DE3008709A1 - PISTON WITH A PISTON RING - Google Patents

Description

FICHTEL & SACHS AG - SCHWEINFURT;

PATENT AND UTILITY MODEL APPLICATION

Pistons with a piston ring

The invention relates to a piston with a piston ring for a hydraulic, hydropneumatic or pneumatic unit, especially for a vibration damper, the piston mounted on a piston rod and damping devices and in a cylinder filled with damping medium is axially movably guided and sealed to the outside, while the piston ring is arranged in an annular recess of the piston and has an axial extent which is a multiple of the ring wall thickness.

Such a piston, the plastic piston ring of which has a relatively large axial extension, is known from DE-GM 7 725 888, for example. The plastic piston ring has a rectangular cross-sectional area in longitudinal section and is arranged in a piston ring groove of the piston that is open on one side. This piston ring groove is closed by an additional sheet metal body. It is also known from DE-OS 2 716 927 to attach a temperature-resistant, wear-resistant, cylindrical sliding bearing element to the outer surface of the damping piston to absorb the radial forces that occur. This plain bearing element consists of thin-walled plain bearing layer material, which is formed by a metallic support and an outer sliding layer made of plastic and only takes over the Führujigs function. The additionally required piston ring is used for sealing.

Disadvantageous for plastic piston rings with a large axial extension is that these tend to clamp at higher temperatures and at low operating temperature the sealing is insufficient or /. There are noises due to excessive axial or radial play.

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The object of the present invention is to create a piston with a piston ring which, on the one hand, has low friction , a perfect seal is guaranteed and radial forces that occur without a noticeable increase in frictional resistance able to absorb. In addition, the parts should be easy and cheap to manufacture and assemble.

According to the invention this object is achieved in that the piston and / or the piston ring has a contact surface provided with a convex curvature. The piston ring can be made of plastic or plain bearing layer material. Through the arch of the piston ring or the piston, a different contact pressure is achieved over the length of the contact surface, so that in the event of greater thermal expansion, the piston ring can give way and does not cause a significant increase in frictional resistance. In particular with forces exerted radially on the piston rod - as occurs in struts with vibration dampers that used to transfer wheel guidance forces - there is a jamming between the inner wall of the cylinder and the piston or the piston ring avoided.

According to one feature of the invention, the inner wall of the cylinder facing contact surface of the piston ring on the curvature, the piston ring, if it is designed as a plastic ring, is pulled over the piston in a closed form and snaps into the piston ring groove due to its own elasticity. Does it on the other hand, it is one made of plain bearing material Piston ring, it is appropriate according to a feature of the invention if the piston ring is approximately Z-shaped Has ring joint. Such a ring joint is guaranteed an extremely good sealing effect of the piston ring.

Another advantageous embodiment of the piston provided with the piston ring is obtained according to the invention by that the piston ring groove in the piston is formed by two cylindrical surfaces offset in diameter, whereby one the movement of the piston ring in the axial direction limiting contact surface and the second contact surface by a valve pressure plate is created

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The axial fixation of the piston ring in the L-shaped Piston ring groove is obtained in a simple manner that according to the invention the piston ring groove at its end Has a bend. This display is advantageous attached after the assembly of the piston ring. A further fastening of the piston ring results according to the invention in that that the piston ring is a self-contained component which is pressed onto the L-shaped piston ring groove.

In a further embodiment of the invention, the piston ring groove has of the piston has a groove base with a convex curvature. In this embodiment, too, it is achieved that the piston ring is only in the middle the piston ring groove is pressed against the inner wall of the cylinder and thus a deflection of the piston ring in the event of greater thermal expansion is guaranteed without the frictional resistance increasing significantly. The piston ring can be cylindrical here Be formed component.

An easy assembly of the piston ring is achieved according to one feature in that the piston is transverse to the piston axis is divided component, wherein the parting line is arranged in the area of the piston ring groove. The two-part piston is here as well easy to manufacture, because here sintered components can be manufactured without reworking, i.e. without subsequent machining of the piston ring groove, be used.

