Two-cycle internal combustion engine

Abstract: To provide a two-cycle internal combustion engine capable of preventing the blow-by phenomenon to improve fuel economy and attain a high exhaust gas purifying performance, and increasing the responsiveness of fuel injection volume. In a two-cycle internal combustion engine, a chamber 29 is disposed in scavenging passages 30, 31 for communicating a crank chamber 9 to a combustion chamber 6, sealable control valves 26, 33 are respectively disposed in an inlet and an outlet of the chamber 29, and a fuel feeding system 37 for the supply of fuel into the chamber 29 is provided. The chamber 29 is communicated to one scavenging passage 18 out of a plurality of parallel scavenging passages. The combustion chamber side control valve 33 disposed at an outlet of the chamber 29 on the downstream side of the crank case side control valve 26 provided at an inlet of the chamber 29, is positioned at the bottom portion of a scavenging passage 18 communicated to the chamber 29.

Description: Technical Field of the Invention The present invention relates to a two-cycle internal combustion engine capable of preventing a blow-by phenomenon of a mixture in a combustion chamber to improve fuel economy and attain an exhaust gas purifying performance. Related Art In a related art two-cycle internal combustion engine, fuel supplied by a carburetor, etc. is mixed with intake air, and the resulting mixture is sucked into a crank chamber and is then supplied into a combustion chamber through a scavenging port. In this case, since the timing of opening an exhaust port is set earlier than that of the scavenging port (an upper edge of the exhaust port is higher than that of the scavenging port), the mixture fed into the combustion chamber is discharged into an exhaust passage, thus causing a so-called blow-by phenomenon easily. Although the blow-by phenomenon is suppressed by an exhaust pulsating effect in an exhaust chamber, it is difficult for the suppression to cover the whole operation range, resulting in that both the fuel economy and exhaust purifying performance are affected. In an effort to solve the above-mentioned problem, two-cycle internal combustion engines have been proposed in Japanese Patent Laid-open Nos. Hei 3-100318 and Hei 5-302521. In the two-cycle internal combustion engine disclosed in Japanese Patent Laid-open No. Hei 3-100318, a high pressure chamber is connected to a crank chamber through a check valve, the high pressure chamber is connected to the combustion chamber through an air passage, a solenoid valve is disposed in the lower end of the air passage, and a fuel injection valve capable of injecting fuel toward the combustion chamber is provided at the upper end of the air passage. In the two-cycle internal combustion engine disclosed in Japanese Patent Laid-open N° Hei 5-302521, a chamber is formed in a position adjacent to both crank case and cylinder block, an intake control valve is interposed between a crank chamber and said chamber, a scavenging control valve is interposed between said chamber and a combustion chamber in a cylinder, and a fuel injection valve is provided for injection of fuel toward said chamber. Document US-3 921 608 A discloses a two-cycle internal combustion engine having a charging pump cylinder and a working cylinder. A pump piston and a working piston driven by a common crank-shaft are located in the cylinders. The pump piston is provided with a separating wall defining a first chamber fed with air and a second chamber fed with a fuel and air mixture. Two separate channels interconnect each of the chambers with the working cylinder. Document DE 39 05903 A discloses a two-cycle internal combustion engine having two rotary valves rotating in interlocking relation with rotation of the crank shaft. A first of these valves controls the communication between the cylinders and an air and fuel mixture injection passage. The second valve controls the communication between the cylinders and an air injection passage. Problems to be Solved by the Invention In the two-cycle internal combustion engine described in Japanese Patent Laid-open N° Hei 3-100318, with respect to the fuel injected from the fuel injection valve, part of the fuel deposited on the air passage falls by gravity, entering the crank chamber through a check valve disposed at the bottom of the air passage, and flows in a state being atomized into the combustion chamber from the crank chamber through another scavenging port. As a result, it is difficult to sufficiently prevent the blow-by phenomenon and to obtain stable combustion ; and further, it is difficult to suitably control the amount of fuel fed into the combustion chamber, resulting in the degraded responsiveness. In the two-cycle internal combustion engine described in Japanese Patent Laid-open N° Hei 5-302521, the whole of the intake air in the crank chamber is introduced through the intake control valve and is mixed with the fuel introduced into the said chamber through the fuel injection valve, and the whole of the resulting mixture flows into the combustion chamber through the scavenging control valve. Accordingly, the two-cycle internal combustion engine is not so configured as to permit