is it possible to convert a solenoid "on/off" hydraulic valve into a proportional valve
is it possible to convert a solenoid "on/off" hydraulic valve into a proportional valve
is it possible to convert a solenoid "on/off" hydraulic valve into a proportional valve
You can turn it on and off very quickly, it's called pulse width modulation. But you'll only achieve volume control, not flow control.
how quickjly are we talking? i assume the spool has inertia if you add to that the spring thats going to be quite a heavy load for the coil
Depends how smooth you want it.
>PWM
>on a physical mechanism
It's like you hate reliability or something.
not like it hasn't been done for the last 20+ years in the harsh environment that is an internal combustion engine
I suspect there's hysteresis in a conventional valve that will prevent it from being used as a linear proportional valve. You can try just feeding it a slowly variable voltage under pressure, but I'm guessing it will suddenly latch. If there's no hysteresis but the active area is too small, you might be able to use a pressure sensor or two and operate it with feedback. If it does have hysteresis such feedback will just cause it to oscillate, like the other anon's suggested PWM method.
Well if you buffer the flow with some sort of elastic membrane it might smooth out the PWM enough to get flow speed control.
Some proportional valves are designed with this in mind, while others are designed to be controlled linearly.
>Well if you buffer the flow with some sort of elastic membrane
easier said than done pal
If the piston or however you cgall the movable element is visible, then you could drive it with an actuator instead of a solenoid. I think it would be easier to add an actuated valve inline with the solenoid valve.
I know they make electronic proportional valves, but I don't know the specifics of them. I'm sure they are way more costly than the on/off solenoid valves are.
My Altec digger derrick truck has electronic proportional valves to run most of the functions. One of these days I need to pull it into the shop and fiddle around with it and see if I can figure out how to integrate a cheap wireless crane remote onto it. Would be handy as hell to be at the hook and running the thing.
>I know they make electronic proportional valves, but I don't know the specifics of them
They're big and they use a servomotor, but I've only opened and worked on repairing a small one that I'm pretty sure was custom built by the machine manufacturer.
It was just a rotary valve with this stepper motor+encoder connected via a teeth belt, at power on it will zero itself by ramming it completely close and then operate proportionally using the encoder position
So, I work in a specialized testing environment where we tried this. Management told us that proportional valves were too costly (despite the device that was being controlled by it costing several orders of magnitude more than a new array of valves), and it did not work. It was run by a PLC, and was frequently hunting for a specific pressure/load that it could not find with the resolution given by a on/off (bang-bang) valve.
It really depends on your application. But for most instances, the proportional valve will be superior. The cost difference was not significantly different. (If memory serves, proportional valves were ~30% more than an on-off valve).