JP2020133506A - Fuel injection pump - Google Patents

Abstract

To provide a fuel injection pump capable of suppressing cavitation erosion of a tappet slide portion.SOLUTION: A roller 51 constituting a driving mechanism 50 of a fuel injection pump 101 is brought into contact with a cam 17, and reciprocated while rotated along a shape of the cam 17. A tappet 54 is guided by a guide portion 42 constituted by an inner wall of a tappet chamber 41, and reciprocated between a lowest point and an uppermost point while interlocking with movement of the roller 51. The driving mechanism 50 converts a rotating motion of the cam 17 into a reciprocating motion of the tappet 54 through the roller 51. A housing 40 is opened to a cam 17 side with respect to a center in a height direction at the lowest point of the tappet 54, and a communication passage 45 communicated with the tappet chamber 41 directly from a fuel supply flow channel or through the cam chamber 18, is formed. Further a fluid holding chamber 61 receiving a fluid supplied from the communication passage 45, is formed on an outer wall of the tappet 54 opposed to the opening of the communication passage 45 at least at the lowest point of the tappet 54.SELECTED DRAWING: Figure 5

Description

The present invention relates to a fuel injection pump.

Conventionally, it has been applied to the common rail system of diesel engines, etc., and the fuel injection pump that reciprocates the tappet according to the rotation of the cam to reciprocate the plunger and pressurizes and discharges the fuel sucked into the pressurizing chamber is known. Has been done. For example, in the high-pressure fuel pump disclosed in Patent Document 1, a supply path (50) for guiding fuel to a tappet sliding portion is formed in a housing (48).

Germany DE10201622556333A1 specification

The rotation of the cam increases the radius of the cam at the point of contact with the roller, and when pushing up the tappet, the lower end of the tappet is pushed forward in the direction of rotation, and a force that tilts the tappet acts. Then, behind the rotation direction, the clearance between the outer wall of the tappet and the inner wall of the tappet chamber increases, and a negative pressure is generated due to the expansion of the gap volume. Since the amount of cavitation generated increases due to this negative pressure, the erosion (that is, surface defects) generated by the impact pressure at the time of cavitation collapse increases.

In addition, in response to a request to increase the pumping amount, a multi-cylinder fuel injection pump in which multiple sets of tappets, plungers, etc. are arranged for one cam, and the pump unit including each plunger alternately pumps the pumps at different timings. May be used. For example, in a V-shaped two-cylinder fuel injection pump, the force for laterally moving the tappet is further increased due to an increase in the moving speed of the camshaft due to a change in the applied load direction when the pumping cylinder is switched. Therefore, there is a possibility that cavitation erosion at the tappet sliding portion will increase more.

In the high-pressure fuel pump of Patent Document 1, the supply path is formed above the center of the tappet in the height direction, that is, on the side opposite to the cam. The introduction of fuel from the supply path is intended to improve the lubricity of the sliding portion, and is considered to be less effective in suppressing cavitation erosion.

The present invention has been created in view of these respects, and an object of the present invention is to provide a fuel injection pump that suppresses cavitation erosion of a tappet sliding portion.

The fuel injection pump of the present invention includes a camshaft (16) having a cam (17), a housing (40), and one or more drive mechanisms (50) having rollers (51) and tappets (54). It is provided with one or more plungers (31) and one or more cylinders (20), and pressurizes and discharges fuel supplied from the fuel tank (1) via the fuel supply flow path (5).

The camshaft has a cam that rotates in conjunction with the output shaft of the internal combustion engine. The housing has a cam chamber (18) for accommodating the cam and a tappet chamber (41) communicating with the cam chamber, and fuel or oil is retained in the cam chamber.

The rollers constituting the drive mechanism come into contact with the cam and reciprocate while rotating along the shape of the cam. The tappet is guided by a guide portion (42) formed by the inner wall of the tappet chamber, and moves back and forth between the lowest point closest to the camshaft and the highest point farthest from the camshaft in conjunction with the movement of the rollers. To do. The drive mechanism converts the rotational motion of the cam into the reciprocating motion of the tappet via the rollers.

The plunger is driven by a drive mechanism and reciprocates integrally with the tappet. The cylinder is fixed to the housing, and the fuel sucked by the reciprocating motion of the plunger is pressurized at the plunger sliding hole (23) on which the plunger slides and at the end opposite to the drive mechanism of the plunger sliding hole. A pressurizing chamber (24) is formed.

