JP2011256863A - Method and device for controlling internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently compensate for torque jump resulting from a large difference in filling volume and in particular, to reduce emission of NOx.SOLUTION: A device and a method for controlling an internal combustion engine having overcome the drawbacks of the prior art are provided in a method for controlling the torque characteristics of an internal combustion engine capable of lean combustion, wherein the internal combustion engine comprises a stroke change device 220 for changing at least one stroke 200 of at least one intake valve 160, a filling volume change device 100 for changing the filling volume, in particular, a throttle valve, and an ignition device 120 and in switching stages (t, t), the valve stroke change device 220 changes the stroke 200 of at least the one intake valve 160.

Description

  The invention relates to a method as described in the claims. The invention further relates to a computer program, an electrical storage medium and a control and adjustment device.

  Internal combustion engines connected to an engine control unit for performing a plurality of operating modes and a plurality of injections per combustion cycle are generally known. Similarly, techniques for switching the intake valve stroke (Einlassventilhub) of an internal combustion engine to reduce consumption are generally known. This can significantly reduce the throttle loss (androsselverluste) and thus the consumption, especially in homogeneous gasoline engines. The switching of the intake valve stroke can also be performed in particular by a cylinder selective actuator mechanism.

  An intake valve stroke switching system with only one actuator for switching all intake valve strokes is particularly inexpensive. These systems require simultaneous intake valve stroke switching for all cylinders. In such a system with reduced costs, it is a disadvantage that an extremely large difference occurs in the filling amount in successive combustion cycles when all cylinders are switched simultaneously. Such a large filling amount difference causes a large torque jump that is felt uncomfortable.

  Such a torque increase caused by overfilling can be compensated by shifting the ignition angle to a later time or adjusting the throttle valve. In the above system with only one actuator, the difference in filling amount is very large, and it is impossible to completely compensate for the torque jump caused by shifting the ignition angle to a later time. Adjustment with the throttle valve can only be carried out with significant disadvantages. Such an adjustment would necessitate switching of the intake valve stroke already when the intake pipe pressure is very low. This will eliminate most of the possibility of undrawing (Entdrosselungspotential).

  In addition to torque compensation by shifting the ignition angle, the method according to the invention with the features of the independent claims can be used in addition to lean combustion when the torque jump cannot be sufficiently compensated by shifting the ignition angle. Torque is compensated for. This has the advantage that torque jumps due to large filling differences can be fully compensated.

  When the ignition angle is below the stipulated threshold ignition angle (vorgebbare Schwellzundwinkel), the end of the lean combustion phase is particularly short, which is particularly advantageous for low emissions, especially NOx .

  If the definable threshold ignition angle is the maximum ignition angle that ensures reliable combustion, the lean combustion phase is as short as possible. Therefore, such a threshold ignition angle selection is particularly suitable for minimizing exhaust gas emissions, particularly NOx.

  Steady filling amount, that is, the filling amount changing device so that the average filling amount becomes equal at the start and end of the switching stage over a plurality of combustion cycles without changing the filling amount changing device and without changing the valve stroke Is controlled, the advantage is that the ignition angle can be changed and the air-fuel ratio λ different from 1 can be limited to a particularly short time.

  However, if the air-fuel ratio is stochiometrische in the switching stage other than the lean combustion stage, it has the special advantage that exhaust gas emissions, in particular NOx, can be minimized.

  The method according to the invention has the particular advantage that it is particularly simple when the ignition angle is constant in the lean burn phase.

  In the lean combustion stage, the lean combustion stage can be made particularly short if the filling quantity changing device changes the value characterizing the filling, in particular the throttle valve position. This has the advantage that exhaust gas emissions, in particular NOx, can be minimized.

  The method according to the invention has the advantage that the method according to the invention is particularly short and therefore particularly simple if the filling quantity changing device changes the value characterizing the filling, in particular the throttle valve position, in the switching phase.

  Embodiments of the present invention will now be described in detail with reference to any drawing.

