WO2018196835A1

WO2018196835A1 - Magnetoresistive linear position sensor

Info

Publication number: WO2018196835A1
Application number: PCT/CN2018/084750
Authority: WO
Inventors: 刘明峰; 薛松生
Original assignee: 江苏多维科技有限公司
Priority date: 2017-04-27
Filing date: 2018-04-27
Publication date: 2018-11-01
Also published as: CN207007092U

Abstract

A magnetoresistive linear position sensor, comprising a permanent magnet (1) and a magnetoresistive sensor chip (2); one of the permanent magnet (1) and the magnetoresistive sensor chip (2) is fixed; the permanent magnet (1) and the magnetoresistive sensor chip (2) are in relative motion along a fixed motion path; the sensitive direction of the magnetoresistive sensor chip (2) is a direction perpendicular to the fixed motion path; the magnetoresistive sensor chip (2) senses the change in the magnetic field caused by the change in the relative positions of the magnetoresistive sensor chip (2) and the permanent magnet (1), outputs a voltage signal changing with the position, and converts same into position information by means of signal processing.

Description

Magnetoresistive linear position sensor

Technical field

The invention belongs to the technical field of magnetic sensors, in particular to a magnetoresistive linear position sensor for detecting a linear position of a permanent magnet by a magnetoresistive sensing chip.

Background technique

In the actual linear position measurement, the position information to be measured is converted into a magnetic field that changes with the position by the permanent magnet, and the position information to be measured can be obtained by detecting the magnetic field by a Hall element or the like. In the actual test, for space-limited close-range high-precision position measurement, due to the close distance between the permanent magnet and the magnetosensitive element, the magnetic field generated by the permanent magnet is very high and can be as high as several thousand Gauss. In this way, only a large number of Hall elements can be used. Since the noise level of the Hall element itself is relatively high, the resolution of linear position detection is relatively low; and anisotropic magnetoresistance (AMR) and giant magnetoresistance ( Giant Magnetoresistance (GMR), Tunnel Magnetoresistance (TMR) sensor has a relatively small dynamic range of magnetic field, AMR can only reach several Gauss to tens of Gauss, and GMR and TMR can only reach tens to hundreds. Gauss, so in the actual work, it is easy to saturate the magnetoresistive sensor chip and not work properly, which limits its normal application in linear position measurement.

Summary of the invention

In view of the above problems, in order to overcome the problem of space-limited close-range high-precision position measurement, the magnetic field generated by the permanent magnet is too large to make the magnetoresistive sensor chip saturated and cannot work. The present invention provides a magnetoresistive linear position sensor.

The invention is implemented according to the following technical solutions:

A novel magnetoresistance linear position sensor, comprising:

a permanent magnet

a magnetoresistive sensing chip, the magnetoresistive sensing chip comprising a magnetoresistive sensing element;

Wherein one of the permanent magnet and the magnetoresistive sensor chip is fixedly disposed, and the other is movably disposed along a fixed motion path, the fixed motion path being a straight line;

The sensitive direction of the magnetoresistive sensor chip is a direction perpendicular to the fixed motion path;

The magnetoresistive sensor chip is configured to sense a change of a magnetic field caused by a change in a relative position of the magnetoresistive sensor chip and the permanent magnet, and output a voltage signal that changes with a position, and convert the signal into a position by signal processing. information.

Preferably, the magnetoresistive sensor chip is a TMR tunnel magnetoresistive sensor chip or a GMR giant magnetoresistive sensor chip.

Preferably, the magnetization direction of the permanent magnet is a direction parallel to the z-axis, and the sensitive direction of the magnetoresistive sensor chip is parallel to the x-axis or the y-axis in the xy plane.

More preferably, the fixed motion path extends along the z-axis.

Preferably, the magnetoresistive sensor chip is a gradient half-bridge magnetoresistive sensor chip, and the gradient half-bridge magnetoresistive sensor chip comprises two magnetoresistive sensing elements, and the two magnetoresistive sensing elements are symmetrically distributed in the Both sides of the magnetoresistive sensor chip.

