Abstrict An intake structure having a throttle body and an intake body connected
to the upstream end of the throttle body and provided with a by-pass
air passage for mounting an air flow meter. Locating construction
is provided on the joint surfaces of the throttle body and the intake
body so as to locate these bodies coaxially to each other.
Claims What is claimed is:
1. An intake structure for an internal combustion engine comprising:
a first body having therein a main passage through which intake
air is introduced to said engine and a bypass passage bypass a portion
of said main passage and accommodating an air flow sensor therein;
a second body connected to said first body and having therein an
intake passage in which is disposed a throttle valve;
locating projection means provided on the joint surface of one
of said first body and said second body; and
locating recess means formed in the joint surface of the other
of said first and second bodies, said locating projection means
and said locating recess means being adapted to fit each other and
being determined such that, when said locating projection means
and said locating recess means fit each other, said first and second
members are positioned substantially coaxially to each other, wherein
said locating projection means includes a pair of cylindrical projections,
while said locating recess means includes a cylindrical hole for
engaging one of said cylindrical projections and an elongated hole
for engaging the other of said cylindrical projections.
2. An intake structure according to claim 1 wherein said locating
projection means includes at least one projection which is detachably
secured to said joint surface of said one of said first and second
members.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an intake structure of an internal
combustion engine and, more particularly, to an intake structure
of the type in which a first body having an air flow sensor and
a second body having a throttle valve are connected to each other
so as to form an intake passage.
2. Description of the Prior Art
Japanese Unexamined Patent Publication No. 56-107957 discloses
an intake structure for an internal combustion engine which is composed
of a first body having an air flow sensor and a second body having
a throttle valve, the first and the second body being connected
to each other. More specifically, in this intake structure, one
of the first and the second bodies is provided with a threaded bore,
while the other is provided with a bore of a diameter which is determined
to be large enough to accommodate any fluctuation in the location
and diameter of the screw.
SUMMARY OF THE INVENTION
In the known intake structure of the type described above, it is
difficult to coaxially connect the first body having the air flow
sensor and the second body having the throttle valve. In consequence,
an offset having a step is inevitably formed at the juncture between
the first body and the second body so as to cause a disturbance
in the flow of air flowing through the intake passage. This in turn
causes a fluctuation in the pressure within the intake structure
together with at the outlet side of the passage which accommodates
the air flow sensor. This fluctuation in the pressure causes a fluctuation
in the flow rate of air flowing through a by-pass passage. In consequence,
the output from the air flow sensor, which is typically of hot-wire
type, is caused to change.
Accordingly, an object of the present invention is to provide an
intake structure of an internal combustion engine, which is improved
to minimize the offset between the axes of the first body and the
second body, i.e., to minimize the size of the step formed at the
juncture between the first and the second bodies.
To this end, according to the present invention, there is provided
an intake structure for an internal combustion engine comprising:
a first body having therein a main passage through which intake
air is introduced to the engine and a by-pass passage by-passing
a portion of the main passage; a second body connected to the first
body and having therein an intake passage in which is disposed a
throttle valve; locating projection means provided on the joint
surface of one of the first body and the second body; and locating
recess means formed in the joint surface of the other of the first
and second bodies, the locating projection means and the locating
recess means being adapted to fit each other and being determined
such that, when the locating projection means and the locating recess
means fit each other, the first and second members are positioned
substantially coaxially to each other.
The above and other objects, features and advantages of the present
invention will become clear from the following description of the
preferred embodiment when the same is read in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical sectional view of an intake structure in accordance
with the present invention;
FIG. 2 is a plan view of a body 7;
FIG. 3 is a sectional view taken along the line III--III of FIG.
2;
FIG. 4 is a plan view of a body 8; and
FIG. 5 is a sectional view taken along the line V--V of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will be described
hereinunder with reference to the accompanying drawings.
Referring first to FIG. 1 a preferred embodiment of the intake
structure in accordance with the present invention has a first body
7 which is provided therein with a main passage 1 through which
intake air is introduced to an internal combustion engine and a
by-pass passage 2 which by-passes a portion of the main passage
1. A hot-wire-type air flow sensor 3 is disposed in the vicinity
of the by-pass passage 2. This air flow sensor 3 has a hot wire
4 and a cold wire 5 both of which are disposed in the by-pass passage
2. The intake air introduced into the body 7 is supplied to a second
body 8 through the main passage 1. A portion of the intake air is
supplied to the body 8 through the by-pass passage 2 and an opening
6.
The second body 8 is provided therein with an intake passage which
is adapted for introducing intake air from the first body 7 into
the internal combustion engine. A throttle valve 9 is mounted in
this intake passage.
As shown in FIGS. 2 and 3 the joint surface 10 of the body 7 at
which the body 7 contacts the joint surface 12 of the body 8 is
provided with cylindrical pins 11 which tightly fit in a hole formed
in this joint surface 10 of the body 7.
On the other hand, as shown in FIGS. 4 and 5 the joint surface
12 of the body 8 is provided with a circular hole 13 of diameter
D and an elongated hole 14 of width h.
Various dimensions of the bodies 7 and 8 as shown in FIGS. 1 to
4 are determined to meet the following conditions.
X.sub.1 =X.sub.1 'Y.sub.1 =Y.sub.1 'X.sub.2 =X.sub.2 'Y.sub.2 =Y.sub.2
'
D-d=.epsilon..sub.1 h-d=.epsilon..sub.2
The symbol .epsilon. represents a positive value which is determined
to be as small as possible but to allow movement of the bodies 7
and 8 away from each other. The tolerances in the X and Y directions
also are selected to be as close as possible to zero.
For connecting the bodies 7 and 8 to each other, one of the pins
11 is press-fit into the circular hole 13 while the other pin 11
is received in the elongated hole 14. With this arrangement, it
is possible to locate both bodies 7 and 8 substantially coaxially
to each other by a simple operation. In consequence, no substantial
step is formed at the juncture between the bodies 7 and 8 so that
fluctuation in the output of the air flow sensor 3 is remarkably
decreased.
As will be understood from the foregoing description, according
to the present invention, a first body having an air flow sensor
and a second body having a throttle valve are connected substantially
coaxially to each other, without requiring any laborious work for
aligning both bodies with each other. This in turn improves the
accuracy of the air flow sensor, as well as the efficiency of assembly
work.
Although a preferred embodiment of the present invention has been
described, it is to be understood that the described embodiment
is only illustrative and various changes and modifications may be
imparted thereto without departing from the scope of the invention
which is limited solely by the appended claims. |