Fuel System

The fuel system serves to feed fuel in metered amounts (depending on the load) into the turbulence combustion chambers under a high pressure, to atomize the fuel into minute particles and to assure regularity and requisite sequence of the injections.

Fuel system, 5Д2, 5Д2-1, 5П2, 8П2 and 10П2 diesel engines

Fig. Fuel system, 5Д2, 5Д2-1, 5П2, 8П2 and 10П2 diesel engines: l – drain lube; 2 — fuel injection pump; 3 — high-pressure line; 4 — injector; 5 — leak-off tube; 6 — fuel filter; 7 — line from filter to fuel injection pumps; 8 — line from fuel feed pump to filter; 9 — fuel inlet; 10 — fuel feed pump

Fuel system; 4ч, 6ч, ДС8, ДС12, П12, П21 and П22 diesel engines

Fig. Fuel system; 4ч, 6ч, ДС8, ДС12, П12, П21 and П22 diesel engines: 1 — drain tube; 2 — fuel injection pump; 3 — high-pressure line; 4 — injector; 5 — leak-off tube; 6 — fuel filter; 7 — line from filter to fuel injection pump; 8 — line from fuel feed pump to filter; 9 — fuel inlet; 10 — fuel feed pump

Fuel is drawn by fuel feed pump 10 from a service tank and delivered to fuel filter 6. The clean fuel leaving the filter reaches fuel injection pump 2 wherefrom it fed into injectors 4 which inject fuel into the turbulence combustion chambers. At the instant fuel passes through the injector orifice it is atomized. Any fuel leaking between the nozzle valve and the nozzle body is returned into the filter through a leak-off hole in nut 8 and bolt 14.


Fig. Injector: 1 — nozzle body; 2 — nozzle valve; 3 — nozzle body nut; 4 — nozzle body holder; 5 — spindle; 6 — spring; 7, 13 — gasket; 8 — nut; 9 — adjusting screw; 10 — lock nut; 11 — cap; 12 — bushing; 14 — bolt

Fuel feed pump

Fig. Fuel feed pump: 1, 16 — plug; 2 — stop; 3 — piston spring; 4 — housing; 5, 24 — piston; 6 — guide sleeve; 7 – ball; 8, 20 — piston rod; 9 — tappet; 10 — roller; 11, 18 — fulcrum pin; 12 — pin; 13 – union; 14 — delivery valve; 15 — valve spring; 16 — union; 17 — fuel drain tube; 19 – pump body; 21 — cap holder; 22 — cap; 23 — piston ring; 25 — gasket; 26 — suction calve; 27 — bypass tube; 28 — fuel delivery line

The fuel feed pump is of the reciprocating type installed on the breather cover (this applies to the 5Д2, 5Д2-1, 5П2, 8П2 and 10П2 engines) or on the fuel injection pump body (ДС8, ДС12, 1112, П21, П22, 4 ч and 6 ч engines) and is actuated either by the respective cam of the camshaft (5Д2, 5Д2-1, 5П2, 8П2 and 10П2 engines) or by the fuel injection pump spindle. Piston 5 accomplishes its delivery stroke due to the action of spring 3 depending on the amount of the fuel consumed by the engine so that the pressure is maintained at a constant level. For priming the fuel system and purging it of trapped air preparatory to starting the engine, a hand-operated pump comprising body 19, piston 24 and piston rod 20 with cap 22 is provided in the suction line. To prime the system, unscrew cap 22 and give the pump a few strokes. On finishing with the priming, screw cap 22 on cap holder 21 so that piston 24 tightly presses gasket 25 against pump body 19.

