JP3754828B2 - Fuel injection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device (fuel injection pump) for a diesel engine.
[0002]
[Prior art]
In a fuel injection device of a diesel engine, fuel sucked into a pressurizing chamber is pressurized by a plunger to be pumped to the fuel injection nozzle side, and at the end of the plunger pumping stroke, a lead on the outer periphery of the plunger is connected to an oil reservoir chamber. By communicating with the spill port, the fuel in the pressurized chamber is released, thereby terminating the fuel injection.
[0003]
In such a fuel injection device, a sleeve in which a spill port is formed is fitted to the plunger, and a fuel gallery is formed on both sides of the oil reservoir around the sleeve along the arrangement direction of the plunger. A gallery has a timing rod capable of displacing the sleeve, and the sleeve is displaced in the axial direction of the plunger to change the fuel pumping start timing and the pumping end timing of the plunger, thereby making the oil feeding rate variable. (JP-A-5-87012, Japanese Utility Model Laid-Open Nos. 6-49768, 43260, etc.).
[0004]
[Problems to be solved by the invention]
However, in such a fuel injection device, cavitation erosion may occur in the plunger or the like near the spill port of the sleeve.
[0005]
That is, at the end of the pumping stroke of the plunger, the lead on the outer periphery of the plunger communicates with the spill port of the sleeve, and high pressure fuel is ejected from the spill port, but cavitation is generated in the oil reservoir chamber by the ejection of the high pressure fuel. become. And
The generated cavitation is collapsed by the high-pressure fuel from the spill port, and erosion is generated in the plunger or the like by the shock wave when the collapse occurs.
[0006]
In recent years, in order to improve fuel consumption, exhaust performance, and output performance, fuel injection devices that vary the fuel feed rate and inject fuel that meets engine operating conditions have been designed to perform high-pressure fuel injection. Therefore, such cavitation erosion is a problem.
[0007]
Such cavitation erosion is due to the stagnation of fuel in the oil reservoir near the spill port of the sleeve.
[0008]
Japanese Utility Model Laid-Open Nos. 6-49768 and 43260 disclose a device that prevents cavitation erosion of the housing portion at the bottom of the oil sump chamber, but in addition to a plurality of fuel galleries, a fuel oil supply passage may be provided. If a plurality of feed pumps are provided, a significant increase in cost cannot be avoided. In this case, erosion of the plunger or the like is difficult to prevent. In addition, there are some which attenuate the energy of jetting fuel from the spill port so that cavitation erosion is less likely to occur (JP-A-7-54735, 293395, 5-87012, JP-A-6-2555, etc.) ) These are complicated in structure and lack reliability. Further, only tilting the spill port (Japanese Utility Model Laid-Open No. 6-2555 etc.) has only a partial effect.
[0009]
An object of the present invention is to provide a fuel injection device that can suppress cavitation erosion without increasing the cost and without complicating the structure.
[0010]
[Means for Solving the Problems]
According to a first aspect of the present invention, there are provided a plunger arranged in the same number as the number of cylinders of an engine, a sleeve formed with a spill port that is fitted to the plunger and opens a fuel passage leading to a pressurizing chamber, and is formed around the sleeve An oil reservoir chamber, a fuel gallery formed on both sides of the oil reservoir chamber along the arrangement direction of the plungers to guide the fuel, a timing rod provided in the fuel gallery on one side thereof, the sleeve being displaceable, and driving the timing rod A pre-stroke actuator;
The fuel gallery further includes a fuel inlet of a fuel gallery opened in the housing of the pre-stroke actuator, wherein the fuel feed rate is variable according to the displacement of the sleeve, and the fuel gallery in which the timing rod is disposed. A passage area reducing means for reducing the passage area of the fuel inlet is provided.
[0011]
In a second aspect based on the first aspect, the channel area reducing means is provided in a fuel gallery provided with a timing rod.
[0012]
In a third aspect based on the second aspect, the channel area reducing means is provided in parallel with a bearing that supports the timing rod at the inlet of the fuel gallery.
[0013]
In a fourth aspect based on the third aspect, the flow path area reducing means includes a thin ring plate between a bearing and a screw nut for fixing the bearing.
[0014]
In a fifth aspect based on the third aspect, the channel area reducing means includes a washer between the bearing and a gallery wall portion into which the bearing is fitted.
[0015]
In a sixth aspect based on the third aspect, the channel area reducing means is a screw nut for fixing a bearing.
[0016]
【The invention's effect】
According to the first and second aspects of the invention, the fuel is almost sent to one fuel gallery, and the flow rate of the fuel sent to the other fuel gallery is reduced, so that the fuel flows from one fuel gallery side to the oil around the sleeve. It can flow to the other fuel gallery side through the reservoir, and this can sufficiently suppress the occurrence of cavitation erosion such as plunger caused by high pressure fuel jetting from the spill port of the sleeve. The reliability of the fuel injection device that makes the oil feed rate variable is improved.
