EP0448566B1 - Process for controlling ignition in an internal combustion engine - Google Patents

Abstract

Process for controlling ignition in an internal combustion engine, in which the ignition of a spark plug is determined by an ignition coil associated with each spark plug, and by a first counter which, when a reference mark independent of the angle is reached, counts up or down from a predetermined value, by means of a timing signal dependent on the angle, in order to trigger the ignition of a spark plug of the internal combustion engine. The spark plug to be ignited is determined by a cylinder identification device. The process is characterized in that the moment at which charging of all ignition coils of the internal combustion engine begins is determined by means of a single additional counter whose tally varies in function of the angle-dependent timing signal and to which a starting value corresponding to the interval until the start of charging of the next coil is pre-assigned. Hence, while the first counter triggers the ignition process, the second counter determines the moment at which the charging process of an ignition coil begins.

Description

State of the art

The invention relates to a method for controlling the ignition of an internal combustion engine according to the preamble of claim 1 and a control device for controlling the ignition of an internal combustion engine according to the preamble of claim 8.

In known methods for controlling the ignition of an internal combustion engine or in known ignition control devices, the individual spark plugs are controlled via a distributor. If the internal combustion engine has many cylinders, and at high speeds, the closing angle is often no longer sufficient to sufficiently charge the coil.

An attempt was therefore made to extend the closing angle even at high speeds using what is known as a stationary distribution, which does not require a rotating distributor finger. Single spark coils were used, which were each assigned to a spark plug. With such a control, however, it is problematic if more than one coil is to be loaded at the same time. It takes a lot of tax to enable such an operation. Ignition control devices that allow nasty shooting angles must be provided with as many counters as the ignition coils are to be controlled. This has the disadvantage that the control devices are not only very large, but also very expensive. In addition, the computing time for control programs, which must be provided in such control devices, is very long. This affects other functions that the device must also perform.

From US-A-265 211 an internal combustion engine with static high voltage distribution is known, the ignition at an ignition coil being realized by using a counter, the content of which is changed as a function of an angle-dependent clock signal. Several counters and registers are required to implement the start of charging at the individual ignition coils, so that this circuit is relatively complex.

Advantages of the invention

The method for controlling an internal combustion engine with the features listed in claim 1 has the advantage that with a relatively simple control unit, in particular, internal combustion engines with more than 6 cylinders can be controlled without problems even at very high speeds. It is particularly advantageous that only a first counting means or first counter for the ignition timing and a second counting means or a second counter for the start of the charging process of the ignition coils are required for all ignition coils. Although not every individual ignition coil is assigned its own counter, a closing angle overlap can be easily implemented.

In a preferred embodiment of the method, the counter reading of the second counter is gradually reduced depending on an angle-dependent clock signal. An initial value corresponding to the next ignition coil to be charged is entered into the second counter. The loading process of this coil is initiated as soon as the counter reading of the second counter assumes the value ZERO. The higher the initial value entered, the later the charging of the next coil will begin. The start of the charging process can thus be controlled by selecting the initial value. It also shows that this type of control is particularly easy to carry out.

A particularly preferred embodiment of the method is characterized in that the initial value associated with a coil is calculated one or more, preferably two, crankshaft revolutions in advance from the equation

${\text{A1 = 720 ° - (A2R + A3 + A4 + ... + An + α}}_{\text{s1}}\text{).}$

With A1 the distance to the start of the charging process of coil 1, with α _s1 the closing angle of coil 1, with A2R the remaining distance value, which is stored in the second counter for the second coil, while the ignition point of the first coil has been reached. Correspondingly, A3, A4 and An denote the distance values of the coils 3, 4 and n. From the equation it can be seen that the effort for the determination the next distance value of a coil is relatively small, so that the control process is very simple.

Further advantages of the method result from the remaining subclaims.

The control device according to the invention for controlling the ignition of an internal combustion engine with the features listed in claim 6 has the advantage over known ignition control devices that it has only two counters for any number of controllable cylinders. The first counter is used to trigger the ignition process and the second counter to initiate a charging process for a coil.

Further refinements of the ignition control device result from the remaining subclaims.

drawing

Figur 1

ein Steuerdiagramm für eine Brennkraftmaschine mit sechs Zylindern;

Figur 2

ein Blockschaltbild einer Zündsteuerung und

Figur 3

ein Flußdiagramm für das Steuerverfahren.

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

Figure 1

a control diagram for an internal combustion engine with six cylinders;

Figure 2

a block diagram of an ignition control and

Figure 3

a flow chart for the control process.

Description of the embodiment

FIG. 1 shows the voltage curve at six individual spark coils of an ignition control device for an internal combustion engine with six cylinders above the crankshaft angle α. The voltage curve on the coil of the sixth cylinder in FIG. 1 is arranged at the lowest point. It can be clearly seen how the voltage on the individual coils rises and drops suddenly when an associated spark plug is activated.

