apparatus includes a constant voltage power source 1.
[0005]
The constant voltage power source 1 is connected to an AC power source (for example, AC 200V), and outputs a constant voltage V shown as an output voltage pattern a in FIG. 2 from the welding start time t _S to the welding end time t _{E during} welding.
[0006]
The constant voltage of the constant voltage power source 1 is applied to the constant speed constant amplitude oscillator 2.
[0007]
The vibrator 3 outputs an ultrasonic wave based on the output signal of the constant speed constant amplitude type oscillator 2.
[0008]
The horn 4 amplifies the ultrasonic output of the vibrator 3.
[0009]
Further, this ultrasonic welding apparatus includes a displacement amount sensor 9 that detects the descending amount of the horn holding portion 8 in order to indirectly detect the deformation amount of the joint interfaces 6a and 7a between the workpiece 6 and the workpiece 7 during welding. Prepare.
[0010]
Further, this ultrasonic welding apparatus inputs a detection signal from the displacement amount sensor 9 and stops the output of the constant voltage power source 1 when the lowering amount of the horn holding portion 8 reaches a predetermined set value. The control apparatus 10 which complete | finishes is provided.
[0011]
By the way, not only the ultrasonic welding method using the ultrasonic welding apparatus as described above, but also when performing ultrasonic welding, as shown in FIG. a biting amount L _e1 of the slip prevention knurled 4a of the horn 4 for the workpiece 6, the biting amount L _e2 of the anvil 5 for the other workpiece 7, two of the workpiece 6 and 7 of the joint interface 6a, deformation amount of 7a L _W is the sum of L _W and is expressed by L = L _e1 + L _e2 + L _W. ) A large proportion of the deformation L _W leads to an increase in bonding strength.
[0012]
[Problems to be solved by the invention]
However, the friction between the workpieces 6 and 7 in the initial stage of welding is large. Further, when the constant speed constant amplitude oscillator 2 is used, a large horn driving force is required in the initial stage in order to make the amplitude of the horn 4 constant.
[0013]
Therefore, according to the conventional ultrasonic welding method, as shown as an output pattern a in FIG. 3, at the initial stage of welding (usually, when about 0.03 seconds to 0.05 seconds have elapsed from the welding start time t _S ). The peak of the output W of the horn 4 appears, and there is a sudden change in the horn output W in the initial stage of welding (usually, a period from about 0.3 seconds to 0.5 seconds after the welding start time t _S ). Arise.
[0014]
If the grip force of the horn 4 with respect to the workpiece 6 is insufficient due to fluctuations in the applied pressure during such a sudden change in the horn output W (the initial stage of welding), the workpiece 6 exceeds the horn 4 as shown in FIG. The ultrasonic vibration of the horn 4 cannot be sufficiently transmitted to the work 6 due to the inability to follow the sonic vibration, slipping, and the frictional cleaning and the temperature rise at the joint interfaces 6a and 7a of the work 6 and 7 become insufficient. As a result, the bonding strength decreases. In FIG. 8, the arrow v _P represents the direction and magnitude of the vibration of the horn 4 and the arrow v _W represents the direction and magnitude of the vibration of the work 6 for convenience.
[0015]
When the above-described slip occurs between the horn 4 and the workpiece 6, as shown in FIG. 8, the amplitude amount of the horn 4 becomes larger than the amplitude amount of the workpiece 6, and the knurl 4a of the horn 4 keeps the workpiece 6 for a long time. is plastically deformed, biting amount L _e1 knurl 4a with respect to the workpiece 6 is increased. For this reason, the ratio of the amount of biting L _{e1 to} the total amount of displacement L due to welding becomes a large biting amount Le _{1 of} about 0.15 to 0.2 mm with respect to the amount of displacement L of about 0.3 mm, which increases the bonding strength. The amount of deformation L _W directly involved decreased and the bonding strength was unstable.
[0016]
Therefore, conventionally, in order to stabilize the bonding strength, a method of improving a jig or a horn or changing a pressing force during welding has been used. However, the method of improving jigs and horns is difficult to adapt to various workpieces, and there is a limit in optimizing the welding process. Further, the method of changing the applied pressure has a problem that the durability of the apparatus is lowered because the applied pressure is changed during welding.
