Information
-
Patent Grant
-
6622701
-
Patent Number
6,622,701
-
Date Filed
Tuesday, November 27, 200122 years ago
-
Date Issued
Tuesday, September 23, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 514
- 123 467
- 123 456
- 137 512
- 137 5123
- 138 26
- 251 118
-
International Classifications
-
Abstract
An accumulator fuel injection apparatus is provided which may be employed in a common rail system for diesel engines. The fuel injection apparatus includes a pressure relief valve designed to relieve an unwanted rise in pressure of the fuel within an accumulator. The pressure relief valve includes a pressure pulsation minimizing mechanism designed to minimize pressure pulsations which are generated in a drain line and propagated to a valve mechanism of the pressure relief valve, causing a valve-opening pressure of the pressure relief valve to change. The pressure pulsation minimizing mechanism may be implemented by an orifice or a check valve.
Description
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to an accumulator fuel injection system for internal combustion engines, and more particularly to an improved structure of such a system designed to avoid a failure in operation of a pressure relief valve caused by pressure pulsations of a drain line.
2. Background Art
Accumulator fuel injection systems are known which supplies a high-pressure fuel to an accumulator of a common rail through a supply pump and distributes the fuel stored in the accumulator to a plurality of fuel injectors installed one in each cylinder of an internal combustion engine. The accumulator fuel injection systems usually have a pressure relief valve connected to the accumulator of the common rail.
FIG. 7
shows an example of such a pressure relief valve.
The pressure relief valve
100
works as a pressure limiter and consists essentially of a valve
101
, a cylindrical housing
102
, and a hollow screw
103
. The valve
101
is made up of a valve body having a valve hole
111
formed therein and a valve ball
105
selectively opening and closing the valve hole
111
.
The housing
102
has an inlet side fuel hole
112
, a small-diameter hole
113
, and an outlet side fuel hole
114
. Within the inlet side fuel hole
112
, a spring guide
107
and a spring
108
are disposed which urge the valve ball
105
to close the valve hole
111
at all times. The hollow screw
103
has formed therein a longitudinal hole
115
communicating with the outlet side fuel hole
114
and a lateral hole
116
extending perpendicular to the longitudinal hole
115
. The lateral hole
116
communicates with a fuel passage
117
in a low-pressure pipe
109
(i.e., a drain line) through which the fuel is returned back to a fuel tank (not shown).
A valve-opening pressure at which the ball valve
105
is to be opened is determined by a contact area between the valve body
104
and the valve ball
105
and a set load produced by the spring
108
. The valve-opening pressure may be adjusted by changing the thickness of shims
118
and
119
. The lateral hole
116
of the hollow screw
103
has a fuel-flowing sectional area substantially identical with that between the valve
101
and the longitudinal hole
115
of the hollow screw
103
.
If some flow resistance exists in the low-pressure pipe
109
, it may cause pressure pulsations of the fuel returned from the supply pump or the fuel injector back to the fuel tank through the low-pressure pipe to be transmitted to the valve
101
of the pressure relief valve
100
, so that the valve ball
105
bounces within the valve body
104
, thereby resulting in a change in valve-opening pressure of the pressure relief valve
100
.
SUMMARY OF THE INVENTION
It is therefore a principal object of the invention to avoid the disadvantages of the prior art.
It is another object of the invention to provide an improved structure of an accumulator fuel injection system capable of avoiding a failure of a pressure relief valve caused by pressure pulsations occurring in a drain line.
