JPS6336403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust valve for an internal combustion engine, the exhaust valve comprising a stationary valve part and an axially movable part, a cooperating seating surface on said valve part, and at least one of said valve parts.
The valve includes an annular chamber formed in and passing through the combustion chamber of the engine cylinder when the valve is closed. Upstream of this cooperating seating surface, the opposing surfaces are spaced apart and form a narrow annular gap when the valve is closed.

The object of the present invention is to obtain an extended life of the valve by reducing the rate at which the seating surface of the valve becomes progressively fouled by corrosive and corrosive attack by noxious components present in the exhaust gases. These components are particularly sodium and vanadium, which occur when the engine is operating on heavy fuel oil.

It is well known that the erosiveness of these components increases rapidly with increasing temperature, and on the basis of this knowledge direct or indirect air cooling of the seating surfaces should be provided and static valve sections, if present. has been proposed as an adjunct to liquid cooling.

In this regard, a valve of the above type is disclosed in US Pat. communicates with the combustion chamber through a bore opening adjacent the edge of the combustion chamber. Via a non-return valve, the two chambers in the valve section are in communication with a source of pressurized air, and when the exhaust valve is opened, the outwardly flowing exhaust gas is removed by the injection action from relatively cool air from these chambers. This air exhibits an evacuation period and some cooling effect on the seating surface.

However, this relatively cold air has only a slight cooling effect. This is because the surfaces of the two parts of the valve that form the annular gap are generally convex and form a flow path that leads the exhaust gas directly to the valve seat surface.

In the exhaust valve disclosed in U.S. Pat. No. 4,106,468,
The stationary and moving parts of the valve are cylindrically shaped and define a narrow annular space upstream of the seating surfaces, i.e. between those surfaces and the combustion chamber of the engine cylinder. The purpose of this interval is to effectively prevent combustion gases from escaping from the cylinder until the lower end of the seating surface on the moving part separates from the cylindrical surface of the stationary part during the initial opening of the valve. A similar valve has a German patent no.
Also shown in No. 744250.

The exhaust valve according to the present invention is disclosed in U.S. Pat.
1873119, in which the annular chamber is formed as a recess in the surface of one or both valve parts, which recess opens along its entire circumference towards the opposite surface of the other valve part. Regarding the point.

This configuration and location of the annular chamber creates a reservoir in the flow path from the combustion chamber to the seating surface of the valve section, ensuring that the chamber is currently filled with clean, relatively cool air during the compression process. When the engine cylinders or from a connected external source of compressed air, that amount of air acts as a barrier between the hot combustion gases and the seating surface from the time the fuel ignites until the exhaust valve opens. Function. Therefore, the combustion gases cannot escape directly through the leaks formed by the local gaps between the seating surfaces, as in known valves. Instead, what will seep out through the leak will be just the air in the reservoir, or at most a mixture of air containing a relatively small percentage of combustion gases.

The present invention provides that the above-mentioned attack by the active components contained in the combustion gases on the seating surface sooner or later occurs due to deposits previously formed on the seating surface, e.g. by corrosion, or between the surfaces when the valve closes. It is recognized that the slag and coke squeezed out leave small indentations on these surfaces, resulting in localized leaks that occur predominantly during the time the valve is closed without providing a complete seal. It is based on. Measurements of the surface temperature of the stationary valve section have shown that a temperature increase of approximately 200°C and an average temperature increase of approximately 100°C occur around such localized leaks immediately after top dead center. In contrast, the temperature rise at the beginning of the exhaust period immediately after the valve opens is only about
The temperature was only 20°C to 25°C. Therefore, the additional cooling of the seating surface during the evacuation period has only a small effect on corrosion phenomena or on the spread of an initially very small leakage into a larger combustion area. These phenomena are further reduced to a greater extent when, according to the features of the invention, both the temperature of the gas escaping from the seating surface when the valve is closed and the content of active components in this gas are reduced. Since the corrosion rate of materials commonly used for seating surfaces doubles at temperatures of about 70°C, the present invention allows for the refurbishment of seating surfaces by repolishing even the slightest localized leaks. It can be seen that this greatly increases the time it takes to reach a normal burnout condition of the magnitude required. This therefore results in an extended valve life.

