JPH11151529A - Formation of heming part in car body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce energy used in preheating (precure) by a hot air method. SOLUTION: An adhesive composition 30 in which hard particles 31 are mixed is applied to a joining part 11 of an outer panel 10 forming a door of a car body or the like, a joining part 21 of an inner panel 20 is superposed on that, and a hem part 12 is pressed on the joining part 21 and folded. The hard particles 31 are bit into over between both joining parts 11, 21 by pressing them by a relatively high pressure, and when they are especially flat heming parts, combined strength sufficient for temporal tacking is secured with high reliability by the frictional engagement or mechanical engagement. Thus, in the preheating process by the hot air method executed succeeding to a pressing process, such a preheating for the heming parts is eliminated and energy for heating is reduced that much more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hemming portion of an engine hood or the like of an automobile, that is, a periphery of an outer panel is folded in two with a periphery of an inner panel sandwiched therebetween.
Further, the present invention relates to a method for forming a hemming portion of a vehicle body having a structure in which an adhesive is filled between joints between an outer panel and an inner panel and both panels are connected to each other.

[0002]

2. Description of the Related Art Panels made of a metal plate such as an engine hood (bonnet), a luggage (luggage compartment door, a trunk lid), and a door that form a body of an automobile or the like have a structure whose peripheral edge is called a "hemming structure". It is generally configured as an assembly of a combined outer panel and inner panel. In other words, the two panels have a structure in which the joint at the periphery of the inner panel is overlapped with the outer panel, and the periphery of the outer panel is folded in two so as to sandwich the joint between the inner panels, that is, a folded structure. And assembled.

However, a joint between the outer panel and the inner panel due to such a hemming structure, that is, a portion where the outer panel is folded in two and sandwiches and joins the joint of the inner panel (refer to the specification of the present application). In this case, the connection portion between the two panels is simply referred to as a “hemming portion”. However, since there is a gap between the tip of the inner panel and the bent corner of the outer panel, the connection is not perfect, and excessive force or When vibration or the like is applied, a gap occurs between the panels. In addition, the hemming portion has poor throwing power at the time of electrodeposition coating, which is an undercoating for the purpose of rust prevention, and the electrodeposition coating film tends not to be sufficiently formed in the fine structure. Therefore, the joint between the inner panel and the outer panel of the hemming portion is also filled with an adhesive to complete the permanent connection between both panels,
They prevent rainwater from entering and prevent rust. In addition, along the boundary between the front edge of the bent edge (hem portion) of the outer panel and the inner panel surface,
Further, a sealing material is applied for sealing.

[0004] More specifically, such an adhesively bonded hemming portion is generally formed as follows. That is, an adhesive is applied to the outer panel in which the peripheral edge is bent at a right angle in advance, and the hem portion (turned edge) is formed in a flange shape, and then the inner panel is set on the outer panel, and then the hem portion of the outer panel is removed. Bend on the inner panel,
Press and fold (hemming). by this,
The adhesive is spread between the joints of the outer panel and the inner panel, and is filled in the gap. Then, after the assembly having the hemming portion is assembled to the vehicle body,
Pretreatments such as degreasing, washing, and chemical treatment are performed, and then electrodeposition coating is performed as a primer coating. The adhesive between the joints is heated during baking and drying of the electrodeposition coating film. Are baked and hardened together, thereby finally forming a hemmed portion which is adhesively bonded. In other words, the curing of the adhesive is performed by using the heat of baking and drying of the electrodeposition coating film, which is performed later, in order to save heat energy.

In the step of forming the hemmed portion, hemming of the hemmed portion is generally performed by using a press die (hem blade) or a press roll.
It is performed by a press pressure of about 0 to 300 kgf / cm ² ). As the adhesive for the hemming portion, a thermosetting composition that can be completely cured under the conditions of baking and drying an electrodeposition coating film is used. Specifically, a composition mainly containing an epoxy resin is used. Pseudo-curable (pregel-type) compositions in which fine particles of a thermoplastic resin such as an acrylic resin are dispersed in a sol, a vinyl chloride-based plastisol composition, and the like are used.

Incidentally, as described above, the adhesive filled between the joints of the outer panel and the inner panel is hardened, and the adhesive strength is developed when the electrodeposition coating film is baked and dried. If excessive force or vibration is applied to the hemming assembly during transfer or handling before the baking and drying step, mutual displacement or twisting between the outer panel and the inner panel may occur. And the occurrence of such displacement between the two panels is, in particular, linearized,
This is a serious hindrance in the automated vehicle body manufacturing process. Therefore, in recent years, a hemmed portion formed by applying an adhesive and hemming is immediately preliminarily heated (preheated) immediately thereafter, and the adhesive between the joint portion of the outer panel and the inner panel is partially precured (precured). Thereby, the two panels are temporarily fixed to each other, so that mutual displacement during the initial handling before the baking and drying process of the electrodeposition coating film is surely prevented.

One of the typical preheating means is a method in which the hemming portion is induction-heated using a high-frequency induction heating device. Specifically, this induction heating method uses a high-frequency induction heating device in which inductors are arranged along the hemming portion of the panel assembly,
The hemming part is heated efficiently. However, such equipment requires a large initial cost (equipment cost), such as an expensive high-frequency generator and inductors corresponding to various hemming assemblies. For this reason, the most frequently used preheating means at present is hot air heated to about 500 ° C. from a heater nozzle connected to a blower blower at several heating points (heater portions) in the hemming portion on the periphery of the panel assembly. Is sprayed in a spot shape (with a spot length of about 10 cm). According to this hot air method, there is an advantage that the equipment for this can be formed at a relatively low cost, and the number and arrangement of the heater nozzles can be easily adjusted according to the specific shape and the like of the panel assembly. The number of heating points is, for example, 6 to 8 in the case of luggage.

