FUEL INJECTION SYSTEM OF A VEHICLE

TECHNICAL FIELD

The present subject matter described herein, in general, relates to a fuel injection system of a vehicle and in particular, relates to a variable pressure fuel injection system with a fuel injector mounted on the cylinder head of an internal combustion engine of a vehicle.

BACKGROUND

A fuel management system for an internal combustion engine includes a fuel injection system that replaces a carburetor to meter the required quantity of air and fuel to the engine.

Among various injection systems, a port injection (PI) system is commonly used in vehicles. In a PI system, fuel is injected into an intake manifold of an air intake system of a vehicle at a standard injection pressure. Conventionally, in a PI system, a fuel injector is mounted on the inlet manifold of the engine cylinder. Such an arrangement of the fuel injector causes wetting of the walls of the inlet port or the manifold by the injected fuel. This wall wetting process leads to unburned hydrocarbon emission in the exhaust. Such effects also lower the engine power and the fuel efficiency of the vehicle.

Typically, a fuel injection system employs an electronic control unit (ECU), which takes input from various sensors to determine the engine's operating condition. The fuel injection system processes the sensor inputs with respect to pre-stored data within the ECU and determines actuator parameters, such as injector opening duration, ignition timing, fuelling corrections based on the environmental condition, etc.

Generally, fuel from a fuel tank is pressurized before entering into the fuel injector. The pressure of fuel is raised by a pump that is powered by a DC motor. Due to fluctuations in the voltage supplied to the DC motor, there are fluctuations in the pressure of fuel supplied to the fuel injector. Typically, a fuel pressure regulator is located in line with the fuel injector to overcome such fluctuations and to supply fuel at a desired pressure to the fuel injector.

Typical mechanical fuel pressure regulators utilizes a spring with a known spring rate in the air reference chamber of the fuel pressure regulator in order to maintain a constant fuel pressure across the fuel injector for different operating conditions of the vehicle. However, as a result of maintaining a constant fuel pressure across the fuel

injector by using such a mechanism, there remains a possibility of insufficient mixing of the fuel with air in the engine cylinder. This may lead to a reduced power output developed by the engine, thereby reducing the fuel efficiency and fuel economy of the vehicle. Moreover, inappropriate air-fuel mixture lowers the performance and reliability of the engine in addition to increased amount of emissions.

Further, during different engine states, such as running, cranking, idling and wide open throttle, the emissions in terms of Hydro-Carbon (HC) and Carbon monoxides (CO) needs to be minimized, and also an operator economic feature of increasing fuel economy should be achieved. Typically, during the operation of an internal combustion engine, with reduction in

HC emissions, there is a substantial increase in CO emissions and vice versa. This is usually a trade-off that engine programmers have to resort to, during the programming of an ECU, in order to balance the engines' overall fuel efficiency.

However, the emissions requirements are getting stringent with legislation and there is a latent requirement not only to maximize on the reduced emissions but also to increase fuel efficiency of the internal combustion engine. SUMMARY

The subject matter described herein is directed to a variable pressure fuel injection system of a vehicle. In one embodiment, the variable pressure fuel injection system includes a fuel inlet line, a fuel outlet line, a cylinder head, and a fuel injector mounted on the cylinder head. The fuel injector is hydraulically connected to the fuel inlet line and has a fuel injector axis along its centre. The fuel injector has at least one orifice adapted to spray a fuel stream at a pre determined pressure and velocity. The fuel stream defines a cone angle α and has a central axis. The central axis forms a bent angle β with the fuel injector axis. A fuel pressure regulator is provided in line between a fuel pump and the fuel injector. The fuel pressure regulator has a fuel chamber and an air chamber. The fuel chamber is hydraulically connected to the fuel inlet line and the fuel outlet line. The fuel chamber houses a movable pressure plate assembly for controlling the fuel flow from the fuel inlet line to the fuel outlet line. The fuel injector is capable of rotation along the fuel injector axis such that the orifice is capable of achieving a maximum rotational angle λ at pre determined angles α and β and the fuel stream enters into the engine by hitting the rear of an inlet valve without wetting walls of the fuel inlet line. In addition, an air source is provided that is hydraulically connected to the air chamber. A communicating device

