GB2383097A

GB2383097A - High pressure seal

Info

Publication number: GB2383097A
Application number: GB0223420A
Authority: GB
Inventors: Markus Nieslony
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-10-19
Filing date: 2002-10-09
Publication date: 2003-06-18
Anticipated expiration: 2022-10-09
Also published as: GB2383097B; JP2003139010A; DE10151711A1; GB0223420D0

Abstract

A high pressure delivery unit (1) having a distributor body assembly (2) and a valve assembly (13). The valve assembly (13) comprises an actuation unit (14) for a control part (21) which can be moved in the valve body assembly (13). The control part (21) is influenced by high pressure from a high pressure chamber (11), wherein the high pressure chamber (11) is defined by a sleeve-shaped body ( 4), which encompasses a distributor piston (10), and the valve body assembly (13). The sleeve-shaped body (4) and the valve body assembly (13) are provided on their end sides (5,48) facing the high pressure chamber (11) with surfaces (32,36) having different shapes, such as spherical and conical, which surfaces co-operate to form a sealing region (38).

Description

DESCRIPTION

DEVICE FOR THE SEALING OF COMPONENTS WHICH

ARE SUBJECTED TO HIGH PRESSURE

s The invention is concerned with devices for the sealing of components which are subjected to high pressure.

In fuel injection systems, distributor injection pumps are used, which include 10 solenoid valves for controlling the quantity of fuel. The quantity-controlling solenoid valves of the valve injection pump work together with valve bodies which generate high pressure. The quantitycontrolling solenoid valves and the valve bodies, which generate high pressure, of the distributor injection pump are sealed with respect to each other by means of sealing elements.

For the purpose of sealing distributor injection pumps, sealing rings are used in current solutions between a quantity-controlling solenoid valve and valve body which generates high pressure, which rings are unhardened. However, the sealing surfaces on the valve body and control sleeve, on which the unhardened steel 20 sealing ring lies, are hardened. By means of the axial force, which is created when screwing together by means of a clamping screw, the unhardened steel sealing ring undergoes a plastic deformation on two mutually opposing, knife-shaped edges, whereby the effective sealing surfaces are produced. It must be guaranteed that deformation occurs to such an extent that all the occurring measurement, shape -

25 and position tolerances of the components involved can be compensated and an effective sealing effect is ensured. -

-.-. Owing to higher operating pressures and greater pressure gradients in the pump:-

element of a distributor injection pump, a sealing arrangement with a higher 30 loading capability without an additional sealing element between the distributor

His body and the solenoid valve is desirable.

The current solution for a sealing arrangement which does not comprise a sealing ring and is subjected to high stresses between pressure-loaded components is 5 executed such that the sealing partners are provided with planar, hardened sealing surfaces and are clamped together under a high axial force. This requires either that the surface and tolerance on the components are of a high quality or the element which is to be clamped must have a relatively high elasticity for the purpose of compensating for the tolerances. If the sealing arrangement is not 10 sufficient to produce the necessary characteristics, it results, for example, in overstressing, lack of sealing effect and fluid leakages and damage from erosion.

In a worst case scenario, the distributor pump can break down.

In accordance with the present invention there is provided a high pressure delivery 15 unit having a distributor body assembly which comprises an actuation unit for a control part which can be moved in a valve body assembly and which is influenced by high pressure from a high pressure chamber defined by a sleeve shaped body which encompasses a distributor piston, and the valve body assembly, wherein the sleeve- shaped body and the valve body assembly are 20 provided on their end sides facing the high pressure chamber with surfaces having different dimensions, which surfaces form a sealing surface.

According to the solution in accordance with the invention, different dimensions are formed in place of plane faces on the two sealing partners involved, whereby 25 the sealing function is directly undertaken by means of a control sleeve and a valve body without the requirement of an additional sealing element. As a consequence a cumbersome, expensive and prolonged surface working of the sealing partners can be avoided.

