MXPA98002782A - Packing resistant to the excoriac - Google Patents

Abstract

A cylinder head gasket of the present invention includes a main body of the gasket and a generally U-shaped metal flange that couples the internal periphery of an opening of the combustion orifice, formed in the main body of the gasket. A coating that includes tetrafluoroethylene and a high temperature resin bond such as a polyamide to a polyamide-imide polymer is applied to at least the flange after it is formed and the entire package is then cured at high temperatures in a series of stages including sintering to securely bind the coating to the flange. An optional plate layer disposed between the liner and the base material of the additional flange to the ligadu

Description

PACKING RESISTANT TO EXCURSION FIELD OF THE INVENTION The present invention relates generally to the manufacture of a motor cylinder head gasket. More particularly, the invention relates to a package with improved abrasion resistance to reduce the possibility of flange cracking.

BACKGROUND OF THE INVENTION Packs are often used as a seal between matching mechanical components.

A common application involves placing the packing between the engine block and the cylinder head of an internal combustion engine. The block of. The motor and cylinder head are bolted and the packing depends on the strength of the connection by bolts to seal the various openings between the two matching components. In particular, cylinder head gaskets typically extend around cylinder bores to provide a combustion seal, keeping the high temperature combustion gases within the bores of the cylinder. Simultaneously, the packages also seal the fluid flow openings such as the oil and cooler openings to avoid undesirable mixes. Typically, a cylinder head gasket includes a main body of the gasket with an opening in the cylinder bore, whose periphery is surrounded by a generally metal U-shaped flange. The flange engages both the upper surface and the lower surface of the main body of the package. The flange provides improved protection to the package body from the high-temperature combustion gases and serves to dissipate the heat of combustion in the package body and out of the opening of the cylinder bore. In some applications, the main body of the packaging is metallic. However, a main body of the package that is metallic has a limited thermal conductivity. In this way, the use of mixed materials with improved thermal conductivity is known. However, many of these mixed materials have a reduced capacity to withstand the shear stresses and deformations induced by the bolted connection of the matching components. Even, the flange depends on the main body of the packaging for support. As a result, the flange is subject to increased dynamic shear stresses induced through the use of a composite main body formed of mixed materials and may fail over time in a commonly known form of fatigue failure of the combustion seal, "cracking". eyelash". A cracked, insulated flange does not necessarily result in a failure of the combustion seal. However, if the cracking is long enough to allow the mixed material of the main body of the gasket to be extruded, the likelihood of loss of the sealing shear stress and an explosion of the cylinder head gasket greatly increases. The phenomenon of flange cracking has been a particular concern with the main bodies of mixed packing based on graphite. Graphite has been an optimal material for use in a variety of mixed head package designs. It includes improved conformability, heat resistance and relaxation properties when compared to other asbestos replacement materials. It even has a very low shear strength which allows the thermally induced lateral movement of the cylinder head and the motor block to drag the flange laterally forward and backward. In addition, the graphite also includes a relatively low spring rate that can allow greater dynamic lift deflections at the opening of the cylinder bore. Unfortunately, the low spring regime remains almost constant even after prolonged exposure to heat. Therefore, dynamic fatigue can not decrease over time. The prior art methods for converting flange cracking, have typically focused on the base material of the metal flange. In particular, it is known that the fatigue strength of the flange can be increased by changing the base material of a low carbon steel to a stainless steel. Despite the sacrifice in cost associated with the use of a stainless steel flange, experience has shown that flange cracking is not completely eliminated. Low-friction coatings, typically based on moly and Teflon®, applied to the surface of the flange sporadically have represented an attempt in the past with limited success. It was believed that such coating would help reduce the shear stresses. However, known coatings are applied to the base material of the flange before the flange is formed into its final configuration. As a result, the lining must be smooth or have the ability to be formed to withstand the process of forming the flange. The use of the coatings with a capacity to be formed reduces the resistance to chafing in the long term and the coatings eventually break. Therefore, the flange cracking is postponed but not eliminated.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to a package that includes a main packing body with an upper and lower surface, and a generally U-shaped metal flange with an external surface that couples the internal periphery of an opening of the combustion orifice, formed in the body of the main package. The flange includes opposed ends separated by a central section disposed within the fluid flow opening, an upper end that couples the upper surface of the main body and a lower end that engages the lower surface of the main body of the package. A coating that includes a tetrafluoroethylene and a high temperature resin bond such as a polyamide-imide or polyamide resin bond is applied around the outer surface of the U-shaped flange after the flange has been formed and attached to the main body of the package and has been cured. In such circumstances a polyamide resin bond can also be used. Preferably, the coating is of the Teflon-S® 958 Series or the 1000 Series of Xylan® resin-bonded lubricants. The resulting coating is extremely hard and non-formable. The Healing process includes intermittent drying of the coating for about two and five minutes at a metal temperature of between about 93 and 121 ° C (200 and 250 ° F). After intermittent drying, the coating is sintered at a metal temperature rate of between about 343 and 399 ° C (650 and 750 ° F) for five to fifteen minutes. The coating significantly reduces the dynamic shear stresses and the possibility of fatigue cracking of the flange when compared even with the flanges having formable moly and Teflon®-based coatings such as molybdenum disulfide. Due to the curing temperatures, however, a main body of the graphite-based package is preferred despite the very low shear strength and low spring rate that promotes cracking in prior packing designs. Also preferred is a plate layer formed primarily of nickel disposed between the outer surface of the flange and the liner as it promotes ligation of the liner to the lug.