According to one aspect of the invention, there is provided an accumulator fuel injection apparatus which may be employed in a common rail system for diesel engines. The accumulator fuel injection apparatus comprises: (a) a high-pressure supply pump pumping fuel out of a fuel tank, the high-pressure supply pump pressuring and discharging the fuel; (b) an accumulator storing therein the fuel discharged from the high-pressure supply pump; (c) a fuel injector injecting the fuel stored in the accumulator into an internal combustion engine; (d) a high-pressure fuel line extending from the high-pressure supply pump to the fuel injector through the accumulator; (e) a relief valve having an inlet communicating with the high-pressure fuel line, an outlet, and a valve mechanism disposed between the inlet and the outlet, the valve mechanism being responsive to a rise in pressure of the fuel within the high-pressure fuel line beyond a given level to establish communication between the inlet and the outlet for relieving the rise in pressure of the fuel within the high-pressure fuel line; and (f) a pressure pulsation absorbing mechanism disposed between the valve mechanism of the relief valve and a pressure pulsation source existing downstream of the outlet of the relief valve. The pressure pulsation absorbing mechanism works to absorb a pressure pulsation propagated from the pressure pulsation source to the valve mechanism of the relief valve, thereby avoiding an undesirable change in a valve-opening pressure at which the valve mechanism opens the inlet to drain the fuel within the accumulator.
In the preferred mode of the invention, the valve mechanism includes a valve body in which the inlet of the relief valve is formed and a valve member movable to open and close the inlet selectively. The relief valve includes a hollow cylindrical housing having a fuel hole formed between the inlet and the outlet. The pressure pulsation absorbing mechanism includes a hollow screw which is fitted in an open end of the housing as defining the outlet of the relief valve and has formed therein an orifice working to absorb the pressure pulsation to be propagated from the pressure pulsation source to the valve mechanism. A valve-urging mechanism is disposed in the fuel hole of the housing which urges the valve member to close the inlet constantly.
The hollow screw includes a sleeve and a flange head. The sleeve is retained within the open end of the housing and has formed therein a longitudinal chamber communicating with the fuel hole of the housing through an end of the sleeve. The flange head is formed on an end of the sleeve opposite the housing.
The orifice is implemented by a hole formed in the sleeve which extends perpendicular to the longitudinal chamber of the sleeve. The hole is smaller in diameter than the fuel hole of the housing and the longitudinal chamber of the sleeve.
The relief valve communicates at the inlet thereof with the accumulator for relieving a rise in pressure of the fuel within the accumulator beyond the given level to keep the pressure in the accumulator constant.
The relief valve may alternatively communicate at the inlet thereof with an outlet of the high-pressure supply pump for relieving a rise in pressure of the fuel flowing into the accumulator beyond the given level to keep the pressure of the fuel supplied to the accumulator constant.
The relief valve may alternatively communicate at the inlet thereof with a portion of the high-pressure fuel line extending from the accumulator to the fuel injector for relieving a rise in pressure of the fuel supplied to the fuel injector beyond the given level to keep the pressure of the fuel supplied to the fuel injector constant.
According to another aspect of the invention, there is provided an accumulator fuel injection apparatus which comprises: (a) a high-pressure supply pump pumping fuel out of a fuel tank, the high-pressure supply pump pressuring and discharging the fuel; (b) an accumulator storing therein the fuel discharged from the high-pressure supply pump; (c) a fuel injector injecting the fuel stored in the common rail into an internal combustion engine; (d) a high-pressure fuel line extending from the high-pressure supply pump to the fuel injector through the accumulator; (e) a relief valve having an inlet communicating with the high-pressure fuel line, an outlet, and a valve mechanism disposed between the inlet and the outlet, the valve mechanism being responsive to a rise in pressure of the fuel within the high-pressure fuel line beyond a given level to establish communication between the inlet and the outlet for relieving the rise in pressure of the fuel within the high-pressure fuel line; and (f) a check valve disposed between the valve mechanism of the relief valve and a pressure pulsation source existing downstream of the outlet of the relief valve. The check valve works to block transmission of a pressure pulsation from the pressure pulsation source to the valve mechanism of the relief valve.
In the preferred mode of the invention, the valve mechanism includes a valve body in which the inlet of the relief valve is formed and a valve member movable to open and close the inlet selectively. The relief valve includes a hollow cylindrical housing having a fuel hole formed between the inlet and the outlet. A hollow screw is provided which is fitted in an open end of the housing as defining the outlet of the relief valve and has disposed therein the check valve. A valve-urging mechanism is disposed in the fuel hole of the housing which urges the valve member to close the inlet constantly.
