Electronic pen

Abstract

Provided is an electronic pen that suppresses displacement of an initial axial direction when a pen tip is pressed against an input surface, thereby enacting a state of applying writing pressure.　This invention comprises: a cylindrical pen case provided with an opening at a pen tip side; a core that is attached in a state where a distal end part thereof protrudes out to the exterior of the pen case from the pen tip-side opening; a pressure detection unit that is provided inside a hollow part of the pen case and to a rear end side, which is the side opposite the distal end part of the core in the axial direction, and that detects pressure applied to the distal end part of the core; and an elastic member provided so as to urge the core to the opposite side in the axial direction from the pen tip side in the hollow part of the pen case even when there is no pressure being applied to the distal end part.

Description

Electronic pen

[0001] The present invention relates to an electronic pen having a pressure detection unit that detects pressure (writing pressure) applied to the tip of a core body.

[0002] Coordinate input systems consisting of a position detection device equipped with a position detection sensor and an electronic pen come in various types, such as electromagnetic coupling and electrostatic coupling, depending on the method of signal exchange between the position detection sensor and the electronic pen.

[0003] Electronic pens used in this type of coordinate input system are generally configured to detect pressure (writing pressure) applied to the tip (pen tip) of a core and transmit it to a position detection device. In this case, to detect the pressure applied to the core, the tip of the core protrudes from an opening in an electronic pen housing (hereinafter referred to as a pen case), and the core is arranged so as to be movable in its axial direction within the hollow portion of the pen case. A pressure detection unit is provided on the rear end side of the core, opposite the tip in the axial direction, and this pressure detection unit is configured to detect the axial displacement of the core in response to the pressure applied to the tip as an electrical change such as a change in capacitance, a change in inductance value, or a change in resistance.

[0004] Known pressure detection units that detect changes in capacitance include those in which the capacitance changes as the contact area between a dielectric and a conductive elastic member changes in response to the applied pressure (see, for example, Patent Document 1 (JP 2011-186803 A)), and those consisting of a semiconductor device in which the distance between two electrodes facing each other via a dielectric air layer changes in response to the applied pressure (see, for example, Patent Document 2 (JP 2013-161307 A)).

[0005] Also known is a pressure detection unit that detects the axial displacement of the core body in response to applied pressure as a change in inductance value (see, for example, Patent Document 3 (JP 2017-216002 A)). Furthermore, a pressure detection unit that detects the axial displacement of the core body in response to applied pressure as a change in resistance value is known to use a strain gauge (see, for example, Patent Document 4 (JP 2019-016038 A)).

[0006] In the electronic pen, the tip of the core body is brought into contact with the input surface of the position detection sensor, and the tip of the core body of the electronic pen is pressed against the input surface, thereby applying pressure to the tip of the core body. The pressure detection unit detects the pressure applied to the tip of the core body. In the coordinate input system, the position detection device receives information corresponding to the pressure detected by the pressure detection unit of the electronic pen and outputs it as information on the value of the writing pressure applied to the tip of the core body of the electronic pen.

[0007] JP 2011-186803 A JP 2013-161307 A JP 2017-216002 A JP 2019-016038 A

[0008] Recently, with the spread of position detection devices, electronic pens have come to be used as substitutes for writing instruments such as pencils that leave marks on paper, and there is a growing demand for electronic pens to be as easy to use as writing instruments such as pencils.

[0009] Conventionally, in electronic pens, when the pen tip is not pressed against the input surface of the position detection device (when not touching the input surface), the core body is either biased in a direction away from the pressure detection unit, or is in a free state where it is not subjected to any biasing force.

[0010] For this reason, in an electronic pen, when the pen tip is changed from a state in which it is not pressed against the input surface of the position detection device (a state in which it is not touching the input surface) to a state in which writing pressure is applied by pressing the pen tip against the input surface, an initial displacement occurs in the axial direction of the core body. Since such displacement does not occur at all in writing implements such as pencils and ballpoint pens, the user may perceive this displacement as a so-called rattle in the axial direction, which can cause discomfort.

[0011] SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic pen that can solve the above problems.

[0012] In order to solve the above problem, we provide an electronic pen comprising: a cylindrical pen case with an opening on the pen tip side; a core body that is attached with its tip protruding outside the pen case from the opening on the pen tip side; a pressure detection unit that is provided within the hollow portion of the pen case on the rear end side opposite the tip of the core body in the axial direction, and that detects the pressure applied to the tip of the core body; and an elastic member that is provided within the hollow portion of the pen case so as to urge the core body in the axial direction opposite the pen tip side even when no pressure is applied to the tip.

[0013] With the electronic pen having the above-described configuration, the core is biased in the axial direction opposite to the pen tip side within the hollow portion of the pen case by the elastic member even when no pressure is applied to the tip, so that when the pen tip is pressed against the input surface to apply pressure (writing pressure), there is almost no initial axial displacement. Therefore, the user can use the electronic pen in the same way as with a writing instrument such as a pencil.

[0014] FIG. 1 is an explanatory diagram of a configuration example of a first embodiment of an electronic pen according to the present invention. FIG. 2 is an exploded perspective view of an explanatory diagram of a configuration example of a portion of the configuration example of the electronic pen of the first embodiment of FIG. 1. FIG. 3 is an exploded perspective view of an explanatory diagram of a portion of the configuration example of the electronic pen of the first embodiment of FIG. 1. FIG. 4 is an explanatory diagram of an explanatory diagram of a configuration example of a main part of a second embodiment of an electronic pen according to the present invention. FIG. 5 is an explanatory diagram of an explanatory diagram of a main part of a third embodiment of an electronic pen according to the present invention. FIG. 6 is a characteristic diagram of an explanatory diagram of an explanatory diagram of a main part of a fourth embodiment of an electronic pen according to the present invention. FIG. 7 is an explanatory diagram of an explanatory diagram of an explanatory diagram of a main part of a fourth embodiment of an electronic pen according to the present invention. FIG. 8 is an explanatory diagram of an explanatory diagram of a main part of a fourth embodiment of an electronic pen according to the present invention. FIG. 9 is an explanatory diagram of an explanatory diagram of a part of a flowchart of an explanatory diagram of an explanatory diagram of an operation of a main part of a fourth embodiment of an electronic pen according to the present invention. FIG. 11 is an explanatory diagram of an explanatory diagram of an explanatory diagram of a main part of a fourth embodiment of an electronic pen according to the present invention.

[0015] Hereinafter, several embodiments of the electronic pen according to the present invention will be described with reference to the drawings. The embodiments of the electronic pen described below are active capacitance type electronic pens.

[0016] [First embodiment] <Outline of electronic pen of first embodiment> Fig. 1A is a diagram showing the appearance of an example of an electronic pen 1 of a first embodiment as seen from the side. Fig. 1B is an enlarged cross-sectional view of a portion of the electronic pen 1 on the pen tip side taken along line A-A in Fig. 1A.

[0017] 1A, the electronic pen 1 of this embodiment is configured such that a main body unit 3 of an active capacitance type electronic pen and, in this example, a primary battery 4 are housed in the hollow space of an elongated cylindrical pen case 2. In this case, as shown by the dotted line in FIG. 1A, in the electronic pen 1 of this embodiment, the main body unit 3 is disposed on the pen tip side in the axial direction of the hollow space of the pen case 2, and the primary battery 4 is disposed on the rear end side opposite the pen tip side.

[0018] The pen case 2 comprises a cylindrical case portion 21 made of a conductive material with a constant diameter, such as SUS, a tapered sleeve portion 22 connected to the pen tip side of the cylindrical case portion 21 and tapering toward the pen tip, and a rear end closure portion 23 connected to the rear end of the cylindrical case portion 21 in the axial direction. The sleeve portion 22 and the rear end closure portion 23 are made of an insulating material, in this example, resin. In this embodiment, the cylindrical case portion 21 made of a conductive material is electrically connected to the earth conductor of the circuit board 34, which will be described later.

[0019] The sleeve portion 22 has a space that communicates with the hollow space of the cylindrical case portion 21, and has an opening 22a at its tapered tip side (see FIG. 1B ), which is an opening on the pen tip side of the pen case 2. In the electronic pen 1 of this embodiment, the core body 5, which is configured to have conductivity, is attached to a pen tip side component 32 (described later) of the electronic pen 1 with its tip portion 5a protruding outward from the opening 22a of the sleeve portion 22.

[0020] The rear end closing portion 23 is fitted and coupled to the cylindrical case portion 21 so as to close the opening on the rear end side of the cylindrical case portion 21. In this example, the rear end closing portion 23 includes a clip portion 23a as shown in FIG.

[0021] In the electronic pen 1 of this embodiment, when the rear end closing portion 23 is removed from the cylindrical case portion 21, the primary battery 4 can be stored in and removed from the battery storage portion 4a inside the cylindrical case portion 21. Then, when the primary battery 4 is stored in the battery storage portion 4a inside the cylindrical case portion 21, the rear end closing portion 23 can be fitted into the cylindrical case portion 21, so that the primary battery 4 can be locked in the battery storage portion 4a inside the cylindrical case portion 21.

[0022] The main body unit 3 is arranged in a space on the pen tip side of the battery storage section 4a within the hollow portion of the cylindrical case section 21, and the main body unit 3 itself is fixed and arranged so that it does not move axially within the hollow portion of the pen case 2.

[0023] In this example, the main body unit 3 includes a boat-shaped resin unit holder 31 whose longitudinal direction coincides with the axial direction of the pen case 2, and a pen tip side component 32 is attached to the pen tip side of the unit holder 31. The space between the pen tip side component 32 and the battery storage section 4a of the unit holder 31 is used as a board mounting section 33, and a long, rectangular circuit board 34 is mounted on and held by the board mounting section 33.

[0024] 1A, the circuit board 34 is provided with an electronic circuit 340 including a signal transmission circuit that transmits a signal to the position detection sensor of the position detection device through the core body 5. The voltage from the primary battery 4 stored in the battery storage section 4a is supplied to the electronic circuit 340 as a power supply voltage. As will be described later, the electronic pen 1 of this embodiment is also provided with a peripheral electrode 6 (see FIG. 1B) surrounding the periphery of the core body 5. In this embodiment, the peripheral electrode 6 is configured to receive signals from the position detection sensor and control the timing of signals exchanged with the position detection device, and to transmit signals to the position detection sensor so that the position detection device can detect the tilt of the electronic pen 1.

[0025] <Example of Internal Configuration of Pen Tip Side of First Electronic Pen 1> Next, an example of the internal configuration of the pen tip side of the electronic pen 1 of the first embodiment will be described with reference to the enlarged cross-sectional view of the pen tip side in FIG.

[0026] 1(B), as described above, the sleeve portion 22 has a space that communicates with the hollow space of the cylindrical case portion 21, and has an annular protrusion 22b that protrudes in an annular shape in the axial direction at the opening on the side opposite the pen tip side. The outer diameter of this annular protrusion 22b is equal to or slightly smaller than the inner diameter of the cylindrical case portion 21, and this annular protrusion 22b is inserted and fitted into the cylindrical case portion 21 and joined appropriately, thereby joining the sleeve portion 22 to the cylindrical case portion 21 and forming the pen case 2.

[0027] 1B, a pen tip side component 32 of the main body unit 3 is provided in the hollow space of the cylindrical case 21 and the hollow space of the sleeve 22 that communicates with the hollow space of the cylindrical case 21. Fig. 2 is an exploded perspective view illustrating an example configuration of the pen tip side component 32. The following description will also refer to Fig. 2.

