Patent Publication Number: US-8967011-B2

Title: Double rack gear structure for supporting pop-up monitor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2011-0074184, filed on Jul. 26, 2011, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a gear structure for supporting a vertical motion of an electric pop-up monitor, and in particular, to a double rack gear structure for supporting a pop-up monitor. 
     BACKGROUND 
     Recently, as the functions and quality of vehicles are highly enhanced, various monitors for controlling an air-conditioning apparatus, a navigator, a Liquid Crystal Display (LCD) television (TV), etc. are installed in the vehicles. Such monitors are categorized into rear monitors and front monitors. The rear monitor is disposed in the rear of a driver&#39;s seat or a console and operated by a passenger of a back seat. The front monitor is installed on a display panel in front of a vehicle body and operated by a passenger of a front seat such as a driver&#39;s seat or a passenger seat. 
     The front monitor mounted on the display panel is configured such that a frame with a monitor mounted thereon is popped up in order for a driver to more easily look at the front monitor. As such pop-up types, there are a pop-up type where the monitor frame is vertically popped up, a pop-up type where the monitor frame is popped up while rotating, and a pop-up type where the monitor frame moves horizontally and then is popped up while rotating vertically. 
     Among such pop-up types, the pop-up type where the monitor frame is vertically popped up is illustrated in  FIG. 1 . 
       FIG. 1  is a partially cut rear view illustrating an operation of a related art electric pop-up monitor for a vehicle. 
     Referring to  FIG. 1 , a related art electric pop-up monitor  1  for a vehicle includes a body  3  mounted on one side of a crush pad of a vehicle, a monitor  4  disposed in the body  3 , and a driver  5  that lifts and drops the monitor  4  with respect to the body  3 . 
     That is, a guide protrusion  6  being a guide that allows the monitor  4  to ascend and descend with respect to a space portion formed inside the body  3  is lengthily formed upward and downward to protrude in an internal direction from one side of the body  3 . Such a guide groove  7  coupled to the guide protrusion  6  is formed in one side of the monitor  4 . 
     The driver  5  is disposed between the body  3  and a rear surface on the reverse of a portion forming a screen  8  in front of the monitor  4 . Herein, the driver  5  includes a motor  9  generating a torque, and a plurality of gears such as a driven gear  10  transferring the torque of the motor  9 . A worm gear  11  is disposed in a rotational axis of the motor  9 , and a worm wheel gear  13  is disposed in a driven shaft  12  interlocking with the driven gear  10 . A pinion gear  14  coupled to the driven gear  10  rotates about a pinion axis  15 . In this case, the pinion axis  15  and the driven shaft  12  are supported in one side of the body  3 . Furthermore, a rack gear  17  where a spur gear  16  is vertically formed is disposed in a rear surface of the monitor  4 . 
     As described above, a related art pop-up monitor drives a monitor upward and downward by coupling with the spur gear that is formed in the pinion gear and the rack gear, and the monitor that has completely ascended in an upper direction with respect to the body is supported by gear engagement. In this case, since a portion supporting the ascended monitor is narrow, the monitor is easily shaken upward and downward or from side to side by vibration that occurs in driving a vehicle. 
     Moreover, in the related art, since the spur gear formed in the rack gear is exposed to the outside, there is much possibility that the driving of a vehicle is failed due to foreign substances. 
     SUMMARY 
     Accordingly, the present disclosure provides a double rack gear structure, which allows the vertical driving of a monitor to be performed by an internally touched double rack gear that is disposed in each of both sides of the monitor, and thus increases a support power to the monitor when the monitor has ascended to the maximum with respect to a body. 
     The object of the present invention is not limited to the aforesaid, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below. 
