JP4831975B2 - Small centrifugal pump and operation method of small centrifugal pump - Google Patents

Description

  The present invention relates to a small centrifugal pump. Specifically, the present invention relates to a small centrifugal pump in which it is difficult to ensure processing accuracy and assembly accuracy compared to size.

  Centrifugal pumps are configured to give energy to the fluid by rotating the impeller at high speed in the liquid to create a pressure difference between the central part and the outer peripheral part. Used in the field. As a factor affecting the efficiency of the centrifugal pump, the size of the axial clearance between the impeller and the casing inner wall can be considered. When this gap is large, the pressurized fluid flows backward to the upstream side where the pressure is low through the gap. Therefore, by setting the gap small, the head and flow rate are increased, and the pump efficiency is also improved.

  The conventional impeller has a rotating shaft integrally extending, and holds the rotating shaft so that it cannot move in the axial direction so that the gap is as small as possible. In order to set the gap small, it is necessary to increase the processing accuracy and assembly accuracy of the component parts.

  In addition, when the operation is performed for a long time, the set gap is often increased due to wear of the bearing and the like, the head and flow rate are reduced, and the efficiency of the pump is also reduced. For this reason, maintenance such as parts replacement is required.

For example, there is a configuration in which the gap is adjusted using an inner ring or the like.
JP 2002-317794 A

  In recent years, various machines have been miniaturized, and in the field of pumps, micro pumps having dimensions much smaller than those of conventional pumps have been provided and are used as artificial heart pumps or drug solution injection pumps.

  However, these pumps are much smaller than conventional pumps, and there is a limit to improving the processing accuracy and assembly accuracy of parts. In addition, it is difficult to provide a bearing mechanism or the like for adjusting the gap between the impeller and the casing. For this reason, it has been difficult to obtain a high head with a small centrifugal pump, and the range of use has been limited. In particular, it has been difficult to accurately set the axial rotation position of the impeller by the bearing mechanism or the like.

  The present invention has been devised in order to solve the above-mentioned problems, and solves the above-mentioned conventional problems, and drastically improves the head and discharge flow rate of a small centrifugal pump.

The invention described in claim 1 of the present application includes an impeller, a casing that rotatably accommodates the impeller, and a drive mechanism that rotates the impeller, and opens toward the center of the impeller. A small centrifugal pump configured to suck fluid from a fluid suction port and to discharge pressurized fluid pressurized by rotation of the impeller from a discharge port provided on an outer peripheral portion of the casing, A disk part rotating away from the inner surface of the casing provided with the fluid suction port, and an outer side in the radial direction from the center of the disk to the side surface of the disk part opposite to the inner surface of the casing A plurality of blades extending radially toward the surface of the blade, and are held so as to be movable in the axial direction , and rotate around the fluid suction port so as to face the casing inner surface. Side edge A taper surface that is spaced apart from the inner surface of the casing in the rotational direction, and a negative pressure generated in the fluid suction port or a central portion of the impeller is employed in the impeller so that the impeller is connected to the fluid suction port. The side edge portion of the impeller is configured not to contact the inner surface of the casing by a fluid wedge action generated between the tapered surface and the inner surface of the casing .

  In a small pump, it is extremely difficult to rotate the impeller while holding the impeller at the optimum axial position. In particular, as the gap between the inner surface of the casing provided with the fluid suction port and the impeller opposed thereto increases, the lift and the like decrease. In the present invention, by holding the impeller so as to be movable in the axial direction, the rotating impeller is displaced as much as possible in the axial direction, the gap between the casing and the impeller is adjusted to be small, and the lift and discharge amount are adjusted. The pump efficiency can be improved.

  In the present invention, the impeller is held so as to be movable in the axial direction, an axial force is applied to the impeller, and a plurality of forces acting on the impeller are rotated in a balanced state. Therefore, by rotating at a position close to the inner surface of the casing provided with the fluid suction port, the discharge flow rate and the head are increased, and the pump efficiency is improved.

