Mechanical pencil guide pipe and mechanical pencil

Abstract

To realize abrasion resistance and good writing feeling.SOLUTION: Provided is a guide pipe for a mechanical pencil made of ceramics with a crystal grain size of 0.1 μm or more and 1 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a guide pipe for a mechanical pencil and a mechanical pencil. [Background technology]

[0002] A metal guide pipe is provided at the pen tip, which is the end of the mechanical pencil on the writing surface side (see, for example, Patent Documents 1 and 2). Also known as a mechanical pencil mechanism is an extension mechanism in which the lead is advanced from the pen tip when the guide pipe comes into contact with the writing surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Jikko No. 58-130791 [Patent Document 2] Japanese Patent Application Publication No. 6-155987 Summary of the Invention [Problem to be solved by the invention]

[0004] Because the guide pipe is located at the pen tip, wear due to friction with the writing surface and a deterioration in writing feel due to wear and other factors are problems. Furthermore, in mechanical pencils with a feeding mechanism, the lead is fed by contact between the guide pipe and the writing surface, so wear and a deterioration in writing feel are particularly problematic. However, prior art has not attempted to improve the wear resistance and writing feel of the guide pipe.

[0005] An object of the present invention is to provide a guide pipe for a mechanical pencil and a mechanical pencil that can achieve wear resistance and a good writing feel. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides "1. The crystal grain size is 0. 4 μm or more and 1 μm or less zirconia A guide pipe for a mechanical pencil. 2. The zirconia crystal grain size is 0.4 μm or more and 0.5 μm or less. 3. A guide pipe for a mechanical pencil according to claim 1. 3. 3. The guide pipe for a mechanical pencil according to claim 1 or 2, wherein the zirconia is colored with a colorant, and the content of the colorant relative to the total amount of the zirconia constituting the guide pipe for a mechanical pencil is 0.1% by mass or more and 5% by mass or less. 4. Crystal grain size is between 0.1 μm and 1 μm and Colored with at least one of metal oxide, metal sulfide, and organic acid metal salt A ceramic guide pipe for mechanical pencils. 5. Surface roughness Ra is 0.1 μm or less, Item 1 ~ Any one of clauses 4 The guide pipe for a mechanical pencil according to claim 1. 6. Section 1 ~ No. Any one of the five items A mechanical pencil having the mechanical pencil guide pipe described in 1. 7. Axial tube and The mechanical pencil guide pipe is provided in the barrel so as to be slidable along the extension direction of the barrel, and has a through hole along the extension direction through which a writing lead is inserted. No. 4 Item 1. A mechanical pencil according to item 1. 8. A feeding mechanism is provided that feeds the writing lead from the writing surface side end of the mechanical pencil guide pipe by contact between the writing surface and the writing surface. No. 7 Item 1. A mechanical pencil according to item 1. 9. The mechanical pencil guide pipe is retractably held within the barrel. No. 7 Section or Article 8 "The mechanical pencil described in paragraph 1. [Effects of the Invention]

[0007] The present invention can provide a guide pipe for a mechanical pencil and a mechanical pencil that can achieve wear resistance and a good writing feel. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a vertical cross-sectional view of an example of a mechanical pencil according to this embodiment. [Figure 2] FIG. 2 is an enlarged vertical cross-sectional view of an example of a main part of the mechanical pencil of FIG. [Figure 3] FIG. 3 is a cross-sectional view of the example of the mechanical pencil shown in FIG. 2 taken along the line AA. [Figure 4] FIG. 4 is a vertical cross-sectional view showing an example of the mechanical pencil of FIG. 2 in a state where the guide pipe is retracted. [Figure 5] FIG. 5 is a vertical cross-sectional view showing an example of a state in which the intermediate gripping member advances from the state shown in FIG. 4 and the chuck comes into contact with the first contact portion. [Figure 6] FIG. 6 is a vertical cross-sectional view showing an example of a state in which the intermediate gripping member has further advanced from the state of FIG. 5 and the cylindrical body and the second contact portion have come into contact with each other. [Figure 7] FIG. 7 is a vertical cross-sectional view showing an example of a state in which the intermediate holding member has further advanced from the state shown in FIG. 6 and the locked state between the guide pipe and the tip member has been released. [Figure 8] FIG. 8 is a vertical cross-sectional view showing an example of a state in which the guide pipe has advanced from the state shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE INVENTION In the present specification, the terms "parts", "%", "ratio" and the like indicating the composition are based on mass unless otherwise specified.

[0010] (Mechanical pencil guide pipe) The mechanical pencil guide pipe of this embodiment is a ceramic guide pipe provided at the pen tip, which is the end of the mechanical pencil on the writing surface side. Hereinafter, the mechanical pencil guide pipe may be simply referred to as the guide pipe.

[0011] The guide pipe is a component that protects the writing lead of a mechanical pencil and guides the writing lead toward the end of the mechanical pencil on the writing surface side. The guide pipe is sometimes called a lead guide, a lead protection tube, etc.

[0012] The guide pipe of this embodiment is made of ceramics with a crystal grain size of 0.1 μm or more and 1 μm or less.

[0013] It has been revealed that the guide pipe of this embodiment, when made of ceramics with a crystal grain size of 0.1 μm or more and 1 μm or less, can achieve wear resistance and a good writing feel.

[0014] First, the components of the guide pipe will be described in detail.

[0015] (ceramics) The guide pipe of this embodiment is made of ceramics with a crystal grain size of 0.1 μm or more and 1 μm or less.

[0016] The type of ceramic constituting the guide pipe of this embodiment is not limited. The ceramic constituting the guide pipe of this embodiment is primarily composed of a metal oxide, and contains trace components such as silicide, nitride, fluoride, or boride. Specific examples of the ceramic constituting the guide pipe include alumina (Al2O3), zirconia (ZrO2), titania (TiO2), silicon carbide (SiC), silicon nitride (Si3N4), boron nitride (BN), and composites of two or more of these ceramics.

