Rotor drive mechanism and pump apparatus including the same

A rotor drive mechanism 25 is configured to transfer rotation of a driving shaft 38 to an external screw type rotor 22 of a uniaxial eccentric screw pump 23 via a connecting shaft 39, the driving shaft 38 being rotated such that the center thereof is located at a fixed position. The rotor drive mechanism 25 is configured such that: the driving shaft 38 includes an inner space 46 which is open toward the rotor 22; the connecting shaft 39 is inserted in the inner space 46; and a first seal portion 55 seals between an inner peripheral surface of an opening of the driving shaft 38, the opening being open toward the rotor 22, and an outer peripheral surface of the rotor shaft 37 connected to the rotor 22 configured to carry out an eccentric rotational movement.

TECHNICAL FIELD

The present invention relates to a rotor drive mechanism applicable to a uniaxial eccentric screw pump capable of transferring various fluids, such as gases, liquids, and powder, and a pump apparatus including the rotor drive mechanism.

BACKGROUND ART

One example of conventional pump apparatuses will be explained in reference toFIG. 6. As shown inFIG. 6, a pump apparatus1includes a uniaxial eccentric screw pump2and a rotor drive mechanism4configured to rotate a rotor3provided in the uniaxial eccentric screw pump2. The uniaxial eccentric screw pump2is configured such that the external screw type rotor3is fittingly inserted in an internal screw type inner hole5aof a stator5. By rotating the rotor3in a predetermined direction, a transfer fluid, such as a liquid, can be suctioned from a suction port6for example, held in a space between the rotor3and the stator5, transferred, and then discharged from a discharge port7. At this time, the rotor3carries out an eccentric rotational movement, i.e., rotates while carrying out a revolution movement about a central axis8of the stator inner hole5ashown inFIG. 6. The rotor drive mechanism4realizes the eccentric rotational movement of the rotor3.

The rotor drive mechanism4shown inFIG. 6includes a driving shaft9rotated by a rotary driving portion (for example, an electric motor)11and a connecting shaft10connected to a tip end portion of the driving shaft9. A tip end portion of the connecting shaft10is connected to a rear end portion (base end portion) of the rotor3.

To be specific, when a rotating shaft11aof the rotary driving portion11rotates, this rotation is transferred through a coupling18, the driving shaft9, and the connecting shaft10to the rotor3, and thus, the rotor3carries out the eccentric rotational movement. With this, the transfer fluid can be suctioned from the suction port6and discharged from the discharge port7.

As shown inFIG. 6, the tip end portion of the connecting shaft10and the rear end portion of the rotor3are connected to each other via a first joint portion (universal joint)12, and the tip end portion of the driving shaft9and a rear end portion of the connecting shaft10are connected to each other via a second joint portion (universal joint)13. The first and second joint portions12and13and the connecting shaft10are covered with a joint cover14made of, for example, synthetic rubber. The joint cover14prevents the transfer fluid, suctioned from the suction port6to a fluid accommodating space16of a casing15, from contacting the first and second joint portions12and13and the connecting shaft10.

Another example of the pump apparatus1is disclosed in PTL 1.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, in the conventional pump apparatus1shown inFIG. 6, the second joint portion13, the connecting shaft10, and the first joint portion12are connected to the tip end portion of the driving shaft9, and the driving shaft9, the second joint portion13, and the like are arranged in series. Therefore, the total of longitudinal lengths of the driving shaft9, the second joint portion13, the connecting shaft10, and the first joint portion12is a factor for an increase in the entire length of the pump apparatus1.

To be specific, the pump apparatus1shown inFIG. 6is used as, for example, a dispenser. For example, such dispenser may be attached to a tip end portion of a robot hand and used for an application work of applying a liquid to an inner surface of a narrow space. To improve workability, there is a need for a reduction in size of the dispenser used in such application work.

As shown inFIG. 6, the connecting shaft10and the first and second joint portions12and13, covered with the joint cover14, are arranged in the fluid accommodating space16of the casing15. Therefore, the fluid accommodating space16increases in volume by the lengths of these components10,12, and13. This increases the amount of transfer fluid accommodated in the fluid accommodating space16having a large volume. When washing the pump apparatus1, the transfer fluid accommodated in the fluid accommodating space16is discarded. Therefore, there is a need for a reduction in the amount of transfer fluid to be discarded. To be specific, since some of transfer fluids are expensive, a reduction in the loss of the transfer fluid is an important object.