only air to flow from the crank chamber into the combustion chamber through a scavenging port, and hence the blow-by phenomenon is unavoidable. Further, although an upstream side of the scavenging control valve is opened to the lower portion of said chamber, the opening position thereof is not lowest, so that the fuel injected into said chamber remains at the bottom of said chamber, thus giving rise to a problem that the amount of fuel fed into the combustion chamber cannot be accurately proportional to the amount of fuel injected from the fuel injection valve, resulting in the degraded responsiveness. Means for Solving the Problem To provide an improved two-cycle internal combustion engine capable of solving the above-described problems, there is provided a two-cycle internal combustion engine according to claim 1. In the invention described in claims 1, fuel is supplied into the combustion chamber through the communication passage, so that at the scavenging stroke, a burned gas in the combustion chamber can be positively discharged from the exhaust port by introducing air not mixed with fuel into the combustion chamber through the scavenging passage. As a result, it is possible to prevent blow-by of the mixture in the combustion chamber and to improve a scavenging efficiency due to air scavenging upon low load running. Since at least the control portion of the control valve is positioned lower than the communicating portion at which the communication passage is communicated to the chamber continuous to the fuel injection device, even if the fuel supplied from the fuel injection device into said chamber remains at a bottom portion of said chamber and/or at lower portions of both the communication passage communicated to said chamber and the control valve, the remaining fuel can be almost positively discharged into the combustion chamber. As a result, it is possible to suitably, responsively control the amount of the fuel supplied into the combustion chamber and hence to obtain a stable combustion state. Further, since the chamber continuous to the fuel injection device is juxtaposed on a side of the combustion chamber, the entire engine can be compactly formed into a substantially square shape in a side view, and thereby the vertical length of the entire engine can be shortened as compared with the case where said chamber is disposed over the combustion chamber. As a result, in the case of mounting the engine on a vehicle, it is possible to increase the degree of freedom in layout, and particularly, in the case of mounting the engine on a motorcycle, it is possible to eliminate an inconvenience in which the vehicular height and the minimum ground clearance become higher. In addition a relatively small amount of air to be mixed with fuel supplied to the combustion chamber through the communication passage between the combustion chamber and the chamber continuous to the fuel injection device can be positively sucked in said chamber, and also a pressure enough to feed the mixture into the combustion chamber through the communication passage can be obtained. Further, the mixture becomes rich and the resulting rich mixture flows into the combustion chamber which has been sufficiently scavenged by the air (not mixed with fuel) passing another scavenging passage, so that it is possible to suitably adjust the concentration of the mixture in the combustion chamber and hence to obtain a desirable combustion state. This makes it possible to improve fuel economy and attain a high exhaust gas purifying performance. In addition, at the beginning of scavenging, the valves (gate valve and control valve) at the outlet and the inlet of said chamber are closed and air not mixed with fuel is introduced from another scavenging port into the combustion chamber, to positively discharge the burned gas in the combustion chamber from the exhaust port. This is effective to prevent blow-by of the mixture introduced in the combustion chamber through the communication passage upon completion of scavenging (upon closing of the scavenging port). According to claim 2, in addition to the configuration of the invention described in claim 1, the fuel supplied into the combustion chamber scavenges the remaining burned gas without occurrence of the blow-by thereof, with a result that the fuel can be positively fed into the combustion chamber. According to claim 3, in addition to the configuration of the invention described in claim 1 or 2, it is possible to easily control opening/closing of the control valve in synchronization with rotation of the crank shaft of the engine. Brief Description of the Drawings Fig. 1 shows A vertical sectional view of a first embodiment of the present invention. Fig. 2 shows A vertical sectional view taken on line II-II in Fig. 1 Fig. 3 shows A vertical sectional view taken on line III-III in Fig. 1. Fig. 4 shows An enlarged vertical sectional side view of a principal portion of Fig. 1. Fig. 5 shows A transverse sectional plan view taken on line V-V in Fig. 4. Fig. 6 shows A transverse sectional plan view taken on line VI-VI in Fig. 1. Fig. 7 shows A view as seen in the direction of arrows VII-VII in Fig. 1, wherein dotted portions indicate faces of abutment with the crank case. Fig. 