US2729167A - Fuel injection pump - Google Patents

Description

Jan. 3, 1956 H. K. LINKS FUEL INJECTION PUMP 2 Sheets-Sheet 1 Filed March s, 195o w w 2 5 A .r 4r 4 7.00

Jan- 3, 1956 H. K. LINKS 2,729,167

FUEL INJECTION PUMP Filed March 3, 1950 2 Sheets-Sheet 2 United States Patent() FUEL INJECTION PUMP Heinrich K. Links, Stuttgart, Germany, assigner to Daimler-Benz Aktiengesellschaft, Stuttgart-Unterturkheim, Germany Application March 3, 1950, Serial No. 147,359 Claims priority, application Germany March 4, 1949 7 Claims. (Cl. 1613-41) The invention relates to fuel injection pumps for internal combustion engines.

The primary object of the invention is to provide a simply and economically made injection pump in which an accurate and reliable control of the quantity of injected fuel or of the injection period is effected by opening and closing a bypass line by piston type slide valve means and preferably by rotary valve means.

A further object of the invention is-in case rotary valve means are used--the utilization of the drive gear train of the rotary valve for additional purposes, for instance for the transfer of fuel.

According to the invention the bypass or spill controlling slide valve means which are preferably rotary valves are connected with the bypass ports of the pump cylinders by means of conduits common to all or at least to two of the pump cylinders. If a rotary valve is used the rotary valve which is preferably a distributor type valve is coacting with a rotatable sleeve disposed concentrically to said rotary valve in order to control the end of the injection period of the individual pump elements. The beginning of the injection period will preferably be left constant and can for instance be controlled by the closing of the fuel inlet port by the pump piston and the consequent opening of the delivery valve. The shaft of the delivery valve is preferably shaped cylindrically so as to be able to act as additional control means for the by-passing of the fuel.

The rotary valve is preferably arranged parallel to the camshaft -of the pump. The drive of the rotary valve is taken off the pump camshaft and can for instance be effected by a pair of spur gears which at the same time can serve as a gear pump for the transfer of fuel to the inlet ports of the injection pump.

Further features of the invention will become apparent by reference to the following detailed description and drawings illustrating one modification of the invention.

Fig. 1 of the drawings is a cross section of the pump taken on line A-B of Figure 2.

Fig. 2 is a horizontal longitudinal section of the pump taken on line C-D of Figure l.

Fig. 3 is a schematic longitudinal view of the pump cylinders and a sectional view of the rotary valve showing the fuel circuits of the pump.

Fig. 4 is a schematic View of a single pump cylinder and a cross section of the rotary valve in combination with an injection timing diagram.

Fig. l shows a fuel injection pump mounted on the cylinder head cover 1 of an internal combustion engine which can for instance be an engine operating with gasoline injection, the base 3 of the pump housing 2 being fastened to cover 1. The drive of the pump camshaft 4 is not shown and can be effected in any suitable manner. The injection pump is a four cylinder pump with pump cylinders 5 and pump pistons 6, the latter being actuated by the camshaft 4 by means of the spring biased cam followers 7, which, as shown in Fig. 2, have at side surfaces 8, said surfaces 8 of adjacent cam followers contacting one another.

Y 2,729,167 Patented Jan. 3, 1956 a pair of drive gears 10, 11 is pump housing which is located opposite the driven end 4' of the camshaft 4, the gear 10 being fastened to the end of shaft 4, the gear 11 being fastened to the rotary valve 12 which is arranged parallel to the camshaft and adjacent to the cam followers and is supported by the bushings 12 and 12". The function of the rotary valve will be described in another part of thc description. The gears 10 and 11 have the same diameter so that the rotary valve is driven at camshaft speed. The rotary valve drive gears act as a gear pump for transferring fuel from the tank 13 (Fig. 3) to the inlet ports 16 of the fuel injection pump. A filter 14 can be provided in then fuel feed line.

