High-pressure fuel pump

Abstract

High-pressure fuel pump, which includes: a pump housing (1) in which a concave section (1a) is formed, a cylinder (6) that is fitted into the concave section of the pump housing (1) and that defines a pressure chamber (11) of the high-pressure fuel pump, and a plunger piston (2) which pressurizes fuel in the pressure chamber (11) by sliding against the cylinder (6), wherein the high-pressure fuel pump pressurizes fuel drawn into the pressure chamber (11) by reciprocating movement of the plunger piston (2), whereupon the fuel is expelled from the pressure chamber (11), wherein the cylinder (6) is formed from a cylindrical element having a ceiling section (6A) in which the pressure chamber (11) is subdivided, and wherein a fuel suction path formed in the pump housing (1) reaches the pressure chamber (11) through the cylinder (6) and a fuel discharge path formed in the pump housing (1) is connected to the pressure chamber (11) through the cylinder (6), characterized in that the cylinder (6) is attached to the pump housing (1) by fitting an outer circumferential surface section to an inner circumferential surface section of the concave section (1a) of the pump housing (1), wherein the cylinder (6) is pressed in through a press-fit section (6c) to be held in the pump housing (1).

Description

Technical area

[0001] The present invention relates to a high-pressure fuel pump and, in particular, to one having a cup-shaped cylinder according to claim 1. State of the art

[0002] Japanese Unexamined Patent Application Publication No. 2007-231959 A discloses a high-pressure fuel pump in which a pressure chamber is formed by press-fitting a cup (called a bung in Japanese Unexamined Patent Application Publication No. 2007-231959 A) and a cylinder to a cylinder inner surface portion (inner peripheral portion) of a concave portion formed in a pump housing. In the high-pressure fuel pump, the cylinder containing the cup is press-fitted into the inner periphery of the pump housing by a screw thrust of a cylinder holder. It is also noted that the cup and the cylinder may be integrally structured. Citation listPatent literature

[0003] Patent literature: Publication of Japanese Unexamined Patent Application No. 2007-231959 A Summary of the inventionTechnical problem

[0004] The pot and cylinder fitted to the cylinder inner surface portion (inner peripheral portion) of the pump casing are subject to the thrust forces of other components such as the cylinder bracket, so they cannot be fixed unless held by pressure.

[0005] This makes it necessary to locate the cylinder mount in a lower section of the pump housing. This leads to an increase in the number of components and the overall size of the high-pressure fuel pump.

[0006] When the fuel is compressed, the cylinder, which serves as part of the pressure chamber, is subjected to pressure in a direction that causes the cylinder to protrude downward from the pump housing. Thus, it is necessary to increase the fastening force of the cylinder mount as the fuel discharge pressure increases. This raises concerns that the cylinder mount may need to be made larger and more complicated.

[0007] An object of the present invention to solve the above problem is to provide an inexpensive, compact, lightweight, highly reliable high pressure fuel pump.

[0008] More specifically, a mechanism for simplifying the structure of a cylinder holder is provided.

[0009] In addition, a mechanism for preventing cylinder displacement caused by fuel discharge pressure is provided. Solution to the problem

[0010] According to the high pressure fuel pump of the present invention, the above object is achieved by fitting a cup-shaped cylinder to a cylinder inner surface portion (inner peripheral portion) of a concave portion formed in a pump housing, and by forming a pressure chamber through the cylinder inner surface portion (inner peripheral portion) and through a ceiling portion of the cylinder. Advantageous effects of the invention

[0011] According to the high-pressure fuel pump of the present invention structured as described above, even in cases where the fuel discharge pressure (pressure in the pressure chamber) is set to a high pressure, the cylinder is pressed against the pump housing by the pressure in the pressure chamber. This makes it possible to simplify the cylinder mounting and realize a compact, lightweight high-pressure fuel pump. Brief description of the drawings Fig. 1 shows an example of a fuel supply system using a high pressure fuel pump in accordance with a first embodiment of the present invention. Fig. 2 is a vertical sectional view of the high pressure fuel pump in accordance with the first embodiment of the present invention. Fig. 3 is a vertical sectional view of the high pressure fuel pump in accordance with the first embodiment of the present invention, compared with Fig. 2 is shifted in a vertical direction. Fig. 4 shows dimensions of a plunger 2 and a cylinder of the high pressure fuel pump in accordance with the first embodiment of the present invention. The following Fig. 5 - 11 and their explanations in the following text serve to generally describe the context of the present invention and are helpful for understanding the invention. Fig. 5 is an enlarged view of a suction solenoid valve mechanism 30 in a state with a de-energized solenoid coil 52 of the high pressure fuel pump in accordance with the first embodiment of the present invention. Fig. 6 is an enlarged view of the suction solenoid valve mechanism 30 in a state with an energized solenoid coil 52 of the high pressure fuel pump in accordance with the first embodiment of the present invention. Fig. 7 is an enlarged view of a suction solenoid valve mechanism 30 in a state with a de-energized solenoid coil 52 in accordance with a known type of high pressure fuel pump. Fig. 8 shows the suction solenoid valve mechanism 30 in a pre-assembled state before being mounted in the pump housing 1 of the high-pressure fuel pump in accordance with the first embodiment of the present invention. Fig. Fig. 9 is an external view of a flange 41 and bushings 43 included in the high-pressure fuel pump according to the first embodiment of the present invention. Fig. 9, no component other than the flange 41 and the bushings 43 is shown. Fig. 10 is an enlarged view of a portion around a welding portion 41a of the high-pressure fuel pump according to the first embodiment of the present invention. Fig. 11 is an enlarged view, which is stronger than Fig. 11 is enlarged, of a portion around the welding portion 41a of the high pressure fuel pump in accordance with the first embodiment of the present invention. Fig. 12 is a vertical sectional view of a high pressure fuel pump in accordance with a second embodiment of the present invention. Fig. 13 is a vertical sectional view of a high pressure fuel pump in accordance with a third embodiment of the present invention. Fig. 14 is a vertical sectional view of a high pressure fuel pump in accordance with a fourth embodiment of the present invention. Fig. 15 is a vertical sectional view of a high pressure fuel pump in accordance with a fifth embodiment of the present invention. Fig. 16 is a vertical sectional view of the high pressure fuel pump in accordance with the fifth embodiment of the present invention, which is different from Fig. 15 with respect to the fixed cylinder position. Description of embodiments

[0012] Embodiments of the present invention are described below with reference to the drawings. First embodiment

[0013] The following will be based on Fig. 1 to 11 an embodiment of the present invention is described.