The housing opens to the cam side from the center in the height direction at the lowest point of the tappet, and communicates with the tappet chamber directly from the fuel supply flow path or via the cam chamber (45). Is formed. Also, at least at the lowest point of the tappet, at least one of the outer walls of the tappet facing the opening of the tappet or at least one of the guide portions around the opening of the passage, holds one or more fluids that receive the fluid supplied from the passage. Chambers (61, 63, 64, 65, 66) are formed.

In the conventional technology for improving the lubricity of the sliding part, the supply path is basically formed on the plunger side with respect to the center in the height direction of the tappet in order to distribute the fuel to more parts of the sliding part. Will be done. On the other hand, the communication passage of the present invention is formed on the cam side from the center in the height direction at the lowest point of the tappet. Therefore, in the present invention, when the tappet tilts with the rotation of the cam and the gap volume of the tappet sliding portion rearward in the rotation direction expands, fuel is supplied to the fluid holding chamber from the communication passage. As a result, the pressure drop in the volume expansion portion is suppressed, and the amount of cavitation generated is reduced. Since the amount of cavitation generated is reduced, erosion can be reduced.

Overall configuration diagram of a V-shaped two-cylinder fuel injection pump according to the present embodiment. The schematic diagram explaining the movement of the camshaft by the change of the applied load direction at the time of switching a pumping cylinder. The schematic diagram explaining the influence on the lateral movement of a tappet by the movement of a camshaft. The whole block diagram which shows the pump unit of one of the fuel injection pumps by 1st Embodiment. FIG. 4 is a cross-sectional view of a drive mechanism portion at the lowest point of the tappet of the fuel injection pump of FIG. (A) FIG. 5 is a sectional view taken along line VIa-VIa, and (b) is a sectional view taken along line VIb-VIb. Sectional drawing of drive mechanism part when tappet rises. Sectional drawing of the drive mechanism part at the time of tappet descent. The cross-sectional view of the drive mechanism part of the fuel injection pump according to 2nd Embodiment. FIG. 9A is a sectional view taken along line Xa-Xa of FIG. 9, and FIG. 9B is a sectional view corresponding to FIG. 10A of a modified example of the second embodiment. FIG. 3 is a cross-sectional view of a drive mechanism portion of a fuel injection pump according to a third embodiment. FIG. 6 is a cross-sectional view of a drive mechanism portion of a fuel injection pump according to a fourth embodiment. (A) A cross-sectional view corresponding to the line XIIIa-XIIIa of FIG. 12 according to a modified example of the fourth embodiment, and (b) the same as above according to another modified example of the fourth embodiment. FIG. 5 is a cross-sectional view of a drive mechanism portion of a fuel injection pump according to a fifth embodiment. FIG. 6 is a cross-sectional view of a drive mechanism portion of a fuel injection pump according to a sixth embodiment. (A) sectional view taken along line XVIa-XVIa in FIG. 14, and (b) sectional view taken along line XVIb-XVIb in FIG.

Hereinafter, a plurality of embodiments of the fuel injection pump will be described with reference to the drawings. In a plurality of embodiments, substantially the same configuration is designated by the same reference numerals and description thereof will be omitted. Further, the first to sixth embodiments are collectively referred to as "the present embodiment". The fuel injection pump 100 of the present embodiment is applied, for example, as a supply pump for pumping high-pressure fuel to the common rail in a common rail system of a diesel engine.

First, with reference to FIG. 1, the overall configuration of the V-shaped two-cylinder fuel injection pump 100 will be described. The fuel injection pump 100 includes two pump units, a first pump unit 110 and a second pump unit 120, for one camshaft 16. The camshaft 16 has a cam 17 that rotates in conjunction with the output shaft of the internal combustion engine. In the present specification, one pump unit is referred to as a "cylinder", and a method including a plurality of pump units is referred to as a "multi-cylinder type".

Each pump unit includes a plunger 31 that reciprocates in the cylinder 20 to pressurize fuel, and a drive mechanism 50 that drives the plunger 31. That is, the multi-cylinder fuel injection pump includes a plurality of sets of cylinders 20, a plunger 31, and a drive mechanism 50. The drive mechanism 50 includes a roller 51 that abuts on the cam 17 and a tappet 54 that reciprocates along the inner wall of the tappet chamber 41 in response to the rotational movement of the cam 17. The detailed operation of the drive mechanism 50 will be described later.

