Steering wheel

Abstract

This steering wheel comprises a rim core portion, a resin portion molded on the rim core portion, and a skin that coats at least a part of the surface of the resin portion, wherein the skin is an artificial material and satisfies the relationships of expression (1) and expression (2):　Expression (1): 0.65≤G / L≤0.95, and Expression (2): 1.05≤G / R≤1.35, where L, R, and G are hardnesses according to a type C durometer.

Description

Steering wheel

[0001] The present invention relates to a steering wheel.

[0002] Known steering wheel configurations include, for example, a configuration consisting of an elastomer resin layer on the surface of a metal rim material, with the surface modified as needed to provide wear resistance, and a configuration in which the elastomer resin layer on the surface of the metal rim material is covered with leather and glued or sewn on. Other known technologies include modifying or improving the covering material itself on the steering wheel surface or inserting a functional material between the covering material and the elastomer resin layer to impart various functions to the steering wheel or change the surface feel. For example, Patent Document 1 discloses a steering wheel in which the leather covering the ring body has a coating film, as an invention in which the covering material itself is modified or improved. The coating film imparts different functions to the leather than the uncoated portion. Examples of such different functions include slip resistance or slipperiness. Patent Document 2 discloses a steering wheel with a configuration consisting of a rim material and an elastomer resin layer, as an invention in which the rim core is surrounded by a resin portion, the resin portion being made of a hard foamed polyurethane with a specific surface hardness. It is described that the rigid foamed polyurethane can provide abrasion resistance and weather resistance. Patent Document 3, like Patent Document 1, is an invention for changing or modifying the covering material itself, and describes a method for changing the compressive properties of the surface of the skin member to a maximum load of 1 cm. ２ In the displacement-load characteristics in the range of 30 g or less per load, the load is 30 g / cm ２ The document discloses a skin member characterized by a compressive strain of 0.00527 to 0.0110 cm, a compression recovery of 56 to 65%, and an average coefficient of friction on the surface of the skin member of 0.2 to 0.4. The document also describes that the skin member improves grip comfort.

[0003] Unlike seats and door trim, steering wheels, which are constantly touched by drivers, are primarily made of natural leather for their luxurious feel and tactile texture. However, in recent years, there has been a demand for replacing natural leather with artificial materials due to animal welfare and other factors. As with Patent Document 1, development has been underway to modify or alter the covering material itself, resulting in synthetic leathers suitable for use in automobiles and other components. For example, Patent Document 4 discloses synthetic leather for automobiles, which is composed of a fibrous base material, a surface layer made of polyurethane resin, and a protective layer made of polyurethane resin, laminated in this order. Patent Document 5 discloses a steering wheel with a covering made of soft urethane or the like. Patent Document 6 discloses synthetic leather, which is composed of a fibrous base material, a tactile layer made of a gel-like substance, and a surface layer made of polyurethane-based resin, laminated in this order.

[0004] Japanese Patent Application Laid-Open No. 2018-69766 Japanese Patent Application Laid-Open No. 59-11963 Japanese Patent Application Laid-Open No. 2006-101935 International Publication No. 2015 / 001732 Japanese Patent Application Laid-Open No. 2021-20561 Japanese Patent Application Laid-Open No. 2019-77961

[0005] Furthermore, in order to enhance the luxurious feel and tactile sensation provided by the surface leather of steering wheels, synthetic leathers such as suede-like and grain-like leathers have been replaced with natural leather. Simply replacing the surface leather is well known. However, as a method for changing the grip feel of a steering wheel, the idea of ​​changing the components other than the surface leather has not been considered, as they are recognized as the basic structure of the steering wheel. Therefore, efforts have been made to change the grip feel by focusing only on the surface leather, changing its hardness and feel. The synthetic leather for automobiles described in Patent Document 4 is suitable for vehicle seats, but because it is based on a circular knit fabric, it is soft and stretchy, making it unsuitable for use as a steering wheel cover material. Furthermore, Patent Document 4 does not disclose its application as a surface leather material for steering wheels. Patent Document 5 also describes that if the covering material has an Asker C hardness of 30 to 50, the driver can grip the grip portion with a comfortable feel that is neither too soft nor too hard. In Patent Document 6, the Asker C hardness of the tactile sensation-imparting layer is 0 to 15, so the Asker C hardness of the synthetic leather is thought to be about 45. However, the synthetic leathers described in Patent Documents 5 and 6 are both difficult to provide the severe abrasion resistance required for a steering wheel, and a solid steering feel when suddenly operating the steering wheel during an emergency, etc. There is a demand for a steering wheel that uses synthetic leather as the surface leather material and that can achieve both a gentle grip and a solid steering feel.

[0006] To provide a steering wheel that provides a gentle grip when gripped lightly and a firm steering feel when gripped firmly.

[0007] As a result of intensive research to solve the above problems, the present inventors have conceived the following invention and found that the above problems can be solved.