     In one general aspect, a rack gear structure of a pop-up monitor, which is connected to a monitor frame of the pop-up monitor to enable a vertical motion of the monitor frame, includes: an outer gear coupled at a side of the monitor frame to operate integrally with the monitor frame, and enabling the vertical motion of the monitor frame with an ascending or descending motion, and an inner gear received inside the outer gear, wherein the inner gear performs an ascending or descending motion simultaneously with the outer gear, and supports forward and rearward or right and left shaking, which occurs in the outer gear, by maximizing a portion overlapping with the outer gear when the outer gear has ascended to the maximum. 
     A rail groove may be formed along a length direction, at one surface inside the outer gear. A rail may be formed along a length direction, at one surface of the inner gear, and the inner gear may be received inside the outer gear through coupling between the rail and the rail groove. 
     A spur gear teeth may be formed in one row along a length direction, at one side inside the outer gear, and a spur gear teeth may be formed in one row along a length direction, at one side inside the inner gear. 
     A through hole may be formed in the inner gear, and a guide shaft may be disposed in the through hole. 
     The outer gear may change a first rotational motion, transferred from a motor, to a first rectilinear motion, and the inner gear may change a second rotational motion, transferred from the motor, to a second rectilinear motion. 
     The outer gear and the inner gear may be coupled to a driving unit which transfers a rotational motion generated by a motor, the driving unit may include a spur gear set configured with first and second spur gears, the first spur gear may be coupled to the outer gear, and the second spur gear may be coupled to the inner gear. 
     The first spur gear and the second spur gear may be coupled to rotate integrally, and a diameter of the first spur gear may be formed greater than a diameter of the second spur gear. 
     The driving unit may include: a motor; a first gear set transferring a torque of the motor to a rotational shaft; a second gear set coupled to the first gear set; and a rotational shaft rotating according to an output of the motor, and the first and second spur gears may be fixed and coupled to both ends of the rotational shaft, respectively. 
     The first gear set may include: a clutch gear coupled to a worm gear which is installed in a driving shaft of the motor; and a complex gear coupled to the clutch gear. 
     The clutch gear may include: a shaft; a helical gear disposed in an upper portion with respect to the shaft; a spur gear disposed in a lower portion with respect to the shaft; an extension spring placed inside the helical gear; and a friction pad placed between the helical gear and the spur gear, the helical gear may be coupled to a worm which is installed in the driving shaft to receive a motive power from the motor, and the spur gear may be coupled to the complex gear while rotating integrally with the helical gear to transfer a motive power. 
     The clutch gear may include a helical gear in an upper portion thereof, and a spur gear in a lower portion thereof, the helical gear may be coupled to the worm gear installed in the driving shaft to receive a motive power from the motor, and the spur gear may be coupled to the complex gear while rotating integrally with the helical gear to transfer a motive power. 
     The second gear set may be configured with a complex gear which is fixed and coupled to the rotational shaft and includes a helical gear and a spur gear which rotate integrally with the rotational shaft, the helical gear of the second gear set being coupled to the helical gear of the complex gear to receive a motive power. 
     The rack gear structure may further include a pressurizing member applying a pressure in a direction perpendicular to a vertical moving direction of the outer gear. 
     A groove having a certain width may be formed along a length direction, in an outer surface of the outer gear, and the pressurizing member may continuously apply a constant pressure to the outer gear along the groove, when the monitor frame ascends or descends in a vertical direction. 
     In another general aspect, a rack gear structure of a pop-up monitor, including a monitor frame which ascends and descends, includes: a linear outer gear coupled to the monitor frame; and a linear inner gear disposed inside the outer gear, wherein the linear inner gear ascends or descends according to an ascending or descending motion of the linear outer gear. 
     The linear outer gear may ascend within a distance range of about 100 mm to 130 mm, and the linear inner gear may ascend within a distance range of about 50 mm to 65 mm according to an ascending motion of the linear outer gear. 
     The linear outer gear may ascend within a distance range of about 105 mm to 115 mm, and the linear inner gear may ascend within a distance range of about 55 mm to 60 mm according to an ascending motion of the linear outer gear. 
