Title of Invention

"FUEL INJECTION TYPE ENGINE"

Abstract

In a fuel injection type two-cycle engine (1) including a diaphragm operated poppet valve (20) for injecting a mixture gas obtained by a carburetor (53) into a combustion chamber (8); characterized in that it comprises a mixture gas passage having an outlet connected to a mixture gas inlet of said poppet valve to supply said mixture gas to said poppet valve (27), a reciprocating piston type air pump (54) provided in said mixture gas passage (51) and adapted to be driven by a crankshaft as a driving source, and a pilot line (71) for leading an outlet pressure of said air pump to a diaphragm operating port (29) of said poppet valve.

Full Text

[DETAILED DESCRIPTION OF THE INVENTION] [Field of the Invention] The present invention relates to an improvement in a fuel injection type two-cycle engine. [Prior Art] A conventional fuel injection type two-cycle engine including a diaphragm operated poppet valve for injecting a mixture gas into a combustion chamber is known from Japanese Patent Laid-open No. 7-310554 entitled "Crankcase Compression Type Two-cycle Engine". This conventional technique will now be described, in which reference numerals are cited from the above publication. According to FIG. 6 of the above publication, a scavenging valve 21 adapted to be driven by a diaphragm actuator 100 is mounted on the upper side of a combustion chamber 9, and a scavenging port 22 as an inlet port of the scavenging valve 21 communicates with a crankcase 5 through a scavenging passage 23. The scavenging passage 23 is branched to form an operating air passage 23a communicating with a pressure chamber 33 of the diaphragm actuator 100. Further, a fuel supply device 200 with a carburetor 52 is provided in the scavenging passage 23 in the vicinity of the scavenging port 22. When a piston 2 is lowered to increase the pressure in the crankcase 5, the pressurized air in the crankcase 5 is fed through the scavenging passage 23 and the operating air passage 23a into the pressure chamber 33, thereby operating a diaphragm 31. At the time the pressure in the pressure chamber 33 overcomes the biasing force of a spring 29 and the pressure in the combustion chamber 9, the scavenging valve 21 is opened to supply a mixture gas in the scavenging port 22 to the combustion chamber 9. Thus, a force for opening the scavenging valve 21 is assisted by the pressure applied to the diaphragm 31. Accordingly, the biasing force of the spring 29 can be set large, so that the responsiveness of the scavenging valve 21 can be improved. [Problem to be Solved by the Invention] In the above prior art, however, the operating pressure acting on the diaphragm 31 is affected by the actual volume of the crankcase 5, the scavenging volume of the scavenging passage 23, etc., and must be determined so as to prevent a reverse flow from the fuel supply device 200 through the scavenging passage 23 to the crankcase 5. It is not easy to determine a stable operating pressure acting on the diaphragm 31 in consideration of these various factors to determine a timing of injecting the mixture gas into the combustion chamber. It is accordingly an object of the present invention to provide a technique for reliably setting a timing of injecting the mixture gas into the combustion chamber with a simple configuration. [Means for Solving the Problem] According to the invention as defined in claim 1, there is provided in a fuel injection type two-cycle engine including a diaphragm operated poppet valve for injecting a mixture gas obtained by a carburetor into a combustion chamber; the improvement comprising a mixture gas passage having an outlet connected to a mixture gas inlet of the poppet valve to supply the mixture gas to the poppet valve, a reciprocating piston type air pump provided in the mixture gas passage and adapted to be driven by a crankshaft as a driving source, and a pilot line for leading an outlet pressure of the air pump to a diaphragm operating port of the poppet valve. The operating pressure for the diaphragm operated poppet valve is determined by the outlet pressure ( discharge pressure) of the reciprocating piston type air pump driven by the crankshaft as a driving source. Accordingly, the operating pressure for the diaphragm can be changed according to the- rotating speed of the crankshaft. That is, the poppet valve is opened by using the crankshaft as a driving source, so that a timing of injecting the mixture gas into the combustion chamber can be reliably set with a simple configuration. Accordingly, the mixture gas can be injected at a proper crank angle of the crankshaft. Further, unlike