[0008] [1] A steering wheel comprising: a rim core; a resin portion molded on the rim core; and a skin covering at least a portion of the surface of the resin portion, wherein the skin is made of an artificial material and satisfies the relationships of the following formulas (1) and (2): Formula (1): 0.65≦G / L≦0.95 Formula (2): 1.05≦G / R≦1.35 L is the durometer hardness, measured by contacting a Type C durometer with the surface side of a sheet of the skin placed on a flat plate with a Type D durometer hardness of 80 or more, and represents the median value obtained from 10 measurements, where L is between 10 and 100. R is the durometer hardness, measured by contacting a Type C durometer with the surface of the resin portion molded on the rim core, and represents the median value obtained from 10 measurements, where R is between 10 and 100. The G is a durometer hardness, and represents the median value obtained from ten measurements taken by contacting a Type C durometer with the surface side of the skin in a state where the surface of the resin portion molded on the rim core is covered. However, G is 10 or more and 100 or less. [2] The steering wheel described in [1] above, in which G is 50 or more and 90 or less. [3] The steering wheel described in [1] or [2] above, in which R is 75 or less. [4] The steering wheel described in any of [1] to [3] above, in which L is 90 or less. [5] The steering wheel described in any of [1] to [4] above, in which L is 75 or more. [6] The steering wheel described in any of [1] to [5] above, in which the artificial material has a grain finish. [7] The steering wheel described in any of [1] to [6] above, in which the artificial material is a laminate including a fiber substrate layer and a resin coating layer. [8] The steering wheel according to [7], wherein the fiber base material layer is a nonwoven fabric to which a resin is applied. [9] The steering wheel according to any one of [1] to [8], wherein at least a part of the skin is not bonded to the surface of the resin portion.

[0009] According to the present invention, it is possible to provide a steering wheel that provides a gentle grip when gripped lightly and a firm steering feel when gripped firmly.

[0010] 1 is a plan view of an example of a circular steering wheel according to the present embodiment, as seen from the driver's seat side; FIG. 2 is a plan view of an example of a D-shaped steering wheel according to the present embodiment, as seen from the driver's seat side; and FIG. 3 is a cross-sectional view of a rim portion of the example of the steering wheel according to the present embodiment.

[0011] The following description is based on an example of an embodiment of the present invention. However, the embodiment described below is merely an example for embodying the technical concept of the present invention, and the present invention is not limited to the following description. Furthermore, although preferred embodiments are shown in this specification, a combination of two or more of the individual preferred embodiments is also a preferred embodiment. For matters indicated by numerical ranges, when there are several numerical ranges, the lower limit and upper limit can be selectively combined to form a preferred embodiment. Note that, in this specification, when a numerical range is described as "XX to YY," it means "XX or more and YY or less." In this embodiment, a "steering wheel" refers to the part that a driver grips and turns to steer a vehicle. As will be described later, the shape of the "steering wheel" in this embodiment is not limited to a ring shape.

[0012] The steering wheel of this embodiment includes at least a rim core, a resin portion, and a skin, the skin being made of an artificial material. The term "artificial material" as used herein refers to any material whose base structure is formed through an artificial process rather than using natural materials as is, and does not mean that the raw materials are made entirely of artificial materials. Specifically, natural leather seats and natural wood panels, which are obtained by using animal or plant skins without destroying their shape, are natural materials. However, materials formed into base structures such as woven fabrics, knitted fabrics, nonwoven fabrics, and molded sheets using crushed animal or plant skins such as natural leather or natural wood, or natural fibers such as cotton or silk, as well as materials impregnated or coated with resin, are all artificial materials. Furthermore, materials formed into base structures using artificial materials such as synthetic fibers or synthetic resins are all artificial materials. The inventors conducted extensive research into steering wheel formulations that provide a comfortable grip when gripped lightly and a solid steering feel when making sudden maneuvers, such as during emergency avoidance maneuvers. In conventional techniques, it was difficult to change the grip feel by simply changing the hardness or feel of the surface leather material. However, the present inventors focused on the hardness of the resin portion and the skin, and found that an effective formulation was to have the hardnesses satisfy a specific relationship (specifically, the relationship between the above formulas (1) and (2)). Based on this result, the present inventors discovered that satisfying the relationship between the above formulas (1) and (2) can solve the above problem, and that by shaping at least the base structure of the material used for the skin through an artificial process, it is possible to relatively freely manufacture a skin that satisfies the matching with the resin portion required by the above formula (1). This ultimately led to the discovery that a combination of the skin and the resin portion that satisfies the relationship between the above formulas (1) and (2), i.e., the character of the steering wheel, can be precisely designed. This led to the present invention.

[0013] When the steering wheel of this embodiment is lightly gripped, the palm of the hand does not feel repulsive like rubber, but rather provides a soft and gentle grip, with the palm sinking into the grip. Additionally, when the hand is lightly placed on the grip and then quickly gripped, a solid steering feel can be obtained, with a responsive reaction force and a comfortable grip. As a specific example, if the steering wheel of this embodiment is a steering wheel for an automobile, for example, when the steering wheel is turned quickly from the neutral position to a steering angle of 30°, alternating left and right three times, a solid steering feel can be obtained, with a responsive reaction force and a comfortable grip.

[0014] [Steering Wheel] A steering wheel according to the present invention will be described below using a steering wheel used in an automobile as an example. However, the steering wheel according to the present invention is not limited to these examples. FIGS. 1 and 2 are plan views of an example of a steering wheel according to this embodiment, as viewed from the driver's seat. The steering wheel 1 shown in FIGS. 1 and 2 includes at least a rim portion (also referred to as a handle portion) 10, a pad portion 11, and spoke portions 12. The rim portion 10 is a portion that is gripped by the driver and rotated. The rim portion 10, the pad portion 11, and the spoke portions 12 may optionally be provided with components such as a decorative panel or a display panel.

[0015] In the steering wheel 1, the driver's seat side is referred to as the front side, and the side of the steering shaft (not shown) attached to the steering wheel 1 is referred to as the rear side. Figures 1 and 2 are plan views of the steering wheel 1 as seen from the front side. Furthermore, the direction in which the steering wheel 1 stands in a direction perpendicular to the rotation axis of the steering wheel 1 is referred to as the up-down direction. As another explanation, the 0° direction in Figures 1 and 2 is referred to as the up-down direction, and the 180° direction is referred to as the down-down direction. Furthermore, the 90° direction is referred to as the right-hand direction, and the 270° direction is referred to as the left-hand direction.

