JP3813722B2 - Centrifuge control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a centrifuge control method, and more particularly to a centrifuge control method for preventing abnormal vibration operation of a rotor.
[0002]
[Prior art]
In a centrifuge, a plurality of buckets containing tubes (test tubes) are engaged with a rotor, and the rotor is rotated at a high speed to centrifuge samples and the like in the tube. Thus, for example, if you forget to engage one of the buckets with the rotor, do not set the tubes symmetrically in each bucket, or if the amount of sample dispensed is uneven, the rotor will become unbalanced. If the rotor is rotated at a high speed in this state, abnormal vibration may occur and mechanical failure such as breakage of the drive shaft may occur, and mechanical failure such as breakage may not occur. Gives fear to the operator.
[0003]
Therefore, various imbalance detection devices have been provided for the purpose of preventing such a failure (Japanese Patent Laid-Open Nos. 9-982, 4-145967, 2-1088749, Sho-57). No. 175033, Japanese Utility Model Laid-Open No. 2-48143, Japanese Utility Model Laid-Open No. 62-109744, Japanese Patent Application Laid-Open No. Hei 5-104031). In these unbalance detection devices, the drive shaft or rotor in which the oscillation is most noticeable in the unbalance operation is measured, and a non-contact sensor is disposed so as to face the drive shaft or rotor. The horizontal distance between them is measured and controlled based on the measured value.
[0004]
[Problems to be solved by the invention]
However, the non-contact type sensor not only has a high cost of the sensor itself but also needs to block the rotating magnetic field of the motor when, for example, a hall element is used. It is necessary to prepare measures such as the need to take countermeasures, and the overall cost of the device is inevitable.
[0005]
Therefore, an object of the present invention is to provide a control method for realizing a centrifuge that prevents abnormal vibration operation of a rotor that is inexpensive and highly accurate.
[0006]
[Means for Solving the Problems]
In claim 1 of the control method of the centrifuge according to the present invention, a control method of the centrifuge mounted on the case body via a rubber cushion the rotor drive motor, deflection with respect to the case body of the non-rotating portion of the motor The amount is measured, and when the amount of deflection exceeds a preset threshold value, the driving of the motor is stopped.
[0007]
Some centrifuges have a motor for driving a rotor attached to a case body via a vibration-proof rubber. In the case of such a centrifuge, if the rotor is unbalanced, the motor is also swung together with the rotor. Therefore, in the control method of the centrifuge of the present invention, the amount of rocking of the rotor is measured by bringing the sensor into contact with the non-rotating portion of the motor, that is, by using a contact type sensor.
[0008]
According to a first aspect of the present invention , there is provided a control method for a centrifuge , wherein the threshold value is set in accordance with a temperature characteristic of the vibration-proof rubber.
[0009]
As a characteristic of rubber, energy absorption rate (loss factor) tends to change with changes in temperature. That is, the energy absorption rate is high in a certain temperature range, but the energy absorption rate decreases when the temperature is lower or higher than the temperature range. There is no problem even if the rotor is operated at a high speed in the above-mentioned fixed temperature range, but if the rotor is operated at a high temperature outside that temperature range, the drive shaft of the motor may be damaged. Therefore, in the control method for the centrifuge of the present invention, the threshold value is set in accordance with the temperature of the vibration isolating rubber.
DETAILED DESCRIPTION OF THE INVENTION
[0010]
Examples of the contact-type sensor include an acceleration sensor, a limit switch, a piezoelectric ceramic sensor, a strain gauge, and the like. A strain gauge is preferable because sufficient accuracy required for a centrifuge can be obtained. The strain gauge is low-cost, and as a result of experiments, sufficient sensitivity and reliability are obtained.
[0011]
The unbalance amount of the rotor itself can be detected even when the rotor is stopped, but in order to increase the measurement accuracy, the rotor is rotated and the swing amount is amplified by the centrifugal force to measure the swing amount. It is preferable. Since the amount of rocking of the rotor becomes maximum at the first resonance point (700 to 2000 rpm), it is preferable to measure at the number of revolutions in the vicinity thereof.
[0012]
The temperature characteristics of the anti-vibration rubber are preferably measured by bringing the temperature sensor into direct contact with the anti-vibration rubber.However, since the temperature sensor inhibits the deformation of the anti-vibration rubber, the measurement is performed at a position close to the anti-vibration rubber. Preferably it is done.
[0013]
【Example】
FIG. 1 shows a centrifuge for carrying out the centrifuge control method according to the present invention. In this centrifuge, the upper end of the housing 1 a of the motor 1 is fixed to the bracket 2. And the bracket 2 is installed in the motor base 4a of the case main body 4 via the anti-vibration rubber | gum 3 arrange | positioned at three places of the periphery at equal intervals.
[0014]
Further, in this centrifuge, a polyacetal projection 5 having high wear resistance is disposed downward on the peripheral edge of the lower surface of the bracket 2, and a holder 6 is disposed on the motor base 4 a below the projection 5. A strain gauge assembly 7 is installed on the upper surface of the holder 6. As shown in FIG. 2, the strain gauge assembly 7 has a U-shaped cut 8a formed in an elastic plate 8, and a tongue piece 8b defined by the cut 8a is fixed to the holder 6, and the cut 8a defines the image. A strain gauge 9 is attached to the boundary between the annular piece 8c and the tongue piece 8b. Then, the protrusion 5 is brought into contact with the free end of the annular piece 8c.
[0015]
