JP2005315416A - Metal gasket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal gasket free of setting of its foaming rubber layer at a high temperature and with high pressure, free of contraction of the foaming rubber layer at a low temperature, and capable of sealing a cylinder block in good performance even if it involves blowhole(s) or asperity on the surface. <P>SOLUTION: The metal gasket is composed of a metal sheet having an opening for cylinder, a first resilient base board of metal having an opening mating with the cylinder opening in the metal sheet, where beads are formed in the surrounding area of the opening, and furnished with an unfoamed rubber layer on each surface, a second resilient base board of metal having an opening mating with the cylinder opening in the metal sheet, where beads are formed in the surrounding area of the opening, and furnished with an unfoamed rubber layer on each surface, and a third resilient base board of metal having an opening capable of accommodating the first base board, where beads are formed in the surrounding area of the opening, and furnished with a foaming rubber layer on each surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an improvement in a metal gasket interposed between a cylinder block and a cylinder head of an internal combustion engine.

  In an internal combustion engine, a sealing function is imparted by tightening a joint surface between a cylinder block and a cylinder head with a metal gasket interposed therebetween. In particular, the seal in the region surrounding the cylinder opening is important. If the seal in this portion is insufficient, the pressure in the combustion chamber is reduced and overheating appears. Therefore, the present applicant has previously made a metal thin plate having an opening corresponding to the cylinder opening between a pair of elastic metal substrates having a bead concentric with the opening for the cylinder as a metal gasket with higher sealing performance. The metal gasket of the structure laminated | stacked by arranging is proposed (for example, refer patent document 1). In this metal gasket, the sealing function of the peripheral portion surrounding the cylinder opening is enhanced by utilizing the repulsive force of the bead generated when the metal gasket is tightened. However, in the surface of the cylinder block or cylinder head, a cast hole (a fine concave portion on the surface based on bubbles at the time of casting; see FIG. 3) is often formed or the surface is rough. It may be impossible to sufficiently follow the nest or rough surface, which may reduce the sealing performance. Further, there is a metal gasket in which an unfoamed rubber layer is formed on an elastic metal substrate, but there is a risk that the sealing performance may be lowered due to a cast hole or a rough surface.

  On the other hand, a foamed rubber layer is formed on the surface of a metal gasket to improve sealing performance (see, for example, Patent Document 2 and Patent Document 3). However, the conventional foamed rubber layer is generally excellent when there is a cast hole of φ1.5 mm or less on the seal surface or when the surface roughness is 12.5 Ra (10-point average roughness according to JIS B0601-1994) or less. However, it may not be possible to secure sufficient sealing performance. Further, in order to form a foamed rubber layer, generally, if the rubber layer before foaming (unfoamed rubber layer) has a thickness of about 70 μm or more, it is difficult to foam (particularly, the foaming ratio is twice or more). . The expansion ratio is the ratio of the thickness of the rubber layer after foaming to the thickness of the rubber layer before foaming. Moreover, since the rubber layer before foaming is thick, the foamed rubber layer sags under high temperature and high pressure, and the axial force of the bolt decreases. Furthermore, in order to obtain a foamed rubber layer, there are generally a microcapsule method and a thermal decomposition method using a chemical foaming agent. However, since the foamed rubber layer obtained by the microcapsule method has a low foaming ratio, The effect is small, and most of the foamed rubber layer is closed-celled (bubbles with independent foamed cells), so the closed-cell shrinkage occurs at low temperature (under minus temperature), causing a decrease in the axial force of the bolt, and sealing. When the surface pressure is low, the foamed rubber layer is not completely immersed, so that there is a problem that the foamed rubber layer falls during use and the bolts relieve stress. In addition, since the temperature around the cylinder opening is considerably high, the foamed rubber layer may be thermally deteriorated relatively early to cause a decrease in sealing performance.

JP 2003-287135 A Japanese Utility Model Publication No. 5-86070 Japanese Utility Model Publication No. 6-32836

  The present invention has been made in view of the above problems, and there is no settling of the foamed rubber layer under high temperature and high pressure, and there is no shrinkage of the foamed rubber layer at low temperature, and the cast block and the rough cylinder block However, an object is to provide a metal gasket that can seal well.

