Distant scheming

Abstract

This centrifuge is configured to be capable of detecting, with high accuracy, the rotational speed of a rotor even in a low-speed range. In the centrifuge which employs a rotation detector for generating m-number (where m≥1) of pulse signals per rotation of a motor, a control unit compares a time interval T (n-1, m) of pulse signals in one rotation prior to the immediately preceding pulses detected by a rotation detector with a time interval T (n, m) of recent detection pulse signals, and then, from an increase or decrease between the time interval T (n-1, m) and the time interval T (n, m), calculates the rotational speed by using a formula of rotation speed N (n, m)=N (n-1, m)×T (n-1, m) / T (n, m).

Description

Technical Field

[0001] The present invention is related to a centrifuge that rotates a rotor, and accurately detects the rotational speed of the rotor.

Background Art

[0002] A centrifuge (centrifugal separator) separates a sample by rotating a rotor containing the sample at high speed. The rotor to be used can be equipped with various shapes such as an angle rotor and a swinging rotor, and the size of the rotor varies depending on the size of the container for accommodating the sample. Accurately detecting the rotational speed of the rotor in a centrifuge is important. Patent Document 1 is known as a centrifuge that performs such speed detection. In the centrifuge of Patent Document 1, a rotor is attached to the rotating shaft of a motor, and since the motor and the rotor rotate synchronously, the rotational speed of the rotor is detected by detecting the rotational speed of the motor. A speed detector is provided on the rotating shaft of the centrifuge motor, and the time of the pulse signal for one revolution generated when rotating is measured to detect the rotational speed of the rotor.

[0003] In a conventional centrifuge, when the rotational speed of the rotor is in the extremely low speed range, the rotational speed may be calculated from one pulse or several pulses less than one revolution instead of one revolution of the motor. However, in the case of an encoder in which the pulse generation interval is not uniform and has a slight variation, there is a risk of generating a large error in detecting the rotational speed in the extremely low speed rotation region. In order to eliminate this error, a method of detecting the rotational speed of the rotor by using the output of a sensor that detects a magnet provided on the bottom surface of the rotor with a hall element is also conceivable. However, this method cannot be applied when no magnet is provided on the rotor side.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] To improve the accuracy of rotational speed detection in Reference 1, a high-precision rotation detector for detecting the motor's rotational speed should be installed on either the motor or the rotor. However, installing a new rotation detector would require modifying the centrifuge's structure, which would increase manufacturing costs.

[0006] This invention was made in view of the above background, and its purpose is to provide a centrifuge that can accurately detect the rotational speed of the rotor even in the low-speed range. Another object of the present invention is to realize a centrifuge that switches the rotor rotation speed detection control based on the rotor's acceleration, constant speed, and deceleration states. Another object of the present invention is to realize a centrifuge that switches the rotor rotation speed detection control depending on the rotor rotation speed range. [Means for solving the problem]

[0007] The following are some of the representative features of the invention disclosed in this application. According to one feature of the present invention, in a centrifuge having a rotor for holding a sample, a motor for rotating the rotor, 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, the rotation detector generates M pulse signals (where M≧1) for one rotation of the motor, and in the nth speed detection, the control unit compares the time interval T(n,m) of the immediately preceding pulse signal detected by the rotation detector (where m is the mth pulse in one rotation, and 1≦m≦M) with the time interval T(n-1,m) of the pulse signal from one rotation prior to the said pulse, and determines the rotational speed N of the rotor from the time interval T(n-1,m) and the increase or decrease in the time interval T(n,m). Furthermore, in addition to the rotational speed N for each rotation, the rotational speed N(n,m) at finer intervals is calculated using the formula N(n,m)=N(n-1,m)×T(n-1,m)÷T(n,m).

[0008] According to another feature of the present invention, the rotor rotation control includes acceleration control to increase the rotor rotation speed over time, deceleration control to decrease the rotor rotation speed over time, and constant speed control (settlement) to rotate at a constant rotation speed, and the speed is calculated from the increase or decrease in the pulse time interval T(n,m) during the rotor acceleration control or deceleration control. Furthermore, the control unit calculates the speed from the increase or decrease in the pulse time interval T(n,m) in the speed range where the rotor rotation speed is lower than a predetermined threshold speed. In the speed range where the rotor rotation speed is higher than the threshold speed, the rotation speed of the pulse signal (unit: per minute) for each rotation of the motor is calculated as N(n) = 60 / [T(n,1) + T(n,2) + ... T(n,m) + ... + T(n,M)]. The rotation detector is configured to include a disc attached to the motor's rotating shaft that transmits or blocks light, and a photointerrupter attached to the non-rotating part of the motor, with M pulse signals output from the photointerrupter per revolution of the motor. Alternatively, the rotation detector may be configured to include multiple magnets attached to the rotor and a magnetic detection element attached to the non-rotating part near the rotor, with M pulse signals output from the magnetic detection element per revolution of the motor.

