Ballpoint pen tip, ballpoint pen refill, and ballpoint pen

Abstract

To suppress the wear of a ball embracing chamber, and restrain a ball from being damaged by contact between the ball and an inner surface of the ball embracing chamber.SOLUTION: A ball-point pen tip 40 comprises a ball 42, and a tip body 50 for holding the ball 42. In the ball-point pen tip 40, the tip body 50 has a ball embracing chamber 52 for embracing the ball 42, and a swaged part 60 for hindering the ball 42 from coming off the ball embracing chamber 52. A nitrided layer 70 is formed on an outer peripheral surface 65 of the tip body 50 and an inner surface of the ball embracing chamber 52. The thickness T1 of the nitrided layer 70 of the inner surface 53 of the ball embracing chamber 52 is smaller than the thickness T2 of the nitrided layer 70 of the outer peripheral surface 65 of the tip body 50 in a region R from a rear end 62 of the swaged part 60 to 0.2 mm backward from the rear.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a ball pen tip, a ball pen refill, and a ball pen.

Background Art

[0002] Conventionally, a technique of nitriding the surface of a ball pen tip has been known. Patent Document 1 discloses a ball pen tip that has been nitrided in the manufacturing process. In the technique disclosed in Patent Document 1, a metal tube is nitrided, and then, cutting is performed on the inner surface of the tip portion of the nitrided metal tube to form a ball holding chamber, a ball pedestal, an ink guiding hole, and the like. Finally, a caulking process is performed in which a ball is inserted into the ball holding chamber and the peripheral edge portion at the tip of the ball holding chamber is pressed inward and bent. By going through such steps, there is an advantage that burrs are suppressed from being generated during cutting and the caulking process can be performed stably.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, a nitrided surface becomes hard and wear resistance is improved. In the technique disclosed in Patent Document 1, since cutting is performed after nitriding to form a ball holding chamber, the nitride layer is removed during cutting. Therefore, the ball pen tip disclosed in Patent Document 1 does not have a nitride layer on the inner surface of the ball holding chamber. In this case, by repeatedly writing with the ball pen, the inner surface of the ball holding chamber, particularly the inner surface at the caulking portion at the tip, may wear. If the inner surface at the caulking portion wears, there is a risk that the ball may come out of the ball holding chamber.

[0005] In order to solve such problems, the inventors of the present invention considered performing nitriding treatment on the inner surface of the ball holding chamber as well. This suppresses wear on the inner surface of the ball holding chamber. On the other hand, it was found that simply performing nitriding treatment on the inner surface of the ball holding chamber makes the inner surface of the ball holding chamber hard, and damage such as scratches may occur on the ball.

[0006] The present invention has been made in consideration of such points, and an object thereof is to suppress wear on the inner surface of the ball holding chamber and to suppress damage to the ball caused by contact between the inner surface of the ball holding chamber and the ball.

Means for Solving the Problems

[0007] The ball pen tip of the present embodiment [1] is a ball pen tip including a ball and a chip body that holds the ball, wherein the chip body has a ball holding chamber that holds the ball and a caulking portion that prevents the ball from coming out of the ball holding chamber, a nitriding layer is formed on the outer peripheral surface of the chip body and the inner surface of the ball holding chamber, and the thickness of the nitriding layer on the inner surface of the ball holding chamber is smaller than the thickness of the nitriding layer on the outer peripheral surface of the chip body in a region from the rear end of the caulking portion to 0.2 mm rearward, which is the ball pen tip.

[0008] The ball pen tip of the present embodiment [2] is the ball pen tip according to [1], wherein the thickness of the nitriding layer on the front end surface of the caulking portion is larger than the thickness of the nitriding layer on the outer peripheral surface of the chip body in the region.

[0009] The ball pen tip of the present embodiment [3] wherein the ball holding chamber includes a ball receiving seat that receives the writing pressure from the ball during writing, The ball pen tip according to [1], wherein the thickness of the nitride layer of the ball receiving seat is smaller than the thickness of the nitride layer of the inner surface of the ball holding chamber.

[0010] The ball pen refill of the present embodiment [4] A ball pen refill comprising the ball pen tip according to any one of [1] to [3], and an ink storage cylinder for storing ink.

