Information
-
Patent Grant
-
6802300
-
Patent Number
6,802,300
-
Date Filed
Friday, December 6, 200221 years ago
-
Date Issued
Tuesday, October 12, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 450
- 123 506
- 123 459
- 123 462
- 123 510
- 123 511
- 123 514
-
International Classifications
-
Abstract
A lift-controlled valve as a fuel metering device of an injection system for internal combustion engines has a valve needle which may be actuated axially against the resistance of a spring, the valve needle being situated in a graduated coaxial recess in a valve body and interacting with a valve seat formed in the recess of the valve body in this case controlling the fuel injection process; the valve has in addition a high-pressure area which is connected to an assigned injection nozzle and which is located upstream from the valve seat, a low-pressure area which is located downstream from the valve seat and which opens out into a fuel return flow, and a low-pressure equalizing piston which coaxially adjoins the valve and which is fixedly connected to the valve needle. The characterizing feature is that a first control edge is formed on the low-pressure equalizing piston, the control edge interacting with a second control edge on the valve body recess in the area of the fuel return flow or in such a way that a throttle cross-section which is dependent on the valve lift is formed between the two control edges.
Description
FIELD OF THE INVENTION
The present invention relates to a lift-controlled valve.
BACKGROUND INFORMATION
The valve seat of the fuel metering device of modem valve-controlled fuel injection systems, diesel injection systems in particular, is exposed to a very high thermal load. Opening the valve completes the injection and the fuel under high pressure is diverted into the return flow via the open valve seat. The pressure energy of the fuel is for the most part converted into thermal energy. This results in the fuel and the surrounding components being very severely heated. Severe thermal expansions of the components resulting from this change the working clearances of the moved components to a corresponding degree. At the same time, the leakage characteristics are changed and accordingly the entire function of the injection system. In an extreme case, the working clearance between the moved components may be reduced to zero. The consequence is jamming or wear in the form of welding of the moved components, resulting in a complete failure of the injection system.
Known high-pressure valves of diesel injection systems have a low-pressure equalizing piston located in the low-pressure area in the cutoff flow direction downstream from the valve seat, the purpose of the low-pressure equalizing piston being to avoid pressure surges on the bottom of the valve needle which occur during valve switching operations.
Such undesirable pressure surges would otherwise bring about a malfunction of the valve needle movement caused by undefined forces. In known valves of the type under discussion, the low-pressure equalizing piston forms an annular gap between the valve needle and the valve body, the angular gap developing a permanent, unchangeable throttling effect, as a result of which a consistent quantity of fuel is withdrawn from the injection system.
The overflow quantity flowing off through the annular gap is continuously replaced by fuel flowing back into the cutoff area (low-pressure area), the fuel thus cooling the high-pressure and filling area of the injection system. The fuel permanently withdrawn via the annular gap flows back into the fuel tank via the return flow.
The object of the present invention is to improve the cooling effect while retaining the total overflow quantity.
SUMMARY OF THE INVENTION
According to the present invention, the object is achieved in a lift-controlled valve.
The present invention is based on the idea of draining an increased fuel quantity from the cutoff area into the return flow via the annular gap under discussion when, and only when, the fuel in the cutoff area has been heated to a maximum. This is the case immediately after the opening of the valve seat and the associated cutoff of the fuel under high pressure. This results in an improved cooling of the filling area and cutoff area and a simultaneous increase in the efficiency of the entire injection system.
In addition, the improved cooling reduces the introduction of heat into the components of the valve and thus minimizes the thermal expansion of the components. As a result it is accordingly possible to improve the functional reliability since the working clearances of the moved components of the valve remain more dimensionally stable in operation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
shows a lift-controlled valve (according to the related art), i.e., with an annular gap acting as a constant throttle, in a vertical longitudinal section and greatly enlarged.
FIG. 2
shows an embodiment of the lift-controlled valve according to the present invention in a (partial) depiction according to FIG.
1
.
FIG. 3
shows another embodiment of the lift-controlled valve according to the present invention in a depiction according to FIG.
2
.
DETAILED DESCRIPTION
The reference symbol
10
denotes a valve body and
11
denotes a valve needle of a lift-controlled valve as a fuel metering device of an injection system for internal combustion engines. Valve body
10
is integrated in a pump body
12
of an injection pump (which is otherwise not shown). Valve needle
11
is arranged to be movable in axial direction
14
in a coaxial recess
13
in valve body
10
, the diameter of the coaxial recess changing a plurality of times. An upper area of recess
13
identified as
15
is used as a guide bore for valve needle
11
.
A valve cone
16
is formed on valve needle
11
, the valve cone interacting with a valve seat
17
which is incorporated into valve body
10
, i.e., into recess
13
.
Valve cone
16
and valve seat
17
form a lift-controlled valve for directing the high-pressure fuel stream to an assigned (not shown) injection nozzle of the fuel injection system. For this purpose, recess
13
is expanded into a pressure chamber
18
in the area of valve cone
16
and valve seat
17
, fuel under high pressure being delivered to pressure chamber
18
via channels
19
,
20
. Fuel is distributed to the injection nozzle (not shown) via a distributor slot
21
.
