Patent Publication Number: US-2021165466-A1

Title: Foldable electronic device including hinge assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2019-0158437, filed on Dec. 2, 2019, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     The disclosure relates generally to a foldable electronic device including a hinge assembly. 
     2. Description of Related Art 
     With the development of digital technologies, electronic devices are provided in various forms, such as a smart phone, a tablet personal computer (PC), or a personal digital assistant (PDA). The electronic device is also developed such that it is portable or worn by a user to improve portability and user accessibility. 
     Recently, a portable electronic device such as a smart phone or a table PC, has been made lighter and thinner for ease of portability, and has been developed in various fields for convenience of use. In particular, despite that a foldable electronic device with a flexible display provides a relatively larger screen than a typical bar-type electronic device, portability can be improved since a size thereof is decreased when folded, thereby being satisfying consumers&#39; preferences. 
     A foldable electronic device may include a flexible display and a plurality of housings. The plurality of housings and the flexible display may be coupled in a state of being supported by a hinge assembly, and may rotate the housing within a specified range according to a user&#39;s manipulation. The electronic device may be switched from a folded state to an unfolded state or from the unfolded state to the folded state through a process of rotating the plurality of housings. 
     There is a need to dispose various structures in order for the hinge assembly to rotate the housing. However, since a space to which the various structures can be disposed is narrow in a foldable electronic device with a narrow folding region, it may be difficult to dispose the various structures. Accordingly, there is a method that has been proposed to decrease a size of the hinge assembly by integrating the various structures. However, in the case of the aforementioned method, some regions of the flexible display may not be supported by the hinge assembly in a process in which the foldable electronic device is folded. Therefore, it is difficult to prevent some regions of the flexible display from being sagged or damaged. 
     SUMMARY 
     The present disclosure has been made to address the above-mentioned problems and disadvantages, and to provide at least the advantages described below. 
     According to an aspect of the disclosure, an electronic device includes a first housing, a second housing, a hinge assembly coupling the first housing and the second housing so that the second housing is rotatable with respect to the first housing, and a flexible display disposed from one region of the first housing to at least one region of the second housing across the hinge assembly. The hinge assembly includes a first bracket coupled to at least one region of the first housing to rotate about a virtual first rotation axis, a second bracket coupled to at least one region of the second housing to rotate about a virtual second rotation axis, a fixing bracket supporting the first bracket and the second bracket, a first shaft rotating about a third rotation axis different from the virtual first rotation axis, a second shaft adjacent to the first shaft to rotate about a fourth rotation axis different from the virtual second rotation axis, a first arm portion coupled to the first shaft to rotate about the third rotation axis, and having one side coupled to at least one region of the first bracket, a second arm portion coupled to the second shaft to rotate about the fourth rotation axis, and having one side coupled to at least one region of the second bracket, and a support portion located between the first arm portion and the second arm portion. The support portion supports at least one region of the flexible display when the electronic device is in an unfolded state, and may be spaced apart from the flexible display as the electronic device rotates from the unfolded state to a folded state. 
     According to another aspect of the disclosure, a hinge assembly includes a hinge housing, and at least one hinge structure disposed inside the hinge housing. The hinge structure includes a first bracket rotating about a virtual first rotation axis, a second bracket adjacent to the first bracket and rotating about a virtual second rotation axis different from the virtual first rotation axis, a fixing bracket supporting the first bracket and the second bracket, a first shaft rotating about a third rotation axis different from the virtual first rotation axis, and having a first gear coupled thereto, a second shaft adjacent to the first shaft to rotate about a fourth rotation axis different from the virtual second rotation axis, and having a second gear coupled thereto, a shaft bracket supporting the first shaft and the second shaft, a first idle gear gear-coupled with the first gear, a second idle gear gear-coupled with the first idle gear and the second gear, a first arm portion coupled to the first shaft to rotate about the third rotation axis, and having one side coupled to at least one region of the first bracket, a second arm portion coupled to the second shaft to rotate about the fourth rotation axis, and having one side coupled to at least one region of the second bracket, and a support portion moving up and down with the rotation of the first arm portion and second arm portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a block diagram of an electronic device in a network environment, according to an embodiment; 
         FIG. 2A  is an exploded view of an electronic device in an unfolded state, according to an embodiment; 
         FIG. 2B  illustrates a folded state of an electronic device, according to an embodiment; 
         FIG. 3  illustrates a hinge assembly of an electronic device, according to an embodiment; 
         FIG. 4  illustrates a hinge structure constructing a hinge assembly of an electronic device, according to an embodiment; 
         FIG. 5  is an exploded perspective view of the hinge structure of  FIG. 4 , according to an embodiment; 
         FIG. 6A  illustrates a configuration of a hinge structure when an electronic device is in an unfolded state, according to an embodiment; 
         FIG. 6B  illustrates a configuration of a hinge structure when an electronic device rotates from an unfolded state to a folded state, according to an embodiment; 
         FIG. 6C  illustrates a structure of a hinge structure when an electronic device is in a folded state, according to an embodiment; 
         FIG. 7  illustrates elements of a fixing portion and a detent structure of a hinge structure, according to an embodiment; 
         FIG. 8  illustrates a coupling relationship between elements of an arm structure and a detent structure of a hinge structure, according to an embodiment; 
         FIG. 9  is an enlarged view illustrating elements of a hinge structure, according to an embodiment; 
         FIG. 10A  is a cross-sectional view of a hinge structure when an electronic device is in an unfolded state, according to an embodiment; 
         FIG. 10B  is a cross-sectional view of a hinge structure when an electronic device is in a folded state, according to an embodiment; 
         FIG. 11A  is a cross-sectional view of a hinge structure when an electronic device is in an unfolded state, according to another embodiment; 
         FIG. 11B  is a cross-sectional view of a hinge structure when an electronic device is in a folded state, according to an embodiment; 
         FIG. 12A  is a cross-sectional view of a hinge structure when an electronic device is in an unfolded state, according to an embodiment; 
         FIG. 12B  is a cross-sectional view of a hinge structure when an electronic device is in a folded state, according to an embodiment; 
         FIG. 13A  is a cross-sectional view of a hinge structure when an electronic device is in an unfolded state, according to another embodiment; and 
         FIG. 13B  is a cross-sectional view of a hinge structure when an electronic device is in a folded state according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the disclosure provide an electronic device having a structure capable of supporting a flexible display even in a folding process to prevent some regions of the flexible display from being sagged or damaged in a process in which the foldable electronic device is folded. 
       FIG. 1  is a block diagram illustrating an electronic device  101  in a network environment  100  according to various embodiments. Referring to  FIG. 1 , the electronic device  101  in the network environment  100  may communicate with an electronic device  102  via a first network  198  (e.g., a short-range wireless communication network), or an electronic device  104  or a server  108  via a second network  199  (e.g., a long-range wireless communication network). According to an embodiment, the electronic device  101  may communicate with the electronic device  104  via the server  108 . According to an embodiment, the electronic device  101  may include a processor  120 , memory  130 , an input device  150 , a sound output device  155 , a display device  160 , an audio module  170 , a sensor module  176 , an interface  177 , a haptic module  179 , a camera module  180 , a power management module  188 , a battery  189 , a communication module  190 , a subscriber identification module (SIM)  196 , or an antenna module  197 . In some embodiments, at least one (e.g., the display device  160  or the camera module  180 ) of the components may be omitted from the electronic device  101 , or one or more other components may be added in the electronic device  101 . In some embodiments, some of the components may be implemented as single integrated circuitry. For example, the sensor module  176  (e.g., a fingerprint sensor, an iris sensor, or an illuminance sensor) may be implemented as embedded in the display device  160  (e.g., a display). 
     The processor  120  may execute, for example, software (e.g., a program  140 ) to control at least one other component (e.g., a hardware or software component) of the electronic device  101  coupled with the processor  120 , and may perform various data processing or computation. According to one embodiment, as at least part of the data processing or computation, the processor  120  may load a command or data received from another component (e.g., the sensor module  176  or the communication module  190 ) in volatile memory  132 , process the command or the data stored in the volatile memory  132 , and store resulting data in non-volatile memory  134 . According to an embodiment, the processor  120  may include a main processor  121  (e.g., a central processing unit (CPU) or an application processor (AP)), and an auxiliary processor  123  (e.g., a graphics processing unit (GPU), an image signal processor (ISP), a sensor hub processor, or a communication processor (CP)) that is operable independently from, or in conjunction with, the main processor  121 . Additionally or alternatively, the auxiliary processor  123  may be adapted to consume less power than the main processor  121 , or to be specific to a specified function. The auxiliary processor  123  may be implemented as separate from, or as part of the main processor  121 . 
     The auxiliary processor  123  may control at least some of functions or states related to at least one component (e.g., the display device  160 , the sensor module  176 , or the communication module  190 ) among the components of the electronic device  101 , instead of the main processor  121  while the main processor  121  is in an inactive (e.g., sleep) state, or together with the main processor  121  while the main processor  121  is in an active state (e.g., executing an application). According to an embodiment, the auxiliary processor  123  (e.g., an ISP or a CP) may be implemented as part of another component (e.g., the camera module  180  or the communication module  190 ) functionally related to the auxiliary processor  123 . 
     The memory  130  may store various data used by at least one component (e.g., the processor  120  or the sensor module  176 ) of the electronic device  101 . The various data may include, for example, software (e.g., the program  140 ) and input data or output data for a command related thereto. The memory  130  may include the volatile memory  132  or the non-volatile memory  134 . 
     The program  140  may be stored in the memory  130  as software, and may include, for example, an operating system (OS)  142 , middleware  144 , or an application  146 . 
     The input device  150  may receive a command or data to be used by another component (e.g., the processor  120 ) of the electronic device  101 , from the outside (e.g., a user) of the electronic device  101 . The input device  150  may include, for example, a microphone, a mouse, a keyboard, or a digital pen (e.g., a stylus pen). 
     The sound output device  155  may output sound signals to the outside of the electronic device  101 . The sound output device  155  may include, for example, a speaker or a receiver. The speaker may be used for general purposes, such as playing multimedia or playing a record, and the receiver may be used for an incoming call. According to an embodiment, the receiver may be implemented as separate from, or as part of the speaker. 
     The display device  160  may visually provide information to the outside (e.g., a user) of the electronic device  101 . The display device  160  may include, for example, a display, a hologram device, or a projector and control circuitry to control a corresponding one of the display, hologram device, and projector. According to an embodiment, the display device  160  may include touch circuitry adapted to detect a touch, or sensor circuitry (e.g., a pressure sensor) adapted to measure the intensity of force incurred by the touch. 
     The audio module  170  may convert a sound into an electrical signal and vice versa. According to an embodiment, the audio module  170  may obtain the sound via the input device  150 , or output the sound via the sound output device  155  or a headphone of an external electronic device (e.g., an electronic device  102 ) directly (e.g., wiredly) or wirelessly coupled with the electronic device  101 . 
     The sensor module  176  may detect an operational state (e.g., power or temperature) of the electronic device  101  or an environmental state (e.g., a state of a user) external to the electronic device  101 , and then generate an electrical signal or data value corresponding to the detected state. According to an embodiment, the sensor module  176  may include, for example, a gesture sensor, a gyro sensor, an atmospheric pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a proximity sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, or an illuminance sensor. 
     The interface  177  may support one or more specified protocols to be used for the electronic device  101  to be coupled with the external electronic device (e.g., the electronic device  102 ) directly (e.g., wiredly) or wirelessly. According to an embodiment, the interface  177  may include, for example, a high definition multimedia interface (HDMI), a universal serial bus (USB) interface, a secure digital (SD) card interface, or an audio interface. 
     A connecting terminal  178  may include a connector via which the electronic device  101  may be physically connected with the external electronic device (e.g., the electronic device  102 ). According to an embodiment, the connecting terminal  178  may include, for example, an HDMI connector, a USB connector, an SD card connector, or an audio connector (e.g., a headphone connector). 
     The haptic module  179  may convert an electrical signal into a mechanical stimulus (e.g., a vibration or a movement) or electrical stimulus which may be recognized by a user via his tactile sensation or kinesthetic sensation. According to an embodiment, the haptic module  179  may include, for example, a motor, a piezoelectric element, or an electric stimulator. 
     The camera module  180  may capture a still image or moving images. According to an embodiment, the camera module  180  may include one or more lenses, image sensors, ISP, or flashes. 
     The power management module  188  may manage power supplied to the electronic device  101 . According to one embodiment, the power management module  188  may be implemented as at least part of, for example, a power management integrated circuit (PMIC). 
     The battery  189  may supply power to at least one component of the electronic device  101 . According to an embodiment, the battery  189  may include, for example, a primary cell which is not rechargeable, a secondary cell which is rechargeable, or a fuel cell. 