In the present specification, the shafts of the pump units 110 and 120 are mainly represented with reference to the shafts Z1 and Z2 of the plunger 31. In the V-shaped two-cylinder fuel injection pump 100 shown in FIG. 1, the axes Z1 and Z2 of the two plungers 31 extend in different directions with respect to the camshaft 16, for example, in directions having an angle difference of about 90 °. ing. Further, when viewed from the side of the paper surface of FIG. 1, the axes Z1 and Z2 of the two plungers 31 are arranged on the same plane orthogonal to the camshaft 16.

Next, the fuel flow will be described. The solid arrow indicates the flow of fuel supplied from the fuel tank 1 to the fuel injection pump 100. The single-point chain arrow indicates the flow of fuel inside the fuel injection pump 100, and the fuel is sucked from the tappet chamber 41 into the pressurizing chamber 24 through the suction valve 22. The alternate long and short dash arrow indicates the flow of return fuel returned to the fuel tank 1. The dashed arrow indicates the flow of high-pressure fuel discharged from the pressurizing chamber 24 through the discharge valve 26, and the common rail at the tip of the dashed arrow is omitted. The high-pressure fuel supplied to the common rail is distributed to a plurality of fuel injection valves and injected into the cylinders of the internal combustion engine.

Regarding the flow indicated by the solid line arrow, the fuel pumped from the feed pump 2 installed in the fuel tank 1 is filtered by the main filter 3 and the secondary filter 4 in the fuel injection pump 100, and then the fuel supply flow path. It branches at 5 and flows into the cam chamber 18 and the regulate valve 7. The regulate valve 7 adjusts the fuel pressure within a predetermined range. The fuel after the regulate valve 7 merges with the fuel that has passed through the overflow orifice 8 from the fuel injection pump 100, and is returned to the fuel tank 1 through the return fuel path.

Further, fuel is directly supplied to the fluid holding chamber 61 provided in the tappet 54 of the second pump unit 120 from the branch point 6 of the fuel supply flow path 5 located upstream of the regulate valve 7, that is, on the fuel tank 1 side. To. On the other hand, fuel is supplied from the fuel supply flow path 5 to the fluid holding chamber 61 provided in the tappet 54 of the first pump unit 110 via the cam chamber 18. The configuration and operation of the fluid holding chamber 61 will be described later.

In the V-shaped two-cylinder fuel injection pump 100, the total pumping amount can be increased by alternately pumping fuel by the two pump units 110 and 120 at different timings. On the other hand, a unique problem arises due to the V-shaped arrangement. Next, problems peculiar to the V-shaped arrangement will be described with reference to FIGS. 2 and 3.

Of the two pump units 110 and 120, the pump unit that is pumping at that time is called a "pumping cylinder". In the two-cylinder fuel injection pump 100, the pressure feed cylinders are alternately replaced. At the timing of (I) in FIG. 2, the first pump unit 110 is a pumping cylinder, and at the timing of (II), the second pump unit 120 is a pumping cylinder. The block arrow indicates the camshaft acting force Fc. The enlarged view at the bottom of each figure shows the displacement of the camshaft 16 in the bush 15, and the hatched block arrow indicates the bush reaction force Fbr. The bush reaction force Fbr acts in the direction opposite to the camshaft acting force Fc.

The direction of the bush reaction force Fbr is the lower right direction at the time when the pumping of the first pump unit 110 is completed (I), but changes to the upper right direction during the pumping of the second pump unit 120 (II). Along with this, the position of the camshaft 16 in the bush moves. In this way, the moving speed of the camshaft 16 increases due to the change in the applied load direction when the pumping cylinder is switched.

FIG. 3 shows the behavior of the tappet 54 in the tappet chamber 41 of the housing 40. As will be described later, in the cam mechanism regardless of whether it is a single cylinder or a multi-cylinder, a force Fs that laterally moves the tappet 54 is generated as the cam 17 rotates. In addition to this, in the V-shaped arrangement, as shown in FIG. 2, the force Fmv of increasing the moving speed due to the change in the applied load direction has an influence. Therefore, the gap volume behind the cam 17 in the rotation direction is expanded, and the amount of cavitation generated is increased. Therefore, there is a possibility that cavitation erosion at the tappet sliding portion will increase more.

Therefore, the fuel injection pump 100 of the present embodiment forms a fluid holding chamber at a portion where the gap volume increases and negative pressure is generated in the tappet sliding portion, and supplies positive pressure fuel from the continuous passage to perform cavitation. Reduce the amount generated. Then, erosion is suppressed by reducing the amount of cavitation generated.

