JP6544418B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device, and more particularly to a catalyst early warm-up control device for an engine, and belongs to the technical field of emission control of an internal combustion engine.

  In an engine that performs combustion by spark ignition, an accelerated warm-up system (AWS) may be used in order to achieve early activation of an exhaust purification catalyst (hereinafter referred to as "catalyst device") provided in an exhaust passage. . For example, in Patent Document 1, as the AWS, as the catalyst is in an inactive state immediately after cold start of the engine, the air-fuel mixture is expanded by retarding the ignition timing beyond the compression top dead center. A technique is disclosed which promotes combustion of the catalyst device by burning it in, thereby increasing exhaust gas temperature and exhaust heat quantity.

  Further, in Patent Document 1, in order to suppress the deterioration of combustion due to the retardation of the ignition timing in the execution of the above-described AWS, this cavity is formed by injecting the fuel into a concave cavity provided on the upper surface of the piston. It is disclosed that a rich fuel concentration of air-fuel mixture is formed around a spark plug provided at a position corresponding to.

  By the way, in recent years, for vehicle engines, for the purpose of achieving high output and high fuel efficiency performance, practical use of SPCCI (SPark Controlled Compression Ignition) combustion has been promoted.

  This SPCCI combustion sparks the mixture in the combustion chamber and starts the SI (Spark Ignition) combustion that propagates the generated flame to the surrounding mixture, and the pressure rise due to the SI combustion and the flame propagation causes the combustion to occur. The surrounding mixture is instantaneously compression-ignited throughout the combustion chamber. According to this, by CI (Compression Ignition) combustion, the mixture within the combustion chamber is completely burned in a short period of time, and the combustion energy is efficiently converted into torque.

  Further, in order to realize the SPCCI combustion, it is necessary to form an air-fuel mixture having a uniform concentration in the combustion chamber and to sufficiently increase the in-cylinder temperature for compression ignition. For the former, the fuel injection valve is disposed at the upper center of the combustion chamber. For the latter, for example, in order to set the in-cylinder temperature to 1000 K or more, a compression ratio of, for example, about 16 that is even higher than the compression ratio of the conventional high compression ratio gasoline is required.

  In such an engine, an operating region for performing SPCCI combustion and a region for performing SI combustion are provided according to the operating state. For example, when the load on the engine increases, the fuel injection amount increases and the temperature in the combustion chamber also increases. Therefore, even if SPCCI combustion is performed, CI combustion occurs with the start of SI combustion, so the engine load is high. In the operating range of load, SI combustion is performed.

  However, abnormal combustion such as knocking or preignition may be more likely to occur due to high compression in the low-rotation high-load operating region where only SI combustion is performed. By retarding the injection timing and quickly transporting the injected fuel to the spark plug (early fuel transport), measures are taken to avoid premature ignition.

  And, in the engine of SPCCI combustion, the distance between the bottom of the cavity and the spark plug periphery can be increased by shallowing the cavity of the part corresponding to the spark plug in at least a part of the cavity from the above-mentioned request for early fuel transport. It has been shortened. As a result, the fuel injected into this cavity is quickly transported near the spark plug.

JP, 2014-136989, A

  However, for example, in an engine with a small cavity configured for SPCCI combustion described above, when AWS is performed in which SI combustion is normally performed, the injection timing is retarded, so rich mixing necessary for ignition around the spark plug is performed. You need to create a mind. However, since the cavity is small, only a part of the injected fuel is retained in the cavity, which may deteriorate the ignitability and combustion of the air-fuel mixture.

  Such problems may occur not only in engines that perform SPCCI combustion, but also in engines with relatively high compression ratios and engines with small cavities.

  Then, this invention makes it a subject to aim at the improvement of the ignitability at the time of AWS implementation, and combustion stability in the above engines.

  In order to solve the above-mentioned subject, a control device of an engine concerning the present invention is characterized by having constituted as follows.

First, the invention according to claim 1 is
An exhaust purification catalyst provided in an exhaust passage of the engine;
A piston provided in a combustion chamber of the engine and having a cavity on an upper surface thereof;
A plurality of injection ports are provided, and a first injection port portion for injecting fuel so that the injection direction of fuel injected from a part of the plurality of injection ports is directed to the cavity, and injection directions of fuel injected from other injection ports are An injector having a second injection port for injecting fuel to be directed to the outside of the cavity;
A spark plug disposed facing the cavity;
A control device for an engine, comprising: a controller connected to each of the injector and the spark plug and configured to operate the engine by outputting a control signal to each of the injector and the spark plug. ,
The first injection port portion of the injector and the second injection port portion have a plurality of injection ports having injection direction axes different from each other, and the injection direction of the adjacent injection ports of the first injection port portion when viewed from the axial direction of the piston Since the angle formed between the shafts is set smaller than the angle formed between the injection direction axes of the adjacent injection ports of the second injection port section, the mixture in the cavity is more than the mixture in the outside of the cavity. The rich air-fuel ratio is
A swirl forming portion for generating a swirl flow exceeding a predetermined strength is provided in the combustion chamber,
When the catalyst temperature of the exhaust purification catalyst is low, the controller causes the spark plug to ignite the air-fuel mixture at a timing delayed from that in the non-cold state to raise the catalyst temperature of the exhaust purification catalyst. Output control signal,
When not cold, the swirl forming portion forms a swirl flow,
The piston is provided with a second cavity, and the cavity is a small cavity smaller than the second cavity .

The invention according to claim 2 is
An exhaust purification catalyst provided in an exhaust passage of the engine;
A piston provided in a combustion chamber of the engine and having a cavity on an upper surface thereof;
A plurality of injection ports are provided, and a first injection port portion for injecting fuel so that the injection direction of fuel injected from a part of the plurality of injection ports is directed to the cavity, and injection directions of fuel injected from other injection ports are An injector having a second injection port for injecting fuel to be directed to the outside of the cavity;
A spark plug disposed facing the cavity;
A control device for an engine, comprising: a controller connected to each of the injector and the spark plug and configured to operate the engine by outputting a control signal to each of the injector and the spark plug. ,
By setting the size of the injection port of the first injection port in the injector to be larger than the size of the injection port of the second injection port, the air-fuel mixture in the cavity is made richer than the air-fuel mixture outside the cavity,
A swirl forming portion for generating a swirl flow exceeding a predetermined strength is provided in the combustion chamber,
When the catalyst temperature of the exhaust purification catalyst is low, the controller causes the spark plug to ignite the air-fuel mixture at a timing delayed from that in the non-cold state to raise the catalyst temperature of the exhaust purification catalyst. Output control signal,
When not cold, the swirl forming portion is characterized in that a swirl flow is formed.

In the invention described in claim 3, in the invention described in claim 1 or claim 2,
The controller is characterized in that it does not form a swirl flow when cold, or forms a swirl flow with a weaker strength than when not cold.

In the invention described in claim 4, in the invention described in any one of claims 1 to 3,
The swirl formation portion is a swirl control valve provided in the intake passage,
The controller controls the opening degree of the swirl control valve so that the swirl ratio is 2 or more and less than 4.

In the invention described in claim 5, according to the invention described in any one of claims 1 to 4,
The engine includes an intake valve having a stem portion;
Equipped with a blow-by system,
The controller has a misfire determination means,
When the misfire determination means determines a misfire, the swirl flow is intensified.

In the invention described in claim 6, according to the invention described in any one of the above-mentioned claims 1 to 5,
In the high load and low speed operation region, the engine is
The controller outputs a control signal to the injector so as to perform fuel injection at a delayed timing after the late stage of the compression stroke as compared with the other operation range, and then outputs a control signal to the spark plug so as to ignite. It is characterized by

The invention described in Claim 7,
An exhaust purification catalyst provided in an exhaust passage of the engine;
A piston provided in a combustion chamber of the engine and having a cavity on an upper surface thereof;
A plurality of injection ports are provided, and a first injection port portion for injecting fuel so that the injection direction of fuel injected from a part of the plurality of injection ports is directed to the cavity, and injection directions of fuel injected from other injection ports are An injector having a second injection port for injecting fuel to be directed to the outside of the cavity;
A spark plug disposed facing the cavity;
A control device for an engine, comprising: a controller connected to each of the injector and the spark plug and configured to operate the engine by outputting a control signal to each of the injector and the spark plug. ,
The first injection port portion of the injector and the second injection port portion have a plurality of injection ports having injection direction axes different from each other, and the injection direction of the adjacent injection ports of the first injection port portion when viewed from the axial direction of the piston Since the angle formed between the shafts is set smaller than the angle formed between the injection direction axes of the adjacent injection ports of the second injection port section, the mixture in the cavity is more than the mixture in the outside of the cavity. The rich air-fuel ratio is
A swirl forming portion for generating a swirl flow exceeding a predetermined strength is provided in the combustion chamber,
When the catalyst temperature of the exhaust purification catalyst is low, the controller causes the spark plug to ignite the air-fuel mixture at a timing delayed from that in the non-cold state to raise the catalyst temperature of the exhaust purification catalyst. Output control signal,
When not cold, the swirl forming portion forms a swirl flow,
The compression ratio of the engine is 14 or more.

