JP2002248379A - Centrifuge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to surely absorb the vibration of a rotor with a relatively simple structure, to lower the height of the device and to reduce a size and cost. SOLUTION: A drive shaft 17 of a drive motor 13 is composed of a hollow shaft 27 which is freely rotatably pivoted by bearings 31 and 32 and has high rigidity and a central shaft 28 which is inserted to this hollow shaft 27 so as to have a requires space, is fixed at its bottom end into the hollow shaft 27 and has elasticity. The top end 28b of the central shaft 28 is fitted with a rotor 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal separator for separating a liquid sample such as blood using centrifugal force, and more particularly to the structure of a drive shaft of a drive motor.

[0002]

2. Description of the Related Art In general, small centrifuges widely used in hospitals, research laboratories, and the like, transmit the rotation of a drive motor directly to the rotor and rotate the rotor at high speed, thereby utilizing the liquid by centrifugal force. The sample is separated according to the difference in density. During centrifugation, normally a balanced rotor is driven.However, even when a perfectly balanced rotor is driven, when the rotor is rotated at a high speed, the drive shaft vibrates, and the rotor and the drive motor itself vibrate. Resulting in. Further, when the center of gravity of the rotor is not located on the axis of the drive shaft, the rotor rotates eccentrically, so that the vibration is further increased. Then, if this vibration is transmitted to the casing of the centrifuge as it is, loud noise will be generated. Also, the drive shaft may bend due to vibration,
Since uneven lateral pressure in the radial direction is applied to the bearing that supports the drive shaft, the drive shaft is likely to be damaged or the bearing is likely to be unevenly worn, and as this wear progresses, the stator inside the motor and the rotor come into contact. As a result, smooth rotation of the drive shaft cannot be obtained, vibration and noise are generated, and the bearing itself may be damaged at an early stage.

Therefore, conventionally, a drive motor is elastically supported by being mounted on a housing with a cushioning material such as a coil spring or a vibration-proof rubber interposed therebetween, and the drive motor is displaced with the vibration of the rotor. A load applied to the drive shaft is absorbed to reduce the deflection of the drive shaft (for example, Japanese Utility Model Laid-Open No. 7-24450, Japanese Patent Laid-Open No. 2000-7).
9355, JP-A-10-180147, JP-A-11-042443, etc.).

[0004]

As described above, conventionally, a structure is employed in which a drive motor is elastically supported by a cushioning material such as a spring or a vibration-proof rubber to absorb and reduce vibration. Such a vibration-proof structure alone cannot sufficiently suppress the vibration of various rotors during rotation, and is still insufficient as a vibration-proof measure.

[0005] As a means for solving such a problem, for example, a centrifuge disclosed in Japanese Patent Publication No. 51-34137 is known. As shown in FIG. 3, the centrifugal separator employs a relatively elongated elastic shaft 2 as means for absorbing the vibration of the rotor 1 and protects the shaft 2 with a protective tube 3. However, since this centrifuge employs a structure in which the elongated shaft 2 is simply extended at the tip of the drive shaft 4, it has the following problems, and there is still room for improvement. Since the elongated elastic shaft 2 extends above the drive shaft 4, the distance from the drive motor 5 to the rotor 1 is increased.
As a result, the height of the device itself naturally increases,
The balance of the center of gravity may be lost. In particular, in a table-top centrifuge, when the height of the apparatus itself is increased, it becomes difficult for a user to attach and detach a sample container to and from the rotor 1, and the workability is reduced. Because the device itself becomes large,
Manufacturing costs increase.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. It is an object of the present invention to be able to absorb the vibration of the rotor with a relatively simple structure and to reduce the height of the device. An object of the present invention is to provide a centrifugal separator which can be relatively reduced in size and which can reduce the size and cost.

[0007]

According to the present invention, there is provided a centrifugal separator in which a rotor is mounted on a drive shaft of a drive motor, wherein the drive shaft is rotatably supported by a bearing. A hollow shaft having a high height, and a central shaft having elasticity inserted into the hollow shaft with a required gap therebetween and having a lower end fixed in the hollow shaft, and an upper end portion of the central shaft protruding from the hollow shaft. The rotor is attached to the above. In the present invention, the central shaft bends due to the vibration of the rotor, thereby absorbing the vibration of the rotor and interrupting the transmission of the vibration to the hollow shaft. As for the central axis, the projecting dimension of the upper end protruding from the hollow axis can be shortened because most of the bending deformation portion is housed in the hollow axis. Thereby, the distance from the drive motor to the rotor can be shortened. Further, since the distance from the bearing to the position of the center of gravity of the rotor is also reduced, the load applied to the bearing can be reduced. The gap between the hollow shaft and the center shaft limits the bending deformation of the center shaft.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a sectional view showing a structure for mounting a drive motor and a rotor of a centrifuge according to the present invention, and FIG. 2 is an enlarged sectional view of a drive shaft. In these figures, a centrifuge generally designated by reference numeral 10
A drive motor 13 is provided, which is elastically supported therein.

The drive motor 13 is an induction motor, and includes a housing 14, a stator 15, a rotor 16 and a drive shaft 17 disposed in the housing 14. The housing 14 includes a cylindrical body 18, an upper cover 19 and a lower cover 20 that cover both ends of the cylindrical body 18, and a motor mounting plate in which a flange 19 a of the upper cover 19 is provided in the housing 12. 21 is fixed via a vibration isolator 22 such as a rubber isolator, thereby elastically supporting the drive motor 13.

The stator 15 has a coil 23 and is fixed to the inner surface of the cylinder 18.

The rotor 16 is opposed to the stator 15 while maintaining a slight magnetic gap by the drive shaft 17.
Is fixed to the outer periphery of.

