A force-sensitive handwriting device based on magnetic elastomer

Abstract

The present invention relates to the field of handwriting input, and is a force-sensitive handwriting device based on a magnetic elastic body, comprising a pen tip (1), a front end protective sleeve (2), a force-sensitive device (3), a resonant circuit board (4), a pen holder, a first key (7), and a second key (8). The pen tip (1) is a rigid body with a conical front end and a columnar or trapezoidal step columnar rear end, the front end protective sleeve (2) is a conical sleeve with front and rear end openings, the pen holder is a sleeve connected to the pen tip (1) in a detachable manner, the front end of the pen tip (1) is in the front end protective sleeve (2), the head of the pen tip (1) protrudes from the protective sleeve (2), the tail of the pen tip (1) is in the pen holder, the force-sensitive device (3) and the resonant circuit board (4) are both in the sleeve, the first key (7) and the second key (8) are on the side wall of the pen holder, and the force-sensitive device (3), the first key (7), and the second key (8) are electrically connected to the resonant circuit board (4).

Description

Technical Field

[0001] The present invention relates to the field of handwriting input, and in particular to a handwriting device capable of sensing writing pressure. Background Art

[0002] There are many input methods for mobile phones and tablets, including touch, keyboard, and even wireless connection to the mouse for input. Among them, handwriting input devices are the most commonly used devices, including finger touch and stylus. The most common handwriting input electromagnetic board consists of an antenna board covered with electromagnetic coils and a stylus containing an inductor coil. As a user input tool, the pen's writing force plays a vital role in simulating the feel of paper.

[0003] Chinese patent CN01145283 discloses a stylus pen, which includes at least a pen core, an elastic element, a first magnetic element with a coil formed by at least one strand of wire wound around the outside, a second magnetic element, a sliding member, a hollow sleeve with an annular spacer inside, and an inductor-capacitor resonant circuit. The inductor-capacitor resonant circuit is electrically connected to the coil. When an external force is applied upward to the pen core, the external force acts on the sliding member through the pen core, so that the sliding member drives the second magnetic element to move upward to compress the elastic element to deform, causing the relative position of the first magnetic element and the second magnetic element to change, thereby changing the inductance value of the coil outside the first magnetic element, and then changing the resonant frequency of the resonant circuit. Therefore, when in use, the tip of the stylus pen will be displaced along the pen shaft.

[0004] Chinese patent CN103076904B discloses an electromagnetic handwriting device and an electromagnetic pen, the electromagnetic pen includes a hollow pen shell and a pen core arranged in the pen shell, and the electromagnetic pen also includes: a first magnetic ring movably accommodated in the pen shell; a second magnetic ring fixedly arranged in the pen shell opposite to the first magnetic ring, and the opposing surfaces of the first magnetic ring and the second magnetic ring are mutually adapted curved surfaces; and a resonant circuit that generates an electromagnetic signal according to the position change of the first magnetic ring relative to the second magnetic ring. It can be seen that when the handwriting pen disclosed in the patent is writing, the pen tip also needs to drive the magnetic ring to move to cause the position change of the first magnetic ring relative to the second magnetic ring.

[0005] At present, the stylus pens on the market can be divided into two categories based on energy supply: passive and active. Active stylus pens are inconvenient to write because they need to be powered by batteries or connected wires, so they are now less used. From the perspective of identifying writing force, they can be divided into pressure-sensitive writing pens and non-sensitive writing pens. Non-sensitive writing pens can only identify writing trajectories. Most mobile phones, tablets, etc. currently use this writing method. The text written on the handwriting board by such a pen cannot reflect the user's emotions and artistic expression. For professional calligraphers, this problem is more prominent. Pressure-sensitive writing pens can sense the pressure of users when writing and painting, and express the writer's emotions and art. They are mostly used in high-end input devices such as calligraphy and painting boards. However, the current pressure-sensing stylus pens all use the change of inductance value by changing the position of the magnetic core in the coil. The stylus contains an elastic element. The displacement of the pen tip-magnetic core-elastic element during writing changes the inductance, that is, the displacement of the inductor magnetic core causes the inductance to change, and then detects the force on the pen tip. Due to the existence of displacement, the feeling of use is inconsistent with the feeling of daily pen use, resulting in a poor user experience. Therefore, a stylus that can sense pressure without changing the position of the pen tip is very necessary for the user's writing experience. Summary of the invention

[0006] The technical problem to be solved by the present invention is: how to provide a stylus pen which can sense pressure without changing the position of the pen tip.

