Field of the Invention

The present invention relates to an EGR cooling system and method which enables to keep the temperature of the coolant used in the EGR system at a desired temperature range, and which changes the flow rate of the coolant when the temperature of the coolant exceeds the desired temperature range.

Background of the Invention

In gasoline powered and diesel internal combustion engines, harmful gases such as carbon monoxide (CO), nitrogen oxide (NOx), hydrocarbon (HC) are created as a result of combustion. The emission of harmful gases generated as a result of combustion directly to the atmosphere is very dangerous and forbidden in terms of environmental and human health. Before the harmful gases created as a result of combustion are discharged, their emission values should be reduced to values that do not harm the environment. In internal combustion engine-powered vehicles, there are several systems and applications in order to reduce the harmful gases to acceptable emission levels. One of these applications is exhaust gas recirculation (EGR) system. In EGR system, some part of exhaust gases is sent to the combustion chamber again. The gases included into the combustion process do not burn in the engine; they reduce combustion temperature in the engine and prevent the harmful gases from being discharged from the exhaust system. By means of EGR system, combustion temperature is reduced, and the generation of nitrogen oxide gas is decreased. The amount of the gas to be circulated in EGR system is provided with EGR valve according to engine calibration targets, and generally poppet valve or butterfly valve is used. The generation of nitrogen oxide (NOx) is reduced almost in ratio of 30-40% by means of the EGR system. In EGR system, the exhaust gas generated as a result of combustion in the engine increases the density of the gas in the EGR system, and it is subjected to cooling in order to send more gas into the combustion chamber. After the exhaust gas generated as a result of combustion is cooled and condensed in the EGR system, it is given to the engine fresh air inlet. Cooling exhaust gas is provided with cooling exchanger present inside the EGR system. By means of the cooling exchanger, exhaust gas (EGR gas) in desired density and temperature is given to the engine air suction again. The exhaust gas which is given to the engine suction by being cooled by means of the cooling exchanger is more condensed than the gases inside the engine, and nitrogen oxide (NOx) emission in the engine is decreased.

The cooling exchanger used in EGR systems are usually comprised of tubes and coolant such as water enabling cooling by passing around the tubes. EGR exhaust gas passes through the tubes, and water passes around the tubes, and thus water cools the surface of the surface, thereby cooling the gas passing through the tubes. In EGR system, cooling is provided with engine coolant. The surrounding of the cooling tubes is covered with engine coolant. Therefore, a heat flow from the gas passing through the tube towards the engine coolant is provided, and thus exhaust gas is cooled. While the exhaust gas is being cooled, the coolant is heated. During cooling, exhaust gas flow rate is not the same at each point where the engine coolant passes, in some places the flow rate of the gas is more while the flow rate of the engine coolant is less. In this case, in order to cool the gas to a desired temperature, it cases more heat to pass to the engine coolant and the engine coolant to increase more than desired. The temperature of the engine coolant increasing more than desired emerges the possibility of boiling in the coolant. The boiling on the engine coolant is one of the most important technical problems experienced in current applications.

Another technical problem commonly experienced in current systems is that gas leakages occur in the water system due the vehicle being used for too long without stopping. The gas leakages occurring in the cooling system cause the pressure in the water tank to drop. When the pressure of the coolant drops, the boiling point also decreases and it causes the water to boil more easily. At the same time, the temperature difference between the engine coolant inlet and outlet temperatures in EGR cooler being high challenges the EGR cooler in terms of thermal fatigue. While the EGR system is designed, the flowrate of the engine coolant wanted to pass through the EGR cooler is calculated considering the boiling problem in the EGR cooler and the temperature change of the engine coolant, and the water pump is selected accordingly. The engine coolant temperature passing through the EGR cooler increasing too much and occurrence of boiling damages the cooling tubes and deflector plates in the EGR system. The hot water passing on the cooling tubes and the deflector plates causes the stress level on the parts to increase, the temperatures of the metal to increase, even the tube and the deflector plates to break. A malfunction or break in the EGR system causes the system to become unusable, the emission values to increase in an unwanted manner, and decrease in water level. The decrease in water level may cause the engine to be badly damaged, even become unusable. In case the said internal parts in the EGR system break, it is not possible to repair these parts, they should be replaced completely.

