Device for measuring the position of an object moving linearly along a direction of movement, in particular a brake pedal sensor

Abstract

Device (100) for measuring the position of an object (10) that moves linearly along a direction of movement (M), in particular a brake pedal sensor (200), comprising two Hall sensors (20) and a first magnetic element (11) and a second magnetic element (12), each of which is movable relative to the Hall sensors (20), wherein a magnetization direction (51) of the first magnetic element (11) is perpendicular to a magnetization direction (52) of the second magnetic element (12), characterized in that the first magnetic element (11) is magnetized transversely to the direction of movement (M) and the second magnetic element (12) is magnetized along the direction of movement (M) and that the first magnetic element (11) and the second magnetic element (12) are arranged one behind the other in the direction of movement (M).

Description

[0001] The invention relates to a device for measuring the position of an object moving linearly along a direction of movement, in particular a brake pedal sensor, comprising two Hall sensors and a first and a second magnetic element, each of which is movable relative to the Hall sensors, wherein a magnetization direction of the first magnetic element is perpendicular to a magnetization direction of the second magnetic element.

[0002] To enable interference-free position measurement, devices exist with two Hall sensors and a first and a second magnetic element, each movable relative to the Hall sensors. The use of two Hall sensors allows for a differential measurement of the magnetic field generated by the magnetic elements, without homogeneous disturbances, for example from an electric motor, influencing the measurement.

[0003] However, a disadvantage of the existing systems is that the measurement range is limited, since either the difference signal is small or the measured values ​​only allow a clear assignment to a position signal within a limited range.

[0004] EP 2 581 707 A1 discloses a position sensor in which two field sensors are placed along a line parallel to the movement to be detected. Two magnets are arranged at an angle of approximately 90° to each other and at an angle of approximately 45° to the direction of movement.

[0005] DE 10 2016 205 766 A1 relates to an actuating device with a measuring system for detecting the displacement position of a switching element. A magnetic sensor unit detects at least two directional components of a magnetic field. A magnetic unit has two magnets arranged relative to each other such that a first dipole axis, connecting a north pole and a south pole of the first magnet, is oriented obliquely to a second dipole axis, connecting a north pole and a south pole of the second magnet.

[0006] DE 10 2009 055 104 A1 relates to a magnetic field sensor arrangement for position detection of moving components. The spatial components of the magnetic field of a magnetic system on the moving component change their direction along the path to be detected. At least one magnet is located on the linearly and rotationally movable component as part of the magnetic system. The angle to the linear direction of movement of the rotationally moving component is 45° to the axis of rotation.

[0007] DE 10 2004 011 591 A1 discloses a connecting element used for measuring the force of a relative motion between a magnetic system and a magnetic sensor. The magnetic system is arranged relative to the magnetic sensor such that a component of the magnetic field perpendicular to the relative motion is linearized.

[0008] DE 10 2012 203 822 A1 relates to a stroke detection device comprising a magnetism or magnet detection unit, a first magnetic field generation unit, and a second magnetic field generation unit. The two magnetic field generation units have opposite polarities. Their arrangement is intended to allow magnetic or magnetizable foreign bodies to collect in the area of ​​the gap ends and not impede the magnetic flux at the open ends.

[0009] The object of the invention is to provide a solution in which measurements can be taken over a large measuring range.

[0010] According to the invention, this is solved by the fact that the first magnetic element is magnetized transversely to the direction of movement and the second magnetic element is magnetized along the direction of movement, and that the first magnetic element and the second magnetic element are arranged one behind the other in the direction of movement.

[0011] This solution results in a clear measurement signal over a larger measuring range, while simultaneously ensuring a sufficiently large difference in the measured magnetic field for accurate measurement. The magnetization direction along and perpendicular to the direction of movement simplifies both the measurement and the data analysis.

[0012] The magnetization directions of the two magnetic elements form an angle that is not equal to 0 or 180 degrees. Consequently, the magnetizations are neither parallel nor anti-parallel to each other.

[0013] The solution according to the invention can be further improved with the following developments and embodiments, each of which is advantageous in itself and can be combined with each other as desired.

[0014] The angle between the magnetization direction of the first magnetic element and the magnetization direction of the second magnetic element can be between 5 and 175 degrees. This allows for accurate measurement. Preferably, the angle is between 45 and 135 degrees to further improve the measurement.

[0015] In a particularly advantageous embodiment, the angle can be 90 degrees. Such a perpendicular alignment allows for particularly accurate measurement.

[0016] The magnetization direction of the first magnetic element preferably runs along a measuring direction of the Hall sensors.

[0017] The magnetization direction of the first and second magnetic elements can be considered a principal direction of magnetization within the magnetic element. This magnetization direction can run from a south pole to a north pole of the magnetic element.

[0018] The magnetization directions can be skew to each other. The angle between the two magnetization directions can then be determined by projecting one onto a plane that contains the other.

[0019] For a brake pedal sensor, the measuring range can typically be divided into two areas: a linear range and a clamping range, whereby in the linear range the sensor can provide a signal linear to the movement of the moving object and in the clamping range a constant signal.

[0020] To achieve a good distribution of the magnetic field, the ratio of the length of the first magnetic element along the direction of movement to the length of the second magnetic element along the direction of movement can be greater than 3.

[0021] Preferably, the ratio of the length of the first magnetic element along the direction of movement to the length of the second magnetic element along the direction of movement is less than 10.

[0022] In an advantageous embodiment, the first magnetic element and the second magnetic element are spaced apart, with the distance being greater than the length of the second magnetic element. This distance can be measured in the direction of movement.

[0023] The distance can be less than three times the length of the second magnetic element.

[0024] Alternatively or additionally, the distance can correspond to between 5% and 30% of a measuring span along the direction of movement. In particular, it can be approximately 15% of the measuring span. As with the other configurations, this can lead to a good distribution of the magnetic field lines. The measuring span can be the span along which the movement of the object is to be measured.

[0025] For a sufficient distribution of the magnetic field, the ratio of the length of the first magnetic element to the width of the first magnetic element can be at least 2.

[0026] To enable accurate measurement while keeping the device compact, the ratio of the length of the second magnetic element to the width of the first magnetic element can be no more than 2 / 3.

[0027] The parameters mentioned above can be interdependent. A change in one parameter may necessitate an adjustment of another. In particular, the lengths, distances, and widths mentioned may also depend on the magnetic field strength generated by the magnetic elements. Preferably, the parameters are coordinated such that the Hall sensors enable unambiguous measurements with a sufficiently good measurement signal across the entire measuring range.

[0028] Preferably, the device comprises exactly two magnetic elements. The solution according to the invention eliminates the need for additional magnetic elements. This makes manufacturing particularly simple and cost-effective.

[0029] In particular, the first and second magnetic elements can be arranged in a straight line, one behind the other. This allows for a compact design.

[0030] In a simple design, the magnetic elements can be connected to the object in a way that transmits movement. The Hall sensors can be stationary and mounted on other elements, such as a housing.

[0031] In an alternative configuration, the Hall sensors can be connected to the object in a motion-transmitting manner. In such a configuration, the magnetic elements can be stationary and attached to other elements, such as the housing.

[0032] Preferably, the device is designed such that the two magnetic elements are a fixed distance apart. This can be ensured, for example, by spacers or by attaching them to the object or a housing.

[0033] The magnetic elements may include permanent magnets to keep operation simple.

[0034] The object can be, in particular, a transmission element connected to a brake pedal, such as a rod.

[0035] The device is preferably designed to operate the Hall sensors differentially.

[0036] The Hall sensors preferably each comprise two measuring plates for measurements in two mutually perpendicular directions. One direction preferably runs along the direction of movement of the object. A second direction is perpendicular to the direction of movement and towards the object.

[0037] Preferably, the device is housed in a brake pedal sensor for an automobile.

[0038] The invention is explained in more detail below by way of example with reference to advantageous embodiments and the drawings. The advantageous developments and embodiments shown are independent of each other and can be combined as required in any application.

[0039] They show: Fig. 1 a schematic perspective view of a device in a brake pedal sensor; Fig. 2 a schematic perspective view of the device Fig. 1; Fig. 3 A schematic side view of the two magnetic elements of the device from the Fig. 1 and Fig. 2; Fig. 4. A diagram of the differential angle as a function of the position of the magnetic elements for the device of Fig. 1, Fig. 2 to Fig. 3; Fig. 5 a diagram showing the variation of the magnetic field depending on the position of the magnetic elements for the device of Fig. 1, Fig. 2 to Fig. 3; Fig. 6 A representation of a simulation of the magnetic field lines for the embodiment shown.

