DE202011005606U1 - Device for positioning a piston rod of a magnetorheological damper - Google Patents

Abstract

Device (100) for positioning a piston rod (18) of a magnetorheological damper (10) which is connected to a seat (200) and to a chassis (202), in particular a mobile working means, wherein a distance between the seat (200) and the chassis (202) is associated with a predetermined position of the piston rod (18) within the damper (10) and the distance is variable by volume change of an air spring which is controllable by a pump-valve unit (102) with a controller (104 ), comprising - a displacement sensor (106) for determining an actual distance between the seat (200) and the chassis (202), and - a memory (108) containing a minimum distance and a maximum distance corresponding to the extreme points of the Position of the piston rod (18), and - a mean value (M) of the minimum distance and the maximum distance from the controller (104) can be determined, and - a comparator (110) of the controller (104) within a s predeterminable time interval a difference between the means of displacement sensor ...

Description

The present invention relates to a device for positioning a piston rod of a magnetorheological damper. The invention further relates to a seat with inventive device and a seat with a horizontal damping and / or vertical damping, which is controlled by the device and equipped with a magnetorheological damper.

Technical area

A European Directive 2002/44 / EC requires employers to do what is technically feasible to protect employees from harm to health caused by human vibration - so-called whole-body vibration. The vertical damping dampens vibrations - such as a pothole - that may occur to a mobile work operator as a stretching and compression load on the spine and discs. Offering an optimally vibration-damped workplace is part of a modern occupational health protection. The aim is to isolate a vehicle seat of a commercial vehicle from high and low frequency vibrations.

Passive dampers are only for one type of high or low frequency vibrations to optimize. Active vibration dampers are unsuitable as a further solution in vehicle use, since the energy consumption is usually very high.

A good alternative form semi-active damper whose damper characteristics can be changed for example by magnetorheological fluids in a hydraulic damper.

For the magnetorheological damper control methods such as skyhook control and modified control methods have been used. A generic method is from the WO 97/40993 known. The features defined in this document will be referred to below. The controller disclosed there uses a relative displacement of the damper as a controlled variable and compares this with an absolute speed of the seat with respect to its signs. To determine the absolute speed, an acceleration sensor is used on the seat and the measured values are integrated.

This controller "responds" only to an acceleration of the seat and then controls the damper. Here are already relatively large masses, composed of seat, substructure and a person sitting on it to fear movement or stress on the spine.

Analog uses one from the WO 97/10118 A1 disclosed Sitzdämpfersystem a displacement sensor for determining a seating position, wherein the controller uses the change of the seat position as a control variable for the change of the damper characteristic. The sitting position can also be changed without harmful vibration, for example by changing the seating position of the person sitting on it. The disturbance of the system due to the vibration to be damped can only be detected here.

The object of the present invention is to provide a device for positioning a piston rod of a magnetorheological damper, which avoids the problems described above, wherein a maximum damper travel in the compression and expansion direction of the seat is to be provided.

This object is achieved with the features of the main claim. The memory is provided with the measurements of the displacement sensor, which correspond to the extreme points at maximum expansion or maximum compression of the damper. The arithmetic or weighted mean value ensures optimum adjustment of the piston rod, wherein a piston arranged on the piston rod can be positioned approximately in the middle of a working space filled with the magnetorheological fluid. A correspondingly well-suited Einrohrdämpfer is disclosed in a same day filed with the German Patent and Trademark Office second application with internal file number "IWS 1" and is fully included in this description. The volume of the air spring is actually "automatically" adapted to the person weight of the person sitting on the seat. The pump-valve unit can thus contribute to the compensation of very low frequencies.

The controller according to the invention uses the acceleration sensor, which is arranged on the chassis to control the damper. Decisive for the invention here is the realization that only the chassis has to accelerate into one of the three spatial coordinates until the seat experiences an acceleration - that is to say oscillation. The controller thus "reacts" in advance to the external disturbance of a balance between the seat and the chassis, before the mass to be damped starts to move at all.

The necessary data for controlling the damper as a function of frequency and person weight are unique for each damper-seat combination. However, this data can be optimized and determined in the simulator. By assignment corresponding acceleration values for the chassis, the controller can read out corresponding output signals from the memory. The person weight can be determined by means of a weight sensor and is stored, for example, at the beginning of the operation of the controller in the memory and can be overwritten if necessary.

