JP2009103037A - Internal combustion engine - Google Patents

Abstract

An internal combustion engine capable of introducing EGR gas into a combustion chamber and further improving the responsiveness when a vehicle operating state changes is provided.
An internal combustion engine includes two intake passages connected to a combustion chamber via an intake valve, two exhaust passages connected to the combustion chamber via an exhaust valve, and a cylinder arrangement direction. A central passage 30 connected to the combustion chamber 1 via a central valve 31 installed between two exhaust valves 21 disposed in the center, and intake air from the intake passage 10 and exhaust gas from the exhaust passage 20 are selected to be central. And communication control means 41 for flowing in the passage 30.
[Selection] Figure 1

Description

  The present invention relates to an internal combustion engine that recirculates exhaust gas.

  Conventionally, exhaust gas from an internal combustion engine is recirculated to an intake passage, and the exhaust gas thus recirculated (hereinafter referred to as “EGR gas”) suppresses an increase in combustion temperature in the combustion chamber to reduce nitrogen oxide (NOx). An internal combustion engine equipped with an exhaust gas recirculation device is known.

Patent Document 1 discloses an internal combustion engine that recirculates EGR gas to an intake collector installed in an intake passage to suppress generation of NOx and improve fuel consumption.
JP 2005-30339 A

  By the way, in the internal combustion engine described in Patent Document 1, when reducing fuel consumption during low load operation, EGR gas is recirculated into the intake collector of the intake passage. In this way, when the intake collector is filled with a large amount of EGR gas, when the vehicle operating state changes from low load operation to high load operation, the EGR gas in the intake collector flows into the combustion chamber. Therefore, there is a problem that the amount of fresh air in the intake air in the combustion chamber does not increase immediately and the responsiveness deteriorates when the vehicle operating state changes.

  Therefore, the present invention has been made in view of the above-described problems, and provides an internal combustion engine that can introduce EGR gas into a combustion chamber and further suppress deterioration in responsiveness when the vehicle operating state changes. With the goal.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  An internal combustion engine (100) according to a first aspect of the present invention includes two intake passages (10) connected to a combustion chamber (1) via an intake valve (11), and an exhaust valve (21) in the combustion chamber (1). The center connected to the combustion chamber (1) via the two exhaust passages (20) connected via the central valve (31) installed between the two exhaust valves (21) arranged in the cylinder arrangement direction A passage (30); and communication control means (41) for selecting intake air from the intake passage (10) and exhaust from the exhaust passage (20) to flow to the central passage (30).

  Further, the internal combustion engine (100) according to the second invention includes two intake passages (10) connected to the combustion chamber (1) via the intake valve (11), and an exhaust valve (21) to the combustion chamber (1). ) And the central valve (31) installed between the two exhaust valves (21) connected to the exhaust passage (20) and arranged in the cylinder arrangement direction. A central passage (30) connected to the combustion chamber (1) through the flow passage, flow generating means (13, 14) for generating a gas flow in the combustion chamber (1), and the combustion chamber (1) from the central passage (30). A central passage side flow generating means (30) for generating a flow in the same direction as the gas flow generated by the flow generating means (13, 14) in the exhaust gas flowing into the exhaust gas.

  According to the first aspect of the present invention, intake air from the intake passage and exhaust from the exhaust passage can be selected by the communication control means and can flow from the central passage to the combustion chamber. Therefore, when exhaust gas (EGR gas) is introduced into the combustion chamber from the central passage, NOx reduction and fuel consumption improvement can be achieved. In addition, when intake air is introduced into the combustion chamber from the central passage, the amount of fresh air in the intake air introduced into the combustion chamber can be increased immediately, improving responsiveness due to changes in vehicle operating conditions. can do.

  Further, according to the second invention, the exhaust gas from the exhaust passage is allowed to flow from the central passage to the combustion chamber, so that exhaust gas (EGR gas) can be introduced into the combustion chamber as in the first invention, NOx reduction and fuel efficiency can be improved. During high-load operation or the like, the amount of exhaust from the central passage relative to the amount of fresh air in intake air is small, so the responsiveness due to changes in the operating state does not deteriorate. Further, since a strong gas flow occurs in the combustion chamber, stratification of the EGR gas can be achieved, and deterioration of the combustion performance can be suppressed.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of an internal combustion engine 100 according to the first embodiment. FIG. 1A is a plan view of the combustion chamber 1. FIG. 1B is a cross-sectional view taken along the line BB in FIG.

  As shown in FIG. 1A, the internal combustion engine 100 includes two intake ports 10, two exhaust ports 20, and one central port 30.

  The intake port 10 is arranged on the right side in the figure with respect to the center of the combustion chamber where the ignition plug 2 is arranged, and allows intake air to flow into the combustion chamber 1. The intake port 10 is provided with an intake valve 11 that opens and closes the intake port 10.

  The exhaust port 20 is arranged on the left side in the drawing with respect to the center of the combustion chamber in which the ignition plug 2 is arranged, and flows the exhaust discharged from the combustion chamber 1. The exhaust port 20 is provided with an exhaust valve 21 that opens and closes the exhaust port 20.

The central port 30 is disposed between the two exhaust ports 20 disposed in the cylinder arrangement direction. The central port 30 is connected to the exhaust port 20 and communicates the combustion chamber 1 and the exhaust port 20. An axis C ₁ of the center port 30 is set so as to pass through the cylinder center axis P. The central port 30 is connected to a communication pipe 40 that allows the intake port 10 and the central port 30 to communicate with each other. The communication pipe 40 allows intake air from the intake port 10 to flow to the central port 30. A communication opening / closing valve 41 is installed at a connection portion between the communication pipe 40 and the central port 30.

  As described above, the internal combustion engine 100 having five ports for one cylinder includes the cylinder block 50 and the cylinder head 60 as shown in FIG.

  The cylinder block 50 houses the piston 52 inside the cylinder 51. The piston 52 receives a combustion pressure by the combustion of fuel in the combustion chamber 1 and reciprocates the cylinder 51.

  The cylinder head 60 is formed with the intake port 10, the exhaust port 20, and the central port 30 described above. In FIG. 1B, the intake port 10 and the central port 30 are shown for convenience of explanation.

  The intake port 10 includes an intake valve 11, a fuel injection valve 12, and a partition wall 13, and flows intake air taken from outside into the combustion chamber.

