US3486696A

US3486696A - Fuel injector

Info

Publication number: US3486696A
Application number: US687779A
Authority: US
Inventors: Alexander Dreisin
Original assignee: Allis Chalmers Corp
Current assignee: Deutz Allis Corp
Priority date: 1967-12-04
Filing date: 1967-12-04
Publication date: 1969-12-30
Anticipated expiration: 1986-12-30
Also published as: DE1812735A1

Description

A. DREISIN FUEL INJECTOR Dec. 30, 1969v 2 Sheets-Sheet 1 Filed Dec. 4, 1967 Dec. 30, 1969 A. D'REISIN FUEL INJECTOR Fild Dec. 4, 1967 LG PO 2 Sheets-Sheet 2 www 19 mmmlw United States Patent US. Cl. 239-89 3 Claims ABSTRACT OF THE DISCLOSURE A fuel injector having hydraulic means to increase the nozzle closing pressure at the termination of fuel injection.

This invention relates to a fuel injector and more particularly to a means for hydraulically assisting the closing of the differential valve terminating fuel injection.

Ideal operating conditions for a diesel engine require that the injection timing and the injection termination be precisely controlled. For uniform metering of fuel delivery per cycle the differential valve must open completely to give full delivery during the injection and when the injection is terminated, the termination must be complete without any dribble of fuel, or h'esitancy in the closing of the differential valve.

This invention relates to unit injectors equipped with differential type nozzle.

Such a unit injector includes a pump pressurizing fuel to operate the differential valve in the nozzle against a spring force biasing the differential valve to a closed position. Differential valve in the nozzle presents a surface between its large guide diameter and its smaller, seat diameter, to the injection pressure developed by the pump plunger. After opening, an additional area, under the valve seat becomes subject to the injection pressure. For a given biasing force of the nozzle spring, the pressure at which the differential valve closes is always lower than its opening pressure. FOr practical executions it is on the order of 60 percent to 75 percent of the opening pressure. This is undesirable for the following reason: start of injection occurs towards the end of engine compression stroke, when gas pressure in the cylinder is due only to compression of aspirated air. After start of injection, fuel sprayed into compressed air is ignited and, towards the end of injection, pressure in the cylinder, due to combustion. is considerably higher. This combustion pressure communicates itself across the spray orifices of the nozzle towards the inside of the injector and acts on the exposed areas of the differential valve in the direction opposing the nozzle spring, therefore delaying the closing of the differential valve at end of injection.

To assure a speed of valve closing comparable with its opening speed it would therefore require a larger closing force. It is intended to augment the closing force on the differential valve by utilizing a portion of the high pressure fluid which is spilled at the termination of fuel injection. The spring chamber which houses the closing spring for the differential valve is of a substantially larger area than the area of the differential valve biasing the valve open. The spring chamber receives high pressure fluid from the spill passage and the fluid force against the plunger combined with the spring force on the dif' ferential valve to close the valve accelerates the termination of injection. In this manner, the opening pressure is not increased but the closing pressure is increased and the result is a crisp opening and closing of the differential valve to initiate and terminate fuel injection.

It is an object to provide a quicker closing of the fuel injection valve.

It is another object of this invention to provide a high closing pressure without raising the opening pressure of the differential valve for fuel injection.

3,486,696 Patented Dec. 30, 1969 It is a further object of this invention to provide hydraulically assisting means augmenting the spring force for increasing the closing pressure for the differential valve in a fuel injector.

It is a further object of this invention to utilize the action of the spill pressure at the termination of fuel injection on a large surface area of the spring plunger to increase the closing pressure of the differential valve at termination on fuel injection.

