DE19927759A1 - Magnetic distance measuring device - Google Patents

Abstract

The device monitors the relative spacing between an object and a active organ (1) with permanent magnetic teeth (3), or a passive organ of a ferromagnetic material, using a permanent magnet attached to the object, at least one electromagnetic transducer (9) and an evaluation device. One pole face of the permanent magnet faces the organ, with the electromagnetic transducer attached to its side face, the position of the neutral zone within the permanent magnet unaffected by the position of the monitored organ.

Description

Technical field

The invention relates to a device for magnetic Ab level measurement to monitor the distance between one Object and an organ with teeth made of permanent magnets is occupied (active organ) or that of ferromagnetic Material exists (passive organ). Preferred application The present invention is to monitor the dis dance between a ferromagnetic toothed magnet wheel and a magnetically sensitive, in the immediate vicinity of the pole wheel positioned sensor for determining speed, Speed, distance, acceleration and direction of rotation of the Pole wheel.

State of the art

For the contactless detection of the rotation of a fer romagnetic (passive) or permanent magnetic (ak tive) gearwheel are sensors with magneto-electrical Transducers used the movement of the gear in the form of Detect field strength changes and convert them into electrical signals convert (DE-PS 30 41 041). In practice, they will like this neto-electrical converter very close to the gear posi tioned to a high immunity, for example against to ensure external magnetic interference fields. Typical Ab stands are in the range of 0.1 to 1.5 mm. With these ger Ingen intervals there is a slight risk that the sensor un is damaged, for example due to Ver signs of wear in the axle bearings, which the magnet wheel tra gen. Especially in the dynamic operating state of z. B. It is important for rail vehicles to change the distance to know about undetected damage to the sensor and thus preventing its failure (safety aspect). The Distance determination is currently on the stationary gear a feeler gauge (spy) depending on the individual feeling  of the inspector (full but not jammed seat of the sensor teaching) carried out accordingly inaccurately. Besides, it is necessary to dismantle one or more parts, until the gear is accessible.

Presentation of the invention

Proceeding from this, the invention is based on the object specify a device with which the distance between egg nem sensor and a magnet wheel both in the idle state and in dynamic operating state measured in a simple manner and can be monitored.

This object is achieved by a device with solved the features of claim 1. The main advantage of Invention is as follows:

The key point of the invention is the use of a permanent magnet, the pole face facing the toothed organ of which is sufficiently large in relation to the pole wheel module, so that the position of the neutral zone in the permanent magnet is almost unaffected by the respective pole wheel position. The pole wheel module is understood to mean the ratio of the number of teeth to the pitch circle diameter (depending on the tooth shape, approximately the mean diameter) of the pole wheel. The ratio mentioned at the outset is determined by the dimension lp of the permanent magnet in the direction of the magnet wheel movement (see FIG. 1) and the tooth period lz determined by the magnet wheel module (see FIG. 1). This ratio lp to lz should be more than 1.5 if possible.

Because the neutral zone is unaffected by the respective pole wheel position, can be placed on the side of the Perma Magnet attached to the magneto-electrical converter Distance d0 between the face of the magnet wheel and the sensor front edge or its surface facing the organ also in The rest position of the magnet wheel can be determined. Will be beneficial the magneto-electrical converter in the neutral zone itself  attached, because then the measurement signal is zero, since the radial portions of the. responsible for signal generation magnetic field over the entirety of the magnetic field cancel each other out.

In practice, the procedure is as follows:

With a pulse generator known per se (see, for example, DE-PS 30 41 041) the working distance (nominal distance) is known. The pole wheels are usually standardized. Because of the known working distance is also clear where the new central zone is in the operating state. Therefore at Manufacturing the encoder a magneto-electric converter like this be attached to the side surface of the permanent magnet, that he is in the neutral zone when the Im pulse generator is positioned at a working distance from the magnet wheel. This means that when installing such a pulse generator the disadvantages known from the prior art (see above) can be avoided, since only care is taken during installation must be that the side of the permanent magnet brought an output signal from magneto-electrical converters Displays zero. Due to the above-mentioned ratio of lp / lz it is ensured that the respective pole wheel position is none Role plays, so that in the result a statically integrating Distance measurement takes place. For safety's sake, after the one dynamic distance measurement, d. H. at rotating magnet wheel. This should also be the starting point result in signal zero. With a relatively small ratio lp / lz there may be slight deviations. With bigger lp / lz the influence of the respective tooth position (Pol wheel position) on the static measurement, so that the distance measurements in static and dynamic states result in the output signal zero. Operation of the magneto electrical converter in the neutral zone has the advantage that the converter is operated in zero adjustment and thus also thermally shows the most stable behavior. Of course the converter can also be installed outside the neutral zone  become. In this case it is a suitable calibration required, so that a certain output signal a particular the distance (e.g. the nominal distance) of the front edge of the sensor or the surface of the permanentma facing the pole wheel corresponds to the face of the magnet wheel. Since the magneto electrical converters in this case no longer in the zero adjustment is operated, the thermal influences on the Measurement signals to be considered.

