Information
-
Patent Grant
-
6553971
-
Patent Number
6,553,971
-
Date Filed
Friday, June 30, 200024 years ago
-
Date Issued
Tuesday, April 29, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Yuen; Henry C.
- Huynh; Hai
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 198 D
- 123 198 DB
- 123 450
- 123 510
- 123 495
- 417 206
- 417 349
- 417 440
- 417 494
- 417 470
- 417 255
- 417 441
- 417 454
- 137 4544
- 137 4545
-
International Classifications
-
Abstract
The pump has a body including at least a fuel compression chamber and an actuating chamber enclosing the actuating members of the pump. The on-off valve has a shutter sliding inside a hole in the body to close a fuel feed conduit. The shutter is held in the closed position by a compression spring, which rests directly or indirectly on a shoulder in the hole. In one embodiment, the spring rests on the shoulder via a perforated disk held by a retaining ring, which clicks removably inside an annular groove in the hole. In a further embodiment, the spring rests directly on the shoulder.
Description
The present invention relates to a high-pressure pump with an on-off valve for feeding fuel to an internal combustion engine, particularly a vehicle engine.
BACKGROUND OF THE INVENTION
Various types of high-pressure fuel feed pumps are known, and which are generally supplied with fuel from a normal tank by a low-pressure pump powered by an electric motor. The high-pressure pump normally comprises an on-off valve, which is opened automatically by the fuel fed to it by the low-pressure pump.
The body of known high-pressure pumps encloses at least a fuel compression chamber, and an actuating chamber housing pump actuating members; and the on-off valve comprises a shutter designed to ensure fuel flow to the actuating chamber, even when the valve is closed, to lubricate and cool the actuating members.
In one known radial-piston pump in particular, the pump body houses three cylinders, in which slide respective pistons activated by a common cam carried by a shaft activated by the drive shaft; the cam is housed inside the actuating chamber or case of the pump; and the shutter is in the form of a hollow cylinder and slides along the wall of a radial hole in the pump body.
The pump body also has a fuel feed conduit for feeding fuel from the radial hole to the cylinders; the feed conduit is closed by the lateral wall of the shutter; and, to lubricate and cool the pump shaft, the cam, and the various pump body and piston friction surfaces, the shutter also has a calibrated axial hole permitting continuous fuel flow to the case.
To prevent fuel accumulating in an engine cylinder, in the event the respective injector breaks down, or to prevent fuel from being drawn from the actuating chamber in the event of poor or no supply by the low-pressure pump, e.g. due to a fault, the shutter is closed automatically by a compression spring when the pressure of the incoming fuel falls below a given value.
The compression spring is housed inside the shutter and rests on a perforated plate, which has a surface for receiving the end of the spring and is normally fixed, e.g. welded, to the opposite end of the guide hole of the shutter.
In this known type of pump, machining the radial hole in the pump body, fixing the plate, and assembling the spring are difficult, high-cost operations involving considerable time and highly skilled personnel. Moreover, the perforated plate at the end of the hole facing the case limits to a certain extent the outside diameter of the cam and, hence, the capacity of the pump under given conditions.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an extremely straightforward, reliable high-pressure pump having an on-off valve which is cheap to produce and easy to assemble, so as to eliminate the aforementioned drawbacks of known pumps with on-off valves
According to the present invention, there is provided a high-pressure pump with an on-off valve for feeding fuel to an internal combustion engine, wherein the pump comprises a body including at least a fuel compression chamber and an actuating chamber enclosing actuating members of said pump, and wherein said valve comprises a shutter sliding inside a hole in said body to close a fuel feed conduit; said feed conduit being formed in said body, between said hole and said compression chamber; and said shutter being held in the closed position by a compression spring; characterized in that said spring rests directly or indirectly on a shoulder inside said hole; said shoulder being formed in one piece with said body.
In a first embodiment of the invention, the spring rests on the shoulder by virtue of means fixed removably inside the hole and comprising a perforated disk inserted removably inside the hole, and an elastic C-shaped metal element located, between the disk and the shoulder, inside an annular groove adjacent to the shoulder
In a further embodiment of the invention, the spring rests directly on the shoulder, and the wall of the hole has an annular groove permitting precision machining of the wall.
BRIEF DESCRIPTION OF THE DRAWINGS
Two preferred, non-limiting embodiments of the invention will be described by way of example with reference to the accompanying drawings, in which:
FIG. 1
shows a partly sectioned side view of a high-pressure pump with an on-off valve for feeding fuel to an internal combustion engine, in accordance with the invention;
FIG. 2
shows a larger-scale section of the valve and a portion of the pump, according to a first embodiment of the invention;
FIG. 3
shows a larger-scale plan view of a detail in
FIG. 2
;
FIG. 4
shows a section of a further detail of a variation of
FIG. 2
;
FIG. 5
shows a larger-scale section of the valve and a portion of the pump, according to a further embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Number
5
in
FIG. 1
indicates as a whole a high-pressure pump for feeding fuel to an internal combustion engine, e.g. of a vehicle. Pump
5
is supplied with fuel from a normal tank by a low-pressure pump (not shown) powered by an electric motor energized when the engine is turned on.
