Note: Descriptions are shown in the official language in which they were submitted.
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EXHAUST GAS SENSOR INSTALLATION STRUCTURE FOR FOUR-CYCLE
ENGINE
FIELD OF THE INVENTION
The present invention relates to an exhaust gas sensor installation structure
for a
four-cycle engine in which an exhaust gas sensor is installed in a cylinder
head of
an engine main body, the exhaust gas sensor including a sensor main part an
end
portion of which is exposed in an exhaust port and a cap which is fitted to a
rear
portion of the sensor main part and from a side of which a cord extends.
BACKGROUND OF THE INVENTION
There have been exhaust gas sensor installation structures, for example, one
disclosed in JP-A No. 2004-316430, in which an exhaust gas sensor is installed
in a
portion around an exhaust port of a cylinder head.
An exhaust gas sensor has a cap, from a side of which a cord extends. In the
installation structure described in JP-A No. 2004-316430, the direction in
which a
cord extends from an exhaust gas sensor is not fixed when the exhaust gas
sensor
is installed in a cylinder head. This poses a problem in terms of handling the
cord.
The present invention has been made in view of the above problem, and it is an
object of the present invention to provide an exhaust gas sensor installation
structure for a four-cycle engine wherein, when the exhaust gas sensor is
installed in a cylinder head, the direction in which a cord extends from the
exhaust gas sensor is fixedly defined to facilitate handling of the cord.
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SUMMARY OF THE INVENTION
The present invention provides an exhaust gas sensor installation structure
for a
four-cycle engine, in which an exhaust gas sensor is installed in a cylinder
head
of an engine main body, the exhaust gas sensor including a sensor main part an
end portion of which is exposed in an exhaust port and a cap which is fitted
to a
rear portion of the sensor main part and from a side of which a cord extends.
In
the exhaust gas sensor installation structure, a sensor installation hole for
installing the sensor main part is provided in a portion around the exhaust
port
of the cylinder head, the cap is at least partly covered by a sensor guard
fixedly
positioned relative to the cylinder head, and a direction in which the cord
extends is fixedly defined by the sensor guard relative to the cylinder head.
According to the present invention, the direction in which the cord extends
from
the cap of the exhaust gas sensor installed in the sensor installation hole
provided in a portion around the exhaust port of the cylinder head is fixedly
defined by the sensor guard fixedly positioned relative to the cylinder head.
Thus, the direction in which the cord extends is fixedly defined with the
exhaust
gas sensor protected by the sensor guard, so that the cord can be handled with
ease.
An aspect of the invention provides the exhaust gas sensor installation
structure
for a four-cycle engine according to the above, wherein the sensor guard
formed
discretely from the engine main body is attached to the exhaust gas sensor
such
that the sensor guard engages with a positioning part provided on the engine
main body.
According to this aspect of the invention, the sensor guard formed discretely
from the engine main body is attached to the exhaust gas sensor such that it
engages with the positioning part provided on the engine main body. This
improves workability in attaching the sensor guard, in a fixed position
relative to
the cylinder head, to the exhaust gas sensor.
Another aspect of the invention provides the exhaust gas sensor installation
structure for a four-cycle engine according to the above, wherein: the sensor
guard integrally includes a sensor positioning part having an engaging part to
engage with the positioning part provided on the engine main body and
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covering the cap; a cover part formed continuously with the sensor positioning
part such that the cover part covers an outer open end of an air passage
communicating with an interior of the sensor main part and opening in an outer
surface of the cap; and a cord positioning part formed continuously with the
sensor positioning part such that the cord positioning part defines a
direction in
which the cord extends.
According to this aspect of the invention, the outer open end of the air
passage is
covered by the cover part of the sensor guard. Therefore, the sensor guard can
prevent foreign matter such as dust and water from entering the exhaust gas
sensor via the air passage, and the direction in which the cord extends can be
easily defined by the cord positioning part formed continuously with the
sensor
positioning part engaged with the positioning part provided on the engine main
body.
A further aspect of the invention provides the exhaust gas sensor installation
structure for a four-cycle engine according to above, wherein the positioning
part
provided on the engine main body includes two adjacent ones of a plurality of
cooling fins projectedly formed on an outer circumference of the cylinder
head.
According to this aspect of the invention, no special part for positioning the
sensor guard relative to the cylinder head is required, so that the position
of the
sensor guard can be defined without causing an increase in the number of
components required.
Yet another aspect of the invention provides the exhaust gas sensor
installation
structure for a four-cycle engine according to the above, wherein the sensor
guard is formed integrally with the cylinder head or a head cover included in
the
engine main body.
