JP2009035046A - Automobile hood - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automobile hood allowing obtaining of high dimension accuracy of the surface and excellent designability by suppressing adhesion shrinkage to a target level or less, in a form for constituting the hood by adhering outer member and inner member constituted of CFRP (Carbon Fiber Reinforced Plastics) single plate structures. <P>SOLUTION: This hood is constituted by joining the outer member and inner member of the CFRP single plate structures by using adhesive. A triple ratio (to<SP>3</SP>/ti) of thickness to (unit:mm) of the outer member to thickness ti (unit:mm) of the inner member is ≥0.7. An elastic modulus of the adhesive after curing is ≤2,000 Mpa. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an automotive hood made of carbon fiber reinforced resin (hereinafter abbreviated as “CFRP”. CFRP: Carbon Fiber Reinforced Plastics), and in particular, joins an outer member and an inner member of a CFRP single plate structure. Thus, the present invention relates to a hood for automobiles that exhibits high surface dimensional accuracy and good design properties so as to suppress the deformation of the surface of the outer member on the design surface side when the hood is configured.

  In recent years, an automobile hood made of fiber reinforced resin is being developed for the first purpose of weight reduction, and various structures for improving the strength and rigidity of necessary parts have been proposed. Among these, from the viewpoint of improving strength and rigidity, a CFRP automobile hood is being studied (for example, Patent Document 1).

  Conventional CFRP automobile hoods have a sandwich panel structure (structure with a CFRP skin layer on one or both sides of a lightweight core material) and CFRP single plate on the inner member to increase rigidity. A structure is known in which a hood is configured by adopting a structure and bonding both members (for example, Patent Documents 2 and 3).

  However, when a sandwich panel structure is adopted for the outer member, there is often a case where the overall thickness cannot be sufficiently reduced because there is a lower limit on the thickness of the skin layer. In general, when the thickness of the skin layer is reduced, the pressure at the time of molding is also limited, so that it becomes difficult to obtain sufficient smoothness on the surface of the outer member.

In order to cope with such a problem, it is conceivable to adopt a CFRP single plate structure for the outer member and to join the outer member and the inner member of the single plate structure with an adhesive. By simply adopting the structure, the inner member is generally structured to have a higher structural or shape rigidity, so that when the adhesive is cured, the outer member is interposed via an adhesive that shrinks by curing. The member and the inner member are locally pulled, and the outer member is locally deformed (displaced locally) toward the inner member having higher rigidity, so that a phenomenon of so-called adhesion sink occurs on the surface of the outer member. . When this adhesion sink exceeds a certain level, the dimensional accuracy of the outer member surface decreases, and when the outer member is viewed from the surface side, which is the design surface, for example, the reflected light appears distorted and good design properties are obtained. Hateful.
JP 2003-146252 A JP 2006-123788 A JP 2002-284038 A

  Accordingly, an object of the present invention is to form a hood by bonding an outer member and an inner member, both of which are made of a single plate of CFRP, to suppress adhesion sinks to a target level or less and to have a high dimensional accuracy and a good design property. The object is to provide a CFRP automobile hood capable of obtaining the above.

In order to solve the above-described problems, an automobile hood according to the present invention is an automobile hood formed by joining an outer member and an inner member having a carbon fiber reinforced resin single plate structure using an adhesive, and the inner member. The ratio (to ³ / ti) of the cube of the thickness to (unit: mm) of the outer member to the thickness ti (unit: mm) is 0.7 or more, and the elasticity after curing of the adhesive The rate is 2000 MPa or less.

The inner member of the CFRP single plate structure has a structure with increased rigidity in terms of shape, particularly in cross-sectional shape, in order to reinforce the outer member and ensure the necessary rigidity as the entire hood. The rigidity of the inner member itself is , Approximately a linear function of its thickness. On the other hand, the rigidity of the outer member itself of the CFRP single plate structure is dominated by the surface rigidity, and the rigidity acts on the cube of the thickness. In the automobile hood according to the present invention, in consideration of the basic characteristics regarding the rigidity of each of these members, the outer member when a local tension between the outer member and the inner member occurs via an adhesive that shrinks by curing. In order to suppress local deformation on the side, the rigidity of the outer member relative to the rigidity of the inner member at the joint is increased to a predetermined level or more. The rigidity relationship of each member is defined as a ratio of the actually acting rigidity, that is, the ratio of the cube of the outer member thickness to (unit: mm) to the inner member thickness ti (unit: mm) (to ³ / ti), and by setting the ratio (to ³ / ti) to 0.7 or more, the local deformation (displacement) of the outer member falls below a desired level as shown in the test results described later. It is suppressed small (that is, so-called adhesive sink marks are suppressed to a desired level or less), and the dimensional accuracy and design of the outer member surface are improved. The local tension between the outer member and the inner member accompanying the curing of the adhesive greatly depends on the local moment generated by the curing shrinkage of the adhesive, and the generated local moment is an elastic modulus after the curing of the adhesive. Therefore, in the present invention, the elastic modulus after curing of the adhesive is set to 2000 Mpa or less in order to suppress the generated local moment. Specifically, an optimum adhesive having an elastic modulus of 2000 Mpa or less is selected. With the setting of the ratio (to ³ / ti), the use of such an adhesive will surely improve the dimensional accuracy and design of the surface of the outer member.

