Patent Publication Number: US-2021169518-A1

Title: Sensor insertion device

Description:
TECHNICAL FIELD 
     The present invention relates to a sensor insertion device that inserts a sensor for measuring biological information into a patient&#39;s body to perform continuous blood glucose measurement, for example. 
     BACKGROUND ART 
     The configuration of a conventional sensor insertion device is as follows. 
     Specifically, a conventional sensor insertion device comprises a lower case that has an upper surface opening, an upper case that covers the outer periphery of the lower case from above, a sensor base that is disposed inside the lower case and holds a sensor, a needle holder that is disposed above the sensor base so as to be movable up and down and in which a guide needle of the sensor is held, and a needle holder raising mechanism that raises the needle holder. 
     The needle holder raising mechanism is disposed inside the upper case, and includes a spring that is compressed when the upper case is pushed down. After the needle holder has been lowered, the stored energy in this spring is released to raise the needle holder (for example, Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2015-509011 
     SUMMARY 
     Technical Problem 
     A problem encountered with the conventional example given above is that when the guide needle is pulled out from the upper arm of the patient, the patient ends up experiencing more discomfort. 
     That is, with a conventional sensor insertion device, the guide needle is pulled out from the upper arm of the patient by the release of the stored energy of the spring, and the guide needle that has been pulled out hits a stopper and comes to a stop. The loud snap produced when the guide needle and the stopper collide increases discomfort (fear) on the part of the patient. 
     In view of this, it is an object of the present invention to reduce patient discomfort when using a sensor insertion device. 
     Solution to Problem 
     In order to achieve this object, the sensor insertion device of the present invention comprises a lower case that has an upper surface opening; an upper case that is disposed around the outer periphery of the lower case, covering from above, and slidably with respect to the lower case, and that is operated downward by a user when performing a needle insertion operation; a sensor base that is disposed inside the lower case and that holds a sensor for acquiring biological information; a needle holder that is disposed above the sensor base so as to be movable up and down, and that holds a guide needle which is to be inserted into a patient&#39;s body in order to guide the sensor into the body; and a needle holder raising mechanism that raises the needle holder holding the guide needle that has been inserted into the patient&#39;s body, wherein the needle holder raising mechanism has a pinion gear that raises the needle holder; a first rack gear that is provided to the needle holder and is engaged with the pinion gear; and a second rack gear that is provided to the upper case and is engaged with the pinion gear. As the upper case descends, the pinion gear raises the needle holder by engagement with the second rack gear. 
     The present invention achieves its intended purpose by this configuration. 
     Advantageous Effects 
     As described above, with the present invention, after the guide needle of the needle holder has been inserted, the needle holder is raised by the pinion gear provided to the needle holder raising mechanism, so there is no snap noise produced by a spring, and patient discomfort (fear) can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an oblique view of the usage state of the sensor insertion device according to Embodiment 1 of the present invention; 
         FIG. 2  is a front view of the mounted state of the sensor base and the biological information measuring device in  FIG. 1 ; 
         FIG. 3  is an oblique view of the sensor insertion device in  FIG. 1 ; 
         FIG. 4  is an exploded oblique view of the sensor insertion device in  FIG. 1 ; 
         FIG. 5  is an exploded oblique view of the sensor insertion device in  FIG. 1 ; 
         FIG. 6  is an exploded perspective view of the lower case of the sensor insertion device in  FIG. 1 ; 
         FIG. 7  is an exploded cross section of the sensor insertion device in  FIG. 1 ; 
         FIG. 8  is a partially cut-away oblique view of the lower case of the sensor insertion device in  FIG. 1 ; 
         FIG. 9  is an exploded oblique view of the upper case of the sensor insertion device in  FIG. 1 ; 
         FIG. 10  is a cross section of the sensor insertion device in  FIG. 1 ; 
         FIG. 11  is a cross section of the sensor insertion device in  FIG. 1 ; 
         FIG. 12  is a detail cross section of  FIG. 11 ; 
         FIG. 13  is a detail cut-away oblique view of the upper case of the sensor insertion device in  FIG. 1 ; 
         FIG. 14  is a cross section of the operating state of the sensor insertion device in  FIG. 1 ; 
         FIG. 15  is a detail cross section of  FIG. 14 ; 
         FIG. 16  is a cross section of the operating state of the sensor insertion device in  FIG. 1 ; 
         FIG. 17  is a detail cross section  FIG. 16 : 
         FIG. 18  is a cross section of the operating state of the sensor insertion device in  FIG. 1 ; 
         FIG. 19  is a cross section of the operating state of the sensor insertion device in  FIG. 1 ; 
         FIG. 20  is across section of the operating state of the sensor insertion device in  FIG. 1 : 
         FIG. 21  is a detail oblique view of  FIG. 20 ; 
         FIG. 22  is an oblique view of the usage state of the sensor insertion device according to Embodiment 2 of the present invention: 
         FIG. 23  is a front view of the usage state of the sensor base and the biological information measuring device in  FIG. 22 ; 
         FIG. 24  is an oblique view of the sensor insertion device in  FIG. 22 ; 
         FIG. 25  is an exploded oblique view of the sensor insertion device in  FIG. 22 ; 
         FIG. 26  is a partially cut-away oblique view of the sensor insertion device in  FIG. 22 ; 
         FIG. 27  is a partially cut-away oblique view of the sensor insertion device in  FIG. 22 : 
         FIG. 28  is a detail oblique view of the A portion of the sensor insertion device in  FIG. 26 : 
         FIG. 29  is a detail oblique view of the B portion of the sensor insertion device in  FIG. 26 ; 
         FIG. 30  is a detail oblique view of the C portion of the sensor insertion device in  FIG. 26 ; 
         FIG. 31  is a cross section of the operating state of the sensor insertion device in  FIG. 22 ; 
         FIG. 32  is a cross section of the operating state of the sensor insertion device in  FIG. 22 ; 
         FIG. 33  is a cross section of the operating state of the sensor insertion device in  FIG. 22 ; 
         FIG. 34  is a cross section of the operating state of the sensor insertion device in  FIG. 22 ; 
         FIG. 35  is a partially cut-away oblique view of a partial modification example of the sensor insertion device in  FIG. 26 ; and 
         FIG. 36  is a detail oblique view of the D portion of the sensor insertion device in  FIG. 35 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will now be described in detail with reference to the drawings. 
     Embodiment 1 
     In Embodiment 1, “upper” and “lower” refer to “upper” and “lower” in the usage state of the sensor insertion device  1  shown in  FIG. 11 , etc. (a state in which the sensor is attached to a patient  2 ). The “up and down direction” means the insertion direction of the guide needle  20  in the sensor insertion device  1  (the needle insertion direction and the needle extraction direction). 
       FIG. 1  shows the usage state of the sensor insertion device  1 . In  FIG. 1 , a sensor unit  3  is mounted on a part of the body of the patient  2  along with a sensor base  4  by means of the sensor insertion device  1 . After this, a measuring device  5  (an example of a biological information measuring device) is mounted on the upper surface of the sensor base  4 . 
       FIG. 2  shows a state in which the sensor base  4  and the measuring device  5  are mounted on the patient  2 . In  FIG. 2 , a sensor  6  of the sensor unit  3  is left in the body of the patient  2 . Consequently, biological information about the patient  2  is sensed by the sensor unit  3  and measured by the measuring device  5 . The measurement result is transmitted from the measuring device  5  to a mobile telephone (not shown), for example. 
