Fluid sprinkling – spraying – and diffusing – Unitary injection nozzle and pump or accumulator plunger – Plunger interconnected or mounted valve
Reexamination Certificate
1999-04-12
2002-05-21
Yuen, Henry C. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Unitary injection nozzle and pump or accumulator plunger
Plunger interconnected or mounted valve
C239S088000, C239S095000, C239S533400, C239S533120
Reexamination Certificate
active
06390384
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an injection device for a diesel engine, and more particularly to a unit injector for high pressure injection for a diesel engine.
BACKGROUND ART
In recent years, a unit injector for a high pressure injector for high pressure injection for a diesel engine has been strongly desired in order to improve air pollution due to the diesel engine and reduce fuel consumption. For example, in Japanese Patent No. 2524657, there is suggested a high pressure unit fuel injector provided with a variable length hydraulic link, for controlling an injection timing, and an injection pressure control valve. The fuel injector achieves improved pressure control without adversely influencing a controlled amount of a timing fluid.
FIG. 4
is a cross sectional view of a fuel injector
50
for high pressure injection described in the publication. An upper plunger
51
, subject to a drive force from a cam shaft (not shown), is closely arranged in a cylinder hole
53
in such a manner as to freely slide in a vertical direction due to an upward force by a spring
52
. A timing chamber
55
capable of changing a volume is formed between a lower end of the upper plunger
51
and an intermediate plunger
54
. A timing fluid
56
such as a fuel is supplied to the timing chamber
55
via a narrow timing fluid passage
59
formed in an injector barrel
58
. The timing fluid
56
forms a hydraulic link between the intermediate plunger
54
and the lower plunger
61
, and is preferably discharged under a certain condition via a first drain passage
62
formed in a direction of a central axis through the intermediate plunger
54
. Further, the timing chamber
55
communicates with a compensation chamber
63
via a valve mechanism
70
in a bottom portion of the first drain passage
62
. The valve mechanism
70
is held between the lower end portion of the intermediate plunger
54
and the upper end portion of the lower plunger
61
arranged within the compensation chamber
63
. When the valve mechanism
70
is opened, the timing fluid
56
flows within the compensation chamber
63
from the timing chamber
55
via the first drain passage
62
and is discharged out of the fuel injector
50
via a second drain passage
64
. The valve mechanism
70
controls a pressure of the timing fluid
56
within the timing chamber
55
, and next, the pressure controls an upper limit of the injection pressure of the fuel and a timing of the injection. The valve mechanism
70
is normally closed by application of a force due to a timing spring
65
arranged within the compensation chamber
63
and a valve spring
66
arranged within the lower plunger
61
. Further, the force of the timing spring
65
pulls up the lower plunger
61
and operates so that three plungers, comprising the lower plunger
61
, the intermediate plunger
54
, and the upper plunger
51
, are integrated until a controlled amount and a timing in the next cycle start after a completion of the injection cycle. A supply of the timing fluid
56
to the timing chamber
55
is performed through the narrow timing fluid passage
59
. The injection timing is changed in accordance with a supplied amount of the timing fluid
56
. For example, when the supplied amount is much, the injection timing is quickened. The timing spring
65
moves the lower plunger
61
upwardly a degree sufficient to feed out the fuel to an injection chamber
73
adjacent to an injection nozzle
71
.
Next, when the injection timing is established by the supply of the timing fluid
56
within the timing chamber
55
, the injected fuel flows within the injection chamber
73
via a supply orifice
75
of a fuel supply passage
74
. The injected fuel in the injection chamber
73
is accurately controlled in accordance with a known pressure/time principle. An amount of the injected fuel controlled in the above manner becomes a function of a total control time for fluid flow through the fuel supply passage
74
and a supply pressure, and the fuel supply passage
74
has a hydraulic property so as to give a control capacity having a desired pressure/time.
Here, when the upper plunger
51
is driven downwardly due to a rotation of the cam, the timing fluid
56
is returned through the timing fluid passage
59
until the timing fluid passage
59
is closed by the lower portion of the upper plunger
51
. The timing fluid
56
is trapped between the intermediate plunger
54
and the upper plunger
51
, so that a hydraulic link for integrally moving all three plunger elements toward the nozzle
71
, disposed on the bottom portion of the injection chamber
73
, is formed. During downward motion of three plunger elements, when the timing fluid pressure becomes more than a maximum predetermined pressure determined by a resultant force of the valve spring
66
and the timing spring
65
, the valve mechanism
70
is opened, so that the timing fluid
56
is discharged from the timing chamber
55
through the first and second drain passage
62
and
64
so as to reduce a pressure to conform to a predetermined limit value. Then, the supply orifice
75
of the fuel supply passage
74
is closed when the lower plunger
61
moves downwardly, so that a control of a fuel amount is finished. Further the lower plunger
61
moves downwardly, thereby injecting the controlled fuel in the injection chamber
73
from a plurality of orifices in the injection nozzle
71
within the combustion chamber (not shown).
However, the valve mechanism
70
mentioned above has a complex structure, so that a highly accurate dimension, flatness and the like are required for parts thereof. Further, since the valve mechanism
70
controls the pressure of the timing fluid
56
, there is a problem in that an amount of leakage is not fixed due to a temperature, a viscosity, and the like of the fluid, so that the pressure is not fixed.
Further, in the case wherein the injection timing is controlled by an amount (a volume) of the timing fluid
56
supplied within the timing chamber
55
, the amount of the timing fluid
56
is controlled by a magnitude of the timing fluid passage
59
and the control time. In accordance with the present publication, since the timing fluid is supplied through the timing fluid passage
59
in the form of the narrow fixed orifice, the amount of the timing fluid
56
is changed by a kind, a temperature, or a viscosity of the fluid, so that the injection timing is not fixed. On the contrary, when making the timing fluid passage
59
greater in cross-section, a range of the injection timing is narrowed. Further, when making the control time long, the volume of the timing chamber
55
is increased, so that there is a problem in that the fuel injector
50
itself becomes large.
Further, when controlling a little amount of fuel under a low rotational speed or a no load operation, it is necessary to make the timing fluid passage
59
of the fixed orifice narrow; however, when making it narrow, the control time becomes long in the case of intending to suddenly increase the fuel, so that a response of the engine is delayed. Particularly, in a vehicle having a great load change applied to the engine, such as a construction machine and the like, it is a great disadvantage that the response of the engine is delayed. Further, in the narrow fixed orifice, a dispersion (i.e., statistical variance) of the diameter thereof increases a rate of a dispersion in an area of the orifice, and increases a dispersion in the injection timing and the volume of the fuel.
In addition, the fuel to the injection chamber
73
is supplied via the supply orifice
75
in the fuel supply passage
74
. The supply orifice
75
is also required to be made narrow for controlling a little amount of fuel at a time of the low rotational speed or the no load operation. However, when being made narrow, the control time becomes long in the case of intending to suddenly increase the fuel, so that there is a problem that the response of the engine is delayed.
SUMMARY OF THE INVENTION
An object of the present in
Akagi Jiro
Sato Hiroki
Kim Christopher S.
Komatsu Ltd.
Sidley Austin Brown & Wood LLP
Yuen Henry C.
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