A static pressure bearing system for CNC machine tools

Abstract

The present invention relates to a static pressure bearing system for numerically controlled machine tools, belonging to the technical field of fluid-supported bearings, and comprising: a bearing body, a piezoelectric throttling assembly, and a bearing seat; a plurality of oil chambers are evenly arranged along the circumference of the bearing body, each oil chamber is connected to a piezoelectric throttling assembly, and a plurality of piezoelectric throttling assemblies are arranged opposite to each other in pairs; each oil chamber is connected to an oil inlet, and the oil inlets of two oil chambers arranged opposite to each other are connected; the bearing body is arranged in the bearing seat, and a cooling channel is provided inside the bearing seat; an oil film is formed on the inner working surface of the bearing body, and a plurality of micro grooves are provided on the inner working surface of the bearing body for suppressing the thermal effect of the oil film. The present invention realizes rapid dynamic pressure regulation by directly connecting the piezoelectric throttling assembly to the oil chamber. At the same time, the oil film flow path is optimized by the micro grooves to suppress the thermal effect of the oil film; combined with the forced circulation heat dissipation of the cooling channel in the bearing seat, the influence of the thermal effect on the bearing accuracy is significantly suppressed.

Description

Technical Field

[0001] The invention belongs to the technical field of fluid support bearings, and in particular relates to a static pressure bearing system for a numerically controlled machine tool. Background Art

[0002] Hydrostatic bearings achieve contactless support by forming a hydrostatic oil or air film between the bearing and the shaft. They offer advantages such as strong load-bearing capacity, high precision, and long life. As core equipment in high-precision manufacturing, the stability and precision of the spindle system of CNC machine tools directly impact machining quality. Due to their non-contact, high-rigidity, and low-wear properties, hydrostatic bearings have become a key structural element in the spindle support of precision CNC machine tools. However, with the increasing demand for complex working conditions such as high-speed machining and heavy-duty cutting, traditional hydrostatic bearings face significant challenges in terms of load-bearing capacity and adaptability to extreme environments.

[0003] To maintain stable load-bearing capacity, hydrostatic bearings require a certain oil film stiffness. This necessitates a constant oil film thickness during operation, necessitating continuous oil pressure compensation. Existing oil pressure compensation structures primarily utilize multiple oil chambers, each independently adjusting the oil supply pressure via an external mechanical control valve to maintain a constant oil film thickness, thereby improving the load-bearing capacity of hydrostatic bearings. However, while oil pressure compensation structures using mechanical control valves can adjust the oil film thickness by adjusting the opening of the mechanical valve, significant response lag in the proportional control valve during spindle emergency stops or impact loads can result in a 50-100ms delay between actual proportional adjustment and execution. This in turn causes cutting chatter due to the transient drop in oil film stiffness. The intermediate piping connecting the throttle and hydrostatic bearing further increases system latency, compromising the rapid response performance of the hydraulic bearing system. Furthermore, thermal effects are an unavoidable issue for hydrostatic bearings. Especially during high-speed rotation, heat transfer from the viscous oil film can cause localized deformation of the bearing or spindle, severely impacting the bearing's accuracy.

[0004] Therefore, in order to solve the problems of dynamic adjustment response lag and thermal effect, it is necessary to propose a new type of hydrostatic bearing system for CNC machine tools. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a hydrostatic bearing system for CNC machine tools. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] The present invention provides a hydrostatic bearing system for a CNC machine tool, comprising: a bearing body, a piezoelectric throttling assembly and a bearing seat; wherein, a plurality of oil chambers are evenly arranged along the circumference in the bearing body, each of the oil chambers is connected to the piezoelectric throttling assembly, and the plurality of piezoelectric throttling assemblies are arranged opposite to each other in pairs; each of the oil chambers is connected to an oil inlet, and the oil inlets of the two oppositely arranged oil chambers are connected; the bearing body is arranged in the bearing seat, and a cooling channel is provided inside the bearing seat; an oil film is formed on the inner working surface of the bearing body, and a plurality of micro grooves are provided on the inner working surface of the bearing body for suppressing the thermal effect of the oil film.

[0007] In one embodiment of the present invention, each of the oil chambers includes a first oil chamber connected to the inner working surface of the bearing body through an oil outlet channel, and a second oil chamber surrounding the first oil chamber and connected to the first oil chamber; through the oil outlet channel, multiple oil chambers are connected to the inner working surface of the bearing body and form an oil film; each of the second oil chambers is connected to an oil inlet, and the two oppositely arranged oil inlets are connected through a first connecting groove arranged on the bearing body.

[0008] In one embodiment of the present invention, each of the piezoelectric throttling components includes a connecting seat, a piezoelectric ceramic, a push rod and an elastic oil chamber seat; the elastic oil chamber seat is connected to the bearing body, and the connecting seat is sealed and connected to the elastic oil chamber seat; the piezoelectric ceramic is connected to the first end of the push rod, the push rod is slidably connected to the connecting seat, and the second end of the push rod is in contact with the elastic oil chamber seat; the first side of the elastic oil chamber seat forms an annular space with the connecting seat and the second end of the push rod, the second side of the elastic oil chamber seat forms a flow-blocking space with the first oil chamber, and the second side of the elastic oil chamber seat is connected to the second oil chamber through a connecting hole.

[0009] In one embodiment of the present invention, both ends of the bearing body are sealed with end plates, and a second communicating groove corresponding to the first communicating groove is provided on one side of each end plate close to the bearing body. The first communicating groove and the second communicating groove are matched to form a communicating groove, and the two oppositely arranged oil inlets are connected through the communicating groove, and when the pressure of one of the second oil chambers changes, the pressure of the other second oil chamber connected through the communicating groove changes in the opposite direction.

