US20130205995A1

US20130205995A1 - Sealing ring for a piston pump

Info

Publication number: US20130205995A1
Application number: US13/817,170
Authority: US
Inventors: Daniel Gosse
Original assignee: Individual
Current assignee: Robert Bosch GmbH
Priority date: 2010-08-18
Filing date: 2011-06-21
Publication date: 2013-08-15
Also published as: EP2606232A1; EP2606232B1; CN103069169A; WO2012022519A1; DE102010039439A1; CN103069169B

Abstract

A sealing ring is configured to dynamically seal a pistol in a piston pump. The piston is guided in a piston housing or in a guide ring. The sealing ring is arranged on an outer circumference of the piston. The outer circumference of the piston forms a running surface. The sealing ring has an outer circumferential surface with at least one circumferential groove. The sealing ring also has an inner circumferential surface with at least one circumferential sealing When the sealing ring is in an installed state, limbs of the at least one sealing lip each form a defined angle with the running surface. The defined angles are formed, starting from an initial angle, by deforming the sealing ring during installation. The sealing ring is twisted about a center of its profile during the installation.

Description

PRIOR ART

The invention relates to a sealing ring for a piston pump according to the generic type of independent patent claim 1 and to a piston pump according to the generic type of independent patent claim 7.
DE 101 16 658 A1 describes, for example, a piston pump with a sealing ring which is provided for the dynamic sealing of a piston of the piston pump, said piston being guided in a piston housing, wherein the sealing ring is to be arranged on an outer circumference of the piston, said outer circumference forming a running surface. The sealing ring comprises an annular basic body which has a substantially quadrangular cross section, and four encircling sealing lips which are formed at the corners of the basic body and between which encircling grooves are formed.
DE 10 2004 010 498 A1 discloses a sealing ring which seals a piston of a piston pump and is composed of an elastomeric material. The sealing ring comprises an annular basic body which has a substantially quadrangular cross section, and four sealing lips which are formed at the corners of the basic body and have grooves arranged in between. In order to improve the durability characteristics, the sealing ring has a coating.

DISCLOSURE OF THE INVENTION

By contrast, the sealing ring according to the invention with the features of independent patent claim 1 has the advantage that, starting from initial angles, the defined angles are achieved by deformation of the sealing ring during installation. This advantageously results in a sealing ring which has an increased sealing effect and a longer service life by the sealing ring taking up its functionally relevant shape only in the installed state. A sealing ring is advantageously produced, said sealing ring being able to be fitted in an undirected manner or not having to be aligned during fitting, thus permitting simple and cost-effective fitting of the sealing ring. This also means that a separate identification process can be omitted. The risk of erroneous fitting, in which a massive leakage can subsequently occur and which cannot be detected during operation of the piston pump, and a subsequent failure of a complete unit can therefore be reliably avoided. In particular, the configuration of the construction space in the piston housing or guide ring can be designed in such a manner that the sealing ring is fixable in an asymmetric position by the deformation of its profile, thus making it possible to achieve the function of an asymmetric sealing ring. In comparison to the production of an asymmetric sealing ring, this also results in lower tool costs, since the production of symmetrical parts is more cost-effective. In an advantageous manner, the sealing ring comprises a groove in the outer cross section or on the outer circumferential surface thereof in order to support the pressing on of the sealing lip at higher pressures.
Advantageous improvements to the sealing ring indicated in independent patent claim 1 are possible by means of the measures and developments cited in the dependent claims.
In a refinement of the invention, the sealing ring undergoes twisting about a center point of its profile during fitting. In this case, the sealing ring advantageously takes up its functionally relevant shape only in the installed state. The distortion of the profile of the sealing ring is preferably between 19° and 22°.
In a refinement of the invention, the sealing ring has two encircling grooves on the inner circumferential surface, said grooves forming two lips, between which the sealing lip is formed. It is particularly advantageous that the sealing lip protrudes over the lips in the radial direction. The refinement makes it possible for the lips to advantageously be kept away from the adjacent components of the piston pump even at high pressures, i.e. neither touch the running surface nor are at risk of gap extrusion.
In addition, the structure of the piston pump can remain unchanged, since the existing construction space in the piston pump easily permits a change in the geometry of the sealing ring in the radial direction.
The sealing lip preferably has a radius which is between 0.1 and 0.4 mm. This advantageously results in a simple and cost-effective production of the sealing ring.
A substantial advantage of the piston pump according to the invention consists in that the sealing ring is arranged via at least three contact surfaces in a groove running between two components of the piston pump. After the piston pump is fitted and the sealing ring is installed, this advantageously results in a secure position of the sealing ring within the groove. By means of the positional stability of the sealing ring, the desired dynamic sealing function is permanently maintained during the operation of the piston pump and, during the course of the operation, the sealing ring withstands the existing pressure in the piston pump.
In a refinement of the piston pump according to the invention, a first limb of the sealing ring is acted upon axially with a higher pressure and a second limb of the sealing ring is acted upon axially with a lower pressure. In an advantageous manner, the sealing ring is securely mounted in the groove, and the hydraulic pressure can now only act slightly on the sealing ring, and therefore the sealing ring according to the invention can reliably carry out its sealing function. This advantageously increases the service life of the sealing ring according to the invention, and therefore the maintenance interval can be lengthened and the downtimes of the piston pump due to defective sealing rings minimized.
In a further refinement of the piston pump according to the invention, the defined angle between the first limb and a running surface of the piston is between 16° and 18° and the defined angle between the second limb and the running surface of the piston is between 59° and 61°. A sealing ring designed in such a manner can also better withstand the high hydraulic pressure. As a result, the service life of the sealing ring and therefore of the piston pump according to the invention is lengthened and the downtimes of piston pump due to defective sealing rings are further minimized.
Advantageous embodiments of the invention are illustrated in the drawings and are described below. In the drawings, the same reference numbers denote components or elements which carry out identical or analogous functions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows part of a piston pump having a filter and a guide ring before the filter and the guide ring are joined together, wherein a groove, in which a sealing ring according to the invention is inserted in a first embodiment, is formed between the two components.

