Rotary connector

Abstract: A rotary connector (1) for an electric apparatus comprising a stator housing (2) mounted on a vehicle body of an automobile; a rotor housing (3) rotatably mounted to the stator housing (2) and coupled to a steering wheel (11); an attachment (4) that couples the rotor housing (3) to the stator housing (2) so that the rotor housing is rotatably relative to the stator housing; a flat cable (5) accommodated in a space A defined by the rotor housing (3) and the stator housing (2); wherein the attachment (4) has an annular flange (4a) formed at an outer periphery thereof, and a slip-ring mechanism is provided between the flange (4a) and a bottom (2a) of the stator housing (2). The rotary connector is provided in a steering wheel and consumes relatively large current.

Description: Detailed Technical Field The present invention relates to a rotary connector that electrically connects between a steering wheel and a body of an automobile, and more particularly to a rotary connector that incorporates a slip-ring mechanism. Prior art Among this type of conventional rotary connectors is one disclosed in, for example, Japanese Patent No. 3-55955. This conventional connector includes a rotor housing and a stator housing assembled to each other into a complete housing assembly in which a flat cable in the shape of a spiral is housed and electrically connects the vehicle body and the steering wheel. This rotary connector is used for an air bag system or an alarm device mounted to the steering wheel. Thus, the current that flows through the connector is small. Accordingly, the flat cable includes thin wires covered with thin film. Problem to be Solved by the Invention However, the aforementioned conventional rotary connector can be used only for low current applications. Thus, the conventional rotary connector cannot be applied to a heater that heats a steering wheel, because the heater requires a large current. If the heater current flows through a flat cable, the conductors in the flat cable generate heat that is sufficient to melt the film covering the conductors. The present invention was made in view of the aforementioned problems. Document JP-A-6400067, discloses a connector according to the preamble of claim 1. An object of the invention is provide a rotary connector suitable for an electric apparatus that is assembled into a steering wheel and consumes a relatively large current. Means for Solving the Problem The present invention was made to solve the problems associated with the aforementioned conventional art. The present invention provides the following advantages. The invention defined in Claim 1 is a rotary connector having: a stator housing mounted on a vehicle body of an automobile; a rotor housing rotatably mounted to the stator housing and coupled to a steering wheel; an attachment that couples the rotor housing to the stator housing so that the rotor housing is rotatably relative to the stator housing; a flat cable accommodated in a space defined by the rotor housing and the stator housing; wherein the attachment has an annular flange formed at an outer periphery thereof, and a slip-ring mechanism is provided between the flange and a bottom of the stator housing. This construction allows electrical connection between the steering wheel and the vehicle body by means of the flat cable and slip-ring mechanism, so that more electric circuits can be accommodated on the steering wheel and steering pad. The current supplied to the slip-ring mechanism does not flow through the flat cable. Thus, a device that consumes relatively large current can be mounted on the steering wheel. The invention defined by Claim 2 is the rotary connector according to Claim 1 wherein the rotary connector has the flat cable and the cord, wherein the cord has one end thereof connected to a device mounted on the steering wheel and the other end thereof connected to the slip-ring mechanism through a shaft sleeve. Thus, the cord can be routed by getting out of the way of the rotative steering shaft so that the cord does not wrap around the steering shaft and steering wheel. The invention defined by Claim 3 is the rotary connector according to Claim 1 or Claim 2, wherein the flange of the attachment supports the movable contact plates of the slip-ring mechanism thereon; and wherein the bottom of the stator housing has a non-movable contact plate thereon on which the movable contact plate slides. The structure allows the movable contact plate and non-movable contact plate to be mounted without increasing the number of parts, thereby reducing cost. The invention defined by Claim 4 is the rotary connector according to Claim 3, wherein the movable contact plate is provided on the flange of the attachment and connected to the cord, the non-movable contact plate is insert-molded in the bottom of the stator housing. Thus, the structure reduces the number of parts and assembly time, thereby contributing to cost reduction. Description of the Drawings Fig. 1 is a top view of a rotary connector according to an embodiment of the invention, showing the rotary connector when it is mounted to a combination switch. Fig. 2 is a cross-sectional view of the embodiment according to the present invention. Embodiments Reference numeral 1 denotes a rotary connector that electrically connects the vehicle body of an automobile to a steering wheel 11 of the automobile. The rotary connector 1 includes a stator housing 2, a rotor housing 3, an attachment 4, and a flat cable 5. The stator housing 2 is mounted to a combination switch 9 that is fixed to the steering column (not shown). The rotor housing 3 engages the underside of the steering wheel 11 and rotates together with the steering wheel 11. The attachment 4 rotatably engages the rotor housing 3. The flat cable 5 is in the shape of a spiral accommodated in a space defined between the stator housing 2 and the rotor housing 3. The stator housing 2 is a stationary parts that is fixed on a base 10 of the combination switch 9 by means of a screw or a fastening portion 2c. The stator housing 2 includes a bottom section 2a and a side section 2b that are assembled together. Specifically, the side section 2b has engagement holes (not shown), while the bottom section 2a has claws (not shown). The bottom section 2a and side section 2b are assembled together with the claws fitted into the engagement holes. Alternatively, the bottom section 2a and side section 2b may be formed in one piece construction. thereby providing the stator housing 2 in one piece. The upper surface of the bottom section 2a holds one end of the flat cable 5 as shown in Fig. 2 and has a guide (not shown) in a space A defined by the stator housing 2 and the rotor housing 3. The guide guides the flat cable 5 accommodated in the space A. The space has a slide sheet 13 placed on the inner bottom floor of the bottom section 2a. Disposed below the guide is a connector 2d provided on the side section 2b of the rotor housing 2. As shown in Fig. 1, the bottom section 2a has a plurality of ring-shaped non-movable contact-plates 7 that are exposed. The non-movable contact-plates 7 are, for example insert-molded in the bottom surface of the stator housing 2. As shown in Fig. 2, one ends of the non-movable contact-plates 7 are exposed within the bottom section 2a and the other ends are exposed as terminals 7a in the connector 2d. The connector 2d has terminals (not shown) that are connected via the flat cable 5 to a wire harness 12 disposed on the rotor housing 3. The terminals (not shown) connected to the flat cable 5 and the terminals 7a of the non-movable contact-plate 7 may be disposed in the connector 2d or may be disposed in separate connectors (not shown). The side section 2b has a substantially ring-shaped cylindrical portion 2e and a frame section 2f formed on an outer periphery around the lower end of the cylindrical portion 2e, the frame section 2f and the cylindrical portion 2e being in one piece construction. The frame section 2f has the connector 2d and the fastening portion 2c by means of which the rotary connector 1 is fixed to the base 10 of the combination switch 9. The attachment 4 has a fitting portion 4b and a projection 4c shown in Fig. 2 that couples the stator housing 2 to the rotor housing 3. The attachment 4 also has an annular flange 4a around the outer surface of the attachment 4, and a through-hole 4d formed below the flange 4a. A cord 8 passes through the through-hole 4d. In other words, the attachment 4 couples the stator housing 2 to an rotor housing 3 by using such a means as disclosed in Laid-open Japanese Patent No. 10-22029. The flange 4a supports a plurality of movable contact plates 6 that are formed of an electrically conductive, resilient material as shown in Figs. 1 and 2. For example, two movable contact plates 6 are used, but more movable-contact plates may be used as required. The movable contact plate 6 is crimped to securely attach to the flange 4a and a crimped portion projects downwardly of the flange 4a. The projecting portion of the movable contact plate 6 is soldered to a cord 8. The cord 8 inserted through the through-hole 4d near the flange 4a passes through a shaft sleeve 1a, and is connected to a device such as a steering wheel heater mounted to the steering wheel 11. The cord 8 has a large diameter such that a relatively large current can flow through the cord 8. The flat cable 5 has a plurality of, for example, belt-shaped wires that are arranged at predetermined intervals and sandwiched between two sheets of resin films made of insulation resin pressed together with heat applied thereto. The flat cable 5 has one end connected to the terminals in the connector 2d of the stator housing 2 and the other end connected to the wire harness 12 of the rotor housing 3. The flat cable 5 is accommodated in a doughnut-shaped space defined by the stator housing 2 and rotor housing 3 such that the flat cable is rotated clockwise and counterclockwise through more than two complete rotations from a neutral position at which the vehicle runs straight. The embodiment of the present invention is of the aforementioned construction. The rotary connector apparatus 1 and movable contact plate 6 are such that when the steering wheel 11 is rotated, the cord 8 rotates together with the steering wheel 11, attachment 4, and rotor housing 3. Thus, there is no chance of the cord being twisted. The movable contact plate 6 slides while also being in pressure contact with the non-movable contact plate 7 at all times. The cord 8, movable contact plate 6, and non-movable contact plate 7 are thicker than the conductors of the flat cable 5, so that a larger current can flow therethrough.

