US2180138A - Power unit - Google Patents

Description

Nov. 14,1939. BRUNNER 2,180,138

POWER UNIT Filed Feb. 5, 1937 Patented Nov. 14, 1939 UNITED STATES POWER UNIT Adolf Brunner, Winte'rthur, Switzerland, assignor to Sulzer Friares, Socit, Anonyme, Winterthur, Switzerland Application February 5, 1937, Serial No, 124,345

In Switzerland February 26, 1936 x This invention relates to internal combustion engine-electric power units and particularly to units in which the engine drives a generator having field-regulating means operated by a servo- ,5 motor, whereby the generator is controlled to maintain the engine torque constant.

In power units of this type, when the servomotor comprises a double-acting piston and a valve whereby the supply of oil under pressure to 9,9 the servo-cylinder on opposite sides of the piston is controlled so as to move a field-regulating rheostat in one direction or the other, failure of the supply of oil under pressure to the servo-piston may result in the rheostat stopping in a position ;15 which will result in the engine being overloaded.

With a view to improving reliability in operation, it has been proposed to supply pressure medium 'to the servo-cylinder only on one side of a singleacting piston for increasing the excitation current of the main generator, the return movement of the piston being efiected by spring pressure. Such arrangements are, however, open to the disadvantage that at starting of the engine the fieldregulating servo-motor sets the excitation current at a minimum value so that acceleration of a vehicle driven by the power unit is liable to be delayed on, account of insuflicient excitation. This is more particularly the case when the generator is furnished with an unregulated shunt excitation p and a regulated separate excitation, since the servo-motor regulating the separate excitation takes an appreciable time to reach the position corresponding to maximum excitation.

According to the present invention, means are 5 provided whereby, in the event of the power supply for operating the field-regulating servomotor becoming defective, the fuel supply to the engine is automatically reduced or cut off.

Preferably the arrangement is such that, when L4:0 the fuel supply is automatically reduced or cut ofithe field-regulating servo-motor is automatically adjusted towards a setting corresponding to maximum excitation of the main generator, so that if the engine is automatically stopped a ve 45 hicle driven by power derived from the power unit can be rapidly accelerated when the engine is restarted.

In a preferred arrangement according to the invention an automatic control device isprovided 50 which is normally held inoperative by power derived from the source which supplies the power for actuating the servo-motor, and interconnecting means are provided between the automatic control device and a fuel regulator for the engine 5 so that the event of the said power supply 7 Claims. (01. 290-17) failing the automatic control device operates the fuel regulator to reduce or cut off the *fuel supply.

Two constructiona each according to the invention,- are diagrammatically illustrated by Way oi example in Figures 1 and 2 respectively of the .5 accompanying drawing.-

In the construction shown in Figure l, the engine l, which is of the fuel injection compression ignition typ e,'drives a main generator 2 and also an auxiliary generator 3. The main 10 generator 2 supplies the current for driving the motors l of a vehicle and is provided with a shunt field winding 5. The separate excitation machine 3 supplies current to a separate field winding-6 the efiective value of which is controlled by a resistance I. The main generator 2 is also furnished with a counter-compound winding 8. i

. The engine crankshaft is coupled through gear wheels 9 to a camshaft l0 which not only drives a governor i I but also operates the plungers of a fuel injection pump l2. The sleeve B3 of the governor Hisengaged by one end of a lever l4 pivoted on afixed part at l5, the other end of the lever l4 cooperating with the spindle iii of a valve I! for controlling the supply of pressure fluid, such for example as oil, from a main supply p pe. is to theoppositesides of a piston l9; arranged within a field-regulating servomotor, 25]. The piston i9 0:" the servo-motor is connected, as shown, to a rheostat arm 2! which regulates the efiective value of the resistance 1,- thus influencing the excitation of the main generator 2. The excitationof the generator 2 is thus automatically regulated so that the engine torque tends to be maintained constant for any given engine speed.

