Patent Application
20190120153
The subject disclosure relates to bypass actuation detection during a low-efficiency indication of an exhaust gas recirculation (EGR) system.
In internal combustion engines, such as a diesel engine, for example, an EGR system may function to reduce nitrogen oxide (NOx) emission. Many vehicles (e.g., automobiles, trucks, construction equipment, farm equipment) use internal combustion engines. The EGR system recirculates a portion of engine exhaust gas back to the engine cylinders, diluting the oxygen in the incoming air stream and providing gases inert to combustion to act as absorbents to combustion heat. This reduces peak in-cylinder temperatures which are needed along with high cylinder pressures to produce NOx. An EGR system may have two different paths—one through a cooler module and one through a bypass module—such that the gases through the EGR system are sometimes cooled in addition to being recirculated. Over time, as the EGR system becomes clogged with soot, efficiency of the cooler module decreases such that the temperature reduction of gases that go through the EGR cooler module decreases. When this happens, the temperature differential that is typically used to discern whether gases followed a path through the EGR cooler module or the EGR bypass module is less effective. Thus, a bypass actuation detection is needed during a low-efficiency indication of the EGR system.
In one exemplary embodiment, a method of performing bypass actuation detection includes alternating control of a bypass valve within an exhaust gas recirculation (EGR) system of a vehicle to direct flow of gas through a cooler module or a bypass module within the EGR system. The method also includes determining a position of an EGR valve that directs the gas into the EGR system, and verifying operation of the bypass valve based on the position of the EGR valve.
In addition to one or more of the features described herein, the determining the position of the EGR valve includes using a position sensor.
In addition to one or more of the features described herein, the verifying includes determining whether the position of the EGR valve indicates that the EGR valve is more open when the flow is through the cooler module than when the flow is through the bypass module.
In addition to one or more of the features described herein, the method includes determining that efficiency of the cooler module is below a threshold value prior to the verifying the operation of the bypass valve.
In addition to one or more of the features described herein, the determining that the efficiency of the cooler module is below the threshold value includes controlling the bypass valve to direct the flow of the gas through the cooler module.
In addition to one or more of the features described herein, the determining that the efficiency of the cooler module is below the threshold value further includes determining temperature of the gas at an input of the EGR system and at an output of the cooler module.
In addition to one or more of the features described herein, the method includes issuing information that the efficiency of the cooler module is below the threshold value based on the verifying indicating that the operation of the bypass valve is correct.
In addition to one or more of the features described herein, the method includes issuing information that the bypass valve operation is not correct based on the verifying indicating that the operation of the bypass valve is not correct.
In another exemplary embodiment, a system to perform bypass actuation detection includes an EGR valve that directs gas into an exhaust gas recirculation (EGR) system of a vehicle. The system also includes a bypass valve within the EGR system, and a controller to alternate control of the bypass valve to direct flow of the gas through a cooler module or a bypass module within the EGR system, determine a position of the EGR valve for each change in the control of the bypass valve, and verify operation of the bypass valve based on the position of the EGR valve.
In addition to one or more of the features described herein, a position sensor is coupled to the EGR valve to provide the position of the EGR valve.
In addition to one or more of the features described herein, the controller is configured to determine whether the position of the EGR valve indicates that the EGR valve is more open when the flow of the gas is through the cooler module than when the flow of the gas is through the bypass module.
In addition to one or more of the features described herein, the controller determines that efficiency of the cooler module is below a threshold value prior to verifying the operation of the bypass valve.
In addition to one or more of the features described herein, the controller determines that the efficiency of the cooler module is below the threshold value based on controlling the bypass valve to direct the flow of the gas through the cooler module.
In addition to one or more of the features described herein, the controller determines temperature of the gas at an input of the EGR system and at an output of the cooler module to determine that the efficiency of the cooler module is below the threshold value.
In addition to one or more of the features described herein, the controller issues information that the efficiency of the cooler module is below the threshold value based on verifying that the operation of the bypass valve is correct.
In addition to one or more of the features described herein, the controller issues information that the bypass valve operation is not correct based on verifying that the operation of the bypass valve is not correct.
In addition to one or more of the features described herein, the EGR valve includes a direct current (dc) motor.
In addition to one or more of the features described herein, the bypass valve is a pneumatic valve.
In addition to one or more of the features described herein, the controller is an electronic control unit (ECU) that controls various operations of the vehicle.
