US2434182A - Engine control - Google Patents

Description

Jan. 6, 1948. J. F. TARLIN 2,434,182

' ENGINE CON-T-ROL Filed July 29, 1944 "v as INVENTOR. 101m 1?]6'1 4/171 BY Q M CH -l zuli;

Patented Jan. 6, 1948 ENGINE CONTROL JohnF. Taplln, Westileld, N. J., assignor, by

memo assignments, to Power Industries, Incorporated, New York, N. Y., a corporation of Delaware Application July 29, 19, Serial No. 547,223

3 Claims. (01. 290-40) This invention relates to engine controls, particularly to engine-generator sets, and has for an object the regulation of engine output so that momentary overloads will not stall the engine.

It is the usual practice in vehicles requiring electric current for the operation of electrical apparatus thereon to couple an electric generator to a prime mover, such as an internal combustion engine, the capacity of which is, in general, designed to take care of the normal full load requirements of the generator. In such enginedriven generator arrangements no trouble would be experienced were the engine and generator operating characteristics at full load similar but it is well known that the full load output of the generator may under certain circumstances exceed the capacity of the engine, and thus stall the engine.

The power output of an internal combustion engine is primarily limited by its capacity to breathe as an air pump, that is, the quantity of air which it is able to take into its cylinders in a given time, which capacity in turn is dependent upon the position of the throttle valve and also upon the altitude at which the air is introduced. At any particular speed an increase of power may be obtained by increasing the throttle opening up to its maximum. Within the usual operating range of these engines an increase of power is also available by increasing the speed. It is also appreciated that altitude has an important bearing upon the operation of the engine; for, at high altitudes the engine output is reduced because of the reduction in its air intake ability, decrease in the air density, and, to a lesser extent, by reduction in the cooling factor of the surrounding air.

The power output of an electric generator, on the other hand, is limited by its internal electrical characteristics and cooling ability. At high altitudes the internal characteristics thereof remain substantially the same as at low altitudes while the cooling ability of the generator decreases. However, th reduction of available cooling at high altitudes is of comparatively small effect, so that the generator output is substantially unaffected thereat; whereas, as indicated hereinbefore, the engine output is reduced to a greater degree because of its diminished breathing capacity. It is therefore possible to have an internal combustion engine operating at some altitudes where its maximum output equals the generator input corresponding to some safe electrical output. Under this condition, since the engine is limited in output by its air intake capacity, the generator may be capable, at high altitudes, of

making brief power demands upon the engine in excess of the maximum engine capacity at those altitudes. This would generally stall the engine were not preventative precautions taken.

The simplest means for the prevention of engine stalling would no doubt reside in an oversize engine, which is uneconomical, or in a flywheel, which could store sufficient energy to carry the generator through any desired overload period. But in many cases such a flywheel may be prohibitively large and, particularly in the case of air-borne equipment, any flywheel larger than the minimum size required to keep the prime mover running between power impulses represents undesirable excess weight.

It is therefore a primary object of this invention to limit the output of the engine, as it approaches its maximum value, to the particular set of conditions to be encountered by the gen erator. Thus limitations in engine output will likewise limit the generator output.

A further object of the invention is to prevent the generator from stalling the prime mover at altitudes where the output of the prime mover is insufficient to meet the possible demands of the enerator.

It is a further object of the invention to prevent the engine from being stalled in the event of some generator deterioration that mightincrease the mechanical input required for a given electrical output. Specifically, since the generator efficiency is a function of temperature, an increase of temperature caused by operation at severe load conditions ,may cause a pronounced decrease in eniciency and thus call on the engine for mechanical output in excess of its capacity.

erator with a shunt field, a series of auxiliary resistances that are cut into the field circuit step by step after the throttle valve has been opened a predetermined amount, that is, just short of the throttle position that would stall the engine. The resistance actuating mechanism in one of the embodiments shown includes a member having a projection, which is operated through a linkage by a speed-responsive governor. and a resistance-contacting lever, which is responsive to engagement of the projection at a predetermined position of the member and which inserts resistance elements into the field circuit by disengaging short-circuiting contact arms step by step through a tapered bar.