In the EGR system, not controlling the coolant temperature and boiling of the coolant causes malfunction in the EGR system and in the engine. In the current EGR systems, there is no application for controlling temperature by increasing the flowrate of the water when the temperature of the coolant exceeds the preferred temperature range by controlling the temperature of the coolant.

The Unites States patent document US7380544, an application in the state of the art, discloses an EGR system having two cooling systems. The cooling systems are placed sequentially along the exhaust pipe. In the structure disclosed in the said patent document, controlling the temperature of the coolant and changing the flow rate of the coolant is not disclosed. The most obvious difference between the said patent document and the invention pf the present application is to measure the coolant temperature, and control the coolant temperature by changing the flowrate of the coolant. The EGR system operates more efficiently, and the EGR system malfunctions and engine malfunctions due to overheating and boiling of the coolant by means of the said difference.

The Unites States patent document US6244256, an application in the state of the art, discloses an EGR system having a second cooling system. Further cooling is provided by means of each cooling system having a separate radiator. There is no explanation in the said patent document about controlling the temperature of the coolant and controlling the coolant temperature by changing the flowrate of the coolant. The most obvious difference between the said patent document and the invention pf the present application is to measure the coolant temperature, and control the coolant temperature by changing the flowrate of the coolant.

In the current applications, there is not a system and control method which enables to control EGR coolant flowrate depending on the coolant temperature. Many malfunctions are prevented by means of controlling the coolant temperature.

The Objective of the Invention

The objective of the present invention is to provide an EGR cooling system and method which keeps the temperature of the coolant used in EGR system at a preferred range.

Another objective of the present invention is to provide an EGR cooling system and method which controls the temperature of the coolant used in EGR system by changing the flowrate of the coolant. A further objective of the present invention is to provide an EGR cooling system and method which prevents EGR system malfunctions and engine malfunctions occurring due to boiling of the coolant. Summary of the Invention

In the first claim developed in order to fulfil the objective of the present invention and other claims dependent to the first claim, the temperature and flowrate of the coolant used in EGR system is controlled by the EGR system and method.

The EGR cooling system operates by changing the flowrate of the coolant to be used in the system according to the temperature value of the coolant present in the EGR cooler. The EGR cooling system controls the temperature of the coolant by changing the flowrate of the coolant. For this, a secondary liquid tank other than radiator is used. The coolant present in the secondary tank is activated according to the temperature of the coolant present in the cooler. If the temperature of the coolant increases much, the liquid present in the secondary tank is included into the system and the flowrate of the coolant is increased, and thus the overheating of the coolant is prevented. Therefore, the EGR system operates more effectively with the coolants supplied by two different sources, and more effective cooling is provided.

Detailed Description of the Invention An EGR cooling system and method developed to fulfill the objectives of the present invention is illustrated in the accompanying figures, in which:

Figure 1 is the schematic view of the EGR cooling system.

Figure 2 is the flowchart of the EGR cooling method. The components shown in the figures are each given reference numbers as follows:

1. EGR cooling system

2. EGR valve

3. EGR cooler

4. Radiator

5. Water pump

6. Secondary valve

7. Secondary pump

8. Flowrate control valve

9. Return valve

10. Temperature sensor

11. Control unit

M: Engine

EG: Exhaust manifold

EM: Intake manifold

100. EGR cooling method An EGR cooling system (1); which enables to keep the temperature of the coolant used in EGR systems of the vehicles at a preferred temperature range, and changes the flowrate of the coolant when the temperature of the coolant exceeds the preferred temperature range; comprises

at least one EGR valve (2) which enables exhaust gas to be received from the exhaust manifold (EG),

at least one EGR cooler (3) which cools the exhaust gas,

at least one radiator (4) from which the liquid used for cooling is received, at least one water pump (5) which pumps the liquid in the radiator (4), preferably water, to the EGR cooler (3),

- at least one secondary tank (6) wherein the coolant is stored independent from the radiator (4), at least one secondary pump (7) which pumps the liquid in the secondary tank (6) to the EGR cooler (3),

flowrate control valve (8) which increases the flowrate of the coolant sending additional coolant to the EGR cooler (3) according to the temperature of the coolant.

