JP2014062535A - Uniaxial eccentric screw pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent abrasion caused by solid-contact sliding of a rotor and a stator.SOLUTION: In a uniaxial eccentric screw pump 1, a rotor 2 is made of austenitic stainless steel, and provided with micro dimples of 0.1 μm- 20 μm on its surface, and carbon sold-solution diffusion treatment for diffusing carbon in a solid-solution state, is performed in austenite structure on the surface of the rotor 2.

Description

  The present invention relates to a uniaxial eccentric screw pump that is suitable for applications in which viscous liquids such as food raw materials, chemical raw materials, and sewage sludge are pumped quantitatively.

  An example of this type of single-shaft eccentric screw pump is disclosed in Patent Document 1. In this uniaxial eccentric screw pump, an externally threaded rotor is housed in a fixed stator having an internally threaded inner surface. The rotor is connected to a drive shaft via a universal joint, and the drive shaft is connected to a motor shaft. According to this single-shaft eccentric screw pump, when the drive shaft is rotated by a motor, the rotor rotates with respect to the stator shaft center and performs an eccentric motion to guide the viscous liquid from the suction side to the suction portion and be sucked in. The viscous liquid can be pumped to the discharge side.

JP 59-153992 A (FIG. 1)

Here, there are many raw materials containing a large amount of salt in food raw materials. Therefore, in a uniaxial eccentric screw pump that pumps food materials, SUS316, which has excellent corrosion resistance against salt, is often used as a material for the rotor. In contrast, conventional uniaxial eccentric screw pumps have a mirror finish on the surface of the rotor, but this rotor rotates in an elastomeric stator with a certain amount of tightening allowance and generates a pumping action. For this reason, solid contact sliding also occurs in the seal line formed by the rotor and the stator, and the wear of the rotor and the stator is promoted.
In order to reduce the wear of the rotor made of SUS316, the surface of the rotor is coated with excellent wear resistance, such as ceramics, or subjected to nitriding treatment to increase the hardness of the rotor surface and wear resistance. Measures to improve

However, when the ceramic coating is applied to the rotor surface, the construction cost is high, and when the ceramic surface layer is chipped, there is a problem that ceramic fragments are mixed into the food. In addition, when nitriding the rotor surface, carbon is bonded to the metal crystal to form the surface as a compound (cementite structure, etc.), so that the rotor surface becomes brittle or has corrosion resistance due to carbon precipitation or the like. There is a problem that it is deteriorated and premature corrosion due to salt occurs.
Therefore, the present invention has been made paying attention to such problems, and in a single-shaft eccentric screw pump in which the rotor rotates in the stator and generates a pumping action, the rotor and the stator are in solid contact sliding. The purpose is to prevent or suppress the wear caused by.

  In order to solve the above problems, a uniaxial eccentric screw pump according to an aspect of the present invention includes a stator having a female screw-shaped inner surface, and a rotor in which a male screw-shaped spiral portion is inserted into the stator. The rotator is a uniaxial eccentric screw pump that pumps the viscous liquid sucked from the suction side to the discharge side by rotating the rotor, and the rotor is made of austenitic stainless steel, and the surface of the rotor is FPB The dimples having a diameter of 0.1 μm to 20 μm are provided.

  Here, FPB (Fine Particle Bombarding) is a shot of fine particles having a hardness equal to or higher than the surface hardness of the rotor on the surface of the austenitic stainless steel rotor at a surface speed of 100 m / sec or more. Is increased to a predetermined value (for example, A3 transformation point or higher), and a surface dampening process is performed on the surface of the sliding portion of the rotor. is there. An example of this type of surface processing heat treatment method is WPC treatment (registered trademark).

  According to this uniaxial eccentric screw pump, micro dimples having a diameter of 0.1 μm to 20 μm of a recess formed by FPB are provided on the surface of an austenitic stainless steel rotor as an oil reservoir. The liquid can be retained. For this reason, fluid lubrication is achieved in which the sliding surfaces of the rotor and the stator do not run out of liquid. Thereby, the wear resulting from the solid contact sliding can be prevented or suppressed by sliding the rotor and the stator close to each other without contact.

