Fuel pump

Abstract

To secure excellent workability between a plunger and a plunger barrel, and suppress increase in machining costs, in a fuel pump.SOLUTION: A fuel pump comprises: a pump head; a plunger barrel provided with a support hole, and having one axial end side of the support hole fastened to the pump head; a plunger supported in the support hole so as to be movable along an axial direction; a pressurization chamber defined by one end of the support hole and one axial end of the plunger; a fuel discharge passage, one end of which communicates with the pressurization chamber; a fuel suction passage, one end of which communicates with the fuel discharge passage; and a recess provided on at least one of the inner surface of the one end of the support hole and the outer surface of the one end of the plunger.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a fuel pump applied to an internal combustion engine.

Background Art

[0002] For example, a common rail type fuel injection device applied to a diesel engine includes a fuel pump, a common rail, and a fuel injection valve. The fuel pump sucks and pressurizes the fuel in the fuel tank and supplies it to the common rail as high-pressure fuel. The common rail holds the high-pressure fuel supplied from the fuel pump at a predetermined pressure. The fuel injection valve injects the high-pressure fuel in the common rail into the combustion chamber of the diesel engine by opening and closing the injection valve. The fuel pump includes a plunger barrel, a plunger, a suction valve, and a discharge valve. When the plunger moves in one direction inside the plunger barrel, the suction valve is opened to suck fuel into the pressurizing chamber. When the plunger moves in the other direction inside the plunger barrel, the fuel in the pressurizing chamber is pressurized, the discharge valve is opened, and the high-pressure fuel is discharged. As such a fuel pump, for example, there is one described in Patent Document 1 below.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The fuel pump sucks low-pressure fuel into the pressurizing chamber by the reciprocating movement of the plunger and discharges the pressurized high-pressure fuel. The plunger is movably supported in a support hole provided in the plunger barrel, and the pressurizing chamber is provided at an end of the support hole. Since the pressurizing chamber holds high-pressure fuel, a high-precision clearance is required between the plunger and the support hole. Further, the plunger moves through the support hole at high speed and Under high pressure conditionsSince it moves, high reliability against seizure is also required.

[0005] Conventionally, the plunger barrel is bolted to the pump body. In this case, a plurality of bolts passing through the pump body are screwed around the support holes in the plunger barrel, so that the plunger barrel is fastened to the pump body. Since high sealing performance needs to be ensured between the pump body and the plunger barrel, they are fastened with a high bolt axial force. At this time, the plunger barrel is elastically deformed by the fastening force of the bolts, and the roundness of the support holes decreases. Then, it becomes difficult to ensure a high-precision clearance between the plunger and the support holes, leading to the problem of a decrease in reliability against seizure. As a countermeasure, it is conceivable to perform grinding on the support holes after fastening using a jig that is the same as the actual elastic deformation. However, this processing requires a dedicated jig, resulting in an increase in manufacturing cost and working time.

[0006] The present disclosure solves the above-described problems, and an object thereof is to provide a fuel pump that ensures good operability between the plunger and the plunger barrel and suppresses an increase in processing cost.

Means for Solving the Problems

[0007] The fuel pump of the present disclosure for achieving the above object includes a pump head, a plunger barrel provided with support holes and having one end side in the axial direction of the support holes fastened to the pump head, a plunger movably supported along the axial direction in the support holes, a pressurizing chamber defined by one end of the support holes and one end of the plunger in the axial direction, a fuel discharge passage having one end communicating with the pressurizing chamber, a fuel suction passage having one end communicating with the fuel discharge passage, and a recess provided on at least one of the inner surface of one end of the support holes or the outer surface of one end of the plunger.

Effects of the Invention

[0008] According to the fuel pump of the present disclosure, good operability between the plunger and the plunger barrel can be ensured, and an increase in processing cost can be suppressed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited by this embodiment, and when there are a plurality of embodiments, those configured by combining each embodiment are also included. In addition, the constituent elements in the embodiments include those that can be easily assumed by those skilled in the art, substantially the same ones, and those within the so-called equivalent range.

