JP3211712B2 - Vibration welding method of resin molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying a relative vibration to a pair of resin moldings to rub their contact surfaces with each other and to melt the contact portions by heat generated by the friction, thereby integrating the two and then vibrating. And a method for vibration welding a resin molded body in which a molten portion is solidified and welded. INDUSTRIAL APPLICABILITY The present invention is used in the resin molding industry where a resin molded body is welded and integrated.

[0002]

2. Description of the Related Art Conventionally, when a small part has an irregular or complicated shape, or when a composite material such as engineering plastic is used, it is divided into a plurality of parts and then partially molded to form an O-ring. , Screws, adhesives, etc. Recently, a vibration welding method has been adopted in this joining method.

[0003] In this vibration welding method, a pair of compacts are brought into contact with a predetermined pressing force applied thereto, and in this state, a relative vibration is applied between the two, and the contact portions are fused by frictional heat and welded. is there. Normally, relative vibration applies a vibration of several mm parallel to the contact surface, a center frequency of 240 Hz, and a maximum output of 3.7.
A mini vibration welder equipped with a KW power supply is used.

In the conventional welding method, vibration is applied under a certain pressure to melt the resin in the abutting portion of the molded body, the vibration is stopped in that state, and the resin is solidified in the pressed state. Since the same pressure is continuously applied during vibration application, the resin in the contact part melts more than a certain amount, the molten resin protrudes from the contact part due to vibration, and becomes burrs, and conversely it is necessary for the contact surface There was a problem that the welding strength of the welded portion was reduced without leaving a sufficient amount of the molten resin.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended for vibration welding of a resin molded article.
An object of the present invention is to provide a vibration welding method having a high welding strength by appropriately controlling a welding pressure applied to a welding portion.

[0006]

According to the vibration welding method of the present invention,
This is a vibration welding method in which a pair of compacts are pressed against each other and welded by applying vibration, wherein vibration is applied in a state of being pressed at a first pressure, and the pressure is continuously reduced immediately after the vibration is applied. 0.5 to 5.0 seconds in 2nd pressure
To reach, the addition of vibration while pressed in this state continuously for a predetermined time period characterized by welding.

The second pressure is 4/5 to 1 of the first pressure.
/ 5 is preferred. Further, it is preferable that the application of vibration is stopped when the interval between the pair of compacts to be welded becomes narrower by a predetermined interval. Immediately after the vibration is applied, the press contact pressure is continuously reduced. Immediately after the vibration is applied means that the pressure is continuously reduced as soon as possible after the predetermined vibration is stably applied. Specifically, it means within about 5 seconds after the input of vibration addition.

According to the vibration welding method of the present invention, the vibration is started in a state of being pressed at the maximum pressing pressure which is the first pressing pressure, the pressure is immediately reduced, and the second pressing pressure is reduced in 0.5 to 5.0 seconds . To reach. The application of the vibration is further continued for a predetermined time at the second pressure, and the application of the vibration is stopped. Thereafter, pressurization is continued at the second press contact pressure for a while to complete welding. In the method of the present invention, since the pressurization is performed at the first press-contact pressure, which is the maximum press-contact pressure at the start of the application of the vibration, the input energy is the highest at the start of the application of the vibration, and the calorific value is also large. Then, as the time elapses, the pressing pressure decreases, the input energy decreases, and the calorific value also decreases. Therefore, the welding surface generates the most heat at the start of vibration application, and the amount of heat generation gradually decreases.

If all welding surfaces are uniformly heated in vibration welding, welding can be relatively easily performed. However, when the shape of the molded body is complicated or the welding surface is dispersed, uniform heat generation cannot be expected. A portion having a large calorific value per unit welding surface is heated and melted faster than other portions. When heated and melted, the portion becomes extremely soft and cannot maintain the pressing pressure. For this reason, the press-contact pressure is taken over by the other welding parts that have not yet been melted. That is, if the pressure does not change, the pressure of the other welded portions increases per unit area. The increase in the press-contact pressure per unit area increases as the portion melts later. The inventor has considered that the extremely large pressing pressure per unit area applied to a portion to be subsequently melted is the largest cause of poor welding.

