Ceramic friction pair thrust disc suitable for high temperature working condition of sealless pump

Abstract

The application belongs to the technical field of fluid machinery and tribology, and discloses a ceramic friction pair thrust disc suitable for high-temperature working conditions of a seal-free pump, which comprises a metal thrust disc base, a ceramic friction ring, a metal lining ring and fastening screws. The application achieves uniform transmission of circumferential stress by arranging the integral metal lining ring on the outer periphery of the ceramic friction ring and adopting the interference fit amount determined based on the thermal expansion difference and strength checking, which effectively avoids the problem of local stress concentration or cracking of the ceramic ring caused by empirical interference amount in the prior art, and by reasonably controlling the interference interval, the metal lining ring can maintain the pressing effect on the ceramic ring under high-temperature working conditions and will not exceed the allowable strength of the ceramic material, so that the ceramic end face can be kept in a flat state for a long time, compared with the traditional scheme which simply relies on large interference pressing, the application can provide stable and controllable pressing force under high temperature.

Description

Technical Field

[0001] This invention belongs to the field of fluid machinery and tribology, specifically a ceramic friction pair thrust disc suitable for high-temperature operation of sealless pumps. Background Technology

[0002] Sealless pumps are widely used in high-temperature, high-pressure, and corrosive media applications because they do not require traditional mechanical seals, resulting in a compact structure and low leakage risk. The thrust disc, as an important component in the pump body that bears axial loads, often uses a friction pair structure composed of metal and ceramic to take advantage of the high hardness and wear resistance of ceramics.

[0003] However, under high-temperature operating conditions, there is a significant difference in the coefficient of thermal expansion between metal and ceramic. When the conventional integral interference fit is used, the expansion of the metal ring is significantly greater than that of the ceramic ring, resulting in uneven distribution of contact stress in the circumferential and end face directions. This can easily cause warping or even local cracking of the ceramic friction ring end face, thus causing the friction pair to degenerate from surface contact to line contact, significantly increasing the wear rate and reducing reliability.

[0004] Meanwhile, under the influence of high-speed rotation and complex fluid disturbances, the operating environment of sealless pumps is generally accompanied by periodic vibration and axial impact loads. If the wear ring assembly relies solely on a single interference fit or a single-sided fastening screw for limitation, it often cannot maintain stability in both the radial and axial directions at the same time. This can easily lead to ring assembly deflection or movement, resulting in instability of the friction pair and a shortened service life.

[0005] To address this, existing technologies have proposed increasing the interference fit, introducing limiting fastening screws, or setting fillers between the ring assembly and the seat groove. However, these solutions generally have limitations: excessive interference fit can cause the ceramic to become brittle; single-sided fastening screws are prone to failure under high-frequency vibration; and fillers suffer severe performance degradation in high-temperature environments, making it difficult for them to function effectively for a long time.

[0006] Therefore, existing improvements are mostly single-point measures, lacking systematic design, and have not yet solved the comprehensive stability problem of friction pairs under high temperature and vibration coupled conditions. Existing sealless pump thrust pairs generally face potential failure risks such as ceramic end face warping, thermal expansion mismatch and ring group movement under high temperature conditions. Summary of the Invention

[0007] The purpose of this invention is to provide a ceramic friction pair thrust disc suitable for high-temperature operating conditions of sealless pumps, so as to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a ceramic friction pair thrust disc suitable for high-temperature operation of a sealless pump, the ceramic friction pair thrust disc comprising: fastening screws, a metal bushing, a ceramic friction ring, and a metal thrust disc base;

[0009] The outer circumference of the metal thrust plate base forms a longitudinal groove. The metal bushing is an integral annular structure and is installed on the outer circumference of the ceramic friction ring with an interference fit, so that the circumferential stress generated by the interference fit is evenly distributed along the outer circumference of the ceramic friction ring, thereby keeping the end face of the ceramic friction ring flat. The ceramic friction ring and the metal bushing form a wear-resistant ring assembly, which is installed in the groove of the metal thrust plate base with a clearance fit. The clearance is used to compensate for the difference in thermal expansion between the metal and the ceramic. The back of the metal thrust plate base is symmetrically machined with threaded holes, and the fastening screws are installed in the threaded holes and work together with the clearance to provide radial and axial limiting for the wear-resistant ring assembly.