8 shows A view as seen in the direction of arrows VIII-VIII in Fig. 1. Fig. 9 shows A vertical sectional front view of a cylinder block. Fig. 10 shows A transverse sectional plan view taken on line X-X in Fig. 9. Fig. 11 shows A view as seen in the direction of arrows XI-XI in Fig. 1. Fig. 12 shows A diagram showing a state of 45° before arrival at the top dead center (TDC). Fig. 13 shows A diagram showing a state of 45° after passing the top dead center (TDC). Fig. 14 shows A diagram showing a state of arrival at the bottom dead center (BDC). Fig. 15 shows A diagram showing a state of 90° before arrival at the top dead center (TDC). Fig. 16 shows A view illustrating an operational cycle of the embodiment. Fig. 17 shows A vertical sectional side view of a second embodiment of the present invention. Fig. 18 shows A transverse sectional view taken on line XVIII-XVIII of Fig. 17. Fig. 19 shows An enlarged view of a principal portion of Fig. 17. Fig. 20 shows A vertical sectional side view showing a schematic configuration of a mechanism of transmitting a power between a crank shaft and a rotary valve in the embodiment shown in Fig. 17. Fig. 21 shows A partly vertical sectional view of the rotary valve in the embodiment shown in Fig. 17. Fig. 22 shows A vertical sectional view taken on line XXII-XXII of Fig. 21. Fig. 23 shows A vertically sectional side view taken on line XXIII-XXIII of Fig. 21. Fig. 24 shows A view illustrating an operational cycle of the embodiment shown in Fig. 17. Fig. 25 shows A plan view of a cylinder block in a third embodiment of the present invention. Fig. 26 shows A vertical sectional side view taken on line XXVI-XXVI of Fig. 25, showing a state in which a cover is mounted. Fig. 27 shows A transverse sectional plan view taken on line XXVII-XXVII of Fig. 26, showing a state in which the cover is removed. Fig. 28 shows A vertical sectional side view taken on line XXVIII-XXVIII of Fig. 26. Fig. 29 shows A partly vertical sectional view of a rotary valve in the embodiment shown in Fig. 28. Fig. 30 shows A diagram showing a state at the time of compression/filling of air chamber/suction in the embodiment shown in Fig. 25. Fig. 31 shows A diagram, similar to Fig. 30, showing a state at the time of expansion. Fig. 32 shows A diagram, similar to Fig. 30, showing a state at the time of fuel injection/exhaust/scavenging. Fig. 33 shows A diagram, similar to Fig. 30, showing a state at the time of exhaust/supply of mixture/suction. Fig. 34 shows A view illustrating an operational cycle of the embodiment shown in Fig. 25. Embodiments of the Invention One embodiment carrying out the inventions described in claims 1 to 4 (hereinafter, referred to as "a first embodiment") will be described with reference to Figs. 1 to 16. In a spark ignition type two-cycle internal combustion engine 1 of the present invention which is mounted on a motorcycle (not shown), a cylinder block 3 and a cylinder head 4 are sequentially stacked above a crank case 2 and integrally combined with each other. A piston 6 is vertically slidably inserted into a cylinder bore 5 formed in the cylinder block 3. The piston 6 and a crank shaft 8 are connected to each other by a connecting rod 7 in such a manner that the crank shaft 8 is rotated with ascent and descent of the piston 6. An intake passage 10 extending from the back to the front of the vehicle body is connected to the crank case 2, with a throttle valve 11 and a reed valve 12 interposed in series in the intake passage 10. The throttle valve 11 is connected to a throttle grip (not shown) through a connecting means (not shown) in such a manner that the opening of the throttle valve 11 is increased by twisting the throttle grip in one direction. A total of four, two each on the right and left sides, of air supply scavenging passages 14 and 15 for communicating an upper portion of the cylinder bore 5 to a crank chamber 9 are formed in the crank case 2 and the cylinder block 3. A rich mixture supply scavenging passage 18 is formed in a position closer to the rear portion of the vehicle body. A scavenging port 19 of the rich mixture supply scavenging passage 18 is located higher than scavenging ports 16 and 17 of the air supply scavenging passages 14 and 15. The rich mixture supply scavenging passage 18 extends downward from the scavenging port 19 toward the intake passage 10 and is opened to a valve receiving hole 20 formed in the crank case 2 in parallel with the crank shaft 8. A cylinder bore 5 side exhaust port 22 formed in an exhaust passage 21 is located opposite to the scavenging port 19. A generally semispherical combustion chamber 13 formed above the cylinder bore 5 is offset toward the exhaust port 22, and an ignition plug 23 is disposed in the combustion chamber 13. An air passage 24 is formed in the cylinder block 3 at a position directly above the intake passage 10, and air introducing grooves 25 are formed in an underside of the cylinder block 3 brought in contact with the crank case 2. The air introducing grooves 25 extend around an outer periphery of the cylinder bore 5 to communicate the air supply scavenging passages 14 positioned closer to the intake passage 10 to the air passage 24. A reed valve 26 as a crank chamber side control