Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
1999-01-25
2001-06-19
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S070000
Reexamination Certificate
active
06249735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle state estimation method and a vehicular auxiliary brake control apparatus which uses the estimation method. In particular, the invention relates to a method for estimating the vehicle state of a commercial vehicle capable of carrying loads or passengers such as a truck or a bus and to a vehicular auxiliary brake control apparatus using that estimation method.
2. Description of the Related Art
In commercial vehicles, the load amount greatly varies from an empty state to a loaded state even though the engine is small for the vehicle's own weight. When such a commercial vehicle is heavily loaded with goods, passengers, or the like and its weight (total weight) is increased accordingly, sufficient braking performance is not attained on a downhill slope or the like because the engine braking becomes less effective. This necessitates control of the driving force or the braking force in consideration of the vehicle weight (total weight)
Conventionally, in estimating the vehicle state, a comprehensive parameter of a vehicle load as represented by vehicle load torque TI that is the sum of aerodynamic drag torque Ta, rolling resistance torque Tr, and surface gradient resistance torque T&thgr; is estimated based on the relationship between the driving torque and the acceleration by using a vehicle weight sensor, a torque sensor, or the like. However, this method causes an estimation error when the road surface has a gradient as in the case of running on a sloping road. Further, in this method, the vehicle weight and the road surface gradient cannot be separated properly from the vehicle load torque.
In general, in automobiles, the road surface gradient can be estimated relatively easily with an assumption that the vehicle weight is constant, because no large variation occurs in vehicle weight. On the other hand, in vehicles such as commercial ones in which the vehicle weight varies greatly, it cannot be judged whether a vehicle load variation is due to a variation in road gradient or a variation in vehicle weight. This necessitates estimation of the road surface gradient, and hence the estimation method for automobiles cannot be used for commercial vehicles.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems in the art and an object of the invention is therefore to make it possible to estimate the road surface gradient accurately even when the vehicle weight varies by separating the vehicle weight and the road surface gradient from the vehicle load.
Another object of the invention is to provide a vehicular auxiliary brake control apparatus by using the above estimation method.
To attain the above objects, according to the invention, the vehicle weight and the road surface gradient are estimated based on driving torque and vehicle acceleration when behavior occurs in a vehicle.
In the above method, since the vehicle weight and the road surface gradient are estimated based on driving torque and vehicle acceleration, the vehicle weight and the road surface gradient can be determined if driving torque and vehicle acceleration are determined.
If behavior at a time of a gear shift in the vehicle is employed as the above-mentioned behavior, the vehicle weight and the road surface gradient can be estimated based on driving torque values and vehicle acceleration values before and after the gear shift.
If the estimation is performed at a time of a shift from the low to the second gear, the estimation can be performed when a large variation in driving torque occurs, whereby the estimation errors can be reduced.
If the driving torque is determined by using a torque map, a torque sensor is no longer necessary because the driving torque can be determined by using an engine torque map, a torque converter torque map, or the like.
The invention makes it possible to estimate the vehicle weight and the road surface gradient based on driving torque and vehicle acceleration and to optimize the control of driving force or braking force by using the estimated vehicle weight and road surface gradient. For example, in the case of an auxiliary braking device, a braking operation is performed by employing, as a target vehicle speed, a vehicle speed at a time point when road surface gradient detecting means has detected a downhill slope and brake state detecting means has detected a change from a brake operating state to a brake non-operating state during running downhill.
In this manner, the invention provides an auxiliary brake control apparatus which can decelerate a vehicle properly and sufficiently so as to reflect the driver's intention by controlling an auxiliary brake so that an actual vehicle speed becomes a target vehicle speed that is a vehicle speed obtained when a change from a brake operating state to a brake non-operating state occurs during running downhill.
It is preferable that an accelerator state detecting means for detecting the state of an accelerator be further provided, and that the auxiliary brake device be activated when the accelerator state detecting means has detected a non-operating state of the accelerator. This enables braking in a state that the driver is not pushing the accelerator (i.e., no acceleration request is made).
According to another aspect of the invention, road surface gradient detecting means for detecting a road surface gradient, brake state detecting means for detecting an operation state of a brake, and vehicle speed detecting means for detecting a speed of the vehicle are used, and a vehicle speed at a time point when the road surface gradient detecting means has detected a downhill slope and the brake state detecting means has detected a change from a brake operating state to a brake non-operating state during running downhill is employed as a target vehicle speed, and an auxiliary brake control is performed by operating an auxiliary brake device for decelerating the vehicle so that an actual vehicle speed becomes the target vehicle speed.
In this method, by controlling the auxiliary brake so that the actual vehicle speed becomes the target vehicle speed that is a vehicle speed obtained when a change from a brake operating state to a brake non-operating state occurs during running downhill, a proper auxiliary brake operation becomes possible that reflects the driver's intention. As a result, the driver need not perform cumbersome manipulations any more.
If the auxiliary brake apparatus is activated when the brake state detecting means has detected that a brake non-operating state has been established after a brake operating state continued for a predetermined time, the auxiliary brake device can operate so as to realize a speed that satisfies the driver's deceleration request more properly.
REFERENCES:
patent: 4548079 (1985-10-01), Klatt
patent: 5925087 (1999-07-01), Ohnishi et al.
patent: 60-222330 (1985-11-01), None
patent: 2-278069 (1990-11-01), None
patent: 09002225 (1997-01-01), None
Ishiguro Toshiaki
Yamada Naoki
Aisin Seiki Kabushiki Kaisha
Cuchlinski Jr. William A.
Pipala Edward
Sughrue Mion Zinn Macpeak & Seas, PLLC
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