Piston arrangement of a piston pump

Abstract

Piston arrangement (12) of a piston pump (10) comprising a piston (16), a return spring (28) which provides axial preload to the piston (16), a spring support (30; 46) arranged on the piston (16) for the return spring (28) and a sealing element (32; 48) arranged on the piston (16) which seals radially against a cylinder (14), wherein the spring support (46) and the sealing element (48) are formed in one piece and the sealing element (48) is designed with an axial groove (52) which is open to the high-pressure area (24) surrounding the return spring (28), characterized in that the sealing element (48) has a first and second support section (60, 62) radially on both sides of the axial groove (52), which form the spring support (46).

Description

State of the art

[0001] The invention relates to a piston assembly of a piston pump comprising a piston, a return spring axially biasing the piston, a spring support for the return spring arranged on the piston, and a sealing element arranged on the piston and sealing radially against a cylinder. The invention further relates to a piston assembly of a piston pump comprising a piston and a sealing element arranged on the piston and sealing radially against a cylinder. The invention also relates to a piston pump of a vehicle brake system with such a piston assembly.

[0002] A component of modern vehicle braking systems is a hydraulic unit, which is used in motor vehicles such as passenger cars or trucks to provide regulated brake pressures to their braking system. To meter this brake pressure, the hydraulic unit has a pump, which is usually a piston pump in which a piston moves within a cylinder. The piston moves in a two-stroke cycle. In the first stroke, a fluid to be pumped, such as brake fluid, is drawn in through an inlet valve. In the second stroke, the fluid is expelled through an outlet valve. The piston is sealed against the inner surface of the cylinder by a sealing element, which also guides it within the cylinder during its stroke. Such a piston pump is known, for example, from DE 10 2005 017 131 A1.

[0003] The invention is based on the objective of creating a piston pump with a piston arrangement in which a largely optimal seal between the piston and the cylinder is achieved under all operating conditions. Disclosure of the invention

[0004] According to the invention, a piston arrangement of a piston pump is provided, comprising a piston, a return spring which springs the piston in the axial direction, a spring support for the return spring arranged on the piston and a sealing element arranged on the piston which seals radially against a cylinder, in which the spring support and the sealing element are formed in one piece.

[0005] With the solution according to the invention, the spring seat of a return spring on a piston assembly of a piston pump, in particular a piston pump of a vehicle brake system, can be designed to be axially shorter. This enables a more compact design overall with a smaller internal volume. Furthermore, the preload force of the return spring can be used to additionally preload and axially compress the sealing element, causing it to be forced apart radially with increasing piston stroke and providing better guiding and sealing properties for the piston in the cylinder. At the same time, a large contact or bearing surface can be provided for the return spring, allowing it to be made larger, particularly radially. This also improves the available installation space.

[0006] According to a first advantageous embodiment of the piston arrangement according to the invention, the spring support is formed with a valve housing of an inlet valve for the piston pump.

[0007] With this further development, the spring seat of the piston's return spring on the valve housing of an intake valve and the sealing element are designed as a single piece. This results in significant advantages with regard to manufacturing costs and the associated assembly processes. The valve housing serves to support a spring that presses the closing element of the intake valve against a valve seat formed on the piston. Such a valve housing is also referred to as a valve cage or valve cover.

[0008] According to a second advantageous embodiment of the piston arrangement according to the invention, the sealing element is designed with an axial groove which is open to the high-pressure area surrounding the return spring.

[0009] In this type of piston arrangement, the pressure prevailing in the high-pressure area surrounding the return spring forces its way into the axial groove, causing it to widen. In particular, this presses the radially outer part of the sealing element against the inner wall of the adjacent cylinder. Thus, as the pressure increases, the sealing element's contact with the cylinder is strengthened, resulting in a better seal. Furthermore, the piston's guidance and leakage characteristics within the cylinder are improved.

[0010] According to a third advantageous embodiment of the piston arrangement according to the invention, the sealing element has a first and second support section radially on both sides of the axial groove, which form the spring support.

[0011] In other words, in this design, the return spring rests against two support sections on either side of the axial groove. Advantageously, the return spring is shaped at its end such that it essentially forms two annular, flat contact surfaces at the two edges of the axial groove. This allows for a maximum contact area for the return spring, despite the axial groove weakening the sealing element. This contact surface projects radially far outwards, so the return spring can be designed as a helical spring with a correspondingly large radius. Furthermore, the preload force of the return spring, which also increases with increasing stroke, contributes to the radial widening of the axial groove on both sides. This improves the guidance and sealing of the piston in the cylinder.

