JP2014211135A - Exhaust gas recirculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation device for effectively draining trapped condensed water without giving influences to engine performance.SOLUTION: The exhaust gas recirculation device includes an EGR pipe 20 connecting an exhaust system 17 and an intake system 11 for an engine 10, an EGR cooler 21 provided on the EGR pipe 20 for cooling EGR gas flowing from the exhaust system 17 into the intake system 11, a condensed water storage tank 23 provided in the EGR pipe 20 at the further downstream side than the EGR cooler 21 for storing condensed water, a compressed intake air supply mechanism 30 connected to the EGR pipe 20 for supplying compressed air, and an ECU 40 for controlling the compressed intake air supply mechanism 30 to be driven. The ECU 40 drives the compressed intake air supply mechanism 30 to drain the condensed water when a fuel injection amount is zero.

Description

  The present invention relates to an exhaust gas recirculation device.

  An internal combustion engine such as a diesel engine is known that includes an exhaust gas recirculation device that recirculates a part of exhaust gas to an intake system. In general, an exhaust gas recirculation device cools recirculated exhaust gas (hereinafter referred to as EGR gas) by exchanging heat with engine cooling water using an EGR cooler.

  When the temperature of the EGR gas decreases due to cooling of the EGR cooler, condensed water is generated due to condensation of moisture contained in the EGR gas. This condensed water dissolves oxides in the exhaust and shows strong acidity, so it accumulates in the EGR pipe, and further flows into the intake system and adheres to the intercooler and the compressor of the turbocharger. This is a factor that causes a decrease in durability.

  Focusing on such problems, for example, Patent Document 1 discloses collecting condensed water generated by cooling an EGR cooler, and Patent Document 2 discloses a technique for discharging condensed water, for example. Has been.

JP 2012-122337 A JP 2008-2351 A

  By the way, in the structure in which the collected condensed water is discharged by the pressure increase in the EGR pipe, the engine performance may be affected depending on the timing of executing the discharge. For example, when condensed water is discharged during engine load operation during the fuel injection period, it becomes difficult to control the EGR gas amount to the target flow rate, which causes deterioration of exhaust gas and fuel consumption. Further, since it is necessary to control the amount of EGR gas even during idle operation, it is not preferable to discharge condensed water during such idle operation, as in load operation.

  This invention is made | formed in view of such a point, The objective is to discharge the collected condensed water effectively, without affecting engine performance.

  In order to achieve the above object, an exhaust gas recirculation system according to the present invention is provided in a recirculation pipe that connects an exhaust system and an intake system of an internal combustion engine, and the recirculation pipe, and the intake system is configured to receive the intake air from the exhaust system A cooler that cools the recirculated exhaust flowing into the system, a storage section that is provided in a recirculation pipe downstream of the cooler and stores condensed water, and is connected to the recirculation pipe, Compressed air supply means for supplying compressed air to the piping, and control means for controlling the drive of the compressed air supply means, the control means when the fuel injection amount of the internal combustion engine is zero, the compressed air The supply means is driven to discharge the condensed water stored in the storage hand portion.

  Further, the compressed air supply means may be connected to a junction with the intake system of the recirculation pipe.

  The compressed air supply means may be driven by power extracted from at least one front wheel of the vehicle.

  The compressed air supply means may have an intake intake pipe that takes in intake air from an intake system between an intake flow sensor and an air filter.

  Also, a filter provided in the exhaust system for collecting particulate matter in the exhaust, one end of which is connected to the reservoir, and the other end is connected to the exhaust system of the outlet of the filter. And a discharge pipe for discharging the condensed water stored in the storage unit.

  According to the exhaust gas recirculation device of the present invention, the collected condensed water can be effectively discharged without affecting the engine performance.

1 is a schematic overall configuration diagram showing an exhaust gas recirculation device according to an embodiment of the present invention. It is a typical perspective view which shows the condensed water storage tank provided in the bending part of the exhaust gas recirculation apparatus which concerns on one Embodiment of this invention. It is typical plane sectional drawing which shows the current transformation plate provided in the bending part of the exhaust gas recirculation apparatus which concerns on other embodiment. It is a typical top view which shows piping for condensed water discharge of the exhaust gas recirculation apparatus which concerns on other embodiment. It is a flowchart which shows the discharge control of the exhaust gas recirculation apparatus which concerns on one Embodiment of this invention.

