DE102016207102A1 - Linear force limiter and use of such a linear force limiter for testing of test objects - Google Patents

Abstract

Linearkraftbegrenzer, comprising a cylinder having a pressure space for a pressure medium, wherein a volume of the pressure chamber is variable by a movable piston in the cylinder and wherein the pressure chamber is connected via a arranged in a first line pressure relief valve with a reservoir for the pressure medium, so that the pressure medium is displaceable over the first line from the pressure chamber into the reservoir when a release pressure of the pressure relief valve is exceeded. Furthermore, a use of a linear force limiter according to the invention for testing friction clutches for motor vehicles is proposed.

Description

The present invention relates to a Linearkraftbegrenzer, which serves in particular the limitation of forces acting on a test object. Linear force limiters are used, for example, in connection with linear drives, by means of which, for example, machine elements and / or plant parts are translational or otherwise movable.

Such linear drives are used for example on test benches for determining or for simulating characteristic curves of friction clutches for motor vehicles. To avoid overloads or damage to the friction clutches Linearkraftbegrenzer on the type of springs, such as disc springs in series, are used on such test benches. However, despite the known linear force limiters, damage to the friction clutches can occur.

The object of the invention is therefore to solve the problems described with reference to the prior art at least partially and in particular to provide a linear force limiter, with the overloads or damage to test objects are reliably avoidable. In addition, a use of such a Linearkraftbegrenzers should be specified, can be prevented by the damage to friction clutches on test benches.

This object is achieved with a linear force limiter and a use of the linear force limiter according to the features of the independent claims. Further advantageous embodiments of the invention are specified in the dependent formulated claims. It should be noted that the features listed individually in the dependent claims can be combined in any technologically meaningful manner and define further embodiments of the invention. In addition, the features specified in the claims are specified and explained in more detail in the description, wherein further preferred embodiments of the invention are shown.

The linear force limiter proposed here is, in particular, a hydraulic linear force limiter. The linear force limiter has a cylinder with a pressure chamber for a pressure medium, which is in particular at least partially made of metal and / or plastic. In particular, the pressure medium is a substantially incompressible medium, such as a hydraulic fluid. The pressure chamber is at least partially bounded by the cylinder and a piston, wherein a volume of the pressure chamber is variable by a movement of the piston. For this purpose, the piston is at least partially movable in the cylinder along a travel of the piston. The piston is also at least partially made of metal and / or plastic. Furthermore, the piston is movable in particular parallel to a longitudinal axis of the linear force limiter.

By a relative movement between the cylinder and the piston, a pressure of the pressure medium in the pressure chamber can be generated or varied. On a test bench, the linear force limiter is arranged in particular in a force flow between a drive and a test object. The piston is acted upon in particular by the drive, for example, an (electric) linear drive, with a force which is transferable via the piston, the pressure medium in the pressure chamber and the cylinder to a test object. In this case, the test object generates a counter force, in particular on the cylinder of the linear force limiter.

To prevent overloading of the test object, the pressure chamber is connected via a arranged in a first line pressure relief valve with a reservoir for the pressure medium. The pressure relief valve protects against an inadmissible pressure increase of the pressure medium in the pressure chamber and thereby prevents damage to the test object. If the forces acting on the linear force limiter are too high or too high in the pressure medium in the pressure chamber, the overpressure valve opens so that the pressure medium flows out of the pressure chamber and thus the piston and / or the cylinder can yield. For this purpose, the pressure relief valve on a release pressure, when exceeded, the pressure relief valve releases the first line between the pressure chamber and the reservoir. As a result, the pressure medium can flow from the pressure chamber via the first line into the reservoir, as a result of which the piston can be moved further into the pressure chamber so that the forces acting on the piston and / or cylinder are reduced. In other words, this means that when the triggering pressure is exceeded, an (axial) length of the linear force limiter can be reduced or the linear force limiter yields. As soon as the pressure of the pressure medium in the pressure chamber drops to a value below the triggering pressure, the pressure relief valve closes the first line again. The first line is in particular a channel of the cylinder and / or a hydraulic line, for example in the manner of a (flexible) hose. The reservoir may be formed both in the cylinder and outside, that is separate from the cylinder. That through the reservoir Recordable volume of the pressure medium corresponds at least to the volume of the pressure medium, which is displaceable by the piston from the pressure chamber at a maximum displacement of the piston along the travel. Due to the proposed linear force limiter, linear drives used on test benches can have greater braking distances on reaching the maximum permissible loads on the tested objects, without the test objects being overloaded. Furthermore, the pressure medium acts dampening against a solution with springs.

