US3471763A - Frequency multiplication and displacement - Google Patents

Description

Oct. 7, 1969 R. GERMANN ETAL FREQUENCY MULTIPLICATION AND DISPLACEMENT Filed March 29. 196'? 4 Sheets-Sheet i foi, www

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United States Patent O 3,471,763 FREQUENCY MULTIPLICATION AND DISPLACEMENT Reimar Germann and Kurt Wiederwohl, Graz, Austria,

assignors, by mesne assignments, to Mobil Oil Corporation, New York, N.Y., a corporation of New York Filed Mar. 29, 1967, Ser. No. 626,755 Claims priority, application Austria, Jan. 12, 1967, A 321/67 Int. Cl. H021) 5/34, 7/42 ABSTRACT F THE DISCLOSURE A method and means for driving a synchronous motor characterized by novel circuitry for multiplying the frequency of a signal and displacing it by 90. The frequency multiplication system is characterized by the discharge of a capacitor to a constant current circuit for the production of a sawtooth voltage which in turn actuates a Schmitt trigger. The leading and trailing edges of the Schmitt trigger signal, upon differentiation and addition, produce pulses having a frequency twice that of the initial signal. The phase shifting circuit is characterized by doubling the frequency of a first square wave signal to produce a second square wave signal wherein the trailing edge actuates a bistable device to result in a 90 phase displaced square wave signal, in relation to the first square Wave signal.

Cross-reference This invention is suitable for use with the engine analyzer synchronization system of copending application Ser. No. 587,096, Oct. 17, 1966, Germann, Wiederwohl and Schwertfhrer, commonly assigned. In said copending application the pressure patterns at the fuel injection lines to the cylinders of a diesel engine are displayed on an oscilloscope. The synchronization of such a system is provided Aby photosensitive devices actuated by a motor driven by a signal from a transducer in one of the fuel injection lines. The motor is driven at a rate proportional to the speed of the engine or of the fuel injection pump.

The present invention is directed to an alternative system for driving the synchronous motor referred to in said copending application.

Summary of the invention The frequency multiplication method of this invention is characterized by the storage of initial pulses in an integrating circuit, the discharge of these pulses to a constant current circuit for the formation of a sawtooth signal, the actuation of a Schmitt trigger by the sawtooth signal to provide a square wave, differentiation of the square wave to produce pulses representative of its leading and trailing edge, and the addition of these pulses to provide a signal which has a frequency twice that of the initial pulses.

The method of producing 90 phase displaced pulse is characterized by the generation of an initial square wave, the doubling of this initial signal to produce a square wave having twice the initial frequency, the differentiation of the new square wave to produce a signal lrepresentative of its trailing edge, and the use of this differentiated signal to actuate a bistable device to produce a square Wave pulse which has the same frequency as the initial pulse but is displaced by 90.

The above methods find use in the generation of signals for driving a synchronous motor at a speed controlled by the frequency of the initial pulses.

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Brief description of the drawings FIGURE 1 is a block diagram of this invention.

FIGURES 2-5 show portions of the circuitry used in this invention.

FIGURE 6 indicates the signal produced at the various points indicated in FIGURE 1.

