JP2009013850A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control technology for an internal combustion engine capable of switching between a multi-point ignition and a single-point ignition in response to a change in the combustion state in a combustion process of each cycle and saving electric energy required for ignition. <P>SOLUTION: This internal combustion engine is equipped with a plurality of ignition plugs for each cylinder, and ignition is sequentially performed from a central ignition plug in each cylinder. The control device has a function for detecting secondary voltage applied to the central ignition plug, and a function for determining whether or not gas flow velocity in the cylinder is fast based on the detected secondary voltage. When the control device determines that the gas flow velocity is fast, ignition of side ignition plugs which are ignition plugs other than the central ignition plug is inhibited. In a prompt response to the change in the combustion state in the combustion process of an air-fuel mixture, the multi-point ignition and the single-point ignition can be switched during the combustion process, and electric energy required for ignition can be saved by reducing unneeded ignition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine having a plurality of spark plugs for each cylinder, and more particularly to a control technique for an internal combustion engine capable of igniting spark plugs sequentially from a first spark plug in each cylinder.

  In an internal combustion engine, in order to improve the combustion speed of the air-fuel mixture formed in the cylinder, an internal combustion engine provided with a plurality of ignition plugs for each cylinder and igniting and burning a plurality of portions of the air-fuel mixture, so-called multipoint ignition Conventional internal combustion engines are known.

  In such a multipoint ignition type internal combustion engine, if the combustion speed becomes too fast, there is a problem that knocking is likely to occur in the cylinder, and more than one spark plug is used for each cylinder. There is a problem that electric energy consumed as an internal combustion engine increases as compared with a case where ignition is performed once with one spark plug (hereinafter referred to as one-point ignition).

  In order to counter this problem, in the ignition control technique described in Patent Document 1 below, when the engine load of the internal combustion engine (engine load) continues to be high, the ignition of the sub plug is stopped and only the main plug is used. It has been proposed to suppress the occurrence of knocking in the cylinder by performing ignition. The ignition control device for an internal combustion engine disclosed in Patent Document 1 detects an engine load, an engine rotation speed, a cooling water temperature, and a sub-plug temperature at regular intervals, and the high-load operation of the internal combustion engine is continued, so that the temperature of the sub-plug is increased. When a predetermined time elapses after the value exceeds the determination value, the ignition of the sub plug is temporarily stopped to suppress the occurrence of pre-ignition due to the high temperature sub plug.

JP 2005-155546 A

  In such a multipoint ignition type internal combustion engine, even when the gas flow rate of the air-fuel mixture or the like in the cylinder is high, the flame propagation after ignition in the air-fuel mixture is sufficiently fast even with single-point ignition. In such a case, if multipoint ignition is performed, there is a risk that knocking may occur, and electrical energy is unnecessarily consumed by performing multipoint ignition.

  In addition, even if the internal combustion engine has the same control parameters indicating the operating state such as the engine speed and the engine load, the combustion state in the combustion process of each cycle may change during the combustion process. With the ignition control technique described in Patent Document 1, ignition cannot be controlled in response to changes in the combustion state in each cycle.

  As described above, in a multipoint ignition type internal combustion engine, in order to prevent knocking in a cylinder with high accuracy and to suppress power consumption as much as possible, in response to changes in the combustion state in each cycle of the air-fuel mixture, There is a need for an ignition control technique that can switch between multipoint ignition and single point ignition during the combustion process.

  The present invention has been made in view of the above, and it is possible to reduce electrical energy required for ignition by switching between multipoint ignition and single point ignition in response to changes in the combustion state in the combustion process of each cycle. An object of the present invention is to provide a control technique for an internal combustion engine.

  In order to achieve the above object, an internal combustion engine control device according to the present invention includes a plurality of spark plugs for each cylinder, and in each internal combustion engine capable of igniting the spark plug sequentially from the first spark plug in each cylinder. Secondary discharge detection means for detecting a secondary current flowing through the first spark plug or a secondary voltage applied to the first spark plug, and gas flow in the cylinder based on the detected secondary current or secondary voltage Gas flow determination means for determining whether or not the speed is greater than or equal to the determined flow speed, and ignition of spark plugs other than the first spark plug is prohibited when it is determined that the gas flow speed is greater than or equal to the determined flow speed And an ignition prohibition means.

  In the control device for an internal combustion engine according to the present invention, the gas flow determining means determines the gas flow rate when the discharge sustaining voltage, which is the secondary voltage after reaching the dielectric breakdown voltage, is equal to or higher than the determination voltage. It can be determined that the speed is greater than or equal to.

  In the control device for an internal combustion engine according to the present invention, the gas flow determination means determines that the gas flow speed is equal to or higher than the determination flow speed when the secondary voltage after the elapse of a predetermined time becomes equal to or higher than the determination voltage. Can be.

  In the control device for an internal combustion engine according to the present invention, the gas flow determination means determines that the gas flow speed is equal to or higher than the determination flow speed when the secondary current after a predetermined time has elapsed from the generation is equal to or less than the predetermined current. It can be.

  In the control apparatus for an internal combustion engine according to the present invention, the spark discharge part of the first spark plug may be disposed in the center of the ceiling wall of the combustion chamber, and the internal combustion engine may be other than the first spark plug. The spark discharge part of the spark plug may be arranged on the peripheral part of the ceiling wall of the combustion chamber.

