Scraper ring and assembly comprising the scraper ring

Abstract

The present invention proposes a scraper ring (22) placed in an annular chamber (19) between a piston (3) and a cylinder (2) within a piston / cylinder unit (1) of a power braking pressure generator of a hydraulic vehicle brake system, wherein the scraper ring moves together with the piston (3) and distributes lubricant onto the cylinder (2) from the inside in the direction of displacement of the piston (3).

Description

Technology Field

[0001] The present invention relates to a scraper ring and an assembly comprising a scraper ring having the features of the preamble of claim 2. In particular, the assembly is a piston / cylinder unit provided particularly to generate braking pressure and / or to transfer brake fluid in a hydraulic, particularly slip-controlled vehicle brake system, or comprises a piston / cylinder unit.

[0002] An assembly according to the present invention having the features of claim 2 comprises an outer member having a cylindrical hole and an inner member that is axially movable within the hole and preferably also cylindrical. The cross-section of the inner member is smaller than the cross-section of the hole within the outer member for at least a portion of its length in the direction of displacement of the inner member within the hole of the outer member, so that a gap or free space exists between the hole wall of the hole within the outer member and the inner member for at least a portion of its length, and such gap or free space is referred to herein as an “annular chamber.” A scraper ring is positioned within the annular chamber, and the scraper ring surrounds the inner member within the annular chamber. The scraper ring of the present invention is preferably in contact with the hole wall of the hole within the outer member from the inside with its outer circumference and / or with the inner member from the outside with its inner circumference, and sealing between the scraper ring and the outer member and / or sealing between the scraper ring and the outer member is possible, but not mandatory. Insofar as the scraper ring seals, the scraper ring can also be interpreted as a sealing ring.

[0003] The scraper ring of the present invention is provided, on the one hand, to distribute lubricant in the direction of displacement of the inner member within the hole of the outer member, and for this purpose, moves together with the inner member when the inner member is displaced within the hole of the outer member. The scraper ring of the present invention moves completely together with the inner member and, in this case, moves along the complete displacement path of the inner member, or the scraper ring of the present invention moves only partially together with the inner member and is displaced less than the inner member. The scraper ring of the present invention distributes lubricant in the direction of displacement of the inner member on the hole wall of the hole within the outer member through its own displacement when the inner member is displaced. By moving the lubricant in the direction in which the lubricant accumulates and remains when the inner member is displaced, the scraper ring of the present invention prevents the absence of any lubricant or the presence of only a small amount of lubricant on the hole wall of a large portion of the length of the hole within the outer member in the direction of displacement of the inner member.

[0004] The scraper ring of the present invention compensates for a variable radial width of an annular chamber and / or a variable diameter of an annular chamber. The dimensions of the annular chamber may be varied, for example, through temperature changes.

[0005] The scraper ring of the present invention is preferably composed of a material having a lower hardness than the parts surrounding the annular chamber and / or the parts that the scraper ring contacts, and is the subject of claim 1 as an individual member.

[0006] Dependent claims include improvements and preferred embodiments of the invention specified in the independent claims.

[0007] An assembly according to the present invention is, in particular, a piston / cylinder unit in which its cylinder forms an external member having a hole, or comprises a piston / cylinder unit in which a piston as an internal member can be moved axially, that is, displaced (Claim 10). The piston has an undersize relative to the cylinder for at least a portion of its length, so that the annular chamber described above exists on this portion of its length. By displacing the piston within the cylinder, or conversely by displacing the cylinder on the piston, the piston draws fluid into the cylinder, displaces fluid from the cylinder to the outside, and / or generates pressure within the cylinder. In a hydraulic vehicle brake system, the fluid is brake fluid. Additionally, the piston / cylinder unit can also be used as an actuator for generating linear movement by supplying pressurized fluid to the cylinder, conversely, such that the pressurized fluid moves the piston within the cylinder, or conversely, moves the cylinder on the piston.

[0008] All features disclosed in the specification and drawings may be realized in embodiments of the present invention individually, either by themselves or in any combination thereof. Embodiments of the present invention that include only one or more features, rather than all features of a single claim or an embodiment of the present invention, are also essentially possible.

[0009] The present invention is described in more detail below according to an embodiment illustrated in the drawings. Brief explanation of the drawing

[0010] FIG. 1 is an axial cross-sectional view illustrating a piston / cylinder unit according to the present invention. FIG. 2 is a perspective view illustrating a scraper ring of a piston / cylinder unit. FIG. 3 is a cross-sectional view of a ring showing an enlarged view of the scraper ring in FIG. 2 in an embedded state. Specific details for implementing the invention

[0011] The drawing is a partially schematic and simplified drawing.