[0010] In one embodiment of the present invention, the plurality of micro grooves are spaced apart and arranged in a plurality of rows along the axial direction of the inner working surface of the bearing body, wherein the depth of each of the micro grooves is greater than or equal to 0.02 mm.

[0011] In one embodiment of the present invention, the cooling channel is configured as a bionic tree-shaped microchannel, and the bionic tree-shaped microchannel is conformally fitted with the outer surface of the bearing body; coolant flows in the bionic tree-shaped microchannel, and the outlet and inlet of the coolant are respectively arranged at both ends of the bearing seat to form a cooling flow channel.

[0012] In one embodiment of the present invention, the bionic tree-shaped microchannel includes multiple levels of tree-shaped branch passages, the diameters of the multiple levels of the tree-shaped branch passages decrease successively, and the multiple levels of the tree-shaped branch passages have the same or different coolant inlets and outlets.

[0013] In one embodiment of the present invention, an angle is set between the extension direction of the multi-level tree-shaped branch passages and the axial direction of the CNC machine tool spindle connected to the bearing body, and the angle range of the angle is 15° to 30°.

[0014] In one embodiment of the present invention, a composite material layer is provided between the bearing seat and the outer surface of the bearing body, and the composite material layer includes multiple layers of stacked heat-conducting materials, and the thermal expansion coefficients of the multiple layers of heat-conducting materials increase or decrease sequentially from the outside to the inside.

[0015] In one embodiment of the present invention, the composite material layer includes a silicon carbide ceramic layer and an Invar layer stacked in sequence from the outside to the inside, and the silicon carbide ceramic layer and the Invar layer are pressed together by carbon fiber reinforced resin; wherein, the thickness of the silicon carbide ceramic layer ranges from 1.5 to 2.0 mm, and the thickness of the Invar layer ranges from 0.5 to 1.0 mm.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention's hydrostatic bearing system for CNC machine tools features a piezoelectric throttling assembly directly connected to the oil chamber, eliminating the response lag associated with traditional mechanical valves. This allows for rapid dynamic pressure regulation, ensuring that the oil film thickness matches load changes in real time. Micro-grooves optimize the oil film flow path, reducing viscous shear heat generation and suppressing the film's thermal effects. Combined with forced circulation heat dissipation in the cooling channels within the bearing seat, the impact of thermal effects on bearing accuracy is significantly suppressed. The present invention achieves high-precision, high-reliability hydrostatic support through the coordinated optimization of dynamic response and thermal management.

[0018] The present invention's hydrostatic bearing system for CNC machine tools utilizes a piezoelectric throttling assembly, replacing a mechanical regulating valve. The piezoelectric throttling assembly is directly mounted on the bearing body. The piezoelectric ceramic utilizes electro-deformation to control the size of the flow-blocking space in real time, reducing response delay and achieving millisecond-level dynamic compensation of oil film thickness and pressure. This facilitates handling sudden changes in oil film stiffness during spindle emergency stops or impact loads, improving the precision and stability of the hydrostatic bearing system. Furthermore, a connecting groove forms a pressure-reversal compensation mechanism between the first and second oil chambers. The dual-chamber linkage achieves pressure equalization, enabling automatic balancing of oil film pressure distribution under extreme loads and overcoming the stability bottleneck of traditional multi-chamber independent regulation. Furthermore, micro-grooves on the inner working surface of the bearing body suppress the thermal effects of the oil film, improving the oil film flow state, significantly reducing the intensity of viscous shear heating, and minimizing the impact of thermal deformation on bearing accuracy. The present invention improves the performance of the hydrostatic bearing system from three perspectives: dynamic response speed, pressure equalization stability, and thermal effect control. It can provide high-precision, high-reliability, contactless support for CNC machine tool spindles, thereby improving machining accuracy and extending service life.

[0019] The present invention forms a synergistic heat conduction control system through bionic tree-shaped microchannels and composite material layers. The bionic tree-shaped microchannels simulate plant root or leaf vein transport through multi-level tree-shaped branch pathways, optimize the coolant flow pattern through the tree-shaped branch pathways with decreasing diameters, and enhance the convective heat transfer efficiency in combination with the inclined channel direction, which can quickly extract the heat from the bearing body and eliminate local temperature rise hot spots. The composite material layer adopts a gradient laminated structure, which can achieve rapid lateral equalization of heat while filling the gap between the bearing seat and the bearing body, and can also suppress axial thermal deformation. Under the synergistic effect of the bionic tree-shaped microchannels and the composite material layer, the bionic tree-shaped microchannels achieve the effect of directional heat conduction to reduce the overall temperature rise, and the composite material layer provides a heat conduction path by filling the gap, thereby evenly distributing the heat. At the same time, the gradient thermal expansion coefficient difference offsets the deformation accumulation, reduces the deformation error caused by the thermal effect, and significantly improves the geometric accuracy and operating stability of the CNC machine tool hydrostatic bearing system under extreme working conditions.

[0020] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following preferred embodiments are specifically cited and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic structural diagram of a hydrostatic bearing system for a CNC machine tool provided by an embodiment of the present invention;

[0022] Figure 2A cross-sectional view of the structure of a hydrostatic bearing system for a CNC machine tool provided by an embodiment of the present invention;

[0023] Figure 3 A schematic structural diagram of a bearing body provided by an embodiment of the present invention;

[0024] Figure 4 A cross-sectional view of the structure of a bearing body provided by an embodiment of the present invention;

[0025] Figure 5 Schematic diagram of the expanded structure of the bionic tree-shaped microchannel provided by the embodiment of the invention;

[0026] Figure 6 Schematic diagram of the unilateral expansion structure of the bionic tree-shaped microchannel provided by an embodiment of the invention;

[0027] Figure 7 Schematic diagram of the structure of the composite material layer provided by an embodiment of the invention.

