CN111350622A

CN111350622A - High pressure pump

Info

Publication number: CN111350622A
Application number: CN201911289034.6A
Authority: CN
Inventors: 今村凌大
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2018-12-20
Filing date: 2019-12-13
Publication date: 2020-06-30
Anticipated expiration: 2039-12-13
Also published as: CN111350622B; JP7205211B2; DE102019127935A1; JP2020101100A

Abstract

The high-pressure pump (101) includes a cylinder (20) and a plunger (25) slidably provided in the cylinder (20), and pressurizes fuel flowing from a fuel inlet (41) into a pressurizing chamber (24) and discharges the fuel by operation of the plunger. The high-pressure pump (101) has a leakage fuel collecting passage (60) that collects leakage fuel that leaks from the pressurizing chamber (24) through a clearance between the cylinder (20) and the plunger (25) and discharges the leakage fuel to the outside of the cylinder (20). In the fuel collection passage (60), when a portion where the leak fuel flows is defined as an upstream portion and a portion where the leak fuel is discharged is defined as a downstream portion, the leak fuel collection passage (60) communicates with the fuel inlet (41) only in the downstream portion.

Description

High pressure pump

Technical Field

The present invention relates to a high-pressure pump.

Background

Conventionally, a high-pressure pump has a leakage fuel collecting passage that collects leakage fuel that leaks through a gap between a cylinder and a plunger and discharges the leakage fuel from a pressurizing chamber to the outside.

For example, in the fuel supply device disclosed in patent document 1, an annular leakage collecting groove is formed on an inner wall of a plunger insertion hole in a cylinder. Fuel flowing into the fuel gallery is supplied to the leakage collection trough via a fuel bypass passage. The fuel flowing into the leak collection tank is returned to the fuel tank through the return passage hole and the return fuel pipe. The return passage hole communicates with the fuel gallery through a pressure relief (relief) passage hole.

Documents of the prior art

Patent document 1 JP 2016-

Disclosure of Invention

The axial direction of the plunger is defined as the vertical direction of the cylinder, the pressurizing chamber side is defined as the upper cylinder portion, and the side opposite to the pressurizing chamber is defined as the lower cylinder portion. In patent document 1, a return passage hole connecting the leakage collection groove and the return fuel pipe and formed in a lower portion of the cylinder corresponds to a "leakage fuel collection passage". The downstream portion of the return passage hole located at the upper portion of the cylinder communicates with the fuel inlet through a pressure-releasing passage hole. An upstream portion of the return passage hole located in the lower portion of the cylinder communicates with the fuel inlet from the leak collection groove via the fuel bypass passage.

Hereinafter, in the present specification, "high temperature" and "low temperature" with respect to the fuel temperature refer to relative temperatures. When low-temperature fuel flows from the fuel tank into the upstream portion of the leak fuel collection passage while the temperature of the plunger sliding on the inner wall of the cylinder increases, the lower portion of the cylinder is cooled. As a result, a gap between the outer wall of the high temperature plunger and the inner wall of the low temperature cylinder may be reduced due to a difference in thermal expansion, thereby having a possibility of failure of the plunger.

The present invention has been made in view of the above problems, and has as its object to reduce the temperature difference between the plunger and the cylinder in the upstream portion of the leak fuel collecting passage and prevent the plunger from malfunctioning.

The present invention is a high-pressure pump that includes a cylinder and a plunger slidably disposed in the cylinder and pressurizes fuel flowing from a fuel inlet into a pressurizing chamber and discharges the pressurized fuel by operation of the plunger.

The high-pressure pump has a leakage fuel collecting passage that collects leakage fuel that leaks from the pressurizing chamber through a gap between the cylinder and the plunger and discharges the leakage fuel to the outside of the cylinder. In the leaked fuel collecting passage, when a portion where the leaked fuel flows is defined as an upstream portion and a portion on a side where the leaked fuel is discharged is defined as a downstream portion, the leaked fuel collecting passage communicates with the fuel inlet only at the downstream portion.

