JP4231853B2 - Radial plain bearing mechanism and rotating shaft - Google Patents

Description

  The present invention relates to a radial sliding bearing mechanism and its rotating shaft, and more particularly to a radial sliding bearing mechanism suitable for medical manipulators and the like to which no lubricant is supplied and its rotating shaft.

  The following techniques are known as means for preventing wear and seizure of the bearing and galling associated therewith. That is, in order to prevent seizure, a technique for providing a taper at the end of the ceramic bearing in order to make it difficult to receive concentrated load (see Patent Document 1), and in order to improve seizure resistance, a concave portion is formed in the ceramic sleeve to form a sliding portion. In order to improve the slidability so as to withstand dry operation (see Patent Document 2), a technique for attaching a metal sleeve as a buffer member (see Patent Document 3), and the like are known. . These conventional techniques are means for improving the slidability and lubricity when used in a state where a lubricant such as oil or grease is normally supplied, and have a function of suppressing wear itself. It is designed not to occur in large quantities.

However, in the above prior art, it is not considered to prevent galling due to clogging of wear powder in an environment where wear is likely to occur when the lubricant is not supplied. Therefore, in order to avoid leakage of lubricating oil to the surroundings, it is not applicable to a bearing that needs to be usable without being supplied with a lubricant, for example, a medical manipulator (see, for example, Patent Document 4).
JP-A-5-202939 JP-A-9-210051 JP 2000-266058 A JP 2002-102248 A

  When a ceramic bearing (for example, a combination of a stainless steel shaft and a zirconium oxide bearing) is used in an environment where lubricant (oil, grease, solid lubricant, etc.) cannot be used. Even if wear occurs, adhesion does not occur, and wear powder may clog the minute gaps and cause galling.

  The present invention is intended to solve such problems, and is a radial sliding bearing mechanism used in a state where no lubricant is supplied, and prevents or suppresses galling and seizure that occur when wear powder accumulates in the sliding portion. For the purpose.

According to one aspect of the invention, a rotating shaft;
A bearing made of a material harder than the rotating shaft, facing at least a portion of the rotating shaft and supporting the rotating shaft in a radial direction so as to be slidable without being supplied with a lubricant;
In a radial plain bearing mechanism having
Indentations are provided at positions of the rotating shaft that face opposite ends of the bearing,
The bearing is formed of a material harder than the rotating shaft ,
Provided is a radial sliding bearing mechanism provided with an outflow path that is provided in communication with the recess and removes wear powder generated by sliding between the rotating shaft and the bearing to the outside of the bearing. Is done.

Further, according to one aspect of the present invention, there is provided an outflow path that is provided in communication with the indentation and removes wear powder generated by sliding between the rotating shaft and the bearing to the outside of the bearing. A radial sliding bearing mechanism according to claim 1 or 2 is provided.

  According to the present invention, in a radial sliding bearing mechanism to which no lubricant is supplied, wear powder generated between the bearing and the shaft does not collect in the sliding portion, which is the smallest gap, and easily falls off into the recess. And seizure can be prevented or suppressed.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing an embodiment of a radial sliding bearing mechanism to which a lubricant according to the present invention is not supplied. For example, the radial sliding bearing mechanism is applied as a bearing mechanism of a surgical manipulator tip. FIG. 2 is a perspective view when only the rotating shaft of FIG. 1 is taken out. A rotating shaft 1 is supported in a radial direction so as to be rotatable by a radial plain bearing 2 to which no lubricant is supplied. The rotating shaft 1 is a shaft made of metal such as stainless steel, and the bearing 2 is made of a ceramic material such as silicon nitride or zirconia ceramics and is made of a material harder than the rotating shaft 1. The rotating shaft 1 and the bearing 2 are adapted to slide opposite each other with a cylindrical sliding portion 3.

  A recess (groove) 5 extending in the circumferential direction (a direction orthogonal to the axial direction of the rotating shaft 1) is rotated on the rotating shaft 1 side at a position facing the end 4 of the bearing 2 with respect to the axial direction of the rotating shaft 1. It is formed around the shaft 1. The recess 5 prevents the end portion 4 of the bearing 2 and the rotating shaft 1 from directly contacting each other.

  When the rotating shaft 1 rotates in such a configuration, the rotating shaft 1 that is relatively softer than the bearing 2 is scraped by the sliding of the rotating shaft 1 and the bearing 2, and wear powder 6 is generated. In particular, a large amount of wear powder 6 is generated when no lubricant is supplied. At this time, since the wear powder 6 enters the recess 5, further wear of the rotating shaft 1 due to the wear powder 6 is suppressed, and seizure and galling due to the wear powder are suppressed.