[0028] In this embodiment, as shown in Figure 1 (B), the pen tip side component 32 holds a peripheral electrode 6 on the pen tip side, and is configured to include a core holder 7, a pressure transmission member 8, a pressure detection unit (pen pressure detection unit) 9, and a core 5 that is detachably attached to the core holder 7.

[0029] The peripheral electrode 6 is cylindrically formed from a conductive material, such as a conductive metal, and as will be described later, is arranged to surround the rear end side opposite the tip end of the core body 5, which includes the conductive center electrode.In this example, it serves as an electrode that receives signals from the position detection sensor and transmits signals to the position detection sensor.

[0030] 1(B), the pen tip side component 32 includes a component storage holder 321 that forms the outer casing of the pen tip side component 32. The component storage holder 321 has a cylindrical shape, and the diameter (outer diameter) of its outer peripheral surface is approximately equal to or slightly smaller than the diameter (inner diameter) of the inner wall surface of the sleeve portion 22. A flange 321b consisting of a protrusion perpendicular to the axial direction is formed around the outer peripheral surface of an opening 321a on the rear end side of the component storage holder 321. This flange 321b engages with the annular protrusion 22b on the rear end side of the sleeve portion 22, thereby preventing the pen tip side component 32 from moving axially toward the pen tip side within the pen case 2 of the electronic pen 1. Therefore, when the flange portion 321b of the component storage and holding holder 321 engages with the annular protrusion 22b on the rear end side of the sleeve portion 22, as shown in Figure 1 (B), the outer side surface of the component storage and holding holder 321 is almost in close contact with the inner wall surface of the sleeve portion 22, so that no gap is created between the two.

[0031] 1(B), the peripheral electrode 6 is held by a peripheral electrode holding member 322 having an outer circumferential surface that is approximately equal to or slightly smaller than the diameter (inner diameter) of the inner wall surface of the component storage / holding holder 321, and constitutes part of the pen tip side constituent part 32. The peripheral electrode holding member 322 is made of an elastic resin, and is configured so that a portion of it protrudes toward the pen tip from the pen tip side of the component storage / holding holder 321, and the portion protruding toward the pen tip side holds the peripheral electrode 6.

[0032] In this embodiment, as shown in FIG. 1B , the peripheral electrode 6 includes a tapered portion 6a whose outer diameter corresponds to the gradually decreasing inner diameter of the sleeve portion 22 on the pen tip side, and a rear end portion 6b whose outer and inner diameters are constant. In this case, the inner diameter of the tapered portion 6a of the peripheral electrode 6 is a constant diameter that is smaller than the inner diameter of the rear end portion 6b. Therefore, as shown in FIG. 1B , a step portion 6c is formed inside the peripheral electrode 6 at the boundary between the tapered portion 6a and the rear end portion 6b. Furthermore, as shown in FIGS. 1B and 2 , a flange portion 6d having a protrusion perpendicular to the axial direction is formed around the opening of the rear end portion 6b of the peripheral electrode 6.

[0033] The diameter (inner diameter) of the inner wall surface of the peripheral electrode holding member 322 is equal to or slightly smaller than the outer diameter of the rear end side portion 6b of the peripheral electrode 6, and a step portion 322a that engages with the flange portion 6d of the peripheral electrode 6 is formed on the inner wall surface of the peripheral electrode holding member 322. A part of the rear end side portion 6b of the peripheral electrode 6 is inserted into the peripheral electrode holding member 322, and the flange portion 6d engages with the step portion 322a on the inner wall surface of the peripheral electrode holding member 322, thereby holding the peripheral electrode 6 in the peripheral electrode holding member 322.

[0034] 1(B), when the main body unit 3 is stored in the pen case 2, the tapered portion 6a of the peripheral electrode 6 is in contact with the inner wall surface of the sleeve portion 22. In this case, in this embodiment, the portion of the inner wall surface of the tapered sleeve portion 22 corresponding to the rear end portion 6b of the peripheral electrode 6 has a cylindrical inner wall portion 22c configured to have a constant inner diameter in accordance with the outer peripheral surface of the rear end portion 6b of the peripheral electrode 6. As a result, the outer peripheral surface of the rear end portion 6b of the peripheral electrode 6 and the inner wall surface of the cylindrical inner wall portion 22c of the sleeve portion 22 are configured to be in contact with each other or face each other with a small gap therebetween.

[0035] 1B and 2, an O-ring 13 made of an elastic material, for example elastic rubber, is provided on the outer peripheral surface of the rear end side portion 6b of the peripheral electrode 6, and the O-ring 13 is configured so that there is no gap between the cylindrical inner wall portion 22c of the inner wall surface of the sleeve portion 22 and the outer peripheral surface of the rear end side portion 6b of the peripheral electrode 6. The O-ring 13 completely separates the space on the pen tip side of the O-ring 13 (the space that communicates with the external space of the electronic pen 1) from the hollow space inside the pen case 2 on the rear end side of the O-ring 13, thereby realizing moisture-proofing of the electronic pen 1.

[0036] 1(B), the core holder 7, pressure transmission member 8, and pressure detection unit (pen pressure detection unit) 9 are arranged in series in the axial direction with their central axes aligned, and are housed in the hollow space of the peripheral electrode 6 held by the peripheral electrode holding member 322 attached to the component storage holder 321, and in the hollow spaces of the component storage holder 321 and the peripheral electrode holding member 322 which communicate with the hollow space of the peripheral electrode 6. In this embodiment, the pressure detection unit 9 is housed in a pressure detection unit holder 91, as will be described in detail later.

[0037] 1(B) and 2, a pressure detection unit holder storage section 310 that stores and holds the pressure detection unit holder 91 is provided on the pen tip side of the unit holder 31. Then, as shown in Fig. 1(B), the pressure detection unit holder storage section 310 part of the unit holder 31 is inserted into and held at the rear end side of the component storage and holding holder 321.

[0038] 2, the pressure detection unit holder storage section 310 includes a cylindrical section 311 having an opening 311a on the pen tip side, and a storage space section 312 having a storage space communicating with the hollow space of the cylindrical section 311. The pressure detection unit holder 91 is stored in the storage space of the hollow space of the cylindrical section 311 of the pressure detection unit holder storage section 310 and the storage space of the storage space section 312.

[0039] As shown in Fig. 2, the pressure detection unit holder 91 has a cylindrical appearance, and a storage recess 91a is formed in the axial middle of the cylindrical shape as a recess in a direction perpendicular to the axial direction. Also, as shown in Fig. 1(B) and Fig. 2, a through-hole 91b is formed in the center of the cylindrical shape on the pen tip side of the pressure detection unit holder 91 in the axial direction so as to spatially communicate with the storage recess 91a.

[0040] 1(B) and 2, an axial recess 91c is formed on the rear end side of the pressure detection unit holder 91, and a columnar protrusion 91d is formed extending axially from the center of the bottom of the recess 91c. In this embodiment, a coil spring 92 having a winding diameter larger than the outer diameter of the columnar protrusion 91d is provided, and the coil spring 92 is attached so as to be wound around the columnar protrusion 91d, as shown in FIG.

[0041] This coil spring 92 functions as a shock absorber, that is, to absorb the impact load applied to the tip side of the core body 5 when the electronic pen 1 of this embodiment is dropped, etc. This coil spring 92 has an elastic modulus such that it does not elastically deform when writing pressure is applied to the tip of the core body 5 of the electronic pen 1 during writing input, but elastically deforms only when an impact load greater than the writing pressure is applied.

[0042] 1B and 2, a partition wall 313 is provided at the rear end of the storage space 312 of the pressure detection unit holder storage portion 310, extending in a direction perpendicular to the axial direction. A recess 313a and a through-hole 313b having a diameter similar to that of the recess 91c of the pressure detection unit holder 91 are provided in the axial direction of this partition wall 313, as shown in FIG. 1B. The diameter of the through-hole 313b is larger than the diameter of the columnar protrusion 91d on the rear end side of the pressure detection unit holder 91, but smaller than the outer diameter of the winding diameter of the coil spring 92. In other words, the diameter of the through-hole 313b is determined so that the rear end of the coil spring 92 cannot move in the axial direction due to the presence of the partition wall 313.

[0043] In this embodiment, the pressure sensing unit 9 is a semiconductor device (see Patent Document 2, cited above) in which the distance between two electrodes facing each other via a dielectric air layer changes in response to applied pressure. As shown in FIG. 2, the pressure sensing unit 9 includes a pressure-receiving protrusion 9a that receives the pressure to be sensed. The pressure-receiving protrusion 9a is configured to change the distance between the two electrodes facing each other via the air layer in response to the pressure to be sensed, but to return to its original state when the pressure to be sensed is removed. This configuration is publicly known, as shown in Patent Document 2, and therefore a description thereof will be omitted here.

[0044] 1B and 2, the pressure detection unit 9 is attached to one end in the longitudinal direction of an elongated flexible substrate 93. In this case, the pressure detection unit 9 is disposed on the flexible substrate 93 in such a manner that the opposing directions of the two electrodes that face each other with an air layer interposed therebetween are perpendicular to the substrate surface of the flexible substrate 93.

[0045] The pressure detection unit 9 is then stored and fixed in the pressure detection unit holder 91 as follows: First, the pressure detection unit holder 91, with the coil spring 92 attached around the columnar protrusion 91d, is inserted into the cylindrical portion 311 of the pressure detection unit holder storage portion 310 of the unit holder 31 from the opening 311a side. Then, the pressure detection unit holder 91 is positioned so that the opening of the storage space portion 312 of the pressure detection unit holder storage portion 310 and the opening of the storage recess 91c of the pressure detection unit holder 91 are in the same position (overlapping position), and the pressure detection unit holder 91 is inserted into the cylindrical portion 311 of the pressure detection unit holder storage portion 310 from the opening 311a side.

[0046] 1B, the columnar protrusion 91d of the pressure detection unit holder 91 is inserted into the recess 313a and through-hole 313b of the partition wall 313 of the pressure detection unit holder housing 310. In this state, the end of the coil spring 92 abuts against the wall surface of the partition wall 313, and the elastic biasing force of this coil spring 92 elastically displaces the pressure detection unit holder 91 toward the pen tip, so that it is locked in the axial direction when normal writing pressure is applied to the tip 5a of the core 5 of the electronic pen 1. When an impact load is applied to the tip 5a of the core 5, the coil spring 92 contracts and absorbs the impact load.

[0047] 2, the pressure detection unit 9 provided on the flexible substrate 93 is inserted into the storage recess 91a of the pressure detection unit holder 91 from the opening side of the storage space 312. In this case, the portion of the flexible substrate 93 on which the pressure detection unit 9 is attached is bent relative to the other portions of the flexible substrate 93, and the pressure detection unit 9 is inserted and stored in the storage recess 91a of the pressure detection unit holder 91 so that the two electrodes of the semiconductor device that constitutes the pressure detection unit 9 face each other in the axial direction with an air gap between them. In this stored state, as shown in FIG. 1B, the surface of the pressure detection unit 9 on which the pressure-receiving protrusion 9a is formed faces the through-hole 91b of the pressure detection unit holder 91, and the position of the pressure-receiving protrusion 9a is located at the center of the through-hole 91b.

