U.S. patent application number 14/593926 was filed with the patent office on 2015-05-07 for fluid conveying device and driving method for fluid conveying device.
The applicant listed for this patent is SEIKO EPSON CORPORATION. Invention is credited to Makoto KATASE.
Application Number | 20150125316 14/593926 |
Document ID | / |
Family ID | 46199579 |
Filed Date | 2015-05-07 |
United States Patent
Application |
20150125316 |
Kind Code |
A1 |
KATASE; Makoto |
May 7, 2015 |
FLUID CONVEYING DEVICE AND DRIVING METHOD FOR FLUID CONVEYING
DEVICE
Abstract
A fluid conveying device includes: a tube; a cam having
protrusions; fingers arranged along the tube between the tube and
the cam; a driving rotor which rotates the cam to sequentially push
the fingers by the protrusions in a flowing direction of a fluid,
repeatedly pressuring and opening of the tube, driving the cam; a
detection unit which detects a rotating position of the cam; a
control unit which calculates a cam rotation angle along a
cumulative ejection volume, using a first approximation formula for
an ejection area H where the cumulative ejection volume increases
substantially in proportion to the rotation angle of the cam and a
second approximation formula for a constant area J where the
cumulative ejection volume little increases or decreases even if
the cam rotates, driving the driving rotor until a rotating
position of the cam corresponding to a designated cumulative
ejection volume is reached.
Inventors: |
KATASE; Makoto;
(Azumino-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEIKO EPSON CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
46199579 |
Appl. No.: |
14/593926 |
Filed: |
January 9, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13315253 |
Dec 8, 2011 |
8961156 |
|
|
14593926 |
|
|
|
|
Current U.S.
Class: |
417/212 ;
417/474 |
Current CPC
Class: |
F04B 43/0081 20130101;
F04B 43/08 20130101; F04B 43/082 20130101; F04B 43/12 20130101 |
Class at
Publication: |
417/212 ;
417/474 |
International
Class: |
F04B 43/12 20060101
F04B043/12; F04B 43/00 20060101 F04B043/00; F04B 43/08 20060101
F04B043/08 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 2010 |
JP |
2010-274319 |
Claims
1. A fluid conveying device which ejects a fluid, the device
comprising: an elastic tube; a plurality of pressing shafts
arranged along the tube; a cam having a plurality of fixed
protrusions selectively contacting the plurality of pressing
shafts, each protrusion including a first region over which a
cumulative ejection volume of the fluid ejected from the elastic
tube increases based on rotation of the cam and a second region
over which there is little increase or decrease in the cumulative
ejection volume of the fluid ejected from the elastic tube based on
rotation of the cam; a driving unit which rotates the cam to
sequentially push the plurality of pressing shafts by the cam; and
a control unit which controls the driving unit in rotating the cam,
wherein, when a predetermined volume is conveyed along the elastic
tube, the control unit stops rotation of the cam at the first
region.
2. The fluid conveying device of claim 1, wherein the first region
terminates below a vertex of each protrusion.
3. The fluid conveying device of claim 1, wherein the second region
terminates at an end of each vertex of each protrusion.
4. The fluid conveying device of claim 1, wherein the second region
includes a vertex of each protrusion.
5. The fluid conveying device of claim 1, further comprising a
third region at which the cumulative ejection volume of the fluid
decreases based on the rotation of the cam.
6. The fluid conveying device of claim 1, further comprising a
fourth region at which the cumulative ejection volume of the fluid
is compensated for backflow of the fluid.
7. A fluid conveying device which ejects a fluid, the device
comprising: an elastic tube; a cam having a plurality of regions
formed on an outer surface of the cam, the plurality of regions
comprising: a first region at which a cumulative ejection volume of
the fluid increase based on the rotation of the cam; a second
region at which the cumulative ejection volume of the fluid does
not increase or decrease based on the rotation of the cam; a third
region at which the cumulative ejection volume of the fluid
decreases based on the rotation of the cam; and a fourth region at
which the cumulative ejection volume of the fluid is compensated; a
plurality of pressing shafts arranged along the tube between the
tube and the cam; a driving unit which rotates the cam to
sequentially push the plurality of pressing shafts by the cam in a
flowing direction of the fluid, and thus repeats pressurized
closure and opening of the tube; a detection unit which detects a
rotating position of the cam; and a control unit which controls
rotation of the cam by the driving unit through the first region,
the second region, the third region, and the fourth region,
wherein, when the predetermined volume is conveyed along the tube,
the control unit stops rotation of the cam at the first region.
8. The fluid conveying device of claim 7, wherein the cam includes
n (n being an integer equal to or greater than 2) protrusions, each
protrusion extending over at least a portion of the first and
second regions.
9. The fluid conveying device of claim 8, wherein the second region
includes a vertex of each protrusion, the vertex being formed
concentrically about a center of rotation of the cam.
10. The fluid conveying device of claim 7, wherein fluid backflows
into the tube at the third region of the cam.
11. The fluid conveying device of claim 7, wherein the fourth
region compensates for fluid backflow into the tube at the third
region of the cam rotation, the cumulative ejection volume at the
end of the fourth region matches the cumulative ejection volume at
the end of the second region.
12. The fluid conveying device of claim 7, wherein over the second
region, the third region, and the fourth region there is little
increase or decrease in the cumulative ejection volume.
13. The fluid conveying device according to claim 7, wherein in the
constant area, a rotation speed of the cam is made higher than a
rotation speed of the cam in the ejection area.
