US3722490A

US3722490A - Method of and apparatus for injecting fuel into a diesel engine

Info

Publication number: US3722490A
Application number: US00872825A
Authority: US
Inventors: A Nishina; M Yamaguchi; K Araya; A Enomoto
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 1968-11-15
Filing date: 1969-10-31
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27
Also published as: FR2023365A1; SU374858A3; GB1285975A; FR2023365B1; DE1957370A1; JPS4940569B1

Abstract

A fuel injection system for diesel engine effects a two-stage fuel injection for starting the engine and a single stage fuel injection for operating the engine. During start-up, during each piston cycle, a portion of the fuel is initially injected at a first point during the latter half of the suction stroke and the initial half of the compression stroke of each piston, and an additional amount of the same fuel is subsequently injected at a second point near the end of the same compression stroke of each piston. When the engine has reached a predetermined number of rpms the regular operation of the engine continues with the fuel being injected only in a single stage at approximately the same point in the cycle as the second injection of fuel in the start up procedure.

Description

United States Patent [1 1 [111 3,722,490

Araya et al. 1 Mar. 27, 1973 [54] METHOD OF AND APPARATUS FOR Inventors: Kenji Enomoto, Kyoto;

Araya, Kameoka; Akihiro Akira Nishina,

Otsu; Masahiro Yamaguchi, Kameoka, all of Japan [73] Assignee: Mitsubishi Jukogyo Kabushiki Kaisha, Tokyo, Japan [22] Filed: Oct. 31, 1969 [21] Appl. No.: 872,825

[30] Foreign Application Priority Data Nov. 15,1968 Japan ..43/8339l [52] U.S. Cl. ..l23/179 L, 123/32 G, 123/179 G [51] Int. Cl. ..F02b 3/00, F02n 17/00 [58] Field of Search ..123/326 1, 179 L [56] References Cited UNITED STATES PATENTS 3,339,848 9/1967 Geiger ..239/453 830,144 9/1906 Frantz ....123/32.61 959,951 5/1910 LOrange ....l23/32.61 1,586,623 6/1926 Heidelberg... ....123/32.6l 2,005,063 6/1935 Wild ....l23/32.61 2,010,469 8/1935 Triebnigg..... ....l23/32.6l 2,871,796 2/1959 Dreisin..... ...1123/32.61 2,960,079 11/1960 Monnot. ....123/32.6l 3,014,466 12/1961 Monnot ..123/32.61 3,439,655 4/1969 Eyzat ..l23/32.61

llb I2 I OPERATE START autumn 1 '5 POSITION FOREIGN PATENTS OR APPLICATIONS OTHER PUBLICATIONS Society of Automotive Engineers, Progress in Technology, Volume 11 pages 263-290 Primary Examiner-Laurence M. Goodridge Assistant ExaminerRonald B. Cox Att0rney-McGlew and Toren [57] ABSTRACT A fuel injection system for diesel engine effects a twostage fuel injection for starting the engine and a single stage fuel injection for operating the engine. During start-up, during each piston cycle, a portion of the fuel is initially injected at a first point during the latter half of the suction stroke and the initial half of the compression stroke of each piston, and an additional amount of the same fuel is subsequently injected at a second point near the end of the same compression stroke of each piston. When the engine has reached a predetermined number of rpms the regular operation of the engine continues with the fuel being injected only in a single stage at approximately the same point in the cycle as the second injection of fuel in the start up procedure.

10 Claims, 8 Drawing Figures O STARTING posmow PATENTEDHARZT ms SHEET 10F 2 NOZZLE NEEDLE VALVE LIFT Ill (Prior An) THE TOP DEAD CENTER ANGLE 0F CRANK 9} E N mm 5 F S n MP0 mwm SC F FIG.2

