TECHNICAL FIELD

The invention relates to an exhaust gas recirculation (EGR) valve assembly for internal combustion engines.

BACKGROUND

Single Cylinder Naturally Aspirated Diesel Engines are currently being used on three and four wheeled goods carrying vehicles, known as Low Priced Vehicles (LPV), with mechanical fuel injection systems. Such vehicles are more economical and a practical solution to the growing traffic situation in emerging economies. Although meeting the emission limits with these vehicles is an engineering challenge. EGR - Exhaust Gas Recirculation, where a part of the exhaust gas is mixed with the fresh air at the inlet manifold, is an extensively used strategy for reduction of Oxides of Nitrogen (NOx).

For the cost sensitive applications of LPV, currently vehicles use a concept of continuous EGR where a pipe from exhaust is shorted to the inlet without any control from an EGR valve. The pipe parameters for e.g. the diameter and length are optimized with several engine/vehicle trials. Such a solution is very simple to realize but has a limitation on the extendibility to meet future emission norms.

Various other control options are used to obtain closed loop and variable EGR control. Most widely used is an air mass sensor upstream inlet manifold. A typical EGR circuit includes an air mass sensor, an EGR valve either electrical operated or pneumatic operated. During the optimization of the diesel engine for emissions, several trials are done on the engine test bench by varying the EGR rates. After the evaluation of the data, the best trade off points is selected for both NOx and particulate matter. The required EGR rate is then programmed as an air mass set point map. Electronic control unit(s) (ECU) controls the EGR valve to achieve the set point air mass thereby achieving the closed loop control of EGR. When such a sensor is used on a single cylinder engine where the air mass is fluctuating, the output from sensor is also pulsating. Hence precise EGR control becomes difficult to achieve and will have a wider emission tolerance. Also the above solution is Vxpensive for the LPV market.

SUMMARY:

To overcome the above limitations of the present state of art, a mechanically operated EGR valve concept is proposed here. The proposed design will have the flexibility of having variable flow of EGR based on the requirement of the engine. The valve will be connected to the accelerator pedal and the variation of flow in the EGR will happen based on the pedal demand. The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed aspects. This summary is not an extensive overview and is intended to neither identify key or critical elements nor delineate the scope of such aspects. Its purpose is to present some concepts of the described features in a simplified form as a prelude to the more detailed description that is presented later.

In one aspect, an exhaust gas recirculation valve for an internal combustion engine is provided. The EGR valve comprises a valve housing having a passage for recirculated exhausted gas and a spindle movement space which perpendicularly gets through the passage, a main spindle moving in the spindle movement space, an auxiliary spindle co-axially connecting and moving together with the main spindle, in the spindle movement space, to close and open the passage at different proportions.
In another aspect, an EGR assembly for an internal combustion engine is provided. The EGR assembly comprises: an acceleration pedal to control speed of a vehicle, an EGR valve to control flow of recirculated exhaust gas, a connecting means operably connecting the accelerator pedal to the EGR valve to actuate and control stages of the EGR valve.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1 is a sectional drawing of an EGR valve according to an exemplary embodiment.
Fig.2a is a sectional drawing of part of an EGR valve, in which an auxiliary spindle is stepped-designed according to an exemplary embodiment.
Fig.2b is a sectional drawing of part of an EGR valve, in which an auxiliary spindle is cone-designed according to another exemplary embodiment.
Fig.3a - Fig.3c are drawings describing valve at different stages corresponding to different positions of an acceleration pedal.
Fig.4 is a block diagram of the control logic.

DETAILED DESCRIPTION

Fig.1 shows a cross-sectional drawing of an EGR valve according to an exemplary embodiment. The EGR valve comprises a first part of housing 1, stopper plate 2, a gasket 3, a spacer 4, a spring 5, a second part of housing 6, a third part of housing 7, a main spindle 8 and an auxiliary spindle 9. The first part of housing 1, the second part of housing 6, the third of housing 7 are hollow cylindrical. When combined by bolts or welding, these parts of housing 1, 6 and 7 form a passage for exhaust gas and a spindle movement space 10 inside them. Inside the spindle movement space 10, the spring 5 surrounding the main spindle 8 is blocked by the spacer 4 in order to bring the spindles 8 and 9 back to initial position when there is no force from an actuator outside, such as an accelerator pedal (not shown here), for example. The gaskets 3 and the stopper plates 2 are placed between the first part of housing 1 and the second part of housing 6 to absorb the exceeded elastic force of the spring. The main spindle 8 is threaded, for example, to the auxiliary spindle 9.

