Patent Publication Number: US-2022233057-A1

Title: Bending operation mechanism for endoscope, and endoscope

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of PCT/JP2019/040323 filed on Oct. 11, 2019, the entire contents of which are incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a bending operation mechanism for an endoscope, the bending operation mechanism including an operation lever that is tiltable in a predetermined direction, and the endoscope. 
     2. Description of the Related Art 
     Recently, an endoscope has been widely used in medical and industrial fields. With the endoscope, it is possible to observe a site to be examined in a subject by inserting an elongated insertion portion into the subject. 
     In a well-known configuration, a bending portion that is actively and selectively bendable in any of up, down, right, and left directions or in a combined direction of two directions of the up, down, right, and left directions is provided at a distal end side of the insertion portion of the endoscope. 
     When bent, the bending portion can improve progressiveness of the insertion portion through an inflected portion in the subject and can also change an observation direction of an observation optical system provided at a distal end portion positioned on a distal end side in a longitudinal axial direction of the insertion portion relative to the bending portion. 
     For example, one pair of, that is, two pulling wires or two pairs of, that is, four pulling wires, distal ends of which in the longitudinal axial direction are fixed to the bending portion are inserted in an operation portion of the endoscope, the operation portion being provided continuously in the insertion portion of the endoscope and at a proximal end of the insertion portion in the longitudinal axial direction. Note that three of the pulling wires may be inserted in the operation portion. 
     Any of the two or four pulling wires, or two of the four pulling wires are pulled by a bending operation device provided at the operation portion of the endoscope. 
     With this configuration, the bending portion is actively and selectively bendable in any of the up and down directions, any of the right and left directions, any of the four directions of the up, down, right, and left directions, or a combined direction of two directions of the up, down, right, and left directions. 
     Note that a configuration of the bending operation device configured to pull pulling wires is well known. For example, International Publication No. 2016/199485 discloses a configuration of an endoscope in which a known joystick device is used for the bending operation device. 
     The joystick device actively and selectively bends the bending portion by pulling wires through a bending operation mechanism along with a tilt operation of a lever. 
     Specifically, in the endoscope disclosed in International Publication No. 2016/199485, an operation lever of the joystick device is selectively tiltable in the up direction or the down direction. With this configuration, the bending portion is selectively bendable in the up and down directions. 
     The operation lever is also selectively tiltable in the left direction or the right direction. With this configuration, the bending portion is selectively bendable in the right and left directions. 
     The operation lever is also selectively tiltable in a combined direction of the up direction and the right direction, a combined direction of the up direction and the left direction, a combined direction of the down direction and the right direction, and a combined direction of the down direction and the left direction. 
     With this configuration, the bending portion is selectively bendable in a combined direction of two of the up, down, right, and left directions. 
     More specifically, the operation lever is connected to and rising up from a center of a wire pulling member having, for example, an X plane shape with four arms, and each arm of the wire pulling member is tiltable along with tilt of the operation lever. 
     Each of the arms is connected to one end of a corresponding one of four pulling wires extending in the longitudinal axial direction, the other end of which is fixed to the bending portion, and each of the pulling wires moves with tilt of the corresponding arm. 
     In the operation portion of the endoscope, pulleys corresponding to the respective arms are disposed in a space on a side opposite to a side on which the operation lever is connected to the arms in an extension direction of the operation lever when not operated, the pulleys having outer peripheral portions around which the pulling wires are wound and being capable of changing moving directions of the pulling wires from the extension direction of the operation lever to the longitudinal axial direction of the insertion portion. 
     With this configuration, when the operation lever is tilted in a predetermined direction, each arm of the wire pulling member is tilted, and one or two pulling wires corresponding to the tilt direction of the operation lever among the four pulling wires connected to the respective arms are pulled. As a result, the bending portion bends in a direction corresponding to the tilt direction of the operation lever. 
     International Publication No. 2016/199485 also discloses a configuration for size reduction of the operation portion of the endoscope, in which a connection portion for a suction button is disposed in a region between two adjacent pulleys among the four pulleys to avoid the pulling wires. 
     Note that the suction button is disposed at a position that overlaps a central axis of the operation portion of the endoscope and at which the operation portion can be held in a hand of an operator grasping the operation portion so that a button operation can be easily performed by the operator grasping the operation portion with a right hand or a left hand. 