The diagram in FIG. 1 is not intended to represent a realistic operating case; rather, a closing angle overlap is to be shown here, that is, the operating case in which several ignition coils are charged simultaneously. Seen from left to right, there is a closing angle overlap between the second and third coil and then again between the fifth and sixth coil. In the later course of the diagram, there is a simple overlap of the closing angle between the coils 2 and 3 and between the coils 3 and 4. Later there is a multiple overlap of the closing angle for the coils 3, 4 and 5, then for the coils 4, 5 and 6. In the further course of the crank angle α there is a further, simple closing angle overlap between the first and sixth coil.

In order to achieve optimal charging of the coils, the charging process must be maintained for a certain time before the spark plug is ignited. This time is essentially always constant. For the voltage profiles shown above the crankshaft angle α on the ignition coils it follows that at high speeds the charging process extends over a larger angular range than at lower speeds.

As a result, the loading processes shown in FIG. 1 extend over differently large angular ranges.

The angular range during which a coil is loaded is referred to as the closing angle α _s . It is shown here by way of example in the voltage profile of the coil 1.

The ignition coils are controlled here as follows:
The ignition point is triggered by a first counter, which is loaded with a predetermined value at an angle-synchronous reference mark. This value is gradually reduced by an angle-synchronous clock signal until the value ZERO is reached. As soon as this is the case, the ignition of the associated spark plug is initiated via a suitable output stage. The clock signal can be generated here, for example, with the aid of a sensor wheel which is provided with sixty teeth. The teeth are scanned by a suitable sensor. With each negative edge, a pulse, a clock signal, is sent to the counter and the counter reading is decreased by one level.

In order to be able to determine the correct time for a coil to start charging, it must be defined and calculated at what angular distance a given the position the next coil should be loaded. The starting point for the calculation can be a crankshaft-synchronous mark or the ignition point of a coil. In the following, the calculation at the ignition point of the coil 1 is to be carried out as an example.

A second counter is used to determine the distance to the next operating state "load coil". Whenever a charging process for a coil is initiated, a new initial value is entered for the next coil to be loaded. The counter reading is clocked by an angle increment, that is to say by an angle-synchronous clock signal. This will gradually reduce its counter reading. The clock signal is also generated here, for example, by a sensor wheel, the negative edges of which are used to clock the counter.

If the second counter is entered with a high initial value, it takes longer until it has counted down to the value ZERO due to the clock signal. The crank angle range until the next coil is loaded after the ignition of the preceding coil is therefore larger if a high initial value is entered in the second counter. This shortens the angular range for the charging process of this coil.

This will now be explained in more detail with reference to FIG. 1.

The second counter is loaded with an initial value A1 at the beginning of a cycle. The count is successively reduced by the clock signal until the value NULL is reached. At this moment the charging process the coil 1 initiated. In Figure 1, the voltage in the first coil is increased.

As soon as the second counter has reached the value ZERO, the next starting value is the value A2. After the second counter has been clocked down from this initial value to ZERO, the charging process of the second coil is initiated. The increase in voltage in the second coil is clearly evident from FIG. 1. As soon as the second counter has reached the value ZERO, the next starting value is A3. This value corresponds to the angular distance up to the start of the charging process of the coil 3. As soon as the second counter has counted down from the initial value A3 to ZERO, the charging process of the third coil is initiated. It can be clearly seen from Figure 1 that the voltage in the third coil increases while the second coil is still being charged. So there is a closing angle overlap here.

The initial value A4, then A5 and finally A6 is then entered into the second counter.

The various initial values A1 to A6 are stored in a suitable memory, for example in a RAM.

The initial values, from which it can be seen at what angular distance the charging of the next coil is initiated at the start of the charging process of one coil, are calculated in advance. In the exemplary embodiment shown here, the initial values A1 to A6 are calculated 720 ° in advance. 720 ° correspond to one cycle.

If the individual initial values are calculated one full cycle in advance, a maximum of n-1 closing angle overlaps can occur, where n corresponds to the number of cylinders. In order to achieve better dynamics of the method, the initial values can also be calculated at a different point in time, for example only 360 ° in advance. However, this reduces the number of possible closing angle overlaps.

In the embodiment shown in FIG. 1, the initial values A1, A2, ..., A6 had already been calculated and stored in a memory. It is now a matter of calculating the new initial distances A1 to A6 for the following ignition processes. This is to be done in the following using the initial value A1 for coil 1:
The new initial value A1 is calculated according to the following equation

${\text{A1 = 720 ° - (A2R + A3 + A4 + A5 + A6 + α}}_{\text{s1}}\text{).}$

As stated above, it is assumed in this exemplary embodiment that the initial value A1 is determined during the ignition process of the coil 1. Similarly, the initial value A2 is calculated in the ignition process of the coil 2 and so on.

