JP2005325778A - Fuel injection pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a problem that a plunger barrel easily cracks at a boundary part and is easily broken if a packing is arranged between an end part of male screw on a side close to a plunger of a plug and an opening end surface of a fuel pressure chamber. <P>SOLUTION: This fuel injection pump is constructed to close an opening of a cylinder 2a of the plunger barrel 2 by the plug 3 and to grip the packing 40 between the opening part end surface 2m of the plunger barrel 2 and a packing abutment part 3c of the plug 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel injection pump configured to close an upper opening of a plunger barrel with a plug, and more particularly to the structure of the plunger barrel and the plug.

2. Description of the Related Art Conventionally, a fuel injection pump having a configuration in which fuel is pumped by a plunger that slides within a plunger barrel is known (see, for example, Patent Document 1).
In the conventional example shown in FIG. 9, a cylindrical plunger barrel 102 is shrink-fitted to the hydraulic head 100, and one end of the plunger 104 protrudes from an opening on one side of the plunger barrel 102, while the other side The opening is configured to be closed by the plug 101.
The plunger barrel 102 is subjected to a quenching process.
The plug 101 is engraved with a male screw 109, and the plug 101 is screwed into the plunger barrel 102. Further, the packing 106 is arranged in the direction in which the plug 101 is screwed.

JP 2003-106240 A

However, the arrangement of the packing 106 described above has the following problems.
In the plunger barrel 102, when the end of the male screw 110 of the plug 101 with respect to the female screw 120 (threaded end) is defined as a boundary portion 107, the female screw 12 and the male screw are located at the bottom of the female screw 120 of the boundary portion 107. An upward tensile load generated by engaging the screw 11 acts. Further, a downward tensile load generated when the packing 106 presses the opening end surface 105 a of the plunger barrel 105 acts on the valley bottom of the female screw 120 in the boundary portion 107. For this reason, stress concentration occurs at the location of the female screw 120 corresponding to the boundary portion 107.
Due to this stress concentration, the quenched plunger barrel 102 has a problem in that the boundary portion 107 is easily cracked and easily broken.
Therefore, in the present invention, the arrangement of the packing 106 is studied and a technique for solving the above problem is proposed.
In addition, a number of new plunger barrel and plug configurations are proposed in relation to the arrangement of the packing 106.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, as described in claim 1, in the fuel injection pump configured to close the opening of the cylinder of the plunger barrel with a plug, between the opening end face of the plunger barrel and the packing contact portion of the plug, The packing is to be sandwiched.

  In addition, as described in claim 2, in the threaded portion of the plunger barrel with the plug, the inner stealing portion where the female screw is not engraved at the place where the screwed end portion of the male screw engraved in the plug is disposed. It is set as the structure which provides.

  In addition, as described in claim 3, in either one or both of the thread shape of the male thread of the plug and the thread shape of the female thread of the plunger barrel, the tip of the thread is omitted. Let it be a shape.

  Further, as described in claim 4, in either one or both of the thread shape of the male thread of the plug and the thread shape of the female thread of the plunger barrel, the height of the thread becomes closer to the plunger. The shape should be low.

  According to a fifth aspect of the present invention, the plug surrounds an insertion portion inserted into the cylinder of the plunger barrel and an outer peripheral surface of the plunger barrel surrounding the insertion portion, and is engraved on the outer peripheral surface. It is assumed that the male screw part and the female screw part screwed together are provided, and the packing surrounds the outer periphery of the insertion part.

  Further, as described in claim 6, the plug surrounds the outer peripheral surface of the plunger barrel and has a female screw portion screwed with a male screw engraved on the outer peripheral surface. An annular sandwiching surface sandwiched between the opening end surface of the plunger barrel and the plug, and a pressure chamber upper surface protruding into the cylinder of the plunger barrel from the sandwiching surface side; To do.

  As effects of the present invention, the following effects can be obtained.

  That is, in the invention according to the first aspect, the plunger barrel is compared with the conventional configuration in which the packing is disposed between the end of the male screw near the plunger and the opening end surface of the fuel pressure chamber. It can be set as the structure which is hard to generate | occur | produce a crack and destruction.

  In the invention according to claim 2, the threaded end portion of the male screw is not engaged with the female screw, and stress concentration occurs on the female screw side due to a defect in the shape of the threaded end portion of the male screw. Can be prevented, and the female thread can be prevented from being lost.

  In the invention according to claim 3, it is possible to avoid the problem that the tip of the thread is damaged or missing.

  In the invention according to claim 4, the engagement area between the male screw of the plug and the female screw of the plunger barrel becomes smaller as it gets closer to the plunger, and the compressive load acting on the side closer to the plunger is reduced. can do. As a result, the load is equalized in the entire range of the screw-fitting portion, and breakage and omission of each screw can be prevented.

