Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle diagnosis or maintenance indication
Reexamination Certificate
1998-02-09
2001-06-05
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle diagnosis or maintenance indication
C701S114000
Reexamination Certificate
active
06243630
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to Japanese Patent Application Nos. Hei 9-63372 and Hei 9-63373, incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to vehicle control systems, and more particularly to a vehicle control system in which learned value data is stored into an electrically rewritable nonvolatile ROM such as an EEPROM.
2. Description of Related Art
Conventionally, in a vehicle control system for controlling a vehicle engine or automatic transmission, a learning control method is in widespread use for correcting control parameters and logic data through evaluation of past control results to eliminate an adverse effect due to deterioration with age or individual difference of a controlled object. Learned value data including control parameters attained by means of learning control is held in a standby RAM (backup RAM which is always supplied with battery power).
However, if a battery is disconnected from a vehicle intentionally or accidentally, learned value data held in the standby RAM will be lost. Therefore, in recent years, learned value data has been stored into an electrically rewritable nonvolatile ROM such as an EEPROM. On occurrence of a battery disconnection, the learned value data is transferred from the nonvolatile ROM to an ordinary RAM. In this manner, previously attained learned value data is used continuously.
In the abovementioned arrangement, by increasing a frequency of updating learned value data in the electrically rewritable nonvolatile ROM(EEPROM), the latest possible learned value data can be used for control operation in the event of a battery disconnection. Under the present-day technological constraints, however, this kind of nonvolatile ROM has a guaranteed upper limit of rewritable count, which is specified by each semiconductor device manufacturer. If it is attempted to rewrite data thereinto beyond the guaranteed upper limit of rewritable count, the data may not be stored accurately therein. Therefore, it is not desirable to frequently update learned value data in the electrically rewritable nonvolatile ROM.
In Japanese Unexamined Patent Publication No. 79379/1993, for example, there is disclosed a vehicle control system arranged for writing the latest learned value data into an EEPROM at intervals of a certain period of time. In consideration of a useful lifetime of an automobile (up to 15-20 years), the possibility of exceeding a specific guaranteed upper limit of rewritable count of the EEPROM is very high. Furthermore, in this kind of vehicle control system in which operating power is supplied when an engine ignition switch of a vehicle is turned on, the vehicle is not always run while the vehicle control system is activated by turning on the ignition switch. Consequently, useless learned value data may be written into the EEPROM at the time of updating, thereby causing a count of writing data into the EEPROM to increase more than necessary.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to obviate the abovementioned disadvantage by providing a vehicle control system in which a count of writing learned value data into an electrically rewritable nonvolatile ROM can be kept below a specific guaranteed upper limit of rewritable count thereof without sacrificing performance of learning control.
In carrying out the present invention and according to one aspect thereof, there is provided a vehicle control system equipped with an electrically rewritable nonvolatile ROM and arranged so that learned value data attained through learning control of vehicle operation is written into said nonvolatile ROM under a predetermined condition and retained therein. More specifically, after an ignition switch of a vehicle is turned on, drive detecting means checks whether the vehicle is actually run, counting means calculates the number of detections made by the drive detecting means in case of actual drive of the vehicle, and then drive count checking means determines whether a count value indicated by the counting means reaches a predetermined value.
In said vehicle control system, if the drive count checking means determines that the count value indicated by the counting means reaches the predetermined value, the learned value data retained in said nonvolatile ROM is updated and also the count value in the counting means is reset.
In the vehicle control system arranged as mentioned above according to the present invention, when the ignition switch is turned on and the vehicle is run actually, a count value in the counting means is incremented by one. Then, when the count value indicated by the counting means reaches a predetermined value, the contents of said nonvolatile ROM are updated and also the count value in the counting means is reset. In this fashion, after the vehicle is run actually the predetermined number of times, the latest learned value data is written into said nonvolatile ROM.
Therefore, in the vehicle control system according to the present invention, when the vehicle is not actually run, even if the ignition switch is turned on, the contents of said nonvolatile ROM are not updated and thus the learned value data useful for actual drive control of the vehicle is retained therein. Still more, since the latest learned value data is written into said nonvolatile ROM only after the vehicle is run actually the predetermined number of times, it is possible to substantially reduce a count of writing data into said nonvolatile ROM.
Thus, a count of writing learned value data into said nonvolatile ROM can be kept below a specific guaranteed upper limit of rewritable count thereof without sacrificing performance of learning control.
Still more, the drive detecting means may be configured so that it recognizes actual drive of the vehicle when an engine rotating speed of the vehicle reaches a predetermined level of rotating speed. This configuration makes it possible to detect an actual drive of the vehicle positively with ease.
On the other hand, in a conventional type of vehicle control system in which operating power is supplied when an ignition switch of a vehicle is turned on as aforementioned, if a driver of the vehicle turns off the ignition switch while a processing operation of writing learned value data into a nonvolatile ROM is in progress, the write processing operation is interrupted to damage the learned value data therein.
To solve this problem, according to the present invention, there is provided an arrangement which further comprises travel state detecting means for checking whether or not a vehicle is run at a vehicle travel speed higher than or equal to a predetermined travel speed level. When the drive count checking means determines that a count value indicated by the counting means reaches a predetermined value and also said travel state detecting means recognizes that the vehicle is run at a vehicle travel speed higher than or equal to the predetermined travel speed level, learned value data is written into the nonvolatile ROM and a count value in the counting means is reset.
More specifically, unless the vehicle is run at a vehicle travel speed higher than or equal to the predetermined travel speed level even when the drive count checking means determines that a count value indicated by the counting means reaches the predetermined value, the learned value data is not written into the nonvolatile ROM. It is written into the nonvolatile ROM under condition that the vehicle is run at a vehicle travel speed higher than or equal to the predetermined travel speed level and also a count value indicated by the counting means reaches the predetermined value.
In such an arrangement as mentioned above, the learned value data is written into the nonvolatile ROM only in a situation where there is no possibility that the vehicle driver does not turn off the ignition switch, thereby making it possible to positively prevent the learned value data from being damaged.
The above and other objects, features and a
Nakai Kazuhiko
Oguro Hirokazu
Oohara Kouichi
Takaba Katsumi
Yamamoto Yuko
Cuchlinski Jr. William A.
Denso Corporation
Nixon & Vanderhye P.C.
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