Centrifugal machine

Abstract

In a centrifuge, the rotation speed of a rotor is detected with good precision even in a low-speed region. In a centrifuge using a rotation detector that generates m (where m > = 1) pulse signals when a motor rotates once, a control unit compares a time interval T (n-1, m) from an immediately preceding pulse detected by the rotation detector to a pulse signal before rotation once with a time interval T (n, m) at which the pulse signal is detected this time, and determines whether the pulse signal is detected according to the time interval T (n-1, m). The rotational speed is calculated by increasing or decreasing the rotational speed N (n, m) = N (n-1, m) * T (n-1, m) / T (n, m) according to the increase or decrease of the time interval T (n, m) and the rotational speed N (n, m) = N (n-1, m) * T (n-1, m) / T (n, m).

Description

Technical Field

[0001] The present invention detects the rotation speed of a rotor with high accuracy in a centrifuge that rotates a rotor. Background Art

[0002] A centrifuge (centrifuge separator) separates a sample by rotating a rotor containing the sample at high speed. The rotor used may be an angle rotor, a swing rotor, or other rotors of various shapes. In addition, the size of the rotor varies depending on the size of the storage container that contains the sample. It is important to detect the rotation speed of the rotor with good accuracy in the centrifuge. Patent document 1 is known as a centrifuge that performs speed detection. In the centrifuge of Patent document 1, a rotor is mounted on the rotating shaft of a motor, and the motor rotates synchronously with the rotor. Therefore, the rotation speed of the rotor is detected by detecting the rotation speed of the motor. A speed detector is provided on the rotating shaft of the motor of the centrifuge, and the time of a pulse signal of one revolution generated during rotation is measured to detect the rotation speed of the rotor.

[0003] In existing centrifuges, when the rotation speed of the rotor is in the extremely low speed range, the rotation speed is sometimes calculated not based on the motor rotation amount but based on a pulse or several pulses that are less than the motor rotation amount. However, in the case of an encoder in which the pulse generation intervals in the encoder are uneven and have slight deviations, there is a risk of large errors in the detection of the rotation speed in the extremely low speed rotation area. In order to eliminate the error, a method of detecting the rotation speed of the rotor using the output of a sensor that detects a magnet provided on the bottom surface of the rotor using a Hall element can also be considered. However, the method is not applicable to the case where a magnet is not provided on the rotor side.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2005-230750 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In order to improve the detection accuracy of the rotation speed of Reference 1, a high-precision rotation detector for detecting the rotation speed of the motor may be provided in either the motor or the rotor. However, providing a new rotation detector requires improvement of the structure of the centrifuge, which increases the manufacturing cost.

[0009] The present invention has been made in view of the above background, and an object of the present invention is to provide a centrifuge capable of detecting the rotation speed of a rotor with high accuracy even in a low speed range.

[0010] Another object of the present invention is to realize a centrifuge that switches the rotation speed detection control of the rotor based on each state of the rotor: acceleration, constant speed, and deceleration.

[0011] Another object of the present invention is to realize a centrifuge that switches the rotation speed detection control of the rotor according to the rotation speed range of the rotor.

[0012] Technical means of solving problems

[0013] The representative features of the invention disclosed in this application are described as follows.

[0014] According to one feature of the present invention, there is provided a centrifuge comprising: a rotor for holding a sample; a motor for driving the rotor to rotate; a rotation detector for detecting the rotation of the motor; and a control unit for controlling the rotation of the motor based on the output from the rotation detector, wherein the rotation detector generates M (where M≧1) pulse signals when the motor rotates once, and the control unit compares the time interval T(n, m) (where m represents the mth pulse in one rotation, 1≦m≦M) of the immediately preceding pulse signal detected by the rotation detector with the time interval T(n-1, m) of the pulse signal before the rotation of the pulse once in the nth speed detection, and calculates the rotation speed N of the rotor based on the increase or decrease between the time interval T(n-1, m) and the time interval T(n, m). Furthermore, in addition to the rotation speed N per rotation, the rotation speed N(n, m) at a fine interval is calculated by N(n, m)=N(n-1, m)×T(n-1, m)÷T(n, m).

[0015] According to another feature of the present invention, the rotation control of the rotor includes acceleration control for increasing the rotation speed of the rotor over time, deceleration control for decreasing the rotation speed of the rotor over time, and constant speed control (setting) for rotating the rotor at a constant rotation speed, and the speed is calculated according to the increase or decrease of the pulse time interval T(n, m) to set the rotor in the acceleration control or deceleration control. In addition, the control unit calculates the speed according to the increase or decrease of the pulse time interval T(n, m) to set the speed domain where the rotation speed of the rotor is lower than a predetermined threshold speed. In the speed domain where the rotation speed of the rotor is higher than the threshold speed, the rotation speed (unit: per minute) of the pulse signal is calculated by N(n)=60 / [T(n, 1)+T(n, 2)+··T(n, m)+·+T(n, M)] ​​every time the motor rotates once. The rotation detector includes the following components: a disk mounted on the rotating shaft of the motor, which transmits or blocks light; and a photointerrupter mounted on the non-rotating part of the motor, and M pulse signals from the photointerrupter are output every time the motor rotates once. In addition, the rotation detector may include the following components: a plurality of magnets mounted on the rotor; and a magnetic detection element mounted on the non-rotating part near the rotor, and the pulse signal from the magnetic detection element may be output M every time the motor rotates once.

