Method for manufacturing a piston and piston

Abstract

Method for manufacturing a piston (1) which can be attached to a piston sliding assembly (2) which is oriented along its longitudinal axis (A L ) is movable in a cylinder (3), wherein the piston (1) has a disc-shaped base body (4), wherein the piston (1) is suitable and intended to seal two regions (5, 6) of the cylinder (3) filled with a medium (7) against each other, comprising the steps: a. Production of the piston (1) by pressing a material into a piston mold; b. Smoothing the surface of the piston (1) and / or pressing at least one flow path (11) into the piston (1) by means of an embossing tool (20) which has an annular, raised and rotationally symmetrical structure (21). characterized in that the piston (1) has an annular piston collar (8), wherein the annular piston collar (8) has at least one meandering protrusion and / or indentation (32), which preferably has at least one section oriented radially (33) and one tangentially (34) to the piston (1).

Description

[0001] The invention relates to a method for producing a piston and to a piston which can be fastened to a piston sliding unit which is movable along its longitudinal axis in a cylinder, wherein the piston has a disc-shaped base body, wherein the piston is suitable and intended to seal two regions of the cylinder filled with a medium against each other.

[0002] Dampers, especially purely progressive ones, i.e. dampers in which the force required to push and / or pull the piston sliding unit into or out of the cylinder increases more quickly than with a linear relationship with increasing spring travel, have pistons with fixed bypasses or flow paths through which the medium flows from one area of ​​the cylinder to another when the piston sliding unit is pushed into or pulled out of the damping cylinder. The resistance to the flow of the displaced medium increases with the flow velocity and thus creates progressivity. The dimensioning of the bypasses is of crucial importance for the progressivity and the damping characteristic curve. These are usually incorporated into the tool side, as in the case of sintered or plastic parts, or by machining, as in the case of aluminum pistons.Especially in the case of sintered pistons, these bypasses are usually formed when the piston is pressed from the sinterable powder.

[0003] EP1347199B1 describes a method for manufacturing a hydraulic shock absorber, according to which one method step includes the formation of a piston main body by sintering. It also discloses the embossing of a flow path into the piston using an embossing tool.

[0004] DE102015217764A1 discloses a damper valve for a vibration damper, wherein the damper valve has a permanently open and non-closable fluid channel for the damping medium. The fluid channel, in turn, has a first opening, a second opening, and a connecting portion. The invention is characterized in that the fluid channel is designed such that a cross-section of the second opening is a multiple of a cross-section of the first opening, and that a cross-section of the connecting portion increases over its entire length from the first opening to the second opening.

[0005] DE19621639A1 discloses a damping piston consisting of a piston body provided with valve plates on both ends and rigidly connected to a piston rod. The piston body has a group of openings for the rebound and compression directions. Each opening in the piston body is blind-hole-like and parallel to the continuous recesses of a piston axis. Each continuous opening around the piston axis can be formed by a continuous circular-arc-shaped recess parallel to the end surfaces of the piston body. Each recess at the outlet end can have a larger cross-section than the area of ​​the recess base. DE19846460C2 describes a method for producing a piston valve part, according to which through-channels are produced by punching and stamping the piston valve part in such a way that they have annular projections.

[0006] DE4404835A1 discloses a piston comprising an annular piston collar and inner and outer walls with segment-like recesses.

[0007] DE102011004739A1 also discloses a piston with a raised, annular piston collar and inner and outer walls with segment-like recesses that are offset from one another.

[0008] DE2950888A1 discloses a piston having a long, continuous, labyrinth-like channel, the inner and outer walls of which have recesses that form the channel.

[0009] FR2661726A1 discloses a piston with a raised, annular piston collar and inner and outer walls.

[0010] DE19615584A1 discloses a throttle valve for a piston-cylinder unit, wherein the piston has an annular channel formed by two support webs.

[0011] Machining reaches its limits with particularly small bypasses, as the process-related tolerances become too large relative to the bypass. Possible reasons for process-related tolerances include tool wear, temperature changes on the machine, or setup accuracy.

[0012] The same problem arises when pressing sintered pistons with regard to the process-related tolerances of the bypasses. When pressing and subsequently sintering sintered pistons, manufacturing tolerances ranging from ISO tolerance 7 (IT 7) to IT 6 (in favorable cases) can be achieved. However, this is not sufficient, especially for the production of small bypasses. Furthermore, the pressing process is often followed by a surface treatment to deburr the component, for example, by vibratory grinding or shot peening, which can negatively impact the tolerances of the bypasses.

[0013] The object of the present invention is to provide a method for manufacturing a piston and a piston which make it possible to produce pistons with lower manufacturing tolerances in industrial mass production and thus to counteract the problem described above.

[0014] The object is achieved by a method for producing a piston that can be attached to a piston sliding unit that is movable along its longitudinal axis in a cylinder. The piston comprises a disc-shaped base body, which is suitable and intended to seal two areas of the cylinder filled with a medium from each other. The method according to the invention for producing a piston comprises the following steps: a. manufacturing the piston by pressing a material into a piston shape; b. Smoothing the surface of the piston and / or pressing at least one flow path into the piston by means of a stamping tool having an annular, raised and rotationally symmetrical structure.

[0015] According to the invention, the piston has an annular piston collar. Furthermore, the annular piston collar has at least one meandering protrusion and / or indentation, which preferably has at least one section oriented radially and one tangentially to the piston.

[0016] In a first process step, a material is pressed into a piston shape. The material is preferably metal, such as steel or iron, a ceramic or a sinterable powder, such as a metal powder, for example aluminum or iron powder, or a ceramic powder such as aluminum oxide or silicon carbide. Furthermore, the use of any other sinterable material in powder form known to those skilled in the art is conceivable, or even the use of any other metal. During the pressing process, the material is pressed into a piston shape. Various pressure distributions on the material are conceivable. For example, pressing can be uniaxial and / or isostatic. The piston produced in this way preferably does not yet have a bypass with a flow path for the medium after the pressing process. However, it is also conceivable for the piston to already have a preform of a bypass or the bypass itself after the pressing process.The piston is preferably pressed by means of cold forging or another cold forming technique known to those skilled in the art.

[0017] If the previously manufactured piston is made of a sinterable powder, the piston produced in the pressing process is then sintered in a subsequent sintering process under the influence of, for example, temperature and / or pressure. In this process step, properties such as hardness, strength, and thermal conductivity of the piston can be adjusted.