[0017]
As a proposal for the bonding strength stabilizing, setting the total amount of displacement L in advance to a large value, it is considered possible to increase the deformation amount L _W. However, setting the displacement L to a large value, on the other hand, increases the welding time and decreases the number of weldings per hour, which is not preferable in terms of production efficiency. Furthermore, the amount of horn knurled biting into the workpiece tends to increase, and the concave portion of the workpiece surface caused by the horn knurling biting deepens, so it cannot be said that it is suitable for manufacturing products and the like whose appearance is important. The problem occurs. For this reason, the idea of setting the displacement amount L to a large value is not a sufficient solution.
[0018]
The present invention has been made in view of the above problems, and an object of the present invention is to reduce the horn output peak and abrupt changes in the initial stage of welding and stabilize the joining strength of the workpiece.
[0019]
[Means for Solving the Problems]
In the ultrasonic welding method of the present invention, as described in claim 1, the horn output is reduced in the initial stage of welding. For this reason, in the initial stage of welding, the work gripped by the horn can sufficiently follow the ultrasonic vibration of the horn, and slip hardly occurs. Therefore, the time during which the workpiece is plastically deformed by the horn is shortened, and the amount of biting of the horn is reduced.
[0020]
And after a horn output fall, a horn output increases gradually, the joining interface of a workpiece | work heat | fever-generates, and workpiece | work is joined.
[0021]
As described above, according to the ultrasonic welding method of the present invention, the amount of biting of the horn is reduced, so that the deformation amount of the workpiece joining surface with respect to the total displacement during welding is increased, and the joining strength of the workpiece is stabilized. Can do.
[0022]
Here, the horn output lowering period in the initial stage of welding is a period from when the peak of horn output and a sudden change appear to about 0.3 seconds to 0.5 seconds from the start of welding. Therefore, as described in claim 2, it is desirable to set the period from the welding start time to the time when at least 0.2 seconds elapses.
[0023]
Further, the horn output may be controlled by open loop control, but it is preferable to accurately perform feedback control as described in claim 3.
[0024]
Further, according to the ultrasonic welding method of the present invention, since the workpiece can sufficiently follow the ultrasonic vibration of the horn at the initial stage of welding as described above, the ultrasonic welding method of the present invention is described in claim 4. As described above, it is suitable for welding of large workpieces that are inherently difficult to follow the ultrasonic vibration of the horn, and as described in claim 5, it is suitable for multilayer lap welding in which it is necessary to suppress vibration with positioning pins. Is also suitable.
[0025]
The ultrasonic welding method of the present invention uses the ultrasonic welding apparatus according to claim 6 and starts ultrasonic welding while pressurizing a plurality of workpieces at a constant pressure. The output voltage of the voltage variable power supply is controlled so as to decrease the output of the horn, and then the output voltage of the voltage variable power supply is controlled by the control device so as to gradually increase the output of the horn.
[0026]
As the oscillator of the ultrasonic welding apparatus, a constant-speed constant-amplitude type oscillator that drives a horn at a constant speed and a constant amplitude, in which a peak and abrupt output change occurs in the initial stage of welding, as described in claim 7 is used. Is done.
[0027]
The ultrasonic welding apparatus may perform open-loop control of the horn output, but as described in claim 8, detects an output pattern of the horn based on a detection signal from an output detection sensor, and It is preferable in terms of accuracy to feedback control the output voltage of the voltage variable power supply so that the detected output pattern matches the optimum output pattern.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0029]
FIG. 1 shows the configuration of an ultrasonic welding apparatus for carrying out the ultrasonic welding method according to this embodiment.
[0030]
The ultrasonic welding apparatus shown in FIG. 1 includes a voltage variable power source 11, a constant speed / constant amplitude oscillator 2, a vibrator 3, a horn (ultrasonic tool) 4, a horn holder 8, a displacement sensor 9, and an output detection sensor 12. A control device 13 and a display device 14 are provided.
[0031]
An AC power supply (for example, AC 200 V) is connected to the voltage variable power supply 11. The voltage variable power supply 11 applies an output voltage V to the constant speed constant amplitude oscillator 2, and the output voltage V is controlled by the control device 13.
[0032]
The constant speed constant amplitude oscillator 2 drives the horn 4 at a constant speed and constant amplitude, and outputs a signal having an amplitude corresponding to the applied voltage, that is, the output voltage V of the voltage variable power supply 11.
