JP2022051346A - Internal combustion engine - Google Patents

Abstract

To provide an internal combustion engine including auxiliary chamber combustion that promotes temperature rise to a temperature enabling activation of a catalyst provided in an exhaust passage.SOLUTION: In an engine 1, in an exhaust stroke, an engine control unit 30 executes control for igniting an air-fuel mixture in an auxiliary combustion chamber 44a to which fuel is sprayed from an injector 48 by using an ignition plug 49 to inject a torch flame F from a jet hole 45 and sending the torch flame F together with a combustion gas EX CAS to an exhaust port 24 in which an exhaust valve 26 is opened. Thus, in the engine, due to the torch flame, the combustion gas of which a temperature has been further increased heats a catalyst, so that a period until the temperature of the catalyst reaches an activation temperature enabling purification of the combustion gas can be shortened.SELECTED DRAWING: Figure 1

Description

The present invention relates to a lean-burn internal combustion engine provided with an auxiliary combustion chamber that promotes temperature rise of an exhaust gas purification catalyst.

In recent years, lean burn technology has been attracting attention as one of the methods for improving the thermal efficiency of gasoline engines. This lean-burn technology reduces the amount of fuel put into the combustion chamber to create a lean mixture that burns quickly to improve fuel economy.

In lean combustion technology, for example, as disclosed in Patent Document 1 and Patent Document 2, a sub-combustion chamber (pre-chamber) combustion method is known in order to reduce heat loss and exhaust loss.

In the sub-combustion chamber combustion method, an ignition plug arranged in the combustion chamber is covered with a semi-circular cap having a plurality of minute holes to form a sub-combustion chamber, and a fuel injection device is installed in this sub-combustion chamber. Deploy. Then, when a small amount of fuel is injected into the sub-combustion chamber and ignited, the fuel in the sub-combustion chamber burns at once, and the torch flame blows out into the combustion chamber from a plurality of minute holes. This torch flame ignites the dilute air-fuel mixture in the cylinder and enables rapid combustion in a short time. As a result, stable combustion in a dilute environment and self-ignition at the bore end can be suppressed.

Japanese Unexamined Patent Publication No. 7-026961 Japanese Unexamined Patent Publication No. 2018-105171

By the way, in a vehicle having a power unit of an internal combustion engine or the like, a catalytic converter for purifying harmful components in exhaust gas is provided in the exhaust passage. The catalyst (three-way catalyst) in this catalyst converter is heated to the activation temperature for purifying harmful components by the heat of the exhaust gas.

However, in the internal combustion engine of the sub-combustion chamber combustion type, since the combustion speed of the dilute mixture is high, it is difficult to raise the temperature of the catalyst provided in the exhaust passage at an early stage, and the catalyst is activated at the time of cold start or the like. There was a problem that it took a long time to reach the conversion temperature.

Therefore, in view of the above circumstances, it is an object of the present invention to provide an internal combustion engine having a sub-chamber combustion that promotes a temperature rise to a temperature at which a catalyst provided in an exhaust passage is activated.

The internal combustion engine according to one aspect of the present invention is an internal combustion engine including a cylinder head and a cylinder block, the cylinder formed in the cylinder block, a piston slidably inserted in the cylinder, and the above. A plurality of engines formed in the cylinder and formed in the cylinder head so as to communicate with the main combustion chamber between the piston and the cylinder head and the main combustion chamber, and the exhaust valve and the intake valve are provided so as to be openable and closable. A port, a chamber provided in the cylinder head with a bottom facing the piston side and having at least one auxiliary combustion chamber, an injector provided in the cylinder head and spraying fuel, and an injector provided in the cylinder head. An ignition plug that ignites the fuel in the sub-combustion chamber, an injection port formed in the chamber so as to communicate with the sub-combustion chamber and injecting a torch flame, and an engine control that drives and controls the injector and the ignition plug. The engine control unit comprises a unit, and the engine control unit ignites the air-fuel mixture in the sub-combustion chamber in which the fuel is sprayed from the injector by the ignition plug and injects the torch flame from the injection port during the exhaust stroke. Then, the control of sending the torch flame together with the combustion gas to the port opened by the exhaust valve is executed.

According to the present invention, it is possible to provide an internal combustion engine having a sub-chamber combustion that promotes a temperature rise to a temperature at which a catalyst provided in an exhaust passage is activated.

