JPS59201920A - Liquid fuel engine - Google Patents

Abstract

PURPOSE:To improve the efficiency of combustion of an engine which has a fast burning means, namely, a device for quickening combustion of air-and-fuel mixture by making the piston stroke of the engine larger than the diameter of a cylinder and completing combustion of the mixture before the crank angle reaches a specified angle. CONSTITUTION:Mixture which is produced by a carbureter is fed through an intake passage 16, properly guided by a straight part which extends from the point L inside the intake passage 16 to an intake port 8, that is, flows at an angle with trespect to the center axis O of a cylinder, into the cylinder 2 in the form of a swirl. The straight part functions as a fast burn means. The distance between the top dead center and the bottom dead center of the piston 4, namely, a piston stroke is set longer than the diameter of the cylinder 2. Combustion of mixture shall be completed until a crankshaft is turned by 100 deg. after the cylinder reaches the top dead center.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to liquid fuel engines, and particularly to reducing the fuel consumption rate of four-cycle engines.

Recently, various research proposals have been made in an attempt to reduce the fuel consumption rate of engines, but the most effective way to reduce the fuel consumption rate of engines is to improve the combustion efficiency of the air-fuel mixture supplied to the engine. .

By the way, in general, in a liquid fuel engine, if the air-fuel mixture supplied into the engine cylinder is ignited when it is a mixture of gasified fuel and fine particulate fuel, the air-fuel mixture will burn well and the combustion efficiency will increase. It is said that it is good. However, as is well known, the liquid fuel contained in the air-fuel mixture is a highly volatile oil such as gasoline or diesel oil, so it easily absorbs heat from the surrounding thermal environment and gasifies. It is difficult to keep the air-fuel mixture supplied to the engine in a mixed state of gasified fuel and fine particulate fuel at the time of ignition.

The reason for this is that the thermal environment within the cylinder is not suitable for maintaining such a state of the air-fuel mixture. However, in engines that are used under various operating conditions, maintaining a mixture of gasified fuel and fine particulate fuel as much as possible contributes to improving combustion efficiency, so it is practical from a practical point of view. It is possible to reduce the fuel consumption rate.

This invention was made in view of these circumstances, and aims to improve combustion efficiency by making the air-fuel mixture sucked into the engine into a mixed state with as much gasified fuel as possible during ignition. The aim is to improve the fuel consumption rate.

The purpose of this is to make the piston stroke larger than the cylinder diameter in a four-stroke engine equipped with a fuel supply device that mixes liquid fuel into the intake air and a first burn means that quickly burns the air-fuel mixture. , and can be achieved by configuring the engine so that combustion of the air-fuel mixture is completed within 100 degrees from top dead center in terms of crank angle.

An embodiment of the overhead valve type four-stroke engine shown in the figure will be described below. Furthermore, this engine has a displacement of 50
This is a small displacement CC engine that is used as a prime mover for relatively small two-wheeled motor vehicles. ■ is the engine,
2 is a cylinder, 3 is a cylinder head, and 4 is a piston. The cylinder 2 is made of aluminum alloy with an iron cylinder liner, and air cooling fins 5 are formed on the outer periphery. The lower surface of the cylinder head 3 constitutes an end wall of the combustion chamber, and a shallow spherical recess 6 is formed approximately in the center of this end wall surface. This recess 6 is provided with an intake port 8, an exhaust port 9, and a spark plug mounting hole 10 (see FIG. 3). As is clear from the drawings, the diameter of the intake port 8 is larger than that of the exhaust port 9. This is to increase the filling efficiency of intake air into the cylinder 2. In the figure, 11 is an intake valve, 12 is an exhaust valve, and 13 is a spark plug, and these valves 8.9 are opened and closed by swinging a rocker arm 14.15 via a camshaft and an operating lever (not shown). It has become. An air-fuel mixture mixed with gasoline (liquid fuel) is supplied to this intake port 8 via an intake passage 16 via vaporized gas (fuel supply device) not shown. An intake passage 16 connected to the intake port 8 extends linearly to the intake port 8 downstream from the center of FIG. Therefore, the flow direction of the air-fuel mixture supplied into the cylinder 2 is adjusted in this straight portion, and the air-fuel mixture flows into the cylinder at an angle with respect to the cylinder center axis 0 direction. As a result, the air-fuel mixture swirls around the cylinder center axis 0 within the cylinder, which functions as a fast burn means in the present invention. As is well known, the piston 4 is configured to interlock with a crankshaft 17 via a connecting rod 16, and a shallow spherical recess 18 is formed on the upper surface of the piston 4 so that the cylinder bore center line 0
The layout is biased towards one example. The fourth part 6 of the cylinder head example described above is also arranged to face this recess 18, and the two surfaces of the piston other than this recess 18 form a squish area with the lower surface of the cylinder head 3. The spark plug 13 is disposed in the cylinder head on the biased side of these recesses 6.18, and a relatively large amount of compressed air-fuel mixture is secured in the electrode portion 19 of the spark plug 13. Ignition by the spark plug 13 is improved. In the engine 1 configured in this way, the distance (piston stroke) S between the top dead center position shown by a solid line in FIG. 2 and the bottom dead center position (not shown by an imaginary line) is larger than the cylinder diameter. .