[0018] If the previously manufactured piston is made of a sinterable powder, the previously sintered piston is deburred after sintering. This is preferably done by shot peening or vibratory grinding, but other deburring methods known to those skilled in the art are also conceivable.

[0019] In the final process step, the surface of the piston is smoothed using an embossing tool. For this purpose, the embossing tool is pressed flat against the piston with a defined force and / or a defined amount on the surfaces to be smoothed. In addition, the embossing tool preferably has a raised, rotationally symmetrical structure, which is embossed into the piston when the embossing tool is pressed against the piston. This creates a negative impression of the raised, rotationally symmetrical structure in the piston surface. The piston is then pressure-formed by the embossing tool. However, it is also conceivable that the surface of the piston is not smoothed by the embossing tool in this process step, but rather that the embossing tool merely embosses the raised, rotationally symmetrical structure into the piston. It is also conceivable that the embossing tool only smoothes the surface of the piston.However, both steps—smoothing the surface and pressing in the flow path—are preferably performed. The particularly smooth surface in the flow path area allows for a particularly homogeneous and controlled flow along the flow path.

[0020] The stamping tool is preferably designed as a calibration stamp, but it can also be designed as any other tool type known to those skilled in the art for forming or smoothing a surface. Calibration stamps are preferably used following the basic shaping of a component, for example, to smooth the surface of the component or to optimize the shape with regard to a lower manufacturing tolerance. However, it is also possible to form a component directly using a calibration stamp. The calibration stamp is preferably rotationally symmetrical so that it can be regularly and precisely reworked in order to maintain the low manufacturing tolerance, preferably in the range of IT 3 to IT 4 (batch variation) and IT 4 to IT 6 (across batches).

[0021] According to at least one further embodiment, the raised, rotationally symmetrical structure of the stamping tool, when placed on the piston, which comprises an annular piston collar, has at least one intersection point with the annular piston collar.

[0022] The piston preferably has an annular piston collar. The piston collar is preferably designed as a raised structure on the piston surface. The surface of the piston collar represents a sealing surface which, when pressed against a counter-sealing surface, seals two areas of the cylinder filled with a medium against each other. The counter-sealing surface is the surface of a sealing element, for example a sealing ring, made for example of metal or plastic. It is conceivable for the sealing element to be flexible. Furthermore, it is conceivable for the sealing element to be rotationally symmetrical or to have non-rotationally symmetrical elements, for example for passing the medium through. The sealing element is arranged on the surface of the piston which has the annular piston collar. The sealing element can be fixed directly against this surface.A joint arrangement of the piston and sealing element on the piston sliding unit is conceivable, or an arrangement in which only the piston or the sealing element is arranged on the piston sliding unit. Furthermore, it is conceivable for the sealing element to be arranged floatingly on the piston and to be pressed against the surface of the piston only upon axial actuation of the piston sliding unit in a specific direction (into or out of the cylinder) by a pressure difference between the two areas of the cylinder.

[0023] When the stamping tool is placed on the piston surface, the stamping tool is positioned relative to the piston such that the raised, rotationally symmetrical structure of the stamping tool and the annular piston collar of the piston come into contact with each other at at least one point and have at least one intersection point. At the intersection point, the rotationally symmetrical structure of the stamping tool crosses the piston collar from the side facing the piston center, i.e., the inside of the piston collar, to the side facing away from the piston center, i.e., the outside of the piston collar, or from the side of the piston collar facing away from the piston center to the side of the piston collar facing the piston center.

[0024] The stamping tool is then pressed against the piston in the previously described arrangement relative to the piston, or the piston is pressed against the stamping tool, whereby the contact pressure and / or the defined dimension can be precisely adjusted in both cases. The contact pressure or the dimension is selected depending on various parameters, for example, the strength, elasticity, and plasticity of the materials used or their specific yield point or the process temperature, so that the piston can be plastically deformed in a targeted manner by pressing the stamping tool against it. It is also conceivable that the contact pressure and / or the defined dimension are selected depending on other parameters known to those skilled in the art.

[0025] According to at least one further embodiment, by pressing the raised, rotationally symmetrical structure of the stamping tool into the piston at at least one intersection point of the raised, rotationally symmetrical structure of the stamping tool with the annular piston collar, the annular piston collar is at least partially pressure-formed into a more flattened and / or recessed shape.

[0026] During the press-fitting process, the raised, rotationally symmetrical structure of the stamping tool and the annular piston collar are pressed against each other at at least one intersection point. The raised, rotationally symmetrical structure of the stamping tool presses the annular piston collar at at least one intersection point or in at least one intersection region into a more flattened shape, so that the annular piston collar is pressure-formed into a flatter shape at least at this point. The annular piston collar is thus flattened at at least one point by the raised, rotationally symmetrical structure of the stamping tool. This implies that the height of the piston collar, relative to the direction perpendicular to the plane defined by the disc-shaped base body and parallel to the piston sliding unit (when the piston is arranged on the piston sliding unit), is reduced at the flattened point.The intersection point or intersection area is defined by the contact area between the rotationally symmetrical structure and the piston collar. The piston collar is flattened across the entire contact area between the rotationally symmetrical structure and the piston collar.

[0027] Due to this flattening of the annular piston collar, the surface of the piston collar no longer rests on the sealing mating surface when arranged on a sealing element in the area of ​​the flattening. At the intersection point where the flattening of the piston collar runs from the side of the piston collar facing the piston center to the side of the piston collar facing away from the piston center, the surface of the piston collar therefore no longer rests on the sealing mating surface of the sealing element, creating a flow path for the medium from one of the two areas of the cylinder filled with a medium, which are sealed from one another by the piston, to the other area. This flow path represents the previously described bypass, which determines the damper's damper characteristic curve. The reduction in the height of the piston collar at at least one flattened point is so great that a bypass is created through which the medium can flow along the flow path.

[0028] By manufacturing the bypass with a stamping tool, in particular with a calibration stamp, a reduced manufacturing tolerance in the range of IT 3 to IT 4 (batch variation) and IT 4 to IT 6 (batch-wide) can be achieved and thus a piston can be manufactured in industrial series production in accordance with the task according to the invention.

