JP2003214167A - Engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the combustion over the whole area of an engine operation area, and to reduce the concentration of Nox. <P>SOLUTION: A tumble flow generating means (intake port 13) is mounted for generating the tumble flow T of air-fuel mixture in a cylinder. A squish flow generating means (inclined face 25 and recessed part 26 of piston top part 7a, and combustion chamber wall 31 of cylinder head 2) is mounted for generating the squish flow S flowing in the direction opposite to the tumble flow T in the cylinder. The tumble flow T and the squish flow S are generated in such manner that they are opposite to each other at the end of a compression stroke. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine in which a tumble flow and a squish flow are generated in a cylinder to improve combustion.

[0002]

2. Description of the Related Art In recent years, an engine is burned with an air-fuel ratio leaner than a stoichiometric air-fuel ratio (lean combustion), or a part of exhaust gas is recirculated in a cylinder (EGR).
We are working to improve fuel efficiency and purify exhaust gas. Fuel is mixed with air and sucked into the cylinder in a mixture.
In a so-called premixed engine, combustion is improved by compressing the air-fuel mixture while flowing it, so that the lean combustion and the EGR limit described above are increased. In order to compress the air-fuel mixture while flowing the air-fuel mixture in a conventional engine, a tumble flow, a swirl flow, a squish flow or the like composed of the air-fuel mixture is generated in the cylinder.

[0003]

However, in the conventional engine for flowing and compressing the air-fuel mixture as described above, the flow direction of the air-fuel mixture is substantially one direction and the flow velocity of the air-fuel mixture in the cylinder is equal to that of the engine. There is a problem in that the combustion can be improved only in a narrow rotation range because it changes according to the rotation speed and the load. this is,
For example, if the engine is designed so that the flow velocity of the air-fuel mixture in the cylinder is optimum when the engine operating region is in the low rotation speed / low load region, the flow velocity becomes excessive in the high rotation speed / high load region. This is because it will end up.

As described above, when the flow rate of the air-fuel mixture becomes excessively high, misfiring occurs, the flame kernel spreading around the spark plug is obstructed by the air-fuel mixture, or the air-fuel mixture is strongly blown to the electrodes of the spark plug for ignition. There are many problems such as the need to increase the voltage because it tends to be unstable. However, if the engine operating range is set to the optimum speed of the mixture when the engine speed is in the high speed / high load range, combustion becomes unstable when the engine speed is in the low speed / low load range. It will be easier.

Further, the conventional engine described above has a problem that the concentration of Nox in the exhaust gas becomes high. It is considered that this is because the air-fuel mixture flows in almost one direction. More specifically, the initial combustion gas generated in the vicinity of the spark plug rapidly spreads mainly in the direction of flow of the air-fuel mixture, and since the initial combustion gas is held at a high temperature, the concentration of Nox becomes high. Conceivable.
This phenomenon is prominent when lean combustion and sufficient oxygen are present.

The present invention has been made in order to solve such a problem, and in an engine in which an air-fuel mixture is made to flow in a cylinder, it is possible to improve combustion over the entire engine operating range. The purpose is to reduce the concentration of Nox.

[0007]

In order to achieve this object, an engine according to the present invention comprises a tumble flow generating means for generating a tumble flow composed of a mixture in a cylinder, and a tumble flow opposite to the tumble flow in the cylinder. And a squish flow generating means for generating a squish flow flowing in a direction, and the tumble flow and the squish flow are generated so as to face each other at the end of the compression stroke.

According to the present invention, the tumble flow and the squish flow collide with each other, whereby the air-fuel mixture is dispersed as minute vortices (microturbulence), and the tumble flow and the squish flow are combined. The gas flow is to move to the top side of the piston. Therefore, the micro-turbulence promotes the growth of the flame kernel, and the flame spreads to the top side of the piston, so that the combustion is rapidly performed. On the other hand, the collision of the tumble flow and the squish flow attenuates the kinetic energy of the mixed air flow,
The state of the air-fuel mixture after the collision does not change significantly even if the engine speed or load changes. For this reason,
The phenomenon of rapid combustion as described above also occurs over a wide operating range. Further, since the flow of the air-fuel mixture in the cylinder continues after ignition, unburned gas is continuously supplied to the initial combustion gas portion grown near the top of the piston. Therefore, since the initial combustion gas diffuses while being stirred with the unburned gas, it is not held at a high temperature.