  Hereinafter, an exhaust gas recirculation apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  First, an intake / exhaust system to which the exhaust gas recirculation apparatus of the present embodiment is applied and a vehicle drive system will be described with reference to FIG.

  An intake pipe 10 is connected to an intake manifold 10a of a diesel engine (hereinafter simply referred to as an engine) 10, and an exhaust pipe 17 is connected to an exhaust manifold 10b. The intake pipe 11 is provided with an air cleaner 12, an intake flow rate sensor (hereinafter referred to as MAF sensor) 13, an intake throttle 14, a turbocharger compressor 15a, and an intercooler 16 in order from the intake upstream side. In the exhaust pipe 17, a turbocharger turbine 15 b and a diesel particulate filter (hereinafter, DPF) 18 that collects particulate matter contained in the exhaust are provided in order from the exhaust upstream side.

  The output shaft of the engine 10 is connected to the input shaft of the transmission 3 via the clutch 2. The output shaft of the transmission 3 is connected to the left and right drive wheels 7L and 7R via the propeller shaft 4, the differential 5 and the drive shaft 6, respectively. Note that reference numerals 8L and 8R in FIG. 1 indicate left and right steering wheels (front wheels) for turning the vehicle.

  Next, based on FIGS. 1-4, the detailed structure of the exhaust gas recirculation apparatus which concerns on this embodiment is demonstrated.

  The exhaust gas recirculation apparatus according to the present embodiment includes an EGR pipe 20, an EGR cooler 21, an EGR valve 22, a condensed water storage tank 23, a condensed water discharge pipe 24, a compressed intake air supply mechanism 30, and an electronic control unit. (Hereinafter referred to as ECU) 40.

  The EGR pipe 20 communicates the exhaust pipe 17 on the exhaust downstream side with respect to the turbine 15b and the intake pipe 11 on the intake upstream side with respect to the compressor 15a. That is, the exhaust gas recirculation device of the present embodiment is configured as a low pressure EGR device. The EGR pipe 20 is bent and formed at a plurality of locations from a branch portion with the exhaust pipe 17 to a junction with the intake pipe 11.

  The EGR cooler 21 is provided in the EGR pipe 20 on the upstream side of the condensed water storage tank 23, and cools the EGR gas passing therethrough by exchanging heat with the engine cooling water. The EGR pipe 20 upstream of the EGR cooler 21 is provided with a backflow prevention valve 25 for preventing condensed water generated by cooling by the EGR cooler 21 from flowing back from the EGR pipe 20 to the exhaust pipe 17. .

  The EGR valve 22 adjusts the flow rate of EGR gas flowing from the exhaust pipe 17 to the intake pipe 11 by opening and closing in accordance with an instruction signal input from the ECU 40. The EGR valve 22 is provided at the downstream end of the EGR pipe 20, that is, at the junction with the intake pipe 11, and when discharging condensed water, the intake air compressed by a pressurizing pump 33 described later is EGR valve 22. 22 is prevented from flowing into the intake pipe 11 side.

  The condensed water storage tank 23 is provided below the first bent portion 20 a closest to the outlet of the EGR cooler 21 among the plurality of bent portions formed in the EGR pipe 20. As shown in FIG. 2, the bent portion 20a is formed with a collection opening 23a that opens downward, and the condensed water storage tank 23 has a condensed water intake pipe at the opening 23a. 23b is connected.

  Thus, by providing the condensed water storage tank 23 in the first bent portion 21a closest to the outlet portion of the EGR cooler 21, condensed water generated by condensation of water in the EGR gas by cooling of the EGR cooler 21 is generated. It can be collected effectively. In addition, by providing the condensed water storage tank 23 in the bent portion 20a where the flow of EGR gas changes, water contained in the EGR gas adhering to the inner peripheral surface of the bent portion 20a can be effectively collected. Can do.

