Engine speed control system and method

An engine speed control apparatus employs a governor responsive to predetermined control input signals for controlling engine speed. An accelerator sensor produces an accelerator control input signal corresponding to the position of an accelerator. A mode selector selects one of a governor mode and a throttle mode, and produces one of a governor mode control input signal and a throttle mode control input signal corresponding to the mode selected. The governor is responsive to the governor mode control input signal for permitting the selection of an upper limit of engine speed within a predetermined range of speeds and thereafter for controlling the engine speed to maintain the engine at this upper limit when the accelerator control signal corresponds to a maximum accelerator position. The governor is responsive to the throttle mode control input signal for permitting the selection of a lower limit of engine speed within a predetermined range and for thereafter controlling the engine speed to maintain the engine at this lower limit of engine speed when the accelerator control signal corresponds to a minimum accelerator position.

BACKGROUND OF THE INVENTION 
This application is directed generally to the area of controls for internal 
combustion engines. While the invention may find other applications, the 
present disclosure is directed more particularly to an engine speed 
control system for use with an off road vehicle, and still more 
particularly with a relatively small off-road vehicle adapted for turf or 
landscape maintenance applications, such as on a golf course, park areas 
or similar relatively large landscaped areas. 
One particularly useful type of light truck or vehicle for golf course or 
similar landscaping use is made by the Jacobsen Division of Textron Inc., 
the owner of this application. This off-road vehicle is adapted to mount a 
variety of implements for working on a golf course or similar landscaping 
application. These implements include various hydraulically powered 
implements such as a sprayer for applying pesticides or fertilizers in 
liquid form, as well as a spreader attachment for spreading granular 
materials such as fertilizer, seeds, and the like, or various combinations 
of materials, such as are used in what is commonly referred to as top 
dressing of greens in golf course applications. The vehicle may also 
optionally be equipped with a dump body for hauling and dumping various 
materials or with hydraulically operated pruning equipment for trees and 
bushes. In order to operate the various hydraulic implements which may be 
utilized therewith, the vehicle is equipped with a hydraulic system 
including a power take-off (PTO) for providing power to the drive motors 
of these various implements. 
In addition to the above-mentioned implements, such implements as drum 
aerators may be utilized. The vehicle's hydraulic system provides power 
(e.g. at the PTO) for a hydraulic cylinder to lower the aerator as desired 
for working on fairways, and to lift the aerator for example, to transport 
across other areas to a fairway to be aerated. Other aerators utilize 
reciprocating aerating heads which may also require a source of power, 
such as the PTO. 
Other implements may also utilize the hydraulic power take-off for 
performing other landscape applications in golf courses or in similar 
environments. For example, various hydraulically powered tree pruners and 
saws for maintaining trees and shrubs may also be driven by the hydraulic 
system of the vehicle. 
In order to properly utilize the vehicle in the many and varied 
applications and with the numerous implements or tools mentioned 
hereinabove, it is proposed to provide a speed control system for the 
engine. That is, in many jobs to be performed utilizing various ones of 
the foregoing implements or devices, it is desirable to maintain control 
of the engine speed within various limits, both to control the ground 
speed of the vehicle and also to control the hydraulic power take-off 
system for driving various implements or tools under given circumstances. 
For example, when operating on or around a green, such as for top dressing 
or the like, it is desirable to maintain constant speed across the green, 
and yet maintain the ability to reduce speed and attain maneuverability, 
by stopping or turning at reduced speed, if desired once off the green. We 
have proposed utilizing what we have termed a governor mode of speed 
control in which the operator may select a maximum engine speed for use on 
greens, or other similar work in confined areas, and yet reduce speed by 
use (release)-of the accelerator pedal when desired, to attain 
maneuverability. 
On the other hand, when working in relatively large open areas such as 
fairways or the like, it is generally desirable to maintain a fixed 
constant minimum speed which may be released (e.g. by braking) if and when 
desired. For this application we have proposed utilizing a speed control 
in what we have termed a throttle mode wherein a lower limit of engine rpm 
or speed may be selected and maintained without use of the accelerator 
pedal. This throttle mode of operation may also be utilized in remote or 
stationary applications wherein implements such as a tree pruner, or saw, 
or the like are to be connected to the hydraulic system of the vehicle and 
used while the vehicle remains stationary. These applications may also 
require some preset engine speed or rpm in order to provide the required 
hydraulic power to the implement or tool. Basically, in this mode the idle 
speed or lower limit of the engine speed is preset and maintained without 
use of the accelerator pedal, which pedal can be used to attain elevated 
engine speeds. 
