DE2451064A1 - FOUR-STROKE COMBUSTION ENGINE - Google Patents

Description

Dipl. Iη ο. H J. Huebner

8SG0 Κ .. .T.o-en / AHp. Su. 52 · ie, * iion 0 <J5i / 2J2f ι

5 · 10th 1974

VIBRTAKT - COMBUSTION ENGINE

The invention relates to a four-stroke internal combustion engine, the first Has a camshaft for actuating the intake valves and a second camshaft for actuating the exhaust valves.

809850/0258

The emission of pollutants as a result of the operation of combustion engines has become a matter of serious social unrest. Increasingly stringent restrictions on these air pollutants are being put in place, and there is an urgent need for engines that comply with European regulations. The best solution will be one in which essential parts of the existing technology and tools refuse ;;: which can and which can be used for engines of the current construction without the need for radical changes. Solutions ^ radical new designs and extreme changes in Kotorei-iX & nscptionen and K _o nstruktionen bring with them are probably due dec resistance to changes in buyers and those müseo learn the production and maintenance of the new mechanisms;. "wer-ige;: effective. As a result, delays and inefficiencies can be expected if significant deviations from existing technologies are necessary.

It is an object of Erf _y indung for a solution to the problem dso emissions to ensure contaminants ^ in which a substantial portion of the existing Technologio can be used and which when used ·. · In some or even most conventional Vorbrer.-RRAR .g:> motors only makes relatively small changes and constructions necessary. Other conventional engines can be bigger ;; Modifications need to be made, but these are clearly understandable and easy to use. are. It can therefore be expected that these will cause minimal resistance to their use.

5 0 9 8 5 0/0258 BAD ORIGINAL

2A51064

It is another object of the invention ^ internal combustion engines and To create methods for their operation in which the emission of impurities, especially carbon monoxide (CO), unburned hydrocarbons (hereinafter generally referred to as HC) and Stickctoffoncyao (hereinafter generally referred to as 110κ) can be minimized. Testing;, which with engines using some features of the present. Invention have shown that in 1974 the for 1S77 anticipated provisions for automobiles can be met.

"Fundamental to this invention is the fact that the emissions of the three major impurities, namely CO, KC and KOa: mininalisiort can be made by using an internal combustion engine with an air / fuel ratio operated, the leaner than the stoGchiometricche Ratio is. A "stoichiometric mixture" is a mixture in which after the end of the combustion, as far as the limiting substance (fuel or oxygen) permits, neither an excess of Oxygen still remains an excess of fuel. Using of gasoline is the numerical fourth of the stoochionetric ratio about 15 that is, the carburetor mixes about 15 weight units. Air for ever Unit of weight of gasoline that is brought into the air stream. Kit the iiior The term "fuel" is used to refer to gasoline and similar liquids Hydrocarbon-free means substances. Lean mixes have one relatively larger numerical value of their air / fuel ratio sec ■ and have excess oxygen. Lean kishunge; a are used here as Mixtures with a higher air / fuel ratio than the stichiometric one Mixture defines. The term "ratio ·" is sometimes used alternately with its numerical value. In contrast to

B0-9 8B0 / 0258

BATH ORIGINAL

2A51064

Richer mixes have a relatively smaller rich mixes are here than mixes with a smaller Lyft / I fuel ratio defined as the stoechiometric mixture. In a rich mixture is not enough oxygen to use up all of its fuel. Rich mixes have excess fuel and tend to cause the emission of CO and unburned EC.

Although it is economically and environmentally desirable to have one. Operating an engine with lean mixtures has so far not been practicable under all engine operating conditions. It is currently possible to operate an engine with lean mixtures at constant load under relatively high load conditions, but not at relatively low load conditions. Until now it has not been possible ,, an M ₀ tor, lower with lean mixtures of both and operate high load conditions, and especially not when the load of Kotora more or less suddenly changes. The opportunity to minimize the emission of contaminants by running an engine with lean mixtures could therefore not be fully exploited.

It turned out that mainly two measures are necessary are. In the first case, care must be taken that the operating conditions allow a lean mixture to be used. This can be done by Control of the residue can be achieved. Furthermore, the mixture must be flammable, which is achieved by ensuring good atomization.

