Abstract:
A governor for use in an engine, the governor including a drive shaft and a plurality of weights carried by the drive shaft. The weights are rotatable with the drive shaft and are moveable relative to the drive shaft. A lever is moveable in response to movement of the weights, the lever being moveable against the action of a return biasing arrangement. The governor further includes a further arrangement for holding at least one of the weights against movement so as to permit adjustment of the operating speed of the governor.

Description:
TECHNICAL FIELD 
     This invention relates to a governor for use in controlling the operation of a diesel engine. The invention is particularly applicable to engines used to drive alternator sets. 
     It is known to provide a mechanical governor to control the rate at which fuel is supplied to a compression ignition internal combustion engine for driving an alternator set, thereby permitting the alternator set to be driven at a substantially constant speed irrespective of the load on the engine. Such a governor typically comprises a plurality of weights which are pivotally mounted upon a drive shaft driven at a speed associated with the output speed of the engine. Typically, six weights are provided. The weights act upon a lever which is moveable against the action of a return spring. The lever is coupled to a metering valve of a fuel pump for use in supplying the engine with fuel under high pressure. The governor is arranged such that, in use, if the load on the engine falls, then the engine operating speed will increase. Such an increase in engine speed will cause the weights to pivot outwardly as a result of an increase in the magnitude of the centrifugal force acting upon the weights. The movement of the weights causes the lever to move, the movement of the lever, and hence the weights, occurring against the action of the return spring. The movement of the lever is transmitted to the metering valve, adjusting the metering valve to restrict the supply of fuel to the engine and reduce the engine speed. Similarly, a reduction in engine speed will cause the governor to operate to increase the rate at which fuel is supplied to the engine. 
     BACKGROUND OF THE INVENTION 
     A governor is usually designed to operate at a chosen speed, for example to cause the engine to drive an alternator set at 50 Hz or 60 Hz. Modification of a governor intended to operate at a first speed to operate at a second speed may require the throttle to be moved through a large distance, and the droop of the governor will not be constant at both speeds. Rather than adjust the position of the throttle, it is known to replace the governor spring or to modify the rate of the spring in some way. 
     It is an object of the invention to provide a governor, the operating speed of which can be adjusted without requiring the replacement of parts of the governor and without requiring a significant adjustment of the throttle position. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a governor comprising a drive shaft, a plurality of weights carried by the drive shaft, the weights being rotatable with the shaft and being moveable relative to the shaft, a lever moveable in response to movement of the weights, the lever being moveable against the action of return biasing means, and means whereby at least one of the weights can be held against movement to adjust the operating speed of the governor. 
     Conveniently, the weights may be pivotally moveable relative to the shaft, at least one of the weights being held against pivotal movement to adjust the operating speed of the governor. 
     Conveniently, six weights are provided, the weights and the return spring being chosen such that the governor operates at an alternator speed of 50 Hz. The governor is conveniently arranged such that two of the weights can be held against pivotal movement, under which circumstances the governor will operate at an alternator speed of approximately 61.2 Hz, and only a slight adjustment of the throttle will be necessary to ensure that the governor controls the associated engine to operate at an alternator speed of 60 Hz. 
     As there is no need to move the throttle through a large angle, the droop of the governor is not significantly altered when the governor is modified to operate at an alternative speed. Further, there is no need to replace components of the governor in order to change the operating speed. 
     The governor preferably includes a cage which is rotatable with the drive shaft, the weights being housed within the cage. 
     The weight(s) may be held against pivotal movement by, for example, wedges or pins, by jacking, by the use of pinch bolts, by use of a sliding collar or by any other suitable arrangement. For example, the governor may comprise at least one pin associated with each weight to be held against movement, whereby the or each pin cooperates with the cage to hold the associated weight against movement. Alternatively, a collar may be provided, the collar being slidably movable with respect to the drive shaft between an operative position, in which at least one of the weights is held against movement, and an inoperative position in which the weights are free to move. 
     Preferably, the return biasing means take the form of a return spring. 
     Conveniently, adjustment of the governor operating speed can be achieved without disassembling the pump housing, the adjustment being achieved, for example, by inserting a suitable tool through the pump housing drain port. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will further be described, by way of example, with reference to the accompanying drawings in which: 
     FIG. 1 is a diagrammatic sectional view illustrating a governor arrangement in accordance with an embodiment of the invention; 
     FIG. 2 is a sectional view illustrating the governor of FIG. 1 in an alternative mode of operation; 
     FIG. 3 is a sectional view along the line  3 — 3  of FIG. 2; 
     FIG. 4 is a perspective view of an alternative embodiment of the invention; and 
     FIG. 5 is a perspective view of a part of the governor in FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The accompanying drawings illustrate a governor for use in controlling the operation of a compression ignition internal combustion engine intended to drive an alternator set. The governor controls the supply of fuel to a fuel pump associated with the engine in such a manner as to ensure that the engine drives the alternator at a substantially uniform speed. 
