JP2017044192A - Intake structure of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To homogenize EGR rates of cylinders.SOLUTION: This intake structure of an internal combustion engine comprises: an intake manifold 2 which distributes intake air to intake ports 1 of cylinders of the multi-cylinder internal combustion engine; an intake duct 4 connected to an inlet 3 of the intake manifold; and two EGR discharge pipes 5, 6 which are connected to the intake duct, and discharge an EGR gas into the intake duct. The intake duct has a folded part 14 which is folded to a vertical direction as progressing toward a downstream side from an upstream side, and a curved outlet part 15 which extends from a downstream end of the folded part, is bent to a sideway, and connected to the inlet of the intake manifold. The two EGR discharge pipes are connected to an out-corner part of a front-half curved part at the folded part. The curved outlet part is bend so as to form an elbow shape.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an intake structure of an internal combustion engine, and more particularly to a structure advantageous for evenly distributing EGR gas to each cylinder of a multi-cylinder internal combustion engine.

  In general, in an internal combustion engine, it is known to perform EGR (Exhaust Gas Recirculation) for circulating a part of exhaust gas into an intake passage.

JP 2008-286130 A

  When performing EGR in a multi-cylinder internal combustion engine, it is desired to distribute EGR gas evenly to each cylinder and to make the EGR rate of each cylinder uniform.

  Accordingly, the present invention has been made in view of such circumstances, and an object thereof is to provide an intake structure for an internal combustion engine capable of equalizing the EGR rate of each cylinder.

According to one aspect of the invention,
An intake manifold that distributes intake air to the intake ports of each cylinder of the multi-cylinder internal combustion engine;
An intake duct connected to the inlet of the intake manifold;
Two EGR exhaust pipes connected to the intake duct and exhausting EGR gas into the intake duct;
With
The intake duct has a folded portion that is folded up and down as it goes from the upstream side to the downstream side, a curved outlet portion that extends from the downstream end of the folded portion and is bent sideways and connected to the inlet of the intake manifold. Have
The two EGR discharge pipes are connected to an out corner portion of a bent portion in the first half of the folded portion,
The curved outlet portion is bent so as to have an elbow shape. An intake structure for an internal combustion engine is provided.

  Preferably, the curved outlet portion has a passage cross-sectional area that is once increased and then decreased as it goes from the upstream side to the downstream side.

  Preferably, the folded portion is folded in a U shape, and the two EGR discharge pipes are connected to an out corner portion of a first bent portion in the folded portion.

  Preferably, one of the two EGR discharge pipes is a straight tube and the other is a bent tube.

  Preferably, the inlet of the intake manifold is disposed at a central portion in the longitudinal direction of the manifold and on a side portion of the intake manifold.

  According to the present invention, an excellent effect that the EGR rate of each cylinder can be made uniform is exhibited.

1 is a top view of an intake structure for an internal combustion engine according to an embodiment of the present invention. It is the left side view. It is a right perspective view. It is the left perspective view. It is a principal part enlarged top view of this embodiment. It is a principal part enlarged top view of a comparative example. It is a graph which shows the EGR rate for every cylinder of this embodiment, and its dispersion | variation. It is a graph which shows the EGR rate for every cylinder of a comparative example, and its dispersion | variation. It is a top view which shows typically the mode of the flow of the curved exit part periphery of this embodiment. It is a top view which shows typically the mode of the flow around the curved exit part of a comparative example. It is a side view which shows typically the mode of a flow when an intake manifold inlet is seen from the center direction downstream. It is a schematic perspective view which shows the EGR rate distribution in the intake duct in this embodiment. It is a schematic perspective view which shows the EGR rate distribution in the intake duct in a comparative example. It is the schematic which shows the passage cross-sectional area of one EGR discharge pipe. It is the schematic which shows the passage cross-sectional area of two EGR discharge pipes.

