RU2288510C2 - Electromagnetic system of display pixel drive - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: magnetic chain of display pixel consists of permanent magnet in the pixel valve and electromagnet with a magnet core. The named permanent magnet is formed in a pressure die casting process and is divided into two areas with ant parallel magnetization direction which is also at a 90 degree angle to the surface and axis of valve rotation. Electromagnet is located under the valve and has a U-shaped magnet core which is oriented parallel to the rotation axis.

EFFECT: lowered energy consumption.

9 cl, 7 dwg

Description

DESCRIPTION

The objectives of the invention are the design, materials and production process of the magnetic circuit of the display pixel on the electromagnetic display panel, which activates the rotation of the valve of the display pixel.

FIELD OF THE INVENTION

The present invention relates to bistable magnetic drives, which are based on the interaction of the magnetic field of a permanent magnet embedded in the pixel display valve and the magnetic field of the core of the electromagnet.

According to the international patent classification, a patent application is classified into groups H 01 F 3/14, H 01 F 7/14 and H 01 F 7/121, its application is classified into groups G 09 F 3/4 and G 09 F 9/37 .

Technical problem

The technical problem solved by the present invention should provide a new, simple, compact design of the display pixel drive electromagnetic system at a low production cost.

This electromagnetic system is a bistable drive that must switch the display pixel from the first bistable position to the second bistable position (and vice versa) with minimal power consumption. Therefore, the magnetic circuit must be specially designed, including materials with special magnetic properties. In addition, the design of the magnetic circuit must be optimized to reduce the magnetic interaction between adjacent display pixels as much as possible. The system must operate over a wide temperature range and must ensure the stability of both bistable valve positions of the display pixel. If the external forces resulting from mechanical impact: shock, vibration, etc., change the position of the display pixel valve, the magnetic forces in the display pixel valve must be sufficient to restore the required position immediately after the external forces disappear.

State of the art

Electromagnetic display panels have been known for over two decades and have played an important role in applications that require relatively large size display panels, medium information loading, high contrast and excellent visibility in a fairly lit environment. Bistable electromagnetic display panels (US 3871945, US 4577427, US 4860470, EP 0 084 959, EP 0 731 435 A1, US 4243978, US 5771616, US 6272778, US 6025825, US 5898418, US 6603458, ...) used for road signs, route signs in buses and trains, like large information display panels at airports, at bus and railway stations and at sports facilities, and it seems that they very well comply with the above requirements. Using bright reflective colors in selected image elements and black in unselected areas, these displays provide good contrast and excellent angular visibility in well-lit environments.

The operational principle of the solutions of the prior art is mainly based on a movable pixel valve, rotating around a rotating axis, typically ≤ 180 ° inside mechanically limited positions and having the size of an entire display pixel. The valve on its front and back side is covered in very contrasting colors (EP 0327250, US 6272778, US 6025825, US 5898418, ...). In order to switch between the “ON” and “OFF” positions of the display pixel, usually one fixed permanent magnet is used that is built into the pixel’s movable valve and a built-in solenoid wound around either the straight line (EP 0327250, US 6603458, US 6272778, ...) or around a U-shaped magnetic core (US 4243978, US 6025825, US 5898418, US 5005305, ...). Some technical solutions use an additional fixed permanent magnet to improve the stability of the bistable valve positions (US 4243978, US 4531318).

Another, fundamentally different principle of operation is known, based on display pixels, which are divided into two parts. Each pixel is provided with a rotatably mounted bistable tilting valve, which is asymmetrical about its axis of rotation. The tilt valve covers one of the two parts of the panel surface in the pixel area when the valve lies in each of its two stable positions. The side of the tilting valve facing the front side of the panel and the part of the panel in the pixel area covered by it are coated with paint on one and the opposite side of the valve and the rest of the pixel area is coated with a different, very contrasting color when compared with the first (US 6603458, DE 3501912C2 DE 3601018A1). In order to switch between the “ON” and “OFF” positions of the display pixel, this solution uses a permanent magnet integrated in each tilt valve near the axis of rotation. The tilting valve rotates from the first bistable position to the second bistable position using an electromagnet with a direct magnetic core, which is located on the back of each display pixel. This design has a definite advantage over other solutions, because the whole structure can be noticeably thinner (only one half of the pixel surface rotates around a rotating axis!) than with the technical solutions described above.

