Mechanical engine governor with pressure responsive minimum droop limiting speed control

An idle speed-limiting speed engine governor utilizes a friction damped air piston as the sole speed setting means which actively opposes the speed responsive flyweights in a particular range of engine speed operation, the governor limiting speed being controllable by adjusting the air pressure acting against the piston. A minimum droop governor characteristic results with hysteresis limited by minimum friction damping of the piston. A multi-condition air pressure control system is disclosed which is capable of providing various operational modes for the air controlled limiting speed governor.

TECHNICAL FIELD 
This invention relates to engine governors and, more particularly, to 
mechanical limiting speed-idle speed governors having variable limiting 
speed control. 
BACKGROUND OF THE INVENTION 
It is known in the art relating to mechanical limiting speed governors to 
provide a fluid actuated piston, such as an air piston, operative as a 
part of the governor limiting speed setting means to modify the 
established limiting speed upon application or variation of air pressure 
acting against the piston. 
As an example, U.S. Pat. No. 2,771,788 Frick and HIckson shows in FIGS. 2 
and 5 a speed setting arrangement in which the compression of the high 
speed spring 111 is varied by the movement of an air piston 105 in 
response to the application of air pressure against the piston under 
predetermined conditions, thus varying the governor limiting speed. 
Another arrangement is shown in U.S. Pat. No. 2,656,174 Crookston, wherein 
an overspeed spring 54 and an air bias piston 66 are arranged to act in 
parallel fashion against the speed related force generated by the 
flyweights 17' of the governor. These devices, acting together with a 
hydraulic dashpot piston 68, are combined to provide smooth speed setting 
operation over a relatively wide range of speeds. 
In still another arrangement, shown in applicant's U.S. Pat. No. 4,082,074 
which is assigned to the assignee of the present invention, an air biased 
piston 92 is arranged to act in a direction supplementing the force of the 
speed responsive flyweights to thus provide a reduction in the governor 
limiting speed setting in proportion to the pressure of air applied 
against the piston 92. 
These prior art arrangements utilize the application of fluid pressure to a 
piston in various ways to modify the limiting speed setting of a 
mechanical engine governor. However, they all combine the fluid piston 
speed modifying means with a conventional spring to provide at least a 
portion of the speed setting force that acts against the speed responsive 
flyweights, or similar mechanism. The biasing force thus created 
establishes the limiting speed setting which is matched by the speed 
related force of the flyweights at the point of governor balance. The use 
of such biasing springs in mechanical engine governors in which the speed 
balanced condition may occur at various positions of spring compression 
inherently introduces a certain amount of speed droop, or limiting speed 
variation with load, into the system. In addition, some degree of friction 
is provided which creates hysteresis but has the advantage of damping 
oscillations of the mechanism, thus helping to provide a stable speed 
control system. 
While a certain amount of speed droop and hysteresis is acceptable for most 
engine speed governing functions, these characteristics are not so 
desirable when it is desired to use the governor for some other related 
purposes. For example, the speed droop characteristic inherent in the 
governor arrangement of the previously mentioned U.S. Pat. No. 4,082,074 
causes a variation in the controlled speed under varying load conditions, 
which is undesirable when the engine governor is used as a vehicle speed 
control, one of the uses of the governor described in the patent. This 
speed variation is, however, quite acceptable when the governor is 
performing its primary function of engine speed control or while it is 
used to control the engine speed for an auxiliary drive system. 
SUMMARY OF THE INVENTION 
The present invention provides an improved mechanical engine governor with 
fixed or variable limiting speed settings which is particularly adapted 
not only for use in controlling engine speed and auxiliary engine powered 
devices, but also to provide relatively constant vehicle speed control 
when incorporated in a suitable speed control system. 
It is a feature of the invention that it essentially eliminates or 
minimizes the speed droop characteristic in a mechanical engine governor 
over the active range of controlled engine limiting speeds. This is 
accomplished by completely eliminating the use of a biasing spring as an 
operative element in controlling governor limiting speeds in the normal 
range of controlled limiting speeds. Instead, a fluid, and preferably air, 
actuated piston is utilized as the sole operative element utilized to 
provide a speed setting force that opposes the speed responsive force of 
the flyweights in establishing a fixed or variable limiting speed within 
the range of available limiting speeds for the governor. 