  According to the first aspect of the present invention, during the AWS control for raising the temperature of the exhaust purification catalyst, for example, the exhaust temperature is raised by retarding the ignition timing to realize the early warm-up of the catalyst. doing. Then, the mixture in the cavity is ignited by the spark plug facing the cavity. In the present invention, the injector has a first injection port for injecting fuel to direct the inside of the cavity and a second injection port for injecting fuel to direct the outside of the cavity, and the first injection port and the second injection port are And a plurality of injection ports each having a different injection direction axis. Further, when viewed from the axial direction of the piston, the angle formed between the injection direction axes of the adjacent injection holes of the first injection port portion is greater than the angle formed between the injection direction axes of the adjacent injection holes of the second injection port portion. It is set up. As a result, the air-fuel mixture in the cavity is made richer than the air-fuel mixture outside the cavity, so it is possible to secure sufficient fuel in the cavity to compensate for the deterioration of the ignition caused by retarding the ignition timing. The ignitability can be secured.

  Furthermore, in the configuration of the present invention, the fuel in the combustion chamber can be rapidly homogenized by forming the swirl flow by the swirl formation portion when not cold. For example, as in the case of CI combustion, combustion stability can be ensured in the operating state of the engine that requires homogenization of the fuel concentration in the combustion chamber.

Therefore, it is possible to achieve both the rich mixture formation in the cold state and the homogeneous mixture formation in the non-cold state.
In addition, since the cavity comprises the small cavity and the large cavity and ignites the mixture near the small cavity, the small cavity reaches the fuel injection earlier than the large cavity. That is, since it is possible to shorten the time for fuel transportation until the fuel reaches the cavity after fuel injection, it is possible to shorten the time from the fuel injection timing to the ignition timing by delaying the fuel injection timing. it can. As a result, it is possible to effectively prevent pre-ignition by delaying the fuel injection.

  According to the second aspect of the invention, as in the first aspect, during the AWS control for raising the temperature of the exhaust purification catalyst, for example, the exhaust temperature is raised by retarding the ignition timing, We have realized early warm-up of the catalyst. Then, the mixture in the cavity is ignited by the spark plug facing the cavity. In the present invention, the size of the injection port of the first injection port for injecting fuel to direct the inside of the cavity is larger than the size of the injection port of the second injection port for injecting fuel to direct the outside of the cavity. Since sufficient fuel can be secured in the cavity to compensate for the deterioration of ignition due to retarding the timing (a rich mixture can be formed in the cavity), the ignitability can be secured. .

  Furthermore, in the configuration of the present invention, the fuel in the combustion chamber can be rapidly homogenized by forming the swirl flow by the swirl formation portion when not cold. For example, as in the case of CI combustion, combustion stability can be ensured in the operating state of the engine that requires homogenization of the fuel concentration in the combustion chamber.

  According to the third aspect of the present invention, in the cold state, for example, in AWS for raising the temperature of the exhaust gas purification catalyst, sufficient for securing the ignitability caused by delaying the ignition timing. A quantity of fuel spray is directed into the cavity. At this time, no swirl flow is formed in the combustion chamber, or the swirl flow is formed with a strength weaker than that in the non-cold state, so that the fuel spray directed to the inside of the cavity is suppressed from flowing out of the cavity. It can be secured.

  According to the fourth aspect of the present invention, the swirl forming means of the first or second aspect is specifically shown, and the opening degree of the swirl control valve is determined according to the operating state of the engine. By controlling so that the swirl ratio is 2 or more and 4 or less, a homogeneous mixture can be formed in the combustion chamber even in different operating conditions, and combustion can be promoted.

  By the way, for example, the blowby oil mixed in the intake air and the carbon in the combustion chamber are mixed by the internal EGR for knocking prevention and adhere as a deposit to the stem portion of the intake valve. If this deposit accumulates on the stem portion, the swirl flow will be weakened, which may make it difficult to diffuse the air-fuel mixture in the combustion chamber, which may make it impossible to form a homogeneous air-fuel mixture in the combustion chamber.

  On the other hand, according to the invention described in claim 5, when the controller determines the misfire by the misfire determination means, the swirl valve is controlled to intensify the swirl flow to strengthen the weakened swirl flow. To prevent engine misfires.

  According to the invention as set forth in claim 6, at the time of high load and low rotation where the time required for the crank angle to change by 1 ° is long, the injector injects the fuel at a late timing after the late stage of the compression stroke. The fire plug is controlled to fire. Thereby, it is possible to suppress the occurrence of pre-ignition due to the progress of the reaction of the fuel.

According to the invention as set forth in claim 7 , during the AWS control for raising the temperature of the exhaust purification catalyst, for example, the exhaust temperature is raised by retarding the ignition timing to realize the early warm-up of the catalyst. doing. Then, the mixture in the cavity is ignited by the spark plug facing the cavity. In the present invention, the injector has a first injection port for injecting fuel to direct the inside of the cavity and a second injection port for injecting fuel to direct the outside of the cavity, and the first injection port and the second injection port are And a plurality of injection ports each having a different injection direction axis. Further, when viewed from the axial direction of the piston, the angle formed between the injection direction axes of the adjacent injection holes of the first injection port portion is greater than the angle formed between the injection direction axes of the adjacent injection holes of the second injection port portion. It is set up. As a result, the air-fuel mixture in the cavity is made richer than the air-fuel mixture outside the cavity, so it is possible to secure sufficient fuel in the cavity to compensate for the deterioration of the ignition caused by retarding the ignition timing. The ignitability can be secured.
Furthermore, in the configuration of the present invention, the fuel in the combustion chamber can be rapidly homogenized by forming the swirl flow by the swirl formation portion when not cold. For example, as in the case of CI combustion, combustion stability can be ensured in the operating state of the engine that requires homogenization of the fuel concentration in the combustion chamber.
Therefore, it is possible to achieve both the rich mixture formation in the cold state and the homogeneous mixture formation in the non-cold state.
Further, even when the compression ratio of the engine is set to a high compression ratio of 14 or more in order to carry out SPCCI combustion, the above-described effect can be obtained.

It is a system figure showing the composition of the control device of the engine concerning the embodiment of the present invention. It is the top view and sectional drawing which show the structure of the combustion chamber in the embodiment. It is a top view which shows the structure of the combustion chamber and intake system in the same embodiment. (A) An explanatory view showing a rig testing device for measuring a swirl ratio, and (b) a view showing a relationship between an opening ratio of a secondary passage and a swirl ratio. It is a block diagram showing composition of a control device of an engine in the embodiment. It is a driving | operation area | region map of an engine. It is an explanatory view showing fuel injection timing, ignition timing, and a combustion waveform in each operation field. It is an explanatory view showing the state of a combustion chamber when performing fuel injection in each operation field. It is explanatory drawing of (a) mild misfire determination using the average value of in-cylinder pressure in the embodiment, (b) It is explanatory drawing which shows the swirl control valve-opening degree according to the frequency | count of mild misfire detection. It is explanatory drawing which shows the light misfire determination method using (a) combustion stability in the embodiment, and the swirl control valve-opening degree according to the light misfire detection frequency. It is the top view which shows the structure of the combustion chamber in a modification, and an enlarged view of a nozzle.

  Hereinafter, details of an engine control device according to an embodiment of the present invention will be described.

  The engine is a multi-cylinder engine and is a cylinder injection type engine. The engine 1 includes a cylinder block 11 and a cylinder head 12 disposed above the cylinder block 11. A plurality of cylinders 13... 13 are formed in the cylinder block 11. Only one cylinder 13 is shown in FIGS. 1 and 2.

  The piston 3 is slidably inserted into the cylinder 13. The piston 3 is connected to a crankshaft 15 via a connecting rod 14. The crankshaft 15 is housed in a crankcase 16. The piston 3 forms a combustion chamber 17 together with the cylinder 13 and the cylinder head 12.

