Numerically-controlled machine tool hydrostatic bearing system

Abstract

The invention relates to a hydrostatic bearing system of a numerical control machine tool, which belongs to the technical field of fluid supporting bearings and comprises a bearing body, a piezoelectric throttling assembly and a bearing seat. A plurality of oil cavities are evenly formed in the bearing body in the circumferential direction, each oil cavity is connected with a piezoelectric throttling assembly, and the piezoelectric throttling assemblies are oppositely arranged in pairs. Each oil cavity is connected with an oil inlet, and the oil inlets of the two oppositely-arranged oil cavities communicate with each other. The bearing body is arranged in the bearing seat, and a cooling channel is arranged in the bearing seat; an oil film is formed on the inner working surface of the bearing body, and a plurality of micro grooves are formed in the inner working surface of the bearing body and used for restraining the heat effect of the oil film. Dynamic pressure rapid adjustment is achieved through direct connection of the piezoelectric throttling assembly and the oil cavity. Meanwhile, the oil film flowing path is optimized through the micro grooves, and the oil film heat effect is restrained; and in combination with forced circulation heat dissipation of a cooling channel in the bearing seat, the influence of the heat effect on the bearing precision is remarkably inhibited.

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 can achieve contactless support by forming a layer of hydrostatic oil film or air film between the bearing and the shaft. They have the advantages of strong load-bearing capacity, high precision, and long life. As the core equipment in the field of high-precision manufacturing, the stability and precision of the spindle system of CNC machine tools directly affect the processing quality. Hydrostatic bearings have also become the key structure of the spindle support of precision CNC machine tools due to their non-contact, high rigidity, and low wear characteristics. With the increasing demand for complex working conditions such as high-speed processing and heavy-load cutting, traditional hydrostatic bearings face severe challenges in terms of load-bearing capacity and adaptability to extreme environments.

[0003] In order to maintain a stable load-bearing capacity, the hydrostatic bearing needs to maintain a certain oil film stiffness, which requires the oil film thickness to be kept constant during operation, so the oil pressure needs to be continuously compensated. The existing oil pressure compensation structure mainly sets multiple oil chambers and independently adjusts the oil supply pressure of each oil chamber through an external mechanical regulating valve to maintain a constant oil film thickness, thereby improving the load-bearing capacity of the hydrostatic bearing. However, the oil pressure compensation structure using a mechanical regulating valve can adjust the oil film thickness by adjusting the opening of the mechanical valve. However, when the spindle is stopped suddenly or the impact load is applied, due to the obvious response lag in the adjustment process of the proportional control valve, there is a delay of 50 to 100 ms between the actual proportional adjustment and the execution, which in turn causes the cutting vibration caused by the instantaneous decrease in the oil film stiffness. The intermediate pipeline connecting the throttle and the hydrostatic bearing will further increase the system delay and deteriorate the rapid response performance of the hydraulic bearing system. In addition, thermal effect is also an unavoidable problem for hydrostatic bearings. Especially in the process of high-speed rotation, the heat conduction of the viscous oil film will cause local deformation of the bearing or spindle, which seriously affects the accuracy of the hydrostatic bearing.

[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 static pressure bearing system for a CNC machine tool. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] The present invention provides a static pressure bearing system for a numerically controlled machine tool, comprising: a bearing body, a piezoelectric throttling component and a bearing seat; wherein, a plurality of oil chambers are evenly arranged in the circumferential direction in the bearing body, each of the oil chambers is connected to the piezoelectric throttling component, and the plurality of piezoelectric throttling components 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 arranged 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 arranged on the inner working surface of the bearing body to suppress 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 connecting groove corresponding to the first connecting groove is provided on one side of each end plate close to the bearing body, and the first connecting groove and the second connecting groove are matched to form a connecting groove, and the two oppositely arranged oil inlets are connected through the connecting groove, 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 changes in the opposite direction.

[0010] In one embodiment of the present invention, a plurality of the 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.

