Method for determining wet clutch temperature

{
  "publication_number": "US2012261228A1",
  "country": "US",
  "kind": "A1",
  "title": "Method for determining wet clutch temperature",
  "abstract": "A method for determining clutch temperature. The method provides an accurate real-time clutch temperature that can be used to improve shift quality and protect against failure due to clutch overheating. A counter is incremented every time the clutch exceeds a threshold temperature to track cumulative high temperature conditions. Determining the clutch temperatures includes taking account of heat generation, clutch cooling by transmission oil flow from a groove when the clutch is engaged, clutch cooling by open transmission oil flow when the clutch is disengaged, oil vaporization, and heat conduction.",
  "claims": [
    "1. A method of measuring and preventing clutch overheating, said method comprising: calculating a clutch temperature as a function of at least clutch pressure, incrementing a counter within a vehicle control system each time the clutch temperature exceeds a first predetermined temperature value, and taking corrective action based on a value of the counter. 2. The method of claim 1, further comprising: recording in the vehicle control system the total time the clutch is maintained at a temperature above a second predetermined temperature value. 3. The method of claim 2, wherein the first predetermined temperature value is equal to the second predetermined temperature value. 4. The method of claim 2, wherein the act of taking corrective action includes taking corrective action based on the value of the counter and on the total time the clutch is maintained at a temperature above a second predetermined temperature value. 5. The method of claim 2, further comprising: predicting a failure of the clutch based on at least one of the value of the counter and the total time the clutch is maintained at a temperature above the second predetermined temperature value. 6. The method of claim 2, further comprising: diagnosing root causes of clutch failures based on at least one of the value of the counter and the total time the clutch is maintained at a temperature above the second predetermined temperature value. 7. The method of claim 2, further comprising: determining at least one of shift quality and driver habits based on at least one of the value of the counter, the total time the clutch is maintained at a temperature above the second predetermined temperature value, and a change in temperature for at least the most recent shift. 8. The method of claim 1 further comprising: predicting a temperature increase for a requested shift prior to executing the requested shift. 9. The method of claim 8, wherein taking corrective action involves providing real-time compensation within the vehicle control system. 10. The method of claim 9, wherein the real-time compensation includes modifying shift schedules based on at least one of clutch temperature and the predicted increase in clutch temperature for the requested shift. 11. The method of claim 9, wherein the real-time compensation includes modifying shift logic based on at least one of clutch temperature and the predicted increase in clutch temperature for the requested shift. 12. The method of claim 9, wherein the real-time compensation includes providing clutch overheat protection based on at least one of clutch temperature and the predicted increase in clutch temperature for the requested shift. 13. The method of claim 12, wherein the real-time compensation includes enabling clutch overheat protection only if the clutch temperature is above a threshold value. 14. The method of claim 1, wherein taking corrective action involves providing information via a vehicle display. 15. The method of claim 14, wherein the information provided to the vehicle display includes at least one of a shift quality indicator, a clutch temperature warning, a clutch lifecycle indicator, and a clutch overheat protection indicator. 16. The method of claim 1, further comprising recording the change in temperature for at least the most recent shift. 17. The method of claim 1, wherein calculating the clutch temperature is based on at least one of heat generation, clutch cooling by transmission oil flow from a groove when the clutch is engaged, clutch cooling by open transmission oil flow when the clutch is disengaged, oil vaporization, and heat conduction. 18. The method of claim 1, wherein calculating the clutch temperature is based on the assumption that during contact the clutch temperature, a separator plate temperature and a friction lining temperature are substantially equal and that heat transfer is proportional to physical material properties. 19. The method of claim 1, wherein taking corrective action based on the counter includes taking corrective action when the counter reaches predetermined value."
  ],
  "description_excerpt": "The invention relates to methods and systems for determining real-time temperatures of the wet clutches in an automatic transmission.\n\nAutomatic transmissions have long employed hydraulically-applied clutches to effect ratio changes in planetary gear trains, for example, through the synchronized opening and closing of select clutches attached to different elements of the planetary systems. The clutch assembly used in automatic transmissions typically consists of multiple separators, friction plates and other components. The friction plate is made of a low carbon steel core plate with friction material bonded on each side, which is splined to the input shaft while the separator plates are lugged to the clutch housing or vice versa. The clutch housing could link to another shaft (rotating clutches) or to the transmission case (brake clutches).\n\nDue to their desirable friction characteristics for shift quality and cost effectiveness, wet paper-based friction materials have been primarily used as clutch facings for automatic transmissions in cars and brake materials for industrial vehicles. However, because of the lack of heat and chemical stability under extremely high temperature conditions, the paper-based cellulose fiber often breaks down causing material break out, high-friction-lining thickness loss and, eventually, loss of appropriate friction characteristics. Indeed, it is believed that thermal degradation of the friction material due to high temperature is the major factor for determining the life cycle of a wet clutch.",
  "cpc": [
    "F16D 48/06",
    "F16D 2500/30405",
    "F16D 2500/5102",
    "F16D 2500/5106",
    "F16D 2500/70673",
    "F16D 2500/7104"
  ],
  "ipc": [
    "F16D 23/00",
    "B60K 6/38",
    "B60K 6/383",
    "B60K 6/387"
  ],
  "assignees": [
    "Chrysler Group LLC"
  ],
  "inventors": [
    "Gang Chen",
    "Yimeng Jin"
  ],
  "filing_date": "2012-04-12",
  "publication_date": "2012-10-18",
  "priority_date": "2011-04-12",
  "application_number": "US-201213445146-A",
  "family_id": "45977072",
  "cited_by_count": 17,
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    "FR2936034A1"
  ]
}