SENSOR UNIT FOR FLUIDIC CYLINDER AND FLUIDIC CYLINDER

Abstract

A sensor unit for a fluidic cylinder having a base carrier on which a circumferential seal is formed, so that an interior of the fluidic cylinder is sealable, and having a position sensor for detecting a position of the piston, and having a pressure sensor for detecting a pressure in the interior.

Claims

1. A sensor unit for a fluidic cylinder having a base carrier on which a circumferential seal is formed, so that an interior of the fluidic cylinder is sealable, and having a position sensor for detecting a position of the piston, wherein the sensor unit has a pressure sensor for detecting a pressure in the interior.

2. The sensor unit as claimed in claim 1, wherein the position sensor and the pressure sensor are arranged in the interior.

3. The sensor unit as claimed in claim 1, wherein a pressure-variable region is formed on a surface of the base carrier in the interior, and in that a pickup for detecting a pressure-dependent shape change of the pressure-variable region is arranged, preferably outside the interior.

4. The sensor unit as claimed in claim 3, wherein the pressure-variable region is formed as a membrane, which is incorporated into the base carrier or is formed by thinning a wall region.

5. The sensor unit as claimed in claim 1, wherein the base carrier has means for fastening in a fluidic cylinder, for example, a circumferential groove, in which a grub screw can engage.

6. The sensor unit as claimed in claim 1, wherein the base carrier has an external thread, so that the base carrier can be screwed into an internal thread inside a fluidic cylinder, or in that the base carrier has a flange connection for connecting to a fluidic cylinder.

7. The sensor unit as claimed in claim 1, wherein the position sensor is designed to detect a relative movement between two components, in particular between piston and base carrier, in particular by ultrasound, magnetostriction, or induction.

8. The sensor unit as claimed in claim 1, wherein the base carrier has an evaluation unit, in which the sensor values are detected, outside the interior.

9. A method for determining an operating state of a fluidic cylinder, wherein a position of a piston is detected by means of a position sensor, in that a pressure in an interior of the fluidic cylinder is detected by means of a pressure sensor, and in that the operating state is determined from the detected position and the detected pressure.

10. The method as claimed in claim 9, wherein the operating state is used to determine a weight load and/or a ground support.

11. The method as claimed in claim 9, wherein an error state is recognized from the operating state, in that a position change is related to a pressure change, in particular wherein a position change without pressure change can indicate an error state.

12. A fluidic cylinder having a piston movable by fluid and having a position sensor for detecting the position of the piston, wherein the fluidic cylinder has a pressure sensor for detecting the pressure within the fluid.

13. The fluidic cylinder as claimed in claim 12 having a sensor unit as claimed in claim 1 and an evaluation unit, which is designed in particular to carry out the method as claimed in claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the figures:

[0032] FIG. 1: shows a sectional illustration of a fluidic cylinder having a magnetostrictive position sensor,

[0033] FIG. 2: shows a detail view of the sensor unit of FIG. 1,

[0034] FIG. 3: shows a sectional illustration of a fluidic cylinder having a cable pull position sensor,

[0035] FIG. 4: shows a detail view of the sensor unit of FIG. 3,

[0036] FIG. 5: shows a sectional illustration of a fluidic cylinder having an ultrasound position sensor,

[0037] FIG. 6: shows a detail view of the sensor unit of FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 shows a fluidic cylinder 1 having a cylinder tube 2, a cylinder base 3, a piston 4, and a cylinder head 5. Such fluidic cylinders 1 are known, for example, as hydraulic cylinders or pneumatic cylinders The piston 4 is arranged movably in the axial direction inside the cylinder tube 2 here.

[0039] Two fluid fittings 6 are arranged in the cylinder tube 2 in such a way that they permit a maximum movement of the piston 4, i.e., at the greatest possible axial distance. The cylinder tube 2 can have an arbitrarily shaped, preferably a circular cross section.

[0040] The cylinder tube 2 and the cylinder base 3 are integrally formed in the example. However, it is also possible that the cylinder tube 2 and the cylinder base 3 are two separate parts. The two parts could then be connected to one another, for example, by a thread or a flange connection.

[0041] The cylinder head 5 is designed in the example so that it can be placed on the cylinder tube 2 and a circumferential collar 7 radially overlaps the cylinder tube 2. A piston rod 8, which protrudes through the cylinder head 5, is connected to the piston 4.

[0042] Eyes 9 for installing the fluidic cylinder 1 are arranged in each case on the free end of the piston rod 8 and on the cylinder base 3.