14. A fluid conveying device which ejects a fluid, the device
comprising: an elastic tube; a cam having an outer surface with a
plurality of fixed protrusions extending from the outer surface; a
plurality of pressing shafts arranged along the tube between the
tube and the cam; a driving unit which rotates the cam to
sequentially push the plurality of pressing shafts by the cam in a
flowing direction of the fluid; and a control unit which controls
rotation of the cam by the driving unit to rotate the cam through a
first region, a second region, a third region, and a fourth region
of the outer surface of the cam, wherein a first region of the
outer surface corresponds with an increase in a cumulative ejection
volume of the fluid from the rotation of the cam; a second region
of the outer surface correspond with no increase or decrease in the
cumulative ejection volume of the fluid from the rotation of the
cam; a third region of the outer surface corresponds with a
decrease in the cumulative ejection volume from the rotation of the
cam; and a fourth region of the outer surface corresponds with a
compensation to the cumulative ejection volume of the fluid.
15. The fluid conveying device of claim 14, wherein the first
region is a slope part extending towards a vertex of each
protrusion.
16. The fluid conveying device of claim 15, wherein the second
region extends from a location on the slope part below the vertex
of each protrusion to the vertex.
17. The fluid conveying device of claim 16, wherein the third
region extends from the vertex to a portion of the outer surface
near a start of the slope part, an inclination of the third region
begin greater than the slope part.
18. The fluid conveying device of claim 17, wherein the fourth
region extends from the terminal end of the third region to the
start of the slope part.
19. The fluid conveying device of claim 14, wherein the second
region commences before a vertex of each protrusion to accommodate
variance in flow of fluid in the elastic tube.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 13/315,253, filed Dec. 8, 2011, which
patent application is incorporated herein by reference in its
entirety. U.S. patent application Ser. No. 13/315,253 claims the
benefit of and priority to Japanese Patent Application No.
2010-274319 filed Dec. 9, 2010, the contents of which are hereby
incorporated by reference in its entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to a fluid conveying device
which ejects a small volume of fluid at a low speed, and a driving
method for this fluid conveying device.
[0004] 2. Related Art
[0005] A peristaltic pump is traditionally known as a device for
conveying a liquid at a low speed. In the peristaltic pump, plural
rollers are arranged on the same circumference on a rotor, and a
tube is arranged to surround the outer circumference of the rotor.
As the rotor is rotated, the tube is squeezed in a liquid flowing
direction by the plural rollers. The squeezing position is moved
gradually, thus ejecting the liquid (for example, see
JP-A-2004-92537).
[0006] In the case of ejecting a minuscule volume of fluid, the
rotor in the peristaltic pump is rotated by being driven and
stopped intermittently. Therefore, a pulsating current unique to
the peristaltic pump is generated and the ejection volume becomes
irregular. Thus, according to JP-A-2004-92537, the ejection volume
at each of intermittent driven and stop positions of the rotor is
measured and stored in advance, then the sum of the ejection
volumes corresponding to the rotation angles of the rotor is
calculated, and the rotation angle of the rotor is controlled
according to a required total ejection volume.
[0007] However, the peristaltic pump has such a characteristic that
the ejection volume changes each at rotation angle of the rotor in
the process of liquid flowing. Therefore, it is necessary to finely
divide the rotation angle of the rotor, measure and store the
ejection volume at each of the divided angles, and calculate the
sum of the ejection volumes at each angle every time the rotation
of the rotor proceeds. Therefore, there is a problem that a rotor
rotation angle control unit, including a CPU which is charge of the
calculation and a memory for storing and rewriting the rotation
angle of the rotor and the result of calculating the ejection
volume, bears a heavy load.
[0008] JP-A-2004-92537 also discloses that data of the total
ejection volume per turn of the rotor is stored in a memory in
advance so that the rotation angle of the rotor is found. However,
since the ejection volume fluctuates at each rotation angle of the
rotor during one turn of the rotor, there is a problem that an
accurate total ejection volume is difficult to grasp.
SUMMARY
[0009] An advantage of some aspects of the invention is to solve at
least a part of the problems described above, and the invention can
be implemented in the following forms or application examples.
APPLICATION EXAMPLE 1
[0010] This application example is directed to a fluid conveying
device which ejects a fluid. The device includes: an elastic tube;
a cam having n (n being an integer equal to or greater than 2)
protrusions; plural pressing shafts arranged along the tube between
the tube and the cam; a driving unit which rotates the cam to
sequentially push the plural pressing shafts by the protrusions in
a flowing direction of the fluid, and thus repeats pressurized
closure and opening of the tube; a detection unit which detects a
rotating position of the cam; and a control unit which calculates a
cam rotation angle in relation to a cumulative ejection volume,
using a first approximation formula that expresses an ejection area
where the cumulative ejection volume increases in proportion to the
rotation angle of the cam and a second approximation formula that
expresses a constant area where the cumulative ejection volume does
not increase or decrease even if the cam rotates, and which drives
the driving unit until the detection unit detects a rotating
position of the cam corresponding to a designated cumulative
ejection volume.
