JP2016031060A - Intake device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intake device capable of suppressing release of an intake air flow and effectively reducing pressure loss in a curved portion of an intake passage.SOLUTION: An intake port portion 20 of this intake air device 100 includes an intake pipe 1 connected to an internal combustion engine 90 and having a curved portion 3. The curved portion 3 includes a curved upstream portion 4 and a curve downstream portion 5. In a cross-section C2 of the curved downstream portion 5 orthogonal to an extension direction of the intake pipe 1, a distance H2 between an intake passage inner surface 5a on a curve outer side of the curved downstream portion 5 and an intake passage inner surface 5b on a curve inner side is gradually reduced along an intake air flow direction (arrow B direction) of the curved downstream portion 5 and a distance W2 between intake passage inner surfaces 5c and 5d orthogonal to and facing the intake passage inner surfaces 5a and 5b facing each other at the distance H2 is gradually increased along the intake air flow direction so that a cross-sectional area S of the curved downstream portion 5 is made constant along the intake air flow direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an intake device, and more particularly, to an intake device having an intake passage connected to an internal combustion engine.

  Conventionally, an intake device having an intake passage connected to an internal combustion engine is known (see, for example, Patent Document 1).

  Patent Document 1 discloses an intake manifold (intake device) that includes an intake pipe that is curved in the middle of an intake passage and is connected to an internal combustion engine. The intake pipe in the intake manifold described in Patent Document 1 has a cylindrical portion formed at both ends and a flow passage cross section having a flat shape (oval flat shape) in which the flatness (cross-sectional shape) is kept constant. And a gradually changing portion that is formed between the cylindrical portion and the curved portion, and gradually returns the cross section of the elliptical flat shape to the circular shape from the curved portion toward the cylindrical portion. Yes. That is, in the intake pipe, the flow path is configured in the order of the cylindrical portion, the gradually changing portion, the flat curved portion, the gradually changing portion, and the cylindrical portion along the intake flow direction. Since the bending portion is bent in a state in which the flatness (cross-sectional shape) is kept constant, it is considered that the curved inner side and the inner inner surface each have a constant radius of curvature.

JP-A-11-210578

  However, in the intake manifold described in Patent Document 1, since the flatness (cross-sectional shape) is constant, each of the curved outer side and the inner inner surface of the curved portion is bent with a constant radius of curvature. Therefore, when the intake air flow that has passed through the first half portion of the curved portion passes through the second half portion, it is considered that it is likely to peel off from the vicinity of the inner surface of the curved inner side due to a continuous constant bending radius. In addition, when the intake flow is separated at the latter half of the curved portion, the generation of a separation vortex behind (the wake region including the gradually changing portion) leads to an increase in the pressure loss of the intake pipe. For this reason, there is a problem that the pressure loss cannot be effectively reduced due to separation of the intake flow passing through the curved portion of the intake pipe (intake passage).

  The present invention has been made to solve the above-described problems, and one object of the present invention is to effectively suppress pressure loss in the curved portion of the intake passage by suppressing separation of the intake flow. It is to provide an intake device capable of this.

  In order to achieve the above object, an intake device according to one aspect of the present invention includes an intake passage that is connected to an internal combustion engine and has a curved portion in which both an outer surface of the passage and an inner surface of the passage are curved. The curved downstream portion includes a curved upstream portion, which is an upstream portion of the curved portion, and a curved downstream portion, which is a downstream portion of the curved portion, in a cross section orthogonal to the direction in which the intake passage extends in the curved downstream portion. The first downstream interval between the outer intake passage inner surface and the curved inner intake passage inner surface is gradually decreased along the intake flow direction of the curved downstream portion, and the intake air is opposed to the downstream first interval. By gradually increasing the downstream second interval between the inner surfaces of the intake passages that are orthogonal to the inner surface of the passage, the sectional area of the curved downstream portion becomes constant along the intake flow direction. Composed That.

  In the intake device according to one aspect of the present invention, as described above, in the cross section orthogonal to the extending direction of the intake passage in the curved downstream portion, the intake passage inner surface on the curved downstream side and the intake passage inner surface on the curved inner side in the curved downstream portion. The downstream first interval is gradually decreased along the intake flow direction, and the downstream second interval between the intake passage inner surfaces that are orthogonal to the opposed intake passage inner surfaces and have the first downstream interval. Is gradually increased along the intake flow direction, so that the curved portion of the intake passage is configured such that the cross-sectional area of the curved downstream portion is constant along the intake flow direction. Thereby, in the curved downstream portion where the separation of the intake flow is likely to occur, the flow path length in the vicinity of the inner surface of the intake passage on the outer side of the curve is reduced by reducing the downstream first interval between the inner surface of the intake passage and the outer side of the curve. Since the difference from the flow path length in the vicinity of the inner surface of the intake passage inside the curve is reduced, the separation of the intake flow from the inner surface of the intake passage inside the curve is suppressed. Further, by gradually changing the first downstream distance between the curved outer side of the curved downstream portion and the inner intake passage inner surface without suddenly changing, the flow path length and the curved inner side in the vicinity of the curved inner surface of the intake passage Since the difference with the flow path length near the inner surface of the intake passage can be gradually reduced without abruptly decreasing, it is possible to more effectively suppress the separation of the intake flow from the inner surface of the intake passage inside the curve. Can do. As a result, the pressure loss in the curved portion of the intake passage can be effectively reduced. Further, when the flow path cross-sectional shape is changed so as to decrease the downstream first interval between the inner surface of the intake passage on the outer side of the curve and the inner surface of the intake passage on the inner side of the curve, the second interval of the downstream portion is increased. Thus, by keeping the cross-sectional area constant, it is possible to effectively suppress an increase in the pressure loss of the intake flow in the curved downstream portion where the downstream first interval is narrowed. This can also effectively reduce the pressure loss in the curved portion of the intake passage.

  In the intake device according to the above aspect, the inner surface of the intake passage inside the curved downstream portion preferably has a larger radius of curvature than the inner surface of the intake passage inside the curved upstream portion, and the direction in which the intake passage extends In the cross section orthogonal to the first portion, the downstream first interval is smaller than the first upstream interval between the inner curved inner surface of the intake passage and the inner curved intake passage. With this configuration, in the curved downstream portion where the separation of the intake flow is likely to occur, the curvature radius of the inner surface of the intake passage on the inner side of the curve can be increased to easily approach the inner surface of the intake passage on the outer side of the curve. It is possible to easily reduce the downstream first interval in the curved downstream portion with respect to the upstream first interval in the portion. That is, since the difference between the flow path length in the vicinity of the inner surface of the intake passage outside the curve and the flow path length in the vicinity of the inner surface of the intake passage on the inner side of the curve is relatively large in the upstream portion of the curve, The flow path length in the vicinity of the inner surface of the passage can be increased to approach the flow path length in the vicinity of the inner surface of the intake passage on the outside of the curve, and the difference can be easily reduced. Accordingly, it is possible to easily provide a curved downstream portion capable of suppressing the separation of the intake air flow from the inner surface of the intake passage inside the curve.

