US20150322939A1

US20150322939A1 - Liquid transport device and liquid transport method

Info

Publication number: US20150322939A1
Application number: US14/710,475
Authority: US
Inventors: Makoto Katase
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2014-05-12
Filing date: 2015-05-12
Publication date: 2015-11-12
Also published as: JP2015214931A; CN105079916A

Abstract

A liquid transport device includes an elastic tube, fingers that line up along a transport direction, a drive mechanism that drives the fingers, a temperature sensor that measures the ambient temperature of the tube, and a control unit. The control unit controls the drive mechanism such that the finger on the most upstream side of the transport direction starts a closing operation of squeezing the tube after the finger on the most downstream side of the transport direction completes the closing operation of squeezing the tube, and the finger second from the downstream side completes an opening operation of being pressed back by the tube. The control unit controls the rate of driving of the drive mechanism in a corrective manner based on a result of measurement by the temperature sensor. The liquid transport device can transport a liquid with high accuracy regardless of the ambient temperature of the tube.

Description

BACKGROUND

1. Technical Field
The present invention relates to a liquid transport device and a liquid transport method.
2. Related Art
As a liquid transport device, there is known a device in which a plurality of fingers arranged along an elastic tube is pressed by a cam and sequentially squeezes the tube to transport a liquid in the tube. Such a liquid transport device is used for injecting a liquid medicine such as insulin into a body. However, depending on the ambient temperature at which the liquid transport device is used, the rigidity of the tube differs, and the rate of flow of the liquid flowing through the tube is not constant. Thus, there is proposed a method that controls the speed of rotation of a motor on the basis of a temperature that is detected by a temperature sensor disposed in the vicinity of the tube.
As described above, in the device that transports a liquid with the fingers squeezing the tube, the amount of transport of a liquid is determined by the amount of a liquid that is captured in the tube when the fingers on the upstream side of the tube squeezes the tube. Therefore, simply changing the speed of rotation of the motor depending on the temperature in the vicinity of the tube, as disclosed in JP-A-10-216226, causes the state of restoration of the tube that is squeezed by the finger on the downstream side to vary when the finger on the upstream side squeezes the tube, and variations occur in the amount of a liquid that is captured in the tube, that is, the amount of a liquid to transport. Thus, it is not possible to transport a liquid with high accuracy.

SUMMARY

An advantage of some aspects of the invention is to provide a liquid transport device and a liquid transport method that transports a liquid with high accuracy regardless of the ambient temperature of a tube.
An aspect of the invention is directed to a liquid transport device including a tube that has elasticity and is intended to transport a liquid in a transport direction, a plurality of fingers that is lined up along the transport direction, a drive mechanism that drives the plurality of fingers, a temperature sensor that measures the ambient temperature of the tube, and a control unit that controls the drive mechanism in a manner in which a liquid inside the tube is transported in the transport direction by repeating a closing operation of squeezing the tube with the finger and an opening operation in which the finger is pressed back by the shape of the squeezed tube being restored, in which the control unit controls the drive mechanism in a manner in which the finger on the most upstream side of the transport direction starts the closing operation after the finger on the most downstream side of the transport direction completes the closing operation, and the finger that is second from the downstream side of the transport direction completes the opening operation, and controls the rate of driving of the drive mechanism in a corrective manner on the basis of a result of measurement by the temperature sensor.
Other features of the invention will become more apparent from the disclosure in the present specification and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 is an exploded view of a liquid transport device.

FIG. 2 is a transparent top view of the inside of the liquid transport device.

FIG. 3 is a cross-sectional view of the liquid transport device.

FIG. 4A is a diagram describing the inside of a finger base, and FIG. 4B is a block diagram describing a control unit of the liquid transport device.

FIG. 5 is a diagram describing control of operation of a finger in an embodiment.

FIG. 6 is a diagram describing control of operation of the finger in the embodiment.

FIG. 7 is a diagram describing control of operation of a finger in a comparative example.

FIG. 8 is a diagram describing control of operation of the finger in the comparative example.

FIG. 9 is a graph illustrating the amount of transport of a liquid when the ambient temperature of a tube and the speed of rotation of a cam are changed.

FIG. 10 is a diagram representing a difference in the cross-sectional extent of the tube due to a difference in the ambient temperature of the tube.

FIG. 11 is a correction table for the amount of rotation of the cam.

FIG. 12 is a flowchart of the flow of a liquid transport method in the liquid transport device.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

