EP0695879A1 - Power cylinder - Google Patents

Power cylinder Download PDF

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Publication number
EP0695879A1
EP0695879A1 EP95102202A EP95102202A EP0695879A1 EP 0695879 A1 EP0695879 A1 EP 0695879A1 EP 95102202 A EP95102202 A EP 95102202A EP 95102202 A EP95102202 A EP 95102202A EP 0695879 A1 EP0695879 A1 EP 0695879A1
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EP
European Patent Office
Prior art keywords
strip
working cylinder
piston rod
cylinder according
magnetic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP95102202A
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German (de)
French (fr)
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EP0695879B1 (en
Inventor
Johannes Volzer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Festo SE and Co KG
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Festo SE and Co KG
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Publication date
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Publication of EP0695879A1 publication Critical patent/EP0695879A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/28—Means for indicating the position, e.g. end of stroke
    • F15B15/2815—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT
    • F15B15/2861—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT using magnetic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/28—Means for indicating the position, e.g. end of stroke
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/28—Means for indicating the position, e.g. end of stroke
    • F15B15/2815—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT
    • F15B15/2846—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT using detection of markings, e.g. markings on the piston rod

Definitions

  • the invention relates to a working cylinder, with a housing in which there is an axially movable piston, which is connected to a piston rod protruding from the housing on at least one end face, which has at least one axially extending and flat shape on the outer circumference, in which a longitudinal groove is provided which receives a measuring strip which can be scanned by a sensor device fixed to the housing.
  • a working cylinder of this type emerges from the German utility model G 92 09 980.7. It is equipped with a position measuring system which enables the position of the piston or the piston rod to be determined. It includes, for example, a measuring section designed as a resistance strip, which is accommodated in a longitudinal groove of the piston rod and by one as a sensor device acting sliding contact is applied and tapped.
  • the measuring strip is a magnetic strip which has a plurality of magnetically magnetized magnet zones which are arranged one after the other in the axial direction and which can be scanned contactlessly by the sensor device, and that the magnetic strip is secured by a cover strip fixed to the piston rod and made of a material permeable to a magnetic field is covered, the outer surface of which faces away from the magnetic strip forms at least part of the flat section of the surface section of the piston rod.
  • the interaction of the sensor device with the magnetic strip with alternating poles enables extremely reliable and exact position determination even at relatively high piston speeds.
  • the sensor device expediently comprises Several semiconductor sensors, for example so-called Hall sensors, which are attached to the housing of the working cylinder in such a way that they are penetrated by the differently polarized magnetic fields of the magnetic strip when the piston rod is moving and supply usable signals from an evaluation electronics.
  • the contactless “scanning” prevents any wear on the parts contributing to the position determination.
  • the cover strip additionally arranged above the magnetic strip has the further effect that the magnetic strip is protected from damage even when a housing-side end wall and a guide and / or sealing arrangement provided there are penetrated, and at the same time an optimal sealing of the passage area between the end wall and the piston rod is realized can, whose quality is in no way inferior to that of sealing conventional piston rods.
  • the cover strip forms at least one component of the flat section of the piston rod which has the longitudinal groove and is therefore a component of the outer surface of the piston rod, which can cooperate with the guide and / or sealing arrangement mentioned in a manner known per se.
  • the flat section has a flat section which allows the piston rod to be secured in a cost-effective manner so that the magnetic strip is always in the correct position with respect to the sensor device arranged on the housing. Since the cover strip can be designed to withstand high mechanical loads, even high torques acting on the piston rod can be compensated for without impairing the accuracy of the position determination.
  • a relatively simple design of the working cylinder provides that the cover strip is at least partially and preferably completely embedded in the longitudinal groove of the flat or straight surface section. By the realized here positive connection between the cover strip and the piston rod, the cover strip is securely fixed.
  • Spring steel has proven to be a particularly suitable material for the cover strip, for example the steel of the specification 13 X RM 19 supplied by Sandvik.
  • a particularly advantageous fastening measure for the magnetic strip and the cover strip has been found to be an adhesive connection in which the parts are connected to the piston rod by means of a high-strength adhesive.
  • a further advantageous embodiment provides for the sensor device to be equipped with a sensor head containing the corresponding sensors, which can be integrated into the end wall of the housing which is generally formed by a cover.
  • Signal evaluation electronics can be integrated directly into the sensor head, signal amplification and processing can take place directly in the sensor head, which has the advantage of very good signal stability.
  • the working cylinder comprises a housing 1 in which a piston 2 is arranged to be axially movable.
  • the piston 2 tightly separates two working spaces 3, 4, into each of which a housing channel 5 opens, which in a manner known per se serves to supply and remove a fluid driving the piston, such as compressed air.
  • the two end faces of the housing 1 are closed by end walls 6, 7, which are designed as removable covers.
  • a piston rod 8 is attached, which extends axially and which passes through an end wall 6 coaxially to the outside.
  • the end wall 6 is a bearing wall which supports and guides the piston rod 8 in the transverse direction.
  • a guide device 13 which is fixed to the housing and is a sliding guide for the piston rod 8, is arranged in the passage opening 12 of the end wall 6 through which the piston rod 2 passes. It is also located in the passage opening 12 a sealing device 14, for example formed in a structural unit with the guide device 13, which is fixed on the one hand to the end wall 6 and on the other hand is in dynamic sealing contact with the piston rod 8 all around. It prevents fluidic pressure medium from the neighboring working space 3 from escaping through the passage opening 12.
  • the guiding and / or sealing device 13, 14 could at least partially also be arranged outside the passage opening 12.
  • a fastening part 15 is provided at the end of the piston rod 8 lying outside the housing 1. It enables the attachment of any component to be moved by the working cylinder.
  • the working cylinder is equipped with a position determining device, generally designated by reference number 16. It is a position measuring system that allows the distance traveled by the piston rod 8 or its current position to be determined. This enables path-dependent control and actuation of the working cylinder.
  • the piston rod 8 has at least one axially extending and flat shape surface section 17 on its outer circumference.
  • This flat, straight surface section 17 extends over at least a large part of the length of the piston rod 8 and is at least arranged and designed such that it is independent of the respective axial position of the piston 2 or the piston rod 8 is always radially opposite with a portion of its length to a sensor device 18 fixed on the housing 1.
  • Said sensor device 18 is attached in the exemplary embodiment to the end wall 6 functioning as a bearing cover.
  • the sensor device 18 works together with a magnetic strip 22 which is accommodated in an axially extending longitudinal groove 23 which is introduced into the flat section 17 having a flat shape.
  • the sensor device 18 practically runs along the magnetic strip 22 and is actuated by the latter, so that sensor signals result which are processed in a connected processing device 24 in the desired manner.
  • the sensor signals can be processed to control valves, which in turn control the actuation of the working cylinder as a function of the current stroke position.
  • the tape-shaped magnetic strip 22 is a plastic-bound part, it is a plastic strip with magnetizable components or particles, in principle comparable to the magnetic tapes of tape or video devices that serve as sound carriers. However, it expediently has a thickness such that it has a certain intrinsic stability. In the exemplary embodiment, it is fastened in a sandwich-like manner on a carrier strip 25, which preferably consists of non-magnetic material and is a steel strip in the exemplary embodiment. The consisting of the magnetic strip 22 and the carrier strip 25 The strip unit is inserted with the carrier strip 25 ahead and at the bottom into the longitudinal groove 23, its flat underside 26 facing the flat groove base 27. The groove width corresponds to the strip width as well as the groove length corresponds to the strip length.
  • the strip unit is immovably centered in the longitudinal groove 23 in the strip plane.
  • the attachment in the longitudinal groove 23 is advantageously carried out in the context of a high-strength adhesive connection, which ensures that the magnetic strip 22 always remains unchanged with respect to the piston rod 8 even in the event of strong vibrations.
  • the magnetic strip 22 is divided into a plurality of magnetized magnetic zones 28, 28 ′ which follow one another in the longitudinal direction of the strip, the magnetization of the individual magnetic zones having an alternating pole.
  • the magnetic field alignment of two magnetic field zones 28, 28 'adjacent in the longitudinal direction of the strip thus deviates from one another in that the north and south poles are interchanged.
  • the individual magnetic field zones 28, 28 ' are axially polarized, ie their north poles (N) and south poles (S) are aligned in the longitudinal direction of the strip and thus in the axial direction of the piston rod 8.
  • the polarization is preferably such that successive magnetic field zones 28, 28 ′ face each other with polarization of the same name.
  • the sensor device 18 is fixed on the end wall 6 in such a way that it lies opposite the upper side 32 of the magnetic strip 22 opposite the groove base 27 at a distance perpendicular to the plane of the strip. During a stroke movement of the piston 2, the magnetic strip 22 is thus moved past the sensor device 18 in the longitudinal direction, the latter successively coming into the influence of the magnetic fields caused by the individual magnetic field zones 28, 28 '. These magnetic fields penetrate the sensor device 18, which in the exemplary embodiment contains two magnetic field-sensitive semiconductor sensors, not shown, for example so-called Hall sensors or field plate sensors.
  • the two semiconductor sensors of the sensor device 18 which are generally offset by 90 °, provide two sine signals offset by 90 °, which, depending on the fine interpolation division of a downstream evaluation electronics, finely interpolate to the desired resolution - for example 0.01 mm can be.
  • the signals obtained thus provide information about the current position of the piston rod 8 and each component connected to it.
  • the magnetic strip 22 is scanned by the sensor device 18 without contact, the components of the position determining device 16 are exposed to practically no mechanical wear and ensure a long service life of the working cylinder.
  • the thickness of the strip unit composed of the magnetic strip 22 and the carrier strip 25 is less than the depth of the longitudinal groove 23 receiving it.
  • the magnetic strip 22 therefore sits in the longitudinal groove 23 at a distance from the flat section 17.
  • the remaining depth section of the longitudinal groove 23 is taken up by a cover strip 33 which is fitted into the longitudinal groove 23 and rests on the magnetic strip 22.
  • the arrangement is preferably made such that the cover strip 33 is received completely recessed in the longitudinal groove 23, as can be seen from the exemplary embodiments.
  • the longitudinal groove is just filled by the cover strip 33, the magnetic strip 22 and the carrier strip 25, so that the outer surface 34 of the cover strip 33 opposite the magnetic strip 22 merges flush into the two surface portions 35 of the piston rod 8 adjoining the longitudinal groove 23 along the longitudinal side.
  • the outer surface 34 then, together with the two surface portions 35 flanking it, forms the flat portion 17 having the flat shape.
  • the cover strip ultimately gives the piston rod 8 the shape which it would have had in the case of a conventional, grooveless design.
  • the outer surface 34 and the adjacent surface portions 35 lie in a common plane that forms the surface section 17.
  • the cover strip 33 is firmly anchored in the longitudinal groove 23.
  • it is advantageously glued into the longitudinal groove 23.
  • Their layout corresponds to that of the longitudinal groove 23, so that the latter is completely closed by the cover strip 33.
  • the cover strip 33 ensures an optimal seal in the penetration area between the piston rod 8 and the end wall 6 while protecting the sensitive magnetic strip 22 from damage. Since the outer surface 34 of the sealing strip 33 forms at least a part of the flat section 17, it is in contact with the guide and / or sealing arrangement 13, 14 in the same way as the other outer surface regions of the piston rod 8 when passing through it is possible to form the transition area between the cover strip 33 and the adjacent surface portions 35 of the piston rod 8 in such a way that there is no space or depression, the pressure medium contained in the working space 3 has no overflow path in order to flow past the sealing device 14. According to the example, this is achieved by also introducing adhesive into the mentioned transition regions 36, so that the transition regions 36 are filled with adhesive up to the outer surface and a smooth transition is established between the adjoining outer surface regions.
  • the cover strip 33 So that the effectiveness of the position determining device 16 is not impaired by the cover strip 33, it is advisable to produce the cover strip from non-magnetizable material.
  • it consists of spring steel with low permeability, which is also extremely wear-resistant and corrosion-resistant.
  • Such a metal is sold, for example, by the Sandvik company under the designation 13 X RM 19.
  • the cover strip 33 for the magnetic fields of the magnetic strip 22 permeable which can thus act on the sensor device 18 in the desired manner.
  • the piston rod 8 has been ground in the exemplary embodiment after the cover strip 33 has been glued to the surface section 17. As a result, all unevenness levels out.
  • the sensor device 18 is formed by an extremely compact sensor head 37, which is excellently suited for integration into the housing 1 and, above all, as in the present case, into the end wall 6 penetrated by the piston rod 8.
  • the end wall 6 has a radially extending recess 38 in the region of the outlet opening 12, which is open on the one hand radially inwards to the piston rod 8 and on the other hand radially outwards to an outer surface 42 of the end wall 6.
  • the cartridge-like sensor head 37 for example, is inserted into this recess 38, so that it maintains the required distance from the cover strip 33 which it does not touch and which lies between it and the magnetic strip 22.
  • a dashboard evaluation electronics 43 is integrated, which evaluates the signals of the semiconductor sensors in the required manner.
  • the evaluation electronics are arranged externally and belong, for example, to the processing device 24.
  • a square rod as the piston rod 8, one of its four flat outer surfaces 45 forming the flat portion 17 having the flat shape.
  • the square section of the piston rod 8 preferably having a square cross section.
  • a further measuring strip in particular designed as a magnetic strip, could also be integrated in the area of at least one of the further flat outer surface sections 45 of the piston rod 8, which also cooperates with a sensor device. This would enable a coupled overall evaluation or an independent multiple evaluation.
  • piston rod cross-sections that have at least one flat surface section would also be conceivable. Examples include triangular bars or round bars with a flattened section.
  • the integration of a displacement measuring system with a material measure made of an alternating-pole magnetization lies Magnetic strips and an associated sensor head in a fluid-operated anti-rotation working cylinder.
  • the cross-section of the piston rod has at least one rectilinear partial flank, into which a longitudinal groove is embedded, which receives the magnetic strip fixed by means of a high-strength adhesive.
  • the non-magnetic cover strip which is permeable to magnetic fields, ensures a tribologically compatible covering of the magnetic strip due to its rustproof, low-permeability properties and is securely fixed by a high-strength adhesive.
  • a Sony PL 20 read head could be used as the sensor head of the present arrangement.
  • the lattice constant for dividing the magnetic strip into individual magnetic field zones is, for example, 5 mm. If necessary, more than two semiconductor sensors can be used for the scanning.
  • the magnetic strip and the cover strip are expediently glued into the longitudinal groove 23 one after the other and independently of one another.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Actuator (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Abstract