  The means for storing condensed water is not limited to the tank, and may be a recess formed on the lower surface of the bent portion 20a. Further, in order to actively collect moisture contained in the EGR gas, as shown in FIG. 3, a plurality of current transformation plates A for transforming the flow of the EGR gas are provided in the EGR pipe 20. Also good. The position where the current transformation plate A is provided is not limited to the bent portion 20a, and may be a linear portion.

  The condensed water discharge pipe 24 discharges condensed water from the condensed water storage tank 23, and connects the condensed water storage tank 23 and the exhaust pipe 17. The condensed water discharge pipe 24 is provided with a discharge valve 24a that opens and closes in response to an instruction signal input from the ECU 40 when condensed water is discharged. In addition, the discharge side end of the condensed water discharge pipe 24 is not necessarily connected to the exhaust pipe 17 and may be released to the atmosphere. Further, as shown in FIG. 4, the discharge side end of the condensed water discharge pipe 24 may be connected to the outlet portion of the DPF 18. Thus, if condensed water is discharged to the exit part of DPF 18, condensed water can be effectively evaporated by the exhaust which becomes high temperature at the time of forced regeneration of DPF18.

  The compressed intake air supply mechanism 30 supplies intake air compressed when the condensed water is discharged (hereinafter referred to as compressed intake air), and includes an intake intake pipe 31, a compressed intake air supply pipe 32, and pressurization. And a pump 33.

  The intake intake pipe 31 feeds intake air (hereinafter referred to as intake air) taken from the intake pipe 11 to the pressurizing pump 33, and the upstream end is connected to the intake pipe 11 between the air cleaner 12 and the MAF sensor 13. While being connected, the downstream end is connected to the pressurizing pump 33. The intake intake pipe 31 is provided with a backflow prevention valve 34 for preventing a backflow of intake air taken from the intake pipe 11.

  The compressed intake air supply pipe 32 supplies the intake air compressed by the pressurizing pump 33 to the condensed water storage tank 23, and the upstream end is connected to the pressurizing pump 33 and the downstream end is connected to the EGR pipe 20. Are connected to a junction between the intake pipe 11 and the intake pipe 11.

  A rotation shaft (not shown) of the pressurizing pump 33 is connected to the right steering wheel 8R via a clutch 37, a pulley 36, and a belt 35. That is, when the clutch 37 is controlled to contact according to the instruction signal input from the ECU 40, the pressure pump 33 is driven by the rotational force of the steering wheel 8R transmitted via the belt 35, the pulley 36, and the clutch 37. It is configured as follows.

  The ECU 40 performs various controls of the engine 10 and the like, and includes a known CPU, ROM, RAM, input port, output port, and the like. In order to perform these various controls, output signals from various sensors such as the MAF sensor 13, the vehicle speed sensor 51, the accelerator opening sensor 52, and the brake pedal sensor 53 are input to the ECU 40. Further, the ECU 40 includes a braking force determination unit 41 and a discharge control unit 42 as some functional elements. In the present embodiment, these functional elements are described as being included in the ECU 40, which is an integral piece of hardware. However, any one of these functional elements may be provided in separate hardware.

  The braking force determination unit 41 determines whether braking force is generated based on the sensor values of the vehicle speed sensor 51, the accelerator opening sensor 52, and the brake pedal sensor 53. In the present embodiment, the braking force determination unit 41 detects an engine brake operation in which deceleration of the vehicle is detected in a state where the accelerator opening is zero (fuel injection amount is zero) or a depression of the brake pedal by the driver. It is determined that braking force is generated when the brake is operated.

  When a braking force is generated in the vehicle, the discharge control unit 42 drives the pressurizing pump 33 of the compressed intake air supply mechanism 30 to execute discharge control for discharging condensed water from the condensed water storage tank 23. More specifically, when the braking force determination unit 41 determines that the braking force is generated, the discharge control unit 42 engages the clutch 37, fully closes the EGR valve 22, and fully opens the discharge valve 24a. Is output.

  In this way, when condensed water discharge control is executed, the pressure pump 33 is driven by the power of the steering wheel 8R by the engagement of the clutch 37, whereby the intake air taken in from the intake air intake pipe 31 is compressed intake air. It is pumped to the supply pipe 32. At this time, since the EGR valve 22 is fully closed, the compressed intake air is pumped through the EGR pipe 20 and supplied to the condensed water storage tank 23. Then, the pressure in the condensed water storage tank 23 rises due to the compressed intake air, so that the condensed water in the condensed water storage tank 23 enters the exhaust pipe 17 from the condensed water discharge pipe 24 in which the discharge valve 24a is fully opened. It is configured to be discharged.

