Patent Publication Number: US-10309143-B2

Title: Refrigerator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2017-0061099, filed on May 17, 2017, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Field 
     Embodiments of the present disclosure relate to a refrigerator having an improved door opening and closing structure. 
     2. Description of the Related Art 
     Generally, a refrigerator is an apparatus to keep food fresh by having a storage compartment for storing food and a cold supply device for supplying cold air to the storage compartment. 
     The refrigerator may be classified by a type of a storage compartment and a door. 
     Particularly, the refrigerator may be classified into Top Mounted Freezer (TMF) type refrigerator having a storage compartment divided into an upper side and a lower side by a horizontal partition and thus a freezing compartment is formed in the upper side and a refrigerating compartment is formed in the lower side, and Bottom Mounted Freezer (BMF) type refrigerator in which a refrigerating compartment is formed in the upper side and a freezing compartment is formed in the lower side. 
     In addition, the refrigerator may be classified into Side by Side (SBS) type refrigerator having a storage compartment divided into a left side and a right side by a vertical partition and thus a freezing compartment is formed in one side and a refrigerating compartment is formed in the other side, and French Door Refrigerator (FDR) type refrigerator having a storage compartment divided into an upper side and a lower side by a horizontal partition and thus a refrigerating compartment is formed in the upper side and a freezing compartment is formed in the lower side, wherein the refrigerating compartment is opened or closed by a pair of doors. 
     The door for opening and closing the storage compartment of the refrigerator may be configured to be opened and closed by a user manually. However, sometimes, a user cannot use his or her hands for opening or closing the door of the refrigerator since the user holds foods to put the foods or takes the foods out of the refrigerator. In this case, the user should put the foods to another place, and then the user can open or close the door of the refrigerator with his or her hands. To relieve the inconvenience, a structure capable of automatically opening or closing the door has been suggested. 
     SUMMARY 
     Therefore, it is an aspect of the present disclosure to provide a refrigerator having a structure capable of automatically opening and closing a door. 
     It is another aspect of the present disclosure to provide a refrigerator having an improved structure to improve the durability of a door opening and closing apparatus. 
     It is another aspect of the present disclosure to provide a refrigerator capable of reducing a load of a motor. 
     Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the disclosure. 
     In accordance with an aspect of the present invention, a refrigerator includes a body provided with a storage compartment; a door rotatable with respect to a hinge shaft on the body and configured to open and close the storage compartment; and a door opening and closing apparatus configured to open and close the door. The door opening and closing apparatus includes a motor configured to generate power; a first gear rotated in conjunction with the power generated by the motor; a second gear configured to transmit a rotational force to the hinge shaft as the door opens and closes; and a pair of intermittent gears configured to transmit the power from the first gear to the second gear and configured to prevent an external force from being transmitted from the second gear to the first gear while the external force is applied to open and close the door. 
     The pair of intermittent gears may include a first intermittent gear and a second intermittent gear rotated with respect to the same axis as the first intermittent gear. The first intermittent gear may be detachably coupled to the second intermittent gear in the axial direction. 
     The first intermittent gear may be moved between a coupling position in which the first intermittent gear is coupled to the second intermittent gear to transmit the power to the second intermittent gear, and a separated position in which the first intermittent gear is separated from the second intermittent gear. 
     A refrigerator may further include an intermittent gear elastic member configured to generate an elastic restoring force toward the axial direction to resiliently return the first intermittent gear from the separated position to the coupling position. 
     The second intermittent gear may be operated depending on the rotation of the second gear. 
     The first and second intermittent gears may include at least one first and second inclined boss portion formed on surfaces facing each other. 
     The first and second inclined boss portions may include first and second inclined surfaces configured to come into contact with each other to transmit the power from the first intermittent gear to the second intermittent gear, and the first inclined surface and the second inclined surface being formed to be inclined in a circumferential direction with respect to a direction in which the first and second intermittent gears face each other. The first and second inclined surfaces may be configured to generate a slip therebetween due to the external force. 
     The at least one first and second inclined boss portion may include a plurality of first and second inclined boss portions alternately disposed. 
     The refrigerator may further include a third gear engaged with the first gear; and a pair of idle gears moved in a circumferential direction by the rotation of the third gear so as to selectively transmit the rotational force of the third gear to the pair of intermittent gears. 
     The pair of idle gears may be moved between a first position in which a first idle gear of the pair of idle gears is engaged with the pair of intermittent gears while the third gear is rotated in a first direction; a second position in which a second idle gear of the pair of idle gears is engaged with the pair of intermittent gears while the third gear is rotated in a second direction opposite to the first direction; and a third position in which the first and second idle gears are separated from the pair of intermittent gears. 
     The refrigerator further may include a switching member provided with the pair of idle gears and configured to allow the pair of idle gears to be moved from the first position to the third position, in conjunction with the third gear. 
     In the first position, a forward rotational force of the motor may be transmitted to open the door, and in the second position, a reverse rotational force of the motor may be transmitted to close the door. 
     The refrigerator may further include a pressure device configured to press the body to open the door; and a mounting member provided with a pressing protrusion configured to transmit the power to the pressure device, and configured to be rotated together with the third gear such that the switching member may be disposed between the mounting member and the third gear. The switching member may be operated independently of the mounting member. 
