Electronic pen

Abstract

The present application realizes further slimming of an electronic pen without degrading the function of the electronic pen. A cylindrical ferrite core (212) has a through hole (212a) and is composed of a front portion (212F), a middle portion (212M), and a back portion (212B). The outer diameter of the middle portion (212M) is shorter than the outer diameters of the front portion (212F) and the back portion (212B), so as to become a shape in which the middle portion (212M) is slim like a so-called dumbbell as a gymnastic apparatus. Since a coil (211) is formed by winding an insulated wire around the middle portion (212M), the portion of the ferrite core (212) in which the coil (211) is wound does not become thick, and the slimming of the electronic pen can be facilitated.

Description

Technical Field

[0001] The present invention relates to a pen-type position indicator, i.e., an electronic pen, for use with a position detection device. Background Technology

[0002] An electronic pen is held by the user and used to indicate position via a sensor on a position detection device. Because it is constructed with a circuit board, it is thicker than conventional writing instruments such as ballpoint pens and fountain pens. However, with the miniaturization and thinning of electronic devices such as tablet PCs (personal computers) and smartphones, which are equipped with position detection devices, there is a growing demand for thinner electronic pens.

[0003] Therefore, Patent Document 1, described later, discloses an invention related to the main body of an electronic pen, wherein the main body of the electronic pen is formed to the same size as the refill (replacement) of a ballpoint pen, and can be mounted on an existing ballpoint pen housing. Furthermore, Patent Document 2, described later, discloses an invention related to an electronic pen with increased strength, such as a tip portion that does not bend or break even when made thin and easily subjected to external pressure.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-224178

[0007] Patent Document 2: International Publication No. 2017 / 183526 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In position input devices consisting of an electronic pen and a position detection device, there are, for example, position input devices using electromagnetic induction or electrostatic capacitance methods. In the case of an electronic pen using electromagnetic induction, in order to exchange magnetic signals with the electromagnetic induction position detection device, a coil forming a resonant circuit together with a capacitor needs to be provided on the pen tip side. In the case of an electronic pen using electrostatic capacitance, for example, sometimes a coil connected to the battery is provided on the pen tip side for wireless charging of the built-in battery, and the battery is charged through electromagnetic induction (magnetic field coupling).

[0010] In these cases, a coil is formed by winding an insulated conductor around a magnetic core. This is because the magnetic core has the ability to increase the impedance of the insulated wire and suppress the propagation of noise current flowing into the coil, depending on its magnetization. However, since the coil is formed by winding the insulated wire around a magnetic core, as described in Patent Document 1 above...Figure 3 Patent Document 2 Figure 3 As shown in Figure 7, the coil portion of the electronic pen will always become thicker, regardless of the method.

[0011] In recent years, there has been a growing demand for further miniaturization of electronic pens that incorporate coils. For example, there is a need to make electronic pens thinner than ever before, in a way that allows them to be easily stored in the casing of portable devices. In addition, there is also a need for further miniaturization of electronic pens in order to more easily incorporate electronic pen functionality as one of the functions of so-called multi-color pens (multi-functional pens).

[0012] In view of the above, the object of the present invention is to achieve further miniaturization of the electronic pen without reducing its functionality.

[0013] Methods for solving problems

[0014] To address the aforementioned issues, an electronic pen is provided, which includes:

[0015] coil;

[0016] A columnar magnetic core, with the coil wound around it, and having a through hole in the axial direction;

[0017] The capacitor, together with the coil, forms a resonant circuit; and

[0018] A rod-shaped core is inserted through the through hole of the magnetic core.

[0019] The electronic pen and the position detection sensor transmit and receive signals via electromagnetic induction, characterized in that...

[0020] The magnetic core comprises a front portion, a rear portion, and a middle portion. The front portion is a defined area extending from the front end of the pen tip towards the rear end opposite to the pen tip. The rear portion is a defined area extending from the rear end towards the front end. The middle portion is the portion sandwiched between the front and rear portions.

[0021] The outer diameter of the middle portion is shorter than the outer diameters of the front and rear portions.

[0022] The coil is wound in the middle section.

[0023] According to this electronic pen, the cylindrical magnetic core has a through hole and consists of three parts: a front part, a middle part, and a rear part. The outer diameter of the middle part is shorter than the outer diameters of the front and rear parts, making the middle part tapered and resembling a dumbbell, a type of gymnastic apparatus. Because an insulated wire is wound around this middle part to form a coil, the portion of the magnetic core with the coil does not become thicker, contributing to the pen's slim profile. Attached Figure Description

[0024] Figure 1 This is a diagram used to illustrate the electronic pen used in the implementation and the tablet terminal using the electronic pen.

