JP2007024066A - Metal gasket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal gasket having less permanent strain without the need for a stopper. <P>SOLUTION: The metal gasket comprises a bead plate having a bead in a sectionally trapezoidal-shape. A width W of the top of the trapezoid and a length L of a portion forming the side face of the trapezoid are within ranges of 2.0×t≤W≤6.0 and 1.5×t≤L≤3.0×t, respectively, where t is the thickness of the metal gasket. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a metal gasket particularly suitable for use in a cylinder head of an automobile engine.

  A metal gasket used around the bore of a cylinder head gasket is a metal plate with a bead. However, the bead will sag when subjected to a tightening load or repeated vibrations. It is provided to prevent deformation beyond a certain level. Examples of the stopper include folding, shim, and a hard resin coat.

  On the other hand, Japanese Patent Application Laid-Open No. Sho 61-255253 (Patent Document 1) proposes a method in which a metal plate is provided with a highly rigid protrusion having a U-shaped cross section, and this is used as a stopper. In addition, as an advanced form thereof, Japanese Patent Application Laid-Open No. 2001-289323 (Patent Document 2) discloses that the center portion of the convex shape protrudes on the opposite side of the convex shape and has an M-shaped cross section, so that A metal gasket that is in contact with a mating surface at three points at the bottom and obtains high sealing performance is disclosed.

JP-A 61-255253 JP 2001-289323 A

  Among these, in the case of using a fold or shim as a stopper, the surface pressure is difficult to adjust because the thickness is constant, and depending on the engine structure, bore deformation may occur due to partial surface pressure concentration. With hard resin coating, the surface pressure can be adjusted more easily, but there is a risk that the coating itself may sag or break at locations where vibrations or heat loads are severe, and a separate seal coating is often required. There is also a problem that it takes.

  Further, in the method described in Patent Document 1, there is a case where the amount of elastic deformation is small, so that it is not possible to sufficiently follow vibration with a large amplitude. In addition, since the load is extremely concentrated on the upper and lower ends of the ridge, the end of this ridge may cause indentation on the cylinder head or cylinder block, and stress concentration at the end may cause long-term use. Then, there is a risk of causing fatigue failure. Moreover, it is assumed that the U-shaped portion is provided separately from the bead portion, and a space for it is required. In particular, the layout is difficult for a small engine or the like, and the degree of freedom in bead design is limited. Further, the technique described in Patent Document 2 is intended for sealing properties, and is not intended to eliminate a stopper or reduce sag.

  This invention is made | formed in view of such a situation, and makes it a subject to provide a metal gasket with few sags, without providing a stopper.

A first means for solving the above problem is a metal gasket comprising a bead plate having a bead having a trapezoidal cross-sectional shape, and the width of the top of the trapezoid when the thickness of the metal gasket is t. W and the length L of the part forming the side surface of the trapezoid are
2.0 × t ≦ W ≦ 6.0 × t
1.5 × t ≦ L ≦ 3.0 × t
It is the metal gasket characterized by being in the range of.

  Here, “the cross-sectional shape is trapezoidal” means that the shape of the bead plate rises diagonally at the bead part, and then falls diagonally after passing through the top parallel to the part other than the bead part. That is. Further, the width W of the top of the trapezoid is a value obtained by measuring the parallel top on the upper surface (surface of the convex portion of the bead portion serving as a convex portion). The length L of the trapezoidal side is measured by measuring the sloped side of the trapezoid on the back side of the convex bead. is there. These meanings will be described in more detail in the description of the embodiment.

A second means for solving the above-mentioned problem is a metal gasket comprising a bead plate having an M-shaped bead having an open cross-sectional shape, where the thickness of the metal gasket is t. The width W between the tops of the mold and the length L of the part that forms the oblique rising part of the M-shape,
2.0 × t ≦ W ≦ 6.0 × t
1.5 × t ≦ L ≦ 3.0 × t
The metal gasket is characterized in that the portion on the bottom side of the central portion of the M-shape is located on the top side of the bottom portion of the bead portion.

