Cylindrical pair lubrication structure

Abstract

The utility model relates to a cylindrical pair lubrication technical field, especially a kind of cylindrical pair lubrication structure, a kind of cylindrical pair lubrication structure, including outer cylindrical sleeve, inner cylindrical sleeve, outer cylindrical sleeve, inner cylindrical sleeve are mutually sleeved, and internal cavity is formed, the size of cavity changes along with the reciprocating motion of outer cylindrical sleeve, inner cylindrical sleeve, inner cylindrical sleeve outer surface is provided with microtextured groove, the cross-sectional shape of microtextured groove is rectangle, the space structure of microtextured groove is equal pitch cylindrical helix, and the spiral rectangular cavity structure of microtextured groove has excellent water-based lubricant storage capacity, can form stable lubricant reserve in the contact area of friction pair. When friction pair is in relative motion state, microtextured groove can continuously supplement water-based lubricant for contact interface, under the action of fluid power, lubricant in microtextured groove will form higher lubricating film pressure.

Description

Technical Field

[0001] This utility model relates to the field of cylindrical pair lubrication technology, and in particular to a cylindrical pair lubrication structure. Background Technology

[0002] Lubrication design is an indispensable part of mechanical design. Traditional lubrication methods include oil lubrication, grease lubrication, and self-lubrication, among which oil lubrication and grease lubrication are widely used due to their excellent lubrication properties. However, in modern design concepts, due to the increasing emphasis on environmental protection, oil and grease lubrication pose problems such as environmental pollution and the inconvenience of changing lubricating oil and grease. Therefore, the research and application of water lubrication have developed rapidly. Compared with traditional oil and grease lubrication, water lubrication has the advantages of readily available resources and no pollution. These two advantages have led to the rapid development of all-water lubrication equipment in recent years. However, the disadvantages of water lubrication are also quite prominent: First, its viscosity is low. Water has a very low viscosity compared to lubricating oil, making it difficult to form an effective lubricating film between key moving parts, thus failing to provide effective support. Without a stable and continuous lubricating film, the moving parts experience harsh stress conditions, easily leading to frictional wear on key friction pairs. This affects performance such as flow rate, vibration noise, and volumetric efficiency. In cases of severe wear, it may even cause malfunctions and component damage.

[0003] Secondly, the viscosity varies significantly with temperature. At 0℃, the viscosity is approximately 1.79 mPa·s, decreasing to 0.28 mPa·s at 100℃. During the startup and stable operation of equipment, the ambient temperature typically changes by tens of degrees Celsius, causing a substantial decrease in the viscosity of the lubricating medium. During the startup phase, the lower ambient temperature and higher water viscosity may create resistance to startup. Conversely, during stable operation, the higher ambient temperature and lower water viscosity make it difficult to form a continuous and effective lubricating film, leading to increased friction and wear on moving parts.

[0004] To address the various problems associated with water lubrication, traditional cylindrical pairs typically employ a combination of stainless steel and composite materials, leveraging the wear resistance of the composites. However, this approach is prone to issues such as excessive wear and heat buildup at high speeds. There is an urgent need for a microscopic surface structure design that enables the formation of a continuous and uniform water film on the surfaces of critical friction pairs to compensate for the insufficient viscosity of water-based lubricants. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this utility model is to provide a cylindrical pair lubrication structure. By designing micro-textured grooves on the surface of the cylindrical pair, the outer and inner surfaces of the cylindrical pair are subjected to tangential forces during relative movement. This tangential force will cause resistance to be formed at the micro-textured grooves and generate a micro-support band with a certain pressure, thereby ensuring the continuity and stability of the water film.

