US3926153A

US3926153A - Closed throttle tip-in circuit

Info

Publication number: US3926153A
Application number: US457680A
Authority: US
Inventors: Junuthula N Reddy
Original assignee: Bendix Corp
Current assignee: Bendix Corp; Siemens Automotive LP
Priority date: 1974-04-03
Filing date: 1974-04-03
Publication date: 1975-12-16
Anticipated expiration: 1992-12-16

Abstract

A tip-in fuel enrichment circuit is disclosed for the fuel delivery system of an internal combustion engine which senses a closed throttle position signal generated by a switch associated with the engine''s throttle in its closed position and generates a fuel enrichment signal providing a predetermined increase in the fuel delivery to the engine each time the closed throttle position signal is terminated.

Description

' United States Patent Reddy Dec. 16, 1975 [54] CLOSED THROTTLE TIP-IN CIRCUIT 3,720,191 3/1973 Rachel 123/139 BG x 3,726,261 4/1973 Sauer 123/32 EA [751 lnvemor' Junuthula Reddy Troy 3,747,576 7/1973 Gordon et a1. 123/32 EA [73] Assignee; The Bendix Corporation, s hfi ld 3,749,065 7/1973 Rothfusz et =11. 123/32 EA Mich. Primary ExaminerCharles J. Myhre [22] Flled' 1974 Assistant Examiner-Tony Argenbright 211 App} 457 0 Attorney, Agent, or FirmJames R. lgnatowski;

William F. Thornton [52] US. Cl. 123/32 EA; 123/139 BG [51] Int. CI. F02M 51/00 1 R T. [58] Field of Search 123/32 EA 32 R 139 B6 A tip-1n fuel enrichment circuit is disclosed for the 123/32 fuel delivery system of an internal combustion engine which senses a closed throttle position signal gener- [56] References Cited ated by a switch associated with the engines throttle in its closed position and generates a fuel enrichment UNITED STATES PATENTS signal providing a predetermined increase in the fuel I? 1 4 2 1? a! e delivery to the engine each time the closed throttle e e .t 3,661,126 5/1972 Baxendale 123/32 EA posmon slgnal ls termmated' 3,673,989 7/1972 Aono et a1 123/32 EA 14 Claims, 11 Drawing Figures US. Patent Dec. 16,1975 Sheet10f3 3,926,153

Sheet 2 of 3 3,926,153

US. Patent Dec. 16, 1975 US. Patent Dec. 16, 1975 Sheet3of3 3,926,153

CLOSED THROTTLE TIP-IN CIRCUIT FIELD OF THE INVENTION This invention is related to the field of fuel enrichment systems for internal combustion engines and particularly to enrichment systems of the type known as tip-in fuel enrichment providing a fuel enrichment pulse each time the closed throttle signal is terminated by moving the throttle from the closed position.

BACKGROUND OF THE INVENTION The advent of solid-state electronics, pending fuel shortages and the necessity for reducing atmospheric pollution resulting from the noxious exhausts of internal combustion engines have given great impetus to the development of fuel injection systems for internal combustion engines having electronic fuel control computers computing the engines fuel requirements from a plurality of engine operating parameters. Because the electronic fuel control computer has inputs from a plurality of sensors, the computer is capable of more accurately computing the fuel requirements of the 'engine thereby reducing both gas consumption and exhaust emissions. Present fuel control computers are designed to accurately control fuel delivery over the entire dynamic operating range of the engine, including idle, acceleration, deceleration and constant speed operation. Typical electronically controlled fuel injection systems are disclosed in US. Pats. Nos. 3,593,692 Electrical Fuel Injection Arrangement for Internal Combustion Engine issued to H. Scholl et al., US. Pat. No. 3,726,261 Acceleration Enrichment Signalling Means for Electronic Fuel Systems By R. G. Sauer, and US. Pat. No. 3,720,191 Acceleration Enrichment Circuitry for Electronic Fuel System by T. L. Rachel. Referring to the H. Scholl patent, fuel enrichment during acceleration is provided by an acceleration enrichment switch attached to the throttle which generates electrical pulses as the throttle is advanced or opened. These pulses are subsequently converted by the fuel control computer into fuel injection pulses which increase the fuel delivery to the engine during acceleration. In the Rachel or Sauer patents, a lost motion link is connected between the accelerator pedal and the throttle. A potentiometer generating an electrical signalis mechanically linked to the accelerator pedal. The combination of the accelerator pedal, potentiometer and lost motion link to the throttle provide a means for generating an acceleration demand signal prior to the actual movement of the throttle. Sauer provides two separate circuits for providing fuel enrichment to the engine. The first circuit increases the length of the electrical pulse provided by the electronic computer in direct proportion to the rate and magnitude of the acceleration demand. The second circuit initiates an immediate electrical pulse to the fuel injectors when the rate and magnitude of the acceleration demand exceeds predertermined limits.