[0010] Furthermore, the interference fit between the metal bushing and the ceramic friction ring is calculated and preset according to the design operating temperature, so that the metal bushing maintains the clamping force on the ceramic friction ring under high temperature operating conditions, while the additional load generated by the interference fit is less than the fracture strength of the ceramic material of the ceramic friction ring.

[0011] Furthermore, the fastening screws are symmetrically arranged along the diameter direction of the metal thrust plate seat. The limiting force formed by the fastening screws and the gap work together to prevent the wear-resistant ring assembly from radially rotating or axially moving when the pump body generates rotational load or vibration.

[0012] Furthermore, the gap ranges from 0.05mm to 0.20mm to ensure that the thermal expansion of the metal bushing under high-temperature conditions can be absorbed by the gap.

[0013] Furthermore, the fastening screws are installed through threaded holes formed by symmetrical drilling and tapping on the back of the metal thrust plate seat, forming a stable mechanical connection. The radial and axial limiting effects provided by the fastening screws work in conjunction with the compensation effect of the gap for thermal expansion differences.

[0014] Furthermore, the outer surface of the metal bushing is precision machined and ground to ensure that the dimensional accuracy and surface roughness of the metal bushing match the interference fit between the metal bushing and the ceramic friction ring.

[0015] Furthermore, the ceramic friction ring is made of high-temperature resistant alumina ceramic or silicon carbide ceramic, and its end face is polished to make the stress transmission between the ceramic friction ring and the metal bushing more uniform, and to maintain straight contact and reduce wear under high-temperature friction conditions.

[0016] Furthermore, the metal bushing, the gap, and the fastening screw cooperate with each other to achieve uniform transmission of interference stress, compensation for the difference in thermal expansion between metal and ceramic under high-temperature conditions, and radial and axial limiting of the wear-resistant ring assembly.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. This invention achieves uniform transmission of circumferential stress by setting an integral metal bushing around the outer periphery of the ceramic friction ring and using an interference fit determined based on thermal expansion difference and strength verification. This structure effectively avoids the problem of local stress concentration or cracking of the ceramic ring caused by empirically determining the interference fit value in the prior art. By reasonably controlling the interference range, the metal bushing can maintain the pressing effect on the ceramic ring under high temperature conditions without exceeding the allowable strength of the ceramic material, ensuring that the ceramic end face remains flat for a long time. Compared with the traditional solution that simply relies on large interference fit, this invention can provide a stable and controllable pressing force at high temperatures, improving the contact uniformity and crack resistance reliability of the friction pair.

[0019] 2. This invention introduces a reasonable gap between the wear-resistant ring assembly and the thrust disc seat groove, and arranges the fastening screws symmetrically in pairs along the diameter direction to form a synergistic effect of thermal compensation and bidirectional limiting. The gap range is set between 0.05 and 0.20 mm, which can absorb the dimensional changes caused by the difference in thermal expansion coefficients between metal and ceramic, and avoid the ceramic ring from being passively tightened and warping under high temperature conditions. The symmetrical fastening screws cooperate with the gap during operation, and can provide radial and axial limiting for the wear-resistant ring assembly under vibration and rotational loads, preventing deflection and movement. Unlike the existing technology that only uses single-sided fastening screws or simple fillers, this invention ensures the stability and durability of the friction pair under high temperature vibration conditions through the combination design of gap and fastening screws.

[0020] 3. This invention achieves a closed-loop synergistic relationship by integrating interference stress homogenization, gap thermal compensation, and symmetrical fastening screw limiting. The interference provides a lower limit guarantee for the flatness of the ceramic ring end face, the gap setting avoids the stress upper limit exceeding the limit caused by thermal expansion mismatch, and the fastening screw provides dynamic constraint under the condition of gap. Thus, together, the reliable operation of the friction pair under high temperature conditions is achieved. Unlike the single-point strengthening or simple material replacement approach in the prior art, this invention significantly improves the service life and operational reliability of the friction pair under high temperature and vibration coupling environment through a systematic design of structural chain. It has outstanding substantive features and significant progress. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the ceramic friction pair thrust disc structure applicable to high-temperature conditions of sealless pumps according to the present invention.