[0028] Figure markings: 100-bearing body; 110-oil chamber; 120-oil inlet; 130-connecting groove; 140-micro groove; 200-piezoelectric throttling assembly; 210-connecting seat; 220-piezoelectric ceramic; 230-push rod; 240-elastic oil chamber seat; 250-flow-blocking gasket; 260-locking seat; 270-flange cover; 280-pad; 290-adjusting locking screw; 300-bearing seat; 400-bionic tree-shaped microchannel; 500-composite material layer; 600-end plate. DETAILED DESCRIPTION

[0029] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description of a CNC machine tool hydrostatic bearing system proposed according to the present invention in conjunction with the accompanying drawings and specific implementation methods.

[0030] The aforementioned and other technical contents, features, and effects of the present invention are clearly presented in the following detailed description of the specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a deeper and more specific understanding of the technical means and effects adopted by the present invention to achieve the intended purpose can be obtained. However, the accompanying drawings are provided for reference and illustration purposes only and are not intended to limit the technical solutions of the present invention.

[0031] Example 1

[0032] With the development of precision CNC machine tools and the increasing demands of actual machining conditions, traditional hydrostatic bearings face severe challenges under high-speed, heavy-load conditions. CNC machine tool spindle speeds range from several thousand to tens of thousands of revolutions per minute, and they are used to cut hard alloy materials such as titanium. Under high-speed, heavy-load conditions, CNC machine tools are required to have high rigidity and load-bearing capacity. Therefore, higher requirements are placed on the load-bearing capacity of the oil film and the stiffness of the hydrostatic bearing. Failure to do so can easily lead to oil film rupture, bearing wear, or machine tool vibration. Factors affecting the load-bearing capacity of the oil film and the stiffness of the hydrostatic bearing are primarily: the response delay in the adjustment process of the mechanical control valve, which can easily cause cutting chatter due to sudden changes in the oil film stiffness during sudden stops or impact loads. Viscous heating of the oil film causes local temperature rise and thermal deformation, severely reducing the operating accuracy of the hydrostatic bearing. In view of this, the present invention provides a hydrostatic bearing system for CNC machine tools that balances dynamic response speed with thermal stability, ensures the precision and stability of the hydrostatic bearing system, and improves the performance of CNC machine tools.

[0033] like Figures 1 to 4 As shown, Figure 1 This is a schematic structural diagram of a hydrostatic bearing system for a CNC machine tool provided by an embodiment of the present invention; Figure 2 A cross-sectional view of the structure of a hydrostatic bearing system for a CNC machine tool provided by an embodiment of the present invention; Figure 3 A schematic structural diagram of a bearing body provided by an embodiment of the present invention; Figure 4 A structural cross-sectional view of a bearing body provided by an embodiment of the present invention.

[0034] In this embodiment, the hydrostatic bearing system of a CNC machine tool includes: a bearing body 100, a piezoelectric throttling component 200 and a bearing seat 300; wherein, a plurality of oil chambers 110 are evenly arranged along the circumference in the bearing body 100, each oil chamber 110 is connected to a piezoelectric throttling component 200, and the plurality of piezoelectric throttling components 200 are arranged opposite to each other in pairs; each oil chamber 110 is connected to an oil inlet 120, and the oil inlets 120 of the two oppositely arranged oil chambers 110 are connected; the bearing body 100 is arranged in the bearing seat 300, and a cooling channel is provided inside the bearing seat 300; an oil film is formed on the inner working surface of the bearing body 100, and a plurality of micro grooves 140 are provided on the inner working surface of the bearing body 100 to suppress the thermal effect of the oil film.

[0035] In an optional embodiment, each oil chamber 110 includes a first oil chamber connected to the inner working surface of the bearing body 100 through an oil outlet channel, and a second oil chamber surrounding the first oil chamber and connected to the first oil chamber; through the oil outlet channel, multiple oil chambers 110 are connected to the inner working surface of the bearing body 100 to form an oil film.

[0036] In the present invention's hydrostatic bearing system for CNC machine tools, the piezoelectric throttling assembly 200 is directly connected to the oil chamber 110, eliminating the response lag associated with traditional mechanical valves. This allows for rapid dynamic pressure regulation, ensuring that the oil film thickness matches load changes in real time. Micro-grooves 140 simultaneously optimize the oil film flow path, reducing viscous shear heat generation and suppressing the film's thermal effects. Combined with the forced circulation heat dissipation of the cooling channels within the bearing seat 300, the impact of thermal effects on bearing accuracy is significantly suppressed. The present invention achieves high-precision, high-reliability hydrostatic support through the coordinated optimization of dynamic response and thermal management.

[0037] In this embodiment, each piezoelectric throttling assembly 200 includes a connecting seat 210, a piezoelectric ceramic 220, a push rod 230 and an elastic oil chamber seat 240; the elastic oil chamber seat 240 is connected to the bearing body 100, and the connecting seat 210 is sealed with the elastic oil chamber seat 240; the piezoelectric ceramic 220 is connected to the first end of the push rod 230, the push rod 230 is slidingly connected to the connecting seat 210, and the second end of the push rod 230 is in contact with the elastic oil chamber seat 240; the first side of the elastic oil chamber seat 240 forms an annular space with the connecting seat 210 and the second end of the push rod 230, the second side of the elastic oil chamber seat 240 forms a flow-blocking space with the first oil chamber, and the second side of the elastic oil chamber seat 240 is connected to the second oil chamber through a connecting hole.

[0038] Exemplarily, the first side of the elastic oil chamber seat 240 and the connecting seat 210 are sealed by an O-ring.

[0039] Exemplarily, the push rod 230 and the connecting seat 210 are sealed by an annular sealing ring.