[0014] The dashed line box in Fig. 1 represents a pump housing 1 of a high-pressure pump. This means that the mechanisms and components shown in the dashed-line box are integrally incorporated into the pump housing 1 of the high-pressure pump.

[0015] The fuel contained in a fuel tank 20 is pumped up by a feed pump 21 based on a signal from an engine control unit 27 (hereinafter referred to as an "ECU") and, after being pressurized to a suitable feed pressure, is sent through a suction pipe 28 to a suction port 10a of the high-pressure fuel pump.

[0016] After the fuel passes through the suction port 10a, it passes through a filter 102 mounted in a suction connection 101 and reaches a metal diaphragm damper 9 and a low-pressure fuel chamber 10c via a suction flow path 10b, wherein a suction port 30a of a suction solenoid valve mechanism 30 forms a volume changing mechanism.

[0017] The suction filter 102 included in the suction connection 101 plays a role of absorbing foreign matter present in the high-pressure fuel pump by means of the fuel flow between the fuel tank 20 and the suction port 10a.

[0018] Fig. 5 is an enlarged view of a suction solenoid valve mechanism 30 in a state where a solenoid coil 53 is de-energized.

[0019] Fig. 6 is an enlarged view of the suction solenoid valve mechanism 30 in a state where the solenoid coil 53 is energized.

[0020] The pump housing 1 includes, in a central portion thereof, a concave portion 1a for receiving a cylinder 6 containing a pressure chamber 11, wherein a hole 30A for fitting the suction solenoid valve mechanism 30 is formed so as to communicate with the pressure chamber 11.

[0021] A piston rod 31 includes three sections, namely a suction valve section 31a, a rod section 31b, and an armature attachment section 31c. An armature 35 is firmly welded to the armature attachment section 31c at a welding section 37b.

[0022] A spring 34 is fitted to an armature inner circumference 35a and to an inner circumference 33a of a first core portion 33, and its spring force is exerted in the direction of separating the armature 35 and the first core portion 33 from each other.

[0023] A valve seat 32 includes a suction valve seat portion 32a, a suction passage portion 32b, a press-fit portion 32c, and a sliding portion 32d. The press-fit portion 32c is firmly pressed into the first core portion 33. The suction valve seat portion 32a is firmly pressed into the pump housing 1 in such a manner that the pressure chamber 11 and the suction port 30a are completely separated from each other by the press-fit portion.

[0024] The first core portion 33 is firmly welded to the pump housing 1 at a welding portion 37c, whereby the suction port 30a is separated from the exterior of the high-pressure fuel pump.

[0025] A second core portion 36 is attached to the first core portion 33 at a welded portion 37a, thereby completely separating the interior of the second core portion 36 from the exterior. The second core portion 36 is provided with a magnet opening portion 36a.

[0026] In a state in which the solenoid coil 53 is de-energized and in which there is no fluid pressure difference between a suction flow path 10b (suction port 30a) and the pressure chamber 11, the piston rod 31 is in a position which is achieved by being urged by the spring 34 as shown in Fig. 5. In this state, a suction port 38 is closed, with the suction valve portion 31a and the suction valve seat portion 32a in contact with each other.

[0027] If the pump, as in Fig. 2, in a suction stroke in which a plunger 2 is displaced downward by the rotation of a cam 5 described later, the volume of the pressure chamber 11 increases, causing the fuel pressure in the pressure chamber 11 to decrease. If the fuel pressure in the pressure chamber 11 becomes lower than the pressure in the low-pressure fuel chamber 10c (the suction port 30a) in this stroke, the fluid pressure difference causes a valve opening force (force in the direction of displacement of the suction valve portion 31a, as shown in Fig. 1, to the left).

[0028] The suction valve portion 31a is configured to overcome the preloading force of the spring 34 to open the suction port 38 when subjected to the valve-opening force due to the fluid pressure difference. When the fluid pressure difference is high, the suction valve portion 31a opens fully, bringing the armature 35 into contact with the first core portion 33. When the fluid pressure difference is small, the suction valve portion 31a does not open fully, and the armature 35 does not come into contact with the first core portion 33.

[0029] In this state, when a control signal from the ECU 27 is applied to the solenoid valve mechanism 30, an electric current flows through the solenoid coil 53 of the solenoid valve mechanism 30, generating a magnetic bias force between the first core portion 33 and the armature 35, causing them to attract each other. As a result, a magnetic bias force is applied to the piston rod 31 to move the piston rod 31 to the left, as shown in the figure.

[0030] When the suction valve portion 31a is fully open, the open state is maintained. When the suction valve portion 31a is not fully open, the magnetic bias force promotes the opening of the suction valve portion 31a, allowing the suction valve portion 31a to fully open. This brings the armature 35 into contact with the first core portion 33, whereupon their contact state is maintained.

[0031] As a result, the state in which the suction port 38 has been opened by the suction valve portion 31a is maintained, and the fuel coming through the suction port 30a flows into the pressure chamber 11 via the suction passage portion 32b and the suction port 38.

[0032] When the plunger 2 completes the suction stroke with an input voltage applied to the suction solenoid valve mechanism 30 and proceeds to a compression stroke in which the plunger 2, as shown in Fig. 2, the suction valve portion 31a is still left open, maintaining the magnetic preload force.

[0033] As the compression movement of the plunger 2 progresses, the volume of the pressure chamber 11 decreases. In this state, the fuel once sucked into the pressure chamber 11 is returned to the suction flow path 10b (the suction port 30a) through the suction port 38 in an open state, so that the pressure in the pressure chamber does not increase. This phase is referred to as a return phase.