Hereinafter, specific solutions will be described for each embodiment. The code of the fuel injection pump of each embodiment is the number of the embodiment in the third digit following "10". In the following embodiment, the configuration of one pump unit will be described in detail. Further, for convenience, the plunger 31 side in one pump unit is referred to as "upper", and the cam 17 side is referred to as "lower". However, as is clear from the V-shaped arrangement, the direction connecting the plunger 31 and the cam 17 may be inclined with respect to the vertical direction.

(First Embodiment)
The fuel injection pump 101 of the first embodiment will be described with reference to FIGS. 4 to 8. FIG. 4 shows the same fuel flow as in FIG. 1 by rewriting the figure of one pump unit. The meaning of each line arrow conforms to FIG. The high-pressure fuel pressurized in the pressurizing chamber 24 is discharged to the common rail 9 through the discharge valve 26. 5, FIG. 7, and FIG. 8 show the lowest point of the tappet 54, and the cross sections of the drive mechanism 50 at the time of ascending and descending, respectively. 6 (a) and 6 (b) show the VIa-VIa line cross section and the VIb-VIb line cross section of FIG. 5, respectively.

The vertical center lines in FIGS. 5, 7 and 8 indicate the axis Z of the plunger 31 (hereinafter, referred to as “plunger axis Z”) that slides in the plunger sliding hole 23 of the cylinder 20. The roller 51 and the cam 17 rotate about a rotation axis orthogonal to the paper surface of FIG. 5, respectively. Ideally, when the lateral load shown in the figure is not applied to the cam 17 and the tappet 54, the rotation axis Yr of the roller 51 and the rotation axis Yc of the cam 17 intersect the plunger axis Z. The plane including the plunger axis Z and the rotation axis Yr of the roller 51 (or the rotation axis Yc of the cam 17) is referred to as Pyz. The plane Pyz overlaps the plunger axis Z in FIGS. 5, 7, and 8. Further, the plane Pyz is parallel to the paper surface of FIG. 6A, and overlaps the rotation axis Yr of the roller 51 and the axis Y parallel to the rotation axis Yc of the cam 17 in FIG. 6B.

First, mainly refer to FIGS. 5 and 6. The housing 40 is formed with a cam chamber 18 for accommodating the cam 17 and a tappet chamber 41 communicating with the cam chamber 18. Fuel or oil is retained in the cam chamber 18. The drive mechanism 50 including the tappet 54 is housed in the tappet chamber 41. The cylindrical inner wall of the tappet chamber 41 constitutes a guide portion 42 that guides the reciprocating movement of the tappet 54.

The drive mechanism 50 includes a roller 51, a shoe 52, and a tappet 54. The roller 51 comes into contact with the cam 17 and reciprocates while rotating along the shape of the cam 17. The shoe 52 is interposed between the roller 51 and the tappet 54 and rotatably supports the roller 51. The tappet 54 has a substantially cylindrical shape, is guided by a guide portion 42 formed by an inner wall of the tappet chamber 41, and reciprocates in conjunction with the movement of the roller 51. The drive mechanism 50 drives the plunger 31 by converting the rotational motion of the cam 17 into the reciprocating motion of the tappet 54 via the roller 51 and further transmitting the reciprocating motion of the tappet 54 to the plunger 31.

Hereinafter, the "radius of the cam 17 at the contact point between the cam 17 and the roller 51" is abbreviated as "contact radius". When the contact radius increases due to the rotation of the cam 17, the roller 51 and tappet 54 rise, and when the contact radius decreases, the roller 51 and tappet 54 descend. In this way, the tappet 54 reciprocates between the "lowest point" closest to the camshaft 16 and the "highest point" farthest from the camshaft 16.

The plunger 31 is driven by the drive mechanism 50 and reciprocates in the plunger sliding hole 23 of the cylinder 20 together with the tappet 54. The return spring 32 urges the tappet 54 toward the cam 17 via a seat 33 fixed to the lower end of the plunger 31. When the contact radius increases due to the rotation of the cam 17, the tappet 54 rises against the urging force of the return spring 32.

The cylinder 20 is fixed to the housing 40, and in addition to the plunger sliding hole 23 on which the plunger 31 slides, a suction passage 21, a pressurizing chamber 24, a discharge passage 25, and the like are formed. In the pressurizing chamber 24, the fuel sucked by the reciprocating motion of the plunger 31 is pressurized at the end of the plunger sliding hole 23 opposite to the drive mechanism 50.

Specifically, in the fuel suction stroke, the plunger 31 is lowered, the suction valve 22 is opened by a command from an ECU (not shown), and fuel is sucked from the suction passage 21 into the pressurizing chamber 24. In the pressurizing stroke, after the suction valve 22 is closed, the plunger 31 rises to pressurize the fuel in the pressurizing chamber 24. In the discharge stroke, the discharge valve 26 is opened by the pressure of the pressurized fuel, and the high-pressure fuel is discharged through the discharge passage 25.

