Plunger assembly capable of forming hydrodynamic oil film and provided with needle bearing and hydraulic motor

Abstract

The plunger assembly comprises a plunger, a spring pin and the needle roller bearing, the needle roller bearing comprises an outer ring and a needle roller, a shaft core is arranged in the center of the needle roller bearing, the needle roller is arranged between the shaft core and the outer ring, fixing grooves are formed in the two sides of the plunger, and the spring pin is arranged in the fixing grooves. The two sides of the shaft core are inserted into the fixing grooves, a spring pin is further arranged at one end of the shaft core, a needle bearing cavity for the needle bearing to be installed is formed in the plunger, when the needle bearing rotates at a high speed, a liquid dynamic pressure oil film is formed between the needle bearing and the needle bearing cavity, and the liquid dynamic pressure oil film provides supporting force for the needle bearing. The shaft core and the liquid dynamic pressure oil film jointly support the downward pressure of the needle bearing, and the needle bearing is characterized in that the liquid dynamic pressure oil film can provide supporting force, the liquid dynamic pressure oil film and the shaft core jointly bear the downward pressure of the needle bearing, frictional resistance is reduced, mechanical efficiency is improved, part abrasion is reduced, and meanwhile the supporting stability of the needle bearing is enhanced.

Description

Technical Field

[0001] This utility model relates to the field of hydraulic motors, and in particular to a plunger assembly with needle roller bearings that can form a hydrodynamic oil film and a hydraulic motor. Background Technology

[0002] In various hydraulic systems, hydraulic motors play an indispensable role as key actuators. Their working principle is based on energy conversion, precisely and efficiently converting hydraulic energy into mechanical energy to drive the output shaft to rotate stably. A common type of hydraulic motor mainly consists of a stator, rotor assembly, front cover, and rear cover. The rotor assembly, closely connected to the output shaft, undertakes the core task in power transmission and is crucial for achieving energy conversion and power output. The rotor assembly has a complex internal structure, including a rotor and a piston assembly composed of rollers, plungers, oil-free bearings, spring pins, piston rings, and plunger baffles.

[0003] During operation, hydraulic oil serves as the power transmission medium, playing a crucial driving role. High-pressure oil is injected into the plunger cavity, pushing the plunger to move linearly within the plunger, which in turn drives the rollers to move in a wave-like motion along the inner wall of the stator. Due to the special curved design of the stator's inner wall, the movement of the rollers causes the rotor to drive the output shaft to rotate, completing the conversion of hydraulic energy into mechanical energy.

[0004] However, existing technologies have significant drawbacks in the connection between the roller and the plunger. Currently, rollers and plungers are generally connected using oilless bearings, with the roller rotating relative to the oilless bearing during operation. However, the friction between the oilless bearing and the roller is sliding friction, resulting in a high coefficient of friction. According to the principles of mechanical motion, a high coefficient of friction means that the hydraulic motor must overcome a large frictional torque at startup. This not only increases energy consumption during startup but also prolongs startup time, leading to severely low startup efficiency of the hydraulic motor.

[0005] To effectively address the aforementioned problems, existing technologies have attempted to replace traditional roller bearings with needle roller bearings. Needle roller bearings are mounted within the plunger cavity via a shaft, and rotate around the center of the shaft during operation. However, when the hydraulic motor is rotating at high speed, the needle roller bearing is subjected to strong compression from the stator towards the plunger cavity. Under this external force, the shaft deforms to overcome this compression. This deformation, in turn, affects the normal rotation of the needle roller bearing, increasing noise during operation and significantly reducing its lifespan, ultimately impacting the long-term stable operation of the entire hydraulic motor. Utility Model Content

[0006] The technical problem to be solved by this utility model is to provide a plunger assembly with needle roller bearings and a hydraulic motor that can form a hydrodynamic oil film, wherein the hydrodynamic oil film provides support force to the needle roller bearings.