Disclosure of invention

An object of the present invention is to increase the efficiency and reliability of a magnetic display pixel drive system that moves a display pixel valve between “ON” and “OFF” pixel positions. The proposed solution minimizes energy consumption, increases the stability of the valve in both bistable positions, minimizes the interaction between adjacent display pixels and increases the compactness of the pixel design with fewer components and automated pixel production, and also thins the display pixel.

The present invention provides a new design of a magnetic circuit that generates a magnetic torque acting in a pixel display valve in two separate areas according to claim 1. With two effective regions, the magnetic torque on the display pixel is increased.

This is preferably achieved using a U-shaped solenoid core and (one or two) permanent magnets in the valve. The U-shaped core 3u (FIG. 1) is located under the axis of rotation of the display pixel valve 2d, as close to the valve as possible and parallel to the axis of rotation 2d of the display pixel valve, unlike other technical solutions using a U-shaped magnetic core. This position and orientation of the U-shaped core of the coil significantly reduces the dependence of the valve position on the magnetic torque compared to the above solutions and reduces the thickness of the display. The permanent magnet is placed in the valve either in the form of a single element with an antiparallel magnetization direction, which is also perpendicular to the valve surface and perpendicular to the axis of rotation, or in the form of two separate segments that are also magnetized antiparallel. The magnets are preferably made of NdFeB bonded in plastic or ferrite material bonded in plastic by injection molding the plastic.

The design of the magnetic circuit can be optimized by the appropriate selection of materials using the finite element method to minimize the energy consumption required to switch from one stable position of the pixel display valve to another. The effectiveness of the magnetic system, the reliability and stability of both bistable valve positions of the display pixel valve are ensured by increased magnetic torque. The proposed design of the magnetic circuit minimizes the stray magnetic field and reduces the magnetic interaction between adjacent pixels. Therefore, there is no need for antiparallel orientation of the magnets in adjacent display pixel valves, as in US Pat. No. 6,606,458.

Description of drawings

This invention can be better understood, and the objectives and advantages will become apparent to a person skilled in the art by using the following drawings:

figure 1 - magnetic switching system using a U-shaped electromagnet (3u + 5), including:

- a rotary valve 2 with integrated magnets (bonded in NdFeB plastic or ferrite bonded in plastic) 2c ₁ , 2c ₂ and axis of rotation 2d; the two surfaces of the valve 2a and 2b are covered in very contrasting colors,

- solenoid 5,

- U-shaped magnetic core, 3u;

figure 2 - design of a display segment with electromagnetic switchable display pixels,

FIG. 3 - spurious magnetic field;

figa - computer simulation of the magnetic field in a stable position of the valve for a U-shaped magnetic core;

fig.3b - computer simulation of the magnetic field in the unstable position of the valve for a U-shaped magnetic core;

figs - computer simulation of the magnetic field in a stable position of the valve for a direct magnetic core;

fig.3d - computer simulation of the magnetic field in the unstable position of the valve for a direct magnetic core;

4 is a display pixel valve product concept.

The implementation of the invention

The display pixel electromagnetic drive system according to the present invention is described in detail using FIG. 1-4.

In a magnetic system for switching a display pixel between “ON” and “OFF” positions according to the present invention, the electromagnet preferably has a U-shaped magnetic core oriented along the axis of rotation of the valve, the orientation of the magnets in all display valves being the same.

The display pixel valve has a built-in permanent magnet, which is divided into two areas 2c1 and 2c2. The directions of magnetization of these two regions are antiparallel to each other and perpendicular to the axis of rotation of the valve 2d and also the surface of the valve. The magnet in the valve 2 can be divided into two divided segments 2c ₁ and 2c ₂ , as shown in figure 1. In this figure, the magnetic system consists of valve 2 with two permanent magnets and an electromagnet (3u + 5). The relative directions of magnetization of these two segments of the magnet are the same as in the case of a single magnet with two regions. Magnets are made of NdFeB bonded in plastic, or bonded in plastic ferrite material. The production of a pixel display valve consists of a two-stage injection molding process during which magnets are molded during the first stage and the rest of the valve is filled with plastic in the second. Magnets are molded in the presence of a magnetic field, which creates anisotropic magnetic properties, increases the magnetic flux density and, therefore, gives a higher magnetic torque. Such a process results in substantial magnetic torque for the display pixel valve. Despite the use of hard magnetic materials bound in plastic, the magnetic properties of which are noticeably worse expressed than in materials obtained by sintering, the above process nevertheless provides sufficient magnetization of the permanent magnets integrated in the display pixel valve. The magnetization of a plastic-bound ferromagnet is preferably performed by permanent rare-earth magnets integrated in the casting device. In the case of using NdFeB bonded in plastic, magnetization is preferably carried out by a special current loop integrated in the casting device, to which a very short pulse of very strong electric current is supplied. The magnetization of the built-in magnets in the form of a ferrite bound in plastic is carried out simultaneously for all (for example, 14) valves (Fig. 4). All the valves on the display have the same magnetic orientation, in contrast to the direct magnetic core solution, as described in US 6603458. This greatly simplifies the production and automation of the processing process.