It is the schematic which shows the fuel-injection system of the internal combustion engine which has a valve stroke change apparatus. FIG. 6 schematically shows a change in characteristic size of an internal combustion engine in the method according to the invention. FIG. 6 schematically shows a change in characteristic size of an internal combustion engine in the method according to the invention. Fig. 2 is a flow diagram illustrating a method according to the invention. Fig. 2 is a flow diagram illustrating a method according to the invention.

  FIG. 1 shows a cylinder 10 of an internal combustion engine having a combustion chamber 20 and a piston 30 connected to a crankshaft 50 by a connecting rod 40. The crankshaft angle sensor 60 senses the angular position of the rotating crankshaft 50. Such information regarding the angular position of the crankshaft 50 is transmitted to the controller 70.

  The combustion air is sucked into the combustion chamber 20 through the intake pipe 80 in a known manner during the downward movement of the piston 30. The burned air is pushed out of the combustion chamber 20 through the exhaust pipe 90 when the piston 30 moves upward. The amount of air sucked through the intake pipe 80 is adjusted by the filling amount changing device, in this embodiment, the throttle valve 100. The position of the throttle valve 100 is adjusted by the control device 70.

  In this embodiment, the fuel is injected into the air sucked from the intake pipe 80 through the injection valve 110 arranged directly inside the combustion chamber 20, and a fuel / air mixture is generated inside the combustion chamber 20. . However, the injection valve 110 may be attached to the inside of the intake pipe 80, for example. A spark plug or igniter 120 ignites the fuel / air mixture. The control device 70 generally adjusts the injection timing of the injection valve 110 and the ignition timing of the spark plug 120 relative to the angular position of the crankshaft 50. The angular position of the crankshaft 50 at the time of injection is called the injection angle, and the angular position of the crankshaft 50 at the time of ignition is called the ignition angle.

  A lambda sensor 130 that detects the air-fuel ratio λ and transmits it to the control device 70 is located inside the exhaust pipe 90. The NOx storage catalytic converter causes the NOx ratio in the exhaust gas to be significantly reduced inside the exhaust pipe 90.

  An intake valve 160 provided at the introduction portion of the intake pipe 80 to the combustion chamber 20 is driven by a camshaft 190 via a cam 180. Similarly, the exhaust valve 170 provided at the introduction portion of the exhaust pipe 90 to the combustion chamber 20 is driven by the camshaft 190 via the cam 182. The camshaft 190 is connected to the crankshaft 50. Normally, the camshaft 190 rotates once for every two rotations of the crankshaft 50. The size of the cams 180 and 182 determines the movement of the intake valve 160 or the exhaust valve 170. FIG. 1 shows a valve stroke (Ventilhub) 200 of the intake valve 160.

  The cam adjustment device 210 that can be controlled by the control device 70 can switch the cam 180 of the intake valve 160 between a small cam 180a and a large cam 180b. When the cam 180 of the intake valve 160 is a small cam 180a, the valve stroke 200 is smaller than when the cam 180 of the intake valve 160 is a large cam 180b. Therefore, the cam adjusting device 210, the small cam 180a, and the large cam 1890b form a valve stroke changing device 220.

  Similarly, the cam 182 of the exhaust valve 170 can be switched from a small cam 182a and a large cam 182b. It is also possible to provide a cam adjustment device 210 specific to each cylinder 10 of the internal combustion engine. However, it is also possible for the cam adjustment device 210 to switch the cams of several cylinders 10 or all cylinders 10 at the same time.

  FIG. 2 shows characteristic parameter characteristics of the internal combustion engine when the cam 180 of the intake valve 160 is switched from the small cam 180a to the large cam 180b. The position N of the cam adjusting device 210, the position DK of the throttle valve 100, the filling amount indicating the amount of air supplied to the combustion chamber 20 for each combustion cycle, the air-fuel ratio λ, and the ignition angle ZW are shown.