According to a feature of the invention, a circumferential receiving groove for a pressure ring is provided in the piston under the piston ring, wherein the pressure ring presses the piston ring against the inner wall of the cylinder. This also makes a targeted and precisely definable one Contact pressure of the piston ring against the inner wall of the cylinder achieved with a curved contact surface.

The invention is illustrated below with reference to the drawings Embodiments explained in more detail. It shows:

Fig. 1 shows a shock absorber insert in longitudinal section j

2 shows the piston section of this shock absorber in an enlarged Dar stowage; 130039/0099

Pig. 3 the axial fixation of the piston ring with the valve pressure plate;

FIG. K shows a piston ring with a Z-shaped joint ; FIG.

5 shows a piston ring made of plain bearing material, which is supported on the one hand on the piston and on the other hand on the piston rod

6 shows a piston ring groove with a convex curvature

Fig. 7 shows the arrangement of a pressure ring for the piston rings

Fig, 8 shows a plastic piston ring with pressure ringj

9 shows the axial fixation of the piston ring by bending the piston end and

10 shows the axial fixation of the piston ring by caulking.

The shock absorber shown in Fig. 1 is designed as a strut insert and consists of the container I ₃ in which the cylinder 2 centered by the bottom valve 3 and the piston rod guide 4 is arranged. The piston 6, which is attached to the piston rod 5 and provided with damping valves, slides on the inner wall of the cylinder 2. This piston 6 separates the interior of the cylinder 2 into a working space 7 above the piston and a working space 8 below the piston. These two working spaces 7 and 8 are filled with damping liquid and are connected to one another via the damping valves located in the piston 6; The piston ring 11 is located in the piston ring groove 10 of the piston 6.

As shown in Fig. 2 in an enlarged view ₃ , the piston ring 11 has a contact surface provided with a convex curvature. before 12 on. This piston ring 11 can consist of plastic or be formed by a plain bearing layer material. at

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A so-called sliding bearing layer material is a metallic support carrier with an outer sliding layer made of plastic. As a result of the curved contact surface, the piston ring 11 rests against the inner wall of the cylinder 2 only over part of its axial extent, whereby a favorable friction behavior between the piston and the cylinder tube is achieved. Also, upon expansion of the ^pla% toffes due to temperature rise of the piston ring can deflect and prevents jamming between the piston 6 and the cylinder 2. By between the piston ring 11 and the cylinder 2 free spaces formed, wedge-shaped builds up in each direction of movement of the piston, a lubricating wedge, which leads to favorable coefficients of friction and low wear on the piston ring.

In Fig. 3, a piston construction is shown in which the piston ring 11 is arranged in an L-shaped piston ring groove 16 of the piston 6 and the piston ring 11 in the axial direction is limited by a contact surface formed by the valve pressure plate 13. This ensures that the Piston ring 11 created in the piston ring groove 16 and this piston ring can, for example, easily open as a closed ring the piston 6 can be pushed on. This applies in particular to plastic piston rings, but if the piston ring consists of one metallic support carrier with an outer sliding layer made of plastic, this ensures a good sealing effect in the area of the piston ring joint achieved that this a portion 14 with an inclined course having. According to Fig, * J is an embodiment of the piston ring 11, which has an approximately Z-shaped piston ring joint 15.

The embodiment shown in Fig. 5 has a piston ring 17, which consists of a metallic support beam with an outer sliding layer and is integrally connected to the radial flange 18. With this radial flange 18, this piston ring 17 is on the Approach 19 of the piston rod 5 attached. For this purpose, the extension 19 is formed at its free end with an approximately tubular extension, which is bent after inserting the radial flange 18. At the other end of the piston ring 17 is in the L-shaped Piston ring groove 16 of the piston 6 and is therefore perfectly centered on the piston and attached to it. Between the the Valve spring supporting nut and the radial flange 18 can

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Intermediate rings are arranged, so that thereby the mother in their Location is secured.

