The Bosch centrifugal mechanical governor is mounted on the fuel-injection pump. The pump’s control rack is connected by a rod linkage to the governor. The control lever on the governor housing forms the link to the accelerator pedal.
There are two possible governor movement designs with centrifugal governors:
Type RQ and RQV governors: The gover- nor springs are fitted inside the flyweights. The two flyweights then each act directly on a set of springs, which are dimen- sioned for the relevant nominal speed and corresponding proportional response. Type RSV, RS and RSF: The centrifugal
force acts via a lever system on the gover- nor spring that is external to the two fly- weights. The two flyweights then act via the sliding bolt on the tensioning lever to which the governor spring is attached and acting in the opposite direction.
On the Type RSV governor (variable-speed governor) the driver sets the desired engine speed by tensioning the governor spring by means of the control lever. On the Type RS/RSF governor (minimum/maximum-speed gov- ernor) the governor spring setting for the high-idle speed is fixed and cannot be altered by means of the accelerator pedal. The gov- ernor springs in the movements are chosen so that the spring force and the centrifugal force are in equilibrium at the desired speed. When that speed is exceeded, the greater centrifugal force of the weights moves the control rack by means of a lever system and reduces the pump’s delivery quantity. Type RQ minimum/maximum- speed governor
Design
The governor hub is driven via a vibration damper by the fuel-injection pump camshaft (Figure 3, Items 14 and 18). Mounted on the hub are the two flyweights (17) with their bell cranks (13). A set of springs (16) is fitted in-
side each flyweight. The bell cranks convert the radial travel of the flyweights into an ax- ial movement on the part of the sliding bolt (12) which the latter transmits to the sliding block (10). The sliding block, which is guided in a straight line by the guide pin (11), com- bines with the variable-fulcrum lever (5) to form the link between the flyweight speed- sensing element and the control rack (7). The lower end of the variable-fulcrum lever locates in the sliding block. Inside the vari- able-fulcrum lever is a sliding-block guide. The movable pivot block is attached radially to a linkage lever which is connected to the control lever (2) on the same axis. The control lever is operated either manually or via a rod linkage by the accelerator pedal. Movement of the control lever moves the position of the guide block so that the variable-fulcrum lever pivots around the clevis pin on the sliding block. When the governor comes into action, the pivot of the variable-fulcrum lever on the guide block. The sliding block thus varies the transmission ratio of the variable-fulcrum lever. Consequently, there is sufficient force to move the control rack even at idle speeds when the centrifugal force is relatively small. The spring sets inside the flyweights (Figure 1) generally consist of three concentrically arranged helical springs, namely the idle-speed
58 Governors and control systems for in-line fuel-injection pumps Mechanical governors
Fig. 1
1 Adjusting nut 2 Outer spring seat 3 Maximum-speed
springs 4 Idle-speed spring 5 Flyweight 6 Inner spring seat
1 2 3 4 5 6
Flyweight of Type RQ governor
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U M K1 1 85-1YGovernors and control systems for in-line fuel-injection pumps Mechanical governors 59 Fig. 2 11 Control rack 12 Link fork 13 Play compensating spring 14 Adjusting nut 15 Governor spring 16 Flyweight 17 Bell crank 18 Sliding bolt 19 Sliding block 10 Guide pin 11 Control lever 12 Variable-fulcrum lever 13 Guide block 14 Linkage lever Fig. 3 11 Shutoff stop 12 Control lever 13 Full-load stop 14 Guide block 15 Variable-fulcrum lever 16 Link fork 17 Control rack 18 Pump plunger 19 Control-rod stop (buffered) 10 Sliding block 11 Guide pin 12 Sliding bolt 13 Bell crank 14 Governor hub 15 Adjusting nut 16 Governor spring 17 Flyweight 18 Fuel-injection pump camshaft 1 2 3 4 5 6 11 12 13 14 7 8 9 10
Type RQ minimum/maximum-speed governor
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K0496-1Y
Shutoff Full power
1 2 3
4
5 6 7 8 9
10 11 12 13 14 15 16 17 18
Type RQ minimum/maximum-speed governor in stop position
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spring (4) and the two maximum-speed springs (3).
Starting the engine
The manual for the vehicle specifies the re- quired accelerator position when starting the engine.
A fully depressed accelerator pedal provides the required start quantity for starting the engine from cold at cold outside temperatures. If the engine is already warm, the injected fuel quantity obtained when the control lever is in the idle-speed position is usually sufficient for starting. In this situation, fully depressing the accelerator pedal would merely result in un- necessary emission of smoke (Figures 4 and 7).
