JPH07189859A - Fuel injection pump - Google Patents

Abstract

PURPOSE:To provide a fuel injection pump while decreases the production of the swirl of fuel flow jetting into a feed hole and thereby reduces the erosion in a feed hole. CONSTITUTION:In a feed hole 100, a specific diameter portion 101 of specific inner diameter is formed on the side of inner wall 12a of a cylinder 12, and following on this, a rounded portion 102 of inner diameter increasing radially toward outside of the cylinder 12 is formed. Axis of the rounded portion 102 is eccentric up and in parallel to axis of the specific diameter portion 101, and also in left direction, as viewed inward in radial direction of the cylinder 12 from outer wall of the cylinder 12. That is, in the rounded portion 102, the eccentric direction is deeper on the upper side than on the lower, and deeper on the left side than on the right. Accordingly, after finish of fuel pressure sending, eddy current is suppressed in fuel flow jetting into the feed hole 100, so that erosion in the feed hole is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection pump for a diesel engine, and more particularly to the shape of a feed hole formed in a cylinder.

[0002]

2. Description of the Related Art Conventionally, as a fuel injection pump for supplying high-pressure fuel to a fuel injection valve, one disclosed in Japanese Patent Publication No. 59-7026 is known. At the end of the fuel pressure feeding, the pressurized high pressure fuel is recirculated to the low pressure fuel chamber through a feed hole having a constant inner diameter penetrating the side wall of the cylinder.

[0003]

In recent years, air pollution due to exhaust gas emitted from diesel engines has become a problem, and exhaust gas regulations are being strengthened. As a means for coping with this exhaust gas regulation, it has been considered to increase the pressure of the fuel pumped from the fuel injection pump to improve the combustion efficiency. In the fuel injection pump disclosed in Japanese Examined Patent Publication No. 59-7026, a swirl is generated by the high-pressure fuel flow discharged from the pressurizing chamber to the feed hole at the end of fuel pressure feeding, and the inner wall of the feed hole is eroded. There's a problem.

To solve this problem, a fuel injection pump shown in FIG. 9 has been considered. However, the structure of the fuel injection pump of the comparative example shown in FIG. 9 is not known. Cylinder 5
2 is fixed to the housing 11, and the plunger 13 is accommodated in the inner wall 52a of the cylinder 52 so as to be slidable in the axial direction. The pressurizing chamber 21 is defined by part of the inner wall of the cylinder 52, one end surface of the plunger 13, and part of the delivery valve 30. The feed hole 53 is formed penetrating the side wall of the cylinder 52, and connects the pressurizing chamber 21 and the fuel chamber 11a formed in the housing 11 with each other. The delivery valve 30 is screwed and fixed in the housing 11 on the fuel downstream side of the plunger 13. By screwing the holder 31 to the housing 11,
The valve seat 32 is locked to the shoulder portion 52b of the cylinder 52. The valve 33 is biased toward the fuel upstream side by a compression coil spring 34 whose one end is fixed to the inner wall of the holder 31, and is in contact with the seat portion 32a of the valve seat 32. The high-pressure fuel supplied from the delivery valve 30 is delivered to the fuel injection valve 42 via the injection steel pipe 41.

The shape of the feed hole 53 is shown in FIG.
0 and FIG. 11. Feed hole 5
3 includes a constant diameter portion 54 having a constant inner diameter d ₁ and a chamfered portion 55 that follows the constant diameter portion 54 and whose inner diameter increases toward the radially outer side of the cylinder 52. The chamfer 55 has a maximum inner diameter D
₁ and chamfer angle θ ₁ . Figure 11
As shown in, the center 54a of the constant diameter portion 54 and the chamfered portion 55
Both of them are on the same circle center. That is, the eccentric amount δ _x of the shaft center 55a in the direction parallel to the shaft center 54a in the direction perpendicular to the axis of the cylinder 52, and the shaft center in the direction parallel to the shaft center 54a downstream of the cylinder 52 in the axial fuel direction. 55
The eccentricity δ _{y of a} is 0.

