WO1987005967A1

WO1987005967A1 - Process and digital control unit for determining and controlling pulse-width modulated operating values in an internal combustion engine

Info

Publication number: WO1987005967A1
Application number: PCT/DE1986/000507
Authority: WO
Inventors: Rüdiger Jautelat; Werner Jundt; Norbert Miller; Peter Werner
Original assignee: Robert Bosch Gmbh
Priority date: 1986-03-29
Filing date: 1986-12-11
Publication date: 1987-10-08
Also published as: DE3669906D1; DE3610717A1; EP0298960B1; EP0298960A1; JPH0758060B2; JPH01501880A

Abstract

In a process and digital control unit for determining, controlling and/or adjusting pulse-width modulated operating-value signals, a timer design is proposed which, while leaving unchanged the two existing 16-bit timers (8O51-chip processor family), indicates to the first timer the output of the consumption and injection Ti-signal. During an external TD-interrupt, first the smallest signal value of the signals to be emitted is loaded into the timer register and the timer is started, and during the next timer interrupt, ignoring the timing register, the difference in relation to the previously-emitted signal is loaded into the time register for the emission of the next signal. If signal values are obtained which are larger than the maximum signal duration obtained from this timer for a predetermined quantification, then, when this value is exceeded, an overflow-flag requiring servicing by the timer-interrupt routine is established and the switching of the first signal is effected with the following timer interrupt. The second timer serves in an unsolicited manner with any preset time pattern desired of the period duration measurement for calculation of the rotation speed and for controlling any desired counting registers in order to produce further pulse-width modulated operating-value signals.

Description

Method and digital control device for determining and controlling pulse width modulated operating variables in an internal combustion engine

State of the art

The invention is based on a method according to the preamble of the main claim or a digital control device according to the preamble of claim 7.

The use of digital control devices for determining, controlling and regulating pulse-width-modulated signals as operating variables for an internal combustion engine is known; For example, the applicant's so-called α / n mono-jetronic uses a single-chip processor or microcomputer (μC) for the generation of output signals and for time measurement, the control being carried out via so-called interrupt-capable timers is carried out, the components of the single-chip processor can be additionally sorted ^* uch an¬ kön¬ NEN or a device on the control board.

To clarify the invention, the state of the art is explained in the following with the aid of a special embodiment known per se, the use of such a single-chip processor, and here again the 8051 family, in particular. Such a one-chip processor provides the user with two 16-bit timers, namely timer T0, timer T1, both of which can be interrupted, one of the timers, namely timer T0, being split into two 8-bit timers can be. However, the consequence then is that the remaining 16-bit timer T1 loses its interrupt capability. Basically, in such digital control devices, the control and the output of the pulse-width-modulated signals is carried out in such a way that counting registers can be controlled via the timer interrupts that occur, each of which is loaded with certain signal values, so that this timer control results in real-time signal output.

The timer assignment conception of such digital control devices is then to be carried out in such a way that, for example, the following tasks can be solved: Output of two pulse-width-modulated signals with a quantization of 2 μsec (such as consumption signal, injection signal Ti), the output of these two signals has to be synchronous to a so-called TD pulse, which is generated as an external interrupt signal, for example by the ignition Signals can be derived from speed signals of the internal combustion engine or from a signal resulting at terminal 1 of the internal combustion engine;

- Output of three further pulse-width-modulated signals with a coarser quantization (e.g. 2 msec) as an adaptive idle control signal ALS, as a tank ventilation signal or as an intermediate spray output signal;

- Generation of any time grid and

Period measurement between the external interrupt or TD pulses (for the speed calculation) and therefore as a basis for the calculation of the fuel to be supplied to the internal combustion engine, together with an air flow sensor signal, for example.

In order to generate these signals, the procedure for a known timer assignment is to split a known 16-bit timer T0 into two 8-bit timers (timer 0 low; timer 0 high), their respective use in the following 1-3, both for the basic explanation of a possible, but known exemplary embodiment for a timer occupancy concept in a digital control device for better understanding as a whole and for creating the possibility, the invention is delimited - and to present it in an understandable way.

