JP4907101B2 - Stiffener and steel plate reinforcement method - Google Patents

Description

  The present invention relates to a method for reinforcing a thin steel plate used for an automobile door or the like.

  The body of an automobile is mainly made of steel, and the steel plates that make up doors and roofs use thin plates to reduce weight. Stiffeners are used for spot welding and adhesives to improve rigidity. Is pasted. However, when a stiffener is used, the weight increases and a spot welding process is required. Therefore, a reinforcing method for adhering and fixing a resin sheet to a steel sheet has been proposed.

The resin sheet is mainly composed of an uncured material of a thermosetting resin, and a constraining layer of glass cloth is stuck on the resin sheet surface to be reinforced. For attachment to a steel plate member, an uncured thermosetting resin sheet having adhesiveness is attached to the steel plate and temporarily fixed, and the thermosetting resin is cured by using heat at the time of paint baking of the steel plate to be strong on the steel plate. It is to be fixed to.
However, when the adhesiveness of the thermosetting resin is reduced in some cases, the temporarily fixed resin sheet is displaced from a predetermined position of the steel plate during the hot water washing and chemical conversion treatment process until reaching the heat baking, or falls off. There was a fear.

In order to improve the temporary fixing performance of the resin sheet, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 5-152117), a proposal has been made to add a magnetic powder and a foaming agent to a thermosetting resin.
JP-A-5-152117

  A conventional reinforcing magnetic sheet is made of an uncured thermosetting resin, a foaming agent, and magnetic powder. The thermosetting resin has adhesiveness, so in order to prevent adhesion between sheets and dust on the surface of the sheet during storage to reduce the adhesiveness, a release paper is applied to the surface. In addition, it was an operation procedure in which the release paper was peeled off at the time of use and attached to the steel plate to be reinforced.

Since it requires a procedure to peel the release paper, it becomes a burden on the workers, and the release paper is a temporary member up to the sheet sticking work and is unnecessary after sticking, so the peeled release paper is waste Was occurring as.
Also, if the release paper is peeled off from the sheet, and once temporarily attached to the steel plate, it is peeled off for correction of the attachment position and reattached, because the adhesive force of the thermosetting resin is weakened, There were occasions when it slipped or dropped.
This invention makes it possible to temporarily fix the reinforcing sheet to the steel plate by using only the magnetic force without the need for a release paper, facilitates correction of the sticking position, prevents slippage and peeling after the position correction, and enables accurate positioning. It is to reduce the distortion which arises in a steel plate.

A steel sheet reinforcing method in which a reinforcing sheet in which a magnetic powder is mixed with a rubber-based synthetic resin is temporarily fixed to a predetermined position on the surface of a steel sheet by a magnetic force and heat-sealed, and a sheet of 1,2-polybutadiene rubber in which a magnetic powder is mixed In addition, a constraining layer is provided on the surface of the steel plate, and the end portion is obliquely cut and chamfered to reduce strain generated in the steel sheet by heat fusion.
Furthermore, the constraining layer is made of at least one material selected from any of glass cloth, carbon fiber, organic fiber-based nonwoven fabric, and metal foil.

The rubber-based synthetic resin constituting the reinforcing magnetic sheet is a conjugated diene system such as polybutadiene rubber, 1,2-polybutadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, polyisoprene rubber, chloroprene rubber, isobutylene-isoprene rubber, etc. A polymer is mentioned. In particular -OH, -COOH, -NH _2, -NCO, is preferably a rubber having a functional group such as -CH = CH _2, polybutadiene rubber, 1,2-polybutadiene rubber, styrene - butadiene rubbers, isobutylene - isoprene rubber is preferable .

  Examples of the magnetic powder include ferrite powder (for example, barium or strontium ferrite powder), rare earth cobalt magnet powder, alnico magnet powder, and the like, which are used alone or in combination. The mixing amount of the magnetic powder is determined according to the magnetic force obtained by the magnetic powder and the weight of the reinforced magnetic sheet, but is 200 to 600 parts by weight, preferably 250 to 450 parts by weight with respect to 100 parts by weight of the synthetic rubber resin. Part.