  Next, based on FIG. 5, the flow of the exhaust control by the exhaust gas recirculation device of this embodiment will be described. This control starts simultaneously with the start of the engine 10 (ignition switch key switch ON).

  In step (hereinafter, step is simply referred to as S) 100, the braking force determination unit 41 determines whether or not the braking force is generated. When the braking force is generated, the present control proceeds to S110, while when the braking force is not generated, the control is returned.

  In S110, in order to execute the condensed water discharge control, the clutch 37 is engaged, the EGR valve 22 is fully closed, and the discharge valve 24a is fully opened in accordance with an instruction signal output from the discharge control unit 42. That is, the pressure in the condensed water storage tank 23 is increased by driving the pressurizing pump 33, and the condensed water is discharged to the exhaust pipe 17 through the condensed water discharge pipe 24.

  Thereafter, in S120, the braking force determination unit 41 determines whether or not the braking force is continued. When the braking force is continuously generated, the present control is returned to S110. That is, the driving of the pressurizing pump 33 is continued and the condensed water is continuously discharged.

  On the other hand, when the braking force is not continued, the present control proceeds to S130. In S130, the clutch 37 is disengaged and the discharge valve 24a is fully closed, and the opening and closing of the EGR valve 22 is switched to normal control based on the operating state of the engine 10, and the present control is returned. Thereafter, each step of S100 to 130 is repeatedly executed until the engine 10 is stopped (key switch OFF of the ignition switch).

  Next, the function and effect of the exhaust gas recirculation apparatus according to this embodiment will be described.

  Condensed water generated by condensation of moisture in the EGR gas due to cooling of the EGR cooler 21 tends to accumulate in the EGR pipe 20 at the outlet of the EGR cooler 21. Further, the moisture contained in the EGR gas tends to adhere to and accumulate on the inner peripheral surface of the bent portion 20a where the flow of the EGR gas changes. Since these condensed waters dissolve in oxides in the exhaust gas and show strong acidity, they cause corrosion and deterioration of durability.

  In the exhaust gas recirculation device of the present embodiment, a condensed water storage tank 23 for storing condensed water is provided below the first bent portion 20a closest to the outlet portion of the EGR cooler 21. That is, the condensed water generated by cooling the EGR cooler 21 and the water in the EGR gas adhering to the inner peripheral surface of the bent portion 20a are condensed water storage tanks provided in the bent portion 20a where these condensed water is most likely to collect. 23 is configured to be collected effectively.

  Therefore, according to the exhaust gas recirculation device of the present embodiment, it is possible to effectively collect condensed water due to cooling of the EGR cooler 21 and moisture in the EGR gas adhering to the inner peripheral surface of the bent portion 20a. Thus, corrosion and durability deterioration due to the condensed water can be surely prevented. In particular, since the exhaust gas recirculation device of the present embodiment is configured as a low pressure EGR device, it is possible to effectively prevent condensed water from flowing into the intake system and adhering to the compressor 15a, the intercooler 16, and the like.

  In the exhaust gas recirculation device of the present embodiment, the condensed water stored in the condensed water storage tank 23 is supplied to the compressed intake air supply mechanism 30 when the engine brake is operated when the accelerator opening is zero or when the brake pedal is operated. It is discharged by operating and supplying compressed intake air from the EGR pipe 20 to the condensed water storage tank 23. That is, the condensed water discharge accompanied by the pressure increase in the EGR pipe 20 is configured to be executed only when the engine brake is operated without operating the EGR gas recirculation or when the brake pedal is operated.

  Therefore, according to the exhaust gas recirculation apparatus of the present embodiment, exhausting condensed water is performed at the time of engine brake operation or brake operation without performing flow rate control of the EGR gas amount, thereby reducing engine performance such as exhaust gas deterioration and fuel consumption deterioration. Can be reliably reduced.

