BRPI0902794A2 - process and control device for starting an internal combustion engine - Google Patents

Abstract

PROCESS AND CONTROL DEVICE FOR STARTING AN INTERNAL COMBUSTION ENGINE. The present invention relates to a process for starting an internal combustion engine with at least one cylinder, which with a piston guided in the cylinder forms a combustion chamber, an air intake suction channel or a mixture air-fuel through at least one combustion chamber inlet valve, a throttle valve for controlling or regulating the air flow in the suction channel and a fuel adduction for adding a fuel to the combustion chamber or to a suction tube from the suction channel. The invention further relates to a control unit for controlling an internal combustion engine with at least one combustion chamber formed by a cylinder and a piston, to which through a suction channel with a throttle valve and a suction pipe, air, or air-fuel mixture is added, with a fuel adduction fuel adduction to the combustion chamber or suction pipe, the control unit containing adduction control program routines and adjusting the throttle valve. It is therefore provided that the control unit has a program for closing the throttle valve during an internal combustion engine starting phase with simultaneous fuel adduction during an internal combustion engine suctioning phase.

Description

Report of the Invention Patent for "PROCESS AND CONTROL DEVICE FOR STARTING AN INTERNAL COMBUSTION ENGINE".

State of the Art

The invention relates to a process for starting an internal combustion engine with at least one cylinder, which with a cylinder-guided piston forms a combustion chamber, with an air intake or air-fuel mixture aspiration channel. by means of at least one inlet valve in the combustion chamber, a throttling valve for controlling or regulating the air flow in the suction channel and a fuel adduction for adding a fuel to the combustion chamber or suction tube of the suction channel.

The invention further relates to a control unit for controlling an internal combustion engine with at least one combustion chamber formed by a cylinder and a piston, which through a suction channel with a throttle valve and a pipe or an air-fuel mixture is added, with a fuel adduction fuel adduction to the combustion chamber or the suction pipe, the control unit containing program routines for fuel adduction control and throttling valve adjustment.

For engine starting, a certain mass of injected fuel must be sprayed to produce an ignitable air / fuel mixture. At very low ambient temperatures, however, Otto motor fuels vaporize only insufficiently and thus make the formation of the mixture difficult.

Otto engine-based internal combustion engines are generally run on refined petroleum-based fossil material hydrocarbon fuel. To this fuel is increasingly added ethanol produced from regenerable raw materials (plants) in different mixing ratios. In the USA and Europe a mixture of 75-85% ethanol and 15-25% gasoline is often used under the brand name E85. The internal combustion engines provided for this purpose are so designed that they can be operated with pure gasoline as well as with mixtures up to E85 or E100; This is called "Flex-Fuel" operation.

Ethanol and gasoline have a distinct vaporization feature. Ethanol vaporizes at a lower temperature to a lesser extent than gasoline, so that with a cold start more ethanol should be injected than gasoline. Using a fuel mixture of ethanol and gasoline, a cold start of the internal combustion engine occurs almost exclusively with the gasoline fraction in the fuel mixture. With a high fraction of ethanol in the fuel mixture, a much larger amount of fuel should therefore be injected. The fraction of ethanol thus added to the internal combustion engine is not only non-essential or involved in combustion, and is displaced to the exhaust gas installation and transferred to the engine oil through the piston rings, thereby increasing the emission of unburned hydrocarbons. and engine oil rarefaction occurs. In addition, fuel consumption increases during the starting phase.

In internal combustion engines, which are operated with a high fraction of ethanol in the fuel, at ambient temperatures below -10 ° C the hydraulic system is heavily loaded. Safe starting can only be ensured by proper design of the fuel adduction with extra transport quantities or with a high rail volume, thus increasing manufacturing costs for the fuel system. An unadjusted high-pressure system containing components such as the fuel pump, fuel lines, manifold, and injection valves can lead to poor internal combustion engine acceleration or an interruption of starting to a situation where the internal combustion engine can no longer start.

