Claims:1. A mechanical exhaust gas recirculation (EGR) valve assembly comprising:
a piston; and
a spring;
wherein, the piston rests on the lowermost inner portion of the valve body against a pressure exerted by the spring such that when the exhaust manifold pressure increases, the piston gets lifted against pressure of the spring thereby opening a passage for the flow of exhaust gas from manifold to intake manifold.

2. Valve assembly as claimed in claim 1 wherein, the piston comprises a circumferential groove.

3. Valve assembly as claimed in claim 1 wherein, the pressure in exhaust manifold pushes the piston against the spring force causing the groove in the piston to coincide with the aperture in the exhaust gas recirculation valve housing.

4. Valve assembly as claimed in claim 3 wherein, the position of groove on the valve coinciding with aperture changes the size of flow area for exhaust gas thereby resulting in change of quantity of exhaust gas recirculation passing on to the intake manifold.

5. Valve assembly as claimed in claim 1 wherein, the outlet to intake manifold lies just opposite to the inlet for exhaust gas from manifold.

6. Valve assembly as claimed in claim 1 wherein, flow of exhaust gas from manifold is allowed during engine loading.

7. Valve assembly as claimed in claim 6 wherein, the flow of exhaust gas is allowed during 0% to 75% of the engine loading.

8. Valve assembly as claimed in claim 6 wherein, beyond 75% of the engine loading the passage for flow of exhaust gas from manifold gets sealed by the lowermost body of a piston.

9. Valve assembly as claimed in claim 1 wherein, the amount of exhaust gas recirculation is controlled by the difference of spring stiffness, aperture opening to the passage and the exhaust gas pressure that is dependent on percentage loading of the engine.

10. Valve assembly as claimed in claim 1 wherein, the valve provides an opening against the gas flow that does not cause disturbance and pressure drops.

11. Valve assembly as claimed in claim 1 wherein, the spring stiffness and dampness determine the optimum response time during changes in exhaust manifold pressure.
, Description:FIELD OF THE INVENTION

[001] The subject matter of the present invention, in general, pertains to exhaust gas recirculation (EGR), and more particularly to a spring operated mechanical exhaust gas recirculation valve assembly.

BACKGROUND OF INVENTION

[002] Exhaust gas recirculation is employed in connection with internal combustion engines to aid in reducing regulated emissions by metering exhaust gas to the intake manifold for mixing with incoming charge air prior to delivery to the engine combustion chamber. In internal combustion engines, EGR is a nitrogen oxide (NOx) emissions reduction technique. The valve is used to regulate the amount of exhaust gas recirculation in the engine to reduce NOx emission.

[003] An exhaust gas recirculation valve is typically used to control the quantity of exhaust gas delivered to the intake based on the operating conditions of the engine. EGR works by re-circulating a portion of an engine's exhaust gas back to the engine cylinders. This dilutes the O2 in the incoming air stream and provides gases inert to combustion to act as absorbents of combustion heat to reduce peak in-cylinder temperatures. NOx is produced in a narrow band of high cylinder temperatures and pressures.

[004] Because NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature, the lower combustion chamber temperatures caused by EGR reduces the amount of NOx the combustion generates at the cost of loss of engine efficiency. Gases re-introduced from EGR systems contain near equilibrium concentrations of NOx and CO, the small fraction initially within the combustion chamber inhibits the total net production of these and other pollutants when sampled on a time average. Most modern engines now require exhaust gas recirculation to meet emissions standards.

[005] Conventional EGR valves utilize linear solenoid actuators to move a biased pintle or poppet valve, thereby metering the flow of hot exhaust gas to the intake. In order to rapidly manipulate the valve member against its normally closed bias, as well as the gas load forces caused by the differential pressure between the exhaust and intake manifolds, the solenoid actuator must be powerful, as well as energy efficient, small, lightweight and environmentally durable.

