DE102007062344A1 - Control circuit for petrol engine of vehicle, has minimum value forming unit forming minimum value from desired value and upper limit value in operating mode of heating converter and providing correcting variable for sucked air mass - Google Patents

Abstract

The circuit (10) has an air mass calculation circuit for calculation of a desired value (LS) for air mass sucked into a suction tube of a petrol engine. An air mass limiter (11) calculates an upper limit value for the air mass sucked into the suction tube in an operating mode of heating a catalytic converter. A minimum value forming unit (17) forms the minimum value from the desired value and the upper limit value in the operating mode of heating the catalytic converter and provides a correcting variable for the sucked air mass. An independent claim is also included for a method for controlling a petrol engine.

Description

The invention relates to a control circuit for a gasoline engine, and a method for controlling a gasoline engine. Catalysts are used to clean the exhaust gases from engines. A common catalyst is the 3-way catalyst, which cleans the exhaust gas of the gasoline engine from the gases HC, CO and NOx. The US 6,345,466 indicates the problem that the catalyst poorly cleans the exhaust gases when it is not yet heated to its operating temperature. For this reason, the injection of the fuel is divided into two phases in which the mixing ratio of the air-fuel ratio is set differently. Nevertheless, in the catalyst heating phase, relatively many emissions of the above three gases are released.

It is therefore an object of the present invention, a control circuit to provide for a gasoline engine with which the quantity Emissions in the exhaust gas is reduced. It is also an object of the invention to provide a method of controlling an engine with which the emissions be reduced in the exhaust.

These The object is achieved by the subject matter of the independent claims solved. Advantageous developments emerge from the Dependent claims.

According to the invention provided a control circuit for a gasoline engine, the air mass calculation circuit, and a Luftmassenbegrenzer having. In the air mass calculation circuit is a setpoint Calculates the air mass to suck in a suction pipe of the gasoline engine is. In Luftmassenbegrenzer is an upper limit for the air mass to be sucked into the intake manifold in the operating mode of the Catalyst heating calculated.

The control circuit includes also a minimum value for forming images of the minimum value from the target value L _S and the upper limit L _H and outputting this minimum value as the manipulated variable for the sucked air mass. The air mass limiter in conjunction with the minimum value images ensures that the manipulated variable for the air mass to be drawn in during catalyst heating does not exceed an upper limit. This ensures that only as much air is drawn in as is necessary to heat the catalytic converter. As less air is drawn in, less fuel is injected into the engine compartment. The amount of fuel thus decreases, so that the emissions of the gases HC, CO, NOx decrease.

The upper limit value L _H is calculated as a function of the ambient pressure of the gasoline engine. By calculating the limit value L _H as a function of the ambient pressure, it is ensured that the intake manifold pressure of the engine can be adjusted in accordance with the ambient pressure. This will provide enough brake vacuum for the brake system. Since the air mass is limited by the upper limit L _H , the additionally required torque can be ensured by an adjustment of the ignition timing of the air-fuel mixture. With high requested torque, this is no longer possible, so that the o limit limit L _{H is} also calculated as a function of the requested torque. This ensures that even high torques can be provided by the engine in the catalyst heating. This is z. As is the case when electrical consumers report a high energy demand, so that the torque must be increased.

additionally may still have a lean mixing ratio of the air-fuel mixture during the catalyst heating can be adjusted so that the ratio for example, to 16.2 in the operation of the catalyst heating 14.7 is set in normal operation. There are also embodiments in which a slightly richer mixture is set in the catalyst heating becomes.

In one embodiment, the control circuit includes an injection control circuit for calculating the ignition timing of a spark plug of the gasoline engine. The injection circuit is designed such that in the operating state of the catalytic converter the spark plug is ignited earlier in the case L _H <L _S than in the case L _H ≥ L _S. Thus, the required torque can be provided even in the case where the air mass is limited by the upper limit L _H.

If the manipulated variable for the air mass to be sucked is used to drive a throttle flap of the gasoline engine, the air mass is directly controlled by the minimum value images. In one embodiment, the air mass limiter is designed so that the upper limit value L _{H is} increased ceteris paribus with increasing ambient air pressure. Ceteris paribus means that the other conditions, including the requested torque and engine type, remain the same. This ensures that the pressure in the intake manifold is so small that there is always enough negative pressure available for the brake system.

The upper limit L _H remains constant depending on the requested torque up to a predetermined torque, and then increases if the requested torque exceeds the predetermined torque.

If the control circuit is part of a microprocessor, the dependency can the air mass limitation of the ambient pressure programmed by software and so easily adapted to different engine types. It is advantageous in particular that already existing engine controls can be extended to the presented air mass limit, without the ready calculation units for the to change to be sucked air mass.