The drive shaft 17 comprises a hollow shaft 27 having sufficient rigidity, and a central shaft 28 having elasticity inserted into the hollow shaft 27 with an appropriate gap.

The hollow shaft 27 has bearings 31, 3 whose upper and lower ends are provided at the center of the inner surfaces of the upper cover 19 and the lower cover 20.
2, the lower end 28a of the central shaft 28 is fixed. Lower end 27A of hollow shaft 27
In FIG. 2, the inner diameter is set substantially equal to the outer diameter of the central shaft 28, and forms a fixed portion of the central shaft 28.

The center shaft 28 is made of spring steel or the like and has an appropriate spring property (elasticity). The center shaft 28 has an outer diameter substantially equal to the inner diameter of the fixing portion 27A of the hollow shaft 27. The portion 28a is fitted to the fixing portion 27A and is fixed by a set screw 33. For this reason, the set screw 3 is provided on the peripheral surface of the lower end 28a of the central shaft 28.
A concave portion 34 into which the distal end portion 3 is engaged is formed. The method of fixing the center shaft 28 to the hollow shaft 27 is not limited to the set screw 33, but may be a shrink fit or an adhesive.

An upper end 28b of the center shaft 28 projects above the hollow shaft 27, and a rotor 35 is mounted via a hub 36. That is, the upper end 28b is
Of the mounting portion. The length L1 of the upper end 28b is
Since the length is required for mounting the rotor 35,
Even if the length L of the drive shaft 17 is slightly different depending on the drive motor 13 used, the length is set to a substantially constant length. Center axis 2
The characteristic equivalent to the spring constant of No. 8 is the flexibly deformable portion 2
It can be changed by adjusting the length L2 of 8c. The adjustment can be made by fitting the collar 38 inside the hollow shaft 27 and adjusting the length L2 of the portion 28c as shown in FIG. The collar 38 may be composed of a single color having a required length L3, or a plurality of colors having an appropriate length may be used as the color having the length L3. Since the hollow shaft 27 and the center shaft 28 always rotate integrally, there is no need to fix the collar 38 to these shafts.

The rotor 35 is formed such that a plurality of non-penetrating storage holes 40 are formed at an outer peripheral portion on the upper surface side at substantially equal intervals in the circumferential direction and inclined at a required angle inward with respect to the axis of the rotor 35. A sample tube 42 for accommodating a liquid sample 41 to be centrifuged is inserted into these holes 40.

The hub 36 is fitted to the upper end 28b of the center shaft 28, and the rotor 35 is fixed to a screw hole formed in the hub 36 by a set screw 44 screwed through a washer 43. A plurality of drive pins 4 for transmitting the rotation of the central shaft 28 to the rotor 35
Five.

In the centrifuge 10 having such a structure, when the coil 23 is energized to generate a magnetic field and the rotor assembly 16 is rotated, the hollow shaft 27 is rotated.
The rotation is transmitted to the rotor 35 via the central shaft 28. For this reason, the rotor 35 rotates at a high speed (eg, 12
0 rpm) to apply a centrifugal force to the liquid sample 41 to move the high-density sample radially outward of the rotor 35 and the low-density sample radially inward to separate them.

In the centrifugal separation of the liquid sample 41, the rotor 35 inevitably vibrates when rotated at a high speed. Rotor 35
Is vibrated, the central shaft 28 bends and deforms.
Is bent as shown by a two-dot chain line in FIG.
5 is absorbed, and the transmission of the vibration to the hollow shaft 27 is reduced or cut off. Therefore, the hollow shaft 27 does not receive a large bending load, and there is no possibility of bending and breaking. Also,
If the deflection of the hollow shaft 27 is small, the uneven lateral pressure applied to the bearings 31 and 32 supporting the drive shaft 17 in the radial direction is also small, and the occurrence of uneven wear, vibration and noise of the bearings 31 and 32 is reduced. Thus, the durability of the drive motor 13 can be improved, and the characteristics of the motor can be maintained in a stable state for a long period of time.

The center shaft 28 is mostly inserted into the hollow shaft 27, and only the upper end 28b to which the rotor 35 is fixed protrudes upward. , And the height of the centrifuge 10 can be reduced. Also, the rotor 3
If the position of the center of gravity of 5 becomes lower, the bending moment with respect to the drive shaft 17 and the side pressure applied to the bearing 31 can be reduced.

In the above-described embodiment, an induction motor is used as the drive motor 13, but the present invention is not limited to this, and a synchronous motor may be used.

[0022]

As described above, the centrifugal separator according to the present invention can reliably absorb the vibration of the rotor by the bending deformation of the central shaft, and reduce the generation of vibration and noise during high-speed rotation. Can be. In addition, since the height of the apparatus itself can be suppressed, the operation of attaching and detaching the sample and the rotor is easy particularly in the case of the desktop type. Further, since the device can be manufactured compactly, the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a mounting structure of a drive motor and a rotor of a centrifuge according to the present invention.

FIG. 2 is an enlarged sectional view of a drive shaft.

FIG. 3 is a sectional view of a main part of a conventional centrifuge.

[Explanation of symbols]

10: centrifuge, 12: housing, 13: drive motor, 1
4 ... housing, 15 ... stator, 16 ... rotor, 17 ...
Drive shaft, 27: hollow shaft, 28: central shaft, 31, 32: bearing, 35: rotor.

Claims (1)

[Claims] 1. A centrifugal separator in which a rotor is mounted on a drive shaft of a drive motor, wherein the drive shaft is provided with a rigid hollow shaft rotatably supported by a bearing, and a required gap is maintained in the hollow shaft. A centrifugal separator, wherein the rotor is attached to an upper end of the central shaft protruding from the hollow shaft, the rotor being attached to an upper end of the central shaft protruding from the hollow shaft.