Rotary connector

Abstract

The invention provides a rotary connector capable of obtaining good impedance characteristics and bending resistance. The rotary connector includes: a fixing member having a first external connection portion; the rotating piece is provided with a second external connecting part and can rotate relative to the fixing piece; the flexible cable is accommodated in an annular space between the fixed part and the rotating part, and is electrically connected with the first external connecting part of the fixed part and the second external connecting part of the rotating part respectively; the flexible cable has: a first insulating layer; a second insulating layer; the signal conductor is formed between the first insulating layer and the second insulating layer; the shielding layer is laminated on one side, opposite to the signal conductor, of the first insulating layer; the first insulating layer is thicker than the second insulating layer.

Description

Technical Field

[0001] The invention relates to a rotary connector. Background Art

[0002] Conventionally, in vehicles such as automobiles, there is a known rotary connector that electrically connects an electrical device on the steering wheel side and an electrical device on the vehicle body side. It is known that when such a rotary connector is used for high-speed digital communications, there is a problem of electromagnetic compatibility (EMC) caused by electromagnetic noise and the like. For example, a twisted pair flat cable having a twisted pair structure formed by folding back a sheet of insulators around a plurality of conductors for signal propagation at a predetermined interval together with the insulator is used for a steering roller connector (rotary connector). (For example, refer to Patent Document 1). In addition, it is also known to provide a shielding member on one side of the flat cable to shield and absorb electromagnetic waves. (Refer to Patent Document 1) Figure 6 (b))

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-104907 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] However, in high-speed digital communications, if there is a conductive layer such as a shielding layer near the signal wiring, the impedance of the signal wiring is affected. On the other hand, in order to obtain the best impedance characteristics, the thickness of the insulating resin layer between the shielding layer and the signal wiring is adjusted, which sometimes affects the elasticity of the entire cable and makes it difficult to deform. In particular, when there is a cable reversing part inside, such as a rotary connector, there is a problem of reduced bending resistance (bending durability).

[0008] Therefore, an object of the present invention is to provide a rotary connector capable of suppressing a decrease in bending resistance and obtaining good impedance characteristics.

[0009] Technical means of solving problems

[0010] A rotary connector according to an embodiment of the present invention comprises: a fixed member having a first external connection portion; a rotating member having a second external connection portion, the rotating member being configured to be relatively rotatable relative to the fixed member; and a flexible cable accommodated in an annular space between the fixed member and the rotating member and electrically connected to the first external connection portion of the fixed member and the second external connection portion of the rotating member, respectively; the flexible cable comprises: a first insulating layer; a second insulating layer; a signal conductor formed between the first insulating layer and the second insulating layer; and a shielding layer stacked on a side of the first insulating layer opposite to the signal conductor; the first insulating layer is thicker than the second insulating layer.

[0011] Effects of the Invention

[0012] It is possible to provide a rotary connector capable of suppressing a decrease in bending resistance and obtaining good impedance characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is an external perspective view of the rotary connector 100 according to the embodiment.

[0014] Figure 2 yes Figure 1 An exploded perspective view of the rotary connector 100 is shown.

[0015] Figure 3 yes Figure 2 An enlarged perspective view of the peripheral structural components of FPC 110 is shown.

[0016] Figure 4 This is a three-dimensional view of the appearance of FPC110, lead block, etc.

[0017] Figure 5 This is an external perspective view of a state where the FPC 110 is held by the holder 7 .

[0018] Figure 6 1 is a perspective view of the external appearance of the annular space S in a state where the FPC 110 is not accommodated.

[0019] Figure 7 This is a diagram showing an example of a cross-sectional structure of a comparative FPC.

[0020] Figure 8 It is a diagram showing an example of a cross-sectional structure of an FPC according to an embodiment.

[0021] Fig. 9 It is a cross-sectional view showing a state where FPCs according to the embodiment are stacked.

[0022] Fig.10 It is a cross-sectional view showing a state where the FPC according to the embodiment is bent. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of a rotary connector to which the present invention is applied will be described.

[0024] <Implementation Method>

[0025] Figure 1 is a perspective view of the appearance of a rotary connector 100 according to an embodiment. Figure 2 yes Figure 1 The exploded perspective view of the rotary connector 100 is shown. Figure 3 yes Figure 2 The enlarged perspective view of the peripheral structural components of FPC1 10 is shown. Figure 4 This is a three-dimensional view of the appearance of FPC110, lead block, etc. Figure 5 This is a perspective view of the appearance of the FPC 110 being held by the retainer 7. Figure 6 It is a perspective view of the external appearance of the annular space S in a state where the FPC 110 is not accommodated.

[0026] like Figures 1 to 6 As shown, the rotary connector 100 includes a fixed member 2 and a rotating member 3 rotatably connected to the fixed member 2. The FPC 110 is accommodated in a wound state in the annular space S formed between the fixed member 2 and the rotating member 3. The connecting terminal portions 110a and 110b (see FIG. 1 ) at both ends of the FPC 110 are connected to the rotating member 3. Figure 2 ) are connected with lead blocks 11 and 21. The fixed member 2 has the lead block 11, and the rotating member 3 has the lead block 21. The lead block 11 is an example of a first external connection portion provided on the fixed member 2 side, and the lead block 21 is an example of a second external connection portion provided on the rotating member 3 side.