communicates the air source with the air chamber. An electronic control unit controls the communicating device based on different operating conditions of the vehicle, thereby providing variable air pressure in the air chamber at different operating conditions of the vehicle. In another embodiment, the variable fuel pressure injection system includes a electronic fuel pressure regulator that hydraulically connects the fuel inlet line and the fuel outlet line. The electronic fuel pressure regulator includes a housing having an inlet chamber and an outlet chamber. The inlet chamber is connected to the inlet line and the outlet chamber is connected to the outlet line. An actuator assembly having an armature and a coil is provided. The armature is capable of reciprocating whereas the coil encloses the armature. The actuator assembly also includes a passage that connects the inlet chamber and the outlet chamber. The armature reciprocates and regulates flow of fuel from the inlet chamber to the outlet chamber. Further, an electronic control unit energizes the coil based on different operating conditions of the vehicle. The energization of the coil provides reciprocating motion to the armature in the passage, thereby regulating fuel pressure in the fuel injector at different operating conditions of the vehicle.

In yet another embodiment, the electronic fuel pressure regulator of the variable fuel pressure injection system includes a housing, an actuator assembly, and a pressure plate assembly. The housing has an actuator chamber and a fuel chamber that are separated by a diaphragm. The fuel chamber connects the fuel inlet line and the fuel outlet line. The actuator assembly is disposed in the actuator chamber and includes a movable armature assembly and a coil enclosing the armature assembly. The pressure plate assembly is disposed in the actuator chamber and is attached to the armature assembly for regulating the flow of fuel from the inlet line to the outlet line. An electronic control unit energizes the coil based on different operating conditions of the vehicle and thereby reciprocates the armature in the passage to regulate the fuel pressure across the fuel injector at different operating conditions of the vehicle.

The electronic control unit (ECU) as described in the previous embodiments operates the fuel injector and the fuel pressure regulator with the help of inbuilt data sets and evaluating modules. A first data set and a second data set provide relationship between engine speed and engine load. The first data set identifies the values for the required quantity of fuel to be injected in the intake manifold at different operating conditions of the vehicle. Similarly, the second data set identifies the differential pressure of the fuel

across the fuel injector at different operating conditions of the vehicle. A third data set is provided within the ECU that identifies multiple gain values based on the different differential pressures in the second data set.

The outputs from the first data set and the third data set are utilized by a first evaluating module for generating an output signal corresponding to the duration of fuel injector opening for a particular operating condition. Likewise, the output from the second data set along with intake manifold pressure value is utilized by a second evaluating module for generating an output signal corresponding to the pressure of fuel required within the fuel injector for a particular operating condition. The above mentioned features of the fuel pressure system provide flexibility to vary the fuel efficiency and the CO emission for any vehicle. The fuel injection system of the present subject matter is calibrated in such a manner that it can be tuned for better fuel efficiency and reduced CO emissions in order to suite the regulations of various governments or to suite any market in the world. These and other features, aspects, and advantages of the present subject matter will become better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The above and other features, aspects, and advantages of the subject matter will become better understood with regard to the following description, appended claims, and accompanying drawings where: Fig. 1 illustrates a schematic representation of a variable pressure fuel injection system of a vehicle.

Fig. 2 illustrates a block diagram of a variable pressure fuel injection system of a vehicle in accordance with one embodiment of the present subject matter.

Fig. 3 illustrates a fuel pressure regulator of the variable pressure fuel injection system of Fig. 2.

Fig. 4 illustrates a variable pressure fuel injection system having an electronic fuel pressure regulator in accordance with another embodiment of the present subject matter.

FIG. 5 illustrates a sectional view of a fuel pressure regulator of the variable pressure fuel injection system of Fig. 4 according to a first embodiment of the present subject matter.

FIG. 6 illustrates a sectional view of a fuel pressure regulator of the variable pressure fuel injection system of Fig. 4 according to a second embodiment of the present subject matter. FIG. 7 shows a sectional view of a fuel pressure regulator of the variable pressure fuel injection system of Fig. 4 according to a third embodiment of the present subject matter.

Fig. 8 illustrates a sectional view of a fuel injector mounted on a cylinder head of a fuel injection system.

Fig. 9 illustrates a sectional view of a fuel injector mounted within an injector sleeve on a cylinder head.

Fig. 10 illustrates a perspective view of a fuel injector mounted within an injector sleeve depicting a rotational angle of the fuel injector.

