JP2007232013A - Rotary machine for pure water using ceramic slide member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary machine for pure water using a ceramic slide member capable of being used stably in pure water or ultrapure water over a long period of time. <P>SOLUTION: The rotary machine includes the ceramic slide member equipped with a rotating side member 51 and a fixed side member 52 for sliding against each other and rotatably supporting a shaft. At least one of the rotating side member 51 and the fixed side member 52 is made of SiC containing β-SiC in at least one portion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rotary machine using a ceramic sliding member provided with a bearing or a seal member suitable for use in a rotary machine such as a pump, turbine, compressor, blower, etc., and in particular, the handled liquid is pure water or ultrapure water. The present invention relates to a pure water rotating machine using a ceramic sliding member.

  For example, a canned motor pump, which is a rotating machine, generally includes two radial plain bearings that support a main shaft on both sides and two thrust plain bearings that support thrust loads in both axial directions on the load side and the anti-load side. As these sliding bearings, ceramic bearings having excellent wear resistance and corrosion resistance are widely used. Then, the handling liquid is self-circulated, and the sliding liquid (ceramic bearing) is lubricated and the motor is cooled by the handling liquid.

Many rotating machines have a structure that is operated in contact with the end surfaces and sliding surfaces of both the fixed and rotating parts, and the parts that are attached to the part where the rotating body and the fixed body mechanically slide, For example, sliding members such as sliding bearings and seal members are used.
For example, a slide bearing has a rotating side member that is fixed to the main shaft side and rotates integrally with the main shaft side, and a solid side member that is fixed to the casing side. One of these rotating side members and stationary side members is widely composed of silicon carbide (SiC) and the other is composed of a carbon material (C), or both are composed of SiC. This SiC is composed of α-SiC having a wurtzite type crystal structure including hexagonal crystals.

Further, in a rotating machine, a ceramic seal member made of α-SiC is widely used as a seal member for watertightly sealing between a main shaft and a casing.
That is, ceramic sliding members such as ceramic bearings and ceramic seal members are widely used in rotating machines.

  For example, in a canned motor pump using tap water having an electrical resistance of about 0.01 MΩ · cm or more as a handling liquid and using a ceramic bearing as a sliding bearing, the sliding surface of the ceramic bearing (sliding bearing) is changed to tap water ( Ceramic bearings can be used over a long period of time while being effectively lubricated with the handling fluid). However, in the case of a canned motor pump that uses pure water with an electrical resistance of about 1 MΩ · cm or more and ultrapure water with an electrical resistance of about 10 MΩ · cm or more and uses a ceramic bearing as a sliding bearing, the ceramic bearing When the sliding surface is lubricated with pure water or ultrapure water (handling solution), sliding wear marks are gradually generated on the sliding surface in pure water or ultrapure water. May lead to wear.

  Table 1 below shows a circumferential speed of 7.59 m / s while pressing α-SiCs with a pressure of 0.5 MPa in the presence of handling liquids (tap water, pure water and ultrapure water) having different electrical resistances. The results of a friction and wear test in which the surfaces are slid with each other for 100 hours are shown.

The cause of this is not necessarily clear, but when the sliding surface of the ceramic bearing comes into sliding contact in the presence of tap water, silicon-based hydroxide or gel-like silicon-based hydrate is used as a lubricating film on the sliding surface. It is thought that this will protect the sliding surface, but when the sliding surface of the ceramic bearing is rubbed in pure water or ultrapure water with extremely low dissolved oxygen, these films are applied to the sliding surface. It is thought that this is because no is formed.
The same applies to ceramic seal members made of SiC.

  The present invention has been made in view of the above circumstances, and provides a rotary machine for pure water using a ceramic sliding member that can be used in pure water or ultrapure water and can be used stably over a long period of time. For the purpose.

The invention according to claim 1 is provided with a rotation side member and a fixed side member that slide relative to each other and rotatably support the shaft, and at least one of the rotation side member and the fixed side member is at least partially. It is a rotary machine for pure water using a ceramic sliding member made of SiC containing β-SiC.
SiC member containing β-SiC with zinc blend type and cubic crystal structure has good friction even under severe sliding conditions where needle-like crystals are strongly entangled with each other and no lubricating film is formed. It is considered to show wear characteristics. In fact, it has been confirmed that even when the sliding surface (surface) is brought into sliding contact with pure water or ultrapure water, the wear generated on the sliding surface can be suppressed to a minimum. As a result, the ceramic sliding member made of SiC including at least part of β-SiC at least one of the rotating side member and the stationary side member is in sliding contact with pure water or ultrapure water, for example. Even if it does, it will become possible to use it stably over a long period of time.

