Axial piston pump shoe pair oil film thickness active control device and method

Abstract

The application discloses an axial plunger pump sliding shoe pair oil film thickness active control device and method, and belongs to the technical field of hydraulic pump lubrication control. The application improves the traditional mechanical return mechanism into an electrically controlled tension and compression force mechanism, and the core execution components are composed of a servo motor, a transmission mechanism, a screw rod assembly, a spring seat and a spring. The rotation component power supply and communication are realized by cooperating with the brush-conductive copper ring. When working, the control system collects working condition parameters such as rotation speed and pressure in real time, drives the servo motor to adjust the spring compression amount according to the rotation speed-pressure-optimal oil film thickness mapping relationship, adaptively changes the sliding shoe pressing force, and realizes the active and accurate control of the oil film thickness. The oil film thickness is increased at low rotation speed to reduce wear, and the oil film thickness is reduced at high rotation speed to reduce leakage and power loss. The application can keep the sliding shoe pair in the best lubrication state in a wide rotation speed range, and significantly improves the working condition adaptability, comprehensive efficiency and service life of the axial plunger pump.

Description

Technical Field

[0001] This invention relates to the field of axial piston pump technology, and more specifically to an active control device and method for the oil film thickness of the slipper pair in an axial piston pump. Background Technology

[0002] Axial piston pumps are core power components of hydraulic systems, widely used in engineering machinery, aerospace, shipbuilding, and new energy fields. The slipper pair is one of the key friction pairs in an axial piston pump, and its lubrication condition directly affects the pump's power loss, volumetric efficiency, and service life. Improving the slipper pair's friction reduction, wear resistance, and energy efficiency are effective measures to expand the high-efficiency range of axial piston pumps.

[0003] With the development trend of electrohydraulic and intelligent systems, axial piston pumps face an urgent need for operation over a wide speed range. Under wide speed conditions, the slipper pair needs to maintain good lubrication under different speed conditions, which poses a severe challenge to traditional passive lubrication methods. Currently, scholars at home and abroad have conducted a lot of research on friction reduction, wear resistance, and energy efficiency improvement of slipper pairs, mainly including the following measures: First, using friction-reducing and wear-resistant materials: reducing the coefficient of friction by selecting self-lubricating composite materials or coatings, but the material performance is limited by the operating conditions and is difficult to adapt to the needs of a wide speed range; Second, designing new slipper pair structures: improving load-bearing characteristics by optimizing the shape and geometric parameters of the slipper structure, but once the structure is determined, it cannot be adjusted in real time according to changes in operating conditions; Third, surface texturing of the slipper pair: processing microtextures (such as pits, grooves, etc.) on the surface of the slipper sealing strip to improve the oil film load-bearing capacity using the hydrodynamic pressure effect, but the texture parameters are fixed and only effective in specific operating condition ranges; Fourth, optimizing the structural parameters of the slipper pair: optimizing parameters such as sealing strip width and chamber pressure through simulation and experiments, but the optimization results are usually only optimal near the design operating conditions.

[0004] These methods are all passive methods and have the following common defects: First, they have poor adaptability to operating conditions: they can only keep the slipper pair in a good lubrication state within a specific or narrow operating range and cannot adapt to the needs of a wide speed range; second, they cannot be adjusted in real time: once the structure and parameters are determined, the oil film thickness cannot be dynamically adjusted according to the actual operating conditions. Summary of the Invention

[0005] The purpose of this invention is to provide an active control device and method for the oil film thickness of the slipper pair in an axial piston pump, which overcomes the shortcomings of traditional passive lubrication that is difficult to adapt to wide speed conditions, and realizes real-time active and precise control of the oil film thickness of the slipper pair; by adaptively adjusting the slipper clamping force, the slipper pair maintains the best lubrication state in the entire speed range, reduces friction loss and leakage loss, and improves the overall efficiency and service life of the axial piston pump.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Firstly, the present invention proposes an active control device for the oil film thickness of an axial piston pump slipper pair, comprising a cylinder body and multiple pistons circumferentially arranged on the cylinder body, wherein the centerline of each piston is parallel to the centerline of the cylinder body. The device is characterized in that each piston is independently equipped with a servo motor, a transmission mechanism, and a lead screw assembly; the axis of the servo motor is parallel to the centerline of the piston; the transmission mechanism is located on the same side of the piston and the servo motor; the transmission mechanism contains three sequentially meshing gears; the output shaft of the servo motor is connected to the driving gear; one end of the lead screw is connected to the driven gear; and the intermediate gear serves as a transmission wheel. The lead screw assembly is installed inside the piston cavity and includes a lead screw and a nut threadedly connected to the lead screw. A spring is provided inside the piston; one end of the spring rests against the end of the spring cavity, and the other end is fixed to a spring seat; the spring seat is sleeved on the lead screw and fixedly connected to the nut.

