US3612008A

US3612008A - Vacuum-responsive voltage generator for a fuel injection system

Info

Publication number: US3612008A
Application number: US11428A
Authority: US
Inventors: Richard B Beishir
Original assignee: ACF Industries Inc
Current assignee: Carter Automotive Co Inc
Priority date: 1970-02-16
Filing date: 1970-02-16
Publication date: 1971-10-12
Anticipated expiration: 1988-10-12
Also published as: AR192569A1; DE2106160A1; JPS5023457B1; CA925594A; SE361705B; FR2083068A5; GB1336332A

Abstract

An arrangement for generating an irregularly varying voltage for an automobile fuel injection system includes a potentiometer having a plurality of voltage input taps connected to taps on a voltage divider, and an output tap movable along the potentiometer by a vacuum motor which responds to the pressure in the intake manifold of the automobile engine. The voltage input taps are elongated and are adjustable longitudinally and angularly to provide the required voltage distribution on the potentiometer.

Description

United States Patent Inventor Richard B. Beishir St. Louis, Mo.

Appl. No. 11,428

Filed Feb. 16, 1970 Patented Oct. 12, 1971 Assignee ACF Industries, Incorporated New York, N.\.

VAC UUM-RESPONSIVE VOLTAGE GENERATOR FOR A FUEL INJECTION SYSTEM 5 Claims, 4 Drawing Figs.

11.5. CI 123/32 EA, 123/119 R, 338/120, 338/176 Int. Cl F02n 5/12, F02m 39/00 Field of Search 73/119;

338/120,160,162,176,l79,180185,l88,137, 117, 118; 123/32 EA References Cited UNITED STATES PATENTS 6/1955 Goeppinger et al. 3/1957 Matthew 1 8/1966 Anderson 3/1970 Long Primary Examiner-Mark M. Newman Assistant Examiner-Cort R. Flint Attorney-Edward H. Casey ABSTRACT: An arrangement for generating an irregularly varying voltage for an automobile fuel injection system includes a potentiometer having a plurality of voltage input taps connected to taps on a voltage divider, and an output tap movable along the potentiometer by a vacuum motor which responds to the pressure in the intake manifold of the automobile engine. The voltage input taps are elongated and are adjustable longitudinally and angularly to provide the required voltage distribution on the potentiometer.

PATENTEBUBHZIHY: 3.612.008

SHEET 1 0F 2 2 TO INTAKE MANIFOLD FUEL DELIVERY.

VACUUM -|N. HG.

INVENTOR RICHARD E5. 'BEISHIR ATTORNEY.

PATENTED 0m 1 2 IB'ZI SHEEI 2 [1F 2 E F TO g/ACUUM T T M TOR. I I

)T f Y 2 Z 2 $1 4 ELECTRONIC \28 TIME - CONTROL.

E? F/F- CONTROL VOLTAGE// GENERATOR.

FIG. 4.

INVENTOR RICHARD E5 BIESHIR ATTORNEY.

VACUUM-RESPONSIVE VOLTAGE GENERATOR FOR A FUEL INJECTION SYSTEM BACKGROUND OF THE INVENTION In electronically controlled fuel injection systems it is important to control the rate of fuel feed, and hence the airfuel ratio, precisely according to a predetermined optimum schedule, in order to keep exhaust emissions to a minimum. A principal engine parameter is the intake manifold pressure drop, since it is a measure of the airflow per cycle. The manifold pressure drop varies with engine speed and throttle valve position. The optimum fuel schedule, for at least some engines, requires a voltage versus manifold pressure drop curve having varying curvature and several sharp breaks or changes of curvature. It is an object of the invention, therefore, to produce an output voltage closely in accordance with such a curve over the entire operating range of the engine.

SUMMARY OF THE INVENTION In an electronically controlled fuel injection system a voltage is produced having a desired variation as a function of the intake manifold pressure. A potentiometer has an output tap movable by a piston motor which is connected to sense and respond to the manifold pressure. The potentiometer has a smooth resistive coating on a flat strip and a plurality of voltage input taps. These taps have a linear knife edge resting on the resistive strip and can be turned as well as moved longitudinally. Each input tap is connected to a separate tap on a voltage divider circuit, so that a different voltage can be supplied to each input tap of the potentiometer. Thus, great flexibility is obtained in adjusting the output voltage characteristic of the potentiometer.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagram of an arrangement according to the invention.

FIG. 2 is a section taken along line 2-2 of FIG. 1.