[0007] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: a plunger assembly with a needle roller bearing that can form a hydrodynamic oil film, characterized in that it includes a plunger, a spring pin, and a needle roller bearing. The needle roller bearing includes an outer ring and needle rollers. A shaft core is provided in the center of the needle roller bearing. The needle rollers are disposed between the shaft core and the outer ring. Fixing grooves are provided on both sides of the plunger. Both sides of the shaft core are inserted into the fixing grooves. A spring pin is also provided at one end of the shaft core. A needle roller bearing cavity is provided on the plunger for the needle roller bearing to be installed. When the needle roller shaft rotates at high speed, a hydrodynamic oil film is formed between the needle roller bearing cavity and the needle roller bearing. The hydrodynamic oil film provides support force for the needle roller bearing. The shaft core and the hydrodynamic oil film together support the downward pressure of the needle roller bearing.

[0008] A further preferred embodiment of this utility model is: the gap between the needle roller bearing and the needle roller bearing cavity is H, the diameter of the needle roller bearing is D, and the value of H / D is between 0.0032 and 0.0048.

[0009] A further preferred embodiment of this utility model is: the diameter of the needle roller bearing is D, the width of the outer ring of the needle roller bearing is B, and the value of B / D is between 0.8 and 1.2.

[0010] A further preferred embodiment of this utility model is that the thickness of the liquid dynamic pressure oil film is not less than 0.015 mm.

[0011] A further preferred embodiment of this invention is that the pressure exerted on the liquid dynamic pressure oil film is between 35 and 45 MPa.

[0012] A hydraulic motor, characterized in that it includes a plunger assembly with needle roller bearings capable of forming a hydrodynamic oil film, as described above.

[0013] This invention presents a novel plunger assembly structure with needle roller bearings capable of forming a hydrodynamic oil film. By inserting both sides of the needle roller bearing shaft into the fixing grooves of the plunger and installing a spring pin at one end of the shaft, a stable installation of the needle roller bearing on the plunger is ensured. When the needle roller shaft rotates at high speed, a hydrodynamic oil film is formed between the needle roller bearing and its cavity. This oil film provides support force, sharing the downward pressure of the needle roller bearing with the shaft. This design allows the plunger assembly to effectively utilize the principle of hydrodynamic lubrication during operation, reducing frictional resistance, improving mechanical efficiency, reducing component wear, and enhancing the support stability of the needle roller bearing, thereby improving the operational reliability and durability of the entire hydraulic system. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model;

[0015] Figure 2A 3D view of the plunger assembly;

[0016] Figure 3 Cross-section of the plunger assembly Figure 1 ;

[0017] Figure 4 Cross-section of the plunger assembly Figure 2 . Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0019] like Figures 1-4 As shown, a plunger assembly with a needle roller bearing capable of forming a hydrodynamic oil film includes a plunger 1, a spring pin 2, and a needle roller bearing 3. The needle roller bearing 3 includes an outer ring 4 and needle rollers 5. A shaft core 6 is disposed in the center of the needle roller bearing 3, and the needle rollers 5 are disposed between the shaft core 6 and the outer ring 4. Fixing grooves 7 are provided on both sides of the plunger 1, and both sides of the shaft core 6 are inserted into the fixing grooves 7. A spring pin 2 is also provided at one end of the shaft core 6. A needle roller bearing cavity 8 is provided on the plunger 1 for the needle roller bearing 3 to be installed. When the needle roller bearing rotates at high speed, a hydrodynamic oil film 9 is formed between the needle roller bearing 3 and the needle roller bearing cavity 8. The hydrodynamic oil film 9 provides support force to the needle roller bearing 3, and the shaft core 6 and the hydrodynamic oil film 9 together support the downward pressure of the needle roller bearing 3. This claim constructs a novel plunger assembly structure with a needle roller bearing capable of forming a hydrodynamic oil film. By inserting the shaft core 6 with needle roller bearing 3 into the fixing grooves 7 of the plunger 1 on both sides, and setting a spring pin 2 at one end of the shaft core 6, the stability of the needle roller bearing 3 installation is ensured. When the needle roller bearing rotates at high speed, a hydrodynamic oil film 9 can be formed between the needle roller bearing 3 and the needle roller bearing cavity 8, which is the key difference from traditional lubrication methods. The hydrodynamic oil film 9 not only has a lubricating effect, effectively reducing friction and component wear, but more importantly, it can generate supporting force, sharing the downward pressure of the needle roller bearing 3 with the shaft core 6. Compared with the only lubricating function of traditional lubricants, this design greatly enhances the support stability of the needle roller bearing 3, thereby improving the operational reliability and durability of the entire hydraulic system, and effectively solving the problem of frequent equipment failures caused by insufficient support in traditional technologies.