  The intake valve 11 is driven by the valve operating device 11 a according to the vertical movement of the piston 52 to open and close the intake port 10. The valve gear 11a is configured to change the valve closing timing of the intake valve 11 in accordance with the driving state of the vehicle.

  The fuel injection valve 12 is installed in the intake port 10 on the upstream side of the intake valve 11 so that an injection port for injecting fuel protrudes. The fuel injection valve 12 injects fuel supplied from a fuel supply pipe (not shown) into an intake port to form an air-fuel mixture. In addition, the fuel injected from the fuel injection valve 12 is adjusted so that it does not spray to the partition wall 13 mentioned later.

  Inside the intake port 10, a partition wall 13 is installed in the length direction of the intake port 10 so as to form an upper passage 13 a and a lower passage 13 b. Further, a tumble control valve 14 that opens and closes the lower passage 13b according to the driving state of the vehicle is provided on the upstream side of the intake port 10. When the lower passage 13b is closed by the tumble control valve 14 and the cross-sectional area in the intake port through which intake air can pass is reduced, the flow velocity of the intake air is increased when passing through the upper passage 13a. The intake air speeded up through the upper passage 13a is directed by the partition wall 13 and flows into the combustion chamber 1, so that a tumble flow is generated in the combustion chamber as indicated by an arrow A in FIG.

  The central port 30 includes a central valve 31 driven by a camshaft 31a. The central valve 31 is set to open during the intake stroke. Details of the operation of the central valve 31 will be described later.

  The central port 30 is configured to communicate the combustion chamber 1 and the exhaust port 20 and to communicate the combustion chamber 1 and the intake port 10 via the communication pipe 40. In addition, a communication opening / closing valve 41 is installed in the central port 30 to which the communication pipe 40 is connected. This communication on / off valve 41 is controlled according to the driving state of the vehicle, and when the communication pipe 40 is opened, the communication between the central port 30 and the exhaust port 20 is cut off, and when the communication pipe 40 is closed, the central port 30 is closed. And the exhaust port 20 are communicated with each other. Since the central valve 31 of the central port 30 is opened in the intake stroke, when the communication on-off valve 41 closes the communication pipe 40 and connects the central port 30 and the exhaust port 20, the central port 30 is the exhaust port. Exhaust gas from 20 flows into the combustion chamber 1. On the other hand, when the communication on / off valve 41 opens the communication pipe 40 to block communication between the central port 30 and the exhaust port 20, the central port 30 directs intake air from the intake port 10 to the combustion chamber 1. Shed.

On the other hand, in this embodiment, in order to reinforce the tumble flow generated in the combustion chamber, the inclination angle θ ₁ of the intake port 10 with respect to the cylinder center axis P is increased (to approach the direction orthogonal to the cylinder center axis P). ) Is set, and the inclination angle θ ₂ of the central port 30 with respect to the cylinder central axis P is set small (so as to approach the cylinder central axis P).

  Although not shown in FIG. 1B, an exhaust valve 21 that is driven in accordance with the vertical movement of the piston 52 is installed in the exhaust port 20 that exhausts exhaust from the combustion chamber 1. The exhaust valve 21 is driven by a camshaft different from the camshaft 31 a that drives the central valve 31 to open and close the exhaust port 20.

  The internal combustion engine 100 includes a controller 70 for controlling the valve gear 11a, the tumble control valve 14, and the communication on / off valve 41. The controller 70 includes a CPU, a ROM, a RAM, and an I / O interface. The controller 70 receives outputs from various sensors that detect the operating state of the vehicle, such as an intake air amount sensor, an engine rotation speed sensor, and an oxygen sensor that detects the oxygen concentration in the exhaust gas. And the controller 70 controls the valve gear 11a, the tumble control valve 14, and the communication on-off valve 41 based on these outputs.

  By the way, conventionally, an internal combustion engine that recirculates a large amount of EGR gas to an intake collector installed in an intake passage to suppress generation of NOx and improve fuel efficiency is widely known. However, in such an internal combustion engine, a large amount of EGR gas is recirculated into the intake collector of the intake passage when reducing fuel consumption during low load operation. In this way, when the inside of the intake collector is filled with EGR gas, if the vehicle operating state changes from low load operation to high load operation, EGR gas in the intake collector flows into the combustion chamber. Therefore, there is a problem that the amount of fresh air in the intake air in the combustion chamber does not increase immediately and the responsiveness deteriorates when the vehicle operating state changes.

  Therefore, in the present embodiment, a central port 30 that connects the combustion chamber 1 and the exhaust port 20 is installed between the two exhaust ports 20, and the central port 30 and the intake port 10 are further connected by the communication pipe 40. . And by controlling the communication on-off valve 41 according to the driving state of the vehicle, not only a large amount of EGR gas is introduced into the combustion chamber, but also the deterioration of the responsiveness at the time of changing the vehicle driving state is suppressed.

  Here, the control content of the internal combustion engine 100 performed by the controller 70 will be described with reference to FIG. FIG. 2 is a flowchart showing a control routine of control performed by the controller 70. This control is executed when the operation of the internal combustion engine is started, and is performed under a constant cycle (for example, 10 milliseconds).

  In step S101, the controller 70 sets the target intake fresh air amount V from a map obtained beforehand through experiments or the like based on the engine speed and the required load, and proceeds to step S102.

  In step S102, the controller 70 executes a valve timing control process, and proceeds to step S103. In this valve timing control process, the valve timings of the intake valve 11, the exhaust valve 21, and the central valve 31 are set according to the driving state of the vehicle. In the present embodiment, the exhaust gas flowing backward from the combustion chamber 1 to the intake port 10 is reintroduced into the combustion chamber 1 as internal EGR gas by this valve timing, or the exhaust gas from the central port 30 is combusted as external EGR gas. Or introduced into chamber 1. Details of the valve timing control processing will be described later with reference to FIGS.

In step S103, the controller 70 based on the engine rotational speed and the required load, the map obtained by an experiment or the like in advance, and sets a target total EGR fraction R ₁ of the EGR gas introduced into the combustion chamber 1, in step S104 Move.