FIG. 3 is a circuit diagram of the apparatus of FIG. 1.

FIG. 4 is a diagram of a fuel injection system utilizing the apparatus of the invention.

FIG. 5 is a plot of fuel delivery versus manifold vacuum for a fuel system employing the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT One type of fuel injection system in which the present invention may be used is shown in FIG. 4. Control voltage generator 10, according to the invention, includes a vacuum sensor (described below) connected by pipe 12 to intake manifold 14 of an internal combustion engine at a point below throttle valve 16. Voltage generator has output terminals E, F connected to electronic control circuits 18 designed to generate pulses having a duration determined by the value of the voltage produced by generator 10. Control circuits 18 are triggered by pulses produced by switch 20, which is actuated by cam 22 driven by the engine, so that switch applies a pulse from battery 24 to control circuits 18 during each switch closing. The output pulses of circuits 18 are fed through a suitable amplifier 26 to the solenoids 28 of a plurality of solenoid injection valves, which remain open for the duration of the pulses supplied to them, and thereby control the amount of fuel fed to the engine. Systems of this type are well known in the art.

In order to obtain maximum engine power and minimum exhaust emissions throughout the engine operating range, the fuel supply must be varied precisely in a complex manner in response to the manifold vacuum. To achieve this result, voltage generator 10 is required to have a predetermined voltage characteristic having three sharply distinct sections of varying curvature, including a section of small slope, another section of medium slope, and a section having a large slope. The apparatus 10 shown in FIGS. 1 to 3 for obtaining the required voltage characteristics includes a voltage source connected to terminal 30,

variable resistors

32, 34, voltage divider 36, and ground terminal F. The voltage divider 36 has a number of parallel connected potentiometers 38 to 43, and

end terminals

44, 46. Potentiometer 50 has

end terminals

52, 54 connected to

terminals

44, 46. The movable taps of potentiometers 38 to 43 are connected to movable taps 56-61 of potentiometer 50. Taps 56-61 are slidable in slot 62 of support plate 64, and are turnable to different angles. Each tap has an elongated edge 66 in contact with the smooth flat surface of resistor strip 67 of potentiometer 50. Resistor strip 67 may include a strip of insulation having a long-wearing resistive coating. The uppermost end of each tap is threaded to receive a locknut 68 for holding its tap in position.

Output tap 70 is slidable in slot 72 of plate 64. Tap 70 is connected to output terminal E by wire 74, and is moved by vacuum motor 76. The latter includes piston 78 movable. in housing or cylinder 80. Coil spring 82 urgespiston 78 tothe left. Conduit 12 applies the vacuum of pressure drop in the in- 1 take manifold to the right-hand end of cylinder 80. Thus, the

higher the vacuum the more piston 78 is moved by air pressure to the right, against the action of spring 82, causing a similar the values of resistances 38-43 are known, the variable resistors can be replaced with fixed resistors and the system will then operate satisfactorily for the particular engine-vehicle combination.

Variable resistors

32, 34 are retained as shown and are used for making slight adjustments in fuel delivery for curb idle and wide open throttle conditions.

The knife edges 66 are useful primarily as a calibration expedient. Once the location and orientation of these edges are determined for a particular engine-vehicle combination, they can be replaced, if desired, by some form of easily manufactured electronic circuitry. An example of such permanent taps would be the familiar printed circuit or even simple solder bars or strips laid down on the surface of the conductive plastic 67.

From the foregoing, it is apparent that the rather complex device of FIG. I can be reduced to a simple, low cost electrical circuit using fixed resistors and conventional techniques to replace the many variables shown. This of course would be done after the system is fully calibrated for a given engine.

Referring to FIG. 5, fuel delivery is plotted against manifold vacuum for a typical engine. Since the injection system delivers a predetermined quantity of fuel for each stroke of each cylinder, the fuel delivery as plotted can be considered to be the amount of fuel delivered for two full revolutions of the engine, e.g. one power stroke from each cylinder. Fuel delivery curve has a portion A of little slope representing curb idle and low part throttle operating conditions of the engine. The portion 8" represents heavier part throttle load and the portion C is representative of maximum load and/or wide open throttle.

