SPARK-IGNITION ENGINE WITH SUBSEQUENT CYLINDERS

Abstract

The present invention concerns an engine comprising at least one working cylinder (1) which has valves (16) and/or nozzles for the feed or injection of fuel and air and for the outlet of exhaust gas and a method of operating such an engine. In order to provide an engine and a corresponding method by which the fuel is used considerably more efficiently without excessively high temperatures occurring, which entail the risk of misfires, it is proposed according to the invention that each working cylinder (1) is coupled to a subsequent cylinder (11) which is driven by the pressure of hot exhaust gases from the working cylinder (1) and which is so designed and arranged that on the other hand it feeds pre-compressed combustion air to the working cylinder (1), a cooling device (17) which cools the pre-compressed gas, a device (9, 7) for transferring the cooled pre-compressed gas into the working cylinder (1) and a transfer valve (16) which for a further stroke of the subsequent cylinder (1) transfers exhaust gas under pressure from the working cylinder (1) into the subsequent cylinder (11).

Claims

1. An engine comprising at least one working cylinder (1) which has valves (16) and/or nozzles for the feed or injection of fuel and air and for the outlet of exhaust gas, characterised in that each working cylinder (1) is coupled to a subsequent cylinder (11) the subsequent cylinder being driven by the pressure of hot exhaust gases from the working cylinder (1) and the subsequent cylinder being so designed and arranged that on the other hand the subsequent cylinder feeds pre-compressed combustion air to the working cylinder (1), a cooling device (17) which cools the pre-compressed gas, a device (9, 7) for transferring the cooled pre-compressed gas into the working cylinder (1) and a transfer valve (16) which for a further stroke of the subsequent cylinder (1) transfers exhaust gas under pressure from the working cylinder (1) into the subsequent cylinder (11).

2. An engine as set forth in claim 1 characterised in that the subsequent cylinder is of a larger volume than the working cylinder.

3. An engine as set forth in claim 2 characterised in that the volume of the subsequent cylinder is between 1.2 and 4 times the volume of the working cylinder.

4. An engine as set forth in claim 1 characterised in that the compression ratio () of the subsequent cylinder is between 2 and 5.

5. An engine as set forth in claim 1 characterised in that an intercooler is provided between the outlet of the subsequent cylinder and the inlet of the working cylinder.

6. An engine as set forth in claim 1 characterised in that disposed downstream of the subsequent cylinder is an inverse turbine having an inlet stage for expansion under ambient pressure, an intercooler connected downstream of the inlet stage and a compression stage for concluding compression to ambient pressure as the outlet stage.

7. An engine as set forth in claim 1 characterised in that the engine has an exhaust gas recirculation means.

8. An engine as set forth in claim 1 characterised in that it is in the form of a four cylinder engine with respectively four working cylinders and four subsequent cylinders and two crankshafts (8, 22), of which one is associated with the working cylinders and the other with the subsequent cylinders.

9. A engine as set forth in claim 1 characterised in that the crankshafts (8, 22) are adjustably coupled together.

10. An engine as set forth in claim 1 characterised in that the compression ratio of the working cylinder is between 6 and 10.

11. An engine as set forth in claim 1 characterised in that the cylinders are arranged in a V-shape, wherein one bank of the V-shape is formed by the working cylinders and the other bank of the V-shape is formed by the subsequent cylinders.

12. An engine as set forth in claim 1 characterised in that the subsequent cylinder or cylinders are in the form of a 4-stroke cylinder.

13. An engine as set forth in claim 1 characterised in that the subsequent cylinder or cylinders are in the form of 2-stroke cylinders, wherein the number of subsequent cylinders is half the number of working cylinders and each subsequent cylinder is associated with two different working cylinders, the working strokes of which are displaced relative to each other substantially through 180.

14. A method of operating an engine as set forth in claim 1 in which in a first stroke of a subsequent cylinder (11) ambient air is drawn in, in a second stroke it is compressed and after intercooling it is transferred to a working cylinder (1), wherein after or during a corresponding working stroke of the working cylinder (1) the exhaust gas of the working cylinder, that is under residual pressure is transferred to the subsequent cylinder (11) which in a third stroke receives the hot exhaust gas, relieves its pressure and in a fourth stroke of the subsequent cylinder (11) ejects it with a reduced residual pressure.