     In this embodiment, the biological information to be measured is the blood glucose level. For example, so-called continuous blood glucose measurement is performed in which a patient&#39;s blood glucose level is continuously measured every five minutes for one or two weeks. This makes it possible to spot any tendencies of the glucose level of the patient within a certain period, and to ascertain the glucose level during sleep. 
     As shown in  FIGS. 3 to 10 , the sensor insertion device  1  in this embodiment comprises a lower case  7 , an upper case  8 , a sensor base  4 , a needle holder  26 , and a needle holder raising mechanism  30 A. 
     The lower case  7  and the upper case  8  have a rectangular shape that is wider than it is long in plan view. 
     As shown in  FIG. 4 , the lower case  7  has an upper surface opening  9  formed on the upper surface side, and as shown in  FIGS. 7 and 8 , has a bottom outlet  10  formed on the bottom side in order to eject the sensor unit  3  and the sensor base  4  downward. 
     As shown in  FIG. 5 , the upper case  8  has a lower surface opening  11 , and as shown in  FIG. 3 , covers the outer periphery of the lower case  7  from above. More specifically, the upper case  8  and the lower case  7  both have a rectangular shape that is wider than it is long in plan view, and are stacked one over the other so that the lower case  7  is disposed on the inside. 
     As shown in  FIG. 3 , grip portions  13  are provided to the two long side surfaces  12  of the upper case  8  disposed opposite each other, extending from top to bottom in the center portion in the longitudinal direction, and recessed in a stepped shape from the outer surface side to the inner surface side. Also, slide guides  14 , which protrude in a stepped shape from the outer surface side to the inner surface side of the grip portions  13  and over which inward protrusions slide, are provided as shown in  FIGS. 4 to 6  to the portions of the lower case  7  corresponding to the grip portions  13 , to line up with the grip portions  13 . 
     The slide guides  14  are provided to the two long side surfaces  15  of the lower case  7  disposed opposite each other, and are formed so as to protrude in a stepped shape from the inner surface, in the central portion in the longitudinal direction, from top to bottom. In a state in which the rear surfaces of the grip portions  13  of the upper case  8  are in contact with the surface of the slide guides  14 , these rear surfaces are slid in the up and down direction (usage state). 
     Because the long side surfaces  12  of the upper case  8  are thus provided with the grip portions  13  that are recessed toward the inner surface side, the grip portions  13  are smaller, and do not protrude out from the outer surface of the upper case  8 . Therefore, as shown in  FIG. 1 , it is easier for user to hold the upper case  8  in the right hand. Also, because the grip portions  13  are provided in the central portion of the long side surfaces  12  of the upper case  8 , they afford a more stable grip, so the usage state (discussed below) is extremely stable. 
     The user of the sensor insertion device  1  may be the patient himself, or may be a third party such as a nurse or a caregiver. 
     The detailed configurations of the various components will be described below. 
     As shown in  FIGS. 6 to 8 , a cylindrical antibacterial wall  17  is provided in the lower case  7 . The antibacterial wall  17  has an upper opening  16  and a bottom outlet  10 , and is provided so as to protrude from around the periphery of the bottom outlet  10  toward the inside of the lower case  7 , so as to surround the bottom outlet  10 . 
     As mentioned above, the sensor base  4  is disposed at the bottom outlet  10  portion in the interior of the antibacterial wall  17 . The antibacterial wall  17  has in its interior a needle unit  19  held by a sensor holder  18 , above the sensor base  4 . More precisely, as shown in  FIG. 8 , the sensor holder  18  holds the needle unit  19  on the upper surface side, and holds the above-mentioned sensor unit  3  on the lower surface side. 
     In this state, the sensor unit  3  of the sensor  6  (see  FIG. 6 ) is being held inside the guide needle  20  of the needle unit  19 . When the guide needle  20  is lowered by a needle insertion operation, the sensor  6  is inserted into the body of the patient  2  along with the guide needle  20 , after which just the guide needle  20  is pulled upward and withdrawn. Consequently, just the sensor  6  is left in the body of the patient  2  (see  FIG. 2 ). 
     The sensor base  4  has formed in it a through-hole  21  for moving the guide needle  20  up and down in a state of being inserted. 
     One of the main features of this embodiment is that, as shown in  FIG. 8 , the sensor unit  3 , the sensor holder  18 , the sensor base  4 , the needle unit  19 , and the guide needle  20  are housed within the antibacterial wall within  17 . In this state, as shown in  FIG. 7 , an antibacterial sheet (first antibacterial sheet)  22  that is sealed so as to cover the upper opening  16  is attached to the upper opening  16  of the antibacterial wall  17 . 
     Also, as shown in  FIG. 7 , an antibacterial sheet (second antibacterial sheet)  24  that seals the bottom outlet  10  so as to cover the bottom outlet  10  is mounted on the bottom surface  23  of the lower case  7  (see  FIG. 5 ). The antibacterial sheet  24  has a larger surface area than the opening portion of the bottom outlet  10 , and is bonded to the bottom surface  23 . Thus, the antibacterial sheet  24  constitutes a part of the bottom surface  23  of the lower case  7 . 
     That is, an antibacterial chamber  25  has the upper opening  16  on the upper side, and the bottom outlet  10  (an example of the lower opening of the antibacterial chamber  25 ) on the lower side. The upper opening  16  is sealed by the antibacterial sheet  22 , and the bottom outlet  10  is sealed by the antibacterial sheet  24 . Consequently, the space inside the antibacterial wall  17  becomes the antibacterial chamber  25 . 
     In the state prior to the use of the sensor insertion device  1 , the sensor unit  3 , the sensor holder  18 , the sensor base  4 , the needle unit  19 , the guide needle  20 , and the like are housed inside the antibacterial chamber  25  as mentioned above. 
     In a state in which the space inside the antibacterial wall  17  has been sealed by the antibacterial sheet  22  and the antibacterial sheet  24 , it is irradiated from the outside with an electron beam. Consequently, the sensor unit  3 , the sensor holder  18 , the sensor base  4 , the needle unit  19 , and the guide needle  20  disposed within the antibacterial wall  17  are subjected to a sterilization treatment, and are kept in a sterile state. 
     Meanwhile, as shown in  FIG. 5 , the cylindrical needle holder  26  whose the lower surface side is open is disposed inside the upper case  8 . The needle holder  26  is provided so as to be movable by a needle holder raising mechanism  30 A (discussed below; see  FIG. 7 ) within the sensor insertion device  1  in the up and down direction. Furthermore, the upper case  8  is provided with engaging arms  27  in between the needle holder  26  and the grip portions  13 . 
     The engaging arms  27  are engaged with engagement holes  28  (see  FIG. 9 ) formed in the side surfaces of the needle holder  26 . During needle insertion, the user pushes down on and lowers the upper case  8 , whereupon the engagement between the engaging arms  27  and the engagement holes  28  causes the needle holder  26  to descend along with the upper case  8 . At this point, the pinion gear  30  is lowered along with the needle holder  26  and the upper case  8  in a non-rotating state. 
     As will be described in detail below, during descent of the upper case  8 , needle holder  26  is holding the needle unit  19  (see  FIG. 16 ), and the result of the needle holder  26  descending through the sensor insertion device is that the needle insertion operation of the guide needle  20  is performed. Also, in the needle removal operation following the needle insertion operation, the guide needle  20  is pulled out when the needle holder  26  rises inside the sensor insertion device  1 . 
