EP0104223A1

EP0104223A1 - Diesel fuel pump with priming mechanism

Info

Publication number: EP0104223A1
Application number: EP83901146A
Authority: EP
Inventors: Walter Edward Basch; Robert Cullen Mcdonald
Original assignee: ACF Industries Inc
Current assignee: ACF Industries Inc
Priority date: 1982-02-24
Filing date: 1983-02-18
Publication date: 1984-04-04
Also published as: WO1983002980A1; IT1161092B; EP0104223A4; IT8319759A0

Abstract

Pompe de combustible (1) servant à alimenter en combustible un moteur diesel. Une enceinte (3) définit un orifice d'admission de combustible (5), un orifice de sortie de combustible (7) et possède une extrémité creuse ouverte (9). Un corps de pompe (23) présente une cavité (27) et une extrémité du corps est fixée à l'extrémité ouverte de l'enceinte. Un diaphragme flexible (33) forme une chambre de pompage (35) avec l'extrémité creuse de l'enceinte et une tige (43) fixée au diaphragme s'étend dans la cavité. Un levier (51) actionné par une came du moteur (C) provoque la course de la pompe de combustile, permettant de pomper le combustible de l'orifice d'admission vers l'orifice de sortie. Un mécanisme d'amorçage (61) à actionnement manuellement pompe un volume initial de combustible vers le moteur avant le démarrage de celui-ci à la manivelle. Le mécanisme d'amorçage agit sur le levier pour produire la course de pompage initiale qui est égale à au moins un tiers de celle produite par le fonctionnement de la came pendant le fonctionnement normale du moteur même lorsque le moteur est arrêté à la position haute de la came.Fuel pump (1) for supplying fuel to a diesel engine. An enclosure (3) defines a fuel inlet (5), a fuel outlet (7) and has an open hollow end (9). A pump body (23) has a cavity (27) and one end of the body is fixed to the open end of the enclosure. A flexible diaphragm (33) forms a pumping chamber (35) with the hollow end of the enclosure and a rod (43) fixed to the diaphragm extends into the cavity. A lever (51) actuated by an engine cam (C) causes the fuel pump to travel, allowing the fuel to be pumped from the inlet port to the outlet port. A manually actuated priming mechanism (61) pumps an initial volume of fuel to the engine before cranking the engine. The priming mechanism acts on the lever to produce the initial pumping stroke which is equal to at least one third of that produced by the operation of the cam during normal engine operation even when the engine is stopped in the high position of drug.

Description

DIESEL FUEL PUMP WITH PRIMING MECHANISM BACKGROUND OF THE INVENTION

This invention relates to fuel pumps and more parti¬ cularly, to a fuel pump for diesel engines.

A requirement of many fuel pumps used with diesel engines is they be capable of priming the engine prior to cranking. This means the fuel pump must deliver a charge of fuel to the engine prior to cranking so the engine has sufficient fuel for starting. Typically, a diesel engine fuel pump includes a manually operable priming lever with which a fuel pump stroke is made to deliver the fuel from its'supply tank to the engine. Conventional mechanical fuel puiπps are driven by cam operated levers which produce fuel pumping strokes as they proceed from their high cam through their low cam and back to their high cam positions. One problem with these pumps occurs when the engine stops and the cam is at its high cam position. In this instance, because of the construction of conventional fuel pumps, it is difficult to obtain any significant pump stroke by man¬ ual operation of the priming lever. This is because at high cam position the fuel pump is at its maximum stroke position. Thus, there is little or no additional movement possible of the stem operating the pumping diaphragm with¬ in the pump to produce the pump stroke needed to deliver a charge of fuel to the engine sufficient to start it. Another problem affecting conventional diesel engine fuel pumps is binding of the manually operable mechanism by which this preliminary pump stroke is produced. Typi¬ cally, binding occurs because of the interference fit with which portions of the mechanism is installed. Binding, if it occurs, may not only render the self-priming portion of the pump inoperative but effect normal operation of the pump.

