JP7334636B2 - Pre-chamber ignition system - Google Patents

Description

The present invention relates to a pre-combustion chamber type ignition system that ignites fuel in a pre-combustion chamber of a combustion chamber divided into a main chamber and a pre-combustion chamber.

The pre-combustion chamber type ignition system has a partition wall that divides the combustion chamber of the engine into a pre-combustion chamber and a main chamber, a spark plug that ignites the fuel in the pre-combustion chamber, and an ignition control section that controls the spark plug. In some cases, the partition wall is provided with a communication hole for communicating the sub-chamber and the main chamber. As a document showing such a technique, there is the following Patent Document 1.

JP 2009-270541 A

In the above pre-chamber ignition system, first, the flame ignites the fuel in the pre-chamber and spreads in the pre-chamber, and then the flame is ejected from the communication hole into the main chamber and the flame spreads in the main chamber. become. Therefore, the time from ignition to spread of the flame in the main chamber becomes longer. Such a problem becomes particularly conspicuous when the load applied to the engine is low. That is, when the load is low, such as when the accelerator pedal is not depressed, the amount of fuel supplied to the combustion chamber is reduced. This is because the progress of combustion in the main chamber slows down. Therefore, when the load is low in the pre-combustion chamber type ignition system, the time from ignition to spread of the flame in the main chamber becomes noticeably longer.

Therefore, the present inventor has noticed that the following problem occurs when the optimal ignition control described below is attempted in a low load state in the pre-combustion chamber type ignition system. Hereinafter, the timing at which the spark plug ignites is referred to as "ignition timing", and the timing after the ignition timing at which a predetermined amount of fuel in the combustion chamber is burned is referred to as "combustion timing". The time from ignition timing to combustion timing is defined as "combustion time".

In the optimum ignition control, the optimum ignition timing, which is earlier than the optimum combustion timing by the combustion time, is calculated. Control the ignition timing to its optimum ignition timing. However, when the load is low in the pre-combustion chamber type ignition system, as described above, the time from ignition to spread of the flame in the main chamber increases, resulting in a longer combustion time. As a result, the optimum ignition timing, which is earlier than the optimum combustion timing by the combustion time, becomes too early.

If the calculated optimum ignition timing is too early, it becomes practically impossible to control the ignition timing to the optimum ignition timing. When actual ignition occurs at the optimum ignition timing, the amount of combustion before the compression top dead center, that is, in the compression stroke, becomes too large, and the reverse torque generated by that combustion, that is, the reverse torque applied in the direction of damping the rotation of the engine. This is because the directional torque cancels out some of the engine torque and reduces the torque.

Therefore, when the load is low in the pre-chamber type ignition system, there is no choice but to control the ignition timing to a timing later than the optimum ignition timing. However, in that case, the combustion timing becomes later than the optimum combustion timing, making it impossible to efficiently obtain torque.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its main object is to control the ignition timing to the optimum ignition timing even when the load is low in the pre-chamber type ignition system.

The pre-combustion chamber type ignition system of the present invention applies a voltage to a partition dividing a combustion chamber of an engine into a pre-combustion chamber and a main chamber, and to a predetermined discharge gap to generate discharge sparks, thereby igniting fuel in the pre-combustion chamber. It has a spark plug that ignites and an ignition control section that controls the spark plug. A communication hole is formed in the partition wall to allow communication between the sub-chamber and the main chamber.

Hereinafter, a state in which the load applied to the engine is a predetermined magnitude is defined as a high load state, and a state in which the load applied to the engine is less than the predetermined magnitude is referred to as a low load state. Further, the timing at which the spark plug starts discharging in the discharge gap is ignition timing, and the timing at which a predetermined amount of fuel in the combustion chamber is burned after the ignition timing is combustion timing. The time from the ignition timing to the combustion timing is defined as the combustion time.

The ignition control unit calculates an optimum ignition timing that is earlier than the optimum combustion timing as the optimum combustion timing by the combustion time, and performs optimum ignition control that controls the ignition timing to the optimum ignition timing, This is done in the high load state.

Hereinafter, the timing between the ignition timing and the combustion timing at which the flame generated in the auxiliary chamber starts to be ejected from the communicating hole into the main chamber is defined as ejection timing. Then, the time from the ignition timing to the ejection timing is defined as the ejection time.

The ignition control unit has an injection control unit that performs an injection delay suppression control that suppresses the injection time from becoming longer in the low load state than in the high load state. In the low load state, the injection delay suppression control is performed by the injection control unit to suppress the combustion time from becoming longer than in the high load state, and the ignition control unit controls the Optimal ignition control.

According to the present invention, it is possible to prevent the combustion time from becoming longer than in the high load state by performing the injection delay suppression control in the low load state. Therefore, it is possible to prevent the optimal ignition timing, which is earlier than the optimal combustion timing by the combustion time, from becoming too early. As a result, it is possible to control the ignition timing to the optimum ignition timing even when the load is low in the pre-chamber type ignition system. By actually performing the optimum ignition control, the ignition timing is controlled to the optimum ignition timing. As a result, the combustion timing is controlled to the optimum combustion timing, and torque can be efficiently generated.