FIG.4

INVENTORS KENJI ARAYA AKIHIRO ENOMOTO BY AKIRA NISHINA MASAHIRO YAMAGUCHI Zzcjwz fl FIG.3

ATTORNEYS PATEI-HEUHARZT 1915 p. a -l 5 u 1 3 1| THE FIRST STAGE FUEL INJECTION FOR STARTING ENGINE SHEET 2 BF 2 A :1 a START OPERATE RUNNING '5 POSITION (1* O STARTING I POSITION I3 ENGINE STARTS THE SECOND STAGE FUEL INJECTION FOR STARTING ENGINE 22%1 Ila STARTING l POSITION 'L Ila RUNNING POSITION FIG.8

INVENTORS KENJI ARAYA AKIHIRO ENOMOTO BY AKIRA NISHINA MASAHIRO YAMAGUCHI ATTORNEYS METHOD OF AND APPARATUS FOR INJECTING FUEL INTO A DIESEL ENGINE SUMMARY OF THE INVENTION The present invention is directed to improvements in the fuel injection system of a diesel engine and, more particularly, it is concerned with a two-stage fuel injection for the start up of the diesel engine and a single stage fuel injection during normal operating conditions. The present invention provides better starting characteristics than have been attainable in the past, especially at low temperatures.

In ordinary conventional diesel engines, the fuel injection is commenced when the piston in the compression stroke has reached a point several degrees to 3) below the top dead center, both during start up and normal running of the engine.

At start up, if the atmospheric temperature is low, the entire engine remains cold and the suction temperature is low. As a result, the air compressed in the cylinders is not heated to a temperature sufficient for effecting ignition, and the ignition lag is extended. With the injection timing during start up at several degrees before top dead center of the compression stroke, the period of time during which the fuel oil particles contact the hot air in the combustion chambers is shortened and it becomes difficult to obtain ignition of the fuel particles.

Such start up conditions are particularly noticeable in a antechamber type diesel engine in which the air is compressed in a main chamber by the upward or compression stroke of a piston and flows through a communication port into an antechamber with the disadvantage that throttling losses at the communication port in combination with low ambient temperature tend to cool the air inside the antechamber to such an extent that it is difficult to reach the ignition temperature even toward the end of the compression stroke. In starting the engine, the fuel is sprayed from a fuel injection pump through a nozzle into the antechamber from where it passes into the main chamber by way of the communication port. However, because the flow velocity of the air from the main chamber through the communication port is fairly high, it is extremely difficult for the fuel spray to pass in the opposite direction into the main chamber. Accordingly, as a rule, antechamber type engines have shown very poor starting characteristics at low temperatures.

Some diesel engines are designed with auxiliary fuel injection during an earlier stage of the compression stroke prior to the fuel injection which takes place as the piston reaches a point several degrees short of top dead center. In a diesel incorporating such a system, the total amount of fuel to be injected is substantially constant both at the start up and during operation of the engine. Such a fuel injection system affords improved fuel combustion, enhanced efficiency, and easy control.

The present invention is directed to improvements in the fuel injection system for diesel engines to overcome the disadvantages of ordinary fuel injection while following a procedure which is different entirely from that of the auxiliary injection system. Therefore, in accordance with the present invention, during start up of the engine, a first stage fuel injection is carried out during the cycle of the piston within the chamber between a point near the end of the intake or expansion stroke and a point at the beginning of the compression stroke and, after the first stage fuel injection is terminated, a second stage fuel injection is performed toward the end of the compression stroke. After the engine reaches a predetermined number of revolutions per minute a change over in the fuel injection system is made and a single stage injection is carried out at a point substantially corresponding to the second stage of the fuel injection at start up. As indicated above, during start up a two stage fuel injection is employed, consequently, even if atmospheric pressure is low and the air is not adequately heated, the fuel delivered in the first stage injection is thoroughly mixed with the air and heated over a relatively extended period of time during the compression stroke, and the ignition lag is sufficiently shortened to ensure a positive ignition. The second stage fuel injection provides a torque high enough to drive the engine and to start it in a fool proof manner.

Further, after start up, and with the engine temperature at a sufficiently high level, the fuel is injected only at a point substantially corresponding to the second stage fuel injection during the start up. As a result, the engine moves smoothly with an adequate supply of fuel which is neither too great or too small. Moreover, the rate of fuel injection during normal operation can be considerably reduced as compared with the amount employed during start up, thus precluding a drop in thermal efficiency.