Fuel filler

Fig. Fuel filler: 1 — case; 2 — filter element; 3 — cover; 4 — tube from fuel feed pump; 5 — union; 6 – tube returning fuel from injectors; 7 — clamping nut; 5 — air bleed screw; 9 – tube to fuel injection pump; 10 — clamping bolt; 11 — seal; 12 — disc; 13 — spring; 15, 16 — drain plugs; 17 — blanking-off plug; I — operating position; II — position for flushing

The fuel filter serves the purpose of separating sediments from fuel and is interposed between the fuel feed pump and the fuel injection pumps. The filter has a paper filter clement 2 and drain plug 15 in the bottom of filler case 1 which must be removed every 100-150 running hours to drain sludge. Filter element 2 must be washed every 200 to 300 running hours.

The procedure of washing the filter element is as follows:

  1. Close the fuel shutoff cock, disconnect tube 6 and set inlet lube 4 into the position for flushing the filter (II in Fig.).
  2. Back off drain plug 15 through 3 or 4 revolutions, open the fuel shutoff cock and hand-prime the system until clean fuel starts issuing through the plug. At this stage, fuel is flowing through the filter element in the direction opposite to that in which it flows during operation, removing all the sediments accumulated in the fuel filler and carrying them away with the outflov through plug 15. If no fuel flows through the plug hole, remove the plug and clean the passages.
  3. Return tubes 4 and 6 into their operating position (I in Fig.) and screw home plug 15.

Fuel injection pump, 5Д2, 5Д2-1, 5П2, 8П2 and 10П2 diesel engines

Fig. Fuel injection pump, 5Д2, 5Д2-1, 5П2, 8П2 and 10П2 diesel engines: 1 — pump housing; 2 — lower spring retainer; 3 — tappet; 4 — upper spring retainer; 5 — pump control rack; 6, 15, 17 — gaskets; 7 — adjusting screw; 6 — seal; 9 — gasket; 10 — delivery valve assembly; 11, 22 — springs; 12, 16 — unions; 13 — blanking off plug; 14 — bleed screw; 18 — bushing; 19 — union bolt; 20 — control quadrant; 21 — plunger-and-barrel assembly; 23 — retainer ring

The fuel injection pump of Fig. is of the single-plunger type and fitted on the engine are two dual pumps. Each of such pumps comprises pump housing 1 accommodating lappet 3, rack 5, control quadrant 20, plunger assembly 21 and delivery valve assembly 10.

Tappet 3 is provided with a circumferential mark on its external surface which must register, when the pump is being fitted to the engine, with the mark on the pump housing when the plunger is set into its lowermost position. The relevant adjustment is made by means of the tappet adjusting screw. Rack 5 meshes quadrant 20 of the control sleeve. When rack 5 is displaced, the quadrant is caused to rotate and, since the quadrant is linked up with the plunger, the plunger rotates too. Special marks facilitate the meshing of the rack with the quadrant and that of the control sleeve with the plunger arm while assembling the pump.

Dual fuel injection pumps, 5Д2, 5Д2-1, 5П2, 8П2 and 10П2 diesel engines

Fig. Dual fuel injection pumps, 5Д2, 5Д2-1, 5П2, 8П2 and 10П2 diesel engines: 1 — roller; 2 — roller pin; 3 — tappet; 4 — pin; 5 — lock nut; 6 — tappet adjusting screw; 7 — flange; 8 — spring; 9 — pump control rack; 10 — fuel injection pump; 11 — fulcrum pin; 12 — adjusting link; 13 — coupling; 14 — pull rod; 15 — swivel

For fitting the pumps pairwise, use is made at flange 7. The rack of the pumps so linked up are interconnected by means of a hinged link which serves to adjust the racks one with respect to the other.

Plunger-and-barrel assembly 21 comprises a plunger and a barrel which are made with a high degree of precision and are selected to fit one into the oilier with a clearance of 0.001 to 0.002 mm.

Valve assembly 10 consists of a valve and a valve seat. The head of the valve serves to disconnect the high-pressure part of the system (delivery tube and injector) from the delivery chamber of the pump, and the shroud of the valve relieves the high-pressure delivery tube of the pressure. The fact that the high-pressure delivery tube is relieved of the pressure assures rapid settling of the injector nozzle valve back into its seal so that the injector operates snappily and without afterdripping. The valve bushing is threaded from the outside to accommodate a puller for withdrawing the valve assembly from the pump housing.