Moreover, in spreading and spraying applications, it is often desirable to 
maintain a given engine speed in order to drive the spreader or sprayer at 
the desired operating speed to maintain a given spread or spray pattern, 
and at the same time maintain some predetermined ground speed of the 
vehicle, to maintain a desired spread or spray density. The combinations 
of desired engine rpm and desired ground speed can be determined from 
suitable charts and the like. These charts may specify gear selection to 
maintain a given ground speed with a given engine speed, for example. 
However, it may prove difficult in actual applications to properly 
maintain engine rpm and ground speed manually. Therefore our proposed 
governor mode and throttle modes as discussed hereinabove permit required 
engine speeds to be selected and maintained for given applications. 
We have also proposed to permit operation of the vehicle in what we have 
termed an off mode wherein neither the governor mode nor throttle mode are 
selected and the operator selects the engine rpm and ground speed by use 
of the accelerator and gear shift. We also prefer to provide an engine 
speed control lever which permits selection of one of two speed ranges for 
each of the four gears of the vehicle. This in effect doubles the number 
of gears effectively provided by the vehicle transmission. 
OBJECTS AND SUMMARY OF THE INVENTION 
Accordingly, it is a general object of the invention to provide a novel and 
improved speed control apparatus for use with a vehicle, which provides 
means for selecting one of a lower limit of engine speed and an upper 
limit of engine speed for use in various applications. 
Briefly, and in accordance with the foregoing objects, the present 
invention provides an engine speed control apparatus comprising governor 
means responsive to predetermined control input signals for controlling 
engine speed; accelerator sensor means for producing an accelerator 
control input signal corresponding to the position of an accelerator; mode 
selector means for selecting one of a governor mode and a throttle mode; 
mode signaling means for producing one of a governor control mode input 
signal and a throttle control mode input signal corresponding to the mode 
selected by said mode selector means; said governor means being responsive 
to said governor control mode input signal for permitting the selection of 
an upper limit of engine speed within a predetermined range of speeds and 
thereafter for controlling the engine speed to maintain said engine at 
said upper limit when said accelerator control input signal corresponds to 
a maximum position of an accelerator, and said governor means being 
responsive to said throttle control mode input signal for permitting the 
selection of a lower limit of engine speed within a predetermined range 
and for thereafter controlling the engine speed to maintain said engine at 
said lower limit of engine speed when said accelerator control input 
signal corresponds to a minimum position of an accelerator.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
Referring now to the drawings and initially to FIGS. 1 and 2, an engine 
speed control apparatus in accordance with the invention is illustrated in 
diagrammatic form in FIG. 1 and designated by the reference numeral 10. 
This control apparatus 10 includes a governor control unit or governor 
means 12 which is responsive to predetermined control input signals for 
controlling the speed of the engine 14. In accordance with the form of the 
invention illustrated in FIG. 1, this governor means may comprise an 
electronic speed control unit; however, a mechanical governor control 
system may be utilized without departing from the invention. 
An accelerator sensor means or transducer 16 produces an accelerator 
control input signal corresponding to the position of an accelerator 
member or accelerator pedal 18. The transducer 16 may comprise an 
electromechanical transducer (e.g. a potentiometer) for use with a 
governor 12 which comprises an electronic speed control unit. However, the 
transducer 16 may comprise a mechanical transducer or linkage means for 
use with a mechanical governor without departing from the invention. A 
brake pedal 20 of a vehicle the speed of which is to be controlled, is 
also provided with a suitable transducer 22 which may be either 
electromechanical or mechanical, in the same manner as transducer 16, 
depending on the nature of the governor means 12. 
In accordance with a further feature of the invention, a mode selector 
means 24 is provided for selecting one of a governor mode, an off mode, 
and a throttle mode. A mode signalling means 26 is responsive to the mode 
selector means 24 for producing a control input signal corresponding to 
the mode selected by the mode selector means 24. As with the transducers 
16 and 22, the mode selector means 24 and mode signalling means 26 may 
comprise electrical/electromechanical elements or may comprise mechanical 
elements, depending upon the nature of the governor means 12. 
Finally, an increase/decrease control means or selector 28 is provided and 
is movable from a neutral central or off position to either an increase 
(+) or decrease (-) position. An increase/decrease signalling means 30 is 
responsive to the increase/decrease selector means 28 for producing a 
corresponding input control signal to the governor means 12. In similar 
fashion to the mode selector means 24 and mode signalling means 26, the 
increase/decrease selector means 28 and signalling means 30 may comprise 
either electrical/electromechanical elements or mechanical linkage means 
or elements depending upon the nature of the governor means 12. 
