WO2008149385A1

WO2008149385A1 - Variable pressure fuel injection system of a vehicle

Info

Publication number: WO2008149385A1
Application number: PCT/IN2008/000358
Authority: WO
Inventors: K Sasikumar; K Senthur Pandian
Original assignee: UCAL FUEL SYSTEMS Ltd
Current assignee: UCAL FUEL SYSTEMS Ltd
Priority date: 2007-06-08
Filing date: 2008-06-06
Publication date: 2008-12-11
Anticipated expiration: 2009-12-08

Abstract

A variable pressure fuel injection system for regulating fuel pressure across an injector at different operating conditions of a vehicle is described herein. The variable pressure fuel injection system includes a fuel inlet line (102) for supplying fuel to the fuel injector (106) and to a fuel chamber (118) of a fuel pressure regulator (108). Fuel with extra pressure in the fuel chamber (118) is discharged back to a fuel tank (114) through a fuel outlet line (104). An air chamber (120) of the fuel pressure regulator (108) is hydraulically connected to a communicating device (110). The communicating device (110) acts as an air regulating valve between the air chamber (120) and an air source (112). An electronic control unit (124) controls the communicating device (110) precisely so that for different operating conditions of the vehicle, there are different magnitudes of air pressure in the air chamber (120) and hence different magnitudes of fuel pressure in the fuel chamber (118) of the fuel pressure regulator (108).

Description

VARIABLE PRESSURE FUEL INJECTION SYSTEM OF A VEHICLE

TECHNICAL FIELD

The subject matter described herein, in general, relates to a fuel injection system of a vehicle and in particular, relates to regulation of variable fuel pressure in a fuel injection system for different operating conditions of a vehicle.

BACKGROUND

A fuel injection system in a vehicle delivers high pressure fuel an internal combustion engine. Generally, fuel from a fuel tank is pressurized before entering into the combustion chamber of the engine. The pressure of the fuel is increased by a pump that is powered by a DC motor. Due to fluctuations in the voltage supplied by the DC motor, there are fluctuations in the pressure of the fuel supplied to the fuel injector of the fuel injection system. 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.

Conventionally, a mechanical fuel pressure regulator is configured to maintain a constant fuel pressure across the fuel injector. The mechanical fuel pressure regulator utilizes a spring with a known spring rate in the air reference chamber of the fuel pressure regulator in order to maintain the constant fuel pressure across the fuel injector for different operating conditions of the vehicle. As a result of maintaining a constant fuel pressure across the fuel injector, there is insufficient mixing of the fuel with air in the engine cylinder. This may affect the fuel efficiency and fuel economy, thereby leading to reduced power output developed by the engine. Further, inappropriate air-fuel mixture may hamper the efficiency and reliability of the engine in addition to increased amount of emissions.

SUMMARY

The subject matter described herein is directed to a variable pressure fuel injection system of a vehicle. The variable pressure fuel injection system includes a fuel inlet line and a fuel outlet line. A fuel injector is hydraulically connected to the fuel inlet line and injects the fuel into an intake manifold of an internal combustion engine. A fuel pressure regulator is also disposed in the fuel 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 said fuel inlet line and the fuel outlet line and houses a movable pressure plate assembly for controlling the fuel from the fuel inlet line and the fuel outlet line. The air chamber on the other side is hydraulically connected to an air source through a communicating device. The communicating device is controlled by an electronic control unit (ECU) and communicates the pressurized air from the air source to the air chamber.

The electronic control unit actuates the communicating device based on different operating conditions of the vehicle, thereby providing variable air pressure in the air chamber at different operating conditions. This variation in the air pressure in the air chamber causes the pressure of the fuel inlet line to vary at different operating conditions of the vehicle. These and other features, aspects, and advantages of the present subject matter will be 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 exemplarily illustrates a variable pressure fuel injection system of a vehicle in accordance with one embodiment of the present subject matter.

Fig. 2 illustrates a fuel pressure regulator of a variable pressure fuel injection system of Fig. 1.

DETAILED DESCRIPTION

A variable pressure fuel injection system of a vehicle is described herein. The variable pressure fuel injection system supplies fuel to an internal combustion engine of the engine at different pressures for different operating conditions, such as load and speed, of the vehicle. The supply of variable fuel pressure at different operating conditions of the vehicle leads to appropriate mixing of the fuel with air in a combustion chamber of the engine, thereby leading to enhanced atomization and combustion of fuel in the combustion chamber. The variable pressure fuel injection system includes a fuel inlet line for supplying fuel from a fuel tank to a fuel injector and a fuel pressure regulator. The fuel injector is controlled by an electronic control unit (ECU) and injects fuel into an intake manifold of the engine. A fuel outlet line directs the fuel with excess pressure from the fuel pressure regulator to the fuel tank. The fuel pressure regulator controls the fuel pressure across the fuel injector at different operating conditions of the vehicle and is operated by the ECU. The fuel pressure regulator has an air chamber and a fuel chamber separated by a diaphragm. The fuel chamber is hydraulically connected to the fuel inlet line and to the fuel outlet line. The fuel chamber houses a movable pressure plate assembly that controls the quantity of fuel passing from the fuel inlet line to the fuel outlet line. The pressure plate assembly is attached to the diaphragm and moves with the movement of the diaphragm. The required pressure of the fuel in the fuel chamber at different operating conditions of the vehicle is maintained by maintaining the air pressure within the air chamber of the fuel pressure regulator. The air chamber is hydraulically connected to an air source through a communicating device. The communicating device is also controlled by the ECU and controls the air pressure from the air source entering into the air chamber of the fuel pressure regulator. Thus, the air pressure within the air chamber is varied in order to vary the fuel pressure across the fuel injector.

