In-Line Type Fuel Injection Pump for Internal Combustion Engines

This invention relates to fuel injection pumps for internal combustion engines, and more particularly to an in-line type fuel injection pump which facilitates machining of its pump housing.

An in-line type fuel injection pump in general for use with a Diesel engine has a plurality of pump assemblies formed essentially of plungers and plunger barrels corresponding in number to the cylinders of the engine and arranged in a line. Each of the pump assemblies is accommodated in a pump accommodating space formed in the pump housing and has a fuel chamber formed in the pump accommodating space and supplied with fuel from a fuel tank, via a fuel intake connector mounted on the pump housing and connected to the fuel tank. Conventional measures for guiding fuel from the fuel intake connector to the fuel chamber of each of the pump assemblies include a method of boring the fuel chamber to a large interior diameter so that the fuel chambers of adjacent pump assemblies are in communication with each other, at least one of which is in communication with the fuel intake connector, a method of forming communication holes in the pump housing, each communicating the fuel chamber of its corresponding pump assembly with the fuel intake connector, and a method of forming a lateral side hole in the pump housing, which opens in the fuel chamber of each pump assembly, so as to communicate the fuel chambers with each other by the side hole, at least one of the fuel chambers being in communication with the fuel intake connector.

However, any of the above conventional measures requires complicate machining, especially boring, of the pump housing, and the more the number of the pump assemblies of the pump, the more difficult such machining becomes. This results in low productivity and accordingly a high manufacturing cost of the pump, as well as in difficulties in designing the pump compact in size.

It is an object of the invention to provide an in-line type fuel injection pump for internal combustion engines, which facilitates machining of the pump housing, thereby having improved productivity and low manufacturing costs.

It is a further object of the invention to provide an in-line type fuel injection pump for internal combustion engines, in which the pump assemblies can be arranged with small distances therebetween, thus permitting designing compact in size.

An in-line type fuel injection pump according to the invention includes a pump housing having a plurality of pump accommodating spaces formed therein and arranged in a line, and a plurality of partition wall portions separating adjacent ones of the pump accommodating spaces from each other. Accommodated, respectively, in the pump accommodating spaces are a plurality of pump assemblies, each including a plunger barrel mounted within a corresponding one of the pump accommodating spaces, and a plunger disposed for reciprocating motion within the plunger barrel for pressure delivery of fuel. A plurality of fuel passages are formed in the pump housing, which extend from the outer wall surface of the pump housing to respective ones of the partition wall portions. Each of the fuel passages has an interior diameter larger than the width of a corresponding one of the above partition wall portions. Further, each of the fuel passages has an inner end terminating in both of the the inner peripheral wall surfaces of the above two adjacent ones of the pump accommodating spaces at predetermined regions to thus communicate them with each other, and has an outer end terminating in the outer wall surface of the pump housing.

The above and other objects, features and advantages of the invention will be more apparent from the ensuing detailed description taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic front view illustrating a typical conventional in-line type fuel injection pump adapted for use with a Diesel engine;

FIG. 2 is a schematic top plan view illustrating the pump housing of an in-line type fuel injection pump according to an embodiment of the invention;

FIG. 3 is a vertical sectional view taken along line III--III in FIG. 2; and

FIG. 4 is a vertical sectional view illustrating, by way of example, an in-line type fuel injection pump in which the pump housing of FIGS. 2 and 3 is incorporated.

Referring first to FIG. 1, there is illustrated, by way of example, the whole arrangement of an in-line type fuel injection pump which is generally used in Diesel engines. The fuel injection pump has a pump housing 1, and a plurality of, e.g. six, pump assemblies 2-7 corresponding in number to the cylinders of the engine, arranged longitudinally of the pump housing in a line. Each of the pump assemblies 2-7 has a pump accommodating space, not shown, in which are accommodated a plunger barrel and a plunger, neither of which is shown. A fuel chamber, not shown, is formed in each of the pump accommodating spaces, which is supplied with fuel through a fuel intake connector 8 mounted at one end of the pump housing 1. A camshaft 9, which is rotatively driven by the rotating engine, drivingly reciprocates the plungers of the pump assembles 2-7 within the respective plunger barrels to pressurize fuel for pressure delivery of fuel to the cylinders of the engine successively in a predetermined order and in quantities corresponding to the position of a control rod 10 which is interlocked with an accelerator pedal, not shown, to control the effective strokes of the plungers.