[0016] According to another feature of the present invention, in the centrifuge, the rotation detector has a pulse time comparison speed detection mode for performing multiple speed detections within one rotation of the motor, and a normal speed detection mode for performing speed detection for each rotation of the motor, and the control unit detects the rotation speed of the motor with high accuracy in the pulse time comparison speed detection mode when the speed is lower than the switching threshold speed of the speed detection mode, and detects the rotation speed of the motor in the normal speed detection mode when the speed is higher than the switching threshold speed of the speed detection mode. The rotation detector generates M (where M>1) pulse signals when the motor rotates once, and in the pulse time comparison speed detection mode, the control unit detects the time interval T(n-1, m) from the immediately preceding pulse detected by the rotation detector to the pulse signal before one rotation, and calculates the speed by the rotation speed N(n, m)=N(n-1, m)×T(n-1, m)÷T(n, m). In addition, the control unit is configured such that, in the pulse time comparison speed detection mode of the centrifuge, the control unit detects the total time interval T(n-1, m=1,...M) from the immediately preceding pulse detected by the rotation detector to the pulse signal before one rotation, and each time the width P(n, m) of the pulse signal is detected, the speed is calculated by the rotation speed N(n, m)=60 / 〔T(n-1, 1)+T(n-1, 2)+...+T(n-1, M)〕×T(n-1, m)÷T(n, m).

[0017] Effects of the Invention

[0018] According to the present invention, in a centrifuge in which a motor is provided with a rotation detector such as an encoder, the rotation speed is calculated based on the time change of the detected pulse and the pulse of the same rotation position one turn ago, so even if there is a deviation in the interval of each pulse of the output signal of the rotation detector, the rotation speed can be stably calculated. In addition, even in the case of detecting the rotation speed using a pulse signal that is not equally spaced, such as using a Hall integrated circuit (IC) to detect the magnetic position and identify the rotor, in addition, in the state where the pulse signal used to detect the rotation speed using a rotor that generates pulses is more likely to produce deviations, it will not be affected by the strength of the magnetic force or the distance, and the rotation speed can be detected with good accuracy. The speed detection method of the present invention is an effective rotation speed detection method whether it is a conventional rotation detector of a product whose pulse generation interval is not a high-standard product, or a rotation detector in which the pulse generation interval is intentionally made unevenly. In addition, it is an effective method for speed detection in a region where the rotation speed of the motor is relatively low. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] [ Figure 1 ] is a longitudinal sectional view showing the overall structure of a centrifuge 1 according to an embodiment of the present invention.

[0020] [ Figure 2 ](a) can be installed in Figure 1 A perspective view of another embodiment of the rotor 120 of the centrifuge 1, (b) is Figure 1 A perspective view of a motor 8 used in the centrifuge 1.

[0021] [ Figure 3 ] is a timing chart showing the operating conditions of the centrifuge 1 and the rotation speed of the rotor 20 using an embodiment of the present invention.

[0022] [ Figure 4 ] means from Figure 2 Graph of the output signal 90 of the rotation detector 85 .

[0023] [ Figure 5 ] is used to Figure 4 A table is provided to explain the time T(n) and the type of rotation speed N(n) calculated by the output signal 90.

[0024] [ Figure 6 ] is used to Figure 4 The diagram is used to explain a method of calculating the rotation speed N based on the waveform of the output signal 90 shown.

[0025] [ Figure 7] is used to Figure 4 FIG. 1 is a diagram for explaining another method of calculating the rotation speed N using the waveform of the output signal 90 shown.

[0026] [ Figure 8 ] is a flowchart (part 1) showing the speed detection process of the centrifuge 1 according to the second embodiment of the present invention.

[0027] [ Fig. 9 ] is a flowchart (part 2) showing the speed detection process of the centrifuge 1 according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0028] [Example 1]

[0029] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. In addition, in the following figures, the same parts are marked with the same symbols, and repeated descriptions are omitted. In addition, in this specification, the front and rear up and down directions are set as the directions shown in the figures for description.

[0030] Figure 1 : is a longitudinal sectional view showing the overall structure of the centrifuge 1 of the present invention. The centrifuge 1 has a frame (frame) 2 having a quadrilateral cross-sectional shape when viewed from above, a door 6 for opening / closing the upper part of the frame 2, and a chamber 3 arranged in the frame 2, and the rotor 20 is rotated inside the chamber 3 (rotor chamber 4). The frame 2 has a plurality of legs 5 and is arranged on a table or the like. The door 6 is an open-and-close type in which the front side can be swung in the up-and-down direction with a hinge 6a arranged on the rear side as the center. A motor 8 having a rotating shaft 82 is arranged on the lower side of the chamber 3, and the rotor 20 is mounted on the upper end of the rotating shaft 82. The motor 8 is, for example, a brushless motor, and its number of revolutions (rotational speed) can be controlled by the control unit 10. The motor 8 is provided with a rotation detector 85 for detecting the number of revolutions of the rotating shaft. In order to fix the motor 8 to the base portion 2a of the frame 2, a cylindrical support (rod) 13 is provided, and a rubber shock absorber 14 is arranged between the motor 8 and the support 13 to reduce the vibration of the rotor 20 or the motor 8. An operation display panel 12 including a touch liquid crystal display panel or the like is provided on the front side of the frame 2. The operation display panel 12 is an input component for information from the user, and is a display component for information from the control unit 10 (for example, the elapsed operation time, the rotation speed (rpm)).

