EP0443147B1 - Method and device for regulating/controlling the smooth running of an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a method and a device for regulating / controlling the smooth running of an internal combustion engine according to the preambles of the independent claims.

Such a method and such a device for regulating / controlling the smooth running of an internal combustion engine is known from GB-A 21 73 925. There, a method and a device for regulating / controlling the smooth running of an internal combustion engine are described. The cylinder-specific control is switched off when the control deviation exceeds a limit.

From DE-OS 33 36 028 (US-A-4 688 535) a device for regulating / controlling the smooth running of an internal combustion engine is known. The method described there eliminates vibrations of the vehicle in the lower speed range, especially when idling.

Such vibrations are also known as shaking and are based, among other things, on manufacturing tolerances. These manufacturing tolerances mean that different quantities are metered into individual cylinders. In the devices according to the state of the art, these vibrations are eliminated by assigning a control to each cylinder, which regulates the fuel metering for smooth running.

In certain operating states, in particular in systems with a dual mass flywheel, vibrations occur which cannot be compensated for by a method and a device according to the prior art. It is even the case that the vibrations can be amplified by the smooth running control.

Object of the invention

The invention is based, to eliminate all vibrations occurring in a system for regulating / controlling the smooth running of an internal combustion engine of the type mentioned. This object is achieved by the features characterized in claims 1 and 8, respectively.

Advantages of the invention

In a system for regulating / controlling the smooth running of an internal combustion engine of the type mentioned at the outset, vibrations that occur can be eliminated.

The invention is explained below with reference to the embodiments shown in the drawing.

drawings

Figure 1 shows schematically a fuel metering device. FIG. 2 shows the individual areas in which the smooth running control or control is active. FIG. 3 shows a rough flow diagram of the method according to the invention. Figures 4a and 4b show a detailed flow chart. In Figure 5, various signal profiles are entered in a diagram.

Description of an embodiment

The fuel metering device is shown schematically in FIG. An internal combustion engine 10 with a plurality of cylinders receives fuel from a fuel pump 20. An electronic control device 30 calculates control signals for the fuel pump 20 depending on various input variables 35 and the output signals of a sensor 40. A sensor 40 detects the pulses triggered by a segment wheel 50 arranged on the crankshaft.

The torque generated by the internal combustion engine is transmitted directly or via a two-mass flywheel 60 to the drive train 70 of the motor vehicle. The electronic control unit 30 calculates a basic fuel quantity and a correction fuel quantity depending on various variables 35. The function of the electronic control unit 30 is e.g. described in detail in DE-OS 36 04 904 or in DE-OS 33 36 028.

It can happen that different amounts of fuel are metered into the individual cylinders with the same control signal or that individual cylinders deliver a different torque with the same amount of fuel. To avoid uneven running, these differences must be compensated for. This is achieved by assigning a controller to each cylinder. It is particularly advantageous if these controllers have PI behavior. The individual controllers calculate a corrective fuel quantity for each individual cylinder from the different intervals of the segment pulses from combustion to combustion. These correction fuel quantities are stored in the electronic control unit 30 in a cylinder-specific manner.

When the smooth running control is active, the correction fuel quantities are continuously determined, stored and added to the basic fuel quantity in the corresponding cylinder. The amount of correction fuel can take positive or negative values. When the smoothness is controlled, the correction fuel quantities for the individual cylinders are no longer recalculated. In this case, the stored values are added to the basic fuel quantity.

Normally the smooth running control is only activated in idle mode. Outside of idling there is a smooth running control or the fuel metering takes place independently of the smooth running. These different areas are shown by way of example in FIG. 2a and FIG. 2b. The idle speed control is active in the area of the idling speed LLN, whose value is usually around 700 revolutions per minute. Regulation takes place only in a speed range between approx. 550 and 850 revolutions per minute. In the remaining speed ranges, only smooth running is controlled.

The manufacturing tolerances no longer have an effect above a certain limit speed. Therefore, the smooth running program no longer has any advantages above this limit speed. This is usually the case at around 1,500 revolutions per minute. To divide the areas in which the smooth running control or smooth running control is activated, other operating parameters can be used instead of the speed. Such a quantity is, for example, the amount of fuel injected per stroke. As shown in FIG. 2b, the smooth running control is only active with an injected fuel quantity between 3 mg / stroke and 11 mg / stroke.

