US2273670A - Fuel injection control system - Google Patents

Description

Feb. 17, 1942; s. UDALE 2,273,670 I I FUEL INJECTION CONTROL SYSTEM- Filed March 4. 1946 Patented Feb. 17, 1942 FUEL mmc'rron CONTROL SYSTEM Stanley M. Udale, Detroit, Mich, assignor to George M. Holley and Earl Holley Application March 4, 1940, Serial No. 322,103

4 Claims.

is intermittently admitted to each cylinder froman engine driven pump, and in which the air supply is throttled and in which a supercharger is interposed between the throttling means and the engine. With such an arrangement the air admitted to the cylinder can be both below atmospheric and above atmospheric pressure. It is necessary with such an engine to arrange that when the engine is throttled down, the mixture ratio is maintained at what is known as the cruising lean mixture, which is generally assumed to be in the neighborhood of a ratio of weight of fuel to weight of air of 7 to 100. When the amount of air taken into the engine exceeds 70% of the maximum torque, then the added fuel is needed for two reasons: (1) to develop maximum torque and (2) to prevent the engine overheating.

The vast majority of airplane engines today are air-cooled for obvious reasons. These engines are sensitive to overheating and therefore, it is necessary to provide an excessively rich mixture when developing maximum power to prevent the engine being damaged. About 40% excess fuel is provided above that required ,for cruising lean. In other words, the ratio of fuel to air by weight is the ratio of 11 to 100 instead of 7 to 100. It

is obvious that this transition takes place when the fuel flow is approximately 44% or 70% of A1 of the maximum fuel flow, and this invention relatesto the utilization of the excess flow of fuel for the control of the fuel pump.

By excess flow is meant a flow greater than that which just causes the rod 41 to descend. The value of this excess flow is determined by the stiffness of the spring 21 and the relative size of the throat of the venturi .22.

The type of fuel pump to which this invention is adapted is one in which a piston having a variable effective stroke is controlled by a rack and pinion mechanism which varies the cut-off in the piston stroke. Such a mechanism is well known and is no part'of this invention which relates to the control of the rack which extends from such a pump and engages'with pinions on the individual cylinders, in which cylinders the pistons reciprocate which cause the fuel to be injected into the cylinders at various times and in varying quantities.

In the figure thefuel is shown entering the fuel pump through a venturi 22. The air is shown entering the air entrance l and flowing by a manually controlled throttle II to a supercharger which is connected by a pipe B to a chamber M which contains a barometric responsive element IS, The element I is partially evacuated to say of mercury, so that it also responds to temperature changes. The movement of this element l5 indirectly controls the movement of the rack l6 through a servo motor and the movement of the rack l6 controls the discharge of the fuel pump, which control is of a well known type and therefore is not described in detail.

The means whereby the barometric and temperature responsive element controls the rack I6 is as follows:

The element [5 contains a compression spring II and is connected to a valve which. in its turn is controlled by a compression spring IS, the left hand abutment of which is moved by means of the rack I6 which engages through a pin with a slot in the lever H, which lever l1 carries the left hand abutment of the spring I9.- A fulcrum 34 of the lever I1 is pivoted on a lever 33 which in its turn is pivoted on a pin 35 carried by a bracket projecting from the fuel pump. The valve 20 controls the movement of a piston 2| by admitting oil under pressure alternatively on either side of the piston 2|, which piston is connected directly with the rack It.

It will be seen that assuming a reliable source of oil under constant pressure is available for operating the servo mechanism 20, 2|, that a balance will be struck between the compression of the spring Hand the compression of the"- spring 4| and of the barometric and temperature responsive element l5, under all conditions of the air flow past the throttle H.

In order that the element 15 may respond to the temperature of the air entering the engine, a by-pass forms a restricted return passage from the pressure side of the supercharger l2 to the air entrance III on the engine side of the throttle H. As the pressure created by the supercharger I2 is greater than that in the air entrance l0, air circulates through the passage I3 into the chamber formed by the walls l4 down the restricted passage 80 to the air entrance in.

The action of the element I5 is as follows:

When the throttle II is opened and the pressure in the air entrance l0 increases, the pressure in the chamber II also increases due to the effect of the superchargerv I2. Then the barometric and temperature responsive element l5 collapses under the effect of the increased pressure in the chamber It. In the event that without moving the throttle II the temperature drops as it does at altitude, then the limited amount of air contained in the element l5 contracts and the element 15 therefore collapses slightly due to the temperature effect. For either reason the valve 20 thereupon moves to the right under the influence of the compression spring l9 and against the influence of the compression spring 4| contained in the partially evacuated chamber l5. Oil under pressure is admitted from the passage 42 to the right hand side of the piston 2| and oil escapes from the left hand side of the piston 2| along the passage 43. When the piston 2| moves to the left it carries with it the pin l8 which moves the lever l1 and relieves the pressure on the compression spring l9, permitting the valve 20 to move to the left. Anequilibrium is thus reached, out the effect of moving the rack IE to the left is to increase the flow of fuel in a well known manner, this particular type of fuel pump being in general use on Diesel engines and has recently been adopted for fuel injection engines.