A third concern is space availability within the en¬ gine compartment in which the pump is installed. Engine compartments are becoming more and more crowded as various modifications are made to the engine and its associated equipment. Because of the size restrictions created, it is often necessary to fit the fuel pump into a space much smaller than that which it previously occupied. At the sa time, cost is an important factor and it is important from cost standpoint to utilize standardized parts originally d signed for larger sized fuel pumps. SUMMARY OF THE INVENTION

Among the several objects .of the present inventions m be noted the provision of a fuel pump for diesel engines; the provision of such a fuel pump having a manually operab priming mechanism by which an initial charge of fuel is de livered to a diesel engine to aid in starting it; the pro- vision o -such a. fuel pump by which a pumping stroke equal to at least one-third of the normal fuel pump stroke is attainable during priming even though the cam operating th pump during normal running conditions is stopped at its hi cam position; the provision of such a fuel pump wherein th elements comprising the manually operable priming mechanis are non-binding so to permit operation of the priming mech¬ anism at all times; the provision of such a fuel pump to occupy a smaller space in the engine compartment than conv tional fuel pumps; the provision of such a fuel pump to ac- comodate standard components designed for larger fuel pumps even though the pump is smaller in size; and, the provisio of such a' fuel pump utilizing a cam operated lever narrower than conventional levers but still capable of exerting the force needed to produce a pump stroke.

Briefly, a fuel pump of the present invention is for delivering fuel to a diesel engine. A housing defines a fuel inlet and a fuel outlet and the housing has a hollow open end. A pump body has a cavity formed therein and one end of the pump body is attachable to the open end of the housing. A flexible diaphragm is secured between attached portions of the housing and pump body to form a pumping chamber with the hollow end of the housing. A stem is atta hed to the diaphragm and extends into the body cavity. A lever operated by an engine cam has one end contacting the stem to produce reciprocal movement of the stem as the cam rotates from its high cam through its low cam and back to

O PI its high cam position. Each reciprocal movement of the ste creates a pump stroke by which fuel is pumped from the fuel inlet to the fuel outlet. A manually operable priming mech anism is used to pump an initial, volume of fuel to the en- gine prior to cranking so fuel is provided to start the en¬ gine. This priming mechanism acts on the cam operated leve to produce this initial pump stroke. The pump stroke pro¬ duced by operation of the priming lever is equal to at leas one-third the pump stroke produced by rotation of the cam during normal engine operation even when the engine is stop ped at the high cam position. Other objects and features will be in part apparent and in part pointed out hereinafte ^' BRIEF DESCRIPTION OF THE^" DRAWINGS

Figure 1 is a side, el.evati.onal view, in section, of a diesel fuel pump of the present invention;

Figure 2 is a rear elevation l. view of the fuel pump; Figures.3 and 4 illustrate movement of a cam operated . lever to produce a pump stroke during normal engine opera¬ tion; Figure.5 illustrates the initial pump stroke created b operation of a manually operable priming mechanism;

Figure 6 is a rear view of a priming cam operated by a priming lever to produce the initial pump stroke;

Figure 7A and 7B are respective top and side views of one end of a conventional cam operated lever;

Figures 8A and 8B are respective top and side views of a cam operated lever of a diesel fuel pump of the present invention;

Figure 9 is a partial side, view of a cam operated lever of the fuel pump of the invention illustrating a spring seat insert; and,

Figure 10 is a perspective view of the insert. Corresponding reference characters indicate correspond¬ ing parts throughout the several views of the drawings. ^' DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to Figures 1 and 2, a fuel pump for deliver¬ ing fuel to a diesel engine (not shown) is indicated gen-

OMPI erally 1 and includes a sheet metal housing 3 defining a inlet 5 and a fuel outlet 7. Housing 3 is of generally c shape and has a hollow open end 9. Two apertures are for in the base of housing 9 and respective inlet and outlet 5 towers 11 and 13 are received in these openings and attac to the housing, for. example, by brazing. Inlet tower 11 a threaded coupling 15 for attachment of a fuel inlet lin (not shown) . A fuel filter element 17 is mounted inside tower 11 to filter fuel entering the inlet. Tower 11 fur

10 includes a dome 19 and the tower serves as a fuel filter, sediment trap and air dome. Outlet tower 13, which like let tower 11 is of sheet metal construction, has a thread outlet coupling 21 for connection to a fuel line (not sho by which fuel is delivered to the diesel engine.

15 Fuel pump 1 also includes a pump body 23 which is of cast metal. Body 23 is formed with a cavity 25 and a cav 27, Cavity 25 is generally horizontal while cavity 27 is . erally vertical. . The upper, end of pump body 23 is open a has a circumferential rim 29 for attachment of the pump b

20 to circular open end 9 of housing 3. Housing 3 has a cir ferential rim 31 defining the open end of the housing and 31 fits over rim 29 of pump body 23 and is swaged or othe wise crimped over to form a fuel pump unit 1.

