High-pressure water pump based on water or aqueous solution lubrication

Abstract

The invention relates to the technical field of high-pressure water pumps, in particular to a high-pressure water pump based on water or aqueous solution lubrication. According to the high-pressure water pump based on water or aqueous solution lubrication, a driving mechanism comprises an eccentric wheel shaft and a thrust ring, the eccentric wheel shaft comprises a main shaft and an eccentric wheel arranged on the main shaft, the inner circumferential face of the thrust ring is connected to the outer circumferential face of the eccentric wheel in a sleeving mode, and the inner circumferential face of the thrust ring can rotate around the outer circumferential face of the eccentric wheel; the periphery of the thrust ring abuts against the end face of the plunger to roll in a reciprocating mode, and the thrust ring and the plunger form a rolling friction pair. The rolling friction pair pairing material is stainless steel / stainless steel or ceramic / stainless steel. For the rolling friction pair formed by the thrust ring and the end face of the plunger, according to the provided friction pair pairing material and the static friction force achieving method, the achieved water-lubricated high-pressure water pump has long service life and high working reliability.

Description

Technical Field

[0001] This invention relates to the field of high-pressure water pump technology, and more specifically to a high-pressure water pump based on water or aqueous solution lubrication. Background Technology

[0002] As shown in patent EP4455482A1, the newly developed water-lubricated high-pressure water pump represents a significant improvement over traditional water-lubricated high-pressure water pumps. This pump utilizes a thrust ring fitted onto an eccentric wheel shaft, which, through rolling contact with the plunger's contact surface, drives the plunger to move within the plunger cavity, thus pressurizing water or an aqueous solution. The pump also lubricates and cools the moving mechanism using water or an aqueous solution. Benefiting from its hydrostatic support-free structural design, this patented technology can provide significantly higher pressures than traditional water-lubricated high-pressure water pumps (capable of producing water exceeding 35 MPa; Danfoss's water-lubricated water pump has a maximum rated pressure of 16 MPa). Its simpler structure eliminates the need for high-precision filtration devices (ordinary tap water is sufficient), thus promising wider application.

[0003] Traditional oil-lubricated piston pumps, due to the excellent lubricating properties of oil, can achieve good results even under heavy loads using sliding friction. Therefore, in the design of the friction pairs that drive the pistons to perform work, it is common to use a combination of sliding friction pairs (such as patent DE10039210A1) or sliding / rolling friction pairs (such as patent WO2009049776A1) to transmit force and perform work. In patent WO2009049776A1, multiple pistons press against a ring, and the ring and pistons perform work through frictional contact via a combination of sliding and rolling friction. Because the pistons and rings are not in a one-to-one pairing relationship, the relative instantaneous frictional motion between the pistons and rings may be either rolling or sliding friction, rather than simply rolling friction. Due to the good lubrication and load-bearing capacity of lubricating oil, engineers do not need to pursue ideal rolling friction for all piston / ring friction pairs during the medium pressurization stage; and during the piston return stage, because the load on the friction pairs is quite small, it is even less necessary to pursue ideal rolling friction characteristics. Therefore, the design goals of friction pairs in traditional pump drive systems do not revolve around achieving ideal rolling friction characteristics. The spring that drives the plunger back is designed to only push the plunger in its return motion, ensuring that the plunger end face remains in contact with the drive structure. The spring's maximum force is at the initial moment of the plunger's suction stroke, which is also the key design point for the spring to meet the plunger's return function requirements.

[0004] In newly developed water-lubricated high-pressure water pumps, the thrust ring abuts against the plunger end face and rolls. The thrust ring and the plunger end face form a rolling friction pair, and the main shaft rotation speed is usually not less than 1450 rpm. The rolling friction pair formed by the thrust ring and the plunger end face is a high-speed reciprocating motion. Under water medium conditions, unlike the oil lubrication design environment, water has poor lubricity and has no significant lubricating effect on most materials. In the state of the plunger pressurizing water or aqueous solution and in the state of the plunger returning to draw in water or aqueous solution, it is necessary to ensure that the friction pair between the thrust ring and the plunger end face moves as ideal rolling friction. If the friction characteristics are not ideal rolling friction contact, there will be obvious sliding friction mixed in during the operation of the friction pair, and this friction pair formed by the thrust ring and the plunger will be damaged quickly.

[0005] Furthermore, the rolling friction pair formed by the thrust ring and the plunger end face is subject to high-speed, heavy-load conditions. Due to limitations in corrosion resistance, the available materials for the rolling friction pair in aquatic environments are extremely limited. Even martensitic stainless steel, which has high hardness, exhibits significantly lower fatigue resistance in aquatic environments compared to ordinary bearing steels (see reference: Experimental Study on Friction and Wear of Water-Lubricated Hybrid Ceramic Rolling Bearings (Chapter 2), Lou Zhengkun, Master's Thesis, Huazhong University of Science and Technology, China). The reference discloses a speed of 3000 rpm and a temperature of 0.05°C. r Under load conditions, the lifespan of martensitic stainless steel bearings in an aqueous environment is approximately 200 hours, while the lifespan at the same 0.05C temperature is... r Under load conditions, the life of ordinary oil / grease lubricated rolling bearings is at least more than 20,000 hours.

[0006] Furthermore, after prolonged operation, the wear mismatch between the friction surfaces of the rolling friction pair consisting of the thrust ring and the plunger will introduce sliding friction between the plunger and the thrust ring, causing the water pump to seize up.

[0007] In summary, ensuring that the thrust ring and plunger end face form an ideal rolling friction pair in the operation of the newly developed water-lubricated high-pressure water pump, meeting the requirements of high load-bearing capacity and long-term stable operation, has become a key research issue. Summary of the Invention

[0008] The purpose of this invention is to provide a high-pressure water pump based on water or aqueous solution lubrication, which enables the engineering realization of an ideal rolling friction pair formed by the thrust ring and the plunger end face, and can meet the requirements of high load capacity and long-term stable operation.