Operating characteristics
Idle speed
After the engine has started and the control lever (accelerator pedal) has been released, the latter returns to the idle speed position. The control rack then also returns to the idle-speed position as dictated by the now active governor (Figure 5).
The idle speed of an engine is defined as the lowest speed at which it will reliably continue to run when not under load. The only resis- tance overcome by the engine is that created by its internal friction and the auxiliary as- semblies driven by it such as the alternator, fuel-injection pump, radiator fan, etc. In or- der to be able to overcome that minimal level of resistance, it requires a specific quantity of fuel. That is provided when the control lever is in a position that corresponds to the spec- ified idle-speed setting.
Intermediate speeds
When the engine is operating under load (i.e. between no load and full load, Figure 6) and the accelerator pedal is depressed, the engine accelerates. As a result, the flyweights in the governor move outwards. The imme- diate response of the governor is to prevent an increase in engine speed.
60 Governors and control systems for in-line fuel-injection pumps Mechanical governors
Medium power
Medium power Idling
Shutoff Full power
Type RQ minimum/maximum-speed governor in part-load position 6
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U M K050 1-1E Full power ShutoffShutoff Full power Starting
Type RQ minimum/maximum-speed governor in cold-starting position 4
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U M K0499-1E Idling IdlingShutoff Full power
Type RQ minimum/maximum-speed governor in idle-speed position 5
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U M K0500-1EBut as soon as the speed rises above idle by only a small amount, the flyweights come into contact with the spring seats against which the maximum-speed springs are acting and remain in that position until the engine reaches its maximum speed – because the maximum-speed springs are not overcome by the centrifugal force until the engine is about to exceed its nominal speed. Conse- quently, the governor is ineffective between idle speed and maximum speed. In that range, the position of the control rack, and therefore the torque output of the engine, is determined solely by the driver. The torque control phase within that range is described below.
Torque control
On a Type RQ governor, the torque control mechanism is inside the flyweights; to be pre- cise: in between the inner spring seat (Figure 8, Item 9) and the maximum-speed springs (3). The torque-control spring (7) is inside a spring retainer (8) against the outside of which
Governors and control systems for in-line fuel-injection pumps Mechanical governors 61
Fig. 8
1 Adjusting nut 2 Outer spring seat 3 Maximum-speed springs 4 Idle-speed spring 5 Flyweight 6 Shim 7 Torque-control spring 8 Spring retainer 9 Inner spring seat
a Torque-control travel Fig. 7
nlu Minimum idle speed nvo Maximum full-load
speed n1 Start of torque-
control phase n2 End of torque-
control phase nno Maximum no-load
speed 1 2 3 4 5 6 7 8 a 9
Torque-control mechanism for Type RQ minimum/ maximum-speed governor 8
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U M K0503-1Y Engine speedControl rod travel
nlu n1 n2 nvo nno rpm mm Idling speed control Max. speed cutoff Full power Medium power Overrunning L Uncontrolled range Zero load Idling Torque-matching travel Starting-volume travel (control lever: idling)
Starting- volume travel (control lever: full power) Torque-matching range
Characteristic map for Type RQ minimum/maximum-speed governor
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the two maximum-speed springs rest. It there- fore comes into effect before the maximum- speed springs. The distance between the inner spring seat and the spring retainer is the torque-control travel (a). It can be adjusted by means of shims. The point n1at which torque
control comes into effect is dependent on the engine’s fuel characteristic curve.
At a point slightly before maximum speed (n2), the torque-control spring is compressed
to such an extent that the inner spring seat and the spring retainer are touching. Without torque-control springs, the governor is inef- fective between idle speed and maximum speed. Due to the “give” provided by the torque-control springs, the flyweights can move outwards by the distance represented by the torque-control travel at speeds between n1
and n2and thus move the control rack the
corresponding distance towards the stop setting (positive torque control).
Maximum speed
The maximum-speed limiting function comes into operation when the engine exceeds nom- inal speed, nvo. Depending on the control lever
position, therefore, that may take place at full or part load (Figure 9). As soon as the maxi- mum-speed limiting function is active, the position of the control rack is no longer con- trolled solely by the driver but also by the gov- ernor. The maximum-speed limiting travel of
the flyweights is designed so as to bring about speed-regulation breakaway between maximum full-load speed and maximum no-load speed. Type RQU minimum/maximum-speed governor
Design
The Type RQU governor is designed for con- trolling very low speeds. It is equipped with a multiplier gear (transmission ratio 1:1.5 to 1:3.7 depending on requirements) between the fuel-injection pump camshaft that provides the drive and the governor hub (Figures 10 and 20). The Type RQU governor was devel- oped for Type ZW, P9 and P10 fuel-injection pumps that are used on larger and generally slower-running diesel engines.
