# US 8,769,931 B2 · Low pressure EGR system and examining method for efficiency of low EGR cooler > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,769,931 B2 - Document ID: US8769931B2 - Status: Granted - Kind: B2 - Application number: 13/315,073 - Filed: 2011-12-08 - Published: 2012-12-13 - Granted: 2014-07-08 - Earliest claimed: 2011-06-13 - Assignees: Hyundai Motor Company; Kia Motors Corporation - Applicants: Kihoon Nam - Inventors: Kihoon Nam - Web page: https://patentgrep.com/patent/US8769931B2 ## CPC - F02B 37/22: by varying cross-section of exhaust passages or air passages {, e.g. by throttling turbine inlets or outlets or by varying effective number of guide conduits} (F02B37/24 takes precedence) - F01N 3/021: by means of filters - F01N 3/106: {Auxiliary oxidation catalysts} - F01N 5/04: the devices using kinetic energy - F02D 41/0072: {Estimating, calculating or determining the EGR rate, amount or flow (sensors in EGR systems F02M26/45)} - F02D 41/221: {relating to the failure of actuators or electrically driven elements} - F02M 26/06: Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor - F02M 26/16: with EGR valves located at or near the connection to the exhaust system - F02M 26/24: with two or more coolers - F02M 26/47: the characteristics being temperatures, pressures or flow rates - F02M 26/49: Detecting, diagnosing or indicating an abnormal function of the EGR system - F02M 26/71: Multi-way valves - F01N 2560/06: the means being a temperature sensor - F01N 2560/08: the means being a pressure sensor - F01N 2560/14: having more than one sensor of one kind - F01N 2900/1404: Exhaust gas temperature - F01N 2900/1406: Exhaust gas pressure - F01P 2060/16: Outlet manifold - F02B 29/0406: {Layout of the intake air cooling or coolant circuit} - F02D 41/1448: {the characteristics being an exhaust gas pressure} - F02D 2041/0067: {Determining the EGR temperature} - F02M 26/05: High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor - F02M 26/15: in relation to engine exhaust purifying apparatus - F02M 26/35: with means for cleaning or treating the recirculated gases, e.g. catalysts, condensate traps, particle filters or heaters - Y02T 10/12: Improving ICE efficiencies - Y02T 10/40: Engine management systems - F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G) - F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16) - F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W) - F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF - F01P: COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES (arrangements in connection with cooling of propulsion units in vehicles B60K11/00; heat-transfer, heat-exchange or heat-storage materials C09K5/00; {cooling of gas-turbine engines F02C7/12}; heat exchange in general, radiators F28) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A low pressure exhaust gas recirculation (EGR) cooler efficiency diagnosis method for an EGR system includes measuring speed and load of an engine, setting a difference threshold between model temperature and detected temperature downstream of the low pressure EGR cooler according to speed and load of the engine, measuring a pressure difference between upstream and downstream sides of the EGR valve, calculating a mass flow rate of an exhaust gas passing through the low pressure EGR cooler based on the measured pressure difference, calculating the efficiency of the low pressure EGR cooler based on the calculated mass flow rate, calculating the model temperature downstream of the low pressure EGR cooler based on the calculated efficiency, and comparing the model temperature downstream of the low pressure EGR cooler with the detected temperature downstream of the low pressure EGR cooler. A low pressure EGR system is also disclosed. ## Claims ### Claim 1 A low pressure exhaust gas recirculation (EGR) cooler efficiency diagnosis method for an EGR system, the method comprising: measuring a speed and a load of an engine; using an ECU to perform the following steps; setting a threshold of a difference between a model temperature and a detected temperature downstream of a low pressure EGR cooler according to the speed and the load of the engine; measuring a pressure difference between an upstream side and a downstream side of a low pressure EGR valve; calculating a mass flow rate of an exhaust gas passing through the low pressure EGR cooler based on the measured pressure difference; calculating an efficiency of the low pressure EGR cooler based on the calculated mass flow rate; calculating the model temperature downstream of the low pressure EGR cooler based on the calculated efficiency; and comparing the model temperature downstream of the low pressure EGR cooler with the detected temperature downstream of the low pressure EGR cooler, wherein the mass flow rate of the exhaust gas is calculated according to a first equation of =ρexhQexh=C·AFlap√{square root over (2ρexhΔP)}=f(ΔP,valve position)√{square root over (2ρexhΔP)} Eq. (1) wherein, the is a mass flow rate of the exhaust gas flowing in a low pressure EGR line, wherein the ρexh is a density of the exhaust gas, wherein the Qexh is a volume flow rate of the exhaust gas, wherein the C is a coefficient, wherein the AFlap is a cross-section of the low pressure EGR valve, wherein the ΔP is the pressure difference between the upstream and the downstream of the low pressure EGR valve, wherein the efficiency of the low pressure EGR cooler is calculated according to a second equation of η=f(,Tcoolant−Tin), Eq. (2) wherein the Tcoolant is a coolant temperature flowing in or flowing out of the low pressure EGR cooler, and wherein the