At least the following items are apparent from the disclosure in the present specification and the appended drawings.
A liquid transport device includes a tube that has elasticity and is intended to transport a liquid in a transport direction, a plurality of fingers that is lined up along the transport direction, a drive mechanism that drives the plurality of fingers, a temperature sensor that measures the ambient temperature of the tube, and a control unit that controls the drive mechanism in a manner in which a liquid inside the tube is transported in the transport direction by repeating a closing operation of squeezing the tube with the finger and an opening operation in which the finger is pressed back by the shape of the squeezed tube being restored, in which the control unit controls the drive mechanism in a manner in which the finger on the most upstream side of the transport direction starts the closing operation after the finger on the most downstream side of the transport direction completes the closing operation, and the finger that is second from the downstream side of the transport direction completes the opening operation, and controls the rate of driving of the drive mechanism in a corrective manner on the basis of a result of measurement by the temperature sensor.
According to the liquid transport device, a liquid can be transported with high accuracy regardless of the ambient temperature of the tube.
In the liquid transport device, it is preferable that the rate of driving of the drive mechanism is the amount of rotation of the drive mechanism.
According to the liquid transport device with this configuration, since the amount of rotation of the drive mechanism is corrected, errors hardly occur in the amount of rotation of the drive mechanism when compared with a case of correcting the speed of rotation of the drive mechanism (amount of rotation per unit time), and a liquid can be transported with high accuracy.
In the liquid transport device, it is preferable that the drive mechanism includes a piezoelectric motor, and the temperature sensor is a sensor that measures the ambient temperature of the piezoelectric motor for use in control of drive of the piezoelectric motor.
According to the liquid transport device with this configuration, the number of components can be reduced when compared with a case where a dedicated sensor that measures the ambient temperature of the tube is disposed separately from a sensor that measures the ambient temperature of the piezoelectric motor, and cost can be reduced.
In the liquid transport device, it is preferable that the control unit controls the drive mechanism in a manner in which the speed of drive of the drive mechanism is constant.
According to the liquid transport device with this configuration, a liquid can be transported with high accuracy regardless of the ambient temperature of the tube, and control by the control unit can be facilitated when compared with a case of changing the speed of drive of the drive mechanism depending on the ambient temperature of the tube.
In the liquid transport device, it is preferable that the control unit changes the speed of the drive mechanism to an extent in which the finger on the most upstream side starts the closing operation after the finger on the most downstream side completes the closing operation, and the finger that is second from the downstream side completes the opening operation.
According to the liquid transport device with this configuration, a liquid can be transported with high accuracy regardless of the ambient temperature of the tube, and the processing time of a transport operation (time of transport of a predetermined amount of a liquid) can be adjusted by adjusting the speed of drive of the drive mechanism according to the corrected rate of driving of the drive mechanism.
In the liquid transport device, it is preferable that the extent of the cross section of the inside of the tube after the opening operation is completed, the cross section being taken by cutting the tube in a direction that is perpendicular to the axial direction of the tube, changes depending on the ambient temperature of the tube.
According to the liquid transport device with this configuration, a liquid can be transported with high accuracy regardless of the ambient temperature of the tube.
In the liquid transport device, it is preferable that the control unit controls the drive mechanism in a manner in which a transport operation of transporting a liquid in the tube with drive of the plurality of fingers and a stopping operation of not transporting a liquid in the tube with stopping of drive of the plurality of fingers are alternately repeated.
According to the liquid transport device with this configuration, a liquid can be transported with high accuracy regardless of the ambient temperature of the tube, and an increase or a decrease in the processing time of the transport operation depending on the corrected rate of driving of the drive mechanism does not pose a problem. Thus, the extent of freedom is increased insetting the speed of drive of the drive mechanism.
A liquid transport method for a liquid transport device that includes a tube which has elasticity and is intended to transport a liquid in a transport direction, a plurality of fingers which is lined up along the transport direction, and a drive mechanism which drives the plurality of fingers, in which a liquid in the tube is transported in the transport direction by repeating a closing operation of squeezing the tube with the finger and an opening operation in which the finger is pressed back by the shape of the squeezed tube being restored, the method includes obtaining the ambient temperature of the tube, and driving the plurality of fingers with the drive mechanism at a rate of driving that is corrected on the basis of the ambient temperature and driving the plurality of fingers in a manner in which the finger on the most upstream side of the transport direction starts the closing operation after the finger on the most downstream side of the transport direction completes the closing operation, and the finger that is second from the downstream side of the transport direction completes the opening operation.
According to the liquid transport method, a liquid can be transported with high accuracy regardless of the ambient temperature of the tube.

Configuration of Liquid Transport Device

FIG. 1 is an exploded view of a liquid transport device 1. FIG. 2 is a transparent top view of the inside of the liquid transport device 1. FIG. 3 is a cross-sectional view of the liquid transport device 1. FIG. 4A is a diagram describing the inside of a finger base 202, and FIG. 4B is a block diagram describing a control unit 110 of the liquid transport device 1. The liquid transport device 1 in the present embodiment includes a main body 10, a cartridge 20, and a patch 30. The main body 10, the cartridge 20, and the patch 30 are separable as illustrated in FIG. 1 but are assembled as a single body when used. The liquid transport device 1 is suitably used for regularly injecting a liquid (for example, insulin) that is retained in the cartridge 20 into a living body while the patch 30 adheres to a living body. In FIG. 1, the side of the liquid transport device 1 where the liquid transport device 1 adheres to a living body is assumed to be a lower side, and the opposite side is assumed to be an upper side.