15. A method as set forth in claim 14 characterised in that the reduced pressure at the outlet of the subsequent cylinder approximately corresponds to the ambient pressure.

16. A method as set forth in claim 14 characterised in that the waste heat of the exhaust gas ejected from the subsequent cylinder is converted into mechanical work by an inverse turbine.

17. A method as set forth in claim 14 characterised in that the gas-fuel mixture in the working cylinder is fired later than 30, preferably later than 25 and up to 10 particularly preferably between 20 and 10, before the top dead center.

18. A method as set forth in claim 14 characterised in that the combustion chamber of the working cylinder is connected to the working volume of the subsequent cylinder in a range of between 30 and 60 after the top dead center.

Description

[0028] Further advantages, features and possible uses of the present invention will be apparent from the description hereinafter of a preferred embodiment and the accompanying Figures in which:

[0029] FIG. 1 shows a diagrammatic plan view of a cylinder block with a respective row of 4 indicated working cylinders and 4 subsequent cylinders respectively associated with a working cylinder,

[0030] FIG. 2 shows a diagrammatic vertical sectional view through a working cylinder and an associated subsequent cylinder,

[0031] FIG. 3 shows a flow chart illustrating the path of the combustion air through a subsequent cylinder to the outlet of an inverse turbine,

[0032] FIG. 4 shows a snapshot at the beginning of the working stroke of the working cylinder with a trailing subsequent cylinder which expels pre-compressed air to an intercooler 17, and

[0033] FIG. 5 shows an alternative flow chart with subsequent cylinders in the form of a two-stroke.

[0034] The diagrammatic plan view in FIG. 1 shows an engine block 10 having a row of four working cylinders 1 and four subsequent cylinders 11 respectively, wherein a respective working cylinder 1 is coupled to a subsequent cylinder 11, more specifically therefore being connected together by way of valves 16, 9 and corresponding transfer conduits 6, 7. In a compression stroke the subsequent cylinder is connected by way of the connection 7 to an intercooler 17 from where pre-compressed combustion air is passed to the associated working cylinder 1. In the course of a working stroke of the cylinder 1 the connection is made by way of the valve 16 to the subsequent cylinder 11 which in a working stroke delivers corresponding power by way of the crankrod 12 to a second crankshaft 22 while the working cylinder 1 drives a crankshaft 8 by way of the connecting rod 2. The crankshafts 8, 22 are preferably coupled together adjustably by way of a transmission (not shown) so that the stroke movements of the working cylinder or cylinders 1 and the subsequent cylinder or cylinders 11 are respectively in fixed but optionally adjustable relationship. After the exhaust gas expulsion stroke of the subsequent cylinder 1 the latter can again draw in air and then compress it (see also FIG. 2).

[0035] In this arrangement the subsequent cylinders 11 are of a larger diameter and a larger volume than the working cylinders 1. FIG. 2 shows substantially a longitudinal section through a working cylinder 1 and an associated subsequent cylinder 11, but not all valves and conduits are illustrated here.

[0036] FIG. 4 is once again an enlarged sectional view of a portion from an engine block 10 with a cylinder head 3. This portion includes a working cylinder 1 and an adjacent subsequent cylinder 11, wherein the mode of operation of the working cylinder 1 and the subsequent cylinder 11 is described in greater detail hereinafter. FIG. 4 shows a moment in the second working stroke of the subsequent cylinder, that is to say the stroke in which the subsequent cylinder expels pre-compressed combustion air into an intercooler through a valve 9 (see FIG. 4). In this view the piston 5 of the working cylinder 1 is in the region of its top dead center with maximum compression of the gas contained therein and begins (optionally after the injection of fuel) then to perform a working stroke with expansion of the burning fuel-air mixture.

[0037] After firing of a fuel-air mixture in the working cylinder 1 the piston of the working cylinder moves downwardly while the fuel-air mixture burns and generates a corresponding pressure. As soon as the piston of the working cylinder 1 has moved away from the top dead center by between 30 and 60, the valve 16 is opened to the subsequent cylinder whose outlet valve 9 is then closed so that the hot combustion gases in the working cylinder also pass into the subsequent cylinder 11 and drive the piston 15 of the subsequent cylinder, that is to say they move it downwardly in FIGS. 2 and 4.