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

  FIG. 1 is a top view of an intake structure for an internal combustion engine according to an embodiment of the present invention. 2 is a left side view, and FIGS. 3 and 4 are a right perspective view and a left perspective view, respectively. The internal combustion engine (engine) of this embodiment is a multi-cylinder compression ignition internal combustion engine for vehicles, that is, a diesel engine. Although the illustrated example shows an in-line 6-cylinder engine, the cylinder arrangement type, the number of cylinders, and the like of the engine are arbitrary. In this embodiment, the engine is scheduled to be placed vertically on the vehicle. The front and rear, right and left, up and down directions of the vehicle and the engine are as illustrated.

  The intake structure of the present embodiment includes an intake manifold 2 that distributes intake air to the intake ports 1 of the cylinders (# 1 to # 6 cylinders) of the engine, and an intake pipe or intake duct 4 connected to the inlet 3 of the intake manifold 2. And two EGR exhaust pipes 5 and 6 that are connected to the intake duct 4 and exhaust the EGR gas into the intake duct 4.

  Two intake ports 1 are provided for each cylinder. Here, the intake port 1 is defined inside a cylinder head (not shown) and actually does not look as shown in the figure, but here the outer shape is shown for the sake of easy understanding. As is apparent from the figure, the # 1 to # 6 cylinders are arranged from the front to the rear of the engine, and the intake manifold 2 also extends from the front to the rear correspondingly. Hereinafter, the longitudinal direction in which the intake manifold 2 extends is referred to as “manifold longitudinal direction”.

  The intake manifold 2 is attached to the cylinder head and communicates with each intake port 1 of each cylinder. The intake manifold 2 has an inlet 3 for introducing intake air. The intake air introduced from the inlet 3 is temporarily stored in the intake manifold 2 and sequentially supplied to the intake ports 1 of the cylinders in the intake stroke. As a result, the intake air is distributed to the intake port 1 of each cylinder.

  In the present embodiment, each intake port 1 of each cylinder is opened in the left side surface portion of the cylinder head, and the intake manifold 2 has a cover shape that collectively covers these intake ports 1. Accordingly, the intake manifold 2 is also referred to as an in-cover. However, the form of the intake manifold 2 is arbitrary, and as usual, it may have a plurality of outlets for each cylinder or each intake port.

  The inlet 3 is disposed at the center in the longitudinal direction of the manifold and at the side of the intake manifold 2. More specifically, the inlet 3 is formed in a cylindrical shape. The center C of the inlet 3 (see FIG. 1) is located slightly behind the intermediate point in the longitudinal direction of the manifold (the boundary position between the # 3 cylinder and the # 4 cylinder) X1. The inlet 3 is disposed on the left side surface portion 7 of the intake manifold 2 and opens toward the left side.

  The intake duct 4 generally extends from the front toward the rear, has a circular cross section, and distributes intake air along the extending direction. The intake duct 4 includes an upstream portion 11, a throttle storage portion 12, a straight pipe portion 13, a folding portion 14, and a curved outlet portion 15 in order from the upstream side. The upstream part 11 is a section part from a to b, the throttle storage part 12 is a section part from b to c, the straight pipe part 13 is a section part from c to d, and the turning part 14 is a section part from d to g, The curved outlet portion 15 is a section portion from g to h. A downstream end h of the curved outlet portion 15 is connected to the inlet 3 of the intake manifold 2.

  Fresh air after passing through a compressor and an intercooler (not shown) of a turbocharger (not shown) in order is introduced from the upstream end a of the upstream part 11 to the upstream part 11. The upstream portion 11 has a front end bent obliquely downward to the left, slightly enlarged in the vicinity of the rear end, and is coaxially connected to the throttle storage portion 12. An electronically controlled throttle valve 16 is stored in the straight tubular throttle storage portion 12. A straight pipe portion 13 is coaxially connected to the throttle storage portion 12, and the straight pipe portion 13 has a predetermined length. The latter half of the upstream portion 11, the throttle storage portion 12, and the straight pipe portion 13 extend from the front to the rear in parallel with the longitudinal direction of the manifold. Further, these are arranged at a position above the intake manifold 2.