The invention according to claim 2 is the rotating machine for pure water according to claim 1, wherein the ratio of β-SiC in SiC is 20% or more.
In the case of SiC partially including a β-SiC crystal structure, the other crystal structure of SiC is α-SiC. However, when the proportion of β-SiC in SiC is 20% or more, pure water or It is possible to further reduce the occurrence of sliding wear marks in the pure water or ultrapure water on the surface of SiC when the ultrapure water is touched. For this reason, the ratio of β-SiC in SiC is preferably 20% or more, and more preferably 30% or more.

The invention described in claim 3 is the rotary machine for pure water according to claim 2, wherein the ceramic sliding member is a radial sliding bearing.
The invention according to claim 4 is the rotary machine for pure water according to claim 2, wherein the ceramic sliding member is a thrust sliding bearing.

The invention according to claim 5 is the rotary machine for pure water according to claim 4, wherein the rotary machine for pure water is a canned motor pump.
As a result, even when pure water or ultrapure water is used as the handling liquid, the sliding surface of the ceramic sliding member such as a ceramic bearing that rotatably supports the spindle is used as pure water or ultrapure water (handling liquid). It is possible to suppress the occurrence of sliding wear traces in pure water or ultrapure water on the sliding surface when lubricated with.

  According to the present invention, even if the sliding surface of the ceramic sliding member is lubricated with pure water or ultrapure water, sliding wear marks are generated on the sliding surface in pure water or ultrapure water. The ceramic sliding member can be used stably over a long period of time.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view of a pure water rotary machine according to an embodiment of the present invention applied to a canned motor pump. As shown in FIG. 1, the canned motor pump (pure water rotary machine) includes a suction-side casing 1, a discharge-side casing 5, and an outer cylinder 9 that connects between the suction-side casing 1 and the discharge-side casing 5. And. The suction-side casing 1, the outer cylinder 9, and the discharge-side casing 5 are provided with flanges 1a, 9a, 9b, and 5a that extend outward at the outer peripheral portion of the end on the opening side. The suction-side casing 1 and the outer cylinder 9 are integrally connected by clamping the flanges 1 a and 9 a adjacent to each other with flanges 20 and 20 made of cast iron or the like and tightening a bolt 45. Similarly, the discharge-side casing 5 and the outer cylinder 9 are connected together by holding the flanges 5a and 9b adjacent to each other with flanges 21 and 21 made of cast iron or the like and tightening the bolt 45. Has been. The suction casing 1, the discharge casing 5 and the outer cylinder 9 constitute a pump casing, and a canned motor 22 is disposed in the pump casing.

  The suction-side casing 1 includes a truncated cone-shaped main body 2 and a suction nozzle 3 extending from the main body 2 toward the suction side. Similarly to the suction-side casing 1, the discharge-side casing 5 also includes a truncated cone-shaped main body 6 and a discharge nozzle 7 extending from the main body 6 toward the discharge side.

  An inner casing 10 is provided inside the suction side casing 1, and the inner casing 10 includes a container-shaped main body portion 11 and a cylindrical suction side portion 12 extending from the main body portion 11 toward the suction side. A seal member 18 made of an elastic material such as an O-ring is interposed between the main body portion 11 and the suction side portion 12. And the guide apparatus 13 which comprises a guide vane or a volute is installed inside the main-body part 11 of the inner casing 10. As shown in FIG. The guide device 13 has a spigot fitting portion, and this spigot fitting portion is fitted with the motor frame 23 of the canned motor 22. The motor frame 23 of the canned motor 22 has high rigidity. Since the guide device 13 is supported by the motor frame 23, as a result, the inner casing 10 is supported by the motor frame 23 of the canned motor 22 having high rigidity.

  One end of the suction side portion 12 of the inner casing 10 extends to the vicinity of the suction nozzle 3. A seal member 14 is interposed in the gap between the end portion of the suction side portion 12 of the inner casing 10 and the suction nozzle 3 of the suction side casing 1, and the suction side (low pressure side) and the discharge are provided by the seal member 14. The side (high pressure side) is sealed.

  An impeller 15 is accommodated inside the inner casing 10, and the impeller 15 is fixed to and supported by the main shaft 16 of the canned motor 22. A suction flange 48 and a discharge flange 49 are fixed to the suction nozzle 3 and the discharge nozzle 7 via intermediate rings 46 and 46, respectively.

