US3737258A - Fuel injection pump with timing port - Google Patents

Abstract

A fuel injection pump for an internal combustion engine having an inlet port shaped to effectively advance the pump timing with increased engine speed. The shape of the inlet port is designed to meter escape of fuel from the pump whereby early injection pressure caused by rapid operation of the pump at high speeds is controlled to give the desired timing advance curve.

Description

United States Patent [191 Krauja et al.

[ 51 June 5, 1973 154] FUEL INJECTION PUMP WITH TIMING PORT [75] Inventors: Ziedonis I. Krauja, East Peoria; Kenton C. Opperman, Morton, both of I11.

[73] Assignee: Caterpillar Tractor Co., Peoria, Ill.

[22] Filed: June 7, 1971 21 Appl. No.: 150,645

[52] US. Cl ..417/499 [51] Int. Cl ..F04b 39/10 [58] Field of Search ..l23/139 AR, 139 R;

[56] References Cited UNITED STATES PATENTS 1,883,980 Lang ..l23/l39 2,438,251 3/1948 Pedersen ..417/494 2,521,919 9/1950 2,537,087 1/1951 2,877,711 3/1959 2,975,776 3/1961 3,438,327 4/1969 Primary ExaminerWilliam L. Freeh Assistant ExaminerJohn T. Winburn Attorney-Fryer, Tjensvold, Feix, Phillips & Lempio [57] ABSTRACT A fuel injection pump for an internal combustion engine having an inlet port shaped to effectively advance the pump timing with increased engine speed. The shape of the inlet port is designed to meter escape of fuel from the pump whereby early injection pressure caused by rapid operation of the pump at high speeds is controlled to give the desired timing advance curve.

4 Claims, 5 Drawing Figures ADVANCE RPM PATENTEDJUH 5 I975 3.737.258

SHEET 10F 2 7 H \9 I8 23 22 i 24- K 3% I f 27 I 33 is: i 26 INVENTORS ZIEDON IS I. KRAUJA KENTON C. OPPERMAN PATENIEDJUR 5 ms SHEET 2 [IF 2 RPM INVENTORS Z I EDONIS l. KRAUJA RPM KENTON C. OPPERMAN FUEL INJECTION PUMP WITH TIMING PORT BACKGROUND OF THE INVENTION This invention relates to fuel injection pumps and more particularly to means for automatically effecting the desired timing advance thereof. In fuel injectiontype engines it is advantageous for optimum combustion to inject fuel into the combustion chamber at a certain time with respect to the piston stroke, such as just prior to the piston reaching top dead center. In timing the operation of the injection pump to provide such injection, it is necessary to allow for pressure wave travel time in the injection fuel line and combustion delay time. These delays are independent of engine speed. Thus as engine speed increases injection will be retarded from the optimal time with respect to piston stroke since the engine will rotate farther during this fixed delay period at higher engine speeds. Therefore, to maintain optimum combustion, the timing of the injection pump must be advanced as engine speed increases.

In the past such advancement has been accomplished by speed or pressure sensitive mechanisms. However, such mechanisms increase the cost and bulk of the fuel system.

BRIEF SUMMARY OF THE INVENTION Briefly, the present invention comprises a fuel injection pump having an inlet port that is shaped to provide a desired advance of pump timing with increases in engine speed. The inlet port is shaped with respect to the path of the pump plunger to regulate the increase of fuel pump pressure to the required pressure for injection at different engine speeds, providing the desired timing advance at any speed.

Accordingly, the present invention provides a simple, inexpensive and compact means for achieving the necessary timing advance of a fuel injection pump with respect to engine speed to insure that fuel injection occurs at the proper time at all speeds in the operating range of the engine.

Other objects and advantages of the present invention and the best mode for carrying them out will be apparent from the following detailed specification wherein reference is made to the accompanying drawings disclosing the preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a vertical sectional view of a fuel injection pump embodying the present invention.

FIG. 2 is an enlarged fragmentary view of the area indicated by the circle II in FIG. 1.

FIG. 3 is an enlarged fragmentary sectional view taken in the direction of arrows III-III in FIG. 2, showing the inlet port together with a graph of the injection pump timing advance with respect to engine speed.

FIG. 4 is an enlarged fragmentary sectional view of another embodiment of the inlet port shown in FIG. 3 together with a graph of timing advance with respect to engine speed for this embodiment.

