A method for assembling a hydrostatic rear-mounted electric spindle

Abstract

This invention relates to a method for assembling a hydrostatic rear-mounted electric spindle, belonging to the field of machine tool spindle assembly technology. It includes: installing a hydrostatic front bearing and a hydrostatic rear bearing in the housing bore; inserting the spindle into the front and rear bearing bores; installing a retaining ring, spacer ring, hydrostatic end face bearing, and sealing ring at the rear end of the spindle; installing a guide sleeve on the rear end face of the spindle; placing a pressure sleeve over the guide sleeve; connecting a screw upwards inside the guide sleeve; installing a pressure cap on the outside of the screw and above the pressure sleeve; sequentially installing a thrust bearing, spherical washer, and flange nut above the pressure cap; inputting pressurized oil into the rotor oil chamber; rotating the flange nut to push the motor rotor downwards; depressurizing the pressure pump, causing the motor rotor to retract; removing the flange nut, spherical washer, thrust bearing, pressure cap, pressure sleeve, screw, and elbow from the rear end of the spindle; and sequentially installing the motor housing, motor stator, and rear end cover. This invention can improve the assembly accuracy of the motor rotor and spindle, and prevent spindle bending from affecting the dynamic balance performance of the spindle system.

Description

Technical Field

[0001] This invention relates to the field of machine tool spindle assembly technology, specifically a method for assembling a hydrostatic rear-mounted electric spindle. Background Technology

[0002] With the development of machining technology, high-speed precision CNC machine tools, characterized by high cutting speed, high feed rate, and high machining accuracy, represent the future direction of equipment manufacturing technology. High-speed precision CNC machine tools not only boast extremely high production efficiency but also significantly improve the machining accuracy and surface quality of parts. The performance of a high-speed precision CNC machine tool primarily depends on the performance of its high-speed spindle unit. By combining a direct-drive motor with the machine tool spindle to form an electric spindle structure, the machine tool's rotational accuracy, rigidity, and speed range are further enhanced, while simultaneously achieving a smaller moment of inertia and rapid start-up and stop functions.

[0003] Hydrostatic and hydrodynamic bearings are widely used in precision machine tools due to their excellent load-bearing capacity, vibration resistance, and service life. Electric spindles designed using the hydrostatic principle have two main structural forms: one is the built-in type, which places the spindle motor between the front and rear bearings, effectively shortening the axial dimension of the spindle unit, improving spindle rigidity, and enabling the output of larger torque, but its heat dissipation performance is relatively poor. The other is the rear-mounted type, which places the motor outside the rear bearing. This design helps reduce the span between bearing supports; because the motor is located outside the bearing support, it has the characteristics of good heat dissipation. However, as the load on the spindle, the motor, located outside the two bearing supports, is prone to deformation of the spindle structure, thus affecting the spindle rigidity.

[0004] There are generally two methods for installing motor rotors: thermal mounting and hydraulic mounting. Thermal mounting involves heating the motor rotor, causing it to expand and enlarge its inner diameter, making it easier to fit onto the spindle. However, thermal mounting is limited by the temperature rise of the motor rotor; excessively high temperatures can cause demagnetization, leading to decreased motor performance or damage. This method is not recommended for high-speed hydrostatic rear-mounted electric spindles, primarily because the interference fit between the spindle and the motor rotor is large. This requires not only low-temperature treatment of the spindle and its assembled components but also heating the motor rotor to a high temperature. Hydraulic mounting involves introducing pressurized oil into the inner cavity of the motor rotor. The pressure of the oil expands the inner diameter of the rotor, allowing it to be pushed into the appropriate position along the spindle's axial direction. For rear-mounted hydrostatic electric spindles, the motor rotor can only be assembled after the front and rear bearings of the spindle are installed. If the motor rotor is not properly aligned and guided during assembly, the spindle will deform. For this type of spindle rear cantilever structure, once the spindle deforms, the dynamic balance will deteriorate, which is not conducive to improving the performance of the spindle unit.

[0005] Given the aforementioned technical background, it is necessary to propose an assembly method for rear-mounted hydrostatic electric spindles to avoid spindle bending affecting the dynamic balance performance of the spindle system. Summary of the Invention

[0006] To address at least one technical problem in the background art, the present invention provides a hydrostatic rear-mounted electric spindle assembly method, which enables the spindle motor rotor to uniformly apply the assembly force to the end face of the motor rotor during the assembly process, thereby allowing it to move well along the spindle axis, thus improving the assembly accuracy of the motor rotor and the spindle and preventing the spindle from bending and affecting the dynamic balance performance of the spindle system.

