DE102018217283A1 - Angle sensor - Google Patents

Abstract

The invention relates to an angle sensor (16) for outputting an output signal which is dependent on an angle of rotation (18), comprising a shaft (38) rotatably mounted about its axis of rotation (37), and a permanent magnet fastened in a rotationally fixed manner to an axial end (39) of the shaft (38) (30) for emitting a magnetic measuring field (32) and a sensor element (28) arranged at a distance from the permanent magnet (30) with an air gap (31) for detecting the magnetic measuring field (32), the sensor element (28) being in a position relative to the axis of rotation (37) is arranged by the radial extent of the permanent magnet (30), the permanent magnet (30) having an axial magnetization with respect to the axis of rotation (37).

Description

The invention relates to an angle sensor for outputting an output signal which is dependent on an angle of rotation, and to a method for producing an angle sensor.

WO 2006/029 946 A1 discloses a sensor with a field transmitter element in the form of a diametrically magnetized, cylindrical permanent magnet and a sensor element with an associated evaluation circuit for detecting a magnetic field emitted by the permanent magnet. The permanent magnet can be moved via a path to be detected, such as an angle of rotation, wherein the sensor element detects the angle of rotation based on the magnetic field emitted by the transmitter magnet and outputs it in an output signal. Such angle sensors can be used in cooperation with corresponding articulated rods as a level sensor for detecting the distance between a vehicle body and a wheel carrier.

The diametrically magnetized permanent magnets used in such sensors generate a sinusoidal flux density curve during their rotation, which can be measured precisely and easily. However, this only applies to a diameter range that corresponds to approximately one third of the total diameter of the cylindrical magnet. Most of the magnet is therefore not used during the measurement. On the other hand, in order to be able to use a magnetic field of sufficient strength in the axial direction for the measurement, high-quality permanent magnets with rare earths must be used, which is why the unused part of the magnet has a particularly negative influence on the comparison of costs and benefits.

It is therefore an object of the invention to provide an angle sensor which is inexpensive and / or efficient.

The object is solved by the features of the independent claim. Preferred developments are the subject of the dependent claims. The claims are made the subject of the description by express reference.

According to the invention, an angle sensor for outputting an output signal which is dependent on an angle of rotation comprises a shaft which is rotatably mounted about its axis of rotation, a permanent magnet which is fixed in a rotationally fixed manner to an axial end of the shaft for emitting a magnetic measuring field and a sensor element which is arranged at a distance from the permanent magnet with an air gap for detecting the magnetic measuring field , wherein the sensor element is arranged in a region limited relative to the axis of rotation by the radial extent of the permanent magnet, the permanent magnet having an axial magnetization with respect to the axis of rotation. In other words, the permanent magnet has a magnetization, the poles of which are arranged parallel to the direction of the axis of rotation. The axially aligned magnetization means that the permanent magnet can have a small diameter, which means that magnetic material and thus costs can be saved.

The sensor element is arranged in a region limited relative to the axis of rotation by the radial extent of the permanent magnet. In other words, the sensor element is arranged vertically below the end face of the permanent magnet or in the area that corresponds to an axial extension of the permanent magnet.

The sensor element is preferably a Hall sensor.

Alternatively, several sensor elements can also be used, which are also arranged in this area. In particular, four sensor elements can be used which ensure an unambiguous measurement over 360 ° by means of an arctan calculation.

It is preferred that the permanent magnet has an uneven contour on the side opposite the sensor element, so that the air gap is variable as a function of the angle of rotation, in particular is variable in accordance with a sinusoidal profile. The variable air gap is preferably defined as a function of the angle of rotation as the shortest distance between the permanent magnet and the sensor element. The uneven contour causes the air gap and thus the measured flux density to vary with the angle of rotation, so that the flux density is a measure of the angle of rotation.

It corresponds to a preferred embodiment that the permanent magnet is a ferrite magnet and in particular has no rare earths, such as neodymium, lanthanum, yttrium, dysprosium, terbium or praseodymium. Although the performance of a ferrite magnet is lower than that of a rare earth magnet, the design of the angle sensor according to the invention allows the use of a magnet with a significantly weaker field. This reduces the costs for the magnet and for the angle sensor as a whole.

The permanent magnet is preferably a plastic-bonded, injection-molded or pressed magnet. Injected or pressed magnets are created as composite materials by embedding for example hard ferrite or rare earth magnet powder in thermoplastic materials. The proportions of the magnetic powder determine the magnetic and mechanical properties. Plastic-bonded, injection-molded magnets are more elastic than plastic-bonded pressed magnets, but usually have lower magnetic values.

It is preferred that the permanent magnet has at least two partial magnets with opposite axial magnetizations in the direction of the axis of rotation.

