Idle air bypass valve silencer

Abstract: A silencer for an idle air bypass valve (12) in an internal combustion engine includes a grid (56) disposed between the outlet of the idle air bypass valve (22) and the intake manifold (14). The grid (56) acts to reduce the air velocity entering into the intake manifold (14) which dampens the vibration of a plastic manifold, thereby reducing noise generated.

Description: The present invention relates to an automotive internal combustion engine having an idle air bypass valve, and is particularly concerned with reducing noise resulting from air flowing through the idle air bypass valve. Automotive engineers have increasingly utilised plastics materials in developing various engine components, including the intake manifold. Unlike prior aluminium manifolds, which have a high vibration dampening effect, plastics manifolds tend to vibrate more readily as high velocity air flows therethrough resulting in excessive noise. To reduce such noise, prior art intake systems require elaborate silencing methods which, if incorporated into a modern internal combustion engine, require substantial packaging and/or redesign of the engine. An object of the present invention is to provide an apparatus for reducing intake air noise. The present invention provides an automotive internal combustion engine having an air intake duct, a throttle valve assembly coupled to the intake duct, an intake manifold coupled to the throttle valve assembly and the engine, an idle air bypass valve having an inlet communicating with the air intake duct and an outlet communicating with the intake manifold to selectively bypass the throttle valve assembly, and a silencer for reducing noise from the air bypass valve, wherein the silencer comprises a housing secured to the idle air bypass valve, which housing defines an inlet chamber connected by an inlet tube to the engine air intake duct and supplying air to the idle air bypass valve, an outlet chamber through which idle air flows from the bypass valve to the intake manifold, the outlet chamber being arranged in the housing side by side with the inlet chamber so that idle air flows through the inlet and outlet chamber in parallel but opposite directions, and a grid plate arranged in the path of the air leaving the outlet chamber and entering the intake manifold. The inventors of the present invention have found that a suitably designed silencer connected between the outlet of the idle air bypass valve and the intake manifold is sufficient to reduce noise generation in the intake manifold, thereby reducing customer complaints. An advantage of the preferred embodiment of the invention is that noise reduction is effected by means of a low cost apparatus which may be easily mounted to an existing engine. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of an engine of the invention incorporating an idle air bypass valve silencer; Figures 2 and 3 are perspective views of the idle air bypass valve silencer; Figure 4 is a plan view of the silencer; Figure 5 is a cross-sectional view taken along line 5-5 of Figure 4; and, Figure 6 is a cross-sectional view taken along line 6-6 of Figure 4. The automotive internal combustion engine 10, shown in Figure 1, includes an engine block 12, an intake manifold 14 and a cylinder head 16 mounted between the engine block 12 and the manifold 14. An air inlet duct 18 directs outside air through a throttle valve assembly 20 into the manifold 14. As is well known to those skilled in the art, air is metered by the throttle valve assembly 20 such that the engine may operate at a speed proportional to the amount of air flowing past throttle valve assembly 20. Also, as is well known to those skilled in the art, when the engine is at idle, the throttle valve assembly 20 is in a closed position. In order for air to be fed to the engine, idle bypass valve assembly 22 is included. Bypass valve assembly 22 includes an intake tube 24 connected to the solenoid valve 26. At engine idle, the valve 26 opens to allow air to flow from the tube 24 through the solenoid valve 26 directly into the manifold 14, thereby bypassing the throttle valve assembly 20. The amount of air flowing through the bypass valve assembly 22 corresponds to the desired engine speed at engine idle. To reduce noise associated with the use of plastics manifolds, a portion of the silencer 30 is disposed between the outlet of valve 26 and manifold 14, as will be readily appreciated hereinafter. A more detailed description of silencer 30 will now be described with reference to Figures 2-6. The silencer 30 includes a generally rectangular housing 32 formed of a plastics material. Mounting holes 34 are conveniently located around the perimeter of the housing 32 to mount silencer 30 to the manifold 14. The silencer 30 further includes an inlet tube 36 formed at one end thereof for receiving air from the tube 24 (see Figure 1). The inlet tube 36 further includes a rib 38, which effectively prevents the tube 24 from being dislodged therefrom. The silencer 30 further includes generally trapezoidal shaped inlet and outlet air chambers 40 and 42. The inlet chamber 40 is disposed between the inlet tube 36 and the inlet to the bypass valve 26, whereas the outlet chamber 42 is disposed between the outlet of the bypass valve 26 and the intake manifold 14. Thus, with the operation of the idle bypass valve 26, air is able to flow (as shown by flow arrow F) from the inlet tube 36 through the inlet chamber 40, into the bypass valve 26 then out of the bypass valve 26 into the outlet chamber 42. Seals 44 and 46 surround chambers 40 and 42, respectively, to sealingly engage the silencer 30 to bypass valve 26. In the embodiment described herein, the seals 44 and 46 are joined at interface 48. Mounting holes 50 are formed in housing 32 to receive the bypass valve 26. The silencer 30 further includes a seal 52 formed around the periphery of housing 32 so that the silencer 30 may be sealingly engaged to the intake manifold 14. Referring now specifically to Figures 4-6, the silencer 30 includes a radius 53 formed between the inlet chamber 40 and the inlet tube 36 to smoothly direct the air flow. This reduces air turbulence and results in noise reduction as air flows through the silencer 30. Continuing with reference to Figures 4-6, the outlet chamber 42 includes walls 54 and a grid plate 56. In a preferred embodiment, the thickness (t) of the grid plate 56 is about 7 mm. The volume of the outlet chamber 42 defined by the walls 54 and the grid plate 56 is sufficient to reduce the velocity of air exiting valve 26 to a predetermined velocity. In addition, the grid plate 56 includes a plurality of equally spaced holes 58 thereby forming a grid, to allow air to flow from chamber 42 to manifold 14. In a preferred embodiment, the diameter (d) of each hole is about 3 mm, and the spacing between holes is about 1.5mm. Thus, a hole diameter (d) to thickness (t) ratio of about 3:7 is preferable. As shown in Figure 5, air flows from the inlet tube 36, through the bypass valve 26, into the outlet chamber 42 and out through the holes 58 in the grid plate 56. As the air strikes the grid plate 56, a portion of the air is reflected back into the outlet chamber 42, which ultimately reduces the air velocity flowing out through the holes 58. Further, as specifically shown in Fig. 6, air flowing through the holes 58 in the grid plate 56 creates turbulent flows 60 which tend to cancel each other due to the equal spacing, described above. This cancellation further reduces noise as air flows from the silencer 30.