Sectional drawing which shows the ignition system of 1st Embodiment Sectional view showing the pre-chamber and its surroundings A circuit diagram showing a spark plug and its peripheral circuits Timing chart showing ignition by spark plug Graph showing control of discharge energy Cross-sectional view showing the pre-chamber and its surroundings in ignition control before top dead center Cross-sectional view showing the pre-chamber and its surroundings in ignition control after top dead center Graph showing flow velocity change of continuous air flow Timing chart showing progress of combustion Flowchart showing control by the ignition control section

Next, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments, and can be modified as appropriate without departing from the gist of the invention.

[First embodiment]
FIG. 1 is a sectional view showing a pre-chamber ignition system 70 of the first embodiment. This pre-chamber type ignition system 70 is installed with respect to the engine 90 . The engine 90 is a four-stroke engine in which one combustion cycle consists of four strokes of intake stroke→compression stroke→expansion stroke→exhaust stroke. Hereinafter, the top dead center between the compression stroke and the expansion stroke is referred to as "compression top dead center tD". The engine 90 has a cylinder 10 and a head 20 attached to the top thereof.

In the following description, the longitudinal direction of the center line X of the cylinder 10 is defined as the up-down direction in accordance with the drawings. However, for example, the engine 90 and the pre-chamber type ignition system 70 are installed with the center line X oblique to the vertical direction, or the engine 90 and the pre-chamber type ignition system 70 are installed with the center line X horizontal. , etc., the engine 90 and the pre-chamber ignition system 70 can be installed in any orientation.

A piston 18 is installed in the cylinder 10 . The piston 18 is connected to the crankshaft 11 via the link 12 and moves up and down as the crankshaft 11 rotates. A combustion chamber 30 is formed above the piston 18 .

The head 20 is provided with an intake passage 21 for drawing gas into the combustion chamber 30 and an exhaust passage 29 for discharging the gas from the combustion chamber 30 . An intake valve 24 is installed in the intake passage 21 and an exhaust valve 26 is installed in the exhaust passage 29 . The intake valve 24 is driven by the intake cam 23 and the exhaust valve 26 is driven by the exhaust cam 27 . A fuel injection device 22 for injecting fuel into the intake passage 21 is installed in the head 20 .

The pre-chamber type ignition system 70 includes the spark plug 40 attached to the head 20, the airflow support structure As for making it easier for the airflow to flow into the discharge gap 45 of the spark plug 40, sensors 51 to 53, and sensors and an ignition control unit 60 that controls the spark plug 40 based on inputs from 51-53.

Each sensor 51 - 53 includes a crank sensor 51 , an intake pressure sensor 52 and a water temperature sensor 53 . A crank sensor 51 detects the crank angle and the rotational speed of the engine 90 . The intake pressure sensor 52 detects the intake pressure, which is the atmospheric pressure of the intake passage 21 . Water temperature sensor 53 detects the temperature of cooling water for cooling engine 90 .

The ignition control unit 60 is a part of an ECU (electronic control unit) or the like, and has an ejection control unit 63 and an airflow control unit 64 . The ejection control unit 63 controls an ejection time t13, which is the time from when the spark plug 40 ignites the fuel in the auxiliary chamber 38 until the flame starts to be ejected into the main chamber.
Specifically, the injection control unit 63 controls the load applied to the engine 90, the air-fuel ratio of the engine 90, the amount of EGR that is the amount of returning the exhaust gas back to the intake air in the engine 90, and the water temperature of the cooling water of the engine 90. and so on, control is performed so that the fluctuation of the ejection time t13 is reduced even by fluctuations in those parameters. The above load may be calculated, for example, from the amount of depression of the accelerator pedal, may be directly detected from the load applied to the engine 90, or may be calculated from changes in the rotational speed of the engine 90. . The airflow control section 64 controls the spark plug 40 so that the discharge spark F of the spark plug 40 is not interrupted even by the airflow from the airflow support structure As.

FIG. 2 is a sectional view showing the auxiliary chamber 38 and its surroundings. The spark plug 40 has a center electrode 44 and an insulator 41 provided on the outer peripheral side thereof. A partition wall 34 is attached to the lower end of the insulator 41 . The partition wall 34 divides the combustion chamber 30 into a main chamber 31 and an auxiliary chamber 38 . Specifically, the sub-chamber 38 is formed inside the partition wall 34 , and the main chamber 31 is formed outside the partition wall 34 . The partition wall 34 is made of a conductor and also serves as the ground electrode of the spark plug 40 .

A plurality of communication holes 35 are formed in the partition wall 34 , and the auxiliary chamber 38 and the main chamber 31 communicate with each other through the plurality of communication holes 35 . A central communication hole 35c, which is one of the plurality of communication holes 35, is provided on the center line X of the cylinder 10 and penetrates the partition wall 34 in the vertical direction.

