Transmission and integrated transfer case

Patent metadata

Field	Value
Publication number	US-9764739-B2
Application number	US-201414552845-A
Country	US
Kind code	B2
Filing date	Nov 25, 2014
Priority date	Nov 25, 2014
Publication date	Sep 19, 2017
Grant date	Sep 19, 2017

Abstract

A transfer case and transmission are designed to permit the transmission hydraulic control system to control a range selection coupler and a torque on demand clutch in the transfer case. Two pressure circuits are transmitted from the transmission to the transfer case: a high range circuit and a low range circuit. The low range circuit is pressurized to engage low range while the range circuit is pressurized to engage high range. The torque on demand clutch is controlled by whichever of these circuits has the higher pressure. Lubrication is provided to a front section of the transfer case via the transmission output shaft, with the fluid returning to the transmission sump through a drainback passageway. The rear portion of the transfer case has a segregated sump. A control strategy is employed to partially fill front section of the transfer case with fluid in preparation for vehicle towing.

First claim

What is claimed is:

1. A transmission hydraulic control system comprising:
a high range circuit and a low range circuit each adapted to transmit fluid across an interface to a transfer case;
a pressure control valve configured to adjust a pressure in a controlled pressure circuit based on a first current; and
a switch valve configured to fluidly connect the controlled pressure circuit to the high range circuit and to the low range circuit, alternately, based on a second current.

2. The hydraulic control system of claim 1 further comprising a controller programmed to adjust the first and second currents to:
momentarily increase a pressure in the high range circuit in response to a high range selection command; and
momentarily increase a pressure in the low range circuit in response to a low range selection command.

3. The hydraulic control system of claim 2 wherein the controller is further programmed to adjust the first current to increase the pressure in the controlled pressure circuit in response to an indication of vehicle rear wheel slip.

4. The hydraulic control system of claim 1 further comprising:
a mechanically driven pump configured to draw fluid from a transmission sump and provide the fluid at elevated pressure to a line pressure circuit; and
a regulator valve configured to adjust the pressure of the line pressure circuit based on a third current.

5. The hydraulic control system of claim 4 further comprising:
a lube circuit adapted to transmit fluid to the transfer case; and
a drainback passageway adapted to transmit fluid from a transfer case sump to the transmission sump.

6. The hydraulic control system of claim 5 wherein the lube circuit transmits fluid to the transfer case through a transmission output shaft.

7. The hydraulic control system of claim 5 further comprising a drainback valve configured to selectively block the drainback passageway.

8. The hydraulic control system of claim 4 further comprising an electrically driven pump configured to draw fluid from the transmission sump and provide the fluid at elevated pressure to the line pressure circuit.

9. The hydraulic control system of claim 7 further comprising a controller programmed to prepare a vehicle to be towed by:
closing the drainback valve;
while the drainback valve is closed, operating the pump to transfer fluid from the transmission sump to the transfer case sump; and
shifting a coupler to disengage a rear driveshaft from a transmission output shaft.

10. The method of claim 9 wherein operating the pump to transfer fluid comprises operating an engine to drive the pump.

11. The method of claim 9 wherein operating the pump to transfer fluid comprises operating an electric motor to drive the pump.

Assignees

• Ford Global Tech Llc

Inventors

• Deutsch Laurence Andrew
• Maurer Jeffrey Edward
• Frait Steven Anatole
• Mccubbin Nicholas E
• Perakes Andreas E

Classifications

• B60K17/344

  having a transfer gear · CPC title

• F16H57/0439

  using multiple pumps with different power sources or a single pump with different power sources, e.g. one and the same pump may selectively be driven by either the engine or an electric motor · CPC title

• F16H57/0446

  the supply forming part of the transmission control unit, e.g. for automatic transmissions · CPC title

• B60W10/10

  including control of change-speed gearings · CPC title

• F16H57/0482

  Gearings with gears having orbital motion · CPC title