The electronic fuel control systems disclosed by either Scholl, Rachel, or Sauer appear to provide adequate acceleration fuel enrichment when the engine is operating with the throttle at least partially open. However, it has been found that both systems fail in response to a tip-in from a closed throttle position, the term tip-in being defined as the initial commencement of opening movement of the throttle frofii the closed position. Unless additional fuel is provided @Qficurrent with the tip-in, there will be a momentary lag between the demand for acceleration and the actual response of the engine. In the system disclosed by the Scholl patent, the fuel enrichment pulse is not generated until the throttle is rotated through a predetermined angle to a position where the acceleration switch produces the first pulse. Because of this predetermined angular dependency, the time when the first acceleration enrichment pulse is generated as a function of the rate at which the throttle is rotated. Likewise, the circuitry disclosed by Rachel is dependent upon the rate at which the throttle is rotated. With the Rachel system, if the tip-in is small, such as a small opening or low opening rate, the only acceleration enrichment provided is that generated by the first described circuit which increases the width of the pulses generated by the computer. However, if the tip-in is large and executed at a relatively fast rate, the system is capable of generating the required instantaneous pulse. Neither of the two systems will always provide a fuel enrichment pulse immediately on commencement of tip-in. The present invention is directed to overcome this problem and in particular is directed to overcome this problem for electronic fu'el control systems using an acceleration switch of the type disclosed in the Scholl patent, but is equally applicable to the fuel control system using closed throttle position switches or a lost motion link as disclosed by Rachel.

The object of the invention is an electronic circuit for an internal combustion engine fuel control system for providing additional fuel to the engine each time the throttle is moved from its closed position. Another object of the invention is to provide additional fuel to the engine each time a signal indicative that the throttle is in the closed position is terminated. A still further object of the invention is to generate a pulse signal injecting a predetermined quantity of fuel into the engine each time the closed throttle position is terminated. Still another objective is to provide a circuit sensitive to the closed throttle position signal generated by an acceleration enrichment switch for generating a pulse signal each time the closed throttle signal is terminated. A final objective is to provide a closed throttle tip-in fuel enrichment system wherein the quantity of fuel injected into the engine when the closed throttle signal is terminated is a function of at least one engine operating parameter.

SUMMARY OF THE INVENTION The present invention is a closed throttle tip-in circuit for generating an acceleration fuel enrichment pulse each time the closed throttle signal is terminated when the operator tips-in the throttle. In general, the inventive circuit senses the termination of the closed throttle signal and generates a fuel enrichment pulse independent of the magnitude or rate at which the throttle is opened. And in the preferred embodiment, the inventive circuit senses the opening of the drag switch of an acceleration enrichment switch of the type disclosed in the Scholl patent and generates a tip-in fuel enrichment pulse, prior to the generation of an acceleration enrichment pulse.

The inventive circuit comprises an input circuit portion and an output circuit portion. The input portion generates a first signal when a closed throttle signal is being generated and generating a second signal when the closed iliffilttle signal is terminated and the output portion generates a fuel fifiehment tip-in pulse signal in response to the second signal generated by theinput portion, whereby the enrichment tip-in pulse signal communicated to the fuel injector means is operative togenerate a tip-in fuel enrichment pulse concurrent with the operators demand for opening the throttle from the closed throttle position. v

In an alternate embodiment of the invention the length of the generated tip-in pulsesignal is an inverse function of the engines temperature. i I

BRIEF DESCRIPTION OF THE ILLUSTRATIONS- FIG. 1 is an illustration of a typical acceleration enrichment switch;

FIG. 2 is an electrical diagram showing electrical path through the switch in the closed throttle position;

FIG. 3 is a circuit diagram of the tip-in fuel enrichment pulse generating circuit;

FIG. 3a is a portion of the circuit diagram in FIG. 3 having a thermistor in series with the resistance in the RC. network;

FIG. 3b is a portion of the circuit diagram in FIG. 3 having a thermistor in parallel with the resistance in the RC. network; j

FIG. 30 is a portion of the circuit diagram in FIG. 3 having a thermistor replacing the variable resistance;

FIG. 4 is a portion of the acceleration switch showing the position of the elements of the drag switch during a counter-clockwise rotation;

FIG. 5 is an end view of the drag switch;

FIG. 6 illustrates a closed throttle switch associated with the accelerator pedal; 1

FIG. 7 illustrates a closed throttle position switch mechanically activated from the throttle shaft; and

FIG. 8 illustrates a closed throttle position switch mechanically activated from a lost motion switch.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A commercial embodiment of such an acceleration I enrichment switch is shown in FIG. 1. The acceleration enrichment switch 10 has a base 12 fixedly attached to the throttle body 13 by means of screw type fasteners such as screws 14. Radial slots 16 are provided in the base 12 to permit rotational adjustment of acceleration enrichment switch for proper alignment of the switch during installation. The acceleration enrichment switch 10 also has a drag switch 18 attached to the throttle shaft 20 of the moveable throttle plate (not shown). Movement of the throttle shaft 20 causes the

slide contacts

22, 24 and 26 attached to drag switch 18 to slide across conductive segments on plate 28. Plate 28 in the preferred embodiment is a printed circuit board having the conductive paths formed thereon by any of the methods well known in the art. However, any comparable element providing the required electrical conductors may be used. The drag switch 18 comprises a drag rotor 30 adapted to rotate about throttle shaft 20 with a predetermined drag force relative to the-base 12. A bevel spring (not shown) disposed between the drag rotor 30 and the base 12 and in friction engagement with both elements provides the desired drag force. Drag switch 18 further comprises a driven rotor 38 fixedly coupled to rotate with throttle shaft 20 Driven rotor 38 being the form of a yoke having two radially extending

arms

39 and 41. Electrical contact posts 32 and 34 are fixedly attached and upstanding from the drag rotor 30. Post 32 is adjacent to the end of arm 39 and post 34 is adjacent to the end of arm 41. Electrical contact post 36 is also fixedlyiattached to and upstanding from the drag rotor 30 centrally disposed near the inner apex of the yoke between