[0011] According to this application example, the cam rotation
angle in relation to the cumulative ejection volume is calculated
using the first approximation formula that expresses the ejection
area where the cumulative ejection volume increases in proportion
to the rotation angle of the cam and the second approximation
formula that expresses the constant area where the cumulative
ejection volume does not increase or decrease even if the cam
rotates, and the cam is rotated until the designated cumulative
ejection volume is reached. Therefore, the configuration of the
control unit can be simplified and the load on the control unit can
be reduced in the form of a reduced number of calculations or the
like, compared with the system where the rotation angle of the
rotor is finely divided, the ejection volume at each divided angle
is measured and stored and the sum of the ejection volumes at each
angle is calculated every time the rotation of the rotor proceeds,
as in the related art. Consequently, there is an advantage that the
current consumed can be reduced. Here, the phrase "in proportion
to" does not necessarily mean being perfectly in proportion and
also refers to cases of being substantially in proportion. The
phrase "does not increase or decrease" refers to cases where the
volume does not increase or decrease in terms of the constant area
as a whole though the volume may increase or decrease partly, and
cases where the volume increases or decreases only by an
insignificant amount that can be ignored, as well as cases where
the volume does not increase or decrease at all.
[0012] Moreover, by using the approximation formulae, it is
possible to eliminate the influence of fluctuations in the ejection
volume during the rotation of the cam or per turn of the cam and
hence grasp a more accurate total ejection volume.
APPLICATION EXAMPLE 2
[0013] In the fluid conveying device according to the above
application example, it is preferable to make the rotation speed in
the constant area higher than the rotation speed of the cam in the
ejection area.
[0014] As the cam rotation speed is thus made higher in the
constant area where the fluid is not ejected, the cumulative
ejection volume in relation to the cam rotation angle can be
expressed substantially by a straight line, and the fluid can be
ejected continuously and at a constant ejection speed in an
ejection designated time.
APPLICATION EXAMPLE 3
[0015] In the fluid conveying device according to the above
application example, it is preferable to create a reference line
expressing a relation between the rotation angle of the cam and the
cumulative ejection volume of the fluid, define the cumulative
ejection volume ejected during 1/n turns of the cam as one ejection
unit, calculate a number of ejection units based on the reference
line, and calculate the rotation angle of the cam in relation to a
cumulative ejection volume corresponding to a difference between
the designated cumulative ejection volume and a cumulative ejection
volume equivalent to the number of ejection units, using the first
approximation formula and the second approximation formula.
[0016] As described above, as the cam rotation speed is made higher
in the constant area where the fluid is not ejected, the cumulative
ejection volume in relation to the cam rotation angle can be
expressed substantially by a straight line. As this straight line
is used as a reference line and the calculation uses the reference
line and the approximation formulae, the rotation angle of the cam
in relation to the designated cumulative ejection volume can be
found easily.
APPLICATION EXAMPLE 4
[0017] In the fluid conveying device according to the above
application example, it is preferable that the first approximation
formula performs approximation using a monotone increasing function
by which the rotation angle of the cam is defined from the
cumulative ejection volume.
[0018] Thus, the relation between the cumulative ejection volume
and the cam rotation angle is not limited to a straight line in the
ejection area, and even a quadratic curve or parabola can be used
as the first approximation formula.
APPLICATION EXAMPLE 5
[0019] A driving method for a fluid conveying device according to
this application example is a driving method for a fluid conveying
device which ejects a fluid. The method includes: rotating a cam
having n (n being an integer equal to or greater than 2)
protrusions; stopping the rotation of the cam when a rotation angle
of the cam is detected; initializing a cumulative ejection volume
and the rotation angle of the cam; calculating a rotation angle of
the cam corresponding to a designated cumulative ejection volume,
using an approximation formula that expresses a relation between
the cumulative ejection volume and the rotation angle of the cam;
starting fluid ejection by rotating the cam to sequentially push
plural pressing shafts in a flowing direction of the fluid by the
protrusions and thus repeating pressurized closure and opening of
an elastic tube; and detecting the rotation angle of the cam, and
stopping the rotation of the cam when the rotation angle
corresponding to the designated cumulative ejection volume is
reached.
[0020] According to this application example, the cam rotation
angle in relation to the designated cumulative ejection volume can
be found easily using the approximation formula. As the cam is
rotated until that cam rotation angle is reached, an accurate total
ejection volume (designated cumulative ejection volume) can be
secured and managed. Thus, this technique is suitable for a medical
fluid administering device for medical purposes which ejects a
minuscule volume of liquid at a low speed or for a driving method
for a liquid separation device of various analysis devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention will be described with reference to the
accompanying drawings, wherein like numbers refer to like
elements.
[0022] FIG. 1 is a plan view showing a schematic configuration of a
fluid conveying device.
[0023] FIG. 2 is a partial sectional view showing an A-A cross
section in FIG. 1.
[0024] FIG. 3 is an explanatory view of configuration showing an
example of a control unit and a detection unit.
[0025] FIG. 4 is a plan view showing a first detection marker
indicating a rotation reference position of a cam.
[0026] FIG. 5 is a plan view showing a second detection marker
indicating a rotation angle of a driving rotor.
[0027] FIG. 6 is a graph showing the relation between cam rotation
angle and cumulative ejection volume.
[0028] FIG. 7 is a graph showing the relation between cam driving
time and cumulative ejection volume.
[0029] FIG. 8 is an explanatory view showing principal steps of a
driving method for a fluid conveying device.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0030] Hereinafter, an embodiment of the invention will be
described with reference to the drawings. The invention can be
applied to a broad range of applications where a minuscule volume
of fluid is ejected at a low speed. However, in the following
embodiment, an example of a fluid conveying device used to inject a
medical fluid into a living body and a driving method for this
fluid conveying device will be described. Thus, the fluid used in
this case is a liquid such as a medical fluid.
