WO2003062614A1

WO2003062614A1 - Engine

Info

Publication number: WO2003062614A1
Application number: PCT/JP2003/000390
Authority: WO
Inventors: Hiromitsu Matsumoto; Noboru Sakamoto; Naoki Onda
Original assignee: Yamaha Hatsudoki Kabushiki Kaisha
Priority date: 2002-01-23
Filing date: 2003-01-17
Publication date: 2003-07-31
Also published as: JP2003214167A

Abstract

An engine has a tumble flow producing means (air inlet port (13)) for producing a tumble flow (T) consisting of mixed gas in a cylinder. It has a squish flow producing means (the slope surface (25) of a piston top (7a), a recess (26), and the combustion chamber wall (31) of a cylinder head (2)) for producing a squish flow (S) moving opposite to the direction of the tumble flow (T) in the cylinder. It is arranged that in the terminal period of compression stroke, the tumble flow (T) and squish flow (S) are produced in opposed relationship to each other.

Description

Technical description Technical field

TECHNICAL FIELD The present invention relates to an engine that improves combustion by generating a tumble flow and a squish flow in a cylinder. Background art

In recent years, engines have been improved in fuel efficiency by reducing the air-fuel ratio to a value lower than the stoichiometric air-fuel ratio and burning them (lean combustion) or by recirculating part of the exhaust gas into the cylinder (EGR). I'm trying. In a so-called premixed engine, in which fuel is mixed with air and sucked into the cylinder in the form of a mixture, the combustion is improved by compressing the mixture while flowing it, as described above. The limits of lean burn and EGR are increased.

In order to compress the air-fuel mixture while flowing it with a conventional engine, a tumble flow, a swirl, and a squish flow of the air-fuel mixture were generated in the cylinder.

However, in the conventional engine that flows and compresses the air-fuel mixture as described above, the flow direction of the air-fuel mixture is almost one-way, and the flow velocity of the air-fuel mixture in the cylinder corresponds to the rotational speed and load of the engine. Therefore, there is a problem that the combustion can be improved only in a narrow rotation range. This is because, for example, if the engine is designed so that the flow rate of the air-fuel mixture in the cylinder is optimal when the engine operating range is in the low rotational speed / low load range, the This is because the flow speed becomes excessive.

As described above, if the flow rate of the air-fuel mixture becomes excessive, Many problems occur, such as the flame nucleus that spreads as the air mixture is hindered by the air-fuel mixture, and the air-fuel mixture is strongly blown to the electrodes of the ignition plug, making ignition prone to instability and raising the voltage. However, if the air-fuel mixture flow rate is set to be optimal when the engine operating range is at high rotational speed and high load, combustion becomes unstable at low rotational speed and low load. It becomes easy to become.

Further, in the above-described conventional engine, there is also a problem that the concentration of NOx in exhaust gas becomes high. This is thought to be due to the mixture flowing in almost one direction. More specifically, the initial combustion gas generated in the vicinity of the spark plug rapidly spreads mainly in the direction in which the air-fuel mixture flows, and since the initial combustion gas is maintained at a high temperature, the concentration of N 0 X decreases. It is expected to be higher. This phenomenon becomes remarkable when there is sufficient surplus oxygen in lean burn.

The present invention has been made in order to solve such problems, and in an engine that allows a mixture 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 N 0 X. DISCLOSURE OF THE INVENTION-To attain this object, an engine according to the present invention comprises: a tumble flow generating means for generating a tumble flow composed of an air-fuel mixture in a cylinder; and a squish flowing in a cylinder in a direction opposite to the evening flow. A squish flow generating means for generating a flow, wherein 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, when the tumble flow and the squish flow collide with each other, the air-fuel mixture is dispersed as minute vortices (microturbulence), and the gas flow formed by combining the tumble flow and the squish flow The piston moves to the top of the piston. Therefore, when the growth of the flame nucleus is promoted by the microturbulence, In both cases, the flame spreads to the top side of the biston, and combustion occurs rapidly. On the other hand, since the kinetic energy of the air-fuel mixture is reduced by the collision of the tumble flow and the squish flow, the state of the air-fuel mixture after the collision does not change significantly even if the engine speed or load changes. Therefore, the above-mentioned phenomenon in which combustion is performed rapidly occurs similarly over a wide operating range.