     The pressure device may include a sliding member moved in a slide manner by being pressed by the pressing protrusion; and a pressing member configured to be rotated by the sliding movement of the sliding member and configured to come into contact with the body to open the door. 
     The pressure device may include a delay member configured to allow an operation of the pressure device and an operation in which the pair of idle gears is placed in the first position, to be sequentially performed. 
     In accordance with an aspect of the present invention, a refrigerator includes a body provided with a storage compartment; a door configured to be rotatable with respect to a hinge shaft disposed at the body and configured to open and close the storage compartment; and a door opening and closing apparatus configured to open and close the door. The door opening and closing apparatus includes a motor configured to generate power; a rotary gear restrained by the hinge shaft; and a driving gear configured to transmit the power generated from the motor to the rotary gear. The driving gear comprises a pair of intermittent gears configured to detach from each other, to prevent a load from being applied in a direction opposite to a rotation direction of the motor, or greater than a rotational force of the motor, to the rotary gear. 
     The pair of intermittent gears may include a first intermittent gear and a second intermittent gear rotated with respect to the same axis as the first intermittent gear. The first intermittent gear may be detachably coupled to the second intermittent gear in the axial direction. 
     The first intermittent gear may be moved between a coupling position in which the first intermittent gear is coupled to the second intermittent gear to transmit the power to the second intermittent gear, and a separated position in which the first intermittent gear is separated from the second intermittent gear. 
     The first and second intermittent gears may include at least one first and second inclined boss portion formed on surfaces facing each other. 
     In accordance with an aspect of the present invention, a refrigerator includes a body provided with a storage compartment; a door configured to open and close the storage compartment; and a door opening and closing apparatus configured to open and close the door. The door opening and closing apparatus includes a motor configured to generate power; a first gear rotated in conjunction with the power generated by the motor; a second gear configured to transmit a rotational force to the hinge shaft of the door as the door opens and closes; a third gear configured to engage with the first gear; and a pair of idle gears configured to selectively transmit the rotational force of the third gear to the second gear, through the rotation of the third gear. The second gear includes a pair of intermittent gears configured to be moved between a coupling position to transfer the power transmitted from the motor to the hinge shaft, and a separated position to prevent a load from the hinge shaft to the motor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIGS. 1 and 2  are perspective views of a refrigerator in accordance with an embodiment. 
         FIG. 3  is an enlarged view of A in  FIG. 2 . 
         FIG. 4  is a perspective view of a door opening and closing apparatus of the refrigerator according to an embodiment. 
         FIG. 5  is a view from above of the inside of the door opening and closing apparatus of the refrigerator according to an embodiment. 
         FIG. 6  is a view from below of the inside of the door opening and closing apparatus of the refrigerator according to an embodiment. 
         FIG. 7  is an exploded-perspective view of the door opening and closing apparatus of the refrigerator according to an embodiment. 
         FIGS. 8 and 9  are perspective views from above and below of the center gear and a switching unit of the refrigerator according to an embodiment. 
         FIG. 10  is an exploded perspective view of the center gear and the switching unit of the refrigerator according to an embodiment. 
         FIG. 11  is a view of a sliding member and a power switching member of the refrigerator according to an embodiment. 
         FIGS. 12 and 13  are views of operations of the sliding member and the power switching member of the refrigerator according to an embodiment. 
         FIG. 14  is a view of the relationship between the pressure device and the driving gear of the refrigerator according to an embodiment. 
         FIGS. 15 to 20  are views of operations of the door opening and closing apparatus of the refrigerator according to an embodiment. 
         FIGS. 21 to 23  are views of an operation of a power conversion member of the refrigerator according to an embodiment. 
         FIG. 24  is an exploded perspective view of an intermittent gear of the refrigerator according to an embodiment. 
         FIG. 25  is a cross-sectional view of the intermittent gear of the refrigerator according to an embodiment. 
         FIGS. 26 and 27  are views of the operation of the intermittent gear in the refrigerator according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments described in the present disclosure and configurations shown in the drawings are merely examples of the embodiments of the present disclosure, and may be modified in various different ways at the time of filing of the present application to replace the embodiments and drawings of the present disclosure. 
     In addition, the same reference numerals or symbols shown in the drawings of the present disclosure indicate elements or components performing substantially the same function. 
     Also, the terms used herein are used to describe the embodiments and are not intended to limit and/or restrict the present disclosure. The singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. In this present disclosure, the terms “including”, “having”, and the like are used to specify features, numbers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more of the features, elements, steps, operations, elements, components, or combinations thereof. 
     It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, but elements are not limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present disclosure, a first element may be termed as a second element, and a second element may be termed as a first element. The term of “and/or” includes a plurality of combinations of relevant items or any one item among a plurality of relevant items. 
     The present disclosure will be described more fully hereinafter with reference to the accompanying drawings. 
       FIGS. 1 and 2  are perspective views of a refrigerator in accordance with an embodiment. 
     A refrigerator  1  may include a body  10 , a storage compartment  20  formed in the body  10  to be divided into an upper portion and a lower portion, a door  30  configured to open and close the storage compartment  20 , and a cold air supply device (not shown) configured to supply cold air to the storage compartment  20 . 
