JP2014185535A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid that an ignition electrode which is exposed into a combustion chamber of a cylinder of an internal combustion engine is unilaterally worn, and its life is shortened.SOLUTION: An internal combustion engine comprises: a positive voltage generation part 6B which generates a positive voltage to be applied to an electrode which is exposed into a combustion chamber of a cylinder; a negative voltage generation part 6A which generates a negative voltage to be applied to the electrode; and a switching part 7 which selectively connects either of the positive voltage generation part 6B or the negative voltage generation part 6A to the electrode in one-time combustion in the cylinder, and applies the positive voltage generated by the positive voltage generation part 6B or the negative voltage generated by the negative voltage generation part 6A to the electrode.

Description

  The present invention relates to an internal combustion engine mounted on a vehicle or the like.

  In an ignition device mounted on a spark ignition type internal combustion engine, a high voltage generated in the ignition coil when the igniter extinguishes is applied to the center electrode of the ignition plug, so that the center electrode of the ignition plug and the ground electrode are A spark discharge is caused between them and ignites.

  Recently, in order to ensure that the air-fuel mixture in the combustion chamber of the cylinder is ignited and a stable flame can be obtained, the high frequency output from the high frequency oscillator or the microwave output from the magnetron is radiated into the combustion chamber. An “active ignition” method has been attempted (see, for example, the following patent document). According to the active ignition method, a high-frequency electric field or a microwave electric field is formed in the space between the center electrode and the ground electrode, and the plasma generated in this electric field grows to form a large flame nucleus that initiates flame propagation combustion. Can be generated.

JP 2011-0664162 A

  The electrode of the spark plug of the internal combustion engine is gradually worn out as the period of use becomes longer. In particular, when the above active ignition method is used, the wear becomes significant. When active ignition is performed by applying a negative high frequency or microwave electric field to the center electrode of the spark plug, the center electrode side is severely shaved. On the contrary, when a positive high frequency or microwave electric field is applied to the center electrode of the spark plug and active ignition is performed, the ground electrode side is severely shaved. As a result, one of the electrodes is damaged in a short period of time and its utility is lost, and the spark plug becomes short-lived, requiring frequent replacement of the spark plug.

  The present invention has been made by paying attention to the above-mentioned problem for the first time, and intends to prevent the ignition electrode exposed in the combustion chamber of the cylinder of the internal combustion engine from being unilaterally worn and shortening its life. Is.

  In the present invention, a positive voltage generator for generating a positive voltage to be applied to the electrode exposed in the combustion chamber of the cylinder, a negative voltage generator for generating a negative voltage to be applied to the electrode, In combustion, either the positive voltage generator or the negative voltage generator is selectively connected to the electrode, and the positive voltage generated by the positive voltage generator or the negative voltage generated by the negative voltage generator is applied to the electrode. And an internal combustion engine having a switching unit applied to the internal combustion engine.

  Plasma is generated in the combustion chamber by mixing the electric field generated in the combustion chamber via the antenna facing the combustion chamber of the cylinder and the spark discharge generated between the center electrode and the ground electrode of the spark plug, and mixing In a spark ignition internal combustion engine that ignites, the antenna is used as the electrode, and a positive electric field generated by the positive voltage generator or a negative electric field generated by the negative voltage generator in one-time combustion in a cylinder. It shall be applied to the antenna.

  According to the present invention, it is possible to prevent the ignition electrode exposed in the combustion chamber of the cylinder from being unilaterally worn and shortening its life.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The circuit diagram of the ignition device in the embodiment. The figure explaining the structure of the electric field generator in the embodiment. The circuit diagram of the H bridge which is an element of the electric field generator in the embodiment.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type 4-stroke gasoline engine, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1.

  FIG. 2 shows an electric circuit for spark ignition. The spark plug 12 receives spark voltage generated by the ignition coil 14 and causes spark discharge between the center electrode and the ground electrode. The ignition coil 14 is integrally incorporated in a coil case together with an igniter 13 that is a semiconductor switching element.