[0016] Figure 3 is a cross-sectional view of the rim portion of an example of a steering wheel according to this embodiment, and corresponds to a cross-section of the steering wheel 1 of Figures 1 and 2 viewed from left to right at the 0° position. The rim portion 2 shown in Figure 3 comprises at least a rim core 20, a resin portion 30 molded on the rim core 20, and a skin 40 covering the resin portion 30. The skin 40 may have portions that are not covered by the resin portion 30 in positions other than those shown in Figure 3. Components equipped with, for example, a temperature control mechanism such as a heater or Peltier element, a sensor mechanism such as a piezoelectric element, and an information transmission mechanism such as a vibration element can be arbitrarily installed between the resin portion 30 and the skin 40, as long as they do not excessively impair the relationship between equations (1) and (2) and the effects of the present invention.

[0017] In the rim portion 2 shown in Figure 3, the portions indicated by 0° to 45° and 315° to 360° are referred to as the outer peripheral portion, the portion indicated by 135° to 225° is referred to as the inner peripheral portion, the portion indicated by 45° to 135° is referred to as the front portion, and the portion indicated by 225° to 315° is referred to as the back portion.

[0018] In the steering wheel of this embodiment, the cover may be provided on the portion gripped by the driver. For example, the cover may be provided on the entire rim portion 10 shown in Figures 1 and 2, or on only a portion thereof, or on a plurality of discontinuous portions such as only the portion of the rim portion 10 indicated by 45° to 90° in Figures 1 and 2 and the portion indicated by 270° to 315° in Figures 1 and 2. Furthermore, for example, the cover may be provided on all of the outer peripheral portion, inner peripheral portion, front portion, and back portion shown in Figure 3, or on only a portion continuing from the outer peripheral portion to the front portion, or on a plurality of discontinuous portions such as only the front portion and the back portion.

[0019] [Shape] The steering wheel of this embodiment is not limited to the shape shown in Figures 1 and 2. The steering wheel of this embodiment may have an annular rim shape, such as a circular shape as shown in Figure 1, an elliptical shape, a rectangular shape, a trapezoidal shape, or an irregular shape such as a D-shape in which part of the rim is formed by straight lines as shown in Figure 2. It may also have a U-shape or H-shape, such as an aircraft control stick, in which the rim is not continuous all the way around and part of the annular shape is missing, or a rod-like shape with an end such as a non-annular I-shape. In the case of an annular steering wheel, the maximum widthwise length is generally defined as the diameter of the steering wheel, regardless of the shape.

[0020] [Durometer Hardness] The steering wheel of this embodiment satisfies the relationships of the following formulas (1) and (2): Formula (1): 0.65≦G / L≦0.95 Formula (2): 1.05≦G / R≦1.35 In other words, formula (1) represents the numerical range indicating the value of the ratio of G to L, which is equal to or greater than 0.65 and equal to or less than 0.95. In addition, formula (2) represents the numerical range indicating the value of the ratio of G to R, which is equal to or greater than 1.05 and equal to or less than 1.35.

[0021] In the above formulas (1) and (2), L, R, and G have the following meanings. L is the durometer hardness, and represents the median value obtained from ten measurements taken by contacting a Type C durometer with the surface side of a sheet of skin placed on a flat plate with a Type D durometer hardness of 80 or more. However, L is between 10 and 100. R is the durometer hardness, and represents the median value obtained from ten measurements taken by contacting a Type C durometer with the surface of a resin portion molded on the rim core. However, R is between 10 and 100. G is the durometer hardness, and represents the median value obtained from ten measurements taken by contacting a Type C durometer with the surface side of a skin covering the resin portion molded on the rim core. However, G is between 10 and 100. In L, R, and G, the "measurement" in which the Type C durometer is brought into contact with the object to be measured refers to the measurement being read immediately after the Type C durometer is brought into contact with the object to be measured. Furthermore, the "10 measurements" in the above "10 measured values" refers to (a) when the measurement locations are the same, the next measurement is taken after an interval of 30 seconds or more, or (b) the nth measurement location and the (n+1)th measurement location are taken at least 1 cm apart (n is an integer from 1 to 9), or a combination of (a) and (b).

[0022] When designing a steering wheel structure having a desired hardness measured in a static test, i.e., a Type C durometer hardness G of the steering wheel surface, it is important to combine a surface that satisfies formula (1) and a resin portion that satisfies formula (2). By satisfying both formulas (1) and (2), the desired balance of the steering wheel hardness measured in a static test and the steering wheel hardness measured in a dynamic test can be achieved. In this embodiment, the steering wheel provides a comfortable grip when gripped lightly, which can be expected to reduce fatigue during long driving operations, and also provides a solid steering feel and grip when gripped tightly and making sudden operations, such as in an emergency, and most importantly, accurate and agile response can be expected. Thus, by satisfying both formulas (1) and (2), the steering wheel can provide both comfort and a sense of security.