[0025] Figure 2 This is a diagram illustrating the structure of the main parts of an electronic pen used to explain an implementation method.

[0026] Figure 3 This is a diagram used to illustrate the structure of the ferrite core portion of the electronic pen in the embodiment.

[0027] Figure 4 This is a diagram illustrating the magnetic flux distribution of the ferrite core portion of the electronic pen of the present invention and the magnetic flux distribution of the ferrite core portion of a conventional electronic pen.

[0028] Figure 5 This is a diagram illustrating the groove provided in the ferrite core of the electronic pen of the present invention.

[0029] Figure 6 This is a diagram illustrating a structural example of applying the electronic pen of the present invention to an active electrostatic capacitive electronic pen. Detailed Implementation

[0030] Hereinafter, an embodiment of the electronic pen of the present invention will be described with reference to the accompanying drawings. It should be noted that, among the position detection methods of the electronic pen and position detection sensor, there are, for example, electromagnetic induction methods and electrostatic capacitance methods. In the electromagnetic induction method (EMR (Electro Magnetic Resonance) method), the position detection device includes a sensor section having multiple loop coils respectively arranged in the X-axis and Y-axis directions. A transmission period is alternately provided, during which power is sequentially supplied to the multiple loop coils of the sensor section to generate a magnetic field, and a reception period is provided, during which power supply is stopped and the magnetic field from the outside is received. The corresponding electronic pen includes a resonant circuit composed of coils and capacitors, which generates a signal by allowing current to flow to the coils according to the magnetic field from the sensor section. This signal includes pen pressure information and is transmitted to the position detection sensor. During the reception period, the position detection device receives this signal and detects the indicated position and pen pressure of the electronic pen.

[0031] In the electrostatic capacitive method, the position detection device includes a sensor unit with multiple linear conductors (line electrodes) arranged in the X-axis and Y-axis directions respectively. This sensor unit detects the indicated position based on the change in electrostatic capacitance (charge) generated on the linear conductors due to the proximity of a finger or electrostatic pen. It should be noted that electrostatic pens include conductive pen-shaped position indicators and so-called active electrostatic pens (AES type) that are battery-powered and send signals. In the active electrostatic coupling method of an active electrostatic pen, the pen includes pen pressure information in the signal from the oscillation circuit mounted on the pen and sends this signal. The position detection device receives this signal and detects the indicated position and pen pressure.

[0032] In the case of active electrostatic pens, a coil is generally unnecessary. However, when charging a battery via contactless charging, a coil is sometimes included for charging purposes. This invention can be applied to electronic pens that require a coil. Therefore, the electronic pen of this invention can be applied to both electromagnetic induction pens and active electrostatic coupling pens that use contactless charging (active electrostatic pens). It should be noted that in the embodiments described below, we will first illustrate the application of this invention to an electromagnetic induction pens where a coil is an essential component.

[0033] [Example of the overall structure of tablet terminal 1 and electronic pen 2]

[0034] <Example of tablet terminal structure>

[0035] Figure 1 This diagram illustrates the electronic pen 2 and the tablet terminal 1 using the electronic pen 2 in the embodiment. The tablet terminal 1 includes, for example, an LCD (Liquid Crystal Display) 11 as a display device, with a structure where a relatively large display screen 1A of the LCD 11 is exposed to the front. A protective glass, for example, is provided on the display screen 1A. A position detection sensor 12 and a position detection device 13 are provided on the back of the display screen 1A. The position detection sensor 12 has a detection area corresponding to the entire surface of the display screen 1A, so as to detect the indicated position regardless of where the electronic pen 2 indicates on the display screen 1A. The position detection device 13 controls the position detection sensor 12 and detects the indicated position and pen pressure based on the output signal from the position detection sensor 12.

[0036] As described above, the position detection sensor 12 is a combination of an X-axis direction sensor composed of multiple loop coils arranged in the X-axis direction (lateral direction) and a Y-axis direction sensor composed of multiple loop coils arranged in the Y-axis direction (vertical direction). The position detection device 13 can be controlled by alternately setting a transmission period in which power is sequentially supplied to the multiple loop coils of the position detection sensor 12 to generate a magnetic field and a reception period in which the power supply is stopped and the magnetic field from the outside is received. The position detection device 13 detects the indicated position and pen pressure based on the signal received during the reception period.

[0037] Additionally, although not shown, a motherboard is housed inside the casing of the tablet terminal 1. This motherboard houses various circuits, including display control circuits, information processing circuits, and communication processing circuits, as well as memory, enabling various information processing operations. Furthermore, although not shown, operation buttons, such as a power button, are located on the side of the tablet terminal 1's casing, allowing it to accept user input and process the corresponding actions.