[0007] The technical solution adopted by the present invention is: a force-sensitive handwriting device based on a magnetic elastomer, comprising a pen tip (1), a front end sheath (2), a force-sensitive device (3), a resonant circuit board (4), a pen holder, a first button (7), and a second button (8); the pen tip (1) is a rigid body with a conical front end and a columnar or trapezoidal step columnar rear end; the front end sheath (2) is a conical sleeve with front and rear end openings; the pen holder is a sleeve connected to the pen tip (1) in a detachable manner; the front end of the pen tip (1) is in the front end sheath (2); the head of the pen tip (1) extends out of the front end sheath (2); the tail of the pen tip (1) is in the pen holder; the force-sensitive device (3) and the resonant circuit board (4) are both in the sleeve; the first button (7) and the second button (8) are on the side wall of the pen holder; and the force-sensitive device (3), the first button (7), and the second button (8) are electrically connected to the resonant circuit board (4).

[0008] The force sensitive device (3) comprises a resonant coil (13), a magnetic elastic body (14), and a permanent magnetic tube. The resonant coil (13) is sleeved on the side wall of the columnar magnetic elastic body (14). The resonant coil (13) is located in the permanent magnetic tube. The permanent magnetic tube is located in the pen tube. One end of the permanent magnetic tube is open. The magnetic elastic body (14) contacts the tail of the pen tip (1) through the end opening on the permanent magnetic tube. The electrical signal of the resonant coil (13) is connected to the resonant circuit board (4).

[0009] A coil frame (12) is provided between the magnetic elastic body (14) and the resonant coil (13). The coil frame (12) is a cylindrical structure with thick ends and a thin middle. The resonant coil (13) is wound on the outside of the thin cylinder in the middle of the coil frame (12). The number of turns of the resonant coil is from dozens to hundreds.

[0010] The permanent magnetic cylinder is a magnetic bias of a magnetic elastic body composed of a front magnetic yoke (9), a rear magnetic yoke (10) and a middle magnetic yoke (11). The front magnetic yoke (9) is composed of a half-cylinder + a round cake with a hole, the rear magnetic yoke (10) is composed of a half-cylinder + a round cake, the middle magnetic yoke (11) is a half-cylinder, the middle magnetic yoke (11) is horizontally magnetized, the front magnetic yoke (9) and the rear magnetic yoke (10) are soft magnetic materials, the front magnetic yoke (9), the rear magnetic yoke (10) and the middle magnetic yoke (11) form a magnetic circuit to ensure that the magnetic lines of force pass vertically through the magnetic elastic material, and the inner diameter of the hole in the front magnetic yoke is larger than the outer diameter of the tail end of the pen tip.

[0011] The resonant circuit board (4) comprises three capacitors connected in series and a plurality of conductors. The resonant circuit board (4), the resonant coil (13), the first button (7) and the second button (8) form a series resonant circuit or a parallel resonant circuit, wherein the first button (7) and the second button (8) are respectively connected in parallel to a different capacitor.

[0012] The magnetic elastic body (14) is made of a magnetic elastic material whose magnetic permeability changes significantly after being subjected to force.

[0013] The magnetic elastic body material is one of nickel-cobalt alloy magnetic elastic material, iron-aluminum alloy magnetic elastic material, iron-cobalt alloy magnetic elastic material and rare earth magnetic elastic material.

[0014] The pen holder is composed of a pen holder (5) and a tail plug (6) which are fixedly connected or detachably connected.

[0015] The detachable connection is a threaded connection.

[0016] The pen tip (1) is made of magnetic conductive material coated with plastic or rubber material.

