JP2515637Y2 - Fuel injection pump - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a fuel injection pump with a variable prestroke mechanism used in an internal combustion engine such as a diesel engine, and particularly to a fuel storage chamber for high-speed and high-pressure fuel. The present invention relates to a fuel injection pump capable of preventing cavitation erosion due to spilling on the fuel.

[Prior Art] Conventionally, some fuel injection pumps are provided with a prestroke varying mechanism for varying the prestroke, and generally, a timing sleeve externally fitted to a plunger that reciprocates vertically. The prestroke is made variable by adjusting the relative positional relationship between the plunger and the plunger. For example, there is Jikkou Sho 62-8381.

Regarding the cavitation erosion generated in the pump housing in the fuel injection pump 1 provided with such a prestroke variable mechanism, for example, JP-A-55-93959, JP-A-57-59054 and JP-A-58-109554 are known.
There are issues, etc.

In addition, it is considered that the plunger barrel has a recess to prevent cavitation erosion.
There is a fuel injection pump according to No. 61-167469, but in this fuel injection pump, it is premised that high pressure fuel that spills collides only with the plunger barrel and buffers the high pressure in the recessed portion. Although it is possible to protect the same, it is difficult for the plunger barrel to protect it.

Cavitation erosion generated in the plunger barrel and the pump housing located outside the timing sleeve will be described below with reference to FIGS. 4 to 6.

FIG. 4 is a vertical cross-sectional view of the main part of the fuel injection pump 1, in which the pump housing 2 is formed with vertical holes 3 of a number corresponding to the number of cylinders of the engine, and the plunger barrel 4 is installed vertically by mounting bolts 5. Insert and fix in the hole 3. A plunger 6 is rotatably and reciprocally inserted into the plunger barrel 4.

As shown in FIGS. 5 and 6, the plunger barrel 4 is provided with an opening window portion 7 in the left-right direction which is orthogonal to the lengthwise direction of the plunger barrel 4 to form a fuel storage chamber 8 therein. The timing sleeve 9 is housed in the fuel storage chamber 8 so as to be vertically movable. The timing sleeve 9 is fitted on the plunger 6 so as to be located between the plunger 6 and the plunger barrel 4. It is assumed that the fuel tank 10 is constantly supplied with fuel from a fuel tank 10 by a fuel supply pump 11.

A delivery valve 12 is provided inside the plunger barrel 4 above the plunger 6, and a fuel pressure chamber (plunger chamber) 13 is formed between the delivery valve 12 and the plunger 6. Further, a fuel outlet 15 is formed in the delivery valve holder 14 above the delivery valve 12, and a fuel injection nozzle 17 is connected via a fuel injection pipe 16.

The lower end of the plunger 6 reciprocates in the vertical direction in the figure by rotationally driving the engine by abutting it on a cam (both not shown) connected to the engine.

Further, a driving surface (not shown) is formed in the lower portion of the plunger 6, and an injection amount adjusting sleeve 18 is engaged with the driving face. The injection amount adjusting sleeve 18 is rotated by an injection amount adjusting control rack 19 connected to an accelerator pedal (not shown) to rotate the plunger 6, and a control lead groove 27 and a cutoff hole 30 to be described later are formed. It is possible to adjust the fuel injection amount by changing the engagement position of and changing the effective stroke of the fuel pressure feeding.

A vertical guide groove 20 is formed on the right side in FIG. 4 and a lateral engagement groove 21 is formed on the left side in FIG. 4 on the timing sleeve 9. A guide pin 22 provided on the plunger barrel 4 is engaged with the guide groove 20, and a control rod 23 is inserted into the engagement groove 21.

The control rod 23 is inserted into a lateral hole 24 formed in the pump housing 2, and rotatably supports the control rod 23 on the pump housing 2 via a bearing (not shown). It is connected to an actuator (not shown) and is driven by the actuator based on a detection signal such as the engine speed.