[0027] The retainer 7 is rotatably disposed between the fixed member 2 and the rotating member 3. The rotary connector 100 is assembled to a steering device of a vehicle and electrically connected between the fixed member 2 provided on a steering column (not shown) of the vehicle and the rotating member 3 connected to a steering wheel (not shown) via the FPC 110.

[0028] The fixing member 2 is roughly composed of an outer cylinder 8 and a bottom plate member 9 made of synthetic resin. The substantially cylindrical outer cylinder 8 is integrated with the outer peripheral edge of the substantially annular bottom plate member 9 by snap-fitting. A connecting portion 8a is provided at a predetermined position on the outer peripheral surface side of the outer cylinder 8, and a connecting portion 9a combined with the connecting portion 8a is integrally formed at a predetermined position on the outer peripheral side of the bottom plate member 9. Figure 1 and Figure 2 As shown, the combination of the connecting portion 8 a , the cylindrical housing 8 b , and the connecting portion 9 a constitutes a fixed-side connecting portion 50 that accommodates the lead block 11 .

[0029] The rotating member 3 includes an upper rotating member 13 and a lower rotating member 15 made of synthetic resin, and the upper rotating member 13 and the lower rotating member 15 are integrated by snap-fit ​​connection. Figures 1 to 3 As shown, the upper rotating member 13 has an annular top plate portion 13a opposed to the bottom plate member 9 and an inner cylinder 13b hanging down from the center of the top plate portion 13a. The inner diameter of the inner cylinder 13b is set to a size that allows the steering shaft (not shown) to be inserted. A rotating side connection portion 13d for accommodating the lead block 21 is integrally formed on the top plate portion 13a of the upper rotating member 13. In addition, the outer peripheral edge portion of the top plate portion 13a is slidably engaged with the outer cylinder 8. In addition, here, an example is shown in which the lead blocks 11 and 21 are used as the first external connection portion and the second external connection portion of the rotary connector 100 for electrical connection to the steering wheel side or the vehicle side, but other structures may also be used as long as the structure can be electrically connected to the steering wheel side or the vehicle side, such as directly connecting the cable from the outside to the first external connection portion and the second external connection portion of the rotary connector 100.

[0030] The lower rotating member 15 is formed into a substantially cylindrical shape through which the steering shaft can be inserted, and is snap-fitted with the inner cylinder 13b of the upper rotating member 13. The lower rotating member 15 is slidably engaged with the inner peripheral edge of the bottom plate member 9, so that the rotating member 3 is rotatably connected to the fixed member 2.

[0031] The FPC 110 is a flexible printed circuit board having a structure in which a strip-shaped conductor is covered with an insulating film made of polyimide, etc. The flexible printed circuit board can be finely processed, and the number of signal lines arranged per unit width can be increased compared to a flat cable in which conductive lines are covered with a laminate resin.

[0032] The FPC 110 is formed in the annular space S (see Figure 6 ) is accommodated in the annular space S so that it can be rolled up and unwound. The FPC 110 has a folded portion 110c folded back by a roller 23 between the connection terminal portions 110a and 110b located at both ends (see Figures 3 to 5 ). The FPC 110 is reversed in its winding direction by the folded portion 110c.

[0033] In addition, if Figure 2 As shown, FPC110 passes through the annular space S (refer to Figure 6 ) so that a portion of the intervals overlap. More specifically, for example, Figure 3 On the inner peripheral side of the folded portion 110c shown in FIG. 1 (the portion shown by arrow A), the FPCs 110 wound around the inner cylinder 13b approach and overlap each other. Figure 3On the outer peripheral side of the folded-back portion 110 c (the portion indicated by the arrow B), the FPCs 110 wound along the cylindrical shape of the outer cylinder 8 are close to each other and overlapped.

[0034] However, even if the steering device is turned to the maximum angle to turn the steering wheel, the length of the FPC 110 (the length between the connection terminals 110a and 110b at both ends) has a margin so that the FPC 110 will not be stretched or broken. Therefore, in the portion where the FPCs 110 overlap, the overlapping FPCs 110 do not completely adhere to each other as in the case of bonding, but overlap more gently as the thinner the air layer is between them.

[0035] Here, the overlapping of the FPCs 110 means that the FPCs 110 are not in close contact with each other, and the more an air layer exists between them, the more gently they overlap.

[0036] In addition, here, in the annular space S (refer to Figure 6 ), but two or more of the same FPCs may be provided. For example, in the case where FPC 110 and another FPC are provided, if the two FPCs are overlapped, they are reversed at the folded portion and wound on the inner circumference or outer circumference of the folded portion, then the FPC 110 and the other FPC can be accommodated in a state where they overlap each other in the annular space S. At this time, if the length of the other FPC is different from the length of the FPC 110 and the folded position is staggered, the FPC can be accommodated in a smoother and more stable manner. The same is true for the case where three or more FPCs are provided.

