US2831632A

US2831632A - Electronic speed controlling apparatus

Info

Publication number: US2831632A
Application number: US268447A
Authority: US
Inventors: John R Boykin
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1950-11-04
Filing date: 1952-01-26
Publication date: 1958-04-22
Anticipated expiration: 1975-04-22

Description

April 22, 1958 J. R. BOYKIN ELECTRONIC SPEED CONTROLLING APPARATUS 4 Sheets-Sheet 1 Original Filed Nov. 4, 1950 uman k4 W INVENTOR Johh R. Boykin.

A ril 22, 1958 J. R. BOYKIN 2,

ELECTRONIC SPEED CONTROLLING APPARATUS Original Filed Nov. 4, 1950 4 Sheets-Sheet 2 Exhaust Idle M 17/ Vary TbroIt/e Fl I 3 I INVENTOR G -John R. Boykin.

REM. .9 /.0

ATTORNEY April 22, 1958 .1. R. BOYKIN ELECTRONIC SPEED CONTROLLING APPARATUS 4 Sheets-Sheet 3 Original Filed Nov. 4, 1950 INVENTOR John R. Boykin.

April 22, 1958 J. R. BOYKIN 2,831,632

ELECTRONIC SPEED CONTROLLING APPARATUS Original Filed Ndv. 4, 1950 4 Sheets-Sheet 4 John R. Boykin.

ATTORNEY United States Patent 7 Claims. (01. 23561) My invention frelates to the control of a jet engine having a fuel valve and avariable exhaust nozzle and,

moreparticularly, of such an engine provided with means operative in response to the speed and temperature of the engine to control automatically the operation of the fuel valve and the exhaust nozzle for adjusting the thrust of the engine. In certain of" the more general aspects, my invention is applicable to an engine of any This is a division of Serial No. 194,153, filed Novemher-"4, 1950, and assigned to the assignee of'this invention.

My application is relatedto" an application of Cyrus F. Wood, filed October 13, 1949, Serial No. 121,171, now Patent No. 2,734,340, and assigned to the Westinghouse Electric Corporation.

A jet engine of the type primarily under consideration involves three variables, namely, engine speed, nozzle area and engine temperature, any two of which may be varied, with the third fixed in relation thereto, to vary the thrust. In its broader aspects, the present invention contemplates movement of a manual throttle lever to increase the thrust by increase in fuel input for operation to the extent of the maximum temperature the engine will stand. Preferably, however, movement of the throttle lever for increase in thrust involves speed and temperature controlling effects or signals for controlling the fuel input and the exhaust nozzle discharge area for development of propulsion thrust over the thrust range. From idling to about 75 or 80% of full engine speed, the speed signal is used to control increase in fuel input for increase in' engine speed and thrust; and, while the speed signal also tends to operate the exhaust nozzle to increase the nozzle discharge. area, as such nozzle is already in maximum area-defining position over this engine speed range, it has no eifect thereon, with the result that increase in power, represented by increase in fuel input, is effective for rapid engine acceleration. With the engine operating at 75 or 80% of full speed and the exhaust nozzle in maximum area position, the thrust may be increased over a relatively much larger percentage of the thrust range by a small percentage of engine speed change coupled with restriction in nozzle area. While each of the speed and temperature. signals exert eifects on the exhaust nozzle and on the fuel input, they do so differently in actual practice--the speed signal tending to increase the fuel input and the exhaust nozzle discharge area when actuated from the idling to the full engine speedpositions and the temperature signal tending to increase the fuel input and to reduce the exhaust discharge area to'increase the thrust when actuated over this range.

Preferably, control of the engine is effected electrically, the engine driving an alternator operating through a frequency meter and amplifiers to control the exhaust nozzle and the fuel valve, and a voltage responsive to temperature is amplified and serves also to control the nozzle and the fuel valve. Such network includes settings 2,831,632, Patented Apr. 22, 1958 adjustable manually to change the fuel input or the latter and the nozzle area to vary the thrust.