The check valve includes a valve body, a check valve member, and a check valve-urging mechanism. The valve body has an orifice formed downstream of the fuel hole of the housing of the relief valve in communication therewith. The check valve-urging mechanism urges the check valve member into constant engagement with the orifice of the valve body.
The relief valve communicates at the inlet thereof with the accumulator for relieving a rise in pressure of the fuel within the accumulator beyond the given level to keep the pressure in the accumulator constant.
The relief valve may alternatively communicate at the inlet thereof with an outlet of the high-pressure supply pump for relieving a rise in pressure of the fuel flowing into the accumulator beyond the given level to keep the pressure of the fuel supplied to the accumulator constant.
The relief valve may alternatively communicate at the inlet thereof with a portion of the high-pressure fuel line extending from the accumulator to the fuel injector for relieving a rise in pressure of the fuel supplied to the fuel injector beyond the given level to keep the pressure of the fuel supplied to the fuel injector constant.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood more fully from the detailed description given hereinbelow and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments but are for the purpose of explanation and understanding only.
In the drawings:
FIG. 1
is a block diagram which shows an accumulator fuel injection system according to the invention;
FIG. 2
is a sectional view which shows a pressure limiter according to the first embodiment of the invention which is designed to relieve a rise in fuel pressure within an accumulator;
FIG. 3
is a schematic illustration which shows an internal structure of the pressure limiter of
FIG. 2
;
FIG. 4
is a sectional view which shows a pressure limiter according to the second embodiment of the invention;
FIG. 5
is a schematic illustration which shows an internal structure of the pressure limiter of
FIG. 4
;
FIG. 6
is a block diagram which shows modifications of a pressure limiter; and
FIG. 7
is a sectional view which shows a conventional pressure limiter installed in typical accumulator fuel injection systems.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, wherein like reference numbers refer to like parts in several views, particularly to
FIG. 1
, there is shown an accumulator fuel injection system according to the first embodiment of the invention.
The shown system is also called a common rail system and consists of a supply pump
2
, a common rail
3
, and a plurality of fuel injectors
4
(only one is shown for the brevity of illustration) each of which is connected to one of output ports of the common rail
3
. The supply pump
2
pumps fuel out of a fuel tank
1
and supplies the fuel to the common rail
3
at a given high pressure. The fuel stored in an accumulator provided in the common rail
3
is supplied to each of the fuel injectors
4
. Each of the fuel injectors
4
injects the high-pressure fuel into one of cylinders of an internal combustion engine
7
such as a diesel engine.
The supply pump
2
has disposed therein a feed pump working as a low-pressure pump which is rotated in synchronism with rotation of a crankshaft of the engine
7
to pump the fuel out of the fuel tank
1
. The supply pump
2
pressurizes the fuel pumped by the feed pump and supplies it to the common rail
3
through a fuel pipe. The supply pump
2
works to control the quantity of fuel to be sent to the common rail
3
to adjust the internal pressure of the accumulator in the common rail
3
(i.e., a common rail pressure).
The common rail
3
is one of surge tanks and designed to store therein the fuel under high pressure. The common rail
3
, as described above, connects with each of the fuel injectors
4
through a fuel pipe. The fuel injectors
4
are installed in a cylinder block of the diesel engine
7
, one for each cylinder, and supply a spray of fuel into combustion chambers at a high pressure. A pressure limiter
6
is installed in a low-pressure pipe
5
(i.e., a drain line) through which the fuel is returned from the supply pump
2
, the common rail
3
, and the fuel injectors
4
back to the fuel tank
1
. The pressure limiter
6
works as a pressure relief valve which relieves a fuel pressure in the accumulator of the common rail
3
beyond a specified limit to keep it at all the time. In this embodiment, the pressure limiter
6
is disposed between the accumulator of the common rail
3
and a fuel passage
10
of the low-pressure pipe
5
, but may alternatively be installed between the low-pressure pipe
5
and an outlet of the supply pump
2
to keep the fuel pressure to be supplied to the common rail
3
at a constant level.