As previously noted, in this type fuel injection pump, conventionally the supply of fuel to each of the pump assemblies 2-7 through the fuel intake connector 8 is effected, for instance, by means of communication bores formed in the pump housing to communicate the fuel intake connector 8 with the respective pump assemblies 2-7, which makes the machining operation of the pump housing 1 rather complicate and hard. Therefore, a measure for feeding of fuel to the pump assemblies is desired, which facilitates such machining operation.

FIGS. 2 and 3 illustrate an in-line type fuel injection pump adapted for use with Diesel engines according to an embodiment of the invention. In the figures, reference numeral 11 designates a pump housing which is formed with a plurality of, for instance three, pump accommodating spaces 13-15 corresponding in number to the cylinders of the engine, arranged in a line at predetermined intervals. More specifically, the pump accommodating spaces 13'-15' are formed, respectively, by cylindrical holes 13-15 each having a circular cross section and vertically formed through the pump housing, and in which are mounted pump elements including plunger barrels and plungers, as hereinafter described.

The pump housing 11 has its upper portion formed integrally with a flange 12 which is formed therein with two bores 16 and 17. The bore 16 extends from a sloped end face 12a of the flange 12 forming part of the outer wall surface of the pump housing, to a partition wall portion 12c formed within in the pump housing 11, intervening between two adjacent pump accommodating spaces 13, 14 and separating them from each other, while the bore 17 extends from an opposite sloped end face 12b forming another part of the outer wall surface of the pump housing, to a partition wall portion 12d in the pump housing, intervening between two adjacent pump accommodating spaces 14, 15 and separating them from each other. Thus, the two bores 16, 17 extend downwardly obliquely at predetermined angles with respect to the upper surface of the pump housing 11. The bores or interior diameters D of the bores 16, 17 are set at a value larger than the width d of the partition wall portions 12c, 12d, that is, the distance between the inner peripheral surfaces of the adjacent pump accommodating spaces 13, 14 or 14, 15. The inner end of the bore 16 terminates in both of the inner peripheral wall surfaces 13a, 14a of the pump accommodating spaces 13, 14 at predetermined regions 13a', 14a'. On the other hand, the inner end of the bore 17 terminates in both of the inner peripheral wall surfaces 14a, 15a of the pump accommodating spaces 14, 15 at predetermined regions 14a", 15a". Consequently, the pump accommodating spaces 13, 14 communicate with each other by way of a fuel passage 41 formed by the opening 13a', the bore 16 and the opening 14a', whereas the pump accommodating spaces 14, 15 communicate with each other by way of a fuel passage 42 formed by the opening 14a", the bore 17 and the opening 15a'.

On the other hand, the other openings 16b, 17b of the bores 16, 17 formed at the end faces 12a, 12b of the flange 12 can serve as a fuel inlet port and a fuel outlet port, respectively, both connected to a fuel tank, not shown, by way of a fuel supply conduit and a fuel return conduit, not shown.

In the above manner, the adjacent pump accommodating spaces 13-15 are communicated with each other through the respective fuel passages 41, 42 for feeding and discharging fuel to and from them.

Referring next to FIG. 4, there is illustrated an example of an in-line type fuel injection pump to which is applied the pump housing of FIGS. 2 and 3 according to the invention. Mounted within the pump accommodating spaces of the pump housing 11 are a plurality of sets of pump elements forming pump assemblies. More specifically, taking the pump accommodating space 13 for instance, a sleeve 20 is fitted in the pump accommodating space 13 and held in a predetermined circumferential position relative to the pump housing 11 by a set screw 31. Fitted in the sleeve 20 is a plunger barrel 21 which is prohibited from circumferential dislocation relative to the pump housing 11, by the above set screw 31, with its upper flange 21a fitted in an annular stepped shoulder 20e formed in the inner peripheral wall of the sleeve 20 to hold the plunger barrel 21 in a predetermined axial position. Slidably fitted within the plunger barrel 21 is a plunger 22 for reciprocating motion therein and engaging with a control sleeve 36 which in turn engages with a control rod 35 via a ball 37 to b5 controlled in circumferential position in response to displacement of the control rod 35. The plunger 22 has its lower end 22a kept in urging contact with a tappet 23 by the force of a plunger spring 25 for returning the plunger 22, and the tappet 23 is disposed in engagement with a camming surface of a camshaft, not shown, connected to the crankshaft of the engine, not shown.

