DE2850115C2 - Ignition system for internal combustion engines - Google Patents

Description

State of the art

The invention is based on an ignition system according to the preamble of the main claim. It is one of those Ignition system from DE-OS 27 01 968, Figures 1 and 2, known, which is also based on the principle of dwell angle enlargement is working. This means that an output signal of a transmitter arrangement or an ignition task and advantages of the invention

The invention is therefore based on the object of a

To develop the ignition system according to the preamble of the main claim in such a way that the dwell angle is determined a better control dynamics, especially when accelerating the internal combustion engine, achieved will.

This object is achieved in an advantageous manner by the characterizing features of the main plan Since the second counting device, designed as a counter, which determines the start of the closing time, already does specifies a speed-dependent closing time, the crste counter, which is also referred to as a Regeki hler will only cover a smaller area. This value only has a correcting effect with initial information on the counter reading of the second Counter.

Another advantage is that the counting system follows this principle of increasing the dwell angle is very similar to systems for reducing the dwell angle (DE-OS 27 46 885, Figures 5 and 6). When designing an integrated circuit, it is desirable to implement both principles as desired to be able to. The more similar these principles are, the easier it is to do it.

The measures listed in the subclaims are advantageous developments and Improvements to the ignition system specified in the main claim are possible. It is particularly advantageous to Set the threshold value for the primary current to a value that corresponds to a value of 60 to 90% of the necessary Primary current corresponds. This reduces or avoids Control oscillations of the closing angle. especially when the residual memory effect occurs.

It should also be noted that the invention is not limited to a digital system - the digital terms were chosen only to simplify the formulation of the main claim. In an equivalent way the invention can also be implemented analogously, with a capacitor instead of a counting device of a counter reading a state of charge and instead of a

Up and down counting a charge and discharge occurs

drawing

An embodiment of the invention is shown in the drawing and in the following description explained in more detail. It shows

Fig.! the circuit design of the implementation example and

F i g. 2 shows a signal diagram to explain the mode of operation.

Description of the example

The output of a transmitter arrangement 10 is via an OR gate 11 with the control input of an electronic one Switch 12 connected, the first switching connection of which via the primary winding of an ignition coil 13 to a terminal 14 connected to the positive pole of a supply voltage source is connected, and the second Schaiian connection via a z. B. as Current measuring resistor trained Stromrr-Eßvorrichtung 15 is connected to ground. Between the secondary winding of the ignition coil 13 and ground is a spark plug 16 switched. In the case of several spark plugs, a mechanical or non-mechanical one can be used in a known manner High voltage distribution can be provided. According to the prior art stated at the beginning the encoder arrangement 10 is a rotating encoder arrangement driven by the internal combustion engine, the a mechanical or electronic device for the parameter-dependent adjustment of the ignition timing The electronic switch 12 is usually designed as a transistor.

A voltage value corresponding to the measured current is fed from the current measuring device 15 to a threshold level 17, the output of which is connected via a NOR gate 18 to the blocking input F (enable) and to the counting direction input U / D (up / down) of a first counter 19 is. The binary number outputs of this first counter 19 are connected to number inputs of a second counter 20, which number outputs are in turn fed to a digital comparator 21. , The binary number X is compared to the number of inputs of this digital comparator 21 preferably by hard wiring, applied instead of a digital comparator 21 could also be realized by a logic gate decode stage used the door Ziihlcnwcrt X. The numerical output of the digital Kor.ipurators 21 is connected once to a further hanging of the OR gate 11 and also to an input of an AND gate 22. The output of the encoder arrangement 10 is connected via an inverter 23 to a further input of the AND gate 22 and also to the counting direction input iy / D (Up / Down) of the second counter 20, to the set input S of this second counter 20 and finally via a Inverter 24 connected to an input of an AND gate 25, the output of which is connected to the blocking input E of the second counter 20. The overflow path CO (carry out) of the second counter 20 is connected both to a second input of the AND gate 25 and, via an inverter 26, to a further input of the AND gate 22.

Kin Taktgcr.eiiMor 27 generates two counting clock frequencies / .cn f \ and f2. The first, higher clock frequency f \ is connected via an LJ ND-Gz lter 28 to the input of an OR gate 29, the output of which is connected to the clock input C of the second counter 20. The second clock frequency / "2 is connected to the clock input C of the first counter 19, as well as via an AND gate JO to a further input of the OR gate 29. The ratio of the two frequencies f \ and (1 essentially corresponds to - see Fig.2 - the duty cycle of the encoder signals t / 10. The output of the encoder arrangement 10 is directly to one

ίο further input of the AND gate 28 and further connected to a further input of the AND gate 30 via an inverter 31.

The mode of operation of the exemplary embodiment will be described in the following on the basis of the method shown in FIG. 2 shown in the signal diagram. The decreasing encoder signal sequence LJ 10 shows a case of acceleration. Due to the encoder signal U 10 applied to the counting direction input U / D of the counter 20, the counter is set to "up counting" during each encoder signal UIQ , while only downward counting processes take place in the signal pauses. In the counter 19, upward counting processes are only possible if the primary current through the ignition coil 13 is above the setpoint value S. Below this setpoint value, the counter 19 is set to "downward counters". While the clock frequency f2 is applied to the counter 19 for both counting directions, the selector 20 is supplied with the higher counting frequency / Ί by blocking the AND gate 30 during the counting up process - during a signal U 10. In the signal pauses in the signal sequence U 10, however, the UND gate 28 is blocked so that the downward process takes place at the frequency / 2.