Further, a temperature sensor 10 is disposed on the motor base 4a in the vicinity of the anti-vibration rubber 3. Further, the centrifuge chamber 11 of the case body 4 is well known for identifying the type of the rotor 12 (for example, Japanese Patent Laid-Open No. Hei 7). -47350) of the rotor identification sensor 13 is provided. The strain gauge 9, the temperature sensor 10, and the identification sensor 13 are connected to a controller 14.
[0016]
The anti-vibration rubber 3 used in the examples has temperature characteristics as indicated by ◯ in FIG. In this temperature characteristic diagram, an unbalanced test rotor is mounted on the motor shaft, and the amount of deflection at the primary resonance point of the rotor at each temperature of the anti-vibration rubber 3 is measured by the strain gauge 9. is there. According to this, when the temperature of the anti-vibration rubber 3 (atmosphere temperature near the anti-vibration rubber) is in the range of 8 to 17 ° C., the output corresponding to the resistance value measured by the strain gauge 9 at the primary resonance point of the rotor. Although the voltage is substantially constant, when the temperature is 17 to 20 ° C. or higher, the output voltage corresponding to the resistance value measured by the strain gauge 9 increases substantially in proportion to the temperature rise.
[0017]
Therefore, in the embodiment, as described above, the temperature characteristic of the energy absorption rate of the vibration isolating rubber 3 is examined in advance, and a threshold value is set corresponding to the temperature characteristic. The threshold value varies depending on the type of the rotor 12, as indicated by a solid line in FIG. For example, solid lines A, B, D, and F are swing-type rotors having four racks around them. A is maximum and B, D, and F are sequentially reduced. Solid lines C and E are swing type rotors having two racks around them. C is large and E is small. Each threshold value is set to a value that does not cause vibration harmful to the machine, that is, considerably lower than the limit of breakage.
[0018]
In this centrifuge, when the rotor 12 is mounted, the type of the rotor 12 is identified by the controller 14 via the sensor 13 (step 21). Then, the controller 14 selects a threshold mode (A to F) corresponding to the type of the rotor 12 (step 22). Further, while the rotor 12 is rotationally driven, the temperature of the anti-vibration rubber 3 is constantly measured by the controller 14 via the temperature sensor 10 (step 23). Then, a threshold corresponding to the temperature of the anti-vibration rubber 3 is selected (step 24). On the other hand, while the rotor 12 is rotationally driven, the amount of deflection (voltage) is measured by the controller via the strain sensor 9 (step 25), and the measured value T is compared with the threshold value S (step 26). When the measured value T is smaller than the threshold value S, the rotor 12 is continuously rotated (accelerated), and when the measured value T exceeds the threshold value S, a warning by sound, light or the like is issued (step 27). The drive of the motor 1 is stopped (step 28).
[0019]
In the above embodiment, the temperature of the anti-vibration rubber is measured and the temperature is used as a threshold setting element. However, when an anti-vibration rubber whose energy absorption rate hardly changes over the entire operating temperature is used, the anti-vibration rubber is used. It is not necessary to measure the temperature of the vibration rubber. Further, although the amount of swing of the rotor 12 (the amount of deflection of the anti-vibration rubber 3) is measured between the mounting bracket 2 of the motor 1 and the motor base 4a of the case body 4, an appropriate portion of the housing 1a of the motor 1 is measured. It is also possible to measure between an appropriate part of the case body 4.
[0020]
Moreover, in the said Example, although the amount of bending at the time of passing a 1st resonance point was measured and the amount of bending (voltage) and a threshold value were compared, the vibration isolator rubber in the number of rotations of various rotors is compared. A threshold value for the temperature (atmosphere temperature) may be set in advance, and the threshold value and the deflection amount may be compared.
[0021]
【The invention's effect】
As described above, in the control method of the centrifuge according to the first aspect of the present invention, the amount of deflection of the non-rotating part of the motor with respect to the case body is measured as the amount of unbalance of the rotor, and the threshold value of the amount of deflection is set in advance. When it exceeds, the driving of the motor is stopped. Therefore, the amount of deflection can be measured by the contact sensor, whereby a centrifuge with high measurement accuracy and low cost at a low rotation of the rotor can be obtained.
[0022]
Moreover, in the control method of the centrifuge according to the present invention of claim 1, since the threshold value is set corresponding to the temperature characteristics of the vibration-proof rubber, there is provided a centrifuge capable of preventing breakage regardless of the environmental temperature. can get.
[Brief description of the drawings]
FIG. 1 is a sectional view conceptually showing a centrifuge for carrying out a centrifuge control method according to the present invention.
FIG. 2 is a perspective view showing a strain gauge assembly used in the centrifuge of the embodiment.
FIG. 3 is a graph showing temperature characteristics of a vibration-proof rubber used in the centrifuge of the example.
FIG. 4 is a graph showing threshold values for each rotor in the centrifuge of the example.
FIG. 5 is a flowchart showing control of the centrifuge according to the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor 1a Housing 1b Drive shaft 2 Bracket 3 Anti-vibration rubber 4 Case body 4a Motor base 5 Protrusion 6 Holder 7 Strain gauge assembly 8 Elastic plate 9 Strain gauge 10 Temperature sensor 11 Centrifugal chamber 12 Rotor 13 Rotor identification sensor 14 Controller

Claims (1)

In the control method of the centrifuge in which the motor for driving the rotor is attached to the case main body via the vibration isolating rubber, the amount of deflection of the non-rotating portion of the motor with respect to the case main body is measured, and the amount of bending is determined by the vibration isolating rubber. A method for controlling a centrifuge, wherein driving of the motor is stopped when a preset threshold value corresponding to a temperature characteristic is exceeded.

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