[0017]
According to the third to sixth inventions, the flow area of the fuel gallery can be narrowed with a simple structure, and the occurrence of cavitation erosion can be sufficiently suppressed without increasing the cost.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 shows a row type fuel injection device (fuel injection pump) of a diesel engine,
Reference numeral 10 denotes a camshaft driven in synchronism with engine rotation, and 11 denotes a plunger which is arranged in the same number as the number of cylinders of the engine and reciprocates in the plunger barrel 12 by the camshaft 10.
[0020]
A sleeve 14 in which a spill port 13 is formed as shown in FIG. 2 is fitted to the plunger 11 below the plunger barrel 12. On the outer periphery of the plunger 11, as shown in FIG. 2, a lead (fuel passage) 16 and a vertical groove 17 connected to the pressurizing chamber 15 through the inside of the plunger 11 are formed.
[0021]
An oil reservoir chamber 18 is formed around the sleeve 14, and first and second fuel galleries 19 and 20 for guiding fuel are disposed along the arrangement direction of the plunger 11 on both sides of the oil reservoir chamber 18 as shown in FIG. 3. It is formed.
[0022]
A guide portion 21 for restricting the rotation of the sleeve 14 is formed on the first fuel gallery 19 side of the sleeve 14, and an engaging portion 23 for a pin 22 described later is formed on the second fuel gallery 20 side. The second fuel gallery 20 is provided with a timing rod 24 that can displace the sleeve 14 in the axial direction of the plunger 11 via a pin 22. The timing rod 24 is rotatably supported by a bearing 25 fitted to the end of the second fuel gallery 20, and a prestroke actuator (not shown) for driving the timing rod 24 is provided at the end of the pump housing 26. Mounted.
[0023]
A fuel inlet 28 is formed in the housing 27 of the prestroke actuator,
Fuel inlets 29 and 30 of the first and second fuel gallery 19 and 20 are opened in the housing 27.
[0024]
A flow path area reducing means for reducing the flow path area of the second fuel gallery 20 is provided.
[0025]
In this case, as a flow path area reducing means, a bearing 25 that supports the timing rod 24 at the end (fuel inlet 30) of the second fuel gallery 20 as shown in FIG.
A shim-shaped thin ring plate 32 is interposed between the screw nut 31 that fixes the bearing 25.
[0026]
The ring plate 32 is sandwiched between the screw nut 31 and the outer race 33 of the bearing 25 and has an inner diameter slightly larger than the inner race 34 of the bearing 25.
[0027]
The fuel gallery overflow passage is provided downstream of the second fuel gallery.
[0028]
5, after the intake of the fuel is completed as shown in FIG. 5, the plunger 11 is lifted as the camshaft 10 is lifted as shown in FIGS. 6 and 7. When the groove 17 is closed, the communication with the oil reservoir chamber 18 is blocked, the pressure in the pressurizing chamber 15 is increased, and the fuel is pumped.
[0029]
Further, when the plunger 11 rises as shown in FIG. 8 and the lead 16 communicates with the spill port 13 of the sleeve 14, the pressurized fuel in the pressurized chamber 15 is ejected from the spill port 13 to the oil reservoir chamber 18 and released. Fuel pumping is terminated.
[0030]
In this case, when the timing rod 24 is driven by the pre-stroke actuator and the sleeve 14 is displaced in the axial direction of the plunger 11, the fuel pumping start timing and the pumping end timing change, that is, the camshaft according to the displacement of the sleeve 14. The oil feed rate is variable by changing the pressure feed section for 10 lifts.
[0031]
On the other hand, the fuel in the housing 27 of the pre-stroke actuator is sent from the fuel inlet 29 having a predetermined diameter into the first fuel gallery 19 on the first fuel gallery 19 side, but on the second fuel gallery 20 side, From between the screw nut 31 and the timing rod 24, it passes through the gap 35 between the ring plate 32 and the inner race 34 of the bearing 25, passes between the balls of the bearing 25, and is fed into the second fuel gallery 20.
[0032]
That is, since the fuel is almost sent to the first fuel gallery 19 and the flow rate of the fuel sent from the fuel inlet 30 to the second fuel gallery 20 is reduced, the fuel flows around the sleeve 14 from the first fuel gallery 19 side. The oil flows into the second fuel gallery 20 through the oil reservoir chamber 18 and flows into the oil reservoir chamber 18 around the sleeve 14 and the oil reservoir chamber 18 near the spill port 13 of the sleeve 14. Stagnation of fuel is eliminated.
[0033]
Therefore, at the end of the pressure feeding stroke of the plunger 11, the lead 16 on the outer periphery of the plunger 11 communicates with the spill port 13 of the sleeve 14, and high pressure fuel is ejected from the spill port 13. Occurrence of cavitation in the oil reservoir 18 is suppressed, and thereby generation of cavitation erosion of the plunger 11 and the like is suppressed.
[0034]
Thus, the occurrence of cavitation erosion is sufficiently suppressed by a simple structure that restricts the flow passage area of the fuel inlet 30 of the second fuel gallery 20. Therefore, the injection waveform in the injection end region can be improved without increasing the cost, and the reliability of the fuel injection device that makes the oil feed rate variable is improved.