[0022] In the diagram: 1. Fastening screw; 2. Metal bushing; 3. Ceramic friction ring; 4. Metal thrust plate seat. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] like Figure 1 As shown, this embodiment of the invention provides a ceramic friction pair thrust disc suitable for high-temperature operating conditions of sealless pumps. The ceramic friction pair thrust disc includes: a metal thrust disc base, a ceramic friction ring, a metal bushing, and fastening screws.

[0025] The outer circumference of the metal thrust plate seat forms a longitudinal groove. The metal bushing is an integral annular structure and is installed on the outer circumference of the ceramic friction ring with an interference fit, so that the circumferential stress generated by the interference fit is evenly distributed along the outer circumference of the ceramic friction ring, thereby keeping the end face of the ceramic friction ring flat. The wear-resistant ring assembly, composed of the ceramic friction ring and the metal bushing, is installed in the groove of the thrust plate seat with a clearance fit. The clearance is used to compensate for the difference in thermal expansion between the metal and the ceramic. Threaded holes are symmetrically machined on the back of the thrust plate seat, and fastening screws are installed in them. Together with the clearance, they provide radial and axial limits for the wear-resistant ring assembly.

[0026] Example:

[0027] A ceramic friction pair thrust disc suitable for high-temperature operation of sealless pumps includes a metal thrust disc seat, a ceramic friction ring, a metal bushing, and symmetrically arranged fastening screws. The outer circle of the thrust disc seat is machined with a longitudinal groove. The wear-resistant ring assembly (composed of a ceramic friction ring and a metal bushing) is installed in the groove with a clearance fit. The back side is fixed and limited by two fastening screws symmetrically distributed along the diameter direction.

[0028] In the specific manufacturing process, the metal bushing is made of 45# steel, and the outer circle is precision machined and ground. The surface roughness is controlled to Ra≤0.8μm and the roundness ≤0.01mm to ensure uniform fit with the ceramic ring.

[0029] The ceramic friction ring is made of alumina ceramic, with a compressive strength of about 2000MPa and a coefficient of thermal expansion that is less than that of metal materials. After polishing, the flatness of the end face is controlled within 0.01mm.

[0030] During assembly, the metal bushing ring and the ceramic friction ring are fitted with an interference fit of about 0.03mm to ensure a firm bond at room temperature and to maintain stable clamping even when the pump is running at 300℃, preventing the ceramic from cracking.

[0031] A gap of approximately 0.10mm is reserved between the wear-resistant ring assembly and the thrust disc seat. This gap can absorb the thermal expansion difference between the metal and the ceramic, preventing the ceramic from being passively pressed together at high temperatures, which could lead to warping.

[0032] The fastening screws are made of M5×16 stainless steel, with a thread engagement length of not less than 1.5 times the diameter. They are symmetrically arranged and tightened along the diameter direction. During operation, the fastening screws provide symmetrical limiting force and work together with the groove clearance to suppress pump body vibration and radial deflection and axial movement of the ring assembly under rotational load. Practical application shows that under continuous high-temperature operation, the flatness of the friction pair end face is maintained within 0.01mm, the friction contact is uniform and stable, and no cracks or abnormal wear appear in the ceramic. Compared with the traditional single interference or single-sided fastening screw limiting scheme, the service life is extended by more than double.