The engine according to the invention described in claim 2 is the engine according to the invention described in claim 1,
The tumble flow generating means is configured to direct the air-fuel mixture from the intake port in the direction opposite to that of the exhaust valve and guide the mixture into the cylinder.
The squish flow generating means is constituted by a slope facing the intake valve at the top of the piston, a recess adjacent to this slope, and a combustion chamber wall on the cylinder head side. According to this invention, since the intake air flows into the cylinder from the intake port to the side opposite to the exhaust valve, the cylinder head is separated from the cylinder head on the intake valve side with respect to the cylinder axis when viewed in the axial direction of the cam shaft. A so-called reverse tumble flow, which is a swirling flow that approaches the cylinder head on the exhaust valve side, is generated. In addition, in this engine, a space (squish area) for generating a squish flow is formed on the intake valve side where the temperature is relatively low.

The engine according to the invention described in claim 3 is the engine according to the invention described in claim 2,
The tumble flow generating means is formed at the downstream end of the intake port by an inclined portion that gradually extends toward the side opposite to the exhaust valve as it goes downstream. According to the present invention, since the direction of intake air flow is restricted by the shape of the intake port, the intake resistance is reduced and the parts are made smaller than when a member for changing the direction of intake air flow is provided in the intake port. The number can be reduced.

The engine according to the invention described in claim 4 is the engine according to the invention described in claim 2,
The tumble flow generating means is formed by providing a guide member for changing the flow direction of intake air in the intake passage. According to the present invention, the strength of the tumble flow can be changed by the guide member.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) An embodiment of an engine according to the present invention will be described in detail below with reference to FIGS. 1 to 9. FIG. 1 is a sectional view of an engine according to the present invention, and FIG. 2 is an enlarged sectional view of a part of the engine.
The drawing is drawn with the piston positioned at the top dead center in the compression stroke. 3 is a plan view of the piston, FIG. 4 is a plan view showing a configuration of a portion near the combustion chamber of the engine as seen from the cylinder head side, and FIG. 5 is a bottom view showing the combustion chamber wall of the cylinder head. 6 is a vertical sectional view of a cylinder and a piston, FIG. 7 is a sectional view taken along line VII-VII in FIG.
FIG. 8 is a time chart showing the opening / closing timing of the intake / exhaust valve and the fuel injection timing, and FIG. 9 is a sectional view showing another example of the piston.

In these figures, reference numeral 1 indicates an engine according to this embodiment. The engine 1 is operated using a gas fuel such as LPG or CNG (compressed natural gas), and the gas fuel is supplied from an injector 3 for supplying a fuel gas of a cylinder head 2 through a nozzle 4 described later to an intake passage 5 It has a structure to inject inside. It should be noted that the number of cylinders of the engine 1 is shown only for one cylinder in FIG. 1 for convenience of description, but it can be used for an engine having a plurality of cylinders. In FIG.
Reference numeral 6 indicates a cylinder body, 7 indicates a piston, and 8 indicates a connecting rod.

As well known in the art, the cylinder head 2 is provided with a DOHC type valve operating device 11 and an ignition plug 12, and an intake port 13 and an exhaust port 14 which form the intake passage 5. Is provided. The valve operating device 11 has two intake valves 15 and two exhaust valves 16 for each cylinder.
5 and 16 are driven by an intake cam shaft 18 and an exhaust cam shaft 19 via a valve lifter 17, respectively.

The ignition plug 12 is arranged in the center of the cylinder surrounded by the four intake / exhaust valves 15 and 16. A screw hole into which the ignition plug 12 is screwed is indicated by reference numeral 20 in FIGS. 4 and 5. In FIG. 5, reference numeral 21
Indicates an intake outlet of the intake port 13 opened and closed by the intake valve 15, and 22 indicates an exhaust inlet of the exhaust port 14 opened and closed by the exhaust valve 16.

In this embodiment, the intake port 13 is provided for each intake valve 15 (see FIG. 4), and penetrates the cylinder head 2 in the vertical direction (direction along the cylinder axis C) as shown in FIG. Is formed. Although not shown, the throttle valve is connected to the upstream side of the intake port 13 through an intake passage of the head cover and an intake pipe attached to the head cover.

The intake port 13 according to this embodiment is
As shown in FIG. 1, the cylinder head 2 is inclined so as to gradually approach the intake valve 15 from the opening of the upper end portion toward the downstream side, and is gradually exhausted toward the downstream side to the exhaust valve 16 toward the downstream side. Slope 2 extending to the opposite side of
3 is provided.

By forming the intake port 13 in this manner, the intake air that has passed through the intake port 13 is introduced into the cylinder from the intake outlet 21 in the direction opposite to the exhaust valve 16 due to the inertia of the intake flow. Get burned. On the other hand, in the exhaust port 14, the exhaust passages of the exhaust valves 16 merge in the cylinder head 2, and the exhaust outlet 2 at one side of the cylinder head 2 is joined.
It is formed so as to extend up to 4.

