Motor vehicles – With means responsive to speed of vehicle for maintaining...
Reexamination Certificate
1999-12-20
2001-03-27
Johnson, Brian L. (Department: 3618)
Motor vehicles
With means responsive to speed of vehicle for maintaining...
C701S093000
Reexamination Certificate
active
06206123
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cruise control method for a vehicle. More particularly, the invention relates to a cruise control method that can improve drive efficiency of a vehicle when the vehicle runs up a slope in an automatic cruise control mode.
2. Description of the Related Art
Generally, in an automatic cruise mode, vehicle speed is maintained at a constant level by an automatic cruise control system.
FIG. 1
shows such a conventional automatic cruise control system.
An automatic cruise control system comprises a vehicle speed sensor
10
for detecting a vehicle speed, a throttle position sensor
11
for detecting a throttle opening, a cruise switch
12
for setting vehicle speed at a predetermined level according to a driver's will, an electronic control unit
13
for controlling a vehicle speed to the predetermined level by receiving signals from the vehicle speed sensor
10
and the throttle position sensor
11
, and a fuel injecting part
14
for injecting fuel according to a control signal transmitted from the electronic control unit
13
.
When a cruise control mode is selected by operating the cruise control switch
12
, the electronic control unit
13
controls the fuel injection part
14
according to vehicle speed and throttle opening signals transmitted from the vehicle speed and throttle position sensors
10
and
11
. That is, by controlling an amount of fuel being injected, the vehicle speed is maintained at a constant level.
FIG. 2
shows graphs illustrating an amount of fuel to be injected with respect to vehicle speeds according to various road conditions during an automatic cruise control mode.
As shown in the drawing, when the vehicle runs on a level ground to point A, since the difference between a current vehicle speed and a target speed is very low, the amount of fuel injected is not varied substantially. That is, the fuel is supplied according to a speed difference between a current speed and a target speed.
However, as the vehicle goes up a slope, since the vehicle speed is reduced, the amount of fuel to be injected is increased. Particularly, when the vehicle reaches a mid-point of the slope, although the amount of fuel delivery is maximized, it is very difficult to increase the vehicle speed to the target speed.
In addition, when the vehicle goes down the slope, since the vehicle speed increases above the target speed, the fuel injection is stopped. In this state, when the vehicle again meets an upward slope, the vehicle speed is reduced since the coasting speed obtained when the vehicle goes down the slope cannot be maintained.
That is, when the vehicle goes up the slope, the vehicle speed is not increased to the target speed even when the fuel is injected at its maximum rate. In addition, when the vehicle goes down the slope, since the coasting speed cannot be maintained, the drive effect in cruise control mode deteriorates.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above problems.
It is an objective of the present invention to provide a cruise control method for improving drive effect when a vehicle goes up and down hills while in a cruise control mode.
To achieve the above objective, the present invention provides an automatic cruise control method for vehicles, comprising the steps of selecting an automatic cruise mode; detecting a current vehicle speed; comparing the current vehicle speed with a target speed; determining a new target speed according to the comparison; and controlling an amount of fuel to be injected according to the new target speed.
The step of comparing the current vehicle speed with the target speed comprises the step of determining if the current speed is lower than the target speed.
The step of determining a new target speed comprises, if the current speed is lower than the target speed, the steps of obtaining a speed difference between the target speed and the current speed, and establishing the new target speed by adding the speed difference to the target speed.
The amount of fuel to be injected is determined by a value obtained by integrating the new target speed.
The automatic cruise control method may further comprise the step of, if the current speed is higher than the target speed, stopping an injection of fuel.
The automatic cruise control method may further comprise the step of setting a current speed as the new target speed after the step of stopping an injection of fuel.
REFERENCES:
patent: 4658929 (1987-04-01), Katou et al.
patent: 5161634 (1992-11-01), Ichihara et al.
patent: 5162998 (1992-11-01), Kondo
Christie Parker & Hale LLP
Hyundai Motor Company
Johnson Brian L.
Klebe G B
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