30 With a preferred solution in accordance with the invention, a conically extending

if' bore similar to a counterbore is formed, for example, on a control sleeve of a distributor injection pump, which encompasses a distributor piston, whereas the end side, facing the control sleeve, of the valve body, which receives an actuating member in the form of a magnet, of the distributor injection pump is formed as a S segment of a spherical surface. In addition, the end-side contour of a conically extending bore can also be formed on the valve body for receiving the solenoid valve and the segment of the spherical surface can also be formed on the end side of the control sleeve.

10 Cone angle and depression diameter on the control sleeve and a corresponding spherical radius on the valve body can be tailored to suit each other in such a way that the sealing surface effective between these sealing partners, taking into consideration the manufacturing tolerances, always extends on a conical peripheral surface, which is provided on one of the sealing partners. The radius 15 centre of the spherical surface segment on one of the sealing partners lies in the plane of a clamping shoulder and on the central axis of the valve body, which favours a mutual self-alignment of the sealing partners during axial bracing. The axial position of the valve in the housing of the distributor injection pump can be retained and does not require any modification.

The sealing partners are assembled inside the housing of the distributor injection pump by joining the solenoid valve assembly in the distributor body, and screwing in a clamping screw for the purpose of producing an axial force which creates the sealing effect. The control sleeve and valve body are each hardened at their 25 mutually facing end side and undergo an elastic deformation when braced against each other, so that it is possible to assemble them numerous times. However, the high pressure sealing ring in accordance with the solution in the Prior Art can only

be used once, as this undergoes a plastic deformation. When dismantling the distributor injection pump and subsequently assembling it, a new, as yet 30 undeformed high pressure sealing ring is always required.

The combination of different dimensions on the sealing partners provides the solenoid valve with a degree of freedom, which permits an automatic alignment with respect to the force inducing clamping screw end surface during the screwing procedure. As a consequence, the surface pressure on the clamping shoulder/screw 5 and on the sealing surfaces of the sealing partners is uniformly distributed. This is particularly advantageous with regard to the mechanical structural stress and the obtainable sealing effect. The spherical contour of one of the sealing partners produces an annular contact surface, having a small annular width, as deformation occurs in connection with the conically extending bore on the other sealing I O partner. As a consequence, owing to the high surface pressure, a small drop in pressure occurs and thus a high sealing effect. The diameter-extending wedge effect of the valve body in the control sleeve bore compensates for any compression of the control sleeve by means of the applied axial force and the associated reduced piston clearance. The solution proposed in accordance with the 15 invention for sealing a high pressure chamber of a distributor injection pump renders it possible to retain all interface dimensions between the solenoid valve, the clamping screw and the distributor body.

The invention is now described further hereinafter, by way of example only, with 20 reference to the accompanying drawings, in which: Figure 1 shows an embodiment of a distributor injection pump, known i the Prior Art, having a plastically deformed high pressure sealing

ring and Figure 2 shows a solution, in accordance with the present invention, having differently iorrned dimensions on the end side of the mutually cooperating sealing partners.

30 A distributor injection pump 1 in accordance with the illustration in Figure 1

- comprises a distributor body assembly 2. On the outer peripheral surface of the distributor body assembly 2 an O-ring 3 can be let into a ring-shaped groove. In the distributor body assembly 2, a sleeve-shaped body 4, which can be provided as a control sleeve, is let into a bore. The sleeve-shaped body 4 in the form of a S control sleeve encompasses a distributor piston 10 on the end of which, remote from the distributor assembly 2, a spring plate 8 is fixed. Between the inner side of the spring plate 8 and a support surface 9 on one side wall of the distributor assembly 2, a stressing element 7 is disposed which is formed here as a coil spring. A pre-stressing force is exerted by means of the pre-stressing element 7 via 10 the spring plate 8 onto the distributor piston 10, whose end side remote from the spring plate 8 defines a high pressure chamber 11.