[0009] A high-pressure water pump based on water or aqueous solution lubrication includes: a cylinder body, a housing, a plunger bore, at least one plunger, a spring, and a drive mechanism;

[0010] The cylinder body is equipped with an inlet check valve and an outlet check valve; the drive mechanism includes an eccentric wheel shaft and a thrust ring. The eccentric wheel shaft includes a main shaft and an eccentric wheel mounted on the main shaft. The inner circumferential surface of the thrust ring is sleeved on the outer circumferential surface of the eccentric wheel, and the inner circumferential surface of the thrust ring can rotate around the outer circumferential surface of the eccentric wheel.

[0011] The plunger can slide back and forth in the plunger hole; the internal space formed after the hydraulic cylinder and the housing are connected is a receiving space, in which the plunger and the thrust ring are disposed, and the receiving space is also used to fill water or aqueous solution;

[0012] The outer circumferential surface of the thrust ring abuts against the end face of the plunger and rolls back and forth, and the thrust ring and the plunger form a rolling friction pair; the mating materials of the rolling friction pair are stainless steel / stainless steel or ceramic / stainless steel;

[0013] The spring force acts on the plunger to apply the normal force between the rolling friction pairs, thereby obtaining the static friction force required for ideal rolling; the spring force acting on the plunger at the midpoint of its reciprocating stroke is defined as F. m ;

[0014] When the rolling friction pair is a stainless steel / stainless steel material friction pair pair...

[0015] F m ≥3meω 2

[0016] When the rolling friction pair is a stainless steel / ceramic material friction pair pair...

[0017] F m ≥2meω 2

[0018] Where m is the mass of the thrust ring (in kilograms), ω is the angular velocity (2πn, where n is the number of rotations per second of the principal axis), e is the eccentricity (in meters), and F... m The unit is Newton.

[0019] According to one embodiment of the present invention, the main shaft is rotatably connected to the housing via two rolling bearings; the outer diameter of the thrust ring is at least 1.5 times the inner diameter of the inner ring of the rolling bearing.

[0020] According to one embodiment of the present invention, when the rolling friction pair mating materials are ceramic / stainless steel: the friction surface material of the thrust ring is stainless steel, and the friction contact surface of the plunger facing the thrust ring is ceramic.

[0021] According to one embodiment of the present invention, when the rolling friction pair is stainless steel / stainless steel, when the thrust ring exhibits a micro-motion of less than 0.05 mm along the axial direction of the main shaft, the original friction contact points on both sides of the plunger friction contact surface along the axial direction of the main shaft still maintain contact with the friction surface of the thrust ring.

[0022] According to one embodiment of the present invention, when the thrust ring exhibits a minute movement of less than 0.05 mm along the axial direction of the main shaft, the original friction contact points on both sides of the friction contact surface of the thrust ring along the axial direction of the main shaft still maintain contact with the friction contact surface of the plunger.

[0023] According to one embodiment of the present invention, two springs are provided, and each plunger is provided with two springs.

[0024] According to one embodiment of the present invention, a friction-reducing sleeve is fixed to the inner ring of the thrust ring or the outer circumference of the eccentric wheel; when the friction-reducing sleeve is disposed on the inner ring of the thrust ring, m is modified to the sum of the masses of the thrust ring and the friction-reducing sleeve.

[0025] According to one embodiment of the present invention, the stainless steel material is martensitic stainless steel or precipitation hardening stainless steel.

[0026] According to one embodiment of the present invention, the ceramic material is alumina ceramic or zirconia ceramic.

[0027] According to one embodiment of the present invention, the surface hardness of the stainless steel is greater than HRC35.

[0028] Beneficial effects:

[0029] In the realized water-lubricated high-pressure water pump, the thrust ring and the plunger end face constitute a rolling friction pair. Through the pairing of martensitic stainless steel, precipitation-hardening stainless steel, and alumina and zirconia ceramic materials, this rolling friction pair can achieve a large load-bearing capacity and a relatively high static friction coefficient under water medium conditions. Based on this, a method of increasing the spring force to achieve sufficient static friction between the friction pairs is proposed to ensure the realization of ideal rolling friction motion. A spring design method with the spring force value at the midpoint of the plunger reciprocating stroke as the design target is also given.

[0030] For the rolling friction pair formed by the thrust ring and the piston end face, according to the proposed friction pair pair matching materials, the method for realizing the static friction force required for ideal rolling friction, and the structure for matching the wear of the rolling friction pair to prevent jamming, the realized water-lubricated high-pressure water pump has a long service life and high working reliability, low manufacturing cost, and can meet the commercialization requirements of the invented water or water-lubricated high-pressure water pump. Attached Figure Description

[0031] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0032] Figure 1 A structural diagram of a high-pressure water pump based on water or aqueous solution lubrication provided by the present invention;

[0033] Figure 2 This is a diagram illustrating the motion characteristics of rolling friction.

[0034] Figure 3 A schematic diagram illustrating the motion characteristics of the drive mechanism and plunger when paired one-to-one according to the present invention;

[0035] Figure 4 A schematic diagram illustrating the principle of force and ideal rolling friction between the thrust ring and the plunger provided by this invention;

[0036] Figure 5 A state diagram of the first type of rolling friction pair provided by the present invention;

[0037] Figure 6 A state diagram of the second type of rolling friction pair provided by the present invention;

[0038] Figure 7 This is a state diagram of the third type of rolling friction pair provided by the present invention.

[0039] Icons: 1. Housing; 2. Cylinder body; 3. Plunger cavity; 301. Plunger bore; 4. Plunger; 401. Recess; 402. Shoulder; 5. Main shaft; 6. Eccentric wheel; 7. Thrust ring; 8. Spring; 9. Spring bracket; 10. Outlet check valve; 11. Inlet check valve; 12. Accommodation space; 13. Anti-friction layer; 18. Anti-friction sleeve; 19. Ceramic disc; 20. Rolling element. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of explanation and not by way of limitation. Indeed, those skilled in the art will recognize that modifications and variations can be made to the invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the invention encompass such modifications and variations falling within the scope of the appended claims and their equivalents.

[0041] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected," "linked," and "set up" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through intermediate components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0042] The present invention provides a high-pressure water pump based on water or aqueous solution lubrication, comprising: a cylinder body, a housing 1, a plunger hole 301, at least one plunger 4, a spring 8, and a drive mechanism.