The pressure limiter
6
consists, as shown in
FIGS. 2 and 3
, of a valve
11
connected to the accumulator of the common rail
3
in a liquid tight seal, a hollow cylindrical housing
12
joined to a downstream side of the valve
11
in a liquid tight seal, a spring
13
disposed within the housing
12
, a spring guide
14
retaining an end of the spring
13
, and a hollow screw
16
fitted in an opened end
15
(i.e., an outlet) of the housing
12
.
The valve
11
is made up of a valve body
21
joined to an outlet pipe (not shown) of the common rail
3
in a liquid tight seal and a valve ball
23
. The valve body
21
has formed in an end surface thereof a valve hole
22
communicating with the accumulator of the common rail
3
through the outlet pipe. The valve body
21
has formed therein a valve chamber within which the valve ball
23
is disposed for selectively opening and closing the valve hole
22
. A valve seat
24
is formed on an inner wall of the valve chamber of the valve body
21
. The valve ball
23
rests on the valve seat
24
to close the valve hole
22
. The valve body
21
also has a sliding chamber
25
formed downstream of the valve chamber which supports the spring guide
14
slidably.
The housing
12
is made of a metallic hollow cylinder and has fitted therein annular shims
17
and
18
for achieving fine adjustment of a valve-opening pressure. The housing
12
defines therein an inlet side fuel hole
31
, a fuel hole
34
smaller in diameter than the inlet side fuel hole
31
, and an outlet side fuel hole
35
. The shims
17
and
18
have fuel holes
32
and
33
formed therein, respectively, which are smaller in diameter than the inlet side fuel hole
31
. The housing
12
has formed in an outer surface of an end thereof an external thread
36
which is fitted in a limiter mount (not shown) of the common rail
3
. The housing
12
also has an internal thread
67
formed in the outlet side fuel hole
35
with which the hollow screw
16
engages.
The spring
13
is a coil spring disposed within the inlet side fuel hole
31
of the housing
12
to produce a set load urging the valve ball
23
into constant engagement with the valve seat
24
to close the valve hole
22
of the valve body
21
. The spring
13
is retained at an end thereof on a rear end surface of a large-diameter portion
42
of the spring guide
14
and at the other end on a front surface of the shim
17
. The seat diameter of the valve ball
23
(i.e., a contact area between the valve body
21
and the valve ball
23
) and the set load of the spring
13
defines the valve-opening pressure acting on the valve ball
23
at which the valve hole
22
of the pressure limiter
6
is to be opened when the fuel pressure within the common rail
3
exceeds a specified limit. Fine adjustment of the valve-opening pressure may be accomplished by changing the thickness of the shim
17
and/or the shim
18
.
The spring guide
14
is disposed within the inlet side fuel hole
31
of the housing
12
and the sliding chamber
25
of the valve body
21
. The spring guide
14
is made up of a small-diameter portion
41
working as a cylindrical slider, the large-diameter portion
42
, and a small-diameter portion
43
working as a spring-retaining boss. The small-diameter portion
41
is fitted to be slidable within the sliding chamber
25
of the valve body
21
. The large-diameter portion
42
is fitted to be slidable within the inlet side fuel hole
31
. The small-diameter portion
43
projects from the large-diameter portion
42
opposite the small-diameter portion
41
.
The small-diameter portion
41
of the spring guide
14
has formed on an outer peripheral surface thereof two flat areas
44
which define fuel passages between themselves and an inner wall of the sliding chamber
25
of the valve body
21
which establish fluid communications between the inlet side fuel hole
31
and the valve hole
22
when the valve ball
23
and the spring guide
14
are moved away from the valve seat
24
over a preselected distance. The flat areas
44
are formed by grinding diametrically opposed portions of the outer peripheral surface of the small-diameter portion
41
. The large-diameter portion
42
is disposed within the housing
12
and defines an annular gap between the outer periphery of the large-diameter portion
42
and the inner wall of the inlet side fuel hole
31
which serves as a fuel passage communicating with the valve hole
22
.
