IE20001077A1 - An air charging assembly for IC engines - Google Patents

Abstract

An air charging assembly comprises a positive displacement supercharger (1) having a diaphragm (4) which is mounted on a piston plate (5) reciprocated by a rod (24) between, in this case, a hole (7) and a reed valve (8) feeding a supercharger air outlet manifold (9) in which is mounted a supercharger valve (10). Reed valves (6) are provided in the piston plate (5). The engine (20) has a conventional air inlet valve (22) in an inlet (26) fed with normally aspirated air from a manifold (15) through a non-return manifold inlet valve (16). In use, the engine (20) receives air from the air manifold in normal manner and before the inlet valve (22) closes, the supercharger diaphragm (4) is in the position illustrated having completed its compression stroke, the supercharger valves (8) and (10) open and a pulse of air is delivered into the air manifold (15) and into the cylinder (23) through the inlet valve (22). Various forms of single and double acting positive displacement supercharger are illustrated. <Figure 2>

Description

The present invention relates to an air charging assembly for an internal combustion (1C) engine of the type comprising a supercharger for feeding air through a supercharger air outlet manifold into the cylinder of the 1C engine. Further, the invention relates to a method of air charging an internal combustion engine, and also to specific constructions of supercharger and their operation. Ία Supercharging, namely, the boosting of the airflow into 1C engines by means of air pumps has been known for over a century. Indeed, in the 19th century, Dr Diesel incorporated an air pump in one of his first ^engines. Further, crankcase scavenging of two stroke engines has been known for a considerable length of time. For example, US Patent Specification No. 5,186,137 (Salzmann) discloses a rocking piston two stroke engine with crankcase scavenging while German Patent Specification No. DP 3725626 (Klaue) describes another scavenging system for a twin cylinder two stroke engine.

For many years, particularly for four stroke engines, supercharging was used mainly for increased power output or, as in the case of aircraft engines, to maintain the output at altitude. During the 1960s, it was discovered that supercharging also had the effect of reducing noxious emissions and there has been considerable interest in the supercharging of engines in recent years as a result of growing environmental concerns. Reciprocating piston and many different types of rotary pumps have been used for supercharging. For example, US Patent Specification No. 2,015,826 (Vincent) describes a wobble-plate pump driven directly off the crankshaft However, in recent years, rotary air pumps driven by turbines running off the exhaust gases of an IC engine have become increasingly common, especially in automobile applications for both diesel and petrol engines, the latter being more commonly called a turbocharger rather than a supercharger, the latter term coming to mean boost pumps driven off the engine directly and the former meaning boost pumps driven by the exhaust gases.

Diaphragm pumps have been used in IC engines for many years. For example, US IE 0 ο 1 ο 7 7 Patent Specification No. 4,137,020 (Ito) shows a mechanically driven diaphragm pump used to increase the flow of air through the exhaust system so as to reduce noxious emissions. However, in general, the use of diaphragm pumps has been restricted to their use in fuel pumps rather than in the general engine itself.

For environmental reasons, the emissions from internal combustion engines are being controlled more closely by relevant regulating authorities in many countries. Many diesel engines which can be sold successfully at present will be prohibited shortly and indeed many models of diesel engine will have to be taken out of production within the next two or three years unless their emissions can be reduced significantly. Many countries, including the USA, Europe and Japan, either currently or soon, will require diesel engines to have emissions below what are called Tier 1 emission levels. The permissible emission levels will be considerably reduced under a further level to be set called Tier 2 which is due to come into operation about the year 2003/4. Further major reduction in emission levels are projected under a Tier 3 level expected to come into effect around 2008/10.

While it is possible to produce internal combustion engines using extremely high pressure injection to get better spray mist formation within the cylinder to give a reduction in emissions, this is a relatively expensive solution. However, it has long been recognised that a very effective way of reducing harmful emissions in burnt fuel in an internal combustion engine is to supercharge the engine. Heretofore, however, supercharging has been relatively expensive both in capital costs and running costs due to the relatively high power consumption.

In our previous PCT Patent Specification No. WO 99/02829, there is described a supercharged internal combustion engine of the type in which the supercharger is of the positive displacement type having a working stroke for delivering air to the engine combustion chamber and a return stroke drawing air through an air inlet into the supercharger in which the supercharger includes a housing divided by a diaphragm into a front delivery chamber communicating via an outlet with the air inlet duct and a rear chamber open to the atmosphere. Effectively, the housing consisted of two shells with a diaphragm sandwiched therebetween. There are means for moving the diaphragm across the chambers towards and away from the outlet and finally there is IE 0 0 1 0 7 7 a one way valve associated with the diaphragm to allow passage of air between the rear and front chamber during the return stroke of the diaphragm away from the outlet Such a positive displacement diaphragm supercharger has many advantages in that it is lightweight, oil free and of relatively low cost.

Various other problems exist in relation to internal combustion engines over and above those problems first described in PCT Patent Specification No. WO 99/02829.

The invention is directed towards providing an improved air feed assembly for an internal combustion engine and a method of air charging an internal combustion engine together with improved constructions of supercharger.

Statements of invention According to the invention, there is provided an air charging assembly for an internal combustion (IC) engine of the type comprising a supercharger for feeding air through a supercharger air outlet manifold into the cylinder of the IC engine characterised in that there is provided a separate aspirated air inlet manifold for naturally aspirated air for delivery of air through a cylinder air inlet and in which the supercharger has a supercharger outlet valve for the delivery of a pulse of pressurised air into the cylinder. Essentially, what is provided is an air charging assembly for an IC engine for feeding a charge or pulse of pressurized air into the cylinder of the IC engine in addition to naturally aspirated air. By naturally aspirating the engine during a portion of the air inlet cycle, there are reduced energy requirements in the sense that the supercharger is not having to pump this air and further, there is the added advantage of the pulse of pressurized air being introduced into the engine at the most appropriate moment for improved breathing. A considerable power saving is made by combining natural aspiration and supercharging, as the natural aspiration consumes no energy at all.

