JPH02168962A - Foam detector - Google Patents

Abstract

PURPOSE:To arbitrarily set the lower limit value of the size of bubble to be detected by providing the blood circuit of an artificial dialyser for the side of feedback to a patient and correcting a sensitivity error to occur by the change of the flow rate of a fluid to be measured. CONSTITUTION:The transmission frequency of a clock pulse generator 509 is changed by a control signal to be given from a signal processing part 508 based on the setting by a flow rate sensitivity setting device 506. The foam detector is adjusted so that detection sensitivity can be flat regardless of the change of a blood flow rate by heightening the frequency and increasing the detection sensitivity when the flow rate is large and lowering the frequency and decreasing the detection sensitivity when the flow rate is small. The lower limit value of the bubble to be detected is set by a bubble detection sensitivity setting device 507. Delay time t2 of a delay circuit 510 is changed by the control signal to be given from the signal processor 508 based on the setting by bubble detection sensitivity setting device 507. While the lower limit value of the bubble to be detected becomes larger when the delay time is set longer, the lower limit value becomes smaller when the delay time is set shorter, and up to a small bubble can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an air bubble detector provided on the return side to a patient of a blood circuit of an artificial dialysis machine.

<Prior art> Figure 3 shows the basic configuration of an artificial dialysis machine. 1 is a patient, 2
partitions an inner chamber 2b and an outer chamber 2c with a tubular membrane 2a,
It is a dial live in which blood and dialysate flow in opposite directions.

3 is a blood circuit connecting between the patient 1 and the dialyzer 2; a blood pump (tube bong) 4 is provided in the blood circuit between the blood side inlet of the dialyzer 2 and the patient 1; The blood circuit between the side outlet and the patient 1 is provided with an air bubble detector 5 and a locking mechanism 6 that closes the blood circuit based on the detection output of this air bubble detector. 7 is a dialysate circuit, and a dialysate pump 8 is provided in the dialysate circuit on the outlet side.

Dialysis is performed by driving a blood pump 4 and a dialysate pump 8. An air bubble detector 5 checks whether air bubbles are mixed in the treated blood returned from the dialyzer 2 to the patient 1.

FIG. 4 shows a conventional bubble detector, and the operation of this device will be explained according to the time chart of FIG. 5.

Reference numeral 501 designates a clock pulse generator that generates the drive pulse shown in FIG.

504 is a delay circuit that generates a latch pulse based on the drive pulse of the clock pulse generator 501, and 505 is a latch circuit.

When the driving pulse shown in FIG. 5 (a) is applied to the transmitting ultrasonic transducer 502, the ultrasonic wave shown in FIG.
Figure 0 (c) shows the received wave. The latch pulse in Figure 0 (d) is set according to the propagation time t of the ultrasonic wave from the transmitting ultrasonic transducer 502 to the receiving ultrasonic transducer 503. , the latch circuit 50 at the timing when the ultrasonic wave is received.
Latch 5. Since ultrasonic waves cannot be transmitted if there are air bubbles, the presence of air bubbles is detected based on this.

In the case of the conventional device, the sensitivity changes depending on the flow rate of blood flowing through the blood circuit 3. FIG. 6 is a characteristic diagram showing this state. The horizontal axis represents the bubble diameter, and the vertical axis represents the detection output (%).
C, , C2, C3 each have a flow rate of vI + v2 * v
3 is the characteristic curve.

Each flow rate has a relationship of vl<v2<v3. When the blood flow rate is large, the time for air bubbles to pass through the ultrasonic transducer portion becomes short, resulting in a decrease in sensitivity. With conventional devices, even if the sensitivity fluctuates depending on the flow rate of blood, it has not been possible to correct this. Further, in the conventional device, it is not possible to change the lower limit value of the bubbles to be detected, and even small bubbles may be detected unnecessarily.

<Problems to be Solved by the Invention> In the bubble detector, it is possible to correct sensitivity errors caused by changes in the flow rate of the fluid to be measured, and to arbitrarily set the lower limit of the size of bubbles to be detected. be.

