US2410947A

US2410947A - Fuel injection pum mechanism

Info

Publication number: US2410947A
Application number: US483633A
Authority: US
Inventors: Lloyd E Johnson
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1943-04-19
Filing date: 1943-04-19
Publication date: 1946-11-12
Anticipated expiration: 1963-11-12

Description

Nov. 12, 1946. l.. JOHNSON FUEL INJECTION PUMP MECHANISM Filed April 19, 1943 4 4 w Z 6 3- 5 Z 5 4 Wm y Z, 7. f d. Z. L A s INVENTOR. l. /ayd E Johnson BY ATTaRAY,

Patented Nov. 12, 1946 FUEL TNJECTToN PUMP MEcnANTsM Lloyd E. Johnson, Fon du Lac Township, Tazewell County, Ill., assignor to Caterpillar Tractor Co., San Leandro, Calif., a corporation of California f Application April 19, 1943, Serial No. 483,633

4 Claims. 1

My invention relates to fuel injection mechanlsm, and more particularly to such mechanism adapted for injection of relatively low viscosity fuel into an internal combustion engine.l

In fuel injection systems for the injection of a relatively low viscosity fuel, such as gasoline, into an internal combustion engine which is provided with pumping mechanism for injecting the fuel into each cylinder of the engine, in a. so-called solid stream, there is the problem of precluding leakage of the fuel past the fuel injection pump plunger during the injection stroke thereof. This is so because a relatively low viscosity fuel, such as gasoline, is also usually quite volatile except for a small portion of a gummy nature; and if it were to leak past the pump plunger, evaporation would cause a gummy deposit that would impede eflicacious operation of the plunger in the pump cylinder within which the plunger is adapted to work.

This problem does not exist so much with Diesel fuel oils of relatively high viscosity because the relatively high viscous nature of the oil tends to preclude the leakage. Furthermore, relatively high viscosity oils are usually of a relatively low volatility', yand therefore do not tend to cause as much gumming as do relatively low viscosity'and '4 relatively highly volatile fuels, such as gasoline. Also, a relatively high viscosity Diesel fuel oil has some lubricating properties which if a low rate of leakage should occur. will result in desirable lubrication between the working surfaces of the cylinder and the plunger, which is not true with more volatile fuels. such as gasoline, which tends to dilute and destroy whatever lubricant is employed for the plunger action.

In the past, provision has been made to preclude such leakage of relatively low viscosity fuels, by introduction of a relatively high viscosity lubricant between the pump plunger and the cylinder wall. However, in prior constructions with which I am familiar, the leakage precluding lubricant has been introduced through the Wall of the cylinder within which the pump plunger works. Such arrangement is not desirable because of the difficulties encountered in making a suitable connection between the cylinder and the housing containing such cylinder, for the introduction of the sealing lubricant.

My invention is designed to overcome this problem by the provision of improved means facilitating the introduction of the sealing lubricant; lwhich is of such character as to enable the sealing lubricant to be employed for lubricating the location of engagement between the pump plunger and actuating means therefor, and to lubricate the bearing means for the pump plunger actuating means; and which is of relatively simple and economical construction. Other objecis of my invention will become apparent from a perusal of the following description thereof.

Referring to the drawing:

Fig. 1 is a transverse vertical sectional view .of a form of fuel injection pump mechanism containing the construction of my invention.

Fig. 2 is a horizontal section taken in a plane indicated by line 2-2 in Fig. l.

Fig. 3 is a horizontal section taken in planes indicated by lines 3-3 in Fig. l.

Fig. 4 is a horizontal section taken in .planes indicated by lines I4 in Fig. 1.

Fig. 5 is a horizontal section taken in a plane indicated by line 5--5 in Fig. 1.

The lubricating and sealing means of my invention may be employed in association with any type of fuel injection pump wherein an impeller located in a pump housing is operated by suitable actuating means. For purposes of explanation,

it is shown in the form of fuel injection mechanism illustrated in Fig. l. Such injection mechanism includes injection housing means comprising a tappet and camshaft casing 2 to which a pump casing 3 is detachably connected by studs 4 and nuts 6. Adjacent the fuel discharge end thereof, pump casing 3 is formed with an internal shoulder I against which is clamped check valve cage 8 containing spring thrust check valve 9; such clamping being through a removably mounted plunger barrel or cylinder II which is clamped in position by means of nut I2 screwed in the inside of casing 3 against shoulder I 3 formed on cylinder II; a suitable sealing ring Il being interposed between nut I2 and shoulder I3. In this connection, nut I2 is formed with inwardly extending slots I6 to enable it to be engaged by a suitable tool for screwing and unscrewing of the nut when y so desired. To hold cylinder II against angular or turning movement, a cap screw I1 screwed into casing 3, is provided with an end extension I8 engaging in a recess I9 formed adjacent the head of cylinder I I.