  According to the present invention, in the combustion process of each cycle of the internal combustion engine, it is determined whether or not the gas flow speed in the cylinder is fast based on the secondary current or the secondary voltage flowing through the first spark plug that ignites first. When it is determined that the gas flow rate is equal to or higher than the determination flow rate, ignition of the spark plugs other than the first spark plug is prohibited. Whether or not to perform multipoint ignition can be determined according to the gas flow speed in the cylinder, and unnecessary multipoint ignition can be reduced to save electrical energy required for ignition.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

  First, a schematic configuration of the internal combustion engine according to the present embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a schematic configuration around a cylinder of an internal combustion engine. FIG. 2 is a view showing the positional relationship between the first spark plug and the second spark plug and the intake / exhaust valves, and is a view of the ceiling wall of the cylinder head as viewed from the piston side. FIG. 1 and FIG. 2 schematically show only main parts related to the present invention.

  The internal combustion engine according to this embodiment is a gasoline engine in which a fuel injection valve injects fuel into an intake passage, and is a spark ignition engine that ignites an air-fuel mixture formed in a cylinder with an ignition plug. In the present embodiment, the internal combustion engine includes an ignition system that supplies electric energy to the ignition plug, and the ignition system controls the ignition timing and discharge time of the ignition plug according to the operating state of the internal combustion engine. An electronic control device (hereinafter simply referred to as “control device”) is provided as the control means. Hereinafter, one cylinder among the plurality of cylinders of the internal combustion engine will be described.

  As shown in FIG. 1, the internal combustion engine 10 is provided with a cylinder block 12, a cylinder head 20, a piston 30, and a connecting rod and a crankshaft (not shown) as parts of an engine body system in which a cylinder is formed. ing. A cylinder bore 14 is formed in the cylinder block 12, and the piston 30 reciprocates along the axis of the cylinder bore 14 (hereinafter referred to as a bore axis and indicated by a one-dot chain line C).

  The reciprocating motion of the piston 30 is converted into a rotational motion and output from a crankshaft (not shown). The internal combustion engine 10 is provided with a crank angle sensor (not shown) that detects a rotational angle position of the crankshaft (hereinafter referred to as a crank angle), and sends a signal related to the crank angle to the control device. Yes.

  A cylinder head 20 is coupled to the cylinder block 12 so as to face the piston 30 and close the cylinder bore 14. A combustion chamber 40 is formed in the cylinder head 20, and an intake port 24 that leads intake air to the combustion chamber 40 is formed on one side across the bore axis C, and on the other side. Is formed with an exhaust port 26 for exhausting exhaust gas from the combustion chamber 40.

  The cylinder head 20 is provided with an intake valve 25 and an exhaust valve 27 corresponding to the intake port 24 and the exhaust port 26, respectively. The intake valve 25 and the exhaust valve 27 are driven by receiving mechanical power from the crankshaft via a camshaft. The intake valve 25 and the exhaust valve 27 are configured to be openable and closable at a predetermined timing according to the rotation angle position of the crankshaft (hereinafter referred to as the crank angle).

  When the intake valve 25 is opened, the intake port 24 and the combustion chamber 40 communicate with each other, and air from an intake passage (not shown) can be taken into the combustion chamber 40 in the cylinder from the intake port 24. When the exhaust valve 27 is opened, the exhaust port 26 and the combustion chamber 40 communicate with each other, and the exhaust gas in the combustion chamber 40 in the cylinder can be discharged from the exhaust port 26 to an exhaust passage (not shown).

  As shown in FIG. 2, each of the intake port 24 and the exhaust port 26 is provided in two, includes a bore axis C, and the axial direction of the crankshaft (hereinafter simply referred to as “crankshaft direction”). They are arranged so as to face each other across a cylinder row plane (indicated by a one-dot chain line E in the figure) which is a virtual plane extending in the figure as indicated by an arrow S. That is, in an internal combustion engine, a plurality of cylinders are arranged in a row in the crankshaft direction, and in each cylinder, the intake port 24 and the exhaust port 26 are arranged in a so-called “cross flow type”.

  In the following description, the side on which the intake port 24 is provided with respect to the cylinder row plane E including the bore axis C is referred to as “intake side”, and is indicated by the symbol IN in the figure. On the other hand, the side on which the exhaust port 26 is provided with respect to the plane E is referred to as “exhaust side” and is indicated by the symbol EX in the figure.

  The cylinder head 20 is formed with a ceiling wall 22 that is a wall surface that defines the shape of the combustion chamber 40. The ceiling wall 22 is formed so as to smoothly continue to the cylinder wall 15 which is the wall surface of the cylinder bore 14 at the peripheral edge 22e. A spark discharge portion 51 of the central spark plug 50 is disposed at the center portion 22a of the ceiling wall of the combustion chamber 40 formed in the cylinder head 20 (hereinafter referred to as the center portion of the ceiling wall). The details of the central spark plug will be described later together with the ignition system.

  Further, among the ceiling wall peripheral portion 22 c of the combustion chamber 40 formed in the cylinder head 20, there is a side portion sandwiched between the outer edge 24 e of the intake port 24, the outer edge 26 e of the exhaust port 26 and the peripheral edge 22 e of the ceiling wall 22. A spark discharge portion 55 of the spark plug is provided. The details of the side spark plug will be described later together with the ignition system.

  As shown in FIG. 2, the “ceiling wall central portion” 22 a means the outer edge 24 e of the intake port 24 and the exhaust port 26 in addition to the portion of the ceiling wall 22 of the combustion chamber 40 through which the bore axis C passes. A portion sandwiched between the outer edge 26e is included. On the other hand, the “ceiling wall peripheral portion” 22 c is a portion sandwiched between the peripheral edge 22 e of the ceiling wall 22 and the outer edge 24 e of the intake port 24 or the outer edge 26 e of the exhaust port 26 in addition to the peripheral edge 22 e of the ceiling wall 22. Is included.

  The space surrounded by the cylinder wall 15 of the cylinder block 12, the ceiling wall 22 of the cylinder head 20, and the top surface 32 of the piston 30 described above is a so-called “cylinder”. In the present embodiment, the cylinder includes a combustion chamber 40 formed in the cylinder head 20 in addition to the cylinder bore 14 formed in the cylinder block 12.

