Cylinder head for internal combustion engine

Abstract: A cylinder head (11) for an international combustion engine comprises at least two separate intake ports (38, 39) which each incorporate one intake valve (17) and at least one exhaust port (37), which in turn incorporates one exhaust valve (19), where the intake ports and the exhaust port have their openings on opposite lateral faces (24, 25) of the cylinder head. The cylinder head also comprises a centrally arranged fuel injector which is driven by a top rocker arm, a push rod passing through the cylinder head, and a bottom camshaft. The camshaft (11) is also designed with a common shaft (44) which incorporates push rods (42, 43, 35) for transferring the drive from the camshaft (35) to the valves (17, 19) and to the fuel injector (21). The shaft is arranged between the two intake ports (38, 39).

Description: This invention relates to a cylinder head according to the preamble to patent claim 1. State of the art The design of a cylinder head normal involves several compromises between a number of conflicting aims. Among other things intake ports are required to be designed with sufficient length to provide suitable intake air control, the intake ports are required to connect to the combustion chamber with a certain inclination to provide a certain vorticity or swirling in the combustion chamber, the exhaust ports are required to be designed sufficiently short to avoid the diffusion of heat in the cylinder head, the mounting holes of the cylinder head are required to be arranged so that they are uniformly distributed to provide even clamping against the engine block, cooling ducts are required to be located in the most suitable position, fuel injectors are required to be fitted centrally to optimise combustion in the combustion changer, provision must be made for supplying fuel to the fuel injectors via suitably shaped feed lines, and the cylinder head is required to be manufactured by a suitable production method. One basic problem is that there is a shortage of sufficient space for the required partial solutions within the limited volume of the cylinder head. In the case of cylinder heads for diesel engines with four valves per cylinder, and with separate intake ports, these problems are more pronounced. Moreover, if the fuel injector is of the type which is referred to in English as "unit injector", it requires a mechanical drive for generating a high injection pressure, and this drive also requires a great deal of space. Normally such a fuel injector is driven by the engine camshaft in a similar fashion to the valve drive. Where the camshaft is located below the cylinder head a number of push rods must therefore be arranged between the camshaft and the cylinder head. These push rods must in turn actuate rocker arms on the cylinder head to control the fuel injector and valves. The push rods are normally arranged to pass through the cylinder head via a number of through holes designed for this purpose. Where the cylinder head is of the so-called crossflow type, which means that the intake ports and exhaust ports open out on opposite sides of the cylinder head, the intake and exhaust ports will occupy a large amount of space, causing problems in finding a suitable space for the through holes of the push rods. Patent specification US-A-4 703 729 describes a cylinder head aimed at obtaining an improved intake system. Each cylinder has two inlet valves arranged in two inlet ports and two exhaust valves arranged in a common exhaust port. The inlet and the exhaust ports have their openings on opposite lateral faces of the cylinder head. A fuel injector is arranged centrally in each cylinder. The inlet valves and the fuel injectors are driven by a first camshaft, and the exhaust valves are driven by a second camshaft. The transmission between the camshafts and the valves includes rocker arms on the top of the cylinder head and push rods arranged in through holes in the cylinder head. The push rods for the intake valves and the fuel injector are arranged in one through hole and the push rod for the exhaust valves are arranged in another through hole. The through hole for the inlet valve push rod and the fuel injector push rod is arranged besides the two inlet ports. In this cylinder head the through holes occupy a large amount of space causing the above mentioned problems. Patent specification US-A-4 945 873 describes a cylinder head having two inlet valves and two exhaust valves, and in which the push rods for the intake and exhaust valves are located in the same through hole. There is no push rod for driving the fuel injectors, and there are no further details given on the design of the cylinder head. To find space for the intake ports, the latter are not designed as separate ports but they are combined to form one common port, which is not only common to the intake ports for one cylinder but for two. This therefore requires a cylinder head which is common to at least two cylinders. In this case it was necessary to sacrifice the design of the intake ports, which is probably not the best design from the flow viewpoint. Patent specification US-A-5 035 209 describes a cylinder head comprising three push rods, one for the intake valve, one for the