US3465737A - Fuel injection system - Google Patents

Description

Sept. 9, 1969 A. DREISIN FUEL INJECTION SYSTEM Filed March 26. 1968 V .I I/ j,

7 y 7 QU .E WW I ,w f, 6,5@ 6 HH United States Patent O M 3,465,737 FUEL INJECTION SYSTEM Alexander Dreisin, Olympia Fields, Ill., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Mar. 26, 1968, Ser. No. 716,107 Int. Cl. F02m 39/00, 45/00; F04b 17/00 U.S. Cl. 123--139 10 Claims ABSTRACT OF THE DISCLOSURE A fuel injection system having a mechanically operated fuel injection pump and control pump and hydraulically controlled fuel injection timing and metering of fuel quantity.

This invention relates to fuel injection for a compression ignition engine and more particularly to a fuel injection system using a fuel pump to increase fuel line pressure during a pumping cycle which is timed in response to engine speed and load for controlling fuel injection timing, and metering of fuel injection quantity.

Fuel injection systems which employ unit injectors usually operate the unit injectors from the cam shaft. There is no convenient way to control injection timing advance in that the cam shaft rotation is directly timed with crank shaft rotation. Furthermore, where injection is made toward the end of the cam lift, the cam velocity is decreasing to zero. Injection atomization of the injected fuel is seriously limited on this portion of the cam rotation at all loads and speeds and especially at low idle. Accordingly, a more satisfactory control for injection timing and metering of the fuel quantity earlier in the cam follower stroke would improve fuel injection and engine efciency.

It is an object of this invention to provide a hydraulically controlled fuel injection timing and fuel quantity metering system for injection of the fuel in an internal combustion engine.

It is another object of this invention to provide a mechanically operated auxiliary pump in combination with a unit injector whereby the injection timing and the metering of fuel quantity is hydraulically controlled by the auxiliary pump.

It is a further object of this invention to provide an auxiliary pump to increase the pressure in the supply line supplying fuel to a unit injector whereby the increase in supply line pressure controls a pressure responsive valve in the unit injector to control timing and metering of fuel quantity of fuel injection.

The objects of this invention are accomplished by employing the unit injector having a pressure sensitive control valve in the fuel supply line. The pressure sensitive control valve merely allows circulation of fuel through the injector nozzle for cooling of the unit injector and returning the fuel to the fuel supply when the injector is not operating during the phase of fuel injection. A control fuel pump is positioned in the supply line preceding the pressure sensitive control valve. A supply fuel pump pumps fuel through the injector. The ilow of pressurized fuel from the supply fuel pump is severed by the action of the control fuel pump which builds up pressure in the supply line to bias the pressure sensitive control valve in the unit injector to a closed position to initiate fuel injection and restores communication between the supply fuel pump to the pressure sensitive valve for termination of injection. The control fuel pump is cam operated and its cycle is timed through a speed responsive drive. The duration of pressure increase in the supply line is controlled by either a manual control or a load responsive control between the engine and the control rack on the control pump. The control fuel pump, the

3,465,737 Patented Sept. 9, 1969 ICC supply fuel pump and the fuel injector pump are all mechanically actuated. The control fuel pump controls the advance and retardation of fuel injection timing as well as the quantity of fuel injection.

The preferred embodiments of this invention will be subsequently described and are illustrated in the attached drawings.

FIG. l illustrates a cross section view of the unit injector with a schematic illustration of the fuel injection system.

FIG. 2 is a cross section view of a modified version of the control valve.

FIG. 3 illustrates another modication of the control valve.

Referring to the drawings, the unit injector is mechanically driven for fuel injection while the timing and the metering is done hydraulically to allow convenient variation of injection timing and quantity control without necessity of mechanical linkages. The unit injector shown consists of an injector body 1 in which there is reciprocally mounted a plunger 2.