In addition, since the flow of the air-fuel mixture in the cylinder continues even after ignition, the unburned gas is continuously supplied to the initial combustion gas portion grown near the top of the piston. For this reason, the initial combustion gas is diffused while being stirred by the unburned gas, and is not maintained at a high temperature. '

The engine according to the second aspect of the invention is the engine according to the first aspect of the invention, wherein the evening gas generation means directs the air-fuel mixture from the intake boat in a direction opposite to the exhaust valve. The squish flow generating means is constituted by a slope facing the intake valve at the top of the biston, a concave portion adjacent to the slope, and a combustion chamber wall on the cylinder head side.

According to the present invention, since the intake air flows from the intake port to the side opposite to the exhaust valve in the cylinder, the cylinder head is inserted into the cylinder on the intake valve side from the cylinder axis when viewed from the axial direction of the force axis. A so-called reverse tumble flow is generated, which consists of a swirling flow that moves away from the cylinder and approaches the cylinder head on the exhaust valve side. 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 third aspect of the invention is the engine according to the second aspect of the invention, wherein the tumble flow generating means gradually exhausts the air from the downstream end of the intake port toward the downstream side. It is formed by a slope extending to the opposite side of the valve.

According to the present invention, since the direction in which the intake air flows is regulated by the shape of the intake boat, compared with a case where a member for changing the direction in which the intake air flows is provided in the intake port. Furthermore, the intake resistance is reduced and the number of parts can be reduced.

The engine according to the invention described in claim 4 is the engine according to the invention described in claim 2, wherein the tumble flow generating means is formed by providing a guide member for changing a flow direction of intake air in an intake passage. It is.

According to the present invention, the strength of the tumble flow can be changed by the guide member.

BRIEF DESCRIPTION OF THE FIGURES

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

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

FIG. 3 is a plan view of the piston.

FIG. 4 is a plan view showing a configuration in a state where a portion near the combustion chamber of the engine is 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 longitudinal sectional view of the cylinder and the piston.

FIG. 7 is a sectional view taken along the 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. FIG. 9 is a sectional view showing another example of the piston.

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

FIG. 11 is a cross-sectional view showing a main part in FIG. 10 in an enlarged manner.

FIG. 12 is a sectional view taken along the line XI I -XI] in FIG.

FIG. 13 is a view showing a guide member.

FIG. 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 cross-sectional view of a part of the engine showing another example of the guide member. FIG. 17 is an enlarged sectional view showing the guide member.

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

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

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

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

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

FIG. 23 is a cross-sectional view taken along 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 a configuration in a state where a portion near the combustion chamber of the engine is viewed from the cylinder head side.

FIG. 27 is a sectional view taken along line AA in FIG. BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment)

Hereinafter, an embodiment of the engine according to the present invention will be described in detail with reference to FIGS.

FIG. 1 is a cross-sectional view of the engine according to the present invention, and FIG. 2 is a cross-sectional view showing a part of the engine in an enlarged manner. In FIG. 1, the piston is positioned at the top dead center in the compression stroke. Fig. 3 is a plan view of the piston, Fig. 4 is a plan view showing the configuration near the combustion chamber of the engine viewed from the cylinder head side, and Fig. 5 is a bottom view showing the combustion chamber wall of the cylinder head. It is. Fig. 6 is a vertical sectional view of the cylinder and biston, Fig. 7 is a sectional view taken along the line VII-VII in Fig. 1, Fig. 8 is a time chart showing the opening and closing timing of the intake and exhaust valves and the fuel injection timing, and Fig. 9 FIG. 4 is a sectional view showing another example of the piston.

