JP2013249799A - Exhaust gas recirculating device for internal combustion engine - Google Patents

Abstract

An exhaust gas recirculation device for an internal combustion engine capable of preventing corrosion from being easily generated due to an allowance of excessive accumulation of condensed water is provided.
An EGR device 40 is disposed below an EGR cooler 42 in the direction of gravity with an EGR pipe 41 and an EGR cooler 42, and bypasses the EGR cooler 42, and at least of the EGR cooler 42 and the bypass pipe 44 The bypass portion 45 has a valve portion 45 that switches the flow path, and the bypass-time flow portion P has a storage portion T that can store condensed water generated by the EGR cooler 42, and the amount of condensed water stored in the storage portion T is a predetermined amount. When the number is larger than α, the exhaust gas is circulated through the bypass pipe 44 among the EGR cooler 42 and the bypass pipe 44.
[Selection] Figure 2

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

  An exhaust gas recirculation device for an internal combustion engine that recirculates exhaust gas from an exhaust system of the internal combustion engine to an intake system is known. An exhaust gas recirculation device is disclosed in Patent Document 1, for example. In the exhaust gas recirculation device disclosed in Patent Document 1, the bypass passage is disposed below the cooler passage. In addition, for example, Patent Documents 2 and 3 disclose techniques that are considered to be related to the present invention in terms of the configuration for storing condensed water.

JP 2010-285897 A JP 2000-87810 A JP 2010-25034 A

  In the exhaust gas recirculation device, moisture contained in the exhaust gas may be condensed. And the condensed water which generate | occur | produced will be collected in the part which is easy to accumulate including the case where the storage part which can store condensed water is intentionally provided. However, if it is allowed that excessive condensate is accumulated, a large amount of condensate may flow into the intake system or the internal combustion engine at any one time, such as when the intake negative pressure increases during deceleration of the internal combustion engine. . On the other hand, NOx and SOx dissolve in the condensed water to generate strong acid. For this reason, when it is allowed that the condensed water accumulates excessively, there is a possibility that each part in the cylinder including the intake system parts and the fuel injection valve is easily corroded.

  In view of the above problems, an object of the present invention is to provide an exhaust gas recirculation device for an internal combustion engine capable of suppressing the occurrence of corrosion due to the fact that excessive condensate is allowed to accumulate. .

  The present invention is provided with a recirculation passage portion connecting an exhaust system and an intake system of an internal combustion engine, a cooler for cooling exhaust gas flowing through the recirculation passage portion, and below the cooler in the direction of gravity action, A bypass passage section that bypasses the cooler, and a valve section that switches a flow path to at least one of the cooler and the bypass passage section, through the bypass passage section of the cooler and the bypass passage section. In the case where exhaust gas is circulated, a storage part capable of storing condensed water generated by the cooler is provided in a part where the exhaust gas circulates, and when the amount of condensed water stored in the storage part is larger than a predetermined amount, the cooler and An exhaust gas recirculation device for an internal combustion engine that circulates exhaust gas through at least the bypass passage portion of the bypass passage portion.

  The present invention further includes an estimation unit that estimates the amount of condensed water stored in the storage unit, and the estimation unit is returned to the intake system from the wall temperature of the cooler, the exhaust temperature in the cooler, and the exhaust system. The storage unit stores the exhaust gas based on at least one of an exhaust flow rate, an exhaust component recirculated from the exhaust system to the intake system, an outside air temperature, and a humidity of exhaust gas recirculated from the exhaust system to the intake system. It can be set as the structure which estimates the amount of condensed water to do.

  This invention can be set as the structure which has given the coating which has water repellency to the inner wall part of the said storage part.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that it becomes easy to generate | occur | produce corrosion because it is permitted that condensed water accumulates excessively.

1 is a schematic configuration diagram of a vehicle. It is a figure which shows the principal part of an EGR apparatus. It is a figure which shows the relationship between the generation amount of condensed water, and the storage amount. It is a figure which shows the control action of ECU with a flowchart. It is operation | movement explanatory drawing of an EGR apparatus.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a vehicle 100. The vehicle 100 is equipped with an internal combustion engine 50. The vehicle 100 can be, for example, a vehicle that automatically stops the operation of the internal combustion engine 50 when traveling is stopped (a vehicle that performs idle stop). Moreover, it can be set as the hybrid vehicle which uses the motive power apparatus (for example, regenerative motor) other than the internal combustion engine 50 and the internal combustion engine 50 as a motive power source.