Fig. 11 illustrates a variable pressure regulation system implemented in an electronic control unit for controlling a fuel injector and a fuel pressure regulator in one embodiment of the present subject matter.

DETAILED DESCRIPTION:

The subject matter relates to a variable pressure fuel injection system for a vehicle. The present subject matter combines the features of both the fuel injector mounted directly on a cylinder head, and variable pressure fuel delivery across a fuel injector. The positive and desirable features of each method mentioned above are utilized by mapping the engine in all the states of the engine. Appropriate controlling strategies within an ECU are performed to derive the maximum positive effect of both the features as described above.

Described herein is a variable pressure fuel injection system with a fuel injector mounted on a cylinder head of an internal combustion engine of a vehicle. The fuel injection system utilizes an electronic control unit for electronically controlling the fuel pressure across the fuel injector. The pressure of fuel can be controlled by controlling the air pressure or the fuel pressure in different embodiments of the present subject matter. By varying the fuel pressure across the fuel injector, there is a substantial reduction in the carbon monoxide emission. Additionally, the fuel injector is mounted on the cylinder head of the engine in such a way that the wetting of walls of the cylinder head is substantially reduced, thereby improving the fuel efficiency.

Fig. 1 illustrates a schematic representation of a variable pressure fuel injection system 100 of a vehicle. The variable pressure fuel injection system 100 has a central

component called an electronic control unit (ECU) 102 to determine different operating conditions of the vehicle. The ECU 102 takes inputs from various sensors provided at different locations in the vehicle and processes the sensor inputs with respect to pre-stored data within the ECU 102. The ECU 102 actuates a fuel injector 104 of the variable pressure fuel injection system 100, thereby controlling various parameters like fuel injector opening duration, ignition timing, etc. In order to control variable fuel pressure across the fuel injector 104 for different operating conditions of the vehicle, an electronically controlled fuel pressure regulator 106 is provided in line between a fuel tank 108 and the fuel injector 104. Fuel from the fuel tank 108 is pressurized by a fuel pump 110 before entering into the fuel injector 104. The fuel injector 104 is mounted on a cylinder head 112 of an internal combustion engine 114 and injects fuel into the engine by hitting the rear of the inlet valve without wetting walls of the inlet line. The fuel mixes with air coming from an air supply 116 in order to create a stoichiometric air-fuel mixture in the combustion chamber of the engine 114.

Various sensors are provided in the variable pressure fuel injection system 100 for determining various operating conditions, such as load acting on the engine and speed of the engine. A throttle position sensor (TPS) 118 is provided in an intake manifold 120 of the engine 114 that determines the load acting on the engine 114. However, the speed of the engine 114 is determined by a crankshaft position sensor 122 provided in the engine cylinder. The ECU 102 takes into account the outputs from the TPS 118 and the crankshaft position sensor 122 in order to operate the fuel injector 104 and the fuel pressure regulator 106.

Fig. 2 illustrates a block diagram of a variable pressure fuel injection system 200 of a vehicle in accordance with one embodiment of the present subject matter. The variable pressure fuel injection system 200 mainly includes a fuel inlet line 202, a fuel outlet line 204, a communicating device 206, an air source 208 in addition to the fuel injector 104, and the fuel pressure regulator 106. Fuel at a low pressure is stored in the fuel tank 108. The fuel pump 110 pressurizes the fuel in the fuel tank 108 and supplies high pressure fuel to the fuel injector 104. In one embodiment, the fuel injector 104 is mounted on the intake manifold 120 of the engine and injects fuel directly into the intake manifold 120. The fluctuation occurring in the fuel pressure due to variations in the voltage supplied to the fuel pump 110 are overcome by the fuel pressure regulator 106.

The fuel pressure regulator 106 is a mechanical fuel pressure regulator that is divided into a fuel chamber 210 and an air chamber 212. The fuel chamber 210 is connected to the fuel inlet line 202 and the fuel outlet line 204. Fuel from the fuel pump 110, at a certain forward pressure, enters the fuel chamber 210 of the fuel pressure regulator 106. The fuel pressure regulator 106, in its closed state, creates a back pressure in the fuel inlet line 202. The difference between the forward pressure and the back pressure in the fuel inlet line 202 facilitates the flow of the fuel at a required pressure to the fuel injector 104.