The split-off low part of the timer T0, as shown in a) in FIG. 1, generates a 512 μsec raster with a quantization of 2 μsec. Derived from this time grid, an additional ALS count registers, as shown at σ), for the output of the ALS signal (signal adaptive idle control) shown in b) over time, as well as the deactivation of the additional count register or counter for tank ventilation, as shown in e) the resulting tank ventilation signal (TE signal), as shown at d) in FIG. 1. Both this explanation and the invention relate specifically to a tiner configuration, and here again specifically to the single-chip processor of the 8051 family mentioned; however, it should be mentioned that the pulse-width-modulated signals to be output or determined, which are determined here, correspond in the digital control device to counter readings which have arisen in a different way, are usually calculated and are each stored in a suitable storage location. Such calculations take place repeatedly, so that the counter readings change, and the present timer occupancy concept then determines, on the basis of these counter readings, which are shown in FIG. 1 at c) and at e) Pulse width modulated duration of the signals to be determined or to be output. If the low part of the timer 0 is assigned the generation of the two pulse-width-modulated ALS signals and TE signals mentioned above, then, as shown in FIG. 2, there remains for the high part of the timer 0, for example, and under an¬ whose generation of the Ti pulse, which is particularly important in a fuel injection system and with which the signal is designated, which is used to control the injection valves of the internal combustion engine and whose duration is therefore decisive for the quantity of fuel to be supplied to the internal combustion engine per unit of time. 2, in a) the high part of the timer 0 then generates the same time pattern as the low part, so that the high part in conjunction with an additional Ti counting register, as shown in c), controls the output of the Ti pulse (among other things). It can be seen that the signal to be output is in a multiple of 512 μsec (see course of the counting register status, which is decremented or driven off each time the high part of timer 0 overflows and by the interrupt generated thereby) and in the remaining ones Remainder divided by the total value with the complement value of which the high part of the timer T0 is precharged at the beginning of an external timer interrupt (ignition pulse as indicated at a) as a TD pulse). Every time the high section overflows, the interrupt generated in this way results in the decrementing of the Ti count register until its content is zero and the Ti pulse is driven off.

Finally, the task of the second 16-bit timer T1, which is used in the period measurement for the speed calculation, will be discussed, as shown in FIG. 3. Since only a maximum time acquisition of 131 msec is possible due to the quantization of 2 μsec per timer increment in a 16-bit timer, an additional counting register, as shown at b) in FIG. 3, must be used. The quantization of this register is 2 msec, so that a time recording by the timer T1 of a maximum of 512 msec can be achieved.

This conception results in a considerable interrupt load, since with all pulse-width-modulated signals to be output, every 512 μsec of the time grid interrupt is triggered, and in particular the time grid limitation for the two divided, then only 8-bit timers with the aforementioned quantization of 2 μsec only permits a maximum time of 512 μsec.

Furthermore, for example, by dividing the Ti time into a multiple of 512 μsec plus the rest, the memory expenditure in the PROM of the digital control device with respect to the preparation for the output control is considerable. It cannot be ruled out that there is a loss of accuracy due to the frequent interrupts, especially in the case of the important output signals for the Ti pulse and a so-called consumption signal.

The invention is therefore based on the object of improving the method and the basic structure of the timer operating concept in such a digital control device in such a way that without the necessity of dividing up the available timers (16-bit timers) with significantly lower ^' interrupt Load a higher accuracy is achieved at least with the important output signals (consumption signal, injection Ti pulse).

Advantages of the invention

The method according to the invention and the digital control device according to the invention achieve this object in each case with the characterizing features of the main claim and of claim 7 and have the advantage that the timer which controls the output for the injection Ti pulse and carries out the consumption signal, triggers an interrupt only when the desired signal is to be switched off, therefore both the counting register, which would otherwise have to be decremented with each interruption, is eliminated and there is no prior division, for example, of the Ti time into a multiple of the previous 512 μsec time grid and a residual value is required.

Therefore, the PROM effort by the invention with regard to the preparation of this output control, since this can now be carried out using a 16-bit timer, is considerably lower.