Ideally, control means are provided to operate the supercharger under defined load conditions. The advantage of this is that, for example, under idling conditions, there is no need to introduce an additional pulse of air into the engine and thus the energy requirements of the supercharger will be minimal.

IE 0 0 1 0 7 7 Ideally, the supercharger feeds the aspirated air inlet manifold through the supercharger outlet valve. It is advantageous that the pulse of air be introduced into the normal air inlet in the same way in which the naturally aspirated air is introduced.

Preferably, the supercharger outlet valve is mounted close to the aspirated air inlet manifold. By using this arrangement, there is little dead volume between the supercharger outlet valve and the air inlet manifold. In this latter embodiment, preferably the supercharger outlet valve is close to the cylinder inlet for the aspirated air inlet manifold. This further reduces the amount of dead volume and further ensures that the whole pulse of air is introduced into the engine and is not, for example, wasted in the manifold.

Ideally, the aspirated air inlet manifold has a one way non-return manifold inlet valve. The advantage of this is that when the pulse of air is introduced into the air inlet manifold, there will be no loss back through the naturally aspirated manifold inlet port.

Preferably, the supercharger outlet valve is a timer valve, the operation of which is controlled by the engine cycle speed. It is undoubtedly ideal to make sure that the supercharger operation is synchronised with the engine speed.

In one embodiment of the invention, the supercharger has an air outlet manifold which feeds the cylinder through an inlet adjacent the bottom dead centre position of the piston of the cylinder. Ideally, the inlet is shaped so as to direct the supercharged air in a swirling motion around the cylinder. By doing this, it is possible to improve swirl which promotes a more complete combustion through improved air/fuel mixing in the engine.

Preferably, the cylinder air inlet incorporates a cylinder inlet valve, the operation of which is synchronised with engine cycle speed and the operation of the supercharger outlet valve is determined by the operation of the cylinder air inlet valve. This synchronisation of both the cylinder inlet valve and the supercharger 0 1 0 7 7i outlet valve is desirable.

Ideally, the supercharger outlet valve opens on or before BDC. Further, the supercharger outlet valve closes after the end of its stroke on or after the cylinder inlet valve closes. Preferably, the supercharger operation is synchronised with the engine cycle speed and is driven at as slow a speed as is practical. Lowering the velocity of the supercharger stroke, reduces pumping losses and improves breathing efficiency thereby optimising energy utilisation and performance.

Preferably, the supercharger comprises a positive displacement supercharger.

In one embodiment of the invention, the positive displacement supercharger comprises a positive displacement piston pump comprising a cylinder housing a piston with associated valving to allow induction and compression strokes.

In one configuration, the cylinder is an enclosed cylinder having an upper wall and a lower wall, the upper wall housing an air inlet valve, the lower wall, an air outlet valve and the piston interposed therebetween carrying an air inlet valve.

In a preferred embodiment of the invention, the positive displacement piston pump is a double-acting supercharger and comprises an enclosed cylinder having an upper wall and a lower wall, each wall having an air inlet valve and an air outlet valve.

Ideally, the piston is mounted on a piston rod projecting through the upper and lower walls, but further development may allow the upper rod element to be dispensed with. When the positive displacement supercharger is a double-acting supercharger, then for a single cylinder, two stroke engine, the supercharger will operate at half the engine speed. Then, for a single cylinder, four stroke engine, the double-acting supercharger will operate at one quarter of the engine cycle speed.

In another embodiment of the invention, the positive displacement piston pump comprises a plurality of cylinders mounted end to end with a common divider wall ΙΕ ο ο 1 Ο 7 1 forming the upper and lower walls of adjacent cylinders. In this latter embodiment, there is a common air inlet duct communicating with each air inlet valve and a common air outlet duct communicating with each air outlet valve.

In one embodiment of the invention, the positive displacement diaphragm supercharger is a single acting supercharger and comprises a housing divided into a non-working chamber and a working chamber by a diaphragm across the housing in which the non-working chamber is open to the atmosphere either permanently or through an inlet valve, the supercharger outlet valve is connected to the other working chamber and a one-way valve is associated with the diaphragm to only allow passage of air between the non-working chamber and the working chamber during the return stroke of the diaphragm away from the outlet valve.

In another embodiment, the positive displacement diaphragm supercharger is a double acting supercharger and comprises a housing divided by a diaphragm into two working chambers, means for moving the diaphragm across the housing and valving associated with the working chambers to allow the passage of air into and out of the chambers, wherein each working chamber has an inlet valve and an outlet valve forming the supercharger outlet valve in the housing, the inlet valve of one chamber being open with the inlet valve of the other chamber closed.

The advantage of a double acting supercharger such as those described above is that each stroke of the supercharger in either direction, is both an inlet stroke and compression stroke and produces a pulse of air. When coupled to a single cylinder four stroke engine, such a double-acting supercharger would ideally operate at quarter engine cycle speed, whereas in a 2 cylinder four stroke engine application, each stroke of the supercharger could supply one cylinder and the supercharger would operate at half engine cycle speed. Ideally, for each stroke in each cylinder of an IC engine, during which or at the end of which a fresh charge of air will enter the cylinder, there will be a matching compression stroke in a positive displacement supercharger built according to the invention. Thus, such a supercharger will, for two stroke engines, ideally provide twice the frequency of compression strokes of a supercharger for four stroke engines with the same IE 0 0 1 0 7 7 number of cylinders. Equally important, other things being equal, a double-acting supercharger (i.e. one in which each stroke provides both an inlet stroke and a compression stroke) will only need to operate at half the cycle speed of a singleacting supercharger. A positive displacement supercharger built according to the invention is very much simpler and cheaper to make than a continuous air pump such as a Roots blower; its intrinsic ability to be more readily designed so as to produce just the volume of air needed and to deliver it when required, results in higher volumetric efficiency and lower pumping energy requirements. Some examples of these important relationships follow.

Ideally, for a single cylinder two stroke engine, a double-acting supercharger will be driven at half the engine cycle frequency with each of the two supercharger working chambers alternately feeding the cylinder.

