JP2001107793A - Control method and control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control system for an internal combustion engine and optimally drive an actuator which controls an exhaust gas recirculation speed and an intake air amount. SOLUTION: A first control signal of a first actuator is controlled depending on a second control signal of a second actuator. The first control signal of the first actuator is used for correcting the second control signal of the second actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention comprises a first actuator for controlling the amount of exhaust gas to be recirculated and a second actuator for controlling at least the amount of fresh air supplied to the internal combustion engine. Setting a first control signal to be applied to the first actuator based on a comparison between a target value and an actual value of the fresh air supplied by the closed loop control circuit;
The second control applied to the second actuator by the open control unit
The present invention relates to a control method for an internal combustion engine that sets a control signal of the internal combustion engine. The present invention also includes a first actuator for controlling the amount of exhaust gas to be recirculated, and at least a second actuator for controlling the amount of fresh air supplied to the internal combustion engine. And a closed-loop control circuit for setting a first control signal applied to the first actuator based on a comparison between the target value and the actual value of the fresh air amount. Control device for internal combustion engine having an open control unit for setting the second control signal

[0002]

2. Description of the Related Art A control method and a control device for an internal combustion engine of this kind are disclosed, for example, in DE-A-196 20.
No. 039 is known. Here, a method and a device are described in which the amount of fresh air supplied to the internal combustion engine and / or the amount of exhaust gas recirculated to the intake line via the throttle valve is controlled by a regulating element which determines the exhaust gas recirculation speed. ing.

What is important in such a system is that the open or closed-loop control device which applies signals to the two actuators is mutually coordinated.

[0004]

The object of the present invention is to provide a control system for an internal combustion engine of the type mentioned at the outset, which optimally drives an actuator for controlling the exhaust gas recirculation speed and the amount of air taken in. That is.

[0005]

This object is achieved by controlling a first control signal of a first actuator in dependence on a second control signal of a second actuator. The problem is also solved by using the first control signal of the first actuator for correcting the second control signal of the second actuator.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS By means of the present invention, two actuators can be optimally driven.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described with reference to the exemplary embodiments illustrated below.

FIG. 1 shows an apparatus for controlling the internal combustion engine 100. The air reaches the internal combustion engine 100 via the supply line 105. Exhaust gas is exhausted through the exhaust pipe 110. The recirculation line 115 connects the exhaust gas line 110 and the supply line 105. An exhaust gas recirculation valve 120 is located in the recirculation line and is referred to as the first regulating element because it controls the amount of recirculated exhaust gas.

[0009] A compressor 125 is arranged in the supply pipe, and compresses the supplied air. Compressor 1
25 is a turbine 140 arranged in the exhaust gas line 110.
Driven by The amount of fresh air taken in is changed by a throttle valve actuator 130 that drives a throttle valve. Throttle valve actuator 130 is referred to as a second adjusting element.

The supplied fresh air amount MLI is detected by a sensor 135. This sensor is also called an air amount sensor.

The control device 150 applies a control signal AD to the throttle valve actuator 130, applies a signal QK to the fuel amount actuator 145, and applies a signal AV to the exhaust gas recirculation valve 120. The exhaust gas recirculation valve has an electropneumatic converter, which converts the control signal AV into pneumatic force and thus moves the actuator 120 to a predetermined position. The controller 150 evaluates the output signal of the speed sensor 165, the output signal of the accelerator pedal position sensor 160, the output signal of the air flow sensor 135, and possibly the signals from other sensors.

The output signal FP of the accelerator pedal position sensor 160 and the rotation speed signal N of the rotation speed sensor 165 are processed by a fuel amount control unit 152, and a control signal QK is applied to the fuel amount actuator 145 by this control unit. Further, the fuel amount control unit 152 sends a signal MLS of a target value of the air amount and a fuel amount signal QK to the exhaust gas recirculation control unit 154. The exhaust gas recirculation control unit 154 further processes the output signal MLI of the air amount sensor 135. The exhaust gas recirculation control unit 154 supplies a signal AV and a signal AD.

The device operates as follows. That is, fresh air supplied through the supply line 105 is supplied to the compressor 1
25. The throttle valve is driven by the throttle valve actuator 130, and the amount of supplied air reaches the internal combustion engine 100 in a suppressed state or in an unrestricted state. Exhaust gas supplied via exhaust line 110 drives turbine 140, which in turn drives compressor 125.