A known process for ensuring the cold starting capability of internal combustion engines is heating the fuel directly before injection. For direct injection, however, a physical limitation results, as the unfavorable relationship of thermal capacity to the vaporization of the fuel causes an essentially larger amount of fuel to be injected. This leads to a drop in pressure and, as a result, poor treatment of the mixture with negative effects on starting the internal combustion engine.

Another process, especially employed in Spanish countries, involves the electric heating of the internal combustion engine. The advantage in this process is the high additional costs for additional heating as well as the dependence on an appropriate supply, preferably through the mains.

It is an object of the invention to provide a process and control unit which enables the safe starting of an internal combustion engine at low ambient temperatures.

Advantages of the Invention

The object of the invention with respect to the process is achieved by the fact that the throttle valve, during the start of the internal combustion engine, is closed and the fuel adduction is done at least partially during the suction phase of the internal combustion engine.

Due to the closed throttle valve an underpressure results, with an inlet valve open during the suction phase of the internal combustion engine in the combustion chamber and suction pipe, thus the region of the suction channel between the throttle valve and the cylinder. Thanks to the reduced pressure, the added fuel can be more easily evaporated. This increases the gas-shaped fuel fraction at the moment of ignition at the end of the next compression phase of the internal combustion engine. At sufficiently low pressure, also less volatile fuel components, such as ethanol, can be even partially vaporized and thus contribute to the air / fuel mixture's deignition capacity.

The process can be applied to both internal combustion engines with direct injection in the combustion chamber and internal combustion engines with injection in the suction pipe. By the process according to the invention, it is possible to safely start the internal combustion engine even at low ambient temperatures. and with hardly volatile fuel aspirations employed, the internal combustion engine starting limit temperature is clearly reduced. It is further advantageous that no additional components are required, so that the process becomes very convenient in cost.

According to a particularly preferred embodiment of the invention, it is envisaged that the fuel will be fed as soon as the gas pressure in the suction pipe or combustion chamber falls below a predetermined threshold value. The threshold value can thus be selected according to, for example, the composition of the fuel, so that as large a fraction of the volume of fuel as possible vaporizes.

It may further be envisaged that the threshold value will be predetermined as a function of the internal combustion engine temperature. The prevailing temperature and pressure at which fuel is fed into the combustion chamber or the suction pipe fundamentally determines how much of a given fuel volume vaporizes and thus the ignition capacity of the air / fuel mixture.

It is envisaged that the throttle valve will be opened after ignition so that the air required for further combustion can be fed into the combustion chamber and the timing required for engine acceleration to be adjusted. internal combustion

To avoid further oscillation of the mixture, the choke valve may be provided to be gradually opened depending on the number of revolutions of the internal combustion engine. The speed or gradation of the throttle valve opening is, inter alia, a function of the structure of the respective internal combustion engine. The important thing is that the choke valve does not open abruptly for its target value.

The aim of the invention with regard to the control unit is achieved by the fact that in the control unit a program is provided for closing the throttle valve during a split phase of the internal combustion engine with simultaneous adduction of during an aspiration phase of the internal combustion engine. Implementing a program on the existing internal combustion engine control unit is cost-effective and possible without additional component expenditures. The required control ducts and adjustment units already exist, whereby the control unit can predetermine the position of the throttle valve and trigger fuel adduction. Remaining the throttle valve closed when the internal combustion engine is started before ignition, during the suction phase with an open inlet valve, underpressure forms in the combustion chamber and the internal combustion engine suction pipe. With a predominance of underpressure, fuel is injected into the combustion chamber or suction pipe, so that at the same temperature a larger fraction of the fuel is vaporized compared to a higher pressure fuel injection. It is thus possible that especially with the use of difficult to volatile fuels and low temperatures a sufficient amount of fuel is vaporized so that an ignitable air / fuel mixture is formed.