Each plunger assembly and delivery valve must be kept and replaced during a repair as a pair only. Bleed screw 14 is provided for bleeding the air trapped in the inlet chamber of the pump.

Diagram of fuel injection pump operation

Fig. Diagram of fuel injection pump operation: 1 — inlet роrt; 2 — delivery port; 3 — cutoff scroll; 4 — longitudinal passage; I — maximum delivery; II — partial delivery; III — zero delivery

Pump operation

The respective camshaft cam causes the pump plunger to reciprocate inside the barrel through tappet 3 of the valve gear and spring 22. When the plunger is in its lowermost position the two ports shown at 1 and 2 in the barrel are open and the space above the plunger is filled up with fuel due to the action of the fuel feed pump. When the plunger is on the upstroke and closes ports 1 and 2, delivery begins. The fuel pressure causes the delivery valve to unseal, opening the way for fuel into the injector. Delivery stops when cut-off scroll 3 approaches the lower edge of port 2 in the barrel. At this instant the cutoff of fuel takes place in spite of the fact that the plunger continues to move on its upstroke. As a result, the pressure in the delivery tube and the space above the plunger sharply decreases, enabljng the delivery valve to return into its seat.

The angle through which the plunger has been turned does not affect the time whereat the pump starts delivery, but said angle controls the end of delivery. If longitudinal passage 4 in the plunger is placed in communication with port 2 in the barrel, the pump fails to deliver because the fuel contained in the space above the plunger will be bypassed into the inlet chamber. This position of the plunger is referred to as the position of zero delivery (III in Fig.).

The angle of injection advance is adjustable with the aid of tappet adjusting screw 6. To advance delivery, the screw must be turned up so as to increase the tappet length: to retard delivery, the screw must be turned down. The turning of the screw through an angle corresponding to a flat of its head changes the delivery timing by 1.5 to 2 degr.

The procedure of fitting fuel injection pumps on the engine is as follows:

  1. Turn tappet adjusting screws 6 down as far as each of them will go and fit the tappets into their places.
  2. Fit two pumps to flange 7, adjust and check racks 9 for freedom of movement.
  3. Secure the pumps in the side compartment of the block and check the rack for freedom of movement (sluggish action of racks is intolerable); set each tappet to its lowermost position and, manipulating with tappet adjusting screw 6, register the mark on the tappet with that on the pump housing.
  4. Check each of the pumps for delivery advance, using a capillary lube, and adjust the angle, if required.
  5. Connect the rack pull rod to the speed governor control lever.

Fuel injection pump and diesel engines

Fig. Fuel injection pump, ДС8, ДС12, П12, П21, П22, 4ч and 6ч diesel engines: 1, 26, 34 — plug; 2 — roller; 3, 11, 12 — gasket; 4, 15, 35 — union; 5 — tappet guide; 6 — tappet adjusting screw; 7 — cover; 8 — control quadrant; 9 — clamping screw; 10 — safety screw; 13 — delivery valve assembly; 14 — blanking-off plug; 16, 20 — spring; 17 — plunger-and-barrel assembly; 18 — control rack; 19 — upper spring retainer; 21 — set screw; 22 — wire; 23 — roller bushing; 24 — roller pin; 25 — pump housing; 27 — camshaft; 28 — bearing housing; 29, 38 — bearing; 30 — tappet; 31 — lock nut; 32 — lower spring retainer; 33 — control sleeve; 36 — cover; 37 — seal; 39 — drain tube

The fuel injection pump of the 4ч diesel engine is a four-plunger one and that of the 6ч diesel engine, a sixplunger unit. Arranged in housing 25 are plunger assemblies 17, delivery valve assemblies 13, tappets 30, control quadrants 8 and racks 18, control sleeves 33 and camashaft 27. The housing is filled with lube oil.

