A cylinder head

Abstract: A cylinder head for an internal combustion engine has a plurality of passageways, each comprising two ducts (12, 18), which connect the inlet ports (2) and the exhaust ports (4) for EGR. A valve member (16) in a gallery (14) selectively opens or closes the passageway. The ducts (12, 18) and the valve member (16) are contained entirely within the cylinder head, and the valve members (16) are part of a single valve, operation of which controls the passage of fluid between each inlet port (2) and associated exhaust port (4).

Description: The present invention relates to a cylinder head for an internal combustion engine. The cylinder head houses the inlet and exhaust ports for the cylinders (combustion chambers) of an engine. The cylinder head also houses valves for controlling the entry of combustible fluid, for example a petrol/air mixture, through the inlet port, and the venting of exhaust gases through the exhaust port. Commonly the cylinder head is provided with one or more external pipes which connect the exhaust ports of the cylinders to the inlet ports so that a proportion of the exhaust gases produced by the engine can be fed back into the cylinders. This is known an exhaust gas recirculation (EGR). EGR helps to reduce the levels of unwanted noxious exhaust materials, for example oxides of nitrogen (NOX), by reducing the temperature of the combustion and by promoting the combustion of fuel and/or carbon monoxide present in the exhaust gas. The quantity of exhaust gas which is fed back is controlled by an EGR valve, which is in turn controlled according, inter alia , to the temperature of the engine. It should be noted that EGR as herein described is quite different from the phenomenon known as "internal EGR", wherein exhaust gas flows directly from the exhaust port of a cylinder, through the cylinder, to its intake port. Internal EGR only occurs during the short time when the inlet and exhaust valves are open simultaneously. It is also known to provide means for channelling air into the exhaust gas stream to allow ignition of the exhaust gases (commonly known as secondary air injection - SAI). SAI is of use, particularly, when the exhaust pipe is provided with a catalytic converter which needs to operate at a relatively high temperature in order to function at maximum efficiency. When the engine is first started, and is running coolly, burning of exhaust gases helps to get the catalytic converter up to its optimum working temperature. EGR and SAI may both be operated in an engine by means of an open loop arrangement whereby certain preset operating conditions initiate EGR, and others initiate SAI. Useful descriptions of EGR and SAI are given in US patent numbers 4 170 112 and 5 271 221. Instead of separately connecting each exhaust outlet to an inlet, it is also known to connect all exhaust outlets to a common collecting container via a single pipe, and to connect the common container to inlet channels of cylinders. EGR can be regulated by means of a valve in the pipe to the common container. An example of this arrangement is disclosed in DE C-40 27 963. Although effective, provision of external pipes and valves for EGR and SAI is expensive, and increases the chances of a leak occurring. European Patent Application number 0 543 704 comprising the features of the preamble of claim 1 describes an internal connection between an exhaust port and an inlet port, into which fuel is injected so that hot exhaust gases help volatilise the fuel. Each internal connection is controlled by a separate valve 8. The above invention eliminates the need for external pipes and valves, but it requires a valve and associated separate control for each passageway and is therefore relatively complex in construction. According to the present invention there is provided a cylinder head for an internal combustion engine, as specified in claim 1. Because each inlet port is connected to an associated exhaust port via a single gallery in the cylinder head, EGR and/or SAI may be controlled by the operation of a single valve in the gallery, allowing simplified manufacture and operation. The invention may be used with all internal combustion engines. For example petrol or diesel engines, and engines with multiple cylinders. Each passageway may connect an exhaust port to an inlet port of the same cylinder. In a multi-cylinder engine, however, it would also be possible for the passageway to connect the exhaust port of one cylinder to the inlet port of another cylinder. This may allow the exhaust emission from one cylinder to be better synchronised with the inlet of fuel/air of the other cylinder to which the exhaust port is connected. In