     The sensor insertion device  1  of this embodiment is provided with the needle holder raising mechanism  30 A that raises the needle holder  26  in order to pull the guide needle  20  (see  FIG. 18 ) that was inserted into the body of the patient  2  out of the body. 
     More specifically, as shown in  FIG. 7 , etc., the needle holder raising mechanism  30 A has two pinion gears  30  disposed so as to sandwich the needle holder  26 , and rack gears  33  and  34  that engage with the pinion gear  30 . 
     As shown in  FIG. 5 , the two pinion gears  30  that raise the needle holder  26  are disposed between the needle holder  26  in upper case  8  and the short side surfaces  29  of the upper case  8 . 
     Also, as shown in  FIG. 7 , shaft support grooves  32  that support the shafts  31  of the pinion gears  30  (see  FIG. 9 ) in a state of being movable in the up and down direction are formed along the up and down direction of the upper case  8  on the inside of the long side surfaces  12  of the upper case  8 . The pinion gears  30  are provided so as to be slidable in the up and down direction along the shaft support grooves  32  during the sensor mounting shown in  FIG. 11 , etc. 
     Rack gears (first rack gears)  33  that engage with the pinion gears  30  are provided along the up and down direction on the inner surface side of the upper case  8 . The rack gears  33  are disposed at the portions opposite the pinion gears  30  on the inner surface side of the short side surfaces  29 . The lower portions of the rack gears  33  are engaged with the two pinion gears  30 . 
     Rack gears (second rack gears)  34  are provided on the outer surface side of the needle holder  26 , along the up and down direction on both side surfaces opposite the pinion gears  30 . The two pinion gears  30  are engaged with the upper portions of the rack gears  34  at both side surfaces of the needle holder  26 . 
     As shown in  FIG. 7 , etc., the rack gears  33  and  34  are disposed such that their engagement teeth are opposite each other. 
     The two pinion gears  30  are disposed so as to be sandwiched on both sides by the rack gears  33  and  34 , and do not rotate until the needle insertion operation shown in  FIG. 18  is complete. Once the needle insertion operation shown in  FIG. 18  is complete, the user then pushes down on the upper case  8 , whereupon the rack gears  33  descend relative to the needle holder  26 , rotating the pinion gears  30 , on both side surfaces of the needle holder  26 . When the pinion gears  30  rotate, the rack gears  34  engaged with the pinion gears  30  are driven by the pinion gears  30 , causing the needle holder  26  to slide upward. As a result, the needle holder  26  is lifted up (raised) by the pinion gears  30  on both sides, and the guide needle  20  held by the needle holder  26  is pulled out of the body of the patient  2 . 
     That is, the pinion gears  30 , the rack gears  33 , and the rack gears  34  constitute the needle holder raising mechanism  30 A that raises the needle holder  26 . With this configuration, after the needle insertion operation shown in  FIG. 14 , the upper case  8  is further operated downward (the direction of needle insertion into the patient  2 ), whereupon the needle holder  26  can be slid upward inside the upper case  8 . 
     Accordingly, the user can perform the needle insertion operation and the needle extraction operation with the guide needle  78  using the sensor insertion device  1  by the same operation as when pushing down on the upper case  8  (in the direction of inserting the needle into the patient  2 ). This makes the device more convenient for the user. 
     Also, the needle holder  26  is provided with a needle carrier  36  whose lower end side is cylindrical, as shown in  FIG. 7 . The needle carrier  36  is disposed opposite the needle unit  19  that is disposed in the lower case  7 . When the lower end side of the needle carrier  36  is engaged with the needle unit  19 , the needle holder  26  holds the guide needle  20  of the needle unit  19 . 
     As described above, because the grip portions  13 , which are recessed inward, are provided to the long side surfaces  12  of the upper case  8 , the grip portions  13  are smaller, so that it is easier for the user to grasp the grip portions  13 . In this embodiment, the pinion gears  30  are disposed in the upper case  8  at the positions of the long side surfaces  12  of the upper case  8  where the grip portions  13  are not formed, that is, at both side portions of the grip portions  13  on the long side surfaces  12 . Thus, pinion gears  30  are provided at positions away from the recessed part of the grip portions  13  of the upper case  8 . Accordingly, the grip portions  13  can be favorably recessed inward, allowing the upper case  8  to have a compact shape that is easy to hold. 
     Engagement protrusions  37  (see  FIG. 6 ) are provided in the four corners on the upper end side of the short sides of the lower case  7 . Also, concave portions  38  are provided in the four corners on the lower end side of the short sides of the upper case  8 . 
     As discussed above, when the upper case  8  is placed over the lower case  7 , the four engagement protrusions  37  (see  FIG. 6 ) of the lower case  7  engage with the four concave portions  38  of the upper case  8  as shown in  FIG. 10 . 
     When using the sensor insertion device  1  configured as above, the user lifts up the sensor insertion device  1  by grasping the grip portions  13  of the upper case  8  shown in  FIG. 3 , peels off the antibacterial sheet  24  (see  FIG. 5 ) from the bottom surface  23  of the lower case  7 , and then presses the bottom surface  23  of the lower case  7  against his or her body  2 . 
       FIG. 11  is a cross section of the sensor insertion device  1  pressed against the patient&#39;s body  2 , and is a cross section along the A plane in  FIG. 4 .  FIG. 12  and  FIGS. 14 to 20  are also cross sections along the A plane in  FIG. 4 . 
       FIG. 12  is a detail cross section of the area around the needle holder  26  in  FIG. 11 . Inside the upper case  8 , the needle holder  26  is provided at a portion opposite the upper surface of the antibacterial sheet  22 . The needle holder  26  is provided with the needle carrier  36  that engages with and holds the needle unit  19  in the antibacterial chamber  25  when the upper case  8  is lowered. 
     The lower end side of the needle carrier  36  is disposed opposite the upper end side of the needle unit  19 , with the antibacterial sheet  22  in between. 
     Furthermore, the lower end portion of the needle carrier  36  has a cylindrical shape which holds an outer peripheral surface of the needle unit  19  as shown in  FIG. 13 . Four blades  39  are formed on a lower opening edge of the cylindrical form of the needle carrier  36 , and the blades  39  are provided to cut out the antibacterial sheet  22 . 
     When the user pushes down on the upper case  8  with at least a specific amount of force from the state shown in  FIG. 11  to a state in which the grip portions  13  are grasped, the engagement between the engagement protrusions  37  of the lower case  7  and the concave portions  38  of the upper case  8  (see  FIG. 10 ) is released, and the upper case  8  is pushed downward all at once. At this point, the grip portions  13  of the upper case  8  are guided by the slide guides  14  of the lower case  7  while descending (see  FIG. 3 ). 
     As shown in  FIG. 9 , the engaging arms  27  of the upper case  8  are engaged with the engagement holes  28  of the needle holder  26  on the inner surface side of the grip portions  13 . Therefore, the needle holder  26  descends along with the upper case  8 . 
     With the needle carrier  36  of the needle holder  26 , as shown in  FIGS. 14 and 15 , the distal end portions of the four blades  39  provided at the lower end poke through and break the antibacterial sheet  22 . 
     That is, in this embodiment, the antibacterial chamber  25  is provided inside the lower case  7  that is unitized with the upper case  8 . Therefore, the sterile state of the antibacterial chamber  25  is maintained until the time of its actual use, so a hygienic state can be maintained. 