In this comparative example, the constant diameter portion 54 and the chamfered portion 5
By forming the feed hole 53 from 5 and 5, the high-pressure fuel discharged through the feed hole 53 is discharged at the end of the pressure feeding of the fuel. However, as shown in FIG. 12, the high-pressure fuel flow 60 discharged through the feed hole 53 is not parallel to the axial direction of the feed hole 53 and is jetted obliquely upward. A vortex 61 is generated in the fuel flow in the vicinity of the upper side, which causes erosion of the inner wall of the feed hole 53.

The vortex generation process will be described in more detail with reference to FIGS. As shown in FIG. 13, the plunger 13 starts to rise when it reaches the bottom dead center. As the plunger 13 moves up, as shown in FIG.
When the fuel reaches the upper end on the a side and closes the feed hole 53, pressurization of fuel is started. When the feed hole 53 is closed, the fuel in the pressurizing chamber 21 flows back into the feed hole 53, and this fuel flow 200 creates a vacuum portion in the fuel flow near the cylinder inner wall 52a side of the constant diameter portion 54. Bubbles 201 are generated.

The plunger 13 is further raised, and FIG.
As shown in FIG. 5, when the plunger lead 13a reaches the lower end of the constant diameter portion 54 on the cylinder inner wall 52a side, the pressurizing chamber 21 and the feed hole 53 communicate with each other via the plunger lead 13a, and the high-pressure fuel is directed obliquely upward. It spouts toward the inside of the feed hole 53. Then, this fuel flow generates a vortex near the upper portion of the constant diameter portion 54, the energy of this vortex breaks the bubble 201, and erosion 203 occurs in the constant diameter portion 54, as shown in FIG.

In order to reduce the occurrence of this erosion,
It is conceivable to reduce the axial length of the constant diameter portion 54 or increase the chamfering depth of the chamfered portion 55. But,
If the axial length of the constant diameter portion 54 is shortened, the thickness of the side wall of the cylinder 52 becomes thin, which causes a problem in strength. Further, when the chamfering depth is increased, the lower part of the feed hole 53 is also chamfered deeply, so that the cylinder 31 is held by the holder 31 as in the comparative example.
In the fuel injection pump configured to clamp and fix 2 in the cylinder 52, the rigidity of the lower portion of the feed hole 53 decreases from the distortion mode on the inner wall 52a side of the cylinder 52 and the distortion is amplified, so that the plunger 13 is fixed to the inner wall 52a of the cylinder 52. I have something to do. It is not technically easy to solve this problem.

The present invention has been made in order to solve the above problems, and provides a fuel injection pump which reduces the generation of vortex of the fuel flow ejected into the feed hole and reduces the generation of erosion in the feed hole. The purpose is to do.

[0011]

SUMMARY OF THE INVENTION A fuel injection pump according to the present invention for solving the above-mentioned problems includes a cylinder having a slide hole for holding a plunger reciprocally and slidably, and a pump housing for containing the cylinder. A fuel gallery formed by the cylinder and the pump housing, to which fuel is supplied, a delivery valve for delivering a fuel pressurized by the plunger and having a certain pressure or more to a fuel injection valve, and one end surface of the plunger And a pressurizing chamber formed by a part of the sliding hole and a part of the delivery valve,
A feed hole formed in the cylinder and connecting the fuel gallery and the pressurizing chamber, and a feed hole formed in the outer wall of the plunger, when the pressurization of the fuel is completed by the rise of the plunger, the pressurizing chamber and the feed hole. In a fuel injection pump provided with a plunger lead formed so as to communicate with, a constant diameter portion in which the feed hole is formed from the inner wall side of the cylinder with a constant inner diameter, and the constant diameter portion. And a chamfer having an inner diameter increasing toward the radially outer side of the cylinder, wherein the axis of the constant diameter section and the axis of the chamfer are eccentric.

