JP4214398B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine that performs exhaust gas recirculation (EGR), and more particularly to an internal combustion engine that performs EGR during stoichiometric operation.

In general, it is known that when exhaust gas is introduced by EGR into a cylinder during engine operation, pump loss and heat loss can be reduced and thermal efficiency can be improved to improve fuel efficiency.
On the other hand, when the exhaust gas recirculation amount (EGR amount) increases, the combustion becomes slow, the isovolume decreases, the thermal efficiency decreases, and the fuel consumption deteriorates. In other words, there is a problem that the EGR amount deteriorates conversely by an increase, although the fuel efficiency can be improved when the amount is small. The equal volume is one of the combustion indices, and is the ratio of time loss due to the fact that combustion is not completed instantaneously. Engines are generally designed to be in the range of about 0.8-0.95.

  Here, paying attention to the fact that the equal volume is not lowered, an engine that directly injects pressurized air into the cylinder when the EGR amount during stoichiometric operation is large (at a high EGR rate) is disclosed in the present invention. (Japanese Patent Application No. 2003-360944). This pressurized air is generated by a pressurized air supply device equipped with an air pump or the like. According to this engine, turbulence (turbulence action) between fuel and air becomes active in the combustion chamber, and the isovolume does not decrease.

  This will be described with reference to FIG. First, when direct injection of pressurized air is not performed in the cylinder (conventional 1), the combustion fluctuation is small at the low EGR rate, the combustion period is not so long, and the equal volume is ensured within the allowable range. Therefore, fuel consumption is improved. However, as the EGR amount increases, the combustion becomes slower, the combustion period becomes longer, and the isovolume decreases, so that the thermal efficiency also decreases, and conversely the fuel efficiency deteriorates.

  On the other hand, when the pressurized air is directly injected into the cylinder as in the proposal of the present inventor (conventional 2), not only at a low EGR rate but also at a high EGR rate with a large EGR amount, Since the turbulent action becomes active and the combustion speed is increased, the combustion fluctuation becomes smaller than that in the conventional case 1, and the combustion period becomes shorter. Therefore, since the equal volume is increased as compared with the conventional case 1, the thermal efficiency is improved and the fuel efficiency is improved.

By the way, in the above-described prior art, a pressurized air supply device is required for generating pressurized air. In other words, the engine requires an additional configuration such as an air pump, and there remains a problem that the manufacturing cost cannot be kept low.
It should also be noted that when the above-described pressurized air is used, it is necessary to reduce the intake air amount in advance. In other words, in order to maintain the stoichiometric operation, it is necessary to close the throttle valve by the amount of pressurized air supplied to finally keep the fresh air amount in the cylinder constant, which increases the pump loss. This is because it hinders improvement in fuel consumption.

  The present invention has been made in view of such problems, and in the case of performing EGR, particularly in the case of performing EGR during stoichiometric operation, an internal combustion engine capable of suppressing the manufacturing cost and improving fuel consumption. The purpose is to provide an engine.

In order to achieve the above object, an internal combustion engine according to claim 1 is provided separately from an exhaust gas recirculation means capable of variably controlling the amount of exhaust gas introduced into the combustion chamber of each cylinder of the engine and an intake / exhaust port communicating with the combustion chamber. A branch port communicating with each combustion chamber, a communication chamber communicating each branch port, and a port opening / closing valve disposed at each branch port to switch communication between the branch port and the combustion chamber And, during the introduction of the exhaust gas into the combustion chamber by the exhaust gas recirculation means, the port opening / closing valve of the predetermined cylinder is temporarily controlled in the latter half of the compression stroke immediately before the combustion of the predetermined cylinder so as to store the pressurized air in the communication chamber. In addition, in order to supply pressurized air to the combustion chambers of other cylinders other than the predetermined cylinder, the port opening / closing valves of the other cylinders are temporarily set between the middle of the intake stroke before the combustion of the other cylinders and the middle of the compression stroke. Open / close control It is characterized in that it comprises a that control means.