At the start of the method, the small cam 180a drives the intake valve 160 and the position N of the cam adjustment device 210 is correspondingly “small”. In the first time point _{t 1,} the controller 70 controls the cam adjustment device 210, thereby, the intake valve 160 is driven by a large cam 180b. This switching step is performed rapidly, usually within a few milliseconds (eg 4 milliseconds). After the switch is made, the position N of the cam adjustment device 210 is “large”.

Loading via an intake pipe 80 is supplied to the combustion chamber 20 is leap to the maximum filling value F _max from the first filling value F ₁ immediately after the first time point t _1. This is because the valve stroke 200 of the intake valve 160 is expanded after switching to the large cam 180b. Position DK of the throttle valve 100, according to the present invention, the switching from the first value DK ₁ if position N is "small", "large" position N to after switching of the cam adjustment device to a second value DK ₂ cases It is done. Switching of such throttle valve position DK ends at a second time point t _2. This time interval t ₂ -t ₁ is, for example, several hundred milliseconds. The value of the second throttle valve position DK ₂ is selected so that the filling amount is again equal to F ₁ after the second time point t ₂ . Therefore, after reaching the maximum filling value F _max , the filling is continuously reduced to F ₁ at the second time point t ₂ by slowly rotating and closing the throttle valve 100.

The time interval t ₂ −t ₁ is called the switching stage (t ₁ , t ₂ ). During this switching phase (t ₁ , t ₂ ), the filling amount of the combustion chamber 20 is increased with respect to the filling amount F ₁ before the time point t ₁ . The additional filling produces additional torque upon ignition of the fuel / air mixture in the combustion chamber 20. According to the present invention, this additional torque reduces the amount of fuel injected from the injection valve 110 immediately after the first time point t ₁ to increase the air / fuel ratio λ from the first value λ ₁ to the maximum value λ _max. Is reduced. At the same time, the ignition angle ZW is increased to the maximum ignition angle _{ZW max} from the first ignition angle ZW _1. These two measures, an increase in the air-fuel ratio λ and an increase in the ignition angle ZW, respectively lead to a reduction in the torque produced during ignition of the fuel / air mixture in the combustion chamber 20.

In order to reliably burn the fuel / air mixture in the combustion chamber 20, the ignition angle ZW must not exceed a predetermined value. The value of the maximum ignition angle ZW _max is selected in relation to the operation so as to correspond in particular to the maximum ignition point at which reliable combustion is still possible. At this maximum ignition point ZW _{max there} is also a maximum possible reduction in the torque produced by the combustion of the fuel / air mixture.

The maximum air-fuel ratio λ _max is selected in conjunction with the selected maximum ignition angle ZW _max so that the torque generated by the combustion with the maximum filling value F _max is reduced to the value of the torque before time t _1. .

Over time, the ignition angle ZW and the air / fuel ratio λ are always selected such that the torque produced by the combustion is equal to the torque before the first time point t ₁ . According to the present invention, first, the ignition angle is maintained at the maximum ignition angle ZW _max, and the surplus torque to be compensated (Uberschussdrehmoment) that is similarly reduced by reducing the filling amount is obtained by reducing the air-fuel ratio λ. From the third time point t ₃ , the air-fuel ratio λ is reduced again towards the value λ ₁ provided before the first time point t ₁ . The surplus torque generated by the overfill amount still shown at this point is now reduced only by the ignition angle ZW. In the further course of the method from the third time point _{t 3} to a second time point _{t 2,} the ignition angle ZW is reduced from _{ZW max} corresponds to the surplus torque drops ZW _1. In the operating range where this is possible, the surplus torque is also compensated by the ignition angle ZW. If it is essential to increase the ignition angle ZW beyond the maximum ignition angle ZW _max in order to fully compensate the surplus torque, the remaining surplus torque is obtained by the increased air-fuel ratio λ.

In order to prevent an increase in NOx emissions, the value of the variable λ ₁ is set equal to 1, for example. The time interval T _m of a between the first time point t ₁ and the third time point t ₃ is referred to as a lean combustion phase. If a NOx storage catalytic converter 140 is provided, it is necessary that the combustion ratio λ takes a value of 1, ie stoichiometric. This is because in the method according to the invention, at a later point in time, for example, a post-injection of the fuel by the injection valve 110 is performed at a crankshaft angle of −130 °, which reduces the air-fuel ratio λ to the value 1, Does not generate torque. Such a torque-neutral after-injection is known, for example, from EP-A-2147205.

