US3006556A

US3006556A - Unit fuel pump-injector

Info

Publication number: US3006556A
Application number: US80063A
Authority: US
Inventors: William S Shade; Conrand A Teichert
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1961-01-03
Filing date: 1961-01-03
Publication date: 1961-10-31
Anticipated expiration: 1978-10-31

Description

Oct. 31, 1961 w. s. SHADE x-:TAL

UNIT FUEL PUMP-INJECTOR Filed Jan. 3, 1961 fwd United States Patent 3,006,556 UNIT FUEL PUMP-INJECTOR i William S. Shade and Conrad A. Teichert, Grand Rapids,

Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Jan. 3, 1961, Ser. No. 80,063 Claims. (Cl. 239-88) This invention relates to fuel injection apparatus, and particularly -to unit type -fuel pump-injectors for diesel engines.

In such ldevices it is necessary to provide a check valve in the injection fuel passageway between the pump plunger cylinder and the injection valve to prevent blow-back of combustion gases from the engine cylinder into the pump cylinder of the injector in the event the injection valve should happen to stick open during operation. Also, while it has been found -that a needle type injection valve enables obtaining better timing and accuracy of the quantity of fuel injection with resultant increased fuel economy of the engine than do inje-ction valves of the poppet type, it is a problem in adapting needle valve type injectors for use on certain engines where the opening in the engine for the injector spray tip or nozzle must be of minimum size.

In accordance with the present invention, `a novel construction of the parts of a unit pump-injector has been devised such that both the diametral extension required for accommodating the check valve 'as well as the diametral extension of the nozzle or spray tipend are substantially reduced, and at the same time the number of parts required and their cost of manufacture is also reduced. By relocating the check valve so as to seat directly on the lower end face of the pump cylinder bushing and redesigning the injection valve spring retainer, necessity for either the conventional separate seat for the check valve or for the usual holding tabs on the periphery of the check valve has been obviated. Also, providing the injection needle valve with an upper piston portion and a reduced diameter lower or stem portion enables employing a relatively long spray tip extension of minimum cross-section without the necessity of the fuel passage to the tip being extended as a drilled passage through the side Wall of the spray tip for substantially the full length of such extension.

A betternnderstanding of these and other objectives and advantages of the invention will be had from the following description having reference to the drawing, wherein:

FIGURE 1 is a longitudinal sectional view through a unit pump-injector showing the improved check valve arrangement.

FIGURE 2 is a transverse sectional view taken substantially along line -2-2 of FIGURE 1.

FIGURE 3 is a fragmentary view similar to FIGURE l but showing the modied injection needle valve and fuel passage arrangement in the lower portion of the injector.

'Referring now in detail to the drawing, and first to FIGURES l and 2, the upper portion of the unit is conventional and comprises a housing 1 in which a plunger 2 is reciprocable. Forming an extension of and threaded to the lower end of the housing 1 is a nut 3 within which fis supported a bushing 4, forming the pump cylinder for the plunger 2. An annular space 5 surrounding the bushing 4 within the nut is supplied with fuel via passages 6 in the housing from an external fuel connection 7. The plunger has the usual external metering groove 8 adjacent its lower end by which opening and closing of

ports

9 and 10 in the bushing are controlled during each downward stroke of the plunger to deliver a predeter- "ice mined volume of fuel through the lower open end 11 of the 'bushing for injection into the engine (not shown) via the spray orices 12 at the bottom of the unit. Other details of the upper or pump part of the unit are not important to the present invention, and are common to constructions shown and described in such prior patents as Engel, lr. 2,951,643 and Teichert 2,898,051, hence will not require further description here.

Within the nut 3 :and clamped between the shoulder 13 in its lower end and the lower end of the bushing 4 are a spring retainer 14, a spacer block 15 and la combined injection valvebody and spray tip 16. The lower end face 17 of the bushing vserves as a closure seat for a circular check Valve disc 13. This disc is disposed in a cavity 19 formed in the upper end of the spring retainer 14, the sides of which cavity extend laterally beyond the lateral extremities of the open end 11 of the pump cylinder, and serve to loosely guide the disc 13. A central protuberance 20 is formed in the bottom of the cavity 19 and serves to limit opening travel of the check Valve or disc 18. The cavity 19 also forms the upper end of passage means connecting the open end 11 of the pump cylinder with the fuel discharge outlets 12, this passage means also including a drilled passage 21 and an annular groove 22 in the retainer 14, a drilled passage 23 through the spacer block 15, a connecting annular groove 24 and drilled passage 2.5 in the valve body 16 which leads to a valve chamber 26 surrounding the lower end of a needle type injection valve 27. At the lower end of this chamber 26 is a fuel discharge outlet which is controlled by the injection valve 27, this outlet being in the yform of a drilled passage 28 connecting the chamber 26 with the spray orifices 12. A conical seat 29 for the injection valve is formed 'at the juncture of this outlet passage with the chamber 26. The upper end of the needle Valve is shown provided with a reduced diameter extension 30 which engages a spring seat -member 31, and located between this seat member and the bottom face of the spring retainer 14 is a spring l32 which biases the needle valve closed against its seat 29. The spacer block 15 forms a chamber 33 for the spring and seat and is provided with an opening 38 in its lower end connecting this chamber with a counterbore 34 at the upper end of the bore 35 which is provided in `the valve body for slidably guiding the needle va'lve 27.