[0038] Therefore, let's assume that a position indication operation is performed by the electronic pen 2 on the display screen 1A in the tablet terminal 1. In this case, based on the detection output from the position detection sensor 12 located on the back of the display screen 1A, the position detection device 13 determines the indicated position on the display screen 1A. Information indicating the indicated position determined by the position detection device 13 is supplied to the information processing circuit mounted on the tablet terminal 1, enabling corresponding processing.

[0039] <Structure Example of Electronic Pen 2>

[0040] As described above, the electronic pen 2 receives signals from the position detection sensor 12 of the position detection device 13 of the tablet terminal 1 via electromagnetic induction, thereby enabling the position detection device 13 of the tablet terminal 1 to detect its indicated position. Apart from the characteristic shape of the magnetic core, the mechanical structure of the electronic pen 2 is the same as that of known electromagnetic induction electronic pens.

[0041] like Figure 1 As shown, the electronic pen 2 of this embodiment has an electronic pen body 21 on the axial opening 20a side of the hollow portion of a cylindrical shell 20 made of resin, for example. The electronic pen body 21 includes a coil 211, a magnetic core (in this example, a ferrite core 212) wound with the coil 211, a reinforcing tube 213, a core 214, a pen pressure detection unit 215, and a capacitor 216 that, together with the coil 211, forms a resonant circuit. Figure 1In order to clearly show the structure of the main parts, the housing 20 is shown as thicker, but in fact, the main body 21 of the electronic pen is made thinner, thus being thinner than conventional electronic pens.

[0042] Figure 2 This is a diagram illustrating an example of the structure of the main body 21 of the electronic pen. (See diagram for example.) Figure 2 As shown in (A), the ferrite core 212 has a through hole 212a of a predetermined diameter r1 (e.g., r1 = 0.91 mm) formed in an axial direction in a cylindrical ferrite material for insertion of the reinforcing tube 213, which will be described later. Further details will be provided later. The ferrite core 212, from the nib side towards the rear end in the axial direction, consists of three parts: a front portion 212F, a middle portion 212M, and a rear portion 212B.

[0043] The outer diameter of the middle portion 212M is shorter than that of the front portion 212F and the rear portion 212B. Thus, because the thickness of the middle portion 212M is thinner than that of the front portion 212F and the rear portion 212B, the overall shape of the ferrite core 212 is similar to that of a dumbbell used as a gymnastic apparatus. Therefore, although an insulated wire is wound around the middle portion 212M to form a coil 211, the outer diameter of the portion where the coil 211 is formed is no longer (thicker) than the outer diameters of the front and rear portions 212F and 212B.

[0044] Furthermore, a tapered portion 212T, which gradually tapers, is formed on the tip side of the front portion 212F of the ferrite core 212. This results in stronger magnetic coupling between the front portion 212F and the position detection sensor 12 of the position detection device section 13 compared to the case without the tapered portion 212T. It should be noted that the outer diameter of the front portion 212F, excluding the tapered portion 212T, is the same as the outer diameter of the rear portion 212B. Therefore, as... Figure 2 As shown in (A), the portion consisting of the ferrite core 212 and the coil 211, except for the tapered portion 212T, has an outer diameter that is approximately the same length in any part of the axial direction.

[0045] like Figure 1 , Figure 2 As shown in (A), in the main body 21 of the electronic pen, a reinforcing tube 213 is provided in the through hole 212a of the ferrite core 212. The reinforcing tube 213 is made of stainless steel such as SUS316, and its outer diameter is slightly shorter than the inner diameter of the through hole 212a of the ferrite core 212. Figure 2 As shown in (A), the reinforcing tube 213 is fixed from one end to the other end of the through hole 212a of the ferrite core 212, with the front end protruding from the front opening of the ferrite core 212 and the rear end protruding from the rear opening of the ferrite core 212. Therefore, as Figure 2As shown in (A), the length of the reinforcing tube 213 in the axial direction is longer than the length of the ferrite core 212 in the axial direction.

[0046] A cylindrical portion 217, for example made of resin, is provided on the rear end side of the ferrite core 212. A pen pressure detection unit 215 is provided near the junction of the cylindrical portion 217 and the ferrite core 212. The pen pressure detection unit 215 may, for example, be a structure using a semiconductor element whose electrostatic capacitance varies according to pen pressure, as disclosed in Japanese Patent Application Publication No. 2013-161307. It should be noted that the pen pressure detection unit 215 may also be a structure using a pen pressure detection unit with a known mechanism structure, such as that described in Japanese Patent Application Publication No. 2011-186803, and a variable capacitance capacitor whose electrostatic capacitance varies according to pen pressure.