In addition to such a basic configuration, particularly in the fuel injection pump 101 of the first embodiment, a communication passage 45 is formed in the housing 40. As described in FIGS. 1 and 4, the communication passage 45 communicates with the tappet chamber 41 directly from the branch point 6 upstream of the regulate valve 7 in the fuel supply passage 5 or via the cam chamber 18. .. The communication passage 45 opens toward the cam 17 from the state shown in FIG. 5, that is, the center in the height direction at the lowest point of the tappet 54. When the plane including the plunger axis Z and orthogonal to the rotation axis Yr of the roller is described as Pxz, as shown in FIG. 6A, the axis X of the communication passage exists on the plane Pxz.

Further, on the outer wall of the tappet 54, a fluid holding chamber 61 for receiving the fluid supplied from the communication passage 45, specifically, the fuel is formed. The fluid holding chamber 61 faces the opening of the communication passage 45 at least in the state of FIG. 5, that is, at the lowest point of the tappet. As shown in FIG. 6B, the fluid holding chamber 61 of the first embodiment is formed as an annular groove on the outer wall of the tappet 54. For example, a fixing pin 53 for fixing the housing 40 and the tappet 54 is provided at one position in the circumferential direction of the tappet 54. However, in other embodiments, the fixing pin may not be provided.

Subsequently, the action of the cam 17 during rotation will be described with reference to FIGS. 7 and 8. As shown in FIG. 7, when the contact radius of the cam 17 increases and the tappet 54 is pushed up, a force that pushes the lower end portion of the tappet 54 forward in the rotation direction and tilts the tappet 54 acts. Then, behind the rotation direction, the clearance between the outer wall of the tappet 54 and the inner wall of the tappet chamber 41 increases, and the gap volume increases.

If the housing 40 is not provided with the communication passage 45, the amount of cavitation generated increases due to the negative pressure generated in the volume expansion portion (* 1), so that the erosion due to the impact pressure at the time of cavitation collapse increases. However, in the first embodiment, fuel is supplied to the fluid holding chamber 61 from the communication passage 45 formed rearward in the rotation direction of the cam 17, so that the pressure drop of the volume expansion portion (* 1) is suppressed and cavitation. The amount of fuel generated is reduced. Since the amount of cavitation generated is reduced, erosion can be suppressed.

As shown in FIG. 8, after the tappet 54 exceeds the uppermost point, the tappet 54 descends as the contact radius of the cam 17 decreases. At this time, due to the urging force of the return spring 32, the tappet 54 is tilted in the direction opposite to that at the time of ascending, that is, so that the gap volume in front of the rotation direction is expanded. When the communication passage is not provided, the erosion generated in the state of FIG. 7 continues until the pressure of the volume expansion portion is restored, for example, to the state shown in FIG. On the other hand, in the first embodiment, the pressure of the volume expansion portion is restored quickly, and the time until the erosion is eliminated is shortened.

(effect)
As described above, in the present embodiment, when the tappet 54 is tilted with the rotation of the cam 17 and the gap volume of the tappet sliding portion rearward in the rotation direction is expanded, fuel is supplied from the communication passage 45 to the fluid holding chamber 61. To. As a result, the pressure drop in the volume expansion portion is suppressed, and the amount of cavitation generated is reduced. Since the amount of cavitation generated is reduced, erosion can be reduced. In particular, when applied to a V-shaped two-cylinder fuel injection pump that is affected by an increase in moving speed due to a change in the applied load direction, a remarkable effect is exhibited.

In addition to Patent Document 1 (Germany DE10201622556333A1), Japanese Patent Application Laid-Open No. 11-200989 and Japanese Patent No. 6394413 also have a configuration in which a passage communicating with the tappet sliding portion of the fuel injection pump is formed. However, all of these conventional techniques supply fuel or oil for lubrication from the upper part of the tappet sliding portion, and do not supply fuel aiming at a location where negative pressure is generated due to the inclination of the tappet. Therefore, the above-mentioned conventional technique does not have the effect of suppressing cavitation erosion of the tappet sliding portion.

The communication passage 45 of the present embodiment is formed behind the cam 17 in the rotation direction. Further, the axis X of the communication passage 45 exists on the plane Pxz including the plunger axis Z and orthogonal to the rotation axis Yr of the roller. As a result, fuel can be accurately supplied to the location where the negative pressure is generated due to the inclination of the tappet 54. Therefore, cavitation erosion can be effectively suppressed.

