FIELD OF THE INVENTION:

The invention relates to a PWM based fuel injection time and quantity control system for vehicle engines, particularly for small cylinder engines,

BACKGROUND OF THE INVENTION:

The US patent4353342 discloses about the Fuel injection control system of an internal combustion engine having fuel injectors inoperative only when the engine speed exceeds a first predetermined value during engine deceleration and for rendering the remaining fuel injectors inoperative when the engine speed exceeds a second predetermined value higher than the first predetermined value during engine deceleration. Control means is provided for rendering the fuel-cut means inoperative when rapid engine is provided for rendering the fuel-cut means inoperative when rapid engine deceleration occurs. The cited patent operates the fuel cut only in deceleration, it does not provide flexibility in injection quantity and timing.

The fuel injection system is mounted on the internal combustion engine for injecting the fuel into the internal combustion engine. If the fuel injector had a poor spray pattern, fuel will not be atomized and vaporized properly. This conditions will cause increased hydrocarbon emission and lean drivability problems, but when the fuel injection system with closed loop operation came along in the field of automobile, especially an electronic fuel injection, it produced less emissions and greatly increased the mileage of the automobile. Conventional fuel injection system for single cylinder engines in small vehicle(typical example - 3 wheeler ), consist of a single plunger pump and a mechanical injector. But this system has limited flexibility with respect to injection timing and injection quantity.

The main object of the electronic fuel injection system is to inject the right amount of fuel into the combustion chamber at the right time. A common rail system has the ability to inject the required amount of fuel into the combustion chamber, which may not be required for such single cylinder. The use of the common rail system is be an expensive system considering the target applications.

Fuel injection systems have gone through a few evolutions as providing electronic control system in fuel Injection process is a difficult step. There Is a need for a system which can enhance the control ability to Inject the fuel in terms of Injection quantity and timing flexibility with the help of simple electronic control arrangement.

With a view to accomplish the above needs, the following solutions are provided in the present Invention.

OBJECT OF THE INVENTION:
The object of the present invention is to achieve the flexibility in injection timing and quantity control.

SUMMARY OF THE INVENTION:
The present invention relates to a fuel injection timing and quantity control device particularly for single cylinder engine vehicles. The Invention comprises of a fuel tank, a electric feed pump, a mechanical Injector, a high pressure pump (single plunger pump), a pressure sensor, a solenoid valve, a combustion chamber and a control unit.

The method of controlling the fuel injection quantity and timing comprises of a control means to achieve the desired timing and quantity control by adopting a driving signal generating means, which Is used to generate the driving signal based on a PWM cycle signal to control the motor of the feed pump and solenoid valve in the high pressure line or on the high pressure pump or on a separate mounting block.

The timing flexibility is achieved by varying the filling of the high pressure pump by varying the flow rate of a electric feed pump. This is achieved by varying the PWM signal given to the electric feed pump.

The quantity control is by means fuel cut-off of the high pressure pump during the Injection process. The high pressure pump used is associated with a solenoid valve for fuel by-pass and the high pressure pump Is designed intentionally bigger than the
injection quantity required, for timing flexibility and there after to ensure that the required quantity for engine is injected, the remaining excess fuel is by-passed to the fuel tank through the solenoid valve.

A pressure signal from a pressure sensor mounted in the high pressure line or on the high pressure pump or on a block along with solenoid valve, is used to estimate the current injection timing. This feed back is used to change the duty cycle to electric feed pump in order to change the injection timing to the next desired value. The same pressure signal is used to estimate the time at which the solenoid valve is to opened in order to achieve a given injection quantity.

DESCRIPTION OF THE DRAWINGS:
S.NO PART NAME PART NO
1. Control means 1
2. Solenoid valve 2
3. Pressure sensor 3
4. Solenoid valve mounting block 4
5. Mechanical injector 5
6. Combustion chamber 6
7. Electric feed pump 7
8. Single plunger pump 8
9. Fuel tank 9

Figure 1 illustrates the circuit arrangement of the injection control unit. Figure 2 illustrates the graph representation between the time and injection range. Figure 3 illustrates the PWM signal based control logic for electric feed pump, solenoid valve for fuel cut off.

DESCRIPTION OF THE INVENTION:

The present invention describes the fuel injection timing and quantity control device for single cylinder engine comprises of a electric feed pump(7), fuel tank(9), a
mechanical injector(5), a single plunger pump (8), combustion chamber(6), a pressure sensor(3), a solenoid valve(2), and a control means (1).

The method of controlling the fuel injection quantity and timing comprises of a control means to achieve the desired timing and quantity control by using a driving signal generating means, which is used to generate the driving signal based on a PWM cycle signal to control the motor of the electric feed pump and solenoid on the high pressure line or mounting block for fuel cut off.

The timing flexibility is achieved by varying the filling of the high pressure pump by varying the flow rate of a electric feed pump. This is achieved by varying the PWM signal given to the electric feed pump. The quantity control is by means of fuel cut-off of the high pressure pump during the injection process

In one aspect, it manages the timing of injection wherein, the fuel injection system has an electric feed pump for pumping the fuel from the fuel tank through the fuel path based on the driving signal. The out put of the feed pump is attached with high pressure pump. The high pressure pump is receiving the fuel from the feed pump and pressurizing the fuel in highly compressed state and will supply the fuel to the injector.

