JP2001107918A - Variable stroke piston cylinder unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a piston cylinder unit capable of performing stepless adjustment of a stroke and not requiring a valve system costing much for a desired function. SOLUTION: A piston rod/cylinder 5; 3 which is a structural group to be operationally related with a position of at least one contact device of the both contact device 7; 27 is constituted free to steplessly displaced in the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable stroke piston / cylinder unit including a cylinder provided with a piston rod including a piston movably in an axial direction, wherein the piston rod is operatively connected to a contact device. The present invention relates to a piston-cylinder unit of the type in which a cylinder is operatively connected to a mating abutment device so that the action points of the abutment device and the mating abutment device can be adjusted.

[0002]

2. Description of the Related Art Actually, there are many uses of a piston / cylinder unit having a variable stroke. Basically, piston
Stroke can be realized by the valve configuration of the cylinder unit. In this regard, German Patent Publication No. 330154
No. 4 is mentioned. In the case of this type of piston-cylinder unit, the piston rod runs automatically to a predetermined stop point, and can then optionally overcome the closing valve in the second opening range and take a new stop position. . In general,
The function is performed reliably. In this case, there is a disadvantage that the required valve device increases the product price.

In the case of the piston-cylinder unit according to DE-A-402 22 145 or DE-A-3 826 862, the stroke adjustment is effected via abutment sleeves having abutment surfaces which are arranged in various axial directions. Can be implemented. In this case, the piston rod rotates together with the piston with respect to the cylinder of the piston-cylinder unit so that the piston comes into contact with a desired contact surface that defines a stroke.

In this solution, increasing the number of selectable set strokes necessarily reduces the size of the abutment surface, thus reducing the surface pressure between the piston and the abutment surface. The disadvantage is that intrinsic limits are rapidly exceeded.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a piston-cylinder unit which achieves a stepless adjustment of the stroke and which does not require an expensive valve arrangement for the desired function. .

[0006]

SUMMARY OF THE INVENTION According to the invention, this object is achieved in that the position of at least one abutment device of both abutment devices is set in the axial direction with respect to a piston rod / cylinder, which is a work-related structural group. It is solved by being able to displace continuously.

[0007] Advantageously, therefore, there is no need to provide a stepped abutment surface as described in the prior art. The stroke of the piston rod is determined solely from the positioning of the abutment device or the mating abutment device.

In view of the simplest possible operation of the stroke adjustment, a screw is inserted between the slidable abutment device and / or the piston rod / cylinder, which is a structural group operatively associated with the mating abutment device. A joint is provided. Stroke adjustment can be performed by simply rotating one of the two abutment devices or the other abutment device.

The abutment device is formed by a piston, taking into account the shortest possible axial construction of the piston-cylinder unit.

In gas springs, it is known to adapt the spring force characteristic curve of the gas spring to the load profile by using one or more compression springs. For this purpose, the piston rod has axially invariant support means which cooperate with the compression spring of the cylinder independently of the set stroke.

[0011] It is advantageous if the abutment device and the mating abutment device have form-fitting surfaces which are arranged with one another and can be engaged for stroke adjustment. The mating contact device and the contact device are in the cylinder. In order to avoid having to actuate the abutment device directly from the outside, the mating surfaces perform an anti-spin function when engaged in order to ensure axial displacement movement of the mating abutment device or the abutment device.

According to another embodiment, the cylinder has at least one bypass groove connecting the two working chambers separated by the piston depending on the piston position.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the following drawings.

The attached drawing shows a piston-cylinder unit 1 in the form of a gas spring. A piston rod 5 having a piston 7 is guided movably in the axial direction in the cylinder 3 whose end face is closed and filled with a high-pressure medium.
The piston 7 divides the cylinder into a piston rod side working chamber 9 and a working chamber 11 remote from the piston rod. The cylinder 3 and the piston rod end outside the cylinder include connecting bearings 13; 15 respectively. The connection bearing 13 is configured not to idle on the piston rod. The cylinder can be rotated with respect to the connection bearing 15. The connecting neck 17 on the cylinder side together with the securing clamp 19 acting in the axial direction of the cylinder serves for this rotation.

The piston rod 5 has a thread 21 on the part 5a which forms a threaded connection 25 with the internal thread of the piston 7. Thus, the axial position of the piston on the piston rod can be steplessly displaced in the part 5a. The position of the piston on the piston rod is
Further, the maximum stroke of the gas spring is determined. This is because the piston is also a contact device. The maximum setting stroke is the thread portion 5a and the screw connection portion 25.
Is calculated from the length difference.

The stroke of the piston in the withdrawal direction is limited by the mating contact device 27. In the case of a very simple structure, the mating contact device is formed from a reduced-diameter portion (for example, a groove) of the cylinder. Of course, it is also possible to use an end face of the piston rod guide 29 facing the piston or a separate disk secured in the axial direction.

When displacing the axial position of the piston,
Pull out the piston rod until the piston contacts the counterpart contact device. Shape-coupling surfaces 31; 33 arranged one above the other
Due to, for example, the provision of a pattern on the upper surface of the piston, a frictional or positive connection is created between the cylinder and the piston when the abutment device and the mating abutment device are engaged. When the piston is rotated relative to a circumferentially fixed piston rod, the piston is steplessly slid axially along the thread of the piston rod by the cylinder. For axial sliding, a form-fitting surface is not necessary, but facilitates the displacement of the piston.

In order to obtain the desired spring force characteristic curve, inside the cylinder, in the working chamber far from the piston rod,
Provision of a compression spring 35 can be selected. When a gas spring is used as a driving assist means for a valve of a vehicle, the stroke range in which the compression spring acts must be independent of the set maximum stroke. In order to satisfy this requirement, the piston rod has axially invariant support means 37. In this case, a disk is used. However, it is also conceivable to support the spring directly on the end face of the piston rod.

[Brief description of the drawings]

FIG. 1 is a drawing of a piston-cylinder unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston cylinder unit 3 Cylinder 5 Piston rod 7 Piston = Contact device 27 Counterpart contact device

Claims (6)

[Claims] 1. A variable stroke piston / cylinder unit including a cylinder provided with a piston rod including a piston movably in an axial direction, wherein the piston rod is operatively connected to a contact device, and the cylinder is connected to a mating contact device. Operatively associated with the contact device and the point of action of the abutment device and the mating abutment device, wherein the position of at least one abutment device of both abutment devices (7; 27) is operatively related. A piston-cylinder unit characterized in that it can be displaced continuously in the axial direction with respect to a group of piston rods / cylinders (5; 3). 2. A screw between a slidable abutment device (7) and / or a piston rod / cylinder (5; 3) operatively associated with a mating abutment device (27). 2. The piston-cylinder unit according to claim 1, wherein a connection is present. 3. The piston-cylinder unit according to claim 1, wherein the piston (7) forms an abutment device. 4. The piston rod (5) has axially invariant support means (37) which cooperates with the compression spring (35) of the cylinder (3) independently of the set stroke. The piston-cylinder unit of claim 1. 5. The abutment device (7) and the mating abutment device (27) have a form-coupling surface (31; 33) which are arranged with one another and can be engaged for stroke adjustment. Item 5. A piston-cylinder unit according to one of Items 1-4. 6. The cylinder according to claim 1, wherein the cylinder has at least one bypass groove connecting the two working chambers separated by the piston depending on the piston position. 6. The piston-cylinder unit according to one of claims 5.