JP3585784B2 - Fuel injection pump - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection pump used for an internal combustion engine such as a diesel engine.
[0002]
[Prior art]
One of the major features of a diesel engine is that it has a fuel injection pump that sends fuel to a fuel injection nozzle. FIG. 5 is a sectional view showing the structure of a conventional Bosch type fuel injection pump. This fuel injection pump has a barrel 3 fixed in a cylindrical housing 1. An oil reservoir 5 is formed between the barrel 3 and the housing 1 for storing fuel oil sent from a supply source. A bolt-shaped deflector 6 is screwed into the housing 1, and a tip of the deflector 6 forms a part of an inner wall of the oil reservoir 5. The rotation of the deflector 6 varies the volume of the oil reservoir 5 to attenuate the pressure wave caused by the injection. The deflector 6 shown in FIG. 5 has both a fuel oil supply port and a fuel oil return port. A fuel oil outflow port 7 is opened on the inner peripheral surface of the barrel 3. The fuel oil outlet 7 communicates with the oil reservoir 5. At the upper end of the barrel 3, an equal pressure valve 9 is provided. The equal-pressure valve 9 has a discharge-side check valve 11 that operates with the pressure of the pressurized fuel oil and discharges the fuel oil to the outside of the barrel 3, and a return-side check valve 13.
[0003]
A plunger 15 is provided inside the barrel 3 so as to be vertically slidable. The inside of the barrel 3 above the plunger 15 is a pump chamber 16. A cutout 17 is formed on the upper peripheral surface of the plunger 15 to open and close the fuel oil outlet 7 with an appropriate stroke. The cutout portion 17 is divided into an upper end surface of the plunger 15 and a spiral lower end edge, and is slidably in contact with the inner peripheral surface of the barrel 3, and a substantially peripheral relief portion 21 recessed from the peripheral surface portion 19. And a vertical groove 23 communicating the upper end surface of the plunger 15 with the relief portion 21.
[0004]
The operation of the conventional fuel injection pump 25 configured as described above is such that when the peripheral surface portion 19 of the plunger 15 closes the fuel oil outflow / inlet port 7 of the barrel 3, the escape portion 21 of the plunger 15 and the oil reservoir 5 are shut off. As the plunger 15 moves up, the pressure of the fuel oil in the barrel 3 rises. The moment when the peripheral surface 19 of the plunger 15 closes the fuel oil outflow / inlet 7 is referred to as the start of pressure feeding. When the plunger 15 is further raised, the discharge side check valve 11 of the equal pressure valve 9 is opened by the pressure of the fuel oil, and the fuel oil is fed to a nozzle (not shown).
[0005]
When the lower end edge of the peripheral surface portion 19 of the notch 17 passes through the fuel oil outflow port 7 with the rise of the plunger 15, and the fuel oil outflow port 7 opens to the escape portion 21 of the notch 17, The high-pressure fuel oil passes through the longitudinal groove 23 of the notch 17, passes through the escape portion 21, and returns to the oil reservoir 5 through the fuel oil outlet 7. The moment when the plunger 15 rises and the fuel oil outflow / inlet 7 opens to the escape portion 21 of the peripheral surface portion 19 of the plunger 15 is referred to as the end of pressure feeding. The length of the movement range of the plunger 15 that is actually pumping the fuel oil from the start of the pumping to the end of the pumping is called an effective stroke. The effective stroke of the plunger 15 is proportional to the injection amount.
[0006]
[Problems to be solved by the invention]
By the way, in the conventional fuel injection pump 25 described above, when the plunger 15 descends, the fuel oil in the oil reservoir 5 passes through the fuel oil outflow port 7 and flows into the pump chamber 16. At that time, the pressure dissolved in the fuel oil outflow / inflow port 7 and the inner wall surface of the deflector 6 causes air dissolved in the fuel oil to be liberated to form bubbles (cavities), thereby generating cavitation. Next, when the plunger 15 is raised, the fuel in the pump chamber 16 flows through the fuel oil outflow port 7 and flows into the fuel oil supply pipe to generate a cavity. When the plunger 15 is further raised, the fuel oil outlet port 7 is closed, and the fuel oil passes through the discharge side check valve 11 and is injected from a nozzle (not shown). When the injection is completed, the high-pressure fuel oil in the pump chamber 16 flows through the fuel oil outflow port 7 to the oil reservoir 5. At this time, the cavity is again dissolved in the fuel oil and collapsed, and this impact repeatedly acts on the inner wall, so that there is a problem that erosion (erosion) occurs in which the inner wall is gradually destroyed.