[0007] To achieve the above objectives, the present invention provides a method for assembling a hydrostatic rear-mounted electric spindle, comprising:

[0008] Step S1: Install the front hydrostatic bearing and the rear hydrostatic bearing in the front and rear of the housing bore, respectively, and install the front end cover on the front side of the front hydrostatic bearing.

[0009] Step S2: After installing the spindle into the front bearing hole and the rear bearing hole in sequence, install the retaining ring, spacer, hydrostatic end face bearing and sealing ring in sequence at the rear end of the spindle;

[0010] Step S3: Stand the components completed in step S2 upright so that the rear end of the main shaft faces upward, and fit the motor rotor into it so that the pressure oil channel faces upward. At this time, the rotor inner hole one and the main shaft section one, as well as the rotor inner hole two and the main shaft section three, begin to form a connection.

[0011] Step S4: Install a guide sleeve on the rear end face of the main shaft, install a elbow joint at the inlet of the pressure oil channel on the second end face of the motor rotor, and connect the pressure pump with a hose; install a pressure sleeve on the guide sleeve, connect a screw rod upward inside the guide sleeve, install a pressure cover on the outside of the screw rod and above the pressure sleeve, and install a thrust bearing, spherical washer and flange nut on the pressure cover in sequence;

[0012] Step S5: Pressure oil is introduced into the rotor oil chamber through a pressure pump via a hose and pressure oil channel, causing static pressure to be generated in the oil chamber formed by the rotor oil chamber and the second section of the main shaft, keeping the motor rotor coaxial with the main shaft. When the pressure of the pressure pump meets a certain requirement, the flange nut is turned, and the force is transmitted to the motor rotor in sequence through the spherical washer, thrust bearing, gland, and pressure sleeve, gradually pushing the motor rotor downward. When the first end face of the rotor and the shoulder of the main shaft meet a certain distance requirement, the flange nut is turned off. Then the pressure pump is depressurized, the motor rotor retracts, and the first section of the main shaft and the first inner hole of the rotor, as well as the third section of the main shaft and the second inner hole of the rotor, form an interference fit connection. After that, the flange nut, spherical washer, thrust bearing, gland, pressure sleeve, screw, and elbow are removed from the rear end of the main shaft.

[0013] Step S6: Install the motor housing, motor stator and rear end cover in sequence.

[0014] Furthermore, a locking nut is provided at the lower end of the screw and on the outside of the guide sleeve to fix the screw.

[0015] Furthermore, the lower end thread of the screw has a smaller diameter than the upper end thread.

[0016] Furthermore, the pressure sleeve is provided with multiple symmetrical notches.

[0017] Furthermore, the inner diameter of the pressure sleeve is 0.005 to 0.02 mm larger than the outer diameter of the guide sleeve.

[0018] Furthermore, the material of the pressure sleeve is selected as a magnetic shielding material, including copper and aluminum.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention provides a method for assembling a hydrostatically pressurized rear-mounted electric spindle. A guide sleeve concentric with the spindle axis guides the pressure sleeve, facilitating coaxiality between the rotor and spindle during rotor movement. Symmetrical notches on the pressure sleeve ensure symmetrical stiffness along its centerline, uniformly transmitting the thrust applied by the flange nut to the motor rotor. A spherical washer and thrust bearing transmission mechanism on the outer side of the pressure sleeve ensures the uniform transmission of the flange nut's locking torque to the pressure sleeve outside the guide sleeve, preventing uneven thrust from the flange nut during force transmission. This design ensures uniform thrust transmission to the motor rotor during assembly, enabling high-quality assembly by allowing the rotor to move along the spindle axis. This improves the assembly accuracy of the hydrostatically pressurized rear-mounted electric spindle, thereby enhancing the performance and reliability of the entire electric spindle system. The invention has a simple structure, is easy to implement, and has significant potential for wider application. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the hydrostatic rear-mounted electric spindle structure involved in the present invention;

[0022] Figure 2 yes Figure 1 Schematic diagram of the spindle section structure connecting the rear-mounted electric spindle and the motor rotor in a medium static pressure type;

[0023] Figure 3 yes Figure 1 Schematic diagram of the internal structure of the motor rotor of a medium static pressure rear-mounted electric spindle;

[0024] Figure 4 This is a schematic diagram of the static pressure rear-mounted electric spindle assembly structure of the present invention when the motor is not installed;

[0025] Figure 5 Is Figure 4 A schematic diagram of a structure incorporating a motor rotor onto a basic structure;

[0026] Figure 6 This is a schematic diagram of the initial assembly position of the motor rotor of the present invention;

[0027] Figure 7 yes Figure 6 A sectional view of the elbow joint connecting the rotor end face of the electric motor;

[0028] Figure 8 This is a schematic diagram showing the final assembly position of the motor rotor of the present invention;

[0029] Figure 9 It is a display Figure 6 A three-dimensional structural diagram of the intermediate pressure sleeve component.

