Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2000-08-31
2001-04-10
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S300000
Reexamination Certificate
active
06213098
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority of Japanese Patent Applications No. H.11-245639 filed on Aug. 31, 1999, No. H.11-308951 filed on Oct. 29, 1999 and No. 2000-36678 filed on Feb. 15, 2000, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel injection device in which fuel may be stepwise injected.
2. Description of Related Art
Conventionally, in a fuel supply system in which fuel is supplied from a high pressure supply pump to an injector that is a fuel injection device, a technology that a needle lift is varied by a value of fuel pressure to change its injection characteristic has been proposed. Injection rate, atomization density and distribution behavior of fuel affect largely on fuel ignitability, formation of NOx, black smoke, HC and the like and combustion efficiency.
For example, well known is a nozzle with two-stage valve opening pressure that has two springs for biasing a needle with a predetermined needle lift interval. According to this technology, the needle lifts due to pressure of fuel delivered by a fuel injection pump. However, a value of pressure of fuel delivered to the fuel injection device from the fuel injection pump becomes variable according to engine operations. Therefore, it is difficult to always realize an optimum injection rate demanded by the engine over an entire range of engine operations.
To cope with this problem, an injector
230
, as disclosed in U.S. Pat. No. 5,694,903 and shown in
FIG. 42
, is known. The injector
230
is provided with a control chamber
260
by which fuel pressure is applied to a needle
231
in a direction of closing an injection hole. A lift of the needle
231
is controlled by making a force acting in a direction of opening the injection hole due to fuel pressure transmitted to a fuel accumulating space
232
larger or smaller than a sum of forces receiving in a direction of closing the injection hole due to the fuel pressure of the control chamber
260
and biasing force of a spring
237
. Even if the fuel pressure is varied according to the engine operations, regulating pressure of the control chamber
260
accurately controls an opening and closing timing by the needle
231
.
Further, a lift of a pilot valve stem
270
is controlled with two steps by biasing forces of two springs
290
for urging the pilot valve stem
270
in a direction of closing the control chamber
260
and an attracting force of a coil
274
. As a result, it is intended that the needle
231
is stepwise lifted to secure a predetermined fuel injection rate.
However, the conventional fuel injection device has a drawback that, even if the stem
270
is stepwise lifted, the needle is not always stepwise lifted simultaneously with the stem
270
, since the needle
231
is lifted when a value of the fuel pressure of the fuel accumulating space
232
exceeds a sum value of pressure of the control chamber
260
and biasing force of the spring
237
. Further, if the electromagnetic attracting force of the coil
274
is varied due to, for example, a change of temperature, a lifting characteristic of the stem
270
such as an opening area characteristic of the stem
270
is forced to change. Furthermore, due to a characteristic change of fuel such as viscosity, the pressure of the control chamber
260
is changed unstably. Accordingly, a lifting characteristic of the needle
231
is also changed so that the fuel injection rate may become unstable. Moreover, since a lifting control amount of the stem
270
is very small, it is difficult to secure a uniform quality in each of the injectors
230
so that an accurate and stable injection control may not be realized.
In the conventional fuel injection devices, though the injection rate may be variably controlled so far, it is impossible to realize a variable control of fuel atomization event such as atomization angle and droplets reaching distance.
Inadequate control of the atomization event causes to harm fuel consumption and an output so that NOx, black smoke, HC and the like may be more formed.
Further, as shown in JP-A-10-54323, well known is a fuel injection valve in which control valves are arranged at an inlet portion through which high pressure is introduced to the control chamber and at an outlet portion through which high pressure is released from the control chamber, respectively. With the plurality of control valves, the lift of the needle is stepwise controlled to obtain the stable lift control, while the leak amount can be reduced, since respective opening and closing controls of the inlet and outlet of the control chamber can be independently controlled.
However, the injection valve mentioned above still has a drawback that the valve becomes larger and is expensive since pluralities of electromagnetic valves are necessary.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fuel injection device in which fuel injection events may be accurately controlled according to engine conditions and the formation of NOx, black smoke and HC may be limited to improve the fuel consumption and the output.
To achieve the object, the injection device is composed of a valve member slidably movable in a valve body to open and close an injection hole, a high pressure fuel passage for generating a basic fuel pressure force to urge the valve member in a direction of opening the injection hole, fuel passages communicated with the high pressure fuel passage and to be communicated with a low pressure fuel conduit, control valve means disposed in the fuel passages, biasing means for generating a biasing force to urge the valve member in a direction of closing the injection hole, and a plurality of control chambers disposed in the fuel passages.
The respective plurality of control chambers are communicated with the high pressure passage when the control valve means is not actuated and respective fuel pressure in the plurality of control chambers are used as chamber fuel pressure forces to urge the valve member in a direction of closing the injection hole, and the respective control chambers are communicated one after another at different timings to the low pressure conduit to reduce fuel pressure therein when the control valve means is actuated.
With the device mentioned above, the valve member may be stepwise lifted to achieve variable fuel injection rate by controlling one after another at different timings the chamber fuel pressure force from selected any one of the plurality of control chambers that is applied to the valve member in order to change a force balance with the basic fuel pressure force and the biasing force that are then applied to the valve member.
According to the fuel injection device mentioned above, even if fuel pressure to be introduced into the device is varied according to engine operating conditions, a timing of the valve member for opening and closing the injection hole may be accurately controlled.
It is preferable for the accurate stepwise lifting of the valve member that the biasing means comprises a first biasing element for generating first biasing force to urge the valve member in a direction of closing the injection hole irrelevantly to a lifting amount of the valve member and a second biasing element for generating second biasing force to urge the valve member in a direction of closing the injection hole after the valve member has established a predetermined lifting amount.
Preferably, the valve member comprises a needle to be seated on the valve seat and a transmitting element provided on an opposite side to the injection hole with respect to the needle for transmitting the biasing force and the chamber fuel pressure forces of the plurality of control chambers to the needle. The transmitting element may be an element integrated into one body having a plurality of cross sectional areas, whose largeness are different from each other, for receiving respective fuel pressure from the plurality of co
Kato Masaaki
Sasaki Satoru
Denso Corporation
Miller Carl S.
Nixon & Vanderhye P.C.
LandOfFree
Fuel injection device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fuel injection device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuel injection device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2484347