The critical period of each working cycle, during which the temperature and pressure within the combustion chamber are high enough to cause the combustion gases escaping from the combustion chamber to breach the seating surfaces, is rather short, and for two-stroke and four-stroke engines. In either case, the rotation ends approximately 20 degrees after top dead center. The desired effects of the invention are thus obtained with a relatively small volume of the annular chamber without any disadvantageous increase in the diameter of the valve section or the so-called wasted space in the engine cylinder. This chamber volume is selected to be slightly larger than the volume of gas through which the gas can flow during said period, in which case said chamber is for example 2-3 times this gas volume. Approximately 0.2mm x 3
It has a cross section of mm.

In order to obtain the desired barrier effect of the air in the annular chamber, in which the mixing of combustion gases from the combustion chamber into the air flowing into this annular chamber is minimal, the annular chamber, through which the axial section is formed, is recessed. It is preferable to shape the valve portion so that it has a maximum value on the surface of the valve portion.

When the annular chamber is formed in only one valve part, it is preferable to design the opposite surface of the other valve part with a step at the inlet from the combustion chamber to the annular chamber, so that the combustion chamber The part of said surface closest to is recessed relative to the part of the surface facing the annular chamber. With this arrangement, the gases exiting the combustion chamber are slowed down and deflected by the steps formed between the surface portions, whereby the gases lose a major part of their kinetic energy. Therefore, pure and relatively cool air from the annular chamber is forced through local leaks, if any, between the seating surfaces of the combustion gases due only to the static pressure drop from the combustion chamber downstream of the valve. Ru. Another advantage of this embodiment is that at the moment the opening of the valve begins, the flow of combustion gases from the cylinder is likewise directed into the annular chamber, so that there is no undesirable build-up of deposits on the walls of the annular chamber during engine movement. contribute to maintaining the

Said effect of the particular shape of the valve section is in one embodiment, namely that the transition between the two surface sections is shaped as a fillet with a direction from the combustion chamber towards the inlet in the axial section.

The present invention will be described below with reference to embodiments and drawings.

As shown in FIGS. 1 and 2, the exhaust valve for a two-equilibrium diesel engine is a stationary part that is removably attached (the detailed method is not shown) to a cylinder cover 3 of an engine cylinder together with a valve housing 2. (or bottom part). The movable part 4 of the exhaust valve is designed as a conventional poppet valve, which contacts the bottom part 1 on a conical surface. Seating surfaces suitable for the two valve parts indicated at 5 and 6 are formed on two claddings or inserts 7 and 8 made of a suitable material such as stellite or hard metal. (see figure).

In this surface of the movable valve part 4 in the direction towards the bottom part 1 there is provided an annular chamber 9 located between the combustion chamber 10 of the engine cylinder and the seating surface 6 of the valve part 4 . As shown in the figure, the ninth axial cross section, i.e. the cross section located in the plane passing through the valve axis, is a trapezoid whose two parallel sides 11 and 1
2 extends generally perpendicular to the seating surface 6 and the opposing surface 13 of the valve portion 1 . Via a circumferential fillet 14 located slightly inboard of the opposite outer surface of chamber 9 whose generatrix is side 12, surface 13 extends towards combustion chamber 10 into surface 15, which surface 15 is shown in FIG. When the valve is closed, it assumes a retracted position from the valve part 4, and a relatively narrow circumferential gap of about 0.2 mm is formed between this part and the surface 16 of the movable part.