Applicant is aware that the broad aspects of varying the generator field excitation in accordance with the-load requirements for the prevention of 7 engine stalling is well known but he is unaware of such automatic means that is operable just prior to the stalling point of the engine, that is, in automatically controlled engine generator sets where manual throttles are not employed.

In another embodiment f the invention M17811. tage is taken of the relationship of the static pressure in the intake manifold of a gasoline engine, at substantially full load, with that of atmospheric pressure. pressure differential corresponding to a heavy load on the engine, just prior to the stalling point, produces a light or substantially negligible pressure on a carbon pile, which in turn adds high resistance to the field circuit; whereas under lighter engine loads the pressure differential is great enough to reduce the resistance to a negligible amount, sothat for practical purposes the resistance is short-circuited.

These embodiments, as well as distinctive features, of the invention will be more fully described in the following specification in which:

Fig, 1 illustrates in an engine-generator power control system, a variable resistance contactor actuated by linkage coupled through a throttle valve to a, speed-responsive governor, and

Fig, 2 illustrates a resistance contactor actuated by a pressure differential device coupled to the engine intake manifold and atmosphere.

Referring now to Fig. 1 of the drawings, there is shown a prime mover of any suitable type, such as an internal combustion engine l0, coupled mechanically to and driving an electric generator ll through a driv shaft 12, the generator I! being adapted for supplying electric power to any suitable load, such as electric motors and other electrical devices. The engine In is provided with the usual carburetor l3, 9. portion of which is shown enlarged for clarity of illustration, within which is rotatably mounted a throttle valve of any suitable type, such as a disk l4 mounted on a shaft l5, for regulating the air intake. In the fully opened position of the throttle valve the valve disk 14 is disposed in parallel relationship with the side walls, that is, at an angle of 180 therewith, so that the pressure within the carburetor is practically atmospheric; Whereas in the partly closed position thereof the disk I4 is at a smaller angle with that of the side walls, so that the pressure in the carburetor above the valve M for an up draft manifold, in view of the air resistance, is less than that of the atmosphere. The engine is also provided with a speed-responsive device, such as the usual centrifugal governor l6, which is mounted upon and responsive to the speed of engine shaft 12 and which controls the position of the throttle valve [4 through a series of linkage levers H. The positions of the throttle valve disk 14 and governor l6, as shown, correspond to a normal operating speed of engine 10.

The generator II, as shown, is of the direct current type and is provided with a shunt field winding l8 having one end thereof connected to commutator brush I9 and the other end thereof connected through a field rheostat 2! or, if de- A predetermined small.

4 sired instead, an automatic voltage regulator, and a series of resistances 22 to the other commutator brush 23 of the generator. Output leads 24, 25, connected to commutator brushes I3, 23, respectively, terminate in an electric load 23. It is well known that the generator output may be varied by changing the resistance in the shunt field circuit. A decrease in the amount of field circuit resistance, will increase the output current; whereas an increase in the field circuit resistance will decrease the output current or the generator. Thus by varying the number of resistance elements 22 cut into the field circuit it can be seen that the output current may be varied inversely. However, in this invention the series of resistances 22, are provided for increasing the field circuit resistanceonly when there is danger of the engine stalling because of an excessive load demand of the generator. Accordingly, the resistance elements 22 are normally short-circuited.

Under normal operating conditions the current output of the generator II is well 'within the capacity of the engine to and the control resistance elements 22 are not required. However, as mentioned hereinbefore, in certain instances the output current of the generator ll, because of high altitude, may exceed the capacity of the engine III, which would otherwise stall were it not for the features of this invention. In an airplane the stalling of the engine would obviously result in serious consequences.