In step S104, the controller 70 sets the target internal EGR rate R ₂ of the internal EGR gas introduced into the combustion chamber 1, the flow proceeds to step S105. The internal EGR opens the intake valve 11 from the end of the exhaust stroke and introduces the exhaust gas in the combustion chamber that has flowed back to the intake port 10 into the combustion chamber again during the intake stroke. It can be calculated based on the vehicle operating state such as the valve opening period.

In step S105, the controller 70 calculates a target external EGR rate R ₃ based on the following equation (1), the flow proceeds to step S106.

  In step S106, the controller 70 executes a communication on / off valve control process, and proceeds to step S107. In this communication on / off valve control processing, the communication on / off valve 41 is controlled in accordance with the driving state of the vehicle, and the exhaust from the exhaust port 20 or the intake air from the communication pipe 40 flows to the central port 30. Details of the communication on / off valve control processing will be described later with reference to FIG.

  In step S107, the controller 70 executes a tumble control valve control process, and proceeds to step S108. In the tumble control valve control process, the tumble control valve 14 is controlled in accordance with the driving state of the vehicle to generate a tumble flow in the combustion chamber 1. Details of the tumble control valve control process will be described later with reference to FIG.

  In step S108, the controller 70 executes a throttle valve opening control process and ends the process. That is, a throttle valve (not shown) is controlled based on the target intake fresh air amount V to adjust the amount of fresh air flowing from the outside into the intake port.

  Here, the valve timing control process will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram showing the relationship between the driving state of the vehicle and the valve timing control. FIG. 4 is a diagram showing the first valve timing control and the second valve timing control set in FIG.

  As shown in FIG. 3, when the vehicle is operating at a low engine speed and a low load, the controller 70 is set to the first valve timing control, and in other operating states, the controller 70 is Set to second valve timing control.

  In the first valve timing control, as shown in FIG. 4A, the exhaust valve 21 opens before the piston bottom dead center (BDC) and closes after the piston top dead center (TDC). The intake valve 11 opens before the piston top dead center (TDC) at the end of the exhaust stroke, and closes before the piston 52 reaches bottom dead center (BDC). The central valve 31 is opened when the intake valve 11 is closed, and is closed before the piston bottom dead center (BDC). That is, as shown in FIG. 4B, at the end of the exhaust stroke, the opening timing of the exhaust valve 21 and the opening timing of the intake valve 11 overlap, and the intake valve 11 is set to close early. . The central valve 31 is set so as to open and close the central port 30 during the intake stroke.

  On the other hand, in the second valve timing control, as shown in FIG. 4C, only the closing timing of the intake valve 11 is different from the first valve timing control. In the second valve timing control, the intake valve 11 is set to close after the piston bottom dead center (BDC). The valve closing timing of the intake valve 11 is controlled by the valve gear 11a.

  Next, the communication on / off valve control process and the tumble control valve control process will be described with reference to FIG. FIG. 5A shows the control of the communication on-off valve 41, and FIG. 5B shows the control of the tumble control valve 14.

  In the communication on / off valve control process, as shown in FIG. 5A, when the vehicle is operating at a low engine speed and a low load, the communication pipe 40 is closed and the central port 30 and the exhaust port 20 are connected. The communication on / off valve 41 is controlled so as to communicate, and the exhaust from the exhaust port 20 is caused to flow to the central port 30. On the other hand, when the vehicle is operating in an operating state other than the above, the communication on / off valve 41 is controlled so as to block the communication between the central port 30 and the exhaust port 20 by opening the communication pipe 40. From the air to the central port 30.

  In the tumble control valve control process, as shown in FIG. 5B, when the vehicle is operating at a low load, the tumble control valve 14 is controlled so as to close the lower passage 13b. As a result, a tumble flow is generated in the combustion chamber to improve the combustion performance. On the other hand, when the vehicle is operating at a high load, the tumble control valve 14 is controlled so as to open the lower passage 13b, and the amount of intake air flowing into the combustion chamber 1 from the intake port 10 is increased to improve the output. Plan.

  The operation of the above-described internal combustion engine 100 of the present embodiment will be described with reference to FIG. FIG. 6 is a diagram showing the flow of intake air and exhaust gas in the combustion chamber when the vehicle is operating at a low engine speed and a low load.

  Since the vehicle is operating at a low engine speed and a low load, the valve timing is set to the first valve timing control, and the communication on-off valve 41 closes the communication pipe 40 so that the central port 30 and the exhaust port 20 communicate with each other. The tumble control valve 14 is controlled so as to close the lower passage 13b.

  As shown in FIG. 6A, the exhaust valve 21 and the intake valve 11 are opened at the end of the exhaust stroke when the piston 52 is near the piston top dead center (TDC). Then, the exhaust from the combustion chamber 1 flows out to the exhaust port 20 and blows back to the intake port 10.

  As shown in FIG. 6B, when the piston 52 is lowered, the exhaust gas that has flowed back to the intake port 10 first flows into the combustion chamber as internal EGR gas, and then the air-fuel mixture flows into the combustion chamber. Here, since the tumble control valve 14 closes the lower passage 13b, the air-fuel mixture flows into the combustion chamber through the upper passage 13a, and into the combustion chamber 1 as shown by the arrow in FIG. A tumble flow is generated in a state where the internal EGR gas and the air-fuel mixture are stratified. Further, since the intake port 10 is inclined so as to approach the direction orthogonal to the cylinder center axis P (see FIG. 1), the tumble flow in the direction of the arrow in FIG.

  Note that the intake valve 11 in the first valve timing control closes earlier than the piston 52 reaches the bottom dead center to limit the intake amount introduced into the combustion chamber (mirror cycle operation).

  Then, as shown in FIG. 6C, when the intake valve 11 closes the intake port 10, the internal EGR gas layer flows near the upper portion of the combustion chamber 1 by the tumble flow. When the intake valve 11 is closed, the central valve 31 is opened as shown in FIG. The communication on / off valve 41 is controlled so that the communication pipe 40 is closed and the central port 30 and the exhaust port 20 are communicated. Therefore, when the central valve 31 is opened, the exhaust from the exhaust port 20 becomes the external EGR gas in the center. It flows into the combustion chamber 1 through the port 30.

  Here, when the piston 52 is lowered as shown in FIG. 6D, the initially formed tumble flow is weakened as the piston 52 is lowered. However, the central port 30 is configured to be inclined in the direction of the cylinder central axis P (see FIG. 1), and the external EGR gas from the central port 30 flows downward in the figure with respect to the layer of the internal EGR gas. Strengthen the tumble flow again.

  As shown in FIG. 6E, when the piston 52 reaches the vicinity of the piston bottom dead center (BDC), the layer of the internal EGR gas and the external EGR gas flows in the vicinity of the crown surface of the piston 52. Thereafter, when the piston 52 rises to the piston top dead center (TDC), as shown in FIG. 6 (F), a layer of internal EGR gas and external EGR gas is formed on the piston crown, and the mixture layer is ignited. It is formed in the vicinity of the plug 2.

  Thus, when the vehicle is operating at a low engine speed and a low load, the air-fuel mixture layer is formed in the vicinity of the spark plug 2 at the ignition timing of the spark plug 2, so that the internal EGR gas and the external EGR gas Even if a large amount of EGR gas is introduced into the combustion chamber, deterioration of the combustion performance is suppressed. In order to stratify the EGR gas and the air-fuel mixture as described above, the intake valve 11 is opened from the end of the exhaust stroke and closed during the intake stroke, as shown in FIG. The central valve 31 is preferably opened during the intake stroke.

  On the other hand, when the vehicle is operating at a high engine speed and a high load, the valve timing of each valve is set to the second valve timing control, and the tumble control valve 14 is controlled to open the lower passage 13b. To do. The communication on / off valve 41 is controlled so as to open the communication pipe 40 and block communication between the central port 30 and the exhaust port. In the second valve timing control, the closing timing of the intake valve 11 is retarded from that in the first valve timing control, and the intake air in the intake port flows through both the upper passage 13a and the lower passage 13b. The amount of intake air introduced from the intake port 10 into the combustion chamber 1 increases. When the central valve 31 is opened, the intake air from the intake port 10 flows into the combustion chamber 1 through the central port 30, so that the intake air amount can be further increased.

  Thus, when the vehicle is operating at a high engine speed and high load, the output is improved by increasing the intake air amount.

  As described above, in the first embodiment, the following effects can be obtained.

  When the vehicle is operating at a low engine speed and a low load, the exhaust gas blown back to the intake port 10 flows into the combustion chamber 1 as internal EGR gas, and the exhaust gas from the central port 30 to the exhaust port 20 serves as external EGR. Since it is made to flow into the combustion chamber 1, a large amount of EGR gas can be introduced into the combustion chamber 1. Thereby, NOx reduction and fuel consumption improvement can be achieved.

  Further, the exhaust gas is not recirculated to the intake collector as in the prior art, but the exhaust gas is flowed from the central port 30 connected to the exhaust port 20 to the combustion chamber 1 so that the vehicle is operated at a low engine speed and a low load, for example. When the engine shifts to high engine rotation speed / high load operation, the communication between the exhaust port 20 and the central port 30 is shielded by the communication on / off valve 41 so that the exhaust does not flow into the combustion chamber. Therefore, it is possible to suppress the deterioration of the responsiveness caused by the change in the vehicle driving state.

  Further, when the vehicle is in an operating state such as a high engine speed and high load, the communication pipe 40 and the central port 30 are communicated with each other by the communication on-off valve 41, and intake air is also introduced into the combustion chamber 1 from the central port 30. As a result, the amount of fresh air in the intake air introduced into the combustion chamber can be increased, and the responsiveness resulting from changes in the vehicle operating state can be improved.

  Further, in the internal combustion engine 100, the intake port 10 is inclined so as to approach the direction orthogonal to the cylinder central axis, and the central port 30 is inclined so as to approach the cylinder central axis, and is generated in the combustion chamber. Strengthen the tumble flow. Then, the valve timings of the intake valve 11 and the central valve 31 are adjusted so that the EGR gas introduced into the combustion chamber 1 and the air-fuel mixture are stratified. As a result, an air-fuel mixture layer can be formed in the vicinity of the spark plug during ignition, and deterioration of combustion performance can be suppressed even when a large amount of EGR gas is introduced.

(Second Embodiment)
FIG. 7 is a diagram illustrating valve timing control of the internal combustion engine 100 of the second embodiment. 7A and 7B show the first valve timing control, and FIG. 7C shows the second valve timing control.

  The configuration of the internal combustion engine 100 of the second embodiment is substantially the same as that of the first embodiment, but the valve timing of the central valve 31 is different. That is, the central valve 31 is opened after the intake valve 11 is closed, and the difference will be mainly described below.

  As shown in FIG. 7A, in the first valve timing control of the second embodiment, the exhaust valve 21 opens before the piston bottom dead center (BDC) and closes after the piston top dead center (TDC). . The intake valve 11 opens before the piston top dead center (TDC) at the end of the exhaust stroke, and closes before the piston 52 reaches bottom dead center (BDC). The central valve 31 is opened after the intake valve 11 is closed, and is closed after the piston bottom dead center (BDC). Therefore, as shown in FIG. 7B, at the end of the exhaust stroke, the opening timing of the exhaust valve 21 and the opening timing of the intake valve 11 overlap, and the intake valve 11 is set to close early. . Further, before the central valve 31 is opened, the sealing period A of the combustion chamber 1 in which the intake valve 11 and the exhaust valve 21 are closed is set.

  On the other hand, in the second valve timing control, as shown in FIG. 7C, only the closing timing of the intake valve 11 is different from the first valve timing control shown in FIGS. 7A and 7B. In the second valve timing control, the intake valve 11 is set to close after the piston bottom dead center (BDC). The closing timing of the intake valve 11 is controlled by the valve gear 11a.

  When the vehicle is operating at a low engine speed and a low load, the first valve timing control is set, and the central port 30 allows the exhaust from the exhaust port 20 to flow into the combustion chamber 1. Here, the central valve 31 is opened after the sealing period A of the combustion chamber 1 has elapsed. In the sealing period A, the piston 52 descends toward the bottom dead center of the piston, so that the pressure in the combustion chamber decreases, and the pressure difference between the combustion chamber 1 and the central port 30 increases. When the central valve 31 is opened in a state where this pressure difference has occurred, the flow rate of the exhaust gas (external EGR gas) flowing from the central port 30 into the combustion chamber 1 is increased, so that the tumble flow generated in the combustion chamber can be reliably ensured. Can be strengthened.

  Further, when the vehicle is operating at a speed other than the low engine speed / low load operation, the second valve timing control is set. Unlike the first valve timing control, the second valve timing control does not set the sealing period of the combustion chamber 1 before the central valve 31 is opened, but intake air from the intake port 10 is sent from the central port 30 to the combustion chamber 1. Therefore, the same effect as in the first embodiment can be obtained.

(Third embodiment)
FIG. 8 is a diagram illustrating an internal combustion engine 100 according to the third embodiment.

  The configuration of the internal combustion engine 100 of the third embodiment is substantially the same as that of the first embodiment, but differs in that the central port 30 and the intake port 10 do not communicate with each other. That is, the central port 30 is configured to communicate the combustion chamber 1 and the exhaust port 20, and the difference will be mainly described below.

  As shown in FIG. 8, in the third embodiment, the communication pipe and the communication opening / closing valve are not installed as in the first embodiment, and the central port 30 communicates only with the combustion chamber 1 and the exhaust port 20. It is configured. Therefore, the communication on / off valve control (see FIG. 5B) is not performed as in the first embodiment, but the other controls are the same as in the first embodiment (see FIGS. 2 to 5).

  Therefore, when the vehicle is operating at a low engine speed and a low load, a tumble control valve (not shown in FIG. 8) is controlled so as to form a tumble flow in the combustion chamber, and the intake valve 11 and the exhaust valve are controlled. 21. The central valve 31 is set to the first valve timing control. Therefore, the central port 30 allows the exhaust (external EGR gas) from the exhaust port 20 to flow into the combustion chamber 1 during low engine speed / low load operation.

  On the other hand, when the vehicle is operating in an operating state other than the low engine speed / low load operation, the tumble control valve is controlled according to the operating state of the vehicle, and the intake valve 11 and the exhaust valve 21 are controlled. The central valve 31 is set to the second valve timing control. In the second embodiment, since the central port 30 and the exhaust port 20 are always in communication, exhaust (external EGR gas) flows into the combustion chamber 1 from the central port 30 even when the engine speed is low and the load is low. Resulting in. However, the exhaust (external EGR gas) flows only from the central port 30. Furthermore, since the intake air amount is large at high engine speed and high load operation, the central port is in relation to the fresh air amount in the intake air. The amount of exhaust (external EGR gas) from 30 is small and does not cause a problem in driving the vehicle.

  As described above, the internal combustion engine 100 of the third embodiment can obtain the following effects.

  When the vehicle is operating at a low engine speed and a low load, the exhaust gas blown back to the intake port 10 flows into the combustion chamber 1 as internal EGR gas, and the exhaust from the exhaust port 20 serves as external EGR and the central port 30 Therefore, a large amount of EGR gas can be introduced into the combustion chamber 1, and NOx reduction and fuel consumption improvement can be achieved.

  In addition, since a tumble flow is generated in the combustion chamber according to the driving state of the vehicle, the air-fuel mixture layer can be formed in the vicinity of the spark plug at the time of ignition, and even if a large amount of EGR gas is introduced, deterioration of the combustion performance can be suppressed. it can.

  In the third embodiment, exhaust gas (external EGR gas) flows into the combustion chamber 1 from the central port 30 even during operations other than the low engine speed / low load operation, but the central port 30 with respect to the amount of fresh air in the intake air. Since the amount of exhaust (external EGR gas) from the engine is small, the responsiveness due to the change in the operating state is not deteriorated.

(Fourth embodiment)
FIG. 9 is a diagram showing a configuration of the internal combustion engine 100 of the fourth embodiment.

  The configuration of the internal combustion engine 100 of the fourth embodiment is substantially the same as that of the first embodiment, but is partially different in the configuration of connecting the piston 52 and the crankshaft. In other words, the piston 52 and the crankshaft are connected by a plurality of links to increase the piston stroke and improve the fuel efficiency. The following description will focus on the differences.

  As shown in FIG. 9, the internal combustion engine 100 of the fourth embodiment includes a variable compression ratio mechanism 110 that changes the mechanical top ratio by changing the piston top dead center position. The variable compression ratio mechanism 110 connects the piston 52 and the crankshaft 120 with the upper link 111 and the lower link 112 and controls the posture of the lower link 112 with the control link 113 to change the mechanical compression ratio.

  The upper link 111 is connected to the piston 52 via a piston pin 114 at the upper end thereof. Further, the lower end of the upper link 111 is connected to one end of the lower link 112 via a connecting pin 115.

  One end of the lower link 112 is connected to the upper link 111 via a connecting pin 115. Further, the other end of the lower link 112 is connected to the control link 113 via a connecting pin 116. The lower link 112 is configured to be divided from the left and right members in the figure, and has a connecting hole 112a at substantially the center. The lower link 112 inserts the crank pin 121 of the crank shaft 120 into the connecting hole 112a and swings about the crank pin 121 as a central axis.

  The crankshaft 120 includes a crankpin 121, a journal 122, and a counterweight 123. The center of the crankpin 121 is eccentric from the center of the journal 122 by a predetermined amount, and the lower link 112 is rotatably connected to the crankpin 121. The journal 122 is rotatably supported by the cylinder block 50 and the ladder frame 130. The axis of the journal 122 coincides with the axis of the crankshaft 120. The counterweight 123 is integrally formed with the crank arm and reduces the rotational primary vibration component of the piston motion.

  The upper end of the control link 113 is rotatably connected to the lower link 112 via a connecting pin 116. Further, the lower end of the control link 113 is connected to a control shaft 141 disposed in parallel with the crankshaft 120 via a connecting pin 117. The connecting pin 117 is eccentric by a predetermined amount from the axis of the control shaft 141, and the control link 113 swings around the eccentric connecting pin 117 as an axis. The control shaft 141 forms a gear 142 on the outer periphery thereof. This gear 142 meshes with the pinion 143. The pinion 143 is provided on the rotating shaft 145 of the actuator 144 attached to the side portion of the cylinder block 50.

  In the internal combustion engine 100 of the fourth embodiment configured as described above, the reciprocating motion of the piston 52 is transmitted to the upper link 111 and is changed to the rotational motion of the crankshaft 120 via the lower link 112. In this case, the lower link 112 rotates counterclockwise in the figure with respect to the center of the crankshaft 120 while swinging about the crankpin 121 as the center axis. The control link 113 connected to the lower link 112 swings around the connecting pin 117 of the control shaft 141 connected to the lower end thereof. Since the control shaft 141 and the connection pin 117 are eccentric, when the control shaft 141 is rotated by the actuator 144, the connection pin 117 moves. Since the swing center of the control link 113 is changed by the movement of the connecting pin 117, the inclination of the upper link 111 and the lower link 112 can be changed, and the top dead center position of the piston 52 can be arbitrarily set within a predetermined range. Can be adjusted.

  The internal combustion engine 100 according to the fourth embodiment described above includes a controller 70 in order to control the actuator 144. The controller 70 includes a CPU, a ROM, a RAM, and an I / O interface. The controller 70 controls the actuator 144 based on the output of a sensor or the like that detects the driving state of the vehicle and rotates the control shaft 141 to change the mechanical compression ratio.

  In the fourth embodiment, as shown in FIG. 10, the mechanical compression ratio is adjusted according to the driving state of the vehicle. That is, when the vehicle is operating at a low engine speed and a low load, the mechanical compression ratio is increased to improve the combustion efficiency. When the vehicle is operating at a high engine speed and a high load, Reduce the mechanical compression ratio to prevent knocking. In other operation regions, the mechanical compression ratio is set to an intermediate level to achieve both combustion efficiency and knocking prevention. Thus, in the fourth embodiment, the mechanical compression ratio can be optimally set according to the driving state of the vehicle.

  Furthermore, in the internal combustion engine 100 of the fourth embodiment, by using the piston 52 with a shortened piston skirt, the piston stroke is lengthened and the fuel consumption performance is improved. Hereinafter, the piston stroke will be described with reference to FIGS. 11 to 13.

  FIG. 11 is a diagram for explaining the reduction of the side thrust load of the piston 52.

As shown in FIG. 11, in the internal combustion engine 100 of the fourth embodiment, by selecting the alignment of the compression ratio variable mechanism 110, the piston 52 is connected in the first half of the expansion stroke in which the internal pressure of the combustion chamber 1 is maximized. The upper link 111 to be maintained can be maintained in a substantially upright posture (a state where the inclination angle θ ₃ of the axis of the upper link 111 with respect to the cylinder axis is close to 0 °). When the inclination angle θ ₃ of the upper link 111 is thus reduced, the side thrust load of the piston 52 generated according to the inclination angle θ ₃ of the upper link 111 is greatly reduced.

  Therefore, as shown in FIGS. 12A to 12C, the piston skirt strength can be ensured even if the piston skirt length of the piston 52 is shortened. Therefore, in the piston 52 in the fourth embodiment, the piston skirt in the direction in which the piston pin 114 is inserted can be shortened as shown in FIG.

  FIG. 13 is a diagram for explaining how to make the piston stroke longer.

  In the internal combustion engine 100 of the fourth embodiment, since the piston 52 with a shortened piston skirt is used, the counterweight 123 of the crankshaft 120 can pass the side of the piston pin 114 as shown in FIG. . Therefore, the upper link 111 is set to a minimum length, the bottom dead center position of the piston 52 can be brought closer to the crankshaft 120, and the piston stroke corresponding to the shortened piston skirt can be expanded.

  As described above, the internal combustion engine 100 of the fourth embodiment can obtain the following effects.

  The internal combustion engine 100 of the fourth embodiment includes a variable compression ratio mechanism 110, and by adjusting the mechanical compression ratio according to the operating state of the vehicle, both improvement in combustion efficiency and prevention of knocking can be achieved.

  Further, since the side thrust load generated in the piston 52 can be reduced by the alignment of the variable compression ratio mechanism 110, the piston skirt of the piston 52 can be shortened, and the piston stroke can be increased. Therefore, the bore diameter can be reduced without reducing the displacement, and the S / V ratio can be increased to improve fuel efficiency.

  The technical idea of the fourth embodiment can be applied not only to the first embodiment but also to the third embodiment.

(Fifth embodiment)
FIG. 14 is a view showing a variable valve apparatus 200 for driving the intake valve.

  The configuration of the internal combustion engine 100 of the fifth embodiment is substantially the same as that of the first embodiment, but is partially different in that a variable valve apparatus 200 is provided. That is, the valve characteristics (operating angle and lift amount) of the intake valve 11 are continuously changed by the variable valve apparatus 200, and the differences will be mainly described below.

  As shown in FIG. 14, the variable valve apparatus 200 includes a swing cam 210, a swing cam drive mechanism 220 that swings the swing cam 210, and valve characteristics (lift amount and operating angle) of the intake valve 11. Is provided with a variable valve characteristic mechanism 230 capable of continuously changing the valve characteristic.

  As shown in FIG. 10, the swing cam 210 is rotatably fitted on the outer periphery of the drive shaft 221. A drive shaft 221 extending in the cylinder row direction is inserted into the swing cam 210.

  In the present embodiment, since two intake valves 11 are provided for one cylinder, a pair of swing cams 210 and a valve lifter 211 are provided for one cylinder. The pair of swing cams 210 are coupled in the same phase by a connecting cylinder 221a that is rotatably inserted into the drive shaft 221, and operates in synchronism with each other. For this reason, the swing cam drive mechanism 220 is provided only for one swing cam 210. Then, the swing cam 210 swings about the drive shaft 221 as a fulcrum in conjunction with the crankshaft by a swing cam drive mechanism 220 described later, and drives the intake valve 11 via the valve lifter 211.

  An eccentric cam 222 is fixed to the drive shaft 221 of the swing cam drive mechanism 220 by press fitting or the like. In the eccentric cam 222 having a circular outer peripheral surface, the center of the outer peripheral surface is offset from the axis of the drive shaft 221 by a predetermined amount. Since the drive shaft 221 rotates in conjunction with the rotation of the crankshaft, the eccentric cam 222 rotates eccentrically around the axis of the drive shaft 221.

  An annular portion 224 on the base end side of the first link 223 is rotatably fitted to the outer peripheral surface of the eccentric cam 222. The distal end of the first link 223 is connected to one end of the rocker arm 226 via a connecting pin 225. The other end of the rocker arm 226 is connected to the upper end of the second link 228 via a connecting pin 227. The lower end of the second link 228 is connected to the swing cam 210 via a connecting pin 229. The substantially central portion of the rocker arm 226 is swingably supported by the eccentric cam portion 232 of the control shaft 231 of the variable valve characteristic mechanism 230.

  When the drive shaft 221 rotates in synchronization with the engine rotation, the eccentric cam 222 rotates eccentrically, and thereby the first link 223 swings in the vertical direction. As the first link 223 swings, the rocker arm 226 swings around the axis of the eccentric cam portion 232, the second link 228 swings up and down, and the swing cam 210 rotates about the axis of the drive shaft 221. Oscillate in an angular range.

  In the variable valve apparatus 200, one end of the drive shaft 221 is inserted into a cam sprocket (not shown). When the drive shaft 221 rotates relative to the cam sprocket, the phase with respect to the cam sprocket can be changed, and the rotation phase of the drive shaft 221 with respect to the crankshaft can be changed. The variable valve characteristic mechanism 230 controls the rotation angle phase of the swing cam 210. An actuator (not shown) is provided at one end of the control shaft 231 of the valve characteristic variable mechanism 230 via a gear or the like. By changing the rotational position of the control shaft 231 by the actuator, the rocker arm 226 becomes a swing center. The shaft center of the eccentric cam portion 232 turns around the rotation center of the control shaft 231, and the fulcrum of the rocker arm 226 is displaced accordingly. As a result, the postures of the first link 223 and the second link 228 change, the distance between the swing center of the swing cam 210 and the rotation center of the rocker arm 226 changes, and the swing characteristics of the swing cam 210 change. To do. Due to the change in the swing characteristic, the variable valve apparatus 200 can continuously change the valve characteristics (lift amount and operating angle) of the intake valve 11 as shown in FIG.

  In the first embodiment, the closing timing of the intake valve 11 is changed in the case of low engine speed / low load operation and in other cases (see FIGS. 3 and 4), but the variable valve of the fifth embodiment Since the apparatus 200 can continuously change the valve characteristics (operating angle and lift amount) of the intake valve 11, the operation of the intake valve 11 can be set in more detail than in the first embodiment as shown in FIG. Therefore, when the vehicle is operating at a low engine speed and a low load, the operating angle of the intake valve 11 is set to be small, and intake is restricted to improve fuel efficiency. When operating with a load, the operating angle of the intake valve 11 is set large, and the intake amount is increased to improve the output. Further, in other operating regions, the operating angle of the intake valve 11 is set to a medium level to achieve both fuel efficiency and output.

  As described above, the following effects can be obtained in the fifth embodiment.

  Thus, since the variable valve apparatus 200 can optimally set the operating angle of the intake valve 11 in accordance with the driving state of the vehicle, it is possible to achieve both improvement in fuel efficiency and output.

  The technical idea of the fifth embodiment can be applied not only to the first embodiment but also to the third embodiment.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  In the first to fifth embodiments, the exhaust valve 21 and the central valve 31 are driven by different camshafts, but may be driven by the same camshaft 80 as shown in FIG. Good. Since the exhaust valve 21 and the central valve 31 have different valve timings, the camshaft 80 is provided with an exhaust valve cam 81 that drives the exhaust valve 21 and a central valve cam 82 that drives the central valve 31. Thus, by driving the exhaust valve 21 and the central valve 31 with the same camshaft 80, the configuration of the valve operating system can be made compact.

  In the first to fifth embodiments, as shown in FIG. 18, a partition wall 32 that forms an upper passage 32a and a lower passage 32b is provided inside the central port 30, and the upper passage 32a is in an operating state. A tumble flow generated in the combustion chamber 1 may be strengthened by installing a tumble control valve 33 that opens and closes accordingly. That is, when exhaust gas (external EGR gas) is introduced into the combustion chamber 1 from the central port 30, the upper passage 32a is closed by the tumble control valve 33, and the flow rate of the external EGR gas flowing through the lower passage 32b is increased. The tumble flow generated in the combustion chamber 1 can be strengthened.

  Further, in the first to fifth embodiments, the flow of intake air into the lower jaw 15 of the intake port 10 without forming a partition wall in the intake port as shown in FIGS. 19A and 19B. A guide wall 16 is provided to direct a tumble flow in the combustion chamber 1, and a guide wall 35 is provided in the upper jaw portion 34 of the central port 30 to direct the flow of exhaust (external EGR) to generate the tumble flow. You may make it strengthen.

  Further, in the first to fifth embodiments, a supercharger (supercharging means) is provided in the intake passage connected to the intake port 10, and supercharging is performed during high load operation to improve intake charging efficiency. The output may be improved. In particular, in the third embodiment, when the charging efficiency of intake air is improved, the amount of exhaust (external EGR gas) from the central port 30 with respect to the amount of fresh air during intake can be reduced.

It is a figure which shows the structure of the internal combustion engine of 1st Embodiment. It is a flowchart which shows the control routine of the control which a controller performs. It is a figure which shows the relationship between the driving | running state of a vehicle, and valve timing control. It is a figure which shows 1st valve timing control and 2nd valve timing control. The communication on / off valve control process and the tumble control valve control process will be described. It is a figure which shows the flow of the intake air and exhaust_gas | exhaustion in a combustion chamber. It is a figure which shows the valve timing control in the internal combustion engine of 2nd Embodiment. It is a figure which shows the structure of the internal combustion engine of 3rd Embodiment. It is a figure which shows the structure of the internal combustion engine of 4th Embodiment. It is a figure which shows control of a mechanical compression ratio. It is a figure explaining reduction of the side thrust load of a piston. It is a figure which shows the structure of a piston. It is a figure explaining the long stroke of a piston stroke. It is a figure which shows the variable valve apparatus which drives the intake valve of the internal combustion engine of 5th Embodiment. It is a figure which shows the valve characteristic (lift amount and operating angle) of an intake valve. It is a figure which shows control of an intake valve. It is a figure which shows the structure which drives an exhaust valve and a center valve with the same cam shaft. It is a figure which shows the other Example which produces a gas flow in a combustion chamber. It is a figure which shows the other Example which produces a gas flow in a combustion chamber.

Explanation of symbols

100 Internal combustion engine 10 Intake port (intake passage)
11 Intake Valve 11a Valve Operating Device 13 Partition 13a Upper Passage 13b Lower Passage 14 Tumble Control Valve (Intake Passage Side Valve Mechanism)
16 Guide wall (Intake passage side guide wall)
20 Exhaust port (exhaust passage)
21 Exhaust valve 30 Central port (Central passage)
31 Central valve 32 Bulkhead 33 Tumble control valve (Central passage side valve mechanism)
35 Guide wall (guide wall on the central passage side)
40 communication pipe 41 communication on-off valve (control means)
70 controller 110 compression ratio variable mechanism 111 upper link 112 lower link 113 control link 120 crankshaft 123 counterweight 141 control shaft 144 actuator 200 variable valve operating device (variable valve operating means)
210 Oscillating cam 221 Drive shaft 222 Eccentric cam 223 First link 226 Rocker arm 228 Second link 231 Control shaft

Claims (21)

Two intake passages connected to the combustion chamber via an intake valve;
Two exhaust passages connected to the combustion chamber via exhaust valves;
A central passage connected to the combustion chamber via a central valve installed between the two exhaust valves arranged in the cylinder arrangement direction;
Communication control means for selecting the intake air from the intake passage and the exhaust gas from the exhaust passage to flow to the central passage;
An internal combustion engine. Two intake passages connected to the combustion chamber via an intake valve;
Two exhaust passages connected to the combustion chamber via exhaust valves;
A central passage that is connected to the exhaust passage and connected to the combustion chamber via a central valve installed between the two exhaust valves arranged in the cylinder arrangement direction;
Flow generating means for generating gas flow in the combustion chamber;
A central passage-side flow generating means for generating a flow in the same direction as the gas flow generated by the flow generating means in the exhaust gas flowing into the combustion chamber from the central passage;
An internal combustion engine. The central passage side flow generating means is:
A central passage side valve mechanism for separating the central passage into upper and lower passages by a partition wall and opening and closing one of the upper and lower passages;
The internal combustion engine according to claim 2. The central passage side flow generating means is:
A central passage side guide wall is provided at the opening of the central passage.
The internal combustion engine according to claim 2. The central passage side flow generating means is:
An inclination of the central passage in the vicinity of the combustion chamber is formed so as to be close to the cylinder axis direction.
The internal combustion engine according to any one of claims 2 to 4, wherein The intake passage includes intake passage side flow generation means for generating a flow in the same direction as the gas flow generated by the flow generation means in the intake air flowing into the combustion chamber from the intake passage.
The internal combustion engine according to any one of claims 2 to 5, wherein The intake passage side flow generating means is:
An intake passage side valve mechanism that separates the intake passage into upper and lower passages by a partition and opens and closes one of the upper and lower passages;
The internal combustion engine according to claim 6. The intake passage side flow generating means is:
An intake passage side guide wall is provided at the opening of the intake passage;
The internal combustion engine according to claim 6. The intake passage side flow generating means is:
An inclination of the intake passage in the vicinity of the combustion chamber is formed so as to be close to a direction perpendicular to the cylinder axis.
The internal combustion engine according to any one of claims 6 to 8, wherein The central passage is connected to the exhaust passage and the intake passage,
Comprising communication control means for selecting intake air from the intake passage and exhaust air from the exhaust passage to flow to the central passage;
The internal combustion engine according to any one of claims 2 to 9, wherein The communication control means includes
When the engine is operating at a low rotational speed and a low load, the communication between the central passage and the intake passage is cut off, and exhaust gas flows from the central passage to the combustion chamber so that the vehicle has a low engine rotational speed and a low load. When the engine is operated in a manner other than the above, the communication between the central passage and the exhaust passage is blocked, and the intake air is allowed to flow from the central passage to the combustion chamber.
The internal combustion engine according to claim 1 or 10, characterized in that In accordance with the engine operating state, comprising a valve timing control means for controlling the valve timing of the intake valve, the exhaust valve, the central valve,
The internal combustion engine according to any one of claims 1 to 11, wherein The valve timing control means includes
When the engine is operating at a low rotational speed and a low load, the exhaust valve is opened near the expansion bottom dead center and closed near the exhaust upper fulcrum, and the intake valve is opened before the exhaust top dead center and exhaust top dead Closing between the point and the intake bottom dead center, opening the central valve between the exhaust top dead center and the intake bottom dead center and closing near the intake bottom dead center,
The internal combustion engine according to claim 12, wherein: The valve timing control means includes
When the engine is operating at a speed other than low rotation speed and low load, the exhaust valve is opened near the expansion bottom dead center and closed near the exhaust upper fulcrum, and the intake valve is opened before the exhaust top dead center and opened under the intake air. Close near dead center, open the central valve between exhaust top dead center and intake bottom dead center and close near intake bottom dead center,
The internal combustion engine according to claim 12, wherein: The central valve is opened after the intake valve is closed and the combustion chamber is sealed, and is opened and closed near the intake bottom dead center.
The internal combustion engine according to claim 13. The exhaust valve, the intake valve, and the central valve are arranged so that the exhaust gas flowing into the combustion chamber from the intake passage and the exhaust gas flowing into the combustion chamber from the central passage are present in substantially the same region. Set the timing,
The internal combustion engine according to any one of claims 12 to 15, wherein The valve timing of the exhaust valve, the intake valve, and the central valve is such that an exhaust layer introduced into the combustion chamber at the time of ignition is formed in the vicinity of the piston crown surface, and an air-fuel mixture layer is formed in the vicinity of the spark plug. Set
The internal combustion engine according to claim 16. The exhaust valve and the central valve are driven by the same camshaft,
The internal combustion engine according to any one of claims 1 to 17, wherein The piston and crankshaft are connected by a plurality of links, and a compression ratio variable mechanism that varies the mechanical compression ratio by changing the piston top dead center position by changing the posture of the plurality of links,
The compression ratio variable mechanism lowers the mechanical compression ratio as the rotational speed and load increase.
The internal combustion engine according to any one of claims 1 to 18, characterized in that Comprising variable valve operating means for continuously changing at least the operating angle of the valve characteristics of the intake valve;
The internal combustion engine according to any one of claims 1 to 19, wherein the variable valve means increases the operating angle as the rotational speed increases and the load increases. The intake passage includes supercharging means for supercharging intake air,
21. The internal combustion engine according to claim 1, wherein the supercharging unit supercharges intake air in accordance with an engine operating state.

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