US3731664A

US3731664A - Control voltage generator for electrical fuel control system

Info

Publication number: US3731664A
Application number: US00122661A
Authority: US
Inventors: Y Tsuzuki; N Hobo
Original assignee: NipponDenso Co Ltd
Current assignee: Denso Corp
Priority date: 1971-03-10
Filing date: 1971-03-10
Publication date: 1973-05-08
Anticipated expiration: 1990-05-08

Abstract

A control voltage generator for receiving input signals representing the various operating conditions of a diesel engine, that is, the rotational speed of the engine and the degree of depression of an accelerator pedal etc., so as to generate control voltages corresponding to the fuel injection quantity characteristics required for the engine.

Description

I United States Patent 1191 1111 3,731,664 T suzuki et al. 1 1 May 8, 1973 [54] CONTROL VOLTAGE GENERATOR 3,407,793 10/1968 Lang ..123 32 EA FOR ELECTRICAL FUEL CONTROL 3,526,212 9 1970 Bassot ..123 119 R SYSTEM 3,575,146 4/1971 Creighton ..123/32 EA a W r H 3,587,540 6/1971 Hofmann et al ..l23/l02 [75] Inventors: Yoshihiko Tsuzuki, Kariya; Nobuhito Hobo, Inuyarna, both of Japan Primary Examiner-Laurence M. Goodridge r .-1 1 T 1 Attorney-Cushman, Darby & Cushman [73] Ass1gnee: Nippondenso Co., Ltd., A1ch1-ken,

Japan [57] ABSTRACT [22] Filed: Mar. 10, 1971 A control voltage generator for receiving mput slgnals PP 122,661 representing the various operating conditions of a diesel engine, that is, the rotational speed of the en- 52 us. (:1 ..123/102 123/119 R 307/265 gine and the degree depress acceleram 51 1111. c1 .rozm 51/00 Pedal m9 as generate whages [58] Field of Search ..123/32 EA 119 R responding the fuel inl'ectim quantity charac- 5 teristics required for the engine.

1 Claim, 9 Drawing Figures [56] References Cited UNITED STATES PATENTS 3,425,401 2/1969 Lang ..l23/32 EA V5 FVG PVG AVG

PATENTEU SHEET 1 0F 2 Ava PVG

20 frfiFa/wA/vce" CURVE 0F F 1 6.

PERFORMANCE CURVE 1/ 0F Pl/G.

V9 PERFORMANCE CURVE [47 0F L5. 2 1 0 I V5 PERFORMANCE CURVE 0F AVG.

V 2e 6 s PERFORMANCE CURVE OF US INVENTORE) CONTROL VOLTAGE GENERATOR FOR ELECTRICAL FUEL CONTROL SYSTEM The present invention relates generally to an electrical fuel control system for a diesel engine, and more particularly, to a control voltage generator for the fuel control system which generates control voltages corresponding to the operating conditions of the engine. The control voltages are employed to vary the amount of fuel injection to suit the requirements of the engine, that is, to perform the so-called fuel metering.

The object of the present invention is therefore to provide a control voltage generator which generates control voltages corresponding to the fuel injection quantity characteristics required for a diesel engine when it receives input signals representing the various operating conditions of the engine, such as, the engine speed and the degree of depression of the accelerator pedal. The control voltage generated by the control voltage generator corresponds to the amount of fuel delivered for a single injection into each cylinder under different operating conditions of the engine. A system exemplary of a type of engine fuel control system is described in Hobb et al. U.S. Pat. No. 3,685,526. This control voltage is employed to control a mono-stable timer circuit which is capable of controlling the width of a time pulse by the control voltage, whereby an electrical fuel control system is realized in which the time pulse of the timer circuit is applied to a solenoid valve to control its valve opening duration so that the fuel quantity to be delivered for each injection by the solenoid valve is determined and the fuel thus delivered is injected into a cylinder of the engine.

According to the control voltage generator of the present invention, control voltages which meet the following operating requirements of the engine can be provided:

1. When starting the engine, an increasing fuel delivery characteristic is ensured,

2. The engine idling speed can be maintained at a constant value,

3. Under the full load conditions, the volume of injection corresponding to the full load conditions can be supplied at any given engine speeds lower than the maximum speed of the engine,

4. Under the partial load conditions of the engine, the engine speed can be set to any given value between the idling speed and the maximum speed so that a characteristic is satisfied according to which the volume of injection is varied to a suitable value between the volume of injection corresponding to the full load condition and the minimum volume to compensate for any deviation of the engine speed from the set value, and

5. At higher engine speeds exceeding the maximum engine speed, the volume of injection is maintained at the minimum volume of injection which is almost a zero quantity.

