JP2003278667A - Fluid pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid pump capable of improving seizure limit of a sliding part of a piston with a low cost. <P>SOLUTION: The fluid pump is equipped with a cylinder 1 formed with the hole 27 for the piston, the piston 4 which contains one end part and another end part located in an opposite side with the one end part, and one end part side is reciprocatively inserted into the hole 27 for the cylinder 1, a pressurizing chamber 15 which is connected to the hole 27 for the piston, one end part of the piston 4 is exposed and pressurizes the fluid and a seal member 5 having a lip part contacting the side wall of the piston 4 in the part including another end part of the piston 4 projected from the hole 27 for the piston. A recessed part 17 containing a part of the surface of the lip part and a part of the side wall of the piston 4 is formed in the area opposing to the cylinder 1 at the lip part. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid pump, and more specifically, it drives a piston capable of reciprocating motion to pressurize a fluid such as fuel introduced into a pressurizing chamber and to apply this fluid. The present invention relates to a fluid pump that supplies a pressurized fluid to the outside.

[0002]

2. Description of the Related Art Conventionally, there is known a high-pressure fuel pump which is mounted on an internal combustion engine such as an automobile engine and supplies fuel to a fuel injection valve or the like. An example of such a high-pressure fuel pump is, for example, Japanese Patent Laid-Open No. 2001-295728.
A piston type (also called a plunger type) high-pressure fuel pump as disclosed in the official gazette is cited. Figure 7
It is a cross-sectional schematic diagram which shows the conventional high pressure fuel pump. Also,
FIG. 8 is a partially enlarged sectional schematic view of the high-pressure fuel pump shown in FIG. 7. A conventional high-pressure fuel pump will be described with reference to FIGS. 7 and 8.

As shown in FIG. 7, the high-pressure fuel pump comprises a cylinder body 101 and a piston 104 reciprocally inserted into a piston hole 127 formed in the cylinder body 101. One end of the piston 104 is exposed to the pump high pressure chamber 115 formed in the cylinder body 101. The high-pressure fuel pump further includes a lifter 111 that is in contact with the other end of the piston 104 opposite to the one end thereof and that is slidable with respect to the cylinder body 101. In the cylinder body 101, a pump high pressure chamber 115 is formed so as to be connected to the piston hole 127 described above.

Further, an inlet valve 102 for supplying fuel into the pump high pressure chamber 115 is arranged so as to be connected to the pump high pressure chamber 115. The inlet valve 102 is connected to a feed pump (not shown) via a fuel pipe not shown. The feed pump is connected to a fuel tank (not shown), and supplies low-pressure fuel from this fuel tank to the inlet valve 102.
It is used for supplying to the pump high-pressure chamber 115 via.

An outlet valve 103 is arranged adjacent to the pump high pressure chamber 115 so as to be connected to the pump high pressure chamber 115. Outlet valve 103
Is used to discharge the fuel, whose pressure has been increased by the method described later, inside the pump high-pressure chamber 115 to the outside of the high-pressure fuel pump.

The other end of the cylindrical piston 104 abuts the lifter 111 as described above, and one end thereof faces the pump high pressure chamber 115. Lifter 111
Has a cylindrical shape having a bottom wall, and is slidably inserted into a lifter guide portion 112 formed on the cylinder body 101. The outer peripheral surface of the side wall of the lifter 111 is in contact with the inner wall 128 of the lifter guide portion 112. A spring retainer 110 is attached to the other end of the piston 104.
Is installed. The lifter guide portion 11 of the end portion of the spring retainer 110 and the cylinder body 101.
The spring 109 is arranged so as to come into contact with the bottom wall surface of No. 2. The spring 109 is installed in a compressed state. Therefore, due to the repulsive force of the spring 109, the other end of the piston 104 is pressed against the bottom wall of the lifter 111 and the lifter 111 is biased toward the arrow 129 side in FIG. 7.

An oil seal press-fitting hole 113 is formed in the bottom wall of the lifter guide portion 112 so as to surround the piston hole 127. In the oil seal press-fitting hole 113,
The end of the oil seal 105 is inserted. The oil seal 105 is located on the other end side of the piston 104 (the lifter 1).
11 side) and one end side (pump high pressure chamber 115 side) are sealed. A fuel return passage 114 is formed at the bottom of the oil seal press-fitting hole 113.

The oil seal 105 includes a lip portion that contacts the piston 104. As shown in FIG. 8, the lip portion includes an oil lip 106 arranged on the other end side of the piston 104 and a fuel lip 107 arranged on the one end side of the piston 104. The oil lip 106
During operation of the high-pressure fuel pump described later, the piston 1
It is used to prevent the engine oil from flowing from the lifter 111 side to the one end side of the piston 104 (the pump high pressure chamber 115 (see FIG. 7) side) accompanying the reciprocating movement (sliding motion) of 04. . Further, the fuel lip 107 is
Similarly, when the piston 104 reciprocates, the piston 104
From the pump high pressure chamber 115 (see FIG. 7) side to the lifter 111.
(See FIG. 7) Used to suppress fuel leakage to the side.

Next, the operation of the high-pressure fuel pump shown in FIGS. 7 and 8 will be briefly described. When the high-pressure fuel pump shown in FIGS. 7 and 8 is applied to an engine in an actual automobile, a cam shaft is arranged below the lifter 111. This camshaft has, for example, a lifter 1
A drive cam that can contact the bottom wall of 11 is provided. The drive cam is formed with a plurality of cam noses (portions formed so as to project from the outer peripheral surface of other regions of the drive cam when viewed from the center of the cam shaft). The cam nose presses the lifter 111 as the cam shaft rotates.
As a result, the lifter 111 reciprocates in the directions indicated by arrows 129 and 130 in FIG. Then, with the movement of the lifter 111, the piston 104 also repeats the reciprocating movement in the directions of arrows 129 and 130.

In the high-pressure fuel pump performing such an operation, when the fuel is discharged from the outlet valve 103 in a high pressure state, for example, the following operation is performed. First, with the inlet valve 102 opened, the piston 104 moves in the direction indicated by the arrow 129. Then, low-pressure fuel pumped up from a fuel tank by a feed pump (not shown) is injected into the pump high-pressure chamber 115 via the fuel pipe and the inlet valve 102 connected to this fuel pipe.

Next, the inlet valve 102 is closed and the piston 104 is raised in the direction indicated by arrow 130. As a result, the volume of the pump high pressure chamber 115 is reduced, so that the fuel supplied into the pump high pressure chamber 115 is pressurized.

When the fuel pressure inside the pump high pressure chamber 115 exceeds a predetermined value, the outlet valve 10
3 is opened. As a result, high-pressure fuel is discharged from the inside of the pump high-pressure chamber 115 via the outlet valve 103 to the outside.

By repeating the above-described operation, it is possible to discharge the high-pressure fuel from the outlet valve 103.

[0014]

In the conventional high-pressure fuel pump shown in FIG. 7 and FIG.
A drive member such as a drive cam for driving in the 29 and 130 directions is mainly lubricated with a lubricating oil such as general engine oil, while the sliding portion 108 between the wall surface of the piston 104 and the piston hole 127 ( (See FIG. 7) is mainly lubricated by fuel leaking from the pump high pressure chamber 115 (see FIG. 7).

However, the viscosity of fuel such as gasoline is much smaller than the viscosity of lubricating oil such as engine oil, which is several tenths. Therefore, the oil film thickness formed by the fuel on the sliding portion 108 of the piston 104 is smaller than the oil film thickness when using a general lubricating oil under the same conditions. Therefore, in the sliding portion 108, the piston 10
A state of solid friction (a state of insufficient lubrication) was likely to occur between the surface of No. 4 and the side wall of the piston hole 127.
That is, in the sliding portion 108, the so-called seizure limit was lower than in other portions.

In contrast to such a low seizure limit of the sliding portion 108, conventionally, for example, a special material is used as the material of the piston 104 or the cylinder body 101,
Alternatively, a measure such as heat treatment or surface treatment is applied to the surface of the piston 104 or the side wall of the piston hole 127.

However, when such a special material or special treatment is applied to a high pressure fuel pump as a fluid pump,
There is a problem that the manufacturing cost of the pump increases. That is, it has been difficult to realize a fluid pump with a sufficiently high seizure limit of the sliding portion and low cost.

The present invention has been made to solve the above problems, and an object of the present invention is to reduce the cost and to improve the seizure limit of the sliding portion of the piston. It is to provide a fluid pump.

[0019]

A fluid pump according to the present invention includes a cylinder having a piston hole formed therein, one end, and the other end opposite to the one end. , A piston whose one end side is reciprocally inserted into the piston hole of the cylinder, and a pressurizing chamber that is connected to the piston hole, exposes one end of the piston, and pressurizes fluid, And a seal member having a lip portion that comes into contact with the side wall of the piston in a portion including the other end portion of the piston that protrudes from the use hole, and a portion of the surface of the lip portion in a region of the lip portion that faces the cylinder. A recess including a part of the side wall of the piston as a wall surface is formed.

Here, the lubricating oil that lubricates the drive member located on the other end side of the cylinder leaks from the other end side of the cylinder to the one end side to some extent along the side wall of the cylinder via the lip portion. To do. In the fluid pump according to the present invention, the lubricating oil that has thus passed through the lip portion and leaked to the one end portion side of the cylinder can be accumulated in the concave portion.
Then, the lubricating oil accumulated in the concave portion adheres to a part of the side wall of the piston forming the wall surface of the concave portion. The part of the side wall of the piston to which the lubricating oil adheres moves to the inside of the cylinder hole as the piston reciprocates. As a result, the lubricating oil accumulated in the recess can be introduced between the wall surface of the cylinder hole and the side wall of the piston. For the lubrication between the wall surface of the cylinder hole and the side wall of the piston (piston sliding part), the fluid that leaks from the pressurizing chamber to the piston hole has been mainly used in the past. Since the lubricating oil can be introduced into the portion, not only the fluid leaked from the pressurizing chamber but also the lubricating oil of the driving portion can be used as the lubricant between the piston and the cylinder hole.

When a fuel such as gasoline is used as the fluid pressurized in the pressurizing chamber and a lubricating oil having a higher viscosity than the fuel such as normal engine oil is used as the lubricating oil of the drive unit,
It is possible to use a lubricating oil having a higher viscosity as a lubricant for the sliding portion of the piston. Here, the thickness t (oil film thickness) of the lubricant formed on the piston sliding portion uses the load W acting on the piston sliding portion, the viscosity μ of the lubricant, the moving speed U of the piston 4, and the coefficient K. Therefore, it can be expressed by the equation t = K × μ × U / W. That is, the thickness t of the lubricant is the viscosity μ of the lubricant.
Proportional to. Therefore, according to the present invention, the thickness of the lubricant (oil film thickness) at the piston sliding portion can be increased. As a result, the seizure limit of the piston sliding portion can be improved.

Further, since the seizure limit of the piston sliding portion can be improved by such a simple process of forming the concave portion on the lip portion, a special material is used for the piston or the cylinder, or the piston or cylinder is made of a special material. It is not necessary to take special measures such as applying a special surface treatment to the surface of the cylinder. Therefore, the manufacturing cost of the fluid pump can be reduced.

In the above fluid pump, the distance between the cylinder surface and the portion of the surface of the lip portion forming the wall surface of the recess closest to the cylinder is shorter than the stroke length when the piston reciprocates inside the piston hole. It may be.

In this case, the portion of the side wall of the cylinder to which the lubricating oil accumulated in the concave portion adheres surely reaches the inside of the piston hole by the reciprocating movement of the cylinder. Therefore, the lubricating oil accumulated in the recess can be reliably supplied to the cylinder sliding portion.

A fluid pump according to the present invention includes a cylinder having a piston hole formed therein, one end portion, and the other end portion opposite to the one end portion. The piston whose side is reciprocally inserted into the piston hole of the cylinder, is connected to the piston hole, and one end of the piston is exposed, and the pressure chamber for pressurizing the fluid and the piston hole protrude from the piston hole. In a portion including the other end of the piston, a seal member having a lip portion that comes into contact with a side wall of the piston is provided, and a region of the lip portion that faces the cylinder is positioned with a gap between the side wall of the piston and A wall portion is formed that extends along the direction in which the side wall of the piston extends.

As described above, the lubricating oil that lubricates the drive member located on the other end side of the cylinder leaks from the other end side of the cylinder to the one end side to some extent via the lip portion. Then, in the fluid pump according to the present invention, the lubricating oil that has passed through the lip portion and leaked to the one end portion side of the cylinder in this way is stored in the recess formed by the wall portion formed on the lip portion and the side wall of the piston. Can be accumulated. The lubricating oil accumulated in the concave portion adheres to the side wall portion of the piston facing the wall portion (a part of the side wall of the piston forming the wall surface of the concave portion). The part of the side wall of the piston to which the lubricating oil adheres moves to the inside of the cylinder hole as the piston reciprocates. As a result, the lubricating oil accumulated in the recess can be introduced between the wall surface of the cylinder hole and the side wall of the piston (piston sliding portion). Conventionally, the fluid that leaks from the pressurizing chamber to the piston hole was used to lubricate the piston sliding part, but since the lubricating oil can be introduced into the piston sliding part as described above, As the lubricant between the cylinder hole and the cylinder hole, not only the fluid leaked from the pressurizing chamber but also the lubricating oil of the drive unit can be used. If a lubricant having a viscosity higher than that of the fluid is used, the thickness of the lubricant (oil film thickness) at the piston sliding portion can be increased. Therefore, the seizure limit of the piston sliding portion can be improved.

Further, since the seizure limit of the piston sliding portion can be improved by such a simple process of providing the wall portion on the lip portion, a special material is used for the piston or cylinder, or There is no need to take special measures such as special surface treatment on the surface of the piston or cylinder. Therefore, the manufacturing cost of the fluid pump can be reduced.

In the above fluid pump, the distance between the portion of the wall portion closest to the cylinder and the cylinder surface may be shorter than the stroke length when the piston reciprocates inside the piston hole.

In this case, the portion of the side wall of the cylinder to which the lubricating oil accumulated in the recess formed by the wall portion of the lip portion and the side wall of the cylinder facing the wall portion adheres reliably by the reciprocating movement of the cylinder. Reach inside the piston hole. Therefore, the lubricating oil accumulated in the recess can be reliably supplied to the cylinder sliding portion.

In the above fluid pump, the cylinder may include a groove formed on the side wall of the piston hole at a position spaced from the pressurizing chamber. Further, the fluid pump may include a recovery pipe line that is connected to the groove and that recovers the fluid leaked from the pressurizing chamber to the groove via the piston hole.

In this case, fluid such as fuel leaking from the pressurizing chamber between the piston hole and the piston can be trapped in the groove provided on the side wall in the middle of the piston hole. And the fluid trapped in the groove is
Since it is recovered via the recovery conduit, the amount of fluid leaking from the groove to the seal member side can be reduced. Therefore, on the seal member side with respect to the groove, in the mixture of the fluid leaked from the pressure chamber as the lubricant between the piston and the side wall of the cylinder hole (piston sliding portion) and the lubricating oil of the drive portion, The proportion of lubricating oil can be increased. Therefore, if a lubricating oil having a viscosity higher than that of the fluid is used, the thickness of the lubricant (oil film thickness) in the piston sliding portion can be increased, so that the seizure limit of the piston sliding portion can be reliably improved. be able to.

The above fluid pump is preferably applied to an engine of an automobile. Also, the fluid pump is preferably used for supplying fuel to an engine of an automobile.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts will be denoted by the same reference numerals and the description thereof will not be repeated.

(Embodiment 1) FIG. 1 is a schematic sectional view of Embodiment 1 of a high-pressure fuel pump as a fluid pump according to the present invention. FIG. 2 is a partial cross-sectional schematic diagram of the high-pressure fuel pump shown in FIG. The high-pressure fuel pump shown in FIGS. 1 and 2 is applied to an automobile engine such as a cylinder injection engine. A high-pressure fuel pump according to the present invention will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the high-pressure fuel pump has a cylinder body 1 as a cylinder and a piston hole 27 formed in the cylinder body 1, and one end of the high-pressure fuel pump is reciprocally inserted. And a piston 4. In the cylinder body 1, a pump high pressure chamber 15 as a pressurizing chamber is formed so as to be connected to the piston hole 27. One end of the piston 4 is exposed in the pump high pressure chamber 15 formed in the cylinder body 1. The high-pressure fuel pump further includes a lifter 11 that is in contact with the other end of the piston 4 opposite to one end thereof and that is slidable with respect to the cylinder body 1.

Further, in the high pressure fuel pump according to the present invention,
An inlet valve 2 for supplying fuel into the pump high pressure chamber 15 is arranged so as to be connected to the pump high pressure chamber 15. The inlet valve 2 is connected to a feed pump (not shown) via a fuel pipe not shown. The feed pump is connected to a fuel tank (not shown). The feed pump is used to supply low pressure fuel from the fuel tank to the pump high pressure chamber 15 via the inlet valve 2.

An outlet valve 3 is arranged adjacent to the pump high pressure chamber 15 so as to be connected to the pump high pressure chamber 15. The outlet valve 3 discharges the fuel whose pressure has been increased by the method described below inside the pump high-pressure chamber 15 to the fuel distribution pipe.

As described above, the other end of the piston 4 contacts the lifter 11 and one end of the piston 4 is exposed in the pump high pressure chamber 15. The lifter 11 has a cylindrical shape having a bottom wall, and is slidably inserted into a lifter guide portion 12 formed on the cylinder body 1. The side wall of the lifter 11 is the inner wall 2 of the lifter guide portion 12.
8 is in contact with. A spring retainer 10 is installed at the other end of the piston 4. Outer peripheral edge of spring retainer 10 and cylinder body 1
The spring 9 is arranged so as to come into contact with the bottom wall surface of the lifter guide portion 12 in FIG. This spring 9 is installed in a compressed state. Therefore, this spring 9
The other end of the piston 4 is pressed against the bottom wall of the lifter 11 by the repulsive force of, and the lifter 11 is urged toward the cam shaft (not shown) (arrow 29 side in FIG. 1).

An oil seal press-fitting hole 13 is formed in the bottom wall of the lifter guide portion 12 so as to surround the piston hole 27. The end portion of the oil seal 5 is inserted into the oil seal press-fitting hole 13. The oil seal 5 is used for sealing between the other end side (the lifter 11 side) and the one end side (the pump high pressure chamber 15 side) of the piston 4. A fuel return passage 14 is formed at the bottom of the oil seal press-fitting hole 13.

The oil seal 5 as a seal member includes a lip portion that comes into contact with the side wall of the piston 4 at a portion including the other end portion of the piston 4 protruding from the piston hole 27. As shown in FIG. 1, the lip portion has an oil lip 6 arranged on the other end side of the piston 4 and a fuel lip 7 arranged on the one end side of the piston 4. A gap 20 (see FIG. 2) is formed between the wall surface of the oil seal between the oil lip 6 and the fuel lip 7 and the outer peripheral side surface of the piston 4.

When the high pressure fuel pump, which will be described later, is operated, the oil lip 6 is such that engine oil as lubricating oil from the lifter 11 side (the one end portion side of the piston 4 Pump high pressure chamber 15
(See FIG. 1) side). Similarly, the fuel lip 7 prevents the fuel as a fluid from leaking from the pump high pressure chamber 15 (see FIG. 1) side of the piston 4 to the lifter 11 (see FIG. 1) side when the piston 4 slides. It is used to Then, the fuel lip 7 forming the lip portion of the oil seal 5
On the upper part (a region facing the cylinder body 1) of the piston 4 along the extending direction of the outer peripheral surface (side wall) of the piston 4 (substantially parallel to the extending direction of the outer peripheral surface of the piston 4). 18 is formed. A gap is formed between the side wall 18 and the outer peripheral surface of the piston 4.
This gap serves as an oil reservoir 17 as a recess. The wall surface of the oil sump portion 17 is constituted by a part of the surface of the fuel lip 7, the side wall 18 and a part of the outer peripheral surface of the piston 4.

Next, the operation of the high-pressure fuel pump shown in FIGS. 1 and 2 will be briefly described. When the high-pressure fuel pump shown in FIG. 1 is applied to an engine in an actual automobile,
Under the lifter 11, for example, a cam shaft is arranged.
The cam shaft may be provided with a drive cam capable of contacting the bottom wall of the lifter 11. The drive cam has a plurality of cam noses (portions formed so as to project from the outer peripheral surface of the other region of the drive cam when viewed from the center of the camshaft).
May be formed. Then, as the cam shaft rotates, the cam nose of the drive cam presses the lifter 11. As a result, the lifter 11 has the arrows 29 and 3 in FIG.
It reciprocates in the direction indicated by 0. As the lifter 11 reciprocates, the piston 4 also reciprocates in the directions of arrows 29 and 30.

In the high-pressure fuel pump performing such an operation, when the fuel is discharged from the outlet valve 3 in a high pressure state, the following operation is performed, for example.
First, with the inlet valve 2 in the open state, the piston 4 moves in the direction indicated by the arrow 29. Then, low-pressure fuel pumped up from a fuel tank (not shown) by a feed pump (not shown) is introduced into the pump high-pressure chamber 15 via the fuel pipe and the inlet valve 2 connected to this fuel pipe.

Next, the inlet valve 2 is closed. Here, for example, an electromagnetic spill valve can be used as the inlet valve 2. The electromagnetic spill valve includes an electromagnetic solenoid. The electromagnetic spill valve is in an open state when no voltage is applied to the electromagnetic solenoid, and is in a closed state when a voltage is applied to the electromagnetic solenoid. Therefore, for example, when the inlet valve 2 is closed, by applying a voltage to the electromagnetic solenoid of the electromagnetic spill valve as the inlet valve 2,
The closed state of the inlet valve 2 can be realized.

Next, the inlet valve 2 is closed and the piston 4 is raised in the direction shown by the arrow 30. As a result, the volume of the pump high pressure chamber 15 is reduced. Therefore, the fuel arranged inside the pump high pressure chamber 15 is pressurized.

When the pressure of the fuel inside the pump high pressure chamber 15 exceeds a predetermined value, the outlet valve 3 is opened. As a result, the high-pressure fuel is discharged from the inside of the pump high-pressure chamber 15 via the outlet valve 3 to a fuel distribution pipe (not shown). Then, the high-pressure fuel is distributed to each fuel injection valve of the engine through the fuel distribution pipe. Thereafter, fuel is supplied from each injection valve into the combustion chamber of the engine.

By repeating the above-described operation, it is possible to discharge the high-pressure fuel from the outlet valve 3.

Next, along with the operation of the high-pressure fuel pump as described above, engine oil is accumulated in the oil sump portion 17 (see FIG. 1), and the accumulated engine oil is formed between the cylinder body 1 and the piston 4. Sliding part 8 which is a contact part
The operation of pulling in (see FIG. 1) will be described with reference to FIGS. 3 to 5 are partial enlarged cross-sectional schematic views for explaining the operation of the high-pressure fuel pump shown in FIGS. 1 and 2. 3 to 5, only a part of the oil seal 5 arranged so as to cover a part of the outer peripheral surface of the piston 4 over the entire circumference is shown.

First, as shown in FIG. 3, when the piston 4 rises in the direction shown by the arrow 22, the engine oil oil film 19 attached to the outer peripheral surface of the piston 4 is
Most of the oil lip 6 is removed from the outer peripheral surface of the piston 4 as the oil lip 6 rises. However, there is an intrusion oil film 21 of engine oil that slightly passes through the oil lip 6. The engine oil that has entered the void 20 as the entry oil film 21 is accumulated inside the void 20. This is because once the engine oil that has entered the air gap 20 moves from the oil lip 6 to the other end of the piston 4, even if the piston 4 moves in the direction opposite to the direction indicated by the arrow 22 (downward). This is because it does not flow out to the part side but remains to some extent inside the void 20. As a result, such arrows 22, 23 (see FIG.
While the reciprocating motion of the piston 4 as shown in FIG. 4) is repeated, the engine oil 24 is gradually accumulated inside the gap 20 as shown in FIG.

While the reciprocating motion of the piston 4 shown by the arrows 22 and 23 (see FIG. 4) is repeated, the amount of the engine oil 24 accumulated in the gap 20 gradually increases until the inside of the gap 20 is increased. Fill up with. Then, when the reciprocating motion of the piston 4 is further repeated, the engine oil in the gap 20 reaches the inside of the oil sump portion 17 beyond the fuel lip 7. As a result, as shown in FIG. 5, the engine oil 25 is accumulated inside the oil sump 17.

In the state shown in FIG. 5, the oil sump portion 17
The side wall of the piston 4 forming a part of the wall surface of the engine is in contact with the engine oil 25 accumulated in the oil sump 17. Therefore, when the piston 4 moves in the direction indicated by the arrow 22 (upward direction), the portion of the surface of the piston 4 on which the oil film having a sufficient thickness is formed by coming into contact with the engine oil 25 is the hole 27 for the piston. (The surface portion of the piston 4 on which an oil film having a sufficient thickness is formed is drawn into the sliding portion 8 between the cylinder body 1 and the piston 4). As a result, the proportion of engine oil in the mixture (lubricant) of engine oil and gasoline in the sliding portion 8 can be increased.

The oil lip 6 or the fuel lip 7 of the oil seal 5 is basically shaped so as to be capable of leak control in one direction but has no sealing property in the opposite direction. That is, when the piston 4 moves upward to the arrow 22 (see FIG. 5) side, in the fuel lip 7, the engine oil 24 (see FIG. 5) easily flows from the oil lip 6 side (that is, the gap 20 side). It can pass through 7 and flow into the oil sump 17.
On the other hand, when the engine oil is discharged to the upper side of the fuel lip 7, when the piston 4 moves downward as shown by the arrow 23 (see FIG. 5), the engine oil 25 accumulated in the oil sump portion 17 is replaced with the fuel. Scraped by lip 7. Therefore, the state in which the engine oil 25 is accumulated in the oil sump 17 can be maintained.

Here, the distance L (see FIG. 5) between the lower end 16 of the cylinder body and the upper end of the side wall 18 as a wall forming the oil reservoir 17 is shown by the stroke length of the piston 4 (arrows 22 and 23). The amount of movement in the reciprocating motion in the direction) is preferably smaller than that. Considering that the side wall 18 is also a part of the lip portion, it can be said that the upper end of the side wall 18 is the portion of the surface of the lip portion forming the wall surface of the oil reservoir 17 that is closest to the cylinder body 1. In this case, a part of the side wall of the piston 4 that was in contact with the engine oil 25 in the oil sump 17 surely reaches the sliding portion 8. As a result, the engine oil 25 accumulated in the oil sump 17 adheres to the side wall of the piston 4 and is reliably drawn into the sliding portion 8.

In the sliding portion 8, the pump high pressure chamber 15
When a high pressure is generated in (see FIG. 1), fuel flows into the sliding portion 8 from the pump high pressure chamber 15 (see FIG. 1) toward the oil seal 5 side. Therefore, in the sliding portion 8, the mixture of fuel and engine oil is located between the side wall surface of the piston hole 27 and the outer peripheral wall surface of the piston 4,
It functions as a lubricant. In this case, the proportion of the engine oil in the mixture of the fuel and the engine oil is increased by forming the oil sump portion 17 as in the present invention and increasing the amount of the engine oil 25 drawn into the sliding portion 8. be able to. As a result, the viscosity of the engine oil is higher than that of the fuel such as gasoline or light oil, so that the viscosity of the mixture of the fuel and the engine oil can be increased. Therefore, since the film thickness of the mixture is proportional to its viscosity, the film thickness of the mixture can be increased. As a result, it is possible to suppress the occurrence of seizure or the like between the piston 4 and the wall surface of the piston hole 27. That is, it is possible to improve the seizure limit and reduce wear of the piston 4 and the cylinder body 1.

Further, the seizure limit of the sliding portion 8 can be improved by such a simple processing that the side wall 18 is formed on the fuel lip 7 of the oil seal 5 and the oil reservoir 17 as a recess is provided. Therefore, it is not necessary to use a special material for the material of the piston 4 or the cylinder body 1 or to perform a special surface treatment on the surface of the piston 4 or the cylinder body 1. Therefore, the manufacturing cost of the high-pressure fuel pump can be reduced.

In the oil sump 17, the pressure of the engine oil coming into contact with the surface of the piston 4 can be increased by the own weight of the accumulated engine oil 25, especially at the bottom of the oil sump 17. As a result, the engine oil 25 can be made to adhere to the surface of the piston 4 more easily than before. Furthermore, since the side wall 18 extends in the direction along the sliding direction of the piston 4, the contact distance and contact time between the engine oil 25 accumulated in the oil sump 17 and the piston 4 can be increased. As a result, the engine oil 25 can be more reliably attached to the side wall surface of the piston 4.

Further, in the sliding portion 8 which is the contact portion between the cylinder body 1 and the piston 4, the lower portion thereof (the region closer to the lower end 16 of the cylinder body (see FIG. 5)) is closer to the cylinder body 1 and the piston 4. The surface pressure between them is generally large. This is for the following reasons. That is, a force (a force that is a source of the above-mentioned surface pressure) from a lateral direction which is a direction perpendicular to the extending direction of the piston 4 is a drive cam (not shown) located under the lifter 11 (see FIG. 1) Due to exercise, etc. Therefore, the force that is the source of the surface pressure is the lower end of the piston 4 (the region near the lifter 11 (see FIG. 1)).
Will be input from.

As described above, since the surface pressure between the cylinder body 1 and the piston 4 is larger in the region closer to the lower end 16 of the cylinder body (see FIG. 5), the entire sliding portion 8 is the same. Even under the lubrication condition, the region closer to the lower end 16 of the cylinder body (see FIG. 5) is more worn and seizure is more likely to occur. According to the present invention, the oil sump portion 1 is provided for each stroke in which the piston 4 moves up and down from the lower end (cylinder body lower end 16) side of the sliding portion 8.
Part of the engine oil 25 collected in 7 adheres to the outer peripheral surface of the piston 4 and is carried to the sliding portion 8. That is, on the lower end side of the sliding portion 8, it is possible to effectively increase the ratio of the engine oil of the mixture of the fuel and the engine oil existing in the sliding portion 8.

As a result, since the viscosity of the mixture of engine oil and fuel existing in the sliding portion 8 on the lower end side of the sliding portion 8 can be improved, the oil film thickness of this mixture can be increased. You can Therefore, it is possible to reduce the frequency of seizure between the piston 4 and the cylinder body 1 on the lower end side of the sliding portion 8 which is the site where seizure is most likely to occur. That is, the seizure limit can be effectively increased, and wear of the cylinder body 1 and the piston 4 can be reduced.

The lower end 1 of the cylinder body shown in FIG.
6 and the upper end of the side wall 18 of the oil sump 17
Is preferably smaller than the stroke of the vertical movement of the piston 4, but the engine oil 25 collected in the oil sump 17 may creep up the side wall surface of the piston 4 above the upper end of the side wall 18 due to surface tension. In this case, the distance L (see FIG. 5) may be set to be larger than the stroke of the piston 4.

(Embodiment 2) FIG. 6 is a schematic sectional view of Embodiment 2 of a high-pressure fuel pump as a fluid pump according to the present invention. A second embodiment of the high-pressure fuel pump according to the present invention will be described with reference to FIG.

As shown in FIG. 6, the second embodiment of the high-pressure fuel pump according to the present invention basically has the same structure as the high-pressure fuel pump shown in FIG.
On the side wall surface of the piston hole 27 formed in the above, a relief groove 26 is formed as a groove at a position spaced from the pump high pressure chamber 15.
Is different. The fuel return flow passage 14 as a recovery pipe is connected to the escape groove 26. The fuel return passage 14 may be connected to a fuel tank (not shown).

By doing so, the same effects as those obtained by the first embodiment of the high-pressure fuel pump according to the present invention can be obtained, and the pump high-pressure chamber 15 to the sliding portion 8 can be obtained.
It is possible to temporarily trap the fuel that has flowed in to the escape groove 26, and to circulate the fuel from the escape groove 26 to the fuel tank side through the fuel return passage 14. Therefore, it is possible to reduce the flow rate of the fuel flowing into the sliding portion 8 below the escape groove 26 (the region near the lifter 11). Therefore, the sliding portion 8 below the escape groove 26
It is possible to reduce the proportion of fuel in the mixture of fuel and engine oil in. As a result, the proportion of engine oil in the mixture can be relatively increased, so that the viscosity of the mixture can be increased. Therefore, the thickness of the oil film of the mixture in the sliding portion 8 can be increased. Therefore, it is possible to further improve the seizure limit in the sliding portion 8 and reduce wear of the piston 4 and the cylinder body 1.

Further, since the flow rate of the fuel flowing downward from the escape groove 26 can be reduced, the oil seal 5
As a result, the flow rate of the fuel that reaches to can be reduced. Therefore, the amount of fuel leaking from the oil seal 5 to the lifter 11 side (leak amount) can be reduced.

Since the total amount of fuel in the vicinity of the fuel lip 7 is small, the proportion of fuel in the lubricant that lubricates the sliding surface between the fuel lip 7 and the piston 4 can be reduced. That is, when the side wall surface of the piston 4 slides with respect to the fuel lip 7, the proportion of engine oil in the lubricant located at the contact portion between the fuel lip 7 and the piston 4 becomes high (the fuel lip 7 and the piston 4 Will be close to oil lubrication). Therefore, the friction coefficient between the fuel lip 7 and the side surface of the piston 4 can be reduced more than in the case where a relatively large amount of fuel is present on the contact surface between the fuel lip 7 and the piston 4. Therefore, wear of the fuel lip 7 can be reduced. Further, the tightening margin of the fuel lip 7, which is determined in consideration of wear of the fuel lip 7, can be reduced. Therefore, since the initial pressing force (compression force) of the fuel lip 7 pressed against the piston 4 can be reduced, the friction in the operation of the piston 4 can be reduced.

