Device for measuring rotary movements

p0001The invention relates to a device for measuring rotational movements and for producing an electrical alternating signal representing the rotational movement, which can be installed in the rotational axis of the rotary movement-carrying part, with a stationary measuring value pick-up having a measuring system arranged in a housing with a signaling ring , Which is designed as a component of a hollow-cylindrical or cup-shaped component. And which can be coupled to the part carrying out the rotary movement.

p0002Such a device is known from the European patent application EP-A-0 226 828. In this publication, a tachogenerator is attached to a drive shaft. The stator of the tachogenerator is connected to a fixed machine part, while the drive shaft, which is designed as a hollow shaft in the connection area, constitutes the rotor. A ball bearing is provided for supporting the rotor in the stator. The tachogenerator includes an encoder disc coupled to the rotating hollow shaft by means of a quick-release device and a measuring system which is arranged parallel to the axis and is attached to the stator and which in turn consists of a transmitter and receiver arranged on the circumference of the coding disk. The entire tachogenerator, consisting of the encoder disc and measuring system, is accommodated in a housing fixed to the stator.

p0003European Patent Application EP-A-0 400 241 also discloses a device for measuring the rotational movement of this shaft arranged on the hollow end portion of a rotating shaft. A measuring coil is arranged in a housing attached to the stationary part of the device and cooperates with a coil mounted on the rotor to measure the rotational movement.

p0004The invention is concerned with devices of this type which are provided for measuring the wheel speeds for anti-lock control, drive slip control or chassis control systems of motor vehicles. In general, in these systems, each vehicle wheel is equipped with such a measuring device or such a wheel sensor. The requirements for the functionality and reliability of the sensors are high. A considerable part of the overall cost of the control system is to be applied to the manufacture and assembly of the sensors. In particular, it is necessary in the known measuring devices to set and maintain the air gap between the stationary sensor or sensor and a toothed disk coupled to the wheel very precisely. The useful signal and the distance of the useful signal from unavoidable interference signals are largely determined by the adjustment and maintenance of the air gap. Therefore, efforts are being made to develop sensors which can be produced with relatively little effort and which can be assembled in a simple manner and, if necessary, exchanged.

p0005Wheel bearing sensors are also known in which the sensor and the pulse generator ring or the toothed wheel are installed directly in the wheel bearing (see "Automotive Engineering", April 91, "Advancements in vehicle wheel speed sensing technology"). This reduces the space required for the sensor. However, accurate assembly and adjustment is still required because tolerances for the air gap between the sensor and the pulse generator ring must be maintained.

p0006The invention is based on the object of developing a measuring device which is suitable in particular for installation in a wheel bearing and which is distinguished by a low production effort, compact design and, in particular, by a simple assembly and nevertheless accurate adjustment of the air gap.

p0007It has been found that this object can be achieved by means of a measuring device of the type mentioned at the outset, the special feature of which is that the measuring transducer is arranged in the axis of rotation of the part carrying out the rotary movement and can be locked and has a at least partially cylindrical housing part, And that the signaling ring is rotatably mounted on the jacket surface of the housing part of the measuring transducer.

p0008Some particularly advantageous embodiments of the invention are described in the appended subclaims.

p0009A particularly simple measuring device can be realized by the design of the signaling ring in the form of a hollow-cylindrical component, which is rotatably mounted directly on the housing of the measuring transducer and which is coupled to the wheel during the mounting of the sensor by means of a driver. Since the signaling ring does not have to transmit any forces, it is generally sufficient to apply a sliding layer for supporting this ring on the sensor housing.

p0010Furthermore, it is advantageous that the signaling ring can already be placed on the sensor ring before mounting the sensor, so that an adjustment is no longer needed when the complete measuring device is installed in the wheel bearing.

p0011An advantageous embodiment of the invention consists in that a double-sided measuring system is arranged perpendicular to the axis of rotation in the sensor housing. As a result, an improvement of the useful signal can be achieved even with a compact design of the transducer. In addition, the requirements on the central position of the sensor with respect to the signaling ring are reduced since an enlargement of the air gap on one side necessarily results in the reduction of the air gap on the other side of the double-sided measuring system.

p0012A particularly expedient double-sided measuring system consists of a measuring coil which contains a permanent magnetic core magnetized perpendicularly to the measuring coil axis. An elongated, plate-shaped pole shoe is arranged on the two pole faces of this permanent magnet, the pole shoes projecting out of the coil on both sides and extending almost as far as the inner surface of the signal transmitter housing. With a suitable arrangement of the pole shoes in relation to the arrangement of the teeth or magnetic segments of the signal generator ring, it can be achieved that the magnetic flux in the core of the measuring coil constantly changes its direction as a result of the rotary movement and thereby induces a comparatively high useful signal in the measuring coil.

p0013Further features, advantages and possible applications of the invention can be gathered from the following description of exemplary embodiments with reference to the figures.

p0014Show it<dl id="dl0001"><dt>FIG</dt><dd>In a schematically simplified side view, a measuring device according to the invention, </dd><dt>FIG</dt><dd>In longitudinal section, an embodiment of the measuring device according to FIG. 1,</dd><dt>FIG</dt><dd>In the same manner as FIG. 2, but reduced, a further embodiment of a measuring device according to the invention, and FIG</dd><dt>FIG</dt><dd>In the same manner as FIG. 2 shows a similar arrangement with a modified signaling ring.</dd></dl>

p0015According to FIG. 1, the device according to the invention consists of a measured value sensor 1, generally referred to as a sensor, and a signal generator ring 2, which is here a component of a cup-shaped signal generator component 3.