The objects of this invention are accomplished as follows. The pump in the fuel injector pressurizes fuel to injection pressure which operates on a differential valve whereby'the pressure operating on the differential valve causes the differential valve to open permitting fuel injection. Fuel injection is terminated by the spilling of high pressure fluid which reduces the pressure on the differential valve and simultaneously raises the fluid pressure in the spring chamber wherein the pressurized fluid operates on a large surface area augmenting the spring pressure on the spring plunger to assist in the closing of the differential valve. Subsequent to closing of the differential valve the pressure in the spring chamber is relieved by a bleed passage which bleeds pressurized fluid to the inlet passage to relieve the pressure in the spring chamber. The pressure in the spring chamber is reduced to a normal low pressure so that when the differential valve is opened for a subsequent injection, the pressure in the spring chamber is low and does not oppose the opening of the differential valve.

The preferred embodiment of this invention is illustrated and described in the following paragraphs. The attached drawings illustrate the following.

FIG. 1 is an end view of the unit injector.

FIG. 2 is a cross section view of the injector taken on line IIII of FIG. 1 showing the inlet passages.

FIG. 3 is a cross section view taken on line IIIIII of FIG. 1.

FIG. 4 is a cross section view taken on line IVIV of FIG. 1.

Referring to the drawings, the mounting flange 1 is formed integral with the barrel 2 which houses the pump plunger 3. The pump plunger 3 is actuated by the follower 4 which engages the pivot nut 5. The pivot nut 5 is operated by a mechanically driven actuator connected to a driving element on the engine (not shown).

The sleeve 6 is positioned axially forward of the barrel 2 with a spacer 7 intermediate the barrel 2 and the sleeve 6. The spacer 7 forms a partition between the high pressure pumping chamber 8 and the spring chamber 9. The clamp nut 10 threadedly engages the periphery of the barrel 2 and has inwardly extending radial flange which engages a mating shoulder on the sleeve 6 locking the sleeve 6, spacer 7 and the barrel 2 in assembly.

The nozzle 11 extends axially from the forward end of the sleeve 6 and is locked in position on the sleeve by the nozzle retaining nut 12. A dowell pin 13 maintains a nonrotative position between the sleeve 6 and the nozzle 11. Similarily the dowel pin 14 maintains a nonrotative position between the barrel 2, the sleeve 6, and the spacer 7.

The unit injector is formed by the assembly of these parts and is actuated by a mechanical means driven by the engine (not shown). The follower 4 is moved axially forward in response to actuation of the driving means and is retracted by the biasing force of the spring 15. The gauging post 16 limits the retractive movement of the follower 4 for shipping purposes only. The follower 4 has a lug 17 which extends radially into an annular groove 18 formed on the pump plunger 3. The pump plunger moves axially to produce a pumping action in the high pressure chamber 8. The pump plunger 3 also can be rotated in response to movement of the pinion 19 which engages the rack 20. The rack 20 is operated by a governor and rotates the pump plunger 3 in response to the speed and load. The termination of fuel injection is controlled by the rotation of the pump plunger 3. The helical edge 21 controls registry of recess 24 with the spill passage 48 which vents the high pressure chamber 8 to the spill passage 48.

It is noted that the central or axial passage 22 extends from the high pressure chamber 8 in the pump plunger 3 to the radial passage 23 in communication with the annular recess 24.

An annular groove 25 extends peripherally around the intermediate portions of the pump plunger 3 and provides across communication between

adjoining passage

44 and 45 extending to the bore 26 in the barrel 2.

The sleeve 6 encloses the spring plunger 27 which receives the spring 28 which is under compression and extends from the central recess 29 in the spacer 7 to the central opening 30 in the spring plunger 27 and biases the plunger to an engaging position with the rearward end 31 of the differential valve element 32. The differential valve element extends forwardly within the nozzle 12 and has a conical forward end portion 33 which engages a mating valve seat 34 on the inner portion of the nozzle. A plurality of nozzle vents 35 are in communication with the central passage 36 extending forwardly from the valve seat 34.