When the present invention is used for antechamber type diesel engines, which usually display poor starting characteristics, it is possible, in starting the engine, to

introduce fuel by means of the first stage injection not only into the antechamber but also into the main combustion chamber via the communication port and then, taking advantage of the higher temperature of the compressed air in the main chamber as compared to the antechamber, for igniting the fuel introduced by the first stage injection. A starting characteristic of these engines can be improved over direct injection type diesel engines which are otherwise easier to start.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a generally schematic vertical sectional view of a conventional fuel injection system for a diesel engine;

FIG. 2 is a graph illustrating the operating principles of the present invention;

FIG. 3 is a partial elevational view, partly in vertical section, of a fuel injection system for a diesel engine embodying the present invention;

FIG. 4 is a view taken along line IV-IV of FIG. 3;

FIG. 5 is an enlarged view, partly in section, of a portion of the embodiment shown in FIG. 3;

FIG. 6 is a generally schematic view illustrating the operation of the present invention;

FIG. 7 is a graph illustrating the relationship of the operation of the apparatus illustrated in FIGS. 3 and 6 for carrying out the fuel injection during the start up and normal operation of the engine; and

FIG. 8 is a schematic illustration of another embodiment of a portion of the apparatus set forth in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a conventional antechamber type diesel engine is shown as comprising a piston a disposed within a main combustion chamber b with a communication port c disposed between the main combustion chamber and an antechamber d. In supplying fuel to the combustion chamber, a fuel injection pump e delivers the fuel through a line 2 into a nozzle ffrom which it is sprayed into the antechamber d. From the antechamber, the fuel enters the main combustion chamber through the communication port c. The fuel is sprayed into the antechamber during the latter part of the compression stroke. As a result, during start up, the flow velocity of the air from the main chamber b through the communication port is relatively high and it is difficult for the fuel sprayed into the antechamber to pass into the combustion chamber. As a result, antechamber type engines of the type illustrated in FIG. 1, have poor starting characteristics at low temperatures.

In the different FIGS. illustrating the present invention, the same reference numerals are used for the same elements.

In FIGS. 3 through 7, a main combustion chamber 1 of a diesel engine is shown with a piston 2 mounted for reciprocation within the chamber through an expansion or intake stroke and a compression stroke. At one end the main chamber 1 is in communication with a precombustion chamber or antechamber 4 through a port 3. 7

At the entrance to the antechamber 4 opposite its connection to the main chamber is a nozzle needle valve 5 mounted within 2 nozzle 6. A fuel injection conduit 7 connects the nozzle 6 with a fuel injection pump 8a.

The fuel injection pump 8a comprises a casing 8 having a longitudinally extending bore 8b. Fitted within the upper end of the bore, as shown in FIG. 3, is a valve housing 10 containing a valve 9 which is in communication with the bore 8b through the casing 8. Extending through the bore 812, from adjacent the end of the valve 9, is a plunger 12 which extends to the opposite end of the bore. The plunger is axially displaceable through the bore. Positioned below the plunger, at the lower end of the bore 8b, is a cam 13 which is arranged to revolve in synchronization with the piston 2 within the chamber 1. As the cam rotates, its surface contacts the lower end of the plunger 12 and causes the plunger to move upwardly and downwardly in controlling the fuel injection into the chamber of the diesel engine.

A rack 14 extends into the housing 8 intermediate its ends and is in meshed engagement with teeth on the circumference of the plunger 12. At its end spaced from the plunger, the rack 14 is connected to one end 1517 of a rockable fork lever 15 pivotally supported at 15a. The opposite end 15c of the fork lever 15 abuts against a sliding shaft 160 of a governor 16. An arm 15d projects outwardly from the fork lever adjacent the point 15a, and is connected at its outer or free end to a governor knob 18 through a spring 17.