The plunger and delivery valve assemblies are of the same design. They function in the same way as their opposite numbers in the single-plunger pump described above.

Camshaft 27 serves to actuate the plungers, fuel feed pump and speed governor.

Each tappet is of the roller type and serves the purpose of transmitting the motion from the camshaft to the plungers; the lappets are accomodated each in guide 5 secured in place in the housing by set screw 21. Tappet adjusting screw 6 used to control the delivery advance is provided at the top of each tappet. The turning of the screw up through an angle corresponding to a flat of its head advances delivery by 1.5 to 2 degr; the turning of the screw down retards delivery by the same amount. Each of screws 6 must be turned home while assembling the pump.

To obtain the correct delivery advance for each pump unit during the process of assembling, the plungers must be set so that their end faces arc below the end faces of the respective barrels by an amount which is 8.8±0.1 mm for the 10Д6 diesel engine and 8.3±0.1 mm for the ДС8, ДС12, П12, П21, П22, 5Д4, 5П4, 5Д6 and 8Д6 engines. Lock each adjusting screw in the position specified. Marks 22 provided on the hub of coupling holder 20 and on the pump bearing cap must register one with the other, ensuring thereby that the first pump unit starts delivery.

On each plunger barrel there is fitted control sleeve 33 with quadrant 8 which meshes rack 18. The plunger arm engages the groove in the control sleeve. In assembling the pump, care must be exercised to register the mark at the hole in the plunger arm with the mark on the control sleeve so that the former mark faces cover 7. The amount of fuel delivered by each of the pump units, which must be the same from unit to unit, is controlled by turning control sleeve 33 integrally with the plunger relatively to the quadrant. On finishing with the adjustment, quadrant 8 must be secured lo the control sleeve by clamping screw 9.

Rack 18 rims all the way along the pump housing in bushings and is pivotally linked up to the speed governor control lever at one end.

The air trapped in the pump intake space is bleeded through bleed screws 34.

Fuel injection pump drive, 6ч diesel engines

Fig. Fuel injection pump drive, 6ч diesel engines: 1, 7 — bolt; 2 — bushing; 3 — pump drive gear; 4 — key; 5 — pin; 6 – flange; 8 — housing; 9 — arm; 10 — gasket; 11 — spring; 12 — nut; 13 — drive shaft; 14 — thrust bushing; 15 — cover; 16 — seal; 17 — auxiliary coupling; 18 — coupling; 19 — elastic spacer; 20 — coupling holder; 21 — aligning fixture; 22 — marks

The fuel injection pump drive found on the 6ч diezel engine consists of drive shaft 13 supported in the block by bearings, gear 3 and a dog coupling. This coupling serves to control the angle of delivery advance of all pump units at a time by turning coupling holder 20 integrally with the toothed shaft in the slots of auxiliary coupling 17. To advance delivery, coupling holder 20 is to be turned clockwise looking from the flywheel end, and to retard delivery the coupling holder must be turned counter-clockwise. Graduations on coupling 18 and the mark on auxiliary coupling 17 facilitate the adjustment, the turning of coupling holder 20 through an angle corresponding to one graduation changing the angle of delivery advance by 4 degr.

If an engine is furnished without the tachometer, all the places for filling the drive and mounting the tachometer arc blanked off.

The procedure of mounting an assembled and adjusted pump on the engine is as follows:

  1. Crank over the engine so as to place the flywheel into the position where the t. d. c. mark on its rim is short of the index by an amount equal to the angle of delivery advance specified to the compression stroke in the first cylinder; the central mark on coupling 18 must register with the mark on auxiliary coupling 17.
  2. Fit the pump to the bracket, register the mark on the hub of coupling holder 20 with that on the pump bearing cap and insert the claws of coupling holder 20 into the slots of elastic spacer 19 so that the axial play of the spacer is between 0.2 and 1.0 mm.
  3. Align the pump with its drive, using fixture 21; the maximum radial misalignment tolerance (the difference in clearance at point 1) is 0.1 mm and the maximum axial misalignment tolerance (the difference in clearance at point II) is. 0.15: 100 mm. The method of gauging the misalignment is the same as that used in aligning the engine with the driven machinery which will be found elsewhere in this publication. For aligning the pump, use foil shims with a total thickness not over 0.5 mm.