[0017] Among these ceramics, it is preferable to use ceramics containing alumina or zirconia as the main component for the guide pipe, and it is even more preferable to use ceramics containing zirconia as the main component. The term "main component" refers to a component that is contained in an amount of 60% by mass or more relative to 100% by mass of all components constituting the guide pipe. By using ceramics containing zirconia as the main component for the guide pipe, it is possible to improve the bending strength, toughness, etc. of the guide pipe. Furthermore, since zirconia sintered grains can be easily made smaller than alumina, it is possible to obtain a sintered guide pipe with a smaller surface roughness. Furthermore, by using zirconia as the main component, it is possible to obtain a guide pipe with a smaller surface roughness by polishing, etc. Therefore, it is possible to provide a guide pipe that achieves a smooth and satisfactory writing feel.

[0018] Zirconia has three phase structures: cubic, tetragonal, and monoclinic, and these three phases are composed of a single layer or a mixed phase. Examples include stabilized zirconia made of cubic crystals and partially stabilized zirconia made mainly of tetragonal crystals, and either can be used. Among these, the use of partially stabilized zirconia is particularly preferred. By using partially stabilized zirconia, a dense sintered guide pipe can be obtained that has good properties such as strength, impact resistance, and toughness.

[0019] In this case, the amount of tetragonal crystals relative to the total zirconia contained in the guide pipe is preferably 50 mol % or more.

[0020] The ceramics constituting the guide pipe of this embodiment may be ceramics containing a stabilizer. Examples of stabilizers include yttria, calcia, magnesia, and ceria. Addition of these stabilizers can further improve the strength, impact resistance, toughness, and other properties of the ceramics. Partially stabilized zirconia containing yttria is most preferred as a ceramic containing a stabilizer. This is because partially stabilized zirconia tends to further improve strength and toughness.

[0021] The amount of stabilizer added is preferably 10 mol% or less. For example, in the case of yttria, the amount is preferably 10 mol% or less, particularly 1 mol% to 5 mol% of the total amount of ceramic. In the case of calcia, the amount is preferably 1 mol% to 9 mol% of the total amount of ceramic.

[0022] The crystal grain size of the ceramic constituting the guide pipe is 0.1 μm to 1 μm, preferably 0.3 μm to 0.8 μm, more preferably 0.3 μm to 0.6 μm, and particularly preferably 0.3 μm to 0.5 μm.

[0023] The crystal grain size of ceramics can be determined by the planimetric method using an SEM image. Specifically, a circle of known area is drawn on the SEM image, and the number of crystal grains within the circle (Nc) and the number of crystal grains around the circumference of the circle (Ni) are counted, and the total number of crystal grains (Nc + Ni) is set to 250±50. Then, the crystal grain size can be calculated using the following formula (A).

[0024] Crystal particle size=2 / {π×(Nc+(1 / 2)×Ni) / (A / M2)}0.5 ···Formula (A)

[0025] In the above formula (A), Nc is the number of crystal particles within a circle, Ni is the number of crystal particles on the circumference of the circle, A is the area of ​​the circle, and M is the magnification of the scanning electron microscope observation (for example, 5,000 to 10,000 times). If the number of crystal particles (Nc + Ni) in one SEM observation image is less than 200, (Nc + Ni) can be set to 250±50 using multiple SEM observation images.

[0026] (coloring agent) The guide pipe of this embodiment may further contain various additives.

[0027] Examples of additives include colorants, organic additives used in the manufacture of the guide pipe, and dispersion media. Adding colorants allows the guide pipe to have a variety of colors and achieve a variety of effects. For example, by using a colorant to color the guide pipe in a similar color to the writing lead, it is possible to make stains caused by lead powder from the writing lead less noticeable. Furthermore, by using a colorant to color the guide pipe in the opposite color to the writing lead, it is possible to make the writing lead more noticeable and improve ease of writing. The organic additives and dispersion media used in the manufacture of the guide pipe will be described later.

[0028] Examples of colorants include metal oxides, metal sulfides, and organic acid metal salts. Specific examples of colorants include iron oxide, magnesium oxide, nickel oxide, other transition metal oxides, iron sulfide, magnesium sulfide, nickel sulfide, nickel acetate, iron acetate, and magnesium acetate.

[0029] The amount of colorant added is not limited as long as it changes the color of the main ceramic component and allows the main ceramic component to be sintered. For example, the amount of colorant added is preferably in the range of 0.1% by mass to 5% by mass of the total amount of ceramics constituting the guide pipe.

[0030] (Guide pipe manufacturing method) An example of a method for manufacturing a guide pipe according to the present embodiment will be described. Note that the method for manufacturing a guide pipe broadly encompasses all embodiments that incorporate the specific features of the invention, and should not be construed as being limited to the embodiment described below.

[0031] The guide pipe of this embodiment is produced by degreasing and firing a ceramic molded body containing ceramic raw materials and additives such as organic additives in a combustion furnace.

[0032] Specifically, the method for producing a guide pipe includes a molding step and a firing step, and may further include a post-process.

[0033] (molding process) The molding step is a step of molding a ceramic compact containing ceramic raw materials and organic additives.

[0034] The ceramic raw material refers to a ceramic powder or granules that can become aggregate particles for the guide pipe. The ceramic raw material is the ceramic powder or granules that form the guide pipe described above.

[0035] The ceramic raw material may be any powder or granular material such as a single type of ceramic, a composite ceramic made of multiple types of ceramic, or a ceramic containing a stabilizer.

[0036] The ceramic crystal grain size may be outside the range of 0.1 μm to 1 μm after the firing process. In this case, a solvent may be added and the ceramic may be pulverized using a ball mill, bead mill, or the like so that the ceramic crystal grain size after the firing process falls within the above range. The pulverized powder may then be used as the ceramic raw material for manufacturing the guide pipe.

[0037] Organic additives are organic substances added as raw materials for ceramic compacts. Examples of organic additives include organic binders and dispersants. Organic additives may also contain inorganic substances, as long as they generate flammable gases by decomposing or burning. Examples of such inorganic substances include carbon.

[0038] The organic binder functions as a reinforcing agent that imparts fluidity, shape retention, handling strength, etc. to the clay or the like that is the raw material for the ceramic molded body. Suitable examples of the organic binder include organic polymers. Specific examples of the organic binder include hydroxypropyl methyl cellulose, methyl cellulose, hydroxyethyl cellulose, carboxyl methyl cellulose, polyvinyl alcohol, etc.

[0039] A dispersant is an additive that promotes the dispersion of ceramic raw materials in a dispersion medium to obtain a homogeneous clay. A surfactant can be suitably used as the dispersant. Specific examples of the dispersant include ethylene glycol, dextrin, fatty acid soap, and polyalcohol.