Mounted'on the upper end of the casing 8, is a starting button 19. It is biased by a spring 19a into an inoperative position. Positioned at the lower end of the button is a rack pin 20 provided on the rack 14 and which is held in the inoperative position by a stop member 21.

In the fuel injection system described above the starting procedure is performed in the following manner. With the engine in an inoperative state, the governor knob 18 is moved to the starting position, as shown in FIG. 6, and the starting button 19, as shown in FIG. 5, is displaced from its inoperative position shown by dotdash lines to the starting position shown in full lines. When the starting button 19 is depressed the rack pin 20 on the rack is released from the stop member 21 and shifts from the position it maintains during normal operating or shut down conditions to the starting position. As the rack pin is shifted the engagement of the rack with the plunger 12 causes the plunger to be rotated so that the upper part of its stepped portion 11 is moved adjacent to a fuel inlet port 22 into the bore 8b.

Next the engine is started by means of a starter, not shown, and the cam 13 is turned counterclockwise, as FIGS. 3 and 6. As the cam rotates its first cam lobe 13a comes into contact with the lower end of the plunger 12 and displaces it axially upward from the lift position (1,) shown at the left hand side of graph in FIG. 7 to the lift position (1 shown at the right side of FIG. 7, while the fuel inlet port 22 is kept closed by the upper part 1 1a of the stepped portion 1 1 of the plunger 12. During this movement of the plunger a first stage fuel injection is accomplished with approximately one-half of the total amount of fuel to be injected flowing into the antechamber 4.

The timing employed in lifting the plunger with the first cam lobe 13a is set to extend from the terminal portion of the intake or expansion stroke to the beginning of the compression stroke, so that the fuel sprayed into the antechamber 4 during the first stage of the fuel injection procedure passes through the port 3 into the main combustion chamber 1, where it is thoroughly mixed with air and heated to an elevated temperature as the compression stroke continues.

As the first lobe 13a of the cam rotates past the lower end of the plunger, the plunger drops downwardly within the bore 8b and the fuel injection is interrupted. Subsequently, the second lobe 13b of the cam which trails the first lobe 13a comes into contact with the bottom of the plunger raising it through the bore 8b to the lift position (1 Between the first and second stage of fuel injection during engine startup, the fuel inlet port 22 is kept closed by the upper part 110 of the plunger. With the plunger again lifted with the upper part 11a of the stepped portion 11 blocking the fuel inlet port 22 the second stage fuel injection commences. With reference to FIG. 2, as the second stage fuel injection begins, the temperature (t,,,) of the gaseous mixture of air and fuel within the main combustion chamber 1 becomes higher than the temperature (t,) in the precombustion chamber or antechamber 4 and is readily ignitible. A portion of the fuel supplied by the second stage injection flows into the main combustion chamber 1 through the port 3 at the point in the cycle where the flow velocity (w) is slightly reduced and is burned together with the gaseous mixture to provide the explosive force required for starting the engine and enabling it to be started with considerable ease.

Once the engine has attained a certain number of revolutions per minute, the centrifugal force of a weight 16b mounted on the governor 16 causes the sliding shaft 16a of the governor to be displaced in the direction of the arrow shown in FIG. 6. As a result, the rack 14 is shifted by means of the fork lever and the plunger is turned angularly about 180 so that the lower portion 11b of the cutaway step portion 11 of the plunger is disposed opposite the fuel inlet port 22.

Since the plunger has been rotated and its lower part 11b is positioned opposite the fuel inlet port no fuel injection takes place since the port is not closed when the plunger is lifted to the lift position (1,) as indicated in FIG. 7, noting the lower left hand representation of the position of the plunger relative to the fuel inlet port 22. When the plunger 12 is lifted upwardly by the second lobe 13b of the cam the lower part 11b of the plunger effects a closure or sealing of the fuel inlet port and the fuel is injected into the combustion chamber 1. In this manner fuel injection is effected at a lower rate of fuel supply than at start up and proceeds to operate in the same manner as in conventional diesel engines, and a sound operation is maintained.

