CN213175900U

CN213175900U - Common rail fuel injector

Info

Publication number: CN213175900U
Application number: CN202022121035.4U
Authority: CN
Inventors: 谭志耀; 徐刚; 孙桂兰
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2020-09-24
Filing date: 2020-09-24
Publication date: 2021-05-11
Anticipated expiration: 2030-09-24

Abstract

The present application provides a common rail fuel injector comprising: an injector body and a needle valve assembly removably connected to the injector body, wherein the injector body has a first chamber and a second chamber in communication via a passage; a spool received in the first chamber and cooperating with a valve seat formed by a wall of the first chamber and a piston assembly received in the second chamber; wherein the piston of the piston assembly is guided by the injector body at one end and supported at the other end in a radially movable manner with respect to the injector body, the piston being in contact with or separated from the valve needle of the needle valve assembly in an axial direction of the fuel injector when the piston moves in the second chamber in the axial direction. Through the structure of this application, the piston only has a rigidity guide in the second chamber inner wall department of sprayer body, has solved the problem of piston overspun.

Description

Common rail fuel injector

Technical Field

The present application relates to a fuel injector, and more particularly, to a common rail fuel injector having an improved piston positioning device.

Background

In the case of known common rail fuel injectors for internal combustion engines, a combined valve structure is usually used for controlling the injection of fuel through the fuel injection openings, in which structure the valve piston, which moves in conjunction with the valve needle, in the valve assembly is often guided rigidly in two regions at the same time, namely in two positions, the valve mounting and the needle valve assembly, which leads to problems with the over-positioning of the valve piston. Moreover, the guidance at two points places very high demands on the components of the entire fuel injector, in particular the piston and its associated components, with regard to the machining precision and the potential wear at the guidance area, which leads to increased machining costs.

Accordingly, there is a need to provide an improved fuel injector that does not create the above-described over-positioning problem at the valve piston of the valve assembly.

SUMMERY OF THE UTILITY MODEL

It is an object of the present application to provide a common rail fuel injector that improves the problem of piston over-positioning in the valve assembly of the common rail fuel injector.

To this end, the present application provides a common rail fuel injector comprising: an injector body and a needle valve assembly removably connected to the injector body, wherein the injector body has a first chamber and a second chamber in communication via a passage; a spool received in the first chamber and cooperating with a valve seat formed by a wall of the first chamber and a piston assembly received in the second chamber; wherein the piston of the piston assembly is guided by the injector body at one end and supported at the other end in a radially movable manner with respect to the injector body, the piston being in contact with or separated from the valve needle of the needle valve assembly in an axial direction of the fuel injector when the piston moves in the second chamber in the axial direction.

In one embodiment, the piston is composed of a large diameter portion that contacts an inner wall of the second chamber to be guided by the inner wall, and a small diameter portion on which a sleeve and an elastic member biasing the sleeve toward the needle valve assembly are fitted.

In one embodiment, the elastic member is a spring disposed between the large diameter portion and the sleeve.

Optionally, one end of the spring abuts a protrusion from an inner wall of the second chamber and the other end abuts the sleeve.

Optionally, the sleeve is made of the same or different material as the injector body.

In one embodiment, the piston is rod-shaped with a uniform diameter, guided at one end near the valve spool by a guide fixed to or integral with the injector body, and sleeved on the other end with a sleeve and a resilient element biasing the sleeve towards the needle valve assembly.

In one embodiment, the needle valve assembly has a needle valve body, the sleeve is formed with an inclined inner wall at an inner wall near one end of the needle valve assembly, a connecting chamber is defined between the piston and the inclined inner wall and the end surfaces of the needle valve and the needle valve body, a control chamber is formed between the piston and the end wall of the second chamber, and pressure action between the control chamber and the connecting chamber causes the piston to move and thus the needle to move in the axial direction.

Optionally, the valve element has a spherical portion at an end thereof, the spherical portion being in contact with or spaced from the valve seat to open or close the inlet of the passage.

Alternatively, the spool is hydraulically driven by a pressure differential applied across it.

Optionally, the valve element is driven by electromagnetic force.

By the fuel injector with the structure, the problem of over-positioning of the piston of the fuel injector is solved, and the piston cannot be positioned at two positions.

The improvement also reduces the requirement on the part machining precision, improves the product quality and reduces the machining cost.

Drawings

The foregoing and other aspects of the present application will be more fully understood from the following detailed description, taken together with the following drawings. It is noted that the drawings may not be to scale for clarity of illustration and will not detract from the understanding of the present application. In the drawings:

FIG. 1 is a schematic cross-sectional view of a fuel injector according to the present application in a closed state;

FIG. 2 is a schematic cross-sectional view of a fuel injector according to the present application during opening;

FIG. 3 is a schematic cross-sectional view of a fuel injector according to the present application in an open state; and

fig. 4A and 4B are enlarged cross-sectional views of a piston assembly in a fuel injector according to the present application in a closed state and an open state, respectively.

