US1727621A - Exhaust valve - Google Patents

Description

Sept. 10, 1929. TAUB 1,727,621

EXHAUST VALVE File d Feb. 18. 1928 Patented Sept. 10, 1929.

UNITED STATES PATENT OFFICE.

ALEX TAUB, OF DETROIT, MICHIGAN, ASSIGNOR TO GENERAL MOTORS CORPORATION,

' OF DETROIT, MICHIGAN, A CORPORATION OF DELAWARE.

EXHAUST VALVE.

Application filed February 18, 1928. Serial No. 255,428.

This invention relates to an internal combustion engine of the poppet valve type and more particularly to an exhaust valve.

In a conventional poppet valve engine the head of the exhaust valve seats over the exhaust opening and is carried by a stem extending across the exhaust passage and through a guide in the engine block or cylinder head. Since the temperature within the exhaust passage remains at about 14:00 to 1700 degrees F. at ordinary engine speeds, the exhaust gases have a very destructive effect on that part of the valve stem within the exhaust passage, causing corrosion or 15 pitting and producing a destructive change in the structure of the metal of the stem, which may cause the stem to lose its requisite strength, hardness and non-breaking qualities and become warped.

This difiiculty has been met in several ways, such as by making the valve stem of a special alloy steel, or by using a hollow valve-stem and providing a cooling fluid in the stem. Eachuof these methods is ex ensive and adds considerably to the cost 0 the product.

According to the present invention I provide simple and inexpensive means for protecting the valve stem from the high tem perature within the exhaust passage. I accomplish this by insulating the main portion of the stem and head within the exhaust passage from direct contact with the exhaust gases, the inclusion of a portion of the head 5 in the insulated zone being an important feature since the amount of heat absorbed by the valve stem is a function of the area exposed to the heat. While various solid non-metallic insulating media may be em- 4 ployed I find that the provision of a dead air space about the stem-connected side of the head and a portion of the stein gives satisfactory results. It is therefore a particular object of the invention to provide insulating means for a portion of the valve exposed to the high temperature of the exhaust passage so that the valve head and stem will be maintained at a lower temperature than has hitherto been practicable. By protecting the valve stem so that it will be maintained at a lower temperature,

a stem of lower grade and hence less expensive metal may {be used with satisfactory results; the expansion of the valve stem will be less and the valve clearance may be reduced, and there will be less danger of the vaive sticking as a result of overheating.

Other objects and advantages of the invention will appear in the course of the following description, taken in connection with the accompanying drawing and appended claims.

In the drawing: C J

Figure 1 is a sectional view through a portion of an internal combustion engine as including an exhaust passage, exhaust valve and associated parts.

Figures 2, 3, 4 and 5 are sectional views of exhaust valves, illustrating modified forms of my invention.

In Fig. 1 is shown a portion of an overhead-valve engine comprising a cylinder head 10 which is formed with an exhaust passage 12, water jacket 14 and valve stem guide 16; Fitted in the guide 16 is a valve stem 18 arrying a valve head 20 which is within the combustion chamber 22 and is seated in the usual manner in the opening to the exhaust passage 12. The valve is controlled in the usual manner by a coil spring 24.and a rocker arm 26, as will be understood.

The valve head 20 may be formed with a. circular undercut groove 28 on its stemconnected side. Surrounding the stem within the exhaust passage is a conoidal shroud '30 consisting of a tapered metal stamping the large end of which is spun into the groove 28. The shape of the large end of the stamping before the spinning co operation is indicated in dotted lines at 32. The shroud tapers away from'the valve head and fits the stem at a point adjacent the end of the guide 16 so that when the valve is seated, the shroud incloses tractically all the stem which is within the exhaust passage and most of the stem-connected side of the valve head.

In Fig. 2 is shown a valve comprising a head 36 anda stem 38. A circular groove 40 is formed on the stem-connected side of the valve head, and the stem is provided with a groove 42 spaced from the valve head. Surrounding the stem is a tapered shroud 44 which comprises a metal stamping the large end of which fits within the groove 40 and the small end of which is formed within an inward turned flange fitting in the groove 42. The shroud is snapped into the'position illustrated, being provided with opposite axially extending slits 46 for permitting it to be slipped along the stem until the flanged end registers with and springs into the groove 42.