[0012] According to a fourth advantageous embodiment of the piston arrangement according to the invention, the sealing element has a sealing lip that rests against the cylinder.

[0013] This further development also results in an axial groove radially inside the sealing lip, which is widened depending on the pressure in order to improve the guidance and the leakage behavior.

[0014] According to a fifth advantageous embodiment of the piston arrangement according to the invention, the sealing lip ends axially recessed relative to the spring support on the side facing away from the return spring.

[0015] The return spring, positioned in this way, cannot influence the axially recessed sealing lip. In particular, the return spring can be pressed onto the sealing element during installation without damaging or injuring the sealing lip. The return spring can be designed as a helical spring with a larger outer diameter. This reduces the axial installation space required for the return spring, resulting in a smaller clearance volume. Due to the axially recessed sealing lip, the return spring has only an annular bearing surface radially inside the axial groove. However, the return spring can still compress the core of the sealing element axially, causing it to push radially outwards and thus improving piston guidance. This also results in a better seal at higher pressures, where the return spring is then under greater preload.

[0016] According to the invention and a sixth advantageous embodiment of the piston arrangement of a piston pump according to the invention, comprising a piston and a sealing element arranged on the piston and sealing radially against a cylinder, the sealing element has axially spaced circumferential sealing webs on its outer surface facing the cylinder.

[0017] With this solution or further development according to the invention, the generated pressure to be sealed in the high-pressure area of ​​the cylinder is sealed by means of several small webs. This contrasts with conventional piston arrangements of piston pumps in a vehicle brake system, in which a single sealing lip is provided for sealing between the piston and cylinder.

[0018] The webs according to the invention are deformable and elastically adapt to the inner surface of the cylinder. This allows the associated piston to calibrate itself within the cylinder. The webs extend along the circumference of the typically circular cylindrical piston. A gap is formed between each pair of webs. A fluid film can build up in these gaps. This film acts as a lubricant, reducing friction between the piston and cylinder. Furthermore, this fluid film enhances the sealing effect, creating a so-called fluid seal. This design can be implemented with or without the aforementioned axial groove. Without the axial groove, a wide radial contact surface is provided for the return spring. This results in optimal utilization of the contact area and an optimal diameter design for the return spring, provided it is a helical spring.

[0019] According to a seventh advantageous embodiment of the piston arrangement according to the invention, the individual sealing web has a wave-shaped cross-section.

[0020] This further development results in a sealing arrangement whose sealing geometry is significantly more robust than that of known seals. The improved sealing is particularly noticeable at high pressures. Overall, this type of sealing arrangement exhibits higher efficiency. Furthermore, an improvement in pump leakage is observed.

[0021] According to an eighth advantageous embodiment of the piston arrangement according to the invention, the sealing element is cylindrical in the area of ​​the sealing webs.

[0022] This type of sealing element is not conical or has a "spoiler" like previous seals, but rather features essentially parallel inner and outer surfaces in the axial direction. This design results in improved piston guidance within the cylinder.

[0023] According to the invention, a piston pump for a vehicle brake system with such a piston arrangement as described above has also been created.

[0024] The solution according to the invention achieves, overall, that the proposed guidance of the piston in the cylinder and the proposed sealing geometry result in improved leakage behavior of the piston pump.

[0025] An exemplary embodiment of the solution according to the invention is explained in more detail below with reference to the accompanying schematic drawings. It shows:

[0026] Fig. 1. A longitudinal section of a piston pump according to the state of the art,

[0027] Fig. 2 the detail II in Fig. 1 on an enlarged scale,

[0028] Fig. 3 a longitudinal section of a piston pump according to the invention,

[0029] Fig. 4 the detail IV in Fig. 3 on an enlarged scale,

[0030] Fig. 5 a partial longitudinal section of a sealing element of the piston pump according to Fig. 3,

[0031] Fig. 6 a perspective longitudinal section of the sealing element according to Fig. 5,

[0032] Fig. 7 a longitudinal section of a valve housing with a sealing element integrally formed on it according to Fig. 5 in its basic form,

[0033] Fig. 8 a longitudinal section of a first modification of the sealing element according to Fig. 7,

[0034] Fig. 9 a side view of a second modification of the valve housing with sealing element according to Fig. 7 and

[0035] Fig. 10 a perspective view of the modification according to Fig. 7.