  An axial force can be applied to the rotating impeller by various methods to displace it in the axial direction. For example, the axial force can be applied from the outside, or a fluid flowing in the casing can be used. Further, it is desirable that the axial force is applied to the impeller by two or more methods, and these forces are balanced to rotate the impeller in a stable state. In the present invention, the rotational position in the axial direction of the impeller is not determined to be a fixed position, but is balanced to a position where the maximum output can be exhibited according to the rotational speed of the impeller, the fluid to be pressurized, and the like. It is intended to rotate.

In the present invention, basically, the negative pressure generated in the vicinity of the fluid suction port or in the central portion of the impeller is applied to the impeller so that the impeller is displaced to the inner surface of the casing on the fluid suction port side. It is configured.

  In the case of the centrifugal pump, the fluid is caused to flow radially outward by the rotation of the impeller, so that the fluid pressure in the vicinity of the fluid suction port is lower than the outer peripheral portion of the impeller. Therefore, the impeller can be brought close to the inner surface of the casing using the pressure difference.

That is, the impeller is rotated from the central portion on the fluid suction port side of the disk portion that rotates away from the inner surface of the casing provided with the fluid suction port, and extends radially outward. And a plurality of blades that rotate around the fluid suction port to face the inner surface of the casing, and cause the negative pressure generated in the vicinity of the fluid suction port to act on the disc part, the impeller Ru is displaced in the fluid inlet side.

In the present invention, the impeller is provided with a disk portion that rotates away from the inner surface of the casing provided with the fluid suction port, and fluid is added between the inner surface of the casing provided with the fluid suction port. Press. At least the central part of the disk part is reduced in pressure by the fluid flowing outward in the radial direction, and a force directed toward the fluid suction port acts on the disk due to the pressure drop. By this force, the impeller can be displaced in a direction close to the inner surface of the casing.

Although it is preferable that the gap between the inner surface of the casing provided with the fluid suction port and the blades of the impeller facing the casing is small, it is necessary to avoid contact. In the present invention, a force acting in a direction of separating the impeller from the inner side surface is generated by a fluid wedge action between the impeller and the casing inner side surface, which are opposed and relatively rotated .

  When the gap between the impeller and the casing inner surface becomes small, a wedge action occurs between them, and a load capacity is generated in the fluid. By using this load capacity, the impeller can be rotated as close as possible without contacting the inner surface of the casing.

In the present invention, a tapered surface that is spaced from the inner surface of the casing in the rotational direction is formed on a side edge portion of the blade that rotates to face the inner surface of the casing , thereby expressing the wedge action.

Greatly affected by the viscosity of the fluid in the field of infinitesimal fluid element, impeller by the wedge action between the inner surface of the casing facing the adjacent the inner wall of the casing, the axial load capacity is generated in the fluid. Since this force acts in inverse proportion to the square of the size of the gap, the force increases as the impeller and the casing come closer. Moreover, the area which an impeller and a casing oppose can be taken large. For this reason, the load capability produced by the wedge action of these opposing surfaces can be set very large. Therefore, using this force, the impeller can be rotated at a position as close as possible without contacting the casing. Further, when the load load pressure generated by the wedge action is set to be equal to or higher than the discharge pressure of the pump, the pressurized fluid is prevented from flowing back to the suction port from the gap between the casing and the impeller. Is possible. The present invention seeks to adjust the force generated by the wedge action according to the rotational speed and fluid characteristics. Furthermore, in order to stably generate the pressure due to the wedge action and to rotate the impeller close to the casing, the impeller that rotates opposite to the casing and the inner surface of the casing are processed to improve the surface roughness and the facing accuracy. It is preferable to set it high.

According to the invention described in claim 2, at the outer periphery of the impeller, the fluid pressure pressurized by the action on the impeller, it is possible to displace said impeller in the axial direction.