[0040] Furthermore, a flow-blocking gasket 250 is disposed between the second side of the elastic oil chamber seat 240 and the first oil chamber. The flow-blocking gasket 250 is a flexible metal film that forms a flow-blocking space with the first oil chamber. The flow-blocking gasket 250 stabilizes pressure fluctuations and provides more precise control over the flow-blocking pressure. For example, the flow-blocking gasket 250 can be replaced with different thicknesses and stiffnesses to pre-adjust the size of the flow-blocking space.

[0041] For example, the baffle 250 may be made of copper foil or aluminum foil.

[0042] like Figure 2As shown, in an optional embodiment, the piezoelectric throttling assembly 200 also includes: a locking seat 260, a flange cover 270, a gasket 280 and an adjusting locking screw 290, wherein the bearing body 100 is arranged in the bearing seat 300, the connecting seat 210 is threadedly connected to the bearing seat 300, and the lower end of the locking seat 260 is threadedly connected to the connecting seat 210; the upper end of the locking seat 260 is provided with a cavity, and the flange cover 270 is detachably connected to the upper end of the locking seat 260; the piezoelectric ceramic 220 is partially located in the cavity, the adjusting locking screw 290 passes through the flange cover 270, and presses the piezoelectric ceramic 220 through the gasket 280; the locking seat 260 is also provided with a through hole, and the connecting push rod 230 is slidably connected to the through hole and passes through the connecting seat 210.

[0043] For example, the flange cover 270 is provided with a wire hole, and the wires of the piezoelectric ceramic 220 can be electrically connected to the outside through the wire hole.

[0044] For example, the piezoelectric ceramic 220 is compressed along its expansion and contraction direction by the spacer 280 and the adjusting locking screw 290 , and the initial position of the piezoelectric ceramic 220 can be adjusted by rotating the adjusting locking screw 290 .

[0045] It is worth noting that existing throttles are often connected to the bearing body 100 via an intermediate pipeline, which increases system latency and degrades rapid response performance. Therefore, the CNC machine tool hydrostatic bearing system of this embodiment installs the piezoelectric throttle assembly 200 directly on the bearing body 100. The lack of an intermediate pipeline shortens the signal transmission path, eliminates intermediate link latency, and achieves millisecond-level response. This also prevents sudden changes in oil film stiffness during spindle emergency stops or impact loads. Furthermore, the elimination of the intermediate pipeline results in a more compact structure and reduces leakage points, further improving system reliability.

[0046] For example, the piezoelectric ceramic 220 can be made of lead zirconate titanate piezoelectric ceramic or barium titanate piezoelectric ceramic, and is composed of multiple piezoelectric ceramic sheets pressed together. A bias voltage is preloaded on the piezoelectric ceramic 220. By preloading the bias voltage on each piezoelectric ceramic sheet, the hysteresis effect of the piezoelectric ceramic sheet can be eliminated, and the initial operating point of the piezoelectric ceramic sheet can be placed in the linear range, thereby maintaining a linear relationship between the expansion and contraction deformation of the piezoelectric ceramic sheet and the voltage amplitude. Furthermore, by preloading the bias voltage, the piezoelectric ceramic sheet can be pre-compressed, thereby improving its dynamic response capability by fixing the initial displacement.

[0047] Furthermore, multiple piezoelectric ceramic sheets can be stacked along their polarization direction (thickness direction), and the electrodes between the sheets are connected with conductive glue or metal foil to ensure that the multiple piezoelectric ceramic sheets have the same polarization direction, and the direction of electric field application is also consistent with the polarization direction. Through the multiple piezoelectric ceramic sheets, linear superposition of output displacement can be achieved, and the driving force and carrying capacity of the piezoelectric ceramic 220 can also be improved.

[0048] Furthermore, a non-uniform electric field can be applied to multiple stacked piezoelectric ceramic sheets, such that the electric field strength of the front piezoelectric ceramic sheet is higher than that of the rear piezoelectric ceramic sheet, thereby compensating for the end displacement hysteresis effect and improving the displacement linearity.

[0049] It is understandable that each piezoelectric ceramic 220 is independently electrically connected to an external control system, and the expansion and contraction of each piezoelectric ceramic 220 can be independently adjusted, such as by adjusting the expansion and contraction of the piezoelectric ceramic 220 through voltage control according to the size and direction of the CNC machine spindle load, so that the pressure in the oil chamber 110 matches the size and direction of the load. In other words, the CNC machine tool hydrostatic bearing system of this embodiment can generate a resultant force in the opposite direction of the load change through voltage control when the CNC machine tool spindle load changes, thereby compensating for the offset of the CNC machine tool spindle and ensuring the position accuracy of the CNC machine tool spindle. It can also timely reduce the impact of the increase in load on the oil film thickness, ensure a constant oil film thickness, and ensure that the hydrostatic bearing is in normal working condition. Since the control of the piezoelectric ceramic 220 is not the focus of the present invention, it will not be described in detail.

[0050] The principle is that when voltage is applied, the piezoelectric ceramic 220 deforms (expands) due to the reverse voltage effect, driving the push rod 230 to push the elastic oil chamber seat 240, thereby changing the size of the flow-blocking space, and then changing the resistance of the oil flowing through the flow-blocking space, causing the pressure of the oil chamber 110 on this side to change, and ultimately changing the thickness and pressure of the oil film. It can be understood that a stable oil film thickness balances the pressure of the oil chamber 110 with the pressure of the CNC machine tool spindle on the hydrostatic bearing. When the load from the CNC machine tool spindle increases, the radial offset of the CNC machine tool spindle will increase, which will seriously affect the spindle accuracy for high-precision CNC machine tools. Even due to uneven oil film thickness, heat will increase, and dry friction will occur locally. Therefore, it is particularly important to ensure a stable oil film thickness. The thickness and pressure of the oil film are ultimately reflected in the oil film stiffness, and the oil film stiffness is closely related to the oil film thickness. Changes in the oil film thickness will lead to changes in the oil film stiffness. Therefore, oil pressure compensation is required to maintain the constant oil film thickness, that is, to maintain the oil film's constant load-bearing capacity.