[0033] Among them, the excess amount 0 is determined by the following steps: Calculate the difference in thermal expansion:

[0034]

[0035] In the formula, : is the coefficient of linear expansion of the metal liner (1 / K), : is the coefficient of linear expansion of the ceramic friction ring (1 / K), : The difference (K) between the operating temperature and the room temperature. : is the interference fit radius (mm);

[0036] Determine the minimum contact pressure required to prevent slippage:

[0037]

[0038] In the formula, : The equivalent axial disturbance force (N) generated by external load. : is the contact width (mm), : is the interfacial friction coefficient;

[0039] The actual contact pressure is determined by the relationship between the interference fit and the material's elastic parameters:

[0040]

[0041] In the formula, : Interference allowance (mm) Here are the elastic modulus (MPa) and Poisson's ratio of the metal bushing. : represents the elastic modulus (MPa) and Poisson's ratio of the ceramic friction ring;

[0042] Check the upper pressure limit of the ceramic:

[0043]

[0044] In the formula, The circumferential stress (MPa) of the ceramic ring is given. : Thickness of the ceramic ring (mm) The allowable stress of the ceramic after temperature reduction (MPa);

[0045] The above steps yield the upper and lower limits of the interference, and the final recommendation is... mm, which ensures that there is still compressive force at high temperatures without damaging the ceramic.

[0046] Among them, the purple-coated screws are symmetrically arranged along the diameter direction of the thrust plate seat, and the effective limiting force of a single fastening screw is set to be (N), geometric lever arm is (mm), then the limiting torque that can be provided is:

[0047]

[0048] Let the external disturbance moment generated by the rotating load be... , must meet In the formula Requirements for controlling axial displacement to ensure a safety factor. ,in This represents the axial displacement of the ring assembly. For permissible values, the symmetrically arranged screws provide mirror-image limiting force, which, together with the thermal compensation effect of the gap, ensures that the ring assembly will not rotate radially or move axially under pump body vibration and rotational load.

[0049] The gap between the wear-resistant ring assembly and the groove edge must meet the following requirements:

[0050]

[0051] In the formula,

[0052] : is the radius of the metal bushing;

[0053] : is the radius of the ceramic ring;

[0054] : For manufacturing and assembly tolerances;

[0055] To avoid passive tightening due to high temperatures, the clearance must not be less than the lower limit. To prevent the ring assembly from wobbling, the clearance must also be less than the upper limit determined by dynamic stability. A reasonable range is obtained by combining the results:

[0056]

[0057] If the gap is too small, it will cause ceramic warping; if it is too large, it will cause the clearance to wobble. By designing the gap within this range, the gap can both compensate for the difference in thermal expansion and prevent instability.

[0058] Preferably, the fastening screw is installed by drilling symmetrical holes on the back and tapping them, with a thread engagement length of [missing information]. ,in Let be the diameter of the fastening screw, and the preload of the fastening screw be approximately:

[0059]

[0060] In the formula,

[0061] : Preload (N);

[0062] : Tightening torque (N·mm);

[0063] : is the torque coefficient (0.15) 0.25);

[0064] This connection method ensures that the screws, even with thermal compensation gaps, can still provide stable positioning, forming a path that resists loosening and impact together with the groove support and symmetrical arrangement.

[0065] The outer circle of the metal bushing must be precision machined and ground before press-fitting: surface roughness Ra≤0.8 m, roundness error mm, coaxiality with the ceramic ring This machining precision (mm) ensures uniform stress distribution after pressing and assembly, preventing cracks or micro-cracks from spreading in ceramics due to localized high pressure.

[0066] Among them, the ceramic friction ring is preferably made of alumina (Al2O3, with a linear expansion coefficient of approximately 8.0 × 10⁻⁶). -6 / K) or silicon carbide (SiC, with a linear expansion coefficient of approximately 4.5 × 10⁻⁶). -6 ( / K), all of which have high compressive strength and high temperature resistance;

[0067] After polishing, the flatness of the ceramic end face is ≤0.01mm, which ensures that the friction pair maintains a surface contact state and avoids local stress concentration caused by line contact. Combined with interference and clearance design, it ensures the wear resistance and stability of the friction pair.