References will be made repeatedly to low load and high load conditions. In the operation of conventional internal combustion engines

509850/0258

BAD ORiGiNAL

at low load conditions, the throttle is almost closed ^ and the suction pressure is normally much lower than the L ^J zv.az- phärendruck. This is usually called a "high vacuum" and occurs when idling and driving at idle _t, as well as in other operating conditions where only a relatively small amount of power is required from the liotor. will. In contrast, when the load is high, the throttle valve is relatively wide open and occurs when driving at high speed on flat roads and when driving uphill. ^T /. ^r hen the throttle valve under high BelastungszusSiänden is open, the suction pressure decreases gogon the atmospheric pressure to go. This condition is commonly called "Low Vacuuru" »

While the borderline between the low-stress and high-stress states is a wide and continuous band, each one contains conventional Combustion engine an operating state that is characterized by a fairly low intake pressure (a fairly closed throttle valve) is where the engine just bumps, if at all, and ignites if a lean mixture is fed to him while he is with the same mixture and with a high suction pressure, (a sufficiently opened Throttle valve) runs satisfactorily. The former botricbs condition is called the low-load condition and the latter operating condition is defined as a high load condition. Any mixture, whether lean or rich, tends to be less ignitable in low boil conditions conditions, but the problem is greater when using lean mixtures will. With conventional engines, the problem of low load operation becomes often due to a higher mixture setting on

509850/0258 bathroom original

gas corrected. Although this setting compensates for the running of the engine, this causes an unacceptably high emission of impurities.

In addition, the ignitability of any mixture is reduced, whether lean or rich, with more or less sudden changes in the stress level of the engine or in the event of more or less sudden changes the throttle position, as there is a change in the air / fuel ratio which can lead to a film of fuel on the Wall of the suction line forms and / or that relatively large droplets of fuel are formed form.

The principal problem when operating an internal combustion engine at Low stress conditions with lean mixtures is the phenomenon of Misfire. As used herein, "misfire" means that a The air / fuel mixture compressed in the cylinder does not ignite properly or does not ignite at all. As a result, there is a significantly lower rate Engine power, uneven engine running, and high pollutant emissions when the misfire occurs. In this invention, means are before-r seen that allow the operation of an engine with lean mixtures at low load conditions without misfiring, where this has not previously been possible was possible. Accordingly, the invention enables the use of lean mixtures in an internal combustion engine under both low load and high load conditions , with only minimal contamination in all operating states be expelled.

The tendency of an engine to misfire is directly related to the numerical value of a mathematical expression, hereinafter referred to as "Residue-

509850/0258

The residue break is defined as follows:

Backlog

Amount of gas residues that remain in the combustion chamber from the previous cycle

Amount of air Amount of gas residues (or air / debris from the pre-fuel mixture), outgoing cycle those for the next in the combustion cycle the combustion chamber remains in the combustion chamber

The term "amount" refers to the weight or volume that the same temperature and pressure is measured. If the numeric The value of the residue breakage decreases, so does the tendency of the engine to the absent. Accordingly, it is an object of the invention to provide means and to create a method to establish such operating conditions in the engine, that the numerical value of the residue fraction is small enough to misfire at constant load under low load conditions largely to prevent.

It is evident that the numerical value of the residue fraction can be reduced to either or both of the following two ways can: (i) by reducing the amount of gas residues in the Combustion chamber remain (the counter of the smell) or (2) through Increase the amount of air (or air / fuel mixture) used for the 'next cycle is sucked into the combustion chamber (part of the denominator in the break). Each of the two means gives the numerical value of the Reduced residue breakage. The achievement of operating conditions in Motor for which the numerical value of the residue break is sufficient

is low, it enables a combustion engine *, with lean mixtures

509850/0258

ζμ work »where previously lean mixtures were not applicable.

In low load conditions where the throttle is nearly is closed, prevails in the suction line before the suction valve lower pressure. Slowed down during a normal valve overlap period this low pressure in the intake line reduces the exhaust gases flowing out ^ when the intake valve and the exhaust valve are open, this Low pressure can even cause the exhaust gases to flow into the: - · Intake line. It is understandable that this effect can be felt in one normal internal combustion engine has a detrimental effect on the residue breakage under low load conditions. It is therefore an object of the invention to this counteract adverse effect.

