JPH07116552A - Centrifugal separator - Google Patents

Abstract

PURPOSE:To suppress the deflection of a shaft at the time of passing the primary resonance region, to prevent the bending of the shaft, to stabilize an accelerating control and to improve reliability in the accelerating control of a centrifugal separator. CONSTITUTION:In the centrifugal separator provided with the controlling part controlling the rotor 2 for centrifuging a sample, the motor 3 for driving a rotor 2 through a thin shaft 8, the sensor 4 for detecting the rotation of the motor 3, and the operating part 6 setting and displaying operational conditions, at the time of the accelerating control of the motor 3, a motor current is increased temporarily just before rotation passes the primary resonance region to change an accelerating gradient, and the deflection of the shaft 8 at the time of passing the primary resonance region is suppressed and the bending of the shaft 8 is prevented, and stable acceleration control is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to acceleration control during passage of a primary resonance region during rotor acceleration in a centrifuge.

[0002]

2. Description of the Related Art In the prior art, during rotor acceleration, the CPU adjusts the motor current from the rotational speed and the elapsed time based on the acceleration gradient designated by the user so that the designated acceleration gradient can be obtained. ,
The motor is driven by passing a certain constant motor current. Centrifuges range from low speed to high speed (1,000
In order to obtain stable rotation, lower the rigidity of the shaft that connects the rotor and motor,
By reducing the natural frequency of the shaft, the structure has a primary resonance range in which the amplitude becomes extremely large below 1,000 rpm, which is outside the normal use range. Normally, the shaft vibration does not increase because it passes through the temporary resonance region quickly, but depending on the separation method, it is possible to slow the acceleration immediately after the start of rotation in order to suppress the liquid disturbance of the sample in the rotor. It can be selected by the user. Therefore, it takes time to pass the first resonance region, and the vibration of the shaft becomes large.

FIG. 2 shows the relationship between the shaft amplitude 11 and the rotational speed 10 and time when the conventional acceleration control is performed. Conventional acceleration control uses the current speed of 1
From 0 and the elapsed time, the CPU 5 gives an acceleration instruction to the motor 3 through the motor drive circuit 7. In the first resonance region, the vibration grows rapidly and the shaft amplitude 11 increases. The amount of energy is proportional to the driving torque, but when trying to slowly pass through the primary resonance region, the shaft amplitude 11 rapidly increases as described above, and the amount of energy consumed by the shaft amplitude 11 accordingly. Also increases. When the amount of energy consumed by the shaft amplitude 11 increases, the amount of energy supplied to the motor 3 inevitably decreases, so that a desired acceleration gradient cannot be obtained. Under such a circumstance, in the conventional acceleration control method, unless the actual rotation speed becomes smaller than the constant value ΔN from the ideal acceleration curve 12, the driving torque 13 required to get out of the primary resonance range is obtained. It didn't change. Therefore, it takes an extra time to obtain the driving torque 13 required to get out of the primary resonance region, and as a result, the acceleration cannot be performed according to the acceleration gradient instructed by the user. Also,
If the shaft vibration is extremely large due to the influence of the rotor imbalance, etc., the vibration will suddenly increase.
If the operation of the vibration detection sensor 9 is delayed, problems such as bending of the shaft 8 may occur.

[0004]

In the conventional device, the shaft vibration occurs when passing through the primary resonance region during rotor acceleration,
The rotation speed cannot be accurately detected due to the lack of the rotation pulse, or the acceleration cannot be performed according to the acceleration mode due to an increase in the amount of energy due to vibration. Alternatively, the shaft may bend due to vibration and imbalance of the rotor when passing through the resonance range, or the amount of amplitude in the primary resonance range may differ depending on the rotor. However, there is a problem that the shaft amplitude exceeds the allowable range and imbalance is detected even if the imbalance amount is within the allowable range. An object of the present invention is to suppress the vibration of the shaft in the primary resonance range and solve the above problems.

[0005]

The above object is to apply a current larger than normal acceleration to the motor from the motor control circuit immediately before the primary resonance region during rotor acceleration. By doing so, the motor temporarily increases the torque and quickly passes through the primary resonance region, so that the vibration of the shaft is suppressed to a small level, and the liquid turbulence of the sample is not affected because it is rapidly accelerated for an extremely short time. Further, after passing through the first resonance region, the normal acceleration control is resumed, so that a stable acceleration gradient can be obtained.

[0006]

[Operation] The rotating shaft swings in the primary resonance range. Therefore, the bending of the shaft and the rotation speed cannot be detected accurately, and the
There are problems such as not being able to accelerate according to the acceleration gradient specified by Za. The product of the present invention is temporarily suspended immediately before the primary resonance range.
By increasing the filter current, the primary resonance region can be passed quickly. Therefore, it is possible to suppress the shake of the shaft and stabilize the acceleration gradient.