[0009] According to yet another feature of the present invention, in a centrifuge, the rotation detector has a pulse time comparison speed detection mode that performs multiple speed detections within one rotation of the motor, and a normal speed detection mode that performs speed detection for each rotation of the motor. The control unit is configured to detect 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 to detect the rotation speed of the motor in the normal speed detection mode when the speed is equal to or greater than the switching threshold speed of the speed detection mode. The rotation detector generates M pulse signals (where M>1) per rotation of the motor. 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 one rotation prior, and calculates the speed using the rotation speed N(n,m) = N(n-1,m) × T(n-1,m) ÷ T(n,m). Furthermore, in the pulse time comparison speed detection mode of the centrifuge, the control unit is configured to detect the sum of the time intervals T(n-1,m=1,...M) of the pulse signals from the immediately preceding pulse detected by the rotation detector to the pulse signal from one rotation ago, and to calculate the speed N(n,m) = 60 / [T(n-1,1) + T(n-1,2) + ... + T(n-1,M)] × T(n-1,m) ÷ T(n,m) each time the width P(n,m) of the pulse signal is detected. [Effects of the Invention]

[0010] According to the present invention, in a centrifuge equipped with a rotation detector such as an encoder on the motor, the rotation speed is calculated based on the time change between the detected pulse and the pulse at the same rotation position one rotation earlier. Therefore, even if there is variation in the interval between each pulse of the output signal of the rotation detector, the rotation speed can be calculated stably. Furthermore, even when detecting the rotation speed using non-equally spaced pulse signals, such as when detecting the magnetization position with a Hall IC to identify the rotor, or when the pulse signals used to detect the rotation speed using a pulse-generating rotor are relatively prone to variation, the rotation speed can be detected with high accuracy without being affected by the strength of the magnetic force or distance. The speed detection method of the present invention is an effective rotation speed detection method for both ordinary rotation detectors that do not have high-standard pulse generation interval precision and rotation detectors that are intentionally manufactured with non-uniform pulse generation intervals. It is also an effective method for detecting speed in the range of relatively low motor rotation speeds. [Brief explanation of the drawing]

[0011] [Figure 1] This is a longitudinal cross-sectional view showing the overall configuration of centrifuge 1 according to an embodiment of the present invention. [Figure 2] (a) is a perspective view of another form of rotor 120 that can be attached to the centrifuge 1 in Figure 1, and (b) is a perspective view of the motor 8 used in the centrifuge 1 in Figure 1. [Figure 3] This is a time chart showing the operating conditions of the centrifuge 1 according to an embodiment of the present invention and the rotational speed of the rotor 20. [Figure 4] Figure 2 shows the output signal 90 from the rotation detector 85. [Figure 5] This table explains the types of time T(n) and rotational speed N(n) calculated from the output signal 90 in Figure 4. [Figure 6] This figure illustrates a method for calculating the rotational speed N from the waveform of the output signal 90 shown in Figure 4. [Figure 7] This figure illustrates another method for calculating the rotational speed N from the waveform of the output signal 90 shown in Figure 4. [Figure 8]This flowchart shows the speed detection procedure for centrifuge 1 according to a second embodiment of the present invention (Part 1). [Figure 9] This flowchart shows the speed detection procedure for centrifuge 1 according to a second embodiment of the present invention (part 2). [Modes for carrying out the invention] [Examples]

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following figures, the same parts are denoted by the same reference numerals, and repeated descriptions will be omitted. Furthermore, in this specification, the front, back, up, and down directions are described as the directions shown in the figures.

[0013] Figure 1 is a longitudinal cross-sectional view showing the overall configuration of the centrifuge 1 according to the present invention. The centrifuge 1 has a housing (frame) 2 having a rectangular cross-sectional shape when viewed from above, a door 6 that opens and closes the top of the housing 2, and a chamber 3 arranged inside the housing 2, in which a rotor 20 is rotated inside the chamber 3 (rotor chamber 4). The housing 2 has a plurality of legs 5 and is installed on a tabletop or the like. The door 6 is an openable and closable type, with the front side swinging vertically around a hinge 6a provided on the rear side. 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 rotation speed can be controlled by a control unit 10. The motor 8 is provided with a rotation detector 85 for detecting the rotation speed of the rotating shaft. A cylindrical support column (pole) 13 is provided to fix the motor 8 to the base portion 2a of the housing 2, and a rubber damper 14 is placed between the motor 8 and the support column 13 to reduce vibrations of the rotor 20 and the motor 8. An operation display panel 12, consisting of a touch-type liquid crystal display panel or the like, is provided on the front side of the housing 2. The operation display panel 12 is a means for inputting information from the user and a means for displaying information from the control unit 10 (for example, elapsed operating time, rotational speed (rpm)).