[0023] For example, increasing the Type C durometer hardness L of the skin tends to decrease the G / L value, while decreasing the Type C durometer hardness L of the skin tends to increase the G / L value. By utilizing this tendency and setting the Type C durometer hardness L of the skin to satisfy formula (1), it is possible to select a skin suitable for obtaining the desired steering wheel hardness G. For example, increasing the Type C durometer hardness R of the resin part tends to decrease the G / R value, while decreasing the Type C durometer hardness R of the resin part tends to increase the G / R value. By utilizing this tendency and setting the Type C durometer hardness R of the resin part to satisfy formula (2), it is possible to select a resin part suitable for obtaining the desired steering wheel hardness G. The hardness G of a steering wheel is set to a desired value by the steering wheel manufacturer depending on the type and characteristics of the vehicle in which it is installed, as well as the characteristics and preferences of the main driver. On the other hand, taking into account various grip strength levels expected of drivers, G is preferably 50 or more, more preferably 53 or more, from the viewpoint of the sense of trust felt from the steering device for operating a vehicle, which is felt through the palm of the hand when the driver is gripping the device lightly in a relaxed state. Furthermore, G is preferably 90 or less, more preferably 85 or less, from the viewpoint of preventing excessive fatigue in the arms, shoulders, etc., even when the driver is gripping the device a little tightly under some tension or when repeated steering is required for a long period of time. Furthermore, taking into account various grip strength levels expected of drivers, R is preferably 30 or more, more preferably 40 or more, from the viewpoint of providing a sufficient reaction force felt through the palm of the hand gripping and steering when a tight grip is required for sudden operation, such as during emergency avoidance, and providing a sense of security that an accurate and agile response can be expected. Furthermore, R is preferably 75 or less, more preferably 72 or less, from the viewpoint of preventing excessive fatigue during the above-mentioned tension or long-term driving. From the viewpoint of the abrasion resistance of the surface of the skin, L is preferably 55 or more, more preferably 75 or more. From the viewpoint of crack resistance of the surface of the skin, L is preferably 90 or less, and more preferably 86 or less.

[0024] The relationship between the above formulas (1) and (2) need only be satisfied on at least a portion of the surface of the rim portion having a skin, and may be satisfied on the entire surface of the rim portion having a skin. The relationship between the above formulas (1) and (2) needs to be satisfied at least in the portion gripped by the driver (grip portion), and is preferably satisfied in areas other than the grip portion. Specifically, when the shape of the rim portion of the steering wheel is circular, elliptical, or D-shaped, the relationship between the above formulas (1) and (2) needs to be satisfied (a) in the portion of the rim portion 10 shown in Figures 1 and 2 indicated by angles between 60° and 90° and between 270° and 300°, or the portion of the rim portion 10 shown by angles between 90° and 120° and between 240° and 270°, and (b) in the front portion and / or rear portion shown in Figure 3. Furthermore, in one example of a preferred embodiment, the relationship between the above formulas (1) and (2) is satisfied in part (a) other than part (b), or in part (a) other than part (b), or in part (a) other than part (b).

[0025] [Rim Core] The material that makes up the rim core is not limited as long as it does not impair the effects of the present invention, and may be an alloy or a material other than an alloy. From the perspective of strength and durability as a steering wheel, suitable materials for making up the rim core include iron, aluminum, magnesium, and alloys thereof.

[0026] [Resin Portion] The resin portion is molded onto the rim core portion. There are no limitations on the material that constitutes the resin portion as long as it satisfies the above-mentioned relational expressions (1) and (2), and known materials can be used. Specific examples of materials that constitute the resin portion include natural elastomers and synthetic elastomers. Among these, synthetic elastomers are preferred from the viewpoint of ease of selecting the durometer hardness. As synthetic elastomers, polyurethane-based elastomers, silicone-based elastomers, and fluorine-based elastomers are preferred, with ether-based polyurethane elastomers being more preferred, and porous synthetic elastomers obtained by micro-foaming these elastomers being even more preferred.

[0027] For example, a resin portion can be molded onto a rim core portion by the following procedure: A composition containing polyol, polyisocyanate, foaming agent, and crosslinking agent is mixed in a high-pressure foaming machine. Next, the composition is injected into a mold in which the rim core portion is placed, and foamed and cured to form a foamed polyurethane resin material covering the rim core portion. At this time, the durometer hardness can be adjusted to the desired value by selecting the raw material composition, such as the hydroxyl value of the polyol, the amount injected into the mold, and molding conditions, such as the temperature and time during foaming and curing.

[0028] [Surface] The surface covers at least a portion of the resin portion and is made of an artificial material. The appearance and feel of the surface may be leather-like, wood-like, figured, metallic, or the like. Furthermore, the surface may have a pattern, lettering, symbol, or the like printed or embossed on the entire surface or a portion thereof. In the case of a leather-like surface, the surface may imitate the appearance and feel of natural leather having a suede or grain finish, etc. Since these are preferred for steering wheel applications, grain finishes and semi-grain finishes in which part of the surface is not grain but exposes the base (for example, the fiber substrate layer described below) are preferred. In other words, it is preferable that the artificial material has a grain finish in which the majority of the surface is covered with a grain finish.

[0029] The artificial material is not limited as long as it satisfies the above-mentioned relational expressions (1) and (2), and known materials can be used. Among these, from the viewpoint of ease of selecting the durometer hardness, the artificial material is preferably a laminate (sheet material) including a fiber substrate layer and a resin coating layer. The thickness of the sheet material may be, for example, about 0.5 to 2.0 mm, but a range of 0.8 to 1.8 mm is preferred because it is easy to obtain a durometer hardness L within the preferred range in this embodiment.