[0011] <Fuel Injection Device> FIG. 1 is a schematic configuration diagram showing the fuel injection device of the present embodiment.

[0012] As shown in FIG. 1, the fuel injection device 10 is mounted on a diesel engine (internal combustion engine). The fuel injection device 10 includes a fuel pump 11, a common rail 12, and a plurality of fuel injection valves 13.

[0013] The fuel pump 11 is connected to the fuel tank 14 via the fuel line L11. The fuel pump 11 sucks the fuel stored in the fuel tank 14 from the fuel line L11, pressurizes it, and generates high-pressure fuel. The fuel pump 11 is connected to the common rail 12 via the fuel high-pressure line L12. The common rail 12 adjusts the high-pressure fuel supplied from the fuel pump 11 to a predetermined pressure. The common rail 12 is connected to the fuel injection valves 13 via a plurality (four in this embodiment) of fuel supply lines L13. The fuel injection valve 13 injects the high-pressure fuel in the common rail 12 into each cylinder (combustion chamber) of the diesel engine by opening and closing the injection valve.

[0014] <Fuel pump> FIG. 2 is a longitudinal sectional view showing the fuel pump of this embodiment, and FIG. 3 is a sectional view taken along line III-III of FIG. 2 showing the longitudinal section of the fuel pump. The fuel pump described below has a form in which three plungers are arranged, but is not limited to the number of plungers.

[0015] Figures 2 and 3 As shown in the figure, the fuel pump 11 is configured with a housing by bolting the retainer 21, the pump case 22, and the pump head 23 together. The pump case 22 has a camshaft 24 disposed inside. The camshaft 24 is rotatably supported by the retainer 21 at each end in the axial direction by bearings 25 and 26. One end of the camshaft 24 in the axial direction protrudes outside the retainer 21, and driving force is input from the diesel engine. The camshaft 24 is provided with a plurality (three in this embodiment) of cams 27, 28, and 29 at intervals in the axial direction. The cams 27, 28, and 29 have different circumferential phases.

[0016] The retainer 21 is fastened to the pump case 22 by a plurality of bolts 30. The plurality of bolts 30 penetrate the retainer 21 and the tip ends are screwed into the pump case 22. The pump head 23 is fastened to the pump case 22 by a plurality of bolts 31. The plurality of bolts 31 penetrate the pump head 23 and are screwed into the pump case 22.

[0017] The pump case 22 and the pump head 23 have three plunger barrels 32, 33, 34 arranged therein. Each of the plunger barrels 32, 33, 34 has a similar configuration. The pump case 22 and the pump head 23 are provided with three accommodation holes 35, 36, 37 along a direction orthogonal to the axial direction of the camshaft 24. The accommodation holes 35, 36, 37 are formed across the pump case 22 and the pump head 23. Each of the plunger barrels 32, 33, 34 is arranged in each of the accommodation holes 35, 36, 37. That is, each of the plunger barrels 32, 33, 34 has a first shaft portion 32a, 33a, 34a, a second shaft portion 32b, 33b, 34b, and a third shaft portion 32c, 33c, 34c along the axial direction. The outer diameters of the plunger barrels 32, 33, 34 decrease in the order of the first shaft portion 32a, 33a, 34a, the second shaft portion 32b, 33b, 34b, and the third shaft portion 32c, 33c, 34c. The plunger barrels 32, 33, 34 are supported by the accommodation holes 35, 36, 37 with the first shaft portions 32a, 33a, 34a.