  A uniaxial eccentric screw pump according to an aspect of the present invention includes a stator having a female screw-shaped inner surface, and a rotor in which a male screw-shaped spiral portion is inserted into the stator, and the rotor rotates in the stator. Thus, the uniaxial eccentric screw pump that pumps the viscous liquid sucked from the suction side to the discharge side, wherein the rotor is made of austenitic stainless steel, and carbon is dissolved in the austenite structure on the surface of the rotor. A carbon solid solution diffusion treatment for diffusion is performed.

This kind of carbon solid solution diffusion treatment is activated by replacing the passivation film (oxide film) of stainless steel with F (fluoride film), and then solidifying C (carbon) in the gaps of the surface crystal lattice. A diffusing pionite treatment (registered trademark) can be exemplified.
According to this uniaxial eccentric screw pump, since the carbon solid solution diffusion treatment for solid solution diffusion of carbon is performed in the austenite structure of the rotor surface, the thickness is 10 μm from the surface and the hardness is HV800 or more in micro Vickers hardness. As a result, there is almost no elution of carbon, and the wear resistance of the rotor can be improved with respect to the viscous liquid with wear without deteriorating the corrosion resistance. Therefore, wear caused by solid contact sliding between the rotor and the stator can be prevented or suppressed.

  Furthermore, a uniaxial eccentric screw pump according to an aspect of the present invention includes a stator having an inner surface of an internal thread shape, and a rotor in which an external thread-like spiral portion is inserted into the stator, and the rotor rotates in the stator. Thus, the uniaxial eccentric screw pump that pumps the viscous liquid sucked from the suction side to the discharge side, wherein the rotor is made of austenitic stainless steel, and the surface of the rotor has a recess formed by FPB. Micro dimples having a diameter of 0.1 μm to 20 μm are provided, and a carbon solid solution diffusion treatment for solid solution diffusion of carbon is performed in the austenite structure of the rotor surface.

  According to this uniaxial eccentric screw pump, the rotor is made of austenitic stainless steel, and a carbon solid solution diffusion treatment for solid solution diffusion of carbon is performed in the austenitic structure on the surface of the rotor. Since the austenite structure has been subjected to carbon solid solution diffusion treatment that diffuses carbon in a solid solution, a hardness of HV800 or higher in micro Vickers hardness is obtained with a thickness of 10 μm from the surface, there is almost no elution of carbon, and corrosion resistance is deteriorated. Therefore, it is possible to improve the wear resistance of the rotor against a viscous liquid with wear, and to maintain the micro dimples formed on the surface of the rotor for a long period of time. Thereby, the rotor and the stator are slid in a state close to non-contact, and there is a further effect in preventing or suppressing wear caused by the solid contact sliding.

  Here, in the single-shaft eccentric screw pump according to an aspect of the present invention, the single-shaft eccentric screw pump is configured such that the stator is rotatably supported, the rotor is fixed to a drive shaft, and the rotation axis of the rotor is the stator. Preferably, the stator is eccentric from the rotation axis by a predetermined distance, and the stator rotates dependently at a rotational speed that is half the rotational speed of the rotor.

  With such a configuration, it is possible to reduce the contact load between the rotor and the stator during high-pressure operation for transmission of the rotational force from the drive shaft to the rotor, for example, compared to a uniaxial eccentric screw pump using a universal joint. it can. Therefore, the viscous liquid is more easily held in the concave portion of the micro dimple. Therefore, the sliding surfaces of the rotor and the stator are fluid lubricated so as not to run out of liquid, can be easily slid in a non-contact state, and can prevent or suppress wear caused by solid contact sliding. It is more suitable as an eccentric screw pump.

  As described above, according to the present invention, wear caused by solid contact sliding between the rotor and the stator can be prevented or suppressed.