In the event the engine fails to reach the predetermined number of revolutions per minute to effect the change over from the start up to the operating positions of the plunger, the governor knob 18 can be moved to the operating position so that the plunger is rotated from the start up position with the lower part 11b in juxtaposition to the fuel inlet port 22.

In the embodiment described, by varying the height of the cutaway stepped portion of the plunger and the lift positions effected by the first lobe of the cam it is possible to adjust the amount of the first stage fuel injection to a value between 25 and 75 percent of the total amount of the fuel to be injected. It is also possible to vary the total fuel injected from 150 to 300 percent of the total amount at the maximum output during the operation of the engine.

In the start of the engine, as described above, the first stage fuel injection is completed in the early portion of the compression stroke when the flow rate through the port 3 is low and permits the introduction of an ample supply of the fuel into the main chamber and the ignition of the charge in the main chamber at a higher temperature than the temperature (t,,) of the compressed air in the antechamber 4. Therefore, better starting characteristics are available than those of direct injection type engines. As an alternative to the stepped configuration of the plunger shown in FIGS. 3, 6 and 7, the upper portion of the plunger can be cut at an acute angle to the longitudinal axis of the plunger, as shown in FIG. 8, for attaining a similar effect to that provided by the stepped arrangement.

The range of the fuel injection timing for start up of the engine, in accordance with the present invention, takes place between 300 124, particularly -270 154 (representing the angle of the crank) in the first stage of fuel injection and between 23 +2", particularly 1 8 3, in the second stage offuel injection.

As indicated above, the drawings are in a generally schematic form, and various embodiments of the elements forming the invention can be effected without departing from the basic spirit of the invention.

What is claimed is:

l. A method of starting and operating a diesel engine comprising the steps of effecting a two-stage fuel injection, during starting of the engine, by initially injecting a portion of the fuel at a first point during the latter half of the suction stroke and the initial half of the compression stroke of each piston, and subsequently injecting an additional amount of the same fuel at a second point near the end of the same compression stroke of each piston; and when the engine has attained a selected operating speed, discontinuing injection of fuel at the first point and thereafter injecting the same fuel at only the second point, in each compression stroke, to effect only a single stage fuel injection during further operation of the engine. 7

2. Fuel injection apparatus for a diesel engine, operable to effect a two-stage injection of a single fuel during starting of the engine and only a single-stage injection of the same fuel during running of the engine, said apparatus comprising, in combination, a casing having an axial bore therethrough; a valve at one end of said bore communicating with an engine combustion chamber; a fuel inlet port communicating radially with said bore intermediate the ends of said bore; a substantially cylindrical plunger reciprocable in said bore; driving means engaged with the outer end of said plunger to reciprocate said plunger to draw fuel into said bore through said inlet port and to eject fuel through said valve into the engine' combustion chamber; said plunger, in an injection stroke, blocking said fuel inlet port; the inner end of said plunger being higher at one end of a diameter than at the other end of said diameter; and rotating means operable to rotate said plunger between a starting position, in which said higher inner end controls said inlet port, and a running position, in which said lower inner end controls said inlet port; said driving mechanism effecting two reciprocations of said plunger in each cycle, with the second inward stroke of said plunger being longer than the first inward stroke of said plunger and terminating with said lower inner end of said plunger at an inlet port blocking level; each outward stroke of said plunger terminating with said lower inner end of said plunger at an inlet port clearing level; said higher inner end of said plunger, in only said starting position, blocking said inlet port between said first and second inward strokes of said plungen' 3. A fuel injection apparatus, as claimed in claim 2, including means operatively associated with said rotating means and operable, responsive to the engine attaining a predetermined running speed, to activate said rotating means to rotate said plunger from its starting 6. A fuel injection apparatus, as claimed in claim 3, in which said rotating means comprises a reciprocable rack meshing with gear teeth on said plunger; said operating means for activating said rotating means comprising a lever secured to and extending from said rack; and an engine speed responsive governor coupled to said lever to operate said rack to rotate said plunger.