     SUMMARY OF THE INVENTION 
     A bending operation mechanism for an endoscope according to an aspect of the present invention includes: an operation lever that is tiltable in a predetermined direction; a wire pulling member connected to the operation lever and including at least two arms that are tiltable along with tilt of the operation lever; pulling wires connected to the at least two arms, respectively, and configured to move with tilt of the wire pulling member; a button connection member for a push button, the button connection member being disposed in a region between each two adjacent arms among the at least two arms in an adjacent direction of the two adjacent arms; and at least two pulleys including outer peripheral portions around which the pulling wires extended from the at least two arms are wound, respectively, the at least two pulleys being rotatable about predetermined rotation axes along with movement of the pulling wires, and each of the two pulleys with the button connection member being disposed in the region is disposed with a respective outer peripheral portion of the outer peripheral portions being tilted so that, in the adjacent direction, a first distance between one end part of the respective outer peripheral portion on a side closer to the two adjacent arms and an axis center of the button connection member is shorter than a second distance between another end part of the respective outer peripheral portion on a side farther from the two adjacent arms and the axis center. 
     An endoscope according to an aspect of the present invention is an endoscope including a bending operation mechanism, the bending operation mechanism including: an operation lever that is tiltable in a predetermined direction; a wire pulling member connected to the operation lever and including at least two arms that are tiltable along with tilt of the operation lever; pulling wires connected to the at least two arms, respectively, and configured to move with tilt of the wire pulling member; a button connection member for a push button, the button connection member being disposed in a region between each two adjacent arms among the at least two arms in an adjacent direction of the two adjacent arms; and at least two pulleys including outer peripheral portions around which the pulling wires extended from the at least two arms are wound, respectively, the at least two pulleys being rotatable about predetermined rotation axes along with movement of the pulling wires, and each of the two pulleys with the button connection member being disposed in the region is disposed with a respective outer peripheral portion of the outer peripheral portions being tilted so that, in the adjacent direction, a first distance between one end part of the respective outer peripheral portion on a side closer to the two adjacent arms and an axis center of the button connection member is shorter than a second distance between another end part of the respective outer peripheral portion on a side farther from the two adjacent arms and the axis center. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view illustrating appearance of an endoscope provided with a bending operation mechanism according to the present embodiment; 
         FIG. 2  is a side view of the endoscope in  FIG. 1  when viewed in II direction in  FIG. 1 ; 
         FIG. 3  is a partial top view of the endoscope in  FIG. 2  when viewed in III direction in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of a distal end portion and a bending portion of an insertion portion of the endoscope in  FIG. 1 , which is taken along line IV-IV in  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of the distal end portion along line V-V in  FIG. 4 ; 
         FIG. 6  is a perspective view schematically illustrating the bending operation mechanism provided in an operation portion in  FIG. 1 ; 
         FIG. 7  is an enlarged perspective view illustrating the bending operation mechanism in  FIG. 6 ; 
         FIG. 8  is a perspective view of a wire pulling member connected to an operation lever and pulling wires in the bending operation mechanism in  FIG. 7  when viewed in VIII direction in  FIG. 7 ; 
         FIG. 9  is a diagram illustrating the bending operation mechanism in  FIG. 7  in a state in which the operation lever is tilted in an up direction, when viewed in IX direction in  FIG. 7 ; 
         FIG. 10  is a diagram of the bending operation mechanism in  FIG. 9  when viewed in X direction in  FIG. 9 ; 
         FIG. 11  is a diagram illustrating a state in which the operation lever of the bending operation mechanism in  FIG. 9  is tilted in right and left directions; and 
         FIG. 12  is a diagram of the bending operation mechanism in  FIG. 11  when viewed in XII direction in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An embodiment of the present invention will be described below with reference to the accompanying drawings. 
       FIG. 1  is a front view illustrating appearance of an endoscope provided with a bending operation mechanism according to the present embodiment,  FIG. 2  is a side view of the endoscope in  FIG. 1  when viewed in II direction in  FIG. 1 , and  FIG. 3  is a partial top view of the endoscope in  FIG. 2  when viewed in III direction in  FIG. 2 . 
       FIG. 4  is a cross-sectional view of a distal end portion and a bending portion of an insertion portion of the endoscope in  FIG. 1 , which is taken along line IV-IV in  FIG. 1 ,  FIG. 5  is a cross-sectional view of the distal end portion along line V-V in  FIG. 4 , and  FIG. 6  is a perspective view schematically illustrating a bending operation mechanism provided in an operation portion in  FIG. 1 . 
       FIG. 7  is an enlarged perspective view illustrating the bending operation mechanism in  FIG. 6 , and  FIG. 8  is a perspective view of a wire pulling member connected to an operation lever and pulling wires in the bending operation mechanism in  FIG. 7  when viewed in VIII direction in  FIG. 7 . 