the prior art, it is unnecessary to provide a high-pressure fuel pump for supplying fuel under high pressures, a solenoid type fuel injection valve for injecting fuel, a solenoid type mixture gas closing valve for supplying a mixture gas to a combustion chamber, a control circuit for controlling the solenoid type fuel injection valve or the solenoid type mixture gas closing valve, etc. According to the invention as defined in claim 2, the fuel injection type two-cycle engine further comprises a pressure control valve provided in the pilot line for controlling a diaphragm operating pressure, the pressure control valve being controlled according to an opening degree of a throttle valve. The timing of injecting the mixture gas from the poppet valve can be changed- according to the opening degree of the throttle valve with a simple configuration. In particular, an injection start timing can be changed over the substantially entire rotating speed region of the crankshaft. According to the invention as defined in claim 3, the fuel injection type two-cycle engine further comprises a phase varying mechanism provided in a driving system for the air pump, for varying a phase between the crankshaft and a driving shaft for the air pump by using a centrifugal force according to a rotating speed of the crankshaft, The timing of injecting the mixture gas from the poppet valve can be changed according to the rotating speed of the crankshaft. In particular, an injection end timing can be changed in a middle rotating speed region of the crankshaft. Therefore, the present invention relates to " a fuel injection type two-cycle engine having a diaphragm operated poppet valve for injecting a mixture gas obtained by a carburetor into a combustion chamber; characterized in that a mixture gas passage having an outlet connected to a mixture gas inlet of said poppet valve is provided to supply said mixture gas to said poppet valve, a reciprocating piston type air pump provided in said mixture gas passage and adapted to be driven by a crankshaft as a driving source, and a pilot line for passing an outlet pressure of said air pump to a diaphragm operating port of said poppet valve. [BRIEF DESCRIPTION OF THE ACCOMPANYING ADRAWINGS ] FIG. 1 is a flow sheet showing a fuel injection type two-cycle engine according to a first preferred embodiment of the present invention. [FIG. 2] FIG. 2 is a sectional view showing a reciprocating piston type air pump shown in FIG. 1. [FIG. 3] FIG. 3 is a graph showing an operating characteristic of a diaphragm operated poppet valve controlled by a pressure control valve in the first preferred embodiment. [FIG. 4] FIG. 4 is a graph showing a control characteristic of the opening timing of the poppet valve in the first preferred embodiment. [FIG. 5] FIG. 5 is a graph showing an open angle Characterize tic of the poppet valve in the first preferred embodiment. [FIG. 6] FIG. 6 is a flow sheet showing a fuel injection type two-cycle engine according td a second preferred embodiment of the present invention. [FIG. 7] FIG. 7 is a sectional view showing a reciprocating piston type air pump shown in FIG. 6. [FIG. 8] FIG. 8 is an exploded view of a phase varying mechanism shown in FIG. 7. [FIG. 9] FIGS. 9a to 9c are views illustrating the operation of the phase varying mechanism shown in FIG. 8. [FIG. 10] FIG. 10 is a graph showing an operating characteristic of a diaphragm operated poppet valve controlled by the phase varying mechanism in the second preferred embodiment. [FIG. 11] FIG. 11 is a graph showing a control characteristic of the closing timing of the poppet valve in the second preferred embodiment. [Preferred Embodiment] Some preferred embodiments of the present invention-,, will now be described with reference to the attached drawings. Each drawing is to be viewed in the same orientation as that of reference numerals shown therein. A first preferred embodiment of the present invention will now be described with reference to FIGS. 1 to 5. FIG. 1 is a flow sheet showing a fuel injection type two-cycle engine 1 according to the first preferred embodiment of the present invention. The engine 1 is a fuel injection type two-cycle single-cylinder engine using gasoline as a fuel and mounted on a scooter type motorcycle (not shown), for example. The engine 1 is composed mainly of a crankcase 2, cylinder block 3, cylinder head 4, crankshaft 5, connecting rod 6, and piston 7. A main combustion chamber 8 is defined at an upper portion of a cylinder 3a of the cylinder block 3, and an auxiliary combustion chamber 9 is defined in the cylinder head 4 so as to communicate with the main combustion chamber 8. Furthermore, a