  The internal combustion engine 50 is a compression ignition type internal combustion engine (for example, a diesel engine). Therefore, the internal combustion engine 50 includes a fuel injection valve 55 that directly injects fuel into the cylinder. The internal combustion engine 50 may be, for example, a spark ignition type internal combustion engine. The internal combustion engine 50 can be an internal combustion engine that performs a plurality of fuel injections (multi-stage injection) in each cylinder during one combustion cycle. In addition to the internal combustion engine 50, the vehicle 100 is equipped with an intake system 10, an exhaust system 20, a supercharger 30, an EGR device 40, and an ECU 70.

  The intake system 10 includes an air flow meter 11, an intercooler 12, a diesel throttle 13, and an intake manifold 14. The air flow meter 11 measures the intake air amount of the internal combustion engine 50. The intercooler 12 cools the intake air of the internal combustion engine 50. The diesel throttle 13 adjusts the amount of fresh air flowing into the internal combustion engine 50 by adjusting the amount of intake air of the internal combustion engine 50. Specifically, the diesel throttle 13 is an electronically controlled throttle valve. The intake manifold 14 distributes intake air to each cylinder of the internal combustion engine 50. The exhaust system 20 includes an exhaust manifold 21 and a catalyst 22. The exhaust manifold 21 joins exhaust from each cylinder of the internal combustion engine 50. The catalyst 22 purifies the exhaust.

  The supercharger 30 supercharges intake air to the internal combustion engine 50. The supercharger 30 is an exhaust-driven supercharger and includes a compressor unit 31 and a turbine unit 32. The compressor unit 31 is provided in the intake system 10, and the turbine unit 32 is provided in the exhaust system 20. For this reason, in the supercharger 30, the compressor unit 31 constitutes a part of the intake system 10, and the turbine part 32 constitutes a part of the exhaust system 20.

  The EGR device 40 is an exhaust gas recirculation device for an internal combustion engine, and includes an EGR pipe 41, an EGR cooler 42, an EGR valve 43, a bypass pipe 44, and a valve portion 45. The EGR device 40 forms an EGR path. The EGR pipe 41 is a return passage section and connects the intake system 10 and the exhaust system 20. The EGR pipe 41 is provided with an EGR cooler 42, an EGR valve 43, and a valve 45a. The EGR pipe 41 may have a plurality of pipes.

  The EGR cooler 42 is a cooler, and cools the exhaust gas that is recirculated (hereinafter referred to as EGR gas). Specifically, the EGR cooler 42 is a heat exchanger that cools the EGR gas by exchanging heat between the cooling water of the internal combustion engine 50 and the EGR gas. The EGR valve 43 is a flow rate adjusting valve and adjusts the flow rate of the EGR gas. The EGR valve 43 is provided in the downstream portion of the EGR pipe 41. This portion is a portion on the downstream side of the EGR cooler 42 in the EGR pipe 41. Specifically, the EGR valve 43 is provided at an end of the EGR pipe 41 on the intake system 10 side.

  The bypass pipe 44 is a bypass passage portion, and is connected to the EGR pipe 41 so as to bypass the EGR cooler 42. The valve unit 45 includes a valve 45 a provided in the EGR pipe 41 and a valve 45 b provided in the bypass pipe 44. Specifically, the valves 45a and 45b are both on-off valves. The valve unit 45 switches the flow path to at least one of the EGR cooler 42 and the bypass pipe 44. The valves 45a and 45b may be flow rate adjusting valves. The valve part 45 may be comprised with one valve | bulb.

  FIG. 2 is a diagram showing a main part of the EGR device 40. FIG. 2 shows the main part of the EGR device 40 as viewed along the horizontal direction. As shown in FIG. 2, the bypass pipe 44 is disposed below the EGR cooler 42 in the direction of gravity action. In this regard, a branch portion B is provided at a portion where the EGR pipe 41 and the bypass pipe 44 branch on the upstream side of the EGR pipe 41 and the bypass pipe 44. Moreover, the junction part J is provided in the part where EGR piping 41 and bypass piping 44 merge on the downstream side among EGR piping 41 and bypass piping 44.

  Both the branch part B and the junction part J have a shape extending along the direction of gravity action. The EGR pipe 41 extends along the horizontal direction from the upper part of the branch part B and the bypass pipe 44 extends from the lower part of the branch part B, and merges at the junction part J. A valve portion 45 is provided adjacent to the upstream side of the junction portion J. More specifically, the EGR pipe 41 and the bypass pipe 44 are provided as follows.