Main Body

10

The main body 10 includes a piezoelectric motor 100, a speed reducing transmission mechanism 103, and a cam 104 as illustrated in FIG. 2. The piezoelectric motor 100 includes a plate-shaped member 101 and a pair of springs 102. The speed reducing transmission mechanism 103 includes a rotor wheel 105, an intermediate wheel 106, and an output shaft 107. The plate-shaped member 101 is biased toward the rotor wheel 105 by the elasticity of the pair of springs 102, and the tip end portion of the plate-shaped member 101 is in contact with the circumferential surface of the rotor wheel 105. In addition, the plate-shaped member 101 includes a piezoelectric layer and two electrodes. The shape of the plate-shaped member 101 is changed by a change in a voltage applied to the two electrodes. The rotor wheel 105 is rotated by, for example, the plate-shaped member 101 repeatedly alternating longitudinal vibrations that change the length of the plate-shaped member 101 in the width direction thereof and flexural vibrations that change the shape of the plate-shaped member 101 into a substantially S shape.
A pinion that rotates together with the rotor wheel 105 is disposed in the rotor wheel 105. The pinion engages with a teeth portion of the intermediate wheel 106 and rotates the intermediate wheel 106. A pinion is also disposed in the intermediate wheel 106. The pinion engages with a teeth portion of a toothed wheel that rotates together with the output shaft 107 and rotates the output shaft 107. The cam 104 is disposed in the output shaft 107. The cam 104 is rotated by rotation of the output shaft 107. As such, rotation of the rotor wheel 105 is transmitted to the cam 104 at a predetermined speed reduction ratio. A motor for rotating the cam 104 is not limited to the piezoelectric motor 100 and may be any motor having a rotating shaft. A secondary battery 108 is disposed on the lower surface of the main body 10 and is capable of supplying a predetermined amount of electricity to each unit of the main body 10.
The main body 10 also includes a control unit 110 and a detector group 112 as illustrated in FIG. 2 and FIG. 4B. The control unit 110 is an electronic substrate that includes a CPU 110 a and a memory 110 b and is intended to control a drive mechanism 111 (the piezoelectric motor 100, the speed reducing transmission mechanism 103, and the cam 104) according to a signal from a program and the detector group 112. The drive mechanism 111 drives a plurality of fingers 21 illustrated in FIG. 4A. The detector group 112 includes a rotary encoder (not illustrated) that measures the amount of rotation of the rotor wheel 105 and the cam 104 (angle of rotation), a temperature sensor 109, and the like. The temperature sensor 109, for example, is disposed in the vicinity (on the electronic substrate, which is the control unit 110, in the present embodiment) of the piezoelectric motor 100 because vibration characteristics of the piezoelectric motor 100 are affected by the ambient temperature. The control unit 110 controls drive (drive frequency) of the piezoelectric motor 100 on the basis of a result of measurement by the temperature sensor 109, that is, the ambient temperature of the piezoelectric motor 100.

Cartridge

20

The cartridge 20 includes a retaining portion 201 that retains a liquid, the finger base 202, a connecting needle 203, the finger 21, and a tube 22 as illustrated in FIG. 3. The tube 22 is a tube that is elastic and is intended to transport a liquid in a transport direction. The end portion of the tube 22 on the upstream side of the transport direction communicates with the retaining portion 201, and the end portion thereof on the downstream side of the transport direction communicates with the connecting needle 203. In addition, as illustrated in FIG. 4A, the tube 22 is arranged along an arc-shaped inner circumferential surface 202A of the finger base 202. When the main body 10 is attached to the cartridge 20, the cam 104 is positioned in the central portion of the finger base 202. In the finger base 202, the plurality of fingers 21 is arranged to be lined up along the arc-shaped tube 22 (along the transport direction), one end of the finger 21 is in contact with the cam 104, and the other end thereof is in contact with the tube 22.
The cam 104 has a plurality (four in FIG. 4A) of protruding portions on the outer circumference thereof. Thus, when the cam 104 rotates, the protruding portions of the cam 104 press the fingers 21 in order from the upstream side of the transport direction, and the fingers 21 squeeze the tube 22 (closing operation). When the fingers 21 are separated from the protruding portions of the cam 104, the shape of the squeezed tube 22 is restored because of the elasticity of the tube 22, and the fingers 21 are pressed back toward the cam 104 (opening operation). The control unit 110 controls the drive mechanism 111 in such a manner that the closing operation and the opening operation are repeated. This moves the tube peristaltically, and a liquid inside the tube 22 is transported to the patch 30 through the connecting needle 203.

Patch

30

The patch 30 includes a catheter 310, an introducing needle 320, an introducing needle folder 321, a port base 330, and a patch base 340 as illustrated in FIG. 3. The patch base 340 is a plate-shaped member that is fixed to the port base 330 and covers the lower surface of the cartridge 20. The patch base 340 adheres to a living body. The catheter 310 is a tube that is comparatively soft and is inserted and implanted in a living body in order to inject a liquid into a living body. The introducing needle 320 is a metal needle for inserting the catheter 310 into a living body and is held by the introducing needle folder 321. The introducing needle folder 321 is attached to the port base 330 at the time of the liquid transport device 1 being mounted on a living body. After the introducing needle 320 is inserted into a living body along with the catheter 310, the introducing needle folder 321 is plucked from the port base 330 along with the introducing needle 320, and only the catheter 310 is inserted in a living body. The side portion on the cartridge 20 side of the port base 330 communicates with the connecting needle 203. A liquid from the connecting needle 203 sequentially passes through the port base 330 and the catheter 310 to be injected into a living body.