In addition to the "pre-cure method" in which the adhesive is pre-heated and pre-cured, the "spot welding method" is also generally used as a temporary fixing means for the hemming portion. That is, it is a method in which an electrode is pressed against the hem portion after the hemming process and spot welding is performed between the hem portion and the inner panel. It is applied to However,
In the spot welding method, particularly when the panel material is made of a plated steel sheet, traces of the electrodes due to thermal strain tend to be formed on the hem portion, which is a drawback.

Various other methods have been conventionally proposed for temporarily fixing the hemming portion. For example, Japanese Patent Application Laid-Open No. 2-75420 discloses a method in which a fine convex emboss is provided at a joint at a peripheral edge of an inner panel, and a hem portion of the outer panel is hemmed so as to engage with the convex emboss. . However, this method has the advantage that neither pre-hardening by pre-heating nor spot welding is required, but it is not easy to precisely process the convex emboss, and a special press die is required for hemming. In practice, it is difficult to put it to practical use. In addition, the fixing by the engagement of such fine unevenness is considered when buckling (spring back, the hem portion after pressing is separated from the surface of the inner panel due to residual elasticity) at the time of the hemming process, The reliability of its strength is also poor.

Further, US Pat. No. 3,279,972,
U.S. Pat. No. 3,692,341, U.S. Pat. No. 3,70
No. 0,514, JP-T 8-510598, and the like, regarding a means for mechanically fixing (locking) two opposing planes to each other in the direction of displacement, hard particles are applied between the two planes. Then pressing the two planes against each other to cause the particles to bite (embed) in both of the planes,
A method is disclosed in which the two planes are fixed to each other in the shift direction by maintaining the overlapping relationship between the two planes. In particular, Japanese Patent Application Laid-Open No. Hei 8-510598 mentions that the mechanical fixing means is applied as a final fixing means of a joint portion of a hemming portion (hem / flange). That is, hard particles such as glass beads are appropriately applied between the joint portion of the outer panel and the inner panel together with a carrier material, and then the hem portion is hemmed at a relatively high press pressure (about 245 to 770 kgf / cm ² ). Forming the hemming structure and embedding the hard particles into both of the panels, thereby forming a permanently secured hemming. According to this, since the adhesive force of the adhesive is not originally required for fixing the hemming portion, the technical feature that the temporary fixing (pre-curing) by the induction heating method as described above is not necessary is also required. It has been stated as an advantage. However, as a carrier material for the hard particles, it is stated that an adhesive commonly used for fixing a hemming portion can also be used, and in Examples, an acrylic adhesive composition is used in accordance with glass beads. Have been. The use of this adhesive here is intended exclusively for its use in tackiness and for the prevention of rusting of the hemming after curing.

[0011]

As described above, various methods have been conventionally known for the method of forming the hemmed portion, particularly, the method of temporarily fixing the hemmed portion. However, in all the methods, the reliability of the temporary fixing is insufficient or the reliability is high, but the equipment cost is high and the power consumption is large.

For example, in the case of fixing with hard particles such as glass beads or the like, the beads bite into the panel flat portion, so that there is a certain effect in temporary fixing at the time of handling the panel in a vehicle body factory. However, due to the thermal distortion during baking of the electrodeposition coating film, the displacement or torsion that occurs between the inner panel and the outer panel is affected by the buckling of the panel curved surface part during hemming and in the peeling direction due to thermal distortion. It is not performing well enough for the reasons it takes.

In the temporary fixing method by preheating by the hot air method, the temporary fixing effect at the time of handling a panel at a vehicle body factory and at the time of baking an electrodeposition coating film is sufficiently reliable. Since the equipment is relatively simple, it has the advantage of not requiring a large initial cost.However, since the air is heated to a high temperature by an electric heater and blown to the hemming part to heat it, the hemming part is directly heated. As compared with the induction heating method, the efficiency of heat and energy utilization is inevitably lower, and the power consumption tends to be relatively high.

Therefore, in the present invention, in the method of forming a hemmed portion including the preheating step by the hot air method as described above, the energy used for the preheating is further reduced, and the reliability of the temporary fixing is secured. It is an object of the present invention to provide a method for forming a hemming portion that can be formed.

[0015]

In order to solve the above-mentioned technical problems, the present inventors have disclosed the technical means disclosed in Japanese Patent Application Laid-Open No. 8-510598, that is, the method for solving the problem between two planes using hard particles. The method of mechanically fixing each other in the deviation direction is insufficient in reliability due to buckling on the curved surface, and there is no temporary fixing effect on the force in the peeling direction, but in the flat part, The fact that a temporary fixing effect can be obtained with a certain degree of reliability, and by combining the hot air method and this mechanical fixing method, it has been found that some of the heating points of the hot air method can be omitted and the above-mentioned problem can be advantageously solved. , Also confirmed.

