US2091401A - Fuel injection system - Google Patents

Description

A g. 3 1931. B. WALKER ET AL 091 401 FUEL INJECTION SYSTEM Filed Jan. 2, 1935 INVEN TOR. BROOKS WALKER.

HARRY E. KENNEDY A TTORNEYS.

4 fuel pressure are automatically relatively regu- Patented Aug. 31, 1937 PATENT OFFICE FUEL INJECTION SYSTEM Brooks Walker, Piedmont, and Harry E. Kennedy, aerllgiley, Calih; said Kennedy assignor to said a er Application January 2, 1935, Serial No. 120 I 3 Claims. (Cl. 123-32) This invention relates to internal combustion engines of the type operating on the Diesel cycle, and is a reflling in part of the abandoned application flied in the United States Patent Ofllce Ser. No. 455,734 dated May 26, 1930 for Fuel injection system by Brooks Walker and Harry E. Kennedy.

Diesel engines heretofore have had their greatest application in fields where flexibiilty'was not a primary requisite. Their outstanding economic advantages, however. makes it certain that they will eventually invade those fields wherein their lack of flexibility has previously barred them. A Diesel cycle with a fuel injection system which would make it comparable with an Otto cycle with regard to flexibility should enable the Diesel engine to enter a hostof new fields.

It is apparent to those skilled in the art, that flexibility implies the ability of the engine to automatically exert its full load torque at any speed, which further implies a constant volume fuel injection per revolution regardless of the speed. The jerk" system deals with thisphase of the problem, but there are many disadvantages to this system which we eliminate and overcome by utilizing a pressure rail system.

It is the principal object of the present invention to increase the flexibility and improve the operation of Diesel engines by providing a line pressure fuel system therefor wherein the angle of the duration of spray valve opening and the lated to obtain a constant quantity fuel injection per cycle at full throttle setting regardless of speed, which, of course, results in the engine automatically exerting its full load torque at any speed.

We desire to point out that if the oil pressure varies approximately as the square of the engine speed constant torque would result in an engine -whose injection valve lifted during a, constant angle of crank shaft movement. Also, a fuel system wherein the fuel injection valve is caused to remain open a constant time duration regard-' less of engine speed and a constant pressure applied to the fuel it is evident that this too. will inject a constant quantity of oil per cycle regardless of speed, and so result in constant opening must vary as the reciprocal of the torque at any speed. While either of the above described systems will make an oil engine operate flexibly, it may prove desirable in engines of great speed range to use both systems cooperatively.

To point out the desirability of doing this, assume that the constant duration injection system is used and the speed range required is extensive. The crank angle during which. injection occurs is then proportional to speed so that at the highest speed it may be necessary to prolong m the fuel injection over an are too long for emcient combustion. Similarly, where the speed controlled pressure system is employed wherein the injection pressure varies approximately with the square of the engine speed, if the speed range be great, the pressure changes required to satisfy the aforementioned relationship may become enormous and impractical.

By utilizing certain features of the two sys- 20 terns in such a manner that equal metering results a system would result which would be applicable to engines of great speed range. The constant time opening arrangement would be improved by a pressure raising with speed, because at the higher speed less time is available for combustion, and it is believed that higher injection pressures are more favorable to rapid combustion. Therefore, less advance will be required. The variable pressure system will be im.. proved by making the pressure change less drastic than is required by the square law because fuel penetration is a function of pressure. The pressure range should notbe too great else excessive penetration and consequent carbonizetion will occur due to fuel oil reaching to the engine parts.

. In the presentvapplication we disclose how certain variables may be coordinated so that proper metering will result. The quantity of oil which will pass through a given oriflce, such as an injection nozzle is approximately proportional to the product of duration of injection and to the square root of the difference in pressure existing on opposite sides of orifice. Assuming that it is desirable to let the pressure vary directly with the engine speed, then the duration of square root of the engine R. P. M. algebraically:

Q=quantity of oil discharge per cycle T=duration of valve opening 5 N=R. P. M.

P=net pressure acting to force oil into the cylinder K=a constant K2=a constant Expressed But Q is to remain constant by hypothesis. Therefore T must vary as If means are employed to vary the pressure, automatic or manual pressure and/or speed actuated members can alter the normal duration 30 of injection as provided by the engine cam or other means to effect equal metering. In practice it is convenient and conventional to interpose taper wedges between disjointed push rods to effect variation in the duration of valve open- 35 ing. It is evident that if the oil pressure be varied that wedges similar to those mentioned above may be advanced or retracted in accordance with these pressure changes so that by properly designing the profile of the wedge, the 40 quantity of oil injected per cycle will remain constant'at full torque.

It may be assumed for example that the pressure varies directly as the engine speed and that it is required that the engine be capable of exert- 45 ing its full load torque at any engine speed. It is clear that any other relationship between pressure and speed may be selected and the taper wedge so shaped as to provide correct metering.

50 In one of our co-pending applications, entitled Fuel injection system for Diesel engines filed September 10, 1930 Serial No. 480,960, it has been shown that if an electro-magnetic fuel valve has supplied to it an interrupted current the mean effective value of which is proportional to the engine speed equal metering will result, provided the oil pressure remains constant. Let us assume as before that the pressure is caused to 'vary directly as the speed of the engine. Then 66 as before the time which the valve is permitted to remain open per revolution must continuously diminish and become proportional to 70 simplified apparatus for maintaining a correct relation between the duration of opening and ,the fuel pressure so as to obtain a constant maximum fuel injection charge per cycle.