     When the linear outer gear and the linear inner gear ascend to the maximum, the linear outer gear and the linear inner gear may overlap with each other within a distance range of about 80 mm to 95 mm. 
     The rack gear structure may further include a pressurizing member applying a pressure in a direction perpendicular to a vertical moving direction of the linear outer gear. 
     The pressurizing member may include: a case-damping spring installed to be externally touched to the linear outer gear; and a torsion spring assembled with the case-damping spring to apply a moment to the case-damping spring. 
     Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially cut rear view illustrating an operation of a related art electric pop-up monitor for a vehicle. 
         FIG. 2   a  and  FIG. 2   b  are a perspective view illustrating a pop-up monitor with a double rack gear structure, according to an embodiment of the present invention. 
         FIG. 3  is a front-sectional view schematically illustrating a rack gear set according to an embodiment of the present invention. 
         FIG. 4  is a top-sectional view schematically illustrating a rack gear set according to an embodiment of the present invention. 
         FIG. 5  is a perspective view schematically illustrating a rack gear set according to an embodiment of the present invention. 
         FIG. 6  is a sectional view illustrating a driving unit according to an embodiment of the present invention. 
         FIG.7  is perspective view illustrating a body housing which includes a damping spring for supporting a vertical motion of a rack gear set, according to another embodiment of the present invention. 
         FIG. 8  is a view illustrating an internal detailed structure of a clutch gear according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Advantages and features of the present invention, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Further, the present invention is only defined by scopes of claims. In the following description, the technical terms are used only for explaining a specific exemplary embodiment while not limiting the inventive concept. The terms of a singular form may include plural forms unless specifically mentioned. 
     Hereinafter, exemplary embodiments of the inventive concept will be described in detail with reference to the accompanying drawings. In adding reference numerals for elements in each figure, it should be noted that like reference numerals already used to denote like elements in other figures are used for elements wherever possible. Moreover, detailed descriptions related to well-known functions or configurations will be ruled out in order not to unnecessarily obscure subject matters of the present invention. 
       FIG. 2   a  and  FIG. 2   b  are a perspective view illustrating a pop-up monitor with a double rack gear structure, according to an embodiment of the present invention. 
     Referring to  FIG. 2  and  FIG. 2   b , the pop-up monitor according to an embodiment of the present invention includes a body housing  10  that is received in a crash pad mounted on the front inside a vehicle, a monitor frame  20  that is installed to be moved in a direction vertical to the body housing  10 , and a driving unit (illustrated in  FIG. 5 ) that is disposed in order for the monitor frame  20  to move in a vertical direction. 
     The body housing  10  is received in the crash pad that is installed in a center facia of the front inside the vehicle, and supports the monitor frame  20  such that the monitor frame  20  is shown in a vertical direction on the crash pad. 
     The inside of the body housing  10  is empty, and thus, the body housing  10  secures a space for receiving portable equipment such as a Personal Digital Assistant (PDA), an MP3 player, and a mobile communication terminal. A connector  11  for supplying a power to the portable equipment is provided in one end of the body housing  10 . 
     A Universal Serial Bus (USB) port enabling communication with the portable equipment may be provided in one end inside the body housing  10 . 
     By coupling a screw (not shown) to the crash pad with a coupling part  12  that is formed to protrude in each of both sides of the body housing  10 , the body housing  10  may be fixed to the crash pad. 
     The monitor frame  20  is installed to be moved in a direction vertical to the body housing  10 . The monitor frame  20  includes a case  23  that is coupled to a rear side of a monitor  21  to support the monitor  21 , and a support frame  25  that is coupled to a rear side of the case  23  to support a vertical motion of the case  23 . 
     The support frame  25  is fixed to the case  23  through screw coupling with the rear side of the case  23 , and includes a wing-shaped coupling member  25 _ 1  that is formed to protrude in each of both sides of the case  23 . 