That is, according to the method of forming a hemming portion according to the present invention, the outer panel is folded in two with the peripheral edge of the inner panel sandwiching the peripheral edge of the inner panel, and the joint between the outer panel and the inner panel is bonded. In a method of forming a hemming portion of a vehicle body having a structure in which the two panels are joined to each other by filling the agent, a joint portion of an outer panel and an inner panel having a flange-shaped hem portion formed by bending a rim in a right angle in advance. An adhesive composition applying step of applying a thermosetting adhesive composition mixed with hard particles, and bonding the inner panel to the outer panel to which the adhesive composition has been applied. After setting, press the hem portion of the outer panel onto the inner panel, and fold the hem portion in two with the periphery of the inner panel sandwiched. And a press step (hemming step) of filling the adhesive composition between the joints of the inner panel and the hard particles into both surfaces of the joints. A hot air spot is sprayed onto the heating points at the peripheral portions of the outer panel and the inner panel, and the adhesive composition filled at the heating points is pre-cured, and a preliminary heating step (pre-curing) for temporarily fixing both panels is performed. Step) and a final heat curing step of finally completely curing the adhesive composition during baking and drying of the applied electrodeposition coating film.

Here, the term "hard" for particles mixed in the adhesive composition refers to the outer panel and the inner panel, which are generally made of a steel plate, with respect to the outer panel and the inner panel. Has sufficient hardness (compressive strength) to be bitten or partially embedded in Further, the particles have a diameter larger than a predetermined gap (filled thickness of the adhesive composition) between joints of both panels because the particles are bitten into both panels, and further, The press pressure in the press process is
It is sufficient that the particles penetrate into both panels. Technical details regarding these points will be described later.

In the method of forming a hemmed portion according to the present invention, an adhesive composition mixed with hard particles is used, and the particles are cut into both the outer panel and the inner panel in a pressing step (hemming step). Because of the frictional engagement or mechanical engagement in the direction of displacement, as is apparent from the test results of the examples described later, if the flat (planar, non-curved) hemming portion is temporarily fixed, For this reason, a sufficiently reliable fixing force can be obtained. Therefore, spot heating by hot air in such a portion (heating point) which has been conventionally required can be omitted, and the energy required for heating the air can be saved correspondingly. That is, energy saving of pre-curing by the hot air method can be achieved.

It should be noted that the method of forming a hemmed portion according to the present invention in which hard particles are used as a part of a fixing means for temporary fixing is also applied to a method of forming a hemmed portion using spot welding as a temporary fixing means. Can be. That is, in such a method of forming the hemmed portion, in the above-described method of forming the hemmed portion, the preliminary heating step (precuring step), which is the temporary fixing step, is performed by the peripheral portion (specifically, the outer panel and the inner panel joined by the pressing step). Specifically, a method is adopted in which spot welding is performed on the hem portion), and a spot welding process for temporarily fixing both panels is performed. And according to the method of forming the hemmed portion including the spot welding step, as described above,
The number of places where spot welding should be performed can be further reduced. And while this saves energy required for temporary fixing, it is rather significant in that the number of welding traces that can be generated by the spot welding can be further reduced.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of forming a hemmed portion will be described below in more detail.

FIG. 1 is a process diagram of a method for forming a hemming portion of a vehicle body according to an embodiment of the present invention. FIG. 2 is an explanatory view schematically showing a state of the periphery of the outer panel and the inner panel before and after the pressing step (hemming processing step), and FIG. 2A is an explanatory view showing a state before the hemming processing. FIG. 2B is an explanatory view showing a state after hemming. FIG. 3 is an explanatory view schematically showing the state of preheating by hot air in the preheating step.
FIG. 4 is an explanatory diagram showing heating points in the case of luggage of preheating by hot air.

As shown in FIG. 1, the method for forming a hemmed portion according to the present invention is basically a method of applying a thermosetting adhesive composition mixed with hard particles to a joint between an outer panel and an inner panel. In the composition applying step A, the joint of the peripheral edge of the inner panel is superimposed on the joint of the outer panel, and the hem of the outer panel is pressed thereon to perform hemming, and an adhesive is provided between the joints of both panels. A pressing step (hemming step) B in which the composition is filled and hard particles are cut into the surfaces (joining surfaces) of both joints, and the adhesive composition is preheated by a hot air method and precured. (Precuring) a preheating step C, and a final heating curing step D for finally completely curing the adhesive composition at the time of baking and drying of the applied electrodeposition coating film. That is, the method of forming the hemmed portion is that the hard particles are mixed in the adhesive composition, and the pressing of the hem portion in the pressing step causes the hard particles to bite into the joint surface of both panels. Or, it is substantially the same as the conventional method including a preheating step by a hot air method, except that the pressure is high enough to be embedded.
Hereinafter, details of each of these steps will be described.

<< Adhesive Composition Application Step A >> In this step, as shown in FIG. 2 (a), a thermosetting adhesive composition 30 is attached to the joint portion 11 of the outer panel 10 with the inner panel 20.
Is applied. The outer panel 10 and the inner panel 2 forming a hemming assembly such as a luggage are provided.
No. 0 is formed by forming a metal plate such as a steel plate into a predetermined shape by deep drawing or the like, and the outer panel 10 on the outer surface side of the vehicle body has its peripheral edge previously bent at a right angle, and is folded back. The hem portion 12 as an edge is formed in a flange shape. The peripheral edge of the inner panel 20 is formed as a joint 21 overlapping the joint 11 of the peripheral edge of the outer panel 10.

The adhesive composition 30 is obtained by mixing hard particles 31 into a thermosetting adhesive composition.