Control of Liquid Transport Device

Filled-Up Time

FIG. 5 and FIG. 6 are diagrams describing control of operation of the fingers 21 in the present embodiment. FIG. 7 and FIG. 8 are diagrams describing control of operation of the fingers 21 in a comparative example. FIG. 5 and FIG. 7 are diagrams illustrating a relationship between the operation of the fingers 21 and a time. FIG. 6 and FIG. 8 are diagrams illustrating the state of the fingers 21 and the tube 22 at a time e. The tube 22 is depicted as a linear shape in FIG. 6 and FIG. 8 for simplification of the drawings. In addition, for descriptive purposes, the fingers 21 are called a first finger 21 a, a second finger 21 b, . . . , and a seventh finger 21 g in order from the upstream side of the transport direction.
As illustrated in FIG. 5, the first finger 21 a, for example, on the most upstream side of the transport direction starts the closing operation (squeezes the tube 22) when pressed by the protruding portions of the cam 104 at a time a and completes the closing operation at a time b, going into a closing state. Completion of the closing operation means a state where the fingers 21 completely squeeze the tube 22, and a liquid cannot pass through the tube 22. This state is called a closing state. After being in the closing state continuously for a predetermined period of time, the first finger 21 a is separated from the protruding portions of the cam 104 at a time c and is just in contact with the tube 22 without pressing the tube 22. Then, the tube 22 presses the first finger 21 a back with the elasticity thereof, and the first finger 21 a completes the opening operation at a time d, going into an opening state. Completion of the opening operation means a state where the shape of the squeezed tube 22 is restored to the original shape thereof. This state is called an opening state. After being in the opening state continuously for a predetermined period of time, the first finger 21 a starts the closing operation again at the time e.
The second to the seventh fingers 21 b to 21 g also operate in the same manner as the first finger 21 a in order from the upstream side of the transport direction while the operation thereof is shifted in time by a predetermined period of time (t seconds in FIG. 5). The first finger 21 a on the most upstream side of the transport direction starts the closing operation t seconds after the seventh finger 21 g on the most downstream side starts the closing operation (that is, at the time e). There is disposed a moment (time h) at which the first finger 21 a on the most upstream side and the seventh finger 21 g on the most downstream side are closed at the same time. This can prevent backflow of a liquid.
A period from the start of the closing operation by one finger 21 (for example, the time a) until the restart of the closing operation by that finger 21 (for example, the time e) is called one cycle. The amount of a liquid transported in one cycle is an amount of a liquid that is captured in the part of the tube 22 where the first finger 21 a to the sixth finger 21 f abut on at the time e in FIG. 5, that is, at a point in time when the seventh finger 21 g is in the closing state, and the first finger 21 a starts the closing operation. For example, in FIG. 6, a liquid with which the area illustrated by the hatched portion inside the tube 22 is filled is the amount of a liquid that is transported in one cycle. The amount of liquid corresponding to one cycle is transported toward the downstream side of the transport direction when the first finger 21 a is closed, the seventh finger 21 g is opened, and the second to the sixth fingers 21 b to 21 f are sequentially closed from the state of FIG. 6.
The resilience of the tube 22 differs depending on a difference in the material and the like that constitute the tube 22. Thus, a difference occurs in a period during which the fingers 21 are separated from the protruding portions of the cam 104, start the opening operation, and complete the opening operation, that is, a period during which the squeezed tube 22 is restored to the original shape thereof (for example, from the time c to the time d). For this reason, when the operation of the fingers 21 in a case of using a tube 22 having weak resilience is controlled in the same manner as in a case of using a tube 22 having strong resilience, the time e at which the first finger 21 a starts the closing operation is earlier than a time f at which the sixth finger 21 f completes the opening operation as illustrated in the comparative example in FIG. 7. Then, as illustrated in FIG. 8, the amount of a liquid captured in the part of the tube 22 where the first to the sixth fingers 21 a to 21 f abut on is less than that illustrated in FIG. 6. As such, when the first finger 21 a starts the closing operation before the sixth finger 21 f completes the opening operation, the amount of transport of a liquid per cycle is less than a defined amount. In addition, variations occur in the state of restoration of the part of the tube 22 where the sixth finger 21 f abuts on, resulting in variations in the amount of transport of a liquid per cycle.
Therefore, in the liquid transport device 1 in the present embodiment, the control unit 110 controls the drive mechanism 111 in a manner in which the first finger 21 a on the most upstream side of the transport direction starts the closing operation after the seventh finger 21 g on the most downstream side of the transport direction completes the closing operation, and the sixth finger 21 f that is second from the downstream side of the transport direction completes the opening operation. That is to say, “filled-up time” that is a period of time e-f obtained by subtracting the time f at which the sixth finger 21 g completes the opening operation from the time e at which the first finger 21 a starts the closing operation is set to be greater than zero. This can reduce variations and errors deviated from a defined amount in the amount of transport of a liquid per cycle (the amount of a liquid illustrated by the hatched portion in FIG. 6), and a liquid can be transported with high accuracy.
Specifically, the period of time of restoration of the tube 22, that is, the period of time from the start of the opening operation until the completion thereof (for example, from the time c to the time d) may be determined in advance, and the speed of rotation of the cam 104 may be adjusted in a manner of satisfying a condition of filled-up time>0. For example, in a case of using a tube 22 having weak resilience, the interval (period of time t) between the start time of the closing operation by the fingers 21 is increased by decreasing the speed of rotation of the cam 104. Then, the start of the closing operation by the first finger 21 a is delayed, and thus the sixth finger 21 f can complete the opening operation before the first finger 21 a starts the closing operation.