[0037] In addition, in the annular space S (refer to Figure 6 ), as another FPC as FPC110, it can be composed of only an insulating layer, and a flexible substrate having substantially the same size as FPC110, a flexible substrate having substantially the same size as FPC110 and provided with a shielding layer, etc. can be overlapped and arranged.

[0038] The connection terminal portion 110a at one end in the length direction of the FPC 110 is electrically connected to the lead block 11 mounted on the fixed member 2, and the connection terminal portion 110b at the other end in the length direction is electrically connected to the lead block 21 mounted on the rotating member 3. Here, the electrical connection also includes a signal processing unit, a control unit, etc. for processing and controlling the electrical signal passing through the lead blocks 11, 21 or the FPC 110, which is provided between the connection terminal portion 110a and the lead block 11 or the connection terminal portion 110b and the lead block 21.

[0039] like Figure 2As shown, the retainer 7 is a synthetic resin molded product, and includes an annular flat plate portion 7a rotatably mounted on the bottom plate member 9 in the annular space S, a plurality of support shafts 7b erected on the annular flat plate portion 7a, and a guide wall portion 7c.

[0040] The roller 23 is rotatably supported on each support shaft 7b. Figure 5 As shown in FIG. 1 , by winding the FPC 110 around the predetermined roller 23 and passing it between the opposing guide wall portion 7c, the winding direction of the FPC 110 is reversed midway at the folding portion 110c. The retainer 7 is provided to be rotatable relative to the fixed member 2 and the rotating member 3. When the rotating member 3 rotates relative to the fixed member 2, the retainer 7 also rotates around the axis of the fixed member 2 and the rotating member 3.

[0041] In the rotary connector 100 having such a structure, even if the relative rotational position between the stator 2 and the rotor 3 changes in conjunction with the rotation of the steering wheel, the change can be effectively absorbed, and application of a large load to the FPC 110 can be avoided.

[0042] like Figure 3 and Figure 4 As shown, the lead block 11 is held by a block holder 71 , and is connected to a connection terminal portion 110 a at the other end of the FPC 110 via a wiring (not shown) fixed to the block holder 71 .

[0043] like Figure 3 and Figure 4 As shown, the lead block 21 is held by the block holder 91 and connected to the connection terminal portion 110b of the FPC 110 via a wiring (not shown) fixed to the block holder 91. Thus, the electrical connection between the lead block 11 of the fixed member 2 and the lead block 21 of the rotating member 3 is maintained via the FPC 110.

[0044] Furthermore, wiring lines electrically connecting the lead block 11 and the connection terminal portion 110 a and the lead block 21 and the connection terminal portion 110 b may be connected using flexible cables such as short FPCs held by the block holders 71 and 91 , respectively, as an example.

[0045] <FPC110>

[0046] Next, the rotary connector 100 (see Figure 1 ) is described below. First, use Figure 7 FPC1 for comparison will be described. Figure 7 1 is a diagram showing an example of a cross-sectional structure of a comparative FPC 1. In addition, the comparative FPC 1 is not conventional technology.

[0047] FPC1 for comparison with Figure 3The FPC 110 of the embodiment shown is also slender and long, has connection terminals at both ends, and can be accommodated in the annular space S (see Figure 6 )Inside.

[0048] Figure 7 The cross section shown is a cross section obtained by cutting the FPC 1 for comparison in a plane perpendicular to the longitudinal direction (the direction connecting both ends) of the FPC 1, and shows a portion having a signal conductor. Hereinafter, the elastic modulus of each layer is represented by Young's modulus (GPa).

[0049] like Figure 7 As shown, the comparative FPC 1 has a structure in which a shielding film 1A, an insulating layer 1B, an adhesive layer 1C, a signal conductor 1D, an adhesive layer 1E, and an insulating layer 1F are stacked.

[0050] The shielding film 1A is a layer formed by forming a metal layer or a metal mesh such as copper or silver on the surface of the insulating layer. The shielding film 1A is stacked on the insulating layer 1B to improve the transmission characteristics of the signal in the signal conductor 1D and stabilize the impedance of the signal conductor 1D. As an example, the thickness of the shielding film 1A is 15 μm and the elastic modulus is 0.8 GPa.

[0051] As an example, the insulating layer 1B is an insulating film made of polyimide and is laminated on the shielding film 1A. The insulating layer 1B may be made of a material other than polyimide as long as it can be rolled. As an example, the insulating layer 1B has a thickness of 25 μm and an elastic modulus of 4.1 GPa.

[0052] The adhesive layer 1C is an insulating layer composed of an adhesive bonding the insulating layer 1B and the signal conductor 1D. The thickness of the adhesive layer 1C is 10 μm as an example, and the elastic modulus is 4.3 GPa. As an example, the signal conductor 1D is a signal conductor obtained by etching a metal layer such as copper foil into a pattern such as wiring. As an example, the thickness of the signal conductor 1D is 35 μm, and the elastic modulus is 30 GPa.

