JP2013253533A - Exhaust gas recirculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent pump loss deterioration and fuel economy deterioration in a low load region, which may arise from a pressure drop by a venturi.SOLUTION: An exhaust gas recirculation device comprises: a venturi 10 provided at an intake passage 2; a bypass passage 22 bringing an intake upstream side into communication with an intake downstream side of the venturi 10 of the intake passage 2; a flow path switching valve 23 provided at a connection part X between the intake passage 2 at the intake upstream side from the venturi 10 and the bypass passage 22 and switching a flow path of an intake to the venturi 10 and the bypass passage 22; operation state detection means 15, 16 detecting operation states of an engine 1; and a flow path switching control means 5 switching and controlling the flow path switching valve 23 in response to the operation states of the engine 1 detected by the operation state detection means 15, 16. The flow path switching control means 5 switches the flow path of the intake to the venturi 10 by the flow path switching valve 23 in a high load range of the engine 1, and switches the flow path of the intake to the bypass passage 22 by the flow path switching valve 23 in a low load region of the engine 1.

Description

  The present invention relates to an exhaust gas recirculation device including a venturi disposed in an intake passage of an engine.

  In a supercharged diesel engine, an exhaust gas recirculation device (hereinafter also referred to as an EGR device) is used to reduce NOx (nitrogen oxide). An EGR device (high-pressure EGR device) generally includes an EGR pipe that communicates an exhaust manifold and an intake pipe on the downstream side of the intake side of the compressor of the turbocharger, and an EGR valve disposed in the middle of the EGR pipe. .

  In a supercharged diesel engine, when the load is low, the intake pressure (intake pipe internal pressure) is lower than the exhaust pressure (exhaust manifold internal pressure). Therefore, when the EGR valve is opened, EGR gas (exhaust gas recirculation) passes through the EGR pipe. Through the exhaust manifold and returned to the intake pipe. However, in a supercharged diesel engine, the intake pressure becomes higher than the exhaust pressure when the load is high, and EGR gas may not return from the exhaust manifold to the intake pipe even if the EGR valve is opened.

  Therefore, a venturi may be used in the EGR device (see, for example, Patent Document 1). For example, the venturi is provided in the intake pipe, and is provided in the intake pipe on the downstream side of the intake pipe, with a nozzle section that restricts the passage area of the intake pipe and an intake pipe on the downstream side of the nozzle section spaced from the nozzle section. A diffuser portion that increases the passage area of the intake pipe as it goes, and an EGR gas merging portion that is provided on the outer periphery of the gap between the nozzle portion and the diffuser portion and to which the EGR pipe is connected.

  Such venturi lowers the internal pressure of the intake pipe at the throttle portion (the portion between the nozzle portion and the diffuser portion), so that the EGR gas returns from the exhaust manifold to the venturi throttle portion even at high loads.

JP 2007-92592 A

  By the way, since the venturi is provided with a diffuser part (expanded part), the internal pressure of the lowered intake pipe is recovered to some extent by the diffuser part, but the recovery rate is about 90%. The pressure loss due to this venturi becomes a pump loss of a supercharged diesel engine, which may lead to deterioration of fuel consumption. In the case of a general EGR device, it is necessary to lower the internal pressure of the intake pipe by the venturi nozzle part only in the high load region, but in the low load region, the above pressure loss is carried and the pump is pumped in the low load region. Loss deterioration and fuel consumption deterioration may occur.

  Accordingly, an object of the present invention is to prevent deterioration of pump loss and fuel consumption in a low load region, which may occur due to pressure loss due to venturi, in an exhaust gas recirculation device including a venturi disposed in an intake passage of an engine. There is to do.

  In order to achieve the above-mentioned object, an exhaust gas recirculation apparatus according to the present invention is provided at a connection portion between an EGR passage for recirculating exhaust gas from an engine exhaust passage to an intake passage, and the EGR passage of the intake passage. And a bypass passage that communicates the intake upstream side and the intake downstream side of the venturi with respect to the vent passage, and a connection portion between the intake passage and the bypass passage on the upstream side of the venturi. A flow path switching valve configured to switch the intake air flow path between the venturi and the bypass passage, operating state detection means for detecting an operating state of the engine, and operation of the engine detected by the operating state detection means Flow path switching control means for switching and controlling the flow path switching valve according to the state, the flow path switching control means in the high load region of the engine Switching the flow path of intake air to the venturi via road switching valve, in the low load region of the engine, it is characterized in that the switching to the bypass passage flow channel of the induction by the flow path switching valve.