In the present invention, since the low-temperature fuel does not flow into the upstream portion of the leaked fuel collecting passage, the leaked fuel in the lower portion of the cylinder is not cooled. Therefore, the heat of the high-temperature leak fuel is easily transmitted to the lower portion of the cylinder. Therefore, the temperature difference between the plunger and the cylinder can be reduced, and an appropriate clearance can be maintained. Therefore, malfunction of the plunger can be prevented.

On the other hand, the low-temperature fuel flows into the downstream portion of the leaked fuel collecting passage from the fuel inlet, thereby cooling the leaked fuel discharged to the outside of the high-pressure pump and reducing the burden on the returned fuel cooling device.

Drawings

Fig. 1 is an overall structural view of a common rail system to which a high-pressure pump according to an embodiment is applied;

FIG. 2 is a cross-sectional view of a high pressure pump according to a first embodiment;

FIG. 3 is a schematic cross-sectional view of a high pressure pump according to a first embodiment;

FIG. 4 is a schematic top view of the high pressure pump according to the first embodiment;

fig. 5A is a temperature analysis diagram of a cylinder and a plunger of a high-pressure pump according to a comparative example;

fig. 5B is a temperature analysis diagram of the cylinder and the plunger of the high-pressure pump according to the present embodiment;

FIG. 6 is a schematic cross-sectional view of a high pressure pump according to a second embodiment;

FIG. 7 is a schematic top view of a high pressure pump according to a second embodiment;

FIG. 8 is a schematic cross-sectional view of a high pressure pump according to a third embodiment;

FIG. 9 is a schematic top view of a high pressure pump according to a third embodiment;

FIG. 10 is a schematic cross-sectional view of a high pressure pump according to a fourth embodiment;

FIG. 11 is a schematic top view of a high pressure pump according to a fourth embodiment; and

fig. 12 is a schematic sectional view of a high-pressure pump according to a fifth embodiment.

Detailed Description

Hereinafter, embodiments of the high-pressure pump will be described with reference to the drawings. In the embodiments, the same reference numerals are used for substantially the same elements, and the description thereof will be omitted. Hereinafter, the first to fifth embodiments are collectively referred to as "the present embodiment". The present embodiment is a high-pressure pump that is applied to, for example, a diesel engine and supplies high-pressure fuel to a common rail.

[ common rail System ]

First, the overall configuration of the common rail system will be described with reference to fig. 1. The common rail system includes: a fuel tank 1, a high-pressure pump 10 (or a supply pump), a common rail 8, a plurality of fuel injection valves 12, and the like, and each component is connected by a pipe. The fuel tank 1 and the high-pressure pump 10 are connected by a low-pressure fuel pipe 2, and a fuel filter 3 for removing foreign substances is provided in the middle of the low-pressure fuel pipe 2. The high-pressure pump 10 and the common rail 8 are connected by a rail-front high-pressure fuel pipe 7. The common rail 8 and the plurality of fuel injection valves 12 are connected by a plurality of after-rail high-pressure fuel pipes 11.

The high-pressure pump 10 pressurizes the low-pressure fuel drawn from the fuel tank 1, and supplies the high-pressure fuel to the common rail 8. The high-pressure fuel supplied to the common rail 8 is distributed to a plurality of (four in the embodiment of fig. 1) fuel injection valves 12. The fuel injection valve 12 injects fuel into a cylinder of the engine. It should be noted that the configuration of the control system and the description of the operation thereof will be omitted.

The return line 14 returns the return fuel not consumed by the injection to the fuel tank 1. The relief pipe 6 is connected between the high-pressure pump 10 and the return pipe 14, the relief pipe 9 is connected between the high-pressure pump 10 and the common rail 8, and the leak pipe 13 is connected between the high-pressure pump 10 and the fuel injection valves 12. In the present embodiment, attention is paid to the return fuel discharged from the high-pressure pump 10 to the return pipe 14 through the overflow pipe 6.