The above-described fuel supply port and the fuel return port to the fuel injection pump 25 are usually provided on both sides of the fuel injection pump 25 so as to face each other. May need to be arranged so as not to interfere with each other, and in some cases, it may be necessary to adopt a structure for improving the attachment of the inlet piping in terms of fuel supply. 6 to 8 schematically illustrate these cases. The example of FIG. 6 is a case where the fuel supply port 26 and the fuel return port 27 have to be arranged in a right angle direction, and the example of FIG. 7 is a case where the block type fuel supply inlet / outlet pipe 28 has to be arranged. FIG. 8 shows a case where the fuel supply pipe 29 must be disposed below the fuel injection pump 25. In such a case, cavitation and erosion may occur particularly in the oil reservoir.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel injection pump capable of suppressing cavitation and erosion generated in an oil reservoir, thereby improving durability and reliability of the fuel injection pump. And
[0007]
[Means for Solving the Problems]
The configuration of the present invention for achieving the above object will be described with reference to the drawings corresponding to the embodiment. The fuel injection pump 53 according to the first embodiment includes a barrel 3 fixed inside a housing 1 and a barrel 3. A plunger 15 slidably housed inside the barrel 3 and an inner wall of the barrel 3 to form a pump chamber 16; an oil reservoir 5 formed between the housing 1 and the barrel 3; A fuel oil outflow port 7 formed in the housing 1 to communicate the pump chamber 16 and the oil reservoir 5; a screw hole 41 formed in the housing 1 to communicate the oil reservoir 5 and the outside of the housing 1; In a fuel injection pump 53 having a deflector 31 screwed into the hole 41 in a liquid-tight manner,
The deflector 31 is provided at a position that does not interfere with the fuel supply port to the fuel injection pump 53 and the fuel return ports 26, 27, 28, 29.
The deflector 31 includes a hollow bolt 33 having a head 37 and a sleeve 35. The hollow bolt 33 has a concave portion 43 formed in the axial direction, and the concave portion 43 has a tip opening in the oil reservoir 5 and the oil reservoir. Forming a part of the inner wall of the chamber 5 to increase the volume of the oil reservoir 5 by the amount of the recess 43;
In the sleeve 35, the hollow bolt 33 is inserted on the inner diameter side, and a circumferential groove 45 is formed in the inner diameter side in a circumferential direction, and the sleeve 35 is provided between one end surface of the sleeve 35 and the housing 1 and the other end surface. A liquid-tight seal is formed between the head 37 and a sealed gap 47 is formed between the inner periphery of the sleeve 35 and the outer periphery of the hollow bolt 33,
By forming a communication hole 51 for communicating the sealing gap 47 and the recess 43 in the hollow bolt 33, the volume of the oil reservoir chamber 5 is further increased by the volume of the sealing gap 47 in addition to the recess 43. By
When the plunger descends, when the fuel flows from the oil reservoir 5 into the pump chamber 16, a decrease in the pressure of the oil reservoir 5 is reduced to suppress the occurrence of cavitation in the oil reservoir 5, When rising, when high-pressure fuel flows into the oil reservoir 5, the pressure in the oil reservoir 5 is suppressed from rising to suppress the occurrence of erosion in the oil reservoir 5 .
[0008]
In this fuel injection pump, the volume of the oil reservoir can be easily increased only by changing the shape of the deflector without changing the shape of the housing or the barrel. When the volume of the oil reservoir increases, the pressure in the oil reservoir at the time of inflow of high-pressure fuel is reduced, so that the occurrence of cavitation is suppressed, and the erosion generated due to cavitation is suppressed. The durability of the room will be increased. In addition, the volume of the oil reservoir can be increased by easy replacement of components by replacing the deflector.
[0010]
In this fuel injection pump, a sealed gap is formed between the outer circumference of the deflector and the inner circumference of the sleeve, and the sealed gap and the recess are communicated by the communication hole, so that the volume of the sealed gap is further increased in addition to the recess. Is added to the increase in the volume of the oil reservoir, so that the pressure in the oil reservoir can be further reduced as compared with the case where only the concave portion is formed, and the occurrence of cavitation and erosion is more effective. Will be suppressed.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a fuel injection pump according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a sectional view showing the structure of the fuel injection pump according to the present invention. Note that the same members as those shown in FIG. 5 are denoted by the same reference numerals, and redundant description will be omitted.
[0012]
A bolt-shaped deflector 31 is screwed into the housing 1, and the tip of the deflector 31 forms a part of the inner wall of the oil reservoir 5. The deflector 31 includes a hollow bolt 33 and a cylindrical sleeve (eye) 35.
[0013]
For example, a hexagonal head 37 is formed at one end of the hollow bolt 33, and a male screw 39 is formed at an outer periphery on a distal end side connected to the head 37. The male screw 39 is formed of the same male screw formed on a conventional deflector. That is, the hollow bolt 33 of the deflector 31 is screwed into a screw hole 41 formed in the housing 1 in the same manner as the conventional deflector 31.