Next, the engine operation of this embodiment will be explained in FIG. 5 during the intake to compression strokes.

(a) When the intake stroke begins, the intake valve 11 opens and the air-fuel mixture enters the cylinder 2 from the intake port 8.

Since the piston 4 is located near the top dead center, the air-fuel mixture is located in the space directly above the top surface of the piston. The air-fuel mixture thus supplied to the space directly above the piston 4 will be referred to as the preceding air-fuel mixture A in this specification.

This preliminary mixing A produces a swirl within the cylinder 2 because the intake passage 16 is provided at an angle with respect to the cylinder center axis 0. (See FIG. 5(a)) (b) Since the piston moves downward while increasing its moving speed, the preceding air-fuel mixture A moves downward as the piston moves at a position directly above the piston 4 while continuing to swirl. Due to this downward movement into the preceding mixture, the upper part of the preceding mixture is filled with a new mixture (hereinafter referred to as succeeding mixture B) from the intake port.

This trailing mixture B also creates a swirl in the preceding mixture. (See Figure 5(b) (C) When the intake stroke ends in this way, the intake valve 11 closes and the piston rises. At this time, the preceding air-fuel mixture A and the following air-fuel mixture B swirl due to inertia. (See Fig. 5 (C)) (d) When the piston 4 rises in this way and reaches near the top dead center, the overall shape of the combustion chamber constituted by the piston changes as shown in Fig. 5. As shown in (d), cylinder 2
It changes from a cylindrical shape and approaches a flattened spherical shape. Since the diameter d of this flat spherical space is smaller than the previous cylinder diameter, the air-fuel mixture that had been swirling along the inner wall of the cylinder 2 until then is gradually pushed out toward the cylinder center axis 0 side. Since the diameter of the swirl is reduced, the decreasing swirl speed of the swirl is compensated for. (Figure 5 (
d)) (e) When the piston 4 further rises, the spark plug 13
Before and after ignition, squish occurs between the cylinder head and the upper surface of the piston 4, resulting in an explosive stroke.

By the way, the squish flow itself directly causes turbulence in the air-fuel mixture near the electrodes of the spark plug to increase the combustion speed, and is also one of the first burn means in the present invention.

The squish in this embodiment is something that is blown against the swirl in the combustion chamber. When the air-fuel mixture is blown against the swirl by squish, the swirl is disturbed and the turbulent state is applied to the electrode portion 19 of the ignition plug 13. This has the effect of increasing the reliability of ignition by the spark plug 13 and the speed of flame transmission.

Next, we will explain why engines that operate in this manner have improved combustion efficiency.

As explained above, the air-fuel mixture sucked into the cylinder 2 includes the preceding air-fuel mixture A and the following air-fuel mixture B.

Most of the preceding air-fuel mixture A continues to swirl for a long period of time from the beginning of the engine's intake stroke until it is ignited, being located near the top surface of the piston, which is the hottest area in the engine. Therefore, there is a very high probability that the fuel particles contained in the air-fuel mixture will gain heat from the upper surface and be gasified by the time of ignition.

On the other hand, the following mixture B takes a shorter time from entering the cylinder to being ignited than the preceding mixture A, and has a higher temperature than the upper surface of the piston, which is the highest temperature in the engine. The preceding mixture A intervenes, and as a result, the amount of heat of gasification of the contained fuel is obtained mainly from the heat from the inner wall of the cylinder 4. Therefore, the amount of heat that the succeeding mixture B obtains in the cylinder is less than that of the preceding mixture A. Not many. By the way, our purpose is to mix gasified fuel and fine particulate fuel in the air-fuel mixture before ignition, so even if the gasified fuel is obtained from the preceding air-fuel mixture A as described above, The most important point in achieving this objective is how to secure fine particulate fuel.