Furthermore, in the invention according to claim 2 , the control means supplies the compressed air in the predetermined cylinder to the combustion chamber of the other cylinder whose ignition timing is continuous with the predetermined cylinder. It is characterized in that each port on-off valve of the cylinder is temporarily controlled to open and close.
According to a third aspect of the present invention, the exhaust gas recirculation means capable of variably controlling the amount of exhaust gas introduced into the combustion chamber of the engine and the intake / exhaust port communicating with the combustion chamber are provided separately, Communicating in the latter half of the compression stroke immediately before combustion of a predetermined cylinder of the engine during the introduction of the exhaust gas into the combustion chamber by the exhaust gas recirculation means, the port opening / closing valve for switching communication between the communication chamber and the combustion chamber The port opening / closing valve of the predetermined cylinder is temporarily controlled to be stored in the chamber so as to store the pressurized air, and is stored in the communication chamber from the middle of the intake stroke before the combustion to the middle of the compression stroke in the next combustion cycle of the predetermined cylinder. Control means for temporarily opening and closing the port opening / closing valve to supply the pressurized air to the combustion chamber of the predetermined cylinder.

Further, the invention according to claim 4 is characterized in that the control means controls the opening / closing of the port opening / closing valve during the stoichiometric operation of the engine.

  Therefore, according to the internal combustion engine of the first aspect of the present invention, the control means controls the operation of the port opening / closing valve and supplies the pressurized air to the combustion chamber during the EGR operation. Even when the amount of EGR is large without using a supply device, turbulence (turbulence action) between fuel and air becomes active in the combustion chamber. Therefore, it is possible to improve the fuel efficiency by increasing the isovolume by increasing the combustion speed and improving the thermal efficiency while keeping the manufacturing cost low.

Further, in addition to the improvement of the fuel consumption, the atomization of the fuel can be promoted in the combustion chamber by activating the turbulence. That is, the fuel adhering to the piston and cylinder is reduced, unburned fuel (HC) is reduced in the cold state, and exhaust gas purification can be promoted.
The air supplied to the or combustion chamber, in view of the fact that pressurized sufficiently pressurized in the latter half of the compression stroke, the control means at this time to temporarily open the port on-off valve of a given cylinder, pressurized air Can be reliably taken into the communication room. Therefore, the manufacturing cost is lower than in the conventional case, and there is no concern of electrical loss as in the case of using an electric pump, for example, and air pressurization can be achieved efficiently.

Furthermore, the air intake stroke metaphase, the low pressure in the combustion chamber (cylinder pressure) occur above turbulence effect is satisfactory, In addition, in the compression stroke mid the turbulence effect and more since they produce the disturbance acting on very shortly before the combustion Be activated. Therefore, if the control means temporarily opens the port opening / closing valve of the other cylinders at this time, it can contribute to an appropriate improvement in fuel consumption.
Furthermore, according to the second aspect of the present invention, since the pressurized air is supplied to the combustion chamber of another cylinder whose ignition timing is continuous with the predetermined cylinder, the throttle valve is used to increase or decrease the amount of fresh air for the pressurized air. Therefore, the throttle valve control can be simplified.

Further, according to the invention described in claim 3 , the same effect as in claim 1 can be obtained.
According to the fourth aspect of the present invention, the pressurized air supplied to the combustion chamber is supplied in advance to perform the stoichiometric operation, in other words, separately from the conventional stoichiometric operation. It is not the air that has been used, but the air that has been inhaled to perform the stoichiometric operation. And if this is utilized, it is not necessary to close a throttle valve separately for supply of pressurized air, and the increase in the pump loss accompanying this can also be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The engine 1 of this embodiment is an in-line four-cylinder engine. The cylinder head 2 of the engine 1 includes four cylinders 11 to 14 # 1 to # 4, and an intake port 4 is formed for each cylinder 11 to 14. Further, an intake valve 8 is provided on the side of the combustion chamber 3 of each intake port 4 to perform communication and disconnection between each intake port 4 and the combustion chamber 3.

One end of an intake passage 10 is connected to each intake port 4. In the intake passage 10, electromagnetic injectors (not shown) for injecting fuel into the cylinders 11 to 14 are attached to the respective cylinders, and the injectors are directed toward the combustion chamber 3 in the exhaust stroke of the piston 5. Inject fuel.
One end of an intake pipe 16 is connected to the intake passage 10. In addition to a motor-driven throttle valve 18 that adjusts the intake air amount, the intake pipe 16 is provided with a sensor that detects the throttle opening and a sensor that detects the intake air amount (both not shown). The fresh air is sucked into the # 1 cylinder 11, # 2 cylinder 12, # 3 cylinder 13 and # 4 cylinder 14 through the intake ports 4.