[0047] A printed circuit board 218 is also housed within the cylindrical portion 217. A capacitor 216 is provided on the printed circuit board 218, which is connected in parallel with the coil 211 to form a resonant circuit. A variable capacitance capacitor formed by the pen pressure detection unit 215 is connected in parallel with the capacitor 216 provided on the printed circuit board 218 to form part of the aforementioned resonant circuit.

[0048] like Figure 2 As shown in (B), the ferrite core 212 is fitted into the recess 217a provided in the cylindrical body portion 217 by the rear end of the rear portion 212B of the ferrite core 212. Although the figure is not shown, when the ferrite core 212 is joined to the cylindrical body portion 217, the extension lines 211a and 211b from both ends of the coil 211 are connected in parallel with the capacitor 216 provided in the printed circuit board 218 of the cylindrical body portion 217.

[0049] In this embodiment, the core 214 is a rod-shaped component with a diameter smaller than the inner diameter of the hollow portion (through hole) inside the reinforcing tube 213 through the through hole 212a of the ferrite core 212. The axial length of the core 214 is longer than the axial length of the reinforcing tube 213. In this embodiment, as... Figure 2 As shown in (B), the core 214 is inserted into the hollow portion of the reinforcing tube 213 through the through hole 212a of the ferrite core 212, and the tail end 214b is fitted into the fitting hole 215a of the pen pressure detection unit 215. In this fitted state, the core 214 is in a state where the pen tip protrudes from the opening on the front end side of the reinforcing tube 213.

[0050] In this embodiment, such as Figure 2As shown in (B), the tip portion 214a of the core 214, together with a portion of the tip side of the reinforcing tube 213 and a portion of the tip side of the ferrite core 212, protrudes outward from the opening 20a of the housing 20 of the electronic pen 2. Therefore, the pen pressure applied to the tip portion 214a of the core 214 is directly transmitted to the pen pressure detection unit 215 through the core 214.

[0051] In this embodiment, the electronic pen 2 receives an AC signal of frequency f0 transmitted by the position detection sensor 12 of the position detection device unit 13 via electromagnetic induction coupling using a resonant circuit. Furthermore, the resonant circuit of the electronic pen 2 feeds back the received AC signal to the position detection sensor 12 via electromagnetic induction coupling. In the position detection device unit 13, the indicated position of the electronic pen 2 is detected by detecting the position of the AC signal fed back from the electronic pen 2 on the position detection sensor 12. Additionally, the position detection device unit 13 detects the pen pressure applied to the electronic pen 2 by detecting changes in the frequency or phase of the AC signal received from the electronic pen 2.

[0052] It should be noted that, in order to minimize energy loss and ensure good interaction of the AC signal between the electronic pen 2 and the position detection sensor 12, the resonant frequency of the resonant circuit of the electronic pen 2 is selected to be equal to the frequency f0 of the AC signal from the position detection device 13.

[0053] <Structure of Ferrite Core>

[0054] Figure 3 This is a diagram used to illustrate the structure of the ferrite core 212 portion of the electronic pen 2 in the embodiment. Figure 3 (A) is a perspective view of the ferrite core 212 portion, which is equipped with coil 211, reinforcing tube 213 and core 214. Figure 3 (B) is a three-dimensional view of only the ferrite core 212. Figure 3 (C) is an appearance view of the ferrite core 212 when viewed from a direction intersecting the axial direction (length direction).

[0055] The coil 211, ferrite core 212, reinforcing tube 213, and core 214 can each be of various sizes. However, in the electronic pen 2 of this embodiment, the shape and size of the ferrite core 212 are designed so that the outer diameter of the part composed of the coil 211, ferrite core 212, reinforcing tube 213, and core 214 is the same as the 4C standard for ballpoint pen refills, and the other parts are also selected with corresponding sizes.

[0056] It should be noted that tolerances are also considered in the 4C standard, including the outer diameter. The diameter is within the range of 2.3mm to 2.4mm. Therefore, hereinafter, the outer diameter of the part consisting of coil 211, ferrite core 212, reinforcing tube 213, and core 214 is defined as such. The outer diameter corresponds to the 4C standard and is approximately 2.3mm. Regarding the outer diameters and lengths of other parts, although the word "approximately" is omitted, tolerances are included, meaning the lengths shown are approximately...

[0057] Ferrite core 212 is a magnetic material made of ferrite (a ceramic mainly composed of iron oxide), such as... Figure 3 As shown in (B), it is formed in a cylindrical shape and has a through hole 212a with the axis as the center line. Additionally, as... Figure 3 As shown in (B) and (C), the ferrite core 212 is composed of three parts: the front part 212F, the middle part 212M, and the rear part 212B. A tapered part 212T that becomes thinner is provided on the tip side of the front part 212F.