[0053] The adhesive layer 1E is an insulating layer composed of an adhesive for bonding the signal conductor 1D and the insulating layer 1F. As an example, the thickness of the adhesive layer 1E is 30 μm, and the elastic modulus is 1.2 GPa. As an example, the insulating layer 1F is an insulating film made of polyimide like the insulating layer 1B. As long as the insulating layer 1F can be wound, it can also be made of a material other than polyimide. As an example, the thickness of the insulating layer 1F is 25 μm, and the elastic modulus is 4.1 GPa.

[0054] Such a comparative FPC 1 is provided with a shielding film 1A to stabilize the impedance of the signal conductor 1D and shield noise in order to cope with high-speed digital signals transmitted in a vehicle-mounted data communication network such as CAN (Controlled Area Network). The comparative FPC 1 is a structure in which the shielding film 1A is mounted on an FPC that does not cope with high-speed digital signals.

[0055] However, it is known that in a structure such as the comparative FPC1, although noise shielding can be achieved, the shorter the distance between the shielding film 1A and the signal conductor 1D, the lower the impedance of the signal conductor 1D. If the signal impedance is lower than the specified value, the signal waveform is disordered, the SN ratio is reduced, and there is a situation where it cannot cope with vehicle-mounted data communication networks such as CAN. In high-speed digital signals, it is important to maintain a high-precision waveform, especially in vehicle-mounted data communication networks such as CAN, the requirements for the accuracy of the signal waveform have become more stringent.

[0056] When used for CAN, for example, an impedance of 120Ω is required, but in fact, through simulation calculation, the impedance of the signal conductor 1D in the FPC 1 used for comparison is 60Ω. In addition, in the simulation, the signal conductor 1D is treated as a pair of signal lines (two signal lines in one set) for differential signals corresponding to the two-wire differential voltage method, and a differential impedance model is used.

[0057] In order to improve the impedance, the distance between the shielding film 1A and the signal conductor 1D can be increased, but the insulating layer 1B between the shielding film 1A and the signal conductor 1D becomes thicker. As a result, the FPC 1 becomes difficult to bend at the folded portion along the roller 23, and the stress applied to the FPC 1 when bent into a predetermined shape becomes large. Therefore, it is easy to be damaged during repeated bending, and the bending resistance of the FPC 1 is reduced.

[0058] Therefore, in the embodiment, it is possible to realize a desired impedance stably and realize the rotary connector 100 including the FPC 110 having high bending resistance.

[0059] <Cross-sectional structure of FPC110>

[0060] Figure 8 1 is a diagram showing an example of a cross-sectional structure of the FPC 110 . Figure 8 The cross section shown is a cross section obtained by cutting the FPC 110 along a plane perpendicular to the longitudinal direction of the FPC 110 (the direction connecting both ends), and shows a portion where the signal conductor 116 is located. Figure 8 The vertical direction in is equivalent to the radial direction of the annular space S. Figure 8 The up and down directions in the Figure 8 The up-down directions shown do not represent universal up-down directions.

[0061] The FPC 110 includes a shielding film 111, an insulating layer 112, an adhesive layer 113, an insulating layer 114, an adhesive layer 115, a signal conductor 116, an adhesive layer 117, and an insulating layer 118. The shielding film 111 is an example of a shielding layer. The insulating layer 112, the adhesive layer 113, the insulating layer 114, and the adhesive layer 115 located between the shielding film 111 and the signal conductor 116 constitute a first insulating layer 110F. The adhesive layer 117 and the insulating layer 118 are located on the side of the signal conductor 116 opposite to the first insulating layer 110F. The adhesive layer 117 and the insulating layer 118 constitute a second insulating layer 110S. Here, as an example, the insulating layer on the side of the signal conductor 116 having the shielding film 111 is referred to as the first insulating layer 110F, and the insulating layer on the side of the signal conductor 116 not having the shielding film 111 is referred to as the second insulating layer 110S.

[0062] When looking at the FPC 110 with the signal conductor 116 as a reference, the first insulating layer 110F is thicker than the second insulating layer 110S. Fig. 9 Explain the reasons for doing so.

[0063] In addition, among the insulating layer 112, the adhesive layer 113, the insulating layer 114 and the adhesive layer 115 included in the first insulating layer 110F, the insulating layers 112 and 114 are examples of two insulating layers included in the first insulating layer 110F, and the adhesive layer 113 bonding the insulating layers 112 and 114 is an example of a bonding layer bonding the two insulating layers. As another example, an adhesive layer may also be used.

[0064] In such an FPC 110, the connection terminal portions 110a and 110b (see Figures 2 to 4 ) are connected to lead blocks 11 and 21 (refer to Figures 2 to 4 ) is connected. Moreover, on the inner peripheral side of the folded portion 110c ( Figure 3 The shielding film 111 is located on the inner side of the annular space S in the radial direction. Figure 3 In the portion indicated by the arrow B), the shielding film 111 is located on the radially outer side of the annular space S. In the folded portion 110c, the shielding film 111 becomes the outer side. Fig. 9 Explain the reasons for doing so.