In a state where the driving shaft9shown inFIG. 6rotates, and the transfer fluid is discharged from the discharge port7, the rotor3receives a force in an axial direction by a discharge pressure (reaction force) of the transfer fluid. At this time, since the connecting shaft10is inclined with respect to the axial direction, a bending force (moment) is applied to the tip end portion of the driving shaft9in a direction perpendicular to the axial direction. The driving shaft9bends by this bending force, and this causes axial runout. The axial runout is a factor for a decrease in life of a seal portion17configured to seal a gap between the driving shaft9and an inner peripheral surface of the casing15. There is a need for a reduction in maintenance cost of the shaft seal portion17and a reduction in work.

The present invention was made to solve the above problems, and an object of the present invention is to provide a rotor drive mechanism capable of reducing the longitudinal size of the pump apparatus and the volume of the fluid accommodating space of the casing and increasing the life of the seal portion, and the pump apparatus including the rotor drive mechanism.

Solution to Problem

A rotor drive mechanism according to a first aspect of the present invention is configured to transfer rotation of a driving shaft to an external screw type rotor of a uniaxial eccentric screw pump via a connecting shaft, the driving shaft being rotated such that a center thereof is located at a fixed position, wherein: the driving shaft includes an inner space which is open toward the rotor, and the connecting shaft is inserted in the inner space; a base end portion of the connecting shaft is connected to the driving shaft, and a tip end portion of the connecting shaft is connected to the rotor; and a first seal portion seals between an inner peripheral surface of an opening of the driving shaft, the opening being open toward the rotor, and an outer peripheral surface of a base end portion of the rotor configured to carry out an eccentric rotational movement or between the inner peripheral surface of the opening of the driving shaft and an outer peripheral surface of the connecting shaft.

In accordance with the rotor drive mechanism of the first aspect of the present invention, the connecting shaft can be used by being connected to the external screw type rotor of the uniaxial eccentric screw pump. To be specific, when the driving shaft is rotated in a predetermined direction, the rotation of the driving shaft can be transferred to the rotor via the connecting shaft to cause the rotor to carry out the eccentric rotational movement. By the eccentric rotational movement of the rotor, a space formed by an inner surface of the stator inner hole and an outer surface of the rotor moves in a direction from one opening of the stator inner hole toward the other opening. Therefore, the transfer fluid can be transferred in this direction.

The connecting shaft is inserted in the inner space of the driving shaft, and the base end portion of the connecting shaft is connected to the driving shaft. Therefore, the axial length of the rotor drive mechanism can be shortened by the overlap of the connecting shaft and the driving shaft. The first seal portion seals between the inner peripheral surface of the opening of the driving shaft and the outer peripheral surface of the base end portion of the rotor or between the inner peripheral surface of the opening of the driving shaft and the outer peripheral surface of the connecting shaft. Therefore, it is possible to prevent the transfer fluid from flowing into the inner space of the driving shaft, and the volume of the fluid accommodating space in the casing can be reduced by the volume of the inner space. The first seal portion seals the inner space of the driving shaft to prevent the transfer fluid from flowing into the inner space. Therefore, the connecting shaft inserted in the sealed inner space can be prevented from contacting the transfer fluid. On this account, it is possible to prevent a case where when the connecting shaft is rotated by the driving shaft to whirl, the whirling of the connecting shaft is inhibited by the transfer fluid.

The rotor drive mechanism according to a second aspect of the present invention is configured such that in the first aspect of the present invention, the tip end portion of the connecting shaft and the rotor are connected to each other via a first joint portion, the base end portion of the connecting shaft and the driving shaft are connected to each other via a second joint portion, and the first and second joint portions and the connecting shaft are arranged in the inner space of the driving shaft, the inner space being sealed by the first seal portion.

For example, a joint including a universal joint can be used as each of the first and second joint portions. The first seal portion can prevent the first and second joint portions and the connecting shaft from contacting the transfer fluid. With this, for example, even if the transfer fluid has corrosivity, the material of each of the first and second joint portions and the connecting shaft does not have to be selected from corrosion-resistance materials, and an appropriate material, such as a high-strength material, can be freely selected. Further, since it is unnecessary to consider adaptability between the transfer fluid and the material of each of the first and second joint portions and the connecting shaft, it is possible to widen the range of use of the transfer fluid which can be transferred by the uniaxial eccentric screw pump.