BRIEF DESCRIPTION OF THE DRAWINGS The aspects and inventive features of the present invention will be more apparent after reading the following detailed description, the claims and the drawings of which the following is a brief description: Figure 1 is a plan view of a head gasket. cylinder according to the following invention. Figure 2 is a partial cross-sectional view of the package, showing an optional plate layer that is applied to the flange before being formed in its operative form. Figure 3 is a partial cross-sectional view of the package along lines 3-3 in Figure 1 showing the package after the final coating has been applied to the flange to at least a portion of the main body of the package. packing. Figure 4 illustrates the process for applying the coating illustrated in Figure 3.

DETAILED DESCRIPTION OF A PREFERRED MODALITY As illustrated in Figure 1, the present invention is directed to a cylinder head gasket 20 having a main body 22, and a plurality of fluid flow openings, the openings including the combustion orifice openings 24. A generally U-shaped flange 26 is received within an opening 24 and disposed around an internal periphery 28. The gasket 20 is used as a seal between an engine block and the cylinder head of an internal combustion engine. The motor block and cylinder head are bolted together. The package 20 depends on the strength of the connection by bolts to seal the various openings between the two matching components. The relationship between the flange 26 and the main body 22 is best illustrated in Figure 2. The main body 22 includes an upper face 30 and a lower face 32. The U-shaped flange 26 has an outer surface 34 and the ends 36, 38 opposite, separated by a central section 40. The end 36 engages the face 30 and the end 38 engages the lower face 32. The central section 40 is generally arcuate and extends radially inwardly in the opening 24 away from the periphery 28. The flange 26 provides improved protection to the main body 22 against high temperature combustion gases and serves to dissipate the heat of the combustion. combustion in the main body 22 and outside the opening 24 of the cylinder bore. Preferably, the main body 22 is formed of a mixed material of improved thermal conductivity when compared to a component that is only metallic. A plurality of optional metal pins 42 are disposed within the main body 22. In a more preferred embodiment, as discussed below with greater amplitude, the main body 22 is formed of graphite. In Figure 2, the outer surface 40 of the flange 26 includes an optional plate layer 44. The preferred plate layer 44 is predominantly nickel, in particular when the main body 22 is formed of graphite. The layer 44 protects the inside of the flange 26 from the corrosive elements found in the graphite such as chlorine and sulfur. As shown in Figure 3, the package 20 includes an outer casing 46 disposed around the outer surface 40 and in contact by optional engagement with the surfaces 30 and 32 of the main body. The coating 46 includes tetrafluoroethylene and a high temperature resin bond. Preferred leagues include either a polyamide-imide polymer or a polyamide. Under certain circumstances a polyamide polymer can be used. A more preferred coating 46 is formed of the Teflon-S® Series 958 or Series 1000 of Xylan® resin-bonded lubricant. The coating 46 is formed as shown in Figure 4. First, the package 20 is previously dried as shown at point 48 for between about two and five minutes at a metal temperature of between about 343 and 371 ° C ( 650 and 750 ° F). Typically, the higher the temperature, the shorter the time required. Then, the coating 46 is applied to the outer surface 34 of the flange 26 as shown at point 50, including at least the outer surface 34 of the flange 26, by means of roller coating, curtain coating, printing by sieve or spray.

