Flexible tube insertion apparatus

An flexible tube insertion apparatus includes a tubular insertion section including a bending portion and a flexible tube portion, variable stiffness sections to cause a change in a level of a bending stiffness of the flexible tube portion, a variable stiffness control section that controls the change in the bending stiffness by the variable stiffness sections; and a time setting section that sets a time period. The variable stiffness control section causes the bending stiffness of the variable stiffness sections to change in such a manner that the relationship of levels between the bending stiffness of adjacent variable stiffness sections is switched at the set time period when the variable stiffness control section determines that the flexible tube portion is passing through a flexure of the subject.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flexible tube insertion apparatus comprising an insertion section including a bending portion located distally on the insertion section and a flexible tube portion located proximal to the bending portion.

2. Description of the Related Art

The large intestine roughly consists of the rectum, the colon, and the cecum from the side of the anus. The colon further consists of the sigmoid colon, the descending colon, the transverse colon, and the ascending colon from the rectum side. Normally, the sigmoid colon and the transverse colon are not fixed in the abdomen, and have freedom of movement. When a flexible, elongated insertion section of a flexible tube insertion apparatus (e.g., an endoscope apparatus) is inserted into such an intestinal tract, the insertion section bends along the intestinal wall while passing through the intestinal tract. However, as the insertion section is further advanced from the hand side, the flexible insertion section may be bent in a direction different from the direction in which the force is applied in the intestine, preventing the distal end of the insertion section from passing smoothly. To address such a problem, a technique for facilitating transmission of a force to the direction in which the insertion section should desirably be inserted by increasing the bending stiffness of the insertion section is known. This is implemented either by increasing the bending stiffness of the insertion section itself, or by attaching a member different from the insertion section, such as an overtube (sliding tube), to the insertion section.

However, when the bending stiffness of the entire insertion section is uniformly changed, the stiffness cannot be changed according to the bending state of the insertion section inside the intestinal tract. Accordingly, the insertion section may be stuck in, for example, the sigmoid colon and excessively extend the sigmoid colon, causing distress to the patient. Such an insertion section is inconvenient for insertion into a deep portion.

Jpn. Pat. Appln. KOKOKU Publication No. 61-37931 discloses an endoscope comprising an insertion section including an elongated, flexible tube portion divided into a plurality of areas in the longitudinal direction to cause the areas to have different levels of flexibility. In the endoscope, having different levels of flexibility at the areas of the flexible tube portion allows distress at a patient during insertion to be reduced, thus the ease of insertion is improved.

BRIEF SUMMARY OF THE INVENTION

According to one embodiment of the present invention, an flexible tube insertion apparatus comprises an insertion section to be inserted into a subject and including a bending portion located distally on the insertion section, and a flexible tube portion proximal to the bending portion; a plurality of variable stiffness sections each provided in a corresponding one of a plurality of segments defined in a longitudinal axis direction of the flexible tube portion and configured to cause a change in a level of a bending stiffness of the flexible tube portion on a segment-by-segment basis; a variable stiffness control section that controls the change in the bending stiffness of the flexible tube portion by the variable stiffness sections; and a time setting section that sets a time period at which the bending stiffness is changed by the variable stiffness sections, wherein the variable stiffness control section controls the changes in the bending stiffness of each of the variable stiffness sections in such a manner that the relationship of levels between the bending stiffness of adjacent variable stiffness sections is switched at the time period set by the time setting section when the variable stiffness control section determines that the flexible tube portion is passing through a flexure of the subject based on a bending shape of the bending portion acquired from a shape acquisition section that acquires the bending shape of the bending portion.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

FIG. 1is a diagram schematically showing a configuration of an endoscope apparatus1, which is a flexible tube insertion apparatus. The endoscope apparatus1comprises an endoscope10, a light source device20, a controller30, and a display device40.

The endoscope10includes a tubular insertion section11to be inserted into a subject, and an operation section14located proximal to the insertion section11. The endoscope10is, for example, a colonoscope. That is, the subject is the large intestine (intestinal tract).