The rotor drive mechanism according to a third aspect of the present invention is configured such that in the first aspect of the present invention, the base end portion of the connecting shaft and the driving shaft are connected to each other via a third joint portion, and the third joint portion and the connecting shaft are arranged in the inner space of the driving shaft, the inner space being sealed by the first seal portion.

A joint including an eccentric joint, such as Oldham coupling, can be used as the third joint portion. The first seal portion can prevent the third joint portion and the connecting shaft from contacting the transfer fluid. With this, for example, even if the transfer fluid has corrosivity, the material of each of the third joint portion and the connecting shaft does not have to be selected from corrosion-resistance materials, and an appropriate material, such as a high-strength material, can be freely selected. Further, it is unnecessary to consider the adaptability between the transfer fluid and the material of each of the third joint portion and the connecting shaft, and it is possible to widen the range of use of the transfer fluid which can be transferred by the uniaxial eccentric screw pump.

The rotor drive mechanism according to a fourth aspect of the present invention is configured such that the second joint portion of the second aspect of the present invention or the third joint portion of the third aspect of the present invention is arranged on a radially inward side of a bearing portion configured to rotatably support the driving shaft.

With this, in a state where the driving shaft rotates, and the transfer fluid is discharged from the discharge port of the uniaxial eccentric screw pump, the rotor receives a force in an axial direction by the discharge pressure (reaction force) of the transfer fluid. At this time, since the connecting shaft is inclined with respect to the axial direction, the bending force (moment) is applied to a portion of the driving shaft in a direction perpendicular to the axial direction, the portion being connected by the second joint portion or the third joint portion. However, since the second joint portion or the third joint portion is arranged on a radially inward side of the bearing portion which rotatably supports the driving shaft, it is possible to prevent the axial runout of the driving shaft by the bending force. With this, it is possible to prevent the occurrence of the vibration of the rotor drive mechanism and lengthen the life of the rotor drive mechanism.

The rotor drive mechanism according to a fifth aspect of the present invention is configured such that in the fourth aspect of the present invention, a second seal portion seals between an outer peripheral surface of the opening of the driving shaft, the opening being open toward the rotor, and an inner peripheral surface of a casing of the uniaxial eccentric screw pump.

With this, since the second seal portion seals a gap between the outer peripheral surface of the driving shaft and the inner peripheral surface of the casing, it is possible to prevent the transfer fluid in the casing from flowing into a space located on the bearing side. Thus, the volume of the fluid accommodating space in the casing can be reduced. Since the axial runout of the driving shaft is prevented, the vibration by the axial runout is not applied to the second seal portion. As a result, it is possible to prevent the life of the second seal portion from being shortened by the axial runout of the driving shaft and lengthen the life of the rotor drive mechanism.

The rotor drive mechanism according to a sixth aspect of the present invention is configured such that in the second aspect of the present invention, each of the first and second joint portions is a universal joint.

With this, the rotation of the driving shaft can be smoothly transferred to the rotor to cause the rotor to accurately carry out the eccentric rotational movement, and the accuracy of the discharge rate of the uniaxial eccentric screw pump can be improved.

The rotor drive mechanism according to a seventh aspect of the present invention is configured such that in the first aspect of the present invention, the connecting shaft is a flexible rod.

With this, the configuration of the rotor drive mechanism can be simplified, and the rotor drive mechanism can be reduced in size, weight, and cost.

A pump apparatus according to an eighth aspect of the present invention is configured to include the rotor drive mechanism of the first aspect of the present invention and the uniaxial eccentric screw pump.

In accordance with the pump apparatus of the eighth aspect of the present invention, the effects explained for the rotor drive mechanism are achieved.

Advantageous Effects of Invention

In accordance with the rotor drive mechanism and pump apparatus of the present invention, the axial length of the rotor drive mechanism can be shortened. Therefore, the axial length of the pump apparatus to which the rotor drive mechanism is applied can be shortened, and the pump apparatus can be reduced in size and weight. For example, in a case where the pump apparatus to which the rotor drive mechanism is applied is attached as a dispenser to a tip end portion of a robot hand and used for an application work of applying a liquid to an inner surface of a narrow space, the workability can be improved.

Since the inner space of the driving shaft is sealed by the first seal portion, and the volume of the fluid accommodating space in the casing is reduced, the amount of transfer fluid, which is accommodated in the fluid accommodating space and is discarded when, for example, washing the pump apparatus, can be reduced, which is economical.