diaphragm operated poppet valve 20 for injecting a mixture of fuel and compressed air is mounted at an upper end of the auxiliary combustion chamber 9. The main combustion chamber 8 and the auxiliary combustion chamber 9 are combined to form one combustion chamber. The engine 1 is fucther provided with an intake port 11 formed through the crankcase 2, a plurality of scavenging ports 12 for making communication of the crankcase 2 and the cylinder block 3, an exhaust port 13 formed through the cylinder block 3, and a spark plug 14 mounted in the cylinder head 4 so as to be exposed to the main combustion chamber 8. Optionally, an additional spark plug dedicated for the auxiliary combustion chamber 9 may be mounted. The diaphragm operated poppet valve 20 is composed of a valve casing 21, a valve stem 22 axially movably extending through the valve casing 21, a valve head 23 formed integrally with the valve stem 22, a diaphragm box 24 mounted on the upper end of the valve casing 21, a diaphragm 25 incorporated in the diaphragm box 24 for driving the valve stem 22 in a valve opening direction, and a return spring 26 for biasing the valve stem 22 in a valve closing direction. The poppet valve 20 is further provided with a mixture gas inlet 27, a valve stem seal 28, an operating port 29 for the diaphragm 25, a vent hole 31, and a return port 32. A fine clearance is defined between the upper end of the valve stem 22 and the diaphragm 25, and this clearance can be adjusted according to the thickness of a shim. Reference numeral 40 generally denotes a combustion air supply system for supplying a combustion air to the engine 1. The combustion air supply system 40 is composed of an air cleaner 41, an air supply passage 43 for connecting the air cleaner 41 and the intake port 11 through a reed valve 42, and a first throttle valve 44 inserted in the air supply passage 43. Reference numeral 50 generally denotes a mixture air supply system for supplying a mixture gas to the engine 1. The mixture gas supply system 50 is composed of a mixture gas passage 51 branching off from the air supply passage 43 and having an outlet led (connected) to the mixture gas inlet 27 of the diaphragm operated poppet valve 20, a carburetor 53 inserted in the mixture gas passage 51, a second throttle valve 52 provided downstream of the carburetor 53, and a reciprocating piston type air pump 54 provided downstream of the second throttle valve 52. The carburetor 53 functions to atomize the fuel supplied from a fuel supply system (not shown), and the mixture gas passage 51 functions to supply a mixture gas obtained by the carburetor-53. The first and second throttle valves 44 and 52 are operatively connected to a throttle grip (accelerator) 55 of a motorcycle, for example. The reciprocating piston type air pump 54 includes a closed cylinder 61, a piston 62 reciprocated in the cylinder 61 by the crankshaft 5 (the engine 1) as a driving source, two suction ports (inlet ports) 63, and two discharge ports (outlet ports) 64. One of the suction ports 63 and one of the discharge 'ports 64 are formed at one end portion of the cylinder 61, and the other suction port 63 and the other discharge port 64 are formed at the other end portion of the cylinder 61. The suction ports 63 are connected to an upstream portion of the mixture gas passage 51, and the discharge ports 64 are connected to a downstream portion of the mixture gas passage 51. Accordingly, every time the piston 62 is reciprocated, the mixture gas is discharged twice from the air pump 54. The air pump 54 is mounted on a side portion of the cylinder head 4, for example. Reference numerals 65 denote check valves provided in the suction ports 63 and the discharge ports 64. Reference numeral 7-0 generally denotes a control system for controlling the poppet valve 20. The control system 70 is composed of a pilot line 71 branching off from the downstream portion of the mixture gas passage 51 downstream of the air pump 54 and having an outlet connected to the diaphragm operating port 29 of the poppet valve 20, and a pressure control valve 72 inserted in the pilot line 71. The pressure control valve 72 is operatively connected to the throttle grip 55. Accordingly, the pressure control valve 72 is controlled according to the opening degrees of the first and second throttle valves 44 and 52. In other words, the control system 70 is configured in such a manner that the pressure at the discharge ports 64 of the air pump 54 is led through the pilot line 71 to the diaphragm operating port 29 and that the pressure control valve 72 is controlled according to the opening degrees of the first and second throttle