The piston 7 has the structure shown in FIGS.
As shown in, a slope 25 and a recess 26 are formed on the top 7a. As shown in FIGS. 2 and 4, the slope 25 is formed at a portion of the top portion 7 a of the piston 7 that faces the intake valve 15 so as to extend in the direction in which the intake valve 15 is arranged in parallel. End face 15c of valve body 15b
It is inclined so as to be parallel to (a surface forming a part of the combustion chamber wall).

As shown in FIGS. 2 and 6, the recess 26 is formed by denting a portion of the top portion 7a of the piston 7 adjacent to the slope 25, which is D-shaped in a plan view, downward in a hemispherical shape. ing. In addition, as the piston 7,
As shown in FIG. 9, a portion of the top portion 7a adjacent to the slope 25 is formed flat, and the flat portion 7b substantially forms the recess 26.
Can also be formed. By using this piston 7, the compression ratio can be increased as compared with the case of using the piston 7 shown in FIG.

The fuel gas injector 3 is provided for each cylinder and is one side of the cylinder head 2.
It is attached to a portion corresponding to between the intake ports 13. Fuel gas is fed under pressure from a fuel tank (not shown), and the injector 3 injects the fuel gas into the fuel passage 28 of the cylinder head 2 from the fuel injection port 27 (see FIG. 7) at the tip at a predetermined fuel injection timing. .

As shown in FIG. 8, the fuel injection by the injector 3 is performed when the intake valve 15 is closed during the exhaust stroke (primary fuel injection) and when the intake valve 15 is opened during the intake stroke ( In the secondary fuel injection), the injection timing and the injection period are set in correspondence with the operating conditions. The period during which the injector 3 injects fuel is set to be longer during the primary fuel injection than during the secondary fuel injection. As the fuel injection amount, for example, about 50 to 70% of the fuel gas supplied in one cycle is injected during the primary fuel injection, and the rest is injected during the secondary fuel injection.

As shown in FIG. 7, the fuel passage 28 through which the injector 3 injects fuel extends from the injector mounting holes 29 toward the respective intake ports 13 and extends toward the intake ports 13.
Hole 30 for each intake port 13 opening at the downstream end of the
And a nozzle 4 formed of a pipe fitted into and fixed to each of these through holes 30 from the intake outlet 21 side of the intake port 13. Each nozzle 4 is shown in FIG.
As shown in FIG. 3, the intake port 13 is arranged in the vicinity of the adjacent intake ports 13, and as shown in FIG. 1, it is bent so that the opening at the tip is directed to the downstream side in the intake air flowing direction.

The term "downstream side of the intake flow" as used herein means the downstream side of intake air whose flow direction is restricted by the inclined portion 23 of the intake port 13, and the intake outlet 2 of the intake port 13
1 is a direction opposite to the exhaust valve 16 and directed obliquely downward. By forming the nozzle 4 in this way, the fuel gas injected from the nozzle 4 into the intake port 13 in the intake stroke is prevented from flowing into the intake valve 15 and the intake outlet as shown by the arrow G filled in black in FIG. The gas flows diagonally downward in a direction away from the exhaust valve 16 in the cylinder through a gap between the exhaust valve 16 and the valve 21.

In the engine 1 constructed as described above, as shown in FIG. 8, when the piston 7 is rising (when the intake valve 15 is closed) in the exhaust stroke, the first fuel is injected by the injector 3. Injection is performed. At this time,
Since the intake valve 15 is closed, the fuel gas stays in the intake port 13. Then, at the end of the exhaust stroke, the intake valve 15 opens immediately before the piston 7 reaches the top dead center, and the piston 7 stays in the intake port 13 as described above in the descending stroke after the piston 7 exceeds the top dead center. The fuel gas that is operating and fresh air are sucked into the cylinder.

The fuel gas is supplied to the intake valve 15 and the intake outlet 2
1 flows into the cylinder from almost the entire gap between
Most of the air is made to flow in substantially the same direction as the intake air by being pushed by the intake air that is drawn obliquely downward into the cylinder from the intake port 13. The fuel gas and fresh air flow to the lower part in the cylinder along the inner peripheral surface of the cylinder.

As described above, the intake air sucked into the cylinder hits the concave portion 26 of the piston top portion 7a and its flow direction is changed, and a tumble flow is generated in the cylinder as indicated by an arrow T in FIG. This tumble flow is shown in Figure 1.
As shown in FIG. 3, a swirling flow is generally formed such that the intake valve 15 side is separated from the cylinder head 2 with respect to the axis C of the cylinder as viewed from the axial direction of the cam shaft, and the exhaust valve 16 side is close to the cylinder head 2, and The so-called reverse tumble flow is a so-called reverse tumble flow in which the swirling direction is opposite. By forming the tumble flow in this way, the fuel gas is mixed with fresh air and diffused in the cylinder to form a lean air-fuel mixture.

