Feed Pump and Regulating Valve


1. Feed pump

The vane type feed pump consists of four blades and a rotor. The rotor is driven by the drive shaft, and the blades push against the inner wall of the pressure chamber due to centrifugal force. As the center of this rotor is eccentric to the center of the pressure chamber, the fuel between the blades is compressed and pushed outward.

2. Regulating valve

The regulating valve adjusts the discharge pressure of the feed pump according to the pump speed. The fuel injection timing is controlled by the timer which responds to the pressure inside the pump housing.

Fuel Diesel Engine Delivery and Injection System

1. The feed pump, cam plate and plunger are driven by the drive shaft and rotate at the rate of half the engine speed.

2. Two plunger springs push the plunger and cam plate against the rollers.

3. The cam plate has the same number of the face cam as that of the cylinder. (Four-cylinder engine has four face cams.) The cam plate pushes the plunger in and out rotating on the fixed roller. Therefore, the plunger follows the face cam movement, and reciprocates in sync with the face cam with rotating. With one turn of the cam plate, the plunger makes one complete turn and reciprocates four times.

4. Fuel for one cylinder is delivered with each 1/4 turn and one reciprocating motion of the plunger (Four-cylinder engine).

5. The plunger has four suction grooves, a distribution port, a spill port and a pressure equalizing groove. The spill port and distribution port are aligned with the access hole of the plunger center.

6. The fuel is drawn from the suction groove of the plunger. Then the highly compressed fuel is sent through the delivery valve from the distribution port, and pumped into the injection nozzle.

1. Suction

When the plunger goes down (moves to the left), one of four suction grooves in the pump plunger will be aligned with the suction port in the distributive head. Thus, the fuel is drawn into the pressure chamber and from there into the interior of the plunger.

2. Delivery

As the cam plate and plunger rotate, the suction port of the distributive head is closed off and the distribution port of the plunger will be aligned with the distribution passage. As the cam plate rides onto the rollers, the plunger goes up (moves to the right) and compresses the fuel. When the fuel pressure reaches the predetermined value, the fuel is injected from the injection nozzle.

3. Termination

When the cam plate rotates further and the plunger goes up (moves to the right), two spill ports of the plunger are pushed out from end of the spill ring. Then, the highly pressurized fuel is returned back to the pump housing through the spill ports. As a result, the fuel pressure drops suddenly and the fuel injection is terminated.

Effective stroke

The effective stroke is the distance that the plunger moves from the start of the fuel compression till the end. As full pump strokes are constant, the spill ring location is changed to increase or decrease the injection volume by the change of the effective stroke. When the effective stroke becomes longer, the compression ends later and the injection volume will be increased. Conversely the compression ends earlier and the injection volume will be decreased when the effective stroke becomes shorter.

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