Preferably, the coating 46 has a dry film thickness of between 0.00127 and 0.00381cm (0.0005 and 0.0015 inches). The package 20 is then cured. The curing process optionally includes intermittent drying of the coating as shown at point 52 for between about two and five minutes at a metal temperature of between about 93 and 121 ° C (200 and 250 ° C). ° F). Then at point 54, the coating 46 is sintered at a metal temperature of between 343 and 399 ° C (650 and 750 ° F) for a time of between five and fifteen minutes. Typically, the higher the temperature, the shorter the sintering time will be required. Once cured, the coating 46 is extremely hard and non-formable. The coating 46 provides numerous unexpected benefits. It significantly reduces the dynamic constant efforts of the flange 26. The flange 26 can be formed of low carbon steels and even ultra-low steels, as opposed to the more expensive stainless steels. However, not only constant dynamic efforts are reduced. The tests show that the fatigue life is improved by a factor of at least 10 minutes with the coating 46 compared to the uncoated flanges when subjected to cyclic stresses only in 1-vertical direction. The tests show an improvement in fatigue life of at least eight times with coating 46 compared to flanges having formable moly and Teflon®-based coatings, such as mol ibdene disulfide. The foregoing has been taught apart from the application of a coating that includes a tet raf luoroetilene resin and a high temperature resin bond such as a polyamide or a polylamide-imide polymer to a finished package, due to the damage that typically results from the high temperature coating discussed above. For example, sintering should be effected at a minimum metal temperature of about 343 ° C (650 ° F) to provide the necessary chemical bond between the cladding and the substrate of the flange 26 or the plate layer 44. Lower temperatures have not delivered the required performance. Preferably, the temperature of the metal is about 399 ° C (750 ° F) which is substantially higher than the maximum recommended metal temperature of 343 ° C (650 ° F) for such coatings. However, the evidence suggests that it is preferable to raise the temperature well beyond - 399 ° C (750 ° F), without compromising the ligation characteristics of the lining in the lining. Even at about 399 ° C (750 ° F) virtually all mixed materials, except a main body 22 formed of graphite are well above their temperature limit. However, it has been found that graphite has such significant resistance to heat that it is completely unaffected by the high sintering temperature. Therefore, graphite is a preferred material for the present invention, in spite of its very low resistance to shear stresses and the low spring rate that promotes the cracking of flanges in prior package designs. In addition, the application of the coating 46 directly to a main graphite body 22 as part of the coating process has not resulted in any harmful side effects. The technique also teaches the inventive use of coating 46 due to the temperatures at which the coating itself is subjected during operation. The technique teaches that a coating containing a tetrafluoroethylene resin and a high temperature resin bond can withstand a maximum use temperature of about 260 ° C (500 ° F). Supposedly, abrasion resistance is reduced at temperatures above 205 ° C (400 ° F). However, tab 26 is routinely subjected to combustion orifice temperatures in an excess of 427 ° C (800 ° F), significantly beyond the maximum usage temperature., but still provides the unexpected results discussed earlier. Finally, as mentioned in the foregoing, the plate layer 44 is optionally applied to provide corrosion resistance. However, it follows that in the application of the plate layer 44 to the external surface 34 of the flange 26, particularly when it is nickel, it significantly aids the ligation of the coating 46 to the flange 26. The performance characteristics Enhanced annotated above include the use of layer 44 of nickel-based plate. The embodiments and examples described to illustrate the present invention are provided. However, they are not intended to limit the scope and spirit of the present invention. Therefore, the present invention should be limited only by the appended claims.

Claims (21)

1. A cylinder head gasket comprising: a main packaging body having an upper face and a lower face, the main body includes a fluid flow opening defined by a periphery of such a main packaging body; a metal tab generally U-shaped with an external surface, the flange having opposite ends separated by a central section disposed within the fluid flow opening, an upper end engaging the upper face and a lower extremity coupling the lower face with the central section, the opening extending radially away from the periphery; a coating around such an outer surface of the U-shaped flange, such coating includes tetrafluoroethylene and a high temperature resin bond.

2. A package as claimed in claim 1, wherein the high temperature resin bond of such a coating is one of a polyamide, a polyamide and a polyamide-imide polymer.

3. The package as recited in claim 2, wherein the coating is from the 958 Series of Teflon-S® and. Series 1000 of lubricant bound by Xylan® resin.