[0030] Examples of fibrous materials constituting the fiber substrate layer include woven, knitted, or nonwoven fabrics containing one or more selected from the group consisting of synthetic fibers such as amide resins, acrylic resins, and ester resins; natural fibers such as cotton and hemp; and regenerated fibers such as rayon and cupra. However, woven fabrics lack the ability to conform to bent shapes, often resulting in the skin bending or wrinkling near the bend. Furthermore, knitted fabrics stretch more easily than woven fabrics, which means that the resin coating layer is prone to partial lifting or peeling due to differences in stretching compared to the resin coating layer. For steering wheels in which much of the exterior surface is covered with a flexible skin rather than a panel or molding to impart a sense of luxury and design, woven or knitted fiber substrate layers cannot adequately adapt to the shape of all areas covered by the skin, making them unsuitable as skins. Nonwoven fabrics are preferred because their denser structure, compared to woven or knitted fabrics, reduces anisotropy of stretch, suppresses excessive stretching, and is less likely to bend or peel or lift at the bonded portion with the resin coating layer. In addition to nonwoven fabrics, the above problems can also be reduced by selecting the appropriate knitting structure for knitted fabrics. From this perspective, warp knits such as tricot fabrics and raschel fabrics, which have a dense knitting structure that can suppress unnecessary stretching, are also preferred. In other words, warp knits are preferable to weft knits such as circular knit fabrics and rib knit fabrics, which have a loose knitting structure. The average fiber diameter of the fibrous material may be, for example, approximately 10 μm or less. From the perspectives of workability when covering the rim portion, appearance such as surface smoothness after covering, and grip comfort, which will be described later, the average fiber diameter of the fibrous material is preferably 0.1 to 6 μm.

[0031] The fiber substrate layer is preferably a resin-imparted fibrous material, and a nonwoven fabric is preferably used as the fibrous material. That is, the fiber substrate layer is preferably a resin-imparted nonwoven fabric. Nonwoven fabrics have a lower apparent density and more void space than woven or knitted fabrics, allowing for higher resin impregnation density. Resin-imparted nonwoven fabrics allow for easy adjustment of the fiber-to-resin ratio and apparent density of the fiber substrate layer. Furthermore, when used as a steering wheel cover, the resin is less likely to break or fall off within the fiber substrate layer, and the durometer hardness of the cover can be easily adjusted. Methods for obtaining resin-imparted nonwoven fabrics include, for example, impregnating nonwoven fabrics with resin and coating the backside of nonwoven fabrics with resin. The desired fiber structure of nonwoven fabrics can be designed by adjusting the apparent density and degree of entanglement, allowing for the selection of a fiber structure that allows the resin to easily penetrate into the interior. Examples of resins used in resin-imparted nonwoven fabrics include urethane resins, acrylic resins, ester resins, and vinyl chloride resins. These resins may be used alone or in combination of two or more. Furthermore, in the nonwoven fabric to which the resin is applied, the ratio of nonwoven fabric to resin [nonwoven fabric / resin] may be approximately 30 / 70 to 95 / 5 by mass. Furthermore, in order to adjust the durometer hardness, the resin is preferably a composition containing fine particles. Examples of the fine particles include metal hydroxides such as talc, magnesium silicate, calcium sulfate, aluminum silicate, calcium carbonate, magnesium oxide, magnesium carbonate, magnesium hydroxide, and aluminum hydroxide, as well as mica. One type of fine particle may be used, or two or more types may be used in combination. Furthermore, from the viewpoint of increasing the durometer hardness while imparting flexibility and appropriate extensibility to the fibrous substrate layer, the Mohs hardness of the fine particles is preferably 1.5 or more, more preferably 2 or more and 9 or less. The ratio of resin to fine particles [resin / fine particles] can be selected in the range of about 5 / 95 to 95 / 5 by mass, and in order to obtain a significant effect from the addition of fine particles, it is preferable to set it in the range of about 15 / 85 to 60 / 40.

[0032] Examples of resin materials that can be used to form the resin coating layer include urethane resin and vinyl chloride resin. Furthermore, from the perspective of ease of selecting the durometer hardness, it is preferable that the resin coating layer be non-porous or have minimal foaming. In this embodiment, the term "a state with minimal foaming" refers to a state in which, when observed cross-sectionally, foaming, if any, is present and is sparsely present, with a size of approximately half or less than the thickness of the resin coating layer. To achieve a durometer hardness L within the preferred range in this embodiment, the thickness of the resin coating layer may be, for example, approximately 0.08 to 0.5 mm. However, a range of 0.1 to 0.4 mm is preferable in terms of the balance with the laminated fiber substrate layer. It is preferable that the resin coating layer be composed of two or more layers rather than one layer. In a two-layer or more structure, the first layer, which is the outermost layer of the skin, contains a large amount of coloring agents such as pigments and water- and oil-repellent agents such as fluororesins and silicone resins, while the second and subsequent layers contain almost no coloring agents but contain large amounts of functional agents such as flame retardants and fragrances. It is also possible to simultaneously achieve sufficient adhesion to the uneven fiber substrate layer and a smooth surface, resulting in a skin that combines a high-quality appearance with high functionality. The thickness of the first layer is preferably in the range of 0.02 to 0.3 mm, and the total thickness of the second and subsequent layers is preferably in the range of 0.06 to 0.4 mm. For example, to increase the amount of functional agents, the total thickness of the second and subsequent layers can be made thicker than the first layer within the above-mentioned resin coating layer thickness range. To increase the amount of pigments and water- and oil-repellent agents, the first layer can be made thicker than the total thickness of the second and subsequent layers within the above-mentioned resin coating layer thickness range.

[0033] Methods for laminating a resin coating layer on a fiber substrate layer include, for example, directly coating the fiber substrate layer with resin, and laminating a release sheet, which transfers a surface design or texture resembling natural leather or wood grain to the surface of the resin coating layer, to the fiber substrate layer. A typical example of a release sheet is release paper. Commercially available release paper can be used. Examples of the resin coating include dry coating and wet coating. Dry coating is a resin coating in which the solvent and dispersant are volatilized from the coated resin solution or resin dispersion to solidify and dry it. Wet coating is a resin coating in which the coated resin solution is brought into contact with a coagulating liquid, which is a good solvent for the solvent in the resin solution and a poor solvent for the resin, by immersion or spraying, to solidify it, and then the remaining solvent and coagulating liquid are replaced and dried. In this embodiment, the combination of any of the above lamination methods and resin coating can be appropriately selected depending on the desired skin design. In the design and manufacture of the skin of this embodiment, a combination of either a method of preparing a resin coating layer using at least a release sheet (release paper) and then bonding it to a fiber base material layer, or dry coating is used, and these combinations are most preferred.