FIG. 5 illustrates still another embodiment of the inlet port of the present invention together with the timing advance response curve for the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a fuel injection pump is depicted as comprising a housing 11 having a bore 12, a lifter 13 reciprocally disposed within the bore and driven by a cam 14 mounted on a camshaft 15 which is driven by the engines crankshaft (not shown). A head 16 is bolted to housing 11 and includes a bore 17 coaxial with bore 12, and a transverse fuel passage 18 which communicates with bore 17 at an inlet port 19. A fuel pump plunger 21 connected to lifter 13 is slidably disposed in bore 17 and includes a face 22. A notch 23 and a helical groove 24 are provided on the plunger for adjustment of the effective plunger stroke by rotation of the lifter and plunger by a gear 25 and a rack 26 in response to changes in engine speed. A spring 27, compressed between head 16 and lifter l3, maintains the lifter in engagement with the cam.

A fuel injection line 28 is connected to the pump head by means of a nut 29 which houses a check valve or first valve means 30 and communicates with a second valve means comprising an injector valve 32. Fuel is supplied to the head of the pump by a fuel manifold 33 and a supply passage 34. The construction of all of the foregoing elements, except the inlet port 19, is well known in the art.

In low speed operation, a fuel pump (not shown) forces fuel under pressure from the fuel manifold 33 through the supply passage 34 and fuel passage 18, through port 19 and into bore 17. It will be apparent that, except for the notch and groove in the plunger, only that portion of bore 17 that is between the plunger face and the check valve at any given time may be occupied by fuel. This portion of the bore will be referred to as the pump chamber.

As the cam rotates, the lifter and plunger are moved upwardly against the force of spring 27, moving plunger face 22 upwardly in bore 17 which tends to compress the fuel in the bore. Until the plunger covers port 19, fuel can escape through the port back into the fuel passage, and there is little pressure rise in the pump chamber. After the port is closed by the plunger, fuel pressure in the pump chamber increases rapidly, opening check valve 30 and sending a pressure wave through injection line 28 to injection valve 32. Valve 32 opens when a predetermined injection pressure is reached and fuel is injected into a combustion chamber (not shown) of the engine.

The injection pump is timed so that fuel injection occurs at the optimum time for the engine, usually a few degrees before the associated piston reaches top dead center prior to the power stroke.

When the speed of the engine is increased, the piston reaches the optimum injection point faster. However, the time required for the pressure wave to travel the length of the injection line after the check valve opens remains constant. Accordingly, fuel injection and combustion will occur later than the optimum injection point and thus the timing of the injection has effectively been retarded as the engine speed has been increased. It is therefore necessary to advance the timing of the fuel injection pump as the engine speed is increased to compensate for the injection line delay.

There may also be a combustion delay caused by a constant rate of advance of the flame front in the combustion chamber. In a properly timed engine, combusoptimum combustion development is attained at the proper time with regard to the stroke of the piston. It will be apparent that the required advance of fuel injection intothe combustion chamber to compensate for combustion delay at higher engine speeds can also be obtained by advancing the fuel injection pump to compensate for combustion delay as well as injection line delay. The present invention accomplishes these timing advances in a simple and inexpensive manner by taking advantage of a phenomenon known as port effect.

When the engine speed is increased, the rotation of the injection pump cam and thus the speed of upward travel of the lifter and pump plunger are increased accordingly. At such increased speeds prior to the time the plunger closes the inlet port, it diminishes the volume of the pump chamber and the fuel contained therein faster than fuel can escape back through port 19 to fuel passage 18. Thus, fuel in the pump chamber reaches the necessary pressure to open check valve 30 earlier in the injection pump cycle. It is, therefore, evident that this port effect tends to advance the timing of the fuel injection pump with increases in engine speed. However, unless the intake port is specially shaped, this pressure increase is experienced only immediately prior to the closing of the inlet port, and the resulting advance of injection pressure in the pump is so small that it has no significant effect on the operation of the engine.

In the present invention the inlet port 19, and especially the upper portion thereof with respect to plunger travel on the pumping stroke, is restricted and shaped to provide a sufficient advance of injection pressure in the pump at any increased speed in engine operation to compensate for the injection line delay with the result that fuel injection into the combustion chamber occurs at the optimum position prior to top dead center. It will be apparent that injection pressure in'the pump can also be additionally advanced to compensate for combustion delay as well. i

To design an inlet port to provide such timing advance, it is necessary to know the operating speed range of the engine, the amount of timing advance required over that range, and the advancement curve that is desired. The amount of advance required over the operating range of the engine will determine the height of the timing port, or the timing portion of the inlet port, which will equal the distance the plunger travels as the engine rotates through the amount of advance required.