A pressure sensor 214 is provided in the fuel inlet line 202 to calculate the pressure of the fuel in the fuel inlet line 202. The pressure sensor 214 sends signals, corresponding to the fuel pressure in the fuel inlet line 202, to the ECU 102. The ECU 102 in turn actuates the communicating device 206 and controls the communicating device 206 precisely. The communicating device 206 is connected to the air source 208 and the air chamber 212 of the fuel pressure regulator 106. The communicating device 206 provides additional air with positive variable pressure to the air chamber 212 of the fuel pressure regulator 106. In one embodiment, the communicating device 206 can be an actuator.

The purpose of the communicating device 206 is to open or close the passage between the air source 208 and the air chamber 212 of the fuel pressure regulator 106. The communicating device 206 also serves the purpose of reducing pressure within the air chamber 212 by bleeding out excess air to ambient or to the low pressure side of the engine 114 due to the vacuum created in the suction stroke.

Additionally, based on the engine requirement and based on known engineering concepts and/or routine experimentation, the communicating device 206 can be operated by appropriate methods to increase or to decrease the air reference pressure, and hence the fuel pressure.

In one embodiment, the air source 208 can be the exhaust gas expelled from the combustion chamber of the internal combustion engine 114 during compression stroke. In another embodiment, the air source 208 can be an external compressor.

Fig. 3 illustrates the fuel pressure regulator 106 of the variable pressure fuel injection system 200 of Fig. 2. As shown herein, the fuel chamber 210 and the air chamber 212 of the fuel pressure regulator 106 are separated by a diaphragm 300. The fuel chamber 210 has a fuel inlet 302 and a fuel outlet 304 connected to the fuel inlet line 202 and the fuel outlet line 204, respectively. In the closed position of the fuel pressure regulator 106, the fuel outlet 304 is closed by a pressure plate assembly 306. The pressure plate assembly

306 covers the fuel outlet 304, thereby restraining the flow of the fuel from the fuel inlet 302 to the fuel outlet 304. The pressure plate assembly 306 is housed in the fuel chamber 210 and is attached to the diaphragm 300. The minimum fuel pressure in the fuel inlet line 202 is defined by a spring 308 provided in the air chamber 212 of the fuel pressure regulator 106. The spring 308 is a pre-stressed compression spring and biases the diaphragm 300 towards the fuel chamber 210, thereby pressing the pressure plate assembly 306 against the fuel outlet 304 of the fuel chamber 210. The air chamber 212 has an air inlet 310 that is hydraulically connected to the communicating device 206. The communicating device 206 facilitates variations in the air pressure within the air chamber 212 in order to match with the varying fuel pressure in the fuel inlet line 202, and hence to vary the differential fuel pressure across the fuel injector 104.

With the reduction in the fuel pressure in the fuel inlet line 202 below a predetermined threshold value for a specific operating condition of the vehicle, the pressure sensor 214 sends a signal to the ECU 102. The signal sent by the pressure sensor 214 corresponds to the magnitude of pressure required in the fuel inlet line 202 for that operating condition of the vehicle. The ECU 102, on receiving such a signal from the pressure sensor 214, actuates the communicating device 206. In one embodiment, appropriate control strategies are developed within the ECU 102 to ensure appropriate gain values for different operating conditions of the vehicle. The communicating device 206, on receiving such signals, opens the passage between the air source 208 and the air chamber 212 of the fuel pressure regulator 106. The opening of the communicating device 206 corresponds to the difference in the threshold pressure and the actual pressure in the fuel inlet line 202. The opening of the passage increases the air pressure in the air chamber 212 of the fuel pressure regulator 106. The supply of air with additional pressure into the air chamber 212 exerts an additional load on the diaphragm. This increase in the load acting on the diaphragm 300 pushes the diaphragm 300 as well as the pressure plate assembly 306 towards the fuel outlet 304, thereby closing the fuel outlet 304. This results in an increase in the fuel pressure in the fuel inlet line 202. On the other hand, when the fuel pressure in the fuel inlet line 202 exceeds the predetermined threshold value for a specific operating condition of the vehicle, the excess pressure is reduced by reducing the air pressure in the air chamber 212 of the fuel pressure regulator 106. The ECU 102, on receiving such a signal from the pressure sensor 214, actuates the communicating device 206. The communicating device 206 in turn reduces