As shown, resistance 22 is subdivided serially into a plurality of resistance elements, preferably of equal value, and taps thereof are connected to individual contact springs 21 of a resistance contactor 28, the free ends of contact springs 21 being biased to rest upon a common contact bar 29, which is fastened in any suitable manner to an insulating base 3|. A conductor 32 interconnects contact bar 29 and the other end of resistance 22 to complete a. bridge around the resistance 22. Contacts 21 are secured intermediate insulating elements 33, 34, of a pile-up or stack 35, which also includes insulatin element 36 and a clamping plate 31, the stack assembly being secured to base 31 in any suitable manner, as by means of studs 38. Also secured to the stack 35, between members 34 and 36, is a plate 39 having a pair of arms 40 to which are riveted flexible spring hinges 4|, which in turn are secured in any suitable manner, such as by rivets 42, to arms 43 of a lever 44, The front portion of each of the arms 43 is bent into a U-shape in order to support a tapered insulating bar 45, which may be attached thereto in any well-known manner, the sloping surface of the bar- 45 being so pitched that upon being actuated the several contact springs 21 will be individually disengaged from contact bar 29 step by step. That is, contact bar 21 at the extreme left would be first disengaged, then the second bar 21 from the left, and in sequence until the last bar at the right is disengaged from the contact bar 29. Intermediate the arms 43 of the lever 44 is a tongue member 46 which projects frontwardly beyond the contact bar 29 and which is adapted for raising the insulating bar 45 by engagement with the bottom edge thereof. The tongue 46 is provided with an overlarge aperture 41 for receiving a push rod 42 therethrough, a projection or bumper 49 being provided a predetermined distance from the end thereof for actuating the tongue 4' upon engagement therewith. It is readily seen that the upper end of the push rod 48 is ineflective to actuate the tongue 46 and that the position of the bumper 49 determines exactly when the tongue 46 is to be actuated to cut the resistance elements 22 into the field circuit. The other end of push rod 48 is fixedly secured to a pin 50 in any suitable manner, which in turn is secured through a, link to throttle valve shaft l5, which is rotatably mounted in the wall of the carburetor it. Other means may be employed to actuate the tongue 46 at the critical moment and applicant is not to be limited to the specific arrangement shown. For example, cam means may be employed to actuate the tongue member 46 at the proper moment.

The operation of the engine-generator control will now be described. Normally, the speed of engine l0 and the relative positions of governor I9 and throttle valve disk N are such that the resistance contactor tongue 46 isunaifected by the movement of push rod 48 through aperture 41. Thus, the series of resistances 22 are shorted in a circuit that can be traced from the one end of resistance 22 over conductor 53, through left contact spring 21, contact bar 29, and thence to the other end of resistance 22 over conductor 32. In the event that the generator output current should momentarily become excessive, the engine ill will begin to labor and reduce its speed. The governor l6 in view of the decrease in-speed of shaft i2 will, through linkage il, actuate the throttle valve l4 to almost its fully opened position, namely, the critical position, which may be assumed to be about short of full throttle opening, that is, at about 170 with the side walls of the carburetor i3. At this throttle position the projection 49 is set to engage the tongue 46, which in turn raises tapered bar 45 to first disengage the. left contact spring 21 from contact bar 29. Immediately upon such disengagement contact resistance element 54 of resistance 22 is cut into the shunt field circuit and the field resistance thereof is'so increased as to reduce the output current of the generator I I in accordance with the value of resistance 54. The shunt field circuit now includes resistance element 54 and this field circuit may be traced from one end of field winding l8 through resistance 54, conductor 56, second contact spring 21, contact bar 29, over conductor 32 through rheostat 2! to the other end of the shunt field windinglii through the commutator brushes 23, I9. If the generator load is still excessive, the engine speed will drop another increment, the throttle valve will open further, and the second contact spring 21 will be disengaged from the contact bar 29 by further movement of push rod 48. Resistance element 51 of resistance 22 will then be cut into the shunt field circuit and as a result further reduce the generator output current. The above procedure may be continued until all elements of resistance 22 are cut step by step into the field circuit. This will result in a substantial drop in the generator output current and will thereupon result in a decrease in the demands of the generator on the engine [0, which will, as a result, increase in speed to such an extent that the governor l6 starts to close the throttle valve disk l4 to its normal'operating position. The push rod 48 follows the throttle valve disk [4 and accordingly permits the contact springs 21 to sequentially retract into engagement with contact bar 29 and short circuit the resistance elements of resistance 22 correspondingly out of the field circuit.

