JPH10227251A - Controlling method and device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict combustion peak pressure to an allowable value, and suppress harmful effect to exhaust gas, by finding out a value for correcting a controlled variable when an amount by which combustion chamber pressure in at least one combustion chamber of an internal combustion engine is characterized exceeds a threshold value. SOLUTION: In a control part 150 to which respective output signals of combustion pressure sensors 110-114 arranged per air cylinder, a rotational speed sensor 130 and a pedal position sensor 160 are inputted when a 4 cylinder internal combustion engine 100 is operated, a target value SBS against injection starting is found out according to driving conditions. This value is compared with the actual value, and a control signal is determined in an adjusting part on the basis of the compared result. Next, a control signal for controlling a setting part is found out from this control signal. Also, at this time, it is judged whether or not combustion chamber pressure is larger than a threshold value, and if it is large, the target value SBS is corrected so as to adjust injection staring to a delay direction, and an injection starting setting part 144 is controlled on the basis of the target value SBS after corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The invention relates to an internal combustion engine, for example a self-igniting internal combustion engine, in which a control variable for influencing fuel metering can be predetermined depending on the operating characteristic variable. The present invention relates to a control method and a control device for performing the method.

[0002]

BACKGROUND OF THE INVENTION A method and a device for controlling an internal combustion engine are described, for example, in DE-OS 2653.
No. 046 (US Pat. No. 4,265,200). It describes a control method and a device for a self-igniting internal combustion engine, in which a fuel quantity, for example a control quantity for influencing the start of injection, is determined in advance depending on the operating characteristic quantity. Can be

In this case, the control variable is predetermined in such a way that a particularly favorable gas is produced in the exhaust gas emission. If there is an unacceptable tolerance of the injector, it is possible that very high peak combustion pressures will occur in individual or all cylinders, which may result in damage to the internal combustion engine.

[0004] Tolerances can be relatively large in controlled systems where no response is made about the actual value. In many cases, no response of the actual value is made. This is because no suitable sensor is available or the sensor cannot be used for another reason.

[0005] Sensors capable of detecting the pressure in the combustion chamber of an internal combustion engine are known. Sensors of this kind are, for example, the magazine MTZ Motortechnische Zeitschrift 57
(1996) 1, pp. 16-22.

[0006]

SUMMARY OF THE INVENTION It is an object of the invention to provide a method and a device for controlling an internal combustion engine in which unacceptably high combustion peak pressures are avoided, while at the same time minimizing exhaust gas emissions. is there.

[0007]

According to the invention, this object is achieved by the features according to claims 1 and 8.

[0008] With the method according to the invention, the combustion peak pressure can be limited to an acceptable value, while at the same time the emission of the exhaust gas is only negatively affected.

Advantageous and advantageous embodiments and improvements of the invention are set out in the other claims.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

Referring to FIG. 1, a fuel metering device will be described based on an example of a distribution type injection pump of a diesel engine. However, the method according to the invention is not restricted to this embodiment, but can be used for other fuel metering devices when the corresponding elements are provided.

An internal combustion engine is shown at 100. The internal combustion engine 100 includes four cylinders in the embodiment shown. Each of the cylinders has a combustion chamber pressure sensor 11
0, 112, 113 and 114 are assigned. In a simplified embodiment of the invention, only one combustion chamber pressure sensor 110 is provided. In addition, injection valves 120, 121, 122 and 123 are assigned to each cylinder.

The fuel pump 1 is connected to the injection valves 120 to 123.
Fuel is supplied from 40. The fuel then reaches the cylinders of the internal combustion engine via the injectors and is burned there.
The fuel pump 140 has a quantity setting unit 142 and an injection start setting unit 144. The control signal A
2 is supplied and the control signal A is supplied to the injection start setting section 144.
1 is supplied. Further, the internal combustion engine is provided with various sensors. These sensors form, for example, a signal N relating to the speed of the internal combustion engine.