  In the intake device according to the above aspect, preferably, at the downstream end of the curved downstream portion, the downstream portion first interval is the smallest and the downstream portion second interval is the largest. With this configuration, the flow velocity and the curve of the intake air flow in the vicinity of the inner surface of the intake passage on the outer side of the curve are reduced by narrowing the first downstream interval in the cross section at the downstream end to the narrowest (the most flat shape). Since the difference with the flow velocity of the intake flow in the vicinity of the inner surface of the intake passage can be minimized, it is possible to maintain a state in which the separation of the intake flow is reduced at the downstream end of the curved downstream portion.

  In this case, preferably, the intake passage further includes a curved small portion that is connected to the downstream end of the curved portion and has a degree of curvature smaller than that of the curved portion, and the curved portion decreases from the downstream end of the curved portion toward the downstream of the curved small portion. And the curved small portion first interval between the intake passage inner surfaces of the curved small portion corresponding to the downstream first interval is gradually increased so that the aspect ratio of the section of the curved portion gradually approaches 1 along the intake flow direction. The second small interval between the curved small portions between the intake passage inner surfaces of the small curved portions corresponding to the second downstream interval is gradually reduced. Here, at the downstream end of the curved downstream portion, since the cross section is the flattest shape, the circumferential length of the inner surface of the intake passage in the cross section of the flow path becomes a maximum value, so that wall friction occurs between the intake flow and the inner surface of the intake passage. A slight pressure loss is caused. However, the curved small portion connected to the downstream end of the curved downstream portion as in the above configuration has a curved small portion first between the intake passage inner surfaces so that the aspect ratio of the cross section gradually approaches 1 along the intake flow direction. By gradually increasing the interval and gradually decreasing the second small curve portion, the flattened cross-sectional shape at the downstream end of the curved downstream portion is not gradually flattened (the aspect ratio is along the intake flow direction). The state can be gradually returned to 1). As a result, the pressure loss due to the wall friction between the intake air flow and the inner surface of the intake passage that occurs as the circumference increases at the downstream end of the curved downstream portion can be immediately eliminated. As a result, the curved downstream portion and the curved small portion can achieve both a reduction in separation of the intake flow and a reduction in wall friction, thereby minimizing the pressure loss in the intake passage including the curved portion. it can.

  The small curved portion in the present invention is a downstream section in which the radius of curvature of the passage outer surface and the inner surface of the intake passage is larger than the curved portion (curved upstream portion and curved downstream portion) and is connected to the downstream end of the curved downstream portion. Means that. That is, the small curved portion is a wide concept including a case where the radius of curvature is close to infinity and extends substantially linearly, in addition to a case where a predetermined radius of curvature is larger than that of the curved portion.

  In the intake device according to the above aspect, preferably, the curved downstream portion of the intake passage has a downstream portion second interval larger than the downstream portion first interval and has four corners in a cross section orthogonal to the direction in which the intake passage extends. It has a rectangular shape provided with an arc-shaped portion, or an elliptical cross-sectional shape. If comprised in this way, in the cross section in which the arc-shaped part was provided in four corners, compared with the cross section in which the arc-shaped part was not provided in four corners, the perimeter of the intake passage inner surface (area of the intake passage inner surface) The arc resistance at the four corners can reduce the flow resistance at the four corners. Accordingly, the wall friction between the intake flow and the inner surface of the intake passage can be further reduced, so that the pressure loss in the curved portion can be further reduced.

  In this case, it is preferable that the curved downstream portion of the intake passage has two arc-shaped portions that are in contact with the inner surface of the intake passage on the inner side of the curve in the cross section orthogonal to the extending direction of the intake passage. It has a smaller radius than the arcuate part. If comprised in this way, the flow-path cross-sectional shape which decreases a downstream part 1st space | interval and increases a downstream part 2nd space | interval can be easily formed in a curved downstream part. In other words, the inner surface of the intake passage inside the curve in the downstream portion of the curve can be easily brought closer to the inner surface of the intake passage outside the curve.

  In the intake device according to the one aspect described above, preferably, the inner surface of the intake passage outside the curved portion in the curved downstream portion has the same radius of curvature as the inner surface of the intake passage outside the curved portion in the curved upstream portion. With this configuration, the flow line (flow state) of the intake flow near the inner surface of the intake passage outside the curve in the upstream portion of the curve can be maintained also near the inner surface of the intake passage outside the curve of the downstream portion of the curve. In this state, the inner surface of the intake passage inside the curve in the downstream portion of the curve can be gradually brought closer to the inner surface of the intake passage outside the curve, so that the intake flow is separated in the vicinity of the inner surface of the intake passage inside the curve. Can be suppressed.

  In the present application, the following configuration is also conceivable in the intake device according to the above aspect.

(Additional item 1)
That is, in the intake device according to the above aspect, the aspect ratio of the cross section of the curved small portion gradually approaches 1 along the intake flow direction from the downstream end of the curved portion toward the downstream of the curved small portion, and the intake air The curved small portion first interval gradually increases and the curved small portion second interval gradually decreases so that the cross-sectional area becomes constant along the flow direction.

(Appendix 2)
In the intake device according to the above aspect, the curved upstream portion and the curved downstream portion have the same cross-sectional area.

(Additional Item 3)
In the intake device according to the one aspect, a boundary between the curved upstream portion and the curved downstream portion is provided in the vicinity of the intermediate portion along the intake flow direction of the curved portion.

  According to the present invention, as described above, it is possible to provide an intake device capable of effectively reducing pressure loss in the curved portion of the intake passage by suppressing separation of the intake flow.

1 is a plan view showing a configuration of an intake device according to an embodiment of the present invention. It is sectional drawing which showed the structure of the intake port part in the intake device by one Embodiment of this invention. It is sectional drawing of the intake port part (intake pipe) along the 110-110 line | wire and 120-120 line | wire of FIG. It is sectional drawing of the intake port part (intake pipe) along the 130-130 line | wire of FIG. It is sectional drawing of the intake port part (intake pipe) along the 140-140 line | wire of FIG. It is sectional drawing of the intake port part (intake pipe) along the 150-150 line | wire of FIG. It is sectional drawing which showed the structure of the intake port part by the 1st modification of the intake device by one Embodiment of this invention. It is sectional drawing which showed the structure of the intake port part by the 2nd modification of the intake device by one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  With reference to FIGS. 1-6, the structure of the intake device 100 by one Embodiment of this invention is demonstrated. In the following description, it is assumed that each cylinder is arranged along the X axis when the internal combustion engine 90 is used as a reference.