FIG. 2 shows a sectional illustration of the piston pump from FIG. 1.

FIG. 3 shows a detail of the sectional illustration of the sealing ring according to the invention from FIG. 2, the sealing ring having a sealing lip, the limbs of which enclose initial angles with the running surface of the piston.

FIG. 4 shows part of the piston pump after the filter and the guide ring are joined together, with the sealing ring according to the invention in the installed state.

FIG. 5 shows a sectional illustration of the piston pump from FIG. 4.

FIG. 6 shows a detail of the sectional illustration of the sealing ring according to the invention from FIG. 5, the sealing ring having the sealing lip, the limbs of which enclose defined target angles with the running surface of the piston, said target angles being achieved by deformation of the sealing ring upon installation.

FIG. 7 shows a sectional illustration of a sealing ring according to the invention in a second embodiment, said sealing ring forming two encircling grooves on its inner circumferential surface, between which grooves the sealing lip is formed.

FIG. 8 shows a detail of the sectional illustration of the sealing ring according to the invention from FIG. 7.

EMBODIMENTS OF THE INVENTION

Various pump components, such as, for example, pump pistons which move during the pumping of a fluid which is to be conveyed or fixed components sealing the moving pump pistons, such as, for example, sealing rings, are generally exposed to increased wear. The wear generally relates to surface regions which are stressed by pressure or surface pressure. For example the pump pistons become relatively greatly worn due to oscillations, transverse forces and friction, wherein gap extrusion may regularly occur at the sealing ring and wear may regularly occur on the guide ring or on the eccentric shaft. For example, via a bearing point between an eccentric and the pump piston, a rotational movement of a pump drive is converted into a lifting movement for generating pressure, as a result of which wear loads may occur in the bearing point. Therefore, pump pistons and sealing rings have to be protected against increased wear in order to be able to maintain their pumping and sealing function.
FIGS. 1 to 6 each show a cutout of a piston pump 12 which is used, for example, as a feed pump or return pump of a hydraulic pumping system of a vehicle. Since piston pumps of this type are known per se in construction and function, the drawing and description for the clear illustration of the invention are restricted to the relevant part according to the invention of the piston pump 12. The piston pump 12 comprises a piston housing 14 which has a filter 50 a and a guide ring 52 a and in which a piston 16 a is arranged, said piston being accommodated in an axially displaceable manner in a stepped piston bore 54 a.
For the dynamic sealing of the piston 16 a guided in the piston housing 14 a, a sealing ring 10 a, 10 b is inserted into an annular step of the piston bore 54 a, wherein the sealing ring 10 a, 10 b is to be arranged on an outer circumference of the piston 16 a, said outer circumference forming a running surface 18 a, 18 b. FIGS. 1 to 6 show a sealing ring 10 a according to the invention in a first embodiment. FIGS. 7 and 8 show a sealing ring 10 b according to the invention in a second embodiment. The tubular filter 50 a which surrounds the piston 16 a and is inserted into the piston bore 54 a holds the sealing ring 10 a, 10 b together with the guide ring 52 a axially in the piston bore 54 a by a groove 24 a, in which the sealing ring 10 a, 10 b is placed, being formed between the two components 50 a, 52 a.
The sealing ring 10 a, 10 b comprises an annular basic body 20 a, 20 b, on the outer circumferential surface 22 a, 22 b of which at least one encircling groove 24 a, 24 b is formed and on the inner circumferential surface 26 a, 26 b of which at least one encircling sealing lip 28 a, 28 b is formed. The limbs 30 a, 30 b, 31 a, 31 b of the sealing lip 28 a, 28 b each enclose a defined angle β_1a, β_2awith the running surface 18 a, 18 b in the installed state of the sealing ring 10 a, 10 b. In the present exemplary embodiments, a first limb 30 a, 30 b is acted upon axially with a higher pressure and a second limb 31 a, 31 b is acted upon axially with a lower pressure.
The sealing lip 28 a, 28 b is preferably formed centrally on the inner circumferential surface 26 a, 26 b and preferably has a radius R of at least 0.1 mm, wherein larger radii, such as, for example, R=0.225 mm and greater, would also be conceivable.
As has already been mentioned, the sealing ring 10 a, 10 b is arranged in an annular step of the piston bore 54 a of the piston pump 12 a, which annular step is designed as a groove 24 a running in the piston housing 14 a and is acted upon axially on one side with a hydraulic pressure. The sealing ring 10 a, 10 b advantageously dynamically seals the piston 16 a which carries out a lifting movement in the inside diameter of the sealing ring 10 a, 10 b.
