Modulus metered fuel injection system

June 13, 1961

F. W. HOTTENROTH 2,988,077

MODULUS METERED FUEL INJECTION SYSTEM

Filed Feb. 24, 1958

<img file="US2988077A_D0001.tif" />

United States Patent Office

2,988,077

Patented June 13, 1961

2,988,077

MODULUS METERED FUEL INJECTION SYSTEM Frederick W. Hottenroth, 2472 Overlook Road, Cleveland Heights, Ohio

Filed Feb. 24,1958, Ser. No. 717,178

Claims. (CI. 123—140)

This invention relates to a fuel injection system for internal combustion engines in which the modulus of elasticity of the fuel itself is the measuring index for the successive charges of fuel delivered to the engine during the cycles of operation thereof.

One of the biggest problems in connection with present day fuel injection systems is the accurate metering of fuel into each cylinder so that each cylinder receives exactly the amount of fuel required for proper proportioning to the mass of induced air under the conditions existing at the moment. It is also extremely desirable that the system be responsive to changes with a minimum of time lag.

One object of my present invention is to provide a system which solves both of these problems and in addition is simple, both structurally and in operation, and is low in cost.

The common method of metering fuel for a fuel injection system measures slugs of fuel and distributes them to individual cylinders through piping having considerable volume. The fuel is injected either directly into the cylinder or at the intake valve. A spring-closed nozzle is generally used. The measurement is generally accomplished by a variable volume cylinder and piston pump. The slug volume is adjusted by suitable means affected by existing conditions.

Another object of my invention is to provide a small container or reservoir for fuel metering purposes preferably located closely adjacent each cylinder and which reservoir has a definite volume proportionally related to the modulus of elasticity of the fuel being used and to the change in volume of such fuel as between the maximum pressure thereof furnished by a fuel pump and the minimum pressure thereof resulting from the opening of a fuel admission valve from the fuel metering reservoir to the engine cylinder or its intake. To prevent undesirable additonal flow of fuel from the fuel pump, a restriction is placed in the line leading from the fuel pump to the fuel metering reservoir, preferably just ahead of the reservoir.

A further object is to provide a fuel injection system in which the fuel charge is essentially dependent upon the fuel pressure so that by regulation of the fuel pressure it is possible to regulate the amount of fuel charge in response to existing conditions.

Still a further object is to provide a system in which the pressure in a fuel manifold is regulated by a by-pass type of regulator which itself is automatically varied to meet fuel requirements in response to manual control to change the speed of the engine modified by other factors such as air charge density, mass air flow, rich start mixture, rich idle mixture, rich mixture to obtain maximum power at full load operation and/or full throttle operation, acceleration and control associated therewith to prevent a momentary lean mixture condition upon sudden opening Of the engine controlling throttle, fuel cut-off during deceleration, barometric pressure, ambient temperature and the like.

An additional object is to provide means in the system to permit use of lower pressures for the same size of container by the inclusion in the fuel metering reservoir of a material such as foam rubber, a rubber bag filled with air or the like, which has a lower modulus of elasticity than the fuel.

A final object is to provide a modulus metered fuel injection system wherein fuel is supplied under pressure to a cylinder of an internal combustion engine and means is provided for controlling the fuel from the supply com⁵ prising a fuel metering reservoir having a volume substantially equal to the change in such volume divided by the product of the modulus of elasticity of the fuel being used and the change in pressure of such volume, a restriction being provided between the fuel supply and the 1° fuel metering reservoir, a fuel admission valve being provided between the fuel metering reservoir and the cylinder, and means being provided which is cyclically operable for opening the fuel admission valve.

With these and other objects in view, my invention consists in the combination of elements constituting my modulus metered fuel injection system, whereby the objects above contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in detail on the accompanying drawing, wherein:

²⁰ FIG. 1 is a diagrammatic view of a modulus metered fuel injection system embodying my invention;

FIG. 2 is a diagrammatic view of an internal combustion engine with a fuel metering reservoir, fuel admission valve and a restriction of my system, shown in conjunc²⁵ tion therewith;

FIG. 3 is a diagrammatic view illustrating the metering action of the fuel metering reservoir of my fuel injection system;

FIG. 4 is a similar diagrammatic view showing a modi⁰ cation of the fuel metering reservoir and the action involved; and

FIG. 5 is a diagrammatic view showing another modification of my system in which a restriction for fuel flow consists of a fuel shut-off valve.

