GB2143580A

GB2143580A - Supercharging arrangement for multi-cylinder internal combustion engine

Info

Publication number: GB2143580A
Application number: GB08415938A
Authority: GB
Inventors: Yasuo Sumi
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1983-07-21
Filing date: 1984-06-22
Publication date: 1985-02-13
Also published as: DE3419077A1; JPS6026125A; GB8415938D0

Abstract

A positive displacement supercharger (44) driven by a mechanical connection (46) with the engine crankshaft (62) provides pressurized air to a first group of cylinders (30A-C) while the remaining cylinders (32A-C) are supplied with supercharging air from an exhaust gas driven turbocharger (54). <IMAGE>

Description

SPECIFICATION Supercharging arrangement for multi-cylinder internal combustion engine The present invention relates generally to a supercharged internal combustion engine and more specifically an engine wherein a mechanically driven "supercharger" and an exhaust gas driven "turbocharger" are used to supercharge separate groups of cylinders.

Turbochargers encounter the problem that at low engine speeds insufficient exhaust gases are available for driving the turbine of the unit. Accordingly, until the engine reaches approximately 2000 RPM (by way of example only) supercharging is not possible and accordingly a notable lack of engine torque occurs under such conditions.

Figure 1 shows an arrangement proposed in Japanese Utility Model Provisional Publication 56127334 which is directed to overcoming this problem. This arrangement, as shown, includes an internal combustion engine 1 which is equipped with a so called "turbocharger" 2 (Viz., a supercharger driven by the exhaust gases of the engine) and a mechanically driven supercharger 3. Drive connection between the engine crankshaft 4 and the compressor 5 of the supercharger 3 is established by a drive train including a gear 6 which meshes with a gear 7 rotatable with the flywheel 8 of the engine, a clutch 9 and a step-up gear arrangement 10. The clutch 9 is engaged in response to a signal produced by a control unit 11 which is reponsive to the output of an engine speed sensor 12.The control unit 11 is arranged to engage the clutch 9 at low engine speeds to rotate the compressor and compensate for the lack of pressure produced by the compressor 13 of the turbocharger 2 under such conditions.

In order to prevent excessive pressure build up in the induction manifold, a vent or relief valve 14 is arranged to relieve excess pressure back to the air cleaner 15 or like device of the engine 1.

The exhaust gases after having passed through the turbine 16 of the turbocharger 2 are discharged to the atmosphere via a catalytic converter, muffler or like device 17.

However, this arrangement has suffered from the drawback of being overly complex. That is to say, the arrangement requires a clutch, a control circuit as well as a pressure relief valve, all of which unduly increase the cost and weight of the vehicle.

One arrangement (known to the inventor) which has been proposed in a effort to overcome the above mentioned drawbacks is shown in Figure 2. In this arrangement the clutch and step-up gearing are omitted and the compressor 18 (blower or the like) constantly driven by a belt and pulley arrangement 19. This "internal prior art" arrrangement while eliminating the need for a clutch and step-up gearing has induced the need for two relief valves 20, 21.

Both of these valves are arranged to permit flow from the respective compressors 18, 22 into the induction manifold, so that upon the compressor 22 oftheturbocharger producing an adequate pressure, the relief valve 18 is held closed cutting off communication between the mechanically driven compressor 18 and the cylinders of the engine. A further drawback is encountered in that a blower type (viz., a centrifugal or axial flow compressor) must be used to avoid mechanical losses which would result if a positive displacement type compressor were permitted to build up unnecessary pressure upstream of the relief valve 18.

It is an object of the present invention to provide a supercharging arrangement for a multi-cylinder internal combustion engine which produces an adequate supercharging pressure both at low as well as medium to high engine speeds and thus boost the torque output under all modes of operation and which does not require complex relief valve and/or control arrangements.

In brief, the above object is fullfilled by an arrangement wherein in order to improve low engine speed torque a positive displacement type "supercharger" driven by a mechanical connection with the engine crankshaft, provides pressurized air to a first group of cylinders while the remaining cylinders are supplied with supercharging air from an exhaust gas driven "turbocharger" to sustain adequate torque generation and the like at medium to high engine speeds.

More specifically, the present invention takes the form of a multi-cylinder internal combustion engine having a crankshaft, wherein the cylinders of the engine are divided into first and second groups and which features a first compressor in drive connection with the crankshaft for supplying air under pressure to the first group of cylinders and a second compressor in drive connection with a turbine rotated by the exhaust gases of the engine for supplying pressurized air to the second group of cylinders.