The piston rod (8) has a flat section (17) extending in the axial direction with a longitudinal groove in which a magnetic strip (22) can be sensed by a stationary detector (18). The strip is divided lengthwise into a number of zones magnetised alternately in opposite directions. The strip is covered by a layer (33) of magnetically permeable material which guarantees an optimal seal between the piston rod and the cylinder end (6) as well as protecting the magnetic strip from damage.

Description

Die Erfindung betrifft einen Arbeitszylinder, mit einem Gehäuse, in dem sich ein axial bewegbarer Kolben befindet, der mit einer an wenigstens einer Stirnseite aus dem Gehäuse herausragenden Kolbenstange verbunden ist, die am Außenumfang wenigstens einen sich axial erstreckenden und Flachgestalt aufweisenden Flächenabschnitt aufweist, in dem eine Längsnut vorgesehen ist, die einen durch eine gehäusefeste Sensoreinrichtung abtastbaren Meßstreifen aufnimmt.The invention relates to a working cylinder, with a housing in which there is an axially movable piston, which is connected to a piston rod protruding from the housing on at least one end face, which has at least one axially extending and flat shape on the outer circumference, in which a longitudinal groove is provided which receives a measuring strip which can be scanned by a sensor device fixed to the housing.

Ein Arbeitszylinder dieser Art geht aus dem deutschen Gebrauchsmuster G 92 09 980.7 hervor. Er ist mit einem Wegmeßsystem ausgestattet, das eine Positionsbestimmung des Kolbens oder der Kolbenstange ermöglicht. Es umfaßt beispielsweise eine als Widerstandsstreifen ausgebildete Meßstrecke, die in einer Längsnut der Kolbenstange untergebracht ist und von einem als Sensoreinrichtung fungierenden Schleifkontakt beaufschlagt und abgegriffen wird.A working cylinder of this type emerges from the German utility model G 92 09 980.7. It is equipped with a position measuring system which enables the position of the piston or the piston rod to be determined. It includes, for example, a measuring section designed as a resistance strip, which is accommodated in a longitudinal groove of the piston rod and by one as a sensor device acting sliding contact is applied and tapped.