More particularly, the invention involves an electronic power regulator controlling the exhaust nozzle and the fuel valve. The regulator includes an alternating-current generator driven by the engine, direct-current sources, and speed and temperat'ure settings, arranged in the cockpit and operable by means of a throttle lever. Speed and temperature direct current voltages are derived from the alternator output and cooperate with setting direct current voltages from the speed and temperature settings to provide, in the event of deviation of the derived and setting voltages from balanced relation, direct-current speed and temperature signals, 'thepolarity of each of which depends upon the direction of deviation. A fre-,

quency determining network is provided to measure the frequency of the alternator, and, therefore the speed of engine, at all times during operation. Temperature is measured by a thermocouple properly disposed in the engine.

There are provided two modulators, one being the exhaust nozzle modulator and. having its output supplied to an electronic amplifying network to control a servo for operating the exhaust nozzle and the other being the fuel input modulator and having its output supplied to an electronic network controlling a servo-motor for operation of the fuelv valve to vary the fuel input. Each of the modulators is supplied with direct-current inputs including said speed and temperature signals and with alternating-current input supplied from the alternator, and operates to provide an alternating-current output, the amplitude of Whose wave is proportional to the directcurrent input and which output, at alternator frequency, isimpressed on the exhaust nozzle and fuel valve electronic control networks. As long as the resultant signal input is zero for each modulator, the alternating-current output of each of its respective electronic network is zero; however, if the signal has a negative or positive polarity, the modulator has an alternating-currentoutput at alternator frequency with the output Wave for a negative signal input 180 degrees out of phase relative to'the output when thesignal is positive. If the speed signal is negative, the alternating-current outputs of the modu-" lators tend to open the exhaust nozzle and'to open wider the fuel valve; and, if the speed signal is positive, the

Gil

contrary operation takes place, the tendency being for the exhaust nozzle to close and for the fuel valve to move in a closing direction. If the temperature signal goes negative, the fuel valve modulator responds in' the same way as for anegatives'peed signal, that is, it'causes the fuelinput to increase; however, because of the differentway in which the temperature signal is applied'to the exhaust nozzle 1nodulator, the alternating-current outputof'the latter will be degrees out of phase compared to its output for a negative speed signal, in consequence of which the exhaust nozzle discharge area will be restricted. If the temperature signal goes positive, the contrary operation takes place. I

When the. enginereaches a certain temperature above which safety maybe in question, temperature control overrides all other controls. With the engine above this safe temperature the control operates to cut down fuel supply regardless of the settings of any of the control components. In the control of an engine equivalent to the J-34- engine (Navy nomenclature). the maximum safe temperature is 1250 F. Above this temperature thecon- I trol operates to cut down fuel supply. If the temperature reaches 1400 F., fuel supply is abruptly cut to minimum flow.

In addition to the signal inputs to the exhaust nozzle and fuel valve modulators, additional inputs are'supplied thereto. A stabilizing feedback input controlled by movement of the exhaust nozzle is supplied to the exhaust nozzle modulator, and the feedback connection is arranged so that a smaller speed or temperature signal is required for moving the exhaust nozzle in a closing direction than in an opening direction. Aside from speed and temperature inputs supplied to the fuel valve modulator, the latter has a stabilizing feedback input and a temperature-limiting input controlled by movement of the fuel valve, the purpose of the temperature limit being to anticipate temperature, that is, to prevent overtravel of the fuel valve in an opening direction and consequent oversupply of fuel and overheating of the engine.

The frequency determining circuit including the voltaeg doublers is analogous to a circuit shown in Fig. 4 of British specification 619,139. This latter circuit includes a frequency doubler comprising a capacitor C1, the output of which varies with frequency and a second frequency doubler including capacitor C4, the output of which varies with the amplitude of the impressed voltage. In the British system the output voltages of the frequency doublers are balanced against each other and a correcting voltage is derived through conductor 1. In operation, I have found that a jet engine including a circuit of this type, at times vibrates violently.

Accordingly, one specific object of my invention is to provide a control for a jet engine which control shall not produce violent vibrations in the operation of the jet engine.

The aspect of my invention involving this object arises from my realization that the cause of the violent vibration may be ascribed to the British frequency determining network. The components of the British system are so related that if a sudden change takes place in an external voltage (such as may be caused by load change on the alternator due to the firing of the fuel valve control thyratrons to change the fuel flow to the engine and hence alternator speed), the output conductor 1 would carry a transient pulse which would produce a transient dlsturbance in the system to which the frequency determining device is applied. This transient pulse so derived at the output conductor would cause the voltage output of the alternator to change suddenly, which would, in turn, introduce a sudden counter-change into the correcting circuit which would, in turn, cause a corresponding sudden counter-change in the alternator. This periodic operation would give to the engine and the craft on which it was mounted an objectionable and vigorous vibration.

