GB2101212A

GB2101212A - A reciprocating piston internal combustion engine having a liquid- cooled exhaust valve seat

Info

Publication number: GB2101212A
Application number: GB08219249A
Authority: GB
Inventors: Alois Bitterli
Original assignee: Sulzer AG; Gebrueder Sulzer AG
Current assignee: Sulzer AG
Priority date: 1981-07-03
Filing date: 1982-07-02
Publication date: 1983-01-12
Also published as: GB2101212B; IT1151187B; DK149390C; JPS5810109A; DE3127122A1; JPS6325165B2; DE3127122C2; IT8221392A0; DK149390B; DK217182A

Abstract

In the cylinder head (4) the exhaust valve seat (2) has an annular cooling chamber (6) fed from an annular coolant distribution chamber (12) via transfer passages (5) passing through a wall (17) separating the two chambers (6, 12). The transfer passages (5) are distributed all around the cooling chamber (6) and are inclined relatively to the radial direction so that a swirling turbulent flow is produced in the cooling chamber (6), such flow taking the form of a liquid ring which rotates symmetrically of the valve axis (18). The turbulence of the flow ensures a satisfactory heat exchange and the fact that the flow is rotationally symmetrical ensures a uniform temperature distribution around the valve seat avoiding the risk of unequal thermal expansion effects causing distortion and twisting of the valve seat (2). <IMAGE>

Description

SPECIFICATION A reciprocating piston internal combustion engine having a liquid-cooled exhaust valve seat The present invention relates generally to a reciprocating piston internal combustion engine, having a liquid-cooled exhaust valve seat, and particularly to an engine in which there is provided an annular coolant distribution chamber which communicates with an annular cooling chamber surrounding the valve seat and from which outlet passages for the heated coolant extend.

It is advantageous to cool the exhaust valve seats of highly stressed internal combustion engines, and an example of this is the arrangement disclosed in Swiss patent specification 272 380. Not only must there be a satisfactory heat transfer from the valve seat to the coolant, but also the transfer of the heat must occur with maximum possible symmetry around the valve seat axis in order to ensure a uniform temperature distribution which is rotationally symmetrical around the valve seat because a nonuniform temperature distribution around the valve seat can cause distortions which may impair the sealing tightness of the valve.

The arrangement disclosed in the abovementioned Swiss patent specification 272 380 does not in fact provide in use a temperature distribution which is very symmetrical around the valve seat axis, because in this known construction the coolant enters a coolant distribution chamber which is in communication with the cooling chamber, through a tangential passage, circulates once around the coolant distribution chamber, and then leaves the same through a substantially radial passage.

Consequently, the coolant backs up near the exit passage and has corresponding dead spaces in the coolant flow. Consequently, the temperature distribution near the adjacent entry and exit passages can become very asymmetrical, leading to distortion of the valve seat.

The present invention seeks to provide a valve seat cooling arrangement in which the temperature distribution in the valve seat is rotationally symmetrical around the valve axis, while also ensuring a satisfactory transfer of heat to the coolant.

According to the invention, therefore, there is provided a reciprocating piston internal combustion engine the exhaust valve or valves of which has or each have a respective liquid-cooled valve seat incorporating an annular cooling chamber which is connected by transfer passages to a surrounding annular coolant distribution chamber which is connected to receive coolant from at least one supply duct or passage, the annular cooling chamber having at least one outlet duct or passage for the heated coolant and the said transfer passages between the annular cooling chamber and the annular coolant distribution chamber being distributed around the entire periphery of the cooling chamber and being inclined in the same directional sense to respective radial lines passing therethrough.

The annular coolant distribution chamber forms a kind of pressure chamber from which the coolant flows into the cooling chamber proper through the transfer passages, which preferably extend substantially in a plane perpendicular to the axis of the valve seat. Since the transfer passages are inclined in relation to the radial direction, a swirling movement is imposed on the coolant entering the cooling chamber so that the flow pattern within the chamber is that of a closed rotating ring of coolant. The ring of coolant is completely rotationally symmetrical about its own axis, which axis coincides with that of the valve; consequently, the coolant ring absorbs heat uniformly from all around the valve seat periphery.

Preferably, and in order to avoid any possible disturbances of this symmetry by a unilateral entry of the coolant into the coolant distribution chamber or by a unilateral exit of the coolant from the cooling chamber, a plurality of supply passages to the coolant distribution chamber and a plurality of outlet passages from the cooling chamber are provided, these being distributed like the transfer passages between the coolant distribution chamber and the cooling chamber, around the periphery of both these chambers.

The supply passages distributed over the periphery of the coolant distribution chamber also serve as cooling passages for the cylinder head.

Advantageously, too, the coolant distribution chamber also communicates directly with the said outlet passages from the cooling chamber via restricted passages. The latter passages also serve to bypass a possible excess of coolant around the valve seat and this bypass connection can also serve as a venting line.

In order to achieve intensive cooling the rate of flow of the coolant in operation of the engine, the total cross-section of the transfer passages and their inclination to the said radial lines, and the volume of the annular cooling chamber are such that a turbulent swirling flow of coolant flows through the cooling chamber.