As the thermosetting adhesive composition itself, those conventionally used for bonding a hemming portion can be used as they are, for example, epoxy resin, polyester resin, phenol resin, urea resin. And the like, and an adhesive composition such as a vinyl chloride resin (plastisol) or the like. However, among these, the use of epoxy resin-based compositions is preferred in terms of adhesiveness to oil-side steel sheets, curability in an electrodeposition coating oven, and rust prevention properties. Preferred are epoxy resin-based precured adhesive compositions and pseudo-cured (pregelled) adhesive compositions that are generally known or used as hemming adhesive compositions that can be cured by using. .

The pre-cured adhesive composition contains an epoxy resin and a heat-activated curing agent for the epoxy resin. Examples of the epoxy resin as a main component forming the adhesive include, for example, glycidyl ether type such as bisphenol A and bisphenol F, glycidyl ester type, glycidylamine type, linear aliphatic epoxide type, alicyclic epoxide type, and ,
Novolak epoxy resins and the like can be mentioned, and these can be used alone or in combination of two or more. Examples of the heat-active curing agent include organic acid dihydrazides such as dicyandiamide (DICY) and isophthalic acid dihydrazide; polyamines such as diaminodiphenylsulfone (DDS); imidazole derivatives such as 2-n-pentadecylimidazole; N'-dialkylthiourea derivatives and the like can be appropriately added depending on the epoxy resin to be used and the curing conditions, but generally about 1 part by weight per 100 parts by weight of epoxy resin.
To 15 parts by weight, preferably 6 to 8 parts by weight.

The quasi-curable adhesive composition further comprises a composition containing the above-described epoxy resin and a heat-activated curing agent thereof, which is insoluble in the epoxy resin at room temperature but is added to the epoxy resin at a high temperature. It is formed by mixing a powdery soluble polymer that dissolves and pseudo-hardens (pregels) it. Examples of the powdery polymer include powders of a soluble thermoplastic resin such as an acrylic acid resin (acrylic or methacrylic polymer), a vinyl chloride resin, polyamide, ethyl cellulose, polyvinyl formal, and polyvinyl butyral. Of these, acrylic acid-based resin powder (acrylic powder) can be particularly preferably used. According to such an adhesive, in the subsequent preheating step, it can be cured with a physical change by a short preheating.

These adhesives may further include a thixotropic agent (thickening agent) such as colloidal silica and colloidal calcium carbonate, heavy calcium carbonate, talc,
Metal powders such as alumina, clay, silica, and aluminum powder, and fillers such as inorganic fibers, coloring pigments, plasticizers, reactive diluents, flexibility-imparting agents, stabilizers, solvents, and other additives. They can be appropriately blended or added.

The hard particles 31 mixed into such an adhesive composition are thermally stable and have a compressive strength (hardness) higher than the yield strength of the metal material constituting the outer panel 10 and the inner panel 20. Can be used, and examples thereof include those made of a hard inorganic material such as glass or ceramic, or a hard metal material such as hard stainless steel. The shape and size may be any shape that can be cut or embedded in the joint surfaces 11a and 21a of the panels 10 and 20 in a later pressing step.
a, 21a having a diameter larger than the gap (thickness of the adhesive layer) (however, sufficient to prevent an excessive stress from remaining on the outer panel 10 or a bulge on the outer surface thereof). A microsphere or a small ellipsoid (having a small diameter), an irregular crushed granule, a short columnar body, or the like can be used. However, particles having a substantially spherical shape are preferred from the viewpoint of the strength at the time of compression (hardness to break) and the handleability (applicability) of the adhesive composition containing the same. Therefore, as the hard particles 31, micro spherical glass beads which are relatively easy to manufacture are particularly suitable. Regarding the size (diameter) of the glass beads, the gap (thickness of the adhesive layer) between the joints 11 and 21 of the outer panel 10 and the inner panel 20 generally needs to be at least about 100 μm. 0, larger (but not too large)
It is preferably about 12 to 1.2 mm, and more preferably about 0.20 to 0.50 mm.

The hard particles 31 can be used in an appropriate amount according to the required temporary fixing strength and the like.
Joints 11 and 12 between outer panel 10 and inner panel 20
The larger the amount (number) interposed between the ones, the higher the fixing strength in the deviation direction can be obtained. However, the fixing strength depends on not only the shape and size of the hard particles, but also the amount of penetration or embedding of the hard particles 31 into the joint surfaces 11a and 21a. By doing so, a sufficiently high fixing strength can be obtained. In the case of a hemming portion such as a hood of an ordinary automobile, the hard particles 31 generally have a ratio of 1.0 to 25% by volume (capacity), preferably 2. It can be mixed and used at a ratio of 0 to 10% by volume.

The adhesive composition 30 containing the hard particles 31 is sufficiently mixed with the hard particles and a previously prepared adhesive composition or a raw material of the composition by a mixer such as a kneader, and then uniformly mixed. And then defoamed.

The adhesive composition 30 is applied along the joints 11 on the outer periphery of the outer panel 10 by a usual application method, that is, a method of applying the adhesive composition 30 by using a sealer gun (nozzle) to discharge and apply the adhesive composition. In general, as shown in FIG. Then, the adhesive composition 30 applied to the joint portion 11 of the outer panel 10 is overlapped with the joint portion 21 of the inner panel 20 and pressed in a later hemming process, so that the two panels 10 and 10 are bonded together. 20 and is spread over the entire area between the joints 11 and 21 to fill the gap. Therefore, the application of the adhesive composition 30 for the purpose of preventing rust of the hemming portion is performed at an application amount necessary to surely fill at least the gap between the joint portions 11 and 21.