  The exhaust gas recirculation device further includes an EGR valve disposed in the EGR passage, and the flow path switching control means is configured to switch the flow rate when the EGR valve is closed regardless of the operating state of the engine. The intake flow path may be switched to the bypass passage by a path switching valve.

  The exhaust gas recirculation device branches from the EGR passage downstream of the EGR gas with respect to the EGR valve, and merges with the intake passage on the intake downstream side of the venturi, and the second EGR passage. And a second EGR valve that opens and closes the second EGR passage, and the flow path switching control means controls the intake flow path by the flow path switching valve in the high load region of the engine. While switching to the venturi, the second EGR valve is closed, and in the low load region of the engine, the flow path switching valve switches the intake air flow path to the bypass passage, and the second EGR valve is opened. Also good.

  According to the present invention, in an exhaust gas recirculation device including a venturi disposed in an intake passage of an engine, it is possible to prevent deterioration of pump loss and fuel consumption in a low load region, which may occur due to pressure loss due to the venturi. There is an excellent effect of being able to.

1 is a schematic configuration diagram of an exhaust gas recirculation device according to a first embodiment of the present invention. It is a figure which shows an example of the driving | running state map of an engine. It is a schematic block diagram of the exhaust gas recirculation apparatus which concerns on 2nd embodiment of this invention. It is a schematic block diagram of the exhaust gas recirculation apparatus which concerns on other embodiment of this invention.

  Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[First embodiment]
FIG. 1 shows an exhaust gas recirculation apparatus according to a first embodiment of the present invention.

  As shown in FIG. 1, an engine (in this embodiment, a supercharged diesel engine) 1 to which an EGR device 20 </ b> A is mounted exhausts exhaust gas from the intake passage 2 that supplies intake air to the engine 1 and the engine 1. An exhaust passage 3, a turbocharger (supercharger) 4 that boosts the intake air supplied to the engine 1, and an electronic control unit (hereinafter referred to as ECU) 5 that controls the engine 1 are provided.

  The intake passage 2 has an intake manifold 6 connected to an intake port of each cylinder of the engine 1 and an intake pipe 7 connected to an upstream end of the intake manifold 6. In the intake pipe 7, an air cleaner 8, a compressor 4 a of the turbocharger 4, an aftercooler (intercooler) 9 that cools the intake air boosted by the compressor 4 a, and a venturi 10 to be described later are arranged in this order from the intake upstream side. Established.

  The exhaust passage 3 has an exhaust manifold 11 connected to the exhaust port of each cylinder of the engine 1 and an exhaust pipe 12 connected to the downstream end of the exhaust manifold 11. In the exhaust pipe 12, a turbine 4 b of the turbocharger 4, a diesel particulate filter (DPF) 13 that collects PM (particulate matter) in the exhaust gas, and a muffler 14 are disposed in order from the exhaust upstream side. Is done.

  The turbocharger 4 includes a turbine 4b that is rotationally driven by exhaust gas from the engine 1 and a compressor 4a that is rotationally driven by the turbine 4b.

  The ECU 5 is attached to the engine 1 and is connected to an engine rotation sensor 15 that detects the engine speed and an accelerator opening sensor 16 that detects a depression amount (accelerator opening) of an accelerator pedal (not shown). Detection values (engine speed, accelerator opening) from the engine rotation sensor 15 and the accelerator opening sensor 16 are input.

  The ECU 5 is connected to an injector (not shown) disposed in each cylinder of the engine 1 and calculates the fuel injection amount by the injector from the detection value of the accelerator opening sensor 16.