Fuel delivered through feed pipe 15 enters the space 5 of the pump cylinder 5 through recess 15 and inlet bore or port 16 when the pump piston is at its lower dead center position. After the closing of inlet port 16 on the upstroke of the pump piston fuel will enter the injection line 13 after lifting the delivery valve 17 from its seat against the pressure of spring 17'. The cylindrical shaft 19' of the delivery valve 17 has a center bore 19 connecting with an annular' groove 19', so that fuel can flow from the pump space 5 to the injection line 18 after valve 17 has been lifted off its seat. The lower edge of the shaft 19 controls an overflow or by-pass port 20. The bypump cylinders are connected to a common conduit 21 which is connected, for instance by one or two'bores 21', to one or several annular grooves 22 on the circumference of the rotary valve 12. The grooves 22 are connected by bores 23 with a cen- A separate housing 9 for flanged to that end of the cumference of the rotary valve.

The portion of the rotary valve containing the control recess 26 is surrounded by the regulating sleeve 27, which is provided with 4 bores or ports 28 (designated as 28a to d in Fig. 4). The ports 28 are distributed equally on the circumference of the rotary valve. 0n rotation of 12 the control recess 26 registers conated manually or by means of a governor (not shown). provided to change the length of the control rod, if this should become necessary. Fuel disbores 28 flows into the chamber 33 which is connected to the fuel tank by a return pipe 34. The return pipe 34 can also serve directly as a suction line for the gear pump 10, 11.

The operation of the device can 3 and 4. The fuel sucked in from the fuel tank 13 is conveyed by the gear pump 10, 11 through the inlet pipe 15 to the inlet ports 16 of the pump cylinders.

The diagram to the right of Fig. 4 shows the lift curves a, b, c of three pump pistons in relation to the position of the rotary valve or to the position of the camshaft.

In Figure 4 the pump piston 6 is assumed to be at lower dead center (point P in the diagram), the pump space 5 having been filled with fuel entering through in let port 16. The by-pass port 20 is closed by shaft 19 of valve 17. The rotary valve is assumed to be in the position shown in Figure 4, the control recess 26 being between ports 28a and 28h at this time.

The total lift of the piston 6 is designated by the letter H. During the first part (hi) of the pump piston upstroke a portion of the fuel in space 5' is pressed back into the inlet port 16 which is still open. As soon as inlet port 16 is closed, the piston 6 begins to compress the fuel trapped in pump space 5', which then lifts the delivery valve 17 off its seat, so that it can pass through bore 19" to injection pipe 18. Injection then begins (point Q in the diabest be seen from Figs.

gram) after an injection lag which is dependent on the speed of the engine. After a further lift (h2) the valve shaft 19 opens the by-pass port 20. However, as port 2819 is not yet in alignment with control recess 26 of the rotary valve, which is rotating in the direction of the arrow, no fuel will be by-passed at this time and injection will continue. After a further lift (ha or point R) the control recess 26 willstart to register with port 28!) of the regulator sleeve, so thatthe fuel can now ow out of the by'pass port 20 through 24, 25, 26 to port 28b and thence to chamber 33 and to the fuel tank 13. The pressure in spaceV is thereby suddenly lowered, thus ending the injection period x which corresponds to the lift between points Q andV R; The fuel delivered by the pump piston on its remaining lift (h4) is by-passed at a very low pressure through port 20 to the tank in the above described manner. The distance ha between the by-pass port 20 and the lower edge of the valve shaft 19 is necessary on account of the provision of a common by-pass conduit (21) and should be kept as small as possible, in order to effect a sudden and, if possible, a complete closing of the delivery valve 17 after thev opening of the by-pass line by the rotary valve. In any case, as soon as the piston has passed its upper dead center position (point S), the valve 17 will be completely closed. Some time thereafter (point T) also the port 2Sb will be closed by the rotary valve 12.

By turning the regulating sleeve 27--as indicated by the angle--the control period y and thereby the end (R) of the injection period (i. e. the moment at which the control recess 26 is beginning to line up with port 285) can be changed, thus permitting a regulation of the injection period x and at the same time regulation of the quantity of injected fuel.