[0058] In this embodiment, the outer diameter of the front portion 212F and the rear portion 212B of the ferrite core 212 is approximately 2.3 mm, and the outer diameter of the middle portion 212M is... The diameter is 1.4mm. That is, the outer diameter of the middle part 212M is 0.9mm shorter than the outer diameters of the front part 212F and the rear part 212B, forming a dumbbell-like shape as a whole. It should be noted that the inner diameter of the ferrite core 212 (the diameter of the through hole 212a) is... The thickness is 0.91 mm regardless of whether it is in the front part 212F, the middle part 212M, or the rear part 212B.

[0059] like Figure 3 (As shown in A, an insulated wire is wound around the middle portion 212M of a ferrite core 212 having this shape to form a coil 211. In this embodiment, the coil 211 is formed by winding an insulated wire with a diameter of 7...) Stranded wire formed by twisting together conductors with a diameter of 0.05mm. Therefore, the diameter of the stranded wire becomes about 0.15 mm, but even if the stranded wire is wound twice in the middle part 212M, such as the first layer (first layer) 26 turns and the second layer (second layer) 24 turns, the thickness of the coil 211 part is about 0.3 mm.

[0060] Therefore, even when an insulated wire is wound around the middle portion 212M of the ferrite core 212 to form a coil 211, the outer diameter of the portion with the coil 211 will not be longer than the outer diameter (approximately 2.3 mm) of the front portion 212F and the rear portion 212B without the coil. That is, the outer diameter of either the portion consisting of the coil 211 and the ferrite core 212 will be approximately 2.3 mm or less. It should be noted that the reinforcing tube 213, as described above, is made of stainless steel (SUS316). Figure 3 As shown in (A), it is the outer diameter. inner diameter The components. Additionally, the core 214 is formed of a resin such as polyacetal (POM), and its diameter... It is 0.56mm.

[0061] Through these various parts, such as Figure 3 As shown in (A), the reinforcing tube 213 is inserted through the through hole 212a of the ferrite core 212 on which the coil 211 is wound, and the core 214 is inserted through the hollow part of the reinforcing tube 213, forming the tip-side portion of the electronic pen body 21. The reinforcing tube 213 not only reinforces the core 214, but also reinforces the ferrite core 212, thereby increasing the strength of the tip-side component of the electronic pen body 21 under external pressure.

[0062] use Figure 3 (C) summarizes the shape and dimensions of the ferrite core 212 in this embodiment. The ferrite core 212 is a cylindrical component with an outer diameter of approximately 2.3 mm, and has a through hole 212a with a diameter of 0.91 mm centered on an axis L. The ferrite core 212 has a total length of 13 mm, but is composed of a front portion 212F with a length of 3.5 mm, a middle portion 212M with a length of 6.5 mm, and a rear portion 212B with a length of 3.0 mm. The front end of the front portion 212F is a tapered portion 212T.

[0063] like Figure 3 As shown in (C), the outer diameter of the middle portion 212M is 1.4 mm, which is 0.9 mm shorter than that of the front portion 212F and the rear portion 212B. Therefore, a 0.45 mm step is formed throughout the entire circumference between the middle portion 212M and the front portion 212F and the rear portion 212B, resulting in a difference of 0.9 mm in outer diameter. Thus, as described above, even when using stranded wire as an insulated conductor… The coil 211 is double-wound to the middle part 212M, and the thickness of the coil 211 is also about 0.3mm. Therefore, the outer diameter of the middle part 212M with the coil 211 wound on it will not exceed approximately 2.3mm, which can form the electronic pen body part 21 with an outer diameter (approximately 2.3mm) that conforms to the standard of ballpoint pen refill, namely the 4C standard.

[0064] Figure 4 This is used to illustrate the magnetic flux distribution of the ferrite core 212 portion of the electronic pen of the present invention. Figure 4 The magnetic flux distribution of the ferrite core 300 portion of the (A) and previous electronic pens ( Figure 4 The diagram is shown in (B). It should be noted that in... Figure 4 The text only shows the ferrite core and coil; details about the core and other components are omitted. Figure 4 The ferrite core 300 of the conventional electronic pen shown in (B) is a cylindrical component with a length of 13 mm in the axial direction and an outer diameter of approximately 2.3 mm for all parts in the axial direction.

[0065] In this case, if the coil is wound around the tip side of the ferrite core 300 in a conventional electronic pen, the coil becomes an obstruction, preventing the front end of the core and the front end of the ferrite core 300 from protruding from the tip side into a tapered electronic pen housing. Therefore, as Figure 4 As shown in (B), in the case of the conventional ferrite core 300 of an electronic pen, an insulated wire is wound around the rear end to form the coil 310. Figure 4 In the case shown in (B), the structure becomes as follows: a 5.4mm unwound portion is provided from the front end of the ferrite core 300 on the tip side toward the rear end side, followed by a 6.0mm long coil, and then a 1.6mm unwound portion is provided.

[0066] Therefore, in order to generate the desired magnetic flux (magnetic field) at the pen tip, it is necessary to increase the self-inductance (L value). Thus, in the case of conventional electronic pens, the coil needs to be wound 300 times or more around the ferrite core, for example, three times, with the outer diameter of the portion containing the coil being... Figure 4 In case (B), the diameter becomes approximately 3.18 mm. Therefore, as... Figure 4 As shown in (B), the desired magnetic flux can be generated on the tip side. However, since the coil 310 is formed on the rear end side of the ferrite core 300, in the case of conventional electronic pens, a larger magnetic flux (magnetic field) is generated on the rear end side of the ferrite core 300 compared to the tip side.

[0067] In contrast, Figure 4 In the case of the ferrite core 212 of the electronic pen 2 shown in (A) of this embodiment, if using Figure 3 As explained in (C), the outer diameter of the front portion 212F and the rear portion 212B is approximately 2.3 mm, but the outer diameter of the middle portion is 1.4 mm. Furthermore, as... Figure 4As shown in (A), the front portion 212F of the ferrite core 212 is a 3.5mm portion from the front end of the nib to the rear end, the middle portion 212M is a 6.5mm portion following the front portion 212F, and the rear portion is a 3.0mm portion following the middle portion 212M.

[0068] In the case of the electronic pen 2 in this embodiment, a coil is formed by double-winding an insulated wire in the middle section, which is 6.5 mm in length. As described above, the coil 211 is made of stranded wire. The insulated wire is formed, and the diameter of the stranded wire is about 0.15 mm. Therefore, even if the coil is formed by double winding, its thickness is about 0.3 mm. As a result, the outer diameter of the portion where the coil is formed is approximately 2.3 mm or less. Therefore, in the case of the electronic pen 2 of this embodiment, the outer diameter of the ferrite core 212 portion, including the portion where the coil 211 is formed, is approximately 2.3 mm or less.

[0069] Moreover, such as Figure 4 As shown in (A), since the coil 211 can be located on the tip side of the ferrite core 212, even if the coil 211 is formed by double-winding the insulated wire only in the middle portion 212M, the desired magnetic flux can be generated on the tip side. Furthermore, in the case of the electronic pen 2 of this embodiment, since the coil 211 can be formed in approximately the central portion of the ferrite core 212, approximately equal magnetic flux (magnetic field) can be generated on both the tip side and the rear end side of the ferrite core 212. Therefore, an unnecessarily large magnetic flux (magnetic field) is not generated on the rear end side of the electronic pen 2.

[0070] Figure 5 This diagram illustrates the groove portion of the ferrite core 212 provided in the electronic pen 2 of the present invention. As described above, the extension lines 211a and 211b from both ends of the coil 211 wound around the ferrite core 212 are connected in parallel with the capacitor 216 provided on the printed circuit board 218. Therefore, a groove portion 212Gr is provided along the axial direction on the side surface of the rear portion 212B of the ferrite core 212 in such a way that the extension lines 211a and 211b from both ends of the coil 211 can be appropriately extended rearward. As a result, the extension lines 211a and 211b do not appear on the side surface of the ferrite core 212, and can extend to the rear section of the printed circuit board 218 through the groove portion 212Gr provided on the side surface of the ferrite core 212.

[0071] [Applications of electronic pens using active electrostatic capacitive technology]

[0072] Figure 6This diagram illustrates a structural example of applying the electronic pen of the present invention to an active electrostatic capacitive electronic pen (active electrostatic pen). The active electrostatic pen 400 in this example includes a double-layer capacitor 401 functioning as a power storage unit, a rectifier diode 402, a voltage conversion circuit 403, and a charging coil 404. Furthermore, the active electrostatic pen 400 includes an oscillation circuit 405, a pen pressure detection unit 406, a signal line 407, and a conductive core 408.

[0073] In this example, one end of the coil 404 is connected to the anode of the rectifier diode 402, and the other end is grounded (GND). Additionally, one end of the double-layer capacitor 401 is connected to the cathode of the rectifier diode 402, and the other end is grounded. The coil 404 does not constitute a resonant circuit for position indication based on electromagnetic induction, but is used as a power supply terminal to receive power from an external source, realizing contactless charging. The conductive core 408 is electrically connected to the oscillation circuit 405 via signal line 407. Furthermore, the pen pressure detection unit 406 is electrically connected to the oscillation circuit 405.