[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; a 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 heat-conducting materials stacked together, 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] In the CNC machine tool hydrostatic bearing system of the present invention, the piezoelectric throttling component is directly connected to the oil chamber, eliminating the response lag problem of traditional mechanical valves, realizing rapid dynamic pressure regulation, and ensuring that the oil film thickness matches the load changes in real time. At the same time, the oil film flow path is optimized by micro-grooves to reduce the viscous shear heat generation of the oil film and 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 thermal effects on the bearing accuracy is significantly suppressed. The present invention realizes high-precision and high-reliability hydrostatic support by synergistically optimizing dynamic response and thermal management.

[0018] The static pressure bearing system of the numerical control machine tool of the present invention adopts a piezoelectric throttling component to replace the mechanical regulating valve of the transmission, and the piezoelectric throttling component is directly arranged on the bearing body. The piezoelectric ceramic uses electro-induced deformation to adjust the size of the flow resistance space in real time, which reduces the response delay and realizes the millisecond-level dynamic compensation of the oil film thickness and pressure, which is conducive to coping with the sudden change of the oil film stiffness when the spindle stops suddenly or the impact load acts, and improves the precision and stability of the static pressure bearing system. At the same time, the first oil chamber and the second oil chamber form a pressure reverse compensation mechanism through the connecting groove, and the pressure balance is achieved through the double oil chamber linkage structure, which can automatically balance the oil film pressure distribution under extreme loads, breaking through the stability bottleneck of the traditional multi-oil chamber independent adjustment. Then, the micro grooves arranged on the inner working surface of the bearing body are used to suppress the thermal effect of the oil film, which improves the flow state of the oil film, significantly reduces the effect of the viscous shear heat generation intensity, and reduces the influence of thermal deformation on the bearing precision. The present invention improves the performance of the static pressure bearing system from the three perspectives of dynamic response speed, pressure balance stability, and thermal effect control, and can provide high-precision and high-reliability contactless support for the spindle of the numerical control machine tool, which is conducive to improving the processing accuracy and extending the 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 passages, optimize the coolant flow state through the tree-shaped branch passages with decreasing diameters, and enhance the convective heat transfer efficiency in combination with the inclined channel direction, which can quickly extract the heat of the bearing body and eliminate local temperature rise hot spots. The composite material layer adopts a gradient laminated structure, which can achieve rapid lateral homogenization 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, so that the heat is evenly distributed, and the gradient thermal expansion coefficient difference is used to offset the deformation accumulation, reducing the deformation error caused by the thermal effect, and significantly improving the geometric accuracy and operation stability of the static pressure bearing system of the CNC machine tool 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 specifically cites a preferred embodiment and describes it in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0022] Figure 2A structural cross-sectional view of a static pressure 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 structural cross-sectional view of a bearing body provided by an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of the unfolded structure of a bionic tree-shaped microchannel provided in an embodiment of the invention;

[0026] Figure 6 A schematic diagram of a unilaterally expanded structure of a bionic tree-shaped microchannel provided in an embodiment of the invention;

[0027] Figure 7 A schematic structural diagram of a composite material layer provided in 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-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 explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a static pressure bearing system for a CNC machine tool proposed according to the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0030] The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