  In the following description, of the directions along the bore axis C, the direction in which the piston 30 faces the ceiling wall 22 is indicated as “head side” and is indicated by an arrow U in the figure. Further, the direction opposite to the head side in the direction along the bore axis C is referred to as “crank side” and is indicated by an arrow D in the drawing.

  The direction perpendicular to the bore axis C and perpendicular to the crankshaft direction S, that is, the direction in which the thrust force and the thrust reaction force act between the piston 30 and the cylinder wall 15 is referred to as “thrust "Direction" and indicated by arrow T in the figure. The thrust direction T is a direction orthogonal to the cylinder row plane E.

  Next, the configuration of the ignition system in the internal combustion engine according to the present embodiment will be described with reference to FIGS. FIG. 3 is a schematic diagram showing the configuration of the ignition system of the internal combustion engine. FIG. 4A is a diagram illustrating a relationship between a secondary voltage applied by the ignition coil to the spark plug and time. FIG. 4B is a diagram illustrating a relationship between the secondary current flowing through the spark plug and time. FIG. 5 is an enlarged view of a spark discharge portion of the central spark plug, and is a diagram showing a state of electric spark (arc) in a normal state. FIG. 6 is an enlarged view of a spark discharge portion of the central spark plug, and shows a state in which an electric spark (arc) is caused to flow by gas flow such as air-fuel mixture in the cylinder.

  The internal combustion engine 10 is provided with an ignition system 60 that generates an electric spark at a preset timing in the combustion chamber 40 in order to ignite the air-fuel mixture formed in the cylinder. As shown in FIG. 3, the ignition system 60 includes two ignition plugs (a central ignition plug 50 and a side ignition plug) and ignition coils 61 and 62 for applying a discharge voltage (secondary voltage) to these ignition plugs. is doing.

  As shown in FIG. 1, the ignition system 60 of the internal combustion engine 10 includes two ignition plugs for each cylinder as a device for igniting an air-fuel mixture (including fuel spray) formed in the cylinder. In detail, as shown in FIG. 2, the center spark plug 50 provided in the ceiling wall central part 22a and the side spark plug (spark discharge part 55) provided in the ceiling wall peripheral part 22c are provided. . As shown in FIG. 3, secondary spark voltages are applied to these spark plugs by first and second ignition coils 61 and 62 provided in correspondence with each other, and spark sparks ( Give rise to electric sparks).

  As shown in FIG. 5, the spark discharge portion 51 of the central spark plug 50 is disposed so as to protrude from the ceiling wall central portion 22 a to the combustion chamber 40. The spark discharge part 51 has a center electrode 51a connected to the secondary coil of the first ignition coil, and a ground electrode 51c grounded (grounded) to the cylinder head 20. As shown in FIG. 4A, when the secondary voltage applied by the secondary coil of the first ignition coil reaches the required breakdown voltage (required voltage) Vb, the spark discharge unit 51 has a center electrode 51a. An electric spark is generated in a gap between the electrode and the ground electrode 51c, that is, a so-called ignition gap.

  On the other hand, the side spark plug has the same configuration and function as the central spark plug 50, and a spark discharge portion 55 is disposed so as to protrude from the ceiling wall peripheral portion 22c of the cylinder head 20 to the combustion chamber 40. (See FIG. 2). As shown in FIG. 4A, when the secondary voltage applied by the second ignition coil reaches the required breakdown voltage Vb, the spark discharge unit 55 is interposed between a center electrode (not shown) and the ground electrode. An ignition spark will be produced.

  Further, as shown in FIG. 3, the ignition system 60 corresponds to the central spark plug 50 and the side spark plug in order to supply the secondary voltage (discharge voltage) to the spark discharge portions 51 and 55 of each spark plug. A first ignition coil 61 and a second ignition coil 62 are provided.

  The first ignition coil 61 has a primary coil 61a, a secondary coil 61c, and an iron core 61b. One end of the primary coil 61 a is connected to a first capacitor 67 described later, and the other end is connected to the collector of the first transistor 65. On the other hand, one end of the secondary coil 61c is connected to the center electrode 51a of the spark discharge part 51 of the central spark plug 50, and the other end is connected to a control device 80 described later. The secondary voltage generated in the secondary coil 61c of the first ignition coil 61 and the secondary current flowing from the secondary coil 61c to the spark discharge portion 51 of the central spark plug 50 can be detected by the control device 80 described later. Yes.

  Similar to the first ignition coil, the second ignition coil has a primary coil 62a, a secondary coil 62c, and an iron core 62b. One end of the primary coil 62a is connected to the second capacitor 68. The other end is connected to the collector of the second transistor 66. On the other hand, one end of the secondary coil 62 c is connected to the center electrode (not shown) of the spark discharge portion 55 of the side spark plug, and the other end is connected to the control device 80. The secondary voltage generated in the secondary coil 62c of the second ignition coil 62 and the secondary current flowing from the secondary coil 62c to the spark discharge portion 55 of the side ignition plug can be detected by the control device 80 described later. .

  In addition, in the ignition system 60, since the primary current flows through the primary coils 61a and 62a of the first and second ignition coils 61 and 62, respectively, the first and second capacitors 67, which store the electric energy of the primary current, 68, first and second energy generating devices 71 and 72 for charging the first and second capacitors 67 and 68, respectively, and first and second primary and second ignition coils 61 and 62 for interrupting the primary current. Two transistors 65 and 66 are provided.

  One end of the first capacitor 67 is connected to the primary coil 61a of the first ignition coil 61 and the first energy generating device 71, and the other end is grounded (grounded). As with the first capacitor 67, one end of the second capacitor 68 is connected to the primary coil 62a of the second ignition coil 62 and the second energy generator 72, and the other end is grounded.