     The communication module  190  may support establishing a direct (e.g., wired) communication channel or a wireless communication channel between the electronic device  101  and the external electronic device (e.g., the electronic device  102 , the electronic device  104 , or the server  108 ) and performing communication via the established communication channel. The communication module  190  may include one or more CPs that are operable independently from the processor  120  (e.g., the AP) and supports a direct (e.g., wired) communication or a wireless communication. According to an embodiment, the communication module  190  may include a wireless communication module  192  (e.g., a cellular communication module, a short-range wireless communication module, or a global navigation satellite system (GNSS) communication module) or a wired communication module  194  (e.g., a local area network (LAN) communication module or a power line communication (PLC) module). A corresponding one of these communication modules may communicate with the external electronic device via the first network  198  (e.g., a short-range communication network, such as Bluetooth™, wireless-fidelity (Wi-Fi) direct, or Infrared Data Association (IrDA)) or the second network  199  (e.g., a long-range communication network, such as a cellular network, the Internet, or a computer network (e.g., LAN or wide area network (WAN)). These various types of communication modules may be implemented as a single component (e.g., a single chip), or may be implemented as multi components (e.g., multi chips) separate from each other. The wireless communication module  192  may identify and authenticate the electronic device  101  in a communication network, such as the first network  198  or the second network  199 , using subscriber information (e.g., international mobile subscriber identity (IMSI)) stored in the subscriber identification module  196 . 
     The antenna module  197  may transmit or receive a signal or power to or from the outside (e.g., the external electronic device) of the electronic device  101 . According to an embodiment, the antenna module  197  may include an antenna including a radiating element composed of a conductive material or a conductive pattern formed in or on a substrate (e.g., PCB). According to an embodiment, the antenna module  197  may include a plurality of antennas. In such a case, at least one antenna appropriate for a communication scheme used in the communication network, such as the first network  198  or the second network  199 , may be selected, for example, by the communication module  190  (e.g., the wireless communication module  192 ) from the plurality of antennas. The signal or the power may then be transmitted or received between the communication module  190  and the external electronic device via the selected at least one antenna. According to an embodiment, another component (e.g., a radio frequency integrated circuit (RFIC)) other than the radiating element may be additionally formed as part of the antenna module  197 . 
     At least some of the above-described components may be coupled mutually and communicate signals (e.g., commands or data) therebetween via an inter-peripheral communication scheme (e.g., a bus, general purpose input and output (GPIO), serial peripheral interface (SPI), or mobile industry processor interface (MIPI)). 
     According to an embodiment, commands or data may be transmitted or received between the electronic device  101  and the external electronic device  104  via the server  108  coupled with the second network  199 . Each of the electronic devices  102  and  104  may be a device of a same type as, or a different type, from the electronic device  101 . According to an embodiment, all or some of the operations to be executed at the electronic device  101  may be executed at one or more of the external electronic devices  102 ,  104 , or  108 . For example, if the electronic device  101  should perform a function or a service automatically, or in response to a request from a user or another device, the electronic device  101 , instead of, or in addition to, executing the function or the service, may request the one or more external electronic devices to perform at least part of the function or the service. The one or more external electronic devices receiving the request may perform the at least part of the function or the service requested, or an additional function or an additional service related to the request, and transfer an outcome of the performing to the electronic device  101 . The electronic device  101  may provide the outcome, with or without further processing of the outcome, as at least part of a reply to the request. To that end, a cloud computing, distributed computing, or client-server computing technology may be used, for example. 
     The electronic device according to various embodiments may be one of various types of electronic devices. The electronic devices may include, for example, a portable communication device (e.g., a smartphone), a computer device, a portable multimedia device, a portable medical device, a camera, a wearable device, or a home appliance. According to an embodiment of the disclosure, the electronic devices are not limited to those described above. 
     It should be appreciated that various embodiments of the present disclosure and the terms used therein are not intended to limit the technological features set forth herein to particular embodiments and include various changes, equivalents, or replacements for a corresponding embodiment. With regard to the description of the drawings, similar reference numerals may be used to refer to similar or related elements. It is to be understood that a singular form of a noun corresponding to an item may include one or more of the things, unless the relevant context clearly indicates otherwise. As used herein, each of such phrases as “A or B,” “at least one of A and B,” “at least one of A or B,” “A, B, or C,” “at least one of A, B, and C,” and “at least one of A, B, or C,” may include any one of, or all possible combinations of the items enumerated together in a corresponding one of the phrases. As used herein, such terms as “1st” and “2nd,” or “first” and “second” may be used to simply distinguish a corresponding component from another, and does not limit the components in other aspect (e.g., importance or order). It is to be understood that if an element (e.g., a first element) is referred to, with or without the term “operatively” or “communicatively”, as “coupled with,” “coupled to,” “connected with,” or “connected to” another element (e.g., a second element), it means that the element may be coupled with the other element directly (e.g., wiredly), wirelessly, or via a third element. 
     As used herein, the term “module” may include a unit implemented in hardware, software, or firmware, and may interchangeably be used with other terms, for example, “logic,” “logic block,” “part,” or “circuitry”. A module may be a single integral component, or a minimum unit or part thereof, adapted to perform one or more functions. For example, according to an embodiment, the module may be implemented in a form of an application-specific integrated circuit (ASIC). 
     Various embodiments as set forth herein may be implemented as software (e.g., the program  140 ) including one or more instructions that are stored in a storage medium (e.g., internal memory  136  or external memory  138 ) that is readable by a machine (e.g., the electronic device  101 ). For example, a processor (e.g., the processor  120 ) of the machine (e.g., the electronic device  101 ) may invoke at least one of the one or more instructions stored in the storage medium, and execute it, with or without using one or more other components under the control of the processor. This allows the machine to be operated to perform at least one function according to the at least one instruction invoked. The one or more instructions may include a code generated by a complier or a code executable by an interpreter. The machine-readable storage medium may be provided in the form of a non-transitory storage medium. Wherein, the term “non-transitory” simply means that the storage medium is a tangible device, and does not include a signal (e.g., an electromagnetic wave), but this term does not differentiate between where data is semi-permanently stored in the storage medium and where the data is temporarily stored in the storage medium. 
     A method according to various embodiments of the disclosure may be included and provided in a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read only memory (CD-ROM)), or be distributed (e.g., downloaded or uploaded) online via an application store (e.g., PlayStore™), or between two user devices (e.g., smart phones) directly. If distributed online, at least part of the computer program product may be temporarily generated or at least temporarily stored in the machine-readable storage medium, such as memory of the manufacturer&#39;s server, a server of the application store, or a relay server. 
     According to various embodiments, each component (e.g., a module or a program) of the above-described components may include a single entity or multiple entities. According to various embodiments, one or more of the above-described components may be omitted, or one or more other components may be added. Alternatively or additionally, a plurality of components (e.g., modules or programs) may be integrated into a single component. In such a case, according to various embodiments, the integrated component may still perform one or more functions of each of the plurality of components in the same or similar manner as they are performed by a corresponding one of the plurality of components before the integration. According to various embodiments, operations performed by the module, the program, or another component may be carried out sequentially, in parallel, repeatedly, or heuristically, or one or more of the operations may be executed in a different order or omitted, or one or more other operations may be added. 
       FIG. 2A  is an exploded view of an electronic device  101  in an unfolded state, according to an embodiment, and  FIG. 2B  illustrates a folded state of the electronic device  101 , according to an embodiment. 
     Referring to  FIG. 2A  and  FIG. 2B , the electronic device  101  includes a foldable housing  210  (a “housing”) including a first housing  211  and a second housing  212 , a flexible display  220 , a hinge assembly  300 , and a cover  230  (a “rear cover”). 
     The first housing  211  and the second housing  212  may form a space in which electronic components (e.g., a PCB, a battery, or a processor) of the electronic device  101  can be disposed, and may form a side face of the electronic device  101 . Various types of components for performing various functions of the electronic device  101  may be disposed inside the first housing  211  and the second housing  212 . For example, electronic components such as a front camera, a receiver, or a sensor (e.g., a proximity sensor) may be disposed inside the first housing  211  and the second housing  212 . The aforementioned electronic components may be exposed to a front face of the electronic device  101  through at least one opening or recess prepared on the flexible display  220 . 
     The first housing  211  and the second housing  212  may be disposed in parallel to each other when the electronic device  101  is in an unfolded state. When the electronic device  101  is in the folded state, the first housing  211  may rotate (or turn) with respect to the second housing  212 , so that one face of the first housing  211  faces one face of the second housing  212 . 
     The first housing  211  and the second housing  212  may construct a recess for accommodating the flexible display  220 , and the flexible display  220  may be supported by the first housing  211  and the second housing  212  by being mounted to the recess. The flexible display  220  may be supported by a first support plate  221  and/or a second support plate  222  located between the flexible display  220  and first housing  211  and the second housing  212 , and details thereof will be described below. The first housing  211  and the second housing  212  may be constructed of a metal material and/or non-metal material having a specified rigidity to support the flexible display  220 . 
     The flexible display  220  may be disposed on the first housing  211  and the second housing  212  to construct a front face (e.g., a face in the +y direction of  FIG. 2A ) of the electronic device  101  when the electronic device  101  is in the unfolded state. That is, the flexible display  220  may be disposed by extending up to at least one region of the second housing  212  across the hinge assembly  300  from one region of the first housing  211 . The flexible display  220  may be disposed on the first housing  211  and the second housing  212  by being mounted to the recess constructed by the first housing  211  and the second housing  212 . 
     The flexible display  220  may include a first region  220   a  corresponding to at least one region of the first housing  211 , a second region  220   b  corresponding to at least one region of the second housing  212 , and a folding region  220   c  located between the first region  220   a  and the second region  220   b  and having a flexible characteristic. 
     The first region  220   a , the second region  220   b , and the folding region  220   c  of the flexible display  220  may also be constructed to have the flexible characteristic. The first region  220   a , the folding region  220   c , and the second region  220   b  may be disposed in parallel to face the same direction (e.g., the +y direction of  FIG. 2A ), when the electronic device  101  is in the unfolded state. Alternatively, when the electronic device  101  is in the folded state, the folding region  220   c  may be bent such that the first region  220   a  and the second region  220   b  are disposed to face each other. 
     At least one of the first region  220   a  or the second region  220   b  of the flexible display  220  may be attached to a face of the first housing  211  and a face of the second housing  212 . The flexible display  220  may be attached to a face of the first housing  211  and a face of the second housing  211  through the support plates  221  and  222  located between the flexible display  220  and the first housing  211  and second housing  212 . 
     The support plates  221  and  222  may include the first support plate  221  attached to at least one region of the first housing  211  to support the first region  220   a  of the flexible display  220  and the second support plate  222  attached to at least one region of the second housing  212  to support the second region  220   b  of the flexible display  220 . The first support plate  221  may be attached to at least one portion of the first region  220   a  of the flexible display  220  to support the flexible display  220 . Similarly, the second support plate  222  may be attached to at least one portion of the second region  220   b  of the flexible display  220  to support the flexible display  220 . The first support plate  221  and the second support plate  222  may be constructed of a material having a rigidity to support the flexible display  220 . 
     The hinge assembly  300  may couple the first housing  211  and the second housing  212 , and may rotate the second housing  212  about the first housing  211  within a specified rotation range, or on the contrary, may rotate the first housing  211  about the second housing  212  within a specified rotation range. 
     A recess may be constructed in a region where the first housing  211  and the second housing  212  are coupled, so that the hinge assembly  300  is disposed between the first housing  211  and the second housing  212 . The aforementioned recess may be constructed in a shape of a groove having a specific coverture. 
     The hinge assembly  300  includes a hinge housing  300   c . The hinge housing  300   c  may be visible to the outside of the electronic device  101  according to a state of the electronic device  101 , or may be hidden by the foldable housing  210 . 
     As shown in  FIG. 2A , when the electronic device  101  is in the unfolded state, the hinge housing  300   c  is hidden by the folding housing  210 , and thus may be invisible to the outside of the electronic device  101 . 
     As shown in  FIG. 2B , when the electronic device  101  is in the folded state, the hinge housing  300   c  may be visible to the outside of the electronic device  101  due to a rotation of the first housing  211  and second housing  212 . 
     The cover  230  may be located at a lower end (e.g., the −y direction of  FIG. 2A ) of the first housing  211  and second housing  212  to construct a rear face of the electronic device  101 . The cover  230  may include a first cover coupled to the first housing  211  and a second cover coupled to the second housing  212 . The first cover and the first housing  211  may be constructed integrally, and the second cover and the second housing  212  may also be constructed integrally. 
       FIG. 3  illustrates a hinge assembly  300  of an electronic device, according to an embodiment. 
     Referring to  FIG. 3 , an electronic device  101  includes the hinge assembly  300 . The hinge assembly  300  includes a hinge housing  300   c  and at least one or more hinge structures  300   a  and  300   b  disposed on the hinge housing  300   c.    
     The hinge housing  300   c  may include a groove (or a recess) to which the at least one or more hinge structures  300   a  and  300   b  can be disposed. The at least one or more hinge structures  300   a  and  300   b  may be disposed inside the groove of the hinge assembly  300 , and the at least one or more hinge structures  300   a  and  300   b  may be supported by the hinge housing  300   c.    
     The hinge assembly  300  may include the first hinge structure  300   a  disposed to one region (e.g., a left region of  FIG. 3 ) of the hinge housing  300   c  and the second hinge structure  300   b  disposed to another region (e.g., a right region of  FIG. 3 ) of the hinge housing  300   c . The first hinge structure  300   a  may be disposed to the left region of the hinge housing  300   c , and thus may be coupled (or connected) to one region of a first housing  211  and second housing  212 . The second hinge structure  300   b  may be disposed to the right region of the hinge housing  300   c , and thus may be coupled (or connected) to the first housing and the second housing. The first hinge structure  300   a  and the second hinge structure  300   b  may rotate within a specified angle range about a virtual first rotation axis L 1  constructed in the hinge housing  300   c  and a virtual second rotation axis L 2  parallel to the virtual first rotation axis L 1 . 