  Considering that the first object of adopting the CFRP automobile hood as in the present invention is weight reduction, the automobile hood is preferably as light as possible while ensuring a predetermined strength and rigidity. . From the viewpoint of obtaining such a lightening effect, the total of the average thickness of the outer member and the average thickness of the inner member is preferably 5 mm or less, for example. The weight of the entire hood is required to be about 8 kg or less as a guide, but in order to realize such a hood weight, the total of the average thickness of the outer member and the average thickness of the inner member is 5 mm or less. It is preferable.

  As described above, according to the automobile hood of the present invention, the adhesion sink in the joining of the outer member and the inner member of the CFRP single plate structure can be suppressed to an allowable level or less, and the surface dimensional accuracy of the outer member can be improved and the surface design can be improved. Can be improved. Therefore, a CFRP automobile hood intended for weight reduction can be realized with desirable quality.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
1 and 2 show an example of the shape of an automobile hood according to an embodiment of the present invention. The automobile hood 1 according to the present invention includes an outer member 2 and an inner member 3 having a CFRP single plate structure as an adhesive. 4 is used for joining. However, the overall shape is not limited to the illustrated example. Moreover, although the inner member site | part of hat-shaped cross-sectional shape is shown in FIG. 2, it is not limited to the thing of the example of illustration also as cross-sectional shape of an inner member. The inner member 3 is set so that the rigidity is increased in the cross-sectional shape.

  As described above, when bonding is performed using the adhesive 4, as shown in FIG. 2, as the adhesive 4 is cured and contracted, a moment M is generated in which the outer member 2 and the inner member 3 are locally pulled. The outer member 2 is locally pulled toward the inner member 3 having higher rigidity and deformed (displaced) locally, and this appears as an adhesive sink. In the present invention, this adhesion sink is kept small.

In the present invention, first, the ratio of the thickness to (unit: mm) of the outer member 2 of the CFRP single plate structure to the thickness ti (unit: mm) of the inner member 3 of the CFRP single plate structure (to ³ / ti) is 0.7 or more. That is, FIG. 3 shows 3 of the thickness (unit: mm) of the outer member 2 relative to the thickness (unit: mm) of the inner member 3 in the result of the test using the low-modulus adhesive “MG5000” described later. The relationship between the ratio of multiplication and the local displacement (mm) of the outer member 2 due to the adhesive sink caused at that time is shown. The test was performed on inner members having a thickness of 1.1 mm and 2.5 mm, but the data representing the relationship between the ratio and the displacement amounted on almost one characteristic line regardless of the thickness of the inner member. . Therefore, the ratio of the cube of the thickness (unit: mm) of the outer member 2 to the thickness (unit: mm) of the inner member 3 is related to the local displacement amount (mm) of the outer member 2 due to adhesion sink. It can be understood that this is a universal value. As described above, the rigidity of the inner member 3 is dominant due to the cross-sectional shape, the rigidity is a linear function of the thickness, the outer member 2 is dominant of the surface rigidity, and the rigidity acts by the cube of the thickness. Therefore, when considering the adhesive sink due to the tension between the two members accompanying the hardening and shrinkage of the adhesive 4, the ratio of the cube of the thickness of the outer member 2 to the thickness of the inner member 3 is locally determined by the adhesive sink. This is a meaningful value for the displacement of the outer member 2. By the way, when the relationship between the thickness of the outer member 2 and the displacement amount of the outer member 2 is simply plotted, it becomes as shown in FIG. 4, and the displacement amount changes depending on the thickness of the inner member 3, and the plotted data is one Do not ride on the characteristic line.

  Referring to FIG. 3 again, in the above embodiment, the ratio of the cube of the thickness (unit: mm) of the outer member 2 to the thickness (unit: mm) of the inner member 3 is set to 0.7 or more. The displacement amount of the outer member 2 was suppressed to a small displacement amount of about 0.08 mm or less.

  Whether or not the displacement amount of the local outer member 2 due to such adhesion sinks has reached the acceptance standard is determined mainly by visual observation, and conversely, if the acceptance standard is grasped by visual determination, The displacement amount (mm) can be set as an acceptance criterion for the displacement amount.