  That is, in the EGR cooler 42 and the bypass pipe 44, when the exhaust gas is circulated through the bypass pipe 44, the bypass circulation part P, which is a part through which the exhaust gas circulates, extends along the horizontal direction at the bypass pipe 44 part. Is provided. Further, it is provided so as to extend obliquely upward from the junction portion J at a portion downstream of the junction portion J. Thus, the bottom portion of the inner wall portion is provided at a portion downstream of the junction portion J so as to be higher than the junction portion J. The bottom of the inner wall of the bypass pipe 44 and the bottom of the inner wall of the junction J are set to have the same height.

  The EGR device 40 has a storage portion T capable of storing condensed water generated by the EGR cooler 42 in the bypass circulation portion P. Specifically, the storage portion T has a bottom portion of the inner wall portion at the junction portion J and is a portion capable of storing condensed water over a portion downstream from the junction portion J. The bottom portion of the inner wall portion is provided at a position lower than the EGR cooler 42. A portion upstream of the merging portion J and the storage portion T in the bypass circulation portion P is divided by a valve portion 45 (specifically, a valve 45b). A coating having water repellency is applied to the inner wall of the reservoir T.

  The storage portion T is a portion capable of storing the condensed water flowing out from the EGR cooler 42 together with the exhaust gas when the flow path is switched to the EGR cooler 42 among the EGR cooler 42 and the bypass pipe 44. In this regard, the portion of the EGR pipe 41 that is connected to the joining portion J from the upstream side and the portion that is connected from the downstream side are provided on the facing wall portion of the joining portion J. On the other hand, the portion connected to the junction J from the upstream side is provided at a higher position than the portion connected from the downstream side. For this reason, the exhaust gas that has circulated through the EGR cooler 42 flows through the merging portion J while changing the flow direction downward at the merging portion J.

  The ECU 70 shown in FIG. 1 is an electronic control unit. The ECU 70 is electrically connected to the diesel throttle 13, the EGR valve 43, the valve unit 45 (specifically, the valves 45a and 45b) and the fuel injection valve 55 as control targets. ing. In addition to the air flow meter 11, an intake air temperature sensor 61, an intake air pressure sensor 62, an exhaust air temperature sensor 63, and an exhaust air pressure sensor 64 are electrically connected as sensors and switches. The intake air temperature sensor 61 and the intake air pressure sensor 62 are the intake air temperature and pressure of the portion of the intake system 10 to which the EGR pipe 41 is connected. The exhaust air temperature sensor 63 and the exhaust air pressure sensor 64 are the EGR pipe 41 of the exhaust system 20. Is provided so that the temperature and pressure of the exhaust gas at the portion to which it is connected can be detected.

  In addition to these, the ECU 70 is electrically connected to a sensor group 65 for detecting the operating state of the internal combustion engine 50 and the vehicle 100. The sensor group 65 detects a crank sensor that can detect the rotation speed of the internal combustion engine 50, an accelerator opening sensor that detects the amount of depression of an accelerator pedal that makes an acceleration request to the internal combustion engine 50, and a cooling water temperature of the internal combustion engine 50. A water temperature sensor, an ignition switch for starting the internal combustion engine 50, and a vehicle speed sensor capable of detecting the vehicle speed. Various types of information based on the output of the sensor group 65 and the output of the sensor group 65 may be acquired via an ECU for controlling the internal combustion engine 50, for example. Alternatively, the ECU 70 may be an ECU for controlling the internal combustion engine 50.

  In the ECU 70, the CPU executes processing based on a program stored in the ROM while using a temporary storage area of the RAM as necessary. As a result, various functional units such as the following control unit and estimation unit are realized.

  When the amount of condensed water stored in the storage unit T (hereinafter referred to as storage amount) is larger than the predetermined amount α, the control unit causes the exhaust gas to flow through at least the bypass pipe 44 among the EGR cooler 42 and the bypass pipe 44. Specifically, the control unit controls the valve unit 45 to circulate the exhaust gas in this way. The EGR device 40 is configured to circulate exhaust gas in this manner by further including an ECU 70 that realizes such a control unit.

  More specifically, the control unit causes the exhaust gas to flow through the bypass pipe 44 among the EGR cooler 42 and the bypass pipe 44 when the storage amount is larger than the predetermined amount α. On the other hand, when the storage amount is smaller than the predetermined amount α (specifically, when it is equal to or less than the predetermined amount α here), the exhaust gas is circulated through the EGR cooler 42 among the EGR cooler 42 and the bypass pipe 44. The controller further reduces the degree of opening of the diesel throttle 13 when the storage amount is larger than the predetermined amount α. Further, the degree of opening of the EGR valve 43 is increased.