valve is provided above the air passage 24, and a partition wall 27 is formed in the cylinder block 3 on a side of the combustion chamber 13 so as to surround the reed valve 26, with a cover 28 being attached removably to an opening edge of the partition wall 27. The partition wall 27 and the cover 28 constitute a chamber 29. Air passages 30 extending in the vertical direction are formed in the cylinder block 3 on right and left sides of the air passage 24, while a mixing chamber 31 is formed in the crank case 2. The mixing chamber 31 is communicated to the air passages 30 through communication holes 32 provided at its both right and left ends communicated to lower ends of the air passages 30. A rotary valve 33 as a combustion chamber side control valve is rotatably inserted in the valve receiving hole 20. The rotary valve 33 has a valve chamber 34 circumferentially opened at its longitudinal central portion and a fuel introducing passage 35 extending from the left end of the rotary valve 33 in such a manner as to be communicated to the valve chamber 34. The rotary valve 33 is, as will be described later, rotated in the same direction as that of the crank shaft (counterclockwise in Figs. 1 and 4). A fuel injection valve mounting hole 36 extending from the rear portion of the vehicle body toward the mixing chamber 31 is formed in the crank case 2, into which a fuel injection valve 37 is mounted; while a fuel injection valve mounting hole 38 extending from the left surface of the crank case 2 toward the fuel introducing passage 35 and communicated to the fuel introducing passage 35 is formed in the crank case 2, into which a fuel injection valve 39 is mounted. As shown in Fig. 6, an exhaust control valve 40 is disposed near the exhaust port 22 of the exhaust passage 21. A gap 43 having a substantially uniform width is formed between a recess 41 formed in the cylinder block 3 into an arcuate shape in vertical cross-section and an exhaust passage member 42 formed substantially into the same shape as that of the recess 41, and the exhaust control vale 40 is fitted in the gap 43. A base portion of the exhaust control valve 40 is integrally mounted on rotating shafts 45 which are rotatably supported by both the exhaust passage member 42 and an exhaust pipe mounting member 44 integrally combined with the exhaust passage member 42. The rotating shafts 45 are connected to an exhaust control servo-motor (not shown). The exhaust control servo-motor operates in accordance with a control signal outputted from a CPU (not shown) on the basis of an exhaust opening map using the degree of opening of the throttle valve 11 and the rotational speed of the spark ignition type two-cycle internal combustion engine 1 as independent variables, whereby the exhaust control valve 40 is rocked for selecting an optimal exhaust opening matched with the operating condition. As shown in Figs. 3 and 11, the crank case 2 is split into a left crank case 21 and a right crank case 2r with respect to split faces 46. A main shaft 47 and a counter shaft 48, positioned behind the crank shaft 8, are rotatably supported by the left crank case 21 and the right crank case 2r. A clutch 49 is mounted on the main shaft 47 and a train of speed change gears 50 are mounted on the main shaft 47 and counter shaft 48. A driven gear 52 of the clutch 49 meshes with a drive gear 51 mounted at the right end of the crank shaft 8. A chain sprocket 53 is integrally mounted at the left end of the counter shaft 48, and an endless chain is provided between the chain sprocket 53 and a chain sprocket mounted to a rear wheel (not shown). When the spark ignition type two-cycle internal combustion engine 1 is operated and the clutch 49 is in an engaged state, a rotating force of the crank shaft 8 is transmitted to the chain sprocket 53 through the driving gear 51, driven gear 52, clutch 49, speed change gears 50, and counter shaft 48. The rear wheel is thus rotated. A balancer weight 54 for canceling a primary force of inertia of the crank shaft 8, which is located at an obliquely upward position behind the crank shaft 8, is rotatably supported by both the left and right crank cases 21, 2r. A balancer gear 55 is integrally mounted at the right end (in the figure) of the balancer weight 54, and a driven gear 56 is integrally mounted on the right side of the rotary valve 33. A drive gear 57 provided on the crank shaft 8, the balancer gear 55, and the driven gear 56, successively mesh with each other. Upon rotation of the crank shaft 8, the balancer weight 54 is rotated in the direction opposed to the crank shaft 8 and the rotary valve 33 is rotated in the same direction as that of the crank shaft, each at the same speed as the rotational speed of the crank shaft 8. A drive gear 58 is fitted at the right end of the rotary valve 33, a plunger type oil pump 59 is disposed adjacently to the right side of the rotary valve 33, and an intermediate gear 62 meshes with both the driving gear 58 and a driven gear 61 integrated with a drive shaft 60 of the oil pump 59. When the rotary valve 33 is rotated with rotation of the crank shaft 8, the oil pump 59 is thus operated. Oil from the oil pump 59 is supplied to a bearing portion of the crank shaft 8 through