The electromagnet consists of a solenoid (coil) 5 and a U-shaped core of a coil 3u. It is installed under the axis of rotation of the valve and parallel to the axis (figure 1 and figure 2). This orientation reduces the influence of the valve position on the magnetic torque in comparison with technical solutions, where the U-shaped core is oriented perpendicular to the axis of rotation.

The solenoid (coil) is wound on the plastic housing of the solenoid 1e (figure 2), which is part of a monolithic block 1, forming several display pixels. The ends of the wires of the solenoid are soldered into the mounting pins 4a and 4b, which are inserted into the slots 1c and 1d.

The magnetic core 3u is given a U-shape and is made of a cylindrically formed semi-rigid magnetic material, which acquires its final magnetic properties only after appropriate heat treatment. One part of the core is inserted into the coil 5, the other part is inserted into the block 1 to fix its position. The U-shaped core makes it possible to produce thinner displays compared to the direct core of the coil.

The magnetic circuit of the display pixel (consisting of the magnetic core of the electromagnet, the magnets in the valve and the air gap between the magnetic core and the magnets) is designed and optimized using 3D computer simulation software and adapted to the magnetic properties of the materials used. The magnetic field in the stable as well as unstable valve positions is shown in FIG. 3.

The present invention is characterized by two simultaneously acting areas of magnetic force in the display pixel valve, which generate magnetic torque. This design increases the magnetic torque, which is also increased due to the increased density of the magnetic field when using an electromagnet with a U-shaped magnetic core. In contrast to the direct magnetic core, the U-shaped magnetic core has a significantly lower spurious magnetic field (figure 3). Higher magnetic torque increases the stability of the display pixel valve in “ON” and “OFF” positions. A lower stray magnetic field reduces the interaction between adjacent pixels, and therefore, all the valves on the display have the same magnetic orientation.

Switching from one valve position to another is carried out by a current pulse through a solenoid 5, which reverses the magnetic field in the magnetic core. Changing the direction of the magnetic field in the magnetic core of the electromagnet makes the current valve position unstable and rotates the valve to another stable position, which remains stable after the current pulse ends.

Example

 An electromagnetic display panel typically consists of a plurality of predominantly square display pixels arranged in a display matrix. Due to the large number of display pixels, standard manufacturing concepts based on mounting components of individual display pixels directly on the display panel of the PC main board prove to be complex and expensive. In order to reduce costs and simplify production, 7 pixels are connected in one monolithic block, which is the main element for constructing a display matrix. The monolithic block 1 (figure 2) is made of black matte plastic during injection molding of plastic. After molding, the block is coated with a contrasting color in 1a regions. Then, mounting pins 4a and 4b are inserted into slots 1c and 1d. The next operation is winding 7 solenoids on a monolithic block 1 and soldering the winding leads to the mounting pins and tests the ohmic resistance of the windings.

The magnetic core 3u has a U-shape and is made of a cylindrically formed rod of semi-rigid magnetic material, which acquires its final magnetic properties only after appropriate heat treatment. One part of the core is inserted into the coil 5, the other part is inserted into the block 1 to fix its position. The ends of both parts of the core are located under the axis of rotation of the valve 2 and are oriented parallel to the above axis.

Rotary valves 2 are made separately. Because 2 in valves must be embedded permanent magnets 2c _1, 2c _2, they are made from a plastic bound ferrite materials in a two-component plastic molding process. Like the monolithic block 1, one side 2a of the valves is coated with the same bright fluorescent paint, and the other half 2b is left unpainted - in the form of a matte black original surface of the plastic.