In order to generate control voltages which meet the operating requirements of the engine described above, the control voltage generator according to the present invention comprises a start and idling control voltage generating circuit which receives, as its input signal, a voltage substantially proportional to the engine speed, i.e., the speed voltage, a full load control voltage generating circuit for generating a control voltage for the full load operation, and a partial load control voltage generating circuit which receives, as its input signal in addition to the speed voltage, a voltage as determined in accordance with the degree of depression of the accelerator pedal, i.e., the set voltage to generate a control voltage for the partial load operation, whereby of those control voltages which are generated by the three control voltage generating circuits, the full load control voltage and the partial load control voltage are introduced into a lower selector circuit which selects the lower limiting value of the two applied voltages, and the lower limiting value is then introduced into an upper selector circuit along with the start and idling control voltage so that the upper selector circuit selects the upper limiting value of the two applied voltages to thereby produce an overall control voltage. Thus, it is possible to generate control voltages which meet all the operating requirements of the engine under starting, idling, full load and partial load conditions.

The above and other objects and features of the present invention will become readily apparent from the following descriptions of the preferred embodiments of the invention taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a block diagram showing the general construction of the control voltage generator according to the present invention;

FIGS. 2a to 2e show the input and output waveforms of the respective control voltage generating circuits incorporated in the control voltage generator shown in FIG. 1;

FIG. 3 is an electrical wiring diagram showing an embodiment of the control voltage generator of the present invention;

FIG. 4 is a diagram showing the output voltage characteristics of the control voltage generator according to the present invention; and

FIG. 5 is an output characteristic diagram of another embodiment of the control voltage generator according to the present invention.

The general construction of the device of the present invention will now be explained with reference to FIG. 1. In this figure, numeral 1 designates a full load control voltage generating circuit; 2 a partial load control voltage generating circuit; 3 a lower selector circuit; 4 a start and idling control voltage generating circuit; 5 an upper selector circuit. The full load control voltage generating circuit 1 receives, as its input signal, a voltage substantially proportional to the engine speed, that is, a speed voltage V to generate a control voltage V; shown in FIG. 2a which corresponds to the amount of fuel injection required for the full load operation of the engine. When the speed voltage V V the control voltage V,- changes to the minimum voltage V corresponding to the minimum amount of fuel injection.

The partial load control voltage generating circuit 2 generates a partial load control voltage V; shown in FIG. 2b, which is determined by two input signals including the speed voltage V and a voltage which is set according to the engine accelerator pedal movement 0, that is, a set voltage V This partial load control voltage V is a control voltage corresponding to the amount of fuel injection required for the partial load operation of the engine.

The lower selector circuit 3 is designed such that when a plurality of input voltages are applied thereto,

the circuit selects as its output voltage the minimal input signal voltage from among the applied input voltages. Thus, when the full load control voltage V and the partial load control voltage V are applied to the selection circuit 3 as its inputs, the smaller one of the two control voltages applied is selected as its output voltage V as shown in FIG. 2c. The start and idling control voltage generating circuit 4 receives the speed voltage V as its input signal and produces a control voltage V,, shown in FIG. 2d, which corresponds to the amount of fuel injection required for the engine at speeds ranging from its start to the idling speed.

The upper selector circuit is a circuit which when a plurality of input voltages are applied thereto, selects the largest input voltage from among the applied input voltages. In operation, the start and idling control voltage V and the output voltage V of the lower selector circuit 3 are applied to the selection circuit 5; as its inputs, so that the larger one of the two control voltages applied is selected as an overall control voltage V,;. This situation is shown in FIG. 2e.

In this way, the overall control voltage V as generated by the upper selector circuit 5 is a control voltage corresponding to the amount of fuel injection required for the engine under all the operating conditions including the starting and idling as well as the partial load and full load conditions.

Next, an embodiment of the control voltage generator according to the present invention will now be explained with reference to the electrical wiring diagram shown in FIG. 3. In this figure, numeral 1 designates the full load control voltage generating circuit; 2 the partial load control voltage generating circuit; 3 the lower selector circuit; 4 the start and idling control voltage generating circuit; 5 the upper selector circuit, 6 a constant DC voltage source.

