A FUEL INJECTION SYSTEM FOR A DIRECT INJECTION INTERNAL COMBUSTION ENGINE AND A METHOD OF CONTROL THEREOF

FIELD OF THE INVENTION

[001] The present invention generally relates to a direct injection internal combustion engine. More particularly, the present invention relates to a fuel injection system of a direct injection internal combustion engine and method of control thereof.

BACKGROUND OF THE INVENTION

[002] Generally, in Gasoline Direct Injection engines, one of the primary components is the high-pressure fuel supply system. The high-pressure fuel is supplied in order to achieve the required injection characteristics such as droplet size, droplet penetration, atomization, fuel- air mixing characteristics and so on. However, in vehicles with a single cylinder engine, due to the small size of the single-cylinder engine, it is an ergonomic challenge to mount a fuel pump onto the cylinder head and to extend a mechanical drive to the mounting position of the fuel pump so as to drive the fuel pump by the crankshaft or camshaft. Also, one of the primary constraints in providing a direct injection system in a single cylinder engine is that the high-pressure fuel supply system must match the fuel flow requirement of the singlecylinder small-bore engine while maintaining the fuel pressure in a fuel reservoir.

[003] In existing direct injection systems, the fuel rails designed are specifically for multicylinder engines and as a result, are bulky. Especially in single cylinder engines, if the fuel pump output is directly connected to the injector, the result is high pressure fluctuations during fuel pumping and fuel injection. The fuel injection pressure needs to be closely monitored and the fluctuations must be minimum to avoid high cycle to cycle variations.

[004] Existing attempts for providing a direct injection engine have only been made in relation to multi cylinder engines, as multi cylinder engines have lower mounting constraints owing to greater mounting space available, provision of double overhead cams in certain cases, the multi cylinder engine being a V type engine allowing greater mounting flexibility, and similar other factors. Provision of a direct injection system on a single cylinder engine is thus, a challenge since the available mounting space for different components is significantly lower and the providing drive to the fuel pump remains a challenge with fewer engine components and smaller engine size.

[005] Thus, there is a need in the art for a fuel injection system for a direct injection internal combustion engine and a method of control thereof, which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION

[006] In one aspect, the present invention is directed towards a fuel injection system for a direct injection internal combustion engine. The fuel injection system has a fuel pump mounted on a cylinder head of the direct injection internal combustion engine. The fuel pump is driven by a camshaft of the direct injection internal combustion engine. The system further has a fuel reservoir provided in fluid communication with the fuel pump. The fuel reservoir is supported on the cylinder head and is configured for storing fuel received from the fuel pump. The system further has an injector for receiving fuel from the fuel reservoir and injecting the fuel into a combustion chamber of the direct injection internal combustion engine. The injector is supported on the fuel reservoir. [007] In an embodiment of the invention, a central axis of the fuel reservoir is in line with a central axis of the injector.

[008] In a further embodiment of the invention, the fuel system has an eccentric cam lobe mounted on the camshaft in connection with a cam chain sprocket. The eccentric cam lobe drives the fuel pump.

[009] In a further embodiment of the invention, the eccentric cam lobe is configured such that the eccentric cam lobe causes a plunger of the fuel pump to operate during an expansion stroke and an exhaust stroke of the direct injection internal combustion engine.

[010] In another embodiment of the invention, the fuel injection system has a base plate attached to the cylinder head, a hollow tubular member supported on the base plate. The hollow tubular member supports the fuel pump and allows the eccentric cam lobe to pass through for connecting the fuel pump to the camshaft.

[011] In a further embodiment of the invention, the fuel pump has a solenoid valve for selectively allowing fuel to pass from the fuel pump to the fuel reservoir.

[012] In another embodiment of the invention, the fuel reservoir has a top portion, a bottom portion that is connected to an inlet of the injector, and a curved portion defining a storage portion for the fuel received from the fuel pump. The curved portion has a channel for allowing fuel from the fuel pump to enter the fuel reservoir.

[013] In a further embodiment of the invention, the fuel reservoir has a substantially cylindrical shape.

[014] In a further embodiment of the invention, the fuel injection system has a fuel pressure sensor provided on the top portion of the fuel reservoir for sensing the pressure of the fuel inside of the fuel reservoir. [015] In a further embodiment of the invention, the fuel injection system has a channel connector connected to the channel on the curved portion of the fuel reservoir. The channel connector is configured to receive a tube from the fuel pump for allowing fuel to pass from the fuel pump to the fuel reservoir.

[016] In a further embodiment of the invention, the fuel injection system has a holding plate and one or more fasteners provided on the holding plate for supporting the fuel reservoir on the cylinder head.