[0034] A surface treatment coating layer may be further provided on the surface side of the resin coating layer for the purpose of finely adjusting the feel and appearance of the surface and imparting antibacterial properties, etc. The type of surface treatment agent may be selected depending on the purpose, but a surface treatment agent that is mainly made of the same type of resin as the resin coating layer used and that contains pigments, fillers, antibacterial agents, etc. depending on the purpose is preferred. It is preferable to coat the surface of the resin coating layer directly with the surface treatment agent by a method such as gravure coating or screen coating. In particular, to obtain a uniform and smooth appearance and feel, the amount of surface treatment agent is 50 g / m2 in solid content. ２Preferably, the thickness of the surface treatment coating layer is 0.03 mm or less, or the thickness of the surface treatment coating layer is 0.03 mm or less. Furthermore, it is preferable to apply a resin coating to the back side of the fiber substrate layer, which does not have the resin coating layer, from the viewpoints of ease of work in the steering wheel manufacturing process described below and the quality of the steering wheel, such as the appearance and smoothness of the touch. The resin material and coating method are the same as those for the resin coating layer described above.

[0035] As an example of an embodiment, for example, the grain-finish artificial leather disclosed in WO 2018 / 221301 can be used as the artificial material.

[0036] The resin portion can be covered with the skin by, for example, wrapping the skin around at least a portion of the resin portion and joining the adjacent edge portions of the skin together with a sewing thread or the like. It is preferable to wrap the skin around the resin portion so that the direction in which the skin has the highest 5% tensile strength is aligned with the direction from the front to the back of the steering wheel. This not only facilitates the process from wrapping the skin around the resin portion to joining the edge portions, but also ensures that a combination of the skin and the resin portion that satisfies the formulas (1) and (2) of this embodiment ensures a stable steering wheel hardness G regardless of the measurement location. The "aligned direction" refers to an angle within a range of approximately ±15 degrees. In other words, it is preferable that the direction in which the skin has the highest 5% tensile strength is aligned with the direction from the front to the back of the steering wheel.

[0037] Furthermore, a bonding layer such as an adhesive or adhesive tape may be interposed between the resin portion and the skin, as long as it does not impair the effects of the present invention. When a bonding layer is interposed, the skin and the resin portion are not directly bonded. That is, one embodiment of the present invention also includes an embodiment in which at least a portion of the skin is not bonded to the surface of the resin portion. The adhesive or adhesive tape may be a typical adhesive or adhesive tape used in this field. The bonding layer may be provided over the entire resin portion to which the skin is bonded. However, from the viewpoints of ease of work in the skin wrapping process and the joining process of bringing together and sewing the skin edges in steering wheel manufacturing, as well as the quality of the resulting steering wheel, such as its appearance and smooth feel, it is preferable to provide the bonding layer only on a portion of the resin portion. Specifically, the bonding layer is preferably not provided on the outer periphery of the steering wheel, but only on the front side of the steering wheel, or only on the front and rear sides. It is also preferable for the bonding layer to contain a functional agent such as a flame retardant. In this case, it is preferable to widen the bonding layer depending on the amount of functional agent to be provided, and provide it over an area close to the entire surface of the resin portion. The adhesive strength does not need to be so strong that it would damage the surface or resin portion when peeled off, but from the viewpoint of ease of work, it is preferable that the adhesive peel strength per 1 cm width be 10 N or more on average. On the other hand, in order to obtain the effects of the steering wheel of this embodiment, including grip comfort, an average range of about 15 to 100 N is preferable.

[0038] [Application] The steering wheel of this embodiment is suitable for applications that require a steering device for a vehicle that has at least a structure that includes portions that the driver grips with both hands for steering. In this specification, the term "vehicle" is a general term for anything that carries or moves a driver as well as other people, objects, etc. Examples of vehicles include trains, electric trains, automobiles, ships, and airplanes.

[0039] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.

[0040] [Examples 1-4] [Comparative Examples 1-4] A resin part made of an ether-based polyurethane elastomer foam was molded around an annular rim core. The entire resin part was then covered with the following artificial material (sheet material), which is a laminate including a fiber substrate layer and a resin coating layer, to form a skin as shown in Figure 3, and a steering wheel with a diameter of 36 cm, as shown in Figure 1, was manufactured. The steering wheel diameter of 36 cm was selected from the range of 34.5 to 37.5 cm. When covering the resin part with the skin, the fiber substrate layer and the resin part were positioned so that they faced each other.