  The EGR device 20A includes an EGR pipe (EGR passage) 21 that recirculates exhaust gas from the exhaust passage 3 to the intake passage 2, and a venturi 10 that is disposed at a connection portion between the EGR pipe 21 of the intake passage 2 and EGR. A bypass pipe (bypass passage) 22 that connects the intake upstream side and the intake downstream side of the venturi 10 of the pipe 21 and a connection portion X between the intake passage 2 and the bypass pipe 22 on the intake upstream side of the venturi 10 are disposed. The flow path switching valve 23 for switching the intake flow path between the venturi 10 and the bypass pipe 22, the operating state detecting means for detecting the operating state of the engine 1, and the operating state of the engine 1 detected by the operating state detecting means. And a flow path switching control means for switching the flow path switching valve 23 accordingly. The engine rotation sensor 15 and the accelerator opening sensor 16 constitute the above-described operation state detection means, and the ECU 5 constitutes the above-described flow path switching control means.

  The EGR device 20A is a so-called high pressure EGR device.

  The EGR pipe 21 communicates the exhaust passage 3 upstream of the turbine 4b with the intake passage 2 downstream of the compressor 4a. Specifically, the EGR pipe 21 has an upstream end connected to the exhaust manifold 11 and a downstream end connected to the intake pipe 7 between the aftercooler 9 and the engine 1. The EGR pipe 21 includes an EGR cooler 24 for cooling the exhaust gas flowing through the EGR pipe 21 and an exhaust gas flow for adjusting the flow rate of the exhaust gas flowing through the EGR pipe 21 in order from the EGR gas upstream side (exhaust passage 3 side). An EGR valve 25 is provided. The EGR cooler 24 is a water-cooled type that cools exhaust gas by exchanging heat with engine cooling water circulating inside the engine 1. The EGR valve 25 is configured such that the valve opening degree can be adjusted continuously. The EGR valve 25 is connected to the ECU 5, and the valve opening degree is controlled by the ECU 5.

  Specifically, the ECU 5 opens the valve opening of the EGR valve 25 based on the detected value (engine speed) of the engine rotation sensor 15 and the fuel injection amount calculated from the detected value of the accelerator opening sensor 16. To decide. For example, the valve opening map of the EGR valve 25 using the engine speed and the fuel injection amount as parameters is stored in advance in the ECU 5, and the ECU 5 detects the detected value (engine speed) of the engine speed sensor 15 and the accelerator opening. The valve opening corresponding to the fuel injection amount calculated from the detection value of the degree sensor 16 is read from the valve opening map. Then, the ECU 5 controls the EGR valve 25 so that the valve opening read from the valve opening map is obtained.

  The venturi 10 is provided in the intake pipe 7 and is provided in the intake pipe 7 which narrows the passage area of the intake pipe 7 and the intake pipe 7 on the intake downstream side of the nozzle section 10a with a gap from the nozzle section 10a. EGR gas merging portion 10c that is provided on the outer periphery of the gap between the diffuser portion 10b that increases the passage area of the intake pipe 7 as it goes downstream of the intake portion 7 and the nozzle portion 10a and the diffuser portion 10b and to which the EGR pipe 21 is connected. And have.

  The bypass pipe 22 has an upstream end connected to the intake pipe 7 between the aftercooler 9 and the venturi 10, and a downstream end connected to the intake pipe 7 between the venturi 10 and the engine 1. The bypass pipe 22 is configured, for example, so that the passage area is substantially the same as that of the intake pipe 7.

  The flow path switching valve 23 is constituted by a three-way valve, for example. The flow path switching valve 23 is connected to the ECU 5, and switching control is performed by the ECU 5.

  Next, the function and effect of the first embodiment will be described.

  The ECU 5 determines whether the operating state of the engine 1 is in the high load region and the low load based on the detected value (engine speed) of the engine rotation sensor 15 and the fuel injection amount calculated from the detected value of the accelerator opening sensor 16. Determine which of the areas. For example, an operation state map (see FIG. 2) of the engine 1 using the engine speed and the fuel injection amount as parameters is stored in advance in the ECU 5, and the ECU 5 detects the detected value (engine speed) of the engine speed sensor 15. And the operation state (high load region or low load region) of the engine 1 corresponding to the fuel injection amount calculated from the detected value of the accelerator opening sensor 16 is read from the above operation state map. Then, the ECU 5 switches the intake air flow path between the venturi 10 and the bypass pipe 22 by the flow path switching valve 23 according to the operating state of the engine 1 read from the operating state map.