     One region of the first hinge structure  300   a  and one region of the second hinge structure  300   b  may rotate about the first rotation axis L 1 , and another region of the first hinge structure  300   a  and another region of the second hinge structure  300   b  may rotate about the virtual second rotation axis L 2 . That is, the first hinge structure  300   a  and the second hinge structure  300   b  may be folded about the virtual first rotation axis L 1  and second rotation axis L 2 , and details thereof will be described below. However, the hinge assembly  300  is not limited to the aforementioned embodiment, and the hinge assembly  300  may include three or more hinge structures (e.g.,  300   a  and  300   b ). 
     The hinge assembly  300  may further include a hinge plate  300   d  disposed between the first hinge structure  300   a  and the second hinge structure  300   b . The hinge plate  300   d  may be supported by the hinge housing  300 , and the hinge plate  300   d  may support some regions of a flexible display  220 . The hinge plate  300   d  may be constructed of a metal or non-metal material having a specified rigidity to support the flexible display. 
       FIG. 4  illustrates the first hinge structure  300   a  and the second hinge structure  300   b  constructing a hinge assembly of an electronic device, according to an embodiment. 
     Referring to  FIG. 4 , the first hinge structure  300   a  and the second hinge structure  300   b  includes a bracket structure  310 , an arm structure  320 , a rotation structure  330 , a detent structure  340 , and a support portion  350 . 
     The bracket structure  310  includes a plurality of brackets  311  and  312  coupled with a first housing  211  and a second housing  212  and a fixing bracket  313  which supports the plurality of brackets  311  and  312 . The plurality of brackets  311  and  312  coupled with the first housing  211  and the second housing  212  may rotate together with the first housing  211  and the second housing  212  in a process in which the electronic device  101  rotates from a folded state to an unfolded state or rotates from the unfolded state to the folded state. 
     The arm structure  320  includes an arm coupled to some components (e.g., a shaft) of the rotation structure  330  and rotatable within a specified range (e.g., 0° to 90° or 10° to 80°). The aforementioned arm may be coupled with one region of a bracket of the bracket structure  310  and thus may be slid with respect to the bracket in a rotation process of the electronic device, as described below. 
     The rotation structure  330  includes a plurality of shafts  331  and  332 , a plurality of gears  331   a  and  332   a  coupled with the plurality of shafts  331  and  332 , a plurality of idle gears  333  and  334  gear-coupled with the plurality of gears  331   a  and  332   a , and a shaft bracket supporting the plurality of shafts. As the plurality of shafts  331  and  332 , the plurality of gears  331   a  and  332   a , and the plurality of idle gears  333  and  334  rotate in an engaged manner, the rotation structure  330  may allow the first housing  211  and the second housing  212  to rotate by the same rotation angle. Arm portions  321  and  322  of the arm structure  320  may be coupled to the shafts  331  and  332  of the rotation structure  330 . Through the aforementioned structure, the arm portion may rotate about a rotation axis (or a turning axis) different from the brackets  311  and  312  of the bracket structure  310  by rotating the electronic device from the folded state to the unfolded state or from the unfolded state to the folded state. 
     The detent structure  340  includes a detent plate  341  having a detent portion constructed thereon, and a plurality of springs  342  and  343 . The detent portion may be constructed to protrude from one region of the detent plate  341  facing the aforementioned arm portion. The detent portion may be constructed in a concavo-convex shape corresponding to a cam portion constructed in one region of the arm portions  321  and  322 . The detent portion may be engaged with the cam portion of the arm portions  321  and  322  to fix a movement of the arm portions  321  and  322  when the electronic device is in the folded state. The plurality of springs  342  and  343  may be disposed between the detent plate  341  and the shaft bracket of the rotation structure  330  in a compressed state, so that the detent plate  341  is in contact with one region of the arm portions  321  and  322 . 
     The support portion  350  is disposed to an empty space between the plurality of arm portions  321  and  322  and the plurality of shafts  331  and  332 . The support portion  350  may move up and down (e.g., a movement in a direction from the +y axis to the −y axis or from the −y axis to the +axis of  FIG. 2A ) between the flexible display and the hinge housing  300   c  due to a rotation of the plurality of arm portions  321  and  322 . 
     The support portion  350  may move in a direction of the flexible display due to the rotation of the plurality of arm portions in the process in which the electronic device rotates from the folded state to the unfolded state. As a result, the support portion  350  may be located to a rear face of the flexible display to support one region of the flexible display. The support portion  350  may be in contact with at least one region of the rear face of the flexible display to support the flexible display. The support portion  350  may be spaced apart by a minute distance from the flexible display to support one region of the flexible display. The first support plate  221  and/or the second support plate  222  may be attached to at least one region of the flexible display by an adhesive member (e.g., an adhesive). In the aforementioned case, the support portion  350  may support at least one region of the rear face of the first support plate  221  and/or the second support plate  222 . 
     On the contrary, in the process in which the electronic device rotates from the unfolded state to the folded state, the support portion  350  may be spaced apart from the flexible display, and thus may not affect a driving trajectory of the flexible display. 
       FIG. 5  is an exploded perspective view of the first hinge structure  300   a  and/or the second hinge structure  300   b  of  FIG. 4 , according to an embodiment. 
     Referring to  FIG. 5 , the hinge structure  300   a  and/or  300   b  includes a bracket structure  310 , an arm structure  320 , a rotation structure  330 , a detent structure  340 , a support portion  350 , a stopper  360 , an elastic member  361 , and/or a screw  362 . At least one of components of the first hinge structure  300   a  and/or the second hinge structure  300   b  of  FIG. 5  may be identical or similar to at least one of components of  FIG. 4 , and redundant descriptions will be omitted hereinafter. 
     The bracket structure  310  includes a first bracket  311 , a second bracket  312 , and a fixing bracket  313 . 
     The fixing bracket  313  may be disposed adjacent to a hinge housing  300   c  to support the first bracket  311  and the second bracket  312 . A first groove  313   a  and a second groove  313   b  may be constructed in an upper face of the fixing bracket  313  (e.g., a face of the +y direction of  FIG. 5 ), and the first bracket  311  and the second bracket  312  may be coupled to the fixing bracket  313  through the first groove  313   a  and the second groove  313   b . The first groove  313   a  and the second groove  313   b  may be constructed in an arc shape having a specific curvature, the first bracket  311  may be coupled to the first groove  313   a , and the second bracket  312  may be coupled to the second groove  313   b.    
     Although the first groove  313   a  and the second groove  313   b  may be constructed in an arc shape having the same curvature, the first groove  313   a  and the second groove  313   b  may be constructed in arc shapes having different curvatures. The first groove  313   a  may be constructed in one region (e.g., a region of the +x direction of  FIG. 5 ) of the fixing bracket  313  adjacent to the first bracket  311 , and the second groove  313   b  may be constructed in another region (e.g., a region of the −x direction of  FIG. 5 ) of the fixing bracket  313  adjacent to the second bracket  312 . A plurality of gear holes  313   d  and a plurality of shaft holes  313   e  may be constructed in one side face (e.g., a face of the +z direction of  FIG. 5 ) of the fixing bracket  313 . A first idle gear  333  and a second idle gear  334 , to be described below, may be fastened to a first shift  331  and a second shift  332  on one side face of the fixing bracket  313  through the aforementioned gear hole  313   d  and shaft hole  313   e.    
     The first bracket  311  includes a first rail portion  311   a , a first slide hole  311   b , and a plurality of coupling holes  311   c . The first rail portion  311   a  may be constructed to protrude in one region of the first bracket  311 . The aforementioned first rail portion  311   a  may be constructed in a shape corresponding to the first groove  313   a  of the fixing bracket  313 , and the first bracket  311  may be coupled to the first groove  313   a  of the fixing bracket  313  through the first rail portion  311   a . The first slide hole  311   b  may be constructed in one region of the first bracket  311  adjacent to the first arm portion  321 , and the first bracket  311  and the first arm portion  321  may be coupled through a first fixing portion  323  which passes through the first slide hole  311   b  and the first arm portion  321 . The first fixing portion  323  may be slid inside the first slide hole  311   b  as the electronic device rotates from the folded state to the unfolded state or rotates from the unfolded state to the folded state, as described below. 
     The plurality of coupling holes  311   c  may be constructed in one face (e.g., a face of the +y direction of  FIG. 5 ) facing a first housing  211  of the first bracket  311 , and the first bracket  311  may be coupled to one region of the first housing through the plurality of coupling holes  311   c . The first bracket  311  coupled to the first housing may be slid along the first groove  313   a  of the fixing bracket  313  with the rotation of the first housing, and may rotate about a virtual first rotation axis L 1 . 
     The second bracket  312  includes a second rail portion  312   a , a second slide hole  312   b , and a plurality of coupling holes  312   c . The second rail portion  312   a  may be constructed to protrude in one region of the second bracket  312 . The second rail portion  312   a  may be constructed in a shape corresponding to the second groove  313   b  of the fixing bracket  313 , and the second bracket  312  may be coupled to the second groove  313   b  of the fixing bracket  313  through the second rail portion  312   a . The second slide hole  312   b  may be constructed in one region of the second bracket  312  adjacent to the second arm portion  322 , and the second bracket  312  and the second arm portion  322  may be coupled through a second fixing portion  324  which passes through the second slide hole  312   b  and the second arm portion  322 . The second fixing portion  324  may be slid inside the second slide hole  312   b  as the electronic device rotates from the folded state to the unfolded state or rotates from the unfolded state to the folded state, as described below. 
     The plurality of coupling holes  312   c  may be constructed in one face (e.g., a face of the +y direction of  FIG. 5 ) facing a second housing (e.g., the second housing  212  of  FIG. 2A ) of the second bracket  312 , and the second bracket  312  may be coupled to one region of the second housing through the plurality of coupling holes  312   c . The second bracket  312  coupled to the second housing may be slid along the second groove  313   b  of the fixing bracket  313  with the rotation of the second housing, and may rotate about a virtual second rotation axis L 2 . In this case, the virtual first rotation axis L 1  and the virtual second rotation axis L 2  are parallel, and may be constructed in a flat face parallel to the flexible display when the electronic device is in the folded state. 
     The arm structure  320  may include a first arm portion  321  and a second arm portion  322 . 
     The first arm portion  321  may include a first cam portion  321   a , a first support rib  321   b , a first insertion hole  321   c , and a first through-hole  321   d . The first insertion hole  321   c  may be constructed in one region of a lower end (e.g., the −y direction of  FIG. 5 ) of the first arm portion  321 , and the first shaft  331  may be inserted to the first insertion hole  321   c  to couple the first arm portion  321  and the first shaft  331 . 
     As the first arm portion  321  and the first shaft  331  are coupled, the first arm portion  321  may rotate about a rotation axis of the first shaft  331 . The first cam portion  321   a  may be constructed in a region adjacent to the first insertion hole  321   c , and may be constructed to protrude in a direction of the detent plate  341  (e.g., the +z direction of  FIG. 5 ). The first cam portion  321   a  may be constructed in a concavo-convex shape in which a plurality of peaks and valleys are repeated, and the first cam portion  321   a  may be disposed to be engaged with the detent portion  341   a  constructed in the detent plate  341  to provide a sense of detent to the first arm portion  321 . 
     In addition, since the first cam portion  321   a  may be disposed to be engaged with the detent portion  341   a  constructed in the detent plate  341 , the first arm portion  321  may be fixed at a specified rotation angle and/or in a specified rotation angle range. As a result, a movement of the electronic device may be fixed at the specified rotation angle and/or in the specified rotation angle range (e.g., the range from 30° to 150°). The first support rib  321   b  may be constructed to protrude from one region of the first arm portion  321 , and may move the support portion  350  in an upper direction (e.g., the +y direction of  FIG. 5 ) when the electronic device rotates from the folded state to the unfolded state. The first through-hole  321   d  may be constructed in one region (e.g., a region of the +x direction of  FIG. 5 ) in the opposite side of a region in which the first insertion hole  321   c  of the first arm portion  321  is constructed. The first fixing portion  323  passing through the first slide hole  311   b  may pass through the first through-hole  321   d  to couple the first bracket  311  and the first arm portion  321 . 
     A first washer ring  325  may be fastened to one end of the first fixing portion passing through the first through-hole  321   d , so that the first fixing portion  323  is fixed to the first arm portion  321 . Alternatively, the first washer ring  325  may be fastened to the other end of the first fixing portion  323 , so that the first fixing portion  323  is fixed to the first bracket  311 . Additionally or alternatively, a protrusion may be constructed in one region of the first bracket  311  (or the first arm portion  321 ), and a coupling groove corresponding to the protrusion may be constructed in one region of the first arm portion  321  (or the first bracket  311 ), so that the first bracket  311  and the first arm portion  321  are coupled with the protrusion through the coupling groove. The first arm portion  321  coupled with the first bracket  311  may rotate about a rotation axis different from that of the first bracket  311  while sliding with respect to the first bracket  311 , in the process in which the electronic device rotates from the folded state to the unfolded state or rotates from the unfolded state to the folded state. 