[0031] The drawings used in the following description are schematic
views in which the vertical and horizontal scales of members or
parts are different from reality, for convenience of
illustration.
Fluid Conveying Device
[0032] FIG. 1 is a plan view showing a schematic configuration of a
fluid conveying device. FIG. 2 is a partial sectional view showing
an A-A cross section in FIG. 1. In FIG. 1 and FIG. 2, a fluid
conveying device 1 includes a reservoir 14 housing a liquid, an
elastic tube 50 continuing to the reservoir 14, fingers 40 to 46 as
plural pressing shafts which pressurize and close the tube 50, a
cam 20 pushing the fingers 40 to 46 toward the tube 50, a driving
rotor 120 as a driving unit for the cam 20, a deceleration
transmission mechanism 2 connecting the cam 20 and the driving
rotor 120, and a first frame 15 and a second frame 16 holding these
parts.
[0033] The tube 50 is shaped partly in a circular arc shape by a
circular arc-shaped tube guide wall 15c formed on the first frame
15. One end continues to the reservoir 14 and the other end is
extended outside. The center of the circular arc of the tube guide
wall 15c coincides with a center of rotation P1 of the cam 20. The
fingers 40 to 46 are arranged between the tube 50 and the cam 20.
The fingers 40 to 46 are arranged radially at equal angles from the
direction of the center of rotation P1 of the cam 20.
[0034] The fingers 40 to 46 have the same shape. The finger 43 is
described as an example with reference to FIG. 2. The finger 43
includes a bar-like shaft part 43a, a tube pressing part 43b formed
in a flange-like shape at one end of the shaft part 43a, and a cam
abutting part 43c formed in a hemispherical shape at the other end.
In this example, the finger 43 is made of a metallic material or a
resin material with high rigidity. The cross section of the finger
43 perpendicular to its axial direction is circular or
quadrilateral.
[0035] As shown in FIG. 2, the cam 20 includes a cam shaft 26, and
a cam gear 28 and cam body 21 which are retained on the cam shaft
26. The cam 20 is axially supported by the first frame 15 and the
second frame 16. As shown in FIG. 1, the cam body 21 has
protrusions 22, 23, 24 and 25 at four positions on an outer
circumference. The protrusions 22, 23, 24 and 25 have the same
circumferential pitch and the same shape. The protrusions 22 to 25
are pushing parts which sequentially push the fingers 40 to 46 from
upstream to downstream. Therefore, the protrusions are hereinafter
referred to as finger pushing parts. The side near the reservoir 14
is referred to as upstream and the far side is referred to as
downstream.
[0036] On the cam body 21, slope parts 22a, 23a, 24a and 25a are
formed which gently continue to the finger pushing parts 22, 23, 24
and 25, respectively, from areas for releasing the fingers 40 to 46
(that is, opening the tube 50).
[0037] The case of four protrusions is illustrated here, but the
number of protrusions may be n (n being an integer equal to or
greater than 2) and is not limited to four.
[0038] Subsequently, the configuration of the deceleration
transmission mechanism 2 will be described with reference to FIG. 1
and FIG. 2. The deceleration transmission mechanism 2 includes the
cam gear 28, a transmission wheel 110, and a rotor pinion 122
retained on a rotor shaft 121. The transmission wheel 110 includes
a transmission wheel shaft 111 with a pinion 113 formed thereon,
and a transmission gear 112. The driving rotor 120 includes the
rotor shaft 121, the rotor pinion 122, and a detection plate 123
retained on the rotor shaft 121. The transmission wheel 110 and the
driving rotor 120 are axially supported together with the cam 20 by
the first frame 15 and the second frame 16. Here, the rotation of
the driving rotor 120 is transmitted to the cam 20 at a
predetermined deceleration ratio by the above deceleration
transmission mechanism 2. In the description of this example, the
deceleration ratio is 40. That is, one turn of the driving rotor is
equivalent to 1/40 turns of the cam 20. The center of rotation of
the driving rotor 120 is P2.
[0039] The driving source for rotating the driving rotor 120 is an
oscillating unit 130. The oscillating unit 130 includes a
piezoelectric element 131, an arm part 132, and a protruding part
133 abutting on the lateral side of the rotor shaft 121. The
oscillating unit 130 has the arm part 132 screwed and fixed with a
screw to a fixed shaft 135 provided upright on the first frame 15.
The configuration of and the driving method for the oscillating
unit 130 will not be described here since the configuration of and
the driving method for a known oscillating unit can be applied. The
driving of the oscillating unit 130 is controlled by a driver 141
(see FIG. 3) included in a control unit 140.
[0040] A step motor can be employed as a driving unit.
[0041] Next, the configuration of the control unit 140 and a
detection unit will be described with reference to FIG. 2 and FIG.
3.
[0042] FIG. 3 is an explanatory view of configuration showing an
example of the control unit and the detection unit. The detection
unit includes a first detection unit which detects a rotation angle
(rotating position) of the cam 20, and a second detection unit
which detects a rotation angle (rotating position) of the driving
rotor.