[0041] The specific configurations and manufacturing methods of the artificial materials used in the examples and comparative examples are as follows. Example 1: A fibrous substrate layer was prepared as follows. A PU solution containing fine particles (polyether-based polyurethane (PU) / fine particles [metal hydroxide, Mohs hardness 3, average particle size 3 μm]) at a mass ratio of 20 / 80 was impregnated into an ultrafine fiber nonwoven fabric made of nylon fibers with an average fiber diameter of 1.3 μm. The PU solution was then immersed in water for wet coagulation and dried to prepare a fibrous substrate layer containing polyether-based PU and fine particles embedded within the ultrafine fiber nonwoven fabric. The fibrous substrate layer had a thickness of 1.2 mm. Next, a resin coating layer was prepared and bonded to the fibrous substrate layer as follows to produce an artificial material. The resin coating layer was prepared as follows. First, a polycarbonate-polyester high-solids PU liquid (solids content 75% by mass, same below) was prepared. Next, this was coated onto a release sheet ("DN-TP (registered trademark) DE-145" release paper manufactured by Dai Nippon Printing Co., Ltd.) capable of imparting a natural leather-like appearance, and dried to form a first surface layer of 40 μm. Next, a second intermediate layer of 200 μm was similarly formed on the first layer using a flame retardant-containing polyester-based high-solid PU liquid. Furthermore, a third layer was coated on the second layer using a polyester-based PU adhesive liquid containing a flame retardant and a crosslinking agent so that the thickness of the third layer after bonding to the above-mentioned fiber substrate layer would be 80 μm. In this way, a resin coating layer consisting of three layers was prepared. After semi-drying, the third layer was bonded to the above-mentioned fiber substrate layer and bonded by sufficient crosslinking with a crosslinking agent at 60°C. Thereafter, the release sheet (release paper) was peeled off. Finally, a polycarbonate-polyester-based PU aqueous dispersion was applied to the obtained laminate at a solid content of 50 g / m ２ The resulting material was gravure coated to a thickness of 100 μm, and then dried. This resulted in the formation of a polycarbonate-polyester PU surface treatment coating layer on the surface (first layer) that had been given a natural leather appearance. In this way, an artificial material was produced.

[0042] Example 2, Comparative Example 4 An artificial material similar to that of Example 1 was produced, except that the polycarbonate-polyester PU surface treatment coating layer was not provided on the resin coating layer.

[0043] Example 3, Comparative Example 2, Comparative Example 3: The same fibrous substrate layer as in Example 1 (but without fine particles) was used. The resin coating layer was prepared as follows: First, a polycarbonate-polyester PU solution was prepared. This solution was then coated onto a release sheet (the aforementioned release paper manufactured by Dai Nippon Printing Co., Ltd.) and dried to form a first surface layer of 20 μm. Next, a second layer was coated on top of the first layer with a polyester-based PU adhesive solution containing a crosslinking agent, so that the thickness of the second layer after bonding to the fibrous substrate layer was 60 μm. In this way, a two-layer resin coating layer was prepared. After semi-drying, the second layer was bonded to the fibrous substrate layer and thoroughly crosslinked with the crosslinking agent at 60°C to achieve adhesion. The release sheet (release paper) was then peeled off. Finally, a polycarbonate-polyester PU surface treatment coating layer identical to that in Example 1 was applied to the surface (first layer) to which the natural leather-like appearance had been imparted. In this way, an artificial material was produced.

[0044] Example 4 An artificial material similar to that of Example 1 was manufactured, except that the thickness of the high-solid coating portion of the resin coating layer was changed (170 μm for the surface layer of the first layer, and 100 μm for the layer after bonding with the third fiber substrate layer).

[0045] Comparative Example 1: The fibrous substrate layer was prepared by impregnating an ultrafine fiber nonwoven fabric similar to that used in Example 1 with the same polyether-based PU solution (but without fine particles) as in Example 1, then coating one side of the ultrafine fiber nonwoven fabric with the same polyether-based PU solution (but without fine particles) as in Example 1, wet coagulating, and drying. The fibrous substrate layer was 1.1 mm thick, with the polyether-based PU applied to the interior of the ultrafine fiber nonwoven fabric, and the wet coating layer on the surface of the ultrafine fiber nonwoven fabric was 30 μm. The resin coating layer was prepared as follows: First, a polycarbonate-polyester PU solution was prepared. Next, this solution was coated onto a release sheet (the aforementioned release paper manufactured by Dai Nippon Printing Co., Ltd.) capable of imparting a natural leather-like appearance, and the solution was immersed in water to wet coagulate and dry, forming a first skin layer (80 μm thick). Next, a second layer was coated on the first layer with the same flame retardant and crosslinking agent-containing polyester-based PU adhesive solution used for the third layer in Example 1, so that the thickness of the second layer after lamination with the fiber substrate layer was 30 μm. In this way, a two-layer resin coating layer was prepared. After semi-drying, the second layer was laminated to the wet-coated surface of the fiber substrate layer, and sufficient crosslinking with the crosslinking agent was carried out at 60°C to achieve adhesion. The release sheet (release paper) was then peeled off. Finally, a polycarbonate-polyester-based PU surface treatment coating layer identical to Example 1 was applied to the surface of the resin coating layer (the side that had been in contact with the release paper) after the release sheet (release paper) was peeled off. In this way, an artificial material was produced. The artificial material used in Comparative Example 1 had significantly worse abrasion resistance (JIS K 7204-1999 Taber abrasion test, load 4.9 N, abrasion wheel H22) than Example 1.

[0046] The resin parts constituting the steering wheels obtained in each of the examples and comparative examples were used after adjusting the Type C durometer hardness (Asker C hardness) to the R values ​​shown in Table 1.

[0047] [Type C Durometer Hardness (Asker C Hardness)] The Type C Durometer hardnesses L, R, and G were measured in accordance with JIS K 7312-1996 by the following measurement method. Measurements of R and G were made at any location in the grip portion of the steering wheel, i.e., in the ranges of 60° to 120° (hereinafter referred to as "right") and 240° to 300° (hereinafter referred to as "left") shown in Fig. 1, and in the front portion covered with the skin in the range of 45° to 135° shown in Fig. 3.