arms

39 and 41. Slide contact 22 is fixedly attached to spring post 36 and is in continuous electrical contact and communication therewith. Slide contacts 24'and 26 are fixedly attached to

posts

32 and 34 respectively and also are in electrical contact therewith. A pickup bar 40 is pivotally mounted on spring post 36 and extending between

arms

39 and 41 of the driven rotor 38 and

posts

32 and 34 terminating outboard of

posts

32 and 34 in a keeper 43. The width of the pick-up bar is slightly less than the width between the two

arms

39 and 41 permitting slight rotation of the driven rotor 38 in either direction before the

arms

39 and 41 contact the pick-up bar 40 and cause it to rotate therewith. Contact pad 47 indicated on FIG. 4 may be formed on both sides of the pick-up bar 40 to limit the movement of the pickup bar between

arms

39 and 41. v

v A hair pin spring 42 having two free ended prongs 44 and'46 is also fixedly attached to and in continuous electrical contact with spring post 36 over pickup bar 40. Keepe'rportion 43 defines a rectangular slot 45 slightly greater than the width of pick-up bar 40 and slightly less than the inner distance between contacts posts 32 and 34. The free ended

prongs

44 and 46 are confined in the rectangular slot 45 of the keeper 43 and are biased towards each other by the ends of the slot 45. The width of the slot 45 is selected so that when arm 41 is in contact with the pick-up bar 40, the prong 44 of the hair pin spring 42 is in electrical contact with contact post 32 and prong 46 is disengaged from electrical contact with contact post 34 as shown in FIG. 1. When arm 39 is in contact with the pick-up bar 40, prong 46 is in electrical contact with contact post 34 and prong 44 is disengaged from contact post 32 as shown in FIG. 4.

a When the throttle shaft 20 is rotated in the clockwise direction, as viewed in FIG. 1, the arm 41 engages pickfup bar 40 and moves pick-up bar.40 in a clockwise direction about its pivot point spring post 36. The hair pin spring 42 rotates with the pick-up arm 40 and prong 44 engages contact post 32. When the pick-up rotor 40 rotates through a predetermined angle, the pick-up bar 40 engages contact post 32 and rotates the drag rotor 30 with the driven rotor 38. Rotating the throttle shaft in the counter-clockwise direction causes arm 39 to engage the pick-up bar 40 and rotate the pick-up bar in the same direction about its pivot point spring post 36. The hair spring 42 moves with the pick-up bar 40 and prong 44 is disengaged from post 32. Continued counter-clockwise motion of bar 40 causes prong 46 to engage contact post 34. With continued rotation of the throttle'shaft 20 in the counter-clockwise direction, the pick-up bar 40 engages contact post 34 and rotates the drag rotor in a counter-clockwise direction. Due to the difference between the width of the pick-up bar 40 and the width between

contact posts

32 and 34, the drag switch 18 is effectively a lost motion link wherein the driven rotor 38 must be rotated through a predetermined angle before the drag rotor 30 begins to move.

Continued rotation of the throttle shaft in the counter-clockwise direction causes the

slide contacts

22, 24

and 26 to slide across the respective contour segments on the plate 28. Although in the preferred embodiment the separation of the

prongs

44 and 46 determined by rectangular slot 45 is such that electrical contact between prong 44 and contact post 32 is broken before contact between prong 46 and post 34 is made and vice versa, the separation may be such that when the pickup bar is symmetrically disposed between the two posts. the two prongs of hair pin spring 42 makes electrical contact with both posts and only breaks electrical contact with either post only when the pick-up bar is displaced from its central location. The combination of the hair spring 42, pick-up arm 40, post 36 and

contact posts

32 and 34 combine to form lost motion switch, dashed box 48, illustrated in FIG. 2.

The plate 28 has a plurality of conductor segments arcuately disposed to be contacted by the

slide contacts

22, 24 and 26.

Conductors

50 and 52 have interleaved tooth-like projections 54 along a portion of their common interface to form in combination with slide contact 26, and alternating switch dashed box 56, illustrated in FIG. 2.

Conductors

58 and 60 are disposed along the arcuate path of slide contact 24. Pad 62 is an electrical terminal at the end of conductor 58 and electrical discontinuity 64 separates

conductors

58 and 60.

Conductors

58 and 60 combined with slide contact 24 form a two position switch 68 illustrated by the dashed box in FIG. 2.

Conductor

70 and 72 follow the arcuate path of slide contact 22 having an electrical discontinuity 66 between them. Conductor 70 is electrically connected to conductor 58 by means of interconnect 74.

Normally the throttle shaft is biased in a clockwise direction by a spring or other resilient means to hold the throttle in a closed position during the absence of an operator demand to open the throttle. To insure contact of prong 44 with post 32 and the proper location of the slide contacts on the conductors in the closed throttle position, a mechanical stop 76 is disposed on the base 12 to limit the rotation of the drag rotor 30 in the clockwise direction. With the drag rotor 30 against the mechanical stop 76, prong 44 is in contact with contact post 32, slide contact 22 is in contact with conductor 70, slide contact 24 is in contact with conductor 60, and slide contact 26 is in Contact with conductor 52.