a preferred embodiment, at least a part of each passageway is adapted to be used to supply secondary air to the exhaust gases for SAI. Preferably the secondary air is supplied from an air cleaner. The secondary air may be supplied via one or more reed valves such as are commonly used for external application. The provision of a secondary air supply may be achieved by the use of a branched passageway in which a first end connects with an inlet port, a second end connects with an exhaust port, and a third end connects with a source of secondary air. The valve member is located in the gallery at the junction of the branches of each passageway and is adapted selectively to connect either the inlet port to the exhaust port, for EGR, or the exhaust port to the secondary air source, for SAI. Any suitable control valve may be used for this; for example an axial "shuttle" valve, a rotary sleeve valve, or a rotary sluice-gate type of valve. The valve may be controlled by conventional means; for example by bellcrank and motor for rotary valves, or directly for an axial valve. A rotary or axial stepper motor or a vacuum motor may also be used. The valve member is preferably continually variable for controlling gas flow rates in EGR or SAI modes, depending on the speed and load at which the engine is running. For example if 10% EGR is required (ie 10% of the gas intake into the cylinder is recycled exhaust gas), at around 1500 rpm the valve member may be open only to a small extent, while at around 4000 rpm the a valve member may be almost fully open. The gallery and passageways may be cast during formation of the cylinder head, or drilled after casting of the cylinder head. The cylinder head may be supplied separately, or as part of an assembled engine. The invention therefore also provides an internal combustion engine which has a cylinder head as hereinbefore described. The invention will now be further described, by way of example, with reference to the following drawings in which: Figure 1 is a section through part of a cylinder head of an engine in accordance with the present invention; Figure 2 is a schematic view from the flame face of a cylinder head in accordance with the present invention; Figure 3 is a section through a rotary sleeve valve for use in a cylinder head in accordance with the present invention; Figure 4 is a section through a sluice-gate type valve for use in a cylinder head in accordance with the present invention; and Figure 5 is a section through an axial valve for use in a cylinder head in accordance with the present invention. Figure 1 shows part of a cylinder head which encloses the top of a cylinder 10. Combustible fluid (eg petrol/air) is supplied to the cylinder 10 via an inlet port 2, and the passage of fuel is controlled by means of a poppet valve 6. Exhaust gases are vented from the cylinder 10 via an exhaust port 4, and the passage of exhaust gases is controlled by means of a poppet valve 8. Timing of the valves 6 and 8 is controlled by means of cams on an overhead camshaft (not shown). The cylinder head is provided with a gallery 14 which houses a rotary valve 16. Rotation of the valve opens or closes a connection between a duct 12 which connects the gallery 14 with the exhaust port 4, and a duct 18 which connects the gallery 14 with the inlet port 2. When the engine is started up it runs cold, and the valve 16 is closed. This prevents EGR, and all of the exhaust gas passes through the exhaust port 4 to be vented through the exhaust pipe (not shown). As the engine warms up, the valve 16 is gradually opened so as to allow some of the exhaust gases to pass from the exhaust port 4 to the inlet port 2 via the ducts 12 and 18 and the gallery 14. The position of the valve 16 is variable, and regulates EGR flow depending on the operating conditions, for example speed and load. This helps to reduce the combustion temperature and to combust uncombusted or partially combusted fuel present in the exhaust gas. Figure 2 is a schematic view from the underneath (flame face) of a cylinder head. The cylinder 10 has two inlet ports 2 and two exhaust ports 4. The gallery 14 is disposed along the cylinder head and houses a valve for each pair of inlet and exhaust ports. Each inlet port 2 is connected to a corresponding exhaust port 4 by a passageway comprising the ducts 12 and 18, and the gallery 14. The duct 12 terminates in a port 20 in the wall of the exhaust port 4, and the duct 18 terminates in a corresponding port 22 in the wall of the inlet port 2. Although not shown in Figure 1 or Figure 2, the gallery 14 may optionally be connected to a third duct 24 which is connected to a source of secondary air for