Here, the adhesive composition 30 is
By making the coating amount relatively large, the hem portion 12
And between the inner panel 20 and the joint 21 of the inner panel 20. Thereby, it is possible to obtain higher rust resistance and bonding strength of the hemmed portion.
However, the hem portion 12 and the inner panel 2
Filling the adhesive composition 30 between the bonding surfaces with the “0” has a possibility that the adhesive composition 30 protrudes from the leading edge of the hem portion 12 at the same time. Then, the extruded adhesive composition 30 adheres to the press die (hem blade) and contaminates the same, which hinders the hemming process to some extent. In addition, since a sealing material is applied to a boundary portion between the leading edge of the hem portion 12 and the surface of the inner panel 20, at least for rust prevention, the filling of the adhesive composition 30 between the joining surfaces is originally required. It is unnecessary. Therefore, the application amount of the adhesive composition 30 is generally, as shown in FIG.
The adhesive composition 30 that has been pushed out between the joint portion 11 of the outer panel 10 and the joint portion 21 of the inner panel 20 and protruded from the gap causes a wedge-shaped gap inside the joint portions 11 and 21 to some extent. While filling, the inner panel 20
It is preferable that the gap between the leading edge and the bent corner of the outer panel 10 is filled and stopped there.

<< Pressing Step B >> This step is a hemming processing step, and the inner panel 2 is placed on the bonding portion 11 of the outer panel 10 on which the adhesive composition 30 has been applied, as in the conventional case.
After the joining portions 21 of the peripheral edge of the outer panel 10 are overlapped and set, the hem portion 12 of the outer panel 10 is pressed on the inner panel 20 to be folded in two and folded. However, at this time, the hem portion 12 is pressed with a sufficiently high pressure to the inner panel 20.
Pressed upward, compressing both joints 11 and 21 together.
Thereby, as shown in FIG. 2, the inner panel 2 is located between the joint 11 of the outer panel 10 and the folded hem 12.
No. 2 bonding part 21 is sandwiched between them to form a hemming structure that is mutually bonded.
0 is filled by being spread and spread over the entirety of the joints 11 and 21 of the panels 10 and 20, and the hard particles 31 mixed therein penetrate or partially penetrate both of the joint surfaces 11a and 21a. Embedded.

The hemming process itself can be performed by a press die or a pressing roll in the same manner as in the prior art. More specifically, the hemming process can be generally performed in several stages. For example, the hem portion 12 which has been bent at a right angle in advance, ie, about 90 °, is bent inward to about 135 ° in the first stage (preliminary hemming), and further, the inner panel 20 Joint 21 of
It can be pressed vertically upward and bent to 180 °, and finally formed into two folds so as to sandwich the joint 21 of the inner panel 20.

Here, the pressure for pressing the hem portion 12 onto the surface of the joint portion 21 of the inner panel 20 depends on the hardness of the adhesive composition 30 mixed between the outer panel 10 and the joint portions 11 and 21 of the inner panel 20. The particles 31 need to be sufficiently high to penetrate or partially bury the respective joining surfaces 11a, 21a, thereby obtaining friction or mechanical engagement in the direction of displacement. However,
The specific pressing pressure depends on the content ratio of the hard particles 31 in the adhesive composition 30, that is, the amount (number) of the hard particles 31 interposed between the joints 11 and 12. Requires a relatively high pressure, and when the amount is small, the hard particles 31 can be sufficiently penetrated or embedded in both joint surfaces 11a and 21a even with a relatively small pressure. . Generally, but not exclusively, the pressing pressure is 20.0-70.0 MPa (200-700 kPa).
gf / cm ² ). 20.0MP
At a pressure lower than a, it is generally generally difficult to obtain sufficient friction or mechanical engagement by the hard particles 31. However, high press pressures, exceeding 70.0 MPa, are not usually required.

Then, by this pressing step,
At the joint between the outer panel 10 and the inner panel 20 where flat processing is performed with high accuracy or sufficiently flat, the hard particles 31 bitten between the joints 11 and 21 of the outer panel 10 and the inner panel 20 cause the two panels 10 and 20 to be joined. Is reliably maintained in a state of friction or mechanical engagement with the displacement direction, so that even if there is no adhesive force of the adhesive composition 30, the adhesive force required for temporary fixing is sufficiently reliable. Can be obtained. Therefore, in the next preheating step by the hot air method, some of the heating points can be omitted, and the heating energy can be saved.

<< Preheating Step C >> The preheating step C is a peripheral part of the outer panel and the inner panel assembled and connected by the above-mentioned pressing step (hemming processing step), that is, a green hemming part where the adhesive composition is not cured. Is preheated by a hot air method in which hot air is sprayed in spots on some heating points (heated portions) on the peripheral portion, and the adhesive composition filled in the heating points is precured (precured). , Thereby temporarily fixing both panels (green hemming part) basically basically,
During transfer or handling until the adhesive composition is completely cured in accordance with baking and drying of the electrodeposition coating film in the subsequent final heat curing step, there is no displacement or twist between the two panels. It is a process to make it.

The preheating by the hot air method is shown in FIG.
In the pressing process, the adhesive composition 30 is provided between the joints 11 and 21 of the outer panel 10 and the inner panel 20.
A heater nozzle 41 (a nozzle with a built-in electric heater) connected to the blower blower 40 is disposed corresponding to a heating point of a green hemming portion formed by filling with, and the heated hot air is blown from the heater nozzle 41. This is performed by heating (heat input) the heating point. The heater nozzle 41 is usually arranged on the side of the hem portion 12 as shown in the figure, but may be arranged on the side of the outer surface of the joint portion 11 of the outer panel 10. In addition, such an outer panel 10 and an inner panel 20
The adhesive composition 30 filled between the joints 11 and 21 is pre-heated and pre-cured through the heat treatment. This pre-heating is generally performed at a temperature of about 450 to 550 ° C. (nozzle opening). This is performed by blowing heated hot air for 20 to 40 seconds.