[0034] Canceling the control signal from the ECU 27 in this state and thereby de-energizing the solenoid 53 causes the magnetic biasing force exerted on the piston rod 31 to disappear after a certain period of time (after a magnetically or mechanically induced time delay). When the electromagnetic force exerted on the piston rod 31 disappears, the suction valve portion 31a subjected to the biasing force of the spring 34 closes the suction port 38. Once the suction port 38 closes, the fuel pressure in the pressure chamber 11 begins to rise with the upward movement of the plunger 2. When the fuel pressure in the pressure chamber 11 exceeds the pressure at a fuel discharge port 12, the fuel remaining in the pressure chamber 11 is discharged at high pressure via a discharge valve unit 8 to be supplied to a common fuel rail 23.This phase is referred to as an exhaust phase. That is, the compression stroke (an ascending stroke from bottom dead center to top dead center) of plunger 2 includes a return phase and an exhaust phase.

[0035] The amount of high-pressure fuel to be discharged can be controlled by controlling the timing of interrupting the energization of the solenoid coil 53 of the suction solenoid valve mechanism 30.

[0036] When the timing of interrupting the energization of the solenoid 53 in a compression stroke is advanced, the proportion of the return phase decreases and the proportion of the discharge phase increases.

[0037] That is, the amount of fuel returned to the suction flow path 10b (suction port 30a) decreases and the amount of fuel discharged at high pressure increases.

[0038] On the other hand, if the timing of de-energizing the solenoid 53 is delayed in a compression stroke, the proportion of the return phase increases and the proportion of the discharge phase decreases. That is, the amount of fuel returned to the suction flow path 10b increases, and the amount of fuel discharged at high pressure decreases. The timing of de-energizing the solenoid 53 is controlled by a command from the ECU.

[0039] Thus, in the structure described above, by controlling the timing of interrupting the energization of the solenoid coil 53, the amount of high-pressure fuel discharged can be adjusted to an amount required by the internal combustion engine.

[0040] Thus, of the fuel supplied to the suction port 10a, a required amount is pressurized to a high pressure in the pressure chamber 11 by a reciprocating movement of the plunger 2 and supplied under pressure from the fuel discharge port 12 to the common fuel line 23.

[0041] The common rail 23 is equipped with injectors 24 and a pressure sensor 26. The number of injectors 24 is equal to the number of cylinders in the internal combustion engine. Each of the injectors 24 injects fuel into the corresponding cylinder by opening / closing its valve in accordance with control signals from the engine control unit (ECU) 27.

[0042] As shown in the figure, at this time, the suction valve portion 31a repeats the opening and closing of the suction port 38, and the piston rod 31 reciprocates left and right while the plunger 2 reciprocates up and down. As shown in the figure, at this time, the sliding portion 32d of the valve seat 32 restricts the movement of the piston rod 31, so that the piston rod 31 can only move laterally. Thus, the sliding movement between the sliding portion 32d and the rod portion 31b is repeated. Thus, the surface roughness of the sliding portion must be low enough so that it does not generate resistance when the piston rod 31 participates in a sliding movement. A sliding portion clearance is determined as follows.

[0043] If the clearance is too large, the piston rod 31 swings like a pendulum around the sliding portion thereof, causing the armature 35 and the second core portion 36 to come into contact with each other. In this state, the sliding movement of the piston rod 31 causes sliding between the armature 35 and the second core portion 36. This increases the resistance to the sliding portion of the piston rod 31, which impairs the responsiveness of the opening / closing movement of the suction port 38. In addition, the armature 35 and the second core portion 36 are each made of a magnetic ferrite stainless steel, and the sliding movement between them may generate abrasion powder. In addition, as described later, the magnetic preload force is larger when the clearance between the armature 35 and the second core portion 36 is smaller.If the clearance is too large, the magnetic preload force will be insufficient to properly control the amount of high-pressure fuel discharged. Therefore, the armature 35 and the second core portion 36 must have as small a clearance as possible between them without contacting each other.

[0044] As in the Fig. 5 and Fig. Thus, as shown in Fig. 6, there is only one sliding range, and the sliding portion 32d has a sufficient sliding length L. The sliding range is defined by the inner diameter of the sliding portion 32d and the outer diameter of the rod portion 31b, both of which inevitably have respective manufacturing tolerances. In addition, there is inevitably a tolerance for a sliding portion clearance to be formed. On the other hand, with respect to the above-mentioned magnetic preload force, there is an upper limit to the clearance between the armature 35 and the second core portion 36. Making the sliding length L large and thereby making the vibration of the piston rod 31 small makes it possible to accommodate the clearance tolerance without allowing the armature 35 and the second core portion 36 to contact each other.

[0045] In this way, the movement of the piston rod 31 to swing like a pendulum is limited because the sliding portion 32d and the rod portion 31b contact each other, causing sliding between them at both ends of the sliding area. This has made it possible to reduce the clearance between the armature 35 and the second core portion 36.

[0046] If the clearance is too small, closing the suction port 38 will not bring the suction valve portion 31a and the suction valve seat portion 32a into full surface contact with each other. This is because the clearance of the sliding portion cannot accommodate errors in the perpendicularity of the suction valve portion 31a and the rod portion 31b of the piston rod 31, as well as the perpendicularity of the suction valve seat portion 32a and the sliding portion 32d of the valve seat 32. If the suction valve portion 31a and the suction valve seat portion 32a do not come into full surface contact, the high-pressure fuel in the pressure chamber 11 may subject the piston rod 31 to excessive torque during a discharge phase, possibly damaging the piston rod 31. The sliding portion may also be subjected to excessive stress, possibly causing it to break or wear.

[0047] Thus, the suction valve portion 31a and the suction valve seat portion 32a must be in complete surface contact with each other when the suction port 38 is in a closed state. In particular, highly accurate perpendicularity of the suction valve portion 31a and the rod portion 31b of the piston rod 31, as well as the suction valve seat portion 32a and the sliding portion 32d of the valve seat 32, is required when the sliding length L is made large as described above to suppress the swinging motion of the piston rod 31.

[0048] This is the reason why the suction valve seat portion 32a and the sliding portion 32d are provided in the valve seat 32. Since the suction valve seat portion 32a and the sliding portion 32d are both included in a single member, they can be manufactured accurately perpendicularly. If the suction valve seat portion 32a and the sliding portion 32d are provided as separate members, their perpendicularity will inevitably deteriorate when they are processed or fixed with parts for coupling. Such a problem does not occur if the suction valve seat portion 32a and the sliding portion 32d are provided as a single member.

