CN111997960A

CN111997960A - Scraper ring and device with scraper ring

Info

Publication number: CN111997960A
Application number: CN202010455977.8A
Authority: CN
Inventors: B.海斯; J.斯蒂芬; M.屈内尔; M.克勒
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-05-27
Filing date: 2020-05-26
Publication date: 2020-11-27
Also published as: DE102019207764B3; KR20200136319A

Abstract

The invention proposes that a scraper ring (22) which moves together with the piston (3) and distributes lubricant on the inside over the cylinder (2) in the direction of movement of the piston (3) is arranged in an annular space (19) between the piston (3) and the cylinder (2) in a piston-cylinder unit (1) of an external-brake pressure generator of a hydraulic vehicle brake system.

Description

Scraper ring and device with scraper ring

Technical Field

The invention relates to a scraper ring and to a device with a scraper ring having the features of the preamble of claim 2.

Background

The invention relates to a scraper ring and to a device with a scraper ring having the features of the preamble of claim 2. In particular, the device is or has a piston-cylinder unit, which is provided in particular for generating a brake pressure and/or for supplying a hydraulic, in particular slip-regulated, brake fluid in a vehicle brake system.

Disclosure of Invention

The device according to the invention having the features of claim 2 has an outer part with a cylindrical bore and an inner part which can be axially moved in the bore and is preferably likewise cylindrical. The cross section of the inner part is smaller than the cross section of the bore in the outer part at least over a part of the length in the direction of movement of the inner part in the bore of the outer part, so that a gap or free space, which is referred to herein as an "annular space", is present between the inner part and the bore wall of the bore in the outer part, which gap or free space surrounds the inner part in the bore of the outer part, at least over a part of the length. In the annular space, a scraper ring is present, which surrounds the inner part in the annular space. The wiper ring preferably bears with its outer circumference on the inside against the bore wall of the bore in the outer part and/or with its inner circumference on the outside against the inner part, wherein a seal between the wiper ring and the outer part and/or a seal between the wiper ring and the outer part can be realized, but this is not mandatory. If the scraper ring is to seal, it can also be understood as a sealing ring.

The scraper ring is provided for distributing lubricant along the direction of movement of the inner part in the bore of the outer part and for this purpose moves together with the inner part when the inner part moves in the bore of the outer part. The scraper ring either moves completely with the inner part and in this case takes up the full travel of the inner part, or it only moves partially with the inner part and moves over a smaller distance than the inner part. By the movement of the scraper ring during the movement of the inner part, the scraper ring distributes the lubricant along the direction of movement of the inner part over the wall of the bore in the outer part. The scraper ring prevents the inner part from moving lubricant in the direction in which it collects and settles as it moves, so that no or only little lubricant is present on the wall of the bore in the direction of movement of the inner part over a large part of the length of the bore in the outer part.

The scraper ring compensates for the varying radial width of the annular space and/or the varying diameter of the annular space. The size of the annular space may change, for example, due to temperature changes.

The scraper ring is preferably composed of a material having a lower hardness than the component surrounding the annular space and/or the component with which it is in contact and is the subject of claim 1 as a single piece.

The subject matter of the dependent claims is the development and advantageous embodiments of the invention specified in the independent claims.

The device according to the invention is in particular a piston-cylinder unit or a piston-cylinder unit, the cylinder of which forms an outer part with a bore in which a piston as an inner part can be moved axially, i.e. can be displaced (claim 10). The piston has a smaller dimension than the cylinder at least over a part of its length, so that the above-described annular space is present over a part of said length. By moving the piston in the cylinder or vice versa, the piston draws fluid into the cylinder, pushes fluid out of the cylinder and/or generates pressure in the cylinder. In hydraulic vehicle brake systems, the fluid is brake fluid. The piston-cylinder unit can also be used as an actuator for generating a linear movement by: conversely, pressurized fluid is supplied to the cylinder, which moves the piston in the cylinder or, conversely, moves the cylinder on the piston.

All features disclosed in the description and the drawings can be implemented in the embodiments of the invention individually or in any combination in principle. The following embodiments of the invention are possible in principle, which do not have all the features of the claims or embodiments of the invention but only one or more features thereof.

Drawings

The invention is explained in detail below with the aid of embodiments shown in the drawings. Wherein:

fig. 1 shows a section through the axis of a piston-cylinder unit according to the invention;

fig. 2 shows a scraper ring of the piston-cylinder unit in a perspective view; and is

Fig. 3 shows an enlarged annular cross section of the scraper ring of fig. 2 in the mounted state.