[0006] The technical solution adopted by this utility model is: A cylindrical lubrication structure includes an outer cylindrical sleeve and an inner cylindrical sleeve, which are nested together to form a cavity. The outer surface of the inner cylindrical sleeve is provided with micro-textured grooves. The cross-sectional shape of the micro-textured grooves is rectangular, and the spatial structure of the micro-textured grooves is a cylindrical helix with equal pitch. The micro-textured groove structure conforms to the following function: Where: k is the number of revolutions the helix makes as it moves from one bottom surface of the inner cylinder to the other, k∈(0,+∞). e The cross-sectional depth of the microtextured groove; h This is the height of the inner cylindrical sleeve; r The radius of the inner cylindrical sleeve; Re It is the Reynolds number.

[0007] The spacing between two micro-textured grooves on the same busbar must meet the following requirements: s j≥ s _ c The critical spacing and cross-sectional depth satisfy the following: The actual spacing meets the following requirements: in: s j This refers to the actual spacing. s _ c This is the critical spacing.

[0008] The beneficial effects of this utility model are: A cylindrical lubrication structure includes an outer cylindrical sleeve and an inner cylindrical sleeve, which are nested together to form an internal cavity. The size of the cavity changes with the reciprocating motion of the outer and inner cylindrical sleeves. The outer surface of the inner cylindrical sleeve has microtextured grooves with a rectangular cross-sectional shape. The spatial structure of the microtextured grooves is a left-handed or right-handed cylindrical helix with equal pitch. The helical rectangular cavity structure of the microtextured grooves possesses excellent water-based lubricant storage capacity, forming a stable lubricant reservoir in the contact area of ​​the friction pair. When the outer and inner cylindrical sleeves are in relative motion, the microtextured grooves not only continuously replenish the contact interface with water-based lubricant, preventing lubrication interruption due to lubricant loss, but also alter the fluid flow path through their geometry. Under hydrodynamic action, the lubricant within the microtextured grooves generates higher lubricating film pressure, significantly enhancing the hydrodynamic effect and thus improving the lubricating film's load-bearing capacity. Attached Figure Description

[0009] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, preferred embodiments are described below in conjunction with the accompanying drawings. However, the embodiments in the drawings do not constitute any limitation on this utility model. For those skilled in the art, other drawings can be obtained based on the following drawings without any creative effort.

[0010] Figure 1 This is a schematic diagram of a cylindrical joint structure; Figure 2 This is a schematic diagram of the cross-sectional structure of the microtextured groove; Figure 3 A schematic diagram of the application structure of the cylindrical pair inside the cylinder; Figure 4 A schematic diagram of the hydrodynamic pressure effect at the microtextured grooves; Figure 5 This is a tiling diagram of a single spatial spiral.

[0011] In the diagram: 1 - outer cylindrical sleeve, 2-Inner cylindrical sleeve, 201-Microtextured groove, 3-Cylinder block. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings.

[0013] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which this utility model can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and purposes that this utility model can produce, should still fall within the scope of the technical content disclosed in this utility model.

[0014] like Figure 1 , Figure 2 As shown, a cylindrical pair lubrication structure includes an outer cylindrical sleeve 1 and an inner cylindrical sleeve 2, which are nested together to form a cavity. The size of the cavity changes with the reciprocating motion of the outer cylindrical sleeve 1 and the inner cylindrical sleeve 2. The outer surface of the inner cylindrical sleeve 2 is provided with microtextured grooves 201. The cross-sectional shape of the microtextured grooves 201 is rectangular, and the spatial structure of the microtextured grooves 201 is a left-handed or right-handed cylindrical helix with equal pitch. The helical rectangular cavity structure of the microtextured grooves 201 has excellent water-based lubricant storage capacity and can form a stable lubricant reservoir in the contact area of ​​the friction pair. When the outer cylindrical sleeve 1 and the inner cylindrical sleeve 2 are in a relative motion state, the microtextured grooves 201 can not only continuously replenish the contact interface with water-based lubricant, avoiding lubrication interruption due to lubricant loss, but also change the fluid flow path through its own geometric shape. Under the action of hydrodynamics, the lubricant in the microtextured groove 201 will form a higher lubricating film pressure, significantly enhance the hydrodynamic effect, thereby improving the load-bearing capacity of the lubricating film, effectively reducing the direct contact between the surfaces of the friction pairs, and reducing energy loss during operation.