[0031] The rotor 20 is a special rotor for cell washing, and has a plurality of (e.g., 24) test tube holders 31 arranged at equal intervals in the circumferential direction when viewed from above. The test tube holders 31 are supported by the rotor plate 22 of the rotor 20 on the inner circumferential side so as to be able to swing (rotate) freely in the centrifugal direction (radial direction). The test tube holder 31 includes a magnetic member and holds the test tube 40 in a manner that the test tube 40 is inserted from the top to the bottom. Figure 1 A sample (liquid) containing biological cells such as red blood cells is placed in advance inside the test tube 40 (only one is shown in the figure), and before the centrifugal separation operation starts, the test tube 40 containing the sample is placed in each test tube holder 31 by the operator's hand.

[0032] The rotor 20 includes a holding member 27 for holding the longitudinal central axis of the test tube holder 31 at a vertical or nearly vertical small swing angle. The holding member 27 uses a magnetic force to adsorb the metal test tube holder 31 so as to maintain a state in which it cannot swing, and uses a magnetic element such as an electromagnet. The holding member 27 can be electrically switched between an adsorption state (a fixed state or a state in which it cannot swing) and a release state (a state in which it can swing) of the test tube holder 31. When the test tube holder 31 is in the adsorption state, it functions as a so-called angle rotor having a negative swing angle, and when the test tube holder 31 is in the release state, it functions as a so-called swing rotor. The swing angle θ formed by the longitudinal direction of the test tube and the rotation axis A1 in the release state is approximately 45 degrees.

[0033] The cell washing rotor 20 can be attached to and detached from the rotating shaft 82. Therefore, a conventional angle rotor (for example, see Figure 2 (a)) or other swinging rotors (not shown). When the rotor 20 for cell washing as in this embodiment is mounted on the rotating shaft 82, a washing liquid dispensing element 25 is mounted on the upper part of the rotor 20, and a washing liquid supply pipe 18 provided in the door 6 is used to supply a liquid such as a washing liquid 17 into the test tube 40 when the rotor 20 rotates (when swinging). The washing liquid dispensing element 25 is inserted into the rotating shaft guide member 21 and is provided on the rotor 20 so as to rotate integrally with the rotor 20 carrying the test tube holder 31 in a circular row.

[0034] At the upper part of the cleaning liquid distribution element 25, a nozzle 19 as an outlet of the cleaning liquid supply pipe 18 is arranged on the rotation axis A1, and the liquid falling from the nozzle 19 flows into the cleaning liquid inlet 25a located on the upper side of the cleaning liquid distribution element 25. The cleaning liquid distribution element 25 has a cleaning liquid inlet 25a at the upper part on the rotation axis A1, forming a space connected to the cleaning liquid passage 25b having a conical internal space. The outer edge of the cleaning liquid passage 25b is divided in the circumferential direction to form a plurality of cleaning liquid injection ports 25c extending in the radial direction.

[0035] A pump (not shown) is coupled to the outer end (the end away from the nozzle 19) of the cleaning liquid supply pipe 18 that supplies the cleaning liquid 17 to the cleaning liquid distribution element 25. By turning on the operating power of the pump using the control unit 10, the cleaning liquid 17 can be supplied from the external cleaning liquid tank (not shown) through the cleaning liquid supply pipe 18 to the nozzle 19 located at the upper part of the centrifuge 1. In the cleaning liquid injection process described later, the cleaning liquid 17 sprayed downward from the nozzle 19 enters the central part of the cleaning liquid distribution element 25 that rotates integrally with the rotor 20, and is diverted to the outer peripheral side by the centrifugal force in the cleaning liquid distribution element 25, branching into each flow path of the same number (24) as the test tubes 40 held in the test tube holder 31, and is strongly injected into each test tube 40 from the cleaning liquid injection port 25c of the cleaning liquid distribution element 25. In order to inject the cleaning liquid 17 into each test tube 40, it is important to maintain the rotation speed of the rotor 20 within a prescribed range (described later). Figure 3 The rotation speed is in the range of N3 to N4).

[0036] A bowl-shaped bottom portion 23 is formed at the lower portion of the rotor 20. The bottom portion 23 is a container for receiving the cleaning liquid 17 that overflows without entering the test tube 40, and also functions as a stopper for limiting the swing angle θ of the test tube holder 31. That is, the test tube holder 31 that holds the test tube rotates in the radial horizontal direction of the circumference of the rotor 20 and tilts until the lower portion of the test tube holder 31 hits the outer edge of the bottom portion 23, and the blood cell or other sample in the test tube 40 is centrifuged in the state of the contact. The cleaning liquid 17 is injected while the rotor 20 is rotated, and the remaining cleaning liquid 17 is discharged from the inside of the test tube 40, so that the overflowing cleaning liquid 17 accumulates on the bottom portion of the chamber 3. Therefore, a drain hose 7 is connected to a part of the bottom surface of the chamber 3, and its discharge port 7a is arranged to reach the outside of the frame 2. The user uses a hose or the like at the front end of the discharge port 7a to recover or discard the remaining cleaning liquid (waste liquid).