[0036] In the Fig. 1 and Fig. 2 is a piston pump 10 illustrated according to the state of the art, which includes, among other things, a piston arrangement 12 includes, which consists of a cylinder 14 and a piston slidably mounted therein 16 is formed. The piston arrangement 12 It also includes an inlet valve. 18 and an exhaust valve 20 These valves 18 and 20 are designed so that the piston 16 during its stroke movement in the cylinder 14 a fluid through an inlet 22 into a high-pressure room or high-pressure area 24 inside the cylinder 14 suck in the fluid and expel it through an outlet. 26 under pressure, back out of the high-pressure area 24 can be extracted. The fluid in question is brake fluid.

[0037] The piston 16 is thereby in the axial direction by means of a structure located in the high-pressure area 24 located return spring 28 The return spring is spring-loaded and pre-tensioned. 28 is related to Fig. 1 at its left end on the front face of the cylinder 14 supported and pressing against a spring rest at its right end 30 The spring rest 30 is with the piston 16 fixedly coupled, so that the return spring 28 accordingly over the spring support 30 against the piston 16 urges.

[0038] Between the piston 16 and the cylinder 14 is also a sealing element 32 arranged, with which the high-pressure area 24 in the cylinder 14 It is sealed. The sealing element 32 It is designed in a ring shape and surrounds the piston. 16on its outer surface. The sealing element is located on this surface. 32 by means of a piston 16 pushed-on valve cage or valve housing 34 of the inlet valve 18 Held in a fixed position. On the valve housing. 34 is also the spring support 30 shaped in the form of a step. The sealing element thus held in place 32 It lies radially inwards against the inner surface of the cylinder. 14 to slide along it and seal it in the process.

[0039] The valve housing 34 It is designed in a cup-shaped cage, inside of which is a helical return spring. 36 located, which is against a spherical closing element 38 urges. The closing mechanism 38 This is therefore (in the Fig. 1 and Fig. 2 (operating state shown) on a valve seat 40 on the front side of the piston 16is formed. The locking mechanism 38 is from this valve seat 40 against the force of the return spring 36 lifted when the piston 16 related to Fig. 1 to the right out of the cylinder 14 is pulled out. During this movement, the inlet valve is therefore... 18 opened and fluid enters the high-pressure area 24 sucked in.

[0040] The sealing element 32 according to the Fig. 1 and Fig. 2 has a basic body that is essentially rectangular in cross-section 42 on, at which one leads to the high-pressure area 24 facing sealing lip 44 is trained.

[0041] The Fig. 3 and Fig. Figure 4 shows a piston pump according to the invention. 10 This one also features a piston arrangement. 12 with a cylinder 14 and a piston that can be moved within it 16Furthermore, there is also an inlet valve. 18 and an exhaust valve 20 provided. The piston 16 is located in a high-pressure area 24 located return spring 28 spring-loaded, which opposes a piston 16 stationary coupled spring support according to the invention 46 urges.

[0042] Furthermore, there is a location between the piston 16 and the cylinder 14 a sealing element according to the invention 48 , which is attached to the piston 16 is fixed in place and attached to the inner surface of the cylinder 14 can slide along this sealing element. 48 is equipped with a valve housing according to the invention 50 so seamlessly formed that even the spring rest 46 and the sealing element 48 are designed as a single piece. The one-piece design of the spring rest 46 and sealing element 48This enables a very short, more compact design with a smaller damaged area. With the return spring 28 can the sealing element 48 It can be additionally pre-tensioned. Furthermore, the return spring is also available. 28 on the spring support 46 A very wide radial contact surface is available.

[0043] The sealing element 48 is as in the Fig. 3 to Fig. 7 and Fig. 10 recognizable, with an axial groove 52 designed in the direction of the high-pressure area 24 is open. Accordingly, this occurs in the high-pressure area. 24 Fluid located and under pressure also enters this axial groove 52 The axial groove 52 is affected by this fluid on its two inner, opposing side surfaces or flanks. 54 and 56 radially pushed apart. This process is found in the Fig. 5 and Fig. Figure 6 illustrates this. In particular, the radial outer edge is separated from the axial groove. 52 the lip-shaped part or section located there 58 of the sealing element 48 , which can also be called a sealing lip, radially outwards (see Fig. 6) and thus against the inner surface of the cylinder 14 compressed. As a result, it leans forward under increasing pressure in the high-pressure area. 24 This section also 58 of the sealing element 48 more strongly on the cylinder 14 This improves the seal. Furthermore, it improves the piston's guidance and leakage behavior. 16 in the cylinder 14 .

