GB2391906A

GB2391906A - Solenoid valve-controlled fuel injection valve for i.c. engines

Info

Publication number: GB2391906A
Application number: GB0315142A
Authority: GB
Inventors: Norbert Lampl; Andreas Rettich; Thomas-Christian Hofmann; Lorenz Zerle; Holger Rapp; Matthias Horn
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-07-12
Filing date: 2003-06-30
Publication date: 2004-02-18
Anticipated expiration: 2023-06-30
Also published as: JP2004044595A; GB2391906B; FR2845426B1; GB0315142D0; FR2845426A1; DE10231623A1

Abstract

The valve has a housing body 10 with a high pressure fluid inlet 29 and an axial recess 16 which accommodates a valve body 23 forming a control chamber 27 and a solenoid valve seat 22. The control chamber 27 is connected to the high pressure inlet 29 via an annular chamber 28 formed in the housing body 10 and via an inlet throttle 30 and is connected to the solenoid valve seat 22 via an outlet throttle 31. The solenoid valve body 23 or the annular chamber 28 is sealed with respect to the housing body 10 on both sides, i.e. at both ends of the annular chamber 28, by means of high pressure seals 33, 35; 34, 36. A leakage point is constructionally and intentionally provided in the region of the (upper) high pressure seal 33,35 which faces the solenoid valve seat 22 eg by one or more radial grooves, or an intentional reduction in surface quality, in the sealing surface of the housing body 10 and/or the valve body 23. The invention prevents infiltration of the high pressure seal 33, 35 and thus limits the deformation and displacement of the valve body 23 caused by high pressure.

Description

DESCRIPTION

SOLENOID VALVE-CONTROLLED SERVO VALVE FOR

AN INJECTOR OF A FUEL INJECTION SYSTEM

FOR INTERNAL COMBUSTION ENGINES

5 The invention relates to solenoid valve-controlled servo valves for controlling a fluid under high pressure in particular to an injector of a fuel injection system for internal combustion engines of the type having a housing body including a high pressure fluid inlet and comprising an axial recess which accommodates a valve body forming a control chamber and a solenoid valve seat, 10 wherein the control chamber is connected to the high pressure fluid inlet via an annular chamber formed in the housing body and via an inlet throttle and said control chamber is connected to the solenoid valve seat via an outlet throttle and wherein the solenoid valve body, or the annular chamber surrounding this body, is sealed with respect to the housing body on both sides, i.e. on the two end sides of 15 the annular chamber, by means of high pressure seals.

Servo valves of the above described type are used in particular as socalled CR-injectors (CR = Common Rail) in fuel injection systems of internal combustion engines. In this case, the injector body is hydraulically connected with a central high pressure reservoir (so-called corornon rail). A nozzle needle is 20 disposed so as to be able to move in an axial manner in an axial recess which is formed so as to have multiple steps and passes through the injector body, which noble needle controls the fuel-injection quantity, which issues out through the injection nozzle in dependence upon the pressure in the control chamber of the

solenoid valve body. With regard to such solenoid valve-controlled servo valves in the Prior Art, reference is made, for example, to DE 196 50 865 Al.

In a current design of a CR-injector of the type in question, the interface of the solenoid valve body and the housing body (injector body) is sealed by means 5 of a hard, metal high pressure seal towards the solenoid valve chamber. In contrast, on the other (lower) end of the annular chamber extending between the injector body and the solenoid valve body a "soft" high pressure seal is disposed which seals the interface between the solenoid valve body and the injector body towards the low pressure return. This "soft" high pressure seal, which is an elastic 10 sealing ring, is protected against extrusion into the sealing gap by means of a so called backup ring consisting of soft iron. With regard to this Prior Art, reference

is made to DE 100 20 870 A 1.

Owing to the high pressure prevailing in the annular chamber surrounding the solenoid valve body, undesired deformations ofthe solenoid valve body occur.

15 Thus the solenoid valve deforms first radially and then axially whereupon a displacement of said body occurs in the direction of the control chamber of the solenoid valve. The result is a corresponding reduction of the annature stroke of the solenoid valve which exerts a disadvantageous influence on the fuel-injection quantity. This influence is particularly disadvantageous when dealing with small 20 injection quantities (pre-injection quantities).