[0017] The magnetic elastomer used in the present invention is a kind of material with the function of mutual conversion of electromagnetic energy and mechanical energy. When the magnetic elastic material is subjected to mechanical force, its internal strain causes the magnetic permeability to change, resulting in the piezomagnetic effect, which is the reverse effect of the magnetostrictive effect. The magnetic elastomer is highly sensitive to mechanical force. When subjected to writing pressure, the magnetic permeability changes significantly without producing obvious deformation.

[0018] The present invention provides a force-sensitive handwriting device based on a magnetic elastomer, which comprises a handwriting pen containing a magnetic elastomer and a handwriting board (such as a mobile phone) that can generate electromagnetic induction with the handwriting pen. The handwriting pen generates electromagnetic induction with a coil in the handwriting board through an induction component containing the magnetic elastomer, and senses the writing pressure on the pen tip through the change in the magnetic permeability of the magnetic elastomer. The electromagnetic handwriting pen has a simple structure and a small size. Since it does not contain a spring element, the pen tip will not retract when writing, and has a higher and better writing experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0020] Figure 2 It is a schematic diagram of the structure of the force-sensitive device of the present invention;

[0021] Figure 3 yes Figure 2 AA section view;

[0022] Figure 4 It is a schematic diagram of a permanent magnetic cylinder;

[0023] Figure 5 It is a schematic diagram of the force detection principle of the present invention;

[0024] Figure 6 This is a schematic diagram of the position detection of the present invention;

[0025] Figure 7 It is a schematic diagram of the resonant circuit and key switch of the present invention (series resonant circuit);

[0026] Among them, 1. pen tip, 2. front end sheath, 3. force sensitive device, 4. resonant circuit board, 5. pen body, 6. tail plug, 7. first button, 8. second button, 9. front magnetic yoke, 10. rear magnetic yoke, 11. middle magnetic yoke, 12. coil frame, 13. resonant coil, 14. magnetic elastomer. DETAILED DESCRIPTION

[0027] This embodiment is only an illustration of one implementation and is not the only implementation of this principle.

[0028] A force-sensitive handwriting device based on a magnetic elastomer comprises a pen tip 1, a front end sheath 2, a force-sensitive device 3, a resonant circuit board 4, a pen body 5, a tail plug 6, a first button 7, and a second button 8.

[0029] The pen tip 1 is composed of a Permalloy material coated with nylon, and the pen tip is pressed against the magnetic elastic material through a front end protective cover 2 with a thread, so as to ensure that the pen tip does not loosen and transmit the force of the pen tip vertically to the magnetic elastic body.

[0030] The magnetic elastic body 14 is made of a nickel-iron magnetic elastic material with low magnetic elasticity. The magnetic elastic material is processed into a cylindrical shape, and its force sensitivity range is about several hundred grams.

[0031] The coil frame 12 around the coil is in close contact with the magnetic elastic material to minimize magnetic leakage, and the number of turns of the coil is hundreds. The combination of the coil and the magnetic elastic material is fixed in a frame formed by injection molding.

[0032] The front and rear yokes are fixed at both ends of the frame. The front and rear yokes are shaped like Figure 4 The front yoke has a hole for the pen tip to pass through, and the yoke is made of pure iron material.

[0033] A middle magnetic yoke made of permanent magnetic material is fixed between the front and rear magnetic yokes. In this embodiment, injection-molded neodymium iron boron is used, which is magnetized longitudinally. The permanent magnetic material and the magnetic yoke together constitute the bias magnet of the magnetoelastic material.

[0034] This embodiment cooperates with a corresponding writing board to sense the writing track, writing pressure and key pressing conditions.