The The invention also relates to an assembly of an inventive Control circuit and one of this control circuit controlled Otto engine.

There is also provided a method of controlling a gasoline engine including the steps of operating in the catalyst heating mode. It is calculated a target value L _S for the air mass, which is to be sucked in a suction pipe of the gasoline engine. The setpoint L _S is calculated as a function of the requested torque.

An upper limit value L _H for the air mass to be sucked into the intake manifold is calculated and a minimum value is formed from the desired value L _S and the upper limit value L _H. The air to be drawn in is adjusted according to this minimum value. The upper limit value is calculated as a function of the ambient pressure of the gasoline engine. The method provides a precise adjustment of the required air mass in the mode of operation of the catalyst heating, so that only as much air is sucked in, as required for heating the catalyst. This has the advantage that less fuel is consumed and thus lower emissions are emitted during catalyst heating.

In one embodiment, the upper limit value is also calculated as a function of the requested torque, so that the upper limit value L _H can be increased in accordance with high torque. This can be changed in sudden requests to increase the torque, the upper limit, but at the same time ensure that only the required air mass is sucked.

In one embodiment, the negative pressure for a brake system of the vehicle from pressure in the intake manifold ( 22 ) fed the gasoline engine. The dependence on the ambient pressure ensures that sufficient pressure for the negative pressure of the brake system is provided.

In summary can be said that the air flow through an ambient pressure-dependent and torque-dependent limit is limited. The limited Air flow provides the amount of heat to the Catalyst to heat, but prevents combustion in a restless idling takes place.

• – Es werden geringere Emissionen während des Katalysatorheizens erreicht.
• – Die Emissionsregulierungsvorschriften wie Euro5 oder SULEV werden besser erfüllt.
• – Auch während des Katalysatorheizens wird der Bremsunterdruck sichergestellt, dass er zum Bremsen ausreicht. Dadurch kann gegebenenfalls auf Zusatzaggregate verzichtet wird, was die Kosten verringert.

The advantages of the invention can be summarized as follows

• - Lower emissions are achieved during catalyst heating.
• - Emissions regulation regulations such as Euro5 or SULEV are better fulfilled.
• - Even during catalyst heating, the brake vacuum is ensured that it is sufficient for braking. This may optionally be dispensed with additional units, which reduces the cost.

By Elimination of tolerances and efficient Catalyst heating control by the air mass limitation method can make significant CO2 reductions and fuel economy reductions be achieved.

The Invention will now be in one embodiment of the figures explained. It shows the

1 a schematic diagram of the air mass limiting circuit,

2 a gasoline engine, which is controlled by the method according to the invention,

3 the air mass limitation as a function of the ambient pressure,

4 the sucked air mass in dependence on the torque request.

1 shows a section of the control circuit 10 , This contains an air mass limiter 11 and a minimum value image 17 , The air mass limiter 11 contains a first characteristic function 12 and a second characteristic function 13 , a first switch 14 , a second switch 15 , an AND gate 16 and a memory 18 , At the entrance 1 the control circuit starts 10 a value P_A for the ambient pressure, which is measured for example by an ambient pressure sensor. However, embodiments are also possible in which the vehicle receives the value for the ambient pressure from outside, for example, via radio.

At the entrance 2 receives the control circuit 10 a value TQI_R for the torque request. This value is calculated in the engine control of the vehicle. The torque request results for example from the pressure on the accelerator pedal, by a setpoint generator of the idle control or a request of an electrical or mechanical load.

The torque request is also the basis for the value air mass target L _{S of} the control circuit 10 at the entrance 3 is entered. From the torque request, the air mass to be optimally sucked in, the so-called air mass target L _{S, is} calculated by an air mass calculation circuit (not shown in the figure). The air mass target L _S is the air mass per time that is drawn in by the engine.

At the entrances 4 . 5 and 6 the control circuit receives digital binary signals. At the entrance 4 It receives the idle bit IS, which is at one, if the driver does not press the accelerator pedal and is equal to zero, if the accelerator pedal is depressed. At the entrance 5 is the signal CH, which is at one, if the catalyst is to be heated. At the entrance 6 the air mass limiter receives 11 the logical value DT, which stands for "powertrain open". This is at one when the powertrain is open and at zero when the powertrain is closed. The latter is, for example, the case when a gear is engaged in an automatic transmission.

The switches 14 and 15 each have three inputs. The first and third inputs are optionally switched to the output. Which of the two inputs is selected depends on the logical value at the second input. If this is at zero, the first input is switched to the output, but if it is at unity, the third input is switched to the output.

The first switch 14 receives at its first input the output of the first characteristic function 12 and at its third input the output of the third characteristic function 13 , At its second input it receives the digital signal DT.