Of these essential units, the control

voltage generating circuits

1, 2 and 3 are circuits which are practically similar in construction and function and therefore the construction and function of the full load control voltage generating circuit 1 will be explained in detail by way of an example. In the full load control voltage generating circuit 1, numeral 21 designates a transistor; 22 a reference diode; 23 a speed voltage source for generating a DC voltage substantially proportional to the speed of the engine; 24, 25 and 26 potentiometers; 27, 28, 29, 30 and 31 resistors. In this construction, the speed voltage source 23 may be comprised of a DC generator operatively associated with the engine crankshaft, for example. Referring to FIG. 3, the sum voltage of a voltage across a voltage dividing point d of the voltage source 6 by the potentiometer 2, i.e., a set voltage V and a voltage across the voltage dividing points a and d of the speed voltage V by the potentiometer 26, is applied between the point a at one end of the reference diode 22 and a grounding point e. Consequently, when the speed voltage V is lower than a predetermined value V the voltage between the points a and e cannot exceed the breakdown voltage of the reference diode 22 (strictly, a voltage higher than the breakdown voltage by a value corresponding to the threshold voltage between the base and the emitter of the transistor 2!) and no biasing voltage is applied to the base of the transistor 21 in the forward direction so that the transistor 21 is cut off and hence the voltage between its collector point c and the grounding point e becomes substantially equal to a voltage V between a voltage dividing point g of the voltage source 16 by the potentiometer 24 and the grounding point e. As the speed voltage V rises so that it becomes higher than the speed voltage V the reference diode 22 is rendered conductive by the voltage between the points and e and a bias voltage is applied to the base of the transistor 21 in the forward direction thus conducting the transistor 21, whereupon the voltage between the collector point 0 of the transistor 21 and the grounding point e gradually decreases as the speed voltage V continues to rise. Then, when the speed voltage V V (V 1 V a full conduction level is attained between the collector and the base of the transistor 21 and hence the voltage between the points c and e assumes a fixed value, i.e., the minimum value V The value of V is determined to correspond to the amount of fuel injection required for the engine at the full load and the value of V is determined to correspond to the minimum amount of fuel injection, while those of V and V 1 are determined to correspond to the engine speed at the maximum output power and the maximum allowable engine speed, respectively. This operation is shown in FIG. 2a. The other control

voltage generating circuits

1, 2 and 3 are practically the same with the full load control voltage generating circuit 1 in construction and function, and therefore they will not be explained in detail but in brief. The start and idling control voltage generating circuit 3 generates the starting control voltage V V, when the speed voltage V V and when V V V 2 the control voltage gradually decreases from V, to V as the speed voltage V increases so that when V 5 V V V 1 (the minimum value). The values of V, and V 1 are determined to correspond to the amounts of fuel injection required for the engine starting and idling, respectively, while the values of V and V 2 are determined to correspond to the engine starting speed and idling speed, respectively. The partial load control voltage generating circuit 2 may be constructed such that its potentiometer 41 varies in association with the movement of the engine accelerator pedal, and in this way the voltage between points f and e, that is, the set voltage can be adjusted as desired in accordance with the movement 6 of the accelerator pedal. Correspondingly, the point where the control voltage V starts to decrease from the maximum value V can be set as desired. If it is set that 0 0,, then V V when V V and when V 5 V V the value of V gradually decreases from V to V as the value of V increases and it reaches the minimum value V when V V With the condition 0 0 0 (where 0 0 indicates the minimum movement of the accelerator pedal and 0,, is the full movement of the accelerator pedal), the value of the speed voltage V at which the value of V starts to decrease from V can be set as desired. Consequently, any given control voltage corresponding to the engine operating conditions at the part load can be generated.

Next, the lower selector circuit 3 will be explained. The basic form of the lower selector circuit 3 for two input voltages comprises diodes 43 and 44 and a resistor 45a and in this embodiment an emitter follower circuit comprising a transistor 45 is also combined for current amplification of the selected output of the circuit. Numeral 46 designates a resistor. The full load control voltage V and the partial load control voltage V are applied to the diodes 43 and 44, respectively, so that the smaller one of the full load control voltage V,- and the partial load control voltage V is selected to appear between a junction point k of the diodes 43 and 44 and the resistor 45a and a grounding point e. Here, the value of the forward voltage drop of either the diode 43 or 44 is so small that it is neglected. The output voltage V of the lower selector circuit 3 appears between points m and e after its current amplification by the emitter follower transistor 45.

Next, the upper selector circuit 5 will be explained. The ba'sic form of the upper selector circuit 5 for receiving two input voltages comprises

diodes

47 and 48 and a resistor 49 and in this embodiment the selector circuit 5 is also combined with an emitter follower circuit comprising a transistor 48a for current amplification of its selected output. Numeral 51 designates a resistor, 52 a capacitor provided for filtering purposes. The output voltage V of the lower selector circuit 3 and the start and idling control voltage V, are applied to the

diodes

47 and 48, respectively, so that the larger one of the two voltages V and V is selected and developed between a junction point n of the

diodes

47 and 48 and the resistor 49 and a grounding point e. Here, the value of the forward voltage drop of the

diode

47 or 48 is neglected. The output voltage of the upper selector circuit 5 is supplied to the emitter follower transistor 48a for current amplification so that the overall control voltage V is produced between points p and e.