[0033]
The vibrator 3 outputs an ultrasonic wave having an amplitude corresponding to the amplitude of the output signal of the constant speed constant amplitude type oscillator 2.
[0034]
The horn 4 amplifies the ultrasonic output of the vibrator 3.
[0035]
The displacement sensor 9 detects the descending amount of the horn holding portion 8 in order to indirectly detect the deformation amount L _W of the joint interfaces 6 a and 7 a between the workpiece 6 and the workpiece 7.
[0036]
The output detection sensor 12 detects the output of the constant speed constant amplitude type oscillator 2 in order to indirectly detect the output W of the horn 4 and inputs it to the control device 13.
[0037]
The control device 13 stores the optimum output pattern of the horn 4 in advance, detects the output pattern of the horn 4 based on the detection signal from the output detection sensor 12, and matches the detected output pattern with the optimum output pattern. The output voltage V of the variable voltage power supply 11 is feedback-controlled.
[0038]
Here, the optimum output pattern is represented as a waveform b in FIG. As is apparent from comparison between this waveform b and the conventional waveform a, the optimum output pattern is output at the initial stage of welding (usually, the period from the welding start time t _S to the time when at least 0.2 seconds elapses). W is low, and then the output W gradually increases.
[0039]
The control device 13 controls the output voltage V of the voltage variable power supply 11 so as to obtain such an optimum output pattern as a waveform b in FIG.
[0040]
Further, the control device 13 inputs a detection signal from the displacement sensor 9 and stops the output of the voltage variable power source 11 and terminates the welding when the descending amount of the horn holding unit 8 reaches a predetermined set value L. Let
[0041]
Next, an ultrasonic welding method using the ultrasonic welding apparatus configured as described above will be described.
[0042]
First, the workpieces 6 and 7 are set between the anvil 5 and the knurl 4a of the horn 4, and a constant pressure P is applied to the workpieces 6 and 7 by a pressurizing means (not shown). The pressurizing means pressurizes so that the pressure P is always constant during welding.
[0043]
Next, the voltage variable power source 11 is turned on, and the horn 4 is ultrasonically vibrated to start welding the workpieces 6 and 7.
[0044]
At the time of this welding, the control device 13 detects the output pattern of the horn 4 based on the detection signal from the output detection sensor 12, and changes the voltage so that the detected output pattern matches the optimum output pattern of the waveform b shown in FIG. The output voltage V of the power supply 11 is feedback controlled.
[0045]
As described above, in the optimum output pattern, the output W is low in the initial stage of welding, and then the output W gradually increases. Therefore, as shown in FIG. 4, in the initial stage of welding, the work 6 gripped by the knurl 4a of the horn 4 can sufficiently follow the ultrasonic vibration of the horn 4, and the amplitudes of the vibrations V _P and V _W are respectively large. Almost consistent and almost no slippage. Accordingly, the time which the workpiece 6 is plastically deformed by the knurling 4a of the horn 4 is shortened, the biting amount L _e1 of the horn 4 is reduced. Then, after the horn output W decreases, the horn output W gradually increases, so that the joining interfaces 6a and 7a of the workpieces 6 and 7 generate heat and the workpieces 6 and 7 are joined together.
[0046]
When the control device 13 determines that the amount of lowering of the horn holding portion 8 has reached a predetermined set value L based on the detection signal from the displacement amount sensor 9, the control device 13 stops the output of the voltage variable power supply 11. This completes the welding.
[0047]
As described above, according to the ultrasonic welding method of the present embodiment, the amount of biting L _e1 of the horn 4 is reduced, so that the deformation amount L _{W of the} workpiece joint surfaces 6a and 7a with respect to the total displacement L during welding. And the joint strength of the workpieces 6 and 7 can be stabilized.
[0048]
Moreover, since the control apparatus 13 can memorize | store an arbitrary optimal output pattern comparatively freely, it can obtain easily the optimal output pattern according to various workpiece | work and materials.
[0049]
Moreover, since there is little transmission loss from the horn 4 to the workpiece | work 6, a horn serration can be simplified.
