A method for controlling static oil film thickness with internal feedback based on PM flow controller

Abstract

The present invention discloses a method for controlling static oil film thickness using internal feedback based on a PM flow controller. The method comprises a first oil tank, a second oil tank, a coarse oil filter, an oil pump, a servo motor, a fine oil filter, a one-way valve, a pilot electromagnetic relief valve, a PM flow controller, a guide rail, a first throttle, a second throttle, an upper static oil pad, a radial static oil pad, a lower static oil pad, and a static pressure worktable. Leveraging the advantages of the PM flow controller, the method increases oil chamber pressure and flow control when the load increases; conversely, decreases oil chamber pressure and flow control when the load decreases. The PM flow controller regulates flow solely by deforming the metal film with a pressure differential, requiring no external energy input or electronic control. The method ensures that the oil film remains constant for extended periods of time while the static pressure system is operating, and operates stably and reliably, ensuring efficient, stable, and long-term operation of the static pressure turntable.

Description

Technical Field

[0001] The invention belongs to the field of liquid hydrostatic support, and in particular relates to an internal feedback hydrostatic oil film thickness control method based on a PM flow controller. Background Art

[0002] Hydrostatic bearings are widely used in machine tools and other mechanical equipment due to their low friction, long service life, excellent vibration resistance, and high rotational precision. However, with the development of industrial technology, particularly in the defense and aviation industries, the requirements for the rotational accuracy and stiffness of hydrostatic bearings under load are becoming increasingly stringent. When the load or operating conditions of the machine tool fluctuate, the hydrostatic oil film thickness becomes unstable, affecting machining accuracy and efficiency. Patents such as CN103341781B, CN107642545A, and CN106094736A all involve hydrostatic oil film thickness control. These patents use feedback signals to control the speed of a servo motor to adjust the oil film thickness of the hydrostatic bearing worktable. This shifts from passive oil film thickness control to active servo motor control of the oil film thickness. The servo motor converts this signal into torque and speed to adjust the oil pump supply, achieving active and precise control of the oil film thickness. However, the sensor requires regular zeroing during use, and the sensor cannot guarantee long-term stability. Therefore, long-term stable operation of the hydrostatic bearing worktable is problematic. The control of oil film thickness also involves the hydraulic control system. The existing hydrostatic support hydraulic control system, such as that described in patents with publication numbers CN102975031B, CN201534283U, and CN201891698U, realizes automatic adjustment of the buoyancy of the hydrostatic worktable under a large load range. However, the system implementation process uses a liquid hydrostatic support with a traditional throttle. When an external load is applied, the support gap decreases with the increase of the external load. The oil film stiffness is low, and each oil circuit corresponds to a separate hydrostatic support. There is no feedback between them, which makes it difficult to adjust the axial position of the rotary table during assembly. When the table rotates, the pressure between the upper and lower radially symmetrical hydrostatic chambers is inconsistent, which can easily cause the workpiece to overturn, affecting the accuracy of the guide rail and shortening the life of the table. In summary, the hydrostatic turntable needs to realize automatic adjustment of the buoyancy of the table under a large range of load and temperature changes during operation. Most existing methods use active signal adjustment combined with a hydrostatic support hydraulic control system to control the oil supply flow to achieve constant oil film thickness. This invention proposes an internal feedback static oil film thickness control method based on a PM flow controller. Leveraging the advantages of a PM flow controller, this method increases oil chamber pressure and, consequently, flow rate when the load increases. Conversely, when the load decreases, the oil chamber pressure and flow rate decrease. The PM flow controller regulates flow solely by deforming the metal film due to a pressure differential, requiring no external energy input or electronic control. This method ensures that the oil film maintains a constant level over extended periods of time while the static pressure system is operating, and provides stable and reliable operation, ensuring efficient, stable, and long-term operation of the static pressure turntable. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to design a method for controlling the oil film thickness of a closed static pressure turntable.