     The body  10  may include an inner case  12  forming the storage compartment  20 , an outer case  14  coupled to the outside of the inner case  12  to form an appearance, and an insulation material (not shown) foamed between the inner case  12  and the outer case  14  to insulate the storage compartment  20 . 
     The cold air supply device may generate cold air using a cooling cycle that compresses, condenses, expands, and evaporates the refrigerant. 
     A front surface of the storage compartment  20  is configured to open, and the storage compartment  20  may be divided into a refrigerating compartment  22  disposed in the upper side and a freezing compartment (not shown) disposed in the lower side by a horizontal partition  25 . The refrigerating compartment  22  may be opened and closed by a pair of door  30  and  40  rotatably coupled to the body  10 . The freezing compartment may be opened and closed by a pair of door  50  rotatably coupled to the body  10 . The shape of the doors  30 ,  40  and  50  is not limited thereto and thus a sliding door configured to open and close the storage compartment in a sliding manner may be employed. 
     The pair of door  30  and  40  opening and closing the refrigerating compartment  22  may be arranged on the left and right. Hereinafter for the convenience of the description, with respect to the drawings, a right side door  30  will be referred to as a first door  30 , and a left side door  40  will be referred to as a second door  40 . In the relationship between the doors  30  and  40  of the refrigerating compartment  22  and the door  50  of the freezing compartment, the doors  30  and  40  of the refrigerating compartment  22  may be referred to as upper doors  30  and  40  and the door  50  of the freezing compartment may be referred to as a lower door  50 . The first door  30  may be provided with a first door handle  30   a  that can be grasped to open and close the first door  30  and the second door  40  may be provided with a second door handle  40   a  that can be grasped to open and close the second door  40 . The lower door  50  may be also provided with a lower door handle  50   a  that can be grasped to open and close the lower door  50 . 
     The doors  30 ,  40  and  50  may be rotatable about the body  10  with respect to a hinge shaft  51  (refer to  FIG. 3 ). 
     The first door  30  may open and close the right part of the refrigerating compartment  22  and the second door  40  may open and close the remaining part of the refrigerating compartment  22 . A door shelf  35  configured to store foods may be provided on the rear surface of the first door  30  and the second door  40 , respectively. As illustrated in  FIG. 2 , door shelf  35  may be provided on rear surface  39  of the first door  30 . 
     The door shelf  35  may include a shelf support portion  35   a  extending vertically from the first and second doors  30  and  40  to support the door shelf  35  on both left and right sides of the door shelf  35 . The shelf support portion  35   a  may be detachably provided in the doors  30 ,  40  and  50  as a separate configuration and according to an embodiment, the door shelf  35  may be extended from the doors  30 ,  40  and  50 . 
     A gasket  36  configured to seal a gap with the body  10  when the first door  30  and the second door  40  are closed, may be provided on an edge portion of the rear surface of the first door  30  and the second door  40 , respectively. 
     The gasket  36  may be installed along the edge portion of the rear surface of the first door  30  and the second door  40  in a loop shape, wherein a magnet (not shown) may be provided inside of the gasket  36 . 
     A bar assembly (not shown) may be provided to seal a gap, wherein the gap is generated between the first door  30  and the second door  40  in a state in which the first door  30  and the second door  40  are closed. 
     The refrigerator  1  may include a display device  60  having an input/output function. The display device  60  may be installed on the front surface of the door  30  for the convenience of the user. 
       FIG. 3  is an enlarged view of A in  FIG. 2 ,  FIG. 4  is a perspective view of a door opening and closing apparatus of the refrigerator according to an embodiment,  FIG. 5  is a view from above of the inside of the door opening and closing apparatus of the refrigerator according to an embodiment,  FIG. 6  is a view from below of the inside of the door opening and closing apparatus of the refrigerator according to an embodiment, and  FIG. 7  is an exploded-perspective view of the door opening and closing apparatus of the refrigerator according to an embodiment. 
     The refrigerator  1  may include a door opening and closing apparatus  100 . 
     The door opening and closing apparatus  100  may be configured to open and close the door  30  of the refrigerator  1 . The door opening and closing apparatus  100  may be installed in each of the pair of upper doors  30  and  40 , but is not limited thereto. The door opening and closing apparatus  100  may be installed on any one of the pair of upper doors  30  and  40 , or on the lower door  50 . For convenience of description, it is assumed that the door opening and closing apparatus  100  is disposed on the first door  30 . 
     The door opening and closing apparatus  100  may include an apparatus body  102 , a driving device  110  accommodated in the apparatus body  102 , and a pressure device  180  separating the door  30  from the body. 
     The apparatus body  102  may be configured to accommodate the driving device  110  and the pressure device  180  therein. The apparatus body  102  may be disposed on the upper portion of the door  30 . The apparatus body  102  may be installed such that the left and right direction of the door  30  is in the longitudinal direction. The apparatus body  102  may include a lower apparatus body  102   b  and an upper apparatus body  102   a  coupled to the lower apparatus body  102   b  such that a plurality of driving gears  122  and a rotary gear  124  are seated inside thereof. 
     The driving device  110  may generate power and transmit the power to the door  30  to open and close the door  30 . 
     The driving device  110  may include a power generator and a power transmitter  120 . 