[0018] Each of the plunger barrels 32, 33, 34 has support holes 38, 39, 40 formed therein along the axial direction. The support holes 38, 39, 40 penetrate each of the plunger barrels 32, 33, 34 in the axial direction. Plungers 41, 42, 43 are arranged in the support holes 38, 39, 40 of each of the plunger barrels 32, 33, 34. Each of the plungers 41, 42, 43 is supported movably along the axial direction in the support holes 38, 39, 40 of each of the plunger barrels 32, 33, 34.

[0019] Tappets 44, 45, 46 and rollers 47, 48, 49 are respectively arranged between plungers 41, 42, 43 and cams 27, 28, 29. The rollers 47, 48, 49 are rotatably supported by the tappets 44, 45, 46 by support shafts 50, 51, 52. Spring sheets 41a, 42a, 43a are arranged at the axial lower ends of the plungers 41, 42, 43. Compression coil springs 53, 54, 55 are arranged between the plunger barrels 32, 33, 34 and the spring sheets 41a, 42a, 43a. The compression coil springs 53, 54, 55 press the plungers 41, 42, 43 against the tappets 44, 45, 46 by the biasing force acting on the spring sheets 41a, 42a, 43a, and press the rollers 47, 48, 49 against the cams 27, 28, 29 via the tappets 44, 45, 46. The outer peripheral surfaces of the rollers 47, 48, 49 contact the outer peripheral surfaces of the cams 27, 28, 29.

[0020] Pressurizing chambers 56, 57, 58 are formed on one axial end side in the support holes 38, 39, 40 of the plunger barrels 32, 33, 34. The pressurizing chambers 56, 57, 58 are partitioned by the inner peripheral surfaces of the support holes 38, 39, 40, the end surfaces on one axial end side of the plungers 41, 42, 43, and the end surfaces of the discharge valves 64, 65, 66 and the intake valves 61, 62, 63 described later. By moving the plungers 41, 42, 43 to one axial end side of the support holes 38, 39, 40, the fuel sucked into the pressurizing chambers 56, 57, 58 can be pressurized.

[0021] The pump head 23 has suction valves 61, 62, 63 and discharge valves 64, 65, 66 disposed therein. The pump head 23 is provided with fuel passages 67, 68, 69 that communicate with the support holes 38, 39, 40 of the plunger barrels 32, 33, 34, respectively. The fuel passages 67, 68, 69 are arranged in a straight line with the support holes 38, 39, 40. One end of each of the fuel passages 67, 68, 69 communicates with the support holes 38, 39, 40, one end of the intake passages (fuel intake passages) 70, 71, 72 communicates with a middle portion thereof, and one end of the discharge passages (fuel discharge passages) 73, 74, 75 communicates with the other end thereof. The intake passages 70, 71, 72 are provided in a direction perpendicular to the fuel passages 67, 68, 69. Note that the fuel passages 67, 68, 69 also serve as part of the fuel intake passage and the fuel discharge passage.

[0022] The intake passages 70, 71, 72 have the suction valves 61, 62, 63 disposed therein. The suction valves 61, 62, 63 are biased in a direction to open the intake passages 70, 71, 72 by compression coil springs 76, 77, 78 and operate to close the intake passages 70, 71, 72 by actuators 79, 80, 81. The discharge passages 73, 74, 75 have the discharge valves 64, 65, 66 disposed therein. The discharge valves 64, 65, 66 are biased in a direction to close the discharge passages 73, 74, 75 by compression coil springs 82, 83, 84 and operate to open the discharge passages 73, 74, 75 by fuel pressure. In this case, the pressurized chambers 56, 57, 58 communicate with the fuel passages 67, 68, 69 and the intake passages 70, 71, 72.