Preferably, the two magnetoresistive sensing elements are fabricated on a single chip by a semiconductor process, and the two magnetoresistive sensing elements are respectively movably disposed on the single chip to adjust the separation distance therebetween .

Preferably, the magnetoresistive sensor chip is a gradient full-bridge magnetoresistive sensor chip, and the gradient full-bridge magnetoresistive sensor chip comprises four magnetoresistive sensing elements, and four magnetoresistive sensing elements are symmetrically distributed in the Both sides of the magnetoresistive sensor chip.

Preferably, the four magnetoresistive sensing elements are fabricated on a single chip by a semiconductor process, and the magnetoresistive sensing elements are respectively movably disposed on the single chip to enable magnetoresistive sensing elements on both sides The separation distance is adjustable.

Preferably, the magnetoresistive linear position sensor further includes a fixing frame, one of the permanent magnet and the magnetoresistive sensing chip is fixedly disposed on the fixing frame, and the other can be fixed along the fixing frame The moving path is movably disposed on the fixed frame.

Compared with the prior art, the invention has the following beneficial effects:

The sensitive direction of the magnetoresistive sensing element is perpendicular to the direction of the fixed motion path such that it senses the magnetic field component of the magnetic field of the permanent magnet along a direction perpendicular to the fixed motion path, and the magnetic field component in a direction perpendicular to the fixed motion path Small, thus ensuring that the magnetoresistive sensor operates in an unsaturated zone, ensuring that it can work normally, overcoming space-limited close-range high-precision position measurement. The magnetic field generated by the permanent magnet in the direction of the fixed motion path is too high and causes saturation. The problem.

Specifically, the present invention has a magnetic field component of the X-axis and the Y-axis of the permanent magnet in the horizontal plane due to the in-plane X-axis and Y-axis directions of the sensitive axis, and the magnetic field components of the X-axis and the Y-axis in the horizontal plane are compared. Small, thus ensuring that the magnetoresistive sensor operates in an unsaturated region, ensuring that it can work normally, and overcoming the problem of saturation of the magnetic field Z component generated by the permanent magnet caused by the space-constrained close-range high-precision position measurement. At the same time, the invention adopts a gradient half bridge and a gradient full bridge design, has the ability to resist external magnetic field interference, and the work is more stable.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any inventive effort.

Figure 1 is a schematic view of a permanent magnet of a rectangular parallelepiped block structure;

2 is a magnetic line arrow diagram of a permanent magnet of a rectangular parallelepiped block structure on a XOZ cut surface;

3 is a graph showing the relationship between the z component Bz of the magnetic field generated on the four linear clusters at different X positions directly above the permanent magnet with the height z;

4 is a graph showing the relationship between the magnetic field x component Bx and the height z of the four linear clusters of permanent magnets at different X positions directly above the permanent magnet;

Figure 5 is a schematic view of a magnetoresistive linear position sensor of the present invention;

Figure 6 (a) is a positional arrangement diagram of the gradient half-bridge magnetoresistive sensor chip;

Figure 6 (b) is a schematic diagram of the electrical connection of the gradient half-bridge magnetoresistive sensor chip;

Figure 7 (a) is a positional arrangement diagram of the gradient full bridge magnetoresistive sensor chip;

Figure 7 (b) is a schematic diagram of electrical connections of a gradient full bridge magnetoresistive sensor chip.

Wherein, the reference numerals are: 1- permanent magnet, 2-magnetoresistive sensor chip.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. It is a partial embodiment of the invention, and not all of the embodiments.

1 is a schematic view of a permanent magnet of a rectangular parallelepiped block structure according to the present invention. As shown in FIG. 1, the magnetization direction of the permanent magnet is vertically downward. For convenience of description, the center point of the upper surface of the selected rectangular parallelepiped is the origin, as shown in FIG. As shown, a spatial Cartesian coordinate system is created. In order to obtain the spatial magnetic field distribution characteristics of permanent magnets, we perform a static magnetic model simulation analysis of permanent magnets by finite element method.