[0014] The rotor 20 is a dedicated rotor for cell washing and has a plurality (for example, 24) of test tube holders 31 arranged at equal intervals in the circumferential direction when viewed from above. The test tube holder 31 is pivotally supported by the rotor plate 22 of the rotor 20 on its inner peripheral side surface, and is held swingably (rotatably) in the centrifugal direction (radial direction). The test tube holder 31 is composed of a magnetic member and holds the test tube 40 so that it is inserted from above downward. Inside each test tube 40 (only one is shown in FIG. 1), a sample (liquid) containing biological cells such as red blood cells in advance is placed. Before the start of the centrifugation operation, the test tube 40 containing the sample is set in each of the test tube holders 31 by the hand of the operator.

[0015] The rotor 20 includes holding means 27 for holding the longitudinal central axis of the test tube holder 31 at a small swing angle that is perpendicular or nearly perpendicular. The holding means 27 maintains a state in which the metal test tube holder 31 cannot swing by adsorbing it by magnetic force, and uses a magnetic element such as an electromagnet. The holding means 27 can electrically switch between the adsorbed state (fixed state or non-swingable state) and the released state (swingable state) of the test tube holder 31. When the test tube holder 31 is in the adsorbed state, it functions as a so-called angle rotor having a negative swing angle, and when the test tube holder 31 is in the released 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 released state is about 45 degrees.

[0016] The rotor 20 for cell washing is detachable from the rotating shaft 82. Therefore, it is also possible to attach a normal angle rotor (see, for example, Fig. 2(a)) that cannot supply the cleaning liquid 17 during rotation to the rotating shaft 82, or another swing rotor (not shown). When attaching the rotor 20 for cell washing as in this embodiment to the rotating shaft 82, a cleaning liquid distribution element 25 is attached to the upper part of the rotor 20, and a liquid such as the cleaning liquid 17 is supplied into the test tube 40 during the rotation (swing) of the rotor 20 using the cleaning liquid supply pipe 18 provided in the door 6. The cleaning liquid distribution element 25 is inserted into the rotating shaft guide member 21 so as to rotate integrally with the rotor 20 mounting the circular row of test tube holders 31 and is installed on the rotor 20.

[0017] On the upper part of the cleaning liquid distribution element 25, a nozzle 19 serving as the outlet of the cleaning liquid supply pipe 18 is arranged on the rotation axis line A1, and the liquid falling from the nozzle 19 flows into the cleaning liquid inlet 25a located above the cleaning liquid distribution element 25. The cleaning liquid distribution element 25 has a cleaning liquid inlet 2aa at the upper part on the rotation axis line A1 and forms a space connected to a cleaning liquid passage 25b having a conical internal space. The outer edge part of the cleaning liquid passage 25b is divided in the circumferential direction, and a plurality of cleaning liquid injection ports 25c extending in the radial direction are formed.

[0018] A pump (not shown) is coupled to the outer end (the end far 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 by the control unit 10, the cleaning liquid 17 can be supplied from an external cleaning liquid tank (not shown) to the nozzle 19 located above the centrifuge 1 through the cleaning liquid supply pipe 18. In the cleaning liquid injection step described later, the cleaning liquid 17 ejected downward from the nozzle 19 enters the central part of the cleaning liquid distribution element 25 that rotates integrally with the rotor 20, is shunted to the outer peripheral side by the centrifugal force in the cleaning liquid distribution element 25, is branched into the same number (24) of each flow path as the test tubes 40 held by the test tube holders 31, and is vigorously injected into each test tube 40 from the cleaning liquid injection port 25c of the cleaning liquid distribution element 25. For the injection of the cleaning liquid 17 into each test tube 40, it is important to keep the rotation speed of the rotor 20 within a predetermined range (the rotation speed range N3 to N4 in Fig. 3 described later).

[0019] A bowl-shaped bottom surface 23 is formed at the bottom of the rotor 20. The bottom surface 23 is a container for receiving the washing solution 17 that spills out without entering the test tube 40, and also acts as a stopper to limit the swing angle θ of the test tube holder 31. In other words, the test tube holder 31 that holds the test tube rotates in the radial horizontal direction around the circumference of the rotor 20, tilting until the bottom of the test tube holder 31 touches the outer edge of the bottom surface 23, and in that state, the sample such as blood cells in the test tube 40 is centrifuged. As the washing solution 17 is injected while the rotor 20 is rotating, and excess washing solution 17 is discharged from inside the test tube 40, spilled washing solution 17 accumulates at the bottom of the chamber 3. For this reason, a drain hose 7 is connected to a part of the bottom of the chamber 3, and its outlet 7a is positioned to reach the outside of the housing 2. The user collects or disposes of the excess washing solution (waste liquid) using a hose or the like at the end of the outlet 7a.

