EP1774157A1

EP1774157A1 - Method and device for controlling an internal combustion engine

Info

Publication number: EP1774157A1
Application number: EP05766777A
Authority: EP
Inventors: Jürgen DINGL; Hong Zhang; Gerhard Schopp
Original assignee: Siemens AG
Current assignee: Continental Automotive GmbH
Priority date: 2004-08-06
Filing date: 2005-07-07
Publication date: 2007-04-18
Also published as: US7654236B2; US20070289564A1; DE102004038338B3; WO2006015919A1

Abstract

An internal combustion engine comprises an intake tract in which a throttle valve is disposed. The engine also comprises a camshaft which acts on gas inlet valves associated with respective cylinders. A phase-adjustment device is used to adjust a phase between the camshaft and a crankshaft. A desired air mass flow (MAF) in a combustion chamber of the cylinder is determined depending on a charge requirement requested by the driver. The desired air mass flow (MAF) is adjusted by varying the phase (PH) between the camshaft and the crankshaft if the desired air mass flow (MAF) can be adjusted by varying the phase (PH) while substantially maintaining an actual pressure difference upstream and downstream of the throttle valve. Otherwise, the desired air mass flow (MAF) is adjusted by varying the opening angle (THR) of the throttle valve.

Description

description

Method and device for controlling a Brennkraftmaschi¬ ne

The invention relates to a method and a device for controlling an internal combustion engine.

On internal combustion engines increasingly high demands are placed on their performance and efficiency. At the same time, emissions must also be low due to strict legal regulations. Such requirements can be met well if the internal combustion engine are equipped with gas exchange valves and corresponding drives for these, in which the valve lift characteristic is different depending on the operating point of the internal combustion engine. As a result, throttling losses during intake of the air can be reduced and, if necessary, high exhaust gas recirculation rates can be set quickly.

It is thus known, for example, to adjust the valve lift of a gas inlet valve of the internal combustion engine between a low and a high lift. Furthermore, it is also known to regulate the phase position between the valve lift of the gas inlet valve and the valve lift of the gas outlet valve. For example, the Porsche 911 Turbo is equipped with a device for adjusting the phase position between the valve lift of the gas inlet valve and the gas outlet valve. Further, the internal combustion engine of this vehicle is provided with a camshaft on which a cam with a small stroke and two further No¬ cken are formed with a higher stroke for each Gaseinlass¬. The cam lift is by means of a transformer unit on the gas inlet valve transfer. The transmitter unit is designed as a bucket tappet, which comprises a cylinder element and a ring-cylinder element arranged concentrically to this. The cam with a small stroke acts on the cylinder element while the cams with the higher stroke act on the ring cylinder element. Depending on a switching position of the bucket tappet, either the low or the higher stroke is transmitted to the gas inlet valve. When the internal combustion engine is idling, the small cam lift is transmitted to the gas inlet valve. This results in reduced friction losses due to the small diameter of the cam used in this Betriebszu¬ and the cylinder member and the lower valve lift.

Furthermore, a higher charge movement is achieved. As a result, the emissions of the internal combustion engine can be reduced and at the same time the fuel consumption is kept low. The low valve lift is maintained at low and medium load. Throttling losses can additionally be reduced by a corresponding phase adjustment between the gas inlet valve and the gas outlet valve and an ensuing internal exhaust gas recirculation rate. At high load requirements of the internal combustion engine is switched to the hö¬ heren valve lift.

The object of the invention is to provide a method and a device for controlling an internal combustion engine which enables low fuel consumption of the internal combustion engine.

The object is solved by the features of the independent claims. Advantageous embodiments of the invention are characterized in the subclaims. The invention is characterized by a method and a corresponding device for controlling an internal combustion engine with an intake tract, in which a throttle valve is angeord¬ net, with a camshaft which acts on gas inlet valves, which are associated with a cylinder. The camshaft is associated with a phase adjusting device, by means of which a phase between the camshaft and the crankshaft is adjustable ver¬. The phase between the camshaft and a crankshaft is understood as meaning a phase angle between the crankshaft and the camshaft relative to respective reference positions on the crankshaft and the camshaft. A desired air mass flow into a combustion chamber of the cylinder is determined as a function of a driver request load request. The driver request load request is preferably a driver request torque, but it can also be any other variable representing the driver's request.

The desired mass air flow is adjusted by varying the phase between the camshaft and the crankshaft when the desired mass air flow is adjustable by varying the phase while substantially maintaining a current pressure difference upstream and downstream of the throttle. Otherwise, the desired air mass flow is set by varying the opening degree of the throttle valve. For determining the current pressure difference, a detected or estimated intake pipe pressure and a detected or estimated ambient pressure can be used easily.