The insertion section11includes a bending portion12located distally on the insertion section11and a flexible tube portion13located proximal to the bending portion12. The bending portion12incorporates, for example, an illumination optical system (illumination window), an observation optical system (observation window), and an image sensor, which are not shown in the drawings. The flexible tube portion13is an elongated tube that is bendable and flexible.

The operation section14is the portion of the endoscope10that is gripped by the user, as shown inFIG. 1. The operation section14includes an angle knob15, which is a bending operation section. The angle knob15is coupled to the bending portion12via an angle wire16(not shown inFIG. 1), which has at least one pulling member inserted through the insertion section11in its longitudinal direction (axial direction).FIG. 2shows the angle wire16extending from the bending portion12to the flexible tube portion13inside the insertion section11along its inner surface. A distal end of the angle wire16is fixed to the bending portion12. When the user rotates the angle knob15, the angle wire16coupled thereto is moved, causing the bending portion12to be bent in a desired direction. Let us assume, for example, that two angle wires are vertically arranged relative to the central axis of the insertion section11to maintain a 180-degree positional relationship. In this case, when one of the angle wires is pulled in by the user's rotation of the angle knob15, the bending portion12is bent in an upward direction, and when the other angle wire is pulled in, the bending portion12is bent in a downward direction.

A shape acquisition section50, which acquires the bending shape (the bend angle, etc.) of the bending portion12, is provided at the operation section14. The shape acquisition section50includes, for example, a rotary encoder whose axis of rotation is attached to the axis of rotation of the angle knob15. The rotary encoder is a rotation angle sensor that converts a displacement in rotation angle into an electric signal and outputs the electric signal. By thus detecting the rotation angle, the rotation amount, or the rotation position of the angle knob15, the shape acquisition section50acquires the bending shape of the bending portion12. The shape acquisition section50is not limited to a rotary encoder. The shape acquisition section50may be configured to acquire the bending shape of the bending portion12by a detection method of detecting an amount of movement of the angle wire16that pulls the bending portion12and calculating the bending state of the bending portion12.

FIG. 2is an enlarged view schematically showing the bending portion12and the flexible tube portion13. For convenience, let us assume that the flexible tube portion13comprises a plurality of continuous segments (virtual units into which the flexible tube portion13is evenly divided as viewed in the longitudinal direction) defined in the longitudinal axis direction thereof. InFIG. 2, segments131,132,133, . . . , and13nof the flexible tube portion13are shown. A variable stiffness section60is provided in each of the segments. The variable stiffness section60is a variable stiffness actuator that allows to change the bending stiffness of the flexible tube portion13on a segment-by-segment basis.

Referring back toFIG. 1, the endoscope10is connected to the light source device20via a universal cord17extending proximally from the operation section14. The universal cord17includes a light guide (optical fiber) connected to the illumination optical system, an electric cable connected to the image sensor, a variable stiffness section control signal cable, a shape acquisition section signal cable, etc. The light source device20supplies light to be emitted from the illumination window in the distal end surface of the bending portion12via the light guide.

The controller30is formed of a device including a CPU and the like. The controller30includes a display control section31including an image processing section32, and a variable stiffness control section33. The display control section31is connected to the electric cable in the universal cord17via a cable71, and thus connected to the endoscope10(the image sensor in the bending portion12). The display control section31is also connected to the display device40via a cable72. The variable stiffness control section33is connected to the variable stiffness section60via the cable71and the variable stiffness section control signal cable included in the universal cord17. The variable stiffness control section33is connected to the shape acquisition section50via the cable71and the shape acquisition section signal cable included in the universal cord17.

FIG. 3is a diagram schematically showing an example of a configuration of the variable stiffness section60. The variable stiffness section60includes a coil pipe61formed of a metal wire, an electroactive polymer artificial muscle (EPAM)62encapsulated in the coil pipe61, and electrodes63provided on both ends of the coil pipe61. The variable stiffness section60is connected to the variable stiffness control section33, and thus a voltage may be applied from the variable stiffness control section33to the EPAM62in the coil pipe61via the electrodes63. The EPAM62is an actuator that extends and contracts when a voltage is applied and changes its stiffness. The variable stiffness section60is incorporated into the flexible tube portion13in such a manner that the central axis of the coil pipe61coincides with or is parallel to the central axis of the flexible tube portion13.