Difference in Cross-Sectional Extent of Tube Depending on Temperature

FIG. 9 is a graph illustrating the amount of transport of a liquid when the ambient temperature of the tube 22 and the speed of rotation of the cam 104 are changed. Here, the amount of transport of a liquid is illustrated in weight according to the method of testing an infusion pump in the IEC standards. FIG. 9 is a graph that plots the amount of a liquid transported by one rotation of the cam 104 when the ambient temperature of the tube 22 is changed to various values (at a pitch of 5° C. from 5° C. to 40° C.), and the speed of rotation of the cam 104 is changed to various values (1500, 3000, 4500, and 9000 (μl/h)) in the liquid transport device 1 in the present embodiment. The horizontal axis indicates a temperature (° C.), and the vertical axis indicates an amount of transport of a liquid (g). The unit of the speed of rotation of the cam 104 is “μl/h”. This unit represents the speed at which the cam 104 is rotated in a manner in which a predetermined amount of a liquid (μl) is transported per hour (h). In addition, FIG. 9 is a result of measurement in a state where the above condition of “filled-up time>0” is satisfied.
In the graph in FIG. 9, when the ambient temperature of the tube 22 is not changed, the amount of transport of a liquid per rotation of the cam 104 is substantially constant even when the speed of rotation of the cam 104 is changed. It is understood from the result that a constant amount of a liquid can be transported even when the speed of rotation of the cam 104 is changed provided that the condition of “filled-up time>0” is satisfied.
Meanwhile, in the graph in FIG. 9, the amount of transport of a liquid is small in the area where the ambient temperature of the tube 22 is low. That is to say, it is understood that errors occur in the amount of transport of a liquid due to a difference in the ambient temperature of the tube 22 even though the condition of “filled-up time>0” is satisfied. This is considered, as will be described below, to be caused by characteristics of the material (for example, a resin material such as a styrene-based thermoplastic elastomer and an olefin-based thermoplastic elastomer), which constitutes the tube 22, changing depending on temperature.
FIG. 10 is a diagram representing a difference in the cross-sectional extent of the tube 22 due to a difference in the ambient temperature of the tube 22. FIG. 10 is a cross-sectional view that is taken by cutting the tube 22 in a direction which is perpendicular to the axial direction (transport direction) of the tube 22. In addition, FIG. 10 is a diagram that represents a state where the opening operation for the tube 22 is completed, that is, a state where the tube 22 is restored with the elasticity thereof from a state where the tube 22 is squeezed by the fingers 21. As illustrated in the left drawing in FIG. 10, when the ambient temperature of the tube 22 is Ta, and the rubberiness (Young's modulus) of the resin material constituting the tube 22 is high, an arc part of the tube 22 tends to extend, and the cross-sectional shape of the tube 22 becomes a shape close to a circle. Meanwhile, as illustrated in the right drawing in FIG. 10, when the ambient temperature of the tube 22 is Tb that is different from Ta, and the rubberiness of the tube 22 is low, a force that extends the arc part of the tube 22 is small, and the cross-sectional shape of the tube 22 becomes an elliptic shape.
As such, when the ambient temperature of the tube 22 changes, the cross-sectional shape of the tube 22 is changed, and the cross-sectional extent (Aa and Ab) of the inside of the tube 22 is changed even in a state where the opening operation for the tube 22 is completed. That is to say, the internal volume of the tube 22 is changed. Thus, even though the condition of “filled-up time>0” is satisfied, the amount of a liquid captured in the part of the tube 22 where the first to the sixth fingers 21 a to 21 f abut on (the amount of a liquid illustrated by the hatched portion in FIG. 6) slightly varies depending on the ambient temperature of the tube 22 when the first finger 21 a starts the closing operation, and errors occur in the amount of transport of a liquid per cycle.
In the liquid transport device 1 in the present embodiment, the control unit 110 controls the rate of driving of the drive mechanism 111, that is, the amount of rotation (angle of rotation) of the cam 104 in the present embodiment in a corrective manner on the basis of the ambient temperature of the tube 22. In doing so, errors in the amount of transport of a liquid due to a difference in the ambient temperature of the tube 22, that is, a difference in the internal volume of the tube 22 are supplemented, and a defined amount of a liquid is transported with high accuracy regardless of the ambient temperature of the tube 22. The rate of driving of the drive mechanism 111 that is corrected on the basis of the ambient temperature of the tube 22 is not limited to the amount of rotation of the cam 104. For example, the rate of driving of the drive mechanism 111 may be the amount of rotation of the rotor wheel 105 or the rate of driving of the piezoelectric motor 100 (the number of longitudinal vibrations or flexural vibrations).

