A Method for Limiting Clutch Torque to Reduce High MU Wheel Slip

Patent metadata

Field	Value
Publication number	US-2016229290-A1
Application number	US-201415027939-A
Country	US
Kind code	A1
Filing date	Oct 8, 2014
Priority date	Oct 9, 2013
Publication date	Aug 11, 2016
Grant date	—

Abstract

A method for limiting the amount of torque biased to a high mu wheel of a vehicle comprises processing clutch torque data to determine an electronic limited slip differential clutch torque limit, processing wheel speed data to generate mu slip data, comparing the generated mu slip data to threshold mu slip data. When the generated mu slip data is greater than the threshold mu slip data, the method comprises reducing the electronic limited slip differential clutch torque limit by a predetermined ratio.

First claim

1 . A method for limiting an amount of torque biased to a high mu wheel of a vehicle, comprising:
processing clutch torque data to determine an electronic limited slip differential clutch torque limit; processing wheel speed data to generate mu slip data; comparing the generated mu slip data to threshold mu slip data; and when the generated mu slip data is greater than the threshold mu slip data, reducing the electronic limited slip differential clutch torque limit by a predetermined ratio.

2 . The method of claim 1 , wherein the step of processing wheel speed data comprises generating a mu wheel slip speed (HiMuSlip) using one of equations 1 or 2:
HiMuSlp=Minimum(wFL, wFR)−Average(wRL, wRR)  eq. 1
HiMuSlp=Minimum(wRL, wRR)−Average(wFL, wFR),  eq. 2
where wFL, wFR, wRL, and wRR respectively stand for the front left, front right, rear left, and rear right wheel speeds.

3 . The method of claim 1 , further comprising:
comparing a current torque command from a traction controller against a torque command calibration value; and processing at least the wheel speed data to determine if a vehicle speed (Vx) of an affiliated vehicle is less than maximum vehicle speed threshold (MaxVx).

4 . The method of claim 3 , further comprising adjusting the clutch torque limit until the clutch torque command is less than the torque command calibration value.

5 . The method of claim 4 , wherein the step of adjusting the clutch torque limit comprises at least one of decreasing the clutch torque limit by a first torque change calibration value, and increasing the clutch torque limit by a second torque change calibration value.

6 . The method of claim 5 , further comprising determining whether mu wheel slip speed is less than a maximum mu wheel slip speed.

7 . The method of claim 6 , further comprising determining whether a current clutch slip speed is greater than a target clutch slip speed.

8 . The method of claim 6 , further comprising comparing a mu wheel slip speed derivative to a threshold mu wheel slip speed.

9 . The method of claim 8 , further comprising processing wheel speed data to determine whether wheel slip is increasing or decreasing, and, when the wheel slip is decreasing, holding a clutch torque limit.

10 . The method of claim 4 , further comprising comparing the clutch torque limit to a maximum allowed clutch torque limit and a minimum allowed clutch torque limit, determining whether the clutch torque limit is closer to the maximum allowed clutch torque limit or to the minimum allowed clutch torque limit, and, based on the determination, saturating the clutch torque limit at the closest of the maximum allowed clutch torque limit and the minimum allowed clutch torque limit.

11 . The method of claim 5 , wherein the first torque change calibration value is a function of the generated mu wheel slip speed.

12 . The method of claim 5 , wherein the second torque change calibration value is a function of a current clutch slip speed.

13 . The method of claim 1 , further comprising receiving and processing vehicle data; and adjusting the clutch torque limit based on the vehicle data.

14 . The method of claim 13 , further comprising calculating a current clutch slip, wherein adjusting the clutch torque limit is done at an adjustable rate, and wherein the adjustable rate is a function of the current clutch slip.

15 . The method of claim 14 , wherein the clutch torque limit is adjusted at a greater rate when the clutch slip is high, but the clutch torque limit is adjusted at a lower rate when the clutch slip is low.

16 . The method of claim 2 , further comprising:
comparing a current torque command from a traction controller against a torque command calibration value; and processing at least the wheel speed data to determine if a vehicle speed (Vx) of an affiliated vehicle is less than maximum vehicle speed threshold (MaxVx).

Assignees

• Eaton Corp

Inventors

• Chimner Christian Thomas

Classifications

• B60W2552/40

  Coefficient of friction · CPC title

• B60W2710/027

  Clutch torque · CPC title

• B60W2510/0275

  Clutch torque · CPC title

• B60K23/04 Primary

  for differential gearing · CPC title

• B60K23/0808

  for varying torque distribution between driven axles, e.g. by transfer clutch · CPC title