In these figures, reference numeral 1 denotes an engine according to this embodiment. is there. The engine 1 is operated using a gas fuel such as LPG or CNG (compressed natural gas). The gas fuel is supplied from a fuel gas supply injector 3 of a cylinder head 2 to a nozzle 4 described later. Injection into the intake passage 5 is carried out. Although the number of cylinders of the engine 1 is shown in FIG. 1 for only one cylinder for convenience of explanation, it can be used for an engine having a plurality of cylinders. In FIG. 1, reference numeral 6 denotes a cylinder body, 7 denotes a piston, and 8 denotes a conrode. As is well known, the cylinder head 2 is provided with a DOHC type valve gear 11 and a spark plug 12, and has an intake port 13 and an exhaust port forming the intake passage 5. 14 are provided.

The valve gear 11 has two intake valves 15 and two exhaust valves 16 for each cylinder, and the intake and exhaust valves 15 and 16 are supplied via a valve lifter 17 respectively. It is driven by a camshaft 18 and an exhaust camshaft 19.

The ignition plug 12 is disposed at the center of the cylinder surrounded by the four intake / exhaust valves 15 and 16. The screw holes into which the ignition plugs 12 are screwed are indicated by reference numeral 20 in FIGS. In FIG. 5, reference numeral 21 denotes an intake outlet of an intake port 13 opened and closed by an intake valve 15, and 2 denotes an exhaust inlet of an exhaust port 14 opened and closed by an exhaust valve 16.

In this embodiment, the intake port 13 is provided for each intake valve 15 (see FIG. 4), and as shown in FIG. 1, the cylinder head 2 is moved vertically (in the direction along the cylinder axis C). It is formed so as to penetrate through. Although not shown, a throttle valve is connected to the upstream side of the intake port 13 via an intake passage of a head cover and an intake pipe attached to the head cover.

As shown in FIG. 1, the intake port 13 according to this embodiment is inclined so as to gradually approach the intake valve 15 from the opening at the upper end of the cylinder head 2 toward the downstream side. At the downstream end, the exhaust valve 16 gradually increases toward the downstream side. Is provided with an inclined portion 23 extending to the opposite side.

By forming the intake port 13 in this way, the intake air that has passed through the intake boat 13 flows in the cylinder from the intake outlet 21 in the direction opposite to the exhaust valve 16 due to the inertia of the intake flow. It is led to.

On the other hand, the exhaust port 14 is formed so that the exhaust passage for each exhaust valve 16 merges in the cylinder head 2 and extends to the exhaust outlet 24 on one side of the cylinder head 2.

As shown in FIGS. 1 to 3 and FIG. 6, the biston 7 has an inclined surface 25 and a concave portion 26 at the top 7a. As shown in FIGS. 2 and 4, the slope 25 is formed so as to extend in a direction in which the intake valves 15 are arranged side by side at a portion of the top 7a of the piston 7 which faces the intake valves 15; The valve body 15 of the intake valve 15 is inclined so as to be parallel to the end surface 15c (the surface forming a part of the combustion chamber wall) of the valve element 15 1). As shown in FIGS. 2 and 6, the concave portion 26 is formed so that a D-shaped portion in plan view adjacent to the slope 25 at the top 7a of the biston 7 is hemispherically recessed downward. It is formed. As shown in FIG. 9, the piston 7 should be formed so that a portion adjacent to the slope 25 of the top portion 7a is flat and the flat portion 7b is substantially a concave portion 26. Can also. The use of the piston 7 makes it possible to increase the compression ratio as compared with the case of using the piston 7 shown in FIG. 1. The fuel gas supply injector 3 is provided for each cylinder, and the cylinder head 2 And is attached to a portion corresponding to a space between the intake ports 13. The injector 3 is supplied with fuel gas from a fuel tank (not shown) under pressure. At a predetermined fuel injection timing, fuel flows from a fuel injection port 27 at the tip (see FIG. 7) to a fuel passage 28 of the cylinder head 2. Inject gas.