[0020] Figure 2(a) is a perspective view of a different type of rotor 120 that can be mounted on the centrifuge 1 shown in Figure 1. The rotor 120 is a so-called angle rotor and is a different rotor from the rotor 20 shown in Figure 1. Various types of rotors, such as angle rotors and swing rotors, can be mounted on the centrifuge 1. On the upper side of the rotor 120, there are many holding holes (not visible in the figure) for holding multiple test tubes 40, arranged at equal intervals in the circumferential direction. A mounting hole 122 that can be fitted into the crown 9a shown in Figure 2(b) is formed at the tip of the rotating shaft of the motor 8. An annular portion 123, which serves as the bottom surface of an annular shape, is formed around the mounting hole 122, and multiple identifiers 124 for identifying the rotor 120 are provided in the circumferential direction of the annular portion 123. The shape of the mounting hole 122 that receives the crown 9a of the rotor 120, and the size and vertical position of the annular portion 123 arranged on the outer circumference of the mounting hole 122 are interchangeable with other rotors, including the rotor 120. Identifier 124 is formed or positioned to detect the rotating rotor 120 from outside the rotor, and identifier 124 is formed, for example, in a recess formed in the annular surface of an aluminum alloy or titanium alloy, or by forming a recess and inserting a cylindrical magnet.

[0021] Figure 2(b) is a perspective view of the motor 8 used in the centrifuge 1 of Figure 1. The rotor and stator of the motor 8 (not shown) are housed inside the motor housing 81, and the upper and lower sides of the rotating shaft 82 are formed to 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 screw holes 83a are formed in the flange portion 83. A crown 9a is connected to one side of the rotating shaft 82. On the other side (lower end side) of the rotating shaft 82 of the motor, a detection means for detecting the rotational speed of the motor 8, i.e., a rotation detector 85, is provided. The rotation detector 85 consists of an encoder disk 86 fixed to the lower end side of the rotating shaft 82 and a photointerrupter 88 that outputs a rotation pulse signal depending on the presence or absence of a slit 87 in the encoder disk 86. The control unit 10 receives the output signal (rotation pulse signal) 90 (see Figure 4 below) output from the photointerrupter 88, and measures the interval between the output signals 90 using an oscillator (clock) not shown, thereby detecting the rotation speed of the motor 8.

[0022] Next, the procedure for executing the washing cycle will be explained using Figure 3. Figure 3 is a time chart showing the rotational speed of the rotor 20 during the washing cycle. In the cell washing centrifuge 1 for washing living cells such as blood cells, the process includes not only the acceleration-constant speed-stop process of the rotor 20 as in a normal centrifuge (corresponding to times t1 to t3), but also the washing solution injection process shown by circle 1, and furthermore, after the centrifugal separation operation is completed (from time t3 onwards), the process includes the supernatant discharge process shown by circle 3 and the agitation process shown by circle 4.

[0023] First, the motor 8 is started between time 0 and time t1 to accelerate the rotor 20 to a centrifugal rotation speed N3. At this time, the swing of the test tube holder 31 is free, that is, the test tube holder 31 is not being held by the holding means 27 (see Figure 1). When the swing amount of the test tube holder 31 reaches its maximum at rotation speed N3 (approximately 1200 rpm) during the acceleration of the rotor 20, the washing solution 17 is dropped downward from the nozzle 19 and injected into the washing solution distribution element 25 from the washing solution inlet 25a. The washing solution 17 that has entered the washing solution distribution element 25 is distributed and supplied to the inside of multiple test tubes 40 through the washing solution passage 25b and the washing solution inlet 25c, through the upper opening of the swinging test tube. The washing solution 17, such as physiological saline, is forcefully injected into each test tube 40 from the washing solution distribution element 25 by centrifugal force. At this time, the blood cells in the test tubes 40 are sufficiently suspended in physiological saline.

[0024] At the point in the acceleration section, when the rotational speed N4, the injection of cleaning fluid 17 is completed, and at time t1, the rotational speed of the rotor 20 is the set rotational speed N for centrifugal separation operation. S Once this is reached, the operation is performed for the set time (centrifugation operation time = t2-t1), and the sample moves to the bottom in the washing solution by centrifugal force. At time t2, velocity N S Once the centrifugal separation operation for the set time is complete, the control unit 10 decelerates the motor 8 and stops the rotation of the rotor 20.

[0025] When the rotor 20 stops rotating at time t3, the supernatant liquid discharge process shown by circle 3 is performed. In this discharge process, the test tube holder 31 is attracted by energizing the coil of the holding means 27. At this time, the state of the test tube 40 is tilted so that the longitudinal central axis is slightly angled outward from the vertical. In this state, the rotor 20 is accelerated to a set speed N2 and operated for a certain period of time to decelerate the rotor 20. By rotating the rotor 20 with the angle of the test tube 40 in a slightly negative state, the supernatant liquid rises along the inner wall surface of the test tube 40 due to centrifugal force and is discharged to the outside, so that most of the supernatant liquid is discharged to the outside of the test tube 40.

[0026] When the rotor 20 stops at time t4, the oscillating process is performed next. The oscillating process is a process (AGITATE) in which the remaining cleaning solution 17 and the sample are stirred by oscillating the test tube holder multiple times in a short period of time. Here, the rotational speed of the rotor 20 is accelerated to N1, rotated at a constant speed for a short time, and then immediately decelerated. This acceleration-constant speed-deceleration-stop operation, with its rapid rotation and stopping, is repeated multiple times (5 times in this case). The cleaning cycle described above, from step 1 to step 4, is repeated multiple times, for example, about 3 to 4 times.