[0023] The three intake passages 70, 71, and 72 communicate with each other through a communication passage (fuel intake side communication passage) 85. The fuel line L11 from the fuel tank 14 (both are shown in FIG. 1) is connected to the communication passage 85. Plugs 86 and 87 are attached to the other ends of the discharge passages 73 and 75 to close them. A connector 88 is attached to the other end of the discharge passage 74. Further, the three discharge passages 73, 74, and 75 communicate with each other through a communication passage (fuel discharge side communication passage) 89. The connector 88 is connected to the common rail 12 (both are shown in FIG. 1) via a fuel high-pressure line L12. Note that the communication passage 89 communicates the discharge passages 73, 74, and 75. It may be arranged in a straight line so as to intersect the discharge passages 73, 74, and 75 and may be in direct communication, or may be arranged offset in a direction perpendicular to the plane of FIG. 2 with respect to the discharge passages 73, 74, and 75 and be in indirect communication.

[0024] Therefore, when the camshaft 24 rotates, the rotational force is converted into a reciprocating force by the cams 27, 28, and 29 and transmitted to the rollers 47, 48, 49 and the tappets 44, 45, 46. The movement of the rollers 47, 48, 49 and the tappets 44, 45, 46 causes the plungers 41, 42, 43 to reciprocate along the axial direction in the support holes 38, 39, 40 of the plunger barrels 32, 33, 34. The intake valves 61, 62, 63 open the intake passages 70, 71, 72. When the plungers 41, 42, 43 move to the other side in the axial direction (the lower side in FIGS. 2 and 3), the low-pressure fuel in the communication passage 85 is inhaled into the pressurizing chambers 56, 57, 58 through the intake passages 70, 71, 72 and the fuel passages 67, 68, 69. After the plungers 41, 42, 43 reach the bottom dead center, when the actuators 79, 80, 81 are actuated in the process of moving toward the top dead center, the intake valves 61, 62, 63 move against the biasing force of the compression coil springs 76, 77, 78 to close the intake passages 70, 71, 72.

[0025] When the plungers 41, 42, and 43 move to one axial side (the upper side in FIGS. 2 and 3) with low-pressure fuel being inhaled into the pressure chambers 56, 57, and 58, before the actuators 79, 80, and 81 operate, the low-pressure fuel is inhaled from the intake passages 70, 71, and 72, passes through the intake valves 61, 62, and 63, and is returned to the communication passage 85. After the actuators 79, 80, and 81 operate, the low-pressure fuel is blocked by the intake valves 61, 62, and 63, and as the volumes of the pressure chambers 56, 57, and 58 decrease, the low-pressure fuel in the pressure chambers 56, 57, and 58 is pressurized. When the low-pressure fuel in the pressure chambers 56, 57, and 58 is pressurized to a predetermined pressure, the discharge valves 64, 65, and 66 move against the biasing force of the compression coil springs 82, 83, and 84 and the pressure received from the common rail 12 to open the discharge passages 73, 74, and 75. Then, the high-pressure fuel in the pressure chambers 56, 57, and 58 is discharged from the fuel passages 67, 68, and 69 to the discharge passages 73, 74, and 75. And the high-pressure fuel in the discharge passages 73, 74, and 75 merges at the communication passage 89 and is discharged from the connector 88 to the fuel high-pressure line L12 (see FIG. 1). After that, when the plungers 41, 42, and 43 reach the top dead center and the discharge of the high-pressure fuel ends, and when the plungers 41, 42, and 43 start to move to the other axial side, as the volumes of the pressure chambers 56, 57, and 58 increase, the pressure in the pressure chambers 56, 57, and 58 decreases, and the discharge valves 64, 65, and 66 move by the biasing force of the compression coil springs 82, 83, and 84 and the pressure received from the common rail 12 to close the discharge passages 73, 74, and 75.

[0026] <Plunger and plunger barrel> FIG. 4 is an enlarged view showing the configuration of the plunger and the plunger barrel. Since each plunger 41, 42, 43 and each plunger barrel 32, 33, 34 have substantially the same configuration, only the plunger 41 and the plunger barrel 32 will be described.