[0043] The cylinder body is equipped with an inlet check valve 11 and an outlet check valve 10; the drive mechanism includes an eccentric wheel shaft and a thrust ring 7. The eccentric wheel shaft includes a main shaft 5 and an eccentric wheel 6 set on the main shaft 5. The inner circumferential surface of the thrust ring 7 is sleeved on the outer circumferential surface of the eccentric wheel 6, and the inner circumferential surface of the thrust ring 7 can rotate around the outer circumferential surface of the eccentric wheel 6.

[0044] The plunger cavity 3 is provided with plunger holes 301 corresponding to the plunger 4, and the plunger 4 can slide back and forth in the plunger holes 301; the internal space formed after the hydraulic cylinder body and the housing 1 are connected is the receiving space 12, the receiving space 12 is provided with the plunger 4 and the thrust ring 7, and the receiving space 12 is also used to fill water or aqueous solution.

[0045] The outer circumferential surface of the thrust ring 7 abuts against the end face of the plunger 4 and rolls back and forth. The thrust ring 7 and the plunger 4 form a rolling friction pair. The mating materials of the rolling friction pair are stainless steel / stainless steel or ceramic / stainless steel.

[0046] Spring 8 acts on piston 3 to apply the normal force between the rolling friction pairs, thereby obtaining the static friction force required for ideal rolling; the force exerted by spring 8 on piston 4 during the midpoint of its reciprocating stroke is defined as F. m (When a single plunger 4 is subjected to force by multiple springs 8, F) m (The sum of the forces of multiple springs, 8);

[0047] When the rolling friction pair is a stainless steel / stainless steel material friction pair pair...

[0048] F m ≥3meω 2

[0049] When the rolling friction pair is a stainless steel / ceramic material friction pair pair

[0050] F m ≥2meω 2

[0051] Where m is the mass of thrust ring 7 (in kilograms), ω is the angular velocity (2πn, where n is the number of rotations per second of the main shaft 5), e is the eccentricity (in meters), and F... m The unit is Newton.

[0052] In this embodiment, as Figure 1 As shown, the cylinder body and plunger cavity 3 are fixedly connected, and the cylinder body and housing 1 are also fixedly connected together. The internal space formed after the cylinder body and housing 1 are connected is the receiving space 12. The plunger cavity 3 is located in the receiving space 12. A plunger hole 301 is provided in the plunger cavity 3. The plunger 4 cooperates with the plunger hole 301, and the plunger 4 can reciprocate in the plunger hole 301. The cylinder body is provided with an inlet check valve 11 and an outlet check valve 10. The inlet check valve 11 and the outlet check valve 10 are connected to the plunger hole 301 by a fluid channel (a channel structure provided on the cylinder body).

[0053] Furthermore, the cylinder body includes a cylinder body 2 connected by threaded fasteners and a cylinder body water inlet component.

[0054] In some embodiments, the cylinder body 2 and the plunger cavity 3 are two independent structural components, which are fixedly connected together by threaded fasteners, or the cylinder body and the plunger cavity 3 are integrally molded.

[0055] In this embodiment, the drive mechanism consists of an eccentric wheel shaft and a thrust ring 7. The eccentric wheel shaft comprises a main shaft 5 and multiple eccentric wheels 6 mounted on the main shaft 5. Each eccentric wheel 6 corresponds to a plunger 4, and a corresponding thrust ring 7 is fitted on the outer circumference of each eccentric wheel 6. The thrust ring 7 is circular and can rotate on the eccentric wheel 6, forming a sliding friction pair. A spring 8 and a spring bracket 9 are provided within the accommodating space 12. The spring bracket 9 is connected to the cylinder body or housing 1 via the spring 8 and is also connected to the plunger 4, thus providing spring force to the plunger 4. When the water pump is working, the spring 8 is in a compressed and pre-tightened state, always providing a force to the plunger 4 in the direction of the eccentric wheel shaft. Under the action of the spring force, the end face of the plunger 4 always remains in contact with the outer circumferential surface of the thrust ring 7. When the eccentric wheel shaft is driven to rotate by the motor, the rotating eccentric wheel 6 drives the center of the thrust ring 7 to simultaneously perform a circular motion around the axis of the main shaft 5. When the center of the thrust ring 7 makes a circular motion, and the direction of motion approaches the direction of the hydraulic cylinder, the thrust ring 7, while abutting against and rolling against the end face of the plunger 4, pushes the plunger 4 to move towards the hydraulic cylinder in the plunger hole 301, squeezing the water or aqueous solution in the injection hole 301. At this time, the inlet check valve 11 is closed, while the outlet check valve 10 is opened. The water or aqueous solution is pressurized and flows through the outlet check valve 10 before being discharged from the water pump. When the center of the thrust ring 7 makes a circular motion, and the direction of motion moves away from the hydraulic cylinder, the spring 8 pushes the plunger 4, causing the plunger 4 to move away from the hydraulic cylinder in the plunger hole 301. Under the action of the spring force, the thrust ring 7 still abuts against the end face of the plunger 4 and rolls. At this time, the inlet check valve 11 is opened, while the outlet check valve 10 is closed. Water enters the plunger hole 301 through the inlet check valve 11. It should be noted that the water or aqueous solution in the containment space 12 can lubricate and cool the sliding friction pair formed by the thrust ring 7 and the eccentric wheel 6, and can also lubricate and cool the sliding friction pair formed by the plunger 4 and the plunger hole 301.

[0056] To reduce friction, a friction-reducing sleeve 18 is fixed on the inner ring of the thrust ring 7 or the outer circumference of the eccentric wheel 6. By utilizing the relative movement and squeezing action of the thrust ring 7 and the eccentric wheel 6, a dynamic pressure lubrication effect can be generated in the sliding friction pair formed by the thrust ring 7 and the eccentric wheel 6, which can reduce the friction force to a very low level.

[0057] In this embodiment, the main shaft 5 is rotatably connected to the housing 1 via two rolling bearings. The inner ring of the rolling bearing is fitted onto the journal of the main shaft 5, and the outer ring is fixed inside the housing 1. To prevent water from entering the bearing and corroding it, a sealing structure is provided between the rolling bearing and the housing 12.