Detailed Description

In the various figures of the present application, features that are structurally identical or functionally similar are denoted by the same reference numerals.

A fuel injector according to the present application includes an injector body 1 and a needle valve assembly 2 removably secured to the injector body 1, as shown in fig. 1, the injector body 1 having a first chamber 3 and a second chamber 4 therein communicating through an elongated passage 5, a spool 6 of a ball valve assembly being located in the first chamber 3, and a piston 7 of a piston assembly being located in the second chamber 4.

The surface of the first chamber 3 adjacent to the passage 5 is formed as a conical surface to constitute a valve seat 8 of the ball valve assembly, and the spool 6 is formed with a spherical portion 9 at one end near the valve seat 8, the spherical portion 9 cooperating with an inlet 10 of the passage 5 to close or open the inlet 10. The other end of the spool 6 abuts against an internal step 12 of the injector body 1 by means of a spring 11, so that the spool 6 is biased towards the passage 5 and against the valve seat 8 under the action of the spring 11, the spherical portion 9 closing the inlet 10.

The piston assembly comprises a piston 7 located in the second chamber 4 and a sleeve 13 sleeved on one end of the piston 7, and a spring 15 also sleeved on the piston 7 and located between the sleeve 13 and a protruding ring 14 protruding from the inner wall of the second chamber 4, wherein the sleeve is biased towards the needle valve assembly 2 under the action of the spring 15. The piston 7 is arranged centrally in the second chamber 4 so as to be movable in the axial direction of the fuel injector.

The needle valve assembly 2 has a needle valve body 20 defining a valve chamber 16 and a needle 17 accommodated within the valve chamber 16, the needle valve body 20 forming an injection port 18 at a tip end, the tip end of the needle 17 being formed as a sharpened end portion 19, the end portion 19 of the needle 17 being insertable into the injection port 18 to close the injection port 18 or exiting from the injection port 18 to open the injection port 18. Wherein the valve needle 17 is arranged centrally in the needle valve body 20 and can be brought into contact with or separated from said piston 7 when said piston 7 is moved in the axial direction of the fuel injector in the second chamber 4.

The sleeve 13 has one end abutting the spring 15 and one end abutting an end face of the needle valve body 20 of the needle valve assembly, and at the end of the sleeve 13 adjacent the needle valve body 20, its inner wall is inclined so that a connecting chamber 22 is formed between the inclined inner wall portion of the sleeve 13 and the end face of the needle valve body 20, the connecting chamber 22 being radially dimensioned to receive the end portion of the needle 17, as shown more clearly in the enlarged views of fig. 4A and 4B. A control chamber 21 is formed between the piston 7 and the inner wall of the second chamber 4 near the passage 5, and the piston 7 moves up and down in the second chamber 4 under the combined action of the pressure difference between the control chamber 21 and the connection chamber 22 and the elastic force of the spring 13.

The functioning of the fuel injector according to the present application is described below in connection with fig. 1-3.

When fuel injection is not required, the valve element 6 is biased towards the valve seat 8 by the spring 12, so that the spherical portion 9 of the valve element 6 abuts against the inlet 10 of the passage 5, the inlet 10 is closed, the pressure in the control chamber 21 is increased until the common rail pressure is balanced with the piston pressure, the piston 7 is pushed to move downwards until abutting against the valve needle 19 of the needle valve assembly, and the valve needle 19 moves towards the injection port 18 under the push of the piston 7, so that the end portion 19 is inserted into the injection port 18, and the injection port 18 is closed, so that the whole fuel injector is closed.

When required, the valve element 6 can be moved away from the valve seat 8, for example by electromagnetic force or hydraulic force, so that the spherical portion 9 is moved away from the inlet 10 of the passage 5, and the piston 7 is moved upwards in the direction of the passage 5, by reducing the pressure in the control chamber 21, to the state shown in fig. 2. As the piston 7 moves upward, the pressure in the connecting chamber 22 decreases, and the needle 17 moves upward by the pressure difference, and the end portion 19 of the needle 17 moves away from the injection port 18, opening the injection port 18, and reaching a fully open state as shown in fig. 3, in which fuel is injected through the injection port 18.

As shown in fig. 4A and 4B, the piston 7 is constituted by a large diameter portion 71 and a small diameter portion 72, and the large diameter portion 71 is brought into abutment with the inner wall of the second chamber 4 so that the movement of the piston 7 is guided by the inner wall of the second chamber 4. The spring 15 and the sleeve 13 are fitted over the small diameter portion 72 so that the small diameter portion 72 can be positioned by the sleeve 13, there is a clearance between the outer wall of the spring 15 and the sleeve 13 and the inner wall of the second chamber 4 so that the piston 7 and the sleeve 13 can move together in the radial direction, and the radial movement range of the sleeve 13 is set so that the opening of the connecting chamber 22 always covers the upper end face of the needle 17 so that the end of the needle 17 can enter the connecting chamber 22 during movement of the sleeve 13. In this way, the piston 7 only needs to be guided by the inner wall of the second chamber 4 at one end and can move together with the sleeve at the other end, thus avoiding the problem of over-positioning of the piston and increasing the service life and the operating accuracy of the entire jet valve assembly.