As a solution to this most important point, we will focus on the exchange of heat between the subsequent air-fuel mixture B and the inner wall of the cylinder 2.

In order to clarify the concept, an explanation will be given using a modeled graph shown in FIG. 6.

First, if we consider the engine cylinder inner wall surface temperature when the crank angle at which the combustion of the air-fuel mixture is completed is θ (degrees) from the second dead center, it is as shown by the solid line P in FIG. In other words, until the air-fuel mixture ignites near top dead center and the crank angle reaches θ, the surface temperature of the inner wall of the cylinder, which is the side wall of the combustion chamber, becomes extremely high because it is exposed to the combustion flame or the high-temperature gas immediately after combustion. , this high-temperature part is not necessarily uniform in temperature depending on the combustion state of the air-fuel mixture, but
The figure was created this way because it is an explanatory diagram of the idea.)

In the following, the inner wall of the cylinder that is on the -dead center side from this combustion completion crank angle θ will be referred to as a high temperature section H.

On the other hand, while the combustion completed crank angle is from the point θ to the bottom dead center, there is burnt gas in the cylinder, and heat is exchanged with this gas and the inner wall of the cylinder is The surface temperature is mainly determined, and the heat exchange time between the burnt gas and the cylinder wall also becomes shorter as it gets closer to the bottom dead center.Therefore,
The closer the cylinder inner wall surface temperature is to the bottom dead center, the lower the surface temperature becomes.

It is assumed that the cylinder inner wall surface temperature has such a tendency.

In the following description, the inner wall of the cylinder that is located on the bottom dead center side from the point at which the combustion is completed crank angle θ will be referred to as the low temperature section.

Here, the significance of the fast burn means in the present invention will be explained as follows.

The imaginary line Q shown in FIG. 6 shows the case where only the combustion completion angle of the engine described above is decreased, and the imaginary line R shows the case where only the combustion completion angle is increased. As shown by the imaginary line Q, when the combustion completion angle is made smaller, the area of the combustion chamber wall is narrower than that shown by the solid line P when combustion is completed, and a certain amount of heat is generated there, forming the side wall of the combustion chamber at that time. The cylinder inner wall surface temperature of the high temperature section H increases. In other words, this means that the temperature of the low-temperature part is lowered.

In other words, by concentrating much of the fixed amount of heat generated by burning a fixed amount of fuel into the high-temperature section H, the area of the low-temperature section is expanded, and as a result, the amount of heat obtained by the low-temperature section is expanded. This is intended to lower the temperature of the low-temperature area by dispersing it. Also, from the perspective of the lower part of the low-temperature section, the end of the high-temperature section H, which is the heat source, is located closer to top dead center than in the case of P, so the heat transfer distance through the cylinder is longer, resulting in a relatively lower temperature. . Furthermore, as the combustion completion position becomes farther away, it takes longer for the burnt gas immediately after combustion to reach the lower temperature area near the bottom dead center.

Contributes to lowering the temperature of low-temperature areas near spots.

On the contrary, as shown by the imaginary line R, when the combustion completion crank angle increases, the wall area of the combustion chamber increases and a certain amount of heat is dispersed, resulting in a decrease in the temperature of the high temperature section H, and the position of the heat source is Since it is located closer to the bottom dead center, the temperature of the cylinder inner wall surface closer to the bottom dead center increases.

That is, in this invention, the fast burn means is a high-temperature part I of the cylinder side wall that becomes the combustion chamber side wall when combustion is completed.
By raising the temperature to a higher temperature, the surface temperature of the inner wall of the cylinder at a lower temperature area closer to the bottom dead center is lowered. Therefore, the amount of heat received by the following mixture I3 that remains in the cylinder 2 for a relatively long period of time is reduced to lower the probability that the fine particulate fuel will be gasified, thereby maintaining the fine particulate state until ignition. ing.

Low temperature section 1 explained above. In order to lower the temperature of the cylinder, the present invention further makes the piston stroke S smaller than the cylinder diameter. This is because even if the combustion completion crank angle is the same, in an engine where the piston stroke is larger than the cylinder diameter, the high temperature part H
This is because the distance from to the bottom dead center can be expanded, and the temperature of the lower part of the low-temperature part can be easily maintained at a relatively low temperature.