[0012] The piston / cylinder unit (1) according to the present invention illustrated in FIG. 1 comprises a cylinder (2) and a piston (3) that can be displaced within the cylinder (2). The piston / cylinder unit (1) may also be interpreted as an assembly (31) according to the present invention comprising a cylinder (2) as an external member (32) having a hole (33) and a piston (3) as an internal member (34) that can be moved axially within the hole (33) of the external member (32). The inner surface of the cylinder (2) generally forms the hole wall (35) of the assembly (31) according to the present invention. The cylinder (2) includes a closed end having a cylinder bottom portion (4) and an open end.

[0013] The piston (3) is a tubular hollow piston, and the end of the hollow piston facing the cylinder bottom (4) is closed through the piston bottom (5) which is integral with the piston (3).

[0014] For displacement of the piston (3) within the cylinder (2), an electric motor (6), illustrated as a circuit symbol in the drawing, a planetary gear unit (7) as a mechanical reduction gear unit, and a ball screw drive, which can also be interpreted as a screw gear unit (8) are provided. The spindle (9) of the ball screw drive is positioned coaxially within the piston (3) and is rigidly connected to the piston (3) by a journal (10) pressed into the bottom portion (5) of the piston. The electric motor (6), the planetary gear unit (7), and the ball screw drive, or generally the screw gear unit (8), form an electromechanical drive unit for displacing the piston (3) within the cylinder (2), or generally for displacing the inner member (34) within the hole (33) of the outer member (32).

[0015] A tubular spindle nut (11) surrounding the spindle (9) likewise protrudes into the piston (3) formed as a hollow piston through an open end coaxially, and protrudes a short portion from the cylinder (2) and piston (3) in the axial direction. The spindle nut (11) is rotatably mounted on the open end of the cylinder (2) by a pivot bearing (12), in the embodiment, a ball bearing, on the outside of the cylinder (2).

[0016] The spindle (9) of the screw gear section (8) simultaneously forms the planetary carrier of the planetary gear unit (7), and the planetary gear unit is likewise positioned outside the piston (3) and cylinder (2) coaxially with respect to the piston (3) and cylinder (2). In short, the planetary gears (13) of the planetary gear unit (7) are rotatably mounted on the front end of the spindle nut (11) protruding from the cylinder (2). The ring gear (14) of the planetary gear unit (7) is firmly fixed on the outer ring of the pivot bearing (12). The sun gear (15) of the planetary gear unit (7) can be rotated by an electric motor (6). By the rotational drive of the sun gear (15), the spindle nut (11) is rotated through the planetary gears (13), and the spindle nut displaces the piston (3) within the cylinder (2) through the spindle (9).

[0017] The piston (3) is sealed within the cylinder (2) by two piston seals (18). The piston seals (18) are positioned within circumferential grooves in the central region of the cylinder (2) in the direction of displacement of the piston (3). Between the cylinder bottom (4) and the piston seals (18), and between the piston seals (18) and the open end of the cylinder (2), the cylinder (2) has an inner diameter larger than the outer diameter of the piston (3), thereby creating a gap that encloses the piston (3) within the cylinder (2). The gap between the piston seals (18) and the open end of the cylinder (2) is referred to here as an annular chamber (19).

[0018] To prevent rotation of the piston (3) and the spindle (9) of the screw gear part (8) that is rigidly connected to the piston, cylinder pins are arranged axially within the annular chamber (19) as rotation-prevention members (20). The cylinder pins are inserted into axially parallel grooves having semicircular groove cross-sections within the annular chamber (19) on the inner circumference of the cylinder (2) with one half of their cross-section. The cylinder pins forming the rotation-prevention members (20) protrude into the annular chamber (19) with the other half of their cross-section.

[0019] The piston (3) includes an annular rim (21) that protrudes radially outward and extends along the outer circumference, depending on the type of flange, by having semicircular cavities (on its open end in the embodiment), and cylinder pins forming anti-rotation members (20) engage within the cavities, thereby allowing the piston (3) to be gripped in a rotationally fixed manner while displaced within the cylinder (2) and, generally, the inner member (34) within the hole (33) of the outer member (32). The embodiment includes three anti-rotation members (20) that are uniformly distributed along the periphery. The number and arrangement of the anti-rotation members (20) and likewise the shape of the anti-rotation members may vary, and the anti-rotation members (20) do not necessarily have to be cylinder pins, but may be, for example, ribs that extend in the displacement direction of the piston (3) and protrude inward from the cylinder (2) within the annular chamber (19) (not shown).