  A folded portion 14 is connected to the downstream side of the straight pipe portion 13. The folded portion 14 is folded in the vertical direction, specifically, from the upper side to the lower side, and is folded in a U shape (or a square U shape) in this embodiment. The folded portion 14 extends from the downstream end d of the straight pipe portion 13 and is bent slightly diagonally to the left and slightly perpendicularly downward, and the straight pipe extending diagonally to the left from the downstream end e of the first bent portion 17. And a second bent portion 19 that extends from the downstream end f of the straight pipe portion 18 and is bent obliquely forward and downward at a substantially right angle (specifically, an obtuse angle slightly larger than the right angle). The first bent portion 17 is a section portion from d to e, the straight pipe portion 18 is a section portion from e to f, and the second bent portion 19 is a section portion from f to g.

  The curved outlet portion 15 extends from the downstream end g of the folded portion 14, that is, the downstream end g of the second bent portion 19, is bent sideways, and is connected to the inlet 3 of the intake manifold 2. In the present embodiment, the curved outlet 15 is bent to the right and is connected to the inlet 3 coaxially. Corresponding to the direction of the outlet portion (the portion immediately after bending) of the second bent portion 19, the inlet portion (the portion immediately before bending) of the curved outlet portion 15 also extends obliquely downward to the front.

  Although not specifically illustrated, as a result of forming the folded portion 14 as described above, the virtual plane including the central axis of the folded portion 14 is not perpendicular to the virtual horizontal plane including the center C of the inlet 3. Make an acute angle. The folded portion 14 is inclined so as to be slightly tilted to the intake manifold 2 side (right side) with the connection point (g) with the curved outlet portion 15 as a base point.

  The two EGR discharge pipes, that is, the first EGR discharge pipe 5 and the second EGR discharge pipe 6 are arranged at the outer corner portion of the bent portion of the first half of the folded portion 14, specifically, the outer corner portion on the outlet side of the first bent portion 17. It is connected. The first EGR discharge pipe 5 and the second EGR discharge pipe 6 extend from the EGR valve 20 shown virtually, discharge the EGR gas into the folded portion 14, and join the fresh air. As is well known, the EGR gas means a part of the exhaust gas taken out from the exhaust passage (not shown) and circulated to the intake passage.

  Each of the first EGR discharge pipe 5 and the second EGR discharge pipe 6 has a vertically long cross-sectional shape that is vertically long and has a constant passage cross-sectional area. The first EGR discharge pipe 5 is a bent tube curved with a predetermined radius of curvature, and is directed to discharge EGR gas toward the center inside the first bent portion 17. The second EGR discharge pipe 6 is a straight tube, but is also directed to discharge the EGR gas toward the center inside the first bent portion 17. By providing the two EGR discharge pipes 5 and 6 as described above, the contact area between the EGR gas and fresh air can be increased as will be described later.

  As shown in FIG. 5, the EGR valve 20 of the present embodiment includes an inlet passage 31 into which EGR gas is introduced, two outlet passages 32 and 33 that are symmetrically and bifurcated from the inlet passage 31, Valve bodies 34 and 35 for opening and closing the inlets of the outlet passages 32 and 33 respectively, a rod 37 connecting the valve bodies 34 and 35, and an actuator for opening and closing the valve bodies 34 and 35 simultaneously by reciprocating the rod 37 36. As the valve bodies 34 and 35, those of the poppet valve type are used. One outlet passage 32 is connected to the first EGR discharge pipe 5, and the other outlet passages 32 and 33 are connected to the second EGR discharge pipe 6. The actuator 36 opens and closes the valve bodies 34 and 35 based on a valve opening signal from the electronic control unit (ECU) 100. Note that the EGR gas after passing through an EGR cooler (not shown) is introduced into the inlet passage 31.