A further feature of the invention is the provision of appropriate control 
systems and devices which in conjunction with the air controlled governor 
provide the capability of an engine speed control system usable for 
various additional purposes such as vehicle speed control or variable 
speed control of engine powered accessory devices. 
These and other features and advantages of the invention will be more fully 
understood from the following description of a preferred embodiment taken 
together with the accompanying drawing.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to the drawings in detail, the best mode now known to me for 
carrying out the invention is exemplified in the engine governor generally 
indicated by numeral 10. Governor 10 comprises a mechanical engine 
governor especially adapted for controlling the position of fuel racks for 
a compression ignition engine and includes a housing 12 having a mounting 
surface 14 which is adapted to be secured to the end face of a blower 
housing or some other suitable portion of a compression ignition engine. 
Within the housing 12 is a rotatable shaft 16 having a splined end portion 
18 that is adapted to be connected to the rotating blower shaft, or other 
suitable portion of the engine, for driving the shaft 16 at a speed 
proportional to engine speed. Shaft 16 carries a pair of pivotally mounted 
flyweights 20 which, upon increasing speed, are increasingly urged 
outwardly by centrifugal force around pivots 22. Fingers 24 extending from 
the flyweights engage a sleeve 26 which acts through a bearing 28 on an 
operating fork 30. The fork 30 is connected to an operating shaft 32 that 
is mounted for oscillation in bearings, only one 34 of which is shown. The 
operating shaft 32 is fixed to an operating shaft lever 36 having a pair 
of angularly disposed arms 38, 40. 
At the end of arm 40 of the operating shaft lever, a differential lever 42 
is pivotally mounted intermediate its ends on a pivot pin 43. One end 44 
of lever 42 is bifurcated to receive the end of a pin 46 extending from 
operating mechanism 48 which is adapted to be connected through an 
external lever 50 with the accelerator, not shown, of a vehicle or other 
means for manual control of the engine by the operator. At its other end, 
differential lever 42 is pinned to a link 52, which is in turn connected 
to an oscillating lever 54 having an end portion 56 connectable with the 
engine fuel rack actuating means, not shown, for moving the engine 
injector racks between their maximum and minimum fuel positions. 
The other arm 38 of operating shaft lever 36 carries an adjusting screw 58 
which engages a cup shaped cap 60 carried for reciprocation within a 
recess 62 of a cylindrical plunger 64. A low (idle) speed spring 66 
extends between the cap 60 and a seat 68, operatively connected to the 
plunger 64 by an adjusting screw 69 for setting the spring preload. 
The portions of the governor mechanism so far described are substantially 
the same as corresponding portions of certain previously known governors, 
including the governor described in my aforementioned U.S. Pat. No. 
4,082,074. Differing portions of the mechanism of the herein disclosed 
governor are described subsequently. 
Cap 60 has an open end 70 that is engagable with a washer-like spring seat 
72, biased by a relatively strong overspeed spring 74 toward engagement 
with an annular seat 76 formed by an enlargement in the plunger recess 62. 
The overspeed spring is in turn seated on a screw plug 78 that is 
threadably received within an open end 80 of the plunger 64. It will be 
noted that plug 78 also threadably retains the idle speed spring adjusting 
screw 69. 
Plunger 64 is reciprocably disposed within a cylindrical bore 82 formed in 
the housing and in an axially spaced relatively smaller cylindrical bore 
84 formed in a support member 86 that forms a further portion of the 
housing. At its extreme rightward position, an annular flange 88, formed 
by a diametral step on the plunger, engages the side of the support member 
86, thereby stopping rightward movement of the plunger at a point where 
its open end 80 is flush with or preferably extends slightly proud of the 
associated outer wall 92 of the housing 12. 
Surrounding the protruding end 80 of the plunger, there is secured to the 
wall 92 of the housing a cylinder 94 having an open end sealingly engaging 
the wall 92 through a gasket 96 that surrounds the end 80 of the plunger. 
