CN106909177B - High-speed precise spindle system based on piezoelectric actuator on-line monitoring and control of spindle-bearing system pretightening force and pretightening displacement - Google Patents
High-speed precise spindle system based on piezoelectric actuator on-line monitoring and control of spindle-bearing system pretightening force and pretightening displacement Download PDFInfo
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- CN106909177B CN106909177B CN201610976385.4A CN201610976385A CN106909177B CN 106909177 B CN106909177 B CN 106909177B CN 201610976385 A CN201610976385 A CN 201610976385A CN 106909177 B CN106909177 B CN 106909177B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D15/00—Control of mechanical force or stress; Control of mechanical pressure
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/0009—Force sensors associated with a bearing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C2229/00—Setting preload
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C2240/00—Specified values or numerical ranges of parameters; Relations between them
- F16C2240/12—Force, load, stress, pressure
- F16C2240/14—Preload
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Abstract
The invention discloses a high-speed precise spindle system for monitoring and controlling the pretightening force and pretightening displacement of a spindle-bearing system on line based on a piezoelectric actuator, which comprises a spindle shell, a front sleeve assembly, a rear sleeve assembly, a piezoelectric actuator assembly and a spindle, wherein the front sleeve assembly is fixedly arranged in the spindle shell, the rear sleeve assembly is slidingly arranged in the spindle shell along the axis of the spindle through a ball cage guide bearing, the spindle is coaxially and fixedly arranged in the front sleeve assembly and the rear sleeve assembly through bearings, and a plurality of piezoelectric actuator assemblies which are parallel to the spindle and are used for applying axial load to the rear sleeve are uniformly distributed on the spindle shell along the circumference of the spindle. The invention has the function of on-line monitoring and controlling the pretightening force and pretightening displacement of the main shaft-bearing system. The invention realizes two modes of positioning pre-tightening and constant pressure pre-tightening by the structural design of the sleeve after the pressure can slide and simultaneously combining an electric actuator, a force sensor and a displacement sensor.
Description
Technical Field
The invention relates to the field of online monitoring and control of pretightening force of a high-speed precise spindle-bearing system, in particular to a high-speed precise spindle system based on online monitoring and control of pretightening force and pretightening displacement of a spindle-bearing system by a piezoelectric actuator.
Background
The main shaft is a core functional component of the machine tool, and the performance of the main shaft directly influences the performance of the whole machine tool. Pretension of high-speed precision spindle bearings is the most dominant factor affecting spindle stiffness, accuracy and reliability. High-speed precision bearings are extremely sensitive to changes in preload. Therefore, the pretightening force and pretightening displacement of the main shaft-bearing system are monitored and controlled on line according to the working conditions of the main shaft such as rotating speed, temperature rise, load and initial assembly in the main shaft processing process, so that the dynamic and thermal state characteristics of the main shaft in the whole rotating speed range including low speed high rigidity and high speed low temperature rise are globally excellent.
The traditional pre-tightening technology of the main shaft-bearing system mostly adopts a pre-tightening mode of positioning or constant pressure, the value of the pre-tightening force is mostly determined according to experience or experimental data, and the constant pre-tightening technology can only be suitable for a certain working condition of the main shaft. Therefore, a great deal of researches are carried out on the pretightening force controllable technology of the spindle bearing by a plurality of scholars at home and abroad. Currently, existing control devices are only closed-loop control based on pretension or closed-loop control of pretension displacement. The closed-loop control based on the pre-tightening displacement can improve the processing performance of the main shaft from the aspect of dynamics, while the closed-loop control based on the pre-tightening force can exert the high-speed performance of the main shaft from the aspect of thermodynamics. Therefore, in order to ensure the overall best of the dynamic characteristic and the thermal state characteristic of the high-speed precise main shaft, the development of the high-speed precise main shaft with the functions of on-line monitoring and controlling the pretightening force and pretightening displacement of the main shaft-bearing system is urgent.
