Steering wheel, segmented slip rings and method of disposing segmented slip rings

Abstract: A segmented slip ring (9, 18) is disposed on an insulated base (8, 17), and has a portion made substantially flush with a surface of the insulated base. A contact pin (12, 13) makes sliding contact with that portion. A method of disposing the segmented slip ring on the insulated base comprises: a mounting process in which a plurality of segmented slip rings are disposed at fixed intervals in a shape of a ring on the insulated base, and a leveling process in which at least a part of the segmented slip ring on the insulated base where the contact pin makes sliding contact is made flush with the surface of the insulated base by means of thermal pressing. A steering wheel comprising: an insulated base (8, 17) having a surface; a plurality of segmented slip rings (9, 18) having surfaces, disposed separately on the insulated base along a circular line such that they are mutually insulated; a plurality of contact pins (12, 13) that make sliding contact with the segmented slip rings along the circular line, and are set facing the surfaces of the segmented slip rings; and interposing pieces provided between the adjacent segmented slip rings such that the contact pins can move smoothly across the segmented slip rings.

Description: The present invention relates to a method of disposing a segmented slip ring according to the preamble of claim 1, and is usable for making a steering wheel furnished with a relay mechanism comprising slip rings and contact pins whose tips come in contact with the slip rings, to segmented slip rings for use in the steering wheel. The JP-A-871-995 shows an electrical sliding contact, which comprises an insulating base into which ring segments are fitted such that the upper surface of the base and the ring segments form a common plane. However, the insulating base according to the GB-A-871 995 must be preformed with recesses, into which the ring segments are fitted. Furthermore, the CH-A-286 987 discloses a commutator for machines with very high voltage. According to this reference the electric members are separated from each other by additional insulated segments and by an air gap. In recent years, audio equipment for vehicles, a computer for drive or the like tends to be assembled in a car. Also, switches for operating the computer for drive or the like are disposed on a pad portion of a steering wheel. In this case, there is provided, as a relay mechanism between the pad portion 916 of the steering wheel and a column portion 918, a multiplex transmission circuit utilizing an optical communication means in which a light emitting element is disposed on the pad portion 916 while a photo detector on the column portion 918. In such a relay mechanism, as shown in Fig. 16, a pad portion 916 has provided thereon switches 930, a transmission side remote control IC 931, an electric signal-optical signal transducing circuit 932, and a power supply circuit 933. A signal relay portion 901 includes the above mentioned electric signal-optical signal transducing circuit 932, a light emitting circuit 934, a photo detector circuit 935, a signal regenerating circuit 936. A column portion 918 has disposed thereon a waveform shaping circuit 937, a receiving side remote control IC 938, an output interface 939, and a power supply circuit 940 having a battery. Further, a power relay portion 941 is provided between the pad portion 916 and the column portion 918. By operating the switches 930 on the pad portion 916, the transmission side remote control IC 931, which is supplied with power from the power supply circuit 933, operates. Next, a plurality of electric signals are transduced into optical signals through the electric signal-optical signal transducing circuit 932. The light emitting circuit 934 emits light signals on the basis of the above light signals. At the same time, the photo detector circuit 935 receives the light signals, and the signal regenerating circuit 936 retransduces them into electric signals. Then, the waveform shaping circuit 937 shapes the electric signals into the original pulse waves. Thereafter, the same pulse waves are transmitted to the output interface 939 through the receiving side remote control IC 938 thereby to actuate electric devices or actuators. However, the above relay mechanism needs the multiplex transmission circuit with a resultant complicated structure and high production cost. An object of the present invention is to provide a method of disposing a segmented slip ring such that the slip ring and an insulated base are on a same plane, at least along a sliding contact line of the contact pins. This object is achieved by the features of claim 1. Advantageous further developments are set out in the dependant claims. By using the present invention a steering wheel can be