Control of Amount of Rotation of Cam 104

FIG. 11 illustrates a correction table for the amount of rotation of the cam 104. FIG. 12 illustrates the flow of a liquid transport method in the liquid transport device 1. In the present embodiment, exemplification is provided for a case where the drive mechanism 111 is driven intermittently, not being driven continuously. That is to say, the control unit 110 controls the drive mechanism 111 in a manner in which a transport operation of transporting a liquid in the tube 22 with drive of the plurality of fingers 21 and a stopping operation of not transporting a liquid in the tube 22 with stopping of drive of the plurality of fingers 21 are repeated alternately.
The memory 110 b that the control unit 110 includes stores the correction table illustrated in FIG. 11. In the correction table, “ambient temperature of the tube 22” is associated with “correction coefficient of the amount of rotation of the cam 104”. In addition, a value obtained by multiplying the reference amount of rotation of the cam 104 (for example, 1000 rotations) by the correction coefficient is a corrected amount of rotation. Here, exemplification is provided for a case where the amount of transport of a liquid when the ambient temperature of the tube 22 is 20° C. is set as a reference amount, the amount of transport of a liquid is less than the reference amount when the ambient temperature of the tube 22 is lower than 20° C., and the amount of transport of a liquid is greater than the reference amount when the ambient temperature of the tube 22 is higher than 20° C. Thus, in the correction table in FIG. 11, the correction coefficient that corresponds to the ambient temperature of the tube 22 of 20° C. is set to one, the correction coefficient that corresponds to the ambient temperature which is lower than 20° C. is set to be greater than one, and the correction coefficient that corresponds to the ambient temperature which is higher than 20 degrees is set to be less than one.
Not only the correction coefficient but also “corrected amount of rotation” may be associated with “ambient temperature of the tube 22” when the amount of a liquid that is transported in one transport operation is fixed. This can facilitate control by the control unit 110 because the control unit 110 does not need to compute the corrected amount of rotation by multiplying the reference amount of rotation by the correction coefficient at each time of association.
A characteristic of change in the amount of transport of a liquid with respect to the ambient temperature of the tube 22 changes when the material and the like that constitute the tube 22 are changed. Thus, although the amount of transport of a liquid is decreased in the area where the ambient temperature of the tube 22 is low in FIG. 9, in addition to this, for example, the amount of transport of a liquid may be decreased in the area where the ambient temperature of the tube 22 is high. The correction table needs to be changed when the tube 22 is changed. Therefore, as illustrated in the graph in FIG. 9, the amount of a liquid that the liquid transport device 1 transports may be actually measured when the ambient temperature of the tube 22 is changed variously, and the correction table for the amount of rotation of the cam 104 may be created on the basis of the result of measurement.
As illustrated in FIG. 12, the control unit 110 first obtains the ambient temperature of the tube 22 when the transport operation is started on the basis of an instruction from a user or at a set timing (S01). The temperature sensor 109 (refer to FIG. 2) that is used in control of drive of the piezoelectric motor 100, that is, the temperature sensor 109 that measures the ambient temperature of the piezoelectric motor 100 is set as a temperature sensor that measures the ambient temperature of the tube 22 in the present embodiment.
This can reduce the number of components when compared with a case of disposing a dedicated temperature sensor that measures the ambient temperature of the tube 22 and thus can reduce cost. Besides the temperature sensor 109, for example, a dedicated temperature sensor that measures the ambient temperature of the tube 22 may be disposed in contact with the tube 22. This can obtain the ambient temperature of the tube 22 with higher accuracy.
Next, the control unit 110 obtains the corrected amount of rotation of the cam 104 in one transport operation on the basis of the ambient temperature of the tube 22 that is obtained from the temperature sensor 109 and the correction table (FIG. 11) that is stored on the memory 110 b (S02). When the ambient temperature of the tube 22 is different from the temperature that is set in the correction table (for example, 22° C.), the control unit 110 obtains the corrected amount of rotation by interpolating a corrected amount of rotation between the corrected amounts of rotation that correspond to the previous and the next temperatures (for example, 20° C. and 25° C.)
Next, the control unit 110 drives the piezoelectric motor 100 in a manner in which the cam 104 rotates by the corrected amount of rotation and drives the plurality of fingers 21 (S03). At this time, the control unit 110 rotates the cam 104 at a speed of rotation that satisfies the condition of filled-up time>0 and controls the speed of rotation of the cam 104 at a constant rate regardless of the ambient temperature of the tube 22. After the cam 104 rotates by the corrected amount of rotation, the control unit 110 stops driving the piezoelectric motor 100 (S04) and transitions from the transport operation to the stopping operation. The control unit 110 drives the piezoelectric motor 100 on the basis of information that is obtained from the rotary encoder which measures the amount of rotation (angle of rotation) of the cam 104 until the cam 104 rotates by the corrected amount of rotation.
As such, in the liquid transport device 1 in the present embodiment, the control unit 110 controls the drive mechanism 111 in a manner in which the first finger 21 a on the most upstream side of the transport direction starts the closing operation after the seventh finger 21 g on the most downstream side of the transport direction completes the closing operation, and the sixth finger 21 f that is second from the downstream side of the transport direction completes the opening operation. This can reduce variations and errors deviated from a defined amount in the amount of transport of a liquid per cycle.
The control unit 110 further controls the amount of rotation of the cam 104 in a corrective manner on the basis of the result of measurement by the temperature sensor 109 that measures the ambient temperature of the tube 22. Thus, even when the cross-sectional extent of the inside of the tube 22 after the opening operation is completed is changed depending on the ambient temperature of the tube 22, errors in the amount of transport of a liquid due to a difference in the ambient temperature (internal volume) of the tube 22 can be supplemented by correcting the amount of rotation of the cam 104. Therefore, the liquid transport device 1 in the present embodiment can transport a liquid with high accuracy regardless of the ambient temperature of the tube 22, and for example, a liquid medicine and the like can be precisely injected into a living body.