According to the invention, the object is achieved in that the motor with means is provided with an air / fuel mixture when the throttle valve is almost closed produce which is leaner than a stoechiometric mixture and that the engine is provided with control means that the rotation of one Camshaft in relation to the other camshaft as a function of the load condition regulate the engine so that under low load conditions where the throttle is almost closed, the valve overlap can be reduced.

By using this construction, the intake valve can be made to open later than normal , thereby minimizing the risk of exhaust gases from the cylinder flowing into the intake manifold and minimizing the amount of burned gases remaining in the cylinder. In this way, even under low load conditions, the

509850/0258

Engine achieved with a lean mixture. As a result, conventional Motors when using the inventive construction High stress and low stress conditions with a lean mix operated, reducing the emission of contaminants on a acceptable level is lowered. The rotation of the camshafts can be regulated in a simple manner if the camshafts are of a common one Timing chain driven and if means for changing the timing chain length are provided between the two camshafts.

Particularly good results are obtained when an in the idle state lean mixture with an air / fuel ratio of about 15-17 is supplied · It is desirable that the fuel is in the air / fuel mixture is well atomized in the suction line, so that a good ignition of the lean mixture is guaranteed under all conditions. One Good atomization of the mixture can be achieved if the wall of the suction line is in an area in front of the suction opening which is approximately the same diameter corresponds to the intake valve, is kept at a temperature between 90 to 135 C, whereby the formation of a fuel film on the Wall of the suction line and the formation of large droplets of fuel prevented and a homogeneous mixture is produced, which is then fed to the cylinder will. A simple and effective way to maintain the desired temperature is to keep the engine running on water and the suction pipe is only cooled with air.

A well-atomized mixture, which can easily ignite, is achieved when the ratio between the diameter d ₀ , the nozzle for the air supply line of the carburetor discharge circuit and the diameter D

509850/0251

the carburetor bore is about 0.035 "to 0.065. Good atomization of the fuel can also be achieved if the fuel is with a Injector cock is injected into the intake manifold, with the injection of fuel from the injector cock during most of the time in that the intake valve is open during the intake stroke, is omitted.

An effective ignition delay over a relatively large angle can be achieved in a simple manner ^ when the delay of the ignition by using two separate sets of breakers in the distributor, which are offset from one another at an angle.

. Ignoring the fact that the engine is under low load conditions works with a lean mixture, a quick start of the engine can be ensured if the air and the Fuel sucked in through a fuel line and a valve in the carburetor and there is an air / fuel mixture behind the closed throttle valve is introduced into the suction line *

The pressure difference is at the moment when the suction valve is opened, especially low, so that when the throttle valve is closed, the The intake valve actuating camshaft must be adjusted so that the opening of the intake valve is delayed.

The invention is now based on the example reproducing it Drawings are explained in more detail and that shows ι

Figure 1 is a diagram showing the emissions of certain impurities in relation to various air / fuel ratios shows

509850/0258

with which a motor is operated, FIG. 2 shows a plan view of an embodiment of an inventive Motors,

FIG. 3 shows a partial cross-section along the line 3-3 of FIG. 2, Figure 4 is a partial cross-section taken along line 4-4 of Figure 2; Figure 5 is a diagram showing the relationship between debris breakage

and the air / fuel ratio shows and Figure 6 is a graph showing the relationship between residue breakage and the suction vacuum.

The diagram shown in Fig. 1 shows in a generalized manner. and · non-dimensional form the emission of pollutants, which are plotted on the ordinate _f in relation to the air / fuel ratio, which is plotted on the abscissa. This diagram is generally valid for all internal combustion engines, ZusStzlich to the impurities CO, HC and NOx the proper gases, K _o hlendioxyd (CO ₂₎ and oxygen (O2) contained in the exhaust gases, as can be seen from the diagram.