In operation, the governor means 12 is responsive to the governor control 
input signal from the mode signalling means 26, indicating selection of 
the governor mode, for permitting the selection of an upper limit of 
engine speed within some predetermined range of engine speeds permitted 
for the engine 14. In the illustrated embodiment, the control system is 
intended for use with a relatively small off-road vehicle for landscaping 
or golf course type maintenance operations, which preferably has a 
predetermined engine speed range of between 900 and 3200 rpm. Other ranges 
may of course be selected without departing from the invention. The 
governor means 12 is thereafter operative for controlling the engine speed 
to maintain the engine speed at this selected upper limit when the 
accelerator control signal from transducer 16 indicates that the 
accelerator 18 is in a maximum position. 
Conversely, the governor means 12 is responsive to a throttle control input 
signal from the mode signalling means 26 indicating that the selector 24 
is in the throttle position for permitting selection of a lower limit of 
engine speeds within the same predetermined range of speeds. The governor 
12 thereafter controls the engine speed to maintain the engine speed at 
this selected lower limit when the accelerator control signal produced by 
transducer 16 corresponds to the accelerator 18 being in its minimum 
position. 
It will be understood in this regard that only one of the governor mode or 
throttle mode may be selected at any given time. Therefore, the controller 
may be utilized either to control the maximum engine rpm achieved by the 
vehicle in response to a maximum depression or position of the accelerator 
18 or alternatively to control the minimum engine speed of the vehicle in 
response to the accelerator 18 being in its minimum position. In the case 
where the accelerator 18 is a floor-mounted pedal movable between a fully 
up and fully down position, the maximum position corresponds to a fully 
down position of the accelerator 18 whereas the minimum position will 
correspond to a fully up position thereof. 
It should be understood at this juncture that the internal details of the 
governor means 12 illustrated in FIG. 1 comprise the internal functional 
components of an electronic speed control unit, and that these elements 
will not be present in the case where a mechanical type of governor means 
is utilized. We have selected a mechanical type governor control and 
associated mechanical embodiments of the elements described above for 
controlling a diesel-type internal combustion engine, whereas we have 
selected an electronic control unit and electrical/electromechanical 
embodiments of the associated elements described above for controlling a 
gasoline-type internal combustion engine. However, the electronic control 
unit and associated elements are also suitable for achieving the desired 
control functions on a diesel engine. 
In the case where an electronic speed control unit is selected, we prefer 
to utilize a speed control unit 12 of the type shown in FIG. 4. This unit 
has been custom designed to our specifications by the Barber-Colman 
Company, 1354 Clifford Avenue, Loves Park, Ill. 61132, and is designated 
as Barber-Colman Model DYN1 10870 Digital Electronic Governor. This model 
of governor control unit is provided equipped with an electromechanical 
actuator 32 which is electrically driven by the control unit 12 and which 
in the case of a gasoline-type engine is operatively coupled to a 
butterfly valve or plate on the carburetor of the engine for fine control 
of the amount by which the butterfly moves to expose the ports in the 
throat of the carburetor. However, it will be understood that a different 
control element, for example, a mechanical linkage, would preferably be 
utilized together with a mechanical governor control arrangement in the 
case of a diesel engine. 
Referring briefly to FIG. 5, a feedback or "actual speed" control signal 
may be derived from a magnetic pickup 34 and fed back to the electronic 
speed control unit in the case where such a unit is used as the governor 
12. The magnetic pickup 34 preferably comprises a magnetic sensor element 
34 as illustrated in FIG. 5 which is inserted through an appropriate 
engine wall 36 to sense the movement of teeth 38 of an appropriate gear or 
fly wheel as the engine rotates. Preferably, the pickup 34 produces pulses 
at a rate commensurate with the rate of passage of the teeth 38 thereby, 
which pulse rate can readily be related to actual engine speed (rpm). 
Referring to FIG. 2, one form of the mode selector means 24 and 
increase/decrease control means 28 is illustrated for use with the 
electronic speed control unit of FIG. 4, in the case of a gasoline-type 
engine. Preferably, both of these control elements 24 and 28 comprise 
three-position electrical toggle switches. The mode selector means or 
switch 24 is preferably a three position detented switch, whereas the 
increase/decrease control 28 is preferably a three position momentary 
contact switch which is normally in its center or off position but may be 
momentarily pressed to either the increase (hare symbol) or decrease 
(tortoise symbol) side. That is, switch 28 will automatically return to 
its neutral or center off position as soon as a force or pressure moving 
it to either the increase or decrease position is released. In the 
embodiment illustrated in FIG. 4, it will be noted that the brake 
transducer 22 comprises a simple electrical switch. Also, the gas pedal 
transducer 16 as illustrated in FIG. 4 comprises a potentiometer. 