The electrodes63(the EPAM62) of the variable stiffness section60are applied with a voltage from the variable stiffness control section33via the cable71and the electric cable in the universal cord17. When such a voltage is applied, the EPAM62tends to extend its diameter with the central axis of the coil pipe61at its center. However, the EPAM62is surrounded by the coil pipe61, and is restrained from extending its diameter. Accordingly, the bending stiffness of the variable stiffness section60increases as the value of the applied voltage increases, as shown inFIG. 4. That is, when the variable stiffness control section33changes the voltage applied to the variable stiffness section60, the stiffness of the variable stiffness section60changes, and the bending stiffness of the flexible tube portion13incorporating the variable stiffness section60also changes.

The above-described configuration of the variable stiffness section60is merely an example. The variable stiffness section60is not limited to the one using the EPAM62, and may have any configuration that allows the bending stiffness to be changed in response to a control signal from the variable stiffness control section33.

Next, the operation of the endoscope apparatus1, which is colonoscopy in this case, will be described.

Let us assume that, at the start of insertion, the flexible tube portion13has a predetermined bending stiffness value that is neither the minimum bending stiffness value nor the maximum bending stiffness value of the variable stiffness section60. That is, each segment of the flexible tube portion13may be stiffened or softened, compared to the state at the start of insertion, by causing the bending stiffness of the variable stiffness section60to change in response to the control signal from the variable stiffness control section33.

The insertion section11of the endoscope10is inserted by the user into an intestinal tract, which is a subject to be examined (from the anus through the rectum into the colon). The insertion section11passes through the intestinal tract while bending to follow the shape inside of the intestinal tract. An optical image of the observation target acquired by the observation optical system on the distal end surface of the bending portion12is converted into an electric signal by the image sensor. The electric signal is output to the display control section31of the controller30. The display control section31causes the image processing section32to generate an image signal of the observation target on the basis of the output electric signal. The display control section31then causes the display device40to display an image of the observation target on the basis of the generated image signal.

FIGS. 5 and 6schematically show an example of the insertion section11inserted into the large intestine. At first, the bending portion12located distally on insertion section11is in a substantially straight state and passes through a substantially straight area in an intestinal tract100. When the bending portion12reaches a flexure101(e.g., the sigmoid colon) in the intestinal tract100, the bending portion12passes while bending to follow the shape of the curvature of the flexure101, as shown inFIG. 5. When the bending portion12passes through the flexure101, the bending portion12is bent along the shape of the flexure101either by causing the angle knob15of the operation section14to rotate by user, or by applying an external force. Accordingly, the bending portion12is necessarily bent when the bending portion12passes through the flexure101.

When the bending portion12further advances and has passed through the flexure101, the flexible tube portion13reaches the flexure101, as shown inFIG. 6. At this time, the bending portion12, which has already passed through the flexure101, has substantially straight to follow the substantially straight shape of the intestinal tract100in the forward direction of passage relative to the flexure101. Thus, when the bending portion12is bent and then has substantially straight, it means that the flexible tube portion13continuous with the bending portion12and located proximal to the bending portion12is just passing through the flexure101(located near the flexure101), namely, that the bending stiffness of the flexible tube portion13should be changed.

Therefore, according to the present embodiment, the shape acquisition section50acquires the bending shape of the bending portion12during insertion, and the variable stiffness control section33determines whether or not the bending stiffness of the flexible tube portion13should be changed based thereon. Hereinafter, variable stiffness control of the flexible tube portion13according to the present embodiment will be described.

FIG. 7is a block diagram illustrating variable stiffness control according to the first embodiment.FIG. 8is a flowchart illustrating variable stiffness control according to the first embodiment. step S11, the shape acquisition section50acquires the rotation angle of the angle knob15of the operation section14at a certain time t1, namely, information about the bending shape (the state of bending) of the bending portion12. The information acquired at the shape acquisition section50is output to the variable stiffness control section33of the controller30, as shown inFIG. 7. The acquired information may be displayed on the display device40via the display control section31.

