Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-05-18
2001-02-13
Rivell, John (Department: 3753)
Internal-combustion engines
Charge forming device
Fuel injection system
C285S386000
Reexamination Certificate
active
06186121
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a common rail and a method of manufacturing the same, which is adapted to accumulate pressure of fuel pressurized by a high-pressure pump so that the high-pressure fuel is supplied by controlling an opening and closing valve from an injection nozzle to a combustion chamber, and more specifically to a device for connecting the common rail with a piping component comprised of a branch pipe, a supply pipe, a blank plug, a pressure sensor, a pressure regulating valve, or the like, and a method therefore.
2. Description of the Prior Arts
High pressurization has being practiced in order to reduce particulates and NOx from a diesel engine. However, as the pressure of fuel is raised higher, more difficulty is encountered in control of timing of a fuel injection pump and a fuel injection nozzle of a fuel injection apparatus, particularly the timing of beginning and ending of injection. To cope with this, a method is proposed that fuel is previously pressurized by a high-pressure pump to accumulate the pressure of the pressurized fuel while providing a mechanically or electrically controlled opening and closing valve to an injection nozzle so that high-pressure fuel is supplied to a combustion chamber by controlling the opening and closing valve. A relatively thick walled metal pipe for the pressure accumulating chamber, in this case, is referred to as a common rail.
In the conventional common rail of this kind, as shown in
FIG. 4
, a thick wall pipe
1
for accumulating the pressure of high-pressure fuel has an inner peripheral surface formed with a thread
1
b
in which screw-fixed is a joint
2
having a thread provided in an outer peripheral surface at opposite ends of a cylindrical wall thereof. On the other hand, to the joint
2
is connected a piping component
3
comprised of a branch pipe or a supply pipe that has therein a flow passage for communication of high-pressure fuel to a high-pressure pump, a combustion chamber, or the like by means of a fastening nut
5
through a sleeve washer
4
. Otherwise, as shown in
FIG. 5
, a fastening nut
5
is fixed by screwing through a ball
6
onto the thread
1
a
formed in the outer peripheral surface of the thick wall pipe
1
to form a piping component comprising a blank plug. Otherwise, as shown in
FIG. 6
, for connecting with a piping component
3
comprised of a pressure sensor, a pressure regulating valve, a flow limiter, or the like, connection is made by screwing a housing
5
′ integral with the piping component
3
or a separate fastening nut onto the thread
1
a
formed at the end of the thick wall pipe
1
so that communication is done to the inside of the thick wall pipe
1
by means of a cable
8
through a reinforcing coil
7
.
With the conventional common rail, however, the number of parts is increased because of the necessity of a separate joint
2
for connection with a piping component such as a branch pipe or a supply pipe. Furthermore, since the structure is to connect both the thick wall pipe
1
and the piping component
3
to the joint
2
, screwing portions increases in number and assembling operation becomes complicate, requiring full attention to leakage at these points. Furthermore, for connecting with a piping component such as a blank plug, a pressure sensor, a pressure regulating valve, a flow limiter, or the like, the fastening nut becomes large in size, and the area of screwing portion increases, thereby requiring sufficient attention to leakage. Furthermore, the requirement of weight-lightening for components has been not met.
SUMMARY OF THE INVENTION
The present invention has been made in view of a present situation for the common rail of this kind as stated, and it is the object to provide a common rail and a manufacturing method thereof, which is simple in structure and capable of connecting a piping component to a thick wall pipe thereof in a highly sealed and light weighted manner.
In order to achieve the above object, a first embodiment of the present invention is characterized by a common rail adapted to connect a pipe component to at least one end of a thick wall pipe having a flow passage therein for accumulating pressure of high pressure fuel so that high pressure fuel is supplied from a high-pressure pump and distribute-supplied to an injection nozzle, the common rail comprising: at least one end portion of the thick wall pipe reduced in diameter by drawing; and a thread portion formed in an outer peripheral surface of the one end portion; wherein a connecting end of the piping component is connected to an end portion of the thick wall pipe by screwing a fastening screw means to the thread portion. It is preferred that the diameter-reduced portion drawing-formed in the at least one end portion of the thick wall pipe comprises a small diameter portion at a tip end and a taper portion continuous with the tip end, and a thread portion is formed in an outer peripheral surface of the small diameter portion at the tip end. The piping component comprises a branch pipe, a supply pipe, a blank plug, a pressure sensor, a pressure regulating valve or a flow limiter, and further the fastening screw means comprises a cap nut or a housing.
Also, a second embodiment of the present invention is characterized by a method of manufacturing a common rail comprising: a step of reducing a diameter by drawing at least one end portion of a thick wall pipe having therein a flow passage for accumulating pressure of high pressure fuel; a step of forming a thread portion in an outer peripheral surface at a tip end portion of the end portion; and a step of connecting a connecting end portion of a piping component to an end portion of the thick wall pipe by screwing a fastening screw means to the thread portion. In this case, it is preferred that the diameter-reducing forming is carried out by rolling, swaging or pressing, and further machine cutting or varnishing is made to an inner peripheral surface of the flow passage of the thick wall pipe.
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Kato Nobuo
Uematsu Tadahiro
Casella Anthony J.
Hespos Gerald E.
Porco Michael J.
Rivell John
Usui Kokusai Sangyo Kaisha Limited
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