[0043] As shown in FIG. 3, the first detection unit includes a
first detection sensor 151 which detects the rotating position of
the cam 20, and a first detection circuit 142. The first detection
sensor 151 is an optical sensor including a light emitting element
and a light receiving element (neither of them shown). As shown in
FIG. 2, on a surface of the cam gear 28 facing the first detection
sensor 151, a first detection marker 30 indicating the rotating
position is provided. The first detection marker 30 reflects light
that exits the light emitting element, and the light receiving
element detects this reflected light.
[0044] As shown in FIG. 3, the second detection unit includes a
second detection sensor 152 which detects the rotation angle of the
driving rotor 120, and a second detection circuit 143. The second
detection sensor 152 is an optical sensor including a light
emitting element and a light receiving element (neither of them
shown). As shown in FIG. 2, on a surface of the detection plate 123
facing the second detection sensor 152, a second detection marker
35 indicating the rotating position of the driving rotor 120 is
provided. The second detection marker 35 reflects light that exits
the light emitting element, and the light receiving element detects
this reflected light.
[0045] The first detection marker 30 and the second detection
marker 35 will be described later with reference to FIG. 4 and FIG.
5. As the first detection sensor 151 and the second detection
sensor 152, the reflection-type sensors are described as an
example. However, transmission-type sensors may also be used, and
non-contact sensors such as magnetic sensor and ultrasonic sensor,
or contact sensors may also be employed.
[0046] The control unit 140 includes a counter 144 which counts the
numbers of detections of the first detection marker 30 and the
second detection marker 35 detected respectively by the first
detection circuit 142 and the second detection circuit 143, a
storage unit 145 which stores the numbers of detections of the
first detection marker 30 and the second detection marker 35, an
arithmetic operation unit 146 which calculates a rotation angle of
the driving rotor 120 for rotating the cam 20 to a rotating
position corresponding to a designated cumulative ejection volume,
and the driver 141 which drives the oscillating unit 130 with a
predetermined frequency and by a calculated time, as shown in FIG.
3.
[0047] Next, an exemplary configuration of the first detection
marker 30 and the second detection marker 35 will be described with
reference to FIG. 4 and FIG. 5.
[0048] FIG. 4 is a plan view showing the first detection marker
indicating a rotation reference position of the cam. FIG. 4 shows
the side facing the first detection sensor 151. The first detection
markers 30 include four first detection markers 30a to 30d. The
first detection markers 30a to 30d are radially formed at equal
distances from the center of rotation P1 and at equal angular
spaces from each other on the surface of the cam gear 28. In this
example, the case of division into four equal parts in the
circumferential direction is illustrated. The first detection
markers 30a, 30b, 30c and 30d are provided respectively at
positions corresponding to the finger pushing parts 22, 23, 24 and
25. Therefore, the number of the finger pushing parts matches the
number of the first detection markers 30 (the number of divisions)
and the angle between the first detection markers 30 is 90
degrees.
[0049] The vertex parts of the finger pushing parts 22 to
(indicated as an area D) on the cam body 21 are formed
concentrically about the center of rotation P1. The area D is an
area where the tube 50 is pressurized and closed by the same
squeezing amount. The cam 20 rotates in the direction of arrow
(counterclockwise). The moment the area D is passed, the pushing of
the fingers is canceled and the pressurized and closed tube 50 is
opened. An area where the tube 50 is opened before pressurized
closure starts again is indicated as an area F. The pressurized
closure area of the tube 50 is set to start before the vertex parts
of the protrusions 22 to 25 are reached (area E) in consideration
of variance. The area F is an area where the liquid that is ejected
from the moment the pushing of the fingers is canceled to open the
pressurized and closed tube 50 flows backward and the cumulative
ejection volume decreases. An area G is a cam rotating area of up
to when the same cumulative ejection volume as in the area D is
reached by the pressurized closure of the tube 50 due to the
rotation of the cam 20.
[0050] An area where the pressurized closure of the tube 50 is
started after the pushing of the fingers is started is an ejection
area H.
[0051] An area J including the area D, the area E, the area F and
the area G is an ejection volume constant area where there is
little increase or decrease in the cumulative ejection volume. The
relation between each rotating area of the cam 20 and the
cumulative ejection volume will be described later with reference
to FIG. 6.
[0052] FIG. 5 is a plan view showing the second detection marker
indicating a rotation angle of the driving rotor. The second
detection markers 35 are formed radially at equal distances from
the center of rotation P2 and at equal spaces from each other on
the surface of the detection plate 123. In this example, the case
where the second detection markers 35 are divided into twelve in
the circumferential direction is illustrated. Therefore, the angle
between the neighboring second detection markers 35 is 30
degrees.
[0053] Here, the deceleration ratio from the driving rotor 120 to
the cam 20 is assumed to be 1/40. For one turn of the driving rotor
120, the cam 20 rotates 1/40 turns (rotates 9 degrees). Since the
second detection markers 35 are divided into twelve, the rotational
resolution of the driving rotor is 30 degrees. The rotational
resolution of the cam 20 is 30/40=0.75 degrees.
[0054] The number of divisions of the second detection markers 35
is not limited to twelve and may be properly set according to the
requirement of angular resolution of the cam 20, deceleration
ratio, or angle detection resolution of the second detection
sensors. It is desirable that the second detection markers 35 are
divided in a number corresponding to the number of protrusions.