[0010] In the method of the present invention, the pressing pressure is continuously reduced. Therefore, even if the melting of the welding surface is partially different, the pressing pressure per unit area of the unmelted portion does not change so much. In this way, the heat generated in this portion is maintained, and with the passage of time, sufficient heat is generated for melting, and the portion is melted. Since the pressing pressure of the melted portion immediately becomes extremely small, heat generation in that portion is not large. Thus, excessive heat generation is suppressed, and unnecessary unnecessary melting is avoided. Thereby, the entire welding surface is relatively uniformly heated. Therefore, more reliable welding can be performed, and problems such as overmelting can be avoided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The vibration welding method of the present invention is a method in which a pair of compacts are pressed against each other and the pressure is gradually reduced while vibrating and welding, and the change in the pressure and displacement during the vibration welding of the present invention. Is shown in FIG. FIG. 2 shows, as a comparative example, changes in the contact pressure and displacement in the conventional vibration welding method in which the contact pressure is not reduced, as in FIG.

In the method of the present invention, the first pressing pressure is changed to the second pressing pressure.
It is necessary to generate the heat required for welding before reaching the pressure for pressing. When the amplitude of vibration is the same, the calorific value is determined by the product of the pressure and the time. The amount of heat required for pressure welding is determined by the welding area of a pair of compacts to be welded by vibration, the type of resin,
It is determined by the temperature of the compact. When a large amount of heat is required, this can be achieved by increasing the first pressure and increasing the time required to reach the second pressure.

The first pressing pressure, the second pressing pressure and the time between them are such that the second pressing pressure is 4/5 to 1st pressing pressure.
It is preferably 1/5, and the time to reach the second press contact pressure is preferably 0.5 to 5.0 seconds after adding vibration. The second pressing pressure needs to be a pressing pressure at which heat generation sufficient to maintain at least the molten welding surface is obtained. More preferably, it is preferable to generate heat to such an extent that the melting of the resin increases. The period during which the second pressure is maintained is a period during which uniform melting of the melted surface is achieved, and promotes the melting of the unmelted portion to achieve melting, thereby maintaining the melting of the melted portion.

For example, the first pressing pressure is 1 second, and the first pressing pressure is 15, 20, 30, 40 kg / cm.
FIG. 3 shows the relationship between the first pressure and the pressure resistance of the sample ^2, which is the second pressure at the horizontal axis and the pressure resistance at the vertical axis. Here, the method of measuring the compressive strength was to seal the welded compact, rupture it with water pressure, and measure the maximum value.
FIG. 3 also shows the pressure resistance of a sample welded by a conventional method (a method in which the pressure is not reduced) for comparison. The reason why the pressure resistance is low when the pressing pressure is low in the conventional method is that the resin to be welded has a warp or the like, which cannot be corrected well and is welded. However, it can be seen that the pressure resistance of the welding of the present invention is higher than the pressure resistance of the conventional method. This is because the deformed welded portion is compressed at a high pressure at the first press contact pressure, the warp is corrected, the welding is started immediately, the pressure becomes low during the welding, and the welded layer is thickened. Because it can be. However, when the second pressure is higher than 20 kg / cm ² , the pressure resistance is lower than that of the comparative example. This is because the welding pressure is too high and the pressure is high, so that the welded layer is thin and the pressure resistance is low. Also, the first pressing pressure is 20 kg / cm
The time of ² indicates the highest compressive strength.

The pressurizing time of the first press contact pressure in FIG.
FIG. 4 shows a case where the time is changed from seconds to 2 seconds. By setting the first press contact pressure from 1 second to 2 seconds, the value of the pressure resistance is reduced as a whole. For this reason, the shorter the pressurization time of the first press contact pressure, the higher the pressure resistance. Thus the first
The pressing pressure is usually preferably from 10 to 30 kg / cm ² . The second pressure is 5 to 20 kg / cm.
It is preferably in the range of ² .

The optimum duration of the second pressure can be determined by trial and error. Further, a method may be adopted in which the application of vibration is stopped when the interval between the pair of compacts is reduced to a predetermined interval, and the period ends. As a result, the entire welding surface is uniformly melted. The melting amount of the molded body on the melting surface, that is, the welding depth is preferably 1 to 2 mm. That is, this depth is a value at which strength can be obtained, and even if welding is performed further, the strength is not increased, and a large amount of welding burrs is generated. Therefore, this value is used in consideration of welding burrs from the beginning.

