SE521969C2 - Device and method for fuel injection in an internal combustion engine and internal combustion engine - Google Patents

Abstract

A device and a method for injecting fuel into a cylinder (2) of a combustion engine (1), including a camshaft influenced injector unit (I), a controllable control valve (22) connected thereto allowing injection in closed or restricted position, wherein a camshaft (27) for influencing the injector unit is synchronised so as to influence the injector unit for injection during the compression phase of the engine. The camshaft (27) is also synchronised to influence the injector unit (I) for injection during the gas exchange phase and a control unit (8) is arranged to influence the control valve (22) for injection synchronously with the first (24) and/or a second (25) cam lobe on the camshaft, as a response to signals indicating the prevailing operational condition of the engine.

Description

»N-.n 521 969 n. U .. met. In total, this results in a more even temperature distribution.

In internal combustion engines of the type which apply the combustion of a homogeneous, premixed fuel-air mixture, it has been found that the emission problems with respect to harmful compounds are thus possible to reduce. However, the engine type suffers from a number of disadvantages, of which a narrow load range can be mentioned. It is required for acceptable operation that the ignition takes place at a limited position near the upper dead center of the work piston.

However, the start of combustion depends on several parameters, but primarily on the temperature and pressure in the combustion chamber. Since the temperature in turn is highly dependent on charge pressure and load, the ignition time of the gas mass will therefore vary significantly. This means poor efficiency for the engine and that the thermal load on the engine becomes large if the ignition timing is too early, which tends to occur at high loads. If, on the other hand, the ignition time is late, the efficiency will also be poor in this case and the combustion will also be incomplete, resulting in high emissions of HC (hydrocarbons).

An additional problem is that the ignition timing is not stable. As an example, the ignition time is assumed to be in the region of above the dead center of the work piston. A slight change in the ignition time relative to the previous ignition ratio to the upper dead center results in a corresponding increase in the engine's thermal load, which will give the next cycle a higher temperature, etc., which further drives the ignition time towards the previous ignition in relation to the upper the deadlock in an escalating process with harmful consequences- SGI '. 70067; 00-05-02. 25 521 969. > a ~ .- It has been proposed to combine in an engine the HCCI process with the Diesel process by injecting a proportion of the fuel into the cylinder in the region of the upper dead center of the piston at the gas exchange rate. This results in the formation of a homogeneous, premixed fuel-air mixture with a first amount of fuel introduced already during the inlet phase. The remaining proportion of the fuel to be included in the combustion is injected directly into the cylinder for the usual initiation of the combustion of this proportion, whereby the first homogeneously mixed amount is used as a preheater and ignition initiator for the subsequently injected amount of fuel. However, this system requires the installation of additional equipment in the form of special injectors and drives therefore and overall a not insignificant cost increase for the engine.

OBJECTS AND MAIN FEATURES OF THE INVENTION It is an object of the present invention to provide an apparatus and method in which the disadvantages of the prior art are eliminated or at least reduced. It is also an object to provide a device and a method by which improved operation of four-stroke internal combustion engines can be obtained.

These objects are achieved according to the invention by a device and a method for fuel injection of the kind mentioned in the introduction in accordance with the characterizing part of claims 1 and 6, respectively.

In this way it is achieved that conventional components present in the internal combustion engine can be used after only a slight modification. The respective fuel components can be controlled in an advantageous manner so that a distribution suitable for each operating case can be obtained. 70067; 00-05-02 lqmø 521 969 - Q v @ a n. ». now The principle of the invention can be applied to all diesel engines and with different diesel fuels. In particular, the invention can be applied in operation with difficult-to-ignite fuels such as e.g. ethanol and methanol.

In conventional diesel engines with ethanol operation, in certain operating cases the engine can be run on pure ethanol, for example at high loads.

At lower loads, however, problems arise during operation with pure ethanol fuel, which is why a so-called ignition improver, such as a nitrated compound or, for example, polyethylene glycol, must conventionally be mixed into the fuel. By the invention, however, diesel operation with difficult-to-ignite fuels, such as ethanol, can be made possible without the addition of ignition improvers, since the first, homogeneously mixed fuel component, at e.g. low load, in practice will act as an ignition improver and, as above, in practice also as a preheater, so that the other, injected, portion is safely ignited at the desired time.