The amount of transport of a liquid per rotation of the cam 104 is substantially constant even when the speed of rotation of the cam 104 is changed provided that the condition of filled-up time>0 is satisfied, and the ambient temperature of the tube 22 is not changed (FIG. 9). That is to say, since errors deviated from a defined amount of transport of a liquid when the cam 104 rotates by a defined amount of rotation (for example, 1000 rotations) do not change independently of the speed of rotation of the cam 104, the correction coefficient that supplements the errors does not need to be obtained by associating the correction coefficient with the speed of rotation of the cam 104. When the condition of filled-up time>0 is not considered, the state of restoration of the sixth finger 21 f that is second from the downstream side varies depending on the speed of rotation of the cam 104 in addition to the internal volume of the tube 22 changing depending on the ambient temperature of the tube 22. Thus, the correction coefficient needs to be associated with not only the ambient temperature of the tube 22 but also the speed of rotation of the cam 104. Therefore, according to the liquid transport device 1 in the present embodiment, the number of correction coefficients that correct the amount of rotation of the cam 104 can be decreased, the capacity of the memory 110 b of the control unit 110 can be decreased, and control by the control unit 110 can be facilitated.
The assumption is made here that the speed of rotation of the cam 104, not the amount of rotation of the cam 104, is corrected on the basis of the ambient temperature (internal volume) of the tube 22. When, for example, the internal volume of the tube 22 is small, errors in the amount of transport of a liquid can be supplemented by rotating the cam 104 at a faster speed than a reference speed and increasing the amount of rotation of the cam 104 in a predetermined period of time. In this case, however, when errors occur in the speed of rotation of the cam 104, the cam 104 cannot be rotated by an amount of rotation that can supplement errors in the amount of transport of a liquid. As a measure against this, the liquid transport device 1 in the present embodiment corrects the amount of rotation of the cam 104 on the basis of the ambient temperature of the tube 22. Thus, errors hardly occur in the amount of rotation of the cam 104 when compared with a case of correcting the speed of rotation of the cam 104, and the cam 104 can be rotated more securely by an amount of rotation that can supplement errors in the amount of transport of a liquid. Therefore, the liquid transport device 1 in the present embodiment can transport a liquid with higher accuracy.
In addition, the transport operation of a liquid and the stopping operation are alternately repeated in the liquid transport device 1 in the present embodiment. Thus, an increase or a decrease in the processing time of the transport operation does not pose a problem because the amount of rotation of the cam 104 is corrected on the basis of the ambient temperature of the tube 22. Therefore, the extent of freedom is high in setting the speed of rotation of the cam 104 even when the amount of rotation of the cam 104 is corrected, and the speed of rotation of the cam 104 can be constant regardless of the ambient temperature of the tube 22 as in the present embodiment. As such, making the speed of rotation of the cam 104 constant can facilitate control by the control unit 110. The condition of filled-up time>0 is also satisfied easily when the extent of freedom is high in setting the speed of rotation of the cam 104.
The speed of rotation of the cam 104 is not limited to a constant value. The control unit 110 may change the speed of rotation of the cam 104 to an extent that satisfies the condition of filled-up time>0. This can adjust the processing time of the transport operation to a desired processing time such as a constant processing time and a shortened processing time regardless of the ambient temperature of the tube 22 by adjusting the speed of rotation of the cam 104 depending on the corrected amount of rotation of the cam 104 while allowing the liquid transport device 1 to transport a liquid with high accuracy. There may be a case, such as a case of controlling a phase difference, where the speed of rotation of the motor (and the cam connected to the motor) is not determined depending on a method of controlling the motor. Even in such a case, a liquid may be transported by driving the motor to an extent in which the speed of rotation of the motor satisfies the condition of filled-up time>0 so that the cam 104 rotates by the corrected amount of rotation. This can transport a liquid with high accuracy.
There are injection methods available when the liquid transport device 1 is used as, for example, an insulin injecting device. One is an injection method (bolus) of increasing the amount of injection of insulin along with a temporary rise in blood sugar when a user takes in food. Another one is a method (basal) of injecting a constant amount of insulin continuously in a normal case. The transport operation and the stopping operation are alternately repeated according to such various injection methods. When, for example, the interval between the transport operations is long, the amount of rotation of the cam 104 may be corrected by obtaining the ambient temperature of the tube 22 prior to the start of the transport operation as illustrated in the flow in FIG. 12. Meanwhile, when the interval between the transport operations is short, the amount of rotation of the cam 104 does not have to be necessarily corrected for each transport operation. The amount of rotation of the cam 104 may be corrected by obtaining the ambient temperature of the tube 22 for every predetermined time (for example, for every 30 minutes) or for every predetermined numbers of the transport operation.
Not limited to being driven intermittently, the liquid transport device 1 may transport a liquid in a manner in which the cam 104 rotates at all times. In this case, the amount of rotation of the cam 104 per unit time is corrected depending on the ambient temperature of the tube 22. Thus, the control unit 110 changes the speed of rotation of the cam 104 to an extent that satisfies the condition of filled-up time>0. The control unit 110 may correct the amount of rotation of the cam 104 per unit time by obtaining the ambient temperature of the tube 22 for every predetermined time (for example, for every 30 minutes).

OTHER EMBODIMENTS

The above embodiment is intended to facilitate understanding of the invention, not intended to interpret the invention in a limited manner. It is needless to say that modifications and improvements may be carried out to the invention without departing from the gist of the invention, and the equivalents of the modifications and the improvements are included in the invention.
In the above embodiment, exemplification is provided for the rotary liquid transport device 1 in which the plurality of fingers 21 is arranged between the arc-shaped tube 22 and the cam 104 radially from the center of rotation of the cam 104. However, the invention is not limited to this. For example, a direct-drive liquid transport device in which a plurality of fingers is arranged along a tube that extends in a linear direction may be used. Even in this case, a drive mechanism of the fingers is controlled in a manner in which the condition of filled-up time>0 is satisfied. The drive mechanism is controlled in a manner in which the fingers 21 are operated for a number of cycles in which errors in the amount of transport of a liquid due to a difference in the ambient temperature of the tube can be supplemented or are operated until reaching positions in the linear direction. This can transport a liquid with high accuracy.
In the above embodiment, the liquid transport device 1 is provided with the catheter 310 and the like because exemplification is provided for a case where the liquid transport device 1 is used to inject a liquid into a living body. However, the invention is not limited to this. The invention is desirably and effectively applied to a peristaltic liquid transport device that is provided with a tube, a plurality of fingers, and a drive mechanism which drives the fingers.
The entire disclosure of Japanese Patent Application No. 2014-98372, filed May 12, 2014 is expressly incorporated by reference herein.

Claims

What is claimed is:

1. A liquid transport device comprising:

a tube that has elasticity and is intended to transport a liquid in a transport direction;

a plurality of fingers that is lined up along the transport direction;

a drive mechanism that drives the plurality of fingers;

a temperature sensor that measures the ambient temperature of the tube; and

a control unit that controls the drive mechanism in a manner in which a liquid inside the tube is transported in the transport direction by repeating a closing operation of squeezing the tube with the finger and an opening operation in which the finger is pressed back by the shape of the squeezed tube being restored,

wherein the control unit

controls the drive mechanism in a manner in which the finger on the most upstream side of the transport direction starts the closing operation after the finger on the most downstream side of the transport direction completes the closing operation, and the finger that is second from the downstream side of the transport direction completes the opening operation, and

controls the rate of driving of the drive mechanism in a corrective manner on the basis of a result of measurement by the temperature sensor.

2. The liquid transport device according to claim 1,

wherein the rate of driving of the drive mechanism is the amount of rotation of the drive mechanism.

3. The liquid transport device according to claim 1,

wherein the drive mechanism includes a piezoelectric motor, and

the temperature sensor is a sensor that measures the ambient temperature of the piezoelectric motor for use in control of drive of the piezoelectric motor.

4. The liquid transport device according to claim 1,

wherein the control unit controls the drive mechanism in a manner in which the speed of drive of the drive mechanism is constant.

5. The liquid transport device according to claim 1,

wherein the control unit changes the speed of the drive mechanism to an extent in which the finger on the most upstream side starts the closing operation after the finger on the most downstream side completes the closing operation, and the finger that is second from the downstream side completes the opening operation.

6. The liquid transport device according to claim 1,

wherein the extent of the cross section of the inside of the tube after the opening operation is completed, the cross section being taken by cutting the tube in a direction that is perpendicular to the axial direction of the tube, changes depending on the ambient temperature of the tube.

7. The liquid transport device according to claim 1,

wherein the control unit controls the drive mechanism in a manner in which a transport operation of transporting a liquid in the tube with drive of the plurality of fingers and a stopping operation of not transporting a liquid in the tube with stopping of drive of the plurality of fingers are alternately repeated.

8. A liquid transport method for a liquid transport device that includes a tube which has elasticity and is intended to transport a liquid in a transport direction, a plurality of fingers which is lined up along the transport direction, and a drive mechanism which drives the plurality of fingers, in which a liquid in the tube is transported in the transport direction by repeating a closing operation of squeezing the tube with the finger and an opening operation in which the finger is pressed back by the shape of the squeezed tube being restored, the method comprising:

obtaining the ambient temperature of the tube; and

driving the plurality of fingers with the drive mechanism at a rate of driving that is corrected on the basis of the ambient temperature and driving the plurality of fingers in a manner in which the finger on the most upstream side of the transport direction starts the closing operation after the finger on the most downstream side of the transport direction completes the closing operation, and the finger that is second from the downstream side of the transport direction completes the opening operation.