     The second arm portion  322  may include a second cam portion  322   a , a second support rib  322   b , a second insertion hole  322   c , and a second through-hole  322   d . The second insertion hole  322   c  may be constructed in one region of a lower end (e.g., the −y direction of  FIG. 5 ) of the second arm portion  322 , and the second shaft  332  may be inserted to the second insertion hole  322   c  to couple the second arm portion  322  and the second shaft  332 . As the second arm portion  322  and the second shaft  332  are coupled, the second arm portion  322  may rotate about a rotation axis of the second shaft  332 . The second cam portion  322   a  may be constructed in a region adjacent to the second insertion hole  322   c , and may be constructed to protrude in a direction of the detent plate  341  (e.g., the +z direction of  FIG. 5 ). Similarly to the first cam portion  321   a , the second cam portion  322   a  may be constructed in a concavo-convex shape in which a plurality of peaks and valleys are repeated, and the second cam portion  322   a  may be disposed to be engaged with the detent portion  341   b  constructed in the detent plate  341  to provide a sense of detent to the second arm portion  322 . 
     In addition, since the second cam portion  322   a  may be disposed to be engaged with the detent portion  341   b  constructed in the detent plate  341 , the second arm portion  322  may be fixed at a specified rotation angle and/or in a specified rotation angle range. As a result, a movement of the electronic device may be fixed at the specified rotation angle and/or in the specified rotation angle range (e.g., the range from 30° to 150°). The second support rib  322   b  may be constructed to protrude from one region of the second arm portion  322 , and may move the support portion  350  in an upper direction (e.g., the +y direction of  FIG. 5 ) when the electronic device rotates from the folded state to the unfolded state. The second through-hole  322   d  may be constructed in a region in the opposite side of the second insertion hole  322   c . The second fixing portion  324  passing through the second slide hole  312   b  may pass through the second through-hole  322   d  to couple the second bracket  312  and the second arm portion  322 . A second washer ring  326  may be fastened to one end of the second fixing portion passing through the second through-hole  322   d , so that the second fixing portion  324  is fixed to the second arm portion  322 . Alternatively, the second washer ring  326  may be fastened to the other end of the second fixing portion  324 , so that the second fixing portion  324  is fixed to the second bracket  312 . Additionally or alternatively, a protrusion may be constructed in one region of the second bracket  312  (or the second arm portion  322 ), and a coupling groove corresponding to the protrusion may be constructed in one region of the second arm portion  322  (or the second bracket  312 ), so that the second bracket  312  and the second arm portion  322  are coupled with the protrusion through the coupling groove. The second arm portion  322  coupled with the second bracket  312  may rotate about a rotation axis different from that of the first bracket  312  while sliding with respect to the second bracket  312 , in the process in which the electronic device rotates from the folded state to the unfolded state or rotates from the unfolded state to the folded state. 
     The rotation structure  330  includes the first shaft  331  coupled with a first gear  331   a , the second shaft  332  coupled with a second gear  332   a , the first idle gear  333 , the second idle gear  334 , a shaft bracket  335 , and a gear cover  336 . 
     One end of the first shaft  331  may be fastened to the shaft hole  313   e  of the fixing bracket  313 , and the other end of the first shaft  331  may pass through a first shaft insertion hole  335   a  of the shaft bracket  335 . The first arm portion  321  may be coupled to one region of the first shaft  331 , and the first arm portion  321  may rotate about the first shaft  331  as the rotation axis. 
     The second shaft  332  may be disposed to a position adjacent to the first shaft  331 . One end of the second shaft  332  may be fastened to the shaft hole  313   e  of the fixing bracket  313 , and the other end of the second shaft  332  may pass through a second shaft insertion hole  335   b  of the shaft bracket  335 . The second arm portion  322  may be coupled to one region of the second shaft  332 , and the second arm portion  322  may rotate about the second shaft  332  as the rotation axis. 
     The first idle gear  333  and the second idle gear  334  may be disposed between the first gear  331   a  coupled to the first shaft  331  and the second gear  332   a  coupled to the second shaft  332 . The first idle gear  333  and the second idle gear  334  may be fastened to the plurality of gear holes  313   d  of the fixing bracket  313 , and the first idle gear  333  and the second idle gear  334  may rotate by being engaged with each other so that the first arm portion  321  and the second arm portion  322  rotate by the same rotation angle. The first idle gear  333  may rotate by being engaged with the first gear  331   a  and the second idle gear  334 , and the second idle gear  334  may rotate by being engaged with the first idle gear  333  and the second gear  332   a . As the aforementioned first gear  331 , second gear  332   a , first idle gear  333 , and second idle gear  334  rotate by the same rotation angle by being engaged with one another, the first shaft  331  and the second shaft  332  may rotate by the same rotation angle in opposite directions. For example, when the first shaft  331  rotates by 30° counterclockwise (e.g., a direction from the +x axis to the +y axis of  FIG. 5 ), the second shaft  332  may rotate by 30° clockwise (e.g., a direction from the −x axis to the +y axis of  FIG. 5 ). As the first shaft  331  and the second shaft  332  rotate by the same rotation angle, the first arm portion  321  and second arm portion  322  coupled to the first shaft  331  and second shaft  332  may rotate by the same rotation angle. 
     The shaft bracket  335  may include the first shaft insertion hole  335   a  to which the first shaft  331  is inserted and the second shaft hole  335   b  to which the second shaft  332  is inserted. The shaft bracket  335  may be disposed inside a hinge housing  300   c  to support the first shaft  331  and second shaft  332  inserted to the shaft bracket  335  through the first shaft hole  335   a  and the second shaft hole  335   b.    
     The gear cover  336  may be inserted to the first shaft  331  and the second shaft  332  to protect the first gear  331   a , the second gear  332   a , the first idle gear  333 , and the second idle gear  334 . The gear cover  336  may prevent the first gear  331   a , the second gear  332   a , the first idle gear  333 , and the second idle gear  334  from being damaged by external force, and may prevent foreign matters from entering the first gear  331   a , the second gear  332   a , the first idle gear  333 , and the second idle gear  334 . 
     The detent structure  340  may include a detent plate  341 , a first spring  342 , and a second spring  343 . 
     A third shaft insertion hole  341   c  to which the first shaft  331  is inserted may be constructed in one region of the detent plate  341 , and a fourth shaft insertion hole  341   d  to which the second shaft  332  is inserted may be constructed in another region of the detent plate  341 . The detent plate  341  may be coupled to the first shaft  331  and the second shaft  332  through the third shaft insertion hole  341   c  and the fourth shaft insertion hole  341   d . The detent plate  341  may include a first detent portion  341   a  constructed to protrude in a direction of the first cam portion  321   a  of the first arm portion  321  and a second detent portion  341   b  constructed to protrude in a direction of the second cam portion  322   a  of the second arm portion  322 . The first detent portion  341   a  and the second detent portion  341   b  may be constructed in a concavo-convex structure in which at least one peak and valley appear repeatedly. The first detent portion  341   a  may be disposed to be engaged with the first cam portion  321   a , and thus, when the electronic device is in the folded state or the unfolded state, may provide a sense of detent to the first arm portion  321  and fix a movement of the first arm portion  321  at a specified rotation angle. Similarly, the second detent portion  341   b  may be disposed to be engaged with the second cam portion  322   a  and thus, when the electronic device is in the folded state or the unfolded state, may provide a sense of detent to the second arm portion  322  and fix a movement of the second arm portion at a specified rotation angle. 
     A pitch between a peak and another peak or between a valley and another valley of the first detent portion  341   a  may be greater than a pitch between a peak and another peak or between a valley and another valley of the first cam portion  321   a , so that the first arm portion  321  is rotatable within a specified rotation range even in a state where the first detent portion  341   a  and the first cam portion  321   a  are engaged. However, a shape of the first detent portion  341   a  is not limited to the aforementioned embodiment. The pitch between the peaks or valleys of the first detent portion  341   a  may be constructed to be identical to the pitch between the peaks or valleys of the first cam portion  321   a  or the pitch between the peaks or valleys of the first cam portion  321   a  may be constructed to be greater than the pitch between the peaks or valleys of the first detent portion  341   a.    
     Similarly, a pitch between a peak and another peak or between a valley and another valley of the second detent portion  341   b  may be greater than a pitch between a peak and another peak or between a valley and another valley of the second cam portion  322   a , so that the second arm portion  322  is rotatable within a specified rotation range even in a state where the second detent portion  341   b  and the second cam portion  322   a  are engaged. However, a shape of the second detent portion  341   b  is not limited to the aforementioned embodiment. The pitch between the peaks or valleys of the second detent portion  341   b  may be constructed to be identical to the pitch between the peaks or valleys of the second cam portion  322   a  or the pitch between the peaks or valleys of the second cam portion  322   a  may be constructed to be greater than the pitch between the peaks or between the valleys of the second detent portion  341   b.    
     The first spring  342  may be disposed to surround one region of the first shaft  331 , and the second spring  343  may be disposed to surround one region of the second shaft  332 . The first spring  342  and the second spring  343  may be disposed in a state of being compressed between the detent plate  341  and the shaft bracket  335 , so that the detent plate  341  is closely in contact in a direction of the first arm portion  321  and the second arm portion  322 . As the detent plate  341  is closely in contact in a direction of the first arm portion  321  and the second arm portion  322 , it is possible to maintain a state where the first detent portion  341   a  and the first cam portion  321   a  are engaged and a state where the second detent portion  341   b  and the second cam portion  322   a  are engaged. 
     When the peak of the first detent portion  341   a  and the peak of the first cam portion  321   a  or the peak of the second detent portion  341   b  and the peak of the second cam portion  322   a  are in contact due to a rotation of the first arm portion  321  and the second arm portion  322 , the detent plate  341  may move in one direction of the first shaft  331  and second shaft  332  (e.g., the +z direction of  FIG. 5 ), so that the first cam portion  321   a  and the first detent portion  341   a  and/or the second cam portion  322   a  and the second detent portion  341   b  are temporarily spaced apart. As the detent plate  341  moves in one direction, the first spring  342  and the second spring  343  may be compressed. When the first arm portion  321  and the second arm portion  322  further rotate by a specific angle, the detent plate  341  may move again in a direction of the first cam portion  321   a  and/or the second cam portion  322   a  due to elastic restoration force of the first spring  342  and second spring  343 . As a result, the first cam portion  321   a  and the first detent portion  341   a  may be disposed in a state of being engaged again with the second cam portion  322   a  and the second detent portion  341   b , thereby maintaining a state where the first cam portion  321   a  and the first detent portion  341   a  are engaged and the second cam portion  322   a  and the second detent portion  341   b  are engaged. 
     A flat linear region may be constructed in at least one region (e.g., a summit region) of the peak of the first cam portion  321   a , the peak of the second cam portion  322   a , the peak of the first detent portion  341   a , and/or the peak of the second detent portion  341   b . Similarly, a flat linear region may also be constructed in at least one region of the valley of the first cam portion  321   a , the valley of the second cam portion  322   a , the valley of the first detent portion  341   a , and/or the valley of the second detent portion  341   b . The linear region constructed in one region of the peak and the linear region constructed in one region of the valley may be constructed to be substantially identical or similar. As the linear region is constructed in the peaks and valleys of the first cam portion  321 , second cam portion  322   a , first detent portion  341   a , and second detent portion  341   b , a movement of the first arm portion  321  and/or second arm portion  322  may be fixed at a specified rotation angle (e.g., 30° or 60°) and/or in a specified rotation angle range (e.g., a rotation angle range of 30° to 150°). As the movement of the first arm portion  321  and/or second arm portion  322  is fixed at the specified rotation angle, a movement of a first housing  211  and second housing  212  of the electronic device may be fixed at the specified rotation angle. 
     The support portion  350  may be disposed to form an empty space between the first arm portion  321  and the second arm portion  322  and the first shaft  331  and the second shaft  332 . When the electronic device is in an unfolded state, the support portion  350  may support one region of a flexible display not supported by the first arm portion  321  and/or the second arm portion  322 . The support portion  350  may move in an upper direction (e.g., the +y direction of  FIG. 5 ) by means of the first arm rib  321   b  constructed in one region of the first arm portion  321  and the second support rib  322   b  constructed in one region of the second arm portion  322 . In a process in which the electronic device rotates from the folded state to the unfolded state, the first support rib  321   b  and the second support rib  322   b  may be in contact with one region of the support portion  350 , and the support portion  350  may move in an upper direction (e.g., in a direction from the −y axis to the +y axis of  FIG. 5 ) by means of the first support rib  321   b  and the second support rib  322   b  with the rotation of the first arm portion  321  and the second arm portion  322 . 
     The stopper  360  may be located at a lower end of the support portion  350  (e.g., the −y direction of  FIG. 5 ). A fifth shaft insertion hole  360   a  may be constructed in one region of the stopper  360 , and a sixth shaft insertion hole  360   b  may be constructed in one region in the opposite side of the fifth shaft insertion hole  360   a . The first shaft  331  and the second shaft  332  may be inserted through the fifth shaft insertion hole  360   a  and the sixth shaft insertion hole  360   b , and the first shaft  331 , the second shaft  332 , and the stopper  360  may be coupled through the aforementioned structure. A through-hole  360   c  may be constructed in one region of an upper end of the stopper  360  (e.g., the +y direction of  FIG. 5 ), and a protrusion region  351  of the support portion  350  may be inserted in a lower direction of the stopper  360  by passing through the through-hole  360   c.    
     The screw  362  may be coupled with the protrusion region  351  inserted to the lower end of the stopper  360 , and the elastic member  361  may be disposed between the screw  362  and the stopper  360 . The elastic member  361  may be a spring, but is not limited thereto. The elastic member  361  may be in contact with one region of the stopper  360 , and the elastic member  361  may be compressed while the support portion  350  moves in an upper direction in a process in which the electronic device rotates from the folded state to the unfolded state. On the contrary, in a process in which the electronic device rotates from the unfolded state to the folded state, the support portion  350  may move in a lower direction (e.g., the −y direction of  FIG. 5 ) due to elastic restoration force of the elastic member  361 . 