  In the exhaust gas recirculation apparatus of the present embodiment, the downstream end of the compressed intake air supply pipe 32 is connected to the immediately downstream side of the EGR valve 22. The EGR valve 22 is provided at the downstream end of the EGR pipe 20 (near the junction with the intake pipe 11). That is, the compressed air supplied from the pressurizing pump 33 when condensed water is discharged is configured to be pumped over a long distance in the EGR pipe 20 from the downstream side of the EGR valve 22 to the condensed water storage tank 23. Yes.

  Therefore, according to the exhaust gas recirculation device of the present embodiment, the condensed water remaining in the EGR pipe 20 on the downstream side of the condensed water storage tank 23 without being collected in the condensed water storage tank 23, or bent The moisture in the EGR gas adhering to the bent inner peripheral surface other than the portion 20a can be effectively discharged by the compressed intake air that is pumped.

  Further, in the exhaust gas recirculation apparatus of the present embodiment, the intake pipe 31 for taking in the intake air from the intake pipe 11 to the pressurizing pump 33 has an upstream end at the intake pipe 11 between the air cleaner 12 and the MAF sensor 13. It is connected to the. In other words, when the condensed water is discharged by driving the pressurizing pump 33, the intake air from which foreign matter has been removed by the air cleaner 12 is supplied.

  Therefore, according to the exhaust gas recirculation device of the present embodiment, the adhesion of foreign matters to the EGR pipe 20, the EGR valve 22, and the EGR cooler 21 is effectively suppressed, and the attachment of these components is reliably prevented. Can do. Further, since the intake air is extracted from the upstream side of the MAF sensor 13, no difference occurs between the MAF sensor 13 and the actual intake flow rate of the engine 10 even when the pressurizing pump 33 is driven. Can be effectively reduced.

  In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.

  For example, the pressurizing pump 33 is driven by the power extracted from the steered wheels 8R, but a retarder or the like that converts braking energy extracted from the drive system into electric power as regenerative energy is used, and the electric power applied to the pressurizing pump 33 It can also be configured as an electric pump driven by

  Further, the exhaust gas recirculation device is not limited to the low pressure EGR device, and the high pressure EGR device in which the EGR pipe 20 communicates the exhaust pipe 17 on the exhaust upstream side of the turbine 15b and the intake pipe 11 on the intake downstream side of the compressor 15a. It can also be configured as.

  Further, the engine 10 is not limited to a diesel engine, and can be widely applied to a gasoline engine or the like.

10 Engine 11 Intake pipe 15a Compressor 15b Turbine 17 Exhaust pipe 18 DPF
20 EGR piping 21 EGR cooler 22 EGR valve 23 Condensed water storage tank 24 Condensed water discharge piping 30 Compressed intake air supply mechanism (compressed air supply means)
40 ECU (control means)
41 braking force determination unit 42 discharge control unit

Claims (5)

A recirculation pipe connecting the exhaust system and the intake system of the internal combustion engine;
A cooler provided in the recirculation pipe for cooling the recirculation exhaust flowing from the exhaust system to the intake system;
A storage part for storing condensed water provided in a recirculation pipe downstream of the cooler;
Compressed air supply means connected to the recirculation pipe and supplying compressed air to the recirculation pipe;
Control means for controlling the drive of the compressed air supply means,
The control means includes
An exhaust gas recirculation device, wherein when the fuel injection amount of the internal combustion engine is zero, the compressed air supply means is driven to discharge condensed water stored in the storage section.   2. The exhaust gas recirculation apparatus according to claim 1, wherein the compressed air supply means is connected to a junction with the intake system of the recirculation pipe.   The exhaust gas recirculation device according to claim 1 or 2, wherein the compressed air supply means is driven by power extracted from at least one front wheel of the vehicle.   The exhaust gas recirculation device according to any one of claims 1 to 3, wherein the compressed air supply means includes an intake intake pipe that takes in intake air from an intake system between an intake flow sensor and an air filter. A filter provided in the exhaust system to collect particulate matter in the exhaust;
A discharge pipe having one end connected to the storage unit and the other end connected to an exhaust system of an outlet of the filter to discharge condensed water stored in the storage unit. Item 5. The exhaust gas recirculation device according to any one of Items 1 to 4.

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