The amount of advance required will depend on the delay characteristics of the injection system involved. The engine speeds encountered and the plunger face area will determine the plungers fuel pumping rate which in turn will determine the total area of the timing port.

The advancement curve will be determined by the shape of the timing port. The desired advancement curve may depend on the application of the engine.

In order to obtain a greater timing advance in one portion of the engines speed range than in another portion, it is necessary that a larger increase in injection pressure be obtained from a proportionally smaller increase in the plungers fuel pumping rate within this portion of the speed range than for the other portion. Thus, an optimum timing port configuration can be designed to obtain the proper advancement curve to meet the requirements of any given engine application and operating speed range. Accordingly, if the application of the engine require a greater timing advance during the lower portion of the engines speed range than for the upper portion thereof, a timing port shaped like the one illustrated at 19a in FIG. 4 would be used to obtain this result. Timing port 19a is shaped so that the area of the upper portion is more restricted than the lower portion which causes the effective position of the plunger to move downward in greater increments for the upper portion than for the lower portion for given incremental increases in engine speed. The associated timing advance curve for FIG. 4 illustrates the advance derived from timing port 19a, wherein the amount of advance is greater in the lower portion of the engine speed range than in the higher portion of the engine speed range.

Conversely, if the application of the engine requires that the timing advance be delayed, as the engine accelerates, until the higher portion of the engine speed range is reached, a timing port shaped like the one illustrated at 19a" in FIG. 5 would be used. The timing port 19a" is shaped so that as much area as possible remains open at the upper portion thereof while the area of the lower portion becomes more restricted. This configuration causes the greatest change in timing to occur during the higher portion of the engine speed range as illustrated in the associated advancement curve for FIG. 5.

If a constant rate of advance is required, as is more normally the case, a timing port shaped like the one illustrated at 19a in FIG. 3 as the preferred embodiment would be used. Timing port 19a will produce a linear advance as illustrated in the associated advancement curve for FIG. 3.

It will also be understood that any desired timing port, or timing portion of the inlet port, may be provided by merely providing inlet port 19 with an upper timing notch 19a as illustrated in FIGS. 2 and 3 and retiming the pump by lowering port 19 in the housing, or by raising plunger 21 or by any other timing means desired. Thus it should be clearly understood that the present invention as illustrated in FIG. 3 does not comprise merely the addition of timing notch 19a to a prior art inlet port, but rather the substitution of the entire inlet port shown at 19, which includes timing portion 19a, for prior art inlet ports.

What is claimed is:

1. In a fuel injection system in an engine including a pump having a housing defining a bore therein, an inlet port communicating with the bore, a plunger reciprocable in the bore and operating past said inlet port, means driving the plunger at a speed proportional to the speed of the engine, a fuel injection line communicating fuel from the bore to a combustion chamber, first valve means responsive to fuel pressure in the bore to open to admit fuel to the injection line, and second valve means responsive to fuel pressure in the injection line to control injection of fuel into the combustion chamber, the improvement comprising timing port means formed as a portion of said inlet port for regulating the flow of fuel escaping through the inlet port in 3. The invention of claim 1 wherein the cross-section of said notch is triangularly shaped with a base thereof intersecting and common with the boundary defining said inlet port.

4. The invention of claim 1 wherein the cross-section of said notch is triangularly shaped with an apex thereof intersecting the boundary defining said inlet port.

Claims (4)

1. In a fuel injection system in an engine including a pump having a housing defining a bore therein, an inlet port communicating with the bore, a plunger reciprocable in the bore and operating past said inlet port, means driving the plunger at a speed proportional to the speed of the engine, a fuel injection line communicating fuel from the bore to a combustion chamber, first valve means responsive to fuel pressure in the bore to open to admit fuel to the injection line, and second valve means responsive to fuel pressure in the injection line to control injection of fuel into the combustion chamber, the improvement comprising timing port means formed as a portion of said inlet port for regulating the flow of fuel escaping through the inlet port in response to the speed of the plunger as it moves past the inlet port for advancing the time at which said first valve means opens in response to an increase in engine speed, wherein said timing port means comprises notch means having a cross-section substantially less than the cross-section of the inlet port and is defined by a boundary which forms an upper continuation of the boundary defining said inlet port.

2. The invention of claim 1 wherein the cross-section of said notch is generally T-shaped.

3. The invention of claim 1 wherein the cross-section of said notch is triangularly shaped with a base thereof intersecting and common with the boundary defining said inlet port.

4. The invention of claim 1 wherein the cross-section of said notch is triangularly shaped with an apex thereof intersecting the boundary defining said inlet port.

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