[0038] When the subsequent cylinder has reached its bottom dead center the valve 16 is closed and a further exhaust gas valve (not shown) of the subsequent cylinder is opened so that, in the renewed upward movement of the piston 15 of the subsequent cylinder 11, the exhaust gas is expelled. The piston 5 of the working cylinder 1, that leads in relation to the piston 15, then moves downwardly again in the third stroke and in so doing receives pre-compressed combustion air from the intercooler 17. The piston 15 of the subsequent cylinder 11, which follows with a certain delay, draws in combustion air or fresh air in its next stroke after closing and opening of corresponding valves.

[0039] After the piston 5 of the working cylinder 1 has moved beyond the bottom dead center it compresses the introduced (pre-compressed) air or a corresponding fuel-air mixture, in which case fuel is optionally also injected only upon or shortly before reaching the top dead center in the region of the cylinder head 3. The piston 15 of the subsequent cylinder 11, with the valve 9 closed, then compresses the combustion air which has been previously drawn in, and pushes it then into an intercooler 17 (see FIGS. 1 and 3) and thereafter the same process can be repeated with the downward movement of the piston 5 in the working cylinder 11 after moving beyond the dead center point and firing of the mixture.

[0040] FIG. 3 shows a flow chart for the engine according to the invention wherein the row of subsequent cylinders 11 is shown here on the one hand before and on the other hand after the row of working cylinders 1 only to illustrate the sequence of the flow chart and the individual strokes. It will further be appreciated that for reasons of simplification in the drawing only the path by way of the intercooler 17 is shown, while in actual fact pre-compressed air is transferred from each of the subsequent cylinders 11 by way of a cooler 17 and from there into an associated working cylinder. The intercooler 17 however can be a cooler which is used jointly by all subsequent cylinders 11 on the transfer path from a subsequent cylinder 11 to a working cylinder.

[0041] The fresh air feed 18 is implemented into a subsequent cylinder 11 where the fresh air is pre-compressed and cooled in a cooler 17. The pre-compressed cooled fresh air is fed to a working cylinder 1 where the described working stroke is then performed, in which the subsequent cylinder 11 is also again involved, being the same subsequent cylinder 11 which has previously drawn in and compressed the fresh air in another stroke.

[0042] After the subsequent cylinder has performed the corresponding working stroke the exhaust gas which has expanded almost to the ambient pressure in the subsequent cylinder 11 is passed by way of a catalytic converter 50 to an inverse turbine 30 whose inlet stage 31 is an expansion stage which is connected downstream of the intercooler 33. This provides that expansion takes place to a level below the ambient pressure so that then compression to ambient pressure takes place again in the compressor stage 32. By virtue of expansion and intermediate cooling kinetic energy can additionally be obtained from the thermal energy contained in the exhaust gas by the turbine 30. By virtue of the intermediate cooling action the compression work in the compressor stage 32 is less than the energy obtained by expansion and cooling in the expansion stage 31.

[0043] FIG. 5 shows a similar flow chart of a simple variant, wherein the subsequent cylinders are here in the form of a two-stroke so that each subsequent cylinder can respectively alternately supply two working cylinders of a four-stroke engine with pre-compressed air and can be driven by the exhaust gas pressure of the working cylinders. The flow of the working and exhaust gases is indicated by corresponding arrows. True intercooling is not provided here, but is at least partially also already implemented by the discharge of heat in the subsequent cylinder and during transfer of the pre-compressed combustion air to the working cylinder. In addition to the flow chart similarly to FIG. 3 however FIG. 5 also shows an exhaust gas recirculation means 40 which takes place at the outlet of the compressor 32 to the fresh air feed 18.

[0044] It will be appreciated that the exhaust gas recirculation can also be implemented in other engine variants according to the invention and provides generally for improved stoichiometric combustion for reducing exhaust emissions with a lower energy input.

[0045] By virtue of the better utilization of energy in all variants the working cylinders 1 can be comparatively small so that the total of the volumes of working cylinder 1 and subsequent cylinder 11 occupies at least approximately the same volume as a conventional working cylinder (with the same overall power).

[0046] The higher compression ratio and the prolonged expansion under approximately isothermal conditions and expansion to the ambient pressure improves the energy yield which can be still further increased by an inverse turbine which utilizes the residual heat of the exhaust gas.