The variable stiffness control section33determines the bending state of the bending portion12on the basis of the output information. Specifically, the variable stiffness control section33determines, at step S12, whether or not the bending portion12is bent to a predetermined degree or higher at the time t1. Hereinafter, the determination in step S12will be referred as a first bending state determination. At this step S12, it is determined whether or not the bending portion12, which passes through the intestinal tract100, is just passing through the flexure101or located at the flexure101, as shown inFIG. 5. The predetermined degree of bending for the first bending state determination may be conveniently set by the user, or a preset value according to the subject may be used for the first bending state determination.

At step S12, when it is determined that the bending portion12is bent to a predetermined degree or higher at the time t1(Yes), the processing proceeds to step S13, and the variable stiffness control section33acquires information about the bending shape of the bending portion12at a time t2later than the time t1(t1<t2) from the shape acquisition section50. When it is determined that the bending portion12is not bent (No), the processing returns to step S11, and the variable stiffness control section33acquires information about the bending shape of the bending portion12again at a new time t1from the shape acquisition section50.

After the variable stiffness control section33has acquired information about the bending shape of the bending portion12at step S13, the variable stiffness control section33determines, at step S14, whether or not the bending portion12is substantially straight at the time t2. Hereinafter, the determination in the step S14will be referred as a second bending state determination. At this step S14, it is determined whether the bending portion12has already passed through the flexure101, as shown inFIG. 6, and has substantially straight to follow the shape of the intestinal tract100in the forward direction of passage relative to the flexure101.

If it is determined, at step S14, that the bending portion12is substantially straight at the time t2(Yes), the processing proceeds to step S15. If it is determined that the bending portion12is not substantially straight (No), the processing returns to step S13, and the variable stiffness control section33acquires information about the bending shape of the bending portion12again at a new time t2from the shape acquisition section50.

At step S15, the variable stiffness control section33transmits a control signal to the variable stiffness sections60to change the bending stiffness of the variable stiffness section60arranged in each of the segments of the flexible tube portion13. Preferably, the segment including the variable stiffness section60whose bending stiffness is to be changed should be at least one segment including the segment next to the bending portion12among the flexible tube portion13.

The variable stiffness control section33transmits, for example, a control signal to the variable stiffness sections60to control the bending stiffness of each variable stiffness section60, in such a manner that at least one variable stiffness section60in the vicinity of the bending portion12or next to the bending portion12among the flexible tube portion13has a low bending stiffness value, that is, at least one segment corresponding to the at least one variable stiffness section60allows to be softened. In the example shown inFIG. 6, the variable stiffness control section33causes the variable stiffness sections60provided in the respective four segments in the flexible tube portion13, namely, segment131closest to the bending portion12to segment134, to have a low bending stiffness value. InFIG. 6, the variable stiffness sections60to be caused to be a low bending stiffness value are dotted. The number of segments whose bending stiffness is to be changed is not limited to the above-described number, and may be conveniently set depending on the axial lengths of the segments and the variable stiffness sections60, the general length of the flexure101, and the like.

For example, when the bending stiffness of the entire flexible tube portion13is wholly high, the flexible tube portion13may not be properly bent in the flexure101, causing extension of the intestinal wall at the flexure101. This causes distress to the patient. Various approaches show that the force that bends the flexible tube portion13during insertion is reduced when the hand side (proximal side) of the flexible tube portion13is soft, and that the force is transmitted to the distal side more easily when the distal side has a bending stiffness higher than that of the proximal side. Accordingly, the variable stiffness control section33transmits, for example, a control signal for reducing the bending stiffness value of the flexible tube portion13in the vicinity of the flexure101(e.g., segments131to134) to the corresponding variable stiffness section60. This allows the segment of the flexible tube portion13in the vicinity of the flexure101to be soft and easily bent along the shape of the flexure101. Since the segment located proximally on the flexible tube portion13is stiffer than the segment located distally on the flexible tube portion13, the force pressing the insertion section11toward the direction of passage is easily transmitted.

Alternatively, the variable stiffness control section33may transmit a control signal to the variable stiffness sections60to control the bending stiffness of each variable stiffness section60, in such a manner that at least one variable stiffness section60in the vicinity of the bending portion12or next to the bending portion12has a high bending stiffness, that is, at least one segment corresponding to the at least one variable stiffness section60allows to be stiffened.