Valve cone
16
is adjoined by a low-pressure equalizing piston which is joined in one piece with valve needle
11
and identified in its entirety as
22
, a compression spring
24
applying force axially (in direction of arrow
25
) to (lower) face
23
of low-pressure equalizing piston
22
. In the opposite direction, compression spring
24
is supported on bottom
27
of recess
13
via a disk
26
.
A shaped area
28
of recess
13
below valve seat
17
functions as a low-pressure area and is connected hydraulically to a return flow
30
extending in the area of compression spring
24
via an annular gap
29
between low-pressure equalizing piston
22
and recess
13
. From return flow
30
, the fuel is returned to the fuel tank (not shown) via channels
31
and
32
in valve body
10
and in pump body
12
, respectively.
Valve
16
,
17
is actuated at upper end
33
of valve needle
11
in direction of arrow
34
, i.e., against the resistance of compression spring
24
. A pressure magnet may be used, for example, as an actuating element of valve needle
11
, the design and function of the pressure magnet being known, for which reason it is not shown.
Given the structural and hydraulic conditions described above, a fuel metering device of this type operates as follows. In order to deliver fuel under high pressure to the assigned injection nozzle (not shown), valve cone
16
is in contact with valve seat
17
, the valve thus being closed. Opening valve
16
,
17
terminates the injection process. The fuel located under high pressure in pressure chamber
18
now flows into low-pressure area
28
of recess
13
via open valve seat
17
, the fuel expanding and most of its pressure energy being converted into thermal energy. A portion of the heated fuel reaches return flow
30
via annular gap
29
and from there it is returned to the fuel tank (not shown) via channels
31
,
32
. The fuel quantity drained off via annular gap
29
is replaced by a corresponding quantity of fuel having a cool temperature which is delivered to low-pressure area
28
via channels
35
,
36
which are connected hydraulically by an annular channel
37
. The hot fuel remaining in low-pressure area
28
is cooled correspondingly as are the components of the valve surrounding low-pressure area
28
.
A disadvantage in the design according to
FIG. 1
is the fact that angular gap
29
—irrespective of the respective position of valve needle
11
—always has a constant cross-section so that it operates only as a constant throttle.
The embodiments according to the present invention according to
FIGS. 2 and 3
create an effective remedy. For the sake of clarity, the components in
FIGS. 2 and 3
corresponding to the design according to
FIG. 1
are identified with the same reference symbols as in FIG.
1
.
The embodiment according to
FIG. 2
of the lift-controlled valve according to the present invention is distinguished from the design according to
FIG. 1
by a valve-needle lift-controlled cross-section
38
or
38
a
which is defined by a first control edge
39
on low-pressure equalizing piston
22
, which is joined in one piece with valve needle
11
, and by a second control edge
40
on valve body
10
.
Control edges
39
,
40
are precisely positioned with respect to valve cone
16
and valve seat
17
, respectively, so that a throttle cross-section dependent on valve lift
41
is formed between control edges
39
,
40
. This is made apparent by comparing throttle cross-sections
38
and
38
a
with valve
16
,
17
open (right half of
FIG. 2
) and with valve
16
,
17
closed (left half of FIG.
2
). Accordingly, throttle cross-section
38
attains a maximum with valve
16
,
17
open, while it is reduced to a minimum
38
a
with valve
16
,
17
closed. The throttle cross-section (
38
, with valve
16
,
17
open) is first determined by the axial spacing of the two control edges
39
and
40
. If the two control edges
39
,
40
finally overlap—with movement of the valve needle in the closing direction, the throttle cross-section is now determined by an annular gap (see reference symbol
38
a
, with valve
16
,
17
closed, left half of
FIG. 2
) extending between the circumferential surface of low-pressure equalizing piston
22
—at
44
—and the circumferential surface of recess
13
in drain area
45
.
With valve
16
,
17
open, it is thus possible to drain off a substantially larger quantity of heated fuel from low-pressure area
28
via throttle cross-section
38
into return flow
30
than with valve
16
,
17
closed. Correspondingly, it is possible to deliver a considerably larger quantity of cool fuel to low-pressure area
28
with valve
16
,
17
open than with valve
16
,
17
closed, as a result of which the cooling effect with respect to the components surrounding low-pressure area
28
is changeable corresponding to the current demand.
In the embodiment according to
FIG. 3
a first control edge
42
is formed on low-pressure equalizing piston
22
and a second control edge
43
is formed on valve body
10
. In contrast to the embodiment according to
FIG. 2
, first control edge
42
faces valve cone
16
while second control edge
43
faces away from valve seat
17
. In this case also, the throttle cross-section (
46
, in this case with valve
16
,
17
closed) is first determined by the axial spacing of the two control edges
42
,
43
.
If valve needle
11
(and thus also low-pressure equalizing piston
22
correspondingly) moves into the open position of valve
16
,
17
(see right half in FIG.