  The first energy generating device 71 includes a power source, and is configured to be able to supply electric energy to the corresponding first capacitor 67 and store a predetermined charge (charge) under the control of the control device 80. Has been. Similarly to the first energy generation device 71, the second energy generation device 72 is configured to charge the corresponding second capacitor 68. The amounts of power stored in the first and second capacitors 67 and 68 by the first and second energy generating devices are controlled by the control device in accordance with the discharge maintenance time.

  The first transistor 65 is a so-called “power transistor” that interrupts the primary current of the first ignition coil 61, the collector is connected to the primary coil 61 a of the first ignition coil 61, and the emitter is grounded. Yes. The base of the first transistor 65 is connected to the control device 80. When a signal current flows from the base to the emitter under the control of the control device 80, the first transistor 65 is short-circuited (ON) between the collector and the emitter, and the primary current is applied to the primary coil 61a of the first ignition coil 61. It is possible to flow.

  Similarly to the first transistor 65, the second transistor 66 has a collector connected to the primary coil 62 a of the second ignition coil 62, an emitter grounded, and a base connected to the control device 80. The second transistor 66 can flow the primary current to the primary coil 62a of the second ignition coil 62 when the signal current flows under the control of the control device 80.

  Further, the ignition system 60 includes a control device 80 that controls the first and second energy generating devices 71 and 72 and the first and second transistors 65 and 66 in accordance with the operating state of the internal combustion engine 10. ing. The control device 80 receives signals relating to the rotational speed of the crankshaft (hereinafter referred to as engine rotational speed) from various sensors or other control devices provided in the internal combustion engine 10 and mechanical signals output from the crankshaft by the internal combustion engine. A signal related to power (hereinafter referred to as engine load), a signal related to the discharge time of the first and second spark plugs, and a signal related to the ignition timing of the first and second spark plugs are received.

  Based on these signals, the control device 80 grasps the operating state of the internal combustion engine, and controls the first and second energy generating devices 71 and 72 in accordance with the operating state, and controls the capacitors 67 and 68. It is possible to adjust the amount of power to be charged. In addition, the control device 80 controls the energization and shut-off of the first and second transistors 65 and 66 so that the primary current flows through the primary coils 61a and 62a of the first and second ignition coils 61 and 62, respectively. It is possible to adjust the period, that is, the timing and time length at which the secondary voltage is generated in the secondary coils 61c and 62c of the first and second ignition coils 61 and 62.

  As described above, the control device 80 controls the first and second energy generating devices 71 and 72 and the first and second transistors 65 and 66 to thereby control the central spark plug 50 and the side spark plug (spark discharge portion 55). It is possible to control the ignition timing and the discharge time. As a result, the ignition system 60 generates a secondary voltage of several tens of kV in the secondary coils 61c and 62c of the first and second ignition coils 61 and 62, and applies them to the central spark plug 50 and the side spark plug, respectively. Thus, a spark discharge is generated in the spark discharge portions 51 and 55. In the present embodiment, the control device 80 performs control so that the central spark plug 50 is first ignited at a normal time, and the side spark plug is ignited with a predetermined time difference.

  At this time, since the control device 80 is connected to the secondary coil of the first ignition coil and the secondary coil of the second ignition coil, the secondary coil 61c of the first ignition coil 61 is applied to the central spark plug 50. And the secondary current flowing from the secondary coil 61c to the central spark plug 50 can be detected. The control device 80 can also detect the secondary voltage applied to the side spark plug by the secondary coil 62c of the second ignition coil 62 and the secondary current flowing from the secondary coil 62c to the side spark plug. That is, the control device 80 has a function of detecting a secondary voltage applied to the central spark plug 50 (first spark plug) or a secondary current flowing through the central spark plug 50 (secondary discharge detecting means). Yes.

  Further, the control device 80 can determine the flow rate of gas in the cylinder, such as an air-fuel mixture (hereinafter simply referred to as “gas flow rate”), based on the detected secondary voltage or current. The details will be described below with reference to FIGS. The spark plug will be described by taking the center spark plug as an example.

  When the first transistor 65 is controlled by the control device 80 and the primary current flowing through the primary coil 61a of the first ignition coil 61 is cut off, as shown at time T0 in FIG. A secondary voltage begins to be applied to. When the secondary voltage applied to the central spark plug 50 reaches the required dielectric breakdown voltage (required voltage) Vb as shown at time T1 in FIG. 4-1, arc discharge occurs in the spark discharge portion 51. As shown in FIG. 5, an ignition spark (electric spark, arc) is generated that extends from the center electrode 51a to the ground electrode 51c in a substantially straight line.

  Thus, once an electric spark is formed between the center electrode 51a and the ground electrode 51c, and arc discharge is started, the gas in the cylinder, such as an air-fuel mixture, is formed along the shape of the electric spark, that is, the discharge path. The molecules to be ionized are reduced, and the electrical resistance between the center electrode 51a and the ground electrode 51c is reduced. As a result, the discharge sustaining voltage Vk (several hundreds to several kilovolts) applied between the center electrode 51a and the ground electrode 51c after time T1 is smaller than the dielectric breakdown voltage Vb (several tens of kilovolts). Become.

  At this time, in a state where the gas flow rate in the cylinder is not so high, that is, lower than the determined flow rate, the shape of the electric spark formed at the time point T1 is almost straight, and the arc discharge ends ( It will be maintained until time T3). In the following description, a state in which a substantially linear electric spark is maintained in the spark discharge portion from the start to the end of the arc discharge is referred to as “normal time”.