Schematic configuration diagram partially showing the cross section of the main part of the lean burn engine Partial cross-sectional view showing the state of the lean burn engine in the intake stroke Partial cross-sectional view showing the state of the lean burn engine in the compression stroke Partial cross-sectional view showing the state of the lean-burn engine at the time of ignition when the torch flame is injected from the first auxiliary combustion chamber. Partial cross-sectional view showing the state of the lean burn engine in the combustion stroke Partial cross-sectional view showing the state of the lean burn engine in the exhaust stroke where the torch flame is injected from the second auxiliary combustion chamber. Partial cross-sectional view showing the state of the lean-burn engine at the time of ignition in which the torch flame is injected from the second auxiliary combustion chamber of the modified example. Partial cross-sectional view showing the state of the lean-burn engine in the exhaust stroke in which the torch flame is injected from the second auxiliary combustion chamber of the modified example.

Hereinafter, embodiments of one aspect of the present invention will be described in detail with reference to the drawings. In the figures used in the following description, the scales are different for each component in order to make each component recognizable on the drawings. It is not limited to the number of components described, the shape of the components, the ratio of the sizes of the components, and the relative positional relationship of each component.

The lean-burn engine (hereinafter, simply abbreviated as an engine) 1 which is an internal combustion engine shown in FIG. 1 indicates a spark-ignition type in-cylinder injection engine, and in the present embodiment, for example, a naturally-intake type. The cross section of the 1-cylinder portion of the 4-cylinder gasoline engine is illustrated.

In the engine 1, a piston 15 is slidably inserted into each cylinder 11 that opens in the cylinder block 10. A piston cavity 15a is formed on the top surface of the piston 15. A main combustion chamber 12 is provided as a space between the piston 15 and the cylinder head 20.

Here, for example, in the region corresponding to each cylinder 11, two intake ports 23 and two exhaust ports 24 are opened on the bottom surface 28 of the cylinder head 20. Further, the two intake ports 23 and the two exhaust ports 24 are respectively provided with an intake valve 25 and an exhaust valve 26 for opening and closing them. In FIG. 1, only one intake port 23 and one exhaust port 24 are shown.

Further, a first sub-combustion chamber unit 40 that functions as a main pre-chamber is provided at a substantially central position of the main combustion chamber 12 on the cylinder head 20 side. Further, a second sub-combustion chamber unit 41 that functions as a sub-pre-chamber is provided on the exhaust port 24 side of the main combustion chamber 12 on the cylinder head 20 side.

The first auxiliary combustion chamber unit 40 holds a first chamber 42, which is a cap body having a bottomed cylinder, a first spark plug 47, and a first injector 46 that functions as a fuel injection valve for injection. ..

The second auxiliary combustion chamber unit 41 holds a second chamber 44, which is a cap body having a bottomed cylinder, a second spark plug 49, and a second injector 48 that functions as a fuel injection valve for injection. ..

The ignition portions formed at the tips of the first and second spark plugs 47 and 49 and the fuel injection ports provided at the tips of the first and second injectors 46 and 48 are the first and first, respectively. It faces the first and second auxiliary combustion chambers 42a and 44a, which are narrow spaces formed by the chambers 42 and 44 of 2.

The first chamber 42 has a plurality of nozzles 43 formed in the bottom portion in the circumferential direction. Eight of these plurality of nozzles 43 are formed at substantially equal intervals, for example, and each hole axis of these eight nozzles 43 has a predetermined angle θ (for example, θ = 45) with respect to the central axis of the first chamber 42. °). That is, the eight nozzles 43 communicate with the first auxiliary combustion chamber 42a, and each hole axis is set so that the openings face radially with a depression angle toward the main combustion chamber 12.

In the second chamber 44, one or two nozzles 45 are formed toward the exhaust valve 26 and the exhaust port 24 side. The nozzle 45 is preferably formed in one case, for example, substantially in the middle of the two exhaust valves 26, and in two cases, for example, individually formed toward each exhaust valve 26. preferable.

The one or two nozzles 45 also have a hole axis having a predetermined angle θ (eg θ = 90 °) with respect to the central axis of the second chamber 44. That is, the hole shaft is set so that the injection port 45 communicates with the second auxiliary combustion chamber 44a and faces the exhaust valve 26 side of the main combustion chamber 12.

Further, the cylinder head 20 holds a third injector 17 that functions as an in-cylinder injection fuel injection valve, and the fuel injection port of the third injector 17 has a predetermined depression angle with respect to the top surface of the piston 15. It faces the inside of the cylinder 11 while holding it.

