JP2005147096A - Delivery valve for fuel injection pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a delivery valve for a fuel injection pump having structure for reducing pressure on an end face of a delivery holder as a seal face between the delivery holder and an annular sleeve, and for preventing occurrence of cavitation erosion. <P>SOLUTION: The delivery valve 30 has the tubular delivery holder 31, and the annular sleeve 32 fit to an inner face of the delivery holder 31. In the delivery valve 30, an outer circumferential groove 40 is formed in an outer peripheral face of the annular sleeve 32, and a damper ring 41 is installed in the outer circumferential groove 40 so that the damper ring 41 can vertically slide therein. With the damper ring 41 brought into contact with an upper face of the outer circumferential groove 40, spaces are formed between an inner circumferential face 31a of the delivery holder 31 and the outer circumferential face of the annular sleeve. Out of the spaces, the space above the damper ring 41 communicates with the space below the damper ring 41 through drilled holes 43 which are formed in the annular sleeve 32. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a structure of a delivery valve in a fuel injection pump.

Conventionally, a fuel injection pump for a diesel engine configured to send fuel that is pumped by sliding the plunger up and down in a plunger barrel to a plurality of discharge valves and to pump the fuel from each discharge valve to a fuel injection nozzle. It has been known.
In this fuel injection pump, the pressure of the passage to the injection nozzle is suddenly lowered to a predetermined pressure in order to perform fuel pumping or when the fuel injection is completed, thereby ensuring the operation of the fuel injection nozzle. In order to perform sucking back to improve cutting, and to block between the plunger chamber and the passage to the injection nozzle in order to maintain the pressure in the passage to the injection nozzle until the next injection is performed, A delivery valve is provided between the passage to the injection nozzle (see, for example, Patent Document 1).

Hereinafter, the structure of the delivery valve disclosed in Patent Document 1 will be described with reference to FIG. FIG. 8 is a sectional view showing a conventional structure of a delivery valve.
The delivery valve 130 includes a tubular delivery holder 131, an annular sleeve 132 fitted to the inner surface of the delivery holder 131, and a check valve 133 that slides inside the annular sleeve 132.

  The annular sleeve 132 is fitted to the delivery holder 131 from the inlet side (plunger side) so that the lower end surface of the delivery holder 131 is in contact with the upper surface of the large diameter portion 132a formed at the lower portion of the annular sleeve 132. A space between the upper surface of the large-diameter portion 132a of the annular sleeve 132 and the lower end surface of the delivery holder 131 is a seal surface 1S. That is, in the delivery valve 130, the pressure of the fuel pressure-fed from the plunger is applied to the seal surface 1S between the delivery holder 131 and the annular sleeve 132, so that the delivery holder 131 is tightened with the annular sleeve 132 fitted to the delivery holder 131. The delivery holder 131 and the annular sleeve 132 are metal-sealed on the sealing surface 1S by plastic deformation.

A check valve 133 is seated on the inner peripheral side of the upper opening end of the annular sleeve 132 through a coil spring 134 and biased in a closing direction. The check valve 133 is formed with a fuel passage 133a that passes through the central portion thereof and communicates with the upstream and downstream sides. The seat member is formed at the opening end of the fuel passage 133a by the tension of the coil spring 135. A spherical isobaric valve 136 seated on 137 abuts.
An inlet passage 138 is provided at the lower portion of the annular sleeve 132.

  The delivery valve having such a configuration is provided between the plunger chamber of the fuel injection pump and the passage to the injection nozzle, and performs the pumping of fuel from the start to the end of pump fuel pumping and the backflow prevention and suck back. ing.

  Specifically, first, the plunger is raised and a fuel compression stroke is started, and the injection pressure from the plunger acts in the annular sleeve 132 via the inlet passage 138. Then, the check valve 133 rises against the coil spring 134, passes the fuel to the outlet passage 139 formed in the delivery holder 131 toward the injection nozzle (not shown), and pumps the fuel. When the fuel injection is completed and the pressure on the inlet side decreases, the suction is performed to ensure the operation of the injection nozzle and improve the fuel injection interruption. Then, in order to maintain the pressure in the passage to the injection nozzle until the next injection is performed, the check valve 133 is seated on the upper end portion of the annular sleeve 132 and the communication between the delivery holder 131 and the annular sleeve 132 is closed and the fuel is closed. To prevent backflow.