[ high pressure Pump ]

Next, the configuration and operational effects of the high-pressure pump 10 will be described for each embodiment. Since the structure and operation other than the structure relating to the leak fuel collecting passage 60 in the high-pressure pump 10 of the present embodiment are substantially the same as those of the fuel supply apparatus described in patent document 1(JP 2016-. In the reference numerals of the high-pressure pump of each embodiment, the third digit after "10" represents the number of the embodiment.

(first embodiment)

The high-pressure pump 101 of the first embodiment will be described with reference to fig. 2 to 5. As shown in fig. 2, the high-pressure pump 101 changes the volume of the pressurizing chamber 24 by sliding the plunger 25 inserted into the plunger hole 23 of the cylinder 20. Hereinafter, according to the vertical direction in fig. 2, the pressurizing chamber 24 side of the plunger hole 23 is referred to as an upper side, and the side opposite to the pressurizing chamber 24 is referred to as a lower side. The plunger 25 reciprocates in the vertical direction along the plunger hole 23. In the case where the high-pressure pump 101 is actually mounted on an engine block or the like, the moving direction of the plunger 25 is not limited to a strictly vertical direction, and the high-pressure pump 101 may be mounted such that the moving direction of the plunger is inclined.

A sheet 29 pushed downward by a spring 28 is connected to the lower end portion of the plunger 25. Rotation of a camshaft (not shown) is transmitted to a lower end portion of the plunger 25, so that the plunger 25 rises against the urging force of the spring 28. Therefore, the fuel flowing into the pressurizing chamber 24 from the fuel inlet 41 is pressurized and discharged to the common rail 8. The discharge port of the high-pressure fuel is not shown in the cross section of fig. 2 but is shown in fig. 3 and 4.

The body 31 of the electromagnetic valve portion 30 is accommodated in a valve body accommodating portion 21 formed above the cylinder 20. In the body 31, a valve passage 32 having an opening 33 is formed extending in the radial direction and communicating with the pressurizing chamber 24. As described below, the valve passage 32 corresponds to a volume chamber having a function other than that of a communication passage between the fuel inlet 41 and a downstream portion of the leak fuel collection passage 60. The term "volume chamber" used herein is a term used as a generic term, which means "a space constituting a part of the communication passage" instead of the name of the lower portion.

A damper 42 for suppressing pulsation of the fuel is mounted on the damper mounting portion 22 of the cylinder 20. The fuel flowing from the fuel inlet 41 reaches the valve passage 32 via the damper 42. When the valve is open, the valve body 35 opens the opening 33 of the valve passage 32; and when the valve is closed, the valve body 35 is seated on the valve seat portion 34 and closes the opening 33, so that the valve body 35 regulates the fuel drawn into the pressurizing chamber 24. A coil 36, a stator core 37, an armature 38, a spring guide stopper 39, and the like constituting the solenoid valve portion 30 are provided above the cylinder 20.

A cap 26 is provided at a lower portion of the cylinder 20 and an oil seal 27 sealing an outer periphery of the plunger 25 is fixed by the cap 26. The leaked fuel, which leaks from the pressurizing chamber 24 through the gap between the inner wall of the cylinder 20 and the outer wall of the plunger 25, accumulates in the annular space above the oil seal 27.

The cylinder 20 has a leaked fuel collecting passage 60, the leaked fuel collecting passage 60 communicating the annular space with the return fuel outlet 68 and the leaked fuel being discharged outside the cylinder 20 in the leaked fuel collecting passage 60. In other words, the annular space forms a "collecting channel inlet 61" in which the leakage fuel flows into the leakage fuel collecting channel 60 at this collecting channel inlet 61. In the leaked fuel collecting passage 60, a portion on a side where the leaked fuel flows is referred to as an "upstream portion", and a portion where the leaked fuel is discharged is referred to as a "downstream portion".