A-flexible diaphragm 33 has its outer margin clamped

25 tween rims 29 and.31 when pump body 23 is attached to hou 3. Diaphragm 33 together with open end 9 of housing 3 de a fuel pumping chamber 35 for pumping fuel from inlet 5. t outlet 1. For this purpose, an inlet check valve 37 is l ted at the base of inlet tower 11 and a similar outlet ch

30. valve (not shown) is located at the Tbase of outlet tower Diaphragm 33 is positioned between a pair of backing plat 39 and 41 respectively. A stem 43 is attached to the dia phragm/bracket assembly; the stem extending vertically in cavity 27, A ste guide 45 has a central opening through

35 which stem 43 extends. Guide 45 fits on a rim formed at opening between the upper end of cavity 27 and the hollow open upper end 47 of pump body 23. A bias spring 49 seat

OMP against lower bracket 41 and the upper side of guide 45 an urges diaphragm 33 upwardly.

Fuel pump 1 is designed to be mounted on the side of the diesel engine block. The engine has an internal cam C (see figures 4-6) which is eccentrically mounted inside the engine block and rotates when the engine is running all as is well known in the art. Fuel pump 1 includes a lever 51 operated by cam C, one end of the lever contacting stem 43 to produce reciprocal movement of the stem as cam C rotates from its high cam through its low cam and back to its high cam position. Each reciprocal movement of s em 43 creates a pump stroke by which fuel is pumped from fuel inlet 5 to fuel outlet 7. Lever 51 has first and second lever arms 53 and 55 respectively, and the lever is held in place by a pi vot pin 57 which is secured to the pump body by, for exampl staking such as shown in figure 2. Stem 43 has a seat 59 a its lower end and the outer end of lever arm 55 contacts this seat to exert leverage on the stem to produce a down¬ ward pumping stroke. This portion of the pumping stroke is produced as cam C moves from its low cam to its high cam positions. The low cam position is that shown in figure 3, while the high cam position is that shown in figure 4. . As cam C rotates back from its high cam to its low cam posi¬ tion, spring 49 urges diaphragm.33 upward to complete the reciprocal movement of stem 43 and a pumping stroke.

With diesel engines, it is necessary to provide an ini tial charge of fuel to the engine prior to cranking so the engine has sufficient fuel to start it. To provide this initial charge of fuel, fuel pump 1 includes a manually operable priming means or mechanism 61. This priming means includes a priming lever 63 connected to a priming cam 65. Priming cam 65 extends across or transversely of pump body cavity 25 above cam operated lever 51 and in particular above lever arm 55 of the cam operated lever. Priming cam 65 contacts lever arm 55 when priming lever 63 is manipula¬ ted. For this purpose, priming cam 65 has a flat contour portion 67 and a rounded contour portion 69. Normally, flat contour portion 67 of priming cam 65 is above cam lever ar 55. However, when priming lever 63 is manually rotated to the position shown in figure 5, the rounded contour portio 69 of priming cam 65 bears against the upper surface of le ver arm 55 to force lever arm 55 and consequently stem 43 downwardly. By acting on cam operated lever 51 in this manner, an initial pump stroke is produced. When priming lever 63 is released and it returns to its position shown in figures- 3 and 4, spring 49 pushes the diaphragm/bracket assembly upwardly and the consequent lifting of stem 43 re turns cam-operated lever 51 to its position shown in figur 4.