The unit injector provides a means for injecting fuel into the combustion chamber of an internal combustion engine. The fuel supply is connected to the inlet conduit 37 which is in communication with the inlet passages 38 in the mounting flange 1 and the inlet passages 39 in the barrel 2. The radial passage 40 connects the passage 39 to the high pressure chamber 8. When the pump plunger 3 is in a normally retracted position, the fuel supply pressure causes the flow of fuel through the high pressure chamber 8 and the passage 41. The fuel flows around the valve element 32 in the chamber 42 of the nozzle 11 and returns through the return passage 43. When the annular recess 25 of plunger 3 is in registry with the

radial passages

44 and 45 the returning fuel will flow through the outlet passage 46 and the outlet conduit 47 and return to the fuel supply. Accordingly, this will provide a cooling of the nozzle and the unit injector when the pump plunger is in its retracted position.

Referring to the unit injector as described above the operation will be set forth in the following paragraphs.

The pivot nut engages injector operating means on the engine the timing of which is controlled in relation to the operating cycle of the engine. The actuating force drives the pump plunger 3 reciprocably to provide fuel injection.

The quantity of fuel which is injected is controlled in response to a governor actuated mechanism operating the rack 20 to rotate the pinion 19 on the pump plunger 3 to cause a variable registry of the helical edge 21 of the plunger 3 with the spill passage 48. The effect of the registry of the helical edge 21 with the spill passage 48 vents the high pressure chamber 8 to a low pressure condition which will be described in the following paragraphs.

As the actuator forces the pivot nut 5, the follower 4 and the plunger 3 forwardly within the barrel 2 the leading edge of the pump plunger 3 passes beyond registry with the radial passage 40. This causes the pump plunger 3 to pressurize fluid within the high pressure chamber 8 forcing fuel in the passage 41 into the chamber 42 in the nozzle 11. A relatively low pressure is present within the spring chamber and this pressure combined with the force of the spring 28 biases the valve element 32 to a closed position engaging the valve seat 34. With a pressure build-up in the chamber 42, the pressure acting on the valve element 32 will overcome the force of the spring 28 causing the spring to retract and permitting the opening of the differential valve 49. As spring plunger 27 lifts, it displaces fuel in the spring chamber. This fuel escapes .4 through the clearance provided between the outside diameter of spring plunger 27 and bore 9'. Further it flows through bleed passage 52 to the inlet passage 39. As the differential valve opens, the pressurized fuel passes through the central passage 36 on the nozzle 11 and the plurality of delivery passages 35 to cause an injection in the combustion chamber of the engine.

The pump plunger 3 continues to move forwardly within the barrel 2 and fuel is delivered to the differential valve and injection continues until the helical edge 21 forming the forward edge of the annular recess 24 comes into registry with the spill passage 48. At this moment the high pressure fuel in the chamber 8 in communication with the axial passage 22, and the annular recess 24 comes in communication with the spill passage 48 and the axial passage 69 and the spring chamber 9. The high pressure fuel is directed into the spring chamber 9 and, across passage 50 to check valve 51. The initial surge of spill pressure rapidly increases the pressure in the chamber causing reaction force on the internal surfaces 30 of the spring plunger 27. The force of the spring 28 plus the force created by the high pressure fuel in the spring chamber 9 biases the spring plunger 27 forwardly. The forward side of the spring plunger 27 engaging the end 31 of valve element 32 causes the valve element 32 to move forwardly. The forward movement of the valve element 32 causes the conical portion 33 to engage its mating valve seat 34 closing the differential valve terminating injection. The gas pressure in the combustion chamber and the force of the pressurized fuel in chamber 42 are not sufficient to reopen the differential valve 49 because they act on substantially smaller areas and consequently the fuel injection is terminated quickly and completely.

Any further forward movement of the pump plunger 3 is ineffective in causing any fuel injection as the fuel is directed into the spill passage 48 and the spring chamber 9 as well as the transfer passage 50 which contains a check valve 51. The check valve 51 is set at a predetermined pressure and fuel in the passage 50 builds up until the check valve releases fuel into the outlet passage 46. The check valve operating pressure is substantially below the nozzle opening pressure but is sufliciently high to aid the closing of the differential valve. The initial surge of high pressure fuel into the spill passage 48 and the passage 69 and spring chamber 9 causes an immediate closing of the differential valve 49.