In addition, it is advantageous if the trigger pressure of the pressure relief valve is variably adjustable. As a result, appropriate triggering pressures can be set after the test object.

Furthermore, it is advantageous if the reservoir is connected to the pressure chamber via a check valve arranged in a second line. The check valve is a component which allows a displacement or flow of the pressure medium in the second line only from the reservoir in the direction of the pressure chamber, but not from the pressure chamber in the direction of the reservoir. In this way, the pressure medium from the reservoir flow back into the pressure chamber when the linear force limiter relieved and / or the piston is moved out of the pressure chamber, for example by a return spring. The second line is also a channel of the cylinder and / or a hydraulic line, for example in the manner of a (flexible) hose.

Moreover, it is advantageous if the check valve prevents displacement of the pressure medium via the second line from the pressure chamber into the reservoir.

Preferably, the pressure medium via the second line from the reservoir to the pressure chamber is displaceable when a first pressure of the pressure medium in the reservoir is greater than a return pressure of the pressure relief valve. The return pressure of the pressure relief valve is, in particular, that pressure which a closing spring exerts on a closing element of the pressure relief valve. After the return pressure is exceeded, the pressure relief valve opens so that the pressure medium can flow back from the reservoir via the second line into the pressure chamber.

Furthermore, it is advantageous if the pressure medium via the second line from the reservoir to the pressure chamber is displaceable when a first pressure of the pressure medium in the reservoir is greater than a second pressure of the pressure medium in the pressure chamber.

In addition, it is advantageous if the pressure medium via the second line from the reservoir to the pressure chamber is displaceable, when a movement of the piston increases the volume of the pressure chamber.

Furthermore, it is advantageous if the volume of the pressure chamber can be increased as a result of a movement of the piston by a return spring. The return spring is arranged in particular at least partially in the pressure chamber and can move the piston out of the pressure chamber when the linear force limiter is relieved of load.

Furthermore, it is advantageous if exceeding the triggering pressure is detectable by means of a sensor. The sensor can in particular detect a movement of the piston in the pressure chamber. The sensor can be connected to a controller that deactivates a drive when the trigger pressure is exceeded.

A further aspect of the invention also proposes a use of a linear force limiter according to the invention for testing test objects, in which the linear force limiter is arranged in a force flow between a drive and the test object. The test object is in particular a friction clutch, such as a single-disc dry clutch, for a motor vehicle. Such friction clutches serve in particular to interrupt a torque flow from a drive motor to a drive train of the motor vehicle. The test is carried out in particular on a test stand for the determination and / or simulation of characteristic curves of such friction clutches. By means of the linear force limiter, the test object is protected against overloading by the drive, in particular linear drive.

The invention and the technical environment will be explained in more detail with reference to the figure. It should be noted that the figure shows a particularly preferred variant of the invention, but this is not limited thereto. It shows by way of example and schematically:

1 : a test stand with a linear force limiter according to the invention.

The 1 schematically shows a test bench 16 for testing a test object 21 , To check the test object 21 is the test object 21 by a drive 15 the test bench 16 loadable with a force. At the test object 21 this is a friction clutch driven by the drive 15 in which this is a linear drive, can be engaged and / or disengaged. To when checking the test object 21 an overload of the test object 21 to prevent is in a power flow between the drive 15 and the test object 21 a linear force limiter 1 arranged. The linear force limiter 1 has a cylinder 2 with a pressure chamber 3 in which a piston is parallel to a longitudinal axis 19 along a travel path 20 in the pressure chamber 3 is hineinverfahrbar, so through the piston 5 a volume of the pressure chamber 3 in the cylinder 2 is changeable. The piston 5 is by means of a seal 12 opposite the cylinder 2 sealed so that no (shown here schematically) printing medium 4 between the cylinder 2 and the piston 5 from the linear force limiter 1 can escape. The drive 15 conducts at a first axial end 17 of the linear force limiter 1 a force F on the piston 5 one that's over the print medium in 4 the pressure chamber 3 at a second axial end 18 of the linear force limiter 1 to the test object 21 is transmitted. The test object 21 thus causes at the second axial end 18 of the linear force limiter 1 one on the print medium 4 acting counterforce. When the pressure of the print medium 4 a trigger pressure of a pressure relief valve 7 exceeds, the pressure relief valve opens 7 so the print medium 4 from the pressure chamber 3 via a first line 6 in a reservoir 8th for the print medium 4 is displaceable. This is the piston 5 against the force of a return spring 11 along the travel path 20 in the pressure chamber 3 hineinbewegbar, so that the test object 21 is protected against overloading. The movement of the piston 5 is through a sensor 14 detectable, so that a force on the test object 21 can be deactivated by a controller, not shown here. The release force of the pressure relief valve 7 is here to a desired value by a user of the linear force limiter 1 adjustable. Decreases the pressure of the pressure medium 4 in the pressure chamber 3 again below the release pressure of the pressure relief valve 7 , the piston becomes 5 through the return spring 11 reset so that the volume of the pressure chamber 3 increased. This opens a check valve 10 so the print medium 4 through a second line 9 from the reservoir 8th in the pressure chamber 3 can flow back. The check valve 10 has a closing spring 13 on which is a closing element 22 on a seat 23 the check valve 10 suppressed.