According to the invention, the driver's request is thus set with respect to the desired air mass flow by varying the phase between the camshaft and the crankshaft, if so the desired air mass flow, is adjustable, and not the throttle used as a main actuator for this purpose, which has the disadvantage that a corresponding throttling by varying the opening degree of Drossel¬ flap to throttle losses and thus to reduce the efficiency of the Internal combustion engine leads. In contrast, varying the phase between the camshaft and the crankshaft merely results in a change in the fraction of an internally recirculated exhaust gas mass flow, thus reducing throttle losses. The region in which the phase between the camshaft and the crankshaft can be varied depends on the one hand on an adjustment range of the phase adjustment device and on the other on boundary conditions with regard to the combustion of an air / fuel in the combustion chamber of the cylinder. mixture. Such boundary conditions take into account a decreasing ignitability and a decreasing burning speed depending on the internal exhaust gas recirculation rate.

In an advantageous embodiment of the invention, a desired pressure difference upstream and downstream of the Dros¬ selklappe is set and set to a near-full range of values, if at a the desired pressure difference entspre¬ chenden actual pressure difference of the desired air mass Ström is adjustable by varying the phase.

With a suitable choice of the range of values, it is thus possible to ensure that a suitable pressure difference is present, for example, for an intended functioning of a possibly existing pressure cell, which can be associated with a switching flap in a suction pipe, or for a tank ventilation system or for a brake system is needed. On the other hand, by the appropriate choice of the full-load Value range throttling losses are kept extremely low. Thus, then the pressure difference is low.

In a further advantageous embodiment of the invention, an adjustment of a valve lift of the gas inlet valve by means of a valve lift adjustment from a niedri¬ Geren to a higher stroke, if the air mass flow, which is adjustable while maintaining the current valve lift by varying the phase, is smaller than the desired air mass flow. This advantageously results in a very wide operating range in which the internal combustion engine can be operated largely de-throttled and yet a driver request load request can be set precisely.

In this context, it is advantageous if a verstel¬ len the valve lift of the gas inlet valve from a higher to a lower valve lift takes place when the ge desired air mass flow at the lower valve lift by varying the phase is adjustable. In this way, a particularly high efficiency of the internal combustion engine can be ensured.

In this context, it is particularly advantageous if, at an adjustment of the valve lift of the gas inlet valve from the higher to the lower valve at the same time the phase is varied such that then flows in this valve lift the desired air mass flow into the combustion chamber of the cylinder. Thus, a torque-neutral transition from the higher to the lower valve lift can be ensured and thus a comfortable operation of the internal combustion engine can be guaranteed. Embodiments of the invention are explained below with reference to the schematic drawings. Show it:

1 shows an internal combustion engine with a control device,

FIG. 2 shows a further view of first parts of the internal combustion engine according to FIG. 1,

FIG. 3 shows a further view of further parts of the internal combustion engine according to FIG. 1,

Figure 4 is a flowchart of a program for controlling the internal combustion engine and

Figure 5 shows different operating ranges of the internal combustion engine based on the torque generated by it aufgetra¬ conditions on the speed.

Elements of the same construction or function are gekennzeich¬ net figures across the same reference number gekennzeich¬ net.

An internal combustion engine (FIG. 1) comprises an intake tract 1, an engine block 7, a cylinder head 3 and an exhaust tract 4. The intake tract 1 preferably comprises a throttle valve 5, furthermore a collector 6 and a suction pipe 7, which lead to a Cylinder Zl is guided via an inlet channel in the Motor¬ block 2. The engine block 2 further includes a crankshaft 8, which is coupled via a connecting rod 10 with the Kol¬ ben 11 of the cylinder Zl.

The cylinder head 3 comprises a valve drive with at least one gas inlet valve 12, at least one gas outlet valve 13 and valve drives 14, 15.

A camshaft 18 is provided which includes cams 16, 17a, 17b acting on the gas inlet valve 12. Furthermore, a valve lift adjusting device 19 (FIG. 3) is provided, which is designed so that either the cam 16 with a low valve lift VL can be brought to act on a plunger of the gas inlet valve 12 or in another switching position of the valve lift. Adjustment 19, the cams 17a, 17b with a high valve lift VL in action on the plunger of Gaseinlassven¬ tils 12 are introduced. The valve lift adjustment device 19 can form, for example, part of a gas inlet valve 12 zu¬ parent bucket tappets. However, it can also be designed as a further element which is mechanically connected between the cams 16, 17a, 17b. It can also be designed such that it, for example, axially displaces the camshaft 18 and, in this way, the switching from a higher to a lower valve lift or vice versa can take place.