On the accompanying drawing, I have used the reference character FT to indicate a fuel tank from which a fuel pump FP pumps fuel through a filter F to a fuel manifold FM. The pressure of the fuel in the manifold FM is regulated by a pressure regulator PR of the by-pass type. Conduits 10, 12 and 14 convey the fuel from the fuel tank FT to the fuel manifold FM and return conduits 16 and 18 convey the by-passed fuel controlled by the pressure regulator PR from the fuel manifold FM 45 back to the fuel tank FT.

The system is shown in FIG. 1 as connected with a four cylinder internal combustion engine, the cylinders of which are indicated at C¹, C², C³ and C⁴. Conduits 20, 22, 24 and 26 lead from the fuel manifold FM to fuel 5θ metering reservoirs FMR and a restriction R is located ahead of each reservoir. The reservoirs communicate with fuel admission valves FAV terminating in nozzles N directed into the respective cylinders or into the intake manifold adjacent the intake valves for the cylinders. An 55 alternative arrangement is shown in my copending application Serial No. 725,384, filed March 31, 1958, now Patent No. 2,924,207, wherein there is one fuel metering reservoir for all cylinders of an engine and the fuel admission valve is also a distributor valve.

In operation, fuel pressure is built up in the system by operation of the fuel pump FP as from an electric motor M and this pressure extends throughout the elements 12, F, 14, FM, 16, 20, 22, 24, 26, R, FMR and FAV of the system. The pressure, of course, must be built up in 65 each fuel metering reservoir FMR between the successive fuel injection cycles thereof, and the restrictions R (in the nature of conduits with capillary bores or pierced diaphragms in which the perforations are only a few thousandths of an inch in diameter) are calculated to 70 take this into consideration. The fuel in each reservoir FMR is compressed an amount proportional to the applied pressure. This compressed fuel is held captive in

2,988,077 the reservoir FMR until the fuel admission valve FAV is opened whereupon a change of fuel is injected into the engine cylinder because of the expansion of the fuel in the fuel metering reservoir. The quantity of the charge of fuel injected is essentially equal to the volume change of the fuel resulting from the effect of the pressure change on the compressibility of the liquid. There will be a small additional amount of fuel delivered because of the flow of fuel through the restriction R while the valve FAV is open but this is negligible because of the small size of the restriction and the valve being open for only a short period of time.

To illustrate the fuel metering action, reference is made to FIG. 3 wherein the fuel metering reservoir FMR has volume V represented by the area of a rectangle b, c, f, e and V_c (rectangle a, b, d, e) represents a change in volume so that V plus V_c is the total volume of fuel when not under pressure and V is the volume thereof when under pressure. When the fuel admission valve FAV is opened, the compressed fuel in FMR expands and displaces the quantity V_c into the engine cylinder.

Assume the fuel to be gasoline. Gasoline has a compressibility factor which gives a reasonable size volume for the reservoir FMR. A typical 8-cylinder gasoline engine consumes about .005 cubic inch per cycle per cylinder at 2,000 r.p.m. which decreases to about .004 cubic inch per cycle at 500 r.p.m., and also at 4,000 r.p.m. it decreases to about .004 cubic inch. A pressure of 1,000 p.s.i. compresses gasoline 0.7 percent or .007 of its original volume. Therefore, using the average figure of .005 for calculations, a volume of reservoir necessary to compress gasoline this amount would be 0.7 cubic inch at each cylinder. In other words, a reservoir having a volume of 0.7 cubic inch and fuel that is compressed 0.7 percent by 1,000 p.s.i. results in the calculation .7X.007 which gives an answer of approximately .005 which is needed as the cubic inch per cycle per cylinder requirement. This can be stated as an equation, as follows:

<img file="US2988077A_D0002.tif" />

in which

F=volume of fuel metering reservoir V_e=desired change in volume of fuel K=modulus of elasticity of the fuel, and P_c=change in pressure of volume V which can be worked out as

XjS7^X1000=S⁼7^{=approximately 7 CU}·ⁱⁿ·

The value .000007 (modulus) is the change in volume per unit volume per square inch.

