LOW-PRESSURE EXHAUST GAS RECIRCULATION SYSTEM

• US 20130104859A1
• Filed: 09/14/2012
• Published: 05/02/2013
• Est. Priority Date: 10/31/2011
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: MIYAZAKI, Shinsuke, HASHIMOTO, Koji, OOHASHI, Takaaki
• Granted Patent: US 9,145,841 B2
• Time in Patent Office: Days
• US Class Current: 123/568.21
• CPC Class Codes: F02D 2009/0276 Throttle and EGR-valve operated together
• CPC Class Codes: F02D 41/0077 Control of the EGR valve or actuator, e.g. duty cycle, closed loop control of position EGR valve position sensor F02M26/48
• CPC Class Codes: F02D 41/042 for stopping the engine
• CPC Class Codes: F02M 26/54 Rotary actuators, e.g. step motors
• CPC Class Codes: F02M 26/64 the EGR valve being operated together with an intake air throttle
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

In a low-pressure EGR system, a mechanical stopper limits a rotation range of a low-pressure EGR regulating valve at a limit opening degree of the low-pressure EGR regulating valve on its fully-open side and outside an EGR amount adjustment opening degree range of the low-pressure EGR regulating valve. After an engine is stopped, a failure detection unit rotates the low-pressure EGR regulating valve to its fully-open position to such an extent that rotation of a linking device is prevented by the mechanical stopper, and is configured to determine that a failure has occurred when an opening degree of the low-pressure EGR regulating valve detected by a low-pressure EGR opening sensor is different from the limit opening degree of the low-pressure EGR regulating valve.

Claims

1. A low-pressure exhaust gas recirculation (EGR) system for an engine having an intake passage which guides intake air into the engine, the system comprising:

a low-pressure EGR passage that guides EGR gas into the intake passage;

a low-pressure EGR regulating valve that is configured to regulate an opening degree of the low-pressure EGR passage;

an electric actuator that is configured to drive the low-pressure EGR regulating valve;

a low-pressure EGR opening sensor that is configured to detect an opening degree of the low-pressure EGR regulating valve;

a control device that is configured to control energization of the electric actuator so as to control the opening degree of the low-pressure EGR regulating valve;

an intake throttle valve that is configured to generate a negative pressure of intake air at a merging part of the intake passage and the low-pressure EGR passage;

a linking device that is configured to change an output characteristic of the electric actuator so as to drive the intake throttle valve;

a mechanical stopper that is provided for the linking device and is configured to limit a rotation range of the low-pressure EGR regulating valve at a limit opening degree of the low-pressure EGR regulating valve on its fully-open side and outside an EGR amount adjustment opening degree range of the low-pressure EGR regulating valve; and

a failure detection unit that is provided for the control device, wherein after the engine is stopped, the failure detection unit rotates the low-pressure EGR regulating valve to its fully-open position to such an extent that rotation of the linking device is prevented by the mechanical stopper, and is configured to determine that a failure has occurred when the opening degree of the low-pressure EGR regulating valve detected by the low-pressure EGR opening sensor is different from the limit opening degree of the low-pressure EGR regulating valve.

2. The low-pressure EGR system according to claim 1, wherein:

the failure detection unit is configured to detect a state of intake air guided into the engine while the engine is in operation; and

the failure detection unit makes the failure determination based on the detected state of intake air.

3. The low-pressure EGR system according to claim 1, further comprising a throttle valve return spring that urges the intake throttle valve (8) in its valve-opening direction.

4. The low-pressure EGR system according to claim 1, further comprising a rotatable shaft that supports the intake throttle valve, wherein:

the intake throttle valve is a butterfly valve including;

a downstream valve plate located on a downstream side of the rotatable shaft in a flow direction of intake air; and

an upstream valve plate located on an upstream side of the rotatable shaft in the flow direction of intake air; and

an intake-air contact area of the downstream valve plate is larger than an intake-air contact area of the upstream valve plate.

5. The low-pressure EGR system according to claim 1, wherein:

the linking device includes a female-side member having a cam groove, and a male-side member having a groove engaging body which is engaged with the cam groove; and

an end portion of the cam groove and the groove engaging body constitute the mechanical stopper.