  The estimation unit estimates the storage amount. Specifically, the estimator includes the wall temperature of the EGR cooler 42, the exhaust temperature in the EGR cooler 42, the flow rate of exhaust gas recirculated from the exhaust system 20 to the intake system 10, and the exhaust gas recirculated from the exhaust system 20 to the intake system 10. The storage amount is estimated based on at least one of the components, the outside air temperature, and the humidity of the exhaust gas recirculated from the exhaust system 20 to the intake system 10. In this regard, the ECU 70 is further electrically connected to a sensor capable of detecting or estimating these parameters as required.

  More specifically, the estimation unit estimates the amount of condensed water generated in the EGR cooler 42 based on these parameters (hereinafter referred to as the generation amount) and estimates the storage amount based on the estimated generation amount. FIG. 3 is a diagram showing the relationship between the amount of condensed water generated and the amount stored. As shown in FIG. 3, the storage amount increases with a degree corresponding to the magnitude of the generation amount. Therefore, the storage amount can be estimated based on the generation amount by grasping the correlation in advance.

  The estimation unit further estimates a drying time necessary for drying the storage unit T based on the temperature of the exhaust gas flowing through the EGR cooler 42 and the cooling water temperature of the internal combustion engine 50. Then, the control unit causes the exhaust gas to flow through the EGR cooler 42 among the EGR cooler 42 and the bypass pipe 44 when the drying time estimated by the estimation unit has elapsed. Further, the state in which the degree of opening of the diesel throttle 13 is decreased and the state in which the degree of opening of the EGR valve 43 is increased are released. The timing for releasing these states may be before the drying time has elapsed.

  Next, the control operation of the ECU 70 will be described using the flowchart shown in FIG. The ECU 70 estimates the storage amount (step S1). Subsequently, the ECU 70 determines whether or not the estimated storage amount is larger than the predetermined amount α (step S2). The predetermined amount α is, for example, 30 g. If the determination is negative, this flowchart is temporarily terminated. If the determination is affirmative, the ECU 70 closes the valve 45a and opens the valve 45b (step S3). Further, the degree of opening of the diesel throttle 13 is decreased and the degree of opening of the EGR valve 43 is increased (step S4).

  By controlling the valves 45a and 45b as described above in step S3, the exhaust gas can be circulated through the bypass pipe 44 of the EGR cooler 42 and the bypass pipe 44. In addition, the flow rate of the exhaust gas to be recirculated can be increased by decreasing the valve opening degree of the diesel throttle 13 and increasing the valve opening degree of the EGR valve 43 in step S4.

  Subsequent to step S4, the ECU 70 estimates the drying time (step S5), and determines whether or not the estimated drying time has elapsed (step S6). If a negative determination is made, the process returns to step S6. If the determination is affirmative, the ECU 70 opens the valve 45a and closes the valve 45b (step S7). Further, the state where the degree of opening of the diesel throttle 13 is decreased and the state where the degree of opening of the EGR valve 43 is increased are released (step S8).

  By controlling the valves 45a and 45b as described above in step S7, the exhaust gas can be circulated through the EGR cooler 42 out of the EGR cooler 42 and the bypass pipe 44. Further, by releasing the state in which the degree of opening of the diesel throttle 13 is decreased and the state in which the degree of opening of the EGR valve 43 is being increased in step S8, normal control of the diesel throttle 13 and the EGR valve 43 is enabled. be able to. After step S8, this flowchart is temporarily terminated.

  Next, main effects of the EGR device 40 will be described. FIG. 5 is an operation explanatory diagram of the EGR device 40. FIG. 5A shows a case where the storage amount is smaller than the predetermined amount α (a state immediately before the storage amount becomes larger than the predetermined amount α). FIG. 5B shows a case where the storage amount is greater than the predetermined amount α (a state immediately after the storage amount exceeds the predetermined amount α). As shown in FIG. 4A, when the storage amount is smaller than the predetermined amount α, the EGR device 40 causes the exhaust gas to flow through the EGR cooler 42 among the EGR cooler 42 and the bypass pipe 44. At this time, the condensed water generated in the EGR cooler 42 gradually accumulates in the reservoir T.