It is also advantageous in the present invention that, in contrast to the generation of a time grid with only an 8-bit timer with a quantization of 2 μsec and a maximum time of 512 μsec that can be achieved thereby, any time grid up to a maximum of 131 msec can now be set.

The significantly lower interrupt load not only affects the output of the Ti pulse and the consumption pulse, but also results from the output of the other signals mentioned above, such as ALS signal or signal for tank ventilation, since not necessarily as with the split 8-bit timer is triggered every 512 μsec, the time raster interrupt is triggered, but a desired raster can be specified by corresponding loading of the 16 bit timer responsible for this, for example with a 2 μsec quantization of the time raster -Interrupt can only be triggered every 2 msec. In this case it is Load timer with a value of 1000 increments.

Finally, it is advantageous that with the important output signals, such as the consumption signal and the injection timing pulse, with the quantization of 2 μsec of the unchanged 16-bit timer, greater accuracy is achieved by the interrupts only being switched off of the signals are generated, in which case the corresponding interrupt has the highest priority.

Advantageous further developments and improvements of the invention are possible through the measures listed in the subclaims.

drawing

Exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the following description. FIGS. 2 and 3 show a known timer occupancy concept in a digital control device (with a single-chip processor of the 8051 family), with FIG. 1 timing diagram sequences of a first 8-bit timer part of an original 16-bit timers shows, with appropriate control, assigned counting registers for outputting pulse-width-modulated signals by the respective timer interrupts and occurring in the time grid of the timer

Fig. 2 timing diagrams of the second 8-bit timer part shows the output of at least one injection Ti pulse with external start control by the occurrence of a TD pulse and also the control of assigned count registers by the timer interrupts and

3 shows the use of the second 16-bit timer for period measurement;

4 shows, as an exemplary embodiment of the present invention, the time diagram of the unchanged timer T1 (16-bit timer) of the 8051 chip family for generating the injection Ti pulse and the consumption signal (without the need to assign corresponding ones) Counting register or other counter) and

FIG. 5 shows the time diagram of the further timer (16-bit timer), which is also unchanged, ie not split, and which is used for counting the period and at the same time for outputting further signals, namely here the ALS signal and the tank ventilation signal .

Description of the embodiments

First of all, it is pointed out that the following explanation represents the invention on the basis of the organization of a digital control device in which two 16-bit timers for the output of pulse-width-modulated signals implement a new timer occupancy concept; it goes without saying, however, that the invention can be applied to any realization options, including in discrete circuit technology, and therefore also those below Explanation given on the basis of flow diagrams does not restrict the invention or specifies this specific exemplary embodiment.

The basic idea of the invention is to determine certain pulse-width-modulated signals without splitting the two existing timers designed as 16-bit timers, namely specifically the consumption and the injection Ti signal without any intermediate timer interrupt, that is to say continuously to generate, so that the first interrupt occurring with this timer also causes the generated signal to be switched off, and to design the other timer that is still available in such a way that, with a freely definable grid, what happens when this timer is loaded when the timer interrupt occurs, to carry out both the period duration count and the output of the remaining pulse width modulated signals.

According to the illustration in FIG. 4, the task of a first timer T1 'is to output a consumption signal VS and the injection Ti signal, this timer additionally being able to be used for the additional intermediate syringe output Ti *, which is shown in FIG Fig. 4 is also shown.

For this purpose, the procedure is such that the signals VS and Ti to be output are sorted according to their size, that is to say according to the signal duration to be expected, which requires a selection logic which checks at the respective sorting time which checks the respective signal Ti or VS allocated storage location has the higher value. Subsequently, when a TD interrupt occurs (external interrupt), which can be, for example, the occurrence of the ignition signal, a speed signal or a signal resulting at terminal 1 of the motor vehicle, the smallest signal value (VS or Ti) is loaded into the timer register, as a complement value in this case described procedure; then the ^' timer is started. A first timer interrupt then results at time t1, and at this time the signal VS, assumed to be smaller here, has also expired, as shown at c) in FIG. 4, ie the consumption signal is switched off. At this timer interrupt (time t1), the difference to the previously output signal (also as a complement value) is loaded into the timer register, in other words the remaining value of the larger signal, in this case Ti to the consumption signal VS. , which represents the difference, is transferred to the timer register, and the second timer interrupt occurring at time t2 then also ends the injection Ti pulse. Subsequently, these two signals Ti or VS are only output again when a new external TD interrupt occurs at time t3 (cf. diagram a) in FIG. 4), so that if the time interval is sufficiently large , an intermediate splash can be dispensed - this will be discussed further below with the aid of the flow diagrams.