In Fig. 1 it is also shown that when using leaner mixtures than the stoechiometric mixture (about 15 for gasoline) in one Engine, the emission of the impurities HC and CO, compared to the use the formation of a rich mixture ^ decreases rapidly. The same also applies to emissions of oxides of nitrogen when mixtures with a ratio greater than

f6 can be used. It is therefore an essential advantage to have an engine to be driven with an air / fuel mixture whose air / fuel ratio is leaner than the stereochiometric ratio and the pre-

509850/0258

is preferably in the range between approximately 16 and 20 to reduce the output of the Minimize contamination.

As mentioned above, running an engine is lean Mixing in high stress conditions with a relatively wide open Throttle valve in general use. On the other hand, in the case of low stress conditions the mixture is normally enriched, whereby the mixture has a smaller ratio than the stoechiometric ratio. The adverse effects of burning rich mixture can be read from FIG. The emission of impurities EC and CO increases markedly and in an unacceptable hatred. Ea is therefore a major advantage of this invention that it is possible to lean Use mixtures for low and high load conditions and at the same time the advantage of the low emission of impurities with both Maintain stressful states.

For further orientation, reference is made to FIG. 5, which shows the relationship. nis between the residue fraction plotted on the ordinate and the shows the air / fuel ratio of the mixture plotted on the abscissa. The curves in this diagram show theoretical boundaries that Identify misfire conditions for various engines. At a Motor operation where the coordinate lines of the residue breakage and the If the air / fuel ratio below the respective curve meet, there will be no significant misfires occur. However, if the coordinate lines meet above the respective curve, misfires often result. It it is obvious that it is when using lean air / fuel ratios in an engine is necessary such conditions in the Kotor

509850/0258

to create where the residue fraction is smaller than a certain numerical Fourth is determined by the parameters of the individual engine is.

It is an object of the invention E _r, which, to avoid in Fig misfire limits shown. 5 This is achieved by operating the engine in such a way that the residue breakage value is acceptable and that the lean mixture is supplied to the combustion chamber in an optimally atomized and homogeneous form.

The diagram shown in Fig. 6 shows the B _e relationship between said fraction and the residue Ansaugvakuumdruck for a representative, conventional motor which no inventive features and that is operated according to the inventive method. This diagram is generally valid for the conditions prevailing in such internal combustion engines. Of the two points marked on the abscissa, one represents a wide-open throttle position (almost atmospheric pressure) and the other represents a state in which the suction vacuum pressure is approximately minus 450 mm HG. This diagram shows that the residue breakage also increases with increasing suction vacuum (lower suction pressure). The solution according to the invention contains agents which counteract the tendency for the residue to break, with the throttle valve increasingly closed, whereby the use of a lean mixture is made possible in the case of load conditions.

Ih Figures 2 to 4, an embodiment of the invention is shown. As can be seen from the figures, contains a four-stroke internal combustion engine

509850/0258

four combustion chambers 11a, 11b, 11c and 11d. The term "cylinder" is sometimes used synonymously with the expression "combustion chamber". The engine 10 is provided with a throttle valve 30a, 30b, 30c and 30d and with a Carburetor 20a, 20b, 20c and 20d each provided for a combustion chamber. Individual Suction lines 12a, 12b, 12c and 12d are each connected to one of the Inlet openings 15a, 15b, 15c and 15d of the combustion chamber 11a, 11b, 11c and 11d connected. Position the suction lines 12a, 12b, 12c and 12d an embodiment of the "injection means" which serve to supply the mixture into the combustion chamber;

Exhaust pipes 14a, 14b, 14c and 14d are connected to the exhaust ports 16a, 16b, 16c and 16d of the combustion chambers 11a, 11b, 11c and 11d and receive the exhaust gases. The exhaust gas lines 14a, 14b, 14c and 14d and an exhaust system P, which collects the exhaust gases from the individual lines, represents an embodiment of the "exhaust means", which serve for the removal of the spent gases from the combustion chambers 11a _y 11b, 11c and 11d.