[0007]

FIG. 1 shows an embodiment of the present invention. The rotor 2 in the rotation chamber 1 is rotated by the motor 3 via the shaft 8. The rotation speed is detected by the rotation detection sensor 4. The signal from the rotation detection sensor 4 is calculated by the CPU 5. The CPU 5 gives an acceleration instruction to the motor 3 through the motor drive circuit 7 based on the acceleration gradient that the user has instructed through the operation unit 6. The first resonance range is 1
In the case of existing from 00 rpm to 300 rpm, when the number of revolutions (80 rpm) immediately before the primary resonance range is reached, a predetermined steep gradient (100 rpm is increased in 7 seconds) from the acceleration gradient instructed by the CPU 5 only for a certain fixed time (3 sec). The motor current is increased by giving an acceleration instruction so that the gradient becomes). In order to make the gradient constant in this way, the centrifuge is not a control method that makes the acceleration gradient constant, because there are many types of rotors 2 mounted and various inertia moments. However, if the motor current is kept constant, the acceleration gradient will not be constant and the rotor 2 with a small inertia moment will have a tight acceleration gradient and will cause liquid turbulence. In addition, as a result of the experiment using the steep gradient described above (gradient of increasing 100 rpm in 7 seconds from 80 rpm for 3 seconds), the liquid turbulence of the sample is almost the same as that in the conventional acceleration control, and no problematic liquid turbulence occurs. It was After a lapse of a certain time, the normal acceleration control is performed again to accelerate the vehicle. If the CPU 5 calculates the signal of the vibration detection sensor 9 in consideration of the case where the amplitude of the shaft 8 is increased without sudden acceleration immediately before the primary resonance region due to a failure or the like, the value exceeds the allowable range. It is desirable to mount a mechanism for quickly stopping the rotation.

FIG. 3 shows the relationship between the shaft amplitude 11, the rotational speed 10, the drive torque 13 to the motor and the time in the case of the acceleration control mechanism according to the present invention. By increasing the motor current and increasing the drive torque 13 immediately before the primary resonance region, the shaft amplitude 11 can be suppressed to a small value by quickly passing through the primary resonance region. Since the number of revolutions can be detected accurately, the acceleration gradient can be stabilized, and even if the imbalance is more than allowable, it exceeds the primary resonance range. The shaft amplitude 11 does not increase sharply due to the phenomenon that the center of gravity of the rotating body approaches a straight line connecting both bearings as the value becomes higher. Therefore, the vibration detection sensor 9 can accurately detect the vibration, and the bending of the shaft 8 can be prevented.

[0009]

According to the present invention, the first resonance region is quickly passed. The amplitude of the shaft does not suddenly increase, and bending of the shaft can be prevented. Further, the number of rotations can be detected accurately, the acceleration gradient can be stabilized, and the product reliability can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an acceleration control mechanism of a centrifuge according to the present invention.

FIG. 2 is a graph showing the relationship between the shaft amplitude, the rotation speed, the driving torque to the motor, and the time when the conventional acceleration control is performed.

FIG. 3 is a graph showing the relationship between the shaft amplitude, the rotation speed, the driving torque to the motor, and the time when the acceleration control mechanism of the present invention is performed.

[Explanation of symbols]

1 is a rotary chamber, 2 is a rotor, 3 is a motor, 4 is a rotation detection sensor, 5 is a CPU, 6 is an operating unit, 7 is a motor drive circuit,
8 is a shaft, 9 is a vibration detection sensor, 10 is the number of revolutions, 1
1 is the shaft amplitude, 12 is the ideal acceleration curve, and 13 is the drive torque.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisanobu Oyama 1060 Takeda, Katsuta City, Ibaraki Prefecture Hitachi Koki Engineering Co., Ltd.

Claims (4)

[Claims] 1. A rotor for centrifuging a sample, a motor for driving the rotor through a thin shaft, a sensor for detecting the rotation of the motor, and the motor. A centrifuge having a control unit for controlling the acceleration, wherein during acceleration control of the motor, the acceleration gradient is changed to a steep gradient immediately before passing through the first resonance region. 2. The centrifuge according to claim 1, wherein after returning to the primary resonance region, the original acceleration control is resumed. 3. The control amount calculated by the CPU is adjusted so that the acceleration gradient becomes constant when passing through the first resonance range, and the control amount to the motor is changed via the motor control unit. 1
Alternatively, the centrifuge according to claim 2. 4. The centrifuge according to claim 3, wherein the acceleration gradient is an acceleration gradient in a range where the sample contained in the rotor does not cause liquid turbulence.