According to the invention, in order to increase the sealing effect of the sealing ring 10 a, 10 b, starting from initial angles α_1a, α_2a, α_1b, α_2b, the defined angles β_1a, β_2aare achieved by deformation of the sealing ring 10 a, 10 b during installation. For this purpose, the sealing ring 10 a, 10 b undergoes a distortion γ_a, γ_babout a center point of its profile during fitting. The distortion γ_a, γ_bof the profile of the sealing ring 10 a, 10 b is preferably between 19° and 22°.
The initial angles α_1a, α_2a, α_1b, α_2bof the limbs 30 a, 30 b, 31 a, 31 b of the sealing lip 28 a, 28 b with respect to the running surface 18 a, 18 b are approximately 38.75°. In this case, a tolerance of at maximum 3 to 5° is preferably permitted. The contact surfaces 42 a, 44 a, 46 a, 48 a of the sealing ring 10 a, 10 b are provided centrally with an angle β_1a, β_2a. If the sealing ring 10 a, 10 b is compressed, provision is made for the ring 10 a, 10 b to be twisted per se about the angle β_1a, β_2across section. By means of the twisting, the sealing lip 28 a, 28 b is likewise twisted, as a result of which the sealing lip limbs 30 a, 30 b, 31 a, 31 b take up an angle of between 16° and 18°, ideally of 17.5° on the air side or low pressure side and an angle of between 59° and 61°, ideally of 60°, on the liquid side or high pressure side.
During fitting, the sealing ring 10 a undergoes a distortion γ_aof its profile through preferably 21°. As a result, the angle α_2achanges from approximately 38° according to FIG. 3 on the fluid side or high pressure side between the second limb 31 a and the running surface 18 a to approximately 60° according to FIG. 6. On the air side or low pressure side, the angle α_1adrops from approximately 38° according to FIG. 3 between the first limb 30 a and the running surface 18 a at the same time to approximately 18° according to FIG. 6. FIG. 3 shows the sealing ring 10 a together with the installation space before the filter 50 a and the guide ring 52 a are fitted. In the installed state according to FIGS. 5 and 6, contact surfaces 42 a, 44 a, 46 a, 48 a of the sealing ring 10 a each bear parallel to one another against the corresponding surfaces 43 a, 45 a of the filter 50 a and the corresponding surfaces 47 a, 49 a of the guide ring 52 a.
By means of the groove 24 a, 24 b in the outer cross section or on the outer circumferential surface 22 a, 22 b, the rigidity of the cross section of the sealing ring 10 a, 10 b acts resiliently such that the inner sealing lip 28 a, 28 b is pressed onto the running surface 18 a, 18 b as soon as the cross section is compressed.
FIGS. 7 and 8 show the second embodiment of the sealing ring 10 b which has two encircling grooves 32 b, 34 b on the inner circumferential surface 26 b of the sealing ring 10 b, said grooves forming two sealing lips 36 b, 38 b, between which the sealing lip 28 b is formed. The sealing lip 28 b protrudes over the lips 36 b, 38 b in the radial direction 40 b. The grooves 32 b, 34 b in the inner radius or on the inner circumferential surface 26 b are configured in such a manner that a radial or wedge-shaped shoulder 58 b can penetrate a gap h and thereby raises an inner edge 56 b until the latter runs parallel to the running surface 18 b. The shoulder 58 b is intended to have the height s and the length f. The outer contour of the shoulder 58 b preferably has a radius corresponding to the radii of the inner grooves 32 b, 34 b. However said inner grooves are intended to be short enough to avoid gap extrusion of the sealing lip 28 b and, in addition, have a rising profile which permits easy raising of the lip 38 b. It is also important for the height h to be of a sufficient size as far as possible in order not to lie on the running surface 18 b in the deformed state and thereby to be at risk of gap extrusion on the non-raised side. The angle δ_bbetween the inner edge 56 b and a side surface 60 b of the sealing ring 10 b is preferably approx. 90°+/−10° in order to provide the sealing ring 10 b with sufficient support on the shoulder 58 b.
An angle difference of the sealing lip limbs 30 b, 31 b of 60° minus 17.5°=42.5° is produced and has to be compensated for per limb 30 b, 31 b in each case by γ_b=42.5°/2=21.25°. This means that the sealing ring 10 b undergoes a distortion γ_b=21.25° in order to form vertical contact surfaces on both sides after the twisting of the sealing ring 10 b. The initial angle α_1b, α_2bis 60°−21.25°=38.75°=17.5°+21.25°. Depending on the dimensions of the sealing ring 10 b, h is predetermined to be of a size such that, when the sealing ring 10 b is twisted, the lips 36 b, 38 b neither touch the running surface 18 b nor are at risk of gap extrusion.
In a refinement of the invention, further sealing lips and/or grooves and also sealing lips and/or grooves of different geometrical shapes may also be provided on the sealing ring 10 a, 10 b according to the invention.
The described pump pistons and sealing rings are used, for example, in pump systems in modern vehicle technology, said pumping systems relating by way of example to safety technology, such as ABS (anti-lock system), ESP (electronic stabilization program), EHB (electrohydraulic brake), TCS (traction control system) or ASR (anti-slip control). However, the sealing ring according to the invention can be used not only in the previously mentioned pumping systems but also in all systems in which sealing rings stressed in a translatory and dynamically changing manner are required.

