EHPV JD Incova vs A Conventional Spool Valve??

[julesk]

Hello, We are in need of an CAN bus electrohydraulic control system for use on a client's vehicle. Other than a fair background in automotive CAN bus sytems our hydraulic expertise is a far to none and we are hoping someone out there can enlighten us. One problem is it would be used in a very, very abusive environment, heavy vibration, extreme deltas in temperature, etc..

We are looking for recomendations to two technologies - electrohydraulic spool valves and distributed electrohydraulic poppet valves. From our research it appears the spool valve will stand up to much a harsher environment and have been around for quite some time?

A while ago I read about an John Deer "InCoVa" technology where they use distributed H-bridge style CAN-bus controllers mounted directly on the cylinders. At first this looked like a good idea but quicly we realized that in reality the electronics could never come close to handling the forces induced on our vehicle's boom arm, especially with accessories such as with a hydraulic hammer. We calculated the forces to be over 40 times greater than any electronics mounted on a cylinder could ever come close to handling, common sense is that using that technology the electronics circuit board would become dust at those forces no matter how much shock mounting was done. I haven't heard anything about it lately. I came across a company Husco that pursued it but it appears they too gave up.

I am also wondering that being exposed to the operating and environmental thermal rises, especially during regeneration (without returning to the tank cooler the hydraulic medium would get excessively hot and break down also transfering heat to the controllers playing havock on the electronics, especially the currnet needed to energize the coils, not to mention a poppet valve's weakness to poor partical contamination suscepitability. I was also told Caterpillar Corporation gave up on trying to get these types of valves working decades ago. I came across a company Husco that pursued it recently but it appears they too gave up.

Does anyone have experience in Can-Bus based spool or EHPV systems? We are guessing the valve would need to be mounted in the operator's area and plumbed out to the cylinders, which appears to be the norm? Has anyone heard of anything new on the EHPV poppet systems or InCoVa?

Jules

 

[Newmanite]

CAN bus systems are used on Terex O&K rh170 mining excavators,it lives in a room under the operators cab the electrical control is run from 24VDC which is reduced and ultimately controls EHC proportional valves between 225mA through to 850mA it also controls the pump management logic control.Poppet valves "can" be forgiving in a fluid cleanliness environment but as anyone here would recommend you to stay as close as the ISO rating as you can so online filtration should be considered as also a priority for the longevity of your components.
It so not an overly big board, the cabinet it is in is pressurized to keep dirt and iron ore dust out.These servo valves are under the cab sending hydraulic signal(60 bar) to a larger control valve that sends oil to the cylinders and the "computer board" also controls the stroke of the pump through variable control from say a joystick elec control to the pump management system to a set of proportional valves to stoke the pump 225mA (minimum pump angle=0 flow)
through to 850mA(max angle=full flow).
In regard to your question about oil cooling problems you really need a cooler on it whether you have a stand alone unit regulated with a fan(think car radiator)or using the cooling system for the prime mover(engine)and running the hydraulic oil through water/oil intercooler (or twin coolers)

Is this the advice you are looking for?

 

[EdDanzer]

We built a load sensing system using HydraForce cartridge proportional valves to control a directional drill mounted on the end of an excavator arm and it has worked fine.

What G force are you subjecting these components to that you cannot vibration isolate the electronics?

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[JPfaff]

Hello, I’m the director or INCOVA at HUSCO.

There are two concerns that you raised that are both areas that we spent considerable time researching and testing. The shock and vibration on construction equipment is severe. The conventional SAE or ISO testing with 1/2wave 100G shock is inadequate. Acceleration testing was performed on a machine under different operating conditions and then a SRS (shock response spectra) was developed and used for qualification of the electronics and hardware. This type of testing is common on very high repeated shock applications like military or aerospace rockets. The testing did expose problems that were address through more rigid mounting of some of the electronic components.

The second issue raised is local heat from regeneration. There is some heat from regeneration, but you must also consider the reduction in heat with INCOVA in comparison to a conventional valve from pressure compensation and other valve losses. The pressure compensation heat is reduced by using regeneration since less flow from the pump is required. The other losses common on a spool valve are also reduced. It is common for a spool valve to have 20-40bar of losses on the outlet to maintain controllability. These are the losses that we are minimizing with the pressure sensor feedback and advanced control. As side points of interest, from memory I believe the heat rise of oil is about 7deg F per 1000PSI of metering loss. From our review of temperature limits, the pump seals are normally the constraint on the machine at about 90-100C. The electronics can easily handle over 115C. High quality valve seals can handle similar temperatures.

Regards,

Joe Pfaff, joe.pfaff@huscointl.com