In the leaked fuel collecting passage 60 according to the first embodiment, the valve portion communication passage 43 that communicates from the valve passage 32 is joined to the joining portion 66 located at the downstream portion. That is, the downstream portion of the leaked fuel collecting passage 60 communicates with the fuel inlet 41 via the valve portion communicating passage 43 and the valve passage 32. A hole 45 is provided in the valve portion communication passage 43 immediately before the engagement portion 66. The diameter and length of the hole 45 are appropriately set. On the other hand, in the upstream portion of the leak fuel collection passage 60, a passage communicating to the fuel inlet 41 is not formed. In short, the leak fuel collecting passage 60 communicates with the fuel inlet 41 only at a downstream portion.

In addition, the leaked fuel collecting passage 60 of the first embodiment is constructed by connecting an upstream-side flow passage 63 and a downstream-side flow passage 64 having different angles with respect to the axis of the plunger 25. In other words, the leaked fuel collecting passage 60 has a shape in which the upstream-side flow passage 63 and the downstream-side flow passage 64 are bent and connected to each other.

In addition, in fig. 2, the Z axis is defined along the axis of the plunger 25, and the upper end position of the pressurizing chamber 24 is described as "0", and the position of the collection passage inlet 61 is described as "a". These descriptions are used in the description of 5A and 5B.

Next, reference is made to the schematic cross-sectional view of fig. 3 and the top schematic view of fig. 4. Drawings of other embodiments are also described with respect to fig. 3 and 4. Fig. 3 shows a schematic representation of an axial cross section of the high-pressure pump 101, in particular the path of the fuel flow. The embodiment shown in fig. 3 differs from the embodiment shown in fig. 2 mainly in that a discharge passage 46, a discharge valve 47, and a discharge port 48 are shown, and in that the solenoid valve portion 30 and the damper 42 are simplified. When the fuel is sucked and regulated, the discharge valve 47 is closed by the spring force. When the plunger 25 rises and the pressure exerted by the fuel pressure in the pressurizing chamber 24 exceeds the spring force of the discharge valve 47, the discharge valve 47 opens and the high-pressure fuel is discharged to the outside through the discharge passage 46 that reaches the outside from the discharge port 48.

Fig. 4 schematically shows the path of the fuel flow with respect to a radial cross section viewed from above the high-pressure pump 101. Fig. 4 is a schematic sectional view in the radial direction, more precisely, but for convenience, referred to as a "schematic plan view". The pressurizing chamber 24 is formed at the center of the cylinder 20, and the fuel inlet 41, the discharge port 48, and the return fuel outlet 68 are appropriately provided in the circumferential direction. These settings are not exact, only indicating that they are set in appropriate positions that do not interfere with each other. In addition, the path indicated by the straight line in the schematic plan view does not necessarily have to be formed straight, but the path indicated by the multi-segment line in the schematic plan view may be formed straight in reality.

At the center of the cylinder 20, the valve body 31 is indicated by a thin dashed line, while the valve passage 32 and the opening 33 are indicated by a solid line. Further, the pressurizing chamber 24 below the valve passage 32 and the discharge passage 46 communicating with the discharge port 48 from the pressurizing chamber 24 are indicated by broken lines. The cross section of the valve body 35 in the opening 33 of the valve channel 32 is not shown. A damper 42 is schematically shown between the fuel inlet 41 and the valve passage 32. When the valve body 35 is opened, the fuel flowing from the fuel inlet 41 into the valve passage 32 through the damper 42 is supplied from the opening 33 to the pressurizing chamber 24 at the rear of the drawing. The fuel flowing into the valve passage 32 joins the leak fuel at a joint portion 66 located at a downstream portion of the leak fuel collecting passage 60 via the valve portion communication passage 43 and the hole 45. The merged fuel is discharged from the return fuel outlet 68.

