US3737100A

US3737100A - Internally cooled unit injector

Info

Publication number: US3737100A
Application number: US00199922A
Authority: US
Inventors: A Dreisin
Original assignee: Allis Chalmers Corp
Current assignee: Deutz Allis Corp
Priority date: 1971-11-18
Filing date: 1971-11-18
Publication date: 1973-06-05
Anticipated expiration: 1990-06-05

Abstract

A unit fuel injector providing cooling of the nozzle by the fuel, with a valve arrangement in the return passage to intermittently stop circulation of the fuel and a check valve in the fuel delivery passage to prevent blow-back of combustion gases during the engine power stroke.

Description

United States Patent 1191 Dreisin 51 June 5,1973

[54] INTERNALLY COOLED UNIT INJECTOR [75] Inventor: Alerrander Dreisin, Olympia Fields,

[73] Assignee: Allis-Chalmers Corporation, Milwaukee, Wis.

[22] Filed: Nov; 18, 1971 [21] Appl. No.: 199,922

[52] US. Cl. ..239/89, 123/139 AK, 239/1325 [51] Int. Cl ..F02m 39/00 [58] Field of Search ..239/88, 89, 90, 9| 239/95, 132, 132.1, 132.3, 132.5, 533;

[56] References Cited UNITED STATES PATENTS 2,260,077 10/1941 Kearney..... ..123/139AK 2,792,259 5/1957 Shallenberg ..l23/l39 AK 7 3,486,494 l2/l969 Dreisin ..239/89 X 2,559,364 7/1951 Mashinter ..l23/139 AK 3,409,225 l [[1968 Maddalozzo et al. ..239l89 Primary Examiner-M. Henson Wood, Jr.

Assistant Examiner-Michael Mar Attorney-Arthur L. Nelson, Robert B. Benson and Charles L. Schwab [57] ABSTRACT A unit fuel injector providing cooling of the nozzle by the fuel, with a valve arrangement in the return passage to intermittently stop circulation of the fuel and a check valve in the fuel delivery passage to prevent blow-back of combustion gases during the engine power stroke.

10 Claims, 5 Drawing Figures INTERNALLY COOLED UNIT INJECTOR This invention relates to cooling of a unit fuel injector and more particularly to a valve arrangement to prevent blow-back of the high pressure combustion gases from the combustion chamber during the power stroke.

In the conventional fuel injector using a differential valve in the nozzle, the closing pressure is always lower than the opening pressure. This is due to the fact that when the needle is closed the hydraulic pressure acts only on the differential area between the outside diameter of the conical needle seat and the maximum cylindrical diameter of the needle. When the needle is open, the hydraulic pressure can act on the entire area corresponding to maximum outside diameter of the needle. It is the practice when using a differential valve, to adjust the spring force acting on the needle in such a way that the closing pressure of the nozzle is several hundred pounds per square inch higher than the maximum pressure developed during the combustion process in the engine cylinder. This condition is required to prevent the combustion gases from penetrating into the interior of the injector after the opening of the spill port and before the needle is seated. If this condition is not met, even a small quantity of high pressure gas, which can penetrate into the interior of the injector, will expand a hundredfold during subsequent relief of the pressure down to the values of the supply pressure and may prevent proper filling of the pump chamber preparatory to the subsequent injection. There is also the possibility of combustion gases penetrating into the interior of the injector after seating of the needle. This possibility may be created by an imperfect seating of the needle in the nozzle body. It is especially important to guard against the penetration of the combustion gases into the interior of the injector during the initial portion of the engine power stroke while the engine cylinder pressures are high. Accordingly, this invention is intended to overcome this problem.

It is an object of this invention to provide a cooling system for a unit fuel injector having a valve arrangement to prevent blow-back of the combustion gases from the internal combustion chamber during the power stroke of the engine.

It is a further object of this invention to provide a fuel cooling means for cooling a unit injector including a check valve between the combustion chamber and the high pressure fuel injection pumping chamber, and a port between the combustion chamber and the return passage which are closed during the power stroke of the engine to prevent blow-back of gases into the differential valve chamber.

The objects of this invention are accomplished by a fuel cooling system which supplies cooling fuel to the unit injector. The supply passage supplies fuel to the high pressure fuel injection pumping chamber. Fuel is delivered from the chamber through a check valve as it passes to the differential valve in the nozzle. The cooling fuel passes through the differential valve chamber and is returned through a return passage to the fuel supply tank. The fuel intermittently flows through differential valve chamber in the fuel injection nozzle for cooling during the phase of the cycle in which there is no fuel injection.

