EP0440942B1 - Method for the disposal of electric information values - Google Patents

Description

The invention relates to a method for providing a plurality of information about the operating state of an internal combustion engine, in particular an internal combustion engine provided with a control unit, the generation of first information, in particular a duty cycle, and at least one further, second, in particular pulse-shaped, periodic information, and the information can be combined in a single electrical combination signal.

Corresponding electrical signals must be transmitted for the display and / or processing of information about the current operating point of an internal combustion engine. If the internal combustion engine has a control unit, this gives, for example, consumption and speed information via electrical Cables provided to the receiving location. This can be, for example, a dashboard that has a fuel consumption display and a tachometer. For the provision or transmission of two pieces of information, such as consumption and speed, two lines with the associated plug contacts of the plug device are required.

From DE-OS 20 34 067 it is known to use a pulse generator for an electronic fuel consumption measuring device, of which at least two operating values, namely the pulse repetition frequency and the height of the pulses or the pulse repetition frequency and the width (duration) of the pulses or the height and the width of the pulses can be changed as a function of the electrical measured quantities (information). In particular, depending on the engine speed, the repetition frequency of the pulse generator and, depending on the pressure in the intake system, the width of each pulse delivered by the pulse generator should be changed. The pulse sequence containing two pieces of information can thus be transmitted via an electrical line. However, if one piece of information fails or its value becomes "zero", the other information is also omitted, because pulses of "zero" width have no repetition frequency or the frequency "zero" leads to pulse width "zero" or "infinite".

Advantages of the invention

The inventive method with the features mentioned in the main claim has the Advantage that only one line and one plug contact are required for the provision and transmission of two pieces of information, but the absence of one of the two pieces of information does not lead to the information content of the other piece of information being lost. The information of the different signals is combined in a single combination signal by adding the pulse widths assigned to the information per combination signal period. If the first information disappears, for example, for a short time, the pulse width of the combination signal is reduced by the amount of the failed information only during this downtime. The first information is preferably assigned to an electrical signal, the information content of which is determined by a pulse duty factor. So it is a pulse train. A further, second piece of information is preferably in the form of a pulse-shaped, periodic, second electrical signal, the information being in the frequency of the second signal.

The first information is preferably consumption information, the pulse duty factor of which depends on the size of the fuel consumption of the internal combustion engine. The second information is speed information of the internal combustion engine. A fuel consumption and speed display on the dashboard of a motor vehicle therefore requires only one line connection leading to the control unit of the internal combustion engine.

The invention is not limited to the consumption information, but can also be implemented with other signals, in particular crankshaft-synchronous signals. This crankshaft-synchronous signal is preferably the output signal of an engine control unit.

According to the invention, it is provided that the consumption information is superimposed with a speed information that extends its pulse duration. As already mentioned, the consumption information is a pulse sequence with the corresponding duty cycle. The speed information is now superimposed in such a way that the pulse duration of the consumption information increases; thus a change in the duty cycle occurs. The combination signal is generated. In particular, the pulse duration of the consumption information is increased by a constant time. To determine the consumption, it is necessary at the receiving location to subtract this constant time period from the combination signal in order to maintain the original duty cycle. On the one hand, there is the duty cycle that determines the consumption and, on the other hand, the frequency that determines the speed. The method according to the invention has the advantage that even if a fuel cut-off takes place in the overrun mode of the internal combustion engine, that is to say there is no fuel consumption during the duration of the coasting operation, speed information is nevertheless transmitted. In the prior art, in which the speed information as a speed signal on one line and the consumption information as a consumption signal on another line transmitted, the consumption signal can therefore not be used as a speed signal at the same time, although in the normal operation of the internal combustion engine there are synchronous pulse train sequences since the consumption information disappears during overrun operation and therefore no speed information would be available. The overlay according to the invention by increasing the pulse duration of the consumption information makes it possible to make do with a single signal, namely the combination signal.

According to one embodiment, a periodic needle pulse signal can be used as speed information. Thus, the consumption information is superimposed on the needle pulse signal, whereby the pulse duration of the consumption information increases only insignificantly, so that the consumption information is hardly falsified. If the error that occurs in the consumption display is negligible, the subtraction of the speed signal from the combination signal to be performed at the receiving location can be omitted.

drawing

Figur 1

ein Impulsdiagramm, daß die bisherige Informationsübertragung auf mehreren Leitungen darstellt und

Figur 2

ein erfindungsgemäßes Impulsdiagramm, daß zur Informationsübertragung ein Kombinationssignal verwendet, welches lediglich eine Leitung benötigt.

The invention is explained in more detail below with reference to the figures. Show it:

Figure 1

a timing diagram that represents the previous information transmission on several lines and

Figure 2

an inventive pulse diagram that uses a combination signal for information transmission, which only requires one line.

Description of the embodiment

In motor vehicle electronics, information from an engine control unit is output via a suitable plug connection which is connected to a number of electrical lines corresponding to the number of information items. A first piece of information having a duty cycle and a second, pulse-shaped, periodic piece of information are considered here, the first piece of information being consumption information TVB and the second piece of information being speed information TD. The duty cycle -related to a period ts- of the consumption information TVB corresponds to the current fuel consumption of an internal combustion engine of a vehicle. The consumption information is transmitted from the engine control unit to the dashboard (fuel consumption display) via the line connection already mentioned. The second information relates to the speed n of the internal combustion engine. This is also indicated by a tachometer on the dashboard and must therefore be transmitted from the engine control unit via a line.