The sleeve 13 may be provided with a portion of larger internal diameter near one end of the spring 15 to form a gap between the inner wall of the sleeve 13 and the outer wall of the piston 7. While the inner wall of the sleeve 13 is brought into contact with the outer wall of the piston 7 at the end close to the needle valve 17.

In the present application, the sleeve 13 may be made of any rigid material resistant to fuel corrosion, for example, the same or different material as the injector body 1.

The present application is not limited to the structure of the above-described embodiment, and for example, the piston 7 does not necessarily have to be shaped to have the large diameter portion 71 and the small diameter portion 72 as shown in fig. 1 to 3 and fig. 4A and 4B, but may be formed in a rod shape having a uniform diameter, in which case a piston guide fixed to and integral with the injector body 1 is provided in the injector body 1, in which case one end of the piston 7 is guided in the piston guide, and the other end can follow the sleeve 13 for a certain amount of radial movement, the radial movement range being set so that the opening size of the connecting chamber 22 always covers the upper end face of the needle 17.

In the present application, the coupling function is satisfied by the use of the connecting spring 15 and the connecting sleeve 13, and moreover, the piston 7 has only one rigid guide at the inner wall of the second chamber 4 of the injector body 1, solving the problem of piston over-positioning.

Although specific embodiments of the present application have been described herein in detail, they have been presented for purposes of illustration only and are not to be construed as limiting the scope of the application. Various substitutions, alterations, and modifications may be conceived without departing from the spirit and scope of the present application.

Claims

1. A common rail fuel injector, comprising:

an injector body (1) and a needle valve assembly (2) detachably connected to the injector body (1), wherein the injector body (1) has a first chamber (3) and a second chamber (4) communicating via a passage (5);

a valve element (6) housed in the first chamber (3) and cooperating with a valve seat (8) constituted by the wall of the first chamber (3), and a piston assembly housed in the second chamber (4);

wherein the piston (7) of the piston assembly is guided by the injector body (1) at one end and is supported in a radially movable manner relative to the injector body (1) at the other end, the piston (7) being in contact with or separated from a valve needle (17) of the needle valve assembly (2) in an axial direction of the fuel injector when the piston (7) moves in the second chamber (4) in the axial direction.

2. The common rail fuel injector according to claim 1, wherein the piston (7) is constituted by a large diameter portion (71) and a small diameter portion (72), the large diameter portion (71) being in contact with an inner wall of the second chamber (4) to be guided by the inner wall, the small diameter portion (72) being fitted over with a sleeve (13) and a resilient member biasing the sleeve (13) toward the needle valve assembly (2).

3. The common rail fuel injector of claim 2, wherein the resilient element is a spring (15) disposed between the large diameter portion (71) and the sleeve.

4. A common rail fuel injector according to claim 3, characterized in that a spring (15) abuts with one end against a protrusion (14) protruding from the inner wall of the second chamber (4) and with the other end against the sleeve (13).

5. Common rail fuel injector according to claim 2, characterized in that the sleeve (13) is made of the same or different material as the injector body (1).

6. Common rail fuel injector according to claim 1, characterized in that the piston (7) is rod-shaped with a uniform diameter, guided at one end near the valve spool (6) by a guide fixed to the injector body (1) or integral with the injector body (1), and sleeved on the other end with a sleeve (13) and an elastic element biasing the sleeve (13) towards the needle valve assembly (2).

7. Common rail fuel injector according to claim 2 or 6, characterized in that the needle valve assembly (2) has a needle valve body (20), that the sleeve (13) is made with an inclined inner wall at the inner wall near one end of the needle valve assembly (2), that a connecting chamber (22) is defined between the piston (7) and the inclined inner wall and the end surfaces of the needle valve (17) and the needle valve body (20), that a control chamber (21) is formed between the piston (7) and the end wall of the second chamber (4), and that the pressure action between the control chamber (21) and the connecting chamber (22) causes the piston (7) and thus the needle valve (17) to move in said axial direction.

8. Common rail fuel injector according to claim 1, characterized in that the valve spool (6) has a spherical portion (9) at its end, the spherical portion (9) being in contact with or away from the valve seat (8) to open or close the inlet (10) of the passage (5).

9. Common rail fuel injector according to claim 1, characterized in that the spool (6) is hydraulically driven by a pressure difference applied across it.

10. Common rail fuel injector according to claim 1, characterized in that the spool (6) is driven by electromagnetic force.