valves 44 and 52. Preferably, the control system 70 further includes a return line 73 for returning the mixture gas flowing from the pilot line 71 into a diaphragm positive pressure chamber (diaphragm operating chamber) 33, to the inlet ports 63 of the air pump 54, and a restriction value 74 and a check valve 75 both insetted in the return line 73, so as to enhance the effect of pressure control by the pressure control valve 72. FIG. 2 is a sectional view of the reciprocating piston type air pump 54 shown in FIG. 1. A driving mechanism for the air pump 54 is composed of a driving pulley 15 mounted on the crankshaft 5, a crank mechanism 66 for reciprocating the piston 62, a driven pulley 67 mounted on a driving shaft 66a of the crank mechanism 66, and a toothed belt 68 wrapped between the driving pulley 15 and the driven pulley 67. A reduction ratio of the driven pulley 67 to the driving pulley 15 is 2:1. As a result, every time the crankshaft 5 is rotated, the air pump 54 discharges a mixture gas once. Accordingly, by adjusting the operational phase of the driving shaft 66a to the crank angle of the crankshaft 5, the air pump 54 can discharge a pressurized mixture gas according to the stroke of the engine 1. The operation of the diaphragm operated poppet valve 20 mentioned above will now be described. FIG. 3 is a graph showing an operating characteristic of the poppet valve 20 controlled by the pressure control valve 72. In FIG. 3, the horizontal axis represents crank angle 6 (deg.) of the crankshaft 5, and the vertical axis represents pressure Pd (Pa) in the diaphragm positive pressure chamber 33 of the poppet valve 20. This graph shows a control characteristic under the conditions that the opening degrees of the first and second throttle valves 44 and 52 are set to 30 % for each and that the rotating speed Ne of the crankshaft 5 is set to 5000 (rpm). Needless to say, when the "piston 7 is at a top dead center TDC, the crank angle 6 is 0 (deg.), whereas when the piston 7 is at a bottom dead center BDC, the crank angle d is 180 (deg.). The same applies to the following. In this graph, the curves A and B show pressure curves obtained by replacing the pressure in the main and auxiliary combustion chambers 8 and 9 by the pressure in the diaphragm positive pressure chamber 33. That is, the curve A shows a rapid decrease in pressure by lowering of the piston 7, and the curve B shows a rapid increase in pressure by rising of the piston 7. The line C shows a pressure line obtained by replacing the set load of the return spring 26 of the poppet valve 20 by the pressure in the diaphragm positive pressure chamber 33, which is set to Pdj. The operational phase of the driving shaft 66a for the air pump 54 is set so that the air pump 54 starts pressurizing a mixture gas when the crank angle of the crankshaft 5 is θ1 . Accordingly, every time the crankshaft 5 is rotated, the pressure Pd in the diaphragm positive pressure chamber 33 is changed as shown by the pressure curves D and E each having a substantially parabolic waveform (the pitch of waves is 360 deg.)- The pressure curve D corresponds to the case where the pressure control valve 72 is fully opened, and the pressure curve E corresponds to the case where the pressure control valve 72 is opened to a given degree according to the opening degrees of the first and second throttle valves 44 and 52. The pressure Pd in the diaphragm positive pressure chamber 33 changes with the opening degree of the pressure control valve 72, and the larger the opening degree of the pressure control valve 72, the larger the waveform of the pressure curve in the diaphragm positive pressure chamber 33. Accordingly, the waveform of the curve D is larger than the waveform of the curve E as also apparent from FIG. In the case that the pressure control valve 72 is fully opened, the curve D intersects the line C of the pressure Pd1 corresponding to the set load of the return spring 26 at a point D1. when the pressure Pd in the diaphragm positive pressure chamber 33 becomes higher than the pressure Pd1, the poppet valve 20 is opened. On the other hand, in the case that the pressure control valve 72 is opened to a given degree, the curve E intersects the line C of the pressure Pd1 corresponding to the set load of the return spring 26 at a point E1. When the pressure Pd in the diaphragm positive pressure chamber 33 becomes higher than the pressure Pd1, the poppet valve 20 is opened. In this manner, by setting the opening degree of the pressure control valve 72, the opening timing of the poppet valve 20 can be changed with respect to the crank angle θ . The closing timing of the poppet valve 