JP2007023949A - Processing method of suction and overflow hole of fuel injection pump for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily process a suction and overflow hole while optimizing a shape of the suction and overflow hole of a plunger barrel of a fuel injection pump. <P>SOLUTION: At least one suction and overflow hole 8 is formed in a pump plunger bush 3. An early control groove 10 is formed in a wall part of the suction and overflow hole 8. The suction and overflow hole 8 is composed of a small diameter hole 81 having an opening surface 14 for peeping at the inside of the pump plunger bush 3 on one end 81A and a large diameter hole 82 communicating with the other end 81B of the small diameter hole 81. This method processes the suction and overflow hole 8 of extending a bottom part 10A of the early control groove 10 by inclining upward in the direction for separating from the opening surface 14, and forms the large diameter hole 82 after forming the small diameter hole 81 after forming a small diameter hole H1 for forming the control groove. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for processing a suction / overflow hole of a fuel injection pump for an internal combustion engine.

  Since the pump chamber of a fuel injection pump for an internal combustion engine has an extremely high pressure, pressure oscillation with a high pressure peak occurs in the suction / overflow hole and the suction chamber when the fuel is controlled to be discharged. Alternatively, a hollow chamber is formed in the fuel, and the already formed hollow chamber is ruptured by this high pressure peak. If such a hollow chamber rupture occurs near the wall of the suction / overflow hole, cavitation erosion occurs, the material forming the pump wears, and this action lasts for a long time. A failure will occur.

  In order to solve this problem, Patent Document 1 discloses that an early control groove is formed on the lower side of the wall portion of the suction and overflow hole opposite to the upper control edge, and the lower side of the pump plunger. In the type in which the control edge first slides on the early control groove and then slides on the main cross section of the suction / overflow hole, the bottom of the early control groove moves upward in a direction away from the sliding surface by the pump plunger. A configuration that is inclined and extended is disclosed.

According to this proposed configuration, the fuel jet generated early flows into the suction / overflow hole along the inclination of the bottom thereof, and sucks the hollow chamber formed in the suction / overflow hole. Since the discharge is made toward the cum overflow hole, it can be expected that the cavitation erosion which has an adverse effect in the suction cum overflow hole is avoided or at least reduced in the hole.
No. 7-54618

  However, in recent years, the use of low-viscosity fuel has increased, and the conditions have become more severe than those for cogeneration. Therefore, cavitation erosion still occurs depending on the above-described conventional technology, and in some cases, about 3000 to 5000 hours. May cause malfunction.

  An object of the present invention is to optimize the shape of the suction / overflow hole of the plunger barrel of the fuel injection pump and to provide a method for processing the suction / overflow hole.

  According to the present invention, a pump plunger bush of a fuel injection pump for an internal combustion engine is provided with a small-diameter hole having an opening that looks into the inside of the pump plunger bush at one end and a large-diameter hole communicating with the other end of the small-diameter hole. A control groove for processing a suction / overflow hole in which the bottom of the early control groove extends obliquely upward in a direction away from the opening from the opening of the small diameter hole toward the large diameter hole. In the method, the small-diameter hole for forming the control groove is formed, then the small-diameter hole is formed, and then the large-diameter hole is formed. A method for processing overflow holes is proposed.

  According to the present invention, the pump plunger bush of the fuel injection pump for an internal combustion engine further includes a small diameter hole having an opening that looks into the inside of the pump plunger bush at one end and a large diameter hole that communicates with the other end of the small diameter hole. The early control groove processes a suction / overflow hole in which the bottom of the early control groove extends obliquely upward in a direction away from the opening from the opening of the small diameter hole toward the large diameter hole. A fuel for an internal combustion engine, characterized in that after forming the large-diameter hole, the small-diameter hole is formed, and then the small-diameter hole for forming the control groove is processed. A method of processing a suction / overflow hole of an injection pump is proposed.

  According to the present invention, the cavitation erosion effect due to the rupture of the hollow chamber in the high-pressure fuel can be remarkably reduced, and the processing of the suction and overflow hole that can effectively suppress the life reduction of the fuel injection pump can be easily performed. .