In order to achieve the above object, the present invention provides the following metal gasket.
(1) In a metal gasket that is interposed between a cylinder head and a cylinder block and seals between both surfaces,
A thin metal plate having a cylinder opening;
A first elastic metal substrate having an opening corresponding to the cylinder opening of the thin metal plate, a bead formed around the opening, and an unfoamed rubber layer formed on both sides;
A second elastic metal substrate having an opening corresponding to the cylinder opening of the thin metal plate, a bead formed around the opening, and an unfoamed rubber layer formed on both sides;
And a third elastic metal substrate having an opening capable of accommodating the first elastic metal substrate, a bead formed around the opening, and a foam rubber layer formed on both sides. ,
The metal thin plate is disposed and laminated between the first elastic metal substrate and the second elastic metal substrate, and the first elastic metal substrate is connected to the third elastic metal via a connecting member. A metal gasket characterized by being fixed to a metal substrate at a plurality of locations.
(2) The foamed rubber layer of the third elastic metal substrate is a foamed rubber layer having a rubber layer thickness of 15 to 50 μm before foaming and foamed at a foaming ratio of 2 to 4 times. (1) The metal gasket according to the above.
(3) A rubber compound in which the foamed rubber layer of the third elastic metal substrate contains 20 to 70% by mass of a polymer having a Mooney value of 10 to 70 and 20 to 60% by mass of a thermal decomposition type chemical foaming agent. The metal gasket according to (1) or (2), wherein the metal gasket is foamed and 80% or more of the foamed rubber layer is open-celled. The open cell is a bubble in which foam cells are continuously connected.

  The metal gasket of the present invention does not have a foamed rubber layer settling under high temperature and high pressure, does not shrink the foamed rubber layer at low temperature, and can seal well even in a cast block or a cylinder block with rough surface roughness.

  Hereinafter, the present invention will be described in detail.

  FIG. 1 is a partially broken top view showing an embodiment of the metal gasket of the present invention, and FIG. 2 is a sectional view taken along line XX of FIG. As shown in the drawing, the metal gasket of the present invention is formed by laminating a metal thin plate B having a cylinder opening 1 between a first elastic metal substrate A1 and a second elastic metal substrate A2, Further, in the plurality of connecting portions C, the first elastic metal substrate A1 and the third elastic metal substrate A3 are fixed by mechanical connecting members 8 such as eyelets and rivets. When the metal gasket is mounted, the second elastic metal substrate A2 is disposed on the cylinder head side, and the third elastic gasket A3 is disposed on the cylinder block side.

  The metal thin plate B has a planar shape in which a ring having an opening corresponding to the cylinder opening 1 is connected. The first elastic metal substrate A1 has an opening corresponding to the cylinder opening 1 of the metal thin plate B, a bead 2 is formed around the opening, and an unfoamed rubber layer 11 is formed on both sides thereof. . The second elastic metal substrate A2 has an opening corresponding to the cylinder opening 1 of the metal thin plate B, two beads are formed around the opening, and an unfoamed rubber layer 11 is formed on both sides thereof. . The third elastic metal substrate A3 has an opening corresponding to the outside of the cylinder opening 1 of the second elastic metal substrate A2, a bead is formed around the opening, and a foam rubber layer 10 is formed on both sides thereof. Has been.

  The rubber compound forming the foamed rubber layer 10 provided on the third elastic metal substrate A3 is preferably blended with a polymer having a Mooney value of 10 to 70 in a proportion of 20 to 70% by mass of the total amount of the rubber compound. . More preferably, the Mooney value is 20 to 60, and the blending amount is 20 to 60% by mass of the total amount of the rubber compound. By blending such a polymer, it is possible to effectively suppress the sag of the foamed rubber layer 10.

  The type of polymer is not limited as long as the Mooney value is in the above range, and NBR, HNBR, fluororubber, EPDM, acrylic rubber, etc. that have been used for gaskets laminated with rubber layers can be used. NBR, HNBR Fluorine rubber is preferably used. Moreover, in order to give oil resistance to NBR, it is preferable to use an AN value (content of acrylonitrile group in NBR) of 39 to 52, more preferably 40 to 48.