provided in which bouncing of the contact pins as they pass between the two slip rings is prevented, thus also preventing the momentary disconnection of the relay between the contact pin and the slip ring during a passage between the two segmented slip rings, and the generation of noise and non-uniform steering torque. Furthermore, a momentary disconnection of a signal circuit and a generation of noise in a relay mechanism are eliminated when a contact pin moves between the slip rings. There is no momentary disconnection of the relay between a specific switch and a specific electrical device due to a vibration of the car body or other disturbance. The advantages of the present invention will become apparent with an understanding of the embodiments described later, Fig. 1 to Fig. 9 show a steering wheel, embodiment of the Fig. 1 is an exploded perspective view showing an entire steering wheel, Fig. 2 is a sectional view showing the same, Fig. 3 is a circuit diagram showing a signal circuit, Fig. 4 is an enlarged perspective view, partly in section, showing an insulated base, Fig. 5 is a partially broken perspective view showing the entire insulated base, Fig. 6 is a partially broken perspective view showing a slip ring and heating means, Fig. 7 is a partially broken perspective view showing the slip ring and the pressing means, Fig. 8 is a partial sectional view showing the state immediately before a leveling process, Fig. 9 is a partial sectional view showing a state immediately after the leveling process, Fig. 10 is a perspective view showing a modification of the embodiment, Fig. 11 is an exploded perspective view showing a process of disposing the slip ring of Fig. 10, Fig. 12 is a partial sectional view showing another modification, Fig. 13 to Fig. 15 are partial sectional views showing the process of disposing the slip ring of Fig. 12, and Fig. 16 is a circuit diagram showing a relay mechanism of a related art. A steering wheel is described with reference to Fig. 1 to Fig. 9. As shown in Fig. 1 and Fig. 2, a boss plate 3 extends outward from a boss portion 2 fixed to an end of a steering shaft 1. A plurality of locking holes 4 for inserting contact pin holders, to be mentioned later, are perforated on this boss plate 3. A ring portion 6 is supported at the ends of a pair of spokes 5 extending from the boss plate 3. A column bearing plate 7 is fitted to the lower part of the boss portion 2 with bearings 29 in between. Column segmented slip ring 9 are disposed on an insulated base 8 having the shape of a flat doughnut, and are fixed to the column bearing plate 7 through this insulated base 8. A column sun gear 10 below the column bearing plate 7 is fixed to or engaged with a column portion 31, and it is always kept at an irrotational state. On the other hand, a contact pin unit 11 is provided above the boss portion 2, comprising column contact pins 12 and pad contact pins 13, that constitute pairs with a coil spring 28 between each pair, contact pin holders 14 for holding the pairs of contact pins 12, 13, and a contact pin mounting piece 15 having the shape of a flat doughnut, for holding the contact pin holders 14 such that the tips of the column and pad contact pins 12, 13 are situated on the same planes, respectively. A pad bearing plate 16 is fitted to the upper part of the boss portion 2. Twelve pad segmented slip rings 18 are disposed in the shape of a ring on an insulated base 17 on the lower surface of the pad bearing plate 16, such that each of the slip rings 18 is facing each of the column segmented slip rings 9. A pad sun gear 19 is fixed to the upper surface of the pad bearing plate 16. Further, two lead wires 20 extend from the insulated base 8 to the column portion 31, and are connected to an electrical device, actuator 39, and others, provided in a car body. Similarly, two lead wires 21 extend from the insulated base 17 to a pad portion 30, and are connected to various switches 37. The electrical device 39 and others mentioned above are operated or induced to stop operating by turning these switches 37 on or off. Thus, in this embodiment, twelve signal circuits are formed between the electrical device 39, and others, and the switches 37. In each signal circuit, a relay mechanism 41 is formed, comprising the circuit: column segmented slip ring 9 - column contact pin 12 - coil spring 28 - pad contact pin 13 - pad sengmented slip ring 18. By means of this structure, when the switches 37 provided on the pad portion 30 is turned on or off, the electrical device, atcuator 39 and others provided on the car body are operated and stopped operating via the relay mechanism 41. Two planetary gears 34, 35 are attached to the boss plate 3 by means of a bearing 33. One planetary gear 35 is composed of two gear segments 35a, 35b. Between these two gear segments 35a, 35b, there are two coupling pieces 