  Particularly in the present embodiment, the curved outlet portion 15 is bent so as to form an elbow shape. As shown in detail in FIG. 5, the curved outlet portion 15 is bent at a right angle so as to form an elbow shape, and has predetermined curvature radii R <b> 1 and R <b> 2 on the in-corner side and the out-corner side, respectively. R1 <R2. There is a straight portion 21 on the out-corner side immediately after bending, but there is no such straight portion on the in-corner side. As a result of such an elbow shape, the passage cross-sectional area of the curved outlet portion 15 once increases and then decreases as it goes from the upstream side to the downstream side in the intake flow direction as indicated by the arrow.

  In the present embodiment, the intake duct 4 between the connection position of the first and second EGR discharge pipes 5 and 6 and the intake manifold inlet 3 has two bent portions (second bent portion 19 and curved outlet portion 15). It is formed.

  Next, the effect of this embodiment is demonstrated.

  According to the present embodiment, the shape of the curved outlet portion 15 is particularly an elbow as described above, so that the EGR gas can be sufficiently brought into contact with fresh air and mixed before flowing into the intake manifold 2. it can. Then, when the intake port 1 is reached through the intake manifold 2, the EGR gas can be evenly distributed to each cylinder, and the variation of the EGR rate for each cylinder is sufficiently suppressed, and the EGR rate of each cylinder, that is, the cylinder Every EGR rate can be made uniform. The EGR rate refers to the ratio (%) of the EGR gas amount to the total value of the fresh air amount and the EGR gas amount per unit time.

  Here, in order to facilitate understanding, the operational effects of the present embodiment will be described in comparison with a comparative example similar to the present embodiment.

  The comparative example differs from the present embodiment only in the configuration of the curved outlet portion. Hereinafter, in the comparative example, the same parts as those in the present embodiment are denoted by the same reference numerals in the drawings, and the description thereof will be omitted. Differences from the present embodiment will be mainly described.

  FIG. 6 shows the configuration of the curved outlet portion 15A of the comparative example in detail. As illustrated, the curved outlet portion 15A is bent so as to form a bend shape. In particular, the curved outlet portion 15A is bent at a right angle so as to form a bend, and the central axis thereof has a predetermined radius of curvature R3. R1 <R2 <R3. As a result of such a bend shape, the cross-sectional area of the curved outlet portion 15A is constant from the upstream end g to the downstream end h in the intake flow direction as indicated by the arrow.

  The inventor conducted a test by computer simulation in order to verify the effects of the present embodiment and the comparative example. The results are shown in FIGS. FIG. 7 relates to this embodiment, and FIG. 8 relates to a comparative example.

  Four modes from mode 1 to mode 4 were set as test modes. Each mode is a test condition in which the engine speed, load, and EGR rate are changed.

  7 and 8 show the EGR rate (%) of each cylinder in each mode. 7 and 8 show the variation (%) in the EGR rate of each cylinder in each mode. The variation in the EGR rate of a certain cylinder (referred to as a target cylinder) is represented by a difference obtained by subtracting the average EGR rate of all the cylinders from the EGR rate of the target cylinder.

  As shown in FIG. 7, in the case of the present embodiment, variations in the EGR rate can be reliably suppressed within the target value ± α% in all modes and cylinders.

  On the other hand, as shown in FIG. 8, in the case of the comparative example, in mode 2 and mode 4 (both are high EGR), there are cylinders whose EGR rate variation does not fall within the target value ± α%.

  Therefore, this embodiment can suppress variation in the EGR rate for each cylinder and make the EGR rate for each cylinder uniform compared to the comparative example.

  9 and 10 schematically show the flow around the curved outlet portions 15 and 15A.