In addition to one or more of the features described herein, the controller includes an electronic control unit (ECU) that controls various operations of the vehicle and processing circuitry coupled to the ECU.
The above features and advantages, and other features and advantages of the disclosure are readily apparent from the following detailed description when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following detailed description, the detailed description referring to the drawings in which:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
As previously noted, an EGR system of an internal combustion engine reduces NOx emission by reducing the peak temperature in the cylinders. The EGR system accomplishes this temperature reduction by reintroducing a portion of engine exhaust gas back to the engine cylinders. As also noted, the EGR system may have a path that further cools the exhaust gas via a cooler module and a path that simply diverts the exhaust gas via a bypass module (e.g., a pipe). Each of the paths of the EGR system may be preferable under different circumstances, and, under certain conditions, the cooler module must be avoided. For example, in low load conditions or when the gas temperature is below a specified value, the bypass module path may be preferable. Also, when the coolant temperature is below a specified value, directing gas through the cooler may result in undesirable hydrocarbon condensation such that the bypass module path is preferred. A bypass valve is actuated to control the path taken by the exhaust gas in the EGR system at a given time. Typically, this bypass valve does not include a position sensor that facilitates verification of the valve operation.
The efficiency of the cooler module of the EGR system must be monitored so that the cooler may be replaced or repaired when it is no longer functioning as it should. A diagnostic trouble code (DTC) may be issued when the cooling efficiency is estimated to be lower that a defined threshold. Typically, the difference between the temperature of gas entering the EGR system and the temperature of the gas exiting the cooler module of the EGR system is used to assess the cooling efficiency. When the temperature difference indicates an efficiency that is at or above the specified threshold, the functioning of the bypass valve is verified. This is because the bypass module cannot achieve the cooling efficiency specified by the threshold for the cooler module. Thus, when the bypass valve is controlled to direct the flow of gas through the cooler module and the temperature at the output of the cooler module is sufficiently lowered according to the specified efficiency, then the bypass value must necessarily have directed the gas through the (sufficiently efficient) cooler module rather than through the bypass module.
However, when this temperature difference indicates an efficiency below the specified threshold, the correct functioning of the bypass valve comes into question. This is because, when the bypass valve is not functioning correctly, the gas may flow through the bypass module even though the bypass valve is controlled to direct flow through the cooler module. In this case, the temperature of the gas at the output of the cooler module would mistakenly indicate inefficient cooler operation even though the gas did not actually flow through the cooler module. That is, during low-efficiency operation of the EGR cooler, there may be an overlap in EGR cooler and EGR bypass efficiency such that temperature of the gas exiting the EGR system does not indicate which path was taken through the EGR system. Thus, verifying the proper functioning of the bypass valve facilitates verification of the efficiency determination. Because the bypass valve does not include a flap position sensor or other direct means of indicating valve operation and the temperature difference cannot be relied on to indicate the flow path, bypass valve operation must be verified in another way.
Embodiments of the systems and methods detailed herein relate to bypass actuation detection during a low-efficiency indication of the EGR cooler. Specifically, when an efficiency below the specified threshold is indicated for the cooler module, a pressure differential rather than a temperature differential is used to determine which path the gas took, as further detailed. By ensuring that the DTC indicating inefficient cooler operation is issued based on efficiency determination only when the gas is actually flowing through the cooler module, unnecessary repair or replacement of the cooler module may be avoided.
In accordance with an exemplary embodiment,
A bypass valve 240 is used to control flow of gas within the EGR system 110 to either be through the cooler module 210 or through the bypass module 205. The bypass valve 240 may be a pneumatic valve that is controlled to be in one of two positions by the ECU 140 based on information from the processing circuitry 130 (e.g., cooler module 210 efficiency) or other information (e.g., load level).
Known temperature sensors 220-1, 220-2b, 220-2c (generally referred to as 220) are used to measure the temperature of exhaust gas at different parts of the EGR system 110. The temperature sensor 220-1 measures the temperature T1 of the exhaust gas at it enters the EGR valve 230. The temperature sensor 220-2b measures the temperature T2b of the exhaust gas at the output of the bypass module 205, and the temperature sensor 220-2c measure the temperature T2c of the exhaust gas at the output of the cooler module 210. In alternate embodiments, one temperature sensor 220 may measure the temperature of gas at the output of the EGR system 110, whether the gas passed through the cooler module 210 or the bypass module 205.