[017] In a further embodiment of the invention, the fuel injection system is configured such that the solenoid valve of the fuel pump is opened and closed based upon the input from a cam position sensor attached to the camshaft and the fuel pressure senor inside the fuel reservoir, thus maintaining the fuel pressure inside the fuel reservoir.

[018] In a further embodiment of the invention, the pressure inside the fuel reservoir ranges between 150 bar and 500 bar.

[019] In another aspect, the present invention relates to a method of fuel injection control in a fuel injection system of a direct injection internal combustion engine. The method has the steps of sensing position of a camshaft; receiving by a control unit, the position of the camshaft; measuring the fuel pressure inside the fuel reservoir; receiving, by the control unit, the fuel pressure inside the fuel reservoir; controlling magnitude of opening of the fuel pump based on the fuel pressure inside the fuel reservoir and position of the camshaft; and controlling timing of opening of the fuel pump based on the fuel pressure inside the fuel reservoir and position of the camshaft.

[020] In an embodiment of the invention, the cam position sensor is synchronized with a crank position sensor in the internal combustion engine. [021] In a further embodiment of the invention, the fuel pump has a solenoid valve, wherein the magnitude of opening of the solenoid valve, and timing of the opening of the solenoid valve are configured to be controlled by the control unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[022] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.

Figure 1 illustrates a perspective view of a fuel injection system of a direct injection internal combustion engine, in accordance with an embodiment of the present invention.

Figure 2 illustrates a top view of the fuel injection system, in accordance with an embodiment of the present invention.

Figure 3A illustrates a section line A-A’ and Figure 3B illustrates a sectional view along section line A-A’ of the fuel injection system, in accordance with an embodiment of the present invention.

Figure 4 illustrates a fuel pump of the fuel injection system in the direct injection internal combustion engine, in accordance with an embodiment of the present invention.

Figure 5 illustrates an eccentric cam lobe of the fuel injection system, in accordance with an embodiment of the present invention.

Figure 6 illustrates variation in lift of a fuel pump with respect to crank angle, in accordance with an embodiment of the present invention. Figure 7 illustrates a perspective view of the fuel pump of the fuel injection system, in accordance with an embodiment of the present invention.

Figure 8 illustrates a base plate of the fuel injection system, in accordance with an embodiment of the present invention,

Figure 9 illustrates a hollow tubular member of the fuel injection system, in accordance with an embodiment of the present invention.

Figure 10 illustrates a fuel reservoir and an injector of the fuel injection system, in accordance with an embodiment of the present invention.

Figure 11 illustrates a perspective view of the fuel reservoir of the fuel injection system, in accordance with an embodiment of the present invention.

Figure 12 illustrates a perspective view of a holder member of the fuel injection system, in accordance with an embodiment of the present invention.

Figure 13 illustrates method steps involved in a method for control for the fuel injection system of the direct injection internal combustion engine, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[023] The present invention generally relates to a direct injection internal combustion engine. More particularly, the present invention relates to a fuel injection system of a direct injection internal combustion engine and method of control thereof. In an embodiment, the vehicle is a saddle type vehicle. In another embodiment, the vehicle is a three-wheeled passenger or cargo vehicle. In another embodiment, the vehicle is a four-wheeled vehicle.

[024] Figures 1 and 2 illustrate a fuel injection system 100 for a direct injection internal combustion engine 60, in accordance with an embodiment of the invention. As illustrated, the fuel injection system 100 has a fuel pump 1 10 for receiving fuel from the fuel tank 40 and pumping the same into the internal combustion engine 60 for combustion. As illustrated, the fuel pump 110 is mounted on a cylinder head 62 of the direct injection internal combustion engine 60. The fuel pump 110 is driven by a camshaft 64 (shown in Figure 4) of the direct injection internal combustion engine 60. Mounting of the fuel pump 110 on the cylinder head 62 itself, ensures that mounting of the fuel pump 110 is allowed in the limited mounting space available in the direct injection internal combustion engine 60, especially in the embodiment wherein the direct injection internal combustion engine 60 is a single cylinder type engine.

[025] The fuel injection system 100 further comprises a fuel reservoir 130 that is provided in fluid communication with the fuel pump 110. Herein, the fuel reservoir 130 is supported on the cylinder head 62. The fuel reservoir 130 is configured for storing fuel received from the fuel pump 110. Herein, in an embodiment, the fuel reservoir 130 is high pressure fuel reservoir capable of storing fuel at a high pressure. In an embodiment, the pressure of the fuel inside the fuel reservoir ranges from 150 bar to 500 bar.