Durch das Entlangschleifen des Schleifkontaktes auf dem Widerstandsstreifen tritt ein allmählicher Verschleiß auf. Dieser beeinträchtigt die Genauigkeit der Positionsbestimmung und kann zu Undichtigkeiten im Durchtrittsbereich zwischen der Kolbenstange und der zugeordneten stirnseitigen Abschlußwand des Gehäuses führen.Gradual wear occurs due to the grinding contact being rubbed along the resistance strip. This affects the accuracy of the position determination and can lead to leaks in the passage area between the piston rod and the associated end wall of the housing.

Es ist daher die Aufgabe der vorliegenden Erfindung, einen Arbeitszylinder zu schaffen, der bei reduziertem Verschleiß eine fortwährend exakte Positionsbestimmung der Kolbenstange und/oder des Kolbens ermöglicht.It is therefore the object of the present invention to provide a working cylinder which, with reduced wear, enables the piston rod and / or the piston to be continuously and precisely determined in position.

Zur Lösung der Aufgabe ist vorgesehen, daß der Meßstreifen ein Magnetstreifen ist, der mehrere in Axialrichtung aufeinanderfolgend angeordnete, wechselpolig magnetisierte Magnetzonen aufweist, die durch die Sensoreinrichtung berührungslos abtastbar sind, und daß der Magnetstreifen durch eine an der Kolbenstange festgelegte, aus magnetfelddurchlässigem Material bestehende Deckleiste abgedeckt ist, deren vom Magnetstreifen abgewandte Außenfläche zumindest einen Teil des Flachgestalt aufweisenden Flächenabschnittes der Kolbenstange bildet.To achieve the object, it is provided that the measuring strip is a magnetic strip which has a plurality of magnetically magnetized magnet zones which are arranged one after the other in the axial direction and which can be scanned contactlessly by the sensor device, and that the magnetic strip is secured by a cover strip fixed to the piston rod and made of a material permeable to a magnetic field is covered, the outer surface of which faces away from the magnetic strip forms at least part of the flat section of the surface section of the piston rod.

Durch das Zusammenwirken der Sensoreinrichtung mit dem wechselpolig magnetisierten Magnetstreifen ist auch bei relativ hohen Kolbengeschwindigkeiten eine äußerst zuverlässige und exakte Positionsbestimmung möglich. Die Sensoreinrichtung umfaßt zweckmäßigerweise mehrere Halbleitersensoren, zum Beispiel sogenannte Hall-Sensoren, die derart am Gehäuse des Arbeitszylinders angebracht werden, daß sie bei sich bewegender Kolbenstange von den unterschiedlich polarisierten Magnetfeldern des Magnetstreifens durchsetzt werden und von einer Auswerteelektronik verwertbare Signale liefern. Durch die berührungslose "Abtastung" wird jeglicher Verschleiß an den zur Positionsbestimmung beitragenden Teilen verhindert. Die zusätzlich über dem Magnetstreifen angeordnete Deckleiste hat den weiteren Effekt, daß der Magnetstreifen selbst beim Durchsetzen einer gehäuseseitigen Abschlußwand und einer dort vorgesehenen Führungs- und/oder Dichtungsanordnung vor Beschädigungen geschützt ist und zugleich eine optimale Abdichtung des Durchgangsbereiches zwischen der Abschlußwand und der Kolbenstange realisiert werden kann, deren Qualität derjenigen einer Abdichtung konventioneller Kolbenstangen in nichts nachsteht. Die Deckleiste bildet wenigstens einen Bestandteil des die Längsnut aufweisenden, Flachgestalt besitzenden Flächenabschnittes der Kolbenstange und ist somit Bestandteil der Außenfläche der Kolbenstange, die mit der erwähnten Führungs- und/oder Dichtungsanordnung in an sich bekannter Weise zusammenarbeiten kann. Dabei besteht die vorteilhafte Möglichkeit, die Deckleiste aus einem den tribologischen Anforderungen entsprechenden Material herzustellen, das hinsichtlich Verschleißfestigkeit und Korrosionsverhalten dem Grundmaterial der Kolbenstange gleichwertig ist. Letztlich liegt eine äußerlich von einer konventionellen Kolbenstange kaum zu unterscheidende Kolbenstange vor, in der der mechanisch sehr empfindliche Magnetstreifen allseits umschlossen geschützt untergebracht ist. Indem die Deckleiste aus magnetfelddurchlässigem Material besteht, beispielsweise aus Metall mit relativ geringer Permeablität, werden die Magnetfelder der einzelnen Magnetzonen durch die Abdeckung nicht oder nur unwesentlich beeinträchtigt.The interaction of the sensor device with the magnetic strip with alternating poles enables extremely reliable and exact position determination even at relatively high piston speeds. The sensor device expediently comprises Several semiconductor sensors, for example so-called Hall sensors, which are attached to the housing of the working cylinder in such a way that they are penetrated by the differently polarized magnetic fields of the magnetic strip when the piston rod is moving and supply usable signals from an evaluation electronics. The contactless "scanning" prevents any wear on the parts contributing to the position determination. The cover strip additionally arranged above the magnetic strip has the further effect that the magnetic strip is protected from damage even when a housing-side end wall and a guide and / or sealing arrangement provided there are penetrated, and at the same time an optimal sealing of the passage area between the end wall and the piston rod is realized can, whose quality is in no way inferior to that of sealing conventional piston rods. The cover strip forms at least one component of the flat section of the piston rod which has the longitudinal groove and is therefore a component of the outer surface of the piston rod, which can cooperate with the guide and / or sealing arrangement mentioned in a manner known per se. There is the advantageous possibility of producing the cover strip from a material which corresponds to the tribological requirements and which is equivalent to the base material of the piston rod with regard to wear resistance and corrosion behavior. Ultimately, there is a piston rod that is hardly distinguishable from the outside of a conventional piston rod, in which the mechanically very sensitive magnetic strip is enclosed and protected on all sides. By the cover strip made of material permeable to magnetic fields, for example made of metal with relatively low permeability, the magnetic fields of the individual magnetic zones are not or only insignificantly affected by the cover.

Die Integration des Magnetstreifens in die Kolbenstange ermöglicht es, kolbenstangenseitig vorgeschriebene Nornabmessungen unverändert beizubehalten. Funktionsbeschränkungen gegenüber Arbeitszylindern konventioneller Art sind nicht zu erwarten, so daß auch die üblichen Lebensdauerkennwerte trotz der Verwendung eines Wegmeßsystems gegenüber Standardausführungen keinerlei Beschränkungen unterliegt. Entsprechendes gilt für die Belastbarkeit des Arbeitszylinders.The integration of the magnetic strip into the piston rod makes it possible to keep the mandrel dimensions prescribed on the piston rod side unchanged. Functional restrictions compared to working cylinders of a conventional type are not to be expected, so that the usual service life values are not subject to any restrictions despite the use of a position measuring system compared to standard designs. The same applies to the load capacity of the working cylinder.

Durch den Flachgestalt aufweisenden Flächenabschnitt läßt sich überdies eine kostengünstige Verdrehsicherung der Kolbenstange erzielen, so daß der Magnetstreifen stets die richtige Lage mit Bezug zu der gehäuseseitig angeordneten Sensoreinrichtung einnimmt. Da die Deckleiste mechanisch hoch belastbar ausgeführt werden kann, lassen sich auch hohe auf die Kolbenstange einwirkende Drehmomente ohne Beeinträchtigung der Genauigkeit der Positionsbestimmung kompensieren.In addition, the flat section has a flat section which allows the piston rod to be secured in a cost-effective manner so that the magnetic strip is always in the correct position with respect to the sensor device arranged on the housing. Since the cover strip can be designed to withstand high mechanical loads, even high torques acting on the piston rod can be compensated for without impairing the accuracy of the position determination.