Further, in the embodiment shown in the figure, a swirl is generated in the intake air as a fast burn means. This swirl ultimately causes turbulence in the air-fuel mixture near the electrode 19 of the spark plug 13 to achieve rapid combustion, but in this embodiment, the swirl continues especially during the intake and compression strokes. Therefore, it has the following significance.

That is, because this swirl causes the subsequent air-fuel mixture B to flow particularly along the inner circumferential wall of the cylinder 2, most of the subsequent air-fuel mixture B receives heat transfer from the inner circumferential wall of the cylinder.

However, the difference in heat transfer between the subsequent air-fuel mixture B that stays in the cylinder 2 for a relatively long time and the subsequent air-fuel mixture B that stays for a short time is only the difference in heat transfer in the low-temperature part 7, so the overall difference in the subsequent air-fuel mixture B is The heating condition is almost uniform. Therefore, a certain amount of heat stored on the inner wall surface of the cylinder is distributed and transferred to many parts of the succeeding mixture B, and due to such heat transfer, the fuel particles contained in the succeeding mixture B become fine. The probability of gasification is small. In this sense, swirl is involved in securing fine particulate fuel.

Further, in this embodiment, a recess 19 is provided on the upper surface of the piston, and this contributes to ensuring a mixture of gasified fuel and particulate fuel for the following reasons. .

In other words, when the recess 19 is formed on the upper surface of the piston, the proportion of the area covered by the piston in the wall area of the combustion chamber during combustion increases, so the amount of heat generated by combustion transferred to the piston increases, and as a result, the amount of heat generated by combustion increases. Increases gasification ability. Conversely, compared to a flat-top piston with the same engine compression ratio and the same space volume, the two surfaces of the piston left around this recess 19 are located closer to the bottom dead center than the top surface of the flat-top screws 1 to 1. Therefore, the amount of heat received by the cylinder side wall is reduced accordingly, and this also has the meaning of moving the position of the high temperature part H away from the bottom dead center side.

Based on this idea, the inventors conducted various experiments using an actual machine to find out how many times beyond the upper point of crank angle the combustion should be completed. The following qualitative characteristics were recognized.

That is, from this qualitative property, it is determined that the above-mentioned idea is valid up to a combustion completion crank angle of 100 degrees.

As explained above, the present invention is a four-cycle engine, and includes a fuel supply device that mixes liquid fuel into intake air;
In an engine equipped with a fast burn means for quickly burning the air-fuel mixture, the piston stroke is made larger than the cylinder diameter, and the air-fuel mixture in this engine is burnt within 100 degrees of the crank angle after top dead center. This is a liquid fuel engine configured to complete the following steps. Therefore, during combustion, the surface temperature of the piston top surface and the cylinder head side portion of the cylinder side wall that constitute the combustion chamber is increased to gasify the fuel in the mixture supplied into the cylinder immediately after the intake valve opens, and at the same time Since the surface temperature of the portion of the cylinder side wall near the bottom dead center can be lowered, the amount of heat transferred to the air-fuel mixture subsequently supplied into the cylinder can be reduced.
Gasification of the fuel in the mixture can be suppressed. As a result, the fine particulate fuel contained in the air-fuel mixture can be maintained until ignition.