[0049] Furthermore, the amount of high-pressure fuel discharged cannot be adequately controlled if the magnetic preload force generated when the solenoid coil 53 is energized is insufficient. Therefore, the magnetic circuit to be formed around the solenoid coil 53 must be capable of generating a sufficient magnetic preload force.

[0050] That is, the magnetic circuit must be one through which as many magnetic fluxes as possible flow when the solenoid coil 53 is energized and a magnetic field is generated around it. Generally, the magnetic resistance is lower and the magnetic fluxes passing through the magnetic circuit are larger, so the generated magnetic preload force is greater when the magnetic circuit is thicker and shorter.

[0051] As in Fig. 5, the magnetic circuit in the present embodiment includes the armature 35, the first core portion 33, a yoke 51, and the second core portion 36, each made of a magnetic material.

[0052] The first core section 33 and the second core section 36 are connected to each other by welding at the welding section 37a. However, it is necessary that the magnetic fluxes pass through the first core section 33 and the second core section 36, not directly, but via the armature 35. This serves to generate a magnetic preload force between the first core section 33 and the armature 35. If magnetic fluxes pass directly through the first core section 33 and the second core section 36, this leads to a reduction in the magnetic fluxes passing through the armature, and the generated magnetic preload force becomes smaller.

[0053] Thus, in one known type of high-pressure fuel pump, an intermediate element is provided between the first core section 33 and the second core section 36. Since the intermediate element is made of a non-magnetic material, fluxes do not pass directly through the first core section 33 and the second core section 36, but only via the armature 35.

[0054] However, the use of such an intermediate element increases the total number of components and also inevitably triggers an increase in cost since it becomes additionally necessary to connect the first core section 33 and the second core section 36 to the intermediate element.

[0055] Thus, in the present embodiment, the first core portion 33 and the second core portion 36 are directly connected at the weld portion 37, and the magnetic opening portion 36a is provided in the second core portion. In the magnetic opening portion 36a, the core thickness is reduced as much as is permissible in terms of core strength, while the core thickness is sufficiently secured in the other parts of the second core portion 36. The magnetic opening portion 36a is provided near the point where the first core portion and the armature 35 contact.

[0056] As a result, most of the generated magnetic flux passes through the armature 35, and only a small portion of the generated magnetic flux passes directly through the first core section 33 and the second core section. This keeps the reduction in the magnetic preload force to be generated between the first core section 33 and the armature 35 within a tolerable range.

[0057] In addition, the largest gap in the magnetic circuit occurs between the second core portion 36 and the armature 35 when the first core portion 33 and the armature 35 are in contact with each other. The gap is non-magnetic and is filled with fuel, so the larger the gap, the higher the magnetic resistance in the magnetic circuit. Therefore, it is preferable that the gap be as small as possible.

[0058] In the present embodiment, the clearance between the second core portion 36 and the armature 35 is reduced as described above by making the sliding length L of the sliding portion large.

[0059] The solenoid coil 53 is formed by winding a lead wire 54 around the axis of the piston rod 31. Both ends of the lead wire 54 are connected to a terminal 56 by welding at a lead wire welding section 55. The terminal is made of a conductive material and is exposed within a connector portion 58 to supply an electric current to the coil when the connector portion 58 is engaged with a mating connector of the ECU and when the terminal 56 is in contact with the terminal in the mating connector.

[0060] Fig. Figure 7 shows a known structure type in which the lead wire welding section 55 is positioned within the magnetic circuit. This increases the overall length of the magnetic circuit because the volume required for the lead wire welding section 55 is not small. As a result, the magnetic resistance in the magnetic circuit increases, which poses a problem that the magnetic preload force generated between the first core section 33 and the armature 35 is reduced.

[0061] In the present embodiment, the lead wire welding portion 55 is positioned outside the yoke 51. Thus, the lead wire welding portion 55 is positioned outside the magnetic circuit, so that the overall length of the magnetic circuit can be reduced, requiring no space for the lead wire welding portion 55. As a result, it is possible to generate a sufficient magnetic preload force between the first core portion 33 and the armature 35.

[0062] Fig. 8 shows the suction solenoid valve mechanism 30 before it is installed in the pump housing 1.

[0063] In the present embodiment, a suction valve unit 37 and a connector unit 58 are first prepared as discrete units. Subsequently, the suction valve seat portion 32a of the suction valve unit 37 is press-fitted firmly into the pump housing 1, and then the weld portion 37c is welded around the entire circumference for connection. In the present embodiment, this is done by laser welding. In this state, the connector unit 58 is press-fitted firmly into the first core portion 33. In this way, the connector unit 58 can be oriented as desired.

[0064] The pump housing 1 has the concave portion 1a for accommodating the cylinder 6, which contains the pressure chamber 11. A hole 11A for installing the discharge valve unit 8 is formed so as to open to the pressure chamber 11 in the direction intersecting the concave portion 1a for accommodating the cylinder 6.

[0065] As in Fig. 1, the discharge valve unit 8 is positioned at the outlet of the pressure chamber 11. The discharge valve mechanism 8 includes a seat member (seat member) 8a, a discharge valve 8b, a discharge valve spring 8c, and a retaining member 8d serving as a discharge valve plug. The discharge valve unit 8 is assembled by welding a welding portion 8e outside the pump housing 1. Subsequently, the thus assembled discharge valve unit 8 is removed from the left side as shown in FIG. Fig. 2 is pressed firmly into the pump housing 1. The pressed-in section has a function of separating the pressure chamber 11 and the discharge port 12 from each other.

[0066] When there is no fuel pressure difference between the pressure chamber 11 and the fuel discharge port 12, the discharge valve 8b is closed by being pressed against the seat member 8a by the biasing force of the discharge valve spring 8c. Only when the fuel pressure in the pressure chamber 11 exceeds the fuel pressure in the fuel discharge port 12 by a predetermined value or more does the discharge valve 8b open by overcoming the biasing force of the discharge valve spring 8c. As a result, the fuel in the pressure chamber 11 is discharged into the common rail 23 via the fuel discharge port 12.

[0067] When the discharge valve 8b opens, its movement is limited by contact with the holding member 8d. That is, the stroke of the discharge valve 8b is appropriately defined by the holding member 8d. If the stroke is too large, the discharge valve 8b cannot close quickly enough. This causes part of the fuel discharged to the fuel discharge port 12 to return to the pressure chamber 11, resulting in a reduction in the efficiency of the high-pressure pump. In addition, the holding member 8d serves as a guide to allow the discharge valve 8b to repeat opening and closing by moving only in the stroke direction. The discharge valve unit 8 structured as described above can serve as a check valve for restricting the fuel flow direction.