an oil feed path 63 (see Fig. 2) and is also supplied through an oil feed path 64 (see Fig. 10) to a sliding portion between the cylinder bore 5 and the piston 6. As shown in Fig. 2, a driven gear 67 integrated with a rotating shaft 66 of a water pump 65 meshes with the drive gear 51 mounted at the right end of the crank shaft 8. Upon start-up of the spark ignition type two-cycle internal combustion engine 1, the water pump 65 is rotated, so that a cooling water in the engine 1 is fed to a radiator (not shown) for cooling and is returned again into a cooling water passage 68 in the engine 1. In the illustrated spark ignition type two-cycle internal combustion engine 1 having the above configuration, when the crank shaft 8 is rotated counterclockwise in Figs. 12 to 15 by means of a starter motor (not shown), the scavenging port 19 of the rich mixture supply scavenging passage 18 is closed by the piston 6 at a time point of 75° ahead of the top dead center (TDC), so that the combustion chamber 13 is compressed and the ignition plug 23 is ignited at a predetermined timing before the top dead center. Further, with ascent of the piston 6, the crank chamber 9 continues to expand and the intake of air is continued (see Fig. 12). After the piston 6 reaches the top dead center (TDC), the mixture in the combustion chamber 13 burns and expands and the crank chamber 9 is compressed with descent of the piston 6 to compress the air present in the crank chamber 9, as shown in Fig. 13. At a time point after an elapse of 90° from the top dead center (TDC), which varies depending on a vertical position of the exhaust control valve 40, the exhaust port 22 is opened to discharge the burned gas from the exhaust passage 21. And, nearly at the same time, the air compressed in the crank chamber 9 flows from the air supply scavenging passage 14 located near the intake passage 10 into the air passage 24 through the air introducing grooves 25 and is then introduced from the air passage 24 into the chamber 29 through the reed valve 26. At a time point after an elapse of about 122° from the top dead center (TDC), the scavenging ports 16 and 17 are opened with descent of the piston 6, resulting in that the air (not containing fuel) present in the crank chamber 9 flows from the ports 16 and 17 into the combustion chamber 13 through the air supply scavenging passages 14 and 15 to force out the burned gas present in the combustion chamber 13 toward the exhaust port 22. In other words, the scavenging is effected with the air alone. At the same time, fuel is injected into the mixing chamber 31 from the fuel injection valves 37 and 39 to produce a rich mixture (see Fig. 14). At a time point after an elapse of about 58° from the bottom dead center (BDC), the scavenging ports 16 and 17 are closed with ascent of the piston 6 to stop the scavenging performed by the inflow of the air from both the ports. And, nearly at the same time, the valve chamber 34 of the rotary valve 33 is opened to both the mixing chamber 31 and the rich mixture supply scavenging passage 18, so that the rich mixture present in the mixing chamber 31 passes through the rich mixture supply scavenging passage 18 and is supplied into the combustion chamber 13 through the scavenging port 19 to scavenge the remaining burned gas. Besides, since the crank chamber 9 expands with ascent of the piston 6, the air is introduced into the crank chamber 9 from the intake passage 10 through the reed valve 12. In addition, there little occurs the blow-by phenomenon of the mixture upon scavenging of the remaining burned gas. Thus, in the spark ignition type two-cycle internal combustion engine 1, since scavenging with only air is performed in the initial stage of scavenging, the blow-by phenomenon that the mixture passes through the combustion chamber 13 and is discharged to the exhaust passage 21, is prevented. This makes it possible to improve fuel economy and prevent air pollution caused by the unburned gas. Since only the air is supplied in the crank chamber 9, even if the bearing portion of the crank shaft 8 and the sliding portion between the cylinder bore 5 and the piston 6 are not lubricated with the oil mixed in the fuel, the oil is supplied from the oil pump 59 to the bearing portion of the crank shaft 8 and the sliding portion between the cylinder bore 5 and the piston 6 through the oil feed paths 63 and 64. Accordingly, the two-cycle internal combustion engine 1 can be operated in a state reduced in frictional loss, while preventing white-smoking caused by the oil mixed in the fuel. Since the rotary valve 33 is provided lower than the communication passage 32 to be communicated to the chamber 29 and the mixing chamber 31, even if the fuel supplied from the fuel injection valves 37, 39 into the mixing chamber 31 is stuck on an inner wall of the mixing chamber 31 and remains on a bottom portion of the mixing chamber 31 and in the valve chamber 34, the remaining fuel can be almost positively discharged into the combustion chamber 13. This makes it possible to suitable, responsively control the supplied amount of the fuel into the combustion chamber 13 and hence to realize a stable combustion state. Since the two fuel injection valves 37 and 39 are