Vorteilhafte Weiterbildungen der Erfindung sind in den Unteransprüchen aufgeführt.Advantageous developments of the invention are listed in the subclaims.

Eine relativ einfach herzustellende Bauform des Arbeitszylinders sieht vor, daß die Deckleiste zumindest teilweise und vorzugsweise vollständig in die Längsnut des ebenen bzw. geradlinigen Flächenabschnittes eingelassen ist. Durch die hierbei verwirklichte formschlüssige Verbindung zwischen der Deckleiste und der Kolbenstange wird die Deckleiste sicher fixiert.A relatively simple design of the working cylinder provides that the cover strip is at least partially and preferably completely embedded in the longitudinal groove of the flat or straight surface section. By the realized here positive connection between the cover strip and the piston rod, the cover strip is securely fixed.

Als besonders geeignetes Material für die Deckleiste hat sich Federstahl herausgestellt, beispielsweise der von der Firma Sandvik gelieferte Stahl der Spezifikation 13 X RM 19.Spring steel has proven to be a particularly suitable material for the cover strip, for example the steel of the specification 13 X RM 19 supplied by Sandvik.

Als besonders vorteilhafte Befestigungsmaßnahme für den Magnetstreifen und die Deckleiste hat sich eine Klebeverbindung herausgestellt, bei der die Teile mittels eines hochfesten Klebers mit der Kolbenstange verbunden werden.A particularly advantageous fastening measure for the magnetic strip and the cover strip has been found to be an adhesive connection in which the parts are connected to the piston rod by means of a high-strength adhesive.

Eine weitere vorteilhafte Ausgestaltung sieht vor, die Sensoreinrichtung mit einem die entsprechenden Sensoren enthaltenden Sensorkopf auszustatten, der in die in der Regel von einem Deckel gebildete Abschlußwand des Gehäuses integriert werden kann. In den Sensorkopf kann unmittelbar eine Signalauswerteelektronik integriert sein, wobei unmittelbar in dem Sensorkopf eine Signalverstärkung und -aufbereitung stattfinden kann, was den Vorteil einer sehr guten Signalstabilität hat.A further advantageous embodiment provides for the sensor device to be equipped with a sensor head containing the corresponding sensors, which can be integrated into the end wall of the housing which is generally formed by a cover. Signal evaluation electronics can be integrated directly into the sensor head, signal amplification and processing can take place directly in the sensor head, which has the advantage of very good signal stability.

Nachfolgend wird die Erfindung anhand der beiliegenden Zeichnung näher erläutert. In dieser zeigen:

Figur 1
eine erste Bauform des erfindungsgemäßen Arbeitszylinders in dem von der Kolbenstange durchsetzten Gehäusebereich,
Figur 2
den in Figur 1 gekennzeichneten Ausschnitt II der Kolbenstange in vergrößerter Darstellung, wobei die Deckleiste zur Sichtbarmachung des Magnetstreifens nicht über ihre gesamte Länge gezeichnet ist, und
Figur 3
einen Längsschnitt durch den Arbeitszylinder aus Figur 1 gemäß Schnittlinie III-III.
The invention is explained in more detail below with reference to the accompanying drawing. In this show:
Figure 1
a first design of the working cylinder according to the invention in the housing area penetrated by the piston rod,
Figure 2
the section II marked in Figure 1 of the piston rod in an enlarged view, the cover strip for the visualization of the magnetic strip is not drawn over its entire length, and
Figure 3
a longitudinal section through the working cylinder of Figure 1 along section line III-III.

Der beispielsgemäße Arbeitszylinder umfaßt ein Gehäuse 1, in dem ein Kolben 2 axial beweglich angeordnet ist. Der Kolben 2 trennt zwei Arbeitsräume 3, 4 dicht voneinander ab, in die jeweils ein Gehäusekanal 5 mündet, der in an sich bekannter Weise der Zufuhr und Abfuhr eines den Kolben antreibenden Fluides wie Druckluft dient.The working cylinder according to the example comprises a housing 1 in which a piston 2 is arranged to be axially movable. The piston 2 tightly separates two working spaces 3, 4, into each of which a housing channel 5 opens, which in a manner known per se serves to supply and remove a fluid driving the piston, such as compressed air.

Die beiden Stirnseiten des Gehäuses 1 sind durch Abschlußwände 6, 7 verschlossen, die als abnehmbare Deckel ausgebildet sind.The two end faces of the housing 1 are closed by end walls 6, 7, which are designed as removable covers.

An dem Kolben 2 ist eine Kolbenstange 8 befestigt, die sich axial erstreckt, und die eine Abschlußwand 6 koaxial zur Außenseite hin durchsetzt.On the piston 2, a piston rod 8 is attached, which extends axially and which passes through an end wall 6 coaxially to the outside.

Die Abschlußwand 6 ist eine Lagerwand, die die Kolbenstange 8 in Querrichtung abstützt und führt. Zu diesem Zweck ist in der von der Kolbenstange 2 durchsetzten Durchtrittsöffnung 12 der Abschlußwand 6 eine sich gehäusefest abstützende Führungseinrichtung 13 angeordnet, die eine Gleitführung für die Kolbenstange 8 darstellt. Ferner befindet sich in der Durchtrittsöffnung 12 eine beispielsgemäß in Baueinheit mit der Führungseinrichtung 13 ausgebildete Dichtungseinrichtung 14, die einerseits an der Abschlußwand 6 festgelegt und andererseits mit der Kolbenstange 8 ringsum in dynamischem Dichtkontakt steht. Sie verhindert, daß fluidisches Druckmittel aus dem benachbarten Arbeitsraum 3 über die Durchtrittsöffnung 12 nach außen dringt.The end wall 6 is a bearing wall which supports and guides the piston rod 8 in the transverse direction. For this purpose, a guide device 13, which is fixed to the housing and is a sliding guide for the piston rod 8, is arranged in the passage opening 12 of the end wall 6 through which the piston rod 2 passes. It is also located in the passage opening 12 a sealing device 14, for example formed in a structural unit with the guide device 13, which is fixed on the one hand to the end wall 6 and on the other hand is in dynamic sealing contact with the piston rod 8 all around. It prevents fluidic pressure medium from the neighboring working space 3 from escaping through the passage opening 12.

Die Führungs- und/oder Dichtungseinrichtung 13, 14 könnte zumindest teilweise auch außerhalb der Durchtrittsöffnung 12 angeordnet sein.The guiding and / or sealing device 13, 14 could at least partially also be arranged outside the passage opening 12.

Am außerhalb des Gehäuses 1 liegenden Ende der Kolbenstange 8 ist eine Befestigungspartie 15 vorgesehen. Sie ermöglicht das Anbringen eines beliebigen durch den Arbeitszylinder zu bewegenden Bauteils.At the end of the piston rod 8 lying outside the housing 1, a fastening part 15 is provided. It enables the attachment of any component to be moved by the working cylinder.

Der Arbeitszylinder ist mit einer allgemein mit Bezugsziffer 16 bezeichneten Positionsbestimmungseinrichtung ausgestattet. Bei ihr handelt es sich um ein Wegmeßsystem, das es erlaubt, den zurückgelegten Weg der Kolbenstange 8 bzw. deren momentane Position zu bestimmen. Dies ermöglicht eine wegabhängige Ansteuerung und Betätigung des Arbeitszylinders.The working cylinder is equipped with a position determining device, generally designated by reference number 16. It is a position measuring system that allows the distance traveled by the piston rod 8 or its current position to be determined. This enables path-dependent control and actuation of the working cylinder.

Vorzugsweise verfügt die Kolbenstange 8 an ihrem Außenumfang über wenigstens einen sich axial erstreckenden und Flachgestalt aufweisenden Flächenabschnitt 17. Dieser ebene, geradlinige Flächenabschnitt 17 erstreckt sich über zumindest einen Großteil der Länge der Kolbenstange 8 und ist zumindest derart angeordnet und ausgebildet, daß er unabhängig von der jeweiligen Axialposition des Kolbens 2 bzw. der Kolbenstange 8 stets mit einem Abschnitt seiner Länge einer am Gehäuse 1 festgelegten Sensoreinrichtung 18 radial gegenüberliegt. Besagte Sensoreinrichtung 18 ist beim Ausführungsbeispiel an der als Lagerdeckel fungierenden Abschlußwand 6 angebracht.Preferably, the piston rod 8 has at least one axially extending and flat shape surface section 17 on its outer circumference. This flat, straight surface section 17 extends over at least a large part of the length of the piston rod 8 and is at least arranged and designed such that it is independent of the respective axial position of the piston 2 or the piston rod 8 is always radially opposite with a portion of its length to a sensor device 18 fixed on the housing 1. Said sensor device 18 is attached in the exemplary embodiment to the end wall 6 functioning as a bearing cover.