As described above, in the first embodiment, in addition to the original function of the "volume chamber" in the metering valve, the valve passage 32 of the body 31 serves as the "communication passage between the fuel inlet 41 and the downstream portion of the leak fuel collecting passage 60". That is, the high-pressure pump 101 of the first embodiment shares the valve passage 32, which is the "volume chamber" of the metering valve, as the "communication passage between the fuel inlet 41 and the downstream portion of the leak fuel collection passage 60".

As described above with reference to fig. 2, in the leak fuel collecting passage 60 of the first embodiment, the upstream-side flow passage 63 and the downstream-side flow passage 64 having different angles with respect to the axis of the plunger 25 are connected. Specifically, a first angle θ 1 formed by the upstream-side flow passage 63 and the axis of the plunger 25 is smaller than a second angle θ 2 formed by the downstream-side flow passage 64 and the axis of the plunger 25. That is, the upstream-side flow passage 63 is oppositely formed along the plunger hole 23 and the downstream-side flow passage 64 is formed away from the plunger hole 23. In fig. 2, the downstream-side flow passage 64 is inclined with respect to the axis of the plunger 25, and satisfies the relationship of the first angle θ 1 < the second angle θ 2 < 90 °. However, the downstream-side flow passage 64 may also be formed orthogonal to the axis of the plunger 25 (i.e., "the second angle θ 2 ═ 90 °").

In addition, since the upstream-side flow path 63 and the downstream-side flow path 64 are generally manufactured by drilling, the cross section is circular. The diameter D1 of the upstream-side flow passage 63 is smaller than the diameter D2 of the downstream-side flow passage 64. Even if the cross-sectional shape of the flow channel is not strictly circular, for example, if the flow channel is elliptical, the average of the major and minor axes may be considered as the diameter.

Next, referring to fig. 5, the effects of the present embodiment will be described in comparison with a comparative example. As described in the "summary of the invention" column, "high temperature" and "low temperature" refer to relative temperatures with respect to the fuel temperature in the present specification. The high-pressure pump of the comparative example had a configuration in which: wherein the fuel inlet is connected to the upstream portion of the leak fuel collecting passage and the low temperature fuel is introduced from the fuel tank into the vicinity of the collecting passage inlet 61. The high-pressure pump disclosed, for example, in the drawing of DE 102017204843B3 in germany corresponds to a comparative example.

The fuel supply device disclosed in fig. 1 and the like of patent document 1(JP No. 2016-.

The horizontal axis in fig. 5A and 5B represents a position on the Z axis shown in fig. 2. "0" in the Z axis is the upper end position of the pressurizing chamber 24, and "a" in the Z axis is the position of the collection passage inlet 61 corresponding to the upper side of the oil seal 27. In the vicinity of 0, which is the upper portion of the cylinder 20, on the Z-axis, the fuel that has just flowed into the pressurizing chamber 24 from the fuel inlet 41 has a relatively low temperature. When the value on the Z axis increases near the lower portion of the cylinder 20, the increase in the temperature of the leaking fuel due to the sliding between the plunger 25 and the cylinder 20 is transmitted, so that both the plunger temperature and the cylinder temperature rise. At the point "a" on the Z-axis where the high-temperature leak fuel accumulates, the temperature becomes highest.

In the comparative example shown in fig. 5A, since the cylinder is cooled by the low-temperature fuel flowing from the fuel inlet to the upstream portion of the leak fuel collection passage, the cylinder temperature decreases and the temperature difference between the cylinder temperature and the plunger temperature increases. As a result, the clearance between the outer wall of the high-temperature plunger and the inner wall of the low-temperature cylinder is reduced due to the thermal expansion difference, and there is a risk of failure of the plunger.

On the other hand, in the present embodiment shown in fig. 5B, since the low-temperature fuel does not flow into the upstream portion of the leaked fuel collecting passage 60, the leaked fuel at the lower portion of the cylinder 20, i.e., at a position near "a", is not cooled. Therefore, the heat of the high-temperature leak fuel is easily transmitted to the lower portion of the cylinder 20. Therefore, the temperature difference between the plunger 25 and the cylinder 20 can be reduced, and an appropriate clearance can be maintained. Therefore, the plunger 25 can be prevented from malfunctioning.

