Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
2002-02-26
2003-11-04
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C251S129150
Reexamination Certificate
active
06640788
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based on and incorporates by reference Japanese Patent Application No. 2001-54486 filed on Feb. 28, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
Embodiment of the present invention relate to a high pressure fuel pump used for a gasoline engine and a diesel engine in which fuel is directly injected into a cylinder and is burned. In particular, at least one embodiment of the invention relates to a high pressure fuel pump provided with a flow amount control valve capable of controlling the flow amount of a high pressure fuel supplied to a delivery pipe such as a common rail (high pressure accumulation pipe), or the like.
2. Description of the Related Art
In recent years, gasoline and diesel engines are required to satisfy not only high power, low noise, and low fuel consumption requirements but also rigorous emission regulations. In order to meet these requirements, attention has been paid to a direct injection type gasoline engine and a direct injection type diesel engine in which the injection timing and the injection amount of the fuel are controlled with high accuracy. Usually in these engines, the fuel is drawn from a fuel tank by a low pressure fuel pump and is further pressurized by a high pressure fuel pump and supplied to a delivery pipe such as a common rail or the like and is directly injected into cylinders through injectors connected to the delivery pipe.
In order to control the injection timing and the injection amount of the fuel with high accuracy, the injectors and the high pressure fuel pump are electronically controlled. Such a high pressure fuel pump electronically controls the fuel supply amount to the delivery pipe according to the injection amount of the injectors. This is unlike a fuel injection pump in the related art for controlling the flow amount of the fuel by adjusting the positional relationship between a reed provided on a plunger and an intake/exhaust port. To be more specific, by controlling the timing of overflowing the fuel in a pump chamber to a low pressure side, the supply amount of the fuel compressed and discharged to the delivery pipe by the plunger is adjusted to keep a fuel pressure in the delivery pipe at a predetermined pressure.
Here, as to the flow amount control valve which is important in controlling the flow amount of the high pressure fuel pump, various propositions have been made and among them, a pilot type flow amount control valve capable of reducing cost is disclosed in JP-A No. 8-49617 and JP-A No. 2000-186649.
A solenoid spill valve
20
disclosed in the JP-A No. 8-49617 is a pilot type inwardly opening (solenoid) valve comprising a needle valve
4
for opening/closing a seat plane
12
provided in the overflow passage of the fuel and a moving member
6
for driving the needle valve
4
. Here, the numerals in the parentheses denote the reference numerals shown in
FIG. 1
in the official gazette. In the solenoid spill valve
20
, a fuel inlet passage
11
, which is to be an overflow passage, is made to communicate with a hydraulic chamber
8
provided on the back of the needle valve
4
by a slim pressure introduction passage
16
. However, since the moving member
6
moves in the hydraulic chamber
8
of a small volume, a pressure pulsation is caused and is propagated through the pressure introduction passage
16
with a time lag and causes variations in the response of the needle valve
4
. Further, the pressure introduction passage
16
is provided with an orifice
14
. In order to eliminate the pressure pulsation causing the variations in the response of the needle valve
4
, the diameter of the orifice
14
needs to be made considerably small, or conversely, the diameter of the pressure introduction passage
16
needs to be made considerably large, which is not realistic in either case because of manufacturing costs.
The high pressure fuel pump
1
disclosed in JP-A No. 2000-186649 has a pilot type outwardly opening (solenoid) valve comprising an intake valve
30
for opening/closing a valve seat
34
provided in the fuel overflow passage and a control valve
50
for driving the intake valve
30
. Here, the numerals in the parentheses denote the reference numerals shown in
FIG. 2
in the official gazette. In the control valve
50
, the fuel in a control chamber
45
provided on the head
48
of the intake valve
30
flows in or out to temporarily make the control chamber
45
a rigid body thereby controlling the opening/closing of the valve seat
34
by the intake valve
30
. Also in this case, since the volume of the control chamber
45
is small, the volume of the control chamber
45
fluctuates substantially by the operation of the control valve
50
, and a large pressure pulsation caused by the fluctuation of the volume of the control chamber
45
is propagated to a fuel well
24
through a communication passage
46
. It is then propagated to a pump chamber
16
in which the valve seat
34
is arranged through an insertion hole
35
to cause variations in the response of the intake valve
30
, which might cause the deterioration of controllability.
Here, as to a valve structure, a “pilot type valve” means a valve part abutting against a valve seat surface is separated from a driving part, and an “inwardly opening valve” means a valve in which the seat surface of a port is disposed on the driving part side (inside) and in which the valve part is opened inwardly. The “outwardly opening valve” means a valve in which the seat surface of a port is disposed on the side opposite to the driving part (outside) and which the valve part is opened outwardly. These descriptions are used throughout the specification and are meant to have the same meaning.
SUMMARY OF THE INVENTION
The present invention has been made in view of these circumstances. It is an object of at least one embodiment of the present invention to provide a high pressure fuel pump having a flow amount control valve of excellent controllability which can suppress the effect of a pressure pulsation caused by the operation of a driving part (moving member) and whose valve shows stable response.
Thus, the present inventor has conducted research to solve the problem described above, and has discovered an idea for making a flow amount control valve of a pilot valve type, that is, an outwardly opening valve. Additionally discovered is a way of increasing the rate of the total volume of an operating chamber, in which the moving member is disposed, to accommodate the variable volume thereof, and thus has achieved a high pressure fuel pump of the present invention.
That is, a high pressure fuel pump in accordance with an embodiment of the present invention is characterized as a high pressure fuel pump including a pump body having a pump chamber formed in such a way as to communicate with a low pressure fuel passage connected to the supply source of a low pressure fuel and a high pressure fuel passage for supplying a high pressure fuel to an injector side. Additionally, a plunger is fitted into the pump chamber and supplied with a driving force from a driving source to slidably move back and forth in the pump chamber thereby to draw and discharge fuel. Also provided is a flow amount control valve for adjusting the flow amount of the high pressure fuel to the high pressure fuel passage by opening or closing a spill port provided in the overflow passage of the fuel which communicates with the pump chamber. The flow amount control valve has a valve body having an operating chamber which is formed on the side opposite to the pump chamber with respect to the spill port and communicates with the overflow passage. A valve part exists which is urged in the direction that seats the valve part on a valve seat formed on the pump chamber side of the spill port and which is separated from or seated on the valve seat to open or close the spill port. Furthermore, there is a moving part which is separated from the valve part and disposed in the operating chamber and electromagnetically controls the opening or
Inoue Hiroshi
Oguri Tatsumi
Denso Corporation
Moulis Thomas N.
Nixon & Vanderhye P.C.
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