0336753 JOHNSON SCREW, Support

(1) A-type Injection Pump The injection pump is a device which forces fuel to the injection nozzle and has a mechanism for increasing or decreasing the pressure feed quantity according to the engine load and speed.The injection pump is constructed as shown in illustration at right. It has one plunger and delivery valve for each cylinder.The plunger, pushed up by the camshaft and pushed back by the plunger spring, moves up and down through the plunger barrel on a predetermined stroke to feed fuel under pressure.Both ends of the camshaft is supported by the taper roller bearings and is driven by the timing gear at 1/2 engine speed.(a) Pressure feed of fuel The plunger has an obliquely cut groove (lead) on its side as shown. At the top of the plunger there is a hole which leads to the groove. The plunger barrel has suction and discharge ports.The fuel delivered to the injection pump is forced by the rotation of the camshaft or reciprocating motion of the plunger as shown below. When the plunger is at the lowest position or bottom dead center (a), fuel flows through the suction and discharge ports into the plunger.Rotation of the camshaft moves the plunger up. When the top surface of the plunger is lined up with the suction and discharge ports, application of pressure to fuel begins (b).As the plunger moves up further (c), and the lead of the plunger meets with the suction and discharge ports, the high pressure fuel flows through the hole in the plunger and runs back from the lead to the suction and discharge ports, and the pressure feed of fuel is completed (d).The plunger stroke during which the fuel is fed under pressure is called the effective stroke.(b) Injection amount control system According to the engine load, the amount of injection is increased or reduced by turning the plunger a certain angle to change the position where the lead meets with the suction and discharge ports on the up stroke and increasing or reducing the effective stroke.The control rack is coupled to the floating lever in the governor. If the control rack is moved to right or left by operation of the accelerator pedal or governor, the control sleeve in mesh with the rack is turned. Since the bottom of the control sleeve is in mesh with the bar of the plunger, the plunger turns with the control sleeve, so the effective stroke changes and the injection amount increases or decreases. The more the control rack is pulled toward the governor, the less the effective stroke and the less the injection amount.Each plunger is in mesh with this single control rack and simultaneously turns the same amount.(c) Delivery valve The delivery valve, provided on the top of the pump housing, performs the function of discharging the pressure in the injection pump.The fuel compressed to a high pressure by the plunger pushes the delivery valve up and spouts out. If the pressure feed stroke of the plunger ends, the delivery valve is brought back to its original position by the pressure of the delivery valve spring to block the fuel path, thereby preventing counter flow of the fuel.The delivery valve is brought down further until the seat surface is held tight. During that stroke the fuel is drawn back from above to instantly lower the residual pressure between the delivery valve and nozzle. The draw-back effect improves the end break of an injection from the nozzle and prevents after-injection dripping.A delivery valve stopper is provided on the top of the delivery valve spring. The stopper limits the lift of the delivery valve and prevents valve surging during high speed rotation. In addition, it reduces the dead volume between the delivery valve and nozzle, thereby stabilizing the injection amount.(d) Overflow valve <4D31, 4D31-T> When the fuel pressure in the injection pump exceeds a set level, the steel ball in the overflow valve goes up to let the fuel flow out of the injection pump and return to the fuel tank, thereby stabilizing the fuel temperature and temperature distribution in the injection pump and maintaining the injection rate into each cylinder constant.(2) Governor (a) RSV type governor The RSV type governor is a centrifugal type all-speed governor coupled to the camshaft of the injection pump. The governor not only controls the maximum and minimum speeds but also automatically controls the engine speed at any intermediate speed position. The governor, as shown, consists of flyweights mounted to the injection pump camshaft. When the flyweights turning on the flyweight supporting shaft open outward, the roller mounted to the end of flyweight arm pushes the end of the sleeve in the axial direction. The governor sleeve, being made integral with the shifter through a bearing, moves only in the axial direction.The shifter, mounted to the guide lever hung on the supporting lever shaft of the governor cover, prevents rotation.The floating lever is mounted to the middle of the guide lever by the shaft with the bottom end as the fulcrum, whereas the top of the lever is coupled through the shackle to the control rack.The start spring, attached to the top end of the floating lever, always pulls the control rack in the direction that fuel is increased.The turning shaft of the swivel lever is fitted into the bushing of the governor cover and its center is eccentric with respect to the mounting position of the governor spring installed to the tension lever. The governor spring is installed to the end of the swivel lever. When the governor spring receives tension, the bottom end of the tension lever touches the adjustable full-load stopper bolt.When the angle of the adjusting lever is changed, the angle of the swivel lever is also changed and the tension of the governor spring changed. This is because the turning center of the swivel lever and the mounting position of the governor spring installed to the tension lever are eccentric to each other as