     Also, the needle unit  19  has a conical portion  40  (or a truncated conical portion) protruding upward at its upper end. Accordingly, the antibacterial sheet  22  broken by the blades  39  is pushed into an antibacterial sheet holder  41  provided in the needle carrier  36 , by the conical portion  40  of the needle unit  19 . 
     When the upper case  8  is further depressed, as shown in  FIGS. 16 and 17 , the needle holder  26  holds the outer surface of the needle unit  19  on the inner wall surface of the needle carrier  36  (the inner wall surface of the antibacterial sheet holder  41 ). 
     In this embodiment, in a state in which the needle carrier  36  holds the needle unit  19 , the top of the conical portion  40  of the needle unit  19  is inserted into the antibacterial sheet holder  41  of the needle carrier  36 . 
     Therefore, the broken antibacterial sheet  22  is pushed into the antibacterial sheet holder  41  by the conical portion  40  of the needle unit  19 . In this state, the antibacterial sheet  22  is then pressed against the inner wall surface of the antibacterial sheet holder  41  by an O-ring  42  provided on the side surface of the needle unit  19 . 
     As a result, the broken antibacterial sheet  22  is held inside the antibacterial sheet holder  41 , and therefore does not hinder the operation of the sensor insertion device  1 . 
     When the upper case  8  is further depressed in a state in which the needle holder  26  holds the needle unit  19 , the sensor unit  3  held by the sensor holder  18  is mounted on the upper surface side of the sensor base  4  as shown in  FIG. 18 . 
     At this point, the sensor  6  protrudes downward from the bottom surface  23  of the lower case  7  along with the guide needle  20 , and the skin is punctured by the guide needle  20 . The sensor base  4  is attached to the patient&#39;s body  2  by an adhesive portion  43  provided on the lower surface of the sensor base  4 . That is, the sensor  6  is inserted into the body  2  along with the guide needle  20 . 
     When the guide needle  20  is inserted, the shafts  31  of the pinion gears  30  move downward in the shaft support grooves  32  and until reaching shaft supports  35  provided to the lower case  7 . 
     The operation of extracting the guide needle  20  will now be described. 
     In this embodiment, as shown in  FIG. 7 , the pinion gears  30 , the rack gears  33 , and the rack gears  34  constitute the needle holder raising mechanism  30 A that raises the needle holder  26 . In the operation of removing the guide needle  20 , the pinion gears  30  are rotated by engagement with the rack gears  33  and the rack gears  34  as the upper case  8  descends further upon completion of the needle insertion operation, and the needle holder  26  is raised. As a result, the guide needle  20  is extracted from the patient&#39;s body  2 . 
     This will be described in detail below. 
     When the user further depresses the upper case  8  after the needle insertion operation shown in  FIG. 18 , the pinion gears  30  are supported by the shaft supports  35  as shown in  FIG. 18 , and therefore do not go down any further. 
     On the other hand, when the upper case  8  slides further downward, the rack gears  33  inside the upper case  8  slide downward. Therefore, the pinion gears  30  engaged with the rack gears  33  on the upper case  8  side rotate on both sides of the needle holder  26 . This rotational force is transmitted to the rack gears  34  on the lower case  7  side that are engaged with the pinion gears  30 . 
     Therefore, the needle holder  26  is lifted up by receiving an upward drive force from the rack gears  34  disposed on both sides, and slides upward (rises) from the state shown in  FIG. 18  to the state shown in  FIG. 19 . 
     As a result, the guide needle  20  held by the needle holder  26  is extracted from the patient&#39;s body  2  and stowed in the lower case  7  as shown in  FIG. 19 . The sensor  6  is left in the patient&#39;s body  2 . 
     The pinion gears  30  rotate while sliding in the upper case  8  along the shaft support grooves  32  with which the shafts  31  on both sides are engaged. 
     The force by which the pinion gears  30  lift the needle holder  26  is greater than the force of engagement between the engaging arms  27  of the upper case  8  and the engagement holes  28  of the needle holder  26 . Therefore, the engagement between the upper case  8  and the needle holder  26  is released, and the needle holder  26  can rise through the upper case  8 . 
     After this, when the user lifts up the upper case  8 , as shown in  FIG. 20 , since the sensor base  4  is affixed to the patient&#39;s body  2  by the adhesive portion  43 , the sensor base  4  detaches from holding prongs  44  in the antibacterial chamber  25  and comes off. 
     As a result, as shown in  FIG. 21 , the sensor base  4  is attached to the patient&#39;s body  2  in a state in which the sensor unit  3  is being held and this concludes the series of operations. 
     As described above, the sensor insertion device  1  of this embodiment comprises the lower case  7 , the upper case  8 , the sensor base  4 , the needle holder  26 , and the needle holder raising mechanism  30 A. The lower case  7  has the upper surface opening  9 . The upper case  8  is placed over the outer periphery of the lower case  7  and is disposed slidably with respect to the lower case, and is operated downward by the user when performing a needle insertion operation. The sensor base  4  is disposed in the lower case  7  and holds the sensor  6 . The needle holder raising mechanism  30 A raises the needle holder  26 , which is disposed so as to be movable up and down above the sensor base  4  and holds the guide needle  20  of the sensor  6 . The needle holder raising mechanism  30 A has the pinion gears  30 , the rack gears  34 , and the rack gears  33 . The pinion gears  30  raise the needle holder  26 . The rack gears  34  are provided to the needle holder  26  and engage with the pinion gears  30 . The rack gears  33  are provided to the upper case  8  and engage with the pinion gears  30 . As the upper case  8  descends, the pinion gears  30  raise the needle holder  26  by engagement with the rack gears  33 . 
     Therefore, after the guide needle  20  of the needle holder  26  has been inserted, the needle holder  26  can be raised by the pinion gears  30  provided in the upper case  8  by further lowering the upper case  8 . As a result, no snapping sound is generated by a spring, and patient discomfort (fear) can be reduced. 
     Also, the sensor insertion device  1  of this embodiment comprises the lower case  7 , the upper case  8 , the antibacterial chamber  25 , the antibacterial sheet  22 , the antibacterial sheet  24 , and the needle carrier  36 . The lower case  7  has the upper surface opening  9  and the bottom outlet  10 . The upper case  8  is placed over the outer periphery of the lower case  7  from above and is disposed slidably with respect to the lower case  7 , and is operated downward by the user when performing a needle insertion operation. The antibacterial chamber  25  is provided in the lower case  7  and houses the needle unit  19 , which includes the guide needle  20  to be inserted into the patient&#39;s body  2 , and the sensor unit  3 , which includes the sensor  6  for acquiring a blood glucose level. The antibacterial sheet  22  is attached to the upper opening of the antibacterial chamber  25 . The antibacterial sheet  24  is attached to the bottom outlet  10  corresponding to the lower opening of the antibacterial chamber  25 . The needle carrier  36  is provided to the portion in the upper case  8  that is opposite the upper surface of the antibacterial sheet  22 , and engages with the needle unit  19  in the antibacterial chamber  25  when the upper case  8  is lowered. 
     That is, since the antibacterial chamber is provided in the lower case  7  that is unitized with the upper case  8 , the sterile state of the antibacterial chamber is maintained until the time of its actual use, and as a result, a hygienic state can be maintained. 
