GB2280480A

GB2280480A - Distributing type fuel injection pump

Info

Publication number: GB2280480A
Application number: GB9414491A
Authority: GB
Inventors: Junichi Kawashima
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1993-07-26
Filing date: 1994-07-18
Publication date: 1995-02-01
Anticipated expiration: 2014-07-18
Also published as: JPH0734995A; DE4426459A1; GB9414491D0; DE4426459C2; GB2280480B

Description

1 j 2280480 1 - FUEL INJECTION PUMP The present invention relates to a

fuel injection pump of a distributor type for use in a Diesel engine, which includes a distributor port for delivery of fuel to engine cylinders.

Japanese Patent Application First Publication No. 3-141859 discloses such a distributor type fuel injection pump for a Diesel engine. The fuel injection pump includes a plunger reciprocally and rotationally movable in a stationary plunger barrel, and an axially movable sleeve fitted on the plunger. The plunger has a spill passage and a gro ove extending from the spill passage to open at an outer peripheral surface of the plunger. Fuel spill from the groove starts in advance of fuel discharge from the spill passage when the groove reaches an axial end of the sleeve during the reciprocal motion of the plunger.

Such a prior art arrangement of the fuel injection pump serves for reduction of fuel injection rate for the engine operation with low speed and low load condition, by the preceding fuel spill from the groove. However, the reduction of fuel injection rate also occurs under low speed and high load condition. This leads to undesired increase in amount of smoke or particulates in exhaust gaq and to decrease in fuel consumption rate.

It would therefore be desirable to be able to provide a fuel injection pump of a distributor type capable of preventing reduction of fuel injection rate under low speed and high load condition and allowing the reduction of fuel injection rate under low speed and low load condition.

According to the present invention, there is 1 - 2 provided a fuel injection pump comprising:

stationary plunger barrel having a bore; plunger slidably disposed in the bore for a to-and-fro movement along an axis with an angular displacement about the axis, the plunger having an outer peripheral surface and an aperture within the outer peripheral surface; and a sleeve on the plunger having an inner peripheral surface mating with the outer peripheral lo surface of the plunger; the sleeve having a first position and a second position axially spaced along the axis from the first position; wherein the sleeve defines a drain port positioned within a predetermined portion of the inner peripheral surface, the predetermined portion being out of passage of the aperture of the plunger during the toand-fro movement of the plunger when the sleeve is in the first position, but in the passage of the aperture of the plunger during the to-and-fro movement of the plunger when the sleeve is in the second position.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic sectional view of a first embodiment of a fuel injection pump according to the present invention, taken along an aXis X-X; Fig. 2 is an enlarged view of a circled part of Fig. 1. showing a plunger and a sleeve f ittelon the plunger; Fig. 3 is a sectional view taken along the line Y-Y of Fig. 2; Fig. 4 is a developed view showing an inner peripheral surface of the sleeve and an outer peripheral surface of the plunger mating therewith, in which the sleeve is in a first position; Fig. 5 is a developed view similar to Fig. 4, 1 but in which the sleeve is placed in a second position; Fig. 6 is a graph showing fuel injection rate of the fuel injection pump of the present invention and fuel injection rate of the prior art fuel injection pump under an engine operating condition;

Figs. 7-9 are graphs showing respective fuel injection rates of the fuel injection pump of the present invention under engine operating conditions different from each other; and Fig. 10 is a view similar to Fig. 3 but showing a modified sleeve.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to Figs. 1 and 2, a fuel injection pump 10 for us e in a four-cylinder Diesel engine includes a pump housing 12 having a pump chamber 14 thereinside. As shown in Fig. 1, a stationary plunger barrel 16 is secured to the pump housing 12. The stationary plunger barrel 16 has a bore 18 receiving a plunger 20 as seen in Fig. 1. The plunger 20 is slidably disposed in the bore 18 for to-and-fro movement along an axis X with angular displacement about the axis X. The angular displacement of the plunger 20 is allowed due to unitary rotation with a drive shaft to which the plunger 20 is connected. The plunger 20 is so constructed and arranged as to move owing to engagement between a cam disc 22 and a roller 24 as seen in Fig. 1.