  If the pressure in the outlet passage 139 after the injection is higher than the set value, the isobaric valve 136 is lowered while the coil spring 135 is compressed by receiving this high pressure, and the fuel passage 133a is opened to open a part of the high-pressure fuel. To the inlet passage 138 and the plunger side. As a result, the outlet passage 139 after completion of the injection is kept in a high pressure state, so that the injection nozzle is not opened carelessly by the action of the combustion gas pressure and the like, and the injection characteristics are stabilized.

JP 11-44274 A

  However, in the structure of the conventional delivery valve as described above, cavitation erosion (fluid at high speed) is caused on the seal surface 1S as the fuel injection pressure becomes higher in order to comply with exhaust emission regulations in recent diesel engines. When the gas flows in the pipe, a negative pressure portion is formed in the vicinity of the joint, so that bubbles are generated in the fluid, and damage to the material surface due to the impact force generated when the bubbles collide with the wall surface of the tube and collapse.

  Hereinafter, a mechanism for generating cavitation erosion in the structure of a conventional delivery valve will be described with reference to FIG. FIG. 9 is a graph showing the change in the delivery holder lower pressure in the conventional delivery valve.

  In the series of operations of the delivery valve 130 as described above, when the fuel is pumped, the check valve 133 rises and the inside of the delivery holder 131 becomes high pressure as shown in part A of FIG. Thereafter, when the check valve 133 is lowered to perform sucking back, the pressure in the delivery holder 131 is drastically lowered. At this time, as shown in part B of FIG. 9, the check valve 133 is lowered, the volume of the cavity in the delivery holder 131 is increased, and the inside of the delivery holder 131 becomes negative pressure. Due to this negative pressure, bubbles are generated in the delivery holder 131. Will occur. That is, cavitation erosion occurs on the end surface of the delivery holder on the seal surface 1S with the annular sleeve 132 of the delivery holder 131 due to the air bubbles generated by the pressure difference from the high pressure to the negative pressure in the delivery holder 131 (A part to B part in FIG. 9). . Further, the sealing performance is deteriorated due to the damage of the material surface due to the cavitation erosion, and there is a problem that oil leakage occurs from the seal portion.

  The above is a problem in the conventional structure. In order to solve such a problem, in the present invention, the pressure applied to the end surface of the delivery holder, which is the seal surface between the delivery holder and the annular sleeve, is reduced by reducing the pressure difference in the delivery valve. It is an object of the present invention to provide a delivery valve for a fuel injection pump having a structure that can reduce cavitation and prevent the occurrence of cavitation erosion.

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

  That is, in claim 1, in a delivery valve of a fuel injection pump having a cylindrical delivery holder and an annular sleeve fitted to the inner surface of the delivery holder, an outer circumferential groove is provided on the outer circumferential surface of the annular sleeve, and the outer circumferential groove A damper ring is slidably attached to the upper surface of the outer circumferential groove and a space formed between the inner circumferential surface of the delivery holder and the outer circumferential surface of the annular sleeve in a state where the damper ring is pressed against the upper surface of the outer circumferential groove. Of these, the annular sleeve is provided with a communication passage that communicates the space above the damper ring and the space below the damper ring.

  According to a second aspect of the present invention, an inner circumferential groove is provided at a position of the inner circumferential surface of the delivery holder facing the outer circumferential groove, and the damper ring can be slid up and down in a space formed by the inner circumferential groove and the outer circumferential groove. It is what was attached.

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

  According to the first aspect, the pulsation of the pressure of the fuel pumped from the plunger is interrupted by the damper ring, and the occurrence of cavitation erosion can be prevented at the end surface of the delivery holder, that is, the seal surface between the delivery holder and the annular sleeve. Thereby, the sealing performance of the sealing surface is maintained, and it is possible to prevent oil leakage.