The inner space of the driving shaft is sealed by the first seal portion to prevent the transfer fluid from flowing into the inner space. Therefore, it is possible to prevent a case where when the connecting shaft inserted in the inner space is rotated to whirl, the whirling of the connecting shaft is inhibited by the transfer fluid. With this, the accuracy of the discharge rate of the uniaxial eccentric screw pump driven by the rotor drive mechanism can be improved.

DESCRIPTION OF EMBODIMENTS

Next, Embodiment 1 of a rotor drive mechanism according to the present invention and a pump apparatus including the rotor drive mechanism will be explained in reference toFIGS. 1 to 3. A pump apparatus21can cause a rotor22shown inFIG. 1to rotate and carry out a revolution movement along a predetermined path (to carry out an eccentric rotational movement). With this, the pump apparatus21can transfer and supply any fluids, such as low to high viscous fluids, with high flow rate accuracy and a long operating life.

As shown inFIG. 1, the pump apparatus21includes a uniaxial eccentric screw pump23, a rotary driving portion24, and a rotor drive mechanism25.

The uniaxial eccentric screw pump23is a rotary volume type pump and includes an internal screw type stator26and the external screw type rotor22.

As shown inFIG. 1, the stator26is formed to have a substantially short cylindrical shape having an inner hole26aof a double thread internal screw shape for example. A longitudinal cross-sectional shape of the inner hole26ais elliptical. The stator26is made of, for example, a rubber-like elastic body, such as synthetic rubber, or engineering plastic, such as fluorocarbon resin. The stator26is attached to be sandwiched between a nozzle27and an end portion of a first casing28. The nozzle27has a first opening31, and the first casing28has a second opening32. An outer tube33is attached to between the nozzle27and the first casing28.

As shown inFIG. 1, a needle nozzle34is attached to a tip end portion of the nozzle27and fastened to the nozzle27by a nut35.

The first opening31can be used as a discharge port (or a suction port), and the second opening32can be used as a suction port (or a discharge port). The first opening31communicates with a tip end opening of the inner hole26aof the stator26, and the second opening32communicates with a rear end opening of the inner hole26a. A fluid accommodating space36is formed between the second opening32and the rear end opening of the inner hole26a.

As shown inFIG. 1, the rotor22is formed to have a single thread external screw shape for example. A longitudinal cross-sectional shape of the rotor22is a substantially perfect circle. A pitch of a spiral shape of the rotor22is set to half a pitch of the stator26. The rotor22is made of a metal, such as stainless steel, and is fittingly inserted in the inner hole26aof the stator26. A rotor shaft37is formed at a rear end portion (base end portion) of the rotor22. The rotor shaft37is included in the rotor drive mechanism25.

As shown inFIG. 2, the rotor drive mechanism25is configured to transfer the rotation of a rotating shaft24a, rotated by the rotary driving portion24, to the external screw type rotor22of the uniaxial eccentric screw pump23. The rotor drive mechanism25includes a driving shaft38, a connecting shaft39, and the rotor shaft37.

As shown inFIG. 2, the driving shaft38is rotatably provided on an inner surface of a second casing29via a bearing portion40, such as a slide bearing. The driving shaft38is a tubular member having a center hole41. The driving shaft38includes a large-diameter portion42at a tip end portion thereof, an intermediate-diameter portion43at a center portion thereof, and a small-diameter portion44at a rear end portion thereof. The small-diameter portion44at the rear end portion of the driving shaft38is connected to the rotating shaft24aof the rotary driving portion24by a coupling45.

An inner space46is formed inside the large-diameter portion42of the tip end portion of the driving shaft38so as to open toward the rotor22. The connecting shaft39is inserted into the center hole41including the inner space46.

As shown inFIG. 2, the connecting shaft39is a rod-shaped body having a predetermined length. A rear end portion of the connecting shaft39is provided at the center hole41formed inside the intermediate-diameter portion43of the driving shaft38, and a tip end portion of the connecting shaft39is provided at the inner space46formed inside the large-diameter portion42of the driving shaft38.

Further, the tip end portion of the connecting shaft39is connected to the rotor shaft37via a first joint portion47, and the rear end portion of the connecting shaft39is connected to the intermediate-diameter portion43of the driving shaft38via a second joint portion48. Each of the first and second joint portions47and48is, for example, a universal joint.