During operation, as fuel pressure is built up in the pump cylinder 4 below the plunger 2 it is simultaneously applied via the cavity 19 and connecting drilled passages and lgrooves to the chamber 26 in the fuel nozzle 16. When this pressure reaches a sui-liciently high value required for injection it raises the needle valve 27 from its seat, permitting discharge of the fuel through the spray orifices 12 in the usual manner. Opening of the needle valve is limited by abutment against the spacer block 15 Within the counterbore 34, and in the event the needle valve should 'for any reason fail to reclose at the end of the injection cycle, a reverse flow of fuel and combustion gases from the engine via the spray orifices, chamber 26 and connecting passages and grooves to the cavity 19 and thence into the pump cylinder, is prevented by closing of the check valve -disc 18 against its seat 17 on the pump cylinder.

The use of such seat 17 for the check vaflve disc not only `eliminates the separate seating part conventionally used therefor but requires a less diametral extension of the parts in this area than is required for a conventional disc having its peripheral extremities scalloped or notched to provide holding tabs, since a considerably reduced overlap of the disc with respect to the end face 17 is required than with a disc having such holding tabs. Also, in lieu of the conventional retaining shoulder for such prior art scalloped discs, the protuberance 20 from the bottom wall of the cavity 19 in the spring retainer serves to limit opening travel of the check valve.

In the modied injector arrangement shown in FIG- URE 3, the spring vretainer 14 and spacer block 15 Vare made integral and the spring chamber 33 therein has its open end facing the valve body 16'. The spring seat member 31 is extended in length so that abutment of its upper end 'against the retainer 14 may limit opening of the needle valve 27. The nozzle body and spray 'tip 16 is considerably extended bellow the nut 3, as is required in certain engines having a relatively small opening into the combustion chamber for the injector. To minimize the diametral extension of the spray tip the needle valve 27 is provided with a piston portion 40 and a reduced diameter stem portion 41. The piston portion 40'slidably ts the valve body bore 35, and the plunger portion y41 is provided with lateral extensions 42 which laterally support and slidably guide it in the bore 35 while accommodating oW of fuel longitudinally of the stem portion. These lateral extensions may conveniently be formed as one or more Hats machined from a land 'section intermediate the piston portion and the lower end of the'needle valve and initially of the same cylindrical diameter as the piston portion 40. By this arrangement the drilled passage 25 in the valve body may be angled more obliquely to intersect the injection valve bore 35 at a point Within the nut 3 Where the Wall thickness of the valve body is of ample dimension for such drilling. As va result, this passage need not extend substantially the whole length -of the extended spray tip Whose diametral extension is `desired to be maintained at a minimum as aforementioned. The Yoperation of the injector is unaffected by this change in the injection valve and passage arrangement.

While the invention has been described with reference to its preferred structural embodiment shown in the drawing, it is appreciated that minor changes may be made therein without departing from the spirit and scope of the following claims.

What is claimed is:

1. In a unit fuel pump-injector, a pump cylinder open at one end for fuel delivery, an injector opposite said cylinder end having a discharge outlet, passage means connecting said cyflinder end and said outlet, a valve movable to close and open said outlet, a spring biasing the valve closed, said valve having a piston portion connected thereto and exposed to fuel pressure in said passage means for moving said valve in the opening direction against theV biasing force of said spring, a retainer for said spring, said passage means including a cavity in said retainer facing and extending laterally of said cylinder open end, and a check valve for preventing reverse ovv through said passage means and into said cylinder, Ysaid cylinder having a seating surface for said check valve when in dlosed position, said retainer having a stop limiting opening movement of the check valve, said stop being located opposite said cylinder open end and laterally Vinvvard thereof from said cavity.

2. The invention of claim 1, ywherein said injector ncludes a valve body having a bore slidably receiving said valve piston portion, said valve having a stem portion of smaller cross-section lthan said piston portion extending 'longitudinally within said bore toward said outlet, said stem portion and said bore defining therebetween a portion of said passage means.

3. In a unit fuel pump-injector, a pump cylinder open at one end for fuel delivery, an injector opposite the open end of the pump cylinder including a valve body, a valve in said body, a valve closing spring and a 4spring retainer interposed between the valve body and said end of the pump cylinder, said rvalve body having a fuel discharge outlet normally olosed by the valve, said valve being openable against the spring by pump fuel pressure, passage means connecting said discharge outlet With the open end of the pump cylinder including a cavity in the spring retainer facing said cylinder open end, and a check valve for closing said passage means against reverse ow to the pump cylinder, said pump cylinder having an end face defining its open end and a closure seat for the check valve, said spring retainer cavity extending 'transversely of the pump cylinder for communication with the pump cylinder when the check valve is displaced from its seat, and a protuberance on the spring retainer 'adjacent said cavity engageable by the check valve to limit its displacement from said seat.

4. The invention of claim 3, wherein said valve body includes a cylindrical bore leading to said outlet and said valve includes a piston portion slidably received in said bore and a stern portion of reduced diameter extending from said piston portion toward said outlet, said stem portion having means extending laterally therefrom inter- -rnediate its ends to slidably engage said bore and support said stem portion therein while accommodating fuel ow longitudinally of said stem, said passage means including passages in said body and spring retainer connecting said 4bore and said cavity.

5. In a unit fuel pump-injector having a pump cylinder open at one end for fuel delivery, said cylinder having an end face dening its said open end, la check valve closable against said face, and an injector opposite said cylinder end including an injection valve openable in response to a predetermined fuel delivery pressure developed by the pump and supporting means for said check valve and injection valve, said means having a passage Yfor fuel flow to the injection valve from said cylinder Aopen end including a cavity surrounding the check valve, and a protuberance in said cavity limiting opening moverment of the check valve.

References Cited inthe tile of this patent UNITED STATES PATENTS 2,378,165 Waeber June 12, 1945 2,793,076 Brehmer May 21, 1957 2,898,051 Teiche'rt v Aug. 4, 1959 2,912,168 LOrange Nov. 10, 1959 2,951,643 Engel Sept. 6, 1960 FOREIGN PATENTS 541,100 Great Britain Nov. 12, 1941