On completing the above procedure, check the pump for correct delivery advance, using a capillary lube, and make final adjustment, if necessary, by manipulating with the coupling.

Drive of fuel injection on pump with flanged mounting

Fig. Drive of fuel injection on pump with flanged mounting: 1 — flange; 2 — packing ring; 3 — lubricating tube; 4 — gear; 5, 12 — sleeve; 6 — shims; 7 — seal; 8 — housing; 9 — arm; 10 — spring; 11 — nut; 13 — washer

The fuel injection pump found on the ДС8, ДС12, П12, П21, П22 and 4ч diesel engines has a flanged mounting. The pump obtains the drive from gear 4 and sleeve 5 and is fitted to the block by means of flange 1. The fact that one of the recesses in gear 4 is smaller than the rest provides for linking up the hub with sleeve 5 in one position only. Gear 4 is meshed with the respective timing gear in accordance with the marks. Shims 6 enable the axial play of gear 4 to be kept within the limits of 0.5 and 1 mm. The drive is lubricated by the oil fed through tube 3.

The pump is adjusted for correct delivery advance by being turned in the grooves of the block and those in the flange.

A counter-clockwise rotation (looking from flywheel end) advances delivery and a clockwise one retards same.

The procedure of fitting the adjusted flange-mounted pump is as follows:

  1. Insert flange 1 and sleeve 5 into the pump, giving them a slight rocking movement, so that the wide recess in sleeve 5 registers with the smaller recess of the splines on gear 4 (opposite the mark).
  2. Attach flange 1 to the block.
  3. Check the pump for correct delivery advance, using a capillary tube, and adjust same, if necessary, by turning the pump.

Each of the injectors the cylinder heads are fitted with injects atomized fuel into the respective turbulence chamber at regular intervals. The orifice in the nozzle body is closed by nozzle valve 2 pressed against the tapered seat by spring 6 acting on splindle 5 and abutting against the collar on adjusting screw 9 with its upper end. The nozzle valve is lapped into the nozzle body, and both these components should be always kept as a pair.

The pressure the spring exerts on the nozzle valve and, consequently, the injection pressure are adjusted by screw 9 which must be locked by lock nut 10 on finishing with the adjustment. Fuel enters an annular passage at the lower end of the nozzle body through passages. As soon as the pressure of fuel exerted on the tapered portion of the nozzle valve exceeds the spring tension, the nozzle valve lifts clear of the seat and fuel is injected into the turbulence combustion chamber. At the end of delivery, when the pressure in the delivery line decreases, the nozzle valve returns into its seat due to the action of the spring, disconnecting the space inside of the injector from the turbulence combustion chamber.

The speed governor maintains the rpm of the engine within the limits specified depending on Hie variations in load, including those occurring unexpectedly. In performing its duty, the governor acts on the fuel injection pump rack, setting delivery so as to cope with the load at given speed.