  The rubber compound is blended with a heat decomposable foaming agent. The kind of the heat decomposable foaming agent is not limited, but a foaming temperature of 120 ° C. or higher is preferable. Furthermore, the thing of 150-210 degreeC is the best. Moreover, it is preferable to mix | blend the compounding quantity in the ratio of 20-60 mass% of rubber compound whole quantity, More preferably, it is 15-35 mass%.

  Moreover, a vulcanizing agent and a vulcanization accelerator are added to the rubber compound. The vulcanizing agent is preferably blended in a large amount so as to increase the vulcanization density. In the case of sulfur vulcanization, it is preferably used at 1.5 to 4.5 phr. As the vulcanization accelerator, it is preferable to use a high-speed vulcanization accelerator that rises within 4 minutes until T50 in the curast data (150 ° C.). The time to T50 in the curast data (150 ° C.) is the time required for the degree of rubber vulcanization to reach T50 when vulcanized at 150 ° C. using a curast tester.

  The above rubber compound is dissolved in an organic solvent to form a coating solution, which is applied to the elastic metal substrate A2. The organic solvent is not limited as long as it can dissolve the above rubber compound, but 10 to 90% by mass of the ester solvent with respect to 10 to 90% by mass of an aromatic hydrocarbon solvent (such as ketone) such as toluene. What mixed in the ratio of -90 mass% can be illustrated. And said rubber compound is melt | dissolved in this organic solvent so that it may become solid content concentration 10-60 mass%.

  Although there is no restriction | limiting in the application | coating method of the coating liquid containing a rubber compound, The method which can control application | coating thickness is preferable and a skimmer coater, a roll coater, etc. are suitable. The coating thickness is 15 to 50 μm, and then the foaming agent is foamed by heat treatment at about 150 to 240 ° C. for 5 to 15 minutes to form a foamed rubber layer. At this time, the foaming ratio of the foamed rubber layer to be obtained is 2 to 4 times, and the foaming conditions such as the vulcanizing agent, the foaming agent, and the heating time to be used are adjusted so that 80% or more is open-celled. In order to freely change the expansion ratio to 2 to 4 times, it can be achieved by blending the polymer having the Mooney value described above, the vulcanizing agent and the foaming agent described above, and in particular, This expansion ratio depends on the Mooney value of the polymer and the vulcanization rate. This is because when the Mooney value of the polymer is low, the deformation of the polymer due to the foaming gas increases, and conversely, when the Mooney value is high, the deformation of the polymer due to the foaming gas decreases. With regard to the vulcanization speed, if the speed is high, vulcanization proceeds before the polymer expands and deforms by the foaming gas, so that the expansion ratio can be suppressed. Conversely, if the vulcanization rate is low, the foaming ratio increases because the deformation of the polymer by the foaming gas has priority over the curing rate of the rubber by vulcanization. For example, a polymer having a Mooney value of 20 to 40, a slow vulcanization accelerator (curast data: rise time to T50 by vulcanization at 150 ° C. of about 5 to 6 minutes), a foaming agent having a low foaming decomposition temperature, When combined, the expansion ratio becomes large, and conversely, a polymer having a Mooney value of 40 to 60 and a vulcanization accelerator with a fast vulcanization rate (curast data: rise time to T50 with vulcanization at 150 ° C. is about 1 to 3 minutes. ) And a foaming agent having a high foaming decomposition temperature, the foaming ratio is reduced. Thus, the expansion ratio can be freely controlled by the combination of the polymer, the vulcanization accelerator and the foaming agent.

  Such a foamed rubber layer 10 is prevented from sagging even under high temperature and high pressure, and maintains a good sealing property over a long period of time. In addition, sufficient sealing performance can be maintained even when there is a cast hole exceeding φ1.5 mm on the surface of the cylinder block or the surface roughness exceeds 12.5 Ra.