  The cylinder head 12 is provided with two intake ports 20a and 20b opened to the combustion chamber 17 and two exhaust ports 21a and 21b, and two intake valves for opening and closing both the intake ports 20a and 20b. 22, 22, two exhaust valves 23, 23 for opening and closing the two exhaust ports 21a, 21b, an injector 18 for injecting fuel into the combustion chamber 17, and an ignition plug for burning the fuel in the combustion chamber 17. 19 and is attached. The injector 18 is disposed at the center of the combustion chamber 17 and injects fuel directly into the combustion chamber 17 from this position. Further, the spark plug 19 is disposed at the peripheral portion of the combustion chamber 17.

A fuel supply system (not shown) is connected to the injector 18. The fuel supply system includes a fuel tank configured to store fuel, and a fuel supply path connecting the fuel tank and the injector 18 to each other. A fuel pump and a common rail are interposed in the fuel supply path. The fuel pump pumps fuel to the common rail. The fuel pump is a plunger type pump driven by the crankshaft 15 in this configuration example. The common rail is configured to store the fuel pumped from the fuel pump at high fuel pressure. When the injectors 18 are opened, the fuel stored in the common rail is injected from the injection port of the injectors 18 into the combustion chamber 17. The fuel supply system is configured to be able to supply fuel with a high pressure of 30 MPa or more to the injectors 18. The maximum fuel pressure of the fuel supply system may be, for example, about 120 MPa. The pressure of the fuel supplied to the injector 18 may be changed according to the operating state of the engine 1. The configuration of the fuel supply system is not limited to the above configuration.

  The engine 1 executes a combustion cycle consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke by the intake valve 22 and the exhaust valve 23. The intake valve 22 and the exhaust valve 23 are configured to change their operation timings by a variable intake valve mechanism as a variable valve timing mechanism and a variable exhaust valve mechanism (not shown). The intake passage 4 is connected to the intake ports 20a and 20b, and the exhaust passage 5 is connected to the exhaust port 21a and 21b.

  In the intake passage 4, an air cleaner 41 for purifying intake air introduced from the outside sequentially from the upstream side, a throttle valve 42 for adjusting the amount of intake air passing therethrough, and a turbocharger 43 for boosting the intake air passing therethrough; An intercooler 44 for cooling the intake air by the outside air or cooling water, and a surge tank 45 for temporarily storing the intake air supplied to the engine 1 are provided.

  A bypass passage 46 is connected to the intake passage 4, and specifically, an upstream portion of the turbocharger 43 and a downstream portion of the intercooler 44 of the intake passage 4 so as to bypass the turbocharger 43 and the intercooler 44. And are connected to each other. The bypass passage 46 is provided with a bypass valve 47 that adjusts the amount of intake air flowing through the bypass passage 46.

  The intake passage 4 is provided with a blow-by gas reduction device 48 for introducing a part of exhaust gas, unburned hydrocarbon and oil mist into the intake system and re-burning them to render them harmless. . The blowby gas reduction device 48 communicates with the fresh air introduction passage 48a communicating the intake passage 4 downstream of the throttle valve 42 with the internal space of the crank chamber 16a formed in the crankcase 16, and the inside of the cylinder head 12 A blowby gas reduction passage 48b communicating with the intake passage 4 upstream of the throttle valve 42 is provided. A PCV valve 48c whose opening degree changes according to the intake negative pressure on the downstream side of the throttle valve 42 is interposed in the fresh air introduction passage 48a.

  In the blow-by gas reduction system 48, the crank chamber 16a is pressurized by introducing fresh air into the crank chamber 16a from the fresh air introduction passage 48a, and the blow-by gas in the crank chamber 16a is the cylinder 13 and cylinder head above the crank chamber 16a. 12, and the intake passage 4 upstream of the throttle valve 42 through the blowby gas reduction passage 48b.

  A catalyst device 51 having a function of purifying exhaust gas is provided in the exhaust passage 5, and on the exhaust passage 5, EGR is caused to recirculate part of the exhaust gas (burned gas) to the intake passage 4 as EGR gas. A device 52 is provided. The EGR device 52 is connected between the upstream side catalyst 51 a and the downstream side catalyst 51 b on the upstream side, and has a downstream end that cools the EGR passage 53 connected to the upstream of the supercharger 43 in the intake passage 4 and the EGR gas And an EGR valve 55 for controlling the amount of EGR gas flowing through the EGR passage 53.

  Here, the structure around the combustion chamber 17 of the engine 1 in the present embodiment will be described in detail with reference to FIG. FIG. 2 shows the piston position at the late stage of the compression stroke.

  The upper surface of the piston 3, that is, the bottom surface of the combustion chamber 17 is a substantially flat surface. A cavity 30 is formed on the upper surface of the piston 3. The cavity 30 is recessed from the upper surface of the piston 3. The cavity 30 faces the injector 18.

  The cavity 30 has a protrusion 31. The convex portion 31 is provided at a position slightly offset from the central axis X1 of the cylinder 13 toward the exhaust side. The convex portion 31 extends upward and gently upward from the bottom of the cavity 30 along an axis X2 parallel to the central axis X1 of the cylinder 13.

  The cavity 30 is formed of a concave large cavity 32 provided around the protrusion 31 and a small cavity 33. The large cavity 32 is provided to surround the exhaust side of the protrusion 31, and the small cavity 33 is provided to surround the intake side of the protrusion 31. The circumferential side surfaces of the large cavity 32 and the small cavity 33 are inclined from the bottom surface of the cavity 30 toward the opening of the cavity 30 with respect to the injection axis X2. The inner diameters of the large cavity 32 and the small cavity 33 gradually increase from the bottom of the cavity 30 toward the opening of the cavity 30.

  Further, the small cavity 33 is provided at a position corresponding to the spark plug 19 and is formed smaller than the large cavity 32 so as to be shallower. Thus, the air-fuel mixture can be easily transported around the spark plug 19. Note that “the cavity in the claims” indicates this small cavity 33. As described above, the small cavity 33 is hereinafter referred to as an ignition cavity 33 in order to ignite the air-fuel mixture in the small cavity 33 by the ignition plug 19.

  The lower surface of the cylinder head 12, that is, the ceiling surface of the combustion chamber 17 is constituted by an inclined surface 12a and an inclined surface 12b, as shown in the lower part of FIG. The inclined surface 12a has an upward slope from the intake side toward the axis X2. The inclined surface 12b is an upward slope from the exhaust side toward the axis X2. The ceiling surface of the combustion chamber 17 has a so-called pent roof shape.

  The shape of the combustion chamber 17 is not limited to the shape illustrated in FIG. For example, the shape of the cavity 30, the shape of the upper surface of the piston 3, and the shape of the ceiling surface of the combustion chamber 17 can be changed as appropriate. For example, the cavity 30 may be symmetrical with respect to the central axis X1 of the cylinder 13. The inclined surface 12 a and the inclined surface 12 b may be symmetrical with respect to the central axis X 1 of the cylinder 13.

  The compression ratio of engine 1 (compression ratio = volume of cylinder when piston is at bottom dead center / volume of cylinder when piston is at top dead center) is set to 13 or more and 20 or less. Preferably it is 14 or more. As described later, the engine 1 performs SPCCI combustion in which SI combustion and CI combustion are combined in a part of the operation range. SPCCI combustion performs CI combustion using heat generation by SI combustion and pressure increase by flame propagation.

  An injector 18 is attached to the cylinder head 12 for each cylinder 13. The injector 18 is configured to inject fuel directly into the combustion chamber 17. The injector 18 is disposed facing the inside of the combustion chamber 17 in the valley portion of the pent roof where the inclined surface 12a on the intake side and the inclined surface 12b on the exhaust side intersect. As shown in FIG. 2, the injector 18 has its injection axis X2 disposed parallel to the center axis X1 of the cylinder. The injection axis X2 of the injector 18 and the position of the convex portion 31 of the cavity 30 coincide with each other. The injector 18 faces the cavity 30. The injection axis X2 of the injector 18 may coincide with the central axis X1 of the cylinder 13. Also in this case, it is desirable that the injection axis X2 of the injector 18 and the position of the convex portion 31 of the cavity 30 be coincident with each other.

  The injector 18 is constituted by a multi-injection-type fuel injection valve having a plurality of injection holes (not shown). The injector 18 injects fuel so that the fuel spray spreads radially from the center of the combustion chamber 17 and spreads obliquely downward from the ceiling portion of the combustion chamber 17 as shown by a two-dot chain line in FIG. The injection angle θ of each injector 18 with respect to the injection axis X2 of the injector 18 is in the range of 30 degrees or more and 60 degrees or less, preferably 45 degrees.