Thus, the pre-stroke is adjusted by moving the timing sleeve 9 up and down by the control rod 23. That is, the prestroke of the plunger 6 is determined by the dimension between the lower end edge of the timing sleeve 9 and the position of the fuel suction / discharge hole 25 (described later) at the bottom dead center of the plunger 6, or the fuel suction / discharge hole 25 from the bottom dead center of the plunger 6. Is defined as the size until the fuel is closed, and when the fuel suction / discharge hole 25 is closed, the fuel injection starts.

Further, in FIG. 4, the plunger 6 slidably inserted into the plunger barrel 4 is reciprocated in the plunger barrel 4 by receiving the rotational driving force of the engine, so that the fuel in the fuel reservoir chamber 8 is transferred to the fuel pressure chamber 13 The fuel in the fuel pressure chamber 13 is further sucked into the fuel pressure chamber 13 from the fuel outlet 15 through the fuel injection pipe 16 and injected from the fuel injection nozzle 17.

That is, the plunger 6 is provided with the fuel intake / exhaust hole in the radial direction, which is a fuel intake port opening to the fuel reservoir chamber 8.
25, a communication hole 26 formed in the central axis direction so as to communicate the fuel suction / discharge hole 25 and the fuel pressure chamber 13, a control lead groove 27 formed on the outer surface of the communication hole 26, and the control lead groove. 27 and a vertical groove 28 for communication that communicates the opening of the fuel intake / discharge hole 25. It is also possible to provide an auxiliary hole 29 in the radial direction of the plunger 6 so as to communicate with the communication hole 26 above the communication vertical groove 28.

Further, a cut-off hole 30 as a spill port is formed through the timing sleeve 9 slidably fitted on the plunger 6 in the radial direction thereof. The cut-off hole 30 is arranged so as to have a vertical positional relationship so that it can communicate with the control lead groove 27 in accordance with the vertical movement of the plunger 6.

In the above-described structure, first, when the plunger 6 is raised from the bottom dead center, the fuel intake / exhaust hole 25 is opened to the fuel reservoir chamber 8, and the fuel reservoir chamber 8 and the fuel pressure chamber 13 are connected to each other. Since it communicates with each other through the communication hole 25 and the communication hole 26, the fuel pressure in the fuel pressure chamber 13 does not rise, and the delivery valve 12
Remains closed.

When the fuel is delivered, the plunger 6 moves up and the fuel intake / exhaust hole 25 is closed by the timing sleeve 9, so that the pressure of the fuel in the fuel pressure chamber 13 rises, the delivery valve 12 is opened, and the fuel exits from the fuel outlet 15. To send
Injection (pressure feeding of fuel) is started.

When the plunger 6 further rises and the control lead groove 27 communicating with the fuel intake / discharge hole 25 communicates with the cutoff hole 30 of the timing sleeve 9, the cutoff hole 30, the control lead groove 27, and the communication vertical groove 28. , Fuel intake / exhaust hole 25 and auxiliary hole 2
The cut-off hole 30 and the fuel pressure chamber 13 communicate with each other through the communication hole 26 and the communication hole 26, whereby the fuel in the fuel pressure chamber 13 flows back to the fuel reservoir chamber 8 and the fuel in the fuel pressure chamber 13 The pressure drops, the delivery valve 12 is closed, and the injection (fuel pumping) ends.

However, when this fuel is ejected so as to flow backward into the fuel storage chamber 8, that is, when it spills, the high-speed, high-pressure fuel flow is suddenly released and collides with the inner wall 4A of the plunger barrel 4, and further to the inner wall 4A. The flow changes along and collides with the inner wall 2A of the pump housing 2 at the collision angle AN (see the arrow in FIG. 6). Therefore, these inner walls 4A and 2A
Cavitation erosion (hereinafter simply referred to as "erosion") E (indicated by a set of points in FIG. 6) in which a surface portion is worn or damaged due to generation of bubbles due to negative pressure and subsequent collapse of bubbles due to fuel pressure wave There is a problem of doing.