The sleeve-shaped body 4 comprises a first end side 5, which faces a valve body assembly 13, whereas the second end side 6 of the sleeve- shaped body 4 faces the 15 spring plate 8. In the embodiment of a distributor injection pump known in the Prior Art and illustrated in Figure 1, a deformed high pressure sealing ring 12 is

received within a annular chamber 19. The deformation of the high pressure sealing ring 12 is achieved by axially stressing the sleeve- shaped body 4 with the valve body assembly 13, this stressing force being applied by means of a clamping 20 screw 16. The clamping screw 16 lies against a clamping shoulder of the valve body 13 and engages the end surface 15 of the valve body assembly 13 against the first end side 5 of the sleeve-shaped body 4. The high pressure sealing ring 12 received between the end sides 15 of valve body 13 and the first end side 5 of the sleeve-shaped body 4 is compressed by means of the axial force and plastically 25 deformed. As the axial force stresses the high pressure sealing ring 12, which is made out of steel, the high pressure sealing ring 12 deforms to such an extent that all the measurement, shape and position tolerances prevailing on the components 4 and/or 13 are compensated. However, since the material of the high pressure sealing ring 12 is mechanically stressed beyond its yield point and remains 30 deformed, the re-use of a high pressure sealing ring 12 once it has been

compressed, i.e. plastically deformed, is no longer possible after the distributor pump l has been disassembled and subsequently assembled, in other words, it is necessary to use an, as of yet, undeformed high pressure sealing ring 12 for sealing the sleeve-shaped body 4 and the valve body 13.

s A plastic deformation, i.e. a radial expansion of the high pressure sealing ring 12, essentially extends in the annular chamber l 9 encompassing the high pressure sealing ring 12. A first sealing ring 17 and a second sealing ring 18 are accommodated axially spaced from each other on the peripheral surface of the 10 valve body assembly 13, which is clamped by means of the clamping screw 16.

An electromagnet 14 whose magnet coils are indicated in the illustration of Figure I is received by the valve body assembly 13. The screw connection between the distributor body assembly 2 and the clamping nut 16, which is screwed in here for the purpose of pre-stressing the body assembly 13 in an axial manner, is indicated 15 by reference numeral 20. A control part 21, which can be actuated by means of the electromagnet 14, is disposed axially with respect to the axis of symmetry of the valve body, which is essentially formed rotationally symmetrical, of the valve body assembly 13. When the magnet coils of the electromagnet 14 are energised, the control part 21 which is connected to the armature of the electromagnet 14 20 performs a piston movement corresponding to the control part 22 within the valve body assembly 13.

A solution in accordance with the invention having different dimensions formed on the sealing partners for the purpose of sealing a distributor injection pump can 25 be seen in the illustration in Figure 2.

As a contrast to the illustration in Figure I the connection between the distributor injection assembly 2 and valve body assembly 13 according to the illustration in Figure 2 does not comprise a high pressure sealing ring, which is plastically 30 deformed between the first end side 5 of the sleeve-shaped body 4 and the end

side 48 of the valve body assembly 13 during its axial force stress by means of the clamping screw 16. The sealing function for the purpose of sealing the high pressure chamber 1 1 between the distributor piston 10 and the valve body assembly 13 occurs by means of this component alone, whose end sides S and 48 5 are formed in different dimensions.

In a preferred embodiment of the solution in accordance with the invention a conical bore 35 is provided on the first end side S ofthe sleeve-shaped body 4.

This bore 35 which is convenient to produce from the manufacturing point of 10 view comprises conical peripheral surfaces 36 extending in a cone angle 37. The cone angle 37 lies in the region between 60 and 180 ; in particular, the cone angle 37 preferably measures 135 .