In another aspect, it manages the quantity of injection wherein, the fuel injection system has a return path extending from between the high pressure pump and fuel tank. The solenoid valve for by-pass of fuel is controlled by means of control unit. The control means opens or closes the by-pass by actuating the solenoid valve.

When the fuel feeding quantity in the high pressure pump is beyond the required injection level then the by pass valve operates to allow the return of the excess amount of fuel through the return path to the fuel tank,

In another aspect, the fuel injection system has the driving signal generating means for generating the above referred driving signal and this is generated based on a PWM cycle signal. The said PWM cycle signal is generated by a control means. During the fuel injection process, the control means considers the various sensor outputs and estimates the required time of injection and quantity to be injected into the injector with respect to present load condition and providing the driving signal to the electric feed pump to vary the flow rate of the electric feed pump and thereby varying the filling of the high pressure pump for required fuel injection period thereby achieving a closed loop timing control.

Further control means also manages the quantity of fuel by providing the driving signal to the solenoid valve for specifying the time at which the by-pass is opened from closed position by energizing the solenoid valve through the driving signal and specifying a injection quantity and thereby achieving estimated quantity level to be injected into the internal combustion engine and removing the excess fuel by returning the fuel back to the fuel tank. The control means generates the PWM cycle signal with a duty ratio corresponding to the required fuel injection period and also simultaneously corresponding to the required fuel injection amount and providing the generated PWM signal to the driving signal generating means, wherein the generated PWM cycle signal is fed to the electric feed pump to control the fuel injection process and thereafter when the fuel in the high pressure pump exceeds the required quantity beyond injection it activates the by-pass valve to return the excess fuel to the fuel tank.

As seen above the unique control means where timing control is achieved by controlling the speed of electric feed pump which varies the pump filling and cut off through the solenoid valve to achieve the quantity control along with selection of a high pressure pump beyond the required size, the method of the fuel injection control is made novel. The control method is essentially comprising the steps of generating a PWM cycle signal with a duty ratio corresponding to the required fuel injection period and which corresponds to the required injection amount and providing this generated PWM cycle signal as a driving signal to an electric feed pump for a required injection period and also selectively to the solenoid valve so that after the required quantity for engine is injected, the remaining excess fuel is returned through the by-pass valve to the fuel tank.

WE CLAIM :

1. A fuel injection system for single cylinder engines in small vehicles comprising of a fuel tank, a single plunger pump, a feed pump to deliver the fuel from the fuel tank to a high pressure pump, a mechanical injector and a control circuit characterized in :

a. an electric feed pump working to pump fuel out of the fuel tank through a fuel path based on a driving signal,

b. a high pressure pump working to pressurize and supply the fuel to the injector as fed from the said fuel feed pump, the said high pressure pump sized bigger than the injection quantity required,

c. a return path extending from between said high pressure pump and said fuel tank,

d. a solenoid valve working to open and close said return path selectively also based on the said driving signal when a fuel feeding quantity that is the quantity of fuel in the fuel path between said high pressure pump and injector exceeds the required fuel quantity. The solenoid valve opens the bypass path to cut of injection and closes the bypass path to enable injection.

e. a driving signal generating means for generating the driving signal based on a
PWM cycle signal and providing the driving signal to the electric feed pump to vary the flow rate of the electric feed pump and thereby varying the filling of the high pressure pump for required fuel injection timing thereby achieving a closed loop timing control, and also providing the driving signal to the solenoid valve for specifying the time at which the by-pass path is opened and solenoid valve is energized for specifying a Injection quantity and thereby achieving quantity control, and

f. a control means for generating the PWM cycle signal with a duty ratio corresponding to the required fuel injection period and also simultaneously corresponding to the required fuel injection amount and providing the generated PWM cycle signal to the driving signal generating means.

g. A pressure sensor In the high pressure line or on the pump or on the solenoid valve mounting block for feed back signal to generate signals for timing and quantity control.

2. A fuel injection control method In a fuel Injector system for single cylinder engines in small vehicles comprising of a fuel tank, a single plunger pump, a feed pump to deliver fuel from the fuel tank to a high pressure pump, a mechanical Injector and a control circuit and characterized with a electric feed pump working to pump fuel out of the fuel tank and supply the fuel to the high pressure pump working to pressurize and supply the fuel to the injector, which high pressure pump Is bigger than the Injection quantity requirement and a by-pass solenoid valve returning the excess fuel beyond the required fuel quantity to the fuel tank, the said control method comprising the steps of generating a PWM cycle signal with a duty ratio corresponding to the required fuel injection timing and also corresponding to the required injection amount and providing this PWM cycle signal as a driving signal to an electric feed pump for a required injection timing and also to the solenoid valve so that after the required quantity for engine is injected, the remaining fuel is returned through solenoid valve to the fuel tank.