The operation of the acceleration enrichment switch is discussed with reference to the circuit diagram FIGS. 1 and 2. With the throttle in the curb idle position, the throttle shaft is biased to its maximum clockwise position with arm 41 of the driven rotor 38 urging the pick-up bar 40 against contact post 32 and drag rotor against the mechanical stop 76. In this position, prong 44 is in contact with contact post 32 and by means of conductor 58, interconnect 74 and conductor 70, slide contact 22, post 36, prong 44, post 32, slide contact 24 and conductor 60, a closed throttle signal applied to pad 62 is electrically communicated to conductor 60. This signal which may be a predetermined voltage or a ground potential on conductor 60 is further communicated to the fuel control computer 61 which may be of the type described in my commonly assigned US. Pat. No. 3,734,068 issued May 22, 1973 and expressly incorporated herein by reference. Computer 61 uses the closed throttle signal to generate appropriate fuel delivery signals to sustain the operation of the engine in the idle mode of operation.

With the initial movement of the throttle from the closed position, the drag rotor 30 remains against the mechanical stop 76 due to the frictional drag force while the driven rotor 38 starts to rotate. Arm 39 now contacts pick-up bar 40 and rotates both the pickup bar and hair pin spring 42. With the counter-clockwise rotation of the hair pin spring 42, prong 44 disengages from post 32 breaking electrical contact and removing the closed throttle signal from conductor 60. This terminates the closed throttle signal being sent to computer 61 and the computer starts to calculate the engines fuel requirements based on the engine operating parameters. Further, opening of the throttle rotates the driven rotor 38 so that the pickup bar 40 and prong 46 of hair pin spring 42 engages post 34 and the singal on pad 62 is applied to conductor 52 through slide contact 26. With still further opening of the throttle, pick-up bar 40 engages post 34 and starts to rotate drag rotor 30 and

slide contacts

22, 24 and 26. Slide contact 26 now alternately

contacts conductors

50 and 52 generating fuel enrichment pulses as disclosed in the Scholl patent or by any equivalent means, and the contact of slide contact 24 is moved from conductor 60 to conductor 58, preventing the reoccurrence of a closed throttle signal on conductor 60 until the throttle is again in its closed position.

It is apparent from the above discussion that the first acceleration enrichment pulse generated by the acceleration enrichment switch occurs only after the throttle shaft 20 has rotated through a predetermined angle sufficient to take up the lost motion of switch 48 and to move slide contact 26 from conductor 52 to conductor 50. Because the throttle shaft must be rotated through the predetermined angle prior to the generation of the first enrichment pulse, the acceleration of the engine will lag the demand, and if the tip-in demand is less than the predetermined angle, no enrichment pulse would be generated at all but for the disclosed circuit.

The disclosed circuit eliminates the hereinabove described problems by detecting the termination of the closed throttle signal on conductor 60 by the disengagement of prong 44 from post 32 in the lost motion switch 48 and generating a fuel enrichment pulse whenever the closed throttle signal is terminated. This effectively reduces the angle through which the throttle shaft 20 must be rotated to generate the first acceleration enrichment pulse and also provides the required tip-in fuel enrichment pulse when the operator tips-in the accelerator pedal an amount insufficient to move slide contact 26 from conductor 52 to conductor 50.

The electronic circuitry including the lost motion switch 48 of the acceleration enrichment switch 10 is shown in FIG. 3. Referring to FIG. 3, pad 62 at the end of conductor 58 is connected to a ground potential and the lost motion switch 48 generates a ground signal on conductor 60 when the throttle is in the closed position and prong 44 is in contact with post 32, the ground signal being communicated to prong 44 of the lost motion switch 48 by means of interconnect 74, conductor 70, slide contact 22 and post 36.

Electrical power is supplied to the tip-in pulse generating circuit from an electrical power supply designated as B+ generating a positive potential. The power supply may be a battery or the engine driven electrical power supply normally associated with an internal combustion engine. The conventional ground symbol is used to designate an alternate terminal of the power supply having a potential other than 8+ and may be the negative terminal of the battery or engine driven power supply. A resistance 102 and a diode 104 are forwardly and serially connected between B-land conductor 60 of the lost motion switch 48. The junction 106 between resistance 102 and diode 104 is connected to the base of transistor 108. The collector of transistor 108 is connected to 8+ through resistance 110 and the emitter of transistor 108 is forwardly connected to ground through diode 112. The collector of transistor 108 is also connected to the base of transistor 114 by means of serially connected capacitance 116 and diode 1 18. A variable resistance 120 is connected between B+ and the junction 122 formed between the serially connected capacitance 116 and diode 118. The collector of transistor 114 is connected to 8+ through resistance 124 while the emitter of transistor 114 is connected to ground potential. A diode 126 is connected forwardly between the junction 128 formed between resistance 122 and the collector of transistor 114 and an OR gate 130. The OR gate 130 receives the normally generated fuel injection pulses, designated as T,,, the acceleration enrichment pulses, designated as AE, and the tip-in pulses generated at the junction 128 between resistance 124 and the collector of transistor 114.

The operation of the circuit is as follows. When the throttle is in the closed position and prong 44- of the lost motion switch 48 is engaged with post 32, a ground potential is communicated to conductor 60. The ground potential at conductor 60 causes current to flow resistance 102 and diode 104 generating a one diode drop potential at junction 106 which is applied to the base of transistor 108. Because of the diode 112 in the emitter circuit of the transistor 108, a potential of at least two diode drops at the base of transistor 108 is required to cause it to conduct. Therefore, when a ground potential appears on conductor 60, transistor 107 is in the nonconducting state and B+ potential appears at the collector of transistor 108 and one side of capacitance 116 by means of resistance 110. In this state capacitance 116 is charged to a value approximately equal to 8+.