Exhaust gas supply pipes 13a, 13b, 13c and 13d are connected to the suction pipes 12a, 12b _# 12c and 12d. The lines 13a to 13d are also connected to an exhaust gas return valve V. A vacuum line 12e (FIGS. 2 and 4) connects the opening 12f in the suction line 12d and the opening 12g in the control valve V. The suction lines 12 $., 12b and 12d are not connected to the opening 12g. The exhaust gas recirculation lines 13a, 13b, 13c and 13d are used when the NOx content is controlled by returning part of the exhaust gases to the intake air / fuel mixture,

509850/0258

Figure 4 shows in detailed form parts of Figure 2 and in particular the parts that are directly connected to the combustion chamber 1Tb. The other cylinders 11a, 11o, and 11d and related parts are identical to Figure 2 so that they are not described individually,

As can be seen from FIG. 4, the intake opening 15d is surrounded by an intake valve seat 18, while the exhaust valve opening 16b is surrounded by an exhaust valve seat 18a. An intake valve 21 and exhaust valve 22 are slidably mounted in the cylinder head and are designed so that when they move against the respective valve seat _f the respective. Close the opening and release the respective opening when moving away from the respective valve seat. Cams 81a and 82a are attached to the associated camshafts 81 and 82 and serve to open the valve openings 15b and 16b, the valves 21 and 22 being spring-loaded so that the valve openings 15b and 16b remain closed when the cams reach the respective valves 21 and 22 don't keep open. The same intake and exhaust valves and seats, cams and lobes and return springs are also provided for the other combustion chambers.

The cylinder head H of the combustion chamber 11b is together with a Cooling jacket C shown. This cooling jacket G only shields the one at the outlet opening 16b adjacent exhaust line 14b and the combustion chamber 11b himself off. A section 17 extending from the inlet valve seat 18 upwards extends into the suction pipe 12b is not cooled by the cooling jacket C. Instead, it is allowed that this separation 17 from the combustion chamber IVo is heated, for reasons that will be described below. This Section 17 can even be insulated from the outside or sheathed hoiss, to maintain the elevated temperature.

509850/0258.

This section 17 preferably extends at least a distance of about 60 to 70mm upwardly from the intake valve 15b into the intake manifold 12b and is considered to be part of the intake manifold 12b, although all or part of the section 17 forms an integral part of the cylinder head H The section 17 is delimited by the inner wall 19 of the intake line 12b, the wall being thermally connected to the cylinder head H, i.e. the inner wall 19 of the intake line 12b is heated by heat from the combustion chamber 11b. This enables the inner wall 19 of the section 17 to be heated, it being undesirable for this section to be cooled by a coolant such as a cooling jacket C for example. Any coolant should be kept sufficiently far away from the section 17 so that the inner wall 19 can reach the necessary temperature as a result of the heat supplied from the cylinder 11b. Part C1 of the KUlmantela C is in Pig. 4 shown in the cylinder head H above the intake port 15b. In liquid-cooled engines, the cooling vents should extend to this side of the cylinder head, although this region is not required to be cooled. It is a sufficiently thick layer of material between the portion C1 of the cooling jacket C and the inner wall 19 present, that the I _n nenwandung 19 may heat sufficiently, although the part C1 of the cooling jacket C is present. The warm section 17 is an exemplary embodiment of atomizing means in order to atomize the fuel adhering to the inner wall 19 of the suction line 12b.

In Figure 2, an ignition distributor 23 is shown schematically _t conventional

Condenser, breaker points, breaker cam and breaker shaft are used to create a spark that ignites the mixture in the combustion chamber.

5 0 9850/0258

As can be seen from FIG. 4, the exhaust gas return valve V contains a piston 200 which is loaded by a spring 201 and which is connected to a membrane 202 which is fastened to the wall of a housing 203. The housing 203 contains a ventilated chamber 204 and a vacuum chamber 205. The spring 201 lifts the piston 200 into the position shown in FIG. 4 in solid lines. When the vacuum in the vacuum chamber 204 ■ increases, the piston 200 is moved downwards. When the piston 200 moves a sufficiently large distance close down! has reduced or eliminates these Durchatrom the exhaust gases from the inlet port 206 would otherwise spread from where d _a s on four gas exhaust ports 207 for recycle to the exhaust gas conduits 13a jerk to 13 <. 1 It follows from this that the amount of the returned exhaust gas forms a function of the size of the vacuum in the suction line 12b.