1 is a side view of a first embodiment of a uniaxial eccentric screw pump according to an aspect of the present invention. In addition, in the same figure, the principal part is shown in the cross section along an axis line (the following is the same). It is a side view of 2nd embodiment of the uniaxial eccentric screw pump concerning one mode of the present invention.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings as appropriate.
FIG. 1 is a cross-sectional structural view of the first embodiment. In the first embodiment, the stator is rotatably supported, and the rotation axis of the rotor fixed to the drive shaft is decentered from the rotation axis of the stator by a predetermined distance. In the uniaxial eccentric screw pump in which the stator is dependently rotated at a rotational speed that is 1/2 of the rotational speed of the rotor, the surface of the rotor is subjected to FPB treatment and carbon solid solution diffusion treatment to form microdimples. It is.

  Specifically, as shown in FIG. 1, the uniaxial eccentric screw pump 1 has a bracket 11 in which a motor (not shown) is accommodated. A housing 7 is attached to the bracket 11 on a surface 11a on the drive shaft 3 side of the motor. The housing 7 includes a suction portion 7a, a main body portion 7b, and a discharge portion 7c in order from the suction side (the right side in the figure) toward the discharge side. A suction port 8 for pumping fluid is formed in the suction portion 7a of the housing 7, and a discharge port 9 for pumping fluid is formed in the discharge portion 7c. This uniaxial eccentric screw pump 1 includes a housing 2 having a male screw-like rotor 2 and a stator 4 having a female screw-like inner surface.

  The rotor 2 includes a male screw-shaped spiral portion 2a on the distal end side and a linear base end portion 2b. The base end 2b is directly connected to the drive shaft 3 of the motor without using a universal joint (universal joint). The spiral portion 2a has a circular cross section that is eccentric with respect to its own rotation axis L2, and this spiral portion 2a is housed in the stator 4 that has an internally threaded oval cross section formed on the inner surface. The rotation axis L <b> 2 of the rotor 2 is arranged to be eccentric with respect to the rotation axis L <b> 1 of the stator 4 by an eccentric amount E that is a predetermined distance, and is eccentric with respect to the axis of the stator 4 while the rotor 2 rotates. By performing the motion, the fluid can be pumped from the suction side to the discharge side.

  Here, the rotor 2 is made of austenitic stainless steel (for example, made of SUS316), and the diameter of a concave portion formed by FPB (Fine Particle Bombarding) on the surface of the spiral portion 2a of the rotor 2 is 0.1 μm to 20 μm. The microdimple is provided, and a carbon solid solution diffusion treatment is performed in which the carbon is dissolved and diffused in the austenite structure on the surface of the spiral portion 2 a of the rotor 2.

  On the other hand, both ends of the stator 4 are rotatably supported by the underwater bearings 5 and 6. Specifically, the stator 4 includes a rubber stator inner cylinder 4a, and a metal stator outer cylinder 4b having a cylindrical shape that is fitted and bonded to the outer peripheral surface of the stator inner cylinder 4a by inlay fitting. . The stator outer cylinder 4b is made of stainless steel or titanium that complies with the food hygiene law. The spiral portion 4e formed inside the stator inner cylinder 4a has a female thread-like pitch twice that of the spiral portion 2a of the rotor 2. The outer surface of the stator outer cylinder 4 b is a sliding surface 4 c for the underwater bearings 5 and 6. The underwater bearings 5 and 6 are respectively arranged with respect to the sliding surfaces 4c at both ends of the stator outer cylinder 4b. The underwater bearings 5 and 6 are cylindrical bearings made of self-lubricating resin, and are made of a resin conforming to the Food Sanitation Law or a material obtained by coating a resin on a metal surface.

  Concave steps 7n and 7m are formed on the inner peripheral surfaces of the suction portion 7a and the main body portion 7b constituting the housing 7, respectively. The underwater bearings 5 and 6 have an inner peripheral surface fitted on the sliding surface 4c of the stator outer cylinder 4b, and an outer peripheral surface fitted on the recessed step portions 7n and 7m. Thereby, the sliding surfaces 4c at both ends of the cylindrical portion of the stator 4 (stator outer cylinder 4b) are rotatably supported in the housing 7 via the underwater bearings 5 and 6.