[0040] The ceramic molded body may contain ceramic raw materials and organic additives, and may further contain other substances as constituent components. Such constituent components may include a dispersion medium such as water or alcohol, as well as a colorant. As mentioned above, using a colorant is preferable because it allows the guide pipe to have various colors and achieve various effects. Specific examples of colorants have been mentioned above, so a description thereof will be omitted here.

[0041] The ceramic molded body can be produced by mixing and kneading the ceramic raw materials, organic additives, dispersion medium, and optionally other additives such as colorants using a conventionally known mixing and kneading method, followed by molding. By adding a colorant to the ceramic raw materials and mixing and kneading them to produce a ceramic molded body, peeling of the colorant can be suppressed even after the guide pipe is constructed, compared to when a colored layer is provided on the ceramic molded body or guide pipe.

[0042] The mixing can be carried out using a conventionally known mixer, such as a butterfly mixer, a ribbon mixer, etc. The kneading can be carried out using a conventionally known kneader, such as a kneader, a Banbury mixer, a screw-type extrusion kneader, a vacuum clay kneader, or a twin-screw continuous kneading extrusion molding machine.

[0043] The molding can be performed by a known ceramic injection molding method, or by a conventional molding method such as extrusion molding or press molding.

[0044] The produced ceramic molded body may be dried prior to the firing step by using a conventionally known drying method such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, or freeze drying.

[0045] (Firing process) The firing step is a step of firing the ceramic molded body obtained in the molding step to obtain a ceramic structure, which is a sintered body of the ceramic raw material.

[0046] The firing step includes, for example, a degreasing step and a sintering step.

[0047] The degreasing step is a step in which the ceramic molded body is heated and held in an oxygen-containing atmosphere, an inert atmosphere, or a reducing atmosphere, thereby removing volatile components generated by heating.

[0048] The inert gas used to create the inert atmosphere is, for example, nitrogen gas or argon gas. The reducing gas used to create the reducing atmosphere is a gas that can react with oxygen, such as hydrogen or hydrocarbon. The heating temperature, heating rate, and heating time in the degreasing step are not particularly limited and may be adjusted appropriately depending on the constituent components of the ceramic molded body.

[0049] Specifically, the heating temperature in the debinding step is relatively lower than that in the subsequent sintering step. Specifically, it is preferably performed at 750°C or lower, and more preferably 600°C or lower. Furthermore, it is not preferable to rapidly increase the temperature of the ceramic molded body in the debinding step. This is because a rapid change in temperature may result in the volatile components generated inside the ceramic molded body not being sufficiently released to the outside of the ceramic molded body, making it impossible to obtain the desired calcined material. For this reason, it is preferable that the temperature increase rate in the debinding step be such that the temperature of the ceramic molded body increases gradually.

[0050] To achieve the desired effect, it is necessary to control the temperature rise of the ceramic molded body. However, depending on the size and shape of the ceramic molded body, a temperature gradient may occur between the surface and center of the ceramic molded body. This makes it difficult to control the temperature of the entire ceramic molded body under the same conditions. Therefore, instead of controlling the temperature of the ceramic molded body itself, it is preferable to control the ambient temperature so that the temperature gradient within the ceramic molded body is small. Specifically, the temperature rise rate is preferably 10°C / hour to 100°C / hour, and more preferably 15°C / hour to 50°C / hour. Alternatively, the temperature rise may be stopped when a constant temperature is reached, and the degreasing process may be continued at the constant temperature.

[0051] The degreasing step can be completed when the resin contained in the ceramic molded body is decomposed by heating and the volatile components other than carbon that are produced are released to the outside of the ceramic molded body. The time until the volatile components are sufficiently released from the ceramic molded body, i.e., the time for the degreasing step, is preferably from 5 hours to 150 hours, and more preferably from 10 hours to 20 hours.

[0052] Furthermore, when the temperature increase is stopped when a constant temperature is reached and the degreasing process is continued at a constant temperature, the duration of the constant temperature is preferably 30 minutes or more and 10 hours or less, and more preferably 1 hour or more and 5 hours or less.

[0053] The sintering step is a step of sintering the ceramic raw material contained in the ceramic formed body degreased in the degreasing step.

[0054] The heating temperature and heating time in the sintering step are not particularly limited, and may be adjusted appropriately depending on the constituent components of the ceramic molded body.

[0055] For example, when zirconia is used as the ceramic raw material, the heating temperature in the sintering step is 1200° C. to 1600° C., preferably 1350° C. to 1500° C. In this case, the heating time is 0.5 hours to 50 hours, preferably 4 hours to 16 hours.

[0056] The firing step may include only the sintering step, without including the degreasing step. In this case, by performing the sintering step, degreasing is performed before sintering or during the temperature rise process of sintering, and volatile components of the ceramic molded body are removed and sintered.

[0057] (post-process) The post-processing includes at least one of a processing step for processing the ceramic structure obtained by the firing step and a polishing step for polishing the ceramic structure. The ceramic structure obtained by the firing step may be used as a guide pipe.

[0058] The processing step is a step of further processing the obtained ceramic structure into a desired shape. Any processing method can be used in the processing step. The processing method may be a general cutting method. Examples of the processing method include one or more of the group consisting of lathe processing, surface grinding, R grinding, and NC (Numerical Control) machining.

[0059] The polishing step is a step of polishing the obtained ceramic structure or a processed ceramic structure. The surface roughness and gloss are adjusted by the polishing step. Any polishing method can be used in the polishing step, and examples thereof include barrel polishing and buff polishing.

[0060] The surface roughness Ra of the guide pipe of this embodiment produced by the above process is preferably 0.1 μm or less, more preferably 0.08 μm or less, even more preferably 0.05 μm or less, and particularly preferably 0.04 μm or less.

[0061] The surface roughness Ra of the guide pipe is measured using a stylus surface roughness meter (product name: Surfcorder SE-3400) manufactured by Kosaka Laboratory Co., Ltd. under the measurement conditions of JIS B 061-2001.

[0062] Furthermore, the guide pipe of this embodiment manufactured by the above process can have various shapes of outer and inner shapes. For example, guide pipes of various shapes, such as a guide pipe with a circular outer shape and a polygonal inner shape, or a guide pipe with a polygonal outer shape and a circular inner shape, can be easily obtained, and guide pipes suitable for various uses can be provided.