The lower end of the center electrode 44 is positioned just above the central communication hole 35c. That is, the lower portion of the center electrode 44 extends downward from the lower end of the insulator 41 and is close to the central communication hole 35c. A discharge gap 45 is formed between the lower end of the center electrode 44 and the peripheral portion of the upper end of the central communication hole 35c in the partition wall 34 . Therefore, the discharge gap 45 is provided in the immediate vicinity of the central communication hole 35c in the auxiliary chamber 38, and is closest to the central communication hole 35c among the plurality of communication holes 35. As shown in FIG.

Since the discharge gap 45 is close to the central communication hole 35 c in this way, the airflow can easily flow through the discharge gap 45 . This structure constitutes the airflow support structure As. That is, as the airflow support structure As, a structure is formed in which the discharge gap 45 is close to the central communication hole 35c. The spark plug 40 generates a discharge spark F by applying a voltage to its discharge gap 45 . The discharge spark F is extended by the airflow from the airflow support structure As, thereby improving the ignitability of the fuel.

FIG. 3 is a circuit diagram showing the circuit of the spark plug 40 and its periphery. Spark plug 40 has primary coil 412 and secondary coil 421 . Primary coil 412 and secondary coil 421 are wound around core 401 . A battery 411 and a switching element 413 are connected in series to the primary coil 412 . On the other hand, the secondary coil 421 is connected in series with the discharge gap 45 and the diode 422 . The switching element 413 is controlled by the ignition control section 60 .

Hereinafter, the direction in which the current flows in the secondary coil 421 when the switching element 413 is turned off from ON is called "forward direction", and the opposite direction is called "reverse direction". Diode 422 is oriented to allow current flow in the forward direction and block current flow in the reverse direction.

FIG. 4 is a timing chart showing control of the spark plug 40. As shown in FIG. As shown in FIG. 4A, when the ignition signal becomes High at a predetermined energization timing t0, the ignition control unit 60 turns on the switching element 413 accordingly. As a result, the primary current shown in FIG. 4B begins to flow through the primary coil 412, and the primary current increases over time. As a result, the discharge energy E is stored in the form of magnetic energy in the primary coil 412, as shown in FIG. 4(e). Then, the ignition signal shown in FIG. 4(a) becomes Low at the ignition timing t1 after the energization timing t0 by the predetermined charging time t01. As a result, a secondary voltage shown in FIG. As a result, a secondary current shown in FIG. Thereafter, as shown in FIG. 4(e), the discharge energy E stored as magnetic energy decreases as the secondary current shown in FIG. 4(d) flows. size is also reduced.

Next, control of the discharge energy E applied to the discharge gap 45 will be described with reference to FIG. FIG. 5(a) is a graph showing temporal changes in the primary current when the discharge energy E is controlled to be relatively small, and FIG. 5(b) is a graph showing the primary current when the discharge energy E is controlled to be relatively large. It is a graph which shows the time change of an electric current. As shown in FIG. 5A, when the discharge energy E is controlled to be relatively small, the charging time t01 is set relatively short, and as shown in FIG. If the control is to be relatively large, the charging time t01 is set relatively long. The ejection control section 63 and the airflow control section 64 control the discharge energy E by the above control.

FIG. 6 is a sectional view showing the pre-chamber 38 and its surroundings in pre-top dead center ignition control in which ignition is performed before compression top dead center tD (that is, in the compression stroke). Such pre-top dead center ignition control is normally performed. Below, the airflow flowing through the central communication hole 35c is referred to as "communication airflow A". At the time of ignition in this pre-top dead center ignition control, an upward communication airflow A flowing from the main chamber 31 side to the sub chamber 38 side flows into the discharge gap 45 . Due to the communicating airflow A, the discharge spark F extends upward in the pre-chamber 38 . The extended discharge spark F ignites the fuel in the auxiliary chamber 38 . The flame generated in the pre-chamber 38 thereby propagates in the pre-chamber 38 and is then emitted into the main chamber 31 through the communication holes 35 .

FIG. 7 is a cross-sectional view showing the pre-chamber 38 and its surroundings in post-top dead center ignition control in which ignition is performed after compression top dead center tD (that is, in the expansion stroke). Such post-top dead center ignition control is performed when the engine 90 is in a predetermined operating condition such as during fast idling. During fast idling, after the engine 90 has started, the idling speed is made higher than normal for purposes such as warming up the catalyst. At the time of ignition in this after-top-dead-center ignition control, a downward communicating air flow A flowing from the auxiliary chamber 38 side to the main chamber 31 side flows into the discharge gap 45 . Due to the communicating air flow A, the discharge spark F extends from inside the auxiliary chamber 38 to inside the main chamber 31 through the central communicating hole 35c. The extended discharge spark F ignites the fuel in both the auxiliary chamber 38 and the main chamber 31 .