  For example, as shown in FIG. 5 corresponding to the data area shown in FIG. 3 above, the fluorescent lamp is arranged above the outer member 2 of the molded hood (or a test piece equivalent to the hood). Then, it is possible to determine by visually observing the distortion of the image of the fluorescent lamp that can be recognized by reflecting the light from the fluorescent lamp on the surface of the outer member 2. As shown in FIG. 5, the ratio of the cube of the thickness (unit: mm) of the outer member 2 to the thickness (unit: mm) of the inner member 3 is less than 0.7, and the displacement amount of the outer member 2 In a region exceeding a certain predetermined level (for example, a displacement amount of about 0.08 mm), the adhesion sink mark 5 can be clearly recognized. On the other hand, the ratio of the cube of the thickness (unit: mm) of the outer member 2 to the thickness (unit: mm) of the inner member 3 is 0.7 or more, and the displacement amount of the outer member 2 is a predetermined level or less. In the region, it is not possible to recognize a clear adhesion sink, and it can be determined that the pass level has no practical problem.

  The occurrence of adhesive sink as described above depends on the elastic modulus of the adhesive as described above. That is, in the adhesive having a low elastic modulus, the moment M generated when the adhesive is cured and contracted as shown in FIG. 2 is suppressed, and the local displacement of the outer member 2 due to the adhesive sink is suppressed small. However, in the case of the adhesive having a high elastic modulus, the local displacement of the outer member 2 due to the adhesive sink is increased. Therefore, it is necessary to select an adhesive having a suitably low elastic modulus.

  FIG. 6 shows the results of testing various adhesives from such a surface. The test shown in FIG. 6 was performed with the inner member 3 having a thickness of 1.1 mm and the outer member 2 having a thickness of 1.0 mm. In the present invention, an adhesive having an elastic modulus after curing of 2000 MPa or less is used. As a result of the test, as shown in FIG. 6, an adhesive having an elastic modulus of 2000 MPa or less, MG7600 (elastic modulus: 30 MPa), MG5000 (elastic modulus: 360 MPa), Fusor (elastic modulus: about 1580 MPa), DP190 (elastic modulus: 270 MPa), a small amount of displacement below a predetermined level is achieved, and adhesives whose elastic modulus exceeds 2000 MPa, XNR-3324 (elastic modulus: 7100 MPa), and XNR-3024 (elastic modulus: 4200 MPa) are small below a predetermined level. The amount of displacement could not be achieved. For reference, the manufacturer catalog physical properties of these adhesives are shown in Table 1.

  In addition, the CFRP automobile hood is preferably as light as possible on the premise of ensuring a predetermined strength and rigidity for the purpose of adoption. FIG. 7 shows an example of the relationship between the average thickness of the outer member 2 and the total thickness of the inner member 3 and the weight of the entire hood. Generally, when adopting a CFRP automobile hood, it is desired to suppress the weight to 8 kg or less. In order to satisfy this requirement, it is understood from the characteristics shown in FIG. 7 that the total thickness of the average thickness of the outer member 2 and the average thickness of the inner member 3 is preferably about 5 mm or less.

  The CFRP matrix resin in the automobile hood according to the present invention is not particularly limited, but typically, epoxy resin can be used. In addition, unsaturated polyester resin, vinyl ester resin, phenol resin, dicyclo Thermosetting resins such as pentadiene resins and polyurethane resins can be used, and thermoplastic resins such as polyamide resins and polyolefin resins can also be used.

  The automobile hood according to the present invention can be applied to any CFRP automobile hood having both a single plate structure for the outer member and the inner member, and can be applied to a trunk lid as well as a so-called bonnet hood.

It is a disassembled perspective view which shows the example of a shape of the hood for motor vehicles based on one embodiment of this invention. It is an expanded sectional view of the junction part of the outer member and inner member of the food | hood for motor vehicles of FIG. It is a relationship figure of ratio of the cube of the thickness of the outer member with respect to the thickness of an inner member, and the amount of displacement of the outer member which arose at that time. It is a related figure of the thickness of an outer member, and the displacement amount of an outer member. It is explanatory drawing which shows a mode that the adhesion sink was determined visually corresponding to the data area | region shown in FIG. It is a related figure of the kind of adhesive agent, and the displacement amount of an outer member. It is a related figure of the total thickness of an outer member and an inner member, and a hood weight.

Explanation of symbols

1 Automotive Hood 2 Outer Member 3 Inner Member 4 Adhesive 5 Adhesive Sink

Claims (2)

An automotive hood formed by joining an outer member and an inner member having a single-plate structure made of carbon fiber reinforced resin using an adhesive, and a thickness to (of the outer member relative to a thickness ti (unit: mm) of the inner member A car hood characterized in that the ratio (to ³ / ti) of the cube of the unit (mm) is 0.7 or more and the elastic modulus after curing of the adhesive is 2000 MPa or less.   The automobile hood according to claim 1, wherein a sum of an average thickness of the outer member and an average thickness of the inner member is 5 mm or less.

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