METHOD AND APPARATUS FOR MANUFACTURING STEERING WHEEL

Abstract: A method and apparatus for manufacturing a steering wheel, in particular, a rim portion, in which, firstly, a sleeve-shaped braided sleeve (21) is formed by a general-purpose braiding machine (12) by interlacing and braiding unidirectional fiber (10). Then, a coil-shaped lightweight core material (9) is inserted by a covering apparatus (14) successively into the braided sleeve, both ends of the braided double-woven belt having a required length for the rim are fastened tightly to the lightweight core material, and the lightweight core material of the required length covered with the braided sleeve is cut out from the remainder. Both ends of the cut-out portion are butted to form a ring-shaped rim (1), and after being joined with a spoke (2), the joined rim and spoke are placed in a metal mold (31), and an outer molded layer (15; 17) is formed by injecting a thermosetting resin (11) into the metal mold and curing by heating.

Description: SPECIFICATION TITLE OF THE INVENTION METHOD AND APPARATUS FOR MANUFACTURING STEERING WHEEL TECHNICAL FIELD The present invention relates to a novel method and apparatus for manufacturing a steering wheel, in particular, its rim portion. BACKGROUND ART . . . In general, a steering wheel for an automobile has a structure as shown in FIGS. 1 and 2, in which FIG. 1 is a side view of the steering wheel secured to a steering shaft, and FIG. 2 is a front view thereof. In FIGS. 1 and 2, reference numeral 1 designates a ring-shaped rim forming a grip for the driver, 2 designates a spoke fixed to the inside of the rim 1, and 3 designates a boss fixed to the spoke 2 at the center of the rim 1, and the boss 3 serves as a mounting portion to a steering shaft 4. In the steering wheel configured as mentioned above, it has been usual to form not only a core material of the rim 1 but the spoke 2 and boss 3 from metal such as a carbon steel or the like, weld the core material of the rim 1 to the spoke 2 and the spoke 2 to the boss 3, and mold the outer layer of the rim 1 with rubber or resin. As described in the foregoing, since most part of the steering wheel is formed from metal and even the lightest one has a weight of 2 Kg, vibrations are caused in the steering wheel, in particular-, when the automobile is running at high speeds. Thus, the drawbacks are involved in that the stability of the steering is degraded and the discomfort is caused to the driver. Accordingly, as a method ' for reducing the weight of the steering wheel without impairing the rigidity and for improving the vibration characteristic, the applicant of the present application proposed in Japanese Patent Laid-Open Publication No. 60-222236 (1985) as to a manufacturing method for a steering wheel which is made lightweight and which is formed from fiber reinforced plastic. FIGS. 3 to 8 show this proposed manufacturing method for a steering wheel, in which FIG. 3 is a front view of the steering wheel, FIG. 4 is a sectional view taken along the line XII - XII in FIG. 3, FIG. 5 is a sectional view taken along the line XIII - XIII in FIG. 3, and FIG. 6 is a perspective view of a coil-shaped lightweight core material for producing the rim continuously, FIG. 7 is a partially enlarged view showing a connecting condition at butting ends of a ring-shaped portion of a predetermined length cut from the coil-shaped core material of FIG. 6, and FIG. 8 is a sectional view taken along the line XVI - XVI in FIG. 3. In the FIGURES, reference numeral 1 designates a rim having a diameter of about 2 cm, and the rim 1 is manufactured in the following manner. A prepreg 5 cured lightly after _impregnating unidirectional f.iber consisting of a ' sole or composite body of carbon fiber, glass fiber, or ara id fiber is wound around a coil- shaped lightweight core material 9 of foamed urethan foam, and the coil-shaped lightweight core material 9 having the prepreg 5 would thereon is cut in a predeter¬ mined length of a ring shape at a connecting portion with a spoke 2. Both ends of the cut-out portion from the remainder are butted, and an outer molded layer 6 is formed surrounding the prepreg 5 by molding a rubber or resin. The diameter of the rim 1 is reduced at the two connecting portions with the spoke 2. Reference numeral 7 designates a slip-preventing portion having an undulate shape formed on the outer molded layer 6. The spoke 2 is made of metal, and is connected to the rim 1 such that one end of the spoke 2 is in contact with the prepreg 5 wound around the coil-shaped light¬ -weight core material 9 at the diameter reduced connect¬ ing portion of the rim 1, and in contact with a joining piece 42 and a U-shaped thin metal sheet 41, and the one end of the spoke 2 is wrapped in a prepreg 5 or a cloth prepreg (not shown) and cured by heating to achieve