Internal-combustion engines – Engine speed regulator – Specific throttle valve structure
Reexamination Certificate
2000-06-01
2001-07-10
Kwon, John (Department: 3747)
Internal-combustion engines
Engine speed regulator
Specific throttle valve structure
C251S306000
Reexamination Certificate
active
06257202
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a throttle valve used in an air flow control assembly for adjusting the amount of air flowing through an air intake passage of an internal combustion engine.
2. Description of the Related Art
An example of a conventional air flow control assembly for an internal combustion engine is shown in FIG.
12
.
In the figure, a generally cylindrical rod-shaped throttle shaft
12
is rotatably supported at both ends by a throttle body
6
having a generally cylindrical inner wall
6
a
. A long, thin rectangular groove is disposed in the throttle shaft
12
, and a disk-shaped throttle valve
1
composed of injection-molded resin is inserted into the groove and secured to the throttle shaft
12
by screws (not shown). The throttle valve
1
rotates together with the throttle shaft
12
and adjusts the amount of air flowing into a combustion chamber (not shown) of the internal combustion engine by changing a gap G between the throttle valve
1
and the inner wall
6
a
of the throttle body
6
.
Next, the method for manufacturing this throttle valve
1
by injection molding will be explained.
FIG. 10
is a cross section explaining the process of injection molding the throttle valve
1
by injecting a resin
5
into an injection mold
10
in the shape of the throttle valve
1
.
In the figure, a flat disk-shaped cavity
11
for forming the throttle valve
1
is disposed in the injection mold
10
. An injection mold gate portion
2
, which is a small-diameter cylindrical opening for injecting the resin
5
into the cavity
11
, is disposed on one side of the center of the cavity
11
, and the resin
5
is injected from a runner
3
, which is a large-diameter cylindrical opening, through the injection mold gate portion
2
to fill the inside of the cavity
11
.
FIG. 11
is a plan showing the resin
5
as it fills the inside of the cavity
11
of the injection mold
10
.
In the figure, the resin
5
is injected into the cavity
11
through the injection mold gate portion
2
and spreads radially from there. Cylindrical pins
16
are disposed inside the cavity
11
to form shaft-securing bores for passage of the screws securing the throttle valve
1
to the throttle shaft
12
.
To permit the engine to perform stable low-fuel-consumption idling, it is necessary to suppress the amount of air leakage, which is the amount of inflow air leaking through the gap G, when the throttle valve
1
is fully closed, that is, the state in which the throttle valve
1
has rotated to be perpendicular to the inner wall
6
a.
However, since the precision of outside diameter dimensions of the throttle valve
1
has been insufficient, the gap G could not be adequately reduced, increasing the air leakage when the throttle valve
1
is fully closed, and making it difficult to achieve stable low-fuel-consumption idling.
It is necessary to improve precision of the outside diameter of the throttle valve
1
to reduce air leakage, but as shown in
FIG. 11
, since there is no means provided for controlling the flow of the resin
5
injected into the cavity
11
through the injection mold gate portion
2
, the speed of the resin
5
flowing through the cavity
11
is not uniform. For that reason, the time at which the resin
5
reaches different positions on the outside diameter mold portion
15
, which forms the outside diameter portion of the throttle valve
1
, is irregular, making the density to which the resin
5
fills the inside of the cavity
11
nonuniform due to irregularities in the hardening time of the resin
5
, thereby leading to deterioration in the precision of the outside diameter dimensions, which includes the outside diameter dimensions, outside diameter roundness, etc., of the throttle valve
1
. Conventionally, the irregularities in the outside diameter dimensions of injection-molded throttle valves
1
are in the order of one percent of the outside diameter dimensions, which is approximately ten times the irregularities in outside diameter dimensions of generally-used conventional throttle valves in which metal material is machined.
In addition, when the cross-sectional shape is asymmetrical as in the throttle valve
21
shown in
FIG. 13
, the time at which the resin
5
reaches different positions on an outside diameter mold portion
22
of the throttle valve
21
is even more irregular, and the deterioration in the precision of the outside diameter dimensions has been significant.
Furthermore, as shown in
FIG. 11
, during the process of injecting the resin
5
, the resin
5
which has started to harden and build up in the vicinity of the injection mold gate portion
2
flows radially outwards through the cavity
11
, but this partially-hardened resin is resistant and causes the flow of the resin
5
being injected into the cavity
11
after it to be non-uniform, leading to deterioration in the precision of the outside diameter dimensions of the throttle valve
21
.
FIG. 14
is a cross section showing a throttle valve
1
manufactured by injecting the resin
5
into the injection mold
10
shown in FIG.
10
.
In the figure, some of the resin from the injection mold gate portion
2
of the injection mold
10
has been left behind and formed a burr
13
at a gate resin portion
17
in the center of the throttle valve
1
where the resin was injected during injection molding. Such burrs
13
catch on the groove in the throttle shaft
12
when the throttle valve
1
is being inserted into and secured to the groove in the throttle shaft
12
, and it has not been easy to install the throttle valve
1
in the throttle shaft
12
.
SUMMARY OF THE INVENTION
The present invention aims to solve the above problems and an object of the present invention is to provide a throttle valve for an air flow control assembly in which dimensional precision is increased, burr removal is eliminated, and assembly in the throttle shaft is made superior by a simple construction.
In order to achieve the above object, according to one aspect of the present invention, there is provided a throttle valve for an air flow control assembly being a disk-shaped throttle valve composed of an injection-molded resin having first and second main surfaces which are generally parallel, the throttle valve including:
a gate resin portion disposed on the first main surface where the resin is injected; and
at least one groove disposed surrounding the gate resin portion following a circle centered on the gate resin portion on at least one main surface selected from the first and second main surfaces.
In the throttle valve for an air flow control assembly according to the present invention, the first main surface may also include a recess portion disposed around the gate resin portion, the recess portion being positioned so that the gate resin portion does not project beyond the first main surface.
According to another aspect of the present invention, there is provided a throttle valve for an air flow control assembly being a disk-shaped throttle valve composed of an injection-molded resin having first and second main surfaces which are generally parallel, the throttle valve including:
a gate resin portion disposed on the first main surface where the resin is injected; and
an accumulated resin portion formed as a protrusion disposed on the second main surface in a position opposite the gate resin portion.
In the throttle valve for an air flow control assembly according to the present invention, the second main surface may also include a recess portion disposed around the accumulated resin portion, and the accumulated resin portion may extend from a bottom surface of the recess portion, the accumulated resin portion being positioned such that an apex portion thereof does not project beyond the second main surface.
REFERENCES:
patent: 3620195 (1971-11-01), Lamm
patent: 4438745 (1984-03-01), Watanabe
patent: 4892288 (1990-01-01), Norbury, Jr. et al.
patent: 4972815 (1990-11-01), Yamamoto et al.
patent: 5081972 (1992-01-01), Daly et al.
patent: 5148787 (1992-09-01
Moriguchi Teruhiko
Ohno Kenichi
Ohta Hirohisa
Sugiyama Takeshi
Kwon John
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
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