  On the other hand, when the gas flow rate is high, that is, equal to or higher than the determination flow rate, as shown in FIG. Between the electrode 51a and the ground electrode 51c, the gas flows in a direction F and may be curved.

  As described above, when the electric spark is flowed and the shape thereof is curved, the path of the electric spark becomes longer compared to the case where the electric spark is formed in a straight line, and the center electrode 51a and the ground electrode 51c. The electrical resistance between the two will increase. For this reason, the discharge sustaining voltage Vk increases as the gas flow rate in the cylinder increases. That is, the discharge sustaining voltage Vk and the gas flow rate have a substantially proportional relationship, and the gas flow rate in the spark discharge portion in the cylinder can be estimated from the discharge sustaining voltage Vk.

  For this reason, when an electric spark is applied as described above, the discharge sustaining voltage Vkf after the start of the arc discharge at the time T1, that is, after the occurrence of the electric spark, is usually as shown by a broken line in FIG. As compared with the discharge sustaining voltage Vkn at the time, the discharge end timing (time T2) is earlier than the normal discharge end (time T3). That is, the gas flow rate of the air-fuel mixture in the cylinder is substantially proportional to the discharge sustaining voltage Vk. When the gas flow rate of the air-fuel mixture in the cylinder is high and an electric spark is flowed, the discharge sustaining voltage is higher than the normal time, and the time from the occurrence of the electric spark to the end of the discharge (hereinafter referred to as the discharge sustaining time). Is shortened).

  When the gas flow rate in the cylinder is equal to or higher than the judgment flow rate and the electric spark of the central spark plug flows, after igniting in the air-fuel mixture, even if it is ignited once with the central spark plug, that is, only one point ignition is performed When the side flame plug is ignited after the central ignition plug is ignited, that is, multi-point ignition is performed, there is a possibility that knocking may occur. Further, in such a case, the electric energy is unnecessarily consumed by performing ignition by the side spark plug.

  In such an internal combustion engine, even if the control parameters indicating the operation state of the internal combustion engine such as the engine speed and the engine load are the same, the combustion state of the air-fuel mixture in the combustion process of each cycle is not changed during the combustion process. May change. For this reason, it is necessary to switch between multipoint ignition and single point ignition during the combustion process in response to a change in the combustion state of the air-fuel mixture in the combustion process of each cycle.

  Therefore, in the control apparatus for an internal combustion engine according to the present embodiment, the function of detecting the secondary voltage applied to the central spark plug and whether the gas flow speed in the cylinder is fast based on the detected secondary voltage. A function for determining whether or not the gas flow speed is equal to or higher than the determination flow speed (gas flow determination means) and it is determined that the gas flow speed in the cylinder is equal to or higher than the determination flow speed Is characterized in that ignition of a side spark plug which is an ignition plug other than the central spark plug is prohibited.

  Ignition control executed by the control device for an internal combustion engine according to the present embodiment will be described with reference to FIGS. 3, 4-1, 7, and 8. FIG. 7 is a timing chart of the secondary voltage applied to the center spark plug and the side spark plug in a normal state. FIG. 8 is a timing chart of the secondary voltage applied to the central spark plug and the side spark plug when the electric spark of the central spark plug is caused to flow by gas flow.

  First, the control device 80 determines the ignition timing of the central spark plug 50 and the discharge maintenance time according to the operating state of the internal combustion engine 10, and ignites the central spark plug 50. Specifically, as shown in FIG. 3, the control device 80 controls the first energy generating device 71 to charge the first capacitor 67 with the electric energy corresponding to the discharge maintaining time, and according to the ignition timing, A signal current is passed through the base of the first transistor 65 and shuts off after a predetermined time has elapsed. In this manner, the control device 80 causes a secondary voltage to be generated in the secondary coil 61c by causing the primary current to flow through the primary coil 61a of the first ignition coil 61 for a predetermined period.

  Then, as shown at time T0 in FIG. 7, the generated secondary voltage starts to be applied to the central spark plug 50 and increases. When the secondary voltage of the central spark plug 50 reaches the required dielectric breakdown voltage Vb (time point T1), a substantially linear electric spark is generated between the center electrode 51a and the ground electrode 51c of the spark discharge portion 51, Ignition of the air-fuel mixture in the cylinder is started. When an electric spark occurs at time T1, the electric resistance between the center electrode 51a and the ground electrode 51c decreases, and the secondary voltage rapidly decreases from the dielectric breakdown voltage Vb to the discharge sustaining voltage Vk.

  Then, the control device 80 determines whether or not the gas flow rate in the cylinder is equal to or higher than the determination flow rate based on the secondary voltage applied to the central spark plug 50. Specifically, control device 80 determines whether or not discharge sustaining voltage Vk, which is a secondary voltage immediately after reaching breakdown voltage Vb (immediately after time T1), is equal to or higher than a predetermined determination voltage Vd. To do.

  The determination voltage Vd is set to a value higher than the sustaining voltage Vkn (see FIG. 4A) when the shape of the linear electric spark is maintained. The determination voltage Vd is obtained in advance by a matching experiment or the like, and is stored in the control device 80 as a control constant. The determination voltage Vd is set corresponding to the determination flow speed for determining whether or not the gas flow speed in the cylinder is fast.

  As shown in FIG. 7, when the discharge sustain voltage immediately after the dielectric breakdown (time T1) is lower than the determination voltage Vd and it is determined that the discharge sustain voltage is not equal to or higher than the determination voltage Vd, the control device 80 causes the central spark plug to It is determined that no electric spark is flowing in the 50 spark discharge portions 51 and the gas flow rate in the cylinder is not so high, and the ignition of the side spark plug is permitted.