The accompanying drawings are partly diagrammatic and simplified representations.

Detailed Description

The piston-cylinder unit 1 according to the invention shown in fig. 1 has a cylinder 2 and a piston 3, which can be moved in the cylinder 2. The piston-cylinder unit 1 can also be understood as a device 31 according to the invention in general, which has a cylinder 2 with a bore 33 as an outer part 32 and a piston 3 as an inner part 34, which can be moved axially in the bore 33 of the outer part 32. The inner circumferential surface of the cylinder 2 generally forms the bore wall 35 of the device 31 according to the invention. The cylinder 2 has a closed end with a cylinder bottom 4 and an open end.

The piston 3 is a tubular hollow piston, the end of which facing the cylinder bottom 4 is closed by a piston bottom 5 which is integral with the piston 3.

For moving the piston 3 in the cylinder 2, there is an electric motor 6, which is indicated in the drawing as a circuit symbol, a planetary gear mechanism 7 as a mechanical reduction gear, and a ball screw drive, which can also be understood as a screw drive 8 in general. The spindle 9 of the ball screw drive is arranged coaxially in the piston 3 and is rigidly connected to the piston 3 by means of a journal 10 pressed into the piston bottom 5. The electric motor 6, the planetary gear mechanism 7 and the ball screw or, in general, the screw drive 8 form an electromechanical drive for moving the piston 3 in the cylinder 2 or, in general, for moving the inner part 34 in the bore 33 of the outer part 32.

A tubular spindle nut 11, which surrounds the spindle 9, likewise projects coaxially through the open end into the piston 3, which is designed as a hollow piston, and axially over a short distance from the cylinder 2 and the piston 3. Outside the cylinder 2, the spindle nut 11 is rotatably supported on the open end of the cylinder 2 by means of a rotary bearing 12, in this embodiment a ball bearing.

The main shaft 9 of the screw drive 8 simultaneously forms the planet carrier of the planetary gear 7, which is likewise arranged coaxially with the piston 3 and the cylinder 2 outside the piston 3 and the cylinder 2: the planet gears 13 of the planetary gear mechanism 7 are rotatably mounted on the end of the spindle nut 11 that projects from the cylinder 2. The ring gear 14 of the planetary gear 7 is rigidly fixed to the outer ring of the rotary bearing 12. The sun gear 15 of the planetary gear 7 can be driven in rotation by the electric motor 6. By the rotational drive of the sun gear 15, the spindle nut 11, which moves the piston 3 in the cylinder 2 via the spindle 9, is rotationally driven via the planet gear 13.

The piston 3 is sealed with two piston seals 18 in the cylinder 2. The piston seal 18 is arranged in a circumferential groove in the middle region of the cylinder 2 in the direction of movement of the piston 3. Between the cylinder bottom 4 and the piston seal 18 and between the piston seal 18 and the open end of the cylinder 2, the cylinder 2 has an inner diameter which is larger than the outer diameter of the piston 3, so that there is a gap which encloses the piston 3 in the cylinder 2. This gap between the piston seal 18 and the open end of the cylinder 2 is referred to herein as the annular space 19.

In order to prevent the piston 3 and the spindle 9 of the screw drive 8, which is rigidly connected to the piston, from rotating, a pin is arranged in the annular space 19 in parallel with the spindle as an anti-rotation element 20. The pin is located with half its cross section in an axially parallel groove with a semicircular groove cross section, which is then located in an annular space 19 on the inner circumference of the cylinder 2. The pin forming the anti-rotation element 20 projects with the other half of its cross section into the annular space 19.

In this exemplary embodiment, the piston 3 has, at its open end, a circumferential annular edge 21 which projects radially outward in the manner of a flange and has a semicircular recess into which a pin forming the anti-rotation element 20 engages, as a result of which the piston 3 is held in the cylinder 2 and generally the inner part 34 in the bore 33 of the outer part 32 in a movable and torsion-resistant manner. This embodiment has three anti-rotation elements 20 arranged uniformly distributed over the circumference. The number and arrangement of the anti-rotation elements 20 and their shaping can vary, which are not necessarily studs but can also be, for example, ribs (not shown) extending in the direction of movement of the piston 3 and projecting inwardly from the cylinder 2 in the annular space 19.