     The power generator may be configured to generate power for opening and closing the door  30 . The power generator may include a motor  112 . The motor  112  may be disposed inside the apparatus body  102  to generate power, wherein the motor  112  may be rotated forward or reverse by receiving a control signal from a controller (not shown). The door  30  may be moved to an open position or a closed position through the forward rotation and the reverse rotation of the motor  112 . 
     The power transmitter  120  may be disposed between the motor  112  and the hinge shaft  51  to transmit the power generated from the motor  112  to the hinge shaft  51 . That is, the power generated by the motor  112  may be transmitted to the hinge shaft  51  through the power transmitter  120  so that the door  30  may be operated. 
     The power transmitter  120  may include a plurality of driving gears  122  rotated in conjunction with the motor  112  and a rotary gear  124  engaged with the plurality of driving gears  122  and mounted on the hinge shaft  51 . The plurality of driving gears  122  and the rotary gear  124  may include gear teeth at least one part of their circumferences. 
     The power transmitter  120  may be configured to convert a power transmission state into a power non-transmission state, wherein the power transmission state may be a state in which the power of the motor  112  is transmitted to the hinge shaft so that the opening and closing of the door  30  is switched to be automatically performed or manually performed, and the power non-transmission state is a state in which the power is not transmitted to the hinge shaft. 
     The power transmitter  120  may include a motor side gear  132  rotated in conjunction with the motor  112 , a door side gear  134  rotated in conjunction with the opening and closing of the door  30 , a center gear  136  engaged with the motor side gear  132 , and a pair of idle gear  138  ( 138   a  and  138   b ) engaged with the center gear  136 . The motor side gear  132  and the door side gear  134  may be configured such that a plurality of gears is engaged with each other in series. 
     The motor side gear  132  may be configured such that one side of the motor side gear  132  is engaged with a rotary shaft  112   a  of the motor  112  and the other side of the motor side gear  132  is engaged with the center gear  136 . In this embodiment, a plurality of motor side gears  132  may be provided, wherein the motor side gear  132  that is the closest to the motor  112  may be engaged with the rotary shaft  112   a , and the motor side gear  132  that is the closest to the hinge shaft  51  may be engaged with the center gear  136 . 
     The door side gear  134  may be configured such that one side of the door side gear  134  is engaged with the center gear  136  and the other side of the door side gear  134  is engaged with the rotary gear  124  coupled to the hinge shaft  51 , but is not limited thereto. A plurality of the door side gear  134  may be provided, wherein the door side gear  134  that is the closest to the motor  112  may be engaged with the center gear  136  and the door side gear  134  that is the closest to the hinge shaft  51  may be engaged with the rotary gear  124 . 
       FIGS. 8 and 9  are perspective views from above and below of the center gear and a switching unit of the refrigerator according to an embodiment, and  FIG. 10  is an exploded perspective view of the center gear and the switching unit of the refrigerator according to an embodiment. 
     The power transmitter  120  may include a switching unit  160 . The switching unit  160  may be configured to rotate the pair of the idle gears  138  ( 138   a  and  138   b ) along the circumference of a rotational axis of the center gear  136 . The switching unit  160  may include a switching member  162  rotated about the rotational axis of the center gear  136  and to which the idle gear  138  is mounted, and a mounting member  170  to which the center gear  136  is mounted. 
     The switching member  162  may include an idle gear mounting shaft  163  on which the pair of idle gears  138  are mounted, and a through hole  164 . The switching member  162  may be formed in a substantially flat plate shape. 
     A mounting elastic member  169  may be mounted to the idle gear mounting shaft  163  and may include an elastic member such as a spring. The mounting elastic member  169  may serve as a buffer against impact transmitted to the idle gear  138 . 
     The mounting member  170  may include a center gear mounting shaft  172  on which the center gear  136  is mounted. The switching member  162  may be disposed between the mounting member  170  and the center gear  136 . The mounting member  170  may be rotated in conjunction with the center gear  136  and configured to be rotated independently of the switching member  162 . That is, the mounting member  170  and the center gear  136  may be configured to be rotated together, and the switching member  162  may be rotated independently of the mounting member  170  and the center gear  136 . 
     The switching member  162  may be positioned on the upper surface of the mounting member  170  as the center gear mounting shaft  172  passes through the through hole  164 . The idle gear  138  may be mounted on the idle gear mounting shaft  163  and thus the center gear  136  may be mounted on the center gear mounting shaft  172 . 
     The mounting elastic member  169  may be mounted on the idle gear mounting shaft  163 , the idle gear  138  may be mounted on the mounting elastic member  169 , and a pressure member  165  pressing the idle gear  138  is passed therethrough so that the upward force of the idle gear  138  from the mounting elastic member  169  may be applied. The pressing member  165  may be configured to be engaged with a concave groove  163   a  formed along the circumferential direction on the outer circumferential surface of the idle gear mounting shaft  163 . 
     According to this configuration, the idle gear  138  may be moved among positions in conjunction with the motor  112 , wherein the positions may include a forward rotation power transmission position  139   a  for transmitting the forward rotation of the motor  112 , a reverse rotation transmission position  139   b  for transmitting the reverse rotation of the motor  112 , and a power non-transmission position  139   c  for not transmitting the power. As the center gear  136  and the switching unit  160  rotate the pair of the idle gears  138  to allow one of the idle gears  138  to engage with the door side gear  134 , the power transmission state may be acquired, and as the engagement between the pair of the idle gear  138  and the door side gear  134  is released, the power non-transmission state may be acquired. 
