Fuel injection system for an internal combustion engine

Abstract

Fuel injection apparatus for an internal combustion engine in which separate electro-mechanical control valves are operated to begin and end each fuel injection period in timed relation to the internal combustion engine by closing off the spill path to begin an injection period and by opening the spill path to end the injection period.

Description

The invention relates to fuel injection apparatus for internal combustion engines and more particularly to apparatus in which fuel is injected into the cylinders of the engine under the control of electro-mechanically operated fuel injection valves.

The present invention has all the advantages of co-pending application Ser. No. 260,882 now U.S. Pat. No. 3,779,225, and in addition avoids the requirement of fast acting solenoid operated control valves for controlling the amount of fuel dispensed by a reciprocating piston pressure pump. In the arrangement described in the co-pending application a single solenoid operated control valve controls the injection period. In the present application separate electromagnetic control valves control the beginning and end of the fuel injection period in timed relation to rotation of the cam shaft or crank shaft of the internal combustion engine.

By using two valves in the manner described briefly above, the time interval for operation of any one valve in an eight cylinder engine is 2.88 milliseconds when the engine is at fast idle at 2600 rpm; whereas when only a single valve is used the valve must open and close in 0.15 milliseconds.

The present invention has further advantages over the apparatus described in copending application Ser. No. 260,882, now U.S. Patent No. 3,779,225, in that the apparatus of the present invention uses a distributor for periodically connecting the high pressure pump to the delivery valves in timed relation with the internal combustion engine and only two electromagnetic valves are needed in the present apparatus for controlling the injection period. One valve starts the injection period and the second valve ends the injection period.

The invention contemplates a fuel injection system for an internal combustion engine having a pumping unit for pressurizing fuel, a distributor connected to the pumping unit and receiving fuel under pressure from the pumping unit for delivery in timed sequence to the engine, and a pair of electro-magnetic valves operated in timed relation to the engine and receiving fuel under pressure from the pumping unit and connected to a spill path, the valves being arranged so that one valve closes the spill path to begin a fuel injection period to the engine and the other valve opens the spill path to end the fuel injection period.

One object of the present invention is to provide fuel injection apparatus which avoids the use of fast acting magnetic valves.

Another object of the invention is to use separate electro-magnetic control valves to begin and end the fuel injection period and to use only two valves regardless of the number of cylinders in the engine.

These and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein two embodiments of the invention are illustrated by way of example. It is to be understood, however, that the drawings are for the purpose of illustration only and are not a definition of the limits of the invention, reference being had to the appended claims.

IN THE DRAWINGS

FIG. 1 is a side view partly in section of a fuel injection pump constructed according to the invention,

FIG. 2 is an end view thereof with a portion in section,

FIG. 3 is a vertical section taken approximately on the line 3--3 of FIG. 2 and shows one of the electro-magnetic valves in detail,

FIG. 4 is a timing chart showing sequence of operation of the electro-magnetic valves in the four cylinder pump of FIGS. 1 to 3,

FIG. 5 is a longitudinal section of a second embodiment of a fuel injection pump constructed according to the invention,

FIG. 6 is an end view showing the cap at one end of the pump shown in FIG. 5,

FIG. 7 is an end view of the pump shown in FIG. 5 with the cap and rotor removed, and

FIG. 8 is a timing diagram for a four cylinder pump as shown in FIGS. 5 to 7.

The fuel injection pump shown in FIG. 1 and constructed according to the invention is intended for use on a four cylinder, four stroke, diesel engine although the pump can be adapted to either diesel or stratified charge engines of two or four stroke design with any practical number of cylinders.

The fuel injection pump shown in FIG. 1 has a cam shaft 3 which is driven for a four-stroke engine, by the engine at one-half engine speed. A high pressure pumping unit 1 has a plunger 4 which reciprocates in a pumping chamber 4A. Plunger 4 is driven by cam shaft 3 through a cam and cam follower in the usual manner. A transfer pump 2 connected to a fuel tank (not shown) delivers fuel to pumping chamber 4A through an inlet port 4B. The fuel in pumping chamber 4A is pressurized by reciprocation of plunger 4 and is pumped through a check valve 5 and passages 6 and 7 to passages 8 and 9.