At step S16, the bending stiffness of each of the variable stiffness sections60is changed, and thereby the variable stiffness control ends up.

In the description given above, the variable stiffness control section33acquires information about the bending shape of the bending portion12from the shape acquisition section50at steps S11and S13. However, the shape acquisition section50may constantly acquire information about the bending shape of the bending portion12during insertion, and the variable stiffness control section33may also be configured to constantly acquire information about the bending shape of the bending portion12from the shape acquisition section50. Accordingly, the variable stiffness control section33may perform the first bending state determination and the second bending state determination while immediately acquiring information about the bending shape of the bending portion12during insertion.

In the present embodiment, since a sensor that detects the bending shape of the flexible tube portion13is not arranged in the flexible tube portion13, the bending shape itself of the flexible tube portion13during insertion cannot be determined. In the present embodiment, however, a shape acquisition section50is provided in the operation section14to acquire the bending shape of the bending portion12. Thus, the bending state of the bending portion12located distally on the insertion section11, which is bent by a rotation operation of the angle knob15of the operation section14is determined.

On the basis of the bending state of the bending portion12acquired by the shape acquisition section50, the variable stiffness control section33determines whether or not the bending portion12has passed through the flexure101in the intestinal tract100, and whether or not the bending portion12has become substantially straight after the passage. When it is determined that the bending portion12has become substantially straight after passing through the flexure101, the flexible tube portion13continuous with the bending portion12and located proximal to the bending portion12is passing just through the flexure101, that is, located in the vicinity of the flexure101. In the present embodiment, although the bending shape of the flexible tube portion13cannot be directly acquired, the bending state of the bending portion12next to the flexible tube portion13is acquired. Using the acquired bending state as a trigger, the variable stiffness control section33determines that the flexible tube portion13is passing through the flexure101, namely, that the bending stiffness of the flexible tube portion13should be changed.

The variable stiffness control section33controls the bending stiffness of each of the variable stiffness sections60in such a manner that the bending stiffness of the variable stiffness section60provided in at least one segment of the flexible tube portion13passing through the flexure101is changed. This allows, for example, the segment of the flexible tube portion13located in the vicinity of the flexure101to be easily bent along the shape of the flexure101, thereby improving the ease of insertion.

In the present embodiment, since no sensor is provided in the flexible tube portion13to acquire its bending shape, the flexible tube portion13does not need to be increased in diameter. It is thus possible to provide a flexible tube insertion apparatus including the flexible tube portion13that has a small diameter and achieves an improved ease of insertion.

According to the present embodiment, it is possible to provide a flexible tube insertion apparatus that changes the bending stiffness of the flexible tube portion13to follow the shape of curvature in the subject and thereby achieves an improved ease of insertion, by acquiring the bending shape of the bending portion12using the shape acquisition section50provided in the operation section14, thus determining the bending state of the flexible tube portion13on the basis of the acquired bending shape, without providing a sensor in the flexible tube portion13. It is also possible to provide a flexible tube insertion apparatus that reduces distress to the patient.

Hereinafter, the second to fifth embodiments of the present invention will be described. In the following, detailed explanations of the structures and operations similar to those in the first embodiment will be omitted, and only matters different from those of the first embodiment will be described.

Second Embodiment

FIG. 9is a diagram schematically showing an example of a state in which the insertion section11is inserted into the large intestine according to the second embodiment.FIG. 9is a view substituting forFIG. 6of the first embodiment.

Of the steps of the variable stiffness control flow shown inFIG. 8, only the specific control of the variable stiffness control at step S15is different in the second embodiment from that of the first embodiment. In the second embodiment, at step S15, the variable stiffness control section33transmits a control signal for controlling the bending stiffness of each variable stiffness section60to the variable stiffness sections60in such a manner that a variable stiffness section60with a low bending stiffness value and a variable stiffness section60with a high bending stiffness value are alternately arranged proximal to flexible tube portion13along the axial direction of the insertion section11in the part of the flexible tube portion13in the vicinity of the bending portion12or next to the bending portion12.