  “Open M-shape” means that the vertical bar portion of the M-shape is not vertical but stands up diagonally. The distance between the tops of the M-shape is measured on the surface side of the bead portion that is a convex portion, and the length L of the M-shaped oblique rising portion is the convex portion. It is measured on the back side of the bead portion. These meanings will be described in more detail in the description of the embodiment.

  The third means for solving the problem is a metal gasket comprising a bead plate having a bead having a trapezoidal shape or an open M-shaped cross section, and the shape of the trapezoidal or open M-shape is: When the metal gasket is tightened during use, the metal gasket becomes an open M shape, and when the tightening force is released, the center portion maintains an open M shape with the top side of the bottom portion. It is a metal gasket characterized by having such a shape.

  A fourth means for solving the above problem is any one of the first means to the third means, wherein the bead portion is coated on both surfaces, and the metal gasket is characterized in that is there.

  A fifth means for solving the above-mentioned problem is a metal gasket configured by combining a bead plate used for the metal gasket of any one of the first to fourth means and another sub-plate. .

  According to the present invention, it is possible to provide a metal gasket with less sag without providing a stopper.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a cross-section of a bead shape of a metal gasket composed of a single bead plate 1 according to the first embodiment of the present invention. FIG. 1A shows a state before tightening, and FIG. 1B shows a state during compression (compressed state). Before tightening, the bead portion has a trapezoidal cross-sectional shape as shown in the figure, the thickness is t, and the width of the trapezoidal top (flat portion) (measured on the upper surface side in the figure) is W1. , The length of the trapezoidal side portion (the slanted portion) (measured on the lower surface side in the figure, not the length along the hypotenuse but in the horizontal direction) is L1. .

  When such a bead plate 1 is pressed between an upper pressing member (for example, a cylinder head) 2 and a lower pressing member (for example, a cylinder block) 3 to seal between the two, as shown in FIG. The part is deformed into an open M shape, and a gap of only h2 is formed between the concave part of the top part and the upper pressing member. There may be a gap of only h <b> 1 between the bottom portion and the lower pressing member 3, or the bottom portion may contact the lower pressing member 3.

  The result of investigating the relationship between the gap between the upper pressing member 2 and the lower pressing member 3 and the pressing force when the bead portion is pressed by the upper pressing member 2 and the lower pressing member 3 is the conventional mere FIG. 2 shows a comparison with a bead portion having a convex shape (a semicircular cross section). As can be seen from FIG. 2, in the comparative example (conventional bead), it is greatly compressed under a low load, and is in a state close to a rigid body near the point indicated by the arrow (about 40 kN). Therefore, when tightening with a larger tightening force (compressing until it becomes narrower than the point indicated by the arrow), the bead height becomes almost zero and it is crushed, and a load cannot be collected in the bore portion. In addition, even a slight displacement greatly reduces the load. That is, the sealing performance is lowered. Therefore, it is necessary to provide a separate stopper so that the gap stops near the point indicated by the arrow.

  On the other hand, in the case of the embodiment of the present invention, it has good elasticity when tightening up to about 100 kN. Therefore, even near such a high tightening point (indicated by an arrow), the compatibility with the mating surface (strain absorption) is excellent, and as a result, variations in surface pressure are reduced.

  Further, since the rigidity becomes high at the time of restoration, the thickness (load) of the bore portion is maintained. That is, the sealing performance is maintained.