  Further, in the invention described in claim 5, when the plug is fastened, contamination that adheres to the screw portion and fragments generated due to missing part of the screw thread are prevented from entering the cylinder. It is possible to prevent such a problem that the debris enters the fuel and causes an injection failure or the like.

  In the invention according to claim 6, the insertion portion can be omitted, and the shape of the plug can be simplified.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the following description, it is assumed that the upper side in FIG. 1 is the upper side and the lower side is the lower side.

  FIG. 1 is a cross-sectional view showing a state in which a plug is screwed into a plunger barrel, and FIG. 2 is an enlarged cross-sectional view of a plug portion related to the first embodiment.

Further, as shown in FIG. 1, the plunger barrel 2 is shrink-fitted to the hydraulic head 1, and the plunger 20 is slid up and down in the cylinder 2a of the plunger barrel 2 to perform fuel pumping. Yes.
In addition, the plunger barrel 2 is subjected to a quenching process in a stage before being fitted into the hydraulic head 1.
Further, the plug 3 is inserted from the upper opening 2 r of the plunger barrel 2, and the opening of the cylinder 2 a is closed by the plug 3. The plug 3 is engraved with a male screw, and the plug 3 is screwed into the opening of the plunger barrel 2.
Further, the lower portion of the plunger 20 protrudes from the lower opening 2s of the plunger barrel 2, and the plunger 20 is slid up and down by the rotation of a cam (not shown).

Further, as shown in FIG. 2, the plug 3 includes a screw fitting portion 3 a screwed into the plunger barrel 2, a diameter larger than the screw fitting portion 3 a, and an opening end face 2 m of the plunger barrel 2. And a plug head 3b disposed on the upper side.
In the screw fitting portion 3 a, a male screw 11 is engraved on the outer periphery thereof, and is screwed into a female screw 12 engraved on the inner periphery of the plunger barrel 2. In addition, as shown in FIG. 2, for example, the portion below the male screw 11 of the screw fitting portion 3a is configured in two stages, that is, a large diameter portion 33a and a small diameter portion 33b. It is set as the structure inserted in 2a.
In the configuration example shown in FIG. 2, the plug head 3 b is configured to have substantially the same diameter as the outer diameter of the plunger barrel 2 and is arranged outside the plunger barrel 2. The plug head 3b is inserted into the hydraulic head 1, and a gap between the plug head 3b and the insertion hole 1A of the hydraulic head 1 is provided by an O-ring 34 provided in the middle of the top and bottom. It is supposed to be closed.

Further, a packing contact portion 3c is formed between the screw fitting portion 3a and the plug head portion 3b, and a ring-shaped portion is formed between the packing contact portion 3c and the opening end face 2m of the plunger barrel 2. The packing 40 is sandwiched. The packing 40 is accommodated in an annular seat 2b formed by lowering the opening end face 2m of the plunger barrel 2 and is sandwiched between the packing contact portion 3c and the seat 2b.
Further, in the screw fitting portion 3a, the diameter between the packing contact portion 3c and the portion where the male screw 11 is engraved is configured to be smaller than the inner diameter of the packing 40, and the small diameter portion 3d is formed.

As described above, the opening of the cylinder 2a of the plunger barrel 2 is closed by the plug 3, and the packing 40 is sandwiched between the opening end face 2m of the plunger barrel 2 and the packing contact portion 3c of the plug 3. It is supposed to be disguised.
Further, the packing 40 is disposed, for example, on the opening end surface 2m of the plunger barrel 2 of the plunger barrel 2, that is, on the opposite side of the plunger 20 with the male screw 11 of the plug 3 interposed therebetween (on the plunger barrel 2). It is disposed on the opposite side of the plunger 20 across the female screw 12.

In the plunger barrel 2 described above, when the end of the male screw 11 with respect to the female screw 12 (screwed end) is defined as a boundary portion 17, a compressive load is applied to the boundary portion 17. This compressive load is due to the plug 3 pressing the opening end face 2m of the plunger barrel 2.
As a result, a compressive load acts on a section 18 (section in which the male screw 11 and the female screw 12 are engaged) between the boundary portion 17 and the plug head 3b (packing contact portion 3c). A compressive load acts on the valley bottom of the female screw 12 corresponding to the boundary portion 17.
As described above, the plunger barrel 2 is less susceptible to cracking and breakage than the conventional configuration in which packing is arranged in the direction in which the plug is screwed and stress concentration occurs at the boundary portion due to the vertical tensile load. can do.