     As illustrated in  FIGS. 1 and 2 , an endoscope  1  is, for example, an endoscope for bronchi. The endoscope  1  has a main part including an insertion portion  2  formed in an elongated shape, an operation portion  3  provided continuously with a proximal end of the insertion portion  2  in a longitudinal axial direction N, an universal code  4  extended from the operation portion  3 , and an endoscope connector  5  provided at an extension end of the universal code  4 . 
     The insertion portion  2  has a main part including, sequentially from a distal end side in the longitudinal axial direction N, a distal end portion  6 , a bending portion  7 , and a flexible tube portion  8  and is formed as a tubal member having flexibility. 
     The operation portion  3  has a main part including a folding prevention portion  30  connected to the flexible tube portion  8  and covering a proximal end of the flexible tube portion  8  in the longitudinal axial direction N, a grasping portion  31  that is provided continuously with the folding prevention portion  30  and can be grasped by a hand of an operator, and an operation portion body  32  continuously provided on the proximal end side of the grasping portion  31  in the longitudinal axial direction N. 
     Note that, in the present embodiment, for example, a direction about an insertion axis O in the operation portion  3  is defined with reference to a state in which the operator grasps the grasping portion  31 . Specifically, front, back, right, and left directions (for example, a front surface, a back surface, and right and left side surfaces) of the operation portion  3  are defined with reference to the operator grasping the grasping portion  31 . 
     As illustrated in  FIG. 1 , the grasping portion  31  of the operation portion  3  is formed in a shape that is symmetric in the right and left directions with respect to the insertion axis O (central axis), and can be grasped by the operator with any of left and right hands. 
     A right-left shape of the operation portion body  32  of the operation portion  3  in  FIG. 1  is formed as a shape bulged symmetrically in the right and left directions with respect to the insertion axis O. 
     A treatment instrument insertion portion  35  is provided at a front surface of the grasping portion  31  on the distal end side in the longitudinal axial direction N in  FIG. 1 . The treatment instrument insertion portion  35  has a treatment instrument insertion opening  35   a  through which various treatment instruments (not illustrated) are inserted. 
     The treatment instrument insertion opening  35   a  communicates with a treatment instrument insertion channel  13  (refer to  FIG. 4 ) inside the operation portion  3 . In addition, a forceps plug (not illustrated) as a lid member for blocking the treatment instrument insertion opening  35   a  is removably attached to the treatment instrument insertion portion  35 . 
     The operation portion body  32  is formed as a hollow member bulged mainly on right, left, and front sides in  FIG. 1  and substantially having a partially spherical shape on the proximal end side of the grasping portion  31  in the longitudinal axial direction N. An operation button group  40  for executing various kinds of functions of the endoscope  1  is disposed on the front surface side of the operation portion body  32  in  FIG. 1 . 
     The operation button group  40  includes, for example, a suction button  41  removably mounted on the operation portion body  32  and formed as a push button, and two button switches  42  to which any functions can be allocated from among various kinds of functions related to the endoscope  1 . 
     As illustrated in  FIG. 1 , the suction button  41  is disposed at a center of the operation portion body  32  in a right-left width direction in  FIG. 1  so that the suction button  41  overlaps the insertion axis O. 
     The two button switches  42  are disposed on the distal end side of the suction button  41  in the longitudinal axial direction N at positions that are symmetric in the right and left directions with respect to the insertion axis O. 
     As illustrated in  FIGS. 2 and 3 , an operation lever  45  in a bending operation mechanism  70  (refer to  FIG. 6 ) according to the present embodiment for performing a bending operation on the bending portion  7  is disposed on the back surface side of the operation portion body  32  in  FIG. 1  so that the operation lever  45  is tiltable in a predetermined direction. 
     As for the tilt direction of the operation lever  45 , as illustrated in  FIG. 3 , for example, right and left directions of the tilt direction of the operation lever  45  are defined to be the left direction and the right direction as a third direction and a fourth direction of the operation portion  3 , respectively, which are orthogonal to the insertion axis O, and up and down directions of the tilt direction of the operation lever  45  are defined to be the up direction and the down direction as a first direction and a second direction of the operation portion  3 , respectively, which are orthogonal to the right and left directions. 
     More specifically, as for the tilt direction of the operation lever  45 , for example, the left side in  FIG. 3  is defined as a left tilt direction for bending the bending portion  7  to the left side, the right side in  FIG. 3  is defined as a right tilt direction for bending the bending portion  7  to the right side, the lower side in  FIG. 3  is defined as an up tilt direction for bending the bending portion  7  to the upper side, and the upper side in  FIG. 3  is defined as a down tilt direction for bending the bending portion  7  to the lower side. 
     In other words, in the present embodiment, the operation lever  45  is tiltable in any of the four directions of the up, down, right, and left directions. The operation lever  45  is also tiltable in a combined direction of any two of the four directions of the up, down, right, and left directions. 