Ideally, for a single cylinder four stroke engine, a double-acting supercharger will be driven at quarter engine cycle speed. Thus, each of the two supercharger working chambers will alternately feed the engine once in a full engine cycle, i.e. once every four engine strokes. Ideally, with these two latter types of diaphragm supercharger, the housing is a two-part housing comprising a pair of shells sandwiching the diaphragm therebetween and a reciprocal shaft is mounted in the housing and connected to the diaphragm. Where space is at a premium, there is provided:a plurality of side-by-side housings; a rod projecting through the housings operatively connected to each diaphragm; and means to reciprocate the shaft to cause the diaphragms to operate. in this latter embodiment, ideally there is a common air inlet duct, communicating with each air inlet valve and a common air outlet duct communicating with each air outlet valve. ΙΕ η 0 1 0 7 7 Another construction of positive displacement supercharger comprises:a sealed working chamber having enclosure walls formed from a flexible material; an air inlet valve and an air outlet valve incorporated in the chamber; and means for moving the walls apart to increase the size of the chamber and draw air into the chamber and means to move the walls together.

The advantage of this is that it has considerable flexibility of operation and can be made of a variety of metals and materials such as, but not exclusive of, vulcanised rubber, polypropylene or glass-filled polypropylene. The advantage of such a construction is that the material would hot require radial stretching as with the conventionally mounted diaphragms and thus would not be subjected to the same loads as conventional diaphragm type pumps. The cost of such a positive displacement supercharger is less than for a diaphragm type. Thus, while they are superficially similar to diaphragms in their general use, they do not have the same requirements for materials as with more conventional diaphragm pumps.

In this latter embodiment, the walls of the sealed working chamber comprises a pair of flexible sheets connected around their periphery. Ideally, the walls of the chamber are made from a semi-rigid but flexible material such as vulcanised rubber or glass-filled polypropylene, which will not significantly lose their operating characteristics at temperatures up to about 100 Centigrade but could also be made from, for example, thin-walled spring steel sheet.

Ideally, for each air induction stroke of a cylinder, there is a corresponding compression stroke of the supercharger.

In one embodiment of the invention, the IC engine is so constructed whereby parts of the IC engine form part of the assembly.

According to the invention, there is provided a method of air charging an IC engine IE 0 ο 1 Β 7 7 of the type comprising a supercharger for feeding air through a supercharger air outlet manifold in the cylinder of the IC engine, the IC engine having an air inlet and an exhaust outlet in the cylinder comprising:naturally aspirating air into the cylinder through a naturally aspirated air manifold, and at about the time the air inlet closes, delivering a pulse of air from the supercharger into the cylinder.

The advantage of this is that the only work carried out is the work required to deliver the. additional air into the engine rather than in a conventional system where the supercharger does all the work of air charging.

Ideally, the pulse of air is only delivered into the cylinder under predefined engine load and/or speed conditions. This ensures that engine emissions and pumping losses are kept to a minimum throughout the engine speed and load ranges, thereby improving overall efficiency and performance.

Further, ideally the pulse of air is delivered into the naturally aspirated air manifold and through the air inlet with the naturally aspirating air. In this latter method, as the pulse of air is being delivered into the cylinder, the inlet in the naturally aspirated air manifold for naturally aspirating air may be shut off. The ideal way of shutting off this will be by a non-return valve.

In this latter method, on delivery of the pulse of air into the cylinder, the supercharger is isolated from the air inlet and the resultant residual air is stored in the naturally aspirated air manifold. By doing this, there is thus retained a quantity of air which is at higher than atmospheric pressure.

Ideally, the air inlet to the cylinder is opened prior to closing the exhaust valve whereby the residual air is delivered through the cylinder as a pulse of secondary air into the exhaust manifold. This process promotes the purification of emissions through the oxidation of the exhaust gases. The timing of the valve overlap is such that the optimum engine performance is achieved with minimum exhaust emissions.

Detailed Description of the Invention The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:Fig. 1 is a perspective view of one construction of supercharger used in the invention, Fig. 2 is a sectional view showing the supercharger of Fig. 1 mounted on an engine, Fig. 3 is a sectional view through 90° of the supercharger illustrated in Fig. 2, Fig. 4 is a sectional view of another construction of supercharger on a portion of an engine, Fig. 5 is a sectional view of another arrangement of supercharger on a portion of an engine, Figs. 6(a) and (b) are sectional views showing a different construction of supercharger, Figs. 7(a) and (b) show a still further construction of supercharger, Figs. 8(a) and (b) show another construction of supercharger, Fig. 9 shows a double acting positive displacement diaphragm supercharger according to the invention, ΙΕ Ο ο 1 ο π Fig. 10 shows the use of a supercharger such as the supercharger of Fig. 9 in a twin cylinder engine, Fig. 11 shows a stacked supercharger according to the invention, Fig. 12 shows a further stacked supercharger according to the invention, Fig. 13 shows a different stacked supercharger according to the invention, Fig. 14 shows a further construction of an air charging assembly according to the invention, Fig. 15 shows a diagrammatic view of the operation of the embodiment of Fig. 14, Fig. 16 shows portion of an air filter of an engine incorporating the supercharger according to the invention, Fig. 17 is a perspective view of a supercharger according to the invention, Fig. 18 is a sectional view of the supercharger of Fig. 17 mounted on an engine, Fig. 19 is a diagrammatic view of the positive displacement supercharger of 25 Fig. 17, Fig. 20 is a diagrammatic view similar to Fig. 19 of a still further construction of supercharger according to the invention, 0 Fig. 21 is a diagrammatic view of a stacked supercharger according to the invention, Figs. 22(a) to (d) are diagrammatic views of another construction of supercharger according to the invention, and π 0 1 0 Figs. 23(a) to (d) are diagrammatic views of a still further construction of supercharger according to the invention.