Therefore, the air-fuel mixture ignited in the cylinder contains a mixture of gasified fuel and fine particulate fuel, which improves combustion efficiency and reduces fuel consumption.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an intake valve and an exhaust valve according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a spark plug, and FIG.
Figure 4 is an explanatory diagram of the cylinder head side combustion chamber shape as seen in the direction III--I11 of the figure. Figure 4 is a top view of the piston seen in the direction IV--IV of Figure 1. Figures 5 (a) to (e) is an explanatory diagram of the intake or compression stroke in the engine of this embodiment, FIG. 6 is an explanatory diagram of a cylinder inner wall surface temperature model, and FIG. 7 is a qualitative diagram showing the relationship between combustion completion crank angle and fuel consumption rate in this embodiment. S: Piston stroke D = Cylinder diameter 2 Niji cylinder 4: Piston patent applicant Yamaha Motor Co., Ltd. Figure 3 Figure 4 Procedural amendment (voluntary) May 31, 1980 Commissioner of the Japan Patent Office Kazu Wakasugi Husband 1, Indication of the incident Patent Application No. 76693 of 1982, 2 Name of the invention Liquid fuel engine 3, ? Relationship with the case of a person who makes a corrective action Patent applicant address 2500 Shingai, Iwata City, Shizuoka Prefecture 438 The "Claims" column of the specification, [Detailed explanation of the invention], "Brief explanation of the drawings" ] Column. and drawings. ÷ 7224~LfTr + 2-1°.s-%'~
Description 10 Title of the invention Liquid fuel engine 2. Claims A four-cycle engine comprising a fuel supply device for mixing liquid fuel into intake air and a fast burn means for rapidly burning the air-fuel mixture. A liquid fuel engine comprising: a piston stroke larger than a cylinder diameter, and combustion of an air-fuel mixture in an IsL engine is completed within 100 degrees after top dead center at a crank angle. 3. Detailed Description of the Invention The present invention relates to a liquid fuel engine, and particularly relates to a liquid fuel engine.
' Concerning reduction of fuel consumption rate of cycle engine. Recently, various research proposals have been made in an attempt to reduce the fuel consumption rate of engines, but the most effective way to reduce the fuel consumption rate of engines is to improve the combustion efficiency of the air-fuel mixture supplied to the engine. . By the way, in general, in a liquid fuel engine, if the air-fuel mixture supplied into the engine cylinder is ignited when it is a mixture of gasified fuel and fine particulate fuel, the air-fuel mixture will burn well and the combustion efficiency will increase. It is said that it is good. However, as is well known, the liquid fuel contained in the air-fuel mixture is a highly volatile oil such as gasoline or diesel oil, so it easily absorbs heat from the surrounding thermal environment and turns into gas, which is harmful to the engine. It is difficult to maintain the supplied air-fuel mixture in a mixed state of gasified fuel and fine particulate fuel at the time of ignition. The reason for this is that the thermal environment within the cylinder is not suitable for maintaining such a state of the air-fuel mixture. However, in engines that are used under various usage conditions, maintaining a mixture of gasified fuel with fine particulate fuel as much as possible contributes to improving combustion efficiency, so it is not a practical fuel. Consumption rate can be reduced. This invention was made in view of this situation, and aims to improve combustion efficiency by making the air-fuel mixture sucked into the engine into a mixed state of gasified fuel and fine particulate fuel as much as possible at the time of ignition. This purpose is to improve the fuel consumption rate by improving the fuel consumption rate.This purpose is to improve the fuel consumption rate.The purpose is to improve the fuel consumption rate.
In an engine equipped with a fast burn means for quickly burning the air-fuel mixture, the piston stroke is made larger than the cylinder diameter, and the combustion of the air-fuel mixture in this engine is completed within 100 degrees from top dead center at a crank angle. This can be achieved by configuring it as desired. An embodiment of the overhead valve type four-stroke engine shown in the figure will be described below. On the other hand, this engine has a displacement of 50
CC small displacement engine, relatively small automatic 2
It is used as the prime mover for wheeled vehicles. ■ is the engine, 2 is the cylinder, 3 is the cylinder head,
4 is a piston. The cylinder 2 is made of aluminum alloy with an inner cylinder made of iron, and air cooling fins 5 are formed on the outer periphery. The lower surface of the cylinder 3 constitutes an end wall of the combustion chamber, and a shallow spherical recess 6 is formed approximately in the center of this end wall surface. This recess 6 is provided with an intake port 8, an exhaust port 9, and a spark plug mounting hole 10 (see Fig. 3).
. - As is clear from the drawings, the diameter of the intake port 8 is larger than that of the exhaust port 9. This is cylinder 2
This is to increase the filling efficiency of intake air. In the figure, 11 is an intake valve, 12 is an exhaust valve, and 13 is a spark plug. These valves 11 and 12 are opened and closed by swinging the opening and the rear arm 14 and 15 via a camshaft and an operation rod (not shown). Gasoline (liquid fuel) is supplied to this intake port 8 through a carburetor (fuel supply device) not shown.