  Specifically, the ECU 5 switches the intake air flow path to the venturi 10 by the flow path switching valve 23 in a high load region where it is necessary to lower the internal pressure of the intake pipe 7 by the nozzle portion 10 a of the venturi 10. By switching the intake air flow path to the venturi 10 by the flow path switching valve 23, the intake air and the EGR gas pass through the venturi 10 and are introduced into the engine 1.

  On the other hand, the ECU 5 switches the intake air flow path to the bypass pipe 22 by the flow path switching valve 23 in a low load region where it is not necessary to lower the internal pressure of the intake pipe 7 by the nozzle portion 10 a of the venturi 10. By switching the intake air flow path to the bypass pipe 22 by the flow path switching valve 23, the intake air bypasses the venturi 10 and passes through the bypass pipe 22 to be introduced into the engine 1. When the intake pipe 7 on the intake upstream side of the venturi 10 is closed by the flow path switching valve 23, the negative pressure generated in the EGR gas junction 10c of the venturi 10 increases, and the EGR gas passes through the venturi 10 and passes through the engine 1. To be introduced.

  Further, when the EGR valve 25 is closed, the ECU 5 switches the intake air flow path to the bypass pipe 22 by the flow path switching valve 23 regardless of the operating state of the engine 1. When the EGR valve 25 is closed, it is not necessary to return the EGR gas from the exhaust manifold 11 to the intake pipe 7, so it is unnecessary to reduce the internal pressure of the intake pipe 7 by the nozzle portion 10 a of the venturi 10. is there.

  In the EGR device 20A according to the present embodiment, a bypass pipe 22 and a flow path switching valve 23 are added, and in a low load region where it is not necessary to lower the internal pressure of the intake pipe 7 by the nozzle portion 10a of the venturi 10, the flow path switching valve By switching the intake air flow path to the bypass pipe 22 by 23, the intake air bypasses the venturi 10 and passes through the bypass pipe 22, so that deterioration of pump loss and fuel consumption in the low load region are prevented.

  Further, even when the flow path switching valve 23 switches the intake flow path to the bypass pipe 22, the passage from the venturi 10 to the engine 1 is not blocked. Therefore, the EGR gas passes through the venturi 10 and returns to the intake pipe 7 regardless of the state of the flow path switching valve 23, so that EGR can be applied in the entire operation region (high load region and low load region) of the engine 1. .

[Second Embodiment]
FIG. 3 shows an exhaust gas recirculation apparatus according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the component substantially the same as 1st embodiment shown in FIG. 1, and the description is abbreviate | omitted.

  As shown in FIG. 3, the EGR device 20B branches from an EGR pipe 21 downstream of the EGR gas with respect to the EGR valve 25, and joins the intake pipe 7 on the intake downstream side with respect to the venturi 10 (second EGR pipe (first A second EGR passage) 26 and a second EGR valve 27 disposed in the second EGR pipe 26 and opening and closing the second EGR pipe 26.

  The second EGR pipe 26 has an upstream end connected to the EGR pipe 21 on the EGR gas downstream side of the EGR valve 25 and a downstream end connected to the intake pipe 7 between the venturi 10 and the engine 1. For example, the second EGR pipe 26 is configured such that the passage area is substantially the same as that of the EGR pipe 21.

  The second EGR valve 27 is composed of, for example, a butterfly valve. The second EGR valve 27 is connected to the ECU 5, and opening / closing control is performed by the ECU 5.

  In a high load region where it is necessary to lower the internal pressure of the intake pipe 7 by the nozzle portion 10a of the venturi 10, the ECU 5 switches the intake flow path to the venturi 10 by the flow path switching valve 23 and closes the second EGR valve 27. (Fully closed) By switching the intake air flow path to the venturi 10 by the flow path switching valve 23 and closing the second EGR valve 27, the intake air and the EGR gas pass through the venturi 10 and are introduced into the engine 1.

  On the other hand, the ECU 5 switches the intake air flow path to the bypass pipe 22 by the flow path switching valve 23 in the low load region where it is not necessary to lower the internal pressure of the intake pipe 7 by the nozzle portion 10a of the venturi 10, and the second EGR valve. 27 is opened (it is fully opened). By switching the intake air flow path to the bypass pipe 22 by the flow path switching valve 23, the intake air bypasses the venturi 10 and passes through the bypass pipe 22 to be introduced into the engine 1. Further, by opening the second EGR valve 27, the EGR gas bypasses the venturi 10 and passes through the second EGR pipe 26 and is introduced into the engine 1.