[0004] The technical solution adopted by the present invention to solve its technical problem is:

[0005] A device for implementing a closed hydrostatic turntable oil film thickness control method, the device constituting the method comprising: a first oil tank, a second oil tank, a coarse oil filter, an oil pump, a servo motor, a fine oil filter, a one-way valve, a pilot-type electromagnetic relief valve, a PM flow controller, a guide rail, a first throttle, a second throttle, an upper hydrostatic oil pad, a radial hydrostatic oil pad, a lower hydrostatic oil pad, and a hydrostatic worktable;

[0006] The structure of the PM flow controller includes: a body, a capillary groove, a throttle port, a shell, a regulating chamber, a film, a pressure stabilizing chamber, and a throttle platform; the PM flow controller includes a first PM flow controller and a second PM flow controller.

[0007] Connections between the various parts that make up the device:

[0008] The guide rail is installed in the middle position of the hydrostatic turntable. The right side of the guide rail is stabilized by the support of the turntable base. The upper hydrostatic oil pad is installed on the upper part of the left side of the guide rail, the lower hydrostatic oil pad is installed on the lower part, and the radial hydrostatic oil pad is installed radially. The three oil pads realize hydrostatic support of the hydrostatic workbench by oil supply.

[0009] The servo motor controls the oil pump in the first oil tank to extract hydraulic oil through the coarse oil filter. The oil then flows through the fine oil filter, the pilot electromagnetic relief valve, and the one-way valve to the oil distribution port. The oil is then divided into two paths through the oil distribution port, flowing through the first PM flow controller and the second PM flow controller respectively.

[0010] The hydraulic oil flowing into the first and second PM flow controllers is divided into two streams upon reaching the oil inlet at the bottom of the body. One stream flows through the capillary grooves and throttle port on the side of the body and enters the pressure regulating chamber above the diaphragm. The other stream flows through two annular rectangular grooves inside the body and is further divided into two parts. One part enters the pressure stabilizing chamber below the diaphragm through the axial hole, then flows through the annular throttle plate and out of the oil outlet. The other part flows through the two annular capillary grooves again and joins the oil flow that passed through the annular throttle plate and flows out of the outlet.

[0011] The hydraulic oil flowing out of the first PM flow controller is divided into two paths again to supply oil to the upper static pressure oil chamber and the lower static pressure oil chamber respectively;

[0012] Hydraulic oil flowing out of the second PM flow controller directly supplies the radial oil chamber. When the oil chamber pressure is zero, the PM flow controller's preload regulation causes the internal diaphragm to bend downward under the preload of the upper chamber. The gap between the diaphragm and the throttle plate is minimized, and the fluid resistance is maximized. At this point, the outflow through the oil outlet is minimal. As the oil chamber pressure increases, the diaphragm bends upward, increasing the gap between the diaphragm and the throttle plate, reducing the fluid resistance at the outlet, and increasing the flow rate entering the oil chamber through the gap, resulting in minimal changes in the thickness of the hydrostatic turntable support oil film.

[0013] After the three-way static pressure oil chamber is filled with hydraulic oil, when there is enough liquid pressure on the guide rail surface to balance the weight of the load, the support part is floated. At this time, the static pressure oil flows out of the oil chamber through the gap between the upper and lower guide rails and the radial oil seal surface, and the pressure outside the cavity drops to almost zero. When the floating amount is greater than the surface unevenness of the upper and lower planes of the guide rail and the radial plane, pure liquid friction is formed.

[0014] The hydraulic oil with constant pressure flows through the first throttle arranged in the upper oil chamber and then flows into the lower oil chamber. The other way flows through the throttle arranged in the lower oil chamber and then flows into the upper oil chamber, forming an axial closed static pressure structure.

[0015] When the guide rail is subjected to a downward force F, a gap change of Δh will occur. At this time, on the one hand, the oil chamber pressure of the upper static oil pad decreases due to the increase in the gap (increased to h0+Δh) and the reduction in the liquid resistance of the oil sealing edge. At the same time, the throttle arranged in the oil chamber of the lower static oil pad for controlling the upper oil chamber increases due to the decrease in the gap (reduced to h0-Δh). The pressure lost due to the liquid resistance in the throttling will increase, making the pressure entering the oil chamber of the upper static oil pad smaller, which plays a feedback role. While through feedback control, the first PM flow controller assists in controlling the oil chamber pressures of the upper and lower static oil pads, and the two cooperate to achieve precise control.