The air-fuel mixture mixed with is supplied through the intake passage 16. An intake passage 16 connected to the intake port 8 extends linearly to the intake port 8 downstream from the center of FIG. Therefore,
This straight portion adjusts the flow direction of the air-fuel mixture supplied into the cylinder 2, and the air-fuel mixture flows into the cylinder at an angle of − with respect to the 0 direction of the cylinder center axis. As a result, the air-fuel mixture inside the cylinder is at the center axis O of the cylinder.
A surrounding swirl is generated, which functions as a fast burn means in the present invention. As is well known, the piston 4 is constructed to be interlocked with a crankshaft 17 via a connecting rod 16, and a shallow spherical recess 18 is arranged on the upper surface of the piston 4 so as to be offset from the cylinder pore center line O. The cylinder head 3 is placed so as to face the concave portion 18.
A side recess 6 is also arranged, and the upper surface of the piston other than this recess 18 constitutes a squish area with the lower surface of the cylinder hen 13. The spark plug 13 is placed in the cylinder head 3 on the biased side of these recesses 6.18, and a relatively large amount of compressed air-fuel mixture is secured near the electrode portion 19 of the spark plug 13. Therefore, the ennon 1 configured in this way, which allows for good ignition by the spark plug 13, has a distance (not shown by the solid line in FIG. 2) between the top dead center position and the bottom dead center position shown by the imaginary line. Piston stroke) S is set larger than the cylinder diameter. Next, the operation of the engine of this embodiment will be explained in FIG. 5 during the intake to compression strokes. (a) During the intake stroke, first the intake valve 11 opens and the air-fuel mixture enters the cylinder 2 through the intake port 8. At this time, since the piston 4 is located near the top dead center, the air-fuel mixture is located in the space directly above the top surface of the piston. The air-fuel mixture thus supplied to the space directly above the piston 4 will be referred to as the preceding air-fuel mixture A in this specification. This preceding air-fuel mixture A causes a swirl within the cylinder 2 because the intake passage 16 is inclined with respect to the cylinder center axis 0 (Fig. 5 (b)). Therefore, the preceding air-fuel mixture A descends as the screws 1 to 1 move at a position directly above the piston 4 while continuing to swirl.The movement of this air-fuel mixture A to the lower blade causes the air-fuel mixture A to A new air-fuel mixture (hereinafter referred to as the subsequent air-fuel mixture B) is filled upward from the intake port.This succeeding air-fuel mixture B also generates a swirl like the preceding air-fuel mixture A (Fig. 5). (See (b)). (C) When the intake stroke ends in this way, the intake valve 11
closes and the piston rises. At this time, the swirl continues due to the inertia of the preceding mixture and the following mixture B (see FIG. 5(C)). (d) In this way, when the piston 4 rises and reaches the vicinity of top dead center, the overall shape of the combustion chamber constituted by the piston changes, as shown in Fig. 5 (d). The shape changes and approaches a flat spherical shape (. Since the diameter d of this flat spherical space is smaller than the cylinder diameter up until then, the air-fuel mixture that had been swirling along the inner wall of cylinder 2 gradually flows into the cylinder. It is pushed out toward the center axis O.Then, as the diameter of the swirl is reduced, the Jk rotational speed of the swirl, which was attenuating, is compensated for (5th
Figure (d)). (e) When the piston 4 further rises, the spark plug 13
Before and after ignition, a squish occurs between the cylinder head and the upper surface of the piston 4, resulting in an explosive stroke. The squish is originally something that causes the flow of the squish itself to directly create a gap in the air-fuel mixture near the electrodes of the spark plug, increasing the combustion speed, and is also one of the first burn means referred to in the present invention. . The squish in this embodiment is something that blows against the swirl in the combustion chamber. When the air-fuel mixture is blown against the swirl by the squish, the swirl is disturbed, and in this disturbed state, the electrode of the spark plug 13 is 19, which has the effect of increasing the reliability of ignition by the spark plug 13 and the speed of flame propagation. Next, we will explain why engines that operate in this manner have improved combustion efficiency. As explained earlier, the air-fuel mixture sucked into the cylinder 2 includes the preceding air-fuel mixture A and the following air-fuel mixture B.
Most of the pistons continue to swirl for a long time from the beginning of the engine's intake stroke until ignition, being located near the top surface of the piston, which is considered to be the hottest area in the engine. Therefore, there is an extremely high probability that the fuel particles contained in the air-fuel mixture will gain heat from the upper surface and be gasified by the time of ignition. On the other hand, the following mixture B takes a shorter time from entering the cylinder to being ignited than the preceding mixture A, and has a higher temperature than the upper surface of the piston, which is the highest temperature in the engine. Preliminary mixture A is present. As a result, the amount of heat for gasifying the included fuel is obtained mainly from the heat G from the inner wall of the cylinder 4, so the amount of heat obtained in the subsequent mixture