     Moreover, the monitor frame  20  may further include a rack gear set  27  that induces a vertical motion of the monitor frame  20  by sliding in a vertical direction with respect to the body housing  10 . The rack gear set  27  may be fixed to the coupling members  25 _ 1  that are respectively formed to protrude in both sides of the support frame  25 , through screw coupling. 
     In the embodiment, the rack gear set  27  includes an outer gear that is fixed and coupled to the coupling members  25 _ 1  to support the vertical motion of the monitor frame  20 , and an inner gear that is received inside the outer gear to support a vertical motion of the outer gear through rail coupling with the outer gear. The rack gear set  27  will be specifically described below with reference to  FIGS. 3 to 5 . 
       FIG. 3  is a front-sectional view schematically illustrating a rack gear set according to an embodiment of the present invention.  FIG. 4  is a top-sectional view schematically illustrating a rack gear set according to an embodiment of the present invention.  FIG. 5  is a perspective view schematically illustrating a rack gear set according to an embodiment of the present invention. 
     The rack gear set  27 , as illustrated  FIGS. 3 to 5 , includes an outer gear  210 , an inner gear  220 , and a guide shaft  230 . 
     The outer gear  210  is installed in each of both sides of the monitor frame  20 . The outer gear  210  is fixed to the coupling member  25 _ 1  of the support frame  25  through screw coupling and operates integrally with the monitor frame  20 . 
     The outer gear  210  has a  -shape with an internal space. A spur gear teeth  211  is formed in one row along a length direction, in one side inside the outer gear  210 . In this case, the spur gear teeth  211  is coupled to a first spur gear of a driving unit  30  (which will be described below with reference to  FIG. 7 ) to change a first rotational motion, transferred through the first spur gear, to a first rectilinear motion, thereby enabling the vertical motion of the monitor frame  20  that is fixed and coupled to the outer gear  210 . 
     Moreover, a rail groove is formed along a length direction in one end inside the outer gear  210 , and the below-described inner gear  220  supports a vertical motion by sliding in a vertical direction along the rail groove. 
     The inner gear  220  is placed in an internal space of the outer gear  210 , and a rail  221  is formed along a length direction, in one end of the inner gear  220 . In this case, the rail  221  may be inserted into the rail groove, and a vertical motion of the inner gear  220  is supported through rail coupling between the rail groove of the outer gear  210  and the rail  221 . 
     Moreover, a spur gear teeth  223  is formed along a length direction even in one side inside the inner gear  220 . The spur gear teeth  223  is coupled to a second spur gear of the driving unit  30  (which will be described below with reference to  FIG. 7 ) to change a second rotational motion, transferred through the second spur gear, to a second rectilinear motion, thereby enabling the vertical motion of the inner gear  220 . 
     The guide shaft  230  is inserted into a through hole  225  that is formed in the inner gear  220 , and guides a vertical motion of the inner gear  220 . The guide shaft  230  supports the inner gear  220  from forward and rearward/right and left shaking that occurs when the inner gear  220  ascends. 
     According to the embodiment, as described above, the vertical motion of the monitor frame  20  is supported by the rack gear set  27 , which includes the outer gear  210  that is fixed and coupled to the monitor frame  20  to directly induce the vertical motion of the monitor frame  20 , and the inner gear  220  that is received in the internal space through rail coupling with the outer gear  210 . 
     That is, in the embodiment, the rack gear set  27  rack gear set is characterized by having the double rack gear structure of the outer gear  210  and inner gear  220 . Herein, the inner gear  220  is not directly associated with the vertical motion of the monitor frame  20 , but when the inner gear ascends simultaneously with the outer gear  210  and then the outer gear  210  has ascended to the maximum, by maximizing a portion overlapping with the outer gear  210 , the inner gear  220  can support forward and rearward/right and left shaking that occurs in the outer gear  210 . 
     Moreover, one or more photo sensors  29  may be further disposed in an lower end of the monitor frame  20 . The photo sensor includes a light emitting part and a light receiving part. Herein, the light receiving part receives light emitted from the light emitting part, and thus, the photo sensor detects whether an object exists on a corresponding path. 