FIG. 8 is a graph showing an image of changes in flow velocity (absolute value) of the continuous air flow A. FIG. The flow velocity flowing through the discharge gap 45 is approximately proportional to the flow velocity of this communicating air flow A. As shown in FIG. Specifically, in the latter half of the compression stroke, the gas in the main chamber 31 flows intensively through the communication holes 35 including the central communication hole 35c, so that the communication air flow A is generated in the main chamber 31 and the auxiliary chamber 38 in the latter half of the compression stroke. Stronger than the internal air current. Therefore, the air current flowing through the discharge gap 45 adjacent to the central communication hole 35c is also stronger than the air currents in the main chamber 31 and the auxiliary chamber 38 . After that, as shown in FIG. 8, the flow velocity of the communication airflow A decreases as it approaches the compression top dead center tD, and once becomes substantially zero at or near the compression top dead center tD. However, the open airflow A quickly reappears after compression top dead center tD. When the piston 18 starts to descend and an air pressure difference begins to occur between the sub-chamber 38 and the main chamber 31, the gas in the sub-chamber 38 conversely passes through the central communication hole 35c. This is because the concentrative flow to each communication hole 35 causes rapid generation.

The pre-chamber type ignition system 70 positively utilizes this communication air flow A to allow the air flow to flow in the discharge gap 45 . That is the airflow support structure As described above. As described above, the communication airflow A becomes stronger as the distance from the compression top dead center tD increases. Specifically, before compression top dead center tD, that is, in the latter half of the compression stroke, the more the crank angle advances from compression top dead center tD, the stronger the airflow flowing through discharge gap 45 becomes. On the other hand, after the compression top dead center tD, that is, in the first half of the expansion stroke, the more retarded the crank angle from the compression top dead center tD, the stronger the airflow flowing through the discharge gap 45 becomes. Therefore, the further the ignition timing t1 is from the compression top dead center tD, the easier it is for the discharge spark F to blow out. Therefore, the airflow control section 64 controls the discharge energy E so that the discharge spark F is not interrupted by the airflow.

Specifically, during the ignition control before top dead center, that is, when ignition is performed in the latter half of the compression stroke, the airflow control unit 64 reduces the The discharge energy E is controlled to increase when the ignition timing t1 is earlier than the predetermined timing. More specifically, for example, control is performed so that the discharge energy E increases as the ignition timing t1 advances.

On the other hand, the anti-airflow control unit 64 controls the ignition timing t1 during the ignition control after top dead center, that is, when ignition is performed in the first half of the expansion stroke, compared to the case where the ignition timing t1 is the predetermined timing. is later than the predetermined timing, the discharge energy E is controlled to increase. More specifically, for example, control is performed so that the discharge energy E increases as the ignition timing t1 becomes later.

FIG. 9 is a timing chart showing the progress of combustion in ignition control before top dead center. Hereinafter, the timing at which the spark plug 40 applies the voltage to the discharge gap 45 is referred to as "ignition timing t1". Further, the timing at which the fuel is ignited by the discharge spark F after the ignition timing t1 is defined as "pre-chamber ignition timing t2". In addition, the timing at which the flame generated in the pre-chamber 38 starts jetting into the main chamber 31 from the communication hole 35 after the pre-chamber ignition timing t2 is defined as "ejection timing t3". Further, the timing at which the fuel in the main chamber 31 starts to be ignited by the ejected flame after the ejection timing t3 is defined as "main chamber ignition timing t4". Also, the timing at which a predetermined amount (for example, 50% of the mass) of the fuel in the combustion chamber 30 is burned after the main chamber ignition timing t4 is defined as "combustion timing t5".

A period from ignition timing t1 to pre-combustion chamber ignition timing t2 is defined as "spark stage period t12". Also, the period from the pre-chamber ignition timing t2 to the ejection timing t3 is defined as "pre-chamber propagation period t23". Also, the period from jetting timing t3 to main chamber ignition timing t4 is defined as "flame jetting period t34". A period from main chamber ignition timing t4 to combustion timing t5 is defined as "main chamber propagation period t45". Also, the time from ignition timing t1 to ejection timing t3 is defined as "ejection time t13". Also, the time from ignition timing t1 to combustion timing t5 is defined as "combustion time t15".

FIGS. 9(a) and 9(b) are timing charts showing the progress of combustion in ignition control before top dead center in a comparative example. In the comparative example, members that are the same as or correspond to those of the first embodiment are denoted by the same reference numerals. The pre-chamber ignition system 70 of the comparative example differs from that of the present embodiment in that it does not have the airflow support structure As shown in FIG. That is, the pre-chamber ignition system 70 of the comparative example has a shorter center electrode 44 than the present embodiment, and has a ground electrode separate from the partition wall 34 . Therefore, the discharge gap 45 is not close to the central communication hole 35c. Furthermore, the auxiliary chamber type ignition system 70 of the comparative example differs from the present embodiment in that the ignition control section 60 shown in FIG.