The second switch 15 receives at its first input the output of the memory 18 who has stored a very high value. This value is always greater than the maximum suction in the suction air mass.

At the second input receives the second switch 15 the output of the first switch 14 , The minimal value images 17 receives at its first input the output of the second switch 15 and at its second entrance, the one at the entrance 3 applied value for the air mass target L _S.

In the event that the vehicle is not idling or the vehicle is not in the catalyst heating mode of operation, the first AND gate is on 16 the value zero. Thus, the second switch gives 15 the output value of the memory 18 at his exit. Because this output value is always greater than that at the input 3 applied value is from the minimum value images 17 in each case the signal L _S at the input 3 given out. At the entrance 3 is the air mass target, ie, a target for the per unit time to be sucked air mass provided. This is calculated from the torque request in the engine control and at the input 3 made available.

If the vehicle is idling and in the operating condition of the catalyst heating, the minimum of the air mass is from the second diverter 14 and thus of one of the characteristic functions 12 or 13 provided. In the characteristic functions, the values for the upper limit value L _H are specified as a function of the ambient pressure and of the torque request. The torque request results from the idle speed control. The ambient pressure depends essentially on the altitude at which the vehicle is located.

In the embodiment shown, the air mass to 60% of the air mass target, the input 3 is limited. This applies in the event that the vehicle is at sea level. In contrast, if the vehicle is at 1,500 m above sea level, the air mass is additionally reduced by 9% points, resulting in an air mass of 51% of the air mass target.

By the reduced air mass becomes the amount of fuel injected reduced. This will also reduce fuel consumption during the Total catalyst heating reduced.

When main measure for the catalyst heating is the ignition timing. While in normal idle the ignition by 20 ° compared to the normal Ignition timing is delayed, is in the operating state the catalyst heating retarded the ignition timing by 30-45 °, in other words retarded.

Of the Timing marks the crankshaft position of the engine Combustion engine. He will crankshaft angle in front of the top in degrees Dead center, d. H. the highest position of the piston in the cylinder, indicated. The ignition timing depends on the speed, the burden and the working principle, d. h., two-stroke or four-stroke engine, at a standard gasoline engine between 6 ° and 40 ° crank angle set before the top dead center. The respective ignition timing becomes idle by about 20 ° and idle with catalyst heating about 30 ° from the ignition timing Delayed at partial load.

2 shows a schematic diagram of a gasoline engine in cross section. The air is released from the environment through a suction port 20 sucked through the throttle 21 in the suction pipe 22 directed and when opening the inlet valve 23 in the combustion chamber 25 introduced. By injecting the fuel through the injection channel 24 in the combustion chamber 25 An air-fuel mixture is formed. The engine shown is a direct injection engine. However, the presented method can be used both for internal and for external mixture formation. The spark plug 26 causes the air-fuel mixture to ignite, causing the piston 27 caused to an up and down movement, which in turn the connecting rod 28 in motion as well as the crankshaft 29 to turn.

After combustion of the air-fuel mixture, the exhaust valve becomes 30 opened, allowing the gas from the combustion chamber 25 into the exit pipe 31 to the catalyst 32 to be led.

The engine control 1 controls, among other things, the throttle 21 , the injection valve 24 , the spark plug 26 , the inlet valve 23 and the exhaust valve 30 , In particular, the throttle is 20 controlled in the operating mode of the catalyst heating so that the intake air mass increases significantly at idle, but is limited in contrast to normal idling, in which the catalyst is not heated. The motor control receives as input signals for this function 1 the temperature Temp of the catalyst 32 to determine if the engine is in the catalyst heating mode. It also receives the value of the ambient pressure P _A from a sensor that measures the pressure outside the vehicle and the value TRQ_G from the accelerator pedal to obtain the value for requested torque.

3 is applied to the external pressure P _A in a schematic diagram of the limit for the sucked air mass per time. The external pressure P _A is entered in bar, whereby the pressure increases from left to right.

The diagram shown is part of the characteristic curve function 13 and shows the section where the required torque TRQ_R is constant. In 3 the target for the air mass L _S depends linearly on the external pressure P _A. Deviations from the linearity result from the back pressure of the engine, but this is in 3 not included for better illustration.

at lower ambient pressure also reduces the air mass. This can also serve, among other things, to maintain the brake vacuum. If less air mass is sucked into the intake manifold, lowered also the pressure in the intake manifold, so that a corresponding brake vacuum can be provided. It is thus in the suction pipe accordingly the ambient pressure reduces the pressure.