     The first hinge structure  300   a  and/or the second hinge structure  300   b  may further include a first auxiliary member  363  and a second auxiliary member  364 . The first auxiliary member  363  may be fastened to one end of the first shaft  331  adjacent to the shaft bracket  335 , and the second auxiliary member  364  may be fastened to one end of the second shaft  332  adjacent to the shaft bracket  335 . A third washer ring  331   b  may be fastened to one end of the first shaft  331 , and thus the first shaft  331  may be fixed to the first auxiliary member  363 . Similarly, a fourth washer ring  332   b  may be fastened to one end of the second shaft  332 , and thus the second shaft  332  may be fixed to the second auxiliary member  364 . A screw nut may be fastened to one end of the first shaft  331  so that the first shaft  331  is fixed to the first auxiliary member  363 , and/or a screw nut may be fastened to one end of the second shaft  332  so that the second shaft  332  is fixed to the second auxiliary member  364 . 
     The first auxiliary member  363  may include a third support rib  363   a , and the third support rib  363   a  may be constructed to protrude from one region of the first auxiliary member  363 . Similarly, the second auxiliary member  364  may include a fourth support rib  364   a , and the fourth support rib  364   a  may be constructed to protrude from one region of the second auxiliary member  364 . The first auxiliary member  363  may rotate by the same rotation angle as the first arm portion  321  through the first shaft  331 , and the second auxiliary member  364  may rotate by the same rotation angle as the second arm portion  322  through the second shaft  332 . When the electronic device rotates from the folded state to the unfolded state, the third support rib  363   a  and the fourth support rib  364   a  may allow the support portion  350  to move in an upper direction together with the first support rib  321   b  of the first arm portion  321  and the second support rib  322   b  of the second arm portion  322 . 
       FIG. 6A  illustrates a configuration of a hinge structure  300   a  when an electronic device is in an unfolded state, according to an embodiment.  FIG. 6B  illustrates a configuration of the hinge structure  300   a  when the electronic device rotates from the unfolded state to a folded state, according to an embodiment.  FIG. 6C  illustrates a structure of the hinge structure  300   a  when the electronic device is in the folded state, according to an embodiment. 
     A movement of a first arm portion  321 , second arm portion  322 , first bracket  311 , and second bracket  312  due to a rotation of an electronic device will be described with reference to  FIG. 6A  to  FIG. 6C . 
     Referring to  FIG. 6A ,  FIG. 6B , and  FIG. 6C , an electronic device  101  includes the hinge structure  300   a . The hinge structure  300   a  may include the first bracket  311 , the second bracket  312 , a fixing bracket  313 , the first arm portion  321 , the second arm portion  322 , a first fixing portion  323 , a second fixing portion  324 , a support portion  350 , a first shaft  331  in which a first gear  331   a  and a first spring  342  are coupled, a second shaft  332  in which a second gear  332   a  and a second spring  343  are coupled, a first idle gear  333 , a second idle gear  334 , a shaft bracket  335 , a first auxiliary member  363 , and a second auxiliary member  364 . At least one of components of the aforementioned hinge structure  300   a  may be identical or similar to at least one of components of  FIGS. 3-5 . 
     The first bracket  311  and the second bracket  312  may be mounted to a first groove  313   a  and a second groove  313   b  constructed in the fixing bracket  313  so as to be supported by the fixing bracket  313 . The first bracket  311  may include a first rail portion  311   a  constructed in a shape corresponding to the first groove  313   a , and the second bracket  312  may include a second rail portion  312   a  constructed in a shape corresponding to the second groove  313   b . The first bracket  311  may rotate by sliding inside the first groove  313   a  through the first rail portion  311   a , and the second bracket  312  may rotate by sliding inside the second groove  313   b  through the second rail portion  312   a.    
     The first bracket  311  may be coupled to at least one region of a first housing  211  to rotate in association with the first housing. Similarly, the second bracket  312  may be coupled to at least one region of a second housing  212  to rotate in association with the second housing. Through the aforementioned structure, the first bracket  311  may rotate within a specified range about a virtual first rotation axis L 1 , and the second bracket  312  may rotate within a specified range about a virtual second rotation axis L 2  adjacent to the first rotation axis L 1 . The first bracket  311  may rotate within an angle range from 0° to an angle (e.g., 90°) at which the electronic device is in the folded state with respect to the +x axis, and the second bracket  312  may rotate within an angle range from 180° to an angle at which the electronic device is in the folded state with respect to the +x axis. When the electronic device is in the unfolded state, the first bracket  311  and the second bracket  312  may be disposed to be horizontal to each other, and when the electronic device is in the folded state, the first bracket  311  and the second bracket  312  may be disposed to face each other. 
     The first arm portion  321  may be coupled to one region of the first shaft  331  to rotate together with the first shaft  331 . The second arm portion  322  may be coupled to one region of the second shaft  332  adjacent to the first shaft  331  to rotate together with the second shaft  332 . The first arm portion  321  may rotate about a rotation axis L 3  (hereinafter, a “third rotation axis”) of the first shaft  331  due to the aforementioned coupling structure. In addition, the second arm portion  322  may rotate about a rotation axis L 4  (hereinafter, a “fourth rotation axis”) of the second shaft  331 . When the electronic device is in the unfolded state, the first arm portion  321  and the second arm portion  322  may be disposed to be horizontal to each other, and when the electronic device is in the folded state, the first arm portion  321  and the second arm portion  322  may be disposed to face each other. 
     The first arm portion  321  and the second arm portion  322  may rotate by the same angle through the first gear  331   a  of the first shaft  331 , the second gear  332   a  of the second shaft  332 , the first idle gear  333 , and the second idle gear  334 . 
     When the first shaft  331  rotates by a specific angle, the first gear  331   a  may also rotate by the same angle. The rotation of the first gear  331   a  may be transferred to the first idle gear  333  engaged with the first gear  331   a , and the rotation transferred to the first idle gear  333  may be transferred to the second gear  332   a  through the second idle gear  334  engaged with the first idle gear  333 . The second shaft  332  may also rotate by a specific angle due to the rotation transferred to the second gear  332   a . Through the aforementioned process, the first arm portion  321  coupled with the first shaft  331  and the second arm portion  322  coupled with the second arm  332  may rotate by the same angle. 
     The first rotation axis L 1  and the second rotation axis L 2  may be constructed between the third rotation axis L 3  and the fourth rotation axis L 4 . In addition, as the first rotation axis L 1  and the second rotation axis L 2  are constructed in an upper end region (e.g., the +y direction of  FIG. 6A ) of the third rotation axis L 3  and fourth rotation axis L 4 , the first rotation axis L 1  and the second rotation axis L 2  may be constructed on a flexible display. That is, the first bracket  311 , the second bracket  312 , the first arm portion  321 , and the second arm portion  322  may rotate within a specified angle range about rotation axes different from one another. 
     The first bracket  311  may be coupled with one region of the first arm portion  321  through the first fixing portion  323 , and the second bracket  312  may be coupled with one region of the second arm portion  322  through the second fixing portion  324 . 
     A first slide hole  311   b  may be constructed in one region adjacent to the first arm portion  321  of the first bracket  311 , and the first fixing portion  323  may pass through the first slide hole  311   b  to couple the first bracket  311  and the first arm portion  321 . Similarly, a second slide hole  312   b  may be constructed in one region adjacent to the second arm portion  322  of the second bracket  312 , and the second fixing portion  324  may pass through the second slide hole  312   b  to couple the second bracket  312  and the second arm portion  322 . 
     As the first bracket  311  rotates together with the first housing, the first fixing portion  323  may be slid inside the first slide hole  311   b . Due to the sliding of the first fixing portion  323 , the first arm portion  321  coupled with the first bracket  311  through the first fixing portion  323  may also be slid together. Similarly, due to the rotation of the second housing, the second fixing portion  324  may be slid inside the second slide hole  312   b . Due to the sliding of the second fixing portion  324 , the second arm portion  322  coupled with the second bracket  312  through the second fixing portion  324  may also be slid together. 
     Referring to  FIG. 6A , when the electronic device in which the first bracket  311 , the second bracket  312 , the first arm portion  321 , and the second arm portion  322  are disposed on the same plane is in the unfolded state, the first fixing portion  323  may be disposed outside the first slide hole  311   b , and the second fixing portion  324  may be disposed outside the second slide hole  312   b.    
     Referring to  FIG. 6B , in a process in which the electronic device rotates from the unfolded state to the folded state, the first housing and the second housing may rotate by a first angle (e.g., 30° with respect to the +x axis or the −x axis) by a user&#39;s manipulation or external force. As the first housing and the second housing rotate, the first bracket  311  and the second bracket  312  coupled to the first housing and the second housing may also rotate by the first angle. 
     In a process in which the first bracket  311  rotates counterclockwise (e.g., in a direction from the +x axis to the +y axis of  FIG. 6B ), the first fixing portion  323  may be slid by a specific distance in an inward direction from the outside of the first slide hole  311   b . The first arm portion  321  may rotate counterclockwise by a second angle greater than the first angle due to the sliding of the first fixing portion  323 . Similarly, the second arm portion  322  may rotate by the second angle clockwise due to the sliding of the second fixing portion  324 . 
     Referring to  FIG. 6C , when the electronic device is in the folded state, the first bracket  311  and the first arm portion  321 , and the second bracket  312  and the second arm portion  322 , may respectively be disposed to face each other in one face. The first bracket  311 , the second bracket  312 , the first arm portion  321 , and the second arm portion  322  may be disposed to be substantially vertical to the +x axis or to have an angle (e.g., 800 to 100°) at which the electronic device is in the folded state. When the electronic device is in the folded state, the first fixing portion  323  may be disposed inside the first slide hole  311   b , and the second fixing portion  324  may also be disposed inside the second slide hole  312   b.    
     That is, the first fixing portion  323  may be slid in an inward direction from the outside of the first slide hole  311   b  in the process in which the electronic device rotates from the unfolded state to the folded state, and on the contrary, may be slid in an outward direction from the inside of the first slide hole  311   b  in the process in which the electronic device rotates from the folded state to the unfolded state. In this case, the second fixing portion  324  may be slid in the same manner as the first fixing portion  323 . 
     In a process in which the first bracket  311  and the second bracket  312  rotate about the virtual first rotation axis L 1  and second rotation axis L 2  by a user&#39;s manipulation or external force, the first fixing portion  323  and the second fixing portion  324  may be respectively slid inside the first slide hole  311   b  and the second slide hole  312   b . Due to the sliding of the first fixing portion  323  and second fixing portion  324 , the first arm portion  321  and the second arm portion  322  may rotate about the third rotation axis L 3  and the fourth rotation axis L 4 . As a result, the first arm portion  321  may rotate about a rotation axis (e.g., L 3 ) different from the first bracket  311  due to the rotation of the first bracket  311 . Similarly, the second arm portion  322  may rotate about a rotation axis (e.g., L 4 ) different from the second bracket  312  due to the rotation of the second bracket  312 . 
       FIG. 7  illustrates elements of a first fixing portion  323  or a second fixing portion  324 , and a detent structure  340  of a hinge structure  300   a , according to an embodiment. Hereinafter, elements of the first fixing portion  323 , the second fixing portion  324 , the first coupling arm portion  321 , the second coupling arm portion  322 , the first bracket  311 , the second bracket  312 , and the detent structure  340  will be described with reference to  FIG. 7 . 
     Referring to  FIG. 7 , the hinge structure  300   a  of an electronic device  101  includes the first bracket  311 , the second bracket  312 , a fixing bracket  313 , the first arm portion  321 , the second arm portion  322 , the first fixing portion  323 , the second fixing portion  324 , a first shaft  331  to which a first gear  331   a  is coupled, a second shaft  332  to which a second gear  332   a  is coupled, a first idle gear  333 , a second idle gear  334 , the detent structure  340 , a support portion  350 , a first auxiliary member  363 , and a second auxiliary member  364 . At least one of components of the hinge structure  300   a  of  FIG. 7  may be identical or similar to at least one of components of  FIG. 5 , and redundant descriptions will be omitted hereinafter. 
     The first bracket  311  and the first arm portion  321  may be coupled through the first fixing portion  323  which passes through one region of the first bracket  311  and first arm portion  321 . The second bracket  312  and the second arm portion  322  may be coupled through the second fixing portion  324  which passes through one region of the second bracket  312  and second arm portion  322 . The first fixing portion  323  and the second fixing portion  324  may be constructed in a pin shape which extends in a longitudinal direction (e.g., the +x direction of  FIG. 7 ). 
     The hinge structure  300   a  may further include a first elastic body  323   a  and a second elastic body  324   a . The first elastic body  323   a  and the second elastic body  324   a  may be a spring or a disk spring, but are not limited thereto. 
     The first elastic body  323   a  may be disposed along an outer circumferential surface of the first fixing portion  323 , and may be disposed in a compressed state between the first arm portion  321  and a first washer ring  325 . Some regions of the first elastic body  323   a  may pass through some regions of the first arm portion  321 , and may be disposed between the first arm portion  321  and the first washer ring  325 . As the first elastic body  323   a  is disposed in a compressed state between the first arm portion  321  and the first washer ring  325 , a frictional force may be generated between the first arm portion  321  and the first bracket  311 . A torque may be generated in a direction opposite to a rotation direction of the first arm portion  321  due to the frictional force generated between the first arm portion  321  and the first bracket  311 , and a movement of the first arm portion  321  may be fixed due to the generated torque. That is, the hinge structure  300   a  may fix the movement of the first arm portion  321  in a free stop manner in the process in which the electronic device rotates from the folded state to the unfolded state or rotates from the unfolded state to the folded state without a separate additional component by using the first elastic body  323   a.    