     Appendix 1 
     The sensor insertion device of the present invention can be specified as follows. 
     That is, the sensor insertion device according to the first invention comprises: 
     a lower case having an upper surface opening: 
     an upper case that is placed over the outer periphery of the lower case from above, is disposed slidably with respect to the lower case, and is operated downward by a user when performing a needle insertion operation; 
     a needle unit and a sensor unit that are disposed in the lower case; 
     a needle holder that is disposed movably in the up and down direction in the upper case; 
     a needle holder raising mechanism that is provided movably in the up and down direction and has pinion gears that raise the needle holder holding the guide needle that has been inserted; 
     an outlet of the sensor unit provided on the bottom surface of the lower case; 
     an engagement mechanism that is disposed on the upper case and the needle holder and that engages the upper case and the needle holder when the upper case is lowered; 
     first rack gears that are provided to the upper case and engage with the pinion gears; and 
     second rack gears that are provided to the needle holder and engage with the pinion gears, 
     wherein 
     the lower case has shaft supports that support the shafts of the pinion gears, and 
     when the pinion gears move downward and reach the shaft supports, the needle holder is raised by the engagement of the pinion gears with the first rack gears and the second rack gears. 
     The sensor insertion device according to the second invention is the sensor insertion device according to the first invention, 
     wherein the shafts of the pinion gears reach the shaft supports in a state in which the operation of inserting the guide needle into the patient&#39;s body is complete. 
     The sensor insertion device according to the third invention is the sensor insertion device according to the first or second invention, 
     wherein the upper case is provided with shaft support grooves that are formed along the up and down direction of the upper case, and that hold the shafts of the pinion gears. 
     The sensor insertion device according to the fourth invention is the sensor insertion device according to the third invention, 
     wherein the shafts of the pinion gears are disposed at the lower ends of the shaft support grooves when the upper case moves downward until the operation for inserting the guide needle into the patient&#39;s body is complete. 
     The sensor insertion device according to the fifth invention is the sensor insertion device according to any of the first to fourth inventions, 
     wherein the upper case has a rectangular shape that is wider than it is long in plan view, is formed on the opposed long surfaces of the upper case, and has grip portions that are recessed stepwise from top to bottom, and inward protrusions that protrude stepwise at positions on the inner surface side corresponding to the grip portions, and 
     the lower case has slide guides that are provided at the portions corresponding to the grip portions and over which the inward protrusions of the grip portions slide. 
     The sensor insertion device according to the sixth invention is the sensor insertion device according to the fifth invention, 
     wherein the grip portions are provided on the long sides of the upper case in the central portion in the longitudinal direction, from above to below, and the pinion gears are disposed on both sides of the grip portions in the upper case. 
     The sensor insertion device according to the seventh invention is the sensor insertion device according to the sixth invention, 
     wherein the second rack gears are provided on both side surfaces of the needle holder. 
     The sensor insertion device according to the eighth invention is the sensor insertion device according to any of the fifth to seventh inventions, 
     wherein the engagement mechanism has a first engagement portion provided to the inside of the grip portions of the upper case, and a second engagement portion provided to the portion of the needle holder opposite the first engagement portion. 
     Appendix 2 
     The sensor insertion device of the present invention can be specified as follows. 
     That is, the sensor insertion device according to the eleventh invention comprises: 
     a cylindrical lower case having an upper surface opening and a bottom outlet; 
     an upper case that has a lower surface opening, is placed over the outer periphery of the lower case from above, is disposed slidably with respect to the lower case, and is operated downward by the user when performing a needle insertion operation: 
     an antibacterial chamber that is provided in the lower case, and in is housed a sensor unit that includes a needle unit including a guide needle to be inserted into a patient&#39;s body, and a sensor for acquiring biological information about the patient&#39;s body; 
     a first antibacterial sheet that is attached to an upper opening of the antibacterial chamber; 
     a second antibacterial sheet that is attached to the bottom outlet corresponding to the lower opening of the antibacterial chamber; and 
     a needle carrier that is provided in a portion of the upper case that is opposite the upper surface of the first antibacterial sheet, and that engages with the needle unit in the antibacterial chamber when the upper case is lowered. 
     The sensor insertion device according to the twelfth invention is the sensor insertion device according to the eleventh invention, 
     wherein the needle carrier has blades that break the first antibacterial sheet when the upper case is lowered. 
     The sensor insertion device according to the thirteenth invention is the sensor insertion device according to the twelfth invention, 
     wherein the needle carrier has a cylindrical shape for holding the outer periphery of the needle unit. 
     The sensor insertion device according to the fourteenth invention is the sensor insertion device according to the thirteenth invention, wherein the blades are formed at the cylindrical lower opening edge of the needle carrier. 
     The sensor insertion device according to the fifteenth invention is the sensor insertion device according to any of the twelfth to fourteenth inventions, 
     wherein the needle unit has a conical portion or a truncated conical portion protruding upward at its upper end portion, and in a state in which the needle unit is held by the needle carrier, the top of the conical portion or the truncated conical portion of the needle unit is inserted into the needle carrier. 
     Embodiment 2 
     As shown in  FIG. 22 , the sensor insertion device  51  according to this embodiment is used to attach a disc-shaped sensor base  54  holding a sensor unit  53  to a patient&#39;s body  52  (upper arm, etc.). 
     As shown in  FIG. 26 , just as with the sensor insertion device  1  in Embodiment 1 above, the sensor insertion device  51  constitutes a needle holder raising mechanism  74  that raises a needle holder  67  by using a pinion gear  71  and two rack gears (a first rack gear  72  and a second rack gear  73 ). Since the needle holder  67  is raised by the pinion gear  71  included in the needle holder raising mechanism  74 , no snapping sound is generated by a spring, and patient discomfort (fear) can be reduced. 
     This will now be described in detail with reference to the drawings. 
     In Embodiment 2, “upper” and “lower” refer to “upper” and “lower” in the usage state of the sensor insertion device  51  shown in  FIG. 31 , etc. (a state in which the sensor is attached to a patient  52 ). The “up and down direction” means the insertion direction of a guide needle  78  in the sensor insertion device  51  (the needle insertion direction and the needle extraction direction). 
       FIG. 22  is a diagram showing the usage state of the sensor insertion device  51 . In  FIG. 22 , with the sensor insertion device  51 , a sensor unit  53  is attached to a part of the patient&#39;s body (such as an upper arm)  52  along with a sensor base  54 . After this, a measuring device  55  (an example of a biological information measuring device; see  FIG. 23 ) is mounted on the upper surface of the sensor base  54 . 
       FIG. 23  shows a state in which the sensor base  54  and the measuring device  55  have been attached to the patient&#39;s body (upper arm)  52 . In  FIG. 23 , a sensor  56  included in the sensor unit  53  is left in the patient&#39;s body  52 . Consequently, biological information about the patient&#39;s body  52  is sensed by the sensor  56  and measured by the measuring device  55 . The measurement result is transmitted from the measuring device  55  to a mobile telephone (not shown), for example. 
     In this embodiment, the biological information to be measured is the blood glucose level. For example, so-called continuous blood glucose measurement is performed in which a patient&#39;s blood glucose level is continuously measured every five minutes for one or two weeks. This makes it possible to spot any tendencies of the glucose level of the patient within a certain period, and to ascertain the glucose level during sleep. 
