JPH10118529A - centrifuge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent overspeed of a rotor when a rotation sensor of the rotor detects a trouble in even one of constituting parts, in an overspeed detecting method of a rotor of a centrifugal separator. SOLUTION: An overspeed disc 2 meeting the allowable revolution is attached to the rotor of a centrifugal separator. The rotation state of the rotor is taken in a processor 8 as the number of pulses of a RPG signal by a RPG sensor 3. By a change in the quotient which is a calculated value of the number of pulses of the RPG signal and that of a MPG signal 7 which is a rotation signal of a motor 5 for driving the rotor 1, abnormality of the RPG sensor 3 is determined, allowing overspeed of the rotor to be prevented when even one of constituting parts of an overspeed detecting circuit of the rotor has a fault.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in reliability of a safety device for preventing a rotor of a centrifuge from reaching a rotation speed exceeding an allowable rotation speed.

[0002]

2. Description of the Related Art Regarding rotor overspeed detection,
Ensuring the reliability of safety devices has become an important issue. From the conventional detection of only one processor, a detection method is proposed in which two processors independently detect each other. Further, in the same application filed by the same applicant, a dual detection method of a processor and an analog circuit is proposed. In order to improve reliability, control circuits are becoming more complicated and redundant. Such a double detection circuit is necessary to reliably prevent the rotor from overspeeding even if there is a single failure in a component. For this purpose, a sensor for detecting an identifier provided on the rotor is required. (Hereinafter referred to as an RPG sensor), an overspeed detection circuit, and a drive circuit for inhibiting the operation of the drive motor must be independent of each other. Therefore, conventionally two RPG sensors are always required.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an RPG.
An object of the present invention is to provide a centrifugal separator that can reliably prevent overspeed of the rotor in the event of a single failure even with a single sensor.

[0004]

In order to cope with a single failure with one RPG sensor, the rotor does not overspeed even when the processor, the analog determination circuit, and the RPG sensor fail independently. is required. The problem here is that since the RPG sensor is shared, if the RPG sensor fails, both the processor and the analog decision circuit make a misjudgment and cannot prevent overspeed. Therefore, it is necessary to always check whether the RPG sensor is normal or abnormal.

For this purpose, the processor always checks whether the RPG signal is abnormal by using a rotation signal of the motor for driving the rotor (hereinafter referred to as MPG signal). Is generated, and the rotor is decelerated and stopped. If the processor fails, the RPG sensor and the analog determination circuit are normal under the condition of a single failure, and the overspeed of the rotor can be prevented. The above object is achieved by such means.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG.

A rotor 1 used in a centrifuge is provided with an overspeed disk 2 which serves as an identifier corresponding to the allowable rotation speed of the rotor. The overspeed rotation speed of the rotor is 15.5 kHz in terms of the frequency of the RPG signal 6.
Is set to That is, when the rotor 1 is rotated at the limit of the allowable rotation speed, the overspeed disc 2
The frequency of the signal received by the PG sensor is always 15.5 kHz
become.

Therefore, when the RPG signal exceeds 15.5 kHz, the processor 8 inhibits the operation of the thyristor 11 and cuts off the supply of power from the power supply 10 to the inverter 12, thereby stopping the centrifuge. Also the same RPG
The analog determination circuit 9 determines the overspeed based on the signal, inhibits the operation of the inverter 12, and stops the centrifuge.

The number of poles of the overspeed disk attached to each rotor is determined by the permissible number of rotations of the rotor. For example, when the permissible rotation speed is around 20,000 rpm, the pole number (the number of stripes) P = 46 of the overspeed disk 2 corresponds to the permissible rotation speed N = 20,217 rpm. When the rotor at P = 46 rotates at 20,217 rpm, the frequency of the signal received by the RPG sensor becomes 15.5 kHz.

Therefore, the number of pulses of the RPG signal per rotation of the rotor is constant (for the number of poles). From this, the count number of the RPG signal fetched by the processor is represented by M
By dividing by the number of counts of the PG signal, the number of poles of the overspeed disk can be calculated. That is,
The calculation of (the number of RPG signal counts) / (the number of MPG signal counts) = the number of poles of the overspeed disk is always performed. If the calculation result is an integer value such as P = 46, the RPG sensor 3 is determined to be normal, the centrifuge continues to operate as it is, and when the calculation result fluctuates or when the calculation result is not an integer, The RPG sensor determines that an abnormality has occurred, generates an alarm, inhibits the operation of the thyristor, and decelerates and stops the rotor.

Next, the operation of the processor will be described with reference to the flowchart of FIG.

When the power is turned on to the centrifuge, the processor reads the number of RPG pulses and the number of MPG pulses within a predetermined time from an external circuit every 120 ms by an internal timer. The read RPG pulse number is stored in the memory addressed by ZMPGCK, and the MPG pulse number is stored in the memory addressed by ZRPGCK.

When the rotor is set in the centrifuge and rotated, and when the number of revolutions reaches about 1000 rpm, the processor determines the number of poles of the overspeed disk from the number of pulses of the RPG signal and the number of pulses of the MPG signal. , Stored in a memory addressed by ZRPSUK.

When the reference value is obtained, the subroutine of SRTSC 13 is started every 120 ms.
FIG. 3 shows the processing procedure.

When this routine starts, the processor 1
The processing of 4 is performed. The number of RPG pulses is read from the ZRPGCK memory and the number of MPG pulses is read from ZMPGCK, and these two data are divided to determine the number of poles of the overspeed disk.

Next, at step 15, the reference value ZRPSUK is subtracted from the current value of the number of poles. If the difference is greater than 5, the pole value is unstable and the RPG sensor is regarded as abnormal. The internal counter indicating that the number is unstable is incremented by +1.

At 17, it is checked whether or not the value of the internal counter has exceeded 10, and if it exceeds 10, an alarm for the rotor is set in the processing at 18.

The processor performs an alarm process in another sequence control routine to decelerate and stop the rotor.

[0019]

The processor constantly checks the normal / abnormal operation of the RPG sensor operation by using the MPG signal of the motor driving the rotor, so that even if a single RPG sensor fails, a single failure of the rotor is ensured. Overspeed can be prevented and the reliability of the centrifuge can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a centrifuge according to the present invention.

FIG. 2 is a front view and a plan view of a rotor provided with an overspeed disk used in the present invention.

FIG. 3 is a flowchart of a processing procedure of a processor.

[Explanation of symbols]

1 is rotor, 2 is overspeed disk, 3 is RP
G sensor, 4 is MPG sensor, 5 is motor, 6 is RPG
Signal, 7 is an MPG signal, 8 is a processor, 9 is an analog decision circuit, 10 is a power supply, 11 is a thyristor, and 12 is an inverter.

Claims (3)

[Claims] 1. A centrifuge having a rotor containing a sample, a motor for driving the rotor, an identifier provided on the rotor, a sensor for detecting the identifier, and a processor for receiving a signal from the sensor. 3. The centrifuge according to claim 1, wherein the processor receives a rotation signal of the motor, and compares a signal from the sensor with a rotation signal of the motor. 2. The method according to claim 1, wherein the processor calculates a ratio between a signal from the sensor and a rotation signal of the motor, and if the ratio is not constant, stops the centrifuge as an abnormality. centrifuge. 3. The centrifuge according to claim 2, wherein the centrifuge is stopped when the ratio is not an integer.