  In the present embodiment, the injector 18 has ten injection ports, and the center lines L1 to L10 of the axes of the fuel sprays injected from the respective injection ports are shown in FIG. The number of injection ports is not limited to ten. For example, it can be suitably set in the range of eight to sixteen.

  Further, the fuel spray injected from the injection ports of the center lines L1, L2 and L3 disposed on the intake side ("first injection port" in the claims) enters the ignition cavity 33, and the other center lines The fuel spray injected from the injection ports L4 to L10 (the "second injection port" in the claims) is disposed outside the ignition cavity 33. That is, the injection direction of the fuel injected from the first injection port portion is directed to the ignition cavity 33, and the injection direction of the fuel injected from the second injection port portion is directed to the outside of the ignition cavity 33.

  Further, when viewed from the axial direction of the piston 3, an angle formed between injection direction axes of the adjacent injection holes of the first injection hole portion (for example, between L1 and L2 or between L2 and L3) is The angle is set smaller than the angle formed between the injection direction axes (for example, between L7 and L8) of the adjacent injection holes of the second injection hole portion.

  The fuel spray injected from the plurality of injection ports (center line L1, L2, L3 injection ports) of the first injection port portion of the injector 18 has an angle range occupied by the ignition cavity 33 in the angle range centered on the injector 18. As compared with the case where the number of the plurality of injection ports of the first injection port is the same and the plurality of injection ports are arranged at equal intervals, the plurality of injection ports of the first injection port (center lines L1, L2, L3 The fuel spray injected from the injection port of (1) may be provided so that the number entering into the ignition cavity 33 may be increased.

  A spark plug 19 is attached to the cylinder head 12 for each cylinder 13. The spark plug 19 forcibly ignites the mixture in the combustion chamber 17. In this configuration example, the spark plug 19 is disposed on the intake side across the central axis X1 of the cylinder 13, as also shown in FIG. The spark plug 19 is adjacent to the injector 18. The spark plug 19 is located between the two intake ports 20. The spark plug 19 is attached to the cylinder head 12 in such a manner as to approach the center of the combustion chamber 17 from the upper side to the lower side. The electrode of the spark plug 19 faces the combustion chamber 17 and is located near the ceiling surface of the combustion chamber 17.

  The engine 1 has a swirl generating portion that generates a swirl flow in the combustion chamber 17. The swirl generating portion is a swirl control valve 20c attached to the intake port 20 as shown in FIG. The swirl control valve 20c is disposed in the secondary passage 20e among the primary passage 20d connected to the first intake port 20a and the secondary passage 20e connected to the second intake port 20b.

  The swirl control valve 20c is an opening adjustment valve capable of reducing the cross section of the secondary passage 20e. When the degree of opening of the swirl control valve 20c is small, the flow rate of intake air flowing into the combustion chamber 17 from the first intake port 20a is relatively relative to the first intake port 20a and the second intake port 20b arranged in the back and forth direction of the engine 1 And the flow rate of intake air flowing from the second intake port 20b into the combustion chamber 17 is relatively reduced, so that the swirl flow in the combustion chamber 17 becomes strong.

  When the opening degree of the swirl control valve 20c is large, the intake flow rate flowing into the combustion chamber 17 from each of the first intake port 20a and the second intake port 20b becomes substantially even, so the swirl flow in the combustion chamber 17 is weak. Become. When the swirl control valve 20c is fully opened, no swirl flow occurs. The swirl flow circulates in the counterclockwise direction in FIG. 3 as indicated by the arrow (see also the white arrow in FIG. 2).

  In addition, instead of attaching the swirl control valve 20c to the intake passage 4, or in addition to attaching the swirl control valve 20c, the swirl generating part shifts the open period of the two intake valves 22, 22 and A configuration in which intake air can be introduced into the combustion chamber 17 only from the valve 22 may be adopted. Since only one intake valve 22 of the two intake valves 22 is opened, the intake air can be unequally introduced into the combustion chamber 17, so that a swirl flow is generated in the combustion chamber 17. be able to. Furthermore, the swirl generating portion may be configured to generate a swirl flow in the combustion chamber 17 by devising the shape of the intake port 20.

  Here, when the swirl ratio is defined, the “swirl ratio” is a value obtained by dividing the value obtained by measuring and integrating the intake flow lateral angular velocity for each valve lift by the engine angular velocity. The intake flow lateral angular velocity can be determined based on the measurement using the rig test apparatus shown in FIG. 4 (a). Specifically, in the device shown in the figure, the cylinder head 12 is installed upside down on the base, and the intake port 20 is connected to an intake supply device (not shown), while the cylinder 35 is mounted on the cylinder head 12. And an impulse meter 37 having a honeycomb rotor 36 at its upper end. The lower surface of the impulse meter 37 is positioned at 1.75 D (where D is a cylinder bore diameter) from the mating surface of the cylinder head 12 and the cylinder block. The torque acting on the honeycomb rotor 36 is measured by the impulse meter 37 by the swirl (see the arrow in FIG. 4A) generated in the cylinder 35 according to the intake supply, and the intake flow lateral angular velocity is determined based thereon. be able to.

  FIG. 4 (b) shows the relationship between the opening degree of the swirl control valve 20c in the engine 1 and the swirl ratio. FIG. 4B shows the opening degree of the swirl control valve 20c by the opening ratio with respect to the full open cross section of the secondary passage 20e. When the swirl control valve 20c is fully closed, the opening ratio of the secondary passage 20e is 0%, and when the opening degree of the swirl control valve 20c is large, the opening ratio of the secondary passage 20e is larger than 0%. When the swirl control valve 20c is fully open, the opening ratio of the secondary passage 20e is 100%. As illustrated in FIG. 4 (b), when the swirl control valve 20c is fully closed, the swirl ratio becomes approximately 6 as shown in FIG. 4 (b).

  The control device includes an ECU (Engine Control Unit) 10 for operating the engine 1.

  As shown in FIG. 5, various sensors S <b> 1 to S <b> 4 are connected to the ECU 10. The sensors S1 to S4 output detection signals to the ECU 10. The sensors include the following sensors.

  As shown in FIG. 5, in the vehicle according to the present embodiment, an engine rotation number sensor S1 for detecting the rotation number of the engine, a crank angle sensor S2 for detecting the rotation angle of the crankshaft, and a driver The accelerator position sensor S3 for detecting the presence or absence of the accelerator operation and the accelerator operation amount, and the catalyst temperature sensor S4 for detecting the temperature of the catalyst device are provided. The ECU 10 is electrically connected to these various sensors.

  The ECU 10 determines the operating state of the engine 1 based on these detection signals and calculates the control amount of each device. The ECU 10 outputs a control signal related to the calculated control amount to the injector 18, the spark plug 19, the throttle valve 42, the EGR valve 55, the air bypass valve 47, and the swirl control valve 20c. For example, the ECU 10 adjusts the charging pressure by adjusting the opening degree of the air bypass valve 47 based on the front-rear differential pressure of the turbocharger 43 obtained from the detection signals of the first pressure sensor and the second pressure sensor (not shown). adjust. Further, the ECU 10 adjusts the opening degree of the EGR valve 55 based on the differential pressure across the EGR valve 55 obtained from the detection signal of the EGR differential pressure sensor (not shown), thereby introducing the external EGR gas introduced into the combustion chamber 17 Adjust the amount.

  The ECU 10 controls the normal operation of the engine 1 based on various information input from the various sensors provided in the vehicle, and also when the catalyst device 51 is in the inactive state at the time of cold start of the engine 1, AWS is implemented to achieve early activation of the catalyst device 51.

  In addition, the above-mentioned sensor and each device show what is related to the early warming-up control of the catalyst of this invention, The sensor and device connected to ECU10 are not restricted to the above-mentioned thing.

  FIG. 6 shows the operating range of the engine 1. The operating region of the engine 1 is determined by the load and the rotational speed, and is divided into four regions for the high and low of the load and the high and low of the rotational number. Specifically, it is divided into a low to middle rotation area A and a high rotation area B having a rotation number higher than that of the middle rotation, and the low to middle rotation area A further includes a low, middle load, low and middle rotation area A1, a high load, low rotation area It is divided into A2 and a high load medium rotation area A3.

  Here, in the low rotation region, the middle rotation region, and the high rotation region, when the entire operating region of the engine 1 is in the direction of the rotational speed and divided into three regions of the low rotation region, the middle rotation region, and the high rotation region, respectively. The low rotation area, the middle rotation area, and the high rotation area may be used. In the example of FIG. 6, the number of rotations less than N1 is low, the number of rotations N2 or more is high, and the number of rotations N1 or more and N2 is medium. For example, the rotation speed N1 may be 1200 rpm, and the rotation speed N2 may be 4000 rpm, for example. The two-dot chain line in FIG. 6 indicates a load-load line (Road-Load Line) of the engine 1.

