US2890657A - Unit injector pump with pilot injection - Google Patents

Description

June 16, 1-959 UNIT INJECTOR PUMP WITH PILOT INJECTION Filed Aug. 12, 1955 I g I I i I 5 k 22 z m 1'66 I 3 1' 5g 1 7. av- 0/ N1 v 5/ 4. J. MAY ,ETAL

2 Sheets-Sheet 1 INVENTORS ATTORNEY 1.1. MAY EFAL UNIT mqsc'roa PUMP WITH PILQTINJECTION June 16, 1959 4 Filed Au 12, 1955 INVENTORS 2 Sheets-Sheet 2 5 6% 1 Fem Y Unite UNIT INJECTOR PUMP WITH PILOT INJECTION John J. May, Birmingham, Mich., and Ray G." Ulrey,

Spring Hill, ,Ala., assignorsto General Motors' Corpo- -ration, Detroit, Mich, a corporation 'of Delaware "Application'August 12, 1955, Serial No. 528,039

- 6 Claims. (Cl. 103-41) This inventionrelates to unit injector pumps such as areused for delivering metered amounts offu'el to internal combustion engines, and'particularly to such de- "vices'wherein the'injection is'effected intwo distinct "phases,'i;e., a pilot or primary injection and a main or' secondary injection with a gap or time interval therebetween.

v lnjectionof the fuel in this manner is advantageous, "particularly with diesel engines, because the primary injection charge which can'be made relatively small in "quantity servesto initiate'the combustion in the engine cylinder in advance of the main charge, thereby reducing the rate of pressure rise'and" the peak pressure developed inthe combustion chamber, with consequent increased f'efiiciency and lowering of the noise level of the com- 'bustion process. While prior unit fuel injector pumps of fthisgeneral type have heretofore been proposed, they h'avebeen subject to a number of objections including an inability to precisely time one or both of the injection charges and have generally been of unduly complicated" designwith attendant excessive cost ofmanufacture.

, It is the object of our invention to overcome the ob "jections of such' prior injector pumps by providing that the'pumping chamber pressure be at or higher than the "primary injection pressureduringthe gap between injections, by providing for 'both injection charges'to be with the invention.

'Figure' 2' is a diagrammatic view showing a full 360 development of the inner end portion of the plunger of "the pump of'Figure 1.

Figures 3-8 are fragmentary views of the pump plunger and cylinder members in their various relative positions during thepumping stroke.

"The'injector pump shown in Figure 1 includes the 1 pump body'2' having a lower removable portion threaded "thereto at 4 and adapted to extend through'an opening "in the cylinder head of a diesel engine so as to locate the fuel nozzle 6 at its lower end within the combustion space of the engine. Small spray orifices 8 in the tip end of this nozzle are supplied by a fuel duct 10 which a is :normally closed by a spring biased 'delivery valve 12 whichopens under predetermined injection pressures developed in the fuel chamber-14 of the pump. Holding -thenozzle 6'seated in the lower end of the housingare S ttes t e rrt upper and lower spacer blocks 13, 15 with connecting passages 16 and 18 and a pump cylinder member in the form of a bushing 20 which has a shoulder 22 abutting the-lower end -of the upper body part 2. The upper spacer block l3-closes the'lower end'ofthe bushing.

The upper end ofthe bushing is of reduced wall thickness "andextends into the body" part 2 and locates a pinion 24'tl1erein between a spacersleeve 26 and a ring"28 which is seated against a shoulder in the body '2. The

bore 30 of the bushing is slidably 'fi'ttedby a pump plunger member 32 whose lower or inner end cooperates with the bushing bore in defining thepumping chamber 14,'-and whose upper end has a poly-sided section 34 slidably spline'd in the pinion'24. -Recip'rocation 'ofthe plunger is-effected by an engine driven rocker 36 'or likemeriiberwhich transmits its movement'to the extreme outer end of the plunger by a push rod38. The upper I end 'of'the push rod is'fiange'd to receive return thrust from'a guide sleeve 40 which'slidablyfitsin-the upper end of'thepump 'body '2 andis biasedtherefrom by a compression spring '42. The lower end 44 of the guide 'sleeve '40 is bifurated to" interengage a necked-in portion "46 adjacent theupper end of the plunger. 7 Meshing with 'the 'pinion "24' is a fuel rack 48 which is 1 suitably guided "for actuation'transversely of the plunger to'rotatively adjustthe plunger-for controlling the durationand timing of the fuel injectioncharges during engine operation.