  The motor frame 23 of the canned motor 22 includes a substantially cylindrical frame outer cylinder 24 and frame side plates 25 and 26 provided at openings on both sides of the frame outer cylinder 24. The frame outer body 24 has a plurality of ribs 24a radially formed along the axial direction on the outer periphery thereof. The plurality of ribs 24a are formed integrally with the frame outer body 24 by press molding, and the outer surface of the ribs 24a is fitted to the inner peripheral surface of the outer cylinder 9 of the pump casing. Both are joined and integrated by spot welding or the like.

  A stator 27 and a rotor 28 are disposed in the motor frame 23. The rotor 28 is supported by the main shaft 16, and a cylindrical can 29 is fitted inside the stator 27. A ceramic bearing (ceramic sliding member) 30 serving as a radial sliding bearing is provided between the frame side plate 25 and the main shaft 16.

  The ceramic bearing (radial sliding bearing) 30 includes a main shaft fixed to the main shaft 16 and an inner ring 51 as a rotation side member that rotates integrally with the main shaft 16, and an outer ring 52 as a fixed side member fixed to the frame side plate 25. It has. The inner ring (rotary member) 51 and the outer ring (fixed member) 52 of the ceramic bearing 30 are both made of SiC containing at least a part of β-SiC.

  An SiC member partially containing β-SiC having a zinc-blende type cubic crystal structure has needle-like crystals entangled firmly with each other, and a silicon hydroxide or gel-like silicon as a lubricating film on the sliding surface. It has been confirmed that the wear generated on the sliding surface can be suppressed to a minimum even if it is used by sliding contact under severe sliding conditions in pure water or ultrapure water in which no system hydrate is formed. As a result, the inner ring (rotation side member) 51 and the outer ring (fixed side member) 52 of the ceramic bearing 30 are both made of SiC containing β-SiC at least in part, so that the sliding surface is made of pure water or ultra-high. Even when lubricated with pure water, the ceramic bearing 30 can be used stably over a long period of time.

  In this example, both the inner ring 51 and the outer ring 52 are made of SiC containing at least part of β-SiC, but only one of the inner ring 51 and the outer ring 52 is made of SiC containing at least part of β-SiC. It may be made.

  Here, SiC that does not contain β-SiC, and that the proportion of β-SiC is 5%, 21%, 32%, 65%, and 72% are in the presence of ultrapure water (10 MΩ · cm). Table 2 shows the results of a friction and wear test in which the surfaces were slid for 100 hours at a peripheral speed of 7.59 m / s while being pressed at a pressure of 0.5 MPa.

  Even if β-SiC powder is used as a starting material, not only β-SiC but also α-SiC exists in sintered SiC. It has been found that the proportion of β-SiC varies depending on the firing conditions and the like.

The quantitative analysis of β-SiC was performed by a quantitative analysis method using polymorphic X-ray diffraction. Polymorphs appearing in many SiC materials used in industry are usually 2H, 3C, 4H, 6H, and 15R. Since the X-ray diffraction peaks from the polymorphs often overlap each other, the theoretical intensity and the measured intensity of a plurality of diffraction lines were compared. Table 3 shows the calculated diffraction intensities of 2H, 3C, 4H, 6H, and 15R up to the lattice spacing d = 0.267 to 0.154 nm.

The polymorphic contents of 2H, 3C, 4H, 6H, and 15R are xi (i = 1, 2,..., 5), respectively, and the measured values of the X-ray diffraction intensity of peaks 1 to 22 are yj (j = 1, 2,. , 22), the coefficient aji of xi is a value shown in Table 3, and the intensity of each peak is as follows.
y ₁ = 39.697x ₁ + 0x ₂ + 9.924x ₃ + 0x ₄ + 3.197x ₅
・ ・ ・ ・ ・ ・
y _j = a _j1 x ₁ + a _j2 x ₂ + a _j3 x ₃ + a _j4 x ₄ + a _j5 x ₅ ,
・ ・ ・ ・ ・ ・
y ₂₂ = 22.172x ₁ + 44.328x ₂ + 22.164x ₃ + 33.243x ₄ + 25.710x ₅
The estimated value of xi that approximates many such equations is determined by regression analysis. In regression, the regression coefficient xi was calculated by taking yj as a dependent variable and aji as an explanatory variable.