[0031] Embodiment 1

[0032] With the development of precision CNC machine tools and the increase in actual processing conditions, traditional hydrostatic bearings face severe challenges under high-speed and heavy-load conditions. The spindle speed of CNC machine tools is between several thousand and tens of thousands of revolutions per minute, and they are used to cut alloy materials with higher hardness, such as titanium alloys. Under high-speed and heavy-load conditions, CNC machine tools are required to have higher rigidity and load-bearing capacity, so the load-bearing capacity of the oil film and the stiffness of the hydrostatic bearing are required to be higher, otherwise it is easy to cause oil film rupture, bearing wear or machine vibration. The factors affecting the load-bearing capacity of the oil film and the stiffness of the hydrostatic bearing are mainly: there is a response delay in the adjustment process of the mechanical regulating valve, which leads to the sudden change of the stiffness of the oil film when encountering an emergency stop or impact load, which may cause cutting vibration. The viscous heat generation of the oil film causes local temperature rise and thermal deformation, which seriously reduces the operating accuracy of the hydrostatic bearing. In view of this, the present invention provides a hydrostatic bearing system for CNC machine tools, which takes into account the dynamic response speed and thermal stability, ensures the accuracy 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 It is a structural schematic diagram of a static pressure bearing system for a CNC machine tool provided by an embodiment of the present invention; Figure 2 A structural cross-sectional view of a static pressure 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, a hydrostatic bearing system for a CNC machine tool comprises: a bearing body 100, a piezoelectric throttling assembly 200 and a bearing seat 300; wherein, a plurality of oil chambers 110 are evenly arranged along the circumferential direction in the bearing body 100, each oil chamber 110 is connected to a piezoelectric throttling assembly 200, and a plurality of piezoelectric throttling assemblies 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 two oppositely arranged oil chambers 110 are connected; the bearing body 100 is arranged in the bearing seat 300, and a cooling channel is arranged 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 arranged 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 CNC machine tool hydrostatic bearing system of the present invention, the piezoelectric throttling component 200 is directly connected to the oil chamber 110, eliminating the response lag problem of traditional mechanical valves, achieving rapid dynamic pressure regulation, and ensuring that the oil film thickness matches the load changes in real time. At the same time, the micro-grooves 140 are used to optimize the oil film flow path, reduce the viscous shear heat generation of the oil film, and suppress the thermal effect of the oil film; combined with the forced circulation heat dissipation of the cooling channel in the bearing seat 300, the influence of thermal effects on the bearing accuracy is significantly suppressed. The present invention realizes high-precision and high-reliability hydrostatic support by synergistically optimizing 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 and connected to 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 and connected via an annular sealing ring.

[0040] Furthermore, a flow-blocking gasket 250 is provided between the second side of the elastic oil chamber seat 240 and the first oil chamber. The flow-blocking gasket 250 is an elastic metal film, and a flow-blocking space is formed by the flow-blocking gasket 250 and the first oil chamber. The flow-blocking gasket 250 can stabilize pressure fluctuations and provide more precise control performance for flow-blocking pressure regulation. 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 plate 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 plate 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 plate 270, and the piezoelectric ceramic 220 is pressed by 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] Exemplarily, the flange cover plate 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] Exemplarily, 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 also be adjusted by rotating the adjusting locking screw 290 .

[0045] It is worth noting that the existing throttle is often connected to the bearing body 100 through an intermediate pipeline, which increases the system delay and causes the rapid response performance to deteriorate. Therefore, the CNC machine tool hydrostatic bearing system of this embodiment directly sets the piezoelectric throttling component 200 on the bearing body 100. Since there is no intermediate pipeline, the signal transmission path is shortened, the delay of the intermediate link is eliminated, and the millisecond response is achieved. The oil film stiffness will not change suddenly when the spindle stops suddenly or the impact load acts. And because the intermediate pipeline is eliminated, the structure is compacted, the leakage point is reduced, and the reliability of the system is further improved.

[0046] Exemplarily, the piezoelectric ceramic 220 can be made of lead zirconate titanate piezoelectric ceramic or barium titanate piezoelectric ceramic, which is pressed together by multiple piezoelectric ceramic sheets, and a bias voltage is preloaded on the piezoelectric ceramic 220. By preloading the bias voltage on each piezoelectric ceramic sheet, the influence of the hysteresis effect of the piezoelectric ceramic sheet can be eliminated, so that the initial working point of the piezoelectric ceramic sheet is located in the linear range, so that the expansion and contraction deformation of the piezoelectric ceramic sheet and the amplitude of the voltage maintain a linear relationship. In addition, by preloading the bias voltage, the piezoelectric ceramic sheet can also 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 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 as the electric field strength of the front piezoelectric ceramic sheet is higher than that of the rear end, 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 the external control system, and the expansion and contraction of each piezoelectric ceramic 220 can be independently adjusted, such as adjusting the expansion and contraction of the piezoelectric ceramic 220 by voltage control according to the size and direction of the CNC machine tool spindle load, so that the pressure of the oil chamber 110 matches the load size and direction. In other words, the CNC machine tool hydrostatic bearing system of this embodiment can generate a combined force in the opposite direction of the load change through voltage control when the CNC machine tool spindle load changes, to compensate for the offset of the CNC machine tool spindle, thereby 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 a normal working state. Since the control of the piezoelectric ceramic 220 is not the focus of the present invention, it will not be repeated.