[0068] The Fig. 4 shows that the cylinder 6 is shaped like a pot with a bottom, with a top portion 6A. The inner circumference of the cylinder member forming the cylinder has a concave portion formed as the pressure chamber 11.

[0069] The cylinder 6 has a plurality of through holes 6a distributed along the circumference, through which the pressure chamber 11 and the suction port 38 communicate with each other, and a plurality of through holes 6b distributed along the circumference, through which the pressure chamber 11 and the fuel discharge port 12 communicate with each other.

[0070] The cylinder outer surface (outer circumference) of the cylinder 6 fits with the cylinder inner surface (inner circumference) of the concave portion 1a formed in the pump housing 1, and the cylinder 6 is press-fitted by a press-fit portion 6c to be held in the pump housing 1.

[0071] The cylinder 6 is fixed to the cylinder inner surface (inner circumference) of the pump housing 1 at two locations, i.e., the press-fit portion 6c and the mounting location 6d. Thus, the coaxiality between the center axis of the pump housing 1 and that of the cylinder 6 is improved.

[0072] With the press-fitting portion 6c and the mounting position 6d positioned away from the position where the cylinder 6 and the plunger 2 slide against each other, deterioration of coaxiality due to press-fitting can be prevented.

[0073] A communication hole 10d is formed through a ceiling portion 10A above the inner cylinder surface (inner periphery) of the pump housing 1, communicating with the low-pressure fuel chamber 10c. When the cylinder 6 is press-fitted into the pump housing 1, the ceiling portion 10A serves as a vent hole. With the communication hole 10d provided, the stress exerted on the cylinder 6 during press-fitting can be reduced and deformation due to warping of the cylinder 6 can be prevented.

[0074] The diameter of the communication hole 10d is smaller than the outer diameter of the cylinder 6, so that the communication hole 10d serves as a plug to prevent the cylinder 6 from coming out to the low-pressure fuel chamber 10c side.

[0075] When Dc is the outer diameter and d is the inner diameter of the cylinder 6, and the diameter D of the connecting hole 10d is such that the relationship "area Ad > ADc - AD" is maintained even when high-pressure fuel passes through the area where the cylinder 6 and the pump housing 1 are pressed together, the high-pressure fuel is released into the low-pressure chamber. Thus, the cylinder 6 is held in place without being forced to leave the pump housing 1 by a pressure difference.

[0076] With the cup-shaped cylinder 6, the upper end portion of the cover portion 6A of the cylinder 6 is pressed against the cover portion 10A of the pump housing 1 by the pressure in the pressure chamber 11, thereby effecting a metal-to-metal seal.

[0077] The effect of the metal-to-metal seal increases as the pressure in the pressure chamber 11 increases.

[0078] A plunger seal 13 is held by a seal retainer 15, which is firmly press-fitted to a cylinder inner peripheral surface 7c of the spring retainer 7, and by the spring retainer 7 to the lower end of a spring retainer 7. The center axis of the plunger seal 13 is coaxial with the center axis of the cylinder inner peripheral surface 7c of the spring retainer 7 and with the center axis of a cylinder fitting portion 7e. The plunger 2 and the plunger seal 13 are mounted so as to be slidable against each other in a lower end portion of the cylinder 6.

[0079] The plunger seal 13 prevents the fuel from flowing out of a sealed chamber 10f into the engine installed on the tappet 3 side, and also prevents the lubricating oil (including engine oil) that lubricates the sliding parts in the engine room from flowing out into the pump body 1.

[0080] The spring retainer 7 is installed by fitting the cylinder fitting portion (outer peripheral portion) 7e thereof to a cylinder inner surface portion (inner peripheral portion) in a lower portion of the pump housing 1. In the present embodiment, the spring retainer 7 is fixed by laser welding.

[0081] The pump housing 1 has a groove 7d on a cylinder outer peripheral surface 7b thereof for fitting an O-ring 61 therein. The O-ring 61, fitted between the inner wall surface of a fitting hole 70 on the engine side and the groove 7d of the pump housing 1, separates the cam side portion of the engine from the outside to prevent the engine oil from flowing out.

[0082] In the structure described above, the cylinder 6 can hold the plunger 2 slidably reciprocating in the pressure chamber 11 along the direction of reciprocating movement.

[0083] The plunger 2 is provided at its lower end with the tappet 3, which converts the rotational movement of the cam 5 attached to a camshaft of the engine into an up-and-down movement and transmits the up-and-down movement to the plunger 2. The plunger 2 is pressed against the tappet 3 by the spring 4 via the retainer 15. The retainer 15 is firmly pressed onto the plunger 2. In this structure, the rotation of the cam 5 causes the plunger 2 to move up and down (reciprocate).

[0084] With the low-pressure fuel chamber 10c connected to the sealed chamber 10f via the suction flow path 10b and a suction flow path 10e provided in the cylinder bracket 7, the sealed chamber 10f is always connected to the pressure of the suction fuel. When the fuel in the pressure chamber 11 is pressurized to a high pressure, a very small amount of the high-pressure fuel flows into the sealed chamber 10f through the sliding portion clearance between the cylinder 6 and the plunger 2. However, since the flowed-in high-pressure fuel is released into the suction pressure, no breakage due to high pressure of the plunger seal 13 occurs.

[0085] The plunger 2 includes a large-diameter portion 2a that slides against the cylinder 6 and a small-diameter portion 2b that slides against the plunger seal 13. The large-diameter portion 2a has a larger diameter than the small-diameter portion 2b, and the two portions are coaxial with each other. The plunger 2 slides against the cylinder 6 at the large-diameter portion 2a and against the plunger seal 13 at the small-diameter portion 2b. In this structure, where the boundary between the large-diameter portion 2a and the small-diameter portion 2b remains in the sealed chamber 10f, the volume of the sealed chamber 10f changes with the sliding movement of the plunger 2.This causes the fuel to reciprocate between the sealed chamber 10f and the suction flow path 10c via the communication hole 10d and the suction flow path 10e.