As shown inFIG. 2, the second joint portion48includes a pair of coupling holes49, which are formed on a side wall of the tubular-shaped intermediate-diameter portion43to be opposed to each other in a radial direction. Both end portions of a connecting pin50are respectively attached to the pair of coupling holes49. The connecting pin50is inserted through a connecting hole51formed at the rear end portion of the connecting shaft39. The connecting hole51is formed to increase in diameter in an axial direction of the connecting shaft39as it extends toward each of two opening end portions of the connecting hole51.

In accordance with the second joint portion48formed as above, the intermediate-diameter portion43of the driving shaft38and the rear end portion of the connecting shaft39are connected to each other such that: the connecting shaft39can swing about a shaft center of the connecting pin50; and the tip end portion of the connecting shaft39can swing about a center of the connecting pin50in an upper-lower direction inFIG. 2.

Further, as shown inFIG. 2, a cylindrical seal cover52is attached to an outer peripheral surface of the intermediate-diameter portion43of the driving shaft38. The seal cover52seals a lubricating liquid filled in the inner space46and center hole41of the driving shaft38and is arranged to cover the pair of coupling holes49. Two O rings53are attached to the outer peripheral surface of the intermediate-diameter portion43so as to sandwich the pair of coupling holes49from both sides. An inner peripheral surface of the seal cover52configured as above and two O rings53seal the pair of coupling holes49to prevent the lubricating liquid, filled in the inner space46and center hole41of the driving shaft38, from leaking through the pair of coupling holes49to the outside of the driving shaft38.

The bearing portion40is attached to an outer peripheral surface of the seal cover52. The driving shaft38and the seal cover52are rotatably supported by the bearing portion40. To be specific, the connecting pin50of the second joint portion48is arranged on a radially inward side of the bearing portion40.

Next, the first joint portion47will be explained. As shown inFIG. 2, the first joint portion47is similar to the second joint portion48and includes a connecting tubular portion54coupled to the rotor shaft37. The connecting tubular portion54includes a pair of coupling holes49, which are formed to be opposed to each other in the radial direction. Both end portions of a connecting pin50are respectively attached to the pair of coupling holes49. The connecting pin50is inserted through a connecting hole51formed at the tip end portion of the connecting shaft39. The connecting hole51is formed to increase in diameter in the axial direction of the connecting shaft39as it extends toward each of two opening end portions of the connecting hole51.

In accordance with the first joint portion47formed as above, as with the second joint portion48, the tip end portion of the connecting shaft39and the rotor shaft37are connected to each other such that: the connecting shaft39can swing about a shaft center of the connecting pin50; and a cross angle (cross angle in a plane parallel to the sheet ofFIG. 2) between a shaft center of the connecting shaft39and a shaft center of the rotor22is changeable.

As shown inFIG. 2, a first seal portion55is attached to an outer peripheral surface of the rotor shaft37. The first seal portion55is made of a rubber-like elastic body, such as synthetic rubber. The first seal portion55seals between the outer peripheral surface of the rotor shaft37and an inner peripheral surface of an opening (large-diameter portion42) of the driving shaft38, the opening being open toward the rotor22. The first seal portion55seals between the fluid accommodating space36formed in the first casing28and the inner space46and center hole41formed in the large-diameter portion42, and thus, the first seal portion55separates the fluid accommodating space36from the inner space46and the center hole41.

Further, as shown inFIG. 2, a rear end opening of the center hole41formed in the small-diameter portion44of the driving shaft38is sealed by a plug56.

As above, the inner space46and center hole41formed inside the driving shaft38are sealed by the first seal portion55and the plug56. The connecting shaft39and the first and second joint portions47and48are accommodated in the inner space46and the center hole41, and the lubricating liquid is filled in the inner space46and the center hole41.

As shown inFIGS. 3(a) and3(b), the first seal portion55is an annular-shaped member. A cross-sectional shape of the first seal portion55is a substantially Z shape. The first seal portion55includes an outer side wall portion57, an inner side wall portion58, and a connecting wall portion59. An outer peripheral surface of the outer side wall portion57is formed to be slightly larger in diameter than the inner peripheral surface of the large-diameter portion42of the driving shaft38and is attached firmly to the inner peripheral surface of the large-diameter portion42. An inner peripheral surface of the inner side wall portion58is formed to be slightly smaller in diameter than the outer peripheral surface of the rotor shaft37and is attached firmly to the outer peripheral surface of the rotor shaft37. The connecting wall portion59has a substantially truncated cone shape and connects a rear end portion of the outer side wall portion57and a tip end portion of the inner side wall portion58.