the connection. The prior art steering wheel is configured as described above, -and it is manufactured in a manufacturing process in which the prepreg unidirectional fiber 5 is wound around the coil-shaped lightweight core material 9 at a constant angle between 10 and 60° by a winding machine, and then, the prepreg unidirectional fiber 5 is further wound at a constant angle between -10 and -60° so that it intersects the previously wound prepreg unidirectional fiber 5 thereby to form a coil-shaped laminated body, and this coil-shaped laminated body is cut to have a length required for the rim 1, and the cut ends of the rim portion are joined to each other to form a joining portion 30 as shown in FIG. 7, and following this, as shown in FIG. 8, it is connected to the spoke 2, wrapped in a prepreg 5, cured by heating, and then, it is placed in a metal mold for molding and the outer molded layer 6 of rubber or resin is formed. In the manufacturing method as described in the foregoing, since it includes the process of winding the prepreg around the coil-shaped lightweight core material 9, an expensive winding machine is required, which performs complicated motions to move along a coil-shaped path while rotating about the coil- shaped lightweight core material 9, and thus the costs are increased. Furthermore, in order that the winding machine moves along the coil-shaped path while rotating " about the coil-shaped lightweight core material 9, a pitch of the coil-shaped lightweight core material 9 is required to be in a range from about 30 to 40 cm, and thus, the winding machine must be large in size. Further, after the winding, curing by heating, and laminating, both ends of the laminated core material are fastened and fixed by a string or the like, and is cut to have a required length for the rim 1. However, in this case, at the time of forming the cut-out portion in the ring- shape, since it is pressed until it becomes flattened, when the pitch is large, the prepreg 5 will be loosened and delaminated, and torsion will be caused in the prepreg 5 resulting in irregular alignment of the fiber. Moreover, since the fiber impregnated with resin is exposed to the outwide at the surface of the outer layer as a result of the process for curing by heating, and laminating the prepreg 5, when the driver grips the steering wheel, the hurt and discomfort will be caused due to projections of the fiber. And, thus, in order to eliminate such discomfort, and also to form the undulation which serves as the slip preventing portion 7, the process for forming the outer- molded layer 6 is needed additionally, and this gives rise to a problem in that the cost of equipment and the number of processes are increased. A manufacturing method and apparatus for a steering wheel in accordance with the present invention was made to solve the problems as mentioned above, and it is an object of the present invention to provide a manufacturing method and apparatus in which the prepreg 5 can be wound around the coil-shaped light¬ weight core material 9 and can be laminated by heating and pressing by a simple apparatus and process, and in which the outer molded layer 6 is not required to be formed in a separate process. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: FIG. 1 is a side view of a steering wheel showing the fixing thereof; FIG. 2 is a front view of the steering wheel of FIG. 1; FIG. 3 is a front view of a prior art steering wheel; FIG. 4 is a sectional view taken along the line IV - IV in FIG. 3; FIG. 5 -is a sectional view taken along the lime V - V in FIG. 3; FIG. 6 is a perspective view showing a coil- shaped laminated body; FIG. 7 is a partially enlarged view showing a connecting condition at butting ends of a ring-shaped portion having a predetermined length cut from the coil-shaped laminated body of FIG. 6; FIG. 8 is a sectional view taken along the line VIII - VIII in FIG. 3; FIGS. 9 to 16 show an embodiment of the present invention in which; FIG. 9 is a front view of a steering wheel; FIG. 10 is a sectional view taken along the line X - X in FIG. 9; FIG. 11 is a sectional view taken along the line XI - XI in FIG. 9; FIG. 12 is a front view illustrating a braiding and covering process; FIG. 13 is a plane view of FIG. 12; FIG. 14 is a front view showing a joining condition of a rim and a spoke; FIG. 15 is a perspective view illustrating a resin injection and heating process; FIG. 16 is a view showing the steering wheel within the metal mold of FIG. 15 as viewed from . above by cutting the metal mold at the boundary between an upper mold and a lower mold; FIG. 17 is a front view illustrating a manufacturing method for a steering wheel of a second embodiment in accordance with the present invention; FIG. 18 is a front view of the steering wheel manufactured in the second embodiment; FIG. 19 is