     In the embodiment, when an obstacle (for example, a person&#39;s hand, and other objects) is in a receiving space formed inside the body housing  10  while the monitor frame  20  is descending (i.e., close) from a vertically ascended location with respect to the body housing  10 , the one or more photo sensors  29  disposed in an lower end of the monitor frame  20  senses the obstacle. 
     A sensing signal detected by the photo sensor  29  is transmitted to a Printed Circuit Board (PCB), including a controller and power source of the below-described motor  310 , through an internal electric line. The controller switches the rotational direction of the motor  310  to a reverse direction to again lift the monitor frame  20 , according to the sensing signal. 
     As an embodiment, in order to prevent an error from occurring in sensing an obstacle, a plurality of photo sensors  29  may be installed in the lower end of the monitor frame  20 . Only when obstacle sensing signals more than a predetermined number of obstacle sensing signals are received from the photo sensors  29  (for example, a case where five photo sensors are installed, and sensing signals are received from three or more photo sensors among the five photo sensors), the controller outputs a control signal that allows the rotational direction of the motor  310  to be switched to a reverse direction. 
     As another embodiment, the photo sensor  29  senses an obstacle that exists in a lower surface of the monitor frame  20 , and delivers a measured distance between the obstacle and the lower surface of the monitor frame  29  to the controller. In this case, the controller may differently control the rotational direction of the motor  310  according to the measured distance. For example, the controller determines whether the measured distance is greater than a predetermined value. When the measured distance is greater than the predetermined value, the controller may output a control signal that allows the rotational direction of the motor  310  to be maintained as-is, but when the measured distance is not greater than the predetermined value, the controller may output a control signal that allows the rotational direction of the motor  310  to be switched to a reverse direction. 
     According to the embodiment, the pop-up monitor may further include a warning unit that emits warning sound. When an obstacle sensing signal is received from the photo sensor  29  while the monitor frame  20  is descending, the controller controls the warning unit to be driven, and determines whether a measured distance between the obstacle and the monitor frame  20  is greater than the predetermined value. When the measured distance is greater than the predetermined value, the controller may outputs a control signal that allows a rotational speed of the motor  310  to be reduced, but when the measured distance is not greater than the predetermined value, the controller may outputs a control signal that allows a rotational direction of the motor  310  to be switched to a reverse direction. 
     The driving unit  30  includes the motor  310 , a first gear set  320 , a rotational shaft  330 , a second gear set  340 , and a spur gear set  350  and  360 . The driving unit  30  will be specifically described below with reference to  FIG. 5 . 
       FIG. 7  is a sectional view illustrating a driving unit according to an embodiment of the present invention. 
     Referring to  FIG. 7 , the driving unit  30  is provided in the body housing  10 , and is installed on a bracket  370  that is provided across an upper portion of the body housing  10 . 
     The motor  310  is installed in one end of the bracket  370 , and the PCB (not shown) including the controller and power source of the motor  310  is disposed on the bracket  370 . 
     A rotational motion of the motor  310  is transferred to the rotational shaft  330  by the first and second gear sets  320  and  340  that are disposed in the bracket  370 . 
     Herein, the first gear set  320  includes a worm gear  321  that is disposed in an end of a driving shaft  311  in the motor  310 , a clutch gear  323  that is coupled to the worm gear  321 , and a complex gear  324  that is coupled to the clutch gear  323 . 
       FIG. 6  is a view illustrating an internal detailed structure of a clutch gear according to an embodiment of the present invention. 
     Referring to  FIG. 6 , the clutch gear  323  is a complex gear that is configured with a helical gear  323 _ 2  disposed in an upper portion of a shaft  323 _ 1 , and a spur gear  323 _ 3  disposed in a lower portion of the shaft  323 _ 1 . 