[0016] The pilot-operated electromagnetic overflow valve is connected to the second oil tank.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) The PM flow controller, as a pressure compensation element in the hydrostatic bearing, has the characteristic that the flow rate increases with the increase of the oil chamber pressure. Since the PM flow controller does not slide, there is no wear and no hysteresis. In addition, the metal elastic film inside the PM flow controller has a small mass, a large adjustment force, a fast response, and good dynamic characteristics. Therefore, it can effectively solve the problem of insufficient oil supply pressure in the remote branch oil circuit due to distance problems after the main oil circuit is supplied. The change in oil film thickness due to load is very small, thereby greatly improving the rigidity of the hydrostatic bearing.

[0019] (2) Due to the combined effect of the upper and lower oil chambers (i.e., closed hydrostatic structure) and the feedback effect of the feedback throttle, the internal feedback closed hydrostatic bearing has higher oil film stiffness and stability than traditional fixed throttle constant pressure and constant flow hydrostatic bearings. The oil film thickness changes less with different loads, and the accuracy retention is better.

[0020] (3) A pilot-type electromagnetic overflow valve is used. When the system does not need to unload, the electromagnetic valve will close the parallel oil tank port. The rated load operation is mainly achieved through the pilot valve. When an emergency occurs, the electromagnetic valve starts to work and the system quickly unloads and returns to a safe state, ensuring the safe operation of the hydrostatic turntable. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Cross-sectional view of the overall structure of the static pressure turntable;

[0022] Figure 2 Based on the principle diagram of the static pressure oil circuit with feedback inside the PM flow controller;

[0023] Figure 3 Schematic diagram of PM flow controller;

[0024] Figure 4 Control fluid resistance diagram; DETAILED DESCRIPTION

[0025] The present invention will be further described with reference to the accompanying drawings as specific embodiments:

[0026] A static pressure turntable overall structure for realizing a closed static pressure turntable oil film thickness control method, such as Figure 1 The apparatus constituting the method, such as Figure 2 , including: first oil tank 1-1, second oil tank 1-2, coarse oil filter 2, oil pump 3, servo motor 4, fine oil filter 5, one-way valve 6, pilot electromagnetic overflow valve 7, first PM flow controller 8-1, second PM flow controller 8-2, guide rail 9, first throttle 10-1, second throttle 10-2, static pressure workbench 11, upper static pressure oil pad 12, radial static pressure oil pad 13, lower static pressure oil pad 14. The PM flow controller structure diagram is as follows Figure 3 , body 15, capillary groove 16, shell 17, throttle port 18, regulating chamber 19, film 20, pressure stabilizing chamber 21, throttle platform 22. The hydraulic resistance diagram of the oil circuit control, such as Figure 4 .

[0027] Connections between the various parts that make up the device:

[0028] The guide rail 9 is installed in the middle of the hydrostatic turntable. The right side of the guide rail is supported by the turntable base to achieve stability. The upper hydrostatic oil pad 12 is installed on the left side, and the lower hydrostatic oil pad 14 is installed on the lower side. The radial hydrostatic oil pad 14 is installed radially to achieve hydrostatic support for the hydrostatic workbench 11 through oil supply.

[0029] The servo motor 4 controls the oil pump 3 in the first oil tank 1-1 to extract the hydraulic oil through the coarse oil filter 2, and the oil flows through the fine oil filter 5, the pilot electromagnetic overflow valve 7, and the one-way valve 6 to the oil outlet;

[0030] The oil is divided into two paths through the oil distribution port, flowing through the first PM flow controller 8-1 and the second PM flow controller 8-2 respectively;

[0031] The hydraulic oil flowing into the first PM flow controller 8-1 and the second PM flow controller 8-2 is divided into two streams upon reaching the oil inlet at the bottom of the body. One stream flows through the capillary groove 16 and throttle port 18 on the side of the body 15 and enters the pressure regulating chamber 19 above the diaphragm 20. The other stream is further divided into two parts by the two annular rectangular grooves inside the body 15. One part enters the pressure stabilizing chamber 21 below the diaphragm 20 through the axial hole, then flows out of the oil outlet through the annular throttle plate 22. The other part flows through the two annular capillary grooves again and merges with the oil flow that passed through the annular throttle plate 22 to flow out of the outlet.