It is preferable that the axis of the chamfer is eccentric to the axial center of the constant diameter portion on the downstream side of the fuel in the axial direction of the cylinder. Further, it is preferable that the axis of the chamfer is eccentric to the axis of the constant diameter portion in a direction perpendicular to the axis of the cylinder. Furthermore, the eccentric amount of the axis of the chamfered portion with respect to the axis of the constant diameter portion in the direction perpendicular to the axis of the cylinder is δ _x , and the cylinder of the axis of the chamfered portion with respect to the axis of the constant diameter portion is the cylinder. Of the eccentricity toward the downstream of the fuel in the axial direction, δ _y , the shortest inner wall length of the constant diameter portion in the axial direction is L ₁ , the axial length of the feed hole is L ₂ , the chamfered angle of the chamfered portion is θ, and When the inner diameter of the constant diameter portion is d and the maximum inner diameter of the chamfered portion is D, the formation range of the feed hole is δ _x = 0.1 to 1.0 mm δ _y = 0.1 to 1.0 mm L ₁ < = L ₂ θ> = 30 ° D> = d × 1.3

[0013]

In the fuel injection pump of the present invention, the feed hole through which the high-pressure fuel is ejected from the pressurizing chamber is composed of the constant diameter portion and the chamfered portion, and the axial center of the constant diameter portion and the chamfered portion are provided. The eccentricity reduces the eddy current generated in the high pressure fuel flow ejected into the feed hole at the end of the fuel pressure feeding process, thereby reducing the erosion of the inner wall of the feed hole due to this vortex flow, and the high pressure fuel Can be supplied.

[0014]

Embodiments of the present invention will be specifically described with reference to the drawings. A fuel injection pump according to a first embodiment of the present invention is shown in FIG. As shown in FIG. 1, the fuel injection pump 1 houses a cylinder 12, a plunger 13, and a delivery valve 30 in a housing 11.

An annular fuel chamber 11a is formed on the inner wall of the housing 11, and low-pressure fuel is supplied to the fuel chamber 11a from a fuel pump (not shown). Cylinder 12
Are fixed to the housing 11. A feed hole 100 that communicates with a fuel chamber 11a and a pressurizing chamber 21, which will be described later, is formed through a sidewall of the cylinder 12.

As shown in FIGS. 2 and 3, in the feed hole 100, a constant diameter portion 101 having a constant inner diameter d ₂ is formed on the inner wall 12a side of the cylinder 12, and the diameter of the cylinder 12 is continued to the constant diameter portion 101. A chamfered portion 102 whose inner diameter increases toward the outside in the direction is formed. The chamfered portion 102 is chamfered to have a chamfer angle θ ₂ and a maximum inner diameter D ₂ , and the maximum inner diameter D ₂ is larger than the inner diameter d _{2 of the} constant diameter portion 101. As shown in FIG. 4, the axial center 102 a of the chamfered portion 102 is δ _x (−), δ relative to the axial center 101 a of the constant diameter portion 101.
Only _y (+) is eccentric in the parallel direction. That is, as shown in FIG. 4, the eccentric directions of δ _x and δ _y are deeper in the chamfer on the upper side than on the lower side of the chamfer 102 and on the left side than the right side, as seen from the direction of arrow A in FIG. It is going to get deeper. In the first embodiment, since the plunger lead 13a is formed upward to the right, when the fuel pumping completion, for ejecting high-pressure fuel when viewed from the direction of the arrow A in FIG. 3 from the lower right of the constant diameter portion 54, [delta] _x And the eccentric direction of δ _y is δ _x (−), δ
becomes the _y (+), when the plunger lead 13a is left up, the eccentric direction of [delta] _x and [delta] _y is δ _x (+), δ _y
It is desirable to be formed so as to be (+).

The plunger 13 is the inner wall 1 of the cylinder 12.
It is supported in a sliding hole formed by 2a so as to be slidable in the axial direction. The plunger lead 13a has a U-shaped cross section and extends downward by a predetermined length from the pressurizing chamber 21 side of the outer wall, and further extends diagonally downward left. The pressurizing chamber 21 is defined by a part of the inner wall 12 a of the cylinder 12, the end surface 13 b of the plunger 13 and a part of the delivery valve 30.