It is possible, therefore, to arrange that the mixture ratio will remain within certain limits substantially constant under all ordinary conditions of temperature and pressure of the air entering the cylinders.

This constant mixture ratio, however, is not a complete solution as maximum power and maximum reliability must also be taken into consideration. For example, it is generally held that '7 parts by weight of fuel to 100 parts by of the venturi 22. The low pressure in the chamber 46 which communicates with the throat of the venturi 22, causes the diaphragm 24 to descend carrying with it the rod 41 upon which is mounted the roller 26 which engages with the bell crank lever 29 which carries with it the roller 25 which engages with the cantilever spring 21 which wraps around the cam-shaped abutment 28. This counter-clockwise movement of the bell crank lever 29 carries with it the valve 3| which permits oil to flow through the restricted opening 48, to pass the valve 3| and through the passage 49 in the center of the piston l8. The ofl pressure entering at 50 communicates through the restricted opening 5| with the right hand side of the piston l8, but there is no flow from the oil pressure entrance 50 through therestriction 5|. Hence the pressure on the right hand ride of I8 is higher than it is on the left hand side of the piston l8. The oil escapes through the opening 49 to the unrestricted oil outlet 52. Hence, as the valve 3| moves to the left, the piston I 8 follows so that the relative weight of air is a satisfactory mixture ratio for economy when cruising lean. power will require a mixture ratio asihigh as 11 parts by weight of fuel to 100 parts by weightof air. 4

This is especially true with air cooled engines.

When the throttle is opened wide enough to develop more than of the maximum mean effective pressure which is equivalent to 70% of the maximum torque, the air flow begins to exceed 70% of the maximum air flow. When an engine operates under cruising conditions the mixture ratio is usually constant at about .069 ratio and this mixture ratio will remain substantially constant over a relatively wide range of air flows. Thej'fair flow corresponds closely to the torque so that the specific fuel consumption pounds per horse power horn is substantially constant over a fairly wide range of air flow. The importance of this is that as torque varies closely with air flow, the fuel flow tends to vary with torque at any given speed. At maximum crease in proportion to air flow and hence in proportion to torque, unless special means are provided to give an increased flow at maximum power. Extra fuel is then required and this extra fuel is obtained by the following mechanism.

The fuel enters the fuel pump through the venturi 22 and as this venturi is connected both on its throat and en its downstream side to opposite sides of the flexible diaphragm 24, the diaphragm 2% begins to move when the pressure exerted by the spring 21 is overcome by the downward pressure exerted by the diaphragm 24. This difference acts against the roller 25 and against the roller 25, and causes the diaphragm stop 44 to move away from the walls of the chamber 45, which chamber communicates with the diaphragm 2 and with the downstream side position of the valves 3| and 18 remain as shown. Hence, as the valve 3| moves so moves the piston I8, and whereas the pressure differences acting on the diaphragm 24 are relatively feeble, a powerful force is available for moving the link 32 and ca yin the fulcrum 34 of the link II in an anti-clockwise direction. The effect of this movement is to enrich the mixture, but having enriched the mixture the temperature and pressure responsive element l5 still continues to control the mixture ratio so that as the pitch of the propeller is changed and the air flow changes, the mixture ratio for any given power will be controlled by the air flow. In other words, the datum line will be changed but the mixture control responsive to air v pressure and a temperature will not be eliminated.

a means for said engine, throttling means therefor, means responsive to the pressure of the air entering said engine for regulating the discharge of said fuel pump, said means being operative throughout the working range of the engine, additional regulating means responsive to the rate of fuel flow to said fuel pump adapted to admit additional fuel to said engine after the fuel flow exceeds approximately 40% of its maxi- 2. A fuel control unit for multi-cylinder internal combustion engines having a fuel injection pump adapted to supply an intermittent supply of fuel independently to each cylinder, air supply means for said engine, throttling .means therefor, means responsive to the pressure of the air entering said cylinders for regulating the discharge of said fuel pump to said cylinders, said means being operative throughout the working range of the engine, additionalregulating means responsive to the rate of fuel flow to said engine adapted to admit additional fuel after the fuel flow exceeds 40% of its maximum flow.

3. 'A fuel control unit for muiti-cylinder internal combustion engines having a fuel injection pump adapted to supply fuel to said engine, air supply means for said engine, throttling means therefor, means responsive to the density of the air entering said cylinders for regulating the discharge of said fuel pump, said means being operative throughout the working ran e of the flow to said fuel pump to regulating means including a valve connected to a movable wall of said evacuated chamber, a

spring engaging with said valve, a servo motor operated by said valve connected to said pump regulating means and to said spring means, additional regulating means responsive to the rate of fuel flow to said fuel pump adapted to operate a second valve, servo mechanism operated by said second valve adapted to act conjointly with the pressure responsive means for regulating the discharge from said fuel pump.

STANLEY M.

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