By the preheating step (precuring step), at least a part of the thermosetting adhesive composition 30 filled between the joints 11 and 21 of the outer panel 10 and the inner panel 20 is cured. When the adhesive force is developed, the panels 10 and 20 are temporarily fixed securely regardless of whether or not a reliable fixing force by the hard particles 31 is obtained in the above-described pressing process. . However, as described above, if the hemming portion is flat or nearly flat, the fixing force required for the temporary fixing can be reliably obtained in the pressing step. The preheating in step ()) can be omitted. That is, it is possible to reduce the number of heating points and reduce the amount of energy (electric power consumption) required for heating the air, without impairing the reliability of the temporary fixing.

FIG. 4 specifically shows an automobile luggage 50 as an example of a heating point (heating portion) of the preheating by the hot air method. Note that FIG.
, The hatched elliptical portion of the hemming assembly (green hemming portion) is the heating point (heated portion), and the dotted elliptical portion is the conventional ellipse that does not use hard particles. This is a heating point that can be omitted when the present invention is implemented, although it is a part that has been regarded as a heating point.

That is, in the case of the luggage (luggage compartment door) 50 shown in FIG. 4, eight heating points are generally set almost uniformly along the hemming portion on the periphery in the prior art. The preheating can be omitted in two places on the upper and lower side edges of the upper side edge, which is flat and is processed with high precision. That is, in the case of the luggage 50, the heating point is
It can be set at a total of four locations, two at the left and right sides of the bent portion and two at the angled bent portions on both lower sides.

<< Final Heat-Curing Step D >> This step is the final step of forming a hemmed portion. At the time of baking and drying of a subsequently applied electrodeposition coating film, the joint portion between the outer panel 10 and the inner panel 20 is simultaneously formed. Adhesive composition 3 between 11 and 21
0 is finally baked to completely cure the outer panel 1
This is a step of finally completely and adhesively bonding the inner panel 20 and the inner panel 20.

That is, the hemming assembly such as the luggage, the hood, and the door temporarily fixed in the preheating step is assembled to the body of the vehicle, and subjected to pretreatment steps such as degreasing, washing, and chemical treatment, and then to the electric power supply. The process is moved to a coating process, and the entire surface is coated with an electrodeposition coating. When the body coated with electrodeposition is transferred to a baking oven to bake and dry the electrodeposited coating film, the heat is applied to the final heating and curing of the adhesive composition 30. This forms a completely adhesively bonded, permanently bonded hemming.

After the hemmed portion is completely formed in this manner (at this time, the entire surface of the hemmed portion is subjected to electrodeposition coating), a border edge between the leading edge of the hem portion 12 and the surface of the inner panel 20 is formed. A sealant is applied along the border to seal between the hem portion 12 and the inner panel 20.

As described above, the method of forming the hemmed portion of the vehicle body according to the present invention includes the step of applying the adhesive composition mixed with the hard particles, the step of pressing B as the hemming step, and the step of temporarily fixing. A preheating step C for preheating the green hemming portion by the hot air method to pre-cure the adhesive composition, and a final heating step for completely and completely curing the adhesive composition in accordance with baking and drying of the electrodeposition coating film. The heating and curing step D is basically performed. In the method of forming the hemmed portion, hard particles are mixed into the adhesive composition, and the hard particles are cut or embedded between the joints of both panels in the pressing step B. Therefore, particularly in the case of a flat or nearly flat hemming portion, even if the adhesive composition is not cured, it is possible to obtain a sufficient fixing strength in the misalignment direction for temporary fixing. For this reason, the temporary fixing of the green hemming portion is basically performed in the preheating step C by a hot air method in which hot air is sprayed in spots to several heating points of the preheating step C, but is particularly flat or almost flat. In some parts, it is possible to reliably obtain the fixing strength required for temporary fixing, so that preheating by the hot air method can be omitted, thereby further reducing the energy required for air heating. it can.

[0047]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples (test examples) conducted on a trial basis.

A thermosetting adhesive composition mixed with hard particles was prepared as follows, and then various hemming structure specimens were prepared using the same. And about these hemming structure specimens, the joining strength (shear adhesive strength) was tested and evaluated.

[Preparation of Adhesive Composition] Bisphenol A
100 parts by weight of glycidyl ether type epoxy resin ("EP828" manufactured by Yuka Shell Epoxy Co., Ltd./epoxy equivalent 190, molecular weight 380), 10 parts by weight of dicyandiamide, and dichlorophenyldimethylurea (curing accelerator)
4 parts by weight, 20 parts by weight of 1,1,1-trimethylolpropane triglycidyl ether (reactive diluent), 5 parts by weight of silicic anhydride ("Aloesil No. 200" manufactured by Nippon Aloesil Co., Ltd.) 5 parts by weight of carboxylated liquid acrylonitrile butadiene rubber ("Hiker CTBN" manufactured by Ube Industries, Ltd.), 5 parts by weight of highly conductive carbon black ("Ketchien Black EC" manufactured by Akzo Co., Ltd.), and 60 parts by weight of calcium carbonate And the department into Knead,
The mixture was sufficiently stirred and mixed to homogenize to prepare an epoxy adhesive composition.