Means for Solving the Problems> In order to achieve the above object, the bubble detector of the present invention has the following features: A. An ultrasonic transducer for transmitting and receiving disposed across a flow path through which a fluid to be measured flows. A first delay circuit whose delay time is set according to the lowest limit value of bubbles to be detected to delay the driving pulse from the driving pulse generating means C whose frequency is changed according to the flow rate of the fluid to be measured; D. A drive circuit E that excites the transmitting ultrasonic transducer based on the drive pulses respectively given from the drive pulse generation means and the first delay circuit. a second delay circuit F that generates a latch pulse; a third delay circuit G that delays the drive pulse from the first delay circuit by the propagation time of the ultrasound wave and generates a second latch pulse; a reception ultrasonic transducer A first latch circuit that latches the signal received by the receiving ultrasonic transducer with the first latch pulse. A second latch circuit that latches the signal received by the reception ultrasonic transducer with the second latch pulse. It is composed of a logic circuit that matches the output of the second latch circuit and outputs a bubble detection signal.

<Operation> In the present invention, the first ultrasonic wave based on a drive pulse directly applied from the drive pulse generating means and the second ultrasonic wave based on a drive pulse delayed by the first delay circuit are A bubble detection signal is output only when bubbles are detected by both ultrasonic waves in addition to the fluid being measured. Sensitivity adjustment based on a change in the flow rate of the fluid to be measured is performed by increasing the frequency of the emitted pulse of the drive pulse generating means when the flow rate is large to increase the detection sensitivity, and match the detection sensitivity when the flow rate is low.

The lower limit value of bubbles to be detected is set by adjusting the delay time of the first delay circuit. Increasing the delay time increases the lowest limit value of bubbles to be detected, and decreasing the delay time increases the minimum value of bubbles to be detected. Even air bubbles can be detected.

<Example> The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention, and FIG. 2 is a time chart showing the operation of this apparatus. In FIG. 1, the same elements as those in FIG. 4 are given the same reference numerals, and explanations thereof will be omitted.

506 is a flow rate sensitivity setting device for adjusting sensitivity based on changes in the flow rate of the fluid to be measured; 507 is a bubble detection sensitivity setting device for setting the lowest limit value of bubbles that should not be detected; 508 is a microprocessor-based The signal processing unit 509 is a clock pulse generator that generates drive pulses.
The oscillation frequency is changed by a control signal given from the signal processing section 508 based on the setting by the flow rate sensitivity setter 506. 510 is a clock pulse generator 509
The delay time is set by a control signal given from the signal processing section 508 based on the setting by the bubble detection sensitivity setting device 507. 5
Reference numeral 11 denotes a drive circuit that excites the transmitting ultrasonic transducer 502 based on a drive pulse directly given from the clock pulse generator 509 and a drive pulse given from the delay circuit 510; 512 a clock pulse generator 5;
513 is a delay circuit 510 that delays the driving pulse from 09 by the propagation time of the ultrasonic wave and generates a latch pulse.
514 is a latch circuit that latches the signal received by the reception ultrasonic transducer 503 with the latch pulse from the delay circuit 512; 515 is a reception A latch circuit that latches the signal received by the ultrasonic transducer 503 using a latch pulse from a delay circuit 513; 516 is a latch circuit I;
This is an AND circuit given an output of M51/1.515.

The operation of the apparatus according to the embodiment of the present invention will be explained according to the time chart shown in FIG. In FIG. 2, (a) shows a driving pulse from the clock pulse generator 509, and (b) shows a driving pulse delayed by a delay time t2 in a delay circuit 510.
Figure (c) shows the ultrasonic wave excited by these drive pulses and emitted from the transmitting ultrasonic transducer 502, Figure (d) shows the latch pulse that is the output of the delay circuit 512, and Figure (e) shows the output of the delay circuit 513. Represents a certain Tsuku pulse.