The cam disc 22 is secured to one end of the plunger 20 and has a cam surface 26. The cam surface 26 is formed with a number of projections corresponding to a number of engine cylinders, viz. four projections in this embodiment which are disposed such that the adjacent two projections make a right angle(relative to the axis X). The cam surface 26 is contacted with the roller 24 disposed in the pump chamber 14. The plunger 20 is moved axially and reciprocally by the contact engagement of the 4 cam surface 26 with the roller 24 during the angular displacement of the plunger 20. The plunger 20 is displaced through a right angle per one toand-fro movement. As the plunger 20 moves reciprocally a 5 compression chamber 28, defined between the other distal end of the plunger 20 and an end wall 30 of the plunger barrel 16, is expanded and compressed. The plunger 20 has four inlet grooves 32 on an outer peripheral surface of the distal end portion. The 10 inlet grooves 32 are circumferentially disposed spaced apart from each other-and axially extend to communicate with the compression chamber 28. Each of the inlet grooves 32 is allowed to communicate with an inlet port 34 of the plunger barrel 16 when the inlet groove 32 is 15 aligned with the inlet port 34 in response to every right angle displacement of the plunger 20. The inlet port 34 is connected with an intake passage 36 for fuel supply, as seen in Fig. 1. Fuel is in turn supplied via the intake passage 36, the inlet port 34, and the inlet 20 grooves 32 to the compression chamber 28. The plunger 20 has an axial fuel passage 38 communicating with the compression chamber 28. A distributor port 40 extends radially outward from the axial fuel passage 38 to open to the bore 18. Four 25 outlet ports 42 are circumferentially spaced apart at a right angle from each other within the plunger barrel 16. The outlet ports 42 are allowed to in turn communicate with the distributor port 40 of the plunger 20 when the distributor port 40 is aligned with the outlet ports 42 30 during the angular and to-and-fro movement of the plunger 20. As shown in Fig. 1, each of the outlet ports 42 is connected via a delivety valve 44 and a high pressure fuel passage 46, with a fuel injection valve 48 for fuel delivery to the corresponding engine cylinder.

As shown in Figs. 1, 2, and 3, four spill passages 50 are formed in the plunger 20 close to the cam disc 22. As best shown in Fig. 3, the four spill passages 50 extend radially outward from a terminal end of the axial fuel passage 38 such that the adjacent two spill passages 50 make a right angle. Each of the spill passages 50 includes an aperture 52 as seen in Fig. 2, opening to the outer peripheral surface of the plunger 20 and extending axially toward the compression chamber 28. As shown in Figs. 4 and 5, the spill passage 50 is of a generally circular shape in section and the aperture 52 of a generally rectangular shape in section.

Referring back to Fig. 1, an annular sleeve 54 is received on a portion of the plunger 20 which projects from the bore 18 of the plunger barrel 18. As shown in Fig. 1, the sleeve 54 has an inner peripheral surface mating with the outer peripheral surface of the plunger 20.

The sleeve 54 defines a drain port 56 positioned within a predetermined portion of the inner peripheral surface of the sleeve 54. In this embodiment as shown in Figs. 1, 2, and 3, four drain ports 56 are provided within the predetermined portion of the sleeve 54. As seen in Fig. 2, the drain ports 56 extend axially outward to open to an axial end face 58 of the sleeve 54 and communicate with the pump chamber 14. As best shown in Fig. 3, the adjacent two of the drain ports 56 are so disposed to make a right angle (with respect to the axis X).

The sleeve 54 is so constructed and arranged as to be axially displaceable by operation of a governor connected with the sleeve 54. Depending on the axial displacement of the sleeve 54, the plunger 20 has different effective strokes for engine operating conditions. The effective stroke is a distance between the aperture 52 and an axial edge of the inner peripheral 6 - surface of the sleeve 54. The sleeve 54 has a first position and a second position axially spaced along the axis X.

Fig. 4 shows that the sleeve 54 is in the first position,in which the plunger 20 has a large effective stroke L for the engine operation with high load condition. As shown in Fig. 4, when the plunger 20 moves along the arrow A, opposed leading edges of the aperture 52 pass as indicated by the broken linesB-B. In this position of the sleeve 54, the predetermined portion of the inner peripheral surface is out of the passage of the aperture 52 of the plunger 20 during the to-and-fro movement of the plunger 20. The drain port 56 is covered with a portion of the inner peripheral surface outside the predetermined portion to be prevented from fluid communication with the aperture 52 of the plunger 20. A part of fuel is prevented from being discharged or spilled out"of the aperture 52 into the pump chamber 14 until the leading edges of the aperture 52 are aligned with the axial edge of the inner peripheral surface of the sleeve 54. Thus, fuel feed to the fuel injection valve 48 is performed without reduction of fluid pressure, and when the leading edges of the aperture 52 reaches the axial edge of the inner peripheral surface of the sleeve 54, fuel discharge from the aperture 52 starts and fluid pressure at the fuel injection valve 48 is reduced.