[0086] As the plunger 2 repeatedly slides against the plunger seal 13 and the cylinder 6, frictional heat is generated, causing the large-diameter portion 2a and the plunger 2 to thermally expand. Of the large-diameter portion 2a, the plunger seal 13 side is closer to the frictional heat source than the pressure chamber 11 side. This causes the large-diameter portion 2a to thermally expand unevenly. As a result, the coaxiality between the plunger 2 and the cylinder 6 deteriorates, possibly causing seizure between them.

[0087] In the present embodiment, the sliding movement of the plunger 2 causes the fuel in the sealed chamber 10f to be continuously replaced, so that the fuel has a heat removal effect. This prevents deformation of the large-diameter portion 2a due to frictional heat and seizure between the plunger 2 and the cylinder 6, which may result from the deformation of the large-diameter portion 2a.

[0088] Furthermore, the smaller the diameter of the portion of the plunger 2 that is to slide against the plunger seal 13, the smaller the area of ​​friction between them and thus the amount of frictional heat generated by the sliding movement of the plunger 2. In the present embodiment, the portion of the plunger 2 that is to slide against the plunger seal 13 is the smallest-diameter portion 2b of the plunger 2, so the amount of frictional heat generated by the sliding of the plunger 2 against the plunger seal 13 can be kept small. This prevents seizure between the plunger 2 and the cylinder 6.

[0089] The metal diaphragm damper 9 includes two metal diaphragms that are secured together by completely welding their outer peripheries with a gas sealed in the space between them. When both sides of the metal diaphragm damper 9 are subjected to low-pressure pulsation, the metal diaphragm damper 9 changes its volume, thereby reducing the low-pressure pulsation.

[0090] The high-pressure fuel pump is mounted on the engine using a flange 41, set screws 42, and bushings 43. The flange 41 is completely welded to the pump housing 1 at a weld portion 41a along its circumference. Laser welding is used in the present embodiment.

[0091] Fig. 9 is an external view of the flange 41 and the bushings 43. In Fig. 9, no further component is shown other than the flange 41 and the bushings 43.

[0092] The two bushings 43 are attached to the side of the flange 41 opposite the engine. The two locking screws 42 are screwed into the corresponding threaded holes formed on the engine side, thereby pressing the two bushings 43 and the flange 41 against the engine to secure the high-pressure fuel pump to the engine.

[0093] Fig. 10 is an enlarged view of a section including the flange 41, a set screw 42 and a bushing 43.

[0094] The bushing 43 includes a rim portion 43a and a sealing portion 43b. The sealing portion 43b is tightly sealed in a mounting hole formed in the flange 41. Subsequently, the bushing 43 is coupled to the pump housing 1 via the flange 41 by laser welding at the welding portion 41a. Subsequently, a resin-made fastener 44 is fitted into the bushing 43, and then the setscrew 42 is inserted through the fastener 44. The fastener 44 serves to temporarily fasten the setscrew 42 to the bushing 43 to prevent the setscrew 42 from being loosened from the bushing 43 before the high-pressure fuel pump is installed on the engine. When the high-pressure fuel pump is installed on the engine, the setscrew 42 is fastened by being screwed into a threaded portion on the side of the engine.At this time, the locking screw can be rotated in the bushing 43 by applying a fastening torque thereto.

[0095] When the high-pressure fuel pump repeatedly pumps out high-pressure fuel, the pressure in the pressure chamber 11 repeatedly increases to a high pressure and decreases to a low pressure. When the pressure in the pressure chamber 11 is high, the high pressure causes the pump housing 1 to be subjected to an upward force, as shown in the figure. When the pressure in the pressure chamber 11 is low, the pump housing 1 is not subjected to such an upward force. That is, the pump housing is repeatedly subjected to an upward force, as shown in the figure.

[0096] As in Fig. As shown in Fig. 10, the pump casing 1 is fixed to the engine via the flange 41 using the two set screws 42. Thus, when the pump casing 1 is repeatedly subjected to an upward force as described above, the flange 42, with its side portions clamped by the two set screws 42 and the two bushings 43, is repeatedly subjected to bending stress at a central portion thereof. There has been a problem that such repeated stresses deform the flange 41 and the pump casing 1, resulting in the generation of repeated stresses that eventually cause the flange 41 and the pump casing 1 to fracture due to fatigue. In addition, the sliding portion of the cylinder 6 may also be deformed, causing seizure between the plunger 2 and the cylinder 6 as described above.

[0097] For productivity reasons, the flange 41 is formed by pressing. Thus, the flange 41 has a limited plate thickness t1, which is 4 mm in the present example. The pump casing 1 and the flange 42 are joined by laser welding at the weld portion 41a. As can be seen in the figure, laser welding requires that a beam be emitted from the bottom side. This is because, with the other components arranged above the weld portion 41a, a downward beam, which would be emitted from the top side as seen in the figure, would not be able to irradiate the weld portion 41a completely along the circumference. In addition, the laser welding beam must penetrate the plate thickness t = 4 mm of the flange 41. Otherwise, laser welding will cause the weld portion to have notches in its edge portions.This allows mechanical stress generated by repeated loading as described above to concentrate at the notches and eventually cause fatigue failure.

[0098] The use of high laser output power allows laser welding to penetrate the flange 41. However, welding always generates heat, so the flange 41 may be thermally deformed. In addition, a large amount of spatter generated by welding adheres to the pump housing 1 and other components. From this perspective, it is desirable that the weld length to be penetrated by laser welding be as short as possible.

[0099] Thus, in the present embodiment, only the weld portion 41a has a plate thickness of t2 = 3 mm. This enables penetrative laser welding of the flange 41 while minimizing spatter generation. Since the weld portion 41a can be formed with a plate thickness of t2 = 3 mm by pressing, high productivity can be achieved.

[0100] The step formed by the difference between the plate thickness t2 = 3 mm of the welded portion 41a and the plate thickness t1 = 4 mm is on the engine side of the welded portion 41a. That is, a concave portion 45 is formed. When the welded portion 41a is welded, its upper and lower surfaces bulge out from the base material. The concave portion 45 prevents the bulge formed on the lower surface of the welded portion 41a from interfering with the engine. If the bulge comes into contact with the engine when the high-pressure fuel pump is fixed to the engine with the set screws 42, this causes the flange 41 to be subjected to bending stress, possibly leading to the fracture of the flange 41.