[0015] In terms of height, the microtextured groove 201 is designed to be at the same height as the contact surface, which enables the medium to form a stable flow state within the groove and improves the overall system operating efficiency.

[0016] This microtextured groove 201 structure can be applied in various cylindrical mating pairs, such as the piston pair of radial piston pumps, cylinder and piston pair, piston pair of axial piston pumps, hydraulic cylinder barrel, valve body and valve core, etc.

[0017] Cylinder body cylindrical pair application structure such as Figure 3 As shown, the cylinder body 3 has a cylindrical cavity inside, and an inner cylindrical sleeve 2 is installed inside the cylindrical cavity. The cylindrical cavity and the inner cylindrical sleeve 2 form a plunger cavity. The outer surface of the inner cylindrical sleeve 2 is provided with microtextured grooves 201. The cross-sectional shape of the microtextured grooves 201 is rectangular, and the spatial structure of the microtextured grooves 201 is a left-handed or right-handed cylindrical helix with equal pitch. Hydraulic flow channels are machined on the cylinder body 3. The inner cylindrical sleeve 2 reciprocates within the cylinder body 3, and the volume of the plunger cavity changes periodically. The hydraulic working medium is drawn in and discharged through the flow hole at the top of the plunger assembly. During the movement of the inner cylindrical sleeve 2, the microtextured grooves 201 can play the following roles: I. Enhanced Hydrodynamic Effect under Fluid Lubrication: The unique cavity structure of the microtextured groove 201 provides excellent water-based lubricant storage capacity, forming a stable lubricant reservoir in the contact area of ​​the friction pair. When the friction pair is in relative motion, the microtextured groove 201 not only continuously replenishes the contact interface with water-based lubricant, preventing lubrication interruption due to lubricant loss, but also alters the fluid flow path through its geometry. Under hydrodynamic action, the lubricant within the microtextured groove 201 forms a higher lubrication film pressure, significantly enhancing the hydrodynamic effect, thereby improving the lubrication film's load-bearing capacity, effectively reducing direct contact between the friction pair surfaces, and lowering energy loss during operation.

[0018] The fluid lubrication at the microtextured groove 201 can be described by the Navier-Stokes equations for incompressible fluids, namely: Where: ρ is the fluid density; U U is the fluid velocity; ▽ is the gradient operator; (U∙▽)U is the convective acceleration term; p ρ is the hydrostatic pressure; μ is the dynamic viscosity of the fluid.

[0019] The moving surface drives the fluid movement within the microtextured groove 201 through viscous forces. However, the fluid velocity varies at different locations within the microtextured groove 201, with higher velocity near the moving surface and lower velocity near the bottom of the groove. This velocity difference causes shear deformation in the fluid. As the sheared fluid flows, it is obstructed by the front and rear sidewalls of the microtextured groove 201. The obstructed fluid cannot continue moving in the sliding direction and can only rotate around itself. Due to the fixed geometry of the microtextured groove 201 and the continuous viscous force on the fluid, fluid continuously replenishes the groove 201. The rotating eddies remain stable within the groove 201, forming localized circulating vortices. Therefore, when the friction pair slides, the fluid flow within the microtextured groove 201 is not unidirectional and linear, but rather forms locally rotating eddies. The fluid forming vortices within the microtextured grooves 201 is subjected to outward centrifugal force. Since the sidewalls and upper and lower surfaces of the microtextured grooves 201 are solid boundaries, the fluid is pressed against the edges and walls of the microtextured grooves 201 by centrifugal force. The compressed fluid molecules collide and accumulate, ultimately forming high pressure within the microtextured grooves 201. When the pressure decreases, dissolved air in the lubricating medium precipitates into tiny bubbles. During the movement of the friction pair, the negative pressure zone generated by the fluid flow within the microtextured grooves 201 causes air to be drawn in from the surface gaps. The liquid storage effect of the microtextured grooves 201 increases the medium residence time, allowing sufficient time for dissolved gases to precipitate and form bubbles. The vortices and bubbles do not act independently but form a synergistic cycle, further enhancing the high pressure. The rotation of the vortices accelerates fluid shearing, promotes dissolved gas precipitation, and increases the number of bubbles. After being drawn into the center by the vortex, the bubbles are compressed by centrifugal force, generating localized high pressure. The pressure difference between the high-pressure and low-pressure areas drives fluid rotation, which in turn enhances the rotational intensity of the vortices. The pressure released by the compressed bubble will squeeze the surrounding fluid, making the fluid's viscous drag stronger, further amplifying the sidewall blocking effect, forming a positive cycle of "vortex strengthening bubble generation, bubble strengthening pressure, and pressure strengthening vortex".

