JP2007255357A - Exhaust recirculation flow control valve for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive exhaust recirculating a flow control valve in a simple structure. <P>SOLUTION: The exhaust recirculating flow control valve for an engine comprises an inlet passage 17 for taking in a part of an exhaust gas in an exhaust passage 3 of the engine, first and second supply passages 18 and 19 which are arranged both sides of the inlet passage 17 and supply the exhaust gas flowing from the inlet passage 17 to an intake passage 2 of the engine, first and second openings 20 and 21 for respectively connecting the first and second supply passages 18 and 19 with inlet passage 17, and a valve 25 in which first and second valve bodies 22 and 23 for respectively opening and closing the first and second openings 20 and 21 are coaxially and integrally formed. Change rates of the gas flow against a lift amount of the valve 25 are respectively different on the first and second valve bodies 22 and 23 of the valve 25. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation amount control valve that adjusts an exhaust gas recirculation amount when a part of exhaust gas in an exhaust passage of an engine is recirculated to an intake passage of the engine.

  An exhaust gas recirculation device (EGR device) for returning a part of exhaust gas in the exhaust passage of the engine to the intake passage of the engine is, for example, an exhaust pipe (or exhaust manifold) and an intake pipe (or intake manifold) of the engine. And an exhaust gas recirculation pipe (EGR pipe) that extracts EGR gas (exhaust gas) from the exhaust pipe, an EGR cooler that is provided in the middle of the exhaust gas recirculation pipe and cools the EGR gas, engine speed, load, and intake A detecting means for detecting an air amount (MAF amount), an accelerator opening degree, and the like, and an exhaust gas recirculation amount (EGR amount) or an exhaust gas recirculation rate (in accordance with a detection value provided in the middle of the exhaust gas recirculation pipe and detected by the detection means) An exhaust gas recirculation amount control valve (EGR valve) whose gas flow path area (opening area) is variable in order to adjust the EGR rate), and E in order to adjust the gas flow path area of the EGR valve Composed of a computer for controlling the lift amount of R valve (opening).

  For example, the engine rotation speed and load are detected, and the EGR valve lift amount is controlled based on a computer instruction so that the set EGR rate is obtained, thereby obtaining a target EGR rate. Alternatively, the engine speed, load, and MAF amount are detected, and the target EGR rate is obtained by controlling the lift amount of the EGR valve based on a computer instruction so that the set MAF amount is obtained. .

  In recent years, it is necessary to perform a large amount of EGR in order to comply with strict exhaust gas regulations, and the EGR valve also requires a large area of the gas flow path with respect to the lift amount of the EGR valve in order to flow a large amount of EGR gas (necessary flow rate of gas) Tend to expand.

  By the way, in diesel premixed combustion (PCI combustion), which is promising as a technology capable of reducing NOx (nitrogen oxide) and PM (particulate matter) in the low load operation region of the engine, premature ignition and knocking are prevented, A large amount of EGR is performed to control the ignition timing of combustion. However, the range in which the EGR rate should be controlled is narrow, and if it falls outside this range, pre-ignition, knocking, etc. occur, causing problems such as the generation of knocking noise during combustion and an increase in PM emissions. Therefore, in the low load operation region of the engine, in order to accurately control the EGR rate within a narrow control range, it is necessary to reduce the rate of change of the gas passage area (gas flow rate) with respect to the lift amount of the EGR valve.

  When NOx is reduced by combining EGR with normal combustion (diffusion combustion), the excess air ratio is reduced in the high-load operation region of the engine mainly used during vehicle acceleration due to the response delay of the turbocharger compared to the steady operation. . Therefore, even in the high load operation region of the engine, in order to accurately control the EGR rate within a narrow control range, it is necessary to reduce the rate of change of the gas passage area (gas flow rate) with respect to the lift amount of the EGR valve. Further, in the high load operation region of the engine, it is necessary to increase the gas flow path area (gas flow rate) of the EGR valve in order to flow a large amount of EGR gas while keeping the EGR rate low.