     That is, the state in which the idle gear  138  is in the forward rotation power transmission position  139   a  or the reverse rotation power transmission position  139   b  is the power transmission state, and the state in which the idle gear  138  is in the power non-transmission position  139   c  is the power non-transmission state. 
       FIG. 11  is a view of a sliding member and a power switching member of the refrigerator according to an embodiment,  FIGS. 12 and 13  are views of operations of the sliding member and the power switching member of the refrigerator according to an embodiment, and  FIG. 14  is a view of the relationship between the pressure device and the driving gear of the refrigerator according to an embodiment. 
     The door opening and closing apparatus  100  may include the pressure device  180  (refer to  FIG. 7 ). The pressure device  180  may be configured to press the body  10  so that the door  30  is opened. In order to open the door  30  in the closed state, it may be required to release the magnetic attraction between the magnet in the gasket  36  of the door  30  and the body  10 . Therefore, after the door  30  and the body  10  are apart from each other by using the pressure device  180 , it may be possible to move the door  30  to a direction in which the door  30  is opened, by using the power transmitter  120 . With the configuration of the pressure device  180 , it may be possible to reduce an initial force, which is needed for switching the door  30  from the closed position to the open position, and thus it may be possible to reduce the size of the motor  112 . 
     The pressure device  180  may be operated when the idle gear  138  is in the power non-transmission position  139   c . That is, after the door  30  and the body  10  are separated from each other by the pressure device  180 , the idle gear  138  may be moved to the forward rotation power transmission position  139   a  to transmit the power in the direction in which the door  30  is opened. The door opening and closing apparatus  100  may include a delay member  194  to allow the pressure device  180  to be operated when the idle gear  138  is in the power non-transmission position  139   c . The delay member  194  will be described later. 
     The pressure device  180  may include a sliding member  182  moved in a slide manner, in conjunction with the power transmitter  120  and a pressing member  184  (refer to  FIGS. 2 to 6 ) rotated by the sliding movement of the sliding member  182  to press the body. The pressing member  184  may be rotatable with respect to a rotary shaft  184   a  in conjunction with the sliding movement of the sliding member  182 . That is, the sliding member  182  may press one side of the pressing member  184  while sliding, and the pressed pressing member  184  may be rotated about the rotary shaft  184   a  to press the body  10  toward the other side of the pressing member  184 . The door  30  may be provided with a pressing hole  185  configured to allow the pressing member  184  to protrude toward the body  10 . 
     The sliding member  182  may be provided to slide along a longitudinal direction thereof. At one end of the sliding member  182 , the pressing member  184  may be disposed. At the other end of the sliding member  182 , the power may be transmitted from the power transmitter  120 . 
     The pressure device  180  may include an elastic return member  186  (refer to  FIGS. 2 to 6 ). The elastic return member  186  may be configured to allow the sliding member  182  and the pressing member  184 , which are pressed by a pressing protrusion  174  and then presses the body  10 , to resiliently return to an initial position. The arrangement of the elastic return member  186  is not limited thereto, and thus there may be no limitation in the arrangement of the elastic return member  186  as long as returning the sliding member  182  and the pressing member  184  to the initial position. In this embodiment, the elastic return member  186  may be disposed on the rotary shaft  184   a  of the pressing member  184  so as to resiliently return the pressing member  184  and the sliding member  182  to the initial position. 
     The pressure device  180  may include a power conversion member  188 . The power conversion member  188  may be disposed at the other end of the sliding member  182 , wherein the power conversion member  188  may be configured to convert the rotational force of the door side gear  134  of the driving gear  122 , into the power in the sliding direction of the sliding member  182 . The power conversion member  188  may be rotatably provided on the sliding member  182 . 
     The power conversion member  188  may include a pressed surface  189  pressed by at least one pressing protrusion  174  provided on the door side gear  134 . Particularly, the at least one pressing protrusion  174  may be provided on a rear surface of the mounting member  170  and the at least one pressing protrusion  174  may press the pressed surface  189  by the rotation of the mounting member  170 . 
     When the motor  112  is reversely rotated to move the door  30  in the direction in which the door  30  is closed, the power conversion member  188  may not transmit the power of the motor  112  to the pressure device  180 . When the motor  112  is forwardly rotated to move the door  30  in the direction in which the door  30  is opened, the power conversion member  188  may transmit the power of the motor  112  to the pressure device  180 . 
     As illustrated in  FIG. 11 , the power conversion member  188  may be disposed at the other end of the sliding member  182 , and when the motor  112  is forwardly rotated, the pressed surface  189  may be pressed by the pressing protrusion  174 . The power conversion member  188  may be provided with a guide surface  190  so that the power conversion member  188  may be rotated by the movement of the pressing protrusion  174  when the motor  112  is reversely rotated. 
     The power conversion member  188  may be moved between a normal position  188   a  in which an external force is not applied, and a rotation position  188   b  in which the power conversion member  188  is rotated about a rotation axis  191  from the normal position  188   a . The rotation position  188   b  is a position in which the power conversion member  188  is rotated in the direction away from the rotation axis of the center gear  136  from the normal position  188   a . The power conversion member  188  may include an elastic portion  192  to resiliently return the power conversion member  188  from the rotation position  188   b  to the normal position  188   a.    