[0037] Figure 2 (a) can be installed in Figure 1 The rotor 120 is a perspective view of another embodiment of the centrifuge 1. The rotor 120 is a so-called angle rotor and is Figure 1 The centrifuge 1 can be equipped with various types of rotors, such as an angle rotor and a swing rotor. On the upper side of the rotor 120, a plurality of holding holes (not visible in the figure) for holding a plurality of test tubes 40 are arranged at equal intervals in the circumferential direction. A hole that can be engaged with the rotating shaft of the motor 8 is formed at the front end. Figure 2(b) shows a mounting hole 122 into which the crown 9a shown in FIG. 1 is fitted. A circular ring portion 123 as a circular ring-shaped bottom surface is formed around the mounting hole 122, and a plurality of identifiers 124 for identifying the rotor 120 are provided in the circumferential direction of the circular ring portion 123. The shape of the mounting hole 122 of the crown 9a receiving the rotor 120, or the size or vertical position of the circular ring portion 123 arranged on the outer circumference of the mounting hole 122 are compatible with other rotors including the rotor 120. The identifier 124 is formed or arranged in order to detect the rotating rotor 120 from the outside of the rotor, and the identifier 124 is formed by, for example, a recess formed on the circular ring surface of an aluminum alloy or a titanium alloy, or is formed by forming a recess and inserting a cylindrical magnet.

[0038] Figure 2 (b) Yes Figure 1 A stereoscopic view of the motor 8 used in the centrifuge 1. The rotor and stator of the motor 8, not shown, are housed inside a motor housing 81, and are formed in such a manner that the upper and lower sides of the rotating shaft 82 extend axially upward and downward from the motor housing 81. A flange portion 83 is formed on the upper side of the motor housing 81, and a plurality of threaded holes 83a are formed in the flange portion 83. A crown portion 9a is connected to one side of the rotating shaft 82. A detection component for detecting the rotation speed of the motor 8, i.e., a rotation detector 85, is provided on the other side (lower end side) of the rotating shaft 82 of the motor. The rotation detector 85 is composed of the following components: an encoding disk 86 fixed to the lower end side of the rotating shaft 82, and a photointerrupter 88 that outputs a rotation pulse signal according to the presence or absence of a slit 87 of the encoding disk 86. By outputting an output signal (rotation pulse signal) 90 (refer to the later-described Figure 4 ) is input to the control unit 10, and the interval of the output signal 90 is measured by using an oscillator (clock) not shown in the figure. The control unit 10 can detect the number of revolutions of the motor 8.

[0039] Next, use Figure 3 The following describes the procedure for executing the cleaning cycle. Figure 3 1 is a timing chart showing the rotation speed of the rotor 20 in the washing cycle. In the cell washing centrifuge 1 for washing biological cells such as blood cells, not only the acceleration-constant speed-stopping process of the rotor 20 like a normal centrifuge (corresponding to time t1 to time t3) is included, but also the washing liquid injection process represented by circle 1, and further after the centrifugal separation operation is completed (after time t3), the supernatant discharge process represented by circle 3 and the shaking process represented by circle 4 are included.

[0040] Initially, the motor 8 is started between time 0 and time t1 to accelerate the rotor 20 to the centrifugal rotation speed N3. At this time, the swing of the test tube holder 31 is in a free state, that is, it is not swung by the holding member 27 (see Figure 1) is in a state of adsorption of the test tube holder 31. In the middle of the acceleration of the rotor 20, at the time point of the rotation speed N3 (approximately 1200 rpm), after the swing amount of the test tube holder 31 reaches the maximum, the cleaning liquid 17 is dropped downward from the nozzle 19, and the cleaning liquid 17 is injected into the interior of the cleaning liquid distribution element 25 from the cleaning liquid inlet 25a. The cleaning liquid 17 entering the interior of the cleaning liquid distribution element 25 passes through the cleaning liquid passage 25b and is distributed and supplied to the interior of multiple test tubes 40 from the upper opening of the test tube in the swinging state through the cleaning liquid injection port 25c. The cleaning liquid 17 such as physiological saline is strongly injected into each test tube 40 from the cleaning liquid distribution element 25 by centrifugal force. At this time, the blood cells in the test tube 40 are fully suspended in the physiological saline.

[0041] The injection of the cleaning solution 17 is completed at the time point of the rotation speed N4 in the middle of the acceleration period. At time t1, the rotation speed of the rotor 20 reaches the set rotation speed N for the centrifugal separation operation. S After that, the centrifugal separation operation is continued for the set time (centrifugal separation operation time = t2-t1), and the sample in the cleaning liquid moves to the bottom by centrifugal force. S After the centrifugal separation operation for the set time period is completed, the control unit 10 decelerates the motor 8 to stop the rotation of the rotor 20.

[0042] After the rotation of the rotor 20 stops at time t3, the supernatant discharge process indicated by circle 3 is performed. In the discharge process, the coil of the holding member 27 is energized to adsorb the test tube holder 31. At this time, the state of the test tube 40 is such that the central axis in the longitudinal direction is tilted so that the opening is slightly more toward the outside than the vertical direction. In this state, the rotor 20 is accelerated to the set speed N2, and the rotor 20 is operated for a certain time, and then the rotor 20 is decelerated. In this way, by rotating the rotor 20 with the angle of the test tube 40 slightly in a negative state, the supernatant causes the inner wall surface of the test tube 40 to rise due to centrifugal force and is discharged to the outside, so most of the supernatant is discharged to the outside of the test tube 40.

[0043] After the rotor 20 stops at time t4, the shaking process is then performed. The shaking process is a process of stirring the remaining cleaning solution 17 and the sample by shaking the test tube holder multiple times in a short period of time (agitation (AGITATE)). Here, the rotation speed of the rotor 20 is accelerated to N1 multiple times (here five times), and then it is rotated at a constant speed for a short period of time and then immediately decelerated, and the acceleration-constant speed-deceleration-stop small-amplitude rotation and stop operation are repeated. The above cleaning cycle from circle 1 to circle 4 is repeated multiple times, for example, three to four times.