2 is a magnetic line arrow diagram of a permanent magnet of a rectangular parallelepiped block structure on the XOZ cut surface. As shown in FIG. 2, the size of the permanent magnet is assumed to be 5×4×1 mm, and the material is the most commonly used N35 yttrium-iron rare earth permanent magnet material. The magnetization direction of the permanent magnet is vertically downward. As can be seen from Fig. 2, inside the permanent magnet, the magnetic field lines are directed from the S pole of the upper surface to the N pole of the lower surface; outside the permanent magnet, the magnetic field lines are closed, and the N pole of the lower surface is outwardly bent and then returned to the upper surface. S pole; the magnetic field line is vertically downwards directly above the permanent magnet; the magnetic lines on the left and right sides are symmetric about the YOZ plane of the center line of the permanent magnet; above the permanent magnet, the magnetic line on the left side is bent to the lower right back to the permanent magnet, right side The magnetic lines of force are deflected to the lower left to return to the permanent magnets. According to the symmetry of the magnetic field lines of the permanent magnet block, the magnetic induction intensity z component Bz is symmetrically symmetrical around the permanent magnet, and the magnetic induction intensity X component Bx is symmetrical, that is, equal in magnitude and opposite in direction. According to the spatial symmetry of the permanent magnet, the same property is present in the y-axis direction, so only the x-axis direction is analyzed below.

Fig. 3 is a graph showing the relationship between the z component Bz of the magnetic field generated by the permanent magnets on the four linear clusters at the different X positions directly above the permanent magnet as a function of the height z, as shown in Fig. 3, for different straight lines in the straight cluster, at X At 0, 0.6, 1.2, and 1.8 mm, the magnetic induction intensity z component Bz decreases with increasing height z, and reaches 800 Gs or more in the range of 0 to 1.5 mm, which far exceeds the current GMR/TMR magnetoresistive sensor. The saturation field makes the GMR/TMR magnetoresistive sensor chip inoperable. At this time, the Hall element having the z-axis sensitivity direction can be used to detect the z component of the magnetic field as a function of the height z, and the relative position of the permanent magnet with respect to the Hall element can be obtained by subsequent signal analysis processing. Since the noise level of the Hall element itself is relatively high, the resolution of the linear position detection is relatively low.

Fig. 4 is a graph showing the relationship between the magnetic field x component Bx and the height z of the four linear clusters of permanent magnets at different X positions directly above the permanent magnet, as shown in Fig. 4, where X is 0, 0.6, 1.2, 1.8. The different straight lines in the straight line cluster at mm, the magnetic induction intensity x component Bx is always equal to zero for the straight line in the linear cluster, that is, for the vertical straight line passing through the positive center of the permanent magnet, the magnetic field lines generated by the permanent magnet are perpendicular to the upper surface of the permanent magnet Without the horizontal x component, the same y component is also zero. For other straight lines in a straight cluster, the magnetic induction x component Bx increases first with an increase in height z and then decreases continuously. Also, for a straight line where x is larger, for example, x = 1.2, 1.8 mm, the distance z at which it starts to decrease is significantly smaller than x = 0.6. At the same time, it can be seen from the figure that for a straight line of x=1.8mm, the maximum value of the magnetic induction intensity x component Bx is 1000Gs; the maximum value of the straight line of x=1.2mm is 450Gs; the maximum value of the straight line of x=0.6mm is 200Gs, and After the peak, it continues to decrease as the distance increases. Since the value of the magnetic induction intensity x component Bx is reduced to less than 500 Gs, and can be adjusted by the distance x from the center of the permanent magnet, it is possible to ensure that the GMR/TMR magnetoresistive sensor chip does not saturate. In this way, the magnetoresistive sensor in the in-plane direction of the sensitivity direction can be used to detect the magnetic field x component generated by the permanent magnet, and then the distance between the magnetoresistive sensor chip and the permanent magnet is obtained by signal processing. In order to simplify the measurement and data processing process, the magnetoresistive sensing chip can be operated in the monotonically decreasing segment of Bx by the distance z between the magnetoresistive sensing chip and the permanent magnet and the distance x from the center of the permanent magnet.