[0027] In the cleaning fluid injection process described above, the supernatant discharge process shown in circle 3, and the oscillation process shown in circle 4, it is important to precisely control the rotational speed of the motor 8. The rotational speed of the motor 8 is normally calculated by measuring the pulse interval for one revolution of the pulsed output signal 90 from the rotation detector 85. When the rotational speed is in the low speed range, the rotational speed may be calculated from the time of one pulse period instead of one revolution of the motor. Figure 4 shows an example of the pulse output signal 90 generated by this rotation detector 85. In Figure 4, for the sake of simplicity, the number of slits 87 in the encoder disk 86 of the rotation detector 85 is four, and the output signal 90 is shown in a configuration in which four pulses Pa, Pb, Pc, and Pd are output from the photointerrupter 88 when the motor 8 completes one revolution.

[0028] The output signal 90 goes high at the portion where light does not pass through where there is no slit 87 on the encoder disk 86 (for example, arrow 90a), and goes low when light passes through the slit 87 (for example, arrow 90b). The interval between each pulse of the output signal 90 is accurately measured by counting the interval with an oscillator (clock) not shown. Here, using the array (n, m), let n be a variable indicating which rotation of the motor 8 it is (n is an integer: 0 < n), and m be a variable indicating the order from the leading pulse at each rotation (m is an integer: 0 < m ≤ M. M represents the number of slits 87, and here M = 4). Therefore, the time interval of the pulse Pa in the n-th round shown in FIG. 4 is denoted as T(n, 1), the time interval of Pb in the n-th round is denoted as T(n, 2), the time interval of Pc in the n-th round is denoted as T(n, 3), and the time interval of Pd in the n-th round is denoted as T(n, 4). Incidentally, when the number of slits 87 on the encoder disk 86 is M (M > 4), during one rotation of the rotor 20 in the n-th time, M time intervals from T(n, 1) to T(n, 2), ··· T(n, M) will be measured.

[0029] FIG. 5 is a table for explaining the types of the calculated time T(n) and rotational speed N(n) from the output signal 90 in FIG. 4. Similar to the conventional rotation detector, without subdividing for each pulse, the time T(n) indicated by the reference numeral 52 is the time measured for one rotation of the rotor 20 in the n-th time, and the rotational speed N(n) for one rotation is indicated by the reference numeral 54. The control unit 10 measures the time intervals T(n, 1), T(n, 2), T(n, 3), and T(n, 4) (unit: seconds) for each of the pulses Pa, Pb, Pc, and Pd that appear when the rotor 20 makes one rotation during the n-th rotation. Then, the time 52 required for the rotor 20 to make one rotation in the n-th time is T(n)=T(n,1)+T(n,2)+T(n,3)+T(n,4) calculated by (unit: seconds). From this T(n), the rotational speed N(n) per minute of the rotor 20 in the n-th time is N(n)=60÷T(n) The speed is calculated as follows. In this embodiment, for this calculation, the time interval T(n,m) of the pulse period indicated by reference numeral 53 is measured for each pulse (Pa, Pb, Pc, Pd) for one rotation of the motor, temporarily stored in the memory area of ​​the control unit 10, and the pulse period time of the previous rotation and the pulse period time of the current rotation (after one rotation) are compared. Then, the motor speed is calculated from the rate of increase or decrease in the measurement time of the same pulse signal. The memory area can be the RAM included in the control unit 10 or a dedicated buffer memory, and by using the value of T(n-1,m) (where m=1~4) for the previous rotation stored in this memory, higher accuracy speed detection can be achieved than in the conventional method.

[0030] Figure 6 is a diagram illustrating the method for calculating the rotational speed N from the waveform of the output signal 90 shown in Figure 4. The waveform of the output signal 90 shown in Figure 6 from the position of arrow 55 to the position of arrow 56 is the output waveform of the output signal 90 shown in Figure 5 during the rotation one rotation ago (n-1 rotations). Here, in order to identify the pulses Pa, Pb, Pc, and Pd, we use the notations P(n-1,1), P(n-1,2), P(n-1,3), and P(n-1,4) to indicate which rotation the motor is on and which pulse it is. In reality, the control unit 10 does not need to identify which rotation the motor is on; it is sufficient to temporarily store the measured value from one or several rotations ago relative to the current rotation (n rotation) in the buffer memory.

[0031] At the point indicated by arrow 56, the motor's rotational speed N(n-1) can be calculated using the formula shown at the bottom of Figure 6(a). In conventional centrifuges, the next speed detection after arrow 56 occurs after the motor 8 has completed one rotation from arrow 56. This method of measuring the rotational speed every rotation is referred to as the "normal speed detection mode" in this specification. In this embodiment, in addition to the "normal speed detection mode," a "pulse time comparison speed detection mode" is provided, which also calculates the rotational speeds N(n,1), N(n,2), and N(n,3) at three additional timings, arrows 56a, 56b, and 56c, where pulse P appears during the process from arrow 56 to the next measurement timing after one rotation.