Further advantageous features of the device will become apparent from the dependent claims.

It is a further object of the present invention to develop a seat such that the seat can be used for a mobile work equipment such as an agricultural vehicle, a crane, an industrial or construction vehicle.

Another object is to effectively reduce the vibration not only in the vertical direction.

Reference to drawings, the invention will now be explained in more detail in the context of embodiments, wherein no limitation of the invention to these embodiments is intended.

In the drawings show:

1 a schematic, not to scale side view of a first embodiment of a device according to the invention;

2 a schematic representation of a control of a second embodiment of the device; and

3 a diagram with contrasted amplitude magnification factors on the excitation frequency of passive dampers, a semi-active damper with a control according to sky-hook method and a first embodiment of a combination of inventive device with a magnetorheological damper.

Unless otherwise stated below, the following description always refers to all embodiments of the 1 to 3 , wherein like reference numerals always describe the same structural features.

In 1 is a magnetorheological damper 10 for damping relative movements between a seat 200 and a chassis 202 , here a mobile work tool, illustrates. This one-pipe damper 10 is by means of piston rod 18 with the seat 200 connected. At the piston rod 18 a piston is arranged inside the damper 10 is displaceable, with a liquid the piston 20 reibbeaufschlagt. This liquid is controllable by means of a magnetic field in its rheological properties and is commercially available under the name MR2978 from BASF SE. The magnetic field can be generated by a magnetic coil, which by means of a controller 104 is supplied with electrical energy.

One end of the piston rod 18 is completely from the piston rod space 24 surround. Approaches the piston rod 18 for example, their maximum penetration point into the damper 10 , so a stop sensor changes 52 at the foot of the piston rod space 24 is arranged, one of its electrically evaluable properties. For example, the resistance of the stop sensor becomes 52 very big or very small and may be from the controller 104 evaluated and monitored to change the damper characteristics before reaching this point. This occurs, for example, in the case of a pothole with rapid lowering of the chassis 202 one.

The control 104 the device 100 continues to operate a pump and / or a valve of the pump-valve unit 102 to control a volume of an air spring. A height adjustment of the seat 200 is controllable by changing the volume of the air spring. The piston rod 18 of the damper 10 is from the controller 104 positioned approximately in the middle.

To determine an actual distance of the seat 200 includes the device 100 a displacement sensor 106 and a memory 108 which contains two extreme positions of the piston position. These stored extreme positions represent the electrically readable state of the displacement sensor 106 when the seat 200 is in its lowest or highest cushioned position. In 2 is a second embodiment of a device 100 shown according to the present invention.

The lowest position corresponds to a smaller distance between seat 200 and the chassis 202 as the highest position. In other words, the maximum distance corresponds to seat 200 to the chassis 202 a "dead center" of the piston rod 18 inside the damper 10 and the minimum distance to the second "dead center". From the extreme points is from the controller 104 an average M by means of a comparator 110 determined. The control 104 determined within a predeterminable time interval, a difference between the applied actual distance and the mean M. The controller 104 opens the valve of the pump-valve unit 102 if the difference is positive, which is equivalent to an actual distance above the mean value M, and the volume of the air spring decreases. Otherwise, the controller operates 104 the pump of the pump-valve unit 102 if the difference is negative or the actual distance is below the mean value M lies, and the volume increases. With a difference of zero, neither valve nor pump is actuated.

The at the in 1 Displacement sensor used in the embodiment shown 106 is a potentiometer 50 located on an inside of the piston rod space 24 is arranged and from one to the piston rod 18 arranged sliding contact and a cooperating resistance element, whose resistance is approximately proportional to a change in position of the piston rod 18 goes up or down. As a displacement sensor 106 Also, a capacitor is contemplated, wherein the capacitance by changing a piston rod distance to a point within the piston rod space 24 increases or decreases roughly in proportion. Inductive displacement transducers are also suitable. The displacement sensor 106 may act as a coil whose inductance increases or decreases approximately proportionally as the piston rod pitch changes. Such coils, capacitors and potentiometers are - albeit for other purposes - known and can be used by the skilled person as a displacement sensor 106 be used. By the arrangement in the piston rod space 24 of the damper 10 is a better space utilization below the seat 200 possible. At the same time, this measuring arrangement is best protected against dirt, moisture and mechanical damage.