As with the Type RQV governor, the linkage lever on the Type RQU model is a two-part construction that runs in a plate cam.
Operating characteristics
The method of operation and operating characteristics are the same as the Type RQ governor.
62 Governors and control systems for in-line fuel-injection pumps Mechanical governors
Fig. 10
1 Full-load stop 2 Plate cam 3 Multiplier gear
Full power
Shutoff Full power
Type RQ minimum/maximum-speed governor in full-load position 9
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U M K0502-1E 1 2 3 ShutoffShutoff Full power
Type RQU minimum/maximum-speed governor in stop position 10
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U M K0504-1EType RQ and RQU maximum-speed governors
Design
The design of the maximum-speed governor differs from that of the minimum/maximum- speed governor essentially by virtue of the fact that the idle-speed stage is omitted.
Operating characteristics
In operation, the maximum-speed governor behaves in the same way as the maximum- speed stage of the Type RQ/RQU minimum/ maximum-speed governor.
Maximum speed
The speed-regulation breakaway function comes into operation when the engine ex- ceeds maximum full-load speed. The maxi- mum-speed limiting travel of the flyweights is designed so as to bring about maximum- speed breakaway between maximum full- load speed and maximum no-load speed.
Type RQV variable-speed governor
Design
The Type RQV governor is similar in design to the Type RQ model. The governor springs are fitted inside the flyweights. However, the fly- weights move continuously outwards as engine speed increases within the specified control range (Figure 11). Every control lever position corresponds to a specific speed at which speed- regulation breakaway begins. The movement of the control lever (1) is transmitted via the two-piece linkage lever (2) and the guide block (4) to the variable-fulcrum lever(5) and thence to the control rack (8). The pivot of the vari- able-fulcrum lever is movable along the slid- ing-block guide; it also runs in a plate cam (3) fixed to the governor housing so that the trans- mission ratio of the variable-fulcrum lever also changes. The sliding bolt (12), which forms the link between the flyweight speed-sensing el- ement and the variable-fulcrum lever, is sprung against pressure and tension (drag spring).
Governors and control systems for in-line fuel-injection pumps Mechanical governors 63
Fig. 11 11 Control lever 12 Linkage lever 13 Plate cam 14 Guide block 15 Variable-fulcrum lever 16 Link fork 17 Full-load stop (automatic) 18 Control rack 19 Pump plunger 10 Start-quantity stop 11 Sliding block 12 Sliding bolt with
drag spring 13 Governor hub 14 Bell crank 15 Adjusting nut 16 Governor spring 17 Flyweight 18 Fuel-injection pump camshaft 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Type RQV variable-speed governor
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U M K050 7 -1YAs with the Type RQ governor, the spring sets fitted inside the flyweights generally consist of three concentric helical springs. The outer spring acts as the idle-speed con- trol spring (Figure 12, Item 4); it is held be- tween the flyweight (5) and the adjusting nut (1) for setting the initial spring tension. After completing the short idle-speed travel (idle-speed stage), the flyweight comes into contact with the spring seat, and the inner springs that are fitted between the spring seat and the adjusting nut come into effect.
64 Governors and control systems for in-line fuel-injection pumps Mechanical governors
Fig. 13 11 Control rack 12 Play compensating spring 13 Full-load stop 14 Adjusting nut 15 Governor spring 16 Flyweight 17 Link fork 18 Variable-fulcrum lever 19 Guide block 10 Linkage lever 11 Plate cam 12 Bell crank 13 Sliding block 14 Sliding bolt
(with drag spring) Fig. 12 1 Adjusting nut 2 Spring seat 3 Maximum-speed springs 4 Idle-speed spring 5 Flyweight a Idle-speed travel 1 2 3 4 5 a
Flyweight for Type RQV variable-speed governor
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U M K0509-1Y 1 12 7 2 3 4 5 6 8 9 10 11 13 14Type RQV variable-speed governor
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Starting the engine
When applying the start quantity, the Type RQV governor operates in the same way as the Type RQ apart from the following difference:
If the driver fully depresses the accelerator pedal the first time the engine is started, when it reaches idle speed, unlike the Type RQ, the governor does not back off to the full-load setting. Instead, the control rack remains in the start quantity position until the engine reaches maximum speed. Only once the speed-regulation breakaway function has first come into action does the full-load stop drop into its normal operating position (Figure 14).