[0043] A sensor unit 10 is arranged in the interior of the cylinder tube 2 between the cylinder base 3 and the fluid fitting 6 closest thereto, as shown in greater detail in FIG. 2. This sensor unit 10 has a base carrier 11, which has a circumference formed tailored to the internal circumference of the cylinder tube 2.

[0044] A circumferential seal 12, which delimits the interior 13 in the cylinder tube 2 in which the piston 4 and the fluid 14 are arranged, is arranged on the circumference of the base carrier 11. The seal 12 is formed in the example as an O-ring, which is inserted into a circumferential groove in the base carrier 11. However, the seal can also be formed in another manner.

[0045] An unpressurized and in particular fluid-free space 15 is formed on the other side of the seal 12. The base carrier 11 axially abuts a circumferential edge 16 in the unpressurized space 15, so that it cannot be axially displaced by the piston 4 due to an axial pressure application. An evaluation unit 21 is arranged on the base carrier 11 in the unpressurized space 15.

[0046] The sensor unit 10 has a position sensor 17 in the interior, which is designed in the example as a magnetostrictive position sensor. The position sensor 17 has a waveguide 18 in the example, which protrudes in the axial direction into a coaxial bore 19 in the piston rod 8. A permanent magnet 20 is arranged on the piston 4. The waveguide 18 protrudes through the base carrier 11 up to the evaluation unit 21, in which a transducer system (not shown) is formed for detecting and evaluating the structure-borne soundwaves in the waveguide 18.

[0047] Moreover, a pressure sensor 23 is arranged on the base carrier 11 in the interior 13. The pressure sensor 23 has a bore 24, which defines a measurement volume 25. The measurement volume 25 is terminated fluid-tight by a membrane 26 toward the interior 13. The membrane 26 is deformable in dependence on the pressure. A pressure pickup 27, which is electrically connected to the evaluation unit 21, is located on the base of the bore 24. The pressure pickup 27 can operate capacitively or resistively, for example. The advantage in this arrangement is that the pressure pickup 27 is not in contact with fluid and accordingly can be made simply and inexpensively. Simple conventional pressure sensors can also be used.

[0048] In the example, a bushing 22, via which the evaluation unit 21 can be electrically contacted, is arranged radially in the cylinder tube 2 in the unpressurized space 15.

[0049] If the cylinder tube 2 and the cylinder base 3 are formed in two parts, it is expedient if the two parts are connected to one another in the region of the unpressurized space 15, since then a pressure-tight seal is not necessary.

[0050] The embodiment shown of the pressure sensor 23 is only an example and is in no way limiting. Manifold other pressure sensors are known on the market, which can be fitted without significant adaptations into the base carrier 11.

[0051] In one advantageous embodiment, however, the membrane 26 is formed by a thinning of the base carrier 11. For this purpose, for example, a bore can be guided from the unpressurized space 15 up to the surface of the base carrier 11 located in the interior 13, until a desired membrane thickness is achieved.

[0052] FIG. 3 shows a fluidic cylinder 1, which is identical to FIG. 1 except for the position sensor 17. Therefore, only the differences from FIG. 1 are described hereinafter. The sensor unit 10 is shown in greater detail in FIG. 4.

[0053] The position sensor 17 is based here on a cable pull pickup. In the example, the position sensor 17 has a measurement cable 28, which is fastened on the piston 4, on the one hand, and can be wound on a cable drum 29, on the other hand. A rotation of the cable drum 29 is transferred in the example into a rotation of a sensor magnet 30. A position sensor 31, for example a Hall sensor, which detects a rotation of the sensor magnet 30, is arranged on the evaluation unit 21 opposite to the sensor magnet 30. The position sensor 31 can detect a position incrementally or in a coded manner.

[0054] FIG. 5 shows a fluidic cylinder 1, which is identical to FIG. 1 except for the position sensor 17. Therefore, only the differences from FIG. 1 are described hereinafter. The sensor unit 10 is shown in greater detail in FIG. 4.

[0055] The position sensor 17 is based here on ultrasound. For this purpose, the sensor unit 10 in the example has an ultrasonic transceiver unit 32, which is oriented in the axial direction. Ultrasonic waves 33 are thus emitted in the direction of the piston 4 and reflected thereon. The reflected ultrasonic waves 34 reach the transceiver unit 32 again. The position of the piston 4 can be determined from the runtime of the ultrasonic waves. The electrical connection to the evaluation unit 21 is established through the base carrier 11.

[0056] In addition to the position sensors shown here, other known position sensors, such as linear potentiometers, are also usable with the invention. The measurement principles shown can also be implemented in another manner. This also applies to the pressure sensors. The invention is therefore not restricted to one of the embodiments shown in any way.