[0014]
A concave portion 43 is formed in the deflector 31 in the axial direction, and the distal end of the concave portion 43 opens in the oil reservoir 5. That is, the volume of the oil reservoir 5 is increased by the amount of the concave portion 43.
[0015]
The eye 35 is formed in an annular shape, and the hollow bolt 33 is inserted into the inner diameter side. A circumferential groove 45 is formed on the inner diameter side of the eye 35 in the circumferential direction. The eye 35 is inserted into the hollow bolt 33, and when the hollow bolt 33 is screwed into the screw hole 41, one end contacts the outer surface of the housing 1 and the other end contacts the head 37 of the hollow bolt 33. An O-ring 49 is interposed between one end of the eye 35 and the housing 1 and between the other end of the eye 35 and the head 37. The O-ring 49 seals both ends of the eye 35 in a liquid-tight manner. I have. That is, by inserting the eye 35 into the hollow bolt 33, a sealed gap 47 is formed between the inner periphery of the eye 35 and the outer periphery of the hollow bolt 33.
[0016]
Further, a radial communication hole 51 is formed in the hollow bolt 33, and one end of the communication hole 51 is opened in the concave portion 43 and the other end is opened in the closed gap 47. That is, the oil reservoir chamber 5 communicates with the recess 43 and the closed gap 47, and the volume is increased accordingly.
[0017]
Next, the operation of the fuel injection pump 53 configured as described above will be described.
When the plunger 15 descends, the fuel in the oil reservoir 5 passes through the fuel oil outflow port 7 and flows into the pump chamber 16. At this time, the pressure dissolved in the fuel oil outflow port 7 and the inner wall surface of the deflector 31 causes the air dissolved in the fuel oil to be liberated to cause cavitation. Is large, the pressure drop is small and the occurrence of cavitation is suppressed.
[0018]
Next, when the plunger 15 is raised, the fuel oil in the pump chamber 16 passes through the fuel oil outlet 7 and flows into the fuel oil supply pipe. When the plunger 15 is further raised, the fuel oil outlet port 7 is closed, and the fuel oil passes through the discharge side check valve 11 and is injected from a nozzle (not shown). When the injection is completed, the high-pressure fuel oil in the pump chamber 16 flows through the fuel oil outflow port 7 to the oil reservoir 5. At this time, the pressure in the oil reservoir 5 increases, but the pressure increase in the oil reservoir 5 is suppressed by the increased volume of the concave portion 43 and the sealed gap 47. This suppresses repeated impact due to the collapse of the cavity, that is, erosion.
[0019]
As described above, according to the fuel injection pump 53 described above, the volume of the oil reservoir 5 can be easily increased only by changing the shape of the deflector 31 without changing the shape of the housing 1 and the barrel 3. Cavitation can be suppressed by lowering the pressure. As a result, erosion can be suppressed and the durability and reliability of the fuel injection pump 53 can be improved. Further, the volume of the oil reservoir 5 can be increased by simply replacing the deflector 31 whose shape has been changed with an existing deflector.
[0020]
Further, since the volume of the closed gap 47 can be further increased in addition to the concave portion 43, the volume of the deflector 31 can be increased to be larger than the volume of the deflector 31, and the pressure of the oil reservoir 5 at the time of high-pressure fuel inflow can be reduced. , Erosion can be suppressed more effectively.
[0021]
【Example】
Next, the results of measuring the pressure in the oil reservoir using the internal volume of the oil reservoir as a parameter will be described with reference to FIGS.
FIG. 2 is a graph of a pressure measurement result of the oil reservoir when a conventional solid deflector is used, FIG. 3 is a graph of a pressure measurement result of the oil reservoir when the deflector according to the present invention is used, and FIG. 7 is a graph comparing the relationship between pressure and pressure between an old shape and a shape according to the present invention.
[0022]
2 and 3, the vertical axis represents pressure, and the horizontal axis represents time. In the figure, the R side is a fuel inlet, and the anti-R is a return side.
Figure 2, as is apparent from FIG. 3, in the case of using the conventional deflector, while the pressure P _G is relatively high, in the case of using a deflector according to the present invention, the pressure of the R-side P _G , substantial pressure drops and the pressure P _G of the anti-R side is confirmed. (P ₁ > P ₃ , P ₂ > P ₄ )
In this case, as shown in FIG. 4, the volume of the oil reservoir is larger in the deflector according to the present invention than in the conventional deflector.
[0023]
From the above results, by increasing the volume of the oil reservoir, it is possible to reduce the pressure of the oil reservoir when the high-pressure fuel oil flows, and as a result, it is possible to suppress the occurrence of cavitation and suppress the occurrence of erosion. I understood.