An ancillary object of the invention is accordingly to provide an improved frequency responsive network which is less subject to objectionable transients than those of the prior art.

An additional ancillary object of the invention is to provide an improved frequency responsive device which will satisfactorily function under the conditions of jet engine control operation.

A further ancillary object is to provide a frequency responsive network which will give a reliable and accurate indication of jet engine operational speeds, with particular emphasis on the maximum safe-operational speed.

A still further ancillary object is to provide a frequency responsive apparatus which can be made an operationally integral part of an electronic control apparatus for a jet engine.

My invention is based on the realization that the transient difiiculty springs from the fact that the transients are caused by the relationship between the impedances in the circuit of the British voltage doublers. The resistor R1 is of too great value compared to the resistor R3 (600,000 ohms as compared to 4,700 ohms) and the relationship between the capacitor shunting the resistor R3 and the capacitor C1 is not proper. Because of this relationship, a sudden change resulting in a pulse supplied through the capacitor C1 is in no respect counterbalanced by an opposite polarity signal applied through the resistor R1 which is of very high magnitude.

In accordance with my invention, a frequency determining network is provided in which the resistors and the capacitors are so related that any transients produced by a sudden change in the voltage impressed from conductor A are suppressed.

In the operation of a jet engine, separate direct-current voltages respectively for speed and temperature are manually preset by the aircraft pilot. These voltages must be compared with direct-current signal voltages which respectively measure the speed up and temperature operational conditions of the engine, and are derived from the engine components which are controlled and detection apparatus suitably disposed to measure the actual speed and temperature of the engine. One of these latter derived signals, the direct-current speed signal, is dependent on the output of an alternator operated by the engine, and is measured by a frequency determining network which gives an output direct-current speed signal corresponding to the frequency of the output voltage from said alternator. Another of the latter derived signal voltages is measured by thermocouples suitably disposed to determine the operational temperature of the jet engine. It is desirable that any change in the values of the preset voltages or the derived voltages will produce immediate correcting action in the operation of the engine.

It is, accordingly, an object of my invention to provide a servo system which is responsive to a plurality of command signals and which shall operate promptly and precisely to produce correcting action.

My invention arises from the realization that polarity changes are more readily identifiable by electrical pickup components than magnitude changes. In accordance with my invention, the preset voltages and the derived signal voltages are balanced against each other so as to supply a zero output voltage to the pick-up device during steady state operation of the engine. So long as the preset voltages are fixed, and the engine speed and temperature remains constant, this output remains at a zero magnitude and the operation of the engine does not vary. If, however, the preset voltages are changed by the aircraft pilot or the engine speed or temperature changes slightly, a positive or negative resultant net voltage is impressed on the pick-up devices.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understod from the following description of specific embodiments when read in connection with the accompanying drawing, in which:

Figure l is a diagrammatic view of a jet engine, the operation of which may be controlled by a regulator in accordance with my invention;

Fig. 2 is a graph showing exhaust nozzle discharge area, thrust, temperature, and speed variations as a function of throttle position for the jet engine shown in Fig. 1;

Fig. 3 is a graph showing the relation of thrust to engine speed at the upper end of the speed range for the jet engine;

Fig. 4 is a schematic diagram of a frequency determining network in accordance with my invention;

Fig. 5 shows a block diagram of the electronic regulator illustrated in Fig. 1;

Fig. 6 is a circuit diagram of a frequency meter embodying a modification of one aspect of my invention;

Fig. 7 is a graph illustrating the operation of the frequency meter network included in Fig. 4 as shown in Fig. 6.

In Fig. 1, there is shown a jet engine 7 having an adjustable exhaust or propulsion jet nozzle 8 and fuel valve 9. In addition to the fuel valve and the jet nozzle, the engine comprises a turbine 10, a compressor 11, and a combustor 12, the compressor delivering air to the come bustor for generation of motive fluid to drive "the turline, the turbine driving the compressor and the exhaust from the turbine undergoing further expansion in the nozzle to provide the propulsion jet. The exhaust nozzle has a component or components 13 moved by the servomotor 14 to vary the exhaust nozzle discharge area and the fuel valve 9 is controlled by the servo-motor 16 to vary the fuel input.