Speed governor

Fig. Speed governor; 5Д2-1, 5П2, 8П2 and 10П2 diesel engines:1, 20, 33 — splindle; 2 — detent; 3, 5 — spring; 4 — pump cutoff handle; 6 — nut; 7 — bar; 8 — cotter pin; 9 — stopper ring; 10 — pump cut off lever; 11 — upper lever; 12 — bracket; 13 — pin; 14 — lower lever; 15 — fulcrum pin; 16 — spider; 17 — tip; 18 — bracket; 19 — handwheel; 21 — screw; 22 — double-arm lever; 23 — housing; 24 — retainer; 25 — retainer holder; 26 — external spring; 27 — internal spring; 28 — carrier sleeve; 29 — bearing; 30 — sleeve; 31 — weight; 32 — gear

The 5Д2, 5Д2-1, 5П2, 8П2 and 10П2 diesel engines are each with a centrifugal constant-speed governor with adjustable speed droop. The governor is located in the forward compartment of the block and obtains the drive from the respective camshaft gear. Its main components are two governor weights 31 fitted to spider 16 by means of fulcrum pins 15, sleeves 29 and 30, springs 26 and 27, a speed-setting mechanism, a fuel pump-controlling leverage and a device for shutting down the engine. The governor weights are fastened to fulcrum pins 15 by pins, and the fulcrum pins work in bushings press-fitted into the lugs of spider 16. In operation, the weights come abutting with their shorter arms against a flange of sleeve 30.

Carrier sleeve 28 press-fitted into a bearing of sleeve 30 is at rest when the governor is in operation and serves the purpose of transmitting the force set up by weights 31 to levers 11 and 14 along with the force set up by spring 26 and 27 to weights 31. Governor springs 26 and 27 differ by the force they are capable of exerting and by the length. Internal spring 27 is shorter than its counterpart hut exerts a higher force; it operates to cope with an increase in the engine speed anywhere to between 700 and 800 rpm.

The speed-selling mechanism comprises housing 23, spindle 20 with flywheel 19 and lever 22. When handwheel 19 is being turned clockwise, retainer 2-1 compresses the springs through the intermediary of lever 22 and spindle 20, thus causing the engine to increase its speed. A counter-clockwise rotation of the handwheel decreases the spring tension with the result that the engine slows down.

The fuel pump-controlling leverage transmits each movement of sleeve 28 to the fuel pump racks and consists of two levers, an upper one and a lower one, and of a pull rod. Lower lever 14 is secured to spindle 1 and engages a groove in the sleeve with its spherical tip. Upper lever 11 is linked up with the pump racks through the intermediary of an adapter, the pull rod and a turnbuckle; it is also connected to spindle 1 by a spring and a detent. This arrangement enables lever 11 to be turned relative to spindle 1 in one direction only, i. e., towards zero delivery, without compressing springs 26 and 27.

The speed droop adjusting mechanism and the device for shutting down the engine are fitted to bracket 12. The speed droop is controlled by spring 5 secured to bar 7 and lever 11 with its ends. To decrease the speed droop, bar 7 must be displaced to the left, i. e., towards the flywheel, along the groove in bracket 18 an increase of the speed droop is achievable by moving the liar to the right. After the speed droop adjustment made at the works, a common mark is applied to bracket 18 and bar 7.

For shutting down the engine use is made of handle 4 and lever 10. A counter-clockwise rotation of handle 4 causes lever 11 to be moved to the left by lever 10 so that lover 11 acts on the pump rack, moving same into the position of zero delivery with the result that the engine is shut down.

The procedure of assembling the speed governor is as follows:

  1. Slip the gear with the spider and sleeves on the pin.
  2. Fit the timing gear cover plate to the pins in the block and secure the plate in its place; slip springs 26 and 27 on carrier sleeve 28, fit retainer 24 and governor housing 23.
  3. Insert the spherical lip of the lower lever into the sleeve groove and secure Hie bracket.
  4. Connect the upper lever to the fuel pump racks by means of the pull rod.

On the 4ч and 6ч diesel engines the speed governor is of the centrifugal constant-speed type with or without the speed droop. The governor is attached to the fuel injection pump and obtains the drive from the fuel pump camshaft.