Furthermore, a phase adjusting device 20 (FIG. 2) is provided, by means of which a phase between the crankshaft 8 and the camshaft 18 can be adjusted. This adjustment of the phase can be carried out, for example, by increasing a hydraulic pressure in high-pressure chambers of the phase adjusting device 20 or decreasing the corresponding pressure, depending on the direction in which the adjustment of the phase is to take place. A possible adjustment range of the phase is indicated by an arrow 21. Preferably, at least two camshafts 18 are provided, one of the camshafts being associated with the respective gas inlet valves 12 and the other camshaft with the respective gas outlet valves 13. In particular, the camshaft, which is associated with the gas outlet valves 13, in a simple embodiment with a fixed phase to the crankshaft 8 may be mechanically coupled thereto. However, it can also be coupled to the crankshaft 8 via a corresponding phase adjustment device. In this case, then also the phase of the camshaft can be changed, which acts on the gas outlet valves 13.

In the following, however, essentially the camshaft 18 and the phase adjusting device 20 associated therewith are used, which acts on the gas inlet valves 12.

By varying the phase between the crankshaft 8 and the camshaft 18, the valve overlap of the gas inlet valve and the gas outlet valve 13 can be changed, that is, the crankshaft angle range during which an inlet and an outlet of the cylinder Z1 are released , The phase adjustment device 20 and also the valve lift adjustment device 19 can also be designed in any desired manner known to the person skilled in the art.

The cylinder head 3 further comprises an injection valve 22 and a spark plug 23. Alternatively, the injection valve 22 may also be arranged in the intake manifold 7.

A control device 25 is provided, which is assigned to sensors which detect different measured variables and in each case determine the value of the measured variable. The control device 25 determined depending on at least one of the measured variables Stell¬ sizes, which are then converted into one or more control signals for controlling the actuators by means of appropriate actuators. The control device 25 can also be referred to as a device for controlling the internal combustion engine.

The sensors are a pedal position sensor 26, which detects an accelerator pedal position of an accelerator pedal 27, a Luftmas- sensor 28, which detects an air mass flow upstream of the throttle valve 5, a throttle position sensor 30 which detects an opening degree of a throttle, a first temperature sensor 32, which Ansauglufttempe¬ a Saugrohrdrucksensor 34, which detects an intake manifold pressure in the collector 6, a Kurbelwellenwink- kelsensor 36 which detects a crankshaft angle, which is then assigned a speed N. A second temperature sensor 38 detects a coolant temperature. Furthermore, a camshaft angle sensor 39 is provided, which detects a camshaft angle. Depending on the embodiment of the invention, any subset of said sensors may be present, or additional sensors may also be present.

The actuators are, for example, the throttle valve 5, the gas inlet and gas outlet valves 12, 13, the valve lift adjustment device 19, the phase adjustment device 20, the injection valve 22 or the spark plug 23.

In addition to the cylinder Zl, further cylinders Z2 to Z4 are preferably also provided, to which corresponding actuators are then assigned. A program for controlling the internal combustion engine is stored in a program memory of the control device 25 and is executed during operation of the internal combustion engine in the control device. The program is started in a step S1 (FIG. 4) in which variables are initialized, if necessary. The start preferably takes place promptly to an engine start of the internal combustion engine.

In a step S2, a desired intake manifold pressure MAP is set in such a way for setting the current intake manifold pressure that the current intake manifold pressure thus set is within a given value range in which the current intake manifold pressure is suitably high in comparison to the ambient pressure Throttle losses to be kept as low as possible, but on the other hand is so low that the negative pressure required for components of the internal combustion engine can be ge available. Such components can be, for example, a pressure cell of a switching flap. Such switching flaps are frequently arranged in intake manifolds of the internal combustion engine. Furthermore, a corresponding negative pressure may also be important for a tank ventilation system. By way of example, the setpoint intake manifold pressure MAP may be predetermined so that the corresponding set intake manifold pressure is within a relatively narrow pressure range around a pressure reduced by approximately 50 hectopascals compared to the ambient pressure. The ambient pressure can be detected by a dedicated ambient pressure sensor. However, it can also be derived by the measuring signal of the intake manifold pressure sensor when the intake manifold is largely de-throttled.