High-pressure pump
5
is of the type comprising three radial pistons
6
, which slide inside three cylinders
7
arranged radially inside a body
8
of pump
5
; each cylinder
7
is closed by a plate
9
supporting an intake valve
11
and a delivery valve
12
; and each cylinder
7
and respective plate
9
are locked to body
8
by a corresponding lock head
13
.
Pistons
6
are activated in sequence by a single cam integral with a shaft
16
powered by the internal combustion engine drive shaft. Cam
14
acts on pistons
6
via a ring
17
having, for each piston
6
, a faced portion
18
cooperating with a shoe
19
fixed to piston
6
; and each shoe,
19
is pushed towards the cam by a corresponding spring
21
.
The gap between the end of each piston
6
and respective plate
9
defines a compression chamber
22
, so that; the three compression chambers
22
are obviously housed inside body
8
. The space inside body
8
housing cylinders
7
and in which shaft
16
and cam
14
rotate forms an actuating chamber
23
of pump
5
, which chamber is closed by a flange
24
fixed in known manner to body
8
; shaft
16
is fitted in rotary and fluidtight manner to flange
24
; and chamber
23
communicates in known manner with a drain conduit
25
draining into the tank.
Body
8
is made of cast iron, and heads
13
of steel; body
8
and heads
13
have three intake conduits
26
communicating with a conduit defined by an annular groove
27
on flange
24
; each conduit
26
also communicates with the corresponding compression chamber
22
via corresponding intake valve
11
; and each head
13
also has a compression conduit
28
, which, via corresponding delivery valve
12
, connects compression chamber
22
to a delivery conduit
29
of pump
5
.
Body
8
also has a feed conduit
30
formed by two holes
31
arranged crosswise to each other and closed outwards by two plugs
32
At one end, conduit
30
communicates with annular groove
27
of flange
24
and, therefore, with compression chambers
22
; and, at the other end, conduit
30
comes out at a cylindrical wall
33
of a cylindrical radial hole
34
formed in body
8
. Hole
34
communicates with actuating chamber
23
and projects partly towards flange
24
; and an inlet conduit
36
connected to the low-pressure pump is inserted inside hole
34
.
Hole
34
houses an on-off valve indicated as a whole by
37
and comprising a hollow, cylindrical shutter
38
. More specifically, shutter
38
is piston- or cup-shaped, and comprises a lateral wall
39
, which slides accurately along wall
33
of hole
34
, so that both wall
33
of hole
34
and wall
39
of shutter
38
must be precision machined.
Shutter
38
also comprises a flat wall
40
, which has a calibrated hole
41
permitting the passage of a certain amount of fuel, even when conduit
30
is closed by shutter
38
. A helical compression spring
42
is inserted inside shutter
38
and rests on a supporting element fixed to the end of hole
34
facing actuating chamber
23
; and the supporting element must be perforated to permit fuel passage from hole
34
to actuating chamber
23
, as described in Italian Patent Application N TO95A 000010.
According to the invention, the supporting element of spring
42
is defined by a shoulder
43
of hole
34
, formed in one piece with body
8
and located at the end of hole
34
adjacent to actuating chamber
23
. Shoulder
43
defines a circular opening
45
(
FIG. 2
) smaller in diameter than hole
34
; and spring
42
rests directly or indirectly on shoulder
43
, thus simplifying assembly of on-off valve
37
.
In the
FIG. 2
embodiment, spring
42
rests on shoulder
43
by virtue of means fixed removably inside hole
34
and comprising a disk
44
having a central opening
46
permitting fuel passage from hole
34
to actuating chamber
23
. Advantageously, the difference in diameter between hole
34
and opening
45
ranges between 1 and 3 mm, and shoulder
43
is of a thickness ranging between 2 and 4 mm.
Opening
46
in disk
44
has a protruding edge
47
for guiding one of the ends of spring
42
; and disk
44
, together with opening
46
and protruding edge
47
, may be formed cheaply from sheet metal by means of a punching and cold forming or embossing press.
The means fixed removably inside hole
34
also comprise a radially flexible C-shaped metal element
48
, e.g. a standard retaining ring (FIG.
3
), housed inside hole
34
(FIG.