A distributor rotor 10 is driven by cam shaft 3 and connects passage 9 sequentially to delivery valve assemblies 30A, 30B, 30C and 30D to which high pressure lines to each engine cylinder are connected. High pressure lines (not shown) are connected to nozzle holder assemblies (not shown) for each cylinder. A plurality of slots 11A, 11B, 11C and 11D are spaced about the periphery of rotor 10 and communicate with passages 12 and 13 and port 14 in rotor 10. Passages 15A, 15B, 15C and 15D are connected to delivery valve assemblies 30A, 30B, 30C and 30D, respectively. As rotor 10 rotates slots 11A, 11B, 11C and 11D in rotor 10, register in sequence with passage 9, and port 14 in rotor 10 registers in sequence with passages 15A, 15B, 15C and 15D (FIG. 2). Fuel flows from passage 9 through a registering slot 11A, 11B, 11C or 11D, passages 12 and 13 and port 14 to passage 15A, 15B, 15C or 15D, respectively, and to the associated delivery valve 30A, 30B, 30C or 30D, respectively, for injection into the associated cylinders.

Fuel is delivered under pressure to the delivery valves only for that period of the actual injection which is controlled by two electro-magnetic valves 16 and 16A (FIG. 2). The purpose of the valves 16 and 16A is to spill to a low pressure region, all the fuel being delivered by pumping unit 1 except during the short injection period which may vary between 1.5 milliseconds at full load operation to as little as .15 millliseconds at fast idle, depending on such factors as engine speed, number of cylinders, etc. Each of the valves when deenergized is open and connects passage 8 to spill passage 28 connected through spill outlet 46 (FIG. 2) to the fuel tank. One valve begins the injection period by closing the spill path and the other valve ends the injection period by opening the spill path.

When valve 16 is in the energized closed position as shown in FIG. 1, fuel under pressure in passage 8 in communication with annulus 21 is blocked and fuel cannot flow through valve 16 to spill passage 28. Similarly, valve 16A when energized is closed so that passage 8 is not in communication with spill passage 28. Thus, when both valves 16 and 16A are energized simultaneously fuel is delivered to one of the cylinders during this time as determined by the angular position of the distributor rotor 10. At the end of a delivery period valve 16 is deenergized and plunger 17 moves to the open position as shown in FIG. 3 so that annulus 21 communicates with groove 22 in the plunger and annulus 27 in communication with spill passage 28 communicates with groove 26 in the plunger. Grooves 22 and 26 are connected by a port 23, a passage 24 and a port 25. Fuel flows from annulus 21, through groove 22, port 23, passage 24, port 25 and groove 26 to annulus 27 through passage 28 and spill outlet 46 to the fuel tank.

A timing diagram for operating electro-mechanical valves 16 and 16A (referred to as valves 1 and 2 in the diagram) under full load at 2500 rpm and at fast idle at 2600 rpm is shown in FIG. 4. At zero degrees injection into cylinder A starts when valve No. 1 closes since valve No. 2 is in closed position having been energized earlier by a power pulse. Under full load at 2500 rpm, injection terminates at 10.degree. when valve No. 2 is deenergized and returns to open position. At 45.degree. valve No. 1 opens and both valves are open until 55.degree. whereupon valve No. 2 closes. At 90.degree. valve No. 1 closes and fuel is injected into cylinder B for 10.degree.. At 100.degree. valve No. 2 again opens and terminates the injection period. The valves continue to operate in this sequence as shown in FIG. 4 under full load at 2500 rpm. Each injection period lasts 10.degree. or 1.33 milliseconds and each valve operates every 45.degree. or 5.98 milliseconds.

When the engine is operating at fast idle at 2600 rpm, at 0.degree. valve No. 2 is closed and valve No. 1 is operated to closed position to start the injection period to cylinder A. At 11/2.degree. valve No. 2 opens and ends the injection period to cylinder A. At 45.degree. valve No. 1 opens and at 461/2.degree. valve No. 2 closes. At 90.degree. valve No. 1 closes and begins an injection period to cylinder B which is terminated at 911/2.degree. upon opening valve No. 2. This sequence is continued for cylinders C and D. The injection periods at fast idle at 2600 rpm are 11/2.degree. or 0.192 milliseconds and each valve operates every 45.degree. or 5.76 milliseconds.