Fig.2a and Fig.2b shows embodiments of the auxiliary spindle 9. In Fig.2a, the auxiliary spindle 9 is stepped-designed. In Fig.2b, the auxiliary spindle 9 is cone-designed. In both embodiments, part of the auxiliary spindle 91 has diameter smaller than one of the spindle movement space 10. This results in progressively decreasing the circumferential area available for the flow, and hence the flow decreases with the accelerator pedal depression. Due to having a smaller diameter part 91, EGR can flow through the circumferential area. This is lesser than the maximum flow and also can be controlled by deciding on the diameter of the auxiliary spindle 9.

Fig.3a to Fig.3c shows how the auxiliary spindle 9 controlling the flow of the EGR through the valve. The geometry of the auxiliary spindle 9 can be varied to vary the flow at different positions of an actuator (not shown), such as an accelerator pedal, and hence control the flow. The auxiliary spindle 9 can be placed in to 3 stages based on what it controls: The stage when the accelerator pedal is pressed 0 - 30% of the total depression length: when the accelerator pedal is at its zero position, it is either no load or idle condition. At idle condition the power requirement is minimal. So there should be EGR flow through the valve. But during sudden accelerations, the engine will be in shortage of oxygen to produce the required power. Hence, at the idle position, the valve should allow less amount of EGR. Here, the diameter of the auxiliary spindle 9 is lesser than that of the slot given for its movement as shown in Fig.3a.

The stage when the accelerator pedal is pressed 30 - 80% of the total depression length: this range of accelerator pedal position usually corresponds to the part loads in the engine load collective region where the fuel ratio values are usually high. Although application of EGR can be achieved easily, the periods for which the engine will be at part loads is very less. Also, the cycle dynamics is such that there are sudden accelerations where in the accelerator pedal is pressed from 0 - 100% in a very short time. For this situation, the engine [air system] reacts slower than the fuel injection system due to inertia and hence the amount of air available will be less. Hence, at this position of the auxiliary spindle 9, there should be no EGR flow. This is achieved by having the diameter of the auxiliary spindle 9 the same as that of the passage and cutting off the EGR flow as shown in Fig.3b The stage when the accelerator pedal is pressed 80 - 100% of the total depression length: this position, as shown in the Fig.3c, corresponds to full loads. In this range the amount of NOx produced is very high as the engine will have very high combustion temperatures. Hence, there should be the application of EGR at this position and also the flow should be as high as possible. Also, the start of the EGR flow should be as delayed as possible to reduce particulate matter emissions. The trade-off between NOx and particulate matter should be achieved. At this stage, the EGR valve should be open. This part is critical as it should also open as late as "possible.

Fig.4 is a block diagram of the control logic. The setup consists of an EGR valve 401 which is connected to the accelerator pedal 402 via connecting means 403, a cable for example. The EGR valve 401 is designed to give variable EGR flow rate in proportion to the accelerator pedal actuation.
During acceleration, the accelerator pedal 402 is depressed which in turn actuates the valve 401. Due to very low air availability it is vital to have no EGR and the valve 401 will restrict the flow of EGR during acceleration. Once the vehicle has achieved constant speed zone there will be sufficient air availability for EGR and the valve 401 will induce the required EGR rate to achieve the NOx reduction.
Such a system ensures that the engine 404 will be operating at a safe relative air to fuel ratio thereby avoiding excessive smoke generation from the engine and at a very low cost.
The foregoing relates to preferred exemplary embodiments of the invention. It is understood that other variants and embodiments thereof are possible within the spirit and scope of the invention which is defined by the appended claims.

WE CLAIM:

1. An exhaust gas recirculation (EGR) valve for an internal combustion engine, a valve
comprising: a valve housing having a passage for recirculated exhausted gas and a spindle movement space which perpendicularly gets through the passage; a main spindle moving in the spindle movement space; an auxiliary spindle co-axially connecting and moving together with the main spindle, in the spindle movement space, to close and open the passage at different proportions.

2. The EGR valve according to claim 1, wherein the auxiliary spindle has a step design that is part of the auxiliary spindle having the diameter smaller than the diameter of the movement space.

3. The EGR valve according to claim 1, wherein the auxiliary spindle has a conical design that is part of the auxiliary spindle having the diameter smaller than the diameter of the movement space.

4. An exhaust gas recirculation (EGR) assembly for an internal combustion engine comprising:
an acceleration pedal to control speed of a vehicle; an EGR valve to control flow of recirculated exhaust gas;a connecting means operably connecting the accelerator pedal to the EGR valve to actuate and control stages of the EGR valve.

5. EGR valve assembly according to claim 4, wherein the connecting means is a cable.

6. EGR valve assembly according to claim 4, wherein the EGR valve is the EGR valve in the claim 1.