New torque converter lockup design questions

[christianroth]

I am looking to build a high torque lockup clutch that would exist in an automatic transmission torque converter. The factory lockup clutch is just a single piston being hydraulically activated against the front cover. There have been a few ideas out there regarding some different designs.

1. Multi disk lockup clutch (hydraulically activated)
2. Cone style lockup clutch (hydraulically activated)
3. Centrifugal lockup clutch (hydraulically and centrifugally activated)

I completely understand the theory on the multi disk and the centrifugal methods. But I have problems understanding the cone clutch. I am aware that cone clutches are very popular in the marine industries and the differentials of automobiles as well. Why do they hold so much torque and how do they wear over time. Would they be a good design choice for an automotive lockup clutch and what concerns would have when designing one? If anyone has some examples or knows of any reading material on clutch design in general, please respond.

 

[patprimmer]

The syncronysers in gear boxes are also cone clutches, as were the clutches on many antique or veteran cars, especially pre 1920. Bentleys of about that vintage, being a prime example. The supercharged Bentleys had considerable power, even by todays standards. Regards
pat

 

[TheBlacksmith]

Cone clutches I have worked with had a common strength/weakness. The cups had power applied (were rotating) and the cone was on the driven shaft with a thread. To engage the clutch, you moved the cone into contact with the cup, which was relatively speaking rotating faster than the cone, then the thread drove the cone into the cup. The more torque you applied, the tighter it locked. Of course unlocking it was a beast of a different color. I can't reveal the exact means used by my former employer, but suffice to say, you have to devise a method of causing the relative speed of the cone to exceed that of the cup. In a locking differential, it is easy to get this unlocking effect - turn and corner and the natural differential action will cause it. Good luck.

Blacksmith

 

[christianroth]

In a torque converter the piston is actually vacuum actuated (pressure is release on the clutch side, which causes the piston to be pressed against the cover). In this application would there be enough of a “vacuum to engage the cone? On the flip side when the lockup clutch is released the clutch side of the piston is filled with high-pressure oil causing the clutch to disengage. Would this be enough to also push the cone off of its seat?

 

[TheBlacksmith]

Yes and no. With the self locking feature we used, it would not; you had to alter the speed relationship to make it want to unlock. Also the types of materials used had a distinct effect. When I left the company, there were 3 generations of cup/cone materials, interesting going generally towards lower friction as the horsepower capability increased. Mixing generations either produced almost complete slippage or a virtual weld. Design is a good principle, but controlling the foce and material properties make it or break it. I'm being vague on purpose as there are patents and such in effect.

Blacksmith

 

[GregLocock]

If there are patents in effect then the knowledge is in the public realm, and it is safe to disclose it! Cheers

Greg Locock

 

[christianroth]

Would you feel that the holding ability would be better in the cone style cluctch than a multi disk clutch?

How much of a factor does the apply pressure contribute to holding force of the cone clutch.

What are the patent numbers.

 

[patprimmer]

The most common cone clutch is the morse taper. It is used as a drive on tools such as mills drills and lathes, and propellor shafts on boats. These are locking tapers and handle extremely high loads per surface area.

The taper angle is critical to the tendency to lock on or release. I am at the end of my knowledge on this, but I expect that it is a subject studied by Toolmakers". Regards
pat