20 is influenced by the pressure in the main and auxiliary combustion chambers 8 and 9. FIG. 4 is a graph showing a control characteristic of the opening timing of the diaphragm operated poppet valve 20 in this preferred embodiment. In FIG. 4, the horizontal axis represents rotating speed Ne (rpm) of the crankshaft 5, and the vertical axis represents crank angle θ (deg.) of the crankshaft 5. The terms of "exhaust start" and "exhaust end" in FIG. 4 mean a start timing of exhaust from the engine 1 and an end timing of exhaust from the engine 1, respectively, and the terms of "scavenging start" and "scavenging end" in FIG. 4 mean a start timing of scavenging to the engine 1 and an end timing of scavenging to the engine 1, respectively (the same applies to the following). In FIG. 4, the curve F is a characteristic curve showing an optimum opening timing of a fuel injection valve to be required by the engine 1, and the curve G is a characteristic curve showing an opening timing inherent to the poppet valve 20. As mentioned above with reference to FIG. 3, the pressure control valve 72 controls the operational characteristic of the poppet valve 20 according to the opening degrees of the first and second throttle valves 44 and 52 (i.e., substantially according to the rotating speed Ne of the crankshaft 5). Accordingly, the curve G showing the opening timing characteristic of the poppet valve 20 can be approximated to the curve F showing the optimum opening timing characteristic. For example, in the case that the rotating speed Ne of the crankshaft 5 is 7000 rpm, and that the crank angle θ is about 105 deg., the poppet valve 20 is opened. FIG. 5 is a graph showing an open angle characteristic of the poppet valve 20 in this preferred embodiment. In FIG. 5, the horizontal axis represents rotating speed Ne (rpm) of the crankshaft 5, and the vertical axis represents range a (deg.) of change of the crank angle. This graph shows a relation such that the poppet valve 20 continues to open over a time duration of change of the crank angle by a certain angle with respect to the rotating speed Ne of the crankshaft 5. This relation will be hereinafter referred to as "open angle characteristic", and the curve showing the open angle characteristic will be hereinafter referred to as "open angle characteristic curve". For example, the open angle characteristic curve H in FIG. 5 shows that in the case where the rotating speed Ne of the crankshaft 5 is 7000 rpm, the poppet valve 20 continues to open over a time duration required for change of the crank angle by about 210 deg. The curve H shows an optimum open angle characteristic curve of a fuel injection valve to be required by the engine 1, and the curve I shows an open angle characteristic curve inherent to the poppet valve 20. As mentioned above, the operational characteristic of the poppet valve 20 can be changed by the pressure control valve 72. Accordingly, the open angle characteristic of the poppet valve" 20 can be approximated to the optimum characteristic shown by the curve H irrespective of the rotating speed Ne of the crankshaft 5. As apparent from the above description of the first preferred embodiment, the operational characteristic of the poppet valve 20 can be changed according to the opening degrees of the first and second throttle valves 44 and 52 by the pressure control valve 72. As a result, an ignition start timing in particular can be changed over the substantially entire rotating speed region of the crankshaft 5. A second preferred-embodiment of the present invention will now be described with reference to FIGS. 6 to 11. The second preferred embodiment is characterized in that a phase varying mechanism 83 to be hereinafter described is provided in the driving system for the air pump 54 in place of the pressure control valve 72 provided in the control system 70. In the following description of the second preferred embodiment, the same components as those of the first preferred embodiment shown in FIGS. 1 and 2 will be denoted by the same reference numerals, and the description thereof will be omitted. FIG. 6 is a flow sheet showing a fuel injection type two-cycle engine 1 according to the second preferred embodiment of the present invention. As shown in FIG. 6, the pilot line 71 is not provided with the pressure control valve 72 (see FIG. 1). FIG. 7 is a sectional view of an air pump 54 shown in FIG. 6. As shown in FIG. 1, the driving system for the air pump 54 includes a phase varying mechanism 83. More specifically, the driving mechanism for the air pump 54 includes a driven pulley 67, an intermediate shaft 81 for mounting the driven pulley 67, a pair