[0068] Among them, the interference provides a lower limit for clamping and the reasonable range is determined by the formula chain calculation; the clearance provides an upper limit for thermal compensation and is guaranteed by a numerical range; the symmetrical fastening screw provides radial and axial bidirectional limiting under the condition of clearance;

[0069] These three elements form a closed-loop synergy with each other as boundary conditions, solving the problems of ceramic warping and vibration sway at high temperatures. Unlike traditional single interference or unilateral limiting designs, this design significantly improves the lifespan and reliability of the thrust pair under high-temperature coupled vibration conditions, demonstrating remarkable innovation.

[0070] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A ceramic friction pair thrust disc suitable for high-temperature operation of sealless pumps, characterized in that: The ceramic friction pair thrust disk includes: fastening screw (1), metal bushing (2), ceramic friction ring (3), and metal thrust disk seat (4). The outer circle of the metal thrust plate seat (4) forms a longitudinal groove edge; the metal bushing (2) is an integral ring structure and is installed on the outer circumference of the ceramic friction ring (3) with an interference fit, so that the circumferential stress generated by the interference fit is evenly distributed along the outer circumference of the ceramic friction ring (3), thereby keeping the end face of the ceramic friction ring (3) flat; the ceramic friction ring (3) and the metal bushing (2) constitute a wear-resistant ring group, and the wear-resistant ring group is installed in the groove edge of the metal thrust plate seat (4) with a clearance fit, the clearance being used to compensate for the thermal expansion difference between the metal and the ceramic; the back of the metal thrust plate seat (4) is symmetrically machined with threaded holes, and the fastening screw (1) is installed in the threaded holes and works in conjunction with the clearance to provide radial and axial limits for the wear-resistant ring group.

2. The ceramic friction pair thrust disc suitable for high-temperature operation of sealless pumps according to claim 1, characterized in that: The interference fit between the metal bushing (2) and the ceramic friction ring (3) is calculated and preset according to the design operating temperature, so that the metal bushing (2) maintains the clamping force on the ceramic friction ring (3) under high temperature operating conditions, and the additional load generated by the interference fit is less than the fracture strength of the ceramic material of the ceramic friction ring (3).

3. The ceramic friction pair thrust disc suitable for high-temperature operation of sealless pumps according to claim 2, characterized in that: The fastening screws (1) are symmetrically arranged along the diameter direction of the metal thrust plate seat (4). The limiting force formed by the fastening screws (1) and the gap work together to prevent the wear-resistant ring assembly from rotating radially or moving axially when the pump body generates a rotational load or vibration.

4. The ceramic friction pair thrust disc suitable for high-temperature operation of sealless pumps according to claim 3, characterized in that: The gap is in the range of 0.05mm to 0.20mm to ensure that the thermal expansion of the metal bushing (2) under high temperature conditions can be absorbed by the gap.

5. A ceramic friction pair thrust disc suitable for high-temperature operation of a sealless pump according to claim 4, characterized in that: The fastening screw (1) is installed by drilling and tapping threaded holes on the back of the metal thrust plate seat (4) to form a stable mechanical connection, and the radial and axial limiting effects provided by the fastening screw (1) work together with the compensation effect of the gap for thermal expansion differences.

6. The ceramic friction pair thrust disc suitable for high-temperature operation of a sealless pump according to claim 5, characterized in that: The outer surface of the metal bushing (2) is precision machined and ground so that the dimensional accuracy and surface roughness of the metal bushing (2) match the interference fit between the metal bushing (2) and the ceramic friction ring (3).

7. A ceramic friction pair thrust disc suitable for high-temperature operation of a sealless pump according to claim 6, characterized in that: The ceramic friction ring (3) is made of high-temperature resistant alumina ceramic or silicon carbide ceramic. Its end face is polished to make the stress transmission between the ceramic friction ring (3) and the metal bushing (2) more uniform, and to maintain straight contact and reduce wear under high-temperature friction conditions.

8. A ceramic friction pair thrust disc suitable for high-temperature operation of a sealless pump according to claim 7, characterized in that: The metal bushing (2), the gap, and the fastening screw (1) cooperate with each other to achieve uniform transmission of interference stress, compensation for the difference in thermal expansion between metal and ceramic under high temperature conditions, and radial and axial limiting of the wear-resistant ring assembly.

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