JP4122504B2 - Exhaust control device for internal combustion engine - Google Patents

Description

[0001]
The present invention relates to an exhaust control device for an internal combustion engine that introduces exhaust into a combustion chamber of the internal combustion engine, and more particularly to a self-ignition operation using backflow exhaust introduced into the combustion chamber from an exhaust port and a spark ignition operation using a spark plug. The present invention relates to an exhaust control device for an internal combustion engine that is switched according to the engine load.
[0002]
[Prior art]
As part of exhaust gas purification, a method for causing an internal combustion engine such as a spark ignition engine (hereinafter referred to as a gasoline engine) to perform not only a spark ignition operation by an ignition plug but also a self-ignition operation by compression is being studied. According to the gasoline engine of this method, although the generation amount of soot and NOx in the exhaust gas is greatly reduced, the self-ignition timing depends on the air-fuel ratio of the mixture, the temperature of the mixture, etc. It is known that it is difficult to cause self-ignition at a desired time in a wide load range to be used.
[0003]
As a technique for expanding the operation range by controlling the self-ignition timing, for example, there is a technique disclosed in Japanese Patent Laid-Open No. 9-287528. This technology recirculates the exhaust discharged from the exhaust port to the intake port, introduces this recirculated exhaust (external EGR gas) into the combustion chamber to control the air-fuel ratio, and cools and mixes the external EGR gas By controlling the temperature of the air, it is intended to expand the operating range where good ignition can be obtained.
[0004]
Further, as disclosed in JP-A-5-59952, an exhaust gas recirculation passage is provided in the vicinity of the intake port to introduce an external EGR gas into the combustion chamber, thereby controlling the air-fuel ratio in the combustion chamber, which is favorable. There is a technique for obtaining a combustion state.
[0005]
Further, as shown in Japanese Patent Application Laid-Open Nos. 5-86992 and 9-4521, a sub exhaust port is provided so that a part of the exhaust gas flows backward into the combustion chamber, that is, the reverse flow exhaust gas (internal EGR gas) is burned. There is a technology that attempts to improve combustion by introducing it indoors.
[0006]
[Problems to be solved by the invention]
However, the conventional techniques as described above have the following problems. That is, in the technique disclosed in the above Japanese Patent Laid-Open No. 9-287528 and Japanese Patent Laid-Open No. 5-59952, the exhaust discharged from the exhaust port is recirculated and introduced into the combustion chamber, or the temperature is adjusted in the middle. Since it is mixed with the fresh air after homogeneously and introduced into the combustion chamber, there is a problem that it is difficult to control the timing of self-ignition due to poor response at the time of transition when the operation mode is switched. .
[0007]
Further, in the techniques disclosed in Japanese Patent Laid-Open Nos. 5-86992 and 9-4521, exhaust gas is caused to flow backward from the exhaust port and introduced into the combustion chamber, but the distribution of the reverse flow exhaust gas and the air-fuel mixture is stabilized. Therefore, there has been a problem that it is difficult to control to a predetermined stratified state, and as a result, it is difficult to stably obtain a desired combustion state.
[0008]
The present invention has been made in view of the problems of the prior art as described above, and the object of the present invention is to easily control the timing of self-ignition and to achieve a stable and good combustion state. It is an object of the present invention to provide an exhaust control device for an internal combustion engine that can reduce the emission amount of HC, NOx, etc.
[0009]
[Means for Solving the Problems]
According to the first aspect of the present invention, the combustion chamber includes two or more intake ports that communicate with each other independently, and two or more exhaust ports that communicate with each other independently. Are provided with intake valves for opening and closing these openings, and each exhaust port is provided with an exhaust valve for opening and closing these openings, and opens the intake valve. An intake camshaft having an intake valve cam is formed, and the at least one exhaust valve is driven to open in the intake stroke by the intake valve cam, and any one of the exhaust valves is connected to the exhaust stroke. In a predetermined region extending from the intake stroke to the intake stroke to control a part of the exhaust in the exhaust port to flow back into the combustion chamber, and to perform a self-ignition operation and a spark ignition operation by a spark plug according to the load. An exhaust control device for an internal combustion engine that is selectively switched to operate, wherein a reverse flow exhaust that flows back into a combustion chamber by an exhaust valve that opens in a predetermined region from the exhaust stroke to the intake stroke is arranged along an outer circumferential direction of the combustion chamber. Backflow exhaust directing means for directing the airflow to flow in, and in the vicinity of the opening of any one of the two or more intake ports, the backflow exhaust introduced from the exhaust port is connected to the outer periphery of the combustion chamber. It is characterized in that it extends in the outer peripheral direction of the combustion chamber and is curved so as to be distributed unevenly in the region.
[0010]
According to a second aspect of the present invention, the backflow exhaust directing means according to the first aspect has an exhaust port provided with an exhaust valve that opens in a predetermined region extending from the exhaust stroke to the intake stroke in a substantially horizontal direction from the combustion chamber. It is formed to be elongated and curved so that the region near the opening extends in the outer circumferential direction of the combustion chamber.
[0011]
According to a third aspect of the present invention, the countercurrent exhaust directing means according to the first or second aspect is provided in an umbrella portion of an exhaust valve that opens in a predetermined region extending from an exhaust stroke to an intake stroke, so that the counterflow exhaust gas is in a combustion chamber. It is a shroud which forms the wall surface which blocks | prevents flowing other than the outer peripheral direction.
[0012]
According to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, the exhaust camshaft for driving the exhaust valve is provided, and the exhaust camshaft includes all of the exhaust valves. The first exhaust valve cam for opening the valve during the exhaust stroke and the second exhaust valve cam for driving the at least one exhaust valve also during the intake stroke.
[0014]
The invention described in claim 5 is the configuration described in any one of claims 1 to 4, except for an intake port formed so as to be curved so that a region near the opening extends in the outer circumferential direction of the combustion chamber. At least one of the other intake ports has an intake passage opening / closing valve for opening and closing the passage.
[0015]
According to a sixth aspect of the present invention, there is provided an exhaust gas recirculation passage for recirculating the exhaust gas discharged from the exhaust port according to any one of the first to fifth aspects to the intake port side, and the exhaust gas recirculation passage according to a load. A recirculation exhaust control valve that opens and closes and controls the flow rate of the recirculation exhaust.
[0016]
The invention described in claim 7 is characterized in that it has temperature adjusting means for adjusting the temperature of the recirculated exhaust gas flowing through the exhaust gas recirculation passage according to claim 7.
[0018]
【The invention's effect】
According to the invention described in claim 1, by providing the backflow exhaust directing means for directing the backflow exhaust that flows back from the exhaust port into the combustion chamber along the outer peripheral direction of the combustion chamber, The high-temperature backflow exhaust gas flowing into the combustion chamber is mainly distributed in the outer peripheral region of the combustion chamber, and the fuel / air mixture is mainly distributed in the central region of the combustion chamber, that is, in an annular shape. A stratified distribution state is formed, and in the subsequent compression stroke, compression is performed while the stratified distribution state is maintained. And, by this adiabatic compression action, the temperature of the backflow exhaust gas distributed in the outer peripheral region in the combustion chamber rises to a temperature exceeding the ignition temperature of the air fuel mixture distributed in the central region, and the interface between this backflow exhaust gas and the air fuel mixture As a starting point, compression self-ignition combustion of the air-fuel mixture occurs.
[0019]
That is, by stably forming a stratified distribution state in which high-temperature backflow exhaust gas is distributed in the outer peripheral region of the combustion chamber, the occurrence of an unburned region in the dead volume region is prevented as in the prior art, and is more nearly complete In addition, combustion can be performed, and at high loads, the amount of backflow exhaust introduced is reduced to lower the temperature of the mixture during the compression stroke, while at low loads, the amount of backflow exhaust introduced is increased. By increasing the temperature of the air-fuel mixture in the compression stroke, it is possible to expand the compression self-ignition combustion operation region in which the above-mentioned good combustion can be obtained, thereby greatly reducing NOx, HC, etc. Moreover, a favorable transient response can be obtained by utilizing the backflow exhaust from the exhaust port.
In addition, when the intake valve that opens and closes the opening is opened in the intake stroke, the fresh air that has flowed through the intake port flows into the combustion chamber as a swirl flow, and a desired swirl flow can be formed. it can. Therefore, the backflow exhaust gas introduced from the exhaust port is affected by the swirl flow and is unevenly distributed in the outer peripheral region of the combustion chamber, thereby causing stable compression self-ignition combustion. be able to.
Further, as a drive means for opening the exhaust valve to generate backflow exhaust, the exhaust valve is driven to open using an intake valve cam of an intake camshaft provided to open the intake valve. Since the configuration is adopted, it is not necessary to separately provide a new camshaft or the like only by providing interlocking means from the intake cam to the exhaust valve. Therefore, it is possible to perform the backflow operation of the exhaust gas from the exhaust port into the combustion chamber at a desired timing without causing any structural complication, in synchronism with the intake stroke.
[0020]
According to the second aspect of the present invention, the exhaust port provided with the exhaust valve that opens in a predetermined region extending from the exhaust stroke to the intake stroke extends in a substantially horizontal direction from the combustion chamber, and is a region near the opening. Is curved so as to extend in the outer circumferential direction of the combustion chamber, and by a simple structure, the backflow exhaust gas can be surely unevenly distributed in the outer circumferential area of the combustion chamber and distributed in a stratified manner. Thus, stable compression self-ignition combustion can be caused.
[0021]
According to the third aspect of the present invention, the backflow exhaust directing means for directing the backflow exhaust from the exhaust port toward the outer peripheral portion of the combustion chamber is an exhaust valve that opens in a predetermined region from the exhaust stroke to the intake stroke. Since the shroud provided in the umbrella is used, the structure can be simplified and stable compression ignition can be achieved. In addition, existing parts such as the cylinder head that forms the exhaust port can be used, resulting in cost of the product. Can be reduced.
[0022]
According to the exhaust control device for an internal combustion engine according to claim 4 of the present invention, at least the opening side region of the exhaust port is used as the backflow exhaust directing means for directing the backflow exhaust from the exhaust port toward the outer peripheral portion of the combustion chamber. Because it uses a shroud that is formed along the outer periphery of the combustion chamber and an umbrella of the exhaust valve, the simple structure makes the backflow exhaust more evenly distributed in the outer periphery of the combustion chamber. It can be distributed in a stratified manner, and thereby more stable compression auto-ignition combustion can be caused.
[0023]
According to the fourth aspect of the present invention, the exhaust camshaft having a cam (first exhaust valve cam) that operates in the exhaust stroke as drive means for opening the exhaust valve so as to generate backflow exhaust is taken into the intake camshaft. Since a dedicated cam (second exhaust valve cam) that operates in the stroke is provided and driven by this dedicated cam, it is not necessary to provide a new camshaft or the like separately. Therefore, the backflow operation of the exhaust gas from the exhaust port into the combustion chamber can be performed at a desired timing without incurring structural complexity.
[0025]
According to the fifth aspect of the present invention, the passage is opened and closed to at least one of the other intake ports excluding the intake port that is curved so that the region near the opening extends in the outer circumferential direction of the combustion chamber. In the intake stroke, the intake passage opening / closing valve is closed so that fresh air is introduced into the combustion chamber from the other intake port, thereby allowing the fresh air to flow in the outer circumferential direction of the combustion chamber. It can be a swirl flow along. Therefore, the backflow exhaust gas introduced from the exhaust port is affected by the swirl flow and is unevenly distributed in the outer peripheral region of the combustion chamber, thereby causing stable compression self-ignition combustion. be able to.
[0026]
According to the sixth aspect of the invention, not only the backflow exhaust from the exhaust port but also the recirculation exhaust that recirculates the exhaust discharged from the exhaust port to the intake port side is introduced into the combustion chamber. In addition, the combustion temperature of the air-fuel mixture can be precisely controlled, and the emission amount of soot, NOx, etc. can be further reduced.
[0027]
According to the seventh aspect of the present invention, not only the backflow exhaust from the exhaust port but also the recirculated exhaust that recirculates the exhaust discharged from the exhaust port to the intake port side is introduced into the combustion chamber. Since the configuration in which the temperature can be adjusted is adopted, the combustion temperature of the air-fuel mixture can be controlled more precisely, and the discharge amount of soot, NOx and the like can be further greatly reduced.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0029]
FIGS. 1 and 2 are a side view and a plan view showing a schematic configuration of an internal combustion engine (gasoline engine) provided with an embodiment of an exhaust control device according to the present invention. In this gasoline engine 10, as shown in FIGS. 1 and 2, the cylindrical bore side surface 11 a of the cylinder block 11, the crown surface 12 a of the piston 12 reciprocating along the bore side surface 11 a, and the lower surface of the cylinder head 13 13a defines a combustion chamber A, and the cylinder head 13 has a first intake port 14 as an independent intake port for introducing fresh air or a mixture of fresh air and fuel into the combustion chamber A. The second intake port 15 and the first exhaust port 16 and the second exhaust port 17 for discharging the exhausted exhaust gas from the combustion chamber A are formed. The cylinder head 13 includes a first intake valve 18 that opens and closes the opening 14a of the first intake port 14, a second intake valve 19 that opens and closes the opening 15a of the second intake port 15, and a first exhaust. A first exhaust valve 20 that opens and closes the opening 16a of the port 16 and a second exhaust valve 21 that opens and closes the opening 17a of the second exhaust port 17 are reciprocally attached. A spark plug 22 for performing spark ignition is attached to a substantially central portion of the lower surface 13a to be defined.
[0030]
The first intake port 14 and the second intake port 15 have substantially the same shape and are formed to communicate with the combustion chamber A with the same inclination angle. An electromagnetic fuel injection valve 23 for injecting fuel is attached, and in the middle of the second intake port 15, opening and closing of the passage is controlled by a drive mechanism (not shown) according to the operating condition of the engine. A swirl control valve 24 as an intake passage opening / closing valve is rotatably attached. The upstream sides of the independent first intake port 14 and the second intake port 15 are joined together to form one intake port.
[0031]
The first exhaust port 16 and the second exhaust port 17 are formed such that the first exhaust port 16 extends in a substantially straight line obliquely upward from the combustion chamber A with a larger inclination angle. The second exhaust port 17 extends from the combustion chamber A in a substantially horizontal direction with a small inclination angle, and a region in the vicinity of the opening 17a in the outer peripheral direction of the combustion chamber A, that is, the cylindrical side surface 11a. It is formed in a shape curved in the middle so as to extend in the tangential direction.
[0032]
By forming the second exhaust port 17 as described above, when the second exhaust valve 21 that opens and closes the opening 17a is opened in the intake stroke, the exhaust remaining in the second exhaust port 17 is As shown in FIG. 3, it is directed toward the outer peripheral direction of the combustion chamber A, and then flows in such a way as to be unevenly distributed in the outer peripheral region along the bore side surface 11a as shown in FIG.
[0033]
That is, the second exhaust port 17 formed as described above constitutes a backflow exhaust directing means for directing the backflow exhaust Gin flowing back into the combustion chamber A so as to flow along the outer peripheral direction of the combustion chamber A. Yes.
[0034]
As shown in FIG. 4, the mechanism for opening and closing the first intake valve 18 and the second intake valve 19 is swingably attached to an intake side rocker shaft 25 fixed to the cylinder head 13. 18 and the intake side rocker arm 27 having contact portions 27a that respectively contact the upper end portions of the second intake valve 19 and the cylinder head 13 are rotatably supported by the intake side rocker arm 27 and contact the intake side rocker arm 27 in the intake stroke. The intake camshaft 29 is provided with an intake valve cam 29a that operates to open the first and second intake valves 18 and 19, and the first exhaust valve 20 and the second exhaust valve 21 are also provided. The mechanism for opening and closing the cylinder is swingably attached to an exhaust side rocker shaft 26 fixed to the cylinder head 13 and abuts on the upper ends of the first exhaust valve 20 and the second exhaust valve 21, respectively. The exhaust-side rocker arm 28 having a contact portion 28a and a cylinder head 13 are rotatably supported so as to contact the exhaust-side rocker arm 28 and open the first and second exhaust valves 20, 21 in the exhaust stroke. The first exhaust valve cam 30a and the second exhaust valve cam 30b that operate to open the second exhaust valve 21 in the intake stroke are configured. Here, the intake valve cam 29a of the intake camshaft 29 and the first exhaust valve cam 30a and the second exhaust valve cam 30b of the exhaust camshaft 30 are shown in FIG. It is formed to have a lift characteristic as shown.
[0035]
Next, the operation of the exhaust control device according to this embodiment will be described.
[0036]
First, when the engine is operated in an intermediate load region, in the exhaust stroke, the first exhaust valve 20 and the second exhaust valve 21 are both pushed down and opened by the operation of the first exhaust valve cam 30a, and the combustion chamber The burnt gas in A is discharged to the outside as exhaust through both the first exhaust port 16 and the second exhaust port 17. In the subsequent intake stroke, the first intake valve 18 and the second intake valve 19 are both pushed down and opened by the operation of the intake valve cam 29a, and the swirl control valve 24 is closed, and the fuel injection valve 23 is opened. A mixture of the fuel injected from the air and fresh air (air) introduced from upstream of the intake system is introduced into the combustion chamber A from the first intake port 14. Further, in this intake stroke, the operation of the first exhaust valve cam 30a is completed, and at the same time, only the second exhaust valve 21 is pushed down again by the operation of the second exhaust valve cam 30b to open the second exhaust valve. Exhaust gas remaining in the exhaust port 17 flows back into the combustion chamber A.
[0037]
At this time, the second exhaust port 17 is formed so that the passage in the opening 17a side region extends in the outer peripheral direction of the combustion chamber A, that is, in the tangential direction of the bore side surface 11a. The remaining exhaust gas flows back along the bore side surface 11a, and also under the influence of the swirl action by the swirl control valve 24, the reverse flow exhaust Gin is annularly formed in the outer peripheral region of the combustion chamber A as shown in FIG. Furthermore, the air-fuel mixture Gmix forms a stratified distribution state so as to gather in the substantially central region of the combustion chamber A.
[0038]
In the subsequent compression stroke, the operation of the intake valve cam 29a and the second exhaust cam 30b ends, and the first and second intake valves 18, 19 and the second Exhaust valve 21 is closed, the piston 12 is raised while the stratified distribution state is maintained, and the mixture Gmix and the backflow exhaust Gin are compressed. In this compression stroke, the temperature of the backflow exhaust Gin distributed in the outer peripheral region in the combustion chamber A rises to a temperature exceeding the ignition temperature of the air-fuel mixture Gmix located in the substantially central portion in the combustion chamber A due to the adiabatic compression change. The air-fuel mixture Gmix starts self-igniting combustion starting from the interface between the heated back-flow exhaust Gin and the air-fuel mixture Gmix. Due to the explosive force generated by the self-ignition combustion, in the subsequent expansion stroke, the piston 12 is pushed down and returned to the exhaust stroke again, and the above-described operation is repeated.
[0039]
In the middle load operation region of the engine, a configuration is adopted in which fresh air is introduced not only from the first intake port 14 but also from the second intake port 15 while the swirl control valve 24 is kept open. Is also possible.
[0040]
When the engine is operated in a high load region, in the exhaust stroke, the first exhaust valve 20 and the second exhaust valve 21 are both pushed down and opened by the operation of the first exhaust valve cam 30a. The burned gas passes through the first exhaust port 16 and the second exhaust port 17 and is discharged to the outside as exhaust. In the subsequent intake stroke, the operation of the first exhaust valve cam 30a is completed, the first and second exhaust valves 20, 21 are closed, and the operation of the intake valve cam 29a causes the first intake valve 18 and the second intake valve 18 to be closed. The intake valve 19 is pushed down to open and the swirl control valve 24 is also opened, and the mixture of the fuel injected from the combustion injection valve 23 and fresh air (air) introduced from the upstream of the intake system is first. Only fresh air (air) is introduced into the combustion chamber A from the first intake port 14 and from the second intake port 15. In this intake stroke, the second exhaust valve 21 is not driven to open by the second exhaust valve cam 30b as in the above-described middle load region, and is in a closed state. In the closed state of the second exhaust valve 21, a known cam selection mechanism (not shown) provided in the exhaust side rocker arm 28 is operated, and the operating force of the second exhaust valve cam 30 b is changed to the second exhaust valve 21. Is maintained by avoiding transmission. The air-fuel mixture introduced by the intake stroke is uniformly distributed in the combustion chamber A.
[0041]
In the subsequent compression stroke, the operation of the intake valve cam 29a is terminated, the first and second intake valves 18 and 19 are closed, and the piston 12 is raised while maintaining the homogeneous distribution of the air-fuel mixture. The air-fuel mixture is compressed, and spark ignition is performed by the spark plug 22 in the vicinity of the end of the compression stroke, so that the air-fuel mixture causes homogeneous combustion. Due to the explosive force generated by the spark ignition combustion, the piston 12 is pushed down in the subsequent expansion stroke, returns to the exhaust stroke again, and the above-described operation is repeated.
[0042]
In the high-load operation region of the engine, the second exhaust valve 21 is maintained in the closed state in the intake stroke and the backflow exhaust Gin is not introduced into the combustion chamber A. It is also possible to adopt a configuration in which a small amount of backflow exhaust gas is introduced by adjusting the valve opening amount and the mixture is self-ignited and combusted.
[0043]
When the engine is operated in the low load region, the operation is basically the same as that in the above-described medium load operation region, but in the intake stroke, the operating force of the second exhaust valve cam 30b is increased by the cam selection mechanism. The first exhaust valve 20 is also opened so as to act on the first exhaust valve 20, so that the reverse exhaust Gin from the first exhaust port 16 as well as from the second exhaust port 17 to the combustion chamber A. It is operated so that more stable self-ignition combustion occurs by increasing the temperature of the air-fuel mixture in the compression stroke by introducing a larger amount of backflow exhaust than in the middle load operation.
[0044]
By operating as described above, the operating range of stable compression self-ignition combustion is expanded, and by introducing backflow exhaust that flows back from the exhaust port instead of recirculation exhaust that recirculates to the intake system, good transient As well as providing responsiveness, there is no need to limit the amount of fresh air that is sucked in during partial load, for example, by a throttle valve provided in the middle of the intake system as in the past, reducing pumping loss due to suction load As a result, fuel efficiency is improved.
[0045]
FIG. 7 shows another embodiment of the backflow exhaust directing means constituting a part of the exhaust control apparatus according to the present invention. As the backflow exhaust directing means in this embodiment, it is formed so as to be along the outer peripheral direction of the combustion chamber A as in the above-described embodiment, and does not employ an exhaust port, but communicates linearly with the combustion chamber A. The first exhaust port 31 and the second exhaust port 32 are employed, and the second exhaust valve 33 in which a curved shroud 34 is provided on the umbrella portion 33a is employed to open and close the opening 32a of the second exhaust port 32. To do.
[0046]
That is, the shroud 34 provided in the umbrella portion 33a of the second exhaust valve 33 prevents the backflow exhaust from the second exhaust port 32 from flowing in a predetermined direction in the combustion chamber A, that is, the outer periphery of the combustion chamber A. It is formed to allow only the flow along the direction. When the second exhaust valve 34 with the shroud 34 is adopted, the axis of the second exhaust valve 33 accompanying the reciprocation so that the shroud 34 always faces a predetermined direction with respect to the combustion chamber A. Means may be provided to prevent rotation around.
[0047]
As the backflow exhaust directing means, it is also possible to adopt a configuration in which the second exhaust port 17 formed along the outer peripheral direction of the combustion chamber A and the second exhaust valve 33 with the shroud 34 are combined. It is.
[0048]
FIG. 8 shows another embodiment of a mechanism for opening and closing the first intake valve 18 and the second intake valve 19 and the first exhaust valve 20 and the second exhaust valve 21 described above. As shown in FIG. 8, the mechanism for opening and closing the first intake valve 18 and the second intake valve 19 is swingably attached to an intake side rocker shaft 40 fixed to the cylinder head 13, so that the first intake valve 18 is driven. And a first contact portion 42a that contacts the upper end portion of the second intake valve 19 and a second contact portion 42b that is provided on the opposite side of the first contact portion 42a and contacts an intake camshaft 44 described later. The intake-side rocker arm 42 and the cylinder head 13 are rotatably supported and contact the second contact portion 42b of the intake-side rocker arm 42 to open the first and second intake valves 18 and 19 in the intake stroke. The intake camshaft 44 is provided with an intake valve cam 44a that operates so as to operate. The mechanism for opening and closing the first exhaust valve 20 and the second exhaust valve 21 is a cylinder head 13. A first exhaust-side rocker arm 43 provided with a contact portion 43a that is swingably attached to the fixed first exhaust-side rocker shaft 41 and abuts against the upper ends of the first exhaust valve 20 and the second exhaust valve 21, respectively. An exhaust valve cam 45a that is rotatably supported by the cylinder head 13 and that contacts the first exhaust-side rocker arm 43 and operates to open the first and second exhaust valves 20 and 21 in the exhaust stroke is provided. The exhaust camshaft 45 and the second exhaust rocker shaft 46 fixed to the cylinder head 13 are swingably attached to the upper end of the second exhaust valve 21 (the upper end of the first exhaust valve 20 depending on the operation mode). (2) a second exhaust side b provided with a first abutting portion 47a that abuts and a second abutting portion 47b that is provided on the opposite side of the first abutting portion 47a and abuts against the intake camshaft 44. It is constituted by Kaamu 47 or the like. The operating force generated by the intake valve cam 44a is not transmitted to the second exhaust-side rocker arm 47, and is transmitted not only to the second exhaust valve 21 but also to the first exhaust valve 20. A known cam selection mechanism (not shown) is provided.
[0049]
That is, in the exhaust stroke, the operation of the exhaust valve cam 45a of the exhaust camshaft 45 causes the first exhaust-side rocker arm 43 to rotate downward (counterclockwise in FIG. 8), and the first exhaust valve 20 In the intake stroke, the intake side rocker arm 42 is rotated counterclockwise in FIG. 8 by the operation of the intake valve cam 44a of the intake camshaft 44. The intake valve 18 and the second intake valve 19 are driven to open, and the second exhaust-side rocker arm 47 is rotated clockwise in FIG. 8 to drive only the second exhaust valve 21 (the engine is in a low load operation). In this case, the first exhaust valve 20 is also driven to open).
[0050]
In this case, the lift characteristics with respect to the crank angle of the first and second exhaust valves 20, 21 and the first and second intake valves 18, 19 are as shown in FIG. As can be understood from FIG. 9, the opening operation of the first and second intake valves 18, 19 and the second exhaust valve 21 can be synchronized, thereby ensuring the backflow exhaust together with the air-fuel mixture in the intake stroke. Can be introduced into the combustion chamber A at a predetermined timing.
[0051]
FIG. 10 is a schematic configuration diagram showing another embodiment of the exhaust control device according to the present invention. In this exhaust control device, the first intake port 14, the second intake port 15, the first exhaust port 16, and the reverse flow exhaust flow in along the outer peripheral direction of the combustion chamber A as in the embodiment shown in FIG. In addition to the formed second exhaust port 17, fuel injection valve 23, swirl control valve 24, etc., from the middle of the first exhaust port 16 (or exhaust manifold (not shown)) to the middle of the first intake port 14. The exhaust gas recirculation passage 50 for recirculating the exhaust gas discharged from the exhaust port to the intake port side, and the recirculation exhaust control for controlling the flow rate of the recirculation exhaust Gout by opening and closing the exhaust recirculation passage 50 according to the engine load. A valve 51 and a cooler 52 as temperature adjusting means for adjusting the temperature of the recirculated exhaust Gout flowing in the exhaust recirculation passage 50 are provided.
[0052]
According to the above configuration, in the intake stroke, the air-fuel mixture Gmix in which fresh air (air), fuel, and cooled recirculated exhaust gas Gout are mixed is introduced from the first intake port 14 into the combustion chamber A. 2 The backflow exhaust Gin is introduced from the exhaust port 17 along the outer peripheral direction of the combustion chamber A, that is, along the bore side surface 11a.
[0053]
At this time, the air-fuel mixture Gmix and the backflow exhaust Gin are distributed in a ring shape in the outer peripheral region of the combustion chamber A, and the recirculation exhaust gas is approximately at the center of the combustion chamber A, as shown in FIG. The gas mixture Gmix containing Gout is distributed. By forming such a stratified distribution state, stable compression self-ignition combustion can be performed as in the above-described embodiment, and the combustion temperature of the air-fuel mixture can be controlled more precisely. Etc. can be further reduced.
[0054]
11 and 12 show an embodiment in which the exhaust control device according to the present invention is applied to a direct injection gasoline engine that directly injects fuel into a cylinder (combustion chamber). In this direct injection engine 60, as shown in FIGS. 11 and 12, a cylindrical bore side surface 61a of a cylinder block 61 and a crown surface 62a provided with a recess 62a ′ of a piston 62 reciprocating along the bore side surface 61a. And a lower surface 63a of the cylinder head 63 define a combustion chamber A, and the cylinder head 63 has a first intake port 64 as an independent intake port for introducing fresh air (air) into the combustion chamber A. A second intake port 65 and a first exhaust port 66 and a second exhaust port 67 for exhausting the exhausted exhaust gas from the combustion chamber A are formed. The cylinder head 63 includes a first intake valve 68 that opens and closes the opening 64a of the first intake port 64, a second intake valve 69 that opens and closes the opening 65a of the second intake port 65, and a first exhaust. A first exhaust valve 70 that opens and closes the opening 66a of the port 66 and a second exhaust valve 71 that opens and closes the opening 67a of the second exhaust port 67 are reciprocally attached. An electromagnetic fuel injection valve 72 that directly injects fuel into the combustion chamber A is attached to a substantially central portion of the demarcating lower surface 63a, and an ignition plug 73 for performing spark ignition is attached in the vicinity thereof. ing.
[0055]
The first intake port 64 and the second intake port 65 are formed so as to extend from the obliquely upward to the combustion chamber A with substantially the same inclination angle, and the first intake port 64 further has its opening. The region in the vicinity of the part 64a is formed in a curved shape so as to extend in the outer circumferential direction of the combustion chamber A, that is, in the tangential direction of the cylindrical bore side surface 61a. A swirl control valve 74 as an intake passage opening / closing valve that is opened and closed according to the operating conditions of the engine by a mechanism (not shown) and opens and closes the passage is rotatably attached. The upstream sides of the independent first intake port 64 and the second intake port 65 are joined together to form one intake port.
[0056]
By forming the first intake port 64 as described above, when the first intake valve 68 that opens and closes the opening 64a is opened in the intake stroke, the fresh air flowing through the first intake port 64 is The swirl flow flows into the combustion chamber A, and the swirl control valve 74 provided in the second intake port 65 is closed to make the swirl flow stronger. Even if the swirl control valve 74 is not provided, a desired swirl flow can be formed by employing the first intake port 64 curved as described above.
[0057]
On the other hand, the first exhaust port 66 and the second exhaust port 67 extend substantially linearly from the combustion chamber A obliquely upward with a larger inclination angle than the first exhaust port 66, as in the above-described embodiment. The second exhaust port 67 is formed so as to extend in a substantially horizontal direction from the combustion chamber A with a small inclination angle, and a region in the vicinity of the opening 67a is the outer circumferential direction of the combustion chamber A, that is, a cylindrical shape. Is formed in a shape that is curved in the middle so as to extend in the tangential direction of the bore side surface 61a.
[0058]
Second exhaust port as above 6 7, when the second exhaust valve 21 that opens and closes the opening 67a is opened in the intake stroke, the exhaust gas remaining in the second exhaust port 17 flows into the combustion chamber A as shown in FIG. 2, and flows further along the outer periphery under the influence of the above-mentioned fresh air swirl flow. Thereafter, as shown in FIG. It will be unevenly distributed in the outer peripheral part area | region along the side surface 61a. That is, the second exhaust port 67 formed as described above constitutes a backflow exhaust directing means for directing the backflow exhaust Gin flowing back into the combustion chamber A so as to flow along the outer circumferential direction of the combustion chamber A. Yes. The operation of the mechanism and the entire device for opening and closing the first and second intake valves 68 and 69 and the first and second exhaust valves 70 and 71 in the present embodiment are the same as the mechanisms and operations in the previous embodiment. Since it is a thing, description here is abbreviate | omitted.
[0059]
In the embodiment described above, the second exhaust valve cam 30b that opens and closes the second exhaust valves 21 and 71 (and also the first exhaust valves 20 and 70 in some cases) is a cam in the entire operating range of the engine. Although a profile with a constant profile (a constant cam height) is applied, for example, as shown in FIG. 13, a variable mechanism that uses, for example, three types of cam profiles according to the operating region of the engine may be adopted. That is, select the exhaust valve cam that maximizes the valve lift amount in the low load operation region, and select the exhaust valve cam that minimizes the valve lift amount in the high load operation region. A structure in which an exhaust valve cam is selected so that a substantially intermediate valve lift amount can be obtained in the operation region may be employed.
[0060]
According to this configuration, in the high-load operation region of the engine, as shown in FIG. 14, a stratified distribution state is formed in which the amount of the backflow exhaust Gin is smaller than the amount of the mixture Gmix, while the low load of the engine In the operation region, as shown in FIG. 15, a stratified distribution state in which the amount of the backflow exhaust Gin is increased as compared with the amount of the air-fuel mixture Gmix is formed. As a result, stable compression self-ignition combustion can be performed, and emissions of soot, HC, NOx, etc. can be greatly reduced.
[0061]
In the embodiment described above, the intake valve cam 29a for opening and closing the first intake valves 18, 68 and the second intake valves 19, 69 has a constant cam profile (cam height) in the entire engine operating range. However, as shown in FIG. 16, a variable mechanism that uses, for example, three types of cam profiles may be employed depending on the operating region of the engine. That is, the intake valve cam that minimizes the valve lift is selected in the low load operation region, and the intake valve cam that maximizes the valve lift amount is selected in the high load operation region. In the region, a structure may be adopted in which an intake valve cam is selected so that a substantially intermediate valve lift amount can be obtained.
[0062]
According to this configuration, in the high-load operation region of the engine, the amount of inflow of the mixture Gmix increases, so that the amount of the backflow exhaust Gin relatively decreases compared to the amount of the mixture Gmix. On the other hand, in the low load operation region of the engine, the inflow amount of the air-fuel mixture Gmix decreases, so that the amount of the backflow exhaust Gin relatively increases compared to the amount of the air-fuel mixture Gmix. Thus, a stratified distribution state as shown in FIG. 15 is formed. As a result, stable compressed self-ignition combustion can be performed as described above, and emissions of soot, HC, NOx, etc. can be greatly reduced.
[0063]
In the embodiment described above, only one cylinder of the engine has been described, but it goes without saying that it can be applied to a multi-cylinder engine.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a part of a gasoline engine equipped with an exhaust control device according to the present invention.
FIG. 2 is a plan view showing a part of a gasoline engine equipped with an exhaust control device according to the present invention.
FIG. 3 is a plan view for explaining the flow of backflow exhaust flowing back from an exhaust port constituting the exhaust control device according to the present invention.
4A and 4B show a mechanism for opening and closing an intake valve and an exhaust valve of an internal combustion engine. FIG. 4A is a longitudinal sectional view, and FIG. 4B is a plan view of an intake camshaft and an exhaust camshaft.
FIG. 5 is a graph showing valve lift characteristics of an intake valve and an exhaust valve with respect to a crank angle.
FIG. 6 is a view showing a distribution state of backflow exhaust gas and air-fuel mixture in a combustion chamber.
FIG. 7 shows another embodiment of the reverse flow exhaust directing means constituting the exhaust control apparatus according to the present invention, wherein (a) is a plan view and (b) is a side view of the exhaust valve.
FIGS. 8A and 8B show another embodiment of a mechanism for opening and closing an intake valve and an exhaust valve of an internal combustion engine. FIG. 8A is a longitudinal sectional view, and FIG. 8B is a view of an intake camshaft and an exhaust camshaft. It is a top view.
FIG. 9 is a graph showing valve lift characteristics of an intake valve and an exhaust valve with respect to a crank angle.
FIG. 10 is a plan view showing another embodiment of the exhaust control device according to the present invention.
FIG. 11 is a longitudinal sectional view showing a part of a direct injection gasoline engine equipped with an exhaust control device according to the present invention.
FIG. 12 is a plan view showing a part of a direct injection gasoline engine provided with an exhaust control device according to the present invention.
FIG. 13 is a diagram showing valve lift characteristics with respect to a crank angle when a configuration in which a cam having three types of cam heights is selected as an exhaust valve cam in accordance with an engine operating condition is employed.
FIG. 14 is a diagram showing a distribution state of backflow exhaust gas and air-fuel mixture in a high load operation region.
FIG. 15 is a diagram showing a distribution state of backflow exhaust gas and air-fuel mixture in a low load operation region.
FIG. 16 is a diagram showing valve lift characteristics with respect to a crank angle when a configuration in which a cam having three types of cam heights is selected as an intake valve cam in accordance with an operating condition of the engine is employed.
[Explanation of symbols]
10 Gasoline engine
11 Cylinder block
11a Bore side
12 piston
12a crown
13 Cylinder head
13a bottom surface
14 First intake port
14a opening
15 Second intake port
15a opening
16 First exhaust port
16a opening
17 Second exhaust port
17a opening
18 First intake valve
19 Second intake valve
20 First exhaust valve
21 Second exhaust valve
22 Spark plug
23 Fuel injection valve
24 Swirl control valve (intake passage open / close valve)
25 Intake rocker shaft
26 Exhaust side rocker shaft
27 Intake rocker arm
28 Exhaust rocker arm
29 Intake camshaft
29a Cam for intake valve
30 Exhaust camshaft
30a First exhaust valve cam
30b Second exhaust valve cam
31 First exhaust port
32 Second exhaust port
33 Second exhaust valve
33a Umbrella
34 Shroud
40 Intake rocker shaft
41 First exhaust side rocker shaft
42 Intake rocker arm
43 First exhaust side rocker arm
44 Camshaft for intake
44a Intake valve cam
45 Exhaust camshaft
45a Cam for exhaust valve
46 Second exhaust side rocker shaft
47 Second exhaust side rocker arm
50 Exhaust gas recirculation passage
51 Recirculation exhaust control valve
52 Cooler (temperature control means)
60 direct injection gasoline engine
61 Cylinder block
61a Bore side
62 Piston
62a Crown surface
62a 'recess
63 Cylinder head
64 First intake port
65 Second intake port
66 First exhaust port
67 Second exhaust port
68 First intake valve
69 Second intake valve
70 First exhaust valve
71 Second exhaust valve
72 Fuel Injection Valve
73 Spark plug
74 Swirl control valve

Claims (7)

The combustion chamber includes two or more intake ports that communicate with each other independently, and two or more exhaust ports that communicate with each other independently.
Each intake port is provided with an intake valve that opens and closes these openings, and each exhaust port is provided with an exhaust valve that opens and closes these openings.
An intake camshaft formed with an intake valve cam for opening the intake valve, and the at least one exhaust valve is driven to open in the intake stroke by the intake valve cam;
Any one of the above exhaust valves is controlled to open in a predetermined region from the exhaust stroke to the intake stroke so that a part of the exhaust in the exhaust port flows back into the combustion chamber, and self-ignition operation is performed according to the load. An exhaust control device for an internal combustion engine that selectively switches between spark ignition operation using a spark plug and a spark ignition operation,
Backflow exhaust directing means for directing backflow exhaust that flows back into the combustion chamber by an exhaust valve that opens in a predetermined region extending from the exhaust stroke to the intake stroke to flow in along the outer circumferential direction of the combustion chamber;
The region in the vicinity of the opening of any one of the two or more intake ports extends in the outer circumferential direction of the combustion chamber so that the backflow exhaust gas introduced from the exhaust port is unevenly distributed in the outer circumferential region of the combustion chamber. And an exhaust control device for an internal combustion engine, wherein the exhaust control device is curved.   The backflow exhaust directing means extends an exhaust port provided with an exhaust valve that opens in a predetermined region from the exhaust stroke to the intake stroke in a substantially horizontal direction from the combustion chamber, and a region in the vicinity of the opening extends to the outer periphery of the combustion chamber. The exhaust control device for an internal combustion engine according to claim 1, wherein the exhaust control device is curved so as to extend in a direction.   The backflow exhaust directing means includes a shroud that is provided on the umbrella portion of the exhaust valve that opens in a predetermined region from the exhaust stroke to the intake stroke, and forms a wall surface that prevents the reverse flow exhaust from flowing in directions other than the outer circumferential direction of the combustion chamber. The exhaust control device for an internal combustion engine according to claim 1 or 2.   The exhaust camshaft for driving the exhaust valve has a first exhaust valve cam that opens and drives all the exhaust valves in the exhaust stroke, and the at least one exhaust valve is in the intake stroke. The exhaust control device for an internal combustion engine according to any one of claims 1 to 3, further comprising a second exhaust valve cam that is driven to open. And at least one of the other intake ports excluding the intake port that is curved so that the region in the vicinity of the opening extends in the outer circumferential direction of the combustion chamber has an intake passage opening / closing valve that opens and closes the passage. An exhaust control device for an internal combustion engine according to any one of claims 1 to 4 . An exhaust gas recirculation passage for recirculating the exhaust gas discharged from the exhaust port to the intake port side, and a recirculation exhaust control valve for opening and closing the exhaust gas recirculation passage according to a load and controlling a flow rate of the recirculation exhaust gas. Item 6. The exhaust control device for an internal combustion engine according to any one of Items 1 to 5 . The exhaust control device for an internal combustion engine according to claim 6, further comprising temperature adjusting means for adjusting the temperature of the recirculated exhaust gas flowing through the exhaust recirculation passage .

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