[0020] The clearance between the needle roller bearing 3 and the needle roller bearing cavity 8 is H, and the diameter of the needle roller bearing 3 is D. The value of H / D is between 0.0032 and 0.0048. Precisely defining the ratio of the clearance H between the needle roller bearing 3 and the needle roller bearing cavity 8 to the diameter D of the needle roller bearing 3 within the range of 0.0032 to 0.0048 is crucial for the stable formation and efficient operation of the hydrodynamic oil film 9, as verified through testing. Within this ratio range, a suitable and stable hydrodynamic oil film 9 can be formed under appropriate operating conditions. A suitable oil film thickness not only fully utilizes its lubricating effect but also ensures sufficient supporting force, effectively separating the needle roller bearing 3 from the cavity surface, preventing direct contact wear, and maintaining good lubrication and support effects. Compared to traditional lubrication methods that cannot precisely control oil film parameters, this optimized parameter significantly improves the working performance and service life of the plunger assembly, reducing energy loss, unstable support, and equipment failure caused by improper clearance.

[0021] The diameter of the needle roller bearing 3 is D, and the width of the outer ring 4 of the needle roller bearing 3 is B, with the B / D ratio between 0.8 and 1.2. Specifying that the ratio of the width B to the diameter D of the outer ring 4 of the needle roller bearing 3 is between 0.8 and 1.2 is crucial for optimizing the performance of the needle roller bearing 3. This ratio range helps to optimize the force distribution and the formation effect of the hydrodynamic oil film 9 when mating with the plunger 1, while ensuring the structural strength of the needle roller bearing 3. A suitable width-to-diameter ratio allows the hydrodynamic oil film 9 to be more evenly distributed between the bearing outer ring 4 and the plunger cavity 8, thereby enhancing the oil film's support force, improving the bearing's load-bearing capacity, reducing local stress concentration, and lowering the risk of wear. Compared to traditional technologies that lack optimization of bearing structural proportions, this design enables the plunger assembly to operate more efficiently and stably under complex working conditions, further highlighting the strong support and lubrication advantages of the hydrodynamic oil film 9 in the optimized bearing structure.

[0022] The thickness of the hydrodynamic oil film 9 is not less than 0.015 mm. Specifying a thickness of at least 0.015 mm for the hydrodynamic oil film 9 is a key indicator for ensuring good lubrication and support performance. A sufficiently thick oil film can effectively separate the needle roller bearing 3 from the surface of the plunger cavity 8, not only effectively avoiding direct contact between the convex peaks of the two surfaces, significantly reducing the coefficient of friction, reducing wear and heat generation, but more importantly, providing strong support force to maintain the stable operation of the needle roller bearing 3. Compared with the extremely thin oil film formed by traditional lubricants, the hydrodynamic oil film 9 at this thickness requirement has better buffering and vibration damping performance, can absorb external vibrations and shocks, improve the smoothness of the plunger assembly operation, and extend the service life of the equipment. At the same time, the stable oil film support force helps maintain the stable operation of the entire hydraulic system, reducing failures caused by poor lubrication and support.

