TWI780559B - Position sensing mechanism - Google Patents

Abstract

A position sensing mechanism provided by the invention comprises an encoding element as a sensing signal source, a reading element for sensing signals of the signal source, and a processing unit for receiving and analyzing sensing signals output by the reading element, the position sensing mechanism has a main technical feature lying in a magneto-resistive unit in the reading element for sensing signals of the signal source being a tunneling magneto-resistor (TMR), and two layers of magnetic moments of a reference layer and a free layer of the tunneling magneto-resistor being perpendicular to each other, and in the reference layer and the free layer with the magnetic moments being perpendicular to each other, the magnetic moment of one of the layers is parallel to a film surface, and the magnetic moment of the other layer is perpendicular to the film surface.

Description

Position Sensing Mechanism

The present invention is related to sensing technology, in particular to a position sensing mechanism which uses tunneling magnetoresistance to sense position.

The sensing technology for performing position resolution by sensing the changes of specific signals such as magnetism or light in the encoding element under position changes is a widely used technical means in the prior art. Specifically, for example, in the prior patent No. US6100681A, two groups of Hall sensor chips with a relative displacement of 90 degrees are used to sense the positional change along a moving direction. Or as disclosed in the US20090102461A patent publication, in the technology of using magnetism as the signal source provided by the encoding element, the two magnetic tracks it has are respectively set to binary system and decimal system, and then the majority The discrete Hall sensing elements sense the magnetic field changes of each magnetic track respectively, and analyze it to obtain its position information. It is a technical means to use Hall elements as magnetic sensing elements. Although it is a common technology in position sensing technology, due to the high power consumption and low sensitivity of Hall elements, it is difficult to use as a position sensor. There are still limitations on the sensing element, especially in applications that require low power consumption and high sensing sensitivity, the Hall sensing element has been difficult to meet the needs of the industry.

Further in the prior art, there is disclosed in US10480963 patent as shown in Fig. 1, although it has also utilized the Hall sensor (1) as the sensing element of the absolute column magnetic track (2), but In the sensing of the incremental magnetic track (3), a spin-valve tunneling magneto-resistance element (4, Spin-Valve Tunneling Magneto-Resistance, SV TMR) or anisotropic magneto-resistance element (Anisotropic Magneto-Resistance, AMR) and other relatively low-power and high-sensitivity magnetoresistive elements are used as sensing elements in order to obtain better sensing sensitivity, but due to spin-valve tunneling magnetoresistive elements (4) or different The directional magnetoresistive element obtains position resolution information by sensing the change of the magnetic field angle caused by the movement of the magnetic track. In order to accurately sense the change of the magnetic field angle in the incremental magnetic track, it is necessary to make the The film surface of the spin-valve tunneling magnetoresistive element or the anisotropic magnetoresistance element is located on the x-z plane, thus forming an absolute column magnetic track sensing element located on the x-y plane, that is, a Hall sensor (1), which is Being in a space state on different planes, it is necessary to assemble each sensing element of the absolute row and the incremental row, after being manufactured independently as parts, and then individually carry out precise alignment and then assemble to the On the substrate (not shown in the figure), this not only increases the assembly process and cost, but also affects the accuracy of position determination, making it difficult to effectively improve the yield of products.

Therefore, the main purpose of the present invention is to provide a position sensing mechanism, which uses tunneling magnetoresistance for position sensing, and forms the sensing element directly on the substrate to obtain a multi-sensing element. The integrated sensor avoids the assembly process of the sensing element being assembled on the substrate as an independent discrete part, so as to ensure that the accuracy of position sensing is not affected by poor assembly process.

The reason is that, in order to achieve the above object, the position sensing mechanism provided by the present invention comprises a coding element as a sensing signal source, a reading element for sensing the signal source signal, and a The processing unit that receives and analyzes the sensing signal output by the reading element, and its main technical feature is that the magnetoresistive unit used to sense the signal source signal in the reading element is a tunneling magnetic Tunneling Magneto-Resistance (TMR), and make the magnetic moments of the reference layer (reference layer) and the free layer (free layer) of the tunneling magnetoresistance perpendicular to each other, and at the same time, the magnetic moments of the reference layer and the free layer are perpendicular to each other In , the magnetic moment of one layer is parallel to the film surface, while the magnetic moment of the other layer is perpendicular to the film surface.

Wherein, the system whose magnetic moment is perpendicular to the film surface can be the reference layer or the free layer.