     As shown in  FIGS. 24 to 27 , the sensor insertion device  51  in this embodiment comprises a lower case  57 , an upper case  58 , a sensor base  54 , a needle holder  67 , and a needle holder raising mechanism  74 . 
     As shown in  FIG. 25 , the lower case  57  has a cylindrical shape, an upper surface opening  59  is provided on the upper surface side of the cylindrical shape, and a bottom outlet  60  is provided on the lower surface side for ejecting the sensor base  54  downward. 
     As shown in  FIG. 25 , the sensor base  54  is a substantially cylindrical member and holds in its interior the sensor unit  53  including the sensor  56  shown in  FIG. 23 . 
     As shown in  FIG. 25 , the upper case  58  has a cylindrical shape that is closed on the upper surface side open on the lower surface side, and has a lower surface opening  61 . The upper case  58  is placed from above so as to cover the outer peripheral surface of the lower case  57  (see  FIG. 24 ). 
     That is, the upper case  58  has a cylindrical shape like the lower case  57 , and these are put together so as to be stacked one above the other. The outer peripheral surface of the upper case  58  is provided with grip portions  62  that are gripped by the user. Furthermore, a contact portion  64  that makes contact with the user&#39;s palm during use is provided on the upper surface portion  63  of the upper case  58 . Also, cylindrical slide guides  65  are provided on the outer peripheral surface of the lower case  57  at the portions corresponding to the grip portions  62  of the upper case  58 . 
     As a result, during use of the sensor insertion device  51 , the user can use the five fingers of the left hand to grasp the grip portions  62  of the upper case in a state in which the palm of the right hand is in contact with the contact portion  64 . This makes the usage state (discussed below) extremely stable. 
     The user of the sensor insertion device  51  may be the patient himself, or may be a third party such as a nurse or a caregiver. 
     The detailed configurations of the various components will be described below. 
     As shown in  FIG. 25 , the sensor base  54  holding the sensor  56  (see  FIG. 23 ), a base holder  66  holding the sensor base  54 , and a needle holder  67  placed over the base holder  66  are disposed in the lower case  57 . A skin tape  68  for attaching the sensor base  54  to the patient&#39;s body  52  is provided to the lower surface of the sensor base  54 . 
       FIGS. 26 and 27  show the sensor insertion device  51  when not in use (before sensor attachment). 
     As shown in  FIG. 27 , the sensor base  54  is inserted from the lower side of the base holder  66 .  FIG. 27  shows a state in which the skin tape  68  has been removed, in order to illustrate the state of the sensor base  54  and the base holder  66 . 
     The base holder  66  is such that three base engaging portions  69  provided at substantially equal angular intervals along the outer peripheral portion engage with first engaging prongs  70  provided at substantially equal angular intervals in the middle of the lower case  57  (see A in  FIG. 26 , and  FIG. 28 ). The needle holder  67  is placed over the outer peripheral surface of the base holder  66 . The needle holder  67 , the base holder  66 , and the sensor base  54  are held in the middle of the lower case  57 , and slide downward from this middle position when attached to the patient. 
     The needle holder  67  is substantially disk shaped, and is provided movably in the lower case  57  in the up and down direction (the insertion direction). The pinion gear  71 , the first rack gear  72 , and the second rack gear  73  constituting the needle holder raising mechanism  74  for raising the needle holder  67  are disposed on the upper surface side of the needle holder  67 , as shown in  FIG. 26 . 
     The needle holder raising mechanism  74  is disposed near the center of the lower case  57  and the needle holder  67 . More precisely, the pinion gear  71  is provided near the center axis of the cylindrical lower case  57  and the substantially disk-shaped needle holder  67 . 
     The pinion gear  71  is connected to a shaft  75  extending from the left and right ends of the gear portion. 
     The shaft  75  is provided as the rotational axis of the pinion gear  71 , and is disposed in a state in which its longitudinal direction is perpendicular to the central axis of the lower case  57 . The ends of the shaft  75  are supported by shaft supports  76  provided on the inner surface of the lower case  57 . Therefore, the pinion gear  71  rotates in the middle of the lower case  57  while being supported by the shaft supports  76 . 
     The first rack gear  72 , which has a substantially quadrangular prism shape, is engaged with the pinion gear  71 . The first rack gear  72  is provided so as to protrude upward from the upper surface of the needle holder  67 . The first rack gear  72  is engaged with the pinion gear  71  on the lower side of the gear portion in the pre-use state shown in  FIG. 27 . 
     Also, as shown in  FIG. 31 , the upper part of the needle unit  77  is embedded in the interior of the first rack gear  72  on the lower side thereof. The guide needle  78  held by the needle unit  77  protrudes from the lower surface side of the sensor base  54  below the first rack gear  72 . 
     The guide needle  78  includes the sensor  56  for measuring biological information (blood glucose level, etc.). 
     In the pinion gear  71 , as shown in  FIG. 26 , a second rack gear  73  having a substantially quadrangular prism shape is disposed on the opposite side from the first rack gear  72 , at the upper part of the pinion gear  71 . 
     The upper end side of the second rack gear  73  is a fixed end that is fixed to the ceiling of the upper case  58 , and the lower end side is a flexible free end. Accordingly, the lower end side of the second rack gear  73  is movable outward in the radial direction from the center axis of the upper case  58 . The second rack gear  73  is disposed so as to sandwich the pinion gear  71  from the left and right sides along with the first rack gear  72 . That is, the first rack gear  72  and the second rack gear  73  are disposed such that their engaging teeth face each other in a state in which the upper case  58  has been lowered (see  FIGS. 32 and 33 ), and the pinion gear  71  is disposed therebetween. Therefore, the second rack gear  73  engages with the pinion gear  71  on the opposite side from the first rack gear  72 . 
     Thus, the needle holder raising mechanism  74  is disposed near the central axis of the lower case  57  and the needle holder  67 . This allows the needle holder  67  that has undergone the needle insertion operation to be pulled up stably. This needle extraction operation will be described below. 
     The needle holder  67  is provided with three (a plurality of) needle holder engaging portions  79  at equal angular intervals along the outer peripheral portion of its upper surface. Needle holder pressing portions  80  are provided on the inner surface of the upper case  58  at the portions opposite the needle holder engaging portions  79  (see the B portion in  FIG. 26 , and  FIG. 29 ). 
     That is, since the needle holder pressing portions  80  are engaged with the needle holder engaging portions  79 , when the upper case  58  is lowered, the needle holder  67  is pushed (slid) downward. 
     Furthermore, as shown in  FIG. 31 , a lower case engaging portion  81  is provided on the upper part of the outer periphery of the lower case  57 . The lower case engaging portion  81  is engaged with an upper case engaging prong  82  provided at the lower part of the inner periphery of the upper case  58  (see the C portion in  FIG. 26 , and  FIG. 30 ). 
     When using the sensor insertion device  51  configured as above, the user grasps the upper case  58  and lifts up the sensor insertion device  51 , and presses the bottom outlet  60  of the lower case  57  against his body  52 .  FIGS. 31 to 34  are cross sections of the sensor insertion device  51 . 
     From here, the operation of inserting the guide needle  78  is performed. 
     More specifically, the user presses the upper case  58  downward (toward his body  52 ) from the state shown in  FIG. 31 . At this point, when the upper case  58  is pressed with at least a certain amount of force, the engagement between the lower case engaging portion  81  and the upper case engaging prong  82  (see  FIG. 30 ) is released, and the hold of the upper case  58  on the lower case  57  is released. Accordingly, the upper case  58  is pushed down all at once. As the upper case  58  descends, the grip portions  62  (outer peripheral surface) are guided by the slide guides  65  (outer peripheral surface) of the lower case  57  (see  FIG. 24 ). 