     The operation lever  45  is provided with a finger contact portion  46  with which a thumb of the operator or the like can be made contact. 
     As illustrated in  FIG. 3 , the universal code  4  is extended from a left side part of the operation portion body  32 . The universal code  4  is a composite cable that reaches the operation portion  3  on the distal end portion  6  side through inside of the insertion portion  2 , in which various signal lines and the like extended from the operation portion  3  are inserted, in which light guides  12  of a light source device (not illustrated) are inserted, and in which an air-water feeding tube extended from an air-water feeding device (not illustrated) is inserted. 
     The endoscope connector  5  includes, at a side surface part, an electric connector portion  5   a  to which a signal cable electrically connected to a video processor (not illustrated) as an external instrument is connected, and also includes a light source connector portion  5   b  connected to a light source device as an external instrument. 
     As illustrated in  FIGS. 4 and 5 , a distal end rigid portion  10  made of metal is provided in the distal end portion  6  and holds distal end sites of an image pickup unit  11 , a pair of the light guides  12 , the treatment instrument insertion channel  13 , and the like in the longitudinal axial direction N, the image pickup unit  11  being including an image pickup device such as a CCD or a CMOS. 
     In the distal end portion  6 , a leading distal end bending piece  20  having a substantially cylindrical shape is externally fitted on the proximal end side of the distal end rigid portion  10  in the longitudinal axial direction N, and an outer periphery of the leading distal end bending piece  20  is covered by a bending rubber  22 . 
     As illustrated in  FIG. 5 , wire fixation portions  21  are provided on an inner periphery of the leading distal end bending piece  20  at four places in the direction about the insertion axis O, and distal ends of four pulling wires  23   a  to  23   d  in the longitudinal axial direction N are fixed to the wire fixation portions  21 , respectively, the pulling wires  23   a  to  23   d  being inserted in the insertion portion  2  in the longitudinal axial direction N. 
     In order to efficiently dispose constituent members without increasing the diameter of the distal end portion  6 , as illustrated in  FIG. 5 , distal end sites of the image pickup unit  11  and the treatment instrument insertion channel  13  as large-sized members in the longitudinal axial direction N are arranged in the right and left directions in the distal end rigid portion  10  and the leading distal end bending piece  20 , and the distal end sites of the light guides  12  in the longitudinal axial direction N are disposed in spaces formed in the up and down directions, respectively, due to the arrangement. 
     In order to avoid interference of the distal end sites of the image pickup unit  11  and the treatment instrument insertion channel  13  in the longitudinal axial direction N with the pulling wires  23   a  to  23   d , the wire fixation portions  21  are provided at positions rotationally shifted in the direction about the insertion axis O by a predetermined angle from positions on the distal end portion  6  in the up, down, right, and left directions. 
     For example, as illustrated in  FIG. 5 , the wire fixation portions  21  are provided to the leading distal end bending piece  20  at positions rotationally shifted to right and left in the direction about the insertion axis O by 30° to 60° from the position on the distal end portion  6  in the up direction and at positions rotationally shifted to right and left in the direction about the insertion axis O by 30° to 60° from the position on the distal end portion  6  in the down direction. 
     The bending portion  7  can be actively and selectively bent in any of the up, down, right, and left directions and a combined direction of two of the up, down, right, and left directions in accordance with an operation input to the operation portion  3  by the operator. 
     Specifically, as illustrated in  FIG. 4 , the bending portion  7  is formed of a plurality of bending pieces  25  coupled to each other in the longitudinal axial direction N through pivot portions  25   a  and  25   b  alternately, the pivot portions  25   a  being disposed at positions on the insertion portion  2  in the up and down directions, the pivot portions  25   b  being disposed at positions on the insertion portion  2  in the right and left directions. 
     A signal cable  11   a , the light guides  12 , and the treatment instrument insertion channel  13  extending from the image pickup unit  11  are inserted inside the plurality of bending pieces  25  in substantially the same disposition as disposition in the distal end portion  6 . 
     Wire guides (not illustrated) into which the respective pulling wires  23   a  to  23   d  are inserted are formed at predetermined bending pieces  25  at substantially the same positions in the direction about the insertion axis O as positions of the above-described wire fixation portions  21 . Outer peripheries of the plurality of bending pieces  25  are covered by the bending rubber  22  extending from the distal end portion  6  side. 
     The flexible tube portion  8  is formed as a tubal member that is flexible and passively bendable. The signal cable  11   a , the light guides  12 , and the treatment instrument insertion channel  13  (all not illustrated in  FIG. 5 ) described above are inserted inside the flexible tube portion  8 . 