[0048] In this embodiment, the pressure detection unit 9 is configured to receive pressure (writing pressure) applied to the tip of the core 5 via the core holder 7 and the pressure transmission member 8. In this embodiment, the pressure transmission member 8 is made of a non-conductive material, such as resin, and is configured with a pusher 81 and a pressing member 82 that presses the pusher 81 in the axial direction. As shown in FIG. 1B , the pusher 81 and the pressing member 82 are housed in a transmission member holder 83 provided in the peripheral electrode holding member 322 in a state where they can move in the axial direction.

[0049] In this case, the pusher 81 of the pressure transmitting member 8 is disposed so as to pass through the through-hole 91b of the pressure detecting unit holder 91 and engage with the pressure receiving protrusion 9a of the pressure detecting unit 9. The pressing member 82 has a recess 82a into which a fitting protrusion 7d (described later) of the core body holder 7 fits. When pressure is applied to the tip 5a of the core body 5, the pressure is transmitted to the pressing member 82 of the pressure transmitting member via the core body holder 7, and this pressing member 82 causes the pusher 81 to press the pressure receiving protrusion 9a of the pressure detecting unit 9, thereby changing the capacitance of the semiconductor device that constitutes the pressure detecting unit 9, and pressure is detected from the change in capacitance.

[0050] As shown in Fig. 1(B), in this example, the core body 5 is configured such that most of the core body 5, except for the rear end of the center electrode 51 made of a conductive material, is covered with a protective member 52 made of a non-conductive material. As shown in Figs. 1(B) and 2, the front end 5a of the core body 5 is shaped such that the egg-shaped portion of the center electrode 51 is covered with the protective member 52 in a conical shape having a tapered portion that tapers toward the front end. As shown in Fig. 1(B), the rear end of the core body 5 beyond the front end 5a has a diameter smaller than the diameter of the opening 22a of the sleeve portion 22 (the opening of the pen case 2), and the rear end of the center electrode 51 is exposed and not covered by the protective member 52.

[0051] In this example, as shown in FIG. 1B , the core 5 has a structure in which a space (air layer) 53 is provided between the center electrode 51 and the protective member 52. The signal (electric field) radiated from the portion of the center electrode 51 of the core 5, which is located on the tip side of the wide portion of the egg-shaped pen tip, is radiated relatively efficiently only through the protective member 52. However, the radiation of the signal (electric field) from the narrow portion of the center electrode 51, which is located on the rear side of the egg-shaped pen tip, is suppressed by the action of the space 53 and the protective member 52. This is because the space 53 and the protective member 52 have different dielectric constants, causing this portion to function like a double capacitor. As a result, even if the electronic pen 1 is tilted relative to the input surface of the position detection sensor, the center electrode 51 can transmit a good signal without excessive broadening.

[0052] 1(B), the rear end side of the tip end 5a of the core 5 is inserted through the opening 22a of the sleeve portion 22 into the internal space of the peripheral electrode 6 inside the pen case 2. Then, the rear end of the center electrode 51, which is exposed and not covered by the protective member 52, is fitted into the core holder 7. In this case, the non-conductive protective member 52 of the core 5 serves as a member for insulating the center electrode 51 from the peripheral electrode 6.

[0053] In this embodiment, when the core 5 is inserted into the sleeve portion 22 of the pen case 2, as shown in Fig. 1(B), the tip 6e on the nib side of the peripheral electrode 6 abuts against the side circumferential surface of the protective member 52 at the small-diameter portion behind the tip 5a of the core 5, restricting the core 5 from moving in a direction perpendicular to the axial direction at the abutting portion. Because of this configuration, the tip 6e on the nib side of the peripheral electrode 6 protrudes inward as shown in Fig. 1(B), and the size of the opening on the nib side of the peripheral electrode 6 is configured to be approximately equal to or slightly larger than the diameter of the abutting portion of the core 5. This prevents the core 5 from rattling in a direction perpendicular to the axial direction at the tip-side opening of the peripheral electrode 6.

[0054] When pressure is applied to the tip 5a of the core 5, the core holder 7 displaces axially together with the core 5, thereby transmitting the pressure to the pressure detection unit 9 via the pressure transmission member 8, and also serves to electrically connect the center electrode 51 of the core 5 and the electronic circuit 340 arranged on the circuit board 34.

[0055] In this embodiment, the core body holder 7 is configured to always be biased toward the pressure detection unit 9, as described below, thereby preventing axial rattle of the core body 5 fitted into the core body holder 7.

[0056] Figure 3 shows the core holder 7 and its surrounding parts arranged in the hollow space of the peripheral electrode 6 and the transmission member holder 83, and is a diagram to explain the two roles of the core holder 7 mentioned above and the configuration for preventing axial rattle of the core 5.

[0057] The core holder 7 is made of a conductive material, in this example, a resin mixed with conductive metal powder. As shown in FIGS. 1B and 3 , it has an enlarged-diameter portion 7b with a recessed fitting 7a into which the rear end of the center electrode 51 of the core 5 fits. The exposed portion of the rear end of the core 5 where the center electrode 51 is located is press-fit into the recessed fitting 7a in the enlarged-diameter portion 7b of the core holder 7, thereby locking the core 5 to the core holder 7. Therefore, when pressure is applied to the tip 5a of the core 5 and the core 5 is displaced axially, the core holder 7 also displaces axially, transmitting the pressure to the pressure detection unit 9. The core 5 can be removed from the core holder 7 by pinching and pulling out the pen tip portion, for example, by hooking it with a fingernail. In other words, the core 5 is replaceable.

[0058] The core holder 7 has a small-diameter portion 7c at the rear end of the large-diameter portion 7b, which is provided with the fitting recess 7a. A coil spring 7e made of a conductive metal is wound around and attached to the small-diameter portion 7c. One end of the coil spring 7e is engaged at a step between the large-diameter portion 7b and the small-diameter portion 7c of the core holder 7 so as to be electrically connected to the core holder 7. As shown in FIG. 2, the other end of the coil spring 7e extends axially and reaches onto the circuit board 34 by passing through a through-hole 311b provided in the cylindrical portion 311 of the pressure detection unit holder housing portion 310 of the unit holder 31. The other end of the coil spring 7e is electrically connected to the electronic circuit 340 arranged on the circuit board 34.

[0059] 1(B) and 3, a fitting protrusion 7d having a smaller diameter than the small diameter portion 7c is provided further rearward of the small diameter portion 7c of the core holder 7, and as described above, this fitting protrusion 7d is fitted into the recess 82a of the pressing member 82 of the pressure transmitting member 8, thereby connecting the core holder 7 and the pressure transmitting member 8 in the axial direction. In this case, in this embodiment, the small diameter portion 7c of the core holder 7 is inserted into the transmitting member holder 83, as shown in FIG. 1(B). Therefore, the coil spring 7e provided around this small diameter portion 7c is also housed in the transmitting member holder 83. The extension portion of the coil spring 7e passes through the transmitting member holder 83 and extends toward the circuit board 34.

[0060] 1B and 2, a coil spring 6f for electrical connection between the peripheral electrode 6 and the circuit board 34 is disposed around the pen tip side portion of the transmission member holder 83. One end of this coil spring 6f is electrically connected to the peripheral electrode 6 as shown in FIGS. 1B and 2. The other end of this coil spring 6f is extended, and its extension 6t (see FIG. 2) passes through the transmission member holder 83 in the peripheral electrode holding member 322, extends toward the circuit board 34, and is connected to the electronic circuit 340 and a signal receiving circuit (not shown) of the circuit board 34.

[0061] Next, we will explain the structure for preventing axial wobble of the core body 5. As shown in Fig. 1(B) , in this embodiment, the rear end of the central electrode 51 of the core body 5 is fitted into the fitting recess 7a of the core body holder 7, and the large diameter portion 7b of the core body holder 7 is positioned within the hollow space of the rear end side portion 6b of the peripheral electrode 6, which has a constant inner diameter.

[0062] 1(B), in this embodiment, a cup-shaped member 10 made of resin is provided within the rear end portion 6b of the peripheral electrode 6 as an example of an insulating member for ensuring electrical insulation between the peripheral electrode 6 and the large-diameter portion 7b of the core holder 7. The outer diameter of this cup-shaped member 10 is equal to or slightly smaller than the inner diameter of the rear end portion 6b of the peripheral electrode 6, and the inner diameter of the recess 10b of the cup-shaped member 10 is larger than the large-diameter portion 7b of the core holder 7.

[0063] Therefore, the cup-shaped member 10 is disposed within the rear end portion 6b of the peripheral electrode 6, with the periphery of the end surface of the cup-shaped member 10 on the pen tip side facing the step portion 6c inside the peripheral electrode 6. In this case, in this embodiment, as shown in Fig. 1(B), an O-ring 12 (see Figs. 2 and 3) having a circular cross section in this example is disposed in an elastically compressed and elastically deformed state between the periphery of the end surface of the cup-shaped member 10 on the pen tip side and the step portion 6c inside the peripheral electrode 6. This O-ring 12 also serves to separate the space on the tapered portion 6a side, which is connected to the external space inside the peripheral electrode 6, from the space on the rear end portion 6b side of the peripheral electrode 6.

[0064] The core body holder 7 is inserted with its large diameter portion 7b in the recess 10b of the cup-shaped member 10 in a state where it can move in the axial direction. As shown in Figures 1(B) and 3, a through hole 10a is provided in the bottom of the recess 10b of the cup-shaped member 10, through which the rear end side of the center electrode 51 of the core body 5 is inserted, and the rear end of the center electrode 51 of the core body 5 is press-fitted through this through hole 10a into the fitting recess 7a of the large diameter portion 7b of the core body holder 7 disposed in the recess 10b of the cup-shaped member 10. Therefore, the core body 5, together with the core body holder 7, is movable in the axial direction toward the pressure detection unit 9 within the internal space of the peripheral electrode 6 and the recess 10b of the cup-shaped member 10.

[0065] In this case, the cup-shaped member 10 is engaged in the peripheral electrode 6 that is attached so as not to move toward the pen tip in the axial direction within the pen case 2, and therefore the cup-shaped member 10 also does not move toward the pen tip in the axial direction within the pen case 2. Therefore, the wall surface at the bottom of the recess 10b of the cup-shaped member 10 is a wall surface that does not move toward the pen tip in the axial direction within the pen case 2.

[0066] In this embodiment, the pen tip side component 32 is configured on the pen tip side of the unit holder 31 when the core holder 7 is coupled to the pressure transmission member 8 and the plunger 81 of the pressure transmission member 8 is in contact with the pressure-receiving protrusion 9a of the pressure detection unit 9. In this case, as shown in Fig. 1(B), the pen tip side component 32 is configured so that a gap is formed between the inner wall surface surrounding the through hole 10a at the bottom of the cup-shaped member 10 and the ring-shaped end surface 7t surrounding the fitting recess 7a of the large-diameter portion 7b of the core holder 7. In this embodiment, an O-ring 11 made of elastic rubber as an example of an elastic member is disposed in this gap, as shown in Figs. 1(B) and 3.

[0067] In this example, the diameter of the O-ring 11's circular cross section is slightly larger than the gap between the inner wall surface around the through-hole 10a at the bottom of the cup-shaped member 10 and the ring-shaped end surface 7t around the fitting recess 7a of the large-diameter portion 7b of the core holder 7. Therefore, the O-ring 11 is disposed in the gap between the inner wall surface around the through-hole 10a at the bottom of the cup-shaped member 10 and the ring-shaped end surface 7t around the fitting recess 7a of the large-diameter portion 7b of the core holder 7, in a state where it is elastically compressed and elastically deformed at least in the axial direction.