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. When the fuel injection (secondary fuel injection) is performed, the injection timing and injection period are set in accordance with the operating conditions.

The period during which the injector 3 injects the fuel is set so as to be longer at the time of the primary fuel injection and at the time of the secondary fuel injection. 'As the fuel injection amount, for example, approximately 50 to 70% of the fuel gas supplied in one cycle is injected at the time of the primary fuel injection, and the remainder is injected at the time of the secondary fuel injection.

As shown in FIG. 7, the fuel passage 28 through which the injector 3 injects fuel extends from the hole 29 for mounting the injector to each intake port 13 side, and is a downstream end of the intake port 13. And a nozzle 4 made of a pipe fitted and fixed in each of the through holes 30 from the intake outlet 21 side of the intake port 13. It is configured. As shown in FIG. 4, each nozzle 4 is disposed in the vicinity of an adjacent intake port 13 in the intake port 13 and, as shown in FIG. The opening is bent so as to be directed. The downstream side of the intake air here means the downstream side of the intake air whose flow direction is regulated by the inclined portion 23 of the intake port 13, and the exhaust air is exhausted from the intake outlet 21 of the intake port 13. The direction opposite to the valve 16 and pointing obliquely downward.

By forming the nozzle 4 in this manner, the fuel gas injected into the intake port 13 from the nozzle 4 during the intake stroke is supplied to the intake valve 1 as shown by a black solid arrow G in FIG. The air flows obliquely downward in a direction away from the exhaust valve 16 in the cylinder through a gap between the air outlet 5 and the air outlet 21. '

In the engine 1 configured as described above, as shown in FIG. 8, when the piston 7 is rising in the exhaust stroke (when the intake valve 15 is closed), the first fuel injection in the injection 3 is performed. Is performed. At this time, the fuel gas stays in the intake port 13 because the intake valve 15 is closed. Then, at the end of the exhaust stroke, just before Viston に reaches the top dead center, the intake valve 15 opens, and Viston 7 crosses the top dead center. In the descending stroke after the intake, the fuel gas remaining in the intake port 13 and the fresh air are sucked into the cylinder as described above.

The fuel gas flows into the cylinder from substantially the entire gap between the intake valve 15 and the intake outlet 21, but is sucked obliquely downward from the intake boat 13 into the cylinder. Most of it is pushed in the same direction as the intake air as it is pushed. The fuel gas and fresh air flow to the lower part of the cylinder along the inner peripheral surface of the cylinder.

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

Then, during the intake stroke, the second fuel injection by the injector 3 is performed.

(See Figure 8). At this time, the fuel gas is injected into the cylinder from 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 turns inside the cylinder so as to ride on the tumble flow T as shown in FIG. Since the nozzles 4 are provided near portions of the two intake ports 13 adjacent to each other, the fuel injected from the nozzles 4 flows in a laminar manner near the spark plugs 12. That is, at the end of the compression stroke, a relatively rich air-fuel mixture is supplied in a stratified manner near the periphery of the spark plug 12.

After the second fuel injection is performed and the intake valve 15 is closed, the piston 7 shifts to the compression top dead center, so that the tumble flow T in the cylinder becomes as shown in FIG. The recess 26 at the top of the piston 7a and the combustion chamber wall 31 on the cylinder head 2 side The diameter is reduced while turning in the space (combustion chamber 3 2) formed between them. On the other hand, at this time, the air-fuel mixture is pushed out from the gap (squish area) between the slope 25 on the top of the piston 7a and the combustion chamber wall 31 on the side of the cylinder head 2, and a squish flow is generated. I will. This squish flow is indicated by arrow S in FIG.

