Method for testing a wheel speed sensor using a conductor loop

Abstract

Method for testing a speed sensor (1) by means of a test device, wherein the speed sensor (1) has at least a first and a second sensitive structure (2, 3), wherein the first and the second sensitive structure (2, 3) are each formed as part of a magnetic field sensor element or are formed as a first and second half-bridge of a magnetic field sensor element, wherein the speed sensor (1) has at least one signal processing circuit, wherein the test device comprises at least a first and a second test conductor section (11, 12) and a current and / or voltage source, wherein the test device is designed in such a way and the test device and the speed sensor (1) are arranged relative to each other in such a way, that the first test conductor section (11) is assigned to the first sensitive structure (2) and the second test conductor section (12) is assigned to the second sensitive structure (3), wherein a current flow (I) of defined current intensity is generated through the two test conductor sections (11, 12) by means of the current and / or voltage source, and wherein the current flow through the first test conductor section (11) and the current flow through the second test conductor section (12) have a substantially opposite flow direction to one another, characterized in that the speed sensor (1) is designed for direction detection, wherein the two sides of the speed sensor, in particular with regard to its chip area (7), on one side the first and a third sensitive structure (2, 4) and on the other side the second and a fourth sensitive structure (3, 5), are assigned to the first and a third test conductor sections (11, 21) on one side and the second and a fourth test conductor sections (12, 22) on the other side.

Description

[0001] The invention relates to a method according to the preamble of claim 1.

[0002] Test methods for testing wheel speed sensors are known. Typically, a rotating magnetic encoder is part of the test device, which is configured in a wheel speed sensor array corresponding to the target to be sensed. These known methods usually require relatively precise positioning between the sensor to be tested and the test device.

[0003] DE 10 2008 050 018 A1 relates to an integrated magnetic sensor circuit comprising a plurality of magnetically sensitive elements and a test conductor, wherein the test conductor generates a differential magnetic field and applies it to the magnetically sensitive elements during a test mode.

[0004] The invention is based on the object of proposing a method for testing a speed sensor in which this positioning can be designed flexibly or relatively generously and / or which is relatively simple and / or cost-effective and / or precise.

[0005] This object is achieved according to the invention by the method according to claim 1.

[0006] The speed sensor is designed for direction detection, wherein the two sides of the speed sensor, in particular with regard to its chip area, are assigned to the first and third sensitive structure on one side and the second and fourth sensitive structure on the other side, the first and third test conductor sections on one side and the second and fourth test conductor sections on the other side.

[0007] The first and second test conductor sections are preferably electrically connected in series and are traversed by a current of equal magnitude but with an inverse direction / orientation, each with respect to the associated sensitive structures, due to their geometric arrangement, in particular because they are formed as two conductor segments of a conductor loop. The current direction through the first and second test conductor sections or through two test conductor sections of a test conductor section pair is expediently defined such that they are arranged substantially parallel to one another or adjacent to one another, and the current through these two conductor sections has an inverse orientation to one another.

[0008] The formulation that the first test conductor section is assigned to the first sensitive structure and the second test conductor section is assigned to the second sensitive structure is preferably understood to mean that the distance of this respective test conductor section to the assigned sensitive structure is smaller than to the other sensitive structures and / or that the respective test conductor section is arranged substantially centrally with a defined distance above or below the assigned sensitive structure.

[0009] A sensitive structure is preferably a magnetic field-sensitive area on a sensor chip. In particular, this sensor chip is designed as an ASIC and includes the sensitive areas and the signal processing circuit integrated on a single chip.

[0010] The test conductor sections are preferably formed by a leadframe or a cable or a conductor track, which in particular has a cross-connection piece whose length corresponds to the distance between the two test conductor sections of a test conductor section pair.

[0011] It is preferred that the first conductor loop has a length that substantially corresponds to the respective length of the first and second test conductor sections. The width of the first conductor loop expediently substantially corresponds to the distance between the first and second test conductor sections.

[0012] It is expedient that the first test conductor section and the second test conductor section are part of a conductor loop, in particular a single conductor loop, which is used to generate a magnetic field that is detected by the sensitive structures of the speed sensor.

[0013] It is preferred that the current flow through the first and second test conductor sections, which is generated by means of the current and / or voltage source, is an alternating current flow and the current and / or voltage source is designed as an alternating current / alternating voltage source.

[0014] The first and the second test conductor sections are preferably arranged substantially parallel to one another and have a defined length, and wherein this length is more than twice, in particular three times or five times, as long as the distance between the first and the second test conductor sections, in particular so that the current through the cross connection between the two test conductor sections plays essentially no role with regard to undesired detection by the at least one sensitive structure.