[0032] Focusing on pulse P(n,1), if the rotational speed is the same for the (n-1)th and (n)th pulses, then T(n-1,1) = T(n,1). When motor 8 is accelerating and the acceleration gradient is constant, the period of pulse P decreases at a constant rate. When motor 8 is decelerating and the deceleration gradient is constant, the period of pulse P increases at a constant rate. Noting that the rate of change of rotational speed is approximately equal to the ratio T(n-1,1) ÷ T(n,1), in this embodiment, the rotational speed at the time of pulse P(n,1) input is calculated by multiplying the previous rotational speed N(n-1) by the rate of change of the rotational speed. Therefore, by multiplying the rate of change of the motor 8's rotational speed detected last time by this rate, N(n,1) is calculated using the formula N(n-1) × T(n-1,1) ÷ T(n,1). This measurement method allows for four speed detections per revolution, rather than just one. This number is equivalent to the number of pulse signals M generated per revolution from the rotation detector 85.

[0033] Similarly, at the point indicated by arrow 56b, the rate of change of the rotational speed of motor 8 is the ratio of T(n-1,2) to T(n,2). Therefore, multiplying the previously detected rotational speed N(n-1) by this ratio, N(n,2)=N(n-1)×T(n-1,2)÷T(n,2) It can be calculated using [this method].

[0034] At point 56c, the rate of change of the rotational speed of motor 8 is the ratio of T(n-1,3) to T(n,3). Therefore, multiply the previously detected rotational speed N(n-1) by this ratio, N(n,3)=N(n-1)×T(n-1,3)÷T(n,3) It can be calculated using [this method].

[0035] Next, when motor 8 has rotated approximately 90 degrees from arrow 56c, that is, when it has completed one rotation from arrow 56, the same equation as in Figure 6(a) applies, i.e., N(n)=60÷[T(n,1)+T(n,2)+T(n,3)+T(n,4)] It can be calculated using [this method].

[0036] Thereafter, the rotational speed of the motor 8 is detected and calculated by repeating the same method. In this embodiment, the rotational speed N is calculated from the time change of pulses corresponding to the same slit 87, so the rotational speed can be calculated stably even if each pulse is non-uniform. Furthermore, even when detecting the rotational speed using non-equally spaced pulse signals, such as when detecting the magnetization position with a Hall IC to identify the rotor, or when the pulse signal is relatively prone to variation due to the strength of the magnetic force or distance, the rotational speed can be detected with high accuracy, making it an effective rotational speed detection method for non-uniform pulse generators. Moreover, the speed detection method according to this embodiment is effective for detecting speed in the region where the motor's rotational speed is relatively low.

[0037] Figure 7 illustrates another method for calculating the rotational speed N from the waveform of the output signal 90 shown in Figure 4. In Figure 6, the rotational speed N was calculated by multiplying the rotational speed N(n-1) by the rate of change of the motor 8's rotational speed for each pulse generation. In contrast, Figure 7 differs in that it calculates the rotational speed Nr for the previous rotation by multiplying it by the rate of change of the motor 8's rotational speed each time, allowing for a more instantaneous rotational speed N to be obtained.

[0038] In Figure 7(a), the rotational speed Nr(n-1,1) is calculated from the time taken for the (n-1)th motor rotation between arrows 55 and 56. For example, the rotational speed for the first rotation at the start of rotation is calculated from the time taken for one rotation of motor 8. In Figure 7(b), the rate of change of the rotational speed of motor 8 at arrow 56a is T(n-1,1)÷T(n,1), so this ratio is multiplied by the previously detected rotational speed Nr(n-1,1). N(n,1)=Nr(n-1,1)×T(n-1,1)÷T(n,1) It can be calculated using [this method].

[0039] At the point indicated by arrow 56a, the pulses for one rotation of motor 8 are (T(n-1,2), T(n-1,3), T(n-1,4), T(n,1)), so the rotational speed Nr(n-1,2) can be obtained from the following equation. Nr(n-1,2)=60÷ [T(n,1)+T(n-1,2)+T(n-1,3)+T(n-1,4)]

[0040] Similarly, at the point indicated by arrow 56b in Figure 7(c), the rate of change of the rotational speed of motor 8 T(n-1,2)÷T(n,2) and the rotational speed of motor 8 for the most recent rotation Nr(n-1,2) are used. N(n,2)=Nr(n-1,2)×T(n-1,2)÷T(n,2) It can be calculated as follows. In addition, the rotational speed Nr of motor 8 for one rotation can be calculated from the pulses for one rotation of motor 8 at the time of arrow 56b using the following formula. Nr(n-1,3)=60÷ [T(n,1)+T(n,2)+T(n-1,3)+T(n-1,4)]