     As illustrated in FIG. 1, the governor comprises a cage  10  rigidly mounted upon a drive shaft  11  which is driven to rotate at a speed associated with the operating speed of the associated engine. The cage  10  houses six weights  12 , each of which is pivotable about a point  12   a  of the weight  12  relative to the cage  10 . Each weight  12  further includes a toe  13  which engages an end of a sleeve  14  which encircles the drive shaft  11 . The sleeve  14  is axially moveable relative to the drive shaft  11 . 
     The end of the sleeve  14  remote from the weights  12  engages a lever  15  which is pivotable about a fulcrum  16 . The lever  15  is coupled to a governor spring  17  which, in turn, is coupled to an angularly adjustable throttle lever  18 . The lever  15  is further coupled using a conventional coupling arrangement  19 , to an angularly adjustable metering valve member  20  of a metering valve  21  of a rotary distributor pump. 
     In use, the drive shaft  11  is driven at a speed associated with the engine operating speed, and hence the centrifugal forces experienced by the weights  12  are related to the engine operating speed. The position occupied by each weight  12  depends upon the engine operating speed and the magnitude of a restoring force transmitted thereto through the lever  15  and the sleeve  14  from the spring  17 . 
     Starting from an equilibrium condition in which the engine is operating at a desired alternator speed, in this case 50 Hz, in the event that the load on the engine falls, then the engine operating speed will increase, and as a result the weights will tend to pivot outwardly, towards the position shown in FIG. 1, due to an increase in the magnitude of the centrifugal force experienced by the weights. The movement of the weights results in the toes  13  of the weights  12  pushing the sleeve  14  and lever  15  against the action of the spring  17 . The movement of the lever  15  is transmitted through the coupling  19 , adjusting the setting of the metering valve  21  to reduce the rate at which fuel is supplied to the pump, and hence to reduce the rate of fuel supply to the engine, compensating for the reduction in the load on the engine. 
     Similarly, starting from the equilibrium condition, in the event that the load on the engine increases, then the speed of operation of the engine, and hence the speed of the shaft  11 , falls. The spring  17  is thus able to move the lever  15  and sleeve  14  to move the weights  12  towards a radially inner position against the action of a reduced centrifugal force experienced by the weights  12 . The movement of the lever  15  is transmitted to the metering valve  21  to increase the rate of fuel supply to the pump and engine to compensate for the increased load on the engine. 
     In the event that the alternator speed when the governor occupies its equilibrium condition is not exactly 50 Hz, then the throttle lever  18  can be moved through a small angle to adjust the magnitude of the load applied by the spring  17 . 
     FIGS. 2 and 3 illustrate the governor of FIG. 1 when it is desired to run an engine with which the governor is associated at an alternator operating speed of 60 Hz rather than 50 Hz. As illustrated in FIG. 2, this is achieved by introducing wedges  22  between the cage  10  and two of the weights  12  to hold those two weights  12  in their radially inner position irrespective of the engine operating speed. The wedges  22  may be held in position simply by being a friction fit or by means of bolts or by any other suitable means. The provision of the wedges  22  effectively disables the associated weights  12  so that the centrifugal forces experienced by those weights  12  are not transmitted to the sleeve  14  and lever  15 , and so play no part in controlling the position of the lever  15  or the setting of the metering valve  21 . 
     Where the governor of FIG. 1 is set to control an associated engine to operate at an alternator speed of 50 Hz, then using the wedges  22  to disable two of the weights  12  will result in the governor controlling the engine to operate at an alternator speed of 61.2 Hz. If the desired alternator operating speed is 60 Hz, then a small adjustment of the throttle lever position can be made to result in the governor controlling the engine to ensure that the alternator operates at a speed of approximately 60 Hz. 
     As the throttle lever  18  does not need to be moved through a large angle to change the operating speed, the responsiveness or droop of the system is not significantly altered by the change in equilibrium operating speed. Further, as no parts of the governor need to be replaced to change the operating speed, alteration of the operating speed is a simple procedure. The step of disabling the weights  12  is conveniently achieved through a drain part provided in the pump/governor housing, in which case the operation of modifying the operating speed does not entail disassembling the pump/governor. 
     Although in the description hereinbefore, the weights are disabled using wedges, it will be appreciated that other techniques could be used to disable the weights. With reference to FIGS. 4 and 5, pins  24  may be introduced into the cage  10  to hold the weights  12  in their inner positions. In the illustration shown in FIGS. 4 and 5, only a single pin  24  is shown, but it will be appreciated that any one or more of the weights  12  may have an associated pin  24 , the pin  24  cooperating with the cage  10  so as to hold the associated weight  12  against movement. It will further be appreciated that more than one pin  24  may be associated with each weight  12 , if desired. 
     In a further alternative embodiment of the invention (not shown in the accompanying drawings), pinch bolts could be used to hold the weights in their inner positions. As a still further alternative, a collar could be provided around the shaft  11  or sleeve  14 , the collar being slidable between an inoperative position in which it does not affect the operation of the governor, and an operative position in which it holds some of the weights in their inner positions, disabling those weights. 
     In the description hereinbefore the governor has six weights, two of which can be disabled to permit operation at either approximately 50 Hz or approximately 60 Hz. It will be appreciated, however, that the invention is also applicable to governors having other numbers of weights, and is not limited to arrangements in which two weights can be disabled. The invention is therefore suitable for use with governors intended to operate at other speeds.