[0029] The annular piston collar preferably has at least one meandering protrusion or indentation and / or at least one change of direction. In the case of a meandering indentation, the annular piston collar does not extend completely circularly on the surface of the piston, but rather, at the beginning of the indentation, describes a first curve toward the center of the piston surface on which the piston collar is arranged, with an adjoining straight section, thus having a piston collar section that is arranged radially with respect to the disc-shaped base body of the piston.

[0030] Further along the indentation, the piston collar preferably has a second curve in the opposite direction, also with an adjoining straight section, and thus has a piston collar section that is arranged tangentially with respect to the disc-shaped base body of the piston. Following this, the piston collar preferably has a third curve in the same direction as the second curve, which is also followed by a straight section. The indentation thus has a second piston collar section that is arranged radially with respect to the disc-shaped base body of the piston. This second radial section is followed by a fourth curve that runs in the same direction as the first curve, so that the piston collar now runs further along the circular basic shape.In the case of a bulge, the piston collar is shaped similarly to this description, with the difference that the curves lead in opposite directions, or rather, that the first radially arranged section of the piston collar leads away from the center of the piston surface on which the piston collar is located. Furthermore, it is conceivable that the piston collar has corners in the area of ​​the indentation or bulge instead of curves.

[0031] The previously described preferred indentation or protrusion has a square "U" shape with or without rounded corners. However, other shaped indentations or protrusions are conceivable, for example, a "V" shape or a semicircular shape, or any other shape known to those skilled in the art in which the raised, rotationally symmetrical structure of the stamping tool intersects the piston collar at least at one point.

[0032] According to at least one further embodiment, at least one intersection point of the rotationally symmetrical structure of the stamping tool is arranged within at least one meandering protrusion or indentation of the annular piston collar.

[0033] According to at least one further embodiment, at least one intersection point of the rotationally symmetrical structure of the stamping tool is arranged in the at least one section of the at least one meander-shaped protrusion or indentation of the annular piston collar that is aligned radially with respect to the piston.

[0034] The piston collar preferably has one or more meandering indentations. The meandering indentations preferably have rectangular corners, which may be rounded. The raised, rotationally symmetrical structure of the stamping tool is preferably annular. It is particularly advantageous if the ring diameter of the raised, rotationally symmetrical structure is smaller than the ring diameter of the piston collar without including the meandering indentations, but larger than the ring diameter of an imaginary ring along the tangentially running sections of the indentations of the piston collar. As a result, at each indentation there are two intersection points between the raised, rotationally symmetrical structure of the stamping tool and the piston collar, each in the radially arranged sections of the piston collar of an indentation.It is particularly advantageous if the ring diameter of the raised rotationally symmetrical structure of the stamping tool is smaller than the ring diameter of the piston collar, but is nevertheless large enough that the raised rotationally symmetrical structure of the stamping tool rests on its outer side, relative to the ring center, along the entire ring circumference, but outside the indentations, with a partial area of ​​the ring width on a partial area of ​​the ring width on the inner side, relative to the ring center, of the piston collar and also pressure-forms this into a flatter shape.

[0035] In the case of meandering bulges on the piston collar, the ring diameter of the raised, rotationally symmetrical structure is advantageously larger than the ring diameter of the piston collar without including the meandering bulges, but smaller than the ring diameter of an imaginary ring along the tangentially extending sections of the piston collar bulges. As a result, two intersection points of the raised, rotationally symmetrical structure of the stamping tool and the piston collar are also located at each bulge, each in the radially arranged sections of the piston collar of a bulge.

[0036] The object of the invention is also achieved by a piston of a hydraulic or pneumatic damper, which can be arranged on a piston sliding unit. The piston sliding unit is movable along its longitudinal axis in a cylinder, and the piston comprises a disc-shaped base body. The piston is suitable and intended to seal two areas of the cylinder filled with a medium from each other.

[0037] The invention is characterized in that the piston comprises an annular piston collar which has at least one outer wall and at least one inner wall, and the at least one inner wall is radially spaced from the at least one outer wall, wherein the at least one inner wall and the at least one outer wall have segment-like recesses, and the recesses of the at least one inner wall and the recesses of the at least one outer wall are arranged offset from one another along the circumference of the piston, so that the medium can flow through the recesses and the space between the at least one inner and at least one outer wall.The piston has a region along at least one flow path in which the flow direction is tangential, i.e., parallel to the circumference of the annular piston collar. The tangentially extending region of the flow path is delimited by the inner and outer walls of the annular piston collar in a region in which neither the inner nor the outer walls have a recess. The recesses of the inner wall extend further than the inner wall itself relative to the circumference of the piston collar.

[0038] It is conceivable for the damper to be designed as a hydraulic or pneumatic damper (for example as a gas spring), in a single-tube or double-tube design, or in any other damper design known to those skilled in the art. The damper comprises at least a cylinder, a piston, a piston sliding unit, a sealing element, and a medium. The medium is located in the cylinder. The piston is arranged at one end of the piston sliding unit. The sealing element is also arranged at this end. The piston sliding unit is arranged at least partially in the cylinder and thus in the medium, but at least with the end to which the piston is attached. The piston separates two areas of the cylinder filled with the medium. The piston sliding unit and the piston arranged on it are movable along the longitudinal axis of the piston sliding unit in the cylinder. The medium is preferably oil or gas.If the medium is oil, the cylinder is preferably not completely filled with oil and the remaining volume is filled with a gas.

[0039] The piston has a disc-shaped base body whose diameter is smaller than the inner diameter of the cylinder. Furthermore, the piston has a thickness in the direction of the piston sliding unit's longitudinal axis. Other piston shapes are also conceivable, however. In addition, the piston comprises a piston collar on the top or bottom side. The piston collar is preferably designed as an annular, raised structure. The piston collar preferably has a flat surface parallel to the surface of the disc-shaped base body. This surface is preferably arranged on a sealing counter surface of the sealing element. The piston collar thus seals the two areas of the cylinder, which are separated from one another by the piston, from one another.One area is fluidically connected to the area on the inside (relative to the ring center of the annular piston collar) of the piston collar and the other area is fluidically connected to the area on the outside of the piston collar.

[0040] The piston collar is preferably annular. The piston collar preferably comprises an inner and an outer wall. The inner and outer walls each have a specific wall thickness (also referred to as the ring width). The outer and inner walls have recesses along the circumference of the piston collar. The piston collar is preferably interrupted at these recesses. Thus, there is no piston collar at these points, but only the disk-shaped base body. Furthermore, it is conceivable that the piston collar is not completely interrupted at the recesses, but merely flattened or shaped in such a way that the surface of the piston collar does not reach as far as the sealing counter surface. The recesses in the outer and inner walls are preferably offset from one another.This means that at the point on the piston collar where the outer wall has a recess, the inner wall has no recess, and vice versa. In other words, the piston has at least one or at least two walls in every radial direction from the piston center to the piston edge.