Claims: A rotary connector having: a stator housing (2) mounted on a vehicle body of an automobile; a rotor housing (3) rotatably mounted to said stator housing (2) and coupled to a steering wheel (11); an attachment (4) that couples the rotor housing (3) to the said stator housing (2) so that the rotor housing (3) is rotatable relative to the stator housing (2); a flat cable (5) accommodated in a space (A) defined by said rotor housing (3) and said stator housing (2); characterised in that : said attachment (4) has an annular flange (4a) formed at an outer periphery thereof, and a slip-ring mechanism is provided between the flange (4a) and a bottom surface section (2a) of the stator housing (2). The rotary connector according to Claim 1, wherein the rotary connector (1) has the flat cable (5) and a cord (8), wherein the cord (8) has one end thereof connected to a device mounted on the steering wheel (11) and the other end thereof connected to the slip-ring mechanism through a shaft sleeve (1a). The rotary connector according to Claim 1 or Claim 2, wherein the flange (4a) of the attachment (4) supports movable contact plates (6) of the slip-ring mechanism thereon; and wherein the bottom (2a) of the stator housing (2) has a non-movable contact plate (7) thereon on which the movable contact plate (6) slides. The rotary connector according to Claim 3, wherein the movable contact plate (6) is provided on the flange (4a) of the attachment (4) and connected to the cord (8), the non-movable contact plate (6) is insert-molded in the bottom section (2a) of the stator housing (2).

Inventors: MATSUMOTO TSUYOSHI, MATSUMOTO, TSUYOSHI, Matsumoto, Tsuyoshi, c/o Niles Parts Co., Ltd.
Applicants: NILES PARTS CO LTD, NILES PARTS CO., LTD.
Application year: 2000
Main classification: H01R39
IPC codes: B60R16, B62D1, H01R35, H01R39, H02G11, B60R21