The principal advantage of using a throttle valve for everyone Combustion chamber is that the pressure in an intake line by the pressure is not reduced in another suction line. In engines where an intake pipe and a throttle valve have a plurality of combustion chambers supplied, the low pressure in a combustion chamber during the intake stroke can adversely affect the pressure at the inlet opening of the other combustion chambers influence . The use of one throttle valve per combustion chamber allows a separate intake condition to be set in each combustion chamber. Because the return lines 13a to 13d connect all suction lines 12a to 12d, there is a tendency to Pressure equalization in the suction lines 12a to 12d, whereby some of the Values are reduced that would otherwise be achievable through the use of one throttle valve per combustion chamber.

509850/0258 · "'^

In order to avoid this disadvantageous result, fuel is in the respective return lines provided. These contain release agents One-way shut-off valves, which open the passage openings between the return pipe and close the respective suction lines when the pressure difference not enough to keep the valves open. If the pressure from valve V is sufficient, all valves can be open, but if so in the line from the valve. V there is a sufficiently large negative pressure, possibly due to a high suction vacuum in "one of the suction lines, the other valves close.

As can be seen from FIG. 4, there is 11a to 11d in each combustion chamber a piston 150 arranged to be movable to and fro. The piston 150 rotates one Crankshaft via a conventional crank pin, connecting rod and crank parts (not shown).

As can best be seen from FIG. 3, the two camshafts 81 are and 82 rotatably attached to the engine block to rotate the cams 81a and 82a which operate the intake valves 21 and exhaust valves 22. The camshafts 81 and 82 extend parallel to each other and are driven by gears 81b and 82b which are attached to the respective camshafts 81 and 82, with the help of a timing chain 85 in the one shown in the gears 81b and 82b, Driven in the direction of the arrow. A camshaft gear 84 is attached coaxially to a drive gear 86, which in turn is supported by a chain 83 which is driven by a gear 87 attached to the crankshaft. This gear drives the camshafts 81 and 82 synchronously with the crankshaft 88.

509850/0258

The timing chain 85 slides over a guide part 210, which by means of a Fastening part is firmly attached to the engine block. A chain tensioner 215 is pivotally attached to the engine block by means of a pin 210. The chain tensioner, 215 includes a guide plate 217 over which the chain 85 slides. The guide plate 17 can move in the direction of arrows 218 and will from a piston 219 ,. which protrudes from a housing 220, daa at a ¥ an ~ tion 221 is attached to the engine block, pressed against the chain 85. A compression spring 222 i »aehöuae 220 pushes the piston 219 in Flg. 3 near rftohte. A second guide part 91 contains spring means 93 with which the chain length 223 of the timing chain 85 between the two camshafts 81 and 82 their minimum length is kept.

When the chain length 223 is at its minimum, it results between the Both camshafts. 81 and 82 have a certain angular relationship, the one minimum valve overlap guaranteed and for low load conditions is used. Valve overlap control means 225 includes a liquid operated one Device 90 with which to enlarge the valve overlap in high stress conditions by enlarging the lungs 223 this Angular relationship is optionally changed. The device 90 includes a Piston 91 which is mounted in a cylinder 92 such that it can move back and forth Compression spring 93 presses end 91a of piston 91 against chain 85, that the chain length 223 does not deviate from its illustrated minimum length. The cylinder 92 is attached to a cover frame with fasteners 226 of the engine. The piston 219 gives way to the section of the timing chain to shorten between the gears 81b and 84 and at the same time 'to lengthen the additionally required chain length 223.

509850/0258

245106Λ

When the piston 91 is pushed down, the chain section To lengthen 223 and to change the angular relationship between the camshafts 81 and 82 (increase in the overlap time), a fluid pressure is created (preferably hydraulic) in cylinder 92. This is achieved by a hydraulic system 94 which includes a tank 84a, a pump 95, an on-off valve 96, which can be used to switch off the hydraulic system and contains a multi-way valve 97 which is controlled by a controller 97a.