     The second elastic body  324   a  may be disposed to an outer circumferential surface of the second fixing portion  324 , and may be disposed in a compressed state between the second arm portion  322  and a second washer ring  326 . Some regions of the second elastic body  324   a  may pass through some regions of the second arm portion  322 , and may be disposed between the second arm portion  322  and the second washer ring  326 . As the second elastic body  324   a  is disposed in a compressed state between the second arm portion  322  and the second washer ring  326 , a frictional force may be generated between the second arm portion  322  and the second bracket  312 . A torque may be generated in a direction opposite to a rotation direction of the second arm portion  322  due to the frictional force generated between the second arm portion  322  and the second bracket  312 , and the movement of the second arm portion  322  may be fixed due to the generated torque. That is, the hinge structure  300   a  may fix a movement of the second arm portion  322  in the process in which the electronic device rotates from the folded state to the unfolded state or rotates from the unfolded state to the folded state without a separate additional component by using the second elastic body  324   a.    
     The detent structure  340  of the hinge structure  300   a  may include the detent plate  341 , a first spring  342 , and a second spring  343 . 
     A shaft insertion hole (e.g., the third shaft insertion hole  341   c  and/or fourth shaft insertion hole  341   d ) may be constructed in at least one region of the detent plate  341 , so that the first shaft  331  and the second shaft  332  are coupled to the detent plate  341 . Additionally or alternatively, a diameter of the shaft insertion hole may be constructed to be greater than a diameter of the second shaft  332 , so that the first shaft  331  and the second shaft  332  can freely rotate in a state of being coupled with the detent plate  341 . The detent plate  341  may include a first detent portion  341   a  constructed to protrude along a longitudinal direction of the first shaft  331  and a second detent portion  341   b  constructed to protrude along a longitudinal direction of the second shaft  332 . The first detent portion  341   a  may be disposed to be engaged with a first cam portion  321   a  of the first arm portion  321 , and the second detent portion  341   b  may be disposed to be engaged with a second cam portion  322   a  of the second arm portion  322 , so that the first arm portion  321  and the second arm portion  322  can provide a sense of detent to the first arm portion  321  and the second arm portion  322 . 
     The first spring  342  may be coupled with the first shaft  331  so as to be located between the detent plate  341  and a shaft bracket  335  supporting the first shaft  331 . The second spring  343  may be coupled with the second shaft  332  adjacent to the first shaft  331 , so as to be located between the detent plate  341  and the shaft bracket  335  supporting the second shaft  332 . 
     The first spring  342  and the second spring  343  may be disposed in a compressed state to the shaft bracket  335  and the detent plate  341 , and pressure may be applied to the shaft bracket  335  in a direction opposite to the detent plate  341  due to elastic restoration force of the first spring  342  and second spring  343 . Due to the elastic restoration force of the first spring  342  and second spring  343 , the first detent portion  341   a  and second detent portion  341   b  of the detent plate  341  may maintain a state of being engaged with the first cam portion  321   a  of the first arm portion  321  and the second cam portion  322   a  of the second arm portion  322 . With the rotation of the first arm portion  321  and second arm portion  322 , the detent plate  341  may be temporarily spaced apart in a direction of the shaft bracket  335 . The first spring  342  and the second spring  343  may be compressed due to the detent plate  341  being spaced apart. Due to elastic restoration force of the compressed first spring  342  and second spring  343 , the detent plate  341  may move again in a direction of the first arm portion  321  and the second arm portion  322 . 
     That is, even if the detent plate  341  is temporarily spaced apart from the first arm portion  321  and the second arm portion  322 , the detent plate  341  may be in contact again with the first arm portion  321  and the second arm portion  322  by means of the first spring  342  and the second spring  343 . The detent structure  340  may maintain an engagement state between the first detent portion  341   a  and the first cam portion  321   a  and between the second detent portion  341   b  and the second cam portion  322   a  through the aforementioned structure. 
       FIG. 8  illustrates a coupling relationship between some elements of a first arm structure  321  and/or a second arm structure  322  and a detent structure  341  of a hinge structure  300   a , according to an embodiment. 
     Referring to  FIG. 8 , a hinge structure  300   a  and/or  300   b  of an electronic device  101  includes the first arm portion  321 , the second arm portion  322 , and the detent plate  341 . 
     The first arm portion  321  may include a first cam portion  321   a  and a first support rib  321   b , and the second arm portion  322  may include a second cam portion  322   a  and a second support rib  322   b . The first support rib  321   b  of the first arm portion  321  and the second support rib  322   b  of the second arm portion  322  may allow a support portion  350  to move in an upper direction. 
     The first cam portion  321   a  of the first arm portion  321  and the second cam portion  322   a  of the second arm portion  322  may be constructed in a concavo-convex structure in which a peak (e.g., A of  FIG. 8 ) and a valley (e.g., B of  FIG. 8 ) appear repeatedly. The first arm portion  321  and the second arm portion  322  may be coupled with the detent plate  341 , and thus may be disposed such that the first cam portion  321   a  is engaged with a first detent portion  341   a , and the second cam portion  322   a  is engaged with a second detent portion  341   b.    
     The detent plate  341  may include the first detent portion  341   a  constructed to protrude in a direction of the first cam portion  321   a  of the first arm portion  321  and the second detent portion  341   b  constructed to protrude in a direction of the second cam portion  322   a  of the second arm portion  322 . The first detent portion  341   a  and the second detent portion  341   b  may be constructed in a concavo-convex structure in which a peak (e.g., a of  FIG. 8 ) and a valley (e.g., b of  FIG. 8 ) appear repeatedly. The peak and valley of the first detent portion  341   a  may be constructed in a shape corresponding to the peak and valley of the first cam portion  321   a , and the peak and valley of the second detent portion  341   b  may be constructed in a shape corresponding to the peak and valley of the second cam portion  322   a . The peak (e.g., a of  FIG. 8 ) of the first detent portion  341   a  and the valley (e.g., B of  FIG. 8 ) of the first cam portion  321   a  may be disposed to correspond to each other, and the valley (e.g., b of  FIG. 8 ) of the first detent portion  341   a  and the peak (e.g., A of  FIG. 8 ) of the first cam portion  321   a  may be disposed to correspond to each other, so that the first detent portion  341   a  and the first cam portion  321   a  are engaged with each other. Similarly, the peak of the second detent portion  341   b  and the valley of the second cam portion  322   a  may be disposed to correspond to each other, and the valley of the second detent portion  341   b  and the peak of the second cam portion  322   a  may be disposed to correspond to each other, so that the second detent portion  341   b  and the second cam portion  322   a  are engaged with each other. 
     As it is disposed such that the first cam portion  321   a  and the first detent portion  341   a  are engaged and the second cam portion  322   a  and the second detent portion  341   b  are engaged, the detent plate  341  may provide a sense of detent to the first arm portion  321  and the second arm portion  322 . A pitch between a peak and peak (or valley and valley) of the first detent portion  341   a  may be constructed to be longer than a pitch between a peak and peak (or valley and valley) of the first cam portion  321   a , so that the first cam portion  321   a  rotates within a specified angle range even if it is in a state of being engaged with the first detent portion  341   a . Additionally or alternatively, the pitch between the peak and peak (or valley and valley) of the first detent portion  341   a  may be constructed to be equal to the pitch between the peak and peak (or valley and valley) of the first cam portion  321   a  or may be constructed to be shorter than the pitch between the peak and peak (or valley and valley) of the first cam portion  321   a . In a process in which the electronic device rotates from a folded state to an unfolded state or rotates from the unfolded state to the folded state, there may be case where the peak of the first cam portion  321   a  of the first arm portion  321  is engaged with the peak of the first detent portion  341   a  so that the first arm portion  321  and the detent plate  341  are temporarily spaced apart. In a process in which the peak of the first cam portion  321   a  is beyond the peak of the first detent portion  341   a , the first detent portion  341   a  may provide a sense of detent to the first arm portion  321 . Additionally or alternatively, the second detent portion  341   b  may also provide a sense of detent to the second arm portion  322  in the same or similar manner as the first detent portion  341   a.    
     The first detent portion  341   a  and the second detent portion  341   b  may not only provide the sense of detent to the first arm portion  321  and the second arm portion  322  but also fix a movement of the first arm portion  321  and second arm portion  322 . 
     A flat linear region may be constructed in at least one region (e.g., a summit region) of the peak of the first cam portion  321   a , the peak of the second cam portion  322   a , the peak of the first detent portion  341   a , and/or the peak of the second detent portion  341   b . Similarly, a flat linear region may also be constructed in at least one region of the valley of the first cam portion  321   a , the valley of the second cam portion  322   a , the valley of the first detent portion  341   a , and/or the valley of the second detent portion  341   b . The linear region constructed in one region of the peak and the linear region constructed in one region of the valley may be constructed to be substantially identical or similar. As described above, as the linear region is constructed in the peaks and valleys of the first cam portion  321 , second cam portion  322   a , first detent portion  341   a , and second detent portion  341   b , the movement of the first arm portion  321  and/or second arm portion  322  may be fixed at a specified rotation angle (e.g., 30° or 60°). As the movement of the first arm portion  321  and/or second arm portion  322  is fixed at the specified rotation angle, a movement of a first housing  211  and second housing  212  of the electronic device may be fixed at the specified rotation angle. 
       FIG. 9  is an enlarged view illustrating elements of a hinge structure  300   a , according to an embodiment. The hinge structure  300   a  of  FIG. 9  illustrates a state where a support portion  350  is removed. 
     Referring to  FIG. 9 , the hinge structure  300   a  of an electronic device  101  includes a first bracket  311 , a second bracket  312 , a first arm portion  321 , a second arm portion  322 , a first fixing portion  323 , a second fixing portion  324 , a first shaft  331  to which a first gear  331   a  is coupled, a second shaft  332  to which a second gear  332   a  is coupled, a first idle gear  333 , a second idle gear  334 , a shaft bracket  335 , a first spring  342 , a second spring  343 , a stopper  360 , a first auxiliary member  363 , and a second auxiliary member  364 . At least one component of the hinge structure  300   a  of  FIG. 9  may be identical or similar to at least one of component of  FIG. 5 , and redundant descriptions will be omitted hereinafter. 
     The first arm portion  321  may include a first support rib  321   b , and the second arm portion  322  may include a second support rib  322   b . The first support rib  321   b  may be constructed to protrude from one region of the first arm portion  321 . In addition, the second support rib  322   b  may be constructed to protrude from one region of the second arm portion  322 . When the electronic device is in an unfolded state, the first support rib  321   b  may be constructed to protrude in a direction of the stopper  360  located between the first arm portion  321  and the second arm portion  322  from the first arm portion  321 . Similarly, the second support rib  322   b  may be constructed to protrude in a direction of the stopper  360  from the second arm portion  322 . 
     The first support rib  321   b  may be constructed integrally with the first arm portion  321 , and may rotate along with a rotation of the first arm portion  321 . In addition, the second support rib  322   b  may be constructed integrally with the second arm portion  322 , and may rotate along with a rotation of the second arm portion  322 . As the first support rib  321   b  and the second support rib  322   b  rotate together with the first arm portion  321  and the second arm portion  322 , a support portion  350  disposed on the stopper  360  may move in an upper direction (e.g., the +y direction of  FIG. 9 ). In a process in which the electronic device rotates from the folded state to the unfolded state, at least one region of the first support rib  321   b  and second support rib  322   b  may be in contact with one region of the support portion (e.g., a rear face of the support portion  350 ). 
     According to an embodiment, as the first arm portion  321  rotates clockwise (e.g., the direction {circle around (1)} of  FIG. 9 ), the first support rib  312   b  may move the support portion  350  in an upper direction. On the other hand, as the second arm portion  322  rotates counterclockwise (e.g., the direction {circle around (2)} of  FIG. 9 ), the second support rib  322   b  may move the support portion  350  in an upper direction. 
     The first auxiliary member  363  may be coupled to one end of the first shaft  331  adjacent to the first arm portion  321 , and the second auxiliary member  364  may be coupled to one end of the second shaft  332  of the second arm portion  322 . The first auxiliary member  363  may be coupled to the first shaft  331  to rotate together with the first shaft  331 . The second auxiliary member  364  may be coupled to the second shaft  332  to rotate together with the second shaft  332 . 
     The first auxiliary member  363  may include a third support rib  363   a  constructed to protrude from one region of the first auxiliary member  363 . In addition, the second auxiliary member  364  may include a fourth support rib  364   a  constructed to protrude from one region of the second auxiliary member  364 . The third support rib  363   a  may be disposed at a position parallel to the first support rib  321   b  of the first arm  321 , and the fourth support rib  364   a  may be disposed at a position parallel to the second support rib  322   b  of the second arm portion  322 . The third support rib  363   a  may be spaced apart from the first support rib  321   b  to rotate by the same rotation angle as the first support rib  321   b  with the rotation of the first shaft  331 . The fourth support rib  364   a  may be spaced apart from the second support rib  322   b  to rotate by the same rotation angle as the second support rib  322   b  with the rotation of the second shaft  332 . 