35d, that serve to regulate the two gear segments 35a, 35b from rotating relative to each other, and a coil spring 35c that acts to push the two gear segments 35a, 35b apart. As shown in Fig. 4 and Fig. 5, the twelve column segmented slip rings 9, each shaped like a fan, are mounted in the shape of a ring on the insulated base 8 having the shape of a flat doughnut, forming a circular sliding contact line 101. The outer circumferential edge and inner circumferential edge of each column segmented slip ring 9 are fixed to the insulated base 8 by means of mounting through holes 22. Further, in each of the column segmented slip rings 9, the region on and near the circular sliding contact line 101 is on the same plane as or made flush with the insulated base 8. Also, conductive patterns 23 are provided on the back side of the insulated base 8. One end of each pattern 23 is electrically connected to one mounting through hole 22 of each of the column segmented slip rings 9 while the other ends are connected to wire connecting through holes 24 concentrated at two locations on the insulated base 8. Some of the mounting through holes 22 are also used as wire connecting through holes 24 (refer to Fig. 5). Pins (not shown) of a connector 25 of the lead wire 20 are connected to the wire connecting holes 24 at the back side of the insulated base 8. The pad segmented slip rings 18 essentially have the same construction as the column segmented slip rings 9. Next, a method of manufacturing the slip rings 9, 18 mentioned above is described. Inasmuch as the parts related to the column portion 31 and pad portion 30 are the same, only the parts related to the column portion 31 are shown in the figures. As shown in Fig. 6, a plurality of the segmented slip rings 9 are disposed by a subtractive method and others at fixed intervals in the shape of a ring on one surface of the insulated base 8 made of synthetic resin such as epoxy resin, and others. Also, the conductive patterns 23 for electrically connecting the column segmented slip rings 9 and the lead wires 20, 21 are formed on the other surface of the insulated base 8 (mounting process). Next, perforations for forming the mounting through holes 22 and wire connecting through holes 24 are provided at fixed locations on the insulated base 8. The holes 22, 24 are then formed by electroless plating. Next, the synthetic resin material of the insulated base 8 and the segmented slip rings 9 in the vicinity of the circular sliding contact line 101, on which the column contact pins 12, to be described later, make sliding contact while moving, are heated with heating means 26 until it becomes soft. Then, as shown in Fig. 7, the heated portion of the segmented slip ring 9 is pressed against the insulated base 8 with pressing means 27 by thermal pressing (leveling process). Here, thermal pressing means make the synthetic resin making up the insulated base 8 soft by heating, and pressing the column segmented slip rings 9 against the synthetic resin at a fixed pressure P, embeds the column segmented slip rings 9 into the insulated base 8. The pressing means 27 used in the leveling process has a length and breadth such that it projects at least a little from the boundaries of the column segmented slip ring 9, at the part where it is to be leveled with the insulated base 8. The pad segmented slip ring 18 is also disposed according to the processes mentioned above. Next, the operation of the present embodiment is described and its effects are mentioned. When the column or pad segmented slip ring 9, 18 is pressed with the pressing means 27 against the area of the insulated base 8, 17 which has been heated and is to be made level with the column or pad segmented slip ring 9, 18, as shown in Fig. 8, the column or pad segmented slip ring 9, 18 is embedded into the insulated base 8, 17, as shown in Fig. 9. As a result, the synthetic resin making up the insulated base 8, 17 is displaced by the column or pad segmented slip ring 9, 18 and forced out of the space occupied by the segmented slip ring 9, 18. Since the pressing means 17 is formed long enough such that it projects from the boundaries of the column or pad segmented slip ring 9, 18, and covers a portion of the insulated base 8, 17, after having pressed the segmented slip ring 9, 18, a fixed amount, at a certain pressing force P, the pressing means 27 encounters the resistance of the displaced synthetic resin, and will no longer be able to press the column or pad segmented slip rings 9, 18 any further. If the thermal pressing stage is halted at this point, the column or pad segmented slip ring 9, 18 will become attached to the insulated base 8, 17, and, at the same time, be on the same plane as the insulated base 8, 17. In the present embodiment, since the column and pad segmented slip rings 9, 18 do not undergo thermal pressing entirely, that