  When the EGR valve 25 is closed, the ECU 5 switches the intake air flow path to the bypass pipe 22 by the flow path switching valve 23 and closes the second EGR valve 27 regardless of the operating state of the engine 1 ( Fully closed).

  According to the EGR device 20B according to the second embodiment, the same operational effects as those of the first embodiment described above can be achieved.

  Further, a second EGR pipe 26 and a second EGR valve 27 are added, and in a low load region where it is not necessary to lower the internal pressure of the intake pipe 7 by the nozzle portion 10a of the venturi 10, the second EGR pipe 26 and the second EGR valve 27 are provided. By opening the second EGR valve 27, the EGR gas bypasses the venturi 10 and passes through the second EGR pipe 26, so that the EGR gas returns more smoothly from the exhaust manifold 11 to the intake pipe 7.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various other embodiments can be adopted.

  For example, as shown in FIG. 4, the EGR device 20C may be a so-called low pressure EGR device. When the EGR device 20C is a so-called low pressure EGR device, the EGR pipe 21 communicates the exhaust passage 3 on the exhaust downstream side with respect to the turbine 4b and the intake passage 2 on the intake upstream side with respect to the compressor 4a. Specifically, the EGR pipe 21 has an upstream end connected to the exhaust pipe 12 between the DPF 13 and the muffler 14, and a downstream end connected to the intake pipe 7 between the air cleaner 8 and the compressor 4a. The bypass pipe 22 has an upstream end connected to the intake pipe 7 between the air cleaner 8 and the venturi 10, and a downstream end connected to the intake pipe 7 between the venturi 10 and the compressor 4a. Further, the second EGR pipe 26 has an upstream end connected to the EGR pipe 21 on the EGR gas downstream side of the EGR valve 25 and a downstream end connected to the intake pipe 7 between the venturi 10 and the compressor 4a. The second EGR pipe 26 and the second EGR valve 27 are not always necessary and can be omitted.

  The engine 1 to which the EGR device 20 is mounted is not limited to a diesel engine, and may be a gasoline engine or the like.

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 3 Exhaust passage 5 ECU (flow-path switching control means)
10 Venturi 15 Engine rotation sensor (Operating state detection means)
16 Accelerator opening sensor (operating state detection means)
20 Exhaust gas recirculation device (EGR device)
21 EGR pipe (EGR passage)
22 Bypass pipe (bypass passage)
23 Flow path switching valve 25 EGR valve 26 Second EGR pipe (second EGR passage)
27 Second EGR valve

Claims (3)

An EGR passage for recirculating exhaust gas from the exhaust passage of the engine to the intake passage; a venturi disposed at a connection portion of the intake passage with the EGR passage; and an intake upstream side of the venturi of the intake passage and the intake air A bypass passage that communicates with the downstream side, and a passage that is disposed at a connection portion between the intake passage and the bypass passage on the intake upstream side of the venturi, and switches the intake passage between the venturi and the bypass passage. A switching valve, an operating state detecting means for detecting the operating state of the engine, and a flow path switching control means for switching and controlling the flow path switching valve in accordance with the operating state of the engine detected by the operating state detecting means; With
The flow path switching control means switches the intake flow path to the venturi by the flow path switching valve in the high load area of the engine, and the intake flow path by the flow path switching valve in the low load area of the engine. Is switched to the bypass passage. An EGR valve disposed in the EGR passage;
2. The exhaust gas according to claim 1, wherein when the EGR valve is closed, the flow path switching control unit switches the intake air flow path to the bypass passage by the flow path switching valve regardless of an operating state of the engine. Recirculation device. A second EGR passage branched from the EGR passage downstream of the EGR gas from the EGR valve and joined to the intake passage downstream of the venturi, and disposed in the second EGR passage; A second EGR valve for opening and closing the second EGR passage,
The flow path switching control means switches the intake flow path to the venturi by the flow path switching valve in the high load region of the engine and closes the second EGR valve, and in the low load region of the engine, The exhaust gas recirculation device according to claim 2, wherein the flow path switching valve switches the intake air flow path to the bypass passage and opens the second EGR valve.

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