  When NOx reduction is performed by combining EGR with normal combustion, there is little fluctuation and a relatively high excess air ratio in the medium-load operation region of the engine that is mainly used during steady running of the vehicle. Therefore, in the medium load operation region of the engine, a large amount of EGR can be performed and the control range of the EGR rate can be set wide.

  In order to perform a large amount of EGR in the medium load operation region of the engine and a large amount of EGR in a narrow control range in the low / high load operation region of the engine, the gas flow path area (gas flow rate) relative to the lift amount of the EGR valve It is necessary to reduce the rate of change and increase the lift amount of the EGR valve.

  However, if the lift amount of the EGR valve is simply increased, (1) the EGR valve becomes larger and hinders mounting on the vehicle. (2) A large driving force is required to quickly move the EGR valve with a large lift amount. (3) In order to increase the lift amount of the EGR valve, there arises a problem that the responsiveness of the EGR valve is rather deteriorated.

  In order to solve such a problem, an EGR valve comprising a plurality of valves having different rates of change in the gas flow path area (gas flow rate) with respect to the lift amount, and drive means for appropriately opening and closing the plurality of valves. Has been proposed. Such an EGR valve is also described in Patent Documents 1 to 3 and the like.

JP-A-8-31470 Japanese Patent Laid-Open No. 11-13558 JP 2002-81571 A

  However, in Patent Documents 1 to 3 and the like, a plurality of valves are all configured separately, and driving means for appropriately opening and closing the plurality of valves is provided, so that the structure becomes large and further costs increase. There is.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust gas recirculation amount control valve with a simple configuration and low cost.

  In order to achieve the above object, an invention according to claim 1 is an exhaust gas recirculation amount control valve for adjusting an exhaust gas recirculation amount when a part of exhaust gas in the exhaust passage of the engine is recirculated to the intake passage of the engine. An intake passage for taking in part of the exhaust gas in the exhaust passage, and a first supply passage provided on both sides of the intake passage for supplying exhaust gas flowing in from the intake passage to the intake passage; A second supply passage, a first opening and a second opening communicating with the first supply passage and the second supply passage and the intake passage, respectively, and the first opening and the second opening. A valve in which a first valve body and a second valve body for opening and closing respectively are coaxially formed, and the first valve body and the second valve body of the valve have a gas flow rate with respect to the lift amount of the valve. Engine characterized by different rates of change An exhaust recirculation amount control valve.

  According to a second aspect of the present invention, the first valve body includes an annular shaft portion that is inserted into the first opening when the valve is closed and is detached from the first opening in accordance with the lift of the valve. The exhaust gas recirculation amount control valve for an engine according to claim 1.

  According to a third aspect of the present invention, the first valve body has a plate-like protrusion that is formed smaller than the diameter of the shaft portion and is inserted into the first opening in accordance with the lift of the valve. The exhaust gas recirculation amount control valve for an engine according to claim 1.

  According to a fourth aspect of the present invention, in the first valve body, the rate of change of the gas flow rate relative to the lift amount of the valve in the small lift region and the high lift region is a change in gas flow rate relative to the lift amount of the valve in the middle lift region. The second valve body is set such that the gas flow rate relative to the lift amount of the valve in the entire lift region is set to increase in accordance with the lift of the valve. It is an engine exhaust gas recirculation amount control valve of description.

  According to a fifth aspect of the present invention, in the first valve body, the rate of change of the gas flow rate relative to the lift amount of the valve in the small lift region is a change in gas flow rate relative to the lift amount of the valve in the middle lift region and the high lift region. The second valve body is set such that the gas flow rate relative to the lift amount of the valve in the entire lift region is set to increase in accordance with the lift of the valve. It is an engine exhaust gas recirculation amount control valve of description.

  According to the present invention, there is an excellent effect that an exhaust gas recirculation amount control valve with a simple configuration and low cost can be provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic view of an engine provided with an exhaust gas recirculation amount control valve according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the exhaust gas recirculation amount control valve of the first embodiment. FIGS. 3A to 3C are schematic diagrams respectively showing the exhaust gas recirculation amount control valve of the first embodiment in the small lift region, the middle lift region, and the high lift region. FIG. 4 is a graph showing the flow characteristics of the exhaust gas recirculation control valve of the first embodiment.