In contrast thereto, the end surface 48 of the valve body, which represents the 1 S second sealing partner, of the valve body assembly 13 is formed as a spherical surface segment 32. The spherical radius 31 of the spherical surface segment 32 is indicated by the reference numeral 31. The central point 34 of the spherical radius 31 lies on the axis of the valve body assembly 13 and in the plane 30 which extends through the clamping shoulder 49 of the valve body assembly 13. The 20 clamping screw 16 lies against the clamping shoulder 49, which can be formed, for example, as a step on the periphery of the valve body assembly 13, with which screw the valve body assembly 13 is axially clamped against the sleeve-shaped body 4, for example, a control sleeve.

25 After the electromagnet 14 has been assembled, the valve body assembly 13 is inserted into the bore of the distributor assembly 2, which bore corresponds to the outer diameter of said valve body assembly. The first and second sealing rings 17 and 18, each of which are received in two annular grooves of the valve body assembly 13, lie against the boundary surface of the bore in the distributor 30 assembly 2. After the preassembled valve body assembly 13 has been inserted,

the clamping screw 16 is screwed into an internal thread of the distributor assembly 2 and tightened. As the clamping screw 16 is tightened, it contacts the clamping shoulder 49 on the outer periphery of the valve body assembly 13 and screws down the valve body assembly 13 against the first end side 5 of the sleeve 5 shaped body 4, on which a conical bore 35 is provided. The end side 48, which is formed as a spherical surface segment 32, of the valve body assembly 13 which transmits the axial pre-stressing force produces an annular contact surface having a small annular width 39 when being deformed in connection with the conical bore 35 on the first end side 5 of the sleeve-shaped body 4. The annular contact 10 surface produces a sealing surface 38 in the contact region between the sleeve shaped body 4 and the end side 48 of the valve body assembly 13. Owing to the high surface pressure a small drop in pressure occurs and thus a high sealing effect is produced with respect to the high pressure chamber 11, which is sealed by means of contact with the sealing partners 4 and 13 without a separate sealing 1 S element, such as for example, the high pressure sealing ring 12 known in the Prior Art (compare illustration in Figure 1).

The combination of different dimensions on the mutually contacting end sides 5 and 48 of the sleeve-shaped body 4 and the valve body assembly 13 permits an 20 automatic alignment with respect to the force-inducing end surface of the clamping screw 16 during the screwing procedure. As a consequence, the surface pressure is uniformly distributed on one clamping shoulder 49 of the valve body assembly 13, on the clamping screw 16 and in the region of the sealing surface 38 between the first end side 5 of the sleeve-shaped body 4 and the spherical surface 25 segment 32 on the end side The uniform distribution of surface pressure is particularly convenient with regard to the obtainable sealing effect and with regard to the mechanical stress of the components 4 and 13. The sleeve-shaped body 4 and the valve body assembly 13 are hardened in the region of the end sides 5, 48, wherein the sealing surfaces are elastically deformed in the sealing region 38 upon 30 initiation of the axial pre-stressing force by means of the clamping screw, so that it

is possible to assemble them numerous times.

A further advantageous effect when using sealing partners 4 and 13 formed having different dimensions lies in the fact that the diameter-extending wedge effect of 5 the valve body assembly 13, which engages in the conical bore 35, in the sleeve shaped body 4 counteracts the compression of the sleeve-shaped body 4 and counteracts an inadmissible reduced piston clearance with reference to the distributor piston 10 encompassed by the sleeve-shaped body 4.

10 In another embodiment of the solution proposed in accordance with the invention the conical bore 35 can also be let in on the end side 48 of the valve body assembly 13, which is pre-stressed via the clamping screw 16, instead of on the sleeve-shaped body 4. Accordingly, the first end side 5 of the sleeve-shaped body 4 (control sleeve) can be provided with a spherical surface segment 32 instead of a 15 conical bore 35.