Current is supplied to the base of transistor 114 by means of resistance 120 and diode 1 18 causing transistor 114 to be conductive. Conductance of transistor 114 causes a current to flow through resistance 124 which produces a low signal at junction 128 between resistance 124 and the collector of transistor 1 14 which is communicated to one of the three input gates of the OR gate 130 by means of diode 126. The low signal at the input gate of OR gate 130 does not generate an output signal at the output of the OR gate.

When the operator tips-in the gas pedal, the throttle shaft starts to rotate moving the driven rotor 38. This causes prong 44 to disengage from contact post 32 terminating the electrical path to ground through lost motion switch 48 and through diode 104. Current from the power supply now flows through resistance 102 to the base of transistor 108 through diode 112 to ground placing transistor 108 in its ON state. Transistor 108 in the ON state provides a low resistance discharge path from one side of capacitance 116 causing capacitance 116 to discharge to a ground potential. This change in potential on one side of capacitance 116 caused by its discharge through transistor 108 is reflected on the other side of capacitance 1 16 which is now forced to go negative. The negative potential on the other side of capacitance 116 is applied to diode 118 and it ceases to conduct. Nonconductance of diode 118 terminates current to the base of transistor 114 and turns transistor 114 OFF thereby terminating current flow through resistance 124. The junction 128 between resistance 124 and the collector of transistor 144 now assumes a high potential approximately equal to 3+ which is communicated to OR gate 130 by means of diode 126. A high potential signal at any one or all of the gates of OR gate 130 causes the OR gate to generate a signal which initiates a fuel injection pulse in the fuel injection means providing an additional quantity of fuel to the engine when the operator tips-in the throttle.

Current flowing through variable resistance starts to recharge capacitance 116 to its initial voltage. When the voltage on capacitance 116 rises above two diode voltage drops, the current through resistance 120 starts to flow through diode 1 18 and the base of transistor 114 turning transistor 114 ON and terminating the high signal at junction 128 and the gate of OR gate 130. Terminating the high signal to OR gate 130 terminates the signal generated by the OR gate in response to the tip-in pulse signal.

Resistance 120 and capacitance 116 form a RC time delay circuit determinative of the length of the generated fuel injection signal. The resistance of variable resistance 120 is adjusted to produce a tip-in fuel enrichment pulse of the proper duration for smooth operation of the engine during tip-in and may be a function of at least one engine operating parameter. Thus it can be seen from the above description the disclosed circuit generates a tip-in fuel enrichment pulse every time the closed throttle signal is terminated.

It would be obvious for a person skilled in the art that the circuit illustrated in FIG. 3 may be modified so that the rate at which capacitance 116 is recharged may be a function of the engine temperature or other engine parameter so that the duration of the generated tip-in pulse signal can be varied in accordance with the engines requirements. The variable resistance 120 may include a thermistor in thermal contact with the engine or its coolant, so that the effective resistance of resistance 120 is an inverse function of the engines temp erature. Variable resistance 120 may comprise a thermistor 132 in series with a fixed or variable resistance 134, or a thermistor 132 in parallel with a fixed or variable resistance 134 or the variable resistance 120 may be just a thermistor 134 as shown in FIGS. 3a, 3b, and 30, respectively. When the engine is cold, the resistance of variable resistance 120 is high and capacitance 1 16 charges at a slow rate producing a long tip-in pulse signal. Conversely when the engine is warm, the resistance of variable resistance 120 decreases, capacitance 116 charges at a faster rate and the tip-in pulse signal becomes shorter.

Alternatively, variable resistance 120 may be replaced by -a temperature dependent current source recharging capacitance 116 from the B+ power supply at a rate proportional to the engines temperature or a temperature dependent current sink may be connected between junction 122 and ground which drains a portion of the current flowing through variable resistance 120 to ground at a rate inversely proportional to the engines temperature. Temperature dependent current sources as described above are well known in the art as evidenced in the referenced Sauer patent and need not be discussed in detail. A current sink is the converse of a current source and is equally well known in the art. Although the circuit is disclosed and described with reference to a particular embodiment of an accelera tion enrichment switch generating a signal indicative that the engines throttle is in the closed position, the

system is equally applicable to other types of closed throttle position switches such as a switch attached to the accelerator or gas pedal (FIG. 6) as for example disclosed in US. Pat. No. 3,757,758 issued Sept. ll, 1973, Stoltman and expressly incorporated herein by reference, a switch attached to the throttle shaft (FIG. 7), or a lost motion switch as disclosed in the Sauer patent and illustrated in FIG. 8. It is also noted that the potentials to the inventive circuit may be reversed as is well known in the art or that the closed throttle signal may be a high signal rather than a ground signal as disclosed in the preferred embodiment. These types of changes are well within the purview of those skilled in the art. The disclosed and illustrated embodiment only serves to set forth the preferred embodiment of the invention and is not intended to limit the scope thereof.

What is claimed is:

1. ln combination with an internal combustion engine fuel control system, having a source of electrical power, an electronic fuel control generating signals indicative of the engines fuel requirements, fuel delivery means for delivering fuel to the engine in response to the signals generated by said fuel control computer and a throttle moveable intermediate a closed and a full open position to control the air delivery to the engine, an improvement comprising:

means for generating a closed throttle signal only when the throttle is in the closed position and for terminating said closed throttle signal when said throttle is intermediate said open and closed position;

input circuit portion means responsive to the termination of said closed throttle signals for generating a pulse width control signal each time said closed throttle signal is terminated; and

output circuit portion means including at least one output transistor switch for generating a fuel enrichment pulse signal in response to a pulse width control signal. 2. The improvement of claim 1 wherein said input circuit portion means comprises:

first circuit means generating a first signal in response to the closed throttle signal and a second signal in the absence of a closed throttle signal; and

second circuit means for generating said pulse width control signal in response to said second signal, said pulse width control signal persisting a predetermined time after the occurrence of said second signal.