  As shown in FIG. 1, an intake apparatus 100 according to an embodiment of the present invention is an apparatus that supplies air to an internal combustion engine 90 that is a multi-cylinder (in-line four-cylinder) engine. The intake device 100 constitutes a part of the intake system of the internal combustion engine 90, and the intake device 100 includes a surge tank 10 and an intake port portion 20 arranged downstream of the surge tank 10. . The surge tank 10 and the intake port portion 20 are both made of resin (polyamide resin), an upper piece in which the upper half of the surge tank 10 and the upper half of the intake port portion 20 are integrally formed, the lower half of the surge tank 10 and the intake air. A lower piece integrally formed with the lower half of the port portion 20 is joined and integrated by vibration welding.

  In addition, the intake port portion 20 has a role of distributing intake air stored in the surge tank 10 to each cylinder in the cylinder head 91. Note that the arrow A direction side in the intake port portion 20 is the intake upstream side connected to the surge tank 10, and the arrow B direction side is the intake downstream side connected to the internal combustion engine 90 (cylinder head 91).

  As shown in FIGS. 1 and 2, the intake port section 20 includes a plurality of (four) intake pipes 1 having a predetermined radius of curvature along the path, and downstream of each intake pipe 1. And a flange portion 7 formed integrally with the end portion. In FIG. 1, each intake pipe 1 is bent from the front side of the drawing to the back of the drawing along the intake flow direction (arrow B direction). In FIG. 2, the thickness of the pipe wall 1c (see FIG. 3) forming the pipe shape of the intake pipe 1 is omitted for convenience. In FIG. 2, the shapes of the passage outer surface 1a and the passage inner surface 1b of the intake pipe 1 are mainly illustrated. The intake pipe 1 is an example of the “intake passage” in the present invention.

  When the intake port portion 20 is viewed along the direction of the arrow X1, as shown in FIG. 2, each intake pipe 1 has an upstream pipe portion 2 and a curved portion 3 along the intake flow direction (arrow B direction). And the return piping part 6 is connected in this order. The upstream piping part 2 is connected to a surge tank 10 (see FIG. 1), and the return piping part 6 has a downstream end 6z connected to a cylinder head 91 via a flange part 7. The return pipe portion 6 is an example of the “curved small portion” in the present invention.

  The intake pipe 1 has a passage outer surface 1a and a passage inner surface 1b in the pipe wall portion 1c (see FIG. 3). In the upstream piping portion 2, the passage outer surface 1a and the passage inner surface 1b are not curved, and the upstream piping portion 2 extends linearly. In the bending portion 3, the passage outer surface 1a and the passage inner surface 1b are both bent in the same direction (counterclockwise direction in FIG. 2). In the return pipe portion 6, a part of the passage outer surface 1 a and a portion of the passage inner surface 1 b are both curved, but the degree thereof is much gentler than that of the curved portion 3 and extends approximately linearly to the flange portion 7. . As described above, in the intake port portion 20, the intake air stored in the surge tank 10 (see FIG. 1) is an intake air having the upstream piping portion 2, the curved portion 3 bent in the middle, and the return piping portion 6. It flows through the pipe 1 and is supplied to the cylinder head 91. In addition, the thickness of the pipe wall part 1c is substantially constant over the whole area to the upstream piping part 2, the bending part 3, and the return piping part 6. FIG.

  Here, in the present embodiment, the bending portion 3 includes a bending upstream portion 4 that is an upstream portion of the bending portion 3 and a bending downstream portion 5 that is a downstream portion of the bending portion 3. The curved upstream portion 4 is bent counterclockwise by about 60 degrees along the intake flow direction, and the curved downstream portion 5 following the curved upstream portion 4 is also bent counterclockwise by about 60 degrees. . Further, the curved upstream portion 4 has a cross-sectional shape such as a cross-section C1 shown in FIG. 3, whereas the curved downstream portion 5 has a cross-sectional shape such as a cross-section C2 shown in FIGS. That is, the cross section C1 of the curved upstream portion 4 and the cross section C2 of the curved downstream portion 5 are different from each other. Hereinafter, the cross-sectional shape corresponding to each section in the bending portion 3 will be described in detail.

  First, as shown in FIG. 2, the curved upstream portion 4 has a curved outside intake passage inner surface 4a curved with a curvature radius R1a and a curved inner side curved with a curvature radius R1b smaller than the curvature radius R1a. And an intake passage inner surface 4b. The intake passage inner surfaces 4a and 4b include portions that face each other in the bending radial direction (arrow R direction) and extend substantially parallel to the X axis. The intake passage inner surface 4a is bent at a constant radius of curvature R1a along the intake flow direction (arrow B direction), and the intake passage inner surface 4b is bent at a constant curvature radius R1b along the intake flow direction. Yes. Therefore, as shown in FIG. 3, the curved upstream portion 4 has a cross-sectional shape including a cross-section C1 at any position in the intake air flow direction. That is, the intake passage inner surfaces 4a and 4b are opposed to each other in the bending radial direction (arrow R direction) with a constant interval H1. The interval H1 is an example of the “upstream first interval” in the present invention. The intake passage inner surface 4a is an example of the “curved outer intake passage inner surface” in the present invention, and the intake passage inner surface 4b is an example of the “curved inner intake passage inner surface” in the present invention.

  Further, as shown in FIG. 3, the curved upstream portion 4 further includes intake passage inner surfaces 4 c and 4 d that face each other in the X-axis direction orthogonal to the opposing direction (arrow R direction) of the intake passage inner surfaces 4 a and 4 b. The intake passage inner surfaces 4c and 4d include portions that face each other in the X-axis direction and extend substantially in parallel along the arrow R direction. Further, the intake passage inner surfaces 4c and 4d are opposed to each other with a constant interval W1. Accordingly, in the curved upstream portion 4, the cross section C <b> 1 is relative to each of the center line 31 in the X-axis direction (indicated by the alternate long and short dash line) and the center line 32 in the radial direction of bending (in the direction of arrow R) (indicated by the alternate long and short dashed line). It has a line-symmetric shape. Further, since the curvature radii R1a and R1b are respectively constant in the curved upstream portion 4, the flow path length in the vicinity of the intake passage inner surface 4a on the outer side of the curve along the intake flow direction and the vicinity of the intake passage inner surface 4b on the inner side of the curve The channel length has a channel length difference corresponding to the difference between the curvature radii R1a and R1b. Further, the flow path length difference can cause a slight difference (flow velocity difference) between the flow velocity of the intake air flow in the vicinity of the intake passage inner surface 4a and the flow velocity in the vicinity of the intake passage inner surface 4b.