The cylinder head 20 is provided with a variable valve mechanism (not shown) capable of variably switching the valve opening state of the intake valve 25 and the exhaust valve 26 for each combustion cycle. The variable valve mechanism can drive the intake valve 25 and the exhaust valve 26 at an arbitrary timing and lift amount, and is driven and controlled by the engine control unit (ECU) 30.

Further, the ECU 30 is mainly composed of a well-known microcomputer having a CPU, ROM, RAM, an input / output interface, etc., and has an intake air amount sensor (not shown) on the input side and an engine that detects the engine rotation speed from the rotation of the crank shaft. Various sensors / switches including a rotation speed sensor are connected.
Further, the ECU 30 is, for example, the temperature of the water temperature sensor 31 that detects the temperature of the coolant of the water-cooled engine, the O2 sensor 32 that detects the amount of oxygen in the exhaust gas, and the temperature of the catalyst 51 of the catalyst converter 50 or the temperature of the exhaust gas immediately after the catalyst outlet. The catalyst temperature sensor 33 for detecting the above is connected.

The O2 sensor 32 is provided in the exhaust pipe 29 connected to the exhaust manifold 27 communicating with the exhaust port 24. Further, the catalyst temperature sensor 33 is provided on the rear side of the case body 52 that functions as a protector of the exterior body that houses the catalyst 51 of the catalyst converter 50.

In the engine 1 configured as described above, as shown in FIG. 2, when the piston 15 descends from the position of the top dead center, the inside of the cylinder 11 becomes negative pressure, and the engine 1 is interlocked with the movement of the piston 15. The intake valve 25 is opened, and an intake stroke in which air (AIR) is sucked into the main combustion chamber 12 from the intake port 23 is performed. Then, as shown in FIG. 3, the engine 1 is subjected to a compression stroke in which the piston 15 rises from the position of the bottom dead center.

During this compression stroke, the engine 1 sprays fuel (gasoline) into the main combustion chamber 12 from the fuel injection port of the third injector 17 under the control of the ECU 30 at a timing according to the required load. Further, in the engine 1, fuel (gasoline) is sprayed into the first auxiliary combustion chamber 42a from the fuel injection port of the first injector 46 under the control of the ECU 30 at a predetermined timing.

Then, as shown in FIG. 4, when the piston 15 moves near the top dead center, the engine 1 generates sparks in the ignition portion of the first spark plug 47 under the control of the ECU 30 to create a narrow space. Ignite the air-fuel mixture in the first auxiliary combustion chamber 42a.

As a result, the air-fuel mixture in the first auxiliary combustion chamber 42a rapidly burns, and eight torch flames F, which are ignition sources, are radially injected into the main combustion chamber 12 from a plurality of, here, eight nozzles 43. Then, a combustion process is performed in which the main combustion chamber 12 is rapidly burned.

Due to this combustion stroke, as shown in FIG. 5, in the engine 1, the piston 15 is pushed down to the bottom dead center by the expansion action of the gas in the burned main combustion chamber 12, the power is transmitted, and the engine 1 is further lowered by the inertial force. Exercise from dead center to top dead center.

At this time, as shown in FIG. 6, the engine 1 has an exhaust stroke in which the exhaust valve 26 opens in conjunction with the movement of the piston 15 and the combustion gas (exhaust gas / EX GAS) is pushed into the exhaust port 24 outside the cylinder 11. Will be done.

Further, when the engine 1 shifts from the combustion stroke to the exhaust stroke, fuel (gasoline) is sprayed into the second auxiliary combustion chamber 44a from the fuel injection port of the second injector 48 under the control of the ECU 30. Then, the engine 1 generates a spark at the ignition portion of the second spark plug 49 under the control of the ECU 30 at a predetermined timing when the exhaust valve 26 is opened (for example, the moment when the exhaust valve 26 is opened). Then, the air-fuel mixture in the second auxiliary combustion chamber 44a in the narrow space is ignited.

As a result, the air-fuel mixture in the second auxiliary combustion chamber 44a is burned, and the torch flame F is injected into the main combustion chamber 12 from the injection port 45 toward the exhaust port 24 in which the exhaust valve 26 is opened. At this time, the torch flame F enters the exhaust port 24 due to the air flow of the combustion gas being swept into the exhaust port 24.