[0055] The position where the second detection unit is provided is
not limited to the driving rotor 120. The second detection unit can
be provided on one part of the deceleration transmission mechanism
2. For example, the second detection markers 35 may be formed at
the position of the transmission gear 112 of the transmission wheel
110, and the second detection sensor 152 may be arranged at a
position facing the second detection markers 35. In such case,
since the deceleration ratio changes, the rotation speed of the cam
20, the deceleration ratio and the number of divisions of the
second detection markers 35 are properly set.
[0056] The first detection markers 30 and the second detection
markers 35 are made of a material that reflects light or absorbs
light. Alternatively, holes penetrating the cam gear 28 and the
detection plate 123 may be provided.
[0057] Next, liquid ejection will be described with reference to
FIG. 1. When a driving signal is inputted to the piezoelectric
element 131 from the control unit 140 (specifically, the driver
141), the protruding part 133 of the oscillating unit 130
elliptically oscillates and causes the driving rotor 120 to rotate
clockwise. The rotating force of the driving rotor 120 rotates the
cam 20 clockwise at the deceleration ratio of 1/40 via the
deceleration transmission mechanism 2. In the state shown in FIG.
1, the protrusion 23 pushes the finger 44, thus pressurizing and
closing the tube 50. The fingers 45 and 46 are on the slope part
23a of the cam body 21 and therefore do not pressurize and close
the tube 50 completely.
[0058] The fingers 41, 42 and 43 are not on the slope part 22a of
the cam body 21 yet. Therefore, the tube 50 is open. The finger 40
starts to get on the slope part 22a and the tube 50 is still open.
There is a fluid in the area of the tube 50 that is pressurized and
closed.
[0059] As the cam 20 is further rotated clockwise, the fingers 40
to 46 are pushed sequentially from upstream to downstream in the
rotating direction of the cam 20. Thus, pressurized closure,
opening, and pressurized closure of the tube 50 are repeated. The
liquid is thus conveyed and ejected in the rotating direction of
the cam 20 by the peristaltic movement of the fingers 40 to 46. The
plural fingers 40 to 46 are configured so that at least one,
preferably two of the fingers 40 to 46 constantly pressurize and
close the tube 50.
[0060] Next, the relation between the rotation angle of the cam 20
and the cumulative ejection volume will be described.
[0061] FIG. 6 is a graph showing the relation between the rotation
angle of the cam and the cumulative ejection volume. The horizontal
axis represents the rotation angle of the cam 20. The vertical axis
represents the cumulative ejection volume (.mu.l: micro liter). The
graph refers to the case where the cam rotation speed is constant,
and the rotation angle of the cam and the cumulative ejection
volume show actual measured values for each fluid conveying device.
A first approximation formula and a second approximation formula
which will be described later are created based on this graph.
Since the respective finger pushing parts have the same action, the
action of the finger pushing part 22 will be described as an
example. FIG. 4 is referred to as well.
[0062] As the cam 20 is rotated from a rotating position K0 (this
position being a reference position 0) of the cam 20 where the
first detection marker 30a is detected, the cumulative ejection
volume increases substantially in proportion to the cam rotation
angle. When the cam 20 is rotated 60 degrees (when a rotating
position K1 is reached), the cumulative ejection volume is 1.5
.mu.l. In an area from the rotating position K1 to a rotating
position K2, the cumulative ejection volume does not increase or
decrease and is substantially constant. This is an area where the
finger 46 continues to pressurize and close the tube 50.
[0063] As the cam 20 is further rotated and reaches a rotating
position over the rotating position K2, the engagement between the
finger pushing part 22 and the finger 46 is canceled and the tube
50 is opened. Then, the cumulative ejection volume decreases by v1
from the rotating position K2 up to a rotating position K3. This
example shows that 0.13 .mu.l of the ejected liquid flows backward.
This phenomenon occurs because when the engagement of the most
downstream finger 46 with the finger pushing part 22 of the cam 20
is canceled to open the tube 50, the capacity part of the tube 50
that is previously pressurized and closed by the finger 46 now has
a negative pressure and therefore sucks the liquid and generates a
backflow. As the cam 20 is further rotated, the slope part 23a of
the cam 20 pushes the most upstream finger 40 to pressurize and
close the tube 50 and the liquid starts to be ejected. At a
rotating position K4, the cumulative ejection volume 1.5 .mu.l is
reached with the ejection decrease compensated for.
[0064] Thus, the cumulative ejection volume can be expressed in
terms of an ejection area H where the cumulative ejection volume
increases substantially in proportion to the rotation angle of the
cam 20 and a constant area J where there is little increase or
decrease in the cumulative ejection volume even when the cam
rotates. In the ejection area H, the relation between the
cumulative ejection volume and the cam rotation angle is expressed
by a first approximation line L1. In the constant area J, the
relation can be expressed by a second approximation line L2. As
shown in the graph of FIG. 6, actual measured values of the
cumulative ejection volume may have minuscule increase or decrease.
However, it is considered that this volume is 0.01 .mu.l or smaller
and therefore need not be taken into account.
[0065] Thus, if the cumulative ejection volume is v and the cam
rotation angle is d, the first approximation line can be expressed
as a linear equation v=.alpha.d+b, which is referred to as a first
approximation formula. The second approximation line can be
expressed by a linear equation v=.beta., which is referred to as a
second approximation formula. In this example, the gradient of the
line .alpha. is 0.025 .mu.l/degree (1.5 .mu.l/60 degrees), b=0, and
.beta. is 1.5 .mu.l.
[0066] This graph shows the action of one of the finger pushing
parts of the cam 20. Since the four finger pushing parts are
formed, the ejection area H and the constant area J are repeated
four times during one turn of the cam 20. If the rotation speed of
the cam 20 is constant, the first approximation formula and the
second approximation formula for each finger pushing part can be
created by a similar way of thinking. For example, when the
protrusion 23 pressurizes and closes the tube 50, a linear equation
with b in the first approximation formula modified to pass through
the rotating position K4 and with a gradient .alpha. of 0.025
.mu.l/degree may be employed, and .beta. in the second
approximation formula may be changed to 3.0.
[0067] Thus, the cam 20 can be rotated until a rotation angle that
is required in relation to a designated cumulative ejection volume
according to the first approximation formula and the second
approximation formula is reached. This rotation angle is detected
by the first detection unit and the second detection unit. Next, a
specific driving method for the fluid conveying device 1 will be
described with reference to FIG. 1 to FIG. 8.
DRIVING METHOD FOR FLUID CONVEYING DEVICE--EXAMPLE 1
[0068] Example 1 is the case where the graph of FIG. 6 showing the
relation between the rotation angle of the cam 20 and the
cumulative ejection volume is used as a basic form and the cam 20
is rotated at a constant speed.
[0069] FIG. 7 is a graph showing the relation between the driving
time of the cam and the cumulative ejection volume. The horizontal
axis represents the driving time of the fluid conveying device 1.
The vertical axis represents the cumulative ejection volume from
the start of the driving.
[0070] FIG. 8 is an explanatory view showing principal steps of the
driving method for the fluid conveying device. In this example, the
case where an ejection speed for ejecting 6.0 .mu.l by rotating the
cam 20 one turn in 60 minutes is provided is described as an
example. This example is described along the steps shown in FIG.
8.
[0071] First, the relation between the cam rotation angle of the
fluid conveying device 1 as a driving target and the cumulative
ejection volume is actually measured in advance. The graph shown in
FIG. 6 is created. The data of the graph is inputted to the control
unit 140 (specifically, the storage unit 145). Based on this data,
the arithmetic operation unit 146 creates the first approximation
formula and the second approximate formula (step S10). In this
example, since the four finger pushing parts are provided on the
cam 20 and the cam rotation speed is constant, the relation between
the rotation angle of the cam and the cumulative ejection volume
can be expressed in FIG. 7 (indicated by a broken line). If the
cumulative ejection volume in "an ejection area H+a constant area
J" is defined as one ejection unit, the driving time of 60 minutes
includes four ejection units (indicated by block B1, block B2,
block B3 and block B4). Therefore, the duration of each block is 15
minutes.
[0072] In this example, the number of finger pushing parts is four.
However, if the number of finger pushing parts is n (n being an
integer equal to or greater than 2), the cumulative ejection volume
to be ejected during 1/n turns is defined as one ejection unit.
[0073] Subsequently, a designated cumulative ejection volume is
inputted, using an input device, not shown (step S20). Here, the
designated cumulative ejection volume is provisionally assumed to
be 5.0 .mu.l.
[0074] Next, the arithmetic operation unit calculates a cam
rotation angle corresponding to the designated cumulative ejection
volume (step S30). To eject 5.0 .mu.l, the cam 20 needs to be
rotated by "three ejection units (three blocks)+a fractional angle"
(see FIG. 7). Therefore, the rotation angle of the cam 20 is 270
degrees+the fractional angle. That is, the first detection unit
detects the first detection markers 30 from the reference position
(position K0) and the cam needs to be rotated additionally by the
fractional angle.
[0075] The fractional angle is calculated using the first
approximation formula and a rotation angle of the driving rotor 120
is found. Here, the fractional angle is equivalent to a cam
rotation angle of 20 degrees following the detection of the third
one of the first detection markers 30. If the deceleration ratio is
1/40, the rotation angle of the driving rotor 120 corresponding to
the cam rotation angle is 20 degrees.times.40=800 degrees. This is
equivalent to two turns and 80-degree rotation of the cam 20. If
the number of divisions of the second detection markers 25 provided
on the driving rotor 120 is twelve, the driving rotor 120 can be
rotated until three marks of the second detection markers 35 is
detected following the detection of the third one of the first
detection markers 30.
[0076] Since the cam rotation angle corresponding to the designated
cumulative ejection volume 5.0 .mu.l is 290 degrees, the rotation
angle of the driving rotor 120 corresponding to the 290 degrees may
also be calculated as 32 turns and rotation by three marks of the
second detection markers 35.
[0077] Next, the driving rotor 120 is rotated (step S40). At a
position where the first detection marker 30 on the cam 20 is
detected, the driving rotor is stopped (step S50). At this point,
the rotating position of the driving rotor 120 is stored as a
detected position of the second detection marker 35 together with
the reference position of the cam 20, and the cumulative ejection
volume and the rotating positions of the driving rotor 120 and the
cam 20 are initialized (step S60).
[0078] Next, the driving rotor 120 is driven to start eject the
liquid, and the cam 20 is rotated by an amount corresponding to the
designated cumulative ejection volume (step S70).
[0079] During the ejection of the liquid, the cam rotation angle is
grasped (step S80). Specifically, the number of detections of the
first detection markers 30 on the cam 20 and the number of
detections of the second detection markers 35 on the driving rotor
120 are counted by the counter 144 and the results are inputted to
the storage unit 145.
[0080] Then, whether the cam rotation angle corresponding to the
designated cumulative ejection volume is reached is determined by
compassion with the stored designated rotation angle (step S90). If
the designated cam rotation angle is reached (step S90, YES), the
driving rotor 120 is stopped and the rotation of the cam 20 is
stopped, thus stopping the ejection of the liquid (step S100). If
the designated cam rotation angle is not reached yet (step S90,
NO), the driving of the driving rotor 120 is continued and the step
S80 and the subsequent steps are continued.
DRIVING METHOD FOR FLUID CONVEYING DEVICE--EXAMPLE 2
[0081] Next, Example 2 will be described. While the above Example 1
is a driving method in the case where the cam 20 is rotated at a
constant speed, Example 2 is a driving method in the case where the
rotation speed in the constant area J is higher than the rotation
speed in the ejection area H. This example will be described with
reference to FIG. 7 and FIG. 8. In step S10, the first
approximation formula and the second approximation formula are
created based on actual measured values, as in Example 1. However,
in the constant area J (see FIG. 6), the cam rotation speed is
higher, for example, approximately 10 to 20 times higher than in
the ejection area H. Therefore, the time in the constant area J is
very short. As shown in FIG. 7, a straight line (indicated as line
L3) can be formed on an extended line of the first approximation
line L1. However, this cannot satisfy the designated ejection speed
of 6.0 .mu.l in 60 minutes.
[0082] Thus, to satisfy the designated ejection speed of 6.0 .mu.l
in 60 minutes, the gradient of the line L3 is corrected (the cam
rotation speed in the ejection area H is slowed down) to create a
line L4, which is used as a reference line.
[0083] Next, a designated cumulative ejection volume is inputted
(step S20). The designated cumulative ejection volume is
provisionally assumed to be 5.0 .mu.l. Next, the arithmetic
operation unit calculates a cam rotation angle corresponding to the
designated cumulative ejection volume (step S30).
[0084] Here, the cam rotation angle corresponding to the designated
cumulative ejection volume is calculated based on the reference
line L4. In this case, to calculated the cam rotation angle, the
number of blocks is found where the cumulative ejection volume
during the rotation by one mark of the first detection markers 30
on the cam 20 is defined as one ejection unit (one block), and
since a fractional angle corresponds to the ejection area, the
fractional angle is calculated as a rotation angle of the driving
rotor 120 using the first approximation formula. Since the first
approximation formula corresponds to the ejection area H of FIG. 6,
the rotation angle of the driving rotor 120 can be calculated
similarly to Example 1. Step S40 and the subsequent steps can be
carried out similarly to Example 1 and therefore will not be
described further in detail.
[0085] The cam rotation angle in the ejection area H may be
adjusted to lie on the reference line L4 so that the designated
ejection speed becomes substantially constant.
[0086] As in JP-A-2004-92537 described above, with the method in
which the rotation angle of the rotor is finely divided, then, the
ejection volume in each division is measured and stored and the sum
of the ejection volumes at each angle is calculated every time the
rotation of the rotor proceeds, access to the memory is frequently
needed in order to read out the data table and therefore reduction
in current consumed is difficult. However, with to the
configuration of the fluid conveying device 1 and the driving
method according to this example, the cam rotation angle in
relation to the cumulative ejection volume is calculated using the
two approximation formulas with different ejection speeds (first
approximation formula and second approximation formula), and the
cam 20 is rotated until the designated cumulative ejection volume
is reached. Therefore, compared with the related art, the
configuration of the control unit 140 can be simplified and the
load on the control unit 140 can be reduced, for example, by
reducing the number of calculations. Consequently, there is an
advantage that the current consumed can be reduced.
[0087] Moreover, by using the approximation formulae, it is
possible to eliminate the influence of fluctuation in the ejection
volume during the rotation of the cam 20 or per turn of the cam 20
and to grasp a more accurate total ejection volume.
[0088] In the constant area J, the cam rotation speed is made
higher than in the cam rotation speed in the ejection area H.
Therefore, the cumulative ejection volume in relation to the cam
rotation angle can be expressed substantially by a straight line
and the fluid can be continuously ejected at a constant ejection
speed in an ejection designated time.
[0089] In Example 2, the relation between the rotation angle of the
cam (cam driving time) and the cumulative ejection volume of the
fluid is linearized to create a reference line, and the number of
ejection units is calculated based on the reference line, where the
cumulative ejection volume ejected during 1/4 turns of the cam 20
is defined as one ejection unit. The rotation angle of the cam 20
corresponding to the difference between the designated cumulative
ejection volume and the cumulative ejection volume equivalent to
the number of ejection units is calculated using the first
approximation formula. Thus, as the cam rotation speed is higher in
the constant area where the fluid is not ejected, the cumulative
ejection volume in relation to the cam rotation angle can be
expressed substantially by a straight line. This straight line is
defined as the reference line L4 and the calculation uses the
reference line L4 and the above approximation formulae. Thus, the
rotation angle of the cam 20 in relation to the designated
cumulative ejection volume can be found easily.
[0090] In Example 1 and Example 2 described above, the case where
the first approximation line L1 is a straight line is described as
an example. However, approximation can be carried out using a
monotone increasing function by which the rotation angle of the cam
20 is defined from the cumulative ejection volume.
[0091] Thus, the relation between the cumulative ejection volume
and the cam rotation angle is not limited to a straight line in the
ejection area, and even a quadratic curve or parabola can be used
as the first approximation formula.
* * * * *