[0030] In the diagram: 1-Spindle, 2-Front end cover, 3-Hydrostatic front bearing, 4-Carcass, 5-Hydrostatic rear bearing, 6-Spacer, 7-Retaining ring, 8-Hydrostatic end face bearing, 9-Sealing ring, 10-Motor rotor, 11-Motor stator, 12-Motor housing, 13-Rear end cover, 14-Pressure sleeve, 15-Guide sleeve, 16-Locking nut, 17-Screw, 18-Pressure cap, 19-Thrust bearing, 20-Spherical washer, 21-... -Flange nut, 22-Hose, 23-Elbow, 101-Shoulder, 102-Main shaft section one, 103-Main shaft section two, 104-Main shaft section three, 301-Front bearing hole, 501-Rear bearing hole, 1001-Rotor first end face, 1002-Rotor inner hole one, 1003-Rotor oil cavity hole, 1004-Rotor inner hole two, 1005-Pressure oil passage, 1006-Rotor second end face. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0034] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0035] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0036] like Figures 1-3As shown, the hydrostatic rear-mounted electric spindle of the present invention includes a spindle 1, a front end cover 2, a hydrostatic front bearing 3, a housing 4, a hydrostatic rear bearing 5, a spacer 6, a retaining ring 7, a hydrostatic end face bearing 8, a sealing ring 9, a motor rotor 10, a motor stator 11, a motor housing 12, and a rear end cover 13. The hydrostatic front bearing 3 and the hydrostatic rear bearing 5 are installed at both ends of the housing 4. The front end cover 2 is provided at the front end of the hydrostatic front bearing 3. The spindle 1 forms radial support through the hydrostatic front bearing 3 and the hydrostatic rear bearing 5. A spacer 6, a retaining ring 7, and a hydrostatic end face bearing 8 are provided at the rear end of the spindle 1 to form a hydrostatic thrust support. The motor rotor 10 is installed at the rear end of the spindle 1. The motor housing 12 is fitted over the outside of the motor rotor 10, and the motor stator 11 is installed inside the motor housing 12. The hydraulic oil is sealed on one side of the inner hole of the motor housing 12 through the sealing ring 9, and the rear end cover 13 is provided on the other side to seal the motor. The connection between the motor rotor 10 and the main shaft 1 is an interference fit. Specifically, the shaft segment connecting the main shaft 1 and the motor rotor 10 has structural features such as a shoulder 101, a first main shaft segment 102, a second main shaft segment 103, and a third main shaft segment 104. The outer diameter of the first main shaft segment 102 is d3, the outer diameter of the second main shaft segment 103 is d2, and the outer diameter of the third main shaft segment 104 is d1, with d3 > d2 > d1. The motor rotor 10 has a first rotor end face 1001, a rotor... The rotor features structural characteristics such as inner bore 1002, rotor oil cavity bore 1003, rotor inner bore 2 1004, pressure oil channel 1005, and rotor second end face 1006. The diameter of rotor inner bore 1002 is D3, the diameter of rotor oil cavity bore 1003 is D2, and the diameter of rotor inner bore 2 1004 is D1, with D3 > D1 and D2 being 0.5–2.0 mm larger than D3. The pressure oil channel 1005 has a threaded inlet and communicates internally with rotor oil cavity bore 1003. The main shaft section 102 and rotor inner bore 1002, and the main shaft section 3 104 and rotor inner bore 2 1004 are interference fit, i.e., d3 > D3, d1 > D1, and the interference amount is determined according to the rotational speed of the main shaft.

[0037] The purpose of this invention is to provide an assembly method for a hydrostatic rear-mounted electric spindle. During the assembly of the rotor of the hydrostatic rear-mounted electric spindle motor, a guide sleeve concentric with the spindle axis is used to uniformly transmit the locking torque of the flange nut to the pressure sleeve outside the guide sleeve through a spherical washer and a thrust bearing.

