DE102017215687A1 - Piston cylinder unit - Google Patents

Abstract

Piston-cylinder unit, comprising a cylinder in which a piston rod, on which at least one piston is arranged, which has on an outer circumferential surface a radially elastic piston ring, depending on the stroke position, starting from a first length portion with a larger diameter in a second cylinder portion retracts with a smaller diameter, wherein an outer sleeve forms a stop for an expansion movement of the piston ring, wherein the stop is formed by a closed ring which is axially supported on the piston.

Description

The invention relates to a piston-cylinder unit according to the preamble of patent claim 1.

The DE 10 2016 202 007 A1 describes a piston-cylinder unit with a piston rod and with a piston having on its outer circumferential surface a radially elastic piston ring. Depending on the stroke position of the piston rod in a cylinder with two cylinder sections of different diameter, the piston ring is surrounded in the cylinder section with the larger diameter and therefore can not develop a sealing effect.

When entering the cylinder section with the smaller diameter, depending on the geometric design of the piston ring, two different effects can occur. If the radially elastic piston ring should produce a sealing effect due to its elastic property, then it is dimensioned in the relaxed state with an excess to the cylinder portion of smaller diameter. Consequently, the piston ring must be radially compressed when entering this section to avoid damage.

If, alternatively or in combination with the elastic internal stress, a radially outwardly acting expander force acts on the piston ring, then this expander force already sets in when the piston ring passes a transition between the cylinder portion with the larger and smaller diameter. At very high piston speeds, this behavior can occur even in the large diameter section, which can lead to discomfort, noise and loss of function.

To minimize these bulge effects, it is of the generic type DE 10 2016 202 007 A1 It is known that the piston ring has a stop in the form of a collar which determines the maximum diameter. For this purpose, the piston ring has an annular groove which joins the sleeve and thereby secures axially. As a cuff, a slotted circlip or an elastic O-ring are proposed. Extensive tests have confirmed the positive effect of such a cuff, but also demonstrated the functional limitations. Although the expansion behavior described could be reduced, but not yet completely suppressed from a certain diameter.

The object of the present invention is to solve the known from the prior art problem of expansion behavior of the piston ring.

The object is achieved in that the stop is formed by a rigid ring which is axially supported on the piston.

With the rigid ring, the expansion behavior of the piston ring can be significantly more precisely influenced and thus limited. The ring itself need not necessarily be closed over the entire circumference, but can also be formed from an arrangement of several ring sections because of the rigid construction. The support on the piston leads to a simplification of the geometry of the piston ring. Compared to the prior art, in which the piston ring still has a circumferential groove, the piston ring can be radially dimensioned slightly stronger or you can reduce the depth of the piston ring groove. Both options improve the service life of the piston-cylinder unit.

In one embodiment, the ring is made in one piece with the piston. The piston is usually made of a metallic material, so that a large radial support effect is possible. Another advantage is that no separate component for the function of the sleeve is necessary.

In order to use the invention even with axially short piston, the ring is part of a Kolbenringnut and limits the Kolbenringnut outside.

So that the piston is not deformed undefined in the Kolbenringnut, the piston ring has at least one stop bar, which cooperates with the ring. With regard to a simple and gentle for the piston ring assembly, the stop bar in the direction of a groove bottom of the piston ring groove on an insertion.

In a further embodiment, the ring has a holding region and a fixing region, wherein the fixing region is supported on an axial stop surface of the piston. Again, you can achieve the fixation of the ring outside the piston ring.

With regard to a simple and axially space-saving design, the stop surface for the ring is part of the groove profile of the piston ring groove.

Alternatively, one can also provide that the stop surface is executed outside of the piston ring groove. Then you can run the stop surface where z. B. radially inward sufficient space is available.

In a further advantageous embodiment, the stop surface part of a retaining of the His butt. A retaining groove offers the advantage of supporting the ring on both sides.

The axial fixing function of the ring can also be taken over by a separate retaining ring. The spatial configuration of the ring is simplified and you can make the optimal choice of material for the function of the radial support and for the axial fixation of the ring.

The invention will be explained in more detail with reference to the following description of the figures.

• 1 Gesamtdarstellung des Kolbenzylinder-Aggregats;
• 2 Ausschnitt aus 1;
• 3 Querschnitt durch den Kolbenring nach 2;
• 4 Draufsicht des Kolbens nach 2;
• 5 Variante mit separatem Ring;
• 6 Ring aus 5 als Einzelteil in einer Draufsicht;
• 7 Alternative zur 5;
• 8 Weitere Alternative zur 5.