When at least one pressure sensor is associated with the control unit for determining the gas pressure in the suction pipe and / or the gas pressure in the combustion chamber of the internal combustion engine, and at least one temperature sensor is associated with the control unit - Fracture to determine internal combustion engine temperature and / or ambient temperature, so this information can be taken into consideration when controlling throttle valve and fuel reduction. Thus, during the program, it is possible that when the ignition is switched on, the starter is initially prepared and the throttle valve is closed. When the starter is activated, the internal combustion engine starts to rotate, thus during the suction phase and underpressure in the combustion chamber and suction pipe.

Release for fuel adduction may be given by the control unit as soon as it falls below a predetermined threshold value for gas pressure. The threshold value can then be adjusted as a function of the internal combustion engine temperature. By considering the temperature and pressure of the gas when determining the moment of injection, an optimum volume of the vaporized fuel can be achieved and thus an ignitable air / fuel mixture can be obtained.

The process and control unit may preferably be applied for starting an internal combustion engine operated with a mixture of gasoline and alcohol, especially a mixture of gasoline and ethanol.

Brief Description of Drawing

The invention will be described in detail below based on the exemplary embodiment shown in the figures. Show:

Figure 1 - In schematic representation, an internal combustion engine with a control unit,

Figure 2 - A program run for controlling a throttle valve and a fuel adduction from an internal combustion engine.

Ways of Implementing the Invention

Figure 1 shows, in a schematic representation, an internal combustion engine 1 with a control unit 50. The representation is restricted to the components necessary for the description of the invention.

A piston 12 is guided in a cylinder 10. The piston and the cylinder limit a combustion chamber 11 of the internal combustion engine 1. Piston 12 is joined by a connecting rod 13 with a crank shaft 14 into a crankcase 15.

Through a suction channel 30, fresh air is fed to the internal combustion engine 1. In the direction of flow of an air stream 36 an air filter 31, a throttle valve 32, a suction tube 34 and an inlet valve are provided. 35

On the exhaust gas side there is an exhaust gas channel 20 with an outlet valve 21. The fuel adduction is made by a fuel adduction40 and an injection valve 41 directly into the combustion chamber 11.

For control of the internal combustion engine 1, a control unit 50 is provided. Through a first signal conduit 51 a temperature sensor 52 and through a second signal conduit 53 a pressure sensor 54, which is disposed in the suction tube 33 of the suction channel 30 are connected with the control unit 50.

A first control duct 55 joins control unit 50 with fuel adduction 40, while a second control duct 56 joins control unit 50 with an adjusting element 33 throttle valve 32.

In regular operation of the internal combustion engine 1, to the combustion chamber 11, through the suction channel 30, fresh air is fed through the air filter 31, the throttle valve 32 and the suction tube 34 and the valve. 35. The fuel is metered through the fuel 40 and the injection valve 41 directly into the combustion chamber 11. The energy released from the combustion of the fuel-air mixture in the combustion chamber 11 is transmitted to the crankshaft via the piston. 12 and connecting rod 13 as motion energy. The burned exhaust gas is ejected through the outlet valve 21 and the exhaust gas channel 20.

Control of the internal combustion engine 1, especially fuel reduction 40 and adjustment of throttle valve 32, is based on appropriate program routines deposited in control unit 50, as well as adjusting elements 33 operable by the control unit. control 50 on the basis of other sensor and control data not represented by control unit 50. Fuel adduction activation40 occurs through the first control conduit 55 and throttling valve adjustment element 33 activation 32 through the second control line 56.

Temperature sensor 52 makes it possible to determine the temperature of internal combustion engine 1, while pressure sensor 54 measures the gas pressure in suction tube 34. The measured temperature is transmitted to the control unit. 50 by the first signal conduit 51, while the gas pressure in the suction pipe determined by the pressure sensor 54 is conducted through the second signal conduit 53 to the control unit 50.