[0051] In addition, the expansion and contraction deformation of the piezoelectric ceramic 220 can be controlled by the voltage amplitude, thereby achieving precise adjustment of the pressure in the oil chamber 110. For example, when the voltage acting on the piezoelectric ceramic 220 increases, the piezoelectric ceramic 220 extends, the flow resistance space decreases, and ultimately the pressure in the oil chamber 110 decreases; or when the voltage acting on the piezoelectric ceramic 220 decreases, the piezoelectric ceramic 220 contracts, the flow resistance space increases, and ultimately the pressure in the oil chamber 110 increases.

[0052] like Figure 3 and Figure 4As shown, in an optional embodiment, each second oil chamber is connected to an oil inlet 120 , and the two oppositely arranged oil inlets 120 are connected through a first connecting groove provided on the bearing body 100 .

[0053] Furthermore, both ends of the bearing body 100 are sealed with end plates 600, and a second connecting groove corresponding to the first connecting groove is provided on the side of each end plate 600 close to the bearing body 100. The first connecting groove and the second connecting groove are matched to form a connecting groove 130, and the two oppositely arranged oil inlets are connected through the connecting groove 130, and when the pressure of one of the second oil chambers changes, the pressure of the other second oil chamber connected through the connecting groove 130 changes in the opposite direction.

[0054] For example, the end plate 600 and the bearing body 100 may be detachably connected by screws.

[0055] Illustratively, the second communicating groove of the end plate 600 is aligned with the first communicating groove of the bearing body 100 in the axial direction, and a through communicating groove 130 is formed through a sealing connection.

[0056] Furthermore, a retaining ring may be provided between the end plate 600 and the bearing body 100 , as well as between the end plate 600 and the spindle of the CNC machine tool, to serve as an oil seal.

[0057] The principle is that the oil inlets 120 of the two oppositely positioned second oil chambers are directly connected via a connecting groove 130, forming a pressure transmission path between the two pairs of piezoelectric throttling assemblies 200 and the corresponding oil chambers 110, creating a quasi-communicating vessel structure. When the pressure in one oil chamber 110 increases, the pressure in the other oil chamber 110 decreases until equilibrium is reached. When the CNC machine tool spindle is subjected to external force, the spindle will deflect, and the pressure in each oil chamber 110 will change accordingly. This is reflected in the oil film. When subjected to an impact load or the spindle stops suddenly, the oil film thickness on one side changes. The pressure transmission path compensates for the oil film on that side, avoiding the instantaneous attenuation of the oil film stiffness caused by a sudden drop in pressure in a single oil chamber. In other words, through pressure linkage compensation, the dynamic balance of the oil film pressure is ensured, the adjustment capability under sudden changes is enhanced, and the impact resistance and stability of the hydrostatic bearing system are improved. Moreover, because this dynamic compensation adjustment method does not require a complex valve control link, it can meet the needs of dynamic adjustment.

[0058] In an optional embodiment, oil inlet 120 may be connected to an external oil control system, including an oil control valve, an inlet pump, and an oil tank, with the oil control valve, the inlet pump, and the oil tank connected via an oil pipeline. Exemplarily, the oil control valve includes one or more of a reversing valve, a relief valve, and a check valve. Each of the multiple oil control valves is connected to the oil pipeline, such as the relief valve connected to the oil tank and the check valve connected to the inlet pump. The relief valve and the check valve can be switched between via a reversing valve. It will be appreciated that the external oil control system is merely an example, and reference may be made to related prior art configurations, so this description will not be repeated.

[0059] It is understandable that the piezoelectric throttling component 200 can be configured as follows Figure 2 The illustrated two-by-two symmetrical structure provides a total of four sets of piezoelectric throttling assemblies 200. Alternatively, six, eight, or even more sets may be provided based on actual needs. Furthermore, the length of the hydrostatic bearing body 100 may be adjusted based on the spindle diameter of the CNC machine tool and the actual load, and multiple sets of piezoelectric throttling assemblies 200 may be provided at intervals along the axial direction. This is not a limitation of the present invention.

[0060] In this embodiment, a plurality of micro grooves 140 are provided on the inner working surface of the bearing body 100 to suppress the thermal effect of the oil film.

[0061] For example, the micro grooves 140 may be arranged in a form of multiple groups of relatively short widths and spaced apart from each other, so as to form flow resistance in a local area of ​​the oil film.

[0062] For example, the depth of each micro groove 140 is greater than or equal to 0.02 mm. In combination with actual processing scenarios, it is found that when the depth is greater than 0.02 mm, the micro groove 140 not only has a good effect of suppressing the thermal effect of the oil film, but also has good processing accuracy and consistency.

[0063] Specifically, the depth of the micro grooves 140 can be set to 0.02 mm, the width to 0.15 mm, and the spacing to 0.4 mm, which has a good effect of suppressing the heat generation rate of the oil film.

[0064] The principle is that the micro-grooves 140 allow the oil to be retained within the micro-grooves 140 while also reducing the flow field velocity of the oil. This means that by changing the oil film flow field morphology and flow velocity distribution, the thermal effect of the oil film is reduced, thereby suppressing the generation of heat in the oil film. Specifically, the micro-grooves 140 form a concave and convex structure on the inner working surface of the bearing body 100. This structure increases local fluid resistance, reduces the average flow velocity of the oil film, and reduces frictional heat generated by the viscous shear effect. In other words, the micro-grooves 140 change the flow path of the oil film, increasing its flow resistance and reducing its flow velocity, thereby reducing the heat generated by the viscous shear effect.