This known structure is illustrated in FIG. 1 with the aid of signal profiles. BM is assigned to the crankshaft of the internal combustion engine Reference mark marked. It has a period of 360 ° cube wave angle.

Below this, an ignition signal Zdg is shown, which is used to control the ignition output stage of the internal combustion engine. Then follows the speed information TD already described with the period ts. It can be seen that the pulse sequence of the ignition signal Zdg runs synchronously with the pulse sequence of the speed information TD.

wobei Zylza gleich der Anzahl der Zylinder der Brennkraftmaschine ist.The speed information TD — in FIG. 1 — shows the consumption information TVB, which likewise runs synchronously with the ignition signal Zdg or with the speed information TD. It therefore consists of a periodic pulse train. The pulse width t _KVA represents - based on the period t - a duty cycle that corresponds to the fuel consumption of the internal combustion engine. The larger the pulse width t _KVA , the greater the fuel consumption. However, there is an exception with regard to the synchronicity of the consumption information TVB with the speed information TD. This is indicated in FIG. 1 by dashed lines. In overrun mode Sch, no fuel is consumed in modern internal combustion engines; one speaks here of "overrun cutoff". The result of this is that no consumption information TVB occurs during the period of overrun operation. However, since the internal combustion engine has a corresponding speed n in overrun mode, depending on the operating point, the speed information TD is retained despite the loss of the consumption information TVB. Therefore, for the transmission of the consumption and the Speed information two lines with corresponding plug contacts etc. required. According to the known method according to FIG. 1, the speed n is:

where Zylza is equal to the number of cylinders of the internal combustion engine.

wobei KD eine Durchflußkonstante bezeichnet. Diese beträgt zum Beispiel

The consumption VB results from the consumption signal TVB from the following relationship:

where KD denotes a flow constant. For example, this is

In contrast to Figure 1, which shows an arrangement of the prior art, in Figure 2 that The method according to the invention illustrates. The upper waveform again shows the reference mark BM, which has a period of 360 °. An ignition signal Zdg is shown below the reference mark BM. The combination signal TD / VB according to the invention is shown underneath. It contains two pieces of information, namely first piece of information, which represents consumption information TVB, and second piece of information, namely speed information TD. The combination signal has the period ts and has a pulse width t _KVB . Within each period ts, the consumption information TVB is overlaid with the speed information TD by adding the pulse widths of the respective information. The pulse width t _KVB thus contains the consumption information TVB specified as the duty cycle and the period duration ts contains the speed information TD, which is formed by corresponding pulse-shaped signals. If there is a fuel cut-off in which there is no fuel consumption and accordingly the consumption information TVB is omitted, the combination signal TD / VB and thus the speed information are retained. This is marked with Sch in FIG. 2. Accordingly, there is only the second, namely the speed information TD.

If one wishes to obtain the consumption information from the combination signal TD / VB, it is only necessary to subtract the pulse width of the speed information TD from the combination signal TD / VB.

In particular, the pulse duration of the second information associated with the speed is constant.

The speed n can be determined according to the relationship:

Ebenso ist es für die Funktion des Drehzahlmessers meist notwendig, daß die Differenz von Periodendauer ts und Impulsdauer t_KVB eine gewisse Zeit nicht unterschreitet, beispielsweise ebenfalls immer größer 1ms ist, also:

${\text{ts - t}}_{\text{KVB}}\text{≧ 1ms.}$

For the function of a tachometer, it is usually necessary that the pulse width t _{KVB of} the combination signal TD / VB does not fall below a certain time, for example, is always greater than 1 ms, that is:

${\text{t}}_{\text{KVB}}\text{≧ 1ms}$

Likewise, for the function of the tachometer, it is usually necessary that the difference between the period ts and the pulse duration t _KVB does not fall below a certain time, for example, is also always greater than 1 ms, that is:

${\text{ts - t}}_{\text{KVB}}\text{≧ 1ms.}$

The last equation shows that within a period there must be sufficient time for the "offset" according to the invention of 1 ms for the speed information.

wobei KDB eine Durchflußkonstante darstellt.The consumption can be determined from the following relationship:

where KDB is a flow constant.

wobei ts min die Periodendauer bei maximaler Drehzahl und t_KVA max die Impulsbreite bei maximalem Kraftstoffverbrauch ist.The relationship between t _KVB and t _KVA is thus:

where ts min is the period at maximum engine speed and t _KVA max is the pulse width at maximum fuel consumption.

This results in the flow constant for the design according to the invention:

Claims (6)

1. Method of providing a plurality of items of information on the operating state of an internal-combustion engine, in particular an internal-combustion engine provided with a control device, having the following steps:

   - generation of a first item of information, in particular having a pulse duty factor,

   - generation of at least one further, second, periodic item of information, in particular in pulse form,

   - the items of information being combined in a single, electric combination signal,

   characterized in that the pulse widths assigned to the items of information are added every combination signal period.
2. Method according to Claim 1, characterized in that the first item of information is an item of information on consumption (TVB), the pulse duty factor of which depends on the level of fuel consumption.
3. Method according to one of the preceding claims, characterized in that the second item of information is an item of information on the speed (TD) of the internal-combustion engine.
4. Method according to one of the preceding claims, characterized in that the pulse duration of the first item of information is increased by a constant time period, assigned to the second item of information, for forming the combination signal (TD/VB).
5. Method according to one of the preceding claims, characterized in that, for determining the first item of information at the receiving location of the combination signal (TD/VB), the constant time period is subtracted again to obtain the original pulse duty factor.
6. Method according to one of the preceding claims, characterized in that the second item of information is formed by a periodic needle pulse signal.

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