[0050] The principle is that when voltage is applied, due to the reverse voltage effect of the piezoelectric ceramic 220, the piezoelectric ceramic 220 is deformed (expanded), 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 finally changing the thickness and pressure of the oil film. It can be understood that the stable oil film thickness balances the pressure of the oil chamber 110 with the pressure of the CNC machine tool spindle on the static pressure 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 the uneven thickness of the oil film, the heat will increase, and dry friction will occur locally, so 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 thickness of the oil film, that is, to keep the oil film with a constant load-bearing capacity.

[0051] In addition, the expansion and contraction deformation of the piezoelectric ceramic 220 can be controlled by the voltage amplitude, so as to realize the precise adjustment of the pressure of the oil chamber 110. For example, when the voltage acting on the piezoelectric ceramic 220 increases, the piezoelectric ceramic 220 stretches and the flow resistance space decreases, which eventually causes the pressure of the oil chamber 110 to drop; or when the voltage acting on the piezoelectric ceramic 220 decreases, the piezoelectric ceramic 220 contracts and the flow resistance space increases, which eventually causes the pressure of the oil chamber 110 to rise.

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

[0053] Furthermore, both ends of the bearing body 100 are sealed and connected with end plates 600, and a second connecting groove corresponding to the first connecting groove is provided on one side of each end plate 600 close to the bearing body 100, and the first connecting groove and the second connecting groove are matched to form a connecting groove 130, and 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] Exemplarily, the end plate 600 and the bearing body 100 may be detachably connected by screws.

[0055] Exemplarily, the second communicating groove of the end plate 600 is axially aligned with the first communicating groove of the bearing body 100 , 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 main shaft of the CNC machine tool to function as an oil seal.

[0057] The principle is that the oil inlets 120 of the two second oil chambers arranged opposite to each other are directly connected through the connecting groove 130, and a pressure transmission path is formed between the two pairs of piezoelectric throttling components 200 and the corresponding oil chambers 110, forming a quasi-connecting vessel structure. When the pressure of one of the oil chambers 110 increases, the pressure of the other oil chamber 110 decreases until a balance is reached. When the spindle of the CNC machine tool is subjected to external force, the spindle will be offset, and the pressure of each oil chamber 110 will change accordingly. Reflected on the oil film, when an impact load is received or the spindle stops suddenly, the thickness of the oil film on one side changes, and the oil film on that side is compensated through the pressure transmission path to avoid the instantaneous attenuation of the oil film stiffness caused by the sudden drop in the pressure of a single oil chamber, that is, through pressure linkage compensation, the dynamic balance of the oil film pressure is guaranteed, the adjustment ability under sudden changes is enhanced, and the impact resistance and stability of the hydrostatic bearing system are improved. And 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, the oil inlet 120 can be connected to an external oil control system, including: an oil control valve, an inlet pump and an oil tank, and the oil control valve, the inlet pump and the oil tank are connected through an oil pipeline. Exemplarily, the oil control valve includes one or more of a reversing valve, a relief valve, and a one-way valve, and the multiple oil control valves are respectively connected to the oil pipelines, such as the relief valve is connected to the oil tank, the one-way valve is connected to the inlet pump, and the relief valve and the one-way valve can be switched through the reversing valve. It can be understood that the external oil control system is only a preferred example, and the relevant prior art settings can also be referred to, so it will not be repeated.