[0027] As shown in FIG. 4, the pump head 23 is fastened to the pump case 22 by bolts 31. The pump case 22 and the pump head 23 are provided with accommodation holes 35 inside, and the plunger barrel 32 is supported by the accommodation holes 35. That is, the first shaft portion 32a of the plunger barrel 32 is accommodated in the accommodation hole 35. One end side in the axial direction of the plunger barrel 32 is fastened to the pump head 23. A plurality of bolts 91 penetrate the pump head 23, and the male screw portion 91a at the tip is screwed into the periphery of the support hole 38 in the plunger barrel 32, that is, the female screw portion 32d of the first shaft portion 32a. Here, the female screw portion 32d is formed in a range of length A1 from the end face of the first shaft portion 32a toward the other end side in the axial direction of the plunger barrel 32.

[0028] The plunger barrel 32 is formed with a support hole 38, and the plunger 41 is movably supported by the support hole 38. The pump head 23 is provided with a fuel passage 67 that communicates with the support hole 38. The fuel passage 67 communicates with the suction passage 70 and also communicates with the discharge passage 73. The suction passage 70 is provided with a suction valve 61 (see FIG. 3), and the fuel passage 67 and the discharge passage 73 are provided with a discharge valve 64.

[0029] The pressurizing chamber 56 is configured to be partitioned by the inner peripheral surface of the support hole 38, the end face 41b of the plunger 41, and the end face of the discharge valve 64. A plurality of bolts 91 penetrate the pump head 23, and the male screw portion 91a is screwed into the female screw portion 32d of the plunger barrel 32, whereby the plunger barrel 32 is fastened to the pump head 23. At this time, the plunger barrel 32 is pulled up by the bolt 91 so that the first shaft portion 32a is pulled toward the pump head 23 side, and the end face 32a1 of the first shaft portion 32a is in close contact with the end face 35a1 of the first hole 35a of the pump head 23, thereby forming a seal portion between the end face 32a1 of the first shaft portion 32a and the end face 35a1 of the first hole 35a, and ensuring the sealing performance.

[0030] Incidentally, as described above, the plunger barrel 32 is fastened to the pump head 23 by a plurality of bolts 91. Then, due to the fastening force of the bolts 91, the plunger barrel 32 is elastically deformed, and the roundness of the support hole 38 decreases. Then, it becomes difficult to ensure a high-precision clearance between the plunger 41 and the support hole 38. In particular, in the support hole 38, one end side in the axial direction of the plunger barrel 32 that is screwed into the male screw portion 91a of the bolt 91 is likely to be deformed.

[0031] Therefore, in the present embodiment, a recess 101 is provided on the outer peripheral surface of one end portion in the axial direction of the plunger 41. That is, the plunger 41 has a cylindrical shape, and the outer peripheral surface is arranged concentrically with the inner peripheral surface of the support hole 38. And the plunger 41 forms the recess 101 by making the outer diameter of one end portion on the pressure chamber 56 side smaller than the outer diameter of other portions.

[0032] The recess 101 is provided in a range of a predetermined length A2 from the end surface 41b on one end side of the plunger 41 toward the other end side. And the recess 101 is provided up to the other end side in the axial direction of the plunger 41 from the screwing position where the male screw portion 91a of the bolt 91 is screwed into the plunger barrel 32. That is, when the plunger 41 is at the top dead center position, the position P2 on the other side (the lower side in FIG. 4) of the plunger 41 in the recess 101 is preferably located on the other side (the lower side in FIG. 4) than the position P1 on the other side (the lower side in FIG. 4) of the female screw portion 32e of the plunger barrel 32. Threaded portion 32d to the plunger barrel 32.