4. The package as recited in claim 2, wherein the coating application includes the steps of: applying the coating to the U-shaped flange; intermittently drying the coating after the application step; and sintering the coating after the intermittent drying step at a minimum metal temperature of about 343 ° C (650 ° F) for a minimum time of about five minutes.

5. The package as recited in claim 4 ° C, wherein the sintering step has a maximum metal temperature of about 399 ° C (750 ° F) and a maximum time of about fifteen minutes.

6. The package as recited in claim 5, wherein the coating has a dry film thickness of between 0.00127 and 0.00381 cm (0.0005 and 0.0015 inches).

7. The package as recited in claim 6, wherein the application step comprises roller coating, curtain coating, screen printing and spraying.

8. The package as recited in claim 7, wherein the step of intermittent drying is between two and five minutes and between about 93 and 121 ° C (200 and 250 ° C).

The package as recited in claim 8, wherein said coating step includes a pre-drying step before the application step, the pre-drying step is performed between about two and five minutes and between about 343 and 371 ° C (650 and 700 ° C).

10. The package as recited in claim 2, wherein the plate layer is disposed between the flange and the liner.

11. The package as recited in claim 10, wherein the plate layer is applied to the base material of the flange before the material is formed into a U-shaped flange.

12. The package as recited in claim 10, wherein the plate layer is predominantly nickel.

13. The package as recited in claim 2, wherein the coating is applied around the outer surface of the flange directly to the main body of the package.

14. The package as recited in claim 1, wherein the main body of the package is a mixed material that predominantly includes graphite.

15. A cylinder head gasket comprising: a main body of the gasket formed predominantly of graphite having an upper face and a lower face, the main skin includes a fluid flow opening defined by a periphery of the body main body; a metal tab generally U-shaped with an external surface, the flange having opposite ends separated by a central section disposed within the fluid flow opening, an upper end that couples the upper face and a lower end that couples the lower face with the central section extending radially in the opening away from the periphery, - a coating applied around the external surface of the U-shaped flange after that the flange engages the main body of the package so that the coating engages at least a portion of both the upper and lower face of the main body of the package and has a dry film thickness of between 0.00127 and 0.00381 cm (0.0005 and 0.0015 inches), the coating includes a high temperature polyamide and one of a high temperature polyamide, polyamide and a polyamideimide resin bond, wherein the coating application includes the coating application steps. to the U-shaped flange by roller coating, curtain coating, screen printing and ion spray, intermittent drying of the coating after the application step for approximately two and five minutes and with a metal temperature of approximately 93 and 121 ° C (200 and 250 ° C), and sintering the coating after the intermittent drying step on a metal temperature scale of between about 343 and 399 ° C (650 and 750 ° F) for a time of between about five and fifteen minutes.

16. The package as recited in claim 15, wherein the plate layer is disposed between the flange and the liner.

17. The package as recited in claim 16, wherein the plate layer comprises predominantly nickel and is applied to the base material of the flange before the base material is formed into the U-shaped flange.

18. The package as recited in claim 15, wherein the coating is one of the Teflon-S® 958 Series and the 1000 Series of lubricant bound by Xylan® resin.

19. A package formed by the process of: making a predominantly graphite packing main body having an upper face and a lower face, the main body includes a fluid flow opening defined by a periphery of the main body of the package; formation of a metal material to a flange generally U-shaped with an external surface, the flange has opposite ends separated by a central section disposed within the fluid flow opening, an upper end coupled to the upper face and a lower extremity coupled to the lower face with the central section extending radially in the opening away from the periphery; application of a coating around the outer surface of the U-shaped flange after the flange engages the main body of the package so that the coating has a dry film thickness of between 0.00127 and 0.00381 cm (0.0005 and 0.0015 inches) ), the liner includes a high-temperature polyethylene and one of a high-temperature polyamide, polyamide and a polyamide-imide resin linkage; intermittently drying the coating after the application step for between about five minutes at a metal temperature of between about 93 and 121 ° C (200 and 250 ° F); and sintering the coating after the intermittent drying step at a metal temperature scale of between about (343 and 399 ° C (650 and 750 ° F).

20. The package formed by the process recited in claim 19 includes coating the outer surface of the flange material prior to the forming step.

21. The package formed by the process recited in claim 20, wherein the coating comprises predominantly nickel.