[0063] (mechanical pencil) The mechanical pencil of this embodiment includes the guide pipe of this embodiment.

[0064] The mechanical pencil of this embodiment may be configured with the above-described guide pipe, and its structure and shape are not limited. The guide pipe of this embodiment is capable of achieving wear resistance and a good writing feel, and is therefore suitable for use in mechanical pencils in which the end of the guide pipe on the writing surface comes into contact with the writing surface, or in writing implements in which writing is possible by coming into contact with the writing surface. Therefore, it is suitable for use in the following mechanical pencils.

[0065] The guide pipe of this embodiment is suitably applied to a mechanical pencil having a barrel in which the guide pipe is slidable along the extension direction of the barrel.

[0066] Furthermore, the guide pipe of this embodiment is suitable for use in a mechanical pencil equipped with a feeding mechanism that feeds the writing lead from the writing surface end of the guide pipe by contact between the writing surface and the writing surface.

[0067] The guide pipe of this embodiment is also suitable for use in a mechanical pencil in which the guide pipe is held retractably within the barrel.

[0068] Fig. 1 is a longitudinal sectional view of an example of a mechanical pencil 1 to which the guide pipe of this embodiment is suitably applied. Fig. 2 is an enlarged longitudinal sectional view of a main part of Fig. 1. Fig. 3 is an enlarged end view of the AA end face of Fig. 2. Figs. 4 to 8 are longitudinal sectional views of examples of states changed from the state of the mechanical pencil 1 of Fig. 1.

[0069] As shown in FIGS. 1, 2, and 3, a mechanical pencil 1 includes a barrel 2, a guide pipe 3, a feeding mechanism 4, an intermediate gripping member 5, and an operating body 6.

[0070] The barrel 2 is a cylindrical member that is long along the extension direction X. The extension direction X of the barrel 2 is a direction along a straight line that passes through the center of a cross section of the cylindrical barrel 2. In other words, the extension direction X is a direction along the central axis of the cylindrical barrel 2.

[0071] The barrel 2 is composed of a tip member 21, a connecting body 22 screwed to the rear part of the tip member 21, and a barrel main body 23 screwed to the rear part of the connecting body 22.

[0072] The tip member 21 is composed of a tip member main body 211 and an inner piece 212 press-fitted into the inner periphery of the rear part of the tip member main body 211 .

[0073] The front inner periphery of the tip member 21 is provided with a front end opening 21a through which the guide pipe 3 emerges and retracts. A recess 21b is provided in the central inner periphery of the tip member 21. The recess 21b functions as a locked portion that engages with the protruding portion 3e of the guide pipe 3. A step 21c is provided in the rear inner periphery of the tip member 21. The recess 21b is formed in the front portion 212a of the inner link 212. A gap is formed between the front portion 212a and the inner periphery of the tip member main body 211. When the protruding portion 3e, which serves as the locking portion of the guide pipe 3, engages with the recess 21b, this gap causes the front portion 212a to bend outward. This configuration makes it easy to lock the guide pipe 3. The front portion 212a may be divided into multiple portions along the circumferential direction to facilitate bending.

[0074] In this embodiment, "front" and "forward" refer to the direction of one end of the barrel 2 of the mechanical pencil 1 in the extension direction X, and refer to the direction of the writing surface in the extension direction X, i.e., the side where the tip member 21 is provided. In this embodiment, "front" and "pen tip" refer to the end of the mechanical pencil 1 on the writing surface side in the extension direction X.

[0075] In this embodiment, "rear" and "rearward" refer to the direction toward the other end of the barrel 2 of the mechanical pencil 1 in the extension direction X, and refer to the direction opposite to the writing surface in the extension direction X, i.e., the direction toward the side where the tip member 21 is not provided. In this embodiment, "rear" refers to the end of the mechanical pencil 1 in the extension direction X on the side where the tip member 21 is not provided. In this embodiment, "forth-and-forth movement" refers to movement or sliding along the extension direction X.

[0076] The barrel body 23 is composed of a front barrel 231 and a rear barrel 232 that is screwed to the rear of the front barrel 231. The inner periphery of the barrel body 23 is provided with a front step 23a formed in a stepped shape on the front inner periphery, and an inner step 23b that protrudes inward on the central outer periphery.

[0077] The guide pipe 3 is a member provided within the barrel 2 so as to be slidable along the extension direction X of the barrel 2, and has a through-hole along the extension direction X through which the writing lead 7 is inserted. The guide pipe 3 is the guide pipe of this embodiment described above.

[0078] Specifically, the guide pipe 3 is arranged slidably along the extension direction X within the tip member 21 arranged at the end of the barrel 2 on the writing surface side in the extension direction X.

[0079] The guide pipe 3 is composed of a guide pipe body 31, an O-ring 32, and a lead holding member 33 press-fitted onto the inner periphery of the guide pipe body 31. The guide pipe 3 also has a guide portion 3a, a step portion 3b, a rear abutment portion 3c, a lead holding portion 3d, and a protrusion 3e.

[0080] The guide pipe 3 has only to be configured such that at least the guide pipe body 31 is made of the specific ceramic of this embodiment described above. It is preferable that all parts constituting the guide pipe 3 are made of the specific ceramic of this embodiment described above.

[0081] The O-ring 32 is a ring-shaped member fitted onto the outer circumferential recess of the guide pipe main body 31. The lead holding member 33 is a member press-fitted onto the inner circumferential portion of the guide pipe main body 31 and holds the writing lead 7. The guide portion 3a is provided on the inner circumferential portion of the guide pipe main body 31 and is the area through which the writing lead 7 is inserted. The step portion 3b is formed on the outer circumferential portion of the guide pipe main body 31, and the rear abutment portion 3c is the area that abuts at its rear end against the guide pipe pressing portion 42c of the cylindrical body 42. The lead holding portion 3d holds the writing lead 7 with weak force. The protrusion 3e is formed by the O-ring 32 that protrudes outward from the outer circumferential portion and engages with the recess 21b.

[0082] A coil spring 8 is stretched between the step 3b of the guide pipe 3 and the step c of the tip member . The coil spring 8 biases the guide pipe 3 forward relative to the tip member .

[0083] The O-ring 32 and the lead holding member 33 are made of elastic materials. Specifically, synthetic rubber, silicone rubber, nitrile rubber, fluororubber, etc. are used for the O-ring 32. Synthetic rubber, silicone rubber, nitrile rubber, fluororubber, etc. are used for the lead holding member 33. The holding force with which the lead holding portion 3d holds the writing lead 7 is, for example, approximately 0.3 N.

[0084] The feeding mechanism 4 is a mechanism that feeds the writing lead 7 from the writing surface end of the guide pipe 3 by contact between the writing surface end and the writing surface. The writing surface is the object on which writing is performed with the writing lead 7 of the mechanical pencil 1. The writing surface is, for example, a recording medium such as paper.

[0085] The payout mechanism 4 has a chuck 41, a cylindrical body 42 fitted onto the outside of the chuck 41, a steel ball 43 disposed between the chuck 41 and the cylindrical body 42, and a coil spring 44.

[0086] The chuck 41 has a chuck main body 411 and a rear cylindrical body 412 press-fitted to the rear of the chuck main body 411. The chuck 41 is configured to be movable back and forth relative to the cylindrical body 42. The head 41a of the chuck 41 is divided into two parts along the extension direction X. The two divided heads 41a are formed so that they gradually move apart toward the front. The heads 41a are configured to bend radially inward, allowing the heads 41a to grip the writing lead 7. The heads 41a also have a chuck recess 41b into which a steel ball 43 is inserted. A stepped rear step 41c is provided at the rear of the chuck 41.

[0087] The cylindrical body 42 has a cylindrical body main body 421 and a front abutment member 422 press-fitted into a front inner hole of the cylindrical body main body 421. The cylindrical body 42 has an inner hole that penetrates in the extension direction X and is configured to be slidable along the extension direction X relative to the barrel 2. A tightening portion 42b, which is an inclined portion whose diameter increases toward the front, is formed at the front of the inner hole. The tightening portion 42b is positioned so that the steel ball 10 inserted into the chuck recess 41b of the chuck 41 comes into contact with it. A central inner step 42a is provided at the center of the inner hole.

[0088] An outer step 42d formed in a stepped shape is provided on the outer periphery of the cylindrical body 42. The outer step 42d abuts against the front step 23a of the barrel main body 23, thereby restricting rearward movement of the cylindrical body 42. In addition, a guide pipe pressing portion 42c that abuts against the rear abutment portion 3c of the guide pipe 3 is provided at the front end of the cylindrical body 42. The guide pipe pressing portion 42c abuts against the rear end of the inner link 212 of the tip member 21, thereby restricting forward movement.

[0089] The coil spring 44 is stretched between the central inner section 42a of the cylindrical body 42 and the rear section 41c of the chuck 41, and springs the chuck 41 forward. That is, the feeding mechanism 4 has a known ball chuck structure in which a steel ball 43 is disposed between the chuck 41 and the tightening section 42b.

[0090] The chuck 41 is resilient backward by the resilience of the coil spring 44. When the chuck 41 is gripping the writing lead 7, a wedging action occurs in the tightening portion 42b of the cylindrical body 42 via the steel ball 43 as the chuck 41 moves backward, allowing the writing lead 7 to be gripped by the chuck 41.

[0091] Another feature of the ball chuck structure is that when a backward pressure (writing pressure) is applied to the writing lead 7, the chuck 41 tightly grips the writing lead 7, restricting the retraction of the writing lead 7. On the other hand, when a forward pulling force is applied to the writing lead 7, the wedge action is immediately released, allowing the writing lead 7 to move forward.

[0092] In the feeding mechanism 4 of this embodiment, when the guide pipe 3 advances with the writing lead 7 held by the lead holding portion 3d of the guide pipe 3, the writing lead 7 also advances in accordance with the advancement of the guide pipe 3.

[0093] The intermediate gripping member 5 is composed of a gripping member main body 51 and a rear tube 52 press-fitted into the rear portion of the gripping member main body 51. The intermediate gripping member 5 is housed inside the barrel 2 so as to be slidable along the extension direction X. The front portion of the intermediate gripping member 5 is divided into four equal parts along the circumferential direction (see Figure 3), forming gripping portions 5a that grip the tubular body 42 with a constant force by elastic force. The inner peripheral portion of the rear portion of the intermediate gripping member 5 is provided with a lead storage portion 5b that stores multiple spare lead cartridges. A coil spring 9 is stretched between the front end of the rear tube 52 and the inner step portion 23d of the barrel main body 23. The elastic force of the coil spring 9 constantly springs the intermediate gripping member 5 rearward.

[0094] In the central inner stage of the intermediate gripping member 5, there are provided a first abutting portion 5c that abuts against the rear end of the chuck 41 and a second abutting portion 5d that abuts against the rear end of the cylindrical body 42 when the intermediate gripping member 5 moves forward. By forming the first abutting portion 5c and the second abutting portion 5d on the inner and outer sides in the same plane respectively, the workability is improved. The intermediate gripping member 5 has a central outer stage on the outer peripheral portion, and the inner stage portion 23b of the shaft cylinder main body 23 abuts against the central outer stage, thereby restricting the backward movement.

[0095] An operating body 6 is detachably attached to the rear portion of the intermediate gripping member 5. As the operating body 6 is pressed forward, the intermediate gripping member 5 is pressed forward.

[0096] The relationship between the pressing force for releasing the locking state between the guide pipe 3 and the tip member 21 and the gripping force of the gripping portion 5a of the intermediate gripping member 5 for gripping the cylindrical body 42 is preferably as follows.

[0097] As shown in FIG. 4, assume a locked state in which the protruding portion 3e of the guide pipe 3 and the recess 21b of the tip member 21 are locked. From this locked state, when the guide pipe 3 is pressed forward along the axial direction by the cylindrical body 42, let the pressing force for releasing the locked state be P, and the gripping force of the gripping portion 5a of the intermediate gripping member 5 for gripping the cylindrical body 42 be Q. In this case, the relationship between the pressing force and the gripping force is configured to satisfy the relational expression of Q < P. For example, the pressing force P is about 2 N, and the gripping force Q is about 1 N.

[0098] Next, in this embodiment, the state in which the refill 7 is fed forward by a knocking operation of pressing the operating body 6 forward from the states of FIGS. 1 and 2 will be described.

[0099] When the operating body 6 is pressed forward against the elastic force of the coil spring 9 from the states of FIGS. 1 and 2, the intermediate gripping member 5 pressed by the operating body 6 also moves forward at the same time. Then, when the intermediate gripping member 5 moves forward, the cylindrical body 42 gripped by the gripping portion 5a of the intermediate gripping member 5 moves forward together with the chuck 41 and the refill 7. At this time, the front end of the refill 7 protrudes from the front end of the guide portion 3a of the guide pipe 3.

[0100] When the guide pipe pressing portion 42c of the cylindrical body 42 abuts against the rear end of the inner link 212 of the tip member 21, stopping the forward movement of the cylindrical body 42, the chuck 41 and the lead 7 held by the chuck 41 also stop moving forward. In this state, when the pressure on the operating body 6 is released, the spring force of the coil spring 9 causes the intermediate holding member 5 and the operating body 6 to move backward, and the cylindrical body 42 held by the holding portion 5a of the intermediate holding member 5 moves backward. At this time, the writing lead 7 is held by the lead holding portion 3d of the guide pipe 3, and the backward movement of the cylindrical body 42 and the chuck 41 applies a forward pulling force to the writing lead 7. As described above, the mechanical pencil 1 of this embodiment employs a ball chuck structure. Therefore, when a forward pulling force is applied to the writing lead 7, the wedging action of the tightening portion 42b on the chuck 41 is immediately released, allowing the writing lead 7 to move forward. Therefore, the writing lead 7 does not move back but maintains its forward position, and as a result, the writing lead 7 is advanced forward relative to the guide pipe 3.

[0101] Next, a state will be described in which, when writing on a writing surface such as a recording medium with the mechanical pencil 1 of this embodiment, the tip knock structure is activated and the writing lead 7 is advanced forward in accordance with the writing action.

[0102] When writing is performed on a writing surface such as a recording medium in the state shown in Figures 1 and 2, and the front end of the writing lead 7 wears down, the front end of the guide pipe 3, which is the end on the writing surface side, comes into contact with the writing surface during writing. When the end on the writing surface side of the guide pipe 3 comes into contact with the writing surface, the guide pipe 3 is pressed by the writing surface and moves back relative to the tip member 21 (barrel tube 2) against the elastic force of the coil spring 8. The writing lead 7 is held by the chuck 41, and the feeding mechanism 4 tightly grips the writing lead 7 when it is pressed backward. As a result, the writing lead 7 does not move back, and only the guide pipe 3 moves back relative to the tip member 21 and the writing lead 7.

[0103] When the front end of the guide pipe 3, that is, the end on the writing surface side, separates from the writing surface, the guide pipe 3 moves forward due to the elastic force of the coil spring 8. At this time, the writing lead 7 is held by the lead holding portion 3d of the guide pipe 3. As a result, a forward pulling force is applied to the writing lead 7, and just as when the writing lead 7 is being extended, the wedge force applied to the chuck 41 by the tightening portion 42b decreases, and the writing lead 7 is released from the chuck 41. As the guide pipe 3 moves forward, the writing lead 7 held by the guide pipe 3 also moves forward, so that writing automatically extends the writing lead 7 forward. A structure that automatically extends the writing lead 7 forward is sometimes referred to as a tip knock structure.

[0104] Next, the state in which the guide pipe 3 and the writing lead 7 are retracted from the state shown in FIGS. 1 and 2 and locked by the tip member 21 will be described with reference to FIGS.

[0105] 1 and 2 to the state of FIG. 8, pressing the operating body 6 forward presses the intermediate gripping member 5 and moves it forward. As the intermediate gripping member 5 moves forward, the chuck 41 moves forward relative to the cylindrical body 42, reducing the wedging action of the tightening portion 42b on the chuck 41 and causing the chuck 41 to release the writing lead 7. Therefore, in the mechanical pencil 1 of this embodiment, when writing, pressing the operating body 6 forward causes the guide pipe 3 and the writing lead 7 to protrude forward from the front end opening 21a of the barrel 2, and the mechanical pencil 1 is ready to write with the writing lead 7.

[0106] When the guide pipe 3 and the writing lead 7 are pressed against a flat surface such as a desk in the state shown in Figure 8, the writing lead 7 first retracts to the front end of the guide pipe 3, and then the guide pipe 3 and the writing lead 7 retract relative to the tip member 21 (barrel tube 2), and the protruding portion 3e of the guide pipe 3 engages with the recessed portion 21b of the tip member 21.

[0107] When the forward pressure on the operating body 6 is released, the elastic forces of the coil springs 9 and 44 move the chuck 41, the tubular body 42, the intermediate gripping member 5, and the operating body 6 backward, resulting in the state shown in Figure 4 in which the writing lead 7 is once again gripped by the chuck 41.

[0108] 4, the front end of the writing lead 7 is positioned approximately at the same position as the front end of the guide pipe 3, and a gap L is formed between the rear contact portion 3c of the guide pipe 3 and the guide pipe pressing portion 42c of the cylindrical body 42. The guide pipe 3 is also retracted into the front end opening 21a of the barrel 2.

[0109] By keeping the mechanical pencil 1 in the state shown in Figure 4, even if you carry it around in a pencil case or a pocket, the tip of the guide pipe 3 will not be damaged by vibration or contact with other items, and at the same time, the thin tip of the guide pipe 3 will not scratch other items.

[0110] Next, an operation of releasing the engagement between the guide pipe 3 and the tip member 21 by pressing the operation body 6 forward from the state shown in FIG. 4 to return to the writing state will be described.

[0111] 4, when the operating body 6 is pressed forward, the intermediate gripping member 5, which is pushed by the operating body 6, moves forward. When the intermediate gripping member 5 moves forward, the cylindrical body 42 held by the gripping portion 5a of the intermediate gripping member 5 moves forward together with the chuck 41 by the gap L until the rear abutting portion 3c of the guide pipe 3 comes into contact with the guide pipe pressing portion 42c of the cylindrical body 42. At this time, the writing lead 7 held by the chuck 41 also moves forward by the gap L relative to the guide pipe 3, and the writing lead 7 protrudes forward from the front end of the guide portion 3a of the guide pipe 3 by the gap L.