Claims: An automotive internal combustion engine having an air intake duct (18), a throttle valve assembly (20) coupled to the intake duct, an intake manifold (14) coupled to the throttle valve assembly and the engine, an idle air bypass valve (22) having an inlet communicating with the air intake duct (18) and an outlet communicating with the intake manifold (14) to selectively bypass the throttle valve assembly (20), and a silencer (30) for reducing noise from the air bypass valve, characterised in that the silencer (30) comprises a housing (32) secured to the idle air bypass valve (22), which housing defines an inlet chamber (40) connected by an inlet tube (24) to the engine air intake duct (18) and supplying air to the idle air bypass valve (22), an outlet chamber (42) through which idle air flows from the bypass valve (26) to the intake manifold (18), the outlet chamber (42) being arranged in the housing side by side with the inlet chamber (40) so that idle air flows through the inlet and outlet chamber (40,42) in parallel but opposite directions, and a grid plate (56) arranged in the path of the air leaving the outlet chamber (42) and entering the intake manifold (18). An engine as claimed in to claim 1, wherein the grid plate (56) has a plurality of holes (58) formed therein, each hole (56) having a diameter of about 3mm. An engine as claimed in claim 2, wherein spacing of said holes (56) is about 1.5mm. An engine as claimed in claim 1, 2 or 3, wherein said grid plate (56) has a thickness of about 7mm. An engine as claimed in any preceding claim, further comprising a seal (44,46) disposed between the inlet and outlet chambers (40,42) and the bypass valve (26).

Inventors: CHOI MICHAEL, DONIELSON MARK BRUCE, CHOI, MICHAEL, DONIELSON, MARK BRUCE
Applicants: FORD GLOBAL TECH INC, FORD GLOBAL TECHNOLOGIES, INC.
Application year: 1998
Main classification: F02M35
IPC codes: F02M35