  The engine 1 performs SPCCI combustion in a low, medium load, low and middle rotation area A1 and a high load, middle rotation area A3 mainly for the purpose of improving fuel efficiency and exhaust gas performance. The engine 1 also performs SI combustion in other regions, specifically, a high load low rotation region A2 and a high rotation region B. Hereinafter, control of the engine 1 in each of the low, medium load, low, and middle rotation area A1, the high load, middle rotation area A3, the high load, low rotation area A2, and the high rotation area B is shown in FIG. A detailed description will be given with reference to the fuel injection timing and the ignition timing in the region.

  In FIG. 7A, the fuel injection timings A11 and A12, the ignition timing A13, and the combustion waveform A14 when the engine 1 is operated in the low, medium load, low and middle rotation area A1 and the high load, medium rotation area A3. An example of (waveform showing change in heat release rate with respect to crank angle) is shown.

  The engine 1 performs CI combustion when operating in a low, medium load, low, and medium rotation area A1 and a high load, medium rotation area A3. In the self-ignition combustion, when the temperature in the combustion chamber before the start of compression varies, the timing of the self-ignition changes significantly. Therefore, the engine 1 performs SPCCI combustion in which SI combustion and CI combustion are combined in the low, medium load, low, and middle rotation area A1 and the high load, middle rotation area A3.

  In SPCCI combustion, when the ignition plug 19 forcibly ignites the mixture in the ignition cavity 33, the mixture is subjected to SI combustion by flame propagation, and the temperature in the combustion chamber 17 is high due to heat generation of SI. And, by the pressure in the combustion chamber rising due to the flame propagation, the unburned mixture performs the CI combustion by the self-ignition.

  In the SPCCI combustion in the low, medium load, low, medium rotation area A1 and the high load, medium rotation area A3, the injector 18 injects the fuel into the combustion chamber 17 divided into two stages, the first stage injection A11 and the second stage injection A12. The first-stage injection A11 starts fuel injection, for example, in the first half of the intake stroke, and the second-stage injection A12 is performed, for example, in the second half of the compression stroke. The first half and the second half of the intake stroke may be the first and second halves of the intake stroke divided into two with respect to the crank angle, respectively. The first-stage injection A11 may start, for example, at 280 ° CA before the compression top dead center TDC, and the second-stage injection A12 may, for example, start at 10 ° CA before the compression top dead center TDC.

  Then, the spark plug 19 ignites the air mixture A13 at a predetermined timing near the compression top dead center TDC after the post-stage injection A12. The spark plug 19 ignites, for example, after compression top dead center. Thereby, SI combustion by flame propagation starts. Heat generation during SI combustion is milder than heat generation during CI combustion. Therefore, the waveform of the heat release rate has a relatively small rising slope.

  When the temperature and pressure in the combustion chamber 17 increase due to SI combustion, the unburned mixture self-ignites. In the example of FIG. 7A, the slope of the heat release rate waveform changes from small to large at the timing of self-ignition. That is, the waveform of the heat release rate has an inflection point at the timing when the CI combustion starts.

  By the completion of the CI combustion, the SPCCI combustion is ended. CI combustion has a shorter combustion period than SI combustion. In the SPCCI combustion, since the combustion end timing is quicker than the SI combustion, the combustion end timing in the expansion stroke can be brought close to the compression top dead center. Therefore, SPCCI combustion is more advantageous for improving the fuel consumption performance of the engine than SI combustion.

  Further, as shown in FIGS. 2 and 8A, the injector 18 injects fuel radially outward from the central portion of the combustion chamber 17 in the radial direction. When the injector 18 performs the pre-injection A11 in the latter half of the intake stroke, the injected fuel spray is discharged from the large cavity 32 on the upper surface of the piston 3 and the ignition cavity because the piston 3 is separated from the top dead center TDC. Reach out of 33. The fuel injected by the pre-injection A11 forms an air-fuel mixture in the outer peripheral portion of the upper surface of the piston 3.

  When the injector 18 performs the post-stage injection A12 within the latter period of the compression stroke, as shown by the phantom line in FIG. 8A, the injected fuel spray is ignited because the piston 3 is close to the top dead center TDC. Into the cavity 33. Further, as shown in FIG. 2, since the fuel spray injected from the injection holes of the center lines L1, L2 and L3 enters the ignition cavity 33, a rich mixture is formed around the ignition plug 19.

  Thereafter, at a predetermined timing before the compression top dead center TDB, the ignition plug 19 ignites the air-fuel mixture, whereby the air-fuel mixture burns SI by flame propagation. After the start of combustion by flame propagation, the unburned mixture is self-ignited to burn CI. The fuel injected by the second-stage injection A12 mainly undergoes SI combustion. The fuel injected by the pre-injection A11 mainly burns CI.

  The fuel injection timings A11 and A12 and the number of injections may be changed according to the load level of the engine 1 when operating in the low, medium load, low and middle rotation area A1 and the high load, medium rotation area A3.

  By the way, in SPCCI combustion of low, medium load, low, medium rotation area A1 and high load, medium rotation area A3, in addition to the rich mixture formed around spark plug 19 for SI combustion, homogeneous mixture for CI combustion Formation is necessary. However, in this embodiment, since the injection hole of the injector injects the spray into the ignition cavity 33, the arrangement is not advantageous for the formation of the homogeneous mixture, and therefore, it is necessary to take measures to compensate for this.

  On the other hand, in the SPCCI combustion in the low, medium load, low and middle rotation area A1 and the high load, middle rotation area A3, a swirl flow having a swirl ratio of 2 or more and less than 4 is formed in the combustion chamber 17. The swirl control valve (SCV) 20c has a predetermined opening (in the present embodiment, the SCV opening is 15% to 36%) as shown in FIG. 4 (b).

  By generating this swirl flow, the air-fuel mixture in the combustion chamber 17 can be rapidly homogenized, and self-ignition at the transition from SI combustion to CI combustion can be generated in the entire combustion chamber 17 in SPCCI combustion. CI combustion is stabilized.

  By controlling the swirl flow in the range of the strength of the above-mentioned swirl flow (swirl ratio 2 or more and less than 4 and the swirl control valve 20c opening degree is 15% to 36%), the mixture in SPCCI combustion can be ignited and burned The experiment confirmed that it could control to a suitable state.

  In the experiment, using the combustion chamber 17 structure according to the present embodiment, the engine speed of 3000 rpm assuming SPCCI combustion, the first stage injection timing is 280 deg before compression top dead center, the second stage injection timing is 10 deg before compression top dead center, and the ignition timing is compressed. At 10 deg after top dead center, the swirl control valve 20c was changed from the fully open state to the fully closed state, and the in-cylinder pressure during one cycle at each swirl control valve opening was detected.

  According to the experimental results, when the swirl ratio is less than 2, improvement in stability of the CI combustion can not be confirmed due to the activation of the turbulent flow due to the swirl flow, and when the swirl ratio is 4 or more, the air-fuel mixture around the spark plug is generated by the swirl flow. Because of the diffusion, the ignitability is inhibited.

  FIG. 7B shows an example of the fuel injection A21 timing, the ignition A22 timing, and the combustion waveform A23 when the engine 1 is operating in the high load low rotation range A2 operating state.

  When the rotational speed of the engine 1 is low, the time required for the crank angle to change by 1 ° becomes long. In the high load low rotation area A2, for example, when fuel is injected into the combustion chamber 17 in the first half of the intake stroke or compression stroke, as in the low, medium load, low, and middle rotation areas A1 and high load, middle rotation area A3, The reaction may proceed too much, which may lead to premature ignition. When the engine 1 is operating in the high load low rotation range A2, it is difficult to perform SPCCI combustion of FIG. 7A or SI combustion of FIG. 7C described later.