The injector is actuated in a normal manner from an engine cam shaft carrying a cam 30 which operates the plunger through the follower 3. The engine 31 also drives the fuel transfer pump 4 and the control pump 32. Fuel is supplied to each unit injector 1 through a control pump 32 which is similar to an injection pump. The control pump can be distributor type or a multiplunger type as shown in FIG. 1. The transfer pump 4 delivers fuel t0 the control pump chamber 5. When the control pump follower 66 is on the base circle of the cam 6, the fuel flows through the chamber 5 and through the supply line 7 into the passages of the unit injector as follows. It reaches the plunger through the passage 8 and crosses to the other side of the plunger through the annular passage 9` in the plunger and ows down to the passages 10 and 11 into the nozzle gallery 12 where the fluid cools the tip. The fuel then returns through the passages 13 and 14 into the unit injector pumping chamber and flows out through the central passage 15 in the plunger 2. The annulus 16 is in communication with the passage 15 and the outlet passage 17 under the spill valve seat 18. The fuel passes through the control valve 34 and through the drain passage 19 and a return conduit 35 to the fuel tank 36. When the unit injector plunger and the plunger in the control pump 32 are in the position shown, the fuel pumped through the unit injector is used for cooling of the unit injector and the nozzle tip.

During engine compression stroke, the unit injector cam 30 lifts the unit injector plunger 2 which begins its pumping movement. As the plunger moves into the charnber 37, it closes communication between the passage 8 and the annulus 9 interrupting fuel supply to the injector. At this point, the control valve 34 is still open and fuel is displaced by the injection plunger 2 into the drain passage 19.

In the meantime, the control pump cam 6 has also moved towards its lifting position and has started the control plunger 33 to move upwardly. A timing device 38 is interposed between the cam 6 and the engine 31. This allows a change in the timing of the pump cycle when the plunger 33 closes the intake port 21. After this instant, fuel in the system is trapped and a pressure Wave originates from the control pump 32 travelling towards the unit injector 1. It will reach the guide side of the control valve through the passage 52. The guide diameter of the spill valve is made at least twice as large as the passage diameter 17 underneath the valve seat 18. When the pressure wave from the control pump 32 reaches the control valve 34 from its large guide side, the valve will move into its closed position. This is accomplished because the pressure in the unit injector at this point has not built up sufficiently to oppose the pressure of the wave arriving from the control pump in passage 52. Once this control valve 34 is closed its differential area will tend to keep it closed even when the unit injector develops its own injection pressure.

A hypothetical illustration of this may be shown by the fact that the maximum unit pressure during injection is 16,000 pounds per square inch. It may be further supposed that the guide portion of the control valve is three times the diameter of the passage 17 under the valve seat which would make the upper area 9 times the area exposed to the unit injector pressure. Therefore, with the unit injection pressure of 16,000 pounds per square inch divided by 9 would equal 1,780 pounds per square inch or higher which will keep the control valve closed. It is easy to develop pressures of this magnitude by the control pump because during the advance of the plunger 33 the fuel displaced by it is completely locked in the closed system of passages and, due to its elasticity, will be compressed developing the desired high pressures.

After the control valve 34 has closed, the unit injector behaves in the conventional manner. Fuel displaced by the plunger 2 is moved into the passages 14 and 13 until the developed fuel pressure will open its nozzle valve 23 and inject fuel into the internal combustion engine cylinder through the orifices 24.

Injection will continue until the helix 39 on the control plunger 33 will uncover communication between the line 7, the control pump chamber and intake port 21. This will relieve the pressure in the line 7 and the passages 52. Now the injection pressure acting on the valve seat 18 will pop the control valve open relieving the injection pressure inside the unit injector which in turn will allow the nozzle valve 23 to close and to terminate the fuel injection.

Referring to the control valve 34, the spring 40 normally biases the valve to an open position while the differential pressure generated by the transfer pump 4 is present on both sides of the valve. A check valve 41 is placed intermediate the fuel tank 36 and the valve 34 to relieve excessively high pressures in the valve chamber.