  The internal combustion engine of the present embodiment is accompanied by electric field generators 6A and 6B that generate an electric field in the combustion chamber of the cylinder 1. The electric field generators 6A and 6B are intended to radiate a high-frequency electric field into the combustion chamber of the cylinder 1 and generate plasma in the combustion chamber.

  3 and 4 show an example of the electric field generators 6A and 6B. Electric field generators 6A and 6B include a circuit that uses a vehicle-mounted battery as a power source and converts low-voltage direct current to high-voltage alternating current. Specifically, a DC-DC converter 61 that boosts a DC voltage of about 12 V provided by the battery to 100 V to 500 V, an H-bridge circuit 62 that converts the DC output from the DC-DC converter 61 into high-frequency AC, A boosting transformer 63 that boosts the alternating current output from the H-bridge circuit 62 to a higher voltage is used as a constituent element.

  In the present embodiment, the first electric field generator 6A, which is a negative voltage generator that applies a negative high-frequency electric field to the center electrode of the ignition plug 12 of the cylinder 1, and the positive high-frequency electric field is applied to the center electrode of the ignition plug 12. The second electric field generator 6B, which is a positive voltage generator, coexists, and the negative electric field generated by the first electric field generator 6A or the positive electric field generated by the second electric field generator 6B is generated at the center electrode of the spark plug 12. Any one of the electric fields can be selectively applied.

  First diodes 64A and 64B and second diodes 65A and 65B are provided at the output ends of the electric field generators 6A and 6B. The first diodes 64 </ b> A and 64 </ b> B have cathodes connected to the signal line of the secondary winding of the step-up transformer 63 and anodes connected to the mixer 66 that is a node with the ignition coil 14. The anodes of the second diodes 65A and 65B are connected to the ground line of the secondary winding of the step-up transformer 63, and the cathodes are grounded.

  The polarities (directions) of the first diodes 64A and 64B and the second diodes 65A and 65B are different between the first electric field generator 6A and the second electric field generator 6B. The first diode 64A and the second diode 65A in the first electric field generator 6A play a role of half-wave rectifying the AC voltage generated by the H bridge circuit 62 into a negative voltage. Similarly, the first diode 64B and the second diode 65B in the second electric field generator 6B play a role of half-wave rectifying the AC voltage generated by the H bridge circuit 62 into a positive voltage.

  A switching unit 7 is interposed between the electric field generators 6A and 6B and the mixer 66 connected to the center electrode of the spark plug 12. Switching unit 7 includes switch 7A for switching connection / disconnection between first electric field generation device 6A and mixer 66 and switch 7B for switching connection / disconnection between second electric field generation device 6B and mixer 66. . For each of the switches 7A and 7B, a semiconductor switching element such as a transistor or a MOSFET may be used, or a mechanical switch such as a relay may be used.

  It is preferable that the mixer 66 has a function of blocking a high-voltage pulse current for spark discharge induced on the secondary side of the ignition coil 14 from flowing toward the electric field generators 6A and 6B. However, this function is not necessary if the high-pressure pulse for spark discharge can be blocked from flowing into the electric field generators 6A and 6B by switching the switches 7A and 7B.

  The high-frequency voltage output by the electric field generators 6A and 6B is normally applied to the center electrode of the spark plug 12 almost simultaneously with the start of the spark discharge, immediately before the start of the spark discharge or immediately after the start of the spark discharge. That is, the center electrode of the spark plug 12 facing the combustion chamber of the cylinder 1 is an antenna that radiates an electric field. Thereby, a high frequency electric field is formed in the space between the center electrode of the spark plug 12 and the ground electrode in the combustion chamber. Then, plasma is generated by the occurrence of spark discharge in a high-frequency electric field, and this plasma generates a large radical plasma flame nucleus that starts flame propagation combustion.