Another suitable displacement sensor 106 is designed as Seilzuglängengeber, with one end of the rope to the seat 200 is connected and when changing the height rotates a rope drum connected to the rope, wherein the rotation of a donor - for example, again a potentiometer - is convertible into a voltage which rises or falls approximately proportionally. A Hall sensor is also used as a contactless displacement sensor 106 employing a position magnet on a shaft of the scissor-type substructure 204 of the seat 200 is arranged. A voltage across a current-charged Hall element increases or decreases approximately proportionally with its angular deviation of the position magnet when changing the height. Such Hall elements are also commercially available from novotechnik in Germany.

The displacement sensor 106 can also be realized by means of a magnetostriction. A waveguide is along all height positions of the seat 200 arranged, with a magnetic encoder on the seat 200 is positioned. By means of a very short current pulse through the waveguide and by interaction with the magnetic field at the seat 200 creates a torsion wave, which is implemented in a wave converter on the waveguide in the sitting position of the magnetic field. Such position sensors are sold by the company MTS Sensors.

In 1 Finally, another embodiment of the displacement sensor 106 shown. A linear variable differential transformer LVDT comprises an AC-loaded primary coil L1, here at the central store of the scissor-type substructure 204 is arranged. In the middle position of the seat 200 are two secondary coils L2 at the leg ends of the substructure 204 arranged symmetrically. Since the legs of the substructure are not divided centrally from the central warehouse and the legs below the central warehouse are shorter than above, the secondary coils L2 shift asymmetrically to the primary coil L1 as the height changes and a voltage across the secondary coils L2 increases or decreases approximately proportionally.

In the 2 shown control 104 is by means of a seat occupancy recognition 112 switchable. The device 100 is automatically put into operation or put out of service, if the controlled seat 200 one or no occupancy with a person signals. The seat occupancy recognition 112 is designed as a seat mat with pressure-sensitive resistors or as a filled cushion with pressure sensor resting on the seat 206 between upholstery and cover is arranged. Alternatively, the seat occupancy recognition evaluates 112 a weight force on at least one point of attachment between seat 200 and chassis 202 - for example, on a bearing of the substructure 204 - off or analyze a signal indicating seat occupancy. A vehicle bus system provides manufacturer-independent information such as the use of a buckle, which a specific seat 200 a land vehicle can be assigned. An example may be the CanBus vehicle bus system.

It remains to be made clear that the displacement sensor 106 only information about the actual distance of the seat 200 to the controller 104 transmitted to the positioning of the piston rod 18 inside the damper 10 make. The internal pressure of the air spring is in fact automatically adjusted to the weight of the seat 200 a seated person.

For vibration damping by means of a magnetorheological damper 10 generates the control 104 a first derivative over the time of an acceleration measurement value recorded at a predetermined time interval. This reading is taken from an accelerometer 208 on the chassis 202 is arranged, wherein accelerations in x-, y- and / or z-direction are determined and to the controller 104 are transferable. The control 104 changes from exceeding one in memory 108 variably stored limit value for the first derivative of acceleration in the vertical direction of the damper 10 such that the controller 104 in the memory 108 filed Data to different on the seat 200 located person weights adapted output signals to the electrical coil of the damper 10 which generates a higher or lower magnetic field. This magnetic field then acts on the magnetorheological fluid and changes its characteristics and friction to the piston.

This in memory 108 stored data are ordered by different masses, which is equivalent to different person weights, ordered and factory-determined by simulation. The control 104 Thus, it does not "react" to an external disturbance - like a pothole - only to a movement of the seat 200 but monitors an acceleration or deceleration of the chassis 202 , If a zero band is left with respect to the acceleration values in the vertical direction (x direction), stored voltages, current or magnetic field strengths are removed from the memory 108 read out and on the magnetorheological damper 10 applied.

As in 3 As shown, passive dampers can be optimized for certain excitation frequencies such that their vibration transmission rate becomes less than 1. A transmission rate or an amplitude magnification factor of less than 1 means that the vibrations of the chassis 202 disproportionately to the seat 200 be transferred or the seat 200 isolated against the vibration. The maximum of the curves shows the natural frequency of a combination of the seat 200 , the passive damper and the substructure 204 at. The higher the natural frequency, the less often beating or a resonance occurs. A known from the prior art semi-active damper with a skyhook-like control avoids a maximum in the frequency response almost and isolated against low-frequency vibrations reliably. Only with the control of the invention 104 operated device 100 however, shows a good decoupling over the entire frequency band and shows no more maximum, since the control of the invention 104 proactive with the magnetorheological damper 10 interacts.