The areas in which the smooth running control is active depend on the idling speed. Since different types of internal combustion engines also have different idling speeds, the ranges deviate from the above values depending on the type of internal combustion engine.

If vibrations with a very high amplitude and / or certain frequencies occur in the motor vehicle internal combustion engine system, the case may arise that these vibrations cannot be compensated for by the smooth running control. This is particularly the case if the vehicle is equipped with a dual mass flywheel. This dual mass flywheel has different resonance frequencies depending on the operating conditions. If these resonance frequencies are excited, these vibrations are transmitted to the entire motor vehicle internal combustion engine system. If these vibrations have a frequency F which is equal to the crankshaft frequency or 1.5 times the crankshaft frequency, these vibrations disturb the smooth-running controller. For example, the case that the amount of correction fuel is continuously increased, although this is not currently necessary. The vibrations are amplified by the increased correction quantities. In this case, the smooth running control must be switched off.

FIG. 3 shows a rough flow diagram of the method according to the invention, with which such vibrations can be avoided. In a first step / 310, the oscillation frequency F or the control difference DN, ie the difference between the setpoint and actual value, is recorded. An interrogation unit 320 recognizes whether the control difference DN or the oscillation frequency F exceeds a certain value.

If the frequency F of the vibration reaches a limit value, that is to say it becomes equal to or greater than the crankshaft frequency, the smooth running controller is switched off in step 330. This means that the smoothness control is no longer active, but only smoothness control takes place. At the same time, two time counters VZ1 and VZ2 are initialized. In the query unit 340, the first time counter VZ1 is used to query whether a waiting time has already expired. This time query ensures that further measures are taken if the vibrations last longer than a predetermined time.

If the measurement of the oscillation frequency F shows that only crankshaft frequencies occur during a number of crankshaft revolutions or over a predetermined period of time, further measures are initiated in step 360. Such measures can include increasing the idle speed, zeroing the integrators of the PI controller or deleting the stored correction amounts. A speed increase between 50 and 100 revolutions per minute has proven to be a favorable value. This increase in speed can bring the system out of the resonance range. If crankshaft frequencies no longer occur, the idle speed is set to the previous value.

If query 320 recognizes that the oscillation frequency or the control difference is less than a threshold, query 370 is used to check whether the control has been switched off until now. When the controller is switched on, the program ends with step 350. When the controller is switched off, an inquiry 380 is made as to whether a further waiting time VZ2 has elapsed. If this waiting time has already expired, the controller is switched on again in step 390. If the waiting time has not yet expired, the program continues with the controller switched off. Due to this further waiting time a too quick switch back from control to regulation operation prevented. The switch from control to regulating operation takes place only after the waiting time VZ2 or after a number of speed pulses, after the control difference DN or the oscillation frequency falls below a certain value again.

A detailed flow chart of the smooth running control subroutine is shown in FIGS. 4a and 4b. In step 400, the smoothness target values and the smoothness actual values are calculated. This calculation is e.g. B. in DE-OS 33 36 028 or in DE-OS 36 04 904 described in detail. The control difference DN is then determined on the basis of these values. In step 402, the change in control difference DDN is then determined from the current and the previous value of the control difference DN. Based on this change in control difference, the amount DDNB and the sign DDNV are calculated. In step 404, a query is made as to whether the segment counter SZ has reached a specific value X. The counting process of the frequency counter FZ is started for a certain number of segments, in our example 2, and stopped again the next time the same number of segments (2) occurs.

If the segment counter has not yet reached a predetermined value X, the program is continued with step 418 or point A. If the segment counter SZ has reached the predetermined value X, this means that two crankshaft revolutions have passed, then an inquiry 406 is made as to whether the frequency counter FZ is greater than or equal to 4. If this is not the case, the program continues with step 418 or at point A. If the frequency counter FZ assumes the value 4 or a larger value, the control counter SW is set to B in step 408. In query 410 it is then checked whether the frequency counter has the value 4 or 5. If this is not the case, the Idle counter NLL 0 set step 412. If the frequency counter FZ has the value 4 or 5, the idle counter NLL is set to 1 step 414. Steps 412 and 414 are followed by step 416, in which the frequency counter FZ goes back to zero is reset.