If there are signal values of Ti and VS that are greater than 131 msec (16-bit timer with a quantization of 2 μsec), a so-called FLAG is set in the structure of the digital control device, which indicates that the signal values of Ti and VS are larger than a timer Register overflow (generation of the corresponding timer interrupt). In this case, the organization is such that this overflow FLAG must first be processed by the timer, ie must be reset, before a first timer interrupt can be given to switch off one of the two signals Ti or VS.

The task of the other timer T0 'still present then consists in generating any time grid, for example, and selected as 2 msec in the exemplary embodiment shown. For this purpose, the timer register of this timer T0 'is precharged with a corresponding value for each timer interrupt. This value is, for example, 1000 increments with the desired 2 msec raster and with an underlying quantization of 2 μsec.

The 2 msec time grid generated with this timer T0 'and shown in a) of FIG. 5 is initially used with the aid of an additional counting register (see b) in FIG. 5), the quantization of which corresponds to the quantization of the time grid, that is to say 2 msec , and the timer register of the period duration measurement necessary for the speed calculation and also serves to control the respectively provided counting registers for the ALS signal, the tank ventilation signal and possibly for the generation of intermediate sprayer signals, provided that the quantity selected here is sufficient.

The speed is calculated using the following formula: TD time = (TD _END -TD _BEGIN ) + status of counting register ^•

where Q = quantization.

5 recognizes / oei a) that the timer T0 'is free running, i.e. the TD pulses shown as ignition pulse symbols (lightning symbols) can occur at any time, i.e. they are not related to the timer interrupts of T0 '. In b) the additional counting register required for this period measurement is shown; The course d) shows the ALS counter or register for generating the ALS signal shown in c), while the corresponding count register courses and signal courses for the tank ventilation signal and the tank ventilation counter are shown at f) and e).

The flowcharts shown below relate to the organizational part of the digital control device which relates to the timer occupancy concept, first of all briefly referring to the flowchart of the external interrupt routine given here.

The external interrupt resulting in this flowchart first serves, via the function blocks 10, 11, 12, to calculate the period duration for determining the speed of the internal combustion engine and then effects the pre-sorting of the signals to be output, namely the Check whether the consumption time is greater than or equal to the injection time. Depending on the result, the timer T1 'is loaded either with the complement of the injection time or with the complement of the consumption time (function blocks 14a, 14b), the two outputs are set, ie the VS signal and the injection Ti signal begin and the timer T1 'is started, then the input of the next internal interrupt (TD signal) is waited for, corresponding to the function blocks 15, 16 and 17.

The flowchart given below relates to the routine which results when an interrupt occurs at timer T0 '- this then relates to the repeated loading of this timer with each timer T0 interrupt in order to ensure the desired grid on function block 20 and the incrementing of the counting register on radio tion block 21, which still belongs to the period measurement.

Simultaneously with this, the count register for the ALS signal is decremented at 22, with the decision check at 23 whether this count register is reduced to zero, the throttle valve motor control then being switched off by removing this signal in the relevant case. At the same time at 24

Ventilation counter register decrements and checks whether there is an injection signal at this time. Only if this is not the case can a subroutine with regard to an intermediate spray output in area 25 still be carried out, which need not be discussed in more detail since the respective function blocks. specify the sequence in its labeling, then RETURN follows to the subsequent timer T0 interrupt.

Finally, it can be seen from the flow diagram of the timer T1 ¹ interrupt routine that decrementing of counting registers is not necessary for the output of the VS or the injection Ti signal - the first occurring timer T1 interrupt means immediately that - after a possible overflow FLAG has been processed via decision block 30 ^" and function blocks 31 and 32, the respectively active signal output is reset, that is, either function block 33a or 33b is addressed and then either, via decision blocks 34a,. 34b, this timer TV, when the output of a second signal is still pending, is loaded with the complement of the consumption injection time difference (at time t1) or, if it was the second timer T1 interrupt (time t2) the timer is stopped and decreased.