[026] The fuel injection system 100 further has an injector 150 for receiving fuel from the fuel reservoir 130 and injecting the fuel into a combustion chamber 66 (shown in Figure 3B) of the direct injection internal combustion engine 60. The droplet size of the fuel entering the direct injection internal combustion engine 60 is driven by the pressure of the fuel inside the fuel reservoir 130 that is being sent to the injector 150. Herein, the injector 150 is supported on the fuel reservoir 130. Such a provision of the fuel reservoir 130 acting as a reservoir for the fuel received from the fuel pump 110 while also acting as a support for the injector 150 ensures that no separate mounting provision needs to be made for the injector 150, thus making the packing more compact while ensuring fewer number of parts required in the assembly of the fuel injection system 100. In an embodiment as referenced in Figure 10, a central axis (X-X’) of the fuel reservoir 130 is in line with a central axis (Y-Y’) of the injector 150. This allows sturdier mounting of the injector 150 on the fuel reservoir 130 while ensuring smooth flow of fuel from the fuel reservoir to the injector 150.

[027] Figure 4 illustrates the fuel pump 110 being driven by the camshaft 64 in accordance with an embodiment of the invention. The fuel injection system 100 comprises an eccentric cam lobe 68 (shown in Figure 5) that mounted on the camshaft 64 for driving the fuel pump 1 10. In an embodiment, the eccentric lobe 68 is provided in connection with a cam chain sprocket 70, that is location pin provided on the camshaft 64 for the cam chain sprocket 70 is also used for locating the eccentric cam lobe 68 and the fasteners used for mounting the cam chain sprocket 70 are also used as the fasteners for mounting the eccentric cam lobe 68, thereby removing the requirement of any additional components to mount the eccentric cam lobe 68 on the camshaft 64.

[028] In an embodiment, the eccentric cam lobe 68 is configured in such a manner that that the eccentric cam lobe 68 causes a plunger of the fuel pump 110 to operate during an expansion stroke and an exhaust stroke of the direct injection internal combustion engine 60. This means that the configuration of the eccentric cam lobe 68 allow for fuel to be pressurised in the fuel pump 110 during the expansion and exhaust stroke of the engine 60. Since the fuel injection event for the direct injection engine 60 is scheduled during the intake and compression stroke of engine 60 operation, the fuel needs to be pressurized each time before the fuel injection event. Such a configuration of eccentric cam lobe 68 by which fuel is pressurised during the expansion and exhaust stroke of the engine 60, helps in developing the required pressure for the fuel injection right before the fuel injection event. Also, by way of such a configuration, the fuel pumping event in the fuel pump 110 is offset from the injection event, which thus helps in minimizing the pressure fluctuations in the fuel reservoir 130. The timing of the pumping event during the expansion stroke which is the power stroke of a four stroke engine further results in reduction of the toque fluctuations.

[029] The variation in lift of the plunger of the fuel pump 110 with respect to the crank angle has been illustrated in Figure 6. As illustrated, the lift of the plunger of the fuel pump 110 declines during the intake and compression stroke of the engine 60, and the lift of the plunger of the fuel pump 110 is increased during the expansion and the exhaust stroke of the engine 60 meaning that the fuel is pressurised during the expansion and exhaust stoke of the engine 60. In an embodiment, the fuel pump 110 further comprises a solenoid valve for selectively allowing fuel to pass from the fuel pump 110 to the fuel reservoir 130.

[030] In an embodiment as illustrated in Figure 7, for mounting of the fuel pump 110 of the cylinder head 62, the fuel injection system 100 comprises a base plate 112 that attached to the cylinder head 62 and a hollow tubular member 114 that supported on the base plate 112. The hollow tubular member 114 supports the fuel pump 110. In addition, the hollow tubular member 114 allows the eccentric cam lobe 68 to pass through for connecting the fuel pump 1 10 to the camshaft 64. In an embodiment, the base plate 112 and the hollow tubular members 114 have through holes that align with corresponding through holes provided on the cylinder head 62 for fasteners to pass through for mounting of the fuel pump 110 on the cylinder head 62. In an embodiment, the fasteners that are provided in the engine 60 for mounting of a cylinder head cover are used as the fasteners for mounting of the fuel pump 1 10 on the cylinder head 62, thereby removing the requirement of any additional fasteners for mounting the fuel pump 110 on the cylinder head 62.

