PROPORTIONAL DOUBLE SOLINOID VALVE ON A VARIABLE DISPLACEMENT PISTON PUMP

[Automaticity]

Dear Memmbers,
I have a problem controlling a swashplate on a vickers variable displacement piston pump which is fitted with a proportioanal double-solinoid valve with a manual override on both sides.
the proportional valve controls the inclination of the swash plate.
when the valve is actuated through its manual overrides, correct and stable swash plate angle occurs: One manual override increases the angle and the other one decreaseses it.
But, with the electrical control from a Rexroth Spider card : as the solinoid current increses to a certain minimum threshold (200mA), the swash plate starts to incline and then goes to its maximum angle and stays stuck there. a subsequent decrease of the current even down to 0 mA does not bring the swash plate to its initial 0° angle.

I used other valves but same results.

Any clues please?

Regards

 

[akkamaan]

Is this a bi-directional pump?
Have the pump ever worked the way you want?
Are there any mechanical springs affecting the swash plate?
Is there a swash plate position transducer/sensor?
What is the (supposed) pump application?
Why using a Rexroth Spider control unit on a Vickers pump?
Can you please post the Vickers pump model and spec codes from the ID plate.

 

[zeusfaber]

With a system built as you describe it, the swash actuating cylinders integrate the effect of the proportional valve. For as long as the valve has enough current to lift it out of its deadband, the pump will keep going further and further onto stroke. To get it off stroke again, you have to operate the valve in the other direction. This is consistent with the behaviour you're getting.

To get proportional control of the pump, it's normal to take a swash angle feedback signal from the pump and to combine that in a servo amplifier to provide closed-loop control. If you have an arrangement like that, a failure of the feedback sensor is a good way of driving the pump hard over (without affecting the operation of the manual overrides).

A.

 

[Automaticity]

Sorry for the delay.
The pump and its load are bidirectional by design, but we need only the forward direction (say,"A").

I attached some photos ( whole hydraulic station, pump nameplate, prop valve)and pump user manual.

For the time being ( due to production constraints):

1. I removed the 02 coils out from the valve body(still wired to the amplifier who constantly checks for the presence of the coils and triggers a fault otherwise).

2. I fitted the valve body with a threading and an adjustment screw on coil "A" side to provide a fixed one-time spool adjustment in contrast to original manual pushing mecanism ( where the spool spring return requires the operator to stay at the pump the whole time).

3. My question now: I was told that there a mecanical limiting way ( like a limit switch) inside the pump to limit the swash plate internal driving piston in either direction. Would you please show me - on the user manual and/or photos- how to do it?

 

[akkamaan]

Unclear what this control valve has for control ability since it is impossible to read the ID number
What I understand is that the pump will put its swash plate at max when the control valve is actuated?!
It is obvious that the swashplate stays in a given position when controlled mechanically. since the control-valve closes the ports when push override pin is released. The problem with the electric control is that it does know when to cut the signal to the control valve. To do that the control unit needs correct feedback from the swashplate position transducer alt limit switches.
The question remains, did this ever function as supposed or are you in a build mode?

 

[Bumblyari]

It's unlikely that the Rexroth card will be able to provide the correct control function to the Eaton proportional directional valve. You really need the Eaton ER 9.3 card which closes the swashplate position loop via the yoke angle sensor. Maximum displacement is normally set by spacers in the control piston.