[0024]
【The invention's effect】
As described in detail above, in the fuel injection pump according to the first aspect of the present invention, since the concave portion serving as a part of the oil reservoir is formed on the wall surface of the deflector in contact with the oil reservoir, the shape of the housing and the barrel is reduced. Without changing, the capacity of the oil reservoir can be easily increased only by changing the shape of the deflector. As a result, cavitation can be suppressed by reducing the pressure in the oil reservoir, and erosion can be suppressed, thereby improving the durability and reliability of the fuel injection pump.
In addition, since the capacity of the oil reservoir can be increased only by changing the shape of the deflector, the volume of the oil reservoir is increased by simply replacing the deflector whose shape has been changed with an existing deflector, and easily replacing the deflector. be able to. Further, the degree of freedom of the fuel supply piping layout is improved.
[0025]
In the fuel injection pump according to the second aspect, a cylindrical sleeve is inserted into the outer periphery of the deflector, and a sealed gap is formed between the outer periphery of the deflector and the inner periphery of the sleeve. As a result, the volume of the closed gap can be further increased in addition to the recess. As a result, the pressure in the oil reservoir can be further reduced as compared with the case where only the concave portion is formed, cavitation can be suppressed, and the occurrence of erosion can be more effectively suppressed.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a structure of a fuel injection pump according to the present invention.
FIG. 2 is a graph of a pressure measurement result of an oil reservoir when a conventional deflector is used.
FIG. 3 is a graph of a pressure measurement result of an oil reservoir when the deflector according to the present invention is used.
FIG. 4 is a graph comparing the relationship between volume and pressure between an old shape and a shape according to the present invention.
FIG. 5 is a sectional view showing the structure of a conventional Bosch-type fuel injection pump.
FIG. 6 is a diagram showing an example of a mounting arrangement of a fuel injection pump in which fuel supply ports are arranged at right angles.
FIG. 7 is a view showing an example of a mounting arrangement of a fuel injection pump having a block-shaped fuel supply port.
FIG. 8 is a diagram showing an example of a mounting arrangement of a fuel injection pump in which fuel supply ports are arranged at right angles.
[Explanation of symbols]
Reference Signs List 1 housing 3 barrel 5 oil reservoir 7 fuel oil outlet 15 plunger 16 pump chamber 31 deflector 35 eye (sleeve)
37 head 41 screw hole 43 recess 47 closed gap 51 communication hole 53 fuel injection pump

Claims (1)

A barrel (3) fixed to the inside of the housing (1), a plunger (15 forming the pump chamber (16) between the inside slidably housed by the inner wall of the barrel (3) of the barrel (3) ) and the housing (1) and the barrel (3) the oil reservoir chamber formed between the (5), said barrel (3) to be drilled being the pump chamber (16) and the oil reservoir chamber ( and 5) the communicated to the fuel oil inlet and outlet opening (7), said drilled in the housing (1) the oil reservoir chamber (5) and the housing (1) a screw hole (41 for communicating the outside),該螺Ko hole ( 41) A fuel injection pump (53) comprising a deflector (31) screwed into a liquid-tight manner to 41) .
The deflector (31) is provided at a position that does not interfere with a fuel supply port to the fuel injection pump (53) and a fuel return port (26, 27, 28, 29).
The deflector (31) comprises a hollow bolt (33) having a head (37) and a sleeve (35), and the hollow bolt (33) has a concave portion (43) formed in the axial direction, and the concave portion (43) The tip opens in the oil sump (5) and forms a part of the inner wall of the oil sump (5) to increase the volume of the oil sump (5) by the amount of the recess (43). Let
The hollow bolt (33) is inserted through the inside of the sleeve (35), and a circumferential groove (45) is formed in the inside of the sleeve in the circumferential direction. (1) and between the other end face and the head (37) are liquid-tightly sealed, and a sealed gap (47) is provided between the inner circumference of the sleeve (35) and the outer circumference of the hollow bolt (33). Is formed,
By forming a communication hole (51) for communicating the sealing gap (47) with the recess (43) in the hollow bolt (33), the volume of the sealing gap (47) can be increased in addition to the recess (43). By further increasing the volume of the oil reservoir (5),
When the plunger is lowered, when the fuel flows from the oil reservoir (5) into the pump chamber (16), a decrease in the pressure of the oil reservoir (5) is reduced to reduce the pressure in the oil reservoir (5). The occurrence of cavitation is suppressed, and when the plunger rises, when the high-pressure fuel flows into the oil reservoir (5), the pressure rise in the oil reservoir (5) is suppressed to prevent erosion in the oil reservoir (5). A fuel injection pump (53) characterized in that generation is suppressed .

Images