The higher the fluid pressure prevailing in the annular chamber and the larger the surface influenced by the pressure, the greater the undesired deformation and displacement of the valve body. With the hard, metal seal, which

seals the annular chamber towards the control clamber of the solenoid valve, a so called infiltration of the sealing surface can occur as fluid pressure increases, whereby the pressurised surface increases in size.

An object of the present invention is to prevent an enlargement of the 5 pressurised surface owing to infiltration of the sealing surface and in this manner to limit to an acceptable degree the deformation and displacement of the valve body caused by high pressure.

In accordance with the present invention, in the case of a solenoid valve controlled servo valve of the generic type described in the introduction, a leakage

10 point is constructionally and intentionally provided in the region of the (upper) high pressure seal which faces the solenoid valve seat and seals the interface of the solenoid valve body to the housing body.

In accordance with one embodiment of the invention which can be realised in a simple and practical manner, one or several radial grooves are incorporated as 15 the intentional leakage point into the sealing surface of the housing body, e.g. the injector body, and/or of the solenoid valve body.

In an alternative manner, it is also possible to achieve the desired leakage effect by means of a intentional reduction in the surface quality of the sealing surface of the housing body and/or of the solenoid valve body.

20 In accordance with a preferred embodiment of the invention, a "soft" high pressure sealing ring, instead of the hitherto conventional "hard" metal seal, is to be used as the (upper) high pressure seal which faces the solenoid valve seat arid seals the interface of the solenoid valve body to the housing body, which soft high

pressure sealing ring is allocated a so-called backup ring consisting of comparatively soft metal for protection against extrusion into the sealing gap. In an expedient manner the "backup ring", as is known per se, consists of soft iron.

The invention serves to prevent the enlargement of the pressurised surface 5 and consequently to limit the reduction of the solenoid valve armature stroke as fluid pressure increases. The influence of the fluid pressure on the fuel-injection quantity is consequently reduced.

With the design in accordance with the invention the sealing function of the "hard" seal is thus removed in that an intentional leakage point is 10 constructionally provided. Hence, the previously described "infiltration of the sealing surface" by the fluid under high pressure can be avoided in a simple manner and consequently the deformation and displacement of the solenoid valve body caused by high pressure can be limited to an acceptable degree.

The invention is described further hereinafter by way of example only, 15 with reference to the accompanying drawings, in which: Figure I shows in a vertical longitudinal sectional view an embodiment of a solenoid valve-controlled CR-injector, and Figure 2 shows the detail "A" from Figure I in an enlarged view, as 20 compared to Figure 1.

Reference numeral 10 designates a housing body (in this case an injector body) having in each case an integrally formed outlet connection piece 11 and connector housing 12 with a supply terminal 13 for an electromagnet, indicated as

a whole by reference numeral 14. Reference numeral IS designates a high pressure connection which is likewise connected to the housing body 10 of the CR-injector. This high pressure connection is connected to a high pressure fuel reservoir (so-called common rail) (not illustrated). An axial recess 16 is 5 incorporated within the housing body 10, which recess is formed so as to have multiple steps and in which a valve control piston 17 and a valve needle 18, which is actuated by the valve control piston, are disposed so as to be able to move in an axial manner.

Furthermore, reference numeral 19 designates a solenoid valve control 10 chamber in which a solenoid valve 20 having a valve ball 21 is disposed. The valve ball 21 co-operates with a conical valve seat 22 of the solenoid valve 20. As can be seen in particular in Figure 2, the solenoid valve seat 22 is a component part of a solenoid valve body, which is indicated as a whole by reference numeral 23 and is disposed in the upper (extended) section of the axial recess 16 (of also 15 the embodiment hereinafter).

The valve needle 18 is maintained in its closed position by means of a return pressure spring 24 (see Figure 1), in which position it seals an injection nozzle 25 incorporated at the lower end of the housing body 10.

20 As can be further seen from Figure 1, a pressure duct 26 extends within the housing body 10 and is hydraulically connected with the high pressure connection 15 and serves to supply fuel to the injection nozzle 25. It is clear from Figure 2 that above the valve control piston 17 a control chamber 27 is formed within the

solenoid valve body 23 and is hydraulically connected with the high pressure connection 15 via an annular chamber 28 surrounding the solenoid valve body 23, via a high pressure inlet 29 and via an inlet throttle 30 and is hydraulically connected with the solenoid valve control chamber 19 (see Figure 1) and a firer 5 return 32 via an outlet throttle 31. The fuel is thus guided from the high pressure connection 15 to the injection nozzle 25 via the pressure duct 26 and is guided into the control chamber 27 via the inlet throttle 30. The hydraulic connection of the control chamber 27 to the fuel return 32 can be produced, via the outlet throttle 31, by opening the solenoid valve 20, wherein the valve ball 21 lifts up from the 10 solenoid valve seat 22.