FIG. 3 is an enlarged cross-sectional view of a plug portion related to the second embodiment.
The thread shape of the threaded end portion (end portion of the spiral) of the male screw 11 is different from the thread shape of other portions, and particularly when the shape of the threaded end of the screw is bad, the threaded end. When the portion is engaged with the female screw 12, stress concentration occurs at the engaging portion, and the thread of the female screw 12 subjected to the quenching process may be lost.
For this reason, in the present Example 2, in the screwing part of the plug 3 in the plunger barrel 2, the female screw 12 is not engraved in the place where the threaded end portion of the male screw 11 engraved in the plug 3 is arranged. The inner stealing unit 2u is provided.
According to the above, the threaded end portion of the male screw 11 is not engaged with the female screw 12, and it is possible to prevent the thread of the female screw 12 from being lost due to the stress concentration.

FIG. 4 is a view showing the distribution of the compressive load acting on the female screw 12, and FIG. 5 is an enlarged cross-sectional view of the male screw 11 portion of the plug in Examples 3 and 4.
In the configuration of FIG. 2, the plug 3 presses the opening end face 2m of the plunger barrel 2, so that the distribution of the load acting on the female screw 12 of the plunger barrel 2 is as shown by the characteristic line L1 in FIG. Will be. That is, the closer to the packing 40 disposed on the opening end face 2m, the larger the tendency. In the configuration of FIG. 3, the load acting on the female screw 12 of the plunger barrel 2 increases as it approaches the screwed end portion of the plug 3, and is opposite to the distribution of the characteristic line L1 (becomes larger as it goes down). In this case, the closer to the packing 40, the larger the load. That is, regardless of the arrangement of the packing 40 in FIGS. 2 and 3, the distribution of the load acting on the female screw 12 becomes larger as the packing 40 is closer to the packing 40.
And since this compressive load is large, there is a problem that the male screw 11 and the female screw 12 are damaged, and in particular, there is a high possibility of breakage / missing of the tip of the screw thread where the thread cross-sectional area becomes small. Become.

Therefore, as shown in FIG. 5, in either one or both of the thread shape of the male thread 11 of the plug 3 and the thread shape of the female thread 12 of the plunger barrel 2, a flat portion is formed at the protruding end of the thread. 13, 13... Is formed, and the shape in which the tip of the screw thread is omitted is to avoid the problem that the tip of the screw thread is broken or missing.
In the example of FIG. 5, in the shape of the thread of the male screw 11 of the plug 3, a portion that is approximately 30% of the height of the entire thread is omitted from the position that should be the top of the thread, and is substantially trapezoidal. It is set as the structure made into this.
The shape of the thread is not particularly limited, but a configuration in which approximately 20% to 50% of the height of the entire thread is omitted from the position to be the top of the thread is suitable. It can be said that there is. In addition, in both the male screw 11 of the plug 3 and the female screw 12 of the plunger barrel 2, the top of the thread may be omitted. Further, the configuration is not limited to the flat portions 13, 13..., And may be a gently curved surface with a small gradient.

FIG. 6 is a diagram showing that the taper angle is given to the height of the thread according to the configuration of the fourth embodiment.
As shown by the characteristic line L1 in FIG. 4, a compressive load acts on the female screw 12 of the plunger barrel 2. And the said compressive load shows the tendency which becomes so large that it is near packing 40, and was not uniform in the whole range of a fitting part. In the configuration shown in FIG. 3 as well, the compressive load tends to increase as the packing 40 is closer.
For this reason, the closer to the packing 40, the more likely to cause problems such as breakage and omission of the female thread 12 thread.

Therefore, as shown in FIG. 6, the height of the thread increases as the packing 40 becomes closer to one or both of the thread shape of the male thread 11 of the plug 3 and the thread shape of the female thread 12 of the plunger barrel 2. The shape is reduced. FIG. 6 shows an example applied to the male screw 11 of the plug 3, whereby a taper angle R is given to the male screw 11 as shown in FIG. 6.
As described above, the engagement area between the male screw 11 of the plug 3 and the female screw 12 of the plunger barrel 2 decreases as the packing 40 becomes closer, and the compressive load acting on the side closer to the packing 40 is reduced. be able to. As a result, as shown by the characteristic line L2 in FIG. 4, the load is equalized in the entire range of the screw fitting portion, and the screws 11 and 12 can be prevented from being damaged or missing.
In addition to the example shown in FIG. 6, both the male screw 11 of the plug 3 and the female screw 12 of the plunger barrel 2 may have a taper angle.