[0044] In the cleaning liquid injection process, the supernatant discharge process represented by circle 3, and the shaking process represented by circle 4, it is important to precisely control the rotation speed of the motor 8. Regarding the rotation speed of the normal motor 8, the pulse interval of the pulse output signal 90 of the rotation detector 85 is measured to calculate the rotation speed N. When the rotation speed is in the low speed range, the rotation speed is sometimes calculated based on the time of one pulse cycle rather than one rotation of the motor. An example of the pulse output signal 90 generated by the rotation detector 85 is Figure 4 .exist Figure 4 In the figure, for simplicity of explanation, the number of slits 87 of the encoder disk 86 of the rotation detector 85 is four, and the output signal 90 in the structure in which four pulses Pa, Pb, Pc, and Pd are output from the photointerrupter 88 when the motor 8 makes one rotation is shown.

[0045] In the output signal 90, in the part where the slit 87 does not exist on the encoder disk 86 and light does not pass through, the output of the photointerrupter 88 becomes high (for example, arrow 90a), and when the light passes through the slit 87, the output of the photointerrupter 88 becomes low (for example, arrow 90b). The intervals between each pulse of the output signal 90 are accurately measured by counting the intervals using an oscillator (clock) not shown. Here, the arrangement (n, m) is used, where n is set as a variable indicating the number of rotations of the motor 8 (n is an integer: 0<n), and m is set as a variable indicating the order starting from the head pulse at each rotation (m is an integer: 0<m≦M; M represents the number of slits 87, here M=4). Therefore, Figure 4 The time interval of the pulse Pa of the nth turn is represented by T(n, 1), the time interval of Pb of the nth turn is represented by T(n, 2), the time interval of Pc of the nth turn is represented by T(n, 3), and the time interval of Pd of the nth turn is represented by T(n, 4). In addition, when the number of slits 87 of the encoder disk 86 is M (M>4), during the period when the rotor 20 makes one turn for the nth time, the time intervals are measured as T(n, 1) to T(n, 2), ... T(n, M).

[0046] Figure 5 It is used to Figure 4The table 10 illustrates the types of time T(n) and rotation speed N(n) calculated from the output signal 90. Similar to the conventional rotation detector, the time T(n) shown by symbol 52 is measured for the rotor 20 to make one revolution for the nth time without subdividing each pulse, and the speed of the one revolution is the rotation speed N(n) shown by symbol 54. When the rotor 20 makes one revolution for the nth time, the control unit 10 measures the time interval T(n, 1), time interval T(n, 2), time interval T(n, 3), and time interval T(n, 4) (in seconds) for each pulse Pa, pulse Pb, pulse Pc, and pulse Pd that appears. Therefore, the time 52 required for the rotor 20 to make one revolution for the nth time can be obtained by

[0047] T(n)=T(n,1)+T(n,2)+T(n,3)+T(n,4)

[0048] By using T(n), the n-th rotation speed N(n) of the rotor 20 per minute is calculated by

[0049] N(n)=60÷T(n)

[0050] To perform such calculation, in the present embodiment, the time interval T(n, m) of the pulse cycle shown by symbol 53 is measured for each pulse (Pa, Pb, Pc, Pd) of one rotation of the motor, and is temporarily stored in the storage area of ​​the control unit 10, and the pulse cycle time before one rotation is compared with the pulse cycle time of this time (after one rotation). Then, the speed of the motor is calculated based on the ratio of the increase or decrease in the measurement time of the same pulse signal. The storage area can use the random access memory (RAM) or dedicated buffer memory included in the control unit 10, and by using the value of T(n-1, m) (here, m=1 to 4) of the immediately preceding rotation stored in the memory, speed detection with higher accuracy than before can be performed.

[0051] Figure 6 It is used to Figure 4 The diagram is used to explain a method of calculating the rotation speed N based on the waveform of the output signal 90 shown. Figure 6 The waveform of the output signal 90 from the position of arrow 55 to the position of arrow 56 is shown as follows: Figure 5The output waveform of the output signal 90 shown in FIG. 1 before one rotation (when rotating n-1 times). Here, in order to identify pulse Pa, pulse Pb, pulse Pc, and pulse Pd, the number of rotations of the motor and the number of pulses are expressed as P(n-1, 1), P(n-1, 2), P(n-1, 3), and P(n-1, 4). In fact, the control unit 10 does not need to identify the number of rotations of the motor, and only temporarily stores the measured values ​​of one or more rotations before the current rotation (nth) in the buffer memory.

[0052] At the time point of arrow 56, the rotation speed N(n-1) of the motor can be obtained by Figure 6 (a) is calculated by the formula shown on the lower side. In the existing centrifuge, the next speed detection at the time point of arrow 56 is performed after the motor 8 rotates once from arrow 56. In this way, the method of measuring the rotation speed for each turn is referred to as the "normal speed detection mode" in this specification. In the present embodiment, in addition to the "normal speed detection mode", in the process from arrow 56 to the next measurement timing after one turn, a "pulse time comparison speed detection mode" is also provided to additionally calculate the rotation speed N (n, 1), the rotation speed N (n, 2), and the rotation speed N (n, 3) at the three timings of arrow 56a, arrow 56b, and arrow 56c where the pulse P appears.