[0023] The pressure exerted on the hydrodynamic oil film 9 is between 35 and 45 MPa. Limiting the pressure on the hydrodynamic oil film 9 to this range provides a suitable pressure environment for the stable formation of the oil film and its effective support force. Within this pressure range, the oil film possesses sufficient load-bearing capacity to support the normal operation of the needle roller bearing 3 under high-speed, heavy-load conditions. The appropriate pressure ensures the thickness and stability of the oil film, enabling it to fully exert its lubricating function while generating a strong and stable supporting force, preventing oil film rupture or failure, thereby reducing wear between parts, improving mechanical efficiency, and reducing energy loss. Compared to traditional lubrication methods that cannot precisely control oil film pressure, this pressure limitation ensures reliable operation of the plunger assembly under various working conditions, further improving the support and lubrication performance of the hydrodynamic oil film 9 under complex working conditions, and providing a guarantee for the efficient operation of the hydraulic system.

[0024] The hydraulic motor, with its powerful hydrodynamic oil film 9, allows for smoother operation, stronger resistance to external vibrations, and lower operating noise. Simultaneously, reduced wear significantly extends the motor's lifespan under stable operating conditions. Compared to conventional lubrication methods used in traditional hydraulic motors, this design allows the motor to adapt to more complex working conditions, improving its reliability and stability under various operating conditions. It fully leverages the supporting and lubricating advantages of the hydrodynamic oil film 9, providing a strong guarantee for the efficient and stable operation of the hydraulic system.

[0025] The above provides a detailed description of the plunger assembly with needle roller bearings and hydraulic motor capable of forming a hydrodynamic oil film, as provided by this utility model. Specific examples have been used to illustrate the principle and implementation of this utility model. The descriptions of the embodiments above are merely for the purpose of helping to understand this utility model and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to this utility model without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A roller pin bearing plunger assembly capable of forming a hydrodynamic oil film, characterized by The plunger assembly comprises a plunger, a spring pin and a needle bearing, the needle bearing comprises an outer ring and needles, a shaft core is arranged in the center of the needle bearing, the needles are arranged between the shaft core and the outer ring, both sides of the plunger are provided with fixed grooves, both sides of the shaft core are inserted into the fixed grooves, one end of the shaft core is further provided with a spring pin, the plunger is provided with a needle bearing cavity for accommodating the needle bearing, when the needle bearing rotates at high speed, a liquid dynamic pressure oil film is formed between the needle bearing cavities, the liquid dynamic pressure oil film provides support force for the needle bearing, the shaft core and the liquid dynamic pressure oil film jointly support the downward pressure of the needle bearing.

2. A hydrodynamic oil film forming plunger assembly with needle roller bearing according to claim 1, characterized in that The gap between the needle bearing and the needle bearing cavity is H, the diameter of the needle bearing is D, and the value of H / D is between 0.0032 and 0.0048.

3. A hydrodynamic oil film forming plunger assembly with needle roller bearing according to claim 1, characterized in that The diameter of the needle bearing is D, the width of the outer ring of the needle bearing is B, and the value of B / D is between 0.8 and 1.

2.

4. A hydrodynamic oil film forming plunger assembly with needle bearing according to claim 1, characterized in that The thickness of the liquid dynamic pressure oil film is not less than 0.015 mm.

5. A hydrodynamic oil film forming plunger assembly with needle bearing according to claim 1, characterized in that The pressure of the liquid dynamic pressure oil film is between 35 and 45 Mpa.

6. Hydraulic motor, characterized in that The plunger assembly comprises a plunger, a spring pin and a needle bearing, the needle bearing comprises an outer ring and needles, a shaft core is arranged in the center of the needle bearing, the needles are arranged between the shaft core and the outer ring, both sides of the plunger are provided with fixed grooves, both sides of the shaft core are inserted into the fixed grooves, one end of the shaft core is further provided with a spring pin, the plunger is provided with a needle bearing cavity for accommodating the needle bearing, when the needle bearing rotates at high speed, a liquid dynamic pressure oil film is formed between the needle bearing cavities, the liquid dynamic pressure oil film provides support force for the needle bearing, the shaft core and the liquid dynamic pressure oil film jointly support the downward pressure of the needle bearing.

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