Output signals from the combustion chamber pressure sensors 110 to 114 and other sensors 130 are supplied to a control unit 150. The control unit generates control signals A1 and A2. The control unit 150 further processes, for example, the output signal of another sensor 160 which corresponds to the position of the travel pedal and which supplies a signal FP indicating the driver's wishes.

The fuel pump and the associated quantity setting units 142 and 144 are merely exemplary. For example, in a conventional device such as a dispensing injection pump, one quantity setting unit and one injection start setting unit are provided. The new device is simply provided with one solenoid valve which takes on the role of the quantity setting and the injection start setting.
In particular, in a common rail system, the pump and the setting are designed to be separate. There is only a pump for generating fuel pressure. The injection start and the injection amount are controlled using the injector.
An injector replaces the injectors 120-123. Even with this device, the technique of the present invention can be used.

Starting from various operating parameters, the control unit 150 determines control signals A1 and A2 which determine the start of injection and / or the amount of fuel to be injected. Starting from these signals, the corresponding setting unit starts and ends the fuel metering at a controlled and set time.

In particular, in a diesel engine, the injection timing has a significant influence on the combustion and, consequently, also on the emission of exhaust gas. In order to be able to achieve as low emission combustion as possible, the start of injection is predetermined depending on various operating parameters such as, for example, the engine speed and the amount of fuel injected. Starting from this value, the control signal A1 for influencing the injection adjustment setting is then obtained.
Is output.

In particular, a fuel pump, an injection start setting unit and / or
Alternatively, the same control signal A
Even at 1, fuel will be metered at different times. Such tolerances result in very high peak combustion pressures under adverse edge conditions. If the characteristic map for the start of injection is optimized in such a way that unacceptable peak pressures do not occur at all edge conditions, under certain conditions an increased exhaust gas emission will occur. This occurs, in particular, at high speeds and / or in the upper load range.

Thus, according to the invention, the injection start control (open-loop control) and / or the injection start adjustment (closed-loop control) are arranged in such a way that an emission value as advantageous as possible is generated. However, there is the danger that, especially at high engine speeds and / or in the upper load range, if there is an unacceptable tolerance of the injector, the combustion peak pressure can be very high. The combustion chamber pressure sensor 110 detects a peak pressure.
When the combustion chamber pressure reaches the limit value, the injection start is adjusted so that the combustion chamber pressure decreases. This approach makes it possible to maintain favorable exhaust gas values under most operating conditions and to produce relatively unfavorable exhaust gas values only under some critical operating conditions. If high combustion chamber pressures are primarily in the tolerance range, but indirectly indicate a relatively early injection start, an advantageous exhaust gas value can be achieved by correction.

FIG. 2 shows a corresponding adjustment for the start of injection in a block diagram. The elements already described in FIG. 1 have corresponding reference numbers.

Reference numeral 200 denotes a target value presetting section, in which an output signal N of the rotational speed sensor 130 and an amount determining section 210 are provided.
Is supplied. The quantity presetter 210 processes output signals of the sensors 130 and 160.
The output signal A2 of the quantity presetting section 210 is further supplied to a quantity setting unit (quantity setting section) 142.

The control signal A2 can be used on the one hand as the fuel quantity signal QK supplied to the target value presetting section 200, and on the other hand another signal characterizing the quantity of fuel to be injected can be used.

The target value presetting section 200 determines a target value SBS for the start of injection in advance. The output signal SBS of the target value presetting unit 200 reaches the injection start adjusting unit 220 via the connection point 240. At the connection point 240, the output signal of the correction value calculation unit 250 is superimposed on the output signal SBS of the target value preset unit 200. The correction value calculation unit detects at least the output signal P of the combustion chamber pressure sensor 110. Starting from this corrected signal, the injection start adjusting unit 220 determines the output amount, and this output amount is supplied to the control signal presetting unit 230. The output signal A1 is supplied to the injection start setting unit 144.

Alternatively, the correction value calculating section 250 can directly influence the value of the target value presetting section 200.