[0020] A schematic diagram of the hydrodynamic pressure effect at the microtextured groove 201 is shown below. Figure 4 As shown, the left side of its rectangular cross-section is a bubble.

[0021] The cross-sectional shape and helical shape of the microtextured groove 201 change the fluid velocity in the equation. U and pressure gradient▽ p This directly affects the hydrodynamic lubrication effect, and the specific relationship is as follows: (1) Influence of the cross-sectional shape of the microtextured groove 201: (1.1) The cross-sectional shape of the microtextured groove 201 affects the velocity distribution: Assuming the fluid velocity along the depth direction (y-axis) of the cross-section is... u ( y ), from the viscosity term of the equation μ▽2 U Derivation shows that the velocity distribution under laminar flow conditions satisfies: in, This represents the pressure gradient along the flow direction (x-axis). U 0 The velocity of the friction pair.

[0022] (1.2) The cross-sectional shape of the microtextured groove 201 affects the pressure gradient: cross-sectional width l and depth e Determine the cross-sectional area of ​​the flow channel S=e • l From the continuity equation (▽∙ U Since =0, when the flow rate Q is fixed: The relationship between pressure gradient and cross-sectional parameters is summarized as follows: It can be seen that the depth of the rectangular cross-section e It will affect the pressure gradient, depth e As the pressure gradient decreases, the dynamic pressure effect increases.

[0023] (2) The influence of the spiral shape: The shape of the helix affects the convective acceleration term by changing the direction and path length of fluid flow. U ∙▽) U And velocity components, thereby modulating the dynamic pressure effect. Taking a right-handed helix as an example, assuming the radius of the inner cylindrical sleeve 2 is... r The height is h The parametric equation for a right-handed spatial helix is: in, θ is the central angle; k is the number of revolutions the helix makes as it travels from one base to the other of the inner cylinder, k∈(0,+∞).

[0024] Unfold a single spatial spiral line, such as Figure 5 As shown, the surface of the inner cylindrical sleeve 2, when unfolded, is a rectangle, and the spiral is the hypotenuse of a right-angled triangle, where one leg is the height of the inner cylindrical sleeve 2. h The other leg is k∙2 πr The spiral angle is a, The relative velocity of the inner cylindrical sleeve 2 to the outer cylindrical sleeve 1 is v The velocity in the direction of extension of the perpendicular helix is v τ The velocity along the direction of the spiral extension is vn .

[0025] in: Perpendicular to the direction of spiral extension v τ The magnitude of this affects the relative velocity term in the hydrodynamic lubrication pressure formula at the microtexture, while v τ The size is determined by the helix angle. α The decision is that this spiral shape can extend the flow path of the medium within a limited space without causing excessive flow resistance. In the Navier-Stokes equations ( U ∙▽) U The inertial force reflecting the fluid velocity gradient is represented by the convective acceleration component perpendicular to the helical direction: in, s Let be the arc length along the spiral. This represents the velocity gradient.

