GB2383378A

GB2383378A - Air intake device having a throttle valve bypass passage with a slanted outlet surface

Info

Publication number: GB2383378A
Application number: GB0224850A
Authority: GB
Inventors: Masao Ino; Yasuhiro Suzuki
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2001-11-26
Filing date: 2002-10-24
Publication date: 2003-06-25
Anticipated expiration: 2022-10-24
Also published as: GB2383378B; JP2003161235A; GB0224850D0

Abstract

A main passage (18) for supplying intake air to an internal combustion engine in a controlled manner and a bypass passage (20) bypassing the main passage for supplying air to the engine at its idling state are formed in an air-intake device (10). A slanted surface (60) along which a bypass air flows is formed at the downstream end of the bypass passage (20), so that a bypass air-stream (B) smoothly joins a main air-stream (M) with a small joining angle ( C ) without generating noises. The downstream end of the bypass passage may be enlarged to reduce a speed of the bypass air-stream and to thereby further reduce noises.

Description

AIR-INTAKE DEVICE HAVING MAIN AND BYPASS PASSAGES FOR INTERNAL COMBUSTION ENGINE This application is based upon and claims benefit of priority of Japanese Patent Application No. 2001-358944 filed on November 26, 2001, the content of which is incorporated herein by reference.

The present invention relates to an air-intake device of an internal combustion engine.

An air-intake device of an internal combustion engine that includes a main passage and a bypass passage is known hitherto. An amount of air flowing through the main passage is controlled by a throttle valve, and intake air required for an idling operation of the engine is supplied through the bypass passage while substantially closing the main passage. An air-adjusting screw for adjusting an amount of air flowing through the bypass passage is disposed in the bypass passage to operate the engine at a desired idling speed.

In the air-intake device of this kind, an airstream flowing through the bypass passage joins an airsteam flowing through a clearance between a throttle valve

and a throttle body in the main passage at a downstream end of the bypass passage. Since, in a conventional air-intake device, the bypass passage is formed to join the main passage with a substantially right angle, the bypass air- stream perpendicularly hits the main air-stream when both air-streams join at the downstream end. Therefore, a high level of noise having a frequency in a wide range of 2-20 kHz is generated at the joining portion. The noise having this frequency range is transmitted through a wall of an intake manifold. Especially, the noise is easily transmitted through the wall without being attenuated if the intake manifold is made of a resin material, causing a noise problem in an automotive vehicle.

The present invention has been made in view of the above-mentioned problem, and an object of preferred embodiments of the present invention is to provide an improved air-intake device of an internal combustion engine, in which the noise generated by the intake air-streams is reduced.

The air-intake device according to the present invention includes a main passage and a bypass passage bypassing the main passage. A throttle valve for controlling an amount of air flowing through the main passage is disposed in the main passage. When an internal combustion engine is at an idling state, the main passage is substantially closed by the throttle valve, and air

necessary for idling operation of the engine is supplied through the bypass passage. A bypass air-stream formed in the bypass passage joins a main air-stream flowing through the main passage at a downstream end of the bypass passage.

A slanted surface along which the bypass air-stream flows is formed at a vicinity of the downstream end of the bypass passage, so that the bypass air-stream smoothly joins the main air-stream with a small joining angle.

Since the bypass air-stream smoothly joins the main airstream without hitting the main air-stream, noises generated at the joining portion are reduced or suppressed.

The bypass passage may be enlarged at its downstream end to reduce a speed of the bypass air-stream joining the main air-stream. The noises at the joining portion are further reduced in this manner. An airadjusting screw for controlling an amount of air flowing through the bypass passage may be disposed in the bypass passage to obtain a desired idling speed of the engine by adjusting the screw. The air-intake device may be structured by connecting in tandem a throttle body in which the throttle valve is disposed and an intake manifold. In this case, the slanted surface is easily formed on an upstream end wall of the intake manifold.

According to the present invention, the bypass airstream smoothly joins the main air-stream at the downstream end of the bypass passage. Therefore, noises otherwise

caused by collision of the bypass air-stream with the main air-stream are suppressed.

Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings, in which :- FIG. 1 is a cross-sectional view showing an airintake device according to the present invention ; FIG. 2 is a cross-sectional view showing the same air-intake device as shown in FIG. 1, in which a main airstream and a bypass air-stream are shown; and FIG. 3 is a graph showing noise levels transmitted through an intake manifold, a noise level of the device according to the present invention being compared with that of a comparative example.

A preferred embodiment of the present invention will be described with reference to accompanying drawings.

First, referring to FIG. 1, a structure of an air-intake device 10 according to the present invention will be described. The air-intake device 10 is composed of a throttle body 12, a throttle valve 14 disposed in the throttle body 12, and an intake manifold 16 connected to the throttle body 12. A main passage 18 through which a

main stream of intake air flows is formed in the throttle body 12 and the intake manifold 16. A bypass passage 20 bypassing the throttle valve 14 is also formed therein.

The throttle body 12 made of a metallic material forms therein an upstream portion 18a of the main passage 18, and the intake manifold 16 forms therein a downstream portion 18b of the main passage 18. An upstream end of the throttle body 12 is connected to an outlet port of an air cleaner (not shown). The throttle valve 14 is disposed in the upstream portion 18a of the main passage 18. The throttle valve 14 is fixed to a valve axis 26 which is rotatably supported in the throttle body 12. An amount of air flowing through the main passage 18 is controlled by rotating the throttle valve 14. Though the throttle valve 14 is closed at an idling state of the engine, a small clearance exists between an inner wall 24 of the throttle body 12 and an outer periphery 27 of the throttle valve 14.

A small amount of air flows through the small clearance.

