Air intake system with composite throttle body

An air intake system for an internal combustion engine. The air intake system includes an intake manifold (24) with a throttle body (22) mounted thereto. The intake manifold (24) and throttle body housing (26) are both formed primarily from a plastic or composite material. A snap-fit joint secures the throttle body (22) to the intake manifold (24). The joint includes a pair of mounting flanges (46,48), with the throttle body flange (46) including a set of lugs (54), and the manifold flange (48) including cutouts (56) and ramps (58) for receiving the lugs (54). The throttle body flange (46) also includes a loop hook (76) and gasket (52), which mate, respectively, with retention surfaces (84) and a sealing surface (70) on the manifold flange (48). The throttle body (22) also includes a main bore extension (62) with pilots (66) that mate with an entrance region (68) in the manifold (24).

FIELD OF THE INVENTION 
The present invention relates to air intake systems for vehicle internal 
combustion engines, and more particularly to throttle bodies and manifolds 
used to control the intake air flow. This patent application is related to 
a patent application titled THROTTLE BODY WITH INTAKE MANIFOLD SNAP-FIT 
ATTACHMENT, filed herewith. 
BACKGROUND OF THE INVENTION 
Conventional throttle bodies and intake manifolds are formed from metals, 
such as aluminum or steel. They are typically attached to the inlet of an 
air intake manifold, in a cantilever fashion, by bolts. The bolts, then, 
support the entire weight of the throttle body. The sealing, of course, is 
accomplished in a conventional fashion with a flat gasket mounted between 
the throttle body and intake manifold. These components have been 
desirable because they are strong and provide accurate flow metering 
without leaks. 
The conventional metal components used within an air intake system, 
however, are heavier and costlier than desirable. Consequently, with 
requirements for reduced weight and improved performance of vehicle 
engines, a desire exists to form more engine components from plastic 
and/or composite materials. Also, with an emphasis on cost, it is 
desirable to reduce the number of parts needed to form an assembly and to 
reduce the service costs by minimizing the time and tools needed for 
servicing. While plastic and composite intake manifolds are starting to 
come into use, plastic and composite throttle bodies are not commonly 
used. The reason is that there are some drawbacks to using these 
alternative materials over conventional metal components. One drawback is 
that it is difficult to maintain a long term sealing load on the gasket 
when using threaded fasteners without the use of metal inserts for 
receiving the fasteners. While this can be made to work, metal inserts add 
to the cost and complexity of the molding process. Also, the plastics and 
composites are generally not as strong as the conventional metals, which 
must support the assembly adequately. Further, for throttle bodies 
generally, the dimensional tolerances must be held very tight in order to 
obtain an accurate amount of desired air flow during engine operation. In 
order to do this, it is preferable to use a low creep material that is 
dimensionally stable and will maintain its dimensional tolerances under 
various humidity and temperature conditions. The conventional metal 
components have no difficulty achieving the desired results, but plastics 
and composites do not necessarily perform as well with these desirable 
characteristics. 
Thus, is desirable to provide an intake assembly that improves weight, cost 
and complexity concerns as compared conventional metal assemblies, but 
still adequately performs the air flow metering function of the 
conventional assemblies. 
SUMMARY OF THE INVENTION 
In its embodiments, the present invention contemplates an air intake 
assembly for use with a vehicle engine. The air intake assembly includes 
an intake manifold including a main bore, and a mounting flange 
surrounding the main bore. The intake assembly also includes a throttle 
body assembly including a throttle body housing having main bore and a 
mounting flange surrounding the main bore of the throttle body in 
alignment with the intake manifold main bore and mounting flange. The 
throttle body housing is formed from a composite thermoplastic material 
that is generally non-hydrophobic with water absorption rates less than 
about 1.5 percent and less dense than aluminum and steel. First mounting 
means, integral with the throttle body, secures the throttle body assembly 
to the intake manifold, and second mounting means, integral with the 
intake manifold, receives the first mounting means and secures the intake 
manifold to the throttle body. 
Accordingly, an object of the present invention is to provide an air intake 
assembly having an intake manifold and throttle body that is lighter 
weight and less costly than metallic components, while still obtaining 
adequate functionality of the air intake flow control. 