[0011] The ball pen of the present embodiment [5] is a ball pen provided with the ball pen refill according to [4].

Advantages of the Invention

[0012] According to the present invention, it is possible to suppress wear of the inner surface of the ball holding chamber and to suppress damage to the ball caused by contact between the inner surface of the ball holding chamber and the ball.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Best Mode for Carrying Out the Invention

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to this specification, for the convenience of illustration and easy understanding, the scale, the aspect ratio of the vertical and horizontal dimensions, etc. are appropriately changed and exaggerated from those of the actual object.

[0015] In addition, with regard to the terms used in this specification for specifying shapes, geometric conditions, and their degrees, such as terms like "parallel", "orthogonal", "identical", etc., and values of lengths and angles, etc., they are not restricted by strict meanings and shall be interpreted to include ranges where similar functions can be expected.

[0016] In this specification, the direction in which the central axis A of the ballpoint pen 10 extends (longitudinal direction, up - down direction in the longitudinal sectional view) is defined as the axial direction da, the direction orthogonal to the central axis A is the radial direction, and the direction along the circumference around the central axis A is the circumferential direction. Also, along the axial direction da, when writing, the side closer to the writing surface such as the paper surface is defined as the front, and the side separated from the writing surface is defined as the rear. That is, the pen tip side is the front, and the side opposite to the pen tip is the rear.

[0017] FIG. 1 is a diagram for explaining an embodiment of the present invention and is a cross - sectional view showing an example of the ballpoint pen 10. In this embodiment, an example in which the ballpoint pen 10 is a so - called side - knock type ballpoint pen will be described, but the ballpoint pen 10 is not limited thereto. The ballpoint pen 10 includes a barrel 20, a ballpoint pen refill 30 incorporated in the barrel 20, a projecting - retracting mechanism 12 for projecting and retracting the tip of the ballpoint pen refill 30 from the barrel 20, a friction member 14 for rubbing the handwriting, and a clip 16.

[0018] The shaft cylinder 20 includes a front shaft 21, a rear shaft 25 connected to the front shaft 21, a rear end cap 28 attached to the rear end portion of the rear shaft 25, and a grip member 29 disposed to surround the outer surface of the front shaft 21. The front shaft 21 is provided at the front end with an opening 22 through which the tip of the ball pen tip 40 of the ball pen refill 30 can protrude and retract, a first engaging portion 23 provided on the inner surface of the front region, and a male screw portion 24 provided on the outer surface of the rear region. The rear shaft 25 has a female screw portion 26 provided on the inner surface of the front region. The front shaft 21 and the rear shaft 25 are coupled to each other by screwing the male screw portion 24 of the front shaft 21 and the female screw portion 26 of the rear shaft 25. The rear end cap 28 is fitted to the rear end portion of the rear shaft 25. The grip member 29 is intended to be grasped by a finger when the user writes with the ball pen 10. The front shaft 21, the rear shaft 25, and the rear end cap 28 are formed of, for example, resin, and the grip member 29 is formed of, for example, rubber, elastomer, or the like.

[0019] In the present embodiment, the clip 16 functions as an operation portion that is operated by the user at the time of knocking. The shaft cylinder 20 is provided with a slide hole 27 that extends in the axial direction da and penetrates the wall portion of the shaft cylinder 20. The slide hole 27 is provided across the rear region of the rear shaft 25 and the front end portion of the rear end cap 28. In the illustrated example, the clip 16 extends from inside the shaft cylinder 20 to outside the shaft cylinder 20 through the slide hole 27. The movement range of the clip 16 in the axial direction da can be defined by the front end and the rear end of the slide hole 27.