exhaust valve and one for the fuel injector, and in which all three push rods are arranged in the same through hole in the cylinder head. The patent is mainly aimed at a solution which prevents a push rods from separation from a rocker arm. Nothing is mentioned how valves, intake ports and exhaust ports are arranged. From the patent drawings it appears as the through hole is so large that it is almost impossible to arrange any intake or exhaust ports on the same side as the through hole, and further the cam shaft and the cam shaft transmission acting on the push rods are positioned where such port would normally be position. Therefore it appears likely that the intake ports and the exhaust ports are arranged on the same side of the cylinder head, thereby not having the same possibilities to optimize the shape of the ports as in a cylinder head of the cross flow type. Object of the invention The object of the invention is to design a cylinder head to provide a suitable location, in terms of the requirements set out in the preamble, for push rods driving fuel injectors and valves in a four-valve engine, even where the engine is provided with separate cylinder heads for each cylinder. The cylinder head must not therefore display the above-mentioned limitations of prior art. The object of the invention is therefore to ensure that all the other components of the cylinder head can be located in the best possible positions in keeping with the requirements set out in the preamble. Brief description of the invention The objects of the invention are achieved by designing the cylinder head with the features indicated in the characterising part of claim 1. By bringing together all the push rods belonging to a cylinder in the same through hole, this hole will occupy relatively little space in the cylinder head. This also allows the push rod and the rocker arm for driving the fuel injector to be located centrally and in a favourable position from the point of view of power transmission. By arranging the through hole in the area between two separate intake ports these ports can be designed with sufficient length and with sufficient deflection to be favourable from the point of view of flow. Advantageous embodiments of the invention are indicated in the attached sub-claims and are described in further detail in the examples below. Brief description of the figures. The description example is given with reference to the attached drawings, in which Fig. 1 shows, in principle, an elevation of a multi-cylinder engine, Fig. 2 shows a horizontal section 2-2, according to Fig. 4, of a separate cylinder head incorporated in the engine, Fig. 3 shows a vertical section, 3-3 according to Fig. 4, of the cylinder head, and Fig. 4 shows a vertical section 4-4 according to Fig. 3. Description of an exemplifying embodiment In principle Figure 1 shows an elevation of a multi-cylinder internal combustion engine 10, for example a diesel engine designed to drive a heavy vehicle such as a truck or bus. Engine 10 consists of an inline engine and in this example comprises six inline cylinders constituting the combustion chamber of the engine. The engine is fitted with separate cylinder heads, and therefore has six cylinder heads 11. On one side of the engine an intake manifold 12 is secured to cylinder heads 11 for supplying the cylinders with combustion air, and an exhaust manifold 15 is secured to the opposite side of the engine for discharging combustion gases. Engine 11 is therefore of the crossflow type, which means that its inlet and outlet are arranged on opposite sides, and that the flow through engine 11 is from one side to the other. All cylinder heads 11 have the same design and only one of them will be described in the following. Figure 2 shows cylinder head 11 designed for one of cylinders 14 in a horizontal cross-section 2-2 according to Figure 4. The horizontal cross-section shown in Figure 2 extends parallel with the bottom of cylinder head 11, and extends perpendicularly in relation to a central line of symmetry of cylinder 14. The extension of cylinder 14 is shown by dash lines in the figure. Cylinder head 11 is provided with two holes 16 for intake valves 17, and two holes 18 for exhaust valves 19, together with a recess or hole 20, arranged centrally relative to cylinder 14, and also concentrically with cylinder 14, for a fuel injector 21. The engine is therefore a four-valve engine. A horizontal line 22 through both intake valves 17 runs parallel with a horizontal line 23 extending through both exhaust valves 19, and both these lines 22, 23 extend in a direction which forms a certain angle a to the lateral faces 24, 25 of the cylinder head. Lateral faces 24, 25 of the cylinder head run parallel with each other and with a vertical plane of symmetry 13 in the longitudinal direction of the engine, thus lines 22, 23 form the same angle a to the vertical plane of symmetry 13 of the engine. Angle a is advantageously approximately 70°, but other angles ranging from 50 to 75° may suitably be selected in modified embodiments. Valves 17, 19 are therefore arranged with angular distortion. The fuel injector 21, which is normally mounted in central hole 20, is shown in Figure 3. Fuel injector 21 is of the type normally referred