[0065] The shielding film 111, the insulating layer 112, the adhesive layer 113, the insulating layer 114, the adhesive layer 115, the signal conductor 116, the adhesive layer 117, and the insulating layer 118 are stacked in this order. As an example, the first insulating layer 110F including the insulating layer 112, the adhesive layer 113, the insulating layer 114, and the adhesive layer 115 is a base insulating layer that becomes a base of the FPC 110, and the second insulating layer 110S including the adhesive layer 117 and the insulating layer 118 is a protective layer provided to protect the signal conductor 116.

[0066] As an example, FPC110 can be manufactured as follows. First, an adhesive layer 115 is used to adhere a metal foil for a signal conductor 116 to an insulating layer 114 in a first insulating layer 110F as a base insulating layer. Next, after the signal conductor 116 is formed by patterning based on etching, an insulating layer 118 is adhered to the signal conductor 116 using an adhesive layer 117. Then, the insulating layer 112 is adhered to the insulating layer 114 using an adhesive layer 113, and finally, a shielding film 111 is attached to the insulating layer 112. As an example, FPC110 can be manufactured using such a manufacturing process. In addition, the manufacturing process can also be performed in a process different from such a process depending on the material, ease of manufacturing, etc.

[0067] Next, the structure of each layer is described. Hereinafter, the elastic modulus of each layer is represented by Young's modulus (GPa).

[0068] The shielding film 111 is a layer formed by forming a metal layer, a metal mesh, or the like, such as copper or silver, on the surface of the insulating layer. In order to improve the transmission characteristics of the signal in the signal conductor 116, stabilize the impedance of the signal conductor 116, and shield noise, the shielding film 111 is stacked on the lower surface side of the insulating layer 112. As an example, the thickness of the shielding film 111 is 15 μm, and the elastic modulus is 0.8 GPa.

[0069] As an example, the insulating layer 112 is an insulating film made of polyimide. The insulating layer 112 may be made of a material other than polyimide as long as it can be rolled. As an example, the insulating layer 112 has a thickness of 12.5 μm and an elastic modulus of 4.1 GPa.

[0070] The adhesive layer 113 is an insulating layer composed of an adhesive for bonding the insulating layer 112 and the insulating layer 114. As an example, the thickness of the adhesive layer 113 is 30 μm and the elastic modulus is 1.2 GPa.

[0071] As an example, the insulating layer 114 is an insulating film made of polyimide. The insulating layer 114 may be made of a material other than polyimide as long as it can be rolled. As an example, the insulating layer 114 has a thickness of 25 μm and an elastic modulus of 4.1 GPa.

[0072] The adhesive layer 115 is an insulating layer made of an adhesive that bonds the insulating layer 114 and the signal conductor 116. As an example, the thickness of the adhesive layer 115 is 10 μm and the elastic modulus is 4.3 GPa. As an example, an epoxy adhesive or the like is used for the adhesive layer 115.

[0073] As an example, the signal conductor 116 is a signal conductor formed by etching a metal layer such as copper foil into a pattern such as wiring. The signal conductor 116 corresponds to a two-wire differential voltage method and includes a pair of signal lines for differential signals (two signal lines in one set). As an example, the thickness of the signal conductor 116 is 35 μm and the elastic modulus is 30 GPa.

[0074] Adhesive layer 117 is an insulating layer made of an adhesive that bonds signal conductor 116 and insulating layer 118. As an example, adhesive layer 117 has a thickness of 30 μm and an elastic modulus of 1.2 GPa. For example, acrylic adhesive, epoxy adhesive, etc. are used for adhesive layers 113 and 117.

[0075] The insulating layer 118 is, for example, an insulating film made of polyimide. The insulating layer 118 may be made of a material other than polyimide as long as it can be rolled. For example, the insulating layer 118 has a thickness of 12.5 μm and an elastic modulus of 4.1 GPa.

[0076] As described above, the total thickness of the insulating layer 112 , the adhesive layer 113 , the insulating layer 114 , and the adhesive layer 115 as the first insulating layer 110F is 77.5 μm, and the total thickness of the adhesive layer 117 and the insulating layer 118 as the second insulating layer 110S is 42.5 μm. Therefore, the first insulating layer 110F is thicker than the second insulating layer 110S.

[0077] In addition, the thickness of the first insulating layer 110F between the signal conductor 116 and the shielding film 111 in the FPC 110 is 77.5 μm. Figure 7 The thickness (55 μm) of the insulating layer (insulating layer 1B and adhesive layer 1C) between the signal conductor 1D and the shield film 1A in the FPC 1 for comparison shown is about 1.4 times thicker.

[0078] Thus, by lengthening the distance between the signal conductor 116 and the shielding film 111 in the FPC 110, the impedance of the signal conductor 116 of the FPC 110 becomes higher, and the value calculated by simulation using the differential impedance model is about 120Ω. Here, the signal conductor width, thickness, and signal conductor spacing are set to the same conditions as those of the comparative FPC 1. Such a high impedance is a good value that can be fully utilized in a two-wire differential voltage data communication network represented by CAN.