Referring to FIG. 2, a modification of the pressure sensitive control valve is illustrated. The pressure passing through the injector pumping chamber 37 passes through the passage 17 and is vented to the peripheral passage 42 to the drain passage 22. Fuel is circulated through unit injector 1 and the nozzle tip and recirculated back through the control valve 53 when the unit injector is not injecting fuel. The needle 54 is biased by pressure in the chamber 55 from the control pump 32 during injection thereby cutting off passage 42.

FIG. 3 illustrates a modification of pressure sensitive control valve. The control pump is in communication with the passages 7 and 52. The fuel flowing through passage 8 tiows through the unit injector and returns through the pressure sensitive control valve via the annulus 61 through the drain passage 22 when unit injector is not injecting fuel. When the control pump pressurizes fuel in the chamber 5, and passage 52, the pressure biases the needle 62 against the force of this spring 63 to close the annulus 61 which in turn initiates fuel injection. To avoid pressures in the passage 52 of excessive magnitudes, a check valve 64 is provided to bypass limited fuel flow and limit the high pressures in the passage 52 to safe levels.

The operation of the fuel injection system will be described in the following paragraphs.

The transfer pump 4 pressurizes fuel in the supply line 7 which passes through the unit injector 1 including the pressure sensitive control valve 34 and returns to the fuel tank 36 when the unit injector is not operating during the phase of injection. The control pump 32 is shown in the inactive position where the cam follower 66 is operating on the base circle of the cam 6. In this position, the pressure in the supply line 7 is controlled by the transfer pump 4. The engine 31 drives the control pump 32, the transfer pump 4 and the unit injector 1. When the cam 30 on the cam shaft of the engine 31 rotates to a position to actuate the plunger 2, the plunger moves into the pressurizing chamber 37 until the annulus 9 is severed from its communicating relationship with the passage 8. Simultaneously the cam 6 which is driven through a speed responsive control 38 also begins to operate the cam follower 66 and drive the plunger 33 into the chamber 5 and communication of the passage 7 with the port 21 is severed. Beyond this point, the plunger 33 pressurizes fuel in the chamber 5 which pressurizes fuel in the passage 52 and the guide side 67 of the pressure sensitive valve 34. The increased pressure in the guide chamber 67 -biases the valve to a closed position which severs communication between the passage 17 and the drain passage 19. At this point, the plunger 2 of the unit injector 1 begins to pressurize fluid in the chamber 37 and fuel passes through the differential valve 23 and is injected into the internal combustion engine chamber.

Continued downward movement of the plunger 2 is caused by the rotation of the cam 30. The cam 6 also continues to move the plunger 33 upwardly until the helix edge 39 restores communication between the port 21 and the passage 7. This in turn reduces the pressure in passage 7 and the guide side 67 in the pressure sensitive valve 34. The spring 40 biases the pressure sensitive valve to an open position which in turn permits the discharge of fuel through the drain passage 19 for termination of fuel injection.

The rotation of cam 30 is directly connected to rotation of the engine and accordingly the movement of plunger 2 is also directly associated with operation of the engine. The initiation of fuel injection is controlled by the closing of port 21 which is also controlled by the engine through the speed responsive control 38 which drives the cam 6. The advance and retardation of timing is controlled through the speed responsive control by the reciprocating movement of the plunger 33.

The quantity of fuel injection is controlled through a manual control means or through a load responsive control 70 which is connected to the rack 71 which rotates the plunger 33 which in turn controls the duration of the increment of time that pressure is maintained in the guide chamber of the pressure sensitive control valve 34. This in turn controls the quantity of fuel injected in the engine.

The pressure sensitive control valve 34 as shown in FIG. l operates in opposition to fuel injection pressure. FIGS. 2 and 3 illustrate a pressure sensitive control valve which is operated by pressure signals from the control pump 32. In FIG. 3, the pressure is applied to pressure chamber 73 which biases the needle 62 against the force of spring 63 to close the annulus 61 from the discharge passage 22. This in turn initiates fuel injection and termination of fuel injection is accomplished by restoring the transfer pump fuel pressure in chamber 73 permitting the biasing force of spring 63 to open the annulus 61 and permit the injection fuel to spill through the annulus 61 and the discharge passage 22. A pressure relief valve 64 limits the peak pressure in the chamber 73 to a reasonable operating magnitude.