Figure 3 shows the time course of characteristic values shown in FIG. 2 when switching the cam 180 of the intake valve 160 to the small cam 180a at a second time _{t 2} from the large cam 180b by the cam adjustment device 210. Position N of the cam adjusting device 210 drastically to values "small" from the value "large" in the second time point t _2. Thus charge in the combustion chamber 20 is reduced sharply to a second time point t _2. The position DK of the throttle valve 100 is thus opened from the second throttle valve position DK ₂ at the first time point t ₁ to the first throttle valve position DK ₁ at the second time point t ₂ . the amount is increased to a maximum filling value of the immediately preceding point of time of switching cam adjusting device 210 from the first filling value F ₁ of the first time point t _1, the second position N from the first position N to after switching of the cam adjusting device 210 "large" To “small”, the size of the filling amount is reduced to just the first filling value F ₁ .

The torque increased by the filling amount increased in the middle is compensated by the increase in the ignition angle ZW starting from the first time point t ₁ and first starting from the first value ZW ₁ . If the ignition angle reaches the maximum ignition angle ZW _max at the third time point t _3, the air-fuel ratio λ begins to rise. Ignition angle ZW and the air-fuel ratio λ are respectively selected to compensate cooperatively excess torque generated by the filling amount that is increased relative to the first loading F _1.

The maximum ignition angle ZW _max is selected to correspond to the maximum ignition angle that allows reliable combustion of the fuel / air mixture. Preferably, λ ₁ = 1 is selected, and the time interval between the third time point t ₃ and the second time point t ₂ is referred to as the lean combustion stage T _m .

FIG. 4 shows the process of the method according to the present invention when the cam 180 of the intake valve 160 shown in FIG. 2 is switched from the small cam 180a to the large cam 180b. Step 1000 marks the start of the method. In the next step 1010, the control device 70 controls the cam adjusting device 210 so that the cam 180 is switched from the small cam 180a to the large cam 180b. This corresponds to the time _{t 1} of FIG. Then step 1020 follows.

In step 1020, for example, by the supplied characteristics map, or controller second throttle valve position DK ₂ based on the supplied model 70 is calculated in the control device 70. In the present embodiment, DK ₂ is calculated so that the steady filling amount at the second time point t ₂ is equal to the steady filling amount at the time point t ₁ . However, it is also possible to calculate the second throttle valve position DK ₂ so that the steady filling amount at the second time point t ₂ is different from the steady filling amount at the first time point t _{1 by} a similarly stipulated filling amount difference. This can be done, for example, when loading required for the first time t ₁ based on the modified torque request at the second time point t ₂ (Momentenanforderung) is meaningful. Then step 1030 follows.

In step 1030, it is checked whether the position DK of the throttle valve 100 has reached the second throttle valve position DK _2. As shown in FIG. 2, when the value of the second throttle valve position DK ₂ is smaller than the first value of the throttle valve position DK _1, for example, the value of the throttle valve position DK is a second throttle valve position DK ₂ below Check whether or not. If so, step 1100 continues and the method according to the invention ends. This corresponds to a second time point t ₂ of FIG.

In step 1040, the position DK of the throttle valve 100 is moved in the second direction of the throttle valve position DK _2. In connection with the type of cam adjustment device 210 and the implementation of the control of the cam adjustment device 210, such movement can be effected, for example, by lowering the target value of the position of the cam adjustment device 210 by a definable increment. . Next is 1050.

In step 1050, in relation to the current position DK of the first filling value F ₁ and the throttle valve, for example, based on the characteristic map (Kennfeld), the current loading exceeded changes the λ hence ignition angle ZW and filling air ratio Thus, the surplus torque to be compensated is calculated. If there is no ignition angle ZW which can compensate for the excess torque or calculated ignition angle ZW is greater than the maximum ignition angle ZW _max, ignition angle ZW is set to a value ZW _max. Then step 1060 follows.