The hollow screw
16
functions to absorb pulsation of fuel pressure and is installed downstream of the valve
11
and the outlet side fuel hole
35
of the housing
12
. The hollow screw
16
closes the open end
15
of the housing
12
and consists of a sleeve
52
and a flanged head
53
. The sleeve
52
has formed therein an external thread
51
engaging the internal thread
67
of the housing
12
. The head
53
which is hexagonal and greater in diameter than the sleeve
52
is formed on an end of the sleeve
52
.
The sleeve
52
has a longitudinal chamber
54
and an orifice
56
formed therein. The chamber
54
extends along a longitudinal center line of the sleeve
52
and communicates with the outlet side fuel hole
35
of the housing
12
. The orifice
56
extends perpendicular to the chamber
54
and establishes fluid communication between the chamber
54
and the fuel passage
10
of the low-pressure pipe
5
. The orifice
56
is smaller in diameter (i.e., a fuel flow sectional area) than the inlet side fuel hole
31
, the fuel hole
34
, the outlet side fuel hole
35
, and the chamber
54
and works to absorb the pulsation of fuel pressure transmitted from a pulsation source to the valve
11
and the spring guide
14
. Seal washers
57
and
58
are installed between the end of the housing
12
and the low-pressure pipe
5
and between the screw head
53
and the low-pressure pipe
5
, respectively, to seal gaps formed among the sleeve
52
, the low-pressure pipe
5
, and the housing
12
.
In operation, when the fuel pressure in the accumulator of the common rail
3
exceeds the valve-opening pressure of the pressure limiter
6
, it will cause the valve ball
23
to be moved out of engagement with the valve seat
24
of the valve body
24
against the spring pressure produced by the spring
13
, so that the valve hole
22
is opened. This causes the fuel stored within the common rail
3
to flow from the valve hole
22
to the orifice
56
through the sliding chamber
25
, the inlet side fuel hole
31
, the fuel hole
34
, the outlet side fuel hole
35
of the housing
12
, and the longitudinal chamber
35
of the hollow screw
16
and back to the fuel tank
1
through the fuel passage
10
of the low-pressure pipe
5
. Specifically, the pressure limiter
6
works to relieve an excess pressure of the fuel stored in the accumulator of the common rail
3
, thereby keeping the fuel pressure within the common rail
3
at a desired level.
Usually, when the fuel is discharged from the supply pump
2
or the injectors
4
and returned back to the fuel tank
1
through the low-pressure pipe
5
, pressure pulsations are generated which may be propagated to the hollow screw
16
of the pressure limiter
6
. If the pressure pulsations are transmitted to the spring guide
14
or the valve
11
of the pressure limiter
6
, it will cause the valve ball
23
to bound in the valve body
21
, which may result in an undesirable change in valve-opening pressure of the pressure limiter
6
. The pressure limiter
6
of this embodiment, however, has the orifice
56
formed between the valve
11
and the low-pressure pipe
5
which works to absorb or block the transmission of the pressure pulsations from the low-pressure pipe
5
to the spring guide
14
and the valve
11
, thereby avoiding the undesirable change in valve-opening pressure of the pressure limiter
6
.
The orifice
56
is formed in the sleeve
52
of the hollow screw
16
, but may alternatively be provided in an end portion of the fuel passage
10
of the low-pressure pipe
5
connecting with the hollow screw
16
or the housing
12
. The orifice
56
may also be formed in the sleeve
52
longitudinally.
FIGS. 4 and 5
show a pressure limiter
6
according to the second embodiment of the invention. The same reference numbers as employed in the first embodiment will refer to the same parts, and explanation thereof in detail will be omitted here.
The hollow screw
16
, like the first embodiment, consists of the sleeve
52
and the screw head
53
. The sleeve
52
has formed therein the longitudinal chamber
54
within which a check valve
70
is disposed for blocking transmission of pressure pulsations from the fuel passage
10
of the low-pressure pipe
5
to the spring guide
14
and the valve
11
. The check valve
70
consists of an orifice
71
, a ball
72
, and a coil spring
74
. The orifice
71
is formed in the end of the sleeve
52
and establishes fluid communication between the inlet side fuel hole
31
and the fuel passage
10
of the low-pressure pipe
5
. The orifice
71
is smaller in diameter than the inlet side fuel hole
31
, the fuel hole
34
, the outlet side fuel hole
35
, and the longitudinal chamber
54
. The spring
74
is disposed within the longitudinal chamber
54
and urges the ball
72
into constant engagement with a valve seat
73
formed on an inner wall of the sleeve
52
to close the orifice
71
.
