US2868184A

US2868184A - Engine load limiting controls

Info

Publication number: US2868184A
Application number: US654401A
Authority: US
Inventors: Jackson Lloyd
Original assignee: Curtiss Wright Corp
Current assignee: Curtiss Wright Corp
Priority date: 1957-04-22
Filing date: 1957-04-22
Publication date: 1959-01-13
Anticipated expiration: 1976-01-13

Description

.Jam 13 1959 l L. J. MouLToN 2,868,184

ENGINE LOAD LIMITING coNTRoLs Filed April 22, 1957 l Huw/nf INVENTOR.. ENG/NE I; FUEL mx/:ss L. J. M0 u1. To/v' 6 vra/1g Hf. V

ENGINE LOADLIMITING CONTROLS Lloyd Jackson Moulton, Mentor, Ohio, assignor to Curtiss-Wright Corporation, a corporation of Delaware Application April z2, 1957, serial No. 654,401

s claims. (c1. 12s-140) This invention relates to an improved mechanism for automatically compensating for changes in air supply pressure in the operation of internal combustion engines, particularly turbo-supercharged diesel engines.

The principal object is to provide` a simple and effectual arrangement acting through a hydraulic engine governor of known type to maintain eflicient combustion in the governed engine particularly by limiting the fuel being supplied to the engine in accordance with variations in engine air supply pressure as well as in accordance with engine speed and other conditions which affect operation of governed engines. t

lt is well known that a supercharged diesel engine and particularly turbo-supercharged diesels cannot operate efficiently at high power level unless its air pressure is properly mated to the rate of fuel supply, and that when engine speed is caused to change by sudden application of load, or when the speed setting of the governor of the `tion of the herewith diagrammatically illustrated embodiment.

The accompanying drawing is a schematic view showing a typical fluid circuit of a hydraulic governor whose casing preferably contains or supports the principal elements required for practice of the present invention.

The hydraulic governonas shown, has a casing A, containing an engine-speed-change-detector or speed weighing mechanism B with liyweights B', a Speeder spring C, settable for engine speed as by member S', and a pilot valve D the movable part of which is valve plunger P. The pilot valve D controls the operating eifect of substantially constant pressure fluid (governor oil as from a `pump and accumulator, not shown, admitted to passage F) on a servomotor, represented by power piston H and itscylinder. Passage F is continuously connected to the cylinder space or pressure chamber l of the servomotor,

` and passage G connects the pilot Valve D with the cyliner chamber l. Governor oil, in the illustrated equilibrium or neutral position of the pilot valve, is trapped by that valve in line G in contact with a relatively larger eifective area of the power piston H whose smaller elfective area is continually subjected to governor oil prest sure in chamber I.

To cause increased-fuel movements of the power piston H (upward as shown) the pilot Valve plunger (by lowering as in response to diminished engine speed, thus opening port E) admits governor oil through passage G to the cylinder chamber J of the power piston; and to cause de- States Patent Patented Jan. 13, 1959 creased-fuel power piston movements the pilot valve plunger P is moved to spill trapped oil from said chamber I at one of the various sump-connected ports, all indicated S..

A hydraulically acting temporary speed droop or` compensation system between the governor power piston H and its pilot valve D is diagrammatically represented by an actuating displacement pump N operatedby power piston H; oil passage O; receiving piston Q which is spring-connected to the pilot valve plunger P, and a needle valve R for reset rate adjustment in a well known manner.

A load limiting valve of known type is represented generally at L, the movable portion of the valve being a valve plunger M. Downward movement of valve plunger M from its illustrated neutral position first blocks passage G leading from the pilot valve D to the power piston cylinder chamber l, and then connects the chamber I to sump. Thereby the mechanism L functions to circumvent operation of the governor pilot valve D to cause fuel-increasing movement of the power piston H such as normally occurs, or would occur, with increase in engine load. The governor pilot valve D dominates fuel-decreasing movement of the power piston H at all times through operation to spill governor o-il from chamber J via a one way operating by pass valve L connected essentially as shown.