     At this point, as shown in  FIG. 29 , the needle holder pressing portions  80  on the upper case  58  press the needle holder engaging portions  79  downward, so that the needle holder  67  descends along with the upper case  58  and pushes the base holder  66  down. 
     Consequently, in the base holder  66 , the three base engaging portions  69  on the outer periphery are disengaged from the first engaging prongs  70 , and the hold of the base holder  66  on the lower case  57  is released. Therefore, as the needle holder  67  held by the upper case  58  descends, the base holder  66  and the sensor base  54  descend all at once. 
     That is, the engagement force between the needle holder pressing portions  80  on the upper case  58  side and the needle holder engaging portions  79  on the needle holder  67  side greater than the engagement force between the base engaging portions  69  on the base holder  66  side and the first engaging prongs  70  on the lower case  57  side. 
     Consequently, the engagement between the needle holder pressing portions  80  on the upper case  58  side and the needle holder engaging portions  79  on the needle holder  67  side is maintained, while the engagement of the base holder  66  with the lower case  57  is released, allowing the base holder  66  to be lowered. 
     When the needle holder  67  is lowered, the first rack gear  72  fixed to the upper surface of the needle holder  67  rotates the engaged pinion gear  71  counterclockwise, going from the state shown in  FIG. 31  to the state shown in  FIG. 32 . More specifically, the pinion gear  71  rotates counterclockwise while moving from the lower end to the upper end of the first rack gear  72 . 
     In the state prior to the needle insertion operation shown in  FIG. 31 , the pinion gear  71  is engaged with the first rack gear  72  and not engaged with the second rack gear  73 . 
     At this point, as shown in  FIG. 32 , the guide needle  78  protrudes downward from the bottom outlet  60  of the lower case  57  and is inserted into the patient&#39;s body  52 . The sensor  56  guided by the guide needle  78  is inserted into the patient&#39;s body  52  together with the guide needle  78 . 
     At this point, as shown in  FIG. 32 , the base holder  66  is held by the lower case  57  because the base engaging portions  69  are engaged with second engaging prongs  83  of the lower case  57 . The sensor base  54  is attached to the patient&#39;s body  52  by the adhesion of the skin tape  68  affixed to the lower surface side. 
     At this point, as shown in  FIG. 32 , the first rack gear  72  is engaged with the pinion gear  71  on its upper side. At the pinion gear  71 , the lower end side of the second rack gear  73  is lowered and engages on the opposite side from the side engaged with the first rack gear  72 . 
     Specifically, when the needle insertion operation shown in  FIG. 32  is complete, the pinion gear  71  is engaged with both the first rack gear  72  and the second rack gear  73 , and this concludes the preparation for the needle extraction operation (discussed below). 
     In this state, the operation of inserting the guide needle  78  ends. 
     Next, the operation of extracting the guide needle  78  will be described. 
     In this embodiment, as shown in  FIG. 26 , the pinion gear  71 , the first rack gear  72 , and the second rack gear  73  constitute the needle holder raising mechanism  74  that raises the needle holder  67 . In the operation of extracting the guide needle  78 , the pinion gear  71  is rotated clockwise by engagement with the first rack gear  72  and the second rack gear  73  as the upper case  58  further descends after the completion of the needle insertion operation, and this raises the needle holder  67 . As a result, the guide needle  78  is removed from the patient&#39;s body  2 . 
     The needle extraction operation will now be described in specific terms. 
     When the user further presses the upper case  58  down from the state in which the needle insertion operation shown in  FIG. 32  is complete, the engagement between the needle holder pressing portions  80  and the needle holder engaging portions  79  is released, and the upper case  58  descends with respect to the needle holder  67  and the lower case  57 . 
     Accordingly, the second rack gear  73  fixed to the upper case  58  moves downward, engages with the pinion gear  71  from the lower end (the free end side), and rotates the pinion gear  71  clockwise. This rotational force is transmitted through the pinion gear  71  to the first rack gear  72 . As a result, as shown in  FIG. 33 , the first rack gear  72  rises. Therefore, the needle holder  67  to which the first rack gear  72  is fixed is pulled up by the clockwise rotation of the pinion gear  71 , and slides (rises) upward. 
     As a result, the guide needle  78  held by the needle holder  67  is pulled out of the patient&#39;s body  52  and stowed in a needle accommodation portion  84  provided to the base holder  66 , leaving the sensor  56  in the patient&#39;s body  52 . Therefore, the guide needle  78  protruding from the bottom outlet  60  of the lower case  57  is stowed in the lower case  57 . The sensor  56  is left inside the patient&#39;s body  52 . 
     After this, when the user lifts up the upper case  58 , as shown in  FIG. 34 , since the sensor base  54  is affixed to the patient&#39;s body  52  by the adhesion of the skin tape  68 , the sensor base  54  is detached from the base holder  66  and remains on the surface of the patient&#39;s body  52 . Consequently, the sensor base  54  is ejected from the bottom outlet  60  of the lower case  57  together with the sensor  56 . 
     As a result of the above operation, the sensor base  54  is mounted on the patient&#39;s body  52  in a state in which the sensor  56  is inserted into the patient&#39;s body  52 , as shown in  FIG. 34 . 
     This concludes the series of operations (needle insertion operation and needle extraction operation) by the sensor insertion device  51 . 
     Accordingly, the user can perform the needle insertion operation and the needle extraction operation of the guide needle  78  using the sensor insertion device  51  by the same operation, namely, pushing down on the upper case  58  (the direction of inserting the needle into patient&#39;s body  52 ). This makes the device more convenient for the user to use. 
     At this point, the guide needle  78  extracted from the patient&#39;s body  52  is stowed in the needle accommodation portion  84  provided to the base holder  66 , so that it is protected by the base holder  66 . That is, the base holder  66  becomes a lid that covers the bottom outlet  60 , and the guide needle  78  is covered by the base holder  66 . This means that the user or another person will not accidentally touch the guide needle  78 , which lowers the risk of blood infection. 
     As described above, with the sensor insertion device  51  in this embodiment, after the guide needle  78  is inserted into the patient&#39;s body  52 , the needle holder  67  is raised by the pinion gear  71  provided to the lower case  57 . This avoids the generation of a snapping sound made by a spring during a conventional needle extraction operation, which reduces patient discomfort (fear). 
     Furthermore, with the sensor insertion device  51  in this embodiment, the pinion gear  71 , the first rack gear  72 , and the second rack gear  73  constituting the needle holder raising mechanism  74  are disposed near the center axis of the cylindrical lower case  57  and near the center axis of the needle holder  67 , as shown in  FIGS. 26 and 31 . Therefore, the needle holder  67  receives the lifting force of the needle holder raising mechanism  74  near its central axis, so the needle holder  67  can be raised stably and with good balance. 
     As a result, a stable needle extraction operation can be performed. 
     With the sensor insertion device  51  in this embodiment, the lower end side of the second rack gear  73  fixed to the upper case  58  is formed as a flexible free end, as shown in  FIG. 31 . Accordingly, when the second rack gear  73  descends and comes into contact with the pinion gear  71 , the distal end side of the second rack gear  73  bends in the direction away from the pinion gear  71 , so the second rack gear  73  can be properly engaged with the pinion gear  71 . 