Next, spherical glass beads having a particle diameter of 0.20 mm (± 0.05 mm) as hard particles were added to this adhesive composition by 5.0 volume (volume) with respect to the whole adhesive composition. %, And further sufficiently mixed to prepare a thermosetting adhesive composition containing glass beads.

[Preparation of Specimen] Using the adhesive composition mixed with the above glass beads, a hemming structure temporary fixing specimen was prepared as follows.

(Test Example 1) As a test panel, a flat plate-shaped steel plate A (corresponding to an outer panel) having a size of 50 mm × 100 mm × 0.8 mm formed by press working,
B (corresponding to the inner panel) was prepared as a set of two sheets, and 10 sets were prepared. In each of the steel plates A, a length range of 10 mm from one end in the longitudinal direction is bent at a right angle in advance to form a hem portion as shown in FIG. The holding piece was fixed to the steel sheet A by welding in advance for a later tensile test. As shown in FIG. 2, the steel plate B is formed by bending a range of 13 mm from one end as a joint.

The thermosetting adhesive composition mixed with the above-mentioned glass beads was applied to the steel plate A at a position of about 5 mm from the hem portion in a build-up form (rod form). Then, one end of the steel sheet B is overlapped on the coated portion of the adhesive composition, and the steel sheets A and
B was set in a straight line, and then the hem portion of the steel plate A was bent over the steel plate B and pressed at a pressure of 30.0 MPa to perform hemming. At this time, the thickness of the adhesive composition layer between the joining surfaces of the steel sheets A and B was about 0.1 mm. Subsequently, the hemming portion of the steel plates A and B was blown with hot air from the heater nozzle connected to the blower blower over the entire width to preheat the adhesive composition, preliminarily hardened, and temporarily fixed the hemming structure test. The body was made. The heating conditions for this preheating were as follows: the air temperature at the nozzle outlet was 500
° C, nozzle distance 15 mm, and heating time 20 seconds.

(Test Example 2) Ten sets of steel panels A and B having the same size and shape as those of Test Example 1 but curved in the width direction were prepared as test panels. The curvature corresponds to an arc of a circle having a radius of about 14 cm. The radius of curvature of the ten steel sheets B was changed in a range up to about 3 cm.

Using these, in the same manner as in Test Example 1,
A hemming structure specimen temporarily fixed by preheating was produced.

(Test Example 3) A hemming structure test piece was prepared in the same manner as in Test Example 1 except that the preheating of the adhesive composition by hot air was omitted.

(Test Example 4) The same procedure as in Test Example 1 was conducted except that the preliminary heating was omitted.
A hemming structure specimen was prepared.

In this manner, in each of the test examples, ten hemming structure specimens were produced.

Among the hemming structure specimens obtained in each of the test examples, one of the specimens was subjected to general heating conditions for baking and drying the electrodeposition coating film of the vehicle body, that is, 170 ° C. in this case. Baking was performed under a heating condition of × 20 minutes, and the adhesive composition was finally completely cured.

[Evaluation Tests] Evaluation tests were performed on the hemming structure specimens prepared in each of the test examples, which were subjected to preheating or not, and were subjected to adhesive bonding strength (temporary fixing strength) in the direction of displacement.

That is, using a tensile tester (manufactured by Shimadzu Corporation), the steel plates A and B of each test piece are pulled in the longitudinal direction at a predetermined pulling speed, and the shear bond strength (bonding strength) between them is measured. did.

[Test Results] Flat steel plates A and B were used as test panels, a thermosetting adhesive composition containing glass beads mixed with the steel plates A was applied, and steel plates B were set and pressed. In Test Example 1, in which the hemming structure was formed and the glass beads were cut into the steel plates A and B, and then the hot air was blown and the adhesive composition was pre-cured, the obtained hemming structure test piece was temporarily fixed. Has sufficient bonding strength (bonding strength in the shift direction) necessary for the steel sheet, and separates the steel plates A and B in the shift direction substantially parallel to their surfaces,
The force required to separate (bond strength) is on average about 8.
It was 5 kgf / cm ² . Also, the variation in the bonding strength of the nine test specimens was small, and the difference between the maximum value and the minimum value was about 1
It was about kgf / cm ² .

Test Example 2 prepared in the same manner as Test Example 1 using curved steel plates A and B as test panels.
The bonding strength of the hemmed structure test piece subjected to the preheating of ( ¹ ) was 5.4 kgf / cm ^{2 to} 8.8 kgf / cm ² (average about 7.8 kgf / cm ² ). Although a slightly larger variation in the bonding strength than in the case of Test Example 1 is seen, the bonding strength for temporary fixing is sufficient.

Further, in the same manner as in Test Example 1, a flat steel plate A,
B, but was not subjected to preheating by blowing hot air, but the hemming structure specimen of Test Example 3 (that is, the hemming structure specimen of Test Example 3 was a test specimen before preheating). (Corresponding to the hemming structure specimen of Example 1), the bond strength is 4.2 kgf / cm ² or more.
5.3 kgf / cm ² (average about 4.7 kgf / cm ² )
Met. This bonding strength is sufficient if the strength normally required for temporary fixing is about 3 kgf / cm ² , and since the dispersion is small, the bonding strength is also sufficient.

