US2537087A - Fuel injection apparatus - Google Patents

Description

Jan. 9, 1951 H. T. PYK ET AL FUEL INJECTION APPARATUS 2 Sheets-Sheet 1 Filed April 2, 1945 A :g%wl ln m A H 5 m Jan. 9, 1951 H. T. PYK ET AL 7 FUEL INJECTION APPARATUS Filed April 2, 1943 2 Sheets-Sheet 2 24/ 25' 26 2 I if Fuel supply I v j-j/l uelJup vly Patented Jan. 9, 1951 FUEL INJECTION APPARATUS Herman Theodor Pyk, Saitsjo-Duvnas, and Hilding Gunnar Camner, Ektorp, Sweden, assignors to Aktiebolaget Sweden Atlas Diesel, Stockholm,

Application April 2, 1943, Serial No. 481,548 In Sweden March 7, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires March 7, 1962 12 Claims. 1

The invention relates to fuel injection apparatus and, in particular, to apparatus of this kind as used in conjunction with internal combustion engines.

Diesel engines, especially high speed engines with solid injection, generally operate in rough and uneven manner when the ordinary injection devices are used, owing to the fact that the ignition takes place more or less explosively. This rough running is a great disadvantage, because not only does it impose extra mechanical strains on the engine but also causes considerable and disturbing noise.

In order to improve this rough running attempts have been made to divide the fuel injection into two entirely separate phases, namely a preliminary and a main injection, respectively, with an interval between the two.

The disadvantage of this arrangement is, however, that after the first injection a certain amount of dripping occurs just as the fuel vave is in the act of closing, which results in smoky exhaust gases and a lowered fuel economy.

The object of our invention is to avoid these disadvantages by effecting the fuel injection in two stages but continuously and so that in the first stage a substantially constant and.relatively low injection pressure is maintained, while in the latter stage, and without any lowering of the pressure between the stages, the pressure is increased to its maximum value. rise of the pressure in the second stage, representing the main injection, may be very rapid. The result of this improved method of injection is a smooth and silent engine without any continuous dripping, and hence the deleterious results above referred to are avoided.

The invention is represented by way of example in the accompanying drawings, where Fig. 1 shows graphically the fuel pressure during the two injection stages, while Figs. 2, 3 and 4 respectively present different embodiments of devices for carrying the process according to the invention into eifect.

In the diagram shown in Fig. 1, the ordinate indicates the fuel pressure and the abscissa the time. The fuel injection begins, after a pressure necessary for opening the valve has been built up in the fuel pump, at the moment a and then continues under a substantially constant and relatively low pressure 121 during a certain time interval between a. and b. The fuel injection then continues directly following the said interval w-b, under the gradually increasing pressure during the time interval This.

b-c to the maximum value 1):, after which the pressure wholly or partly ceases when the feed pressure of the fuel pump drops. The injection thus proceeds uninterruptedly during the time interval a-c in a first stage 0-1) under a relatively low and substantially constant pressure, and in a second stage b-c under gradually increasing pressure up to the maximum value.

The quantity of fuel injected during the first stage should be as small as possible, but should, however, be distributed over a certain period enabling ignition to take place before the second stage of injection has commenced or immediately thereafter.

One embodiment of a device for carrying the said process into eiiect is shown in Fig. 2.

In this figure a fuel pump of known design is shown, comprising the pump casing I, the piston 2 operating therein, the pump chamber 3 and the channels 4 connecting the pump chamber with a fuel reservoir (not shown). In the pump head 5" is provided a non-retum valve I loaded by a spring 6.

The injection valve is indicated by 9 and its nozzle by Ill. The injection passage is regulated by a valve member II with a plunger I2 arranged in a chamber I3 which communicates through a channel I4 in the valve casing, a pipe I5 and the discharge duct regulated by the nonreturn valve I with the fuel pump chamber 3. The valve plunger I2 is loaded by a spring I6 against the fuel pressure in the chamber I 3.