[0007] The device also includes a control system, which is electrically connected to the servo motor. The control system is used to control the servo motor to generate forward and reverse rotation power according to the operating conditions. This power drives the lead screw to rotate through the transmission mechanism, which in turn drives the nut to reciprocate along the axis of the lead screw, thereby adjusting the compression of the spring and the clamping force of the slipper.

[0008] As a further improvement of the present invention, it also includes a working condition parameter acquisition unit, which is connected to the control system and is used to acquire the rotational speed and working pressure of the axial piston pump.

[0009] As a further improvement of the present invention, it also includes a power supply and communication module, which uses a brush-conductive copper ring structure to supply power to the servo motor.

[0010] As a further improvement of the present invention, parallel sliding grooves are provided on the upper and lower walls of the plunger cavity, and sliders that slide in cooperation with the sliding grooves are provided at the top and bottom of the spring seat. The spring seat slides left and right in the plunger cavity but does not rotate.

[0011] Secondly, the present invention also proposes an active control method for the oil film thickness of the axial piston pump slipper pair, applied to the aforementioned active control device for the oil film thickness of the axial piston pump slipper pair, the method comprising the following steps:

[0012] Step S1: Real-time acquisition of axial piston pump operating parameters, including speed and working pressure;

[0013] Step S2: Based on the preset speed-pressure-optimal oil film thickness mapping relationship, determine the target oil film thickness corresponding to the current working condition, and determine the matching target spring clamping force according to the target oil film thickness;

[0014] Step S3: The control system outputs a rotation angle control command to the servo motor;

[0015] Step S4: The servo motor drives the lead screw assembly through the transmission mechanism to convert the rotary motion into linear motion and adjust the spring compression.

[0016] Step S5: Change the spring's clamping force on the slipper to stabilize the oil film thickness of the slipper pair at the target value, thereby achieving active and precise control of the oil film thickness over a wide speed range.

[0017] As a further improvement of the present invention, in step S2, the speed-pressure-optimal oil film thickness mapping relationship is established by theoretical modeling, experimental calibration or a combination of both, and stored in the control system in the form of a data table, fitting function or interpolation model.

[0018] As a further improvement of the present invention, in step S4, the control system calculates the target compression of the spring and the target rotation angle of the servo motor based on the target spring clamping force, spring stiffness, lead screw lead and gear transmission ratio, so as to drive the lead screw assembly to adjust the spring compression.

[0019] As a further improvement of the present invention, in step S5, the spring clamping force and oil film thickness are adaptively adjusted according to the speed condition: under low speed condition, the spring clamping force is reduced to increase the oil film thickness; under high speed condition, the spring clamping force is increased to reduce the oil film thickness.

[0020] Compared with the prior art, the present invention has the following technical effects:

[0021] This invention enables active and precise control of the oil film thickness of the axial piston pump slipper pair. It can adjust the spring clamping force in real time according to the actual working conditions, and has good active control capability. It can keep the slipper pair in the optimal oil film thickness state at all times within a wide speed range, greatly expanding the high-efficiency operating range of the axial piston pump and having excellent wide speed adaptability. It can also adaptively adjust the oil film thickness at different speeds, simultaneously minimizing friction power loss and volumetric leakage loss, and achieving optimal overall efficiency under all working conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention.

[0023] Explanation of reference numerals in the attached drawings: 1-Cylinder block, 2-Plunger, 3-Slipper, 4-Swashplate, 5-Servo motor, 6-Power supply and communication module, 7-Transmission mechanism, 8-Lead screw, 9-Nut, 10-Spring, 11-Spring seat, 12-Drive shaft. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0025] like Figure 1 As shown, the active control device for oil film thickness of the axial piston pump slipper pair of the present invention includes a cylinder body 1 and multiple pistons 2 arranged circumferentially on the cylinder body 1. The center of the cylinder body 1 is a drive shaft 12, and the center line of the pistons 2 is parallel to the center line of the cylinder body 1. Each piston 2 is independently equipped with a servo motor 5, a transmission mechanism 7, and a lead screw assembly. The servo motor 5 is installed in the motor mounting cavity inside the cylinder body. The pistons 2, servo motor 5, transmission mechanism 7, and lead screw assembly rotate synchronously with the cylinder body. The lead screw assembly is installed in the cavity of the piston 2 and includes a lead screw 8 and a nut 9 threadedly connected to the lead screw 8. The axis of the output shaft of the servo motor 5 is parallel to the center line of the piston 2. The transmission mechanism 7 is located on the same side of the pistons 2 and the servo motor 5. The transmission mechanism 7 is provided with three gears meshing in sequence. The output shaft of the servo motor 5 is connected to the driving gear, one end of the lead screw 8 is connected to the driven gear, and the middle gear serves as a transmission wheel. A spring 10 is installed inside the plunger 2. One end of the spring 10 rests against the end of the spring cavity, and the other end is fixed to the spring seat 11. The spring seat 11 is sleeved on the lead screw 8 and fixedly connected to the nut 9. The servo motor 5 is used to generate forward and reverse rotation power, which drives the lead screw 8 to rotate through the gear meshing of the transmission mechanism 7. In turn, it drives the nut 9 to reciprocate along the axis of the lead screw 8. The compression of the spring 10 is adjusted by the reciprocating motion of the nut 9.