  Thus, when the engine is operating in the high load low rotation range A2, the engine 1 performs retarded-SI combustion. Specifically, the ECU 10 injects the fuel into the combustion chamber 17 at a high fuel pressure of 30 MPa or more and at a timing within a period from the late stage of the compression stroke to the early stage of the expansion stroke (hereinafter, this period is referred to as a retard period). Control signal to the fuel supply system and the injector 18. The ECU 10 also outputs a control signal to the spark plug so as to ignite the mixture at a timing near the compression top dead center after fuel injection. In the following, injecting fuel into the combustion chamber 17 at a high fuel pressure and at a timing within the retard period is referred to as high-pressure retarded injection. High pressure retarded injection avoids abnormal combustion by shortening the time during which the mixture reacts. That is, the time for the mixture to react is (1) a period during which the injector injects fuel (that is, the injection period) and (2) after the fuel injection is completed, a combustible mixture is formed around the spark plug. (Ie, the mixture formation period) and (3) the period until the end of the SI combustion initiated by the ignition (ie, the combustion period). When fuel is injected into the combustion chamber at high fuel pressure, the injection period and the mixture formation period become shorter respectively. As the injection period and the mixture formation period become shorter, it becomes possible to bring the timing to start the fuel injection closer to the ignition timing. The high pressure retarded injection injects the fuel into the combustion chamber 17 at a high pressure, so that the fuel is injected at a timing within a retarded period from the late stage of the compression stroke to the early stage of the expansion stroke. Injection of fuel into the combustion chamber at high fuel pressure results in high turbulent energy in the combustion chamber. When the timing of fuel injection approaches the compression top dead center, SI combustion can be started in a state where the turbulent energy in the combustion chamber 17 is high. As a result, the combustion period is shortened. The high pressure retarded injection can shorten the injection period, the mixture formation period, and the combustion period, respectively. High-pressure retarded injection can significantly reduce the time for the mixture to react as compared to injecting fuel into the combustion chamber during the intake stroke. High pressure retarded injection makes it possible to avoid abnormal combustion because the time for the mixture to react becomes short.

  That is, when the engine 1 operates in the high load low rotation range A2, the injector 18 injects the fuel into the combustion chamber 17 in two divided steps, the pre-stage injection A21 and the post-stage injection A22. The first-stage injection A21 is performed, for example, in the first half of the intake stroke, and the second-stage injection A22 is performed, for example, at a timing within a period from the second half of the compression stroke to the first half of the expansion stroke. The second half of the compression stroke may be set to the second half when the compression stroke is divided into three equal parts in the first, second, and third phases. Further, the first half of the expansion stroke may be the first half when the expansion stroke is divided into three equal halves in the first, middle, and second half. Thus, by setting the fuel injection timing to a late timing, it is possible to avoid pre-ignition (hereinafter referred to as “retarded SI combustion”).

  The ignition plug 19 ignites the air-fuel mixture at a timing near the compression top dead center TDC after fuel injection. The spark plug 19 may perform ignition, for example, after compression top dead center TDC. The mixture performs SI combustion in the expansion stroke. Since SI combustion starts in the expansion stroke, CI combustion does not start.

  The injector 18 retards the fuel injection timing as the number of revolutions of the engine 1 decreases in order to avoid the pre-ignition. Fuel injection may end in the expansion stroke.

  Furthermore, when the engine 1 operates in the high load low rotation range A2, the time (A21 to A22) from the start of fuel injection to ignition is short. In order to improve the ignitability of the mixture and to stabilize SI combustion, it is necessary to transport the fuel to the vicinity of the spark plug promptly.

  As shown in FIG. 8 (b), when the injector 18 injects fuel in the period from the late stage of the compression stroke to the early stage of the expansion stroke, since the piston 3 is located near the compression top dead center TDC, the fuel spray is The air flows downward along the convex portion 31 of the cavity 30 and flows radially outward from the central portion of the combustion chamber 17 along the bottom and peripheral side surfaces of the cavity 30. Thereafter, the air-fuel mixture reaches the opening of the cavity 30, and flows radially outward along the intake side inclined surface and the exhaust side inclined surface toward the center of the combustion chamber 17. The fuel injected within the retard period can be transported to the vicinity of the spark plug 19 promptly.

  At this time, no swirl flow is formed in the combustion chamber 17 when the swirl control valve 20c is fully open or substantially fully open. Therefore, as shown in FIG. 2, when the fuel spray injected from the injection holes of the center lines L1, L2, L3 enters the ignition cavity 33 and is transported around the spark plug 19 as described above, The strong swirl flow can suppress the fuel spray in the ignition cavity 33 from coming off around the spark plug 19.

  FIG. 7C shows an example of each of the fuel injection timing B11, the ignition timing B12, and the combustion waveform B13 when the engine is operating in the high rotation speed region B.

  When the rotation of the engine 1 is high, the time required for the crank angle to change by 1 ° becomes short. Therefore, in the high rotation region B, as described above, it is difficult to perform stratification of the mixture in the combustion chamber 17 by performing the split injection during the compression stroke. When the rotational speed of the engine 1 becomes high, it becomes difficult to perform the above-described SPCCI combustion.

  Therefore, when operating in the high rotation range B, the engine 1 performs not the SPCCI combustion but the SI combustion. The high rotation range B extends over the entire load direction from low load to high load.

  When the engine 1 operates in the high rotation range B, the injector 18 starts fuel injection in the intake stroke. The injectors 18 inject fuel at one time. In the example of the operating state shown in FIG. 7C, the load on the engine 1 is high, so the amount of fuel injection is large. The fuel injection period changes according to the fuel injection amount. By starting fuel injection during the intake stroke, it becomes possible to form a homogeneous or substantially homogeneous mixture in the combustion chamber 17. In addition, since the vaporization time of the fuel can be secured as long as possible when the engine speed is high, it is possible to reduce the unburned loss and suppress the generation of soot.

  The ignition plug 19 ignites the air-fuel mixture at a predetermined timing before the compression top dead center TDC after the end of the fuel injection.

  When the engine 1 is operated in the high rotation range B, the swirl control valve (SCV) 20c is fully opened. No swirl flow is generated in the combustion chamber 17, and only the tumble flow is generated. By fully opening the swirl control valve 20c, it is possible to enhance the filling efficiency in the high rotation region B and to reduce the pump loss.

  In addition to the above operating conditions, in the control of the engine, an operating condition in the AWS region to be implemented at idle operation is provided. AWS control is so-called AWS (Accelerated Warm-up System) control, and executes control for warming up and activating these at an early stage when the temperature of the catalyst is low. In the present embodiment, this control is performed based on the upstream side catalyst 51a of the catalyst device 51, but the downstream side catalyst 51a is also warmed up early together with the upstream side catalyst 51a by the execution of this control. The contents of AWS control will be described below. First, in the first step, the estimated catalyst temperature Tcat and the vehicle speed estimated by the catalyst temperature estimation unit are read. The catalyst temperature estimation unit adds the temperature rise amount of the exhaust gas in the upstream catalyst 51a to the temperature of the exhaust gas estimated from the operating state of the engine (engine water temperature, engine load, engine rotation) to obtain the upstream catalyst 51a. Estimate the temperature of Next, as a second step, it is determined whether the estimated catalyst temperature Tcat is less than a preset AWS operation temperature Tcat_AWS. The AWS implementation temperature Tcat_AWS is a temperature of the upstream side catalyst 51a when the upstream side catalyst 51a is lighted off (when the purification rate of the upstream side catalyst 51a is 50%), and is preset by an experiment or the like. If this determination is NO, the estimated catalyst temperature Tcat is higher than the AWS operation temperature Tcat_AWS, and the upstream catalyst 51a is in the light-off state, the processing is ended without performing the AWS control. On the other hand, if the determination in step S12 is YES and the estimated catalyst temperature Tcat is less than the AWS operation temperature Tcat_AWS and the catalyst 51a is not lighted off, the process proceeds to the third step.

  In the third step, it is determined whether the vehicle speed is equal to or less than the preset AWS permitted speed. In the present embodiment, the AWS permitted speed is set to a value near zero. If this determination is NO, that is, if the vehicle speed is greater than the AWS permitted speed, the process ends.

  On the other hand, if the determination in the third step is YES and the vehicle speed is equal to or lower than the AWS permitted speed, the process proceeds to a fourth step to execute the AWS control. Specifically, in the fourth step, the air charge amount of each cylinder is increased and the ignition timing is retarded. In detail, the air charge of each cylinder is made larger than the charge at the time of basic control execution. In the present embodiment, the filling amount of each cylinder is increased by setting the opening degree of the throttle valve to the opening side more than the basic throttle valve opening degree. Further, as described later, the ignition timing is retarded more than the basic ignition timing. As described above, when the ignition timing is retarded, the temperature of the exhaust gas rises and the high temperature exhaust gas is introduced to the upstream catalyst 51a, so that the upstream catalyst 51a can be heated and activated. Moreover, the torque and the engine speed can be maintained by increasing the filling amount of each cylinder.

  FIG. 7D shows an example of a fuel injection timing AWS11 (first fuel injection timing), a fuel injection timing AWS12 (second fuel injection timing), an ignition timing AWS13, and a combustion waveform AWS14 when the engine 1 performs AWS. Is shown.