[0040] In Fig. Figure 1 shows a brake pedal sensor 200 with a device 100. The device 100 serves to measure the position of an object 10 that is linearly movable along a direction of motion M. The object 10 can be connected to a brake pedal, so that the position of the brake pedal can be measured indirectly with the device 10.

[0041] The direction of movement M runs along a direction X, which together with the directions Y and Z spans a three-dimensional coordinate system, where X, Y and Z are each perpendicular to each other.

[0042] As in Fig. As shown in Figure 2, the device 100 comprises, in particular, two Hall sensors 20 housed in a casing 60. Each of the two Hall sensors 20 has two plates that enable measurements of the components of the magnetic field in the X and Z directions. The measurement is a differential Hall measurement, in which a gradient, rather than the absolute magnetic field, is used to determine the position. Such a measurement is largely insensitive to homogeneous disturbances, since these act with the same magnitude on both Hall sensors 20, and any difference remains unaffected.

[0043] A first magnetic element 11 and a second magnetic element 12 are arranged one behind the other, in particular aligned with each other, with respect to the direction of motion M and the direction X. A shell 70, which encloses the two magnetic elements 11, 12, is also shown. The shell 70 need not be a physical shell, but can merely be a mathematical construct that specifies the space defined by the two magnetic elements 11, 12.

[0044] The magnetic elements 51, 52 are guided at a distance D at the Hall sensors 20.

[0045] In Fig. Figure 3 shows the magnetic elements 11 and 12 and their magnetization directions 51 and 52 in more detail. It is particularly important that the magnetization direction 51 of the first magnetic element 11 is perpendicular to the magnetization direction 52 of the second magnetic element 12. The magnetization direction 51 of the first magnetic element 11 is perpendicular to the direction of movement and along direction Z, which is parallel to the measuring direction of the Hall sensors 20. The magnetization direction 52 of the second magnetic element 12 is parallel to the direction of movement M. The magnetization directions 51 and 52 are, in each case, the directions from a south pole S to a north pole N of the magnetic elements 11 and 12.

[0046] In the example shown, an angle 30 between the first magnetization direction 51 and the second magnetization direction 52 is therefore 90 degrees. In other embodiments, this angle can also deviate from 90 degrees, but should not be 0 or 180 degrees. Advantageous values ​​for the angle can be between 45 and 135 degrees or between 60 and 120 degrees.

[0047] Choosing such an angle results in a measuring span of 40 (see Fig. 1) along which the object 10 can be moved along the direction of movement and in which a unique result for position determination can be obtained, is larger than in previous solutions. This is achieved by the magnetization directions 51, 52 running obliquely or perpendicularly to each other. In previous solutions, a so-called roll-over occurred even at smaller measurement ranges 40, meaning that a unique assignment of the values ​​to a single position signal was not possible, but rather that several position signals were possible for certain constellations of measured values.

[0048] In the Fig. 4 and Fig. Figure 5 shows diagrams depicting the differential angle or variation of the magnetic field along a stroke of the magnetic elements 11, 12. Curves for typical tolerances of the device 100 are shown. For all these values, a unique assignment of the measured values ​​is possible at a sufficiently high gradient of the magnetic field, which is necessary for accurate measurement.

[0049] In a linear range 301, the angle signal is particularly important. Fig. 4 essentially linear. Even within a clamping range 303, a clear assignment is still possible. The complete measuring range 302 corresponds to the measuring span 40 and comprises the linear range 301 and the clamping range 303.

[0050] Again with reference to Fig. 3. It should be noted that the lengths L1 and L2 of the magnetic elements 11 and 12 are different. The length L1 of the first magnetic element 11, measured along the direction of movement M, is approximately four times greater than the length L2 of the second magnetic element 12, also measured along the direction of movement M. Furthermore, there is a distance A between the first magnetic element 11 and the second magnetic element 12 along the direction of movement M, which in the example shown is about twice the length L2 of the second magnetic element 12. The configuration shown allows for accurate measurement of the various components of the magnetic field generated by the magnetic elements 11 and 12 and acting on the Hall sensors 20.

[0051] The magnetic elements 11, 12 are each cylindrical and have a diameter 50 measured perpendicular to the direction of motion M. Due to their cylindrical shape, these diameters correspond to widths B1, B2 measured along the lateral direction B, which runs parallel to the direction Y. The widths B1, B2 are approximately three times the length L2 of the second magnetic element 12. The distance A between the two magnetic elements 11, 12 is approximately 15 percent of the measuring span 40.