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of an embodiment of a fuel injection pump in which a suction and overflow hole is processed by the method of the present invention. The fuel injection pump 1 is for injecting and supplying pressurized high-pressure fuel to an internal combustion engine. 2 is a casing, 3 is a pump plunger bush fitted in the casing 2, 4 is a pump plunger, and 5 is a pump. This is a plunger chamber defined by the plunger bush 3 and the pump plunger 4. 6 is a pressure valve, 7 is a pressure valve casing, and the pressure valve casing 7 is screwed to the casing 2.

  The pump plunger bush 3 is formed with a fuel intake / overflow hole 8 processed by the method of the present invention, and the casing 2 is formed with a suction / overflow chamber 9 facing the suction / overflow hole 8. Has been. An early control groove 10 is formed in the suction / overflow hole 8.

  An upper control edge 11 and a lower control edge 12 are formed in the pump plunger 4, and the upper control edge 11 and the lower control edge 12 are moved early by the movement of the pump plunger 4 in the axial direction. Glide on the control groove 10. In this case, the lower control edge 12 that defines the end of supply first slides on the early control groove 10 that extends in an inclined manner at the end of supply, and then opens the entire opening surface 14 of the suction / overflow hole 8. As a result, the pressure in the suction / overflow chamber 9 increases relatively gently due to the fuel jet that has flowed in at an early stage.

  In the fuel injection pump 1 shown in FIG. 1, two sets of the suction / overflow hole 8 and the suction / overflow chamber 9 are provided, and the fuel suction and overflow operations are alternately performed with a phase difference of 180 °. Executed.

  Next, the suction / overflow hole 8 will be described with reference to FIGS. 2 is a cross-sectional view taken along the line AA in FIG. 1, FIG. 3 is a view seen from the direction of arrow B in FIG. 2, and FIG. 4 is a cross-sectional view taken along the line CC in FIG.

  The suction / overflow hole 8 has a cylindrical small-diameter hole 81 having an opening surface 14 with one end 81A opening on the pump plunger 4 side, and one end 82A opening on the suction / overflow chamber 9 side. A large-diameter hole 82 having a diameter greater than 81 is provided, and the inner surface of the other end of the large-diameter hole 82 is a curved surface portion 82C. The other end 81B of the small diameter hole 81 communicates with the large diameter hole 82 so as to look into the large diameter hole 82 from a part of the curved surface portion 82C formed as the bottom surface at the other end of the large diameter hole 82. ing. Here, the shape of the curved surface portion 82C is a shape of a part of a spherical surface, but may be another curved surface shape or the like.

  In the present embodiment, as can be easily understood from FIGS. 3 and 4, the axis 81x of the small diameter hole 81 and the axis 82x of the large diameter hole 82 are shifted by a predetermined value k. This shift direction is such that the axis 82x is opposite to the early control groove 10 with respect to the axis 81x.

  The early control groove 10 is formed as a bowl-shaped groove having a bottom surface 10A having a circular arc shape in a part of the small-diameter hole 81, and the bottom surface 10A of the early control groove 10 forms an angle θ with respect to the axis 81x. (See FIG. 4).

  Next, fuel intake, pressurization, and injection operations in the fuel injection pump 1 will be described.

  The fuel is sucked in the state where the pump plunger 4 is lowered and the upper control edge 11 opens the opening surface 14 of the small diameter hole 81 to the plunger chamber 5. When the pump plunger 4 lifts and the upper control edge 11 blocks the opening surface 14 from the plunger chamber 5, the pressurization of fuel in the plunger chamber 5 is started, and the lower control edge 12 opens the early control groove 10. The high pressure fuel obtained by pressurizing in the plunger chamber 5 when starting to flow flows into the suction / overflow hole 8 as a fuel jet along the early control groove 10.

  Since the fuel jet flows along the bottom surface 10A of the early control groove 10, the flow direction is a direction indicated by an arrow R parallel to the bottom surface 10A (see FIG. 4). As a result, the fuel jet flowing from the small-diameter hole 81 is sent out vigorously into the large-diameter hole 82, but the axes 81x and 82x are shifted by a predetermined value k as described above, and the other end of the large-diameter hole 82 Since a curved surface portion 82C is formed on the bottom surface of the portion, a wide space is secured in front of the fuel jet sent into the large-diameter hole 82.