The controller 97a for controlling the multi-way valve 97 preferably speaks mechanically to a throttle valve connection, which will be described below. Otherwise it can be a pressure-dependent device that is responsive to the suction pressure. With the hydraulic system, cylinder 92 can be pressurized either through line 97b or emptied through line 97c, the pressurized hydraulic fluid through a bypass line 97d into the tank is directed. The hydraulic system 225 is provided with an overpressure valve (not shown) to keep the system at a predetermined pressure level to hold when cylinder 92 is pressurized. The controller 97a selects the respective valve state in response to the throttle valve activation As a result, there are two different angular relationships between the Camshafts 81 and 82 are provided, which depend on whether there is pressure in the cylinder 92, and this in turn depends on whether a There is a low load or high load condition in the engine.

The above-described devices and methods according to the invention can be better understood if some of the terms are considered be stored in a cylinder during the completion of the exhaust stroke

509850/0258

and prevail during the beginning of the intake stroke, The pressure in the exhaust line reaches almost atmospheric pressure because it is a relatively large pipe. The pressure in the intake line or in the intake ^ distributor after the carburetor varies and depends mainly on the throttle setting. There is or is almost in front of the carburetor Ambient pressure, that is / means atmospheric pressure.

If »only one throttle valve is used for one cylinder and the If the throttle valve is open for high load conditions, the suction pressure at the suction port reaches almost atmospheric pressure. At almost finished exhaust stroke and before reaching top dead center, it is common to open the intake valve; while the exhaust valve always is still open. This area is called "overlap". The tendency of the gases in the cylinder during the overlapping period to exit the open exhaust valve is the greater, 'the higher the Suction pressure is. When the suction pressure is relatively low, it results a substantial pressure difference, that of the tendency described above counteracts and can even cause an outflow of the gas residue in the opposite direction into the suction line. As a result, the Amount of gas residues in the combustion chamber for the next cycle all the more greater, the longer the overlap period lasts or the lower the suction pressure is.

If there is a throttle valve for each combustion chamber and the Suction lines are not connected to each other, prevails in every suction line a pressure that depends on its own conditions in each suction line. But if the suction lines are connected to each other, such as through NOx return lines, or if only one throttle valve for several

509850/02 58

BATH ORIGINAL

If there is a combustion pipe, a possibly existing low pressure at one intake port can be transferred to the intake port of another combustion chamber, as a result of which the intake pressure or the average pressure in the intake system is reduced. This phenomenon can cause an increase in the pressure difference between the intake and exhaust systems during the valve overlap time and increase the gas residues, as already described above .

The use of a throttle valve per combustion chamber and the separation of the intake lines from each other optimizes the conditions during the overlap period, so that the amount of gas residues is reduced, since no combustion chamber reduces the pressure in another intake line. If an exhaust gas recirculation line is used and the pressure in one intake line could affect the pressure in another intake line, this can be prevented by using separating agents . It follows that the advantages that can be achieved by using one throttle valve per combustion chamber can also be achieved if exhaust gas recirculation is used to reduce NOx emissions.

When the engine of Figures 2-4 is operating under high load conditions with the throttle valve open fairly wide and a relatively small vacuum (relatively high intake pressure) in the intake lines, there is little difficulty operating the engine with a lean mixture. U _m to eliminate this, a desirable overlapping of the Oeffnungzeit'der intake and exhaust valves 15 and 16 normally _f are allowed approximately 24 ° to 80 °, without the

509850/0258

Misfires occur because the residue ruptures with increasing suction pressure decreases (see Fig. 6). A longer hijacking time increases the Fuel economy. Under relatively low stress conditions however, the amount of gas residues must be reduced if an operation with a lean mixture is to be successful. The amount of gas residue can be achieved by reducing the valve overlap time at low loada states are reduced if means for controlling the overlap time available. The preferred value of the valve overlap time at lower Load is 10 to 32

The position of the overlap time control means shown in FIG. 3 is when Starting and used in low load engine operation. The one shown Valve overlap (depending on the length 223) is in the minimum setting. In this way, the numeric value of the Residue breakage is reduced, allowing the engine to operate at low intake pressure without misfiring.

If the opening time of the intake valve 15 in relation to the. Closure of the exhaust valve 16 presented in high load conditions and thereby the The valve overlap is to be increased actuated. The piston 91 is pressed against the control chain 85 and diverted. The downward movement of the piston 91 extends the chain length 223, whereby the camshaft 81 leads relative to the camshaft 82 and thereby the overlap time increases.