provided, not only a large amount of fuel can be injected but also a fine flow control of the fuel can be easily performed while maintaining the metering accuracy of the fuel at a high level. Since the fuel injection valve 37 is disposed in the radial direction of the rotary valve 33 and the fuel injection valve 39 is disposed in the direction of the rotational axis of the rotary valve 33, both the valves 37 and 39 can be disposed near the rotary valve 33 without interference therebetween and thereby the fuel can be positively injected into the valve chamber 34 of the rotary valve 33; and further the fuel can be prevented from remaining in the mixing chamber 31 by suppressing the amount of fuel injected from the fuel injection valve 37 and the sizes of particles of the fuel injected from the fuel injection valves 37 and 39 can be made further fine by collision of the particles of the fuel injected from the fuel injection valves 37, 39. Since the fuel injection valve 39 is disposed on the rotational axis of the rotary valve 33, the fuel can be injected into the valve chamber 34 irrespective of the opening position of the valve chamber 34 in the rotary valve 33, and the fuel injected from the fuel injection valve 39 can be sufficiently mixed with the sucked air by allowing the fuel to intersect a radial air current passing through the valve chamber 34 in the rotary valve 33, to thereby accelerating the atomization of the fuel. Additionally, since the valve chamber 34 in the rotary valve 33 is communicated to the rich mixture supply scavenging passage 18 in a state being previously communicated to the mixing chamber 31, even if the fuel in a liquid state remains in the vicinity of the rotary valve 33, such a liquid fuel adheres on the rotary valve on the valve chamber 34 side and can be atomized by a current of air from the beginning of the next opening period. Next, an embodiment carrying out the invention described in claim 5 (hereinafter, referred to as "a second embodiment) will be described with reference to Figs. 17 to 24. In this embodiment, the air passage 24 provided in the first embodiment is omitted, and air highly compressed at the compression stroke is sucked from the combustion chamber 13 into the chamber 29 through a pair of air communication passages 70. In the chamber 29, the air thus sucked is mixed with fuel which is injected from fuel injection valves 83, 84 in the same manner as in the first embodiment, to form a rich mixture. The resulting rich mixture is supplied into the combustion chamber 13 through a rich mixture supply scavenging passage 73 upon completion of the scavenging stroke (see Fig. 24). The filling of the chamber 29 with the high pressure air supplied from the combustion chamber 13 starts simultaneously with the compression stroke after completion of the exhaust stroke as shown in Fig. 24, and stops after stopping of the supply of the rich mixture into the combustion chamber 13. The other operations are the same as those in the first embodiment, and therefore, the explanation thereof is omitted. Next, there will be described a means of realizing, according to this embodiment, the timings of filling the chamber 29 with highly compressed air supplied from the combustion chamber 13 and of stopping the filling and the timings of supply of a rich mixture from the chamber 29 into the combustion chamber 13 and stopping the supply of the rich mixture. A control valve capable of commonly opening/closing the pair of the air passages 70 and the rich mixture supply scavenging passage 73 is interposed therein. Such a control valve is constituted of a rotary valve as in the first embodiment. The rotary valve 76 is fitted in a valve receiving hole 82, and the pair of the air passages 70 and the rich mixture gas supply scavenging passage 72 are opened in the valve receiving hole 81. As shown in Figs. 21 to 23, a cutout 77 having a specific length in the peripheral direction and a cutout 78 formed in a substantially crescent in cross-section for opening the pair of the air passages 70 and the rich mixture supply scavenging passage 73 are formed around an outer periphery of the rotary valve 76 at positions corresponding the pair of the air passages 70 and the rich mixture supply scavenging passage 73. These cutouts can realize the timings of filling the chamber 29 with highly compressed air supplied from the combustion chamber 13 and of stopping the filling and the timings of supply of a rich mixture from the chamber 29 into the combustion chamber 13 and stopping the supply of the rich mixture as shown in Fig. 24. A pulley 79 is integrally mounted at an axial end of the rotary valve 76. As shown in Fig. 20, a cog belt 81 is provided between the pulley 79 and a pulley 80 integrally mounted on a balancer shaft 69. When the spark ignition type two-cycle internal combustion engine 1 is operated, the crank shaft 8 is rotated and thereby the drive gear 57 integrally mounted on the crank shaft 8 meshes with the balancer gear 55, so that the balancer weight 54 integrally mounted on the balancer shaft 69 is rotated in the reversed direction to the crank shaft 8 and the rotary valve 76 is also rotated in the reversed direction of the crank shaft 8, each at the same rotational