Fuel supplyandreturnpassages,"one of which is shown at 50, are 'providedin the pump body for connection with a transfer pump or otherpressure fuel source (not These passages lead to andfrom a fuel receiving chamber 52 Which is 'formedas an annular space surrounding the "bushing 20. Passage means are 'provided in this bushing for connectingits bore 30'with the fuel receivingchamber-SZ andthe'passage 18 leading to thefuel nozzle 6. Included in "this passagemeans are inlet and by-pass ports '54, 56 whichiextend through opposite side walls of .the bushing in spaced relation axially thereof as shown, a' fuel discharge port58diametrically opposite the 'port'56 and connected by a longitudinal tip passage 60 with the passage"18,"and a srn'all bleed by-pass port '62 which extends .through the side Wall of the bushing to connect the receiving chamberwith the bore 30 at a distance inwardly from 'theiports 56 =and 58. This bleed port 62 is of substantially smaller. size than the discharge port 58, as shown.

Passage means are provided in the plunger to cooperate with the cylinder ports 54, 56 and 58 in controllingthe start and ending of the main fuel charge. 'Such' passage means includes an external metering groove64 which'encircles the plunger at a distance above its innermostend,

together with transverse and connecting axially'drilled ports 66 and 68 which continuously connect themetering groove with the pumping chamber 14. Themetering groove 64 is defined by axially spaced inner and outer lands 70 and 72 which are best shown in the diagrammatic development of this end of-the plunger :in Figure 2. Indicated in broken outline in Figure '2 'are also the relative locations of the cylinder ports'54, 56,

58 and 62, when the plunger is at the start of its pumping stroke and is angularly rotated to its maximum pump- -ing rate setting by the fuel rack 48.

Referring to Figure 3 which also shows. the plunger in this same position at the start of. its pumping stroke, it will be seen that fuel from the receiving-chamber 52 may flow into the pumping chamber 14. directly via: the ports 56 and 62, and via the port 54 through theplunger metering groove 64 and passages 66, 68. During. the initial downward movement of the plungento the position shown in Figure 4, excess fuel and any air contained in the pumping chamber 14 is displaced or by-passed through the ports 54 and 56 until the inner extremities of the outer and inner lands 72 and 70 close off the ports 54 and 56, respectively, without creating sufficient pressure inthe pumping chamber to open the delivery valve 12 to eflfect injection. A small amount of fuel also is lay-passed through the bleed passage 62 to the receiving chamber during this portion of the plunger travel. The discharge port 58 being still partially uncovered by the inner land at this point, the initial or primary injection then begins at a rate and pressure reduced slightly by the bleed passage 62 being still allowed to bypass some of the fuel to the receiving chamber. Such primary injection continues until the plunger reaches its position shown in Figure 5, when the discharge port becomes fully closed by the inner land of the plunger. This results in an immediate cut-off of further delivery of the fuel to the nozzle, without relieving the pump chamber pressure. A gap thus occurs during which there is no injection until the plunger reaches the position shown in Figure 6 when the inner land starts to again uncover the discharge port. Fuel under pressure in the pumping chamber is then displaced through the plunger passages 66 and 68 to the metering groove 64.

for delivery via the discharge port to the fuel nozzle, the fuel by-pass and inlet ports 56 and 54 in the bushing remaining closed by the plunger inner and outer lands 70, 72, respectively. Main or secondary injection then begins and continues until the plunger reaches the position shown in Figure 7 when the port 56 begins to become uncovered by the inner land 70, resulting in fuel in the pumping chamber being by-passed via the plunger passages 66, 68 and port 56 to the receiving chamber. It will be noted that simultaneously with, or immediately following the start of the secondary injection, the bleed passage 62 is covered by the plunger inner land, augmenting the rate and pressure of the secondary fuel injection. Figure 8 shows the plunger in its innermost position at the end of the pump chamber, with the by-pass port 56 still in communication with the pumping chamber via the metering groove and plunger passages. On the return stroke, fuel under the pressure maintained in the receiving chamber flows into the pumping chamber through the cylinder ports 54 and 56 as they make registry with the plunger metering groove.