B is smaller than that obtained in the preceding mixture. Since our purpose is to mix the gasified fuel and the fine particulate fuel in the air-fuel mixture before ignition, the gasified fuel must be mixed in advance as described above. However, the most important point in achieving this objective is how to secure fine particulate fuel. As a solution to this most important point, we will focus on the exchange of heat with the inner wall of the cylinder 2 that flows into the trailing air-fuel mixture. In order to clarify the concept, an explanation will be given using a modeled graph shown in FIG. 6. First, if we consider the surface temperature of the inner wall of the cylinder of Esogin when the crank angle at which the combustion of the air-fuel mixture is completed is θ (degrees) from the top dead center, it is as shown by the solid line P in FIG. In other words, the air-fuel mixture ignites near top dead center and the crank angle becomes θ.
The surface temperature of the inner wall of the cylinder, which is the side wall of the combustion chamber, becomes extremely high as it is exposed to the combustion flame or high-temperature gas immediately after combustion. Although the temperature is not uniform, the 6th
The figure is an explanatory diagram of the concept, so it was simply created this way on the drawing.) In the following, the inner wall of the cylinder that is closer to the top dead center than the combustion completion crank angle θ will be referred to as a high temperature section H. On the other hand, from the point where the combustion completion crank angle is 0 to the bottom dead center, the cylinder inner wall surface temperature mainly changes due to the exchange of heat with the burnt gas existing in the cylinder and the heat conductor from the high temperature section H. The heat exchange time between the burnt gas and the cylinder wall also becomes shorter as the temperature approaches the bottom dead center. Therefore, the closer the cylinder inner wall surface temperature is to the bottom dead center, the lower the surface temperature becomes -T. For this reason, it is assumed that the cylinder inner wall surface temperature has such a tendency. In the following description, the inner wall of the cylinder that is located on the bottom dead center side from the point at which the combustion is completed crank angle θ will be referred to as the low temperature section. Here, the significance of the fast burn means in the present invention will be explained as follows. The imaginary line Q shown in FIG. 6 shows the case where only the combustion completion angle of the engine described above is decreased, and the imaginary line R shows the case where only the combustion completion angle is increased. As shown by the virtual line Q, when the combustion completion angle is decreased,
When combustion is completed, the combustion chamber wall area is narrower than in the case of the solid line P, and a certain amount of heat is generated there, so at that time, the cylinder inner wall surface temperature of the high temperature part I forming the side wall of the combustion chamber rises. . In other words, this means that the temperature of the low temperature section I- is reduced. Of course, by concentrating much of the fixed amount of heat generated by burning a fixed amount of fuel into the high temperature section H mentioned above, the area of the low temperature section is expanded, and as a result, the area obtained by the low temperature section ■7 is It disperses heat over a wide area to create a temperature image of low-temperature areas. Also, from the bottom of the low temperature part, the end of the high temperature part H, which is the heat source, is located closer to top dead center than in the case of P.
The heat transfer distance through the cylinder is longer and the temperature is relatively lower. Furthermore, as the combustion completion position becomes farther away, it takes longer for the burnt gas immediately after combustion to reach the part of the low-temperature part near the bottom dead center, which contributes to lowering the temperature of the low-temperature part near the dead center. do. On the contrary, as shown by the imaginary line R, when the combustion completion crank angle increases, a certain amount of heat is dispersed as the combustion chamber wall area increases, and as a result, the temperature of the high temperature section H decreases, and the heat source position also increases. Since it is located closer to the bottom dead center, the temperature of the cylinder inner wall surface closer to the bottom dead center increases. That is, in this invention, in the first stage of Fast Burn-1, the temperature of the cylinder inner wall surface of the low temperature part I7, which is closer to the bottom dead center, is increased by further increasing the temperature of the high temperature part H of the cylinder side wall, which becomes the side wall of the combustion chamber when combustion is completed. This reduces the Therefore, the amount of heat received by the following mixture B that remains in the cylinder 2 for a relatively long period of time is reduced to reduce the probability of the fine particulate fuel becoming gaffed, and the particulate state is maintained until ignition. ing. In order to reduce the temperature of the low-temperature portion as described above, the present invention further makes the piston stroke S larger than the cylinder diameter. This is because even if the combustion completion crank angle is the same, in an engine where the piston stroke is larger than the cylinder diameter, the high temperature section 11