FIG. 5 is a schematic diagram of a novel magnetoresistive linear position sensor including a permanent magnet 1, a magnetoresistive sensor chip 2, and a fixed frame necessary for practical application of the sensor (not shown). Out). When the magnetoresistive sensor operates, a relative motion occurs between the permanent magnet 1 and the magnetoresistive sensing chip 2, and the relative distance z changes. Specifically, when the magnetoresistive linear position sensor operates, the permanent magnet 1 can be fixedly disposed on the fixed frame according to different actual conditions, and the magnetoresistive sensor chip 2 can be disposed on the fixed frame by moving up and down; The magnetoresistive sensor chip 2 is fixedly disposed on the fixed frame, and the permanent magnet 1 is disposed on the fixed frame by moving up and down. In other words, one of the permanent magnet 1 and the magnetoresistive sensor chip 2 moves up and down along a fixed motion path which is a straight line extending along the z-axis, and the sensitive direction of the magnetoresistive sensor chip 2 is Vertical to the z-axis. The permanent magnet 1 may have a different shape such as a rectangular parallelepiped, a cube, a thin cylinder or the like. The magnetoresistive sensor chip may be a gradient half-bridge magnetoresistive sensor chip or a gradient full-bridge magnetoresistive sensor chip, and the gradient half-bridge magnetoresistive sensor chip and the gradient full-bridge magnetoresistive sensor chip are respectively taken as an example. The magnetoresistive linear position sensor of the invention is described in detail.

6(a) and 6(b) are respectively a positional arrangement diagram and an electrical connection diagram of the gradient half-bridge magnetoresistive sensor chip. As shown in FIG. 6(a), the gradient half-bridge magnetoresistive sensor chip includes two magnetoresistive sensing elements fabricated on a single chip by a semiconductor process, and the sensing directions of the two magnetoresistive sensing elements are in the xy plane. In the horizontal x direction, the distance between the two magnetoresistive sensing elements is 1, symmetrically distributed on the left and right sides of the magnetoresistive sensor chip, and the two magnetoresistive sensing elements are also distributed in the y-axis direction near the x-axis. In the vicinity, the two magnetoresistive sensing elements are respectively movably disposed on the single chip to adjust the separation distance l therebetween. The electrical connection of the two magnetoresistive sensing elements is shown in Figure 6(b). In operation, the gradient half-bridge magnetoresistive chip is placed directly above the permanent magnet, as shown in Figure 5. During operation, a relative motion occurs between the magnetoresistive sensing chip and the permanent magnet, and the two magnetoresistive sensing elements respectively sense the magnetic field Bx component of the permanent magnet generated in a direction opposite to the distance z, and output a voltage related to the distance z. For the external common mode interference magnetic field along the horizontal x direction, the two magnetoresistive sensing elements sense the same magnetic field and have no output. In the actual sensor design, the magnetic induction intensity x component Bx generated by the permanent magnet sensed by the magnetoresistive sensing chip can be changed by changing the distance l to adapt to different permanent magnet sizes.