On the piston 3, a scraper ring 22, which is made of plastic for example and is shown in fig. 2 as a single piece, is arranged in the annular space 19. Fig. 3 shows a circular cross-section, wherein in fig. 3 the closed ends of the cylinder 2 and the piston 3 are below and the open ends of the cylinder 2 and the piston 3 are above. The scraper ring 22 has a stepped, annular cross section, the inner circumferential surface 23 (to the left in fig. 3) and the outer circumferential surface 24 (to the right in fig. 3) of the scraper ring 22 being frustoconical surfaces, the inner circumferential surface 23 of the scraper ring 22 widening in the direction of the open end of the cylinder 2 and the outer circumferential surface 24 of the scraper ring 22 tapering in the direction of the open end of the cylinder 2, so that the scraper ring 22 rests with a circumferential, sharp edge 25 on its inner circumference 23 on the piston 3 and with a circumferential, sharp edge 26 in the annular space 19 on its outer circumference 24 on the inside of the cylinder 2. The two sharp-

angled edges

25, 26 are located at the transition from the inner circumferential surface 23 or from the outer circumferential surface 24 to the end face of the scraper ring 22 facing the closed end of the cylinder 2. Since the annular cross section of the scraper ring 22 is stepped, the scraper ring is more easily displaced in the direction of its open end than in the direction of the closed end of the cylinder 2. The annular cross-section is a radial section at one circumferential location of the scraper ring 22.

In the end face facing the open end of the cylinder 2, the scraper ring 22 has a circumferential groove 27, which can also be understood as a recess in general.

In the outer circumferential surface 24, the scraper ring 22 has semicircular recesses 28 which are used to form the pins of the anti-rotation element 20. The arrangement and shape of said interspace 28 corresponds to the anti-rotation element 20, which as explained, is not necessarily a pin.

The friction between the scraper ring 22 and the piston 3 is greater than the friction between the scraper ring 22 and the cylinder 2, so that the scraper ring 22 moves together with the piston 3 when the piston 3 moves in the cylinder 2 and so that lubricant is distributed in the region of the annular space 19 on the inside of the cylinder 2 in the direction of movement of the piston 3. Furthermore, the scraper ring 22 distributes the lubricant onto the pins forming the anti-rotation element 20.

The friction between the scraper ring 22 and the piston 3 is higher than the friction between the scraper ring 22 and the cylinder 2, which can be achieved, for example, by material pairing, surface roughness and/or surface structure of the piston 3 and the cylinder 2 and/or by the design that the scraper ring 22 bears on the piston 3 on the inside with greater stress than in the outer bearing in the cylinder 2 and/or by the shape of the annular cross section of the scraper ring 22. The scraper ring 22 can move completely with the piston 3 or it can remain behind with respect to the piston 3, i.e. it executes a shorter displacement stroke than the piston 3.

The wiper ring 22 rests with its circumferential, acute-angled

edges

25, 26 on its end face facing the closed end of the cylinder 2 with mechanical stress on the inside against the piston 3 and on the outside against the cylinder 2, i.e. can be said to be clamped between the piston 3 and the cylinder 2 on its acute-angled

edges

25, 26, there being a bending stress in the annular cross section which causes the annular cross section of the wiper ring 22 to bow in the direction of the open end of the cylinder 2. The circumferential groove 27 in the end face of the scraper ring 22 facing the open end of the cylinder 2 reduces the axial thickness of the annular cross section and supports the curvature of the annular cross section.

Furthermore, the circumferential groove 27 in the end face of the scraper ring 22 facing the open end of the cylinder 2 forms a lubricant reservoir in which lubricant collects when the scraper ring 22 with the piston 3 is displaced in the direction of the open end of the cylinder 2, and when the piston 3 is displaced in the opposite direction of the closed end of the cylinder 2, the flange-like edge 21 of the piston 3 projecting radially outward on the open end of the piston 3 distributes lubricant in the annular space 19 in the inward direction on the cylinder 2 in the displacement direction.

During assembly, the wiper ring 22 is inserted into the cylinder 2 as far as the end of the annular space 19 which is adjacent to the piston seal 18, before grease, for example, in the annular space 19 is subsequently applied to the cylinder 2 in the interior and the piston 3 is then inserted into the cylinder 2 and the wiper ring 22.