     As a result, a stable needle extraction operation can be performed. 
     Furthermore, with the sensor insertion device  51  in this embodiment, as shown in  FIG. 26 , the needle holder engaging portions  79  are provided at three places on the upper surface of the needle holder  67 . The first rack gear  72  is provided between two adjacent needle holder engaging portions  79 . 
     Accordingly, during the needle insertion operation, since the first rack gear  72  is provided between two adjacent needle holder engaging portions  79 , the first rack gear  72  can be lowered stably. Therefore, the first rack gear  72  that has been lowered in a stable state rotates the pinion gear  71 , so a stable needle insertion operation can be performed. 
     Furthermore, with the sensor insertion device  51  in this embodiment, as shown in  FIG. 31 , the needle unit  77  holding the guide needle  78  is fixed between two adjacent needle holder engaging portions  79  on the lower surface of the needle holder  67 . More specifically, the guide needle  78  is provided directly below the first rack gear  72 . 
     Therefore, during the needle insertion operation, the needle unit  77  also descends in a stable state directly below the first rack gear  72  that is lowered in a stable state. As a result, a stable needle insertion operation can be performed. 
     Furthermore, in the sensor insertion device  51  in this embodiment, the needle holder engaging portions  79  of the needle holder  67  are provided at three places at equal angular intervals along the outer peripheral portion of the needle holder  67 . That is, the needle holder engaging portions  79  are disposed so as to form an equilateral triangle. 
     Therefore, since the three needle holder engaging portions  79  press the needle holder  67  down at equal angular intervals, a more stable needle insertion operation can be performed. 
     Furthermore, with the sensor insertion device  51  in this embodiment, as shown in  FIG. 26 , the upper case  58  has a cylindrical shape with an open lower surface, and the contact portion  64  that comes into contact with the palm of the user is formed on the upper surface portion  63  of the upper case  58 . 
     Therefore, the user can press down the upper case  58  with the palm, with which it is easy to apply force, in the needle insertion operation and the needle extraction operation, and thus can perform stable needle insertion and needle extraction. 
     The second rack gear  73  here may be configured such that its lower end side is inclined to the opposite side from the pinion gear  71 , that is, to the side farther away from the pinion gear  71 , as shown in the portion D in  FIG. 35  and in  FIG. 36 . 
     That is, the second rack gear  73  is inclined so as to move away from the pinion gear  71  as it proceeds downward. 
     With this configuration, since the lower end side of the second rack gear  73  is inclined away from the pinion gear  71 , the lower end side of the second rack gear  73  can be gradually engaged with the pinion gear  71 . 
     As a result, proper engagement can be achieved between the second rack gear  73  and the pinion gear  71 , so a stable needle extraction operation can be performed. 
     The height of the engaging teeth formed on the lower end side of the second rack gear  73  may be lower than the height of the engaging teeth formed above the second rack gear  73 . 
     With this configuration, since the lower end side of the second rack gear  73  is engaged with the pinion gear  71  from engaging teeth that are lower in height, the lower end side of the second rack gear  73  can be gradually engaged with the pinion gear  71 . 
     As a result, just as described above, since proper engagement can be achieved between the second rack gear  73  and the pinion gear  71 , a stable needle extraction operation can be performed. 
     As described above, the sensor insertion device  51  in this embodiment comprises the lower case  57 , the upper case  58 , the sensor base  54 , the needle holder  67 , and the needle holder raising mechanism  74 . The lower case  57  has the upper surface opening  59 . The upper case  58  is placed over the outer periphery of the lower case  57  from above, is disposed slidably with respect to the lower case, and is pressed downward by the user when a needle insertion operation is performed. The sensor base  54  is disposed in the lower case  57 , and holds the sensor  56  for acquiring biological information. The needle holder  67  is disposed movably in the up and down direction above the sensor base  54 , and holds the guide needle  78  that is inserted into the patient&#39;s body to guide the sensor  56  into the body. The needle holder raising mechanism  74  raises the needle holder  67  that holds the guide needle that has been inserted into the patient&#39;s body. The needle holder raising mechanism  74  has the pinion gear  71 , the first rack gear  72 , and the second rack gear  73 . The pinion gear  71  raises the needle holder  67 . The first rack gear  72  is provided to the needle holder  67  and is engaged with the pinion gear  71 . The second rack gear  73  is provided to the upper case  58  and is engaged with the pinion gear  71 . As the upper case  58  descends, the pinion gear  71  raises the needle holder  67  by engaging with the second rack gear  73 . 
     That is, with the sensor insertion device  51  in this embodiment, after the guide needle  78  of the needle holder  67  has been inserted the upper case  58  is pressed further downward, so that the needle holder  67  is raised by the pinion gear  71  and the first and second rack gears  72  and  73  included in the needle holder raising mechanism  74 . Therefore, no snapping sound is produced by a spring, and patient discomfort (fear) can be reduced. 
     INDUSTRIAL APPLICABILITY 
     The present invention is anticipated to find use as a sensor insertion device for inserting a sensor for measuring biological information into a patient&#39;s body, for performing continuous blood glucose measurement, for example. 
     REFERENCE SIGNS LIST 
     
         
           1  sensor insertion device 
           2  patient&#39;s body 
           3  sensor unit 
           4  sensor base 
           5  measuring device (biological information measuring device) 
           6  sensor 
           7  lower case 
           8  upper case 
           9  upper surface opening 
           10  bottom outlet (lower opening of antibacterial chamber) 
           11  lower surface opening 
           12  long side surface 
           13  grip portion 
           14  slide guide 
           15  long side surface 
           16  upper opening 
           17  antibacterial wall 
           18  sensor holder 
           19  needle unit 
           20  guide needle 
           21  through-hole 
           22  antibacterial sheet (first antibacterial sheet) 
           23  bottom 
           24  antibacterial sheet (second antibacterial sheet) 
           25  antibacterial chamber 
           26  needle holder 
           27  engaging arm 
           28  engagement hole 
           29  short side surface 
           30  pinion gear 
           30 A needle holder raising mechanism 
           31  shaft 
           32  shaft groove 
           33  rack gear (first rack gear) 
           34  rack gear (second rack gear) 
           35  shaft support 
           36  needle carrier 
           37  engagement protrusion 
           38  concave portion 
           39  blade 
           40  conical portion 
           41  antibacterial sheet holder 
           42  O-ring 
           43  adhesive portion 
           44  holding prong 
           51  sensor insertion device 
           52  patient&#39;s body 
           53  sensor unit 
           54  sensor base 
           55  measuring device 
           56  sensor 
           57  lower case 
           58  upper case 
           59  upper surface opening 
           60  bottom outlet 
           61  lower surface opening 
           62  grip portion 
           63  upper surface 
           64  contact portion 
           65  slide guide 
           66  base holder 
           67  needle holder 
           68  skin tape 
           69  base engaging portion 
           70  first engaging prong 
           71  pinion gear 
           72  first rack gear 
           73  second rack gear 
           74  needle holder raising mechanism 
           75  shaft 
           76  shaft support 
           77  needle unit 
           78  guide needle 
           79  needle holder engaging portion 
           80  needle holder pressing portion 
           81  lower case engaging portion 
           82  upper case engaging prong 
           83  second engaging prong 
           84  needle accommodation portion