Referring to the drawings and initially to Figs. 1 to 3 thereof, there is provided an air charging assembly including a positive displacement supercharger, indicated generally by the reference numeral 1, formed from a housing having an upper shell 2 and a lower shell 3 sandwiching a diaphragm 4 therebetween, which diaphragm 4 is carried by a piston plate 5 having reed valves 6. The upper shell 2 has a permanently open inlet valve formed by a hole 7. The lower shell 3 mounts a reed valve 8 feeding a short supercharger air outlet manifold 9 mounting a conventional pressure release poppet valve forming a supercharger outlet valve 10 which is mounted in an aspirated air inlet manifold 15 in an engine, indicated generally by the reference numeral 20. The engine 20 is shown with a conventional exhaust valve 21 and a conventional air inlet valve 22 mounted in the air inlet 26 of a cylinder 23. The aspirated air inlet manifold 15 has a one-way non-return manifold inlet valve 16. The piston plate 5 is mounted by means of a reciprocal rod 24 iri a casing 25 which in turn carries a cam system, indicated generally by the reference numeral 30 and forms means for moving the diaphragm 4.

Referring now specifically to Figs. 2 and 3, it should be noted that in Fig. 3, the air manifold 15 is not illustrated. The cam system comprises an eccentric cam 31 mounted on a shaft 32 driven by a gear 33 in turn driven by a further gear 34 on a main engine drive shaft 35. The eccentric cam 31 engages a cam follower 36 which reciprocates the rod 24 within the casing 25.

Obviously, in some 2-stroke engines, the air inlet valve 22 is dispensed with.

In operation, with the supercharger 1 in the position illustrated in Figs. 2 and 3, the rod 24 is at the bottom of its travel and the reed valve 8 has opened as well as the supercharger outlet valve 10 which then delivers a charge or pulse of air into the aspirated air inlet manifold 15 which pulse of air is then delivered through the inlet valve 22 and air inlet 26 into the cylinder 23 of the engine. In this specification, IE 0 ο 1 0 Π reference is made to a “pulse” of air while the term “charge” may be more correct. However, the term “pulse” is used to signify that the charging by air is not over a long time such as all or a substantial portion of the engine cycle. Strictly speaking, there is not a need for both the reed valve 8 and the poppet valve 10 to act as a supercharger outlet valve. However, in this embodiment, the poppet valve 10 forms the main supercharger outlet valve. The poppet valve 10 operates under pressure and will only release air into the aspirated air inlet manifold 15 when the pressure is correct so a pulse of air is delivered into the cylinder 23. Then, since the rod 24 is in its lowermost position, it will start to rise, the poppet valve 10 will have shut off, the reed valve 8 will close and the reed valve 6 will open as air is drawn in through the inlet hole 7. When the rod 24 reaches the top of its travel, it will reverse and then the reed valve 6 will close, while the reed valve 8 will remain closed until such stage as the pressure developed in the supercharger is sufficient to overcome the resident pressure acting on the outlet manifold side of the reed valve 8. The air will be pressurised between the piston plate 5 and diaphragm 4, the lower shell 3 and the short supercharger air inlet manifold 9. In this embodiment, the timing of the pulse of air into the cylinder 23 is controlled by the supercharger outlet valve 10. The various timing possibilities are discussed in more detail below.

Essentially, what is provided is a separate, almost totally conventional, air inlet manifold for the naturally aspirated air, namely, the aspirated air inlet manifold 15 and the additional supercharger 1 which has a supercharger outlet valve, in this case, the poppet valve 10 for delivery of a pulse of pressurised air into the cylinder 23.

Strictly speaking, the supercharger 1 has two outlet valves, namely, the poppet valve 10 and the reed valve 8 and only one is required to provide the pulse of air.

Referring now to Fig. 4, again the supercharger is identified by the reference numeral 1, and parts similar to those described with reference to the previous drawings are identified by the same reference numerals. In this embodiment, the supercharger outlet valve is a standard pressure relief high lift poppet valve 40, the air charging assembly operating exactly the same as heretofore, (I Q 1 Q ? Γ Fig. 5 illustrates the same supercharger 1 and again parts similar to those described with reference to the previous drawings, are identified by the same reference numerals. In this embodiment, the aspirated air inlet manifold 15 incorporates a reed valve 42 providing a one-way non-retum manifold inlet valve and the supercharger outlet valve is provided by a pressure relief snap valve 43 of conventional construction.

Referring now to Figs. 6(a) and (b), the supercharger 1 is illustrated in two positions showing the supercharger 1 at the top of its travel and at the bottom of its travel. In this embodiment, the rod 24 has mounted on it, a spool valve 45 which operates as the supercharger outlet valve for delivery of pressured air into the air manifold 15. It will be noted that there is only one supercharger outlet valve in this embodiment. At the start of the supercharger working stroke, as shown in Fig. 6(a), the spool valve 45 is closed and it opens at the end of its working stroke as shown in Fig. 6(b).

Figs. 7(a) and (b) illustrate an alternative construction of offset spool valve 46 mounted in the aspirated air inlet manifold 15. In this embodiment, the spool valve 46 operates not only to allow for the delivery of pressurised air into the air manifold 15 but also operates as a one way aspirated air inlet manifold valve. This will be clearly seen from Fig. 7(a) when it will be noted that the construction of the spool valve 46 is such as to prevent air being delivered through the aspirated air inlet manifold 15.

Now, referring to Figs. 8(a) and (b), there is illustrated an alternative construction of supercharger, indicated generally by the reference numeral 50, again parts similar to those described with reference to the previous drawings, are identified by the same reference numerals. In this embodiment, an upper shell is not used and the lower shell 3 again has an air outlet formed from the reed valve 8 and in this embodiment, an air inlet formed by a further reed valve 51 in the lower shell 3. Thus, in this embodiment, the piston plate 5 does not incorporate any valves. The operation can be easily seen from Figs. 8(a) and (b) wherein 8(a) illustrates the pulse of air being delivered out of the supercharger 50, while Fig. 8(b) shows the supercharger inducing air as it reaches the end of its travel.

All constructions of supercharger 1 described above comprise a housing divided into a non-working chamber and a working chamber with the diaphragm across the housing and the non-working chamber is open to the atmosphere through the hole 7 which is effectively a permanently open inlet valve. Thus, they are all single acting positive displacement superchargers.

