Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
  • F01L3/00—Lift-valve, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces; Parts or accessories thereof
  • F01L3/12—Cooling of valves
  • F01L3/14—Cooling of valves by means of a liquid or solid coolant, e.g. sodium, in a closed chamber in a valve

Definitions

• the invention relates to a hollow valve for internal combustion engines with a filling, consisting of an alkali metal from group 1 a, period 2 to 6 of the periodic system of the elements, which is liquid at least at the operating temperature of the valve, preferably consisting of sodium because of the good thermal conductivity Improved heat dissipation from the hot areas of the valve head to the cooler areas of the valve on the valve stem and on the valve seat in connection with a filler additive to set unavoidable impurities that get into the filler until the cavity is finally closed.
• a filling consisting of an alkali metal from group 1 a, period 2 to 6 of the periodic system of the elements, which is liquid at least at the operating temperature of the valve, preferably consisting of sodium because of the good thermal conductivity
• German patent 32 04 986 describes a valve of the type mentioned at the beginning, for which one of the elements zirconium, hafnium, yttrium or uranium 238 is used as a filler additive. These are getter elements which are added in the form of tablets pressed from powder. This means that impurities can be chemically bound in such a way that, surprisingly, no barrier layer is formed on the cavity walls.
• the following are known contaminants in the cavities: oil residues, moisture, air humidity, oxygen and nitrogen from the air, carbon and hydrogen as decomposition products of the cracked oil, and also hydroxide as a corrosion product of the alkali metals due to the action of moisture on the coolant, for example sodium or other alkali metals which are used as cavity filling.
• brittle carburizing layers which jeopardize the valve's fatigue strength can be produced on the cavity surface by carbon-emitting contaminants.
• the internal pressure in the valve cavity can increase due to the presence of gases such as hydrogen and nitrogen so that static preloads also impair the vibration resistance of the valve and that heat dissipation is also impaired by the impediment to the shaker effect.
• the impurities mentioned are converted into insoluble solid compounds in the presence of the getter, which preferably consists of zirconium, so that the aforementioned disadvantages for heat dissipation and the dangers for the operational strength of the valve are avoided.
• the contaminants enter into the getter chemical compounds that have vapor pressures so low that the remaining vapor pressure in the cavity of the valve corresponds to that of sodium, that is, the cavity of the valve is additionally evacuated as much as physically possible by the gettering, as a result of which the Heat dissipation is strongly promoted by the shaker effect.
• the getter technology described has been in use for more than 6 years and has proven itself functionally in accordance with expectations. So far, around 15 million sodium-filled hollow valves have been successfully saved using this technology.
• the boundary conditions for gettering hollow valves with very fine-grained and therefore also very reactive zirconium powder are therefore much more difficult than those that have to be taken into account, for example, for gettering sodium in cooling circuits of power plants or when evacuating electronic tubes or evacuating Thermos vessels, all of which, in accordance with the prior art, use zirconium or similar getter elements in metallic form, in the form of foils, grids, nets, metal sponges or coarser ground powders and pressed into shaped articles.
• the object of the invention is, contrary to the current state of the art and the underlying understanding that a pure metal must be used for gettering, to create a hollow valve of the type mentioned, the filler addition of which poses no problems when introduced into the valve, in particular with none Risk of self-ignition is associated.
• the invention as a solution to this problem is characterized in that the filling additive consists of a chemical compound of zirconium, namely zirconium tetrafluoride. Because of the close chemical relationship between hafnium and zirconium, hafnium tetrafluoride can also be considered.
• zirconium which is initially chemically bound as fluoride
• one of the other alkali metals lithium, potassium, rubidium and cesium can be used instead of sodium for the reduction of the zirconium tetrafluoride to metallic zirconium.
• sodium is clearly preferred as the heat transfer medium in hollow valves. Alloys of sodium with other alkali metals or metals of the The group of alkaline earths only has disadvantages due to the generally significant, in some cases very significant, drop in thermal conductivity.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Powder Metallurgy (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Compositions Of Oxide Ceramics (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6439918

Family Applications (1)

Country Status (4)

Family Cites Families (1)

• 1991
  • 1991-09-06 DE DE4129519A patent/DE4129519C1/de not_active Expired - Fee Related
• 1992
  • 1992-08-29 EP EP92114808A patent/EP0530720B1/de not_active Expired - Lifetime
  • 1992-08-29 DE DE59201141T patent/DE59201141D1/de not_active Expired - Fee Related
  • 1992-08-29 ES ES92114808T patent/ES2067986T3/es not_active Expired - Lifetime
  • 1992-09-07 JP JP4238128A patent/JPH05195730A/ja active Pending

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