[0041] Similarly, at the point indicated by arrow 56c in Figure 7(d), the rate of change of the rotational speed of motor 8 T(n-1,3)÷T(n,3) and the rotational speed of the most recent rotation Nr(n-1,3) are: N(n,3)=Nr(n-1,3)×T(n-1,3)÷T(n,3) It can be calculated from the following. Also, the rotational speed Nr can be calculated from the pulses for one rotation of motor 8 at the time of arrow 56c using the following formula. Nr(n-1,4)=60÷ [T(n,1)+T(n,2)+T(n,3)+T(n-1,4)]

[0042] As described above, the control unit 10 can sequentially measure the rotational speeds N(n,1), N(n,2), and N(n,3), thereby detecting the speed a number of times equal to the number of times the slits 87 of the rotation detector 85 pass through during one rotation of the motor 8. This speed detection control can be easily implemented by modifying the computer program executed by the microcontroller of the existing control unit 10, so the increase in manufacturing costs is minimal. In the above embodiment, the explanation was based on an example where the rotational speed is calculated using the output of an encoder, but it is also possible to calculate the motor's rotational speed using the above method with the output pulse of a Hall IC that detects the excitation position of a brushless motor, etc., or with the pulse signal of the rotor's identification ID. [Examples]

[0043] Next, a second embodiment of the present invention will be described using Figures 3, 8, and 9. In the first embodiment, it was assumed that the same speed measurement method would be used in all speed ranges. In the second embodiment, instead of using the speed detection method shown in the first embodiment in all speed ranges, speed detection is performed in the low speed range (see Figure 3) using the method of the first embodiment (pulse time comparison speed detection mode), and in the speed range (see Figure 3) above a certain threshold rotational speed (Nc), speed detection is performed once per revolution as in the conventional method (normal speed detection mode). The threshold speed Nc can be set to any value, but for example, if a dedicated rotor 20 for cell washing as shown in Figure 1 is used, it is preferable to set the threshold rotational speed Nc to be higher than the speed range (rotational speed N3~N4) in which the washing solution 17 is injected. By setting the threshold speed Nc in this way, the rotational speed of the rotor 20 in the washing solution injection step shown by circle 1 in Figure 3, the supernatant discharge step shown by circle 3, and the oscillation step shown by circle 4 can all be controlled by pulse time comparison speed detection mode with high accuracy.

[0044] Figure 8 is a flowchart showing the speed detection procedure of a centrifuge 1 according to a second embodiment of the present invention. Control in the second embodiment can be implemented by software, with the microcontroller of the control unit 10 executing a computer program. The control shown in Figure 8 starts when the user presses the start button for centrifugal separation operation on the operation display panel 12 of the centrifuge 1 and the motor 8 is started (step 61). First, a microcontroller (not shown) of the control unit 10 performs a rotational speed calculation process (A) using pulse time comparison speed detection mode (step 62). The microcontroller, having detected the rotational speed N of the motor 8 in the rotational speed calculation process (A), determines whether the rotational speed N has reached the threshold speed Nc for switching (step 63). If the threshold speed Nc for switching has not been reached in step 63, the process returns to step 62. If the switching speed has been reached in step 63, the microcontroller switches to speed detection using the normal speed detection mode for rotational speed calculation (B) and continues to detect the rotational speed N of the motor 8 (step 64).

[0045] The microcontroller continues the speed detection process (B) in step 64, and determines whether the centrifugal separation operation time has elapsed to the user-set time Ts (step 65). If it has not elapsed, it returns to step 64. If the set time Ts has elapsed in step 65, it proceeds to the deceleration process shown in Figure 9 (step 66).

[0046] Figure 9 is a flowchart following Figure 8, and step 67 is a process that continues from step 66. When the deceleration process starts, the rotational speed of motor 8 is calculated in the rotational speed calculation process (B) (step 68). Next, the microcontroller that has detected the rotational speed N of motor 8 determines whether the rotational speed N has become smaller than the threshold speed Nc for switching (step 69). If the rotational speed N is greater than or equal to the threshold speed Nc for switching, the process returns to step 68. If the rotational speed N falls below the threshold speed Nc for switching, the microcontroller of the control unit 10 switches to speed detection in the pulse time comparison speed detection mode rotational speed calculation process (A) and continues to detect the rotational speed N of motor 8 (step 70). In step 71, the microcontroller of the control unit 10 determines whether the motor 8 has stopped (rotational speed N=0) (step 71). If the rotation of motor 8 continues in step 71, the process returns to step 70, and if motor 8 has stopped, the process ends (step 72).