Referring to Fig. 9, there is illustrated another construction of supercharger, indicated generally by the reference numeral 55 and parts similar to those described with reference to the previous drawings are identified by the same reference numerals. In this embodiment, the supercharger 55 is a double acting supercharger in which the upper shell 2 has an air inlet valve 56 and an air outlet valve 57, while the lower shell 3 carries an air inlet valve 58 and an air outlet valve 59. Again, all are reed valves. In operation, the supercharger 55 can operate at half the speed as heretofore because there are two working chambers, namely, above and below the diaphragm 4. Thus, for a single cylinder two stroke engine, it can operate at half the engine cycle speed and for a single cylinder four stroke engine, it can operate at one quarter engine cycle speed.

Fig. 10 illustrates in broad outline, a supercharger, effectively identical to the supercharger 55 and is thus identified by the same reference numeral, except that instead of feeding the one air manifold 15, it feeds two cylinders 60 and 61 respectively, of a four stroke twin cylinder engine, indicated generally by the reference numeral 62.

Referring to Fig. 11, there is illustrated an alternative construction of supercharger, indicated generally by the reference numeral 65, which essentially consists of superchargers identical to the supercharger 55, which are stacked one on top of the other and parts similar to those described with reference to the previous drawings in respect of the supercharger 55, are identified by the same reference numerals. It will be appreciated that the upper shell 2 of some of the units effectively forms both an upper and lower shell. There are effectively side-by-side housings. In this embodiment, there is provided the one supercharger air inlet IE 0 θ 1 0 7 7 manifold 66 and the one supercharger outlet manifold 67 which could in tum be connected to a supercharger outlet valve which is not shown.

Referring now to Fig. 12, there is illustrated the supercharger 65 except that in this case, instead of being driven by a cam arrangement, it is driven by a hydraulic pump 68 and master and slave cylinder drive 69. Fig. 13 illustrates a pneumatic pump 68 with master and twin slave cylinders 69.

Referring now to Figs. 14 and 15, there is illustrated the supercharger 65 having a supercharger outlet valve 69 which, in this case, is a solenoid valve feeding, by means of supercharger outlet pipe 71, the cylinder 23 through an inlet 72 which is adjacent piston bottom dead centre. This piston is identified by the reference numeral 73. It will be seen from Fig. 15 that the pulse of air, when delivered into the cylinder 23, will assume a swirling motion around the cylinder 23.

Referring to Fig. 16, there is illustrated a supercharger 1 now incorporated within an air filter, indicated generally by the reference numeral 75. Since the supercharger 1 is effectively identical in construction to the supercharger illustrated in Fig. 4, parts similar to those identified with reference to Fig. 4, are identified by the same reference numerals. In this embodiment, the upper shell 2 has permanently open inlet valves formed by holes 76, a cover 77 and a filter medium 78 complete the air filter 75.

Referring now to Figs. 17 to 19 inclusive, there is illustrated an air charging assembly including a positive displacement supercharger, in this embodiment, a positive displacement piston pump, indicated generally by the reference numeral 80, formed from an enclosed cylinder 81 having an upper wall 82 and a lower wall 83. The upper wall 82 has an air inlet valve formed from a permanently open hole 84 and an outlet valve 85 formed from a conventional reed valve. A piston 86 mounted on a con rod 87 is housed within the enclosed cylinder 81 and in tum has an inlet valve 88. It will be noted that the con rod 87 is supported in the lower wall 83 by a guideways.

In operation, as the piston 86 moves upwards, the inlet valve 88 opens and air is induced beneath the piston 86. When the piston 86 reverses direction and starts to move downwards towards the lower wall 83, the inlet valve 88 shuts and the outlet valve 85 can open. Depending on the construction of the outlet valve, the time of opening will change and the outlet valve could be a positively controlled outlet valve, in which case it would operate as a supercharger outlet valve to give a pulse of air into the engine.

This embodiment of the invention operates in exactly the same way as the embodiments previously described. Obviously, the arrangement of positive displacement piston pump is such that the speed of operation will be irrelevant and it can be manufactured from suitably rigid and hard wearing materials. Indeed, since such positive displacement piston pumps are relatively easily provided, it will not cause any great manufacturing problems. Such a piston pump will not require lubrication or sealing and because of its better space utilization, it will actually take up less space than diaphragm type arrangements previously described of an equal swept volume.

Referring now to Fig. 20, there is illustrated an alternative construction of doubleacting supercharger, in this case, a double-acting positive displacement piston pump, indicated generally by the reference numeral 90, comprising again a piston 91 mounted within an enclosed cylinder 92 having an upper wall 93 and a lower wall 94, the upper wall 93 housing an inlet valve 95 and an outlet valve 96, while the lower wall 94 houses an inlet valve 97 and an outlet valve 98. The piston 91 is again mounted on a piston rod 99 again projecting through supports 100, 101 in the upper wall 93 and the lower wall 94 respectively. The operation of the positive displacement piston pump 90 forming the positive displacement supercharger can be readily easily seen from the drawings. Whether both upper and lower guideways or supports are required will depend on the operating conditions.

Referring now to Fig. 21, there is shown a still further construction of positive displacement supercharger, in this case, a positive displacement piston pump, indicated generally by the reference numeral 110 comprising, in this case, three cylinders 111 mounted end to end and having divider walls 112 forming combined upper and lower walls of adjacent cylinders, together with one separate upper wall IE 0 ο 1 0 7 7. 113 and one separate lower wall 114. Each cylinder 111 has two air inlet valve 115 and 116 and two air outlet valves 117 and 118. The air inlet valves are still mounted in the upper and lower walls respectively, while the air outlet valves 117 and 118 are now mounted in the cylinder walls. The air inlet valves 115 and 116 all communicate with a common air inlet duct 120 and the air outlet valves 117 and 118 communicate with a common air outlet duct 121. The positive displacement piston pump houses three pistons 123, all on the one piston rod 124 supported within lower and upper guideways 125 and 126 respectively. The advantage of this arrangement is that there is a smaller piston travel required. However, equally well, the stacked arrangement could be so provided that instead of having the outlet valves all connected to an outlet port or outlet duct, they could each in turn be connected to separate outlet ducts, thus allowing the stacked arrangement, in this case, for example, to feed all the cylinders of a six cylinder engine. It will be appreciated that any suitable construction of positive displacement piston pump comprising a cylinder housing a piston with associated valving to allow induction and compression strokes, may be provided, and that the particular example shown are for illustrative purposes only.