  When the catalyst temperature is low, such as immediately after the engine start, and when the engine 1 is in the idle state, AWS for the catalyst warm-up is implemented. Therefore, as in the case of the above-mentioned high load and low rotation region A2, when the rotation speed of the engine 1 is low, the time required for the crank angle to change by 1 ° becomes long. For example, if all the fuel is injected into the combustion chamber in the first half of the intake stroke or the compression stroke, the reaction of the fuel may proceed excessively, which may lead to premature ignition. When the engine 1 is performing AWS, it is difficult to perform SPCCI combustion.

  Therefore, when the engine 1 is executing AWS, the engine 1 performs SI combustion instead of SPCCI combustion.

  When the engine 1 implements AWS, the spark plug 19 retards the ignition AWS 13 timing after compression top dead center TDC, and ignites the mixture at a predetermined timing of the expansion stroke. That is, ignition is performed in an expansion stroke with low combustion efficiency which causes exhaust loss to warm up the catalyst early.

  Furthermore, in order to compensate for the deterioration of the ignitability, the fuel injection AWS 11 timing is further delayed than the region of the retarded-SI combustion A2, for example, from the vicinity of compression top dead center or thereafter to the first half of the expansion stroke (for example, compression top death At 10 ° CA before point to 40 ° CA after compression top dead center, control is performed such that a strong turbulent state in the combustion chamber 17 by fuel injection can be continued until the ignition AWS 12 time. As a result, the ignitability is ensured, the combustion speed of SI combustion is increased, and SI combustion is stabilized. Pre-ignition is also prevented by retarding the fuel injection AWS 11 period. In the present embodiment, because the compression ratio is high compression of 14 or more, retarded combustion is performed promptly, in other words, since the combustion period is short, a sufficient engine torque can be secured.

  In addition, even during the implementation of AWS, the time (AWS11 to AWS22) from the fuel injection start to the ignition is shorter than the retarded-SI combustion in the high load low rotation range A2. In order to improve the ignitability of the mixture and to stabilize SI combustion, it is necessary to transport the fuel immediately to the vicinity of the spark plug 19, and the strong turbulent state formed by the second fuel injection AWS12 is maintained. In order to perform ignition by the spark plug 19 at the same time. Specifically, the interval between the second fuel injection timing AWS12 and the ignition timing AWS13 is within 20 ° CA.

  As shown in FIG. 8B, when the injector 18 injects fuel in the vicinity of the compression top dead center or in the first half of the expansion stroke thereafter, the piston 3 is positioned near the compression top dead center TDC. Therefore, the fuel spray flows downward along the convex portion 31 of the ignition cavity 33 and radiates radially outward from the center of the combustion chamber 17 along the bottom surface and the circumferential side surface of the ignition cavity 33. Flow toward Thereafter, the air-fuel mixture reaches the opening of the ignition cavity 33 and flows radially outward along the intake side inclined surface 12 a toward the center of the combustion chamber 17. Therefore, the injected fuel spray can be quickly transported around the spark plug 19.

  At this time, no swirl flow is formed in the combustion chamber 17 when the swirl control valve 20c is fully open or substantially fully open. As shown in FIG. 2, the fuel sprays injected from the injection holes of the center lines L1, L2 and L3 enter the ignition cavity 33 and are transported around the spark plug 19 as described above. Therefore, the strong swirl flow can suppress the fuel in the ignition cavity 33 from being separated from the vicinity of the spark plug 19.

  By the way, in the engine 1 of the present embodiment, as described above, the blowby gas reduction device 48 is provided as the exhaust gas purification device, and in such an exhaust gas purification device, the intake port 20 and intake air on the intake passage 4 are Deposits mainly composed of exhaust gas, unburned hydrocarbons, and carbon in oil mist tend to adhere to the stem portion 22 a of the valve 22 and the like. If deposition of deposits on the intake port 20 and the stem 22a of the intake valve 22 continues, the amount of deposited deposits increases with time, and this impedes the flow of intake air and worsens the combustion of the engine 1 .

  In particular, in the present embodiment, in order to execute SPCCI combustion, combustion stability is ensured by homogenizing the mixture in the combustion chamber 17 due to the uneven injection direction of the fuel spray injected from the injector 18 Therefore, by adjusting the opening degree of the swirl control valve 20c provided in the intake port 20, control is performed to homogenize the air-fuel mixture in the combustion chamber 17. For this reason, the disturbance of the intake air flow due to the deposits may make it impossible to properly homogenize the air-fuel mixture due to the swirl flow, which may lower the combustion stability of the engine 1 and may lead to a misfire.

  On the other hand, in the present embodiment, in order to ensure the combustion stability of the engine 1 during SPCCI combustion, the ECU 10 performs misfire determination of the engine 1 and a swirl control valve for stabilizing combustion after misfire determination. Implement 20c control. In order to perform this misfire determination, in addition to the aforementioned sensors, the ECU 10 is provided with a misfire determination means 60 as well as the in-cylinder pressure sensor S5 is connected as shown in FIG.

  First, the ECU 10 determines the operating range of the engine from the rotational speed of the engine 1 and the accelerator opening degree, and it is determined that the operating range is the low middle rotation low middle load region A1 and the middle rotation high load A2 in FIG. , SPCCI combustion is performed.

  In the operation by the SPCCI combustion, the ECU 10 sets the injector 18, the spark plug 19, and the swirl control valve 20c based on the predetermined fuel injection timing, the predetermined ignition timing, and the swirl control valve 20c opening degree set in advance. The control signal is output to bring the engine 1 into the SPCCI combustion state.

  Further, in the SPCCI combustion state, the ECU 10 reads the pressure from the in-cylinder pressure sensor S5 provided in the cylinder head 12, and as shown in FIG. 12A, the number of times the average in-cylinder pressure in one cycle becomes less than a predetermined threshold. Count. When the number of times exceeds a predetermined number n, deposits may be deposited on the stem portion 22a of the intake valve 22, which may cause a slight misfire, for example, the flow of intake may be impeded, and swirl may occur. It is judged as a slight misfire as a state where the homogenization of the mixture by the flow can not be appropriately performed (the strength of the swirl flow is reduced).

  When a slight misfire is determined, as shown in FIG. 12B, the ECU 10 opens the swirl control valve 20c at the current SPCCI combustion state in the next SPCCI combustion state, as shown in FIG. 12 (b). A control signal is output from the degree SCV 40 to the swirl control valve 20 c so as to close the predetermined opening degree SCV 30. As a result, the swirl flow is intensified so as to compensate for the reduced swirl flow in the combustion chamber 17, and the homogenization of the mixture by the swirl flow is controlled to be appropriate.

  Furthermore, when the degree of opening of the swirl control valve 20c reaches a predetermined predetermined degree of swirl control valve opening limit SCV20 and the slight misfire determination is made, the ECU 10 lowers the SCV as shown by a virtual line. The warning light 61 of the meter unit is turned on to prompt the occupant to repair.

  In addition, LNV (Lowest Normalized Value: the minimum of the indicated average effective pressure during a predetermined period) which indicates combustion stability by changing the number of times the average value in one cycle of the above-mentioned in-cylinder pressure to below the lower limit The ratio of the value to the average value of the indicated average effective pressure in a predetermined period may be used. The in-cylinder pressure sensor S5 provided on the cylinder head 12 may be used to measure the indicated mean effective pressure.

  Specifically, the ECU 10 reads the pressure from the in-cylinder pressure sensor S5, and based on the minimum value of the indicated mean effective pressure during the predetermined period of the in-cylinder pressure sensor S5 and the average value of the indicated mean effective pressure during the predetermined period. , LNV is calculated. Then, as shown in the upper drawing of FIG. 14, when the LNV becomes less than the threshold of the LNV provided in advance, it is determined that the misfire is mild. The threshold value of LNV may be, for example, 40%.

  Then, when a slight misfire is determined, as shown in the lower diagram of FIG. 14, the ECU 10 opens the swirl control valve 20c at the time of the next SPCCI combustion as the opening degree of the swirl control valve 20c at the current SPCCI combustion. A control signal is output from the SCV 40 to the swirl control valve 20c so as to close the predetermined opening degree SCV30. As a result, the swirl flow is intensified so as to compensate for the reduced swirl flow in the combustion chamber 17, and the homogenization of the mixture by the swirl flow is controlled to be appropriate.