  Next, as shown in FIG. 2, the curved downstream portion 5 is curved with a curvature radius R2a and a curved outer intake passage inner surface 5a that curves and a curvature radius R2b that is smaller than the curvature radius R2a. And an inner intake passage inner surface 5b. The intake passage inner surfaces 5a and 5b include portions that face each other in the bending radial direction (arrow R direction) and extend substantially parallel to the X axis. The intake passage inner surface 5a is bent at a constant radius of curvature R2a along the intake flow direction (arrow B direction), and the intake passage inner surface 5b is bent at a curvature radius R2b that changes along the intake flow direction. It has been. Therefore, the curved downstream portion 5 partially has a cross section C2 as shown in FIG. 4, and the intake passage inner surfaces 5a and 5b are opposed to each other in the bending radial direction (arrow R direction) with the interval H2. doing. The interval H2 is an example of the “downstream first interval” in the present invention.

  Further, the curved downstream portion 5 further includes intake passage inner surfaces 5c and 5d that face each other in the X-axis direction orthogonal to the facing direction (arrow R direction) of the intake passage inner surfaces 5a and 5b. The intake passage inner surfaces 5c and 5d include portions that face each other in the X-axis direction and extend substantially in parallel along the arrow R direction. Further, the intake passage inner surfaces 5c and 5d are opposed to each other with a gap W2. The interval W2 is an example of the “second downstream portion interval” in the present invention. The intake passage inner surface 5a is an example of the “curved outer intake passage inner surface” in the present invention, and the intake passage inner surface 5b is an example of the “curved inner intake passage inner surface” in the present invention. The intake passage inner surfaces 5c and 5d are examples of the “inner-pass opposed inner surfaces” of the present invention.

  Here, in the present embodiment, the curved upstream portion 4 has a cross section C1 (see FIG. 3) at any position in the intake flow direction, whereas the curved downstream portion 5 has a cross section corresponding to the position in the intake flow direction. C2 (see FIGS. 4 and 5) is configured to change. That is, as is clear from a comparison between the cross section C1 (see FIG. 3) of the curved upstream portion 4 and the cross section C2 (see FIG. 4 or 5) of the curved downstream portion 5, the curved downstream portion 5 The intake passage inner surface 5a is bent with a constant radius of curvature R2a along the intake flow direction (arrow B direction), while the curved inner intake passage inner surface 5b gradually increases the curvature radius R2b along the intake flow direction. It is bent so that That is, the cross section C2 in FIG. 4 and the cross section C2 in FIG. 5 have different shapes. Here, the curvature radius R1a of the intake passage inner surface 4a of the curved upstream portion 4 and the curvature radius R2a of the intake passage inner surface 5a of the curved downstream portion 5 are equal (curvature radius R1a = curvature radius R2a). Is structured.

  Therefore, in the cross section C2 orthogonal to the direction (intake flow direction) in which the intake pipe 1 extends in the curved downstream portion 5, the distance H2 between the curved intake outer surface 5a and the curved intake passage inner surface 5b (see FIG. 4 and FIG. 4). The dimension in the direction of arrow R in FIG. 5 is gradually reduced from the state of FIG. 4 to the state of FIG. 5 along the intake flow direction (arrow B direction) of the curved downstream portion 5 and has this interval H2. The distance W2 (the dimension in the X-axis direction in FIGS. 4 and 5) between the intake passage inner surfaces 5c and 5d opposed perpendicular to the opposite intake passage inner surfaces 5a and 5b is along the intake flow direction (arrow B direction). It is gradually increased from the state of FIG. 4 to the state of FIG. That is, the intake passage inner surface 5b inside the curve gradually rises to the intake passage inner surface 5a outside the curve along the intake flow direction. This also gradually reduces the difference between the curvature radius R2b and the curvature radius R2a along the intake flow direction in the curved downstream portion 5, so that the flow path length and the curved inner side in the vicinity of the intake passage inner surface 5a outside the curve are reduced. The flow path length difference from the flow path length in the vicinity of the intake passage inner surface 5b is also reduced. The reduction in the flow path length difference has the effect of reducing the difference (flow velocity difference) between the flow velocity in the vicinity of the intake passage inner surface 5a and the flow velocity in the vicinity of the intake passage inner surface 5b.

  In this embodiment, the section C2 of the curved downstream portion 5 is changed from the state shown in FIG. 4 to the state shown in FIG. 5 (the interval H2 is gradually decreased and the interval W2 is gradually increased). The area of the section C2 of the part 5 (hereinafter referred to as a sectional area S) is configured to be constant along the intake flow direction (arrow B direction). In this case, in the curved downstream portion 5, with the sectional area S and the curvature radius R2a relating to the intake passage inner surface 5a outside the curve being kept constant, the curvature radius R2b relating to the intake passage inner surface 5b inside the curve is set along the intake flow direction. Only the shape of the cross section C2 is changed so as to increase gradually.

  This cross-sectional shape change will be described in comparison with the curved upstream portion 4. That is, as shown in FIG. 2, the curvature radius R2b of the intake passage inner surface 5b of the curved downstream portion 5 is larger than the curvature radius R1b of the intake passage inner surface 4b of the curved upstream portion 4 (R2b> R1b). Thus, unlike the curved upstream portion 4, the curved downstream portion 5 increases the radius of curvature R2b to bring the intake passage inner surface 5b closer to the intake passage inner surface 5a. Then, as is clear from comparison between FIG. 3 in which the cross section C1 of the curved upstream portion 4 is shown and FIG. 4 or FIG. 5 in which the cross section C2 of the curved downstream portion 5 is shown, the curved downstream portion 5 In the cross section C2 orthogonal to the direction in which the pipe 1 extends, the interval H2 (see FIGS. 4 and 5) is larger than the interval H1 (see FIG. 3) between the intake passage inner surface 4a and the intake passage inner surface 4b in the curved upstream portion 4. Is also small (interval H2 <interval H1).

  Further, as shown in FIG. 5, in the vicinity of the downstream end 5z of the curved downstream portion 5, the gradually decreased interval H2 (arrow R direction) becomes the smallest and the gradually increased interval W2 (X (Axis direction) is the largest. That is, the curved downstream portion 5 is configured to have a flat shape in which the shape of the cross section C2 is extended most in the X-axis direction in the vicinity of the downstream end 5z. The sectional area S of the section C2 in the curved downstream portion 5 is equal to the sectional area S of the section C1 (see FIG. 3) in the curved upstream section 4. Further, the cross-sectional area S of the cross-section C1 in the curved upstream portion 4 is equal to the cross-sectional area S of the upstream piping portion 2. Therefore, in the section from the upstream piping part 2 to the curved downstream part 5, the intake air flow is circulated while keeping the cross-sectional area S constant without causing any enlargement or reduction of the flow path cross section.