[0015] It is preferred that the width of the conductor loop and / or the distance between the first and second test conductor sections substantially corresponds to the distance between the first and second sensitive structures of the speed sensor.

[0016] It is preferred that the first and second sensitive structures of the speed sensor are arranged relative to the conductor loop and / or the first and second test conductor sections such that the first and second sensitive structures are each arranged substantially in the middle with respect to the length of the conductor loop and / or the length of the first and second test conductor sections. As a result, the distance of the sensitive structures from an unwanted magnetic field generated by a current through a cross-connection or curved conductor structure not aligned with the test conductor sections is relatively large, and the measurement input of this unwanted magnetic field is relatively small.

[0017] The term length is preferably understood to mean a length or distance or the term longitudinal extent or lengthwise extension.

[0018] The sensitive structures of the speed sensor are expediently designed as GMR, i.e. giant magnetoresistive, sensor structures or alternatively preferably as AMR, as anisotropic magnetoresistive, or TMR, i.e. tunnel magnetoresistive, or Hall structures.

[0019] Preferably, the speed sensor is designed such that the output signals of the first and second sensitive structures are processed / evaluated differentially with respect to one another in the signal processing circuit.

[0020] It is preferred that the speed sensor has four sensitive structures, the output signals of which are processed / evaluated in pairs differentially with respect to one another in the signal processing circuit, and wherein in particular one sensitive structure of this pair is arranged on one side and the other sensitive structure on the other side of the speed sensor, in particular with regard to its chip area.

[0021] It is expedient for the test device to comprise a first and a second conductor loop and / or a first and a second test conductor section as a first test conductor section pair and a third and a fourth test conductor section as a second test conductor section pair, and for the first and the third test conductor section to be assigned to the two sensitive structures on one side of the speed sensor and the second and the fourth test conductor section to be assigned to the two sensitive structures on the other side of the speed sensor, and for the two conductor loops and / or test conductor section pairs and the speed sensor to be arranged / aligned with respect to one another.

[0022] Preferably, the speed sensor is designed such that the distance between the sensitive structures, in pairs or alone, on the chip of the speed sensor, i.e. in particular the distance between the sensitive structures arranged closest to one another from one side to the sensitive structure on the other side of the chip, is designed with respect to the width of the sensitive structures themselves such that this distance from the nearest sensitive structure on one side to the sensitive structure on the other side is at least five times the width.

[0023] Particularly preferred is this ratio of distance to width: at least 10 or 50.

[0024] The at least one conductor loop, in particular comprising a test conductor section pair, is preferably substantially rectangular.

[0025] It is advisable that the first and second conductor loops and / or the first and second test conductor section pairs are not connected in series.

[0026] Preferably, the test device is designed, at least with regard to the interconnection or control of the two conductor loops and / or test conductor section pairs with the at least one current and / or voltage source, such that the current through the two conductor loops or test conductor section pairs is an alternating current or comprises a changing, defined current signal, and the two currents through the two conductor loops or test conductor section pairs have a defined phase offset and / or time offset relative to one another. For this purpose, the test device particularly preferably has two current and / or voltage sources or one current and / or voltage source and a signal processing device with which the defined phase offset or phase offset delta t between the currents I1 and I2 through the two conductor loops and / or test conductor section pairs is provided oris generated, wherein the currents most preferably have a current profile and a defined phase offset from one another. This phase offset between the currents through the two conductor loops and / or test conductor section pairs is expediently used when the speed sensor is designed as a differentially measuring sensor, in particular for detecting the direction of rotation.

[0027] It is preferred that this method be used for end-of-line testing in the course of automotive production or in a sensor test laboratory.

[0028] The speed sensor is preferably designed as a wheel speed sensor, in particular with a direction of rotation detection, and / or transmission speed sensor and / or turbo speed sensor.

[0029] Preferably, the test device has a single conductor loop or exactly two conductor loops, and in particular no coil.

[0030] It is expedient that the test device is designed such that the two conductor loops are arranged next to one another or one above the other with a defined offset in the direction of the spacing direction or the two test conductor section pairs are arranged accordingly with a distance or offset in the spacing direction of the two individual test conductor sections to one another, wherein the distance or lateral offset of the two conductor loops to one another or of the two to one another essentially corresponds to the distance of the sensitive structures from one side to the other side on the chip surface.

[0031] They show in schematic representation, for example, Fig. 1a) and b) each show an embodiment of the chip area with the sensitive structures of the speed sensor, Fig. 2 and Fig. 3 shows an exemplary arrangement of the test device and the speed sensor to each other.

[0032] In the following exemplary calculation regarding the magnetic field detected by the speed sensor through the two test conductor sections, the distance of the conductor loop or the test conductor sections to the respective assigned sensitive structures is designated by R.