  According to the second aspect, the delivery holder is locked to the annular sleeve by the damper ring attached to the inner circumferential groove of the delivery holder, so that the delivery holder can be prevented from coming off (dropping off).

Next, embodiments of the invention will be described.
1 is a side sectional view showing a structure of a fuel injection pump according to the present invention, FIG. 2 is a sectional view showing a structure of a delivery valve according to the present invention, FIG. 3 is a perspective view showing an annular sleeve, and FIG. 4 is an operation of a damper ring. FIG. 5 is a graph showing changes in the lower pressure of the delivery holder in the delivery valve according to the present invention, FIG. 6 is a diagram showing a comparison with changes in the lower pressure in the delivery holder in the delivery valve, and FIG. 7 shows another delivery valve according to the present invention. It is a figure which shows an Example.

  First, a schematic configuration of the fuel injection pump 1 having the delivery valve 30 according to the present invention will be described. In the present embodiment, a description will be given using a distribution type fuel injection pump having a biaxial structure in which a plunger and a distribution shaft are arranged side by side, but the present invention is not limited to this structure. In the following description, the left side of FIG. 1 is the front side.

A fuel injection pump 1 according to the present invention is mounted on a diesel engine, and the fuel injection pump 1 is configured by vertically joining a hydraulic head 2 and a pump housing 3 as shown in FIG. Yes.
A governor device 4 is arranged on the front side of the pump housing 3.

  A plunger barrel 8 is inserted into the hydraulic head 2, a plunger 7 is slidably mounted in the plunger barrel 8, and a tappet roller is rotated by rotation of a cam 6 formed on the pump cam shaft 5. The plunger 7 is configured to move up and down via the 11 and the tappet 12. A cam shaft flange 14 is fixed to the pump cam shaft 5, and a driving force from the engine is transmitted through the cam shaft flange 14.

The space above the plunger 7 serves as a fuel pressure chamber 19 so that the fuel oil pumped from a fuel supply unit (not shown) is compressed by the plunger 7.
More specifically, the fuel pumped from the fuel supply unit is always supplied to the main port provided in the plunger barrel 8, and the plunger 7 is positioned at the lower end (bottom dead center) of the vertical movement range. Then, the fuel pressure chamber 19 and the main port communicate with each other in the plunger barrel 8 and fuel is introduced into the fuel pressure chamber 19. When the plunger 7 is pushed up by the cam 6 and rises, the outer wall of the plunger 7 closes the communication port of the main port to the fuel pressure chamber 19, and the fuel in the fuel pressure chamber 19 moves along with the rise of the plunger 7. From the delivery port 17 penetrating the plunger barrel 8, the pressure is fed to the delivery valve 30 through the delivery shaft 9, and injected from the delivery valve 30 into the engine cylinder through a fuel injection valve provided in the cylinder head portion of the engine. It has a configuration.

Next, the configuration of the delivery valve according to the present invention will be described with reference to FIGS.
As shown in FIG. 2, the delivery valve 30 includes a cylindrical delivery holder 31 fitted in the hydraulic head 2, an annular sleeve 32 fitted to the inner surface of the delivery holder 31, and a slide in the annular sleeve 32. And a check valve 33 that moves.

  The annular sleeve 32 is fitted to the delivery holder 31 from the inlet side (plunger side) so that the lower end surface of the delivery holder 31 is in contact with the upper surface of the large diameter portion 32a formed at the lower portion of the annular sleeve 32. The space between the upper surface of the large-diameter portion 32 a of the annular sleeve 32 and the lower end surface of the delivery holder 31 is a sealing surface S. That is, in this delivery valve 30, since the pressure of the fuel pressure-fed from the plunger is applied to the seal surface S between the delivery holder 31 and the annular sleeve 32, the delivery holder 31 is tightened with the annular sleeve 32 fitted to the delivery holder 31. The delivery holder 31 and the annular sleeve 32 are metal-sealed on the sealing surface S by plastic deformation.