  The present embodiment is applied to a diesel engine (hereinafter referred to as an engine) for a vehicle or the like.

  First, the engine will be described.

  In FIG. 1, 1 is an engine body, 2 is an intake pipe (or intake manifold) that is connected to the engine body 1 and through which intake air flows, and 3 is an exhaust passage that is connected to the engine body 1 and through which exhaust gas flows. The exhaust pipe (or exhaust manifold).

  A compressor 5 of a turbocharger 4 is connected to the intake pipe 2. A turbine 6 of a turbocharger 4 is connected to the exhaust pipe 3.

  The engine includes an exhaust gas recirculation device 7 (hereinafter referred to as an EGR device) for returning a part of the exhaust gas in the exhaust pipe 3 to the intake pipe 2.

  The EGR device 7 connects the exhaust pipe 3 and the intake pipe 2, and an exhaust gas recirculation pipe 8 (hereinafter referred to as an EGR pipe) serving as an exhaust gas recirculation passage for extracting EGR gas (exhaust gas) from the exhaust pipe 3. In order to adjust the exhaust gas recirculation amount (hereinafter referred to as EGR amount) or the exhaust gas recirculation rate (hereinafter referred to as EGR rate) provided in the middle and provided in the middle of the EGR cooler 9 for cooling the EGR gas and the EGR pipe 8. An exhaust gas recirculation amount control valve 10 (hereinafter referred to as an EGR valve) having a variable gas flow path area (opening area) and a lift amount of the EGR valve 10 are controlled in order to change the gas flow path area of the EGR valve 10. And a computer 11.

  The computer 11 detects an actual engine operating state from various sensors, and controls the EGR valve 10 based on the engine operating state. Examples of the sensors include an engine rotation sensor 12 as an engine rotation detection unit that detects the rotation speed of the engine, an engine load sensor 13 as an engine load detection unit that detects an engine load, and an intake air amount (hereinafter referred to as MAF amount). ), An intake air amount sensor 14 as an intake air amount detection means, an accelerator opening sensor 15 as an accelerator opening detection means for detecting an accelerator opening, and the like. The detection signal is input to the computer 11.

  For example, the computer 11 inputs the engine rotation speed detected by the engine rotation sensor 12 and the engine load sensor 13 and the detected value of the load into a map in which a lift amount that gives a set EGR rate is input in advance. The lift amount is obtained, and the EGR valve 10 is controlled according to the obtained lift amount.

  Alternatively, the computer 11 sets the MAF amount (the set MAF amount = the detected MAF amount = the detected value of the engine rotation speed, the load, and the MAF amount detected by the engine rotation sensor 12, the engine load sensor 13 and the intake air amount sensor 14). The lift amount such that MAF amount without EGR−EGR amount) is input to a previously input map to obtain the lift amount, and the EGR valve 10 is controlled according to the obtained lift amount.

  Next, the EGR valve 10 will be described with reference to FIG.

  This embodiment is considered to be used in a medium load operation region to a high load operation region in which the excess air ratio of the engine is low and delicate control of the EGR amount or the EGR rate is required.

  As shown in FIG. 2, the EGR valve 10 includes a casing 16 disposed in the middle of the EGR pipe 8. The casing 16 is provided with intake passages 17 for taking in part of the exhaust gas in the exhaust pipe 3 and both sides (upper and lower in the illustrated example) of the intake passages 17, and exhaust gas flowing from the intake passages 17 is supplied to the casing 16. A first opening 20 and a second supply passage 19 that supply the intake pipe 2, and a first opening 20 and a second passage that communicate between the first supply passage 18, the second supply passage 19, and the intake passage 17, respectively. The opening 21, the first valve body 22 for opening and closing the first opening 20, and the second valve body 23 for opening and closing the second opening 21 are integrated coaxially (on the same shaft portion 24). A formed valve 25 is provided.

  The valve 25 has a shaft portion 24 slidably supported in an insertion hole 26 provided in the casing 16. The first valve body 22 is provided at an intermediate portion of the shaft portion 24, and the second valve body 23 is provided at an end portion (lower end portion in the illustrated example) of the shaft portion 24.