According to this aspect of the invention, the sensor guard is formed
integrally
with the cylinder head or the head cover, so that the number of components
required and the number of man-hours required for installing the sensor guard
can be reduced.
Another aspect of the invention provides the exhaust gas sensor installation
structure for a four-cycle engine according to the above, wherein: the engine
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main body is mounted on a motorcycle such that a side where the exhaust port
is
provided of the cylinder head faces forward; and the sensor guard is formed to
cover the cap from a front side.
According to this aspect of the invention, the exhaust gas sensor can be
protected
against objects coming flying from the front of the motorcycle.
The oxygen sensor used in the following embodiments corresponds to the
exhaust gas sensor according to the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawings, wherein:
Fig. 1 is a side view of an essential part of a motorcycle.
Fig. 2 is an enlarged view of an essential part of Fig. 1.
Fig. 3 is an enlarged cross-sectional view taken along line 3 - 3 in Fig. 2.
Fig. 4 is a perspective view in the direction of arrow 4 in Fig. 2.
Fig. 5 is a perspective view corresponding to Fig. 4 with no sensor guard.
Fig. 6 is a perspective view of a sensor guard.
Fig. 7 is a perspective view of the sensor guard in the direction of arrow 7
in Fig.
6.
Fig. 8 is an enlarged cross-sectional view of the sensor guard taken along
line 8 -
8 in Fig. 3.
Fig. 9 is a perspective view, from diagonally below, of a cylinder head and a
head
cover included in an engine main body according to a second embodiment.
Fig. 10 is a perspective view, from diagonally above, of the cylinder head and
the
head cover included in the engine main body.
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Fig. 11 is a perspective view, from diagonally above, of a cylinder head
according
to a third embodiment.
Fig. 12 is a perspective view of a part of the cylinder head as seen from
diagonally above at an angle different from that of Fig. 11.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described below with reference to
attached drawings.
Figs. 1 to 8 show a first embodiment of the present invention. Fig. 1 is a
side view
of an essential part of a motorcycle. Fig. 2 is an enlarged view of an
essential part
of Fig. 1. Fig. 3 is an enlarged cross-sectional view taken along line 3 - 3
in Fig. 2.
Fig. 4 is a perspective view in the direction of arrow 4 in Fig. 2. Fig. 5 is
a
perspective view corresponding to Fig. 4 with no sensor guard. Fig. 6 is a
perspective view of a sensor guard. Fig. 7 is a perspective view of the sensor
guard in the direction of arrow 7 in Fig. 6. Fig. 8 is an enlarged cross-
sectional
view of the sensor guard taken along line 8- 8 in Fig. 3.
Referring to Fig. 1, a body frame F of the motorcycle includes a main frame 15
extending rearwardly and downwardly from a head pipe (not shown) provided
in a front end portion of the motorcycle. A power unit P including a water-
cooled
four-cycle engine E and a transmission system T which continuously varies the
output of the engine E and enables deceleration is disposed below and
suspendedly supported by the main frame 15.
Referring also to Fig. 2, an engine main body 16A of the engine E included in
the
power unit P includes a crankcase 17, a cylinder block 18 coupled, in a
forwardly
tilted position, to an upper front portion of the crankcase 17, a cylinder
head 19A
coupled to an upper portion of the cylinder block 18, and a head cover 20A
coupled to the cylinder head 19A.
As shown in Fig. 1, an intake system 22 having, at an upstream end thereof, an
air cleaner 21 disposed rearward of the engine main body 16A is connected to
an
intake port (not shown) which is open in a rear side of the cylinder head 19A.
An
exhaust connection pipe section 24 forming a forwardly open exhaust port 23 is
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projectedly provided on a front side of the cylinder head 19A. An exhaust pipe
25 communicated with the exhaust port 23 is connected to the exhaust
connection
pipe section 24. The cylinder head 19A has a spark plug 26 fitted thereto from
the
right side thereof. A radiator 27 disposed forward of the engine main body 16A
is
supported by the main frame 15.
Referring also to Figs. 3 to 5, an oxygen sensor 28 is installed, as an
exhaust gas
sensor, in the cylinder head 19A such that it can detect the oxygen
concentration
in the exhaust gas flowing through the exhaust port 23. To allow the oxygen
sensor 28 to be installed, the cylinder head 19A is provided with a sensor
installation hole 29 formed around the exhaust port 23. In the present
embodiment, the sensor installation hole 29 is provided in the right side of
the
exhaust connection pipe section 24 forming the exhaust port 23.