[0059] It is understandable that the piezoelectric throttling assembly 200 can be configured as follows Figure 2 The two-by-two symmetrical structure shown in the figure means that a total of 4 groups of piezoelectric throttling components 200 are provided. It can also be set to 6 groups, 8 groups or even more groups according to actual needs, and the length of the hydrostatic bearing body 100 can also be set according to the diameter of the CNC machine tool spindle and the actual load, and multiple groups of piezoelectric throttling components 200 can be spaced apart in the axial direction, and the present invention is not limited to this.

[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 the form of a plurality of groups of grooves with a relatively short width and spaced apart from each other, so as to form flow resistance in a local area of ​​the oil film.

[0062] Exemplarily, the depth of each micro groove 140 is greater than or equal to 0.02 mm. Combining 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 oil can be retained in the micro grooves 140 through the micro grooves 140, and the flow field velocity of the oil can also be reduced, that is, by changing the oil film flow field morphology and flow velocity distribution, the thermal effect of the oil film is reduced, which plays a role in suppressing the heat generation of the oil film. Specifically, the micro grooves 140 form a concave and convex structure on the inner working surface of the bearing body 100, and increase the local liquid resistance through the structure, reduce the average flow velocity of the oil film, and reduce the frictional heat generated by the viscous shear effect. In other words, the micro grooves 140 change the flow path of the oil film, increase the flow resistance of the oil film, and reduce the flow velocity of the oil film, thereby reducing the heat generated by the viscous shear effect.

[0065] In addition, the spacing of the micro grooves 140 can be set as sparse as possible, because when the spacing of the micro grooves 140 is too close, it will obviously affect the flow of the oil film, thereby affecting the oil film performance. On the contrary, when the micro grooves 140 are set sparsely enough, the working surface oil film can be regarded as a smooth surface from the overall perspective, so the local impact can be ignored from the overall perspective. In this case, the adverse effect of the micro grooves 140 on the heat generation rate of the oil film can be ignored from the overall perspective, while the effect of the micro grooves 140 in suppressing the thermal effect of the oil film can be retained locally.

[0066] Understandably, Figure 4 The above is only an example. The plurality of micro grooves 140 may be arranged in a plurality of rows along the axial direction of the inner working surface of the bearing body 100 , and the length directions of the plurality of 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 can be maintained, and it cooperates with the micro-grooves 140 to reduce 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 static pressure bearing system of the CNC machine tool of this embodiment is as follows:

[0069] When the spindle of the CNC machine tool is started, the external oil supply system injects high-pressure oil into the bearing body 100 through the oil inlet 120, and the oil enters the annular space through the connecting hole from each second oil chamber, and overflows from the inner working surface of the bearing body 100 along the oil outlet channel connected to the first oil chamber to form a uniform oil film. At this time, the piezoelectric throttling component 200 responds in real time according to the load change of the spindle of the CNC machine tool: when the load change of the spindle causes the oil film thickness in a certain area to increase, the corresponding piezoelectric ceramic 220 is applied with voltage, the piezoelectric ceramic 220 is extended, and the push rod 230 is pushed to deform the elastic oil chamber seat 240, and the flow resistance space is reduced accordingly, resulting in an increase in the resistance of the oil flowing through the space, thereby reducing the pressure of the oil chamber 110 on this side, and the thickness of the oil film is reduced accordingly. Conversely, when the oil film is too thin, reducing the voltage causes the piezoelectric ceramic 220 to shrink, the flow resistance space is expanded, and the resistance of the oil flowing through the space is reduced, so that the pressure of the oil chamber 110 on this side rises, and the thickness of the oil film increases accordingly.

[0070] During this process, the voltage is coordinated and adjusted through the hydraulic pressure of the relatively arranged piezoelectric throttling assembly 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 global oil film pressure, thereby pushing the CNC machine tool spindle to maintain a stable axial position.