FIG. 9(a) is a timing chart showing the progress of combustion in a high load state in ignition control before top dead center in a comparative example. Here, the ignition control section 60 performs the following optimum ignition control. In the optimum ignition control, first, optimum combustion timing T5 is acquired as optimum combustion timing t5. The optimum combustion timing T5 is, for example, the combustion timing t5 at which the torque obtained is substantially maximum, and more specifically, for example, the timing 10CA (crank angle) after the compression top dead center tD. Next, the combustion time t15 is calculated. The details will be described later. Next, the optimum ignition timing T1, which is earlier than the optimum combustion timing T5 by the combustion time t15, is calculated. Next, the ignition timing t1 is controlled to the optimum ignition timing T1. By the above optimum ignition control, the combustion timing t5 is controlled to the optimum combustion timing T5.

FIG. 9(b) is a timing chart showing the progress of combustion in a low load state in ignition control before top dead center in the comparative example. Here, if the optimal ignition timing T1, which is earlier than the optimal combustion timing T5 by the combustion time t15, is calculated by the optimal ignition control, the optimal ignition timing T1 is too early. Therefore, if ignition occurs at this optimum ignition timing T1, the amount of combustion before compression top dead center tD, that is, in the compression stroke, becomes too large, and the reverse torque generated by the combustion causes the torque of engine 90 to decrease. Torque is reduced due to cancellation. Therefore, in this low load state, optimal ignition control cannot be performed, and the ignition timing t1 is controlled to be later than the optimal ignition timing T1. As a result, the timing later than the optimum combustion timing T5 becomes the combustion timing t5.

FIG. 9(c) is a timing chart showing the progress of combustion in a high load state in ignition control before top dead center in this embodiment. Also in this embodiment, the same optimum ignition control as in the comparative example is performed. However, since the present embodiment includes the airflow support structure As, the discharge spark F is extended compared to the high load state of the comparative example shown in FIG. 9(a). As a result, the ignitability in the pre-chamber 38 is improved, and the spark stage period t12 before the pre-chamber ignition timing t2 is shortened. Furthermore, the extension of the discharge spark F strongly and firmly ignites the fuel in the pre-chamber 38 . As a result, the flame propagates easily in the pre-chamber 38, and the pre-chamber propagation period t23 is also shortened. As described above, the ejection time t13 is shortened. Furthermore, along with this, the flame ejection period t34 and the main chamber propagation period t45 are also slightly shortened. Due to the action of the airflow support structure As described above, the combustion time t15 becomes shorter than in the high load state of the comparative example shown in FIG. 9(a).

At this time, if the ignition timing t1 is the same as in the high load state of the comparative example shown in FIG. 9(a) as indicated by the dashed line in FIG. It becomes earlier than the timing T5. Therefore, in this embodiment, compared to the comparative example, the ignition timing t1 is controlled by the optimum ignition control so that the ignition timing t1 is delayed by the shortened combustion time t15.

FIG. 9(d) is a timing chart showing the progress of combustion in a low load state in ignition control before top dead center in this embodiment. Since the present embodiment includes the airflow support structure As, the combustion time t15 is shortened compared to the low load state of the comparative example shown in FIG. 9B. Furthermore, in addition to this, the ejection delay suppression control is performed by the ejection control unit 63 to suppress the ejection time t13 from becoming longer in the low load state than in the high load state, thereby further reducing the combustion time t15. Shorten.

Specifically, when the load is low, the discharge energy E is increased as compared to when the load is high as ejection delay suppression control. As a result, ignitability in the auxiliary chamber 38 is improved. As a result, the spark stage period t12 before the pre-chamber ignition timing t2 is shortened compared to when the ejection delay suppression control is not performed. Furthermore, the increased discharge energy E ignites the fuel in the pre-chamber 38 with a strong flame. Therefore, the flame propagates easily in the pre-chamber 38, and the pre-chamber propagation period t23 is shortened as compared with the case where the ejection delay suppression control is not performed. As a result, the ejection time t13 is shorter than when the ejection delay suppression control is not performed, and accordingly the flame ejection period t34 and the main chamber propagation period t45 are slightly shortened. Due to the effect of the injection delay suppression control as described above, the combustion time t15 is also shortened compared to the low load state of the comparative example shown in FIG. 9(b). That is, due to the effects of both the airflow support structure As and the ejection delay suppression control, the combustion time t15 is significantly shortened compared to the low load state of the comparative example shown in FIG. 9(b).

Therefore, in the low load state of this embodiment shown in FIG. 9D, unlike the low load state of the comparative example shown in FIG. Even if the optimum ignition timing T1 earlier than the optimum combustion timing T5 is calculated, the optimum ignition timing T1 does not become too early. Therefore, even if the ignition timing t1 is controlled to the optimum ignition timing T1, the amount of combustion prior to the compression top dead center tD, that is, in the expansion stroke, will not become excessively large and the counter torque will not become excessively strong. . Therefore, in this embodiment, optimum ignition control can be performed even in a low load state. By actually performing the optimum ignition control, that is, by controlling the ignition timing t1 to the optimum ignition timing T1, the combustion timing t5 can be controlled to the optimum combustion timing T5.