of bearings 82 for supporting the intermediate shaft 81, a driving shaft 66a for reciprocating a piston 62 in the air pump 54, and the phase varying mechanism 83 connecting the opposed ends of the intermediate shaft 81 and the driving shaft 66a. The phase varying mechanism 83 is composed of a disk-shaped drive coupling 84 fixedly mounted on the intermediate shaft 81, a disk-shaped driven coupling 85 axially slidably mounted on the driving shaft 66a through splines or the like in facing relationship to the drive coupling 84, and a plurality of balls 86 interposed between the drive coupling 84 and the driven coupling 85. The balls 86 are received in a plurality of drive grooves 84a formed on the facing surface of the drive coupling 84 and a plurality of driven grooves 85a formed on the facing surface of the driven coupling 85. Each drive groove 84a is a slant groove having a depth gradually decreasing in the radially outward direction, whereas each driven groove 85a is a straight groove having a uniform depth. Reference numeral 87 denotes a spring for normally biasing the driven coupling 85 toward the drive coupling 84 in the axial direction, and-reference numeral 88 denotes a fixed spring seat for receiving the spring 87. FIG. 8 is an exploded view of the phase varying mechanism 83 shown in FIG. 7, showing elevations of the facing surfaces of the drive and driven couplings 84 and 85. As shown in FIG. 8, the drive grooves 84a formed on the facing surface of the drive coupling 84 are narrow curved grooves arranged at circumferentially equal intervals and extending radially so as to be arcuate in a rotational direction R of the drive coupling 84, whereas the driven grooves 85a formed on the facing surface of the driven coupling 85 are narrow straight grooves arranged at circumferentially equal intervals and extending radially straight. Start points PI formed at the radially inner ends of the drive grooves 84a of the drive coupling 84 and start points P2 formed at the radially inner ends of the driven grooves 85a of the drive coupling 85 are initially set in the same phase. The operation of the phase varying mechanism 83 will now be described. FIGS. 9a to 9c show the operation of the phase varying mechanism 83 shown-in FIGS. 7 and 8. More specifically, FIG. 9a is a sectional view of the phase varying mechanism 83; and FIGS. 9b and 9c are elevations of the facing surfaces of the drive and driven couplings 84 and 85 in the operated condition of the phase varying mechanism 83, respectively. When the crankshaft 5 (the intermediate shaft 81) is at rest or in low-speed rotation as shown in FIG. 7, no or almost no centrifugal force acts on the balls 86, so that the balls 86 are maintained at the radially inner ends of the drive and driven grooves 84a and 85a as shown in FLG. 8. In this condition, the drive and driven couplings 84 and 85 are in the same phase. Accordingly, the driving shaft 66a is rotated with the initially set phase according to the crank angle of the crankshaft 5. When the crankshaft 5 (the intermediate shaft 81) is rotated at high speeds, a centrifugal force according to the rotating speed of the crankshaft 5 acts on the balls 86, so that the balls 86 are moved radially outward as shown in FIG. 9a. At this time, the balls 86 roll in the slant drive grooves 84a to axially move the driven coupling 85 against the biasing force of the spring 87. The balls 86 moved-in the arcuate drive grooves 84a as shown in FIG. 9b vary the phase of the driven coupling 85 through the driven grooves 85a as shown in FIG. 9c. In this manner, the phase varying mechanism 83 can vary the phase between the crankshaft 5 and the driving shaft 66a by using a centrifugal force according to the rotating speed of the crankshaft 5. The operation of the poppet valve 20 in the second preferred embodiment will now be described. FIG. 10 is a graph showing an operating characteristic of the poppet valve 20 controlled by the phase varying mechanism 83 in the second preferred embodiment. In FIG. 10, the horizontal axis represents crank angle θ (deg.) of the crankshaft 5, and the vertical axis represents pressure Pd (Pa) in the diaphragm positive pressure chamber 33 of the poppet valve 20. The lines A, B, and C in FIG. 10 are the same as those shown in FIG. 3, so the description thereof will be omitted herein. The operational phase of the driving shaft 66a is initially set so that when the crank angle θ of the crankshaft 5 is θ1, the air pump 54 starts pressurizing a mixture gas. Such an initial set condition of the phase between the crankshaft 5 and the driving shaft 66a will be hereinafter referred to as "first condition". In the case