speed as that of the crank shaft 8. The cutout 77 as a fuel control portion of the rotary valve 76 is, as fully shown in Fig. 19, set to be positioned lower than a mixture suction port 75 as a communication portion of the rich mixture supply scavenging passage 73 to the chamber 29 when the cutout 77 controls the flow of the rich mixture passing through the rich mixture supply scavenging passage 73. In addition, reference numeral 74 indicates a mixture injection port as a communication portion of the rich mixture supply scavenging passage 73 to the combustion chamber 13; 71 is a highly compressed air suction port as a communication portion of the air passage 70 to the combustion chamber 13; and 72 is a highly compressed air injection port as a communication portion of the air passage 70 with the chamber 29. In this embodiment, since the chamber 29 is filled with the air supplied from the combustion chamber 13 under the compression stroke through the pair of the air passages 70 as described above, a higher and nearly constant pressure in the combustion chamber 13 can be used for the filling the chamber 29 with the air; accordingly, as compared with the filling of the chamber 29 with the air using a pressure in the crank chamber 9 in the first embodiment, it is possible to obtain a positive, stable and high chamber pressure without being affected by reduction in pressure due to full-opening of a throttle valve accompanied by the increased engine speed. Since the rich mixture obtained by filling the chamber 29 with the air flows in the combustion chamber 13 which has been sufficiently scavenged with the air (not mixed with fuel) passing through the air supply scavenging passages 14, 15, it is possible to fill the combustion chamber 13 with a mixture at a suitable concentration, and hence to realize a desirable combustion state. This is effective to improve fuel economy and attain a high exhaust gas purifying performance. Since highly compressed air for forming a rich mixture is obtained from the combustion engine 13, the rotary valve 76 in the communication passage for communicating the chamber 29 to the combustion chamber 13 can be provided on a cylinder wall near the combustion chamber 13, so that the length of the communication passage between the rotary valve 76 and the mixture injection port 74 can be shortened, thereby reducing an amount of the air required to allow the fuel to pass through the communication passage. In addition, a time required for the fuel to pass through the communication passage can be shortened, to reduce an effect of the time factor on setting of the timing of opening the rotary valve 76. This makes it possible to easily set the timing of opening the rotary valve 76 and to improve the suitability of the set-up timing of opening the rotary valve 76 to rotational speeds over a wide range. Since the cutout 77 of the rotary valve 76 opens and closes the rich mixture supply scavenging passage 79 and the portion of actually controlling the flow of the rich mixture (control portion of the rotary valve 76) is positioned lower than the mixture suction port 75, even if the fuel injected from the fuel injection valves 83, 84 adheres on an inner wall of the chamber 29 and remains on a bottom portion of the chamber and the lowermost portion of the rich mixture supply scavenging passage 73 communicated to the chamber 29 and in the rotary valve 76, the remaining fuel can be almost positively discharged into the combustion chamber 13, with a result that the amount of the fuel supplied into the combustion chamber 13 can be suitably, responsively performed to result in the stable combustion state. Next, an embodiment carrying out the invention described in claim 6 will be described with reference to Figs. 25 to 34. In this embodiment, a common communication 86 is provided in place of the pair of the air passages 70 and the rich mixture supply scavenging passage 73 in the second embodiment, and correspondingly, only one cutout 90 of a rotary valve 89 is provided as shown in Fig. 29. Accordingly, the filling of the chamber 29 with highly compressed air supplied from the combustion chamber 13 and the supply of a rich mixture from the chamber 29 into the combustion chamber 13 are both performed through the common communication passage 86 during the communication passage 86 is opened through the cutout 90 of the rotary valve 89. And, powers for filling of the highly compressed air and the supply of the rich mixture into respective chambers are based on a pressure balance between both the chambers. As shown in Fig. 34, the timing of stopping the filling of the chamber 29 with high compressed air supplied from the combustion chamber 13 and the timings of supply of the rich mixture from the chamber 29 into the combustion chamber 13 and of stopping the supply of the rich mixture are the same as those in the second embodiment. On the contrary, the timing of starting of the filling of the chamber 29 with the highly compressed air supplied from the combustion chamber 13 is different from that in the second embodiment in that it corresponds to the time when the pressure balance in the combustion chamber 13 is equalized to that of the chamber 29 and the supply of the rich mixture from