     An extension spring  323 _ 4  is disposed in the helical gear  323 _ 2 , and supports a torque of the helical gear  323 _ 2  and an external force applied to the helical gear  323 _ 2 . A friction pad  323 _ 5  is placed between the helical gear  323 _ 2  and the spur gear  323 _ 3 , and spatially separates the helical gear  323 _ 2  and the spur gear  323 _ 3 . 
     A motive power of the motor  310  is transferred to the clutch gear  323  by gear coupling between the worm gear  321  installed in the end of the driving shaft  311  and the clutch gear  323 . The helical gear  323 _ 2  and spur gear  323 _ 3  configuring the clutch gear  323  transfer a motive power to the complex gear  324  while rotating integrally by a frictional force that is generated by the friction pad  323 _ 5 . In this case, the helical gear  323 _ 2  disposed in the upper portion of the clutch gear  323  and the helical gear of the complex gear  324  are disposed to be separated from each other, and the spur gear  323 _ 3  disposed in the lower portion of the clutch gear  323  and the spur gear of the complex gear  324  are coupled to each other to transfer a motive power. 
     When an external force is applied to the clutch gear  323  due to an external force given to the monitor frame  20 , slidingness occurs in the friction pad  323 _ 5  placed in the clutch gear  323 , and therefore, the spur gear  323 _ 3  disposed in the lower portion of the clutch gear  323  cannot receive a motive power from the helical gear  323 _ 2  disposed in the upper portion of the clutch gear  323 . 
     That is, when an external force is applied, the motor  310  is normally driven, but due to slidingness occurring in the friction pad  323 _ 5 , the motive power of the motor  310  is not transferred to the complex gear  324 , the rotational shaft  30 , etc. Such a limitation is sensed by a rotary sensor, and its detailed description will be described below. 
     In the complex gear  324 , the helical gear disposed in an upper portion thereof and the spur gear disposed in a lower portion thereof are coupled integrally and simultaneously rotate with respect to the same shaft. A motive power in the clutch gear  323  is transferred to the spur gear, and thus, the helical gear rotates simultaneously with the spur gear. 
     The rotational shaft  330  is configured with the second gear set  340 . The second gear set  340  includes the helical gear  341  that is installed to be rotatable through gear coupling with the helical gear configuring the complex gear  324 , and the spur gear  342  that is fixed and coupled to the helical gear  341  to rotate simultaneously with the helical gear  341 . 
     That is, a motive power transferred to the complex gear  324  is transferred to the second gear set  340  through gear coupling between the helical gear configuring the complex gear  324  and the helical gear configuring the second gear set  340 , and thus, the second gear set  340  and the rotational shaft  330  are coupled integrally and rotate simultaneously. 
     The spur gear set  350  and  360  that is installed so as to enable integral rotation is disposed in each of both ends of the rotational shaft  330 . 
     The spur gear set  350  and  360  is fixed and coupled to each of both ends of the rotational shaft  330 , and is respectively coupled to engage the spur gear teeth  211  and  223  that are respectively formed inside a portion of the outer gear  210  and a portion of the inner gear  220 . 
     Therefore, a rotational motion generated by the motor  310  is transferred to the outer gear  210  and the inner gear  220  by the spur gear set  350  and  360 . The outer gear  210  and the inner gear  220  change the rotational motion to a rectilinear motion and thus ascend/descend in a vertical direction with respect to the body housing  10 , respectively. 
     The spur gear set  350  and  360  is configured with first and second spur gears  350  and  360  that are provided to have different diameters. The diameter of the first spur gear  350  is greater than that of the second spur gear  360 , and is coupled in engagement with the spur gear teeth  211  that is provided inside the outer gear  210 . The spur gear  360  is coupled in engagement with the spur gear teeth  223  that is provided inside the inner gear  220 . 
     The spur gear set  350  and  360  having different diameters rotates integrally with the rotational shaft  330  to have the same angular velocity, but provides different linear velocities to the outer gear  210  and the inner gear  220 . Therefore, the outer gear  210  may have a linear velocity greater than that of the inner gear  230  and ascend/descend in a vertical direction. 