     The power conversion member  188  may be disposed below the mounting member  170 , wherein the pressed surface  189  and the guide surface  190  may be disposed in the movement path of the pressing protrusion  174  when the power conversion member  188  is in the normal position  188   a.    
     The pressing protrusion  174  may be rotated in conjunction with the rotation of the center gear  136 , and the power conversion member  188  may be configured to convert the rotational force of the pressing protrusion  174  into the power in the sliding direction of the sliding member  182 . According to an embodiment, the pair of the pressing protrusions  174  is arranged in the mounting member  170 , but is not limited thereto. Alternatively, one or more pressing protrusions  174  may be provided. 
     The pressure device  180  may include the delay member  194 . 
     The delay member  194  may be configured to restrict the rotation of the switching member  162  to maintain the power non-transmission position  139   c  in which the idle gear  138  is not engaged with the door side gear  134 . 
     The delay member  194  may be provided on the power conversion member  188 . The switching member  162  may include a delay protrusion  168  in contact with the delay member  194 . 
     The delay protrusion  168  may be formed in a protruding shape on the rear surface of the switching member  162 , wherein the pair of delay protrusions  168  may be provided on the rotation axis of the idle gear  138 , respectively. The delay protrusion  168  may be configured such that when the switching member  162  is rotated, one side of the delay protrusion  168  may be not in contact with one surface of the power conversion member  188 . That is, the delay protrusion  168  may be configured to not be in contact with the power conversion member  188  and configured to be in contact with the delay member  194  disposed on the power conversion member  188 . 
     The delay member  194  may include a delay contact surface  195  on which the delay protrusion  168  abuts, and a rotation guide surface  196 . The delay contact surface  195  may be configured to restrict the movement of the delay protrusion  168  as described above, and to maintain the power non-transmission position  139   c  in which the idle gear  138  is not engaged with the door side gear  134 . The rotation guide surface  196  will be described in the description of the operation of the door opening and closing apparatus  100 . 
     Hereinafter the operation of the door opening and closing apparatus of the refrigerator will be described. 
       FIGS. 15 to 20  are views of operations of the door opening and closing apparatus of the refrigerator according to an embodiment. 
     First, a case of moving the door  30  in the closed position to the opening direction will be described. 
     When the motor  112  is rotated forward in a state in which the door  30  is in the closed position, the switching unit  160  may move the pair of the idle gear  138  from the power non-transmission position  139   c  toward the forward rotation power transmission position  139   a , in conjunction with the rotation of the center gear  136  as illustrated in  FIGS. 15 and 16 . Since the pair of the idle gears  138  is rotated together with the switching member  162 , the delay protrusion  168  provided on the switching member  162  may be rotated toward the delay member  194 . 
     As illustrated in  FIG. 16 , the rotation of the switching member  162  and the rotation gear  138  may be restricted while the delay protrusion  168  comes into contact with the delay member  194 , and thus the power non-transmission position  139   c  of the idle gear  138  may be maintained. 
     When the motor  112  is further rotated forward, the pressing protrusion  174  installed in the mounting member  170  may press the power conversion member  188  and the pressure device  180  by the rotation of the center gear  136  and the mounting member  170 , wherein the rotation of the center gear  136  and the mounting member  170  is performed independently of the switching member  162 , as illustrated in  FIGS. 17 and 18 . 
     Due to the pressure against the pressure device  180 , the sliding member  182  may be moved in a slide manner, and the pressing member  184  may press the body so that the door  30  is separated from the body. 
     When the motor  112  is further rotated forward, the idle gear  138  and the switching member  162 , which were restricted in rotation by the delay member  194 , may be further rotated, and then placed in the forward rotation power transmission positions  139   a  (refer to  FIG. 18 ). The power generated by the motor  112  may be transmitted to the motor side gear  132 , the center gear  136 , the idle gear  138  and the door side gear  134  so that as the door  30  is moved to the opening direction. 
       FIGS. 21 to 23  are views of an operation of a power conversion member of the refrigerator according to an embodiment. The pressure device  180  pressed by the pressing protrusion  174  may be moved to the initial position by the elastic return member  186 . At this time, the idle gear  138  may be placed in the forward rotation power transmission position  139   a  and the delay protrusion  168  may be also located in correspondence with the position of the idle gear  138  at the rear face of the switching member  162 . As the pressure device  180  returns to the initial position, the rotation guide surface  196  of the retardation member  194  may be pressed by the delay protrusion  168 . The rotation guide surface  196  may be formed to be curved in a direction away from the rotation axis of the center gear  136 . As the rotation guide surface  196  may slide along the delay protrusion  168  while the pressure device  180  returns to the initial position due to the above mentioned configuration, the power conversion member  188  may be moved from the normal position  188   a  to the rotation position  188   b . That is, the pressed surface  189  of the power conversion member  188  may be escaped from the movement path of the pressing protrusion  174 . Therefore, although the motor  112  continues to be rotated forward, the pressure device  180  may be not affected by the pressing protrusion  174 . 
     Hereinafter a case of moving the door  30  in the open state to the closing direction will be described. 