[0033] According to a Maxwell equation for the Fig. 2 a) the following applies: H * 2πR = I For example, the thickness of the test conductor sections is 0.8 mm. The distance R between the test conductor sections and the respectively assigned sensitive structures is R = 0.93 + 0.4 = 1.33 mm or 0.00133 m ; H, i.e. the magnetic field strength is 95 A / m, and the current I through the two test conductor sections is I = 0.8 A. This current strength is sufficient to stimulate switching of the speed sensor, in particular with regard to a north-south transition or a tooth-gap transition of a rotating encoder simulated with the test device.

[0034] For this calculation, the current intensity of I = 0.8 A refers to a single current-carrying test conductor section whose magnetic field is detected by a sensitive structure. For example, if two current-carrying test conductor sections 11 and 12 act magnetically on the first and second sensitive structures, respectively, the superimposed magnetic fields will interact in opposite directions, so the current intensity through the test conductor sections should be set to I = 1.3 A and I = 1.4 A, respectively, with a distance of 1.9 mm between the sensitive structures for a speed sensor with rotational direction detection, and a distance of 1.75 mm between the sensitive structures for a speed sensor without rotational direction detection.

[0035] For testing a speed sensor with rotation direction detection, the two currents through the first and second test conductor section pairs have a phase shift to each other.

[0036] Fig. 1a) and Fig. 1b) schematically show the internal structure of an exemplary speed sensor 1. In both figures, the speed sensor 1 has a chip 7, on which the sensitive structures 2, 3, 4, 5 are arranged on its chip surface and in which the signal processing circuit (not shown) is integrated. This chip, designed as an ASIC, is arranged on a leadframe 6 and electrically contacted by bonding wires through contact pads 8 of the leadframe. In addition, the speed sensor 1 has a protective capacitor 9, which is contacted with the left and right conductor paths of the leadframe 6.

[0037] Regarding the distance of the sensitive structures, in pairs as in Fig. 1 a) or alone, as in Fig. 1b), on the chip 7 of the speed sensor, i.e. the distance a of the sensitive structures arranged closest to one another from one side 2, 4 to the sensitive structure on the other side 3, 5 of the chip 7, with respect to the width b of the sensitive structures 2, 3, 4, 5 itself is designed such that this distance a, of the nearest sensitive structure 2, 4 on one side to the sensitive structure 3, 5 on the other side, is at least 10 times greater than or equal to the width b.

[0038] The Fig. 1 a) has four sensitive structures 2, 4, 3, 5, whose output signals are processed / evaluated in pairs 2, 3 and 4, 5 differentially with respect to one another in the signal processing circuit, and wherein in particular one sensitive structure 2, 4 of this pair is arranged on one side and the other sensitive structure 3, 5 on the other side of the speed sensor 1 with respect to its chip area 7. As a result, this speed sensor 1 is made of Fig. 1 a) is designed for direction detection, while the speed sensor 1, from Fig. 1 b) has only two sensitive structures 2, 3, which are also differentially evaluated or measured, but which does not allow direction detection.

[0039] Fig. 2 a) and Fig. 3 a) each show an exemplary test device with test conductor sections 11, 12 and 11, 12, 21, 22, which are assigned to the sensitive structures of a speed sensor 1 and through which the currents I1 and I2 flow.

[0040] Based on the Fig. 2 b) and Fig. 3 b) illustrates the side views. The distance R of the test conductor sections, or more precisely, from their center, to the sensitive structures is shown.

[0041] The example from Fig. 3 a) and b) shows, in contrast to the Fig. 2 a speed sensor 1 for detecting the direction of rotation, which has four sensitive structures 2, 3, 4, 5 for this purpose, and the test device has two test conductor section pairs 11, 12 and 21, 22, which are designed as conductor loops and through which currents I1 and I2 flow, with I1 and I2 having a current value that differs by approximately 10% and, for example, a phase offset from one another. The currents through the test conductor sections of a test conductor section pair are inverse with regard to the current direction. The test conductor sections 11, 12 are assigned to the sensitive structures 2, 3 and the test conductor sections 21, 22 to the sensitive structures 4, 5.The sensitive structures 2, 3, 4, 5 detect the magnetic field generated by the current-carrying test conductor sections 11, 12, 21, 22 and preferably the magnetic field of the associated test conductor section and the signal processing circuit of the speed sensor (not shown) evaluates the output signals of the sensitive structures in pairs 2 and 3 as well as 4 and 5 or in . Fig. 2 only 2 and 3 differentially.

[0042] In Fig. 2a) and Fig. 3a) it can be seen that the speed sensor 1 is arranged with respect to its sensitive structures relative to the conductor loop or the test conductor sections 11, 12, 21, 22 in such a way that the sensitive structures are each arranged substantially in the middle with respect to the length of the conductor loop or the length L of the test conductor sections.