  Specifically, the control device controls the second transistor 66 to cause the electric charge stored in the second capacitor 68 to flow through the primary coil 62a of the second ignition coil 62 for a predetermined time, thereby causing the secondary coil 62c to flow. To generate a secondary voltage. Thereby, the control apparatus 80 will form an electric spark in the spark discharge part 55 of a side spark plug, and will perform multipoint ignition.

  On the other hand, as shown in FIG. 8, when the discharge sustaining voltage Vk immediately after dielectric breakdown (time T1) exceeds the determination voltage Vd, and it is determined that the discharge sustaining voltage Vk is equal to or higher than the determination voltage Vd, the control device 80 Determines that the spark is flowing in the spark discharge portion 51 of the central spark plug and that the gas flow rate in the cylinder is high, and prohibits ignition of the side spark plug.

  The control device 80 performs a one-point ignition in which only the central spark plug 50 is ignited in the cycle without performing ignition of the side spark plug by controlling the base transistor not to flow through the second transistor 66. Become. In this case, since the gas flow speed in the cylinder is fast, the flame propagation speed (combustion speed) due to the ignition of the central spark plug 50 is also sufficiently fast, so it is necessary to perform multipoint ignition by ignition of the side spark plug. There is no.

  The ignition control described above is performed for each combustion process of each cycle of the internal combustion engine. The internal combustion engine 10 first ignites from the central spark plug 50 and then ignites the side spark plug in each cycle of each cylinder. In each cycle of each cylinder, whether or not the second and subsequent ignitions are performed according to the gas flow rate in the cylinder at the time of ignition of the central spark plug 50 that is the first (first) ignition, that is, multipoint Whether or not to fire can be determined. When it is determined that the gas flow rate in the cylinder is equal to or higher than the determination flow rate at the time of ignition of the first point (central spark plug 50), it is unnecessary by prohibiting ignition after the second point, that is, multipoint ignition. Multi-point ignition can be reduced, and the electrical energy required for ignition can be saved.

  As described above, in the present embodiment, the control device 80 detects the secondary voltage applied to the central spark plug 50 (first spark plug) (secondary discharge detection means) and the detected 2 A function of determining whether or not the gas flow rate is high based on the next voltage, that is, whether or not the gas flow rate in the cylinder is equal to or higher than the determination flow rate, (gas flow determination means), When it is determined to be fast, that is, to be equal to or higher than the determined flow speed, ignition of a side spark plug that is a spark plug other than the first spark plug is prohibited.

  When the gas flow rate is fast and the flame propagates sufficiently quickly with only the central spark plug 50 (first spark plug), ignition of the side spark plugs (ignition plugs other than the first spark plug) is prohibited. That is, multipoint ignition is prohibited. By switching between multi-point ignition and single-point ignition during the combustion process in response to changes in the combustion state of the air-fuel mixture, unnecessary ignition can be reduced and the electrical energy required for ignition can be reduced. it can.

  Further, in this embodiment, when the discharge sustaining voltage Vk, which is the secondary voltage after dielectric breakdown, becomes equal to or higher than the determination voltage Vd, it is determined that the gas flow speed in the cylinder is equal to or higher than the determination flow speed. Therefore, it is possible to determine whether or not the gas flow rate is fast immediately after the secondary voltage applied to the central spark plug 50 (first spark plug) reaches the dielectric breakdown voltage Vb. Switching between single-point ignition and multi-point ignition can be determined at an early point in time immediately after dielectric breakdown of the first spark plug.

  In this embodiment, when the discharge sustaining voltage Vk, which is the secondary voltage after reaching the dielectric breakdown voltage Vb, is equal to or higher than the determination voltage, it is determined that the gas flow rate in the cylinder is high. However, the method (gas flow determination means) for determining whether or not the gas flow is equal to or higher than the determination flow speed is not limited to this. For example, the gas flow in the cylinder depends on whether or not the secondary voltage (discharge sustaining voltage) after the elapse of a predetermined time after the secondary voltage applied to the first spark plug is equal to or higher than the determination voltage Vb. It can also be determined whether or not the speed is greater than or equal to the determined flow speed.

  In this embodiment, it is determined whether the gas flow rate in the cylinder is equal to or higher than the determination flow rate depending on whether the discharge sustain voltage is equal to or higher than the determination voltage Vd. The threshold value setting method for determining whether or not is fast is not limited to this. For example, it can be determined whether or not the secondary voltage is zero, that is, whether or not the discharge has been completed, after a predetermined time has elapsed since the generation of the secondary voltage. When the electric spark is caused to flow by the gas flow, the gas flow rate in the cylinder is equal to or higher than the judgment flow rate by utilizing the fact that the discharge ends earlier (see time point T2 in FIG. 8) compared to the normal time when the electric spark is not flown. It can be determined whether there is, that is, whether it is fast.

  Ignition control executed by the control device according to the present embodiment will be described with reference to FIGS. 3, 4-2, 9 and 10. FIG. 9 is a timing chart of the secondary current flowing through the center spark plug and the side spark plug in a normal state. FIG. 10 is a timing chart of the secondary current flowing through the central spark plug and the side spark plug when the electric spark of the central spark plug is applied. The ignition control according to the present embodiment is different from the ignition control according to the first embodiment in that it is determined whether or not the gas flow speed in the cylinder is equal to or higher than the determination flow speed based on the secondary current flowing through the central spark plug. The details will be described below. In addition, about the structure substantially common with Example 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  First, the control device 80 causes a secondary voltage to be generated in the secondary coil 61c by flowing a primary current through the primary coil 61a of the first ignition coil 61 for a predetermined period. Then, the generated secondary voltage is applied to the central spark plug 50 from time T0 shown in FIG. 9, and reaches the required dielectric breakdown voltage Vb at time T1.