As the foaming agent, known inorganic or organic foaming agents can be used. Specifically, sodium bicarbonate, ammonium bicarbonate, sodium carbonate, ammonium carbonate, azodicarbonamide, dinitrosopentamethylenetetramine, dinitrosoterephthalamide, azobusisobutyronitrile, barium azodicarboxylate, sulfonyl hydrazide, toluene Sulfonyl hydrazide and the like. These foaming agents can be used in combination with foaming aids such as urea and urea derivatives. Preferred foaming agents are azodicarbonamide and dinitrosopentamethylenetetramine used alone or in combination, and can be combined with foaming aids such as urea and urea derivatives.
The blending amount of the foaming agent is 3 to 12 parts by weight, preferably 5 to 10 parts by weight with respect to 100 parts by weight of the synthetic rubber resin. When the blending amount is less than 3 parts by weight, the foaming effect is not sufficiently obtained. When the blending amount exceeds 12 parts by weight, a good appearance may not be obtained due to the gas generated from the foaming agent.

  In the present invention, the constraining layer laminated on the synthetic rubber-based resin layer is preferably a material that is lightweight and thin, can impart toughness to the synthetic rubber-based resin layer, and is easy to be tightly integrated. Specific examples include glass cloth, carbon fiber, organic synthetic resin fiber nonwoven fabric, aluminum, steel, metal foils such as various metal alloys, and the like. Of these, glass cloth and aluminum foil are particularly preferable in consideration of cost, weight, adhesion, and strength.

The magnetic sheet for reinforcement is prepared by dispersing and kneading a compound such as a rubber-based synthetic resin, magnetic powder, and a foaming agent with a known mixing and dispersing machine such as a dissolver, a banbury mixer, a planetary mixer, an open kneader, a vacuum kneader, and a calendar roll. The sheet is processed into a sheet by a processing machine such as an extrusion molding machine. Usually, the thickness of the reinforcing magnetic sheet is set to around 1.0 mm.
A steel plate reinforced magnetic sheet comprising a constraining layer and a synthetic rubber-based resin layer is obtained by laminating and bonding a synthetic rubber-based resin layer and a constraining layer and sticking to a steel plate, and then foaming the synthetic rubber resin layer.
In advance, the synthetic rubber resin layer may be foamed, and the obtained foamed resin layer and the constraining layer may be laminated and bonded.

When the reinforcing magnetic sheet is used after being cut to an appropriate size, the glass cloth is easily loosened. For this reason, when using glass cloth, the glass cloth itself is treated with heat-resistant resin such as phenol resin or melamine resin to improve the workability of attaching the reinforcing magnetic sheet. At the same time, the glass cloth is prevented from being loosened during cutting. As the heat-resistant resin used for the sealing treatment, an epoxy resin, an acrylic resin, or the like can be used in addition to a phenol resin, a melamine resin, or the like.
Note that organic fibers such as vinylon and nylon, metal fibers such as silver and stainless steel, and the like can be used instead of glass cloth or the like.

  The reinforcing magnetic sheet of the present invention contains a rubber-based synthetic resin and magnetic powder. When temporarily fixing to a steel plate, it is not necessary to peel off the release paper as in the case of a sheet using an adhesive resin. Since the magnetic sheet is held by a vacuum adsorber and pressed against a predetermined position of the steel sheet and the suction is stopped, the application to the predetermined position is completed, so that robotization is easy.

In addition, even if there is a misalignment, it is easy to return the sticking position to the correct position, and the reinforcing magnetic sheet adheres to the steel plate only by the magnetic force, so the adhesive force changes before and after the position correction. In addition, the position of the reinforcing magnetic sheet is not shifted in the process until heat-sealing, or is not dropped during assembly, and the stiffener is efficiently attached to the steel plate.
Since the end of the reinforcing magnetic sheet is cut obliquely and chamfered, the occurrence of distortion on the surface of the steel sheet due to the shrinkage of the resin layer can be suppressed, and the finish is beautiful, so the work of removing the distortion is omitted, Productivity is improved.

Example 1,2-polybutadiene rubber as a rubber-based synthetic resin, barium ferrite as a magnetic powder, sulfur, a curing agent, and a foaming agent as additives are mixed at a ratio shown in Table 1, and a reinforcing magnet having a thickness of 1.0 mm. A glass cloth 2 molded into a sheet 1 and treated with a melamine resin having a thickness of 0.2 mm was used as a constraining layer. Table 2 shows the specifications of the magnetic sheet in each formulation.