In Fig. 3 is shown a valve which comprises a stem 48 f rmed with a reduced portion 50 which is t readed to receive a valve head 52, the end of the stem being *peened over at 54 for fixing the head securely on the stem. The length of the reduced portion 50 is about equal to the wldth of the exhaust passage in which the valve is designed to operate, this construction providing an annular shoulder 51 on the stem some distance from the head.

The head 52 is .formed on its stem-connected side with an annular ridge 56 having a frusto-conical outer surface fitting within the larger end of a tapered shroud 58, the opposite end of the shroud fitting the reduced portion 50 of the valve stem and abutting against the shoulder 51. The thickness of the shroud may be equal to the difference between theradii of the two parts of the stem, as illustrated, so that the shroud may be extended some distance within the valve stem guide, if desired. The shroud is a metal stamping "similar to the stampings 44 and 30 described above and may be pressed on the stem before the head, or the head may be fixed on the stem first and the small end of the shroud spun into its illustrated posi tion against the shoulder 51-.

In Fig. 4 is shown a valve comprising a stem 60 and head 62, the head being pro- .v1ded on its stem-connected side with a circular flange of malleable metal, -i ndicated in-dotted lines at 64. A shroud 68 sur-f rounds the stem with its valve head attachmg end flanged outward, as at 70, and

fitting within the flange 64.. The shroud is V fixed to the valve by spinning the flange 64 over the flange 70'of the shroud, as shown 1n full lines at 66. The opposite end of the shroud has .a reduced diameter and fits the valve stem. f I v In Fig. 5 is shown a valve comprising a stem 74 threaded to receive a head 76. The head is a casting cored out to forma web 78 fitting the stem somedistance from the .port closing portion of the head, thereby providing an inclosed space '80 at the stem-' connected side of the head. The end of the stem is peened over at 82 to hold the head securely on the stem.

In the form of my invention shown in Figs. 1, 2, 3 and 4, the metal stamping (30, 44, 58 or 68) provides an inclosed space about the stembeneath the valve head for a distance corresponding roughl width of the exhaust passage 0 the engine. The stamping thus provides a dead air space which serves to insulate from direct contact with the hot exhaust gases that portion of the stem andthe side of the valve head which are within the exhaust passage. A similar result is attained by providing the cored" out valve head shown in Fig. 5. The shroud need not provide an airtight space and should not, since the pressures inside and outside the shroud should remain equal. The stampings may be made from deep drawing stock which will retain its shape' vwhile exposed to the hot. exhaust gases.

The main feature of the constructions shown is the provision of an insulator about part of the valve stem and the exhaust port side of the valve head. Since the exhaust gases do not come into direct contact with that part of the valve which is inclosed by the shroud and since a gas is a very poor conductor of heat, nearly all the heat trans mitted to the inclosed part of the valve is b radiation from the shroud, only i a sm amount being transmitted by conduction from the ends of the shroud. The air in the inclosed air space thus constitutes a nonmetallic insulating medium that retards very considerably the passage of heat from the exhaust gases into the valve. As the valve guide is formed in a web of the cylinder head or engine block which-is-water cooled, heat is not permitted to accumulate in the valve stem but is dissipated rapidly,'and the valve stem is maintained at a much lower temperature thanit would be if the insulatin means were not provided.

ince the stem is maintained at a reduced temperature, the elongation due to heating will be less and a less valve clearance will be required, a stem of lower quality steel will be satisfacto the usual hig temperatures, and the probability of the valve stem becoming stuck in theguide will be lessened.

.I claim: Y

1-. A poppet valve comprising a stem and a head, and formed with an inclosed space at the stem-connected side of said head," and a metallic connection'between said head and stem within said inclosed space.

2. A poppet valve comprising a head and with the since it need not withstand a stem, and a shroud extending from said 4 head to a point on the stem spaced from saidvhead.

3. A poppet valve comprising a head and a stem, and a sheet metal shroud inclosing- 4. A poppet valve comprising a stem and a head, and a shroud connected With the stem-connected sideof said head and fitting said stem at a point spaced from said head.

5. In an internal combustion engine including an exhaust passage, a valve comprising a stem and a head" positioned to close said passage, and means for insulating a portion of the under side of said head from direct contact With the exhaust gases.

In testimony whereof I aflix my signature.

ALEX TAUB.

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