- 19 -

All features shown in the description, the following claims and the drawing can be essential to the invention both individually and in any combination with one another.

Claims

1. A method for determining, controlling and / or regulating pulse-width-modulated operating variable signals (fuel injection pulse Ti, consumption signal VS, adaptive idling control signal ALS, tank ventilation signal TE, intermediate sprayer output, speed period duration measurement) in an internal combustion engine, with a digital control device with two interruptible timers (16-bit timers) at least one external interrupt signal (ignition signal TD) is supplied and a signal is output by deactivating counting registers when timer interrupts occur, characterized in that a first, unchanged timer (16-bit timer T1 ¹ ) when an external interrupt signal (TD-I pulse) occurs, loaded with a first smallest of the signal values to be output (consumption signal VS, injection Ti signal), then started, and when the subsequent own timer interrupt occurs, the relevant pulse-width-modulated output signal nal scanned stops and at the same time the timer again with the difference to the second signal to be output value is loaded and that the second unchanged timer (16-bit timer T0 ') is operated continuously by loading its timer register with a corresponding value for generating any time grid, this time grid for controlling further counting registers for Pulse-width-coded operating variable signals (ALS signal, tank ventilation signal TE) to be additionally output and, at the same time, used for period measurement for the speed calculation of the internal combustion engine.

2. The method according to claim 1, characterized in that when signal values occur for the first timer, the maximum time (with 16-bit timer and a quantization of 2 μsec greater than 131 msec) until a first timer interrupt exceed, a flag to be cleared by this timer interrupt is first set such that only the next but one timer interrupt of this timer leads to the switching off of the respectively applied signal with the smallest signal value.

3. The method according to claim 1 or 2, characterized gekenn¬ characterized in that the timer register each with the complement value of the smallest signal value when an external TD interrupt occurs and in the subsequent own timer interrupt with the complement value of the Difference to the previously output signal is loaded.

4. The method according to any one of claims 1-3, characterized in that the first timer (16-bit Timer T1 ') there is an intermediate splash output (Ti *),

5. The method according to any one of claims 1-4, characterized ge indicates that the further timer (16-bit timer T0 ') with a predetermined number of increments (1000 increments with an interrupt pattern of

2 msec and 2 μsec quantization) is loaded with each timer interrupt and the period duration measurement with any. Arrival of the external TD interrupt according to the formula TD time = (TD _END - D _BEGINNING ) + status of counting register ^• Q done, with Q = quantization.

6. The method according to any one of claims 1-5, characterized ge indicates that each occurring - timer interrupt of the further Tirr.ers (T0 ¹ ) the control accordingly, the generation of an adaptive idle control signal (ALS signal ) or serves to serve the tank ventilation signal (TE).

7. Digital control device for determining, controlling and / or regulating pulse-width-modulated operating variable signals (fuel injection pulse Ti, consumption signal VS, adaptive idling control signal ALS, tank ventilation signal TE, intermediate spray output, speed period duration measurement) in an internal combustion engine for carrying out the method according to an of claims 1-6, with two interruptable timers (16-bit timer T0 ', T1 ¹ ) which determine the duration of signals to be output by deactivating counting registers when timer interrupts occur, characterized in that a first Timer by the appearance of an external Interrupt signal (ignition signal TD) and loading of its timer register started and, when the next timer-specific interrupt occurs, either an overflow flag is reset or a signal to be output (consumption signal, injection Ti signal) that is switched on when the timer starts is switched off , without the counting register, and when this timer interrupt leading to signal shutdown occurs, the timer register is reloaded to output a further pulse duration modulated signal (injection Ti signal or VS signal) with the difference between predefined signal and the second available timer is designed to generate a freely definable time grid and for the period duration measurement required for the speed calculation and for the control of the generation of further pulse-width-modulated operating variable signals (ALS signal, TE signal) ) serving counting registers is provided.