With respect to multiple cylinder engines, a plurality of individual injection pumps, one for each cylinder of the engine, is employed; and the injection mechanism housing means contains all of such pumps and the mechanism for actuating the saine.l A longitudinally extending fuel inlet passage or manifold 2| is formed in pump casing 65 3, and receives a constant Supply of fuel at a relatively low pressure of about fifteen (15) to twenty (20) pounds per square inch, fed into it by a fuel transfer pump (not shown) as is customary in the art, and which continuously circulates the fuel from a fuel tank (not shown). Communicating with fuel inlet passage 2| is a fuel inlet orifice or port 22 formed in the wall of the head of each pump cylinder Il; the cylinder wall having a short bleed passage 23 therethrough which communicates with inlet port 22 and with the inside of cylinder Il for a purpose to be subsequently explained.

Slidably mounted in cylinder I| for axial reciprocation therein is a pump plunger 24 which is preferably of the type wherein the quantity of fuel fed or injected past check valve 9 is controlled by angular adjustment or rotation of the pump plunger about its axis. For this purpose, plunger 24 is formed adjacent its discharge or injection end with annular groove 25 around its periphery, which communicates with an axially extending groove 21 adjacent a slanting or scroll edge 28 adapted to work past port 22 as the plunger is reciprocated and angularly adjusted. The fuel discharge end of the plunger is flat, and at a right angle to the axis of the plunger.

Thus, as the plunger is reciprocated by suitable actuating means, and angularly adjusted through suitable engine governing means, metering of fuel injected by the pump is controlled in a well-known manner. When pump plunger 24 is actuated on its compression stroke to inject fuel when port 22 is closed as the plunger works therepast, the pressure imparted to the fuelmay be as high as two thousand (2,000) to four thousand (4,000) pounds per square inch. In Fig. 1, the angular and the axial positions of plunger 24 are shown substantially at the termination of injection, as slanting edge 28 is just about to uncover inlet port 22.

Actuating means in the form of tappet mechanism 29 is provided in casing 2 for imparting the injection or discharge stroke to plunger 24. Each of the tappet mechanisms in casing 2 comprises a sleeve 3| having an intermediate partition wall 32 secured therein by any suitable means, such as welding, and which is slidably mounted for axial reciprocatlon in a bearing wall surface 33 formed in casing 2. A cam follower roller 34 is located at one side of wall 32 and is journalled for rotation about a pin 36, on suitable roller bearings 31; the roller 34 engaging cam 38 on longitudinally extending camshaft 39 which is adapted to be driven from the engine.

The opposite side of wall 32 is formed with a at surface adapted to be freely engaged by a flat end surface 4| formed on the tappet end portion 42 of plunger 24. Thus, as the plunger is moved axially by the tappet mechanism, it may be readily turned angularly for the purpose previously explained. It will be noted from Fig. 4, that the tappet mechanisms 29 are provided with fiats 43 on their sides; and a pin 44 is positioned between the flats of adjacent tappet mechanisms 29, so as to hold such mechanisms against rotation or turning as they are reciprocated.

For effecting the return or suction stroke of plunger 24 after the discharge stroke, a spring 45 is interposed between nut I2 and a spring retainer 41 at the tappet end portion 42 of the plunger. Spring retainer 41 is provided with an inwardly extending slot 48 to enable it to be slipped over plunger 24, and is adapted to be thrust against a shoulder 49 on the plunger, and an end 5| of tappet sleeve 3|. When spring 45 thrusts retainer 41 against sleeve end 5| on the return stroke of the plunger, the spacing between the surface on shoulder 49 adapted to engage retainer 41 and the flat surface 4| at the tappet end of the plunger, is such as to provide a slight clearance between wall 32 and retainer 41, thus enabling plunger 24 to be angularly adjusted with ease.

The means for enabling angular adjustment of the plunger while it is axially reciprocated lncludes a gear sector 52 which is split at 53, and rigidly clamped to plunger end portion 42 by means of cap screw 54. The teeth on gear sector 52 engage a rack 55 which is slidably mounted in a recess in casing 2 between such casing and pump casing 3; a recess 55 being formed in sleeve 3| to allow engagement between such gear teeth and the rack. Rack 55 is connected to suitable governing means (not shown) operated from the engine.