In the example shown inFIG. 9, the bending stiffness of the variable stiffness section60provided in each of four segments131to134is changed, in such a manner that the segment131closest to the bending portion12in the flexible tube portion13allows to be stiffened (the corresponding variable stiffness section60has a high bending stiffness value), the segment132adjacent thereto allows to be softened (the corresponding variable stiffness section60has a low bending stiffness value), the segment133adjacent thereto allows to be stiffened, and the segment134adjacent thereto allows to be softened. InFIG. 9, the variable stiffness sections60to be caused to be a high bending stiffness value are solidly shaded, and the variable stiffness sections60to be caused to be a low bending stiffness value are dotted. Thus, stiff segments and soft segments are alternately set in the flexible tube portion13located in the vicinity of the flexure101. In the present embodiment, the number of segments whose bending stiffness is to be changed is not limited to the above-described number, and may be conveniently set.

In the example shown inFIG. 9, the bending stiffness value of the variable stiffness section60provided in the segment131of the flexible tube portion13is set to be high, and the variable stiffness control section33controls the bending stiffness in such a manner that a stiff segment and a soft segment are alternately arranged. However, the control may be performed in such a manner that a flexible segment and a stiff segment are alternately arranged by setting the bending stiffness value of the variable stiffness section60provided in the segment131to be low.

According to the present embodiment, the variable stiffness control section33transmits a control signal for controlling the bending stiffness of each variable stiffness section60to the variable stiffness sections60in such a manner that a plurality of segments of the flexible tube portion13are alternately set to soft and stiff states along the axial direction of the insertion section11. By such variable stiffness control, it is possible to obtain a flexible tube insertion apparatus that ensures the ease of insertion appropriate for the bending state of the flexible tube portion13during insertion.

Third Embodiment

The third embodiment of the present invention will be described with reference toFIGS. 10 and 11.

FIG. 10is a block diagram illustrating variable stiffness control according to the third embodiment. In the third embodiment, the controller30includes a time setting section34, in addition to the display control section31, the image processing section32, and the variable stiffness control section33. A time T at which the bending stiffness value of each of the variable stiffness sections60is changed, that is, period S at which switching is made between a stiff state and a soft state is input to the time setting section34from, for example, an input section not shown in the drawings. The time T may be conveniently set by the user, or may be set in advance in compliance with the endoscope10to be used.

Of the steps of the variable stiffness control flow shown inFIG. 8, only the specific control of the variable stiffness control at step S15is different in the third embodiment from that of the first embodiment. In the third embodiment, the variable stiffness control section33reads out a time T or period S set by the time setting section34at step S15. As in the second embodiment, the variable stiffness control section33then transmits a control signal for changing the bending stiffness of each variable stiffness section60to the variable stiffness sections60in such a manner that a variable stiffness section60with a low bending stiffness value and a variable stiffness section60with a high bending stiffness value are alternately arranged proximal to the flexible tube portion13. Thereby, a soft segment131and133including a variable stiffness section60with a low bending stiffness value and a stiff segment132and134including a variable stiffness section60with a high bending stiffness value are alternately set in the flexible tube portion13, as shown, for example, by the upper part inFIG. 11. InFIG. 11, the variable stiffness sections60to be caused to be a low bending stiffness value are dotted, and the variable stiffness sections60to be caused to be a high bending stiffness value are solidly shaded.

The variable stiffness control section33further transmits a control signal for changing the bending stiffness of each variable stiffness section60to the variable stiffness sections60to periodically switch the relationship of levels between the bending stiffness values of adjacent variable stiffness sections60at a time T or period S. Thereby, a soft segment131and133including a variable stiffness section60with a high bending stiffness value, and a stiff segment132and134including a variable stiffness section60with a low bending stiffness value, are alternately set in the flexible tube portion13after the time T, as shown, for example, by the lower part inFIG. 11. Thus, the variable stiffness control section33automatically switches the relationship of levels between the bending stiffness of adjacent variable stiffness sections60each time T set by the time setting section34.

As a matter of course, the original relationship between the bending stiffness values of the segments131and133and the bending stiffness value of the segments132and134of the flexible tube portion13may be opposite to the above-described relationship, and the number of segments whose bending stiffness is to be changed is not limited to the above-described number.