Then, during the intake stroke, the injector 3
The second fuel injection is performed (see FIG. 8). At this time, the fuel gas is injected into the cylinder from each of the two nozzles 4 through the gap between the intake valve 15 and the intake outlet 21. Since the tumble flow T is formed in the cylinder as described above, the fuel gas swirls in the cylinder so as to ride on the tumble flow T as shown in FIG. The nozzle 4 is provided near the portions of the two intake ports 13 that are adjacent to each other.
The fuel injected from the fuel flows in layers near the spark plug 12. That is, at the end of the compression stroke, the spark plug 1
A relatively rich air-fuel mixture is supplied in layers near the periphery of 2.

After the second fuel injection is performed and the intake valve 15 is closed in this way, the piston 7 moves to the compression top dead center, whereby the tumble flow T in the cylinder is
As shown in, the diameter is reduced while swirling in the space (combustion chamber 32) formed between the recess 26 of the piston top portion 7a and the combustion chamber wall 31 on the cylinder head 2 side. On the other hand, at this time, the air-fuel mixture is pushed out from the gap (squish area) between the slope 25 of the piston top portion 7a and the combustion chamber wall 31 on the cylinder head 2 side, and a squish flow is generated.
This squish flow is indicated by arrow S in FIG.

Since the squish flow S advances in the combustion chamber 32 along the wall surface of the combustion chamber on the cylinder head 2 side to the exhaust valve 16 side in FIG. 2, the squish flow S and the tumble flow T are ignited by the spark plug. Collide with each other in the vicinity of 12. In this engine 1, the ignition timing is set so that the ignition plug 12 ignites during the period when the air-fuel mixture is ejected from the squish area.

When the tumble flow T and the squish flow S collide with each other, the air-fuel mixture is dispersed as minute vortices (microturbulence) and the tumble flow T and the squish flow S are synthesized. The flow lowers to the piston top portion 7a side. Therefore, the micro-turbulence promotes the growth of the flame kernel after ignition, and the flame spreads to the piston top 7a side, so that the combustion range is rapidly expanded. In this embodiment, the fuel gas is supplied in layers from the nozzle 4 to the vicinity of the spark plug 12, so that even if the total supply amount of the fuel gas is significantly smaller than the stoichiometric air-fuel ratio, ignition is assured. .

Therefore, even though the lean combustion is performed in which the total supply amount of the fuel gas supplied into the cylinder is remarkably reduced as compared with the supply amount at the stoichiometric air-fuel ratio, rapid combustion is possible. Combustion can be improved and fuel consumption can be improved. Further, the collision of the tumble flow T and the squish flow S attenuates the kinetic energy of the mixed air flow, so the state of the mixed air after the collision does not change significantly even if the rotation speed or the load of the engine 1 changes. Therefore, the phenomenon of rapid combustion as described above similarly occurs over a wide operating range, and combustion can be improved over substantially the entire engine operating range.

Furthermore, the flow of the air-fuel mixture in the cylinder (flow downward in the recess 26 of the piston top 7a)
Since the ignition continues even after ignition, the unburned gas is continuously supplied to the initial combustion gas portion grown near the top portion 7a of the piston 7. For this reason, the initial combustion gas diffuses while being stirred by the unburned gas and is not held at a high temperature, so that it is possible to suppress the generation of Nox. It should be noted that even when the EGR amount is increased, the same operation as described above is performed, and it is possible to improve fuel efficiency and reduce Nox.

Furthermore, the collision of the tumble flow T and the squish flow S attenuates the kinetic energy of the mixed air flow, so that the electrodes 12a and 12b of the spark plug 12 are attenuated.
Since the air-fuel mixture does not flow at a high speed in the gap (see FIG. 2), ignition is stabilized and the ignition voltage does not have to be increased, so that the existing ignition device can be used.

Although an example of using a gas fuel is shown in this embodiment, the present invention is an engine 1 that uses gasoline as a fuel.
Can also be applied to. In this case, a configuration equivalent to that of the conventional engine 1 can be adopted, except that the tumble flow T and the squish flow S collide with each other. By using a gas fuel as the fuel, the fuel can be supplied in layers using the nozzles 4, and the fuel gas supplied by the primary fuel injection can be efficiently dispersed in the cylinder. The use of gas fuel is advantageous in improving combustion.