Spark plugs 7 are attached to the cylinder head 2 for each of the cylinders 11 to 14, and spark ignition is performed in the combustion chamber 3 for the air-fuel mixture composed of fresh air from the intake pipe 16 and fuel from the injector. . Note that the ignition order of the present embodiment is the order of # 1 cylinder 11, # 3 cylinder 13, # 4 cylinder 14, and # 2 cylinder 12.
Further, an exhaust port 6 is formed in the cylinder head 2 for each of the four cylinders 11 to 14. Exhaust valves 9 are provided on the side of the combustion chamber 3 of each exhaust port 6 to communicate and block each exhaust port 6 and the combustion chamber 3. The opening / closing timing of the exhaust valve 9 is continuously varied by adjusting the hydraulic pressure by an exhaust valve timing varying device (exhaust gas recirculation means) 50. For example, a vane type variable valve timing mechanism is applied to the exhaust valve timing variable device 50. The vane type variable valve timing mechanism is well known, and a detailed description of the configuration is omitted here.

One end of an exhaust passage 40 is connected to each exhaust port 6. The exhaust passage 40 is provided with a three-way catalyst for purifying exhaust gas and an O ₂ sensor (none of which is shown) for detecting the exhaust air-fuel ratio in the exhaust gas.
Here, in each of the cylinders 11, 12, 13, and 14, branch pipes (branch ports) 31, 32, 33, and 34 communicating with the combustion chamber 3 are provided separately from the intake port 4 and the exhaust port 6. ing. Each branch pipe 31, 32, 33, 34 is equipped with an electromagnetic air valve (port opening / closing valve) 21, 22, 23, 24 that can open and close each branch pipe at an arbitrary time. . Furthermore, a delivery pipe (communication chamber) 20 that connects these branch pipes 31, 32, 33, and 34 is connected.

Specifically, as shown in the sectional view of the # 1 cylinder 11 (FIG. 2), the branch pipe 31 is opened toward the combustion chamber 3 at a position near the opening of the intake port 4 of the cylinder head 2, and the combustion chamber It extends in a direction away from 3. The delivery pipe 20 is provided toward the other branch pipes 32, 33, 34 in a direction substantially orthogonal to the branch pipe 31.
On the other hand, the air valve 21 is attached to the branch pipe 31 from the outside of the cylinder head 2 toward the combustion chamber 3. Then, the valve body 41 of the air valve 21 opens and closes the branch pipe 31 based on a signal from the electronic control unit (ECU) 60, thereby extracting compressed air in the combustion chamber 3 of the cylinder 11 and delivering pipe 20. In addition, the pressurized air from the cylinder 12 is supplied into the combustion chamber 3 of the cylinder 11 through the delivery pipe 20. The configuration of the cylinders 12, 13, and 14 is the same as the configuration of the cylinder 11.

The ECU 60 includes an input / output device, a storage device (ROM, RAM, nonvolatile RAM, etc.), a central processing unit (CPU), and the like, and the ECU 60 performs overall control of the engine 1.
The various sensors are connected to the input side of the ECU 60. On the other hand, the output side of the ECU 60 is connected to various output devices such as the exhaust valve timing variable device 50 in addition to the injector, the throttle valve 18 and the like, and these various output devices include detection information from various sensors. Each signal calculated based on the output is output.

In particular, in the engine 1 of the present embodiment, an air valve control unit (control unit) 61 is provided in the ECU 60, and the air valve control unit (control unit) 61 is, for example, in the # 1 cylinder (one cylinder) 11. The air valve 21 is operated and controlled in accordance with the engine operating state so that the compressed air is supplied as pressurized air into the # 3 cylinder (other cylinders) 13 whose ignition timing continues.
Thus, if the compressed air of the # 1 cylinder 11 is supplied to the # 3 cylinder 13 as the pressurized air by the operation control of the air valve 21 by the air valve control unit 61, the fresh air for the pressurized air is increased or decreased. Therefore, it is not necessary to control the throttle valve 18 as much as possible, and the throttle valve control can be simplified, and the turbulent action of air and fuel is generated in the combustion chamber 3 to improve the fuel consumption even if the EGR amount increases. Can be achieved.

The fuel efficiency improvement control by the supply of pressurized air by the air valve control unit 61 will be described with reference to FIG.
In this control, the opening timing of each air valve is set to the compression stroke while the internal EGR control is being performed at a high EGR rate during the stoichiometric operation using the exhaust valve timing varying device 50. For example, the air valve 21 is temporarily opened at the timing T in the latter half of the compression stroke of the # 1 cylinder 11. The air in the # 1 cylinder 11 at this timing T is still in the state of the air-fuel mixture before combustion, and is already compressed as the piston 5 rises. Therefore, if the air valve 21 is opened at this timing T, the compressed air in the # 1 cylinder 11 is surely taken into the delivery pipe 20 and stored.

