JP4312206B2 - Infusion pump with function to cut off motor applied voltage - Google Patents

Description

  The present invention relates to a medical infusion pump that uses a disposable syringe.

  Since medical devices are required to have high safety, it is required that the motor can be surely stopped when an abnormality occurs. The motor stop circuit had to have a means for confirming that the circuit itself functions normally.

JP, 2004-162647, Syringe pump device JP, 2004-215966, A Syringe pump As conventional technology, it was corresponding to this demand by making it the circuit composition as shown in FIG. 1 is a power supply circuit, 2 is a transistor circuit of a motor drive circuit, 3 is an electrolytic capacitor, 4 is a switch element, 5 is a current detection resistor, 6 is a freewheeling diode, 7 is a motor, 8 is a voltage comparison circuit, and 9 is a comparison threshold voltage Reference numeral 10 denotes a microcomputer having an abnormality monitoring function. In the conventional method, a switch element such as a MOSFET is inserted in the current path from the transistor of the motor drive circuit to the electrolytic capacitor, and the voltage applied to the motor at the time of abnormality is cut off by this switch element. As a method for confirming the cutoff function, the voltage change generated by opening and closing of the switch element is observed.

FIG. 4 shows the opening / closing of the switch element and the change in the current and voltage of each part. Normally, the switch element is closed, the motor is energized, and the switch element is opened for a short period at regular intervals to cut off the current supply to the motor. At this time, if the switch element operates normally, the current tends to continuously flow through the freewheeling diode due to the inductance component of the motor winding, so that the input voltage Vin of the voltage comparison circuit rises to the power supply voltage Vm. . When the value of Vin is equal to or less than the threshold value Vth2 after a predetermined delay time Tth2 after the switch element is opened, it is determined that the switch element has failed, and safety measures such as operation stop and alarm generation are taken.

  Since the action of the current flowing through the motor and the inductance component of the motor winding is used to check the shut-off function, Vin is always zero regardless of the switch element status when no current flows through the motor. It becomes. For example, even if a failure occurs, the device cannot be found before the motor operation, and the failure can be found only after the operation starts. Further, since the current supply is cut off during the motor operation for confirmation, a temporary decrease in the output of the motor occurs, and thus confirmation in a short time that does not affect the operation of the apparatus is necessary. Furthermore, when a phase switching function by a drive circuit such as a stepping motor or a brushless motor is required as a motor, it is necessary to consider so as not to overlap with the motor current switching timing.

  In the method invented this time, the change in voltage due to the opening and closing of the switch element is common, but the insertion position of the switch element is moved between the electrolytic capacitor of the drive circuit and the power supply circuit as shown in FIG. The point is different.

  When the switch element is cut off, the terminal voltage of the electrolytic capacitor, which was initially equal to the input voltage Vin of the voltage comparison circuit, gradually decreases due to the current consumed by the drive circuit even when no current flows through the motor. I will do it. For this reason, it is possible to perform continuous monitoring including when the motor is not driven by determining that the case where the value of Vin holds the threshold value Vth1 or more after the delay time Tth1 according to the situation is abnormal. In addition, if the drive circuit has a function such as PWM control, the motor output can be kept constant even if the terminal voltage of the electrolytic capacitor decreases, and it is possible to check regardless of the phase switching timing. , The degree of freedom of processing is improved.

  The state of the switch element is controlled by the output signal of the microcomputer, and the output signal of the voltage comparison circuit is also input to the microcomputer, so that the failure determination of the cutoff function is executed by the program. As the switch element to be used, a semiconductor element other than a MOSFET, for example, a bipolar transistor may be used. In addition to comparing the reference voltage with a reference voltage using an IC such as a comparator, the voltage comparison circuit uses the operating voltage between the input terminal of the logic IC and the base and emitter of the transistor to digitize the result. Data may be input or compared with reference data by a microcomputer program using an A / D converter.

  FIG. 1 shows a circuit configuration of an embodiment of the device of the present invention, wherein 1 to 10 are the same as those in FIG. Reference numeral 11 denotes a motor control microcomputer independent of 10.

  FIG. 2 shows the opening and closing of the switch element and the changes in the current and voltage of each part associated therewith. If the switch element is opened while the motor is driven, the motor current from the power supply circuit is cut off, but the motor current continues to flow due to the current supplied from the electrolytic capacitor. Then, the terminal voltage of the electrolytic capacitor, which is the input voltage Vin of the voltage comparison circuit, decreases. When this Vin is observed and it is determined that the voltage is lower than a predetermined voltage Vth1 that is lower than the output voltage Vm of the power supply circuit that can occur in a normal use state by a predetermined delay time Tth1, the cutoff circuit is normal. Judge that it worked. Furthermore, the influence on the motor operation is minimized by setting the microcomputer program to close the switch element without waiting for Tth1 when Vin falls below Vth1.

  Since it is possible to improve the safety of the device by adding simple parts, it can be applied for the purpose of preventing damage to human bodies and objects in fields other than medical devices.

Motor applied voltage cutoff circuit of the present invention Voltage and current of each part in the present invention Prior art motor applied voltage cutoff circuit Voltage and current of each part of the conventional technology

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply circuit 2 Motor drive circuit 3 Electrolytic capacitor 4 Switch element 5 Current detection resistance 6 Free-wheeling diode 7 Motor 8 Voltage comparison circuit 9 Comparison threshold voltage 10, 11 Microcomputer Vin Input voltage Vm of voltage comparison circuit Output voltage Vtn1, Vth2 Comparison threshold voltage Tth1, Ttn2 Abnormal judgment delay time

Claims (2)

A medical infusion pump configured to perform an infusion operation by driving a motor,
Includes a blocking function for cutting off power supply to the motor driving circuit, a constant check is available monitoring to that the blocking function operates normally as a safety measure when the motor is uncontrollable become abnormal ,
The motor drive circuit is supplied with power from a power supply circuit and an electrolytic capacitor connected in parallel thereto,
The shut-off function is configured using a switch element inserted in a power supply line between the power supply circuit and the electrolytic capacitor,
The monitoring function opens the switch element for a short period at regular intervals, detects the terminal voltage of the electrolytic capacitor after the switch element is opened, and sets the terminal voltage to a predetermined delay time after the opening. An infusion pump comprising: a microcomputer that determines normal operation of the switch element by lowering the voltage . A infusion pump according to claim 1, in addition to the microcomputer improve reliability, equipped with a microcomputer for controlling the motor driving circuit, a control signal of the motor drive circuit, the control signal for the motor power cutoff function An infusion pump characterized by having a function of stopping the motor more reliably when an abnormality occurs by adopting a configuration that outputs from a different microcomputer.

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