When L1 = a * t and W1 = b * t, a and b are changed as shown in Table 1 (unit: mm), and the upper pressing member 2 and the lower pressing member 3 are pressed. The result of investigating the relationship between the gap with the lower pressing member 3 and the pressing force is shown in FIG.
(Table 1)

  As can be seen from FIG. 3, in each case, a curve similar to that of the embodiment shown in FIG. 2 is obtained, and a high load (indicated by arrows) is obtained in the bead portions A to D. It can be seen that the region in which the load fluctuation during tightening continues is moderate. On the other hand, the bead of E is not sufficient although it is improved as compared with the conventional one. This is because the value of b is outside the scope of the present invention. Also, by selecting W1 and L1 appropriately from FIG. 3, various gaps and tightening load relationships can be obtained, and by controlling these, a bead plate that meets the specifications required by the engine is designed. be able to. The actual tightening force is preferably a point where the slope of the curve indicating the relationship between the gap and the tightening load changes suddenly, that is, a point indicated by an arrow.

  In general, if L1 is made too narrow, the degree of processing of the hypotenuse becomes too high, and there is a possibility that it becomes a starting point of a crack due to a processing error of the mold. On the other hand, if the width is too large, the tightening load point (point indicated by an arrow) is lowered, becoming a state close to a conventional bead, and the load (surface pressure) necessary for the gas seal cannot be secured.

Next, with a bead plate having a thickness t of 0.3 mm, L1 is kept constant at 0.53 mm, W1 is changed as shown in Table 2 (unit: mm), and pressed by the upper pressing member 2 and the lower pressing member 3 The relationship between the clearance and the tightening load was investigated. The result is shown in FIG.
(Table 2)

As can be seen from FIG. 4, for G to I, the same curve as the embodiment shown in FIG. 2 is obtained, but for F, the slope of the curve indicating the relationship between the gap and the tightening load is It can be seen that the load at the point of sudden change, that is, the point indicated by the arrow, is too high, and after this point, the state is close to a rigid state. This is because the range of b is outside the scope of the present invention.

  Thus, a range of 2.0 to 6.0 is appropriate as the range of b. If it is less than 2.0, the tightening load point becomes too high as described above, and there is a concern about indentations and cracks, and because the top cannot be well recessed (because it is difficult to become M-shaped), Adjust in consideration of the relationship with the engine. That is, by appropriately adjusting the range of b, it is possible to set an appropriate tightening load point while suppressing the possibility of indentation and cracking.

  Next, an M-shaped one having an open cross-sectional shape as shown in FIG. 5 was examined. As shown in the figure, the bead shape has a shape in which the M-shaped vertical bar portion is slanted and the top is recessed. As shown in the figure, the width between the tops of the M-shape is W1, and the length of the portion that forms the oblique rising portion of the M-shape is L1. This bead shape is such that the bottom portion of the portion that hangs down as a result of the depression of the top portion is on the top side by h from the bottom portion of the bead. Therefore, when a load is not applied by sandwiching the bead portion between the upper pressing member 2 and the lower pressing member 3, the bottom portion of the portion that hangs down as a result of the concave top portion does not contact the lower pressing member 3.

The characteristics of the M-shaped one having an open cross-sectional shape and the trapezoidal one shown in FIG. 1 were compared. For bead plates having a thickness of 0.3 mm, both W1 = 1.31 mm and L1 = 0.46 mm, and the relationship between the clearance and the tightening load when pressed by the upper pressing member 2 and the lower pressing member 3 was examined (
Note that h shown in FIG. 5 is 0.05 mm). The result is shown in FIG. As can be seen from FIG. 6, the M-shaped one with an open cross-section has a large load when the gap is wide, and the compression is suppressed, as compared with a trapezoidal cross-section. That is, thickness reduction is suppressed and a gap is maintained in the tightening load. Therefore, it can be said that the M-shaped one having an open cross section has better characteristics than the one having a trapezoidal cross section.

  In addition, it is preferable to apply the coating material to the front and back surfaces of the bead portion as described above to further improve the sealing performance. In addition, such a bead plate is not used alone as a metal gasket, but may be a metal gasket combined with a sub plate such as a height adjusting sub plate.