FIG. 10 is a flow chart showing control by the ignition control section 60 having the ejection control section 63 and the airflow control section 64 described above. First, each parameter indicating the operating condition of the engine 90 is acquired by each of the sensors 51 to 53 (S101).

Next, based on those parameters, the discharge energy E and the optimum ignition timing T1 are calculated (S102). That is, the ejection control unit 63 calculates the discharge energy E based on the load applied to the engine 90, the air-fuel ratio of the engine 90, the EGR amount in the engine 90, the temperature of the coolant in the engine 90, and the like.

Specifically, the ejection control unit 63 calculates the discharge energy E to be greater when the air-fuel ratio is higher than the predetermined air-fuel ratio, compared to when the air-fuel ratio is the predetermined air-fuel ratio. More specifically, for example, the discharge energy E is calculated to increase as the air-fuel ratio increases. Further, the ejection control unit 63 performs control so that the discharge energy E is increased when the EGR amount is greater than the predetermined amount as compared to when the EGR amount is the predetermined amount. More specifically, for example, the calculation is performed so that the discharge energy E increases as the EGR amount increases. Further, control is performed so that the discharge energy E becomes larger when the water temperature is lower than the predetermined temperature, compared to when the water temperature is the predetermined temperature. More specifically, for example, the discharge energy E is calculated to increase as the temperature of the cooling water decreases.

On the other hand, the airflow control section 64 calculates the discharge energy E to be greater when the optimum ignition timing T1 is farther from the compression top dead center tD than when it is near the compression top dead center tD. Therefore, the discharge energy E and the optimum ignition timing T1 are calculated simultaneously. This is because, as the discharge energy E increases, the combustion time t15 shortens, thereby retarding the optimum ignition timing T1. Therefore, the discharge energy E affects the optimum ignition timing T1. On the other hand, as described above, the airflow control section 64 increases the discharge energy E when the optimum ignition timing T1 is farther from the compression top dead center tD than when it is near the compression top dead center tD. Therefore, the optimum ignition timing T1 affects the discharge energy E. Thus, the discharge energy E and the optimum ignition timing T1 each affect the other. Therefore, both values of the discharge energy E and the optimum ignition timing T1 are calculated at the same time, for example, by using simultaneous equations or multi-dimensional maps capable of calculating both values at the same time (S102).

Next, the energization timing t0 is calculated from the optimum ignition timing T1 and the discharge energy E (S103). The energization timing t0 is earlier than the optimum ignition timing T1 by the charging time t01. The charging time t01 becomes longer as the discharge energy E becomes larger, and becomes longer as the voltage of the battery 411 becomes lower. Also, even if the charging time t01 is the same, the crank angle occupied by the charging time t01 increases as the rotational speed of the engine 90 increases. Based on the above, the ignition control unit 60 calculates the charging time t01, and further calculates the energization timing t0 based on the charging time t01 (S103). This calculation may be calculated, for example, based on a formula or may be calculated based on a map.

Next, at the calculated energization timing t0, the switching element 413 is turned ON (S104). Next, the switching element 413 is turned off at the calculated optimum ignition timing T1 (S105). That is, the ignition timing t1 is controlled to the optimum ignition timing T1. As a result, ignition is performed by the spark plug 40, and the predetermined amount of fuel (for example, 50% of the mass) is burned at the optimum combustion timing T5. That is, the combustion timing t5 is controlled to the optimum combustion timing T5.

In the above description, the ignition control before top dead center during normal operation and the like has been described. The ignition timing t1 is controlled so as to be later than . Therefore, the optimum combustion control is not performed in the ignition control after the top dead center.

According to this embodiment, the following effects are obtained. The combustion time t15 in the low load state in the ignition control before top dead center can be suppressed by performing the injection delay suppression control in addition to the airflow support structure As. Therefore, it is possible to prevent the optimum ignition timing T1, which is earlier than the optimum combustion timing T5 by the combustion time t15, from becoming too early. This makes it possible to control the ignition timing t1 to the optimum ignition timing T1 even when the load in the pre-combustion chamber type ignition system 70 is low. By actually performing the optimum ignition control, the ignition timing t1 is controlled to the optimum ignition timing T1. As a result, the combustion timing t5 is controlled to the optimum combustion timing T5, and torque can be efficiently generated.

Specifically, the ejection control unit 63 controls the ejection delay suppression control so that the discharge energy E becomes larger in the low load state than in the high load state. As a result, the ejection time t13 can be shortened and the combustion time t15 can be shortened when the load is low.