As shown in FIG. 6, the reaching distance D1 from the cutoff hole 30 to the inner wall 4A of the plunger barrel 4 and the portion where the fuel ejected from the cutoff hole 30 collides with the inner wall 4A from the inner wall 2A of the pump housing 2. Reach D2
Are both linear distances and short ones.

Moreover, there is a throttle portion 31 between the inner wall 4A of the plunger barrel 4 and the outer circumference of the timing sleeve 9. As a result of the fuel pressure increasing at the throttle portion 31, the fuel is further increased in speed and pressure and the inner wall 4A, 2A part is collided and the influence of this collision is increased.
Promote the occurrence of.

There is a problem that the durability of the pump housing 2 and the plunger barrel 4 deteriorates due to the occurrence of such erosion E.

[Problems to be Solved by the Invention] The present invention has been made in view of the above problems. In a fuel injection pump having a variable prestroke mechanism, erosion that occurs on the inner wall of the plunger barrel and the pump housing is prevented. An object of the present invention is to provide a fuel injection pump capable of improving the durability of the plunger barrel and the pump housing.

[Means for Solving the Problems] That is, according to the present invention, a plunger barrel having a fuel pressure chamber, and reciprocating motion in the plunger barrel to suck the fuel from the fuel reservoir chamber and pump the fuel from the fuel pressure chamber. A fuel injection pump having a plunger and a timing sleeve having a spill port formed between the plunger and the plunger barrel so as to be slidably fitted on the plunger, the fuel injection pump comprising: The fuel injection pump is characterized in that the generation of erosion is suppressed by forming a buffer recess on the inner wall surface of the plunger barrel facing the spill port.

In addition to the formation of the buffer recess, the outer peripheral shape of the timing sleeve is formed into an arbitrary shape according to the curvature of the buffer recess, for example, a curved shape to appropriately control the direction of the flow of fuel to be ejected. It is a fuel injection pump that can extend the distance until it collides with the pump housing without squeezing, and diffuse the jet flow to reduce the influence of the fuel flow after the collision of the plunger barrel on the inner wall of the pump housing.

[Operation] In the fuel injection pump according to the present invention, since the buffer concave portion is formed in the inner wall portion of the plunger barrel facing the spill port of the timing sleeve, the fuel ejected when the fuel is completely pumped out of the plunger barrel. It is possible to increase the distance to reach the inner wall, and also to increase the distance that fuel reaches the inner wall of the pump housing after the collision with the inner wall, so that the erosion is suppressed by reducing the fuel pressure. It is possible to increase the durability of the plunger barrel and the pump housing.

[Embodiment] Next, a fuel injection pump 40 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. However, the fourth
The same parts as those in FIGS. 6 to 6 are designated by the same reference numerals, and the detailed description thereof will be omitted.

FIG. 1 is a vertical cross-sectional view of a main part of a fuel injection pump 40 similar to FIG. 4, and shows the conventional fuel injection pump 1 shown in FIG.
3 is that a buffer recess 41 is formed in a portion of the inner wall 4A of the plunger barrel 4 facing the cutoff hole 30 of the timing sleeve 9, as shown in FIG. The other configurations are substantially the same as those of the fuel injection pump 1, and thus the description thereof is omitted.

The curvature of the buffer recess 41 can be designed arbitrarily according to the pressure of the fuel from the cutoff hole 30 and the like.

Further, by forming the outer peripheral portion 9A of the timing sleeve 9 into a curved surface shape having a certain curvature in accordance with the curvature of the buffer recess 41, the spill fuel colliding with the buffer recess 41 has a long reach T2, and Inner wall of pump housing 2
The collision angle an for 2A can be made smaller than the collision angle AN.