[0033] Further, the plunger 41 and the support hole 38 are cylindrical. In order for the plunger 41 to move axially in the support hole 38, it is necessary to ensure a minute gap between the outer peripheral surface of the plunger 41 and the inner peripheral surface of the support hole 38. The minute gap is set, for example, to have a radial length of 0.005 mm (5 microns). On the other hand, at one end of the plunger 41 and the support hole 38, a gap is provided between the outer peripheral surface of one end of the plunger 41 and the inner peripheral surface of one end of the support hole 38 by the recess 101. The recess 101 formed at one end of the plunger 41 is set to have a radial length in the range of 0.05 mm to 0.2 mm. Therefore, the length of the gap formed between the outer peripheral surface of one end of the plunger 41 and the inner peripheral surface of one end of the support hole 38 by the recess 101 is the sum of the length of the minute gap and the length of the recess 101.

[0034] And, the radial length of the recess 101 provided on the outer peripheral surface of the plunger 41 is set to be 10 to 40 times the length of the minute radial gap between the inner peripheral surface of the support hole 38 where the recess 101 is not provided and the outer peripheral surface of the plunger 41.

[0035] Note that since the volume of the pressure chamber 56 when the plunger 41 is at the bottom dead center affects the compression efficiency, it is preferable to design while minimizing the volume increase due to the recess 101.

[0036] Therefore, even if the plunger barrel 32 is elastically deformed by the fastening force of the bolt 91 and the roundness on the one - end side of the support hole 38 is reduced, the recess 101 is provided on the outer peripheral surface of the axially one - end of the plunger 41, so that a gap larger than the minute gap is secured between the outer peripheral surface of the one - end of the plunger 41 and the inner peripheral surface of the support hole 38, and the plunger 41 can move smoothly in the support hole 38.

[0037] <Modification example of the plunger and the plunger barrel> FIG. 5 is an enlarged view showing a modification example of the configuration of the plunger and the plunger barrel.

[0038] In a modification of this embodiment, as shown in FIG. 5, a recess 102 is provided on the inner peripheral surface of one axial end portion in the support hole 38 of the plunger barrel 32. That is, the support hole 38 has a cylindrical shape, and the inner peripheral surface is arranged concentrically with the outer peripheral surface of the plunger 41. And the support hole 38 forms the recess 102 by making the inner diameter of one end portion on the pressure chamber 56 side larger than the outer diameter of the other portion.

[0039] The recess 102 is provided in a range of a predetermined length A3 from the end face 32a1 of the first shaft portion 32a of the plunger barrel 32 toward the other end portion side. And the recess 102 is provided up to the other end portion side in the axial direction of the support hole 38 from the screwing position where the male screw portion 91a of the bolt 91 is screwed into the female screw portion 32e of the plunger barrel 32. That is, the position P3 on the other side (the lower side in FIG. 5) of the support hole 38 in the recess 102 is preferably located on the other side (the lower side in FIG. 5) than the position P1 on the other side (the lower side in FIG. 5) of the female screw portion 32e of the plunger barrel 32.

[0040] Note that the radial length of the recess 102 in the support hole 38 is preferably the same as the length of the recess 101.

[0041] Also, since the volume of the pressure chamber 56 when the plunger 41 is at the bottom dead center affects the compression efficiency, it is preferable to design so as to suppress the volume increase due to the recess 102 as much as possible.

[0042] Therefore, even if the plunger barrel 32 is elastically deformed by the fastening force of the bolt 91 and the roundness of one end portion side of the support hole 38 is reduced, the recess 102 is provided on the outer peripheral surface of one axial end portion in the support hole 38, so that a gap larger than the minute gap is secured between the outer peripheral surface of one end portion of the plunger 41 and the inner peripheral surface of the support hole 38, and the plunger 41 can move smoothly in the support hole 38.

