US2207337A - Pump - Google Patents

Description

July 9, 1940. A. T. BREMSER PUMP Filed Aug. 19', 1937 Fla; 4 FIG. .5

Fla. 3

1 FIG. 6

FIG.

AL 55/97 zma/ffkmvmok ATTORNEY.

Patented July 9, 1940 PUMP Albert T. Bremser, Sidney, N. Y., assignor to Bendix Aviation Corporation,

South Bend,

Ind., a. corporation of Delaware Application August 19, 1937, Serial No. 159,948

8 Claims.

This invention relates to improvements in fuel injection pumps and more particularly to port controlled pumps in which the plunger is used as a slide valve. Pumps of this kind are used to in- 5 ject fuel into the combustion chamber or manifold of internal combustion engines.

In port controlled pumps the sealing quality is a function of the clearance between the pump cylinder and the plunger and the leakage is a lo function of pressure, sealing distance, time,

viscosity and clearance. show more leakage at slow speeds than at high speeds, therefore, the amount of fuel pumped per stroke with a fixed position of the control is less at slow speeds so that the engine power drops at slow speeds and the fuel consumption rises. By improving the seal between the plunger and the cylinder the pumping characteristics can be improved and the engine power increased.

a One of the objects of the present invention is to provide novel fuel injection apparatus for fuel injection engines.

Another object of the present invention is to provide a novel plunger pump for injecting ll variable amounts of fuel into the combustion space of engines,

A further object of the invention is to provide a novel port controlled pump.

A still further object of the invention is to pro,-

vide a superior seal between the pump plunger and cylinder during the effective pumping stroke in order to obtain greater engine power..- at slow speeds.

Another object of the invention is to provide 35 novel means to improve the idling of the engines.

A further object of the invention is to reduce the fuel consumption obtained with similar pumps but which do not have the superior sealing char- 40 acteristics of this pump.

A still further object of the invention is to provide a pressure cavity and a metering cavity on a novel'plunger.

These and other objects will appear more fully from the detailed description of the invention which follows. Although several embodiments of the present invention are described and illustrated in the accompanying drawing, it is to be expressly understood that the drawing is for the construed as a limitation of the scope of the invention, reference being had for this purpose to the appended claims. 5 In the drawing wherein like reference char- All pumps of this type sides of the cylinder.

purpose of illustration only and is not to be acters indicate like parts throughout the several views:

Fig. 1 is an end elevation partly in section and with parts broken away of a portion of a fuel pump showing one form of the present invention. 3

Fig. 2 is a section view taken substantially through line 2--2 of Fig. 1.

Fig. 3 is another view of the plunger shown in Fig. 1.

Fig, 4 represents a modification of the plunger. 10

Fig. 5 represents a further modification of the fuel pump plunger.

Fig. 6 is 'a top View of the plunger shown in Fig. 5 showing the relation of the grooves to each other.

Fig. 7 is an enlarged view of Fig.2 and accentuatingthe clearance of the piston with the piumlp cylinder during the effective pumping s ro e.

Referring now to Figs. 1 to 3 of the drawing, 20

the cylinder I of the pump has near its upper end two ports 2 and 3 substantially on the same vertical centerline as can be seen in Fig. 2. The por: 2 is the inlet port and port 3 is the by-pass por ing the upper portion of'cylinder I. This chamber can be of usual design and has been omitted from the drawing. An annular groove 4 in the cylinder collects any oil that might leak down the valve retainer 9 is held tightly on the cylinder I I by means of a collar or other device not shown.

The plunger or piston H has a metering groove 12 in the form of a helix extending at least partly around the plunger and a cavity or groove l4 arranged substantially opposite groove l2. Passage 40 I3 interconnects groove l2 and cavity l4 and passage l5 extends from passage l3 through the upper face of plunger ll. Thus passages l3 and I5 form a continuous communication between the pumping chamber Ill and the groove l2 and a cavity l4. Cavity I4 is termed a pressure cavity or groove and it is so dimensioned and arranged relative to groove l2 that the fuel pressure in cavity It will cause the plunger to slide on that portion of its surface which carries the metering groove l2. The pressure cavity It may be rectangular as best shown in Fig. 3. A cross member I6 is made integral with or attached to the lower end of plunger H for the purpose of 1 Both ports open into a chamber surround- 8! This annular groove 4 is 8.

rotating the plunger II to regulatethe eflective stroke of the plunger in the usual manner.

Fig. 4 shows a. preferred embodiment of the invention. The plunger 2I is similar to the plunger II except that instead of a rectangular pressure cavity it has a. helical pressure groove 22 which is substantially diametrically opposite the helical metering groove 23. The two grooves are connected by means of a passage 24 which in turn is connected by a passage 25 to the top of the plunger. The pressure groove 22 has a larger area than the metering groove 23. The advantage of this plunger is the fact that it can be machined in one set-up and the area of the pressure groove 22 can be readily increased by simply increasing the width.