Valves 16 and 16A are energized by signals timed to the angular position of the engine crank shaft. The signals may be advanced mechanically or electronically as a function of engine speed if desired. The signals are converted to power pulses by a suitable electronic circuit (not shown) and the duration of the power pulses may be varied as a function of engine parameters and ambient conditions so that the power pulses energize the electro-magnetic valves 16 and 16A to supply the correct quantity of fuel required by the engine for desired operation. The power pulses must precede valve operation by a reaction time which is a function of the electro-magnetic circuit characteristics, physical properties of the valve, friction spring characteristics, etc.

The signals for energizing valves 16 and 16A are generated by a disk 38 of ferrus material having either a slot or projection in its periphery and rotated by cam shaft 3 (FIG. 1). Coils 41 are radially disposed about the periphery of disk 38 so that the signals are induced in the coils and are angularly timed with the engine crank shaft. The signals are transmitted by conductors 40 to the electronic circuit for conversion to power pulses. The power pulses are applied to conductors 29 connected to solenoid coils 20 on valves 16, 16A as shown in FIG. 3. An armature 19 connected to plunger 17 is magnetically attracted to the fixed pole of the solenoid when coil 20 is energized. A conical engagement of the armature and fixed pole is employed to increase the stroke - air gap ratio and solenoid efficiency. When plunger 17 moves through a portion of its stroke and has reached a high speed, communication between annulus 21 and annulus 22 is suddenly interupted and high pressure fuel is permitted to flow from passage 9 through delivery valve 30A to engine cylinder A as previously described. Fuel delivery to the engine cylinder is suddenly terminated when the power pulse is removed from either coil 20 as plunger 17 is moved by a spring 18 to its open position in which annulus 21 communicates with spill outlet 46 and pressure in passage 7 is reduced below that required to hold delivery valve 30A open.

Any fuel that might leak around plunger 17 finds its way into cavity 44 or cavity 42 which are connected with leakage return fitting 39 through passages 45, 31, 32 and 33. Likewise any fuel leaking from distributor 10 passes to cavity 34 which communicates with the leakage return fitting 39 through passage 35, cavity 36, ports 37 and passages 32 and 33. Leakage return fitting 39 communicates with the fuel tank.

While the invention is embodied in a four cylinder pump any type of pump capable of supplying uniform high pressure fuel flow at a rate equal to or greater than the instantaneous engine fuel requirement may be used. Even a pump having a lower flow rate can be used with a suitable accumulator.

FIGS. 5, 6 and 7 show a second embodiment of the invention which operates in the same manner as the embodiment shown in FIGS. 1, 2 and 3, the main difference being in the high pressure fuel supply pump. The embodiment of FIGS. 1, 2 and 3 uses an in-line high pressure fuel supply pump whereas the embodiment of FIGS. 5, 6 and 7 uses a distributor type pump. Other minor differences will be apparent from the following description.

Referring to FIG. 5, the fuel injection pump shown therein has a rotating distributor 106A having plungers 102 which are simultaneously displaced in a radial direction by a stationery internal cam 103 to supply fuel under high pressure. Cam 103 has a number of cam lobes equal in number to the number of high pressure outlets 112. Fuel enters the suction side of transfer pump 104 equipped with a pressure regulating valve 105 through a passage 105A from the fuel tank and filter (not shown) and is delivered through passages 107A at suitable pressure to inlet passages 107 in rotor 106 of distributor 106A. When inlet passages 107 in rotor 106 are closed, that is, inlet passages 107 are not in registry with passages 107A because of the angular position of distributor 106A, fuel from transfer pump 104 is by-passed through pressure regulating valve 105 to the suction side of transfer pump 104.

Rotor 106 is rotated by shaft 122 and timed to the engine crank shaft. As rotor 106 rotates inlet passages 107 register with passages 107A and cam 103 allows plungers 102 to be displaced radially in an outward direction by fuel entering the cylinder between the plungers under transfer pump pressure. Of course, springs may be employed if necessary to increase the outward force on the plungers. As plungers 102 reach their maximum separation, inlet passages 107 close by moving out of registry with passages 107A, and delivery passage 108 in rotor 106 registers with a passage 124 connected to a delivery valve 112A. Simultaneously, plungers 102 are moved radially toward one another by a cam lobe and pressurize the fuel which is displaced through a passage 123 to a registering high pressure delivery passage 124 and associated delivery valve 112A. Fuel also is displaced through groove 125 into annulus 109 in rotor 106 through passages 126 to annuli 127.