  Hereinafter, an example of a method for forming a bead shape as shown in FIG. 1 will be described. As shown in FIG. 7, a plate member 4 to be a bead plate is sandwiched between a female mold 5 and a male mold 6 to form a bead portion by press molding. In the figure, the width W2 of the female concave portion, the radius R1 of the curved portion between the concave portion and the flat portion, the width W3 of the male convex portion, the radius of the curved portion extending from the male flat portion to the flat portion protruding the convex portion By appropriately determining R2, W1 and L1 of the bead portion of the bead plate 1 shown in FIG. 1 can be determined. Such female mold 5 and male mold 6 can be designed by FEM analysis.

  Hereinafter, an example of a method for forming a bead shape as shown in FIG. 5 will be described. As shown in FIG. 8, a plate member 4 serving as a bead plate is sandwiched between a female die 7 and a male die 8 to form a bead portion by press molding. In the figure, the width W4 of the female concave portion, the radius R3 of the curved portion between the concave portion and the flat portion, the width W5 of the convex portion provided in the central portion of the concave portion, the local radius R4 from the concave portion to this convex portion, By appropriately determining the height h4 of the portion, the width W6 straddling the two convex portions of the male mold, the interval W7 between the two convex portions, and the radius R5 of the circular cross section protruding from the flat portion of the male mold, FIG. W1 and L1 of the bead portion of the bead plate 1 shown in FIG. Such female mold 7 and male mold 8 can be designed by FEM analysis.

It is a figure which shows the cross section of the bead shape of the metal gasket which consists of one bead board 1 which is the 1st Embodiment of this invention. It is a figure which shows the result of having investigated the relationship between the clearance gap between an upper pressing member and a lower pressing member, and the pressing force when the bead board which is an Example and comparative example of this invention is pressed with an upper pressing member and a lower pressing member. is there. It is a figure which shows the result of having investigated the relationship between the clearance gap between an upper press member and a lower press member, and pressing force when W1 and L1 are changed and it presses with an upper press member and a lower press member. It is a figure which shows the result of having investigated the relationship between a clearance gap and a fastening load when L1 is kept constant and W1 is changed and it presses with an upper pressing member and a lower pressing member. It is a figure which shows the thing of M shape with open cross-sectional shape. It is the figure which compared and showed the relationship between the clearance gap when it presses with an upper pressing member and a lower pressing member, and a clamping load with a trapezoidal thing and the open M-shaped thing. It is a figure which shows the example of the formation method of a bead shape as shown in FIG. It is a figure which shows the example of the formation method of a bead shape as shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bead board, 2 ... Upper press member, 3 ... Lower press member, 4 ... Plate material, 5 ... Female type, 6 ... Male type, 7 ... Female type, 8 ... Male type

Claims (5)

A metal gasket comprising a bead plate having a trapezoidal bead in cross-sectional shape, where the thickness of the metal gasket is t, the width W of the top of the trapezoid and the length of the portion forming the side surface of the trapezoid L is
2.0 × t ≦ W ≦ 6.0 × t
1.5 × t ≦ L ≦ 3.0 × t
Metal gasket characterized by being in the range. A metal gasket comprising a bead plate having an M-shaped bead having an open cross-sectional shape, where the thickness of the metal gasket is t, the width W between the tops of the M-shape, and the M-shaped The length L of the part that forms the oblique rising part is
2.0 × t ≦ W ≦ 6.0 × t
1.5 × t ≦ L ≦ 3.0 × t
The metal gasket is characterized in that the bottom portion of the M-shaped central portion is on the top side of the bottom portion of the bead portion. A metal gasket comprising a bead plate having a trapezoidal or open M-shaped bead, wherein the trapezoidal or open M-shaped shape is opened when the metal gasket is tightened during use. The metal is characterized in that when the tightening force is released after that, the metal is shaped so as to maintain the shape of the open M-shape with the center portion on the top side rather than the bottom portion. gasket. The metal gasket according to any one of claims 1 to 3, wherein a coating is applied to both surfaces of the bead portion. The metal gasket comprised by combining the bead board used for the metal gasket of any one of Claims 1-3, and another sub board.

Images