Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-04-14
2001-11-06
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S496000
Reexamination Certificate
active
06311674
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to a fuel injection system for internal combustion engines designed to control a fuel discharge from a fuel injection pump by regulating the quantity of fuel sucked into the fuel injection pump.
2. Background Art
U.S. Pat. No. 4,492,534 (Japanese Patent First Publication No. 59-65523) teaches a fuel injection system which has a metering valve disposed in a fuel feed line between a feed pump and a fuel injection pump and controls an on-off duration in which the metering valve is turned on and off cyclically to regulate the quantity of fuel sucked into the fuel injection pump. The metering valve is switched between a fully opened position and a fully closed position. The ratio of a change in sucked quantity of fuel to a change in on-duration in which the metering valve is opened is, thus, increased as the on-duration is prolonged, which leads to difficulty in controlling the quantity of fuel supplied to the fuel injection pump accurately by changing the on-duration of the metering valve.
Usually, the fuel injection pump sucks the fuel in synchronism with rotation of the engine. An increase in engine speed, thus, causes the length of time the fuel injection pump sucks the fuel to be decreased. Switching between the fully opened position and the fully closed position of the metering valve consumes the response time inherent to the metering valve. Therefore, for instance, when the engine is operating at high speeds and high loads, and it is required to increase the quantity of fuel discharged from the fuel injection pump, it will cause the switching between the fully opened position and the fully closed position of the metering valve to become fast, thus resulting in difficulty in controlling the quantity of fuel sucked into the fuel injection pump if the response rate of the metering valve is low.
This problem may be alleviated by elevating the voltage for energizing the metering valve to increase the response rate thereof. This is, however, impractical because of increase in manufacturing cost.
The adjustment of quantity of fuel supplied to the fuel injection pump may alternatively be achieved by changing an opening area of the metering valve. In typical distributor type fuel injection pumps, the current supplied to a timing control valve is controlled to regulate an opening area of the timing control valve in order to control the fuel injection timing. This technique may be employed to regulate the quantity of fuel sucked into the fuel injection pump.
However, when the engine is operating at low speeds, it will cause the length of time the fuel injection pump sucks the fuel to be increased. Therefore, a ratio &Dgr;q/&Dgr;L of a change in quantity of fuel discharged from the metering valve to a change in opened area of the metering valve, as shown in
FIG. 16
, increases as the engine speed decreases. For example, during idle modes of engine operation, it becomes difficult to control the quantity of fuel supplied to the fuel injection pump accurately.
SUMMARY OF THE INVENTION
It is therefore a principal object of the present invention to avoid the disadvantages of the prior art.
It is another object of the present invention to provide an improved pump structure used in a fuel injection apparatus which is capable of controlling the quantity of fuel supplied to a fuel injection pump accurately over a wide range of engine speeds.
According to one aspect of the invention, there is provided a fuel injection apparatus for an internal combustion engine. The fuel injection apparatus comprises: (1) a fuel injection pump which sucks fuel from a feed pump in synchronism with rotation of the engine and pressurizes and discharges the fuel for fuel injection to the engine; (2) a metering valve disposed between the feed pump and the fuel injection pump to regulate the quantity of fuel sucked into the fuel injection pump, the metering valve having formed therein a fluid path communicating at one end with the feed pump and at the other end with the fuel injection pump and a valve member designed to selectively open and close the fluid path and change an area of the fluid path opened by the valve member; and (3) a controller which actuates the metering valve so that a pressure of the fuel discharged from the fuel pump reaches a target pressure, the controller controlling a valve on-off duration in which the valve member of the metering valve opens and closes the fluid path in a cycle to establish and block fluid communication between the feed pump and the fuel injection pump and the opened area of the fluid path independently as a function of an engine operating condition.
In the preferred mode of the invention, the controller actuates the metering valve in a first control mode in which the valve on-off duration and the opened area of the fluid path of the metering valve are both controlled when an engine speed is low and in a second control mode in which only the opened area of the fluid path of the metering valve is controlled when the engine speed is high.
The controller includes (a) a controlled variable determining circuit which determines a first basic controlled variable for determining the valve on-off duration of the metering valve and a second basic controlled variable for determining the opened area of the fluid path of the metering valve according to a quantity of the fuel to be discharged from the fuel injection pump, (b) a correction circuit which, when the pressure of fuel discharged from the fuel injection pump is different from the target pressure, corrects the first basic controlled variable to have the pressure of fuel discharged from the fuel injection pump reach the target pressure, (c) a decision circuit which decides whether the corrected first controlled variable lies within a preselected control range or not, (d) a first target controlled variable determining circuit which determines the corrected first controlled variable as a first target controlled variable that is a target of the valve on-off duration when it is decided that the corrected first controlled variable lies within the preselected control range and which determines one of upper and lower limits defining the control range close to the corrected first controlled variable as the first target controlled variable when it is decided that the corrected first controlled variable lies out of the preselected control range, (e) a second target controlled variable determining circuit which determines the second controlled variable as a second target controlled variable that is a target of the opened area of the fluid path of the metering valve when it is decided that the corrected first controlled variable lies within the preselected control range and which corrects the second controlled variable to produce the second target controlled variable so as to have the pressure of fuel discharged from the fuel injection pump reach the target pressure when it is decided that the corrected first controlled variable lies out of the preselected control range.
The metering valve includes a solenoid valve which moves the valve member. The controller controls an on-off operation of the solenoid valve and a rate of current supplied to the solenoid valve to regulate the on-off duration of the metering valve and the opened area of the fluid path.
The fuel injection pump feeds the fuel to an accumulator chamber storing therein the fuel under high pressure for supplying the fuel to injectors installed in cylinders of the engine. The controller determines the on-off duration of the metering valve and the opened area of the fluid path based on an actual fuel pressure in the accumulator chamber, a target injection quantity of the fuel and a target pressure of the fuel injected to the engine from the injectors, and a speed of the engine so that the actual fuel pressure in the accumulator chamber reaches the target pressure of fuel.
According to the second aspect of the invention, there is provided a fuel injection apparatus for an internal
Enomoto Shigeiku
Horiuchi Yasuhiro
Igashira Toshihiko
Makino Tadaaki
Miyamoto Yutaka
Denso Corporation
Gimie Mahmoud M
Pillsbury & Winthrop LLP
Yuen Henry C.
LandOfFree
Fuel injection system for internal combustion engine 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 system for internal combustion engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuel injection system for internal combustion engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2576077