[0020] The ballpoint pen refill 30 is accommodated in the shaft cylinder 20 so as to be retractable. The ballpoint pen refill 30 includes an ink storage cylinder 32 for storing ink, a tip holder 34 disposed in front of the ink storage cylinder 32, and a ballpoint pen tip 40 disposed in front of the tip holder 34. In the example shown in FIG. 1, the rear end portion of the tip holder 34 is inserted into the front end portion of the ink storage cylinder 32, and the rear end portion of the ballpoint pen tip 40 is inserted into the front end portion of the tip holder 34. The ballpoint pen refill 30 has a second engaging portion 36 provided on the outer surface of the front region. In the illustrated example, the second engaging portion 36 is provided on the outer surface of the tip holder 34. In a state where the ballpoint pen refill 30 is assembled, the second engaging portion 36 of the ballpoint pen refill 30 is located behind the first engaging portion 23 of the front shaft 21, and a coil spring 18 is disposed in a compressed state between the first engaging portion 23 and the second engaging portion 36. Thereby, the coil spring 18 biases the ballpoint pen refill 30 rearward.

[0021] As the ink, ink that can be used for a ballpoint pen can be used without particular limitation. As an example, thermochromic ink can be used as the ink. The thermochromic ink may be a reversible thermochromic ink. As the reversible thermochromic ink, for example, a heat-decoloring type reversible thermochromic ink that changes from a colored state to a decolored state by heating and changes from a decolored state to a colored state by cooling can be used.

[0022] The friction member 14 of the present embodiment is a member for rubbing the handwriting with ink. When the ink is thermochromic ink, the friction member 14 can be a friction member having a function of rubbing the writing surface such as paper on which the handwriting is formed to heat the ink forming the handwriting by frictional heat. In this case, the friction member 14 can be formed of, for example, an elastic material. The friction member 14 can be fixed to the rear end cap 28 by press fitting, engagement, screwing, fitting, adhesion, two-color molding, or the like. Further, when the ink does not have thermochromic properties, the friction member 14 may be, for example, a member that scrapes off the handwriting by rubbing the writing surface such as paper on which the handwriting is formed, such as eraser rubber.

[0023] The protruding and retracting mechanism 12 is a mechanism for alternately switching the ballpoint pen 10 between a knocked state where the tip of the ballpoint pen tip 40 protrudes from the opening 22 of the front shaft 21 and a non-knocked state where the tip of the ballpoint pen tip 40 is retracted into the opening 22. In FIG. 1, the ballpoint pen 10 is shown in the knocked state. In the non-knocked state, due to the elastic force of the coil spring 18, the ballpoint pen refill 30 is biased rearward, and thereby, the tip of the ballpoint pen tip 40 is retracted from the opening 22. When the user presses and slides the clip 16 forward with a finger, the ballpoint pen refill 30 moves forward, and the tip of the ballpoint pen tip 40 protrudes forward from the opening 22. Even when the user releases the finger from the clip 16, the ballpoint pen refill 30 maintains the state where the tip of the ballpoint pen tip 40 protrudes forward from the opening 22. When the user presses and slides the clip 16 forward with a finger again, the ballpoint pen refill 30 moves forward by a minute distance. When the user releases the finger from the clip 16 or relaxes the forward pressing force on the clip 16, due to the elastic force of the coil spring 18, the ballpoint pen refill 30 is biased rearward, and the tip of the ballpoint pen tip 40 is retracted from the opening 22. Since the protruding and retracting mechanism 12 that realizes such a protruding and retracting operation is well-known, a detailed description thereof is omitted. As an example, as the protruding and retracting mechanism 12, it is possible to use the protruding and retracting mechanism disclosed in Japanese Patent Application Laid-Open No. 2012-6315.

[0024] Referring to FIGS. 2 to 4, the ballpoint pen tip 40 will be further described. FIG. 2 is a longitudinal sectional view showing the ballpoint pen tip 40. FIG. 3 is a longitudinal sectional view showing an enlarged tip of the ballpoint pen tip 40. FIG. 4 is an enlarged view showing the portion marked IV in FIG. 3.

[0025] The ballpoint pen tip 40 includes a ball 42 and a tip body 50 that holds the ball 42. The diameter of the ball 42 may exceed 0 mm and be 2.0 mm or less. The diameter of the ball 42 may be 0.2 mm or more and 1.6 mm or less. The diameter of the ball 42 may be 0.4 mm or more and 1.0 mm or less. The tip body 50 has a function of guiding the ink accommodated in the ink storage cylinder 32 to the ball 42. When writing, the user moves the ball 42 on the writing surface such as paper while pressing the ball 42 against the writing surface. As a result, the ball 42 rotates on the writing surface. Thereby, the ink attached to the ball 42 is transferred to the writing surface. Then, a writing trace is formed on the writing surface by the transferred ink. Note that the ink transferred to the writing surface may penetrate into the writing surface.