During the fuel injection phase of the cycle, the check valve is open and the high pressure fuel from the high pressure fuel injection pumping chamber passes through the check valve and through the differential valve. Fuel injection is initiated when a predetermined pressure is reached and the differential valve opens. Fuel injection is terminated when the spill port registers with the upper edge of the pumping land on the plunger and the pressure is relieved from the high pressure pumping chamber. The cross passage on the plunger is closed so no fuel is permitted to return through the return passage for substantially all of the power stroke. With the return passage closed and the check valve closed, the pressure build-up in the combustion cham-' ber which tends to open the differential valve is counteracted since no movement of fuel from the differential valve chamber is permitted. Accordingly, blowback into the differential valve is prevented.

Referring to the drawings, the preferred embodiment of this invention is illustrated.

FIG. 1 is a cross section view taken on line I-I of FIG. 2.

FIG. 2 is a cross section view taken on line 11-11 of FIG. 1. v

FIG. 3 is an enlarged cross section view taken on line III-Ill of FIG. 1.

FIG. 4 is a schematic illustration of the fuel injection pump and a fuel supply system.

FIG. 5 illustrates the timing of fuel injection and opening and closing of the cooling annulus on the plunger.

Referring to FIG. 1, a fuel pump in unit injector l is shown. The unit injector includes the housing 2 receiving a plunger 3 connected to the cam follower 4. The cam follower 4 is biased to the extended position by the follower spring 5, and reciprocates within the housing 2 in response to a cam on an engine driven camshaft 45.

The unit injector housing 2 defines an inlet passage 6 and an outlet passage 7. The inlet passage 6 is connected to the supply pump 44 and the outlet passage 7 is connected through a return conduit 55 to the fuel tank to return fuel which operates as the cooling fluid for cooling the unit fuel injector. The housing 2 houses the barrel 8 which receives the plunger 3 which forms the pumping land 9 and cooling control land 10.'The land 10 forms annular groove or annulus 11 forming cross passage for return flow of fuel. The land 9 on the plunger 3 initiates fuel injection when the leading heli-'v cal edge 12 closes the port 13. The trailing helical edge 14 terminates fuel injection when it registers with the port 15 as the plunger advances in the high pressure chamber 16.

The upper spring retainer 17 forms the lower surface of the high pressure chamber 16 and the passage 18 leads from the high pressure chamber into the passage 19 in the lower spring retainer 20-. The nozzle 21 forms a valve chamber 22 which receives the check valve 23. The passage 24 supplies fuel to the differential valve chamber 25. The differential valve includes the needle 26 seated on the conical seat 27. The check valve 23 is located close to the differential valve 30 and is sensitive to reverse fuel movement from the differential valve chamber. The orifices 28 delivers fuel to the combustion chamber.

When the fuel injection pump is not injecting fuel, the differential valve 30 is closed and fuel is returned to the passage 29 in the nozzle 21. Passage 29 is in communication with

passages

31 and 32 in the lower spring retainer 20 and the upper spring retainer 17. These passages are in turn connected through the return passage 33, the annular groove 11, and passage 35 to the outlet passage 7. The inlet passage 6 is connected to the supply passage 36 which is in communication with the high pressure fuel injection chamber 16, during the phase of cam at which the port 13 is not covered.

Referring to FIG. 2, the inlet passage 36 is shown connected to the inlet port 13. Port 13 is closed to provide fuel injection. The return port 38 is also closed during fuel injection and opens to terminate fuel injection through the return passage 35.

Referring to FIG. 3, it illustrates a section view of the upper portion of the nozzle 21 and the check valve 23. The needle 25 is normally biased to a closed position by the spring 40 as shown in FIG. 1. The spring is compressively positioned under the upper spring retainer 17 and engages on its underside the spring seat 42.

Referring to FIG. 4, the engine 43 drives the fuel supply pump 44 and the camshaft 45. The camshaft 45 has a plurality of

cams

46, 47, 48 and 49 for driving the cam followers of the

fuel injectors

50, 51, 52 and 53. The pump 44 pumps fuel into the supply conduit 54 which is connected by parallel conduits to each of the

fuel injectors

50, 51, 52 and 53. The return conduit 55 returns fuel through the check valve 56 to the fuel tank 57 for cooling of the unit fuel injector. The flow of cooling fuel from each of the fuel injectors is interrupted during fuel injection.

FIG. illustrates a graph showing the sequence of operation of the fuel injector responsive to cam rotation. The angle of cam rotation shows that the annulus or annular groove 11 formed on land of the plunger 3 closes the cross passage for fuel return prior to fuel injection which is slightly beyond 20 of cam rotation. Fuel injection initiates at approximately 30 of cam rotation and terminates slightly beyond 40 of cam rotation and before top dead center. The cam retains the annular groove or annulus l1 closed through the power stroke of the engine. The annulus opening registers at approximately 140 of cam rotation for providing cross passage between

return passage

33 and 35 at which time the pressure in the combustion chamber is so low .that it is incapable of opening the differential valve.