It is often a problem with fuel pumps of the diesel engine type that when the engine stops and cam C is at or near its high cam position, there is insufficient clear¬ ance between the base of stem 43 and the bottom or "base side" of cavity 27 to produce a priming pump stroke suffi¬ cient to pump an adequate amount of fuel to the engine to start it. Since it is difficult to know what position cam C will stop at when the engine is last shut off, it is im¬ portant that the priming lever be capable of producing an adequate pump stroke regardless of the cam position. Fuel pump 1 of the present invention operates in such a manner that even when cam C stops on its high cam position, a pri ming pump stroke equal to at least one-third the pump stro produced by rotation of cam C during normal engine opera¬ tion results. Conventionally, the stem such as stem 43 an the cam operated lever such as lever 51 are designed so th mid-point in a fuel pump stroke occurs essentially at the mid-point between the base side of the cavity such as cavi 27 and the upper open end or "fuel side" of the cavity. A a consequence, the position of the cam operated lever and stem at the bottom of the stroke is similar to that shown in figure ^*5. In such a position, which occurs at high cam, there is little room left for an additional priming pump stroke. In the fuel pump of the present invention however, cam operated -lever 51 and stem 43 are designed such that t mid-point of the stroke produced by the cam operated lever and the stem is substantially above the mid-point between the base side and the fuel side of cavity 27. This is ac¬ complished in two ways: first, the length of stem 43 is made as short as possible and second, the angle of lever arm 53 to contact the stem is changed. Now, the cam oper¬ ated lever and stem position occuring at high cam is that shown in figure 4 and, as a result, there is sufficient clearance to produce an adequate stroke by operation of priming means 61, In sum, a normal pumping stroke is pro¬ duced during normal engine operations, while a priming stroke equal to at least one-third of the normal pump strok is produced even if cam C stops at its high cam position. This means an adequate quantity of fuel is delivered to the engine by operation of priming means 61 to start the engine Referring to figure 6, a priming lever return spring 71 has one end fitted into a vent hole 73 in the side of pump body 23; the other end of spring 71 wraps around pri¬ ming lever arm 63. An 0-ring 75 effects a seal with pri- ming cam 65, A circumferencial groove 77 is formed near the outer end of priming cam 65 and pump body 23 has a ver¬ tical bore 79 in which is received a cylindrical pin 81. ^• Pin 81 comprises retaining means to maintain priming cam 65 in place, . The outer end of bore 79 is closed with a ball 83 which captures pin 81 in the bore. The length of pin 81 is less than that of bore 79 thus for the pin to have a non interference fit with the priming cam. This is important i that it prevents binding of priming means 61 and particular ly priming cam 65 which could not only render priming means 61 inoperative but could also effect normal operation of the fuel pump.

Fuel pump 1 is designed to fit into a smaller space within the engine compartment than conventional diesel fuel pumps. Consequently, various components within the fuel pump have smaller dimensions than similar parts used in con¬ ventional fuel pumps. For example, figures 7A and 7B illus¬ trate the end of a cam operated lever normally contacting the stem by which the fuel pump diaphragm is operated. As shown in figure 7A, the cross hatched area represents the area of the end of the cam operated lever which normally contacts the stem seat to apply force to the stem. The end portion of cam operated lever arm 55 is shown in figure 8A and 8B and as can be seen -from a comparison of figures 7A and 8A, the cam operated lever of fuel pump 1 is much narrower than the prior art cam operated lever. The outer end of lever arm 55 is bifurcated to form a pair of side rails 85 and 87 respectively. Stem 43 fits between these side rails, and the side rails rest on stem seat 59 to apply force to^" the stem. This force is applied to stem 43 solely through the side rails and is substantially equal to the force applied by a conventional cam operated lever. While fuel pump 1 is designed to fit in a smaller spac in the engine compartment, it is also desirable from an eco mic standpoint to use as many conventional parts as possibl in fabricating the fuel pump. Thus, for example, fuel pump 1 includes a spring 89 urging cam operated lever 51 into co tact with cam C. Spring 89 was originally designed for use with a cam operated lever such as that shown in figures 7A and 7B, One end of spring 89 seats against the upper wall of cavity .25 which has a pro cting dimple 91 to properly seat the spring. Conventionally, the other end of spring 8 fits in the channel formed by the side walls of the cam operated lever and seats against the bottom inner wall of the lever. In such case, the outer diameter of spring 89 is only slightly smaller than the width of the channel. Since,^' as noted, cam operated lever 51 is much narrower tha conventional cam operated levers, the width of the channel between side rails 85 and 87 is less than the outer diame- ter of spring^' 89 and the spring cannot therefore seat a- gainst the innter base wall of cam operated lever 51. To provide a seat for spring 89, the side rails of lever arm 53 are each notched as indicated at 93, and an insert 95 fits into the space created by these notches. As shown in figures 9 and 10, insert 95 has a rectangular base section 97 the width of which is slightly less than the width of the channel between the side rails of lever arm 53. Base section 97 is surmounted by a pedestal or base 99 sized to be received in the notches 93. Pedestal 99 is rectangular in shape and its dimensions are equivalent to the outer dia meter of spring 89 so the entire end portion of the spring rests atop the pedestal. A cruciform shaped retainer 101 projects upwardly from the top of pedestal 99 and acts to keep the end of spring 89 in place. The dimensions of re- tainer 101 correspond to the inner diameter of spring 89 so to maintain the spring in place. Further, the position of notches 93 and the insert 95 is such to create the proper arc of spring 89 (this arc shown in figures 1 and 3-5) whic arc it is important to maintain in order for spring 89 to exert the proper force on cam operated lever 51.

