DE102014216621B4 - Piston-cylinder unit and actuation unit - Google Patents

Abstract

Piston-cylinder unit for actuating a clutch in the drive train of a motor vehicle, with a piston (34) arranged in a cylinder (32) so as to be longitudinally displaceable along an actuation direction, the piston (34) having a primary piston (36) and a coaxial one in the primary piston (36 ) lying secondary piston (38), the secondary piston (38) being extendable from the primary piston (36) and having a first secondary piston side (50) and a second secondary piston side (52), the piston-cylinder unit having at least one elastic element (58). comprises for moving the piston (34) back into a starting position (B) and wherein the elastic element (58) is arranged between a spring holder (56) provided in the piston-cylinder unit and the second secondary piston side (52).

Description

The invention relates to a piston-cylinder unit and an actuation unit.

Pressure-controlled or force-controlled piston-cylinder units are known in the prior art, in which a cylinder is designed with an axially displaceable piston provided therein and causes pressurization by moving the piston. The piston is provided in the cylinder to define the volume of the pressure space in the piston. If the piston is moved, the volume of the pressure chamber is changed and pressure is applied by displacing fluid from the pressure chamber of the cylinder. However, the piston needs a certain amount of space in the cylinder so that the piston can be moved to a certain point. In this way, the installation space of the cylinder is predetermined.

From the DE 1 576 175 B a piston-cylinder unit according to the preamble of claim 1 is known. Further state of the art is in the DE 1 989 293 U disclosed.

The task is therefore to provide a compact piston-cylinder unit with good properties, in particular a piston-cylinder unit with a reduced installation space.

The object is achieved according to the invention by a piston-cylinder unit with the features of claim 1, by an actuating arrangement with the features of claim 10. Preferred embodiments of the invention are specified in the subclaims, each of which can represent an aspect of the invention individually or in combination .

The invention relates to a piston-cylinder unit for actuating a transmission and/or at least one clutch, in particular in the drive train of a motor vehicle, with a piston arranged in a cylinder so as to be longitudinally displaceable along an actuation direction, the piston having a primary piston and a secondary piston lying coaxially in the primary piston has, wherein the secondary piston can be extended from the primary piston.

By using a piston with a primary piston and a secondary piston, the required installation space of the piston can be reduced. By extending the secondary piston from the primary piston, the primary piston and the secondary piston can occupy the same installation space as a one-piece piston during actuation of the piston-cylinder unit. However, the installation space of the primary piston and the secondary piston is reduced compared to a one-piece piston due to the inclusion of the secondary piston in the primary piston in an initial position of the piston when the piston-cylinder unit is not actuated. Furthermore, by using a piston with a primary piston and a secondary piston, a larger area of space in a cylinder can be compressed than would be possible with a one-piece piston. Because a spatial area for the starting position of the piston can be made smaller, the saved installation space can be used to extend the travel of the piston, whereby a larger pressurization can be achieved. A return movement of the piston into a starting position after actuation of the piston-cylinder unit can take place, for example, by a pressure or force on an end face of the secondary piston, which causes the secondary piston to be pushed back into the primary piston, by an adjusting device and / or by an elastic element . In particular, the secondary piston can be arranged in the primary piston in such a way that the secondary piston cannot be completely moved out of the primary piston. This can ensure that the secondary piston can be pushed back into the primary piston.

The piston-cylinder unit can be actuated hydraulically or via a piston rod.

The term longitudinally displaceable describes that the piston is displaced along the axial direction of the cylinder.

The primary piston can enclose the secondary piston in such a way that the piston is designed to be telescopic. The primary piston and the secondary piston can have a cylindrical, prismatic or even conical shape. The secondary piston can be moved axially from the primary piston. In another embodiment, the primary piston can only partially enclose the secondary piston. For example, the primary piston can only half enclose the secondary piston when viewed in the radial direction of the cylinder.

A piston with a primary piston and a secondary piston can therefore provide a compact piston-cylinder unit that requires a smaller installation space. This can be particularly advantageous for piston-cylinder units with pistons with a displacement sensor or with components for axial actuation.