In the embodiment shown the beginning of the injection period (point Q) is assumed to be constant and to be determined by the closing of the inlet port 16 by the pump piston. It is, however, also possible to regulate the beginning of the injection, for instance by providing an adjustable delivery valve between pump space. 5' and the injection pipe 18. It is also possible to provide for a relative movement between the two gears 10, 11 in the manner known in pump shaft advance mechanisms, thereby changing the timing between the rotary valve and the pump camshaft and thus changing the beginning of the injection period.

The invention is not limited to the example of construction shown and any modifications showing the main features described herein shall be considered as falling within the scope of the invention.

Whatl claim is:

l. ln a fuel injection pump having a plurality of pump cylinders: a pump piston in each ot`r said pump cylinders, drive mechanism for each of said pump pistons, inlet, outlet and bypass ports in each of said pump cylinders; said bypass ports of said pump cylinders being connected to common conduit', a rotary valve forsaid cylinders, said common conduit being connected to said rotary valve; said rotary valve controlling the quantity of injected fuel by bypassing fuel at the end of the injection stroke of each pump piston to a chamber of low fuel pressure; said rotary valve being actuated in timed relation with the movement of said pistons.

2. In a fuel injection pump having a plurality of pump cylinders: a pump piston in each of said pump cylinders, drive mechanism for said pump pistons, inlets, outlets and bypass ports in each of said pump cylinders; said bypass ports of all said pump cylinders being connected to common conduit; a rotary valve havingy a chamber Cil 4 l therein; said common conduit being connected to a chamber within the rotary valve; said rotary valve controlling the quantity of injected fuel by bypassing fuel at the end of the injection stroke of each pump piston to a chamber of low fuel pressure; said rotary valve being actuated in timed relation with the actuation of the pump pistons.

3. Fuel injection pump according to claim 2 in which said rotary valve is provided on its circumference with a control recess connected to said chamber within the rotary valve; said control recess coacting with a sleeve surrounding said rotary valve; said sleeve having a number of bores equal to the number of pump cylinders; said bores coming into consecutive registration with said control recess of said rotary valve; said sleeve being rotatable in order to control the quantity of bypassed fuel.

4. Fuel injection pump according to claim 2 in which a control member is provided in cach of said pump cylinders; said control member being the shaft of a delivery valve for the fuel outlets, said shaft being of sufcient length to keep said bypass. port closed as long as said delivery valve is seated and opens said bypass port after said delivery valve has been raised a predetermined distance.

5. A fuel injection pump according to claim 2, in which the rotary valve is arranged parallel to the driven cam shaft of the pump, a gear rigidly mounted on the cam shaft and a gear similar to said first-named gear and mounted on the shaft of the rotary valve, said gears engaging each other, and means for operating said gears.

6. A fuel injection pump according to claim 5, in which the driving and the driven gears are arranged in a tightly surrounding housing and at the same time form the pump gears of a feed pump feeding the fuel to the pump cylinders.

7. In a fuel injection pump: a plurality of pump cylinders, a pump piston in each of said pump cylinders, drive means for said pump pistons, inlets, outlets and bypass ports in each of said pump cylinders, delivery valves in said outlets of each of said pump cylinders, thc shaft of said delivery valve keeping said bypass port closed when said delivery valve is on its seat and opening said bypass port after said delivery valve has been lifted a predetermined distance; said bypass ports of said pump cylinders being joined to common conduit connected to a chamberwithin the rotary valve; said rotary valve being arranged parallel to the camshaft which is part of the drive means of said pump pistons, and being rotated at camshaft speed by means of a drive gear fastened to said camshaft and a driven gear fastened to the rotary valve; said drive gear and said driven gear acting as a gear type fuel transfer pump; said rotary valve being provided at its circumference with a control recess connected by suitable passages to said common conduit; said control recess coacting with a rotatable sleeve having a number of bores equal to the number of said cylinders and being arranged concentrically to said rotary valve; said bores coming into consecutive registration with said control recess on rotation of said rotary valve.

References Cited in the' tile of this patent UNITED STATES PATENTS 2,093,477 Parsons Sept. 2l, 1937 2,278,245 Colell Mar. 31, 1942 2,300,313 Pool Oct. 27, 1942 2,310,370 Hoifer Peb. 9, 1943 2,434,329 Meitzler Jan. 13, 1948 2,474,396 Groves June 28, 1949

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