  In the above, the flow of electrons due to the spark discharge and the ions and radicals generated by the spark discharge are vibrated and meandered by the influence of the electric field, resulting in a long path length and a dramatic increase in the number of collisions with surrounding water and nitrogen molecules. This is due to the increase. Water molecules and nitrogen molecules that have been struck by ions and radicals become OH radicals and N radicals, and the surrounding gas that has been struck by ions and radicals is also ionized, that is, a plasma state. In addition, the region of ignition of the air-fuel mixture increases and the flame kernel also increases. As a result, the two-dimensional ignition by only the spark discharge is amplified to the three-dimensional ignition, and the combustion rapidly propagates into the combustion chamber and expands at a high combustion speed.

  Incidentally, a pulsating voltage generation circuit can be adopted instead of the H bridge circuit 62 which is an AC voltage generation circuit. In this case, the pulsating voltage generation circuit only needs to generate a DC voltage whose voltage changes periodically, and the waveform thereof may be arbitrary. The pulsating voltage includes a pulse voltage that varies from a reference voltage (which may be 0V) to a constant voltage in a constant cycle, a voltage obtained by half-wave rectifying an AC voltage, a voltage obtained by adding a DC bias to the AC voltage, and the like. The high frequency voltage oscillated by the electric field generators 6A and 6B preferably has a frequency of about 200 kHz to 3000 kHz and an amplitude of about 3 kVp-p to 10 kVp-p.

  An intake passage 3 for supplying intake air to the cylinder 1 of the internal combustion engine takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for exhausting the exhaust from the cylinder 1 guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  An ECU (Electronic Control Unit) 0 that controls the operation of the internal combustion engine of this embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. An accelerator opening signal c output from a sensor that detects the amount or the opening of the throttle valve 32 as an accelerator opening (so-called required load), and a brake pedaling amount signal d output from a sensor that detects the amount of depression of the brake pedal The intake air temperature / intake pressure signal e output from the temperature / pressure sensor for detecting the intake air temperature and the intake pressure in the intake passage 3 (particularly the surge tank 33), and the water temperature sensor for detecting the cooling water temperature of the internal combustion engine are output. Is the sensor (or shift position switch) to know the coolant temperature signal f and the shift lever range? Shift range signal g outputted, a cam angle signal h or the like to be output from the cam angle sensor is input in a plurality of cam angle of the intake camshaft or an exhaust camshaft.

  From the output interface, an ignition signal i for the igniter 13 of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, and an electric field for the first electric field generator 6A. (I.e., high frequency) application command signal l, electric field application command signal m, etc. are output to second electric field generator 6B.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed and intake air amount, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, and an electric field are generated in the combustion chamber. Various operating parameters such as whether or not and the timing of the electric field generation are determined. The ECU 0 applies various control signals i, j, k, l and m corresponding to the operation parameters via the output interface.

  A high frequency electric field radiated into the combustion chamber using the center electrode of the spark plug 12 as an antenna interacts with a spark discharge generated between the center electrode and the ground electrode of the spark plug 12 to generate plasma and ignite the mixture. When active ignition is performed, either the first electric field generator 6A or the second electric field generator 6B is selected and connected to the mixer 66, and the negative electric field output from the connected electric field generators 6A and 6B is output. Alternatively, a positive high-frequency electric field is applied to the center electrode and radiated from the center electrode into the combustion chamber.

  That is, in one combustion of the air-fuel mixture in the cylinder 1 (in other words, in one cycle (a series of intake stroke-compression stroke-expansion stroke-exhaust stroke)), from the center electrode of the spark plug 12, Radiate either a negative high-frequency electric field or a positive high-frequency electric field. In the combustion of the air-fuel mixture once in the cylinder 1, the ECU 0 switches the switch 7A in accordance with the timing of radiating a high-frequency electric field into the combustion chamber (at substantially the same time as the start of the spark discharge, immediately before the start of the spark discharge or immediately after the start of the spark discharge). Disconnect the switch 7B while connecting and connect only the first electric field generator 6A to the mixer 66, or disconnect the switch 7A while connecting the switch 7B and connect only the second electric field generator 6B to the mixer 66 To do. Then, a high frequency is output from the electric field generators 6A and 6B on the side connected to the mixer 66.

