Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2003-08-21
2004-12-21
Kwon, John T. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S480000, C361S152000
Reexamination Certificate
active
06832601
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to control of a fuel injection valve performing a fuel injection to an internal combustion engine for vehicle and, more specifically, to a control device of a fuel injection valve for driving the fuel injection valve at a high speed.
2. Description of the Related Art
A vehicle is generally mounted with: a sensor for detecting various information in accordance with operating conditions of an internal combustion engine; and control means that operates a valve-opening time and a valve-opening time period of a fuel injection valve on the basis of information from the sensor, and determines an amount of fuel to be supplied to the internal combustion engine to drive the fuel injection valve. This control means includes: valve-opening signal generation means for operating the above-mentioned valve-opening time and valve-opening time period to output an valve-opening signal; power feed control means for driving rapidly at a high voltage an electromagnetic valve of the fuel injection valve in response to the foregoing valve-opening signal and thereafter holding an open valve at a low current; and a power supply apparatus for supplying an electric power to the valve-opening signal generation means and power, feed control means and generating a drive electric power for the fuel injection valve. Hitherto, several attempts have been proposed in the field of arts as follows.
According to the art disclosed in the Japanese Patent Publication (unexamined) No. 71639/1995 (pages 2-4, FIG. 1), a battery power supply, a conduction control transistor and an electromagnetic valve are connected in series. Further provided is an auxiliary power supply for supplying a large current to the electromagnetic valve at the time of closing a circuit of the conduction control transistor. This auxiliary power supply consists of a voltage step-up DC—DC converter and a capacitor for charging a step-up DC voltage. During a predetermined time period at early times of conducting an electric power to the electromagnetic valve, the conduction control transistor is brought into a full conduction state to conduct a current from the auxiliary power supply as well as a current from a battery power supply. Thereafter, the conduction control transistor is subject to conduction control for constant current control. In this arrangement, a predetermined time period at early times of conduction is set to be a sum of a time period when a needle of the electromagnetic valve is full-lifted and a time period when no bound of the needle is observed.
According to the art disclosed in the Japanese Patent Publication (unexamined) No. 234793/2001 (pages 4-6, FIGS. 1 and 2), an electromagnetic valve is provided with: a power feed circuit from a capacitor that charges a step-up DC voltage by means of a voltage step-up DC—DC converter; a power feed circuit from a battery power supply including a back-flow prevention diode; and a current control element for ON/OFF controlling a current flowing through the electromagnetic valve. To this current control element, a current detection resistor is connected in series. First, a step-up voltage is applied to the electromagnetic valve in response to a valve-opening signal, and the electromagnetic valve is driven at a large current. When this current is lowered to a predetermined value, the power feed is switched to be fed from the battery power supply, and a constant current is conducted in response to outputs from the current detection resistor. An electromagnetic energy of the electromagnetic valve when the current control element is OFF is refluxed to the capacitor by means of the diode.
According to the art disclosed in the Japanese Patent Publication (unexamined) No. 351039/1999 (pages 4-6, FIGS. 1 through 3), an electromagnetic valve is driven at a large current at early times of driving, and thereafter driven at a constant current for a predetermined time period. In this known art, a constant voltage circuit outputting a constantly high voltage and a large capacity of capacitor to be charged by this constant voltage circuit are employed as a power supply for driving the electromagnetic valve at a large current level. Further, by automatically performing charge of the capacitor without regard to whether the electromagnetic valve is ON/OFF, opening the valve driven at a large current level can be conducted up to a region of high-speed rotation.
According to the art disclosed in the Japanese Patent Publication (unexamined) No. 269404/1995 (pages 4-6, FIG. 1), an electromagnetic valve is driven by: peak current supply means for conducting a peak current for opening the valve at a high speed upon start-up of the conduction; and holding current supply means for conducting a holding current smaller than the peak current after the peak current has been conducted. In this known art, fault is determined from a charging voltage of a capacitor that charges a step-up voltage, when a step-up circuit for conducting the peak current is faulty. Upon determination of a fault, a valve-opening time is made earlier, and a valve-opening time period is increased, thereby leading to prevention of engine stall.
Among the conventional arts as described above, the art disclosed in the Japanese Patent Publication (unexamined) No. 71639/1995 (pages 2-4, FIG. 1) intends to assist a valve-opening drive energy and reduce load on a high-voltage auxiliary power supply by not solely depending on a step up voltage having been charged at a capacitor in order to get a drive energy for a predetermined time period at early times of conduction to an electromagnetic valve, but also bringing the conduction control transistor into a state of a full conduction to feed the whole voltage from a battery. However, there is no switching means between the capacitor and the electromagnetic valve, and therefore charging to the capacitor cannot be performed during valve open holding time period. Thus, a problem exists in that any follow-up to a region of rotation at a high speed is hard to do, as well as valve-opening drive energy significantly varies due to voltage of the battery resulting in instability of fuel injection characteristic.
In the art disclosed in the Japanese Patent Publication (unexamined) No. 234793/2001 (pages 4-6, FIGS. 1 and 2), since the switching element supplying a high voltage from a capacitor and the switching element applying voltage from a battery are provided, it is certain that sharing of a drive energy at the time of opening the valve is performed with accuracy. An object of this known art, however, is to return to a capacitor an electromagnetic energy having been charged at the electromagnetic valve. Thus a problem exits in that accuracy in controlling a holding current by means of a current control element decreases. That is, a feed current to the electromagnetic valve flows to a current detection resistor as it is when the current control element is in conduction. On the other hand, an induction current of the electromagnetic valve flows dividedly to the capacitor and the current detection resistor when the current control element is in a state of open circuit. Therefore, detection current at the current detection resistor is not coincident with a current flowing through the electromagnetic valve. Further, ripple of the current flowing through the electromagnetic valve becomes larger when the current control element is ON/OFF, and it is necessary that a holding current is kept at a sufficient level in order to hold an open valve without fail. As a result, heat generation at the electromagnetic valve or current control element is increased, and energy loss is increased.
In the art disclosed in the Japanese Patent Publication (unexamined) No. 351039/1999 (pages 4-6, FIGS. 1 through 3). In the same manner as in the Japanese Patent Publication (unexamined) No. 234793/2001, switching elements are separately provided so that sharing a drive energy at the time of opening the valve is performed with accuracy. The current flowing through
Nishida Mitsunori
Nishizawa Osamu
Watanabe Tetsushi
Kwon John T.
Mitsubishi Denki & Kabushiki Kaisha
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