2
), between disk
44
and shoulder
43
. More specifically, wall
33
of hole
34
has an annular groove
49
adjacent to shoulder
43
, and into which ring
48
clicks removably; and the diameter of opening
45
is such as to enable groove
49
to be machined through opening
45
.
Ring
48
is fitted inside groove
49
or removed from the groove by bringing the two ends of ring
48
together, so that the parts of valve
37
are obviously also easy to assemble, the only precaution being to assemble disk
44
with edge
47
facing spring
42
.
To eliminate even the above precaution and/or simplify automatic assembly of valve
37
, in the
FIG. 4
variation, opening
46
of disk
44
may be provided with a ring
51
forming two edges symmetrical with respect to disk
44
and projecting axially in two opposite directions. Ring
51
may be welded to or formed in one piece with disk
44
by compacting and sintering metal powder.
In the
FIG. 5
embodiment, spring
42
rests directly on shoulder
43
. Advantageously, the diameter of opening
45
ranges between 3 and 5 mm, and shoulder
43
is of a thickness ranging between 5 and 8 mm. To permit fine machining of wall
33
of hole
34
from outside body
8
, an annular groove
52
is machined in wall
33
, and which may be shallower than groove
49
in
FIG. 2
, so that valve
37
in
FIG. 5
is even cheaper to produce than that in FIG.
2
.
As compared with known pumps, the advantages of the high-pressure pump according to the invention will be clear from the foregoing description. In particular, removable assembly of disk
44
and ring
48
reduces production cost of the pump; shoulder
43
eliminates the need to fix the supporting element of spring
42
inside hole
34
; and there is no interference between cam ring
17
and the supporting element of spring
42
, so that the diameter of cam
14
can be increased to increase pump capacity.
Clearly, changes may be made to the high-pressure pump as described herein without, however, departing from the scope of the accompanying Claims. For example the pistons of pump
5
may be arranged otherwise than as described; and the pump may be applied to other than a vehicle engine.
Claims
- 1. A high-pressure pump with an on-off valve for feeding fuel to an internal combustion engine, wherein the pump comprises a body including at least a fuel compression chamber and an actuating chamber enclosing actuating members of the pump, and wherein said valve comprises a shutter sliding inside a hole in said body to close a fuel feed conduit; said feed conduit being formed in said body, between said hole and said compression chamber; said shutter being held in a closed position by a compression spring; and wherein, inside said hole, a shoulder is formed in one piece with said body, said spring resting on said shoulder by virtue of means including a disk having an opening permitting fuel flow to said actuating chamber, said disk being inserted removably inside the hole.
- 2. A high-pressure pump as claimed in claim 1, wherein said means also comprise a C-shaped metal element located between said disk and said shoulder; said element being flexible radially; and said hole having an annular groove adjacent to said shoulder and into which said element clicks removably.
- 3. A high-pressure pump as claimed in claim 2, wherein said element is a standard retaining ring.
- 4. A high-pressure pump as claimed in claim 3, wherein said shoulder is defined by a circular opening having a diameter smaller than a diameter of said hole and such as to enable said groove to be machined through said opening.
- 5. A high-pressure pump as claimed in claim 3, wherein a difference between said two diameters ranges between 1 and 3 mm; said shoulder being of a thickness ranging between 2 and 4 mm.
- 6. A high-pressure pump as claimed in claim 1, wherein the opening in said disk has a protruding edge for guiding said spring.
- 7. A high-pressure pump as claimed in claim 6, wherein said edge is formed by cold deformation of said disk.
- 8. A high-pressure pump as claimed in claim 1, further comprising a number of cylinder arranged radially inside said body; and a number of pistons associated with said cylinders and sliding radially; said actuating members comprising a common cam formed in one piece with a shaft; and said cam and said shaft being housed in said actuating chamber.
- 9. A high-pressure pump as claimed in claim 8, wherein said cam activates said pistons via a ring having a number of faced portions; each of said portions engaging a shoe carried by a corresponding piston; and said ring and said shoes being housed in said actuating chamber.
- 10. A high-pressure pump as claimed in claim 1, wherein the opening in said disk has two edges symmetrical with respect to said disk and projecting axially in two opposite directions to simplify positioning of the disk in said hole.
Priority Claims (1)
Number |
Date |
Country |
Kind |
TO99A0572 |
Jul 1999 |
IT |
|
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Number |
Name |
Date |
Kind |
5571243 |
Arnold et al. |
Nov 1996 |
A |
5979297 |
Ricco |
Nov 1999 |
A |
6129518 |
Ricco |
Oct 2000 |
A |
6406278 |
De Matthaeis et al. |
Jun 2002 |
B1 |
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Number |
Date |
Country |
197 38 502 |
Sep 1997 |
DE |
198 18 385 |
Apr 1998 |
DE |