It is envisaged that such a construction would be particularly useful combined with an air filter as the reciprocation of the piston rod could be easily accommodated within the air filter, thus not adding any height to the assembly.

Referring now to Figs. 22(a) to (d), there is illustrated an alternative construction of positive displacement supercharger, indicated generally by the reference numeral 130, which comprises two flexible sheets connected together around their peripheral edge 133 to form enclosure walls 131 and 132 for a sealed working chamber 137 and mounting an actuating rod 134 connected rigidly to the sheet 131 and slidable through the sheet 132. The sheet 131 has an inlet flap valve 135 such as a reed valve and the sheet 132 has an outlet valve 136 which again could be provided by a reed valve. Fig. 17(a) shows the supercharger 130 about to start its power stroke with the inlet valve 135 closed and the outlet valve 86 also closed. In Fig. 22(b), it can be seen that the supercharger 130 has almost reached the end of its compression stroke when the flap valve 136 opens. Then, in Fig. 22(c), it reaches the end of its stroke and the rod 134 starts to move in the opposite l£0 0 1 0 71 direction at which stage the outlet valve 136 closes and the inlet valve 135 opens to induce air. The sheets 131 and 132 do not have to be of the same material as conventional diaphragm material in that they do not have to, as with the common diaphragms, expand in a radial direction. They simply move apart and together. Thus, they could be, for example, of sheet metal such as spring steel, vulcanised rubber or a suitable flexible plastics material such as polypropylene or a glassfilled polypropylene. If a rubber-like material was used, there would be some circumferential expansion, however, it would be relatively minor.

Referring now to Fig. 23, there is illustrated an alternative construction of a single acting, positive displacement supercharger, indicated generally by the reference numeral 140, substantially similar to the supercharger 130 and thus parts similar to those described with reference to Fig. 22, are identified by the same reference numerals. In this embodiment, the two sheets 131 and 132 are anchored at 141 and a rod 142 is connected opposite the anchorage, that is to say, diametrically opposed thereto. Again, it can be seen that in Fig. 23(a), the supercharger is about to start its compression stroke which continues until the outlet valve 136 opens, as illustrated in Fig. 23(b) and then when the supercharger has reached the end of its travel, as shown in Fig. 23(c), the rod 142 reverses travel and the induction stroke is clearly shown in Fig. 23(d).

Control means may be provided to operate the supercharger only at certain load conditions. Such a control means could be by any well known means whether it be simply fuel usage, gearing, a clutch, or the like.

Preferably, the supercharger outlet valve is mounted close to the aspirated air inlet manifold and in tum, it should be close to the cylinder inlet for the aspirated air. While in the embodiments described above, the aspirated air inlet manifold has a one way non-retum manifold inlet valve, these are not always essential. The supercharger outlet valve will generally be a timer valve. Thus, some of the reed valves illustrated may not always be essential. However, as shown, there is no need for the supercharger to feed the engine through the aspirated air inlet manifold. It will be appreciated that essentially, the operation of the supercharger be synchronised with engine cycle speed and that the operation of the IE 0 0 1017 supercharger outlet valve be determined by the operation of the cylinder air inlet valve or by the engine cycle.

Ideally, as mentioned above, the supercharger outlet valve opens on or before bottom dead centre. Because of gas dynamics and other considerations, generally the supercharger outlet valve will close after the air inlet valve has closed. As stated already, the supercharger should be run at such a cycle speed as will provide a pulse of pressurized air to each inlet stroke of the engine. For one or two cylinder engines, the supercharger is likely to be run at either half and quarter engine cycle speed, depending on whether it is a two stroke or four stroke engine and the number of cylinders. The invention is sufficiently cheap and compact to envisage multiple units being mounted on a multi-cylinder engine, for example on the basis of one per cylinder or one per two cylinders.

One of the advantages of the present invention is that the normally aspirated air does not pass through the supercharger which means that there is less work being done by the supercharger.

When the air manifold for the normally aspirated air includes a non-return valve, there is a surprising advantage with the present invention which arises because after the pulse of air has been delivered into the engine and the inlet valve has closed or the supercharger valve has closed as the case may be, there is then an amount of resident air in the air manifold, which air will be at a reasonably elevated pressure because it will be at the same pressure approximately as that of the cylinder when the air inlet shuts. Thus, it will be at approximately the supercharge pressure of the engine at the point of delivery of the supercharged air pulse. Thus, when the air inlet valve of the engine is first opened, there will be a pulse of scavenging air introduced into the engine in the period known as the valve clip, that is to say, in the period between inlet opening and exhaust closing. This effectively produces a secondary air supply to the exhaust manifold. Indeed, it is envisaged that the length of time between the opening of the inlet valve and the closing of the exhaust valve, i.e. the valve dip, may vary compared to conventional engines having regard to the fact that there is this pulse of air delivered into the exhaust which will reduce exhaust emissions. This pulse of air could in fact be diverted into the exhaust system but that is unlikely as it appears the ο 0 1 ο N ideal way to do it is to actually direct that pulse of air into the engine cylinder.

Generally speaking, in a single cylinder four stroke engine application, a single-acting supercharger according to the invention will, be run at half the cycle speed of the engine, while a double-acting supercharger will be operated at quarter the engine cycle speed. This halving of the supercharger operating velocity will substantially improve the volumetric efficiency of each filling stroke of the supercharger, as well as ensuring reduced wear rates. Precise advance or delay in the relative timing between the opening of the supercharger outlet valve and the arrival of the piston at bottom dead centre may well vary in different installations and will depend largely on the particular characteristics of the engine in which it is used.