When the EGR valve 230 is set to direct exhaust gas into the EGR system 110 and the bypass valve 240 is set to direct the exhaust gas into the cooler module 210, the temperatures T1 and T2c are used to determine the efficiency of the cooler module 210. When the efficiency is determined to be at or above the threshold value, then the functioning of the bypass valve 240 in actually sending exhaust gas through the cooler module 210 is not in question. This is because the drop in temperature of the exhaust gas required to make the value of T2c low enough for the efficiency to be at or above the required threshold level is not possible if the exhaust gas instead passed through the bypass module 205. Also T2c is much lower than T2b when the gas flows through the cooler module 210 and the cooler module 210 efficiency is sufficiently high.
If, on the other hand, the efficiency is determined to be below a threshold value, then verifying the functioning of the bypass valve 240 is important to ensuring that unnecessary actions are not taken. For example, a lower than threshold efficiency of the cooler module 210 may lead the EGR valve 230 to divert gas so that it does not flow into the EGR system 110. As another example, a DTC may be issued to trigger repair or replacement of the cooler module 210. To prevent these actions from being taken unnecessarily, the functionality of the bypass valve 240 must be verified.
If the bypass valve 240 is set to control the flow of gas through the cooler module 210, and the efficiency is determined to be below a threshold value, then T2c and T2b may be nearly the same. However, the similarity in temperature at the output of the cooler module 210 and the bypass module 205 may mean one of two different conditions. The similarity in T2c and T2b may mean that the flow of gas was, in fact, through the cooler module 210 as it should have been and the efficiency of the cooler module 210 is, in fact, below the specified threshold. On the other hand, the similarity in T2c and T2b may mean that the flow of gas was through the bypass module 205 even though it should have been through the cooler module 210, according to the setting of the bypass valve 240. Thus, the cooler module 210 did not have an opportunity to cool the gas and reduce T2c at all.
As the description of the two conditions indicates, the temperatures T2b and T2c are not helpful in determining which of the conditions has occurred. Instead, pressure difference is used to verify the functioning of the bypass valve 240 even though pressure sensors are not used and are not needed. When the cooler module 210 efficiency is at or above the threshold value, the pressure difference (from the bypass valve 240 to the output of the cooler module 210 (APc) or from the bypass valve 240 to the output of the bypass module 205 (APb)) is nearly the same or APb is slightly higher than APc. However, when efficiency of the cooler module 210 drops below the threshold, APc increases to a much higher value than APb. As a result, the EGR valve 230 opens more when flow is through the (inefficient) cooler module 210 than through the bypass module 205. This difference in the opening of the EGR valve 230, as determined by the position sensor 235, may be used to verify the functioning of the bypass valve 240.
At block 340, a determination is made by the processing circuitry 130 of whether the efficiency of the cooler module 210 is below the established threshold. If the efficiency is not below the threshold, then normal operation is resumed at block 345. If the efficiency is determined to be below the threshold, at bloc 340, the correct operation of the bypass valve 240 must be verified according to the processes at blocks 350 and 360, which are performed iteratively, as shown. The number of times that the processes at blocks 350 and 360 are repeated may be predefined and controlled by the ECU 140 in combination with the processing circuitry 130.
At block 350, alternating control of the bypass valve 240 refers to changing the direction of gas flow determined by the bypass valve 240. For example, because gas flow is initially to the cooler module 210 when the efficiency determination is made, the first iteration of the process at block 350 may involve changing the bypass valve 240 position to control flow to be through the bypass module 205 instead. The next iteration of the process at block 350 would involve changing the bypass valve 240 position back to directing the flow of gas through the cooler module 210.
Each time the flow of gas is changed between a path through the cooler module 210 and a path through the bypass module 205, at block 350, the process at block 360 is performed. At block 360, verifying bypass valve 240 operation based on the EGR valve 230 position refers to using the position sensor 235. When the bypass valve 240 is supposed to direct flow through the cooler module 210, the position sensor 235 should indicate that the EGR valve 230 is open more than when the bypass valve 240 is supposed to direct flow through the bypass module 205. This is because of the previously discussed difference in the pressure drop of the paths through the cooler module 210 and the bypass module 205.
When the bypass valve 240 operation is verified, at block 360, taking action, at block 370, may include issuing the DTC indicating the drop in efficiency of the cooler module 210. When the bypass valve 240 is found not to be operating correctly, at block 360, then taking action, at block 370, may include issuing a DTC to indicate bypass valve 240 malfunction.
While the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from its scope. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within the scope thereof.