On the other hand, the low-temperature fuel flows from the fuel inlet 41 into the downstream portion of the leaked fuel collecting passage 60, thereby cooling the leaked fuel discharged to the outside of the high-pressure pump 101 and reducing the burden on the returned fuel cooling device. In addition, the high-pressure pump 101 of the first embodiment has the following effects.

The fuel inlet 41 and the downstream portion of the leak fuel collecting passage 60 communicate via the valve passage 32 as a "volume chamber having a function other than that as a communication passage". In other words, the valve passage 32 is included in a part of the path connecting the fuel inlet 41 and the downstream portion of the leak fuel collecting passage 60. Therefore, the volume chambers having other functions can be effectively shared without providing a dedicated communication passage in the high-pressure pump 101.

The leak fuel collecting passage 60 is constituted by sequentially connecting an upstream-side flow passage 63 and a downstream-side flow passage 64 having different angles with respect to the axis of the plunger 25. Thus, the degree of freedom in the layout of the leak fuel collecting passage 60 can be increased according to the position of the return fuel outlet 68 and the ease of hole machining.

In particular, in the first embodiment, the upstream-side flow passage 63 forms a first angle θ 1 with the axis of the plunger 25 smaller than a second angle θ 2 of the downstream-side flow passage 64 with the axis of the plunger 25. Since the upstream-side flow passage 63 through which the high-temperature leak fuel flows is close to the plunger hole 23, the lower portion of the cylinder 20 is effectively heated, so that the temperature difference between the plunger 25 and the cylinder 20 can be made small. In addition, since the diameter D1 of the upstream-side flow passage 63 is smaller than the diameter D2 of the downstream-side flow passage 64, the fuel flow rate at the lower portion of the cylinder 20 can be increased, and the heat transfer coefficient at the lower portion of the cylinder 20 can be increased.

Further, a hole 45 is provided in the valve portion communication passage 43 that communicates the fuel inlet 41 and the downstream portion of the leaked fuel collecting passage 60. If the amount of fuel returned through the valve portion communication passage 43 is excessive compared to the amount of fuel required to cool the leak fuel, the proportion of fuel to be pumped is reduced. That is, since the fuel sucked into the pressurizing chamber 24 is reduced, the discharge amount required for the high-pressure pump 101 cannot be discharged. Therefore, by providing the hole 45 in the valve portion communication passage 43, the amount of fuel merging into the leak fuel collection passage 60 can be appropriately adjusted.

(second embodiment)

Fig. 6 and 7 show a high-pressure pump 102 according to a second embodiment. In the second embodiment, the shape and the like of the leak fuel collecting passage 60 of the first embodiment are simplified. That is, the leak fuel collecting passage 60 is formed linearly with a single diameter from the upstream portion to the downstream portion. Further, the damper 42 between the fuel inlet 41 and the valve passage 32 is omitted, and the hole 45 is not provided in the valve portion communication passage 43.

In short, the high-pressure pump 102 of the second embodiment achieves at least the "configuration in which only the downstream portion of the leak fuel collection passage 60 communicates with the fuel inlet 41". By adopting at least the configuration shown in fig. 6 and 7, the temperature difference between the plunger 25 and the cylinder 20 is reduced and a proper clearance between the plunger 25 and the cylinder 20 is maintained. Therefore, the plunger 25 can be prevented from malfunctioning. Further, in the second embodiment, since the leak fuel collecting passage 60 having a single diameter can be processed in a straight line, the processing man-hours can be reduced.