On the other hand, the hemming structure specimen of Test Example 4 which was produced using the curved steel plates A and B and was not preheated (the hemming structure specimen of Test Example 2 before preheating) ), The bond strength ranges from a minimum of 1.6 kgf / cm ² to a maximum of 4.3 kgf / cm ^2.
In some cases, the temporary fixing strength is sufficient, but in some cases, the strength is insufficient, and the reliability is lacking in certainty or reliability.

Therefore, based on the results of these tests, particularly the results of Test Example 3, hard particles were mixed into the adhesive composition, and the hard particles were used in both the outer panel and the inner panel in the pressing step (hemming step). In particular, by making it bite or embedded between the joints,
It can be seen that if the hemmed portion is flat, it is possible to secure a sufficiently reliable bonding strength for temporary fixing without pre-curing the adhesive composition by pre-heating.

The specimens of Test Examples 1 to 4 were baked under the conditions of baking and drying the electrodeposition coating film, and the adhesive composition filled between the joints was finally completely heated. When cured, the bond strength was 30 kgf / c
It was greater than m ^2. That is, the use of hard particles does not adversely affect the final adhesive strength of the hemmed portion.

[0068]

As described above, according to the method of forming the hemming portion of the vehicle body according to the present invention, the outer edge of the outer panel is folded in two with the outer edge of the inner panel sandwiched, and the outer panel and the inner panel are bent. In a method of forming a hemmed portion of a vehicle body having a structure in which an adhesive is filled between the joined portions and the two panels are connected to each other, an outer panel in which a peripheral edge is bent at right angles in advance to form a flange-shaped hem portion An adhesive composition applying step of applying a thermosetting adhesive composition mixed with hard particles to a joint portion of the inner panel with the inner panel, and an inner panel on the joint portion of the outer panel to which the adhesive composition has been applied. After setting the joint of the outer panel, press the hem part of the outer panel on the inner panel, and fold the hem part into two by sandwiching the periphery of the inner panel. A press step of filling the adhesive composition between the joints of the outer panel and the inner panel, and biting the hard particles into both surfaces (joint surfaces) of the joints; Hot air is sprayed in the form of spots on the heating points at the peripheral edges of the combined outer panel and inner panel, and the adhesive composition filled at the heating points is pre-cured, and the two panels are temporarily fixed. It comprises a heating step (precuring step) and a final heat curing step of finally completely curing the adhesive composition during baking and drying of the applied electrodeposition coating film.

Therefore, in the method of forming a hemmed portion according to the present invention, hard particles are mixed into the adhesive composition, and the hard particles are used in both the outer panel and inner panel joints in the pressing step (hemming processing step). Because it is made to bite into the surface or to be embedded, by its frictional engagement or mechanical engagement in the direction of displacement,
For example, if the hemming portion is flat or nearly flat, it is possible to reliably secure the bonding strength required for temporary fixing. Therefore, the temporary fixing is basically preheated by spraying hot air in spots on several heating points around the outer panel and inner panel (green hemming part) after pressing. This is performed by the hot air method of pre-curing the adhesive composition filled in the portion, but the preheating by blowing the hot air can be omitted for the flat or near-flat hemming portion as described above. Therefore, the energy required for heating the air can be saved correspondingly. That is, according to the method for forming the hemmed portion of the present invention, the energy used for the preheating by the hot air method can be further reduced, and the energy saving of the temporary fixing can be achieved.

[Brief description of the drawings]

FIG. 1 is a process diagram of a method for forming a hemming portion of a vehicle body according to an embodiment of the present invention.

FIG. 2 is an explanatory view schematically showing a state of a peripheral edge of an outer panel and an inner panel before and after a hemming step in a method of forming a hemmed portion of a vehicle body according to an embodiment of the present invention, in a sectional view; FIG. 2A is an explanatory view showing a state before hemming, and FIG. 2B is an explanatory view showing a state after hemming.

FIG. 3 is an explanatory view schematically showing a state of preheating by hot air in a preheating step of a method of forming a hemmed portion of a vehicle body according to one embodiment of the present invention.

FIG. 4 specifically shows an example of a heating point of preheating by hot air in a preheating step in a method of forming a hemmed portion of a vehicle body according to an embodiment of the present invention, and shows heating in a luggage case. It is explanatory drawing which shows an example of a point.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Outer panel 12 Hem part 20 Inner panel 11, 21 Joining part 11a, 21a Joining surface 30 Adhesive composition 31 Hard particles

Claims (1)

[Claims] 1. A peripheral edge of an outer panel is folded in two while sandwiching a peripheral edge of an inner panel, and an adhesive is filled between joints between the outer panel and the inner panel to join the two panels to each other. A method for forming a hemmed portion of a vehicle body having a structure as described above, wherein heat is generated by mixing hard particles into a joint portion of the outer panel with the inner panel, the perimeter of which is bent at right angles in advance to form a flange-shaped hem portion. An adhesive composition applying step of applying a curable adhesive composition, and after setting the joint of the inner panel on the joint of the outer panel to which the adhesive composition has been applied, The hem portion is pressed onto the inner panel, and the hem portion is folded in two with the periphery of the inner panel sandwiched, and the outer panel and the inner panel are folded in two. A press step of filling the adhesive composition between the joints of the inner panel and biting the hard particles into both surfaces of the joints; and the outer panel and the inner joined by the press step Hot air is sprayed in a spot shape on a heating point on a peripheral portion of the panel, the adhesive composition filled in the heating point portion is pre-cured, and a preliminary heating step of temporarily fixing the panels is performed. A final heat-curing step of finally completely curing the adhesive composition at the time of baking and drying the applied electrodeposition coating film.