This is because the distance from to the bottom dead center can be expanded, and the temperature of the lower part of the low-temperature part can be easily maintained at a relatively low temperature. Further, in the embodiment shown in the figure, a swirl is generated in the intake air as a fast burn means. This swirl ultimately causes turbulence in the air-fuel mixture near the electrode 19 of the spark plug 13 to achieve rapid combustion, but in this embodiment, the swirl continues especially during the intake and compression strokes. Therefore, it has the following significance. That is, because this swirl causes the subsequent air-fuel mixture B to flow particularly along the inner circumferential wall of the cylinder 2, most of the subsequent air-fuel mixture B receives heat transfer from the inner circumferential wall of the cylinder. However, the difference in heat transfer between the subsequent air-fuel mixture B that stays in the cylinder 2 for a relatively long time and the subsequent air-fuel mixture B that stays for a short time is only the difference in heat exchange in the low temperature area, so the overall heating of the subsequent air-fuel mixture B The condition is almost uniform. Therefore, a certain amount of heat stored on the inner wall surface of the cylinder is distributed and transferred to many parts of the succeeding mixture B, and due to such heat transfer, it is transferred to the succeeding mixture I3. The contained fuel particles are only reduced to fine particles, and the probability that they will be gasified is small. In this sense, the swirl is involved in maintaining the fine particulate fuel (i). In this embodiment, the piston surface is provided with a recess t9, and this is due to the following reasons. This contributes to ensuring a mixture of gasified fuel and fine particulate fuel.In other words, by forming the recess 19 on the upper surface of the piston, the area ratio of the piston to the combustion chamber wall area during combustion is reduced. Since the amount of heat generated by combustion increases, the amount of heat transferred to the piston increases, and as a result, the gasification ability of the preceding air-fuel mixture A increases. By comparison, the upper surface of the piston remaining around this recess 19 is located closer to the top dead center than the upper surface of the flat-top piston -ζ, which reduces the amount of heat received by the cylinder side wall, and this also It also has the meaning of moving the position away from the bottom dead center side.Based on this idea, the inventors conducted various experiments using actual machines to find out how many crank angles after top dead center the combustion should be completed. The qualitative relationship shown in Figure 7 was observed between the combustion completion crank angle and the fuel consumption rate.In other words, from this qualitative property, it is determined that the above idea is valid up to 100 degrees after top dead center as the combustion completion crank angle. As explained above, the present invention is a four-cycle engine, and includes a fuel supply device that mixes liquid fuel into intake air;
In an engine equipped with a fast burn means for quickly burning the air-fuel mixture, the piston stroke is made larger than the cylinder diameter, and the combustion of the air-fuel mixture in this engine is completed within 100 degrees after top dead center in terms of crank angle. This is a liquid fuel engine configured as follows. Therefore, during combustion, the surface temperature of the piston top surface and the cylinder head side portion of the cylinder side wall that constitute the combustion chamber is increased to gasify the fuel in the mixture supplied into the cylinder immediately after the intake valve opens, and at the same time Since the surface temperature of the part of the cylinder side wall near the bottom dead center can be lowered, the amount of heat transferred to the air-fuel mixture that is subsequently supplied into the cylinder can be reduced, suppressing the gasification of the fuel in the air-fuel mixture. is easy to do. As a result, fine particulate fuel contained in the air-fuel mixture can be maintained until ignition. Therefore, the probability that gasified fuel and particulate fuel are mixed in the air-fuel mixture ignited in the cylinder increases, so combustion efficiency can be improved and fuel consumption rate reduced. . 4. Brief description of the drawings The drawings relate to embodiments of the present invention. Fig. 1 shows the intake valve and exhaust valve (1-1 in Fig. 2).
Figure 2 is a cross-sectional view showing the spark plug (along line ■-■ in Figure 1), Figure 3 is a cylinder viewed in the DI-I11 direction in Figure 1. FIG. 4 is a top view of the piston seen in the IV-IV force direction of FIG. 1. FIGS. A compression stroke explanatory diagram, FIG. 6 is an explanatory diagram of a cylinder inner wall surface temperature model, and FIG. 7 is a qualitative graph showing the relationship between combustion completion crank angle and fuel consumption rate in this example. S: Piston stroke D= Cylinder diameter 2 Niji cylinder 4: Piston patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Claims] A four-stroke engine, which is equipped with a fuel supply device that mixes liquid fuel into intake air, and a fast burn means that quickly burns the air-fuel mixture, in which the piston stroke is expressed as the cylinder diameter. In addition, the combustion of the air-fuel mixture in this engine is increased to 1 after top dead center at the crank angle.
A liquid fuel engine configured to complete within 0.00 degrees.