7. A fuel injection apparatus, as claimed in claim 2, wherein said operating means comprises a rotatable cam cooperable with the outer end of said plunger and having two cam lobes, of different radial extent, for effecting the respective inward strokes of said plunger; said cam having respective cam surfaces interconnecting said cam lobes and controlling the outward movement of said plunger.

8. A fuel injection apparatus, as claimed in claim 6, wherein said lever is pivoted intermediate its ends; and a manual control lever connected to said first-mentioned lever and operable to swing said first-mentioned lever to rotate said plunger from said starting position to said running position.

9. A fuel injection apparatus, as set forth in claim 6, comprising a starting button mounted on said casing, a stop cooperating with said rack for holding said rack in the operating position, a rack pin mounted on said rack and secured in position by said stop in the operating position and reieasable by depressing said button, said rack pin effecting the movement of said rack to the starting position.

10. A fuel injection apparatus, as set forth in claim 2, comprising an injection conduit connected at one end to said valve, a nozzle secured to the opposite end of said conduit, and a needle valve mounted within said nozzle for injecting the fuel into an engine chamber.

Claims

1. A method of starting and operating a diesel engine comprising the steps of effecting a two-stage fuel injection, during starting of the engine, by initially injecting a portion of the fuel at a first point during the latter half of the suction stroke and the initial half of the compression stroke of each piston, and subsequently injecting an additional amount of the same fuel at a second point near the end of the same compression stRoke of each piston; and when the engine has attained a selected operating speed, discontinuing injection of fuel at the first point and thereafter injecting the same fuel at only the second point, in each compression stroke, to effect only a single stage fuel injection during further operation of the engine.

2. Fuel injection apparatus for a diesel engine, operable to effect a two-stage injection of a single fuel during starting of the engine and only a single-stage injection of the same fuel during running of the engine, said apparatus comprising, in combination, a casing having an axial bore therethrough; a valve at one end of said bore communicating with an engine combustion chamber; a fuel inlet port communicating radially with said bore intermediate the ends of said bore; a substantially cylindrical plunger reciprocable in said bore; driving means engaged with the outer end of said plunger to reciprocate said plunger to draw fuel into said bore through said inlet port and to eject fuel through said valve into the engine combustion chamber; said plunger, in an injection stroke, blocking said fuel inlet port; the inner end of said plunger being higher at one end of a diameter than at the other end of said diameter; and rotating means operable to rotate said plunger between a starting position, in which said higher inner end controls said inlet port, and a running position, in which said lower inner end controls said inlet port; said driving mechanism effecting two reciprocations of said plunger in each cycle, with the second inward stroke of said plunger being longer than the first inward stroke of said plunger and terminating with said lower inner end of said plunger at an inlet port blocking level; each outward stroke of said plunger terminating with said lower inner end of said plunger at an inlet port clearing level; said higher inner end of said plunger, in only said starting position, blocking said inlet port between said first and second inward strokes of said plunger.

3. A fuel injection apparatus, as claimed in claim 2, including means operatively associated with said rotating means and operable, responsive to the engine attaining a predetermined running speed, to activate said rotating means to rotate said plunger from its starting position into its running position.

4. A fuel injection apparatus, as claimed in claim 2, in which the inner end of said plunger has a stepped formation providing said higher and lower inner ends, each step being substantially semicircular and said steps being spaced axially from each other.

5. A fuel injection apparatus, as claimed in claim 2, wherein the inner end of said plunger is an oblique surface sloping, at an acute angle to the axis of said plunger, from one end of said diameter to the other end of said diameter.

6. A fuel injection apparatus, as claimed in claim 3, in which said rotating means comprises a reciprocable rack meshing with gear teeth on said plunger; said operating means for activating said rotating means comprising a lever secured to and extending from said rack; and an engine speed responsive governor coupled to said lever to operate said rack to rotate said plunger.

9. A fuel injection apparatus, as set forth in claim 6, comprising a starting button mounted on said casing, a stop cooperating with said rAck for holding said rack in the operating position, a rack pin mounted on said rack and secured in position by said stop in the operating position and releasable by depressing said button, said rack pin effecting the movement of said rack to the starting position.