FIG. 7 is a diagram illustrating the configuration of the plug 3 according to the fifth embodiment.
As shown in FIG. 7, the plug 3 surrounds the insertion portion 3m inserted into the cylinder 2a of the plunger barrel 2 and the outer peripheral surface of the plunger barrel 2 surrounding the insertion portion 3m, and is engraved on the outer peripheral surface. The configuration has a female screw portion 3n that is screwed with the male screw 2g, and the packing 40 surrounds the outer periphery of the insertion portion 3m.
The insertion portion 3m is inserted into the cylinder 2a to reduce the volume in the cylinder 2a, whereby the volume of the fuel pressure chamber 2f is set to a desired value.
The female screw portion 3n is engaged with the male screw 2g of the plunger barrel 2 by a female screw 3g engraved on the inner periphery thereof, and the plug 3 is screwed into the plunger barrel 2. Yes.
And according to the above structure, since the engaging part of the internal thread part 3n of the plug 3 and the external thread 2g of the plunger barrel 2 is arranged outside the cylinder 2a of the plunger barrel 2, the plug Even when a part of the screw thread is missing when fastening 3, the broken piece does not enter the cylinder 2 a.
As described above, according to the fifth embodiment, even when a part of the screw thread is missing when the plug 3 is fastened, it is possible to prevent the fragments from entering the cylinder 2a. It is possible to prevent such a problem that the debris enters the fuel and causes an injection failure or the like.

FIG. 8 is a diagram illustrating the configuration of the plug 3 according to the sixth embodiment.
As shown in FIG. 8, the plug 3 surrounds the outer peripheral surface of the plunger barrel 2 and has a female screw portion 3n screwed with a male screw 2g engraved on the outer peripheral surface. An annular sandwiching surface 40a sandwiched between the opening end surface 2m of the plunger barrel 2 and the plug 3, and a pressure chamber upper surface 40b projecting into the cylinder 2a of the plunger barrel 2 from the sandwiching surface 40a side. And it has composition which has.
In the packing 40, the sandwiching surface 40a and the pressure chamber upper surface 40b are configured continuously via the cylindrical surface 40c. For example, press working such as depression of the center of a disk-shaped member is performed. Is formed.
Further, the pressure chamber upper surface 40b is projected into the cylinder 2a to reduce the volume in the cylinder 2a, and as a result, the volume of the fuel pressure chamber 2f is set to a desired value. Yes.
Thus, according to the sixth embodiment, in the fifth embodiment, the configuration can be made such that the insertion portion 3m (see FIG. 7) is omitted, and the shape of the plug 3 can be simplified. .

  The present invention is applicable to any fuel injection pump as a plug for closing the opening of the plunger barrel.

It is sectional drawing which shows the state which screwed the plug in the plunger barrel. 3 is an enlarged cross-sectional view of a plug portion related to Example 1. FIG. 6 is an enlarged cross-sectional view of a plug portion related to Example 2. FIG. It is a figure shown about distribution of the compressive load which acts on a female screw part. It is an expanded sectional view of the external thread part of the plug regarding Example 3 * 4. It is a figure which shows that a taper angle is given to the height of a thread by the structure of Example 4. FIG. FIG. 10 is a diagram illustrating a configuration of a plug related to Example 5. FIG. 10 is a diagram showing a configuration of a plug related to Example 6. It is a figure shown about the structure of the conventional plug.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydraulic head 2 Plunger barrel 2m Opening end face 3 Plug 3c Packing contact part 40 Packing

Claims (6)

  In the fuel injection pump configured to close the opening of the cylinder of the plunger barrel with a plug, the packing is sandwiched between the end surface of the opening of the plunger barrel and the packing contact portion of the plug. And fuel injection pump. In the threaded part with the plug in the plunger barrel,
In the place where the threaded end of the male screw engraved on the plug is placed,
It is configured to provide an internal stealing part that does not engrave the female screw.
A fuel injection pump characterized by that. The thread shape of the male thread of the plug, and
In either one or both of the thread shape of the female thread of the plunger barrel,
A shape with the tip of the screw thread omitted.
The fuel injection pump according to claim 1, wherein the fuel injection pump is provided. The thread shape of the male thread of the plug, and
In either one or both of the thread shape of the female thread of the plunger barrel,
The shape is such that the height of the thread becomes lower as it gets closer to the packing.
The fuel injection pump according to any one of claims 1 to 3, wherein the fuel injection pump is provided. The plug is inserted into a cylinder of the plunger barrel;
Surrounding the outer peripheral surface of the plunger barrel surrounding the insertion portion, and having a female screw portion screwed with a male screw engraved on the outer peripheral surface,
The packing is configured to surround the outer periphery of the insertion portion.
The fuel injection pump according to claim 1, wherein: The plug surrounds the outer peripheral surface of the plunger barrel, and has a female screw portion screwed with a male screw engraved on the outer peripheral surface,
The packing is
An annular sandwiching surface sandwiched between the open end surface of the plunger barrel and the plug;
A pressure chamber upper surface protruding into the cylinder of the plunger barrel from the clamping surface side;
The fuel injection pump according to claim 5, wherein

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