The combustion gas swept into the exhaust port 24 is further heated by the torch flame F to a high temperature, and is sent to the catalyst converter 50 through the exhaust manifold 27 and the exhaust pipe 29 communicating with the exhaust port 24. This high-temperature combustion gas heats the catalyst 51 of the catalyst converter 50 to raise the temperature. As a result, the catalyst 51 is heated by the high-temperature combustion gas, and the time required to reach the activation temperature for purifying the combustion gas is shortened.

Based on the above description, the engine 1 of the present embodiment has a configuration in which two first and second sub-combustion chamber units 40 and 41 are provided in the combustion chamber. The first sub-combustion chamber unit 40 of the two is the main ignition source of the method of injecting the torch flame F, which is a jet flame, into the main combustion chamber 12 to burn the air-fuel mixture. Ignition of the sub that promotes the temperature rise of the catalyst 51 of the catalyst converter 50 in which the sub-combustion chamber unit 41 injects the torch flame F directly toward the inside of the exhaust port 24 at the timing when the exhaust valve 26 opens. It is the source.

As described above, in the engine 1, the ignition timings of the main first sub-combustion chamber unit 40 and the sub second sub-combustion chamber unit 41 are different, and the second sub-combustion chamber unit 41 is driven when the temperature of the catalyst 51 is low. Then, control is performed to inject the torch flame F according to the timing at which the exhaust valve 26 is opened. Then, since the engine 1 can directly inject the torch flame F injected from the second sub chamber combustion unit 41 into the exhaust system, the warm-up of the catalyst 51 can be promoted.

The ECU 30 controls the drive and stop of the second auxiliary combustion chamber unit 41 under various conditions for promoting the temperature rise to the temperature at which the catalyst 51 whose temperature has dropped due to a cold start or a cold region is activated. It will be carried out at the time of. The ECU 30 executes control of driving and stopping of the second auxiliary combustion chamber unit 41 based on the detection values of the water temperature sensor 31, the O2 sensor 32, the catalyst temperature sensor 33, and the like.

Further, in the engine 1, since the main first sub-combustion chamber unit 40 and the sub second sub-combustion chamber unit 41 are independently controlled, the engine 1 is first during warm-up operation (fast idle). By using the injection of the torch flame F by the sub-chamber combustion unit 40 to ensure combustion stability and using the injection of the torch flame F by the second sub-chamber combustion unit 41 to warm up the catalyst 51, the temperature of the catalyst 51 is reached. It is also possible to suppress the vibration generated by the torque fluctuation due to the misfire of the air-fuel mixture without lowering.

In the above embodiment, the first sub-combustion chamber unit 40 sprays fuel (gasoline) directly onto the first sub-combustion chamber 42a by the first injector 46 and ignites the first ignition plug 47. The so-called active mode of the method of injecting the torch flame F into the main combustion chamber 12 has been exemplified, but the present invention is not limited to this, and the first injector 46 is not provided, and each injection port from the main combustion chamber 12 during the compression stroke. A so-called passive mode may be used in which the air-fuel mixture that has entered the first auxiliary combustion chamber 42a from 43 is injected into the main combustion chamber 12 by the ignition of the first ignition plug 47.

(Modification example)
As shown in FIGS. 7 and 8, the engine 1 of this modification is configured to include only the second sub-combustion chamber unit 41 having the function of the first sub-combustion chamber unit 40. That is, the second sub-combustion chamber unit 41 here has a configuration having the functions of a main pre-chamber and a sub-pre-chamber.

As shown in FIG. 7, the engine 1 here is controlled to ignite the air-fuel mixture in the second auxiliary combustion chamber 44a by generating sparks in the ignition portion of the second spark plug 49 during the combustion stroke. Is performed by the ECU 30. As a result, the torch flame F, which is an ignition source, is injected into the main combustion chamber 12 from the injection port 45, and the main combustion chamber 12 is rapidly burned to carry out the combustion stroke.

Further, the engine 1 generates a spark in the ignition portion of the second spark plug 49 at a predetermined timing when the exhaust valve 26 is opened (for example, the moment when the exhaust valve 26 is opened), and the second engine 1 generates a spark. Control to ignite the air-fuel mixture in the sub-combustion chamber 44a is executed by the ECU 30.

As a result, the air-fuel mixture in the second auxiliary combustion chamber 44a is burned, and as shown in FIG. 8, the torch flame F is the main combustion chamber 12 from the injection port 45 toward the exhaust port 24 in which the exhaust valve 26 is opened. It is sprayed inside. Therefore, the torch flame F is sent into the exhaust port 24 together with the combustion gas.