An actual calculation example will be described below.
The peak intensities obtained from X-ray diffraction are shown in FIG. 2, and the peak intensities written in Table 3 are shown in Table 4.

Table 5 shows the results of regression analysis using commercially available spreadsheet software using the values shown in Table 4. The coefficient shown in Table 5 is the content rate (%) of each polymorph.

Since 4H and 15R were not detected from the X-ray diffraction results, Table 6 shows the calculation so that the total content of 2H, 3C, and 6H is 100% with these contents being 0%.

  Since 2H, 4H, 6H, and 15R are α-SiC and 3C is β-SiC, in this example, the content of α-SiC is 5.5 + 22.1 = 27.6%, and β-SiC The content is 72.4%.

  In the case of SiC partially including a β-SiC crystal structure, the other crystal structure is α-SiC. From Table 2 above, it can be seen that inclusion of β-SiC in SiC can reduce damage to the sliding surface of SiC in ultrapure water. In particular, when the proportion of β-SiC in SiC is 20% or more, further 30% or more, damage to the sliding surface of SiC in ultrapure water can be further reduced. For this reason, the ratio of β-SiC in SiC is preferably 20% or more, and more preferably 30% or more.

  While pressing SiCs with different average aspect ratios (aspect ratios) of crystal structures at a pressure of 0.5 MPa in the presence of ultrapure water (10 MΩ · cm), the peripheral speed is 7.59 m / s for 100 hours. Table 7 shows the results of the sliding friction test.

  As shown in Table 7, when the average aspect ratio of β-SiC in sintered SiC is 13 or more, damage to the sliding surface of SiC in ultrapure water can be further reduced. For this reason, the average aspect ratio is preferably a value exceeding 2, and more preferably 13 or more. A bearing housing 32 is detachably provided on the frame side plate 26 via an elastic body 44, and an outer ring 33 and a fixed side ring 34 are held in the bearing housing 32, respectively. The inner ring 35 fixed to the main shaft 16 slides relative to each other. The outer ring 33 and the inner ring 35 constitute a ceramic bearing (radial sliding bearing) 38 having the same configuration as the ceramic bearing (ceramic sliding member) 30 described above.

  A thrust disk 36 is fixed to the discharge side end portion of the main shaft 16, and the thrust disk 36 is provided with a rotation side ring 37 that is disposed to face the fixed side ring 34 and slides on each other. . The fixed ring (fixed member) 34 and the rotating ring (rotating member) 37 constitute a ceramic bearing (ceramic sliding member) 39 as a thrust sliding bearing. The fixed ring 34 and the rotating ring 37 of the ceramic bearing (thrust sliding bearing) 39 are both made of SiC containing β-SiC at least partially, like the inner ring 51 and the outer ring 52 of the ceramic bearing 30 described above. . One of the fixed side ring 34 and the rotation side ring 37 may be made of SiC containing β-SiC at least in part.

  An end plate 40 constituting a filter is fixed to the frame side plate 26. The end plate 40 has a rectifying portion 41 projecting in a substantially hemispherical shape, and a plurality of slits 42 are formed in the rectifying portion 41 so as to extend radially outward from the inside in the radial direction. The straightening portion 41 of the end plate 40 is formed in a substantially hemispherical shape so as to follow the flow line of the flow in the discharge-side casing 5, and the fluid discharged from the impeller 15 is the outer cylinder 9 and the frame outer body 24. After flowing into the discharge casing 5 through the flow path 50 formed therebetween, the flow is rectified by the rectifying action of the rectifying unit 41 and guided to the discharge port.

  Since the slits 42 are radially formed in the rectifying unit 41, the slits 42 function as a filter. When the fluid flows into the canned motor 22 through the slits 42, foreign substances in the fluid are captured and removed by the slits 42. Is done. Since the slit 42 is formed along the flow direction, the foreign matter once captured by the slit 42 is pushed and moved in the flow direction by the flow velocity, is removed from the slit 42, and the eyes of the slit 42 Clogging is prevented. That is, the slit 42 has a self-cleaning action depending on its shape. The end plate 40 also serves as a presser plate for fixing the bearing housing 32 to the frame side plate 26.

  Explaining the operation of the canned motor pump, the fluid sucked from the suction nozzle 3 is guided into the impeller 15 through the suction side portion 12 of the inner casing 10. The fluid discharged from the rotating impeller 15 is formed between the outer cylinder 9 and the frame outer cylinder 24 of the canned motor 22 after the direction of flow is changed from the centrifugal direction to the axial direction via the guide device 13. It flows into the flow path 50 and flows into the discharge side casing 5 through the flow path 50. Thereafter, the fluid is rectified by the rectification unit 41 of the end plate 40 and then discharged from the discharge nozzle 7 formed integrally with the discharge-side casing 5.

