JP2007023951A - Fuel injection pump for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain generation of cavitation erosion in a suction and overflow hole. <P>SOLUTION: This fuel injection pump 1 is constituted so as to control inlet-outlet of fuel to at least one suction and overflow hole 8 formed in a pump plunger bush 3 by an upper side control edge part 11 and a lower side control edge part 12 of a pump plunger 4 reciprocating in the pump plunger bush 3, and forms an early control groove 10 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. A bottom part 10A of the early control groove 10 extends by inclining upward in the direction for separating from the opening surface 14, and is separately constituted by fitting a cylindrical body 20 with a plunger in a port part on the opposite side of the pump plunger 4 in the suction and overflow hole 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection pump for an internal combustion engine that can reduce the occurrence of cavitation erosion.

  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. When such a hollow chamber rupture occurs near the wall of the suction / overflow hole, cavitation erosion occurs, wear of the material forming the pump occurs, and the function of the pump is caused by such a long-term effect. Will cause trouble.

  In order to solve this problem, Patent Document 1 discloses that an early control groove is formed on the lower side of the suction / overflow wall on the opposite side of the upper control edge. In the type in which the lower 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 is upward in the direction away from the sliding surface by the pump plunger. A configuration that is inclined and extended toward the front 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 cavitation erosion that adversely acts 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. Therefore, when the fuel injection pump is used, periodic inspection is performed, and when a malfunction due to cavitation erosion occurs, the pump plunger bush is inspected. For this reason, it has the problem that the cost of a maintenance expense must be high.

  An object of the present invention is to reduce the cost of maintenance for coping with cavitation erosion of a plunger barrel of a fuel injection pump.

  In order to solve the above-described problems, according to the present invention, the flow of fuel into and out of at least one suction / overflow hole provided in the pump plunger bush is controlled by the pump plunger that reciprocates in the pump plunger bush. A fuel injection pump for an internal combustion engine having an early control groove formed in a wall portion of the suction / overflow hole, wherein the port portion on the opposite side to the pump plunger in the suction / overflow hole However, a fuel injection pump for an internal combustion engine is proposed, characterized in that it is configured separately from the pump plunger.

  According to the present invention, even if cavitation erosion occurs in the port on the outlet side of the high-pressure fuel due to the rupture of the hollow chamber in the high-pressure fuel flowing into the suction and overflow hole along the early control groove, the separate body Since only the port portion of the configuration needs to be converted, maintenance costs can be reduced.

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

  FIG. 1 is a sectional view showing an example of an embodiment of a fuel injection pump according to 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 provided with a fuel suction / overflow hole 8, and a suction / overflow chamber 9 is formed in the casing 2 so as to face the suction / overflow hole 8. An early control groove 10 is formed in the opening 12 portion 14 on the pump plunger 4 side of the suction / overflow hole 8.

  In this embodiment, the suction / overflow hole 8 is a substantially cylindrical hole provided in the pump plunger bush 3, and the suction / overflow hole 8 has an opening end on the suction / overflow chamber 9 side at the pump end. A flanged cylinder 20, which is a separate member from the plunger bush 3, is fitted, and the flanged cylinder 20 constitutes a port portion on the suction / overflow chamber 9 side of the suction / overflow hole 8. Has been.

  This configuration will be described in detail with reference to FIG. The flanged cylinder 20 has a shape in which a flange portion 22 is formed at one end of a cylindrical main body 21, and a central hole 23 is formed in the cylindrical main body 21. On the other hand, the pump plunger bush 3 is formed with a concave portion 81 for receiving the cylindrical main body 21 of the flanged cylindrical body 20 so as to face the suction / overflow chamber 9, and the cylindrical main body 21 is tightly fitted in the concave portion 81. As a result, the pump plunger bush 3 is firmly fixed. Here, a case has been described in which a structure in which the flanged cylinder 20 is fixed to the pump plunger bush 3 by fitting the cylindrical body 21 and the recess 81 is described. However, the present invention is not limited to this. For example, a screw groove is formed on the outer peripheral surface of the cylindrical main body 21 and a screw groove corresponding to the inner peripheral surface of the recess 81 is formed, and both are firmly fixed by screw connection. It is good also as a structure made to do.

  As described above, the flanged cylinder 20 is fitted and fixed in the recess 81, whereby the suction / overflow hole 8 and the center hole 23 are connected to each other. The suction / overflow hole 8 is formed as a part of the suction / overflow hole 8 and the port portion is formed by the flanged cylinder 20.

  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, at the end of the supply, the lower control edge 12 that defines the end of supply first slides on the early control groove 10 extending in an inclined manner, 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 this embodiment, two sets of the suction / overflow hole 8 and the suction / overflow chamber 9 shown in FIG. 2 are provided (see FIG. 1), and the fuel flows alternately with a phase difference of 180 °. Inhalation and overflow operations are performed.

  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 parallel to the bottom surface 10A.

  Thus, the hollow chamber generated in the high-pressure fuel by the fuel jet flowing into the suction / overflow hole 8 enters the suction / overflow chamber 9. The hollow chamber generated in the high-pressure fuel in the suction / overflow hole 8 is ruptured in the vicinity of the outlet port of the suction / overflow hole 8 and cavitation erosion occurs in the outlet port portion. Accordingly, since the damage due to the cavitation erosion mainly occurs in the flange portion 22 of the flanged cylinder 20, when it is determined that the damage is large and the treatment is necessary in the periodic inspection, only the flanged cylinder 20 is replaced. That's enough.

  According to the fuel injection pump 1, as described above, even if cavitation erosion occurs due to the rupture of the hollow chamber generated in the high-pressure fuel in the suction / overflow hole 8, it can be dealt with by replacing the flanged cylinder 20. Therefore, the maintenance cost can be greatly reduced compared to the conventional case.

  In the above-described embodiment, the case where the shape of the suction / overflow hole 8 is a cylindrical hole having a constant diameter is shown, but the shape of the suction / overflow hole 8 is not limited to this. For example, the shape of the suction / overflow hole 8 can be an appropriate shape, for example, the inner diameter on the side having the early control groove 10 is small, and the inner diameter on the suction / overflow chamber 9 side is increased. The inner diameter dimension of the overflow hole 8 and the inner diameter dimension of the center hole 23 are not necessarily the same, and the shape thereof can be any shape other than the cylindrical shape.

Sectional drawing which shows one Embodiment of this invention. FIG. 2 is an enlarged detail view of a main part of FIG. 1.

Explanation 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 Opening Surface 20 Flange Attached cylinder 21 Tubular body 22 Flange 23 Center hole 81 Recess

Claims (1)

The pump plunger bush is configured to be controlled by a pump plunger that reciprocates in the pump plunger bush to and from the at least one suction and overflow hole provided in the pump plunger bush. Is a fuel injection pump for an internal combustion engine in which an early control groove is formed,
A fuel injection pump for an internal combustion engine, wherein a port portion opposite to the pump plunger in the suction / overflow hole is configured separately from the pump plunger.

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