Next, the air valve 23 is temporarily opened at the timing F in the first half of the compression stroke of the # 3 cylinder 13. If the air valve 23 is opened at this timing F, the pressurized air in the delivery pipe 20 is injected vigorously into the combustion chamber 3 of the # 3 cylinder 13, and a strong turbulence is generated in the combustion chamber 3 of the # 3 cylinder 13. Will be.
Here, the combination of the cylinder 11 in the compression stroke and the cylinder 13 that is continuous with the ignition timing of the cylinder 11 has been described. However, as long as it is a combination of a cylinder in the compression stroke and a cylinder in the compression stroke that follows the combination. 3, the cylinder 13 and the cylinder 14 in the compression stroke, the cylinder 14 and the cylinder 12, and the cylinder 12 and the cylinder 11 can be similarly controlled as indicated by an arrow from the timing T to the timing F. The opening and closing of these air valves is repeated sequentially.

  Therefore, in the air valve control unit 61 of the present embodiment, paying attention to the fact that the air supplied into the combustion chamber 3 is sufficiently pressurized in the second half of the compression stroke, the air valve control unit 61 performs the second half of the compression stroke. If the air valve is temporarily opened at (timing T), the pressurized air can be reliably taken into the delivery pipe 20. Therefore, it is possible to generate pressurized air without using an air pump, and the manufacturing cost can be reduced. In addition, there is no electrical loss as in the case of using an electric pump, and air can be pressurized efficiently.

When this pressurized air is supplied to the combustion chamber at a high EGR rate at which the combustion deteriorates, the turbulence (turbulence action) between the fuel and air becomes active in the combustion chamber 3. Therefore, the combustion speed is increased, the thermal efficiency is improved by increasing the isovolume, and the fuel efficiency is improved even if the EGR amount is increased.
Furthermore, this pressurized air is not air supplied separately from the stoichiometric operation, but corresponds to the one that reuses the air that has been sucked in through the throttle valve 18 in order to perform the stoichiometric operation. It is not necessary to close the throttle valve 18 again for supplying air, and an increase in pump loss associated therewith is suppressed.

Furthermore, if the air valve control unit 61 opens the air valve in the first half of the compression stroke (timing F), it is possible to supply pressurized air without using an air pump, and the turbulence effect occurs immediately before combustion. As a result, the fuel consumption is further improved.
Further, the supply of pressurized air can promote the atomization of fuel in the combustion chamber 3. That is, atomization is promoted by supplying pressurized air during the intake stroke, making it difficult for the fuel to adhere to the piston 5 and the like. For example, in the cold state, reduction of unburned fuel (HC) can be achieved.

The description of one embodiment of the present invention is finished above, but the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the air valve control unit 61 opens the air valve in the first half of the compression stroke (timing F) in order to inject pressurized air, but this timing F includes the first half of the compression stroke, It may be set from the middle of the intake stroke to the middle of the compression stroke, or may be set only in the latter half of the intake stroke. This is because the turbulence is favorably generated in the middle of the intake stroke where the in-cylinder pressure is low, and the turbulence is more active in the middle of the compression stroke immediately before combustion, which contributes to the improvement of appropriate fuel consumption. Further, when the second half of the intake stroke is set, the compressed air can be supplied by opening the air valve 23 simultaneously with the opening of the air valve 21 in terms of the relationship between the cylinder 11 and the cylinder 13 described above. . In this case, the air pressurized in the cylinder 11 is not stored in the delivery pipe 20, and the air compressed in the cylinder 11 can be immediately supplied to the cylinder 13 via the delivery pipe 20.

Moreover, although the example of 4 cylinders is shown in the said embodiment, this invention is applicable also to the case of 2 cylinders, Furthermore, the valve body 41 shown in the said one embodiment is urged | biased to the valve seat side. Instead of the valve, a poppet valve type injector that protrudes into the combustion chamber when the valve is opened may be used.
Furthermore, in the above embodiment, a part of the exhaust gas is introduced into the combustion chamber by internal EGR using the exhaust valve timing variable device. In addition to this embodiment, for example, an EGR pipe and an EGR valve are provided outside the cylinder. An external EGR that recirculates part of the exhaust gas to the surge tank by opening and closing the valve may be used.

In the above embodiment, the present invention is applied to a multipoint injection engine (MPI engine) capable of performing fuel injection via an intake port, but may be applied to an in-cylinder injection engine.
Furthermore, although the example applied in the stoichiometric operation is shown in the above-described embodiment, the present invention may be applied during a substantially stoichiometric operation where the air-fuel ratio is leaner or richer than the stoichiometric operation. Also in this case, the same effect as in the stoichiometric operation of the above embodiment can be obtained. Further, the present invention may be applied during lean operation on the lean side further than the substantially stoichiometric operation.