In a preferred embodiment, the cylinder has a first spatial area and a second spatial region, wherein the first spatial region has a larger cross-sectional area pointing in the actuation direction than the second spatial region, wherein a first primary piston side of the first primary piston facing the first spatial region has a larger cross-sectional area than a second primary piston side of the primary piston facing the second spatial region, and one to the first The first secondary piston side of the secondary piston facing the spatial region has a smaller cross-sectional area than a second secondary piston side of the secondary piston facing the second spatial region, the cross-sectional area of the second primary piston side being smaller or equal to the cross-sectional area of the second secondary piston side. Preferably, the primary piston can have a plate-shaped shape on its first primary piston side, and a cylindrical shape can be arranged on a side of the plate-shaped shape facing the second spatial region, which has a smaller cross-sectional area than the second spatial region. Furthermore, the first secondary piston side of the secondary piston can have a smaller cross-sectional area than the surrounding primary piston part of the primary piston. Furthermore, a cylindrical shape can extend from the first primary piston side to the second primary piston side. On the second secondary piston side of the secondary piston, the secondary piston can have a plate-shaped shape that has a larger cross-sectional area than the cylindrical shape of the second primary piston end. The cross-sectional area of the second secondary piston side can be smaller or equal to the cross-sectional area of the second spatial region. Furthermore, a transition from the first spatial area to the second spatial area can be arranged in the piston-cylinder unit. In particular, the transition can be arranged in such a way that, for example, the second spatial region can have a distance for the maximum travel of the secondary piston.

The piston-cylinder unit includes at least one elastic element for moving the piston back to a starting position. In this way it can be ensured that the primary piston and the secondary piston can be moved back into a starting position so that the piston-cylinder unit can be available again for the next actuation.

It is preferred that a first elastic element arranged between the first primary piston side and the second secondary piston side and/or a second elastic element arranged between the second secondary piston side and a side of the cylinder opposite the second secondary piston side is provided. By arranging the first elastic element between the first primary piston side of the primary piston and the second secondary piston side of the secondary piston, wherein the second secondary piston side can have a plate-shaped shape and a larger cross-sectional area than the second primary piston side of the primary piston, and wherein the first elastic element is on the outside of the Primary piston is arranged, it can be ensured that after completion of an actuation of the piston-cylinder unit, the secondary piston is retracted into the primary piston and the primary piston can be returned to a starting position. When the piston-cylinder unit is actuated, the first elastic element can lengthen as soon as the primary piston has reached an end position and no longer moves as a result, so that the secondary piston can be extended from the primary piston. As soon as there is no pressure or no force to actuate the piston-cylinder unit, the first elastic element can contract until a balance of forces is formed, so that the secondary piston is retracted into the primary piston by the first elastic element and in this way the primary piston in is returned to its original position. In an arrangement between the second secondary piston side of the secondary piston and the side of the cylinder opposite the second secondary piston side of the secondary piston, the second elastic element can be compressed by the second secondary piston side of the secondary piston when the piston-cylinder unit is actuated. As soon as the pressure or force decreases, the second elastic element can push the secondary piston back into the primary piston and thereby return the piston to its starting position. The second elastic element can be arranged between an inner wall and a plate in the second spatial region and the second secondary piston side of the secondary piston comes into contact with the plate. In this way it can be ensured that a pressure or force evenly distributed over the surface of the plate acts on the second elastic element, so that the second elastic element cannot tilt when the piston-cylinder unit is actuated. Furthermore, a combination of the two elastic elements can also be used.

In a preferred embodiment, the first elastic element is a tension spring and/or the second elastic element is a compression spring. The tension spring and/or compression spring can be designed in such a way that, for example, they cannot cause natural vibrations or instability of the piston during operation of the piston-cylinder unit.

Preferably, the piston-cylinder unit has a spring holder at a transition from the first spatial region into the second spatial region of the cylinder, the spring holder having a first spring holder side facing the first spatial region and a second spring holder side facing the second spatial region, the first elastic element extending from the second spring holder side extends to the second secondary piston side. By using a spring holder, a shorter first elastic element can be used. Furthermore, in this way, the starting position of the primary piston and the secondary piston can be defined such that when the piston is in a starting position, the first elastic element is arranged between the spring holder and the secondary piston and is contracted. Furthermore, the spring holder can serve as a stop for the primary piston when the plate-shaped shape abuts on the first primary piston side of the primary piston on the first spring holder side of the spring holder. Furthermore, the cylinder can also have a transition at the transition between the first spatial region and the second spatial region, so that the spring holder can have a smaller cross-sectional area than the first primary piston side of the primary piston and at the same time a larger cross-sectional area than the second secondary piston side of the secondary piston.