the opening of the air passage between the air source 208 and the air chamber 214 of the fuel pressure regulator 106. This reduces the air pressure in the air chamber 212, and hence the load acting on the diaphragm 300. The decrease in load on the diaphragm 300 allows the diaphragm 300 and the pressure plate assembly 306 to lift up due to the increased fuel pressure in the fuel chamber 210. The lifting of the pressure plate assembly 306 allows the fuel with excess pressure to drain out of the fuel outlet 304 into the fuel tank 108, thereby decreasing the fuel pressure in the fuel inlet line 202. Once the fuel pressure in the fuel chamber 210 and the air pressure in the air chamber 212 are equal, the pressure plate assembly 306 moves down to close the fuel outlet 304. The opening of the passage corresponds to the difference in the threshold pressure and the actual pressure in the fuel inlet line 202. This causes the air pressure in the air chamber 212 to increase. In such a case, in addition to the spring load, the load acting on the diaphragm 300 increases. This increase in the load on the diaphragm 300 pushes the diaphragm 300 and the pressure plate assembly 306 towards the fuel outlet 304, thereby closing the fuel outlet 304 and in turn increasing the fuel pressure in the fuel inlet line 202. In another embodiment, as shown in Fig. 4, a variable pressure fuel injection system 400 having an electronic fuel pressure regulator 106 can be used to vary the pressure of fuel across the fuel injector 104.

The variable pressure fuel injection system 400, of the present embodiment, utilizes a control system for regulating the fuel pressure to be injected into the internal combustion engine 114. The control system includes the fuel pressure regulator 106, the ECU 102, and a pressure sensor 402.

Fuel pressure regulation is mainly controlled by employing the fuel pressure regulator 106, which is electronically controlled by the ECU 102. The ECU 102 is aided by the pressure sensor 402 that monitors the pressure of the fuel from the fuel pump 110 entering into the fuel injector 104.

The fuel pump 110 pumps the fuel from the fuel tank 108 into the fuel injector 104 and the fuel pressure regulator 106. The fuel, pumped by the fuel pump 110, is at a certain pressure, called as forward fuel pressure. Subsequently, when the fuel approaches the fuel injector 104, it experiences a backward fuel pressure due to the closed state of the injector 104. The fuel with a pressure equal to the difference of the forward and backward fuel pressures enters the fuel pressure regulator 106.

The pressure sensor 402 is provided in line between the fuel pump 110 and the fuel injector 104 to constantly monitor the fuel pressure entering into the fuel injector 104.

Whenever the pressure of the fuel entering the fuel injector 104 exceeds a certain predetermined threshold value, the pressure sensor 402 alerts the ECU 102. On receiving an alert signal from the pressure sensor 402, the ECU 102 communicates with the fuel pressure regulator 106. Depending upon the magnitude of rise in fuel pressure beyond the threshold value, the fuel pressure regulator 106 allows the excess fuel to drain into the fuel tank 108. This leads to a reduction in the back fuel pressure, thereby reducing the pressure of fuel entering the fuel injector 104. The fuel pressure regulator 106, along with the fuel tank 108 and the fuel pump 110, forms a closed loop to achieve the desired fuel pressure, which constantly varies ' according to the operating conditions, such as engine speed and engine load.

FIG. 5 illustrates a sectional view of the fuel pressure regulator 106 of the variable pressure fuel injection system 400 of Fig. 4 according to a first embodiment of the present subject matter. The fuel pressure regulator 106 is hydraulically connected to the fuel inlet line 202 and the fuel outlet line 204. The fuel pressure regulator 106 of the present embodiment is configured as a solenoid valve. The fuel pressure regulator 106 includes a housing 500 having an inlet chamber 502, an outlet chamber 504, and a passage connecting the inlet chamber 502 and the outlet chamber 504. The inlet chamber 502 is connected to the fuel inlet line 202 whereas the outlet chamber 504 is connected to the fuel outlet line 204. In the present embodiment, the housing 500 is a two piece assembly having a cap 506 and a mounting block 508. However, in another embodiment, the housing 500 can be a single piece in structure. The fuel pressure regulator 106 further comprises an actuator assembly having a coil 510 and a movable armature 512 enclosed within the coil 510. The movable armature 512 is provided in the passage connecting the inlet chamber 502 and the outlet chamber 504 and controls the flow of the fuel from the inlet chamber 502 to the outlet chamber 504.