[031] Reference is made to Figure 10 and 1 1 , wherein as illustrated the fuel reservoir 130 comprises a top portion 132, a bottom portion 134 and a curved portion 136. The bottom portion 134 of the fuel reservoir is connected to an inlet of the injector 150, while the outlet of the injector 150 is connected to the combustion chamber 66 of the engine 60, thereby completing the support of the injector 150. The curved portion 136 defines a storage portion for the fuel received from the fuel pump 110. Due to this, in an embodiment, the fuel reservoir 130 has a substantially cylindrical shape. Further, the curved portion 136 has a channel 138 for allowing fuel from the fuel pump 110 to enter the fuel reservoir 130.

[032] As further illustrated in Figure 10, the fuel injection system 100 further has a fuel pressure sensor 142 that is provided on the top portion 132 of the fuel reservoir 130. The fuel pressure sensor 142 senses the pressure of the fuel inside of the fuel reservoir 130.

[033] As further illustrated in Figure 11 , the fuel injection system 100 has a channel connector 140 that is connected to the channel 138 on the curved portion 136 of the fuel reservoir 130. The channel connector 140 is configured to receive a tube 144 from the fuel pump 110 for allowing fuel to pass from the fuel pump 1 10 to the fuel reservoir 130.

[034] For mounting the fuel reservoir 130 on the cylinder head 62, as illustrated in Figure 12, the fuel injection system 100 comprises a holding plate 146 and one or more fasteners 148 provided on the holding plate 146. The holding plate 146 has through holes which align with corresponding through holes on the cylinder head 62, that allow fasteners to pass through, thereby supporting the fuel reservoir 130 on the cylinder head 62.

[035] Further, in an embodiment, the fuel injection system 100 is configured such that the solenoid valve of the fuel pump 110 is opened and closed based upon the input from a cam position sensor attached to the camshaft 64 and the fuel pressure senor 142 inside the fuel reservoir 130, thus maintaining the fuel pressure inside the fuel reservoir 130, as further explained hereinbelow.

[036] In another aspect, the present invention relates to a method of fuel injection control 200 in a fuel injection system 100 of a direct injection internal combustion engine 60. As illustrated in Figure 13, at step 2A, position of the camshaft 64 is sensed by the cam position sensor (not shown). At step 2B, information on the position of the camshaft 64 is received by a control unit (not shown). At step 2C, pressure inside the fuel reservoir 130 is measured by means of the fuel pressure sensor 142. At step 2D, information on the fuel pressure inside the fuel reservoir 130 is received by the control unit. At step 2E, magnitude of opening of the fuel pump 110 is controlled based on the fuel pressure inside the fuel reservoir 130 and position of the camshaft 64. Further at step 2E, timing of opening of the fuel pump 110 is controlled based on the fuel pressure inside the fuel reservoir 130 and position of the camshaft 64. Thus, the amount of fuel being transferred from the fuel pump 110 to the fuel reservoir 130 is controlled based on the fuel pressure inside the fuel reservoir 130 and position of the camshaft 64, which ensures stable pressure inside the fuel reservoir 130 during all operation cycles of the direct injection internal combustion engine 60.

[037] Herein, in an embodiment the cam position sensor is in synchronisation with a crank position sensor provided in the direct injection internal combustion engine 60 thus ensuring that there is no mismatch between the operation cycle of engine 60 and operation of the fuel pump 110 to allow fuel transfer between the fuel pump 110 and the fuel reservoir 130.

[038] In another embodiment, the fuel pump 110 comprises a solenoid valve which can be electronically opened or closed by the control unit. Herein the magnitude of opening of the solenoid valve, and timing of the opening of the solenoid valve are configured to be controlled by the control unit.

[039] Advantageously, the present invention allows for a fuel injection system for a direct injection internal combustion engine in which the fuel pump and the fuel reservoir are mounted directly on the cylinder head, thus allowing for a compact mounting. Such a configuration allows the fuel injection system for the direct injection internal combustion engine to be adapted to single cylinder type direct injection internal combustion engine.

[040] Further, the number of parts required for assembly of the fuel injection system of the present invention would be much lower than convention assemblies since fuel reservoir acts as a support for the fuel injector and the fasteners used for mounting the fuel pump are the fasteners used for mounting the cylinder head cover. The number of parts is further reduced by the fact that the eccentric cam lobe is mounted using the fastener and spacer used for mounting cam chain sprocket on the camshaft. The lower number of parts results in lower cost and ease of manufacturing.

[041] Further, the control method employed in the present invention and operation of the plunger of the fuel pump in exhaust and expansion strokes ensures minimization of pressure fluctuations in the fuel reservoir. The timing of the pumping event during the expansion stroke which is the power stroke of a four stroke engine further results in reduction of the toque fluctuations

[042] Further, provision of fuel injection system which allows for a single cylinder type engine to be a direct injection internal combustion engine, ensures better engine performance.

[043] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.