[0074] The oscillation circuit 405 generates a signal whose frequency varies according to the capacitance of the variable-capacity capacitor (capacitor) of the pen pressure detection unit 406, and supplies this generated signal to the core 408 via the signal line 407. The signal from the oscillation circuit 405 is emitted from the pen tip (front end) of the core 408 as an electric field based on the signal. The oscillation circuit 405 is, for example, an LC oscillation circuit utilizing the resonance of a coil and a capacitor. In a position detection device that detects the coordinate position indicated by the active electrostatic pen 400 in this example, the pen pressure applied to the pen tip of the core 408 can be determined based on the frequency of the signal.

[0075] The voltage conversion circuit 403 converts the voltage stored in the double-layer capacitor 401 into a certain voltage and supplies it as the power source for the oscillation circuit 405. When the active electrostatic pen 400 of this example electrostatic capacitor type is assembled with a charger (not shown), an induced electromotive force is generated in the coil 404 by the alternating magnetic field generated by the charger, which can charge the double-layer capacitor 401 via the rectifier diode 402.

[0076] In this active electrostatic pen 400 with such a structure, a ferrite core, constructed in the same manner as the ferrite core 212 described above, is provided around the core 408, and a charging coil 404 is provided in the middle portion of this ferrite core. This ensures that the outer diameter of the portion consisting of the ferrite core and the coil 404 does not become thicker, thus forming an active electrostatic pen 400.

[0077] [Effects of the Implementation Method]

[0078] According to the above-described embodiment, the electronic pen 2, by making the outer diameter of the middle portion 212M shorter than the outer diameter of the front portion 212F and the outer diameter of the rear portion 212B, and forming the coil 211 in the middle portion 212M, can achieve an overall reduction in the ferrite core 212 portion. This allows for an overall reduction in the size of the electronic pen body 21, thus enabling a reduction in the size of the electronic pen 2 itself. Specifically, the outer diameter of the electronic pen body 21 can be made approximately 2.3mm, similar to the 4C standard for ballpoint pen refills, thus enabling a slimmer electronic pen that can be easily stored in the casing of a portable terminal. Furthermore, by making the electronic pen's outer diameter approximately 2.3mm, similar to the 4C standard for ballpoint pen refills, it can also be used as an electronic pen refill device and equipped with electronic pen functionality as one of the multi-functional pens.

[0079] Furthermore, since the coil 211 can be formed on the tip side of the ferrite core 212, the inductance can be increased. This allows for a wider magnetic flux distribution on the tip side of the electronic pen 2. In other words, a good magnetic flux (magnetic field) can be generated on the tip side of the electronic pen 2 using the coil 211. Therefore, in the case of an electromagnetically coupled electronic pen, the position detection sensor 12 and the position detection device 13 can be appropriately used for position indication and pen pressure transmission. Additionally, in the case of an electrostatic capacitor electronic pen, the double-layer capacitor can be charged efficiently.

[0080] [Variation Example]

[0081] In the above embodiment, the dimensions shown for the coil 211, ferrite core 212, reinforcing tube 213, and core 214 are merely examples and are not limited to these dimensions. For example, the middle portion 212M of the ferrite core 212 can be located on the tip-side, and the coil 211 can be formed on the tip-side. That is, the axial lengths of the front portion 212F, the middle portion 212M, and the rear portion 212B of the ferrite core 212 can be of various lengths. In the case of the electronic pen 2 of the above embodiment, the portion where the coil 211 is formed does not become thicker, so the portion where the coil 211 is formed can also protrude from the housing 20 of the electronic pen 2. That is, the electromagnetic coupling with the position detection device 13 can be strengthened.

[0082] Furthermore, in the case of the electronic pen body 21 described above, in order to make the outer diameter of the portion where the coil 211 is provided approximately 2.3 mm or less, the insulated wire is double-wound (2 layers) around the middle portion 212M of the coil 211. However, if the outer diameter is not approximately 2.3 mm or less, the insulated wire can be triple-wound (3 layers) to form the coil. By increasing the number of coil layers, the wound portions of the insulated wire are brought closer together, which increases the magnetic flux linkage, thus increasing the self-inductance (L value) and enabling the generation of magnetic flux (magnetic field) effectively.

[0083] Furthermore, if the strength of the ferrite core 212 and core 214 is high, a structure without the reinforcing tube 213 can also be used. Also, in the above embodiment, a ferrite core is used as the magnetic core, but it is not limited to this. Where various magnetic materials can be used to achieve the same function as a ferrite core, such magnetic materials can also be used.