a sectional view taken along the line A - A in FIG. 18; FIG. 20 is a sectional view taken along the line B - B in FIG. 18; FIGS. 21 to 23 show another embodiment of the present invention, in which; FIG. 21 is a sectional view of a rim portion; FIG. 22 is an enlarged view of the B portion in FIG. 21; and FIG. 23 is a view illustrating a manufacturing method of the steering wheel shown in FIG. 21. DISCLOSURE OF THE INVENTION In a manufacturing method of a steering wheel • in accordance with the present invention, first, unidirectional fiber is interlaced' and braided by a general-purpose braiding machine to form a braided double-woven belt of a sleeve shape. Then, a coil-shaped lightweight core material is continuously inserted into the sleeve-shaped braided double-woven belt, and it is cut in a length required for a rim after fastening and fixing both ends of the braided double-woven belt having the required length to the lightweight core. Following this, a spoke and the rim portion are joined by wrapping them in a braided double-woven belt of unidirectional fiber formed separately, or in a cloth, and then, the integrally joined rim and spoke are placed in a metal mold. The inside of the metal mold is made vacuum, and the mold is heated, and a fluid thermosetting resin which has been sufficiently dehydrated is injected and is cured. By employing such a manufacturing method, a complicated, expensive winding machine is dispensed with, and an outer layer molding can be achieved at the same time. BEST MODE OF CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIGS. 9 to 16 show an embodiment of a manufacturing method of a steering wheel in accordance with the present invention, in which, FIG. 9 is a front view of the steering wheel manufactured in this embodiment, FIG. 10 is a sectional view taken along the line II - II in FIG. 9, FIG. 11 is a sectional view taken along the line III - III in FIG. 9, FIG. 12 is a front view illustrating a process for braiding by a general-purpose braiding machine and for continuously inserting a lightweight core material by a covering apparatus, FIG. 13 is a plane view illustrating the process in FIG. 12, FIG. 14 is a front view showing a joined condition of a rim and a spoke, FIG. 15 is a perspective view showing a condition in which the rim and the spoke integrally joined are placed in a metal mold which is injected with a liquid thermosetting resin, and FIG. 16 is a plane view of the rim and the spoke in the metal mold viewed from above by cutting the metal mold horizontally at the boundary between the upper mold and the lower mold. In FIGS. 9 to 14, reference numerals 1 to 7 and 9 designate identical or equivalent parts to those in the prior art described in the foregoing, and an explanation thereof is omitted. Reference numeral 10 designates unidirectional fiber consisting of a sole or composite body of carbon fiber, glass fiber, or ara id fiber, which is interlaced and braided by a general-purpose br ' aiding machine 12 and which is made to cover a coil-shaped lightweight core material 9 by a covering apparatus 14. Reference numeral 42 designates a joining piece formed of a braided double- woven belt of unidirectional fiber or a cloth for joining the spoke 2 and the rim 1. Numeral 11 designates a thermosetting resin which is liquid before being cured by heating and composed of at least one of epoxy, polyester, binyl ester, and acryl, and the unidirectional fiber 10 and joining piece 42 are impregnated with the thermosetting resin 11, and also an outer layer is formed of this thermosetting resin 11. The general-purpose braiding machine 12 manufactures braided products such as a rubber string, electric wire, hose, etc., and is known in the art, for example, Composite Materials Handbook authored by Melm Schwartz, P4.97 - 4.101. The braiding machine 12 is structured to include a number of braid driving gears 18 disposed between a lower plate 16 and an upper plate 17, and guide channels (not shown) provided on a disk along the periphery thereof and having a shape of two sine curves intersecting each other with a phase difference of 180°. The gears 18 engage further gears (not shown) provided on a base portion so that a plurality of sets-of bobbins 19a, 19b are moved along the guide channels, wherein the bobbins 19a and 19b, driven by the gears 18, move respectively in opposite directions while crossing over alternately along the guide channels such that the bobbin 19a rotates and moves in a direction of A (FIG. 12) whereas the bobbin 19b rotates and moves in a direction of B (FIG. 12) . As a result, unidirectional fibers 10a and 10b respectively delivered from the bobbins 19a and 19b are braided at a former 20, and a braided sleeve 21 is continuously formed. Further, reference numeral 14 designates a covering apparatus which cooperates with the