[0026] The tip body 50 has a ball holding chamber 52, an ink flow hole 58, and a caulking portion 60. The ball holding chamber 52 has a function of holding the ball 42 and also has a function of holding ink in the ball holding chamber 52 and attaching the ink to the ball 42. The ball holding chamber 52 is formed by a hole portion formed from the front end of the tip body 50 toward the rear. The inner surface 53 of the ball holding chamber 52 includes a side surface 54 and a ball receiving seat 56. The central axis of the tip body 50 coincides with the central axis A of the ballpoint pen 10. Therefore, in this specification, the central axis of the tip body 50 may also be referred to as the central axis A.

[0027] The side surface 54 may be a cylindrical surface having a central axis extending in the axial direction da. The side surface 54 also includes the inner surface 61 of the caulking portion 60. The central axis of the side surface 54 may coincide with the central axis A. The ball seat 56 is located in the rear portion of the ball holding chamber 52. Inside the ball holding chamber 52, the ball 42 is slightly movable in the front-rear direction. The ball seat 56 is the surface that the ball 42 contacts when the ball 42 is located at the most rearward position inside the ball holding chamber 52. The ball seat 56 receives the writing pressure from the ball 42 when writing with the ballpoint pen 10. The ball seat 56 may have a complementary shape to a part of the outer surface of the ball 42. That is, the ball seat 56 may have a shape that constitutes a part of a spherical surface.

[0028] The ink circulation hole 58 is located between the ball holding chamber 52 and the tip holder 34 and communicates the ball holding chamber 52 and the tip holder 34. The ink circulation hole 58 extends linearly along the axial direction da. The ink circulation hole 58 functions as a flow path for ink from the tip holder 34 to the ball holding chamber 52. The central axis of the ink circulation hole 58 coincides with the central axis A of the tip body 50.

[0029] The caulking portion 60 is a portion provided by deforming inward (toward the central axis A side) at the tip of the tip body 50. The caulking portion 60 has a function of preventing the ball 42 from coming out of the ball holding chamber 52. The caulking portion 60 is formed by caulking the tip of the tip body 50 so as to deform inward (toward the central axis A side) after the ball 42 is disposed in the ball holding chamber 52. Thereby, the ball 42 is held in the ball holding chamber 52.

[0030] In this embodiment, a nitride layer 70 is formed at least on the outer peripheral surface 65 of the chip body 50 and the inner surface 53 of the ball holding chamber 52. The nitride layer 70 is formed by a nitriding treatment that diffuses nitrogen atoms from the surface of the chip body 50 into the chip body 50 to form a compound containing metal atoms and nitrogen atoms that make up the chip body 50. Metals that can form a nitride layer by combining with nitrogen include chromium (Cr), aluminum (Al), molybdenum (Mo), titanium (Ti), vanadium (V), and the like. Therefore, the chip body 50 is preferably formed of a metal material containing at least one of chromium, aluminum, molybdenum, titanium, and vanadium. As such a metal material, for example, stainless steel may be used.

[0031] In this embodiment, as will be described later, the nitriding treatment is performed after the ball 42 is assembled to the chip body 50. However, in this nitriding treatment step, it is preferable that the nitride layer 70 is not formed on the surface of the ball 42. Therefore, the ball 42 is preferably made of a material that does not contain any of chromium, aluminum, molybdenum, titanium, and vanadium, a material with an extremely low content of chromium, aluminum, molybdenum, titanium, and vanadium, or a material containing chromium, aluminum, molybdenum, titanium, and vanadium in a stable state. Examples of chromium, aluminum, molybdenum, titanium, and vanadium in a stable state include chromium carbide, vanadium carbide, alumina, and the like. From this perspective, the ball 42 may be formed of a material such as tungsten carbide, silicon carbide, silicon nitride, alumina, zirconia, or the like.