[0048] <G> For the steering wheels manufactured in each example and comparative example, a Type C durometer was first contacted with an arbitrary location on the grip portion (both left and right locations) and measurements were taken 10 times, five times on each side. This measurement method involved measuring the same location at least 30 seconds after the previous measurement. <L> Next, the skin (both left and right locations) including the G measurement location was peeled off. For each peeled skin, L was measured near the G measurement location. To measure L, one skin was spread face-up on a smooth flat plate with a Type D durometer hardness of 85. After 5 minutes or more had passed since the G measurement, a Type C durometer was contacted near the G measurement location, and measurements were taken 10 times, five times on each side. The measurement method was the same as above. <R> Finally, R was measured on the surface of the resin portion after the skin was peeled off near the G measurement location. The R measurement was performed 5 minutes or more after the G measurement, by contacting a Type C durometer with the area corresponding to the G measurement point, and measuring 5 times on each side, for a total of 10 times. The measurement method was the same as above. The median value of the 10 measurements, 5 times on each side, was used for the G, L, and R measurements.

[0049] [Evaluation] The steering wheels obtained in the examples and comparative examples were gripped with both hands in the ranges of 60° to 120° and 240° to 300° (grip portions) shown in Figure 1, and the grip comfort, steering feel, and overall evaluation of these were evaluated according to the following evaluation criteria. The evaluation of grip comfort and steering feel was performed by using the median score of the evaluations of 13 panelists in their 30s to 50s who were accustomed to driving automobiles. The overall evaluation value was the sum of the scores for grip comfort and steering feel. <Grip Comfort> The grip comfort was defined as "the hardness felt in the palms of the hands when lightly gripping the grip portion with both hands." 5: Feels clearly soft, and the palms sink in significantly. 4: No rubber-like rebound is felt, and the palms sink in clearly. 3: No rubber-like rebound is felt, and an extremely slight rebound is felt. 2: A strong rebound like tire rubber is felt. 1: Feels hard like wood. <Steering Feel> In preparation for the evaluation, a steering wheel was set up. Specifically, the steering wheel was attached to a steering shaft that generates torque solely through friction, and the torque required to rotate the steering wheel was set to 27.7 N ± 0.3 N. The steering feel was defined as "when the driver placed both hands lightly on the grip and quickly grasped the wheel, turning the steering wheel from the neutral position to a steering angle of 30°, alternating left and right three times at 0.20 to 0.35 Hz, the steering feel was measured as the overall response, including the reaction force felt in the palm of the hand and the grip feel." 3: The driver felt an extremely responsive reaction to the steering operation, and a very solid response. 2: The driver felt a responsive reaction to the steering operation, and a solid response. 1: The driver felt a delay in response to the steering operation and an unreliable response.

[0050]

[0051] The steering wheel of the example satisfies the relationship of formula (1) and formula (2), and the overall evaluation of grip comfort and steering feel was 5 or higher. On the other hand, the steering wheel of the comparative example did not satisfy the relationship of both or either of formula (1) and formula (2), and the overall evaluation of grip comfort and steering feel was 4 or lower. Therefore, it can be seen that the steering wheel of this embodiment, by satisfying the relationship of formula (1) and formula (2), provides a gentle grip when gripped lightly and a firm steering feel when gripped firmly.

[0052] Even if the diameter of the steering wheel is changed within the range of 34.5 to 37.5 cm, or if the shape of the steering wheel is changed to an oval shape or a D-shape, the grip portion will be positioned in the same manner as the steering wheels of the above-mentioned examples, so it can naturally be expected that evaluation results similar to those of the above-mentioned examples will be obtained.

[0053] When covering the resin part with the skin, even if the area covered by the skin is changed so that it is limited to the grip part rather than the entire resin part, it can be naturally expected that evaluation results similar to those of the above-mentioned examples will be obtained, since the parts that are not gripped do not affect the gripping comfort or steering feel.

[0054] The steering wheel of this embodiment can be used as a steering device for vehicles such as trains, electric trains, automobiles, ships, and aircraft, and can be used for applications that require a structure that has at least a portion that the driver can grip with both hands for steering.

[0055] 1: Steering wheel 2: Rim part 10: Rim part 11: Pad part 12: Spoke part 20: Rim core part 30: Resin part 40: Cover

Claims

1. Rim core, A resin portion molded on the rim core portion; and a skin covering at least a part of a surface of the resin part; The skin is made of an artificial material, A steering wheel that satisfies the relationships of the following formulas (1) and (2). Formula (1): 0.65≦G / L≦0.95 Formula (2): 1.05≦G / R≦1.35 The L is a durometer hardness, and is a median value obtained from ten measured values ​​obtained by contacting a type C durometer with the surface side of one of the skins placed on a flat plate having a type D durometer hardness of 80 or more, where L is 10 or more and 100 or less. The R is a durometer hardness, which is measured by contacting a type C durometer with the surface of the resin portion molded on the rim core and represents the median value obtained from ten measured values, where R is 10 or more and 100 or less. The G is a durometer hardness, and is measured by contacting a type C durometer with the surface side of the skin in a state in which the surface of the resin part molded on the rim core is covered, and represents the median value obtained from ten measured values, where G is 10 or more and 100 or less.

2. 2. The steering wheel according to claim 1, wherein the G is equal to or greater than 50 and equal to or less than 90.

3. 3. The steering wheel according to claim 1, wherein the radius R is 75 or less.

4. 3. The steering wheel according to claim 1, wherein L is 90 or less.

5. 3. The steering wheel according to claim 1, wherein L is 75 or more.

6. 3. A steering wheel as claimed in claim 1 or 2, wherein the artificial material is grained.

7. 3. The steering wheel according to claim 1, wherein the artificial material is a laminate including a fiber substrate layer and a resin coating layer.

8. 8. The steering wheel of claim 7, wherein the textile substrate layer is a resin-loaded nonwoven fabric.

9. 3. The steering wheel according to claim 1, wherein at least a part of the skin is not bonded to a surface of the resin portion.