A check valve 33 urged in a closing direction via a coil spring 34 is seated on the inner peripheral side of the upper opening end of the annular sleeve 32. The check valve 33 is formed with a fuel passage 33a that passes through the central portion thereof and communicates with the upstream and downstream sides. A seat member is formed at the opening end of the fuel passage 33a by the tension of the coil spring 35. A spherical isobaric valve 36 seated on 37 abuts.
An inlet passage 38 is provided in the lower portion of the annular sleeve 32.

Hereinafter, characteristic parts of the configuration of the delivery valve according to the present invention will be described.
In the delivery valve 30 according to the present invention, an outer peripheral groove 40 is provided on the outer peripheral surface of the annular sleeve 32, and a damper ring 41 is slidably mounted on the outer peripheral groove 40. The damper ring 41 is connected to the outer peripheral groove 40. Of the space formed between the inner peripheral surface 31a of the delivery holder 31 and the outer peripheral surface of the annular sleeve 32 in a state of being in pressure contact with the upper surface 40a, a space above the damper ring 41 and the damper ring 41 In addition, the annular sleeve 32 is provided with a drill hole 43 as a communication passage for communicating with a lower space.

  The outer circumferential groove 40 is horizontally formed on the outer circumferential surface of the annular sleeve 32 above the seal surface S of the delivery holder 31 and the annular sleeve 32 over the entire circumference. An annular damper ring 41 is slidably mounted in the outer circumferential groove 40. That is, the outer circumferential groove 40 is fitted with the damper ring 41 by forming its depth so that the outer diameter of the annular sleeve 32 in the outer circumferential groove 40 is smaller than the inner diameter of the damper ring 41. The vertical width of the outer circumferential groove 40 is formed wider than the thickness of the damper ring 41, and the damper ring 41 is mounted so as to be slidable in the vertical direction within the range between the upper surface 40a and the lower surface 40b of the outer circumferential groove 40. Yes.

  Further, the outer peripheral groove 40 has a plurality of drill holes 43 as communication passages for allowing high-pressure fluid to escape, as will be described in detail later. The drill hole 43 prevents the space between the outer peripheral surface of the annular sleeve 32 and the inner peripheral surface of the delivery holder 31 from being divided by the damper ring 41 in a state where the damper ring 41 is in contact with the upper surface 40 a of the outer peripheral groove 40. It is provided to do. Therefore, the drill hole 43 is formed integrally with the outer circumferential groove 40 so that the outer circumferential groove 40 becomes wider only on the upper surface 40a side, and the annular sleeve 32 is deeper than the depth of the outer circumferential groove 40. It is formed toward the axis.

  Further, it is preferable that a plurality of drill holes 43 are formed in the outer circumferential groove 40 at equal intervals in the circumferential direction. In the present embodiment, two locations are provided symmetrically with respect to the axis of the annular sleeve 32. As a result, the pressure applied to the annular sleeve 32 in the drill hole 43 is evenly applied to the shaft center, and no lateral stress is applied to the annular sleeve 32. The shape and the number of drill holes 43 are not limited to the present embodiment.

The damper ring 41 is an annular member having elasticity made of a synthetic resin such as a fluororesin having heat resistance or oil resistance, or rubber.
The damper ring 41 has an inner diameter smaller than the outer diameter of the annular sleeve 32 and larger than the outer diameter of the annular sleeve 32 in the outer circumferential groove 40, and the damper ring 41 is mounted on the outer diameter. It is formed substantially the same as the inner diameter of the delivery holder 31 at the position. That is, the damper ring 41 is mounted so as to be slidable in the vertical direction in the outer circumferential groove 40 with its outer circumferential surface in contact with the inner circumferential surface 31 a of the delivery holder 31.

