FI123042B - Spark ignition reciprocating piston engine ignition control - Google Patents

Description

SPARK IGNITION IGNITION ADJUSTMENT

Technical field

The present invention relates to a spark-ignition internal combustion piston engine powered by natural gas or gasoline.

Background 10

Ignition systems include ignition coils consisting of primary windings and secondary windings where the voltage conversion is performed. The secondary voltage is distributed to the spark plugs, which produce a spark at their apex. Sparks ignite mixtures of air and fuel in the cylinders. The alloys burn and exert a pressure on the cylinders which forces the pistons to move and thus the burns produce mechanical power.

Spark timing is important. The time it takes to burn the fuel in degrees of crank will increase somewhat as the engine speed 20 increases. This means that the faster the engine runs, the sooner the spark has to be produced. Spark timing is called ignition timing. By delaying the timing of the ignition, the maximum cylinder pressures are reduced, which may slightly reduce emissions and eliminate knocking if this is a problem. Late However, the timing of 25 ignitions also reduces the thermal efficiency of the engine ώ and thus increases fuel consumption. The voltage requirements of the spark plugs tend to increase by 1A as the spark plugs age due to electrode wear, x In multi-cylinder internal combustion engines, the voltage requirements for spark plugs tend to be different. In the prior art, the cylinder having the highest secondary voltage requirement of> 30 defines the interval between the spark plugs to prevent the o plugs from sparking, which can lead to engine malfunction.

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U.S. Patent 4,018,202 discloses an adaptive system for digitally adjusting engine performance. A disadvantage of US

4,018,202 the ignition system has a potential ignition failure resulting in 5 motor malfunctions if the motor is operated after the voltage requirement of at least one of the spark plugs has reached a level at which ignition failure may occur. The cylinder with the highest secondary voltage requirement determines the spark plug replacement interval to prevent sparking on the plugs resulting in engine malfunction.

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U.S. Patent No. 5,623,209 discloses a method for determining the condition of a capacitive discharge ignition system. In US

5,623,209 also discloses means for determining the condition of individual spark plugs.

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Brief Description of the Invention

It is an object of the invention to extend the interval between replacement of the spark plugs. The object is achieved as described in the independent claims. Preferred embodiments of the invention are set forth in the dependent claims.

The invention is based on an adaptive control method. Those spark plugs with the highest secondary voltage need are identified by continuously measuring the actual secondary voltage need.

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ώ The timing of the ignition of the individual cylinders is advanced before the g secondary voltage requirement reaches a level at which no spark can occur.

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Significant benefits can be obtained by using the invention. Delaying the timing of the ignition 05 oo 30 reduces the need for secondary voltage because the pressure o in the cylinder decreases as the timing of the ignition is advanced. The real fire

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The effect of the pressure on the secondary voltage requirement at the time of the spark generation is significant. For example, in spark ignited natural gas engines, the secondary voltage requirement may be about 1000 V lower for each crank angle at which the ignition is advanced at full load. This provides 5 additional options for extending the spark plug replacement interval, an important factor in many applications.

BRIEF DESCRIPTION OF THE DRAWINGS 10 The invention is illustrated with reference to the following figures:

Figure 1 is a graph showing the relationship between the spark plug diagnostic number and the voltage requirement; Figure 2 is a graph illustrating an embodiment of the invention showing a diagnostic number and thresholds;

Figure 3 is a graph illustrating another embodiment of the invention showing a diagnostic number and thresholds; 20

Fig. 4 is a flowchart of an ignition control method according to an embodiment of the invention; and

Figure 5 is a view according to another embodiment of the invention

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o 25 ignition flow scheme flow diagram, ώ 0 g Detailed description of drawings 1 CC Q_

The diagnostic curve 11 of the graph of Figure 1 illustrates the diagnostic value of the spark § 30, i.e., the diagnostic number. The diagnostic value of the spark, referred to in Figure 2 as the diagnostic number, is the number that correlates

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4 spark plug needles and can be calculated for each ignition of each cylinder. For example, the diagnostic value of the spark can be obtained by: detecting a voltage across the charge capacitor; the need for a high secondary spark plug voltage for the spark plug can be determined based on this measured time.

Diagnostic curve 11 is provided to provide an understanding of the relationship between the diagnostic value of the spark, which may be dimensionless, and the voltage required to produce the spark. Although there is a certain relationship between the diagnostic value of the spark and the voltage, the diagnostic value of the spark can also be determined using experimental information on the diagnostic value of the spark. For example, when it has been found that a common plug has an ignition malfunction with a diagnostic spark value of about 160, it is also known that it would be best to replace the plug when the spark diagnostic value reaches that value. 20 This information can be saved directly and used when setting offset thresholds described later.

The following values can be determined from the spark diagnostic value. The coefficient of variation of the diagnostic value of the spark is designated here as COV. COV will indicate

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0 25 Relative stability of voltage demand in real time. The mean value of the diagnostic value for the cylinder spark cd is here CAVG. The mean value of the diagnostic value for all cylinders \ g spark is here EAVG.

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Figure 2 is a graph illustrating an embodiment of the invention

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S 30 embodiments wherein the diagnostic number and thresholds are shown, o Reference numeral 21 denotes the CAVG or diagnostic value for cylinder spark

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5 average. Reference numeral 22 denotes an offset threshold that activates the ignition timing control. This provides a limited advance of ignition when the mean value of the spark plug spark diagnostic value 21 exceeds the offset threshold 22. Here, the advantage is obtained that the older spark plugs can be used due to the reduction in pressure caused by the spark plug.

Reference numeral 23 denotes a detection threshold that can also be used as a reset when notifying a user of a spark plug change. It should be noted that additional detection thresholds may be used for similar purposes.

The values of these thresholds 22 and 23 may vary from one engine to another. Thresholds can be predefined and changed based on historical data 15, since the CAVG number varies from one engine to another and from one application to another. However, it is possible to detect that the spark plug starts an ignition fault above a certain CAVG number.

Figure 3 illustrates an embodiment comparing CAVG to EAVG 20 to determine the time of ignition advance. EAVG, the average engine CAVG value, can be calculated by summing all the individual CAVG values and dividing the number by the number of cylinders. When a single cylinder (s) provides a CAVG value that is significantly lower or much higher than the EAVG, the user can be given a C10 alarm. The spark timing adjustment can be performed on a spark plug having an average spark diagnostic value, CAVG (21 in Figure 2), greater than g engine average spark diagnostic value 31, spark plugs x EAVG, with a predetermined amount of deviation.

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g 30 This predefined deviation can be set

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o 2 to 10% EAVG, for example. Early ignition is done on it

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6 after the offset threshold 32 has been exceeded. This may also be detected after the detection threshold 33 has been exceeded. This achieves a lower pressure level at the time of ignition and thus a lower secondary voltage requirement can be used.

This offset threshold 32 may be predetermined based on empirically obtained information from a normal set of spark plugs used under normal conditions.

It should be noted that the embodiment of Figure 3 may be combined with the embodiment of Figure 2. This requires different procedures for different offset thresholds. An offset threshold 32 and an offset threshold 22 for a high CAVG may be used to deviate from the average CAVG of the engine.

This has the advantage that offset threshold 32 can compensate for spark plug misalignment. The use of offset threshold 22 provides an opportunity to prevent ignition failure even when the spark plug life is approaching 100%.

Another alternative to associating the embodiment of Fig. 2 with the embodiment of Fig. 3 is to vary the magnitude of the deviation relative to the CAVG values. Acceptable deviation magnitude is higher when EAVG values are low and lower when EAVG values increase. This can be achieved with a number of offset threshold 32 values or by scaling the offset threshold 32 such that

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δ 25 that a lower offset magnitude triggers the ignition advance,

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ώ when the spark plugs expire. It is noted that the values of the magnitude of the acceptable deviation o ιό may vary. The value of the offset may vary from o x, for example, so that it decreases as the CAVG increases.

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Fig. 4 is a flowchart of the ignition control method according to the invention.

o The method applies to at least two spark plugs

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7 internal combustion engines, in which the primary voltage is taken from a voltage source and converted to a secondary secondary voltage suitable for ignition purposes. The method of Figure 4 carries out the following steps: 5 501) Determining the diagnostic value of the spark, which indicates the need for a secondary voltage, separately for each spark plug while the ignition system is in use.

502) Comparing the diagnostic values of the spark with the predetermined thresholds 10 to determine whether the secondary voltage requirement of any spark plug is approaching a level at which an ignition failure leading to an engine malfunction may occur.

503) Adjusting the ignition timing for the spark plug whose diagnostic value for the spark 15 exceeds the offset threshold by bringing the spark plug ignition timing to an engine angular position lower than the previous engine angular position.

Steps 501 and 502 are performed to determine whether the voltage requirement of any spark plug in the system 20 approaches the level at which an ignition failure may occur and to detect the sparking plug (s) causing the risk.

Thus, the timing of the ignition timing is performed prior to the initiation of the induction before the need for the secondary voltage has approached the level at which the ignition failure can

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o 25 and may result in engine malfunction.

ra g The flow diagram of FIG. 5 differs from FIG. 4 in that the knock level of the cylinder x is taken into account when implementing the ignition timing 503.

By advancing the spark timing and simultaneously keeping O) ra 30 load / charge pressure constant, this cylinder moves closer to knocking, o This is solved by increasing the air / fuel ratio of that cylinder

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8 at the same time as the ignition timing of the same cylinder is advanced. As a result, the knocking margin can be adjusted and kept constant. The control system orders a reduced exhaust gas temperature for a particular cylinder and increases the air / fuel ratio of the cylinder 5 when less fuel (gas) is supplied.

By supplying less fuel (gas) to one cylinder, the load on that cylinder will be reduced and this will slightly increase the load on the other cylinders of the engine (when the engine power is kept constant), but this effect is quite insignificant in multi-cylinder engines, for example 16-20 . The embodiment of Figure 5 has two additional steps: 504) Comparing the knock value to the knock threshold threshold.

15 505) Adjust the air / fuel ratio.

Having described above certain embodiments of the invention, it will now be apparent to one skilled in the art that other embodiments of the invention may be used. Thus, the invention should not be limited to certain embodiments, but rather should be limited only by the scope of the following claims.

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Claims (7)

A method of adjusting the ignition of at least a two-cylinder reciprocating internal combustion engine, wherein in the engine the ignition energy is applied to spark plugs 5 to produce sparks suitable for ignition in the combustion chamber, comprising the steps of: developing a secondary voltage with the engine running 10, characterized in that the method further comprises the step of: adjusting the ignition timing (503) of the spark plug whose diagnostic value (11, 21) exceeds the offset threshold (22, 32) by advancing the spark plug ignition timing. at an engine angle-15 position where the combustion chamber pressure is lower. The method of claim 1, wherein adjusting the ignition timing (503) is performed on the ignition support having the highest diagnostic value of spark (11,21,31). 20 The method of claim 1 or 2, wherein the method further comprises the following sub-step: performing a limited adjustment of the ignition timing (503) when the average spark diagnostic value (21) CM0 25 of the spark plug exceeds the offset threshold (22). i CD O The method of claim 1 or 2, wherein method x further comprises the following sub-step: CC CL is implemented in a limited manner (O) to adjust ignition timing (503) 30 when the average engine spark o diagnostic value (31) of the spark plugs exceeds the offset threshold (32). ). CM The method of claim 4, further comprising the step of: adjusting the ignition timing (503) on the spark plug, wherein the average spark diagnostic value (22) exceeds the average spark diagnostic value (31) of the spark plugs by a predetermined amount of deviation. The method according to any one of the preceding claims, wherein the method 10 further comprises the step of adjusting the air / fuel ratio (504) to be introduced into the cylinder so that the fuel supply to the cylinder where the ignition timing is advanced is reduced to prevent knocking on the cylinder. The method according to any one of the preceding claims, wherein the method further comprises the step of detecting the occurrence of an early timing of ignition if the diagnostic value (11,21) of the spark exceeds the notification threshold (23, 33). C \ J δ (M i CD O tn o X en CL O) 00 00 m O) o o {M