Tin is an exhaust gas temperature of an upstream side of the low pressure EGR cooler, and wherein the calculating of the model temperature downstream of the low pressure EGR cooler is performed by substituting the second equation into a third equation of Tout=Tin−η(Tin−Tcoolant), Eq. (3) wherein the Tout is the model temperature of a downstream side of the low pressure EGR cooler, and wherein the η is the efficiency of the low pressure EGR cooler. ### Claim 2 (depends on 1) The low pressure EGR cooler efficiency diagnosis method of claim 1, wherein the mass flow rate of the exhaust gas passing through the low pressure EGR cooler is calculated using a low pressure EGR valve model. ### Claim 3 (depends on 1) The low pressure EGR cooler efficiency diagnosis method of claim 1, wherein the efficiency of the low pressure EGR cooler is calculated based on the mass flow rate of exhaust gas passing through the low pressure EGR cooler, a coolant temperature, and an exhaust gas temperature at an inlet of the low pressure EGR cooler. ### Claim 4 (depends on 1) The low pressure EGR cooler efficiency diagnosis method of claim 1, wherein the temperature downstream of the low pressure EGR cooler is calculated using a low pressure EGR cooler efficiency model. ### Claim 5 (depends on 1) The low pressure EGR cooler efficiency diagnosis method of claim 1, wherein if the difference between the model temperature and the detected temperature is larger than the predetermined threshold, a debounce is performed. ### Claim 6 (depends on 5) The low pressure EGR cooler efficiency diagnosis method of claim 5, wherein the low pressure EGR system is stopped if errors are continuously generated while the debounce is being performed. ### Claim 7 (depends on 6) The low pressure EGR cooler efficiency diagnosis method of claim 6, further comprising sending an alarm through a warning lamp when the low pressure EGR system is stopped. ### Claim 8 A low pressure EGR system, which includes an intake line through which an intake air is supplied into an engine, an exhaust line through which an exhaust gas of the engine passes, a low pressure EGR line that is diverged from the exhaust line and connected to the intake line, a low pressure EGR valve that is disposed on the low pressure EGR line, and a low pressure EGR cooler that cools the exhaust gas flowing through the low pressure EGR valve, the system comprising: pressure sensors disposed at a downstream side and an upstream side of the low pressure EGR valve; a temperature sensor that is disposed at a downstream side of the low pressure EGR cooler to detect a temperature at the downstream side of the low pressure EGR cooler; an ECU wherein the ECU sets a threshold of a difference between a model temperature and a detected temperature downstream of the low pressure EGR cooler, measures a pressure difference between the upstream side and the downstream side of the low pressure EGR valve by using the pressure sensors, calculates a mass flow rate of the exhaust gas passing through the low pressure EGR cooler based on the measured pressure difference calculates an efficiency of the low pressure EGR cooler based on the calculated mass flow rate, calculates the model temperature downstream of the low pressure EGR cooler based on the calculated efficiency; and compares the model temperature downstream of the low pressure EGR cooler with the detected temperature downstream of the low pressure EGR cooler, wherein the mass flow rate of the exhaust gas is calculated according to a first equation of =ρexhQexh=C·AFlap√{square root over (2ρexhΔP)}=f(ΔP,valve position)√{square root over (2ρexhΔP)} Eq. (1) wherein, the is a mass flow rate of the exhaust gas flowing in the low pressure EGR line, wherein the ρexh is a density of the exhaust gas, wherein the Qexh is a volume flow rate of the exhaust gas, wherein the C is a coefficient, wherein the AFlaP is a cross-section of the low pressure EGR valve, wherein the ΔP is the pressure difference between the upstream and the downstream of the low pressure EGR valve, wherein the efficiency of the low pressure EGR cooler is calculated according to a second equation of η=f(,Tcoolant−Tin), Eq. (2) wherein the Tcoolant is a coolant temperature flowing in or flowing out of the low pressure EGR cooler, and wherein the Tin is an exhaust gas temperature of an upstream side of the low pressure EGR cooler, and wherein the calculating of the model temperature downstream of the low pressure EGR cooler is performed by substituting the second equation into a third equation of Tout=Tin−η(Tin−Tcoolant), Eq. (3) wherein the Tout is the model temperature of the downstream side of the low pressure EGR cooler, and wherein the η is the efficiency of the low pressure EGR cooler. ### Claim 9 (depends on 8) The low pressure EGR system of claim 8, wherein at least one of the pressure sensors are disposed at the downstream side of the low pressure EGR valve and/or at the downstream side of the low pressure EGR cooler. ### Claim 10 (depends on 8) The low pressure EGR system of claim 8, wherein an emergency filter is disposed at the upstream side of the low pressure EGR cooler. ### Claim 11 (depends on 8) The low pressure EGR system of claim 8, wherein a catalyst is disposed at an upstream side of the low pressure EGR line. ### Claim 12 (depends on 11) The low pressure EGR system of claim 11, wherein the catalyst includes a diesel filter catalyst or a diesel oxidation catalyst. ### Claim 13 (depends on 8) The low pressure EGR system of claim 8, wherein a warning lamp is lit to send an alarm of an emergency condition of the system for the low pressure EGR.