Advantageous refinements and developments are with the Features of subclaims 2 to 12 characterized. The Training of the device according to claim 4 has the Advantage of the magneto-electrical converter in operation state, d. H. if the object is arranged at the target distance, no measurement signal is generated, because the signaler generation responsible radial portions of the magnetic Field over the entirety of the magnetic field sensitive area cancel each other out. This configuration has the additional Chen advantage that the magneto-electrical converter through the Operation in zero adjustment also thermally the most stable behavior show. The design according to one of the subclaims 10 to 12 has the particular advantage that you can use only one Permanent magnets needs to move the movement of the Magnetic wheel with magneto-electrical transducers and so on the other hand by the in the neutral zone brought further magneto-electric transducers the distance can be monitored between the sensor and the magnet wheel.

The invention will be explained in more detail using Ausführungsbeispie len and with reference to FIGS . 1 and 2.

Fig. 1 shows a ferromagnetic toothed organ 1 , for example, a gear or a rack, which is movable in the direction of arrow 2 . At a distance d _p from the teeth 3 , a permanent magnet 4 is arranged, the one pole face, z. B. the N-pole face facing the teeth and carries a sensor 5 for detecting the movement of the organ 1 . The target distance of the sensor 5 from the teeth 3 is denoted by d _o . In the operating state, ie during the movement of the organ 1 , care must be taken that the distance d of the sensor 5 from the teeth 3 does not fall below a predeterminable minimum value d _min and does not exceed a predeterminable maximum value d _max . If the minimum value is undershot, there is a risk that the sensor 5 will come into contact with the teeth 3 and be damaged, so that the entire measuring head generally has to be replaced. If the maximum value is exceeded, the function of sensor 5 can be reduced when the measured value is recorded. The sensor 5 consists, for. B. from two magneto-electrical transducer pairs 6 and 7 , which are designed elec trically as a double bridge circuit. One of the sensor is known per se and described in DE-PS 30 41 041. The neutral zone 8 , which is with a free permanent magnet usually in the middle, is here slightly shifted upward by the strong influence of the ferromagnetic organ 1 in the immediate vicinity Chen (shown exaggerated in Fig. 1). In this neutral zone 8 , another electromagnetic transducer 9 , for example a Hall generator, is mounted so that its magnetic field-sensitive surface is aligned parallel to the tangential component of the magnetic field of the permanent magnet. Due to the positioning in the neutral zone, the radial portions of the magnetic field, which are solely responsible for the signal generation in the transducer 9, cancel each other out over the entirety of the magnetic field-sensitive surface, so that the output signal is therefore zero. By operating the transducer around the zero point, it also exhibits the most stable behavior thermally. In general, the positioning of the transducer 9 on the permanent magnet is carried out in such a way that the permanent magnet is held at a distance d from a rotating magnet wheel (test pole wheel) which speaks a desired distance d _{0 of} the sensor 5 from the teeth 3 and that Transducer 9 is observed while observing its output signal in the position on the permanent magnet in which the output signal is zero, the converter 9 is thus in the neutral zone 8 .

If the entire arrangement of permanent magnet 4 , sensor 5 and transducer 9 is brought closer to the organ 1 (distance smaller than sol labstand d ₀ ), this causes a shift in the neutral zone 8 and thus a signed output signal with increasing amount at the transducer 9 . If the arrangement is removed from the organ 1 (distance greater than the desired distance d ₀ ), the sign of the output signal is reversed. It can therefore be seen from the sign of the output signal whether the distance between the sensor 5 and the organ 1 is decreasing or increasing. Curve 1 in Fig. 2 shows schematically the course of the output signal of the converter 9 , z. B. the output voltage U _{H of} a Hall generator, in dependence on the distance d of the sensor 5 from the teeth 3rd At the desired distance d ₀ , the converter 9 is in the neutral zone 8 and U _H is zero. With a reduction in the state from the influence of the ferromagnetic organ 1 increases, which leads to a shift of the neutral zone 8 in the direction of the north pole. Since the converter 9 is then outside the neutral zone, an output signal U _H <O is generated. With further approximation, the value of U _H increases in amount up to a final value U _H (d = 0). With an increase in the distance, the influence of the ferromagnetic organ 1 decreases, which leads to a shift of the neutral zone 8 in the direction of the south pole. The converter 9 is again outside the neutral zone and an output signal U _H <O is present. With increasing distance, the influence of the ferromagnetic organ 1 disappears and a maximum value U _H (d = ∞) is reached. In this case, the neutral zone 8 is in a position as is the case with a free permanent magnet, that is to say generally in the middle, and the transducer 9 is at its maximum distance from this neutral zone. In the operating state, that is to say during the movement of the organ 1 , care must be taken that the deviations of the distance d from the target value d ₀ do not exceed the predetermined limit values d _min and d _max . This is done in a simple manner by monitoring the output signal U _{H of} the converter 9 .