I In the arrangement, thus far described, should the piston Q9 of the field regulating servo-motor 2d bein a position corresponding to a low value 40 of, the resistance 1, that is to say a high excitation current, and the supply of pressure medium to the supply pipe it then fail or become defective, the engine may be seriously overloaded. With a view to overcoming this difiiculty an automatic control device is provided comprising a piston 25, arranged withina cylinder 26 communicating with the supply pipe it, the piston 25, which is upwardly biased by a spring 21, cooperating with.

a stop 28 secured to the spindle it, the spring 2'! thus acting in opposition to the pressure of the medium supplied through the pipe 18. For the purpose of stopping the engine 1 at will, one end 29 of the fuel regulator 24 cooperates with a plunger or stop member 30 which can be moved manually by a lever 3i (provided with a locking device not shown), the plunger 3!) being arranged in a cylinder 32 to which pressure medium can be supplied through a pipe 33 from a remote control to operate the plunger 39.

The lever I4 is yieldingly connected to the spindle 56 by a spring 35 whose lower end bears against a collar 35 carried at the lower end of the spindle l6, while the upper end of this spring bears against a collar 3! carried by the lever I4, the spring 35 thus tending to maintain the collar 37. in contact with a stop 38 carried by the spindle it. The spindle l6, and therefore the valve ll, can thus be moved downwardly independently of the governor H, a suitable packing being provided between the spindle l6 and a sleeve 39 through which the spindle passes so as to prevent pressure medium from leaking through this joint.

With the parts in the positions shown in Figure l, the governor 'l I is in its position of equilibrium since the excitation of the generator 2 has been set by the fie d-regulating servo-motor 20 in such a manner as to correspond to the engine torque which is to be maintained constant at the desired engine speed and to the quantity of fuel supplied as set by the regulator 24. The valve I7 is now also in its position of equilibrium, that is to say the central position in which it prevents either the supply of pressure medium to, or discharge of pressure medium from, the cylinder 20. The pressure medium in the pipe 18 now maintains the piston 25 in its lowermost or inoperative posi- I tion, that is to say with the lower end of the pistcn 25 in contact with the base of the cylinder 26, the spring 2? being compressed and the spindle it together with its stop 23 is free to be moved vertically by the lever l4.

In the event or" the supply of pressure medium to the pipe 13 failing, the spring 21 will move the piston 25 into the position so that the stop 28 is engaged by the piston 25 and the spindle I6 is moved upwardly. Since the spring 27! is stronger than the spring 35, the latter will be compressed owing to the position of the lever I4 remaining unaltered. The upward movement of the spindle l6, however, causes the bell-crank lever 22 to be turned in the clockwise direction as viewed in the drawing, so that the fuel regulator 24 is moved to the left. If the supply pressure in the pipe [8 wholfy falls the bell-crank lever 22 will be moved into the position shown at O and the engine Will be stopped. When the engine has come to rest, the governor sleeve [3 is moved into the position X but, since the spring 35 will be thus compressed, the bell-crank lever 22 will remain in the upward position 0.

After the irregularity which has caused the defect in the supply of pressure medium to the pipe [8 has been rectified,,the fuel regulator 24 is set in an intermediate position, that is to say between the positions and X, suitable for restarting the engine, by turning the lever 22 manually or by transmission mechanism (not shown) in the ccunter-cockwise direction. This rotation of the bell-crank lever causes the spindle IE to be moved downwardly so that the stop 28 pulls the piston 25 downwardly and compresses the spring 25. When the pressure in the pipe I8 is restored, the piston is again held in the lowermost position shown in the drawing.

When it desired to stop the engine independently cf the automatic control apparatus the lever 33 is moved, either manually or by the pneumatic remote control means, from the position X to the position 0 so that the plunger 36 engages the end 29 of the fuel regulator 24 and moves this to the left whereby the bell-crank lever 22 is turned in the clockwise direction into the position 0. Since the valve ii is yieldingly coupled to the lever l4, operation of the fuel regulator 24 by means of the lever St to stop the engine also lifts the valve ll into the position so that pressure medium is supplied to the cylinder 2% above the piston is and the rhecstat arm 2! is moved downwardly so as to decrease the effective value of the resistance 7 to the minimum. Thus, when the engine is stopped, the field-regulating servomotor is automatically set to correspond to maximum excitation of the main generator 2. When therefore the engine is to be restarted, the bellcrank lever 22 is again turned in the counterclockwise direction into the half-load position as above indicated, so that the control valve I! is moved downwardly but not sufiiciently to allow discharge of pressure medium from the cylinder 20 above the piston I9.