A permanent magnet is built into the valve of the display pixel, which is divided into two areas (segments) 2c1 and 2c2. The direction of magnetization of these areas is antiparallel to each other and perpendicular to the axis of rotation of the valve 2d and also the surface of the valve. Magnets are made from plastic bonded NdFeB or plastic bonded ferrite material. The manufacturing of the display pixel valve is a two-stage injection molding process for plastic during which the magnets are molded during the first stage and the remainder of the valve is filled with plastic in the second stage. Magnets are molded in the presence of a magnetic field, which creates anisotropic magnetic properties, increases the magnetic flux density and, therefore, gives a higher magnetic torque. Such a process results in significant magnetic torque for the display pixel valve. Despite the use of solid magnetic materials bound in plastic, the magnetic properties of which are noticeably worse expressed than in materials obtained by sintering, the process described above nevertheless turns out to be sufficient for magnetizing permanent magnets embedded in the display pixel valve. Magnetization of plastic-bound ferromagnets is performed by permanent rare-earth magnets integrated into the casting device. In the case of using magnets connected in NdFeB plastic, magnetization is performed by a special current loop built into the plastic molding device, which is supplied with a short pulse of strong electric current. The magnetization of the integrated ferrite magnets connected in plastic is performed simultaneously for all 14 valves in the set (Fig. 4). All the valves on the display have the same magnetic orientation as opposed to the direct magnetic core solution in US 6603458. This greatly simplifies production and also simplifies automation of the processing process.

In order to achieve the most economic production, 14 valves are made simultaneously in the injection molding process, in two rows of seven valves (see figure 4), connected together by spacers 19, which keep them positioned at exactly the same place / distance as defined by 14 bearings 1f, 1g of the axis of rotation on the monolithic block 1 in order to optimize the final stage of assembly of the display segment (7 pixels). Just like the monolithic block 1, one side 2a of the valves is covered with the same bright fluorescent paint, and the other half 2b remains unpainted - in the form of a matte black original surface of the plastic. After the valves 2 are painted, the spacers 19 are simultaneously cut off, and two columns of 7 valves 2 at the same time “snap” into the 14 bearings 1f, 1g of the rotation axes on the monolithic block 1.

Claims (9)

1. A magnetic system for switching a display pixel solenoid valve in a display pixel, comprising a rotary valve (2) having two bistable positions and an electromagnet (5 + 3u) with a magnetic core (3u) and a solenoid (5) that moves the valve (2) from one bistable position to another by means of a current pulse, the rotary valve (2) having an integrated magnet system (2c), and an electromagnet (5 + 3u) located under the valve (2), characterized in that U is attached to the magnetic core (3u) -shaped and oriented parallel axis of rotation (2d) so that magnetic force and hence magnetic torque are generated simultaneously in two spatially separate regions of the valve (2). 2. The magnetic system for switching the electromagnetic valve of the display pixel according to claim 1, characterized in that the magnet system (2c) in the rotating valve is divided into two regions or formed of two divided segments (2c ₁ and 2c ₂ ) and that these regions or segments magnetized antiparallel and perpendicular to the surface of the valve (2a, 2b) and perpendicular to the axis (2d) of rotation of the valve. 3. The magnetic system for switching the solenoid valve of the display pixel according to claim 2, characterized in that the magnet system (2c) is located near the axis of rotation (2d) and that the two divided segments (2c ₁ and 2c ₂ ) are given a rectangular shape or shape 1 / 4 cylinders. 4. An electromagnetic display panel with a plurality of display pixels having a magnetic system according to any one of claims 1 to 3, characterized in that all the magnet systems (2c) integrated in the display panel valves have the same antiparallel magnetic polarization. 5. A method of manufacturing a magnetic system for switching a display pixel solenoid valve according to claim 1, characterized in that the magnet system (2c) integrated in the valve (2) is made during injection molding of hard magnetic material bound in plastic and that the molding process They are performed in the presence of a strong magnetic field, which imparts anisotropic properties to magnets bound in plastic (2c). 6. The method according to claim 5, characterized in that the system of magnets (2c) is made of ferritic material bound in plastic and magnetized by correspondingly placed permanent rare-earth magnets that are integrated into the casting device. 7. The method according to claim 5, characterized in that the magnet system (2c) is made of NdFeB bonded in plastic and magnetized with a special current loop, which is built into the molding device, and that the current pulse is applied during the casting process while the magnet is binding plastic is in a softened state. 8. The method according to any one of claims 5-7, characterized in that the solenoid (5) is wound directly on the plastic monolithic block (1) and that the ends of the wire of the solenoid are connected to the mounting pins (4a, 4b), which are inserted into the sockets (1c , 1d) in the above monolithic block (1). 9. The method according to any one of claims 5 to 7, characterized in that the spurious magnetic field, as well as the interaction between adjacent pixels, is minimized.

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