3
), control edges
42
,
43
overlap. Throttle cross-section
46
a
is determined in this case by the circumferential surface of low-pressure equalizing piston
22
—at
47
—and the circumferential surface of recess
13
in drain area
48
, thus representing a narrow annular gap. In the embodiment according to
FIG. 3
, a substantially larger quantity of heated fuel is drained off from low-pressure area
28
into return flow
30
via throttle cross-section
46
with valve
16
,
17
closed than with valve
16
,
17
open, which is the reverse of the case with the embodiment according to FIG.
2
. Correspondingly, it is possible to deliver a considerably larger quantity of cool fuel to low-pressure area
28
with valve
16
,
17
closed than with valve
16
,
17
open.
The variant that is advantageous (the embodiment according to
FIG. 2
or the embodiment according to
FIG. 3
) depends on the pressure characteristic and the switching characteristics of the valve in the specific individual case.
In both cases, valve-needle lift-controlled low-pressure cross-section
38
or
46
(be it according to
FIG. 2
or
FIG. 3
) makes it possible to withdraw in a targeted manner the hot fuel cutoff quantity from the filling and cutoff space (low-pressure area
28
) into return flow
30
. Valve-needle lift-controlled overlap length
38
a
(
FIG. 2
) or
46
a
(
FIG. 3
) forms a lift-controlled throttle by the resulting annular gap between valve needle
11
and valve body
10
. It is possible to coordinate both valve-needle lift-controlled cross-sections (
38
and
46
) to the switching characteristics of the valve in such a way that the maximum cooling of the filling and cutoff area (low-pressure area
28
) is achieved with minimum leakage into return flow
30
.
Claims
- 1. A lift-controlled valve as a fuel metering device of an injection system for an internal combustion engine, comprising:a valve body having a graduated coaxial recess; a valve seat formed in the graduated coaxial recess; a spring; a valve needle that is actuated axially against a resistance of the spring, the valve needle being situated in the graduated coaxial recess and interacting with the valve seat in order to control a fuel injection process; a high-pressure area connected to an assigned injection nozzle and located upstream from the valve seat; a low-pressure area located downstream from the valve seat opening out into a fuel return flow; and a low-pressure equalizing piston that coaxially adjoins the valve, the low-pressure equalizing piston being fixedly connected to the valve needle, wherein: a first control edge is formed on the low-pressure equalizing piston, the first control edge interacts with a second control edge on the graduated coaxial recess in an area of the fuel return flow in such a way that a throttle cross-section that is dependent on a lift is formed between the first control edge and the second control edge, and the first control edge and the second control edge are coordinated in such a way that the throttle cross-sectional area reaches a maximum value with the valve closed and a minimum value with the valve open.
- 2. The lift-controlled valve according to claim 1, wherein:the low-pressure equalizing piston includes a collar of an enlarged diameter, on a lower side of which facing away from the valve seat the first control edge is formed, and the graduated coaxial recess includes a graduated narrowing of the enlarged diameter, on an upper end of which facing the valve seat the second control edge is formed.
- 3. The lift-controlled valve according to claim 1, wherein:the throttle cross-section is determined by a gap height between the first control edge and the second control edge at an end position of the valve needle and by an annular gap at another end position of the valve needle.
- 4. The-lift-controlled valve according to claim 3, wherein:annular gap is located at an overlap of a circumferential surface of a collar of the low-pressure equalizing piston with an internal circumference of a drain area of the valve body.
- 5. A lift-controlled valve as a fuel metering device of an injection system for an internal combustion engine, comprising:a valve body having a graduated coaxial recess; a valve seat formed in the graduated coaxial recess; a spring; a valve needle that is actuated axially against a resistance of the spring, the valve needle being situated in the graduated coaxial recess and interacting with the valve seat in order to control a fuel injection process; a high-pressure area connected to an assigned injection nozzle and located upstream from the valve seat; a low-pressure area located downstream from the valve seat opening out into a fuel return flow; and a low-pressure equalizing piston that coaxially adjoins the valve, the low-pressure equalizing piston being fixedly connected to the valve needle, wherein: a first control edge is formed on the low-pressure equalizing piston, the first control edge interacts with a second control edge on the graduated coaxial recess in an area of the fuel return flow in such a way that a throttle cross-section that is dependent on a lift is formed between the first control edge and the second control edge, and the first control edge and the second control edge are coordinated in such a way that the throttle cross-sectional area reaches a minimum value with the valve closed and a maximum value with the valve open.
- 6. The lift-controlled valve according to claim 5, wherein:the low-pressure equalizing piston includes a collar of an enlarged diameter, on an upper side of which facing the valve seat the first control edge is formed, and the graduated coaxial recess includes a graduated narrowing of the enlarged diameter, on a lower end of which facing away from the valve seat the second control edge is formed.
Priority Claims (1)
Number |
Date |
Country |
Kind |
100 59 424 |
Nov 2000 |
DE |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/DE01/04306 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO02/44548 |
6/6/2002 |
WO |
A |
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