[0032] As the nitriding treatment, gas nitriding treatment, gas soft nitriding treatment, salt bath soft nitriding treatment, or the like can be used. For example, the nitride layer 70 may be formed by gas nitriding treatment. The gas nitriding treatment can be performed, for example, by bringing ammonia gas into contact with the surface of the chip body 50 heated to about 400°C to 600°C. Since the nitriding treatment can be performed at a lower temperature compared to other heat treatments such as quenching, deformation of the chip body 50 during the treatment is suppressed.

[0033] By performing nitriding treatment, the hardness of the surface of the chip body 50 is improved. Therefore, the wear resistance of the surface of the chip body 50 can be improved. Here, there is a positive correlation between the thickness of the nitride layer 70 and the hardness of the surface on which the nitride layer 70 is formed. That is, the larger the thickness of the nitride layer 70, the harder the surface on which the nitride layer 70 is formed.

[0034] The outer peripheral surface 65 of the chip body 50 may come into contact with other members during manufacturing or during the use of the ballpoint pen 10. When the nitride layer 70 is formed on the outer peripheral surface 65, the wear resistance of the outer peripheral surface 65 is improved. Therefore, when the outer peripheral surface 65 comes into contact with other members during the manufacturing of the chip body 50 or during the use of the ballpoint pen 10, it is possible to suppress the occurrence of scratches or wear on the outer peripheral surface 65.

[0035] The inventors of the present invention considered performing nitriding treatment on the inner surface 53 of the ball holding chamber 52, particularly the inner surface 61 in the caulking portion 60, in order to prevent the ball 42 from coming out of the ball holding chamber 52 due to wear of the inner surface 53. However, it was found that simply performing nitriding treatment on the inner surface 53 of the ball holding chamber 52 would harden the inner surface 53 of the ball holding chamber 52 and may cause damage such as scratches to the ball 42. As a result of further research on such a nitride layer 70, the inventors of the present invention found that this problem can be solved by controlling the thickness of the nitride layer 70 on the inner surface 53 of the ball holding chamber 52.

[0036] In this embodiment, the thickness T1 of the nitride layer 70 on the inner surface 53 of the ball holding chamber 52 is smaller than the thickness T2 of the nitride layer 70 on the outer peripheral surface 65 of the chip body 50. The thickness T2 of the nitride layer 70 on the outer peripheral surface 65 is measured in the region R from the rear end 62 of the caulking portion 60 to 0.2 mm rearward. Therefore, the thickness T1 of the nitride layer 70 on the inner surface 53 of the ball holding chamber 52 is smaller than the thickness T2 of the nitride layer 70 on the outer peripheral surface 65 of the chip body 50 in the region R from the rear end 62 of the caulking portion 60 to 0.2 mm rearward. Also, the thickness T1 of the nitride layer 70 on the inner surface 53 of the ball holding chamber 52 is measured on the side surface 54 of the inner surface 53. Therefore, it can also be said that the thickness T1 of the nitride layer 70 on the side surface 54 of the ball holding chamber 52 is smaller than the thickness T2 of the nitride layer 70 on the outer peripheral surface 65 of the chip body 50 in the region R from the rear end 62 of the caulking portion 60 to 0.2 mm rearward.

[0037] Since the nitride layer 70 is formed on the inner surface 53 of the ball holding chamber 52, wear of the inner surface 53 can be suppressed. In particular, since the nitride layer 70 is formed on the inner surface 61 in the caulking portion 60, wear of the inner surface 61 of the caulking portion 60 can be suppressed. Thereby, it is possible to suppress the ball 42 from coming out of the ball holding chamber 52. Also, when the thickness T1 and the thickness T2 satisfy the above relationship, the hardness of the inner surface 53 of the ball holding chamber 52 becomes smaller than the hardness of the outer peripheral surface 65 of the chip body 50. In this case, when the ball 42 and the inner surface 53 of the ball holding chamber 52 come into contact with each other, it is possible to effectively suppress damage such as scratches from occurring on the ball 42.

[0038] The caulking portion 60 can come into contact with a surface to be written on, such as a paper surface, when writing with the ballpoint pen 10. Therefore, repeated writing may cause the caulking portion 60 to wear out. In the present embodiment, the thickness T3 of the nitride layer 70 on the front end surface 63 of the caulking portion 60 is greater than the thickness T2 of the nitride layer 70 on the outer peripheral surface 65 of the tip body 50 in the region R from the rear end 62 of the caulking portion 60 to 0.2 mm rearward. In this case, the hardness of the front end surface 63 of the caulking portion 60 becomes greater than the hardness of the outer peripheral surface 65 in the region R. Therefore, the wear resistance of the caulking portion 60 can be improved. Thereby, it is possible to suppress the caulking portion 60 from coming into contact with the surface to be written on and wearing out.

[0039] As described above, the ball seat 56 receives the writing pressure from the ball 42 when writing with the ballpoint pen 10. Generally, the surface roughness of the nitride layer 70 is greater than the surface roughness of the surface where the nitride layer 70 is not formed. Therefore, when the thickness of the nitride layer 70 of the ball seat 56 is large, the rough surface of the nitride layer 70 may hinder the rotation of the ball 42 when writing with the ballpoint pen 10. In this case, there is a possibility that the smooth writing feel of the ballpoint pen 10 may be impaired. In the present embodiment, the thickness T4 of the nitride layer 70 of the ball seat 56 is smaller than the thickness T1 of the nitride layer 70 on the inner surface 53 of the ball holding chamber 52. In particular, the thickness T4 of the nitride layer 70 of the ball seat 56 is smaller than the thickness T1 of the nitride layer 70 on the side surface 54 of the ball holding chamber 52. In this case, the surface roughness of the nitride layer 70 in the ball seat 56 can be reduced. Thereby, when writing with the ballpoint pen 10, it is possible to suppress the surface of the nitride layer 70 from hindering the rotation of the ball 42. Therefore, it is possible to suppress the smooth writing feel of the ballpoint pen 10 from being impaired.

[0040] The thicknesses T1 to T4 of the nitride layer 70 are all the thicknesses measured in the direction perpendicular to the surface of the nitride layer 70. The thicknesses T1 to T4 of the nitride layer 70 are measured in accordance with JIS G0562:1993 "Method for Measuring Nitrided Layer Depth of Steel". When measuring the thicknesses T1 to T4 of the nitride layer 70, first, the ball pen tip 40 to be measured is cut along the plane including the central axis A. After the cut surface is precisely polished, the cut surface is etched using Marble reagent. At this time, only the portions other than the nitride layer 70 are etched, and the nitride layer 70 is not etched. Therefore, the nitride layer 70 and the portions other than the nitride layer 70 can be visually distinguished from each other. Thus, by observing the cut surface with a microscope, the thickness of the nitride layer 70 in each portion can be measured. As the microscope, the lens and the video unit of the micro Vickers hardness tester HM-200 manufactured by Mitutoyo Corporation are used. In addition, when measuring the thicknesses T1 to T4 of the nitride layer 70, the thicknesses of the nitride layer 70 are measured at five points that are sufficiently separated from each other so as to reflect the overall thickness of the portion to be measured, and the arithmetic mean value thereof is taken as the thicknesses T1 to T4 of the nitride layer 70 at that portion.

[0041] Next, with reference to FIGS. 5 to 7, an example of the manufacturing method of the ball pen tip 40 of the present embodiment will be described.

[0042] First, as shown in FIG. 5, a chip body 50 is prepared. At this stage, the caulking portion 60 is not formed on the chip body 50. Next, as shown in FIG. 6, the ball 42 is inserted into the ball holding chamber 52 from the front. Thereafter, as shown in FIG. 7, the tip portion of the chip body 50 is deformed inward (toward the central axis A side) to form the caulking portion 60.

[0043] After that, nitriding treatment is performed on the entire ball 42 and the chip body 50. The nitriding treatment can be performed, for example, by gas nitriding treatment. The gas nitriding treatment can be performed, for example, by bringing ammonia gas into contact with the surface of the chip body 50 heated to about 400°C to 600°C. In the present embodiment, the chip body 50 is formed of a metal material containing at least one of chromium, aluminum, molybdenum, titanium, and vanadium. Such a metal material is, for example, stainless steel. By performing the nitriding treatment, nitrogen atoms diffuse from the surface of the chip body 50 into the chip body 50, and on the surface of the chip body 50, atoms of chromium, aluminum, molybdenum, titanium, or vanadium contained in the chip body 50 combine with nitrogen atoms to form nitrides. As a result, a nitride-containing nitriding layer 70 is formed on the surface of the chip body 50. On the other hand, in the present embodiment, the ball 42 is made of a material that does not contain any of chromium, aluminum, molybdenum, titanium, and vanadium, a material with an extremely low content of chromium, aluminum, molybdenum, titanium, and vanadium, or a material containing chromium, aluminum, molybdenum, titanium, and vanadium in a stable state. Such materials are, for example, tungsten carbide, silicon carbide, silicon nitride, alumina, and zirconia. In this case, even if nitriding treatment is performed, a nitriding layer 70 is not formed on the surface of the ball 42.

[0044] In the state where the ball 42 is assembled to the chip body 50, the gas flow rate passing through the inside of the chip body 50 decreases. That is, by performing gas nitriding treatment in the state where the ball 42 is assembled to the chip body 50, the inflow amount of ammonia gas into the inside of the chip body 50 is suppressed. As a result, the thickness of the nitriding layer 70 formed on the inner surface of the chip body 50 becomes smaller than the thickness of the nitriding layer 70 formed on the outer peripheral surface 65 of the chip body 50. As a result, the thickness T1 of the nitriding layer 70 on the inner surface 53 of the ball holding chamber 52 is smaller than the thickness T2 of the nitriding layer 70 on the outer peripheral surface 65 of the chip body 50.

[0045] When deforming the tip of the chip body 50 to form the caulking portion 60, the thickness of the caulking portion 60 becomes thinner overall. In this case, when gas nitriding treatment is performed, nitrogen atoms enter the front end portion of the caulking portion 60 from three directions: the outer side in the radial direction, the inner side in the radial direction, and the front. Therefore, the thickness of the nitride layer 70 at the front end portion of the caulking portion 60 becomes larger than the thickness of the nitride layer 70 on the other outer peripheral surface 65. As a result, the thickness T3 of the nitride layer 70 on the front end surface 63 of the caulking portion 60 becomes larger than the thickness T2 of the nitride layer 70 on the outer peripheral surface 65 of the chip body 50 in the region R.

[0046] When performing gas nitriding treatment, by arranging the chip body 50 so that the ball 42 is in a horizontal or downward orientation, a gap is generated between the ball 42 and the ball seat 56, and ammonia gas flows into this gap, whereby a nitride layer 70 is also formed on the ball seat 56. If the ball 42 is pressed against the ball seat 56 during the gas nitriding treatment, ammonia gas does not flow into the gap between the ball 42 and the ball seat 56, and further formation of the nitride layer 70 is suppressed. Thereby, the thickness of the nitride layer 70 on the ball seat 56 can be controlled. That is, the thickness T4 of the nitride layer 70 on the ball seat 56 can be made smaller than the thickness T1 of the nitride layer 70 on the inner surface 53 of the ball holding chamber 52.

[0047] The ball pen tip 40 of the present embodiment is a ball pen tip 40 including a ball 42 and a chip body 50 that holds the ball 42. The chip body 50 has a ball holding chamber 52 that holds the ball 42 and a caulking portion 60 that prevents the ball 42 from coming out of the ball holding chamber 52. A nitride layer 70 is formed on the outer peripheral surface 65 of the chip body 50 and the inner surface of the ball holding chamber 52. The thickness T1 of the nitride layer 70 on the inner surface 53 of the ball holding chamber 52 is smaller than the thickness T2 of the nitride layer 70 on the outer peripheral surface 65 of the chip body 50 in the region R from the rear end 62 of the caulking portion 60 to 0.2 mm rearward.

[0048] The ball pen refill 30 of the present embodiment includes the above-described ball pen tip 40 and an ink storage cylinder 32 that stores ink.

[0049] The ballpoint pen 10 of this embodiment includes the above-described ballpoint pen refill 30.