  In the case of the present embodiment shown in FIG. 9, it is found that there are a flow F1 having a relatively high EGR rate and a flow F2 having a relatively low EGR rate, as shown, in addition to a main flow along a passage center axis (not shown). did. In addition, the flow F1 can be rephrased as a flow having a high EGR gas, and the flow F2 can be rephrased as a flow having a thin EGR gas.

  When intake air (generic name for fresh air and EGR gas) bends after passing through the curved outlet portion 15, the cross-sectional area of the passage increases and decreases, thereby disturbing the flow of intake air. The flow F1 is a flow that peels off the inner wall 22 on the exit side of the in-corner after bending the tight in-corner portion. Further, the flow F2 is a flow that circulates from the outside of the passage toward the center of the passage after bending the curved outlet portion 15. By the contact, mixing or stirring action of these flows F1 and F2, mixing of fresh air and EGR gas is promoted, which is advantageous for uniformizing the EGR rate for each cylinder.

  Further, as shown in FIG. 11, when the intake manifold inlet 3 of the present embodiment is viewed from the downstream side in the center (C) direction, a swirling flow in the opposite direction can be generally made in the upper half region and the lower half region. . Such a swirl flow is also advantageous in promoting mixing of fresh air and EGR gas and making the EGR rate for each cylinder uniform.

  On the other hand, in the case of the comparative example shown in FIG. 10, when the intake air passes through the curved outlet portion 15A and is bent, the passage cross-sectional area does not change, so that the intake air tends to flow more smoothly along the passage center axis. Yes, flow disturbance is unlikely to occur. On the in-corner side, the separation of the flow F1 from the in-corner outlet side inner wall 22 is reduced. On the out corner side, the flow F2 tends to flow along the inner wall of the passage, and the flow that goes around the center of the passage is reduced. Thereby, the mixing action of the flows F1 and F2 is inferior to the present embodiment.

  It has been found that all the modes have the same flow tendency as described above.

  12 and 13 show the EGR rate distribution at a plurality of positions between the connection position of the EGR exhaust pipes 5 and 6 and the intake manifold inlet 3. In the figure, a region R1 indicated by white is a low EGR rate region, a region R3 indicated by black is a high EGR rate region, and a region R2 indicated by dot is an intermediate EGR rate region. The intermediate EGR rate region R2 is a preferable region where the mixing of EGR gas and fresh air has progressed to some extent. On the other hand, the low EGR rate region R1 is a region where the EGR rate is lower than that of the intermediate EGR rate region R2, and the high EGR rate region R3 is a region where the EGR rate is higher than that of the intermediate EGR rate region R2.

  As can be seen from these figures, the regions R1 and R3 gradually decrease and the region R2 gradually increases from the start of EGR gas introduction toward the downstream side. This means that mixing of fresh air and EGR gas proceeds toward the downstream side. In particular, in the present embodiment shown in FIG. 12, the position of the region R3 is closer to the center C at the position of the intake manifold inlet 3 than in the comparative example shown in FIG. This means that the region where the EGR gas is deeper is closer to the manifold longitudinal direction intermediate point X1 (see FIG. 1) than in the comparative example, and this embodiment is preferable. On the other hand, in the comparative example, the EGR gas-rich region R3 is unevenly distributed rearward with respect to the center C and the manifold longitudinal direction intermediate point X1, and the EGR rate per cylinder becomes the average EGR rate in the rear cylinder (for example, # 6 cylinder). May be higher. This is disadvantageous for making the EGR rate for each cylinder uniform.

  In the present embodiment shown in FIG. 12, the area of the region R2 is enlarged at the position of the intake manifold inlet 3, and the EGR rate distribution is closer to the central symmetry than the comparative example shown in FIG. These are also advantageous for making the EGR rate for each cylinder uniform.