[0026] In this embodiment, the device further includes a control system and a working condition parameter acquisition unit. The working condition parameter acquisition unit is used to acquire the rotational speed and working pressure of the axial piston pump and transmit the acquired signals to the control system. The control system outputs control commands to the servo motor based on the acquired working condition parameters and a preset speed-pressure-optimal oil film thickness mapping relationship.

[0027] In some embodiments, the device further includes a power supply and communication module 6, which uses a brush-conductive copper ring structure to supply power to the servo motor 5. The brush is fixedly mounted on the outer circumferential surface of the rotating cylinder, and the conductive copper ring is mounted on the pump housing (not shown in the figure). The contacts of the brush slide in contact with the conductive copper ring to ensure a stable power and communication connection for the servo motor 5 when the device is running at high speed.

[0028] In this embodiment, parallel sliding grooves are provided on the upper and lower cavity walls of the plunger 2 cavity, and sliders that slide in cooperation with the sliding grooves are provided on the top and bottom of the spring seat 11. The spring seat 11 slides left and right in the plunger 2 cavity but does not rotate.

[0029] This device adopts a single-plunger independent electronic control adjustment structure, combined with gear transmission and lead screw transmission, to achieve high-precision and fast-response adjustment of spring clamping force; the brush-conductive copper ring structure ensures stable power supply and communication for rotating parts; the groove and slider work together to prevent spring seat deflection, improve adjustment stability and reliability, and provide a stable execution basis for active control of oil film thickness.

[0030] The present invention also provides a method for actively controlling the oil film thickness of the slipper pair in an axial piston pump, comprising the following steps:

[0031] Step S1: Real-time acquisition of axial piston pump operating parameters, including speed and working pressure;

[0032] Step S2: Based on the preset speed-pressure-optimal oil film thickness mapping relationship, determine the target oil film thickness corresponding to the current working condition, and determine the matching target spring clamping force according to the target oil film thickness;

[0033] Step S3: The control system outputs a rotation angle control command to the servo motor 5 on the rotating cylinder 1.

[0034] Step S4: Servo motor 5 drives lead screw assembly via transmission mechanism 7 to convert rotary motion into linear motion and adjust the compression of spring 10.

[0035] Step S5: Change the clamping force of spring 10 on slipper 3 to stabilize the oil film thickness of slipper pair at the target value, thereby achieving active and precise control of oil film thickness over a wide speed range.

[0036] In this embodiment, the speed-pressure-optimal oil film thickness mapping relationship is used to characterize the target oil film thickness corresponding to the optimal lubrication state of the slipper pair under different operating conditions of the axial piston pump. The input parameters of the mapping relationship include at least the axial piston pump speed n and the working pressure p, and the output parameter is the target oil film thickness h*, i.e.: h*=f(n,p). Wherein, the target oil film thickness h* is the oil film thickness value corresponding to the optimal overall performance of the slipper pair. The preferred overall performance target is: under the premise of ensuring that the slipper pair does not experience dry friction, local contact, abnormal wear, or lubrication instability, at least one of friction loss, leakage loss, temperature rise, vibration, and wear is reduced, or at least one of volumetric efficiency, mechanical efficiency, reliability, and service life is improved. The target oil film thickness is not a unique fixed value and can also be a preset target range [h]. min , h max The control system prioritizes ensuring that the actual oil film thickness falls within the target range.