The partial magnets are preferably arranged and formed axially symmetrical with respect to the axis of rotation. Correspondingly, for example, a partial magnet with a north-south magnetization in the direction parallel to the axis of rotation is arranged radially adjacent to a partial magnet which has a south-north magnetization in the direction parallel to the axis of rotation. The end face of the permanent magnet formed by the partial magnets thus has a magnetic north and a south pole.

It is preferred that the partial magnets abut one another and in particular are made in one piece, for example as a plastic-bonded, injection-molded or pressed magnet.

The partial magnets on the side opposite the sensor element or the end face of the permanent magnet preferably each have a hill-like shape in the axial direction. Thus, by appropriately dimensioning the hill-like shape, an uneven contour can be provided, so that the air gap can be changed as a function of the angle of rotation and enables a clear, precise measurement signal.

It is preferred that the sensor element is designed to detect the magnetic measuring field on the basis of its magnetic flux density.

It corresponds to a preferred embodiment that the permanent magnet has an essentially cylindrical outer wall. In other words, it has a constant radius over all angles of rotation about the axis of rotation.

The sensor element is preferably electrically connected to an evaluation circuit, the evaluation circuit being designed to generate an output signal based on the magnetic measuring field that changes with the angle of rotation.

According to a further aspect of the invention, a method for producing an angle sensor set up for outputting an output signal dependent on an angle of rotation, in particular one of the angle sensors specified above, comprises the steps of providing a shaft rotatably mounted about its axis of rotation, injection molding a permanent magnet set up for outputting a magnetic measuring field to an axial end of the shaft so that the permanent magnet has an axial magnetization with respect to the axis of rotation, and arranging a sensor element so that the sensor element is arranged in an area limited relative to the axis of rotation by the radial extent of the permanent magnet.

In one development, the specified method comprises the step of forming an anti-rotation device at the axial end before the permanent magnet is molded on.

According to a further aspect of the invention, the angle sensor for outputting an output signal which is dependent on an angle of rotation is produced according to one of the methods specified.

• 1 einen Winkelsensor, ausgebildet als Höhenstandssensor zum Erfassen eines Weges zwischen einem Rad und einem Fahrwerk in einem Fahrzeug,
• 2 einen Teil einer Welle in einer teilweisen Schnittdarstellung, in die ein Permanentmagnet für den Winkelsensor der 1 anspritzbar ist,
• 3 in einer teilweisen Schnittdarstellung den Teil der Welle aus 2, an die der Permanentmagnet für den Winkelsensor der 1 angespritzt ist.

The above-described properties, features and advantages of this invention and the manner in which they are achieved can be more clearly understood in connection with the following description of the exemplary embodiments, which are explained in more detail in connection with the drawings. Show in a schematic representation

• 1 an angle sensor designed as a level sensor for detecting a path between a wheel and a chassis in a vehicle,
• 2nd a part of a shaft in a partial sectional view, in which a permanent magnet for the angle sensor of 1 is sprayable,
• 3rd in a partial sectional view the part of the shaft 2nd to which the permanent magnet for the angle sensor of the 1 is injected.

In the figures, the same technical elements are provided with the same reference symbols and described only once.

It's going on 1 Reference, which is designed as a height sensor angle sensor 16 shows. Such a level sensor can be used, for example, in the context of a chassis control system in which the lifting, pitching and rolling movements of a chassis relative to a road on which the vehicle's stationary wheels roll in a vertical axis are minimized in order to reduce the driving properties of the vehicle when driving in one direction of travel to improve. For this purpose, the chassis control system in one example from the DE 10 2005 060 173 A1 known way a Control device, which in the present embodiment receives rotation angles from angle sensors arranged on each wheel, which describe a relative position of the corresponding wheel relative to the chassis.

The angle sensor 16 has in the present embodiment a circuit housing which can be connected in the vertical axis in a stationary manner to the chassis 26 on. These are on the circuit housing 26 Mounting holes not visible any further 27 formed through which a fastener, not shown, such as a screw can be passed. In the circuit housing 26 is an evaluation circuit 28 encased by a sensor element to be described in the form of a permanent magnet 30th a physical field in the form of a magnetic field 32 receives. The magnet 30th is from the evaluation circuit 28 with an air gap 31 objected to in the present version of the angle of rotation 18th is dependent. Through a through opening 34 of the circuit housing 26 is one about an axis of rotation 37 rotatable encoder shaft 38 added to the magnet 30th at one axial end 39 is held. From the magnet 30th opposite axial end 40 of the encoder housing 38 a lever protrudes at right angles 41 from, at the radial end of a mounting hole 42 is formed on which the angle sensor 16 is fixedly connected to one of the wheels in the vertical axis.