SAI. Examples of suitable valve arrangements for EGR or SAI are shown in Figures 3 to 5. Figure 3 shows the operation of a rotary valve 16 in the valve gallery 14. The gallery 14 is connected to a duct 12 which leads to the exhaust port 4, a duct 18 which leads to the inlet port 2, and a duct 24 which leads to a secondary air source. With the valve 16 in the EGR position shown in Figure 3a exhaust gases can pass from the exhaust duct 12 to the inlet duct 18. The secondary air duct 24 is blocked off. With the valve 16 in the SAI position shown in Figure 3b, air can flow from the secondary air duct 24 to the exhaust port via the exhaust duct 12. The inlet duct 18 is blocked off. The valve 16 will generally be in the SAI position when the engine is first started up, so as to burn exhaust gases and help to heat up a catalytic converter in the exhaust pipe. When the engine is warmed up, the valve 16 may then be turned to the EGR position. It is also possible however to turn the valve 16 so as to block off communication between any of the ducts, thus preventing both EGR and SAI. The valve 16 may be wholly or partially opened to regulate the gas flow in the EGR or SAI positions. The valve shown in Figure 4 operates in a similar rotary manner to the valve of Figure 3, but it uses a differently shaped a valve member 16a. Figure 5 shows a linear shuttle valve which comprises two valve members 26 and 28, connected by a rod 30. The valve is housed in the galley 14 which is connected to the exhaust duct 12, the inlet duct 18, and the secondary air duct 24. The valve has other similar valve members connected to the rod 30 associated with the exhaust, inlet and secondary air ducts of another inlet and associated exhaust port (not shown). Movement of the rod 30 in the gallery 14 therefore controls EGR and/or SAI for a plurality of inlet and exhaust ports in the cylinder. With the valve in the EGR position shown in Figure 5a the valve members 26 and 28 isolate the ducts 12 and 18 from the rest of the gallery 14, and exhaust gases 32 flow from the exhaust duct 12 through the inlet duct 18. With the valve in the SAI position shown in Figure 5b the valve members isolate the ducts 12 and 24 from the rest of the gallery and air 34 flows from the secondary air duct 24 through the exhaust duct 12. Like the other valve types shown in Figures 3 and 4, the valve position is variable in either the EGR or SAI positions to control the rate of EGR or SAI gas flow. The invention therefore provides a cylinder head which may be used to provide low cost EGR and SAI in an engine, and which reduces the risk of leaks in these processes. Although the invention has been illustrated with reference to a four valve cylinder, it is not limited to this embodiment. The invention may be used with cylinder heads for cylinders with any number of valves, and with both petrol and diesel engines.

Claims: A cylinder head for an internal combustion engine, which cylinder head comprises: a) a plurality of inlet ports (2) for a cylinder (10); b) a plurality of exhaust ports (4) for a cylinder (10); c) a plurality of passageways (12, 18) contained entirely within the cylinder head, each of which connects an exhaust port (4) with an inlet port (2), and each of which is provided with a valve member (16, 26, 28) to control the passage of fluid; characterised in that the cylinder head further includes d) a gallery (14) which is disposed within the cylinder head and which houses the valve members (16, 26, 28); and in that the valve members (16, 26, 28) are part of a single valve, operation of which controls the passage of fluid between each inlet port (2) and associated exhaust port (4). A cylinder head as claimed in Claim 1, characterised in that for each passageway (12, 18) a secondary air duct (24) is provided at the junction of the passageway (12, 18) and the gallery (14) so that selective operation of the valve member (16, 26, 28) allows the passage of fluid between the inlet port (2) and the exhaust port (4) or between the exhaust port (4) and the secondary air duct (24). A cylinder head as claimed in Claim 1 or Claim 2, wherein the valve is a linear shuttle valve. A cylinder head as claimed in any one of the preceding claims, wherein the passageways connect the exhaust port of one cylinder to the inlet port of another cylinder. An engine in which is mounted a cylinder head as claimed in any one of the preceding claims.

Inventors: FARENDEN GEORGE, FARENDEN, GEORGE
Applicants: FORD FRANCE, FORD MOTOR CO, FORD WERKE AG, FORD FRANCE S. A., FORD MOTOR COMPANY LIMITED, FORD-WERKE AKTIENGESELLSCHAFT
Application year: 1995
Main classification: F02D21
IPC codes: F02F1, F02B1, F02B3, F02M25, F02D21