For example, as in the invention described in claim 3 , by forming a pressure receiving surface on which the axial force is applied from the pressurized fluid on the outer peripheral portion of the impeller, and applying fluid pressure to the pressure receiving surface. The impeller can be displaced in the axial direction. When fluid pressure is applied to the outer periphery of the impeller, a force toward the fluid suction port can be generated, or a force moving away from the fluid suction port can be generated.

According to a fourth aspect of the present invention, the impeller and the casing are provided with magnetic force generating means for applying an axial force to the impeller.

  For example, the impeller is formed of a magnetic material such as an iron material, and an electromagnet is provided on the casing side facing the impeller to generate a magnetic force in a direction in which the impeller is brought close to or separated from the impeller, so that the impeller is Can be displaced.

The invention described in claim 5 of the present application is such that the shaft of the impeller is set in the vertical direction, and the impeller is displaced by acting the weight of the impeller in the axial direction.

In the present invention, since the impeller is held movably in the axial direction, when the impeller shaft is set in the vertical direction, the impeller is moved downward by the weight of the impeller itself. The invention described in claim 5 utilizes the weight of the impeller. The direction in which the weight of the impeller acts depends on the vertical positional relationship with respect to the fluid suction port. Further, the acting axial force varies depending on the inclination angle of the shaft. Therefore, the acting force can be adjusted by changing the inclination angle of the shaft of the impeller.

In the invention described in claim 6 of the present application, the impeller is positioned below the fluid suction port, and the force generated by the weight of the impeller set to a predetermined weight is applied to the rotating disk in the vicinity of the fluid suction port. It is configured to oppose the force acting on the.

When the negative pressure acting in the vicinity of the fluid suction port is large, in order to stably rotate the impeller, a force in a direction away from the inner surface of the casing is generated in addition to the force due to the wedge effect due to the tapered surface. Need to be balanced. The present invention generates the force using the weight of the impeller.

The impeller can be held movably in the axial direction using various methods. For example, as in the invention described in claim 7 , a rotary shaft extending on the opposite side of the fluid suction port of the impeller is provided, and the rotary shaft is rotatable on the casing or a bearing provided thereon. It can be held so as to be axially movable. Further, a fixed shaft can be provided in the casing, and the impeller can be held on the fixed shaft so as to be rotatable and movable in the axial direction.

The drive mechanism is not particularly limited. For example, as in the invention described in claim 8 , the drive means includes a drive shaft having one end connected to the impeller or the rotation shaft so as not to be relatively rotatable and to be axially movable. The drive shaft can be rotationally driven by a motor or the like.

According to a ninth aspect of the present invention, the driving means may be provided with a magnetic force driving mechanism provided on the impeller and the casing, respectively, and rotating the impeller by a magnetic force.

Invention described in claim 10 of the present application, operation in a small centrifugal pump comprising an impeller to form a blade of multiple, and a casing which rotatably hold the impeller, and a drive mechanism for rotating the impeller A disk portion that rotates the impeller away from an inner surface of a casing provided with the fluid suction port, and the disk on one side of the disk portion that faces the fluid suction port. And a plurality of blades extending radially outward from the central portion of the blade, and at the side edge of each blade rotating opposite the inner surface of the casing, the rotation direction A tapered surface spaced from the inner surface of the casing toward the inner surface of the casing, and a negative pressure generated in the fluid suction port or a central portion of the impeller is applied to the impeller so that the impeller is moved to the inner surface of the casing on the fluid suction port side. Turn to the side While for, by the fluid wedge effect generated between the taper surface and the casing inner surface, the side edge portion of the impeller, to a method of operating a miniature centrifugal pump to operate so as not to contact with the inner surface of the casing .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the pump 1 according to the present embodiment includes an impeller 2, a casing 3 that rotatably accommodates the impeller 2, and a drive mechanism 4 that rotates the impeller 2. It is configured.