On the upward stroke of the piston 2 and after the piston has closed the channels 4, 4 the pressure rises in the pump chamber 3 and the fuel flows past the open valve I through the pipe I5 and the channel I4 to the valve chamber I3 in the nozzle I0. When the pressure in the chamber I3 has risen to a value sufiicient to overcome the pressure of the spring I6 the needlevalve II opens the passage in the nozzle I0 and injection into the engine cylinder begins.

In this case the desired pressure curve is obtained by means of a pump cam 8 of special design.

Injection begins approximately at the point where the cam 8 presses against the roller ll of the pump at the point m. The part a1b1 of the cam curve is designed to have a slight rise which is so adapted that the pressure during this injection stage is kept substantially constant. The following part b1-c1 of the curve is designed to have a sharper rise so that the movement of the piston 2 becomes more rapid, the result being that the fuel pressure rises owing to the resistance Another arrangement for producing the same injection process is shown in 3.

The fuel pump is of the same design as that shown in Fig. 2, with the difference, however, that the pump cam 8 is of ordinary design with a continuously rising working curve. The injection valve can be of the same design as according to Fig. 2 and is not shown.

A cylinder 23 is screwed into the pump head 5 and the cylinder space thereof communicates through a channel 24 with the pump chamber 3. A piston 25, operates in the cylinder 23 and the outer flanged end thereof engages one end of a compression spring 26, the other end of which rests against the bottom of a spring chamber 21 screwed on to the cylinder 23. Screwed into the bottom of the spring chamber 21 is a setscrew 28 serving as an adjustable abutment for the piston 25.

During the first stage of the injection the piston is displaced towards the right in Fig. 3 against the action of the spring 26, a part of the fuel enters the cylinder 23 and the fuel pressure in the pump and the injection valve will during this stage of the injection be substantially constant and determined by the force of the springs 26. This first stage is concluded when the piston 25 engages the abutment 28, after which the fuel pressure is determined solely by the resistance in the fuel injection nozzle, that is, it will gradually increase in the manner above-described. When the feed pressure drops the piston 25 is returned by the spring 26 into the initial position shown in the figure.

A further arrangement according to the invention is shown in Fig. 4, which in certain respects resembles that according to Fig. 3. Thus in this case too, a cylinder 23 is screwed into the pump head 5 and the cylinder space thereof communicates by 'means of a channel 24 with the pump chamber 3. A piston 25 is movable in the cylinder 23 and loaded by a spring 26. The travel of the piston islimited by an adjustable abutment 28.

seat in the bottom of the cylinder 23. The valve The inner end of the piston is formed as a valve member 29, which under theaction of the spring 26 is kept pressed against a body 29 has a smaller diameter than the piston itself so that an annular space 30 is formed Ata continued injection a part of the fuel will thus pass through the channels 32 and 33 and through the throttle channel 34 and may then flow, for example to the suction chamber of the pump.

By suitable selection of the area of the channel 34 the first stage of theinjection will take place under a substantially constant and relatively low pressure.

that the latter stage of the fuel injection occurs with gradually increased pressure in accordance Y with the idea of the invention.

The channels 32, 33 and 34 may be omitted hi together. When the valve 29 opens, a displace= ment increase will occur in the cylinder space at and around the valve body owing to the valve 2' being displaced towards its abutment, which latter can be so adjusted that the pressure during a required time interval is kept at the desired value during the first stage of the injection.

As regards the devices according to Figs. 3 and 4, no special form of pump cam is necessary, but a cam of the ordinary shape can be employed. A more gradual rise of the cam at the beginning of the pressure stroke may, however, be preferable.

All the devices hereinbefore described can be used in association with different kinds of injection valves, but will be most effective if combined with injection valves having low opening pressure, for example as described in the copending patent application of Hilding Gunnar Camner Ser. No. 400,946 now issued as Patent No. 2,380,148 of July 10, 1945. We therefore claim all combinations of the apparatus described and claimed in the present application with those described and claimed in our said copending application.

It will, of course, be appreciated that the invention is not restricted to the embodiments shown on the drawings. Thus, the resilient regulating piston according to Figs. 3 and 4 can be replaced by a bellows, diaphragm or the like. The resilient piston, bellows or diaphragm or the like, as well as the specially designed pump cam can also be replaced by a piston working in a cylinder in communication with the fuel pipe, and positively governed in such a manner that the desired pressure stages are obtained.