  The valve 25 is closed by an urging means (not shown) while being inserted into a first valve hole 27 provided in the first opening 20 and a second valve hole 28 provided in the second opening 21. It is urged in the direction (upward in the illustrated example).

  The valve portion 29 of the first valve body 22 has an outer diameter larger than that of the first valve hole 27 of the first opening 20, and the intake passage 17 side of the valve seat 30 provided in the first opening 20 (see FIG. In the example shown, it is seated on the lower surface.

  The first valve element 22 has a gas flow rate area (gas flow rate) with respect to the lift amount of the valve 25 in the middle lift region (gas flow rate area relative to the lift amount of the valve 25 in the small lift region and the high lift region). It is set smaller than the rate of change of the gas flow rate.

  The first valve body 22 is enlarged in a range smaller than the diameter of the first valve hole 27 and is inserted into the first opening 20 (first valve hole 27) when the valve 25 (first valve body 22) is closed. The annular shaft portion (expanded shaft portion) 31 is separated from the first opening 20 (first valve hole 27) according to the lift of the valve 25, and is formed smaller than the diameter of the expanded shaft portion 31. It has a disc-shaped projection (projection plate) 32 that is inserted into the first opening 20 (first valve hole 27) according to the lift of the valve 25.

  The diameter-expanded shaft portion 31 is located in the first valve hole 27 in a small lift region, and is formed integrally with the valve portion 29 and the projection portion 32 (on the same shaft portion 24). The enlarged diameter shaft portion 31 is provided continuously to the end portion (the upper end portion in the illustrated example) of the valve portion 29. The outer diameter of the enlarged diameter shaft portion 31 is such that the clearance area between the enlarged diameter shaft portion 31 and the first valve hole 27 when the enlarged diameter shaft portion 31 is inserted into the first valve hole 27 is relatively small. Is set as follows.

  The protruding portion 32 is located in the first valve hole 27 in the high lift region, and is integrally formed coaxially with the valve portion 29 and the enlarged diameter shaft portion 31 (on the same shaft portion 24). The protrusion 32 is provided at a predetermined interval in the axial direction (upward in the illustrated example) with respect to the valve portion 29 and the diameter-expanded shaft portion 31.

  The outer diameter of the projecting portion 32 is such that the clearance area between the projecting portion 32 and the first valve hole 27 when the projecting portion 32 is inserted into the first valve hole 27 is equal to the diameter-enlarging shaft portion 31 being the first valve hole. 27 is set so as to be slightly larger than the maximum opening area between the enlarged diameter shaft portion 31 and the first valve hole 27 until the projection 32 is inserted into the first valve hole 27.

  The valve part 33 of the second valve body 23 has an outer diameter larger than the second valve hole 28 of the second opening 21, and the valve seat 34 provided in the second opening 21 has the second supply passage 19 side ( In the illustrated example, it is seated on the lower surface.

  The second valve body 23 is set so that the gas flow path area (gas flow rate) with respect to the lift amount of the valve 25 in the entire lift region increases linearly according to the lift of the valve 25. The second valve body 23 is set such that its gas flow path area (gas flow rate) is larger than the gas flow path area (gas flow rate) of the first valve body 22 in the entire lift region.

  The operation of this embodiment will be described.

  The valve 25 is lifted in the opening direction (downward in the illustrated example) by driving means (not shown).

  In the first valve body 22 provided with the diameter-expanded shaft portion 31, the first valve is provided during the small lift region (see FIG. 3A) where the diameter-expanded shaft portion 31 is located in the first valve hole 27. The gas flow path area of the body 22 is fixed and defined by the gap area between the enlarged diameter shaft portion 31 and the first valve hole 27, and the gap between the enlarged diameter shaft portion 31 and the first valve hole 27 is made constant. The flow rate of gas passing through is suppressed (see FIG. 4).

  In the first valve body 22, the intermediate lift region (see FIG. 3B) until the enlarged diameter shaft portion 31 is detached from the first valve hole 27 and the protrusion 32 is inserted into the first valve hole 27. ), The enlarged diameter shaft portion 31 and the protruding portion 32 are not located in the first valve hole 27. Therefore, during the intermediate lift region, the gas flow path area of the first valve element 22 increases linearly according to the lift of the valve 25, and the gas flow rate corresponds to the gas flow path area and the lift amount (FIG. 4). reference).