[0026] When the spiral angle rises α Angle decreases, v τ Increase, velocity gradient The pressure is smooth, which ensures efficient fluid introduction and enhances hydrodynamic lubrication, while avoiding pressure fluctuations caused by excessive inertia.

[0027] For the surface microtextured grooves 201, since the microtextured grooves 201 disrupt the boundary layer flow, the resistance increases when the liquid flows through the microtextured grooves 201, which consumes additional mechanical energy and hinders the plunger movement. The actual spacing of the microtextured grooves 201 s j It will affect the resistance at point 201 of the microtexture groove.

[0028] Actual spacing of microtextured grooves 201 s j Factors affecting resistance: When the actual spacing s j The smaller the resistance, the less the eddies and fluid disturbances generated by the previous groove are, the more the disturbances from the next groove are superimposed on them, resulting in increased resistance and greater energy loss.

[0029] To avoid the cumulative effect of disturbances, the actual spacing between the two micro-texture grooves 201 on the same busbar should be... s j Must meet: s j≥ s _ c Generally, the critical spacing and cross-sectional depth satisfy the following: For the actual spacing of the trenches to meet the following requirements: Then we have: in: s j This refers to the actual spacing. s _ c Where Re is the critical spacing, and Re is the Reynolds number. The above describes the helix angle. α Decrease v τ Enlarging the grooves ensures efficient fluid introduction and enhances hydrodynamic lubrication, but at the same time, it is necessary to maintain the actual spacing between the two micro-textured grooves 201 on the same generatrix. s j≥ s _ c， Avoid the cumulative effect of disturbances.

[0030] Therefore, the helix angle α The following conditions must be met: In summary, the cross-sectional shape determines the local pressure generation capacity of the flow channel, while the helical shape determines the overall pressure accumulation efficiency of the fluid. Together, they control the hydrodynamic lubrication effect by regulating the velocity and pressure terms in the Navier-Stokes equations.

[0031] II. Reducing the Coefficient of Friction under Boundary Lubrication Conditions: In boundary lubrication environments, due to relatively insufficient lubricant supply, it is difficult to form a complete fluid lubrication film on the surface of the friction pair. In this case, the microtextured grooves 201 can play a substitute lubrication role. The water-based lubricant stored in the grooves slowly penetrates to the contact interface, forming a thin adsorbed lubricating film on the surface of the friction pair, filling in microscopic unevenness. This lubricating film effectively blocks direct friction between the friction pair surfaces, reduces the molecular attraction between surfaces, thereby significantly reducing the coefficient of friction, avoiding localized high temperatures and surface damage caused by poor boundary lubrication, and extending the service life of the friction pair.

[0032] In summary, the microtextured groove (201) structure conforms to the following function: The following are specific data examples and simulation verification results: Specific data example 1: The cylinder has a height of 200 mm and a radius of 5 mm; a Reynolds number of 5000; a cross-sectional width of 0.1 mm; a moving speed of 2 m / s; a constant flow rate of 5 m³ / h; and a kinematic viscosity of 8 × 10⁻⁶ m³ / h. -4 m² / s; cross-sectional depth 0.05 mm; Table 1 Among them, item 1 is the control group. The helix angle α of items 2-4 gradually increases compared to 13.321° in item 1, and the k value is less than 26.887 in item 1. When the microtextured grooves on the cylinder are spiral, the eddies and fluid generated by the previous groove will not superimpose with the disturbance of the subsequent groove. However, the velocity component perpendicular to the extension line of the helix... v τ As the helix angle α increases, the fluid introduction efficiency decreases, and the hydrodynamic lubrication effect is reduced.

[0033] The helix angle α in item 5 is less than 13.321° in item 1, but the k value is greater than 26.887 in item 1. When the microtextured grooves on the cylinder spiral, the eddies and fluid generated by the previous groove are superimposed with the disturbance of the subsequent groove, resulting in a velocity component perpendicular to the extension line of the helix. v τ Less than the first item v τ The value decreases, reducing fluid introduction efficiency and hydrodynamic lubrication effect.