  When the center line 31 (see FIG. 3) in the X-axis direction in the curved upstream portion 4 (see FIG. 3) having no cross-sectional shape change is directly extended to the cross section C2 at the curved downstream portion 5, FIGS. In the curved downstream portion 5, the distance H2b from the center line 31 to the intake passage inner surface 5b inside the curve is larger than the distance H2a from the center line 31 (illustrated as a virtual line) to the intake passage inner surface 5a outside the curve. Is also small. Here, the distance H2a is half of the interval H1 in the cross section C1 (see FIG. 3). Therefore, in the cross section C2, the distance H2a from the center line 31 (imaginary line) to the intake passage inner surface 5a is kept constant (curvature radius R1a = curvature radius R2a), and from the center line 31 to the intake passage inner surface 5b. The distance H2b is gradually decreased along the intake flow direction (arrow B direction), and the intake passage inner surface 5b is gradually approached toward the intake passage inner surface 5a.

  Thus, in the intake pipe 1, the intake air flow (air) flowing through the upstream pipe portion 2 is bent counterclockwise by a predetermined angle (about 60 degrees) in the curved upstream portion 4, and then the curved downstream portion 5 Passes while being bent counterclockwise by a predetermined angle (about 60 degrees). Note that when passing through the curved upstream portion 4, a difference in flow velocity may occur between the outside and inside of the curve. On the other hand, when passing through the curved downstream portion 5, a part of the intake flow flows along the intake passage inner surface 5b inside the curve where the curvature radius R2b is gradually increased along the intake flow direction. Thus, as described above, the difference between the flow velocity of the intake flow near the intake passage inner surface 5a on the curved outer side and the flow velocity of the intake flow near the intake passage inner surface 5b on the curved inner side is reduced (reduced). That is, the flow in the vicinity of the intake passage inner surface 5b is not disturbed. In addition, the intake air flow is circulated to the downstream return pipe portion 6 without being disturbed in the curved downstream portion 5.

  Further, in the present embodiment, as shown in FIGS. 4 and 5, the curved downstream portion 5 of the intake pipe 1 has a larger interval W2 than the interval H2 in a cross section C2 orthogonal to the direction in which the intake pipe 1 extends. The cross section C2 has an oval cross section in which arc-shaped portions 5e to 5h are provided at four corners. Here, the arc-shaped portion 5e is a portion connecting the intake passage inner surfaces 5a and 5c, and the arc-shaped portion 5f is a portion connecting the intake passage inner surfaces 5a and 5d. The arc-shaped portion 5g is a portion connecting the intake passage inner surfaces 5b and 5c, and the arc-shaped portion 5h is a portion connecting the intake passage inner surfaces 5b and 5d. Further, in both the cross section C2 shown in FIG. 4 and the cross section C2 shown in FIG. 5, the curvature radii Rb of the two arc-shaped portions 5g and 5h contacting the intake passage inner surface 5b are the curved outer intake passage inner surfaces 5a. Is smaller than the radius of curvature Ra of the two arcuate portions 5e and 5f that are in contact with each other (curvature radius Rb <curvature radius Ra). Further, the flow path resistance at the four corners is further reduced by the arc-shaped portions 5e to 5h at the four corners.

  In this way, in the curved downstream portion 5, the flow path length difference between the flow path length (flow velocity) near the intake passage inner surface 5a outside the curve and the flow path length near the intake passage inner surface 5b inside the curve is reduced, In addition, the difference between the flow velocity of the intake flow near the intake passage inner surface 5a and the flow velocity of the intake flow near the intake passage inner surface 5b is also reduced. Accordingly, the intake flow in the vicinity of the intake passage inner surface 5b flows to the downstream end 5z along the shape of the intake passage inner surface 5b without being separated from the intake passage inner surface 5b. Further, since the separation phenomenon of the intake flow does not occur, the generation of separation vortices in the back (wake region) is suppressed, and no significant pressure loss occurs in the curved downstream portion 5.

  As shown in FIG. 2, the return pipe portion 6 includes an intake passage inner surface 6 a extending substantially linearly along the intake flow direction (arrow B direction) and an inner surface having a predetermined radius of curvature. An intake passage inner surface 6b extending in the intake flow direction. Accordingly, the return pipe portion 6 has a cross section C3 as shown in FIG. 6 at the downstream end 6z, and the intake passage inner surfaces 6a and 6b face each other in the direction of the arrow R with a distance H3. . The intake passage inner surfaces 6a and 6b include portions that face each other in the direction of the arrow R and extend substantially parallel to the X axis. The return pipe portion 6 further includes intake passage inner surfaces 6c and 6d that are opposed to each other with an interval W3 in the X-axis direction orthogonal to the facing direction (arrow R direction) of the intake passage inner surfaces 6a and 6b. The intake passage inner surfaces 6c and 6d include portions that face each other in the X-axis direction and extend substantially in parallel along the arrow R direction. The interval H3 is an example of the “curved small portion first interval” in the present invention. The interval W3 is an example of the “curved small portion second interval” in the present invention. The intake passage inner surfaces 6a and 6b are examples of the “intake passage inner surface of a small curved portion corresponding to the first downstream interval” in the present invention. Further, the intake passage inner surfaces 6c and 6d are examples of the “intake passage inner surface of a small curved portion corresponding to the second downstream portion interval” of the present invention.

  In the present embodiment, the aspect ratio (interval H3 and interval H3) of the cross section C3 of the return pipe section 6 along the arrow B direction from the downstream end 5z of the curved section 3 (curved downstream section 5) to the downstream of the return pipe section 6. The interval H3 between the intake passage inner surfaces 6a and 6b of the return pipe portion 6 corresponding to the interval H2 (see FIG. 5) is gradually increased so that the ratio to the interval W3 gradually approaches 1 along the intake flow direction. While being changed, the interval W3 between the intake passage inner surfaces 6c and 6d of the return pipe portion 6 corresponding to the interval W2 (see FIG. 5) is gradually changed to be small. Note that, in the cross section C3 shown in FIG. 6, the aspect ratio is closest to 1 in the entire section of the return pipe section 6. That is, the cross-sectional shape of the return pipe portion 6 is a flat shape until the cross-section C3 (see FIG. 6) at the downstream end 6z starts from the cross-section C2 (see FIG. 5) at the downstream end 5z of the curved downstream portion 5. Is gradually returned to a non-flat state (a state in which the aspect ratio is gradually brought close to 1 along the intake flow direction).

  Thereby, in the intake pipe 1, the intake pipe (air) flowing through the curved portion 3 (curved downstream portion 5) without causing separation is a return pipe portion in which the cross-sectional shape is gradually changed from the cross-section C2 to the cross-section C3. 6 is finally sent to the cylinder head 91 while passing 6 toward the downstream end 6z. In the vicinity of the downstream end 5z, the cross-section C3 is flattened, so that the circumferential length of the intake passage inner surface (the total length of the intake passage inner surface 5a and the intake passage inner surface 5b) reaches a maximum value. For this reason, a slight pressure loss due to wall friction occurs between the intake air flow and the intake passage inner surface (the intake passage inner surface 5a and the intake passage inner surface 5b). However, the return pipe portion 6 connected to the downstream end 5z is appropriately used to gradually return the cross-sectional shape of the flattened cross section C2 to a non-flat state. As a result, the pressure loss due to the wall friction between the intake air flow and the intake passage inner surface (the intake passage inner surface 5a and the intake passage inner surface 5b) generated at the downstream end 5z of the curved downstream portion 5 as the circumference is maximized. Will be resolved immediately.