  When the required dielectric breakdown voltage is reached at time T1, a linear electric spark is generated between the center electrode 51a and the ground electrode 51c in the spark discharge portion 51 of the central spark plug 50, and arc discharge is started. The next current Ib flows. When the secondary current starts to flow at time T1, the secondary current that flows through the central spark plug 50 also decreases at the time of arc discharge start as the secondary voltage suddenly drops from the breakdown voltage Vb to the discharge sustaining voltage Vk. It drops rapidly from the current Ib.

  Based on the secondary current flowing through the central spark plug 50, the control device 80 determines whether or not the gas flow speed in the cylinder is equal to or higher than the determination flow speed, that is, whether or not it is fast. Specifically, the control device 80 starts arc discharge in the spark discharge portion 51 of the central spark plug 50, that is, from the time T1 when the secondary current Ib is generated in the central spark plug 50, for a predetermined time (the length of time in the figure). It is determined whether or not the secondary current flowing through the central spark plug 50 is zero or less than or equal to a predetermined current at a time Td after the elapse (indicated by TL).

  Note that the predetermined time length TL is, as shown in FIG. 4B, from the start of arc discharge (time T1) to the end of discharge (time T3 when the shape of the linear electric spark is maintained until the end of discharge. ) Is set to a longer time. That is, the time Td is set to be earlier than the time T3. The time length TL and the gas flow rate have a substantially inversely proportional relationship. The time length TL or the determination time point Td is obtained in advance by a matching experiment or the like, and is stored in the control device 80 as a control constant.

  As shown in FIG. 9, it is determined that the secondary current after the lapse of the predetermined time TL is not zero or more than the predetermined current from the start of the arc discharge, that is, the time T1 when the secondary current is generated in the central spark plug 50. In this case, the control device 80 determines that no electric spark is flowing in the spark discharge portion 51 of the central spark plug 50 and the gas flow rate in the cylinder is not so fast, and the side spark plug (spark discharge) Allow ignition of part 55).

  Specifically, the control device 80 controls the second transistor 66 to flow through the primary coil 62a of the second ignition coil 62 for a predetermined time to generate a secondary voltage in the secondary coil 62c. Thereby, the control apparatus 80 forms an electric spark in the spark discharge part 55 of the side ignition plug, and performs multipoint ignition.

  On the other hand, as shown in FIG. 10, when it is determined that the secondary current after the lapse of the predetermined time TL is zero from the start of arc discharge, that is, the time T1 when the secondary current is generated in the central spark plug 50, the control device 80, an electric spark is flowing in the spark discharge portion 51 of the central spark plug 50, and it is determined that the gas flow speed in the cylinder is equal to or higher than the determination flow speed, and the ignition of the side spark plug is prohibited.

  The control device 80 performs a one-point ignition in which only the central spark plug 50 is ignited in the combustion process of the cycle by controlling the side spark plug not to be ignited. In this case, since the gas flow speed in the cylinder is fast, the flame propagation speed (combustion speed) by ignition of the central spark plug 50 is also sufficiently fast, and ignition is performed with the side spark plug, that is, multipoint ignition is performed. There is no need.

  The ignition control described above is performed for each cycle of the internal combustion engine. In the combustion process of each cycle, whether or not the second and subsequent ignitions are performed according to the gas flow rate in the cylinder at the time of ignition of the central spark plug 50 that is the first ignition, that is, multipoint ignition is performed. It is determined whether or not. When it is determined that the gas flow rate in the cylinder is fast at the time of ignition of the first point (central spark plug 50), unnecessary ignition is reduced by prohibiting ignition after the second point, that is, multipoint ignition, Electric energy required for ignition of the second and subsequent points (side spark plugs) can be saved.

  As described above, in this embodiment, the controller 80 detects the secondary current flowing through the central spark plug 50 (first spark plug) (secondary discharge detection means) and the detected secondary current. When the gas flow rate in the cylinder is high, that is, whether the gas flow rate in the cylinder is higher than the determination flow rate (gas flow determination means), Is to prohibit ignition of a side spark plug that is an ignition plug other than the first spark plug.

  When the gas flow rate is fast and the flame propagates sufficiently quickly with only the central spark plug 50 (first spark plug), ignition of the side spark plugs (ignition plugs other than the first spark plug) is prohibited. That is, multipoint ignition is prohibited. By switching between multi-point ignition and single-point ignition during the combustion process in response to changes in the combustion state of the air-fuel mixture, unnecessary ignition can be reduced and the electrical energy required for ignition can be reduced. it can.

  Further, in this embodiment, when the secondary current after the elapse of a predetermined time from the generation is zero, it is determined that the gas flow speed in the cylinder is equal to or higher than the determination flow speed, and therefore flows through the spark plug. Only by detecting the presence or absence of the secondary current, it is possible to determine whether or not the gas flow speed in the cylinder is equal to or higher than the determination flow speed. There is no need for the control device 80 to detect a secondary voltage that is a high voltage, and a control device that can easily determine whether or not the gas flow rate in the cylinder is equal to or higher than the determination flow rate can be realized.

  It should be noted that when the secondary current after the elapse of a predetermined time from the generation is equal to or less than the predetermined current, it can be determined that the gas flow speed in the cylinder is equal to or higher than the determination flow speed. After a relatively short time has elapsed from the secondary current, that is, at a relatively early timing from the start of arc discharge (time point T1), it can be determined whether or not the gas flow rate is equal to or higher than the determination flow rate.

  In each of the above-described embodiments, the spark plug 55 is disposed between the outer edge 24e of the intake port 24 and the outer edge 26e of the exhaust port 26 in the side wall spark plug 22c. However, the arrangement of the side spark plugs is not limited to this. The spark discharge part 55 should just be arrange | positioned in the ceiling wall peripheral part 22c of the cylinder head 20, for example, between the outer edges 24e of the two adjacent intake ports 24 in the ceiling wall peripheral part 22c. It is also preferable to arrange the spark discharge portion 55.