  In addition, in the present embodiment, the electric field generators 6A, 6B connected to the mixer 66 in active ignition to suppress the unilateral wear of the center electrode or the ground electrode of the spark plug 12 and prolong the life of the spark plug 12. That is, the high-frequency electric field to be applied to the center electrode is switched as appropriate.

  When active ignition in which a negative high-frequency electric field is applied to the center electrode of the spark plug 12 is executed, electrons are emitted from the center electrode toward the ground electrode. At this time, it is presumed that the constituent material (metal) of the center electrode is scattered together with the electrons, and the center electrode is severely shaved. However, the ground electrode is less worn than the center electrode.

  In turn, when a positive high-frequency electric field is applied to the center electrode of the spark plug 12 to execute active ignition, electrons are emitted from the ground electrode having a relatively low potential toward the center electrode. Also at this time, it is presumed that the constituent material of the ground electrode is scattered together with the electrons, and the ground electrode is severely shaved. However, the center electrode is less worn than the ground electrode.

  In addition, the scattered constituent material of the electrode seems to reattach to the center electrode and the ground electrode.

  In view of the above-described phenomenon, in the present embodiment, by switching the high-frequency electric field to be applied to the center electrode in active ignition, the electrodes that are subject to wear are switched alternately, thereby extending the life of the spark plug 12.

  In addition, while a negative electric field is applied to the center electrode, it is expected that the scattered constituent material reattaches to the ground electrode and recovers the worn portion of the ground electrode (that is, regenerates the electrode). While a positive electric field is applied to the center electrode, it is expected that the scattered constituent material reattaches to the center electrode and recovers the worn portion of the center electrode.

  Needless to say, switching between the negative high-frequency electric field and the positive high-frequency electric field is realized by switching which of the switches 7A and 7B is ON and which is OFF. The switches 7A and 7B may be disconnected except when the high frequency electric field is applied to the center electrode.

  A specific trigger for switching between positive and negative of the high-frequency electric field applied to the center electrode may be arbitrarily determined. For example, it may be switched every trip (the period from when the ignition switch is turned on to start the internal combustion engine until the ignition switch is turned off to stop the internal combustion engine is taken as one trip). Then, the number of times that the active ignition has been executed in the cylinder 1 may be counted and switched each time the cumulative number reaches a predetermined value. Alternatively, the polarity of the high-frequency electric field to be applied may be switched at every opportunity (one cycle) of combustion of the air-fuel mixture in the cylinder 1.

  The first electric field generator 6A that oscillates a negative electric field and the second electric field generator 6B that oscillates a positive electric field may be provided for each cylinder 1 (in the case of a three-cylinder engine, the first electric field generator 6B). The generator 6A and the second electric field generator 6B are three sets), and the total number of both the electric field generators 6A and 6B may be arranged to match the number of cylinders 1 (if the engine is a three-cylinder engine, the first electric field One (or two) generators 6A and two (or one) second electric field generators 6B).

  In the present embodiment, a positive voltage generator 6B that generates a positive voltage to be applied to the electrode exposed in the combustion chamber of the cylinder 1 (the center electrode of the spark plug 12), and a negative voltage to be applied to the electrode are generated. The negative voltage generator 6A to be operated, and in one combustion in the cylinder 1, either the positive voltage generator 6B or the negative voltage generator 6A is selectively connected to the electrode to generate the positive voltage generator 6B. An internal combustion engine comprising a switching unit 7 that applies a positive voltage to be generated or a negative voltage generated by the negative voltage generation unit 6A to the electrodes is configured.