[0020] A scraper ring (22), made of, for example, plastic and shown as an individual member in FIG. 2, is disposed on the piston (3) within the annular chamber (19). FIG. 3 shows a cross-sectional view of the ring, in which the closed ends of the cylinder (2) and piston (3) are located at the bottom and the open ends of the cylinder (2) and piston (3) are located at the top. The scraper ring (22) has a trapezoidal ring cross section, and the inner surface (23) (left in FIG. 3) and outer surface (24) (right in FIG. 3) of the scraper ring (22) are truncated surfaces, and the inner surface (23) of the scraper ring (22) is expanded in the direction of the open end of the cylinder (2), and the outer surface (24) of the scraper ring (22) is tapered in the direction of the open end of the cylinder (2), so that the scraper ring (22) is in contact with the piston (3) with an acute edge portion (25) extending along the outer circumference on its inner surface (23), and is in contact with the cylinder (2) from the inside within the annular chamber (19) with an acute edge portion (26) extending along the outer circumference on its outer surface (24). Two acute edge portions (25, 26) are located on the transition portions toward the end surface of the scraper ring (22) toward the closed end of the cylinder (2), from the inner surface (23) or the outer surface (24). The scraper ring (22) is displaced more easily toward its open end than toward the closed end of the cylinder (2) through the trapezoidal shape of its ring cross-section. The ring cross-section is a radial cross-section at the peripheral position of the scraper ring (22).

[0021] The scraper ring (22) includes a circumferential trough (27) which can generally be interpreted as a depression on the end face facing the open end of the cylinder (2).

[0022] The scraper ring (22) includes semicircular recesses (28) for cylinder pins forming anti-rotation members (20) on the outer surface (24). The arrangement and shape of the recesses (28) correspond to the anti-rotation members (20) that do not need to be cylinder pins as described.

[0023] 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) is displaced within the cylinder (2), and accordingly, the lubricant is distributed on the cylinder (2) from the inside in the direction of displacement of the piston (3) in the area of ​​the annular chamber (19). In addition, the scraper ring (22) also distributes the lubricant onto the cylinder pins forming the anti-rotation members (20).

[0024] Higher friction between the scraper ring (22) and the piston (3) than between the scraper ring (22) and the cylinder (2) can be achieved, for example, through the formation of material pairs of the piston (3) and the cylinder (2), surface roughness and / or surface structure, and / or through the scraper ring (22) being in contact with the piston (3) with higher stress from the inside than being in contact with the cylinder (2) from the outside, and / or through the shape of the ring cross-section of the scraper ring (22). The scraper ring (22) can be moved completely together with the piston (3), or the scraper ring can be left behind relative to the piston (3), that is, it can travel a shorter displacement path than the piston (3).

[0025] A bending stress exists within the ring cross-section that bends the ring cross-section of the scraper ring (22) toward the open end of the cylinder (2) by mechanically pressing the scraper ring (22) against the piston (3) on the inside and the cylinder (2) on the outside with its acute edges (25, 26) extending along the outer circumference on its end surface facing the closed end of the cylinder (2), that is, by fixing it between the piston (3) and the cylinder (2) with its so-called acute edges (25, 26). The circumferential trough (27) within the end surface of the scraper ring (22) facing the open end of the cylinder (2) assists in the bending of the ring cross-section while reducing the axial thickness of the ring cross-section.

[0026] Additionally, the circumferential trough (27) forms a lubricant reservoir within the end surface of the scraper ring (22) facing the open end of the cylinder (2), and within this lubricant reservoir, lubricant is accumulated when the scraper ring (22) is displaced together with the piston (3) in the direction of the open end of the cylinder (2), and the rim portion (21) of the piston (3) protruding outwardly in a flange-like manner on the open end of the piston (3) distributes the lubricant again in the direction of displacement inwardly within the annular chamber (19) onto the cylinder (2) when the piston (3) is displaced in the opposite direction toward the closed end of the cylinder (2).

[0027] When assembling, the scraper ring (22) is inserted into the cylinder (2) up to the end of the annular chamber (19) near the piston seals (18), and then, for example, grease is applied to the cylinder (2) from the inside of the annular chamber (19) as a lubricant, and then the piston (3) is inserted into the cylinder (2) and the scraper ring (22).

[0028] The piston / cylinder unit (1), together with the electric motor (6), planetary gear unit (7), and screw gear unit (8), forms a power braking pressure generator of the piston pump unit of a hydraulic vehicle brake system, which includes a slip control device not otherwise illustrated. The slip control devices are, for example, a brake anti-locking device, a traction control system, a driving dynamic control system, or an electronic driving stability device, and abbreviations such as ABS, TCS, DDCS, or ESP may be used for these. The piston pump unit includes a hydraulic block (29) which has a through bore and is rectangular in shape in this embodiment, and a cylinder (2) is inserted into the through bore so as to protrude from both sides. Additionally, it is possible to form a cylinder (2) that is integral with the hydraulic block (29) in the form of a cylindrical hollow chamber within the hydraulic block (29) (not illustrated).