Referring now to Fig. 5 of the drawing, the plunger 3I has a metering groove 32 the upper edge of which is in the form of a helix. Substantially diametrically opposite the metering groove is a. pressure groove 33 cut in the sideof the plunger 3I. An annular groove 34 connects the metering groove 32 to the pressure groove 33. Pressure groove 33 also serves as communicating passage between the pressure chamber I0 and the grooves 34 and 32, if this plunger is used in place of plunger II.

Operation Plunger II is shown in the lower position and fuel has entered into the pressure chamber I0 through port 2. The plunger is moved upward, by means of a cam arrangement not shown, and the upper edge of the plunger which has an unbroken circumference closes port 2. Pressure is then built up in the pressure chamber l0, passages I5 and I3, and in the metering groove I2 and in the pressure cavity It. This pressure causes the delivery valve 8 to open.

Delivery of fuel through valve 8 continues until the upper edge of the metering groove I2 registers with the lower edge of the by-pass port 3. Opening of the by-pass port 3 by the groove I2 will cause by-passing of fuel out of the pressure chamber In through passages I5 and I3, groove I2 and out of the cylinder into the suction chamber, not shown. The portion of the plunger stroke during which both the suction port 2 and the by-pass port 3 are fully covered by the plunger surface is called effective stroke. If the plunger is rotated so that the upper portion of the metering groove I2 will register with port 3 during most of the upstroke of plunger II then the effective stroke is short and the amount of overlap of the ports 2 and 3 by the plunger surface is small. This relative position between port 3 and groove I2 will cause a fuel quantity delivered through valve 8 corresponding to idling or light load condition of an engine to which the pump delivers the fuel.

If the plunger is rotated into the position shown in Figs. 1 and 2 then the effective stroke and the overlap of the ports 2 and 3 by plunger II are greater than in the first described position. The effective stroke and overlap will increase if the plunger is rotated further. The longest effective stroke will give a delivered fuel quantity corresponding to'about full load condition of an engine.

- Since the pump described has to pump pressures of 2000 to 7000 pounds per square inch and higher, the amount of overlap of the ports 2 and 3 and the seal produced thereby are very important; In order to produce an eflicient seal the plunger surface overlapping ports 2 and 3 must be firmly pressed against the cylinder surface surrounding ports 2 and 3. This is accomplished by dimensioning and arranging grooves I2 and II relative to each other so that the side pressure exerted on the plunger by fuel in groove I2 is substantially less than the side pressure caused by fuel in the pressure groove I4'. Therefore, the fuel film separating the plunger and cylinder surfaces on the metering side of the plunger is put under a pressure substantially in excess of the fuel pressure in the chamber I0 and groove I2, thereby preventing or materially reducing leakage past the plunger into ports 2 and 3. In Fig. 2 line 20-20 is the centerline of the ports 2 and 3 and the plunger is shown in a position in which the side pressure exerted by pressure groove I4 is in the general direction of line 2020. It is evident that if the direction of the side pressure coincides with the centerline of the ports 2 and 3 the best possible sealing condition is obtained. It has been explained that plunger II is shown in a position relative to ports 2 and 3 corresponding to about half load condition of an engine. It is evident that when pressure groove II of Fig. 2 is rotated with respect to the metering groove I2 the direction of side pressure will be changed. Therefore, by changing the angular arrangement of groove I 4 with respect to groove I2 the best sealing condition can be obtained for any one portion of the helical metering groove I2. The seal obtained for the other portions of the metering groove I2 is also far superior to the seal obtained in usual pumps since the radii of the cylinder surface and plunger surface are equal within a few millionths of an inch.

It is also evident that ports 2 and 3 can be arranged angularly with respect to each other without materially impairing the sealing quality of the pump.

During the effective stroke of the piston, as has been stated heretofore, it is forced towards the ported side of the pump cylinder so that the clearance on the side carrying the pressure cavity is increased. This clearance indicated at in Fig. 7 is largest directly opposite the pressure cavity I4 whereas it slowly decreases towards the metering groove. It is evident that the fluid pressure in the pressure cavity I4 is the same as the pumping pressure built up in chamber I 0 whereas the pressures in the gradually diminishing clearance spaces or each side of the pressure cavity are pressure gradients beginning with the full pumping pressure near the pressure cavity and gradually decreasing substantially towards the metering cavity. Therefore, the total side pressure exerted on account of the pressure groove is composed of pressure exerted by fluid in the pressure groove and by fluid in the clearance spaces in the vicinity of the pressure groove.