The injection start adjusting section 220 is configured as follows. The desired value SBS is connected via a connection point 222 to the actual value SBI. The actual value comes from the actual value detection unit 226. For example, a needle movement sensor can be used as the actual value detection unit.

The method of the present invention also provides for a controlled device having an injection start adjuster 220 to have control of the injection start.
That is, it can be used for a device without the injection start adjusting unit 220.

The illustrated device operates as follows: starting from a signal indicating the amount of fuel QK to be injected and at least the speed signal N, the target value presetting unit 200 precedes the target value SBS for the start of injection. Decide with this. This goal is
It is selected so as to result in minimal exhaust emissions.

When an adjustment is provided, this value is compared with the actual value at node 222. Based on this comparison, the adjustment unit determines the control signal in advance. This signal reaches the control signal presetting section 230.

If no adjustment unit is provided, the target value S
The BS directly reaches the control signal preset section 230. Here, the control signal A1 for controlling the setting unit (setting unit) 144 is determined.

The correction value calculating section 250 checks whether the combustion chamber pressure P is larger than a threshold value. If it is, the target value BSB is corrected accordingly. Advantageously, the signal is corrected such that the start of injection is adjusted in a lagging direction.

This technique is shown in the flowchart of FIG.

In a first step 300, a target value SBS for the start of injection is determined in a target value calculating section 250 starting from various operating characteristic quantities. Subsequently, in step 310, the corresponding setting unit is controlled and the fuel metered. The maximum combustion chamber pressure P generated during the combustion period is detected in step 320. Question part 330
Checks whether this peak value of the combustion chamber pressure P is greater than a threshold value. If no, repeat step 3
00 or step 400 is performed in one embodiment of the present invention. If yes, at step 340, the correction value SK is increased by a predetermined value K1.

The following interrogator 350 checks whether the value SK is greater than the threshold value SW. If no
In step 360, the target injection start value SBS is set to the value S.
It is corrected by K.

This means that the combustion chamber pressure P in the combustion chamber
Means that the target value SBS for the start of injection or the control signal A1 is corrected as follows. That is, the injection start is adjusted so that the peak value of the combustion chamber pressure decreases. This is preferably done in such a way that the start of injection is adjusted in a lagging direction. In a particularly advantageous manner, the start of injection is adjusted in a small step, that is to say by the value K1, until the permissible combustion chamber pressure S is realized.

The required maximum correction value SW is known on the basis of knowledge of a possible allowable deviation. The correction value SK is limited in step 350 to this possible maximum value.
That is, if the value SK is greater than SW, in step 370 the value SK is limited to the value SW.

Subsequently, at step 380, the second correction value MK is increased by the second value K2. In the next step 399, the fuel amount QK to be injected is reduced by this correction value MK. That is, if the correction of the injection start is not enough to sufficiently reduce the peak value of the combustion chamber pressure, the injection amount QK is similarly reduced stepwise.

Subsequently, steps 399 and 360 are followed by a new step 300.

It is particularly advantageous if the start of the injection and / or the correction of the injection quantity is canceled when the maximum combustion chamber pressure falls below the maximum permissible value. This cancellation is advantageously performed in steps until the maximum combustion chamber pressure has just reached the threshold value S. This is particularly advantageous when the combustion chamber pressure is increasing due to temporary effects.
This occurs, for example, when the fuel properties change.

In FIG. 3, this embodiment differs from step 40 in FIG.
0 to 430 are shown. The interrogator 400 checks whether the correction value SK is smaller than or equal to zero. If yes, that is, if the injection start has not been corrected, step 420 continues. If no, i.e., the injection start has been corrected, step 410 continues. In step 410, the correction value SK is reduced by the value K1, that is, the correction of the injection start is reversed. The value K1 may be different from the value K1 in step 340. Subsequently, step 420 follows.