In step 1060, it is checked whether the ignition angle ZW is equal to the maximum ignition angle ZW _max . If so, step 1070 continues, otherwise step 1080 follows.

  In step 1070, the air-fuel ratio λ necessary for compensating the surplus torque is calculated based on the set ignition angle ZW and surplus torque. The control device 70 controls the injection valve 110 so that the injected injection amount provides a desired air-fuel ratio λ. Then step 1030 follows.

In step 1080, it is detected that the surplus torque has been completely compensated by adjusting the ignition angle ZW. This corresponds to the time between the third time point t ₃ in FIG. 2 and the second time point t _2. The control device 70 controls the injection amount injected by the injection valve 110 so that the air-fuel ratio λ becomes 1. Then step 1030 follows.

  FIG. 5 shows a method according to the present invention in which the cam 180 of the intake valve 160 is switched from a large cam 180b to a small cam 180a.

Immediately following the start of the method of step 1000, step 1020 follows. In step 1020, the first value of the throttle valve position DK ₁ as constant filling amount _{F 1} of the first time point _{t 1} and the second time point _{t 2} is equal to after switching to the small cam 180a from a large cam 180b of cam 180 Calculated. Structure of step 1020 corresponds to the first time point _{t 1} in FIG. New, it is also possible to differ by as altered loading difference which can define the loading of the first time point t ₁ and the second time point t ₂ based on the torque demand. In this case, the first throttle valve position DK ₁ is selected so that a desired filling amount difference is generated. Then step 1030 follows.

In step 1030, it is checked whether the position DK of the throttle valve 100 has reached the first throttle valve position DK _1. In the embodiment shown in FIG. 3, whether the throttle valve position DK has reached the first throttle valve position DK _1, or checks whether or not it exceeds this. If so, step 1090 follows. Otherwise, step 1040 continues.

In step 1090, the N value of the camshaft position is switched from “large” to “small”. This corresponds to a second time point _{t 2} in FIG. This is followed by step 1100, at which step the method ends.

In step 1040, the throttle valve position DK is moved in the first direction of the throttle valve position DK _1. This is done by increasing the target value definition for the cam adjustment device 210 by increments that the control device 70 can define. Then step 1050 follows.

Steps 1050, 1060, 1070 and 1080 correspond to steps 1050, 1060, 1070 and 1080 shown in FIG. The first construction step 1070 corresponds to the third time point _{t 3} in FIG.

Prior to the end 1100 of the method according to the invention, the ignition angle ZW and the air / fuel ratio λ may be set to the values formed at the first time point t ₁ . This may for example be performed by storing an appropriate value of the time t _1. However, steps 1050, 1060, 1070 and 1080 may be performed again before the method ends.

In the method shown in FIG. 4 in conjunction with FIG. 2, an inquiry in step 1060 for the first time t _1, whether the ignition angle ZW is what reaches the maximum ignition angle ZW _max, or exceeded it, Step 1070 is performed. This is because performing the first time point t ₁ in step 1020, as described above, therefore, step 1070 is first performed when the ignition angle ZW is what reaches the maximum ignition angle ZW _max, or exceeded it. This marks the start of the lean burn phase. In the third time _{t 3,} step 1060 is first branches to step 1080, which indicates the end of the lean burn phase _{T m.}

On the other hand, in the method shown in FIG. 5 in connection with FIG. 3, the process branches from step 1060 to step 1080 between the first time point t ₁ and the third time point t ₃ . In the third time _{t 3,} step 1060 is first branches to step 1070, which indicates the start of a lean combustion phase _{T m.} At the end of the method, when the value of the ignition angle ZW and the air-fuel ratio λ as described above is returned to the value set in the first time point t _1, which indicates the end of the lean burn phase T _m.

Accordingly, the start and end of the lean burn phase T _m is the same as the point in time at which the value of the ignition angle ZW has either reached the first time to the maximum ignition angle ZW _max, or the first time apart.