[006] Some conventional EGR valves are vacuum operated. A vacuum diaphragm is opened and closed, allowing and cutting off exhaust flow. An early refinement was a temperature controlled shut-off in the vacuum source. This kept the EGR valve from opening when the engine was too cool. The cool engine did not require EGR and cutting it off made the engine run smoother. When back pressure is low, such as at an idle, the spring opens the vacuum port. Engine vacuum is bled off and the EGR valve closes. A similar design of EGR valve already in use is shown in Figure 1. In this valve, a vacuum diaphragm opens and closes the valve, allowing and cutting off exhaust flow. When the required suction is provided at the top, the valve is opened against the spring and the exhaust gas is passed to the intake. When the valve needs to be closed the vacuum is released and the spring closes the valve.

[007] The system of Figure 1 uses a vacuum pressure to provide opening of the valve and thus is complicated and expensive. The vacuum diaphragm (3) holds a valve (4) and is assembled in a valve body (1) against a compression spring (2). When the vacuum (6) is created the diaphragm (3) gets lifted against spring (2) causing the lifting of valve (4) from its seat (5). This lifting of valve (4) leads to opening of passage for mixing of exhaust gases (7) with intake air (8). On the other hand when vacuum (6) is not created the spring (2) forces down the diaphragm (3) leading to closing of a valve (4) on seat (5), thus, closing the passage for flow of exhaust gases (7). Such allowing and cutting off of exhaust flow (7) served the purpose of EGR for NOx reduction at higher temperature. The main drawback of this system is that it only provides increased EGR circulation at higher loads and cannot be used if it needs progressively less quantity of EGR as the engine load increases.

[008] Further some manufacturers have developed exhaust gas recirculation valves that are modular in design. This enables individual, customer specific variations for different installation conditions with retention of the electric and pneumatic drive. However in modern gasoline engines emission technology is electronically controlled fuel mixture generation that maintains a fuel-air mixture under all operating conditions. Such measures are complicated and expensive.

[009] The proposed invention will allow for improved permeability as well as a relatively compact structure of an exhaust gas recirculation valve. The valve is mechanically operated using a spring and permits an increase or decrease in the quantity of exhaust gas to pass into the intake manifold.

SUMMARY OF THE INVENTION

[0010] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0011] An object of the present invention is to provide a spring operated mechanical exhaust gas recirculation valve assembly.

[0012] Another object of the present invention is to provide an economical exhaust gas recirculation valve assembly that allows improved permeability with a relatively compact structure.

[0013] Another object of the present invention is to provide an exhaust gas recirculation valve assembly that allows an increase or decrease in the quantity of exhaust gas to be passed into the intake manifold.

[0014] Yet another object of the present invention is to provide the possibility of increasing or decreasing the exhaust gas recirculation quantity according to increase in the engine load as required in a cost effective way with improved reliability and faster response using less number of parts.

[0015] Yet another object of the present invention is the exhaust gas recirculation valve assembly provides an opening against the gas flow that does not cause the usual disturbance and pressure drops.

[0016] Yet another object of the present invention is when the exhaust manifold pressure increases, the piston gets lifted against pressure of a spring opening a passage for the flow of exhaust gas from manifold to intake manifold.

[0017] Yet another object of the present invention is the circumferential cut on piston is such that the flow of exhaust gas from manifold is allowed for 0% to 75% of the engine loading.

[0018] Yet another object of the present invention is beyond 75% of the engine loading, the passage for the flow of exhaust gas from manifold gets sealed by the piston.

[0019] Accordingly, in one aspect of the present invention, a valve device for an exhaust gas flow includes a control valve. At one end there is provided inlet for exhaust gas from manifold and just opposite to inlet there is outlet to intake manifold.

[0020] In another aspect, the product has been designed for four cylinder inline naturally aspirated engine so as to provide exhaust gas recirculation at lower loads and to cut off the exhaust gas supply at 75% engine load. It takes into account factors such as the pressure pulsation in the exhaust manifold, response time of the spring to achieve a particular displacement and the quantity of exhaust gas to be passed in the intake manifold.