[0032] The hydraulic oil flowing out of the first PM flow controller 8 - 1 is divided into two paths again to supply oil to the upper static pressure oil pad 12 and the lower static pressure oil pad 14 respectively;

[0033] Hydraulic oil flowing out of the second PM flow controller 8-2 directly supplies radial oil pad 13. When the oil chamber pressure is zero, the diaphragm bends downward under the preload of the upper chamber due to the preload regulation of the PM flow controller. The gap between the diaphragm and the throttle plate is minimized, and the hydraulic resistance is maximized. At this point, the outflow through the oil outlet is minimal. As the oil chamber pressure increases, the diaphragm bends upward, increasing the gap between the diaphragm and the throttle plate. This reduces the outflow hydraulic resistance and increases the flow rate entering the oil chamber through the gap, minimizing changes in the hydrostatic turntable support oil film thickness.

[0034] After the three-way static pressure oil chamber is filled with hydraulic oil, when there is enough liquid pressure on the guide rail surface to balance the weight of the load, the support part is floated. At this time, the static pressure oil flows out of the oil chamber through the gap between the upper and lower guide rails and the radial oil seal surface, and the pressure outside the cavity drops to almost zero. When the floating amount is greater than the surface unevenness of the upper and lower planes of the guide rail and the radial plane, pure liquid friction is formed.

[0035] The hydraulic oil of constant pressure is throttled through the first throttle 10-1 arranged on the upper static pressure oil pad 12 and then flows into the lower static pressure oil pad 14. The other way is throttled through the second throttle 10-2 arranged on the lower static pressure oil pad 14 and then flows into the upper static pressure oil pad 12, forming an axial closed static pressure structure.

[0036] When the guide rail is subjected to a downward force F, a gap change of Δh will occur. At this time, on the one hand, the oil cavity of the upper static oil pad 12 becomes larger (increased to h0+Δh) and the oil sealing edge liquid resistance R C The oil chamber pressure is reduced, and at the same time, the throttle arranged in the oil chamber of the lower static oil pad 14 for controlling the upper oil chamber has a smaller gap (reduced to h0-Δh) and a throttle edge liquid resistance R H Increase, the pressure due to the loss of fluid resistance in the throttling will become larger, making the pressure entering the upper static oil pad oil chamber smaller, playing a feedback role. At the same time, through feedback control, due to the pre-pressure adjustment effect of the PM flow controller, the film is in the upper chamber pre-pressure P s2 , it bends downward under the action of , the gap between the film and the throttle table is the smallest, the liquid resistance R1 and R2 of the rectangular groove are the largest, and the flow rate q0 flowing out through the outlet Pr is also the smallest at this time; with the increase of external load, the pressure Pr leading to the static oil chamber through the controller is also increasing, which destroys the original force balance state of the metal film, and the film is deformed and bent upward, so that the annular gap between the film and the throttle table increases, and the liquid resistance R5 of the hydraulic oil leading to the static oil chamber through the throttle table of the controller is reduced. The combined result of the film deformation and the pressure difference change causes the liquid resistance R1 and R2 of the annular rectangular groove and the liquid resistance R3 and R4 of the annular capillary groove to change, and the flow entering the static oil chamber through the controller increases. The first PM flow controller 8-1 assists in controlling the oil chamber pressure of the upper static oil pad 12 and the lower static oil pad 14, and the two cooperate to achieve precise control.

[0037] In the description of the invention, it should be understood that the terms "upper", "lower", "radial" and the like indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation structure and operation, and therefore cannot be understood as a limitation on the invention.

[0038] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features.

[0039] In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification, as well as features of different embodiments or examples, unless they are mutually inconsistent.