It shows:

• 1 Overall view of the piston-cylinder unit;
• 2 Extract from 1 ;
• 3 Cross section through the piston ring after 2 ;
• 4 Top view of the piston behind 2 ;
• 5 Variant with separate ring;
• 6 Ring off 5 as an item in a top view;
• 7 Alternative to 5 ;
• 8th Other alternative to 5 ,

The 1 shows a possible embodiment of a piston-cylinder unit 1 according to the invention. In a cylinder 3 is a piston rod 5 axially displaceably mounted, at the first and axially spaced a second piston 7 ; 9 are arranged. In general, the arrangement of the two pistons 7 ; 9 rigid, however, the invention can also be used when one or both pistons 7 ; 9 in limits to the piston rod 5 are movably mounted.

The cylinder 3 includes a first length section 11 with a first diameter D1 , This length section 11 is in this embodiment of a piston rod guide 13 closed at the end. At the opposite end, a second length section closes 15 with a second diameter D2 at, wherein the second diameter D2 smaller than the first diameter D1 ,

Also the two pistons 7 ; 9 have a different nominal diameter. The first piston 7 is the larger diameter D1 of the first length section 11 of the cylinder 3 adapted and has a piston ring 17 on, the first working space 19 in the direction of the piston rod guide 13 for a pin-side second working space 21 between the first piston 7 and a floor 23 of the second length section 15 separates. The separation is not hermetically sealed, but via two mutually durchströmbare damping valves 25 ; 27 certainly. As ground 23 serves in this embodiment, a bottom valve with a mutual flow to an annular compensation chamber 29 between the cylinder 3 and an outer container tube 31 , The entire cylinder 3 is completely filled with a damping medium.

The second piston 9 is the second diameter D2 of the second length section 15 adapted and thus smaller than the first piston 7 ,

The 1 shows the piston-cylinder unit 1 in a defined construction situation in which the first piston 7 sealing in the first length section 11 slides and the damping valves 25 ; 27 in the first piston 7 generate a damping force. This is the second piston 9 also in the first length section 11 , but is lapped by the damping medium, as a piston ring 33 of the second piston 9 no sealing contact with the inner wall of the first length section 11 having. Consequently, the second piston 9 due to the open annular gap do not produce significant damping force.

If the second piston 9 at a corresponding stroke of the piston rod 5 in the second length section 15 dips, then lies the piston ring 33 on the inner wall of the second length section 15 so that then the second piston 9 with its damping valves generates a damping force that is related to the damping force of the first piston 7 added.

In this embodiment, the second length portion 15 from the cylinder 3 educated. However, it would also be possible that z. B. on the ground 23 one in the direction of the second piston 9 pointing open cap would be fastened, which has a smaller inner diameter D2 has as the first length section.

When entering the second length section 15 becomes the piston ring 33 of the second piston 9 slightly reduced in diameter so that the piston ring 33 under radial prestress on the inner wall of the second length section 15 is applied. For a smooth transition and entry of the second piston 9 or piston ring 33 in the second length section 15 , is between the first and the second length section 11 ; 15 of the cylinder 3 a conical transition 35 executed.

Apart from the piston ring 33 and the diameter may be the second piston 9 functionally the same as the first piston 7 , In the 2 the second piston is shown enlarged. It can be seen that a stop, by a closed ring 37 is formed and the himself axially on the piston 9 supports a radial expansion movement limited. The ring 37 is integral with the piston performs and part of a piston ring groove, wherein the ring 37 the piston ring groove 39 bounded on the outside. The ring 37 can also be formed from an arrangement of several ring sections, so that the term ring is not necessarily to be understood as a closed body.

In addition to a sealing surface 41 carrying body 43 has the piston ring 33 at least one stop bar 45 on that with the ring 37 on the piston 9 interacts. ( 3 ) In this particular embodiment, the piston ring 33 to a horizontal central axis 47 symmetrical executed. Consequently, the piston ring 33 optionally in the piston ring groove 39 be used, with a transverse slot 49 ( 4 ) facilitates assembly in the piston ring.