A further object of the present invention is to provide a new attachment 
strategy for attaching non-metallic throttle bodies to intake manifolds 
without employing conventional threaded fasteners, which will adequately 
support the throttle body that will be relatively simple to fabricate and 
will maintain adequate sealing between components, while also being easy 
to service. 
An advantage of the present invention is a lower cost and lighter weight 
air intake assembly which is easy to service. 
A further advantage of the present invention is that it will still maintain 
tight dimensional tolerances and will operate adequately over time by not 
creating concerns with creep of the material over time. 
Another advantage of the present invention is that the throttle body can be 
formed of a material that will allow the throttle body and joint to 
maintain dimensional stability necessary for accurate operation under 
various humidity and temperature conditions. 
An additional advantage of the present invention is the ease of 
serviceability of the assembly since only one portion of a part needs to 
flex, allowing the throttle body to be assembled and disassembled from the 
intake manifold with minimal tools.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An air intake assembly 20 includes a throttle body assembly 22, which 
connects to a composite intake manifold 24. The intake manifold 24 is 
preferably formed from a plastic composite such as glass filled nylon. The 
throttle body assembly 22 includes a composite throttle body housing 26 
having a main bore 32. Within the main bore 32 a throttle shaft 28 and 
throttle plate 30 are mounted transversely via bearings 34. A torsion 
spring 36 biases the rotation of the throttle shaft 28 within the main 
bore 32. 
The main bore 32 splits into two flow paths as it extends downstream 
through the throttle body housing 26. The first flow path is the 
continuation of a downstream portion 38 of the main bore 32 and the second 
flow path is a idle air bypass passage 40, which also extends through to 
the downstream end of the throttle body housing 26. The intake manifold 
includes a main bore 42 aligned with the downstream portion 38 of the 
throttle body main bore 32, and also an idle air bypass passage 44 which 
aligns with the throttle body idle air bypass passage 40. 
In the throttle body 22, the throttle shaft 28 and plate 30 are mounted to 
selectively block flow through the downstream portion 38 of the main bore 
32 by rotation of this assembly via conventional throttle control 
mechanisms, not shown. In order to allow for accurate control of the flow 
of air through the main bore 32 of the throttle body housing 26, the 
throttle plate 30 should seal precisely against the walls of the bore 38. 
Moreover, in maintaining this close seal, the plate 30 needs to move 
freely without sticking or binding against the walls of the downstream 
portion 38 of the main bore 32. Thus a dimensionally stable material is 
desirable for satisfactory operation of the assembly. 
Consequently, one of the potential drawbacks of changing a throttle body 
housing from metal to plastic and/or composite generally is that many of 
the common plastics may not be as dimensionally stable as is desirable. 
Some will absorb moisture under high humidity conditions, causing the 
material to expand, which changes the dimensions of the bore 38 within 
which the throttle plate 30 is mounted. Further, some plastic and/or 
composite materials will expand or contract significantly under various 
temperature conditions, affecting the precision of the gap between the 
throttle plate and the main bore. This can reduce the precision of the 
relative position between the throttle plate and the bore. 
In order to account for this, for the preferred embodiment of the present 
invention, the throttle body housing 26 is formed from a composite 
thermoplastic material having a high (e.g., greater than 40%) 
glass/mineral content, which can sustain continuous high temperatures of 
125.degree. C., is chemically resistant to common automotive fluids, is 
generally non-hydrophobic with water absorption rates less than about 1.5% 
(measured with the water absorption at 23.degree. C. at 100% relative 
humidity), is dimensionally stable, and preferably lower cost and lighter 
than metals. Preferably, then, a material such as polybutylene 
terephthalate or polyphenylene sulfide is employed. By forming the 
throttle body housing 26 of these types of materials, it will minimize any 
changes in precision of air flow control when switching from a 
conventional metal material. 
On the other hand, materials such as these tend to be somewhat brittle, 
which requires maintaining low strain rates on the throttle body housing 
26 during assembly. It can also be difficult to control the 
profile/flatness of formed parts over broad surfaces, requiring limited 
zones/areas of tight tolerance requirements in order to minimize the cost 
of fabrication while not losing functionality. Thus, given a brittle 
material, one must stay within the molding limitations of the material and 
configure the mounting joint so as not to crack the material during 
assembly or during use, while still maintaining the integrity of the 
joint. Consequently, any joint employed to mount the throttle body 
assembly 22 from the intake manifold 24 needs to account for this. 