[0071] The static pressure bearing system of the numerically controlled machine tool of the present invention adopts a piezoelectric throttling component 200 to replace the mechanical regulating valve of the transmission, and the piezoelectric throttling component 200 is directly set on the bearing body 100. The piezoelectric ceramic 220 uses electro-induced deformation to adjust the size of the flow-blocking space in real time, reducing the response delay and realizing the millisecond-level dynamic compensation of the oil film thickness and pressure, which is conducive to coping with the sudden change of the oil film stiffness when the spindle stops suddenly or the impact load acts, and improves the precision and stability of the static pressure bearing system. At the same time, the first oil chamber and the second oil chamber form a pressure reverse compensation mechanism through the connecting groove 130, and the pressure balance is achieved through the double oil chamber linkage structure, which can automatically balance the oil film pressure distribution under extreme loads, breaking through the stability bottleneck of the traditional multi-oil chamber independent adjustment. Then, the micro groove 140 set on the inner working surface of the bearing body 100 suppresses the thermal effect of the oil film, improves the flow state of the oil film, significantly reduces the effect of viscous shear heat generation intensity, and reduces the influence of thermal deformation on the 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 A schematic diagram of the unfolded structure of a bionic tree-shaped microchannel provided in an embodiment of the invention; Figure 6 A schematic diagram of the single-side expansion structure of a 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 coolant or an oil-based coolant.

[0076] Exemplarily, 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, and the coolant control valve, the liquid inlet pump and the coolant storage tank are connected by a pipeline. It can be understood that the external coolant control system is only a preferred example, and the relevant prior art settings can also be referred to, so it will not be repeated.

[0077] Exemplarily, the projection length L of the multi-level tree-shaped branch paths can be set to be equal or gradually reduced, and the bifurcation angle θ of the multi-level tree-shaped branch paths can be set to be equal, and the bifurcation angle θ ranges 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 passages is 1 to 2 mm, the diameter range of the second-level tree-like branch passages is 0.8 to 1 mm, and the diameter range of the third-level tree-like branch passages is 0.5 to 0.8 mm. The main passage connecting the first-level tree-like branch passages can be set according to cooling requirements and flow rates to meet the common coolant requirements of each level of tree branches.

[0079] It can be understood 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 grinding to ensure surface accuracy; 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 conforms to the fractal characteristics through a multi-level bifurcated structure bionic efficient and low-resistance material transport network, and achieves the minimization of the transfer flow resistance compared with 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-stage tree-shaped branch passage to an inclined angle, the coolant is guided to flow progressively through the inclined angle, 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, and improves the flow capacity of the coolant. In addition, the inclined setting of the multi-stage tree-shaped branch passage can also reduce the manufacturing difficulty, which is more suitable for arc-shaped surfaces and ensures the consistency of the inclination angle of the multi-stage 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, excellent temperature uniformity, etc. It can efficiently export the heat of the bearing body 100, and can reduce the overall radial size of the shaft hydrostatic bearing system. It is suitable for compact machine tool layout, and significantly improves the dynamic stiffness and thermal stability of the hydrostatic bearing system. It can effectively respond to oil film disturbances and temperature rise deformations during high-speed commutation and continuous processing, ensuring high-precision processing reliability.

[0084] like Figure 7 As shown, Figure 7 A schematic structural diagram of a composite material layer provided in 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 heat-conducting materials stacked together, and the thermal expansion coefficients of the multiple layers of heat-conducting materials increase or decrease sequentially from the outside to the inside.