Further, in the present embodiment, the fuel supplied to the communication passage 45 is supplied from the branch point 6 upstream of the regulate valve 7, so that the fuel having a stable pressure is supplied. Therefore, it is not affected by the fluctuation of fuel pressure, the amount of cavitation generated can be stably reduced, and erosion can be suppressed.

(Second Embodiment)
Next, the fuel injection pump 102 of the second embodiment will be described with reference to FIGS. 9 and 10. In the cross-sectional view of the drive mechanism 50 portion shown in FIG. 9 and below, the cylinder 20 portion is not shown with respect to FIGS. 5, 7, and 8 of the first embodiment. In the second embodiment, the fluid holding chamber 63 is locally formed in the portion of the outer wall of the tappet 54 facing the communication passage 45 in the circumferential direction with respect to the fluid holding chamber 61 of the annular groove according to the first embodiment. In FIG. 9, the lower outer wall of the tappet 54 is recessed on the side of the passage 45 (right side of the figure) and straight on the side opposite to the passage 45 (right side of the figure).

For example, as shown in FIG. 10A, the local fluid holding chamber 63 has a groove bottom formed in a cylindrical surface shape concentric with the outer wall of the tappet 54. That is, in the axial cross-sectional view, the fluid holding chamber 63 has an arc shape having a constant radial width. In this configuration, it is possible to secure a large wall thickness of the tappet 54 into which the fixing pin 53 is fitted with respect to the annular groove of the first embodiment. In the modified example shown in FIG. 10B, the groove bottom of the local fluid holding chamber 64 is formed to be flat. That is, in the axial cross-sectional view, the groove bottom of the fluid holding chamber 64 corresponds to a circular string constituting the outer wall. With this configuration, grooving becomes easier.

(Third Embodiment)
Next, the fuel injection pump 103 of the third embodiment will be described with reference to FIG. First, in the first embodiment, the communication passage 45 that opens toward the cam 17 side from the center in the height direction at the lowest point of the tappet 54 is paraphrased as "lower communication passage 45". Similarly, the fluid holding chamber 61 formed on the outer wall on the cam 17 side of the center of the tappet 54 in the height direction is paraphrased as the "lower fluid holding chamber 61". In the third embodiment, in addition to the lower passage 45, the upper passage 46 is further formed in the housing 40. Further, in addition to the lower fluid holding chamber 61, an upper fluid holding chamber 62 is formed on the outer wall of the tappet 54.

The upper passage 46 opens toward the plunger 31 from the center in the height direction at the lowest point of the tappet 54. The upper passage 46 communicates with the tappet chamber 41 directly from the fuel supply passage 5 or via the cam chamber 18, similarly to the lower passage 45. The upper fluid holding chamber 62 is formed on the outer wall on the plunger 31 side of the center of the tappet 54 in the height direction, and receives the fluid supplied from the upper communication passage 46.

The upper passage 46 and the upper fluid holding chamber 62 are positioned symmetrically with respect to the lower connecting passage 45 and the lower fluid holding chamber 61 with respect to the visual direction of FIG. 11, that is, the center of the tappet 54 viewed from the rotation axis Yr direction of the roller 51. Is located in. That is, the upper passage 46 is formed in front of the cam 17 in the rotation direction. The lower fluid holding chamber 61 and the upper fluid holding chamber 62 shown in FIG. 11 are both formed as annular grooves, but according to the second embodiment, a portion facing the lower continuous passage 45 or the upper continuous passage 46. A fluid retention chamber may be locally formed in the area.

As shown in FIG. 11, when the contact radius of the cam 17 increases and the tappet 54 is pushed up, the gap volume of the tappet sliding portion expands on the lower left side of the figure and at the same time also on the upper right side of the figure corresponding to the diagonal portion. Expanding. Therefore, fuel is supplied from the upper passage 46 in addition to the lower passage 45 to suppress the pressure drop in both the (* 1) and (* 2) portions where the volume expands, so that the tappet 54 is diagonal. Erosion can be suppressed in the section.

(Fourth Embodiment)
Next, the fuel injection pump 104 of the fourth embodiment will be described with reference to FIGS. 12 and 13. The fourth embodiment faces the lower opposed passage 45C facing the lower passage 45 and the upper passage 46 with the plane Pyz including the plunger shaft Z and the axis Yr of the roller 51 sandwiched between the third embodiment. An upper opposed passage 46C is further formed in the housing 40. That is, the lower opposed passage 45C is formed in front of the cam 17 in the rotation direction, and the upper facing passage 46C is formed in the rear of the cam 17 in the rotation direction.