The invention can be put into practice in various ways, but one embodiment will now be described in greater detail with reference to the accompanying drawings, in which: Figure 1 is a sectional view of part of a cylinder head taken through an exhaust valve on the section line I-I of Figure 2; and Figure 2 is a sectional view taken on the line Il-Il of Figure 1.

Referring now to the drawings, there is shown a cylinder head 4 providing a top closure for a cylinder 8 (not shown in greater detail). In the cylinder head 4 is an opening having a radially inwardly extending step 10 at a lower end 9 near the cylinder chamber. Abutting against the step 10 is a valve seat 2 retained in a valve cage 3 the interior of which constitutes the wall of an exhaust port 11 which is concentric with respect to the valve seat 2 and cage 3 and is closed by the mushroom-shape head of a poppet valve 1.

The opening in the cylinder head which receives the valve seat 2 and the valve cage 3 diverges downwardly (as viewed in Figure 1) to define, with the valve cage 3, a tapering annular coolant distribution chamber 1 2 into which a plurality of coolant supply passages 1 3 extend from below, these passages being distributed around the periphery of the chamber 12; the supply passages 1 3 also serve as cooling passages for the cylinder head 4. The annular coolant distribution chamber 12 is sealed from the combustion chamber 8 by a seal 14 in the valve seat 2.

Generally perpendicularly with respect to the valve axis, that is horizontally as viewed in Figure 1, a plurality of transfer passages 5, which are each inclined in relation to a respective radial line passing therethrough extend from the chamber 12 to an annular cooling chamber 6 formed partly in the cage 3 and partly in the valve seat 2. As can be seen in Figure 2 the fluid transfer passages 5 are distributed generally uniformly around the periphery of the chamber 6. Coolant fluid discharge passages 7, which are also distributed around the whole periphery of the valve port extend from the annular cooling chamber 6 and lead eventually back to the radiator (not shown) of the coolant circuit.

As can be seen in Figure 1, the tapering annular coolant distribution chamber 12 has a triangular cross sectional shape and at its narrow end terminates in an annular gap 1 5 which is bounded radially inwardly by the cage 3 and radially outwardly by the cylinder head 4. Radial passages 16 in an outer part 17 of the wall of the cage 3 connect the annular gap 1 5 to the discharge lines 7. The gap 1 5 and transverse passages 1 6 provide direct connections from the coolant distribution chamber 12 to the discharge passages 7, such connections bypassing the annular cooling chamber 6 and by virtue of the narrow dimensions of the gap 15 this bypass route has a significant resistance to flow. These connections thus serve for venting and in some circumstances as a bypass for surplus quantities of coolant.The construction illustrated, having a separated valve cage 3 in the cylinder head 4, is convenient for manufacture; however, the coolant distribution chamber 12, the axial discharge passages 7 and the transverse passages 5 could alternatively be formed directly in the cylinder head 4 itself which in this case could be produced with its own cooling system passageways, for example as a casting.

The coolant distribution chamber 12 acts as a pressure chamber for the coolant, from which the coolant enters the cooling chamber 6 itself in the form of a number ot similarly directed stream lines which have a circumferential component of motion which encourages swirl in the coolant.

Consequently a liquid ring of coolant which is rotationally symmetrical about the axis 1 8 of the valve port 11 is formed in the cooling chamber 6.

This ring of coolant rotates in a turbulent flow in the cooling chamber 6 and carries away heat from the valve seat 2 equally around the whole of the circumference of the valve seat 2.

Claims

1. A reciprocating piston internal combustion engine the exhaust valve or valves of which has or each have a respective liquid-cooled valve seat incorporating an annular cooling chamber which is connected by transfer passages to a surrounding annular coolant distribution chamber which is connected to receive coolant from at least one supply duct or passage, the annular cooling chamber having at least one outlet duct or passage for the heated coolant and the said transfer passages between the annular cooling chamber and the annular coolant distribution chamber being distributed around the entire periphery of the cooling chamber and being inclined in the same directional sense to respective radial lines passing therethrough.

2. An engine as claimed in Claim 1, in which the coolant distribution chamber also communicates directly with the said outlet passages from the cooling chamber via restricted passages.

3. An engine as claimed in Claim 1 or Claim 2, in which the rate of flow of the coolant in operation of the engine, the total cross-section of the transfer passages and their inclination to the said radial lines, and the volume of the annular cooling chamber are such that a turbulent swirling flow of coolant flows through the cooling chamber.

4. An engine as claimed in any preceding Claim, in which there are provided a plurality of supply passages to the coolant distribution chamber and a plurality of outlet passages from the cooling chamber, these supply and outlet passages being distributed, like the transfer passages, around the peripheries of the chambers.

5. An engine as claimed in Claim 1, in which the transfer passages extend substantially in a plane perpendicular to the axis of the valve seat.

6. A reciprocating piston internal combustion engine with one or more liquid-cooled exhaust valves, substantially as hereinbefore described with reference to the accompanying drawings.