The advantages of the invention are also evident when installing a measuring device according to FIG. 1 in a vehicle, for. B. a rail vehicle. It is no longer necessary to disassemble one or more parts to make the magnet wheel accessible for a feeler gauge. The measuring device or the pulse generator equipped with the distance sensor only has to be pushed into a holder provided for this purpose, the output signal U _{H of} the converter 9 being observable. When U _H = 0, the measuring device is at the desired distance d _o from the pole wheel and can be locked. Whether there is a tooth when installing against the measuring device. 3 or a tooth gap is of minor importance as long as the pole area is large enough in relation to the dimensions of the tooth and tooth gap so that the position of the neutral zone remains as unaffected as possible. In practice (pole wheel according to DIN 867), the ratio of the side length l _{p of} the permanent magnet 4 to the periodic tooth spacing l _z should not be less than 1.5. The result is a distance measurement that is both statically and dynamically integrated.

In a modification of the previously presented embodiment, it is also possible to position the transducer 9 in the neutral zone, as it is in the permanent magnet in the undisturbed state. Then there is the course of the output signal U _H according to curve 2 of Fig. 2. In this case, U _H (d = ∞) = 0 and when the entire arrangement of permanent magnet 4 , sensor 5 and transducer 9 is approached to the organ 1 , the neutral zone 8 is shifted upwards and the output signal U _H increases in amount up to a final value U _H (d = 0). The target distance d ₀ then corresponds to a certain value U _H (d = d ₀ ). The same applies to the limit values d _min and d _max . As a result, the course of the output signal U _{H is} identical to that in the first embodiment. The curve 2 is only shifted downwards and approaches the limit value U _H (d = ∞) = 0 for d → ∞. Since the converter 9 is not operated at zero point (U _H = 0) at the sol lab stand d ₀ , the is thermal stability less than in the first embodiment example.

Reference list

1

toothed organ, e.g. B. gear or rack

2nd

Direction of movement

3rd

teeth

4

Permanent magnet

5

Sensor for detecting the movement of the organ

1

6

,

7

magneto-electrical transducer pairs

8th

neutral zone

9

magneto-electrical converter for monitoring the distance of the sensor

5

to the organ

1

Claims (12)

1. Device for magnetic distance measurement for monitoring the distance between an object and an organ, that has teeth made of permanent magnets (active Or gan) or made of ferromagnetic material (pas sives organ), consisting of a permanent magnet, little At least one magneto-electrical converter and an evaluation device, wherein a pole face of the permanent magnet the Organ facing, the object with the permanent magnet ten is connected in a fixed position, the magneto or the elec trical transducer on a side surface of the permanent magnet are positioned, and the zuge the toothed organ turned pole face of the permanent magnet in relation to the pole wheel module is so large that the location of the neutral zone in the permanent magnet essentially unaffected by the position of the organ. 2. Device according to claim 1, characterized, that the dimension lp of the permanent magnet in the direction of Magnet wheel movement in relation to that through the magnet wheel module certain tooth period lz is more than 1.5. 3. Device according to claim 1 or 2, characterized, that the magneto-electric converter or transducers in the neutra len zone is positioned as they are in the perma nentmagneten in the undisturbed state, and that the Magnetic field sensitive surface of the transducer or transducers in parallel to the tangential component of the magnetic field of the perma magnet is aligned. 4. Apparatus according to claim 1 or 2, characterized in that the one or more magneto-electric transducers is positioned in the neutra len zone as they are in the permanent magnet for a predeterminable distance d _o (target distance) of the object from the Organ is present, and that the magnetic field sensitive surface of the transducer (s) is aligned parallel to the tan component of the magnetic field of the permanent magnet. 5. Device according to one of claims 1 to 4, characterized, that the organ is a rack or a gear (Polrad) acts. 6. Device according to one of claims 1 to 5, characterized, that as a mageneto-electrical converter field plates and / or Hall generators are provided. 7. Device according to one of claims 1 to 6, characterized, that the evaluation device has an electrical bridge circuit having. 8. Device according to one of claims 1 to 7, characterized, that the magneto-electric converter or transducers on the perma Magnets are attached. 9. Device according to one of claims 1 to 8, characterized, that the object is a sensor for detecting the Movement of the organ acts on the organ facing pole face of the permanent magnet is arranged. 10. The device according to claim 9, characterized, that the sensor is one or more magneto electrical transducers with which the movement of the Or goose is detectable in the form of field strength changes.   11. The device according to claim 10, characterized, that it is in the magneto-electric transducers supply detection around field plates and / or Hall generators delt. 12. The apparatus of claim 10 or 11, characterized, that several magneto-electrical transducers for motion detection solution are provided with an electrical bridge circuit.