In the configuration in which the lower fluid holding chamber 61 is formed in an annular shape, the lower fluid holding chamber 61 commonly corresponds to the lower connecting passage 45 and the lower opposed connecting passage 45C. Further, in the configuration in which the upper fluid holding chamber 62 is formed in an annular shape, the upper fluid holding chamber 62 commonly corresponds to the upper connecting passage 46 and the upper opposed connecting passage 46C.

In addition, a configuration example of the fluid holding chamber of the modified example of the fourth embodiment is shown in FIGS. 13 (a) and 13 (b). 13 (a) and 13 (b) exemplify the cross sections of the lower passage 45 and the lower facing passage 45C, but the same applies to the upper passage 46 and the upper facing passage 46C. In the example shown in FIG. 13 (a), two fluid holding chambers 63, 63C having a cylindrical groove bottom according to FIG. 10 (a) are individually formed at symmetrical positions with a plane Pyz in between. In the example shown in FIG. 13 (b), two fluid holding chambers 64 and 64C having a flat groove bottom according to FIG. 10 (b) are individually formed at symmetrical positions with the flat surface Pyz in between.

As shown in FIG. 8, when the contact radius of the cam 17 decreases and the tappet 54 descends from the uppermost point, the gap volume in front of the rotation direction increases. Therefore, fuel is supplied from the lower facing passage 45C and the upper facing passage 46C to suppress both the pressure drop in the (* 3) and (* 4) portions where the volume is expanded, so that the tappet 54 is lowered. Cavitation can be reduced and erosion can be suppressed.

In addition to the lower passage 45 and the upper passage 46, only one of the lower facing passage 45C and the upper facing passage 46C may be formed. Alternatively, the upper passage 46 may not be provided, and only the lower passage 45 and the lower facing passage 45C may be provided.

(Fifth and sixth embodiments)
Next, the fuel injection pumps 105 and 106 of the fifth and sixth embodiments will be described with reference to FIGS. 14 to 16. In the first embodiment and the like, the fluid holding chamber 61 is formed on the outer wall of the tappet 54 facing the opening of the communication passage 451. In the fifth and sixth embodiments, the communication passage 451 is formed on the housing 40 side. Fluid holding chambers 65 and 66 are formed in the guide portion 42 around the opening.

In the fifth embodiment shown in FIGS. 14 and 16 (a), the fluid holding chamber 65 includes the periphery of the opening of the guide portion 42 and is formed as an annular groove along the inner circumference. In the sixth embodiment shown in FIGS. 15 and 16 (b), the fluid holding chamber 66 is locally formed only around the opening of the guide portion 42.

As described above, even in the configuration in which the fluid holding chambers 65 and 66 are formed in the guide portion 42 of the housing 40, the same effect as the configuration in which the fluid holding chamber 61 is formed in the outer wall of the tappet 54 can be obtained. A fluid holding chamber may be formed in both the outer wall of the tappet 54 and the guide portion 42 of the housing 40. Further, in combination with the third and fourth embodiments, a fluid holding chamber corresponding to the upper communication passage 46 may be formed in the guide portion 42 of the housing 40.

(Other embodiments)
(A) In the above embodiment, there is one continuous passage having the same function. In the third embodiment, two types of passages, a lower passage 45 and an upper passage 46, are included, and in the fourth embodiment, four types of passages including the opposite passage are included. For example, rearward in the rotation direction. There is only one communication passage 45 provided at the bottom. On the other hand, for example, a plurality of communication passages may be provided in parallel at the lower portion rearward in the rotation direction. That is, the communication passage from the fuel supply passage 5 may branch in the middle, and fuel may be supplied to the tappet chamber 41 from a plurality of openings.

(B) The drive mechanism of the plunger 31 may be configured so that the shoe 52 is not provided as in the above embodiment and the movement of the roller 51 is directly transmitted to the tappet 54.

(C) The present invention is not limited to the V-shaped two-cylinder fuel injection pump, and many pump units are arranged in parallel on different planes orthogonal to the camshaft 16 at the same angle or at different angles. It may be applied to a tubular fuel injection pump. Further, the present invention may be applied not only to a multi-cylinder fuel injection pump but also to a single cylinder fuel injection pump.

(D) The fuel injection pump of the present invention is not limited to a diesel engine, and may be used as a fuel pump for a gasoline engine or the like.