[0040] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. An internal feedback static oil film thickness control device based on a PM flow controller, characterized by: include: A first oil tank, a second oil tank, a coarse oil filter, an oil pump, a servo motor, a fine oil filter, a one-way valve, a pilot electromagnetic relief valve, a PM flow controller, a guide rail, an upper static pressure oil pad, a radial static pressure oil pad, a lower static pressure oil pad, and a static pressure workbench; the PM flow controller comprises a body, a capillary groove, a throttle port, a diaphragm, a pressure stabilizing chamber, and a throttle platform; the PM flow controller comprises a first PM flow controller and a second PM flow controller; The guide rail is installed in the middle of the hydrostatic turntable. The right side of the guide rail is supported by the turntable base to achieve stability. An upper hydrostatic oil pad is installed on the upper side of the left side of the guide rail, a lower hydrostatic oil pad is installed on the lower side, and a radial hydrostatic oil pad is installed radially. The three oil pads realize hydrostatic support of the hydrostatic workbench by supplying oil. The servo motor controls the oil pump in the first oil tank to extract hydraulic oil through the coarse oil filter. The oil then flows through the fine oil filter, the pilot electromagnetic relief valve, and the one-way valve to the oil distribution port. The oil is then divided into two paths through the oil distribution port, flowing through the first PM flow controller and the second PM flow controller respectively. The pilot electromagnetic relief valve is connected to the second oil tank. The hydraulic oil flowing into the first and second PM flow controllers splits into two streams after reaching the oil inlet at the bottom of the body. One stream flows through the capillary grooves and throttle port on the side of the body and enters the pressure regulating chamber above the diaphragm. The other stream flows through the two annular rectangular grooves inside the body and is further divided into two parts. One part enters the pressure-stabilizing chamber below the diaphragm through the axial hole, then flows out of the oil outlet after passing through the annular throttle plate. The other part flows through the two annular capillary grooves again and joins the oil flow that passed through the annular throttle plate and flows out of the outlet.

2. The method for controlling static oil film thickness based on internal feedback of a PM flow controller using the device of claim 1 is characterized in that: The hydraulic oil flowing out of the first PM flow controller is divided into two paths again, supplying oil to the upper static pressure oil chamber and the lower static pressure oil chamber respectively; the hydraulic oil flowing out of the second PM flow controller directly supplies oil to the radial oil chamber. When the oil chamber pressure is 0, due to the pre-pressure adjustment function of the PM flow controller, the internal film of the PM flow controller bends downward under the action of the upper chamber pre-pressure, the gap between the film and the throttle table is the smallest, the liquid resistance is the largest, and the flow rate flowing out through the oil outlet is the smallest at this time; as the oil chamber pressure increases, the film bends and deforms upward, causing the gap between the film and the throttle table to increase, the oil outlet liquid resistance to decrease, and the flow rate entering the oil chamber through the gap to increase, thereby reducing the change in the thickness of the hydrostatic turntable support oil film.

3. The method for controlling static oil film thickness with internal feedback based on a PM flow controller according to claim 2, characterized in that: After the three-way static pressure oil chamber is filled with hydraulic oil, when there is enough liquid pressure on the guide rail surface to balance the weight of the load, the support part is floated. At this time, the static pressure oil flows out of the oil chamber through the gap between the upper and lower guide rails and the radial oil sealing surface, and the pressure outside the cavity drops to zero. When the floating amount is greater than the surface unevenness of the upper and lower planes of the guide rail and the radial plane, pure liquid friction is formed.

4. The method for controlling static oil film thickness with internal feedback based on a PM flow controller according to claim 2, characterized in that: The hydraulic oil with constant pressure flows into the lower oil chamber after being throttled by the first throttle arranged in the upper oil chamber, and flows into the upper oil chamber after being throttled by the throttle arranged in the lower oil chamber, thereby forming an axially closed static pressure structure.

5. The method for controlling static oil film thickness with internal feedback based on a PM flow controller according to claim 2, characterized in that: When the guide rail is subjected to a downward force F, a gap change of Δh will occur. On the one hand, the oil chamber pressure of the upper static oil pad decreases due to the increase in the gap and the reduction in the liquid resistance of the oil sealing edge. At the same time, the throttle arranged in the oil chamber of the lower static oil pad for controlling the upper oil chamber increases with the increase in the liquid resistance of the throttling edge due to the decrease in the gap. The pressure lost due to the liquid resistance in the throttling will increase, making the pressure entering the oil chamber of the upper static oil pad smaller, which plays a feedback role. While through feedback control, the first PM flow controller assists in controlling the oil chamber pressures of the upper and lower static oil pads, and the two cooperate to achieve precise control.

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