Fig. 1 exemplarily illustrates a variable pressure fuel injection system 100 of a vehicle in accordance with one embodiment of the present subject matter. The variable pressure fuel injection system 100 mainly includes a fuel inlet line 102, a fuel outlet line 104, a fuel injector 106, a fuel pressure regulator 108, a communicating device 110, and an air source 112. Fuel at a low pressure is stored in a fuel tank 114. A fuel pump 116 pressurizes the fuel from the fuel tank 114 and supplies high pressure fuel to the fuel injector 106. In one embodiment, the fuel injector 106 is mounted on an intake manifold of the engine and injects fuel in the intake manifold. Fluctuation occurring within fuel pressure due to variation in the voltage supplied to the fuel pump 116 are overcome by the fuel pressure regulator 108 provided in the line between the fuel pump 116 and the fuel injector 106. The fuel pressure regulator 108 is divided into a fuel chamber 118 and an air chamber 120. The fuel chamber 118 is connected to the fuel inlet line 102 and the fuel outlet line 104. Fuel from the fuel pump 116 at a certain forward pressure enters the fuel chamber 118 of the fuel pressure regulator 108. The fuel pressure regulator 108, in its closed state, creates a back pressure in the fuel inlet line 102. The difference between the forward pressure and back pressure in the fuel inlet line 102 facilitates the flow of fuel at required pressure to the fuel injector 106.

A pressure sensor 122 is provided in the fuel inlet line 102 to calculate the pressure of fuel in the fuel inlet line 102. The pressure sensor 122 sends signals, corresponding to the fuel pressure in the fuel inlet line 102, to an electronic control unit (ECU) 124. The ECU 124 in turn actuates the communicating device 110 for precise control of the communicating device. The communicating device 110 is connected to the air source 112 and the air chamber 120 of the fuel pressure regulator 108. The communicating device 110 provides additional air with positive variable pressure to the air chamber 120 of the fuel pressure regulator 108. In one embodiment, the communicating device 110 can be an actuator.

The purpose of the communicating device 110 is to open or close the passage between the air source 112 and the air chamber 120 of the fuel pressure regulator 108. The communicating device 110 also serves the purpose of reducing pressure within the air chamber 120 by bleeding out excess air to ambient or to the low pressure side of the engine 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 110 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 112 can be the exhaust gas expelled from a cylinder of an internal combustion engine during compression stroke. In another embodiment, the air source 112 can be an external compressor. Fig. 2 illustrates the fuel pressure regulator 108 of the variable pressure fuel injection system 100 of Fig. 1. The fuel chamber 118 and the air chamber 120 of the fuel pressure regulator 108 are separated by a diaphragm 200. The fuel chamber 118 has a fuel inlet 202 and a fuel outlet 204 connected to the fuel inlet line 102 and the fuel outlet line 104 respectively. In the closed position of the fuel pressure regulator 108, the fuel outlet 204 is closed by a pressure plate assembly 206, thereby closing the flow of fuel from the fuel inlet 202 to the fuel outlet 204. The pressure plate assembly 206 is housed in the fuel chamber 118 and is attached to the diaphragm 200. The minimum fuel pressure in the fuel inlet line 102 is defined by a spring 208 provided in the air chamber 120 of the fuel pressure regulator 108. The spring 208 is pre-stressed and biases the diaphragm 200 towards the fuel chamber 118, thereby pushing the pressure plate assembly 206 against the fuel outlet 204 of the fuel chamber 118. The air chamber 120 includes an air inlet 210 that is hydraulically connected to the communicating device 110. The communicating device 110 facilitates the variation of the air pressure within the air chamber 120 in order to vary the fuel pressure in the fuel inlet line 102 and hence the differential fuel pressure across the fuel injector 106.

With the reduction in the fuel pressure in the fuel inlet line 102 below the predetermined threshold value for a specific operating condition of the vehicle, the pressure sensor 122 sends a signal to the ECU 124. The signal sent by the pressure sensor 122 corresponds to the magnitude of pressure required in the fuel inlet line 102 for that operating condition of the vehicle. The ECU 124, on receiving such a signal from the pressure sensor 122, actuates the communicating device 110. In one embodiment, appropriate control strategies are developed within the ECU 124 to ensure appropriate gain values for different operating conditions of the vehicle.