[0034] Specific data example two: The cylinder has a height of 100 mm and a radius of 4 mm; a Reynolds number of 8000; a cross-sectional width of 0.12 mm; a moving speed of 3 m / s; a constant flow rate of 4 m³ / h; and a kinematic viscosity of 6 × 10⁻⁶. -4 m² / s; cross-sectional depth 0.05; Table 2 Among them, item 1 is the control group. The helix angle α of items 2-4 gradually increases compared to 16.525° in item 1, and the k value is less than 13.411 in item 1. When the microtextured grooves on the cylinder are spiral, the eddies and fluid generated by the previous groove will not superimpose with the disturbance of the subsequent groove. However, the velocity component perpendicular to the extension line of the helix... v τ As the helix angle α increases, the fluid introduction efficiency decreases, and the hydrodynamic lubrication effect is reduced.

[0035] The helix angle α in item 5 is less than 16.525° in item 1, but the k value is greater than 13.411 in item 1. When the microtextured grooves on the cylinder spiral, the eddies and fluid generated by the previous groove are superimposed with the disturbance of the subsequent groove, resulting in a velocity component perpendicular to the extension line of the helix. v τ Less than the first item v τ The value decreases, reducing fluid introduction efficiency and hydrodynamic lubrication effect.

[0036] Specific data example three: The cylinder has a height of 400 mm and a radius of 10 mm; a Reynolds number of 10,000; a cross-sectional width of 0.2 mm; a moving speed of 5 m / s; a constant flow rate of 8 m³ / h; and a kinematic viscosity of 6 × 10⁻⁶. -4 m² / s; cross-sectional depth 0.05; Table 3 Among them, item 1 is the control group. The helix angle α of items 2-4 gradually increases compared to 8.295° in item 1, and the k value is less than 43.667 in item 1. When the micro-textured grooves on the cylinder are spiral, the eddies and fluid generated by the previous groove will not superimpose with the disturbance of the subsequent groove. However, the velocity component perpendicular to the extension of the helix... v τ As the helix angle α increases, the fluid introduction efficiency decreases, and the hydrodynamic lubrication effect is reduced.

[0037] The helix angle α in item 5 is less than 8.295° in item 1, but the k value is greater than 43.667 in item 1. When the microtextured grooves on the cylinder spiral, the eddies and fluid generated by the previous groove are superimposed with the disturbance of the subsequent groove, resulting in a velocity component perpendicular to the extension line of the helix. v τ Less than the first item v τ The value decreases, reducing fluid introduction efficiency and hydrodynamic lubrication effect.

Claims

1. A cylindrical pair lubrication structure, comprising an outer cylindrical sleeve (1) and an inner cylindrical sleeve (2), wherein the outer cylindrical sleeve (1) and the inner cylindrical sleeve (2) are sleeved together to form a cavity, characterized in that: The outer surface of the inner cylindrical sleeve (2) is provided with microtextured grooves (201). The cross-sectional shape of the microtextured grooves (201) is rectangular, and the spatial structure of the microtextured grooves (201) is a cylindrical helix with equal pitch. The structure of the microtextured grooves (201) conforms to the following function: Where: k is the number of revolutions the helix makes from one bottom surface of the inner cylindrical sleeve (2) to the other bottom surface, k∈(0,+∞); e The cross-sectional depth of the microtextured groove (201); h The height of the inner cylindrical sleeve (2); r Let be the radius of the inner cylindrical sleeve (2); Re It is the Reynolds number.

2. The cylindrical pair lubrication structure according to claim 1, characterized in that: The spacing between two micro-textured grooves (201) on the same generatrix must meet the following requirements: s j≥ s _ c The critical spacing and cross-sectional depth satisfy the following: The actual spacing meets the following requirements: in: s j This refers to the actual spacing. s _ c This is the critical spacing.

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