At the beginning of a transmitter signal U 10, the current counter reading Za is transferred from the first counter 19 to the second counter 20. This is done by the encoder signal U 10 fed to the set input 5 of the counter 20. This is followed by an upward counting process with the frequency / 1, which is continued from the end of the signal of a signal U 10 by a downward counting advance with the frequency / 2. The electronic switch 12 continues to be closed by the signal end i / 10, as a result of which an ignition spark is generated on the spark plug 16. If the numerical value in the counter 20 reaches the numerical value X as a result of the downward counting process, the digital comparator 21 responds, the output signal of which via the OR gate 11 places the electronic switch 12 in the conductive state. The primary-side current through the ignition coil 13 begins to rise again .. At the same time, the AND gate 22 and the NOR gate 18, the blocking of the counter 19 is canceled AND-GaUer 22 f-follows. The blocking can have two causes, the first of which is the blocking bev / Kkt: Once the start of a new encoder signal U 10 and the overflow signal generated at the overflow output CO when the lowest counter reading is reached in the counter 20. In the first three cycles shown, both alternatives occur simultaneously, while in the fourth cycle the blocking is initially due to the reaching of the lowest count in the counter 20, and the transmitter signal U 10 only starts shortly thereafter. The one not shown

b5 Another possibility is that a transmitter signal U 10 begins before the counter 20 has counted to its lowest count. In this case, the counter 19 is blocked by the transmitter signal U 10 and the counter

20 takes over the count reached by the counter

19 before he has counted on the lowest count. In this case, a better option would be to take over the count of counter 19 from the previous cycle. However, this requires additional expenditure through a required buffer, the holds the counter reading reached in the counter 19 until the next cycle.

The upward counting process in the counter 19 is predetermined by the length of an output signal of the threshold value stage 17, which is generated when the swell unit S is exceeded by the primary-cable current. This signal removes the blocking of the counting process via the NOR gate 1S . In the first shown counting cycle of the counter 19, the steady state is shown with a constant speed. The counting down process corresponds to the counting up process. In the following cycle, the same counting result Za is achieved, but the subsequent upward counting process is shorter as a result of a signal U 10 which is shortened in accordance with the acceleration. In the third cycle, a lower count Zb is reached, which in turn with the rising edge of a signal U 10 in the counter

20 is adopted. The counter 19 does not count up in the third cycle because the primary-side current / threshold value does not exceed 5. In the fourth cycle there is another downward counting process in the counter 19 up to the numerical value Zc . The blocking of this counter 20 from reaching the lowest counter reading up to the beginning of a transmitter signal U 10 takes place via the AND gate 25.

As once in the counter 20 a speed information by the up counting process during a transmitter signal is obtained and, on the other hand, this speed information is obtained by the numerical value taken over

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of the system guaranteed. In the event of a change in speed, the numerical value of the counter 19 does not need so much can be changed as it would if its counter reading would contain only the speed information.

In addition to the circuit shown, it is of course also possible in accordance with that specified at the beginning State of the art, a current limiting device and a device for switching off the quiescent current are provided.

1 sheet of drawings

60

65

Claims (5)

Patent claims: 1. Ignition system for internal combustion engines with an ignition coil, in whose primary circuit an electronic switch and in whose secondary circuit at least one ignition path is connected, with a closing angle control device for controlling the electronic switch as a function of the signals from a rotating sensor arrangement, with a first counter (19) in the Closing angle control device, the counter reading of which can be changed by continuous upward and downward counting processes, the counting processes in one direction being specified by the current flow duration in the primary circuit of the ignition coil from when a threshold value is exceeded and the counting processes in the other direction during counting intervals in a second counter ( 20) run between two definable thresholds, with the second counting device ritr current counter reading of the first counting device being indicated by a signa! eier encoder arrangement is taken over, and when the first definable threshold (X) is reached due to the changing stored count, the electronic switch in the primary circuit of the ignition coil is closed and opened again by a signal from the encoder arrangement, characterized in that in the second counting device (20 ) also continuous downward and count-up operations proceed, the ratio of which is determined by the Taj 'ratio of the encoder signals (UIO), and that a signal of the transmitter arrangement (10), the counting intervals between the two thresholds in the second ^Siähle.:. ririchtung privileged terminated. 2. Ignition system according to claim I, characterized in that the threshold value (S) for the primary current has a value of 60 to 90% of the necessary primary current. 3. Ignition system according to claim 1 or 2, characterized in that that of the second counting device (20) The counter reading adopted is the current counter reading of the first counter (19) is. 4. Ignition system according to claim I or 2, characterized in that that of the second counting device (20) The counter reading accepted is the temporarily stored counter reading of the first counter (19) of the previous cycle. 5. Ignition system according to claim 1, characterized in that the two frequencies (71, / 2) for the up / down and down counting in the second counting device (20) are determined essentially by the duty cycle of the encoder signal sequence (UXd) . angle calculation stage, a minimum basic closing angle for the electronic switch in the primary circuit of the ignition coil specifies Depending the speed is now the closing time for this electronic switch brought forward with the closing time for each of the preceding cycle the following cycle is determined. With the well-known Arrangement, the counter determining the closing time only counts during the open time the counter reading of this counter at the ignition point the following open time. This count becomes determined by another counter. In the case of accelerations, this other counter must have the highest value according to the speed down to the lowest value count to ensure the maximum closing angle at maximum speed. This time will be all the more larger, the higher the threshold value for the primary-side Current is applied, which in turn helps to avoid control oscillations of the dwell angle at the onset the residual memory effect is desirable. The resulting poor dynamics can result in strong Acceleration processes through too weak or make intermittent ignition sparks uncomfortably noticeable.