  By the way, in this embodiment, the contact area of EGR gas and fresh air can be increased by providing the two EGR discharge pipes 5 and 6. That is, rather than discharging EGR gas from one EGR discharge pipe having a passage cross-sectional area A as shown in FIG. 14, EGR gas is discharged from two EGR discharge pipes having a passage cross-sectional area A / 2 as shown in FIG. When the gas is discharged, the EGR gas is brought into contact with fresh air at the portions indicated by S1 and S2 in FIG. 15, and the contact area can be increased. And mixing of EGR gas and fresh air can be promoted, and uniformization of the EGR rate for each cylinder can be promoted.

  As described above, according to this embodiment, it is possible to advantageously equalize the EGR rate for each cylinder.

  In addition, this embodiment has the following advantages.

  (1) In the present embodiment, the variation in the intake air amount among the cylinders is small, and the variation in the EGR rate for each cylinder is small, so that each gas component in the intake air can be evenly distributed to each cylinder.

  (2) Blow-back of EGR gas to the throttle valve 16 can be avoided.

  (3) In the present embodiment, the flow of the intake air is disturbed as much as necessary and sufficient from the introduction of the EGR gas into the intake duct 4 until the intake manifold inlet 3 is reached. It is possible to achieve both mixing and reduction of intake resistance. That is, if mixing is prioritized and the flow of intake air is disturbed more than necessary, the intake resistance increases and the maximum intake air amount obtained by the duct shape decreases. On the other hand, if priority is given to reducing the intake resistance so as not to disturb the intake more than necessary, mixing is naturally insufficient, which is disadvantageous for making the EGR rate for each cylinder uniform. In the present embodiment, the turn-back portion 14, the curved outlet portion 15, and the EGR discharge pipes 5 and 6 are configured so that almost all mixing is just finished when the intake manifold inlet 3 is reached. Therefore, it is possible to satisfy the above conflicting demands while suppressing an increase in the intake resistance to a necessary minimum.

  As mentioned above, although embodiment of this invention was described in detail, other embodiment is possible for this invention. For example, an embodiment in which the configuration of the present embodiment is reversed left and right, an embodiment in which the configuration of the present embodiment is reversed upside down, or an embodiment in which the front and rear and the left and right of the configuration of the present embodiment are interchanged (ie, the horizontal direction as a whole) Long embodiments) and the like are also possible.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

DESCRIPTION OF SYMBOLS 1 Intake port 2 Intake manifold 3 Inlet 4 Intake duct 5 1st EGR exhaust pipe 6 2nd EGR exhaust pipe 14 Folding part 15 Curved exit part

Claims (5)

An intake manifold that distributes intake air to the intake ports of each cylinder of the multi-cylinder internal combustion engine;
An intake duct connected to the inlet of the intake manifold;
Two EGR exhaust pipes connected to the intake duct and exhausting EGR gas into the intake duct;
With
The intake duct has a folded portion that is folded up and down as it goes from the upstream side to the downstream side, a curved outlet portion that extends from the downstream end of the folded portion and is bent sideways and connected to the inlet of the intake manifold. Have
The two EGR discharge pipes are connected to an out corner portion of a bent portion in the first half of the folded portion,
The intake structure for an internal combustion engine, wherein the curved outlet portion is bent so as to form an elbow shape. The intake structure for an internal combustion engine according to claim 1, wherein the curved outlet portion has a passage cross-sectional area that is once increased and then decreased as it goes from the upstream side to the downstream side. 3. The internal combustion engine according to claim 1, wherein the folded portion is folded in a U shape, and the two EGR discharge pipes are connected to an out corner portion of a first bent portion in the folded portion. Engine intake structure. The intake structure for an internal combustion engine according to any one of claims 1 to 3, wherein one of the two EGR exhaust pipes is a straight tube and the other is a bent tube. The intake structure for an internal combustion engine according to any one of claims 1 to 4, wherein an inlet of the intake manifold is disposed at a central portion in a longitudinal direction of the manifold and at a side portion of the intake manifold.

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