It will therefore be seen that the servo-motor 20 is automatically set for maximum excitation of the generator 2 not only when the supply of pressure medium has failed and the engine automatically stopped, but also when the engine is stopped by means of the lever 3|, so that when the engine is restarted and a switch 48 for the separate excitation 6 is closed, maximum excitation of the generator 2 will be available immediately, thereby providing rapid acceleration with consequent saving of time.

In the arrangement illustrated in Figure 2, the automatic control device itself constitutes a servo-motor comprising a piston 46 arranged in a cylinder 4 I, this arrangement allowing the governor II to be made smaller and more'sensitive since the power for controlling the fuel regulator and field-regulating servo-motor is supplied by the pressure medium through the pipe IS.

The sleeve iii of the governor H is connected to one end of a lever 62 which is pivotally connected at an intermediate point to a piston valve 43 and at its other end d4 to the spindle It. The valve 43 controls the supply of pressure medium to, and the discharge of pressure medium from, thecylinder 4|. Since the valve 43 is connected to the spindle t6 constituting the rod of the piston 40, the said valve will always be restored to its normal or central position shown, after a regulation has been completed. The servo-motor 4| constitutes a yielding coupling between the fuel regulator 24 and the governor l I since the spindle I6 is free to slide through a packing 45 in the piston 40. A spring 35 bears at its upper end against the piston 40 and at its lower end against a spring plate 36 secured to the spindle 16. The spring 35 is of such strength that when the piston 40 is moved downwardly within the cylinder 4!, the spindle I6, and therefore the valve H and fuel regulator are operated. The piston 4i) is biased by a spring 6t which tends to move the piston 46 upwardly against the pressure medium within the cylinder ll above the piston In the event of the supply'of pressure medium to the pipe l8 and therefore to the field-regulat ing servo-motor 28 failing or becoming defective, the spring 36 moves the piston 49 upwardly 50 as to engage the stop or collar 33, and thus tends to move the bell-crank lever 22 into the position 0, the engine being thus stopped. When, on the other hand, pressure medium is available from the pipe i8 and the valve 43 is moved upwardly from the position shown, this medium acts on the 'andmeans controlling the supply of fluid to the cylinder, a fuel regulator for the engine, means operatively connecting the piston of the control piston 40 from above so that the spring 48 is compressed and the piston 40 thus descends, the valve 43 returning to the central position shown. The spring 46 cannot now return the piston 40 in the upward direction by reason of the pressure medium enclosed in the cylinder 4| above the piston 40. Further, should pressure medium leak downwardly past the piston 40 or past the valve 43, the latter will automatically be moved upwardly by the resulting upward movement of the piston 40 and spindle I6. Further pressure medium will now be admitted to the cylinder 4| above the piston 40 which is thus restored to its position of equilibrium, i. e. clear of the stop 38.

If the engine I is stopped by operating the lever 3|, the spindle I6 is thus moved upwardly independently of the position of the governor H and independently of the position of the piston 40. Thus, not only is the fuel supply to the engine cut off so as to stop the engine, but the valve H is moved upwardly so that the rheostat arm 2| is moved into the position shown dotted, that is to say corresponding to maximum excitation of the generator 2. During the clockwise movement of the bell-crank lever 22, the lever 42 turns about the sleeve I3 as pivot and the valve 43 is moved upwardly. The fact that the piston 40 is then forced downwardly does not affect the position of the rod l6, fuel regulator 24 and valve H. A stop 41 within the cylinder 4| prevents the piston 40 from moving down sufficiently far within the cylinder to cut off the supply of pressure medium to the cylinder 4| beneath the piston 40.

When the engine has been brought to rest, the supply of pressure medium may also cease. This will not, however, affect the servo- motors 20 and 4| so that the resistance 1 will remain cut out of the circuit and, when the engine is restarted and the switch 48 closed, the maximum excitation current supplied from the auxiliary generator 3 will be immediately available.

It will be understood that the constructions described above are given by way of example only and that details may be modified.