In addition, the pre-chamber ignition system 70 can extend the discharge spark F by facilitating the airflow in the discharge gap 45 with the airflow support structure As. As a result, the ignitability of the discharge spark F can be improved, and the ejection time t13 can be shortened. Thereby, the combustion time t15 can be shortened. Further, by adopting a structure in which the discharge gap 45 is close to the communication hole 35 as the airflow support structure As, the communication hole 35 can be used to efficiently form the airflow support structure As.

Further, the airflow control unit 64 controls the discharge energy E so that the discharge spark F is not interrupted even by the airflow from the airflow support structure As. Therefore, the stability of the discharge sparks F can be ensured even when the airflow support structure As is provided.

Specifically, in the second half of the compression stroke, the earlier the timing, that is, the farther away from the compression top dead center tD, the stronger the airflow flowing through the discharge gap 45 becomes. Therefore, the earlier the ignition timing t1, the easier it is for the discharge spark F to blow out. In this respect, the airflow control unit 64 controls the discharge energy E to be greater when the ignition timing t1 is in the latter half of the compression stroke than when the ignition timing t1 is late. As a result, it is possible to efficiently prevent blow-out.

Further, in the first half of the expansion stroke, the later the timing, that is, the farther away from the compression top dead center tD, the stronger the airflow flowing through the discharge gap 45 becomes. Therefore, the later the ignition timing t1, the easier it is for the discharge spark F to blow out. In this respect, the airflow control section 64 controls the discharge energy E to be greater when the ignition timing t1 is late in the first half of the expansion stroke than when the ignition timing t1 is early. As a result, it is possible to efficiently prevent blow-out.

The partition 34 also serves as the ground electrode of the ignition plug 40 . A communication hole 35 is formed in the partition wall 34 . Therefore, the discharge gap 45 can be efficiently arranged close to the communication hole 35 .

In addition, the injection control section 63 controls the discharge energy E based on each parameter indicating the operating state of the engine 90 such as the air-fuel ratio, EGR, and water temperature. As a result, it is possible to effectively suppress the ejection time t13 from becoming longer under a predetermined situation.

Specifically, when the air-fuel ratio of the engine 90 is high, the fuel in the combustion chamber 30 becomes lean, making it difficult for the fuel to burn and flame to propagate. In this regard, the ejection control unit 63 performs control so that the discharge energy E is increased when the air-fuel ratio is high compared to when the air-fuel ratio is low. Therefore, it is possible to suppress the ejection time t13 from becoming longer when the air-fuel ratio is high than when the air-fuel ratio is low.

Further, when the amount of EGR of the engine 90 is large, the amount of exhaust gas returning to the intake increases, making it difficult for fuel to burn and flame to propagate. In this regard, the ejection control unit 63 performs control so that the discharge energy E becomes larger when the EGR amount is large than when the EGR amount is small. Therefore, it is possible to suppress the ejection time t13 from becoming longer when the EGR amount is large than when the EGR amount is small.

Further, when the temperature of the cooling water of the engine 90 is low, it is difficult for the fuel in the combustion chamber 30 to warm, so that the fuel is difficult to burn and the flame is difficult to propagate. In this regard, the ejection control unit 63 performs control so that the discharge energy E becomes larger when the temperature of the cooling water is lower than when the temperature is high. Therefore, it is possible to suppress the ejection time t13 from becoming longer when the temperature of the cooling water is lower than when the temperature is high.

Further, the following effects are obtained in the ignition control after top dead center. That is, in the ignition control after top dead center, the discharge spark F extends into the main chamber 31 through the central communication hole 35c and directly ignites the fuel in the main chamber 31. Combustion time t15 can be shortened.

[Other embodiments]
The embodiment shown above can be implemented with the following changes. For example, in the first embodiment, the fuel is injected into the intake passage 21 , but instead of or in addition to this, the fuel may be injected into the sub chamber 38 or the main chamber 31 . Further, for example, in the first embodiment, the discharge energy E is controlled by controlling the charging time t01. It may be controlled.

Further, for example, the ejection control unit 63 of the first embodiment changes the discharge energy E based on each parameter of the air-fuel ratio, the EGR amount, and the water temperature. The change of the discharge energy E based on this may be eliminated. Further, for example, in the first embodiment, the discharge energy E is controlled by the airflow control section 64 both when ignition is performed in the latter half of the compression stroke and when ignition is performed in the first half of the expansion stroke. Alternatively, the control of the discharge energy E by the airflow controller 64 may not be performed in one or both of the case of ignition in the latter half of the compression stroke and the case of ignition in the first half of the expansion stroke.

Further, for example, in the first embodiment, the airflow support structure As and the airflow control unit 64 are provided. You can Even in such a case, the effect of the ejection delay suppression control by the ejection control unit 63 can be obtained.