  According to the present embodiment, it is possible to prevent the ignition electrode exposed in the combustion chamber from being unilaterally worn and shortening its life, and maintenance costs for a vehicle or the like on which the internal combustion engine is mounted. It can contribute to the reduction of.

  The wear of the electrode of the spark plug 12 is caused between the electric field generated in the combustion chamber via the antenna facing the combustion chamber of the cylinder 1 (the center electrode of the spark plug 12) and the center electrode and the ground electrode of the spark plug 12. This is noticeable in a spark ignition internal combustion engine that interacts with the generated spark discharge to generate plasma in the combustion chamber and ignites the air-fuel mixture. In such an internal combustion engine, in a single combustion in the cylinder 1, a positive electric field generated by the positive voltage generator 6B or a negative electric field generated by the negative voltage generator 6A is applied to the antenna. This is effective for extending the life of the spark plug 12 and is advantageous for improving practicality. Further, if the high-frequency electric field applied to the center electrode of the spark plug 12 installed in the cylinder 1 is switched according to the cumulative number of active ignitions in the cylinder 1, the wear of the spark plug 12 is controlled appropriately. It becomes possible.

  The present invention is not limited to the embodiment described in detail above. For example, a microwave generator or the like can be employed as an electric field generator (positive voltage generator and negative voltage generator) that generates an electric field in the combustion chamber for the purpose of generating plasma in the combustion chamber of the cylinder of the internal combustion engine. .

  The microwave generator includes a magnetron that uses a vehicle-mounted battery as a power source and a control circuit that controls the magnetron. The microwave generator is electrically connected to the spark plug via a waveguide, a coaxial cable, etc., and the microwave output from the magnetron is applied to the spark plug and radiated from the center electrode into the combustion chamber of the cylinder. Is possible.

  The microwave generated by the magnetron is applied almost simultaneously with the start of the spark discharge, immediately before the start of the spark discharge or immediately after the start of the spark discharge. At this time, the ECU inputs an electric field (ie, microwave) generation command signal to a control circuit that controls the magnetron. The microwave by the magnetron and the high induction voltage for spark discharge by the ignition coil may be superimposed and applied to the center electrode of the spark plug.

  Furthermore, it is also conceivable to apply the present invention not to an internal combustion engine capable of performing active ignition but to a conventional spark ignition internal combustion engine. That is, a plurality of spark ignition circuits for applying a high pulse voltage to the center electrode of the spark plug to cause spark discharge in the spark plug, one of which is a negative voltage generator for generating a negative pulse voltage, and the other is A positive voltage generator that generates a positive pulse voltage is used. Then, any one of the voltage generators is selectively connected to the center electrode of the spark plug via the switching unit.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to an internal combustion engine mounted on a vehicle or the like.

DESCRIPTION OF SYMBOLS 1 ... Cylinder 12 ... Spark plug, antenna 6A ... Negative voltage generation part 6B ... Positive voltage generation part 7 ... Switching part 7A ... Switch 7B ... Switch

Claims (2)

A positive voltage generator for generating a positive voltage to be applied to the electrode exposed in the combustion chamber of the cylinder;
A negative voltage generator for generating a negative voltage to be applied to the electrode;
In one-time combustion in a cylinder, either the positive voltage generator or the negative voltage generator is selectively connected to the electrode, and the positive voltage generated by the positive voltage generator or the negative voltage generated by the negative voltage generator is generated. An internal combustion engine comprising a switching unit that applies a voltage to the electrode. Plasma is generated in the combustion chamber by mixing the electric field generated in the combustion chamber via the antenna facing the combustion chamber of the cylinder and the spark discharge generated between the center electrode and the ground electrode of the spark plug, and mixing A spark ignition internal combustion engine that ignites.
2. The internal combustion engine according to claim 1, wherein the antenna is used as the electrode, and a positive electric field generated by the positive voltage generator or a negative electric field generated by the negative voltage generator is applied to the antenna in one combustion in a cylinder. .

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