The fuel pressure regulation is achieved by energizing the coil 510 placed within the cap 506. When the pressure in the line between the fuel pump 110 and the fuel injector 104 raises above a threshold value, the pressure sensor 402 measures this pressure and immediately sends corresponding signals to the ECU 102. The ECU 102, on receiving such signals from the pressure sensor 402, energizes the coil 510, thereby resulting in the reciprocating movement of the movable armature 512. The reciprocating movement of the movable armature 512 leads to opening of the passage between the inlet chamber 502 and

the outlet chamber 504, thereby leading to draining of the fuel with excess pressure back into the fuel tank 108.

FIG. 6 illustrates a sectional view of the fuel pressure regulator 106 of the variable pressure fuel injection system 400 of Fig. 4 according to a second embodiment of the present subject matter. In the present embodiment, the fuel pressure regulator 106 is configured as a stepper motor 600. The stepper motor 600 is electronically controlled by the ECU 102. The fuel pressure regulator 106 includes a fuel chamber 602 and an actuator chamber 604 separated by a diaphragm 606. The fuel inlet line 202 and the fuel outlet line 204 are provided in the fuel chamber 602 of the fuel pressure regulator 106. The movable armature 512 is disposed in the actuator chamber 604 and is coupled to a pressure plate assembly 608. The pressure plate assembly 608 is disposed in the fuel chamber 602 and controls the flow of the fuel from the fuel inlet line 202 to the fuel outlet line 204.

The fuel enters the fuel chamber 602 through the fuel inlet line 202 and is obstructed by the pressure plate assembly 608. In case the pressure of the fuel in the fuel inlet line 202 exceeds a certain predetermined value, the pressure sensor 402 senses this pressure rise and sends certain signals to the ECU 102. The ECU 102 then regulates the pressure of fuel at an optimum level by energizing the coil 510. The energizing of the coil 510 leads to the reciprocating movement of the movable armature 512. This causes the pressure plate assembly 608 to move up with the movable armature 512, leading to the opening of the fuel outlet line 204, thereby bleeding the excess fuel to the fuel tank 108.

FIG. 7 shows a sectional view of the fuel pressure regulator 106 of the variable pressure fuel injection system 400 of Fig. 4 according to a third embodiment of the present subject matter. In the present embodiment, the movable armature 512 is integrated with a metering needle 700. The metering needle 700 has a tapered end 702. The tapered end 702 of the metering needle 700 characterizes the closing for the fuel outlet line 204. The rise in the fuel pressure above a threshold value for a particular operating condition causes the lifting of the metering needle 700. The position of the tapered end 702 of the metering needle 700 determines the size of the aperture created for bleeding the fuel out to the fuel tank 108. By varying the fuel pressure across the fuel injector 104, there is a substantial reduction in carbon monoxide (CO) emission. However, the emission of hydrocarbons (HC) still needs to be controlled for enhanced fuel efficiency. The HC emission is mainly due to the wetting of the walls of the intake manifold. The wall wetting process leads to

inappropriate burning of fuel in the combustion chamber of the engine, thereby disturbing the fuel efficiency. Thus, the mounting of the fuel injector 104 is very crucial in a fuel injection system. The fuel injector 104 should be mounted in such a way so as to facilitate optimum fuel efficiency and reduced emission of unburned HC by the engine 114. For this purpose, the fuel injector 104 of the present subject matter is mounted directly on the cylinder head 112 in such a way that the wetting of walls of the cylinder head 112 is minimized.

Fig. 8 illustrates a sectional view of the fuel injector 104 mounted on the cylinder head 112 of a fuel injection system. As shown herein, a bore is drilled on the cylinder head 112 to accommodate a fuel injector sleeve 800. The fuel injector sleeve 800 is press fitted within the bore and makes an angle of less than 90 degrees with respect to a transverse axis 802 of the cylinder head 112. The fuel injector 104 is mounted within the fuel injector sleeve 800 and is adapted to receive fuel and inject the same in the form of fuel stream 804 that penetrates directly into the combustion chamber of the engine 114. In addition, an intake port 806 is provided in the cylinder head 112. One end of the intake port 806 communicates with the combustion chamber and the second end is open to draw air. An inlet valve 808 is provided within the intake port 806 to control the flow of air and fuel into the combustion chamber.