[0021] In another aspect, the exhaust gas recirculation valve assembly is designed to allow a specified amount of exhaust gas into the intake manifold that is controlled by the difference of spring stiffness, aperture opening to the passage, and the exhaust gas pressure that is dependent on percentage loading of an engine.

[0022] Briefly, there is a provided an exhaust gas recirculation valve assembly to allow a specified amount of exhaust gas into the intake manifold as per the requirement. The amount being controlled by the difference of spring stiffness, aperture opening to the passage, and the exhaust gas pressure that is dependent on percentage loading of an engine. The pressure in the exhaust manifold pushes the piston against the spring force causing the groove in the piston to coincide with the aperture in the exhaust gas recirculation valve assembly thereby allowing the exhaust gas from the manifold to pass onto the intake manifold through the valve. As the load on the engine increases, the pressure in the exhaust manifold also increases thereby increasing the lift in the valve. The position of groove on the valve coinciding with aperture changes the size of flow area for exhaust gas. These results in change of quantity of exhaust gas recirculation get passed on to intake manifold. The spring stiffness and dampness are decided so as to get optimum response time from the system during changes in exhaust manifold pressure.

[0023] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0024] Figure 1 illustrates a vacuum operated EGR valve for NOx reduction at higher temperatures.

[0025] Figure 2 illustrates the front view of spring operated EGR valve according to one implementation of the present invention.

[0026] Figure 3 illustrates the working principle of spring operated EGR valve according to various implementations of the present invention.

[0027] Figure 4 illustrates the typical progressive curve of EGR operation according to one implementation of the present invention.

[0028] Figure 5 illustrates the exploded perspective view of the spring operated EGR valve according to one implementation of the present invention.

[0029] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0030] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0031] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0032] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0033] It is to be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0034] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0035] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0036] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or component but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0037] The subject invention lies in providing a spring operated mechanical exhaust gas recirculation valve.

[0038] In the present invention, an exhaust gas recirculation valve allows a specified amount of exhaust gas into the intake manifold with the amount being controlled by the difference of spring stiffness, aperture opening to the passage and the exhaust gas pressure that is dependent on percentage loading of an engine. The pressure in the exhaust manifold pushes the piston against the spring force causing the groove in the piston to coincide with the aperture in the exhaust gas recirculation valve housing thereby allowing the exhaust gas from the manifold to pass onto the intake manifold through the valve. As the load on the engine increases, the pressure in the exhaust manifold also increases thereby increasing the lift in the valve with the position of groove on the valve coinciding with aperture changes the size of flow area for exhaust gas thereby resulting in change of quantity of exhaust gas recirculation that gets passed on to intake manifold.

[0039] In one implementation, a spring operated mechanical exhaust gas recirculation valve (1) is provided for.

[0040] In one implementation, an economical exhaust gas recirculation valve (1) that allows improved permeability with a relatively compact structure is provided for.

[0041] In one implementation, the exhaust gas recirculation valve (1) allows an increase or decrease in the quantity of exhaust gas to be passed into the intake manifold (7) is provided for.

[0042] In one implementation, the possibility of increasing or decreasing the exhaust gas recirculation quantity according to increase in the engine load as required in a cost effective way with improved reliability and faster response using less number of parts is provided for.

[0043] In one implementation, the exhaust gas recirculation valve (1) provides an opening against the gas flow that does not cause the usual disturbance and pressure drops is provided for.

[0044] In one implementation, when the exhaust manifold pressure increases, the piston (2) gets lifted against pressure of a spring (3) opening a passage (8) for the flow of exhaust gas from manifold (6) to intake manifold (7) is provided for.

[0045] In one implementation, the circumferential profile cut or groove (2a) (the word “groove” or “profile cut” has been used interchangeably and nonlimitingly in the present document) on piston (2) is such that the flow of exhaust gas from manifold (6) is allowed for 0% to 75% of the engine loading is provided for.

[0046] In one implementation, beyond 75% of the engine loading, the passage (8) for the flow of exhaust gas from manifold (6) gets sealed by the piston (2) is provided for.