[0086] Exemplarily, the composite material layer 500 includes a silicon carbide ceramic layer and an invar steel layer stacked in sequence from the outside to the inside, and the silicon carbide ceramic layer and the invar steel layer are pressed together by a carbon fiber reinforced resin; that is, the outermost layer is a silicon carbide ceramic layer, and the innermost layer is an invar steel layer, and the two are pressed together by a carbon fiber reinforced resin; wherein the silicon carbide ceramic layer (thermal expansion coefficient 4.5×10 -6 / ℃) is treated with rapid heat conduction 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] Exemplarily, by finishing the inner surface of the bearing seat 300 and filling the gaps through 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 working process of the static pressure bearing system of the CNC machine tool of this embodiment is as follows: when the spindle of the CNC machine tool is running at high speed, the oil film thermal effect is mainly suppressed through two paths: on the one hand, the inner working surface of the bearing body 100 guides the oil film to flow in a laminar manner through the micro grooves 140 to reduce the viscous friction thermal effect; on the other hand, the coolant in the bionic tree-shaped microchannel 400 flushes the inner wall of the bearing seat 300 along the multi-stage branch passage with a flow direction inclined at 15° to 30°, and the tree-shaped branch passage structure is used to strengthen the convective heat exchange and quickly export the heat. At the same time, the composite material layer 500 composed of the silicon carbide ceramic layer and the invar layer homogenizes the outer wall temperature field of the bearing body 100 through the high thermal conductivity of silicon carbide, and the invar layer offsets the axial thermal deformation with its low thermal expansion coefficient. The two are thermally decoupled through the stress buffer of the carbon fiber reinforced resin, which reduces the thermal deformation of the working surface.

[0090] The present invention forms a synergistic heat conduction control system through the bionic tree-shaped microchannel 400 and the composite material layer 500. The bionic tree-shaped microchannel 400 simulates the transport of plant roots or leaf veins through a multi-level tree-shaped branch passage, realizes the optimization of the coolant flow state through the tree-shaped branch passage with decreasing diameter, and strengthens the convective heat transfer efficiency in combination with the inclined channel direction, which can quickly export the heat of the bearing body 100 and eliminate the local temperature rise hot spots. The composite material layer 500 adopts a gradient laminated structure, which can fill the gap between the bearing seat 100 and the bearing body 300 while realizing rapid lateral homogenization of heat, and can also suppress axial thermal deformation. Under the synergistic effect of the bionic tree-shaped microchannel 400 and the composite material layer 500, the bionic tree-shaped microchannel 400 realizes the effect of directional heat conduction to reduce the overall temperature rise, and the composite material layer 500 provides a heat conduction path by gap filling, so that the heat is evenly distributed, and the gradient thermal expansion coefficient difference is used to offset the deformation accumulation, thereby reducing the deformation error caused by the thermal effect, and significantly improving the geometric accuracy and operation stability of the static pressure bearing system of the CNC machine tool under extreme working conditions.

[0091] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant is intended to cover non-exclusive inclusion, so that the article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the article or device including the elements. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The orientation or position relationship indicated by "up", "down", "left", "right", etc. is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0092] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and the specific implementation of the present invention cannot be considered to be limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling 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: Bearing body, piezoelectric throttling assembly and bearing seat; wherein, A plurality of oil chambers are evenly arranged in the circumferential direction 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 oil chambers arranged opposite to each other are connected; The bearing body is arranged in the bearing seat, and a cooling channel is arranged 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 arranged on the inner working surface of the bearing body to suppress the thermal effect of the oil film.

2. The static pressure 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 static pressure 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 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.

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 connecting groove corresponding to the first connecting groove is provided on one side of each end plate close to the bearing body. The first connecting groove and the second connecting groove are matched to form a connecting groove, and the two oppositely arranged oil inlets are connected through the connecting groove, 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 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. According to the CNC machine tool hydrostatic bearing system according to claim 1, 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.

7. The static pressure bearing system for CNC machine tools according to claim 6, characterized in that: The bionic tree-shaped microchannel comprises a multi-stage tree-shaped branch passage, the diameters of the multi-stage tree-shaped branch passages decrease successively, and the multi-stage tree-shaped branch passages have the same or different coolant inlets and outlets.

8. The static pressure bearing system for CNC machine tools according to claim 7, 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 connected to the bearing body, and the angle range of the included angle is 15° to 30°.

9. The static pressure bearing system for CNC machine tools according to claim 1, characterized in that: A composite material layer is provided between the bearing seat and the outer surface of the bearing body. 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 sequentially from the outside to the inside.

10. The static pressure bearing system for CNC machine tools according to claim 9, characterized in that: 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.

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