[0038] To achieve the above objectives, the present invention provides a method for assembling a hydrostatic rear-mounted electric spindle, comprising:

[0039] Step S1: Install the front hydrostatic bearing 3 and the rear hydrostatic bearing 5 in the four holes of the body shell respectively, and install the front end cover 2 on the front side of the front hydrostatic bearing 3.

[0040] Step S2: After sequentially inserting the spindle 1 into the front bearing hole 301 and the rear bearing hole 501, install the retaining ring 7, spacer 6, hydrostatic end face bearing 8, and sealing ring 9 sequentially at the rear end of the spindle 1. Figure 4 As shown;

[0041] Step S3: Erect the components completed in step S2, with the rear end of the main shaft 1 facing upwards. Fit the motor rotor 10 onto the rotor, ensuring the pressure oil channel 1005 faces upwards. At this point, the rotor inner hole 1002 and the main shaft section 102, as well as the rotor inner hole 2004 and the main shaft section 304, begin to connect. Figure 5 As shown;

[0042] Step S4: As Figure 6 and Figure 7 As shown, a guide sleeve 15 is installed on the rear end face of the main shaft 1. A elbow joint 23 is installed at the inlet of the pressure oil channel 1005 on the second end face 1006 of the motor rotor 10, and a pressure pump is connected by a hose 22. A pressure sleeve 14 is installed on the outer side of the guide sleeve 15. A screw 17 is connected upward inside the guide sleeve 15. A pressure cover 18 is installed on the outer side of the screw 17 and above the pressure sleeve 14. A thrust bearing 19, a spherical washer 20 and a flange nut 21 are installed in sequence above the pressure cover 18.

[0043] Step S5: Pressure oil is pumped into the rotor oil chamber 1003 via hose 22 and pressure oil channel 1005 through a pressure pump, causing static pressure to be generated in the oil chamber formed by the rotor oil chamber 1003 and the second spindle section 103, keeping the motor rotor 10 coaxial with the spindle 1. When the pressure of the pressure pump meets a certain requirement, the flange nut 21 is turned, and the force is transmitted to the motor rotor 10 in sequence through the spherical washer 20, thrust bearing 19, gland 18 and gland 14, gradually pushing the motor rotor 10 downward. When the first end face 1001 of the rotor and the shoulder 101 of the spindle 1 meet a certain distance requirement, the flange nut 21 is turned off. Then the pressure pump is depressurized, the motor rotor 10 retracts, and the first spindle section 102 and the first rotor inner hole 1002, as well as the third spindle section 104 and the second rotor inner hole 1004, form an interference fit connection. Figure 8 As shown; thereafter, the flange nut 21, spherical washer 20, thrust bearing 19, gland 18, sleeve 14, screw 17 and elbow joint 23 are removed from the rear end of the main shaft 1;

[0044] Step S6: Install the motor housing 12, motor stator 11 and rear end cover 13 in sequence.

[0045] To further optimize the technical solution, a locking nut 16 is provided at the lower end of the screw 17 and on the outside of the guide sleeve 15 to fix the screw 17 and prevent the screw 17 from tilting during the force transmission process, which would affect the force transmission of the pressure sleeve 14 to the motor rotor 10.

[0046] Further optimizing the technical solution, the lower end thread of the screw 17 is smaller than the thread diameter of the upper end thread. This increases the radius of action of the tightening torque of the flange nut 21, which is beneficial for the thrust acting on the spherical washer 20 and the thrust bearing 19 to be located on a larger circumference. This also makes the force transmission path through the gland 18 to the pressure sleeve 14 shorter.

[0047] Further optimize the technical solution, such as Figure 9 As shown, the pressure sleeve 14 is provided with multiple symmetrical notches, which facilitates the installation of the elbow joint 23 and makes the structure of the pressure sleeve 14 symmetrical and rigidly symmetrical, which is beneficial to uniformly transmit the tightening torque of the flange nut 21 to the second end face 1006 of the motor rotor 10.

[0048] The technical solution is further optimized by making the inner diameter of the pressure sleeve 14 0.005 to 0.02 mm larger than the outer diameter of the guide sleeve 15. This is beneficial for the guide sleeve 15 to guide the pressure sleeve 14, so that the motor rotor 10 can be adjusted to be coaxial with the main shaft 1 during the assembly process.

[0049] To further optimize the technical solution, the material of the pressure sleeve 14 is selected from magnetic shielding materials such as copper and aluminum. When the motor is a permanent magnet synchronous motor, it is to avoid the motor rotor 10 having magnetic force that would affect the normal assembly process.