4 shows as a section of the control value the air mass flow L in g / s for above the requested torque TRQ_R. This control value L is at the output of the minimum value image 17 out 1 provided. As the torque request, which is requested from the idle position sensor, from a clutch request, an electrical load or other consumer, the air mass initially increases. The limit already works, but the threshold has not yet been reached. From a threshold T1, the air mass remains constant, since the air mass limit L _H acts here. The higher torque must be provided in the range between T1 and T2 by adjusting the ignition timing.

From the torque request T2, it is no longer possible to provide the required torque TRQ_R solely by adjusting the ignition. The value for L _H increases, whereby the manipulated value L increases. With the dashed line, the control value for air mass flow in the operating modes in which the catalyst is not heated, is shown.

1

motor control

10

control circuit

11

Luftmassenbegrenzer

12

Characteristic function

13

Characteristic function

14

first switch

15

second switch

16

AND gate

17

Minimum value images

18

Storage

20

Intake vent

21

throttle

22

suction tube

23

intake valve

24

Injection channel

25

combustion chamber

26

spark plug

27

piston

28

connecting rod

29

crankshaft

30

outlet valve

31

outlet pipe

32

catalyst

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 6345466 [0001]

Claims (17)

A control circuit for a gasoline engine, comprising: - an air mass calculation circuit for calculating a setpoint value L _S for the intake manifold (in 22 ) of the gasoline engine to be sucked air mass, - an air mass limiter ( 11 ) for calculating an upper limit value L _H for the suction pipe ( 22 ) to be sucked air mass in the operating mode of the catalyst heating, - a minimum value images ( 17 ), which forms the minimum value of the setpoint L _S and the upper limit L _H in the operating mode of the catalyst heating and outputs as a control variable for the air mass to be sucked. Control circuit according to one of claim 1, characterized in that the upper limit value L _{H is} calculated as a function of the ambient pressure (P _A ) of the gasoline engine. Control circuit according to one of the claims 1 or 2, characterized in that the air mass limiter ( 11 ) is designed so that with increasing ambient air pressure (P _A ) ceteris paribus the upper limit L _{H is} reduced. Control circuit according to one of the preceding claims, characterized in that the upper limit value L _{H is} also calculated as a function of the requested torque (TRQ_R). Control circuit according to one of claims 1 to 4, characterized in that the manipulated variable for the air mass to be sucked for driving a throttle valve ( 21 ) of the gasoline engine is used. Control circuit according to one of claims 1 to 5, characterized in that an injection control circuit for calculating the ignition timing of a spark plug ( 26 ) is designed so that it in the operating state of the catalyst heating the spark plug ( 26 ) In the case L _H <L _S ignites earlier than in the case of L ≥ _H L _S. A control circuit according to any one of claims 1 to 6, characterized in that the upper limit value L _H is constant as a function of the requested torque up to a predetermined torque (T2) and subsequently, if the requested torque exceeds the predetermined torque (T2) , Control circuit according to one of the claims 1 to 7, characterized in that the control circuit in a Microprocessor is housed. Assembly of a control circuit according to one of Claims 1 to 8 and a gasoline engine, by the control circuit is controlled. Method for controlling a gasoline engine, which in the operating mode of the catalyst heating comprises the following steps: - calculating a setpoint value L _S for the intake manifold ( 22 Calculating an upper limit value L _H for the air mass to be sucked into the intake manifold in the operating mode of the catalyst heating, forming the minimum value from the desired value L _S and the upper limit L _H and Setting the air mass to be sucked in accordance with the minimum value, A method according to claim 10, characterized in that the upper limit value L _{H is} calculated as a function of the ambient pressure (P _A ) of the gasoline engine. A method according to claim 10 or 11, characterized in that the upper limit value L _{H is} also calculated as a function of the requested torque (TRQ_R). Method according to one of claims 10 to 12, characterized in that a spark plug ( 26 ) of the gasoline engine is controlled so that in the operating state of the catalyst heating the ignition of the spark plug ( 26 ) in the case L _H <L _S earlier than in the case L _H ≥ L _S. Method according to one of claims 10 to 13, characterized in that the minimum value as a control variable for the opening and closing of a throttle valve ( 21 ) of the gasoline engine is used. Method according to one of claims 10 to 14, characterized in that the air mass limiter ( 11 ) is designed so that when the ambient air pressure (P _A ) ceteris paribus the upper limit L _{H is} reduced. Method according to one of claims 10 to 15, characterized in that the upper limit value L _H in dependence on the requested torque (TRQ_R) to a predetermined torque (T2) is constant and increases, if the requested torque (TRQ_R) the predetermined torque (T2) exceeds. Method according to one of claims 10 to 16, characterized in that the negative pressure for a brake system of the vehicle from pressure in the intake manifold ( 22 ) of the gasoline engine is fed.