FIELD OF INVENTION:

The invention relates to an exhaust gas recirculation (EGR) system.

BACKGROUND OF THE INVENTION:

When fuel is burnt in an engine, nitrogen oxides are produced in exhaust gases. An EGR system re-circulates part of the inactive exhaust gas and mixes it with intake air in a combustion chamber of the engine to decrease a combustion temperature, thereby suppressing the amount of nitrogen oxides.

A conventional EGR system includes an exhaust gas passage mounted to a cylinder head and an EGR valve disposed at an exhaust manifold or in the exhaust gas passage. The EGR valve opens/closes the exhaust gas passage to selectively transmit exhaust gas to a combustion chamber. The opening and closing of the EGR valve is normally controlled by an engine control unit.

The United States Patent Application 20080103680 discloses one such EGR system. The invention disclosed may be configured to control the exhaust gas recirculation valve using open-loop control when the flow detection device determines that the exhaust gas recirculation flow rate is below a predetermined flow rate and using closed-loop control when the detection device determines that the exhaust gas recirculation flow rate is at or above the predetermined flow rate.

OBJECT OF THE INVENTION:

The object of this invention is to provide a simple and cost-effective controller to control the exhaust gas re-circulation by detecting the acceleration of the vehicle and closing the EGR valve for a pre-determined time.

BRIEF DESCRIPTION OF THE DRAWINGS:-

FIG. 1 shows a schematic of the invention

DETAILED DESCRITPION OF THE INVENTION:

The present invention is described in the preferred embodiment as follows:-

FIG. 1 shows a schematic of a controller 10 to control exhaust gas re-circulation system 11, according to the invention. Shown in fig. 1 is the controller 10, comprising a detection means 12 to detect acceleration of the vehicle which is not shown, a timer means 14 to generate a time out. Also shown in fig. 1 is an engine 16 with intake manifold 18, a throttle 19, an exhaust manifold 20, a cylinder 22 and an EGR valve 24.

The detection means 12 may be a simple switch fixed on to the accelerator pedal which is not shown or a sensor to sense the position of the accelerator pedal or any means which detects or gets to know about the demand for acceleration of the vehicle. Once there is a demand for acceleration, there may not be enough air available for the combustion to meet the demand because part of the exhaust gas is re-circulated, which may not contribute to the combustion in the cylinder. Under this condition the controller 10 stops the EGR re-circulation temporarily to provide more air for the combustion. This is achieved as below.

The detection means 12 keeps monitoring for the demand for acceleration. The demand for acceleration may be indicated through pressing of the accelerator pedal by the user. Once the user presses the accelerator pedal, there is a demand for more air to meet the demand for acceleration. To meet the demand for more air, the detection means 12 closes the EGR valve 24 and also triggers the timer 14 to generate a predefined time-out. The closing of the EGR valve 24 results in stopping the exhaust gas re-circulation, thereby allowing more air to enter into the cylinder 22. As more air is available for combustion, the demand for acceleration is met accordingly.

The timer 14 generates a signal after the pre-defined time-out and this signal is used to close the EGR valve 24, thereby allowing part of the exhaust gases to re-enter into the cylinder. The timer 14 is reset and the above cycle repeats for further driving cycles. The above procedure ensures that the relative air to fuel ratio is maintained within the specified levels.

The pre-determined time-out is arrived at during the application phase of the engine where the engine is tested and calibrated. This pre-determined time-out is determined by taking into account the amount of time taken by the vehicle to reach the speed value where sufficient air is available for EGR induction.

ADVANTAGES OF THE INVENTION:

The EGR controller provides a simple and cost effective device to control the EGR. The invention proposes a device and a method to control the EGR by using a timer and an acceleration detection means. The invention uses simple components which are already available in the vehicle, without needing any additional components.

In the prior art, the low priced vehicles use typically a continuous or progressive EGR. Though the continuous EGR is simple and cost-effective solution, it does not offer any control over the EGR rate. The problem with continuous EGR is evident during the vehicle acceleration, where the opacity of the exhaust gases increases as the amount of air available is less. This results in more emissions of harmful gases. So it is very important to control the EGR to control the emissions.

The progressive EGR used in the prior arts consists of an electro-pneumatic valve to control the EGR, a vacuum source and an ECU. Due to the additional components, the progressive EGR control is expensive.

The invention proposes a simple and cost effective controller to control the EGR by using simple components which are commonly available in the vehicle. The invention makes use of already available means for detecting the acceleration. Also the timer means can be easily implemented using simple hardware components.

WE CLAIM:

1. A controller (10) to control exhaust gas re-circulation (EGR) in a vehicle, the said controller (10) comprising:

- a detection means (12) adapted to detect an acceleration of the said vehicle and close the EGR valve(24), the said detection means (12) further adapted to start a timer (14)

- the said timer (14) adapted to open the said EGR valve (24) after a predetermined time-out

2. A controller (10) according to claim 1 wherein the said detection means (12) is a switch on the accelerator pedal to detect the pressing of the accelerator pedal.

3. A controller (10) according to claim 1 wherein the said detection means (12) is a sensor to sense the position of the accelerator pedal.

4. A controller (10) according to claim 1 wherein the said timer (14) is implemented using hardware components.

5. A controller (10) according to claim 1 wherein the said timer (14) is implemented using software.

6. A method to control exhaust gas recirculation in a vehicle, the said method comprising the steps:

-detecting demand for acceleration
-closing the exhaust gas recirculation valve to stop exhaust gas recirculation
-starting a timer to generate a time-out
-opening the exhaust gas recirculation valve to start exhaust gas recirculation after the expiry of the said time-out.