In FIG. 2, the squish flow S proceeds in the combustion chamber 32 toward the exhaust valve 16 along the combustion chamber wall on the cylinder head 2 side in FIG. Collide with each other near the ignition plug 12. In the engine 1, the ignition timing is set so that the ignition by the ignition plug 12 is performed 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 gas flow formed by combining the evening flow T and the squish flow S Then, go down to the top of Biston ビ a side. For this reason, the growth of the flame nucleus after ignition is promoted by the microturbulence, and the flame spreads to the piston top 7a side, so that the combustion range is rapidly expanded. In this embodiment, since the fuel gas is supplied from the nozzle in the form of a layer in the vicinity of the spark plug 12, even if the total supply amount of the fuel gas is significantly smaller than the supply amount at the stoichiometric air-fuel ratio, the ignition is reliably performed. You.

Therefore, despite the fact that lean combustion is performed in which the total supply amount of fuel gas supplied into the cylinder is significantly reduced as compared with the supply amount at the operating air-fuel ratio, rapid combustion is possible and combustion is possible. Improvements can be made and fuel efficiency can be improved. Further, the kinetic energy of the air-fuel mixture is attenuated by the collision of the tumble flow T and the squish flow S, so that the state of the air-fuel mixture after the collision does not change significantly even if the rotation speed or load of the engine 1 changes. For this reason, the above-described phenomenon in which combustion is rapidly performed 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 (downward in the recess 26 at the top 7a of the piston) The flow flowing toward the piston continues after the ignition, so that the unburned gas is continuously supplied to the portion of the initial combustion gas that has grown near the top 7a of the piston 7. For this reason, the initial combustion gas diffuses while being stirred by the unburned gas, and is not kept at a high temperature, so that generation of Nox can be suppressed. In addition, when the EGR amount is increased, the same operation as described above is performed, and the fuel efficiency can be improved and the NOx can be reduced.

Furthermore, the kinetic energy of the mixture flow is attenuated by the collision of the tumble flow T and the squish flow S, so that the gap between the electrodes 12a and 12b of the ignition plug 12 (see Fig. 2) is reduced. Since the air-fuel mixture does not flow at high speed, ignition is stable, and the ignition voltage does not need to be high, so that the existing ignition device can be used. In this embodiment, an example using gas fuel has been described, but the present invention can be applied to an engine 1 using gasoline as fuel. In this case, the same configuration as that of the conventional engine 1 can be adopted except that the tumble flow stub and the squish flow S collide with each other. By using gas fuel as the fuel, the fuel can be supplied in a layered manner using the nozzle 4 and the fuel gas supplied by the primary fuel injection can be efficiently dispersed in the cylinder, so that the liquid fuel It is more advantageous to use gaseous fuel to improve combustion.

In this embodiment, a space (a squish area) in which intake air flows from the intake boat 13 to the opposite side of the exhaust valve 16 in the cylinder to generate a so-called reverse tumble flow in the cylinder to generate a squish flow S ) Is formed on the relatively low temperature intake valve 15 side, so that knocking is less likely to occur than when the squish area is formed on the exhaust valve 16 side.

The downstream end of the intake port 13 is provided with a sloping portion 23 that gradually extends toward the opposite side from the exhaust valve 16 toward the downstream side, so that a reverse tumble flow is formed. Because it regulates the direction of air flow, In comparison with a case where members for providing the air pressure are provided in the air intake port 13, the air intake resistance is reduced and the number of parts can be reduced.

(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.

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 part of FIG. 10, FIG. 12 is a cross-sectional view taken along line XI I-XI I in FIG. 13 is a view showing the in-vehicle member, FIG. (A) is a cross-sectional view in a state of being assembled to the intake port, FIG. (B) is a side view, and (b) is (a) The fracture position in the figure is indicated by the line A-A. Fig. 13 (c) is a cross-sectional view taken along the line CC in Fig. (A), Fig. 13 (d) shows a free state before mounting, and Fig. 13 (b) shows a state where the diameter is reduced at the time of mounting. FIG. 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. 14 (b) is a side view, FIG. 3C is a cross-sectional view taken along the line C-C in FIG. 3A, and FIG. In these drawings, the same or equivalent members as those described with reference to FIGS. 1 to 9 are denoted by the same reference numerals, and detailed description will be appropriately omitted.