(third embodiment)

Fig. 8 and 9 show a high-pressure pump 103 according to a third embodiment. The third embodiment differs from the second embodiment in that a passage communicates from the fuel inlet 41 to a downstream portion of the leak fuel collecting passage 60. That is, the fuel inlet 41 and the downstream portion of the leak fuel collecting passage 60 directly communicate via the dedicated side flow communication passage 44. Here, the side flow in the "side flow communication passage" refers only to the side flow with respect to the main flow when the valve portion communication passage 43 passing through the valve passage 32 is regarded as the "main flow" passage. That is, the position where the communication passage is formed is not limited. In fig. 8 and 9, the side flow communication channel 44 is schematically shown as being bent at a plurality of locations, but in practice it may be formed into a shape that is machinable or easily machinable.

In fig. 8 and 9, the valve passage 32 and the downstream portion of the leak fuel collection passage 60 may not communicate with each other, or the valve portion communication passage 43 may be formed as shown by a long line-double short dash line. When the valve portion communication passage 43 is not formed, the fuel inlet 41 and the downstream portion of the leak fuel collection passage 60 communicate only through the side flow communication passage 44. Further, when the valve portion communication passage 43 is formed, the fuel inlet 41 and the leak fuel collection passage 60 communicate with each other, thereby flowing through the side flow communication passage 44 and the valve portion communication passage 43 in parallel.

In the third embodiment, since the dedicated side flow communication passage 44 that communicates the fuel inlet 41 and the downstream portion of the leak fuel collecting passage 60 is formed, it is possible to supply the low-temperature fuel from the fuel inlet 41 to the downstream portion of the leak fuel collecting passage 60 more stably. In the third embodiment, similarly to the first embodiment, a plurality of flow passages having different angles with respect to the axis of the plunger 25 may be connected. Further, the diameters of the plurality of flow paths may be changed, or holes may be provided in the side flow communication path 44.

(fourth embodiment)

Fig. 10 and 11 show a high-pressure pump 104 according to a fourth embodiment. In the fourth embodiment, a damper 51 or a valve 52 is provided at the middle of the side flow communication passage 435, as compared with the third embodiment. The damper 51 basically has the same function of suppressing pulsation as the damper 42 shown in fig. 2, but is installed at a different position. Further, the valve 52 opens and closes the side flow communication passage 435, and the specific configuration is not limited. The volume chambers in the damper 51 and the valve 52 correspond to "volume chambers having a function other than a function as a communication passage between the fuel inlet 41 and the downstream portion of the leak fuel collecting passage 60". Therefore, unlike the side flow communication path 44 of the third embodiment, the side flow communication path 435 of the fourth embodiment may not correspond to a "dedicated communication path". In this way, the communication passage between the fuel inlet 41 and the downstream portion of the leak fuel collecting passage 60 may be configured in any form.

(fifth embodiment)

The high-pressure pump 105 of the fifth embodiment shown in fig. 12 has two leak

fuel collecting passages

601 and 602 that communicate with the return fuel outlet 68 from different positions in the circumferential direction of the collecting passage inlet 61, respectively. Each of the leak

fuel collecting passages

601 and 602 includes an upstream

side collecting passage

631 and 632 having a relatively small angle with respect to the axis of the plunger 25 and a downstream

side collecting passage

641 and 642 having a relatively large angle with respect to the axis of the plunger 25.

Similarly, three or more leak fuel collection passages may be formed. Since a plurality of leaked fuel collecting passages are formed at different positions in the circumferential direction of the collecting passage inlet 61, the circumferential deviation of the amount of discharged leaked fuel can be reduced. Therefore, the cylinder temperature can be made relatively uniform in the circumferential direction.

(other embodiments)

(A) In contrast to the first embodiment, a first angle θ 1 formed by the upstream-side flow passage 63 and the axis of the plunger 25 may be larger than a second angle θ 2 formed by the downstream-side flow passage 64 and the axis of the plunger 25. In this case, the effect of reducing the temperature difference between the plunger 25 and the cylinder 20 cannot be expected. However, the following effects can be similarly obtained: the degree of freedom in the arrangement of the leak fuel collecting passage 60 can be increased and drilling can be easily performed according to the position of the return fuel outlet 68.