It is preferred that the first primary piston side, the first secondary piston side and the second secondary piston side each have a seal on their circumference. In this way, the piston-cylinder unit can also be used in a transmission and/or a clutch of a motor vehicle that requires a seal.

In a preferred embodiment, a cross-sectional area of the first secondary piston side is preferably less than or equal to half of a maximum travel of the secondary piston, particularly preferably less than or equal to a third of a maximum travel of the secondary piston, in particular less than or equal to a fifth of a maximum travel of the secondary piston. In this way, the secondary piston can be prevented from tipping over, so that the secondary piston can compress the second spatial region of the cylinder with its second secondary piston side. In particular, the connection can apply that the larger the first secondary piston side of the secondary piston is in comparison to the maximum travel of the secondary piston, the more stable the secondary piston can compress the second spatial region. This connection can also apply to the design of the first elastic element. The first elastic element can be designed in such a way that, for example, it cannot cause any natural vibration and/or instability of the piston during operation. Furthermore, in a piston-cylinder unit with seals, the pressure gradient of the seals can be taken into account in order to ensure tightness. The pressure gradient can depend on the cross-sectional areas of the primary piston and the secondary piston.

In particular, a design of the surfaces of the first primary piston side and the first secondary piston side can be designed such that the primary piston and the secondary piston can move stably during the actuation of the piston-cylinder unit.

The invention further relates to an actuation arrangement comprising at least one piston-cylinder unit described above for the controlled actuation of a transmission and/or at least one clutch, in particular in the drive train of a motor vehicle.

The installation space can thus be reduced by an actuation arrangement with a piston-cylinder unit described above. This can be particularly advantageous for actuation arrangements with piston-cylinder units with pistons with displacement sensors or with components for axial actuation.

• - Bewegen des Kolbens in dem Zylinder mit Hilfe eines Drucks oder einer Kraft,
• - Stoppen des Primärkolbens an einem Anschlag,
• - Bewegen des Sekundärkolbens bis der Sekundärkolben eine Endposition im Zylinders erreicht hat;
• - automatisches Zurückbewegen des Kolbens in eine Ausgangsposition sobald der Druck oder die Kraft nachlässt.

The invention further relates to a method for actuating a piston-cylinder unit described above, comprising the following steps:

• - moving the piston in the cylinder with the help of a pressure or a force,
• - stopping the primary piston at a stop,
• - Moving the secondary piston until the secondary piston has reached an end position in the cylinder;
• - Automatic movement of the piston back to a starting position as soon as the pressure or force decreases.

A compact piston-cylinder unit can thus be used by the method for actuating a piston with a primary piston and a secondary piston which is included in the primary piston, whereby the installation space can be reduced. This can be particularly advantageous for piston-cylinder units with pistons with a displacement sensor or with components for axial actuation.

• 1 a einen Ausschnitt einer Kolben-Zylindereinheit in einer Ausgangsposition gemäß dem Stand der Technik;
• 1 b einen Ausschnitt einer Kolben-Zylindereinheit in einer Ausgangsposition gemäß eines Ausführungsbeispiels;
• 2a einen Ausschnitt einer Kolben-Zylindereinheit bei Betätigung gemäß dem Stand der Technik; und
• 2b einen Ausschnitt einer Kolben-Zylindereinheit bei Betätigung gemäß eines Ausführungsbeispiels.

The invention is explained below with reference to the accompanying drawings using preferred exemplary embodiments explained, whereby the features presented below can represent an aspect of the invention both individually and in combination. Show it:

• 1 a a section of a piston-cylinder unit in a starting position according to the prior art;
• 1 b a section of a piston-cylinder unit in a starting position according to an exemplary embodiment;
• 2a a section of a piston-cylinder unit during operation according to the prior art; and
• 2 B a section of a piston-cylinder unit when actuated according to an exemplary embodiment.