[0052] In the example shown, the magnetic elements 11, 12 are connected to the object to be measured in a motion-transmitting manner, and the Hall sensors 20 are arranged stationary in the housing 60. In alternative embodiments, the Hall sensors 20 can be connected to the object 10 in a motion-transmitting manner, and the magnetic elements 11, 12 can be stationary.

[0053] In the Fig.Figure 6 shows a simulation of the magnetic field of the illustrated embodiment. It can be seen that at every point in the measuring span, a unique assignment to the position is possible based on the measured values, in particular the angle and the difference between the magnetic field strengths. Reference sign 10 objects 11 first magnetic element 12 second magnetic element 20 Hall sensor 30 angles 40 measuring span 50 diameter 60 cases 70 case 100 Device 200 brake pedal sensor 301 linear range 302 complete measuring range 303 clamping range 402 Curve for typical tolerance 413 Curve for typical tolerance A distance B Latitude direction B1 Width of the first magnetic element B2 Width of the second magnetic element D distance L1 Length of the first magnetic element L2 Length of the second magnetic element South Pole North Pole M Direction of movement X Spatial direction Y spatial direction Z spatial direction

Claims

Device (100) for measuring the position of an object (10) that moves linearly along a direction of movement (M), in particular a brake pedal sensor (200), comprising two Hall sensors (20) and a first magnetic element (11) and a second magnetic element (12), each of which is movable relative to the Hall sensors (20), wherein a magnetization direction (51) of the first magnetic element (11) is perpendicular to a magnetization direction (52) of the second magnetic element (12), characterized in that the first magnetic element (11) is magnetized transversely to the direction of movement (M) and the second magnetic element (12) is magnetized along the direction of movement (M) and that the first magnetic element (11) and the second magnetic element (12) are arranged one behind the other in the direction of movement (M). Device (100) according to claim 1, characterized in that the ratio of a length (L1) of the first magnetic element (11) along the direction of movement (M) to a length (L2) of the second magnetic element (12) along the direction of movement (M) is greater than 3. Device (100) according to claim 1 or 2, characterized in that the ratio of a length (L1) of the first magnetic element (11) along the direction of movement (M) to a length (L2) of the second magnetic element (12) along the direction of movement (M) is less than 10. Device (100) according to one of claims 1 to 3, characterized in that the first magnetic element (11) and the second magnetic element (12) have a distance (A) from each other and the distance (A) is greater than a length (L2) of the second magnetic element (12). Device (100) according to one of claims 1 to 4, characterized in that the first magnetic element (11) and the second magnetic element (12) have a distance (A) from each other and the distance (A) is less than three times the length (L2) of the second magnetic element (12). Device (100) according to one of claims 1 to 5, characterized in that the first magnetic element (11) and the second magnetic element (12) have a distance (A) from each other and the distance corresponds to approximately 15% of a measuring span (40) along the direction of movement (M). Device (100) according to one of claims 1 to 6, characterized in that the ratio of a length (L1) of the first magnetic element (11) to a width (B1) of the first magnetic element (11) is at least 2. Device (100) according to one of claims 1 to 7, characterized in that the ratio of a length (L2) of the second magnetic element (12) to a width (B2) of the first magnetic element (11) is at most 2 / 3. Device (100) according to one of claims 1 to 8, characterized in that the device (100) comprises exactly two magnetic elements (11, 12). Device (100) according to one of claims 1 to 9, characterized in that the magnetic elements (11, 12) are connected to the object (10) in a motion-transmitting manner. Device (100) according to one of claims 1 to 10, characterized in that the lengths (L1, L2) of the first (11) and second magnetic element (12) are of different sizes along the direction of movement (M). Device (100) according to one of claims 1 to 11, characterized in that the first and second magnetic element (11, 12) are each cylindrical and have a diameter (50) measured perpendicular to the direction of movement (M). Device (100) according to one of claims 1 to 12, characterized in that the two Hall sensors (20) are housed in a housing (60). Device (100) according to one of claims 1 to 13, characterized in that the two Hall sensors (20) each have two plates which enable differential Hall measurements of the components of a magnetic field in the direction of movement (M) and in a direction (Z) which runs parallel to the measuring direction of the Hall sensors (20). Brake pedal sensor (200) for an automobile, comprising a device (100) according to one of claims 1 to 14.

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