Claims

1. A sealing ring for dynamically sealing a piston of a piston pump, comprising:

an annular basic body having an outer circumferential surface with at least one encircling groove and having an inner circumferential surface with at least one encircling sealing lip,

wherein the at least one encircling sealing lip has limbs,

wherein, when the sealing ring is in an installed state, the limbs each enclose a defined angle with a running surface of an outer circumference of the piston, and

wherein the defined angles are formed, starting from initial angles, by deformation of the sealing ring during installation.

2. The sealing ring as claimed in claim 1, wherein the sealing ring is configured to be distorted about a center point of a profile during fitting.

3. The sealing ring as claimed in claim 1, wherein the profile of the sealing ring is distorted between 19° and 22°.

4. The sealing ring as claimed in claim 1, wherein:

the inner circumferential surface further includes two encircling grooves configured to form two lips, and

the sealing lip is formed between the two lips.

5. The sealing ring as claimed in claim 4, wherein the sealing lip protrudes over the lips in a radial direction.

6. The sealing ring as claimed in claim 4, wherein the sealing lip has a radius between 0.1 and 0.4 mm.

7. A piston pump comprising:

a piston guided in one of a piston housing and a guide ring; and

a sealing ring configured to dynamically seal the piston, the sealing ring including:

wherein the at least one encircling sealing lip has limbs,

wherein when the sealing ring is in an installed state, the limbs each enclose a defined angle with a running surface of an outer circumference of the piston, and

wherein the limbs have initial angles, and the defined angles are formed by deformation of the sealing ring during installation.

8. The piston pump as claimed in claim 7, wherein the sealing ring is arranged via at least three contact surfaces in a groove running between two components of the piston pump.

9. The piston pump as claimed in claim 7, wherein:

the sealing ring has a first limb and a second limb,

the first limb is configured to be acted upon axially with a higher pressure, and

the second limb is configured to be acted upon axially with a lower pressure.

10. The piston pump as claimed in claim 7, wherein:

a first defined angle between the first limb and a running surface of the piston is between 16° and 18°, and

a second defined angle between the second limb and the running surface of the piston is between 59° and 61°.