What we claim is:

'1. In a fuel injection apparatus operative to providea preliminary injection stage at a substantially constant moderate pressure followed without interruption by a main injection stage at a'ri'sing pressure, a fuel injection valve operable to .open at said moderate fuel pressure, means .for supplying fuel at substantially said moderate pressure-and for maintaining said pressure substantially constant during the preliminary injection stage, means for immediately thereafter increasing the fuel pressure from said moderate "value to a maximum value during a main injection stage, whereby the latter follows said preliminary stage without interruption of fuel injection, and means for closing said fuel injection valve upon termination of said main stage.

2. In a fuel injection apparatus operative to provide a preliminary injection stage at a substantially constant moderate pressure followed without interruption by a main injection stage at a rising pressure. a fuel injection valve operable to open at said moderate fuel pressure, a pump having a reciprocable plunger for supplying fuel to said valve, a cam for reciprocating said plunger, the profile of said cam including a portion having a comparatively gradual rise for advancing said plunger at a rate to supply fuel at substantially said moderate pressure and to maintain said pressure substantially constant tdurin'g'the preliminary injection stage, said cam -.r ise in uninterrupted continuation of the first- The piston 25 will then during continued injection gradually cover the throttle channel 34 and then engage the abutment 28. The pressure in the pump and in the fuelpipe will then rise mem including a further portion having a steep mentioned portion for advancing said plunger at afaster rate to supply fuel at a pressure increasing from said moderate value to a maximum latter follows said preliminary stage without interruption of fuel injection, and means for closing said valve upon the termination of said main stage.

3. In a fuel injection apparatus operative to provide a preliminary injection stage at a substantially constant moderate pressure followed without interruption by a main injection stage at a rising pressure, a fuel injection valve operable to open at said moderate fuel pressure, a pump having a plunger reciprocable within a pressure chamber, means connecting said chamber to said valve, means for reciprocating said plunger for displacing fuel from said chamber,

means providing a resiliently expansible chamber in communication with said pressure chamber for accommodating a portion of the displaced fuel to maintain the pressure thereof at said moderate pressure during the preliminary injection stage, means for arresting the expansion of said expansible chamber to provide an increase in fuel pressure during the main injection stage, whereby the latter follows said preliminary stage without interruption of fuel injection, and means for closing said valve upon termination of said main stage.

4. In a fuel injection apparatus operative to.

provide a preliminary injection stage at a substantially constant moderate pressure followed without interruption by a main injection stage at a rising pressure, a fuel injection valveoperable to open at said moderate fuel pressure, a pump having a plunger reciprocable within a pressure chamber, means connecting said chamber to said valve, means for reciprocating said plunger for displacing fuel from said chamber. means providing a second chamber connected to said pressure chamber, a member movable in said second chamber to vary the volume thereof, resilient means resisting movement of said member in a direction increasing said volume, whereby said second chamber accommodates a portion of the displaced fuel to maintain the pressure thereof at said moderate pressure during the preliminary injection stage, means for arresting the movement of said member to provide an increase in fuel pressure during the main injection stage, whereby the latter follows said preliminary stage without interruption of fuel injection, and means for closing said valve upon termination of said main stage.

5. Fuel injection apparatus as defined in claim 4 in which the means for arresting movement of said member is adjustable to vary the travel of said member.

6. In a fuel injection apparatus operative to provide a preliminary injection stage at a substantially constant moderate pressure followed without interruption by a main injection stage at a rising pressure, a fuel injection valve operableto open at said moderate fuel pressure, a

adjustable abutment for limiting said travel of n the piston to provide an increase in fuel pressure during the main injection stage, whereby the latter follows said preliminary stage when said piston strikes said abutment without interruption of fuel injection, and means for closing said valve upon termination of said main stage.