  When the end portion 4 of the bearing 2 is in contact with the rotary shaft 1, wear tends to occur particularly at this position. Therefore, providing the recess 5 at this position suppresses wear, and further, wear powder 6 is removed. It is preferable when taking it into the recess 5.

  It should be noted that the process of forming the recess (groove) is difficult to apply to a hard material such as ceramics, but is relatively easy to apply to the rotating shaft 1 as in this embodiment.

  FIG. 3 is a schematic perspective sectional view of an example of a surgical manipulator provided with a radial sliding bearing mechanism according to the present invention. FIG. 4 is a longitudinal sectional view of an example of the working unit. FIG. 5 is an enlarged longitudinal sectional view showing the vicinity of the radial plain bearing mechanism. Here, parts common to those in FIGS. 1 and 2 are denoted by common reference numerals.

  The manipulator 100 includes a working unit (manipulator tip) 10 to be inserted into a patient's body, a driving unit 120 having a motor that supplies power to the working unit 10 via a wire 131, and the working unit 10 and the driving unit 120. A hollow shaft to be coupled and a coupling portion 30 having a wire 131 in the hollow portion. The manipulator 100 further includes an operation command unit 140 that is fixed to the drive unit 120 and controls electric power applied to the motor of the drive unit 120 based on the operation of the operator. The working unit 10 of the manipulator 100 having such a configuration often does not use a lubricant such as oil in order to avoid contamination inside the patient's body.

  6 to 9 are diagrams showing a configuration example of the working unit 10 of the medical manipulator according to the first embodiment of the present invention. 6 and 7 show the opened state of the grippers 14a and 14b, and FIGS. 8 and 9 show the closed state of the grippers 14a and 14b.

  The rotating member 50 that is rotatably supported with respect to the connecting portion 30, that is, the rotational member 50 that is rotatably supported with respect to the first rotating shaft 211 is coupled to the pulley 11p, and the driving force of the driving portion 120 is driven by the wire 11w. By being transmitted, the pulley 11p is rotated and the first rotating shaft 211 is driven. The pulleys 12p and 13p are rotatably supported with respect to the rotating member 50, and are fixed to bevel gears or face gears 51a and 52a, respectively. Accordingly, the driving force of the driving unit 120 is transmitted through the wires 12w and 13w, whereby the bevel gears or the face gears 51b and 52b can be rotated. The bevel gears or face gears 51 b and 52 b are supported so as to be rotatable with respect to a direction orthogonal to the first rotating shaft 211 of the rotating member 50, that is, with respect to the second rotating shaft 12. That is, two rotation shafts 12 a and 12 b are arranged on the rotation shaft 12.

  The lower ends (driving side) of the grippers (work links) 14a, 14b are rotatable in parallel directions (rotating shafts 55a, 55b) and orthogonal directions (rotating shafts 56a, 56b) with respect to the rotating shafts 12a, 12b. The grippers 14 a and 14 b are supported with respect to the connecting members 53 and 54, and are rotatably coupled to the rotation shaft 57. The connecting member 53 rotates with respect to the rotating shaft 12 together with the face gear 51b, and the connecting member 54 rotates with respect to the rotating shaft 12 together with the face gear 52b. Therefore, the grippers 14a and 14b can be driven by driving the drive unit 120.

  Similarly, by controlling the rotation shafts 12a and 12b to rotate in the same direction, the rotation operation of the second rotation shaft 12, that is, the roll operation of the grippers 14a and 14b, and the rotation shafts 12a and 12b in the reverse direction are performed. The grippers 14a and 14b can be opened / closed by controlling the rotation of the grippers 14a and 14b. The opening / closing amount of the gripper can be increased by increasing the ratio of the length of the gripper 14a, 14b on the distal end side with respect to the rotating shaft 57.

  In FIG. 4 showing the detailed structure of the working unit 10 having such a configuration, a rotating shaft 1 made of stainless steel is rotatably supported by a bearing 2 made of ceramics. In the example shown in FIG. 5, two bearings 2 are arranged in parallel in the axial direction at both ends of the rotating shaft 1. Each of the bearings 2 has a hollow cylindrical shape, and is entirely held by a cylindrical bearing holder 11. A recess 5 extending in the circumferential direction is formed on the outer peripheral surface of the rotary shaft 1 facing the end 4 of each bearing 2.

  With this configuration, as described with reference to FIGS. 1 and 2, when the rotary shaft 1 rotates, wear powder 6 is generated by sliding between the rotary shaft 1 and the bearing 2, but the wear powder 6 is indented. 5, further wear of the rotating shaft 1 due to the wear powder 6 is suppressed, and seizure and galling due to the wear powder are suppressed.