（配合は重量部）

(Composition is parts by weight)

Test Method (1) Strain is a sample in which a sample is attached to a 0.8 mm steel plate, heated at 180 ° C. for 30 minutes and fixed to the steel plate, then cooled to room temperature, and the strain of the steel plate is visually observed.
The case where the surface of the steel plate was smooth and visually recognized was rated as ◯, and the case where a strain line was observed was marked as x.
(2) Reinforcing property (unit: N) Using a tensile tester, place the steel sheet on top and the steel sheet reinforcing magnetic sheet on the wedge-shaped specimen table with a span of 100 mm, and center the span. Similarly, the wedge-shaped measuring device was lowered from the part and brought into contact with the steel plate. From this state, the measuring instrument was lowered at a speed of 1 mm / min, and the load when the steel plate sample with the reinforcing magnetic sheet adhered was displaced by 1 mm was measured.
(3) The appearance is confirmed by visual observation.
(4) The steel plate adhesion is such that two vertical flat plates (length: 50 mm) are formed in an inverted U-shaped cross-sectional view with a radius of curvature of 5 mm at the upper end of a 0.8 mm steel plate, and the distance between the upper ends is kept at 100 mm. The test piece is bridged between the vertical plates of the test table arranged in parallel on the support table, and a vertical plate (length) having a U-shaped cross section with a radius of curvature of 10 mm from the upper part at the center of the bridged portion. 50 mm), a load was applied to observe whether or not the steel sheet was displaced.
(5) Magnetic force is measured by the magnetic adhesion surface of the magnetic sheet before baking and the constrained layer surface after baking. Further, as shown in FIG. 1, a magnetic sheet for reinforcing a steel plate was attached to the steel plate 3, and the magnetic force at each point of A, B, and C was measured in a state of being heat-sealed. The results are shown in Table 3.

  When the magnetic sheet 1 is affixed to the surface of the steel plate 3, the ends of the steel plate are pulled during the fusion process, causing distortion, and thin lines may be generated on the surface of the steel plate. As shown in FIG. When the edge of the sheet was cut obliquely and chamfered, the occurrence of distortion could be prevented. Although the thickness of the magnetic sheet was 1 to 2 mm, it was confirmed that the oblique cut was effective in preventing the occurrence of distortion.

The magnetic sheet for reinforcement in this invention is a rubber-based synthetic resin mixed with magnetic powder and does not have viscosity in the resin itself.When temporarily fixed to a steel plate, it is attached only by magnetic force and held in place, There is no problem of falling off the steel plate until the paint baking process, and the release work of the release paper is eliminated as before, so that the production efficiency can be improved and the disposal of the release paper is eliminated. Occurrence disappears.
By heating such as paint baking, the rubber-based synthetic resin is fused to the steel plate and foamed by the added foaming agent to expand the resin and increase the volume. As a result, on the surface of the magnetic sheet opposite to the steel sheet, the magnetic force is reduced to 1/10 or less, and the magnetic force does not affect the electronic device or the human body.
In addition, by chamfering the end portion of the resin sheet, generation of distortion on the steel sheet due to thermal shrinkage of the resin was prevented.

Sectional drawing which affixes a magnetic sheet on a steel plate and shows the measurement point of magnetic force. Sectional drawing which shows the chamfering state of the edge part of a magnetic sheet.

Explanation of symbols

1 Magnetic sheet 2 Constrained layer 3 Steel plate

Claims (3)

A restraining layer is provided on the surface of the 1,2-polybutadiene rubber sheet mixed with magnetic powder, and the reinforcing sheet chamfered by obliquely cutting the edge is temporarily fixed to a predetermined position on the steel plate surface using magnetic force. Steel sheet reinforcement method for heat fusion. The steel plate reinforcing method according to claim 1, wherein the constraining layer is made of at least one material selected from any of glass cloth, carbon fiber, organic fiber-based nonwoven fabric, and metal foil. A stiffener for reinforcing steel sheets, in which a constraining layer is provided on the surface of a sheet of 1,2-polybutadiene rubber mixed with magnetic powder, and the end of the sheet is cut obliquely and chamfered.

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