Load limiting can, alternatively, be accomplished through operation of the pilot valve D, conditionally as a function of power piston movement, as is well known (not illustrated); and the present invention can be used with that type of load limiting valve mechanism without substantial modification (e, g. by reversal of output direction of the present linkage or by provision of hydraulic linkage to move pilot valve plunger P upwardly to limit load).

In the load limiting valve mechanism L, as schematically shown, upward or increased-fuel movement of the power piston H beyond a predetermined readily adjustable effective position, as will be described, operates conditionally as through a tailrod H of the piston upon a lever lt), having a normally fixed pivot '11, to depress the valve plunger M and stop further fuel-increasing movement of the power piston. Lever 1li) operates the valve plunger M through the intermediary of a floating lever 2li pivotally connected as at 21 to said valve plunger, the operating connection between the two levers being illustrated as a push rod Z2 in a suitable guide.

In order that the load limiting valve M can be operated irom its illustrated neutral position downwardly to an appropriate fixed stop, the tailrod H has a one-wayyieldable connection with the power piston H. This, as shown, includes a threaded stop collar 24 in a sump-exposed trunk portion of the power piston, and a head portion 25 on the tailrod which is held in upward abutment with the collar 24 by a spring 26 in the piston H below the head portion of the tailrod. Spring 2o has, of course, more eiective force than the return spring M of the valve plunger M. Pivot lll for lever lt) is adjustable vertically, to change the point in upward power-piston-stroke at which the load limiting operation can be made to occur. As shown, a supporting bracket 12 for pivot li is arranged to be raised and lowered by adjustment of a screw 13 swivelled to bracket 12 and inthreaded engagement with a relatively fixed bridge portion T of the governor casing A. A tubular lock nut 14 for the screw 13 and the screw itself via the interior of the nut, are readily accessible for manipulation in an upper portion of the governor casing. A rod 15, slidably guided by casing portion T, cooperates with the adjusting screw 13 to hold the fulcrum-supporting bracket 12 in position horizontally. The guide rod 15, as shown, is connected to operate a load indication device 16 in reference to a suitable dial 17 externally of the governor casing, so that the power piston position at which,

es load limiting under predetermined conditions occurs can be made apparent to an operator.

For operation of the load limiting valve plunger M in response to actual engine speed and/or in response to engine charging air pressure (or an associated forceproducing function) a floating lever Ztl is pivotally attached to the valve plunger M as at 2l, and the pushrod or actuating p in 22 is located for fulcrum-establishing contact with the lever Ztl so that predetermined fuelincreasing movements of the power piston H are communicated provisionally to the floating lever 29, e. g. in accordance with existing engine speed and/or in accordance with -existing engine charging air pressure, each independently of the other and by positive action on the valve M.

Engine-speed-rneasuring or tachorneter mechanism K, as shown, comprises a Well known combination including flyballs K1 and a spring K2 (partially shown) acting oppositely of the flyballs. The spring K2 as a function of decrements of engine operating speed moves the lever 20 about its fulcrum 22, through the intermediary of a push rod K3, tochange the operating relationship between the governor power piston H and the load limiting valve L (such as primarily established by adjustment of fulcrum ll). Thereby, at a sufficiently low speed (subject to adjustment by means not shown) such that increase of fuel can be detrimental to the engine, the fuel cannot be increased beyond a predetermined point. Similar mechanisms in governors are commonly called brake mean effective pressure (B. M. E. P.) limiters, and their manner of operation is well known in the governor art.

The engine-charging-air-pressure-resporisivc mechanism W hereof, as schematically illustrated in part, comprises a diaphragm or bellows device 31 of suitable design mounted in or on the governor casing A and having a signal receiving conduit connection 32 with (e. g.) the engine charging air box, and an output element 34, shown as a rod attached to a movable wall of the bellows device and operatingly connected to the load limiter floating lever 2i) as will be describe-d.