of increasing the rotating speed Ne of the crankshaft 5 to 5000 (rpm) by increasing the opening degrees of the first and second throttle valves 44 and 52 to 30 %, the phase between the crankshaft 5 and the driving shaft 66a is shifted from the first condition to a "second condition". The curve J in FIG. 10 is a pressure curve in the diaphragm positive pressure chamber 33 in the first condition. In the first condition, the operational phase of the driving shaft 66a is set so that when the crank angle θ of the crankshaft 55 is θ1 the air pump 54 starts pressurizing a mixture gas. The curve K is a pressure curve in the diaphragm positive pressure chamber 33 in the second condition. The waveform of the curve J is the same as the waveform of the curve K. As apparent from this graph, a timing of pressurizing the mixture gas is changed from θ1 to θ2 by the shift from the first condition to the second condition. With this change of the pressurizing timing, a start point of the curve J is changed f-rom θ1 to θ2 That is, the phase of the curve J is changed to the phase of the curve K. At a point J1 on the curve J, the set load of the return spring 26 and the pressure Pd1 in the diaphragm positive pressure chamber 33 coincide each other, and at pressures lower than the pressure Pda, the poppet valve 20 is closed. On the other hand, at a point KI on the curve K, the set load of the return spring 26 and the pressure Pd1 in the diaphragm positive pressure chamber 33 coincide each other, and at pressures lower than the pressure Pd1, the poppet valve 20 is closed. As" a result, the closing timing of the poppet valve 20 changes from the point J1 to the point k1 with the change of the phase. In this manner, the closing timing of the poppet valve 20 can be changed with respect to the crank angle θ according to a change in rotating speed of the crankshaft 5. Such a change in the closing timing of the poppet valve 20 results in a change in the opening timing thereof. FIG. 11 is a graph showing a control characteristic of the closing timing of the poppet valve 20 in the second preferred embodiment. In FIG. 11, the horizontal axis represents rotating speed Ne (rpm) of the crankshaft 5, and the vertical axis represents crank angle 6 (deg.) of the crankshaft 5. The terms of "exhaust start", "exhaust end", "scavenging start", and "scavenging end" shown in FIG. 11 are the same as those shown in FIG. 4, so the description thereof will be omitted herein. The curve L is a characteristic curve showing an optimum closing timing of a fuel injection valve to be required by the engine 1, and the curve M is a characteristic curve showing a closing timing inherent to the poppet valve 20. As mentioned with reference to FIG. 10, the timing of pressurizing a mixture gas changes with a change in rotating speed of the crankshaft 5, so that the closing timing characteristic of the poppet valve 20 can be changed. As mentioned with reference to FIG. 8, the drive grooves 84a are curved grooves extending radially so as to be arcuate in the rotational direction R of the drive coupling 84. The balls 86 are moved in the arcuate drive grooves 84a by a centrifugal force according to the rotating speed of the crankshaft 5, thereby varying the phase between the crankshaft 5 and the driving shaft 66a. The phase is most varied at- a position where each ball 86 reaches the crest of the corresponding arcuate drive groove 84a. The rotating speed of the crankshaft 5 for generating a centrifugal force to move the balls 86 to this position corresponds to a middle rotating speed region of the crankshaft 5. Thus, the phase is largely varied in the middle rotating speed region of the crankshaft 5, so that the closing timing characteristic of the poppet valve 20 shown by the curve M can be approximated to the optimum closing timing characteristic shown by the curve L. As apparent from the above description, the operational characteristic of the poppet valve 20 can be changed according to the rotating speed of the crankshaft 5 in the second preferred embodiment. In particular, an injection ending timing in the middle rotating speed region of the crankshaft 5 can be changed. [Effect of the Invention] The present invention can exhibit the following effects by the above configurations. According to the invention as defined in claim 1, there is provided in a fuel injection type two-cycle engine including a diaphragm operated poppet valve for injecting a mixture gas obtained by a carburetor into a combustion chamber; the improvement comprising a mixture gas passage having an outlet connected to a mixture gas inlet of the poppet valve to supply the mixture gas to the poppet