[0041] Furthermore, it is advantageous if, between the locations of a recess in the outer wall and a recess in the inner wall, a region of the piston collar is arranged in relation to the circumference, in which neither the inner nor the outer wall has a recess. In this region, the walls therefore overlap in relation to the circumference of the piston collar. It is conceivable that, in the region of the overlap, the space between the walls is at least partially filled with a piston collar that has been formed into a more flattened shape. Furthermore, it is conceivable that the recesses have a greater extent in relation to the circumference than the wall itself. In the present embodiment, the recesses in the outer wall are preferably small in relation to the circumference. In the present embodiment, it is further preferred if the recesses in the inner wall are designed to be large in relation to the circumference.In particular, it is advantageous if the recesses in the inner wall have a greater extent relative to the circumference of the piston collar than the inner wall itself. However, it is also conceivable for the recesses in the outer wall to have a greater extent relative to the circumference of the piston collar than the outer wall itself and for the recesses in the inner wall to be small relative to the circumference. It is also conceivable for the piston collar to have more than two walls. In this case, it is conceivable for all walls to have recesses which are offset from one another relative to the circumference of the piston collar, or not offset from one another, or at least partially offset from one another.

[0042] According to at least one further embodiment, the recesses and the space between the at least one inner and at least one outer wall of the piston collar can be flowed through by a medium and thus define a flow path of the medium.

[0043] The offset recesses described above create a flow path from the interior of the annular piston collar to an area outside the annular piston collar. The piston collar no longer completely seals the two cylinder regions separated by the piston, but connects both regions via the flow path. This flow path is preferably small in terms of the channel cross-section compared to the cylinder diameter. The channel cross-section is preferably adjustable by the amount of space taken up by the piston collar, which has been formed into a more flattened shape, in the space between the walls. The channel cross-section is thus preferably adjustable by the height of the raised, rotationally symmetrical structure of the stamping tool, which determines the height of the formed piston collar.It is therefore conceivable to emboss a different channel cross-section into the piston by replacing the stamping tool with one with a raised, rotationally symmetrical structure of a different height. Furthermore, it is conceivable that the height of the raised, rotationally symmetrical structure can be changed. This allows different channel cross-sections to be formed with one tool.

[0044] The flow path thus represents the damper bypass described at the beginning. The flow path cross-section thus determines the progressiveness of the damper characteristic curve. When the piston sliding unit with the attached piston is actuated axially, the piston is moved along the longitudinal axis of the piston sliding unit in the cylinder. The medium flows from one area of ​​the cylinder to the other area through at least one flow path in the piston collar.

[0045] According to at least one further embodiment, the flow path of the medium has at least one curved section.

[0046] Known pistons often have bypasses with a radial orientation. This means that the medium can flow through the bypasses in a straight line in a radial direction with respect to the disk-shaped base body of the piston. In these cases, the piston collar often only has a wall with recesses. The recesses directly represent the bypasses and the medium flows in a straight line in the radial direction from one region of the cylinder, which is fluidically connected to the region on the inside of the annular piston collar, to the other region of the cylinder, which is connected to the region on the outside of the annular piston collar, or vice versa. In contrast, the piston according to the invention preferably has a flow path which has at least one curved section. This means that the medium does not flow through the bypass in a straight line along the flow path, but flows around at least one curve.Preferably, the flow path with the curved section is arranged in a plane parallel to the surface of the disc-shaped base body of the piston. Preferably, the flow path in the curved section describes a curve of at least 60, 70, or 80 degrees and at most 100, 110, or 120 degrees, but preferably 90 degrees. However, any other angle value other than 0 degrees is also conceivable.

[0047] According to at least one further embodiment, the flow path of the medium is labyrinth-shaped.

[0048] In the context of the present invention, labyrinthine means that the flow path has at least one, preferably two, or even more than two deflections. In particular, when looking into a labyrinthine (flow) path, the outlet or exit is not visible from the inlet or entrance. The deflections refer to a section in which the flow of the medium is deflected from a straight flow direction by the limitation of the flow path. The deflections preferably represent the curved sections described above.

[0049] According to at least one further embodiment, the flow direction of the medium in at least one inlet and / or outlet point of at least one flow path or any point along at least one flow path is tangential with respect to the piston.

[0050] As previously described, known pistons often have bypasses with a radial orientation. This means that the medium can flow through the bypasses in the radial direction. In contrast, the piston according to the invention has a region along at least one flow path in which the flow direction is tangential, i.e., parallel to the circumference of the annular piston collar. This region is preferably arranged directly at the inlet and / or outlet point of the at least one flow path. According to the invention, this tangentially extending region of the flow path is delimited by the inner and outer walls of the annular piston collar.

[0051] The tangentially running region of the flow path is therefore preferably arranged in a region in which neither the inner nor the outer wall has a recess. The tangentially running region of the flow path is therefore preferably arranged in a region in which the walls overlap with respect to the circumference of the piston collar. The flow of the medium upon axial actuation of the piston sliding unit with the piston arranged thereon preferably runs radially outwards (relative to the disc-shaped base body of the piston) until the medium hits the piston collar. At the piston collar, the medium enters the flow path through at least one bypass. The piston preferably has three bypasses.The medium flows from a region of the cylinder that is fluidly connected to an area on the inside of the annular piston collar, around a segment of the inner wall through the recesses in the inner wall that adjoin the circumference on the left and right. Directly adjacent to this, the flow path has a tangential section that runs between the inner and outer walls, i.e., in the overlapping area of ​​the walls. The flow path thus has a curved section directly at the inlet of the flow path, in which the medium changes flow direction from radial to tangential (relative to the disc-shaped base body of the piston).

[0052] Adjacent to the area with tangential flow direction is another curved section of the flow path, in which the medium changes its flow direction from tangential to radial (relative to the disc-shaped base body of the piston). Following this, the flow path runs radially through a recess in the outer wall out of the annular piston collar. Leaving the recess in the outer wall, the medium flows into the other section of the cylinder, which is fluidly connected to a section on the outside of the annular piston collar.