It is envisaged that in many situations, a single acting supercharger operating at half engine speed may be preferred. It may be that the possible increased breathing efficiency may be outweighed by the extra complexity and costs of a double acting supercharger arrangement It is envisaged that the length of the supercharger diaphragm or piston stroke will be less than that of the engine piston, probably between 1:3 and 1:6. This in tum will reduce the actual average diaphragm or piston velocity during each stroke, which will thus be likely to be between one sixth and one twelfth the speed of the engine piston. This again will have considerable advantages for diaphragm or piston wear and tear as well as improving the volumetric efficiency on each inlet stroke of the supercharger.

It will be appreciated that while in the above, we have always referred to a supercharger as forming part of the air charging assembly, it could equally well be correctly referred to as an air pump. This may, in some ways, be a more correct term to apply to the air charging assembly, namely, a combination of an air pump and natural aspiration since the actual amount of “supercharging” will, in many applications, be relatively slight Various types of valving may be used, such as, pneumatic, hydraulic, electric or electronic. ,£(101077 As has been mentioned above, for good volumetric efficiency, as well as low wear, it is highly desirable that the supercharger moving element® move at as low a velocity as is practical. Therefore, having its operating cycle frequency at one quarter of the engine cycle speed is advantageous. Then again, if the stroke is reduced, the velocity is further reduced. This is one of the advantages of the stacking arrangement shown in that one would, as well as saving space, be able to deliver the amount of air required at relatively slow speeds. It will be appreciated that the timing of the actual pulse of air delivered into the engine can be critical for good performance.

While in the embodiments described above, all the superchargers have been positive displacement superchargers, it will be appreciated that they could be replaced by a more conventional type of supercharger or continuous air pump such as a Roots blower. A continuously operating blower for a multicylinder IC engine could be used to charge a plenum chamber on a continuous basis. The chamber could have a valving and manifold arrangement such as to discharge a pulse or charge of air into the cylinder of the engine at the appropriate time. Such an arrangement does not require further description.

While in the embodiment described with reference to Fig. 18, the supercharger has been shown incorporated in the air filter, it will be appreciated that since the supercharger constructions, according to the present invention, are relatively lightweight, they can be incorporated in other parts of the engine such as, for example, near the air filters and the like, or indeed, as shown, can form part of the air filter.

While in all the embodiments described above, the superchargers have been used with a specific charging assembly, it will be appreciated that the superchargers according to the invention could be used in a conventional supercharger arrangement, namely, delivering all the air to the engine. This would include not only the specific type of construction of supercharger, but also the manner in which they are operated specifically but not exclusively to the matching of supercharger and engine cycle speed. The specific constructions of supercharger and the manner in which they are used have wider applications and uses than described herein as will be readily appreciated by those skilled in the art.

IE Ο Ο 1 ο 7 7 In the specification the terms “comprise, comprises, comprised and comprising” or any variation thereof and the terms “include, includes, included and including” or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described but may be varied in construction within the scope of the claims.

Claims (45)

1. An air charging assembly for an internal combustion (IC) engine of the type comprising a supercharger for feeding air through a supercharger air outlet manifold into the cylinder of the IC engine characterised in that there is provided a separate aspirated air inlet manifold (15) for naturally aspirated air for delivery of air through a cylinder air inlet (26) and in which the supercharger (1) has a supercharger outlet valve (10) for the delivery of a pulse of pressurised air into the cylinder (23).

2. An air charging assembly as claimed in claim 1, in which control means are provided to operate the supercharger (1) under defined load conditions.

3. An air charging assembly as claimed in any preceding claim, in which the supercharger (1) feeds the aspirated air inlet manifold (15) through the supercharger outlet valve (10).

4. An air charging assembly as claimed in claim 3, in which the supercharger outlet valve (10) is mounted close to the aspirated air inlet manifold (15).

5. An air charging assembly as claimed in claim 3 or 4, in which the supercharger outlet valve (10) is mounted close to the cylinder air inlet (26).

6. An air charging assembly as claimed in any preceding claim in which the aspirated air inlet manifold (15) has a one way non-return manifold inlet valve (16).

7. An air charging assembly as claimed in any preceding claim, in which the supercharger outlet valve (15) is a timer valve, the operation of which is controlled by the engine cycle speed.

8. An air charging assembly as claimed in claim 1 or 2, in which the supercharger has an air outlet manifold (67) which feeds the cylinder (23) through an inlet (72) adjacent the bottom dead centre position of the piston ο ο 1 0 7 Τ’ (73) of the cylinder (23).

9. An air charging assembly as claimed in claim 6, in which the inlet (72) is shaped so as to direct the supercharged air in a swirling motion around the 5 cylinder (23).

10. An air charging assembly as claimed in any preceding claim, in which the cylinder air inlet (26) incorporates a cylinder inlet valve (22), the operation of which is synchronised with the engine (20) cycle speed and the 10 operation of the supercharger outlet valve (10) is controlled by the operation of the cylinder air inlet valve (22).

11. An air charging assembly as claimed in any preceding claim, in which the supercharger outlet valve (10) opens on or before BDC.

12. An air charging assembly as claimed in any preceding claim, in which the supercharger outlet valve (10) closes after the end of its stroke on or after the cylinder air inlet (26) closes. 20

13. An air charging assembly as claimed in any preceding claim, in which the supercharger (1) speed is synchronised with the engine (20) cycle speed and is driven at as slow a speed as is practical.

14. An air charging assembly as claimed in any preceding claim, in which the 2 5 supercharger (1) comprises a positive displacement supercharger.

15. An air charging assembly as claimed in claim 14, in which the positive displacement supercharger comprises a positive displacement piston pump (80) comprising a cylinder (81) housing a piston (86) with associated 3 0 valving (84,85,88) to allow induction and compression strokes.

16. An air charging assembly as claimed in claim 15, in which the cylinder is an enclosed cylinder (81) having an upper wall (82) and a lower wall (83), the upper wail (82) housing an air inlet valve (84), the lower wall (83), an air IE 0 ο 1 ο 7 7ί outlet valve (85) and the piston (86) interposed therebetween carrying an air inlet valve (88).