[0037] The mapping relationship can be established in any of the following ways:

[0038] 1. Theoretical modeling method: Based on the fluid lubrication theory of slipper pairs, force balance relationship, leakage model and friction loss model, combined with the variation law of slipper pair load-bearing capacity, oil film stiffness, leakage flow and friction power under different speed n and working pressure p, the target oil film thickness h* that meets the preset performance target is obtained, thereby establishing the analytical relationship, discrete data table or numerical mapping model of h*=f(n,p);

[0039] 2. By measuring parameters such as frictional power loss and leakage of the slipper pair under different speed and pressure conditions through bench tests, the oil film thickness corresponding to the comprehensive evaluation index meeting the preset requirements is selected as the target oil film thickness under the working condition, and a two-dimensional calibration database of speed-pressure-target oil film thickness is constructed accordingly.

[0040] 3. Theoretical and experimental approach: First, an initial mapping relationship is generated based on a theoretical model, simulation model, or empirical model. Then, experimental data is used to correct, fit, or compensate the initial mapping relationship to obtain a target oil film thickness mapping relationship that more closely reflects actual operating conditions. This approach leverages the universality of theoretical models while improving control accuracy and adaptability in practical engineering.

[0041] The mapping relationship is stored in the control system in the form of a two-dimensional lookup table, piecewise function, interpolation model, or fitted surface. Based on the real-time acquired rotational speed n and working pressure p, the control system retrieves or calculates the target oil film thickness h* corresponding to the current operating condition from the preset calibration data. When the real-time operating condition is between adjacent calibration points, the target oil film thickness under the current operating condition can be obtained using methods such as linear interpolation, bilinear interpolation, piecewise interpolation, spline interpolation, or surface fitting. To improve control continuity, interpolation or fitting methods that ensure smooth transitions between adjacent operating conditions are preferred to avoid frequent and significant adjustments by the servo motor.

[0042] After obtaining the target oil film thickness h*, the control system determines the target spring clamping force F* based on the correspondence between the oil film thickness and clamping force of the slipper pair. This correspondence can be established through a force balance model, lubrication model, experimental calibration model, empirical database, or a combination thereof, and can be expressed as: F* = g(h*, n, p). Here, the function g(·) characterizes the target clamping force required to achieve the target oil film thickness h* under the current speed and pressure conditions. Preferably, the functional relationship can consider the influence of the hydraulic support force, centrifugal load, frictional load, inertia, spring preload, and structural parameters on the oil film thickness of the slipper pair.

[0043] In another implementation, to reduce the intermediate variable conversion process and lower the complexity of the control algorithm, the control system can directly establish the correspondence between rotational speed, pressure, and target spring clamping force, i.e., F*=φ(n,p). Using this method, the control system does not need to first solve for the intermediate parameter variables corresponding to the target oil film thickness; instead, it can directly obtain or calculate the target clamping force F* based on the operating parameters, and then the actuator can perform the corresponding adjustment. This method is suitable for situations where calibration data is sufficient, controller computing power is limited, or high real-time response requirements are needed.

[0044] After obtaining the target spring clamping force F*, the control system determines the target spring compression x* based on the spring stiffness k, the initial spring installation state, and the initial force F0 corresponding to the initial preload. Within the spring's linear operating range, the target spring compression can be expressed as: x* = (F* - F0) / k. Where k is the spring stiffness, and F0 is the preload of the spring in its initial assembly state.

[0045] Subsequently, the control system converts the target spring compression x* into the target servo motor rotation angle θ* based on the lead screw lead L, gear ratio i, and the transmission relationship between the servo motor output shaft and the lead screw. This drives the lead screw assembly to generate the corresponding axial displacement, achieving precise adjustment of the spring compression. Preferably, when the transmission ratio i is defined as the ratio of the servo motor rotation angle to the lead screw rotation angle, the target servo motor rotation angle can be expressed as: θ* = 360° × i × x* / L; or, when using radians, as: θ* = 2πix* / L. It should be noted that in practical applications, the above conversion relationship can further consider factors such as transmission clearance, gear meshing error, lead screw transmission efficiency, mechanical backlash, assembly error, and elastic deformation of the actuator. The target rotation angle can be corrected through compensation parameters, correction coefficients, or closed-loop correction methods, thereby improving execution accuracy and control stability.

[0046] The mapping relationship follows these rules: Under low-speed conditions, to ensure a stable lubricating oil film forms on the slipper pair and reduce wear risk, the target oil film thickness is appropriately increased, and the corresponding spring clamping force is appropriately decreased; under high-speed conditions, to reduce leakage and power losses, the target oil film thickness is appropriately decreased, and the corresponding spring clamping force is appropriately increased. For different pressure conditions, the control system can simultaneously correct the target oil film thickness and target clamping force by considering the impact of pressure changes on the slipper pair's load-bearing and lubrication states.