[0053] When focusing on the pulse P(n, 1), if the (n-1)th and (n)th times have the same rotation speed, then T(n-1, 1) = T(n, 1). When the motor 8 is accelerating and the acceleration gradient is constant, the period of the pulse P becomes shorter at a certain ratio. When the motor 8 is decelerating and the deceleration gradient is constant, the period of the pulse P becomes longer at a certain ratio. Focusing on the fact that the rate of change of the rotation speed is roughly equal to the ratio of T(n-1, 1) ÷ T(n, 1), in this embodiment, the rotation speed at the time of input of the pulse P(n, 1) is calculated by multiplying the last rotation speed N(n-1) by the change ratio of the rate of change of the rotation speed. Therefore, the rate of change of the rotation speed of the motor 8 detected last time is multiplied by the above ratio, and is calculated by N(n, 1) = N(n-1) × T(n-1, 1) ÷ T(n, 1).

[0054] In the above-mentioned measuring method, the speed detection may be performed four times per revolution instead of once per revolution, and the number of times is equal to the number M of pulse signals generated per revolution from the rotation detector 85 .

[0055] Similarly, at the time point of arrow 56b, the rate of change of the rotation speed of motor 8 is the ratio of T(n-1, 2) to T(n, 2). Therefore, the rotation speed N(n-1) detected last time can be multiplied by the ratio to obtain

[0056] N(n,2)=N(n-1)×T(n-1,2)÷T(n,2)

[0057] To figure out.

[0058] At the time point of arrow 56c, the rate of change of the rotation speed of motor 8 is the ratio of T(n-1, 3) to T(n, 3). Therefore, the rotation speed N(n-1) detected last time can be multiplied by the ratio, and the value can be obtained by

[0059] N(n,3)=N(n-1)×T(n-1,3)÷T(n,3)

[0060] To figure out.

[0061] Next, when the motor 8 has rotated about 90 degrees from the arrow 56c, that is, once from the arrow 56, the Figure 6 (a) The same formula, i.e.

[0062] N(n)=60÷〔T(n,1)+T(n,2)+T(n,3)+T(n,4)〕

[0063] To figure out.

[0064] Thereafter, the rotation speed of the motor 8 is detected and calculated while repeating the same method. In the present embodiment, the rotation speed N is calculated based on the time change of the pulse corresponding to the same slit 87 for the change in speed, so even if the pulses are not uniform, the rotation speed can be stably calculated. In addition, even in the case of detecting the rotation speed using pulse signals that are not equally spaced, such as using a Hall IC to detect the magnetic position and identify the rotor, and even in the case of being easily affected by the strength of the magnetic force or the distance and the pulse signal is more likely to deviate, the rotation speed can be detected with good accuracy, so it is an effective rotation speed detection method for an uneven pulse generator. Furthermore, the speed detection method based on the present embodiment is effective for speed detection in a region where the rotation speed of the motor is relatively low.

[0065] Figure 7 It is used to Figure 4 FIG. 9 is a diagram for explaining another method of calculating the rotation speed N from the waveform of the output signal 90 shown. Figure 6 In the example, the rotation speed N(n-1) is calculated by multiplying the rate of change of the rotation speed of the motor 8 each time a pulse is generated. Figure 7 , each time the rotation speed Nr of the immediately preceding rotation is multiplied by the rate of change of the rotation speed of the motor 8, which is different in that a more instantaneous rotation speed N can be obtained.

[0066] exist Figure 7 In (a), the rotation speed Nr(n-1, 1) is calculated from the time for the motor to rotate once for the (n-1)th time between arrows 55 and 56. For example, the rotation speed for the first rotation at the start of rotation is calculated from the time for the motor 8 to rotate once. Figure 7 The rate of change of the rotation speed of the motor 8 at the time of the arrow 56a in (b) is T(n-1, 1) ÷ T(n, 1), so the rotation speed Nr(n-1, 1) detected last time can be multiplied by the ratio to obtain

[0067] N(n,1)=Nr(n-1,1)×T(n-1,1)÷T(n,1)

[0068] To figure out.

[0069] The pulses for one rotation of the motor 8 at the time point of arrow 56a are (T(n-1, 2), T(n-1, 3), T(n-1, 4), T(n, 1)), so the rotation speed Nr(n-1, 2) is obtained by the following formula.

[0070] Nr(n-1,2)=60÷〔T(n,1)+T(n-1,2)+T(n-1,3)+T(n-1,4)〕

[0071] Similarly, in Figure 7 The time point of arrow 56b in (c) can be obtained by using the rate of change of the rotation speed of motor 8 T(n-1, 2) ÷ T(n, 2) and the rotation speed Nr(n-1, 2) of the most recent rotation of motor 8.

[0072] N(n,2)=Nr(n-1,2)×T(n-1,2)÷T(n,2)

[0073] In addition, the rotation speed Nr of one rotation of the motor 8 is calculated by the following equation based on the pulses of one rotation of the motor 8 at the time of arrow 56b.

[0074] Nr(n-1,3)=60÷〔T(n,1)+T(n,2)+T(n-1,3)+T(n-1,4)〕

[0075] Below, similarly, in Figure 7 At the time point of arrow 56c in (d), the rate of change of the rotation speed of the motor 8 T(n-1, 3) ÷ T(n, 3) and the rotation speed of the most recent rotation Nr(n-1, 3) can be expressed by

[0076] N(n,3)=Nr(n-1,3)×T(n-1,3)÷T(n,3)

[0077] The rotation speed Nr is calculated by the following equation based on the pulses corresponding to one rotation of the motor 8 at the time of the arrow 56c.