     The third support rib  363   a  and the fourth support rib  364   a  may move the support portion in an upper direction in the process in which the electronic device rotates from the folded state to the unfolded state, similarly to the first support rib  321   b  and the second support rib  322   b . The third support rib  363   a  and the fourth support rib  364   a  may be in contact with one region of the support portion in the process in which the electronic device rotates from the folded state to the unfolded state. As the first shaft  331  rotates clockwise (e.g., the direction {circle around (1)} of  FIG. 9 ), the third support rib  363   a  may move the support portion in an upper direction. Otherwise, as the second shaft  332  rotates counterclockwise (e.g., the direction {circle around (2)} of  FIG. 9 ), the fourth support rib  364   a  may move the support portion in an upper direction. 
     That is, the hinge structure  300   a  may move the support portion in an upper direction in the process in which the electronic device rotates from the folded state to the unfolded state through the first support rib  321   b , the second support rib  322   b , the third support rib  363   a , and the fourth support rib  364   a . Accordingly, the support portion can be in contact with a rear face of a flexible display  220 , thereby preventing the flexible display from being sagged and/or damaged when the electronic device is in the unfolded state. 
       FIG. 10A  is a cross-sectional view of a hinge structure  300   a  when an electronic device is in an unfolded state, according to an embodiment.  FIG. 10B  is a cross-sectional view of the hinge structure  300   a  when the electronic device is in a folded state, according to an embodiment.  FIG. 10A  may illustrate a cross-section of the hinge structure  300   a  of  FIG. 6A , cut along the direction A-A′, and  FIG. 10B  may illustrate a cross-section of the hinge structure  300   a  of  FIG. 6C , cut along the direction A-A′. 
     Referring to  FIG. 10A  and  FIG. 10B , an electronic device includes a flexible display  220 , a first support plate  221  supporting the flexible display  220 , a second support plate  222 , and the hinge structure  300   a.    
     The hinge structure  300   a  may include a first bracket  311 , a second bracket  312 , a first arm portion  321 , a second arm portion  322 , a support portion  350 , a stopper  360 , an elastic member  361 , and a screw  362 . 
     The support portion  350  may move in a direction of a rear face of the flexible display  220  by means of a first support rib  321   b  of the first arm portion  321  and a second support rib  322   b  of the second arm portion  322 , when the electronic device rotates from the folded state to the unfolded state as described above. Through the aforementioned process, the support portion  350  may support one region of the flexible display  220  not supported by the first arm portion  321  and the second arm portion  322 , when the electronic device is in the unfolded state, as illustrated in  FIG. 10A . 
     When the electronic device is in the unfolded state, a gap (e.g., g of  FIG. 10A ) may be constructed between the support portion  350  and/or the first support rib  321   b  of the first arm portion  321  and the second support rib  322   b  of the second arm portion  322 . When the electronic device is in the unfolded state, as the gap is constructed between the support portion  350  and/or the first support rib  321   b  and the second support rib  322   b , the support portion  350  can be prevented from moving in a direction of the flexible display  220  by at least a specified distance. When the electronic device is in the unfolded state, the gap between the support portion  350  and the first support rib  32   b  and the second support rib  322   b  may be constructed to be greater than a gap between a protrusion region (e.g., a fixing region E 1  of  FIG. 12A ) of a shaft bracket  355  or a protrusion region (e.g., a fixing region E 2  of  FIG. 13A ) of the stopper  360   360  and a fixing rib  352  constructed in one region of the support portion  350 . As a result, the support portion  350  can be prevented from moving in a duplicate manner in an upper direction (e.g., the +y direction of  FIG. 10A ) by means of the first support rib  321   b  and the second support rib  322   b . That is, when the electronic device is in the unfolded state, the hinge structure  300   a  can prevent the flexible display  220  from being damaged by the support portion  350  through the gap constructed between the support portion  350  and/or the first support rib  321   b  and the second support rib  322   b.    
     The stopper  360  may be located at a lower end (e.g., the −y direction of  FIG. 10A ) of the support portion  350 , and a through-hole  360   c  may be constructed in one region of the stopper  360 . A protrusion region  351  of the support portion  350  may be located at a lower end of the stopper  360  by passing through the through-hole  360   c , and the screw  362  may be coupled to the protrusion region  351  of the support portion  350  passing through the through-hole  360   c . An outer circumferential surface of one face of the screw  362  facing the protrusion region  351  may be constructed to be greater than an outer circumferential surface of the protrusion region  351 , so that the elastic member  361  is disposed between the stopper  360  and the screw  362 . The elastic member  361  may be a spring, but is not limited thereto. 
     One end of the elastic member  361  may be in contact with one region of the stopper  360  (e.g., a neighboring region of the through-hole  360   c ), and the other end may be in contact with the screw  362  coupled to the protrusion region of the support portion  350 . The elastic member  361  may be compressed when the support portion  350  moves in an upper direction (e.g., the +y direction of  FIG. 10A ), or may be restored to its original state due to elastic restoration force. 
     As the electronic device rotates from the folded state to the unfolded state, the support portion  350  moves in a direction of the flexible display  220 . The screw  362  coupled to the protrusion region  351  may also move in an upper direction (e.g., the +y direction of  FIG. 10A ) due to the movement of the support portion  350 , and the elastic member  361  may be compressed due to the upward movement of the screw  362 . 
     As the electronic device rotates from the unfolded state to the folded state, the first arm portion  321  may rotate counterclockwise (e.g., the direction (of  FIG. 10B ), and the second arm portion  322  may rotate clockwise (e.g., the direction D of  FIG. 10B ), so that the first support rib  321   b  and the second support rib  322   b  are spaced apart from the support portion  350 . As the first support rib  321   b  and second support rib  322   b  are spaced apart from the support portion  350 , pressure may be applied to the screw  362  in a lower direction (e.g., the −y direction of  FIG. 10B ) due to elastic restoration force of the compressed elastic member  361 . Due to the pressure applied to the screw  362 , the screw  362  and the support portion  350  coupled with the screw  362  may move in a lower direction (e.g., the −y direction of  FIG. 10B ). That is, in a process in which the electronic device rotates from the unfolded state to the folded state, the support portion  350  may be spaced apart from the flexible display  220  due to the elastic restoration force of the elastic member  361  located between the stopper  360  and the screw  362 . 
     Through the aforementioned driving process, the support portion  350  may not interrupt a rotation trajectory (or a “driving trajectory”) of the flexible display  220  or the first support plate  221  and the second support plate  222  in the process in which the electronic device rotates from the unfolded state to the folded state. On the other hand, when the electronic device is in the unfolded state, the support portion  350  may support one region of the flexible display  220  not supported by the first arm portion  321  and the second arm portion  322 , thereby preventing the flexible display  220  from being damaged or sagged. 
       FIG. 11A  is a cross-sectional view of a hinge structure when an electronic device is in an unfolded state, according to an embodiment.  FIG. 11B  is a cross-sectional view of the hinge structure when the electronic device is in a folded state, according to an embodiment.  FIG. 11A  may illustrate a cross-section of the hinge structure  300   a  of  FIG. 6A , cut along the direction A-A′, and  FIG. 11B  may illustrate a cross-section of the hinge structure  300   a  of  FIG. 6C , cut along the direction A-A′. 
     Referring to  FIG. 1A  and  FIG. 11B , an electronic device includes a flexible display  220 , a first support plate  221  supporting the flexible display  220 , a second support plate  222 , and a hinge structure  300   a.    
     The hinge structure  300   a  may include a first bracket  311 , a second bracket  312 , a first arm portion  321 , a second arm portion  322 , a support portion  350 , a stopper  360 , and an elastic member  361 . At least one component of the hinge structure  300   a  of  FIG. 11A  and  FIG. 11B  may be identical or similar to at least one of component of  FIG. 10A  and  FIG. 10B , and redundant descriptions will be omitted hereinafter. 
     The hinge structure  300   a  may move the support portion  350  in an upper direction (e.g., the +y direction of  FIG. 1A ) or a lower direction (e.g., the −y direction of  FIG. 1A ) in a manner that is different from  FIG. 11A  and  FIG. 10B . 
     The support portion  350  may move in a direction of a rear face of the flexible display  220  by means of a first support rib  321   b  of the first arm portion  321  and a second support rib  322   b  of the second arm portion  322 , when the electronic device rotates from the folded state to the unfolded state as described above. Through the aforementioned process, the support portion  350  may support one region of the flexible display  220  not supported by the first arm portion  321  and the second arm portion  322 , when the electronic device is in the unfolded state, as illustrated in  FIG. 1A . 
     When the electronic device is in the unfolded state, a gap (e.g., g of  FIG. 11A ) may be constructed between the support portion  350  and/or the first support rib  321   b  of the first arm portion  321  and the second support rib  322   b  of the second arm portion  322 . When the electronic device is in the unfolded state, as the gap is constructed between the support portion  350  and/or the first support rib  321   b  and the second support rib  322   b , the support portion  350  can be prevented from moving in a direction of the flexible display  220  by at least a specified distance. When the electronic device is in the unfolded state, the gap between the support portion  350  and/or the first support rib  32   b  and the second support rib  322   b  may be constructed to be greater than a gap between a protrusion region (e.g., the fixing region E 1  of  FIG. 12A ) of the shaft bracket  355  or a protrusion region (e.g., the fixing region E 2  of  FIG. 13A ) of the stopper  360  and a fixing rib  352  constructed in one region of the support portion  350 . As a result, the support portion  350  can be prevented from moving in a duplicate manner in an upper direction (e.g., the +y direction of  FIG. 11A ) by means of the first support rib  321   b  and the second support rib  322   b . That is, when the electronic device is in the unfolded state, the hinge structure  300   a  can prevent the flexible display  220  from being damaged by the support portion  350  through the gap constructed between the support portion  350  and the first support rib  321   b  and the second support rib  322   b.    
     The stopper  360  may be located at a lower end (or a rear face) of the support portion  350 , and a groove  360   d  may be constructed in at least one region of the stopper  360 . An inner space may be constructed in the stopper  360  due to the groove  360   d  constructed at the stopper  360 , and a protrusion region  351  of the support portion  350  may be located inside the space. 
     The elastic member  361  may be a spring, and may be located inside the inner space of the stopper  360  constructed by the groove  360   d . One end of the elastic member  361  may be coupled to one region of the support portion  350 , and the other end of the elastic member  361  may be coupled to one region of the inner space of the stopper  360 . The elastic member  361  may be attached to one region of the support portion  350  and/or one region of the inner space of the stopper  360  by an adhesive. The elastic member  361  may be coupled to one region of the support portion  350  and stopper  360  through a fixing member located in one region of the support portion  350  and/or one region of the inner space of the stopper  360 . The protrusion region  351  of the support portion  350  may be partially inserted into the elastic member  361  to guide a direction of a motion (e.g., compression or elongation) of the elastic member  361 . 
     According to an embodiment, as the electronic device rotates from the folded state to the unfolded state, the support portion  350  moves in a direction of the flexible display  220  by means of the first support rib  321   b  and the second support rib  322   b . The elastic member  361  coupled to one region of the support portion  350  and one region of the stopper  360  is elongated due to the upward movement of the support portion  350 . 
     As the electronic device rotates from the unfolded state to the folded state, the first arm portion  321  may rotate counterclockwise (e.g., the direction U of  FIG. 11B ), and the second arm portion  322  may rotate clockwise (e.g., the direction D of  FIG. 11B ), so that the first support rib  321   b  and the second support rib  322   b  are spaced apart from the support portion  350 . As the first support rib  321   b  and the second support rib  322   b  are spaced apart from the support portion  350 , the support portion  350  may move in a lower direction (e.g., the −y direction of  FIG. 11B ) due to the elastic restoration force of the elastic member  361 , thereby being spaced apart from the flexible display  220 . 
     That is, when the electronic device is in the unfolded state, the support portion  350  may support one region of the flexible display  220  not supported by the first arm portion  321  and the second arm portion  322 , thereby preventing the flexible display  220  from being damaged or sagged. On the other hand, in a process in which the electronic device rotates from the unfolded state to the folded state, the support portion  350  may be spaced apart from the flexible display  220  due to the elastic restoration force of the elastic member  361 . Accordingly, the support portion  350  may not interrupt a rotation trajectory (“driving trajectory”) of the flexible display  220  or the first support plate  221  and the second support plate  222 . 
       FIG. 12A  is a cross-sectional view of a hinge structure when an electronic device is in an unfolded state, according to an embodiment.  FIG. 12B  is a cross-sectional view of the hinge structure when the electronic device is in a folded state, according to an embodiment.  FIG. 12A  may illustrate a cross-section of the hinge structure  300   a  of  FIG. 6A , cut along the direction B-B′, and  FIG. 12B  may illustrate a cross-section of the hinge structure  300   a  of  FIG. 6C , cut along the direction B-B′. 
     Referring to  FIG. 12A  and  FIG. 12B , a hinge structure  300   b  of an electronic device includes a second bracket  312 , a fixing bracket  313 , a second arm portion  322 , a second fixing portion  324  coupling the second bracket  312  and the second arm portion  322 , a rotation structure  330  including a second shaft  332 , a second idle gear  334 , and a shaft bracket  335 , a support portion  350 , a stopper  360 , an elastic member  361 , and a screw  362 . At least one component of the hinge structure  300   b  of  FIG. 12A  and  FIG. 12B  may be identical or similar to at least one component of  FIG. 5 ,  FIG. 10A  and  FIG. 10B , and redundant descriptions will be omitted hereinafter. 