[0068] As mentioned above, the wall surface at the bottom of the recess 10b of the cup-shaped member 10 does not move axially toward the pen tip within the pen case 2, so the core holder 7 is always biased axially toward the pressure detection unit 9 due to the elastic return force of the elastically deformed O-ring 11 to its original state. Therefore, the core 5 fitted into this core holder 7 is also always biased axially toward the pressure detection unit 9, even when no pressure is applied to the tip 5a.

[0069] In this embodiment, the diameter of the outer circumferential circle of the O-ring 11 is selected to be equal to or slightly larger than the inner diameter of the recess 10b of the cup-shaped member 10. However, in this example, the diameter of the inner circumferential circle of the O-ring 11 is set to a diameter such that it does not come into contact with the rear end of the center electrode 51 of the core body 5.

[0070] Therefore, the O-ring 11 is in contact with the axial wall of the recess 10b of the cup-shaped member 10, and therefore, when the O-ring 11 is elastically compressed and deformed in the axial direction in the gap between the inner wall surface around the through-hole 10a at the bottom of the cup-shaped member 10 and the ring-shaped end surface 7t around the fitting recess 7a of the large-diameter portion 7b of the core holder 7, it elastically deforms so as to elastically stretch slightly in the direction perpendicular to the axial direction. In other words, an elastic biasing force acts on the O-ring 11 toward the center of the ring. This elastic biasing force of the O-ring 11 toward the center serves to suppress displacement of the core holder 7 in the direction perpendicular to the axial direction (rattlement in the direction perpendicular to the axial direction).

[0071] As described above, in the electronic pen 1 of this embodiment, even when pressure is not applied to the tip 5 a, the core 5 is always biased axially toward the pressure detection unit 9 due to the elastic return force of the elastically deformed O-ring 11 to its original state. Therefore, even when the tip 5 a of the core 5 is not pressed against the input surface of the position detection device, but is pressed against the input surface to apply writing pressure, no initial axial displacement of the core 5 occurs, preventing the user from feeling any so-called rattle in the axial direction. Therefore, the electronic pen 1 of this embodiment can achieve a feel similar to that of a writing instrument such as a pencil or ballpoint pen.

[0072] In this embodiment, the elastic biasing force of the compressed O-ring 11 also suppresses displacement of the core holder 7 in a direction perpendicular to the axial direction. Therefore, the core 5 fitted to the core holder 7 is also suppressed from displacement (wobbling) in a direction perpendicular to the axial direction. In this embodiment, the tip 6 e of the peripheral electrode 6 on the pen tip side also suppresses displacement of the core 5 in the axial direction, so both of these factors more firmly suppress displacement of the core 5 in a direction perpendicular to the axial direction. To achieve the effect of suppressing displacement in a direction perpendicular to the axial direction of the core 5 by the tip 6 e of the peripheral electrode 6 on the pen tip side, the size of the opening where the tip 6 e of the peripheral electrode 6 is formed must be precisely determined, and tolerances may prevent the suppression effect from being fully achieved. However, in this embodiment, the presence of the O-ring 11 fully suppresses displacement in a direction perpendicular to the axial direction of the core 5. Since the O-ring 11 alone is effective in suppressing displacement in a direction perpendicular to the axial direction of the core body 5, the tip portion 6e of the peripheral electrode 6 on the pen tip side does not need to be provided.

[0073] Furthermore, in this embodiment, the O-ring 11 also serves to separate the internal space of the pen case 2 on the rear end side of the cup-shaped member 10 from the space that communicates with the external space on the pen tip side through the through-hole 10a of the cup-shaped member 10. Therefore, in the electronic pen 1 of this embodiment, the O-ring 11 and the two O-rings 12 and 13 described above separate the hollow space inside the pen case 2 from the space that communicates with the external space on the pen tip side. This provides the electronic pen 1 of this embodiment with high moisture-proofing properties.

[0074] [Second embodiment] In the first embodiment described above, an O-ring 11 made of elastic rubber is used as an example of an elastic member provided to bias the core body 5 toward the pressure detection unit side opposite the pen tip side in the axial direction even when no writing pressure (load) is applied to the tip 5 a of the core body 5, and the configuration utilizes the elastic force of the O-ring 11 returning from an elastically deformed state to its original state. However, the elastic member is not limited to the configuration described in the above example.

[0075] The second embodiment is an example having a different configuration of an elastic member that is arranged to bias the core body 5 toward the pressure detection unit side, which is on the opposite side of the axial direction from the pen tip side, and in the second embodiment, a coil spring 14 and an O-ring 15, which will be described later, are used as examples of the configuration of the elastic member.

[0076] The appearance and outline of the electronic pen 1A of this second embodiment are similar to those of the electronic pen 1 of the first embodiment shown in Fig. 1A. The electronic pen 1A of this second embodiment differs from the electronic pen 1 of the first embodiment in the configuration for transmitting the pressure applied to the core body 5 to the pressure detection unit 9, but is otherwise similar to the electronic pen 1 of the first embodiment.

[0077] Fig. 4 is a cross-sectional view showing an example of the configuration of the pen tip side of the electronic pen 1A of this second embodiment, and corresponds to Fig. 1B for the electronic pen 1 of the first embodiment. In the configuration of the electronic pen 1A of the second embodiment shown in Fig. 4, components similar to those of the electronic pen 1 of the first embodiment described above are given the same reference numerals, and detailed description thereof will be omitted.

[0078] In the electronic pen 1A of the second embodiment, the writing pressure applied to the core 5 is also transmitted to the pressure detection unit 9 via the core holder 7A and the pressure transmission member 8A.

[0079] Like the core holder 7 of the electronic pen 1 of the first embodiment, the core holder 7A is made of a conductive material, in this example, a resin mixed with conductive metal powder, and has a large diameter portion 7Ab with a fitting recess 7Aa into which the rear end side of the center electrode 51 of the core 5 is fitted. The exposed portion of the center electrode 51 on the rear end side of the core 5 is press-fitted into the fitting recess 7Aa of the large diameter portion 7Ab of the core holder 7A, thereby locking the core 5 to the core holder 7A.

[0080] In this second embodiment of the electronic pen 1A, the core holder 7A also has a small diameter portion 7Ac further rearward than the large diameter portion 7Ab, and a coil spring 7Ae made of a conductive metal that is electrically connected to the circuit board 34 is wound and attached to the other end of this small diameter portion 7Ac, and this coil spring 7Ae electrically connects the core 5 to the electronic circuit 340 arranged on the circuit board 34.

[0081] The pressure transmission member 8A is made of a non-conductive material, such as resin, and in the electronic pen 1A of this second embodiment, it is made up of a pusher 81A and a transmission member holder 83A that houses the pusher 81A in a state where it can move in the axial direction. In this second embodiment, the pressing member 82 in the first embodiment is omitted, and the pen pressure is transmitted to the pressure detection unit 9 by pressing the pusher 81A with the tip on the rear end side of the core holder 7A.

[0082] Next, a description will be given of a configuration for preventing rattles in the axial direction of the core body 5 and rattles in a direction perpendicular to the axial direction in the second embodiment. Note that the rest of the configuration of the electronic pen 1A of the second embodiment is the same as that of the electronic pen 1 of the first embodiment.

[0083] As shown in Figure 4, in this second embodiment, a cup-shaped member 10A made of resin is provided in the hollow space of the rear end side portion 6b of the peripheral electrode 6 as an example of an insulating member for ensuring electrical insulation between the peripheral electrode 6 and the large diameter portion 7Ab of the core holder 7A, and the large diameter portion 7Ab of the core holder 7A is configured to be housed in the recess 10Ab of this cup-shaped member 10A.

[0084] In this case, the core holder 7A is housed in the recess 10Ab of the cup-shaped member 10A with its large-diameter portion 7Ab movable in the axial direction. As shown in Fig. 4, a through-hole 10Aa is provided in the bottom of the recess 10Ab of the cup-shaped member 10A on the pen tip side, through which the rear end of the center electrode 51 of the core 5 is inserted. The rear end of the center electrode 51 of the core 5 is press-fitted through this through-hole 10Aa into the fitting recess 7Aa of the large-diameter portion 7Ab of the core holder 7A disposed in the recess 10Ab of the cup-shaped member 10A. Therefore, the core 5, together with the core holder 7A, is movable in the axial direction toward the pressure detection unit 9 within the internal space of the peripheral electrode 6 and the recess 10Ab of the cup-shaped member 10A. In this second embodiment, the peripheral edge of the end surface of the cup-shaped member 10A on the pen tip side is arranged in a state in which it abuts against the step portion 6c inside the peripheral electrode 6, and the cup-shaped member 10A cannot move toward the pen tip in the axial direction.

[0085] The outer diameter of the cup-shaped member 10A is equal to or slightly smaller than the inner diameter of the rear end portion 6b of the peripheral electrode 6, and the inner diameter of the recess 10Ab of the cup-shaped member 10A is larger than the large-diameter portion 7Ab of the core holder 7A. In this case, the inner diameter of the recess 10Ab of the cup-shaped member 10A and the outer diameter of the large-diameter portion 7Ab of the core holder 7A are determined so that a coil spring 14, which constitutes a part of the elastic member, can be disposed between the side peripheral surface of the large-diameter portion 7Ab of the core holder 7A and the inner peripheral wall surface of the recess 10Ab of the cup-shaped member 10A, as shown in Figure 4.

[0086] In the electronic pen 1A of the second embodiment, a ring-shaped protruding portion 7Af is provided at the rear end (at the boundary with the small diameter portion 7Ac) of the large diameter portion 7Ab of the core holder 7A, protruding perpendicularly from the side surface of the large diameter portion 7Ab to the axial direction. A coil spring 14 is disposed between the ring-shaped protruding portion 7Af and the bottom of the recess 10Ab of the cup-shaped member 10A on the pen tip side, and constantly biases the core holder 7A toward the pressure detection unit 9.

[0087] Furthermore, in this second embodiment, as shown in Figure 4, a ring-shaped end face 83Aa is formed on the pen tip side of the transmission member holder 83A, which faces the ring-shaped protrusion 7Af of the core holder 7A, which is formed by making the inner wall surface stepped, and an O-ring 15 made of an elastic material, for example elastic rubber, is arranged between this ring-shaped end face 83Aa and the ring-shaped protrusion 7Af.

[0088] The O-ring 15 serves as part of the elastic member that biases the core holder 7A toward the pressure detection unit 9, and also serves to isolate the internal space of the transmission member holder 83A from the external space closer to the pen tip, ensuring moisture protection within the internal space of the transmission member holder 83A. Furthermore, in this example, the O-ring 15 also serves to suppress displacement of the core 5 in a direction perpendicular to the axial direction by restricting displacement of the core holder 7A in a direction perpendicular to the axial direction. Therefore, the diameter of the O-ring 15 is equal to or slightly larger than the distance between the ring-shaped protrusion 7Af of the core holder 7A and the ring-shaped end surface 83Aa of the transmission member holder 83A, and is equal to or slightly larger than the distance between the inner wall surface of the transmission member holder 83A and the outer circumferential surface of the core holder 7A.