[0047] In one implementation, the amount of exhaust gas recirculation is controlled by the difference of spring stiffness, aperture opening to the passage, and the exhaust gas pressure that is dependent on percentage loading of an engine is provided for.

[0048] In one implementation, the pressure in the exhaust manifold pushes the piston (2) against the spring (3) force causing the groove (2a) in the piston (2) to coincide with the passage (8) in the exhaust gas recirculation valve housing is provided for.

[0049] In one implementation, the spring stiffness and dampness is decided so as to get optimum response time from the system during changes in exhaust manifold pressure is provided for.

[0050] The spring operated mechanical exhaust gas recirculation valve, as shown in Figure 2, consists of a valve body (1) containing a piston (2) that rests on the lowermost inner portion of a valve body (1) against a pressure exerted by spring (3). When the exhaust manifold pressure (5) increases, the piston (2) gets lifted against pressure of a spring (3). This leads to opening of a passage (8) for the flow of exhaust gas from manifold (6) to intake manifold (7).

[0051] The spring operated mechanical exhaust gas recirculation valve has been designed so as to provide exhaust gas recirculation at lower loads and to cut off the exhaust gas supply at 75% engine load. The design has been made taking factors such as the pressure pulsation in the exhaust manifold, response time of the spring to achieve a particular displacement and the quantity of exhaust gas to be passed in the intake manifold. Further development has been carried out where the pressure difference across the valve in a naturally aspirated engine is very low thus limiting the lift of the piston and thereby the amount of exhaust gas that may be passed into the intake manifold is also low. This may be improved by passing the intake air through a venturi, thus increasing its velocity and reducing its pressure to a value much lower than the exhaust gas pressure creating a higher suction and leading to an increased quantity of exhaust gas passage. An alternative arrangement may be provided to create a vacuum in the volume above the piston by connecting it to a suction pressure creating component in the engine, to help in the piston lift and thus allowing increased quantity of gas passage. Proper profiling of the groove may be done according to the percentage of exhaust gas recirculation to be passed at a particular lift.

[0052] As can be seen from Figure 3, the circumferential profile cut (2a) on piston (2) is provided for in a way that the flow of exhaust gas from manifold (6) is allowed during 0% to 75% of the engine loading. And beyond 75% of the engine loading the passage (8) for the flow of exhaust gas from manifold (6) gets sealed by the lowermost body of a piston (2).

[0053] In order to create a substantial pressure difference across the exhaust gas recirculation circuit (in case of naturally aspirated engines if required), the intake air can be passed through a venturi that would increase its velocity and thus reduce its pressure (according to Bernoulli’s Theorem) to a much lower value than the exhaust pressure. This will help in the passage of the exhaust gas into the intake manifold.

[0054] The exploded perspective view of the spring operated exhaust gas recirculation valve of Figure 5 illustrates that the cap (4) has a vent hole (9) to reduce the back pressure against which the piston has to operate. The cap (4) is screwed onto the housing (1) so as to keep the spring (3) in a compressed condition in order to press the piston against the housing. The typical progressive curve of such exhaust gas recirculation operation has been indicated in Figure 4. The spring (3) is designed to provide a particular lift to the piston (2) against a particular pressure in the exhaust manifold. It may thus open or close the valve at required pressures.

[0055] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. The present invention employs a simple spring mechanism for mechanical exhaust gas recirculation valve;
2. The present invention does not require any external aid when compared to vacuum pump or electric valves;
3. The present invention is completely hard coupled to engine load;
4. The present invention does not require additional sensors;
5. The present invention may be comfortably used on the hot side as no electrical circuitry is involved; and
6. The present invention can give on-off as well as progressive exhaust gas recirculation with minimum cost.

[0056] Although a hassle free, economic and cost effective way to maintain exhaust gas recirculation valve has been described in language specific to structural features and/or methods, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations of a spring operated mechanical exhaust gas recirculation valve.