As described above, the present invention is not limited to the above-described embodiment, and can be implemented in various embodiments without departing from the spirit of the present invention.

100 ... Fuel injection pump, 1 ... Fuel tank, 5 ... Fuel supply flow path,
16 ... camshaft, 17 ... cam, 18 ... cam chamber,
20 ... Cylinder, 23 ... Plunger sliding hole, 24 ... Pressurized chamber,
31 ... Plunger,
40 ... Housing, 41 ... Tappet room, 42 ... Guide section,
45 ... (lower) passageway,
50 ... Drive mechanism, 51 ... Roller 51 ... Tappet,
61, 63, 64, 65, 66 ... (Lower) Fluid retention chamber.

Claims (8)

A camshaft (16) having a cam (17) that rotates in conjunction with the output shaft of an internal combustion engine.
A cam chamber (18) for accommodating the cam and a housing (40) in which a tappet chamber (41) communicating with the cam chamber is formed and fuel or oil is retained in the cam chamber.
It is guided by a roller (51) that comes into contact with the cam and reciprocates while rotating along the shape of the cam, and a guide portion (42) formed by the inner wall of the tappet chamber, and is linked to the movement of the roller. The tappet (54) reciprocates between the lowest point closest to the camshaft and the highest point farthest from the camshaft, and the rotational movement of the cam is performed by the tappet via the roller. One or more drive mechanisms (50) that convert to reciprocating motion,
One or more plungers (31) driven by the drive mechanism and reciprocating integrally with the tappet.
Fuel sucked by the reciprocating motion of the plunger at the plunger sliding hole (23) fixed to the housing and sliding the plunger and the end of the plunger sliding hole on the opposite side of the drive mechanism. One or more cylinders (20) in which a pressurizing chamber (24) to be pressurized is formed, and
A fuel injection pump that pressurizes and discharges fuel supplied from the fuel tank (1) via the fuel supply flow path (5).
One or more of the housings open to the cam side from the center in the height direction at the lowest point of the tappet and communicate with the tappet chamber directly from the fuel supply flow path or via the cam chamber. A continuous passage (45) is formed.
One that receives the fluid supplied from the communication passage to at least one of the outer wall of the tappet facing the opening of the communication passage at the lowest point of the tappet or the guide portion around the opening of the communication passage. A fuel injection pump in which the above fluid holding chambers (61, 63, 64, 65, 66) are formed. The fuel injection pump according to claim 1, wherein at least one axis (X) of the communication passage exists on a plane (Pxz) including the axis (Z) of the plunger and orthogonal to the rotation axis (Yr) of the roller. .. The fuel injection pump according to claim 2, wherein at least one of the communication passages is formed rearward in the rotation direction of the cam. A regulate valve (7) for adjusting the fuel pressure within a predetermined range is provided in the fuel supply flow path.
The fuel injection pump according to any one of claims 1 to 3, wherein the communication passage communicates with the tappet chamber from the fuel tank side of the regulate valve in the fuel supply flow path. A multi-cylinder fuel injection pump including a plurality of sets of the cylinder, the plunger, and the drive mechanism.
The fuel injection pump according to any one of claims 1 to 4, wherein the shafts of the plurality of plungers extend in different directions with respect to the camshaft. A multi-cylinder fuel injection pump including a plurality of sets of the cylinder, the plunger, and the drive mechanism.
The fuel injection pump according to any one of claims 1 to 5, wherein the axes of the plurality of plungers are arranged on the same plane orthogonal to the camshaft. Assuming that the communication passage is a lower communication passage and the fluid holding chamber is a lower fluid holding chamber,
One or more of the housings open toward the plunger side from the center in the height direction at the lowest point of the tappet and communicate with the tappet chamber directly from the fuel supply passage or via the cam chamber. The upper passageway (46) is further formed.
A fluid supplied from the upper passage is applied to at least one of the outer wall of the tappet facing the opening of the upper passage at the lowest point of the tappet or the guide portion around the opening of the upper passage. One or more upper fluid holding chambers (62) to receive are further formed.
The upper communication passage and the upper fluid holding chamber are arranged symmetrically with respect to the center of the tappet as viewed from the rotation axis direction of the roller and the lower communication passage and the lower fluid holding chamber. The fuel injection pump according to any one of 6. The housing has a lower opposed passage (45C) facing the lower passage with a plane (Pyz) including a shaft (Z) of the plunger and a rotation shaft (Yr) of the roller, and the upper passage. The fuel injection pump according to claim 7, wherein at least one of the upper opposed communication passages (46C) facing the vehicle is further formed.

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