In known starting operation of the internal combustion engine 1, the throttle valve 32 is at least partially open, while the starter moves the piston 12 along the crankshaft 13 and bias 13. During the suction phase with a downward movement of the step 12, fresh air is drawn through the suction channel 30 with throttle valve 32 open and with inlet valve 35 open into the combustion chamber 11 and compressed in a compressed phase. next, with inlet valve 35 closed and outlet valve 21 closed. Fuel adduction by fuel adduction 40 occurs entirely during the compression time.

It is therefore disadvantageous that at low temperatures and especially with the use of hardly volatile fuels or fuel fractions, the fuel vaporizes only insufficiently. The formation of the mixture is then hindered. Especially due to the addition of ethanol, gasoline is especially difficult to start because the ethanol fraction in the fuel lowers the vapor pressure and worsens the vaporization behavior for a safe start of the internal combustion engine. This behavior is especially relevant with high ethanol fractions. During the split phase fuel is additionally injected, which is deposited fundamentally as a wall film on the piston bottom and on the cylinder walls and thus is no longer available for combustion. This increases fuel consumption in the starting phase and increases the emission of unburned hydrocarbons.

At ambient temperatures below -10 ° C, the hydraulic system is heavily required or a new projection of fuel adduction 40 with extra transport quantities or a high volume manifold is required to ensure a safe start. In the extreme case, this may lead, with an unadjusted high-pressure system, to poor acceleration of the internal combustion engine 1, an interruption of starting or even an internal combustion engine starting no longer being possible.

According to the invention it is therefore provided that at low ambient temperatures or at low temperatures of the internal combustion engine 1, when the ignition is switched on, the internal combustion engine 1 must be started and the throttle valve 32 closed. The control unit 50 then measures via temperature sensor 52 the internal combustion engine temperature 1 and closes the throttle valve 32 by corresponding activation of the adjusting element 33 via the second control duct 56. With activation of the not shown, the crankshaft starts to rotate. During the suction phase, thus with the piston moving downwards, the pressure in the suction tube 34 drops to a defined pressure level. This level can be adjusted as a function of the internal combustion engine starting temperature 1. Pressure level switching, measured with the aid of the pressure sensor54, the control unit 50 releases fuel injection to fuel adduction 40. Injection does not occur then, as hitherto usual at startup at high stratified pressure, completely at compression time, but at least partially also at aspiration time. Due to the small pressure in the combustion chamber 11, the amount of fuel injected can be more easily vaporized and thus the gaseous fuel fraction increased at the time of ignition. The safety of starting is essentially increased and the starting limit temperature of the internal combustion engine 1 is reduced.

Starting the acceleration of the internal combustion engine 1, throttle valve 32 must be reopened so that the required acceleration time can be adjusted. The throttle valve 32 is opened successively by a corresponding dating as a function of the number of revolutions of the internal combustion engine 1 to prevent further mixing oscillations. The process according to the invention can also be applied to internal combustion engines 1 with suction tube injection, wherein the fuel supply 40 is provided in the suction tube 34 of the suction channel 30.

It may further be provided that the throttle valve 32 during cold start is not completely closed but only to the extent that a sufficiently low pressure level for proper fuel vaporization is achieved.

Figure 2 shows a program run for controlling a throttle valve 32 and a fuel adduction 40 of an internal combustion engine 1 as deposited in the control unit 50. The designations used in the description of the internal combustion engine 1 refer to the designations entered in Figure 1. The course of the program is restricted to the program blocks required to explain the invention.

The program path provides for a program start program block 60 as well as the following program steps, temperature determination block 61, threshold value clamping block 62, throttle valve closure block 63, metering block gas pressure64, gas pressure / threshold value comparison block 66, fuel add-on release block 67 and bypass valve opening block 68. Starting from gas pressure / threshold value comparison block 66 , a closed circuit 65 is provided before gas pressure measuring block 64.