Figures (f) to (q) represent the outputs of the latch circuits 514, 515 and the AND circuit 516 in four different detection states. Figures (f) to (h) represent the outputs of the latch circuit 514 in the first detection state. This detection state represents the output of the latch circuit 515 and the output of the AND circuit 516. This detection state is a state in which there are no bubbles, and the bubble detection signal is not output from the AND circuit 516. Output of latch circuit I#l514 in detection state, latch circuit 51
5 and the output of the AND circuit 516. In this detection state, the diameter of the bubble is small, and the bubble that was present in the detection area when the first ultrasonic wave was emitted remains in the detection area when the second ultrasonic wave is emitted. Figures <1> to (n> represent the output of the latch circuit 514, the output of the latch circuit 515, and the output of the AND circuit 516 in the third detection state are shown in FIG. In the detection state, the diameter of the bubble is sufficiently large, a detection output appears in both latch circuits 514 and 515, and a bubble detection signal is output from the AND circuit 516. Based on this output, the side 6 of the lock 81 is activated to open the blood circuit 3. Figure (q) shows the output of the latch circuit 514 in the fourth detection state, and the latch circuit FI in the fourth detection state.
This detection state represents the output of @515 and the output of AND circuit 516. This detection state is when no air bubbles were detected when the first ultrasonic wave was emitted, but air bubbles were detected when the second ultrasonic wave was emitted. Since the diameter of the bubble is unknown, it is ignored.

Sensitivity adjustment based on flow rate changes is performed by a flow rate sensitivity setter 506. Based on the setting by the flow rate sensitivity setter 506, the oscillation frequency of the tarok pulse generator 509 is changed by a control signal given from a signal processing section 508.

When the flow rate is large, the frequency is raised to increase the detection sensitivity, and when the flow rate is low, the frequency is lowered to lower the detection sensitivity, and the sensitivity is adjusted to be flat regardless of changes in the blood flow rate.

In the case of an artificial dialysis machine, the blood flow rate depends on the rotation speed of the blood pump 4, and it is also possible to automatically change the oscillation frequency of the tarok pulse generator 509 using the rotation drive signal of the blood pump 4. .

The lowest limit value of bubbles to be detected is set by the bubble detection sensitivity setter 507.Based on the setting by the bubble detection sensitivity setter 507, the delay time of the delay circuit 510 is set to 1'ffJt2 by a control signal given from the signal processing unit 508. change. Increasing the delay time increases the lowest limit of detected bubbles, and decreasing the delay time decreases the lowest limit, making it possible to detect even small bubbles.

<Effects of the Invention> According to the present invention, sensitivity can be kept constant even when the flow rate of the fluid to be measured changes, and the lowest value of bubbles to be detected can be set arbitrarily, so even unnecessarily small bubbles can be detected. There is no such thing.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the apparatus according to the embodiment of the present invention, Fig. 2 is a time chart showing the operation of the apparatus according to the embodiment of the present invention, Fig. 3 is a diagram showing the principle block diagram of the artificial dialysis apparatus, and Fig. 4 is a conventional air bubble 5 is a diagram showing the configuration of the detector, FIG. 5 shows timing charts 1 to 1 showing the operation of the conventional device shown in FIG. 4, and FIG. 6 is a characteristic diagram of the conventional device. 3... Blood circuit, 5... Air bubble detector, 502...
Ultrasonic transducer for transmission, 503... Ultrasonic transducer for reception, 506... Flow rate sensitivity setting device, 507... Bubble detection sensitivity setting device, 508... Signal processing unit, 509... Clock pulse generator, 510, 512, 513
Delay circuit, 511... Drive circuit, 514, 515...
・Figure Figure Figure M Mouth G

Claims (1)

[Claims] A bubble detector that emits ultrasonic waves into a flow path through which a fluid to be measured flows and detects air bubbles in the fluid to be measured from the attenuation of the ultrasonic waves, which is comprised of the following components A to I. Features a bubble detector. A Transmitting/receiving ultrasonic transducer arranged across the flow path through which the fluid to be measured flows B Driving pulse generating means C in which the frequency of the emitted pulse is changed according to the flow rate of the fluid to be measured A first delay circuit D whose delay time is set according to the lower limit value and delays the drive pulse from the drive pulse generation means; Ultrasonic vibration for transmission based on the drive pulses respectively given from the drive pulse generation means and the first delay circuit. A drive circuit E that excites the drive pulse. A second delay circuit F that delays the drive pulse from the drive pulse generation means by the propagation time of the ultrasound wave and generates the first latch pulse. A third delay circuit G that delays the propagation time of and generates a second latch pulse.A first latch circuit H that latches the signal received by the reception ultrasonic transducer with the first latch pulse.A reception ultrasonic vibration A second latch circuit I that latches the signal received by the second latch pulse with a second latch pulse.A logic circuit that matches the outputs of the first and second latch circuits and outputs a bubble detection signal.