braiding machine 12, and the coil-shaped lightweight core material 9 is held by a holding fitting 22 so that one end of the lightweight core material 9 is positioned opposing to the former 20. Numeral 23 designates a feed rod disposed at the center of the coil-shaped lightweight core material 9, and numeral 24 designates a guide fitting attached to the feed rod 23 by means of an arm 25, and one end of the arm 25 is secured to the feed rod 23 so that the guide fitting 24 moves in a direction C in FIG. 12 along the coil-shaped lightweight core material 9 'in order to cover the braided sleeve 21 surrounding the coil-shaped lightweight core material 9. Numeral 26 designates a clamp for fixing the front end of the braided sleeve 21 to the guide fitting 24. FIG. 13 shows the covering apparatus 14 in FIG. 12 in more detail, and reference numeral 27 designates a bearing for supporting one end of the feed rod 23, and numeral 28 designates a threaded portion formed on the feed rod 23 at the opposite side of the bearing 27 and having a same pitch as that of the coil-shaped light¬ weight core material 9. Numeral 29 designates a threaded bearing which engages the threaded portion of the feed rod 23, and numeral 30 designates a motor for imparting mechanical power to the feed rod 23 in synchronism with the braiding machine. Further, in FIGS. 15 and 16, reference numeral 31 designates an injection mold consisting of an upper mold 32 and a lower mold 33. Numeral 34 designates a cavity formed in the upper mold 32 and the lower mold 33 for enclosing the rim 1 and the spoke 2 covered with the unidirectional fiber 10, and an evacuating port 35 for drawing a vacuum, and an injec¬ tion port 36 for injecting a thermosetting i esin 11 are provided. Numerals 37a and 37b designate packings for sealing the cavity 34 air.tightly and for preventing . l ak in drawing a vacuum. The steering wheel is manufactured by using the aforementioned machine, apparatus and jigs in a manner as will be described hereinafter. First, the coil-shaped lightweight core material 9 is manufactured, and then a coil-shaped laminated body having the unidirectional fiber 10 orientated is manufactured. More specifically, first, the braid driving gears 18 of the braiding machine 12 are driven, and the unidirec¬ tional fibers 10a and 10b delivered from the bobbins 19a and 19b are braided at the former 20, and the braided sleeve 21 is continuously formed so that the unidirectional fibers 10a and 10b cross each other extending respectively at orientation angles between 10 and 45° in opposite directions with respect to the longer direction of the braided sleeve 21. The orientation angles are determined depending on a circumferential length of the braided sleeve 21, a size and the number of the unidirectional fibers 10a and 10b to be used. Next, in the covering apparatus 14, the front end of the braided sleeve 21 is secured by the guide fitting 24, the coil-shaped lightweight core material 9 is inserted into the braided sleeve- 21, the feed rod 23 is driven by the motor 30, the arm 25 attached to the feed rod 23 is turned, and the guide fitting 24 is moved along the coil-shaped lightweight core material 9 at a circumferential speed of the braided sleeve 21 so that the braided • sleeve belt 21 is advanced in a direction of C in FIG. 12 to cover surrounding the coil- shaped lightweight core material 9. The coil-shaped lightweight core material 9 covered with the braided sleeve 21 is cut at a connecting portion with the spoke 2 so that the cut-out portion from the remaining coil- shaped lightweight core material 9 has a ring shape and a required length. Both ends of the cut-out portion are butted to form the ring shape. Then, in a similar manner as shown in FIG. 8 with respect to the prior art, the connecting portion of the rim 1 to the spoke 2 together with a U-shaped thin metal sheet 41 are wrapped in a joining piece 42 of a braided sleeve of unidirectional fiber produced separately, or of a cloth. In this case, the cutting portion of the coil- shaped lightweight core material 9 is made to be wrapped in one of joining pieces 42. Following this, the joined rim 1 and spoke 2 are set in the cavity 34 of the lower mold 33 of the injection mold 31, and after closing the cavity 34 with the upper mold 32, the cavity is sealed with the packing 37 to render airtight condition, and a vacuum is drawn from the evacuating port 35. Next, the liquid thermosetting resin 11 deaerated sufficiently before¬ hand is injected and cured by heating so that the unidirectional fiber 10 is impregnated with the thermo¬ setting resin 11 and a thin outer molded layer 11 is formed at the outer layer portion. Since the outer m lded layer is void-free, the rim portion with a superior appearance can be formed. Moreover, a further outer molded layer of a material providing