Jet thrust is varied by manual adjustment of a setting of a power regulator controlling the fuel input, or the latter and the exhaust nozzle area, in response to engine speed and temperature. As shown in Fig. 1, the regulator has speed and temperature settings, M17 and at 18, operated by a throttle lever 19. Upon movement of the lever 19 for setting adjustment, the balanced relation of the regulator is disturbed and the latter is thereby rendered effective to adjust the fuel valve, or the latter and the exhaust nozzle, for engine operation to restore the balanced relation and thereby to vary the jet thrust in accordance with lever movement.

Referring to Figs. 2 and 3, with the engine idling, as the throttle lever is moved in the direction of increased speed and thrust, the changing temperature setting has no effect on the automatic control mecahnism until the speed reaches about 75 or 80 percent of full speed, the control during this acceleration period being mainly in response to speed with the exhaust nozzle fully open.

At about this fractional speed, the temperature control comes into play mainly for the purpose of closing the exhaust nozzle so that in going from said 75 to 80 percent speed point to full speed, the ratio of thrust change to speed change rapidly increases with the result that, at full speed, and as may be seen from Figs. 2 and 3 and particularly Fig. 3, only a very smallpercentage of speed change is required for a large percentage of thrust change. Therefore, while the operator moves the throttle lever to vary the thrust, this result is accomplished by varying the nozzle and the fuel input through the intermediary of the automatic control arrangement responsive to speed and temperature, the arrangement assuring of correlated operation of the exhaust nozzle and fuel valve in response to speed and temperature with the maximum development of thrust without going to temperatures too high for allowable turbine toleration.

The regulator includes a speed network (see Fig. 4), which, in conjunction with the manually set speed and temperature settings, provide direct-current signals to the exhaust nozzle modulator, and to the fuel valve modulator, and each of the modulators has an alternating current output, whose frequency is the sameas that of the alternator, and whose amplitude and phase, respectively, depend upon the magnitude and polarity of the directcurrent speed and temperature signals;

Speed-sensitive network The speed-sensitive network 28 comprises (Fig. 4) a reference component 60, a frequency-responsive compo nent 61, and the manual setting at 17. In operation, the currents provided by the reference component 60, by the frequency-responsive component 61, and by the manually-operable setting 17 are in balanced relation, with the result that, if the setting voltage is changed, current is supplied to or drawnfroin the modulator;

The reference component 60 comprises an impedance and rectifier network of the doubler type and it includes a condenser C117 connected to phase A through relatively large line resistors which decrease the effect of harmonics on the system. The frequency-responsive component 61 includes parallel condensers C120 and C139 connected to phase A.. The capacity of the condenser C117 is relatively large compared to that of the parallel-connected condensers C120 and C130 of the frequency counter 61, with the result that the voltage of the former changes quite rapidly with the change in frequency, in consequence of which, for the operating range, a substantially constant reference current and voltage may be provided over a range of frequency variation. On the other hand, because of the relatively much lower capacity of the condensers C120 and C139 of the frequency-responsive network, the frequency-responsive voltage and current vary substantially in linear relation to speed, with the result that a change in setting 17 voltage produces a speed signal which brings about change in engine operation until the saidsigual is restored to zero under the latter condition of operation, the reference 60, the frequency-responsive component 61, and the setting 17 currents are balanced, and the resultantspeed signal onthe line 31 is equal to zero. In the subsequent discussion of the graphical representation of the currents shown in Fig. 7 for the reference branch and the frequency responsive branch 61 this circuit is further explained.

In addition to the condenser C117, the reference component 60 includes

branches

65 and 66 connected to condenser C117. The branch 65 includes a rectifier Cit-1119, conductive from the condenser C117 through the parallel branches 68 and 69 to ground, the branch 63 including a condenser C118 and the branch 69 including resistances R135 and R136. The latter speedsetting resistance R136 is adjustable to vary the potential applied to the condenser C118 and, therefore, the voltage drop across the condenser C117 and its charge. The resistance R136 is preferably adjusted for full speed values of the reference component 60 current and voltage.