1a shows a section of a piston-cylinder unit 10 according to the prior art. The piston-cylinder unit 10 includes a cylinder 12 and a piston 14. The piston 14 has a first side 16 and a second side 18. Furthermore, the cylinder 12 is divided into a first spatial area 20 and a second spatial area 22. It is in 1 It can be seen that the first spatial region 20 has a larger cross-sectional area than the second spatial region 22. The piston 14 has a plate-shaped shape on its first side 16, which merges into a cylindrical shape. The cylindrical shape extends from the plate-shaped shape to the second side 18 of the piston 14. Furthermore, the piston-cylinder unit 10 has seals 24. The dashed line represents the starting position A of the piston 14.

1 b shows a section of a piston-cylinder unit 30 according to one embodiment in comparison to the piston-cylinder unit 10 1a . The piston-cylinder unit 30 includes a cylinder 32 and a piston 34. The piston 34 has a primary piston 36 and a secondary piston 38. Furthermore, the cylinder 32 is divided into a first spatial area 40 and a second spatial area 42. It is in 2 It can be seen that the first spatial region 40 has a larger cross-sectional area than the second spatial region 42. The primary piston 36 has a plate-shaped shape on its first primary piston side 44, which merges into a cylindrical shape. The cylindrical shape extends from the plate-shaped shape to the second primary piston side 46 of the primary piston 36. The primary piston 36 encloses the coaxially arranged secondary piston 38. The primary piston 36 includes a receiving opening 48 in which the secondary piston 38 is arranged. From a first secondary piston side 50 of the secondary piston 38, the secondary piston 38 extends in a cylindrical shape from the first primary piston side 44 to the second primary piston side 46. The secondary piston 38 merges into a plate-shaped shape on the second primary piston side 46. The plate-shaped shape is the second secondary piston side 52 of the secondary piston 38. At the transition between the first spatial region 40 and the second spatial region 42 there is a step in which the spring holder 56 is arranged. The spring holder 56 serves to accommodate a first elastic element 58. The first elastic element 58 is a tension spring and is arranged between the second secondary piston side 52 and the spring holder 56. Furthermore, the piston-cylinder unit 30 has seals 60. The dashed line represents the starting position B of the piston 34. The starting position B corresponds to the starting position A in 1a . Furthermore, in 1b a dashed box C is shown. The dashed box C shows the installation space that can be saved if instead of a piston 14 1a a piston 34 1b is used.

2a shows an actuation of the piston cylinder unit 10 1a . In 2a All the same components have the same reference numbers as in 1a . The actuation of the piston-cylinder unit 10 is indicated by the arrows, which act on the first side 16 of the piston 14. It can be seen that the piston 14 has reached its end position D. The dashed line on the second side 18 of the piston 14 indicates the end position D.

The 2 B shows an actuation of the piston-cylinder unit 30 1b . In 2 B All the same components have the same reference numbers as in 1b . The actuation of the piston-cylinder unit 30 is indicated by the arrows, which act on the first primary piston side 44 of the primary piston 36 and on the first secondary piston side 50 of the secondary piston 38. It can be seen that the secondary piston 38 is moved further as soon as the primary piston 36 has reached an end position at a stop, so that the second secondary piston side 52 of the secondary piston 38 compresses the second spatial region 42 until the piston 34 has reached its end position E. The dashed line on the second side 52 of the secondary piston 38 indicates the end position E. The end position E on the line corresponds to the end position D in 2a . Furthermore, it can be seen that a cross-sectional area of the first secondary piston side 50 is less than a third of a maximum travel of the secondary piston 38. In this way, the secondary piston 38 is prevented from tipping over. The secondary piston 38 cannot be completely moved out of the primary piston 36. Furthermore, the first elastic element 58 is stretched by the operation of the piston-cylinder unit 30. As soon as the operation of the piston-cylinder unit 30 is completed, the first elastic element tightens ment 58 together and in this way brings the piston 34 back to the starting position B.

The method for actuating the piston-cylinder unit 30 works as follows: When the piston-cylinder unit 30 is actuated, for example, the piston-cylinder unit 30 is connected to a pedal, not shown, via a hydrostatic line and when the pedal is pressed, a pressure is applied via the hydrostatic If the line is transferred to the first primary piston side 44 and the first secondary piston side 50, the piston 34 is moved from the first spatial region 40 of the cylinder 32 into the second spatial region 42 of the cylinder 32. When the primary piston 36 reaches an end position at the transition between the first spatial region 40 and the second spatial region 42, the movement of the primary piston 36 stops. The existing pressure causes the secondary piston 38 to be extended and moved further in the direction of the second spatial region 42 until the secondary piston 38 is End position E in the second spatial area 42 of the cylinder 32 has reached. As soon as the pressure decreases, for example by releasing the pedal, the piston 34 is moved back to its starting position B with the aid of the first elastic element 58.