Owing to the previously described hydraulic connections, high pressure, which is located at the high pressure connection 15, thus prevails in the annular chamber 28 as well as in the control chamber 27. An effective seal between the valve body 23 and the housing body 10 is thus necessary. This is accomplished by 15 means of an upper (elastic) high pressure sealing ring 33 and a lower high pressure sealing ring 34. A so-called backup ring 35, 36, consisting of soft iron, is allocated to each high pressure sealing ring 33, 34.

The high fluid pressure prevailing in the annular chamber 28 causes the valve body 23 to be radially and axially deformed, whereby the valve seat 22 is 20 correspondingly axially displaced in the direction of the arrow 37 i.e. in the direction towards the solenoid valve 20. A significant characteristic feature resides in the fact that an intentional leakage point is provided on the (upper) sealing surface 38 of the housing body 10 and/or on the associated sealing surface

39 of the valve body 23, in the region of the backup ring 35. The leakage point can be produced by incorporating corresponding radial grooves or also simply by intentionally reducing the surface quality of the sealing surface(s) 3B and/or 39.

An (undesired) "infiltration', of the high pressure seal 33, 35 by fluid under high 5 pressure is prevented by means of the leakage point(s). The aforementioned axial displacement of the valve body 23 (in the direction of the arrow 37) can consequently be limited to a still acceptable degree.

Claims

1. A solenoid valve-controlled servo valve for controlling a fluid under high pressure, SUCII S in an injector of a fuel injection system for internal 5 combustion engines, having a housing body including a high pressure fluid inlet and comprising an axial recess which accommodates a valve body; forming a control chamber and a solenoid valve seat, wherein the control chamber is connected to the high pressure fluid inlet via an annular chamber formed in the housing body and via an inlet throttle and said 10 control chamber is connected to the solenoid valve seat via an outlet throttle and wherein the solenoid valve body, or the annular chamber surrounding this body, is sealed with respect to the housing body on both sides, i.e. on the two end sides of the annular chamber, by means of high pressure seals, wherein a leakage point is constructionally and intentionally 15 provided in the region of the high pressure seal which faces the solenoid valve seat and seals the interface of the solenoid valve body to the housing body.

2. A solenoid valve-controlled servo valve as claimed in Claim 1, wherein to

20 provide the leakage point, one or several radial groove(s) is/are incorporated into the sealing surface of the housing body.

3. A solenoid valve-conkolled servo valve as claimed in Claim 1, wherein, to

provide the leakage point, one or several radial groove(s) is/are incorporated into the sealing surface of the solenoid valve body.

4. A solenoid valve-controlled servo valve as claimed in Claim 1, wherein to

5 provide the leakage point, one or several radial groove(s) is/are incorporated (in each case) into the sealing surface of the housing body and into the sealing surface of the solenoid valve body.

S. A solenoid valve-controlled servo valve as claimed in Claim 1, having an 10 intentional reduction in the surface quality of the sealing surface of the housing body.

6. A solenoid valve-controlled servo valve as claimed in Claim 1, having an intentional reduction in the surface quality of the sealing surface of the 15 solenoid valve body.

7. A solenoid valve-controlled servo valve as claimed in Claim 1, having an intentional reduction in the surface quality of the sealing surface of the housing body and of the solenoid valve body.

8. A solenoid valve-controlled servo valve as claimed in any one of the preceding Claims, wherein a "soft" high pressure sealing ring functions as the (upper) high pressure seal which faces the solenoid valve seat and seals

the interface of the solenoid valve body to the housing body, which soft high pressure sealing ring is allocated a so-called backup ring consisting of comparatively soft metal for protecting the "soft" high pressure sealing ring (33) against extrusion into the sealing gap.

9. A solenoid valve-controlled servo valve as claimed in Claim 8, wherein the "backup ring" consists of soft iron.

10. A solenoid valve controlled servo valve substantially as hereinbefore 10 described with reference to and as illustrated in the accompanying drawing.