First, please refer to Fig. 2, the position sensing mechanism (10) provided in a preferred embodiment of the present invention mainly includes a coding element (20), a reading element (30) and a processing unit (not shown in the figure).

The encoding element (20) is a conventional magnetic ruler technology using a magnetic field as a signal source, and it is structurally comprised of an absolute row of magnetic tracks (21) and an incremental row of magnetic tracks (22), and the absolute row The magnetic track (21) and the incremental column magnetic track (22) extend side by side along a virtual moving axis, and the magnetic poles are changed in the x-y plane as shown in Figure 2 according to the preset encoding method, generally Generally speaking, the moving axis is usually linear and consistent with the length direction of the magnetic scale, but regarding the magnetic scale technology including the absolute column magnetic track (21) and the incremental column magnetic track (22), Since it belongs to the prior technical content known to those with ordinary knowledge in the technical field of the present invention before the application of the present invention, the specific magnetic pole arrangement, manufacturing process or related technologies will not be repeated here.

The reading element (30) then comprises a first magnetoresistive unit (31) and a second magnetoresistive unit (32), and the quantity of each magnetoresistive unit can be set according to actual needs, and its quantity does not vary. Owing to the achievement of the technical characteristics of the present invention, the numerical value thereof will not be described. As far as the whole of the reading element (30) is concerned, it is separated from the encoding element (20) and adjacent to the encoding element. (20), and the projection range of the reading element (30) to the encoding element (20) can cover the absolute row of magnetic tracks (21) and the incremental row of magnetic tracks (22), so as to be able to Between the reading element (30) and the coding element (20), whether the reading element (30) is moved relative to the coding element (20) or the coding element (20) is moved relative to the reading element When the element (30) moves, when the two generate relative displacement on the moving axis, the magnetic fields of the incremental column magnetic track (22) and the absolute column magnetic track (21) can be changed, and the reading element (30) It is known that, specifically, the first magnetic resistance unit (31) is corresponding to the absolute column magnetic track (21), so as to sense the absolute column magnetic track (21) in the above-mentioned relative displacement state The magnetic field of the track (21) varies, and the second reluctance unit (32) is corresponding to the incremental column magnetic track (22), so as to sense the position of the incremental column magnetic track in the above-mentioned relative displacement state. The magnetic field of (22) varies, thereby sensing the absolute column magnetic track (21) and the incremental column magnetic track (22) by the first magnetic resistance unit (31) and the second magnetic resistance unit (32) After receiving the magnetic field signal, the processing unit can analyze the relative position of the reading element (30) and the encoding element (20) according to the sensing signals outputted, so as to obtain the information of the moving position, For the control of driving components such as linear motors or rotary motors.

What needs to be further explained is that the first magneto-resistance unit (31) and the second magneto-resistance unit (32) are different from the prior art in which different sensing elements are used for the absolute column and the incremental column. , and make the first reluctance unit (31) and the second reluctance unit (32) have the same technical structure, and what is disclosed in this embodiment is to make the first reluctance unit ( 31) and the second magnetoresistance unit (32) are tunneling magnetoresistance (Tunneling Magneto-Resistance, TMR) structures as shown in Figure 3, but wherein, the first magnetoresistance unit (31) can have The tunneling magnetoresistance of a single magnetic tunneling junction (Single Magnetic Tunneling Junction, Single MTJ), and the second magnetoresistive unit (32) is a bridge type tunneling magnetoresistance (Bridge TMR), and makes the tunneling magnetoresistance The magnetic moments (303) of the reference layer (301, reference layer) and the free layer (302, free layer) in the composition are perpendicular to each other, and the magnetic moment of the reference layer (301) is perpendicular to the film surface, And make the magnetic moment of the free layer (302) parallel to the film surface, so that the magnetic moments of the reference layer (301) and the free layer (302) have orthotropic, and make the sensing of tunneling magnetoresistance The film surface is located on the x-y plane as shown in Figure 2. Accordingly, the resistance of the tunneling magnetoresistance can respond to the external magnetic field in the vertical direction (the sensing axis shown in Figure 3 is the z direction shown in Figure 2) The change produces a linear change as shown in FIG. 4 .