[0078] Nr(n-1,4)=60÷〔T(n,1)+T(n,2)+T(n,3)+T(n-1,4)〕

[0079] As described above, the control unit 10 can detect the speed corresponding to the number of times the slit 87 of the rotation detector 85 rotates in one rotation of the motor 8 by sequentially measuring the rotation speed N(n, 1), the rotation speed N(n, 2), and the rotation speed N(n, 3). The speed detection control can be easily implemented by changing the computer program executed by the microcomputer of the existing control unit 10, so the increase in manufacturing cost is also small. In the embodiment, the example of calculating the rotation speed using the output of the encoder is explained as the basis, but even if the output pulse of the Hall IC for detecting the excitation position of the brushless motor or the pulse signal of the rotor identification identifier (identifier, ID) can be used to calculate the rotation speed of the motor by the method.

[0080] [Example 2]

[0081] Next, use Figure 3 , Figure 8 , Fig. 9 The second embodiment of the present invention is described. In the first embodiment, it is assumed that the same speed determination method is used in all speed regions. In the second embodiment, the speed detection method shown in the first embodiment is not used in the entire speed domain, but in the low speed region (refer to Figure 3 ) is performed by the method of the first embodiment (pulse time comparison speed detection mode), and in a speed region higher than a certain threshold rotation speed (Nc) (refer to Figure 3 ), as in the past, a speed detection is performed once when the rotation is performed once (normal speed detection mode). It is arbitrary to set the threshold speed Nc to what extent, for example, when using Figure 1 In the case of a dedicated rotor 20 for cell washing as shown in FIG. 1 , it is preferable to set a rotation speed Nc higher than the speed range (rotation speed N3 to rotation speed N4) for injecting the washing solution 17 as the threshold. If the threshold speed Nc is set in this way, Figure 3 The rotation control of the rotor 20 in the cleaning liquid injection process represented by circle 1, the supernatant liquid discharge process represented by circle 3, and the shaking process represented by circle 4 can all achieve high-precision rotation speed detection in the pulse time comparison speed detection mode.

[0082] Figure 8This is a flow chart showing a speed detection flow of the centrifuge 1 according to the second embodiment of the present invention. The control of the second embodiment can be realized by software by executing a computer program in the microcomputer of the control unit 10 . Figure 8 The control shown starts when the user presses the start button of the centrifugal separation operation from the operation display panel 12 of the centrifuge 1 to start the motor 8 (step 61). Initially, the microcomputer (not shown) of the control unit 10 performs the rotation speed calculation process (A) based on the pulse time comparison speed detection mode (step 62). The microcomputer that detects the rotation speed N of the motor 8 in the rotation speed calculation process (A) determines whether the rotation speed N reaches the threshold speed Nc for switching (step 63). If the threshold speed Nc for switching is not reached in step 63, the process returns to step 62. If the switching speed is reached in step 63, the microcomputer switches to the speed detection based on the rotation speed calculation process (B) of the normal speed detection mode, and continues to detect the rotation speed N of the motor 8 (step 64).

[0083] The microcomputer continues the speed detection of the rotation speed calculation process (B) of step 64, and determines whether the operation time of the centrifugal separation has passed the set time Ts set by the user (step 65), and returns to step 64 if it has not passed. In step 65, after the set time Ts has passed, the microcomputer transfers to Fig. 9 The deceleration process (step 66) is shown.

[0084] Fig. 9 is immediately following Figure 8 , step 67 is the processing immediately following step 66. At the start of the deceleration process, the rotation speed of the motor 8 is calculated by the rotation speed calculation process (B) (step 68). Next, the microcomputer that detects the rotation speed N of the motor 8 determines whether the rotation speed N is less than the threshold speed Nc for switching (step 69). Here, when the rotation speed N is greater than the threshold speed Nc for switching, the process returns to step 68. When the rotation speed N is lower than the threshold speed Nc for switching, the microcomputer of the control unit 10 switches to speed detection based on the rotation speed calculation process (A) of the pulse time comparison speed detection mode, and continues to detect the rotation speed N of the motor 8 (step 70). In step 71, the microcomputer of the control unit 10 determines whether the motor 8 stops (rotation speed N=0) (step 71). In step 71, when the rotation of the motor 8 continues, the process returns to step 70, and after the motor 8 stops, the process ends (step 72).

[0085] In the second embodiment, the method of switching the rotation speed calculation process of the motor 8 between the pulse time comparison speed detection mode and the normal speed detection mode has been described. Figure 8 , Fig. 9The premise of the method is that the rotation of the motor 8 is transferred from a low speed to a high speed. Figure 3 In the supernatant discharge process shown in circle 3 or the shaking process shown in circle 4, only the low speed rotation area where the rotation speed does not reach the threshold speed Nc for switching the speed detection mode is controlled. In this case, as long as Figure 8 , Fig. 9 In the above, the control may be set to not use the high-speed rotation speed calculation process (B).

[0086] The present invention has been described above based on two embodiments, but the present invention is not limited to the embodiments, and various changes can be made without departing from the scope of the subject matter. For example, in the embodiments, the microcomputer of the control unit 10 configured to control the centrifuge 1 performs speed detection, but the present invention can also be applied when another microcomputer is used to monitor the rotation speed of the motor 8 and perform abnormality detection.