Further, there is another potential drawback with employing plastic or 
composite material as opposed to conventional metal in that the material 
will generally have lower strength limits and will be much more 
susceptible to creep. Still further, with repair costs rising, any new 
joint is preferably quick and easy to assemble and disassemble with a 
minimum of tools. 
The mounting of the throttle body 22 to the intake manifold 24 for the 
preferred embodiment of the present invention is achieved chiefly through 
a gasketed flange interface between the two components that includes four 
major elements; three lugs, a loop hook, a piloted surface and a gasket. 
For the mounting joint, both the throttle body housing 26 and the intake 
manifold 24 include flanges, 46 and 48 respectively. The throttle body 
flange 46 includes a recess 50 within its downstream face for receiving a 
gasket 52, which will act to seal between the two flanges 46,48. 
The throttle body flange 46 also includes the three lugs 54 extending 
therefrom in a generally downstream direction. Although, other numbers of 
lugs can be used if so desired. The intake manifold flange 48 includes 
three cutouts 56, each corresponding to one of the three lugs 54. On the 
downstream side of the flange 48, adjacent each cutout are ramps 58. 
The lugs 54 are shaped and sized so that they deflect, although minimally, 
during assembly of the throttle body 22 to the intake manifold 24. The 
lugs 54 are curved so that the open side of each lug 54 faces its 
corresponding ramp 58 on the intake manifold flange 48. As for the radii, 
length and thickness of this curved shape, it allows for adjustment in the 
design as needed to distribute the stresses along the length of each lug 
54 in order to avoid overstressing them during assembly and engine 
operation. If desired, the backs of these lugs 54 can be gusseted to 
provide extra strength. 
The ramps 58 are located adjacent cutouts 56 in the mounting flange 48 in 
order to allow the lugs 54 to easily slide initially onto the downstream 
side of the manifold flange 48 during assembly. The lugs 54 also include 
curls 60 opposite the main direction of curvature at their very ends to 
assure that during assembly the lugs 54 do not catch on the wrong 
(upstream) side of the manifold flange 48. Functionally, the lugs 54 and 
corresponding ramps 58 act as cams to pull and hold the two mounting 
flanges 46,48 together with the proper amount of pre-load and thereby 
compress the gasket 52 to assure a good seal. 
By, in essence, overlapping the parts to mount them together, the sealing 
performance can still be maintained even as there may be some material 
creep over time. For throttle body housings 26 made of the preferred 
materials, the lug/ramp configuration thus accounts for the brittle nature 
of the material by allowing for minimal deformation of the lugs 54 as they 
cam-up on the ramps 58 while still providing sufficient clamping load so 
that creep will not become a concern. 
The throttle body housing 26 also includes a main bore extension 62, which 
is a portion of the main bore 38, that extends downstream of the throttle 
body flange 46. It includes an outer generally cylindrical surface 64. On 
this outer surface are eight pilots 66, which are raised portions, 
extending radially outward from the outer surface 64. Each of the pilots 
66 tapers radially inward as it extends downstream. These pilots 66 help 
to guide the throttle body housing 26 into an entrance region 68 of the 
intake manifold main bore 42. Preferably, the entrance region 68 also 
tapers the same amount and direction as the pilots 66 so they will have 
good surface area contact between them. Once in place, the pilots 66 will 
carry the radial loads associated with supporting the throttle body 22 
cantilevered from the manifold 24, while also limiting the amount of 
mating surfaces on which tight tolerances are held. Here, only tight 
tolerances need to be held on the pilots 66 themselves to achieve proper 
alignment, not the entire surface 64. 
The throttle body housing 26 additionally includes the gasket recess 50 
within the downstream face of its flange 46 that not only extends all of 
the way around the main bore extension 62, but also around the idle air 
bypass passage 40 for complete sealing between the throttle body 22 and 
the intake manifold 24. The rubber gasket 52 fills the recess 50 and 
presses against a sealing surface 70, which is formed on the upstream face 
of the intake manifold flange 48. Also, for improved sealing, tolerance 
zones 72 are located generally mid-way between the lug cutouts 56 on the 
downstream face of the throttle body flange 46. These three zones 72 are 
held to close tolerances. The other areas will maintain good sealing due 
to their close proximity to the lugs 54 themselves. This arrangement eases 
manufacturing by requiring tight control of the tolerances only over the 
tolerance zones 72 and yet maintains a good seal all of the way around. 