  Further, as shown in FIG. 2, the upstream piping portion 2 has an intake passage inner surface 2 a (passage inner surface 1 b in the upstream piping portion 2) extending linearly along the intake flow direction (arrow B direction). That is, the upstream piping portion 2 has the same cross-sectional shape as the cross-section C1 (see FIG. 3) at the position where the curved upstream portion 4 is started, and extends to the surge tank 10 without having a bent portion. Further, the intake port portion 20 has a flange portion 7 connected to a cylinder head 91 via a gasket member 92.

  Further, as shown in FIG. 1, each intake pipe 1 constituting the intake port portion 20 is connected in parallel to the surge tank 10. Further, in intake device 100, intake air that reaches via an air cleaner and a throttle (not shown) as an intake passage flows into surge tank 10. The intake device 100 in the present embodiment is configured as described above.

  In the present embodiment, the following effects can be obtained.

  That is, in the present embodiment, as described above, in the cross-section C2 (see FIGS. 4 and 5) orthogonal to the direction in which the intake pipe 1 extends in the curved downstream portion 5, the intake passage inner surface 5a outside the curved portion in the curved downstream portion 5. And the intake passage inner surface 5b on the curved inner side are gradually reduced along the intake flow direction (arrow B direction) and perpendicular to the opposed intake passage inner surfaces 5a and 5b with the interval H2. The interval W2 between the opposing intake passage inner surfaces 5c and 5d is gradually increased along the intake flow direction (arrow B direction). The curved portion 3 of the intake pipe 1 is configured so that the cross-sectional area S of the cross-section C2 of the curved downstream portion 5 is constant along the intake flow direction. Accordingly, in the curved downstream portion 5 where the separation of the intake flow is likely to occur, the distance H2 between the intake passage inner surfaces 5a and 5b is reduced, so that the flow path length in the vicinity of the intake passage inner surface 5a and the vicinity of the intake passage inner surface 5b are reduced. Therefore, the separation of the intake flow from the curved inner surface of the intake passage 5b is suppressed. Further, by gradually changing the interval H2 between the intake passage inner surfaces 5a and 5b of the curved downstream portion 5 without rapidly changing, the flow path length in the vicinity of the intake passage inner surface 5a and the flow in the vicinity of the intake passage inner surface 5b are changed. Since the difference from the path length can be gradually decreased without rapidly decreasing, it is possible to more effectively suppress the intake air flow from separating from the intake passage inner surface 5b on the curved inner side. As a result, the pressure loss in the curved portion 3 of the intake pipe 1 can be effectively reduced. Further, even when the shape of the cross section C2 is changed so as to reduce the interval H2 between the intake passage inner surfaces 5a and 5b, the interval H2 is narrowed by keeping the cross sectional area S constant by increasing the interval W2. It is possible to effectively suppress an increase in the pressure loss of the intake air flow in the curved downstream portion 5 formed. Also by this, the pressure loss in the curved portion 3 of the intake pipe 1 can be effectively reduced.

  In the present embodiment, the curvature radius R2b of the intake passage inner surface 5b inside the curve of the curved downstream portion 5 is larger than the curvature radius R1b of the intake passage inner surface 4b inside the curve of the curved upstream portion 4 (curvature radius R2b> curvature). Radius R1b). In the cross section C2 orthogonal to the direction in which the intake pipe 1 extends, the interval H2 is configured to be smaller than the interval H1 between the intake passage inner surface 4a and the intake passage inner surface 4b in the curved upstream portion 4. Accordingly, in the curved downstream portion 5 where the separation of the intake flow is likely to occur, the radius of curvature R2b of the intake passage inner surface 5b can be increased to easily approach the intake passage inner surface 5a. On the other hand, the interval H2 in the curved downstream portion 5 can be easily reduced. That is, from the state in which the difference between the flow path length in the vicinity of the intake passage inner surface 4a on the curved outer side and the flow path length in the vicinity of the intake passage inner surface 4b on the curved inner side in the curved upstream portion 4 is relatively large, It is possible to increase the flow path length in the vicinity of the curved inner intake passage inner surface 5b to approach the flow path length in the vicinity of the curved outer intake passage inner surface 5a and easily reduce the difference. Accordingly, the curved downstream portion 5 that can suppress the separation of the intake air flow from the intake passage inner surface 5b inside the curve can be easily provided.

  In the present embodiment, the curved downstream portion 5 is configured so that the interval H2 is the smallest and the interval W2 is the largest at the downstream end 5z of the curved downstream portion 5. As a result, in the curved downstream portion 5, the flow rate of the intake air flow in the vicinity of the intake passage inner surface 5a on the outer side of the curve and the intake air on the inner side of the curve are reduced by narrowing the interval H2 in the cross section C3 at the downstream end 5z. Since the difference with the flow velocity of the intake flow in the vicinity of the passage inner surface 5b can be minimized, the state where the separation of the intake flow is reduced at the downstream end 5z of the curved downstream portion 5 can be maintained.

  Further, in the present embodiment, the intake pipe 1 is provided with a return pipe portion 6 that is connected to the downstream end 5z of the bending portion 3 and has a bending degree smaller than that of the bending portion 3 (the bending upstream portion 5 and the bending downstream portion 5). Then, from the downstream end 5z of the curved portion 3 toward the downstream of the return pipe portion 6, the aspect ratio (ratio between the interval H3 and the interval W3) of the cross section C3 of the return pipe portion 6 is in the intake flow direction (arrow B direction). The interval H3 between the intake passage inner surfaces of the return pipe portion 6 corresponding to the interval H2 gradually increases so as to gradually approach 1 along the intake passage inner surfaces 6a and 6b of the return pipe portion 6 corresponding to the interval W2. The return pipe portion 6 is configured so that the interval W3 therebetween becomes gradually smaller. Here, in the vicinity of the downstream end 5z of the curved downstream portion 5, the cross section C3 is the flattest shape, so that the circumferential length of the intake passage inner surface in the flow passage section (the total length of the intake passage inner surface 5a and the intake passage inner surface 5b). Therefore, a slight pressure loss is caused between the intake air flow and the intake passage inner surfaces (intake passage inner surfaces 5a and 5b) due to wall friction. However, the return pipe portion 6 connected to the downstream end 5z of the curved downstream portion 5 has an interval H3 between the intake passage inner surfaces 6a and 6b so that the aspect ratio of the cross section C3 gradually approaches 1 along the intake flow direction. By gradually increasing and gradually decreasing the interval W3, the flattened cross section C2 at the downstream end 5z of the curved downstream portion 5 is not gradually flattened (the ratio between the interval H3 and the interval W3 is the direction of intake air flow) The state can be gradually returned to 1). As a result, the pressure loss due to the wall friction between the intake air flow and the intake passage inner surfaces (intake passage inner surfaces 5a and 5b) generated at the downstream end 5z of the curved downstream portion 5 due to the maximization of the circumference is immediately eliminated. can do. As a result, it is possible to achieve both the reduction of the separation of the intake flow and the reduction of the wall friction, so that the pressure loss of the intake pipe 1 including the curved portion 3 can be minimized.