The interrogator 420 checks whether the correction value MK is smaller than or equal to zero. If yes,
That is, when the injection start is not corrected,
00 follows. If no, i.e., when the start of injection has been corrected, step 430 continues. In step 430, the correction value MK is reduced by the value K2, that is, the correction of the injection start is retracted. The value K2 is the value K in step 380.
It may be different from 2. Subsequently, step 300 follows.

2 and 3, the present invention has been described based on an example of a combustion chamber pressure sensor. According to the invention, one combustion chamber pressure sensor can be provided for each cylinder, in which case the corresponding correction described in FIGS. 2 and 3 is performed for each cylinder.

According to the present invention, the correction values SK at all operating points can be used. That is, in this case, the correction value applies to all target value characteristic maps. In addition and / or alternatively, only corrections depending on the operating point can be made. For example, it is advantageous if the correction takes place in the upper load and / or speed range. This means that the correction of the target value takes place only at operating points and / or characteristic map values where the rotational speed N is greater than the threshold value and / or the fuel quantity QK to be injected is greater than the threshold value. I do.

According to the method of the present invention, the degree of freedom in designing the injection start characteristic map 200 can be obtained. This is because too high a combustion peak pressure need not be taken into account, only the correct emission values need to be optimized. It is particularly advantageous to directly measure the fuel peak pressure, which is the critical engine quantity. The evaluation of the combustion chamber pressure signal P is very simple. This is because it is only necessary to detect the peak value, that is, the maximum value of the combustion chamber pressure during combustion.

[Brief description of the drawings]

FIG. 1 is a block diagram of an internal combustion engine and a control unit thereof.

FIG. 2 is a block diagram of the device of the present invention.

FIG. 3 is a flowchart illustrating a method of the present invention.

[Explanation of symbols]

Reference Signs List 100 internal combustion engine, 110 to 114 combustion chamber pressure sensor, 120 to 124 injection valve, 130 rotation speed detection sensor, 140 fuel pump, 142 injection amount setting unit, 144 injection start setting unit, 150 control unit
160 travel pedal position detection sensor, 200 target value presetting section, 210 quantity presetting section, 220 injection start adjusting section, 230 control signal presetting section, 250 correction value calculating section

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Manfred Strahlmann Karlsruhe sch Netzlerstrasse 9 Germany

Claims (8)

[Claims] In a method for controlling an internal combustion engine, a control variable for influencing fuel metering can be predetermined depending on an operating characteristic variable. A value for correcting the control variable when the variable characterizing the combustion chamber pressure in at least one combustion chamber of the internal combustion engine exceeds a threshold value, depending on the variable characterizing the chamber pressure. Is determined in advance. 2. The control method for an internal combustion engine according to claim 1, wherein the control amount affects the start of injection and / or the amount of fuel to be injected. 3. The amount of fuel to be adjusted for the start of injection and / or to be injected when the quantity characterizing the combustion chamber pressure in at least one combustion chamber of the internal combustion engine exceeds a threshold value. The method for controlling an internal combustion engine according to claim 1 or 2, wherein the control is reduced. 4. The fuel to be injected earlier and / or to be injected when the quantity characterizing the combustion chamber pressure in at least one combustion chamber of the internal combustion engine falls below a threshold value again. 4. The method according to claim 3, wherein the amount is increased again. 5. The control method for an internal combustion engine according to claim 1, wherein the combustion pressure in all combustion chambers can be measured, and individual correction values are determined for each combustion chamber. 6. The control method for an internal combustion engine according to claim 1, wherein the correction value is used at all operating points or only in an upper rotational speed and / or load range. 7. The control method for an internal combustion engine according to claim 1, wherein the correction value is limited. 8. A control device for an internal combustion engine, comprising: first means for determining in advance a control variable for influencing fuel metering as a function of an operating characteristic variable. Depending on the quantity characterizing the combustion chamber pressure in the combustion chamber, the control quantity is increased when the quantity characterizing the combustion chamber pressure in at least one combustion chamber of the internal combustion engine exceeds a threshold value. A control device for an internal combustion engine, further comprising means for determining a value for correction in advance.