[0089] In the second embodiment, the core holder 7A is displaced toward the pressure detection unit 9 by the elastic displacement force of the coil spring 14, which deforms the O-ring 15 so that it is elastically crushed. Therefore, the space between the ring-shaped protruding portion 7Af of the core holder 7A and the ring-shaped end surface 83Aa of the transmission member holder 83A is tightly sealed by the elastic restoring force of the crushed O-ring 15, and together with the presence of the moisture-proof O-ring 13 provided between the peripheral electrode 6 and the sleeve portion 22, moisture can be prevented from separating the internal space of the transmission member holder 83A from the space on the pen tip side of the electronic pen 1A.

[0090] In the second embodiment, not only the elastic displacement force of the coil spring 14 but also the elastic return force of the O-ring 15, which has been elastically crushed and displaced, acts as a biasing force that elastically displaces the core holder 7A toward the pressure detection unit 9. That is, in the second embodiment, the elastic member that is provided to bias the core 5 toward the pressure detection unit 9 even when no pressure is applied to the tip 5a of the core 5 is made up of the coil spring 14 and the O-ring 15. Therefore, the effect of suppressing axial displacement of the core 5 attached to the core holder 7A is greater than that of the electronic pen 1 of the first embodiment.

[0091] According to the electronic pen 1A of this second embodiment, when the tip 5a of the core body 5 is changed from a state in which it is not pressed against the input surface of the position detection device to a state in which writing pressure is applied by pressing the tip 5a against the input surface, no initial displacement of the core body occurs in the axial direction, and it is possible to more reliably prevent the user from feeling so-called rattle in the axial direction, and it is possible to more reliably achieve a feeling of use similar to that of a writing instrument such as a pencil or ballpoint pen.

[0092] [Third Embodiment] The third embodiment is a modification of the second embodiment. Fig. 5 is a cross-sectional view showing an example of the configuration of the pen tip side of an electronic pen 1B of the third embodiment, and corresponds to Fig. 4 for the electronic pen 1A of the second embodiment. The appearance and overview of the electronic pen 1B of the second embodiment are similar to those of the electronic pen 1 of the first embodiment shown in Fig. 1(A).

[0093] In the electronic pen 1B of the third embodiment, as with the electronic pen 1A of the second embodiment, a coil spring 14B and an O-ring 16, which will be described later, are used as examples of elastic members. In the electronic pen 1A of the second embodiment described above, the O-ring 15, which also serves as a moisture-proofing element, is located closer to the rear end than the coil spring 14, but in the electronic pen 1B of the third embodiment, the O-ring 16, which also serves as a moisture-proofing element, is located closer to the pen tip than the coil spring 14B, which is different from the second embodiment.

[0094] That is, in the electronic pen 1B of the third embodiment, the pressure transmission member 8B is configured, like the pressure transmission member 8A of the electronic pen 1A of the second embodiment, to include a pusher 81B made of, for example, resin and a transmission member holder 83B that houses the pusher 81B in a state that allows it to move in the axial direction, as shown in Fig. 5. The core holder 7B in the electronic pen 1B of the third embodiment has a configuration similar to that of the core holder 7A of the electronic pen 1A of the second embodiment, and as shown in Fig. 5, includes a large-diameter portion 7Bb having a fitting recess 7Ba into which the exposed portion of the center electrode 51 on the rear end side of the core 5 is press-fitted, and a small-diameter portion 7Bc on the rear end side of the large-diameter portion 7Bb, and the tip of the small-diameter portion 7Bc presses the pusher 81B.

[0095] In the electronic pen 1B of the third embodiment, the large-diameter portion 7Bb of the core holder 7B is housed in a recess 10Bb of a cup-shaped member 10B having a configuration similar to that of the cup-shaped member 10A of the electronic pen 1A of the second embodiment, so as to be movable in the axial direction. However, in the third embodiment, the cup-shaped member 10B is movable in the axial direction within the hollow space of the rear end side portion 6b of the peripheral electrode 6.

[0096] The rear end of the center electrode 51 of the core 5 is press-fitted into the fitting recess 7Ba of the large-diameter part 7Bb of the core holder 7B through a through-hole 10Ba provided in the bottom part of the pen tip side of the recess 10Bb of the cup-shaped member 10B. In this third embodiment, too, a coil spring 7Be made of conductive metal and having the other end electrically connected to the circuit board 34 is wound and attached to the small-diameter part 7Bc of the core holder 7B, thereby electrically connecting the core 5 to the electronic circuit 340 arranged on the circuit board 34.

[0097] Furthermore, the core holder 7B has a protruding portion 7Bf similar to the protruding portion 7Af of the core holder 7A of the electronic pen 1A of the second embodiment, and similar to the electronic pen 1A of the second embodiment, a coil spring 14B is provided between this protruding portion 7Bf and the bottom of the recess 10Bb of the cup-shaped member 10B on the pen tip side. Due to the elastic displacement force of this coil spring 14B, the electronic pen 1B of the third embodiment is also configured so that the core holder 7A is always biased toward the pressure detection unit 9, similar to the electronic pen 1A of the second embodiment.

[0098] Furthermore, in this third embodiment, as shown in Fig. 5, an O-ring 16 made of an elastic material, for example elastic rubber, is disposed between the end surface of the cup-shaped member 10B on the pen tip side and the step portion 6c inside the peripheral electrode. Like the O-ring 11 of the electronic pen 1 of the first embodiment and the O-ring 15 of the electronic pen 1A of the second embodiment, this O-ring 16 serves as part of the elastic member that biases the core holder 7B toward the pressure detection unit 9, as well as providing a moisture-proof function and preventing rattling in a direction perpendicular to the axial direction of the core 5.

[0099] 5, the O-ring 16 is configured such that two O-rings of different diameters are concentrically arranged and the opposing peripheral surfaces are joined together. However, the O-ring 16 is not limited to such a special shape and may be configured as a single O-ring.

[0100] In the third embodiment, the elastic displacement force of the coil spring 14B displaces the cup-shaped member 10B toward the pen tip within the hollow space in the rear end portion 6b of the peripheral electrode 6, thereby elastically crushing and deforming the O-ring 16. Therefore, the elastic restoring force of the crushed O-ring 16 tightly seals the gap between the peripheral edge of the end surface of the core holder 7B on the pen tip side and the internal step portion 6c of the peripheral electrode 6, ensuring moisture protection by isolating the internal space of the transmission member holder 83A from the space on the pen tip side of the electronic pen 1B. Note that a moisture-proof O-ring 13 is provided between the outer periphery of the peripheral electrode 6 and the inner wall surface of the sleeve portion 22. Therefore, in the electronic pen 1B of the third embodiment, the O-ring 13 and the O-ring 16 also shield the electrical components, including the pressure detection unit 9, inside the electronic pen 1B from the external space on the pen tip side, thereby achieving moisture protection for the electronic pen 1B.

[0101] In the third embodiment, not only the elastic displacement force of the coil spring 14B but also the elastic return force of the O-ring 16, which has been elastically crushed and displaced, acts as a biasing force that elastically displaces the core holder 7B toward the pressure detection unit 9. That is, in the third embodiment, the elastic member that is provided to bias the core 5 toward the pressure detection unit 9 even when no pressure is applied to the tip 5a of the core 5 is composed of the coil spring 14B and the O-ring 16. Therefore, the effect of suppressing axial displacement of the core 5 attached to the core holder 7B is greater than that of the electronic pen 1 of the first embodiment.

[0102] The electronic pen 1B of the third embodiment can also provide the same effects as the electronic pen 1A of the second embodiment.

[0103] [Fourth embodiment] In the electronic pens 1, 1A, 1B of the above-described embodiments, even when no pressure is applied to the tip 5a of the core 5, the core holders 7, 7A, 7B are configured to be biased toward the pressure detection unit 9 by the elastic members (O-ring 11, coil spring 14 and O-ring 15, coil spring 14B and O-ring 16). In other words, a preload is applied to the core holders 7, 7A, 7B, thereby preventing the core 5 attached to the core holders 7, 7A, 7B from wobbling in the axial direction.

[0104] Therefore, even when the writing pressure (load) applied to the core body of the electronic pen is zero, the pressure detection unit 9 detects a pressure value corresponding to the preload pressure (load) due to the elastic member (hereinafter referred to as preload value Lpre). The electronic pens 1, 1A, 1B do not directly transmit the writing pressure value (hereinafter referred to as writing pressure raw value Po) detected by the pressure detection unit 9 to a position detection device equipped with a position detection sensor that receives writing input from the electronic pen, but instead generate a writing pressure output value OP from the writing pressure raw value Po and transmit the value to the position detection device.

[0105] In the electronic pens 1, 1A, and 1B, a writing pressure value Po corresponding to a preload value Lpre of the elastic member is set as a zero offset value OFS. In this example, this zero offset value OFS is set to be the same as the preload value Lpre when the load applied to the pressure detection unit 9 is the same as the preload value Lpre, but it may also be set to be the writing pressure value Po when the load is not the same as the preload value Lpre but is slightly larger than the preload value Lpre.

[0106] When the writing pressure raw value Po detected by the pressure detection unit 9 is equal to or less than the zero offset value OFS, the electronic pens 1, 1A, and 1B output a writing pressure output value OP of zero. When the writing pressure raw value Po detected by the pressure detection unit 9 becomes greater than the zero offset value OFS, the electronic pens 1, 1A, and 1B transmit the value obtained by subtracting the zero offset value OFS from the writing pressure raw value Po to the position detection device as the writing pressure output value OP.

[0107] The position detection device generates handwriting information from the writing pressure output value OP transmitted from the electronic pens 1, 1A, and 1B and the detection output of the position indicated by the electronic pens 1, 1A, and 1B. That is, the position detection device determines that no writing force is being applied when the writing pressure output value OP is zero, and generates handwriting information from information about the position detected when the writing pressure output value OP is zero or greater. Then, a display device connected to the position detection device displays the handwriting input by the electronic pens 1, 1A, and 1B based on the generated handwriting information.

[0108] Incidentally, in the electronic pens 1, 1A, and 1B of the above-described embodiments, the presence of the preload elastic member also affects the transmission of the pressure applied to the tip 5a of the core 5 to the pressure detection unit 9. For this reason, there is no problem when the pressure (load) applied to the tip 5a of the core 5 is small, but after a large pressure (load) is applied to the tip 5a of the core 5, when the pressure application to the core 5 is stopped, there is a risk that the writing pressure value Po will not return to the zero offset value OFS and will take on a value slightly larger than the zero offset value OFS.

[0109] That is, the pressure detection unit 9 detects a writing pressure value corresponding to the pressure transmitted through the plunger 81. In this case, if the change characteristics when the pressure increases and when the pressure decreases are exactly the same, a state in which the writing pressure value Po does not return to the zero offset value OFS will not occur. However, generally, the change characteristics when the pressure increases and when it decreases are different, and hysteresis occurs when the pressure increases and decreases. However, if the plunger 81 is simply pressed down by the transmission member 82 or the small diameter portions 7Ac and 7Bc of the core holders 7A and 7B, the hysteresis is small and can be ignored.

[0110] However, in the electronic pens 1, 1A, and 1B of this embodiment, the elastic members for preloading are configured to participate in the transmission of pressure applied to the tip portion 5a of the core body 5 to the pressure detection unit 9. Therefore, there is a risk that hysteresis caused by the influence of these elastic members will be added together, resulting in a non-negligible degree of hysteresis. Note that this risk is more likely to occur in the electronic pens 1A and 1B of the second embodiment, which involve a larger number of elastic members than in the electronic pen 1 of the first embodiment.