[0058] In some embodiments, a friction-reducing layer 13 is provided on the inner wall of each plunger hole 301, the friction-reducing layer 13 being used to reduce the friction between the plunger 4 and the plunger hole 301.

[0059] It should be noted that the friction-reducing sleeve 18 and the friction-reducing layer 13 are made of plastic, preferably thermoplastic materials, such as polyetheretherketone, polyphenylene sulfide, polyamide, polyarylether, etc. The tribological properties can be effectively improved by adding fibers, graphite, polytetrafluoroethylene, etc. to the plastic.

[0060] When the water pump is working, the thrust ring 7 abuts against the end face of the plunger 4 and reciprocates, forming a rolling friction pair. The spindle 5 typically rotates at a speed of no less than 1450 rpm, resulting in high-speed reciprocating motion of the rolling friction pair between the thrust ring 7 and the plunger 4. In an aquatic environment, unlike oil-lubricated environments, water has poor lubricity and therefore provides little to no lubrication for most materials. Whether the plunger 4 is pressurizing water or an aqueous solution or is drawing water or an aqueous solution back into the system, it is crucial to ensure that the friction pair between the thrust ring 7 and the plunger 4 exhibits ideal rolling friction. If the friction characteristics are not ideal, significant sliding friction will occur during operation, and in an aquatic environment, this friction pair will quickly fail. Therefore, throughout the entire pump operation, it is essential to ensure that the frictional contact characteristics between the thrust ring 7 and the plunger 4 are ideal rolling friction.

[0061] It should be noted that if the working medium of the pump drive structure is lubricating oil, under oil lubrication conditions, the drive structure can still function well even under heavy load and high-speed motion of the sliding friction pair. According to the tribological theorem, the realization of ideal rolling friction requires sufficient static friction between the two friction pairs. For example, when a car is moving, the ground and the car tires must have sufficient static friction to prevent the tires from slipping. If there is water on the ground, the car can still maintain normal driving because water has poor lubricity. However, if the ground is covered with lubricating oil, the tires will have difficulty rolling normally, and sliding can be a better alternative (such as on a sled). Therefore, in a water-medium environment, the design of the water pump must strive to achieve ideal rolling friction in the rolling friction pair formed by the thrust ring 7 and the end face of the plunger 4.

[0062] like Figure 2 As shown, based on the principles of physics, the key characteristics of rolling friction are: sufficient static friction between the friction pairs ensures that the rolling element 20 has a contact point D on the rolling contact surface, and the instantaneous velocity of this point in the relative motion direction is zero; simultaneously, in the rolling direction, the instantaneous velocity ν of the center of rotation O of the rolling element 20 is:

[0063] v=rΩ (1)

[0064] Where r is equal to the distance between the rotation center O of the rolling element 20 and the contact point D where the instantaneous velocity is zero, and Ω is the rotational angular velocity of the rolling element 20.

[0065] When the instantaneous velocity ν undergoes acceleration or deceleration, the angular velocity Ω also changes simultaneously, becoming:

[0066] v' = rΩ' (2)

[0067] ν' is the derivative of the instantaneous velocity ν with respect to time, which is the instantaneous acceleration of the rotation center O of the rolling body 20, and Ω' is the derivative of the rotational angular velocity Ω of the rolling body 20 with respect to time, which is the rotational angular acceleration of the rolling body 20.

[0068] like Figure 3 As shown, when the main shaft 5 rotates, the eccentric wheel 6 drives the center O of the thrust ring 7 to perform circular motion, and the center O of the thrust ring 7 also rotates around the center z of the main shaft 5 with an angular velocity ω. In the x-coordinate direction, the plunger 4 and the thrust ring 7 are in contact during operation, and the center O of the plunger 4 and the thrust ring 7 remain relatively stationary. In the y-coordinate direction, the displacement along the y-coordinate direction generated by the center O of the thrust ring 7 rotating around the center z of the main shaft 5 with time t is:

[0069] y=esin(ωt) (3)

[0070] Where e is the eccentricity, which is the distance between the rotation center z of the main shaft 5 and the center O of the thrust ring 7;

[0071] Since the center O of the plunger 4 and the thrust ring 7 is relatively stationary in the x-coordinate direction, the plunger 4 and the thrust ring 7 can be regarded as a rolling friction pair that only moves relative to each other in the y-coordinate direction, and the motion characteristics are high-speed reciprocating acceleration and deceleration motion.

[0072] like Figure 4 As shown, the thrust ring 7 undergoes high-speed reciprocating acceleration and deceleration motion in the y-coordinate direction. The instantaneous velocity y' of the center O (also the center of mass) of the thrust ring 7 in the y-direction can be obtained by differentiating the displacement y of the center O of the thrust ring 7 with respect to time, as follows:

[0073] y'=eωcos(ωt) (4)

[0074] Furthermore, by taking the derivative of the instantaneous velocity y' of the center O of the thrust ring 7 in the y direction, the instantaneous acceleration y" of the center O of the thrust ring 7 is obtained as follows:

[0075] y" = -eω 2 sin(ωt) (5)

[0076] In the y-coordinate direction, the thrust ring 7 is subjected to a force F exerted by the eccentric wheel 6 on the center of mass of the thrust ring 7. y Static friction f between thrust ring 7 and plunger 4 s And the sliding friction f between the thrust ring 7 and the eccentric wheel 6 k The resultant force F of these forces causes the center O of the thrust ring 7 to produce an acceleration in the y-coordinate direction, that is...

[0077] F=-meω 2 sin(ωt) (6)

[0078] Where m is the mass of the thrust ring 7. In the above calculation, if the calculated value is negative, it means that the direction of the velocity, acceleration or force has changed in the opposite direction compared to the state where the calculated value is positive.

[0079] To ensure ideal rolling friction between the thrust ring 7 and the plunger 4, the contact point D between the thrust ring 7 and the plunger 4 must maintain an instantaneous velocity of zero. The thrust ring 7 needs to undergo acceleration motion corresponding to the center of the circle. s and f k The resultant force produces an angular acceleration Ω' with the center O of the thrust ring 7 as the center of rotation, that is...