To calibrate a fuel injection system for a given engine so as to minimize exhaust emissions, the apparatus shown in FIG. 1 can be adjusted to the degree necessary to cause the fuel delivery curve to have an optimum form, for example, as shown in FIG. 5. Of course for other engines the curve may shift in some degree or other. The necessary calibrating adjustments are achieved by sliding contact arrangements 56 through 61 to any necessary position to match the desired fuel delivery curve. At the same time each blade 66 can be rotated if necessary to further refine the matching characteristics of the curve. Finally any or all of the potentiometers 38 through 43 can be adjusted and when this is accomplished the fuel delivery curve should be exactly as desired. Once the values for the resistances 38-43 are known then each can be replaced with suitable fixed resistances for economical and low cost manufacture of a complete system for a given engine vehicle combination.

lclaim:

1. In a fuel injection system for an automobile internal combustion engine including a potentiometer controlling the rate of fuel injection; means for applying voltage to the potentiometer, the potentiometer having a movable output tap, and vacuum sensing means connected to the intake manifold of the engine for moving the output tap in accordance with the pressure in the intake manifold; electronic control circuit means having its input'connected to the movable tap of the potentiometer and its output connected to a plurality of electronically operated fuel injection valves; the improvement consisting in that the potentiometer includes an elongated resistive member having a series of input taps spaced longitudinally therealong; means for mounting each input tap for longitudinal adjustment and independent transverse adjustment toward and away from the path of the output tap, said means for applying voltage being connected to each input tap for applying independently adjustable voltages thereto.

2. Apparatus according to claim 1 wherein said input taps have an elongated substantially linear contact with said resistive member and each of said input taps is adjusted transversely by rotating the line of contact of each tap on the resistive member.

3. In a fuel injection system for an automobile internal combustion engine including a potentiometer controlling the rate of fuel injection; means for applying voltage to the potentiometer, the potentiometer having a movable output tap, and

vacuum sensing means connected to the intake manifold of the engine for moving the output tap in accordance with the pressure in the intake manifold; electronic control circuit means having its input connected to the movable tap of the potentiometer and its output connected to a plurality of electronically operated fuel injection valves; the improvement consisting in that the potentiometer includes an elongated flat resistive strip having resistive material on at least one surface thereof; a row of input taps on one side of the resistive strip spaced longitudinally therealong, the path of the movable tap being parallel to and near one edge of said resistive strip, said means for applying voltage being connected to the input taps for applying progressively increasing adjustable voltages thereto, each of said input taps having an elongated narrow edge in contact with said surface of the resistive strip; and means for mounting said input taps for limited longitudinal adjustment along the resistive strip and for rotation of the elongated edge of each input tap on the resistive strip.

4. Apparatus according to claim 3, wherein each input tap is turnable for setting the line of contact thereof with the resistive strip to any angle between a longitudinal and a transverse position.

5. Apparatus according to claim 4, wherein the input taps have an inverted T-shape consisting of a stem perpendicular to the surface of the resistive strip and a blade at the end of the stem having an elongated edge in contact with the surface of the resistive strip, said stem being rotatable on its axis for turning the elongated edge thereof.

Claims

1. In a fuel injection system for an automobile internal combustion engine including a potentiometer controlling the rate of fuel injection; means for applying voltage to the potentiometer, the potentiometer having a movable output tap, and vacuum sensing means connected to the intake manifold of the engine for moving the output tap in accordance with the pressure in the intake manifold; electronic control circuit means having its input connected to the movable tap of the potentiometer and its output connected to a plurality of electronically operated fuel injection valves; the improvement consisting in that the potentiometer includes an elongated resistive member having a series of input taps spaced longitudinally therealong; means for mounting each input tap for longitudinal adjustment and independent transverse adjustment toward and away from the path of the output tap, said means for applying voltage being connected to each input tap for applying independently adjustable voltages thereto.

3. In a fuel injection system for an automobile internal combustion engine including a potentiometer controlling the rate of fuel injection; means for applying voltage to the potentiometer, the potentiometer having a movable output tap, and vacuum sensing means connected to the intake manifold of the engine for moving the output tap in accordance with the pressure in the intake manifold; electronic control circuit means having its input connected to the movable tap of the potentiometer and its output connected to a plurality of electronically operated fuel injection valves; the improvement consisting in that the potentiometer includes an elongated flat resistive strip having resistive material on at least one surface thereof; a row of input taps on one side of the resistive strip spaced longitudinally therealong, the path of the movable tap being parallel to and near one edge of said resistive strip, said means for applying voltage being connected to the input taps for applying progressively increasing adjustable voltages thereto, each of said input taps having an elongated narrow edge in contact with said surface of the resistive strip; and means for mounting said input taps for limited longitudinal adjustment along the resistive strip and for rotation of the elongated edge of each input taP on the resistive strip.