3. The improvement of claim 2 wherein said second circuit means further includes sensor means responsive to an engine operating parameter for controlling the length of the predetermined time said pulse width signal persists after the occurrence of said second signal as a function of said engine operating parameter.

4. The improvement of claim 3 wherein said sensor means is a temperature sensor responsive to the temperature of the engine and the length of said pulse width signal is an inverse function of the engines temperature.

5. The improvement as claimed in claim 2 wherein said means for generating a closed throttle signal is an electrical switch mechanically linked to the throttle and said closed throttle signal is a ground potential signal, said first curcuit means comprises:

a transistor switch having an emitter, collector, and

base wherein the electrical potential applied to said 10 base controls the current flow from said collector to said emitter;

a first resistance connected between the source of electrical power and said base;

a diode connected between said base and said electrical switch;

a second resistance connected between said source of electrical power and said collector; and

a second diode connected between said emitter and ground.

6. The improvement as claimed in claim 5 wherein said second circuit means includes:

a capacitor having one end connected to said input transistor for storing an electrical charge in response to said first signal and to discharge in response to said second signal; and

a resistance connected between the source of electrical power and the other side of said capacitance to recharge said capacitance to its original value at a predetermined rate after being discharged by said second signal, wherein the charge on said capacitance is said pulse width control signal.

7. The improvement as claimed in claim 6 wherein said output circuit means includes:

said output transistor switch having an emitter, collector and base wherein the electric potential applied to said base controls the current flow from said collector to said emitter;

a diode connecting the base of said output transistor switch to the other end of said capacitance;

a resistance connecting the collector of said output transistor switch with said source of electrical power and means connecting the emitter of said transistor switch to ground wherein said tip-in fuel enrichment pulse signal is generated at the collector of said output transistor switch when the charge on said capacitance is below a predetermined value.

8. The improvement as claimed in claim 7 wherein the fuel delivery means includes gate means having a plurality of input gates receiving the signals generated by the electronic fuel control computer, said gate means further includes an input gate for receiving said tip-in fuel enrichment pulse signals from said tip-in fuel enrichment circuit.

9. In combination with an internal combustion electronic fuel control system having a source of electrical power, an electronic fuel control computer for generating signals indicative of the engines fuel requirements, at least one electrically actuated fuel injector valve for delivering fuel to the engine in response to the signals generated by the computer and a throttle controlling the air delivery to the engine wherein said fuel control system further includes an acceleration enrichment switch mechanically linked to said throttle for generating acceleration fuel enrichment pulses, and wherein said acceleration enrichment switch further includes a closed throttle position switch generating a closed throttle signal indicative that the throttle is in the closed position, a closed throttle tip-in circuit for generating a fuel enrichment pulse signal activating said fuel delivery means to deliver a predetermined quantity of fuel to the engine each time the closed throttle signal is terminated comprising:

input circuit means for generating a first signal in response to said closed throttle signal and a second signal inre'sponse to the absence of the closed throttle signal;

a capacitance and resistance forming an RC network, said capacitance being charged to a predetermined value by said first signal and discharged bysaid second signal and said resistance recharging said capacitance from its discharged state to its initial charged value at a predetermined rate; and

output circuit means responsive to the charge on said capacitance for generating said tip-in fuel enrichment signal when the charge on said capacitance is below a predetermined value.

10. The enrichment tip-in circuit as claimed in claim 9 wherein said acceleration enrichment switch further includes a drag switch terminating said closed throttle signal prior to the opening of said closed throttle position switch, said input circuit means generates said second signal in response to the termination of said closed throttle signal by said drag switch.

11. In combination with an acceleration enrichment switch mechanically linked to the throttle of an internal combustion engine, said acceleration enrichment switch having a two position drag switch, said two position drag switch operative to be in a first position when the throttle is moved in a direction tending to open the throttle providing electrical continuity through the acceleration switch with the acceleration pulse forming elements, and operative to be in a second position breaking electrical continuity with the acceleration pulse forming elements when the throttle is moved in a direction tending to close the throttle, further when the throttle is in the closed position the drag switch in the second position provides electrical continuity to a closed throttle switch, and generates a closed throttle signal, the drag switch operative to move from said second position to said first position prior to the opening of said closed throttle switch and the generation of said first acceleration enrichment pulse, a circuit for generating a tip-in fuel enrichment pulse with the throttle in the closed position in response to the drag switch switching from its first position to its second position comprising:

input circuit means for generating a first signal in response to the closed throttle signal generated by the acceleration switch with the throttle in the closed position and the drag switch in the second position, and for generating a second signal in response to the termination of the closed throttle signal generated by the acceleration switchwith the throttle in the closed position and the drag switch in the second position;

a capacitance and a current source forming an RC.

network, said capacitance being charged to a predetermined value by said first signal, and discharged by said second signal, and said current source recharging said capacitance from its discharged state to its initial value at a predetermined rate; and

12. The combination of claim 11 wherein said acceleration switch has a base fixedly attached to the stationary throttle body and is mechanicallyv linked to the moveable throttle shaft biased in the closed position.

