# US 2014/0196527 A1 · Method for diagnosing a low pressure exhaust gas recirculation system of an internal combustion engine and device for carrying out the method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0196527 A1 - Document ID: US20140196527A1 - Status: Published application - Kind: A1 - Application number: 14/156,955 - Filed: 2014-01-16 - Published: 2014-07-17 - Earliest claimed: 2013-01-16 - Assignees: Robert Bosch GmbH - Inventors: Thomas BOSSMEYER; Stefan Motz; Jens Pawlak - Web page: https://patentgrep.com/patent/US20140196527A1 ## CPC - 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 - F02D 21/08: the other gas being the exhaust gas of engine - F02D 41/0072: {Estimating, calculating or determining the EGR rate, amount or flow (sensors in EGR systems F02M26/45)} - F02D 41/18: by measuring intake air flow - 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 26/49: Detecting, diagnosing or indicating an abnormal function of the EGR system - F02D 41/22: Safety or indicating devices for abnormal conditions {(in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809)} - F02M 26/15: in relation to engine exhaust purifying apparatus - F02M 26/24: with two or more coolers - F02M 26/25: with coolers having bypasses - Y02T 10/40: Engine management systems - F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF - 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) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A method and device for diagnosing a low pressure exhaust gas recirculation system (LPEGRS) of an internal combustion engine having an intake area for supplying fresh air which includes in succession in the flow direction a first section having a low pressure in which an air mass flow sensor is situated, a compressor and a second section having a high pressure, the engine exhaust area including a second section having a low exhaust gas pressure, and the LPEGRS which has an adjustable LPEGR valve recirculating at least a portion of the exhaust gas in the second section of the exhaust area to the first section of the intake area. The fresh air mass flow taken in is measured by the air mass flow sensor, the total mass flow flowing through the compressor being ascertained, the LPEGR mass flow being ascertained from the difference between the total mass flow and the fresh air mass flow taken in, an estimated value being calculated for the LPEGR mass flow, the difference between the ascertained LPEGR mass flow and the estimated value being formed, and an error signal being output for a deviation. The procedure is for detecting exhaust gas-relevant errors. ## Claims ### Claim 1 A method for diagnosing a low pressure exhaust gas recirculation system of an internal combustion engine, the method comprising: measuring, the internal combustion engine having an intake area for supplying fresh air which includes in succession in the flow direction a first section having a low pressure in which an air mass flow sensor is situated, a compressor and a second section having a high pressure, the exhaust area of the internal combustion engine including a first section having a low exhaust gas pressure, and the low pressure exhaust gas recirculation system which has an adjustable low pressure exhaust gas recirculation valve recirculating at least a portion of the exhaust gas in the second section of the exhaust area to the first section of the intake area, by the air mass flow sensor the fresh air mass flow taken in; ascertaining the total mass flow flowing through the compressor; ascertaining the low pressure exhaust gas recirculation mass flow from the difference between the total mass flow and the fresh air mass flow; determining an estimated value for the low pressure exhaust gas recirculation mass flow; forming a difference between the ascertained low pressure exhaust gas recirculation mass flow and the estimated value; and outputting an error signal in the event of a deviation. ### Claim 2 (depends on 1) The method of claim 1, wherein the difference is compared to a threshold value in a comparator, and wherein the error signal is output only if the threshold value is exceeded. ### Claim 3 (depends on 1) The method of claim 1, wherein the total mass flow flowing through the compressor is ascertained with the aid of a model. ### Claim 4 (depends on 3) The method of claim 3, wherein the model takes at least the following variables into account: (a) a speed of the compressor; (b) a pressure upstream from the compressor; (c) a pressure downstream from the compressor; (d) a temperature upstream from the compressor; and (e) a temperature downstream from the compressor. ### Claim 5 (depends on 1) The method of claim 1, wherein the estimated value for the low pressure exhaust gas recirculation mass flow is ascertained with the aid of a model. ### Claim 6 (depends on 5) The method of claim 5, wherein the model takes at least one of the following variables into account: (a) the opening cross section of the low pressure exhaust gas recirculation valve; (b) a pressure upstream from the low pressure exhaust gas recirculation valve; (c) a pressure downstream from the low pressure exhaust gas recirculation valve; and (d) a temperature upstream from the low pressure exhaust gas recirculation valve. ### Claim 7 (depends on 1) The method of claim 1, wherein a low pressure exhaust gas recirculation valve is perceived as stuck open if the ascertained low pressure exhaust gas recirculation mass flow exceeds the estimated value. ### Claim 8 (depends on 1) The method of claim 1, wherein a low pressure exhaust gas recirculation valve is perceived as stuck closed if the estimated value exceeds the ascertained low pressure exhaust gas recirculation mass flow. ### Claim 9 A device for diagnosing a low pressure exhaust gas recirculation system of an internal combustion engine, comprising: a control device having at least one unit for determining an estimated value for a low pressure exhaust gas recirculation mass flow, and a subtractor for determining a difference; wherein the control device is configured for: measuring, the internal combustion engine having an intake area for supplying fresh air which includes in succession in the flow direction a first section having a low pressure in which an air mass flow sensor is situated, a compressor and a second section having a high pressure, the exhaust area of the internal combustion engine including a first section having a low exhaust gas pressure, and the low pressure exhaust gas recirculation system which has an adjustable low pressure exhaust gas recirculation valve recirculating at least a portion of the exhaust gas in the second section of the exhaust area to the first section of the intake area, by the air mass flow sensor the fresh air mass flow taken in; ascertaining the total mass flow flowing through the compressor; ascertaining the low pressure exhaust gas recirculation mass flow from the difference between the total mass flow and the fresh air mass flow; determining an estimated value for the low pressure exhaust gas recirculation mass flow; forming a difference, by the subtractor, between the ascertained low pressure exhaust gas recirculation mass flow and the estimated value; and outputting an error signal in the event of a deviation. ### Claim 10 (depends on 9) The device of claim 9, wherein the difference is compared to a threshold value in a comparator, and wherein the error signal is output only if the threshold value is exceeded. ### Claim 11 A computer readable medium having a computer program, which is executable by a processor, comprising: a program code arrangement having program code for diagnosing a low pressure exhaust gas recirculation system of an internal combustion engine, by performing the following: measuring, the internal combustion engine having an intake area for supplying fresh air which includes in succession in the flow direction a first section having a low pressure in which an air mass flow sensor is situated, a compressor and a second section having a high pressure, the exhaust area of the internal combustion engine including a first section having a low exhaust gas pressure, and the low pressure exhaust gas recirculation system which has an adjustable low pressure exhaust gas recirculation valve recirculating at least a portion of the exhaust gas in the second section of the exhaust area to the first section of the intake area, by the air mass flow sensor the fresh air mass flow taken in; ascertaining the total mass flow flowing through the compressor; ascertaining the low pressure exhaust gas recirculation mass flow from the difference between the total mass flow and the fresh air mass flow; determining an estimated value for the low pressure exhaust gas recirculation mass flow; forming a difference between the ascertained low pressure exhaust gas recirculation mass flow and the estimated value; and outputting an error signal in the event of a deviation.