The control pump 32 is essentially a pressure pump and the amount of fuel actually pumped is a very small amount. The amount of fuel pumped is only necessary to fill the chamber 73 and bias the needle 62 to close annulus 61 from the drain passage 22. When the pressure is released, the valve again automatically opens and the transfer pump 4 supplies the fuel to the unit injector.

The preferred embodiments of this invention have been illustrated and described and will be defined by the attached claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A fuel injection system comprising a fuel injector including a housing defining an injection pumping chamber, a plunger reciprocating in said housing for 4pressurizing fuel in said injection pumping chamber, means dening an injection nozzle adapted for injecting fuel in a combustion chamber, means defining passage means cornmunicating with said injection pumping chamber and said nozzle, a valve in said nozzle for controlling the discharge of fuel from said nozzle, a pressure sensitive injection control valve normally biased to an open position having the chamber intermittently communicating with said injection pumping chamber and adapted for receiving pressurized supply fuel, means `defining return passage means communicating with said nozzle valve and said control valve for returning fuel through said control valve when said control valve is open, an engine for actuating said plunger, a control pump in communication with said control valve, a speed and load responsive means connected to said engine and driving said pump, a fuel supply and fuel transfer pump for supplying low pressure fuel to said control pump, return conduit means connecting said control valve to said fuel supply for returning fuel from said control valve, said control pump increasing the pressure in said supply line and said chamber of said control valve thereby causing said valve to close during the interval when said plunger is actuated thereby initiating injection and restoring normal low pressure in said chamber of said control valve causing said control valve to open for terminating fuel injection.

2. A fuel injection system as set forth in claim 1 wherein said control pump is operated by a speed and load responsive means including a device to advance and retard the pumping cycle relative to the engine speed and thereby control fuel injection timing.

3. A fuel injection system as set forth in claim 1 wherein said control pump is operated by a speed and load responsive means including a device connected to said engine to control the duration of pressure rise and thereby the quantity of fuel injected by said injector.

4. A fuel injection system as set forth in claim 1 wherein said control pump pressurizes fuel and supplies pressure signals to a unit injector to control the timing and quantity of fuel injection to each of a plurality of injectors.

5. A fuel injection system as set forth in claim 1 wherein the timing of fuel injection in said injector is controlled by a speed responsive device driving said control pump and the quantity of fuel injection of said injector is controlled by a load responsive device connected to a rack to rotate a plunger in said control pump.

6. A fuel injection system as set forth in claim 1 wherein said pressure sensitive control valve in the injector is biased to a closed position in response to pressure in the chamber to initiate fuel injection and peak pressures in said chamber are limited by a pressure relief valve in communication with said chamber.

7. A fuel injection system as set forth in claim 1 wherein said pressure sensitive control valve includes a chamber receiving pressurized fuel from said control pump biasing said valve to close a peripheral passage in communication with the drain passage to thereby initiate fuel injection of said unit injector.

8. A fuel injection system as set forth in claim 1 wherein said pressure control pump increases and restores the original supply pressure to provide two level pressure signals to initiate and terminate fuel injection.

9. A fuel injection system as set forth in claim 1 wherein the two levels of control pressure are the supply line pressure of a transfer pump and the pressure level of the control pump which are applied to the pressure sensitive control valve to initiate and terminate fuel injection.

10. A fuel injection system as set forth in claim 1 wherein the transfer pump, the control pump, and the injector pump are mechanically operated and the initiation and termination of fuel injection are hydraulically controlled in response to the advance, retardation, and duration of the pumping cycle of the control pump relative to the cycle of the engine.

References Cited UNITED STATES PATENTS 2,116,337 5/1938 Broeze et al. 12S-139 2,173,814 9/1939 Bischof 123-139 2,274,315 2/1942 Amery 123-139 XR 2,279,010 4/1942 Nichols 123-139 LAURENCE M. GOODRIDGE, Primary Examiner U.S. Cl. X.R. 123-32; 10B-50

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