I claim:

1. In an internal combustion engine-electric power unit, the combination with a field-regulating servo-motor, of valve means for controlling the supply of power to the servo-motor, a governor driven by the engine, a fuel regulator for the engine, interconnecting means through which the governor controls both the said control valve and the fuel regulator, said governor being yieldingly coupled to the interconnecting means so that the fuel regulator can be adjusted to reduce or cut off the fuel supply, independently of the governor, an automatic control device normally held inoperative by power derived from the source which supplies the servo-motor, and means whereby in the event of the said power supply becoming defective the automatic control device acts through the interconnecting mechanism on the fuel regulator so as to reduce or cut off the fuel supply to the engine.

2. In an internal combustion engine-electric power unit having a generator driven by the engine, the combination which comprises a field regulator for the generator, a field-regulating servo-motor operatively connected to the field regulator, a source of fluid under pressure for operating the servo-motor, an automatic control device comprising a cylinder, a piston in the cylinder biased by a spring, means connecting the cylinder to the source of fluid under pressure,

device with the control valve of the servo-motor,

separate means operatively connecting the piston of the control device with the fuel regulator, whereby movement of the piston in one direction against the action of the biasing spring transmits movement to the fuel regulator and to the valve of the servo-motor increasing the fuel supply and decreasing the excitation, and movement of the piston in the other direction causes the fuel regulator to decrease the fuel supplied to the engine and the servo-motor to increase the excitation.

3. In an internal combustion engine-electric power unit, the combination with a field-regulating servo-motor, of an automatic control device' normally held inoperative by power derived from the source which supplies the power for actuating the servo-motor, interconnecting means between the automatic control device and a fuel regulator for the engine, so that in the event of the said power supply becoming defective the automatic control device operates the fuel regulator to reduce or cut off the fuel supply, means for controlling the fuel supply to the engine at will comprising a stop member which is operable to cause the fuel regulator to reduce or cut off the supply of fuel to the engine, and means for setting the field-regulating servomotor for maximum excitation of the main generator when the stop member cuts off the fuel supply.

4. A power unit which comprises in combination, an internal combustion engine, an electrical generator driven by the engine, field-exciting means for said generator, 2. servo-motor operatively connected to the field-exciting means, a fuel regulator for said engine, means responsive to the engine speed for controlling the fuel regulator, an automatic control device for imposing an additional control on the fuel regulator, manual means for operating the'fuel regulator connected to the servo-motor, whereby the field. excitation may be varied simultaneously with variations in the fuel regulator and means operatively interconnecting the servo-motor, the means responsive to engine speed and the automatic control device, whereby an interruption or defect in the servo-motor action may cause the fuel to be cut off, and operating the fuel regulator by said manual means may cause the field.- excitation to be set at a maximum.

5. In an internal combustion engine-electric power unit, the combination with a field-regulating servo-motor, of an automatic control device normally held inoperative by power derived from the source which supplies the power for actuating the servo-motor, interconnecting means between the automatic control device and a fuel regulator for the engine, so that in the event of the said power supply becoming defective the automatic control device operates the fuel regulator to reduce or cut off the fuel supply, means for controlling the fuel supply to the engine at will comprising a stop member which is operable by suitable remote control means to cause the fuel regulator to reduce or cut off the supply of fuel to the engine, and means for setting the field-regulating servo-motor for maximum excitation of the main generator when the stop member cuts off the fuel supply.

6. In an internal combustion engine-electric power unit, the combination with a field-regulating servo-motor, of an automatic control device normally held inoperative by power derived from the source which supplies the power for actuating the servo-motor, interconnecting means between the automatic control device and a fuel regulator for the engine, so that in the event of the said power supply becoming defective the automatic control device operates the fuel regulator to reduce or cut off the fuel supply, means for controlling the fuel supply to the engine at will comprising a stop member which is operatively connected to the field-regulating servomotor to cause the fuel regulator to reduce or out off the supply of fuel to the engine, and means for setting the field-regulating servomotor for maximum excitation of the main generator when the stop member cuts 01f the fuel supply.

7. The combination with an internal combustion engine driving an electric generator which comprises a field regulator for the generator, a servo-motor arranged to operate the field regulator, a governor driven by the engine, a fuel regulator for the engine, a valve controlled means operatively connected to the servo-motor, a rodsystem connecting the valve controlled means to the fuel regulator and to the governor, a manually operated device for shutting 01f the supply of fuel to the engine, a yieldable coupling in the rod-system, said rod-system being operable both by means of the speed governor and the manual control means through the yieldable coupling.

ADOLF BRUNNER.

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