To seal against leakage past the plunger of relatively low viscosity fuel which the pump may inject, I provide an interior passage 51 in the pump plunger for conducting lubricant between the plunger and the cylinder wall, at a pressure above that at which the fuel is supplied by the transfer pump through inlet port 22 but considerably below the fuel injection pressure; such lubricant pressure being preferably about twenty (20) to thirty (30) pounds per square inch. Be-

cause of the higher pressure of the sealing lubricant, compared to that of the fuel supply pressure, an emcacious seal is obtained. Furthermore. the lubricant will also serve to lubrlcate the working surfaces of the plunger and the cylinder. In this connection, it will be noted that the tappet end portion 42 of the plunger extends beyond the tappet end of cylinder throughout the entire stroke of the plunger. Such arrangement enables interior passage 51 to lead to the flat end surface 4| of the plunger for supplying of lubricant thereto at that location, which makes for a simple construction. Intermediate the plunger ends, passage 51 terminates in radially extending orifices 58 communicating with a peripheral groove 59 formed in the plunger. Thus a sealing ring of fluid will be maintained in groove 59 as sealing fluid is supplied through passage 51.

For supplying fluid to passage 51, I provide a. passage 5| in tappet partition wall 32, which is open to a side of tappet sleeve 3| adjacent one end, and which includes an orifice 62 at its opposite end in communication with passage 51. As fluid flows from tappet passage 5| into plunger passage 51, the location of engagement between the plunger and its actuating means will be well lubricated, which facilitates angular adjustment of the plunger when tappet wall 32 engages plunger end surface 4I during the injection stroke of the pump.

Means is provided for continuously pumping lubricant through passages 5| and 51, and at the same time lubricating bearing 33 in which the tappet mechanism slides. Casing 2 is adapted to contain a supply of lubricant which is continuously fed by means of a pump 53 including meshing gears 54, one of which is driven from camshaft 39. The pump gears draw lubricant into the pump through inlet passage 55, and discharge lubricant through passage 51 which communicates with a lubricant feed manifold or passage 68 in the inside wall of casing 2 adjacent tappet sleeves 3|. A suitable pressure relief valve -69 communicates with passage 61. Feed passage 68 is open to sleeve 3| and the portion of sleeve 3| adjacent feed passage 68 is formed with a recess 1| which communicates with passage 6|. Such arrangement allows free flow of lubricant into passage 6|; and at the same time, the lubricant will lubricate bearing 33.

During injection of fuel at the previously mentioned high pressure, leakage might occur past the plunger irrespective of the sealing fluid in groove 59, but this is prevented by the previously mentioned bleed passage 23. The inner end of passage 23 is in such position that during the time fuel is actually injected by the pump plunger, it communicates with a peripheral groove '|2 in the plunger, which is located between the injection end of the plunger and sealing uid groove 59. As a result, high pressure injection fuel can only leak past the plunger as far as groove 12, as passage 23 will bleed the pressure off to the low pressure which obtains in fuel inlet manifold 2|.

Although the construction of my invention is particularly adapted for employment in fuel injection pumps adapted for the injection of a relatively low viscosity fuel, such as gasoline, to be supplied to spark ignition engines, it may be used, if so desired, in Diesel or compression ignition fuel injection pumps where relatively low viscosity fuel oil is employed, and leakage thereof past the pump plunger might prove detrimental.

I claim:

1. Fuel injection mechanism comprising a. pump cylinder, a. pump plunger reciprocably mounted therein, a reciprocable tappet member engageable with an end of the plunger. a bearing wall for guiding said tappet member, and lubricating means comprising passages through the plunger and tappet for supplying lubricant to ond circumscribing recess spaced farther from the head of the plunger, and means for supplying lubricant under pressure to said second recess.

3. Fuel injection mechanism comprising a pump which includes a plunger reciprocably mounted in a cylinder for transferring fuel in metered quantities from a source of supply to an engine, said plunger having a circumscribing recess spaced from its head and communicable with said source of supply for return thereto of fuel leaking past the head of the plunger, a second circumscribing recess spaced farther from the head of the plunger, and means for supplying lubricant under pressure, exceeding the pressure of the source of fuel supply, to said second recess.

4. Fuel injection mechanism comprising a pump which includes a plunger reciprocably mounted in a cylinder for transferring fuel from a source of supply to an engine, means for relieving pressure on fuel leaking past the head of the plunger, and means for supplying lubricant to the cylinder walls at a pressure exceeding that of the leakage fuel.

LLOYD E. JOHNSON.