[0084] Label Explanation

[0085] 1…Tablet terminal, 1A…Display screen, 11…LCD, 12…Position detection sensor, 13…Position detection device, 2…Electronic pen, 20…House, 20a…Opening, 21…Electronic pen body, 211…Coil, 211a, 211b…Extension lines, 212…Ferrite core, 212a…Through hole, 212T…Conical part, 212F…Front part, 212M…Middle part, 212B…Rear part, 212Gr…Slot, 213…Reinforcing tube, 214…Core, 214 a… Pen tip, 214b… Tail end, 215… Pen pressure detection section, 215a… Fitting hole, 216… Capacitor, 217… Cylindrical body, 217a… Recess, 218… Printed substrate, 300… Ferrite core, 310… Coil, 400… Active electrostatic pen, 401… Double-layer capacitor, 402… Rectifying diode, 403… Voltage conversion circuit, 404… Charging coil, 405… Oscillating circuit, 406… Pen pressure detection section, 407… Signal line, 408… Conductive core

Claims

1. An electronic pen, comprising: coil; A columnar magnetic core, with the coil wound around it, and having a through hole in the axial direction; The capacitor, together with the coil, forms a resonant circuit; and A rod-shaped core is inserted through the through hole of the magnetic core. The electronic pen and the position detection sensor communicate and transmit signals via electromagnetic induction. The electronic pen is characterized in that... The magnetic core comprises a front portion, a rear portion, and a middle portion. The front portion is a defined area extending from the front end of the pen tip towards the rear end opposite to the pen tip. The rear portion is a defined area extending from the rear end towards the front end. The middle portion is the portion sandwiched between the front and rear portions. The outer diameter of the middle portion is shorter than the outer diameters of the front and rear portions. The coil is wound in the middle section.

2. The electronic pen according to claim 1, characterized in that, The middle portion of the magnetic core becomes the wound portion with the coil wound around it, while the front and rear portions become the unwound portions without the coil wound around them. The outer diameter of the wound portion, in which the coil is wound, is less than or equal to the outer diameter of the unwound portion.

3. The electronic pen according to claim 1, characterized in that, The front portion of the magnetic core gradually tapers to a point, forming a cone.

4. The electronic pen according to claim 1, characterized in that, On the side of the rear portion of the magnetic core, a groove is provided along the axial direction for extending an insulated wire toward the rear end, the insulated wire being derived from the coil wound in the middle portion of the magnetic core.

5. The electronic pen according to claim 1, characterized in that, The electronic pen includes a reinforcing tube fixed from one end to the other end of the through hole in the magnetic core, with the front end of the reinforcing tube protruding from the front opening of the magnetic core. The core is capable of sliding within the reinforcing tube along the axial direction.

6. The electronic pen according to claim 1, characterized in that, The pen is used with at least a portion of the front side portion of the magnetic core and the pen tip of the core protruding from the electronic pen housing.

7. The electronic pen according to claim 1, characterized in that, The electronic pen includes a reinforcing tube fixed from one end to the other end of the through hole in the magnetic core, with the front end of the reinforcing tube protruding from the front portion of the magnetic core. The pen is used with at least a portion of the front side of the magnetic core, the front end of the reinforcing tube, and the pen tip of the core protruding from the electronic pen housing.

8. The electronic pen according to claim 1, characterized in that, The length of the middle portion of the magnetic core in the axial direction is equal to the length obtained by adding the length of the front portion and the length of the rear portion of the magnetic core in the axial direction.

9. The electronic pen according to claim 1, characterized in that, The length of the middle portion of the magnetic core in the axial direction is equal to the length obtained by adding the lengths of the front and rear portions of the magnetic core in the axial direction. The length of the front portion in the axial direction is slightly longer than the length of the rear portion in the axial direction.

10. The electronic pen according to claim 1, characterized in that, The outer diameter of the front and rear portions of the magnetic core is in the range of 2.3 mm to 2.4 mm.

11. An electronic pen, which is an electrostatic capacitive electronic pen, the electronic pen having: A coil is connected to the charging circuit of a storage battery, which supplies driving power. A columnar magnetic core, with the coil wound around it, and having a through hole in the axial direction; A rod-shaped core is inserted through the through hole of the magnetic core; and An oscillation circuit generates a signal that is transmitted through the core. The electronic pen is characterized in that... The magnetic core comprises a front portion, a rear portion, and a middle portion. The front portion is a defined area extending from the front end (which becomes the pen tip) towards the rear end (opposite to the pen tip). The rear portion is a defined area extending from the rear end towards the front end. The middle portion is the portion sandwiched between the front and rear portions. The outer diameter of the middle portion is shorter than the outer diameters of the front and rear portions. The coil is wound in the middle section.

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