In this embodiment, the intake port 1
3 to the side opposite to the exhaust valve 16 in the cylinder to generate a so-called reverse tumble flow in the cylinder,
Space where squish flow S is generated (squish area)
Is formed on the side of the intake valve 15 which is relatively low in temperature, knocking is less likely to occur than when the squish area is formed on the side of the exhaust valve 16.

Further, the downstream end portion of the intake port 13 is provided with the inclined portion 23 which gradually extends toward the opposite side to the exhaust valve 16 toward the downstream side, whereby the intake air flows so that a reverse tumble flow is formed. Since the direction is regulated, the intake resistance is reduced and the number of parts can be reduced as compared with the case where a member for changing the flow direction of intake air is provided in the intake port 13.

(Second Embodiment) In order to generate a tumble flow, the guide member shown in FIGS. 10 to 15 can be attached to the intake port. 10 is a cross-sectional view of an engine provided with a guide member, FIG. 11 is an enlarged cross-sectional view of a main portion of FIG. 10, and FIG. 12 is XII-X in FIG.
II sectional view, FIG. 13 is a diagram showing the guide member, the same (a)
Is a cross-sectional view in the state where it is assembled to the intake port, the same figure (b)
Is a side view, and in (b), the breakage position in (a) is indicated by line AA. FIG. 13C shows (a)
A sectional view taken along the line C-C in the figure, (d) shows a free state before mounting, and (b) shows a state in which the diameter is reduced at the time of mounting. 14 is an exploded perspective view of the guide member shown in FIG. 13, FIG. 15 is a view showing another example of the guide member, FIG. 14 (a) is a plan view, FIG. 15 (b) is a side view, and FIG. 6C is a cross-sectional view taken along the line CC in FIG. 7A, and FIG. 8D is a plan view showing a state in which the diameter is reduced at the time of mounting. In these figures, FIG.
The same or equivalent members as those described with reference to FIG. 9 are designated by the same reference numerals, and detailed description thereof will be appropriately omitted.

The engine 1 according to this embodiment is shown in FIG.
As shown in FIG. 0, the intake port 13 has a guide member 4 which will be described later.
1 has the same configuration as the engine 1 shown in the first embodiment except that the engine 1 is provided. The guide member 4
As shown in FIGS. 13 and 14, 1 comprises a C-shaped fixing ring 42 and a shroud 43 welded to the ring 42.

The ring 42 is made of a spring material and is formed so that it can be expanded in diameter and engaged with a concave groove 44 (see FIG. 11) formed at the downstream end of the intake port 13 by its own elastic force. ing. Also, at both ends of this ring 42,
A hook 45 for hanging a tool (not shown) is integrally formed.

The shroud 43 includes a support plate 46 curved along the inner peripheral surface of the ring 42 in an arc shape in a plan view, and a fan-shaped shroud main body 47 integrally formed with the support plate 46. It is composed by.
The support plate 46 is formed with an opening 48 through which the hook 45 of the ring 42 is inserted.
One end of the ring 42 is welded to the ring 42 while being overlapped with the inner peripheral portion of the ring 42 with the hook 45 inserted therethrough. Support plate 46
The welding range of the ring 42 is indicated by the symbol W in FIG.

The shroud 43 is inclined so as to gradually extend downward (downstream of the intake air flow) from the support plate 46 toward the center of the ring 42, and is curved so as to form a part of a conical surface. . Further, the guide member 41 is provided for the intake valve 1 in which the lower end of the shroud 43 is closed.
It is arranged so as to face 5 with a clearance.

The guide member 41 thus formed is assembled to the intake port 13 before the intake valve 15 is assembled to the cylinder head 2. More specifically, first, as shown in FIG. 13 (d), the hook 45 of the ring 42 of the guide member 41 in the free state is pinched with a tool such as pliers (not shown) to resist the elastic force of the ring 42. The diameter is reduced {see FIG. 13 (e)}, and the guide member 41 is inserted into the intake port 13 from the combustion chamber side. Then, the hook 45 is released while the ring 42 is engaged with the groove 44 of the intake port 13. At this time, the guide member 41 is positioned so that the shroud 43 is located on the exhaust valve 16 side. By releasing the tool, the ring 42 expands in diameter by its own elastic force and is fixed to the intake port 13 (cylinder head 2).

The guide member 41 shown in FIGS. 10 to 14 is formed so that the hook 45 of the ring 42 is positioned above the shroud 43.
It can also be formed as shown in FIG. In the guide member 41 shown in FIG. 15, the support plate 46 of the shroud 43 is welded to the inner peripheral portion 42a of the ring 42 that faces the hook 45.

The ring 42 of this guide member 41 is shown in FIG.
The free state shown by the solid line in (a) is reduced in diameter as shown in FIG. After mounting, this ring 42 is in a reduced diameter state from the free state as shown by the chain double-dashed line in the same figure (a), and is fixed to the intake port 13 by its own elastic force.

By forming the guide member 41 in this way, the hook 45 can be visually recognized from below, and therefore, when the hook 45 is pinched with pliers or the like, the hook 4 can be grasped.
The position of 5 can be easily confirmed, and the assembling work becomes easy. The position where the guide member 41 is attached is shown in FIGS.
It is the same as the guide member 41 shown in FIG.

By providing the guide member 41 shown in FIGS. 10 to 15 in the intake port 13, the shroud 43 substantially extends the inclined portion 23 of the intake port 13 and hits the intake valve 15 so as to contact the intake outlet 21. It is possible to reduce the intake air flowing into the exhaust valve 16 side from the gap between and. As a result, the tumble flow T can be generated even more strongly.

Therefore, since the strength of the tumble flow T can be changed by the guide member 41, the tumble flow T is generated by the guide member 41 so that the tumble flow T has an optimum strength with respect to the generated squish flow S. This makes it possible to reliably generate microturbulence. Therefore, the combustion can be further improved.

(Third Embodiment) The guide member can be formed as shown in FIGS. 16 to 24. FIG.
17 is a sectional view of a part of the engine showing another example of the guide member, FIG. 17 is an enlarged sectional view of the guide member, and FIG. 18 is a view showing a portion near the combustion chamber of the engine as seen from the cylinder head side. FIG. 19 is a schematic view for explaining a tumble flow, FIG. 20 is a bottom view of a fuel gas supply nozzle,
21 is a sectional view taken along the line AA in FIG. 16, and FIG. 22 is FIG.
6 is a sectional view taken along line BB in FIG. 6, and FIG. 23 is C in FIG.
It is a -C line sectional view. FIG. 24 is an enlarged perspective view showing the guide member and the valve body of the intake valve.

In these figures, the same or equivalent members as those described with reference to FIGS. 1 to 15 are designated by the same reference numerals and detailed description thereof will be appropriately omitted. FIG.
24 to 24, the intake valve 15 is provided with a guide member 51. As shown in FIG. 24, the guide member 51 is made of a metal plate having a shape of a part of a cone, and is welded to the upper surface of the valve body 15b of the intake valve 15.

The shape of the guide member 51 will be described in more detail. As shown in FIG. 22, the guide member 51 is formed in a fan shape in plan view in which the width increases as it goes upward, and as shown in FIG. In a side view, the intake valve 15 is inclined so as to be unevenly distributed outward in the radial direction as it goes upward. As shown in FIGS. 17 and 18, the position where the guide member 51 is attached to the intake valve 15 is one side portion of the intake valve 15 that is close to the exhaust valve 16, and as shown in FIG. Inner surface 51
The center of the arc of a is positioned so as to substantially coincide with the axis of the intake valve 15.

The height of the guide member 51 is as shown in FIG.
As shown in FIGS. 6 and 17, when the intake valve 15 is opened, the upper end portion faces the upstream side of the intake outlet 21 of the intake port 13,
As shown by the chain double-dashed line in FIG. 17, even if the intake valve 15 is closed, the upper end portion is set so as not to contact the inner wall surface of the intake port 13. In this embodiment, in order to prevent the intake valve 15 from rotating around the valve stem 15a and changing the position of the guide member 51 with respect to the intake port 13, as shown in FIG. The valve stem 15a is formed to have a quadrangular cross section, and the quadrangular cross section is slidably engaged with the valve stem guide 52 on the cylinder head 2 side.

As shown in FIG. 16, the intake port 13 of the cylinder head 2 according to this embodiment has a cylinder head 2 which is often used in a general engine 1.
It is formed so as to extend obliquely from one side portion 2a toward the combustion chamber 32. The intake port 13 is formed so that the intake passage 5 is branched into branch passages 5a and 5b for each intake valve 15 on the way.

When the intake port 13 is formed in this way,
When the intake valve 15 is opened, the intake air is inertial and the combustion chamber 2
A large amount of the intake air hits the guide member 51, and the flow direction can be changed according to this embodiment. That is, since the intake air flows toward the direction opposite to the exhaust valve 16 by hitting the guide member 51, the engine 1 also has a reverse tumble in the cylinder as in the first and second embodiments. A flow occurs.