     As illustrated in  FIG. 7 , a rotary sensor  40  that senses the transfer of a motive power from the driving unit  30  may be further disposed on the bracket  370  that is provided across an upper portion of the body housing  10 . 
     The rotary sensor  40  is disposed to be separated from the complex gear  324  with a certain space therebetween. The rotary sensor  40  is coupled to the spur gear of the second gear set  340  that is driven integrally with the rotational shaft  330 , and thus is rotation-driven identically to the rotational shaft  330 . 
     While the motive power is normally being transferred, the motive power of the motor  310  is transferred to the rotational shaft  330  as-is, and thus, the rotational shaft  330  also rotates in the rotational direction of the motor  310 . At this point, the rotary sensor  40  rotates identically to the rotational shaft  330  to output a normal state signal. 
     When the motive power is abnormally transferred, for example, when an external force exceeding a predetermined reference is given to the monitor frame  20 , the motive power of the motor  310  is not transferred to the rotational shaft  330  due to the structural feature of the clutch gear  323 . 
     Therefore, even when the motor  310  is rotating, the rotational shaft  330  does not rotate, and moreover, the rotary sensor  40  coupled to the rotational shaft  330  does not rotate. That is, even though the motor  310  is rotating, when the rotary sensor  40  does not rotate, this is determined as an abnormal state by the rotary sensor  40 , and thus, the rotary sensor  40  outputs an abnormal state signal. 
     The normal or abnormal state signal outputted from the rotary sensor  40  is transmitted to the PCB, which is configured with the controller and power source of the motor  310 , through an internal electric line. The controller outputs a control signal that allows the rotational direction of the motor  310  to be switched to a reverse direction, according to the sensing signal. 
     That is, the controller controls the rotational direction of the motor  310  according to state information regarding whether the rotational shaft  330  rotates and state information regarding whether the motor  310  rotates, and its detailed description will be described below. 
     As an embodiment, while the monitor frame  20  is ascending/descending in a vertical direction with respect to the body housing  10 , when the motive power is normally transferred, the motor  310  and the rotational shaft  330  rotate together. However, when the motive power is abnormally transferred, the motor  310  rotates, but the rotational shaft  330  does not rotate. In this case, the controller, which receives state information regarding whether the rotational shaft  330  rotates and state information regarding whether the motor  310  rotates, determines an external force as being given to the pop-up monitor and controls the motor  310  to rotate in a reverse direction with respect to the original rotational direction. That is, while the monitor frame  20  is ascending, when an external force is applied to the pop-up monitor, the controller controls the rotational direction of the motor  310  in a reverse direction in order for the monitor frame  20  to descend. While the monitor frame  20  is descending, when an external force is applied to the pop-up monitor, the controller controls the rotational direction of the motor  310  in a reverse direction such that the monitor frame  20  ascends. 
     As another embodiment, in a state where the monitor frame  20  has ascended to the maximum with respect to the body housing  10 , when an external force is applied to the pop-up monitor, the motor  310  is in a stopped state, but the rotational shaft  330  may rotate by the external force. 
     That is, when the controller receives state information indicating that the rotational shaft  330  is rotating when the monitor frame  20  has been opened and state information indicating that the motor  310  does not rotate, the controller controls the rotational direction of the motor  310  in a direction where the monitor frame  20  descends. 
     In the above description, the state information regarding the rotation of the rotational shaft  330  has been described as being obtained from the sensing signal of the rotary sensor  40 , but the spirit and scope of the embodiments are not limited thereto. The spirit and scope of the embodiments should be construed as including other elements for obtaining the state information regarding the rotation of the rotational shaft  330 . 
     As another embodiment, as illustrated in  FIG. 8 , a damping spring  13  for supporting the vertical motion of the rack gear set  27  may be disposed in each of both sides of the body housing  10 . 