The in 1 seat shown 200 for an agricultural vehicle is by means of in 2 shown device 100 vibration-damped. The device 100 controls the magnetorheological damper 10 by changing the magnetic field strength of his coil. The weight adjustment of the seat 200 takes place by means of the LDVT displacement sensor 106 , The seat 200 can instead of the scissor-shaped substructure shown 204 also include variable-length posts. To those on the seat 200 To determine the mass to be measured is a weight sensor 114 between the seat 200 and the substructure 204 used, which sends its measurement data to the controller 104 transmitted. This happens at least initially with the activation of the control by seat occupancy recognition 112 and, if necessary, with significant change in mass. These weight sensors 114 are on both sides of the "front edge" of the seat 206 arranged, with the other edge with the backrest at position L2 with hinges hinged to the substructure 204 is attached. This variant has the advantage of a relatively low influence of the air spring on the mass measurement.

In addition to vibrations in the vertical direction - within this description, the z-direction refers to a movement of the seat, the chassis to the ground and away from it - also intercept vibrations in the horizontal in the x and y direction, is the substructure 204 exclusively via a horizontal damper device 300 with the chassis 202 connected. The horizontal damper device 300 is from the device 100 controlled, with the control 104 one single tube damper each 10 for vibration damping in y-direction and z-direction drives. By means of the acceleration sensor 208 become the directional components of the acceleration of the chassis 202 to the controller 104 logged on and the controller 104 Changes the damper characteristic according to the manner described above for the vertical vibration.

The aforesaid devices 100 can be used instead of land vehicles for mobile work equipment such as stages, cranes and the like to minimize vibration loads. Also, an insert for aircraft, especially helicopters, due to corresponding vibration loads for operating personnel and "driving" guests of particular technical importance.

LIST OF REFERENCE NUMBERS

10

monotube

18

piston rod

19

Long hole

24

Piston rod space

50

potentiometer

52

stop sensor

100

contraption

102

Pump valve unit

104

control

106

displacement sensor

108

Storage

110

comparator

112

Seat occupancy recognition

114

weight sensor

CPU

program-controlled central unit

M

Average

200

Seat

202

chassis

204

substructure

206

seat

208

accelerometer

L1

primary coil

L2

secondary coil

LVDT

linear variable differential transformer

300

Horizontal damper device

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 97/40993 [0005]
• WO 97/10118 A1 [0007]

Cited non-patent literature

• Directive 2002/44 / EC [0002]

Claims (8)