Since the intake port 13 is obliquely extended from the side portion of the cylinder head 2 as described above, the nozzle 4 for supplying the fuel gas is provided with the intake valve 15 from the one side portion 2a of the cylinder head 2. It is formed so as to extend to the vicinity. As shown in FIGS. 20 and 21, the nozzle 4 includes pipes 4a, 4a for each intake valve 15 and a pipe holder 4 to which the upstream ends of these pipes 4a are connected.
and b. The pipe 4a has a first
Similarly to the case of adopting the second embodiment, the downstream end portion has the intake ports 13 adjacent to each other in the intake port 13.
16 and is bent so that the opening at the tip is directed toward the downstream side in the intake air flow direction, and the upstream side end portion is inside the intake port 13 and the intake port upper wall 13a (FIG. 16).
(See) and extend to the upstream side.

As shown in FIG. 20, the nozzle holder 4b has a fuel passage 4c communicating with the pipe 4a for each pipe. As shown in FIG. 16, the nozzle holder 4b is fixed to the intake port upper wall 13a. It is fixed by bolts 53. In the cylinder head 2 according to this embodiment, a through hole 54 for inserting a tool is formed in the lower wall 13b of the intake port so that the fixing bolt 53 can be easily attached and detached with a tool (not shown). In FIG. 16, the reference numeral 55 provided at the opening end of the through hole 54 indicates the through hole 5
4 is a plug member for closing 4.

The fuel passage 4c of the pipe holder 4b is
The fuel gas is injected from the fuel gas injector 3 mounted on the cylinder head 2 and opened at the upstream end of the pipe holder 4b. Even if the guide member 51 and the cylinder head 2 are configured as shown in this embodiment, the same effect as when the first and second embodiments are adopted can be obtained.

(Fourth Embodiment) When the intake port is formed so as to extend obliquely to the cylinder head, the fuel gas supply nozzle can be formed as shown in FIGS. 25 to 27. FIG. 25 is a cross-sectional view showing another example of the fuel gas supply nozzle, FIG. 26 is a plan view showing a configuration of a portion near the combustion chamber of the engine as seen from the cylinder head side, and FIG. 27 is A- in FIG. It is an A line sectional view.
In these figures, the same or equivalent members as those described with reference to FIGS. 1 to 24 are designated by the same reference numerals, and detailed description thereof will be omitted as appropriate.

The fuel gas supply nozzle 4 shown in FIGS. 25 to 27 is composed of a pipe provided for each intake valve 15, and is fitted into the fuel gas supply through hole 61 of the cylinder head 2 from the intake port 13 side to intake air. It is arranged in the vicinity of the adjacent intake ports 13 in the port 13. Further, as shown in FIG. 25, these nozzles 4 are bent so that the opening at the tip is directed toward the downstream side in the intake air flowing direction.

The fuel gas supply through hole 61 is a first gas hole 62 extending linearly obliquely along the intake port 13 from above the inlet of the intake port 13 in the one side portion 2a of the cylinder head 2, The second gas holes 63 (see FIG. 27) extend from the downstream end of the first gas hole 62 to the intake port 13 of each intake valve 15. The nozzle 4 is attached to the second gas hole 63. Further, as shown in FIG. 26, the upstream end of the first gas hole 62 is opened inside a hole 29 into which the fuel gas supply injector 3 (not shown) is mounted. By forming the nozzle 4 in this way, the fuel gas injected from the nozzle 4 into the intake port 13 in the intake stroke is connected to the intake valve 15 and the intake outlet 21 as shown by a black arrow G in FIG. Through the gap between them and flows obliquely downward in the direction opposite to the exhaust valve 16 in the cylinder.

[0061]

As described above, according to the present invention, when the tumble flow and the squish flow collide with each other, the air-fuel mixture is dispersed as microturbulence, and the tumble flow and the squish flow are synthesized. The gas flow is to move to the top side of the piston. Therefore, the micro-turbulence promotes the growth of the flame kernel, and the flame spreads to the top side of the piston, so that the combustion is rapidly performed.

On the other hand, the collision of the tumble flow and the squish flow attenuates the kinetic energy of the mixed air flow. Therefore, the state of the mixed air after the collision does not change significantly even if the engine speed or load changes. Absent. Therefore, the phenomenon of rapid combustion as described above similarly occurs over a wide operating range.

Therefore, the combustion is similarly performed over a wide operating range and the combustion can be improved, so that the fuel consumption can be further improved. Further, since the flow of the air-fuel mixture in the cylinder continues after ignition, unburned gas is continuously supplied to the initial combustion gas portion grown near the top of the piston. Therefore, the initial combustion gas is
It becomes diffused while being stirred by unburned gas, and is not kept at a high temperature. As a result, even though the air-fuel mixture is made to flow in the cylinder to achieve rapid combustion,
It is possible to reduce the concentration of Nox in the exhaust gas.

According to the second aspect of the invention, the so-called reverse tumble flow is formed, and the space (squish area) for generating the squish flow is formed on the intake valve side where the temperature is relatively low. Therefore, knocking is less likely to occur as compared with the case where the squish area is formed on the exhaust valve side, and thus the limit of lean combustion can be further improved.