[0080] f s r o +f k r i =JΩ' (7)

[0081] Where J is the moment of inertia of the thrust ring 7, and r o r is the outer radius of the thrust ring 7. i The radius of the inner ring of thrust ring 7.

[0082] The angular acceleration Ω' is:

[0083] Ω' = y" / r o =-eω 2 sin(ωt) / r o (8)

[0084] The moment of inertia J of thrust ring 7 is:

[0085] J = m(r o 2 +r i 2 ) / 2 (9)

[0086] Substituting formulas (8) and (9) into formula (7), we get:

[0087] f s r o +f k r i =-eω 2 msin(ωt)(r o 2 +r i 2 ) / 2r o (10)

[0088] Because the thrust ring 7 is a thin-walled circular ring, its wall thickness is much smaller than the inner radius r of the thrust ring 7.i and the outer diameter of the thrust ring 7 r o To simplify calculations, let r o Replace r i It will not have a significant impact on the calculation results, but it greatly simplifies the calculation. After simplifying formula (10), we can obtain:

[0089] f = (f s +f k )=-meω 2 sin(ωt) (11)

[0090] In the above formula, f represents the friction force, meaning that the thrust ring 7 needs sufficient friction force and f to ensure the realization of ideal rolling during operation.

[0091] f k The force is generated by the sliding friction between the thrust ring 7 and the eccentric wheel 6, and its direction of action is similar to that of f. s The forces are not always the same; in different states of motion, the direction of the force may also be the same as f. s Conversely, if f s If it remains unchanged, then the frictional force and f decrease. Furthermore, to achieve high mechanical efficiency in the pump, a very low sliding frictional force f is required. k To minimize the resulting frictional power loss.

[0092] Therefore, to satisfy a sufficiently large frictional force and f, it is necessary to ensure that f is sufficiently large. s f s The static friction coefficient μ between the rolling friction pair formed by the thrust ring 7 and the plunger 4 is generated by multiplying the normal force N between the plunger 4 and the thrust ring 7. Ignoring the direction of the force, we can obtain:

[0093] |f s |=Nμ; (12)

[0094] This invention ensures that the friction pair has a sufficiently large static friction force from two aspects.

[0095] The first aspect is to find paired materials with a relatively high static friction coefficient that can withstand corrosion in water-based media, have high load-bearing capacity, and good resistance to contact fatigue. Through tribological testing, under water-based environmental conditions, it was found that stainless steel paired friction pairs have a relatively high friction coefficient, with a static friction coefficient μ exceeding 0.4.

[0096] Although the contact fatigue performance of stainless steel is much lower than that of traditional bearing steel, the rolling friction pair composed of thrust ring 7 and plunger 4 can have a long service life through the following measures:

[0097] 1) The outer diameter of the thrust ring 7 is designed to be at least 1.5 times the inner diameter of the rolling bearing's inner ring. By increasing the outer diameter of the thrust ring 7, the rolling friction pair is characterized by a large-scale circular ring and a plane contact. According to Hertz's contact theorem, this design can effectively reduce contact stress. The larger the outer diameter of the thrust ring 7, the smaller the contact stress and the longer the contact fatigue life.

[0098] 2) Martensitic stainless steel or precipitation hardening stainless steel is preferred as the mating material for the friction pair, and the martensitic stainless steel or precipitation hardening stainless steel is heat-treated to make the surface hardness of the material exceed HRC35. The hardened martensitic stainless steel or precipitation hardening stainless steel has higher fatigue resistance.

[0099] In some embodiments, based on tribological studies of different materials under aquatic environmental conditions and considering factors such as manufacturing costs, the thrust ring 7 is determined to be made of stainless steel, preferably martensitic stainless steel or precipitation-hardening stainless steel. When the plunger 4 is made solely of stainless steel, preferably martensitic stainless steel or precipitation-hardening stainless steel, the plunger 4 and the thrust ring 7 can directly form a rolling friction pair of stainless steel / stainless steel materials.

[0100] As a first specific embodiment, the thrust ring 7 and the plunger 4 are both made of martensitic stainless steel with a heat treatment hardness exceeding HRC35.

[0101] As a second specific embodiment, the thrust ring 7 and the plunger 4 are both made of precipitation-hardened stainless steel with a heat treatment hardness exceeding HRC35.

[0102] As a third specific embodiment, the thrust ring 7 is made of martensitic stainless steel with a heat treatment hardness exceeding HRC35, and the plunger 4 is made of precipitation hardening stainless steel with a heat treatment hardness exceeding HRC35.

[0103] As a fourth specific embodiment, the plunger 4 is made of martensitic stainless steel with a heat treatment hardness exceeding HRC35, and the thrust ring 7 is made of precipitation hardening stainless steel with a heat treatment hardness exceeding HRC35.

[0104] Furthermore, in aquatic environments, stainless steel paired with certain ceramic materials can achieve a higher static friction coefficient. Preferably, alumina ceramic materials or zirconia ceramic materials are paired with stainless steel materials to form a friction pair, where the static friction coefficient μ can exceed 0.5.

[0105] In some embodiments, both the thrust ring 7 and the plunger 4 are made of stainless steel, and a ceramic layer is uniformly sprayed on the outer circumferential surface of the thrust ring 7 to form a rolling friction pair of ceramic / stainless steel materials.

[0106] In some embodiments, both the thrust ring 7 and the plunger 4 are made of stainless steel, and a ceramic coating is prepared on the end face of the plunger 4 facing the thrust ring 7 or a ceramic block is installed to form a rolling friction pair of ceramic / stainless steel materials.

[0107] It is important to understand that friction pairs made of stainless steel / stainless steel materials are economical and have good resistance to vibration and impact; friction pairs made of ceramic / stainless steel materials have better friction and wear performance, but the manufacturing cost is relatively high and the impact resistance is relatively poor.