In a step S8, a phase PH to be set between the crankshaft 8 and the camshaft 18 is dependent on the desired intake manifold pressure MAP, the desired air mass flow MAF in the cylinder Zl to Z4, the rotational speed N, the valve lift VL, the opening degree THR of the throttle valve 5 and, if appropriate, further measured variables or variables derived therefrom er¬ averages. For this purpose, corresponding characteristic fields are preferably stored in a data memory of the control device 25 and / or a corresponding physical model of the absorption behavior of the internal combustion engine is stored in the control device 25. Such a model comprises, for example, a section-wise linear relationship between the phase PH and the desired intake manifold pressure MAP. The parameters, a slope and an offset, which are necessary for the section-wise linear relationship between the phase PH and the nominal intake manifold pressure MAP, are preferably determined from characteristic fields as a function of the other variables. The characteristic fields are determined in advance by tests on, for example, an engine test bench or by simulation. The determination of the phase PH between the crankshaft 8 and the camshaft 18 in the step S8 takes place with the objective of setting the desired air mass flow MAF substantially by varying the phase PH.

In a step S10, it is subsequently checked whether the phase determined in step S8 is greater than a maximum value PH_MAX. The maximum value PH_MAX is that value at which, taking into account the boundary conditions relevant for the combustion process of the air / fuel mixture, such as, for example, sufficient ignition capability and sufficient burning speed of the air / fuel mixture, a stable engine run is made possible.

The maximum value PH_MAX can be predefined in a particularly simple embodiment, but it can also be dependent of at least one measure or a derived quantity.

If the phase PH is greater than the maximum value PH_MAX in the step S10, then it is checked in a step S12 whether a changeover to a higher valve lift VL is possible. Whether this is possible depends on the current valve lift VL and the design of the valve lift adjusting device 19 and the respective cams 16, 17a. In a particularly simple embodiment, no adjustment of the valve lift can be possible at all. Alternatively, it is possible to switch between a high and a low valve lift or else to switch between several stages from the lowest and the highest valve lift.

If the condition of step S12 is not met, setting of a desired air mass flow MAF, which is derived from a driver request load request, takes place essentially by correspondingly varying the throttle valve opening degree THR and thus changing the current intake manifold pressure. The throttle valve opening degree THR is dependent on the desired air mass flow MAF, the rotational speed N and taking into account the Ven¬ tilhubs VL of the gas inlet valve 12 and the phase PH between the crankshaft 8 and the camshaft 18 optionally wei¬ teren measured variables or thereof derived quantities.

Subsequent to step S13, a corresponding activation of the throttle valve 5 then takes place in order to set the desired air mass flow. Optionally, a corresponding adjustment of the valve lift and / or the phase between the camshaft 18 and the crankshaft 8, depending on which steps since the last calculation run of the Program were processed. Decisive, however, is the setting of the desired air mass flow MAF in step S13 by means of a corresponding variation of the degree of opening THR of the throttle valve 5. Supporting, however, also the phase can be varied.

Subsequent to step S13, the program remains in a step S6 for a predetermined waiting time T_W, during which other programs in the control device can be processed. The predefined waiting time T_W is suitably selected so that the desired air mass flow MAF can be set sufficiently precisely during the entire operation of the internal combustion engine. Alternatively, in step Sβ, the program can also remain for a given crank angle range.

Subsequent to step S6, the processing is continued again in step S2.

If, on the other hand, the condition of step S12 is satisfied, the valve lift VL is increased by calculation in a step S14, and the phase PH is then recalculated in step S8 taking into account the new valve lift VL.

If, in contrast, the phase is smaller than or equal to the maximum value PH_MAX in the step S10, the valve lift VL is reduced by calculation in a step S16 if this is possible due to the formation of the cams 16, 17a, 17b and the valve lift adjusting device 19. In this case, the actual readjustment of the valve lift VL does not take place in steps S14, S16, but this only serves as a calculation quantity for determining the further control variables in the following steps. Subsequently, in a step Sl8, the phase PH is again determined according to the procedure of step S8 on the basis of the valve lift VL determined in step S16.

Subsequently, it is checked in a step S20 whether the phase PH is greater than the maximum value PH_MAX. If this is the case, the valve lift VL must be increased again in a step S22 and the phase PH determined in the step S8 must actually be set in a step S24. In step S24, depending on which steps have been carried out previously, if appropriate, the actual adjustment of the valve lift VL is also optionally carried out.