  The movement of the stator 4 in the axial direction is also restrained by the underwater bearings 5 and 6. That is, the stator outer cylinder 4b is formed with a convex portion 4m that forms an axial contact surface with the underwater bearings 5 and 6 at the center thereof, and the housing 7 side corresponds to the convex portion 4m. The recessed part 21 to be formed is formed in an annular shape. And the underwater bearings 5 and 6 are interposed between these convex part 4m, the recessed part 21, and opposing surfaces (between reference numerals 7t and 4u), respectively. Thereby, both ends of the convex portion 4 m of the stator 4 are supported while being sandwiched by the underwater bearings 5 and 6. In addition, between the both ends 4d of the stator outer cylinder 4b and the housing 7 (between the mutually opposing surfaces in the axial direction), sanitary annular seal members 16, 18 are provided on the suction side and the discharge side, respectively. It is interposed so as to seal between the housing 7.

Next, the operation and effect of this uniaxial eccentric screw pump will be described.
The uniaxial eccentric screw pump 1 includes a male screw-like rotor 2 directly connected to a drive shaft 3 and a stator 4 having a female screw-like inner surface, and the stator 4 is rotatably supported via underwater bearings 5 and 6. In addition, the rotation axis L1 is arranged eccentrically with respect to the rotation axis L2 of the rotor 2, and the rotor 2 rotates and performs an eccentric movement with respect to the axis of the stator 4, thereby pumping fluid from the suction side to the discharge side. Therefore, when the rotor 2 is rotated by the drive shaft 3 of the motor, the rotor 2 rotates about the rotation axis L2, and the stator 4 also centers on the rotation axis L1 as the spiral portion 2a of the rotor 2 moves. As a result, the pumped fluid can be pumped from the suction port 8 to the discharge port 9 by being driven and rotated in synchronization with the rotation of the rotor 2.

Therefore, it can be set as the structure which does not use a universal joint, and a structure is simple. In particular, when food is pumped as a pumping fluid, the problem of cleaning the dead space of the universal joint is solved, so compared with a uniaxial eccentric screw pump in which a universal joint is interposed between the drive shaft 3 and the rotor 2. It is possible to improve the disassembly / assembling property, cleaning property and cleaning property.
In particular, according to the uniaxial eccentric screw pump 1, the rotor 2 is made of austenitic stainless steel, and micro dimples having a concave portion formed by FPB having a diameter of 0.1 μm to 20 μm are formed on the surface of the rotor 2 (spiral portion 2a). Since it is provided, the viscous liquid can be held in the concave portion of the microdimple. Therefore, fluid lubrication is achieved in which the sliding surfaces of the rotor 2 and the stator 4 do not run out of liquid. As a result, the rotor 2 and the stator 4 can be slid in a non-contact state, and wear caused by solid contact sliding can be prevented or suppressed.

  Moreover, according to this uniaxial eccentric screw pump 1, since the carbon solid solution diffusion process which carries out solid solution diffusion of carbon is performed in the austenite structure of the surface of the rotor 2 (spiral part 2a), the thickness is 10 μm from the surface. A micro Vickers hardness of HV800 or higher is obtained, there is almost no elution of carbon, and the wear resistance of the rotor 2 can be improved with respect to a viscous liquid with wear without deteriorating the corrosion resistance. Also, the micro dimples on the surface of the rotor 2 can be held for a long time. Thereby, the rotor 2 and the stator 4 are slid in a state close to non-contact, and there is a further effect in preventing or suppressing wear caused by solid contact sliding.