is, only the regions away from the mounting holes 22 and wire connecting holes 24 undergo thermal pressing, these holes 22, 24 do not undergo any deformation. Therefore, the locking capabilities of the column and pad segmented slip rings 9, 18 with the insulated bases 8, 17 are maintained. The steering wheel having the structure described above is attached to the steering shaft of a car body. In the steering operation, when the switch 37 on the pad portion 30 is turned on or off, the contact pin unit 11 rotates with the boss plate 3 and the column and pad contact pins 12, 13 make sliding contact with the column and pad segmented slip rings 9, 18, respective, along the circular sliding contact line 101. Since the column and pad segmented slip rings 9, 18 are very accurately situated on the same plane as those of the insulated bases 8, 17, when the column and pad contact pins 12, 13 pass through the slip rings 9, 18, there is no momentary disconnection of the signal circuit, and noise in the relay mechanism 41 is not generated. In addition, the operating torque is uniform. Hence, compared to the related art, the quality of the steering wheel of the present embodiment is remarkably improved. The present embodiment can also be concretized with the following modifications. (1) The column and pad segmented slip rings 9, 18 can undergo thermal pressing on the insulated bases 8, 17 not only on the parts corresponding to the circular sliding contact line 101 but entirely, that is, as a whole. (2) As shown in Fig. 10, the column and pad segmented slip rings 9, 18 can be mounted on a wheel portion 8a of the column and pad sun gears 10, 19, which can serve as insulated bases, and the part corresponding to the circular sliding contact line 101 can be made to be on the same plane as that of the wheel portion 8a. In this modification, the column and pad segmented slip rings 9, 18 can be disposed on the wheel portion 8a according to the following methods. A first method is as shown in Fig. 11. This method involves integrally forming leg portions 9a at the corners of the lower surface of each of the column and pad segmented slip rings 9, 18 made of phosphor bronze, and inserting these leg portions 9a into mounting holes 8x provided on the wheel portion 8a. The leg portions 9a inserted into the mounting holes 8x are attached to the wheel portion 8a by soldering them to the through holes of the printed circuit board (not shown) provided on the back side of the wheel portion 8a. A second method is as shown in Fig. 13. This method involves setting a catalyst 103 by screen printing, letterpress, or other methods on the parts where the column and pad segmented slip rings 9, 18 are to be disposed, on recessed portions 23a where the conductive patterns 23 are to be formed, and on perforations 40 connecting them. Then, electroless plating with copper is performed, forming a highly conductive ground layer 36, conductive patterns 23, and a connecting portion 38 connecting them, as shown in Fig. 14. In this method, as shown in Fig. 15, the column and pad segmented slip rings 9, 18 are formed by performing electrolytic plating or electroless plating with Ni-B, or other hard metals, at locations on the wheel portions 8a corresponding to the conductive patterns 23, where these slip rings 9, 18 are to be formed. Then, lastly, the wheel portions 8a are heated, and the column and pad segmented slip rings 9, 18 are made to be at the same plane as those of the wheel portions 8a, as shown in Fig. 12, by thermal pressing. In this modification, the conductive patterns 23 on the back side of the wheel portions 8a are formed on the recessed portions 23a. In the thermal pressing stage of the column and pad slip rings 9, 18, the connecting portions 38 are prevented from being destroyed by the presence of these recessed portions 23a. (3) The main material used as synthetic resin is thermoplastic resin, but a thermosetting synthetic resin with weak crosslinks can be used, and then made to harden in a later process. (4) As methods of softening the synthetic resin, there are the external heating methods using hot blast, hot plate, flame, and others, and internal heating methods using high frequency waves, supersonic waves, and others. (5) In the mounting porcess, first, recessed portions having approximately the same shape as the plane figures of the column and pad segmented slip rings 9, 18, and depth slightly shallower than the thickness of the slip rings 9, 18 are formed on the insulated bases 8, 17, and then the planes are made even after the column and pad segmented slip rings 9, 18 are set in these recessed portions. (6) This method in the present invention can also be applied as a method of disposing any type of segmented slip ring on an insulated base, other than the segmented slip ring used in the relay mechanism 41 of a steering wheel.