When the solenoid of either or both valves 111 are deenergized and in open position pressurized fuel flows through the spill path to the fuel tank. Fuel flows through the deenergized valve to the spill path through annulus 127, through annulus 128, passages 129, 130 and 131 and annulus 132 in the valve and through annulus 133, passage 134, annulus 110, passages 135 and 136 and through an outlet fitting 142 to the fuel tank.

Injection of fuel into the appropriate engine cylinder occurs when both solenoid valves are energized to their closed position to close the spill path. Fuel under high pressure then flows through passage 123 in rotor 106 to the registering passage 124 and associated delivery valve 112A to the engine cylinder.

Fuel leaking from solenoid valve pistons 137 into cavities 138 is returned to the suction side of the transfer pump through passage 139. Also, fuel leaking into cavity 140A is returned through similar passages (not shown) to the suction side of the transfer pump. Valves 111 are closed by energization of a solenoid 141 by signals generated by a rotor 113 which is angularly timed to the engine crank shaft to pass the pole of a trigger coil 117 and induce a pulse in the trigger coil. The trigger coil is connected by conductors 118 to terminals 115 molded in cap 119. Terminals 115 are connected to an electronic circuit (not shown) for converting the signals to power pulses for energizing the solenoid valves. Suitable electrical conductors (not shown) connect the electronic circuit to terminals 115A (FIG. 6) also molded in cap 119. From terminals 115 power pulses flow through conductors 116 and spring terminals 114 to the grounded coils 141 of the solenoid valves 111. Valves 111 are opened by springs 140 when coils 141 are deenergized. With this arrangement in case of failure of the electrical system generating the control pulses, the engine will stop.

At the beginning of each pumping period of plungers 102 one valve 111 is closed and the other valve is open so that fuel is displaced through the open valve to the spill path. Injection begins by energizing the open valve 111 to closed position. High pressure fuel delivery to the engine continues until the first valve 111 is deenergized and opens to permit fuel to flow to the spill path.

The timing arrangement for a four cylinder pump shown in FIGS. 5 to 7 is shown in FIG. 8. The injection pulses occur every 90.degree. of cam rotation and each valve opens or closes every 45.degree.. The injection period .theta..sub.m is varied by changing the angular overlap in which both valves 101 and 102 are closed to vary the quantity of fuel delivered to the engine cylinders. If injection advance or retardation is desired, .theta..sub.t is varied by advancing or retarding the events of both valves 111 simultaneously with respect to a fixed point in the engine cycle.

A fuel injection pump constructed according to the invention avoids the use of extremely fast acting valves and requires the use of only two valves regardless of the number of cylinders in the engine.

Claims

What is claimed is:

1. A fuel injection system for an internal combustion engine having a pumping unit for pressurizing fuel;

a distributor connected to the pumping unit and receiving fuel under pressure from the pumping unit for delivery in timed sequence to the engine; and

a pair of electro-magnetic valves receiving fuel under pressure from the pumping unit and connected to a spill path, and means for providing electrical signals in timed relation to the engine to operate one valve to close the spill path to begin a fuel injection period to the engine and to operate the other valve to open the spill path to end the fuel injection period.

2. A fuel injection system as described in claim 1 in which only two electro-magnetic valves are required irrespective of the number of cylinders in the engine.

3. A fuel injection system as described in claim 1 in which both valves are closed during the fuel injection period.

4. A fuel injection system as described in claim 3 in which both valves are energized during a fuel injection period.

5. A fuel injection system as described in claim 1 in which the means for pressurizing the fuel are reciprocating pistons operated by a cam in timed relation to the engine to periodically pressurize the fuel during a fuel injection period.

6. A fuel injection system as described in claim 1 in which the means for providing electrical signals comprises a rotor timed to the engine crank shaft and a plurality of trigger coils associated therewith.