smooth feeling such as rubber, foamed plastic, or the like may be molded on a part or all of the rim over the outer surface of the aforementioned outer molded layer 11 which is made to be now an inner molded layer. As a ' result of this, a steering wheel providing soft touch feeling can beObtained. As described in the foregoing, according to the manufacturing method of the present invention, a braided sleeve formed by braiding unidirectional fiber in a sleeve shape covers continuously around a coil-shaped lightweight core material having a small pitch by using a general-purpose braiding machine and a simple covering -apparatus, and a rim is produced by cutting -the core material covered with the unidirectional ' fiber to obtain a required length, and by forming the cut-out portion of the core material in a ring shape. Accordingly, the productivity is high, and since only a slight twist is caused in the core material, the rim having no delamination and slack of the unidirectional fiber, and having no irreguralities in the orientation of the fiber can be manufactured. Further, in the next process, the formation of an outer ' molded layer by injection and heating of a resin, and the impregnation of the unidirectional fiber with the resin and curing thereof can be carried out by lumping together in the same process, and thus, the number of processes can be reduced advantageously. FIGS. 17 to 20 illustrate another embodiment of this invention wherein a steering wheel which is tough against bending and torsion is realized. More specifically, as shown in FIGS. 9 to 16, when it is planed to improve the strength of the rim by braiding unidirectional fiber 10 around a coil-shaped lightweight core material 9 by a braiding machine, such a plan is normally attained by increasing the number of unidirectional " fibers 10 or by increasing the size of the unidirectional fiber..10. However, there arise -the following problems: (1) When unidirectional fiber 10 having a large size, or increased number of unidirectional fibers 10 are used unreasonably for a rim which is required, in particular, to be bent and twisted, rubbing of the fibers is caused during braiding. As a result, the strength is reduced, and the impregnation with an injected liquid thermosetting resin becomes difficult, and sometimes unimpregnated portions remain. Thus, such a braid involves serious defects as a composite material. (2) Against the bending, it is advantageous to braid the fiber at an orientation angle of nearly 0° with respect to a longer direction, and against the torsion, an orientation angle of 45° is advantageous. Accordingly, it is impossible to manufacture a steering wheel which satisfies the required strength against both bending and torsion by merely braiding one kind of fiber in a single layer at one orientation angle. The second embodiment was made to solve the problems mentioned above, and it is designed to obtain a steering wheel which is strong against the bending and..torsion by covering in two? outer and inner layers, around a coil-shaped lightweight core material with a braided double-woven belt formed by braiding unidirectional fiber in a sleeve shape. FIG. 17 illustrates a manufacturing method of the steering wheel in the second embodiment, FIG. 18 is a front view of the steering wheel manufactured in this embodiment, FIG. 19 is a sectional view taken along the line A - A in FIG. 18, and FIG. 20 is a sectional view taken along the line B - B in FIG. 18. In the FIGURES, reference numerals 1 to 4, 6, 7, 9 to 26, 30, 31 and 32 designate parts and members described in connection with the prior art, and thus, descriptions thereof are omitted, In the FIGURES, reference numeral 27 designates a lower plate located at the bottom portion of a braiding machine 12, and constitutes a part of the braiding machine 12. Between the lower plate 27 and an upper plate 28 which is paired with the lower plate 27, there are provided with a number of braid driving gears 18, and on the upper plate 28, there are provided with bobbins 19a' and 19b' which are movable respectively along two sine-curve shaped channels (not shown) inter¬ secting each other with a phase difference of 180° and formed along the periphery on a disk. Unidirectional fibers 10. are dilivered from these bobbins 19a' and 19b 1 , and a first braided sleeve 21a is produced in which respective angles (orientation angles) of the unidirectional fibers 10 with respect to a perpen¬ dicular direction are +10° and -10°. Also, in this embodiment, a further delivery section of unidirectional fibers 10a and 10b comprised of a lower plate 16 having a hole at the center thereof for passing the uni¬ directional fibers therethrough, an upper plate 17, driving gears 18, and bobbins 19a, 19b is positioned above the delivery section of unidirectional fibers 10 comprised