A delivery valve holder 26 is threadedly fitted in the sleeve 20 and held in liquidtight engagement therewith by an O-ring 34 fitted therearound, and the sleeve 20 is fixed to the pump housing 11 by means of an element holder 32 secured to the pump housing 11 by fastening bolts 33. The above delivery valve holder 26 holds a valve seat 27b of a delivery valve 27 in contact with the plunger barrel 21, and accommodates a valve spring 28 urging a valve body 27a of the delivery valve 27 against a valve seat 27b of same in which the valve body 27a is slidably fitted. O-rings 29 and 30 are fitted in the outer periphery of the sleeve 20, respectively, at upper and lower locations to seal the sleeve 20 against the cylindrical hole 13' in a liquidtight manner. An annular stepped recess 20a is formed in the outer peripheral surface of the sleeve 20 over the whole circumference at a location opposite the opening 13a' in the inner peripheral surface 13a of the pump accommodating space 13 to define an annular communication passage 20b in cooperation with an annular stepped recess 13a" formed in the above inner peripheral surface 13a. Defined between an annular groove 20c" formed in the inner peripheral surface of the sleeve 20 and the outer peripheral surface of the flange 21a of the plunger barrel 21 is an annular chamber 20c as a fuel chamber which is in communication with the above annular communication passage 20b through a plurality of through holes 20d formed through the peripheral wall of the sleeve 20, only one of which is shown. A feed hole 21c is formed through the flange 21a of the plunger barrel 21 at a predetermined axial position, which communicates the fuel chamber 20c with an internal space 21b as a delivery chamber, defined between the plunger barrel 21 and the plunger 22. Thus, a first pump assembly 2' is mounted in the pump accommodating space 13, which is arranged as above. As noted above, the annular communication passage 20b of the first pump assembly 2' communicates on one hand with the delivery chamber 21b in the plunger barrel 21 through the holes 20d, the fuel chamber 20c and the feed hole 21c, and on the other hand with the bore 16 through the opening 13a'.

Though not illustrated, the other pump accommodating spaces 14, 15 accommodate second and third pump assemblies having identical constructions with that of the first pump assembly described above. As will be learned from FIG. 2, a second annular communication passage, not shown, formed in the second pump assembly, which corresponds to the annular communication passage 20b appearing in FIG. 4, is in communication with the bores 16, 17 via the openings 14a', 14a", and that formed in the third pump assembly with the bore 17 via the opening 15a', respectively. Thus, the first to third pump assemblies continuously communicate with each other via the fuel passages 41, 42.

The operation of the in-line type fuel injection pump is as follows: In the first pump assembly, fuel from the fuel tank is supplied to the fuel chamber 20c via the opening (fuel inlet) 16b of the bore 16, the fuel passage 41, the annular communication passage 20b and the holes 20d, and then the fuel in the fuel chamber 20c is fed into the delivery chamber 21b in the plunger barrel 21 through the feed hole 21c. To the second and third pump assemblies, fuel is supplied, respectively, through the fuel passage 41 and the fuel passage 42 communicating with the second annular communication passage, in the same manner as in the first pump assembly 2'.

On the other hand, the camshaft, not shown, rotating in unison with the rotating engine, the roller 24 and the tappet 23 are reciprocatingly moved to cause a reciprocating motion of the plunger 22 within the plunger barrel 21. Pressurization of fuel takes place in the delivery chamber 21b from the time the upper end face of the plunger 22 blocks the feed hole 21c to the time the upper edge of a control groove 22b formed in the plunger 22 reaches the feed hole 21c, and the pressurized fuel forces the valve body 27a of the delivery valve 27 to lift against the force of the valve spring 28 so that the pressurized fuel is fed through a hole 26a formed in the delivery valve holder 26, an injection pipe and an injection nozzle, which are not shown, to be injected into an associated cylinder of the engine. After each delivery of fuel, the plunger spring 25 forces the plunger 22 downward in unison with the rotating camshaft, into the initial position shown in FIG. 4. The other pump assemblies operate in a manner identical with the first pump assembly 2'. An amount of fuel in excess of required one in the pump assemblies is guided to the opening (fuel outlet) 17b of the bore 17 through the fuel passages 41, 42, and returned to the fuel tank.

Although in the illustrated embodiment the fuel chamber 20c is provided between the inner peripheral surface of the sleeve 20 and the outer peripheral surface of the plunger barrel 21 fitted in the sleeve 20, such fuel chamber may alternatively be formed in the outer peripheral surface of the sleeve 20.

The arrangement according to the invention described above greatly facilitates machining of the pump housing, enhancing the productivity or yield, resulting in a reduced manufacturing cost. Further, it permits arranging the pump assemblies with smaller distances between them, enabling the whole size of the pump compact.

While a preferred embodiment of the invention has been described, obviously modifications and variations are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.