  The operation of the damper ring 41 mounted with the above configuration will be described with reference to FIG. In this description, for the sake of convenience, of the space formed by the inner peripheral surface of the delivery holder 31 and the outer peripheral surface of the annular sleeve 32, the space above the damper ring 41 is the upper space 46a and the lower space is the lower space 46b. And

  FIG. 4A is a view showing a state of the damper ring 41 when the upper space 46a is at a high pressure. That is, for example, when the fuel is fed by the delivery valve 30. When the upper space 46a is at a high pressure, the pressure from the upper space 46a acts downward on the damper ring 41, and the damper ring 41 is pressed downward. That is, when the bottom surface 41 b of the damper ring 41 is in pressure contact with the lower surface 40 b of the outer circumferential groove 40, the space formed by the inner circumferential surface of the delivery holder 31 and the outer circumferential surface of the annular sleeve 32 is divided. That is, the lower space 46 b forms a closed space surrounded by the bottom surface 41 b of the damper ring 41, the outer peripheral surface below the outer peripheral groove 40 of the annular sleeve 32, and the inner peripheral surface 31 a of the delivery holder 31. Thereby, it can seal that high pressure gas flows in into the lower space 46b from the upper space 46a, and can prevent that a high pressure is applied to the sealing surface S. FIG.

  On the other hand, FIG.4 (b) is a figure which shows the state of the damper ring 41 when the upper space 46a is a low pressure. That is, when sucking back by the delivery valve 30 after fuel injection. When the upper space 46a is at a low pressure, the damper ring 41 rises due to a pressure difference between the pressure of the upper space 46a that has become a low pressure and the pressure in the above-described closed space in the lower space 46b. Is brought into pressure contact with the upper surface 40 a of the outer circumferential groove 40. In this state, since the drill hole 43 is provided, the upper space 46a and the lower space 46b are not divided. That is, when the damper ring 41 is raised, the upper space 46 a and the lower space 46 b are in communication with each other through the drill hole 43. As a result, when the upper space 46a shown in FIG. 4 (a) is at a high pressure, the high-pressure fluid that gradually accumulates in the lower space 46b that has become a closed space is cut into the upper space 46a that has become a low-pressure state. You can escape through 43.

  Thus, by providing the damper ring 41, the pressure applied to the lower part of the delivery holder 31 changes as shown in the graph of FIG. That is, as shown in FIG. 6, compared with the case of the conventional delivery valve shown in FIG. 9, it is formed by the inner peripheral surface of the delivery holder 31 and the outer peripheral surface of the annular sleeve 32 as in the case of fuel pumping in the delivery valve 30. The pressure applied to the lower part of the delivery holder 31 when the space to be produced becomes high (A portion in the figure), and when the suction by the delivery valve 30 is performed, the inner peripheral surface of the delivery holder 31 When the space formed by the outer peripheral surface of the annular sleeve 32 is at a low pressure, the pressure applied to the lower portion of the delivery holder 31 is increased and does not become negative pressure as in the prior art (B portion in the figure). That is, by providing the damper ring 41, the pressure difference applied to the lower part of the delivery holder 31 at the time of high pressure and low pressure in the delivery valve 30 can be reduced.

  With the configuration described above, the pulsation of the pressure of the fuel pumped from the plunger 7 is blocked by the damper ring 41, and cavitation erosion is generated on the end surface of the delivery holder 31, that is, the seal surface S between the delivery holder 31 and the annular sleeve 32. Can be prevented. Thereby, the sealing performance of the sealing surface S is maintained, and it becomes possible to prevent the occurrence of oil leakage.

Further, the delivery valve 30 according to the present invention can also be configured as follows. Hereinafter, another embodiment of the delivery valve 30 will be described.
The delivery valve 30 in the present embodiment is provided with an inner circumferential groove 45 at a position facing the outer circumferential groove 40 on the inner circumferential surface of the delivery holder 31, and the damper ring is formed in a space formed by the inner circumferential groove 45 and the outer circumferential groove 40. 41 is slidable up and down.

  That is, as shown in FIG. 7, the inner circumferential groove 45 is horizontally formed over the entire circumference at a position of the inner circumferential surface 31 a of the delivery holder 31 that faces the outer circumferential groove 40 provided in the annular sleeve 32. The inner circumferential groove 45 is formed so that its vertical width is substantially the same as or wider than the outer circumferential groove 40 of the annular sleeve 32, and when the damper ring 41 rises, the upper surface 41a of the damper ring 41 is The contact with the upper surface 40a of the groove 40 is not prevented.