Claims: A method of disposing a segmented slip ring (9, 18) on an insulated base (8, 8a, 17) of synthetic resin, comprising the steps of disposing a plurality of segments of said segmented slip ring (9, 18) at fixed intervals in a ring on said insulated base (8, 8a, 17), and leveling at least that portion of each segment which is in sliding contact with at least one contact pin (12, 13) by means of thermal pressing so that said portion is flush with the surface of said insulated base (8, 8a, 17), wherein said thermal pressing comprises heating of said segments and the insulated base (8, 8a, 17) by heating means (26) and pressing said segments by pressing means (27) over a length longer than said portion to be leveled until contact of said pressing means (27) with said insulated base (8, 8a, 17) is made. A method of disposing a segmented slip ring, according to claim 1, characterized in that said thermal pressing is performed by means of heating means (26) for heating said insulated base (8, 8a, 17) and pressing means (27) for pressing said segmented slip ring (9, 18), said pressing means (27) having a length longer than said portion of said segmented slip ring (9, 18) to be leveled, exceeding a length of said segmented slip ring (9, 18) during pressing, and coming in contact with said insulated base (8, 8a, 17). A method of disposing a segmented slip ring, according to any of claims 1 or 2, charcterized in that said insulated base (8, 17) comprises a wheel portion (8a) of a sun gear (10, 19) having a shape of a circular plate. A method of disposing a slip ring, according to claim 3, characterized in that said disposing is performed by inserting a plurality of leg portions (9a) protruding from said segmented slip ring (9, 18) into holes (8x) provided on said wheel portion (8a) at locations corresponding to said leg portions (9a). A method of disposing a slip ring according to claim 3, characterized in that said step of disposing comprises the steps for: forming a recessed portion (23a) for forming a conducting pattern (23) on a surface opposite to a surface of said wheel portion (8a) on which said segmented slip ring (9, 18) is to be disposed, forming a hole (40) connecting said recessed portion (23) and an area on said wheel portion (8a) on which said segmented slip rings (9, 18) are to be disposed, and plating said hole (40), said recessed portion (23a) and said area on said wheel portion (8a) on which said seqemented slip rings (9, 18) is to be disposed. A method of disposing a segmented slip ring, according to any of claims 1 to 5, characterized in that said thermal pressing is performed only on said portion of said insulated base (8, 8a, 17) with which said contact pin (12, 13) makes sliding contact.

Inventors: HAYASHI CHIKAHISA, HIROSAWA KUNIKAZU, INUI SHUJI, KANAI MAKOTO, KAWAI MAKOTO, KIKUTA MITSUHIRO, ONO SATOSHI, SANO YOSHIO, HAYASHI, CHIKAHISA C/O TOYODA GOSEI CO., LTD., HIROSAWA, KUNIKAZU C/O TOYODA GOSEI CO., LTD., INUI, SHUJI C/O TOYODA GOSEI CO., LTD., KANAI, MAKOTO C/O TOYODA GOSEI CO., LTD., KAWAI, MAKOTO C/O TOYODA GOSEI CO., LTD., KIKUTA, MITSUHIRO C/O TOYODA GOSEI CO., LTD., ONO, SATOSHI C/O TOYODA GOSEI CO., LTD., SANO, YOSHIO C/O TOYODA GOSEI CO., LTD.
Applicants: TOYODA GOSEI KK, TOYODA GOSEI CO., LTD.
Application year: 1988
Main classification: H01R43
IPC codes: B60R16, H01H19, B62D1