     As illustrated in  FIG. 6 , the bending operation mechanism  70  is provided inside the operation portion body  32 . 
     As illustrated in  FIGS. 6 to 8 , the bending operation mechanism  70  has a main part including a housing  51 , the operation lever  45 , a wire pulling member  54 , the pulling wires  23   a  to  23   d  extended in the longitudinal axial direction N in the insertion portion  2  and the operation portion  3 , a cylinder  43  as a button connection member for the suction button  41 , and four pulleys  68   a  to  68   d.    
     As described above, the operation lever  45  is formed as a joystick-type lever tiltable in any of the up, down, right, and left directions or a combined direction of any two directions of the up, down, right, and left directions. 
     Specifically, as illustrated in  FIG. 6 , the operation lever  45  has a main part including a shaft  44 , a base member  53  connected to one end of the shaft  44  in an extension direction E in the housing  51  formed in a substantially cylindrical shape, and the finger contact portion  46  connected to the other end of the shaft  44  in the extension direction E. 
     As illustrated in  FIG. 8 , the wire pulling member  54  is formed in an X plane shape with four arms  54   b   1 ,  54   b   2 ,  54   b   3 , and  54   b   4 , and the base member  53  of the operation lever  45  is fixed to a center  54   a  by a screw or the like. Note that the wire pulling member  54  may be formed in a cross plane shape. 
     With this configuration, the arms  54   b   1  to  54   b   4  of the wire pulling member  54  are tiltable in the tilt direction of the operation lever  45  in cooperation with tilt of the operation lever  45 . 
     Note that detailed tilt configurations of the operation lever  45  and the wire pulling member  54  are well known, and thus description of the configurations will be omitted. The wire pulling member  54  may be formed integrally with the operation lever  45 . 
     As illustrated in  FIGS. 6 and 8 , the arms  54   b   1  to  54   b   4  are disposed at positions rotationally shifted in a direction about a central axis O 1  of the operation lever  45  by 30° to 60° (for example, 45°) from respective positions in the up, down, right, and left tilt directions defined for the operation lever  45 . With this configuration, the wire pulling member  54  is formed in the X plane shape. 
     Wire fixation holes  54   c   1 ,  54   c   2 ,  54   c   3 , and  54   c   4  are drilled at sides of the respective arms  54   b   1  to  54   b   4  farther from the center  54   a.    
     As illustrated in  FIG. 8 , a proximal end of the pulling wire  23   a  in the longitudinal axial direction N is connected to the wire fixation hole  54   c   1 . A proximal end of the pulling wire  23   b  in the longitudinal axial direction N is connected to the wire fixation hole  54   c   2 . A proximal end of the pulling wire  23   c  in the longitudinal axial direction N is connected to the wire fixation hole  54   c   3 . A proximal end of the pulling wire  23   d  in the longitudinal axial direction N is connected to the wire fixation hole  54   c   4 . 
     The pulling wires  23   a  to  23   d  move in the longitudinal axial direction N and the extension direction E with tilt of the wire pulling member  54 . 
     As illustrated in  FIG. 7 , two pulleys  68   a  and  68   b  pivotally supported to a rotation shaft  71  in the operation portion body  32  are engaged at halfway positions on the pulling wires  23   a  and  23   b , respectively. Two pulleys  68   c  and  68   d  pivotally supported to a rotation shaft  72  in the operation portion body  32  are engaged at halfway positions on the pulling wires  23   c  and  23   d , respectively. 
     The pulleys  68   a  to  68   d  change, from the extension direction E to the longitudinal axial direction, directions of the pulling wires  23   a  to  23   d  extended from the respective arms  54   b   1  to  54   b   4  and wound around respective outer peripheral portions  68   ag ,  68   bg ,  68   cg , and  68   dg  (the outer peripheral portions  68   cg  and  68   dg  are not illustrated), and are rotatable about the predetermined rotation shafts  71  and  72  with rotation centers at the rotation shafts  71  and  72  along with movement of the pulling wires  23   a  to  23   d.    
     In such a configuration, for example, when the operator grasps the grasping portion  31  of the operation portion  3  and tilts the operation lever  45  in the left tilt direction with the thumb of a grasping hand, mainly the two pulling wires  23   b  and  23   d  coupled to the two arms  54   b   2  and  54   b   4  positioned in the right tilt direction are pulled and loosened. The bending portion  7  is bent to the left side by the pulling of the two pulling wires  23   b  and  23   d.    