By means of the EGR cooling system (1), the exhaust gas generated as a result of combustion occurring in the engine (M) is received from the exhaust manifold (EG) and subjected to cooling, and included into the combustion again by mixing into the combustion air through the intake manifold (EM). In the EGR cooling system (1), the exhaust gas is preferably received from the exhaust manifold (EG). There is preferably at least one gas outlet on the exhaust manifold (EG), and this gas outlet is controlled with the EGR valve (2). The EGR valve (2) is turned on, and it is enabled that the exhaust gas in the exhaust manifold (EG) is included into the EGR cooling system (1). Similarly, the EGR valve (2) is turned off, and it is prevented that the exhaust gas in the exhaust manifold (EG) is included into the EGR cooling system (1). In a preferred embodiment of the invention, the gas in the exhaust manifold (EG) is directed to the EGR cooler (3) via the EGR valve (2). The EGR cooler (3) cools the exhaust gas by means of the coolant. In a preferred embodiment of the invention, the EGR cooler (3) comprises cooling tubes through which the exhaust gas passes. The exhaust gas received from the exhaust manifold (EG) passes through the said cooling tubes, and the cooling tubes are cooled with the coolant. In a preferred embodiment of the invention, liquids such as antifreeze are used as coolant.

There is preferably at least one exhaust gas inlet, exhaust gas outlet, and at least one coolant inlet on the EGR cooler (3). In the preferred embodiment of the invention, there are at least two coolant inlets independent from each other on the EGR cooler (3).

In an alternative embodiment of the invention, the coolants are combined before entering into the EGR cooler (3). In this embodiment, the EGR cooler (3) has one coolant inlet.

One of the EGR cooler (3) inlets is connected to the radiator (4) line. The coolant in the radiator (4) is transferred to the EGR cooler (3) via the water pump (5). The coolant is initially taken from the radiator (4). The EGR cooler (3) is started to be cooled with the coolant taken from the radiator (4). Cooling is performed with the liquid in the radiator (4) until the coolant is heated too much.

The secondary tank (6) is connected to the one of the inlets of the EGR cooler (3) which is not connected to the radiator (4). The secondary tank (6) supplies coolant independent from the radiator (4). The volume of the secondary tank (6) may vary according to the cooling capacity, engine type and size. Preferably water is used as coolant in the secondary tank (6). The coolant in the secondary tank (6) is transferred to the EGR cooler (3) via the secondary pump (7). The secondary pump (7) is preferably connected to the secondary tank (6), and it is activated when an additional liquid is required for cooling and it preferably pumps water to the EGR cooler (3). The secondary tank (6) and the secondary pump (7) are preferably connected to the EGR cooler (3) with a different link. In the preferred embodiment of the invention, there is a flow rate control valve (8) provided between the secondary tank (6) and the EGR cooler (3). The flow rate control valve (8) controls the passage of the coolant in the secondary tank (6) to the EGR cooler (3). The flowrate control valve (8) preferably operates proportionally, and it allows liquid passage in different ratios. When the flow rate control valve (8) is turned on, the coolant in the secondary tank (6) is transferred to the EGR cooler (3), and thus the flowrate of the coolant in the EGR cooler (3) is increased and the coolant is prevented from heating.

After the coolant in the secondary tank (6) is used in the EGR cooler (39, it exits from the outlet line of the EGR cooler (3) and comes to the secondary tank (6) again according to the on-off position of the return valve (9). Therefore, coolant performs closed circulation. After it increases the flowrate of the coolant in the EGR cooler (3), it is stored in the secondary tank (6) again. The return valve (9) turns the line between the EGR cooler (3) and the secondary tank (6) on and off, therefore it enables the coolant to complete its closed circuit circulation.

The inventive EGR cooling system (1) comprises at least one temperature sensor

(10) . In the preferred embodiment of the invention, the temperature sensor (10) is present in the EGR cooler (3) or at the EGR cooler (3) outlet. The temperature of the coolant present in the EGR cooler (3) and the cooler (3) outlet is measured with the temperature sensor (10). The temperature sensor (10) continuously measures temperature value and transfers this data wirelessly.