Below, the modification of the said embodiment is demonstrated.
In the above embodiment, an example in which a branch pipe communicating with each combustion chamber and a common delivery pipe communicating these branch pipes is shown.
On the other hand, in the modified example, a plurality of delivery pipes (communication chambers) communicating with each cylinder individually, and an air valve for communicating and blocking between the combustion chamber of each cylinder and the delivery pipe are provided. And in the case of the modification which provided the independent delivery pipe for every cylinder, an air valve is controlled as follows by an air valve control part. That is, the air valve is temporarily opened and closed in the latter half of the compression stroke of the predetermined cylinder so as to store the compressed air compressed in the predetermined cylinder in the delivery pipe, and compressed from the middle of the intake stroke in the next combustion cycle of the predetermined cylinder. During the middle of the stroke, the air valve is temporarily opened and closed to supply the pressurized air stored in the delivery pipe into the combustion chamber of the predetermined cylinder. Thereby, the same effect as the case of the said embodiment which provided the common delivery pipe is acquired.

  In the case of this modification, that is, when compressed air compressed in the same cylinder is stored in the delivery pipe, and the pressurized air stored in the delivery pipe is supplied into the combustion chamber in the next combustion cycle. Can be applied to a single cylinder engine without being limited to a multi-cylinder.

1 is a schematic configuration diagram of an internal combustion engine according to an embodiment of the present invention. It is a fragmentary sectional view of the engine of FIG. It is explanatory drawing of the fuel consumption improvement control by the engine of FIG. It is explanatory drawing of the fuel consumption improvement by the conventional engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Combustion chamber 4 Intake port 6 Exhaust port 11, 12, 13, 14 Cylinder 20 Delivery pipe (communication chamber)
21, 22, 23, 24 Air valve (Port open / close valve)
31, 32, 33, 34 Branch pipe (branch port)
50 Exhaust valve timing variable device (exhaust gas recirculation means)
60 Electronic control unit (ECU)
61 Air valve control unit (control means)

Claims (4)

Exhaust gas recirculation means capable of variably controlling the amount of exhaust gas introduced into the combustion chamber of each cylinder of the engine;
A branch port disposed separately from the intake / exhaust port communicating with the combustion chamber, and communicating with each combustion chamber;
A communication chamber for communicating the branch ports;
A port opening / closing valve disposed at each branch port, for switching communication between the branch port and the combustion chamber;
During the exhaust gas introduction into the combustion chamber by the exhaust gas recirculation means, the port opening / closing valve of the predetermined cylinder is temporarily controlled in the latter half of the compression stroke immediately before the combustion of the predetermined cylinder so as to store pressurized air in the communication chamber. In addition, in order to supply pressurized air to the combustion chambers of other cylinders other than the predetermined cylinder, the port opening / closing valves of the other cylinders are set between the middle of the intake stroke and the middle of the compression stroke before the combustion of the other cylinders. An internal combustion engine comprising: control means for temporarily controlling opening and closing. The control means temporarily controls the port opening / closing valves of the predetermined cylinder and other cylinders to supply the air compressed in the predetermined cylinder to the combustion chambers of other cylinders whose ignition timing continues to the predetermined cylinder. 2. The internal combustion engine according to claim 1 , wherein opening and closing control is performed in a controlled manner . Exhaust gas recirculation means that can variably control the amount of exhaust gas introduced into the combustion chamber of the engine;
A communication chamber arranged separately from the intake and exhaust ports communicating with the combustion chamber, and communicating with the combustion chamber;
A port opening / closing valve for switching communication or blocking between the communication chamber and the combustion chamber;
During the introduction of exhaust gas into the combustion chamber by the exhaust gas recirculation means, the port opening / closing valve of the predetermined cylinder is temporarily stored so as to store pressurized air in the communication chamber in the latter half of the compression stroke immediately before combustion of the predetermined cylinder of the engine. The port is controlled to open and close and to supply pressurized air stored in the communication chamber from the middle of the intake stroke before combustion in the next combustion cycle of the predetermined cylinder to the middle of the compression stroke to the combustion chamber of the predetermined cylinder. Control means for temporarily opening and closing the on-off valve;
An internal combustion engine comprising: The internal combustion engine according to claim 1 or 3 , wherein the control means controls the opening / closing of the port opening / closing valve during the stoichiometric operation of the engine.

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