In accordance with the first seal portion55, when the rotor shaft37carries out the eccentric rotational movement in accordance with the rotor22, to be specific, when the rotor shaft37carries out the revolution movement while rotating about a central axis60of the inner hole26aof the stator26, as shown inFIG. 2, the first seal portion55deforms such that the inner side wall portion58can move in the radial direction, so that the rotor22can freely carry out the eccentric rotational movement, the transfer fluid in the fluid accommodating space36can be prevented from flowing into the inner space46and center hole41formed inside the driving shaft38, and the lubricating liquid filled in the inner space46and the center hole41can be prevented from leaking to the fluid accommodating space36.

Even in a state where the rotor22carries out the eccentric rotational movement, the first seal portion55does not rotate in accordance with the rotor22and is in a stationary state and attached firmly to the inner peripheral surface of the large-diameter portion42of the driving shaft38.

As shown inFIG. 2, a second seal portion61is attached to an annular-shaped gap between an outer peripheral surface of the large-diameter portion42of the driving shaft38and an inner peripheral surface of the first casing28. The second seal portion61seals this annular-shaped gap. The second seal portion61is made of engineering plastic, such as fluorocarbon resin or ultrahigh molecular weight polyethylene. The second seal portion61seals between the fluid accommodating space36formed in the first casing28and a space which is located on a rear side of the second seal portion61and accommodates the bearing portion40, and thus, the second seal portion61separates the fluid accommodating space36from this space.

As shown inFIG. 2, the second seal portion61is an annular-shaped member. A cross-sectional shape of the second seal portion61is a substantially inverted C shape. An outer peripheral surface of the second seal portion61is formed to be slightly larger in diameter than the inner peripheral surface of the first casing28and is attached firmly to the inner peripheral surface of the first casing28. An inner peripheral surface of the second seal portion61is formed to be slightly smaller in diameter than the outer peripheral surface of the large-diameter portion42of the driving shaft38and is attached firmly to the outer peripheral surface of the large-diameter portion42.

In accordance with the second seal portion61, the transfer fluid in the fluid accommodating space36of the first casing28can be prevented from flowing into a space located on the bearing portion40side, and foreign matters which may exist in the space located on the bearing portion40side can be prevented from getting into the fluid accommodating space36.

As shown inFIG. 2, a third casing30is arranged between the first casing28and the second casing29. A second seal portion62is attached to between an inner peripheral surface of the third casing30and the outer peripheral surface of the large-diameter portion42of the driving shaft38. The second seal portion62is the same in configuration as the second seal portion61and acts in the same manner as the second seal portion61, so that an explanation thereof is omitted.

Next, in accordance with the pump apparatus21including the rotor drive mechanism25configured as above, when the rotary driving portion24shown inFIG. 1rotates, the rotation of the rotary driving portion24can be transferred through the rotating shaft24a, the driving shaft38, the second joint portion48, the connecting shaft39, the first joint portion47, and the rotor shaft37to the rotor22of the uniaxial eccentric screw pump23to rotate the rotor22in a predetermined direction. Then, the rotor22carries out the eccentric rotational movement. Thus, the rotor22can cause a liquid, such as the transfer fluid, to flow into the pump apparatus21through the second opening32and to be discharged from the needle nozzle34.

To be specific, by the eccentric rotational movement of the rotor22, a space formed between an inner surface of the stator inner hole26aand an outer surface of the rotor22moves in a direction from an opening, located on the second opening32side, of the stator inner hole26ato an opening, located on the first opening31side, of the stator inner hole26a, so that the transfer fluid can be transferred in this direction. At this time, the rotor22carries out the eccentric rotational movement, i.e., rotates while carrying out the revolution movement about the central axis60of the stator inner hole26ashown inFIG. 2. The rotor drive mechanism25realizes the eccentric rotational movement of the rotor22.

In accordance with the rotor drive mechanism25shown inFIG. 2, the connecting shaft39and the first and second joint portions47and48are arranged in the inner space46and center hole41of the driving shaft38, and the rear end portion (base end portion) of the connecting shaft39is connected to the intermediate-diameter portion43of the driving shaft38via the second joint portion48. Therefore, the axial length of the rotor drive mechanism25, that is, the axial length of the pump apparatus21can be shortened by the overlap of the connecting shaft39, the first and second joint portions47and48, and the driving shaft38. Thus, the pump apparatus21can be reduced in size and weight. For example, in a case where the pump apparatus21to which the rotor drive mechanism25is applied is attached as a dispenser to a tip end portion of a robot hand and used for an application work of applying a liquid to an inner surface of a narrow space, the workability can be improved.

As shown inFIG. 2, the first seal portion55seals a ring-shaped gap between the inner peripheral surface of the opening formed at the large-diameter portion42of the driving shaft38and the outer peripheral surface of the rotor shaft37. Therefore, the transfer fluid can be prevented from flowing into the inner space46and center hole41of the driving shaft38, and the volume of the fluid accommodating space36in the first casing28can be reduced by the volume of the inner space46and the center hole41. On this account, the amount of transfer fluid, which is accommodated in the fluid accommodating space36and is discarded when, for example, washing the pump apparatus21, can be reduced, which is economical.

The first seal portion55seals the inner space46and center hole41of the driving shaft38to prevent the transfer fluid from flowing into the inner space46and the center hole41. Therefore, the connecting shaft39and first and second joint portions47and48inserted in the inner space46and the center hole41can be prevented from contacting the transfer fluid. On this account, it is possible to prevent a case where when the connecting shaft39and the first and second joint portions47and48are rotated by the driving shaft38to whirl, the whirling of the connecting shaft39and the first and second joint portions47and48is inhibited by the transfer fluid. With this, the accuracy of the discharge rate of the uniaxial eccentric screw pump23driven by the rotor drive mechanism25can be improved.

Further, as described above, the first and second joint portions47and48and the connecting shaft39can be prevented from contacting the transfer fluid. Therefore, for example, even if the transfer fluid has corrosivity, the material of each of the first and second joint portions47and48and the connecting shaft39does not have to be selected from corrosion-resistance materials, and an appropriate material, such as a high-strength material, can be freely selected. Then, it is unnecessary to consider adaptability between the transfer fluid and the material of each of the first and second joint portions47and48and the connecting shaft39, and it is possible to widen the range of use of the transfer fluid which can be transferred by the uniaxial eccentric screw pump23.

As shown inFIG. 2, when the driving shaft38rotates to cause the rotor22to carry out the eccentric rotational movement, a bending force (moment) is applied in a direction perpendicular to the axial direction to the intermediate-diameter portion43(radial load applied point63) of the driving shaft38to which the second joint portion48is connected. However, since the second joint portion48is arranged on a radially inward side of the bearing portion40which rotatably supports the intermediate-diameter portion43of the driving shaft38, it is possible to prevent axial runout of the driving shaft38by this bending force. Therefore, it is possible to prevent the occurrence of the vibration of the rotor drive mechanism25and lengthen the life of the rotor drive mechanism25.

As shown inFIG. 2, the second seal portions61and62seal a ring-shaped gap between the outer peripheral surface of the large-diameter portion42of the driving shaft38and the inner peripheral surface of the first casing28. Therefore, the transfer fluid in the first casing28can be prevented from flowing into the space located on the bearing portion40side. With this, the volume of the fluid accommodating space36can be reduced. As described above, since the axial runout of the driving shaft38is prevented, the vibration by the axial runout is not applied to the second seal portion61. As a result, the life of the second seal portion61can be prevented from being shortened by the axial runout of the driving shaft38.

Further, since the first and second joint portions47and48are universal joints, they can smoothly transfer the rotation of the driving shaft38to the rotor22to cause the rotor22to accurately carry out the eccentric rotational movement, and this can improve the accuracy of the discharge rate of the uniaxial eccentric screw pump23.

Next, Embodiment 2 of the pump apparatus including the rotor drive mechanism according to the present invention will be explained in reference toFIG. 5. A pump apparatus65of Embodiment 2 shown inFIG. 5is different from the pump apparatus21of Embodiment 1 shown inFIG. 2in that: in Embodiment 1 shown inFIG. 2, the driving shaft38and the rotor shaft37are connected to each other via the second joint portion48, the connecting shaft39, and the first joint portion47; but in Embodiment 2 shown inFIG. 5, the driving shaft38and the rotor shaft37are connected to each other via a flexible rod66. Other than the above, the pump apparatus of Embodiment 2 is the same as that of Embodiment 1 shown inFIGS. 1 and 2, so that the same reference signs are used for the same components, and explanations thereof are omitted.

As above, even in a case where the driving shaft38and the rotor shaft37are connected to each other via the flexible rod66, it is possible to cause the rotor22to carry out the eccentric rotational movement and discharge the transfer fluid from the needle nozzle34as with Embodiment 1.

As shown inFIG. 5, a connection portion where a rear end portion (base end portion) of the flexible rod66and the intermediate-diameter portion43of the driving shaft38are connected to each other is arranged on a radially inward side of the bearing portion40. Therefore, it is possible to prevent the axial runout of the driving shaft38as with Embodiment 1.

By using the flexible rod66as above, the configuration of a rotor drive mechanism67can be simplified, and the rotor drive mechanism67can be reduced in size, weight, and cost.

In Embodiment 2, as shown inFIG. 5, the first seal portion55is attached to the outer peripheral surface of the rotor shaft37. Instead of this, Embodiment 2 may be such that: the rotor shaft37is omitted; the first seal portion55is attached to an outer peripheral surface of a tip end portion of the flexible rod66, and the axial length of the large-diameter portion42of the driving shaft38is shortened by the omission of the rotor shaft37. In this case, the axial length of the rotor drive mechanism67can be shortened by the omission of the rotor shaft37, that is, the entire length of the pump apparatus65can be shortened.

In Embodiments 1 and 2, the first seal portion55shown inFIGS. 3(a) and3(b) is used. However, instead of this, a first seal portion69shown inFIGS. 4(a) and4(b) may be used. Differences between the first seal portion69shown inFIGS. 4(a) and4(b) and the first seal portion55shown inFIGS. 3(a) and3(b) are a connecting wall portion70and the connecting wall portion59.

A cross-sectional shape of the first seal portion69shown inFIGS. 4(a) and4(b) is a substantially C shape. The first seal portion69includes the outer side wall portion57, the inner side wall portion58, and the connecting wall portion70. The connecting wall portion70is a substantially annular-shaped and plate-shaped body and connects a tip end portion of the outer side wall portion57and a tip end portion of the inner side wall portion58.

In accordance with the first seal portion69, as shown inFIG. 4(a), a left side surface of the first seal portion69faces the fluid accommodating space36of the first casing28. The left side surface is formed as a flat surface by the connecting wall portion70. Therefore, even if, for example, a high-viscosity transfer fluid in the fluid accommodating space36adheres to the left side surface of the first seal portion69, the adhered fluid does not interfere with the deformation of the first seal portion69. On this account, the rotor22can accurately carry out the eccentric rotational movement.

In Embodiments 1 and 2, as shown inFIG. 2and the like, the rotating shaft24aof the rotary driving portion24is connected to the driving shaft38by the coupling45to transfer the rotational power. However, instead of this, the rotational power of the rotating shaft24aof the rotary driving portion24may be transferred to the driving shaft38by rotational power transfer means, such as gears, or timing belt pulleys and a timing belt.

In Embodiment 1, as shown inFIG. 2, the driving shaft38and the rotor shaft37are connected to each other via the second joint portion48(universal joint), the connecting shaft39, and the first joint portion47(universal joint). However, instead of this, the driving shaft38and the rotor shaft37may be connected to each other by using an Oldham coupling (third joint portion, not shown).

In the case of using the Oldham coupling as above, for example, the rear end portion of the connecting shaft39and the intermediate-diameter portion43of the driving shaft38inFIG. 2are connected to each other via the Oldham coupling.

Even in this case, as with Embodiment 1, it is possible to cause the rotor22to carry out the eccentric rotational movement to discharge the transfer fluid from the needle nozzle34. Then, since there is only one joint portion, the configuration of the rotor drive mechanism25can be simplified, the rotor drive mechanism25can be reduced in size, weight, and cost, and the entire length of the pump apparatus21can be shortened.

Since the Oldham coupling is arranged on a radially inward side of the bearing portion40which rotatably supports the intermediate-diameter portion43of the driving shaft38, it is possible to prevent the axial runout of the driving shaft38, as with Embodiment 1. With this, it is possible to prevent the occurrence of the vibration of the rotor drive mechanism and lengthen the lives of the second seal portions61and62.

INDUSTRIAL APPLICABILITY

As above, each of the rotor drive mechanism according to the present invention and the pump apparatus including the same has excellent effects that are the reduction in the longitudinal size of the pump apparatus, the reduction in the volume of the fluid accommodating space of the casing, and the increase in the life of the seal portion. Thus, the present invention is suitably applicable to the rotor drive mechanism and the pump apparatus including the same.

REFERENCE SIGNS LIST