Pumps – Motor driven – Magnetostrictive chamber
Reexamination Certificate
2001-08-22
2004-06-22
Tyler, Cheryl J. (Department: 3746)
Pumps
Motor driven
Magnetostrictive chamber
C417S413200
Reexamination Certificate
active
06752601
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART
The present invention relates to a micro pump preferably having a small and thin structure.
In recent years, a micro pump driven by electrostatic force has been proposed in the field of micro machines which are produced by finely structuring a silicon substrate. Such a micro pump can be used either in a device embedded in a human body for injecting a very small amount of medicine thereinto or a small instrument for chemical analyses. It is known that such a micro pump is normally made of silicon, and it will be assumed that the micro pump is increasingly used in the field of medical treatment, chemical analyses and so on. In this case, it is preferable that the micro pump should have a small and thin structure, and in spite of these requirements, the micro pump ensures a greater amount of discharge (or a greater amount of displacement) for the fluid used.
In such a micro pump, however, it is very difficult to attain either a higher speed in pumping action or a greater amount of discharge (a greater magnitude of displacement) for a fluid.
In order to overcome such problems, the following pump has been proposed in Japanese Unexamined Patent Application Publication No. 2000-314381.
FIG. 2
is a sectional view of the pump, which has a small and thin structure and at the same time provides a greater amount of discharge (a greater amount of displacement) for the fluid. The pump
110
comprises a casing
114
, into which a fluid is supplied, a supply valve member
118
disposed so as to face the inside of the casing
114
, a pump member
116
, a discharge valve member
120
, and a pump main body
112
. A fluid channel is selectively formed in the inside of the casing
114
by the selective displacement of the supply valve member
118
the pump member
116
, and the discharge valve member
120
in the approaching/departing direction, such that the flow of the fluid can be controlled by selectively forming the fluid channel.
In such a pump
110
, however, the following problems exists. Since the displacement action of the pump member
116
resulted from the bending movement of a vibrating member
142
, both the compression force and the magnitude of stroke in the discharge direction of the fluid were restricted, so that there was a limitation in manufacturing a pump having a small and thin structure in order to obtain a higher performance. The upper limit of the bending deformation of the vibrating member is determined by the toughness of the vibrating member
142
, so that it is effective to decrease the thickness of the vibrating member
142
, if the magnitudes of the bending deformation and the stroke can be increased in order to obtain a greater compression force. However, if so designed, the rigidity of the vibrating member
142
decreases and thus a high responsiveness is reduced. On the contrary, if the area of the vibrating member
142
can be increased, this causes an increase in the size of the vibrating member, hence making it impossible to provide a pump having a small and thin structure. On the other hand, an excellent responsiveness requires an increase of the rigidity. For this purpose, it is effective to increase the thickness of the vibrating member
142
in the pump
110
. However, if so designed, the obtainable displacement is decreased and therefore the required compression force cannot be obtained. In other words, it was difficult to simultaneously attain both a greater compression force and a high responsiveness by the bending deformation of the vibrating member
142
in the pump
110
.
Taking the above-mentioned problems into account, the object of the present invention is to provide a micro pump, which has a small and thin structure, and at the same time, ensures an increased amount of discharge (increased magnitude of displacement) and a high responsiveness. After many investigations were done regarding the structure for micro pumps, components for producing the displacement action and methods for producing the displacement action, it has been found that the above-mentioned object can be attained by the micro pump of the present invention, which is described below.
There is provided, in accordance with the invention, a micro pump having at least one pump member for conveying a fluid by the action of pressure, characterized in that, pump member comprises a pump unit which is formed from at least one actuator member for generating a pressure fluctuation and a fluid channel member in which a fluid flows. The actuator member is provided with a cell formed by disposing two side walls made of piezoelectric/electrostrictive elements or antiferrodielectric elements on a connecting plate, and a cover plate is positioned on the side walls and faces the connecting plate. The actuator member selectively forms a fluid channel and generates pressure fluctuation in the fluid channel member due to the displacement of the cell caused by expansion/contraction of the side walls.
In the pump unit, electrode layers are formed on both surfaces of the side walls in the actuator member, and the side walls are preferably expanded/contracted in the up/down direction in accordance with the driving electric field by applying a voltage to the electrode layers. For this purpose, the electric field for polarizing the piezoelectric/electrostrictive elements forming the side walls of the actuator member is aligned in the same direction as the driving electric field. Moreover, it is preferable that the state of crystalline grains on the surfaces of the side walls in the actuator member is that the crystalline grains suffering the fracture inside the grains are less than 1% and that the degree of profile of the surfaces of the cell in the actuator member is approximately 8 &mgr;m or less.
In the pump unit, moreover, it is preferable that the ratio of the inside width to the height of the cell in the actuator member is approximately 1:2 to 1:40, and that the inside width of the cell in the actuator member is approximately less than 60 &mgr;m. It is further preferable that the surface roughness Rt of the side walls in the actuator member is approximately 10 &mgr;m or less.
In the actuator member of the pump unit, it is preferable that the connecting plate is made of piezoelectric/electrostrictive elements or antiferroelectric elements and joined to the side walls to form one body, and it is also preferable that the cover plate is made of piezoelectric/electrostrictive elements or antiferrodielectric elements and joined to the side walls to form one body.
In the present invention, for example, one of pump unit (A), pump unit (B) and pump unit (C) (which are each described below in detail) can be employed in the various embodiments. The pump unit (A) is constituted in such a manner that the cell in the actuator member is filled with a system fluid and another fluid, which is unsoluable in the system fluid flows in a fluid channel that is formed in advance in the fluid channel member. The cell is in communication with the fluid channel via a communicating hole, and the fluid channel has substantially the same size in the width direction as the diameter of the communicating hole, at least at the position where the communicating hole is in communication with to the fluid channel. The expansion/contraction (in the up/down direction) of the side walls forming the cell provides a change in the volume of the portion at which the system fluid stored in the cell is ejected from the communicating hole into the fluid channel, such that the fluid channel can be selectively formed.
The pump unit (B) is constituted in such a manner that the fluid channel is formed by a displacement transmitting member, at least a part of which is bonded to the cover plate of the cell in the actuator member, and a casing facing a part of the surface of the displacement transmitting member on the side opposite to the actuator member. The expansion/contraction of the side walls forming the cell provides an approaching/departing displacement of the displacement transmitting member relativ
Kitamura Kazumasa
Takahashi Nobuo
Takeuchi Yukihisa
Tsuji Hiroyuki
Burr & Brown
NGK Insulators Ltd.
Tyler Cheryl J.
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