Therefore, as shown in FIG. 3, since the reaching distance T1 from the cutoff hole 30 to the inner wall 4A is larger than the reaching distance D1, it is possible to reduce the influence of the collision to the inner wall 4A. The reaching distance T2 from to the inner wall 2A of the pump housing 2 is larger than the reaching distance D2. In other words, due to the curvature of the buffering recess 41 of the inner wall 4A and the outer peripheral shape of the timing sleeve 9, the ejected fuel is bent in the ejecting direction and extends the distance until it collides with the inner wall 2A of the pump housing 2 without being throttled. Therefore, the jet flow is diffused and the collision force is reduced, so that the occurrence of erosion E can be prevented and the durability of the pump housing 2 and the plunger barrel 4 can be improved.

[Advantages of the Invention] As described above, according to the present invention, the shape and timing of the inner wall of the plunger barrel can be reduced so that the pressure of the ejected fuel can be reduced in the spill process following the fuel injection accompanying the rise of the plunger. Since the shape of the outer peripheral portion of the sleeve is designed, it is possible to prevent erosion from occurring and increase the durability of the plunger barrel and the pump housing.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of a fuel injection pump 40 according to an embodiment of the present invention, FIG. 2 is a front view of the plunger barrel 4 seen from the direction II in FIG. 1, and FIG. III-III line sectional view, FIG. 4 is a longitudinal sectional view of a main part of the conventional fuel injection pump 1, FIG. 5 is a front view of the plunger barrel 4 seen from the V direction in FIG. 4, and FIG. FIG. 6 is a sectional view taken along the line VI-VI in the figure. 1 ... Fuel injection pump 2 ... Pump housing 2A ... Inner wall of pump housing 2 ... Vertical hole 4 ... Plunger barrel 4A ... Inner wall of plunger barrel 5 ... Mounting bolt 6 ... Plunger 7 ... Opening Window 8 …… Fuel reservoir 9 …… Timing sleeve 9A …… Outer peripheral portion of timing sleeve 9 …… Fuel tank 11 …… Fuel supply pump 12 …… Delivery valve 13 …… Fuel pressure chamber (plunger chamber) 14… … Delivery valve holder 15 …… Fuel outlet 16 …… Fuel injection pipe 17 …… Fuel injection nozzle 18 …… Injection amount adjusting sleeve 19 …… Injection amount adjusting control rack 20 …… Vertical guide groove 21 …… Horizontal Engaging groove 22 …… Guide pin 23 …… Control rod 24 …… Horizontal hole 25 …… Fuel intake / exhaust hole (fuel intake port) 26 …… Communication hole 27 …… Control lead groove 28 …… Vertical groove for communication 29 ... supplement Hole 30 ...... Cut-off hole (spill port) 31 ...... Throttle portion 40 ...... Fuel injection pump 41 ...... Buffer recess D1, T1 ...... Distance from cut-off hole 30 to inner wall 4A of plunger barrel 4 D2, T2: Reaching distance from the part where the fuel injected from the cutoff hole 30 collides with the inner wall 4A to the inner wall 2A of the pump housing 2 E: Cavitation erosion AN, an ... The injected fuel is the pump housing 2 Angle of collision with inner wall 2A

Claims (1)

(57) [Scope of utility model registration request] 1. A plunger barrel having a fuel pressure chamber, a plunger for reciprocating in the plunger barrel to suck the fuel from the fuel reservoir chamber, and pumping the fuel from the fuel pressure chamber; A fuel injection pump having a timing sleeve having a spill port formed in the fuel storage chamber between the plunger and the plunger barrel so as to be externally fitted to the fuel storage chamber, On the inner wall surface of the plunger barrel facing the spill port of the timing sleeve, a circular arc-shaped buffering recess communicating with the fuel reservoir is formed, and ejected from the spill port to collide with the buffering recess for reflection. So that the direction of the flow of the fuel to the fuel reservoir can be controlled, and the plunger barrel and the A fuel injection pump, characterized in that a shape of an outer peripheral portion of the timing sleeve is formed into a curved surface shape in accordance with the buffer recess so that a space between the timing sleeve and the timing sleeve is widened.