FIG. 5 illustrates the cycle for any cylinder and the cam operation for fuel injection in its mating combustion chamber.

The operation of the unit fuel injector will be described in the following paragraphs.

The unit injector shown in the drawings is provided with a cooling circuit which allows supply fuel to flow around the nozzle tip during the time interval between fuel injections. The supply fuel from the supply pump 44 is maintained at a low pressure which may be in the vicinity of 10-40 pounds per square inch. It enters through the inlet passage 6 flowing through the supply passage 36. Normally the plunger of the fuel injector is in the position as shown in FIG. 1 when the cam follower is operating on the base circle of the cam. It is understood that cam lift or rise refers to a condition where the cam lobe on the camshaft causes the cam follower to move away from the base circle although this may be indicated as a downward movement in FIG. 1. Likewise when spring 5 returns the cam follower 4 to the base circle, the cam follower is considered to fall in response to the biasing force of the spring 5.

The inlet port 6 is connected to the pump and allows fuel to enter into the pumping chamber 16 through the inlet passage 36 and port 13. The fuel flows through the high pressure pumping chamber 16, the

passages

18, 19, and 24 and check valve 23 to the differential valve chamber 25. When the fuel injector is not injecting fuel, the fuel is allowed to return through the

passages

29, 31, 32 and annular groove 11 and return passage 35 to the outlet passage 7. i

Fuel has free-flow from the high pressure fuel injection chamber 16 through the check valve 23 to the differential valve chamber 25. The check valve prevents any return flow from the differential valve chamber 25.

FIG. 4 illustrates the unit fuel injectors on the engine which are connected in parallel to the fuel supply line and in turn the fuel outlets are connected in parallel to the fuel drain manifold equipped with a pressure relief valve 56, the downstream side of which leads to the fuel tank 57.

Because of the flow resistance of the internal passages in the unit fuel injectors there is always a pressure drop between the fuel inlet and the fuel outlet. The barrel is fitted snuggly in the counterbore in the injection nozzle housing 2 so that outside of negligible leakage the main quality of supply fuel flow has to move through the injector as described above.

When the engine piston is on its compression stroke, the injection plunger begins its movement responsive to injector cam lift. At the approximate point in time which may be approximately 20 to 30 degrees before engine top dead center, the annular groove 11 will over-ride the cross passages of the

return passages

33 and 35, thereby interrupting the flow cooling fluid. As the plunger continues to lift, the leading helical edge 12 will be advanced sufficiently to close the inlet port 13, trapping fuel in the pumping chamber. This commences fuel injection. Fuel pressure in the injector builds up until it exceeds the opening pressure of the differential valve 30, and then the needle 26 opens injecting fuel into the cylinder. This continues until the trailing helical edge 14 registers with the spill port 15. The plunger proceeds toward the top of the cam lift, leaving the spill port open. The injection pressure in the injector starts falling after the opening of the spill port and as it decays to the value of the nozzle closing pressure, the needle starts falling back towards its seat. When the differential valve is completely closed, fuel flow from the high pressure chamber 16 through check valve 23 stops. Any tendency of return flow through the check valve 23 will immediately close the check valve 23. The annular groove 11 still remains out of registry with the cross passages between

return passages

33 and 35. Accordingly, the inlet and outlet fuel passages communicating with the differential valve chamber are closed. Consequently, any possibility of blow-back into the differential valve is eliminated. The annular groove 1 1 remains out of registry with the cross passages 33 aand 35 for substantially all of the power stroke. It is noted on the graph in FIG. 5 that the termination of the power stroke at bottom dead center is approximately the same point in the cycle that the cooling annulus opens. When the cooling annulus 11 opens and supply fuel is permitted to pass through the cooling annulus, the pressure in the combustion chamber is reduced to a value where there is no longer any danger of blow-back of combustion gases into the differential valve.

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

l. A unit fuel injector having fuel cooling means comprising a fuel injector housing defining an inlet passage and an outlet passage, a plunger reciprocating in said housing and defining a fuel injection pumping chamber with said inlet passage intermittently communicating with said pumping chamber, means defining an injection nozzle adapted for injecting fuel in a combustion chamber, means defining supply passage means connected between said injection pumping chamber and said injection nozzle, a differential valve in said injection nozzle, a check valve positioned in said supply passage means adjacent said differential valve, return passage means connected between said differential valve and said outlet passage through said plunger, said plunger defining a passage providing port means in said return passage means to selectively close said return passage means during fuel injection, said check valve and said port means on said plunger operating as means for trapping fuel in said differential valve chamber to prevent high pressure gases from entering said differential valve from the combustion chamber.