Fig 9 illustrates a sectional view of the fuel injector 104 mounted within the injector sleeve 800 on a cylinder head 112. The fuel injector 104 is adapted to receive fuel from one end and inject the same from the other end through an orifice at a pre-determined pressure and velocity. The fuel injector 104 injects fuel in the form of fuel stream 804. In one embodiment, the upper portion of the fuel injector 104 remains outside the cylinder head 112 whereas the lower portion, having the orifice, is disposed within the cylinder head 112. The positioning of the fuel injector 104 within the cylinder head 112 ensures better atomization of the fuel stream 804 entering into the combustion chamber due to high temperature within the cylinder. The fuel injector 104 has a fuel injector axis 900 along its centre. A longitudinal axis along the centre of the fuel stream 804 is defined as a central axis 902 of the sprayed fuel stream 804 hereinafter. The fuel stream 804 forms an angle when measured with respect to two outermost stream lines of the fuel stream 804. This angle is defined as a cone angle α 904. The central axis 902 of the fuel stream 804 forms a bent angle β 906 with the fuel injector axis 900. In order to substantially eliminate the wall wetting, the cone angle α 904 ranges between 9 to 15 degrees and the bent angle β 906 ranges between 13 to 23 degrees.

Fig 10 illustrates a perspective view of the fuel injector 104 mounted within the injector sleeve 800. The injector sleeve 800 includes a longitudinal axis along its center. This axis is defined as the injector sleeve axis 1000 in the present subject matter. The injector sleeve 800 is so positioned that the tip of the fuel injector 104 faces the rear of the intake port 808. The fuel injector 104 is mounted on the cylinder head 112 at the specified angles α 904 and β 906 and is capable of rotation along its own axis such that the orifice is capable of achieving a maximum rotational angle λ 1002. The rotational angle λ 1002 is defined as the angle allowed for the fuel injector 104 to rotate along the fuel injector axis 900. This positioning of the fuel injector 104 allows the fuel stream 804 to enter directly into the combustion chamber without wetting walls of the cylinder head 112. During mounting of the fuel injector 104 within the injector sleeve 800, the rotational angle λ 1002 is kept less than or equal to 18 degrees to achieve the desired result. The rotational angle λ 1002 is the summation of anticlockwise rotational angle A 1004 and clockwise rotational angle B 1006 with respect to the fuel injector axis 900. It should be noted that values of α 904, β 906 and λ 1002 are determined empirically. Engines with different constructional features will have different values of α 904, β 906 and λ 1002.

The fuel injector 104 and the fuel pressure regulator 106 as described in the previous embodiments can be operated by the ECU 102 in many ways as would be clear to a person skilled in the art. To give example, in one embodiment, various data sets and evaluating modules are provided in the ECU 102 for controlling the fuel injector 104 and the fuel pressure regulator 106.

Fig. 11 illustrates a variable pressure regulation system 1100 implemented in the ECU 102 for controlling the fuel injector 104 and the fuel pressure regulator 106 in one embodiment of the present subject matter. The variable pressure regulation system 1100 within the ECU 102 determines the duration of opening of the fuel injector 104 and the variation in the differential pressure across the fuel injector 104 at different operating conditions of the vehicle.

The variable pressure regulation system 1100 utilizes a plurality of data sets, also referred to as maps, and evaluating modules for operating the fuel injector 104 and the fuel pressure regulator 106. A fuelling data set 1102 determines the quantity of fuel, in milligrams, required to be injected into the engine 114 at different operating conditions of the vehicle. The fuelling data set 1102 is a predefined data set that depicts the relationship between load and speed of the engine at different operating conditions of the vehicle. In

one embodiment, the load on the engine 114 is determined by a load sensor disposed within a throttle body of the engine whereas the speed of the engine is determined by a speed sensor disposed at a crankshaft of the engine 114. The load sensor and speed sensor send signals corresponding to the load and the speed of the engine 114 respectively to the ECU 102 at different operating conditions of the vehicle. For a particular operating condition, a value depicting the required quantity of fuel is determined by the fuelling data set 1102.

The variable pressure regulation system 1100 further includes a fuel injection gain data set 1104 that provides different gain values for various differential pressures across the fuel injector 104. The fuel injection gain data set 1104 determines the time, in milliseconds, during which the fuel injector 104 needs to be opened in order to inject one milligram of fuel into the intake manifold 120. The fuel injection gain data set 1104 contains different gain values corresponding to various differential pressures across the fuel injector 104. A duration evaluating module 1106 determines the duration of the opening of the fuel injector 104 based on the outputs from the fuelling data set 1102 and the fuel injection gain data set 1104.