  Further, in the first valve body 22, during the high lift region (see FIG. 3C) where the protrusion 32 is located in the first valve hole 27, the gas flow path area of the first valve body 22 is the protrusion. It is defined by the clearance area between the portion 32 and the first valve hole 27, and is constant within a range that does not fall below the maximum opening area between the enlarged diameter shaft portion 31 and the first valve hole 27 up to the middle lift region. The gas flow rate passing through the gap between the portion 32 and the first valve hole 27 is suppressed (see FIG. 4).

  On the other hand, in the second valve body 23 in which the enlarged diameter shaft portion 31 and the protrusion portion 32 are not provided, the gas flow path area of the valve 25 is in the entire lift region (see FIGS. 3A to 3C). It increases linearly according to the lift, and becomes a gas flow rate according to the gas flow path area and the lift amount (see FIG. 4).

  Accordingly, the rate of change of the gas flow path area (gas flow rate) with respect to the lift amount of the valve 25 changes in three stages of the small lift region, the middle lift region, and the high lift region as the entire valve 25 (see FIG. 4).

  Specifically, in the high lift region used in the PCI combustion region (low load operation region of the engine) and the low lift region used in the high load operation region, the gas flow path area of the valve 25 relative to the lift amount of the valve 25 by the second valve element 23. While sufficiently securing (gas flow rate), the sensitivity of the rate of change of the gas flow path area (gas flow rate) with respect to the lift amount of the valve 25 is reduced by the first valve body 22, and in the middle lift region used in the medium load operation region, The first valve body 22 and the second valve body 23 can sufficiently secure the gas flow path area (gas flow rate) of the valve 25 with respect to the lift amount of the valve 25 with a small lift amount.

  In the present embodiment, the first valve body 22 has a rate of change of the gas flow passage area (gas flow rate) relative to the lift amount of the valve 25 in the small lift region and the high lift region with respect to the lift amount of the valve 25 in the middle lift region. The gas flow passage area (gas flow rate) is set to be smaller than the rate of change of the gas flow passage area (gas flow rate), and the second valve element 23 has a gas flow passage area (gas flow rate) corresponding to the lift amount of the valve 25 in the entire lift region. Therefore, the rate of change of the gas passage area (gas flow rate) with respect to the lift amount of the valve 25 in the small lift region and the high lift region is set as the overall value of the valve 25 in the middle lift region. The rate of change of the gas flow path area (gas flow rate) with respect to the lift amount can be made smaller, and the EGR rate in the small lift region and the high lift region can be accurately controlled within a narrow control range.

  Further, in the present embodiment, the first valve body 22 and the second valve body 23 are integrally formed on the same axis (on the same shaft portion 24), so it is necessary to provide a plurality of drive means for moving the valve 25. Therefore, the structure is not increased in size or cost.

  In short, according to the present embodiment, it is possible to provide an exhaust gas recirculation amount control valve with a simple configuration and low cost.

  Next, a second embodiment will be described with reference to FIGS.

  The same members as those in the first embodiment are denoted by the same reference numerals, description thereof is omitted, and only differences are described.

  FIG. 5 is a cross-sectional view of the exhaust gas recirculation amount control valve of the second embodiment. FIGS. 6A to 6C are schematic views respectively showing the exhaust gas recirculation amount control valve of the second embodiment in the small lift region, the middle lift region, and the high lift region. FIG. 7 is a graph showing the flow characteristics of the exhaust gas recirculation control valve of the second embodiment.

  It can be considered that the present embodiment is used in a low load operation region to a medium load operation region where the excess air ratio of the engine is high.

  In the present embodiment, the first valve body 22 is not provided with the protrusion 32 (see FIG. 2).

  Therefore, in the present embodiment, the valve 25 as a whole has a gas flow passage area (gas) with respect to the lift amount of the valve 25 in two stages, a small lift region and a middle / high lift region (see FIGS. 6A to 6C). The rate of change in the flow rate changes (see FIG. 7).