[0112] For example, assume that the gap L is set in the range of 0.3 mm to 0.5 mm. In this case, the length by which the writing lead 7 protrudes from the front end of the guide portion 3a of the guide pipe 3 is also in the range of 0.3 mm to 0.5 mm.

[0113] As described above, the relationship between the pressing force P for releasing the locked state between the guide pipe 3 and the front member 21 and the gripping force Q with which the gripping portion 5a of the intermediate gripping member 5 grips the cylindrical body 42 satisfies the relational expression Q < P. For this reason, when the rear contact portion 3c of the guide pipe 3 abuts against the guide pipe pressing portion 42c of the cylindrical body 42, the forward movement of the cylindrical body 42 stops, and the gripping portion 5a of the intermediate gripping member 5 moves forward along the outer surface of the cylindrical body 42 in a sliding manner. Then, the state shown in FIG. 5 is reached where the first contact portion 5c of the intermediate gripping member 5 abuts against the rear end of the chuck 41.

[0114] When the operating body 6 is further pressed and the intermediate gripping member 5 moves forward, the chuck 41 moves forward with respect to the cylindrical body 42 against the elastic force of the coil spring 44. Due to the forward movement of the chuck 41, the wedging action on the chuck 41 by the clamping portion 42b via the steel ball 43 is reduced, and the refill 7 is released from the chuck 41 without moving forward. The forward movement of the chuck 41 stops when the rear end of the cylindrical body 42 abuts against the second contact portion 5d of the intermediate gripping member 5, reaching the state shown in FIG. 6.

[0115] When the intermediate gripping member 5 further moves forward from the state shown in FIG. 6, the guide pipe pressing portion 42c of the cylindrical body 42 presses the guide pipe 3, and the locked state between the protruding portion 3e of the guide pipe 3 and the concave portion 21b of the front member 21 is released, reaching the state shown in FIG. 7.

[0116] When the locked state between the guide pipe 3 and the front member 21 is released, the guide portion 3a of the guide pipe 3 moves forward by the elastic force of the coil spring 8 and protrudes forward from the front end opening 21a of the front member 21. Further, the refill 7 held by the core holding portion 3d also moves forward while maintaining the positional relationship in the extending direction X with the guide pipe 3, reaching the state shown in FIG. 8.

[0117] When the pressing state of the operating body 6 is released from the state shown in FIG. 8, the intermediate gripping member 5, the cylindrical body 42, and the chuck 41 move backward by the elastic forces of the coil spring 9 and the coil spring 44 and return to their original positions, reaching the states shown in FIGS. 1 and 2.

[0118] Here, the guide pipe 3 provided in the mechanical pencil 1 of this embodiment is the guide pipe 3 of this embodiment described above. That is, the guide pipe 3 of this embodiment is made of ceramics with a crystal grain size of 0.1 μm or more and 1 μm or less, and is capable of achieving wear resistance and a good writing feel.

[0119] Therefore, by including the guide pipe 3 of this embodiment, the mechanical pencil 1 can achieve wear resistance and a good writing feel.

[0120] Furthermore, even in the case of a mechanical pencil 1 in which the guide pipe 3 is configured to be slidable within the barrel 2 along the extension direction X of the barrel 2, the inclusion of the guide pipe 3 of this embodiment makes it possible to achieve wear resistance and a good writing feel.

[0121] Furthermore, even in a mechanical pencil 1 configured such that the writing surface side end, which is the front end of the guide pipe 3, comes into contact with the writing surface during writing, thereby advancing the writing lead 7, the inclusion of the guide pipe 3 of this embodiment makes it possible to provide a mechanical pencil 1 that is highly wear-resistant and capable of achieving a good writing feel. In other words, even in a mechanical pencil configured such that the guide pipe 3 comes into contact with the writing surface, the inclusion of the guide pipe 3 of this embodiment makes it possible to provide a mechanical pencil 1 that is highly wear-resistant and capable of achieving a good writing feel.

[0122] However, by applying the guide pipe 3 of this embodiment to the mechanical pencil 1 of this embodiment, which is configured so that the guide pipe 3 can be retracted and stored within the barrel 2, it is possible to prevent the guide pipe 3 from cracking or chipping. [Example]

[0123] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0124] Example 1 Zirconia powder (partially stabilized zirconia containing 3 mo1% yttria and 0.25 mass% alumina powder, particle size 0.04 μm, manufactured by Tosoh Corporation, product name TZ-3Y-E) was prepared as a ceramic raw material.

[0125] To this ceramic raw material, 20% by mass of polyvinyl alcohol as an organic binder, 5% by mass of fatty acid soap as a dispersant, 2% by mass of magnesium stearate as a release agent, and other additives were added, and the mixture was kneaded using a kneader (Kneader, manufactured by Toshin Co., Ltd.) to obtain a kneaded product.

[0126] This kneaded material was subjected to injection molding to produce a ceramic molded body having a shape similar to that of the finished guide pipe. The conditions for applying injection molding to the production of the ceramic molded body were similar to those used in known ceramic injection molding methods.

[0127] The ceramic compact was then debindered in a nitrogen atmosphere at 500°C for 2 hours (debinding step). The temperature increase rate in the debinding step was 30°C / hour. The ceramic compact that had undergone the debinding step was fired and sintered in an air atmosphere at 1350°C for 2 hours to obtain a ceramic structure. The end faces of the obtained ceramic structure were polished with a diamond sheet #6000, and a tubular ceramic structure with an outer diameter of 2.0 mm and an inner diameter of 0.6 mm was produced as the guide pipe of Example 1.

[0128] Example 2 Colorant-containing zirconia powder (containing 92 mass% zirconia, 4.2 mass% yttria, and 3.8 mass% Cr-Mn-Co composite oxide as a colorant, particle size 0.1 μm, manufactured by Daiichi Kigenso Co., Ltd., product name TRZ-NB) was prepared as a colorant-containing ceramic raw material.

[0129] A ceramic molded body was produced by ceramic injection molding in the same manner as in Example 1, except that the ceramic raw material of Example 1 was replaced with the colorant-containing ceramic raw material prepared in Example 2.