[0079] In addition, in order to achieve easy bending and high bending resistance, FPC110 divides the portion of the insulating film other than the adhesive layer included in the first insulating layer 110F into two insulating layers 112 and 114, and uses a 30μm thick adhesive layer 113 to bond them. In addition, the elastic modulus of the adhesive layer 113 is smaller than the elastic modulus of the two insulating layers 112 and 114. The elastic modulus of the adhesive layer 113 is 1.2Gpa, and it is a member that is very easy to bend and relieves stress, so the thickness of the first insulating layer 110F can be obtained and easy bending can be achieved. In addition, due to easy bending, the high bending resistance of the first insulating layer 110F is achieved. In addition, even in the case where the elastic modulus of the adhesive layer 113 is not less than that of the insulating layers 112 and 114, the bending resistance can be improved by using a material with strong adhesion to the insulating layers 112 and 114 or a material with strong toughness.

[0080] However, the FPC 110 is provided on the inner peripheral side of the folded portion 110c ( Figure 3 The portion indicated by arrow A) and the outer peripheral side of the folded portion 110c ( Figure 3 The wound FPC 110 overlaps with each other (see the portion indicated by arrow B).

[0081] On the inner peripheral side of the folded portion 110c ( Figure 3 The shielding film 111 is located on the radially inner side of the annular space S, and the adhesive layer 117 and the insulating layer 118 are located on the radially outer side of the annular space S. Therefore, the signal conductor 116 overlaps with the shielding film 111 on the outer side of the circle via the adhesive layer 117 and the insulating layer 118, i.e., the second insulating layer 110S.

[0082] In addition, on the outer peripheral side of the folded portion 110c ( Figure 3 The shielding film 111 is located on the radially outer side of the annular space S, and the adhesive layer 117 and the insulating layer 118 are located on the radially inner side of the annular space S. Therefore, the signal conductor 116 overlaps with the shielding film 111 on the inner side of the circle via the adhesive layer 117 and the insulating layer 118, i.e., the second insulating layer 110S.

[0083] Thus, the shield film 111 of the adjacent FPC exists with the second insulating layer 110S thinner than the first insulating layer 110F interposed therebetween, and the impedance of the signal conductor 116 may be reduced due to the shield film 111 near the signal conductor 116. However, as described below, the FPC 110 can achieve stable impedance of the signal conductor 116. Fig. 9 It is a cross-sectional view showing a state where the FPC 110 is overlapped.

[0084] As described above, since the length of the FPC 110 is tolerant, the overlapping portions of the FPC 110 are not completely adhered to each other as in the case where the overlapping FPC 110 are bonded to each other, but the more air layer there is between them, the more gently they overlap. Fig. 9 As shown, there is an air layer between FPC110-1 and FPC110-2 which is one circle inside FPC110-1, and the shielding film 111 of FPC110-1 overlaps with the signal conductor 116 of FPC110-2 which is one circle inside through the adhesive layer 117 and the insulating layer 118 of FPC110-2 which is one circle inside and the air layer. As a result, the shielding film 111 of FPC110-1 and the signal conductor 116 of FPC110-2 which is one circle inside are kept at a sufficient distance through the air layer which is an insulator. Therefore, even if the shielding films 111 of adjacent FPC110-1 are overlapped, it is not necessary to make the thickness of the second insulating layer 110S the same as the first insulating layer 110F, and even if the second insulating layer 110S is set to be thinner than the first insulating layer 110F, it is possible to prevent the impedance from being reduced due to the influence of the shielding film 111 of FPC110-1. Furthermore, by setting the second insulating layer 110S thinner, the FPC 110 is easier to bend than when the second insulating layer 110S is set to have the same thickness as the first insulating layer 110F, and stress generated during bending can be suppressed, thereby suppressing a decrease in bending resistance.

[0085] Furthermore, the same effect can be obtained even if other FPCs are overlapped in addition to FPC 110. That is, if the other FPC is an FPC without a shielding layer, the insulating layer of the other FPC exists with the FPC 110 separated by an air layer, so the impedance characteristics of FPC 110 are greatly affected by the shielding film 111 of FPC 110, and even if the second insulating layer 110S is made thinner than the first insulating layer 110F, good impedance can be ensured.

[0086] In addition, even when the adjacent FPC has a shielding layer like FPC 110, or when it is only a shielding layer, since there is an air layer between them, even if the second insulating layer 110S is made thinner than the first insulating layer 110F, good impedance can be ensured. In addition, as long as the first insulating layer is set to be thinner, the bending resistance can be improved.

[0087] In this embodiment, the first insulating layer 110F has a structure in which the two insulating layers 112 and 114 are bonded by the adhesive layer 113, but a single insulating layer may form the two insulating layers 112 and 114 and the adhesive layer 113. However, by making the second insulating layer 110S thinner, the bending resistance can be ensured.