The inventive EGR cooling system (1) preferably comprises at least one control unit (11). The control unit (11) controls the process of receiving exhaust gas and cooling exhaust gas. The control unit (11) turns EGR valve (2), water pump (5), secondary pump (7), flowrate control valve (8) and the return valve (9) on and off, and thus enables the cooling to be at maximum efficiency and the preferred coolant temperature range. The control unit (11) is adapted to control the coolant flowrate according to the coolant temperature value which it receives from the temperature value (10). The control unit (11) transfers the liquid in the secondary tank (6) to the EGR cooler (3) according to the temperature value of the coolant, thereby increasing the flowrate of the coolant in the cooler (3). The control unit

(11) is adapted to operate the secondary pump (7) and turn the flowrate control valve (8) when the temperature of the coolant exceeds the preferred values. The control unit (11) turns on the return valve (9) when the coolant temperature reaches the preferred values, and transfers the coolant which it transfers to the EGR cooler (3) to the secondary tank (6) again.

The EGR cooling system (1) operates such that the temperature of the coolant inside the EGR coolant (3) will remain in the preferred range. The EGR cooling system (1) provides the temperature of the coolant by controlling the flowrate of the coolant. For this, coolant is supplied to the system (1) with the secondary tank

(6) . The coolant in the secondary tank (6) is transferred via the secondary pump

(7) . The secondary pump (7) preferably has a drive motor, and it provides the power required to transfer the liquid. The flowrate control valve (8) is turned on in order to transfer the coolant in the secondary tank (6) to the EGR cooler (3). Therefore, the liquid compressed by the secondary pump (7) is transferred to the EGR cooler (3), and the flowrate of the coolant inside the EGR cooler (3) is increased. When the coolant temperature decreases to a preferred temperature value, the return valve (9) is turned on the and the coolant added into the system (1) fills into the secondary tank (6) again. Therefore, the EGR cooling system (1) is cooled with the liquid taken from two different coolants.

The temperature of the coolant present inside the EGR cooler (3) is adjusted with the inventive EGR cooling method (100) by controlling the flowrate of the liquid. Therefore, cooling is performed by controlling the temperature value of the coolant.

The EGR cooling method (100) which controls the temperature of the coolant by changing the flowrate of the coolant according to the temperature value of the coolant comprises the steps of

measuring the temperature of the coolant (101),

operating the secondary pump (7) according to temperature value (102), turning the flow rate control valve (8) according to temperature value (103), - transferring coolant from a different source other than the radiator (4) into the EGR cooler (3) (104), changing the flow rate of the coolant present inside the EGR cooler (3) (105), reducing the temperature value of the coolant (106),

turning the return valve (9) on (107),

transferring the additional coolant into the secondary tank (6) again (108).

The flowrate of the coolant is changed according to the temperature value of the coolant with the EGR cooling method (100), and thus the temperature of the coolant is kept under control. The temperature of the coolant is measured by the temperature sensor (101). It is not wanted that the coolant reaches the boiling point. If the coolant temperature is raised and the boiling point is reached, the secondary pump (7) is operated according to the temperature value (102). At the same time, the flowrate control valve (8) is turned on (103). Therefore coolant from a different source other than the radiator (4) is transferred into the EGR cooler (3) (104).

The flowrate of the coolant inside the EGR cooler (3) is changed by transferring coolant into the EGR cooler (3) from an additional source (105). The temperature value of the coolant is reduced (106). When the temperature value of the coolant is reduced to the preferred temperature range, there is no need for additional coolant anymore. The return valve (9) is turned on in order to pull the additional coolant back (107). Therefore, the additional coolant completes its closed circuit circulation, and it is transferred to the secondary tank (6) again (108). By means of the EGR cooling system (100), the temperature of the coolant in the EGR cooler (3) is continuously kept under control. When the temperature of the coolant increases and reaches to dangerous levels, additional coolant is provided from a coolant source other than the radiator (4), and the flowrate of the coolant is increased. Therefore, cooling is provided with a cooling method (100) wherein the flowrate of the coolant is decreased and increased.