[0047] In the second embodiment, a method for switching the rotational speed calculation process of the motor 8 between a pulse time comparison speed detection mode and a normal speed detection mode was described. However, the methods in Figures 8 and 9 assume that the rotation of the motor 8 transitions from low speed to high speed. However, in the supernatant discharge process shown by circle 3 in Figure 3 and the oscillation process shown by circle 4, the control is limited to the low-speed rotation region where the rotational speed does not reach the threshold speed Nc for switching the speed detection mode. In that case, the control in Figures 8 and 9 can be simplified by not using the high-speed rotational speed calculation process (B).

[0048] Although the present invention has been described above based on two embodiments, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, in the embodiments described above, the microcontroller of the control unit 10 that controls the centrifuge 1 is configured to perform speed detection, but the present invention may also be applied when a separate microcontroller monitors the rotational speed of the motor 8 and detects abnormalities. [Explanation of symbols]

[0049] 1...Centrifuge, 2...Housing (frame), 2a...Base, 3...Chamber, 4...Rotor chamber, 5...Legs, 6...Door, 6a...Hinge, 7...Drain hose, 7a...Outlet, 8...Motor, 9...Crown, 10...Control unit, 12...Operation display panel, 13...Support column, 14...Damper, 17...Cleaning fluid, 18...Cleaning fluid supply pipe, 19...Nozzle, 20...Rotor, 21...Rotating shaft guide member, 22...Rotor plate, 23...Bottom surface, 25...Cleaning fluid distribution element, 2 5a...Cleaning fluid inlet, 25b...Cleaning fluid passage, 25c...Cleaning fluid inlet, 27...Holding means, 31...Test tube holder, 40...Test tube, 81...Motor housing, 82...Rotation shaft, 83...Flange section, 83a...Screw hole, 85...Rotation detector, 86...Encoder disk, 87...Slit, 88...Photo interrupter, 90...Output signal, 120...Rotor, 122...Mounting hole, 123...Ring ring section, 124...Identifier, A1...(Motor) rotation axis

Claims

1. A rotor having a plurality of test tubes arranged at equal intervals in the circumferential direction in a swingable state for performing cell washing, an inlet for introducing washing solution on the axis of rotation, and a washing solution distribution element for distributing the washing solution introduced from the inlet to the plurality of test tubes, A motor that rotates the rotor, A rotation detector for detecting the rotation of the motor, A centrifuge having a control unit that controls the rotation of the motor based on the output from the rotation detector and controls the supply of the cleaning liquid to the inlet while the rotor is rotating, The rotation detector has a pulse time comparison speed detection mode that performs speed detection multiple times within one rotation of the motor, and a normal speed detection mode that performs speed detection for each rotation of the motor. The control unit, A speed threshold for switching the speed detection mode is set within a speed range that is higher than the speed range in which the cleaning fluid flows in, and lower than the set rotational speed of the motor. If the rotational speed of the rotor is lower than the threshold, the rotational speed of the motor is detected in the pulse time comparison speed detection mode and the rotor speed is controlled. A centrifuge characterized in that, when the rotational speed is equal to or greater than the threshold, the rotational speed of the motor is detected in the normal speed detection mode and the speed of the rotor is controlled.

2. The centrifuge according to claim 1, characterized in that the control unit controls the injection of the cleaning solution into the inlet of the rotor when the pulse time comparison speed detection mode is active.

3. The rotation detector generates M pulse signals (where M > 1) for each rotation of the motor. In the pulse time comparison speed detection mode, the control unit detects the time interval T(n, m) of the pulse signal immediately preceding the one detected by the rotation detector and the time interval T(n-1, m) of the pulse signal one rotation earlier. The centrifuge according to claim 1, characterized in that the rotational speed is calculated using the formula N(n,m) = N(n-1,m) × T(n-1,m) ÷ T(n,m).

4. The rotation detector generates M pulse signals (where M > 1) for each rotation of the motor. In the pulse time comparison speed detection mode, the control unit detects the sum of the time intervals T(n-1, m=1, ...M) of the pulse signals from the immediately preceding pulse detected by the rotation detector to the pulse signal from one rotation earlier. Each time the width P(n,m) of the pulse signal is detected, Rotational speed N (n, m) = 60 / [T (n-1, 1) + T (n-1, 2) + ... + T (n-1, M)] ​​× T (n-1, m) ÷ T (n, m) The centrifuge according to claim 1, characterized in that it calculates speed using [a specific method].

5. The centrifuge according to claim 3 or 4, characterized in that in the normal speed detection mode, the control unit calculates the rotational speed of the pulse signal for each rotation of the motor using the formula N(n) = 60 / [T(n,1) + T(n,2) + ... + T(n,M)].

6. The rotation detector is A disc attached to the rotating shaft of the motor, which transmits or blocks light, The system includes a photointerrupter attached to the non-rotating portion of the motor, The centrifuge according to claim 5, characterized in that M pulse signals are output from the photointerrupter per rotation of the motor.

7. The rotation detector comprises a plurality of magnets attached to the rotor, It is configured to include a magnetic detection element attached to a non-rotating portion near the rotor, The centrifuge according to claim 5, characterized in that M pulse signals are output from the magnetic detection element per rotation of the motor.

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