The oxygen sensor 28 includes a sensor main part 31 and a cap 32 removably
fitted to a rear portion of the sensor main part 31. The sensor main part 31
has a
housing 30 which is attached to the cylinder head 19A by having an end portion
thereof screwed in the sensor installation hole 29. The sensor main part 31 is
installed in the cylinder head 19A with an end portion thereof exposed in the
exhaust port 23.
The housing 30 is shaped cylindrically. It has an engaging part 30a provided
in
an axial intermediate portion thereof, the engaging part 30a radially
outwardly
projecting so that it can engage with a rotary tool and having, for example, a
hexagonal cross-sectional shape. A male thread 33 to be screwed in the sensor
installation hole 29 that is a threaded hole is formed on the external surface
of a
portion of the housing 30, the portion being closer to the end of the housing
30
than the engaging part 30a.
The cap 32 is made of an elastic material, for example, rubber and integrally
includes a bottomed cylindrical part 32a which is elastically fitted to a rear
portion of the housing 30 included in the sensor main part 31 and a pair of
cylindrical projections 32b and 32c laterally projecting from a rear portion
of the
bottomed cylindrical part 32a. The projections 32b and 32c have an axis
disposed
over and along a diameter line of the bottomed cylindrical part 32a and
project to
upward and downward sides, respectively, from the rear portion of the bottomed
cylindrical part 32a.
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Of the projections 32b and 32c, the projection 32b downwardly projecting from
the bottomed cylindrical part 32a forms an air passage 34 for leading air into
the
sensor main par 31. The air passage 34 is open at an outer end of the
projection
32b, i.e., in the external surface of the cap 32. Of the projections 32b and
32c, the
projection 32c upwardly projecting from the bottomed cylindrical part 32a is
connected with a cord 35 extending sidewardly therefrom. A connection terminal
36 provided in the cap 32 continuously with the cord 35 is electrically
connected
to a connection terminal 37 provided on the sensor main part 31 side when the
cap 32 is fitted to the rear portion of the main sensor part 31. The cord 35
extends
to a side opposite to the side where the air passage 34 is open, i.e.,
upwardly
from a rear side of the oxygen sensor 28, i.e., from a side of the cap 32.
The cap 32 of the oxygen sensor 28 is, at least partly, covered by a sensor
guard
40 fixedly positioned relative to the cylinder head 19A. The direction in
which the
cord 35 extends from the oxygen sensor 28 is fixedly defined relative to the
cylinder head 19A by the sensor guard 40. The sensor guard 40 is formed
discretely from the engine main body 16A and attached to the oxygen sensor 28
with its position relative to the cylinder head 19A fixedly defined by
engaging
with a positioning part 41 provided on the cylinder head 19A included in the
engine main body 16A.
Referring to Figs. 6 and 7, the sensor guard 40 covering the cap 32 integrally
includes a sensor positioning part 40a which engages with the positioning part
41
on the engine main body side, a cover part 40b provided continuously with the
sensor positioning part 40a such that it covers the outer open end of the air
passage 34, and a cord positioning part 40c provided continuously with the
sensor positioning part 40a such that it defines the direction in which the
cord 35
extends. The sensor guard 40 is produced by bend-forming a flat metal plate.
The sensor positioning part 40a includes: a center end plate part 40aa which
is a
flat plate part covering the outer-end bottom portion of the bottomed
cylindrical
part 32a included in the cap 32; a first side plate part 40ab which is formed
perpendicularly to and continuously with the center end plate part 40aa so
that it
faces, from the front side, the outer circumference of the oxygen sensor 28
installed in the cylinder head 19A; a second side plate part 40ac which is
formed
perpendicularly to and continuously with the center end plate part 40aa such
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that it faces, from the rear side, the outer circumference of the oxygen
sensor 28
installed in the cylinder head 19A, the second side plate part 40ac being
shorter
than the first side plate part 40ab; an engaging part 40ad which
perpendicularly
outwardly projects from a middle portion of the end portion, away from the
center end plate part 40aa, of the second side plate part 40ac so that it
engages
with the positioning part 41 on the engine main body side provided in the
cylinder head 19A; a pair of abutting parts 40ae which inwardly
perpendicularly
project from both sides of the end portion, away from the center end plate
part
40aa, of the first side plate part 40ab so that they abut on the outer
circumference
of the housing 30 included in the sensor main part 31 of the oxygen sensor 28;
and a pair of abutting parts 40af which inwardly perpendicularly project from
both sides of the end portion, away from the center end plate part 40aa, of
the
second side plate 40ac so that they abut on the outer circumference of the
housing 30.