[0050] According to such a ballpoint pen tip 40, ballpoint pen refill 30, and ballpoint pen 10, since the nitride layer 70 is formed on the inner surface 53 of the ball holding chamber 52, it is possible to suppress wear of the inner surface 53. In particular, since the nitride layer 70 is formed on the inner surface 61 of the caulking portion 60, it is possible to suppress wear of the inner surface 61 of the caulking portion 60. Thereby, it is possible to suppress the ball 42 from coming out of the ball holding chamber 52. Further, when the thickness T1 and the thickness T2 satisfy the above relationship, the hardness of the inner surface 53 of the ball holding chamber 52 is smaller than the hardness of the outer peripheral surface 65 of the tip body 50. In this case, when the ball 42 and the inner surface 53 of the ball holding chamber 52 come into contact with each other, it is possible to effectively suppress damage such as scratches on the ball 42.

[0051] In the ballpoint pen tip 40 of this embodiment, the thickness T3 of the nitride layer 70 on the front end surface 63 of the caulking portion 60 is larger than the thickness T2 of the nitride layer 70 on the outer peripheral surface 65 of the tip body 50 in the region R.

[0052] According to such a ballpoint pen tip 40, the hardness of the front end surface 63 of the caulking portion 60 is larger than the hardness of the outer peripheral surface 65 in the region R. Therefore, the wear resistance of the caulking portion 60 can be improved. Thereby, it is possible to suppress the caulking portion 60 from coming into contact with the writing surface and wearing.

[0053] In the ballpoint pen tip 40 of this embodiment, the ball holding chamber 52 includes a ball receiving seat 56 that receives the writing pressure from the ball 42 during writing, and the thickness T4 of the nitride layer 70 of the ball receiving seat 56 is smaller than the thickness T1 of the nitride layer 70 of the inner surface 53 of the ball holding chamber 52.

[0054] According to such a ballpoint pen tip 40, the roughness of the surface of the nitride layer 70 in the ball seat 56 can be reduced. Thereby, when writing with the ballpoint pen 10, it is possible to suppress the surface of the nitride layer 70 from hindering the rotation of the ball 42. Therefore, it is possible to suppress the smooth writing feeling of the ballpoint pen 10 from being impaired.

Explanation of reference numerals

[0055] 10 Ballpoint pen 12 Retracting mechanism 14 Friction member 16 Clip 18 Coil spring 20 Shaft cylinder 21 Front shaft 22 Opening 23 First engaging portion 24 Male screw portion 25 Rear shaft 26 Female screw portion 27 Slide hole 28 Rear end cap 29 Grip member 30 Ballpoint pen refill 32 Ink storage cylinder 34 Tip holder 36 Second engaging portion 40 Ballpoint pen tip 42 Ball 50 Tip body 52 Ball holding chamber 53 Inner surface 54 Side surface 56 Ball seat 58 Ink flow hole 60 Caulked portion 61 Inner surface 62 Rear end 63 Front end face 65 Outer peripheral surface 70 Nitride layer A Central axis line A R Region da Axial direction da

Claims

1. A ballpoint pen tip comprising a ball and a tip body for holding the ball, wherein the tip body has a ball holding chamber for holding the ball and a caulking portion for preventing the ball from coming out of the ball holding chamber, a nitride layer is formed on the outer peripheral surface of the tip body and the inner surface of the ball holding chamber, and the thickness of the nitride layer on the inner surface of the ball holding chamber is smaller than the thickness of the nitride layer on the outer peripheral surface of the tip body in a region from the rear end of the caulking portion to 0.2 mm rearward, a ballpoint pen tip.

2. The ballpoint pen tip according to claim 1, wherein the thickness of the nitride layer on the front end surface of the caulking portion is larger than the thickness of the nitride layer on the outer peripheral surface of the tip body in the region.

3. The ball holding chamber includes a ball receiving seat for receiving the pen pressure from the ball during writing, and the thickness of the nitride layer on the ball receiving seat is smaller than the thickness of the nitride layer on the inner surface of the ball holding chamber, the ballpoint pen tip according to claim 1.

4. A ballpoint pen refill comprising the ballpoint pen tip according to any one of claims 1 to 3, and an ink storage cylinder for storing ink.

5. A ballpoint pen comprising the ballpoint pen refill according to claim 4.

Images