[0088] Alternatively, lubricant or the like may be applied to the surface of FPC 110 or other FPCs. In this case, lubricant is interposed in the air layer, but the distance between the signal conductor 116 of FPC 110 and the shield layer of other FPCs is ensured, so the same effect can be obtained.

[0089] As described above, the thickness of the second insulating layer 110S on the side of the signal conductor 116 opposite to the side on which the shielding membrane 111 is arranged is 42.5 μm, which is thinner than the thickness of the first insulating layer 110F (77.5 μm). However, the FPC 110 used in the rotating connector 100 has a stable signal impedance even in the overlapping portion, and can obtain the optimal impedance for communication and ensure bending resistance.

[0090] That is, for the FPC 110 of the rotary connector 100, by setting the relationship of the thickness of the first insulating layer 110F > the thickness of the second insulating layer 110S to be established, a predetermined impedance can be ensured, and a decrease in the bending resistance of the FPC 110S can be suppressed. The relationship of the thickness of the first insulating layer 110F > the thickness of the second insulating layer 110S can be achieved, for example, by increasing the thickness of the first insulating layer 110F at the design stage, or by reducing the thickness of the second insulating layer 110S at the design stage.

[0091] In addition, on the outer peripheral side of the folded portion 110c ( Figure 3 Since the shielding film 111 is located on the radially outer side of the annular space S, the FPC 110 can shield noise from the outside.

[0092] <Effect>

[0093] As described above, the rotary connector 100 includes: a fixed member 2 having a lead block 11; a rotating member 3 having a lead block 21, which is arranged to be relatively rotatable relative to the fixed member 2; and an FPC 110, which is accommodated in an annular space S between the fixed member 2 and the rotating member 3 and has two ends connected to the fixed member 2 and the rotating member 3, respectively. The FPC 110 includes: a first insulating layer 110F; a second insulating layer 110S; a signal conductor 116 formed between the first insulating layer 110F and the second insulating layer 110S; a shielding film 111, which is laminated on the side of the first insulating layer 110F opposite to the signal conductor 116; and the first insulating layer 110F is thicker than the second insulating layer 110S.

[0094] Therefore, since the first insulating layer 110F is thicker than the second insulating layer 110S, the distance between the shielding film 111 and the signal conductor 116 can be sufficiently ensured, and the impedance of the signal conductor 116 can be stabilized. In addition, when the FPC 110 is accommodated in the annular space S and wound, a layer of air is interposed between the overlapping FPCs 110, so that even if the thickness of the second insulating layer 110S is thinner than the thickness of the first insulating layer 110F, the distance from the shielding film of the adjacent FPC can be ensured, so that the optimal impedance of the FPC 110 can be ensured, and by setting the thickness of the second insulating layer S to be thinner than the thickness of the first insulating layer F, it is possible to suppress the reduction in bending resistance.

[0095] Therefore, it is possible to provide the rotary connector 100 that achieves good impedance characteristics and bending resistance.

[0096] In addition, the first insulating layer 110F includes two insulating layers 112 and 114 and an adhesive layer 113 that joins the two insulating layers 112 and 114. The portion of the insulating film included in the first insulating layer 110F is divided into the two insulating layers 112 and 114, and the two insulating layers are joined by the adhesive layer 113. Therefore, it is possible to provide a rotary connector 100 that achieves both stabilization of the impedance of the shielding film 111 by ensuring the thickness of the first insulating layer 110F and improvement of the bending resistance of the first insulating layer 110F.

[0097] Furthermore, since the elastic modulus of the adhesive layer 113 is smaller than the elastic moduli of the two insulating layers 112 and 114 , stress applied to the first insulating layer 110F when it is bent can be alleviated, thereby improving the bending resistance.

[0098] In addition, the FPC 110 has a folded portion 110c that is folded back in the annular space S and whose winding direction is reversed. On the inner circumference side of the folded portion 110c, the shielding film 111 is located radially inward, and on the outer circumference side of the folded portion 110c, the shielding film 111 is located radially outward. Therefore, it is possible to shield noise from outside the rotary connector 100, and it is possible to realize a state in which a high-speed digital signal transmitted in the signal conductor 116 has a good waveform.

[0099] In addition, the above description is about the method of using FPC 110, but the same structure can be realized in a flat cable in which a conductive wire is coated with a laminated resin instead of FPC 110. In this case, the following structure can be adopted: a conductive wire is used instead of the signal conductor 116, and the conductive wire is coated with a laminated resin, for example, the thickness of the laminated resin is changed above and below the conductive wire, or a resin layer is provided between the laminated film and the shielding layer.

[0100] In addition, the above description is about the case where the first insulating layer 110F is the base insulating layer of the FPC 110 and the second insulating layer 110S is the protective layer, that is, the shielding film 111 is formed on the base insulating layer side. However, even in the structure where the shielding film 111 is present on the protective layer side of the FPC 110, the same effect can be obtained. In this case, for example, first, an adhesive layer 115 is provided on the insulating layer 114 as the base insulating layer, and a metal foil for the signal conductor 116 is attached to the adhesive layer 115. Then, after the metal foil is patterned to form the signal conductor 116, an adhesive layer 117, an insulating layer 118, an adhesive layer similar to the adhesive layer 113, and an insulating layer similar to the insulating layer 112 are formed on the signal conductor 116 as a protective layer. Then, the shielding film 111 is provided on the insulating layer to make it possible to manufacture. In this case, the protective layer becomes the first insulating layer, and the base insulating layer becomes the second insulating layer.