[0108] Secondly, sufficient normal pressure N between the plunger 4 and the thrust ring 7 is provided to ensure the realization of ideal rolling friction. When the water pump is working, as the thrust ring 7 pushes the plunger 4 to pressurize and drain the water, the pressurized water reacts with the plunger 4, resulting in a considerable contact force between the plunger 4 and the thrust ring 7 (over 2000 Newtons in a typical small-power water pump). This normal pressure N is sufficient to guarantee the static friction required for ideal rolling of the thrust ring 7. However, when the plunger 4 returns and draws in water, there is no contact force between the plunger 4 and the thrust ring 7 due to high water pressure. If a traditional oil-lubricated plunger return spring is designed, it is only necessary to consider that the designed spring force can meet the acceleration requirements of the plunger 4 during its return stroke, ensuring that the plunger 4 and the drive structure remain in contact, and leaving a certain engineering design margin to ensure reliability. It is not necessary to consider whether the normal pressure between the plunger 4 and the drive structure meets the requirements; because the requirements are not high, the force exerted by the spring 8 on the plunger 4 is usually small, and a single spring 8 design can meet the requirements.

[0109] In this invention, to ensure that the thrust ring 7 can roll ideally against the end face of the plunger 4 during the return stroke, the core design objective of the spring 8 is changed to meet the static friction requirements between the thrust ring 7 and the plunger 4. That is, the significantly increased spring force is used to provide the normal force N necessary for ideal rolling friction. The spring 8 no longer only meets the return stroke requirements of the plunger 4. At this time, the design of a single spring 8 is usually difficult to meet the normal force N requirement. It is preferable to use two springs 8 of the same specification to apply the spring force.

[0110] When plunger 4 draws in water, the contact force N between plunger 4 and thrust ring 7 is the force F of spring 8 minus the force N generated by the acceleration and deceleration of plunger 4 and spring support 9. a The vacuum generated by the movement of plunger 4 in plunger cavity 3 creates a suction force N. v And the frictional force N between the plunger 4 and the plunger bore 301 during movement. f .

[0111] N = FN a -N v -N f (13)

[0112] Spring 8 moves with plunger 4. The spring force is required to be at its maximum when plunger 4 begins to draw water during its return stroke. Therefore, in the design of return springs for traditional oil-lubricated plunger pumps, the spring force value at the beginning of the water-drawing stroke is a core design consideration for engineers. In this invention, when plunger 4 is in its return stroke, it moves from the initial position where water draw begins to the halfway point of the plunger 4's water-drawing end position (the midpoint of the plunger 4's stroke). At this point, the thrust ring 7 is at the peak of its accelerated motion, and the y" value is at its maximum. This means that the positive pressure N required to ensure ideal rolling is also at its maximum, representing the most stringent design state for achieving ideal rolling friction in the friction pair. The designed spring force value of spring 8 meets this requirement and is also sufficient to meet the spring force requirements of plunger 4 during its initial water-drawing stroke and the end of its water-drawing stroke, among other operating conditions.

[0113] Define the force exerted by spring 8 on piston 4 at the midpoint of its reciprocating stroke as F. m When the plunger 4 reaches the midpoint of its stroke during the water intake stroke, the acceleration of the plunger 4 and the spring support 9 is zero, i.e., N. a N is zero v and N f It is relatively small and can be ignored in engineering design. Therefore, in this state, the normal force N that ensures ideal rolling between the plunger 4 and the thrust ring 7 is approximately equivalent to the spring force F of the spring 8. m .

[0114] By carefully designing the sliding friction pair between the thrust ring 7 and the eccentric wheel 6, the hydrodynamic pressure effect is effectively stimulated to reduce the sliding friction coefficient. The sliding friction coefficient between the thrust ring 7 and the eccentric wheel 6 can be reduced to 0.02 or lower, meaning that the sliding friction coefficient between the thrust ring 7 and the eccentric wheel 6 is much smaller than the static friction coefficient between the thrust ring 7 and the plunger 4. Because when the thrust ring 7 and the eccentric wheel 6 undergo sliding frictional motion, the normal force on the friction surfaces is the same as the normal force N between the thrust ring 7 and the plunger 4; therefore, under the same normal force, f s Much greater than f k Equation (11) can therefore be simplified to:

[0115] f s =-meω 2 sin(ωt) (14)

[0116] Substituting equation (14) into equation (12), we get:

[0117] Nμ=|-meω 2 sin(ωt)| (15)

[0118] When the plunger 4 reaches the midpoint of its stroke after drawing water, sin(ωt) = 1 on the right side of equation (15), and the required normal force N is at its maximum, which is provided by the spring. Therefore, as shown in equation (16), the spring force F is designed... mWhen the required positive pressure N is greater than or equal to the positive pressure, theoretically, ideal rolling of the thrust ring 7 on the end face of the plunger 4 can be achieved, that is:

[0119] F m ≥emω 2 / μ (16)

[0120] However, vibration occurs during actual operation of the water pump. Vibration has a friction-reducing effect. Through extensive testing, it is considered to adjust the spring force F by appropriately increasing the tightening factor α. m By making corrections, the design requirements for spring 8 when using different material pairings can be obtained. After increasing the tightening factor α, equation (16) becomes:

[0121] F m ≥αemω 2 / μ (17)

[0122] For friction pairs made of stainless steel / stainless steel materials, α / μ=3; α=1.2, μ=0.4;

[0123] That is, F m ≥3meω 2 (18)

[0124] For friction pairs of stainless steel / ceramic materials, α / μ=2.2; α=1.1, μ=0.5;

[0125] That is, F m ≥2meω 2 (19)

[0126] Where m is the mass of thrust ring 7 (in kilograms), ω is the angular velocity (2πn, where n is the number of rotations per second of the main shaft 5), e is the eccentricity (in meters), and F... m The unit is Newton, and μ is the coefficient of static friction.

[0127] It should be further explained that when the friction-reducing layer 18 is placed on the inner ring of the thrust ring 7, because the friction-reducing layer 18 is made of plastic, its density is less than 1 / 5 that of stainless steel, and it is also a thin-walled circular ring, so its impact on the calculation results is relatively small; to reflect the effect of the friction-reducing layer 18 on the spring force F m The influence of this can be directly corrected for m, which is defined as the sum of the masses of the thrust ring 7 and the anti-friction layer 18.