p0016The measured value sensor or sensor 1 has a cylindrical housing part 4 in which the actual measuring system is arranged and on which the signal generator ring 2 is rotatably mounted and supported. A housing part 5 of the sensor preferably serves for holding and fastening the sensor 1 to a stationary component of the motor vehicle or the wheel bearing. In addition, an electrical cable 6 for connecting the measured value pickup 1 to an evaluation logic unit (not shown in FIG. 1) is guided through this component 5.

p0017The signal transmitter component 3 is equipped with a driver 7 symbolically indicated in FIG. 2 and 3, the driver 7 engages in a corresponding recess of the wheel or of the wheel bearing part which carries out the rotation, so that the signal transmitter component 3 rotates with the part carrying out the rotary movement to be measured ; On the other hand, the measuring sensor 1 is held stationary in the axis of rotation, which is symbolized by a dash-dotted line in FIG.

p0018FIG. 2 shows in detail a measuring device constructed according to the principle described with reference to FIG. 1, which in this case is installed in a wheel bearing of a vehicle. 8 is a portion of the fixed wheel bearing outer ring, and 9 is the end portion of the corresponding wheel bearing inner ring which rotates with the wheel. In this case, this is a plug-in measuring sensor or sensor 10, which is seated in a holder 11, which here is inserted into the grease cap 12 of the wheel bearing 8, 9 or is formed as a component of this fat cap 12. In the holder 11, the sensor 10 is held in a predetermined angular position by means of a latching lug 13, which engages in a corresponding recess of the sleeve-shaped holder 11. A spring 14 also belongs to the support mechanism. Such a mounting is characterized by a simple design and, in particular, permits very rapid assembly and disassembly.

p0019This is an inductive transducer. The measuring system includes a double-sided measuring coil 15 which is arranged perpendicular to the axis of the sensor 10 which coincides with the axis of rotation of the wheel (not shown). The measuring coil 15, the individual parts of which are not shown here, preferably has a permanent magnetic core and pole shoes, which protrude from the coil core on both sides and extend as far as the wall 16 of the cylindrical housing part 17 of the illustrated sensor 10. The measuring coil itself, in the interior of which the permanent magnetic core and the pole shoes are located, essentially consists of a coil former 18 and of at least one winding.

p0020A signaling ring, which has already been explained with reference to FIG. 1, is arranged rotatably in relation to the fixed sensor 10 on the cylindrical housing 17. The signaling ring 19 has an internal toothing 20. The change of teeth and tooth gaps as a result of a rotary movement leads in a known manner to the change of a magnetic flux generated by a permanent magnet arranged in the interior of the measuring coil 15. This change in the magnetic flux in turn leads to the induction of a voltage in the winding of the measuring coil 15. Instead of the internal toothing, a perforated ring or a ring consisting of magnetic and non-magnetic segments can, of course, also be used.

p0021The signal transmitter ring 19 is formed in FIG. 2 as a component of a cup-shaped or stepped, hollow-cylindrical component 21, which in this exemplary embodiment is coupled by a fit or by a driver with the bearing inner ring 9, which rotates with the wheel. Since the cylindrical part of the signal generator component 21 forming or supporting the signal transmitter ring 19 is supported by the cylindrical housing of the sensor 10 and does not need to transmit any forces, a stable fastening of the component 21 to the bearing inner ring 9 is superfluous; It merely has to be ensured that the signal-generator component 21 is "carried along" by the component carrying out the rotary movement. These requirements are characterized by a relatively simple design, which allows easy and fast assembly and, where appropriate, Exchange of the complete measuring device according to the invention.

p0022The embodiment of the invention according to FIG. 3 differs from the construction according to FIG. 2 by an even more compact construction of the measuring device. In this case, the measuring value pickup 22 is inserted, together with the signaling ring 23 already rotatably mounted on the sensor housing, into a holder provided for this purpose. A measuring coil 24, which is arranged perpendicular to the axis of rotation, is once again located in the sensor housing in the region of the signal transmitter ring 23. A holder 25 for receiving, positioning and locking the inserted sensor 22 is in turn embodied as a component of the wheel bearing fat cap 27. An axial bore is provided for the signal generator ring 23 in the rotatably mounted shaft 26 of a wheel. When the complete measuring device consisting of the signal transmitter ring 23 and the sensor 22 is inserted, the signaling ring 23 is brought into engagement with the wheel shaft 26 in some known manner so that the signaling ring 23 can rotate with the wheel on the cylindrical housing of the stationary measuring value pickup 22. In such a design, the adjustment of the air gap between the housing of the sensor 22 and the signaling ring 23 is ensured within narrow tolerances merely by inserting, without additional adjustment.

p0023FIG. 4 shows an embodiment according to the invention in which the coupling of a signaling ring 28 to the bearing inner ring 9 'or a steering knuckle which rotates with the rotary movement-executing part is solved in a particularly clever manner. Moreover, the design of the sensor 10 ', the holder 11' and its insertion into a fat cap 12 'largely resembles the exemplary embodiment described with reference to FIG.

p0024The signaling ring 28 of the device according to FIG. 4 is in turn mounted on the cylindrical housing part 17 'of the sensor 10'. With the aid of a leaf spring 30 which is supported on the end face 29 of the sensor housing, the signaling ring 28 is pressed against the bearing inner ring provided with a toothing 31 in this exemplary embodiment. Cams 32, which are comparable with the driver 7 according to FIG. 1, ensure that the rotary movement of the inner ring 9 'is transmitted to the signaling ring 28.

p0025This design allows the use of very small gears because the air gap between the signaling ring 28 and the sensor pole shoes can be kept very small. The sensor signal quantity is also largely independent of the usually occurring bearing deformations.