[0029] In an embodiment, the hydraulic block (29) further comprises a brake master cylinder bore (30) for a brake master cylinder not illustrated that can be actuated by muscle force. The hydraulic block (29) is used to mechanically fix and hydraulically interconnect hydraulic components of a slip control device, including solenoid valves, check valves, hydraulic accumulators, and damper chambers disposed within and on the hydraulic block (29) and hydraulically connected to one another in correspondence with the hydraulic circuit diagram of the vehicle power brake system and the slip control device through an unillustrated perforation of the hydraulic block (29), in addition to a power braking pressure generator comprising a piston / cylinder unit (1) according to the present invention having an electric motor (6), a planetary gear unit (7), and a screw gear unit (8). The hydraulic block (29), with the components mounted, otherwise forms a hydraulic unit for slip control of a hydraulic vehicle brake system not illustrated, and for generating muscle braking pressure and / or power braking pressure. The above slip control devices and hydraulic blocks (29) are known by themselves to a person skilled in the art and are not described in more detail herein.

Claims

Claim 1 An assembly comprising an outer member (32) having a cylindrical hole (33) and an inner member (34) movable in the axial direction within the hole (33) of the outer member (32), wherein the cross-section of the inner member is smaller than the cross-section of the hole (33) within the outer member (32), so that an annular chamber (19) exists between the hole wall (35) of the hole (33) within the outer member (32) and the inner member (34), wherein a scraper ring (22) is disposed within the annular chamber (19), the scraper ring having a trapezoidal ring cross-section, wherein the inner surface (23) and outer surface (24) are truncated cone faces, and the scraper ring having a circumferential depression within the end face, the scraper ring surrounds the inner member (34) within the annular chamber (19), and is in close contact with the piston (3) by an acute edge portion (25) extending along the outer circumference on its inner surface (23), and its An assembly characterized in that an acute angle edge portion (26) extending along the outer circumference on the outer surface (24) is in close contact with the cylinder (2) from the inside within the annular chamber (19) and moves together with the inner member (34) when the inner member (34) moves in the axial direction relative to the outer member (32), the outer member (32) includes a rotation prevention member (20) extending in the displacement direction of the inner member (34), said rotation prevention member protrudes inward from the hole wall portion (35) within the annular chamber (19) in the direction of the inner member (34), said inner member (34) is supported so as to be displaceable in the circumferential direction and prevent rotation on said rotation prevention member, said scraper ring (22) includes a recess (28) for the rotation prevention member (20) within its outer surface (24), and the inner member (34) includes an annular rim portion (21) protruding outwardly having a cavity for the rotation prevention member (20). Claim 2 delete Claim 3 An assembly according to claim 1, wherein the scraper ring (22) has a higher frictional force on the inner member (34) than on the hole wall (35) of the hole (33) inside the outer member (32). Claim 4 An assembly according to claim 1 or 3, characterized in that the inner surface (23) of the scraper ring (22) is enlarged in the axial direction, or the outer surface (24) of the scraper ring (22) is tapered in the axial direction. Claim 5 An assembly according to claim 1 or 3, wherein the scraper ring (22) includes a circumferential trough (27) within the end face. Claim 6 delete Claim 7 delete Claim 8 An assembly according to claim 1 or 3, characterized in that the assembly (31) includes an electromechanical drive unit (6, 7, 8) for displacing an inner member (34) within a hole (33) inside an outer member (32). Claim 9 An assembly according to claim 1 or 3, characterized in that the annular chamber (19) includes a lubricant storage section. Claim 10 An assembly according to claim 1 or 3, wherein the assembly (31) comprises a piston and cylinder unit (1) having a cylinder (2) as an external member (32) and a piston (3) that can be displaced within the cylinder (2) as an internal member (34), and an annular chamber (19) having a scraper ring (22) disposed therein between the external member and the internal member. Claim 11 A hydraulic block of a vehicle power brake system or a slip-controlled and hydraulic vehicle brake system comprising a piston and cylinder unit according to claim 10 for generating power braking pressure or for conveying brake fluid, wherein the cylinder (2) of the piston and cylinder unit (1) is disposed within the hydraulic block (29). Claim 12 A hydraulic vehicle brake system comprising a piston and cylinder unit according to claim 10 for generating power braking pressure or for transferring brake fluid.

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