     For example, when the operator grasps the grasping portion  31  of the operation portion  3  and tilts the operation lever  45  in the right tilt direction with the thumb of a grasping hand, mainly the two pulling wires  23   a  and  23   c  coupled to the two arms  54   b   1  and  54   b   3  positioned in the left tilt direction are pulled and loosened. The bending portion  7  is bent to the right side by the pulling of the two pulling wires  23   a  and  23   c.    
     For example, when the operator grasps the grasping portion  31  of the operation portion  3  and tilts the operation lever  45  in the down tilt direction with the thumb of a grasping hand, mainly the pulling wires  23   c  and  23   d  coupled to the two arms  54   b   3  and  54   b   4  positioned in the up tilt direction are pulled and loosened. The bending portion  7  is bent to the lower side by the pulling of the two pulling wires  23   c  and  23   d.    
     For example, when the operator grasps the grasping portion  31  of the operation portion  3  and tilts the operation lever  45  in the up tilt direction with the thumb of a grasping hand, mainly the pulling wires  23   a  and  23   b  coupled to the two arms  54   b   1  and  54   b   2  positioned in the down tilt direction are pulled and loosened. The bending portion  7  is bent to the upper side by the pulling of the two pulling wires  23   a  and  23   b.    
     For example, when the operator grasps the grasping portion  31  of the operation portion  3  and tilts the operation lever  45  in a lower-left tilt direction with the thumb of a grasping hand, mainly the pulling wire  23   d  coupled to the one arm  54   b   4  positioned in an upper-right tilt direction is pulled and loosened. The bending portion  7  is bent to a lower-left side by the pulling of the pulling wire  23   d.    
     For example, when the operator grasps the grasping portion  31  of the operation portion  3  and tilts the operation lever  45  in a lower-right tilt direction with the thumb of a grasping hand, mainly the pulling wire  23   c  coupled to the one arm  54   b   3  positioned in an upper-left tilt direction is pulled and loosened. The bending portion  7  is bent to a lower-right side by the pulling of the pulling wire  23   c.    
     For example, when the operator grasps the grasping portion  31  of the operation portion  3  and tilts the operation lever  45  in the upper-left tilt direction with the thumb of a grasping hand, mainly the pulling wire  23   b  coupled to the one arm  54   b   2  positioned in the lower-right tilt direction is pulled and loosened. The bending portion  7  is bent to an upper-left side by the pulling of the pulling wire  23   b.    
     For example, when the operator grasps the grasping portion  31  of the operation portion  3  and tilts the operation lever  45  in the upper-right tilt direction with the thumb of a grasping hand, mainly the pulling wire  23   a  coupled to the one arm  54   b   1  positioned in the lower-left tilt direction is pulled and loosened. The bending portion  7  is bent to an upper-right side by the pulling of the pulling wire  23   a.    
     The suction button  41  is removably attached to the cylinder  43 , and similarly to the suction button  41 , and the cylinder  43  is disposed at the center of the operation portion body  32  in the right-left width direction so that the cylinder  43  overlaps the insertion axis O. 
     Accordingly, for example, as illustrated in  FIG. 6 , the cylinder  43  is disposed in a region B 1  (refer to  FIG. 9 ) to be described later between the two arms  54   b   1  and  54   b   2  of the wire pulling member  54  in an adjacent direction B of the two arms  54   b   1  and  54   b   2 . 
     Subsequently, a detailed disposition position of the cylinder  43  and detailed disposition positions and angles of the two pulleys  68   a  and  68   b  will be described below with reference to  FIGS. 9 to 12 . 
       FIG. 9  is a diagram illustrating the bending operation mechanism in  FIG. 7  in a state in which the operation lever is tilted in the up direction, when viewed in IX direction in  FIG. 7 , and  FIG. 10  is a diagram of the bending operation mechanism in  FIG. 9  when viewed in X direction in  FIG. 9 . 
       FIG. 11  is a diagram illustrating a state in which the operation lever of the bending operation mechanism in  FIG. 9  is tilted in the right and left directions, and  FIG. 12  is a diagram of the bending operation mechanism in  FIG. 11  when viewed in XII direction in  FIG. 11 . 
     As illustrated in  FIGS. 9 and 11 , the pulleys  68   a  and  68   b  are disposed on both sides of the cylinder  43  in the adjacent direction B. 
     As illustrated in  FIGS. 9 and 11 , the cylinder  43  is disposed in the region B 1  between the two arms  54   b   1  and  54   b   2  of the wire pulling member  54  in the adjacent direction B of the two arms  54   b   1  and  54   b   2 . 
     As illustrated in  FIGS. 9 and 11 , the pulleys  68   a  and  68   b  are disposed with the predetermined rotation shaft  71  tilted so that an extended line of the predetermined rotation shaft  71  intersects with the cylinder  43 . 