The engine 1 according to this embodiment is the same as the engine 1 shown in the first embodiment except that a guide member 41 described later is provided in an intake port 13 as shown in FIG. The configuration is adopted.

As shown in FIGS. 13 and 14, the guide member 41 includes a C-shaped fixing ring 42 and a shroud 43 welded to the ring 42. 2 is made of a spring material, and is formed so that it can be engaged with a concave groove 44 (see FIG. 11) formed at a downstream end of the intake port 13 by its own elastic force. . A hook 45 for attaching a tool (not shown) is formed integrally with the rain end of the ring 42. The shroud 43 includes a support plate 46 curved in an arc shape in plan view along the inner peripheral surface of the ring 42, and a fan-shaped shroud body 4 formed integrally with the support plate 46 in plan view. It is composed of 7 and. The support plate 46 is formed with an opening 48 through which the hook 45 of the ring 42 is inserted. When the hook 45 is passed through the opening 48, the inside of the ring 42 is formed. One end is welded to the ring 42 over the periphery. The welding area between the support plate 46 and the ring 42 is indicated by the symbol W in Fig. 13 (a).

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 part of a conical surface. are doing.

The guide member 41 is disposed such that the lower end of the shroud 43 faces the intake valve 15 in a closed state with a clearance.

The guide member 41 thus formed is attached to the intake port 13 before the intake valve 15 is attached to the cylinder head 2. More specifically, first, as shown in FIG. 13 (d), the hooks 45 of the ring 42 of the guide member 41 in the free state are sandwiched between tools such as pliers (not shown) to spring the ring 42. The guide member 41 is inserted into the intake port 13 from the combustion chamber side by reducing the diameter by staking the force {see FIG. 13 (e)}. Then, the hook 45 is released while the ring 42 is engaged with the concave 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. When the tool is released, the ring 42 expands with its own elasticity and is fixed to the intake port 13 (cylinder head 1).

The guide member 41 shown in FIGS. 10 to 14 is formed so that the hook 45 of the ring 42 is positioned on the shroud 43, but the guide member 41 is shown in FIG. It can also be formed as follows.

A guide member 41 shown in FIG. 15 has a support plate 46 of a shroud 43 welded to an inner peripheral portion 42 a of the ring 42 facing the hook 45. The ring 42 of the guide member 41 is attached to the intake port 13 with a reduced diameter as shown in FIG. 15 (d) from the free state shown by the solid line in FIG. 15 (a). After mounting, the ring 42 is reduced in diameter from the free state as shown by the two-dot chain line in FIG. 7A, and is fixed to the intake port 13 by its own elastic force.

By forming the guide member 41 in this manner, the hook 45 can be visually recognized from below, so that the position of the hook 45 can be easily confirmed when the hook 45 is sandwiched by pliers or the like. The assembly work becomes easy. The mounting position of the guide member 41 is the same as the guide member 41 shown in FIGS.

By providing the guide member 41 shown in FIGS. 10 to 15 at the intake port 13, the inclined portion 23 of the intake port 13 is substantially extended by the shroud 43, The intake air flowing into the exhaust valve 16 from the gap between the intake valve 21 and the intake outlet 21 can be reduced. As a result, the tumble flow T can be generated 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 strength becomes optimum with respect to the generated squish flow S. Therefore, it is possible to surely generate a microturbulence. Therefore, the combustion can be further improved.

(Third embodiment)

The guide member can be formed as shown in FIGS.

Fig. 16 is a cross-sectional view of a part of the engine showing another example of the guide member. Fig. 17 is a cross-sectional view showing the guide member on an enlarged scale. Fig. 18 is a cylinder head showing a portion near the combustion chamber of the engine. FIG. 19 is a schematic view for explaining a tumble flow, FIG. 19 is a bottom view of a fuel gas supply nozzle, and FIG. 21 is A—A in FIG. 16. 22 is a sectional view taken along the line BB in FIG. 16, and FIG. 23 is a sectional view taken along the line CC in FIG. FIG. 24 is an enlarged perspective view showing the guide member and the valve body of the intake valve. You.