A portion of the exhaust gas reaches supply line 105 via recirculation line 115. The cross-sectional area of the recirculation line can be changed by the exhaust gas recirculation valve 120, whereby the component of the amount of exhaust gas to be recirculated can be adjusted.

The fuel amount control unit 152 controls the control signal QK for determining the fuel amount to be injected based on the driver's request FP detected by the accelerator pedal position sensor 160, the rotational speed N, and possibly another operation amount. Is calculated. This signal drives the fuel amount actuator 145. Further, a target value MLS of the fresh air amount is set by the fuel amount control unit 152. This target value corresponds to the desired air quantity required for the combustion of the fuel quantity QK. The exhaust gas recirculation control unit 154 drives the throttle valve actuator 130 and the exhaust gas recirculation valve 120 such that the fuel in the internal combustion engine burns with as little emission as possible.

In a system in which the amount of air supplied to the internal combustion engine is controlled by a throttle valve and an exhaust gas recirculation actuator, the two actuators are coordinated to adjust the respective desired air flow and the throttle loss is reduced by the throttle valve. The task arises to keep it as small as possible based on the action of.

According to the invention, the amount of fresh air per stroke is adjusted by replacing part of the fresh air with recirculated exhaust gas. When the exhaust gas recirculation speed is high, the pressure difference between the fresh air and the exhaust gas side is increased by the throttle valve. Due to the throttle losses occurring in the throttle valve in this connection, according to the invention the throttle valve is closed, so that the adjustable distance available in the exhaust gas recirculation valve is hardly used in a controlled manner. This means, in particular, that the exhaust gas recirculation valve is located in the vicinity of the end stop or reaches the end stop completely. Alternatively, if the air quantity control circuit regulates a very low exhaust gas recirculation rate, the exhaust gas recirculation valve is completely closed.

To avoid reaching the end stop, the adjustment range of the air flow control circuit is adapted by adjusting the throttle valve. The air amount control circuit controls the air amount by adjusting the exhaust gas recirculation valve, and preferably has PID characteristics.

In a particularly advantageous embodiment, a pre-control value is added to the output signal of the closed-loop control circuit.

In order to avoid residual control deviations, the throttle valve is optionally partially closed and the exhaust gas recirculation valve is not locked in a limit position.

Two corresponding embodiments are shown in FIGS.

FIG. 2a shows a first embodiment of the means of the present invention. Elements already described with reference to FIG. 1 are provided with corresponding reference numerals.

The signal MLS representing the desired fresh air quantity is prepared by the fuel quantity control 152, on the one hand to the closed loop control circuit 200 via the connection point 205, and on the other hand to the pre-open control 210 and the characteristic map 220. . Instead of this characteristic map, a non-linear function is preferably used. The output signal MLI of the air quantity sensor 135 representing the actually supplied fresh air quantity is applied to the second input side of the connection point 205 with a negative sign. The output signal N of the rotation speed sensor 165 is further supplied to the characteristic map 220.

The output signals of pre-open control 210 and closed-loop control circuit 200 reach node 230 with a positive sign. The closed loop control circuit 200 is advantageously a so-called PID
It is configured as a closed loop control circuit, which has a proportional part, an integral part, and a differentiating part. At the other input of the node 230, the output signal of the correction circuit 240 is applied with a negative sign, which is indicated by the dashed line.

The correction circuit 240 mainly includes the DT1 element 24
4 and a limiting circuit 246. DT1 element 24
4 is supplied with an output signal of the characteristic map 220. The output signal of the characteristic map 220 further reaches the throttle valve actuator 130 as an output signal AD. The output signal at node 230 reaches exhaust gas recirculation valve 120 as control signal AV.

The two signals AV, AD are preferably designed as signals representing the position of the respective actuator. Preferably, a corresponding keying ratio is set. Alternatively, a signal indicating the stroke of the valve and / or the position of the throttle valve actuator may be applied to one or both of the actuators. This signal is converted into a corresponding control signal inside each actuator.

Based on a comparison between the target value MLS of the amount of intake air and the actual value MLI, the closed loop control circuit 200 determines a control signal applied to the exhaust gas recirculation actuator, and thereby determines the exhaust gas recirculation speed. It is adjusted so that a desired amount of air is supplied to the internal combustion engine. In order to improve the dynamics of the system, a pre-open control 210 is provided, which controls the control signal AV for the exhaust gas recirculation actuator 120 depending on the target value MLS. The output signal of the pre-open control is preferably added to the output signal of the closed-loop control circuit. The use of the pre-open control allows the system to respond to changes in the target value without much delay.