The injection of the first part of the fuel takes place during a phase when hot residual gases from a previous combustion cycle remain in the cylinder, which promotes the evaporation of the injected fuel. This is particularly effective with the diesel oil case. Ethanol could be injected later, as it is more volatile. At the suction rate, intake (or intake) air is allowed to mix efficiently with the vaporized or at least substantially vaporized fuel so that a homogeneous fuel-air mixture results throughout the combustion chamber.

By varying the ratio between the first and second part depending on the prevailing operating condition, the engine operation can be optimized. The efficiency of a wide range of operating cases will thus increase. As an example it may be mentioned that at nor- 70067; 00-05-02 u a> | : in -30 1 »n, 25 521 969 o. e. u - - fn of mill driving at full load it may be possible to cope with a small first proportion of fuel added to establish a homogeneous fuel mixture, while at lower loads it is desirable to have a larger amount of established homogeneous fuel-air mixture .

According to the invention, low NOX emissions are obtained, and it may be advantageous also for this reason to ensure that the supplied fuel at idle and low load consists exclusively, or to a large extent, of the "first proportion" of fuel. The invention also has significant potential to reduce soot formation. One can also expect some reduced fuel consumption.

Due to the design with double cam cams on the camshaft affecting the injector unit, in principle the motor only needs to be supplemented with a cam cam, which affects the injector at a time selected from the ordinary cam cam and software. Control of the amount of fuel, which is to be injected at the various influences, is ensured by controlling a control valve, which roughly functions as a bleeding valve, so that injection takes place when it is closed but not when it is open. Therefore, according to the invention, the control system must be programmed for correspondingly changed control of the control valve.

By, according to an aspect of the invention, the first cam cam having an injector influencing the injector unit with a different pitch than the corresponding edge of the second cam cam, it is achieved that the injection pressure of the injections can be controlled, which i.a. a. can be used to influence the duration of the injections.

In that, according to a further aspect, the first cam cam is synchronized to actuate the injector unit before substantially 70067; 00-05-02 J> | A | 521 969 | Q ~ | u: suction has taken place in the gas exchange phase, the remaining heat energy in residual gases, piston tops, etc. is utilized to the greatest extent.

Additional advantages are achieved with various aspects of the invention and will be apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail with reference to exemplary embodiments and with reference to the accompanying drawings, in which: Fig. 1 schematically shows a detail of an internal combustion engine equipped according to the invention, Fig. 2 shows a first variant with differently designed camshaft, Figs. Fig. 3 shows a second variant with an even differently designed cam cam, Fig. 4 schematically shows the use of the control possibilities of the invention in a torque / speed curve for a diesel engine, and Fig. 5 shows a PV diagram for a diesel engine.

Description of exemplary embodiments Fig. 1 schematically shows a multi-cylinder (single cylinder shown) internal combustion engine 1 of diesel type and comprising a cylinder space 2 and a piston 3 movable in the cylinder. are equipped with appropriate valves (this is not shown). As usual, (at least) an injection nozzle 6 is inserted for direct injection of fuel into the fuel chamber. The nozzle 6 is connected to a cam-driven 70067; 00-05-02.,.

H .. '30 U. ¿25 u I a | oo 521 969 II- a »:. .o injector I of a conventional type comprising a piston (not shown) in a cylinder 20 (not shown). A camshaft 27 carries on the one hand a conventional second cam cam 25, which acts on the injector I during the ignition phase, and on the other hand a first cam cam 24, displaced by about 180 ° relative to the second cam cam to allow injector action during the gas exchange phase of the engine. A control valve 22 is arranged in a manner known per se in an outlet from the injector, so that when the valve is closed and the injector is actuated by a cam cam, injection takes place. The open control valve causes bleeding of the amount of fuel present in the cylinder to tank T. The amount of fuel can thus be controlled by controlling the closing time of the valve 22 and possibly also its degree of opening. This is done by the control unit 8.

The control system in Fig. 1 comprises a control unit 8, which is supplied with signals 9 regarding operating parameters for the engine operation, which can refer to speed, load, engine temperature, accelerator pedal position, exhaust composition, etc. The control unit 8 is arranged to control the control valve 22 to thereby control at each opportunity.