The hollow screw
16
also includes an adjustor screw
75
which is fitted in a threaded hole formed in an end of the bolt head
53
in alignment with the spring
74
and works to adjust the pressure produced by the spring
74
which defines a valve-opening pressure at which the ball
72
is to be moved away from the valve seat
73
to open the orifice
71
. The sleeve
52
also has formed therein a radial hole
86
which traverses the longitudinal chamber
54
to establish fluid communication between the fuel passage
10
and the longitudinal chamber
54
.
In operation, when the fuel pressure in the accumulator of the common rail
3
exceeds the valve-opening pressure of the pressure limiter
6
, it will cause the valve ball
23
to be moved out of engagement with the valve seat
24
of the valve body
24
against the spring pressure produced by the spring
13
, so that the valve hole
22
is opened. This causes the fuel stored within the common rail
3
to flow from the valve hole
22
to the outlet side fuel hole
35
through the sliding chamber
25
, the inlet side fuel hole
31
, and the fuel hole
34
. When the fuel pressure in the outlet side fuel hole
35
exceeds the valve-opening pressure of the check valve
70
set by the spring
74
, it will cause the ball
72
to be moved away from the valve seat
73
against the valve-opening pressure, thereby opening the orifice
71
. The fuel within the outlets side fuel hole
35
, thus, flows into the longitudinal chamber
54
of the hollow screw
16
and is discharged to the fuel passage
10
from the radial hole
86
, thereby keeping the fuel pressure within the common rail
3
at a desired level.
When pressure pulsations are generated in the low-pressure pipe
5
and enter the pressure limiter
6
, the check valve
70
works to block the propagation of the pressure pulsations to the spring guide
14
and the valve
11
, thereby avoiding, like the first embodiment, an undesirable change in valve-opening pressure of the pressure limiter
6
.
The pressure limiter
6
in each of the first and second embodiments may also be used with a common rail fuel injection system in which the fuel stored in a common rail is injected to a diesel engine using a single fuel injector. In this case, instead of the common rail
3
, a high-pressure pipe working as an accumulator may alternatively be installed between the supply pump
2
and the injector.
The supply pump
2
used in the above embodiments is a distributor type pump designed to distribute fuel to a plurality of cylinders of the engine using a single or two pairs of plungers or less, but may alternatively be implemented by an in-line pump which has as many plungers as the cylinders of the engine and supplies the pressurized fuel through each of the plungers every turn of a cam shaft.
The valve ball
23
and the spring guide
14
may alternatively be made of a one-piece member. The housing
12
and the valve body
21
may also be of one-piece construction. Instead of the spring
13
, an air cushion, a rubber, or an elastic plate may alternatively be used to urge the valve ball
23
into constant engagement with the valve seat
24
through the spring guide
14
.
The check valve
70
is installed in the sleeve
52
of the hollow screw
16
, but may alternatively be provided in an end portion of the fuel passage
10
of the low-pressure pipe
5
connecting with the hollow screw
16
or the housing
12
.
The pressure limiter
6
in each of the first and second embodiments is joined directly to the accumulator in the common rail
3
, but however, may alternatively be installed, as shown in
FIG. 6
, between an outlet of the supply pump
2
and the low-pressure pipe
5
. In this case, the inlet (i.e., the valve hole
22
) of the pressure limiter may be connected to a downstream side of a check valve
2
a
of the supply pump
2
or an upstream side of the check valve
2
a
, as indicated by a broken line, to keep the pressure of the fuel flowing into the common rail
3
at a desired level. Further, the pressure limiter
6
may alternatively be installed, as indicated by a broken line on the right side of the drawing, between a portion of a high-pressure fuel line
90
between the outlet of the common rail
3
and the inlet of the fuel injector
4
to keep the pressure of the fuel supplied to the fuel injector
4
at a desired level.