As shown in FIG. 1, the delivery valve 30 has a valve seat 3 in which the male screw portion 31a of the holder 31 is screwed to the female screw portion 11b of the housing 11.
2 is locked to the shoulder 12b of the cylinder 12. The valve 33 is housed in the holder 31 and the valve seat 32,
Compression coil spring 3 with one end fixed to the holder 31
4, the fuel is urged to the upstream side of the fuel, and is in contact with the seat portion 32a of the valve seat 32.

The large-diameter fuel passage 3 is provided on the fuel upstream side of the holder 31.
1b is formed, a small-diameter fuel passage 31c is formed following the large-diameter fuel passage 31b, and penetrates the holder 31 in the axial direction. The high-pressure fuel pressurized to a certain pressure or higher in the pressurizing chamber 21 is supplied from the small-diameter fuel passage 31c to the fuel injection valve 42 via the injection steel pipe 42. A large-diameter fuel passage 33a is formed on the fuel downstream side of the valve 33, and a small-diameter fuel passage 33b is formed on the fuel upstream side, and penetrates the valve 33 in the axial direction. The large-diameter fuel passage 33a includes a stopper 35 and a ball 36.
And a piston 37. The stopper 35 is
A fuel passage 35a is fixed to the inner wall of the end of the large-diameter fuel passage 33a on the downstream side of the fuel, and penetrates the stopper 35 in the axial direction. The ball 36 is a recess 37 of the piston 37.
It is in contact with a. The piston 37 has a large diameter fuel passage 33a.
Is urged toward the fuel downstream side by a compression coil spring 38 having one end fixed at the boundary between the small diameter fuel passage 33b and
The ball 36 is brought into contact with the seat portion 35b of the stopper 35.

Next, the fuel flow to the feed hole 100 in the first embodiment will be described in comparison with the comparative example. When the end surface 13b of the plunger 13 on the pressurizing chamber 21 side reaches above the constant diameter portion 101 and closes the feed hole 100, pressurization of fuel is started. When the feed hole 100 is closed, as shown in FIG.
Since the fuel No. 1 flows back into the feed hole 100, a vacuum portion is created in the fuel in the space 101b shown in FIG.

The plunger 13 is further raised, and the plunger lead 13a is moved to the cylinder inner wall 12a of the constant diameter portion 101.
When reaching the lower end of the side, the pressurizing chamber 21 and the feed hole 10
It communicates with 0 through the plunger lead 13a, and high-pressure fuel is jetted obliquely upward into the feed hole 100. In the first embodiment, since the space 102b in the vicinity of the upper part surrounded by the chamfered portion 102 is wide, the fuel flow velocity sharply decreases, and the fuel flow resistance from the constant diameter portion 101 to the chamfered portion 102 decreases, so that the space 101b is formed. Vortex flow is less likely to occur and bubble collapse is reduced.

The shortest length of the inner wall in the axial direction of the constant diameter portion 101 is L ₁ and the axial length of the feed hole 100 is L _2, and the range of the optimum shape of the feed hole 100 obtained by simulation is shown below. Eccentricity: δ _x = 0.1 to 1.0 mm δ _y = 0.1 to 1.0 mm Shaft length: L ₁ <= L ₂ Chamfer angle: θ ₂ > = 30 ° Chamfer diameter: D ₂ > = d ₂ × 1.3 It can be seen that the erosion amount generated in the feed hole formed so as to satisfy this optimum range is significantly reduced as compared with the comparative example, as shown in FIG.

A second embodiment of the present invention is shown in FIGS. 7 and 8. The feed hole 61 formed in the cylinder 60 includes a constant diameter portion 62 and a chamfered portion 63, and the axial center 63 a of the chamfered portion 63 is δ more than the axial center 62 a of the constant diameter portion 62.
_It is eccentric upward by _y (+), and the eccentric amount of δ _x is 0.
In the second embodiment, since the chamfered portion 63 is eccentric only in the upper direction and is not eccentric in the left-right direction, it is possible to similarly reduce the generation of the vortex flow even if the plunger lead is formed in the left-right direction. Can be shared.