7. In a fuel injection apparatus operative to provide a preliminary injection stage at a substantially constant moderate pressure followed without interruption by a main injection stage at a rising pressure, a fuel injection valve operable to open at said moderate fuel pressure, a pump having a plunger reciprocable within a pressure chamber, means connecting said chamber to said valve, means for reciprocating said plunger for displacing fuel from said chamber, means providing an expansion chamber connected to said pressure chamber, means providing a throttled relief opening communicating with said expansion chamber for discharging a portion of the displaced fuel to maintain the pressure of the fuel supplied to said valve at substantially said moderate pressure during the preliminary injection stage, and means to close said relief opening to provide an increase in fuel pressure during the main injection stage, whereby the latter follows said preliminary stage when the opening is closed without interruption of fuel injection, and means for closing said valve upon termination of said main stage.

8. In a fuel injection apparatus operative to provide a preliminary injection stage at a substantially constant moderate pressure followed without interruption by a main injection stage at a rising pressure, a fuel injection valve operable to open at said moderate fuel pressure, a pump having a'plunger reciprocable within a pressure chamber, means connecting said chamber to said valve, means for reciprocating said plunger for displacing fuel from said chamber, means providing a second chamber connected to said pressure chamber and having a relief opening, a member movable in said second chamber in response to increasing fuel pressure to increase the volume thereof and to close said opening, resilient means resisting movement of said member, whereby said second chamber accommodates a portion and said opening discharges a portion of the displaced fuel to maintain the pressure of the fuel supplied to said valve at substantially said moderate pressure during the preliminary injection stage, means to arrest movement of said member after said Opening is closed to provide an increase in fuel pressure during the main injection stage, and means for closing said valve upon termination of said main stage.

9. In a fuel injection apparatus operative to provide a preliminary injection stage at a substantially constant moderate pressure followed without interruption by a main injection stage at a rising pressure, a fuel injection valve operable to open at said moderate fuel pressure, a pump having a plunger reciprocable within a pressure chamber, means connecting said chamber to said valve, means for reciprocating said plunger for displacing fuel from said chamber, means pro-. viding an expansion chamber connected to said pressure chamber, means providing a throttled relief opening communicating with said expansion chamber, valve means for controlling communication between said pressure chamber and said opening and for controlling flow through said opening, resilient means normally holding said valve means in a position interrupting said communication but with said opening open, said valve means being movable in response to increasing fuel pressure to first establish said communication and to maintain said opening open, whereby a portion of the displaced fuel is discharged through said opening to maintain the pressure of the fuel supplied to said injection valve at substantially said moderate pressure during the preliminary injection stage, said valve means being movable further to close said-opening for providing an increase in fuel pressure during the main injection stage, and means for closing said injection valve upon termination of said main stage.

10. The method of effecting a single continuous injection of fuel to a cylinder of an internal combustion engine which consists in raisin the pressure of the fuel to a predetermined intermediate pressure at which injection is initiated, maintaining said intermediate pressure at substantially constant value for a preliminary period to effect preliminary injection at said intermediate pressure and then raising the pressure of the injected fuel without interrupting the injection to a higher value to complete the injection at pressure higher than said intermediate pressure.

11. The method set forth in claim 10 in which said intermediate pressure is relatively low compared with the final injection pressure.

12. Fuel injection apparatus for stage injection of fuel atdifferent pressures during a single continuous injection period comprising a fuel injector operable to open at an intermediate pressure materially below desired final injection pressure, means for supplying fuel to the injector at said intermediate pressure to initiate injection at the intermediate pressure, means for maintaining said intermediate pressure substantially constant for a preliminary portion of said injection period to continue the injection at substantially the intermediate pressure and means for raising the pressure substantially above said intermediate pressure for the remainder of said period to complete the injection at higher pressure.

HERMAN THEODOR PYK. HILDING GUNNAR CAMNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,953,449 Thege et al. Apr. 3, 1934 1,974,851 Hurst Sept. 25, 1934 2,126,985 Buckwalter Aug. 16, 1938 2 173,813 Bischof Sept. 19, 1939 2,223,755 Dillstrom Dec. 3, 1940 2,225,796 Perrine Dec. 24, 1940 2,278,245 Colell Mar. 31, 1942 2,306,364 Skaredoff Dec. 22, 1942 2,380,148 Pyk et al. July 10,' 1945 FOREIGN PATENTS Number Country Date 165,935 Switzerland Feb. 16, 1934

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