  Furthermore, according to the uniaxial eccentric screw pump 1, as described above, the stator 4 is rotatably supported, the rotor 2 is fixed to the drive shaft 3, and the rotation axis L2 of the rotor 2 is the rotation axis of the stator 4. Since the stator 4 is configured to be eccentric from L1 by a predetermined amount of eccentricity E, and the stator 4 is dependently rotated at a rotational speed that is 1/2 of the rotational speed of the rotor 2, transmission of rotational force from the drive shaft 3 to the rotor is performed. In addition, the contact load between the rotor and the stator during high-pressure operation can be further reduced as compared with, for example, a uniaxial eccentric screw pump using a universal joint. Therefore, the viscous liquid is more easily held in the concave portion of the micro dimple. Therefore, the sliding surfaces of the rotor 2 and the stator 4 are fluid lubricated so as not to cause liquid breakage, facilitate sliding in a non-contact state, and prevent or suppress wear caused by solid contact sliding. It is suitable as a uniaxial eccentric screw pump that can be used.

As described above, according to the uniaxial eccentric screw pump 1, wear caused by solid contact sliding between the rotor 2 and the stator 4 can be prevented or suppressed. The uniaxial eccentric screw pump according to the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the rotor 2 is made of austenitic stainless steel, and the surface of the rotor 2 (spiral portion 2a) is provided with microdimples having a diameter of a recess formed by FPB of 0.1 μm to 20 μm. In the austenite structure on the surface, the carbon solid solution diffusion treatment for solid solution diffusion of carbon has been described. However, not limited to this, the surface of the rotor 2 (spiral portion 2a) is subjected to FPB treatment and Wearing due to solid contact sliding can also be prevented or suppressed by applying either one of the carbon solid solution diffusion treatments.

  That is, the rotor 2 is made of austenitic stainless steel, and the micro dimples of 0.1 μm to 20 μm formed by FPB are provided on the surface of the rotor 2 (spiral portion 2a) without performing carbon solid solution diffusion treatment. Also good. Even in such a configuration, the surface of the rotor 2 (spiral portion 2a) is provided with micro dimples having a recess diameter of 0.1 μm to 20 μm, so that the viscous liquid is held in the recesses of the micro dimple. Can do. For this reason, fluid lubrication is achieved in which the sliding surfaces of the rotor and the stator do not run out of liquid. Thereby, the rotor and the stator slide in a state close to non-contact, and wear due to solid contact sliding can be prevented or suppressed.

  Further, the rotor 2 may be made of austenitic stainless steel and may be subjected to a carbon solid solution diffusion treatment in which carbon is dissolved and diffused in the austenite structure on the surface of the rotor 2 (spiral portion 2a) without performing the FPB treatment. . Even with such a configuration, a hardness of HV800 or higher in micro Vickers hardness is obtained with a thickness of 10 μm from the surface of the rotor 2 (spiral portion 2a), there is almost no elution of carbon, and wear does not deteriorate the corrosion resistance. It is possible to improve the wear resistance of the rotor against a viscous liquid. Therefore, the rotor 2 and the stator 4 slide in a state close to non-contact, and wear caused by solid contact sliding can be prevented or suppressed.

  Further, for example, in the above-described embodiment, as the single-shaft eccentric screw pump, the stator 4 is rotatably supported, the rotor 2 is fixed to the drive shaft 3, and the rotation axis L2 of the rotor 2 is predetermined from the rotation axis L1 of the stator 4. In this example, the stator 4 is configured to be eccentric by the amount of eccentricity E, and the stator 4 is subordinately rotated at a rotational speed that is 1/2 of the rotational speed of the rotor 2. Thus, for example, it is applicable also to the uniaxial eccentric screw pump using a universal joint.

FIG. 2 is a cross-sectional structural view of a second embodiment of a uniaxial eccentric screw pump according to one aspect of the present invention, which is a uniaxial eccentric using a universal joint for transmission of rotational force from a drive unit to a rotor. In the screw pump, an FPB process and a carbon solid solution diffusion process for forming micro dimples are performed on the surface of the rotor.
That is, as shown in the figure, this uniaxial eccentric screw pump 10 has a male-threaded rotor 17 built in a fixed stator 14 having a female-threaded inner surface. The male threaded rotor 17 is connected to the drive shaft 12 via a universal joint (universal joint) 13, and the drive shaft 12 is connected to a shaft 21 a of a motor 21 via a coupling 19.