2. A unit fuel injector having fuel cooling means as set forth in claim 1 wherein said check valve defines a pressure sensitive valve element permitting unidirectional flow of hydraulic fuel from said fuel injection chamber to said differential valve.

3. A unit fuel injector having fuel cooling means as set forth in claim 1 wherein said port means on said plunger defines an annular groove, said annular groove normally opening said return passage means for connection to a drain manifold of the fuel injection system.

4. A unit fuel injector having fuel cooling means as set forth in claim 1 wherein said plunger defines a land for initiating and terminating fuel injection upon register with said inlet passage means and said outlet passage means when said plunger is reciprocated, a cooling land defining said port means as an annular groove normally opening said return passage means to provide flow of cooling fluid through said return passage when said fuel injector is not injecting fuel.

5. A unit fuel injector having fuel cooling means as set forth in claim 1 wherein said nozzle defines a differential valve chamber, said differential valve positioned in said differential valve chamber, means connecting said supply passage means and said return passage means to said valve chamber for circulating fuel for cooling said nozzle.

6. A unit fuel injector having fuel cooling means as set forth in claim 1 wherein said nozzle includes a differential valve, a check valve in said nozzle adjacent said differential valve to increase sensitivity to return flow from said differential valve to said high pressure chamber.

7. A unit fuel injector having fuel cooling means as set forth in claim 1 including a cam driven by said engine, a cam follower operating in response to rotation of said cam for operating said plunger, said cam defining a cam lobe for driving said plunger to close said port means prior to initiation of the power stroke of the engine and open said port means substantially at the end of the power stroke.

8. A unit fuel injector having a fuel cooling means as set forth in claim 1 including a cam, means for driving said cam, a cam follower engaging said cam and connected to said plunger, said cam driving said cam follower and said plunger to initiate and terminate fuel injection on the rising portion of said cam with a sufficient dwell for maintaining the port means in a closed position during the greater portion of the power stroke of the corresponding cylinder.

9. A unit fuel injector having a fuel cooling means as set forth in claim 1 wherein said plunger includes a pumping land on said plunger for initiation and termination of fuel injection upon closing of said inlet port and opening of said return port respectively, a cam for driving said cam, a cam follower driven by said cam driving said plunger, said cam defining a lobe for lifting said cam follower and said plunger to maintain the port means in the closed position for substantially 90 of cam rotation.

10. A unit fuel injector having a fuel cooling means as set forth in claim 1 wherein said plunger includes a land defining initiation and termination of fuel injection upon closing of an inlet port with said high compression chamber and opening of an outlet port with said high pressure chamber, a second land on said plunger defining said port, a cam defining a lobe having a dwell of substantially whereby said cam follower maintains said return passage means in a closed position for trapping fuel in said differential valve chamber to prevent blow-back in said differential chamber.

Claims

1. A unit fuel injector having fuel cooling means comprising a fuel injector housing defining an inlet passage and an outlet passage, a plunger reciprocating in said housing and defining a fuel injection pumping chamber with said inlet passage intermittently communicating with said pumping chamber, means defining an injection nozzle adapted for injecting fuel in a combustion chamber, means defining supply passage means connected between said injection pumping chamber and said injection nozzle, a differential valve in said injection nozzle, a check valve positioned in said supply passage means adjacent said differential valve, return passage means connected between said differential valve and said outlet passage through said plunger, said plunger defining a passage providing port means in said return passage means to selectively close said return passage means during fuel injection, said check valve and said port means on said plunger operating as means for trapping fuel in said differential valve chamber to prevent high pressure gases from entering said differential valve from the combustion chamber.

9. A unit fuel injector having a fuel cooling means as set forth in claim 1 wherein said plunger includes a pumping land on said plunger for initiation and termination of fuel injection upon closing of said inlet port and opening of said return port respectively, a cam for driving said cam, a cam follower driven by said cam driving said plunger, said cam defining a lobe for lifting said cam follower and said plunger to maintain the port means in the closed position for substantially 90* of cam rotation.

10. A unit fuel injector having a fuel cooling means as set forth in claim 1 wherein said plunger includes a land defining initiation and termination of fuel injection upon closing of an inlet port with said high compression chamber and opening of an outlet port with said high pressure chamber, a second land on said plunger defining said port, a cam defining a lobe having a dwell of substantially 70* whereby said cam follower maintains said return passage means in a closed position for trapping fuel in said differential valve chamber to prevent blow-back in said differential chamber.