Centrifugal constant-speed governor ДС8, ДС12, П12, П21, П22, 4ч and 6ч diesel engines

Fig. Centrifugal constant-speed governor: ДС8, ДС12, П12, П21, П22, 4ч and 6ч diesel engines: 1 — spider: 2 — sleeve; 3 — ball (roller) bearing; 4 — fulcrum pin of weigh; 5, 19 — housing, 6 — cover; 7 — weight; 8 — fork-end lever; 9 — spring; 10 — knob; 11 — handle; 12, 21 — bushing; 13 — governor spring; 14 — handwheel, 15 — screw; 16 — eccentric shaft; 17 — screw; 18 — tever; 20 — spring-loaded pull rod; 22, 25 — gear; 23 — drain plug; 24 — collar; 26 — roller; 27 — oil level gauge; 28 — fulcrum pin

The centrifugal constant-speed governor illustrated in Fig. consists of a shaft with governor weights, sleeve 2, spring 13, a fuel pump-controlling mechanism, a speed-setting mechanism and a device for setting down the engine, all contained in housing 5. The weights are attached by pins to fulcrum pins 4 which work in bushings of the shaft spicier.

The weights are provided with rollers, i. e., roller bearings 3, serving to transmit the force exerted by the weights to sleeve 2 which rotates integrally with the shaft 1 and which is capable of moving along same. Lever 8 of the fuel pump-controlling mechanism rests with its rollers on the sleeve through the intermediary of a thrust hearing and collar 24. The other arm of the pump-controlling lever is linked up with the pump rack and spring 13 through spring-loaded pull rod 20. The other end of spring 13 is connected to the speed-setting mechanism which consists of handwheel 14 with a screw and shaft 16 with levers. Clockwise rotation of the handwheel decreases the tension of spring 13 with the result that the engine slows down whereas the counter-clockwise rotation adds to the spring tension, causing the engine to gain speed. The speed limit is set by screw 17.

Spring-loaded pull rod 20 is of a design which enables the distance between lever 8 and the pump rack to be adjusted so as to cut off fuel delivery and shut down the engine by means of handle 11 without moving lever 8, sleeve 2 and weights 7, said movements being compensated by the compression of the spring provided in the pull rod. For stopping the engine, handle 11 must be pulled and locked by being turned as far as it will go. As a result, knob 10, acting through the adjusting screw of spring-loaded pull rod 20, displaces the pump rack into the position of zero delivery. On shutting down the engine, the handle must be returned into its original, i. e., operating, position.

Governor with speed droop adjusting mechanism

Fig. Governor with speed droop adjusting mechanism; 4ч and 6ч diesel engines:1 — housing; 2 — adjusting screw; 3 — washer; 4 — handwheel; 5 — arm; 6 — nut; 7 — bushing; 8, 11 — spring; 9 — spring shell; 10 — cover; 12 — rod; 13 — sleeve; 14 — spider; 15 — roller fulcrum pin; 16 — floating washer; 17 — pivot; 18 — ring; 19 — seal; 20 — gear; 21 — weight; 22 — drain plug; 23 — roller; 24 — fork-end lever; 25 — collar; 26 — dashpol arm; 27 — dashpot needle; 28 — dashpot spring; 29 — housing; 30 — cutoff handle; 31 — quadrant

The centrifugal constant-speed governor illustrated in Fig. is provided with the speed droop adjusting mechanism. The main components of the governor are a rotor, a fuel pump-controlling leverage, a speed droop adjusting mechanism, a speed-setting mechanism, a shutdown device and a dashpot.

The governor rotor consists of spider 14 rotating on pivot 17 and carrying two fulcrum pins swinging whereon are governor weights 21. The centrifugal forces of the weights act on the plate of sleeve 13 through the intermediary of rollers 15 and are brought at balance by the tension of main spring 8. An end piece of the sleeve enters a slot in pivot 17. The axial loads set up by the spider arc carried by floating washer 16 and hardened ring 18 press-fitted on pivot 17.