  Since the third elastic metal substrate A3 and the first elastic metal substrate A1 are point contact by the connecting member 8, the amount of heat transferred from the cylinder opening 1 is small, and further, the third elastic metal substrate A3 is connected to the third elastic metal substrate A3. Since the holes through which the cooling water flows are opened, the cooling effect also contributes, so that the foamed rubber layer 10 is not thermally deteriorated. In addition, the first elastic metal substrate A1 and the second elastic metal substrate A2 are formed with a cylinder opening 1 and are exposed to a high temperature. However, the unfoamed rubber layer 11 has high heat resistance, so that there is no practical use. No problem. Although there is no restriction | limiting in the non-foamed rubber layer 11 in this invention, It is preferable to use the thing excellent in heat resistance for such a reason.

  In the present invention, although not shown, it is preferable to form the bent portions of the beads of the elastic metal substrates A1 and A2 so as to start from a curved portion having a radius of curvature (R) of 0.5 mm or more. A cast hole is often formed on the surface of the cylinder head or cylinder block (see FIG. 3), and there is a large cast hole exceeding φ1.5 mm. If the bent part of the bead is bent in a straight line and a corner is formed, the sealing performance deteriorates due to the gap between the corner and the cast hole. The seal is secured by elastic deformation so as to cover. Such a curved portion is effective in that the contact width with the cylinder head or the cylinder block surface obtained under the same tightening condition can be increased by 1.5 to 20 times or more compared to the conventional gasket. The general elastic metal substrates A1 and A2 are made of stainless steel plate having a thickness of 0.2 to 0.3 mm, and in order to reliably cover a cast hole exceeding φ1.5 mm by elastic deformation, a curved shape is used. The curvature radius (R) of the starting point is 0.5 mm or more, preferably 1.5 mm or more. Such a bent portion C can be easily formed by bending while applying R. The curved portion of the bead and the foamed rubber layer combine to provide a further sealing effect with respect to a cylinder block or a cylinder head having a rough cast hole or a rough surface. Moreover, the metal thin plate B is preferably made of stainless steel, and the thickness is preferably 0.05 to 0.15 mm.

  Examples The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereto.

(Examples 1-3, Comparative Examples 1-7)
[Preparation of sample]
As shown in Table 1, a rubber compound containing a polymer and a foaming agent was dissolved in a mixed organic solvent of toluene and ethyl acetate so as to have a solid concentration of 40% by mass to prepare a coating solution. And the primer process was performed to the stainless steel plate which carried out the non-chromium treatment, and after apply | coating the coating liquid with a roll coater (application thickness is as Table 1), it heat-processed for 10 minutes at 210 degreeC, and obtained the sample. Each sample was evaluated as follows.

[Evaluation methods]
1. Foaming ratio For measuring the foaming ratio, the thickness of the rubber layer before foaming and the thickness of the rubber layer after foaming were measured with a micrometer, and the foaming ratio was calculated from the following formula.

2. Measurement of open cell ratio A sample is immersed in water and vacuum degassed to replace water in the foam rubber layer cell. The test was performed until the weight after substitution in water was constant, and the open cell ratio was calculated from the following formula.

3. Heat-resistant flow property The sample was allowed to stand under conditions of a surface pressure of 100 MPa and 150 ° C. × 22 Hr, and the appearance of the sample after the test was observed with a microscope and evaluated according to the following criteria.
Evaluation criteria ○: No rubber flow ×: With rubber flow

4). Torque down rate Each sample was subjected to the following test to evaluate the torque down rate.
(1) The sample was set on the flange, the bolt was tightened with a torque wrench, and the torque value (initial torque value) when tightened was measured.
(2) The sample was cooled to −35 ° C. in the state of (1). In that state, markings were made on the contact surfaces of the bolt and flange, and the bolt was removed.
(3) The bolt was tightened to the marking part again using a torque wrench, and the torque value at that time (torque value when cooled to -35 ° C.) was measured.
Further, the initial torque value (normal temperature) of the sample was compared with the torque value when cooled to -35 ° C., and the torque down rate was calculated from the following equation.