     The support portion  350  may be located on the stopper  360 , and may include a protrusion region  351  and a fixing rib  352 . The protrusion region  351  may be constructed to protrude in a lower direction (e.g., the −y direction of  FIG. 12A ) of the support portion  350 , and may be coupled with the screw  362  as described above to compress the elastic member  361  in a process in which the electronic device rotates from the folded state to the unfolded state. The fixing rib  352  may be constructed to protrude in a lower direction of the support portion  350  similarly to the protrusion region  351 , and in a lateral view, may be constructed in a hook shape curved in a direction of the shaft bracket  335 . 
     The fixing rib  352  may be fixed to one region of the shaft bracket  335  to prevent the support portion  350  from moving by at least a specified distance in an upper direction (e.g., the +y direction of  FIG. 12A ) or in a direction of a flexible display (e.g., the flexible display  220  of  FIG. 2A ) in the process in which the electronic device rotates from the folded state to the unfolded state. 
     The shaft bracket  335  may include a fixing region E 1 . The fixing region E 1  may be constructed to protrude in a direction of the stopper  360  from one region of the shaft bracket  335 . As the electronic device rotates from the folded state (e.g., see  FIG. 12B ) to the unfolded state (e.g., see  FIG. 12A ), the support portion  350  may move in an upper direction, and the fixing rib  352  of the support portion  350  may be in contact with the fixing region E 1  of the shaft bracket  335  due to the upward movement of the support portion  350 . 
     When the electronic device is in the unfolded state, the hook-shaped fixing rib  352  may be in contact with a lower region of the fixing region E 1  so that the fixing rib  352  of the support portion  350  is caught at the fixing region E 1  of the shaft bracket  335 . When the support portion  350  moves in an upper direction by at least a specified distance, pressure may be applied in the upper direction to the flexible display disposed to an upper end of the support portion  350 , and some regions of the flexible display may be damaged due to the pressure applied by the support portion  350 . When the electronic device is in the unfolded state, the fixing rib  352  of the support portion  350  may be disposed to be in contact with the fixing region E 1  of the shaft bracket  335  without a gap, so that the support portion  350  can be prevented from moving in the upper direction by at least a specified distance. 
     When the electronic device rotates from the unfolded state to the folded state, the support portion  350  may move in a lower direction (e.g., the −y direction of  FIG. 12B ) due to elastic restoration force of the elastic member  361  as described above. Accordingly, the fixing rib  352  may be spaced apart from the fixing region E 1  of the shaft bracket  335 . As the fixing rib  352  is spaced apart from the fixing region E 1  of the shaft bracket  335 , the support portion  350  may move in a lower direction without being affected by the fixing region E 1 . 
     That is, the hinge structure  300   b  may control the movement of the support portion  350  so that the support portion  350  moves in an upper direction within a specified range through the fixing rib  352  of the support portion  350  and the fixing region E 1  of the shaft bracket  335 . 
       FIG. 13A  is a cross-sectional view of a hinge structure when an electronic device is in an unfolded state, according to another embodiment.  FIG. 13B  is a cross-sectional view of the hinge structure when the electronic device is in a folded state, according to an embodiment.  FIG. 13A  may illustrate a cross-section of the hinge structure  300   a  of  FIG. 6A , cut along the direction B-B′, and  FIG. 13B  may illustrate a cross-section of the hinge structure  300   a  of  FIG. 6C , cut along the direction B-B′. Referring to  FIG. 13A  and  FIG. 13B , a hinge structure  300   b  of an electronic device includes a second bracket  312 , a fixing bracket  313 , a second arm portion  322 , a second fixing portion  324  coupling the second bracket  312  and the second arm portion  322 , a rotation structure  330  including a second shaft  332  and a second idle gear  334 , a support portion  350 , a stopper  360 , an elastic member  361 , and a screw  362 . 
     The hinge structure  300   b  of  FIG. 13A  and  FIG. 13B  can prevent the support portion  350  from moving in an upper direction (e.g., the +y direction of  FIG. 13A ) in a manner different from the manner in  FIG. 12A  and  FIG. 12B . At least one component of the hinge structure  300   b  of  FIG. 13A  and  FIG. 13  may be identical or similar to at least one component of  FIG. 10A  and  FIG. 10B , and redundant descriptions will be omitted hereinafter. 
     The support portion  350  may be located on the stopper  360 , and may include a protrusion region  351  and a fixing rib  352 . The protrusion region  351  may be constructed to protrude in a lower direction (e.g., the −y direction of  FIG. 13A ) of the support portion  350 , and may be coupled with the screw  362  to compress the elastic member  361  in a process in which the electronic device rotates from the folded state to the unfolded state. The fixing rib  352  may be constructed to protrude in a lower direction of the support portion  350 , and in a lateral view, may be constructed in a hook shape curved in a direction of the stopper  360 . 
     The fixing rib  352  may be fixed to one region of the stopper  360  to prevent the support portion  350  from moving by at least a specified distance in an upper direction (e.g., the +y direction of  FIG. 13A ) or in a direction of a flexible display  220  in the process in which the electronic device rotates from the folded state to the unfolded state. 
     The stopper  360  may include a fixing region E 2 . The fixing region E 2  may be constructed to protrude in a direction of the shaft bracket  335  from one region of the stopper  360 . As the electronic device rotates from the folded state, as illustrated in  FIG. 13B , to the unfolded state, as illustrated in  FIG. 13A , the support portion  350  may move in an upper direction, and the fixing rib  352  of the support portion  350  may be in contact with the fixing region E 2  of the stopper  360  due to the upward movement of the support portion  350 . 
     When the electronic device is in the unfolded state, the hook-shaped fixing rib  352  may be in contact with a lower end of the fixing region E 2  of the stopper  360  so that the fixing rib  352  of the support portion  350  is caught at the fixing region E 2 . 
     When the support portion  350  moves in an upper direction by at least a specified distance, some regions of the flexible display may be damaged due to the pressure applied by the support portion  350 . When the electronic device is in the unfolded state, the fixing rib  352  of the support portion  350  may be disposed to be in contact with the fixing region E 2  of the stopper  360 , so that the support portion  350  can be prevented from moving in the upper direction by at least a specified distance. 
     Additionally or alternatively, when the electronic device rotates from the unfolded state to the folded state, the support portion  350  may move in a lower direction (e.g., the −y direction of  FIG. 13B ) due to elastic restoration force of the elastic member  361  as described above. Due to the movement of the support portion  350 , the fixing rib  352  may be spaced apart from the fixing region E 2  of the stopper  360 . As the fixing rib  352  is spaced apart from the fixing region E 2  of the stopper  360 , the support portion  350  may move in a lower direction without being affected by the fixing region E 2 . 
     That is, unlike  FIG. 12A  and  FIG. 12B , the hinge structure  300   b  of  FIG. 13A  and  FIG. 13B  may control the movement of the support portion  350  so that the support portion  350  moves in an upper direction within a specified range through the fixing rib  352  of the support portion  350  and the fixing region E 2  of the stopper  360 . 
     According to an embodiment, an electronic device may include a first housing, a second housing, a hinge assembly coupling the first housing and the second housing so that the second housing is rotatable with respect to the first housing, and a flexible display disposed from one region of the first housing to at least one region of the second housing across the hinge assembly. The hinge assembly may include a first bracket coupled to at least one region of the first housing to rotate about a virtual first rotation axis, a second bracket coupled to at least one region of the second housing to rotate about a virtual second rotation axis, a fixing bracket supporting the first bracket and the second bracket, a first shaft rotating about a third rotation axis different from the virtual first rotation axis, a second shaft adjacent to the first shaft to rotate about a fourth rotation axis different from the virtual second rotation axis, a first arm portion coupled to the first shaft to rotate about the third rotation axis, and having one side coupled to at least one region of the first bracket, a second arm portion coupled to the second shaft to rotate about the fourth rotation axis, and having one side coupled to at least one region of the second bracket, and a support portion located between the first arm portion and the second arm portion. The support portion may support at least one region of the flexible display when the electronic device is in an unfolded state, and may be spaced apart from the flexible display as the electronic device rotates from the unfolded state to a folded state. 
     The first arm portion may include a first support rib supporting at least one region of the support portion when the electronic device is in the folded state. The second arm portion may include a second support rib supporting at least one region of the support portion when the electronic device is in the folded state. 
     The first support rib and the second support rib may move the support portion in a direction of the flexible display, as the electronic device rotates from the folded state to the unfolded state. 
     The electronic device may further include a first auxiliary member coupled to the first shaft to rotate about the third rotation axis, and including a third support rib, and a second auxiliary member coupled to the second shaft to rotate about the fourth rotation axis, and including a fourth support rib. 
     The electronic device may further include a stopper having a through-hole through which a protrusion region of the support portion passes, a screw coupled to the protrusion region of the support portion, and an elastic member located between the stopper and the screw and in contact with at least one region of the stopper. 
     The elastic member may be compressed, as the electronic device rotates from the folded state to the unfolded state. 
     The support portion may be spaced apart from the flexible display due to restoration force of the elastic member, as the electronic device rotates from the unfolded state to the folded state. 
     The electronic device may further include a stopper located at a lower end of the support portion and having a groove constructed in at least one region, and an elastic member located inside the groove and having one side fixed to at least one region of the support portion and another side fixed to at least one region of the stopper. 
     The elastic member may be elongated in a direction of the flexible display as the electronic device rotates from the folded state to the unfolded state. 
     The support portion may further include a fixing rib constructed to protrude in a lower direction of the support portion. 
     The electronic device may include a shaft bracket supporting the first shaft and the second shaft. The fixing rib may be in contact with one region of the stopper or one region of the shaft bracket as the electronic device rotates from the folded state to the unfolded state, so that the support portion is prevented from moving by more than a specified height. 
     The electronic device may further include a detent plate including a detent portion of a concavo-convex structure constructed to protrude in a direction of the first arm portion and second arm portion. 
     A first cam portion corresponding to the detent portion may be constructed in one region of the first arm portion. A second cam portion corresponding to the detent portion may be constructed in one region of the second arm portion. 
     The electronic device may further include a first gear coupled to the first shaft, a second gear coupled to the second shaft, a first idle gear engaged with the first gear, and a second idle gear engaged with the first idle gear and the second gear. 
     A first slide hole may be constructed in one region of the first bracket corresponding to the first arm portion. A second slide hole may be constructed in one region of the second bracket corresponding to the second arm portion. 
     The first bracket and the first arm portion may be coupled through a first fixing portion which passes through the first slide hole and one region of first arm portion. The second bracket and the second arm portion may be coupled through a second fixing portion which passes through the second slide hole and one region of second arm portion. 
     The first fixing portion may be slid from an outer region to inner region of the first slide hole, as the electronic device rotates from the unfolded state to the folded state. The second fixing portion may be slid from the outer region to inner of the second slide hole as the electronic device rotates from the unfolded state to the folded state. 
     According to an embodiment, a hinge assembly may include a hinge housing, and at least one hinge structure disposed inside the hinge housing. The at least one hinge structure may include a first bracket rotating about a virtual first rotation axis, a second bracket adjacent to the first bracket and rotating about a virtual second rotation axis different from the virtual first rotation axis, a fixing bracket supporting the first bracket and the second bracket, a first shaft rotating about a third rotation axis different from the virtual first rotation axis, and having a first gear coupled thereto, a second shaft adjacent to the first shaft to rotate about a fourth rotation axis different from the virtual second rotation axis, and having a second gear coupled thereto, a shaft bracket supporting the first shaft and the second shaft, a first idle gear gear-coupled with the first gear, a second idle gear gear-coupled with the first idle gear and the second gear, a first arm portion coupled to the first shaft to rotate about the third rotation axis, and having one side coupled to at least one region of the first bracket, a second arm portion coupled to the second shaft to rotate about the fourth rotation axis, and having one side coupled to at least one region of the second bracket, and a support portion moving up and down with the rotation of the first arm portion and second arm portion. 
     The first arm portion may include a first support rib supporting at least one region of the support portion when the first arm portion and the second arm portion are in a horizontal state. The second arm portion may include a second support rib supporting at least one region of the support portion when the first arm portion and the second arm portion are in the horizontal state. The hinge assembly may further include a stopper having a through-hole through which a protrusion region of the support portion passes, a screw coupled to the protrusion region of the support portion, and an elastic member located between the stopper and the screw and in contact with at least one region of the stopper. 
     According to an embodiment, an electronic device can reduce a size of a hinge assembly by integrating various structures for rotating a housing. 
     According to an embodiment, an electronic device can support a flexible display even when the electronic device is in an unfolded state without affecting a driving trajectory of the flexible display. 
     According to an embodiment, an electronic device can prevent a flexible display from being damaged in a process of using the electronic device, and can the flexible display to be more flat than traditional flexible displays. 
     In the aforementioned specific embodiments of the present disclosure, components included in the disclosure are expressed in singular or plural forms according to the specific embodiments disclosed herein. However, the singular or plural forms (i.e., terms and/or expressions) are selected for a situation disclosed for the convenience of explanation, and thus various embodiments of the disclosure are not limited to a single or a plurality of components. Therefore, a component expressed in a plural form can also be expressed in a singular form, or vice versa. 
     While the present disclosure has been particularly shown and described with reference to certain embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents.