DE10041093A1 - Sensor arrangement in anti-friction roller bearing of vehicle, has sensor arranged on fixed bearing capsule, such that gap between sensors is half the angular separation of balls in bearing capsule - Google Patents

Abstract

A pair of strain sensitive sensors (7,8) are arranged on a fixed bearing capsule (4) of anti-friction roller bearing (1). The gap between the sensors is half the angular separation of balls (6) in the bearing capsule. An Independent claim is also included for method for evaluating output signal of sensor.

Description

State of the art

The invention relates to a sensor arrangement in one Rolling bearings and embodiments of methods for Auswer device of the output signal of the sensor arrangement, in particular re in a wheel bearing, according to the generic term of the main entitlement.

It is known in itself that on rotating Tei len, which are performed with a roller bearing, such as. B. on Wheel bearings of a motor vehicle, various measured quantities occur which are of high relevance for the driving and possibly also steering systems. The so stored Components are often part of anti-lock braking systems, Anti-slip regulations or other driving behavior  or tax that positively influences driving safety assurance systems. Here it can be very important Measurement data e.g. B. on the speed, the wheel forces, the loading acceleration or tire pressure or tempera to maintain the forces and moments created by the Road over the wheel and over the wheel bearing on the driving be transferred to evaluate.

From EP 0 992 797 A1 it is known, for example, that a speed sensor is attached within a ball bearing is arranged. The ball bearings offer a great deal here advantageous, protected installation space for appropriate Sensors. By integrating the sensors into the Ku gel bearing also creates a significant system and Simplification of assembly, although a more extensive one Recording of the bearing forces in the prior art is not is provided.

In the known arrangements, however, the degree of Integration of the sensor elements in the rolling bearing structure quite low, since you usually plug sensors here used, which the bearing manufacturer from the manufacturer of Sensors or other assemblers can be supplied. The problem here is due to the so-called plug-in principle the mechanical tolerances especially with regard to air gap between rotating parts and the sensors we solved satisfactorily.

Advantages of the invention

A sensor arrangement of the type specified, esp special for the utilization of a speed signal, is with the characteristic features of claim 1 further developed.  

Advantageously, the fact that the fixed bearing shell of the rolling bearing, by Rolling elements of the rolling bearing caused expansion forces with strain-sensitive sensors are detected that two sensors each by half the angle the rolling elements are offset from each other on the La cup are attached.

In principle, wheel forces in a rolling bearing can be way with strain gauges or strain gauges strips are recorded, which at suitable points of the Bearings must be attached. So preferably egg Attachment to the outer fixed part of the bearing take place on a circumference over the barrel path of the rolling elements both at the vertical vertex (Contact forces Fz) as well as by an angle of 90 ° in Direction of rotation of the wheel offset, especially for the detection of braking and acceleration as well as lateral and insurgents.

Other suitable positions are also possible here, whereby also for complete registration of the forces any combination of mounting locations can be advantageous NEN. At each mounting point, the Wheel direction tangential and axial local expansion on the Bearing shell captured. The strain gauges (DMS) are usually in voltage divider configuration or switched as a Wheatstone measuring bridge, in particular to increase the measuring effect and to eliminate Parasitics.

At some positions the strain gauges experience especially the tangentially oriented one medium elongation, which is mainly the contact force Fz corresponds, which can typically be approx. 5 kN,  however, this basic signal becomes significant in its strength modulates when a rolling element, e.g. B. a ball this point just happened because of the wheel rotation. The Rolling elements are usually so with the two Bearing shells mounted so that they are under tension and have no radial play.

In a typical case, the number of balls is in a wheel bearing for a motor vehicle, for example de 14; they are in the rolling bearing by a so-called Ka fig at a certain distance from each other. When the wheel moves, they roll and take the cage with you so that it is flat if circulates.

Since the riot force is just over half the Balls (e.g. 7 pieces) distributed and at least 6 of them have always been under force, it was previously assumed that the local modulation of the ball caused by the ball movement Elongation in some sensor element arrangements Does not exceed 1/7 of the riot force Fz. Operational however, it shows that the local modulation of the strain typically accounts for approximately 50 to 100%, d. H. the mean of the Elongation is dramatically in positive and through the balls changed negative direction. This way you win the front part that the modulation can also be used at the same time version of the speed. Between the wheel speed and the number of cages or balls in circulation with a fixed connection, whereby by the high and in effective riot force Fz ensures that There is virtually no slip between the two speeds stands.

The invention can in a particularly advantageous manner an embodiment can be realized when as sensor elements  two strain gauges connected in series at half a ball spacing on the outer bearing shell are brought and with an evaluation circuit the difference the signals of both sensor elements is evaluated. Consequently is guaranteed according to the invention that the Deh voltage measuring strips recorded modulation of the at the camp force signals acting on the shell by 180 ° if possible is out of phase.

A difference evaluation of the two previously described Partial resistances are particularly good for speed detection suitable. Due to the diameter tolerances of the balls in the rolling bearing, however, is the sine-like modulation of the Stretch signals not quite regular; therefore it remains one additional modulation from the period of a radum runs, which are either tolerable in their disruptive effect is, or by an accompanying frequency filter can be suppressed, but here by the Frequency filter caused time factor in the evaluation is taken into account.

According to a further embodiment of the invention also by evaluating the rolling element or Ku gel modulation the forces acting on the rolling bearing be recorded. This takes advantage of the local Deformation of the bearing shells due to the ball movement strongly coupled to the force transmitted by the ball is. The ball does not transmit any force to the bearing shell len, there is no modulation of the local expansion chip ratios take place due to the ball movement. The first approximation is therefore the amplitude of these modules tion proportional to that transmitted by the ball force and that transmitted by a single ball  Force is in turn proportional to the total force that acts on the entire rolling bearing.

The resistance values R (t) of a strain gauge resistor placed on the bearing shell are therefore approximately as follows:
R (t) = A0 + A1. sin (ωt) +. , , , (Terms of higher order, such as quadratic, cubic or higher harmonic terms; 2ω, 3ω, etc.)

In a first approximation, the coefficient A0 is proportional to the mean local voltage, that is, to the force F, which acts on the entire bearing and is proportional to it, but in a first approximation the coefficient A1; which represents the amplitude of the modulation. A more detailed description of the coupling of these coefficients A0 and A1 is possible with the following functions:

A0 = f (F)

A1 = g (F)

The previously described embodiment of the invention therefore takes advantage of the fact that the size of the modula tion is a function of the force F and then none at all eliminating disturbance variable by means of complex filtering is to be suppressed. From observing the modulation you can also on the speed and thus on the close future position of the ball. From knowledge the location of the balls and knowledge of the measurement signal can thus clearly be closed on the acting force and the dynamics of the evaluation significantly be raised.  

Furthermore, with a third embodiment according to the invention force form feasible, this also due to the elastic deformations of the bearing shells due to the external forces and moments is possible. If you want to for the purpose of force measurement before Modu described using the first embodiment not use it, on the contrary, even suppress it you can also add a second sensor element, whose position on the circumference of La shell by half a ball distance from the first is separate, avoid modulation if you have both Partial expansion resistors be like a single resistor seeks and switches in series. So the sum of the remains two partial resistances from the ball circulation in the rolling bearing largely unaffected. If the one contra stood straight stretched to a maximum by a ball the other partial resistor is currently in the gap and undergoes a relative minimum of stretch.  

With these embodiments according to the invention forth in an advantageous manner redundant information the sensor signals of the sensor arrangement are obtained. It is possible in principle, for example the force that acts on a wheel bearing, on two different Wei to determine. If the signal of the strain gauge is stands z. B. filtered by means of a low pass, so obtained one takes the time average, that of the mechanical chip voltage of the camp corresponds, whereby one then the same evaluates the current component of the signal. If you look at it only the fast oscillating part of the signal that is from the amplitude of this sig results from the spherical movement nals also information about the active force.

In summary, it can be said that the inventions sensor arrangement according to the invention in a simple manner a rotation Number acquisition on a rolling bearing enables without z. B. egg NEN separate speed sensor as plug-in part with associated Use the polar wheel and plug. Can continue also the z. B. air gap arising in magnetic sensors problems are avoided and there is one beyond also a direction detection when evaluating the two Expansion resistance sig offset by half the ball distance possible. According to the invention, it is therefore a higher one Degree of integration of the sensor elements in the rolling bearing achievable with an uncritical signal decoupling.

These and other features of preferred training gene of the invention go out not only from the claims the description and the drawings, the individual characteristics individually or for more ren in the form of sub-combinations in the execution form of the invention and realized in other fields be and advantageous as well as protective designs  can represent, for which protection is claimed here becomes.

drawing

Embodiments of a sensor arrangement according to the invention tion are explained with reference to the drawing. Show it:

Fig. 1 is a sectional view of a rolling bearing equipped with a sensor arrangement for a rotating axle in a vehicle chassis;

Figure 2 is a detail view of the bearing shells of the rolling bearing with two by half the angular spacing of the bearing balls offset strain gauge as the sensor elements.

Fig. 3 is a block diagram of the switch together quantitative th strain gauges;

Fig. 4 shows an embodiment of a mechatronic arrangement of connected strain gauges stands on a substrate and

Fig. 5 is a diagram from which the determination of the force acting on the bearing from the amplitudes of the rolling element modulation is possible.

Description of the embodiments

In Fig. 1 is a simplified sectional view of a rolling bearing 1 for a rotating axle 2, which device is fixedly inserted in a vehicle chassis 3. A fixed bearing shell 4 sits on the chassis 3 and the rotating bearing shell 5 is located on the wheel axle 2 ; Force components Fx and Fz occur on the rolling bearing. In the rolling bearing 1 there are also the rolling elements, here balls 6 . On the outer fixed bearing shell 4 sensor elements 7 and 8 are indicated, with which a detection of the strains is to be carried out, the stresses upon rotation of the wheel axis 2 and the associated mechanical stresses of the balls 6 and the bearing shells 4 and 5 occur.

In the illustration of FIG. 2, the bearings 4 and 5 and the balls 6 are enlarged fragmentary showing ge, said balls 6 α at an angular spacing are disposed zuein other. The sensor elements 7 and 8 are strain gauges (strain gauges) or strain resistors which are intended to carry out a measurement at location A on the circumference of the outer bearing shell 4 . In order to record and evaluate a speed-dependent modulation of the mechanical stresses in the bearing shell 4 , these strain gauges 7 and 8 at location A are each offset by half the angular distance α / 2 of the balls 6 .

A first possibility for an evaluation of the sensor signals is that the two strain gauges 7 and 8 are evaluated with regard to the difference in the signals, for. B. by a voltage divider circuit, since a differential evaluation is particularly well suited for speed detection. In order to reduce unwanted effects of undesired modulations, these can be suppressed by a tracking frequency filter (not shown here).

If, on the other hand, you only want to use the modulation described above for force measurement in the rolling bearing 1 , but on the contrary, you even want to suppress it, the second possibility is to consider the two strain gauges 7 and 8 as a single resistor and connect them in series according to FIG the electrical circuit diagram of the strain gauges 7 and 8 connected in series is shown. Here, the sum of the two partial resistances remains largely unaffected by the ball circulation in the rolling bearing. While one resistor (e.g. resistor 7 ) is just stretched to a maximum by a ball 6 , the other partial resistor (e.g. resistor 8 ) is just in the gap and experiences a relative minimum of stretching ,

FIG. 4 shows a view of strain gauging resistors connected to a respective measuring bridge, for example sensor 7 . This previously described strain gauge resistance 7 can possibly over an insulation layer, not shown here, on a metallic intermediate support 61 , z. B. a plate 62 or a circular shape, inexpensive to apply. This intermediate carrier 61 can then be welded or pressed in at the previously described locations of the rolling bearing or the corresponding vehicle parts or otherwise non-positively connected. On the plate 62 then both axially and tangentially measuring strain gauges can be applied in full or half-bridge circuit.

This bridge circuit according to FIG. 4 can then also be connected to electronic modules 63 , with which signal evaluation and transmission to further measuring points or another evaluation circuit is possible. The signal transmission via connection means 64 , 65 can z. B. serial over a digital bus or an analog bus. This so-called mechatronic arrangement allows the additional direct assignment of components for electronic signal processing, so that, for example, digital output signals can be generated directly and the sensor arrangement can be directly connected to a bus system, e.g. B. in a motor vehicle can be turned on.

From Fig. 5, a diagram shows, as is shown in the Mo dulationssignal an analog output signal of a voltage measuring resistor Deh or the sensor array over time. There are the amplitudes caused by a large number of influences 13 of the rolling body modulation, the amplitudes 14 , 15 and 16 being identified for the determination of the force F acting on the rolling bearing 1 . The amplitude 14 is here an acting force F ₁ = 2 kN, the amplitude 15 an acting force F ₂ = 4 kN and the amplitude 16 is an acting force F ₃ = 6 kN.

In the evaluation according to this exemplary embodiment, use is made of the fact that the local deformation of the bearing shell 4 according to FIG. 1 is strongly coupled to the force transmitted by the ball 6 due to the movement of the balls 6 . If the ball 6 does not transmit any force to the bearing shell 4 , then no modulation of the local expansion stress conditions will take place due to the ball movement.

Claims (7)

1. Sensor arrangement in a roller bearing ( 1 ) for detection and evaluation of speed-dependent and / or other physical quantities during the movement of the components in the roller bearing ( 1 ) ( 2 ), characterized in that the fixed bearing shell ( 4 ) of the Rolling gers ( 1 ) acting, caused by rolling elements ( 6 ) of the rolling bearing ( 1 ) expansion forces with strain sensitive sensors ( 7 , 8 ) are detected by the fact that two sensors ( 7 , 8 ) each by half the angular distance (α) the rolling elements ( 6 ) in the direction of rotation to each other on the bearing shell ( 4 ) are brought to. 2. Sensor arrangement according to claim 1, characterized in that as sensors two mutually assigned strain gauges ( 7 , 8 ) or strain gauges measuring bridge circuits ( 10 , 11 ) on the outer La gerschale ( 4 ) are attached. 3. A method for evaluating the output signal of the sensor arrangement according to claim 2, characterized in that for a speed measurement of the rotating parts ( 2 ) guided through the roller bearing ( 1 ) with an evaluation circuit, the difference between the signals of the two sensors ( 7 , 8 ; 10 , 11 ) is evaluated. 4. The method for evaluating the output signal of the sensor arrangement according to claim 2, characterized in that for a measurement of the forces occurring in the rolling bearing ( 1 ) with an evaluation circuit, the sum of the signals of both sensors ( 7 , 8 ; 10 , 11 ) is evaluated. 5. The method according to claim 3 or 4, characterized net that the speed obtained with the evaluation circuit dependent signals processed with a frequency filter become. 6. The method for evaluating the output signal of the sensor arrangement according to claim 4, characterized in that with an evaluation circuit the amplitudes ( 13 ; 14 , 15 , 16 ) caused by the rolling elements ( 6 ) of the modulation of the output signal of the sensors ( 7 , 8 ; 10 , 11 ) and thus the forces (F; F ₁ , F ₂ , F ₃ ) acting on the roller bearing ( 1 ) are recorded. 7. The method according to claim 6, characterized in that the resistance values R (t) of a strain measuring resistor ( 7 , 8 ; 10 , 11 ) applied to the bearing shell ( 4 ) result approximately as follows:
R (t) = A0 + A1. sin (ωt) + (higher-order terms),
wherein the coefficient (A0) and the coefficient (A1) are in a first approximation proportional to the mean local force (F) which acts on the entire rolling bearing ( 1 ).