Fluid sprinkling – spraying – and diffusing – Including valve means in flow line – Reciprocating
Reexamination Certificate
2002-08-05
2004-09-21
Mar, Michael (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Including valve means in flow line
Reciprocating
C239S533200, C239S585500
Reexamination Certificate
active
06793161
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a needle lift damper device in an injector for fuel injection, and a needle lift damping method. In particular, it relates to a device and method for damping needle valve lift in order to decrease the initial injection rate of a common rail injector in a diesel engine.
BACKGROUND ART
FIG. 4
shows an outline of a common rail-type fuel injection device in a diesel engine. As shown in the drawing, in this device, fuel within a fuel tank
1
is supplied to a high-pressure pump
4
through a filter
2
and a feed pump
3
. After being pressurized to a high pressure (tens to hundreds of MPa) by the high-pressure pump
4
, the fuel goes through a passage
5
and is stored in an accumulator called a common rail
6
. The fuel inside the common rail
6
is supplied to each injector
8
through a fuel supply passage
7
.
As shown in
FIG. 5
, a portion of the high-pressure fuel that is supplied to each injector
8
is supplied to a pressure control chamber
10
through a passage
9
and the remaining portion is supplied through a passage
11
to a fuel puddle
13
at the tip of a needle valve
12
. The fuel pressure inside the pressure control chamber
10
is maintained and released by a relief valve
14
. The relief valve
14
is depressed by a conventional spring
15
and closes a relief hole
16
, maintaining the fuel pressure in the pressure control chamber
10
. When an electromagnetic solenoid
17
is driven by an electric current, the relief valve
14
resists the spring
15
and is lifted up, thereby opening the relief hole
16
and releasing the fuel pressure in the pressure control chamber
10
. Further, the needle valve
12
is constantly forced downwards by a spring
18
.
In such injectors
8
, when the electric current to the electromagnetic solenoid
17
is turned off, the relief hole
16
is closed by the relief valve
14
that is pressed down by the spring
15
; and since the fuel pressure in the pressure control chamber
10
is maintained, the downward force on the needle valve
12
created by such fuel pressure and the spring
18
becomes greater than the upward force thereon created by the fuel pressure in the pressure-receiving portion
19
at the tip (fuel puddle
13
) of the needle valve
12
; and accordingly the needle valve
12
moves downward. Consequently, a conical portion
20
at the tip of the needle valve
12
is mounted to a seat
21
, closing a spray hole
22
of the injector
8
so that fuel injection does not occur. thereon created by the fuel pressure in the pressure-receiving portion
19
at the tip (fuel puddle
13
) of the needle valve
12
; and accordingly the needle valve
12
moves downward. Consequently, a conical portion
20
at the tip of the needle valve
12
is mounted to a seat
21
, closing a spray hole
22
of the injector
8
so that fuel injection does not occur.
Further, when the electromagnetic solenoid
17
is driven by an electric current, the relief valve
14
resists the spring
15
and is lifted up; and since the relief hole
16
is opened and the fuel pressure in the pressure control chamber
10
is released, the upward force on the needle valve
12
created by the fuel pressure in the pressure receiving portion
19
at the tip (fuel puddle
13
) of the needle valve
12
becomes greater than the downward force thereon created by the fuel pressure and the spring
18
; and accordingly the needle valve
12
lifts upward. Consequently, the conical portion
20
at the tip of the needle valve
12
becomes detached from the seat
21
and high pressure fuel is injected from the spray hole
22
of the injector
8
. Note that the fuel flowing out of the pressure control chamber
10
is returned to the fuel tank
1
through a fuel return passage
23
(See FIG.
4
).
In the above-mentioned injector
8
, it is desirable that the needle valve
12
is made to lift upward comparatively smoothly (slowly). If the needle valve
12
is made to lift upwards comparatively smoothly, the initial injection rate of the fuel injected from the spray hole
22
decreases, and since the first ignition after an ignition delay occurs with a low injection rate and a small amount of fuel, a smooth first ignition can be guaranteed, resulting in less NOx emitted and a decrease in noise.
FIG. 6
shows an injector that is known to lift the needle valve
12
comparatively slowly (for example, Japanese Patent Application Laid-open No. S59-165858). Note that since this injector
8
a
has some constituent parts that are the same as the previously mentioned injector
8
, identical reference numerals are used for the same constituent parts, and explanations are omitted. Only the different parts are explained.
In the injector
8
a
shown in
FIG. 6
, a member
24
is attached to the upper end of the needle valve
12
, and the pressure control chamber
10
is formed above the member
24
. The relief hole
16
is formed on the ceiling of the pressure control chamber
10
. A seat
25
that is in a raised position is formed around the relief hole
16
. The relief hole
16
is opened and closed by the relief valve
14
, having an orifice hole
26
in its center, when it mounts to and disengages from the seat
25
.
The relief valve
14
is pressed onto the seat
25
by a conventional spring
27
, thereby closing the relief hole
16
; and when fuel is supplied from a three-way valve
28
, due to the fuel pressure, the relief valve
14
resists the spring
27
and is pushed downward, opening the relief hole
16
. The three-way valve
28
is positioned in the passage
9
leading from the common rail
6
(see
FIG. 4
) to the pressure control chamber
10
and is switched over as appropriate between a state where X-Y are linked to each other and a state where Y-Z are linked to each other.
FIG. 6
shows the state when fuel injection has ceased. At this time, X-Y are linked to each other, the relief valve
14
is mounted to the seat
25
, and the downward force on the needle valve
12
created by the fuel pressure inside the pressure control chamber
10
and the spring
18
is greater than the upward force thereon created by the fuel pressure in the fuel receiving portion
19
at the tip (fuel puddle
13
) of the needle valve
12
. Consequently, the needle valve
12
moves downward and the conical portion
20
is mounted to the seat
21
, closing the spray hole
22
so that fuel injection does not occur. From this state, when the three-way valve
28
operates so that Y-Z are linked to each other, since the fuel in the pressure control chamber
10
is gradually squeezed from the orifice hole
26
in the relief valve
14
and flows out, the fuel pressure in the pressure control chamber
10
decreases at a smooth pace and the needle valve
12
lifts upward comparatively slowly. In this way lift damping of the needle valve is achieved and the initial injection rate from the spray hole
22
is decreased.
Subsequently, when the three-way valve
28
operates so that X-Y are linked to each other for a second time, since the fuel in the common rail
6
flows through passages
7
and
9
in a high-pressure state into the pressure control chamber
10
, the relief valve
14
resists the spring
27
and is depressed due to the fuel pressure. The fuel flows into the pressure control chamber
10
in one burst and the fuel pressure in the pressure control chamber
10
rises at once, so the needle valve
12
moves downward rapidly. Consequently, the injection cut-off of the fuel injected from the spray hole
22
is improved.
However, in the above-mentioned injector
8
a,
since damping the lift of the needle valve
12
is achieved by mounting the relief valve
14
to the seat
25
as well as making the fuel in the pressure control chamber
10
leak out while being squeezed from the orifice hole
26
, disturbance in the leak flow that occurs at the time of leakage from the orifice hole
26
can cause the relief valve
14
to vibrate and momentarily become dislodged from the seat
25
.
When this occurs, since the fuel in the pressure control chamber
10
l
Breitbach Hermann
Fujita Mahoro
Minato Akihiko
Nishimura Terukazu
Takase Shigehisa
Bui Thach H.
Isuzu Motors Limited
Mar Michael
McCormick Paulding & Huber LLP
LandOfFree
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