As shown in FIG. 5, where the welding time is plotted on the horizontal axis and the welding depth is plotted on the vertical axis, the welding depth of the comparative example is lower than that of the embodiment . Figure 5 shows that uniform heat generation is expected
When vibration welding is performed on a compact having a welding surface
This is a diagram showing the relationship between welding time and welding depth. Examples are
Even if an unmelted portion occurs due to vibration at the first pressure,
The pressure that continuously decreases from the pressure to the second pressure
By the force and the vibration at the second pressure, the melted part
For melting unmelted parts without excessive melting
Therefore, a uniform melting is generated on the melting surface. But
However, the comparative example is not melted without uniform heat generation on the welding surface.
Even if there is a part, the pressing pressure does not change,
It does not melt. Also, measurement of welding depth
Is a pair of jigs that hold each of a pair of compacts
It is done using the displacement sensor provided in each
Therefore, if unmelted parts occur, the welding depth will actually
Measured as a value smaller than the amount of melting at
Will be In Comparative Examples for this long welding time is to be obtained as per setting welding depth to obtain a predetermined welding strength, it becomes deeper melting depth. Here, in the comparative example,
The welding depth and the amount of melting actually on the melting surface
Is actually different from the melting surface
The amount was the melt depth. The difference between the melt depth and the welding depth of the time this is Bali. In the comparative example, the setting of the welding depth is 1.5 mm.
Even in this case, burrs are generated because they are actually melted by 2 mm or more. Since the generated burrs cause problems, it is necessary to suppress the generation of burrs. Therefore, it is necessary to control the welding depth. As a control method, for example, there is a time control used in the conventional method. However, in the case of time-based control, if the resin slips at the initial stage of vibration, the welded portion becomes insufficiently melted, causing insufficient pressure resistance. Therefore, in the conventional method, when the welding pressure is reduced, the welding strength is increased, but the welding depth is insufficient due to the occurrence of slip, and the pressure resistance is reduced.

For this reason, more direct control of the welding is preferable, and the monitoring of the welding depth is performed by detecting the melting of the joining resin at the welded portion and measuring the displacement of the resin position near the welded portion. Can be detected. For example, it is possible to accurately measure and monitor the welding depth of the welded part of the resin by attaching sensors above and below the joining resin and measuring the interval, measuring the interval between welding jigs, or using both together. it can.

After stopping the application of the vibration, the same second pressing pressure is maintained. Vibration is not given, and there is no longer heat generation at the welding surface. The molten resin is deprived of heat by the surroundings, is cooled, and solidifies. This ensures that the pair of compacts is welded. In this state, the application of the second pressing pressure is stopped, and an integrated molded body is obtained by welding. It should be noted that more optimal values such as the amplitude of vibration welding and the frequency per unit time should be used. These values can be determined by trial and error. In the pressure welding, it is necessary to take care that the entire welding surface is uniformly pushed in so that the pair of molded bodies to be welded are not inclined and pressed.

According to this method, it is possible to prevent the resin from protruding from the welding surface and to generate burrs, etc., and to melt-bond a required amount of the resin to the welding portion to increase the resin strength at the bonding surface. The resin molded article to which the method for vibration welding of the resin molded article of the present invention can be applied is a molded article formed of a thermoplastic resin. Specifically, molded articles such as an ABS resin, a styrene resin, a polyester resin, a polyamide resin, a polyethylene resin, a polypropylene resin, and a resin containing glass fibers thereof can be given. The molding method is injection molding,
A conventionally known molding method such as extrusion molding can be employed.

[0021]

According to the method of the present invention, the pressing pressure is continuously reduced. Therefore, even if the melting of the welding surface is partially different, the pressing pressure per unit area of the unmelted portion does not change so much. In this way, the heat generated in this portion is maintained, and with the passage of time, sufficient heat is generated for melting, and the portion is melted. Since the pressing pressure of the melted portion immediately becomes extremely small, heat generation in that portion is not large.
Therefore, excessive heat generation is suppressed, and unnecessary melting is avoided. Thereby, the entire welding surface is relatively uniformly heated. Therefore, more reliable welding can be performed, and problems such as overmelting can be avoided.

Further, after the resin in the welded portion is melted, a pressing force of a set value or more is not applied to the welded portion, so that the molten resin does not protrude from the welded portion, stays in the welded portion, and the thickness of the welded layer is increased during curing. As a result, the resin strength of the welded portion is improved. Further, even if the shape of the resin molded product to be joined is complicated and the time at which the resin begins to melt in the initial stage of welding varies, all the welded portions are reduced while the pressure is reduced from the first pressure to the second pressure. Can be reliably welded because it is uniformly melted.