to in English as a "unit injector". Fuel injector 21 is fed with fuel at moderate pressure via a feed line from a fuel pump not shown, whereupon a high pressure suitable for the injection is generated by mechanical actuation of injector 21 to perform a pumping movement. Fuel injector 21 is also connected to the fuel pump by a pipe for return fuel and a pipe for transmitting a control pressure. These three pipes mentioned are designed in the cylinder head as drilled ports 26 in a wall 32 located between one of intake valves 17 and one of exhaust valves 19, as shown in Figure 2. The mechanism used to generate the pumping movement of the fuel injector is shown diagrammatically in Figure 3. A bearing bracket 27, which supports three rocker arms 28-30, both for driving the intake and exhaust valves 17 and 19 respectively, and for driving fuel injector 21, is secured by means of a bolted joint so that it can be mounted on cylinder head 11. The engine camshaft 31 is arranged at the bottom or underneath cylinder head 11, in the engine block not shown, and is driven by a method of prior art by the engine crankshaft. Camshaft 31 is designed with cams which actuate the rocker arms at the top by means of valve tappets and push rods. One of rocker arms 28 actuates a bridge between intake valves 17 so that both intake valves 17 are actuated simultaneously by the same rocker arm 28. Similarly a bridge causing both exhaust valves 19 to be actuated by the second rocker arm 29 is arranged between exhaust valves 19. A third rocker arm 30, which is in this case used to drive fuel injector 21 by a similar method, is arranged between both these rocker arms 28, 29. The injector is therefore imparted its pumping movement from a cam 33 on camshaft 31, which actuates central rocker arm 30, by means of a tappet 34 and a push rod 35, and which in turn rests against a pump rod 36 on fuel injector 21. Cylinder head 11 is designed with an exhaust port 37 via which exhaust gases escaping from exhaust valves 19 of the engine can be fed to its opening at exhaust manifold 15, and on one side 24 of cylinder head 11. Exhaust port 37 is common to the exhaust gases from both exhaust valves 19. The engine is constructed with two intake ports 28, 39, which are designed as separate ports for the respective intake valves 17, for feeding intake air from intake manifold 12 to the combustion chamber. Intake ports 38-39 have their opening on the other, opposite side 25 of cylinder head 11. Furthermore, cylinder head 11 is designed with a number of mounting holes 40 intended for bolted joints enabling cylinder head 11 to be mounted on the engine block. Mounting holes 40 have been chosen to lie in a position which is approximately concentric relative to the cylinder and hence relative to hole 20 for fuel injector 21. Similarly, bolt holes 40 are chosen to lie in a position where there is essential equal mutual angular distribution. This provides even clamping to the engine block which does not subject cylinder head 11 to unfavourable stress concentrations. Cylinder head 11 is provided, by a method of prior art, with a number of cooling ducts 41 through which coolant is pumped to dissipate heat from cylinder head 11. Figure 3 shows a cross-section 3-3 according to Figure 4, indicating that push rod 35, actuating the central rocker arm, extends through a through hole 44 which constitutes a lead-through passage between the top and bottom of the cylinder head. Moreover, Figure 3 should be regarded as diagrammatic because the other parts of cylinder head 11 have not been fully reproduced, and are instead shown by dash-dot lines. Figure 4 shows this through hole 44 viewed in a section 4-4 according to Figure 3, indicating that the through hole extends in the area beetween the two intake ports 38, 39, and that push rod 35 for fuel injector 21 is arranged between a push rod 42 for intake valves 17 and a push rod 43 for exhaust valves 19. Push rod 35 for fuel injector 21 requires a relatively high force, and therefore has a larger diameter than the other two. Push rod 35 of the fuel injector extends essentially vertically and in a plane perpendicular to the extension of camshaft 31 in its longitudinal direction. Push rod 35, fuel injector 21 and rocker arm 30 for fuel injector 21 are also mutually arranged essentially in the same vertical plane, which extends at right angles to camshaft 31. This position ensures that fuel injector 21 can be driven both with great force and great accuracy, and that the fuel injection Is also very accurate. Push rods 42, 43 for valves 17, 19 are arranged with a certain inclination relative to the extension of push rod 35 of the fuel injector, which is due mainly to the shortage of space prevailing at the top of cylinder head 11. However, this inclination is no major inconvenience. Firstly the forces required for the valve control are smaller than those required for actuating the injector, and secondly a minor deviation in the control of valves 17, 19 would not cause a major difficulty. Similarly, rocker arms 28, 29 for valves 17, 29 are arranged at a slight angle to each other to reduce the space occupied by push rods 35, 42, 43 between intake ports 38, 39. As is evident from the above valves 17, 19 are arranged with