[0111] FIG. 6 shows a characteristics diagram illustrating the relationship between the load (pressure) applied to the pressure detection unit 9 and the writing pressure value Po detected by the pressure detection unit 9, and the above-mentioned problem will be further explained using this FIG.

[0112] 6, in this example, when the load (pressure) applied to the pressure detection unit 9 is a preload value Lpre, the pen pressure raw value Po becomes a zero offset value OFS corresponding to this preload value Lpre. At this time, the pen pressure output value OP of the electronic pens 1, 1A, and 1B becomes zero.

[0113] When the load applied to the pressure detection unit 9 increases, the pen pressure value Po also increases in response to the increase in load, but when the pressure detection element configured with the MEMS described above is used, the pen pressure value Po exhibits a linear change characteristic as shown by the solid line in Fig. 6. When the load applied to the pressure detection unit 9 decreases from a state in which a large load is applied, the pen pressure value Po also decreases in response to the applied load, as shown by the dotted line in Fig. 6. However, even when the load applied to the pressure detection unit 9 reaches the preload value Lpre, the pen pressure value Po may not become the zero offset value OFS. In such a state, the pen pressure output value OP of the electronic pen 1, 1A, 1B becomes a value greater than zero, even though the pen pressure is actually zero, resulting in a state in which pen pressure is being applied.

[0114] That is, even when the application of writing pressure to the core 5 is stopped, the writing pressure raw value Po does not return to a value equal to or less than the zero offset value OFS, but becomes a value slightly larger than the zero offset value OFS. As a result, the writing pressure output value OP transmitted from the electronic pens 1, 1A, and 1B to the position detection device becomes a value larger than zero, even though no writing pressure is being applied to the tip 5a of the core 5. This causes the position detection device to consider that the tip 5a of the core 5 of the electronic pens 1, 1A, and 1B is in contact with the input surface of the position detection sensor and that writing force is being applied, even when the tip 5a of the core 5 of the electronic pens 1, 1A, and 1B is not actually in contact with the input surface of the position detection sensor and no writing force is being applied, resulting in a problem in which an unwritten portion is generated in the displayed image of the handwriting.

[0115] The fourth embodiment provides an electronic pen that overcomes the above-mentioned drawbacks and can be applied to all of the electronic pens 1, 1A, and 1B of the first to third embodiments. The electronic pen of the fourth embodiment is characterized by the circuit portion in the electronic circuit 340 that generates the writing pressure output value.

[0116] 7 is a diagram showing an example of an electronic circuit 340 in the electronic pen of the fourth embodiment, which has a signal transmission circuit 341, a signal reception circuit 342, a switch circuit 343, a writing pressure output value transmission circuit 344, and a control circuit 345. Although not shown in the figure, the control circuit 345 in this example is made up of a microprocessor including a CPU (Central Control Unit) and memory, and acts as a software processing function unit that executes various processes according to programs stored in the memory.

[0117] The signal transmission circuit 341 has an oscillation circuit of a predetermined frequency, generates a position detection signal under the control of the control circuit 345, supplies the signal to the center electrode 51 of the core body 5 via the switch circuit 343, and transmits the signal to the position detection sensor by electrostatic coupling with the center electrode 51. The position detection signal is transmitted as a burst signal of a predetermined frequency.

[0118] The peripheral electrode 6 receives a signal from the position detection sensor by electrostatic coupling. As shown in Fig. 7, the signal received by the peripheral electrode 6 from the position detection sensor is supplied to a control circuit 345 via a signal receiving circuit 342. The control circuit 345 controls the output timing of the signal from the signal transmitting circuit 341 and controls the switching of the switch circuit 103 based on the timing based on the signal received from the position detection sensor.

[0119] In this example, a variable capacitance capacitor 9C that constitutes the pressure detection unit 9 is connected to the control circuit 345. The control circuit 345 detects a pen pressure raw value Po from the capacitance of this variable capacitance capacitor 9C and includes a pen pressure output value generation circuit 3451 that generates a pen pressure output value OP from the detected pen pressure raw value Po. In this example, the pen pressure output value generation circuit 3451 is configured as a software function unit that generates the pen pressure output value OP by executing a program stored in memory. The operation of this pen pressure output value generation circuit 3451 will be described in detail later.

[0120] The writing pressure output value OP generated by the writing pressure output value generation circuit 3451 of the control circuit 345 is supplied to the writing pressure output value transmission processing circuit 344. The writing pressure output value OP from the writing pressure output value generation circuit 3451 is, for example, a 12-bit binary digital signal, and the writing pressure output value transmission processing circuit 344 performs transmission processing on the binary digital signal using, for example, ASK (Amplitude Shift Keying) modulation, PSK (Phase Shift Keying) modulation, or OOK (On Off Keying) modulation to transmit it to the position detection sensor via the central electrode 51 of the core body 5. Information on the writing pressure output value OP that has been subjected to transmission processing in this manner is transmitted to the position detection sensor via the central electrode 51 of the core body 5 through the switch circuit 343.

[0121] In this example, the control circuit 345 controls the switch circuit 343 to switch between the position detection signal (burst signal) from the signal transmission circuit 341 and the pen pressure output value OP information processed for transmission by the pen pressure output value transmission processing circuit 344, and transmit them to the position detection sensor via the center electrode 51 of the core 5 in a time-division manner. Note that the position detection signal is not limited to a burst signal, and the position may be detected using a PSK-modulated signal. Next, the operation of the pen pressure output value generation circuit 3451 will be described. The pen pressure output value generation circuit 3451 transmits the pen pressure output value OP as is when the detected pen pressure raw value Po is smaller than a predetermined first threshold value θf1 (see FIG. 6 ), within which hysteresis due to the influence of the elastic member is likely to be small. This first threshold value θf1 is a threshold value for determining whether the pen pressure raw value Po has increased to the point where it does not return to the zero offset value OFS when the application of pen pressure to the core 5 is stopped. In this example, this first threshold value θf1 is set to a value equal to or greater than the pen pressure value that is slightly larger than the zero offset value that the pen pressure value Po exhibits when the pen pressure application to the core body 5 is no longer applied and does not return to the zero offset value OFS.

[0122] Furthermore, when the detected pen pressure raw value Po becomes larger than the predetermined threshold value θf1 and the hysteresis due to the influence of the elastic member becomes large, the pen pressure output value generation circuit 3451 sets a flag FLG (FLG="1") to recognize this state. When this flag FLG is set (FLG="1") and the pen pressure raw value Po becomes smaller than the predetermined return threshold value θre (see FIG. 6), the pen pressure output value OP is forcibly set to zero. This makes it possible to improve the problem of the pen pressure output value OP becoming larger than zero even when no pen pressure (load) is being applied to the tip 5a of the core 5.

[0123] In this case, the return threshold θre may be a predetermined constant value, but in this example, it is dynamically determined from the maximum value of the past pen pressure raw values. That is, in this example, the pen pressure output value generation circuit 3451 detects the pen pressure raw value Po from the capacitance of the variable capacitor 9C, for example, every few milliseconds, and determines the return threshold θre from the maximum value of the past 100 pen pressure raw values ​​Po. For example, if 100 detected pen pressure raw values ​​Po are stored, the return threshold θre is determined from the maximum value among them, and this process is repeated for every 100 detected pen pressure raw values ​​Po.

[0124] The flag FLG (FLG="1") is set to return to its original state (FLG="0") when the detected pen pressure raw value Po becomes equal to or less than a predetermined second threshold value θf2 (see Figure 6), which is equal to or less than the zero offset value OFS, in this example, which is the pen pressure output value OP=0.

[0125] Next, the flow of operation of the writing pressure output value generation circuit 3451 will be described with reference to the flowcharts shown in Fig. 8 and Fig. 9. In the following description, the control circuit 345 will be described as executing the operations of the steps in Fig. 7 and Fig. 8.

[0126] The control circuit 345 determines whether or not the position detection sensor is in a coupled state, for example, by monitoring the received signal of the signal receiving circuit 342 (step S101), and if it determines that the position detection sensor is not in a coupled state, it continues step S101.

[0127] When it is determined in step S101 that the position detection sensor is in a connected state, the control circuit 345 detects the pen pressure raw value Po from the capacitance 9C of the pressure detection unit 9 (step S102), and determines whether the detected pen pressure raw value Po is less than or equal to the zero offset value OFS (Po≦OFS) (step S103).

[0128] If it is determined in step S103 that the detected writing pressure raw value Po is equal to or less than the zero offset value OFS, the control circuit 345 outputs zero (OP=0) as the writing pressure output value OP (step S104).

[0129] Next, the control circuit 345 determines whether it is time to next detect the pen pressure raw value Po (step S105), and if it determines that it is not time to next detect, it determines whether the coupling with the position detection sensor has been released (step S106). If it determines in step S106 that the coupling with the position detection sensor has not been released, the control circuit 345 returns the process to step S105 and repeats step S105 and subsequent steps. If it determines in step S106 that the coupling with the position detection sensor has been released, the control circuit 345 ends this processing routine.

[0130] Then, when it is determined in step S105 that the next timing for detecting the writing pressure raw value Po has arrived, the control circuit 345 returns the process to step S102 and repeats step S102 and subsequent steps.

[0131] If it is determined in step S103 that the detected writing pressure value Po is not equal to or less than the zero offset value OFS but is greater than the zero offset value OFS, the control circuit 345 determines whether the writing pressure value Po is increasing or decreasing (step S107). If it is determined in step S107 that the writing pressure value Po is increasing, the control circuit 345 determines whether the writing pressure value Po is greater than the first threshold value θf1 (Po>θf1) (step S108).

[0132] When it is determined in step S108 that the pen pressure raw value Po is greater than the first threshold value θf1, the control circuit 345 sets the flag FLG (FLG="1") (step S109), and then generates and outputs a pen pressure output value OP from the pen pressure raw value Po (step S110).

[0133] Furthermore, if it is determined in step S108 that the writing pressure raw value Po is equal to or less than the first threshold value θf1, the control circuit 345 bypasses step S109 and proceeds to step S110 without processing the flag FLG, where it generates and outputs a writing pressure output value OP from the writing pressure raw value Po. After step S110, the control circuit 345 proceeds to step S105 to determine whether or not it is time to next detect the writing pressure raw value Po, and performs the processing from step S105 onwards depending on the result of this determination.

[0134] If it is determined in step S107 that the writing pressure raw value Po has decreased, the control circuit 345 determines whether the flag FLG is set (FLG="1" or not) (step S111 in FIG. 9). If it is determined in step S111 that the flag FLG is not set (FLG="0"), the control circuit 345 outputs the generated writing pressure output value OP as is (step S112). The control circuit 345 then proceeds to step S105 in FIG. 8, and executes the processes from step S105 onwards.

[0135] If it is determined in step S111 that the flag FLG is set (FLG="1"), the control circuit 345 determines whether the writing pressure raw value Po is equal to or less than the return threshold value θre (Po≦θre) (step S113). If it is determined in step S113 that the writing pressure raw value Po is not equal to or less than the return threshold value θre but is greater than the return threshold value θre, the control circuit 345 proceeds to step S112, where it outputs the writing pressure output value OP generated from the writing pressure raw value Po as is, and then proceeds to step S105 in FIG. 8, where it executes the processes from step S105 onwards.