  Next, the results of an endurance test using the surgical manipulator having the structure shown in FIGS. 4 and 5 will be described. However, the apparatus used for the test shown here differs from FIG. 5 in that the bearings 2 are arranged one by one at both ends of the rotating shaft 1. The diameter of the rotating shaft 1 was 1.6 mm at the portion without the recess 5 and 1.54 mm at the portion with the recess 5. The axial width of one bearing 2 was 1.5 mm. Then, a load of 15.4 N is given to the manipulator tip 10, the operation range is only the roll axis of +90 degrees to −90 degrees of the manipulator tip 10, and the operation speed is 180 degrees / 2 sec (0.5 Hz), It was driven by an electric motor (not shown).

  FIG. 10 is a graph showing the current change of the electric motor at this time. As shown in this figure, according to the embodiment of the present invention, there was no particular change until at least 4400 seconds, and the manipulator operated normally. For comparison with this, FIG. 11 shows a test result in the case where there is no depression of the rotating shaft 1 and all other conditions are the same as those in FIG. In FIG. 11 (prior art), the current value starts to increase with an increase in the load applied to the electric motor from about 3700 seconds, and the wire breakage occurs due to the influence of caulking (burn-in) in about 4100 seconds, and the load applied to the electric motor is reduced. The current value decreased due to the extreme decrease. Thus, according to the Example of this invention, it turns out that a galling does not occur easily.

  Also, in other endurance tests, it can be confirmed that the sliding surface is smooth and wear and galling (burn-in) are unlikely to occur according to the embodiment of the present invention by visual observation of the sliding surface after the test. It was.

  Note that a normal surgical manipulator usually has a maximum continuous use time within one day and night, and can be reused by cleaning it after each operation and removing the abrasion powder 6 in the dent 5.

  FIG. 12 shows a modification of the embodiment shown in FIGS. That is, in the example shown in FIG. 2, the recess (groove) 5 makes a round along the circumference of the rotary shaft 1, but in the example of FIG. 12, the recess 5 is only part of the circumference of the rotary shaft 1. Is formed. Even with such a structure, the wear powder can escape to the indentation 5, and the same effect as that of the above embodiment can be obtained.

It is a typical longitudinal section of an embodiment of a radial slide bearing mechanism concerning the present invention. FIG. 2 is a perspective view when only the rotating shaft of FIG. 1 is taken out. It is a typical perspective sectional view showing an example of a surgical manipulator provided with a radial slide bearing mechanism concerning the present invention. It is a longitudinal cross-sectional view of embodiment which shows the example which applied the radial sliding bearing mechanism which concerns on this invention to the operation part of the manipulator for a surgery. FIG. 5 is an enlarged longitudinal sectional view showing the vicinity of a radial plain bearing mechanism of the surgical manipulator of FIG. 4. FIG. 3 is a longitudinal sectional view showing a state in which a gripper is open in a working part of the medical manipulator according to the first embodiment of the present invention. FIG. 7 is a side view taken along line AA in FIG. 6. FIG. 5 is a longitudinal sectional view showing a state where the gripper is closed in the working part of the medical manipulator according to the first embodiment of the present invention. It is an AA arrow directional side view of FIG. FIG. 6 is a graph showing results of an endurance test by the radial plain bearing mechanism of FIGS. 4 and 5, wherein the horizontal axis represents time and the vertical axis represents motor current. It is a graph which shows the endurance test result by the conventional radial sliding bearing mechanism, Comprising: A graph whose horizontal axis is time and whose vertical axis is motor current. It is a perspective view which shows the modification of the rotating shaft of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rotary shaft 2 ... Bearing 3 ... Sliding part 4 ... End part 5 of bearing ... Indentation (groove)
6 ... Wear powder 10 ... Manipulator tip 11 ... Bearing holder

Claims (2)

A rotation axis;
A bearing made of a material harder than the rotating shaft, facing at least a portion of the rotating shaft and supporting the rotating shaft in a radial direction so as to be slidable without being supplied with a lubricant;
In a radial plain bearing mechanism having
Indentations are provided at positions of the rotating shaft that face opposite ends of the bearing,
The bearing is formed of a material harder than the rotating shaft ,
A radial sliding bearing mechanism comprising an outflow path that is provided in communication with the recess and removes wear powder generated by sliding between the rotating shaft and the bearing to the outside of the bearing.   The radial sliding bearing mechanism according to claim 1, wherein the rotating shaft is made of metal, and the bearing is made of ceramics.

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