[0087] Explanation of symbols

[0088] 1: Centrifuge

[0089] 2: Frame

[0090] 2a: Base

[0091] 3: Chamber

[0092] 4: Rotor chamber

[0093] 5: Feet

[0094] 6: Door

[0095] 6a: Hinge

[0096] 7: Drain hose

[0097] 7a: Discharge outlet

[0098] 8: Motor

[0099] 9: Crown

[0100] 10: Control Department

[0101] 12: Operation display panel

[0102] 13: Pillar

[0103] 14: Shock absorber

[0104] 17: Cleaning fluid

[0105] 18: Cleaning fluid supply pipe

[0106] 19: Nozzle

[0107] 20: Rotor

[0108] 21: Rotating axis guide component

[0109] 22: Rotor plate

[0110] 23: Bottom

[0111] 25: Cleaning fluid distribution element

[0112] 25a: Cleaning fluid inlet

[0113] 25b: Cleaning fluid passage

[0114] 25c: Cleaning fluid injection port

[0115] 27: Keep the parts

[0116] 31: Test tube support

[0117] 40: Test tube

[0118] 81: Motor housing

[0119] 82: Rotation axis

[0120] 83: Flange

[0121] 83a: threaded hole

[0122] 85: Rotation detector

[0123] 86: Encoding disk

[0124] 87: Slit

[0125] 88: Photochopper

[0126] 90: Output signal

[0127] 120: Rotor

[0128] 122: Mounting hole

[0129] 123: Ring

[0130] 124: Identifier

[0131] A1: (motor) axis of rotation

Claims

1. A centrifuge comprising: Rotor, to hold the sample; A motor for driving the rotor to rotate; a rotation detector for detecting the rotation of the motor; as well as A control unit controls the rotation of the motor based on the output from the rotation detector, wherein the centrifuge is characterized in that: The rotation detector generates M (where M≧1) pulse signals when the motor rotates once, The control unit detects the speed for the nth time. The time interval T(n, m) of the immediately preceding pulse signal detected by the rotation detector (where m represents the mth pulse in one revolution, 1≦m≦M) is compared with the time interval T(n-1, m) of the pulse signal before the pulse rotates once. The rotation speed N of the rotor is calculated based on the increase and decrease of the time interval T(n-1, m) and the time interval T(n, m).

2. The centrifuge according to claim 1, characterized in that The rotation speed N (n, m) is obtained by It can be calculated by N(n,m)=N(n-1,m)×T(n-1,m)÷T(n,m).

3. The centrifuge according to claim 2, characterized in that The rotation control of the rotor includes acceleration control for increasing the rotation speed of the rotor as time passes, and deceleration control for decreasing the rotation speed of the rotor as time passes. The speed is calculated based on the increase or decrease of the pulse time interval T (n, m) to determine whether the rotor is accelerating or decelerating.

4. The centrifuge according to claim 2, characterized in that The control unit calculates the speed based on the increase or decrease of the pulse time interval T (n, m) in a speed range where the rotation speed of the rotor is lower than a threshold speed. In a speed range higher than the threshold speed, the rotation speed of the pulse signal is calculated by N(n)=60 / [T(n, 1)+T(n, 2)+···+T(n, M)] ​​every time the motor rotates once.

5. The centrifuge according to claim 2, characterized in that: The rotation detector comprises the following components: a disk mounted on the rotating shaft of the motor, transmitting or shielding light; and The photo-chopper, mounted on the non-rotating part of the motor, The photointerrupter outputs M pulse signals every time the motor rotates once.

6. The centrifuge according to claim 2, characterized in that: The rotation detector comprises the following components: a plurality of magnets mounted on the rotor; and The magnetic detection element is mounted near the non-rotating part of the rotor. The magnetic detection element outputs M pulse signals every time the motor rotates once.

7. A centrifuge comprising: Rotor, to hold the sample; A motor for driving the rotor to rotate; a rotation detector for detecting the rotation of the motor; as well as A control unit controls the rotation of the motor based on the output from the rotation detector, wherein the centrifuge is characterized in that: The rotation detector has a pulse time comparison speed detection mode for performing multiple speed detections within one rotation of the motor, and a normal speed detection mode for performing speed detection for each rotation of the motor. The control unit detects the rotation speed of the motor in the pulse time comparison speed detection mode when the speed is lower than the switching threshold of the speed detection mode, When the speed detection mode switching threshold is reached or exceeded, the rotation speed of the motor is detected in the normal speed detection mode.

8. The centrifuge according to claim 7, characterized in that The rotation detector generates M (where M>1) pulse signals when the motor rotates once, In the pulse time comparison speed detection mode, the control unit detects the time interval T(n, m) of the immediately preceding pulse signal detected by the rotation detector and the time interval T(n-1, m) of the pulse signal before one rotation, and The speed is calculated by the rotation speed N(n,m)=N(n-1,m)×T(n-1,m)÷T(n,m).

9. The centrifuge according to claim 7, characterized in that The rotation detector generates M (where M>1) pulse signals when the motor rotates once, In the pulse time comparison speed detection mode, the control unit detects the total of the time intervals T (n-1, m=1, . . . M) of the pulse signal from the immediately preceding pulse detected by the rotation detector to the pulse signal before one rotation. Whenever the width P(n, m) of the pulse signal is detected, Rotation speed N(n,m)=60 / 〔T(n-1,1)+T(n-1,2)+···+T(n-1,M)〕×T(n-1,m)÷T(n,m) To calculate the speed.

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