Referring again to Figure 2, it will be seen that rotation of the plunger in the direction of the arrow 80 results in delaying both the start and ending of the primary fuel injection period, as well as the start of the secondary injection. This is by reason of the inner and outer extremities 82 and 84 of the inner land and the outer extremity 86 of the outer land being inclined in the same direction to the plunger axis, whereby the closure of the port 54 and closure and reopening of the discharge port 58 are successively delayed. That portion 88 of the inner land outer extremity which controls the opening of the bypass port 56 is shown extending normal to the plunger axis so that the start of the secondary injection may be advanced or retarded relative to the termination thereof, thereby enabling the duration of this secondary injection charge to be varied by rotation of the plunger. Since the primary injection timing only need by varied, and not its duration, and since its advancement and retardation may be equal to that of the main charge, the inclination of extremities 82 and 86 are equal and in the same direction to the plunger axis as the inclination of 84. Locating the by-pass port 56 diametrically opposite the discharge port enables the latter to be drilled through the port 56, thus obviating the need for plugging an access hole for the drill on the discharge port side of the bushing. Proper timing of the uncovering of the by-pass port 56 so aligned with the 4 of the plunger inner land 70 on the side thereor facing the port 56. Also, the herein described arrangement of cylinder ports, plunger metering groove and passages, enables the provision of but a single discharge port 58 and its connecting passage to the nozzle.

While only a single preferred embodiment of the invention has been disclosed, it is appreciated that numerous minor changes in the construction and arrangement of the parts may be made without departing from the spirit and scope of the invention as defined in the following claims.

We claim:

1. In an injector pump, a pump cylinder closed at one end, means defining a fluid receiving chamber externally of the cylinder, two ports axially spaced from each other and from said closed end along the cylinder axis and connecting the interior of the cylinder with said receiving chamber, a fluid injection nozzle, a fiuid discharge port connecting the nozzle with the interior of the cylinder .at a distance axially thereof intermediate said closed end and the more remote of said two ports from said closed end, a plunger operable in said cylinder having two axially spaced lands slidably fitting the internal side walls of the cylinder to control the passage of fluid through said ports and an internal passage connecting the inner end of the plunger with the space between said lands, the relative spacing of said lands and ports being such that during movement of the plunger in its pumping direction said two ports are closed in advance of closing said discharge port to initiate a primary injection, after which the inner land traverses over the discharge port while said two ports remain closed to first terminate said primary injection without decreasing the chamber pressure and then initiate a secondary injection through said passage and discharge port when said passage and discharge port are in communication, the more adjacent of said two ports to said closed end of the cylinder being then subsequently uncovered by the inner land to terminate said secondary injection.

2. The injector pump defined by claim 1, wherein the more adjacent of said two ports to the closed end of the cylinder is diametrically opposite said discharge port, and the outer extremity of said inner land on the side facing said more adjacent port is extended toward the inner end of the plunger to delay the uncovering of said more adjacent port by said inner land during the plunger pumping movement after said inner land has uncovered the discharge port. a

3. The injector pump defined by claim 1, wherein the plunger is axially rotatable and the inner and outer extremities of said inner land on the discharge port side of the plunger are inclined to the plunger axis, whereby rotation of the plunger relative to the cylinder varies the timing of both the termination of said primary injection and the initiation of said secondary injection.

4. The injector pump defined by claim 3, wherein the inner extremity of said outer land on the side of the plunger facing said more remote port is parallel with said inclined inner land inner extremity, whereby rotation of the plunger relative to the cylinder varies the timing of initiation of said primary injection equally with its termination.

5. The injector pump defined by claim 1, wherein the cylinder has a bleed port of smaller capacity than said discharge port and connecting said fuel receiving chamber with the interior of the cylinder at a distance axially thereof toward said closed end from the discharge port for closure by said inner land only after said discharge port is closed during the plunger pumping movement.

6. In an injector pump, a pump cylinder closed at one end and having an inlet port and a discharge port, said ports being spaced from each other and from said closed end, a plunger operable in said cylinder having two axially spaced lands slidably fitting the internal side walls discharge port requires only extending the inner extremity 75, of th cylinder to control the flow of fluid through said ports and a passage connecting the inner end of the plunger With the space between said lands, the relative spacing of said ports and lands being such that during movement of the plunger in its pumping direction said inlet port is closed in advance of closing said discharge port to initiate a primary injection, after which the inner land traverses over the discharge port While said inlet port remains closed to first terminate said primary injection Without decreasing the chamber pressure and then initiate a secondary injection through said passage and disc'hange port when said passage and discharge port are in communication, said inlet port being then subsequently uncovered by the inner land to terminate said secondary injection.

References Cited in the file of this patent UNITED STATES PATENTS Stockmeyer Mar. 12, 1935 LOrange Apr. 30, 1935 Skaredoff Dec. 22, 1942 Bremser May 6, 1947 Bremser Nov. 11, 1947 Kammer Sept. 5, 1950 Rogers June 3, 1952 Junge et a1 Dec. 14, 1954 FOREIGN PATENTS Canada Aug. 5, 1952

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