Referring also to Fig. 8, the cover part 40b includes: a lower end plate part
40ba
which downwardly extends from, and in the same plane as, the end plate part
40aa of the sensor positioning part 40a so as to cover the projection 32b of
the cap
32 from the right side of the cylinder head 19A; an air passage cover part
40bb
which is formed continuously with a lower end portion of the lower end plate
part 40ba and perpendicularly to the lower end plate part 40ba so that it
covers,
from below, the outer open end of the air passage 34 that is open at the outer
end
of the projection 32b; and a pair of holding parts 40bc which are formed, at
both
sides of the lower end plate part 40ba, perpendicularly to and continuously
with
the lower end plate part 40ba so that they elastically engage with the
projection
32b from the front and rear sides to elastically hold the projection 32b.
The cord positioning part 40c includes: an upper end plate part 40ca which
upwardly extends from, and in the same plane as, the end plate part 40aa of
the
sensor positioning part 40a so as to cover the projection 32c of the cap 32
from
the right side of the cylinder head 19A; and a pair of holding parts 40cb
which
are formed, at both sides of the upper end plate part 40ca, perpendicularly to
and
continuously with the upper end plate part 40ca so that they elastically
engage
with the projection 32c from the front and rear sides to elastically hold the
projection 32c.
Of the sensor guard 40, the abutting parts 40ae and 40af of the sensor
positioning
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part 40a are abutted on the outer circumference of the housing 30 included in
the
sensor main part 31 of the oxygen sensor 28, the holding parts 40bc of the
cover
part 40b elastically hold the projection 32b of the cap 32, and the holding
parts
40cb of the cord positioning part 40c elastically hold the projection 32c of
the cap
32. This allows the sensor guard 40 to be attached to the oxygen sensor 28 in
a
fixed position relative to the oxygen sensor 28. Also, the engaging part 40ad
of
the sensor positioning part 40a is engaged with the positioning part 41 on the
engine main body side provided on the cylinder head 19A to fixedly define the
position relative to the cylinder head 19A of the sensor guard 40, that is, of
the
oxygen sensor 28.
With the sensor guard 40 attached, in a fixedly defined position relative to
the
cylinder head 19A, to the oxygen sensor 28, the direction in which the cord 35
extends from the oxygen sensor 28 is defined by the cord positioning part 40c,
the air passage cover part 40bb of the cover part 40b covers the outer open
end of
the air passage 34 that is open in the outer surface of the cap 32, and the
first side
plate part 40ab of the sensor positioning part 40a covers the cap 32 from the
front
side.
The cylinder head 19A are integrally provided with plural cooling fins 42
projectedly formed on its outer circumference, the plural cooling fins 42
being
spaced out along the cylinder axis. The positioning part 41 on the engine main
part side is made up of two adjacent ones of the cooling fins 42. The engaging
part 40ad of the sensor guard 40 is engaged between the two adjacent cooling
fins 42.
The first embodiment of the present invention has the following effects. The
cap
32 of the oxygen sensor 28 installed in the sensor installation hole 29
provided in
a portion around the exhaust port 23 of the cylinder head 19A is, at least
partly,
covered by the sensor guard 40 fixedly positioned relative to the cylinder
head
19A, so that the direction relative to the cylinder head 19A in which the cord
35
extends from the oxygen sensor 28 is fixedly defined by the sensor guard 40.
Thus, the direction in which the cord 35 extends is fixedly defined with the
oxygen sensor 28 protected by the sensor guard 40, so that the cord 35 can be
handled with ease.
The sensor guard 40 is formed discretely from the engine main body 16A and
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attached to the oxygen sensor 28 such that it engages with the positioning
part 41
on the engine main body side provided on the cylinder head 19A included in the
engine main body 16A. This improves workability in attaching the sensor guard
40, in a fixed position relative to the cylinder head 19A, to the oxygen
sensor 28.
The sensor guard 40 integrally includes the sensor positioning part 40a having
the engaging part 40ad to engage with the positioning part 41 on the engine
main
body side and covering the cap 32 of the oxygen sensor 28, the cover part 40b
formed continuously with the sensor positioning part 40a such that it covers
the
outer open end of the air passage 34 formed in the cap 32 and being open in
the
outer surface of the cap 32, and the cord positioning part 40c formed
continuously with the sensor positioning part 40a such that it defines the
direction in which the cord 35 extends. The sensor guard 40 can, therefore,
prevent foreign matter such as dust and water from entering the oxygen sensor
28 via the air passage 34. Furthermore, the direction in which the cord 35
extends
can be easily defined by the cord positioning part 40c formed continuously
with
the sensor positioning part 40a that engages with the positioning part 41 on
the
engine main body side.