Before going into the specific illustrations of the mechanical apparatus for accomplishing our The invention is exemplified in the following I objects. it is desired to point out that it is one of the inherent characteristics of anengine operating on the Diesel principle that the volume of air drawn into the cylinder per cycle remains substantially constant neglecting the small effect of volumetric efficiency regardless of engine speed or load as compared to a carburator engine where the intake is throttled at part. Therefore, the effective maximum fuel charge per cycle is limited by this air charge and should be substantially constant in quantity for injection to maintain the mixture ratio substantially constant under all speed changes for full torque operation. excess of this constant is waste and causes excessive smoking as itdoes not produce greater torque; reducing this constant injection quantity, of course, reduces the torque.

In Fig. 1 we have shown a simplified arrangement for maintaining a correct relation between;

the duration of opening of av fixed area discharge valve fuel pressure so as to obtain a constant maximum fuel injection charge per cycle. This apparatus includes a fuel supply tank 20 connected to the fuel pump cylinder 2i through check valve 25. A piston 2&1 is operated by connecting rod 23 and crank 22 to create fuel pressure in the rail line 30; said pressure is retained by check valve 26 accumulated in the container 21 and controlled as to pressure by relief valve 65 and waste oil from valve 65 being returned through pipe 3! to the reservoir 20. From rail 30 the fuel is admitted to the engine cylinder I! through spray valve l which includes, valve stem ll spring pressure regulatornut BI and packing nut 82; another packing might be required between stem H and nut 8|. Valve stem l is lifted for proper fuel injection by lever- 70 and push rod 68 and other mechanisms to be described later. The loading on the spring above pressure control valve t5 includes the speed sensitive gover nor 6? driven in synchronism with the engine.

This governor operates against a lever 63 having a varying fulcrum point being the curved surface of the anchored block which lever 63 pivots so as to change the leverage of the governor with respect to the pressure regulating needles in such v a way as to vary the pressure as some function under the square of the engine speed.

By varying the pressure on the valve 65 through the medium of the governor 62 the fuel pressure in the line is varied, which varying pressure influences the operation of a plunger 56 reciproca bly mounted in a cylinder 61 and operating against a spring 68. The plunger 66 is directly connected to a wedge fitwhich controls the position of the throttle wedge it. A spring H bears against the wedge 70 and constantly tends to maintain the wedge 10 in operative relation to the wedge 69. A separate speed sensitive governor i2 is provided which is also operatively associated with the wedges 69 and "I0 and is capable of adjustment in order to maintain the speed of the engine constant at any given throttle setting.

Now, in operation of this form of the apparatus the effect of the speed varying the pressure causes the adjustment of the wedge 68 which in turn controls the position of the throttle wedge '10 so that the product of the duration of opening times the velocity of discharge times the orifice size remains a constant which results in a constant maximum quantity of discharge.

By this construction as the speed of the engine increases the fuel pressure will be increased but, however, below the square of the speed so that this alone is insuflicient-to maintain correct metering with a constant arc of injection. Therefore, the pressure acting to control the position of the wedge 69 varies the angle of duration of opening as a function of the pressure so that the quantity-of discharge as above pointed out will remain constant.

From the foregoing it is obvious that by controlling twovariables in a Diesel engine fuel system we are enabled to effect proper metering so as to obtain a maximum fuel injection and torque at full throttle setting regardless of engine speed.

Having thus described our invention, what we claim and desire to secure by Letters Patent is:

1. In a fuel injection system for an oil engine,

the combination of a fuel supply line, means for feeding fuel under pressure to said line, automatic adjustable means for varying the pressure of fuel maintained in said line, means responsive to the engine speed for regulating said adjusting means, a power actuated fuel injection valve associated with said fuel supply line, engine driven means periodically opening said valve for a constant crank angle of injection duration within a given throttle setting and constant speed and means responsive to pressure variations in said fuel supply line for varying the crank angle duration of said valve opening to maintain the quantity of fuel injected through said valve substantially constant per injection at the varying 0 fuel pressures and varying engine speeds at a given throttle setting.

2. In a fuel injection system for an oil engine, the combination of a fuel supply line, means for feeding fuel under pressure to said line, auto- 35 matic adjustable means for varying the pressure of fuel maintained in said line, means responsive to the engine speed for regulating said adjusting means, a power actuated fuel injection valve associated with said fuel supply line, engine driven means periodically opening said valve for a constant cranlr angle of injection duration within a given throttle setting and constant speed, means responsive to pressure variations in said fuel supply line for varying the crank angle duration of said valve opening to maintain the quantity of fuel injected through said valve substantially constant per injection at the varying fuel pressures and varying engine speeds at a given throttle setting and additional means for manually varying the crank angle of injection duration to give a throttle control.

3. In a fuel injection system for an oil engine, the combination of a fuel supply line, means for feeding fuel under pressure to said line, automatic adjustable means for varying the pressure of fuel maintained in said line, means responsive to the engine speed for regulating said adjusting means, a power actuated fuel injection valve associated with said fuel supply line, engine driven means periodically opening said valve for a constant crank angle of injection duration within a given throttle setting and constant speed, means responsive to pressure variations in said fuel supply line for varying the crank angle duration of said valve opening to maintain the quantity of fuel injected through said valve substantially constant per injection at the varying fuel pressures and varying engine speeds at a given throttle setting and additional means controlled by speed sensitive means for controlling the throttiing of said fuel injection.

HARRY E. KENNEDY. aaooxs WALKER.

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