[0136] Furthermore, if it is determined in step S113 that the writing pressure raw value Po is equal to or less than the return threshold value θre, the control circuit 345 forcibly outputs the writing pressure output value OP as zero (OP=0) regardless of the detected writing pressure raw value Po (step S114).Then, the control circuit 345 determines whether the detected writing pressure raw value Po is equal to or less than the second threshold value θf2 (step S115), and if it determines that the detected writing pressure raw value Po is not equal to or less than the second threshold value θf2, the control circuit 345 proceeds to step S105 in Figure 8 and executes the processes from step S105 onwards.

[0137] Furthermore, if it is determined in step S115 that the detected writing pressure raw value Po is equal to or less than the second threshold value θf2, the control circuit 345 resets the flag FLG to its original value (FLG="0") (step S116).Then, the control circuit 345 proceeds to step S105 in FIG. 8 and executes the processes from step S105 onwards.

[0138] As described above, with the electronic pen of the fourth embodiment, when the application of writing pressure to the core body 5 is stopped, the writing pressure raw value Po does not return to the zero offset value OFS, and a writing pressure output value OP greater than zero is output, which can be improved.

[0139] In the above description of the electronic pen of the fourth embodiment, the writing pressure output value OP is transmitted to the position detection sensor via electrostatic coupling along with the position detection signal in a time-division manner through the central electrode 51 of the core body 5, but the configuration for transmitting the writing pressure output value OP to the position detection device is not limited to this. For example, the peripheral electrode 6 may be configured to serve both as a receiver and a transmitter, so that the position detection signal is transmitted through the central electrode 51 of the core body 5 and the writing pressure output value OP is transmitted through the peripheral electrode 6. Furthermore, wireless communication means may be provided in the electronic pen and the position detection device, and the writing pressure output value OP may be transmitted through this wireless communication means.

[0140] Furthermore, in the fourth embodiment described above, the electronic pens 1, 1A, and 1B generate a pen pressure output value OP from the pen pressure raw value Po in the pen pressure output value generation circuit 3451 of the control circuit 345, and transmit the generated pen pressure output value OP to the position detection device side. However, the electronic pens 1, 1A, and 1B may be configured to transmit the pen pressure raw value to the position detection device side, and the position detection device may be provided with a pen pressure output value generation circuit that performs the same operation as the pen pressure output value generation circuit 3451.

[0141] [Other Embodiments or Modifications] The core holders 7, 7A, and 7B are not limited to those made of conductive resin with a conductive metal mixed in as described above. For example, the core holders 7, 7A, and 7B may be made of resin made of an insulating material, a conductive member may be provided at the fitting portion of the center electrode 51 of the core 5, and the conductive member at the fitting portion may be electrically connected to the circuit board through a conductive coil spring similar to the example described above.

[0142] Furthermore, the first pressure transmitting member 8 is not limited to being divided into two parts, the plunger 81 and the pressing member 82 that presses the plunger 81 in the axial direction, as in the above example. For example, the pressure transmitting member 8 may be configured as a single pressure transmitting member that integrally includes the fitting portion of the core holder 7 and the pusher portion that presses the pressure-receiving protrusion 9 a of the pressure detecting unit 9.

[0143] Furthermore, in the electronic pen 1 of the first embodiment described above, the O-ring 11, which is an example of an elastic member, is arranged between the ring-shaped end surface on the pen tip side of the core holder 7 and the wall portion (the wall portion on the bottom surface of the recess 10b) having the through-hole 10a of the cup-shaped member 10 fitted and locked inside the peripheral electrode 6 locked in the pen case 2. However, this is just one example, and in the electronic pen 1 of the embodiment described above, the O-ring 11, which is an example of an elastic member, may be arranged between the ring-shaped end surface on the pen tip side of the core holder 7 and a wall portion in a direction perpendicular to the axial direction that is prevented from moving in the axial direction within the pen case 2.

[0144] Furthermore, the elastic member for biasing the core body 5 toward the pressure detection unit 9 is not limited to an O-ring or a coil spring. The elastic member for biasing the core body 5 toward the pressure detection unit 9 may be any member as long as it can bias the core body 5 toward the pressure detection unit 9 by a force that elastically restores the core body 5 from an elastically deformed state to its original state. In this case, it is preferable that the elastic member for biasing the core body 5 toward the pressure detection unit 9 also suppresses displacement in a direction perpendicular to the axial direction of the core body 5.

[0145] Furthermore, although the electronic pens 1, 1A, and 1B in the above-described embodiments are active capacitance type electronic pens, this invention is not limited to active capacitance type electronic pens and is applicable to all electronic pens that have a pressure detection unit that detects pressure applied to the tip of the core body.

[0146] Fig. 10 is a diagram showing the main part of the pen tip side of an electromagnetic induction type electronic pen 1D to which the present invention is applied. As shown in Fig. 10, in this example of electronic pen 1D, an electromagnetic induction type main body unit 3D is disposed within the hollow space of a pen case 2D. Note that in the example of electronic pen 1D in Fig. 10, components similar to those of the electronic pen 1 of the above-described embodiment are designated by the same reference numerals with the suffix D added.

[0147] In this example, the electronic pen 1D includes a pen tip side component 32D on the pen tip side of a boat-shaped unit holder 31D of a main body unit 3D. As shown in Fig. 10, this pen tip side component 32D includes a magnetic core around which a coil 101 is wound, a ferrite core 102 in this example, a pressure transmitting member 8D, and a pressure detecting unit 9D.

[0148] In this example, the ferrite core 102 has a through-hole 102a formed in the axial direction. The core 103 of the electronic pen 1D has a tip portion 103a that protrudes outward from the pen tip-side opening 2Da of the pen case 2D, as shown in FIG. 10 , and a slender, rod-shaped core body portion 103b with a diameter smaller than the maximum diameter of the tip portion 103a, which is integrally formed at the rear end of the tip portion 103a. The core 103 is made of, for example, resin. The diameter of the core body portion 103b of the core 103 is smaller than the through-hole 102a of the ferrite core 102, and the axial length of the core body portion 103b is selected to be longer than the axial length of the ferrite core 102. Therefore, the core body main body portion 103b of the core body 103 is inserted through the through hole 102a of the ferrite core 102 and protrudes toward the rear end side of the ferrite core 102, as shown in Fig. 10. The rear end side of this protruding core body main body portion 103b of the core body 103 is fitted into the pressure transmission member 8D, and moves integrally with the pressure transmission member 8D in the axial direction.

[0149] Like the pressure detection unit 9 of the electronic pen 1 of the above-described embodiment, the pressure detection unit 9D is configured using a semiconductor device that detects pressure applied to the pressure-receiving protrusion 9Da through changes in capacitance. Like the electronic pen 1 of the above-described embodiment, the pressure detection unit 9D is stored and held in a storage recess 91Da of a pressure detection unit holder 91D, and the pressure detection unit holder 91D is stored and held in a pressure detection unit holder storage section 310D provided on the pen tip side of the unit holder 31D.

[0150] In this example, the pressure transmitting member 8D is made of resin and is configured by integrally forming a pusher portion 81D that pushes the pressure-receiving protrusion 9Da of the pressure detecting portion 9D and a pressing member portion 82D. The pressure transmitting member 8D is housed in a state in which it can move axially within the hollow space of a cylindrical transmitting member holder 83D held in the pressure detecting portion holder housing portion 310D of the unit holder 31D.

[0151] When housed in the hollow space of the transmission member holder 83D, the pusher portion 81D of the pressure transmission member 8D is configured to pass through a through-hole 83Da of the transmission member holder 83D and a through-hole 91Db of the pressure detection unit holder 91D to press the pressure-receiving protrusion 9Da of the pressure detection unit 9D. A fitting recess 82Da is formed on the pen tip side of the pressing member portion 82D, into which the rear end of the core body main body portion 103b of the core 103 is fitted.

[0152] 10, in the electronic pen 1D of this example, a cylindrical ferrite core holding portion 84 is provided on the pen tip side of the transmission member holder 83D, and the rear end side of the ferrite core 102 is configured to fit into the hollow portion of this ferrite core holding portion 84. As a result, in the electronic pen 1D of the example of Fig. 10, the ferrite core 102 around which the coil 101 is wound is configured to be held on the pen tip side of the transmission member holder 83D.

[0153] In this case, as shown in Fig. 10, a ring-shaped protrusion 84a extending in a direction perpendicular to the axial direction is formed on the inner wall surface of the hollow portion of the cylindrical ferrite core holding portion 84. The height (length in the direction perpendicular to the axial direction) of this ring-shaped protrusion 84a is set to a value such that it does not come into contact with the rear end side of the core body main body portion 103b of the core body 103 through which the ferrite core 102 is inserted. As shown in Fig. 10, the ferrite core 102 is held by the ferrite core holding portion 84 with the end face on the rear end side abutting against this ring-shaped protrusion 84a.

[0154] As shown in Figure 10, in the hollow space of the ferrite core holding portion 84, the pen tip side of the pressing member portion 82D of the pressure transmission member 8D is stored rearward of the ring-shaped protrusion 84a, and the rear end portion of the core body main body portion 103b of the core body 103 is fitted into the fitting recess 82Da formed in this pressing member portion 82D.

[0155] At this time, a gap of a predetermined size is formed between a ring-shaped end surface 82Dt around the fitting recess 82Da on the pen tip side end surface of the pressing member portion 82D of the pressure transmitting member 8D and a ring-shaped end surface in a direction perpendicular to the axial direction of the ring-shaped protrusion 84a of the ferrite core holding portion 84. In the electronic pen 1D of this example, an O-ring 11D having a circular cross-sectional diameter slightly larger than the size of the gap is disposed in this gap, as shown in Fig. 10. Therefore, the O-ring 11D is disposed in a state in which it is elastically compressed and elastically deformed at least in the axial direction.

[0156] In this example of the electronic pen 1D, the ferrite core holding portion 84 is prevented from moving axially toward the pen tip within the pen case 2D. Therefore, the elastic return force of the elastically deformed O-ring 11D to its original state constantly biases the pressure transmission member 8D toward the pressure detection unit 9D in the axial direction. Therefore, the core 103 fitted to the pressure transmission member 8D is also constantly biased axially toward the pressure detection unit 9D, even when no pressure is applied to its tip 103a. In the example of Figure 10, the protrusion 84a of the ferrite core holding portion 84 forms a wall that cannot move axially toward the pen tip within the pen case 2D.

[0157] 10, the outer diameter of the O-ring 11D is set to be equal to or slightly larger than the inner diameter of the hollow portion on the rear end side of the ferrite core holding portion 84. However, in this example, the diameter of the inner circumference of the O-ring 11D is set to be such that it does not come into contact with the rear end portion of the center electrode 51 of the core body 5.

[0158] Therefore, the O-ring 11D is in contact with the axial wall of the hollow portion of the ferrite core holding portion 84 that is closer to the rear end than the ring-shaped protrusion 84a, and as a result, when the O-ring 11D is elastically compressed and deformed in the axial direction, it also elastically deforms so as to expand slightly in the direction perpendicular to the axial direction. In other words, an elastic biasing force acts on the O-ring 11D toward the center of the ring. This elastic biasing force toward the center of the O-ring 11D acts as a force to suppress displacement of the pressure transmitting member 8D in the direction perpendicular to the axial direction (rattlement in the direction perpendicular to the axial direction).