Further, the gasket 52 is shaped to avoid wiping on any voids in the 
sealing surface 70 of the intake manifold flange 48. This will help to 
avoid any leakage problems that could occur due to wear of the gasket 52. 
In particular, the gasket 52 extends circumferentially beyond the edge of 
the idle air bypass passage 44 to avoid wiping across it during assembly. 
The composite throttle body housing 26 with a single gasket 52 sealing 
around all of its air flow paths allows for the idle air by-pass passage 
40 to be molded integrally with the structure, thus minimizing parts and 
weight. Further, in today's engines, it is important to meter the intake 
air flow accurately. Any leakage in the air intake system will create an 
error in the measurement, thus limiting the precision of the engine 
operation. 
With the lugs 54, pilots 66 and gasket 52 in place, the throttle body 
housing 26 is secured to the intake manifold 24 in all but the rotational 
direction. For this, the loop hook 76 acts as a locking feature, which 
assures that once installed, the throttle body 22 will remain in its 
proper mounted position relative to the manifold 24. The loop hook 76 is 
cantilevered from one edge of a cutout 78 in the throttle body flange 46 
and oriented to extend along the downstream edge of the flange 46. The 
topology of the hook 76 is similar to a flat cantilevered beam with a hole 
near its free end. On the manifold flange 48 is a flat portion of an 
engagement surface 80, which is a flat surface along which the loop hook 
76 slides, and a ramped portion 82. Adjacent the engagement ramp 82 is a 
pair of retention surfaces 84. Since the loop hook 76 has a small depth 
dimension, the deflection occurs with minimal force and allows for just 
the small ramped surface 82 to minimize the deflection. This allows for a 
securing feature without overstraining a brittle material. Once in place, 
the loop hook 76 will support all loads in the rotational direction and 
prevent rotation from occurring. 
The assembly process will now be described. FIG. 1 illustrates the air 
intake components prior to assembly. For this, one merely needs to align 
the loop hook 76 with the engagement surface 80 and each of the lugs 54 
generally with its corresponding cutout 56. The lugs 54 are spaced around 
the throttle body flange 46 such that if a given lug 54 is aligned with a 
non-corresponding cutout 56, then the other lugs 54 will not align with an 
improper cutout 56. This assures that an improperly oriented assembly will 
not occur. At this point, the main bore extension 62 of the throttle body 
22 is pushed into the entrance region 68 of the manifold main bore 42. As 
the one is pushed into the other, the pilots 66 will become engaged and 
assure the proper alignment of the bore 38 and the manifold main bore 42. 
The lugs 54 then will pass through the cutouts 56 and extend beyond the 
downstream surface of the manifold mounting flange 48 as the gasket 52 
first contacts the sealing surface 70 of the manifold mounting flange 48. 
FIGS. 7, 9 and 11 illustrate the partial assembly after the push motion 
has occurred. The push motion does not require force sufficient to 
compress the gasket 52. 
The next step for assembly is a twisting motion. The throttle body assembly 
22 is now twisted about the centerline of the main bores relative to the 
intake manifold 24, which causes the lugs 54 to cam-up on the ramps 58, 
pulling the two closer together and compressing the gasket 52 to form a 
tight seal. The twisting continues until the loop hook 76 slides up the 
engagement ramp 82 and engages the retention surfaces 84, preventing any 
further rotational motion in either direction. The throttle body assembly 
22 is now secured to the intake manifold 24 in the proper position. FIGS. 
2, 8, 10 and 12 illustrate after the twist motion has occurred and the two 
are fully mounted relative to one another. 
Should the need then arise to later remove the throttle body assembly 22 
from the intake manifold 24 for repair or service, then one only needs to 
lift the loop hook 76 from the retention surfaces 84 while rotating the 
throttle body assembly 22 in the opposite direction of that used for 
assembly. Further, this can generally be done quite easily with no tools. 
Moreover, a strong sealed joint is formed that will allow for the use of a 
more brittle composite material for the throttle body housing 26, with the 
benefits of composite material over metals, without degradation of 
performance of the throttle body 22 relative to a metal one. 
While certain embodiments of the present invention have been described in 
detail, those familiar with the art to which this invention relates will 
recognize various alternative designs and embodiments for practicing the 
invention as defined by the following claims.