According to the present embodiment, a plurality of segments of the flexible tube portion13are alternately set to a stiff state and a soft state along the axial direction of the insertion section11, and are automatically and periodically switched between the stiff and soft states at a preset time period. By performing such variable stiffness control, even if one of the segments of the flexible tube portion13has a bending stiffness that is not appropriate for passage through the flexure101at a certain timing, that segment will have a bending stiffness appropriate for passage through the flexure101at a timing when the bending stiffness is switched next. Such switching allows the user to advance the flexible tube portion13, thus improving the ease of insertion.

Moreover, such periodic switching allows the force at the hand side to be easily transmitted to the distal end when the insertion section11is advanced. Furthermore, the distress on the large intestine is reduced, and the time required for insertion is reduced. Thus, according to the present embodiment, it is possible to provide a flexible tube insertion apparatus that conforms to complicated shapes of curvature inside of the intestinal tract and ensures the ease of insertion.

Fourth Embodiment

The fourth embodiment of the present invention will be described with reference toFIGS. 12 to 14.

FIG. 12is a diagram schematically showing a configuration of an endoscope apparatus1aaccording to the fourth embodiment. In the endoscope apparatus1a, a shape acquisition section50afor acquiring the bending shape of the bending portion12, in place of the shape acquisition section50of the first embodiment, is provided in the bending portion12at the distal end of the insertion section11. The shape acquisition section50acomprises a known sensor configured of one of a sensor using magnetism (a magnetic sensor), a sensor using ultrasound waves (an ultrasonic sensor), a sensor using loss of light (an optical fiber sensor), a sensor using distortion (a distortion sensor), and a sensor using an X-ray absorbent material, or a combination thereof.

The shape acquisition section50ais arranged at least a part of the bending portion12. That is, the shape acquisition section50amay be arranged across the entire length of the bending portion12or only in a part thereof. The shape acquisition section50ais connected to the variable stiffness control section33of the controller30via the cable71and the shape acquisition section signal cable included in the universal cord17.

FIGS. 13 and 14are diagrams schematically showing an example of the state in which the insertion section11is inserted into the large intestine according to the fourth embodiment.FIG. 13corresponds toFIG. 5in the first embodiment, andFIG. 14corresponds toFIG. 9in the second embodiment.

The flow of the variable stiffness control according to the fourth embodiment is similar to the flow shown inFIG. 8, and the specific control of the variable stiffness control at step S15is similar to that of the second embodiment. According to the present embodiment, the variable stiffness control section33performs the first bending state determination and the second bending state determination on the basis of the bending shape of the bending portion12acquired by the shape acquisition section50aprovided in the bending portion12. The variable stiffness control section33transmits a control signal for controlling the bending stiffness of each variable stiffness section60to the variable stiffness sections60, in such a manner that a variable stiffness section60with a low bending stiffness value and a variable stiffness section60with a high bending stiffness value are alternately arranged proximal to the flexible tube portion13in the part of the flexible tube portion13in the vicinity of the bending portion12or next to the bending portion12.

In the present embodiment, the actual bending shape of the bending portion12is detected by the shape acquisition section50aprovided in the bending portion12, instead of detecting the bending shape of the bending portion12on the basis of the amount of rotation operation of the angle knob15of the operation section14. Thereby, the bending shape of the bending portion12is more reliably detected, allowing the variable stiffness control section33to perform the first bending state determination and the second bending state determination based thereon. It is thus possible to provide a flexible tube insertion apparatus capable of changing the bending stiffness of the flexible tube portion13on the basis of the more reliable detection of the bending shape.

Furthermore, according to the present embodiment, the shape acquisition section50ais arranged only in the bending portion12at the distal end of the insertion section11, and the shape acquisition section50ais not arranged in the long flexible tube portion13of the insertion section11. Accordingly, the flexible tube portion13is not increased in diameter. It is thus possible to provide a flexible tube insertion apparatus comprising a small-diameter flexible tube portion13and achieving an improved ease of insertion.

By arranging the shape acquisition section50aonly in the bending portion12, manufacturing costs can be reduced, compared to when the shape acquisition section50ais arranged across the entire length of the insertion section11. By changing the bending stiffness of the variable stiffness section60of each segment of the flexible tube portion13on the basis of the bending state of the bending portion12, it is possible to improve the ease of insertion while reducing the cost.