[0159] 10, the core 103 is always biased toward the pressure detection unit 9D in the axial direction even when no pressure is applied to the tip 103a. Therefore, even when the tip 103a of the core 103 is not pressed against the input surface of the position detection device, and the tip 103a is pressed against the input surface to apply writing pressure, no initial axial displacement of the core 103 occurs, preventing the user from feeling any rattle in the axial direction. Therefore, the electronic pen 1D of this embodiment can achieve a feel similar to that of a writing instrument such as a pencil or ballpoint pen.

[0160] Furthermore, in the electronic pen 1D of the example of Figure 10, the elastic biasing force of the compressed O-ring 11D also suppresses displacement of the pressure transmission member 8D in a direction perpendicular to the axial direction, and therefore the core body 103 fitted to this pressure transmission member 8D is also suppressed from displacement (play) in a direction perpendicular to the axial direction.

[0161] 10, a cap member 104 made of an elastic member having an outer peripheral surface that conforms to the inner wall surface of the tapered portion on the pen tip side of the pen case 2D is placed over the pen tip side of the ferrite core 102. As shown in FIG. 10, the cap member 104 has a through hole that is larger than or equal to the diameter of the through hole 102a of the ferrite core 102 so that the rear end side of the core body main body 103b of the core 103 can be inserted therethrough.

[0162] 10, in the electronic pen 1D of this example, the cap member 104 on the pen tip side of the ferrite core 102 is disposed so as to be elastically pressed against the inner wall surface of the tapered portion on the pen tip side of the pen case 2D, thereby configuring the outer peripheral surface of the cap member 104 to fit tightly against the inner wall surface of the tapered portion on the pen tip side of the pen case 2D. In other words, the cap member 104 has the function of separating the space on the pen tip side of the ferrite core 102 that communicates with the outside through the opening 2Da of the pen case 2D from the hollow space inside the pen case 2D in which the ferrite core 102 and the main body unit 3D are housed.

[0163] In this example of the electronic pen 1D, as is clear from the above-described configuration, the O-ring 11D also has the function of separating the movement space of the pressure transmission member 8D within the transmission member holder 83 from the external space which is connected to the through hole 102a of the ferrite core 102 and the space on the pen tip side of the pen case 2D.

[0164] Therefore, in the example electronic pen 1D of Figure 10, the O-ring 11D and the cap member 104 separate the external space, which is connected through the opening on the pen tip side of the electronic pen 1D, from the space in which the main body unit 3D is stored within the hollow space of the pen case 2D, and the electronic pen 1D has a moisture-proof configuration.

[0165] 10, the ferrite core 102 is held by the ferrite core holding portion 84, the ferrite core holding portion 84 is provided with a wall portion (protrusion 84a in the example of FIG. 10) in a direction perpendicular to the axial direction, and an O-ring 11D, as an example of an elastic member, is provided between the wall portion and the end face of the pressure transmission member 8D into which the core body 103 is fitted. However, since the end face on the rear end side of the ferrite core 102 can be configured to form the surface of the wall portion perpendicular to the axial direction, an O-ring 11D, as an example of an elastic member, may be provided between the end face on the rear end side of the ferrite core 102 and the end face of the pressure transmission member 8D.

[0166] In the example of electronic pen 1D in Figure 10, a coil spring as a shock absorber is not provided at the rear end of the pressure detection unit 9D, but it is possible to provide a coil spring as a shock absorber at the rear end of the pressure detection unit 9D in the same manner as electronic pen 1.

[0167] [Other Embodiments or Modifications] In the electronic pens 1, 1A, 1B, and 1D of the above-described embodiments, the pressure detection unit is made of a semiconductor device in which the distance between two electrodes facing each other via a dielectric air layer changes in response to the applied pressure (see Patent Document 2, mentioned above). However, it goes without saying that the present invention is not limited to this. For example, it is also possible to use a pressure detection unit configured to change the capacitance by changing the contact area between a dielectric and a conductive elastic member in response to the applied pressure (see Patent Document 1, mentioned above).

[0168] In addition, the pressure detection unit (pen pressure detection unit) 9 is not limited to a capacitive sensor that detects pressure (pen pressure) based on a change in capacitance as in the above-described embodiment, but may also be an inductance sensor that detects pressure (pen pressure) based on a change in inductance, or a resistance sensor that detects pressure (pen pressure) based on a change in resistance.

[0169] 1, 1A...electronic pen, 2, 2A...pen case, 3, 3A...main body unit, 5...core body, 6...peripheral electrode, 7...core body holder, 7t...ring-shaped end surface, 8, 8A...pressure transmission member, 9, 9A...pressure detection unit, 10...cup-shaped member, 11, 12, 13...O-ring, 31, 31A...unit holder, 32, 32A...pen tip side component, 34...circuit board, 51...center electrode, 52...protective member, 101...coil, 102...ferrite core, 103...core body, 104...cap member

Claims

1. An electronic pen comprising: a cylindrical pen case with an opening on the pen tip side; a core body attached with its tip protruding from the opening on the pen tip side to the outside of the pen case; a pressure detection unit located within the hollow portion of the pen case on the opposite side of the axial direction from the tip of the core body, for detecting pressure applied to the tip of the core body; and an elastic member located within the hollow portion of the pen case so as to urge the core body in the opposite side of the axial direction from the pen tip side even when pressure is not being applied to the tip.

2. The electronic pen described in claim 1, characterized in that the elastic member is configured so as to bias the core body in the axial direction opposite to the pen tip side within the hollow portion of the pen case by a restoring force from the elastically deformed state to its original state, even when no pressure is applied to the tip portion.

3. The electronic pen according to claim 1, wherein the elastic member is further provided to suppress displacement of the core body in a direction perpendicular to the axial direction.

4. An electronic pen as described in claim 1, characterized in that it is provided with a pressure transmission member into which a rear end portion of the core body is fitted on the opposite side of the axial direction from the tip end portion, the pressure applied to the tip end portion of the core body is transmitted to the pressure detection unit via the pressure transmission member, and the elastic member is arranged to bias the pressure transmission member into which the rear end portion of the core body is fitted in the opposite direction of the axial direction from the pen tip side.

5. The electronic pen described in claim 4, characterized in that the pressure transmission member has a fitting recess into which the rear end of the core body is fitted, and has a ring-shaped end face around the fitting recess with its surface direction intersecting the axial direction of the pen case, and the elastic member is arranged to urge the ring-shaped end face in the opposite direction to the pen tip side in the axial direction.

6. An electronic pen as described in claim 5, characterized in that it is provided with a wall portion that faces the ring-shaped end face of the pressure transmission member at a predetermined distance in the axial direction and that is immovable within the pen case toward the pen tip in the axial direction, and the elastic member is provided in the elastically deformed state between the ring-shaped end face and the wall portion.

7. An electronic pen as described in claim 6, characterized in that the wall portion has a through hole through which the rear end portion of the core body is inserted, and the elastic member is provided between the periphery of the through hole in the wall portion and the ring-shaped end surface of the pressure transmission member.

8. The electronic pen according to claim 7, wherein the elastic member is an O-ring.

9. An electronic pen as described in claim 5, characterized in that it comprises a pressure transmission member holder that is arranged in the pen case in a state where it cannot move in the axial direction, but that stores at least the mating side of the core body of the pressure transmission member in a state where the pressure transmission member can move in the axial direction, the pressure transmission member holder facing the ring-shaped end face of the pressure transmission member at a predetermined distance in the axial direction, and comprising a wall portion that has a through hole through which the rear end part of the core body is inserted, and the elastic member is arranged between the periphery of the through hole in the wall portion and the ring-shaped end face of the pressure transmission member.

10. The electronic pen according to claim 9, wherein the elastic member is an O-ring.

11. The electronic pen described in claim 1, characterized in that it comprises a sealing member made of an elastic material that is provided between the inner wall surface of the pen case and the outer peripheral surface of a component within the pen case, and that separates a space within the hollow portion of the pen case in which the pressure detection unit is provided and a space within the hollow portion of the pen case that communicates with the external space from which the tip of the core body protrudes, the elastic material being provided to separate the space within the hollow portion of the pen case in which the pressure detection unit is provided and a space within the hollow portion of the pen case that communicates with the external space from which the tip of the core body protrudes.

12. An electronic pen as described in claim 1, characterized in that it comprises a core holder into which the rear end of the core is fitted, pressure applied to the tip of the core is transmitted to the pressure detection unit via the core holder, and the elastic member is arranged to urge the core holder into which the rear end of the core is fitted in the opposite direction to the pen tip in the axial direction.

13. The electronic pen according to claim 12, characterized in that the core and the core holder are made of conductive materials, and are of an active capacitance type in which a signal from a signal transmission circuit is sent through the core holder and the core.

14. An electronic pen as described in claim 12, characterized in that a pressure transmission member is provided between the core holder and the pressure detection unit, and the pressure applied to the tip of the core is transmitted to the pressure detection unit via the core holder and the pressure transmission member.

15. The electronic pen described in claim 12, characterized in that the core holder has a fitting recess into which the rear end of the core is fitted, and has a ring-shaped end surface around the fitting recess, the surface direction of which is in a direction intersecting the axial direction of the pen case, and the elastic member is arranged to urge the ring-shaped end surface in the opposite direction to the pen tip side in the axial direction.

16. An electronic pen as described in claim 15, characterized in that it is provided with a wall portion that faces the ring-shaped end face of the core holder at a predetermined distance in the axial direction and is unable to move in the axial direction within the pen case, and the elastic member is provided in an elastically deformed state between the ring-shaped end face and the wall portion.

17. An electronic pen as described in claim 16, characterized in that the wall portion has a through hole through which the rear end portion of the core body is inserted, and the elastic member is provided between the periphery of the through hole in the wall portion and the ring-shaped end surface of the core body holder.

18. The electronic pen according to claim 17, wherein the elastic member is an O-ring.

19. The electronic pen described in claim 15, characterized in that: the core and the core holder are made of conductive material; and are provided with a peripheral electrode arranged to surround the side of the rear end of the core, and an insulating member arranged between the peripheral electrode and the core holder; the insulating member is arranged in a state where it cannot move in the axial direction within the pen case, and is arranged to accommodate at least the fitting portion of the core holder with the rear end of the core while allowing the core holder to move in the axial direction; the insulating member faces the ring-shaped end face of the core holder at a predetermined distance in the axial direction, and is provided with a wall portion having a through hole through which the rear end of the core is inserted; and the elastic member is arranged between the periphery of the through hole in the wall portion and the ring-shaped end face of the core holder.

20. The electronic pen according to claim 19, wherein the elastic member is an O-ring.

21. The electronic pen according to claim 1, characterized in that it is of an electromagnetic induction type, having a through hole through which the rear end of the core body passes and a magnetic core around which a coil is wound.

22. The electronic pen according to claim 1, wherein the elastic member comprises a coil spring and an O-ring.

23. An electronic pen as described in claim 1, further comprising a pen pressure output value generation circuit that generates a pen pressure output value from the pen pressure raw value detected by the pressure detection unit, wherein the pen pressure output value generation circuit outputs zero as the pen pressure output value when the pen pressure raw value becomes greater than a first predetermined value and then becomes equal to or less than a second predetermined value that is smaller than the first predetermined value.

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