According to the method of the present invention, the variation in the welding strength of the joined resin product is reduced, and the durability of vibration welding can be improved even for a resin product having a complicated shape, and the reliability of the resin product is increased and the cost is reduced. Is possible.

[0024]

The present invention will be described more specifically with reference to the following examples. In the present embodiment, a pair of molded products obtained by half-injecting an intake manifold obtained by injection molding 6 nylon containing 35% by weight of glass fiber is subjected to vibration welding. FIG. 7 schematically shows a cross section of the welded portion. The convex portion 11 at the center of the lower end of the upper molded product 1 is one welded portion, and the concave portion 21 at the upper end of the lower molded product 2 is the other welded portion. Displacement sensors 31, 32 are provided on the upper molded product 1 and the lower molded product 2, respectively.
Was attached, and the interval between the two was measured over time. In addition,
The displacement sensor may be fixed to welding jigs 41 and 42 as shown in FIG.

The welding area in contact is 14.4 c.
m ² , the specific gravity of the molding material is 1.37 g / cm ³ , and the specific heat is 0.38 cal / g ° C. A Branson model 2850 was used as a vibration welding machine. The amplitude of the vibration welding was 1.7 mm and the frequency was 240 Hz. In the vibration welding, as shown in FIG. 1, both molded bodies are pressed at a predetermined first pressing pressure, vibration is applied in that state, and the pressing pressure is continuously reduced immediately and reduced to a second pressing pressure in a predetermined time. ,
The second press-contact pressure is maintained, the application of vibration is stopped for a predetermined time, and thereafter, the second press-contact pressure is maintained for a predetermined time to complete the welding. As shown in FIG. 1, the welding time is equal to the vibration addition time. In addition, the second after stopping the addition of vibration
The pressing time of the pressing pressure is the pressure holding time.

Table 1 also shows the welding conditions and the pressure resistance of the welded intake manifold. The resin used is 35% nylon 6 GF.

[0027]

[Table 1]

By using the vibration welding method of the present invention, the sample No. Comparison of 1 to 5 and 6 and 7 to 11 and 12 confirms that the pressure resistance is improved. Also,
As the welding conditions, Sample No. having no change from the first pressure to the second pressure was used. Sample Nos. 6 and 12, in which the pressure change from the first pressure to the second pressure is continuously and slowly performed. In addition to 1 to 5 and 7 to 11, welding conditions in which after vibration at the first pressing pressure, the pressure is decreased not slowly but rapidly to the second pressing pressure can be considered. That is, welding in which the pressure is rapidly changed during welding is not suitable for welding because of poor welding. For this reason, it is necessary to gradually reduce the pressure from the first pressure to the second pressure.

[0029]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a process management state according to a method of the present embodiment.

FIG. 2 is an explanatory diagram of a process management state according to a conventional method.

FIG. 3 is a graph showing the relationship between the primary pressurization time and the pressurizing strength when the pressurizing force is changed to 1 second.

FIG. 4 is a graph showing a relationship between the primary pressurization time and the pressure resistance when the pressurizing force is changed to 2 seconds.

FIG. 5 is a graph showing the welding depth in the method of the present invention and the conventional method.
It is rough.

FIG. 6 is a schematic diagram illustrating a detection method according to the present embodiment.
You.

FIG. 7 is a schematic diagram illustrating another detection method according to the present embodiment.
is there.

[Explanation of symbols]

 1, 2: resin, 11, 21: welding part 31, 32: displacement sensor, 41, 42: welding jig O>

Claims (3)

(57) [Claims] 1. A vibration welding method in which a pair of compacts are welded to each other by applying pressure and applying vibration, wherein vibration is applied in a state of being pressed at a first pressure and pressure is applied immediately after the vibration is applied. 0.5 to 5.0 seconds
Vibration welding method characterized in that to reach the second pressing pressure, the addition of vibration while pressed in this state continuously for a predetermined period of time to weld. 2. The second pressing pressure is 4 times the first pressing pressure.
/ 5-1 / 5 a vibration welding method of the resin molded body according to claim 1, wherein. 3. The method according to claim 1, wherein the application of the vibration is stopped when the interval between the pair of moldings is reduced to a predetermined interval.