(B) In contrast to the first embodiment, the leak fuel collecting passage 60 may be constituted by sequentially connecting three or more flow passages having different angles with respect to the axis of the plunger 25 as long as machining is possible.

(C) The upstream-side flow passage 63 and the downstream-side flow passage 64 in the first embodiment are each formed in a straight shape, that is, formed to have a single diameter D1, D2 that is constant in diameter. On the other hand, for example, the leaked fuel collecting passage 60 may be formed in a tapered state in which the leaked fuel collecting passage continuously expands from the upstream portion to the downstream portion. Even in this configuration, the diameter of the leak fuel collecting passage 60 on the upstream side is smaller than that on the downstream side. Therefore, the fuel flow rate in the lower portion of the cylinder 20 increases and the heat transfer coefficient in the lower portion of the cylinder 20 increases.

(D) The configurations relating to the leaked fuel collecting passage and the communication passage in each of the above embodiments may be used in appropriate combinations as long as they are not contradictory.

(E) The high-pressure pump of the invention is not limited to a diesel engine, and may be used as a fuel pump for fuel injection or other fuels.

The present disclosure is not limited to the above-described embodiments, and various modifications may be adopted within the scope of the present disclosure without departing from the spirit thereof.

Claims

1. A high pressure pump comprising:

a cylinder (20);

a plunger (25) configured to be slidably disposed in the cylinder; and

a plenum chamber (24) into which fuel flows from a fuel inlet (41),

wherein the high-pressure pump pressurizes and discharges the fuel in the pressurizing chamber by operation of the plunger, further comprising

A leaked fuel collecting passage (60, 601, 602) configured to collect leaked fuel that leaks from the pressurizing chamber through a gap between the cylinder and the plunger and configured to discharge the leaked fuel to an outside of the cylinder, wherein,

when a portion on a side where the leak fuel flows in the leak fuel collecting passage is defined as an upstream portion and a portion on a side where the leak fuel is discharged is defined as a downstream portion,

the leaked fuel collecting passage communicates with the fuel inlet only at the downstream portion.

2. The high pressure pump of claim 1, further comprising

A volume chamber (32, 51, 52) that is provided in at least a part of a passage (43, 435) that communicates the fuel inlet and the downstream portion of the leaked fuel collecting passage, and that has a function other than a function as a communicating passage.

3. The high pressure pump of claim 1 wherein

The fuel inlet and the downstream portion of the leaked fuel collecting passage directly communicate with each other through a dedicated passage (44).

4. The high-pressure pump according to any one of claims 1 to 3, wherein,

the leak fuel collecting passage is constituted by sequentially connecting a plurality of flow passages (63, 64) having different angles with respect to the axis of the plunger.

5. The high pressure pump of claim 4 wherein

The leak fuel collecting passage is configured to connect an upstream side flow passage (63) and a downstream side flow passage (64) having different angles with respect to the axis of the plunger, and a first angle (θ 1) formed by the upstream side flow passage and the axis of the plunger is smaller than a second angle (θ 2) formed by the downstream side flow passage and the axis of the plunger.

6. The high-pressure pump according to any one of claims 1 to 3, wherein,

the diameter (D1) of the leaked fuel collecting passage on the upstream portion is smaller than the diameter (D2) on the downstream portion.

7. The high-pressure pump according to any one of claims 1 to 3, wherein,

an aperture (45) is provided in a passage communicating with the fuel inlet and a downstream portion of the leaked fuel collecting passage.

8. The high-pressure pump according to any one of claims 1 to 3, wherein,

the leakage fuel collecting passage has a plurality of the leakage fuel collecting passages (601, 602).

9. The high pressure pump of claim 2, wherein

When a valve body (35) is opened, the fuel flowing from the fuel inlet into the volume chamber is supplied to the pressurizing chamber.

10. The high pressure pump of claim 9,

the fuel having flowed into the volume chamber merges with the leaked fuel at a junction (66) located at the downstream portion of the leaked fuel collecting passage, and the merged fuel is discharged from a return fuel outlet (68).