[0065] Furthermore, the spacing of the micro-grooves 140 can be set as sparsely as possible. This is because when the micro-grooves 140 are too closely spaced, they significantly affect the flow of the oil film, thereby affecting its performance. Conversely, when the micro-grooves 140 are sufficiently sparsely spaced, the oil film on the working surface can be considered smooth overall, and thus any local effects can be ignored. In this case, the adverse effects of the micro-grooves 140 on the oil film's heat generation rate can be ignored overall, while the local effects of the micro-grooves 140 on suppressing the oil film's thermal effects can be retained.

[0066] Understandably, Figure 4 The above is only an example. Multiple micro grooves 140 can also be arranged in multiple rows along the axial direction of the inner working surface of the bearing body 100, and the length directions of the multiple micro grooves 140 are distributed along the circumferential direction of the inner working surface of the bearing body 100.

[0067] It is worth noting that the piezoelectric throttling component 200 is directly set on the bearing body 100. Since the oil film pressure adjustment time is shortened, the oil film stiffness is maintained, and the synergistic effect with the micro-grooves 140 reduces the frictional heat generated by the viscous shear effect, further improving the effect of reducing the thermal effect of the oil film.

[0068] The working process of the CNC machine tool hydrostatic bearing system of this embodiment is as follows:

[0069] When the CNC machine tool's spindle starts, the external oil supply system injects high-pressure oil into the bearing body 100 through the oil inlet 120. The oil flows from each of the second oil chambers through the connecting holes into the annular space and overflows from the inner working surface of the bearing body 100 along the oil outlet channel connected to the first oil chamber, forming a uniform oil film. At this time, the piezoelectric throttling assembly 200 responds in real time to the CNC machine tool's spindle load changes: When the spindle load changes cause the oil film thickness in a certain area to increase, voltage is applied to the corresponding piezoelectric ceramic 220, causing it to extend, pushing the push rod 230 and deforming the elastic oil chamber seat 240. This reduces the flow resistance, increasing the resistance to oil flow through that space, thereby reducing the pressure in the oil chamber 110 on that side and the oil film thickness. Conversely, when the oil film is too thin, reducing the voltage causes the piezoelectric ceramic 220 to contract, expanding the flow resistance, reducing the resistance to oil flow through that space, and increasing the pressure in the oil chamber 110 on that side and the oil film thickness.

[0070] During this process, the voltage is coordinated and adjusted through the hydraulic pressure of the relatively arranged piezoelectric throttling components 200, and the pressure reverse linkage is realized in conjunction with the connecting groove 130. For example, when the pressure in the oil chamber 120 on one side increases, the pressure balance on the opposite side is automatically adjusted through the connecting groove 130, that is, the pressure on one side is automatically balanced to the opposite side, forming a dynamic balance of the oil film pressure in the entire region, thereby pushing the CNC machine tool spindle to maintain a stable axial position.

[0071] The present invention's hydrostatic bearing system for CNC machine tools utilizes a piezoelectric throttling assembly 200, replacing a mechanical regulating valve. The piezoelectric throttling assembly 200 is directly mounted on the bearing body 100. The piezoelectric ceramic 220 utilizes electro-deformation to control the size of the flow-blocking space in real time, reducing response delay and achieving millisecond-level dynamic compensation of oil film thickness and pressure. This facilitates coping with sudden changes in oil film stiffness during spindle emergency stops or impact loads, thereby improving the precision and stability of the hydrostatic bearing system. Furthermore, the first and second oil chambers form a pressure reversal compensation mechanism via a connecting groove 130. Pressure balancing is achieved through a dual-chamber linkage structure, enabling automatic balancing of oil film pressure distribution under extreme loads and overcoming the stability bottleneck of traditional multi-chamber independent regulation. Furthermore, micro-grooves 140 disposed on the inner working surface of the bearing body 100 suppress the thermal effects of the oil film, improving the oil film flow state and significantly reducing the intensity of viscous shear heating, thereby reducing the impact of thermal deformation on bearing precision. The present invention improves the performance of the hydrostatic bearing system from three perspectives: dynamic response speed, pressure balance stability, and thermal effect control. It can provide high-precision, high-reliability contactless support for the spindle of a CNC machine tool, which is beneficial to improving machining accuracy and extending service life.

[0072] In order to further reduce the influence of thermal effect, a bionic tree-shaped microchannel 400 is provided inside the bearing seat 300. Figures 1 to 6 As shown, Figure 5 Schematic diagram of the expanded structure of the bionic tree-shaped microchannel provided by the embodiment of the invention; Figure 6 Schematic diagram of the unilateral expansion structure of the bionic tree-shaped microchannel provided in an embodiment of the invention.

[0073] In this embodiment, a bionic tree-shaped microchannel 400 is provided inside the bearing seat 300, and the bionic tree-shaped microchannel 400 is conformally fitted with the outer surface of the bearing body 100; coolant flows in the bionic tree-shaped microchannel 400, and the outlet and inlet of the coolant are respectively arranged at both ends of the bearing seat 300 (not shown in the figure) to form a cooling flow channel, thereby reducing the flow resistance through the fractal structure.

[0074] In an optional embodiment, the bionic tree-shaped microchannel 400 includes a multi-level tree-shaped branch passage, the diameter of each level of the tree-shaped branch passage decreases successively, and the multi-level tree-shaped branch passage can have the same or different coolant inlets and outlets, that is, the entire bionic tree-shaped microchannel 400 can have a unified coolant inlet and outlet, or separate coolant inlets and outlets can be set for some of the tree-shaped branch passages.

[0075] For example, the coolant may be a water-based or oil-based coolant.

[0076] For example, the bionic tree-shaped microchannel 400 can be connected to an external coolant control system, including a coolant control valve, a liquid inlet pump, and a coolant storage tank, which are connected by pipelines. It will be appreciated that the external coolant control system is merely an example, and reference can be made to related prior art configurations, so this description will not be repeated here.