  In the present embodiment, in the cross section C2 orthogonal to the direction in which the intake pipe 1 extends, the interval W2 is larger than the interval H2, and the oval cross-sectional shape is provided with the arc-shaped portions 5e to 5h at the four corners. The curved downstream portion 5 of the intake pipe 1 is configured to have Thereby, in the cross section in which the arc-shaped portions 5e to 5h are provided in the four corners, the intake passage inner surface 5a and the intake passage inner surface 5b are compared with the cross section in which the arc-shaped portions 5e to 5h are not provided in the four corners. The total length (peripheral length: area of the inner surface of the intake passage) can be further reduced, and the flow path resistance at the four corners can be reduced by the arcuate portions 5e to 5h at the four corners. Therefore, the wall friction between the intake air flow and the intake passage inner surface (the intake passage inner surface 5a and the intake passage inner surface 5b) can be further reduced, so that the pressure loss in the curved portion 3 can be further reduced.

  Further, in the present embodiment, in the cross section C2 orthogonal to the direction in which the intake pipe 1 extends, the curvature radii Rb of the two arcuate portions 5g and 5h that are in contact with the intake passage inner surface 5b on the curved inner side are the intake passage inner surface 5a on the curved outer side. The curved downstream portion 5 of the intake pipe 1 is configured so as to be smaller than the curvature radius Ra of the two arc-shaped portions 5e and 5f that are in contact with each other. Thereby, the flow path cross-sectional shape that decreases the interval H2 and increases the interval W2 can be easily formed in the curved downstream portion 5. That is, the intake passage inner surface 5b inside the curve in the curved downstream portion 5 can be easily brought closer to the intake passage inner surface 5a outside the curve.

  In the present embodiment, the curvature radius R2a of the intake passage inner surface 5a outside the curve of the curved downstream portion 5 and the curvature radius R1a of the intake passage inner surface 4a outside the curve of the curved upstream portion 4 are configured to be equal. Thereby, the flow line (flow state) of the intake flow in the vicinity of the intake passage inner surface 4 a in the curved upstream portion 4 can be maintained also in the vicinity of the intake passage inner surface 5 a of the curved downstream portion 5. In this state, the inner intake passage inner surface 5b in the curved downstream portion 5 can be gradually brought closer to the outer intake passage inner surface 5a in the curved outer portion. Can be prevented from peeling.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above-described embodiment, an example in which the intake pipe 1 is configured by connecting the upstream piping section 2 and the return piping section 6 extending linearly to the upstream side and the downstream side of the bending section 3 has been described. Is not limited to this. For example, the intake pipe 201 as an example of the “intake passage” of the present invention may be configured as in the first modification shown in FIG.

  Specifically, as shown in FIG. 7 (first modification), the intake pipe 201 is bent with a predetermined curvature radius and an upstream pipe section 202 bent with a predetermined curvature radius. The return pipe portion 206 is connected to the upstream side and the downstream side of the bending portion 3, respectively. Here, the curvature radii of the upstream piping part 202 and the return piping part 206 are larger than the curvature radii of the bending part 3. In particular, the curvature radius of the intake passage inner surface 206a outside the curved portion in the return pipe portion 206 is sufficiently larger than the curvature radius R2a of the intake passage inner surface 5a of the curved downstream portion 5. Further, the radius of curvature of the intake passage inner surface 206b on the curved inner side is sufficiently larger than the radius of curvature R2b of the intake passage inner surface 5b of the curved downstream portion 5. Also in this case, the return pipe portion 206 can be used to gradually return the flattened cross section C2 of the curved downstream portion 5 to a non-flat state. Pressure loss due to wall friction between the intake passage inner surfaces (intake passage inner surfaces 5a and 5b) can be easily eliminated. The return piping part 206 is an example of the “curved small part” in the present invention. The intake passage inner surfaces 206a and 206b are an example of the “inner surface of the intake passage having a small curved portion corresponding to the first interval at the downstream portion” in the present invention.

  Moreover, in the said embodiment, in the cross section C2 (refer FIG. 4 and FIG. 5), the space | interval W2 is larger than the space | interval H2, and the elliptical cross-sectional shape by which the arc-shaped part 5e-5h was provided in four corners is used. Although the example in which the curved downstream portion 5 is configured to have the above is shown, the present invention is not limited to this. For example, the curved downstream portion 205 as an example of the “curved downstream portion” of the present invention may be configured as in the second modified example shown in FIG.

  Specifically, as shown in FIG. 8 (second modification), the curved downstream portion 205 has a rectangular cross section C2a in which arc-shaped portions 205e to 205h are provided at four corners. That is, the cross section C2a has intake passage inner surfaces 205a to 205d that are made closer to a square shape (rectangular shape) as a whole compared to the cross section C2 (see FIGS. 4 and 5). Even with respect to the intake port portion 220 in which the curved portion 3 includes the curved downstream portion 205 having such a cross section C2a, the intake passage inner surface 205a and the intake passage inner surface 205a and the curved portion 3 are kept constant. The interval H2 of 205b may be gradually decreased along the intake flow direction, and the interval W2 between the intake passage inner surfaces 205c and 205d may be gradually increased along the intake flow direction. In the manufacturing process, there may be a case where the intake port portion 230 including a portion formed in a rectangular shape so as to have the cross section C2a is formed. Also in the cross section C2a, the flow path resistance at the four corners can be reduced by the arc-shaped portions 205e to 205h at the four corners. The intake passage inner surface 205a is an example of the “curved outer intake passage inner surface” in the present invention, and the intake passage inner surface 205b is an example of the “curved inner intake passage inner surface” in the present invention. In addition, the intake passage inner surfaces 205c and 205d are examples of the “inversely opposed intake passage inner surfaces” of the present invention.