Reference symbol list

10

Piston-cylinder unit

12

cylinder

14

Pistons

16

first page

18

second page

20

first spatial area of the cylinder

22

second spatial area of the cylinder

24

poetry

30

Piston-cylinder unit

32

cylinder

34

Pistons

36

Primary piston

38

Secondary piston

40

first spatial area of the cylinder

42

second spatial area of the cylinder

44

first primary piston side

46

second primary piston side

48

Recording opening

50

first secondary piston side

52

second secondary piston side

56

Pen holder

58

elastic element

60

poetry

A

Starting position of the piston 14

b

Starting position of the piston 34

C

freed up space

D

End position of the piston 14

E

End position of the piston 34

Claims (10)

Piston-cylinder unit for actuating a clutch in the drive train of a motor vehicle, with a piston (34) arranged in a cylinder (32) so as to be longitudinally displaceable along an actuation direction, the piston (34) having a primary piston (36) and a coaxial one in the primary piston (36 ) lying secondary piston (38), the secondary piston (38) being extendable from the primary piston (36) and having a first secondary piston side (50) and a second secondary piston side (52), the piston-cylinder unit having at least one elastic element (58). comprises for moving the piston (34) back into a starting position (B) and wherein the elastic element (58) is arranged between a spring holder (56) provided in the piston-cylinder unit and the second secondary piston side (52). Piston-cylinder unit Claim 1 , wherein the cylinder (32) has a first spatial region (40) and a second spatial region (42), the first spatial region (40) having a larger cross-sectional area pointing in the actuation direction than the second spatial region (42), one corresponding to the first spatial region ( 40) facing the first primary piston side (44) of the first primary piston (36) has a larger cross-sectional area than a second primary piston side (46) of the primary piston (36) facing the second spatial region (42), and the first secondary piston side (40) facing the first spatial region (40) 50) of the secondary piston (38) has a smaller cross-sectional area than the second secondary piston side (52) of the secondary piston (38) facing the second spatial region (42), the cross-sectional area of the second primary piston side (46) being less than or equal to the cross-sectional area of the second secondary piston side (52 ) is. Piston-cylinder unit Claim 2 , wherein a first elastic element (58) arranged between the first primary piston side (44) and the second secondary piston side (52) and / or a second between the second secondary piston side (52) and one of the second secondary piston side (52) opposite side of the cylinder (32) arranged elastic element (58) is provided. Piston-cylinder unit Claim 3 , wherein the first elastic element (58) is a tension spring and / or the second elastic element is a compression spring. Piston-cylinder unit according to one of the Claims 1 until 4 , wherein the spring holder (56) is arranged at a transition from the first spatial region (40) into the second spatial region (42) of the cylinder (32), wherein the spring holder (56) has a first spring holder side facing the first spatial region (40) and a the second spring holder side facing the second spatial region (42), the first elastic element (58) extending from the second spring holder side to the second secondary piston side (52). Piston-cylinder unit according to one of the preceding claims, wherein the first primary piston side (44), the first secondary piston side (50) and the second secondary piston side (52) each have a seal (60) on their circumference. Piston-cylinder unit according to one of the preceding claims, wherein a cross-sectional area of the first secondary piston side (50) is less than or equal to half of a maximum travel of the secondary piston (38). Piston-cylinder unit Claim 7 , characterized in that the cross-sectional area of the first secondary piston side (50) is less than or equal to one third of a maximum travel of the secondary piston (38). Piston-cylinder unit Claim 8 , characterized in that the cross-sectional area of the first secondary piston side (50) is less than or equal to one fifth of a maximum travel of the secondary piston (38). Actuating arrangement comprising at least one piston-cylinder unit according to one of Claims 1 until 9 for the controlled actuation of a transmission and/or at least one clutch, in particular in the drive train of a motor vehicle.

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