It can be seen from the illustration in FIG. 1 that with the start of the charging process of the coil 1, the initial value A2 is entered into the second counter. The counter is activated by the angularly synchronous clock signal counted down. At the moment the coil 1 is ignited, it has reached a residual counter reading A2R.

In Figure 1, the initial distances A1 to A6 are shown above the voltage profiles on the coils 1 to 6. From the first ignition process on the left in the diagram of coil 1 to the subsequent ignition process, two crankshaft revolutions take place. A shift by one cycle, i.e. by 720 °, has therefore taken place on the horizontal angular axis. It can now be seen that the next following initial value A1 of the coil 1 can be calculated by subtracting the residual running value of the second coil A2R, the initial value A3 and the initial values A4, A5 and A6 from the full period. Finally, the closing angle of the first coil α _{s1 is} subtracted.

The newly calculated initial value A1 for the coil 1 is stored in the memory for the initial values.

The initial value A2 for the second coil can now be calculated in a similar manner. However, it can be seen from FIG. 1 that the initial value A3 has already passed completely while the ignition process of the second coil is being initiated. The remaining time A4R of the fourth coil must therefore be taken into account in the equation, which reads as follows:

${\text{A2 = 720 ° - (A3 + A4R + A5 + A6 + A1 + α}}_{\text{s2}}\text{).}$

The closing angles α _{s of} the individual coils are also stored in a suitable memory. These Values can then easily be called up for the calculation of the various initial values.

It follows from the above that errors in the calculation of an initial value only have an effect within a period. At the beginning of the next period, the initial values A1 to A6 are recalculated, previous errors no longer have any effect. It can thus be seen that this method or an ignition control device operating according to this method is very insensitive to interference. Monitoring the calculation can therefore be omitted.

It also shows that the second counter, which counts down from a predetermined initial value in this embodiment, can also be designed to count up. The start of charging a coil must be triggered when the corresponding initial value of the corresponding coil has been reached. In any case, comparators are required to determine whether the second counter has reached the value ZERO or the specified initial value. If this is the case, the corresponding charging process is triggered.

It can also be seen from the illustration in FIG. 1 that the method is not restricted to internal combustion engines with six cylinders. The number of cylinders is therefore arbitrary. In addition, the method described here can be applied not only to static ignition distribution but also to so-called dual-circuit distributors or distributors with rotating systems. It can also be used with double spark coils.

An ignition control device operating according to this method will now be explained with reference to FIG. 2, which shows a block diagram of such a control.

For example, with an angularly synchronous encoder wheel 1, an angle interrupt signal or an angle increment is generated, which is passed on to a first counter 3 and to a second counter 5. It was stated above that the ignition timing is determined using the first counter 3. It is loaded with an initial value that is gradually reduced to ZERO when an angular reference mark is reached. As soon as the value ZERO is reached, the ignition process is triggered in that a signal is emitted to a first pointer 7, which emits an output signal to an output stage 9 which ignites the associated spark plug. At the same time, the first pointer 7 outputs a signal x to a register 11 assigned to the second counter 5. This signal ensures that a value calculated in the adder 13 is stored in the correct memory cell.

According to what has been said above, it is also clear that the second counter 5 is counted down gradually from an initial value with the aid of the signals of the sensor wheel until the value ZERO is reached.

The addresses for the initial values A1 to A6 are indicated in register 11.

The adder 13 is used to calculate the initial values according to the equation given above. The calculation always takes place when the first counter 3 reaches the value ZERO and triggers an ignition process Has. If the coil 1 has triggered an ignition process in FIG. 1, the next initial value A1 is calculated and stored in the register 11 at the point which is responsible for calling the next value A1. The storage at the correct address is ensured by the output signal x of the first pointer 7.

As soon as the second counter 5 has reached the value ZERO based on the clock signals of the sensor wheel 1 starting from an initial value A, the next output value is loaded into the second counter 5. An output signal y from the second counter 5 to a second pointer 15 ensures that the correct output value is loaded into the second counter. At the same time, the output signal y of the second pointer 15 is output to the output stage control 9 of the control device, so that the correct coil begins with the charging process.

The method according to the invention and the ignition control device for executing this method are explained again with reference to FIG. 3. In order to facilitate understanding, the same parts in FIGS. 2 and 3 are provided with the same reference symbols.

The flowchart in this figure shows that an angle interrupt signal 1 is fed to a first counter 3.

In a first step a, the count of the first counter 3 is decreased by one level by the angle interrupt signal of the encoder wheel 1. In a next step b, a query is made as to whether the counter reading has the value Has reached zero. If this is the case, the next initial value Ax is calculated in one step according to the equation explained with reference to FIG. 1. This value is stored in the second counter 5. At the same time, the associated spark plug is ignited. Then, in a step d, the first pointer 7 is shifted by one step from x to x + 1.