When the engine is working again in the low load range, the Valve overlap control 225 via line 97d relieves the pressure

509850/0258

BATH ORIGINAL

Chain under the spring force of the chain tensioner 215 pushes the piston 91 into the in Figure 3 can push back the starting position shown, the chain length 223 is shortened and the valve overlap time is reduced.

The controller 97a may be a mechanical controller that is controlled by a direct connection to the throttle, for example through a connection to the throttle arm 32a, can be actuated by this connection makes the two different valve settings for the two different carburetor settings. The control 97a can, however, also be pressure-dependent and operated by the suction pressure in that the valve setting is a function of two different suction pressures. When the throttle is closed, there is a low load condition in which the suction vacuum is high, whereby the throttle valve 33 and the connection to the control valve is in a position in which the Steering Committee in the in J? Ig. 3 is brought into position in which the Control via line 97d is relieved. When the throttle is open there is a high load condition in which the suction vacuum is low, as a result of which the control circuit is in an opposite condition by line 97b and cylinder 92 are pressurized so that the piston is pressed down and the overlap period of the valves is increased. The overlap period now extends approximately over 30 to 80 for high stress conditions.

When the engine is started, the exhaust gas recirculation valve V remains closed, whereby the exhaust gas recirculation prevents or is limited..It is advantageous to reduce the exhaust gases during this time not fed back into the system, as the exhaust gases are numerical fourth

509850/0288

of the residue breakage would increase, which is detrimental to the running of the tlotors could affect.

The exhaust gas control valve 46 opens by reducing the vacuum in the suction line (increase in suction pressure), with the respective opening of valve 46 varies according to the degree of vacuum in the suction line. Exhaust gases are released through exit port 44, line 44a, exhaust gas control valve 46 and line 44b. If there is insufficient vacuum, the valve 46 closes.

It can be seen that the tightness of the gas residues in the exemplary embodiment according to Figures 2 to 4 · partly from the overlap time of the intake and Exhaust valves and the degree of opening of the exhaust return valve V depends. Both the control of the overlap time and the limitation of the exhaust gas recirculation serves to maintain a suitable residue breakage value under low load conditions in the engine. The valve V can either be a simple on-off valve or a regulating valve that also has an off-on position.

A fuel injection cock can also be used instead of a carburetor that of the the the fuel behind the throttle valve in the intake line injects.

If an injection valve and a throttle valve are used for each cylinder, the injection of fuel from the injection valve will occur during a period between 30 ° and 150 ° after dea extends top dead center of the intake stroke, advantageously omitted so that no fuel is injected when the intake valve is relatively

509850/0258

is wide open.

In this way, the fuel in the relatively poor intake line atomized before opening the suction valve, so that also when in use a lean mixture has good ignition and combustion and a minimal one The emission of impurities is guaranteed.

609850/0251

Claims (4)

PATENTAHSPRUEGES Four-stroke internal combustion engine which has a first camshaft for actuating the intake valves and a second camshaft for actuating the exhaust valves, characterized in that means are provided which, when the throttle valve is relatively closed, generate a leaner air / fuel mixture than a stoechiometric mixture and that control means are provided are that to allow the rotation of a camshaft in 3ezug to the other camshaft as a function of the B _e lastungszustandes de3 Motors regulate at nearly closed throttle at low-load conditions of the engine, a reduction in the Ventilüberlappzeit to. 2) internal combustion engine according to claim 1, characterized in that the Camshaft! Are connected to one another via a timing chain and that Means for changing the length of the timing chain are provided between the two camshafts. 3) internal combustion engine./according to claims 1 or 2, characterized in that that to maintain the chain tension between the two camshafts, j 'a spring-loaded device acting on the timing chain is provided is and that an adjustable device is provided that the timing chain transversely to its longitudinal direction between the two camshafts emotional. 4) Internal combustion engine according to one or more of claims 1 to 3, characterized characterized in that the regulated by the control means, the suction 509 8 50/0 2 58 valve-actuating camshaft with almost closed throttle valve, the opening of the suction valves is delayed. Internal combustion engine according to one or more of claims 1 to 4 »thereby characterized in that the control means are operated hydraulically as a function of the engine speed. 509850/0258