In the embodiment according to FIG. 6, the piston ring 11 is with rectangular cross-section, while the piston ring groove 20 incorporated in the piston β has a groove base with a contact surface 21 has, which has a convex curvature. As a result, between the piston ring 11 and the contact surface 21 are annular Created cavities into which the piston ring 11 can escape when it expands.

According to the embodiment according to FIG. 7, the piston 6 formed by two piston parts 26 and 27. The parting line 28 of these piston parts is located in the area of the piston ring groove 10. In addition, a receiving groove 22 is provided in the piston 6, in which a pressure ring 23 is arranged, which the piston ring 11 presses against the inner wall of the cylinder 2. As a result of this force of the pressure ring 23 acting in the center of the piston ring 11 a convexly curved contact surface of the piston ring 11 arranged in the piston ring groove 10 is achieved.

The embodiment of FIG. 8 differs from that of FIG. 7 essentially in that the piston ring as a relative thin-walled plastic part is made.

The fastening of the piston ring 11 in the annular piston ring groove 16 of the piston 6 is shown in FIGS. According to FIG. 9, the lower end of the piston 6 is here provided with a bend 24 after the assembly of the piston ring 11. 10, the piston ring 11 is axially in the Piston ring groove 16 fixed in that the cylindrical part of this piston ring groove 16 at the end of the piston ring 11 is caulked 25 is attached.

January 25, 1980
TIP-I Be / whm-

130039/0099

Claims (1)

PICHTEL & SACHS AG - SCHWEINFURT PATENT CLAIMS .) Piston with a piston ring for a hydraulic, hydropneumatic or pneumatic unit, in particular for a vibration damper, the piston on a piston rod is attached and has damping devices and in one with damping medium filled cylinder is guided axially movable and sealed to the outside, while the piston ring in a annular recess of the piston is arranged and has an axial extent that is a multiple of the ring wall thickness is, dad. gek. That the piston (6) and / or the piston ring (11, 17) is provided with a convex curvature Has contact surface (12, 21). 2. Piston according to claim 1, dad. gek. that the inner wall of the cylinder (2) facing contact surface (12) of the piston ring (11, 17) has the curvature. 3. Piston according to claims 1 and 2, dad. gek. that the piston ring (11) has an approximately Z-shaped annular joint (15). 4. Piston according to claims 1 to 3 ₅ dad. gek. that the piston ring groove (1-6) in the piston (6) is formed by two cylinder surfaces with a offset diameter, whereby a contact surface is created that limits the movement of the piston ring (11) in the axial direction and the second contact surface is formed by a valve pressure plate (13) is created 5. Piston according to claims 1 to 3 * dad, gek. That for the axial fixation of the piston ring (11) in the L-shaped piston ring groove (16) this has a bend (2k) at its end. 6. Piston according to claim 1, dad. that the piston ring groove (20) of the piston (6) has a groove base with a convexly curved contact surface (21) owns .1 3 0 039/0099 -O- 7. Piston according to claims 1 to 3 _S dad. gek. That the piston ring (11) is a self-contained component which is pressed onto the L-shaped piston ring groove (16). 8. Piston according to claims 1 to J, dad. gek. That the piston is a component divided transversely to the piston axis, the parting line (28) being arranged in the area of the piston ring groove (10) 9. Piston according to claims 1 to 8, dad. gek. that in the flask (6) a circumferential receiving groove (22) for a pressure ring (23) is provided under the piston ring (11) and the pressure ring (23) presses the piston ring (11) against the inner wall of the cylinder. 10. Piston according to claims 1 to 3, dad. gek. That the piston ring (17) having the curvature is in one piece with a radial flange (L8) is formed and is thus supported on the piston rod (5), while the other end of the piston ring (17) comes to rest on a cylindrical extension of the piston (piston ring groove l6). 25.OI.I98O
TIP-I Be / whm- 1 30039/00 99