The spring chamber 9 is vented by means of the peripheral passage formed by a loose fitting tolerance between the external periphery of the spring plunger 27 and the internal periphery of the sleeve 6 which permits the flow of fluid forwardly around the spring plunger 27. The fluid is then vented to the bleed passage 52 which extends axially from the forward end of the spring chamber 9 to the inlet passage 39. The bleed passages permit a decay of pressure in the spring chamber 9 between injections to substantially the level of the inlet pressure in passages 37, 38 and 39.

The pump plunger 3 is permitted to retract until the annular recess 25 is again in registry with the

passages

44, 45. The plunger remains in this position and the incoming fuel from the inlet passage 38 is again permitted to flow through the unit injector providing a cooling process of the nozzle and differential valve and the assembly in general.

It can be seen from the above description that the differential valve 49 is opened in response to the differential fuel pressure on the rearward side of the stem 31 of the valve element 32 and on the forward side of the valve element 32. The high pressure of the injection fluid when the pump is in operation is in the order of several thousand pounds per square inch which will bias the valve element 49 to a rearward position and quickly open the valve against the force of the spring 28 in the spring chamber 9 which operates against the spring plunger 27 Once the differential valve is opened the continued high pressure of the fuel passing through the nozzle will maintain the valve in an open position.

Once the helical edge 21 on the pumper plunger 3 is in communication with the spill passage 48, the pressure in the high-pressure chamber 8 and

passages

48 and 69 is directed into the spring chamber 9. The forward surface internally of the spring plunger 27 is substantially larger than the combination of radial surfaces on the forward side of the differential valve element 32. Accordingly, the high pressure fuel acting in the spring chamber 9 will immediately close the differential valve because of the differential of areas of the plunger defining the spring chamber and the valve element 32 resulting in a force immediately closing the valve. The high pressure fluid in the spring chamber will then bleed off through the bleed passage 52 and reduce the pressure within the spring chamber prior to opening again in response to fuel injection as the fuel injector goes through another cycle.

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

1. A fuel injector having hydraulic means to augment closing of the differential valve comprising means defining inlet passage means, means defining outlet passage means, means defining an injection pump having a high pressure pumping chamber intermittently connected to said inlet passage means and said outlet passage means, a differential valve having a valve element in an injector nozzle in communication with said high pressure pumping chamber operating in response to high pressure fluid to open said differential valve to provide fuel injection, means including a plunger of larger cross sectional area than said differential valve element reciprocating in a sleeve defining a low pressure chamber and a spring chamber receiving a spring driving said plunger and biasing said differential valve to a normally closed position, means defining a spill passage connected to said spring chamber and intermittently connected to said high pressure chamber for receiving pressurized fluid from said high pressure chamber when fuel injection is terminated, pressure retaining means in said outlet passage'means to direct a surge of high pressure fluid into said spring chamber acting on said plunger to augment the differential valve closing force of said spring and positively terminate fuel injection, means defining a bleed passage means connected between said inlet passage means said low pressure chamber and said spring chamber for relieving pressure in said spring chamber subsequent to closing of said differential valve.

2. A fuel injector as set forth in claim 1 wherein said bleed passage means is partially formed by said plunger and said sleeve defining a loose fit thereby providing restricted flow from said spring chamber to said low pressure chamber to relieve the pressure in said spring chamber to permit ease of opening of said differential valve when fuel injection is initiated on the next cycle of operation.

3. A fuel injector as set forth in claim 1 wherein said pressure retaining means consists of a check valve operating at a predetermined pressure to create a surge of pressurized fluid into said spring chamber to positively close said differential valve to terminate fuel injection.

References Cited UNITED STATES PATENTS 2,055,580 9/1936 Larsson et a1. 239-89 2,071,237 2/1937 Rupprecht 23990 2,279,010 4/ 1942 Nichols -5 239-92 2,401,579 6/1946 Miller 23990 3,115,304 12/1963 Humphries 23990 3,257,078 6/ 1966* Mekkes 239-90 EVERETT W. KIRBY, Primary Examiner US. Cl. X.R. 239533, 584, 96