the chamber 29 to the combustion chamber 13 is stopped due to the fact that the communication passage 86 is made continuously in a communication state during from the starting of the supply of the rich mixture from the chamber 29 into the combustion chamber 13 to the stopping of the filling of the chamber 29 with the highly compressed air supplied by the combustion chamber 13 by the action of the cutout 90 having the specific length in the circumferential direction of the rotary valve 89. Since the port 87 as the communication portion of the communication passage 86 to the combustion chamber 13 is enlarged in its longitudinal length and also has a cross-section with both sides thereof largely expanded toward the combustion chamber 13 in order to facilitate the suction of a sufficient amount of the highly compressed air into the chamber 29 (see Figs. 26, 28). In this embodiment, the communication passage 86 includes a communication passage 86a, an obliquely, upward extending communication passage 86b, and an obliquely, upward communication passage 86c bend perpendicularly from the communication passage 86b. The communication passages 86a, 86b are respectively disposed on the combustion chamber 13 side and the chamber 29 side with respect to the control portion of the rotary valve 89. An end portion of the communication passage 86c is communicated to the chamber 29 through an opening 88. The fuel injected from two fuel injection valves (not shown) passes through the right and left portions of the communication passage 86b and is mixed with highly compressed air sucked from the chamber 29 through the communication passage 86c, to form a rich mixture. The resulting rich mixture is injected into the combustion chamber 13 through the control portion of the rotary valve 89. Accordingly, since the control portion of the rotary valve 89 is positioned lower than the portion of the communication passage 86c bend perpendicularly to the communication passage 86b (portion at which the air sucked from the chamber 29 collides with the injected fuel) as well as the opening 88, even if the fuel remains in the communication passage 86b and in the control portion of the rotary valve 89, the remaining fuel is almost positively discharged into the combustion chamber 13 by the strong mixed air flow moved by an intermittent opening/closing of the rotary valve 89. As a result, it is possible to suitably, responsively control the amount of the fuel supplied into the combustion chamber 13, and hence to obtain a stable combustion state. The detailed explanation of states of the engine at points of compression/filling of air chamber/suction, expansion, fuel injection/exhaust/scavenging, and exhaust/ supply of mixture /suction shown in Figs. 30 to 33 is omitted. In addition, reference numeral 88 indicates an opening as a communicating portion of the communication passage 86 to the chamber 29, and 91 indicates a receiving hole for the rotary valve 89, and 92 is a fuel injection valve mounting hole. According to the embodiment having the above configuration, it is possible to simplify the structures of the highly compressed air passage and the rich mixture supply scavenging passage as well as the structure of the control valve, and hence to facilitate the manufacture thereof.

Claims: A two-cycle internal combustion engine in which a control valve (33) for openably controlling a communication passage (18) which communicates a combustion chamber (13) to a chamber (29) continuous to a fuel injection device (37) is disposed in said communication passage (18) and fuel is fed into said combustion chamber (13) via said communication passage (18), and in which said chamber continuous to said fuel injection device (37) is juxtaposed on a side of said communication chamber (13) and at least a control portion of said control valve (33) is positioned lower than a communicating portion (14,25,24) through which said communication passage (18) is communicated to said chamber (29) continuous to said fuel injection device (37), characterized in that said chamber (29) continuous to said fuel injection device (37) is communicated to a crank chamber (9) of said engine, and said communicating portion (14,25,24) includes a gate valve (26) for communicating said crank chamber (9) to said chamber (29) continuous to said fuel injection device (37) only at the exhaust stroke of said engine. A two-cycle internal combustion engine according to claim 1, wherein said control valve (33) opens said communication passage (18) nearly upon closing of a scavenging port (16,17) after a down dead center of said engine, and closes said communication passage (18) in the midway of the compression stroke after closing of an exhaust port (22). A two-cycle internal combustion engine according to claim 1 or 2, wherein said control valve (33) is a rotary valve rotating in interlocking with rotation of a crank shaft (8) of said engine.

Inventors: ASAI MASAHIRO, ISHIBASHI YOICHI, ISOMURA SHINICHI, NISHIDA KENJI, NORITAKE HIDEKI, TAKUBO MASAMI, ASAI, MASAHIRO, ISHIBASHI, YOICHI, ISOMURA, SHINICHI, NISHIDA, KENJI, NORITAKE, HIDEKI, TAKUBO, MASAMI
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1997
Main classification: F02B25
IPC codes: F02B75, F02B25