Cylinder 94 also has a closed end including a threaded opening 98 adapted 
for connection to a supply of pressurized air. 
Within the cylinder 94 there is reciprocably disposed a piston 100 having 
an annular groove 102 in which is disposed a sealing ring 104. The end 106 
of the piston adjacent the sealing ring is closed to define with the 
closed end of the cylinder an air chamber 108 to which the threaded 
opening 98 is connected. 
Opposite its closed end 106, the piston has a hollow skirt portion 110, the 
end of which is adapted to engage the open end 80 of the plunger 64. 
Within the hollow skirt is disposed a minimum speed spring 112 having a 
biasing force substantially less than that of the overspeed spring 74 and 
on the order of that of the idle spring 66. Spring 112 operatively acts 
against the inner side of the piston closed end 106 and the plunger 64 
through engagement with the screw plug 78, thus providing a predetermined 
biasing force acting on the plunger and urging the piston 100 and plunger 
64 apart. 
To provide for normal operating of the governor as so far described, it is 
necessary to provide a suitable source of air at controlled pressure to 
the air chamber 108. This is accomplished by connecting to the threaded 
opening 98 any suitable source of pressurized air such as an air pump or 
pressurized air storage tank as represented in FIG. 2 by numeral 114. 
Between the air pressure source 114 and the chamber 108, there is 
connected a pressure regulator 116 which may be preset to a predetermined 
control pressure or provided with means to vary the pressure as desired. 
Regulator 116, which may be of any type available commercially or 
otherwise, is operative to maintain the preset pressure within the air 
chamber 108 of the cylinder under substantially all conditions of engine 
operation. 
GOVERNOR OPERATION 
The operation of the governor arrangement of FIGS. 1 and 2 as above 
described is as follows. 
When its associated engine is in operation, the shaft 16 of the governor 
will be rotated at a speed proportional to engine speed, causing the 
flyweights 20 to move outwardly and apply a force that increases with 
increasing engine speed and tends to rotate the operating shaft lever 36 
in counterclockwise direction as viewed in FIG. 2. Such movement of the 
speed responsive means (which includes lever 36) moves the pivot pin 43 
laterally, causing the differential lever 42 to swing in a clockwise 
direction, as shown in FIG. 2, around the pin 46. This movement in turn 
moves the internal actuating means comprising link 52 and lever 54 in a 
direction tending to move the external fuel rack actuating mechanism, not 
shown, of the engine toward the minimum fuel position. 
The force generated by the flyweights is opposed initially by the bias of 
low speed spring 66, the force of the control air pressure supplied to 
chamber 108 being normally sufficient to hold the plunger 64 in its 
farthest rightward position with its flange 88 against the side of the 
support member 86. At idle speeds, the low speed spring 66 extends cap 60 
against the adjusting screw 58 in the lever 36 and controls the engine 
idle speed by yielding or extending as necessary to permit the flyweight 
force to control fuel flow at the required amount for maintaining idle 
speed. 
Actuation of the foot throttle or accelerator of the vehicle by the 
operator to increase engine speed moves the lever 50 so that pin 46 is 
moved generally downwardly as shown in FIG. 2, pivoting lever 42 and the 
internal actuating means toward a fuel increasing position of increased 
injector rack (assuming a diesel engine is involved). The resultant speed 
increase causes an increase in force from the flyweights which completely 
compresses spring 66, causing the open end 70 of the cap 60 to engage the 
high speed spring set 72. This seat is firmly held in engagement with the 
annular seat 76 of the plunger by the relatively high biasing force of the 
overspeed spring 74. Thus, engagement of the cap end 70 with the spring 
seat 72 stops further leftward movement of the cap 60 until accompanied by 
either movement of the plunger 64 or yielding of the overspeed spring 74. 
Between idle and the air pressure controlled maximum limiting speed, the 
fuel rack position is set manually by the engine operator. However, when 
the maximum controlled limiting speed is reached, the force of the 
flyweights 20 becomes high enough to balance and subsequently overcome the 
biasing force caused by the controlled air pressure supplied to the 
cylinder chamber 108. As this occurs, the plunger 64 and the engaged 
piston 100 are moved leftwardly, as shown in FIG. 2, as necessary to 
reduce the engine injector output by moving the injector racks toward 
their minimum fuel position so that the established governor limiting 
speed is not exceeded by the engine. 