For easier assembly, the piston ring 33 in the direction of a groove bottom 51 the piston ring groove 39 an insertion bevel 53 on that at the stop bridge 45 is executed. This forms the stop bar 45 a snap connection with the piston ring groove 39 ,

In the execution after the 5 points to the piston 9 separate ring 37 a holding area 55 and a fixing area 57 on, with the fixation area 57 supported on an axial stop surface of the piston. In synopsis with the 6 It can be seen that the fixation area of a variety of tongues 61 is formed, which is radial in the direction of the piston 9 are angled and attached to the stop surface 59 support.

For a fixation of the ring 37 in two directions is the stop surface 59 outside the piston ring groove 39 executed and part of a retaining groove 63 of the piston 9 , The holding groove 63 can be dimensioned radially much smaller than the piston ring groove 39 , A comparison of the cross section of the piston rings in the 2 and 5 shows that the radial width of the piston ring in the 5 can be significantly narrower dimensioned, so that a wall thickness to a passageway 65 as part of a damping valve 67 can be bigger again.

During assembly, the piston ring 33 in the piston ring groove 39 used. After that, the ring becomes 37 over the piston 9 striped. In doing so, the piston ring must 33 by no means from the ring 37 be axially biased. Is the predetermined axial position of the ring 37 reached, then the fixing area 57 deformed radially inward and thus engages in the retaining groove 63 one. Over two groove side surfaces as stop surfaces 59 becomes a bilateral axial fixation of the ring 37 reached.

In the execution after 7 comes a simple closed ring 37 for use, which is also on a stop surface 59 of the piston 9 is supported, but part of the groove profile of the piston ring groove 39 is and thus practically a paragraph within the piston ring groove 39 represents. When assembling the ring 37 over the piston 9 threaded (left half section) and then slightly at one in the direction of the stop surface 59 pointing end deformed radially inward, for example by a rolling tool (right half section). Also in this embodiment, the piston ring 33 have a simple L-section and therefore only a radially flat piston ring groove 39 needed.

The variant after 8th shows a ring 37 that of a separate circlip 69 is held axially. The advantage is that the ring 37 itself does not have to be deformed at all. The axial holding function of the ring 37 takes over the separate circlip 69 , Again, an advantageous piston ring 33 be used with a simple L-section

LIST OF REFERENCE NUMBERS

1

Piston cylinder unit

3

cylinder

5

piston rod

7

first piston

9

second piston

11

first length section

13

Piston rod guide

15

second length section

17

piston ring

19

first working space

21

second workspace

23

ground

25

damping valve

27

damping valve

29

compensation space

31

container tube

33

piston ring

35

crossing

37

ring

39

piston ring

41

sealing surface

43

body

45

stop web

47

central axis

49

transverse slot

51

groove base

53

chamfer

55

holding area

57

fusing

59

stop surface

61

tongues

63

retaining groove

65

Passageway

67

damping valve

69

circlip

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102016202007 A1 [0002, 0005]

Claims (10)

Piston-cylinder unit (1), comprising a cylinder (3), in which a piston rod (5) on which at least one piston (9) is arranged, which has on an outer circumferential surface a radially elastic piston ring (33) in dependence the stroke position, starting from a first length section (11) with a larger diameter (D1), enters a second cylinder section (15) with a smaller diameter (D2), wherein an outer collar (37) has a stop for a widening movement of the piston ring (33). forms, characterized in that the stop (37) is formed by a closed ring which is axially supported on the piston (9). Piston cylinder unit after Claim 1 , characterized in that the ring 37 is integral with the piston 9 performs. Piston cylinder unit after Claim 2 , characterized in that the ring 37 is part of a piston ring groove 39 and the piston ring groove 39 bounded on the outside. Piston cylinder unit after Claim 1 , characterized in that the piston ring 33 has at least one stop web 45 which cooperates with the ring 37. Piston cylinder unit after Claim 4 , characterized in that the stop web 45 in the direction of a groove bottom 51 of the piston ring groove (39) has an insertion bevel (53). Piston cylinder unit after Claim 1 , characterized in that the ring 37 has a holding portion 55 and a fixing portion 57, wherein the fixing portion 57 is supported on an axial stop surface 59 of the piston 9. Piston cylinder unit after Claim 6 , characterized in that the stop surface 59 is part of the groove profile of the piston ring groove 39. Piston cylinder unit after Claim 7 , characterized in that the stop surface 59 is executed outside of the piston ring groove 39. Piston cylinder unit after Claim 8 , characterized in that the stop surface 59 is part of a retaining groove (63) of the piston. Piston cylinder unit after Claim 1 , characterized in that the ring (37) is held axially by a separate locking ring (69).

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