SEALING RING FOR A PISTON PUMP

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 50a and a guide ring 52a and in which a piston 16a is arranged, said piston being accommodated in an axially displaceable manner in a stepped piston bore 54a.

For the dynamic sealing of the piston 16a guided in the piston housing 14a, a sealing ring 10a, 10b is inserted into an annular step of the piston bore 54a, wherein the sealing ring 10a, 10b is to be arranged on an outer circumference of the piston 16a, said outer circumference forming a running surface 18a, 18b. FIGS. 1 to 6 show a sealing ring 10a according to the invention in a first embodiment. FIGS. 7 and 8 show a sealing ring 10b according to the invention in a second embodiment. The tubular filter 50a which surrounds the piston 16a and is inserted into the piston bore 54a holds the sealing ring 10a, 10b together with the guide ring 52a axially in the piston bore 54a by a groove 24a, in which the sealing ring 10a, 10b is placed, being formed between the two components 50a, 52a.

The sealing ring 10a, 10b comprises an annular basic body 20a, 20b, on the outer circumferential surface 22a, 22b of which at least one encircling groove 24a, 24b is formed and on the inner circumferential surface 26a, 26b of which at least one encircling sealing lip 28a, 28b is formed. The limbs 30a, 30b, 31a, 31b of the sealing lip 28a, 28b each enclose a defined angle β_1a, β_2a with the running surface 18a, 18b in the installed state of the sealing ring 10a, 10b. In the present exemplary embodiments, a first limb 30a, 30b is acted upon axially with a higher pressure and a second limb 31a, 31b is acted upon axially with a lower pressure.

The sealing lip 28a, 28b is preferably formed centrally on the inner circumferential surface 26a, 26b 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 10a, 10b is arranged in an annular step of the piston bore 54a of the piston pump 12a, which annular step is designed as a groove 24a running in the piston housing 14a and is acted upon axially on one side with a hydraulic pressure. The sealing ring 10a, 10b advantageously dynamically seals the piston 16a which carries out a lifting movement in the inside diameter of the sealing ring 10a, 10b.

According to the invention, in order to increase the sealing effect of the sealing ring 10a, 10b, starting from initial angles α_1a, α_2a, α_1b, α_2b, the defined angles β_1a, β_2a are achieved by deformation of the sealing ring 10a, 10b during installation. For this purpose, the sealing ring 10a, 10b undergoes a distortion γ_a, γ_b about a center point of its profile during fitting. The distortion γ_a, γ_b of the profile of the sealing ring 10a, 10b is preferably between 19° and 22°.

The initial angles α_1a, α_2a, α_1b, α_2b of the limbs 30a, 30b, 31a, 31b of the sealing lip 28a, 28b with respect to the running surface 18a, 18b are approximately 38.75°. In this case, a tolerance of at maximum 3 to 5° is preferably permitted. The contact surfaces 42a, 44a, 46a, 48a of the sealing ring 10a, 10b are provided centrally with an angle β_1a, β_2a. If the sealing ring 10a, 10b is compressed, provision is made for the ring 10a, 10b to be twisted per se about the angle β_1a, β_2a cross section. By means of the twisting, the sealing lip 28a, 28b is likewise twisted, as a result of which the sealing lip limbs 30a, 30b, 31a, 31b 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 10a undergoes a distortion γ_a of its profile through preferably 21°. As a result, the angle α_2a changes from approximately 38° according to FIG. 3 on the fluid side or high pressure side between the second limb 31a and the running surface 18a to approximately 60° according to FIG. 6. On the air side or low pressure side, the angle α_1a drops from approximately 38° according to FIG. 3 between the first limb 30a and the running surface 18a at the same time to approximately 18° according to FIG. 6. FIG. 3 shows the sealing ring 10a together with the installation space before the filter 50a and the guide ring 52a are fitted. In the installed state according to FIGS. 5 and 6, contact surfaces 42a, 44a, 46a, 48a of the sealing ring 10a each bear parallel to one another against the corresponding surfaces 43a, 45a of the filter 50a and the corresponding surfaces 47a, 49a of the guide ring 52a.

By means of the groove 24a, 24b in the outer cross section or on the outer circumferential surface 22a, 22b, the rigidity of the cross section of the sealing ring 10a, 10b acts resiliently such that the inner sealing lip 28a, 28b is pressed onto the running surface 18a, 18b as soon as the cross section is compressed.

FIGS. 7 and 8 show the second embodiment of the sealing ring 10b which has two encircling grooves 32b, 34b on the inner circumferential surface 26b of the sealing ring 10b, said grooves forming two sealing lips 36b, 38b, between which the sealing lip 28b is formed. The sealing lip 28b protrudes over the lips 36b, 38b in the radial direction 40b. The grooves 32b, 34b in the inner radius or on the inner circumferential surface 26b are configured in such a manner that a radial or wedge-shaped shoulder 58b can penetrate a gap h and thereby raises an inner edge 56b until the latter runs parallel to the running surface 18b. The shoulder 58b is intended to have the height s and the length f. The outer contour of the shoulder 58b preferably has a radius corresponding to the radii of the inner grooves 32b, 34b. However said inner grooves are intended to be short enough to avoid gap extrusion of the sealing lip 28b and, in addition, have a rising profile which permits easy raising of the lip 38b. 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 18b in the deformed state and thereby to be at risk of gap extrusion on the non-raised side. The angle δ_b between the inner edge 56b and a side surface 60b of the sealing ring 10b is preferably approx. 90°+/−10° in order to provide the sealing ring 10b with sufficient support on the shoulder 58b.

An angle difference of the sealing lip limbs 30b, 31b of 60° minus 17.5°=42.5° is produced and has to be compensated for per limb 30b, 31b in each case by γ_b=42.5°/2=21.25°. This means that the sealing ring 10b undergoes a distortion γ_b=21.25° in order to form vertical contact surfaces on both sides after the twisting of the sealing ring 10b. The initial angle α_1b, α_2b is 60°−21.25°=38.75°=17.5°+21.25°. Depending on the dimensions of the sealing ring 10b, h is predetermined to be of a size such that, when the sealing ring 10b is twisted, the lips 36b, 38b neither touch the running surface 18b 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 10a, 10b 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, andwherein 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, andthe 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; anda sealing ring configured to dynamically seal the piston, the sealing ring including: 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, andwherein 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, andthe 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°, anda second defined angle between the second limb and the running surface of the piston is between 59° and 61°.