The branch 66 is connected through the rectifier CR-llS, to be conductive toward the condenser C117 from

parallel branches

70, 71 and 72. The branch is connected, through resistance R138 and

parallel connections

74 and 75 to ground: the connection 74 including the condenser C121 and the connection 75 including the resistances R139 and R140. The branch 71 includes a resistance R137 connected to the reference line 76. The branch 72 is connected through the condenser C119 to ground.

When phase A is positive relative to phase B, conductionfrom A to B occurs through the condenser C117, the rectifier CR109, and thercondenser C118. If B is positive, then conduction occurs through the condenser C119, rectifier CR- and the condenser C117. Since the condensers C118 and C119 are in effect connected in series between 55a and 56a, with the ground, or phase B, serving as a midpoint connection between the condensers, and since such condensers are charged on successive half cycles, the voltage from 55a to 5641 is double the input voltage to C117. I

Thecycle counter or frequency'sensitive component 61 includes parallel-connected condensers C .and C130, joining the phase A line 62 with the branches 78 and79. The branch 78 includes a rectifier CR-110 conductive from ground, or phase B, through the parallelconnected resistance R155 and condenser C122. The branch 79' includes a rectifier CR-111 conductive to terminal 80 to which the reference line 76 is connected; On positive half cycles, conduction occurs through the condenser C120 and C and the rectifier CR-111 to the terminal 80. On negative half cycles, conduction occurs from ground, or phase B, through the parallelconnected resistor R and condenser C122, the rectificr CR-110, and the parallel conne'cted condensers C126 and C133 to line Due to the parallel-connected condensers C120 and C136, there is provided impedance varying inversely to frequency, in consequence of which direct current in the connection 81 is proportional to frequency.

The terminal 80 is connected to ground through the condenser C123, and through the connection 82 to the speed setting line from the manual speed setting.

Representing the reference direct current in the line 76 (Fig. 4) as x, the frequency current of line 81 as y and the setting current provided by the speed setting line 84 (Fig. as z, a steady state or balanced condition exists when the

terminals

80 and 83 are at equal potentials. This exists when 1 is equal to x minus 2. If 2 is decreased with increase in speed-setting, current is drawn through the line 31 from the modulators, that is, a negative speed signal is furnished to the modulators. On the other hand, if z is increased, a positive speed signal is applied. In other words, as long as x minus 1 is made larger than y, a negative speed signal is applied, and, when the difference is smaller than y, a positive speed signal is applied.

To suppress transients and the resultant engine vibration induced thereby, respecting the frequency network components, it was found that, roughly, the capacitor C119 should be of the same magnitude as the capacitor C117, and the capacitor C118 should be 50% greater than the capacitor C117: the resistor R137 should be substantially equal to the sum of resistors R135 and R136. The frequency responsive network 61 has so short a time constant as not to be materially affected by the transients. In a preferred system in accordance with the invention, the resistor R137 has a magnitude of 50,000 ohms: the resistors R135 and R136 combined have a resistor slightly greater than 50,000 ohms (the voltage divider R136 has a maximum resistance of 10,000 ohms) the capacitor C119 has a capacitance of .5 microfarad and capacitor C118 has a capacity of .75 microfarad. In this system the capacitor C117 has a capacity of .5 microfarad. The magnitudes given here were determined by careful selection after it was realized that the objectionable vibrations which arise if a system such as is disclosed in the British Patent 619,319 is used, could be suppressed by such selection.

System as a whole In Fig. 5 is shown a simplified block diagram showing some of the major control components of the control system in block diagram. The frequency meter 28 is shown as a block diagram having its output fed through line 31 to the exhaust nozzle modulator 33 which is also shown as a block. The D. C. speed signal output from the frequency meter which passes along line 31 is fed to fuel valve modulator 34 along speed signal cross fed con nections 31a and 31b. The thermocouple amplifier 29, shown as a block, amplifies the very low D. C. voltage output of the thermocouple 26 to give a D. C. temperature signal output which is also fed to modulator 34. The temperature signal crossfed connection 32a from the thermocouple amplifier 29 to the exhaust nozzle modulator 33 is shown. ship between modulator 33, exhaust nozzle amplifier 36, and phase sensing power amplifier 37 to cntrol the exhaust nozzle servo 14 is shown. The relatively direct line relationship between modulator 34, fuel valve of modulator44 and phase sensing power amplifier 45 to control the fuel valve motor 16 is also shown. The exhaust nozzle feedback network 116 is shown coupled through line 118 back through a variable resistance circuit to be fed into the input of modulator 33. The fuel valve feedback circuit comprising potentiometer 121 connected through lead 123 back to the input of modulator 34 is shown. The pilots manual lever 19 which changes the resistance of potentiometers 18a and 17a to introduce speed and temperature change voltage components is shown. The various limiting circuits and variable resistance networks are shown in their proper circuit relationship.