[0077] For example, the projection lengths L of the multi-level tree-shaped branch paths can be set to be equal or gradually reduced, and the bifurcation angles θ of the multi-level tree-shaped branch paths can be set to be equal, and the bifurcation angles θ range from 20° to 75°.

[0078] Exemplarily, the bionic tree-shaped microchannel 400 includes at least three levels of tree-like branch passages, wherein the diameter range of the first-level tree-like branch passage is 1 to 2 mm, the diameter range of the second-level tree-like branch passage is 0.8 to 1 mm, and the diameter range of the third-level tree-like branch passage is 0.5 to 0.8 mm. The main passage connecting the first-level tree-like branch passage can be set according to the cooling requirements and flow rate to meet the common cooling liquid requirements of each level of tree branches.

[0079] It is understandable that the bionic tree-shaped microchannel 400 can be processed by micro-milling and laser composite processing, such as first rough milling the contour, then scanning along the tree-like branch path by laser processing, and finally ensuring the surface accuracy by grinding; or after laser selective melting additive manufacturing, secondary finishing by laser is performed to ensure processing accuracy, but the present invention is not limited to this.

[0080] It is worth noting that the bionic tree-shaped microchannel 400 has a multi-level bifurcated structure that mimics a high-efficiency and low-resistance material transport network, which conforms to fractal characteristics and minimizes the transfer flow resistance compared to the straight cooling channel structure.

[0081] Furthermore, an included angle is provided between the extension direction of the multi-stage tree-shaped branch passages and the axial direction of the main shaft to which the bearing body 100 is connected, and the included angle ranges from 15° to 30°.

[0082] The principle is that by setting the extension direction of the multi-level tree-shaped branch passage to an inclined angle, the inclined angle is used to guide the coolant to produce a progressive flow, forming a synergistic effect with the rotation direction of the CNC machine tool spindle, optimizing the coolant turbulence effect, and improving the heat exchange efficiency. When the coolant flows along the inclined branch, the centrifugal force can also enhance the radial penetration ability of the fluid, so that the coolant covers the outer surface of the bearing body 100 more evenly, thereby improving the flow capacity of the coolant. In addition, the inclined setting of the multi-level tree-shaped branch passage can also reduce the manufacturing difficulty, and is more suitable for arc-shaped surfaces, ensuring the consistency of the inclination angle of the multi-level tree-shaped branch passage (especially the lower branch).

[0083] It is worth noting that the bionic tree-shaped microchannel 400 has a compact structure and has the advantages of high heat transfer coefficient, low flow resistance, and excellent temperature uniformity. It can efficiently export the heat of the bearing body 100, reduce the overall radial size of the shaft hydrostatic bearing system, and adapt to the compact machine tool layout. It significantly improves the dynamic stiffness and thermal stability of the hydrostatic bearing system, and effectively responds to oil film disturbances and temperature rise deformations during high-speed reversing and continuous processing, ensuring high-precision processing reliability.

[0084] like Figure 7 As shown, Figure 7 Schematic diagram of the structure of the composite material layer provided by an embodiment of the invention.

[0085] Furthermore, a composite material layer 500 is provided between the bearing seat 300 and the outer surface of the bearing body 100 . The composite material layer 500 includes multiple layers of thermally conductive materials stacked together, and the thermal expansion coefficients of the multiple layers of thermally conductive materials increase or decrease sequentially from the outside to the inside.

[0086] For example, the composite material layer 500 includes a silicon carbide ceramic layer and an invar layer stacked in sequence from the outside to the inside, and the silicon carbide ceramic layer and the invar layer are pressed together by carbon fiber reinforced resin; that is, the outermost layer is the silicon carbide ceramic layer, and the innermost layer is the invar layer, and the two are pressed together by carbon fiber reinforced resin; wherein the silicon carbide ceramic layer (thermal expansion coefficient 4.5×10 -6 / ℃) is subjected to rapid heat conduction treatment outside, and the Invar layer (thermal expansion coefficient 1.2×10 -6 / ℃) to suppress deformation and offset thermal stress through gradient difference.

[0087] Preferably, the thickness of the silicon carbide ceramic layer is in the range of 1.5 to 2.0 mm, and the thickness of the invar layer is in the range of 0.5 to 1.0 mm.

[0088] For example, by fine-machining the inner surface of the bearing seat 300 and filling the gaps with the composite material layer 500 , the tree-like branch passages can be set to an open groove surface structure, wherein the depth of each level of the tree-like branch passages can range from 1 to 1.5 mm.

[0089] The hydrostatic bearing system for CNC machine tools in this embodiment operates as follows: When the CNC machine tool spindle is operating at high speed, the oil film thermal effect is primarily suppressed through two pathways: First, the inner working surface of the bearing body 100 uses micro-grooves 140 to guide the oil film into laminar flow, reducing the viscous frictional thermal effect. Second, coolant within the bionic tree-shaped microchannels 400 flows along multiple branching pathways at an angle of 15° to 30° against the inner wall of the bearing seat 300. This tree-shaped branching pathway structure enhances convective heat transfer and rapidly dissipates heat. Simultaneously, the composite material layer 500, composed of silicon carbide ceramic layers and invar layers, homogenizes the outer wall temperature field of the bearing body 100 through the high thermal conductivity of silicon carbide, while the invar layer offsets axial thermal deformation with its low thermal expansion coefficient. The stress buffering of carbon fiber reinforced resin achieves thermal decoupling between the two, reducing thermal deformation of the working surface.