[0050] This invention, through the combined action of the thrust bearing 19 and the spherical washer 20, avoids the frictional torque generated when the flange nut 21 transmits force directly between the flange nut 21 and the gland 18. This frictional torque also generates frictional torque between the gland 14 and the motor rotor 10. Since the screw 17 and the gland 18 are generally asymmetrically installed during assembly, this will generate uneven thrust on the motor rotor 10, causing the motor rotor 10 to be out of concentric with the center line of the spindle 1. Thus, under the combined action of axial force and frictional torque around the axis, the motor rotor 10 causes the spindle 1 to bend, ultimately leading to a decrease in the dynamic balance accuracy of the spindle system.

[0051] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for assembling a hydrostatic rear-mounted electric spindle, characterized in that, include: Step S1: Install the front hydrostatic bearing (3) and the rear hydrostatic bearing (5) in the hole of the body shell (4) respectively, and install the front end cover (2) on the front side of the front hydrostatic bearing (3). Step S2: After the spindle (1) is installed into the front bearing hole (301) and the rear bearing hole (501) in sequence, the retaining ring (7), the spacer (6), the hydrostatic end face bearing (8) and the sealing ring (9) are installed in sequence at the rear end of the spindle (1). Step S3: Erect the components completed in step S2 so that the rear end of the main shaft (1) faces upward, and fit the motor rotor (10) into it so that the pressure oil channel (1005) faces upward. At this time, the rotor inner hole one (1002) and the main shaft section one (102), as well as the rotor inner hole two (1004) and the main shaft section three (104) begin to form a connection. Step S4: Install guide sleeve (15) on the rear end face of the main shaft (1), install elbow joint (23) at the inlet of pressure oil channel (1005) on the second end face (1006) of the motor rotor (10), and connect pressure pump with hose (22); outer sleeve (14) of guide sleeve (15), screw (17) is connected upward inside guide sleeve (15), pressure cover (18) is installed on the outside of screw (17) and above pressure sleeve (14), thrust bearing (19), spherical washer (20) and flange nut (21) are installed in sequence above pressure cover (18); Step S5: Pressure oil is pumped into the rotor oil chamber (1003) via a pressure pump through a hose (22) and a pressure oil channel (1005), causing static pressure to be generated in the oil chamber formed by the rotor oil chamber (1003) and the second section of the main shaft (103), so that the motor rotor (10) and the main shaft (1) remain coaxial. When the pressure of the pressure pump meets certain requirements, the flange nut (21) is turned, and the force is transmitted to the motor rotor (10) in sequence through the spherical washer (20), the thrust bearing (19), the gland (18), and the pressure sleeve (14), gradually pushing the motor rotor (1003). 0) Move downwards, and stop rotating the flange nut (21) when the first end face (1001) of the rotor and the shoulder (101) of the main shaft (1) meet a certain distance requirement; then the pressure pump depressurizes, the motor rotor (10) contracts, and the first section of the main shaft (102) and the first inner hole of the rotor (1002) and the third section of the main shaft (104) and the second inner hole of the rotor (1004) form an interference fit connection; thereafter, remove the flange nut (21), spherical washer (20), thrust bearing (19), gland (18), sleeve (14), screw (17) and elbow (23) from the rear end of the main shaft (1); Step S6: Install the motor housing (12), motor stator (11) and rear end cover (13) in sequence.

2. The method for assembling a hydrostatic rear-mounted electric spindle as described in claim 1, characterized in that, A locking nut (16) is provided at the lower end of the screw (17) and on the outside of the guide sleeve (15) to fix the screw (17).

3. The method for assembling a hydrostatic rear-mounted electric spindle as described in claim 1, characterized in that, The thread diameter of the lower end of the screw (17) is smaller than the thread diameter of the upper end.

4. The method for assembling a hydrostatic rear-mounted electric spindle as described in claim 1, characterized in that, The pressure sleeve (14) has multiple symmetrical notches.

5. A hydrostatic rear-mounted electric spindle assembly method as described in claim 1 or 4, characterized in that, The inner diameter of the pressure sleeve (14) is 0.005 to 0.02 mm larger than the outer diameter of the guide sleeve (15).

6. The method for assembling a hydrostatic rear-mounted electric spindle as described in claim 5, characterized in that, The material of the pressure sleeve (14) is a magnetic shielding material, including copper and aluminum.

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