Even with such a configuration, in the engine 1, the time until the combustion gas heated to a higher temperature heats the catalyst 51 by the torch flame F and the catalyst 51 reaches the activation temperature for purifying the combustion gas can be shortened. , The configuration has the effects described in the above embodiment.

Further, since the engine 1 has only the second auxiliary combustion chamber unit 41, the structure can be simplified and the cost can be suppressed. Further, the engine 1 can increase the diameters of the intake port 23, the exhaust port 24, the intake valve 25 and the exhaust valve 26 on the bottom surface 28 of the cylinder head 20, and can improve the intake / exhaust efficiency to the cylinder 11.

In the above-described embodiment and modification, the engine 1 illustrates the configuration of the in-cylinder injection engine, but the present invention is not limited to this, and the engine 1 is a port injection engine that injects fuel into the intake pipe to generate an air-fuel mixture. It is a technology that can be applied.

By the way, the ECU 30 has a processor including a central processing unit (CPU), a storage device such as a ROM and a RAM, and the like. Further, the configuration of all or a part of the plurality of circuits of the processor may be executed by software. For example, the CPU may read and execute various programs corresponding to each function stored in the ROM.

Further, all or a part of the functions of the processor may be configured by a logic circuit or an analog circuit, or the processing of various programs may be realized by an electronic circuit such as FPGA.

The inventions described in the above embodiments are not limited to those embodiments, and various modifications can be carried out at the implementation stage without departing from the gist thereof. Further, each of the above forms includes inventions at various stages, and various inventions can be extracted by an appropriate combination of the plurality of disclosed constituent requirements.
For example, even if some constituents are deleted from all the constituents shown in each form, if the described problem can be solved and the stated effect is obtained, this constituent is deleted. The configuration can be extracted as an invention.

1 ... Engine 10 ... Cylinder block 11 ... Cylinder 12 ... Main combustion chamber 15 ... Piston 15a ... Piston cavity 17 ... Third injector 20 ... Cylinder head 23 ... Intake port 24 ... Exhaust port 25 ... Intake valve 26 ... Exhaust valve 27 ... Exhaust manifold 28 ... Bottom surface 29 ... Exhaust pipe 30 ... Engine control unit (ECU)
31 ... Water temperature sensor 32 ... O2 sensor 33 ... Catalyst temperature sensor 40 ... First sub-combustion chamber unit 42 ... First chamber 42a ... First sub-combustion chamber 43, 45 ... Injection 44 ... Second chamber 44a ... Second 2 sub-combustion chamber 46 ... 1st injector 47 ... 1st spark plug 48 ... 2nd spark plug 49 ... 2nd ignition plug 50 ... Catalytic converter 51 ... Catalyst 52 ... Case body F ... Torch flame

Claims (4)

An internal combustion engine equipped with a cylinder head and a cylinder block.
The cylinder formed in the cylinder block and
A piston that is slidably inserted into the cylinder,
A main combustion chamber formed in the cylinder and between the piston and the cylinder head,
A plurality of ports formed in the cylinder head so as to communicate with the main combustion chamber and provided with an exhaust valve and an intake valve that can be opened and closed, and
A chamber provided on the cylinder head with a bottom facing the piston side and having at least one auxiliary combustion chamber.
An injector provided on the cylinder head and spraying fuel,
An ignition plug provided on the cylinder head and igniting the fuel in the sub-combustion chamber,
A nozzle formed in the chamber so as to communicate with the sub-combustion chamber and injects a torch flame,
An engine control unit that drives and controls the injector and the spark plug,
Equipped with
At the time of the exhaust stroke, the engine control unit ignites the air-fuel mixture in the sub-combustion chamber to which the fuel is sprayed from the injector by the spark plug, injects the torch flame from the nozzle, and causes the combustion gas together with the combustion gas. An internal combustion engine characterized by executing control of sending a torch flame to the port opened by the exhaust valve. The internal combustion engine according to claim 1, wherein the injection port is formed so as to face the exhaust valve side. It comprises two chambers individually provided with the spark plugs for igniting the fuel in the sub-combustion chamber.
The engine control unit ignites the air-fuel mixture in the sub-combustion chamber of one of the chambers by one of the spark plugs during the combustion stroke, injects the torch flame into the main combustion chamber, and in the exhaust stroke. The internal combustion engine according to claim 1, wherein the air-fuel mixture in the sub-combustion chamber of the other chamber is ignited by the other spark plug to inject the torch flame. The internal combustion engine according to claim 3, wherein the injection port of the other chamber is formed so as to face the exhaust valve side.

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