  Therefore, the hollow chamber generated in the high-pressure fuel when the fuel jet flows into the suction / overflow hole 8 enters the suction / overflow chamber 9 through the secured wide space. As a result, the probability that the hollow chamber generated in the high-pressure fuel in the suction / overflow hole 8 bursts in the vicinity of the inner wall surface of the large-diameter hole 82 can be significantly reduced, and the occurrence of cavitation erosion can be effectively suppressed. If the curved surface portion 82C can secure a wide space that can reduce the influence of cavitation erosion in front of the fuel jet sent into the large-diameter hole 82, it is not always necessary to shift the axis 81x and the axis 82x. The predetermined value k may be zero.

  Next, an embodiment of a method of processing the suction / overflow hole 8 according to the present invention will be described with reference to FIG. First, as shown in FIG. 5A, a hole H1 is made in the pump plunger bush 3. The pore H1 is a processing step for forming the early control groove 10, and its diameter is determined according to the curved surface of the bottom surface 10A of the early control groove 10. 5 indicates the center line position of the small-diameter hole 81, and the hole H1 is formed in the wall portion of the pump plunger bush 3 with an angle P with respect to the alternate long and short dash line Y. (See FIG. 4).

  In this case, the hole H1 is drilled so that the one end opening H1a of the hole H1 coincides with the opening end of the early control groove 10. Next, as shown in FIG. 5 (b), a through hole H 2 for forming the small diameter hole 81 is formed in the pump plunger bush 3. The through hole H2 is formed in the pump plunger bush 3 so that the alternate long and short dash line Y is the center line. Thereby, the small diameter hole 81 provided in the state where the early control groove 10 is shown in FIG. 4 is formed.

  Finally, as shown in FIG. 5C, a large hole H3 is formed from the outside of the pump plunger bush 3. The thick hole H3 is a hole whose center line is the alternate long and short dash line Y, and its bottom surface has a curved surface shape forming a part of a spherical surface. The drilling depth of the large hole H3 is set to a predetermined depth that does not reach the early control groove 10.

  The suction / overflow hole 8 having the early control groove 10 is formed in the pump plunger bush 3 by the above three drilling steps. These drilling processes can be performed by drilling or end milling. Therefore, according to the processing method shown in FIG. 5, the suction / overflow hole 8 can be easily processed in the pump plunger bush 3.

  FIG. 6 is a view for explaining a processing method of the suction / overflow hole 8 according to the present invention. In the processing method shown in FIG. 6, first, a large hole H3 is formed (FIG. 6A), then a through hole H2 is formed (FIG. 6B), and finally a fine hole H1 is formed (FIG. 6). (C)) Thereby, the suction / overflow hole 8 having the early control groove 10 is formed in the pump plunger bush 3. Also in this case, the suction / overflow hole 8 can be easily formed in the pump plunger bush 3 by the three drilling steps.

Sectional drawing which shows the fuel-injection pump which has the suction and overflow hole processed by this invention. AA sectional view taken on the line AA of FIG. The figure seen from the arrow B direction of FIG. CC sectional view taken on the line of FIG. The figure for demonstrating one Embodiment of the processing method by this invention. The figure for demonstrating other embodiment of the processing method by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection pump 2 Casing 3 Pump plunger bush 4 Pump plunger 5 Plunger chamber 8 Suction / overflow hole 9 Suction / overflow chamber 10 Early control groove 10A Bottom surface 11 Upper control edge 12 Lower control edge 14 Open surface 81 Small diameter Hole 81A, 82A One end 81B The other end 81x, 82x Axis 82 Large diameter hole 82C Curved surface k Predetermined value H1 Small hole H2 Through hole H3 Large hole Y Center line position of small diameter hole

Claims (1)

A pump plunger bush of a fuel injection pump for an internal combustion engine has a small-diameter hole having an opening that looks into the inside of the pump plunger bush at one end and a large-diameter hole that communicates with the other end of the small-diameter hole, and an early control groove has the small-diameter hole In order to process a suction / overflow hole of a fuel injection pump for an internal combustion engine in which the bottom of the early control groove extends obliquely upward in a direction away from the opening from the opening toward the large-diameter hole In the method of
An intake and overflow hole for a fuel injection pump for an internal combustion engine, wherein the small diameter hole for forming the control groove is formed, then the small diameter hole is formed, and then the large diameter hole is formed. Processing method.

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