     As described above, the rack gear set  27  receives the motive power of the motor  310  though gear coupling with the spur gear set  350  and  360  of the driving unit  30 . At this point, a gap is formed between the spur gear and the rack gear, and consequently, when the monitor frame  20  ascends/descends, shaking occurs in proportion to the gap. Also, rattle noise is caused by the shaking of the monitor due to the vibration of the vehicle. 
     In order to solve limitations such as the shaking of the monitor due to the gap between the gears and noise due to the shaking, in the embodiment, the pop-up monitor is characterized by including the damping spring  13  that supports the vertical motion of the rack gear set  27 . 
     Specifically, the damping spring  13  is disposed in each of the both sides of the body housing  10 , and configured with a case-damping spring  13 _ 1  and a torsion spring  13 _ 2 . 
     A groove  212  is formed along a length direction, at an outer surface of the outer gear  210  of the rack gear set  27 . When the monitor frame  20  ascends/descends, the damping spring  13  applies a constant pressure to the outer gear  210  along the groove  212 . 
     The torsion spring  13 _ 2  of an elastic material applies a constant moment to the case-damping spring  13 _ 1  when assembled with the case-damping spring  13 _ 1 . Due to the moment, the damping spring  13  continuously applies a constant pressure to groove  212  that is formed at the outer surface of the outer gear  210 . 
     The pressure applied from the damping spring  13  removes a gap between the rack gear set  27  and the spur gear set  350  and  360 , and thus, shaking is prevented from occurring when the monitor frame  20  ascends/descends. 
     The rack gear structure may further include a pressurizing member applying a pressure in a direction perpendicular to a vertical moving direction of the outer gear. 
     A groove having a certain width is formed along a length direction, in an outer surface of the outer gear. When the monitor frame ascends or descends in a vertical direction, the pressurizing member continuously applies a constant pressure to the outer gear along the groove. 
     The pressurizing member includes a case-damping spring installed to be externally touched to the linear outer gear; and a torsion spring assembled with the case-damping spring to apply a moment to the case-damping spring. 
     The rack gear structure may include a linear outer gear coupled to the monitor frame, and a linear inner gear disposed inside the outer gear. The linear inner gear ascends or descends according to an ascending or descending motion of the linear outer gear. 
     The linear outer gear ascends within a distance range of about 100 mm to 130 mm, and the linear inner gear ascends within a distance range of about 50 mm to 65 mm according to an ascending motion of the linear outer gear. 
     The linear outer gear ascends within a distance range of about 105 mm to 115 mm, and the linear inner gear ascends within a distance range of about 55 mm to 60 mm according to an ascending motion of the linear outer gear. 
     The linear outer gear and the linear inner gear ascend to the maximum, the linear outer gear and the linear inner gear overlap with each other within a distance range of about 80 mm to 95 mm. 
     According to embodiments of the present invention, the vertical motion of the monitor frame is supported by the rack gear set, which includes the outer gear that is fixed and coupled to the monitor frame to directly induce the vertical motion of the monitor frame, and the inner gear that is received in the internal space through rail coupling with the outer gear. 
     That is, the rack gear set is characterized by having the double rack gear structure of the outer gear and inner gear. Herein, the inner gear is not directly associated with the vertical motion of the monitor frame, but when the inner gear ascends simultaneously with the outer gear and then the outer gear has ascended to the maximum, by maximizing a portion overlapping with the outer gear, the inner gear can support forward and rearward/right and left shaking that occurs in the outer gear. 
     Moreover, in embodiments of the present invention, the receiving space for receiving portable equipment or the like is formed in the body housing, and a connector, a USB port, etc. for supplying a power to the portable equipment or communicating with the portable equipment are provided in one side of the body housing, thus enhancing a user&#39;s convenience. 
     A number of exemplary embodiments have been described above. Nevertheless, it will be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and/or if components in a described system, architecture, device, or circuit are combined in a different manner and/or replaced or supplemented by other components or their equivalents. Accordingly, other implementations are within the scope of the following claims.