of the aforementioned upper plate 28, lower plate 27, driving gears 18, and bobbins 19a', 19b' so that the center of the further delivery section is aligned with a coil-shaped lightweight core material 9. Reference numeral 21b designates a second braided sleeve produced by braiding the unidirectional fibers 10a and 10b extending from the bobbins 19a and 19b to a former 20 whose position being shifted in the upward direction, and the second braided sleeve 21b is formed outside and surrounding the first braided sleeve 21a, and is braided with orientation angles of +45° and -45° respectively for the unidirectional fibers 10a and 10b. The steering wheel is manufactured by the apparatus described above in the following manner. First, the coil-shaped lightweight core material 9 is manufactured, and then, a coil-shaped laminated body having unidirectional fiber 10 orientated is manu¬ factured as will be described below. Firstly, the unidirectional fibers 10, for example, glass fibers extending at the orientation angles +10° and -10° toward the coil-shaped light¬ weight core material 9 from the delivery section of the unidirectional fibers 10 comprised of the series of gears 18 and bobbins l9a' , 19b' and located at the lower portion of the braiding machine 12 are braided, and the first braided sleeve 21a is produced. Then, the unidirectional fibers 10a and 10b, for example, carbon fibers extending from the delivery section located above the aforementioned delivery section and comprised of the driving gears 18 and bobbins 19a, 19b are braided at orientation angles of +40° and -40° surrounding the first braided sleeve 21a, and the second braided double-woven belt 21b is produced, and thus, at the former 20, the first and second braided sleeve 21a and 21b formed in two layers are continuously manufactured. In this respect, the first and second braided double-woven fibers 21a and 21b may be formed with the same kind of unidirectional fibers.- However, as described in the foregoing, when the glass fiber which is particularly inexpensive is used in the inner layer, and the carbon fiber which has high strength and which is light is used in the outer layer, a steering wheel which is strong against the bending and torsion, and which is lightweight can be obtained. Next, in a covering apparatus 14, the front ends of the first and second braided sleeves 21a and 21b are secured by a guide fitting 24, and the coil- shaped lightweight core material 9 is inserted into the first and second braided sleeves 21a and 21b. Then, by turning the guide fitting 24, the first and second braided sleeves 21a and 21b are advanced in a direction of C in FIG. 17 so as to cover surrounding the coil-shaped lightweight material 9. Then, the coil-shaped lightweight core material 9 covered with the first and second braided sleeves 21a and 21b is cut at a connecting portion with a spoke 2 so that the cut-out portion from the coil-shaped lightweight core material 9 has a ring shape and a required length. Both ends of the cut-out portion is butted to form the ring shape. Then, in a similar manner as shown in FIG. 8 with respect to the prior art, a U-shaped thin metal sheet 41 is butted against the rim portion and- is wrapped in a joining pie'ce 42 of a braided sleeve of unidirectional fiber to form an integral structure. Then, this integral structure is placed in a metal mold (not shown) , and a liquid thermosetting resin 11 is injected, impregnating the braided sleeves with the resin, and cured by heating. In this manner, the steering wheel strengthened against being and torsion, and having a thin outer molded layer 11 at the outer layer portion, and having two layers of the braided sleeves 21a and 21b braided at two different angles is manufactured. In the present invention, besides the first and second embodiments described in the foregoing, various modified embodiments are further considered. First, as described in connection with the prior art apparatus, in the prior art steering wheel, primarily, in order to insure the required strength, the carbon steel is used in the core material of the rim 1, spoke 2, and boss 3. As a result, in winter, especially, in a cold district, portions of the core material of the rim 1, spoke 2, etc., formed of the carbon steel are cooled, and consequently, the steering wheel is at a low temperature. Thus, when the driver touches the steering wheel at the.start of driving or- getting into the vehicle from the outside, his fingers will be cooled and driving feelings will become dull. Such a situation poses a problem in that rapid steeeing in a critical moment will be disturbed and a serious accident cannot be dentied to be caused. FIGS. 21 and 23 show another embodiment of a steering wheel in which a braided sleeve including a heating wire is used surrounding a core material of a rim, and