[0053] According to at least one further embodiment, at least two pistons (1) are arranged in the damper on the piston sliding unit (2).

[0054] As already described, it is possible to arrange the sealing element in a floating manner on the piston. In this case, when the damper is actuated in one (forward) direction, the sealing element is pressed against the piston by the pressure difference between the two sections of the cylinder, and the medium can only flow from one section to the other section of the cylinder via the flow path. When the damper is actuated in the other (backward) direction, the sealing element is pressed away from the piston due to the pressure difference now in reverse. In this case, the medium can flow back into the first section through a much larger flow cross-section. The damper can therefore be actuated much more easily in this second (backward) direction than in the first (forward) direction.It is conceivable for the piston and the floating sealing element to be arranged in reverse on the piston sliding unit, so that the first (forward) direction is easier to actuate than the second (backward) direction. Furthermore, it is also conceivable for two pistons and one or more floating sealing elements to be arranged on the piston sliding unit. The pistons are preferably arranged with the side on which a flow path has been impressed facing each other. On the side on which a flow path has been impressed, one sealing element is preferably arranged in a floating manner, whereby in the case of two pistons in an arrangement with the flow path facing each other, one floating sealing element may be sufficient. In this way, the damping behavior of the forward direction corresponds to that of the back direction. It is also conceivable here for the two pistons to have a different flow cross-section.In this case, the damping behavior of the forward and reverse directions is different and can be adapted to a wide variety of requirements, particularly by selecting the flow cross-sections. In this case, the damping behavior of the forward and reverse directions can be adjusted completely independently of each other.

[0055] Further advantages, objects, and features of the present invention will be explained in the following description of the accompanying figures. Similar components may have the same reference numerals in the various embodiments.

[0056] The figures show: Fig. 1 is an overview view of the piston according to the invention arranged in a damper in a preferred embodiment; Fig. 2 a perspective view of the piston in a preferred embodiment; Fig. 3a is a schematic representation of the embossing tool according to a preferred embodiment in plan view; Fig. 3b a schematic representation of the embossing tool according to a preferred embodiment as a section along the line AA (see Fig. 3a); Fig. 4 a schematic representation of the piston and the raised rotationally symmetrical structure of the stamping tool according to a preferred embodiment in plan view; Fig. 5 a schematic representation of the piston and the stamping tool according to a preferred embodiment as a section along the line BB (see Fig. 4).

[0057] In the Fig. 1 schematically shows a piston 1 of a hydraulic or pneumatic damper 100, which can be arranged on a piston sliding unit 2. The piston sliding unit is arranged along its longitudinal axis A Lmovable in a cylinder 3 and the piston 1 comprises a disc-shaped base body 4, wherein the piston 1 is suitable and intended to seal two areas 5, 6 of the cylinder 3 filled with a medium 7 against each other.

[0058] The invention is characterized in that the piston 1 comprises an annular piston collar 8, which has at least one outer wall 9 and at least one inner wall 10 and the at least one inner wall 10 is radially spaced from the at least one outer wall 9, wherein the at least one inner wall 10 and the at least one outer wall 9 have segment-like recesses 11, 12 and the recesses of the at least one inner wall 12 and the recesses of the at least one outer wall 11 are arranged offset from one another along the circumference of the piston 1, so that the recesses 11, 12 and the space between the at least one inner and at least one outer wall 9, 10 can be flowed through by the medium 7 (not in Fig. 1 shown, see Fig. 2).

[0059] The damper 100 comprises at least a cylinder 3, a piston 1, a piston sliding unit 2, a sealing element 15, and a medium 7. The medium 7 is located in the cylinder 3. The piston 1 is preferably arranged at one end of the piston sliding unit 2. The sealing element 15 is also arranged at this end. The piston sliding unit 2 is arranged at least partially in the cylinder 3 and thus in the medium 7, but at least with the end to which the piston 1 is attached. The piston 1 separates two regions 5, 6 of the cylinder 3 filled with the medium 7. The piston sliding unit 2 and the piston 1 arranged thereon are arranged along the piston sliding unit's longitudinal axis A. L movable in cylinder 3. The cylinder 3 is preferably not completely filled with the medium 7, e.g. an oil, and the remaining volume is filled with a gas.

[0060] The piston 1 has a disc-shaped base body 4 whose diameter is smaller than the inner diameter of the cylinder 3. Furthermore, the piston 1 has a thickness in the direction of the piston sliding unit's longitudinal axis A L In addition, the piston 1 comprises a piston collar 8 on the top and / or bottom side. The piston collar 8 is preferably designed as an annular, raised structure. The piston collar 8 preferably has a flat surface parallel to the surface of the disc-shaped base body. This surface is preferably arranged on a sealing counter surface of the sealing element 15. The piston collar thus seals the two regions of the cylinder, which are separated from one another by the piston, from one another. One region is fluidically connected to the region on the inside (relative to the ring center point of the annular piston collar) of the piston collar, and the other region is fluidically connected to the region on the outside of the piston collar.

[0061] Fig. 2 shows a perspective view of the piston 1. The piston collar 8 is preferably annular. The piston collar 8 preferably comprises an inner wall 10 and an outer wall 9. The inner wall 10 and the outer wall 9 each have a specific wall thickness (also referred to as the ring width). The outer wall 9 and also the inner wall 10 have recesses 11, 12 along the circumference of the piston collar 8. The piston collar 8 is preferably interrupted at these recesses 11, 12. Thus, there is no piston collar 8 at these locations, but only the disk-shaped base body 4. Furthermore, it is conceivable that the piston collar 8 is not completely interrupted at the recesses 11, 12, but merely flattened or shaped in such a way that the surface of the piston collar 8 does not reach as far as the sealing counter surface of the sealing element 15. The recesses 11, 12 of the outer 9 and inner wall 10 are preferably arranged offset from one another.