Description of specific embodiments In FIGURE l numerals 2 through 5 refer to those ligures in which detailed embodiments of the circuitry are shown. The initial signal used in this invention is derived from a transducer 10 situated in the fuel injection line of a diesel engine (not shown). The signal from the transducer is transmitted by a source follower amplifier 12 to a phase inverter 14 to provide a signal indicated by I. A trigger level adjuster 16 controls the amplitude to which signal I must reach (see signal II) in order to actuate Schmitt trigger 18. The Schmitt trigger emits square wave pulses illustrated by signal III. The Schmitt trigger actuates monostable vibrator 20 which emits signal IV, which has sufficient duration to eliminate multiple triggering as indicated by the first pulses in signals II and III. The monostable vibrator pulses are amplified and inverted in amplifier 22 which emits pulses V. These signals from the amplifier are ldifferentiated in means 24 to produce signal VI. The differentiated signal does not actually have the negative portion below the broken line illustrated diagrammatically in VI, due to clipping device 26 which removes the negative excursion as indicated by signal VII. This effect is shown repeated below. The positive peaks of signal VII charge integrator 28, illustrated diagrammatically by signal VIII prior to discharge. The integrator is discharged to a constant current circuit 30 to provide a sawtooth signal IX which is repositioned on the zero line by DC decoupler 32 as indicated by signal X. This signal actuates Schmitt trigger 34 to produce the controlled square Wave voltage XI. The trigger level adjuster ensures equal duration of the pulses of signal XI. In place of the Schmitt trigger, and those referred to below, any other suitable level detector may be used, such as a conventional voltage comparator. Schmitt trigger signals XI are differentiated at 36 to produce signal XII, which has its negative portion removed in clipper 38 as indicated by signal XIII. These positive peaks, representative of the leading edge of Schmitt trigger signal XI are then transmitted to the OR gate 40. Schmitt trigger signals XI are also transmitted to phase inverter 42 to produce signal XIV which is differentiated in means 44 to produce signal XV. Differentiated signal XV is clipped by .means 46, and the positive peaks, signal XVI, representative of the trailing edge of Schmitt trigger signal XI, are transmitted to OR gate 40. The OR gate produces a series of positive peaks, signal XVII having twice the frequency of the initial signal I. The signal XVII, Whi-ch may be amplified at this point, is then directed through integrator 48, discharge means 50, decoupler 52 and Schmitt trigger 54, which correspond respectively with means 28, 30, 32 and 34. The modification of signal XVII is indicated in its various stages by signals XVIII through XXI. Schmitt trigger signal XXI has a frequency equal to twice that of the previously produced Schmitt trigger signals, XI. The trailing edge of signal XXI triggers a bistable vibrator 56 to provide signal XXII. Signal XXII has the same frequency as signal XI, and its phase is displaced by Signals XI and XXII, amplified at 62 and `60, may be used to drive synchronous motor S8 in a manner similar to that described in copending application Ser. No. 587,096.

The electrical components described are conventional and may be found in a number of sources, such as the Transistor Manual, General Electric Company, 6th ed., Reference Data for Radio Engineers, International Telephone and Telegraph, 4th ed., and other standard works. An embodiment for several of these components is shown below, however, it will be appreciated that numerous electrical designs could be derived within the scope of the above disclosure.

FIGURES 2, 3, 4 and 5 present a more detailed embodiment of the system of FIGURE 1. Like numbers in these figures refer to like components. The letter R refers to resistors; the Values for the resistors and other components can readily be chosen by one skilled in the art to match the requirements of this system.

FIGURE 2 shows the generation of signals VII, having the same frequency as the initial pulses, I. FIGURE 3 depicts a system for the storage in an integration circuit of a series of signals and the production of a square wave of controlled duration having the same frequency as said stored signals. The system of FIGURE 3 is useful for generating the signals shown in FIGURE 6 as VIII-XI and XVIII-XXI. FIGURE 4 depicts a system for differentiating a square wave pulse to produce a signal having twice the frequency, signals XII-XVII. FIGURE 5 depicts a system for displacing a signal by 90 and using two square waves to drive a synchronous motor, signal XXII and signal XI.

In FIGURE 2 the signal from transducer 10 is directed to the base of field effect transistor 100. The output from transistor 100 is connected through the indicated resistors and condenser 200 to transistor 102 which serves as a phase inverter. As indicated the potential applied to these transistors is +12 volts and -12 volts. Throughout these figures, arrows are used to indicate connections to power supply lines (not shown). The output of transistor 102 is connected through the indicated diode 300 and condensers 202 and 204 to the trigger level adjuster comprising the indicated variable resistor 206. In place of elements 102, 300 and 202, a simple Miller integrator circuit with appropriate emitter followers -could be used. The clipped signal from the trigger level adjuster actuates Schmitt trigger 18 which in turn is connected to monostable vibrator 20. Each of the major elements which are not shown in detail, such as the Schmitt trigger and the monostable vibrator, is of conventional circuitry and is available as an on-the-shelf unit. The signal from the monostable vibrator 20 is connected to the base of transistor 104 which acts as an amplifier and inverts the signal. The inverted signal is directed to the base of transistor 106 which is arranged as an emitter follower. The signal from the emitter follower is differentiated by the circuit cornprising condenser 208 and the resistor which follows it. The negative portion of the differentiated signal is clipped [by means of diode 302.

