Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
1998-12-16
2003-12-30
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S055000, C701S056000, C701S064000, C701S065000, C477S037000, C477S043000, C477S107000, C477S108000, C477S109000, C477S110000
Reexamination Certificate
active
06671601
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a continuously variable transmission controller (hereinafter referred to as “CVT controller”) capable of controlling a continuously-variable transmission (hereinafter abbreviated to “CVT”) for appropriate downshift operation while a vehicle mounted with the CVT is in an uphill traveling mode or in a downhill traveling mode.
2. Description of the Related Art
A conventional CVT controller for controlling a CVT determines a speed change ratio on the basis of throttle opening, and a parameter indicating an operating condition, such as a traveling speed or an engine speed, and determines a desired primary pulley speed by making reference to a basic speed change characteristic map, and varies the speed change ratio of the CVT continuously in the range of a low speed change ratio to an overdrive speed change ratio in a follow-up control mode so that actual primary pulley speed approaches the desired primary pulley speed.
In most cases, the basic speed change characteristic map is produced empirically on the basis of experimental results so that the vehicle loaded with a standard load is able to travel properly on a horizontal and flat road. Accordingly, if the speed change ratio is determined on the basis of such a basic speed change characteristic map, the torque of the driving system of the vehicle may be insufficient and the driver will feel an unpleasant feeling while the vehicle is in the uphill traveling mode, and an appropriate effect of engine brake is unavailable and the driver will feel unpleasant.
A technique disclosed in JP-A No. 6-81931 or 6-81932 subtracts running resistance including air resistance, acceleration resistance, rolling resistance and cornering resistance from the traction of an engine, calculates weight incline resistance during uphill traveling, determines a desired primary pulley speed correction corresponding to the weight incline resistance and a throttle opening by making reference to a map, adds the desired primary pulley speed correction to a desired primary pulley speed corresponding to the throttle opening and a traveling speed determined by making reference to a basic speed change characteristic map to correct the desired primary pulley speed.
If an estimated running resistance is excessively high and the traction is increased by an incremental traction corresponding to an excess running resistance over an expected running resistance, the CVT will be downshifted by an excessively large downshift amount and the engine speed will excessively be increased. A technique disclosed in JP-A No. 8-68448 decreases the rate of increase of an amount corresponding to a downshift amount (incline resistance, desired primary pulley speed) with the increase of incline resistance or throttle opening or sets an upper limit to the downshift amount to reduce an unpleasant sensation that may be felt by the driver.
However, if an incremental running resistance is compensated by downshift while the vehicle is traveling at a high traveling speed, downshift will increase engine speed greatly even if the incremental running resistance is small. Accordingly, the engine needs to operate at a high engine speed and noise and fuel consumption increase in a high traveling speed range. In a state where the vehicle is traveling at a small throttle opening, the output torque of the engine declines as engine speed increases, increase in traction exceeding a predetermined value cannot be expected from downshift and traction has a declining tendency, deceleration due to downshift will give an unpleasant feeling to the driver.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a CVT controller for controlling the shifting operation of a CVT, capable of properly determining a downshift amount by which the CVT is to be downshifted for the uphill or downhill traveling of a vehicle, of preventing excessive increase in engine speed, of suppressing increase in vibrations and noise, and of improving the maneuverability of the vehicle.
According to one aspect of the present invention, a CVT controller for controlling a CVT mounted on a vehicle comprises: an incremental running resistance setting means for setting an incremental running resistance based on a running resistance that will act on the vehicle when the vehicle is traveling in a flat road traveling mode on a horizontal, flat road according to traveling mode; a desired traction setting means for deciding whether the vehicle is in an uphill traveling mode or in a downhill traveling mode on the basis of the incremental running resistance, setting a desired traction for a full-open throttle state where a throttle valve is fully open on the basis of the incremental running resistance if the vehicle is in the uphill traveling mode and setting a desired traction for a fill-closed throttle state where the throttle valve is fully closed on the basis of the incremental running resistance if the vehicle is in the downhill traveling mode; a correction setting means for comparing the desired traction and an achieved traction in the full-open throttle state at a present traveling speed if the vehicle is in the uphill traveling mode, comparing the desired traction and an achieved traction in the fill-closed throttle state at a present traveling speed if the vehicle is in the downhill traveling mode, and determining a correction for adjusting the achieved traction to the desired traction; a speed change characteristic correcting means for correcting a basic speed change characteristic stored in a basic speed change characteristic map toward a downshift side; and a desired speed change ratio setting means for setting a desired speed on the basis of the corrected basic speed change characteristic.
The desired traction and an achieved traction in the full-open throttle state at a present traveling speed are compared if the vehicle is in the uphill traveling mode, the desired traction and an achieved traction in the full-closed throttle state at a present traveling speed are compared if the vehicle is in the downhill traveling mode, and a correction for adjusting the achieved traction to the desired traction is determined. A basic speed change characteristic stored in a basic speed change characteristic map is corrected toward a downshift side and a desired speed is set on the basis of the corrected basic speed change characteristic. Therefore, the speed change ratio can automatically be shifted by an appropriate amount of downshift according to the incremental running resistance based on the running resistance that may act on the vehicle while the vehicle is in the flat road traveling mode, the speed change ratio can properly be shifted toward the downshift side in the uphill traveling and the downhill traveling mode, excessive rise in engine speed due to inappropriate downshift can be avoided, and vibrations and noise can be suppressed. Since the speed change ratio is shifted toward the downshift side according to the increase of the incremental running resistance when the vehicle is in the uphill traveling mode, control input to the throttle valve (accelerator pedal) can be reduced. Since the speed change ratio is shifted toward the downshift side according to the reduction of the incremental running resistance when the vehicle is in the downhill traveling mode, operation necessary for using engine brake for downhill traveling can be simplified and hence the operation of the vehicle is improved greatly. Accordingly, the frequency of setting the engine for an accelerating mode during uphill traveling is reduced, and the frequency of fuel injection control operations for an accelerating mode can be reduced. Since the basic speed change characteristic is shifted toward the downshift side when the vehicle is in the downhill traveling mode to maintain the lowest speed change line on a high level to improve fuel consumption, a fuel cut region during downhill traveling can be expanded and, consequently, fuel consumption is improved.
Broadhead Brian J
Cuchlinski Jr. William A.
Fuji Jukogyo Kabushiki Kaisha
Smith , Gambrell & Russell, LLP
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