Furthermore, the tunneling magnetoresistance of the second magnetoresistive unit (32), which is located on the sensing film surface on the x-y plane as shown in Figure 2, can be subjected to such The sinusoidal wave field in the z direction shown in Figure 2, to produce the sensing signal as Figure 5, at the same time, the tunneling magnetoresistance of the first magneto-resistive unit (31), which is located in the sensor on the x-y plane as shown in Figure 2 To measure the film surface, it is only necessary to judge the positive and negative of the absolute column magnetic track (21) on the magnetic field in the z direction as shown in Figure 2. Therefore, under the above-mentioned relative displacement, the wear of the first magnetic resistance unit (31) The free layer (302) in the tunneling magnetoresistance will change direction as the magnetic pole changes, while the reference layer (301) will maintain the same direction, thus causing a difference in high and low resistance to generate the sensing signal as shown in Figure 6 , to determine its magnetic polarity.

By means of the magnetic moment orthotropy between the reference layer (301) of the tunneling magnetoresistance and the free layer (302), the absolute column magnetism in the magnetic scale can be sensed through the tunneling magnetoresistance with the same structure. The magnetic field changes of the track and the incremental track, so as to obtain the correct position information.

More importantly, except that the first magnetoresistance unit (31) and the second magnetoresistance unit (32) have the same structure, their relative positions to the encoding element (20) are also based on the same plane, That is, the x-y plane shown in Figure 2, so that the tunneling magnetoresistance that constitutes the first magnetoresistive unit (31) and the second magnetoresistive unit (32) can pass through the known semiconductor manufacturing process to In the same thin film deposition, lithography and etching processes, a predetermined number of first magnetoresistive units (31) and second magnetoresistive units (32) with defined relative positions are molded on a substrate (33, shown in FIG. (shown by the dotted line), so as to avoid the defect derived from assembling different discrete sensing elements as in the prior art, so as to obtain a position sensing mechanism that does not need to assemble the sensing elements to ensure the sensing accuracy.

(1): Hall sensor (2): Absolute column track (3): Incremental column track (4): Spin-valve tunneling magnetoresistive element (10): Position sensing mechanism (20): coding element (21): Absolute column track (22): Incremental column track (30): read components (301): Reference layer (302): free layer (303):Magnetic moment (31): the first magnetic resistance unit (32): The second reluctance unit (33):Substrate

Fig. 1 is a three-dimensional schematic view of the prior art. Fig. 2 is a schematic perspective view of a preferred embodiment of the present invention. Fig. 3 is a schematic plan view of tunneling magnetoresistance as a magnetoresistance unit in a preferred embodiment of the present invention. Fig. 4 is a diagram showing the relationship between resistance and magnetic field in a preferred embodiment of the present invention. FIG. 5 is a waveform diagram of sensing signals for incremental columns in a preferred embodiment of the present invention. FIG. 6 is a waveform diagram of sensing signals for absolute columns in a preferred embodiment of the present invention.

(301): Reference layer

(302): free layer

(303): Magnetic moment

Claims (5)

A position sensing mechanism comprising: an encoding element having an absolute column magnetic track and an incremental column magnetic track extending parallel to each other along a virtual axis of movement; a read element adjacent to the The coding element is separated from it, and there is a relative position change between the moving shaft and the coding element. The reading element has a first magneto-resistive unit affected by the absolute column magnetic track, and a The second magnetoresistive unit affected by the incremental column magnetic track; a substrate, and the first magnetoresistive unit and the second magnetoresistive unit having the same technical structure are deposited in the same thin film, lithography and etching The manufacturing process is formed on the substrate at the same time, and the relative positions of the first magnetoresistance unit and the second magnetoresistance unit are based on the same plane; a processing unit is electrically connected to the reading unit connected to receive the signals generated by the first magnetoresistance unit and the second magnetoresistance unit under the action of the absolute column magnetic track and the incremental column magnetic track respectively, so as to analyze the position; it is characterized in that : The first magnetoresistive unit is a tunneling magnetoresistance with a single Magnetic Tunneling Junction (Single Magnetic Tunneling Junction, Single MTJ), the second magnetoresistive unit is a bridge tunneling magnetoresistance (Bridge TMR), And make the reference layer (reference layer) and the free layer (free layer) magnetic moments perpendicular to each other, and at the same time make the reference layer and the free layer, the magnetic moment of one layer is parallel to the film surface, while the magnetic moment of the other layer is perpendicular to the film surface, so that the magnetic moments of the reference layer and the free layer have orthotropy. The position sensing mechanism as claimed in claim 1, wherein the encoding element moves relative to the reading element along the moving axis. The position sensing mechanism as claimed in claim 1, wherein the reading element moves relative to the encoding element along the moving axis. The position sensing mechanism according to claim 1, wherein the magnetic moment perpendicular to the film surface is the reference layer. The position sensing mechanism according to claim 1, wherein the free layer has a magnetic moment perpendicular to the film surface.

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