Modified frequency meter In Fig. 6 is shown a modified circuit for use as the frequency meter network 28. In lieu of the rectifiers CR-109 and CR-115, as shown in Fig. 4, two vacuum

tube diode rectifiers

210 and 212 may be employed; and, instead of the selenium rectifier elements CR-110 and CR-111 shown in Fig. 4, there may be substituted two

vacuum tube diodes

214 and 216. The remaining circuit The relatively direct line relationof the frequency network 28 remains basically the same as that shown in Fig. 4. Condenser C154 which has been chosen to compensate for the temperature effects on the valves of the various other components has been substituted for previous condensers C and C130. This condenser has a negative capacity temperature coefiicient. The substitution of the vacuum tube diode rectifiers under certain conditions of operation may be more suitable in view of the effect of high temperatures upon the characteristics of certaintypes of rectifier elements, such as selenium rectifier elements.

Operation of frequency meter In Fig. 7 are shown the current curves, plotted with frequency F as the abscissa and the current divided by the impressed signal voltage,

as the ordinate, for the two

branch networks

60 and 61 of the frequency meter 28. The curve 200 of the current output of the frequency responsive rectifier branch 61 is substantially linear over the frequency range of operation of the engine, since the current derived from branch 61 varies directly with frequency. The current of branch 60 varies directly with frequency over a short range at low frequencies and beyond this change is substantially constant. This current is represented by curve 201. Accordingly, the current of branch 61 may be expressed as a function of frequency by the equation and, beyond the low frequency range where the current of branch 60 varies, this latter may be expressed by the equation At a frequency F the two currents are equal. At this frequency kF =K That is, F is a constant independent of the voltage E The summation current represented by curve 202 is balanced against the current received over line 84 (in Fig. 5) from the manual speed setting 17. When the latter currents are balanced, the speed signal sent to the modulators over line 31 is zero to bring about no change in the engine operation.

The frequency F corresponds to the condition of opera tion at which the currents through

branches

60 and 61 are balanced against each other. This frequency arises in actual operation only if the current from potentiometer 17 is zero, that is, at the highest engine speed (military speed). At other speeds of the engine the actual frequency is less than F At these latter speeds the current from the potentiometer 17 is balanced against the net current from the frequency meter; that is the different current between the current of curve 200 and the current of curve 201 is balanced against the current from potentiometer 17 It is essential that the frequency F be maintained constant independent of temperature variations. It is for this reason that I have provided the temperature compensating condenser C150. This condenser is so selected as to compensate for the variations with tempera ture of all of the components of the meter.

Operation area in response to magnitude and polarity of speed and temperature signals applied to the modulator 33, and 1t controls the fuel valve in response to the magnitude and polarity of the algebraic sum of speed and temperature signals applied to the moduiator 34. Each

modulator

33 or 34 operates to provide an alternating-current output wave 244 whose amplitude depends upon the magnitude of a speed and temperature direct-current signal input wave 242, with the wave 244 for a negative signal out of phase by 180 degrees with respect to that for a positive signal. The alternating current output of each modulator is amplified and furnished to a phase-sensitive amplifier supplying the corresponding servo, t to arrangement being such that negative speed signals cause in-. crease in nozzle area and in fuel input and vice versa and negative temperature signals cause decrease in nozzle area and increase in fuel input and vice versa.

The direct current speed and temperature signal inputs are provided by means responsive to engine speed and temperature and by manually-controlled adjustments. The speed signal, by means of the manually-movablesetting 17, is made to give a negative speed signal effective on the modulator 33 to cause opening of the exhaust nozzle and effective on the modulator 34 to increase the fuel input.