  In the present embodiment, the first valve element 22 has a rate of change of the gas flow path area (gas flow rate) with respect to the lift amount of the valve 25 in the small lift region with respect to the lift amount of the valve 25 in the middle lift region and the high lift region. The gas flow passage area (gas flow rate) is set to be smaller than the rate of change of the gas flow passage area (gas flow rate), and the second valve element 23 has a gas flow passage area (gas flow rate) corresponding to the lift amount of the valve 25 in the entire lift region. Therefore, the rate of change of the gas flow path area (gas flow rate) with respect to the lift amount of the valve 25 in the small lift region is set as the overall value of the valve 25 in the middle lift region and the high lift region. The change rate of the gas flow path area (gas flow rate) with respect to the lift amount can be made smaller, and the EGR rate in the small lift region can be accurately controlled within a narrow control range.

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

It is a schematic diagram of an engine provided with an exhaust gas recirculation amount control valve concerning a first embodiment of the present invention. It is sectional drawing of the exhaust gas recirculation amount control valve of 1st embodiment. (A)-(c) is the schematic which shows the exhaust gas recirculation amount control valve of 1st embodiment in a small lift area, a middle lift area, and a high lift area, respectively. It is a graph which shows the flow volume characteristic of the exhaust gas recirculation amount control valve of a first embodiment. It is sectional drawing of the exhaust gas recirculation amount control valve of 2nd embodiment. (A)-(c) is the schematic which each shows the exhaust gas recirculation amount control valve of 2nd embodiment in a small lift area, a middle lift area, and a high lift area. It is a graph which shows the flow volume characteristic of the exhaust gas recirculation amount control valve of a second embodiment.

Explanation of symbols

2 Intake pipe (intake passage)
3 Exhaust pipe (exhaust passage)
10 Exhaust gas recirculation control valve (EGR valve)
17 Intake passage 18 First supply passage 19 Second supply passage 20 First opening 21 Second opening 22 First valve body 23 Second valve body 25 Valve 31 Expanded shaft portion (shaft portion)
32 Protrusion

Claims (5)

An exhaust gas recirculation amount control valve for adjusting an exhaust gas recirculation amount when a part of the exhaust gas in the exhaust passage of the engine is recirculated to the intake passage of the engine,
An intake passage for taking in part of the exhaust gas in the exhaust passage, and a first supply passage and a second supply passage which are provided on both sides of the intake passage and supply exhaust gas flowing in from the intake passage to the intake passage. A supply passage, a first opening and a second opening communicating between the first supply passage and the second supply passage and the intake passage, and opening and closing the first opening and the second opening, respectively. A valve having a first valve body and a second valve body integrally formed on the same axis,
An exhaust gas recirculation control valve for an engine, wherein the first valve body and the second valve body of the valve have different rates of change in gas flow rate with respect to the lift amount of the valve.   The said 1st valve body is inserted in said 1st opening part at the time of valve closing of the said valve | bulb, and has the cyclic | annular axial part removed from said 1st opening part according to the lift of the said valve | bulb. Engine exhaust recirculation control valve.   3. The engine exhaust gas return according to claim 2, wherein the first valve body has a plate-like protrusion that is formed smaller than the diameter of the shaft portion and is inserted into the first opening in accordance with a lift of the valve. Flow control valve. The first valve body is set such that the change rate of the gas flow rate with respect to the lift amount of the valve in the small lift region and the high lift region is smaller than the change rate of the gas flow rate with respect to the lift amount of the valve in the middle lift region,
The exhaust gas recirculation amount of the engine according to any one of claims 1 to 3, wherein the second valve body is set such that a gas flow rate with respect to a lift amount of the valve in an entire lift region increases according to the lift of the valve. Control valve. The first valve body is set such that the change rate of the gas flow rate with respect to the lift amount of the valve in the small lift region is smaller than the change rate of the gas flow rate with respect to the lift amount of the valve in the middle lift region and the high lift region,
The exhaust gas recirculation amount of the engine according to any one of claims 1 to 3, wherein the second valve body is set such that a gas flow rate with respect to a lift amount of the valve in an entire lift region increases according to the lift of the valve. Control valve.

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