In one preferred embodiment, the differential pressure across the fuel injector 104 can be obtained with the help of a fuel pressure data set 1108 in conjunction with a manifold pressure data set 1110. The fuel pressure data set 1108 depicts the relationship between the load and the speed of the engine 114 at different operating conditions of the vehicle and indicates the operating fuel pressure value required at different speed and load values of the engine 114.

The manifold pressure data set 1110, on the other hand, indicates the value of the pressure within the intake manifold 120 at different operating conditions of the vehicle. In one embodiment, the manifold pressure data set 1110 takes input from a manifold absolute pressure (MAP) sensor provided in the intake manifold 120. The MAP sensor determines the absolute pressure within the intake manifold 120 of the engine 114 and sends the corresponding signals to the ECU 102. The difference in the outputs obtained from the fuel pressure data set 1108 and the manifold pressure data set 1110 is calculated in a fuel pressure evaluating module 1112. The fuel pressure evaluating module 1112 calculates a value corresponding to the differential fuel pressure required across the fuel injector 104 at a particular operating condition of the vehicle. Subsequently, a gain value corresponding to the value of the differential fuel pressure is selected from the fuel injection gain data set 1104.

Once the gain value from the fuel injection gain data set 1104, and the required fuel quantity value from the fuelling data set 1102 are selected, the duration of opening of the fuel injector 104 is calculated by the duration evaluating module 1106. The duration evaluating module 1106 utilizes the outputs of the fuelling data set 1102 and the fuel injection gain data set 1104 for calculating the duration of the opening of the fuel injector 104 for the particular operating condition of the vehicle. The duration evaluating module 1106 produces a signal corresponding to the calculated value of the required duration of opening of the fuel injector 104 and sends this signal to the fuel injector 104. On receiving such signal from the duration evaluating module 1106, the fuel injector 104 gets operated accordingly.

The fuel pressure data set 1108 provides the value for the fuel pressure required by the fuel injector 104 under a particular operating condition and the manifold pressure data set 1110 provides the pressure within the intake manifold 120. A fuel pressure evaluating module 1112 calculates the difference between the outputs obtained from the fuel pressure data set 1108 and the manifold pressure data set 1110 and determines a value corresponding to the fuel pressure required across the fuel injector 104 for a particular operating condition of the vehicle. The fuel pressure evaluating module 1112 produces a signal corresponding to the calculated value for the required fuel pressure and sends this signal to the variable fuel pressure unit 1114. In one embodiment, the fuel pressure unit 1114 can be a fuel pressure regulator.

The variable fuel pressure unit 1114, on receiving such signal from the fuel pressure evaluating module 1112, regulates the pressure of the fuel across the fuel injector 102.

The previously described embodiments of the present subject matter and its equivalent thereof have many advantages, including those which are described below. By regulating the fuel pressure across the fuel injector, there is a substantial reduction in CO emissions. On the other hand, by mounting the fuel injector directly on the cylinder head in the manner as described above, there is a substantial reduction in HC emissions and hence a substantial increase in the fuel efficiency. Thus, by combining the above mentioned features of the fuel pressure system, there flexibility to vary the fuel efficiency and the CO emission for any vehicle. The fuel injection system of the present subject matter is calibrated in such a manner that it can be tuned for better fuel efficiency and reduced CO emissions in order to suite the regulations of various government or to suite any market in the world.

The subject matter described above combines the positive and desirable elements and minimizes the non-desirable elements, by the use of mapping the engine in all the states of the engine. These are then converted to controlling strategies and the ECU is programmed with these strategies to derive the maximum positive effect of the features as described earlier.

Since the fuel pressure regulator and the fuel injector of the present subject matter are electronically controlled, the fuel injection system of the present subject matter gives a dynamic choice of suiting government regulations of different countries or market needs worldwide, thereby making the fuel injection system universal for any engine or vehicle. It is also experimentally observed that the fuel efficiency increases by at least 8-

9%, which is more than the combined effects of both the methods. Additionally, the control strategy within the ECU enables the reduction of HC and CO emissions while achieving the increased fuel efficiency.

Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein.