JP2013155702A - Supply pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supply pump capable preventing cavitation erosion without causing delay breakage.SOLUTION: A plug 4 closing a pressurizing chamber α (an end of a cylinder chamber 1) is composed of two components of a "seat component 5 closing the end of the cylinder chamber 1" and a "fastening plug 6 fastened to a cylinder 2 and pressing the seat component 5 to the cylinder 2". Thereby, hardness of the seat component 5 exposed to the pressurizing chamber α can be increased without increasing the hardness of the fastening plug 6 provided with a male screw 6a. That is, prevention of cavitation erosion by increasing the hardness of the seat component 5 exposed to the pressurizing chamber α can be compatible with prevention of occurrence of delay breakage by providing the fastening plug 6 without increasing the hardness thereof. Furthermore, the provision of first and second annular protrusions 21, 22 can increase surface pressure of a contact portion of the cylinder 2 with the seat component 5, and surely provide sealability.

Description

  The present invention relates to a supply pump that pumps high-pressure fuel, and more particularly to a closing technique for a pressurizing chamber (pump chamber) that compresses fuel.

The main part of the supply pump will be described with reference to FIG.
The supply pump shown in FIG. 3 includes a cylinder 2 in which a cylindrical cylinder chamber 1 is provided, a plunger 3 that is reciprocated along the cylinder chamber 1, and a plug 4 that closes an end of the cylinder chamber 1. A pressurizing chamber α for sucking and compressing fuel is formed in a space (inside the cylinder chamber 1) surrounded by the cylinder 2, the plunger 3, and the plug 4.

When the plunger 3 is driven to reciprocate, a fuel suction operation into the pressurizing chamber α and a fuel suction operation into the pressurizing chamber α are performed.
During the fuel suction process, air is generated in the pressurizing chamber α. During the fuel compression process, the generated air collides with the plug 4 due to the flow of fuel and collapses. For this reason, cavitation erosion (erosion by bubbles) is caused in the plug 4 in the portion exposed to the pressurizing chamber α.

As a countermeasure technique for this cavitation erosion, it is conceivable to increase the hardness of the member forming the plug 4.
However, since the plug 4 is a screw part provided with a male screw for fastening the cylinder, there is a concern that delayed damage may occur when the hardness is increased. For this reason, the hardness of the member which comprises the plug 4 cannot be raised.

JP 2007-309191 A

  The present invention has been made in view of the above problems, and an object thereof is to provide a supply pump capable of preventing cavitation erosion without causing delayed damage.

[Means of Claim 1]
The plug is provided with two parts, “a seat part that closes the end of the cylinder chamber” and “a fastening plug that is fastened to the cylinder and presses the seat part against the cylinder”.
Thereby, the hardness of the sheet component exposed to the pressurizing chamber can be increased without increasing the hardness of the fastening plug.
That is,
(I) increasing the hardness of the sheet component exposed to the pressurizing chamber to prevent cavitation erosion;
(Ii) can be provided without increasing the hardness of the fastening plug, and prevents delayed breakage of the fastening plug that is a screw part;
It can be compatible.

[Means of claim 2]
A first annular protrusion having a diameter larger than the inner diameter dimension of the cylinder chamber is provided on at least one of “a portion where the seat component contacts in the cylinder” and “a portion where the cylinder contacts in the seat component”.
As a result, the contact area between the cylinder and the seat part can be reduced, the surface pressure of the part where the cylinder and the seat part come into contact can be increased, and the sealing performance (oil tightness) by the plug (seat part + fastening plug). Can be increased.

[Means of claim 3]
At least one of the “part where the sheet component comes into contact with the fastening plug” or “the part where the fastening piece comes into contact with the sheet part” is provided with a second annular projection that is concentric with and has the same diameter as the first annular projection.
As a result, the fastening force of the fastening plug (the force with which the fastening plug is screwed into the cylinder) can be efficiently applied to the first annular protrusion via the second annular protrusion. As a result, the surface pressure of the portion where the cylinder and the seat component come into contact can be reliably increased, and the sealing performance (oil tightness) by the plug (seat component + fastening plug) can be more reliably obtained.

It is principal part sectional drawing of a supply pump (Example). It is sectional drawing of the site | part in which a plug is provided (Example). It is sectional drawing of the site | part in which a plug is provided (conventional example).

[Description of Embodiments] [Mode for carrying out the invention] will be described with reference to the drawings.
The supply pump is driven by an engine and repeatedly performs a fuel suction process and a compression process.
A cylinder 2 provided with a cylindrical cylinder chamber 1;
A plunger 3 that is driven back and forth along the cylinder chamber 1;
A plug 4 that closes the end of the cylinder chamber 1;
Is provided.

A pressurizing chamber α for sucking and compressing fuel is formed in a cylinder chamber 1 surrounded by a cylinder 2, a plunger 3, and a plug 4.
And the plug 4 is
A seat part 5 for closing the end of the cylinder chamber 1;
A fastening plug 6 that is fastened to the cylinder 2 and presses the sheet component 5 against the cylinder 2;
Of two parts,
The hardness of the sheet component 5 is higher than the hardness of the fastening plug 6.

Hereinafter, a specific example (example) of the present invention will be described with reference to FIGS. The following examples show specific examples, and it goes without saying that the present invention is not limited to the examples.
In the following examples, the same reference numerals as those in the “DETAILED DESCRIPTION OF THE INVENTION” denote the same functional objects.

The common rail system installed in diesel engines (compression ignition engines)
A plurality of injectors that atomize and inject fuel (light oil, alcohol fuel, etc.) compressed to high pressure into the engine;
A common rail that stores high-pressure fuel to be supplied to each injector;
-A supply pump that pumps high-pressure fuel toward this common rail,
It is configured with.

The supply pump is as shown in FIG.
A feed pump 11 (for example, a trochoid pump) that pumps up fuel stored in the fuel tank;
A regulating valve that maintains the pressure of the fuel pumped up by the feed pump 11 at a constant pressure;
A plurality of (for example, two) high-pressure pumps 12 that compress and discharge the fuel pumped up by the feed pump 11 to a high pressure;
A fuel metering valve that adjusts the amount of fuel supplied to each high-pressure pump 12;
An intake valve (check valve) that sends fuel from the feed pump 11 only to the high-pressure pump 12;
A discharge valve (check valve) 13 that sends fuel pumped from the high-pressure pump 12 only to the common rail;
It is configured with.

Here, the feed pump 11 and the high-pressure pump 12 are driven by a camshaft 14 that is rotationally driven by an engine.
Specifically, the high pressure pump 12 is a plunger pump,
A cylinder 2 in which a cylindrical cylinder chamber 1 extending in a direction perpendicular to the rotation axis of the camshaft 14 is formed;
A plunger 3 that is driven back and forth along the cylinder chamber 1;
A plug 4 that is fastened to the cylinder 2 and closes the end of the cylinder chamber 1 is provided.
In the cylinder chamber 1 surrounded by the cylinder 2, the plunger 3 and the plug 4, a pressurizing chamber α for sucking and compressing fuel is formed.

The large-diameter portion provided on the camshaft 14 side of the plunger 3 is pressed against a cam ring 16 mounted around the excelin cam 15 of the camshaft 14 by a return spring 17, and when the camshaft 14 rotates, the cam ring 16 The plunger 3 is reciprocated by the eccentric operation.
When the plunger 3 descends and the pressure in the pressurizing chamber α decreases, the discharge valve 13 closes and the intake valve opens, so that the fuel metered by the fuel metering valve is in the pressurizing chamber α. Supplied in.
Conversely, when the plunger 3 rises and the pressure in the pressurizing chamber α rises, the intake valve closes. When the pressure in the pressurizing chamber α rises above a predetermined pressure, the discharge valve 13 is opened, and the pressurized fuel compressed in the pressurizing chamber α is pumped toward the common rail.

  During the fuel inhalation step described above, air is generated in the pressurizing chamber α. During the fuel compression process, the generated air collides with the plug 4 due to the flow of fuel and collapses. For this reason, cavitation erosion may be caused in the plug 4 in the portion exposed to the pressurizing chamber α.

(Feature Technology 1 of Example 1)
As a countermeasure, in the supply pump of this embodiment, the plug 4 is
A seat part 5 for closing the end of the cylinder chamber 1;
A fastening plug 6 that is fastened to the cylinder 2 and presses the sheet component 5 against the cylinder 2;
Provided with two parts,
The hardness of the sheet component 5 is set higher than the hardness of the fastening plug 6.
A specific example will be described below.

On the extension of the cylinder chamber 1 in the cylinder 2, a plug fastening hole 18 in which the plug 4 (sheet component 5 + fastening plug 6) is assembled is provided.
The plug fastening hole 18 is a substantially cylindrical hole that is concentric with the axial center of the cylinder chamber 1 and has a larger inner diameter than the inner diameter of the cylinder chamber 1, and has an internal thread formed on the inner peripheral surface.

The sheet component 5 is a substantially disc-shaped component that is assembled to the bottom surface of the plug fastening hole 18 and is provided with high hardness in order to prevent cavitation erosion.
As a specific example, the hardness of the sheet component 5 is set to a hardness equivalent to that of the cylinder 2.

Specifically, the cylinder 2 is made of iron and then has a hardness increased by carburizing, and cavitation erosion is prevented by the high hardness.
On the other hand, the sheet component 5 is formed of iron and then is hardened to a hardness equivalent to that of the cylinder 2 by quenching, and prevents cavitation erosion with a high hardness equivalent to that of the cylinder 2. Can do.

On the other hand, the fastening plug 6 is one in which the sheet component 5 is incorporated into the bottom surface of the plug fastening hole 18 and then screwed into the plug fastening hole 18 to press the sheet component 5 against the bottom surface of the plug fastening hole 18. A male screw 6 a that is screwed into the female screw of the plug fastening hole 18 is formed on the outer peripheral surface.
In addition, a tool engaging portion 6b that engages with a tool that applies rotational torque to the fastening plug 6 (a tool for fastening and fastening release) is provided at the center of the outer end surface of the fastening plug 6.

The fastening plug 6 has a hardness that does not cause delayed damage even when used for a long time (a hardness lower than that of the sheet component 5).
As a specific example, the fastening plug 6 of this embodiment is provided with iron and, unlike the sheet component 5, is not subjected to a treatment for increasing hardness.
Further, since the fastening plug 6 is partially exposed to the atmosphere, corrosion resistance is required. Therefore, the fastening plug 6 is subjected to corrosion-resistant plating (zinc plating, nickel plating, zinc nickel plating, etc.).

  The O-ring 19 mounted around the fastening plug 6 is pressed between the fastening plug 6 and the plug fastening hole 18 when the fastening plug 6 is fastened to the plug fastening hole 18, and is sealed. This is to more reliably prevent fuel leakage due to defects.

In the supply pump of this embodiment, as described above, the plug 4 is made up of “the seat component 5 that closes the end of the cylinder chamber 1” and “the fastening plug 6 that is fastened to the cylinder 2 and presses the seat component 5 against the cylinder 2”. It is provided with two parts.
For this reason, the hardness of the sheet component 5 exposed to the pressurizing chamber α can be increased without increasing the hardness of the fastening plug 6 provided with the male screw 6a.

That is,
(I) increasing the hardness of the sheet component 5 exposed to the pressurizing chamber α to prevent cavitation erosion;
(Ii) can be provided without increasing the hardness of the fastening plug 6, and prevents delayed breakage of the fastening plug 6 that is a screw component;
It can be compatible.