Die Sensoreinrichtung 18 arbeitet zur Positionsbestimmung mit einem Magnetstreifen 22 zusammen, der in einer in den Flachgestalt aufweisenden Flächenabschnitt 17 eingebrachten, sich axial erstreckenden Längsnut 23 untergebracht ist. Bei einer Axialbewegung der Kolbenstange 8 läuft die Sensoreinrichtung 18 praktisch an dem Magnetstreifen 22 entlang und wird durch diesen betätigt, so daß sich Sensorsignale ergeben, die in einer angeschlossenen Verarbeitungseinrichtung 24 in gewünschter Weise verarbeitet werden. Beispielsweise können die Sensorsignale zur Ansteuerung von Ventilen aufbereitet werden, die ihrerseits die Betätigung des Arbeitszylinders in Abhängigkeit von der momentanen Hubstellung steuern.For determining the position, the sensor device 18 works together with a magnetic strip 22 which is accommodated in an axially extending longitudinal groove 23 which is introduced into the flat section 17 having a flat shape. When the piston rod 8 moves axially, the sensor device 18 practically runs along the magnetic strip 22 and is actuated by the latter, so that sensor signals result which are processed in a connected processing device 24 in the desired manner. For example, the sensor signals can be processed to control valves, which in turn control the actuation of the working cylinder as a function of the current stroke position.

Der bandförmige Magnetstreifen 22 ist ein kunststoffgebundenes Teil, es handelt sich um einen Kunststoffstreifen mit magnetisierbaren Bestandteilen oder Partikeln, prinzipiell vergleichbar mit den als Tonträgern dienenden Magnetbändern von Tonband- oder Videogeräten. Er besitzt allerdings zweckmäßigerweise eine derartige Dicke, daß er eine gewisse Eigenstabilität aufweist. Er ist beim Ausführungsbeispiel sandwichartig auf einem Trägerstreifen 25 befestigt, der vorzugsweise aus unmagnetischem Material besteht und beim Ausführungsbeispiel ein Stahlband ist. Die aus dem Magnetstreifen 22 und dem Trägerstreifen 25 bestehende Streifeneinheit ist, mit dem Trägerstreifen 25 voraus und untenliegend in die Längsnut 23 eingelegt, wobei ihre flache Unterseite 26 dem ebenen Nutgrund 27 zugewandt ist. Die Nutbreite entspricht der Streifenbreite wie auch die Nutlänge der Streifenlänge entspricht. Auf diese Weise ist die Streifeneinheit in der Längsnut 23 in der Streifenebene unbeweglich zentriert. Die Befestigung in der Längsnut 23 geschieht zweckmäßigerweise im Rahmen einer hochfesten Klebeverbindung, die gewährleistet, daß der Magnetstreifen 22 seine Lage bezüglich der Kolbenstange 8 auch bei starken Erschütterungen stets unverändert beibehält.The tape-shaped magnetic strip 22 is a plastic-bound part, it is a plastic strip with magnetizable components or particles, in principle comparable to the magnetic tapes of tape or video devices that serve as sound carriers. However, it expediently has a thickness such that it has a certain intrinsic stability. In the exemplary embodiment, it is fastened in a sandwich-like manner on a carrier strip 25, which preferably consists of non-magnetic material and is a steel strip in the exemplary embodiment. The consisting of the magnetic strip 22 and the carrier strip 25 The strip unit is inserted with the carrier strip 25 ahead and at the bottom into the longitudinal groove 23, its flat underside 26 facing the flat groove base 27. The groove width corresponds to the strip width as well as the groove length corresponds to the strip length. In this way, the strip unit is immovably centered in the longitudinal groove 23 in the strip plane. The attachment in the longitudinal groove 23 is advantageously carried out in the context of a high-strength adhesive connection, which ensures that the magnetic strip 22 always remains unchanged with respect to the piston rod 8 even in the event of strong vibrations.

Durch eine geeignete Magnetisierung ist der Magnetstreifen 22 in mehrere in Streifenlängsrichtung aufeinanderfolgende magnetisierte Magnetzonen 28, 28' eingeteilt, wobei die Magnetisierung der einzelnen Magnetzonen wechselpolig erfolgt ist. Die Magnetfeldausrichtung zweier in Streifenlängsrichtung benachbarter Magnetfeldzonen 28, 28' weicht somit voneinander ab, indem die Nord- und Südpole jeweils vertauscht sind. Beim Ausführungsbeispiel sind die einzelnen Magnetfeldzonen 28, 28' axial polarisiert, d.h. ihre Nordpole (N) und Südpole (S) sind in Streifenlängsrichtung und somit in Axialrichtung der Kolbenstange 8 ausgerichtet. Vorzugsweise ist die Polarisierung derart, daß sich aufeinanderfolgende Magnetfeldzonen 28, 28' jeweils mit gleichnamiger Polarisierung zugewandt sind. In Figur 2 sind die Übergangsstellen zwischen jeweils benachbarten Magnetfeldzonen 28, 28' durch strichpunktierte Linien angedeutet, die in der Praxis selbstverständlich nicht sichtbar sind. Man erkennt, daß die Nordpolseite einer jeweiligen Magnetfeldzone wiederum der Nordpolseite der sich anschließenden Magnetfeldzone gegenüberliegt.By means of a suitable magnetization, the magnetic strip 22 is divided into a plurality of magnetized magnetic zones 28, 28 ′ which follow one another in the longitudinal direction of the strip, the magnetization of the individual magnetic zones having an alternating pole. The magnetic field alignment of two magnetic field zones 28, 28 'adjacent in the longitudinal direction of the strip thus deviates from one another in that the north and south poles are interchanged. In the exemplary embodiment, the individual magnetic field zones 28, 28 'are axially polarized, ie their north poles (N) and south poles (S) are aligned in the longitudinal direction of the strip and thus in the axial direction of the piston rod 8. The polarization is preferably such that successive magnetic field zones 28, 28 ′ face each other with polarization of the same name. In Figure 2, the transition points between adjacent magnetic field zones 28, 28 'are indicated by dash-dotted lines, which of course are not visible in practice. It can be seen that the north pole side of a respective magnetic field zone is in turn opposite the north pole side of the adjoining magnetic field zone.

Die Sensoreinrichtung 18 ist derart an der Abschlußwand 6 festgelegt, daß sie der dem Nutgrund 27 entgegengesetzten Oberseite 32 des Magnetstreifens 22 mit Abstand rechtwinkelig zur Streifenebene gegenüberliegt. Bei einer Hubbewegung des Kolbens 2 wird somit der Magnetstreifen 22 an der Sensoreinrichtung 18 in Längsrichtung vorbeibewegt, welche letztere nacheinander in den Einfluß der von den einzelnen Magnetfeldzonen 28, 28' hervorgerufenen Magnetfelder gelangt. Diese Magnetfelder durchsetzen die Sensoreinrichtung 18, die beim Ausführungsbeispiel zwei nicht näher dargestellte magnetfeldempfindliche Halbleitersensoren enthält, beispielsweise sogenannte Hall-Sensoren oder Feldplatten-Sensoren. Entsprechend der beispielsgemäßen Einteilung des Magnetstreifens 22 liefern die beiden in der Regel um 90° versetzt angeordneten Halbleitersensoren der Sensoreinrichtung 18 zwei um 90° versetzte Sinus-Signale, die je nach Feininterpolationsteilung einer nachgeschalteten Auswerteelektronik auf die gewünschte Auflösung - beispielsweise 0,01 mm - feininterpoliert werden können. Die erhaltenen Signale geben somit Aufschluß über die momentane Position der Kolbenstange 8 und jedes mit dieser verbundenen Bauteils.The sensor device 18 is fixed on the end wall 6 in such a way that it lies opposite the upper side 32 of the magnetic strip 22 opposite the groove base 27 at a distance perpendicular to the plane of the strip. During a stroke movement of the piston 2, the magnetic strip 22 is thus moved past the sensor device 18 in the longitudinal direction, the latter successively coming into the influence of the magnetic fields caused by the individual magnetic field zones 28, 28 '. These magnetic fields penetrate the sensor device 18, which in the exemplary embodiment contains two magnetic field-sensitive semiconductor sensors, not shown, for example so-called Hall sensors or field plate sensors. In accordance with the division of the magnetic strip 22 according to the example, the two semiconductor sensors of the sensor device 18, which are generally offset by 90 °, provide two sine signals offset by 90 °, which, depending on the fine interpolation division of a downstream evaluation electronics, finely interpolate to the desired resolution - for example 0.01 mm can be. The signals obtained thus provide information about the current position of the piston rod 8 and each component connected to it.