[0128] In summary, in this embodiment, to ensure that the frictional contact characteristics between the thrust ring 7 and the plunger 4 are ideal rolling frictional contact, sufficient static friction force must be guaranteed between the friction pairs. Therefore, the following improvements were made: First, by using a combination of martensitic stainless steel, precipitation-hardening stainless steel, and alumina and zirconia ceramic materials, the rolling friction pair can achieve a large load-bearing capacity and a relatively high static friction coefficient under water medium conditions. Second, a spring 8 with a large preload is used to apply the normal force N between the plunger 4 and the thrust ring 7 during the return stroke of the plunger 4. Therefore, it can be ensured that during the water suction stroke of the plunger 4, the rolling friction pair composed of the thrust ring 7 and the plunger 4 has sufficient static friction force, and the frictional motion during the contact process is ideal rolling.

[0129] Because the frictional contact characteristics between the thrust ring 7 and the plunger 4 are guaranteed to be ideal rolling frictional contact, the friction pair formed by the thrust ring 7 and the plunger 4 is not easily damaged in water medium conditions, which makes the water-lubricated high-pressure water pump have a long service life and high operational reliability.

[0130] Because the lubricating properties of water are significantly inferior to those of lubricating oil used in traditional power machinery, the design method of the spring 8 acting on the plunger 4 in the water-lubricated pump of this invention is completely different from that of the traditional oil-lubricated plunger pump. In the water-lubricated pump of this invention, the design of the spring 8 is centered on achieving the static friction required for ideal rolling between the thrust ring 7 and the plunger 4; in the traditional oil-lubricated plunger pump, the spring 8 design only meets the return motion requirements of the plunger 4. In the water-lubricated pump of this invention, the spring force applied by the spring 8 is much greater than that of the spring force in the traditional oil-lubricated plunger pump; for a typical power water-lubricated pump, according to the spring design method of the traditional oil-lubricated plunger pump, the maximum spring force required for the spring 8 (i.e., the spring force at the beginning of the plunger 4's suction stroke) usually does not exceed the spring force F at the midpoint of the plunger's suction stroke in the water-lubricated pump of this invention. m 30% (equivalent to about 20% of the spring force at the start of the suction stroke of the plunger 4 of the water-lubricated pump of the present invention).

[0131] To further explain, in an oil- or grease-lubricated environment, the static friction coefficient μ is less than 0.1. To achieve ideal rolling of the rolling friction pair during the plunger 4's intake stroke, the spring force required by spring 8 would need to be increased several times. This large spring force significantly increases the size and weight of spring 8, severely increasing the weight and size of the water pump and affecting its economic efficiency. These comparisons once again demonstrate that the design of rolling friction pairs under water-lubricated conditions differs significantly from that under oil-lubricated conditions.

[0132] It should be further explained that the thrust ring 7 rolls back and forth against the end face of the plunger 4 at high speed, and wear is inevitable after long-term operation.

[0133] The plunger 4 has a flat end face, and the thrust ring 7 is annular with a circular outer circumference. If both the thrust ring 7 and the plunger 4 end face are made of stainless steel to form a rolling friction pair, the entire outer circumference of the thrust ring 7 can serve as a friction surface, and this friction surface will achieve relatively uniform wear during the operation of the water pump. However, the friction surface area of ​​the plunger 4 end face is much smaller than that of the outer circumference of the thrust ring 7. Therefore, the wear on the friction surface of the plunger 4 end face is significantly higher than that on the outer circumference of the thrust ring 7.

[0134] like Figure 5 As shown, assuming the axial width of the thrust ring 7 along the main shaft 5 is smaller than the width of the piston 4 end face, after long-term operation, the thrust ring 7 will wear slightly, but a local pit 401 may be worn on the piston 4 end face. This local pit 401 exists in the middle part of the piston 4 end face; moreover, along the axial direction of the main shaft 5, there are unworn shoulders 402 on both sides or one side of the piston 4 end face that are higher than the pit 401. When the water pump is working, the thrust ring 7 is affected by shaft deformation, deflection, and vibration, and there is axial movement, which causes the thrust ring 7 end face and the shoulder 402 to come into contact and slide. Because the sliding friction coefficient is high in water lubrication, a considerable force may be generated after contact, causing the thrust ring 7 to seize and the water pump to fail completely.

[0135] The solution is to design the axial width of the friction surface to match the friction pairs made of different materials. Specifically, for example... Figure 6 As shown, when using a stainless steel / stainless steel friction pair, the width of the friction surface of the plunger 4 end face needs to be smaller than the width of the friction surface of the thrust ring 7 along the axial direction of the main shaft 5. Under this design, the entire friction surface of the plunger 4 end face will show wear, but it will not form a wear morphology of pit 401 plus shoulder 402. Furthermore, because the wear amount exhibited by the friction surface of the plunger 4 end face is significantly higher than the wear amount on the surface of the thrust ring 7, it will take a considerable amount of time for the thrust ring 7 to develop a wear morphology of pit 401 plus shoulder 402. This long time exceeds the expected lifespan of the water pump.

[0136] When the thrust ring 7 is made of stainless steel and the friction surface material of the plunger 4 end face is ceramic, such as Figure 7 As shown, since the wear resistance of ceramic materials is much greater than that of stainless steel materials, the wear of the thrust ring 7 will exceed that of the ceramic material on the end face of the plunger 4. To achieve a longer pump life, along the axial direction of the main shaft 5, the width of the friction surface of the ceramic material on the end face of the plunger 4 needs to be greater than the width of the friction surface of the thrust ring 7. This prevents the friction surface of the thrust ring 7 from developing a wear pattern of pits 401 and shoulders 402, ensuring the reliability of the water pump and guaranteeing its service life.

[0137] As can be seen, this embodiment adopts different edge contact forms of friction pairs according to different material pairings, which solves the problem of drive mechanism jamming caused by mismatch in friction pair wear, and improves the reliability and service life of water pump.