Fig. 5 shows that the sleeve 54 is in the second position. in which the plunger 20 has a small effective stroke L for the engine operation with low load condition. As the plunger 20 moves along the arrow A, the leading edges of thd aperture 52 pass as indicated by the broken linesB-B. In the second position of the sleeve 54. the predetermined portion of the inner peripheral surface is present in the passage of the aperture 52 during the to-and-fro movement of the plunger 20. The drain port 56 is uncovered to fluidly communicate with the aperture 52 of the plunger 20. A part of fuel is spilled via the aperture 52 from the drain port 56 into the pump chamber 14 and fluid pressure at the fuel injection valve 48 is reduced.

Thus, when the sleeve 54 is placed in the first position, fuel spill from the aperture 52 is restricted. On the other hand, when the sleeve 54 is placed in the second position, fuel spill from the aperture 52 and the drain port 56 is allowed.

Fig. 6 shows that, under low speed and high load condition of the engine operation, the fuel injection pump of the present invention has a higher fuel injection rate,as indicated in solid line, than a fuel injection rate,as indicated in broken line, of the prior art fuel injection pump.

Fig. 7 shows a slow curve of a fuel injection rate of the fuel injection pump according to the present invention, under low speed and low load condition.

Fig. 8 shows a fuel injection rate of the fuel injection pump of'the invention under high speed and high load condition.

Fig. 9 shows a fuel injection rate of the fuel injection pump of the invention under high speed and low load condition. An amount of the fuel injected of Fig. 9 is larger than an amount of the fuel injected of Fig. 7 due to increased rate of fuel feed under the high speed condition.

As is appreciated from the aforementioned description, the arrangement of the drain port 56 within the predetermined portion of the inner peripheral surface of the sleeve 54 allows decrease in fuel injection rate under low speed and low load condition and prevents the decrease in fuel injection rate under low speed and high load condition by controlling the fuel spill from the drain ports 56. This serves for reduction of smoke or particulates in exhaust gas and for rise of fuel consumption rate. The arrangement and size of the drain ports 56 of the sleeve 54 may be modified to thereby readily control timing of the fuel spill and amount of the fuel spilled.

Referring to Fig. 10, there is shown a second embodiment of the present invention, which differs in arrangement of drain ports of the sleeve from the aforementioned first embodiment. Like numerals denote like parts of the first embodiment and therefore detailed descriptions thereabout are omitted. Two drain ports 60 are so arranged in the inner peripheral surface of the sleeve 54 as to make a right angle. The number of the drain ports 60 in the second embodiment is half of the number of the drain ports 56 in the first embodiment so that the drain ports 60 have an increased size if a given amount of fuel is spilled therefrom. The increase in size of the drain ports 60 serves for facilitating the manufacturing process with an improved accuracy to thereby save the manufacturing cost.

1

Claims

C 1 a i m s:

A fuel injection pump comprising:

stationary plunger barrel having a bore; plunger slidably disposed in said bore for to-and-fro movement along an axis with. angular displacement about said axis, said plunger having an outer peripheral surface and an aperture within said outer peripheral surface; and a sleeve on said plunger, having an inner peripheral surface mating with said outer peripheral surface of said plunger; said sleeve having a first position and a second position axially spaced along said axis from said first position; wherein said sleeve defines a drain port positioned within a predetermined portion of said inner peripheral surface, said predetermined portion being out of passage of said aperture of said plunger during said to-and-fro movement of said plunger when said sleeve is in said first position, but in the passage of said aperture of said plunger during said to-and-fro movement of sAid plunger when said sleeve is in said second position.
2. A fuel injection pump as claimed in claim 1, whereip said drain port is in the form of a plurality of ports ' two adjacent ports beinga predetermined angle -about the so disposed as to make said axis.
3. A fuel injection pump as claimed in claim 2, wherein said plurality of ports are four drain ports and said predetermined angle is a right angle.
4. A fuel injection pump as claimed in claim 2, wherein said plurality of ports are two drain ports and said Dredetermined angle is a right angle.
5. A fuel injection pump substantially as described with reference tR, and gs shown in, Figures 1 to 5 or Figure 10 of the accompanying drawings.

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