As engine air pressure, or its operative equivalent in terms of supplying a combustion-supporting medium under pressure to the engine, is reduced or becomes depleted-the output rod 34 of mechanism W is moved by a reactance or operating spring 35, shown as acting on the rod 34, to oppose the pressure-produced motion of the rod, and movements of the rod are communicated to the tioating lever Ztl as through a bell crank 36 and link 3%5 as clearly shown. The link 38 has an abutment portion 39 underhanging the same effective portion of the oating lever Ztl as is acted upon by the engine speed measuring mechanism K. The arrangement is such that the two mechanisms K and W are mutually independent, both acting upon the lever 2Q in the same direction but without possibility for the action of either mechanism interfering with the action of the other in complementing governor power piston action to limit increase of engine fuel.

In order to minimize sliding friction the vario-us points or regions of input action on the floating lever Ztl (and similar points on the lever ill) are preferably along a common longitudinal axis (such `as indicated at 20a in respect to the floating lever 20 for example). Axis 20a intersects the axis of pivotal connection 2l or the output point of the floating lever 20 in reference to load limiting valve plunger M.

ln order to mate the operation of present mechanism W to an engine it is necessary to be able to oppose the force being exerted on the output element 34 of enginecharging-pressure-responsive mechanism W with a loadlimiting-valve-operating force proportional to the eliective charging air pressure force or whatever pressure signal is used. An appropriate operating-force-adjustment is shown in the form of a screw 35 serving as a normally stationary reactance element for spring 3S. The spring 35 is in such position in the governor that it can be readily replaced by a spring of a different scale when that is necessary in order to meet specific engine requirements, e. g., in order to adapt the mechanism fo-r service on different types or makes of engines. Stroke of the mechanism W, as applied to the lloating lever 20, can be adjusted by moving the upper end of the link 38 along the lower arm 36 of the bell crank lever 36 by shiftable pivot device 37 including suitable locking means not shown. Additionally the

brackets

31a, 35a and 36a which, as shown, support theprincipal operating elements of the mechanism W can be shifted horizontally into different positions on the superstructure of the governor casing.

All the necessary adjustments pointed out -above can be accomplished or effected externally of the principal governor casing; i. e., at its upwardly exposed or top side, after removal of a suitable casing cap or cover (not shown).

Emergency. shutdown devices, such as represented by rod 4t) and solenoid 41, can be arranged to act directly upon the load limiting Valve plunger M without interfering with the hereinbefore described load limiting operations. A hand shut-down device such as 44 is shown as arranged to operate more or less independently of the other load control and shut-down mechanisms (e. g., via the rod 4u).

l claim:

l. An internal combustion engine control mechanism, including a hydraulic governor of the servomechanism type, wherein speed responsive means in the governor operates through a governor pilot valve to change the position of a governor output motor element whereby to increase and decrease fuel to the engine, and wherein means associated with the engine operates to supply air under variable pressure capable of supporting combustion; the combination of a load limiting valve mechanism in the governor operative to prevent normal speed responsive action of the pilot valve from increasing engine fuel via the output motor element, means capable of actuating said load limiting valve mechanism primarily and conditionally as a function of movements of said output motor element in `its fuel-increasing direction to limit such movements, and pressure responsive means in the governor connected for operation as a function of the air supply pressure producing means and operating on said load limiting valve mechanism to change the operating relationship between the output motor ele ment and said valve mechanism.

2. The engine control mechanism according to claim l wherein a main casing houses the governor elements mentioned, the air pressure responsive means includes a diaphragm or bellows device in fixed position on the casing and having an output member connected to operate the load limiting valve mechanism, a spring connected to oppose pressure operated motion of the output member of said device, and readily laccessible adjusting means operable on the spring to vary its force.