According to the third aspect of the invention, since the direction of intake air flow is restricted by the shape of the intake port,
Compared to the case where a member for changing the flow direction of intake air is provided in the intake port, the intake resistance becomes smaller, and
Since the number of parts is reduced, the number of assembling steps can be reduced. Therefore, it is possible to realize both output improvement and cost reduction by reducing the number of assembly steps.

According to the fourth aspect of the invention, the strength of the tumble flow can be changed by the guide member, so that the tumble flow has an optimum strength with respect to the generated squish flow.
By generating the tumble flow with the guide member, the microturbulence can be reliably formed, and the combustion can be further improved.

[Brief description of drawings]

1 is a cross-sectional view of an engine according to the present invention.

FIG. 2 is a cross-sectional view showing an enlarged part of the engine.

FIG. 3 is a plan view of a piston.

FIG. 4 is a plan view showing a configuration of a portion of the engine in the vicinity of a combustion chamber as viewed from the cylinder head side.

FIG. 5 is a bottom view showing the combustion chamber wall of the cylinder head.

FIG. 6 is a vertical cross-sectional view of a cylinder and a piston.

7 is a sectional view taken along line VII-VII in FIG.

FIG. 8 is a time chart showing opening / closing timings of intake / exhaust valves and fuel injection timings.

FIG. 9 is a sectional view showing another example of a piston.

FIG. 10 is a cross-sectional view of an engine provided with a guide member.

FIG. 11 is a cross-sectional view showing an enlarged main part in FIG.

12 is a sectional view taken along line XII-XII in FIG.

FIG. 13 is a diagram showing a guide member.

14 is an exploded perspective view of the guide member shown in FIG.

FIG. 15 is a diagram showing another example of the guide member.

FIG. 16 is a partial cross-sectional view of the engine showing another example of the guide member.

FIG. 17 is an enlarged sectional view showing a guide member.

FIG. 18 is a plan view showing the configuration of a portion of the engine in the vicinity of the combustion chamber as viewed from the cylinder head side.

FIG. 19 is a schematic diagram for explaining a tumble flow.

FIG. 20 is a bottom view of the fuel gas supply nozzle.

21 is a cross-sectional view taken along the line AA in FIG.

22 is a sectional view taken along line BB in FIG.

23 is a cross-sectional view taken along the line CC in FIG.

FIG. 24 is an enlarged perspective view showing a guide member and a valve body of an intake valve.

FIG. 25 is a cross-sectional view showing another example of the fuel gas supply nozzle.

FIG. 26 is a plan view showing the configuration of a portion of the engine in the vicinity of the combustion chamber as viewed from the cylinder head side.

27 is a cross-sectional view taken along the line AA in FIG.

[Explanation of symbols]

1 ... Engine, 2 ... Cylinder head, 5 ... Intake passage, 7
... piston, 7a ... top, 13 ... intake port, 15 ... intake valve, 16 ... exhaust valve, 23 ... inclined part, 25 ... slope, 26
... recesses, 31 ... combustion chamber wall, 51 ... guide member, T ... tumble flow, S ... squish flow.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02B 23/08 F02B 23/08 Z F02F 1/42 F02F 1/42 F (72) Inventor Naoki Onda Shizuoka Prefecture Yamaha Motor Co., Ltd., F-Term, 2500 Shinkai, Iwata City (Reference) 3G023 AA01 AA05 AB03 AC05 AD02 AD05 AD07 AD08 AD09 AD12 AG01 3G024 AA09 BA00 DA01 DA06 DA08 FA00

Claims (4)

[Claims] 1. A compression stroke comprising: a tumble flow generating means for generating a tumble flow composed of an air-fuel mixture in a cylinder; and a squish flow generating means for generating a squish flow flowing in a direction opposite to the tumble flow in the cylinder. The engine configured such that the tumble flow and the squish flow are generated so as to face each other at the end of. 2. The engine according to claim 1, wherein the tumble flow generating means is configured so that the air-fuel mixture is directed from the intake port in the direction opposite to the exhaust valve and guided into the cylinder, and the squish flow generating means is the piston top portion. An engine including a slope facing the intake valve, a recess adjacent to the slope, and a combustion chamber wall on the cylinder head side. 3. The engine according to claim 2, wherein the tumble flow generating means is formed at an end portion of a downstream side of the intake port by an inclined portion that gradually extends toward the side opposite to the exhaust valve toward the downstream side. 4. The engine according to claim 2, wherein the tumble flow generating means is formed by providing a guide member for changing a flow direction of intake air in the intake passage.