[Brief description of drawings]

FIG. 1 is a sectional view showing a fuel injection pump according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a main part of a cylinder according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of the cylinder according to the first embodiment of the present invention.

FIG. 4 is a schematic explanatory view of a feedhole according to the first embodiment of the present invention.

FIG. 5 is an explanatory view of a fuel flow ejected into a feed hole according to the first embodiment of the present invention.

FIG. 6 is a characteristic diagram showing an erosion amount generated in a comparative example and the first embodiment of the present invention.

FIG. 7 is a vertical sectional view of a main part of a cylinder according to a second embodiment of the present invention.

FIG. 8 is a schematic explanatory view of a feedhole according to a second embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a fuel injection pump of a comparative example.

FIG. 10 is a vertical sectional view of a main part of a cylinder of a comparative example.

FIG. 11 is a schematic explanatory view of a feed hole of a comparative example.

FIG. 12 is an explanatory diagram of a fuel flow ejected to a feed hole of a comparative example.

FIG. 13 is a cross-sectional view of a main part showing a fuel pressure feeding process of a comparative example.

FIG. 14 is a cross-sectional view of a main part showing a fuel pressure feeding step of a comparative example.

FIG. 15 is a cross-sectional view of a main part showing a fuel pressure feeding process of a comparative example.

FIG. 16 is a sectional view of a main portion showing erosion generated in a feed hole of a comparative example.

[Explanation of symbols]

 1 Fuel Injection Pump 11 Pump Housing 11a Fuel Chamber (Fuel Gallery) 12 Cylinder 13 Plunger 13a Plunger Lead 21 Pressurizing Chamber 30 Delivery Valve 100 Feed Hole 101 Fixed Diameter Section 102 Chamfer

Claims (4)

[Claims] 1. A fuel which is formed by the cylinder and the pump housing, the cylinder having a slide hole for holding the plunger reciprocatingly and slidably, the pump housing housing the cylinder, and the fuel to which the fuel is supplied. A gallery, a delivery valve for delivering fuel pressurized by the plunger and having a pressure equal to or higher than a certain pressure to a fuel injection valve, an end face of the plunger, a part of the sliding hole, and a part of the delivery valve. A pressurizing chamber, a feed hole formed in the cylinder for communicating the fuel gallery with the pressurizing chamber, and an outer wall of the plunger formed at the end of pressurization of the fuel due to the lifting of the plunger. In a fuel injection pump including a pressure chamber and a plunger lead formed so as to communicate with the feed hole, The hole comprises a constant diameter portion formed from the inner wall side of the cylinder with a constant inner diameter, and a chamfered portion formed following the constant diameter portion, the inner diameter increasing toward the radially outer side of the cylinder, A fuel injection pump, wherein an axis of the constant diameter portion and an axis of the chamfer are eccentric. 2. The fuel injection pump according to claim 1, wherein an axial center of the chamfered portion is eccentric to an axial fuel downstream side of the cylinder with respect to an axial center of the constant diameter portion. 3. The fuel injection pump according to claim 2, wherein an axis of the chamfered portion is eccentric to an axis of the constant diameter portion in a direction perpendicular to an axis of the cylinder. 4. An eccentric amount of the axial center of the chamfered portion with respect to the axial center of the constant diameter portion in the direction perpendicular to the axis of the cylinder, δ _x , of the axial center of the chamfered portion with respect to the axial center of the constant diameter portion. The amount of eccentricity of the cylinder toward the downstream of the axial fuel is δ _y , the shortest axial inner wall length of the constant diameter portion is L ₁ , the axial length of the feed hole is L ₂ , and the chamfer angle of the chamfer is θ. ,
When the inner diameter of the constant diameter portion is d and the maximum inner diameter of the chamfered portion is D, the formation range of the feed hole is δ _x = 0.1 to 1.0 mm δ _y = 0.1 to 1.0 mm L ₁ The fuel injection pump according to claim 3, wherein <= L ₂ θ> = 30 ° D> = d × 1.3.