What has been described is a fuel pump for use with diesel engines. The fuel pump is capable of providing an initial fuel pump stroke, prior to cranking, which is at least equal to one-third of a normal pump stroke. This ini- tial pump stroke is provided even if the engine is stopped at a high cam position. Further, fuel pump 1 in^'c-ludes a cam operated lever which is narrower than conventional fuel pump levers and this helps to reduce the size of fuel pump 1 so i fits into a smaller space in the engine compartment than con ventional fuel pumps. At the same time, provision is made to use a conventional or standard size return spring with th narrower lever, the^" spring being capable of exerting the ap¬ propriate force on the lever to urge it against the engine operated cam. In view of the above, it will be seen that the several objects of the invention are achieved and other advantage¬ ous results obtained.

As various changes could be made in the above construc¬ tions without departing from the scope of the invention, it is intended that all matter contained in the above descrip¬ tion and shown in the accompanying drawing shall be inter¬ preted as illustrative and not in a limiting sense.

Claims

What is claimed is:

1. A fuel pump for delivering fuel to a diesel engine or the like comprising: a housing defining a fuel inlet, a fuel outlet and ha ing a hollow, open end; a pump body having a cavity formed therein, one end of the pump body being attachable to the open end of the hous¬ ing; a flexible diaphragm secured between the attached por- tions of the housing and the pump body to form a pumping chamberjtf th the hollow end of the housing; a stem attached to the diaphragm and extending into th body cavity; a lever operated by an engine cam, one end of the leve contacting the stem to produce reciprocal movement thereof as the cam rotates from its high cam through its low cam an back to its high cam position, each reciprocal movement of the stem creating a pump stroke by which fuel is pumped fro the fuel inlet to the fuel outlet; and, a manually operable priming means for pumping an initi volume of fuel to the engine prior to cranking so fuel is provided to start the engine, the priming means acting on t cam operated lever to produce this initial pump stroke, the pump stroke produced by operation of the priming means ^"bein equal to at least one-third the pump stroke produced by ro¬ tation of the cam during normal engine operation even when the engine is stopped at the high cam position.

2. The fuel pump of claim 1 wherein the priming means includes a priming lever connected to a priming cam, the priming cam contacting the cam operated lever when the pri¬ ming lever is manipulated to force the cam operated lever t act on the stem to produce a pump stroke.

3. The fuel pump of claim 2 wherein the pump body ca¬ vity has a vertical section in which the stem is disposed, the vertical section having a lower closed base side and an upper open fuel side and the cam operated lever and stem be ing so configured that the mid-point of the stroke produced by the cam operated lever acting on the stem is substan¬ tially above the mid-point between the base side and the fuel side of the vertical section,

4. The fuel pump of claim 3 wherein the priming cam extends across the pump body cavity above the cam operated lever and has a flat contour portion and a rounded contour portion, the rounded contour portion of the priming cam contacting the cam operated lever when the priming lever is operated. „ 5, . The fuel pump of claim 2 further including means . effecting-a seal with the priming cam and retaining means maintaining the priming cam in place, the retaining means providing a non-interference fit whereby binding of the priming cam is prevented, 6. The fuel pump of claim 2 wherein the stem has a seat at its lower, end and the cam operated lever has a le¬ ver arm whose outer end contacts the seat, the outer end of the lever being bifurcated to form side rails between which the stem fits, the force produced by the cam opera- ting on-the lever being transmitted to the s em seat throug the side rails,

7, . The fuel pump of claim 6 further including a sprin seated against one. wall of the pump body cavity and urging the cam operated lever into contact with, the engine cam, th diameter of the spring being greater than the width of the cam operated lever,

8, The fuel pump- of -claim 7 wherein the cam operated lever has a second lever arm, this second lever arm being contacted by the spring, and the second lever arm having a portion thereof removed,

9, The fuel pump of claim 8^'further including an in¬ sert fitting into the removed portion of the second lever arm, the insert having a pedestal acting as a seat for the return spring with the size of the. pedestal being such as to fully seat the spring,

10. The fuel pump of claim 9 wherein the insert inclu¬ des a cruciform retainer projecting outwardly therefrom,

OMPI the retainer preventing the return spring from slipping of the retainer and helping the return spring maintain a pre¬ determined curvature, so to apply a proper force on the se¬ cond lever arm.