Preferably, the control unit is programmed to optimize the ratio between the injected fuel quantities as well as the total amount of injected fuel as well as possibly also, to some extent, the time when each injection takes place in relation to the engine crank angle.

The invention can be varied within the scope of the claims, and in particular the ratio between the different proportions, as indicated above, can be adapted for different operating conditions. 70067; 00-05-02 -Q | -; n | n. u. o u. » nu II I n e. on u o o. n 4 u »u nu I n -v -v n o en n v u u: n o va» .n u c v o. »nu I III 'I n. , n - n 1. u o u. u q I o n ~ n »en 1. n .. n. .en It is also possible to arrange the location and number of the injection nozzles to the conditions prevailing in the present engine. The nozzle 6 and the associated fuel circuit may have a conventional design and location as well as the control valve 22.

Figure 2 shows alternatively designed cam cams where the first cam cam 24 has a flank influencing an injector unit with a larger extent and thus a greater pitch than the corresponding flank of the second cam cam 25. Figure 3 shows further alternatively designed cam cams where the first cam cam 24 has a flank influencing an injector unit with a smaller extent and thus less pitch than the corresponding flank of the second cam cam 25. By choosing the design of the flanks in this and similar manner, it is achieved that the length of the injection time can be controlled for the different injection occasions. In general, it can be said that injection over a longer period of time with lower injection pressure results in less rise.

Fig. 4 illustrates an example of the possibility of varying the ratio between the first and second proportions depending on the prevailing operating condition, so that the motor operation can be optimized.

The efficiency of a wide range of operating cases will thus increase. As can be seen from the example, during normal driving with a high load (upper area in the figure above approx. 50 - 60% of full load) it is possible to drive in “diesel mode” (combustion according to the diesel process) and thus manage without or with a small initial proportion of fuel added to establish a homogeneous fuel mixture. At low loads (lower range below about 15% of full load), it is desirable to have a larger amount of established homogeneous fuel-air mixture for best operation.

Here you thus run on "HCCI mode" (combustion according to the HCCI process). In the intermediate area, care is taken to obtain a 70067; 00-05-02 e v .... .- .25. .. -30. U. 521 969 varying mixture in the direction of more "diesel mode" with increasing load. It should be noted that the example shown only roughly describes the principle of the invention.

The PV diagram in Fig. 5 shows a diesel cycle with exhaust phase 12, intake phase 13, compression phase 14, ignition phase 15 and expansion phase 16. In principle, the first portion is injected at the inlet 17 of the intake phase 13, while the second portion is injected as conventional at the inlet 18 of the ignition phase 15 or the end of the compression phase 14.

The timing of the injection of the first portion of the fuel is controlled so as to ensure that the fuel is injected so close to the top dead center of the piston that no fuel risks hitting the cylinder liner. If, instead, fuel had been injected during a part of the suction phase, where the feed is exposed, this would have a negative effect on the lubricating film in the prevailing environment. In addition, sucked in cold air would counteract the evaporation of the fuel due to the cooling that occurred.

The injection should also take place so that the spray of fuel droplets is directed down into a cavity in the piston top, whereby the heat of the piston is also used to promote combustion. The injector can also be actuated directly by an overhead camshaft.

The compression is adapted to the fuel and in the case of diesel oil it is preferably a compression range between about 9-14: 1, while in the case of ethanol it is preferably about 19-24: 1. It can also be a question of a so-called

"PLD" injectors, i.e. an injector with the pump separated from, and with a pipe connected to, the injector itself, giving 70067; OO-05-02 | »1» | »» Ø: uu 521 969 .p n .. greater freedom to place these parts in relation to the camshaft.

Preferably, the control unit is arranged so that in operation 0 - 100% of the total amount of fuel is injected synchronously with the influence of the first cam cam on the injector unit for optimal coverage of the main part of the operating case, which can be expected. However, other, significantly narrower ranges may also occur: about 3 - 20% of the total amount of fuel, and it is preferred that about - 15% be injected synchronously with the influence of the first cam cam on the injector unit. At about 3 - 10% pre-injection, it is desired that the additive burns prematurely, and constitutes a preheater, while at a higher proportion of pre-injected fuel, about 10 - 60%, everything should burn at the same time, ie. at ÖD to e.g. Avoid knocking.