7(a) and 7(b) are schematic diagrams showing the positional arrangement and electrical connection of the gradient full-bridge magnetoresistive sensor chip. As shown in FIG. 7(a), the gradient full-bridge magnetoresistive sensor chip includes four magnetoresistive sensing elements fabricated on a single chip by a semiconductor process, and the sensing directions of the four magnetoresistive sensing elements are in the xy plane. In the horizontal x direction, the distance between the two magnetoresistive sensing elements on the left side and the two magnetoresistive sensing elements on the right side is l, symmetrically distributed on the left and right sides of the magnetoresistive sensing chip. At the same time, the two sensing elements are symmetrically distributed in the y-axis direction in the vicinity of the x-axis, and the magnetoresistive sensing elements are respectively movably disposed on the single chip to make the magnetoresistive sensing elements on both sides The separation distance l is adjustable. The electrical connection of the four magnetoresistive sensing elements is shown in Figure 7(b). In operation, the gradient full-bridge magnetoresistive chip is placed directly above the permanent magnet, as shown in Figure 5. During operation, the relative motion between the magnetoresistive sensing chip and the permanent magnet occurs, and the four magnetoresistive sensing elements R1/R3 and R2/R4 respectively sense the magnetic field Bx component of the direction of the permanent magnet generated by the distance z, and output The voltage associated with the distance z. For the external common mode interference magnetic field along the horizontal x direction, the magnetic fields induced by the four magnetoresistive sensing elements R1/R2/R3/R4 are the same, and there is no output. In the actual sensor design, the magnetic induction intensity x component Bx generated by the permanent magnet sensed by the magnetoresistive sensing chip can be changed by changing the distance l to adapt to different permanent magnet sizes.

All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention. While the invention has been shown and described with respect to the preferred embodiments of the present invention, it will be understood that

Claims

A magnetoresistive linear position sensor, comprising:

a permanent magnet

a magnetoresistive sensing chip, the magnetoresistive sensing chip comprising a magnetoresistive sensing element;

Wherein one of the permanent magnet and the magnetoresistive sensor chip is fixedly disposed, and the other is movably disposed along a fixed motion path, the fixed motion path being a straight line;

The sensitive direction of the magnetoresistive sensing element is a direction perpendicular to the fixed motion path;

The magnetoresistive sensor chip is configured to sense a change of a magnetic field caused by a change in a relative position of the magnetoresistive sensor chip and the permanent magnet, and output a voltage signal that changes with a position, and convert the signal into a position by signal processing. information.
A magnetoresistive linear position sensor according to claim 1, wherein the magnetoresistive sensor chip is a TMR tunnel magnetoresistive sensor chip or a GMR giant magnetoresistive sensor chip.
A magnetoresistive linear position sensor according to claim 1, wherein the magnetization direction of the permanent magnet is parallel to the z-axis, and the sensitive direction of the magnetoresistive sensor chip is in the xy plane. The x-axis or y-axis are parallel to each other.
A magnetoresistive linear position sensor according to claim 3, wherein said fixed motion path extends along the z-axis.
The magnetoresistive linear position sensor according to any one of claims 1 to 3, wherein the magnetoresistive sensor chip is a gradient half-bridge magnetoresistive sensor chip, and the gradient half-bridge magnetoresistive sensor The chip includes two magnetoresistive sensing elements, and two magnetoresistive sensing elements are symmetrically distributed on both sides of the magnetoresistive sensing chip.
A magnetoresistive linear position sensor according to claim 5, wherein said two magnetoresistive sensing elements are fabricated on a single chip by a semiconductor process, and said two magnetoresistive sensing elements are respectively movably It is disposed on the single chip to adjust the separation distance between the two.
The magnetoresistive linear position sensor according to any one of claims 1 to 3, wherein the magnetoresistive sensor chip is a gradient full bridge magnetoresistive sensor chip, and the gradient full bridge magnetoresistive sensor The chip includes four magnetoresistive sensing elements, and four magnetoresistive sensing elements are symmetrically distributed on both sides of the magnetoresistive sensing chip.
A magnetoresistive linear position sensor according to claim 7, wherein said four magnetoresistive sensing elements are fabricated on a single chip by a semiconductor process, and said magnetoresistive sensing elements are respectively movably disposed On the single chip, the spacing distance between the magnetoresistive sensing elements on both sides is adjustable.
A magnetoresistive linear position sensor according to claim 1, wherein the magnetoresistive linear position sensor further comprises a fixed frame, one of the permanent magnet and the magnetoresistive sensor chip. The fixing frame is fixedly disposed, and the other is movably disposed on the fixing frame along the fixed motion path.