Parallel hybrid EV with direct torque coupling - torque ratings of components 1

[123MB]

Hi All

We are designing a parallel hybrid vehicle which has an ICE engine driving a transmission and an electric motor coupled to the transmission output shaft.

A direct torque coupling is used between the motor and transmission output shaft - the motor is basically driven via a belt drive where the driven pulley is directly connected to the transmission output.

The philosophy is that the motor speed will match the tranny output speed and be applying more or less torque than the output shaft ie to regen, assist, etc. If something goes wrong it will match speed and torque so in theory should present no load.

My confusion relates to the fact that the transmission output is capable of applying a lot more torque than the motor and belt can handle and above the motor rated torque.

For example, the motor might be able to apply a max of 100 Nm and the tranny output Being 1000 Nm.

Will this break something? What will
The torque on the motor shaft and belt be in this case?


Cheers

 

[GregLocock]

"I'm confused on why you and others seem to be suggesting that potentially 1000Nm of output from the transmission could be fed to the belt/electric moto"

I'm confused why any engineer would ignore inertia. Assuming the wheels are slipping -if the belt doesn't break or slip then the 1000 Nm will be used to accelerate the drivetrain including the motor. Now, any sensibly designed system will control that at source - even the old NASCAR trick of limiting the maximum slew rate of the engine would help.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[human909]

"I'm confused on why you and others seem to be suggesting that potentially 1000Nm of output from the transmission could be fed to the belt/electric moto"

I'm confused why any engineer would ignore inertia. Assuming the wheels are slipping -if the belt doesn't break or slip then the 1000 Nm will be used to accelerate the drivetrain including the motor. Now, any sensibly designed system will control that at source - even the old NASCAR trick of limiting the maximum slew rate of the engine would help.

You are correct that inertia needs to be considered.

I don't see how you suddenly jump to a 1000Nm figure simply due to slip. The inertia of an electric motor is low and what matters is the speed of the drive train. A slip doesn't mean you suddenly jump to 1000Nm imposed on the belt.

 

[GregLocock]

If the engine/transmission is supplying 1000 Nm as the wheels slip that 1000 Nm is available to accelerate the drivetrain/motor.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[human909]

If the engine/transmission is supplying 1000 Nm as the wheels slip that 1000 Nm is available to accelerate the drivetrain/motor.

The key word they is AVAILABLE. Just because it is available doesn't mean that it will be delivered. In fact it is a given that the majority WON'T be delivered. The as anybody would know the engine speeds rise when wheels slip this is precisely because there is a reduction in LOAD, AKA torque. So it is clearly ture that the 1000Nm is no longer being delivered.

It the actual toque derived depends on how the change in speed of the drive train and the inertia of the electric motor. You've already mentioned the word inertia, but you seem to have quickly forgotten how it behaves by suggesting that 1000Nm will be available to accelerate the drivetrain/motor.

Your description is like saying that if I staying that if I touch a car battery then I'm going to have 500amps through my body. Or if my pet elephant and I both stand 5T hoist and the elephant steps off then suddenly I'm going to have the full 5T load on me.

 

[GregLocock]

I suggest you stop digging. A matter of practical experience is that if the engine is at full throttle and the transmission breaks for whatever reason, the full engine torque is available to accelerate whatever is left.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[LittleInch]

In that case the fact the electric motor connection might break seems relatively inconsequential. If the belt slips a bit so what. So long as its not toothed then it will survive

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[human909]

I suggest you stop digging. A matter of practical experience is that if the engine is at full throttle and the transmission breaks for whatever reason, the full engine torque is available to accelerate whatever is left.

I will stop engaging with you because you do not seem to be willing to engage in a mature engineering discussion.

Like I've already said saying the "full engine torque is available" is not the same as the delivered torque. Your interpretation of your practical experience isn't an accurate description of engineering mechanical reality.

 

[mfgenggear]

Op
Build it test it,
Investigate face clutch, it will disengage if it starts to spin to fast
Maybe an option. The use them to start turbo props,

 

[CWB1]

The vehicle is an on highway freight prime mover with traction control.

If you havent already, I'd review the hybrid semi transmissions sold by Eaton and others along with the plethora of accessories driven by full and part-time PTOs, many of which have belts or gear drives to adjust speed.