At the same time, a control signal for the throttle valve actuator 130 is set on the basis of the characteristic map 220 and preferably the rotational speed N on the basis of the air mass target value MLS. This control signal is set by the characteristic map 220 so that the exhaust gas recirculation valve does not reach the mechanical stopper,
That is, the throttle valve is closed so as not to shift to the limit position.

The characteristic map 220 is preferably embodied as a non-linear function. In this case, the control signal AD of the throttle valve actuator 130 is equal to the target fresh air amount MLS.
And the rotation speed N. The function of the non-linear function part is shown in FIG. In the non-linear function part, a plurality of value regions for the operating state are defined.
The air amount MLS and the rotation speed N define a predetermined operation state. The regions of different values are separated from one another by double lines. The value of the control signal AD is assigned to each value area. A region of this type of value is also called a zone. The region of the first value is indicated by a thick solid line and a broken line. In the region of this value, the control signal takes the value X. The control signal takes the value Y in the region of the adjacent second value. When the operating state changes and transitions from the first value range to the second value range, the control signal changes at the location of the dashed line. When the operation state changes and shifts from the second value area to the first value area,
The control signal changes at the solid line. This means that the alternation between the two value regions has a hysteresis. The value range and the hysteresis threshold are selected such that the adjustment distance of the exhaust gas recirculation actuator is always well utilized.

In order to allow the air flow to move as smoothly as possible during the adjustment of the throttle valve 130, that is to say that the air flow does not change exponentially, a control signal to the exhaust gas recirculation valve is provided. Is corrected via the dynamic pre-opening control unit in dependence on the control signal AD for the throttle valve 130. This is performed by the correction circuit 240.

In the first variation of FIG. 2A, the correction circuit 240 mainly comprises a filter 244,
This filter advantageously has a DT1 characteristic. That is, this filter has a differential characteristic and a delay function. Particularly advantageously, the output signal of the DT1 element is connected to a subsequent limiting circuit 246.
Within the maximum and minimum values.

In the means for controlling an internal combustion engine according to the present invention, the first actuator controls the amount of exhaust gas to be recirculated. The second actuator 130 is used to control at least the amount of fresh air supplied to the internal combustion engine. The closed loop control circuit sets the control signal AV based on a comparison between the supplied fresh air target value MLS and the actual value MLI,
Apply to the first actuator 120. Open control unit 22
0 sets the control signal AD, and the second actuator 13
Apply to 0. The control signal of the first actuator is
Can be controlled depending on the control signal of the actuator 130 of FIG. In the embodiment shown, the value formed by filtering the control signal of the second actuator is added to or subtracted from the control signal of the first actuator. In another embodiment, a control unit that performs closed loop control may be used instead of the open control unit 220.

A DT1 element is preferably used for filtering. Via the filter, a change in the angle of the throttle valve results in a change in the stroke of the ARF valve, which acts temporarily and in the opposite direction. For example, when the throttle valve is partially closed, the MLI decreases, and similarly, when the ARF valve is partially closed, the MLI increases. Overall, the MLI is kept almost unchanged for the time being. In this case, the correction value sent from the correction circuit 240 gradually decreases in accordance with the value, and the closed loop control circuit sets the adjustment amount to M
LI = MLS.

This means that it is necessary to change the stroke of the ARF valve for the same air amount MLI after adjusting the throttle valve. The dynamic correction circuit is A
The stroke of the RF valve is pre-opened at this point. Adjustment of the throttle valve is used to again establish a predetermined reserve adjustment amount for the ARF valve. Therefore DT
With one element, an abrupt change in the MLI is avoided. MLI
If is changed quickly, a change in the rotational torque may be recognized. Advantageously, a slow transition is realized with the DT1 element. Control is performed such that the correction value is constantly zero by the D component. The primary part of the filter, T1, prevents the needle pulse from reaching an unlimited level due to the differentiation of the D part.

It is particularly advantageous for the filtering unit to have a limiting circuit. The correction value for a predetermined time range is kept constant by this limiting circuit. Furthermore, the maximum correction value is independent of the difference between the values of the characteristic map.