FIG. 6 is a diagram similar to FIG. 1 illustrating in somewhat simplified 
form, the operation of the electronic speed control unit as the governor 
means 12 in connection with the engine 14, showing in functional block 
form some details of the internal operation or functions of the electronic 
speed control unit. Similarly, FIG. 7 illustrates in functional form yet 
further details of a typical electronic speed control unit. Both FIGS. 6 
and 7 are in accordance with the discussion of electronic speed control 
contained in the publication Basic Governing Information by Barber-Colman 
Company, which is incorporated herein by reference. 
Referring now briefly to FIG. 3, in the case of a diesel engine, an 
alternate form of control apparatus is utilized in place of the mode 
selector 24 and increase/decrease control 28. In this case, a single 
mechanical lever 24a is utilized, and is movable from a center or neutral 
off position 40 to either a first or throttle control position 42 or a 
second or governor control position 44. The lever 24a is continuously 
movable to any position intermediate the off position 40 and the extreme 
forward end of the throttle position 42. A suitable mechanical linkage 
(not shown) determines the relative position of the lever 24a in this 
regard. In the case of a diesel engine, a mechanical governor system is 
operative for setting one of minimum and maximum engine speeds in response 
to the position of the lever 24a, together with the position of the 
accelerator pedal 18. 
Having described the apparatus of the invention, it will be instructive to 
briefly review the manner in which the various control modes are selected 
and utilized in the case of a gasoline engine and in the case of a diesel 
engine, respectively. Referring initially to the control members 24 and 28 
as illustrated in FIG. 2, in the case of a gasoline engine, the operator 
may select one of a governor mode, an off mode or a throttle mode by 
utilizing the toggle switch 24. Operation in each of these three modes 
will next be described. 
Upon selecting the governor mode by operation of the toggle switch 24, the 
upper limit of engine speed (rpm) can be decreased to any value between 
3200 and 900 rpm in the illustrated embodiment. As mentioned hereinabove, 
this mode of operation is especially useful when working in confined areas 
such as golf greens. Then, with the transmission in neutral and parking 
brake applied, the operator fully depresses the accelerator 18. With the 
accelerator fully depressed, the operator utilizes the increase/decrease 
toggle 28 to set the engine speed to the desired value, for example by 
observing the rpm reading on a tachometer. Thereupon, the accelerator may 
be released. The upper limit of engine rpm is now set by the governor 
means 12, such that the accelerator pedal will operate normally below this 
engine rpm, however, full depression of the accelerator will achieve only 
this selected upper limit of engine rpm. 
Thus, when working in confined areas, an engine speed corresponding to the 
desired speed of operation of the vehicle may be selected. When operating 
spraying or spreading implements or the like, a desired engine speed to 
provide appropriate hydraulic power for operating the implement may be 
selected from a chart or the like. Thereupon, reference to the same or 
another chart may also determine an appropriate gear selection for 
maintaining a given ground speed with the selected engine speed for 
implement operation. In the case of top dressing of greens, or similar 
spreading or spraying applications, some particular ground speed may also 
be desired to maintain a desired spread density, and thus reference to an 
appropriate chart can determine what gear selection is appropriate for 
maintaining this ground speed given the engine speed selected for 
operation of the implement. 
When operating in the governor mode, to reduce speed and attain increased 
maneuverability, for example to stop or turn, the accelerator is merely 
released to the extent necessary to decrease the speed or stop. That is, 
the accelerator operates normally up until the preset maximum engine speed 
is reached. 
When the throttle mode is selected by operation of the toggle 24 to the 
throttle position, a lower limit of engine speed between 900 and 3200 rpm 
may be selected with the accelerator 18 in its fully up or undepressed 
position. Again, the transmission is shifted to neutral and the parking 
brake applied, whereupon the increase/decrease toggle 28 is utilized to 
set the engine rpm to the desired value. This mode of operation is often 
desirable for working in larger or unconfined areas such as fairways or 
the like. As with the governor mode, the desired engine speed may be 
selected either to maintain a given ground speed with a given gear 
selection, or may be selected initially to attain desired operation of an 
implement from the hydraulic power system of the vehicle. The ground speed 
of the vehicle can then be selected by choosing an appropriate gear given 
the engine speed or rpm selected for implement operation. In operation 
this speed will be maintained without use of the accelerator pedal. The 
throttle mode may also be utilized in stationary applications, that is, 
when the vehicle is not moving but some desired minimum engine speed is 
required in order to provide hydraulic power to an implement such as a 
saw, pruning shears or the like. Upon selecting minimum engine speed in 
the throttle mode, and for stationary operation, the transmission of the 
vehicle is left in neutral and the parking brake is applied while 
operating the implement. 