It is realized that a reduction in clearance between the plunger and cylinder on one side will cause an increase in clearance on the other side. This, however, is immaterial for practical purposes since the distance of the lower edge of groove I4 to the leakage groove 4 is long enough so that the resistanceagainst leakage is great despite increased radial clearance.

When the pressure is relieved thev valve 8 will seat and the plunger is forced downward in a known manner by a spring. While the plunger is on its downward stroke a vacuum is created in the pressure chamber I0 and as soon as the top of the plunger II overlaps the top portion of the inlet port 2, fuel is drawn into the pressure chamher.

The plungers shown in Figures 4 and 5 may be placed in the same type-of cylinder as shown in Fig. 1 and they will function in the identical manner as the plunger ll.

5 While several embodiments of the invention have been described and illustrated in the drawing, it will be apparent to those skilled in the art that the invention is capable of a wide variety of mechanical expressions, while changes may be made in the form, details and proportions of the parts without departing from the spirit of the invention. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What I claim is: v

- 1. In a fuel injection pump having'a cylinder and a piston movable therein, suction and bypass ports in the cylinder, a helical metering groove on said piston, the piston cooperating with said ports, and a rectangular cavity opposite said metering groove, said cavity having a larger area than the metering groove and said groove and cavity having constant communication with the pressure chamber of the pump.

2. In a fuel injection pump, a cylinder, having a piston movable therein, said cylinder having inlet and by-pass ports, a metering groove on said piston and a pressure groove substantially'opposite said metering groove, said ports being sub- 80 stantially on the same vertical center-line, the metering groove cooperating with said by-pass port, and a conduit connecting said grooves, a second conduit connecting the first conduit with the top of the piston, and the top of said piston 85 cooperating with said inlet port, the relative areas of said grooves being such that the resultant of radial components of pressures acting on said plunger during each pressure stroke thereof acts in the direction of said ports.

40 3. In a fuel pump of the class described, a

second helical groove being of a larger area than I the helical metering groove and being substantial- 5 1y opposite the helical metering groove, the pressure transmitted from the working chamber to said helical grooves being such that the pressure exerted on the metering edge of the metering helical groove is substantially greater than the 5 pressure exerted on the edge of the other helical groove.

4. A piston for a fuel injection pump having a metering cavity, an annular groove in communication with said metering cavity, and a longiw tudinal groove substantially diametricallyopposite said metering cavity in communication with said annular groove and extending to the top of the piston, said longitudinal groove having a larger area than the metering cavity.

5. A fuel pump consisting of a'delivery valve, a cylinder, a piston movable therein, said cylinder having an inlet port and a by-pass port, substantially on the same vertical centerline, said piston having a helical metering groove adapted 5 to cooperate with said by-pass port to control the pump output, a second helical groove substantially diametrically opposite to the metering groove, communicating means connecting the first helical groove with the second helical groove, and a sec- 10 0nd communicating means connecting the working chamber of the pump to the said first communicating means, the area of the second helical groove being larger than the said first helical groove whereby the side pressure exerted on the 15 piston by the fuel contained in the said second helical groove will force the piston against the portion of the cylinder wall opposite said second helical groove, said by-pass port and inlet port being located in said portion of the cylinder wall. 20 I 6. In a fuel injection pump, a cylinder having an inlet port and an outlet port on the same side thereof, a plunger reciprocable in said cylinder, said plunger having a metering groove in one side thereof adapted to cooperate with said outlet port, a pressure groove in the other side thereof having constant communication with the pres sure chamber of the pump-and with said metering groove, said pressure groove having a greater area than said metering groove whereby the resultant of radially directed pressures acting on said plunger during each pressure stroke of the latter is slight and effective to press said plunger to-, ward said ports. T

7 In a fuel injection pump, a cylinder having an inlet port and an outlet port on the same side thereof, a plunger reciprocable in the said cylinder, the upper end of said plunger being adapted to cover and uncover said inlet port, said plunger having a metering groove in one side thereof do adapted to cooperate with said outlet port and apressure groove in the other side thereof, said grooves having constant communication with the pressure chamber of the pump and said pressure groove having a greater area than said metering 46 groove whereby the resultant of the radial components of pressures acting on said plunger during each pressure stroke of the latter is effective to press said plunger toward said ports.

8. In a fuel injection pump, a cylinder having 50 an inlet port and an outlet port on the same side thereof, a plunger reciprocable in said cylinder, said plunger having a metering groove in one side thereof adapted to cooperate with said outlet port and a pressure groove in'the other side. 55.

thereof, said grooves having constant communication with the pressure chamber of the pump, the relative areas of said grooves being such that the resultant of radial components of pressures act- 'ing on said plunger during each pressure stroke v thereof tends to press said plunger toward said ports.

ALBERT T. BREIVISER.

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