[0101] As described above, the flange 41 can be prevented from being broken due to repeated stresses generated when the fuel is repeatedly pumped out at high temperatures. Furthermore, the flange 41 can be prevented from being broken as a result of contact between the bulge at the weld portion 41a and the engine.

[0102] As described above, when the pump casing 1 is subjected to repeated loads, the clamped by the two set screws 42 and two bushings 43 bends along the direction of repeated loads. When the weld portion 41a is laser-welded all along the circumference, the bending of the flange 41 is distributed throughout the pump casing 1. On the other hand, the spring retainer 7 and the pump casing 1 contact each other only at the threaded portions 7g and 1b. The threaded portion 1b of the pump casing 1 and the weld portion 41a are separated by a distance m. The minimum thickness of the pump casing 1 at a portion thereof at a distance m from the weld portion 41a is n.The values ​​of m and n are determined in such a way that even if the pump casing 1 is deformed due to curvature of the flange 41, the deformation is absorbed by the portion at a distance m from the weld portion 41a and, at a thickness n of the pump casing 1, does not allow the deformation to spread to the threaded portion 1b.

[0103] In the manner described above, deformation of the cylinder 6 due to curvature of the flange 41 can be prevented. However, in this way, the curvature of the flange 41 must be fully absorbed by the pump housing 1, and if the mechanical stress repeatedly generated in the pump housing 1 exceeds a tolerable value, the pump housing 1 may fracture due to fatigue, resulting in fuel leakage.

[0104] There are two methods to prevent such fatigue fracture of the pump housing 1. (1) Forming the pump casing 1 in such a way that the generation of mechanical stress does not exceed the tolerable value. (2) Reducing the curvature of the flange 41.

[0105] The two procedures are described below.

[0106] First, the method (1) is described. Fig. Fig. 11 shows an enlarged view of a section around the welding section 41a. When the pump casing 1 is pulled upwards by repeated loads as shown in the figure and the flange 41 is bent, causing the generation of stress, the maximum stress on the surface of the pump casing 1 is measured in the ranges indicated by the Fig. 11 as "maximum mechanical stress." The pump casing 1 must be shaped to maximize the distribution of the mechanical stress generated therein, preventing any concentration of the mechanical stress.

[0107] In the present embodiment, the curved sections 1c and 1e are connected via a linear section 1d, as shown in the figure, and optimum values ​​have been determined based on this structure. The stress generated in the linear section 1d formed between the two curved sections 1c and 1e is evenly distributed. As a result, stress concentration is avoided and the maximum generated stress is reduced.

[0108] Method (2) is described below. To reduce the curvature of the flange 41, there is no other method than increasing the rigidity of the flange 41. As mentioned above, it is very difficult to make the plate thickness t of the flange 41 greater than 4 mm from a productivity perspective. Therefore, it was determined that the diameter of each bushing 43 intended only for fastening one set screw 42 be increased. Hereinafter, an effective curvature distance O represents the shortest distance between the end portions of the two bushings 43, that is, the portion actually curved due to repeated loads. Reducing the effective curvature distance O leads to an increase in the rigidity of the flange 41.

[0109] In the present embodiment, each bushing 43 has a rim portion 43a to reduce the effective curvature distance O. Regarding the height, each bushing 43 must be at least high enough to allow the insertion of the fastener 44. If the outer diameter of each bushing 43 having such a height and lacking a rim portion is increased, problems such as interference with the pump casing 1 and an increase in the amount of material of the bushing 43 will be caused. Providing each bushing 43 with a rim portion 43a makes it possible to prevent these problems and reduce the effective curvature distance O.

[0110] The methods (1) and (2) achieved by applying the structure described above make it possible to keep the mechanical stresses repeatedly generated in the pump casing 1 at or below a tolerable value. Second embodiment

[0111] The following will be based on Fig. 12 describes the structure of a second embodiment of the present invention.

[0112] In the present embodiment, the outer shape of the pump housing 1 is downsized by using a discrete spring retainer 7A and a discrete plunger seal retainer 7B for cost reduction.

[0113] The spring retainer 7A is provided at a cylinder outer portion 7b thereof with a groove 7d for fitting an O-ring 61. The O-ring 61 is held between the inner wall of a mounting hole on the engine side and the groove 7d of the spring retainer 7A, and separates the cam side of the engine from the outside to prevent the engine oil from leaking to the outside.

[0114] The plunger seal retainer 7B and the cylinder retainer 7A are fixed to each other before being mounted in the pump housing 1. In the present embodiment, they are fixed by laser welding and seal the fuel.

[0115] The outer peripheral cylindrical surface portion 7k of the spring retainer 7A is press-fitted into the inner peripheral cylindrical surface portion of the pump housing 1 and fixed thereto by laser welding to seal the fuel.

[0116] The plunger seal 13 is held at the lower end of the spring retainer 7A by the seal retainer 15, which is tightly pressed onto the inner peripheral cylindrical surface of the plunger seal retainer 7B and the spring retainer 7A. The plunger seal 13 is held coaxially with the cylinder fitting portion 7e by the cylinder inner peripheral surface 7c of the spring retainer 7A. The plunger 2 and the plunger seal 13 are mounted so as to be slidable against each other in a lower end portion of the cylinder 6, as shown in the figure. Third embodiment

[0117] The following is based on Fig. 13 describes the structure of a third embodiment of the present invention.

[0118] The cylinder 6 has, on its outer peripheral surface portion, a stepped portion 6f including two or more steps, each formed of a large-diameter portion and a small-diameter portion. The stepped portion 6f has a cylindrical groove 6g formed coaxially with the cylinder inner side surface (inner periphery) of the cylinder 6. The cylindrical groove 6g absorbs mechanical stress generated when the cylinder 6 is press-fitted into the pump housing 1 or generated as a result of thermal expansion of the cylinder 6. This prevents deterioration of the coaxiality of a sliding surface 6h, against which the plunger 2 slides, on the inner peripheral surface of the cylinder 6 and seizure between the plunger 2 and the sliding surface 6h. Fourth embodiment

[0119] The following is based on Fig. 14 describes the structure of a fourth embodiment of the present invention.