[0101] <Modification>

[0102] Fig.10 FIG. 1 is a diagram showing a state where the FPC 110 of a modified example of the embodiment is bent. In the modified example, the connection terminal portions 110a and 110b (see FIG. 110b ) are bent so that the shielding film 111 is located inside the folded portion 110c. Figures 2 to 4 ) are connected to lead blocks 11 and 21 (refer to Figures 2 to 4 )connect.

[0103] Therefore, on the inner peripheral side of the folded portion 110c ( Figure 3 The shielding film 111 is located on the radially outer side of the annular space S. In addition, on the outer peripheral side of the folded portion 110c ( Figure 3 The shielding film 111 is located on the inner side of the annular space S in the radial direction (as shown by the arrow B).

[0104] Thus, the folded portion 110c of the FPC 110 connected between the lead blocks 11 and 21 is as shown in FIG. Fig.10 As shown, the first insulating layer 110F and the shielding film 111 are located on the inner side, and the second insulating layer 110S is located on the outer side.

[0105] like Fig.10 As shown, in the folded portion 110c, the outer side in the thickness direction of the FPC 110 is stretched in the extending direction of the FPC 110, and the inner side is compressed. The thinner side has a higher resistance to stretching, and the thicker side has a higher resistance to compression.

[0106] Since the second insulating layer 110S is thinner than the first insulating layer 110F, the second insulating layer 110S is located outside the folded portion 110c, thereby improving the tensile resistance of the FPC 110. In addition, the first insulating layer 110F and the shielding film are located inside the folded portion 110c, thereby improving the compression resistance of the FPC 110.

[0107] When the FPC 110 is connected between the lead blocks 11 and 21, the shielding film 111 is formed in the folded portion 110c. Fig.10 Whether to locate inside or outside as shown can be determined based on the balance between resistance to noise from the outside and resistance to tension and compression in the folded portion 110 c.

[0108] As described above, in the modified example, the FPC 110 has the folded portion 110c folded in the annular space S and having the winding direction reversed, and the shielding film 111 is located inside the folded portion 110c. Therefore, the tensile resistance of the FPC 110 can be improved, and the compression resistance of the FPC 110 can be improved.

[0109] As mentioned above, the rotary connector according to the exemplary embodiment of the present invention has been described, but the present invention is not limited to the specifically disclosed embodiment, and various modifications and changes can be made without departing from the scope of the claims.

[0110] In addition, the present international application claims priority based on Japanese Patent Application No. 2022-099836, filed on June 21, 2022, the entire contents of which are incorporated herein by reference.

[0111] Description of reference numerals:

[0112] 2Fixing parts

[0113] 3 Rotating parts

[0114] 100 Rotary Connector

[0115] 110FPC (an example of a flexible cable)

[0116] 110a Connection terminal portion

[0117] 110b connection terminal part

[0118] 110c folded portion

[0119] 110F first insulation layer

[0120] 110S second insulation layer

[0121] 111 Shielding film (an example of a shielding layer)

[0122] 112 insulation layer

[0123] 113 Adhesive layer (an example of a bonding layer)

[0124] 114 Insulation layer

[0125] 115 adhesive layer

[0126] 116 signal conductor

[0127] 117 Adhesive layer

[0128] 118 insulation layer

Claims

1. A rotary connector, wherein: have: A fixing member having a first external connection portion; A rotating member having a second external connection portion, wherein the rotating member is configured to be relatively rotatable relative to the fixed member; as well as a flexible cable, accommodated in the annular space between the fixed member and the rotating member, and electrically connected to the first external connection portion of the fixed member and the second external connection portion of the rotating member respectively; The flexible cable has: a first insulating layer; a second insulating layer; a signal conductor formed between the first insulating layer and the second insulating layer; as well as a shielding layer, stacked on a side of the first insulating layer opposite to the signal conductor; The first insulating layer is thicker than the second insulating layer.

2. The rotary connector according to claim 1, wherein: The first insulating layer has: Two insulation layers; as well as A bonding layer is bonded between the two insulating layers.

3. The rotary connector according to claim 2, wherein: The elastic modulus of the bonding layer is smaller than the elastic moduli of the two insulating layers.

4. The rotary connector according to any one of claims 1 to 3, wherein: The flexible cable has a folded portion folded in the annular space and having a reverse winding direction, wherein the shield layer is located radially inward on the inner circumference of the folded portion and radially outward on the outer circumference of the folded portion.

5. The rotary connector according to any one of claims 1 to 3, wherein: The flexible cable has a folded portion that is folded back in the annular space and whose winding direction is reversed, and in the folded portion, the shield layer is located inside the folded portion.

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