The fuel pump-controlling mechanism serves to transmit the movement of sleeve 13 to the pump rack and consists of shell 9, main spring 8, fork-end lever 24 and rod 12. Shell 9 is fitted to Fork-end lever 21 by means of fulcrum pins, and in the bottom of the shell an adjusting screw is provided the spherical head whereof engages a recess in the plate of sleeve 13. The lever is attached to a fulcrum pin secured in the governor housing. Rod 12 is pivotally attached to the pump rack with one of its ends and to fork-end lever 24 with the other end, a flexible link capable of acting in one direction only being interposed between the lever and the rod. By virtue of this arrangement, every movement of the lever so as to decrease delivery is positively transmitted to the rod through an adjustable stop whereas the movement towards an increase in delivery is transmitted through the spring with the result that there is the possibility to shut off the delivery of fuel while the lever remains immovable.

The speed droop adjusting mechanism relics for its operation on the tension of the springs which act on the governor sleeve, this tension being controlled by changing the angular position of auxiliary spring 11 and fork-end lever 24 relative to each other. The speed droop is adjusted by quadrant 31 provided on the front end face of the governor housing. The range of adjustment is between (1 and 6) ±1%. The preferred speed droop is 3%.

For changing the engine speed, the tension of main spring 8 must be changed, using handwheel 4. The rotation of same clockwise increases the speed and the counter-clockwise rotation slows down the speed. The head of adjusting screw 2 and washer 3 coming abutting against which is collar 25 serves to limit the maximum and minimum speeds, respectively, of the engine. For a maximum speed adjustment, back off nut 6 and rotate screw 2, using a screwdriver, either clockwise to increase the rpm or clockwise to decrease same. For a minimum speed adjustment, remove handwheel 4 and, giving support to bushing 7, turn washer 3 counter-clockwise by means of arm 5 to increase the minimum speed and clockwise to decrease same.

The dashpot provides a means of enhancing the stability of speed governing, enabling thus the governing to be carried out when the speed droop is a very small one.

Operation of speed governor

When the diesel engine is at rest, the spring, acting through the intermediary of the governor sleeve and the fuel pump-controlling leverage, sets the pump for maximum delivery which facilitates the forthcoming starting.

When the diesel engine has picked up the cycle and gains speed, the weights swing outward due to the action of centrifugal forces, displacing the sleeve against the action of the springs so as to reduce delivery through the intermediary of the pumpcontrolling leverage. At this stage, the engine speed increases to a point when the centrifugal funkces of the weights become at balance with the spring tension. From this moment and onwards the governor maintains the speed at a constant level as given.

If the springs are either further compressed or more expanded, using the speed-setting device, the speed governing system attains an equilibrium when the engine speed is of a higher order for a higher inertia force or, in other words, a higher speed is required to keep the weights in their original position.

Diesel engines ДС8, ДС12 (transverse section)

Fig. Diesel engines ДС8, ДС12 (transverse section): 1 — cylinder and crankcase block; 2 — breather body; 3 — camshaft; 4 — fuel feed pump; 5 — tappet; 6 — fuel injection pump; 7 — cover plate; 8 — pushrod; 9 — asbestos stell gasket; 10 — heater plug; 11— cylinder head; 12 — injector; 13 — lifting fixture; 14 — manifold with expansion tank; 15 — cylinder liner; 16 — piston; 17 — connecting rod; 18 — packing ring; 19 — starter motor; 20 — manhole cover; 21 — cooler

Should the load on the engine change either gradually or all of a sudden, the delivery will fail to conform to the load with the result that the engine speed will change too. If, for example, the load has decreased, a superfluous delivery at the first instant will bring about an increase in the engine speed which will cause the governor weights to move outwards up to the point whereat delivery decreases to a value corresponding to the new load. The system will consequently come to equilibrium at a new, somewhat higher, engine speed.

An increase in the load brings about a decrease in the speed with the result that the spring action causes the weights to move inwards and the sleeve, acting through the intermediary of the pump-controlling leverage, increases delivery in proportion to the load so as to restore the system to equilibrium.