The piston-cylinder unit 1 forms, together with the electric motor 6, the planetary gear mechanism 7 and the screw drive 8, an external force-brake pressure generator of a hydraulic piston pump assembly of a hydraulic vehicle brake system with a slip control mechanism, which is not shown in any other respects. Such slip control devices are, for example, anti-lock brake control devices, drive slip control devices and driving dynamics control devices or electronic stability programs, which are often abbreviated by ABS, ASR and FDR or ESP. The piston pump assembly has a hydraulic block 29, which is square in the exemplary embodiment and has a through-opening, into which the cylinder 2 is inserted such that it protrudes on both sides. An integrated construction (not shown) of the cylinder 2 and the hydraulic block 29 can also be realized in the form of a cylindrical cavity in the hydraulic block 29.

In this exemplary embodiment, the hydraulic block 29 additionally has a main brake cylinder bore 30 for a main brake cylinder, not shown, which can be actuated by muscle force. The hydraulic block 29 serves to mechanically fix and hydraulically connect the hydraulic and electrohydraulic components of the slip control mechanism, which, in addition to the external force brake pressure generator with the piston-cylinder unit 1 according to the invention having the electric motor 6, the planetary gear 7 and the screw drive 8, comprise solenoid valves, non-illustrated check valves, hydraulic accumulators and damping chambers, which are arranged in and on the hydraulic block 29 and are hydraulically connected to one another by means of a non-illustrated drilling structure of the hydraulic block 29 according to the hydraulic circuit diagram of the external force vehicle brake system and the slip control mechanism. With the structural elements in place, the hydraulic block 29 forms a hydraulic unit for muscle-and/or external-brake pressure generation and for slip control of a hydraulic vehicle brake system, which is not shown in any other way. Such a slide adjusting mechanism and hydraulic block 29 are known per se to the person skilled in the art and will not be explained in detail here.

Claims

1. Scraper ring, characterized in that the scraper ring (22) has a stepped annular cross section and a circumferential recess in the end face.

2. Device with an outer part (32) having a cylindrical bore (33), with an inner part (34) axially movable in the bore (33) of the outer part (32), the cross section of the inner part being smaller than the cross section of the bore (33) in the outer part (32), so that an annular space (19) is present between a bore wall (35) of the bore (33) in the outer part (32) and the inner part (34), characterized in that a scraper ring (22) is arranged in the annular space (19), which scraper ring encloses the inner part (34) in the annular space (19), and which scraper ring moves together with the inner part (34) when the inner part (34) moves axially relative to the outer part (32).

3. Device according to claim 2, characterized in that the scraper ring (22) has a higher friction on the inner part (34) than the hole wall (35) of the hole (33) in the outer part (32).

4. A device according to claim 2 or 3, characterized in that the inner circumferential surface (23) of the scraper ring (22) is enlarged in the axial direction and/or the outer circumferential surface (24) of the scraper ring (22) is tapered in the axial direction.

5. A device according to claim 2 or 3, characterised in that the scraper ring (22) has a circumferential groove (27) in the end face.

6. Device according to one or more of claims 2 to 5, characterized in that the outer part (32) has anti-rotation elements (20) which extend in the direction of movement of the inner part (34), which protrude in the annular space (19) from the bore wall (35) inwardly in the direction of the inner part (34), and the inner part (34) is supported in a movable manner in the circumferential direction on the anti-rotation elements against rotation, and the scraper ring (22) has in its outer circumferential surface (24) a clearance (28) for the anti-rotation elements (20).

7. Device according to claim 6, characterized in that the inner part (34) has an outwardly projecting annular edge (21) with clearance for the anti-rotation element (20).

8. The device according to one or more of claims 2 to 7, characterized in that the device (31) has an electromechanical drive device (6, 7, 8) for moving the inner part (34) in the bore (33) of the outer part (32).

9. Device according to one or more of claims 2 to 8, characterized in that the annular space (19) has a lubricant filling.

10. The device according to one or more of claims 2 to 9, characterized in that the device (31) has a piston-cylinder unit (1) with a cylinder (2) as an outer part (32) and a piston (3) movable in the cylinder (2) as an inner part (34), between which an annular space (19) is present in which the scraper ring (22) is arranged.

11. Hydraulic block of an external force-regulated and/or slip-regulated hydraulic vehicle brake system having a piston-cylinder unit as an external force-brake pressure generator according to claim 10 and/or for delivering brake fluid, wherein the cylinder (2) of the piston-cylinder unit (1) is arranged in the hydraulic block (29).

12. Hydraulic vehicle brake system with a piston-cylinder unit as an external force-brake pressure generator according to claim 10 or 11 and/or for delivering brake fluid.