[0050]
Further, according to the ultrasonic welding method of the present embodiment, since the workpiece can follow the ultrasonic vibration of the horn at the initial stage of welding, it is difficult to follow the ultrasonic vibration of the horn, and the area of the joint surface is 100 mm ² or more. This embodiment is suitable for welding large workpieces and multilayer lap welding of workpieces 15, 16 and 17, which need to suppress vibration with positioning pins 5a as shown in FIG. For example, a copper plate (t = 0.5 mm), an iron plate (t = 2 to 3 mm), and an aluminum plate (t = 1 to 2 mm) having a ring shape of about 120 mm ² are positioned by positioning pins 5a. However, when lap welding was performed, the shear strength was 300 to 450 kgf in the conventional method, but stabilized to 400 to 450 kgf in the method of the present invention.
[0051]
In the embodiment described above, the horn output W is feedback-controlled, but the output detection sensor 12 may be removed and open-loop control may be performed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an ultrasonic welding apparatus for carrying out an ultrasonic welding method according to an embodiment.
FIG. 2 is a graph showing a comparison between an output voltage V of a voltage variable power supply in the method of the present invention and an output voltage V of a constant voltage power supply in a conventional method.
FIG. 3 is a graph showing a comparison between a horn output W in the method of the present invention and a horn output W in a conventional method.
FIG. 4 is an explanatory diagram for explaining a welding process in the method of the present invention.
FIG. 5 is an explanatory diagram for explaining multilayer lap welding as an application field of the method of the present invention.
FIG. 6 is a configuration diagram of an ultrasonic welding apparatus for performing a conventional ultrasonic welding method.
FIG. 7 is an explanatory diagram for explaining the relationship among the total displacement amount by welding, the horn biting amount, the deformation amount of the joint surface, and the anvil biting amount.
FIG. 8 is an explanatory diagram for explaining a welding process in a conventional method.
[Explanation of symbols]
2 Constant-speed constant-amplitude oscillator (oscillator)
3 vibrator 4 horn 5 anvil
5 a Positioning pins 6, 7, 15, 16, 17 Work 11 Voltage variable power supply 12 Output detection sensor 13 Control device

Claims (8)

In the ultrasonic welding method of joining the plurality of workpieces by setting a plurality of workpieces between the anvil and the horn and ultrasonically vibrating the horn while pressurizing these workpieces at a constant pressure,
A positioning pin that penetrates the plurality of workpieces protrudes upward from the anvil, and
An ultrasonic welding method characterized by lowering the output of the horn at an initial stage of welding and then gradually increasing the output of the horn. 2. The ultrasonic welding method according to claim 1, wherein the horn output reduction period in the initial stage of welding is set to a period from the start of welding to a point at which at least 0.2 seconds elapses. The ultrasonic welding method according to claim 1, wherein the horn output is feedback-controlled. 4. The ultrasonic welding method according to claim 1, wherein each of the workpieces is a large workpiece having a joint surface area of 100 mm ² or more . The ultrasonic welding method according to claim 1, wherein each of the workpieces is a workpiece that is positioned by a positioning pin and is subjected to multilayer lap welding. A variable voltage power supply having a variable output voltage, an oscillator that outputs a signal having an amplitude corresponding to the output voltage of the variable voltage power supply, and a vibrator that outputs an ultrasonic wave having an amplitude corresponding to the amplitude of the output signal of the oscillator And an ultrasonic welding method for joining a plurality of workpieces using an ultrasonic welding device having a horn for amplifying the ultrasonic output of the vibrator and a control device for controlling the output voltage of the voltage variable power source. ,
The plurality of workpieces are set between the anvil and the horn so that the positioning pins projecting upward from the anvil penetrate the plurality of workpieces.
Ultrasonic welding is started while pressing these workpieces at a constant pressure,
In the initial stage of welding, the control device controls the output voltage of the voltage variable power supply so as to reduce the output of the horn,
Then, the output voltage of the voltage variable power supply is controlled by the control device so as to gradually increase the output of the horn. The ultrasonic welding method according to claim 6, wherein the oscillator is a constant speed constant amplitude type oscillator. While providing an output detection sensor for detecting the output of the horn, the optimal output pattern of the horn is stored in advance in the control device,
An output pattern of the horn is detected based on a detection signal from the output detection sensor, and feedback control is performed on the output voltage of the voltage variable power source so that the detected output pattern matches the optimum output pattern. The ultrasonic welding method according to claim 6 or 7.

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