valve, a reciprocating piston type air pump provided in the mixture gas passage and adapted to be driven by a crankshaft as a driving source, and a pilot line for leading an outlet pressure of the air pump to a diaphragm operating port of the poppet valve. The operating pressure for the diaphragm operated poppet valve is determined by the outlet pressure ( discharge pressure) of the reciprocating piston type air pump driven by the crankshaft as a driving source. Accordingly, the operating pressure for the diaphragm can be changed according to the rotating speed of the crankshaft. That is, the poppet valve is opened by using the crankshaft as a driving source, so that a timing of injecting the mixture gas into the combustion chamber can be reliably set with a simple configuration. Accordingly, the mixture gas can be injected at a proper crank angle of the crankshaft. Further, unlike the prior art, it is unnecessary to provide a high-pressure fuel pump for supplying fuel under high pressures, a solenoid type fuel injection valve for injecting fuel, a solenoid type mixture gas closing valve for supplying a mixture gas to a combustion chamber, a control circuit for controlling the solenoid type fuel injection valve or the solenoid type mixture gas closing valve, etc. According to the invention as defined in claim 2, the fuel injection type two-cycle engine further comprises a pressure control valve provided 'in the pilot line for controlling a diaphragm operating "pressure, the pressure control valve being controlled according to an opening degree of a throttle valve. The timing of injecting the mixture gas from the poppet valve can be changed according to the opening degree-of the throttle valve with a simple configuration. In particular, an injection start timing can be changed over the substantially entire rotating speed region of the crankshaft. According to the invention as defined in claim 3, the fuel injection type two-cycle engine further comprises a phase varying mechanism provided in a driving system for the air pump, for varying a phase between the crankshaft and a driving shaft for the air pump by using a centrifugal force according to a rotating speed of the crankshaft. The timing of injecting the mixture gas from the poppet valve can be changed according to the rotating speed of the crankshaft. In particular, an injection end timing can be changed in a middle rotating speed region of the crankshaft . [Explanation of Reference Numerals] 1: engine 5: crankshaft 8: combustion chamber (main combustion chamber) 9: combustion chamber (auxiliary combustion chamber) 14: spark plug 20: diaphragm operated poppet valve 27: mixture gas inlet of the diaphragm operated poppet valve 29: diaphragm operating port 51: mixture gas passage 53: carburetor 54: reciprocating piston type air pump 64: outlet port (discharge port) of the reciprocating piston type air pump 66a: driving shaft 71: pilot line 72: pressure control valve 44, 52: throttle valve 83: phase varying mechanism WE CLAIM: 1. A fuel injection type two-cycle engine (1) having a diaphragm operated poppet valve (20) for injecting a mixture gas obtained by a carburetor (53) into a combustion chamber (8); characterized in that a mixture gas passage (51) having an outlet connected to a mixture gas inlet (27) of said poppet valve (20) is provided to supply said mixture gas to said poppet valve (20), a reciprocating piston type air pump (54) provided in said mixture gas passage (51) and adapted to be driven by a crankshaft as a driving source, and a pilot line (71) for passing an outlet pressure of said air pump to a diaphragm operating port (29) of said poppet valve. 2. The fuel injection type two-cycle engine as claimed in claim 1, wherein said pilot line (71) is provided with a pressure control valve (72) for controlling a diaphragm operating pressure. 3. The fuel injection type two-cycle engine as claimed in claim 1, wherein said air pump (54) is provided with a phase varying mechanism (83), for varying a phase between said crankshaft and a driving shaft (69). 4. A fuel injection type two-cycle engine substantially as herein described with reference to the accompanying drawings.

Documents:

1275-del-1998-abstract.pdf

1275-del-1998-claims.pdf

1275-del-1998-correspondence-others.pdf

1275-del-1998-correspondence-po.pdf

1275-del-1998-description (complete).pdf

1275-del-1998-drawings.pdf

1275-del-1998-form-1.pdf

1275-del-1998-form-13.pdf

1275-del-1998-form-19.pdf

1275-del-1998-form-2.pdf

1275-del-1998-form-3.pdf

1275-del-1998-form-4.pdf

1275-del-1998-form-6.pdf

1275-del-1998-gpa.pdf

1275-del-1998-petition-137.pdf

1275-del-1998-petition-138.pdf