China has imported several bathes of hydraulic vibratory road roller from a German company, BAUKEMA. The main component of the road roller is the electro-hydraulic valve. There was no such component in the market, so road rollers were hard to repair at that time.

Our company improved 7 sets of road rollers which remain running well today.


Current going through the controlling coil makes the baffles turn around with the fulcrum. One of the gap between the nozzle and the baffle widens with the narrowing of the other one. And the pressure increases in one of the gap and decreases in the other one. The different pressure moves the spool and makes the fuel entrance meet the controlling chamber. The moving spool drives the small ball under the feedback rod to give a restoring torque opposite to the electromagnet torque. When the two torques become equal, the spool will stop at a position proportional to the input current. If the pressure in the fuel entrance is constant, the flow can be controlled proportionately by the input current.