[0138] The friction pairs used in this invention employ different material pairings, and the edge contact form of the friction pairs can also be defined as follows: That is, when the friction pairs are made of stainless steel / stainless steel, when the thrust ring 7 exhibits a slight movement along the axial direction of the main shaft 5 (defined in this invention as a movement of less than 0.05 mm), the outermost original friction contact points on both sides of the plunger 4 friction contact surface along the axial direction of the main shaft 5 still maintain contact with the friction surface of the thrust ring 7. When the friction surface of the thrust ring 7 is stainless steel and the end face friction surface of the plunger 4 is ceramic, when the thrust ring 7 exhibits a slight movement along the axial direction of the main shaft 5 (a movement of less than 0.05 mm), the outermost original friction contact points on both sides of the thrust ring 7 friction contact surface along the axial direction of the main shaft 5 still maintain contact with the friction contact surface of the plunger 4. Furthermore, it should be further explained that, for purposes such as corrosion prevention, functional coatings may be sprayed on the outer periphery of the plunger 4 and the thrust ring 7. If the coating cannot participate in the rolling friction motion of the end faces of the thrust ring 7 and the plunger 4 for a long time, the water pump will still be dominated by stainless steel / stainless steel or ceramic / stainless steel materials in terms of rolling friction characteristics, and this state is still within the scope of the present invention.

[0139] In summary, this embodiment achieves a high load-bearing capacity and a relatively high static friction coefficient under water medium conditions by using martensitic stainless steel, precipitation-hardening stainless steel, and alumina and zirconia ceramic materials in combination. It also proposes a method to ensure the realization of ideal rolling friction motion by relying on the spring force of spring 8 to provide sufficient static friction force, and provides a spring 8 design method with the spring force of the plunger 4 stroke at the midpoint as the design target.

[0140] For the rolling friction pair formed by the thrust ring 7 and the end face of the plunger 4, according to the proposed friction pair pair matching material, static friction force realization method and rolling friction pair edge contact form, the realized water-lubricated high-pressure water pump has a long service life and high working reliability, low manufacturing cost, and can meet the commercial promotion requirements of the invented water or water-lubricated high-pressure water pump.

[0141] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-pressure water pump based on water or aqueous solution lubrication, characterized in that, include: The cylinder body, housing (1), plunger bore (301), at least one plunger (4), spring (8) and drive mechanism; The cylinder body is provided with an inlet check valve (11) and an outlet check valve (10); the drive mechanism includes an eccentric wheel shaft and a thrust ring (7). The eccentric wheel shaft includes a main shaft (5) and an eccentric wheel (6) disposed on the main shaft (5). The inner circumferential surface of the thrust ring (7) is sleeved on the outer circumferential surface of the eccentric wheel (6). The inner circumferential surface of the thrust ring (7) can rotate around the outer circumferential surface of the eccentric wheel (6). The plunger (4) can slide back and forth in the plunger hole (301); the internal space formed after the hydraulic cylinder and the housing (1) are connected is a receiving space (12), the plunger (4) and the thrust ring (7) are provided in the receiving space (12), and the receiving space (12) is also used to fill water or aqueous solution; The outer circumferential surface of the thrust ring (7) abuts against the end face of the plunger (4) and rolls back and forth. The thrust ring (7) and the plunger (4) constitute a rolling friction pair. The mating materials of the rolling friction pair are stainless steel / stainless steel or ceramic / stainless steel. The spring (8) acts on the plunger (4) to apply the normal force between the rolling friction pairs, so as to obtain the static friction force required for ideal rolling; the force of the spring (8) acting on the plunger (4) at the midpoint of its reciprocating stroke is defined as F. m ; When the rolling friction pair is a stainless steel / stainless steel material friction pair pair... F m ≥3meω 2 When the rolling friction pair is a stainless steel / ceramic material friction pair pair... F m ≥2meω 2 Where m is the mass of the thrust ring (7) (in kilograms), ω is the angular velocity (2πn, where n is the number of rotations per second of the main axis (5)), e is the eccentricity (in meters), and F is the angular velocity. m The unit is Newton.

2. The high-pressure water pump based on water or aqueous solution lubrication according to claim 1, characterized in that, The main shaft (5) is rotatably connected to the housing (1) via two rolling bearings; the outer diameter of the thrust ring (7) is at least 1.5 times the inner diameter of the inner ring of the rolling bearing.

3. The high-pressure water pump based on water or aqueous solution lubrication according to claim 1, characterized in that, When the rolling friction pair is made of ceramic / stainless steel: the friction surface of the thrust ring (7) is made of stainless steel, and the friction contact surface of the plunger (4) facing the thrust ring (7) is made of ceramic.

4. The high-pressure water pump based on water or aqueous solution lubrication according to claim 1, characterized in that, When the rolling friction pair is made of stainless steel / stainless steel, when the thrust ring (7) exhibits a micro-motion of less than 0.05 mm along the axial direction of the main shaft (5), the original friction contact points on both sides of the friction contact surface of the plunger (4) along the axial direction of the main shaft (5) will still maintain contact with the friction surface of the thrust ring (7).

5. The high-pressure water pump based on water or aqueous solution lubrication according to claim 3, characterized in that, When the thrust ring (7) moves by a distance of less than 0.05 mm along the axial direction of the main shaft (5), the original friction contact points on both sides of the friction contact surface of the thrust ring (7) along the axial direction of the main shaft (5) still maintain contact with the friction contact surface of the plunger (4).

6. The high-pressure water pump based on water or aqueous solution lubrication according to claim 1, characterized in that, Two springs (8) are provided, and each plunger (4) is provided with two springs (8).

7. The high-pressure water pump based on water or aqueous solution lubrication according to claim 1, characterized in that, A friction-reducing sleeve (18) is fixed to the inner ring of the thrust ring (7) or the outer circumference of the eccentric wheel (6); when the friction-reducing sleeve (18) is set on the inner ring of the thrust ring (7), m is corrected to the sum of the masses of the thrust ring (7) and the friction-reducing sleeve (18).

8. The high-pressure water pump based on water or aqueous solution lubrication according to claim 1, characterized in that, The stainless steel material is martensitic stainless steel or precipitation hardening stainless steel.

9. The high-pressure water pump based on water or aqueous solution lubrication according to claim 1, characterized in that, The ceramic material is either alumina ceramic or zirconia ceramic.

10. The high-pressure water pump based on water or aqueous solution lubrication according to claim 1, characterized in that, The surface hardness of the stainless steel is greater than HRC35.

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