In these drawings, members that are the same as or similar to those described with reference to FIGS. 1 to 15 are denoted by the same reference numerals, and detailed description is omitted as appropriate.

The engine 1 shown in FIGS. 16 to 24 has a guide member 51 provided on an intake valve 15. As shown in FIG. 24, the guide member 51 is formed of a metal plate (formed of a part of a cone) and is welded to the upper surface of the valve element 15 b 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 a plan view in which the width increases upward and as shown in FIG. 17. In addition, the intake valve 15 is inclined so as to be unevenly distributed radially outward of the intake valve 15 as it goes upward in a side view. The position where the guide member 51 is attached to the intake valve 15 is located on one side of the intake valve 15 near the exhaust valve 16 as shown in FIG. 17 and FIG. As shown in the figure, the center of the arc of the inner surface 51 a of the guide member 51 is positioned so as to substantially coincide with the axis of the intake valve 15.

As shown in FIGS. 16 and 17, the height of the guide member 51 is such that when the intake valve 15 is opened, the upper end faces upstream from the intake outlet 21 of the intake port 13, As shown by the two-dot chain line in FIG. 17, even when the intake valve 15 is closed, the upper end 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, FIG. As shown in FIG. 23, the valve stem 15a is formed in a rectangular cross section, and the rectangular cross section is slidably engaged with the valve stem guide 52 on the cylinder head 2 side. .

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

When the intake port 13 is formed in this manner, a large amount of intake air flows into the central portion of the combustion chamber 23 due to inertia when the intake valve 15 is opened. Most of the contact with the guide member 51 changes the flowing direction. That is, since the intake air flows in the opposite direction to the exhaust valve 16 by hitting the guide member 51, the engine 1 also has the same structure as the first and second embodiments, A reverse tumbling flow occurs in the cylinder.

As described above, since the intake port 13 extends obliquely from the side of the cylinder head 2 as described above, the nozzle 4 for supplying the fuel gas is supplied from one side 1a of the cylinder head 2 through the intake port. It is formed so as to extend to the vicinity of the valve 15. As shown in FIGS. 20 and 21, the nozzle 4 has pipes 4 a, 4 a for each intake valve 15, and a pipe holder 4 b connected to the upstream end of each pipe 4 a. It is composed of As in the case of the first and second embodiments, the pipe 4a has a downstream end disposed in the vicinity of the adjacent intake port 13 in the intake port 13 and flows the intake air. The downstream end in the direction is bent so that the opening at the tip is directed, and the upstream end extends in the intake port 13 to the upstream side along the intake port upper wall 13a (see Fig. 16). Let me.

In the nozzle holder 4b, as shown in FIG. 20, a fuel passage 4c communicating with the pipe 4a is formed in each pipe, and as shown in FIG. It is fixed to 3a by fixing bolts 53. The cylinder head 2 according to this embodiment has a through hole 5 4 for tool passage in the lower wall 13 b of the intake port so that the fixing bolt 53 can be easily attached and detached by a tool (not shown). Are drilled. In FIG. 16, the reference numeral 55 provided at the open end of the through hole 54 is a plug member for closing the through hole 54.

The fuel passage 4c of the pipe holder 4b opens at the upstream end of the pipe holder 4b. The fuel gas is injected from the fuel gas injector 3 mounted on the cylinder head 2.

Even when the guide member 51 and the cylinder head 2 are configured as shown in this embodiment, the same effects as those in the first and second embodiments can be obtained.

(Fourth embodiment)

When the intake port is formed to extend obliquely to the cylinder head, a 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 a fuel gas supply nozzle, and FIG. 26 is a plan view showing a configuration near the combustion chamber of the engine viewed from the cylinder head side. FIG. 26 is a sectional view taken along line AA in FIG. 25. In these figures, the same or equivalent members as those described with reference to FIGS. 1 to 24 are denoted by the same reference numerals, and detailed description will be appropriately omitted.