means disposed between said drag rotor and the switchb ase for generating a frictional force retarding movement of the drag rotor relative to the base;

two upstanding contact posts separated from each other by a first predeterminable separation dis- .tance and radially disposed from the center of the throttle shaft, a first predetermined radial distance;

an upstanding spring post, angularly disposed between said contact posts and radially disposed a second radial distance from the center of the throttle shaft, said second radial distance being substantially less than said first radial'distance;

means for making electrical contact to said two contact posts and said spring post individually;

a driven rotor, fixedly attached to said throttle shaft and adapted to rotate therewith, said driven rotor having two parallel arms stradling said spring post, said parallel arms being separated by a distance slightly greater than the distance between said Contact posts, and having a radial length less than said first radial distance and greater than said second radial distance;

a pickup bar pivotally attached to said spring post I and disposed between said two arms of the driven rotor and said two contact posts, said pickup bar radially extending slightly beyond said contact posts and having a width less than the distance between said two contact posts permitting said pickup bar to freely pivot about said spring post through a predetermined angle defined by said two contact posts;

a hair pin spring in continuous electrical contact with said spring post, said hair pin being disposed over said pickup arm and rotatable therewith, said hair 7 pin spring further having two free ended prongs extending radially outward from said spring post a short distance beyond said contact posts, and said prongs further being separated by a distance greater than the width of said pickup bar; and

a keeper fixedly disposed at the end of said pickup bar beyond said contact posts, said keeper having a rectangular slot biasing the free ends of said prongs towards each other so-that the separation of said prongs proximate said contact posts is slightly less than the distance between said contact posts;

. wherein the spring bias on the throttle shaft in the closed throttle position causes one arm of the driven rotor to bias the pickup bar against one of the contact posts placing one prong of the hair pin spring in electrical contact with said one contact post and the initial rotation of the throttle shaft 7 against the spring bias causes the other arm of the driven rotor to move the pickup bar away from said one contact post removing said prong away from said one contact post breaking said electrical contact prior to said pickup bar engaging the other contact post and rotating said drag rotor with said driven rotor,

i 13. The combination of claim 12 wherein said input circuit me ans includes an input transistor switch having a first state in response to the closed throttle signal and a second state in the absence of said closed throttle signal, saidtransistor switch in said first state generates said first signal, and in said second state generates said secon'd signal; and

wherein said output circuit means includes at least one output transistor switch. said at least one output transistor switch generating said tip-in enrich- 13 14 ment signal when the charge on said capacitance is temperature of the internal combustion engine for conbelow a predetermined value. trolling said predetermined rate at which said capaci- 14. The combination of claim 12 wherein said curtance recharges.

rent source includes sensor means responsive to the s UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENTNQ: 3,926,153

DATED December I6, I975 INVENTOR(S) Junuthula N. Reddy It is certified that error appears in the ab0ve-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE CLAIMS CoI 9 I Ine 66, delete the word "curcutt" and add "ci rcui t".

CoI I I I ine 65, after "shaft" add the word "spring".

Signed and Scaled this Third Day of August 1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oj'Palents and Trademarks

Claims

1. In combination with an internal combustion engine fuel control system, having a source of electrical power, an electronic fuel control generating signals indicative of the engine''s fuel requirements, fuel delivery means for delivering fuel to the engine in response to the signals generated by said fuel control computer and a throttle moveable intermediate a closed and a full open position to control the air delivery to the engine, an improvement comprising: means for generating a closed throttle signal only when the throttle is in the closed position and for terminating said closed throttle signal when said throttle is intermediate said open and closed position; input circuit portion means responsive to the termination of said closed throttle signals for generating a pulse width control signal each time said closed throttle signal is terminated; and output circuit portion means including at least one output transistor switch for generating a fuel enrichment pulse signal in response to a pulse width control signal.

2. The improvement of claim 1 wherein said input circuit portion means comprises: first circuit means generating a first signal in response to the closed throttle signal and a second signal in the absence of a closed throttle signal; and second circuit means for generating said pulse width control signal in response to said second signal, said pulse width control signal persisting a predetermined time after the occurrence of said second signal.

4. The improvement of claim 3 wherein said sensor means is a temperature sensor responsive to the temperature of the engine and the length of said pulse width signal is an inverse function of the engine''s temperature.

5. The improvement as claimed in claim 2 wherein said means for generating a closed throttle signal is an electrical switch mechanically linked to the throttle and said closed throttle signal is a ground potential signal, said first curcuit means comprises: a transistor switch having an emitter, collector, and base wherein the electrical potential applied to said base controls the current flow from said collector to said emitter; a first resistance connected between the source of electrical power and said base; a diode connected between said base and said electrical switch; a second resistance connected between said source of electrical power and said collector; and a second diode connected between said emitter and ground.

6. The improvement as claimed in claim 5 wherein said second circuit means includes: a capacitor having one end connected to said input transistor for storing an electrical charge in response to said first signal and to discharge in response to said second signal; and a resistance connected between the source of electrical power and the other side of said capacitance to recharge said capacitance to its original value at a predetermined rate after being discharged by said second signal, wherein the charge on said capacitance is said pulse width control signal.

7. The improvement as claimed in claim 6 wherein said output circuit means includes: said output transistor switch having an emitter, collector and base wherein the electric potential applied to said base controls the current flow from said collector to said emitter; a diode connecting the base of said output transistor switch to the other end of said capacitance; a resistance connecting the collector of said output transistor switch with said source of electrical power and means connecting the emitter of said transistor switch to ground wherein said tip-in fuel enrichment pulse signal is generated at the collector of said output transistor switch when the charge on said capacitance is below a predetermined value.