5). Seal Test Using Examples 1 to 10, gaskets of Examples 1 to 3 and Comparative Examples 1 to 7 having the shapes shown in Table 2 below were created. Each gasket was incorporated in the flange shown in Table 2 and evaluated as follows.
Cast hole seal test (1) As shown in FIG. 3, the sample was processed into a half bead shape having a height of 0.2 mm × width of 1.5 mm and a center diameter of the half bead of φ51.5 mm to form a gasket. It is assembled to a flange provided with a nest (φ2.5 mm × depth 2.5 mm) so that the cast hole is positioned at the half bead center, and tightened under the condition of a bead linear pressure of 10 N / mm.
(2) In the state of (1), air (200 KPa) was sent from the nozzle at the center of the flange, and the amount of leakage was measured.
・ Surface roughness seal test (1) The sample was processed into a half bead shape with a height of 0.2 mm × width of 1.5 mm and a half bead center diameter of φ51.5 mm to form a gasket, which was used as a flange with a surface roughness of 50 Ra. Then, the cast hole is assembled so that the position of the casting hole is φ51.5, and tightened under the condition of a bead linear pressure of 10 N / mm.
(2) In the state of (1), air (200 KPa) was sent from the nozzle at the center of the flange, and the amount of leakage was measured.

  The results of the above measurements and tests are summarized in Table 3. In the evaluation of each seal test, “◯” indicates that there is no air leak, and “X” indicates that there is an air leak.

  From Table 3, it can be seen that the sample of the example having the foamed rubber layer according to the present invention gives good results for any of heat-resistant flow, torque-down rate, and seal test. On the other hand, the sample of Comparative Example 1 in which the rubber layer thickness before foaming is excessive has poor heat resistance flow properties, and the torque down rate is slightly inferior. Since the sample of Comparative Example 2 used a microcapsule-type foaming agent, the open cell rate was low and the torque down rate was also inferior. The sample of Comparative Example 3 having an excessive Mooney value has a low expansion ratio and inferior sealing performance. The sample of Comparative Example 4 having an excessively small amount of foaming agent also has a low foaming ratio and is inferior in sea performance. The sample of Comparative Example 5 having an excessively small amount of polymer has a low open cell ratio, inferior heat-resistant flow properties, and the largest torque-down rate. Since the sample of Comparative Example 6 uses a microcapsule type foaming agent and the rubber layer before foaming is excessive, the foaming ratio and the open cell ratio are the lowest and the sealing performance is poor. Since the sample of Comparative Example 7 does not use a foaming agent, it has poor sealing properties.

It is a top view which shows one Embodiment of the metal gasket of this invention. It is XX sectional drawing of FIG. It is a schematic diagram for demonstrating the test method of the cast hole seal test implemented in the Example.

Explanation of symbols

A1 1st elastic metal substrate A2 2nd elastic metal substrate A3 3rd elastic metal substrate B Metal thin plate C Fixed part 1 Cylinder opening 2 Bead 3 Opening part 6 Fixed part 8 Connecting member 10 Foam rubber layer 11 Unfoamed rubber layer

Claims (3)

In a metal gasket that is interposed between the cylinder head and the cylinder block and seals between both sides,
A thin metal plate having a cylinder opening;
A first elastic metal substrate having an opening corresponding to the cylinder opening of the metal thin plate, a bead formed around the opening, and an unfoamed rubber layer formed on both sides;
A second elastic metal substrate having an opening corresponding to the cylinder opening of the thin metal plate, a bead formed around the opening, and an unfoamed rubber layer formed on both sides;
And a third elastic metal substrate having an opening capable of accommodating the first elastic metal substrate, a bead formed around the opening, and a foam rubber layer formed on both sides. ,
The metal thin plate is disposed and laminated between the first elastic metal substrate and the second elastic metal substrate, and the first elastic metal substrate is connected to the third elastic member via a connecting member. A metal gasket characterized by being fixed to a metal substrate at a plurality of locations.   2. The foamed rubber layer of the third elastic metal substrate is a foamed rubber layer having a rubber layer thickness of 15 to 50 [mu] m before foaming and foamed at a foaming ratio of 2 to 4 times. Metal gasket.   The foamed rubber layer of the third elastic metal substrate foams a rubber compound containing 20 to 70% by mass of a polymer having a Mooney value of 10 to 70 and 20 to 60% by mass of a thermal decomposition type chemical foaming agent. The metal gasket according to claim 1, wherein 80% or more of the foamed rubber layer is open-celled.

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