In a next step e, the counter reading of the second counter 5 is decreased by one level. This is carried out immediately if it has been determined in step b that the first counter 3, also referred to as the ignition counter, has assumed the value ZERO.

Subsequently, in a step f, a query is made as to whether the second counter 5 has assumed the value NULL. If this is the case, in a next step g the associated coil is switched on according to the second pointer 15 and its loading process is started.

In a further step h, the content of the corresponding memory cell is entered in the second counter 5 in the register 11.

Finally, in step i, the second pointer 15 is shifted by one step.

The flowchart is now run through again. If the query in step f shows that the counter reading of the second counter assumes the value NULL the flow diagram is run through from the beginning.

After all, it can be seen that a simple solution for controlling the ignition of an internal combustion engine has been found with the illustrated method for controlling the ignition of an internal combustion engine and with the described ignition control device even with overlapping closing angles. The ignition control device is characterized in particular by the fact that only two counters are required for switching the individual spark coils of the ignition device on and off. This means a significant simplification of the hardware and thus a reduction in the susceptibility to failure of the device. In addition, the costs for such a device were significantly reduced, since a known counter had to be provided for each coil in known devices.

According to what has been said above, it is readily apparent that the counting means or counters can be implemented not only by hardware but also by suitable software.

Claims (10)

1. Method for controlling the ignition of an internal combustion engine with a plurality of ignition coils, each ignition coil being assigned at least one spark plug, and having a first counting means (3) which is incremented or decremented at an angularly fixed reference mark starting from a predeterminable value by means of an angle-dependent clock signal in order to trigger ignition at a spark plug of the internal combustion engine, the spark plug to be fired being determined by means of a cylinder detection, characterized in that in each case the start of charging at all the ignition coils of the internal combustion engine is triggered with the aid of a single further counting means (5) whose counting state is changed as a function of the angle-dependent clock signal, and in that whenever a charging process is triggered at one of the ignition coils in each case one initial value is prespecified which corresponds to the time interval between the triggering of the charging process of this one ignition coil and the start of charging of the next coil according to the ignition sequence, and in that after the initial value of the further counting means (5) is processed the charging process begins at this next ignition coil.
2. Method according to Claim 1, characterized in that the second counting means (5) decrements as a function of the clock signal, and in that the charging process of the coil is initiated when the counter state assumes the value zero.
3. Method according to Claim 2, characterized in that the second counting means is loaded with the initial value assigned to the subsequent coil as soon as the said counting means has reached the value zero.
4. Method according to one of Claims 1 to 3, characterized in that the initial value associated with a coil for the start of charging following a discharge is determined from the residual interval value of the subsequent coil present in the second counting means when the ignition time of the first coil is reached, and from the initial values of the other coils, the initial value to be determined being calculated in advance.
5. Method according to Claim 4, characterized in that the initial value associated with one coil is calculated one or more, preferably two crank shaft revolutions in advance from the following equation
   
   ${\text{A1 = 720° - (A2R + A3 + A4 + ... + An + α}}_{\text{s1}}\text{),}$

   

   
   
   A1 being the distance up to the start of charging of the coil 1, α_s1 being the closing angle of the associated coil 1, A2R being the residual interval value, that for the second coil in the second counter when the ignition time of coil 1 is reached, and A3, A4 ... A_n being the interval values of coils 3, 4 to n.
6. Method according to Claim 1, characterized in that a pointer (15) is provided which determines the ignition coil to be charged.
7. Method according to Claim 6, characterized in that the pointer (15) receives a signal from the second counter (5) at the start of the charging process at an ignition coil and switches from one ignition coil to the next ignition coil to be charged.
8. Control device for controlling the ignition of an internal combustion engine with a plurality of ignition coils, each ignition coil being assigned at least one spark plug, and having a first counting means which is incremented or decremented at an angularly fixed reference mark starting from a predeterminable value by means of an angle-dependent clock signal in order to trigger ignition at a spark plug of the internal combustion engine, the spark plug to be fired being determined by means of a cylinder detection, characterized in that a second counting means (5) which increments or decrements as a function of the angle-dependent clock signal is provided for controlling the start of charging of the corresponding ignition coil when a prescribed value of the counting state of the second counting means (5) is reached, and in that an initial value which corresponds to the start of charging of the next ignition coil to be charged is loaded into the second counting means at the start of charging of an ignition coil.
9. Control device according to Claim 8, characterized by a register for the initial values, to be entered into the second counting means, for controlling the start of charging of the ignition coils.
10. Control device according to Claim 8 or 9, characterized by an adder (13) for calculating the next initial value for the start of charging of an ignition coil after its discharge.

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