Temperature-responsive means 29 operates to provide an output, normally negative, and which, with positive and negative limits, provides a steady-state temperature signal which is made negative by throttle adjustment for increase in speed. The steady-state temperature signal so provided and modified is applied to both

modulators

33 and 34. It is applied to the exhaust nozzle modulator 33 in such a manner that the alternating current wave caused thereby is 180 degrees out of phase with respect to the wave caused by a speed signal of like polarity, with the result that a negative temperature signal tends to close the exhaust nozzle and open the fuel valve.

The means by which a speed signal is applied to the fuel valve modulator 34 has means limiting the extent of negative polarity of such signal to limit the increase in the fuel input thereby.

In addition "to the speed and temperature signal inputs for the modulator 33, the latter is also supplied with neutralizing or follow-up inputs depending upon exhaust nozzle position. Therefore, if a negative combinationspeed and temperature signal is applied to the modulator to bring about opening of theexhaust nozzle, such opening results in the application of an increase in positive feedback signal to the modulator to neutralize the negative combination signal, whereupon movement of the exhaust nozzle ceases. This follow-up or feedback connection includes means whereby a smaller combination signal is required for closing the exhaust nozzle than for opening it, so the nozzle may be closedmore rapidly thanit is opened. I

In addition to the limited speed signal and the steadystate temperature signal applied to the fuel valve modulator 34, there are temperature limit and fuel valve feedback or follow-up signals. Assuming a negative input signal to be applied to the fuel valve modulator 34, then, as the fuel valve opens, an increase in positive signal is fed back to neutralize the negative input signal to stop further opening of the fuel valve.

A temperature limit signal is applied to the modulator to avoid excessive fuel input, particularly when the engine is accelerating. To this end, there is provided the temperature limit line 128, including first and second sections 127 and 129 connected by a rectifier CR-103a which is conductive from the first section 127 to the second section 129. The first section is connected to the outlet terminal of the thermocouple amplifier 29 through a resistance R168 and the second section 129 is connected through a resistance R118 to the modulator 34. Normally, the potential of the first section 127 is negative, and the second section 129 is kept from going negative by a rectifier CR-103b which is conductve from ground thereto. The resistance R118 connecting the sec- 10 ond section 129 to the modulator-34 assures, not only of a signal applied to the latter which is normally negative relative to the second section 129 at ground potential, but it serves to limit the extent to which the terminal 53a of the modulator 34 may go negative. As long as no direct current is fed back from the fuel valve to the first section 127, there is no effect on the steady-state operation; however, just as soon as the feedback is sufiicient to make the first section 127 positive relative to ground, the negative signal causing opening of the fuel valve and consequent rise in engine temperature are limited. I

Since the setting voltages are obtained from rectifiers supplied from the alternator, such voltages are lowered for increase in speed and temperature, with the result that the closest regulation is secured at top speed and temperature.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited; but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

I claim as my invention:

1. In an electrical network for controlling the speed of a moving body, said network being operative with a source of control voltage which is proportional to said speed, the combination of a source of speed setting volt age, a first branch circuit including a first capacitor, a second branch circuit including a second capacitor, said first capacitor having a larger capacitance than the capacitance of the second capacitor, with said first branch circuit connected to said source of control voltage and being operative to provide an output reference voltage, with said second branch circuit connected to said source of control voltage and being operative to provide an output frequency-responsive voltage, and a circuit junction connected to said first branch circuit, said second branch circuit and said source of speed setting voltage for combining said output reference voltage, said output frequency-responsive voltage and said speed setting voltage to produce a resultant voltage .at said junction forcontrolling the speed of said body.

2. In speed sensitive apparatus which is operable with a source of control voltage, said control voltage being proportional to the speed of a moving body, the com bination of a source of speed-setting voltage, a first circuit means including a first capacitor having a pair of plates, with one of said plates connected to said source of [control voltage, said first circuit means also including aifirst pair of unidirectional conductive devices which are connected to be respectively conductive toward and away from the other plate of said first capacitor, a second circuit means including a second capacitor having a pair of plates, with one of the plates of the second capacitor being connected to said source of control voltage, said second circuit means including a second pair of unidirectional devices which are connected to be respectively conductive toward and away from the other plate of said second capacitor, said first capacitor having a capacitance which is larger than the capacitance of the second capacitor, said first circuit means further including a first parallel circuit connected in series with one of said first pair of devices and a second parallel circuit connected in series with the other of said first pair of devices, with each of said first and second parallel circuits including a parallel-connected resistor and capacitor and a circuit junction connected to said source of speed-setting voltage, said first circuit means and said second circuit means to produce a resultant voltage at said junction for con trolling the speed of said body.

