Internal-combustion engines – Starting device – Condition responsive control of starting device
Reexamination Certificate
2003-04-23
2004-11-16
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Starting device
Condition responsive control of starting device
Reexamination Certificate
active
06817330
ABSTRACT:
The disclosure of Japanese Patent Application No. 2001-006528 filed on Jan. 15, 2001, including the specification, drawings and abstract are incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to an internal combustion engine that performs an automatic stop/start control of a vehicular internal combustion engine and, more particularly, to an internal combustion engine control apparatus that permits the aforementioned automatic stop if the temperature of a cooling medium of the internal combustion engine used as an air-conditioning heat source by a cabin air-conditioner is higher than a threshold, and prohibits the automatic stop/start if the temperature of the cooling medium is lower than the threshold.
2. Description of Related Art
Automatic air-conditioners for cabin air-conditioning in motor vehicles are known. The automatic air-conditioner is an apparatus that automatically maintains a set temperature in the cabin. The apparatus detects an outside air temperature and a cabin temperature using temperature sensors, and adjusts the blow-off air temperature and the air flow through the processing by an electronic control unit, thereby maintaining an appropriate air-conditioned state in the cabin. The automatic air-conditioner, when heating, efficiently uses heat from the cooling water of the internal combustion engine so as to adjust the blow-off air temperature and thereby maintain a comfortable room temperature in the cabin (Japanese Patent Application Laid-Open Publication No. 5-221233).
For improvements in fuel economy, there exist vehicles equipped with a generally-termed economy-running (hereinafter, referred to as “eco-run”) system, that is, an automatic stop/start system capable of automatically stopping the internal combustion engine when the vehicle has stopped running at an intersection or the like, and allowing the vehicle to launch through automatic start-up of the engine achieved by operating a motor-generator or the like at the time of a launching operation performed by a driver. If an automatic air-conditioner is used in such a vehicle, the heating utilizing the cooling water of the internal combustion engine may become impossible due to a drop in the cooling water temperature during an automatic stop of the engine. To avoid this situation, a control of prohibiting the automatic stop of the internal combustion engine and starting the internal combustion engine is performed in some cases.
For example, a threshold value of cooling water temperature is provided. If the cooling water temperature is above the threshold value, the automatic stop of the internal combustion engine is permitted. If the cooling water temperature becomes lower than the threshold value, the automatic stop of the internal combustion engine is prohibited and the engine is started. If in this case, the required blow-off air temperature of the automatic air-conditioner is relatively low, no heating problem occurs despite a reduced cooling water temperature during a stop of the internal combustion engine. Conversely, if the required blow-off air temperature of the automatic air-conditioner is relatively high, a drop in the cooling water temperature will likely make it impossible to maintain a requested heating. Therefore, if the required blow-off air temperature is higher, the threshold value is raised so that if the cooling water temperature decreases, operation of the internal combustion engine is resumed at an early stage of the decrease in cooling water temperature, whereby the cooling water temperature is kept relatively high. In this fashion, control is performed so that the sufficient heating by the automatic air-conditioner is possible over a broad range.
At the time of transition of the cooling water temperature caused by discontinuation or start of generation of heat by the internal combustion engine due to, for example, an automatic stop or an automatic startup of the engine, the cabin temperature changes with a delay from the change in the cooling water temperature. Due to this delay, after the engine has been stopped through the automatic stop, there exists a period during which the cabin heating using the cooling water whose temperature is decreasing can be continued without any problem in the cabin comfort. According to the related-art technology, however, the automatic stop of the internal combustion engine is prohibited and operation of the engine is restarted when the cooling water temperature decreases to a threshold value (which may include a hysteresis width set so as to prevent hunting in control) that is the same as the threshold value used for the increasing cooling water temperature. Thus, the automatic stop of the internal combustion engine is ended when there still is no heating problem. This indicates that the use of a threshold as in the related-art technology does not allow full exploitation of the fuel economy improvement advantage of the automatic stop.
In a region of low blow-off air temperatures, the threshold value is set low. A reduced threshold value increases the length of time consumed for the cooling water temperature to reach the threshold value if the internal combustion engine is automatically stopped. Therefore, in that case, the automatic stop state can be maintained for a long time, and therefore, fuel economy can be sufficiently improved. Conversely, in a region of high blow-off air temperatures, the threshold value is set high due to the need for sufficiently high blow-off air temperature. Therefore, if the internal combustion engine is automatically stopped, the cooling water temperature soon reaches the threshold value, and therefore, the automatic stop ends in a short time. However, it has been found that if the cooling water temperature decreases when the required blow-off air temperature is within a high temperature region, the cabin comfort can be retained for a relatively long time despite decreasing cooling water temperature since the internal combustion engine is automatically stopped while the cabin temperature is sufficiently high. Thus, the related-art technology ends the automatic stop in a short time although the comfort of air-conditioning can be retained for a relatively long time following an automatic stop of the internal combustion engine. The related-art technology cannot be said to achieve sufficient improvement in fuel economy.
SUMMARY OF THE INVENTION
It is an object of the invention to increase the duration of the automatic stop of the internal combustion engine and therefore enhance the fuel economy improving effect by reducing the region of prohibiting the automatic stop of the internal combustion engine corresponding to the air-conditioned state in the cabin.
Means for achieving the aforementioned object and the operation and advantages thereof will be described below.
A vehicular internal combustion engine control apparatus according to a first aspect of the invention includes: engine automatic stop-startup means for automatically stopping the internal combustion engine if a state of operation of the internal combustion engine satisfies an automatic stop condition, and for automatically starting the internal combustion engine if the state of operation of the internal combustion engine satisfies an automatic startup condition; and engine automatic stop permission-prohibition means for permitting an automatic stop of the internal combustion engine if a temperature of a cooling medium of the internal combustion engine used as an air-conditioning heat source by a cabin air-conditioner is higher than a threshold value, and for prohibiting the automatic stop if the temperature of the cooling medium is lower than the threshold value. The control apparatus is characterized in that the threshold value related to the engine automatic stop permission-prohibition means is variable in accordance with at least one of an inside-cabin temperature and values related to the inside-cabin temperature, and that a hysteresis width of the threshold value is set greater tha
Hayashi Ryuji
Ogawa Noriko
Castro Arnold
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
Yuen Henry C.
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