During the combustion process, the annular chamber 9 is filled with relatively cool pure scavenging or charging air, but if the aforementioned small local leakage exists between the seating surfaces 5 and 6; Instead of the above air there will be hot and highly corrosive fuel gases forced through leaks in the seating surfaces in response to the pressure increase due to combustion of the fuel injected into the engine cylinders. . High-temperature phenomena occurring in the material surrounding existing leaks in the seating surfaces are a result of the engine's working cycle under conditions that would otherwise result in high temperatures in the combustion chamber due to high pressure and a high density of combustion gases, as well as high concentrations of corrosive components. Although it occurs during the period, it can be avoided as a result. The shape of the step or transition as shown and described, formed as a fillet 14 between the two surface portions 13 and 15, is such that its concave surface faces from the combustion chamber 10 to the inlet gap. This serves to limit undesired mixing of the pure relatively cold air in the annular chamber 9 with the incoming hot combustion gases.

Reducing the rate at which small local leakages between seating surfaces due to corrosive and erosive effects increase
In the area surrounding these leaks, the bottom part 1 is somewhat cooler from the movable valve part 4 which is directly exposed to the high temperatures in the combustion chamber 10 during the period when the valve is closed.
A more effective heat transfer is maintained. Thus, a lower average temperature of the particular area of concern and thus a more even average temperature of the entire seating surface can be maintained. This means that the corrosion of the seating surface that inevitably occurs during the service life of the valve is distributed evenly, so that the effect of corrosion on the sealing function of the valve is less than that of selective localized corrosion of the seating surface. guarantee that the

In the illustrated and described embodiments, the annular chamber is formed only in the movable valve part or only in the stationary valve part; however, it may also consist of two opposing recesses, one in each valve part. Can be done. As an alternative to, or as an adjunct to, the above-described use of compressed air from the engine cylinders to fill the annular chamber, an external source of pressurized air supplies cold air at an appropriate pressure to the annular chamber via a check valve. It is also possible to provide Said pressure must not be lower than the compression pressure within the engine cylinder and may be substantially the same as the maximum pressure occurring within the cylinder. The required consumption of air is relatively small, and this air can be supplied by a compressor with a correspondingly relatively low power.

[Brief explanation of the drawing]

FIG. 1 is an axial sectional view through a valve according to the invention, showing only those parts deemed necessary for understanding the invention, and FIG. 2 is a considerably enlarged portion of the area enclosed by in FIG. 1. 3 is a similar axial sectional view of FIG. 1 through a second embodiment of the exhaust valve according to the invention, and FIG. 4 is a partial view corresponding to FIG. 2 of the area enclosed by FIG. 3. It is. In the figure, numerals 1...bottom part, 2...valve housing, 3...cylinder cover, 4...movable valve part,
5... Seating surface, 6... Seating surface, 7... Insert, 8... Insert, 9... Annular chamber, 10... Combustion chamber, 11... Side, 12... Side, 13... Surface Portion, 14... fillet, 15, 16... surface portion.

Claims (1)

Claims: 1 Consists of a stationary part 1 and an axially movable part 4, both parts 1, 4 having cooperating seating surfaces 5, 6, facing each other upstream of the seating surface. Surface 15,
16 are spaced apart so as to form a narrow annular space even when the valve is closed, and at least one of said two parts of the valve is provided with an annular chamber 9 which also forms a narrow annular space when the valve is closed. In an exhaust valve for an internal combustion engine that communicates with the combustion chamber 10 of the cylinder of the engine through an annular gap, the opposing surfaces have a conical shape, and the annular chamber 9 has a continuous annular space between the opposing surfaces. It is a recess extending over the entire circumference formed directly in one of the holes, and is located between the seating surfaces 5, 6 and the annular space, so that the annular chamber 9 is located between the annular spaces. forms an enlarged part, so that when the valve is closed, the gas flowing from the combustion chamber through the annular gap enters this annular chamber 9 and reaches the combustion engine seating surface 5,
6. An exhaust valve for an internal combustion engine, characterized in that gas passing through the gap between 6 and 6 first passes through an annular chamber 9. 2. Said annular chamber 9 is formed in the movable part 4 of the valve, and in the conical surface 15 of the stationary part 1 of the valve forming a narrow annular space, located opposite the annular chamber 9 and with a combustion chamber. 2. Exhaust valve for an internal combustion engine according to claim 1, characterized in that there is a fillet (14) extending all around the circumference, pointing in the direction of the inlet between the exhaust valve and the exhaust valve.