If, on the other hand, the condition of step S20 is not satisfied, it is checked in a step S26 if the phase PH is less than a minimum value PH_MIN which also predetermines boundary conditions for a respective minimum air charge in the current valve lift VL under decisive boundary conditions is. If the condition of step S26 is not met, then the phase determined in step S18 is set in step S24 and if the determined valve lift VL has changed since the last calculation run of the program, this phase too is set. Subsequent to the processing of step S24, the processing in step S6 is continued.

If, on the other hand, the condition of step S26 is satisfied, it is checked in a step S28 whether the determined valve lift VL can be further reduced. If this is the case, the valve lift VL is reduced by calculation in a step S30. Subsequent to step S30, the processing in the Step S18 continues, in which the phase PH is recalculated taking into account the valve lift VL determined in step S30. If, on the other hand, the condition of step S28 is not met, the processing is continued in step S13 and the setting of the desired air mass flow MAF by means of a corresponding variation of the opening degree THR of the throttle valve then takes place.

4, different operating ranges of the internal combustion engine are dependent on a driver request torque TQI_SP, which is preferably an air path torque and thus that torque which can be adjusted by correspondingly varying actuators that adjust the air supply into the respective cylinders Z1 to Z4. Furthermore, the dependence on the rotational speed N is shown. In a region BEI, a low valve lift VL is set and the desired air mass flow MAF is set by correspondingly varying the opening degree THR of the throttle valve. In a region BE2, furthermore, the low valve lift VL is set and the setting of the desired air mass MAF ensues by correspondingly varying the phase PH. In a third area BE3, a high valve lift VL is set and the desired air mass flow is set by correspondingly varying the phase PH. In the region of the transition from the second to the third region BE2, BE3, it may be necessary to throttle as in the first region BEI.

Claims

claims

Method for controlling an internal combustion engine with an intake tract (1) in which a throttle valve (5) is arranged, with a camshaft (18) acting on gas inlet valves (12) associated with a cylinder (Z1 to Z4), and associated with a phase adjusting device (19) by means of which a phase (PH) between the camshaft (18) and a crankshaft (8) is adjustable, in which

A desired air mass flow (MAF) is determined in a combustion chamber of the cylinder (Z1 to Z4) as a function of a driver request load request,

the desired mass air flow (MAF) by varying the phase (PH) between the camshaft (18) and the crankshaft

(8) is set when the desired mass air flow (MAF) is adjustable by varying the phase (PH) while substantially maintaining a current pressure difference upstream and downstream of the throttle, and otherwise the desired mass air flow (MAF) through the Va¬ riieren the degree of opening (THR) of the throttle valve (5) einge¬ is adjusted.

2. The method of claim 1, wherein a target pressure difference upstream and downstream of the throttle valve is set and set to a full load range, if the desired air mass flow is adjustable by varying the phase at one of the desired pressure difference aktuel¬ len pressure difference.

3. The method according to any one of the preceding claims, wherein an adjustment of the valve lift (VL) of the Gaseinlaßven¬ tils (12) by means of a valve lift adjusting device (20) from a lower to a higher valve lift (VL) follows when the air mass flow, which is adjustable while maintaining the current valve lift (VL) by varying the phase (PH), is smaller than the desired air mass flow (MAF).

4. The method of claim 3, wherein an adjustment of the valve lift (VL) of the Gaseinlaßven¬ tils (12) from a higher to a lower Ventil¬ stroke (VL) takes place when the desired air mass flow (MAF) at the lower valve lift ( VL) is adjustable by varying the phase (PH).

5. The method of claim 4, wherein an adjustment of the valve lift (VL) of Gaseinlassven¬ tils (12) from a higher to a lower Ventil¬ stroke (VL) takes place while the phase is varied such that then at the lower Valve lift the desired air mass flow flows into the combustion chamber of the cylinder.

6. A device for controlling an internal combustion engine with an intake tract (1), in which a throttle valve (5) is arranged, with a camshaft (18) acting on Gas¬ inlet valves (12), which a cylinder (Zl to Z4), and to which a phase adjusting device (19) is assigned, by means of which a phase (PH) between the no. cam shaft (18) and a crankshaft (8) is adjustable, where the device is designed for

Determining a desired air mass flow (MAF) into a combustion chamber of the cylinder (Z1 to Z4) as a function of a driver request load request,

- Setting the desired air mass flow (MAF) by Va¬ riieren the phase (PH) between the camshaft (18) and the crankshaft (8) when the desired air mass flow (MAF) by varying the phase (PH) is adjustable while substantially maintaining a current pressure difference upstream and downstream of the throttle, and anson¬ th setting the desired air mass flow (MAF) by varying the opening degree (THR) of the throttle valve (5).