The start of the program routine takes place by the start of program 60 when the ignition of the internal combustion engine 1 is switched on. In the following temperature determination 61 the internal combustion engine temperature 1 is determined using the temperature sensor 52 shown in FIG. 1. Depending on the measured temperature, in the threshold setting block 62, the pressure level below which the fuel injection in the combustion chamber 1 takes place is set. In the closing block the throttle valve 63 a control signal occurs by the control unit 50 to the throttle valve adjustment unit 33 to close the throttle valve 32. Then, in the pressure block gas pressure 64, the pressure is determined. gas in the exhaust pipe 34 of the internal combustion engine 1. During start-up, the gas pressure in the exhaust pipe 34 is measured and in the comparison block gas pressure / threshold value 66 compared to the level of pressure set in the clamping block 62. Since the measured gas pressure is greater than the threshold value, the program run jumps through the closed circuit 65 before the gas pressure measuring block 64. The pressure gas measured below the In the threshold value, the program switches to fuel release block 67. In fuel supply release block 67, control unit 50, by activating the fuel adduction 40 through control line 55 promotes release for fuel injection into the combustion chamber 11. Injection thus occurs at a subpressure, whereby difficult to volatile fuel fractions also vaporize less partially and contribute to the formation of a passive mixture. ignition

After the ignition has been carried out, the program runs through the choke valve opening block 68. In the choke valve opening block 68, the choke valve 32 is gradually opened as a function of the engine speed. internal combustion 1. By successively opening the throttle valve 32 further mixing oscillations are avoided.

Claims (8)

Process for starting an internal combustion engine (1) with at least one cylinder (10) which with a piston (12) guided in the cylinder (10) forms a combustion chamber (11) with a suction channel (30) for supplying air or a fuel-air mixture through at least one inlet valve (34) in the combustion chamber (11), with a throttle valve (32) for controlling or regulating the flow of air (35) in the suction duct (30) and with a fuel supply (40) for the addition of a fuel to the combustion chamber (11) or to a suction pipe (33) of the suction duct (30), characterized in that that the throttle valve (32) during the start of the internal combustion engine (1) is closed and the fuel supply is at least partially made during the suction phase of the internal combustion engine (1). Method according to Claim 1, characterized in that the fuel is fed as soon as the pressure of the suction nozzle gas (33) or in the combustion chamber (1) falls below a pre-given threshold value. Process according to Claim 2, characterized in that the threshold value is predetermined as a function of the internal combustion engine temperature (1). Process according to one of Claims 1 to 3, characterized in that the throttle valve (32) is opened after ignition. Process according to Claim 4, characterized in that the throttle valve (32) is gradually opened as a function of the number of revolutions of the internal combustion engine (1). 6. Control unit (50) for controlling an internal combustion engine (1) with at least one combustion chamber (11) formed by a cylinder (10) and a piston (12) to which, through a suction channel (30) with a throttle valve (32) and a suction pipe (33), air or an air-fuel mixture is fed, with a fuel port (40) for adding fuel to the combustion chamber (11) or the suction pipe (33), the control unit (50) having program routines for controlling fuel adduction (40) and for adjusting the throttle valve (32), characterized by of which control unit (50) a program is provided for closing the throttle valve (32) during an internal combustion engine starting phase (1) with simultaneous fuel delivery during an internal combustion engine suction phase (1) . Control unit (50) according to Claim 6, characterized in that the control unit (50) is associated with at least one pressure sensor (54) for determining the pressure of the suction gas (33) and / or gas pressure in the combustion chamber (11) of the internal combustion engine (1) and associated with the control unit (50) is at least one temperature sensor (52) for determining the internal combustion engine temperature (1) and / or ambient temperature. Use of the process or control unit (50) as defined in one of the preceding claims for starting an internal combustion engine (1) operated with a gasoline-alcohol mixture, especially a gasoline-alcohol mixture. ethanol.