Da die Abtastung des Magnetstreifens 22 durch die Sensoreinrichtung 18 berührungslos erfolgt, sind die Bestandteile der Positionsbestimmungseinrichtung 16 praktisch keinerlei mechanischem Verschleiß ausgesetzt und gewährleisten eine lange Funktionsdauer des Arbeitszylinders.Since the magnetic strip 22 is scanned by the sensor device 18 without contact, the components of the position determining device 16 are exposed to practically no mechanical wear and ensure a long service life of the working cylinder.

Die Dicke der sich aus dem Magnetstreifen 22 und dem Trägerstreifen 25 zusammensetzenden Streifeneinheit ist bei dem gezeigten Ausführungsbeispiel geringer als die Tiefe der sie aufnehmenden Längsnut 23. Der Magnetstreifen 22 sitzt daher mit Abstand zu dem Flachgestalt aufweisenden Flächenabschnitt 17 in der Längsnut 23 ein. Der verbleibende Tiefenabschnitt der Längsnut 23 wird von einer Deckleiste 33 eingenommen, die in die Längsnut 23 eingepaßt ist und auf dem Magnetstreifen 22 aufliegt. Bevorzugt ist die Anordnung derart getroffen, daß die Deckleiste 33 vollständig versenkt in der Längsnut 23 aufgenommen ist, wie es aus den Ausführungsbeispielen hervorgeht. Die Längsnut wird dabei von der Deckleiste 33, dem Magnetstreifen 22 und dem Trägerstreifen 25 gerade ausgefüllt, so daß die dem Magnetstreifen 22 entgegengesetzte Außenfläche 34 der Deckleiste 33 bündig in die beiden sich längsseits an die Längsnut 23 anschließenden Flächenpartien 35 der Kolbenstange 8 übergeht. Die Außenfläche 34 bildet dann zusammen mit den beiden sie flankierenden Flächenpartien 35 den Flachgestalt aufweisenden Flächenabschnitt 17. Durch die Deckleiste erhält die Kolbenstange 8 also letztlich die Gestalt zurück, die sie bei konventioneller, nutenloser Ausgestaltung hätte. Beispielsgemäß liegen die Außenfläche 34 und die angrenzenden Flächenpartien 35 in einer gemeinsamen Ebene, die den Flächenabschnitt 17 bildet.In the exemplary embodiment shown, the thickness of the strip unit composed of the magnetic strip 22 and the carrier strip 25 is less than the depth of the longitudinal groove 23 receiving it. The magnetic strip 22 therefore sits in the longitudinal groove 23 at a distance from the flat section 17. The remaining depth section of the longitudinal groove 23 is taken up by a cover strip 33 which is fitted into the longitudinal groove 23 and rests on the magnetic strip 22. The arrangement is preferably made such that the cover strip 33 is received completely recessed in the longitudinal groove 23, as can be seen from the exemplary embodiments. The longitudinal groove is just filled by the cover strip 33, the magnetic strip 22 and the carrier strip 25, so that the outer surface 34 of the cover strip 33 opposite the magnetic strip 22 merges flush into the two surface portions 35 of the piston rod 8 adjoining the longitudinal groove 23 along the longitudinal side. The outer surface 34 then, together with the two surface portions 35 flanking it, forms the flat portion 17 having the flat shape. The cover strip ultimately gives the piston rod 8 the shape which it would have had in the case of a conventional, grooveless design. For example, the outer surface 34 and the adjacent surface portions 35 lie in a common plane that forms the surface section 17.

Die Deckleiste 33 ist in der Längsnut 23 fest verankert. Zu diesem Zweck ist sie vorteilhafterweise in die Längsnut 23 eingeklebt. Ihr Grundriß entspricht demjenigen der Längsnut 23, so daß letztere durch die Deckleiste 33 vollständig geschlossen ist.The cover strip 33 is firmly anchored in the longitudinal groove 23. For this purpose, it is advantageously glued into the longitudinal groove 23. Their layout corresponds to that of the longitudinal groove 23, so that the latter is completely closed by the cover strip 33.

Die Deckleiste 33 gewährleistet eine optimale Abdichtung im Durchdringungsbereich zwischen der Kolbenstange 8 und der Abschlußwand 6 bei gleichzeitigem Schutz des empfindlichen Magnetstreifens 22 vor Beschädigungen. Indem die Außenfläche 34 der Dichtleiste 33 wenigstens einen Teil des Flachgestalt aufweisenden Flächenabschnittes 17 bildet, steht sie beim Durchlaufen der Führungs- und/oder Dichtungsanordnung 13, 14 in gleicher Weise mit dieser in Berührkontakt wie die übrigen Außenflächenbereiche der Kolbenstange 8. Da es ohne weiteres möglich ist, den Übergangsbereich zwischen der Deckleiste 33 und den benachbarten Flächenpartien 35 der Kolbenstange 8 derart auszubilden, daß keinerlei Zwischenraum oder Vertiefung vorliegt, hat das im Arbeitsraum 3 enthaltene Druckmittel keinen Überströmweg, um an der Dichtungseinrichtung 14 vorbei auszuströmen. Beispielsgemäß erreicht man dies dadurch, daß man auch in die erwähnten Übergangsbereiche 36 Klebstoff einbringt, so daß die Übergangsbereiche 36 bis zur Außenfläche hin mit Klebstoff befüllt sind und sich ein gleichmäßiger Übergang zwischen den sich einander anschließenden Außenflächenbereichen einstellt.The cover strip 33 ensures an optimal seal in the penetration area between the piston rod 8 and the end wall 6 while protecting the sensitive magnetic strip 22 from damage. Since the outer surface 34 of the sealing strip 33 forms at least a part of the flat section 17, it is in contact with the guide and / or sealing arrangement 13, 14 in the same way as the other outer surface regions of the piston rod 8 when passing through it is possible to form the transition area between the cover strip 33 and the adjacent surface portions 35 of the piston rod 8 in such a way that there is no space or depression, the pressure medium contained in the working space 3 has no overflow path in order to flow past the sealing device 14. According to the example, this is achieved by also introducing adhesive into the mentioned transition regions 36, so that the transition regions 36 are filled with adhesive up to the outer surface and a smooth transition is established between the adjoining outer surface regions.

Damit die Wirksamkeit der Positionsbestimmungseinrichtung 16 durch die Deckleiste 33 nicht beeinträchtigt wird, empfiehlt es sich, die Deckleiste aus unmagnetisierbarem Material herzustellen. Beim Ausführungsbeispiel besteht sie aus einem Federstahl mit geringer Permeabilität, der zudem äußerst verschleißfest und korrosionsbeständig ist. Ein derartiges Metall wird beispielsweise von der Firma Sandvik unter der Bezeichnung 13 X RM 19 vertrieben. Auf diese Weise ist die Deckleiste 33 für die Magnetfelder des Magnetstreifens 22 durchlässig, die somit in gewünschter Weise die Sensoreinrichtung 18 beaufschlagen können.So that the effectiveness of the position determining device 16 is not impaired by the cover strip 33, it is advisable to produce the cover strip from non-magnetizable material. In the exemplary embodiment, it consists of spring steel with low permeability, which is also extremely wear-resistant and corrosion-resistant. Such a metal is sold, for example, by the Sandvik company under the designation 13 X RM 19. In this way, the cover strip 33 for the magnetic fields of the magnetic strip 22 permeable, which can thus act on the sensor device 18 in the desired manner.