Referring to Fig. 2, a second embodiment of the invention is illustrated in which a pressiireresponsive device 60 is actuated by a difference inpressures existing between the atmosphere and that part of the carburetor it beyond the throttle valve I4, a portion of which is only shown. It can be seen that the portion of the carburetor l3 below the throttle valve l4 for an up draft manifold is at atmospheric pressure, since it is connected to the open air, whereas the portion above the throttle valve l4 may be at various pressures depending upon the angular position of the throttle valve 14. In other words, when the throttle valve i4 is fully opened, the portion of the carburetor l3 above the throttle valve I4 is substantially at atmospheric pressure but when the valve I4 is closed, the pressure thereabove is substantially lower than that in the portion therebelow. Oi course. intermediate Pressures will be found between the closed and opened positions of the valve l4.

The pressure-responsive device comprises a casing 62 having openings 63 to the atmosphere. Within the casing 62 is mounted a sealed chamber 64 having a wall 65, which may be rigid, and a diaphragm 66.- An opening is provided in chamber 64 for entrance of tube 6 i, which is connected at the other end to the carburetor l3 at a point beyond the throttle valve l4. Thus one side of the diaphragm 66 is vented to the atmosphere through ports 63 and the other side thereof is in communication with the intake passage of the carburetor l3. The diaphragm 86 carries a pin or red 61, the free end of which is movable through an opening 68 in the wall 69. At the extreme free end of the rod 61 is mounted an insulator 69, which is adapted for engagement with a contact member ll of carbon blocks 12. The rod 61 may be slightly overlong in order to bias the insulator 69 against the contact member II and thereby increase the pressure upon the carbon blocks 12. In view of the opening 69 for rod 61, the diaphragm chamber 64 may be further sealed in any suitable manner, as by a low rate bellows 13 disposed around rod 61.

The carbon resistance blocks 12 may be mounted in any satisfactory enclosure, such as a tube 14 of ceramic material, surrounded by a finned metallic heat-radiator 16, at one end of which is mounted a metallic plate 11 insulated therefrom by an insulating plate 78. Plate I1 is secured to radiator 16 in any suitable manner, such as by screws I9 threadedly engaging radiator 16, plate 11 being further insulated therefrom by insulating bushings 9| around screws 19. An adjusting. screw 82 is threadedly mounted in plate 11 and the point thereof is adapted to engage the end carbon block contact member 83. A terminal 94, which is mounted on adjusting screw 82 by means of a nut 83, facilitates connection of conductor 81 to one side of the carbon blocks 12, the other side thereof having connected thereto a conductor 88, which may be secured to contact member II in any suitable manner.

As indicated hereinbefore, at or near full load of the engine in the intake manifold pressure is substantially at atmospheric pressure, so that the pressures within and without the chamber 64 are almost identical. In other words, the diaphragm 66 at full load is practically at its neutral position, that is, there is hardly any pressure exerted upon it by the atmosphere. Since rod 61 is retracted by diaphragm 66 to the left under this condition, the carbon blocks 12 have substantially little pressure exerted thereupon, the

pressure being also dependent upon the length oi' rod 87, and as a result a resistance or comparatively high value is inserted into the shunt field circuit. At lighter loads of the engine III the pressure at the intake manifold is lower than the atmospheric pressure and as a result the diaphragm 68 is moved to the right by the atmospheric pressure. Thus rod 81 may be adapted to exert a substantial pressure against the carbon pile 12 in the normal operating range 01' the engine, so that there will be very little resistance inserted in the generator field circuit; for practical purposes this resistance may be considered negligible.