With the circuit construction described above, the overall control voltage V produced between the points p and e can satisfy all the operating requirements of a diesel engine under starting, idling, full loading and partial load conditions as shown in FIG. 4 (where the abscissa represents the speed voltage V and the ordinate represents the overall control voltage V In FIG. 4, the reference characters are identical with those which are used in the foregoing explanation. in practice, when the engine is started with the accelerator pedal movement 0 0, the value of the speed voltage V is determined according to the speed of the engine so that the value of the corresponding control voltage V is determined along the line drawn through points A, B, C and D on the graph. On the other hand, if the accelerator pedal movement 0 0 (the maximum), then the control voltage V corresponding to the speed voltage V is similarly determined along the line drawn through the points A, B, G and H. Similarly, if the value of the accelerator pedal movement 0, is 0 0, 0 then the control voltage V is determined along the line drawn through the points A, B, C, E and F according to the speed voltage V In this way, the characteristics shown in FIG. 4 represent the control voltage characteristics which have practically the same form with that of the fuel quantity controlling characteristics by the so-called all-speed governor for a diesel engine.

hile both the full load control voltage generating circuit 1 and the start and idling control voltage generating circuit 4 have been described in the form of circuits adapted to provide the most fundamental control voltage characteristics, these control voltage generating circuits may comprise, for example, analogical functiongenerators which provide any functional relations. Therefore, by employing control voltage generating circuits which are capable of providing, as shown in FIG. 5, the curve l-J-K-L-M as the control voltage characteristic of the start and idling control voltage generating circuit and the curve K-N-O-P-Q as the control voltage characteristic of the full load control voltage generating circuit, control voltages which more precisely suit the operating conditions of an engine may be generated.

What is claimed is:

1. A control voltage generator for an electrical fuel control system used with pulse generating means for generating pulses, and fuel injection solenoid valves controlled by the pulses generated by said pulse generating means, said control voltage generator comprising:

first means for generating a voltage representative of an actual engine speed,

a first circuit electrically connected to said first means for generating a voltage corresponding to the amount of fuel injection required for the full load operation of the engine at said actual engine speed,

second means for generating a voltage representative of an actual engine load,

a second circuit electrically connected to said first and second means for generating a voltage corresponding to the amount of fuel injection required for the engine at said actual engine load and said actual engine speed,

a third circuit electrically connected to said first means for generating a voltage which varies from a value corresponding to the amount of fuel injection for the engine at starting where said actual en gine speed is below a predetermined first speed and to another value corresponding to the amount of fuel injection for the engine at idling where said actual engine speed is higher than a predetermined second speed,

a lower selector circuit electrically connected to said first and second circuits for selecting a smaller one of said voltages generated by said first and second circuits and permitting said smaller voltage to be applied to an upper selector circuit, and

said upper selector circuit electrically connected to said lower selector circuit and said third circuit for selecting a larger one of said smaller voltage derived from said lower selector circuit and said voltage generated by said third circuit, said larger voltage being adaptable to be utilized for controlling the widths of the pulses produced by the pulse generating means.

l F i l t UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,731,66 Dated May 8, 1973 Patent No.

Inventor(s) Yoshihiko Tsuzuki and Nobuhito Hobo It' is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

11 the headigg:

Item [30] Foreign Application Priority Data March 12, 1970 Japan. 2lO33/7O Signed and sealed this 27th day ofNovember 1973.

(SEAL) Attest;

EDWARD M.FLETCHER,JR. RENE 1). TEGTMEYER Attesting Officer Aqting Commissioner of Patents USCOMM'DC 6Q376-F'69 9 U.S GOVERNMENT PRINTING OFFICE: I96! 0-366-334 F ORM FO-IOSO (10-69)

Claims

1. A control voltage generator for an electrical fuel control system used with pulse generating means for generating pulses, and fuel injection solenoid valves controlled by the pulses generated by said pulse generating means, said control voltage generator comprising: first means for generating a voltage representative of an actual engine speed, a first circuit electrically connected to said first means for generating a voltage corresponding to the amount of fuel injection required for the full load operation of the engine at said actual engine speed, second means for generating a voltage representative of an actual engine load, a second circuit electrically connected to said first and second means for generating a voltage corresponding to the amount of fuel injection required for the engine at said actual engine load and said actual engine speed, a third circuit electrically connected to said first means for generating a voltage which varies from a value corresponding to the amount of fuel injection for the engine at starting where said actual engine speed is below a predetermined first speed and to another value corresponding to the amount of fuel injection for the engine at idling where said actual engine speed is higher than a predetermined second speed, a lower selector circuit electrically connected to said first and second circuits for selecting a smaller one of said voltages generated by said first and second circuits and permitting said smaller voltage to be applied to an upper selector circuit, and said upper selector circuit electrically connected to said lower selector circuit and said third circuit for selecting a larger one of said smaller voltage derived from said lower selector circuit and said voltage generated by said third circuit, said larger voltage being adaptable to be utilized for controlling the widths of the pulses produced by the pulse generating means.