by energizing the heating wire to warm the braided sleeve, the driver will feel warm when he touches the steering wheel with his fingers. Specifically, FIG. 21 is a sectional view of the rim portion corresponding to FIG. 19, FIG. 22 is an enlarged view of a B portion in FIG. 21, and FIG. 23 shows a braiding machine. In FIGURES, reference numeral 9 designates a coil-shaped lightweight core material formed of foamed ure hane or the like, numeral 10 designates unidirectional fiber consisting of a sole or composite body of carbon fiber, glass fiber, or ara id fiber, and numeral 13 designates a heating wire having a nichrome wire 13a covered around thereof with electrically insulating unidirectional fiber such as the glass fiber or the like. Reference numeral 21 designates a braided sleeve formed by braiding the unidirectional fiber 10 and the heating wire 13 covered with glass fiber, and it covers sur¬ rounding the coil-shaped lightweight core material 9 constituting a rim 1. The coil-shaped lightweight core material 9 covered with the sleeve 21 is produced by a braiding machine 12 and a covering apparatus 14 as will be described later. In FIG. 23, like numerals refer to like parts in FIG. 12, and descriptions of these parts are omitted, Reference numerals 19a and 19b designate bobbins movable respectively in opposite directions of A and B while crossing over alternately along two sine-curve shaped guide channels (not shown) intersecting with a phase difference of 180° and formed along the periphery on the circumference of an upper plate 17. The unidirectional fibers 10a and 10b are set on the bobbins 19a and 19b. Reference numerals 23a and 23b designate bobbins also mounted on the upper plate 17 and movable respectively in the opposite directions of A and B, and the heating wires 13a and 13b covered with glass fibers are set on the bobbins 23a and 23b. Reference numeral 20 designates a former in which the unidirectional fibers 10a, 10b and the heating wires 13a, 13b covered with glass fibers are braided to form the braided sleeve belt " 21. Further, the covering apparatus 14 is comprised of a feed rod 23 located at the center of the coil-shaped lightweight core material 9, a guide fitting 24 attached to the feed rod 23 through an arm 25, and a clamp 26 for securing the front end of the braided sleeve 21 to the guide fitting 24. In manufacturing the steering wheel con¬ figured as described in the foregoing by the braiding machine 12 and the covering apparatus 14, the braided sleeve 21 is braided from the unidirectional fibers 10a, 10b and the heating wires 13a, 13b covered with glass fibers, and the coil-shaped lightweight core material 9 is, after being covered with the braided sleeve is cut at a connecting portion 30 with the spoke 2 so that the cut-out portion has a predeter¬ mined length of a ring shape, and the cut-out portion is made in the, ring shape by butting both ends at the connecting portion 30 with the spoke 2. In this case, wiring for the heating wire 13 is effected at this cut surface, and the cut surface is worked so that -the heating wire 13 can be connected to an energizing section (not shown) prepared in a steering shaft to which the steering wheel is attached. As a further modified embodiment, as described with reference to FIGS. 15 and 16, at the' time when the thermosetting resin 11 is injected into the cavity 34, delustering treatment is made on the inside of the cavity 34, in particular, on a portion such as the . joining portion between the rim and spoke in which portion irregularity of the fiber alignment is apt to be caused. By virtue of the effect of the diffuse reflection at such portion alone, the irregularity of fiber in the inside is not visible, and thus, a fine appearance of the steering wheel can be improved. Furthermore, in another modified embodiment, although not shown in FIGURES, a drawing, a character, or a decorative pattern is displayed partially or all over a coil-shaped lightweight core material of a rim, and the coil-shaped lightweight core material is covered with a braided sleeve formed with uni¬ directional fiber, and the braided sleeve is impreg¬ nated with a transparent thermosetting resin and cured by heating so that a steering wheel having in the inside thereof, the drawing, character or decora¬ tive pattern visible from the outside through the braided sleeve and the transparent thermosetting resin is obtained. Accordingly, by merely changing the display, steering wheels or various kinds of color tones can be molded with the same outer layer mold, and the advantage of such steering wheels is that the colors appear visibly without being stained or vanished even when the steering wheels are used for a long time, and the steering wheels providing the feeling or sense which has not been realized in the prior art can be obtained.