Contraption ( 100 ) for positioning a piston rod ( 18 ) of a magnetorheological damper ( 10 ), with a seat ( 200 ) and with a chassis ( 202 ), in particular a mobile working means, wherein a distance between the seat ( 200 ) and the chassis ( 202 ) a predetermined position of the piston rod ( 18 ) within the damper ( 10 ) is assigned and the distance is variable by means of volume change of an air spring, which by a pump-valve unit ( 102 ) is controllable with a controller ( 104 ), which - a displacement sensor ( 106 ) for determining an actual distance between the seat ( 200 ) and the chassis ( 202 ), and - a memory ( 108 ), which contains a minimum distance and a maximum distance which correspond to the extreme positions of the position of the piston rod ( 18 ), and - a mean value (M) of the minimum distance and the maximum distance from the controller ( 104 ), and - a comparator ( 110 ) of the controller ( 104 ) within a predeterminable time interval a difference between the by means of displacement sensor ( 106 ) provides the actual distance and the mean value (M), wherein - the pump-valve unit ( 102 ) from the controller ( 104 ) is controlled such that the volume of the air spring decreases, if the difference (positive), the actual distance is greater than the average value (M) and - the pump-valve unit ( 102 ) from the controller ( 104 ) is controlled such that the volume of the air spring increases, if the difference (negative) shows that the actual distance is smaller than the mean value (M). Contraption ( 100 ) according to claim 1, characterized in that the displacement sensor ( 106 ) on an inner side of a piston rod ( 18 ) receiving piston rod space ( 24 ) and - a potentiometer ( 50 ), with one on the piston rod ( 18 ) arranged sliding contact and a cooperating resistive element whose resistance is proportional to a change in position of the piston rod ( 18 ) rises or falls, and / or - is a capacitor, the capacity being increased by changing a piston rod distance to a point inside the piston rod space ( 24 ) proportionally increases or decreases, and / or - is a coil whose inductance increases or decreases proportionally when a piston rod distance changes, and / or - the displacement sensor ( 106 ) is a linear variable differential transformer (LVDT), wherein to an AC biased primary coil (L1) on the seat ( 200 ) symmetrically two secondary coils (L2) on a substructure ( 204 are arranged, which shift asymmetrically when the actual distance to the primary coil (L1) changes and a voltage across the secondary coils (L2) increases or decreases proportionally, and / or - a cable length transmitter, wherein one end of the cable with the seat ( 200 ) and when changing the actual distance rotates a rope drum connected to the rope and the rotation is convertible by a donor into a voltage which rises or falls proportionally, and / or - is a Hall sensor, wherein a position magnet on a shaft of a scissor-type substructure ( 204 ) of the seat ( 200 is arranged and a voltage across a current-charged Hall element increases or decreases proportionally with its angular deviation of the position magnet when changing the actual distance, and / or - is realized by means of a magnetostriction, wherein a waveguide along all positions of the seat ( 200 ) is arranged and a magnetic encoder on the seat ( 200 ) and by means of current pulse through the waveguide and by interaction with the magnetic field at the seat ( 200 ) A torsion wave is generated, which is in a wave converter on the waveguide in the sitting position of the magnetic field can be implemented. Contraption ( 100 ) according to claim 1, characterized in that the controller ( 104 ) by means of a seat occupancy recognition ( 112 ) is switchable, wherein the seat occupancy recognition ( 112 ) a seat mat with pressure-sensitive resistors and / or a filled cushion with pressure sensor on the seat surface ( 206 ) and / or a weight force at least one connection point between seat ( 200 ) and chassis ( 202 ) or a pressure switch between seat ( 200 ) and chassis ( 202 ) and / or analyzed via a vehicle bus system, a seat occupancy indicating signal, in particular a buckle. Contraption ( 100 ) according to claim 1 or 3, characterized in that the memory ( 108 ) at least one reading to the mass of one on the seat ( 200 ) by a weight sensor ( 114 ), in particular the weight sensor ( 114 ) with the seat occupancy recognition ( 112 ), wherein in particular the weight sensor ( 114 ) is arranged on a seat bottom end and the seat ( 200 ) hinged to the chassis at the other end of the seat ( 202 ) connected is. Contraption ( 100 ) according to claim 4, characterized in that the controller ( 104 ) generates a first derivative over the time of an acceleration measurement value recorded at a predetermined time interval, wherein an acceleration sensor generating this value ( 208 ) on the chassis ( 202 ) and accelerations in x, y and / or z-direction and sent to the controller ( 104 ), whereby the controller ( 104 ) - from exceeding one in the memory ( 108 ) variably stored limit value for the first derivative of the acceleration in the vertical direction - the magnetorheological damper ( 10 ) so changed, that the controller ( 104 ) in memory ( 108 ) stored data to different on the seat ( 200 ) located mass adapted output signals to the magnetorheological damper ( 10 ) transmits, wherein a higher or lower magnetic field is generated. Contraption ( 100 ) according to claim 1, 3 or 5, characterized in that the controller ( 104 ) with a stop sensor ( 52 ) is connected when approaching the piston rod ( 18 ) to a turning point in the piston rod space ( 24 ) of the magnetorheological damper ( 10 ) is electrically switchable and the controller ( 104 ) an output signal to the damper ( 10 ) which generates a higher or lower magnetic field. Seat ( 200 ) for a mobile work equipment, such as an agricultural vehicle, a crane, an industrial or construction vehicle, with a device ( 100 ) according to one of the preceding claims, wherein the control is within a piston rod ( 18 ) receiving piston rod space ( 24 ) is arranged. Seat ( 200 ) according to claim 7, with a horizontal damper device ( 300 ), whereby when the acceleration in the x and / or y direction changes, the control ( 104 ) the magnetorheological damper ( 10 ), with the seat ( 200 ) and the horizontal damping ( 300 ) is connected in the x-direction or y-direction, controls changeable in its damper characteristic.

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