Further, for example, in the first embodiment, the ejection control unit 63 performs the ejection delay suppression control by controlling the discharge energy E, but instead of this, the ejection delay suppression control is performed as follows. You may do so. That is, by providing a blowing device for blowing an airflow onto the discharge gap 45 and controlling the blowing device by the blowout control unit 63, the airflow is blown more strongly against the discharge gap 45 in a low load state than in a high load state. may In this case, when the load is low, the discharge spark F extends longer, thereby improving ignitability and suppressing the ejection time t13 from becoming longer than when the load is high.

DESCRIPTION OF SYMBOLS 30... Combustion chamber 31... Main chamber 34... Partition wall 35... Communication hole 38... Pre-chamber 40... Spark plug 45... Discharge gap 60... Ignition control part 63... Ejection control part 70... Pre-chamber Formula ignition system, 90... engine, F... discharge spark, T1... optimum ignition timing, T5... optimum combustion timing, t1... ignition timing, t3... injection timing, t5... combustion timing, t13... injection time, t15... combustion time.

Claims (10)

A discharge spark (F) is generated by applying a voltage to a partition wall (34) that divides a combustion chamber (30) of an engine (90) into a pre-chamber (38) and a main chamber (31) and a predetermined discharge gap (45). and an ignition control section (60) for controlling the spark plug, wherein the partition wall separates the sub chamber and the main chamber from each other. A communication hole (35) for communication is formed,
A state in which the load applied to the engine is a predetermined magnitude is defined as a high load state, and a state in which the load applied to the engine is less than the predetermined magnitude is defined as a low load state,
Ignition timing (t1) is the timing at which the spark plug starts discharging in the discharge gap, and combustion timing (t5) is the timing at which a predetermined amount of fuel in the combustion chamber is in a state of combustion after the ignition timing. Assuming that the time from the ignition timing to the combustion timing is the combustion time (t15),
The ignition control unit calculates an optimum ignition timing (T1) that is earlier than the optimum combustion timing (T5) as the optimum combustion timing by the combustion time, and controls the ignition timing to the optimum ignition timing. performing optimum ignition control to be performed in the high load state,
In the pre-chamber ignition system (70),
The timing between the ignition timing and the combustion timing at which the flame generated in the auxiliary chamber starts to be ejected from the communication hole into the main chamber is defined as an ejection timing (t3), and the time from the ignition timing to the ejection timing. is the ejection time (t13),
an ejection control unit (63) that performs ejection delay suppression control to suppress the ejection time from becoming longer in the low load state than in the high load state;
In the low load state, the injection delay suppression control is performed by the injection control unit, thereby suppressing the combustion time from becoming longer than in the high load state, while the ignition control unit controls the optimum ignition. Controlled pre-chamber ignition system. 2. The ejection control unit performs control such that, as the ejection delay suppression control, the discharge energy (E) applied to the discharge gap is greater in the low load state than in the high load state. The pre-chamber ignition system described in . Having an airflow support structure (As) for facilitating airflow in the discharge gap,
3. The auxiliary chamber according to claim 1, wherein a plurality of said communication holes are formed in said partition wall, and said discharge gap is close to one of said plurality of said communication holes as said airflow supporting structure. formula ignition system. 4. The pre-chamber ignition system according to claim 3, further comprising an anti-airflow controller (64) for controlling the discharge energy applied to the discharge gap so that the discharge spark is not interrupted by the airflow from the airflow support structure. The airflow control section controls the discharge energy based on the ignition timing, and the airflow control section controls the ignition timing at a predetermined timing when the ignition timing is in the latter half of a compression stroke. 5. The pre-chamber ignition system according to claim 4, wherein said discharge energy is controlled to increase when said ignition timing is earlier than said predetermined timing. The airflow control section controls the discharge energy based on the ignition timing, and the airflow control section controls the ignition timing at a predetermined timing when the ignition timing is in the first half of an expansion stroke. 6. The pre-chamber ignition system according to claim 4, wherein said discharge energy is controlled to increase when said ignition timing is later than said predetermined timing. The discharge gap is formed between two electrodes (34, 44), and the barrier rib is made of a conductor and also serves as one electrode (34) of the two electrodes. The pre-chamber ignition system according to any one of 3 to 6. The injection control section controls the discharge energy applied to the discharge gap based on the air-fuel ratio of the engine, and the air-fuel ratio is higher than that when the air-fuel ratio is a predetermined air-fuel ratio. 8. The pre-chamber ignition system according to any one of claims 1 to 7, wherein said discharge energy is controlled to increase when it is greater than the fuel ratio. The injection control unit controls the discharge energy applied to the discharge gap based on the EGR amount, which is the amount of returning the exhaust gas back to the intake air in the engine. 9. The pre-chamber ignition system according to claim 1, wherein said discharge energy is controlled to increase when said EGR amount is greater than said predetermined amount. The jet control unit controls the discharge energy applied to the discharge gap based on the water temperature of the cooling water of the engine. 10. The pre-chamber ignition system according to any one of claims 1 to 9, wherein control is performed so that the discharge energy is increased when the discharge energy is low.

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