Claims: CLAIM 1. A method for manufacturing a steering wheel which has a ring-shaped rim forming a grip, a boss for connecting to a steering shaft, and a spoke connecting the rim and the boss integrally, said method comprising the steps of: forming a braided sleeve by braiding -in a sleeve shape one or a plurality of kinds of uni¬ directional fibers; covering around a lightweight core material constituting a core material of said rim with said braided sleeve; cutting said core material covered with said unidirectional fiber in a predetermined length of a ring shape; butting both ends of said cut-out portion of the ring shape and engaging with each other; joining said ring-shaped rim and said spoke; and forming an outer molded layer, after the joining, by placing said joined rim and spoke in a metal mold, injecting a thermosetting resin into the metal mold, and curing said thermosetting resin. 2. A method according to claim 1, wherein in said step of covering around a lightweight core material, said core material is formed in a coil shape. 3. A method according to claim 1, wherein in said step of covering around a lightweight core material, said core material has a display of a drawing, a character, or a decorative pattern on the outer surface thereof. 4. A method according to claim 1, wherein in said step of forming a braided sleeve, said braided double-woven belt has ' two layers of braided uni¬ directional fibers of outer and inner layers thereby to cover said core material with said two layers. 5. A method according to claim 1, 2 or 3 , wherein in said step of forming a braided sleeve, after braiding glass fiber in a sleeve shape, carbon fiber is braided in a sleeve shape surrounding the braided glass fiber to form said braided sleeve having two layers of outer and inner layers thereby to cover said core material with said two-layer sleeve. 6. A method according to claim 1, 2 or 3, wherein in said step of forming a braided sleeve, unidirectional fiber incorporating a heating wire and sole unidirection¬ al fiber are braided to form said braided sleeve. 7. A method according to claim 1, 2 or 3, wherein in said step of forming an outer moded layer, said unidirectional fiber covering said rim is impregnated with said thermosetting resin, and a layer of said thermosetting resin along is formed surrounding said unidirectional fiber. 8. A method according to claim 1, 2, or 3, wherein in said step of forming an outer molded layer, after said joined rim and spoke are placed in said metal mold, said metal mold is made to be a vacuum condition, and said thermosetting resin is injected therein. 9. A method according to claim 1, wherein in said step of forming an outer molded layer, at least a part of the inside of a cavity of said metal mold is subjected to delustering treatment. 10. A method according to claim 1, wherein in said step of joining said ring-shaped rim and said spoke, a joining piece of a braided sleeve of uni¬ directional fiber, or of a cloth is used to join said ring-shaped rim and said spoke. 11. A method according to claim 1, wherein in said step of covering around a lightweight core material, said lightweight core material has a coil shape, and said coil-shaped lightweight core material is disposed so that one end thereof is, opposing to a .braided end of said braided sleeve, and said braided end ' is moved successively along said coil- shaped lightweight core material. 12. A method according to claim 1, wherein in said step of forming an outer molded layer, after said thermosetting resin is injected and cured, an outer layer of a material having smooth feeling such as rubber or ' foamed plastic is molded surrounding the layer of said thermosetting resin. 13. In an apparatus for manufacturing a steering wheel which has a ring-shaped rim forming a grip, a boss for connecting to a steering shaft, and a spoke con¬ necting the rim and the boss integrally, a braiding machine (12) constituted by said braiding machine (12) and a covering apparatus (14) comprises: a plurality of bobbins (19a, 19b) having unidirectional fibers (10a, 10b) wound thereon; a driving device for rotating and moving said plurality of bobbins along predetermined tracks; and a former (20) for continuously forming a braided sleeve (21) by interlacing and braiding the unidirectional fibers respectively delivered from said plurality of bobbins; and said covering apparatus (1 ' 4) comprises: a holding device (22) for holding a lightweight core material (9) constituting said rim portion so that an end of said lightweight core material is disposed opposing to said former; a feed rod (23) supported rotatably at the center of said lightweight core material (9) ; a guide device (24) secured to said feed rod (23) through an arm to turn along said lightweight core material (9) ; a clamp device (26) for fixing to said guide device . a front end of said braided sleeve braided at said former; and driving means for driving in rotation said feed.rod.. 14. A apparatus according to claim 13, wherein said core material is formed in a coil shape.

Inventors: HANI KIYOSHI, KAWABATA KAZUO, KOGURE NAOYUKI, YAMASHITA SHU, YANO ISAMU, HANI, KIYOSHI, KAWABATA, KAZUO, KOGURE, NAOYUKI, YAMASHITA, SHU, YANO, ISAMU
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1986
Main classification: B62D1
IPC codes: B29C53, B29C70, B62D1