angular distortion, which has enabled intake ports 38, 39 to be designed with a longer extension than would otherwise be possible. This has the advantage that the intake air to the cylinder can be better controlled because its flow can be influenced along a longer section. It also means, however, that the hot exhaust gases are able to heat the cylinder head along a longer section. The distortion chosen actually represents a compromise in which the advantages of long intake ports 38, 39 are fully utilised without the disadvantage of too long an exhaust port 37 becoming obvious. By designing through hole 44, extending through the cylinder head, for push rods 35, 42, 43, as a through hole common to all the push rods, the space required has generally been reduced to accommodate the longer extension of intake ports 38, 39. From the production point of view the construction of a longer through hole 44 has the advantage over several smaller holes that cylinder head 11 can be cleaned more easily from mould cores and cylinder head 11 can also be produced relatively simply and cheaply. Constructing through hole 44 between the two intake ports 38, 39 also has the advantage that the volume of cylinder head 11 will still be limited, and that the components required for each cylinder are housed within the available space. This provides the possibility of constructing cylinder heads 11 as separate units, with the advantages this brings in terms of simple, standardised production among other things. This does not rule out the possibility of using the invention to advantage in modified designs where the engine is fitted with a cylinder head which is common to several cylinders. The invention is not therefore restricted to the exemplified embodiment but can be modified in alternative designs within the scope of the attached claims. Therefore the number of valves need not necessarily be four per cylinder but may be either a smaller or larger number. Similarly the exhaust port may alternatively be constructed as exhaust ports separate from each valve. In the example shown the separate intake ports are connected to corresponding separate port sections of the intake manifold. In an alternative embodiment the intake manifold need not be designed with such separate port sections.

Claims: Cylinder head for an internal combustion engine, comprising at least two separate intake ports (38, 39), each housing an intake valve (17), at least one exhaust port (37), incorporating at least one exhaust valve (19), where the intake ports (38, 39) and the exhaust port (37) have their openings on opposite lateral faces (24, 25) of the cylinder head (11), and where the valves (17, 19) are driven by top rocker arms (28, 29) and push rods (42, 43) passing through the cylinder head, from a bottom camshaft (31), the cylinder head also incorporating a centrally arranged fuel injector (21), which is also driven by a top rocker arm (30) and a push rod (35) passing through the cylinder head, from the bottom camshaft (31), characterised in that the push rod (35) for transferring the drive to the fuel injector (21) is arranged in a through hole (44) common to the push rods (42, 43) for driving the intake and exhaust valves (17, 19), and in that the through hole (44) is arranged between the two intake ports (38, 39). Cylinder head according to claim 1, comprising two intake valves (17) and two exhaust valves (19), characterised in that the push rod (35) for the fuel injector (21) in the through hole (44) is arranged between the push rod (42) for the intake valves (17) and the push rod (43) for the exhaust valves (19). Cylinder head according to claim 1, characterised in that the push rod (35) for the fuel injector (21) extends in a plane which is perpendicular to the extension of the camshaft (31). Cylinder head according to claim 3, characterised in that the push rods (42, 43) for the valves (17, 19) extend at an inclination to this plane. Cylinder head according to claim 1, characterised in that the cylinder head (11) is constructed as a separate cylinder head designed for one cylinder. Cylinder head according to claim 2, characterised in that the exhaust port is constructed as an exhaust port (37) common to both exhaust valves (19). Cylinder head according to claim 2, characterised in that the valves are arranged so that there is angular distortion between them. Cylinder head according to claim 7, characterised in that a line through the intake valves forms an angle (a) to the longitudinal direction of the engine, and in that this angle is between 50° and 75°, advantageously around 70°. Cylinder head according to claim 2, characterised in that the rocker arms (42, 43) for the valves (17, 19) and the rocker arm (35) for the fuel injector (21) are mounted in a common bearing bracket (27) on the cylinder head. Cylinder head according to one of the preceding claims, characterised in that it is incorporated in a multi-cylinder engine (10), and in that each cylinder has a cylinder head (11) of essentially the same design.

Inventors: FAERNLUND JONNY, SPERLE PETER, FAERNLUND, JONNY, SPERLE, PETER, Färnlund, Jonny
Applicants: SCANIA CV AB, SCANIA CV AKTIEBOLAG
Application year: 1993
Main classification: F02F1
IPC codes: F02M57, F01L1, F02F1, F02B3