3. The apparatus of claim 2 with the capacitor of said first parallel circuit having a capacitance which is sub 11 stantially equal to the capacitance of said first capacitor.

4. The apparatus of claim 3 with the capacitor of the second parallel circuit having a capacitance which is at least one and one-half times greater than the capacitance of said first capacitor.

5. The apparatus of claim 2 with the resistor of the first parallel circuit having a resistance Which is substantially equal to the resistance of the resistor of the second parallel circuit.

6. 'In an electrical apparatus operable with an electrodynamic generator having a pair of terminals and being capable of supplying alternating voltages, the combination of a first capacitor having a pair of plates with one of its plates connected to one terminal of said generator, a pair of rectifiers having a pair of electrodes With one electrode of each of said rectifiers connected to the other plate of said first capacitor in such a manner as to conduct current respectively to and away from said first capacitor, a second capacitor connected between the remaining electrode of one of said rectifiers and the other terminal of said generator, a third capacitor connected between the remaining electrode of the other of said rectifiers and said other terminal of said generator, a fourth capacitor of substantially smaller magnitude than said first capacitor, said fourth capacitor having a pair of plates and having one plate connected to said one terminal of said generator, 21 second pair of rectifiers having a pair of electrodes, with one electrode of each of said second pair of rectifiers connected to the other plate of said fourth capacitor in such manner as to conduct current respectively to and away from said fourth capacitor, a first resistor having one terminal connected to the second capacitor and the electrode of the first pair of rectifiers to which said second capacitor is connected, said first resistor having another terminal connected to the remaining electrode of one of said second pair of rectifiers, a second resistor having one terminal connected to said third capacitor and to the electrode of said first pair of rectifiers to which said third capacitor is cnnected, said second resistor having another terminal connected to said other terminal of said generator, said first and second resistors being of substantially equal magnitude and said second and first capacitor being of substantially equal magnitude, a source of speed-setting voltage, and means interconnecting the junction of the other terminal of said first resistor and said remaining electrode of the said one of the second pair of rectifiers with said source of speed setting voltage to produce a resultant voltage for controlling the speed of said generator.

7. In an electrical network operable with an electrodynamic generator capable of supplying an alternating voltage, said generator having a pair of terminals, the combination of a first capacitor connected to one terminal of said generator, a pair of rectifiers, each of said rectifiers having a pair of electrodes and one electrode of each rectifier connected to said first capacitor in such manner as to conduct current to and away from said first capacitor, a second capacitor connected between the remaining electrode of one of said rectifiers and the other terminal of said generator, a third capacitor connected between the remaining electrode of the other of said rectifiers and said other terminal of said generator, a fourth capacitor of smaller magnitude than said first capacitor connected to said one terminal of said generator, a second pair of rectifiers having respectively a pair of electrodes and one electrode'of each rectifier connected to said fourth capacitor in such manner as to conduct current respectively to and away from said fourth capacitor, a first resistor having one terminal connected to said second capacitor and said remaining electrode of said one rectifier of the first pair of rectifiers, said first resistor having another terminal connected to the remaining electrode of one of said second pair of rectifiers, a second resistor having a terminal connected to said third capacitor and to said remaining electrode of said other of the first pair of rectifiers, said second resistor having another terminal connected to said other terminal of said generator, said first and second resistors having substantially equal resistances, said third capacitor having a capacitance substantially one and one-half times greater than the capacitance of said first capacitor and the capacitance of said second capacitor, such that transients arising from sudden changes in the amplitude of the voltage of said generator are substantially suppressed, a source of speed setting voltage, and means interconnecting the junction of the other terminal of said first resistor and said remaining electrode of the said one of the second pair of rectifiers with said source of speed setting voltage to produce a resultant voltage for controlling the speed of said generator.

References Cited in the file of this patent OTHER REFERENCES Electronic Instruments (Greenwood), 1948, pages 340-.