JP4185887B2 - Fuel injection pump - Google Patents

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 it easily cracks at the boundary portion 107 and is 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.

In the fuel injection pump according to claim 1, wherein the opening of the cylinder (2a) of the plunger barrel (2) is closed by the plug (3), the opening end face (2m) of the plunger barrel (2), The packing (40) is sandwiched between the packing contact portion (3c) of the plug (3), and the male screw (11) engraved on the plug (3) is engraved on the plunger barrel (2). The threaded shape of the male screw (11) engraved on the plug (3), and the female screw (12) engraved on the plunger barrel (2). ) In either one or both of the thread shapes, a flat portion (13) is formed at the tip of the thread, and the tip is omitted, and the male screw (11) of the plug (3) Thread shape and female of the plunger barrel (2) On the other hand either di thread profile of the (12), or in both, the height of the nearer threads on the packing (40) is obtained by a shape to decrease.

The fuel injection pump according to claim 1, wherein the plug (3) includes an insertion portion (3m) inserted into a cylinder (2a) of the plunger barrel (2) and the insertion portion (3m). ) Surrounding the outer peripheral surface of the plunger barrel (2), and having a female screw portion (3n) screwed with a male screw (2g) engraved on the outer peripheral surface, 40) is configured to surround the outer periphery of the insertion portion (3m) .

According to a third aspect of the present invention, in the fuel injection pump according to the first aspect, the plug (3) surrounds the outer peripheral surface of the plunger barrel (2) and is screwed with a male screw (2g) engraved on the outer peripheral surface. The packing (40) has an annular clamping surface (nipping) between the opening end surface of the plunger barrel (2) and the plug (3). 40a) and a pressure chamber upper surface (40b) protruding from the clamping surface (40a) side into the cylinder (2a) of the plunger barrel (2) .

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

According to the first aspect of the present invention, in the fuel injection pump configured to close the opening of the cylinder (2a) of the plunger barrel (2) by the plug (3), the opening end face (2m) of the plunger barrel (2). And a packing contact portion (3c) of the plug (3), and a male screw (11) engraved on the plug (3) is sandwiched between the plunger barrel (2 ) And the female thread (12) engraved on the plug (3) and the female thread engraved on the plunger barrel (2). In either one or both of the thread shapes of the screw (12), the flat portion (13) is formed at the tip of the screw thread and the tip is omitted. Between the end of the screw and the open end face of the fuel pressure chamber, Compared with the conventional structure in which emission is disposed, cracking of the plunger barrel, destruction can be configured to hardly occur.
Further, it is possible to avoid the problem that the tip of the screw thread is damaged or missing.

Further, the packing (40) in either or both of the thread shape of the male screw (11) of the plug (3) and the thread shape of the female screw (12) of the plunger barrel (2). Since the thread height is reduced as the distance from the valve becomes smaller, the engagement area between the male thread of the plug and the female thread of the plunger barrel becomes smaller as it is closer to the plunger, acting on the side closer to the plunger. The compression load to be reduced can be reduced. 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.

The fuel injection pump according to claim 1, wherein the plug (3) includes an insertion portion (3m) inserted into a cylinder (2a) of the plunger barrel (2) and the insertion portion (3m). ) Surrounding the outer peripheral surface of the plunger barrel (2), and having a female screw portion (3n) screwed with a male screw (2g) engraved on the outer peripheral surface, 40) is configured to surround the outer periphery of the insertion portion (3m), and therefore, when the plug (3) is fastened, the contamination attached to the screw portion or a part of the screw thread is missing. It is possible to prevent the broken pieces from entering the cylinder (2a), and it is possible to prevent such a problem that the broken pieces are mixed into the fuel and cause an injection failure or the like.

Further, the volume of the cylinder 2a is reduced by projecting the insertion portion (3m) into the cylinder 2a, whereby the volume of the fuel pressure chamber 2f can be set to a desired value. It became.

According to a third aspect of the present invention, in the fuel injection pump according to the first aspect, the plug (3) surrounds the outer peripheral surface of the plunger barrel (2) and is screwed with a male screw (2g) engraved on the outer peripheral surface. The packing (40) has an annular clamping surface (nipping) between the opening end surface of the plunger barrel (2) and the plug (3). 40a) and the pressure chamber upper surface (40b) protruding from the side of the clamping surface (40a) into the cylinder (2a) of the plunger barrel (2), The surface 40a and the pressure chamber upper surface 40b are configured continuously via the cylindrical surface 40c, and can be formed, for example, by pressing such as depression of the center of a disk-shaped member. It is.

Further, the pressure chamber upper surface 40b is protruded into the cylinder 2a to reduce the volume in the cylinder 2a, whereby the volume of the fuel pressure chamber 2f can be set to a desired value. It became possible.

  In addition, it is possible to prevent contamination that has adhered to the screw part or part of the screw thread from entering the cylinder when the plug is fastened. Thus, it is possible to prevent such a problem that injection failure or the like occurs.

Moreover, as shown in FIG. 7, it can be set as the structure which excluded the insertion part (3m) provided in a plug (3), and simplification of the shape of a plug can be achieved.

  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.

  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, 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 screwed 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 relating to the third and fourth embodiments. 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,... Are formed, and the tip of the screw thread is omitted to avoid the problem that the tip of the screw thread is damaged 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. Moreover, it is not limited to comprising in flat part 13 * 13 ..., It may be set as a gentle curved surface with few gradients.

  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 (3)

In the fuel injection pump configured to close the opening of the cylinder (2a) of the plunger barrel (2) with the plug (3), the opening end face (2m) of the plunger barrel (2) and the packing of the plug (3) A packing (40) is sandwiched between the contact portion (3c) and a male screw (11) engraved on the plug (3) is inserted into an internal screw (12) engraved on the plunger barrel (2). ) And the thread shape of the male screw (11) engraved on the plug (3) and the thread shape of the female screw (12) engraved on the plunger barrel (2). In either one or both, a flat portion (13) is formed at the tip of the screw thread, the tip is omitted, the thread shape of the male screw (11) of the plug (3), and Screw thread of the female thread (12) of the plunger barrel (2) Either one of Jo, or both, a fuel injection pump, characterized in that the height of the nearer threads on the packing (40) has a shape to decrease. The fuel injection pump according to claim 1, wherein the plug (3) includes an insertion portion (3m) inserted into a cylinder (2a) of the plunger barrel (2) and a plunger barrel surrounding the insertion portion (3m). The outer peripheral surface of (2) is further surrounded and has a female screw portion (3n) screwed with a male screw (2g) engraved on the outer peripheral surface, and the packing (40) A fuel injection pump characterized by surrounding the outer periphery of the portion (3 m) . 2. The fuel injection pump according to claim 1, wherein the plug (3) surrounds the outer peripheral surface of the plunger barrel (2) and is screwed with a male screw (2 g) engraved on the outer peripheral surface. (3n), and the packing (40) includes an annular clamping surface (40a) sandwiched between the opening end surface of the plunger barrel (2) and the plug (3), A fuel injection pump comprising: a pressure chamber upper surface (40b) protruding into the cylinder (2a) of the plunger barrel (2) from the mounting surface (40a) side .

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