[0047] To improve control stability and system safety, the control system can also be configured with upper and lower limits for target oil film thickness, maximum spring compression limit, maximum servo motor output torque limit, and abnormal operating condition protection thresholds. When real-time operating conditions exceed the preset calibration range, the control system can employ boundary value control, nearest neighbor condition control, or a safety default control mode to ensure reliable operation of the device.

[0048] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes that can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention are all within the protection scope of the claims of the present invention.

Claims

1. An active control device for oil film thickness of an axial piston pump slipper pair, comprising a cylinder body and a plurality of pistons circumferentially arranged on the cylinder body, wherein the centerline of the pistons is parallel to the centerline of the cylinder body, characterized in that, Each plunger is independently equipped with a servo motor, a transmission mechanism, and a lead screw assembly. The axis of the servo motor is parallel to the center line of the plunger. The transmission mechanism is located on the same side of the plunger and the servo motor, and is connected between the output end of the servo motor and the lead screw to transmit the output torque of the servo motor to the lead screw. The lead screw assembly is installed in the plunger cavity and includes a lead screw and a nut threadedly connected to the lead screw. A spring is provided inside the plunger, with one end of the spring pressing against the end of the spring cavity and the other end fixed to a spring seat. The spring seat is sleeved on the lead screw and fixedly connected to the nut. The nut or spring seat has an anti-rotation limiting structure, allowing the nut to move axially along the lead screw when the lead screw rotates. The device also includes a control system, which is electrically connected to the servo motor. The control system is used to control the servo motor to generate forward and reverse rotation power according to the operating conditions. This power drives the lead screw to rotate through the transmission mechanism, which in turn drives the nut to reciprocate along the axis of the lead screw, thereby adjusting the compression of the spring and the clamping force of the slipper.

2. The active control device for oil film thickness of the axial piston pump slipper pair according to claim 1, characterized in that, The transmission mechanism is a gear transmission mechanism, including a driving gear, an intermediate gear and a driven gear. The driving gear is connected to the output shaft of the servo motor, and the driven gear is connected to the lead screw.

3. The active control device for oil film thickness of the axial piston pump slipper pair according to claim 1, characterized in that, It also includes a working condition parameter acquisition unit, which is connected to the control system and is used to acquire the speed and working pressure of the axial piston pump.

4. The active control device for oil film thickness of the axial piston pump slipper pair according to claim 1, characterized in that, It also includes a power supply and communication module, which uses a brush-conductive copper ring structure to supply power to the servo motor.

5. The active control device for oil film thickness of the axial piston pump slipper pair according to claim 1, characterized in that, Parallel sliding grooves are provided on the upper and lower walls of the plunger cavity. Slider blocks that slide in cooperation with the sliding grooves are provided at the top and bottom of the spring seat. The spring seat slides left and right in the plunger cavity but does not rotate.

6. A method for actively controlling the oil film thickness of the axial piston pump slipper pair, applied to the active control device for the oil film thickness of the axial piston pump slipper pair as described in any one of claims 1-5, characterized in that, The method includes the following steps: Step S1: Real-time acquisition of axial piston pump operating parameters, including speed and working pressure; Step S2: Based on the preset speed-pressure-optimal oil film thickness mapping relationship, determine the target oil film thickness corresponding to the current working condition, and determine the matching target spring clamping force according to the target oil film thickness; Step S3: The control system outputs a rotation angle control command to the servo motor; Step S4: The servo motor drives the lead screw assembly through the transmission mechanism to convert the rotary motion into linear motion and adjust the spring compression. Step S5: Change the spring's clamping force on the slipper to stabilize the oil film thickness of the slipper pair at the target value, thereby achieving active and precise control of the oil film thickness over a wide speed range.

7. The method for actively controlling the oil film thickness of the axial piston pump slipper pair according to claim 6, characterized in that, In step S2, the speed-pressure-optimal oil film thickness mapping relationship is established through theoretical modeling, experimental calibration, or a combination of both, and stored in the control system in the form of a data table, fitting function, or interpolation model.

8. The method for actively controlling the oil film thickness of the axial piston pump slipper pair according to claim 6, characterized in that, In step S4, the control system calculates the target spring compression and the target servo motor rotation angle based on the target spring clamping force, spring stiffness, lead screw lead and gear transmission ratio, so as to drive the lead screw assembly to adjust the spring compression.

9. The method for actively controlling the oil film thickness of the axial piston pump slipper pair according to claim 6, characterized in that, In step S5, the spring clamping force and oil film thickness are adaptively adjusted according to the operating speed: at low speed, the spring clamping force is reduced to increase the oil film thickness; at high speed, the spring clamping force is increased to decrease the oil film thickness.

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