A particularly advantageous embodiment is shown in FIG. FIG. 2b shows the correction circuit 240 in detail. In this embodiment, the DT1 element 244 includes the characteristic curve section 24.
5 is connected upstream. The characteristic curve portion 245 assigns a predetermined correction value AVK to the control signal AD. This is done so that the output signal of the correction circuit is always scaled around the same value when transitioning from a predetermined keying ratio to an adjacent value.

FIG. 2c shows a corresponding characteristic curve by way of example. The relationship between the control signal AD for the throttle valve and the correction value AVK preferably corresponds to a step function having equally spaced step levels.

Since the control signal AD for the throttle valve actuator takes only a discrete value, the adjustment of the throttle valve is constant even when the change in the target value is small. This separates a smaller signal area from a larger signal area. The throttle valve is activated only in a large signal range, that is, only when the change in the target value is large. This extends the life of the throttle valve actuator. The material cost of the actuator can be reduced accordingly. The correction circuit of the control signal AV for the exhaust gas recirculation actuator depends on the control signal AD of the throttle valve actuator, and reduces errors in the dynamic air amount.

Another embodiment is shown in FIG. Elements already shown in FIGS. 1 and 2 have corresponding reference numerals.

The output signals of the pre-opening control section 210 and the closed-loop control circuit 200 reach a connection point 300 from which a control signal A is sent to the exhaust gas recirculation actuator 120.
V is applied. The signal AV is applied to the exhaust gas recirculation actuator and reaches the summing point 360 via the correction circuit 340. The output signal of the characteristic map 220 is applied to a second input side of the addition point 360. The output signal of the addition point 360 reaches the throttle valve actuator 130 as a control signal AD. The correction circuit 340 mainly includes 3
It comprises a point element (Dreipunktglied) 346 and an integration circuit 344. The integration circuit exchanges signals with the adaptation circuit 350. The adaptation circuit exchanges signals with the characteristic map 220.

In this embodiment, the control signal AD of the throttle valve actuator is corrected depending on the control signal AV of the exhaust gas recirculation actuator.

If the exhaust gas recirculation valve 120 is in the advantageous operating range, the control of the throttle valve 130 is not performed. Only when the exhaust gas recirculation valve is driven very little or almost at maximum, the throttle valve angle is corrected accordingly. As a result, the throttle valve is closed only while it is necessary to keep the exhaust gas recirculation valve in the advantageous operating area.

The value of the integrator 344 is preferably diverted to a characteristic map 220 via an adaptation circuit 350. That is, the value of the characteristic map 220 is adapted depending on the value of the integration circuit. If, at a later point in time, an already adapted operating point is achieved, the throttle valve adopts advantageous values based on the control of the characteristic map.

A three-point characteristic curve having hysteresis (Drei
By using the punktkennlinie as the characteristic map 220, rattling of the throttle valve actuator is avoided. Jitter is high frequency chatter at the switching threshold. This problem also occurs, for example, with a two-point characteristic curve (Zweipunktkennlinie). A three-point characteristic curve (dead zone) or a hysteresis threshold is used as a counter measure. In order to easily avoid rattling (chattering), a normal three-point characteristic curve is sufficient in this case. An additional hysteresis threshold is used for further stabilization of the throttle valve. With this threshold value, a predetermined insensitivity to a small fluctuation of the keying ratio is obtained.

The non-linear function part 220 is easily applicable. Especially in applications, this function can be replaced by zero. The correct value is learned during operation by the adaptation circuit.

According to the measures of the present invention, the first actuator 120 is used to control the amount of exhaust gas that is recirculated. The second actuator 130 controls at least the amount of fresh air supplied to the internal combustion engine. The closed loop control circuit includes a target value MLS and an actual value ML of the supplied fresh air amount.
A first control signal AV applied to the first actuator 120 is set based on the comparison with I. The opening control unit sets a second control signal AD applied to the second actuator 130. In this case, the first actuator
Is controllable depending on the second control signal AD of the second actuator, and / or
Is used for correcting the second control signal AD of the second actuator.

A characteristic map for setting the control signal of the second actuator is preferably used. Instead of the second
A closed loop control circuit for setting the control signal of the actuator may be used.

In order to correct the control signal of the second actuator, the value of the characteristic map and / or the control signal of the second actuator are corrected.

It is particularly advantageous to use a non-linear function as the characteristic map.