Operating characteristics
Idle speed (Figure 15)
After the engine has started and the control lever (accelerator pedal) has been released, the latter returns to the idle-speed position. The control rack then also returns to the idle-speed position as dictated by the now active gover- nor (position L in Figure 17 overleaf). Intermediate speeds (Figure 16)
If a load is applied to or removed from the engine at any speed set by the control lever (accelerator pedal), the variable-speed gov- ernor maintains the speed setting by increas- ing or reducing the fuel delivery quantity within the limits determined by the propor- tional response.
Example: The driver moves the control lever from the idle-speed position to a position that corresponds to a desired vehicle speed. The movement of the control lever is transmitted to the variable-fulcrum lever via the linkage lever. The transmission ratio of the variable- fulcrum lever is variable, and at a position just above the idle-speed setting is such that even a relatively small amount of control-lever or centrifugal-weight travel is enough to move the control rack to the set full-load position (dis- tance L – B in Figure 17); consequently, a fixed (i.e. unbuffered) control-rod stop must exist.
Governors and control systems for in-line fuel-injection pumps Mechanical governors 65
Fig. 14
1 Stop setting stop 2 Maximum-speed
stop
Fig. 16 1 Sliding block 2 Sliding bolt with
drag spring Full power 1 2 Medium power Intermediate speed Idling Shutoff
Type RQV variable-speed governor in part-load position 16
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U M K05 1 3-1E 1 2 StartingShutoff Full power
Type RQV variable-speed governor in cold-starting position 14
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U M K05 1 1-1E Idling Idling ShutoffShutoff Full power
Type RQV variable-speed governor in idle-speed position 15
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U M K05 1 2-1EFurther movement of the control lever ap- plies tension to the drag spring. The control rack remains at “full load” so that the engine rapidly increases speed (Figure 17, distance B’ – B’’). The flyweights move outwards but the control rack remains at “full load” until the drag spring is no longer under tension. Only then do the flyweights start to act on the variable-fulcrum lever, and the control rack is then moved towards the stop setting. Consequently, the fuel delivery quantity is reduced again and the engine’s speed is lim- ited. The engine speed limit corresponds to the setting of the control lever and the posi- tion of the flyweights (distance B’’ – C).
Thus, under normal operation, every con- trol lever position corresponds to a specific range of engine speeds, provided the engine is not overloaded or is driven by the road wheels (overrunning, e.g. on a descent). If the load on the engine increases, e.g. due to an uphill gradient, the speed of the engine and governor drops. As a result, the flyweights move inwards and move the control rack to- wards the “full load” setting, thereby holding the engine at a constant speed as determined by the control lever position and the propor-
tional response. If, however, the gradient (which equates to the load) is such that even when the control rack is moved right up to the “full load” stop the engine speed still drops, the flyweights retract even further and move the sliding bolt to the left. The flyweights are thus attempting to move the control rack further in the same direction beyond the stop setting. Since, however, the control rack is already in contact with the “full load” stop and cannot therefore move any further in that direction. The drag spring is tensioned. This means that the engine is overloaded. Under such circumstances, the driver will have to change down to a lower gear. When traveling downhill, precisely the opposite will apply. The engine is driven and acceler- ated by the road wheels. As a result, the fly- weights move outwards and the control rack is moved towards the stop setting. If the en- gine speed continues to increase (control rack has reached the stop setting), the drag spring is extended in the other direction.
66 Governors and control systems for in-line fuel-injection pumps Mechanical governors
Engine speed
Control rod travel
Max. speed cutoff Warm-starting travel Cold-starting travel L 20 15 10 5 0 mm A1 B1 B, B,, C1 D1 E1 F1 C Example nvo n2 n1 nno rpm
Characteristic map for Type RQV variable-speed governor
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U M K05 1 0-1EThe governor response described above applies in principle to all control lever positions if the engine load or speed alters for any reason to such a degree that the control rack comes into contact with either of its end positions. Torque control
Torque control comes into effect between n1
and n2(Figure 17) along the line C1– D1
under full load. On the Type RQV governor, the torque-control mechanism is fitted in a special control-rod stop or a torque-control bar that replaces the normal link fork (for a detailed description refer to the section “Control-rod stops”).
Maximum speed (Figure 18)
When the engine exceeds the maximum full- load speed, full-load speed regulation E1– F1
(Figure 17) comes into operation. The fly- weights move outwards and the control rack moves towards the stop setting. The maximum no-load speed, nno, is reached when the engine
load is entirely removed.
Type RQUV variable-speed governor