The established governor limiting speed may be fixed if the air pressure 
regulator 116 controlling the pressure of air in chamber 108 is preset to 
a fixed pressure. If desired, however, the governor limiting speed may be 
made adjustable by providing means for adjusting the pressure supplied by 
the pressure regulator 116 to the air chamber 108. 
Because control of the preset limiting speed established by the governor is 
controlled by an air pressure source external to the governor, two 
additional provisions are made in the governor structure for operation of 
the engine on occasions when air pressure is temporarily unavailable or is 
improperly controlled. For example, in the case of a vehicle mounted 
engine where an engine driven pump pressurizing a storage tank is utilized 
as the source of pressurized air, it is necessary to provide some means of 
operating the engine at idle speed under conditions when no pressurized 
air is available in the system for controlling the governor. In such a 
situation, the minimum speed spring 112 extending between the piston 100 
and plunger 64 urges the plunger rightwardly as shown in FIG. 2 with a 
biasing force sufficient to hold the plunger in its rightward position 
against the slightly lower force of the idle speed spring 66. Thus, the 
minimum speed spring 112 provides sufficient biasing force to operate the 
engine at idle speed and thereby permits building up air pressure in the 
air system to a point where sufficient pressure is available to charge the 
chamber 108 to a pressure suitable for operation of the engine at normal 
governor controlled speeds. On the other hand, should improper control of 
the air pressure system lead to a situation where the air pressure in 
chamber 108 is raised above the normal speed controlling pressure to exert 
a force greater than the bias of the overspeed spring 74, then increase of 
the engine speed to an overspeed condition will cause the overspeed spring 
74 to yield, allowing the force of the flyweights acting through the cap 
60 and spring seat 72 to compress the overspeed spring without moving the 
plunger 64. In this case, the engine fuel racks will be moved to a reduced 
fuel position without the necessity of moving the plunger or the air 
biased piston 100, thereby maintaining the engine speed at or below its 
predetermined overspeed level. 
OPTIONAL AIR CONTROL SYSTEM 
FIG. 3 of the drawings illustrates an optional air control system for use 
in a vehicle provided with an air controlled minimum droop governor in 
accordance with the present invention. In the figure, numeral 120 
generally indicates the governor of a vehicle mounted engine wherein the 
governor includes the features described with respect to the governor of 
FIGS. 1 and 2. Governor 120 includes a control air cylinder 122 having a 
piston 124 which is capable of being biased by air pressure supplied to 
the cylinder to provide preestablished governor and engine limiting speeds 
in the manner previously described. 
The governor is also provided with a throttle lever 126 which corresponds 
to the lever 50 in the embodiment of FIGS. 1 and 2. A second air cylinder 
128 and associated piston 130 are provided which, when charged with 
pressurized air, engage the throttle lever 126 to move it into its full 
fuel rack position for a purpose to be subsequently described. 
The system includes a suitable pressure air supply 132 which is controlled 
by a three-way valve 134. This valve directs air either directly to a 
preset regulator 136, which establishes the maximum air pressure supplied 
to cylinder 122, or indirectly to the preset regulator 136 through an 
adjustable regulator 138 which is capable of reducing the pressure of air 
supplied to the preset regulator. When the three-way valve is adjusted to 
supply air to the adjustable regulator, it also supplies air pressure to a 
shut off valve 140. When opened, valve 140 permits passage of the air to 
air cylinder 130, thus causing the piston 128 to move the manual throttle 
to its full fuel position. 
OPERATION OF THE OPTIONAL CONTROL SYSTEM 
The optional air pressure control system of FIG. 3 may be operated to 
control the engine in any one of three possible modes. In a first mode, 
movement of the three-way valve 134 to a first position, wherein air is 
passed directly to the preset regulator 136, brings about what might be 
considered normal operation of the engine governor, with a preset fixed 
maximum engine limiting speed provided by the governor in the normal 
manner. Speeds below the preset limiting speed are controlled 
conventionally by the operator's movement of his foot throttle to control, 
at will, the position of the throttle lever 126. 