Um den exakten und stufenlosen Übergang zwischen der Deckleiste 33 und den sich längsseits anschließenden Bereichen der Kolbenstange 8 zu erhalten, ist die Kolbenstange 8 beim Ausführungsbeispiel nach dem Einkleben der Deckleiste 33 an dem Flächenabschnitt 17 überschliffen worden. Dadurch nivellieren sich sämtliche Unebenheiten aus.In order to obtain the exact and stepless transition between the cover strip 33 and the regions of the piston rod 8 adjoining on the longitudinal side, the piston rod 8 has been ground in the exemplary embodiment after the cover strip 33 has been glued to the surface section 17. As a result, all unevenness levels out.

Die Sensoreinrichtung 18 ist beim Ausführungsbeispiel von einem äußerst kompakt bauenden Sensorkopf 37 gebildet, der sich ausgezeichnet für eine Integration in das Gehäuse 1 und vor allem - wie vorliegend - in die von der Kolbenstange 8 durchsetzte Abschlußwand 6 eignet. Die Abschlußwand 6 hat vorliegend im Bereich der Austrittsöffnung 12 eine sich radial erstreckende Ausnehmung 38, die einerseits radial nach innen zur Kolbenstange 8 hin und andererseits radial nach außen zu einer Außenfläche 42 der Abschlußwand 6 hin offen ist. In diese Ausnehmung 38 ist der zum Beispiel patronenartige Sensorkopf 37 eingesetzt, so daß er den erforderlichen Abstand zu der von ihm nicht berührten Deckleiste 33 einhält, die zwischen ihm und dem Magnetstreifen 22 liegt.In the exemplary embodiment, the sensor device 18 is formed by an extremely compact sensor head 37, which is excellently suited for integration into the housing 1 and, above all, as in the present case, into the end wall 6 penetrated by the piston rod 8. In the present case, the end wall 6 has a radially extending recess 38 in the region of the outlet opening 12, which is open on the one hand radially inwards to the piston rod 8 and on the other hand radially outwards to an outer surface 42 of the end wall 6. The cartridge-like sensor head 37, for example, is inserted into this recess 38, so that it maintains the required distance from the cover strip 33 which it does not touch and which lies between it and the magnetic strip 22.

In den Sensorkopf 37 ist eine gestrichelt angedeutete Auswerteelektronik 43 integriert, die die Signale der Halbleitersensoren in der erforderlichen Weise auswertet. Denkbar wäre aber auch eine Lösung, bei der die Auswerteelektronik extern angeordnet ist und zum Beispiel zu der Verarbeitungseinrichtung 24 gehört.In the sensor head 37, a dashboard evaluation electronics 43 is integrated, which evaluates the signals of the semiconductor sensors in the required manner. However, a solution would also be conceivable in which the evaluation electronics are arranged externally and belong, for example, to the processing device 24.

Der Flachgestalt besitzende Flächenabschnitt 17 bewirkt zusammen mit dem an ihm flächig anliegenden Führungsabschnitt 44 der Führungseinrichtung 13 zweckmäßigerweise eine Verdrehsicherung der Kolbenstange 8 bezüglich der Ahschlußwand 6. Damit ist gewährleistet, daß die Sensoreinrichtung 18 und der Magnetstreifen 22 stets die richtige Zuordnung beibehalten.The flat-shaped surface section 17, together with the guide section 44 of the guide device 13 lying flat against it, expediently prevents the piston rod 8 from rotating with respect to the end wall 6. This ensures that the sensor device 18 and the magnetic strip 22 always maintain the correct assignment.

Es hat sich als besonders vorteilhaft erwiesen, eine Vierkantstange als Kolbenstange 8 einzusetzen, wobei eine ihrer vier ebenen Außenflächen 45 den Flachgestalt aufweisenden Flächenabschnitt 17 bildet. Eine derartige Bauform ist beim Ausführungsbeispiel verwirklicht, wobei der Vierkantabschnitt der Kolbenstange 8 vorzugsweise einen quadratischen Querschnitt aufweist. Bei Bedarf ließe sich im Bereich mindestens einer der weiteren ebenen Außenflächenabschnitte 45 der Kolbenstange 8 ein weiterer, insbesondere als Magnetstreifen konzipierter Meßstreifen integrieren, der ebenfalls mit einer Sensoreinrichtung zusammenarbeitet. Dadurch wäre eine miteinander gekoppelte Gesamtauswertung oder eine voneinander unabhängige Mehrfachauswertung möglich.It has proven to be particularly advantageous to use a square rod as the piston rod 8, one of its four flat outer surfaces 45 forming the flat portion 17 having the flat shape. Such a design is realized in the exemplary embodiment, the square section of the piston rod 8 preferably having a square cross section. If necessary, a further measuring strip, in particular designed as a magnetic strip, could also be integrated in the area of at least one of the further flat outer surface sections 45 of the piston rod 8, which also cooperates with a sensor device. This would enable a coupled overall evaluation or an independent multiple evaluation.

Denkbar wären im übrigen auch noch weitere Kolbenstangenquerschnitte, die mindestens einen ebene Flächenabschnitt aufweisen. Zu nennen wären beispielsweise Dreiecksstangen oder eine Abflachung aufweisende Rundstangen.In addition, other piston rod cross-sections that have at least one flat surface section would also be conceivable. Examples include triangular bars or round bars with a flattened section.

Somit liegt beim Ausführungsbeispiel die Integration eines Wegmeßsystems mit einer Maßverkörperung aus einem wechselpolig magnetisierten Magnetstreifen und einem dazugehörigen Sensorkopf in einen fluidbetätigten verdrehgesicherten Arbeitszylinder vor. Der Kolbenstangenquerschnitt hat mindestens eine geradlinige Teilflanke, in die eine Längsnut eingelassen ist, welche den mittels eines hochfesten Klebers fixierten Magnetstreifen aufnimmt. Die magnetfelddurchlässige, nicht magnetische Deckleiste sorgt aufgrund ihrer nichtrostenden, niederpermeabilen Eigenschaften für eine tribologisch verträgliche Abdeckung des Magnetstreifens und ist durch einen hochfesten Kleber sicher festgelegt.Thus, in the exemplary embodiment, the integration of a displacement measuring system with a material measure made of an alternating-pole magnetization lies Magnetic strips and an associated sensor head in a fluid-operated anti-rotation working cylinder. The cross-section of the piston rod has at least one rectilinear partial flank, into which a longitudinal groove is embedded, which receives the magnetic strip fixed by means of a high-strength adhesive. The non-magnetic cover strip, which is permeable to magnetic fields, ensures a tribologically compatible covering of the magnetic strip due to its rustproof, low-permeability properties and is securely fixed by a high-strength adhesive.

Als Sensorkopf der vorliegenden Anordnung ließe sich beispielsweise ein Lesekopf des Typs Sony PL 20 verwenden. Die Gitterkonstante für die Einteilung des Magnetstreifens in einzelne Magnetfeldzonen beträgt zum Beispiel 5 mm. Für die Abtastung können bei Bedarf auch mehr als zwei Halbleitersensoren eingesetzt werden.For example, a Sony PL 20 read head could be used as the sensor head of the present arrangement. The lattice constant for dividing the magnetic strip into individual magnetic field zones is, for example, 5 mm. If necessary, more than two semiconductor sensors can be used for the scanning.

Der Magnetstreifen und die Deckleiste werden zweckmäßigerweise nacheinander und unabhängig voneinander in die Längsnut 23 eingeklebt.The magnetic strip and the cover strip are expediently glued into the longitudinal groove 23 one after the other and independently of one another.