17. An air charging assembly as claimed in claim 15, in which the positive displacement piston pump (90) is a double-acting supercharger and comprises an enclosed cylinder (92) having an upper wall (93) and a lower wall (94), each wall (93, 94) having an air inlet valve (84, 97) and an air outlet valve (96, 98).

18. An air charging assembly as claimed in claim 17, in which the piston (91) is mounted on a piston rod (99) projecting through the upper and lower walls (93, 94).

19. An air charging assembly as claimed in claim 17 or 18, in which for a single cylinder, four stroke engine, the supercharger speed is half the engine cycle speed.

20. An air charging assembly as claimed in claim 17 or 18, in which for a single cylinder, four stroke engine, the supercharger speed is quarter the engine cycle speed.

21. An air charging assembly as claimed in any of claims 15 to 20, in which the positive displacement piston pump (110) comprises a plurality of cylinders (111) mounted end to end with a common divider wall (112) forming the upper and lower walls of adjacent cylinders.

22. An air charging assembly as claimed in claim 21, in which there is a common air inlet duct (120) communicating with each air inlet valve (116, 117) and a common air outlet duct (121) communicating with each air outlet valve (117,118).

23. An air charging assembly as claimed in claim 14, in which the positive displacement diaphragm supercharger is a single acting supercharger (1) and comprises a housing divided into a non-working chamber and a IE 0 0 1 0 7 7 working chamber by a diaphragm (4) across the housing in which the nonworking chamber is open to the atmosphere through a permanently open inlet valve (7), the supercharger outlet valve (10) is connected to the other working chamber and a one-way valve (16) is associated with the diaphragm to only allow passage of air between the non-working chamber and the working chamber during the return stroke of the diaphragm (4) away from the outlet valve (10).

24. An air charging assembly as claimed in claim 14, in which the positive displacement diaphragm supercharger is a double acting supercharger (55) and comprises a housing divided by a diaphragm (4) into two working chambers, means for moving the diaphragm across the housing and valving (56, 57, 58, 59) associated with the working chambers to allow the passage of air into and out of the chambers, wherein each working chamber has an inlet valve (56, 58) and an outlet valve (57, 59) forming the supercharger outlet valve in the housing, the inlet valve (56) of one chamber being open with the inlet valve (58) of the other chamber closed.

25. An air charging assembly as claimed in claim 24, in which for a single cylinder, two stroke engine, the supercharger operating speed is half the engine cycle speed.

26. An air charging assembly as claimed in claim 24, in which for a single cylinder, four stroke engine, the supercharger operating speed is quarter the engine cycle speed.

27. An air charging assembly as claimed in any of claims 23 to 26 , in which the housing is a two-part housing comprising a pair of shells (23) sandwiching the diaphragm (4) therebetween and a reciprocable rod (24) is mounted in the housing and connected to the diaphragm (4).

28. An air charging assembly as claimed in claim 27, in which there is provided:28 IE Ο 0 1 Ο 7 3 a plurality of side-by-side housings; a rod (24) projecting through the housings operatively connected to each diaphragm (4); and means to reciprocate the rod (24) to cause the diaphragms (4) to operate.

29. An air charging assembly as claimed in claim 28, in which there is a 10 common air inlet duct (66), communicating with each air inlet valve (56, 58) and a common air outlet duct (67) communicating with each air outlet valve (57, 59).

30. An air charging assembly as claimed in claim 14, in which the positive 15 displacement supercharger (130) comprises:a sealed working chamber (137) having enclosure walls (131, 132) formed from a flexible material; 20 an air inlet valve (135) and an air outlet valve (136) incorporated in the chamber; and means for moving the walls (131, 132) apart to increase the size of the chamber and draw air into the chamber and means to move the 2 5 walls (131, 132) together.

31. An air charging assembly as claimed in claim 30, in which the walls (131, 132) of the sealed working chamber comprises a pair of flexible sheets connected around their periphery (133).

32. An air charging assembly as claimed in claim 30 or 31, in which the walls (131, 132) of the chamber are made from a substantially rigid but flexible material. IE 0 0 1 01 Ί'

33. An air charging assembly as claimed in claim 32, in which the material is thin walled steel sheet.

34. An air charging assembly as claimed in claim 33, in which the material is vulcanised rubber.

35. An air charging assembly as claimed in claim 32, in which the material is polypropylene.

36. An air charging assembly as claimed in claim 32, in which the material is glass-filled polypropylene.

37. An air charging assembly as claimed in any of claims 14 to 36, in which, for each air induction stroke of a cylinder (23), there is a corresponding compression stroke ofthe supercharger (1).

38. An air charging assembly as claimed in any preceding claim incorporated in the IC engine (20) whereby parts of the IC engine forms part of the assembly.

39. A method of air charging an IC engine of the type comprising a supercharger for feeding air through a supercharger air outlet manifold in the cylinder of the IC engine, the IC engine having an air inlet and an exhaust outlet in the cylinder comprising:naturally aspirating air into the cylinder through a naturally aspirated air manifold, and at about the time the air inlet closes, delivering a pulse of air from the supercharger into the cylinder.

40. A method of air charging as claimed in claim 39, in which the pulse of air is only delivered into the cylinder under predefined engine load conditions.

41. A method as claimed in claim 39 or 40 in which the pulse of air is only IE 0 0 1 Q 7 7 delivered into the cylinder under predefined engine speed conditions.

42. A method of air charging as claimed in any of claims 39 to 41, in which the pulse of air is delivered into the naturally aspirated air manifold and through 5 the air inlet with the naturally aspirating air.

43. A method of air charging as claimed in claim 42, in which, as the pulse of air is being delivered into the cylinder, the inlet in the naturally aspirated air manifold for naturally aspirating air is shut off.

44. A method of air charging as claimed in claim 43, in which, on delivery of the pulse of air into the cylinder, the supercharger is isolated from the air inlet and the resultant residual air is stored in the naturally aspirated air manifold.

45. A method of air charging as claimed in claim 44, in which the air inlet to the cylinder is opened prior to closing the exhaust valve whereby the residual air is delivered through the cylinder as a pulse of secondary air into the exhaust manifold.