[0120] The ceiling portion 6A of the cylinder 6 includes a sliding portion 6m having a smaller diameter than the large diameter portion 2a of the plunger 2. The sliding portion 6m is formed coaxially with the sliding portion 6h at the large diameter portion 2a of the plunger 2.

[0121] The plunger 2 includes a coaxial small-diameter portion 2c in its upper portion. The small-diameter portion 2c is fitted to the sliding portion 6m provided in the ceiling portion 6A of the cylinder 6. This increases the sliding area between the plunger 2 and the cylinder 6. As a result, displacement and inclination of the plunger axis are reduced, and seizure and sticking of the plunger 2 are reduced. Fifth embodiment

[0122] The following is based on Fig. 15 describes the structure of a fifth embodiment of the present invention.

[0123] In this embodiment, the cylinder 6 has a plurality of transverse holes 6p forming through holes (6a, 6b) through the side portion of the cylinder 6. The transverse holes 6p forming through holes (6a, 6b) are distributed at two or more locations so that the fuel can flow through the intake path to the exhaust path regardless of the circumferential location where the cylinder 6 is mounted.

[0124] The features of the above embodiments can be summarized as follows.

[0125] (1) A hole is formed in the ceiling portion of the pump casing.

[0126] The hole serves as a vent hole when the cylinder body is press-fitted into the pump housing. If no vent hole is provided, press-fitting the cylinder requires the application of a load on the order of several tons. In this case, the body shell and cylinder are deformed. In the above embodiments, the nominal load for press-fitting the cylinder is 1 ton, and in normal cases, the cylinder can be pressed in by applying a load of up to 8000 N.

[0127] (2) The higher the pressure applied to the inside of the cylinder, the higher the surface pressure of the contact sealing surface between the outer circumference of the cylinder and the inner circumference of the pump casing, resulting in higher sealing ability.

[0128] (3) The cylinder outer portion (outer circumference) of a cup-shaped cylinder element is pressed firmly into the cylinder inner portion (inner circumference) of the pump housing by applying a force such that, during a suction stroke of the plunger, the pressure difference between outside and inside the cylinder does not force the cylinder to come out of the pump housing.

[0129] (4) The cylinder is shaped like a pot with a lid, and a hole is formed between the cylinder and the low-pressure chamber side of the pump body lid section. The hole has a diameter D that satisfies the relationship "outer diameter area Ad of the plunger > outer diameter area ADc of the cylinder - area AD of the hole." This can reliably prevent the pressure in the cylinder from generating a force in the direction that causes the cylinder to protrude downward from the pump housing.

[0130] (5) The press-fit surface is formed to be closer to the ceiling than the finished inner diameter portion of the cylinder, so that the inner diameter is not deformed by the press-fit. List of reference symbols 1 pump housing 1a concave section 2 plungers 6 cylinders 6A Ceiling section (of the cylinder) 10A Ceiling section (of the pump housing) 11 Pressure chamber 30 Suction solenoid valve mechanism

Claims

[1] High pressure fuel pump, which includes: a pump housing (1) in which a concave portion (1a) is formed, a cylinder (6) fitted into the concave portion of the pump housing (1) and defining a pressure chamber (11) of the high-pressure fuel pump, and a plunger (2) which pressurises fuel in the pressure chamber (11) by sliding against the cylinder (6), wherein the high-pressure fuel pump pressurises fuel sucked into the pressure chamber (11) by reciprocating movement of the plunger (2), whereupon the fuel is ejected from the pressure chamber (11), wherein the cylinder (6) is formed from a cylinder element having a ceiling portion (6A) and in which the pressure chamber (11) is divided, and wherein a fuel suction path formed in the pump housing (1) reaches the pressure chamber (11) through the cylinder (6) and a fuel discharge path formed in the pump housing (1) is connected to the pressure chamber (11) through the cylinder (6), characterized by , that the cylinder (6) is fixed to the pump housing (1) by fitting an outer peripheral surface portion to an inner peripheral surface portion of the concave portion (1a) of the pump housing (1), wherein the cylinder (6) is pressed in by a press-in portion (6c) to be held in the pump housing (1). [2] High-pressure fuel pump according to claim 1, wherein a communication hole (10d) is formed in a ceiling portion (10A) of the concave portion (1a) of the pump housing (1), and wherein the communication hole (10d) is covered by an outer surface of the ceiling portion (6A) of the cylinder (6) fitted into the concave portion (1a) of the pump housing (1). [3] High-pressure fuel pump according to claim 2, wherein the communication hole (10d) has a smaller diameter (D) than an outer diameter (Dc) of the cylinder (6). [4] High-pressure fuel pump according to one of claims 1 to 3, wherein a counter force of a pressure generated by the compression movement of the plunger (2) in the pressure chamber (11) of the cylinder (6) pushes the cylinder (6) toward an inner wall surface of the ceiling portion (10A) of the pump housing (1). [5] High-pressure fuel pump according to one of claims 2 or 3 to 4, as far as dependent on claim 2, wherein a sealing portion is formed between the outer peripheral surface portion of the cylinder (6) and the inner peripheral surface portion of the pump housing (1). [6] A high-pressure fuel pump according to claim 5, wherein the sealing portion is a metal sealing portion formed for sealing by metal contact between the outer peripheral surface portion of the cylinder (6) and the inner peripheral surface portion of the pump housing (1). [7] High-pressure fuel pump according to one of claims 2 or 3 to 6 when dependent on claim 2, wherein the outer peripheral surface portion of the cylinder (6) has a step portion (6f) including two or more steps each formed of a large diameter portion and a small diameter portion, the large diameter portion of the step portion (6f) fitting to the inner peripheral surface of the pump housing (1) and having an inner ring groove (6g). [8] High-pressure fuel pump according to one of claims 1 to 7, wherein the ceiling portion (6A) of the cylinder (6) has a sliding portion (6m) and the plunger (2) has on an upper end surface thereof a coaxial portion (2c) whose diameter is smaller than an outermost diameter of the plunger (2), the sliding portion (6m) and the coaxial portion (2c) sliding against each other. [9] A high-pressure fuel pump according to any one of claims 1 to 8, wherein the cylinder (6) has two or more transverse holes (6p) each formed as a fuel suction path and a fuel discharge path through a side portion of the cylinder (6).

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