If the corresponding wheel moves in the vertical axis in relation to the chassis, the wheel also moves the lever 41 and thus rotates the encoder shaft 38 compared to the circuit housing 26 with the rotation angle to be transmitted 16 . This also moves the magnetic field 32 compared to the evaluation circuit 28 with the angle of rotation 18th . The moving magnetic field 32 changes depending on the angle of rotation 18th compared to the evaluation circuit 28 in its magnetic field strength or flux density, what from the evaluation circuit 28 metrologically, for example, via a Hall element known per se in the evaluation circuit 28 captured and at an output interface 46 in a the angle of rotation 18th carrying output signal, not shown, can be transmitted to a control device.

The permanent magnet 30th can to the axial end 39 the encoder shaft 38 be injected. To do this, first click on the 2nd Referenced in the encoder shaft 38 is shown in a state before the magnet 30th to the encoder shaft 38 is injected.

At the axial end 39 the encoder shaft 38 is an elliptical and hollowed-out holding element in the present embodiment 62 trained in two walls 64 are included, which are used as an anti-rotation device for the magnet 30th should serve.

In this hollowed out holding element 62 a magnetic material is injected. A plastic such as polyamide, polyphenylene sulfide or the like can be used as the filler, for example, as the magnetic material. A magnetic powder, for example based on hard ferrite or NdFeB, can be embedded in this plastic. The magnetization of the injected material can take place directly during the injection or afterwards when the injection process has already been completed.

Alternatively, at the axial end 39 the encoder shaft 38 a magnet prepared beforehand, for example by sintering, can be attached, for example by gluing.

In 3rd is an example of a molded magnet 30th shown in which the permanent magnet 30th two partial magnets arranged and formed axisymmetrically to the axis of rotation 30a , 30b with in the direction of the axis of rotation 37 has opposite axial magnetizations. The two magnetizations are by one N for the North Pole or through a S clarified for the South Pole.

The permanent magnet 30th has an uneven contour on the front side, which lies opposite the sensor element, so that the air gap 31 depending on the angle of rotation 18th is variable according to a sinusoidal curve. For this purpose, each of the partial magnets points in this exemplary embodiment 30a , 30b each have a hill-shaped shape in the axial direction. The hill-shaped formations are designed so that when the shaft rotates 38 with the permanent magnet 30th the formations passing by the sensor element show a sinusoidal change in the air gap 31 cause and thus information about the angle of rotation 18th give.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included 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.

Patent literature cited

• DE 102005060173 A1 [0025]

Claims (11)

Including angle sensor (16) for outputting an output signal dependent on an angle of rotation (18) a shaft (38) rotatably mounted about its axis of rotation (37), - A permanent magnet (30) fixed to an axial end (39) of the shaft (38) for emitting a magnetic measuring field (32) and - A sensor element (28) arranged at a distance from the permanent magnet (30) with an air gap (31) for detecting the magnetic measuring field (32), the sensor element (28) in one relative to the axis of rotation (37) by the radial extent of the permanent magnet (30 ) limited area is arranged, the permanent magnet (30) having an axial magnetization with respect to the axis of rotation (37). Angle sensor (16) according to Claim 1 , characterized in that the permanent magnet (30) has an uneven contour on the side opposite the sensor element (28), so that the air gap (31) is variable as a function of the angle of rotation (18), in particular is variable according to a sinusoidal profile. Angle sensor (16) according to one of the preceding claims, characterized in that the permanent magnet (30) is a ferrite magnet. Angle sensor (16) according to one of the preceding claims, characterized in that the permanent magnet (30) is a plastic-bonded, injection-molded or pressed magnet. Angle sensor (16) according to one of the preceding claims, characterized in that the permanent magnet (30) has two partial magnets (30a, 30b) with opposite axial magnetizations in the direction of the axis of rotation (37). Angle sensor (16) according to Claim 5 , characterized in that the partial magnets (30a, 30b) are arranged and formed axisymmetrically with respect to the axis of rotation (37). Angle sensor (16) according to Claim 5 or 6 , characterized in that the partial magnets (30a, 30b) abut each other and in particular are formed in one piece. Angle sensor (16) according to one of the Claims 5 to 7 , characterized in that the partial magnets (30a, 30b) each have a hill-like shape in the axial direction on the side opposite the sensor element (28). Angle sensor (16) according to one of the preceding claims, characterized in that the sensor element (28) is designed to detect the magnetic measuring field (32) on the basis of its magnetic flux density. Angle sensor (16) according to one of the preceding claims, characterized in that the permanent magnet (30) has a substantially cylindrical outer wall. Angle sensor (16) according to any one of the preceding claims, characterized in that the sensor element (28) is electrically connected to an evaluation circuit (28), the evaluation circuit (28) for generating an output signal based on the changing with the angle of rotation (18) magnetic measuring field (32) is formed.

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