[0062] This means that at the point on the piston collar 8, relative to the circumference, at which the outer wall 9 has a recess 11, the inner wall 10 has no recess 12, and vice versa. Furthermore, it is advantageous if, between the points of a recess 11 in the outer wall 9 and a recess 12 in the inner wall 10, a region of the piston collar 8 is arranged, relative to the circumference, in which neither the inner wall 10 nor the outer wall 9 has a recess 11, 12. In this region, there is therefore an overlap of the walls 11, 12 relative to the circumference of the piston collar 8. It is also conceivable for the recesses 11, 12 to have a greater extent relative to the circumference than the walls 9, 10 themselves. In the present embodiment, the recesses 11 of the outer wall 9 are preferably small relative to the circumference.In the present embodiment, it is further preferred if the recesses 12 of the inner wall 10 are designed to be large relative to the circumference. According to the invention, the recesses 12 of the inner wall 10 have a greater extent relative to the circumference of the piston collar 8 than the inner wall 10 itself. However, it is also conceivable for the recesses 11 of the outer wall 9 to have a greater extent relative to the circumference of the piston collar 8 than the outer wall 9 itself. It is also conceivable for the piston collar 8 to have more than two walls. In this case, it is conceivable for all walls to have recesses which are offset from one another relative to the circumference of the piston collar, or not offset from one another, or at least partially offset from one another.

[0063] The recesses 11, 12 and the space between the at least one inner and at least one outer wall 9, 10 of the piston collar 8 can preferably be flowed through by a medium 7 and thus define a flow path 13 of the medium 7. The previously described, offset arrangement of the recesses 11, 12 thus creates a flow path 13 from the interior of the annular piston collar 8 into an area outside the annular piston collar 8. The piston collar 8 no longer completely seals the two areas of the cylinder 5, 6, which are separated from one another by the piston, but rather connects both areas with the aid of the flow path 13. This flow path 13 is preferably small in terms of the channel cross-section compared to the diameter of the cylinder 3. This flow path 13 thus represents the bypass of the damper 100 described at the beginning. The flow path cross-section therefore determines the progressivity of the damper characteristic curve.When the piston sliding unit 2 with the piston 1 arranged thereon is actuated axially, the piston 1 is moved along the longitudinal axis A. L of the piston sliding unit 2 in the cylinder 3. The medium 7 flows through at least one flow path 13 in the piston collar 8 of the piston 1 from one area 5 into the other area 6 of the cylinder, or vice versa.

[0064] The flow path 13 of the medium 7 preferably has at least one curved section 14. This means that the medium 7 does not flow through the bypass along the flow path 13 in a straight line, but rather flows around at least one curve. Preferably, the flow path 13 with the curved section 14 is arranged in the plane parallel to the surface of the disc-shaped base body 4 of the piston 1. Preferably, the flow path 13 describes a 90-degree curve in the curved section 14.

[0065] The flow path 13 of the medium 7 is preferably labyrinth-shaped. In the context of the present invention, labyrinth-shaped means that the flow path 13 has at least one, preferably two, or even more than two deflections. In particular, when looking into a labyrinth-shaped (flow) path, the outlet or exit is not visible from the inlet or entrance. The deflections designate a section in which the flow of the medium 7 is deflected from a straight flow direction by the limitation of the flow path 13. The deflections preferably represent the previously described, curved sections 14.

[0066] The flow direction of the medium 7 is preferably tangential with respect to the piston 1 at at least one inlet and / or outlet point of at least one flow path 13 or at any point along at least one flow path 13. The piston 1 according to the invention has at least one point, but preferably a region along at least one flow path 13, in which the flow direction is tangential, i.e. parallel to the circumference of the annular piston collar 8. This point or region is preferably arranged directly at the inlet and / or outlet point of the at least one flow path 13. This tangentially running region of the flow path 13 is preferably delimited by the inner wall 10 and outer wall 9 of the annular piston collar 8. The tangentially running region of the flow path 13 is therefore preferably arranged in a region in which neither the inner wall 10 nor the outer wall 9 has a recess 11, 12.The tangentially extending region of the flow path 13 is therefore preferably arranged in a region in which the walls 9, 10 overlap with respect to the circumference of the piston collar 8. The flow of the medium 7 upon axial actuation of the piston sliding unit 2 with the piston 1 arranged thereon preferably runs radially outward (relative to the disc-shaped base body 4 of the piston 1) until the medium 7 encounters the piston collar 8. At the piston collar 8, the medium 7 enters the flow path 13 through at least one bypass. The piston 1 preferably has two or three bypasses. The medium 7, coming from a region 6 of the cylinder 3, which is fluidically connected to a region on the inside of the annular piston collar 8, flows around a segment of the inner wall 10 through the recesses 12 of the inner wall 10, which adjoin the circumferential left and right edges.Directly adjacent to this, the flow path 13 has a tangentially running section which runs between the inner wall 10 and outer wall 9, i.e. in the overlapping region of the walls 9, 10. The flow path 13 thus has a curved section 14 directly at the inlet of the flow path 13, in which the medium 7 changes the flow direction from radial to tangential (relative to the disc-shaped base body 4 of the piston 1). Adjacent to this is another curved region 14 of the flow path 13, in which the medium 7 changes the flow direction from tangential to radial (relative to the disc-shaped base body 4 of the piston 1). Directly adjacent to this, the flow path 13 runs radially through a recess 11 in the outer wall 9 out of the annular piston collar 8.Emerging from the recess 11 of the outer wall 9, the medium 7 flows into the other region 5 of the cylinder 3, which is fluidly connected to a region on the outside of the annular piston collar 8. A reverse flow direction is also conceivable.

[0067] To produce the piston 1 according to the invention, according to the method of claim 1, the surface of the piston 1 is smoothed and / or a flow path 13 is pressed into the piston 1. Both or only one of these steps is carried out by means of an embossing tool 20, which has a raised and rotationally symmetrical structure 21.

[0068] The embossing tool 20 is in the Fig. 3a (top view) and 3b (section along AA) are shown schematically. In the corresponding process step, the surface of the previously deburred piston 1 is smoothed using an embossing tool 20. For this purpose, the embossing tool 20 is pressed flat against the piston 1 with a defined force and / or a defined amount on the surfaces to be smoothed. In addition, the embossing tool 20 has a raised, rotationally symmetrical structure 21, which is embossed into the piston 1 when the embossing tool 20 is pressed against the piston 1. This creates a negative impression of the raised, rotationally symmetrical structure 21 in the piston surface. The piston 1 is thereby pressure-formed using the embossing tool 20. However, it is also conceivable that in this process step, the surface of the piston 1 is not smoothed by the embossing tool 20, but rather the embossing tool 20 merely embosses the raised, rotationally symmetrical structure 21 into the piston 1.It is also conceivable that the stamping tool 20 only smoothes the surface of the piston 1.