Furthermore, the valve body assembly 13, whose region remote from the sleeve shaped body 4 accommodates the magnet coil of the electromagnet 14, is provided with a control part bore 40 in which the control part 21 moves in a 20 reciprocating manner. The control part bore 40 issues into a chamber 41 which is within the valve body assembly 13 and accorn nodates a spring element 42. One end of the spring element 42 lies against a disc 43 in the chamber 41 whereas the mutually opposing end to this end of the spring element 42 lies against the end side of the control part 21. By means of a connection from the high pressure 25 chamber 1 1, which is sealed by means of the first side S of the sleeve- shaped body 4 and the end side 48 placed against this side, said end side 48 having a spherical surface segment 32 of the valve body assembly 13, a high pressure bore 44 extends, by means of which the high pressure prevails in a control chamber 47 encompassing the control part 21. A seating 45 for the control part 21 is fixed on 30 the control chamber 47, which is closed or opened depending upon the axial

stroke movement 22 of the control part 21. Below the setting 45 of the control part 21 in the valve body 13 an exit bore 46 branches off, through which the controlled amount of fluid flows into an annular chamber 19 which is formed in the assembly 2 encompassing the end side 48 of the valve body assembly 13.

When using the solution proposed in accordance with the invention designing the end sides of the components 4 and 13 which are to be stressed axially with respect to each other of a distributor injection pump 1 in different dimensions - it is possible to avoid using a separate sealing element in the form of a high pressure 10 sealing ring 12. On the other hand it is guaranteed by means of the solution proposed in accordance with the invention that the interface dimensions between the solenoid valve 14, the clamping screw 16 and the distributor body assembly 2 remain essentially unaltere d and require no modification whatsoever.

Claims

1. A high pressure delivery unit having a distributor body assembly, which comprises an actuation unit for a control part which can be moved in a 5 valve body assembly and which is influenced by high pressure from a high pressure chamber defined by a sleeve-shaped body which encompasses a distributor piston,wherein the sleeve-shaped body and the valve body assembly are provided on their end sides facing the high pressure chamber with surfaces having different dimensions, which surfaces co-operate to 10 form a sealing region.

2. A high pressure delivery unit as claimed in Claim 1, wherein a conical

bore having a conical peripheral surface is formed on the end side of the sleeve-shaped body.

3. A high pressure delivery unit as claimed in Claim 1, wherein the end side of the valve body assembly is produced as a spherical surface segment.

4. A high pressure delivery unit as claimed in Claim 1, wherein the first end 20 side of the valve body assembly and of the sleeve-shaped body is produced as a spherical surface segment.

5. A high pressure delivery unit as claimed in Claim 1, wherein a conical bore having a conical peripheral surface is formed on the end side of the 25 valve body assembly.

6. A high pressure delivery unit as claimed in Claims 2 and 3, wherein the contact surface of the end sides of the sleeve-shaped body and of the valve body assembly form the sealing surface.

7. A high pressure delivery unit as claimed in Claims 4 and 5, wherein the contact surface of the end sides of the sleeve-shaped body and of the valve body assembly form the sealing surface.

5

8. A high pressure delivery unit as claimed in Claim 2 or 5, wherein the cone angle of the conical peripheral surface is greater than 60 and less than 180 .

9. A high pressure delivery unit as claimed in Claim 8, wherein the cone 10 angle preferably rr;easures 135 .

10. A high pressure delivery unit as claimed in Claim 3, wherein the central point of the spherical radius lies on the central axis of the valve body assembly.

11. A high pressure delivery unit as claimed in Claim 3, wherein the central point of the spherical radius lies in the plane of the clamping shoulder of the valve body assembly.

20

12. A high pressure delivery unit as claimed in Claim 1 1, wherein the axial pre- stressing force producing the sealing effect is initiated by means of a clamping screw which lies against the clamping shoulder of the valve body assembly. 25

13. A high pressure delivery unit, substantially as hereinbefore described with reference to and as illustrated in Fig. 2 of the accompanying drawings.