     When the motor  112  is rotated in the reverse direction in a state in which the door  30  is in the open position, the mounting member  170  may be rotated in conjunction with the center gear  136  as shown in  FIGS. 19 and 20 , and thus the plurality of pressing protrusions  174  may be rotated toward the power conversion member  188 . As the pressing protrusion  174  comes into contact with the guide surface  190  of the power conversion member  188  and presses the guide surface  190 , the power conversion member  188  may be moved from the normal position  188   a  to the rotation position  188   b  by the pressure of the pressing protrusion  174 . Therefore, the power conversion member  188  may be not affected by the pressing protrusion  174 , which is different from the case in which the door  30  is moved from the closed position to the open position. 
     The power of the motor  112  in the reverse rotation direction may move the idle gear  138  to the reverse rotation transmission position  139   b . Accordingly, the power generated by the motor  112  may be transmitted to the motor side gear  132 , the center gear  136 , the idle gear  138  and the door side gear  134  so that the door  30  is moved to the closing direction. 
       FIG. 24  is an exploded perspective view of an intermittent gear of the refrigerator according to an embodiment, and  FIG. 25  is a cross-sectional view of the intermittent gear of the refrigerator according to an embodiment. 
     The door side gear  134  may include a pair of intermittent gears  140 . When the door  30  is moved by an external force in a state in which the door opening and closing apparatus  100  is not operated, or when an external force is applied to the direction opposite to the rotation of the motor  112  in a state in which the door opening and closing apparatus  100  is operated, or when an external force greater than the rotational force of the motor  112  is generated in the same direction, an unnecessary load may be applied to the driving gears  122  engaged with the rotary gear  124  of the hinge shaft  51 . Therefore, the driving gears  122  or the motor  112  may be damaged. The intermittent gear  140  may be configured to prevent the external force from being transmitted to the driving gears  122  or the motor  112 . 
     When the door opening and closing apparatus  100  is operated normally to move the door  30  from the closed position to the open position or from the open position to the closed position, the pair of intermittent gears  140  may be operated as the driving gear  122 . That is, the pair of intermittent gears  140  may be configured to interrupt the power when the external force is applied to the door  30 , so that the external force is not transmitted to the driving gears  122  or the motor  112 . That is, the intermittent gear  140  may be arranged to transmit the power from the motor side gear  132  to the door side gear  134 , while being arranged to interrupt the load transmitted from the door side gear  134  to the motor side gear  132 . 
     The pair of intermittent gears  140  may include a first intermittent gear  141  and a second intermittent gear  151 . The first intermittent gear  141  may be configured to be engaged with one of the pair of the idle gears  138 . The second intermittent gear  151  may be provided to be rotated about the same axis as the first intermittent gear  141  and rotated together with the first intermittent gear  141 . That is, when the motor  112  is rotated forward, the pair of intermittent gears  140  may receive the power from the idle gear  138  in the forward power transmission position  139   a  and transmit the power to the rotary gear  124 . In contrast, when the motor  112  is rotated in the reverse direction, the pair of intermittent gears  140  may receive the power from the idle gear  138  in the reverse power transmission position  139   b  and transmit the power to the rotary gear  124 . 
     The first intermittent gear  141  may be moved between a coupling position  141   a  in which the first intermittent gear  141  is engaged with the second intermittent gear  151  to transmit the power to the second intermittent gear  151 , and a separated position  141   b  in which the first intermittent gear  141  is moved from the coupling position  141   a  and separated from the second intermittent gear  151 . The first intermittent gear  141  may be moved between the coupling position  141   a  and the separated position  141   b  along an intermittent gear rotary shaft  148 . According to an embodiment, the first intermittent gear  141  may be configured to receive the power from the idle gear  138  so that the first intermittent gear  141  may be moved between the coupling position  141   a  and the separated position  141   b , but is not limited thereto. Therefore, the first intermittent gear  141  may be configured to receive the power from the idle gear  138  so that the second intermittent gear  151  may be moved between the coupling position  141   a  and the separated position  141   b . The first intermittent gear  141  may be provided with an intermittent gear elastic member  149  so that the first intermittent gear  141  in the separated position  141   b  resiliently returns to the coupling position  141   a . The intermittent gear elastic member  149  may be disposed with respect to the intermittent gear rotary shaft  148  and configured to resiliently support the first intermittent gear  141 . 
     The first intermittent gear  141  has been described to be engaged with the idler gear  138 , but is not limited thereto. For example, the pair of intermittent gear  140  may be engaged with the rotary gear  124 , and when the plurality of the door side gear  134  is provided, the intermittent gear  140  may be located in an intermediate position and transmit or interrupt the power. 
     The first and second intermittent gear  140  may include first and second gear bodies  142  and  152 , and first and second inclined boss portions  144  and  154 . The first and second gear bodies  142  and  152  may form a body of the first and second intermittent gears  141  and  151 , respectively, wherein first and second hollow portions  142   a  and  152   a  may be provided in the first and second gear bodies  142  and  152  so that the intermittent gear rotary shaft  148  is passed through. 
