US 5,993,354 A · Transfer case shift control system using automatic shutdown relay circuit

Abstract

A transfer case includes an input shaft driven by the output of an engine and transmission, a first output shaft connected to a first driveline, a second output shaft connected to a second driveline, and a power transfer mechanism for transferring drive torque from the input shaft to at least one of the output shafts. The power transfer mechanism includes a gear reduction unit driven by the input shaft and a range clutch operable for engaging the gear reduction unit to establish high-range and low-range drive modes between the input shaft and the first output shaft. A transfer case shift control system controls actuation of the range clutch during motive operation of the motor vehicle, thereby permitting on-the-move shifting of the transfer case between its high-range and low-range drive modes. The transfer case shift control system includes a mode selector for generating a mode signal, a relay circuit interconnected between the engine's fuel and ignition systems and a powertrain control module of the motor vehicle, and a transfer case control module receiving the mode signal and vehicle input signals from the powertrain control module. The transfer case module generates a control signal based on the mode signal and the input signals and, if necessary, sends the control signal to the relay circuit for varying characteristics of the vehicle's fuel and ignition systems to reduce the amount of engine torque delivered to the input shaft independent of the powertrain control module. Thereafter, the transfer case control module generates a shift signal for actuating the range clutch to establish the selected one of the high-range and low-range drive modes.

Claims22

Dependent claims

A four-wheel drive system for a motor vehicle having an engine and a transmission providing drive torque to first and second drivelines, the system comprising:

a transfer case having an input shaft receiving drive torque from the engine and transmission, a first output shaft connected to the first driveline, a second output shaft connected to the second driveline, a gear reduction unit driven by said input shaft, a range clutch for establishing first and second drive connections between said gear reduction unit and at least one of said first and second output shafts so as to define high-range and low-range drive modes, and an actuator for actuating said range clutch;
a mode selector for generating a mode signal indicative of the selected drive mode;
a powertrain control module controlling a fuel system and an ignition system of the engine;
a relay circuit interconnected between the fuel and ignition systems and said powertrain control module;
and
a transfer case control module receiving said mode signal and operable for sending a control signal to said relay circuit for controlling the fuel and ignition systems of the engine to modify the drive torque supplied to said input shaft and sending a shift signal to said actuator for causing said range clutch to establish the selected one of said high-range and low-range drive modes.

3 more elements

A method for shifting between high-range and low-range drive modes provided by a transfer case in a four-wheel drive vehicle having an engine including fuel and ignition systems and which supplies drive torque to the transfer case, comprising the steps of:

providing a mode selector for generating a mode signal indicating a request to shift from the current one of said high-range and low-range drive modes to a selected drive mode;
providing a powertrain control module for monitoring and controlling operation of said fuel and ignition systems;
providing an interruptable circuit between at least one of said fuel and ignition systems and said powertrain control module;
supplying said mode signal to a transfer case control module;
supplying an input signal to said transfer case control module indicating whether a throttle for said vehicle is open or closed;
and
supplying a shift signal from said transfer case control module to said transfer case for shifting into said selected drive mode when said throttle is closed, otherwise supplying a control signal to said interruptable circuit for controlling operation of said fuel and ignition systems to modify the drive torque supplied to said transfer case and then supplying said shift signal to said transfer case.

4 more elements

Dependencies are inferred from the claim text.

Transfer case shift control system using automatic shutdown relay circuit

Life of this patent

Transfer case shift control system using automatic shutdown relay circuit

Life of this patent

Abstract

Claims22