Hydraulic valves for transmission control
Hydraulic valves for transmission control
(OP)
I've been researching available hydraulic valves for a transmission control application. The need is for proportional (PWM) control of pressure in a clutch slave cylinder. It's not a standard clutch, instead the springs keep the plates apart and hydraulic pressure clamps the clutch. This is so drive disconnects for a failure of hydraulic pressure.
What kind of hydraulic circuit & valve type is normally used to control clutches for torque converter lockup or in twin-clutch gearboxes like DSG?
I'm thinking this type of hardware could be adapted for our application.
Thanks, Ian
What kind of hydraulic circuit & valve type is normally used to control clutches for torque converter lockup or in twin-clutch gearboxes like DSG?
I'm thinking this type of hardware could be adapted for our application.
Thanks, Ian





RE: Hydraulic valves for transmission control
ISZ
RE: Hydraulic valves for transmission control
You can buy servohydraulic valves from the common industrial hydraulic component suppliers (Bosch-Rexroth, Parker, etc) but they will be overkill for your application and REALLY expensive. A normal hydraulic directional solenoid valve isn't designed for use with PWM.
Any problem like this is solvable with money. How much do you have?
RE: Hydraulic valves for transmission control
DSG solenoids are of the VFS type which operate at a higher electrical frequency, but directly control the clutch pressure. VFS are also typically used to control line pressure in a planetary automatic, but without the flow demand of the clutch control solenoid.
Solenoids are designed for specific leakages, pressures, flow rates. Hardware could be adapted, but the electronic control will be the bigger challenge.
RE: Hydraulic valves for transmission control
Does anyone know if the clutch control on the current auto-shift manual gearboxes is done as a closed loop slip control, or a closed loop pressure / position control?
Thanks, Ian
RE: Hydraulic valves for transmission control
Keep in mind that an old fashioned centrifugal clutch varies its engagement pressure according to input speed. But, you can't disengage those during gear changes.
RE: Hydraulic valves for transmission control
I guess I'm asking if anyone knows the control feedback mechanism(s) in use for that type of clutch during vehicle launch. But as you say, maybe those that do know aren't here or can't tell.
Regards, Ian
RE: Hydraulic valves for transmission control
I think from memory, the VW version used a torque converter plus a servo operated clutch and pressure plate system.
Regards
Pat
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