[0069] The stamping tool 20 is preferably designed as a calibration stamp. The calibration stamp is preferably rotationally symmetrical so that it can be regularly and precisely reworked to maintain the low manufacturing tolerance, preferably in the range of IT 3 to IT 4 (batch variation) and IT 4 to IT 6 (batch-wide).

[0070] The raised, rotationally symmetrical structure 21 of the stamping tool 20 preferably has, when placed on the piston 1, which comprises an annular piston collar 8, at least one intersection point 30 with the annular piston collar 8. When placing the stamping tool 20 on the piston surface, which in the Fig. 4 and Fig. 5 (section along B, Fig. 4), the stamping tool 20 is arranged relative to the piston 1 such that the raised, rotationally symmetrical structure 21 of the stamping tool 20 and the annular piston collar 8 of the piston 1 come to rest on one another at at least one point and have at least one intersection point 30. At the intersection point 30, the rotationally symmetrical structure 21 of the stamping tool 20 crosses the piston collar 8 from the side of the piston collar 8 facing the piston center to the side of the piston collar 8 facing away from the piston center, or from the side of the piston collar 8 facing away from the piston center to the side of the piston collar 8 facing the piston center.

[0071] The stamping tool 20 is now pressed against the piston 1 in the previously described arrangement with the piston 21, or the piston 1 is pressed against the stamping tool 20, whereby the contact pressure or the amount can be precisely adjusted in both cases. By pressing the raised, rotationally symmetrical structure 21 of the stamping tool 20 into the piston 1 at at least one intersection point 30 of the raised, rotationally symmetrical structure 21 of the stamping tool 20 with the annular piston collar 8, the annular piston collar 8 is preferably at least partially pressure-formed into a more flattened shape 31. During the press-fitting process, the raised, rotationally symmetrical structure 21 of the stamping tool 20 and the annular piston collar 8 are pressed against one another at at least the at least one intersection point 30.The raised, rotationally symmetrical structure 21 of the stamping tool 20 presses the annular piston collar 8 at least at the at least one intersection point 30 into a more flattened and / or recessed shape 31, so that the annular piston collar 8 is pressure-formed into a flatter shape at least at this point. The annular piston collar 8 is thus flattened at least at one point by the raised, rotationally symmetrical structure 21 of the stamping tool 20. This implies that the height of the piston collar 8, relative to the direction perpendicular to the plane defined by the disc-shaped base body 4 and parallel to the piston sliding unit 2 (when the piston 1 is arranged on the piston sliding unit 2), is reduced at the flattened point.

[0072] Due to this flattening of the annular piston collar 8, the surface of the piston collar 8, when arranged on a sealing element 15, no longer rests against the sealing counter surface in the region of the flattening. At the intersection point 30, at which the flattening of the piston collar 8 extends from the side of the piston collar 8 facing the piston center to the side of the piston collar 8 facing away from the piston center, the surface of the piston collar 8 therefore does not rest at all on the sealing counter surface of the sealing element 15, creating a flow path 13 for the medium 7 from one of the two regions 6 of the cylinder 3 filled with a medium 7, which are sealed from one another by the piston 1, into the other region 5. This flow path 13 represents the previously described bypass, which determines the damper characteristic curve of the damper 100.The reduction in the height of the piston collar 8 at the at least one flattened point is so great that a bypass is created through which the medium 7 can flow along the flow path 13.

[0073] By manufacturing the bypass with a stamping tool 20, in particular with a calibration stamp, a reduced manufacturing tolerance in the range from IT 3 to IT 4 (batch variation) and IT 4 to IT 6 (across batches) can be achieved and thus a piston 1 can be manufactured in industrial series production in accordance with the object of the invention.

[0074] The annular piston collar 8 preferably has at least one meandering protrusion and / or indentation 32, which preferably has at least one section oriented radially 33 and one tangentially 34 to the piston 1. In the case of a meandering indentation 32, the annular piston collar 8 does not run completely circularly on the surface of the piston 8, but rather describes a first curve at the beginning of the indentation 32 in the direction of the center point of the piston surface on which the piston collar 8 is arranged, with an adjoining straight section, and thus has a piston collar section 33 which is arranged radially with respect to the disc-shaped base body 4 of the piston 1.Further along the indentation 32, the piston collar 8 has a second curve in the opposite direction, also with an adjoining straight section, and thus has a piston collar section 34 which is arranged tangentially with respect to the disc-shaped base body 4 of the piston 1. Following this, the piston collar 8 has a third curve in the same direction as the second curve, which is also followed by a straight section. The indentation 32 thus has a second piston collar section 33, which is arranged radially with respect to the disc-shaped base body 4 of the piston 1. This second radial section 33 is followed by a fourth curve which runs in the same direction as the first curve, so that the piston collar 8 now runs further along the circular basic shape.In the case of a bulge, the piston collar is shaped similarly to this description, with the difference that the curves lead in the opposite direction, or that the first radially arranged section 33 of the piston collar leads away from the center of the piston surface on which the piston collar 8 is arranged. Furthermore, it is conceivable that the piston collar 8 has corners in the area of ​​the indentation or bulge 32 instead of curves.

[0075] The previously described preferred indentation or protrusion 32 has a square "U" shape with or without rounded corners. However, differently shaped indentations or protrusions 32 are conceivable, for example, a "V" shape or a semicircular shape, or any other shape known to those skilled in the art with which the raised, rotationally symmetrical structure 21 of the stamping tool 20 intersects the piston collar 8 at at least one point.

[0076] Preferably, at least one intersection point 30 of the rotationally symmetrical structure 21 of the stamping tool 20 is arranged within at least one meandering protrusion or indentation 32 of the annular piston collar 8. Furthermore, at least one intersection point 30 of the rotationally symmetrical structure 21 of the stamping tool 20 is preferably arranged in the at least one section 33 of the at least one meandering protrusion or indentation 32 of the annular piston collar 8 that is aligned radially with respect to the piston 1. The meandering indentations 32 preferably have rectangular corners, which may be rounded. The raised, rotationally symmetrical structure 21 of the stamping tool 20 is annular.It is particularly advantageous if the ring diameter of the raised, rotationally symmetrical structure 21 is smaller than the ring diameter of the piston collar 8 without including the meandering indentations 32, but larger than the ring diameter of an imaginary ring along the tangentially extending sections 34 of the indentations 32 of the piston collar 8. As a result, at each indentation 32, there are two intersection points 30 of the raised, rotationally symmetrical structure 21 of the stamping tool 20 and the piston collar 8, each in the radially arranged sections 33 of the piston collar 8 of an indentation 32.It is particularly advantageous if the ring diameter of the raised rotationally symmetrical structure 21 of the stamping tool 20 is smaller than the ring diameter of the piston collar 8, but is nevertheless large enough that the raised rotationally symmetrical structure 21 of the stamping tool 20 rests on its outer side, relative to the ring center, along the entire ring circumference, but outside the indentations 32, with a partial area of ​​the ring width on a partial area of ​​the ring width on the inner side, relative to the ring center, of the piston collar 8 and also pressure-forms this into a flatter shape (see . Fig. 5 right).