[0035] The force-sensitive detection principle of the present invention is as follows Figure 5 As shown. The circuit consists of a magnetic elastic body, a self-inductance formed by a coil, and an induction plate with a coil. The induction plate and the resonant coil also form a pair of mutual inductance. According to the principle of iron core inductance, the magnetic flux generated by the iron core inductor coil is divided into two parts: one part is the main magnetic flux passing through the iron core magnetic circuit, and the other part is the leakage magnetic flux passing through the gap between the coil and the iron core column. According to the basic definition of inductance, we call the inductance generated by the main magnetic flux the main inductance L L , the inductance generated by the leakage flux is called leakage inductance L S , the inductance L1 of the iron core inductor should be the sum of the two inductances, that is, L1 = L L +L S .Due to the high magnetic permeability of the magnetoelastic material, the leakage inductance Ls can be ignored. The induction plate is composed of multiple sets of coils, and the inductance of each set of coils is L2. The induction plate coil, through the magnetic pen tip, the magnetoelastic material and the resonant coil L1 form a mutual inductance, and the mutual inductance is M.

[0036] The resonant frequencies of the resonant circuit formed by L1 and C1 on the force-sensitive pen resonant circuit board and the induction plates L2 and C2 are:

[0037]

[0038]

[0039] The quality factor of the resonant circuit composed of the force-sensitive pen L1 and C1 is:

[0040]

[0041] According to Kirchhoff's law, we can conclude that:

[0042]

[0043] After sorting, the impedance of the input terminal is:

[0044]

[0045] When the input signal source frequency is f, the mutual inductance and coupling coefficient are as follows:

[0046]

[0047] The input impedance can be described as:

[0048]

[0049] From the above formula, it can be obtained that when the frequency f of the test end signal source is equal to the resonant frequency f2 of the combination of the resonant coil and the resonant circuit on the force sensitive pen, the input impedance reaches its maximum value, and its actual part is:

[0050]

[0051] It can be seen from the above formula that by measuring the resonant impedance at the input end, the resonant frequency of the force-sensitive pen side can be measured, and then the force on the pen tip can be measured.

[0052] The position measurement principle of the pen tip is as follows Figure 6 As shown, there are several groups of coils arranged in the horizontal and vertical directions on the sensing board. When the pen tip falls on the position A shown in the figure, coils L1 and L3 form a strong coupling with the resonant coil of the force-sensitive pen through the pen tip, and a strong resonant signal can be detected, while the signals detected by other coils are weaker; when the pen tip falls on the position B shown in the figure, coils L2 and L4 form a strong coupling with the resonant coil of the force-sensitive pen through the pen tip, and a strong resonant signal can be detected, while the signals detected by other coils are weaker; in this way, the horizontal (or vertical) coordinates of the writing pen can be determined. According to the requirements of detection accuracy, the coils can be appropriately arranged on the sensing board to measure the horizontal (vertical) position of the pen tip. By continuously detecting the changes in the position, the movement trajectory of the pen tip in the horizontal (vertical) direction can be obtained. Figure 5 As an illustration of position detection in one direction, the two sets of detection coils are arranged perpendicularly to each other on the induction detection board, so that the planar position of the pen tip on the induction board can be detected.

[0053] In order to facilitate the use of the writing pen, two buttons are added to the resonant circuit. Figure 6As shown, R and L are the equivalent resistance and inductance of the resonant coil, C is the main resonant capacitor, C' and C" are additional resonant capacitors. When buttons K1 and K2 are pressed, the corresponding capacitors are short-circuited and the resonant frequency of the circuit changes. By measuring the resonant frequency on the induction board, it can be known which button is pressed.

[0054] The resonant impedance detection at the sensing board detection board end can adopt various impedance measurement methods.

[0055] The handwriting pen of the present invention adopts a device based on a magnetic elastomer as a force-sensitive device, so the pen tip will not be displaced along the pen shaft when in use, which can greatly improve the writing experience of the writer.

[0056] The permanent magnet and the front and rear magnetic yokes form a bias magnetic field of the magnetoelastic material, so that the magnetoelastic body reaches an optimal magnetostriction coefficient.

[0057] Although only a preferred embodiment of the present invention is described herein, it is not intended to limit the scope, applicability and configuration of the present invention. On the contrary, the detailed description of the embodiment can enable those skilled in the art to implement it. It should be understood that some details can be appropriately changed and modified without departing from the spirit and scope of the present invention as determined by the attached claims.