3. An internal combustion engine control mechanism, including a hydraulic governor of the servomechanism type, wherein speed responsive means in the governor operates through a governor pilot valve to change the position of a governor output motor element whereby to increase and decrease fuel to the engine, and wherein means associated with the engine operates to supply air under variable pressure capable of supporting combustion; the combination of a load limiting valve mechanism in the governor operative to prevent normal speed responsive action of the pilot valve from increasing engine fuel via the output motor element, a lever capable of actuating said load limiting valve mechanism primarily as a function of movements of said output motor element in its fuel-increasing direction to limit such movements, a first means operating on a portion ofthe lever in one direction of operation of the lever to change the operating relationship between the output motor element and the load. limiting valve mechanism, and a second means operated variably as a function of the air supply pressure producing means and operating on said lever to change said relationship, said first and second means operating on an effectively common portion of the lever in a single direction but without being capable of operating thereon in an opposite direction, whereby the operations of neither of said two means can affect the operation of the other.

4. An internal combustion engine control mechanism, including a hydraulic governor of the servomechanism type, wherein speed responsive means in the governor operates through a governor pilot valve to change the position of a governor output motor element connected to increase and decrease fuel to the engine, and wherein means associated with the engine operates to supply air under variable pressure capable of supporting combustion; the combination of a load limting valve in the governor between its pilot valve and its output motor element so as to be operative to prevent pilot valve action from increasing fuel via the output motor element, a lever capable of actuating said load limiting valve primarily as a function of movements of said output motor element in its fuel-increasing direction to limit such movements, engine speed responsive means operating on a portion of the lever in one direction of operation of the lever to change the operating relationship between the output motor element and the load limiting valve so as to limit increase of fuel to the engine as a function of decrements of operating speed of the engine, and an additional means operated variably as a function of the air supply pressure producing means to change said relationship, said engine speed responsive means and additional means operating on an effectively common portion of the lever in a single direction but without being capable of operating thereon in an opposite direction, whereby the operations of neither of the two means can affect the operation of the other.

5. An internal combustion engine load control, mechanism, including a hydraulic governor of the servomechanism type, wherein speed responsive means in the governor operates through a governor pilot valve to change the position of a governor output motor element connected to increase and decrease fuel to the engine, and wherein means associated with the engine operates to supply air under variable pressure capable of supporting combustion; the combination of a load limiting valve plunger in a motor element fluid supply passage of the governor between its pilot valve and its output motor element so as to be operative to prevent pilot valve action from increasing fuel via the output motor element, a floating lever pivotally connected to the plunger of the load limiting valve, abutment means connected for operation on a portion of the lever as a function of movements of said output motor element in its fuel-increasing direction thereby provisionally to cause load limiting movement of the valve plunger, engine speed responsive means in the governor operating on another portion of the floating lever in a direction to change the operating relationship between the output motor element and the floating lever, and pressure operated means connected for operation variably as a function of the air supply pressure producing means to change said relationship, said engine speed responsive means and said pressure operated means operating on .an effectively common portion of the floating lever in a single direction, whereby the operations of neither of the two means tends to affect the operation of the other.

6. The mechanism according to claim 5, wherein the load limiting valve plunger and the governor output motor element are guided for movement in mutually parallel paths, motion of said motor element is provisionally imparted to the valve plunger via a lever having a normally Xed fulcrum, a supporting member for the fulcrum, and means connected to the supporting member and movable for adjustment in a direction parallel to the movement of the motor element and valve plunger so as to change the provisionally operating relationship between the motor element and the floating lever.

7. The mech-anism according to claim 6, wherein a device `connected to the lever fulcrum supporting member is moved thereby when the supporting member is adjusted in position, and means on the governor externally thereof connected for and capable of indicating to an operator various positions of said device as moved by the fnlcrum supporting member.

8. The mechanism according to claim 5, wherein the abutment means operated as a function of governor output motor element movement, the engine speed responsive means and the pressure operated means act upon the floating lever in a common plane along a longitudinal axis of the floating lever.

References Cited in the file of this patent UNITED STATES PATENTS 2,690,167 Moulton Sept. 28, 1954