In inquiry 418, FIG. 4b, a check is carried out to determine whether the change in control difference DDN is greater than a threshold S. If the change in control deviation does not exceed the threshold, the program continues with step 428. If the change in control deviation is greater than the threshold, a query is made in 420 as to whether the frequency counter is 0. If this is the case, then in step 422 the frequency counter is set to 1, the sign of the frequency counter VZZ is set to the sign of the change in control deviation DDNV. If the frequency counter is not equal to 0, a query is made in step 424 as to whether the sign of the frequency counter VZZ is equal to the sign of the current control difference DDNV. If the sign of the change in control deviation has not changed, the computer jumps to step 428. If, on the other hand, the sign changes, the frequency counter FZ is increased by 1 and the sign of the frequency counter VZZ is reset with the current value, see step 426 Steps 422, 426 and 424 are followed by step 428. In this step the control counter is reduced by 1. In inquiry 430 it is checked whether the control counter is 0. If this is not the case, then step 432 switches over to smooth running control.

If the control counter is 0, it is set to 1 in step 434. Inquiry 436 a check is made as to whether it is necessary to switch to smooth running control for other reasons. This is e.g. B. the case when the speed is outside the idle range. In this case, the control counter is set to B in step 440. If query 436 recognizes that there are no requests for smooth running control, then step 438 switches to smooth running control.

Various counter values and the control difference DN are entered in a diagram in FIG. The values which the segment counter SZ assumes are shown in FIG. 5a. The measuring range MB is determined by means of this count. The measuring range begins at a certain value of the segment counter SZ, in this example at the value 2. The measuring range ends when the segment counter assumes the same value (2) again. In our example, the segment counter in a six-cylinder internal combustion engine runs from the value 12 to the value 1. It counts the impulses triggered by the segment degree arranged on the crankshaft. In this example, the counting process runs over two engine revolutions. This means that 12 pulses occur in the course of two crankshaft revolutions.

The control difference DN is plotted in FIG. 5b. Changes to the control difference that lead to an increase in the frequency counter are marked with arrows. Each time the control difference changes, the certain conditions are met, as shown in FIG. 5c, the frequency counter FZ is increased by one.

The frequency counter is only increased if the change in control deviation exceeds a certain threshold and at the same time the sign of the change in control difference changes. When the control difference A1 changes, both conditions are met, therefore the frequency counter increases by one. With the change A2, the control difference changes by a certain amount, but since its sign does not change, the frequency counter retains its old value.

It is particularly advantageous in the invention that the smooth running control only works when external disturbances which cause vibrations have subsided. Such disorders can e.g. B. caused by resonance vibrations of a two-mass flywheel, an accelerator pedal or clutch pedal actuation when a gear is engaged. When such faults are detected, a switchover from regulation to control takes place immediately. Detuning of the integrators can thereby be prevented.

Claims (8)

1. Method for the closed-loop/open-loop control of the smooth running of an internal combustion engine, in which a closed-loop control difference (DN) is determined as a function of a required value and an actual value, a closed-loop smooth-running control or an open-loop smooth-running control taking place, depending on the operating conditions, characterised in that the closed-loop smooth-running control is switched off if a vibration frequency (F) of the closed-loop control difference (DN) reaches a limiting value.
2. Method according to Claim 1, characterised in that the closed-loop smooth-running control is only switched on again when the vibration frequency (F) has again become less than a certain value and a delay period has elapsed.
3. Method according to one of Claims 1 or 2, characterised in that the vibration frequency of the closed-loop control difference is recorded by means of a frequency counter.
4. Method according to Claim 3, characterised in that a frequency counter increase only takes place if the closed-loop control difference change exceeds a certain threshold and the sign of the closed-loop control difference change reverses at the same time.
5. Method according to at least one of Claims 1 to 4, characterised in that when the closed-loop smooth-running control is switched off for longer than a specified period, use is made of at least one of the following measures, increasing the required idling speed, setting the integrators of the PI controller to 0 or erasing the stored correction quantities.
6. Method according to Claim 5, characterised in that the required idling speed is increased by 50 to 100 revolutions per minute.
7. Method according to one of the preceding claims, characterised in that the correction fuel quantity determined in the case of active smooth-running control is stored and is added to the basic fuel quantity during the metering into the corresponding cylinder.
8. Device for the closed-loop/open-loop control of the smooth-running of an internal combustion engine in which a closed-loop smooth-running control or an open-loop smooth-running control is active depending on the operating conditions, means being provided which record a closed-loop control difference, characterised in that means are provided which switch off the closed-loop smooth-running control in the case where the vibration frequency of the closed-loop control difference reaches a limiting value.

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