The position of the escape groove 26 can be appropriately selected. Further, at the position of the escape groove 26, the viscosity of the lubricant containing fuel and engine oil becomes sufficiently high in the sliding portion 8 below the escape groove 26 (fuel lip 7 side),
It is preferable to determine the position such that seizure resistance and abrasion resistance can be sufficiently secured.

Further, in the high-pressure fuel pumps according to the first and second embodiments of the present invention described above, the shape of the oil sump portion 17 can store the engine oil 25 (see FIG. 5), and the accumulated engine oil can be stored. Other shapes may be adopted as long as the oil 25 can contact a part of the side surface of the piston 4. For example, the side wall 18 (see FIG. 5) may be inclined so as to approach the side surface of the piston 4 toward the cylinder body 1 side. In this case, the engine oil 2 may be vibrated from above the oil sump 17 due to vibration or the like.
The engine oil 25 can be reliably held inside the oil sump 17 by suppressing the splashing of the oil 5. Alternatively, the surface of the side wall 18 may be curved or convex outward when viewed from the piston 4 side. In this case, the volume of the oil reservoir 17 can be increased. Further, the side wall 18 may be convex toward the side surface of the piston 4.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above-described embodiments but by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

[0069]

As described above, according to the present invention, in a fluid pump such as a high-pressure fuel pump, an engine is provided at a sliding portion between a cylinder and a piston by a simple structure in which an oil reservoir is formed in a seal portion. Lubricating oil such as oil can be introduced efficiently. Therefore, a low-cost fluid pump with a high seizure limit can be realized.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of Embodiment 1 of a high-pressure fuel pump as a fluid pump according to the present invention.

2 is a schematic partial cross-sectional view of the high-pressure fuel pump shown in FIG.

FIG. 3 is a schematic partial enlarged cross-sectional view for explaining the operation of the high-pressure fuel pump shown in FIGS. 1 and 2.

FIG. 4 is a partially enlarged schematic cross-sectional view for explaining the operation of the high-pressure fuel pump shown in FIGS. 1 and 2.

5 is a partial enlarged cross-sectional schematic diagram for explaining the operation of the high-pressure fuel pump shown in FIGS. 1 and 2. FIG.

FIG. 6 is a schematic cross-sectional view of a second embodiment of a high-pressure fuel pump as a fluid pump according to the present invention.

FIG. 7 is a schematic sectional view showing a conventional high-pressure fuel pump.

8 is a partially enlarged schematic sectional view of the high-pressure fuel pump shown in FIG.

[Explanation of symbols]

1 cylinder body, 2 inlet valve, 3 outlet valve, 4 piston, 5 oil seal, 6
Oil lip, 7 Fuel lip, 8 Sliding part, 9 Spring, 10 Spring retainer, 11 Lifter,
12 Lifter guide part, 13 Oil seal press-fitting hole, 1
4 fuel return flow path, 15 pump high pressure chamber, 16 cylinder body lower end, 17 oil sump, 18 side wall,
19 engine oil oil film, 20 air gap, 21 entry oil film, 22, 23, 29, 30 arrow, 24, 25 engine oil, 26 escape groove, 27 piston hole, 2
8 inner walls.

Claims (5)

[Claims] 1. A cylinder for which a piston hole is formed, one end portion, and the other end portion opposite to the one end portion, the one end portion side being the piston hole of the cylinder. A piston that is reciprocally inserted into the piston, a pressurizing chamber that is connected to the piston hole, one end of the piston is exposed, and pressurizes a fluid, and the piston that protrudes from the piston hole A seal member having a lip portion that comes into contact with the side wall of the piston in a portion including the other end portion, and a portion of the surface of the lip portion and the seal member in a region of the lip portion that faces the cylinder. A fluid pump in which a recess including a part of a side wall of a piston as a wall surface is formed. 2. The distance between the cylinder surface and the portion of the surface of the lip portion constituting the wall surface of the recess closest to the cylinder is the stroke when the piston reciprocates inside the piston hole. The fluid pump according to claim 1, which is shorter than the length. 3. A cylinder hole having a piston hole, one end portion, and the other end portion opposite to the one end portion, the one end portion side being the piston hole of the cylinder. A piston that is reciprocally inserted into the piston, a pressurizing chamber that is connected to the piston hole, one end of the piston is exposed, and pressurizes a fluid, and the piston that protrudes from the piston hole And a seal member having a lip portion in contact with the side wall of the piston in a portion including the other end of the piston, and a region of the lip portion facing the cylinder is spaced apart from the side wall of the piston. And a wall portion that extends along the direction in which the side wall of the piston extends is formed. 4. The distance between a portion of the wall portion closest to the cylinder and the cylinder surface is shorter than a stroke length when the piston reciprocates inside the piston hole. 3. The fluid pump according to item 3. 5. The cylinder includes a groove formed at a position spaced from the pressurizing chamber on a side wall of the piston hole, is connected to the groove, and extends from the pressurizing chamber to the groove. The fluid pump according to any one of claims 1 to 4, further comprising a recovery conduit for recovering a fluid leaked through the piston hole.