The periodic change of the bending stiffness of the variable stiffness section60employed in the third embodiment may be combined with the present embodiment. It is thus possible to provide a flexible tube insertion apparatus that achieves an improved ease of insertion and conforms to complicated shapes of curvature in the intestinal tract.

Fifth Embodiment

The fifth embodiment of the present invention will be described with reference toFIGS. 15 and 16.

FIG. 15is a diagram schematically showing a configuration of an endoscope apparatus1baccording to the fifth embodiment. In the endoscope apparatus1b, a distal speed detection section80is provided in the bending portion12located distally on the insertion section11, in addition to the shape acquisition section50provided in the operation section14. The distal speed detection section80is, for example, a known acceleration sensor that detects the rate of change of speed with respect to time. The distal speed detection section80is incorporated into the bending portion12, for example, into the distal portion of the bending portion12.

The controller30includes the time setting section34, as in the third embodiment. However, the time setting section34in the present embodiment is different from that of the third embodiment in that the time setting section34is connected to the distal speed detection section80via the cable71and the distal speed detection signal cable included in the universal cord17. Speed information of the bending portion12detected by the distal speed detection section80is output to the time setting section34. The time setting section34sets a time T at which the bending stiffness of each of the variable stiffness sections60is periodically changed, that is, period S at which switching is made between stiff and soft states on the basis of the output speed information. In the present embodiment, the time T or period S is calculated by the time setting section34on the basis of the speed information of the bending portion12output from the distal speed detection section80.

An example of the method of calculating the period S will be described. Let us assume that the longitudinal length of the variable stiffness section60in each segment of the flexible tube portion13is L, as shown inFIG. 16. Assuming that the speed of the bending portion12detected by the distal speed detection section80is V, the time setting section34calculates and sets the period S as S=L/V.

Of the steps of the variable stiffness control flow shown inFIG. 8, only the specific control of the variable stiffness control at step S15is different in the fifth embodiment from that of the first embodiment, and the control is similar to that of the third embodiment. In the fifth embodiment, at step S15, the variable stiffness control section33reads out the time T or period S set by the time setting section34. The variable stiffness control section33transmits a control signal for changing the bending stiffness of each variable stiffness section60to the variable stiffness sections60in such a manner that a variable stiffness section60with a low bending stiffness value and a variable stiffness section60with a high bending stiffness value are alternately arranged toward the proximal side of the flexible tube portion13. Thereby, a soft segment131and133including a variable stiffness section60with a low bending stiffness value and a stiff segment132and134including a variable stiffness section60with a high bending stiffness value are alternately set in the flexible tube portion13, as shown, for example, by the upper part inFIG. 16.

The variable stiffness control section33further transmits a control signal for changing the bending stiffness of each variable stiffness section60to the variable stiffness sections60to periodically switch the relationship of levels between the bending stiffness values of adjacent variable stiffness sections60at a time T or period S calculated by the time setting section34on the basis of speed information from the distal speed detection section80. Thereby, a soft segment131and133including a variable stiffness section60with a high bending stiffness value, and a stiff segment132and134including a variable stiffness section60with a low bending stiffness value, are alternately set in the flexible tube portion13after the time T, as shown, for example, by the lower part inFIG. 16.

In the present embodiment, the distal speed detection section80is provided in the bending portion12, and the time setting section34calculates the period S at which the bending stiffness is changed, on the basis of the speed of the bending portion12detected by the distal speed detection section80. By thus changing the bending stiffness of each of the variable stiffness sections60on the basis of the speed of the bending portion12, the bending stiffness can be changed in accordance with the movement of the bending portion12. It is thus possible to provide a flexible tube insertion apparatus with an improved ease of insertion.

The present invention has been described above based on the embodiments and the variants thereof, but the present invention is not limited to those embodiments. The present invention may be modified and changed in various manners, without departing from the spirit and scope of the invention. For example, the flexible tube insertion apparatus is not limited to the endoscope apparatus1, and includes a wide range of insertion apparatuses comprising a flexible insertion section.