As shown in FIGURE 3 the differentiated signal is passed to diode 304 which is part of the integrator circuit comprising condenser 210. The charge stored on condenser 210 is discharged at a controlled rate by means of transistor 108 arranged in a constant current circuit. The sawtooth signal which is generated passes through transistors 110, 112, and 114 which serve the function of maintaining the form of the signal by matching the impedance in the circuit and by passing the signal through an emitter follower. The sawtooth signal is then decoupled of its DC component in condenser 212 from which it passes to the trigger level adjuster including variable resistor 214. The signal then passes through emitter follower 116 which is used to actuate a Schmitt trigger 34. As indicated in FIGURE 1, this circuit is duplicated to provide another means for producing a square wave signal -(referred to below).

In FIGURE 4 the signal from Schmitt trigger 314, of FIGURE 3, is differentiated by means of condenser 216 and the resistor which follows it. The negative portion of the differentiated signal is clipped by means of diode 306. In a parallel circuit the Schmitt trigger signal from 34 is passed to transistor 11S which acts as a phase inverter. The inverter signal is differentiated by means of condenser 218 and the resistor which follows it. The negative portion of the differentiated signal is clipped by means of diode 308. The positive peaks of the differentiated signals from condensers 216 and 218 are passed in parallel to an OR gate comprising diodes 310 and 312. These positive signals are in effect added through the OR gate and appear as a composite signal XVII having twice the frequency of XIII or XVI.

Signal XVII passes through lter condenser 219 to a circuit which is a duplicate of that shown in FIGURE 3. In this duplicate the Schmitt trigger is referred to as 54, as in FIGURE 1. The signal from 54 is used to actuate a bistable vibrator 56. In a suitable bistable vibrator, for example, that shown in Transistor Circuit Design, by Texas Instruments, Inc. (McGraw-Hill Book Company, 1963), the square wave XXI would be differentiated and the positive portion clipped to provide a square wave output, XXII, which is shaped by the trailing edges of signal XXI. The signal from bistable vibrator 56 and the signal from Schmitt trigger 34 (respectively signals XXII and XI) are passed to amplifiers 60 and 62 and then to synchronous motor 58. The speed of the synchronous motor is thusly controlled by the frequency of the initial signal I.

This invention has been described in terms of specific embodiments set forth in detail, but it should be understood that these are by way of illustration only and that the invention is not necessarily limited thereto. Alternative constructions will become apparent to those skilled in the art in view of this disclosure, and accordingly modifications of the apparatus and process disclosed herein are to be contemplated within the spirit of this invention and the following claims.

What is claimed is:

1. Means for driving a synchronous motor at a speed responsive to the frequency of a first series of pulses, which comprises:

(a) means to store a charge representative of each of said pulses,

(b) operatively connected therewith constant current discharge means to produce a sawtooth signal,

(c) a Schmitt trigger device actuated by a voltage approximately midway between the peak and valley of said sawtooth signal, to produce a first square wave voltage,

(d) means to generate a second square wave voltage of twice the frequency and half the pulse duration of said first square wave voltage, and

(e) means to generate a third square wave voltage which has its leading and trailing edges defined by the trailing edges of said second square wave voltage, wherein said synchronous motor is driven by said first and third square wave voltages.

2. The system of claim 1 wherein said means (d) to generate a second square wave voltage includes:

(f) means to provide as an output a second series of pulses representative of the leading and trailing edges of said first square wave voltage,

(g) second means to store a charge representative of each of said second series of pulses,

(h) operatively connected therewith second constant current discharge means to produce a second sawtooth signal, and

(i) a second Schmitt trigger device actuated by a voltage approximately midway between the peak and valley of said second sawtooth signal, to produce said second square wave voltage.

3. The system of claim 2 wherein said means (f) to prove as an output a second series of pulses includes:

(j) means to differentiate said first square wave voltage,

(k) operatively connected therewith means to provide two series of pulses of the same polarity, one of 3,471,763 5 `6 which is representative of the positive peaks and the 3,264,541 8/ 1966 Mell 318--171 other representative of the negative peaks from said 3,356,921 12/ 1967 Bradford et al. 318-341 XR means to diierentiate and (i) an OR gate responsive to said two series of pulses. CRIS L RADER, Primary EXamrler EN R B N References Cited 5 G E U I SON, Ass1stant Exammer UNITED STATES PATENTS 1 U.s. C1. XR. 2,863,108 12/1958 Raifensperger 31a- 171 3 8441

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