  Moreover, in the said embodiment, the example which comprised the intake pipe 1 so that the thickness of the pipe wall part 1c was substantially constant over all the sections to the upstream piping part 2, the curved part 3, and the return piping part 6 was shown. However, the present invention is not limited to this. That is, the present invention can also be applied to the bending portion 3 configured such that the thickness of the tube wall portion 1c varies depending on the location. Regardless of the thickness of the pipe wall portion 1c, the interval H2 between the intake passage inner surfaces 5a and 5b is gradually reduced along the intake flow direction while keeping the cross-sectional area S at the curved downstream portion 5 constant, and the intake passage inner surface The interval W2 between 5c and 5d may be gradually increased along the intake flow direction.

  Moreover, in the said embodiment, the curvature radius R1a of the intake passage inner surface 4a outside the curve in the curved upstream portion 4 and the curvature radius R2a of the intake passage inner surface 5a outside the curve in the curved downstream portion 5 were shown to be equal. However, the present invention is not limited to this. That is, if the interval H2 is gradually decreased and the interval W2 is gradually increased while the cross-sectional area S is kept constant in the curved downstream portion 5, the curvature radius R2a of the intake passage inner surface 5a is set to the curvature radius of the intake passage inner surface 4a. The bending portion 3 may be configured differently from R1a.

  Moreover, in the said embodiment, in the cross section C2 (refer FIG. 4 and FIG. 5) of the curved downstream part 5, the curvature radius Rb of the two circular arc-shaped parts 5g and 5h which contact | connect the curved intake inner surface 5b is taken out of the curved outer intake. Although an example in which the two arcuate portions 5e and 5f that are in contact with the passage inner surface 5a are configured to be smaller than the curvature radius Ra has been described, the present invention is not limited thereto. That is, the curvature radius Rb of the arc-shaped portions 5g and 5h may be equal to the curvature radius Ra of the arc-shaped portions 5e and 5f.

  In the above embodiment and the first and second modifications of the above embodiment, the example in which the intake port portion 20 (230) is made of resin (polyamide resin) is shown, but the present invention is not limited to this. That is, the intake port portion 20 (230) including the intake pipe 1 (201) may be made of metal.

  In the above embodiment, an example in which the “intake device” of the present invention is applied to an in-line four-cylinder engine for automobiles is shown, but the present invention is not limited to this. The intake device of the present invention may be applied to an internal combustion engine other than an automobile engine. Further, the present invention may be applied to an in-line multi-cylinder engine other than an in-line four-cylinder engine, a V-type multi-cylinder engine, a horizontally opposed engine, and the like even for an automobile engine.

  In the above-described embodiment, the example in which the present invention is applied to the intake device 100 connected to the internal combustion engine 90 including a multi-cylinder engine has been described. However, the present invention is not limited to this. For example, the present invention may be applied to an intake device for a single cylinder engine. As the internal combustion engine 90, a gasoline engine, a diesel engine, a gas engine, or the like can be applied.

1,201 Intake pipe (intake passage)
DESCRIPTION OF SYMBOLS 1a Passage outer surface 1b Passage inner surface 1c Pipe wall part 2,202 Upstream piping part 3 Curved part 4 Curved upstream part 4a Intake passage inner surface (intake passage inner surface of the curve outer side)
4b Inner surface of intake passage (inner surface of intake passage inside curve)
5, 205 Curved downstream portion 5a, 205a Inner surface of intake passage (inner surface of intake passage outside curve)
5b, 205b Inner surface of intake passage (inner surface of intake passage inside curve)
5c, 5d, 205c, 205d Intake passage inner surface (intake passage inner surface facing orthogonally)
5e, 5f, 5g, 5h, 205e, 205f, 205g, 205h Arc-shaped part 6, 206 Return pipe part (curved small part)
6a, 6b, 206a, 206b Inner surface of intake passage (inner surface of intake passage of small curved portion corresponding to first interval of downstream portion)
6c, 6d Inner surface of intake passage (inner surface of intake passage of curved small portion corresponding to second interval in downstream portion)
7 Flange portion 10 Surge tank 20, 230 Intake port portion 90 Internal combustion engine 100 Intake device C1, C2, C2a, C3 Cross section H1 interval (upstream portion first interval)
H2 interval (downstream first interval)
H3 interval (curved small part first interval)
W1 interval W2 interval (downstream second interval)
W3 interval (curved small part second interval)

Claims (7)

An intake passage which is connected to the internal combustion engine and has a curved portion in which both the outer surface of the passage and the inner surface of the passage are curved;
The curved portion of the intake passage includes a curved upstream portion that is a portion on the upstream side of the curved portion, and a curved downstream portion that is a portion on the downstream side of the curved portion,
In a cross section perpendicular to the direction in which the intake passage extends in the curved downstream portion, a downstream first interval between the curved outer intake passage inner surface and the curved inner intake passage inner surface in the curved downstream portion is defined as the curved downstream portion. While gradually decreasing along the intake flow direction, the downstream second interval between the intake passage inner surfaces facing each other perpendicularly to the opposed intake passage inner surface with the downstream first interval is arranged along the intake flow direction. An air intake apparatus configured such that the cross-sectional area of the curved downstream portion becomes constant along the direction of intake air flow by gradually increasing the size. The inner surface of the intake passage inside the curved downstream portion has a larger radius of curvature than the inner surface of the intake passage inside the curved upstream portion.
In the cross section orthogonal to the direction in which the intake passage extends, the first downstream interval is smaller than the first upstream interval between the inner surface of the intake passage outside the curve and the inner surface of the intake passage inside the curve. The air intake device according to claim 1.   3. The intake device according to claim 1, wherein at the downstream end of the curved downstream portion, the downstream portion first interval is the smallest and the downstream portion second interval is the largest. The intake passage further includes a small curved portion connected to a downstream end of the curved portion and having a curved degree smaller than that of the curved portion,
Corresponds to the downstream first interval so that the aspect ratio of the cross section of the curved small portion gradually approaches 1 along the intake flow direction from the downstream end of the curved portion toward the downstream of the curved small portion. The curved small portion first interval between the intake passage inner surfaces of the curved small portion gradually increases, and the curved small portion second interval between the intake passage inner surfaces of the curved small portion corresponding to the downstream second interval is The intake device according to claim 3, which is gradually reduced.   The curved downstream portion of the intake passage has a cross section perpendicular to the direction in which the intake passage extends, the downstream portion second interval being larger than the downstream portion first interval, and arc-shaped portions at four corners. The intake device according to any one of claims 1 to 4, wherein the intake device has a rectangular shape or an elliptical cross-sectional shape.   In the cross section orthogonal to the direction in which the intake passage extends, the curved downstream portion of the intake passage has two arc-shaped portions in contact with the inner surface of the intake passage on the inner side of the curve. The intake device according to claim 5, wherein the intake device has a smaller radius than the arcuate portion.   The intake device according to any one of claims 1 to 6, wherein an inner surface of the intake passage on the outer side of the curved downstream portion has the same radius of curvature as an inner surface of the intake passage on the outer side of the curved portion.

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