The fuel gas supply nozzle 4 shown in FIG. 25 to FIG. 27 consists of a pipe provided in the intake valve 15 每, and the fuel gas supply through hole 61 of the cylinder head 1 and the intake port 1 3 The suction port 13 is inserted from the side, and is disposed near the adjacent intake port 13 in the intake port 13. Further, as shown in FIG. 25, these nozzles 4 are bent so that the opening at the tip thereof is directed to the downstream side in the direction in which the intake air flows.

The fuel gas supply through hole 61 is a first gas hole extending obliquely and linearly along the intake port 13 from above the inlet of the intake port 13 on one side 2 a of the cylinder head 2. 62 and second gas holes 63 extending from the downstream end of the first gas hole 62 to the intake port 13 of each intake valve 15 (see FIG. 27). ing. The nozzle 4 is mounted on the second gas hole 63. As shown in FIG. 16, an upstream end of the first gas hole 62 is opened inside a hole 29 for mounting a fuel gas supply injector 3 (not shown). .

By forming the nozzle 4 in this manner, the fuel gas injected into the intake port 13 from the nozzle 4 during the intake stroke is sucked as shown by a black arrow G in FIG. The gas flows obliquely downward through the gap between the air valve 15 and the intake outlet 21 in the direction opposite to the exhaust valve 16 in the cylinder. Industrial applicability

As described above, according to the present invention, the tumble flow and the squish flow collide with each other, so that the air-fuel mixture is dispersed as a microturbulence, and the gas flow formed by combining the tumble flow and the squish flow. It moves to the top side of Biston. Therefore, the growth of the flame nucleus is promoted by the micro evening bulence, and the flame spreads to the top side of the biston, and the combustion is rapidly performed.

On the other hand, the kinetic energy of the air-fuel mixture is attenuated by the collision between the evening stream and the squish flow. Absent. Therefore, the above-mentioned phenomenon in which combustion is performed rapidly occurs similarly over a wide operating range.

Therefore, the combustion can be similarly performed over a wide operating range to improve the combustion, so that the fuel efficiency can be further improved.

In addition, since the flow of the air-fuel mixture in the cylinder continues even after ignition, the unburned gas is continuously supplied to the initial combustion gas portion grown near the top of the piston. For this reason, the initial combustion gas is diffused while being stirred by the unburned gas, and is not kept at a high temperature. As a result, the concentration of N 0 X in the exhaust gas can be reduced, despite the fact that the mixture is caused to flow in the cylinder to achieve rapid combustion. A tumble flow is formed, and a space (squish area) for generating a squish flow is formed on the intake valve side where the temperature is relatively low. For this reason, knocking is less likely to occur than in the case where the squish area is formed on the exhaust valve side, so that the limit of lean burn can be further improved. According to the third aspect of the present invention, the shape of the intake port regulates the direction in which the intake air flows, so that the intake resistance is lower than when a member for changing the direction in which the intake air flows is provided in the intake port. As the size becomes smaller, the number of parts is reduced and the number of assembly parts can be reduced. Therefore, both output improvement and cost reduction by reducing the number of assembly steps can be realized.

According to the invention described in claim 4, since the strength of the tumble flow can be changed by the guide member, the guide member generates the tumbling flow so that the strength becomes optimum with respect to the generated squish flow. By doing so, the microturbulence can be reliably formed, and the combustion can be further improved.

Claims

The scope of the claims

1. 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 in the cylinder in a direction opposite to the tumbling flow. An engine having a configuration in which the tumble flow and the squish flow are generated so as to face each other at the end.

2. The engine according to claim 1, wherein the tumble flow generating means is configured to direct the air-fuel mixture from the intake port to the direction opposite to the exhaust valve and to guide the mixture into the cylinder. An engine comprising a slope facing the intake valve, a concave portion 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 by an inclined portion that is formed at a downstream end of the intake port and gradually extends to the opposite side 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 direction in which the intake air flows in the intake passage.