A second mode of operation is provided by moving the three-way valve 134 to 
a second position in which air is supplied through the adjustable 
regulator 138 to the preset regulator 136, and the valve 140 is maintained 
closed. In this operating mode, the engine throttle is also operated 
normally, but the governor limiting speed is adjustable by adjustment of 
the regulator 138 to any selected air pressure. This pressure may be 
controlled by the operator, if desired, or it may be selected by 
connection with some engine connected device such as the transmission of 
the vehicle so that, for example, a higher engine limiting speed may be 
provided in lower gears, while a predetermined lower limiting speed would 
be provided in the high gear of the transmission, thereby limiting maximum 
vehicle speed in a desired manner. 
A third mode of operation corresponds to what might be desirable for use of 
the governor as a vehicle speed control. In this mode, the three-way valve 
134 is again moved to the second position so that air is supplied through 
the adjustable regulator 138 to the preset regulator 136. In addition, 
valve 140 is opened to supply full pressure air to the air cylinder 128, 
thereby actuating the piston 130 to move the throttle lever 126 to its 
full fuel position. With this arrangement, engine speed control is 
separated from movement of the manual throttle by the operator and is 
instead taken over by the governor, as determined by the air pressure 
provided thereto through adjustment of the adjustable regulator 138. 
Control of this regulator by the operator provides operation of the engine 
at a controlled engine speed of the operator's selection for as long as 
the system is maintained in the particular operating mode. Cutoff of the 
control system and return to the first or normal mode of operation could 
be accomplished by any desired system such as, for example, the control 
system described in my previously mentioned U.S. Pat. No. 4,082,074. 
It may be seen from the foregoing that the present invention provides a 
novel air pressure control governor system and optional associated air 
control system which permit considerable flexibility of application and 
use in conjunction with vehicle mounted engines as well as for other 
engine applications. It should be noted that, in operation of a governor 
in accordance with the present invention, control of the engine at the 
governor provided limiting speed is accomplished without the movement of 
any of the springs provided within the governor. Thus, it is apparent 
that, during normal speed limiting operation at the governor limiting 
speed setting, the sole operative speed setting biasing element is the air 
piston provided as a part of the governor speed setting means. The 
operation of the various springs provided within the governor occur solely 
under various extremes of governor operation such as during an overspeed 
condition, at engine idle or at operation where no air pressure is present 
to provide the normal governor control. 
As a result of the feature of speed limiting control by an air piston as 
the sole operative element in the biasing system, the present invention 
provides a governor system which is essentially free of speed droop of the 
type normally caused by mechanical movement of governor mechanisms to 
various positions in response to varying loads. This is because when the 
air pressure on the piston is controlled to a fixed amount, the pressure 
does not vary because of movement of the piston. Thus the force of the 
piston acting against the speed responsive flyweight mechanism does not 
vary with position. This differs from the usual governor arrangements in 
which compression of the usual speeder spring, or high speed spring, 
causes a change in the biasing load of the spring at various positions 
which results in the speed droop characteristic. 
While it might be considered that operation of an engine governor without 
significant speed droop would result in an unstable governing condition, 
initial testing of this concept has indicated that minimum hysteresis in 
the system, caused by the friction forces of the piston within the 
cylinder and the other mechanism within the governor, is sufficient to 
adequately damp the system and provide for stable operation. However, 
should some need for additional damping be present under certain 
conditions of engine operation, it would be possible within the scope of 
the present invention to introduce into the system additional means for 
damping oscillations such as additional friction devices, fluid dashpots 
or other well known devices suitable for accomplishing the desired 
purpose. 
While the invention has been disclosed by reference to a preferred 
embodiment and system, it should be understood that numerous changes could 
be made in specific design and structural features without departing from 
the inventive concepts disclosed. Accordingly, it is intended that the 
invention not be limited to the features of the described embodiment, but 
that it have the full scope permitted by the language of the following 
claims.