Referring to FIG. 4, if a compressible body B is placed in the fuel metering reservoir, the volume of the reservoir can be reduced inversely proportional to the modulus ratio of such body to gasoline. The body B must, of course, have a lower modulus of elasticity than the gasoline and sponge rubber is suitable for this purpose. The volume of the body B is indicated as V_x (the entire solid line circle) whereas an applied pressure may reduce the volume to V₂ (the small dotted circle). The compressed volume of the fuel equals the sum of the two volumes to be compressed. One of these is the volume of the body B and the other is the volume of the difference between the volume of the reservoir FMR and the body B. This sets up an equation as follows:

V_c—Desired total change in volume of fuel V_e=K_lV₁P_e+K(V-V₁)P_e

V^K^P.+KVP.-KViP.

KVP_e= V_a-K₁V₁P_c+KV₁P_c

V_c Κ,Υ,Ρ, ,kv,p_cKP_a KP„ ⁺ KP„

Transposing:

„__V_c , KFi-Κ,Τι ' kpS K in which

K!=Modulus of elasticity of compressible body, and T^z'₁=Initial volume of compressible body

In my system it will be noted that the fuel charge is essentially dependent upon the fuel pressure. Therefore, by regulation of the fuel pressure it is possible to regulate the size of fuel charges to match existing conditions. Primarily this regulation may be done at the fuel manifold FM by the pressure regulator PR, by electric variation of the energization of the pump motor M, or by any other suitable means.

The pressure in the fuel manifold FM is regulated by the regulator PR which in itself may be automatically varied to meet fuel condition requirements by a diaphragm 28 which, in addition to sensing the pressure in the line 16 to provide automatic pressure regulation of by-pass type, senses air intake manifold conditions (AIM in FIG. 1) which in turn are varied by foot acceleration position by reason of the accelerator controlling a butterfly valve for the intake to the engine cylinder. The 4 action of the pressure regulator may be modified by other factors such as rich start mixture, fast idle throttle, * barometric pressure, etc. These modifying conditions are indicated RSM, FIT and BP respectively in FIG. 1. ^r

During the operation of the system the fuel passes through the restriction R and builds up pressure in the fuel metering reservoirs FMR until it reaches the manifold pressure value before it is time to open the valve FAV. This valve opens during the intake stroke of the engine piston shown at 30 in FIG. 2 in the cylinder C¹. For instance, it may be opened by a push rod 31 actuated by a cam 32 on the intake cam shaft 34 which also actuates the intake valve 36 of the engine. When the pressure of the fuel held in the metering reservoir FMR is released, the fuel expands and the volume of expansion is discharged through the nozzle N. Shortly thereafter the valve FAV is reclosed and pressure again builds up in the container FMR as the fuel is admitted through the restriction R.

Alternate arrangements may be used based on the same basic operating principle that the modulus of elasticity of the fuel itself is the metering characteristic of the system. Instead of a restriction R as in FIG. 1, a ’ fuel shut-off valve FSV may be used as shown in FIG.

which closes before the valve FAV opens and reopens after the valve FAV recloses. A desired quantity of fuel _fis thus held captive in the reservoir FMR between the closing of the valve FSV and the opening of the valve FAV. This makes a system which is theoretically correct volume-wise since it eliminates the flow through the restriction R during the charge period of the reservoir FMR, and it also eliminates the small hole of the restriction R which is subject to clogging during operation in case the fuel is dirty.

Some changes may be made in the construction and arrangement of the parts of my modulus metered fuel injection system without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may reasonably be included within their scope.