  As described above, when the inner circumferential groove 45 is provided on the inner circumferential surface of the delivery holder 31, the damper ring 41 is mounted in the space formed by the outer circumferential groove 40 of the annular sleeve 32 and the inner circumferential groove 45 of the delivery holder 31. It will be. That is, in this case, the damper ring 41 is mounted so as to be slidable in the vertical direction with its outer peripheral surface in contact with the bottom surface 45 a of the inner peripheral groove 45.

  That is, in the present embodiment, the damper ring 41 has an outer diameter substantially the same as the inner diameter of the position where the inner circumferential groove 45 of the delivery holder 31 is provided, and when the annular sleeve 32 is fitted to the delivery holder 31, By utilizing the elasticity of the ring 41, the damper ring 41 is fitted into the delivery holder 31 together with the annular sleeve 32 in a contracted state, and when the damper ring 41 reaches the inner peripheral groove 45, the elastic state is restored to the normal state. Thus, the outer periphery of the damper ring 41 is in contact with the bottom surface 45a of the inner peripheral groove 45.

With such a configuration, when the delivery holder 31 is pulled out of the annular sleeve 32 when the inside of the delivery holder 31 is at a high pressure, the upper surface 41a of the damper ring 41 has the outer periphery of the annular sleeve 32. Since the bottom surface 41 b of the damper ring 41 abuts on the top surface 40 a of the groove 40 and the bottom surface 45 b of the inner circumferential groove 45 of the delivery holder 31, the delivery holder 31 can be prevented from coming off.
That is, the delivery holder 31 is locked to the annular sleeve 32 by the damper ring 41 attached to the inner circumferential groove 45 of the delivery holder 31, so that the delivery holder 31 can be prevented from coming off, and the delivery holder 31 is connected to the hydraulic head 2. Can be prevented from falling off.

  The present invention is not only a biaxial fuel injection pump having a biaxial structure in which a plunger and a distribution shaft are arranged side by side, but also a uniaxial structure in which the plunger reciprocates and rotates and has a distribution function in itself. And, moreover, can be widely applied to row type fuel injection pumps.

The side sectional view showing the composition of the fuel injection pump concerning the present invention. Sectional drawing which shows the structure of the delivery valve concerning this invention. The perspective view which shows an annular sleeve. Operation | movement explanatory drawing of a damper ring. The graph which shows the change of the delivery holder lower part pressure in the delivery valve which concerns on this invention. The figure which shows the comparison with the past of the change of the delivery holder lower part pressure in a delivery valve. The figure which shows another Example of the delivery valve which concerns on this invention. Sectional drawing which shows the conventional structure of a delivery valve. The graph which shows the change of the delivery holder lower part pressure in the conventional delivery valve.

Explanation of symbols

1 Fuel Injection Pump 30 Delivery Valve 31 Delivery Holder 32 Annular Sleeve 40 Outer Groove 41 Damper Ring 43 Drill Hole 45 Inner Groove

Claims (2)

  In a delivery valve of a fuel injection pump having a cylindrical delivery holder and an annular sleeve fitted to the inner surface of the delivery holder, an outer circumferential groove is provided on the outer circumferential surface of the annular sleeve, and a damper ring can be slid up and down in the outer circumferential groove. Of the space formed between the inner peripheral surface of the delivery holder and the outer peripheral surface of the annular sleeve in a state where the damper ring is in pressure contact with the upper surface of the outer peripheral groove. A delivery valve for a fuel injection pump, characterized in that a communication passage that communicates between this space and a space below the damper ring is provided in the annular sleeve.   An inner circumferential groove is provided at a position of the inner circumferential surface of the delivery holder facing the outer circumferential groove, and the damper ring is slidably mounted in a space formed by the inner circumferential groove and the outer circumferential groove. The delivery valve of the fuel injection pump according to claim 1.