The throttle body 12 also includes an outer wall 28 and an inner structure 28a between which the bypass passage 20 is formed. An upstream end 32 of the bypass passage 20 communicates with the upstream portion 18a of the main passage 18, and a downstream end 34 of the bypass passage 20 is open to a downstream end of the upstream portion 18a. Air flows through the bypass passage 20 from its upstream end 32 to its downstream end 34, bypassing the throttle valve 14. The downstream end 34 of the bypass passage 20

is enlarged, thereby forming an enlarged portion 36. A slanted surface 60 is formed on an upstream end wall 38 of the intake manifold 16, which is connected to an end wall 30 of the throttle body 12. The slanted surface 60 forms a downstream wall of the enlarged portion 36.

An air-adjusting screw 42 having a tip 44 is disposed in the bypass passage 20. The air-adjusting screw 42 is screwed in a screw hole 40 formed in the outer wall 28 and is air-tightly sealed by an 0-ring disposed in the screw hole 40. An amount of air flowing through the bypass passage 20 is controlled by the air-adjusting screw 42.

The intake manifold 16 is made of a material such as resin. An upstream portion of the intake manifold 16 connected to the throttle body 12 forms the downstream portion 18b of the main passage 18. The downstream portion 18b also serves as a surge tank 50 of the intake manifold 16. The surge tank 50 is branched out at its downstream end, forming plural branch pipes 52 each of which is connected to respective cylinders of the engine.

The upstream end wall 38 of the intake manifold 16 is chamfered, thereby forming the slanted surface 60 which forms a part of the enlarged portion 36 of the bypass passage 20. In this manner, the slanted surface 60 is easily formed. A slant angle 0 is formed between the slanted surface 60 and a direction Y which is perpendicular to a direction X of the air-stream in the main passage 18.

Now, referring to FIG. 2, operation of the airintake device 10 will be described. At the idling state of the engine, the throttle valve 14 is closed, i. e. , the throttle valve 14 is rotated to its upright position.

Intake air sucked into the throttle body 12 forms two airstreams. One is a main air-stream M (shown by a solid line) flowing through the clearance between the outer periphery 27 of the throttle valve 14 and the inner wall 24 of the throttle body 12. The other is a bypass air-stream B (shown by a dotted line) flowing through the bypass passage 20. The bypass air-stream B flows out from the bypass passage 20 along the slanted surface 60 and joins the main air-stream M with a joining angle T.

If the slanted surface 60 were not made, the bypass air-stream B would hit the main air-stream M perpendicularly with a right angle, thereby generating noises. Since the direction of the bypass air-stream B is made closer to the direction of the main air-stream M by the slanted surface 60, the bypass air-stream B smoothly joins the main air-stream M. In other words, the joining angle 1p'is made smaller by the slanted surface 60, and therefore both streams join smoothly. Therefore, the noises generated by the collision of both streams are suppressed. Further, since the bypass passage 20 is enlarged at its downstream end, the peed of the bypass airstream B is reduced before it joins the main air-stream M.

Accordingly, the noises generated at the joining point are further reduced.

Referring to FIG. 3, effects in noise reduction according to the present invention will be explained in comparison with a comparative example. The comparative example is the same as the air-intake device of the present invention except that no slanted surface 60 is formed in the comparative example and the downstream end of the bypass passage is perpendicularly directed to the main passage. The noise level shown in FIG. 3 is measured at a distance 1 meter apart from the engine when the engine is running at an idling speed. The noise level shows an overall value of the noises having frequencies in a range of 2-20 kHz which are transmitted through the air-intake device. As shown in FIG. 3, the noise level is reduced by 2 dB in the embodiment of the present invention.

The present invention is not limited to the embodiment described above, but it may be variously modified. For example, the slanted surface 60 may not be limited to a plane surface, but it may be made as a convex or a concave surface. Though the slanted surface 60 is made at a corner of the upstream end wall 38 of the intake manifold 16 which is made separately from the throttle body 12 in the foregoing embodiment, the slanted surface 60 may be formed on the end wall 30 of the throttle body 12. Alternatively, the throttle body 12 and the intake manifold 16 may be made as a single body, and the slanted surface 60

may be made on an inner wall of the single body. A second bypass passage for installing an idle speed control valve therein may be made separately from the bypass passage 20, and the present invention may be applied to the second bypass passage.

While the present invention has been shown and described with reference to the foregoing preferred embodiment, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.

Claims

1. An air-intake device for an internal combustion engine, the air-intake device comprising: a member for forming air passages; a main passage formed in the forming member for supplying intake air to the internal combustion engine; a throttle valve disposed in the main passage for controlling an amount of air flowing through the main passage; and a bypass passage formed in the forming member for supplying intake air to the internal combustion engine, bypassing the main passage, wherein: a main air-stream formed in the main passage and a bypass air-stream formed in the bypass passage join together at a downstream end of the bypass passage; and the downstream end of the bypass passage includes a slanted surface along which the bypass air-stream flows, so that the bypass air-stream smoothly joins the main airstream with a small joining angle.

2. An air-intake device as in claim 1, wherein: an air-adjusting screw for controlling an amount of air flowing through the bypass passage is disposed in the bypass passage.

3. An air-intake device as in claim 1 or 2, wherein: a portion for enlarging the bypass passage is formed at the downstream end of the bypass passage.

4. An air-intake device as in any one of the claims 1-3, wherein: the air-passage forming member is composed of a throttle body in which the throttle valve is disposed and an intake manifold connected to the throttle body at a vicinity of the downstream end of the bypass passage; and the slanted surface is formed at an upstream end of the intake manifold where the intake manifold is connected to the throttle body.

5. An air-intake device as in claim 4, wherein: the intake manifold is made of a resin material

6. An air-intake device substantially as described herein and with reference to the drawings hereof.