Claims

1. A force-sensitive handwriting device based on a magnetic elastomer, characterized in that: The invention comprises a pen tip (1), a front end sheath (2), a force sensitive device (3), a resonant circuit board (4), a pen holder, a first button (7), and a second button (8). The pen tip (1) is a rigid body with a conical front end and a columnar or trapezoidal step columnar rear end. The front end sheath (2) is a conical sleeve with front and rear ends opened. The pen holder is a sleeve connected to the pen tip (1) in a detachable manner. The front end of the pen tip (1) is in the front end sheath (2). The head of the pen tip (1) protrudes from the front end sheath (2). The tail of the pen tip (1) is in the pen holder. The force sensitive device (3) and the resonant circuit board (4) are both in the sleeve. The first button (7) and the second button (8) are in the sleeve. The button (8) is located on the side wall of the pen holder, and the force sensitive device (3), the first button (7), and the second button (8) are electrically connected to the resonant circuit board (4); the force sensitive device (3) comprises a resonant coil (13), a magnetic elastic body (14), and a permanent magnetic tube; the columnar magnetic elastic body (14) is sleeved with the resonant coil (13) on the side wall, the resonant coil (13) is located in the permanent magnetic tube, the permanent magnetic tube is located in the pen holder, one end of the permanent magnetic tube is open, the magnetic elastic body (14) is in contact with the tail of the pen tip (1) through the end opening on the permanent magnetic tube, and the resonant coil (13) is electrically connected to the resonant circuit board (4); the magnetic elastic body (14) There is a coil frame (12) between the coil frame (12) and the resonant coil (13). The coil frame (12) is a cylindrical structure with thick ends and thin middle. The resonant coil (13) is wound on the outside of the thin cylindrical body in the middle of the coil frame (12). The number of turns of the resonant coil is from tens to hundreds of turns. The permanent magnetic cylinder is a magnetic bias of a magnetic elastic body composed of a front magnetic yoke (9), a rear magnetic yoke (10), and a middle magnetic yoke (11). The front magnetic yoke (9) is composed of a half-cylinder + a round cake with holes, the rear magnetic yoke (10) is composed of a half-cylinder + a round cake, the middle magnetic yoke (11) is a half-cylinder, the middle magnetic yoke (11) is horizontally magnetized, and the front magnetic yoke (9) and the rear magnetic yoke (10) are magnetically biased. The invention relates to a soft magnetic material; a front magnetic yoke (9), a rear magnetic yoke (10) and a middle magnetic yoke (11) form a magnetic circuit to ensure that magnetic lines of force pass vertically through the magnetic elastic material; the inner diameter of the hole in the front magnetic yoke is larger than the outer diameter of the tail end of the pen tip; the resonant circuit board (4) comprises three capacitors connected in series and a plurality of conductors; the resonant circuit board (4), the resonant coil (13), the first button (7) and the second button (8) form a series resonant circuit or a parallel resonant circuit, wherein the first button (7) and the second button (8) are respectively connected in parallel to a different capacitor; and the magnetic elastic body (14) is made of a magnetic elastic material whose magnetic permeability changes significantly after being subjected to force.

2. A force-sensitive handwriting device based on a magnetic elastomer according to claim 1, characterized in that: The magnetic elastic body material is one of nickel-cobalt alloy magnetic elastic material, iron-aluminum alloy magnetic elastic material, iron-cobalt alloy magnetic elastic material and rare earth magnetic elastic material.

3. A force-sensitive handwriting device based on a magnetic elastomer according to claim 1, characterized in that: The pen holder is composed of a pen shaft (5) and a tail plug (6) which are fixedly connected or detachably connected.

4. The force-sensitive handwriting device based on magnetic elastomer according to claim 1, characterized in that: The detachable connection is a threaded connection.

5. The force-sensitive handwriting device based on magnetic elastomer according to claim 1, characterized in that: The pen tip (1) is made of magnetic conductive material coated with plastic or rubber material.

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