Claims

[1] Method for testing a speed sensor (1) by means of a test device, wherein the speed sensor (1) has at least a first and a second sensitive structure (2, 3), wherein the first and the second sensitive structure (2, 3) are each formed as part of a magnetic field sensor element or are formed as a first and second half-bridge of a magnetic field sensor element, wherein the speed sensor (1) has at least one signal processing circuit, wherein the test device comprises at least a first and a second test conductor section (11, 12) and a current and / or voltage source, wherein the test device is designed in such a way and the test device and the speed sensor (1) are arranged relative to each other in such a way, that the first test conductor section (11) is assigned to the first sensitive structure (2) and the second test conductor section (12) is assigned to the second sensitive structure (3), wherein a current flow (I) of defined current intensity is generated through the two test conductor sections (11, 12) by means of the current and / or voltage source, and wherein the current flow through the first test conductor section (11) and the current flow through the second test conductor section (12) have a substantially opposite flow direction to one another, characterized by , that the speed sensor (1) is designed for direction detection, wherein the two sides of the speed sensor, in particular with regard to its chip area (7), on one side the first and a third sensitive structure (2, 4) and on the other side the second and a fourth sensitive structure (3, 5), are assigned to the first and a third test conductor sections (11, 21) on one side and the second and a fourth test conductor sections (12, 22) on the other side. [2] Method according to claim 1, characterized in that the first test conductor section (11) and the second test conductor section (12) are part of a conductor loop, in particular a single conductor loop, which is used to generate a magnetic field which is detected by the sensitive structures (2, 3) of the speed sensor (1). [3] Method according to claim 1 or 2, characterized bythat the current flow (I) through the first and second test conductor section (11, 12), which is generated by means of the current and / or voltage source, is an alternating current flow and the current and / or voltage source is designed as an alternating current / alternating voltage source. [4] Method according to at least one of claims 1 to 3, characterized by that the first and the second test conductor section (11, 12) are arranged substantially parallel to one another and have a defined length (L), and wherein this length (L) is more than twice, in particular three times or five times, as long as the distance between the first and the second test conductor section (11, 12), in particular so that the current through the cross connection between the two test conductor sections plays essentially no role. [5] Method according to at least one of claims 1 to 4, characterized bythat the width of the conductor loop and / or the distance between the first and second test conductor sections essentially corresponds to the distance between the first and second sensitive structures (2, 3) of the speed sensor (1). [6] Method according to at least one of claims 1 to 5, characterized by that the first and the second sensitive structure (2, 3) of the speed sensor (1) are arranged relative to the conductor loop and / or the first and second test conductor sections such that the first and the second sensitive structure are each arranged substantially in the middle with respect to the length (L) of the conductor loop and / or the length of the first and second test conductor sections. [7] Method according to at least one of claims 1 to 6, characterized by that the sensitive structures (2, 3, 4, 5) are designed as GMR sensor structures. [8] Method according to at least one of claims 1 to 7, characterized bythat the speed sensor (1) is designed such that the output signals of the first and second sensitive structure (2, 3) are processed / evaluated differentially with respect to one another in the signal processing circuit. [9] Method according to at least one of claims 1 to 8, characterized by that the speed sensor (1) has four sensitive structures (2, 3, 4, 5), the output signals of which are processed / evaluated in pairs differentially with respect to one another in the signal processing circuit and wherein in particular one sensitive structure of this pair is arranged on one side and the other sensitive structure on the other side of the speed sensor, in particular with regard to its chip area (7). [10] Method according to at least one of claims 1 to 9, characterized bythat the test device comprises a first and a second conductor loop and / or a first and a second test conductor section (11, 12) as a first test conductor section pair and a third and a fourth test conductor section (21, 22) as a second test conductor section pair, and the first and the third test conductor section (11, 21) are assigned to the two sensitive structures (2, 4) on one side of the speed sensor and the second and the fourth test conductor section (12, 22) are assigned to the two sensitive structures (3, 5) on the other side of the speed sensor and the two conductor loops and / or test conductor section pairs and the speed sensor are arranged / aligned accordingly to one another. [11] Method according to at least one of claims 1 to 10, characterized bythat the distance (a) of the sensitive structures, in pairs or alone, on the chip (7) of the speed sensor is formed with respect to the width (b) of the sensitive structures themselves, so that this distance (a) is at least five times the width (b). [12] Method according to at least one of claims 1 to 11, characterized by that this method is used for testing at the end of the production line of motor vehicles or in a sensor test laboratory. [13] Method according to at least one of claims 1 to 12, characterized by that the speed sensor (1) is designed as a wheel speed sensor.

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