  As shown in FIGS. 1 and 2, the impeller includes a disk portion 5, a plurality of blades 6 formed on one side surface of the disk portion 5, and the other side surface of the disk portion 5. The rotary shaft 7 extends from the central portion. As shown in FIG. 2, the blades 6 extend radially from the center of the disk portion 5, and the side edges 8 of the blades 6 face the inner surface 21 of the casing 3. It is configured to rotate.

  The casing 3 is composed of two casing members 9 and 10, and an impeller housing space 11 for housing the impeller 2 and a bearing housing space 13 for housing the bearing 12 between the casing members 9 and 10. Is formed. A fluid suction port 14 and a fluid discharge port 15 are formed on the inner surface of the impeller housing space 11. The fluid suction port 14 is formed so as to open to a fluid suction space 17 formed between the radially inner edge 16 of each blade 6 and the disk portion 5 at the center of the impeller 2. Has been. On the other hand, an annular space 18 is provided on the outer peripheral portion of the impeller 3 to allow the fluid pressurized by the impeller 3 to flow in the rotational direction of the impeller 3. The outlet 15 is formed toward the flow direction of the pressurized fluid.

  The drive mechanism 4 includes a motor 19 provided outside the casing member 10, a bearing 12 accommodated in the casing member 10, and extends from the motor 19 to the casing member or the bearing 12. The drive shaft 20 is connected to the rotary shaft 7 of the impeller 2. The rotary shaft 7 and the drive shaft 20 are connected inside the bearing 12 so as not to be relatively rotatable and to be relatively displaceable in the axial direction.

As shown in FIG. 3, in this embodiment, by cutting the tip portion of the drive shaft 20 and the rotating shaft 7 in semicylindrical each other, fitted with aligning it heavy notches surfaces 7a and 20a Thus, these are held in the bearing 12 so as to be relatively displaceable in the axial direction. Although not shown, a sealing mechanism for preventing liquid leakage is provided between the rotating shaft or the driving shaft and the casing.

In the pump 1 configured as described above, when the impeller 2 is rotated by the motor 19 , fluid is sucked into the fluid suction space 17 from the fluid suction port 14 and is pressurized by the impeller 2. It is discharged from the discharge port 15 through the annular space 18.

  In the present embodiment, a fluid suction space 17 whose one side is closed by the disk portion 5 is formed in the central portion of the impeller where the fluid suction port 14 opens. For this reason, the negative pressure generated in the fluid suction space 17 causes a force toward the fluid suction port 14 to act on the disk portion 5. As a result, as shown in FIG. 4, the impeller 2 and the casing inner surface 21 provided with the fluid suction port 14 are brought close to each other, and the gap 22 formed therebetween is reduced. Thereby, it is possible to prevent the pressurized fluid from flowing back through the gap 22, thereby increasing the discharge flow rate and the head and improving the pump efficiency. On the other hand, in the present embodiment, the impeller 2 is set so as to be positioned below the liquid suction port 14, and the weight of the impeller 2 is exerted downward so that the impeller 2 moves upward as the fluid is sucked. It is configured to balance with power. Thereby, the impeller 2 can be stably rotated at a position close to the fluid suction port 14.

  If the upward force generated by the rotation of the impeller 2 is too large, the side edge portion 8 of the blade 6 of the impeller 2 and the casing inner side surface 21 on the side where the liquid suction port 14 is provided are formed. Although it is possible to make contact, the pump according to the present invention has a very small size, and the influence of the viscosity of the fluid is larger than that of a normal pump. For this reason, if the impeller 2 and the casing inner side surface 21 are too close to each other, the force of separating the impeller 2 from the casing inner side surface 21 rapidly increases due to the wedge action of the intervening fluid. Moreover, the area of the opposing surface of the edge part of an impeller and the said casing inner surface is also large. Therefore, the impeller 2 can be stably rotated without contacting the casing inner side surface 21 by the wedge action.

  The wedge action is a phenomenon that occurs when the impeller 2 is too close to the casing, but the magnitude of the force due to the wedge action is adjusted to stably rotate the impeller 2 at a desired position. It can also be made. FIG. 5 shows a wedge action generating mechanism 23 that positively generates the wedge action and rotates the impeller 2 more stably.

The wedge action generating mechanism 23 shown in FIG. 5 is formed by forming a tapered surface 24 inclined in the rotational direction at the side edge of the blade 6 that rotates opposite to the casing inner surface 21. By changing the inclination angle and length of the tapered surface 24, the force generated by the wedge action can be adjusted. Since the force due to the wedge action acts in inverse proportion to the square of the size of the gap, the force increases as the impeller and the casing come closer. Therefore, this force can be used to prevent contact between the impeller and the casing. On the other hand, it is desirable to process the facing surfaces of the impeller and the casing so as to increase the surface accuracy so that a stable wedge action is generated . From the theory of thrust bearings, the load capacity increases in proportion to the opposed area and relative speed of the impeller and casing. In particular, in this embodiment, since the wedge action is generated between the impeller and the casing, not only the facing area can be set large, but also the wedge is formed at the high speed portion of the outer peripheral portion of the impeller. An action can also be generated. Therefore, it is possible to stably rotate the impeller by generating a large force in a direction away from the casing inner surface and applying a force balanced with the force from the outside.

  FIG. 6 shows an embodiment in which the impeller 2 is moved in the axial direction using magnetic force.

The impeller 2 shown in FIG. 6 is formed from a magnetic material such as iron. On the other hand, a magnetic force generator 25 is provided on the inner surface 21 of the casing provided with the fluid suction port 14. The magnetic force generator 25 is formed of a known electromagnet, and a magnetic force is generated by passing an electric current, and the impeller 2 can be attracted. In addition, the force applied to the impeller 2 can be adjusted by controlling the current or voltage applied to the electromagnet.

  In the small centrifugal pump having the configuration shown in FIG. 8, the impeller is operated under the same conditions as when the impeller is operated with the gap between the casing inner surface provided with the fluid suction port fixed to 0.25 mm. The characteristic curve (flow rate-head) of a pump at the time of hold | maintaining so that direction movement is possible is shown. The fluid was water, and the experiment was performed at an impeller rotation speed of 12000 rpm. Note that the value of the gap when the axial position of the impeller is fixed is a value when the small centrifugal pump having the same configuration is performed with the highest accuracy that can be assembled. As is apparent from this figure, by holding the impeller movably in the axial direction, the impeller can be stably rotated with a gap smaller than the conventional gap, and as a result, the lift for the same flow rate, In addition, the flow rate for the same head can be greatly increased.

  In the present invention, a rotating impeller is held so as to be movable in the axial direction, and a fluid suction port is provided for the axial position of the impeller using a pressure generation mechanism and other methods of a centrifugal pump. It can be rotated as close to the casing side as possible. As a result, it is possible to prevent the flow that flows backward from the gap between the impeller and the casing to the fluid suction port, and it is possible to increase the discharge flow rate and the head, and to greatly improve the efficiency of the pump.

It is an axial sectional view showing the structure of a small centrifugal pump according to the present invention. It is a top view of the small centrifugal pump shown in FIG. It is a figure which shows the mechanism which hold | maintains an impeller so that an axial direction displacement is possible. It is an axial sectional view showing the state where the impeller is rotated and the pump is operated. It is a figure which shows the example of a wedge action generation | occurrence | production mechanism, and is sectional drawing which follows the VV line in FIG. It is axial sectional drawing which shows the Example which provided the magnetic force generation means. It is the figure which drawn the characteristic curve for comparing the characteristic in the pump which fixed the axial direction position of the pump which concerns on this invention, and an impeller. It is a figure which shows the structure of the pump shown in FIG.

1 pump 2 impeller 3 casing 4 drive mechanism 14 fluid suction port 15 fluid discharge port 21 casing inner side surface 22 gap

Claims (10)

An impeller, a casing that rotatably accommodates the impeller, and a drive mechanism that rotates the impeller, and sucks fluid from a fluid suction port that opens toward the center of the impeller, and A small centrifugal pump configured to discharge a pressurized fluid pressurized by rotation of an impeller from a discharge port provided in an outer peripheral portion of the casing,
The impeller is rotated radially away from the center of the disc on a disc portion that rotates away from the inner surface of the casing provided with the fluid suction port, and a side surface of the disc portion that faces the inner surface of the casing. And a plurality of blades radially extending toward the direction, and is configured to be movable in the axial direction,
A tapered surface that is spaced from the inner surface of the casing in the rotational direction is provided at a side edge of each blade that rotates opposite to the inner surface of the casing around the fluid suction port,
While the negative pressure generated in the fluid suction port or the central portion of the impeller is adopted by the impeller, the impeller is displaced toward the casing inner surface side of the fluid suction port,
A small centrifugal pump configured so that a side edge portion of the impeller does not contact the inner surface of the casing by a fluid wedge action generated between the tapered surface and the inner surface of the casing.   The small centrifugal pump according to claim 1, wherein a pressurized fluid pressure is applied to the impeller at an outer peripheral portion of the impeller to displace the impeller in an axial direction.   A pressure receiving surface on which an axial force acts from a pressurized fluid is formed on an outer peripheral portion of the impeller, and the impeller is displaced in an axial direction by applying a fluid pressure to the pressure receiving surface. A small centrifugal pump according to any one of claims 1 and 2.   4. The compact according to claim 1, wherein the impeller and the casing are provided with magnetic force generation means for applying an axial force to the impeller to displace the impeller in the axial direction. 5. Centrifugal pump.   The shaft according to any one of claims 1 to 4, wherein the shaft of the impeller is set so as to be directed in a vertical direction, and the weight of the impeller is applied in an axial direction to displace the impeller. Small centrifugal pump.   The impeller is positioned below the fluid suction port, and the weight of the impeller set to a predetermined weight is configured to counter negative pressure acting in the vicinity of the fluid suction port. The small centrifugal pump according to any one of 5.   A rotary shaft extending on the opposite side of the impeller from the fluid suction port is provided, and the rotary shaft is held rotatably and axially movable on the casing or a bearing provided thereon. Item 7. The small centrifugal pump according to any one of Item 6.   8. The drive unit according to claim 1, further comprising: a drive shaft having one end connected to the impeller or the rotation shaft so as not to rotate relative to the impeller and to move in the axial direction. A small centrifugal pump according to the item. 8. The compact device according to claim 1 , wherein the driving means is provided on each of the impeller and the casing, and includes a magnetic force driving mechanism that rotationally drives the impeller by a magnetic force. 9. Centrifugal pump. An operation method in a small centrifugal pump comprising an impeller formed with a plurality of blades, a casing for rotatably holding the impeller, and a drive mechanism for rotating the impeller,
A disk portion rotating away from the inner surface of the casing provided with the fluid suction port, and a radius from the central portion of the disk on one side surface of the disk portion facing the fluid suction port. And comprising a plurality of blades radially extending outward in the direction,
A tapered surface that is spaced from the inner surface of the casing in the rotational direction is provided on the side edge of each blade that rotates opposite to the inner surface of the casing.
While the negative pressure generated in the fluid suction port or the central portion of the impeller is adopted by the impeller, the impeller is displaced toward the casing inner surface side of the fluid suction port,
An operation method of a small centrifugal pump, wherein the side edge portion of the impeller is operated so as not to contact the inner surface of the casing by a fluid wedge action generated between the tapered surface and the inner surface of the casing.

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