Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
2001-09-25
2003-09-16
Vo, Hieu T. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S478000, C123S436000, C701S104000
Reexamination Certificate
active
06619270
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application corresponds to Japanese Patent Application No. 2000-069984 filed in JPO on Mar. 14, 2000, the entire disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an engine fuel injection control device that controls the amount of fuel injection in cold running when the engine temperature has not yet risen sufficiently immediately after engine startup.
2. Description of the Related Art
Conventionally, fuel injection control of, for example, a diesel engine performed when the engine is in the startup operating condition is performed with a startup fuel injection amount found as the fuel injection amount which is a maximum for the engine, from the cooling water temperature and/or engine rotational speed. After engine startup, the target fuel injection amount is determined by using a map which is previously found from the engine rotational speed and amount of depression of the accelerator pedal. For example, when the condition of the engine shifts to the idling operating condition in which there is scarcely any accelerator pedal depression immediately after engine startup, this map is determined such that the target fuel injection amount increases as the engine rotational speed falls, in the low range of engine rotational speed. Therefore, fuel injection amount control is performed under feedback control such that engine rotational speed is constant.
A diesel engine fuel injection control device in which the maximum value of fuel injection amount is made variable in response to an external air pressure is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 58-204941. With the fuel injection control device disclosed in this publication, in order to cope with the fuel injection amount becoming excessive relative to the air intake amount when the atmosphere becomes thin during running at high altitudes, prevention of combustion deterioration is aimed at by detecting the external air pressure, inputting the detected external air pressure signal to a control circuit that controls the maximum load of the fuel injection pump and automatically controlling the fuel injection amount in accordance with the reduced oxygen amount in the air intake amount.
A fuel injection control device which aims to guarantee vehicle running characteristics and guarantee engine startup characteristics even when there is an abrupt change in the air intake amount or the detected value of the air intake amount falls below the normal value is disclosed in Japanese Patent Application Laid-Open Publication No. 11-6459. With this fuel injection control device, a maximum injection amount calculated from the air intake amount is employed under normal condition, and an allowed maximum injection amount is employed in the vicinity of maximum supercharging. In this manner, it is aimed at to stabilize the fuel injection even if the air intake amount changes abruptly and to enable minimum engine operation even if there is abnormality of the air intake amount detection means by setting a maximum injection amount as small as possible.
In an ordinary diesel engine, the engine is insufficiently warmed-up immediately after startup is carried out when the engine is cold, so there is an unstable condition of engine rotation in which there are large fluctuations of speed. However, with constitution of a conventional fuel injection control device, the fuel injection amount is calculated at time of startup, and rapid startup is performed by using this fuel injection amount at startup. On the contrary, after startup, a mode shifts to an ordinary mode, so that immediately after startup, the fuel injection amount cannot be sufficiently increased, causing the engine to stall or to take some time to settle down in a stable condition.
A problem to be solved is therefore how to achieve early stabilization of engine rotational speed when it is concluded that the engine operating condition is cold condition, that is the engine has not yet warmed up sufficiently.
SUMMARY OF THE INVENTION
With the foregoing in view, an object of the present invention is to provide an engine fuel injection control device whereby stabilization can be achieved at an early stage by raising the engine rotational speed by determining the limited fuel injection amount a little on the high side if the engine is not fully warmed up. This limited fuel injection amount is carried out by a calculation other than a calculation in the ordinary engine operating condition.
In order to achieve the above object, one embodiment of the present invention is constructed as follows. Specifically, there is provided an engine fuel injection control device including basic fuel injection amount calculation means for calculating a basic fuel injection amount in accordance with engine operating condition, limited fuel injection amount calculation means for calculating a limited fuel injection amount in accordance with the engine operating condition, and target fuel injection amount determining means for comparing the basic fuel injection amount with the limited fuel injection amount and for determining the smaller of these as a target fuel injection amount. The limited fuel injection amount calculation means includes a normal condition limited fuel injection amount calculating unit that calculates a limited fuel injection amount for normal condition in accordance with the engine operating condition on the assumption that the engine is in normal operating condition, a cold condition limited fuel injection amount calculating unit that calculates a limited fuel injection amount for cold condition on the assumption that the engine is in cold operating condition, and a limited fuel injection amount selecting unit that selects, as the above-mentioned limited fuel injection amount, the larger of the limited fuel injection amount for normal condition and the limited fuel injection amount for cold condition, in response to the water temperature of the engine being lower than a prescribed temperature and in response to the lapse time after changeover of the engine from startup operating condition to normal operating condition being shorter than a prescribed time.
With this engine fuel injection control device, the normal condition fuel injection amount calculating unit calculates a limited fuel injection amount for normal condition on the assumption that the engine operating condition is normal operating condition, and the cold condition limited fuel injection amount calculating unit calculates a limited fuel injection amount for cold condition on the assumption that the engine operating condition is cold operating condition. The limited fuel injection amount selecting unit selects, as a limited fuel injection amount, the larger of the limited fuel injection amount for normal condition and the limited fuel injection amount for cold condition, in response to the engine water temperature being lower than a prescribed temperature and the lapse time after changeover of the engine from startup operating condition to normal operating condition being shorter than a prescribed time. That is, if the engine water temperature is lower than a prescribed temperature and the lapse time after changeover of the engine from startup operating condition to normal operating condition is shorter than a prescribed time, it is concluded that the engine has not yet sufficiently warmed-up, so that the larger of the limited fuel injection amount for normal condition and limited fuel injection amount for cold condition is selected as the limited fuel injection amount. The target fuel injection amount determining means compares the basic fuel injection amount calculated in accordance with engine operating condition and the limited fuel injection amount selected as described above, and determines the target fuel injection amount as the smaller of these. That is, the limited fuel injection amount is limited by the basic fuel injection amount.
The normal condition
Huynh Hai
Isuzu Motors Limited
McCormick Paulding & Huber LLP
Vo Hieu T.
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