  Further, in each of the above-described embodiments, one side spark plug (spark discharge portion 55) is provided at the ceiling wall peripheral portion 22c. However, the number of side spark plugs is not limited to this. . In the side spark plug, the spark discharge portion 55 may be disposed on the peripheral edge portion 22c of the ceiling wall. For example, in the ceiling wall peripheral portion 22c, the spark discharge portion 51 of the central spark plug 50 is centered in the crankshaft direction S. It is also preferable to arrange two side spark plugs on both sides.

  In each of the above-described embodiments, the central spark plug 50 is first ignited, and then it is determined whether or not the side spark plug is ignited. The order is not limited to this. For example, whether or not the gas flow rate is fast based on the secondary voltage applied to the side spark plug at this time or the secondary current flowing in the side spark plug at the time when the side spark plug is first ignited. That is, it is possible to determine whether or not the flow rate is equal to or higher than the determined flow speed and determine whether or not to execute ignition of the central spark plug 50.

  As described above, the present invention is useful for an internal combustion engine having a plurality of spark plugs for each cylinder, and is particularly suitable for an internal combustion engine capable of igniting the spark plugs sequentially from the first spark plug in each cylinder. .

1 is a cross-sectional view illustrating a schematic configuration around a cylinder of an internal combustion engine according to a first embodiment. It is a figure which shows the arrangement | positioning relationship of the center spark plug of the internal combustion engine which concerns on Example 1, and a side spark plug, and an intake / exhaust valve, and is the figure which looked at the ceiling wall of the cylinder head from the piston side. 1 is a schematic diagram illustrating a configuration of an ignition system for an internal combustion engine according to a first embodiment. It is a figure which shows the relationship between the secondary voltage which the ignition coil which concerns on Example 1 applies to an ignition plug, and time. It is a figure which shows the relationship between the secondary current which flows into the ignition plug which concerns on Example 1, and time. It is an enlarged view of the spark discharge part of the central spark plug which concerns on Example 1, and is a figure which shows the aspect of the electric spark (arc) in normal time. It is an enlarged view of the spark discharge part of the central spark plug which concerns on Example 1, and is a figure which shows the aspect by which the electric spark was poured by the gas flow in cylinders, such as air-fuel | gaseous mixture. 2 is a timing chart of secondary voltages applied to a central spark plug and a side spark plug in a normal state in the first embodiment. It is a timing chart of the secondary voltage applied to a center spark plug and a side spark plug when the electric spark of a center spark plug is flowed by gas flow in Example 1. 6 is a timing chart of secondary current flowing through a central spark plug and a side spark plug in a normal state in Embodiment 2. 6 is a timing chart of a secondary current flowing through the central spark plug and the side spark plug when an electric spark of the central spark plug is flowed in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder block 14 Cylinder bore 20 Cylinder head 22 Combustion chamber ceiling wall 22a Ceiling wall center part 22c Ceiling wall peripheral part 24 Intake port 25 Intake valve 26 Exhaust port 27 Exhaust valve 30 Piston 40 Combustion chamber 50 Central spark plug 1 spark plug)
51 Spark discharge part of central spark plug 51a Center electrode 51c Ground electrode 55 Spark discharge part of side spark plug 60 Ignition system of internal combustion engine 61 First ignition coil 61a Primary coil 61c Secondary coil 62 Second ignition coil 62a Primary coil 62c Secondary coil 65 First transistor 66 Second transistor 67 First capacitor 68 Second capacitor 71 First energy generator 72 Second energy generator 80 Electronic control device (control device) for internal combustion engine
Vb Dielectric breakdown voltage (secondary voltage, required voltage)
Vk discharge sustaining voltage (secondary voltage)

Claims (5)

In an internal combustion engine that includes a plurality of spark plugs for each cylinder and can ignite the spark plugs sequentially from the first spark plug in each cylinder.
Secondary discharge detection means for detecting a secondary current flowing through the first spark plug or a secondary voltage applied to the first spark plug;
Gas flow determination means for determining whether or not the gas flow speed in the cylinder is equal to or higher than the determination flow speed based on the detected secondary current or secondary voltage;
When it is determined that the gas flow speed is equal to or higher than the determination flow speed, ignition prohibiting means for prohibiting ignition of spark plugs other than the first spark plug;
A control apparatus for an internal combustion engine, comprising: The control apparatus for an internal combustion engine according to claim 1,
Gas flow judgment means
A control apparatus for an internal combustion engine, characterized in that, when a discharge sustaining voltage that is a secondary voltage after reaching a dielectric breakdown voltage becomes equal to or higher than a determination voltage, it is determined that a gas flow rate is equal to or higher than a determination flow rate. . The control device for an internal combustion engine according to claim 1 or 2,
Gas flow judgment means
A control device for an internal combustion engine, characterized in that, when a secondary voltage after a predetermined time has elapsed from occurrence becomes equal to or higher than a determination voltage, the gas flow speed is determined to be equal to or higher than a determination flow speed. The control apparatus for an internal combustion engine according to claim 1,
Gas flow judgment means
A control apparatus for an internal combustion engine, characterized in that, when a secondary current after a predetermined time has elapsed from occurrence is less than or equal to a predetermined current, the gas flow rate is determined to be equal to or higher than a determined flow rate. The control device for an internal combustion engine according to any one of claims 1 to 4,
The internal combustion engine
The spark discharge part of the first spark plug is disposed in the center of the ceiling wall of the combustion chamber,
The spark discharge part of the spark plug other than the first spark plug is disposed on the peripheral edge of the ceiling wall of the combustion chamber.
A control device for an internal combustion engine.

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