In operation, when the predetermined current output of the generator I I is exceeded, the engine III in attempting to meet this output will have its throttle valve I! automatically moved to a position Just short or full opening, that is, to its critical position, as mentioned hereinbefore, whereupon the pressure differential in chamber 64, as heretofore described, will become small enough to retract the rod 81 and loosen the carbon block pile-up I2, so that a substantially high resistance will be cut into the shunt field circuit. This circuit can be traced from one end of field winding 18 over conductor 81. terminal 84, adlusting screw 82, contact member 83, carbon blocks 12, contact member I I, and back over conductor 88, through field rheostat 2| to the other side of the field 18 through commutator brushes 23, 19, In view of the increased resistance inserted in the shunt field circuit the current output of the generator II will be decreased and the throttle valve will be automatically shifted away from its fully opened position. Thus the engine resumes its normal speed and is prevented from stalling, further closure of the throttle valve [4 producing a differential pressure that causes the diaphragm 66 to force rod 61 against the contact blocks I2 and thereby reduce the resistance thereof to a negligible amount.

While the features of this invention have been disclosed with reference to specific embodiments shown, it is, of course, understood that various modifications may be made in the details of construction without departing from the scope of this invention as defined in the appended claims.

What is claimed is:

1. In combination, an engine, an electric generator adapted to be driven by said engine, a field excitation circuit for said generator, a plurality of resistance elements in said circuit for varying the generator output, a throttle valve for controlling the output of said engine, a governor responsive to the speed of the engine for regulating the position of the throttle valve, a resistance contactor for inserting said resistance elements step by step into said circuit, means including a push rod for interconnecting said contactor with said throttle valve only after the valve has reached a predetermined position, and a bumper on said. push rod, said contactor comprising a plurality of contacts connected to said resistance elements, a tapered member for opening said contacts sequentially, whereby said resistance elements are inserted into said circuit sequentialiy, and a tongue for actuating said tapered member, said tongue having an oversize aperture for loosely receiving said push rod and being actuated only when engaged by said bumper.

2. In combination, an engine, an electric generator adapted to be driven by said engine, a field excitation circuit for said generator, a plurality of resistance elements of equal value in said circuit for varying the generator output, a bridge around said resistance elements, a throttle valve for controlling the output 01' said engine, a governor responsive to the speed 01' the engine for regulating the position oi! the throttle valve, a resistance contactor for opening said bridge and for inserting said resistance elements step by step into said circuit, means including a push rod for interconnecting said contactor with said throttle valve only after the valve has reached a predetermined position, and a bumper on said push rod, said contactor comprising a plurality of contacts connected to said resistance elements, a tapered member for opening said contacts sequentially, whereby said resistance elements are inserted into said circuit sequentially, and a tongue for actuating said tapered member, said tongue having an oversize aperture for loosely receiving said push rod and being actuated only when engaged by said bumper.

3. In combination, an engine, an electric generator adapted to be driven by said engine, a field excitation circuit for said generator, a plurality of resistance elements of equal value in said circuit for varying the generator output, a sectional bridge for short circuiting said resistance elements, a throttle valve for controlling the output of said engine, a governor responsive to the speed 01 the engine for regulating the position of the throttle valve, a resistance contactor for opening said bridge and for inserting said resistance elements step by step into said circuit, linkage in-- cluding a push rod for-interconnecting said contactor with said throttle valve only after the valve has reached a predetermined position, and a bumper on said push rod, said contactor comprising a plurality of contacts connected to said resistance elements, a tapered member for opening said contacts sequentially, whereby sections of said bridge are opened and said resistance elements are inserted into said circuit sequentially, and an arm for actuating said tapered member, said arm having an oversize aperture for loosely receiving said push rod and being actuated only when engaged by said bumper.

JOHN F. TAPLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 840,013 Routin Jan. 1, 1907 1,216,237 Lemp Feb. 13, 1917 1,745,130 Turner Jan. 28, 1930 1,768,165 Stokes June 24, 1930 1,831,823 Pope, Jr .Q Nov. 17, 1931 1,929,382 Arthur Oct. 3, 1933 2,008,057 Bohli July 16, 1935 2,178,355 Brunner Oct. 31, 1939 2,345,409 Mason Mar. 28, 1944 2,356,629 Stratton Aug. 22, 1944 FOREIGN PATENTS Number Country Date 465,588 Great Britain May 10, 1937

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