[0035]
For cavitation, the smaller the flow rate of the fuel sent from the fuel inlet 30 to the second fuel gallery 20, the better. However, if the flow path is blocked, the fuel stagnates near the bearing 25 and the cooling performance deteriorates.
[0036]
FIG. 9 shows another embodiment. This is because, as a flow path area reducing means, at the end of the second fuel gallery 20 (fuel inlet 30), between the bearing 25 supporting the timing rod 24 and the gallery wall 40 on which the bearing 25 is fitted. The washer 41 is interposed.
[0037]
The washer 41 is formed in a shape in which the inner diameter side is somewhat curved inward of the fuel gallery 20. Therefore, the fuel passes between the screw nut 31 and the timing rod 24 and between the balls of the bearing 25, and the inner race of the bearing 25. The fuel is fed into the second fuel gallery 20 through a gap 43 between 34 and the curved portion of the washer 41.
[0038]
FIG. 10 shows another embodiment. As a flow path area reducing means, the bottom surface 50 of the screw nut 31 that fixes the bearing 25 of the timing rod 24 is enlarged at the end (fuel inlet 30) of the second fuel gallery 20.
[0039]
Accordingly, the fuel passes through the gap 51 between the bottom surface 50 of the screw nut 31 and the inner race 34 of the bearing 25 from between the screw nut 31 and the timing rod 24, passes between the balls of the bearing 25, and enters the second fuel gallery 20. Sent to.
[0040]
FIG. 11 shows another embodiment. This is to reduce the flow passage area of the first fuel gallery 19, and to the fuel inlet 29 of the first fuel gallery 19, a small hole 60 (diameter φd of the small hole 60 as a flow passage area reducing means). <A plug 61 having a diameter φD of the first fuel gallery 19 is fastened. In this case, the flow passage area of the fuel inlet 30 of the second fuel gallery 20 is made sufficiently larger than the area of the small hole 60 of the plug 61.
[0041]
In this way, the fuel enters almost from the fuel inlet 30 of the second fuel gallery 20 and passes from the second fuel gallery 20 side to the first fuel gallery 19 side through the oil reservoir chamber 18 around the sleeve 14. It begins to flow. Therefore, the cooling performance of the timing rod 24 is improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a fuel injection device.
FIG. 2 is a perspective view of a plunger and a sleeve.
FIG. 3 is a partial cross-sectional view in the plunger arrangement direction.
FIG. 4 is a cross-sectional view of an inlet portion of a fuel gallery.
FIG. 5 is an operation explanatory view of a plunger.
FIG. 6 is an explanatory view of the operation of the plunger.
FIG. 7 is a diagram illustrating the operation of the plunger.
FIG. 8 is a diagram illustrating the operation of the plunger.
FIG. 9 is a cross-sectional view of an inlet portion of a fuel gallery according to another embodiment.
FIG. 10 is a cross-sectional view of an inlet portion of a fuel gallery according to another embodiment.
FIG. 11 is a cross-sectional view of an inlet portion of a fuel gallery according to another embodiment.
[Explanation of symbols]
11 Plunger 13 Spill port 14 Sleeve 15 Pressurizing chamber 16 Lead 17 Vertical groove 18 Oil reservoir chamber 19 First fuel gallery 20 Second fuel gallery 24 Timing rod 25 Bearing 29, 30 Fuel inlet 31 Screw nut 32 Ring plate 35 Gap 41 Washer 43, 51 Gap 60 Small hole 61 Plug

Claims (6)

Plungers arranged in the same number as the number of cylinders of the engine,
A sleeve formed with a spill port that is fitted to the plunger and opens the fuel passage leading to the pressurizing chamber;
An oil reservoir formed around the sleeve;
A fuel gallery formed on both sides of the oil sump chamber along the arrangement direction of the plungers to guide the fuel;
A timing rod provided in the fuel gallery on one side and capable of displacing the sleeve;
A pre-stroke actuator for driving the timing rod;
A fuel inlet of a fuel gallery opened in the housing of the prestroke actuator;
In the fuel injection device in which the oil feed rate is variable according to the displacement of the sleeve,
A fuel injection device, comprising: a passage area reducing means for reducing a passage area of a fuel inlet of the fuel gallery in which the timing rod is disposed .   The fuel injection device according to claim 1, wherein the flow path area reducing means is provided in a fuel gallery provided with a timing rod.   The fuel injection device according to claim 2, wherein the flow path area reducing means is juxtaposed with a bearing that supports a timing rod at an inlet of the fuel gallery.   The fuel injection device according to claim 3, wherein the flow path area reducing means includes a thin ring plate between a bearing and a screw nut for fixing the bearing.   4. The fuel injection device according to claim 3, wherein the flow path area reducing means includes a washer between a bearing and a gallery wall portion on which the bearing is fitted.  The fuel injection device according to claim 3, wherein the flow path area reducing means is a screw nut for fixing a bearing.

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