9. In combination with an internal combustion electronic fuel control system having a source of electrical power, an electronic fuel control computer for generating signals indicative of the engine''s fuel requirements, at least one electrically actuated fuel injector valve for delivering fuel to the engine in response to the signals generated by the computer and a throttle controlling the air delivery to the engine wherein said fuel control system further includes an acceleration enrichment switch mechanically linked to said throttle for generating acceleration fuel enrichment pulses, and wherein said acceleration enrichment switch further includes a closed throttle position switch generating a closed throttle signal indicative that the throttle is in the closed position, a closed throttle tip-in circuit for generating a fuel enrichment pulse signal activating said fuel delivery means to deliVer a predetermined quantity of fuel to the engine each time the closed throttle signal is terminated comprising: input circuit means for generating a first signal in response to said closed throttle signal and a second signal in response to the absence of the closed throttle signal; a capacitance and resistance forming an RC network, said capacitance being charged to a predetermined value by said first signal and discharged by said second signal and said resistance recharging said capacitance from its discharged state to its initial charged value at a predetermined rate; and output circuit means responsive to the charge on said capacitance for generating said tip-in fuel enrichment signal when the charge on said capacitance is below a predetermined value.

11. In combination with an acceleration enrichment switch mechanically linked to the throttle of an internal combustion engine, said acceleration enrichment switch having a two position drag switch, said two position drag switch operative to be in a first position when the throttle is moved in a direction tending to open the throttle providing electrical continuity through the acceleration switch with the acceleration pulse forming elements, and operative to be in a second position breaking electrical continuity with the acceleration pulse forming elements when the throttle is moved in a direction tending to close the throttle, further when the throttle is in the closed position the drag switch in the second position provides electrical continuity to a closed throttle switch, and generates a closed throttle signal, the drag switch operative to move from said second position to said first position prior to the opening of said closed throttle switch and the generation of said first acceleration enrichment pulse, a circuit for generating a tip-in fuel enrichment pulse with the throttle in the closed position in response to the drag switch switching from its first position to its second position comprising: input circuit means for generating a first signal in response to the closed throttle signal generated by the acceleration switch with the throttle in the closed position and the drag switch in the second position, and for generating a second signal in response to the termination of the closed throttle signal generated by the acceleration switch with the throttle in the closed position and the drag switch in the second position; a capacitance and a current source forming an R.C. network, said capacitance being charged to a predetermined value by said first signal, and discharged by said second signal, and said current source recharging said capacitance from its discharged state to its initial value at a predetermined rate; and output circuit means responsive to the charge on said capacitance for generating said tip-in fuel enrichment signal when the charge on said capacitance is below a predetermined value.

12. The combination of claim 11 wherein said acceleration switch has a base fixedly attached to the stationary throttle body and is mechanically linked to the moveable throttle shaft biased in the closed position, said drag switch comprises: a drag rotor pivotally mounted to the moveable throttle shaft; means disposed between said drag rotor and the switch base for generating a frictional force retarding movement of the drag rotor relative to the base; two upstanding contact posts separated from each other by a first predeterminable separation distance and radially disposed from the center of the throttle shaft, a first predetermined radial distance; an upstanding spring post, angularly disposed bEtween said contact posts and radially disposed a second radial distance from the center of the throttle shaft, said second radial distance being substantially less than said first radial distance; means for making electrical contact to said two contact posts and said spring post individually; a driven rotor, fixedly attached to said throttle shaft and adapted to rotate therewith, said driven rotor having two parallel arms stradling said spring post, said parallel arms being separated by a distance slightly greater than the distance between said contact posts, and having a radial length less than said first radial distance and greater than said second radial distance; a pickup bar pivotally attached to said spring post and disposed between said two arms of the driven rotor and said two contact posts, said pickup bar radially extending slightly beyond said contact posts and having a width less than the distance between said two contact posts permitting said pickup bar to freely pivot about said spring post through a predetermined angle defined by said two contact posts; a hair pin spring in continuous electrical contact with said spring post, said hair pin being disposed over said pickup arm and rotatable therewith, said hair pin spring further having two free ended prongs extending radially outward from said spring post a short distance beyond said contact posts, and said prongs further being separated by a distance greater than the width of said pickup bar; and a keeper fixedly disposed at the end of said pickup bar beyond said contact posts, said keeper having a rectangular slot biasing the free ends of said prongs towards each other so that the separation of said prongs proximate said contact posts is slightly less than the distance between said contact posts; wherein the spring bias on the throttle shaft in the closed throttle position causes one arm of the driven rotor to bias the pickup bar against one of the contact posts placing one prong of the hair pin spring in electrical contact with said one contact post and the initial rotation of the throttle shaft against the spring bias causes the other arm of the driven rotor to move the pickup bar away from said one contact post removing said prong away from said one contact post breaking said electrical contact prior to said pickup bar engaging the other contact post and rotating said drag rotor with said driven rotor.

13. The combination of claim 12 wherein said input circuit means includes an input transistor switch having a first state in response to the closed throttle signal and a second state in the absence of said closed throttle signal, said transistor switch in said first state generates said first signal, and in said second state generates said second signal; and wherein said output circuit means includes at least one output transistor switch, said at least one output transistor switch generating said tip-in enrichment signal when the charge on said capacitance is below a predetermined value.

14. The combination of claim 12 wherein said current source includes sensor means responsive to the temperature of the internal combustion engine for controlling said predetermined rate at which said capacitance recharges.