The invention can be combined with control of valve overlap so that an increased amount of residual gases remains in the cylinder for improved fuel evaporation. This can lead to the possibility of pre-injecting a larger proportion of the fuel. In addition, EGR feedback is preferably used to obtain further optimized operation and emission reduction, especially for loads above about 50% load. 70067; 00-05-02. . one.

Claims (16)

'f,; 3o 10 15 20 _25 - - v u nu 521 969 ll Patent claims: Apparatus for injecting fuel into a cylinder (2) of an internal combustion engine (1), comprising a camshaft actuated injector unit (I), a controllable control valve (22) connected thereto, which allows injection in closed or throttled position, wherein an injector unit actuating camshaft (27) is synchronized to actuate the injector unit for injection during the compression phase of the engine, characterized in that the camshaft (27) is also synchronized to actuate the injector unit (I) for injection during the gas exchange phase of the engine and that a control unit (8) is arranged to actuate the control valve (22) for injection synchronously with a first (24) and / or a second (25) cam cam on the camshaft (27) for injection during the gas exchange phase and during the compression phase, respectively, in response to signals indicating the the current operating condition of the engine. Device according to claim 1, characterized in that the first cam cam (24) has a flank influencing an injector unit (I) with a different pitch than the corresponding edge of the second cam cam (25). Device according to claim 1 or 2, characterized in that the first cam cam is synchronized to actuate the injector unit at the beginning of the suction phase. Device according to Claim 1, 2 or 3, characterized in that the cam cams are displaced by approximately 180 °. Device according to one of the preceding claims, characterized in that the control unit is so arranged that in operation 3 - 100% of the total amount of fuel is injected synchronously with the influence of the first cam on the injector unit. 70067; 00-05-02 10 15 20 25 u u u ~ u: n. -1- v v nu u: I 'I' u n. U; .o u. n a a »a en I u a» en no u. a u an: q u n en. u. n nu nu n .. n so; ø o n> u u u n u. n n a a o u u. n n 1 .n o. n. n.. | - u o »12 A method for injecting fuel into a cylinder (2) of an internal combustion engine comprising a camshaft actuated injector unit (I), a controllable control valve (22) connected thereto, which allows injecting in closed or throttled position, an injector unit actuating camshaft (27) synchronously affects the injector unit for injection at the end of the compression phase of the engine, characterized in that the camshaft (27) is also synchronized to actuate the injector unit (I) for injection during the gas exchange phase of the engine and that the control valve (22) is controlled for injection synchronously with a first (24) and / or a second (25) cam cam for injection during the gas exchange phase and the compression phase, respectively, in response to signals indicating the present operating condition of the engine. Method according to claim 6, characterized in that the first cam cam acts on the injector unit at the beginning of the suction phase. Method according to Claim 6 or 7, characterized in that the injector unit is actuated by the cams displaced by approximately 360 crankshaft degrees corresponding to approximately 180 camshaft degrees. Method according to one of Claims 6 to 8, characterized in that in operation 0 to 100% of the total amount of fuel is injected synchronously with the influence of the first cam cam on the injector unit. Method according to claim 9, characterized in that in operation about 3 - 20% of the total amount of fuel, and preferably about 5 - 15% is injected synchronously with the influence of the first cam cam on the injector unit. 70067; 00-05-02 ||||: | 10 15 20 521 969 13 n. --- Method according to one of Claims 6 to 10, characterized in that at the observed low engine load and moderate speeds, the injection rate at the end of the compression phase is minimized. Method according to one of Claims 6 to 11, characterized in that the injection part is maximized at the end of the compression phase when a high engine load is detected. Method according to one of Claims 6 to 12, characterized in that at the observed low engine load and high speeds, the injection rate at the end of the compression phase is at an average value. A diesel engine including a device according to any one of claims 1 to 5 for each of its cylinders. wherein it also includes Diesel engine according to claim 14, equipment for controlled EGR gas recirculation. A diesel engine according to claim 14 or 15, wherein it also comprises equipment for controlling the opening times of the inlet and outlet valves. 70067; 00-05-02 -. ~ ~ u