Claims (17)

Arbeitszylinder, mit einem Gehäuse, in dem sich ein axial bewegbarer Kolben befindet, der mit einer an wenigstens einer Stirnseite aus dem Gehäuse herausragenden Kolbenstange verbunden ist, die am Außenumfang wenigstens einen sich axial erstreckenden und Flachgestalt aufweisenden Flächenabschnitt aufweist, in dem eine Längsnut vorgesehen ist, die einen durch eine gehäusefeste Sensoreinrichtung abtastbaren Meßstreifen aufnimmt, dadurch gekennzeichnet, daß der Meßstreifen ein Magnetstreifen (22) ist, der mehrere in Axialrichtung aufeinanderfolgend angeordnete, wechselpolig magnetisierte Magnetzonen (28, 28') aufweist, die durch die Sensoreinrichtung berührungslos abtastbar sind, und daß der Magnetstreifen (22) durch eine an der Kolbenstange (8) festgelegte, aus magnetfelddurchlässigem Material bestehende Deckleiste (33) abgedeckt ist, deren vom Magnetstreifen (22) abgewandte Außenfläche (34) zumindest einen Teil des Flachgestalt aufweisenden Flächenabschnittes (17) der Kolbenstange (8) bildet.Working cylinder, with a housing in which there is an axially movable piston which is connected to a piston rod which projects out of the housing on at least one end face and which has at least one axially extending and flat shape on the outer circumference, in which a longitudinal groove is provided which receives a measuring strip which can be scanned by a sensor device fixed to the housing, characterized in that the measuring strip is a magnetic strip (22) which has a plurality of magnetically magnetized magnetic zones (28, 28 ') which are successively arranged in the axial direction and which can be scanned by the sensor device in a contactless manner, and that the magnetic strip (22) by a fixed on the piston rod (8), consisting of magnetic field permeable material Cover strip (33) is covered, the outer surface (34) of which faces away from the magnetic strip (22) forms at least part of the flat section (17) of the piston rod (8). Arbeitszylinder nach Anspruch 1, dadurch gekennzeichnet, daß die Deckleiste (33) zumindest teilweise in die Längsnut (23) eingelassen ist.Working cylinder according to claim 1, characterized in that the cover strip (33) is at least partially embedded in the longitudinal groove (23). Arbeitszylinder nach Anspruch 2, dadurch gekennzeichnet, daß die Deckleiste (33) vollständig versenkt in der Längsnut (23) aufgenommen ist, wobei ihre Außenfläche (34) bündig in die sich seitlich anschließenden kolbenstangenseitigen Partien (35) des Flachgestalt aufweisenden Flächenabschnittes (17) übergeht.Working cylinder according to claim 2, characterized in that the cover strip (33) is received completely recessed in the longitudinal groove (23), its outer surface (34) merging flush with the laterally adjacent portions (35) of the flat-shaped surface section (17) . Arbeitszylinder nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Deckleiste (33) aus Material mit geringer Permeabilität besteht.Working cylinder according to one of claims 1 to 3, characterized in that the cover strip (33) consists of material with low permeability. Arbeitszylinder nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die Deckleiste (33) aus unmagnetischem Material besteht.Working cylinder according to one of claims 1 to 4, characterized in that the cover strip (33) consists of non-magnetic material. Arbeitszylinder nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Deckleiste (33) aus verschleißfestem, korrosionsbeständigem Metall wie Federstahl besteht, insbesondere in der Spezifikation 13 X RM 19.Working cylinder according to one of claims 1 to 5, characterized in that the cover strip (33) consists of wear-resistant, corrosion-resistant metal such as spring steel, in particular in the specification 13 X RM 19. Arbeitszylinder nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß der Magnetstreifen (22) ein magnetisierbare Bestandteile enthaltender Kunststoffstreifen ist.Working cylinder according to one of claims 1 to 6, characterized in that the magnetic strip (22) is a plastic strip containing magnetizable components. Arbeitszylinder nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, daß der Magnetstreifen (22) auf einem Trägerstreifen (25) befestigt ist und zwischen diesem Trägerstreifen (25) und der Deckleiste (33) liegt.Working cylinder according to one of claims 1 to 7, characterized in that the magnetic strip (22) is fastened to a carrier strip (25) and lies between this carrier strip (25) and the cover strip (33). Arbeitszylinder nach Anspruch 8, dadurch gekennzeichnet, daß der Trägerstreifen (25) aus unmagnetisierbarem Metallmaterial besteht.Working cylinder according to claim 8, characterized in that the carrier strip (25) consists of non-magnetizable metal material. Arbeitszylinder nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß die einzelnen Magnetzonen (28, 28') axial, d.h. in Längsrichtung der Kolbenstange (8), polarisiert sind, wobei axial benachbarte Magnetzonen (28, 28') einander zweckmäßigerweise mit gleichnamiger Polung zugewandt sind.Working cylinder according to one of claims 1 to 9, characterized in that the individual magnetic zones (28, 28 ') axially, i.e. are polarized in the longitudinal direction of the piston rod (8), axially adjacent magnetic zones (28, 28 ') expediently facing one another with the same polarity. Arbeitszylinder nach einem der Ansprüche 1 bis 10, dadurch gekennzeichnet, daß der Magnetstreifen (22) in die Längsnut (23) eingeklebt ist.Working cylinder according to one of claims 1 to 10, characterized in that the magnetic strip (22) is glued into the longitudinal groove (23). Arbeitszylinder nach einem der Ansprüche 1 bis 11, dadurch gekennzeichnet, daß die Deckleiste (33) durch Klebung an der Kolbenstange (8) festgelegt ist.Working cylinder according to one of claims 1 to 11, characterized in that the cover strip (33) is fixed by gluing to the piston rod (8). Arbeitszylinder nach einem der Ansprüche 1 bis 12, dadurch gekennzeichnet, daß die Kolbenstange (8) im Bereich des Flachgestalt aufweisenden Flächenabschnittes (17) bei in die Längsnut (23) eingesetzter Deckleiste (33) überschliffen ist.Working cylinder according to one of claims 1 to 12, characterized in that the piston rod (8) in the region of the flat shape having surface section (17) with the cover strip (33) inserted into the longitudinal groove (23). Arbeitszylinder nach einem der Ansprüche 1 bis 13, dadurch gekennzeichnet, daß die Kolbenstange (8) über mehrere Flachgestalt aufweisende Flächenabschnitte (17, 45) verfügt, wobei wenigstens einem (17) dieser Flächenabschnitte ein Magnetstreifen (22) mit Deckleiste (33) zugeordnet ist.Working cylinder according to one of claims 1 to 13, characterized in that the piston rod (8) has a plurality of flat sections (17, 45), a magnetic strip (22) with a cover strip (33) being assigned to at least one (17) of these sections . Arbeitszylinder nach Anspruch 14, dadurch gekennzeichnet, daß die Kolbenstange (8) im Bereich der Flachgestalt aufweisenden Flächenabschnitte (17, 45) als Vierkantstange mit insbesondere quadratischem Querschnitt ausgebildet ist.Working cylinder according to claim 14, characterized in that the piston rod (8) in the region of the flat sections (17, 45) is designed as a square rod with a square cross section in particular. Arbeitszylinder nach einem der Ansprüche 1 bis 15, dadurch gekennzeichnet, daß die Sensoreinrichtung (18) einen im Innern einer von der Kolbenstange (8) durchsetzten Abschlußwand (6) des Gehäuses (1) angeordneten Sensorkopf (37) aufweist.Working cylinder according to one of claims 1 to 15, characterized in that the sensor device (18) has a sensor head (37) arranged in the interior of an end wall (6) of the housing (1) through which the piston rod (8) passes. Arbeitszylinder nach Anspruch 16, dadurch gekennzeichnet, daß in den Sensorkopf (37) eine Signalauswerteelektronik (43) integriert ist.Working cylinder according to claim 16, characterized in that a signal evaluation electronics (43) is integrated in the sensor head (37).
EP95102202A 1994-08-02 1995-02-17 Power cylinder Expired - Lifetime EP0695879B1 (en)

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DE9412435U DE9412435U1 (en) 1994-08-02 1994-08-02 Working cylinder
DE9412435U 1994-08-02

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DE59508445D1 (en) 2000-07-13
DE9412435U1 (en) 1994-09-29
BR9503521A (en) 1996-05-28
EP0695879B1 (en) 2000-06-07
KR960008085A (en) 1996-03-22
KR100194164B1 (en) 1999-06-15
US5568760A (en) 1996-10-29

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