[0077] In the case of meander-shaped bulges of the piston collar 8, the ring diameter of the raised rotationally symmetrical structure 21 is advantageously larger than the ring diameter of the piston collar 8 without including the meander-shaped bulges, but smaller than the ring diameter of an imaginary ring along the tangentially running sections 34 of the bulges of the piston collar 8. As a result, there are also two intersection points 30 of the raised rotationally symmetrical structure 21 of the stamping tool 20 and the piston collar 8 at each bulge, namely in each case in the radially arranged sections 33 of the piston collar 8 of a bulge.

[0078] The applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided they are novel, individually or in combination, over the prior art. It is further noted that the individual figures also describe features that may be advantageous in and of themselves. The skilled person will immediately recognize that a specific feature described in a figure may be advantageous even without adopting further features from that figure. Furthermore, the skilled person will recognize that advantages may also arise from a combination of several features shown in individual or different figures. List of reference symbols 1 piston 2 piston sliding unit 3 cylinders 4 disc-shaped base bodies 5 an area of ​​the cylinder 6 another area of ​​the cylinder 7 Medium 8 piston collar 9 outer wall 10 inner wall 11 Recess in the outer wall 12 Recess in the inner wall 13 Flow path 14 curved section of the flow path 15 Sealing element 20 embossing tools 21 raised rotationally symmetrical structure 30 crossing point 31 flatter shape of the piston collar 32 Protrusion or indentation of the piston collar 33 radial section of the piston collar 34 tangential section of the piston collar

Claims

[1] Method for producing a piston (1) which can be fastened to a piston sliding unit (2) which is arranged along its longitudinal axis (A L ) is movable in a cylinder (3), wherein the piston (1) has a disc-shaped base body (4), wherein the piston (1) is suitable and intended to seal two areas (5, 6) of the cylinder (3) filled with a medium (7) against each other, comprising the steps: a. manufacturing the piston (1) by pressing a material into a piston shape; b. Smoothing the surface of the piston (1) and / or pressing at least one flow path (11) into the piston (1) by means of a stamping tool (20) which has an annular, raised and rotationally symmetrical structure (21). characterized byin that the piston (1) has an annular piston collar (8), wherein the annular piston collar (8) has at least one meander-shaped protrusion and / or indentation (32), which preferably has at least one section oriented radially (33) and tangentially (34) to the piston (1). [2] Method according to claim 1, characterized by that the raised, rotationally symmetrical structure (21) of the stamping tool (20) has at least one intersection point (30) with the annular piston collar (8) when placed on the piston (1). [3] Method according to claim 1, characterized bythat by pressing the raised, rotationally symmetrical structure (21) of the stamping tool (20) into the piston (1) at at least one intersection point (30) of the raised, rotationally symmetrical structure (21) of the stamping tool (20) with the annular piston collar (8), the annular piston collar (8) is at least partially pressure-formed into a more flattened and / or recessed shape (31). [4] Method according to one of claims 2-3, characterized by that at least one crossing point (30) of the rotationally symmetrical structure (21) of the stamping tool (20) is arranged within at least one meander-shaped protrusion or indentation (32) of the annular piston collar (8). [5] Method according to one of claims 2-4, characterized bythat at least one crossing point (30) of the rotationally symmetrical structure (21) of the stamping tool (20) is arranged in the at least one section (33) of the at least one meander-shaped protrusion or indentation (32) of the annular piston collar (8) that is aligned radially with respect to the piston (1). [6] Piston (1) of a hydraulic or pneumatic damper (100), which can be arranged on a piston sliding unit (2) which is arranged along its longitudinal axis (A L ) is movable in a cylinder (3), wherein the piston (1) comprises a disc-shaped base body (4), wherein the piston (1) is suitable and intended to seal two areas (5, 6) of the cylinder (3) filled with a medium (7) against each other, characterized bythat the piston (1) comprises an annular piston collar (8) which has at least one outer wall (9) and at least one inner wall (10), and the at least one inner wall (10) is radially spaced from the at least one outer wall (9), wherein the at least one inner wall (10) and the at least one outer wall (9) have segment-like recesses (11, 12), and the recesses of the at least one inner wall (12) and the recesses of the at least one outer wall (11) are arranged offset from one another along the circumference of the piston (1), so that the medium (7) can flow through the recesses (11, 12) and the space between the at least one inner and at least one outer wall (9, 10), wherein the piston (1) has a region along at least one flow path (13) in which the flow direction is tangential, i.e. parallel to the circumference of the annular piston collar (8),wherein the tangentially extending region of the flow path (13) is delimited by the inner (10) and outer wall (9) of the annular piston collar (8), in a region in which neither the inner nor the outer wall (9, 10) has a recess (11, 12), wherein the recesses (12) of the inner wall (10) have a greater extent than the inner wall 10 itself with respect to the circumference of the piston collar (8). [7] Piston (1) according to claim 6, characterized by that the recesses (11, 12) and the space between the at least one inner and at least one outer wall (9, 10) of the piston collar (8) can be flowed through by a medium (7) and thus define a flow path (13) of the medium (7). [8] Piston (1) according to claim 6 or 7, characterized by that the flow path (13) of the medium (7) has at least one curved section (14). [9] Piston (1) according to one of claims 6-8, characterized bythat the flow path (13) of the medium (7) is labyrinth-shaped. [10] Piston (1) according to one of claims 6-9, characterized by that the flow direction of the medium (7) in at least one inlet and / or outlet point of at least one flow path (13) is tangential with respect to the piston (1). [11] Damper (100) characterized by that at least two pistons (1) according to one of claims 6-10 are arranged on the piston sliding unit (2).

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