[0043] [Advantages and effects of this embodiment] The fuel pump according to the first aspect includes a pump head 23, plunger barrels 32, 33, 34 provided with support holes 38, 39, 40 and having one axial end portion side of the support holes 38, 39, 40 fastened to the pump head 23, plungers 41, 42, 43 movably supported along the axial direction in the support holes 38, 39, 40, pressure chambers 56, 57, 58 defined by one end portion of the support holes 38, 39, 40 and one axial end portion of the plungers 41, 42, 43, fuel passages (fuel discharge passages) 67, 68, 69 having one end portion communicating with the pressure chambers 56, 57, 58, suction passages (fuel suction passages) 70, 71, 72 having one end portion communicating with the fuel passages (fuel discharge passages) 67, 68, 69, and recesses 101, 102 provided on at least one of the inner surface of one end portion of the support holes 38, 39, 40 or the outer surface of one end portion of the plungers 41, 42, 43.

[0044] According to the fuel pump according to the first aspect, the recesses 101, 102 are provided on at least one of the inner peripheral surface of the support holes 38, 39, 40 or the outer peripheral surface of the plungers 41, 42, 43, so that a gap is secured between the outer peripheral surface of one end portion of the plunger 41 and the inner peripheral surface of the support hole 38. Therefore, even if the plunger barrel 32 is elastically deformed by the fastening force of the bolt 91 and the roundness of one end portion side of the support holes 38, 39, 40 is reduced, the plungers 41, 42, 43 can smoothly move in the support holes 38, 39, 40. As a result, good operability between the plungers 41, 42, 43 and the plunger barrels 32, 33, 34 can be ensured. In addition, post-processing of the support holes 38, 39, 40 is not required, and an increase in processing cost can be suppressed.

[0045] In the fuel pump according to the second aspect, the bolt 91 passes through the pump head 23, and the tip is screwed around the support holes 38, 39, 40 in the plunger barrels 32, 33, 34, so that the plunger barrels 32, 33, 34 are fastened to the pump head 23. The recesses 101, 102 are provided from the screwing position of the bolt 91 in the plunger barrels 32, 33, 34 to the other end side in the axial direction of the support holes 38, 39, 40 or the plungers 41, 42, 43. As a result, the plunger barrel 32 is elastically deformed by the fastening force of the bolt 91, and the roundness of the support holes 38, 39, 40 decreases. Region By securing a gap, the smooth operation of the plungers 41, 42, 43 and the support holes 38, 39, 40 can be ensured.

[0046] In the fuel pump according to the third aspect, the plunger barrels 32, 33, 34 have a first shaft portion (small diameter portion) 32a, 33a, 34a and a second shaft portion (large diameter portion) 32b, 33b, 34b provided on the other end side in the axial direction from the first shaft portions 32a, 33a, 34a. Second shaft portions 32b, 33b, 34b The bolt 91 is screwed to the end face on one end side in the axial direction in, Second shaft portions 32b, 33b, 34b so that the end face on one end side in the axial direction in is in close contact with the pump head 23 to form a seal portion. As a result, high sealing performance of the pressurized chambers 56, 57, 58 can be ensured.

[0047] In the fuel pump according to the fourth aspect, the inner peripheral surface of the support holes 38, 39, 40 and the outer peripheral surface of the plungers 41, 42, 43 are arranged concentrically. The radial length of the recess 102 provided on the inner peripheral surface of the support holes 38, 39, 40 or the recess 101 provided on the outer peripheral surface of the plungers 41, 42, 43 is set to 10 to 40 times the radial gap length between the inner peripheral surface of the support holes 38, 39, 40 and the outer peripheral surface of the plungers 41, 42, 43 where the recesses 101, 102 are not provided. As a result, the variation in the volume of the pressurized chambers 56, 57, 58 can be minimized, and the smooth operation of the plungers 41, 42, 43 and the support holes 38, 39, 40 can be ensured.

[0048] In the fuel pump according to the fifth aspect, the radial lengths of the recesses 101 and 102 are set in the range of 0.05 mm to 0.2 mm. Thereby, the gap due to the recesses 101 and 102 can be set to an appropriate value.