[0044] In the Fig. 3 to Fig. In the illustrated embodiment 7, the spring support 46 of the sealing element 48 on both sides of the axial groove 52 a first edition 60 and a second edition 62up. The return spring 28 This is due to these two printing sections. 60 and 62 and pushes the sealing element 48 also at its section 58 towards the piston 16 . With increasing preload force of the return spring 28 , whereby this preload force increases with increasing stroke, is carried by the return spring 28 that is, on both sides of the axial groove 52 to an axial compression of the sealing element 48 at.

[0045] The Fig. Figure 8 illustrates an exemplary embodiment of a sealing element. 48 , in which the lip-shaped section 58 or the sealing lip of the sealing element 48 at its end relative to the radially directed plane of the spring support 46 to the one from the return spring 28 It is axially recessed on the opposite side. It is therefore only radially inward from the axial groove. 52a ring-shaped contact or support surface for the return spring 28 formed so that the return spring 28 the lip-shaped part 28 cannot compress or influence the return spring. 28 but continues to push against the core of the sealing element. 48 axially together, so that it is pushed radially outwards.

[0046] In the embodiment according to the Fig. 9 and Fig. 10 is the sealing element 48 also with the valve housing 50 formed in one piece and, moreover, has a feature on one of the cylinder 14 facing exterior surface 64 axially spaced, circumferential sealing ribs 66 on.

[0047] The sealing element 48 is indeed in the area of ​​these sealing bridges 66 essentially cylindrical in shape, but within the area of ​​this outer surface 64It is not smooth, but rather intentionally features raised and recessed areas. These raised and recessed areas run around the circumference of the sealing element. 48 around. Between the densely packed walkways that rise up in this way. 66 This results in individual, also circumferential, gaps in which, during the operation of the associated piston pump, 10 a fluid film can form. This acts as a lubricating film and also develops a sealing effect as a liquid seal.

[0048] The individual sealing strips 66 They are particularly wavy in cross-section, i.e., their flanks are rounded. QUOTES INCLUDED IN THE DESCRIPTION

[0049] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0050] DE 102005017131 A1

[0002]

Claims

[1] Piston arrangement ( 12 ) a piston pump ( 10 ) with a piston ( 16 ), one of the pistons ( 16 ) axially spring-loaded return spring ( 28 ), one on the piston ( 16 ) arranged spring support ( 30 ; 46 ) for the return spring ( 28 ) and one on the piston ( 16 ) arranged radially against a cylinder ( 14 ) sealing sealing element ( 32 ; 48 ), characterized by , that the spring support ( 46 ) and the sealing element ( 48 are designed as a single piece. [2] Piston arrangement according to claim 1, characterized in that the spring support ( 46 ) with a valve housing ( 50 ) of an inlet valve ( 18 ) for the piston pump ( 10 ) is formed. [3] Piston arrangement according to claim 1 or 2, characterized in that the sealing element ( 48 ) with an axial groove ( 52) is designed, which also includes the return spring ( 28 ) surrounding high-pressure area ( 24 ) is open. [4] Piston arrangement according to claim 3, characterized in that the sealing element ( 48 ) radially on both sides of the axial groove ( 52 ) a first and second edition section ( 60 , 62 ) has which the spring support ( 46 ) form. [5] Piston arrangement according to one of claims 1 to 3, characterized in that the sealing element ( 48 ) one against the cylinder ( 14 ) adjacent sealing lip ( 58 ) exhibits. [6] Piston arrangement according to claim 4, characterized in that the sealing lip ( 58 ) relative to the spring support ( 46 ) on the return spring ( 28 ) ends axially recessed on the opposite side. [7] Piston arrangement ( 12 ) a piston pump ( 10), in particular according to one of claims 1 to 6, with a piston ( 16 ) and one on the piston ( 16 ) arranged radially against a cylinder ( 14 ) sealing element 32 ; 48 ), characterized in that the sealing element ( 48 ) on its cylinder ( 14 ) facing outer surface 64 ) axially spaced, circumferential sealing ribs ( 66 ) exhibits. [8] Piston arrangement according to claim 7, characterized in that the individual sealing web ( 66 ) is designed with a wave-like cross-section. [9] Piston arrangement according to claim 7 or 8, characterized in that the sealing element ( 48 ) in the area of ​​the sealing strips ( 66 ) is cylindrical in shape. [10] Piston pump ( 10 ) a vehicle braking system with a piston arrangement ( 12 ) according to any of the preceding claims.

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