The communicating device 110 in turn opens the passage between the air source 112 and the air chamber 120 of the fuel pressure regulator 108. The opening of the communicating device 110 corresponds to the difference in the threshold pressure and the actual pressure in the fuel inlet line 102. This increases the air pressure in the air chamber 120 of the fuel pressure regulator 108. The supply of air with additional pressure into the air chamber 120 exerts an additional load on the diaphragm. This increase in the load acting on the diaphragm pushes the diaphragm 200 and the pressure plate assembly 206 towards the fuel outlet 204, thereby closing the fuel outlet 204 and in turn increasing the fuel pressure in the fuel inlet line 102. On the other hand, when the fuel pressure in the fuel inlet line 102 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 120 of the fuel pressure regulator 108. The ECU 124, on receiving signal from the pressure sensor 122, actuates the communicating device 110. The communicating device 110 reduces the opening air passage between the air source 112 and the air chamber 120 of the fuel pressure regulator 108. This reduces the air pressure in the air chamber 120 and hence the load acting on the diaphragm 200 and the pressure plate assembly 206. The decrease in load on the diaphragm 200 allows the diaphragm 200 and the pressure plate assembly 206 to lift up due to the increased fuel pressure in the fuel chamber 118. The lifting of the pressure plate assembly 206 allows the fuel with excess pressure to drain out of the fuel outlet 204, thereby decreasing the fuel pressure in the fuel inlet line 102. Once the fuel pressure in the fuel chamber and the air pressure in the air chamber are equal, the pressure plate assembly 206 moves down to close the fuel outlet 204. The opening of the passage corresponds to the difference in the threshold pressure and actual pressure in the fuel inlet line 102. This causes the air pressure in the air

chamber 120 to increase. In such a case, load, in addition to the spring load, acting on the diaphragm increases. This increase in the load on the diaphragm pushes the diaphragm 200 and the pressure plate assembly 206 towards the fuel outlet 204, thereby closing the fuel outlet 204 and in turn increasing the fuel pressure in the fuel inlet line 102.

By providing fuel at different pressures across the fuel injector 106 for different operating conditions of the vehicle, an appropriate mixing of fuel with air is ensured. This leads to proper atomization of fuel at all the operating conditions of the vehicle, thereby enhancing fuel efficiency and fuel economy of the vehicle in addition to the performance of the engine.

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.

Claims

I/We claim

1. A variable pressure fuel injection system 100 of a vehicle, said variable pressure fuel injection system 100 comprising: a fuel inlet line 102; a fuel outlet line 104; a fuel injector 106 hydraulically connected to said fuel inlet line 102; and a fuel pressure regulator 108 having a fuel chamber 118 and an air chamber 120, said fuel chamber 118 being hydraulically connected to said fuel inlet line 102 and said fuel outlet line 104, wherein said fuel chamber 118 houses a movable pressure plate assembly 206 for controlling fuel flow from said fuel inlet line 102 to said fuel outlet line 104; characterized in that an air source 112 hydraulically connected to said air chamber 120; a communicating device 110 for communicating said air source 112 with said air chamber 120, and an electronic control unit 124 for controlling said communicating device 110 based on different operating conditions of said vehicle, thereby providing variable air pressure in said air chamber 120 at different operating conditions.

2. The variable pressure fuel injection system 100 as claimed in claim 1 further comprises a pressure sensor 122 disposed in said fuel inlet line 102 for measuring pressure in said fuel inlet line 102, and communicating with said electronic control unit 124 for precise control of said communicating device 110.

3. The variable pressure fuel injection system 100 as claimed in claim 1, wherein said fuel inlet line 102 is hydraulically connected to a fuel pump 116.

4. The variable pressure fuel injection system 100 as claimed in claim 1, wherein said fuel regulator 108 generates a back pressure in said inlet line 102 in its closed state.

5. The variable pressure fuel injection system 100 as claimed in claim 1, wherein said air chamber 120 and said fuel chamber 118 are separated by a diaphragm

200.

6. The variable pressure fuel injection system 100 as claimed in claim 1, wherein said air chamber 120 encloses a spring 208 exerting a uniform pressure on said diaphragm 200.

7. The variable pressure fuel injection system 100 as claimed in claim 1, wherein said air source 112 is either an external compressor or a compressed air from an engine combustion chamber.

8. The variable pressure fuel injection system 100 as claimed in claim 1, wherein said communicating device 110 is an actuator.

9. The variable pressure fuel injection system 100 as claimed in claim 1, wherein said electronic control unit 124 regulates said communicating device 110 based on different engine speeds and engine loads.

10. The variable pressure fuel injection system 100 as claimed in claim 1, wherein said fuel outlet line 104 hydraulically connects said fuel chamber 118 to a fuel tank 114.

11. The variable pressure fuel injection system 100 as claimed in claim 1, wherein said fuel injector 106 injects pressurized fuel into an engine intake manifold.