  On the other hand, since a gap is formed between the main plate 15a of the impeller 15 and the frame side plate 25, disk friction is generated in the gap by the rotation of the impeller 15, and a pressure reducing effect is produced in the gap. Therefore, the fluid that has flowed into the canned motor 22 from the slit 42 of the end plate 40 passes through the opening 32a of the bearing housing 32 and further passes through the gap between the rotor 28 and the can 29 of the stator 27, as indicated by arrows. A circulation path that flows out from the opening 25a of the frame side plate 25 to the back side of the main plate 15a of the impeller 15 is formed. While the handling liquid circulates inside the canned motor 22, the sliding surfaces of the ceramic bearings 30, 38, 39 are lubricated with the handling liquid, and at the same time, the canned motor 22 is cooled by the handling liquid.

Even if pure water having an electric resistance of about 1 MΩ · cm or more or ultrapure water having an electric resistance of about 10 MΩ · cm or more is used as the handling liquid, it is generated on the sliding surfaces of the ceramic bearings 30, 38, and 39. Abrasion is suppressed to a slight extent, and this enables stable use of the ceramic bearings 30, 38, and 39 over a long period of time.
In the above example, an example is shown in which the present invention is applied to a canned motor pump (rotary machine) using a ceramic bearing as a ceramic sliding member. However, a rotary machine using a ceramic seal member made of SiC as a ceramic sliding member. It can also be applied to.

  FIG. 3 shows a main part of a rotary machine for pure water according to another embodiment of the present invention using a ceramic seal member as a ceramic sliding member. In this example, a sleeve 62 is attached to the rotating shaft 60, and the periphery of the sleeve 62 is sealed with a mechanical seal 68 having a movable seal member 64 and a stationary seal member 66 that are in sliding contact with each other. In this example, both the movable seal member 64 and the stationary seal member 66 are made of SiC containing β-SiC at least partially. Only one of the movable seal member 64 and the stationary seal member 66 may be made of SiC containing β-SiC at least in part, and the other may be made of SiC or other ceramics.

  Even in this example, even if pure water having an electric resistance of about 1 MΩ · cm or more or ultrapure water having an electric resistance of about 10 MΩ · cm or more is used as the handling liquid, the movable seal member of the mechanical seal 68 is used. The wear generated on the sliding surface between the stationary seal member 64 and the stationary seal member 66 is suppressed to a slight level, and the mechanical seal 68 can be used stably over a long period of time.

It is sectional drawing which shows the rotary machine for pure water of embodiment of this invention applied to the canned motor pump. It is a graph which shows each peak intensity obtained from the X-ray analysis. It is sectional drawing which shows the principal part of the rotary machine for pure water of other embodiment of this invention using the ceramic sealing member as a ceramic sliding member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Suction side casing 3 Suction nozzle 5 Discharge side casing 7 Discharge nozzle 10 Inner casing 13 Guide apparatus 15 Impeller 16 Main shaft 22 Canned motor 23 Motor frame 27 Stator 28 Rotor 29 Can 30 Ceramic bearing (radial sliding bearing)
32 Bearing housing 33 Outer ring (fixed side member)
34 Fixed ring (fixed member)
35 Inner ring (rotary member)
36 Thrust disk 37 Rotating ring (Rotating member)
38 Ceramic bearings (radial sliding bearings)
39 Ceramic bearings (thrust sliding bearings)
51 Inner ring (rotary member)
52 Outer ring (fixed side member)
60 Rotating shaft 64 Movable seal member 66 Stationary seal member 68 Mechanical seal

Claims (5)

A rotation side member that slides on each other and rotatably supports the shaft, and a fixed side member,
A pure water rotating machine using a ceramic sliding member in which at least one of the rotating side member and the fixed side member is made of SiC containing at least part of β-SiC.   The rotary machine for pure water according to claim 1, wherein the proportion of β-SiC in SiC is 20% or more.   3. The pure water rotating machine according to claim 2, wherein the ceramic sliding member is a radial sliding bearing.   The rotary machine for pure water according to claim 2, wherein the ceramic sliding member is a thrust sliding bearing.   The rotary machine for pure water according to claim 3 or 4, wherein the rotary machine for pure water is a canned motor pump.

Images