Therefore, in the switching stage (t ₁ , t ₂ ), the position of the throttle valve 100 is changed, and thus the steady filling amount change caused by the switching of the valve stroke 200 of the intake valve 160 is compensated. During this switching phase (t ₁ , t ₂ ), an overfill, and thus an increased torque, occurs. Such excessive torque is compensated by an increase in the ignition angle ZW. Since ignition angle ZW can not exceed the maximum ignition angle ZW _max, in order to compensate for the excess torque generated by the excessive loading, if not sufficient for increasing the ignition angle ZW to the maximum ignition angle ZW _max, lean combustion phase _Tm is added. In lean combustion phase T _m, the air-fuel ratio lambda, is selected to a size excess torque is exactly compensated when simultaneously increased to the maximum ignition angle ZW _max ignition angle ZW (especially greater than 1).

DESCRIPTION OF SYMBOLS 10 Cylinder 20 Combustion chamber 30 Piston 40 Connecting rod 50 Crankshaft 60 Crankshaft angle sensor 70 Adjustment apparatus 80 Intake pipe 90 Exhaust pipe 100 Throttle valve, filling amount change apparatus 110 Injection valve 120 Ignition apparatus 130 Lambda sensor 140 NOx accumulation | storage catalyst converter 160 Intake Valve 170 Exhaust valve 180, 182 Cam 180a, 182a Large cam 180b, 182b Small cam 190 Camshaft 200 stroke 210 Cam adjusting device 220 Stroke changing device

Claims (12)

A method for controlling torque characteristics of a lean burnable internal combustion engine comprising:
A stroke change device (220) for the internal combustion engine to change at least one stroke (200) of at least one intake valve (160), and a filling amount changing device (100) for changing the filling amount, particularly a throttle valve. And an ignition device (120), wherein the valve stroke changing device (220) changes the stroke (200) of at least one intake valve (160) in the switching stage (t ₁ , t ₂ ),
When the ignition angle (ZW) exceeds the maximum ignition angle (ZW _max ), the lean combustion phase (T _m ) is started, and the air-fuel ratio takes a value greater than 1 during the lean combustion phase (T _m ) A method characterized by. The method according to claim 1, wherein the lean combustion stage (T _m ) is terminated when the ignition angle falls below a maximum ignition angle (ZW _max ). The method according to claim 1, wherein the maximum ignition angle (ZW _max ) is set to a maximum ignition angle that ensures reliable combustion. At the start (t ₁ ) of the switching stage (t ₁ , t ₂ ), the stroke of at least one intake valve (160) takes a first value, and
At the end of the switching stage (t ₁ , t ₂ ) (t ₂ ), the stroke of the at least one intake valve (160) takes a second value;
The method according to claim 1, characterized in that: Controlling the filling amount changing device (100), said switching stage _(t 1, _{t 2)} and the steady loading of the start of the _{(t 1),} the switching stage _(t 1, _{t 2)} at the end _(t 2) The method according to claim 1, wherein the steady-state filling amount is equal. 6. The air / fuel ratio is stoichiometric during the switching stage (t ₁ , t ₂ ) other than the lean combustion stage (T _m ), according to claim 1. Method. 7. The method according to claim 1, wherein the ignition angle is constant during the lean burn stage ( _Tm ). 8. The characteristic of filling, in particular the throttle valve position (DK), is changed by the filling quantity changing device (100) during the lean combustion stage (T _m ). The method as described in any one of. From the switchover stage (t ₁ , t ₂ ), the filling amount changing device (100) changes the size characterizing the filling, in particular the throttle valve position (DK). 9. The method according to any one of up to 8. In a computer program,
Computer program programmed for use in the method according to any one of claims 1-9. In an electrical storage medium for at least one of an internal combustion engine control and regulation device (70),
An electrical storage medium, wherein a computer program for use in the method according to any one of claims 1 to 9 is stored in the electrical storage medium.   10. Control and / or regulating device (70) for an internal combustion engine, programmed for use in the method according to any one of the preceding claims.