     More specifically, the pulleys  68   a  and  68   b  are disposed at positions on a rotation trajectory K 1  formed by the arms  54   b   1  and  54   b   2  with a rotation center at the central axis O 1  of the operation lever  45  as illustrated in  FIG. 10  when the operation lever  45  is tilted closer to the cylinder  43 , in other words, is tilted in the down direction, the positions being separated from the two arms  54   b   1  and  54   b   2  in a direction of the rotation trajectory K 1  and the adjacent direction B. 
     As illustrated in  FIGS. 9 and 11 , each of the pulleys  68   a  and  68   b  is disposed with the corresponding one of the outer peripheral portions  68   ag  and  68   bg  tilted so that, in the adjacent direction B, a first distance B 2  between one end part  68   ai  or  68   bi  of the corresponding one of the outer peripheral portions  68   ag  and  68   bg  positioned on a side closer to the arms  54   b   1  and  54   b   2  in the extension direction E and an axis center J of the cylinder  43  is shorter than a second distance B 3  between the other end part  68   aj  or  68   bj  of the corresponding one of the outer peripheral portions  68   ag  and  68   bg  positioned on a side farther from the arms  54   b   1  and  54   b   2  in the extension direction E and the axis center J of the cylinder  43  (B 2 &lt;B 3 ). 
     Note that, as illustrated in  FIGS. 11 and 12 , a tilt angle of the pulley  68   a  as one of the two pulleys  68   a  and  68   b  disposed with the outer peripheral portions  68   ag  and  68   bg  being tilted aligns with a tangent line direction V of a circular rotation trajectory K 2  formed by the arms  54   b   1  and  54   b   2  with a rotation center at the central axis O 1  of the operation lever  45  at a maximum tilt angle θ 1  of the operation lever  45  in the right direction. A tilt angle of the other pulley  68   b  aligns with a tangent line direction W of the circular rotation trajectory K 2  of the operation lever  45  at a maximum tilt angle θ 2  of the operation lever in the left direction. 
     Note that the other configuration of the bending operation mechanism  70  is same as that in conventional cases, and thus description thereof will be omitted. 
     As described above, in the present embodiment, the pulleys  68   a  and  68   b  are disposed on both sides of the cylinder  43  in the adjacent direction B in the bending operation mechanism  70  provided in the operation portion body  32 . 
     As described above, the cylinder  43  is disposed in the region B 1  between the two arms  54   b   1  and  54   b   2  of the wire pulling member  54  in the adjacent direction B of the two arms  54   b   1  and  54   b   2 . 
     As described above, the pulleys  68   a  and  68   b  are disposed at positions on the rotation trajectory K 1  formed by the arms  54   b   1  and  54   b   2  when the operation lever  45  is tilted closer to the cylinder  43 , in other words, is tilted in the down direction, the positions being separated from the two arms  54   b   1  and  54   b   2  in the direction of the rotation trajectory K 1  and the adjacent direction B. 
     As described above, as illustrated in  FIGS. 9 and 11 , each of the pulleys  68   a  and  68   b  is disposed with the corresponding one of the outer peripheral portions  68   ag  and  68   bg  being tilted so that, in the adjacent direction B, the first distance B 2  between the one end part  68   ai  or  68   bi  of the corresponding one of the outer peripheral portions  68   ag  and  68   bg  and the axis center J of the cylinder  43  is shorter than the second distance B 3  between the other end part  68   aj  or  68   bj  and the axis center J of the cylinder  43  (B 2 &lt;B 3 ). 
     With these configurations, in order to achieve size reduction of the operation portion  3 , the pulleys  68   a  and  68   b  are disposed at a tilt as described above although the cylinder  43  is disposed in the region B 1  between the two pulleys  68   a  and  68   b.    
     Thus, it is possible to dispose the pulleys  68   a  and  68   b  without interference with tilt of the cylinder  43  and the arms  54   b   1  and  54   b   2  and reduce an interval between the pulleys  68   a  and  68   b  on both sides of the cylinder  43  in the adjacent direction B, thereby further achieving size reduction of the operation portion  3 . 
     In the present embodiment described above, the tilt angle of the pulley  68   a  as one of the two pulleys  68   a  and  68   b  aligns with the tangent line direction V of the circular rotation trajectory K 2  of the operation lever  45  at the maximum tilt angle θ 1  of the operation lever  45  in the right direction, and the tilt angle of the other pulley  68   b  aligns with the tangent line direction W of the circular rotation trajectory K 2  of the operation lever  45  at the maximum tilt angle θ 2  of the operation lever in the left direction. 
