JPS59126142A - Constant speed running device for car - Google Patents

Abstract

PURPOSE:To automatically apply an engine brake to check an increase in car speed by shifting down when the car speed increases more than a preset car speed by a predetermined value because the engine brake does not work well on a steep downhill road during constant speed running in an overdrive range. CONSTITUTION:A discrimination circuit 12 for discriminating whether a difference between a preset car speed VM and an actual car speed VA is larger than a fixed value VB or not, a timer circuit 13 and an overdrive solenoid 14 are disposed on a conventional constant speed running device. When (VA-VM)- VB>0 is discriminated by the discrimination circuit 12, the overdrive solenoid 14 is operated to be shifted from the overdrive range down to the third speed range to enlarge the effectiveness of the engine brake. At the time of (VA-VM)- VB<=0, an output signal from the discrimination circuit is stopped, and after a fixed time is counted up by the timer circuit 13, the overdrive solenoid 13 is stopped operating to be shifted up to the overdrive range.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic transmission with an overdrive.Some modern vehicles are equipped with a constant speed traveling device that automatically drives the vehicle at a constant speed. In such vehicles, when the driver sets the desired constant speed using a vehicle speed setting switch, the opening of the carburetor's throttle valve is adjusted to zero the deviation between the actual vehicle speed and the set vehicle speed. Speed control is performed so that the actual vehicle speed becomes the set vehicle speed. This constant-speed traveling device is convenient for the driver because it does not require the driver to constantly press the accelerator pedal when driving at a constant speed on a highway or the like.

FIG. 1 is a block diagram of a conventional constant speed traveling device of this type, where 1 is a vehicle speed sensor that outputs a vehicle speed signal according to the vehicle speed, and 2 is a vehicle speed memory circuit 3 that stores the actual vehicle speed set by the driver as the vehicle speed. The vehicle speed setting switch 4 outputs a memory command signal when commanded to do so, and compares the set vehicle speed vM stored in the vehicle speed memory circuit 3 with the actual vehicle speed, and outputs a vehicle speed difference signal according to the difference. The actuator drive circuit 5 determines the operating amount of the actuator 6 based on the output of the differential amplifier 4, opens and closes the throttle valve 7, and controls the engine 8. Furthermore, when the brake is operated while driving at a constant speed, a release signal is output from the release signal generation circuit 10 in response to a signal from the brake switch 9, which cuts off the actuator drive power supply circuit 11 and stops the operation of the actuator drive circuit 5 to maintain the constant speed. Cancel running state.

By the way, it is known that in vehicles equipped with automatic transmissions with overdrive, the engine braking effectiveness is relatively poor because the gear ratio in the overdrive range is low. If a vehicle equipped with this comes to a steep downhill slope (for example, 4X or higher) while driving at a constant speed in the overdrive range,
Since the difference in vehicle speed between the set vehicle speed and the actual vehicle speed becomes large, the actuator must perform deceleration control by fully closing the throttle, or the engine brake is relatively slow, so the deceleration effect is small and the vehicle speed increases. There is a problem.

The present invention has been made in view of the above-mentioned points.In order to ensure that a vehicle equipped with an automatic transmission with an overdrive can maintain constant speed, it is possible to avoid sudden descents while traveling at a constant speed in the overdrive range. When the vehicle speed increases by more than a predetermined value on a slope, the system shifts down from the overdrive range to improve the effectiveness of engine braking.

The present invention will be explained below based on the drawings.

FIG. 2 shows an embodiment of a constant speed traveling device according to the present invention, in which the same numbers as in FIG. 1 indicate the same components. This embodiment includes a determination circuit 12 for determining whether the vehicle speed difference between the set vehicle speed VM and the actual vehicle speed is greater than a predetermined value VB, and a timer circuit 13 in the conventional constant speed traveling device shown in FIG. , and an overdrive solenoid 14 are provided.

In this way, the discrimination circuit 12 (■E1■M)
-When it is determined that vB>0, an output signal is output, and the overdrive solenoid 14 is operated to shift down from the overdrive range to the 3rd gear range, increasing the effectiveness of the engine brake. . As a result, the engine brake is effective (■E-vM) -v, ≦
When it becomes 0, the output signal from the discrimination circuit 12 stops,
After a certain period of time has been counted by the timer circuit 13, the overdrive solenoid 13 is deactivated to shift up from the 3rd speed range to the overdrive range.

As explained above, in the present invention, in a vehicle equipped with an automatic transmission with overdrive, while driving at a constant speed in the overdrive range, the engine brake is not effective on a steep downhill slope and the vehicle speed drops below the set vehicle speed value. If the increase exceeds a predetermined value, it will shift down from the overdrive range, so even if you approach a steep downhill slope while driving at a constant speed, it will automatically shift down to improve the effectiveness of engine braking. As a result, the increase in vehicle speed is suppressed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a conventional constant speed traveling device for a vehicle, and FIG. 2 is a block diagram showing a schematic configuration of an embodiment of a constant speed traveling device according to the present invention. 1...Vehicle speed sensor 2...Vehicle speed setting switch 3...
・Vehicle speed memory circuit 4... Differential amplifier 5... Actuator drive circuit 6... Actuator 7... Throttle valve 8
...Engine 9...Brake switch 10...
Release signal generation circuit 11... actuator drive type, source circuit 12...
Discrimination circuit, path 13...Timer circuit 14...Overdrive solenoid Patent applicant Hiroo Tsuchi Suzuki, attorney for Nissan Motor Co., Ltd.

Claims (1)

[Claims] In a device that allows a vehicle to travel at a constant speed set by the vehicle speed setting operation in a vehicle equipped with an automatic transmission with overdrive, while driving at a constant speed in the overdrive range,
A constant speed traveling device for a vehicle, characterized in that it is provided with a shift switching means that shifts down from an overdrive range when the vehicle speed increases by more than a predetermined value from a set vehicle speed value on a steep downhill slope.