(Feature Technology 2 of Example 1)
In the supply pump of this embodiment, at least one of “a part where the seat part 5 comes into contact with the cylinder 2” and “a part where the cylinder 2 comes into contact with the seat part 5” has a first diameter larger than the inner diameter dimension of the cylinder chamber 1. An annular protrusion 21 is provided.
Specifically, the first annular protrusion 21 is provided on the “bottom surface of the plug fastening hole 18” corresponding to “the part of the cylinder 2 where the sheet component 5 contacts”.

The first annular protrusion 21 bulges in an annular shape from the bottom surface of the plug fastening hole 18 toward the seat component 5, and can reduce the contact area between the cylinder 2 and the seat component 5.
Thereby, the surface pressure of the part where the cylinder 2 and the seat component 5 come into contact can be increased, and the sealing property (oil tightness) of the pressurizing chamber α by the plug 4 (the seat component 5 + the fastening plug 6) can be increased. .

(Feature Technology 3 of Example 1)
Furthermore, in the supply pump of this embodiment, the first annular protrusion 21 is concentric with at least one of “the portion where the seat component 5 contacts the fastening plug 6” or “the portion where the fastening plug 6 contacts the seat component 5”. In addition, a second annular protrusion 22 having the same diameter is provided.
Specifically, the second annular protrusion 22 is provided in “around the back end surface of the fastening plug 6” corresponding to “a portion of the fastening plug 6 that contacts the sheet component 5”.

By this second annular protrusion 22, the fastening force of the fastening plug 6 (the force by which the fastening plug 6 is screwed into the cylinder 2) can be efficiently applied to the first annular protrusion 21.
Thereby, the surface pressure of the part where the cylinder 2 and the seat component 5 come into contact with each other can be reliably increased, and the sealing performance by the plug 4 (the seat component 5 + the fastening plug 6) can be more reliably obtained.

In the above embodiment, as an example of reducing the cost, an example in which the sheet component 5 is hardened by increasing the hardness is shown. However, the embodiment is not limited. Hardness may be increased.
Further, since the sheet component 5 is a separate member different from the fastening plug 6, the sheet component 5 may be provided with a material having high hardness different from that of the fastening plug 6 (for example, stainless steel).

DESCRIPTION OF SYMBOLS 1 Cylinder chamber 2 Cylinder 3 Plunger 4 Plug 5 Sheet component 6 Fastening plug 21 1st annular protrusion 22 2nd annular protrusion α Pressurizing chamber

Claims (3)

A cylinder (2) provided with a cylindrical cylinder chamber (1), a plunger (3) reciprocally driven along the cylinder chamber (1), and a cylinder chamber (1) fastened to the cylinder (2) A plug (4) for closing the end of
In the supply pump in which a pressurizing chamber (α) for sucking and compressing fuel is formed in the cylinder chamber (1) surrounded by the cylinder (2), the plunger (3), and the plug (4).
The plug (4)
A seat part (5) for closing the end of the cylinder chamber (1);
A fastening plug (6) fastened to the cylinder (2) to press the seat part (5) against the cylinder (2);
Of two parts,
The supply pump according to claim 1, wherein the hardness of the seat part (5) is higher than the hardness of the fastening plug (6). The supply pump according to claim 1, wherein
At least one of the part where the seat part (5) contacts in the cylinder (2) or the part where the cylinder (2) contacts in the seat part (5) is based on the inner diameter of the cylinder chamber (1). A supply pump comprising a first annular protrusion (21) having a large diameter. The supply pump according to claim 2,
At least one of the portion of the fastening plug (6) that contacts the seat component (5) or the portion of the seat component (5) that contacts the fastening plug (6) is the first annular protrusion (21). And a second annular projection (22) having the same diameter and the same diameter.

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