  As shown in FIG. 4B, when the amount of condensed water is greater than the predetermined amount α, the EGR device 40 causes the exhaust gas to flow through the bypass pipe 44 among the EGR cooler 42 and the bypass pipe 44. For this reason, the EGR device 40 can suppress the storage amount to a predetermined amount α or less. As a result, it is possible to suppress corrosion from being easily caused due to the fact that excessive condensate is allowed to accumulate. In this case, since the temperature of the exhaust gas flowing through the bypass pipe 44 is high, the storage amount can be reduced by evaporation.

  Specifically, the EGR device 40 includes the wall temperature of the EGR cooler 42, the exhaust temperature in the EGR cooler 42, the flow rate of exhaust gas recirculated from the exhaust system 20 to the intake system 10, and the exhaust gas recirculated from the exhaust system 20 to the intake system 10. The amount of storage is provided with an ECU 70 that realizes an estimation unit that estimates the amount of storage based on at least one of the following components, the outside air temperature, and the humidity of the exhaust gas recirculated from the exhaust system 20 to the intake system 10. Is greater than the predetermined amount α, exhaust can be circulated as described above.

  The EGR device 40 can make it easy to discharge condensed water from the storage portion T when the exhaust gas is circulated as described above by applying a coating having water repellency to the inner wall portion of the storage portion T. As a result, it is possible to more suitably suppress the occurrence of corrosion due to the fact that excessive accumulation of condensed water is allowed.

  The EGR device 40 further increases the flow rate of exhaust gas to be recirculated by further decreasing the opening degree of the diesel throttle 13 and increasing the opening degree of the EGR valve 43 when the storage amount is larger than the predetermined amount α. it can. In this case, since the condensed water is easily discharged from the storage portion T, it is possible to shorten the time for circulating the exhaust gas through the bypass pipe 44 when discharging the condensed water from the storage portion T. As a result, it is possible to suitably suppress the occurrence of corrosion due to the fact that the condensed water is allowed to be excessively accumulated from the point that the time required for returning to the normal control can be shortened.

  The EGR device 40 estimates the drying time based on the temperature of the exhaust gas flowing through the EGR cooler 42, and causes the exhaust gas to flow through the EGR cooler 42 of the EGR cooler 42 and the bypass pipe 44 when the estimated drying time has elapsed. Thus, it is possible to return to the normal control in a state where condensed water does not remain in the storage portion T.

  In this case, it is possible to prevent the estimation accuracy of the storage amount from being reduced by the condensed water remaining in the storage unit T. For this reason, the EGR device 40 has excessively accumulated condensed water in that the estimated accuracy of the stored amount is reduced by the condensed water remaining in the storage portion T and the situation where the stored amount exceeds the predetermined amount α can be avoided. Therefore, it is possible to suitably suppress the occurrence of corrosion due to being allowed.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

EGR device 40
EGR piping 41
EGR cooler 42
EGR valve 43
Bypass piping 44
Valve unit 45
Internal combustion engine 50
ECU 70

Claims (3)

A recirculation passage connecting the exhaust system and the intake system of the internal combustion engine;
A cooler for cooling the exhaust gas flowing through the reflux passage portion;
A bypass passage portion disposed below the cooler in the direction of gravity and bypassing the cooler;
A valve portion that switches a flow path to at least one of the cooler and the bypass passage portion, and
A storage part capable of storing condensed water generated by the cooler in a portion where the exhaust gas flows when the exhaust gas flows through the bypass channel part among the cooler and the bypass channel part;
An exhaust gas recirculation device for an internal combustion engine that circulates exhaust gas through at least the bypass passage portion of the cooler and the bypass passage portion when the amount of condensed water stored in the storage portion is larger than a predetermined amount. An exhaust gas recirculation device for an internal combustion engine according to claim 1,
An estimation unit for estimating the amount of condensed water stored in the storage unit;
The estimation unit determines the wall temperature of the cooler, the exhaust temperature in the cooler, the flow rate of exhaust gas recirculated from the exhaust system to the intake system, the component of exhaust gas recirculated from the exhaust system to the intake system, An exhaust gas recirculation device for an internal combustion engine that estimates an amount of condensed water stored in the storage unit based on at least one of air temperature and humidity of exhaust gas recirculated from the exhaust system to the intake system. An exhaust gas recirculation device for an internal combustion engine according to claim 1 or 2,
An exhaust gas recirculation device for an internal combustion engine, wherein an inner wall portion of the storage portion is provided with a water-repellent coating.

Images