While the present invention has been disclosed in terms of the preferred embodiments in order to facilitate better understanding thereof, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible embodiments and modifications to the shown embodiments witch can be embodied without departing from the principle of the invention as set forth in the appended claims.
Claims
- 1. An accumulator fuel injection apparatus comprising:a high-pressure supply pump pumping fuel out of a fuel tank, said high-pressure supply pump pressuring and discharging the fuel; an accumulator storing therein the fuel discharged from said high-pressure supply pump; a fuel injector injecting the fuel stored in said accumulator into an internal combustion engine; a high-pressure fuel line extending from said high-pressure supply pump to said fuel injector through said accumulator; a relief valve having an inlet communicating with said high-pressure fuel line, an outlet, and a valve mechanism disposed between the inlet and the outlet, the valve mechanism being responsive to a rise in pressure of the fuel within said high-pressure fuel line beyond a given level to establish communication between the inlet and the outlet for relieving the rise in pressure of the fuel within said high-pressure fuel line; and a pressure pulsation absorbing mechanism disposed between the valve mechanism of said relief valve and a pressure pulsation source existing downstream of the outlet of paid relief valve, said pressure pulsation absorbing mechanism working to absorb a pressure pulsation propagated from the pressure pulsation source to the valve mechanism of said relief valve; wherein said valve mechanism includes a valve body in which the inlet of said relief valve is formed and a valve member movable to open and close the inlet selectively, wherein said relief valve includes a hollow cylindrical housing having a fuel hole formed between the inlet and the outlet, wherein said pressure pulsation absorbing mechanism includes a hollow screw which is fitted in an open end of the housing as defining the outlet of said relief valve and has formed therein an orifice working to absorb the pressure pulsation to be propagated from the pressure pulsation source to the valve mechanism, and further comprising a valve-urging mechanism disposed in the fuel hole of the housing which urges the valve member to close the inlet constantly; said hollow screw includes a sleeve and a flange head, the sleeve being retained within the open end of the housing and having formed therein a longitudinal chamber communicating with the fuel hole of the housing through an end of the sleeve, the flange head being formed on an end of the sleeve opposite the housing; and said orifice is implemented by a hole formed in the sleeve which extends perpendicular to the longitudinal chamber of the sleeve, the hole being smaller in diameter than the fuel hole of the housing and the longitudinal chamber of the sleeve.
- 2. An accumulator fuel injection apparatus as set forth in claim 1, wherein said relief valve communicates at the inlet thereof with said accumulator for relieving a rise in pressure of the fuel within said accumulator beyond the given level to keep the pressure in said accumulator constant.
- 3. An accumulator fuel injection apparatus as set forth in claim 1, wherein said relief valve communicates at the inlet thereof with an outlet of said high-pressure supply pump for relieving a rise in pressure of the fuel flowing into said accumulator beyond the given level to keep the pressure of the fuel supplied to said accumulator constant.
- 4. An accumulator fuel injection apparatus as set forth in claim 1, wherein said relief valve communicates at the inlet thereof with a portion of said high-pressure fuel line extending from said accumulator to said fuel injector for relieving a rise in pressure of the fuel supplied to said fuel injector beyond the given level to keep the pressure of the fuel supplied to said fuel injector constant.
- 5. An accumulator fuel injection apparatus comprising:a high-pressure supply pump pumping fuel out of a fuel tank, said high-pressure supply pump pressuring and discharging the fuel; an accumulator storing therein the fuel discharged from said high-pressure supply pump; a fuel injector injecting the fuel stored in said common rail into an internal combustion engine; a relief valve having an inlet communicating with said high-pressure fuel line, an outlet, and a valve mechanism disposed between the inlet and the outlet, the valve mechanism being responsive to a rise in pressure of the fuel within said high-pressure fuel line beyond a given level to establish communication between the inlet and the outlet for relieving the rise in pressure of the fuel within said high-pressure fuel line; and a check valve disposed between the valve mechanism of said relief valve and a pressure pulsation source existing downstream of the outlet of said relief valve, said check valve working to block transmission of a pressure pulsation from the pressure pulsation source to the valve mechanism of said relief valve.
- 6. An accumulator fuel injection apparatus as set forth in claim 5, wherein said valve mechanism includes a valve body in which the inlet of said relief valve is formed and a valve member movable to open and close the inlet selectively, wherein said relief valve includes a hollow cylindrical housing having a fuel hole formed between the inlet and the outlet, further comprising a hollow screw which is fitted in an open end of the housing as defining the outlet of said relief valve and has disposed therein said check valve and further comprising a valve-urging mechanism disposed in the fuel hole of the housing which urges the valve member to close the inlet constantly.
- 7. An accumulator fuel injection apparatus as set forth in claim 6, wherein said check valve includes a valve body, a check valve member, and a check valve-urging mechanism, the valve body having an orifice formed downstream of the fuel hole of the housing of said relief valve in communication therewith, the check valve-urging mechanism urging the check valve member into constant engagement with the orifice of the valve body.
- 8. An accumulator fuel injection apparatus as set forth in claim 5, wherein said relief valve communicates at the inlet thereof with said accumulator for relieving a rise in pressure of the fuel within said accumulator beyond the given level to keep the pressure in said accumulator constant.
- 9. An accumulator fuel injection apparatus as set forth in claim 5, wherein said relief valve communicates at the inlet thereof with an outlet of said high-pressure supply pump for relieving a rise in pressure of the fuel flowing into said accumulator beyond the given level to keep the pressure of the fuel supplied to said accumulator constant.
- 10. An accumulator fuel injection apparatus as set forth in claim 5, wherein said relief valve communicates at the inlet thereof with a portion of said high-pressure fuel line extending from said accumulator to said fuel injector for relieving a rise in pressure of the fuel supplied to said fuel injector beyond the given level to keep the pressure of the fuel supplied to said fuel injector constant.
- 11. An accumulator fuel injection apparatus comprising:a high-pressure supply pump pumping fuel out of a fuel tank, said high-pressure supply pump pressuring and discharging the fuel; an accumulator storing therein the fuel discharged from said high-pressure supply pump; a fuel injector injecting the fuel stored in said accumulator into an internal combustion engine; a high-pressure fuel line extending from said high-pressure supply pump to said fuel injector through said accumulator; a relief valve having an inlet communicating with said high-pressure fuel line, an outlet, and a valve mechanism disposed between the inlet and the outlet, the valve mechanism being responsive to a rise in pressure of the fuel within said high-pressure fuel line beyond a given level to establish communication between the inlet and the outlet for relieving the rise in pressure of the fuel within said high-pressure fuel line, said valve mechanism including a valve body in which the inlet of said relief valve is formed and a valve member movable to open and close the inlet selectively, said relief valve including a hollow cylindrical housing having a fuel hole formed between the inlet and the outlet; and a pressure pulsation absorbing mechanism disposed between the valve mechanism of said relief valve and a pressure pulsation source existing downstream of the outlet of said relief valve, said pressure pulsation absorbing mechanism working to absorb a pressure pulsation propagated from the pressure pulsation source to the valve mechanism of said relief valve, said pressure pulsation absorbing mechanism including a hollow screw which is fitted in an open end of the housing as defining the outlet of said relief valve and has formed therein an orifice working to absorb the pressure pulsation to be propagated from the pressure pulsation source to the valve mechanism, said hollow screw including a sleeve, the sleeve being retained within the open end of the housing and having formed therein a longitudinal chamber communicating with the fuel hole of the housing through an end of the sleeve; and a valve-urging mechanism disposed in the fuel hole of the housing which urges the valve member to close the inlet constantly; wherein said orifice is implemented by a hole formed in the sleeve which extends perpendicular to the longitudinal chamber of the sleeve, the hole being smaller in diameter than the fuel hole of the housing and the longitudinal chamber of the sleeve.
Priority Claims (2)
Number |
Date |
Country |
Kind |
2000-358774 |
Nov 2000 |
JP |
|
2001-034849 |
Feb 2001 |
JP |
|
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