The features and advantages of the arrangement of the present invention will become more clearly appreciated from the following description taken in conjunction with the accompanying drawings in which: Figure 1 schematically shows the prior arrangement discussed in the opening paragraphs of the present disclosure; Figure 2 shows schematically the "internal prior art" arrangement also discussed earlier in the specification; and Figures 3and 4 respectively show first and second embodiments of the present invention.

Figure 3 shows a first embodiment of the present invention. In this arrangement the six cylinders of the engine 34 are divided into first and second groups (Viz., 30A, 30B, 30C and 32A,32B,32C) each of which communicate respectively with induction and exhaust manifolds 36,38,40,42. The first group of cylinders (30A-C) are supercharged by a supercharger 44. As shown, this device is arranged to be driven by a suitable belt and pulley arrangement 46 which establishes a drive connection between the crankshaft 62 of the engine 34 and the supercharge 44. The air compressed by the compressor 50 of the supercharger 44 is inducted from the atmosphere via an air cleaner 52 or like device.

The second group of cylinders (32A-C) are arranged to be supercharged by a turbocharger 54.

In this embodiment the turbine 56 oftheturbochar- ger 54 is arranged to be rotated by the exhaust gases discharged from the second group of cylinders (32A-C).

The supercharger 44 is preferably of the positive displacement type. For example, a Rootes type, while the turbocharger 54 of the centrifugal com pressortype. Examples of such devices may be found by reference to pages 288 to 291 of the "Automotive Encylopedia 1979 edition published by The Goodheart-Willcox Company, Inc.

With this arrangement when the engine 34 is operating a low engine speeds the supercharger 44 delivers supercharged air to the first group of cylinders (30A-C) incresing the torque output of the engine under such conditions. As the engine speed rises and the volume of exhaust gases discharged from the second group of cylinders (32A-C) rises the pressure produced by the compressor 58 of the turbocharger increases providing a desirable level of supercharging in the second group of cylinders.

With this arrangement the radius ratio of the pulley 60 (supercharger) and the pulley 62 (crankshaft) can be selected so that the compressor 50 of the supercharger is driven at a suitable speed to provide the required amount of charging at low engine speeds. Further, as the supercharger 44 and turbocharger 54 are arranged in parallel and essentially independent of each other, it is unnecessary to provide a relief or check valve arrangement therebetween. In addition, as the charging provided bythe aforementioned supercharger 44 is effective at only low engine speeds and tends to become essentially constant above a given blower rotational speed, the provision of a clutch or the like between it and the engine is obivated.

Figure 4 shows a second embodiment of the present invention. This arrangement is essentially the same as the first differing only in that the a single exhaust manifold 64 is used and the exhaust gases from both groups of cylinders used to drive the turbine 56 of the turbocharger 54. This embodiment features improved turbocharger response characteristics especially during vehicle acceleration.

Although the embodiments of the invention have been disclosed in connection with six cylinder engines, it will be appreciated that the present invention may be applied to any multi-cylinder engine. For example in the case of a three cylinder engine one cylinder may be associated with supercharger while the remaining two connected with the turbocharger or vice versa.

Further, with the present invention the supercharger is relatively small due to its limited low speed use and accordingly obviates the consumption of large amounts of otherwise useful engine output which would be expected in the instance that the whole engine were to supercharged by the one mechanically driven unit. Moreover, a synergistic effect may be expected with the present invention.

That is to say, as the supercharging pressure provided by the turbocharger is increasing before that provided by the supercharger peaks, highly desirable supercharging characteristics are obtained in frequently used low to medium engine speed ranges (viz., ranges in which vehicle acceleration is often required).

Claims

1. In a multicylinder internal combustion engine having a crankshaft and wherein the cylinders of the engine are divided into first and second groups a first compressor in drive connection with said crankshaft for supplying air under pressure to said first group of cylinders; and a second compressor in drive connection with a turbine rotated by the exhaust gases of the engine for supplying pressurized air to said second group of cylinders.

2. A engine as claimed in claim 1, wherein said first compressor is in constant drive connection with said crankshaft.

3. An engine as claimed in claim 1, wherein said first compressor takes the form of a positive displacement type compressor.

4. An engine as claimed in claim 1, wherein said turbine is rotated by the exhaust gases from said second group of cylinders.

5. An engine as claimed in claim 1, wherein said turbine is rotated by the exhaust gases from both said first and second groups of cylinders.

6. An engine substantially as hereinbefore described with reference to Figures 3 and 4 of the accompanying drawings.