When the vehicle is to be driven in the throttle mode, such as while 
operating an implement such as spreader, sprayer, aerator or the like, the 
accelerator operates normally above the preselected minimum engine speed, 
but is not needed to attain the preset minimum engine speed which is 
maintained automatically as the engine idle speed. However, in order to 
release the speed control, for example to slow down or stop, or if for 
some other reason it is desired to decrease engine speed below the 
selected minimum, application of the brake pedal 20 will release the speed 
control, much in the fashion of automotive "cruise control" operation. In 
order to reset the speed control, the toggle 24 must be first returned to 
its center or off position and then again returned to its throttle 
position. 
When the off mode is selected by operation of the toggle switch 24, the 
operator controls the ground speed and engine speed of the vehicle in the 
normal fashion by use of the accelerator and by selection of an 
appropriate gear. When returning from the off mode to either the governor 
mode or the throttle mode by use of the toggle 24, the electronic speed 
control unit 12 of FIG. 4 is arranged to return to the engine speed limit 
previously set in the governor or throttle mode. That is, once an upper or 
lower engine speed limit is selected in either the governor mode or the 
throttle mode, this upper or lower engine speed limit remains in effect 
whenever the same mode is again selected, until a new engine speed limit 
is selected by repeating the operations described above for upper/lower 
speed limit selection. 
Referring now to FIG. 3, in the case of a diesel engine, lever 24a is 
utilized to operate in the governor mode, off mode and throttle mode. The 
off mode permits selection of engine speed by use of the accelerator and 
gear selection. To enter the governor mode, the transmission is shifted to 
neutral and the parking brake applied, the lever 24a is pulled toward the 
governor control position 44, and is utilized to set the engine speed as 
desired by observing rpm on a tachometer. That is, operation of the lever 
24a is continuous, such that the lever 24a may be moved any incremental 
distance in the direction 44 and the engine speed will decrease in 
proportion to the position of lever 24a. Thereupon, the accelerator may be 
released, and the speed thus set becomes the upper limit of engine speed 
for operation in the governor mode. In operation, the accelerator is kept 
fully depressed in order to operate the engine at this preset speed. The 
accelerator otherwise operates normally below this speed, and thus to 
reduce speed to stop, turn, etc. the accelerator is merely released from 
its fully depressed position to the appropriate extent. 
In order to select a lower limit of engine speed and operate in the 
throttle mode with the control system of FIG. 3, the accelerator pedal 18 
is left in a fully up or undepressed condition, and the engine speed is 
selected by use of the control lever 24a. As mentioned above, the lever 
24a is pushed in the direction of the throttle control position 42 to set 
the engine speed to a desired value by observing a tachometer. Operation 
of the lever 24A in the direction 42 is also continuous, that is, the 
lever may be pushed any incremental distance in the direction of full 
forward position 42, and the engine speed will increase in proportion to 
the position of the lever 24a. Thereupon, in operation, the lever 24a is 
left in the selected position (at which desired engine rpm was observed), 
and the lower limit of engine rpm will be in effect with the accelerator 
18 in its fully up or undepressed condition. 
In all other respects, the subsequent operation of the vehicle in the 
governor mode or in the throttle mode (including stationary applications) 
with the use of control lever 24a is the same as described above. 
What has been shown and described herein is a novel engine speed control 
system for controlling engine speed in different modes of operation. It 
should be noted that the electronic speed control unit 12 illustrated and 
described with reference to the FIG. 4, has been custom designed for the 
operation as described herein. This is in contrast to the usual design and 
configuration of such electronic speed control units, which normally 
permit the selection of a single engine speed by use of a control 
component such as a potentiometer or the like, and thereafter maintain 
this engine speed. In contrast, the present invention permits the 
selection of a maximum engine speed under certain conditions and the 
selection of a minimum engine speed under certain conditions, and the 
electronic speed control unit 12 is especially designed and adapted to 
achieve these different modes of operation. 
While particular embodiments of the invention have been shown and described 
in detail, it will be obvious to those skilled in the art that changes and 
modifications of the present invention, in its various aspects, may be 
made without departing from the invention in its broader aspects, some of 
which changes and modifications being matters of routine engineering or 
design, and others being apparent only after study. As such, the scope of 
the invention should not be limited by the particular embodiment and 
specific construction described herein but should be defined by the 
appended claims and equivalents thereof. Accordingly, the aim in the 
appended claims is to cover all such changes and modifications as fall 
within the true spirit and scope of the invention.