     The first and second inclined boss portions  144  and  154  may be formed on surfaces facing each other in the first and second gear bodies  142  and  152 . The first and second inclined boss portions  144  and  154  may protrude from the first and second gear bodies  142  and  152 , respectively. When the first intermittent gear  141  is in the coupling position  141   a , a side surface of the first and second inclined boss portions  144  and  154  may come into contact with each other. Particularly, when the first intermittent gear  141  is in the coupling position  141   a , a side surface of the first and second inclined boss portions  144  and  154  may come into contact with each other so as to transmit the power from the first intermittent gear  141  to the second intermittent gear  151 . In addition, when the first intermittent gear  141  is in the separated position  141   b , the first and second inclined boss portions  144  and  154  may be separated from each other so that any one inclined boss portion is not placed on the movement path of the other boss portion. 
     A plurality of the first and second inclined boss portions  144  and  154  may be alternately disposed along the circumferential direction. In this embodiment, the first and second inclined boss portions are respectively provided three each, wherein three second inclined boss portions  154  may be disposed between three first inclined boss portions  144 . 
     The first and second inclined boss portions  144  and  154  may include first and second inclined surfaces  146  and  156 , respectively. The first and second inclined surfaces  146  and  156  may be formed inclined with respect to the intermittent gear rotary shaft  148 . That is, the first inclined surface  146  may be inclined toward the circumferential direction with respect to a direction in which the first intermittent gear  141  is directed to the second intermittent gear  151 , and the second inclined surface  156  may be inclined toward the circumferential direction with respect to a direction in which the second intermittent gear  151  is directed to the first intermittent gear  141 . When the first intermittent gear  141  is in the coupling position  141   a , the first and second inclined surfaces  146  and  156  may come into contact with each other to transmit the power from the first intermittent gear  141  to the second intermittent gear  151 . When the first intermittent gear  141  is in the separated position  141   b , the first and second inclined surfaces  146  and  156  may be separated from each other to interrupt the transmission of the power between the first intermittent gear  141  and the second intermittent gear  151 . 
     Hereinafter the operation of the intermittent gear  140  in the door opening and closing apparatus  100  of the refrigerator  1  will be described. 
       FIGS. 26 and 27  are views of the operation of the intermittent gear in the refrigerator according to an embodiment. 
     When the first intermittent gear  141  is in the coupling position  141   a , the first and second inclined boss portions may be alternately disposed, as illustrated in  FIG. 26 . 
     As mentioned above, when the external force is applied to the door  30 , the load may be generated in the hinge shaft  51 . 
     The load generated in the hinge shaft  51  may be transmitted to the second intermittent gear  151  through the door side gear  134 . When the load generated in the hinge shaft  51  is equal to less than the normal rotational force of the motor  112 , the first and second inclined boss portions  144  and  154  of the first and second intermittent gears  141  and  151  may be rotated with each other while being in contact with each other. 
     When the external force equal to greater than the normal rotational force of the motor  112  is applied or when the external force in the direction opposite to the rotation direction of the motor  112  is applied, a slip may be generated between the first inclined surface  146  of the first inclined boss portion  144  and the second inclined surface  156  of the second inclined boss portion  154 . 
     For the convenience of description, a threshold of the power transmitted between the intermittent gears  141  and  142  is referred to as Lc. A case in which the door is opened or closed by an external force La, which is greater than Lc, without operating the door opening and closing apparatus, will be described. In this case, La may be transmitted to the hinge shaft and the hinge shaft gear. Since the intermittent gear transmits the power only when an external force less than Lc is applied, a slip may be generated and the power may be not transmitted. Accordingly, it may be possible to prevent the external force from being transmitted to the gears and the motor. 
     In a case of operating the door opening and closing apparatus, a case in which an external is applied to the direction in which the door is closed during the door is opened by the door opening and closing apparatus, or a case in which an external is applied to the direction in which the door is opened during the door is closed by the door opening and closing apparatus will be described. In addition, a case in which an external is applied to the direction in which the door is opened during the door is opened by the door opening and closing apparatus, or a case in which an external is applied to the direction in which the door is closed during the door is closed by the door opening and closing apparatus may be the same as the above mentioned case. In this case, Lm may be generated by the rotational force of the motor. Lm may be typically maintained to be less than Lc and thus when the door opening and closing apparatus is operated normally, a slip may be not generated between the intermittent gears  141  and  142 . However, when Lm+Lb is greater than Lc since an external force corresponding Lb is applied, a slip may be generated between the intermittent gears  141  and  142  and thus it may be possible to prevent the power from being transmitted from the motor to the hinge shaft or to prevent the external force from being transmitted from the hinge shaft to the motor. 
     Therefore, a lower surface of the first inclined boss portion  144  may come into contact with an upper surface of the second inclined boss portion  154  and thus the power may be not transmitted between the first and second intermittent gears  141  and  151 . That is, the first intermittent gear  141  may be moved to the separated position  141   b  and thus the power may be not transmitted between the first and second intermittent gears  141  and  151 . 
     When the external force disappears, the first intermittent gear  141  may be moved from the separated position  141   b  to the coupling position  141   a  by the intermittent gear elastic member  149 , and thus the first and second intermittent gears  141  and  151  may become a state in which the transmission of the power is available. 
     As is apparent from the above description, according to the proposed refrigerator, it may possible to automatically open and close a door by applying a door opening and closing apparatus. 
     It may possible to reduce the load transmitted to a motor when an external force is applied to the door of the refrigerator. 
     It may possible to reduce the size of the motor and the door opening and closing apparatus by reducing the load transmitted to the motor. 
     It may possible to improve the durability of the door opening and closing apparatus. 
     Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.