Hybrid powertrain system and operation with transfer case in low gear

Patent metadata

Field	Value
Publication number	US-10899351-B2
Application number	US-201816190514-A
Country	US
Kind code	B2
Filing date	Nov 14, 2018
Priority date	Nov 17, 2017
Publication date	Jan 26, 2021
Grant date	Jan 26, 2021

Abstract

A hybrid powertrain includes a torque provider, an automatic transmission without a torque converter, and a transfer case configured for providing four wheel drive low range. A controller receives a signal indicative of the transfer case being in low range and determines if brake pedal torque is indicative of a brake pedal being released and, if so, commands engagement of a launch clutch of the transmission up to maximum creep torque capacity at a predetermined maximum gradient. The controller determines when torque provider speed is synchronized with vehicle creep speed, and upon such determination, controls the launch clutch to fully engage to a lock up state to mimic behavior of engagement of a manual transmission gear when the hybrid powertrain is in low range to thereby substantially eliminate a time lag associated with automatic transmissions having a torque converter or a constantly slipping launch clutch.

First claim

What is claimed is:

1. A hybrid powertrain system of a vehicle, the hybrid powertrain system comprising:
a torque provider for providing drive torque to wheels of the vehicle;
a hybrid automatic transmission including a launch clutch and an electric motor capable of providing drive torque to the wheels, the hybrid powertrain being free of a torque converter;
a transfer case configured to be selectively activated to provide four wheel drive low range gear selection; and
a control system configured to control the hybrid powertrain between (i) a normal driving mode where the hybrid automatic transmission mimics operating behavior of a vehicle with a torque converter, and (ii) a four wheel drive low range mode where the hybrid automatic transmission mimics operating behavior of a manual transmission, the control system configured to:
operate in the normal driving mode when the transfer case is not in four wheel drive low range; and
operate in the four wheel drive low range mode when the control system receives a signal indicative of the transfer case being in four wheel drive low range and determines, based on the signal, if brake pedal torque is less than a threshold indicative of a brake pedal being released;
wherein in the four wheel drive low range mode, the control system is configured to:
command engagement of the launch clutch up to maximum creep torque capacity at a predetermined maximum gradient based on determining the brake pedal torque is less than the threshold;
determine when the torque provider speed is synchronized with vehicle creep speed; and
upon such determination, control the launch clutch to fully engage to a lock up state to mimic a behavior of engagement of a manual transmission gear when the hybrid powertrain is in low range to thereby substantially eliminate a time lag associated with automatic transmissions having a torque converter or a constantly slipping launch clutch.

2. The hybrid powertrain system of claim 1 , wherein commanding engagement of the launch clutch up to maximum creep torque capacity at the predetermined maximum gradient is based solely on determining the brake pedal torque is less than the threshold.

3. The hybrid powertrain system of claim 1 , further comprising communicating the maximum creep torque as a torque request to one or both of the torque provider and the electric motor to move the vehicle to the vehicle creep speed.

4. The hybrid powertrain system of claim 1 , wherein determining when the torque provider speed is synchronized with vehicle creep speed includes determining when a slipping speed of the launch clutch is at least substantially equal to the vehicle creep speed.

5. The hybrid powertrain system of claim 4 , wherein the torque provider is an internal combustion engine coupled to the hybrid automatic transmission.

6. The hybrid powertrain system of claim 4 , wherein the torque provider is the electric motor.

7. The hybrid powertrain system of claim 1 , wherein the predetermined maximum gradient for ramping up engagement of the launch clutch to maximum creep torque is calibrated to mimic the rate of gear engagement of a selected gear of a manual transmission when an associated clutch pedal is released.

8. The hybrid powertrain system of claim 1 , wherein the hybrid automatic transmission requires engagement of three clutches to establish powerflow, and wherein when the vehicle is at rest and the transmission is in drive gear, two of the three clutches are controlled to be fully engaged and the third clutch is the launch clutch, which is controlled to be at a touch point before the brake pedal torque is less than the threshold.

9. The hybrid powertrain system of claim 8 , wherein the vehicle is initially at rest and the launch clutch is being controlled to engage first gear of the hybrid automatic transmission.

10. The hybrid powertrain system of claim 1 , wherein the engagement of the launch clutch at maximum creep torque capacity is maintained independent of vehicle speed until the torque provider speed is determined to be at least substantially equal to the vehicle creep speed, the torque capacity of the launch clutch will only then be increased.

11. The hybrid powertrain system of claim 1 , wherein the maximum creep torque is a function of brake torque only, and is free of being a function of slip across the launch clutch, and wherein the launch clutch is engaged to maximum creep torque capacity only when the transfer case is in the four wheel drive low range gear selection.

12. The hybrid powertrain system of claim 1 , wherein a disengage speed to open the launch clutch is below vehicle creep speed and is free from being a function of a position of an accelerator pedal of the vehicle.

13. The hybrid powertrain system of claim 1 , wherein the vehicle is initially at rest and the hybrid automatic transmission is being controlled to engage first gear.

Assignees

• Smyczynski Robert S
• Patel Nadirsh
• Senft Stefan
• Fca Us Llc

Inventors

• Smyczynski Robert S
• Patel Nadirsh
• Senft Stefan

Classifications

• B60W30/18063 Primary

  Creeping · CPC title

• B60W10/08

  including control of electric propulsion units, e.g. motors or generators · CPC title

• Y02T10/62

  Hybrid vehicles · CPC title

• B60W2710/083

  Torque · CPC title

• B60W2520/10

  Longitudinal speed · CPC title