The non-linear function part differs from a normal non-linear characteristic map in that it has a non-linear hysteresis transition between individual cells. Due to this hysteresis transition, constant rattling at the throttle valve does not occur even with small N fluctuations or MLS fluctuations at the cell edge. The non-linear function part may be called a characteristic map having hysteresis.

In a predetermined function part, the history determines both the values of the output amounts. In the case of FIG. 4, the value of the transition area between the solid line and the dashed line depends on whether X or Y was valid before.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the apparatus of the present invention.

FIG. 2 is a diagram showing an embodiment of the means of the present invention.

FIG. 3 is a diagram showing another embodiment of the means of the present invention.

FIG. 4 is a diagram showing a characteristic map.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 internal combustion engine 105 supply line 110 exhaust line 115 recirculation line 120 exhaust gas recirculation valve 125 compressor 130 throttle valve actuator 135 air flow sensor 140 turbine 145 fuel flow actuator 150 control device 152 fuel flow control unit 154 exhaust gas flow Circulation control unit 160 Accelerator pedal position sensor 165 Rotation speed sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 41/14 320 F02D 41/14 320Z F02M 25/07 550 F02M 25/07 550R 550Q (72) Inventor Torsten Heidrich Germany Weihingen / Enz Roggenweg 1

Claims (9)

[Claims] 1. A first method for controlling an amount of exhaust gas to be recirculated.
Actuator (120) and a second actuator (1) for controlling at least the amount of fresh air supplied to the internal combustion engine.
30), and the target value (M) of the fresh air supplied by the closed loop control circuit.
LS) and a first control signal (AV) to be applied to the first actuator (120) based on a comparison between the actual value (MLI) and the first control signal (AV) applied to the second actuator (130) by the open control unit. A second control signal (AD) to be set, wherein the first control signal (AV) of the first actuator is changed to a second control signal (AD).
Controlling the internal combustion engine according to a second control signal (AD) of the actuator. 2. Filtering a second control signal (AD) of a second actuator after filtering the first control signal (AD) through a DT1 element.
2. The method according to claim 1, wherein the first control signal is coupled to a first control signal of the actuator. 3. The method according to claim 1, wherein the second control signal (AD) of the second actuator is limited and then coupled to the first control signal (AV) of the first actuator. 4. A first method for controlling an amount of exhaust gas to be recirculated.
Actuator (120) and a second actuator (1) for controlling at least the amount of fresh air supplied to the internal combustion engine.
30), and the target value (M) of the fresh air supplied by the closed loop control circuit.
LS) and a first control signal (AV) to be applied to the first actuator (120) based on a comparison between the actual value (MLI) and the first control signal (AV) applied to the second actuator (130) by the open control unit. A second control signal (AD) to be set, wherein the first control signal (AV) of the first actuator is changed to a second control signal (AD).
A method for controlling an internal combustion engine, wherein the method is used for correcting a second control signal (AD) of the actuator. 5. The method as claimed in claim 1, wherein the characteristic map is used for setting a second control signal (AD) of the second actuator. 6. The method according to claim 4, wherein the value of the characteristic map and / or the second control signal of the second actuator are corrected. 7. The method according to claim 5, wherein a non-linear function part is used as the characteristic map. 8. A first method for controlling an amount of exhaust gas to be recirculated.
, And at least a second actuator (130) for controlling the amount of fresh air supplied to the internal combustion engine, and a target value (MLS) for the amount of fresh air to be supplied. A closed loop control circuit for setting a first control signal (AV) applied to the first actuator (120) based on a comparison with an actual value (MLI); Second applied
A control device for an internal combustion engine having an open control unit for setting the first control signal (AD) of the first actuator.
Means for controlling the actuator in accordance with a second control signal (AD) of the internal combustion engine. 9. A first method for controlling an amount of exhaust gas to be recirculated.
, And at least a second actuator (130) for controlling the amount of fresh air supplied to the internal combustion engine, and a target value (MLS) for the amount of fresh air to be supplied. A closed loop control circuit for setting a first control signal (AV) applied to the first actuator (120) based on a comparison with an actual value (MLI); Second applied
A control device for an internal combustion engine having an open control unit for setting the control signal (AD) of the first actuator, wherein the first control signal of the first actuator is used for correcting the second control signal of the second actuator A control device for an internal combustion engine, comprising: