JP2008064008A - Stratified combustion type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a dense mixture supplied to a center part region in a combustion chamber from being diluted by lean mixture supplied to an outer peripheral part region in the combustion chamber. <P>SOLUTION: In a stratified combustion type internal combustion engine which holds a lean mixture in an outer peripheral part region 23 in a combustion chamber 6 and a dense mixture in a center part region 24 in the combustion chamber 6 which an electrode of a spark plug 10 faces before the ignition by the spark plug 10, an annular projecting wall 16 projecting so as to partition the outer peripheral part region 23 and center part region 24 is integrally formed with a top surface of a piston 5 facing the combustion chamber 6. A main intake port 11 for supplying the lean mixture to the outer peripheral part region 23 so as to give a first swirl S1. An auxiliary intake port 12 for supplying the dense mixture to the center part region 24 so as to give a second swirl S2 in the same direction as the first swirl S1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention ignites a lean air-fuel mixture in the outer peripheral region of the combustion chamber defined between the cylinder head and the piston, and a rich air-fuel mixture in the central region of the combustion chamber facing the spark plug electrode. The present invention relates to an improvement of a stratified combustion internal combustion engine which is held until ignition by a plug.

Such a stratified combustion internal combustion engine is already known, as disclosed in Japanese Patent Application Laid-Open No. H10-228707.
Japanese Utility Model Publication No. 63-13382

  In the stratified charge combustion internal combustion engine described in Patent Document 1, the swirl direction of the lean mixture generated in the outer peripheral region of the combustion chamber and the swirl direction of the rich mixture generated in the central region of the combustion chamber are determined. They are set in opposite directions to suppress the diffusion of the rich mixture due to centrifugal force. However, in such a case, the swirl of the lean mixture and the swirl of the rich mixture collide with each other at the boundary between them, and as a result, the outer periphery of the rich mixture is diluted, and the rich mixture The area is reduced, and the ignitability is impaired.

  The present invention has been made in view of such circumstances, and the rich mixture supplied to the central region of the combustion chamber is diluted by the lean mixture supplied to the outer peripheral region of the combustion chamber. It is an object of the present invention to provide a stratified combustion internal combustion engine capable of preventing the above and always ensuring good ignitability.

  In order to achieve the above object, the present invention provides a lean air-fuel mixture in the outer peripheral region of the combustion chamber defined between the cylinder head and the piston, and a central portion of the combustion chamber facing the electrode of the spark plug. In a stratified combustion internal combustion engine in which a rich air-fuel mixture is held in the region until ignition by the spark plug, the piston protrudes so as to partition the outer peripheral region and the central region on the top surface facing the combustion chamber A main intake port for supplying a lean mixture to the outer peripheral region and supplying a swirl in a certain direction to the outer peripheral region, and a secondary intake for supplying the rich mixture to the central region The cylinder head is provided with a port, a main intake valve and a sub intake valve that open and close the main intake port and the sub intake port, respectively, and a valve mechanism that opens and closes the main intake valve and the sub intake valve. 1 And features.

  Further, in addition to the first feature, the present invention provides the valve operating mechanism in which the opening timing of the auxiliary intake valve is delayed from the opening timing of the main intake valve, and the closing timing of the main intake valve is advanced from the closing timing of the auxiliary intake valve. The second feature is that the above is configured.

  Furthermore, in addition to the first feature, the present invention provides the sub-intake port with a swirl in the same direction as the swirl of the rich mixture generated in the outer peripheral region, to the lean mixture supplied to the central region. The third feature is that it is formed as described above.

  Furthermore, the present invention is characterized in that, in addition to the first feature, the auxiliary intake port is disposed adjacent to an exhaust port that opens to the combustion chamber.

  In addition to the first feature of the present invention, a concave groove is provided on the ceiling surface of the combustion chamber formed in the cylinder head to communicate between the electrode of the spark plug and the outlet of the auxiliary intake port. This is the fifth feature.

  Furthermore, in the sixth aspect of the present invention, in addition to the first feature, a sixth guide wall is provided at the outlet of the main intake port to guide the rich air-fuel mixture coming from the outlet to the combustion chamber toward the outer peripheral region side. Features.

  According to the first aspect of the present invention, in the combustion chamber, the outer peripheral region where the swirl of the lean mixture is generated and the central region where the rich mixture is supplied are formed on the top surface of the piston. By partitioning with the convex wall, it is possible to effectively avoid the dilution of the rich mixture due to the lean mixture. Therefore, the rich air-fuel mixture in the central region can be ignited accurately when the spark plug is ignited, and the lean air-fuel mixture can be reliably burned by the flame and stable stratified combustion can be achieved, improving fuel efficiency. Can be achieved.

  According to the second feature of the present invention, the supply of the rich mixture to the central region is delayed rather than the supply of the lean mixture to the outer peripheral region. As a result, the lean mixture becomes a rich mixture. As a result, the influence of the lean mixture due to the lean mixture can be more effectively avoided.

  According to the third aspect of the present invention, the first swirl of the lean mixture and the second swirl of the rich mixture take the same direction, thereby preventing mutual interference between the swirls and avoiding the mixture of the two mixtures. be able to.

  According to the fourth feature of the present invention, the rich air-fuel mixture passing through the auxiliary intake port is accelerated by the heating by the exhaust heat, and the ignitability can be further enhanced.

  According to the fifth aspect of the present invention, the concave groove on the combustion chamber ceiling surface cooperates with the cavity inside the annular convex wall of the piston to constitute a thick and compact reservoir of thick mixture. This contributes to the prevention of the diffusion of the rich mixture to the outer peripheral region, and since this concave groove is immobile unlike the above-mentioned cavity, the retention of the rich mixture is good and the ignitability of the rich mixture is enhanced. be able to.

  According to the sixth aspect of the present invention, the lean air-fuel mixture is guided to the outer peripheral region side by the guide wall when leaving the outlet of the main intake port, thereby preventing the lean air-fuel mixture from entering the central region. be able to.

  Embodiments of the present invention will be described below on the basis of preferred embodiments of the present invention shown in the accompanying drawings.

  1 is a plan view of a stratified charge combustion internal combustion engine according to the present invention when the main intake valve is opened, FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, and FIG. 3 is an open state of the auxiliary intake valve. 4 is a cross-sectional view taken along line 4-4 of FIG. 3, FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 1, and FIG. 6 is an open / close characteristic diagram of main and auxiliary intake valves and exhaust valves. is there.

  First, in FIG. 1, FIG. 2 and FIG. 5, an engine body 1 of an internal combustion engine includes a cylinder block 2 having a cylinder bore 2a and a cylinder head 4 joined to the upper end surface of the cylinder block 2 via a gasket 3. A combustion chamber 6 is defined between the opposed surfaces of the piston 5 and the cylinder head 4 that are configured to move up and down the cylinder bore 2a.

  An annular main intake valve seat member 7, auxiliary intake valve seat member 8, and exhaust valve seat member 9 are attached to the cylinder head 4 so as to be embedded in the ceiling surface of the combustion chamber 6. The electrode is screwed so as to face the combustion chamber 6.

  At that time, the main intake valve seat member 7 is disposed on the outermost peripheral portion of the combustion chamber 6, and the auxiliary intake valve seat member 8 is adjacent to one side of the main intake valve seat member 7 and is more than the main intake valve seat member 7. Located near the center of the combustion chamber 6, the exhaust valve seat member 9 is disposed adjacent to one side of the auxiliary intake valve seat member 8 opposite to the main intake valve seat member 7, and the electrode of the spark plug 10 is The main intake valve seat member 7 and the exhaust valve seat member 9 are arranged as close as possible to the center of the combustion chamber 6.

  The cylinder head 4 is provided with a main intake port 11 connected to the main intake valve seat member 7, an auxiliary intake port 12 connected to the auxiliary intake valve seat member 8, and an exhaust port 13 connected to the exhaust valve seat member 9. 12 and the exhaust port 13 are arranged adjacent to each other. Thus, the main intake valve seat member 7 hits the outlet opening to the combustion chamber 6 of the main intake port 11, and the auxiliary intake valve seat member 8 hits the outlet opening to the combustion chamber 6 of the auxiliary intake port 12. The main intake port 11 is connected to a lean mixture supply device 14 for supplying a mixture having an air / fuel ratio larger than the stoichiometric air / fuel ratio, that is, a lean mixture, and the auxiliary intake port 12 has an air / fuel ratio equal to the theoretical air / fuel ratio. A rich mixture supply device 15 for supplying a smaller mixture, that is, a rich mixture is connected.

  On the ceiling surface of the combustion chamber 6, a concave groove 22 (see FIG. 5) that communicates between the outlet 8 of the auxiliary intake port 12 and the electrode of the spark plug 10 is provided.

  The cylinder head 4 has a main intake valve 11 that opens and closes the main intake port 11, the auxiliary intake port 12, and the exhaust port 13 in cooperation with the main intake valve seat member 7, the auxiliary intake valve seat member 8, and the exhaust valve seat member 9, respectively. There are provided a valve 18, a sub intake valve 19 and an exhaust valve 20, and a valve operating mechanism 21 for individually opening and closing the main intake valve 18, the sub intake valve 19 and the exhaust valve 20.

  An annular convex wall 16 that divides the combustion chamber 6 into an annular outer peripheral region 23 and a central region 24 surrounded by the outer peripheral region 23 is integrally formed on the top surface of the piston 5 facing the combustion chamber 6. At the same time, the inside of the annular convex wall 16 is formed in a cavity 17 deeper than the outer peripheral region 23. Thus, most of the main intake valve seat member 7 is disposed in the outer peripheral region 23, and the entire sub intake valve seat member 8 is disposed in the central region 24.

  Moreover, the main intake port 11 is formed in a helical shape so as to reach the main intake valve seat member 7 while turning from the outside in the radial direction of the combustion chamber 6, and the rich mixing supplied from the main intake port 11 to the combustion chamber 6. The first swirl S1 (see FIGS. 1 and 2) in a certain direction is given to the outer peripheral region 23. A guide wall 27 for guiding the rich air-fuel mixture coming out of the valve seat member 7 to the outer peripheral region 23 side is integrally formed at a portion of the main intake valve seat member 7 protruding toward the central region 24 side. The

  On the other hand, the auxiliary intake port 12 is formed so as to be directed in the tangential direction of the central region 24 in the direction of the first swirl S1. As a result, the concentrated air-fuel mixture supplied from the auxiliary intake port 12 to the combustion chamber 6 is given the second swirl S2 (see FIGS. 3 and 4) in the same direction as the first swirl S1 in the central region 24. Yes.

  The valve mechanism 21 opens and closes the main intake valve 18, the auxiliary intake valve 19 and the exhaust valve 20 with the characteristics shown in FIG. In particular, the main intake valve 18 is controlled by the valve mechanism 21 so that it starts to open at substantially the start time of the intake stroke and closes at the almost end time of the intake stroke, whereas the sub intake valve 19 has the intake stroke of the intake stroke. The valve operating mechanism 21 is controlled to start opening in the second half and close in the first half of the compression stroke after the main intake valve 18 is closed. Thus, the closing of the main intake valve 18 is advanced and the closing of the auxiliary intake valve 19 is delayed in order to draw the rich mixture into the cylinder bore 2a due to the negative pressure remaining in the cylinder bore 2a in the first half of the compression stroke.

  Further, the opening lift amount of the auxiliary intake valve 19 is sufficiently smaller than that of the main intake valve 18, and is set to approximately ½ of that in the illustrated example, thereby reducing the amount of the rich mixture to be drawn into the cylinder bore 2a. It is adjusted to be sufficiently smaller than the amount of the lean mixture.

  Next, the operation of this embodiment will be described with reference to FIG.

  When the intake stroke of the engine starts, as shown in FIGS. 1 and 2, the main intake valve 18 is first opened, so that the lean air-fuel mixture is introduced into the combustion chamber 6 from the main intake port 11. At this time, the lean air-fuel mixture is guided by the helical main intake port 11 and generates a first swirl S1 in a certain direction in the outer peripheral region of the combustion chamber 6. Further, since the lean air-fuel mixture is guided to the outer peripheral region 23 side by the guide wall 27 when exiting the outlet 7 of the main intake port 11, the lean air-fuel mixture is prevented from entering the central region and the outer peripheral region 23. Assists in the reliable formation of the first swirl of the lean mixture at

  Thus, during the intake stroke, a strong first swirl S1 of the lean mixture is generated in the outer peripheral region 23, and unnecessary scattering of the lean mixture to the central region 24 can be prevented.

  The auxiliary intake valve 19 begins to open in the second half of the intake stroke, and the opening of the auxiliary intake valve 19 continues even when the main intake valve 18 is closed at the end of the intake stroke, and closes in the first half of the compression stroke. As a result, the rich air-fuel mixture is supplied from the auxiliary intake port 12 to the central region 24 of the combustion chamber 6 as shown in FIGS. As described above, the auxiliary intake port 12 is formed so as to be directed in the tangential direction of the central region 24 in the direction of the first swirl S1, so that the rich air-fuel mixture is formed in the central region 24 in the first swirl S1. The second swirl S2 is generated in the same direction. In this way, the second swirl S2 of the rich mixture is generated later than the first swirl S1 of the lean mixture, so that the mixture of the lean mixture and the rich mixture can be avoided as much as possible.

  Moreover, in the combustion chamber 6, the outer peripheral region 23 and the central region 24 surrounded by the outer peripheral region 23 are partitioned by the annular convex wall 16 of the piston 5. Since it is formed in the deeper cavity 17, the mixture of the lean mixture and the rich mixture is prevented by the annular convex wall 16, and the rich mixture is held by the cavity 17. In addition, it is also effective for the first swirl S1 of the lean air-fuel mixture and the second swirl S2 of the rich air-fuel mixture to take the same direction in order to prevent mutual interference between the swirls and to avoid mixing of both air-fuel mixtures.

  Thus, the rich air-fuel mixture in the center region 24 reaches the end of the compression stroke without being diluted by the lean air-fuel mixture in the outer peripheral region 23, so that it can be ignited accurately when the spark plug 10 is ignited. As a result, the lean air-fuel mixture can be reliably burned by the generated flame, stable stratified combustion can be performed, and fuel efficiency can be improved.

  In addition, the concave groove 22 provided on the ceiling surface of the combustion chamber 6 and communicating between the electrode of the spark plug 10 and the outlet 8 of the auxiliary intake port 12 cooperates with the deep cavity 17 to provide a thick compact Thus, a rich air-fuel mixture storage portion is formed, which contributes to preventing diffusion of the rich air-fuel mixture into the outer peripheral region 23. In particular, the concave groove 22 is immovable unlike the cavity 17, so that the retention of the rich mixture is good and the ignitability of the rich mixture can be enhanced.

  Further, since the auxiliary intake port 12 is disposed adjacent to the exhaust port 13, vaporization of the rich air-fuel mixture passing through the auxiliary intake port 12 is promoted by heating with exhaust heat, and the ignitability can be further enhanced.

  The present invention is not limited to the above embodiment, and various design changes can be made without departing from the scope of the invention.

The top view shown in the open state of the main intake valve of the stratified combustion internal combustion engine of this invention. FIG. 2 is a sectional view taken along line 2-2 in FIG. 1. The corresponding figure with FIG. 1 which shows the open state of a sub intake valve. FIG. 4 is a sectional view taken along line 4-4 of FIG. FIG. 5 is a sectional view taken along line 5-5 in FIG. Opening / closing characteristics diagram of main and auxiliary intake valves and exhaust valves.

Explanation of symbols

4 ... Cylinder head 5 ... Piston 6 ... Combustion chamber 7 ... Main intake port outlet (Main intake valve seat member)
8 ... Sub-intake port outlet (sub-intake valve seat member)
10... Spark plug 11... Main intake port 12... Sub intake port 13... Exhaust port 16. · Sub-intake valve 21 ··· Valve mechanism 22 ··· Groove 23 ··· Outer peripheral region 24 ··· Central region S1 ··· Swirl S2 due to lean mixture ··· Swirl with rich mixture

Claims (6)

A lean air-fuel mixture is introduced into the outer peripheral region (23) in the combustion chamber (6) defined between the cylinder head (2) and the piston (5), and an ignition plug (10 In the stratified charge combustion internal combustion engine, the rich air-fuel mixture is held in the central region (24) where the electrode of) faces until ignition by the spark plug (10).
An annular projecting wall (16) protruding so as to partition between the outer peripheral region (23) and the central region (24) is integrally formed on the top surface of the piston (5) facing the combustion chamber (6), A main intake port (11) that supplies a lean mixture to the outer peripheral region (23) and a swirl (S1) in a certain direction to the outer region (23), and a secondary mixture that supplies a rich mixture to the central region (24) An intake port (12), a main intake valve (18) and a sub intake valve (19) for opening and closing the main intake port (11) and the sub intake port (12), and the main intake valve (18) and the sub intake port (12). A stratified combustion internal combustion engine, characterized in that a valve mechanism (21) for opening and closing the intake valve (19) is provided in the cylinder head (2). The stratified charge combustion internal combustion engine according to claim 1,
The valve mechanism (19) is configured to delay the opening timing of the auxiliary intake valve (19) from the opening timing of the main intake valve (18) and advance the closing timing of the main intake valve (18) earlier than the closing timing of the auxiliary intake valve (19). A stratified combustion internal combustion engine characterized by comprising 21). The stratified charge combustion internal combustion engine according to claim 1,
A swirl (S2) in the same direction as the swirl (S1) of the rich mixture generated in the outer peripheral region (23) is applied to the lean air-fuel mixture supplied to the central region (24) through the auxiliary intake port (12). A stratified combustion internal combustion engine, characterized in that it is configured to be applied. The stratified charge combustion internal combustion engine according to claim 1,
A stratified combustion internal combustion engine, wherein the auxiliary intake port (12) is disposed adjacent to an exhaust port (13) that opens to the combustion chamber (6). The stratified charge combustion internal combustion engine according to claim 1,
A concave groove (22) formed in the cylinder head (2) and communicating with the ceiling surface of the combustion chamber (6) between the electrode of the spark plug (10) and the outlet (8) of the auxiliary intake port (12). A stratified combustion internal combustion engine characterized in that The stratified charge combustion internal combustion engine according to claim 1,
The outlet (7) of the main intake port (11) is provided with a guide wall (27) for guiding the rich air-fuel mixture exiting from the outlet (7) to the combustion chamber (6) toward the outer peripheral region (23). A stratified charge combustion internal combustion engine.

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