  Furthermore, when the degree of opening of the swirl control valve 20c reaches a predetermined predetermined degree of swirl control valve opening limit SCV20 and the slight misfire determination is made, the ECU 10 lowers the SCV as shown by a virtual line. The warning light 61 of the meter unit is turned on to prompt the occupant to repair.

  FIG. 11 shows a modification of the injection direction of the fuel injected from the plurality of injection holes of the injector 18 of FIG. 2 and the injection holes of the plurality of injection holes. In addition, about the component similar to the above-mentioned embodiment shown in FIG. 2, while using the same code | symbol in FIG. 11, the description is abbreviate | omitted.

  Specifically, in the above-described embodiment, among the plurality of injection ports of the injector 18, the distance between the center lines is set so that the fuel spray injected from the injection ports of the center lines L1, L2 and L3 enters the ignition cavity 33. It is narrowed. Instead of this, in the modification, as shown in FIG. 11, center lines L11 to L20 of the axes of the fuel sprays injected from the plurality of injection holes H1 to H10 of the injector 18 are arranged radially equally. .

  Further, among the center lines L11 to L20 of the fuel spray injected from the plurality of injection holes H1 to H10, the fuel sprays injected from the injection lines H1 and H2 of the center line L11 and the center line L12 are in the ignition cavity 33. The fuel sprays injected from the injection ports H3 to H10 of the center lines L13 to L20 are directed to the outside of the ignition cavity 33 in the opposite direction.

  Further, the injection holes of the injection holes H1 and H2 of the center lines L11 and L12 directed into the ignition cavity 33 are formed larger than the injection holes of the injection holes H3 to H10 of the center lines L13 to L20.

  As a result, it is possible to secure a sufficient amount of fuel spray flowing into the ignition cavity 33 for ignition. As a result, the fuel can be transported quickly around the spark plug 19, and the ignition performance of the mixture can be improved and the SI combustion can be stabilized.

  Specifically, as in the above embodiment, during AWS control for raising the temperature of the exhaust purification catalyst 51, for example, the exhaust temperature is raised by retarding the ignition timing, and the catalyst is warmed up early. Machine is realized. Then, the mixture in the ignition cavity 33 is ignited by the ignition plug 19 facing the inside of the ignition cavity 33.

  At this time, since the injection holes of the injection holes H1 and H2 directed to the ignition cavity 33 are larger than the injection holes of the injection holes H3 to H10 directed to the outside of the ignition cavity 33, the ignition timing is retarded. Since sufficient fuel to compensate for the deterioration can be secured in the ignition cavity 33, the ignitability can be secured.

  Furthermore, by changing the degree of opening of the swirl control valve 20c when not cold, by forming a swirl flow in the combustion chamber 17, the fuel in the combustion chamber 17 can be rapidly homogenized. For example, combustion stability can be ensured in the operating state of the engine 1 where the fuel concentration in the combustion chamber 17 needs to be homogenized as in CI combustion.

  As described above, according to the present invention, in an engine with a relatively high compression ratio and an engine with a small cavity, ignition performance and combustion stability can be achieved when AWS is implemented. There is a possibility.

1 engine 3 piston 4 intake passage 5 exhaust passage 10 ECU (controller)
17 combustion chamber 18 injector 19 spark plug 20 c swirl control valve (swirl control valve)
22 intake valve 22a stem portion 32 large cavity (second cavity)
33 Ignition cavity (cavity, small cavity)
48 Blow-by system 50 Catalyst device (exhaust purification catalyst)
60 Misfire Determination Means H1 to H10 Multiple Nozzles

Claims (7)

An exhaust purification catalyst provided in an exhaust passage of the engine;
A piston provided in a combustion chamber of the engine and having a cavity on an upper surface thereof;
A plurality of injection ports are provided, and a first injection port portion for injecting fuel so that the injection direction of fuel injected from a part of the plurality of injection ports is directed to the cavity, and injection directions of fuel injected from other injection ports are An injector having a second injection port for injecting fuel to be directed to the outside of the cavity;
A spark plug disposed facing the cavity;
A control device for an engine, comprising: a controller connected to each of the injector and the spark plug and configured to operate the engine by outputting a control signal to each of the injector and the spark plug. ,
The first injection port portion of the injector and the second injection port portion have a plurality of injection ports having injection direction axes different from each other, and the injection direction of the adjacent injection ports of the first injection port portion when viewed from the axial direction of the piston Since the angle formed between the shafts is set smaller than the angle formed between the injection direction axes of the adjacent injection ports of the second injection port section, the mixture in the cavity is more than the mixture in the outside of the cavity. The rich air-fuel ratio is
A swirl forming portion for generating a swirl flow exceeding a predetermined strength is provided in the combustion chamber,
When the catalyst temperature of the exhaust purification catalyst is low, the controller causes the spark plug to ignite the air-fuel mixture at a timing delayed from that in the non-cold state to raise the catalyst temperature of the exhaust purification catalyst. Output control signal,
When not cold, the swirl forming portion forms a swirl flow,
A control device of an engine, wherein the piston is provided with a second cavity, and the cavity is a small cavity smaller than the second cavity . An exhaust purification catalyst provided in an exhaust passage of the engine;
A piston provided in a combustion chamber of the engine and having a cavity on an upper surface thereof;
A plurality of injection ports are provided, and a first injection port portion for injecting fuel so that the injection direction of fuel injected from a part of the plurality of injection ports is directed to the cavity, and injection directions of fuel injected from other injection ports are An injector having a second injection port for injecting fuel to be directed to the outside of the cavity;
A spark plug disposed facing the cavity;
A control device for an engine, comprising: a controller connected to each of the injector and the spark plug and configured to operate the engine by outputting a control signal to each of the injector and the spark plug. ,
By setting the size of the injection port of the first injection port in the injector to be larger than the size of the injection port of the second injection port, the air-fuel mixture in the cavity is made richer than the air-fuel mixture outside the cavity,
A swirl forming portion for generating a swirl flow exceeding a predetermined strength is provided in the combustion chamber,
When the catalyst temperature of the exhaust purification catalyst is low, the controller causes the spark plug to ignite the air-fuel mixture at a timing delayed from that in the non-cold state to raise the catalyst temperature of the exhaust purification catalyst. Output control signal,
An engine control device characterized in that a swirl flow is formed by a swirl formation portion when not cold.   The engine control device according to claim 1 or 2, wherein the controller does not form a swirl flow when cold, or forms a swirl flow with a weaker strength than when not cold. . The swirl formation portion is a swirl control valve provided in the intake passage,
The engine control device according to any one of claims 1 to 3, wherein the controller controls the opening degree of the swirl control valve to be a swirl ratio of 2 or more and less than 4. The engine includes an intake valve having a stem portion;
Equipped with a blow-by system,
The controller has a misfire determination means,
The engine control device according to any one of claims 1 to 4, wherein the swirl flow is intensified when the misfire determination means determines a misfire. In the high load and low speed operation region, the engine is
The controller outputs a control signal to the injector so as to perform fuel injection at a delayed timing after the late stage of the compression stroke as compared with the other operation range, and then outputs a control signal to the spark plug so as to ignite. The engine control device according to any one of claims 1 to 5, characterized in that: An exhaust purification catalyst provided in an exhaust passage of the engine;
A piston provided in a combustion chamber of the engine and having a cavity on an upper surface thereof;
A plurality of injection ports are provided, and a first injection port portion for injecting fuel so that the injection direction of fuel injected from a part of the plurality of injection ports is directed to the cavity, and injection directions of fuel injected from other injection ports are An injector having a second injection port for injecting fuel to be directed to the outside of the cavity;
A spark plug disposed facing the cavity;
A control device for an engine, comprising: a controller connected to each of the injector and the spark plug and configured to operate the engine by outputting a control signal to each of the injector and the spark plug. ,
The first injection port portion of the injector and the second injection port portion have a plurality of injection ports having injection direction axes different from each other, and the injection direction of the adjacent injection ports of the first injection port portion when viewed from the axial direction of the piston Since the angle formed between the shafts is set smaller than the angle formed between the injection direction axes of the adjacent injection ports of the second injection port section, the mixture in the cavity is more than the mixture in the outside of the cavity. The rich air-fuel ratio is
A swirl forming portion for generating a swirl flow exceeding a predetermined strength is provided in the combustion chamber,
When the catalyst temperature of the exhaust purification catalyst is low, the controller causes the spark plug to ignite the air-fuel mixture at a timing delayed from that in the non-cold state to raise the catalyst temperature of the exhaust purification catalyst. Output control signal,
When not cold, the swirl forming portion forms a swirl flow,
A control device for an engine, wherein a compression ratio of the engine is 14 or more .

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