The positioning part 41 on the engine main body side is made up of two
adjacent
ones of the plural cooling fins 42 projectedly provided on the outer
circumference of the cylinder head 19A, so that no special part for
positioning the
sensor guard 40 relative to the cylinder head 19A is required. This makes it
possible to define the position of the sensor guard 40 without causing an
increase
in the number of components required.
The engine main body 16A is mounted on a motorcycle such that the side where
the exhaust port 23 is provided of the cylinder head 19A faces forward. Since
the
sensor guard 40 is formed to cover the cap 32 from the front side, the oxygen
sensor 28 is protected against objects coming flying from the front of the
motorcycle.
Figs. 9 and 10 show a second embodiment of the present invention. Fig. 9 is a
perspective view, from diagonally below, of a cylinder head and a head cover
included in an engine main body. Fig. 10 is a perspective view, from
diagonally
above, of the cylinder head and the head cover included in the engine main
body.
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The engine main body 16B is mounted on a motorcycle (not shown) such that an
exhaust port 23 of a cylinder head 19B included in the engine main body 16B
faces forward and obliquely downward. An oxygen sensor 28 is installed in a
portion around the exhaust port 23 of the cylinder head 19B such that a
projection 32b forming an air passage 34 faces forward and obliquely upward.
A head cover 20B included in the engine main body 16B and coupled to the
cylinder head 19B is formed integrally with a sensor guard 44. The sensor
guard
44, by engaging with the projection 32b, defines, relative to the cylinder
head
19B, the position of the oxygen sensor 28 and the direction in which a cord 35
extends from the oxygen sensor 28 and covers the outer open end of the air
passage 34 and at least a part of the cap 32 included in the oxygen sensor 28.
Moreover, the sensor guard 44 is formed such that, with the engine main body
16B mounted on a motorcycle, it covers the cap 32 from the front side.
In the second embodiment, the cap 32 of the oxygen sensor 28 is, at least
partly,
covered by the sensor guard 44 fixedly positioned relative to the cylinder
head
19B, so that the direction relative to the cylinder head 19B in which the cord
35
extends from the oxygen sensor 28 is fixedly defined by the sensor guard 44.
Thus, the direction in which the cord 35 extends is fixedly defined with the
oxygen sensor 28 protected by the sensor guard 44, so that the cord 35 can be
handled with ease.
Since the sensor guard 44 covers the outer open end of the air passage 34,
foreign
matter such as dust and water can be prevented from entering the oxygen sensor
28 via the air passage 34. Also, since the sensor guard 44 is formed to cover
the
cap 32 from the front side, the oxygen sensor 28 is protected against objects
coming flying from the front of the motorcycle.
Furthermore, since the sensor guard 44 is formed integrally with the head
cover
20B, the number of components required and the number of man-hours required
for installing the sensor guard 44 can be reduced.
Figs. 11 and 12 show a third embodiment of the present invention. Fig. 11 is a
perspective view, from diagonally above, of a cylinder head. Fig. 12 is a
perspective view of a part of the cylinder head as seen from diagonally above
at
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an angle different from that of Fig. 11.
An engine main body 16C is mounted on a motorcycle (not shown) such that an
exhaust port 23 of a cylinder head 19C included in the engine main body faces
forward and obliquely downward. An oxygen sensor 28 is installed in a portion
around the exhaust port 23 of the cylinder head 19C such that a projection 32b
forming an air passage 34 faces rearward and such that a projection 32c
letting a
cord 35 extend outward faces forward.
Moreover, a sensor guard 45 is formed integrally with the cylinder head 19C,
the
sensor guard 45 covering the outer open end of the air passage 34 and at least
a
part of the cap 32 of the oxygen sensor 28.
The sensor guard 45 is comprised of a concave portion which is provided in the
cylinder head 19C such that its inner side surface faces the outer open end of
the
air passage 34 and such that it accommodates most part of the oxygen sensor
28.
A wall portion 45a covering the oxygen sensor 28 from the front side and
forming a part of the side surface of the concave portion is provided with a
restrictive concave portion 46 through which the projection 32c of the cap 32
of
the oxygen sensor 28 extends and which prevents, by engaging with the
projection 32b, the oxygen sensor 28 from turning about its axis.
Of plural cooling fins 47 provided on the outer circumference of the cylinder
head 19C, some are provided with a concave portion 48 forming space required
to allow the oxygen sensor 28 to be attached to and detached from the cylinder
head 19C.
The third embodiment can produce effects similar to those of the second
embodiment.
Although various preferred embodiments of the present invention have been
described herein in detail, it will be appreciated by those skilled in the
art, that
variations may be made thereto without departing from the spirit of the
invention or the scope of the appended claims.
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