Pumps – Expansible chamber type – Biasing means effects induction stroke of abutment driven,...
Reexamination Certificate
2002-07-16
2004-10-05
Yu, Justine R. (Department: 3746)
Pumps
Expansible chamber type
Biasing means effects induction stroke of abutment driven,...
C092S129000, C092S140000, C092S072000
Reexamination Certificate
active
06799954
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a tappet turning-prevention structure for a fuel supply apparatus for supplying fuel to a fuel injector in a cylinder injection type engine.
2. Description of the Related Art
FIG. 7
is a schematic view of a conventional fuel supply apparatus. In
FIG. 7
, a fuel supply apparatus
1
is arranged to be fitted in an unillustrated housing or the like of an engine, and is driven via a cam
28
that rotates at half rotational speed of the engine. A casing
2
of the fuel supply apparatus
1
is provided with unillustrated suction pipe and discharge pipe disposed therein. In addition, a cylindrical concaved housing section
3
is formed in the fuel supply apparatus in the downward section in FIG.
7
.
A sleeve
5
having a cylinder section
4
is disposed within the concaved housing section
3
. The sleeve
5
is disposed in the manner in which one end thereof faces toward a bottom
3
a
of the concaved housing section
3
. The sleeve
5
comprises the hollow cylindrical cylinder section
4
, a thick section
6
being formed by thickening a part of a bottom
4
a
of the cylinder section
4
, and a securing section
8
being formed into the shape of a flange at the edge of the bottom
4
a
of the cylinder section
4
.
A substantially cylinder-shaped piston
9
is disposed within the cylinder section
4
of the sleeve
5
in a way allowing its reciprocating motion. The piston
9
comprises a fuel pressurizing chamber
10
together with the cylinder section
4
. A compression coil spring
11
is compressedly housed within the fuel pressurizing chamber
10
. The compression coil spring
11
is held in place by a spring holder
12
.
Disposed around the sleeve
5
is a housing
13
surrounding the sleeve
5
. The housing
13
having the form of a substantially bottomless cup is provided with a cylinder-shaped flange section
13
a
at the outer circumference thereof. A holder
14
is fastened to the piston
9
at the end opposite to the side where the fuel pressurizing chamber
10
is formed. Bellows
15
made of metal are disposed between the housing
13
and the holder
14
. The bellows
15
serve as a receptacle for fuel leaking out of the space between the piston
9
and the sleeve
5
.
A tappet
16
, or a driving member, having the form of a bottomed cylinder is abutted against the piston
9
at the end opposite to the side where the fuel pressurizing chamber
10
is formed. The tappet
16
comprises a cam roller
18
rotatably supported by a roller-supporting pin
17
. The cam roller
18
is brought into contact with the cam surface of the cam
28
. A spring holder
19
is fastened to the tappet
16
, and a compression coil spring
20
is compressively mounted in a space between the spring holder
19
and the housing
13
.
A bracket
21
is disposed around the compression coil spring
20
for the purpose of fastening the fuel supply pump
1
to an unillustrated housing and the like of an engine. The bracket
21
is substantially cylinder-shaped and has a flange section
21
a
formed therein at about half its height. The flange section
21
a
is provided with a plurality of unillustrated holes that pierce the flange section and are formed along its circumference at predetermined positions. The casing
2
is provided with unillustrated internally threaded holes in the positions corresponding to the unillustrated through holes. Bolts are inserted in the unillustrated through holes and are fastened to the unillustrated internal threaded holes. Thus, the bracket
21
is firmly attached to the casing
2
. With the outer circumference of the bracket
21
being supported, the fuel supply pump
1
is fastened to an unillustrated housing and the like of an engine.
In a high-pressure fuel supply pump thus composed, piston
9
is pushed toward the tappet
16
by the compression coil spring
11
. The tappet
16
on the other hand is pushed by the compression coil spring
20
so that it is always in contact with the cam
28
. Thus, upon receiving force generated by the rotations of the cam
28
, the piston
9
reciprocates within the cylindrical section
4
.
In a conventional fuel supply apparatus having a construction as above described, as shown in
FIGS. 7 and 8
, the tappet
16
that faces toward the rotating cam
28
when the fuel supply pump is mounted to the housing or the like of the unillustrated engine and that is provided with the cam roller
18
driven by the cam
28
and transmits the motion of the cam
28
to the piston
9
, and the arrangement for preventing the tappet
16
from turning about the axis of the piston is such that the pin
25
press-fitted into the outer circumference surface of the tappet
16
is brought into a loose engagement with a groove formed in the inner surface of the bracket
21
accommodating the tappet
16
.
In the tappet turning prevention structure in a fuel supply apparatus having a construction as above described, however, the tappet
16
is provided with the pin
25
press-fitted in the outer circumference of the tappet
16
and a roller supporting pin
17
as functionally separate parts, and so both the process for press-fitting the pin
25
into the outer circumference of the tappet
16
and the process for positioning the cam roller
18
and the roller-supporting pin
17
in relation to the tappet
16
by a snap ring
27
that fits in both the inside slot formed within the tappet
16
and the outside slot formed at the outer circumference of the roller supporting pin
17
are involved in the tappet
16
assembly process.
Because the tappet
16
is provided with both the roller supporting pin
17
and the pin
25
press-fit in the outer circumference of the tappet
16
, the number of parts is not small. In addition, because a slot into which the tappet turning-prevention pin
25
is press-fitted must be formed in the tappet
16
, the number of processing stages is increased. Further, it is necessary to control the pressure load during the press-fitting the pin
25
into the outer circumference of the tappet
16
for the purpose of eliminating the deformation of the tappet
16
.
Furthermore, because the pin
25
press-fit into the outer circumference of the tappet
16
and the roller supporting pin
17
are at right angles to each other within the tappet
16
, the tappet
16
can be assembled only from a certain limited direction due to the shape of the bracket.
SUMMARY OF THE INVENTION
The present invention has been made to solve the problems discussed above and has as its object the provision of a tappet turning prevention structure in a fuel supply apparatus that requires lesser numbers of parts, part processing stages and items to be controlled in the assembly process and provides a larger degree of freedom of part assembling in the assembly process.
With the above object in view, the present invention resides in the tappet turning prevention structure in a fuel supply apparatus that comprises a piston disposed within the cylindrical section in a manner allowing its reciprocating motion and defining a fuel pressurizing chamber together with the cylindrical section. A tappet is disposed at one end of the piston opposite to the fuel pressurizing chamber and having accommodated therein a roller driven by a cam of an engine and a roller supporting pin for rotatably supporting the roller for transmitting a force of the cam to the piston. The tappet is housed by a bracket fastened to the casing for allowing a reciprocating motion, and the bracket has a groove in an inner surface thereof for allowing an end portion of the roller supporting pin to engage therein.
Thus, the number of parts can be decreased because the turning prevention pin for the tappet and the roller supporting pin have been integrated as a single common part, and therefore the need of controlling of the press-fit loads is eliminated because no process for thrusting the tappet turning prevention pin into the outer circumference of the tappet is involved.
The bracket may have two grooves in an inner surface
Ikegami Tatsuya
Uryu Takuya
Mitsubishi Denki & Kabushiki Kaisha
Sayoc Emmanuel
Yu Justine R.
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