[0090] The present invention forms a synergistic heat conduction control system using bionic tree-shaped microchannels 400 and composite material layers 500. The bionic tree-shaped microchannels 400 simulate plant root or leaf vein transport through multi-level tree-shaped branching pathways. The decreasing diameter of the tree-shaped branching pathways optimizes the coolant flow pattern, and the tilted channel orientation enhances convective heat transfer efficiency, enabling rapid heat removal from the bearing body 100 and eliminating localized temperature rise hotspots. The composite material layer 500 utilizes a gradient laminated structure, filling the gap between the bearing seat 100 and the bearing body 300 while achieving rapid lateral heat equalization and suppressing axial thermal deformation. Through the synergistic effect of the bionic tree-shaped microchannels 400 and composite material layer 500, the bionic tree-shaped microchannels 400 achieve directional heat conduction to reduce overall temperature rise, while the composite material layer 500 provides a heat conduction path by filling the gap, thereby evenly distributing heat. The gradient thermal expansion coefficient difference also offsets deformation accumulation, reducing deformation errors caused by thermal effects and significantly improving the geometric accuracy and operational stability of the CNC machine tool hydrostatic bearing system under extreme operating conditions.

[0091] It should be noted that, in this document, relational terms such as first and second are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not explicitly listed. Without further limitation, an element defined by the phrase "comprising a..." does not preclude the presence of additional identical elements in the article or device comprising the element. Terms such as "connected" or "connected" are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. References to orientations or positional relationships, such as "upper," "lower," "left," and "right," are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate description and simplify the description of the present invention. They do not indicate or imply that the device or element referred to must have, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention.

[0092] The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention cannot be considered to be limited to these descriptions. For those skilled in the art of the present invention, simple deductions or substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the scope of protection of the present invention.

Claims

1. A static pressure bearing system for a CNC machine tool, characterized in that: include: A bearing body, a piezoelectric throttling assembly, and a bearing seat; wherein, the bearing body is uniformly provided with a plurality of oil chambers along the circumferential direction, each of the oil chambers is connected to the piezoelectric throttling assembly, and the plurality of piezoelectric throttling assemblies are arranged opposite each other in pairs; each of the oil chambers is connected to an oil inlet, and the oil inlets of two oppositely arranged oil chambers are connected; the bearing body is arranged in the bearing seat, and a cooling channel is provided inside the bearing seat; an oil film is formed on the inner working surface of the bearing body, and a plurality of micro grooves are provided on the inner working surface of the bearing body to suppress the thermal effect of the oil film; The cooling channel is configured as a bionic tree-shaped microchannel, and the bionic tree-shaped microchannel is conformally fitted with the outer surface of the bearing body; a coolant flows in the bionic tree-shaped microchannel, and the outlet and inlet of the coolant are respectively provided at both ends of the bearing seat to form a cooling flow channel; the bionic tree-shaped microchannel includes a multi-stage tree-shaped branch passage, the diameter of the multi-stage tree-shaped branch passage decreases successively, and the multi-stage tree-shaped branch passage has the same or different coolant inlet and outlet; A composite material layer is provided between the bearing seat and the outer surface of the bearing body, wherein the composite material layer includes multiple layers of heat-conducting materials stacked together, and the thermal expansion coefficients of the multiple layers of heat-conducting materials increase or decrease from the outside to the inside; the composite material layer includes a silicon carbide ceramic layer and an Invar layer stacked together from the outside to the inside, and the silicon carbide ceramic layer and the Invar layer are pressed together by carbon fiber reinforced resin; wherein the thickness of the silicon carbide ceramic layer ranges from 1.5 to 2.0 mm, and the thickness of the Invar layer ranges from 0.5 to 1.0 mm.

2. The hydrostatic bearing system for CNC machine tools according to claim 1, characterized in that: Each of the oil chambers includes a first oil chamber connected to the inner working surface of the bearing body through an oil outlet channel, and a second oil chamber surrounding the first oil chamber and connected to the first oil chamber; through the oil outlet channel, multiple oil chambers are connected to the inner working surface of the bearing body and form an oil film; each of the second oil chambers is connected to an oil inlet, and the two oppositely arranged oil inlets are connected through a first connecting groove arranged on the bearing body.

3. The hydrostatic bearing system for CNC machine tools according to claim 2, characterized in that: Each of the piezoelectric throttling components includes a connecting seat, a piezoelectric ceramic, a push rod and an elastic oil chamber seat; the elastic oil chamber seat is connected to the bearing body, and the connecting seat is sealed with the elastic oil chamber seat; the piezoelectric ceramic is connected to the first end of the push rod, the push rod is slidably connected to the connecting seat, and the second end of the push rod is in contact with the elastic oil chamber seat; the first side of the elastic oil chamber seat forms an annular space with the connecting seat and the second end of the push rod, the second side of the elastic oil chamber seat forms a flow-blocking space with the first oil chamber, and the second side of the elastic oil chamber seat is connected with the second oil chamber through a connecting hole.

4. The static pressure bearing system for CNC machine tools according to claim 3, characterized in that: Both ends of the bearing body are sealed with end plates, and a second communicating groove corresponding to the first communicating groove is provided on one side of each end plate close to the bearing body. The first communicating groove and the second communicating groove are matched to form a communicating groove, and the two oppositely arranged oil inlets are connected through the communicating groove, and when the pressure of one of the second oil chambers changes, the pressure of the other second oil chamber connected through the communicating groove changes in the opposite direction.

5. The static pressure bearing system for CNC machine tools according to claim 1, characterized in that: The plurality of micro grooves are arranged in a plurality of rows along the axial direction of the inner working surface of the bearing body, wherein the depth of each of the micro grooves is greater than or equal to 0.02 mm.

6. The hydrostatic bearing system for CNC machine tools according to claim 1, characterized in that: An included angle is provided between the extension direction of the multi-level tree-shaped branch passages and the axial direction of the CNC machine tool spindle to which the bearing body is connected, and the included angle ranges from 15° to 30°.

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