The present invention is characterized in particular by the fact that test objects can be protected particularly reliably against overloads.

LIST OF REFERENCE NUMBERS

1

 Linearkraftbegrenzer

2

 cylinder

3

 pressure chamber

4

 print media

5

 piston

6

 first line

7

 Pressure relief valve

8th

 reservoir

9

 second line

10

 check valve

11

 return spring

12

 poetry

13

 closing spring

14

 sensor

15

 drive

16

 test bench

17

 first axial end

18

 second axial end

19

 longitudinal axis

20

 Travel Range

21

 test article

22

 closing element

23

 Seat

Claims (10)

Linear force limiter ( 1 ), comprising a cylinder ( 2 ) with a pressure chamber ( 3 ) for a print medium ( 4 ), wherein a volume of the pressure chamber ( 3 ) by at least partially in the cylinder ( 2 ) movable piston ( 5 ) is variable and wherein the pressure chamber ( 3 ) via a in a first line ( 6 ) arranged pressure relief valve ( 7 ) with a reservoir ( 8th ) is connected to the pressure medium so that the pressure medium is exceeded when a release pressure of the pressure relief valve ( 7 ) over the first line ( 6 ) from the pressure chamber ( 3 ) in the reservoir ( 8th ) is displaceable. Linear force limiter ( 1 ) according to claim 1, wherein the release pressure of the pressure relief valve ( 7 ) is variably adjustable. Linear force limiter ( 1 ) according to one of the preceding claims, wherein the reservoir ( 8th ) via a in a second line ( 9 ) arranged check valve ( 10 ) with the pressure chamber ( 3 ) connected is. Linear force limiter ( 1 ) according to claim 3, wherein the check valve ( 10 ) a displacement of the pressure medium via the second line ( 9 ) from the pressure chamber ( 3 ) in the reservoir ( 8th ) prevented. Linear force limiter ( 1 ) according to any one of the preceding claims, wherein the pressure medium via the second line ( 9 ) from the reservoir ( 8th ) to the pressure chamber ( 3 ) is displaceable when a first pressure of the pressure medium in the reservoir ( 8th ) is greater than a return pressure of the pressure relief valve ( 7 ). Linear force limiter ( 1 ) according to one of the preceding claims, wherein the pressure medium via the second line ( 9 ) from the reservoir ( 8th ) to the pressure chamber ( 3 ) is displaceable when a first pressure of the pressure medium in the reservoir ( 8th ) is greater than a second pressure of the pressure medium in the pressure chamber ( 3 ). Linear force limiter ( 1 ) according to one of the preceding claims, wherein the pressure medium via the second line ( 9 ) from the reservoir ( 8th ) to the pressure chamber ( 3 ) is displaceable when a movement of the piston ( 5 ) the volume of the pressure chamber ( 3 ). Linear force limiter ( 1 ) according to one of the preceding claims, wherein the volume of the pressure chamber ( 3 ) as a result of movement of the piston ( 5 ) by a return spring ( 11 ) is enlargeable. Linear force limiter ( 1 ) according to claim 8, wherein exceeding the triggering pressure by means of a sensor ( 14 ) is detectable. Use of a linear force limiter ( 1 ) according to one of the preceding claims for testing test objects ( 21 ), the linear force limiter ( 1 ) into a power flow between a drive ( 15 ) and the test object ( 21 ) is arranged.

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