     With these configurations, when the operation lever  45  is tilted to the maximum angle in the right direction or the left direction, the tilt angles of the outer peripheral portions  68   ag  and  68   bg  of the pulleys  68   a  and  68   b  align with the tangent line directions V and W of the rotation trajectory K 2 . Accordingly, a pulling loss of the outer peripheral portions  68   ag  and  68   bg  when passing through the pulleys  68   a  and  68   b  for the pulling wires  23   a  and  23   b  is small. 
     Note that the above-described loss of the wires  23   a  and  23   b  along with tilt of the operation lever  45  in the up and down directions cannot be reduced by tilting the pulleys  68   a  and  68   b . However, the above-described wire pulling loss can be minimized by, in addition to the above-described condition, disposing the pulleys  68   a  and  68   b  with the outer peripheral portions  68   ag  and  68   bg  at appropriate positions in the longitudinal axial direction N, specifically, positions directly below the wire fixation holes  54   c   1  and  54   c   2  at a maximum tilt position of the operation lever  45  in the up and down directions as illustrated in  FIGS. 9 and 11 . 
     With the above-described configuration, since the pulling loss of the pulling wires  23   a  and  23   b  is small, it is possible to avoid a heavy tilt operation of the operation lever  45  due to a large amount of pulling force for pulling the pulling wires  23   a  and  23   b  and avoid small pulling amounts of the pulling wires  23   a  and  23   b  when the operation lever  45  is tilted by an angle same as that in conventional cases. 
     Note that, as illustrated in  FIG. 8 , when the wire pulling member  54  has an X plane shape, a length (rotation radius) α from the central axis O 1  to the arms  54   b   1  and  54   b   2  in the up and down tilt directions is longer than a length (rotation radius) β in the right and left tilt directions (α&gt;β), and accordingly, the rotation trajectory K 1  in the up and down directions with a rotation center at the central axis O 1  of the operation lever  45  is longer than the rotation trajectory K 2  in the right and left directions as illustrated in  FIGS. 9 and 11 . In other words, the operation lever  45  has a smaller tilt amount in the right and left directions than in the up and down directions. 
     Thus, it is understood that a tilt operation of the operation lever  45  in the right and left directions has larger influence on the above-described wire pulling loss due to the tilt operation than a tilt operation in the up and down directions. 
     In other words, it is understood that, when a wire pulling loss is generated by a tilt operation of the operation lever  45  in the up and down directions due to tilt of the pulleys  68   a  and  68   b , the influence of the tilt operation is smaller than the influence of the tilt operation in the right and left directions because of α&gt;β. 
     With the above-described configurations, it is possible to provide the bending operation mechanism  70  for the endoscope, which has a configuration that achieves size reduction of the operation portion  3  of the endoscope  1  without loss generation in the amount of pulling force on the pulling wires  23   a  and  23   b  along with tilt of the operation lever  45  in the configuration in which the cylinder  43  is disposed in the region between the two pulleys  68   a  and  68   b.    
     A modification will be described below. As illustrated in  FIGS. 11 and 12 , when the operation lever  45  is tilted in the right and left directions, tension that would cause deviation from the outer peripheral portions  68   ag  and  68   bg  of the pulleys  68   a  and  68   b  to a side farther from the cylinder  43  in the adjacent direction B is applied to the pulling wires  23   a  and  23   b.    
     This is because the pulling wires  23   a  and  23   b  are likely to violently move at the outer peripheral portions  68   ag  and  68   bg  along with pulling and loosening since the operation lever  45  has a larger tilt amount, in other words, a larger pulling amount in the up and down directions than in the right and left directions as described above. 
     Thus, in order to prevent removal of the pulling wires  23   a  and  23   b  from the outer peripheral portions  68   ag  and  68   bg , removal prevention flanges for the pulling wires  23   a  and  23   b  may be provided at outer peripheral edge portions  68   ah  and  68   bh  of the outer peripheral portions  68   ag  and  68   bg  on the side farther from the cylinder  43 . 
     Although the above description of the present embodiment is made with the example in which the number of arms of the wire pulling member  54  is four, the number of pulling wires is four, and the number of pulleys is four, the present embodiment is not limited to the configuration described above but is applicable to a configuration in which the numbers are at least two. 
     Although the above description is made with the example in which the connection portion for a push button is the cylinder  43  connected to the suction button  41 , it goes without saying that the present embodiment is not limited to the configuration described above but is also applicable to a connection portion for any other electric button or any other push button such as a button of an engagement mechanism or an angle lock button of the bending portion  7 . 
     Although the above description is made with the example in which the endoscope  1  is an endoscope for bronchi, it goes without saying that the present embodiment is not limited to the configuration described above but is also applicable to any other endoscope.