JP2016196843A - Ignition device and ignition method of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate ignition even under an operational condition where combustion is easy to be unstable while suppressing abrasion of an electrode.SOLUTION: By supplying primary current to a primary coil 15a of an ignition coil 15 and cutting off the primary current, discharge voltage is generated between electrodes of an ignition plug 9 connected to a secondary coil 15b. An ignition device includes a changeover circuit 18 that switches the polarity of the second coil 15b between positive polarity and negative polarity by switching the flow direction of current through the primary coil 15a. Under a predetermined operational condition with low combustion stability, the polarity of the secondary coil 15b is set to positive polarity, and under operational conditions other than the above operational condition, it is set to negative polarity.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ignition device and an ignition method for an internal combustion engine using an ignition coil including a primary coil and a secondary coil.

  In an ignition device using an ignition coil, a primary discharge current is applied to the primary coil, and then the primary current is cut off at a predetermined ignition timing, thereby generating a high discharge voltage in the secondary coil and A discharge is generated between the electrodes of the connected spark plug.

  Patent Document 1 describes a technique for switching the polarity of a secondary coil connected to a spark plug between a positive polarity and a negative polarity in order to make the wear of the spark plug uniform.

JP 2013-64358 A

  When the polarity of the secondary coil (that is, the electrode of the ignition coil connected to the secondary coil) is set to a negative polarity, wear of the spark plug electrode can be suppressed. It is said. On the other hand, when the secondary coil has a positive polarity, compared to the negative polarity, although the wear of the spark plug electrode is likely to proceed, the discharge voltage becomes high, so the ambient temperature during discharge becomes high, Ignition performance is improved. Also, the positive polarity is more resistant to the spark plug contamination, and current leakage due to the contamination can be suppressed.

  Therefore, the present invention suppresses the wear of the electrode of the spark plug, and makes it easy to perform ignition even under operating conditions in which ignition is difficult and combustion is likely to be unstable, such as during cryogenic starting, and combustion stability is improved. It is an object of the present invention to provide a novel internal combustion engine ignition device and ignition method capable of improving the engine.

  The present invention relates to an ignition device and an ignition method for an internal combustion engine in which a discharge current is generated between electrodes of an ignition plug connected to a secondary coil by supplying and interrupting a primary current to the primary coil of the ignition coil.

  In the case of predetermined operating conditions including a polarity switching means for switching the polarity of the electrode of the spark plug connected to the secondary coil, i.e., the secondary coil, between positive polarity and negative polarity, and when the combustion stability is low, In the case of operating conditions other than the predetermined operating condition, the polarity of the secondary coil is set to negative polarity.

  According to the present invention, for example, when the ignition energy or discharge temperature is low, such as at a very low temperature, a low temperature using alcohol fuel, or a low pulse, fuel spray formation or flame formation becomes unstable, Although normal flames are not formed and combustion tends to be unstable, under certain operating conditions including the case where combustion becomes unstable in this way, by making the polarity of the secondary coil positive, Compared to the case, the discharge voltage and the discharge temperature can be increased, the ignition performance can be improved, and the combustion can be stabilized.

  On the other hand, in normal operating conditions other than the predetermined operating conditions including the case where such combustion becomes unstable, by making the polarity of the secondary coil negative, compared to the case where it is positive, The wear of the electrode can be suppressed and the durability can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing of the internal combustion engine provided with the ignition device of one Example of this invention. The block diagram which shows the structure of the ignition device in case a secondary coil is made into negative polarity. The block diagram which shows the structure of the ignition device in case a secondary coil is made into positive polarity. The flowchart which shows the flow of the polarity switching control which concerns on a present Example.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration explanatory view showing a system configuration of an internal combustion engine 1 provided with an ignition device according to an embodiment of the present invention. A piston 3 is disposed in each of a plurality of cylinders 2 of the internal combustion engine 1. In addition, an intake port 5 that is opened and closed by the intake valve 4 and an exhaust port 7 that is opened and closed by the exhaust valve 6 are connected to each other. In addition, a fuel injection valve 8 is provided for injecting and supplying fuel into the cylinder. The fuel injection timing and fuel injection amount of the fuel injection valve 8 are controlled by an engine control unit (ECU) 10. In order to ignite the air-fuel mixture generated in the cylinder by the fuel injection valve 8, a spark plug 9 is disposed at the center of the ceiling surface, for example. The illustrated example is configured as an in-cylinder direct injection internal combustion engine, but a port injection configuration in which a fuel injection valve is disposed in the intake port 5 may be used. The engine control unit 10 receives detection signals from a number of sensors such as an air flow meter 21 that detects the intake air amount, a crank angle sensor 22 that detects the engine speed, and a temperature sensor 23 that detects the coolant temperature. Has been.

  The ignition plug 9 is connected to an ignition unit 11 that outputs a discharge voltage to the ignition plug 9 in response to an ignition signal from the engine control unit 10. These engine control unit 10 and ignition unit 11 are connected to a vehicle-mounted battery 13.

  As shown in detail in FIGS. 2 and 3, the ignition unit 11 includes an ignition coil 15 including a primary coil 15a and a secondary coil 15b, and a primary coil of the ignition coil 15 based on an ignition signal from the engine control unit 10. And an igniter 16 for controlling energization / cutoff of the primary current to 15a. A spark plug 9 is connected to the secondary coil 15 b of the ignition coil 15, and a resistor 17 is provided between the secondary coil 15 b and the spark plug 9.

  A switching circuit 18 is provided between the battery 13 and the primary coil 15a to switch the direction of current flowing from the battery 13 to the primary coil 15a. The switching circuit 18 includes a battery side contact 18a connected to the battery 13, an igniter side contact 16 connected to the igniter 16, and a first coil side contact 18c and a second coil side contact 18d connected to the primary coil 15a. Have.

  As shown in FIG. 2, when the battery side contact 18a and the first coil side contact 18c are connected, and the igniter side contact 16 and the second coil side contact 18d are connected, current flows in the direction indicated by the arrow Y1 in the figure. The primary coil 15a is positive and the secondary coil 15b is negative. Therefore, the electrode of the spark plug 9 connected to the secondary coil 15b has a negative polarity and the ground electrode has a positive polarity, and a discharge voltage is generated between both electrodes.

  On the other hand, as shown in FIG. 3, when the battery side contact 18a and the second coil side contact 18d are connected, and the igniter side contact 16 and the first coil side contact 18c are connected, as shown by an arrow Y2 in the figure. 1, a current flows in the opposite direction, the primary coil 15a has a negative polarity, the secondary coil 15b has a positive polarity, and the polarity of the secondary coil 15b connected to the spark plug 9 has a positive polarity. Therefore, the electrode of the spark plug 9 connected to the secondary coil 15b has a positive polarity and the ground electrode has a negative polarity, and a discharge voltage is generated between both electrodes.

  Thus, the switching circuit 18 functions as polarity switching means for switching the polarity of the secondary coil 15b between positive polarity and negative polarity, and the operation of the switching circuit 18 is controlled by the engine control unit 10.

  FIG. 4 is a flowchart showing the flow of switching control of the switching circuit 18. The routine of this flowchart is repeatedly executed in the control unit 10 in a manner synchronized with the ignition interval of the internal combustion engine 1, for example.

  In step S11, it is determined whether the operating condition of the internal combustion engine 1 is an operating condition with low combustion stability. That is, based on the coolant temperature detected by the temperature sensor 23, the engine temperature is very low, such as during cold start, or the internal combustion engine using alcohol fuel is cold, or the power of the battery 13 is low. When the pulse signal to the spark plug 9 is low due to shortage or the like, it is determined whether fuel spray formation, flame formation, or ignition itself becomes unstable and combustion stability is lowered.

  In step S12, for example, based on the operation history or the like, it is determined whether or not the spark plug 9 has reached a predetermined level.

  If either step S11 or step S12 is negative, the process proceeds to step S13, and the secondary coil 15b of the ignition coil 15 is set to a negative polarity as shown in FIG.

  On the other hand, when at least one of step S11 and step S12 is affirmed, the process proceeds to step S14, and the secondary coil 15b of the ignition coil 15 is made positive as shown in FIG.

  As described above, in this embodiment, when the ignition energy or the discharge temperature is low, such as at a very low temperature, at a low temperature using alcohol fuel, or at a low pulse, fuel spray formation or flame formation is not possible. It becomes stable and combustion is likely to be unstable without forming a normal flame. However, under predetermined operating conditions in which combustion becomes unstable in this way, by making the polarity of the secondary coil 15b positive, As compared with the case, the discharge voltage and the discharge temperature can be increased, the ignition performance can be improved, and the combustion can be stabilized.

  Further, even when the spark plug 9 has reached a predetermined level, the polarity of the secondary coil 15b is made positive so that current leakage is suppressed and stable compared to the case where the secondary coil 15b is made negative. Combustion can be realized. By improving the combustion stability in this way, it is possible to suppress an increase in the fuel injection amount for improving the ignitability, to improve the fuel consumption, and to reduce the ignition timing to avoid the occurrence of knocking. It is possible to suppress the decrease in output.

  On the other hand, under normal operating conditions other than the predetermined operating conditions in which combustion is likely to be unstable, the polarity of the secondary coil 15b is set to be negative, so that the polarity of the electrode is smaller than that of positive polarity. Wear can be suppressed and durability can be improved.

  As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, A various change is possible.

Claims (4)

In an ignition device for an internal combustion engine that generates a discharge voltage between electrodes of an ignition plug connected to a secondary coil by energizing and interrupting a primary current to the primary coil of the ignition coil.
Polarity switching means for switching the polarity of the secondary coil between positive polarity and negative polarity;
The polarity of the secondary coil is positive in the case of predetermined operating conditions including a case where combustion stability is low, and the polarity of the secondary coil is negative in the case of operating conditions other than the predetermined operating conditions. An ignition device for an internal combustion engine.   2. The ignition device for an internal combustion engine according to claim 1, wherein the polarity switching means switches a direction of a current flowing through the primary coil.   3. The ignition device for an internal combustion engine according to claim 1, wherein the predetermined operating condition includes a case where the contamination of the spark plug reaches a predetermined level. In an internal combustion engine ignition method for generating a discharge voltage between electrodes of an ignition plug connected to a secondary coil by energizing and interrupting a primary current to the primary coil of the ignition coil,
Polarity switching means for switching the polarity of the secondary coil between positive polarity and negative polarity;
In the case of predetermined operating conditions including the case where combustion stability is low, the polarity of the secondary coil is positive, and in other operating conditions, the polarity of the secondary coil is negative. A method for igniting an internal combustion engine.

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