According to this single-shaft eccentric screw pump 10, when the drive shaft 12 is rotated by the motor 21, the rotor 17 rotates eccentrically with respect to the shaft center of the stator 14, thereby sucking viscous liquid from the suction side 20. It can be pumped to the discharge side 22 via the part 15.
Here, the rotor 17 is made of austenitic stainless steel, and the surface of the rotor 17 is provided with micro dimples having a diameter of a recess formed by FPB of 0.1 μm to 20 μm. In the austenite structure, carbon solid solution diffusion treatment is performed in which carbon is dissolved and diffused.

  According to the uniaxial eccentric screw pump 10 of the second embodiment, the rotor 17 is made of austenitic stainless steel, and the surface of the rotor 17 is provided with micro-dimples of 0.1 μm to 20 μm formed of FPB. Further, since the carbon solid solution diffusion treatment for solid solution diffusion of carbon is performed in the austenite structure on the surface of the rotor 17, the thickness is reduced to 10 μm from the surface in the same manner as the effect described in the first embodiment. A Vickers hardness of HV800 or higher can be obtained, there is almost no elution of carbon, and the wear resistance of the rotor 17 can be improved against a viscous liquid with wear without deteriorating the corrosion resistance. The micro dimples on the surface of this can also be retained for a long time. Thereby, the rotor 17 and the stator 14 slide in a state close to non-contact, and wear caused by solid contact sliding can be prevented or suppressed.

DESCRIPTION OF SYMBOLS 1 Uniaxial eccentric screw pump 2 Rotor 3 Drive shaft 4 Stator 5, 6 Underwater bearing 7 Housing 8 Suction port 9 Discharge port 11 Bracket 12 Drive shaft 16, 18 Seal member E Eccentricity L1, L2 Rotation axis

Claims (4)

A stator having a female-threaded inner surface; and a rotor in which a male-screw-shaped spiral portion is inserted in the stator, and rotating the rotor in the stator, whereby viscous liquid sucked from the suction side is discharged to the discharge side. A uniaxial eccentric screw pump for pumping,
The rotor is made of austenitic stainless steel, and the surface of the rotor is provided with micro dimples having a recess diameter of 0.1 μm to 20 μm formed by FPB (Fine Particle Bombarding). Uniaxial eccentric screw pump. A stator having a female-threaded inner surface; and a rotor in which a male-screw-shaped spiral portion is inserted in the stator, and rotating the rotor in the stator, whereby viscous liquid sucked from the suction side is discharged to the discharge side. A uniaxial eccentric screw pump for pumping,
The rotor is made of austenitic stainless steel, and is subjected to a carbon solid solution diffusion treatment in which carbon is dissolved and diffused in the austenitic structure on the surface of the rotor. A stator having a female-threaded inner surface; and a rotor in which a male-screw-shaped spiral portion is inserted in the stator, and rotating the rotor in the stator, whereby viscous liquid sucked from the suction side is discharged to the discharge side. A uniaxial eccentric screw pump for pumping,
The rotor is made of austenitic stainless steel, and the surface of the rotor is provided with microdimples having a diameter of a recess formed by FPB of 0.1 μm to 20 μm, and carbon in the austenitic structure of the rotor surface. A uniaxial eccentric screw pump characterized by being subjected to a carbon solid solution diffusion treatment for solid solution diffusion.   The single-shaft eccentric screw pump is configured such that the stator is rotatably supported, the rotor is fixed to a drive shaft, and the rotation axis of the rotor is eccentric from the rotation axis of the stator by a predetermined distance. The single-shaft eccentric screw pump according to any one of claims 1 to 3, wherein the single-shaft eccentric screw pump is dependently rotated at a rotational speed that is 1/2 of the rotational speed of the rotor.

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