[0049] In the above-described embodiment, the support holes 38, 39, and 40 have the same diameter in the axial direction, and one end portion communicates with the fuel passages 67, 68, and 69. However, this configuration Limited is not essential. For example, the support hole may be composed of a main body hole having the same diameter as the support holes 38, 39, and 40 and a reduced-diameter portion having a diameter smaller than that of the support holes 38, 39, and 40, and the reduced-diameter portion may communicate with the fuel passages 67, 68, and 69. In this case, the plungers 41, 42, and 43 are movably supported only by the main body hole. The recess 101 is provided at one end portion of the plungers 41, 42, and 43, and the recess 102 is provided at one end portion of the main body hole.

[0050] In the above-described embodiment, the recess 101 is provided in the plungers 41, 42, and 43, or the recess 102 is provided in the support holes 38, 39, and 40 of the plunger barrels 32, 33, and 34. However, the recess 101 may be provided in the plungers 41, 42, and 43, and the recess 102 may be provided in the support holes 38, 39, and 40 of the plunger barrels 32, 33, and 34.

[0051] Further, the form of the fuel injection device 10 and the form of the fuel pump 11 are not limited to the above-described embodiment. For example, the number of the common rail 12 and the fuel injection valves 13, the connection position of the fuel pump 11, the number of the plungers 41, 42, and 43 and the plunger barrels 32, 33, and 34 may be set as appropriate.

Explanation of Reference Numerals

[0052] 10 Fuel injection device 11 Fuel pump 12 Common rail 13 Fuel injection valve 14 Fuel tank 21 Retainer 22 Pump case 23 Pump head 24 Camshaft 25, 26 bearings 27, 28, 29 cams 30, 31 bolts 32, 33, 34 plunger barrels 35, 36, 37 receiving holes 38, 39, 40 support holes 41, 42, 43 plungers 44, 45, 46 tappets 47, 48, 49 rollers 50, 51, 52 support shafts 53, 54, 55 compression coil springs 61, 62, 63 intake valves 64, 65, 66 discharge valves 67, 68, 69 fuel passages 70, 71, 72 intake passages 73, 74, 75 discharge passages 76, 77, 78 compression coil springs 79, 80, 81 actuators 82, 83, 84 compression coil springs 85 communication passage 86, 87 plugs 88 connectors 89 communication passage 101, 102 recesses L11 fuel line L12 fuel high-pressure line L13 fuel supply line

Claims

1. A pump head, a plunger barrel provided with a support hole and having one end side in the axial direction of the support hole fastened to the pump head, a plunger movably supported along the axial direction in the support hole, a pressurizing chamber defined by one end of the support hole and one end in the axial direction of the plunger, a fuel discharge passage having one end communicating with the pressurizing chamber, a fuel suction passage having one end communicating with the fuel discharge passage, a recess provided on at least one of the inner surface of one end of the support hole or the outer surface of one end of the plunger, and comprising: A plurality of bolts penetrate the pump head, and the tip end is screwed around the support hole in the plunger barrel, whereby the plunger barrel is fastened to the pump head. The recess is provided from the screw engagement position of the bolt in the plunger barrel to the other end side in the axial direction of the support hole or the plunger. A fuel pump.

2. The plunger barrel has a small diameter portion and a large diameter portion provided on the other end side in the axial direction from the small diameter portion. The bolt is screwed into the end face on one end side in the axial direction of the large diameter portion, so that the end face on one end side in the axial direction of the large diameter portion is in close contact with the pump head to form a seal portion. The fuel pump according to claim 1.

3. The inner peripheral surface of the support hole and the outer peripheral surface of the plunger are arranged concentrically. The radial length of the recess provided on the inner peripheral surface of the support hole or the outer peripheral surface of the plunger is set to 10 to 40 times the radial clearance length between the inner peripheral surface of the support hole where the recess is not provided and the outer peripheral surface of the plunger. The fuel pump according to claim 1 or claim 2.

4. The recess is set to have a radial length in the range of 0.05 mm to 0.2 mm. The fuel pump according to claim 3.

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