[0130] The ceramic compact was then debindered in a nitrogen atmosphere at 500°C for 2 hours (debinding step). The temperature increase rate in the debinding step was 20°C / hour. The ceramic compact obtained after the debinding step was fired and sintered in an air atmosphere at 1450°C for 2 hours to obtain a ceramic structure. The end faces of the obtained ceramic structure were polished with a diamond sheet #6000, and a tubular ceramic structure with an outer diameter of 2.0 mm and an inner diameter of 0.6 mm was produced as the guide pipe of Example 2.

[0131] (Comparative Example 1) Alumina powder (particle diameter 0.2 μm, manufactured by Sumitomo Chemical Co., Ltd., trade name AKP-50) was prepared as a ceramic raw material.

[0132] A ceramic molded body was produced by ceramic injection molding in the same manner as in Example 1, except that the ceramic raw material prepared in Comparative Example 1 was used instead of the ceramic raw material of Example 1.

[0133] The ceramic compact was then debindered in a nitrogen atmosphere at 500°C for 2 hours (debinding step). The temperature increase rate in the debinding step was 30°C / hour. The ceramic compact that had undergone the debinding step was fired and sintered in an air atmosphere at 1700°C for 2 hours to obtain a comparative ceramic structure. The end faces of the obtained comparative ceramic structure were polished with a diamond sheet #6000, and a tubular ceramic structure with an outer diameter of 2.0 mm and an inner diameter of 0.6 mm was produced as the guide pipe for Comparative Example 1.

[0134] (Comparative Example 2) As a comparative guide pipe for Comparative Example 2, a guide pipe made of brass and chrome-plated, which is a guide pipe for Dr. GRIP (manufactured by Pilot Co., Ltd., product name G Spec 05), was prepared.

[0135] The colors of the guide pipes of Examples 1 and 2 and the comparative guide pipes of Comparative Examples 1 and 2 were checked, and were the colors shown in Table 1.

[0136] (Physical Properties) The crystal grain size, surface roughness Ra (μm), Vickers hardness (HV), bending strength (Mpa), and Young's modulus (GPa) were measured for the guide pipes of Examples 1 and 2 and the comparative guide pipes of Comparative Examples 1 and 2. The measurement results are shown in Table 1. The measurement conditions were as follows:

[0137] The crystal grain size was calculated by the planimetric method after observing the cross section of each of the guide pipe and the comparative guide pipe with a SEM (scanning electron microscope).

[0138] The surface roughness Ra (μm) was measured using a stylus surface roughness meter (manufactured by Kosaka Laboratory Co., Ltd., trade name Surfcorder SE-3400).

[0139] Vickers hardness (HV) was measured using a Vickers hardness tester manufactured by Akashi Seisakusho Co., Ltd. under the condition of a test force of 1 kgf.

[0140] The bending strength (MPa) was measured using a universal testing machine manufactured by Shimadzu Corporation under the condition that the distance between outer supports was 20 mm.

[0141] The Young's modulus (GPa) was measured using a universal testing machine manufactured by Shimadzu Corporation under the condition of an outer support distance of 20 mm.

[0142] (evaluation) -Writing feel (on paper)- For the guide pipes of Examples 1 and 2, and the comparative guide pipes of Comparative Examples 1 and 2, each sample was placed perpendicularly on the surface of paper and moved 50 mm at a speed of 4 m / min with a load of 150 g applied, and the writing resistance was measured. The results of the writing resistance measurements are shown in Table 1. The writing feel was then evaluated using the writing resistance values. The evaluation criteria are shown below. The evaluation results are also shown in Table 1.

[0143] A: Good writing feel: Writing resistance value less than 0.2. B: Slightly poor writing feel: Writing resistance value of 0.2 or more but less than 0.5. C: Poor writing feel: Writing resistance value 0.5 or more.

[0144] -Wear resistance- For the guide pipes of Examples 1 and 2 and the comparative guide pipes of Comparative Examples 1 and 2, each sample was placed perpendicularly against #1000 sandpaper and moved 700 mm at a speed of 4 m / min under a load of 500 g, and the amount of wear (μm) was measured with a micrometer. The results of the wear amount measurements are shown in Table 1. The wear resistance was then evaluated using the amount of wear. The evaluation criteria are shown below. The evaluation results are also shown in Table 1.

[0145] A: Good abrasion resistance: Abrasion amount less than 10 μm. B: Slightly poor abrasion resistance: Abrasion amount is 10 μm or more and less than 50 μm. C: Poor abrasion resistance: Abrasion amount 50 μm or more.

[0146] [Table 1]

[0147] As shown in Table 1, it was confirmed that the guide pipes of Examples 1 and 2 achieved better wear resistance and a better writing feel than the comparative guide pipes of Comparative Examples 1 and 2. [Industrial Applicability]

[0148] The guide pipe for a mechanical pencil according to the present invention can be used as a guide pipe for a mechanical pencil. [Explanation of symbols]

[0149] 1 mechanical pencil 3 Guide pipe 4. Feeding mechanism

Claims

1. A guide pipe for a mechanical pencil made of zirconia having a crystal grain size of 0.4 μm or more and 1 μm or less.

2. The zirconia crystal particle size is 0.4 μm or more and 0.5 μm or less. The guide pipe for a mechanical pencil according to claim 1.

3. The zirconia is colored with a colorant, The content of the colorant relative to the total amount of the zirconia constituting the guide pipe for a mechanical pencil is 0.1% by mass or more and 5% by mass or less.

3. The guide pipe for a mechanical pencil according to claim 1 or 2.

4. The crystal grain size is 0.1 μm or more and 1 μm or less, A guide pipe for a mechanical pencil made of ceramics colored with at least one of a metal oxide, a metal sulfide, and an organic acid metal salt.

5. The guide pipe for a mechanical pencil according to any one of claims 1 to 4, wherein the surface roughness Ra is 0.1 µm or less.

6. The guide pipe for a mechanical pencil according to any one of claims 1 to 5, A mechanical pencil having a

7. A shaft cylinder and The mechanical pencil guide pipe is provided in the barrel so as to be slidable along the extension direction of the barrel, and has a through hole along the extension direction through which a writing lead is inserted. The mechanical pencil according to claim 6.

8. a feeding mechanism that feeds the writing lead from the writing surface side end of the mechanical pencil guide pipe by contact between the writing surface and the writing surface; The mechanical pencil according to claim 7.

9. The mechanical pencil guide pipe is held retractably within the barrel. The mechanical pencil according to claim 7 or 8.

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