Disclosure of Invention
The invention aims to solve the technical problem of providing a high-speed precise spindle system based on-line monitoring and controlling of the pretightening force and pretightening displacement of a spindle-bearing system by a piezoelectric actuator, which simultaneously has the function of on-line monitoring and controlling of the pretightening force and pretightening displacement of the spindle-bearing system.
The invention adopts the technical proposal for solving the technical problems in the prior art that:
a high-speed precise spindle system based on-line monitoring and controlling the pretightening force and pretightening displacement of a spindle-bearing system of a piezoelectric actuator, which comprises a spindle shell, a front sleeve assembly, a rear sleeve assembly, the piezoelectric actuator assembly and a spindle,
the front sleeve assembly is fixedly arranged in the main shaft shell, the rear sleeve assembly is slidingly arranged in the main shaft shell along the axis of the main shaft through a ball cage guide bearing, the main shaft is coaxially and fixedly arranged in the front sleeve assembly and the rear sleeve assembly through bearings,
a plurality of piezoelectric actuator assemblies which are parallel to the main shaft and used for applying axial load to the rear sleeve are uniformly distributed on the main shaft shell along the circumference of the main shaft, each piezoelectric actuator assembly comprises a piezoelectric actuator, a force sensor and a pretightening force adjusting bolt, wherein the piezoelectric actuators are slidably arranged in light holes which are uniformly distributed around the axis of the main shaft and are parallel to the axis of the main shaft, the force sensor is fixed at one end of each piezoelectric actuator, which is opposite to a flange plate of the rear sleeve, and the other end of each piezoelectric actuator is connected with the pretightening force adjusting bolts embedded on the main shaft shell;
cooling water channels are arranged on the outer cylinder walls of the front sleeve and the rear sleeve along the circumferences of the front sleeve and the rear sleeve;
temperature sensors are embedded in the front sleeve and the rear sleeve and used for detecting the working temperature of the bearing;
an encoder for monitoring the rotating speed of the rotor is arranged in the main shaft shell;
and a rear sleeve displacement sensor is arranged on the rear sleeve and is used for monitoring the axial displacement of the rear sleeve.
According to the technical scheme, the front sleeve assembly comprises a front sleeve, a positioning end cover and a front end cover, wherein the front sleeve is fixedly arranged in a main shaft shell through bolts, the positioning end cover is fixedly connected with the inner end of the front sleeve through bolts, and the front end cover is fixedly connected with the outer end of the front sleeve through bolts and is used for compressing the bearing outer ring; the front sleeve is internally provided with a bearing I and a bearing II for installing the main shaft, and the bearing I and the bearing II are axially locked on the main shaft through a first locking nut.
In the above technical scheme, the embedding is provided with bearing I temperature sensor and bearing II temperature sensor in the front sleeve, bearing I temperature sensor's probe is located near bearing I for detect bearing I's operating temperature, bearing II temperature sensor's probe is located near bearing II for detect bearing II's operating temperature.
In the above technical scheme, a spindle displacement sensor is further arranged in the spindle housing, the spindle displacement sensor is fixed on the inner wall of the spindle housing through a bracket, a probe of the spindle displacement sensor is aligned with a stepped surface of the spindle, and axial displacement of the spindle is monitored by detecting distance change from the probe to the stepped surface of the spindle.
In the technical scheme, the rear sleeve assembly comprises a rear sleeve, a pre-tightening end cover and a rear end cover, wherein the pre-tightening end cover is fixedly connected with the inner end of the rear sleeve through a bolt, and the rear end cover is fixedly connected with the outer end of the rear sleeve through a bolt and is used for compressing the bearing outer ring; the rear sleeve is internally provided with a bearing III and a bearing IV for installing the main shaft, and the bearing III and the bearing IV are axially locked on the main shaft through a second locking nut.
In the technical scheme, a bearing III temperature sensor and a bearing IV temperature sensor are embedded in the rear sleeve, a probe of the bearing III temperature sensor is positioned near the bearing III and used for detecting the working temperature of the bearing III, and a probe of the bearing IV temperature sensor is positioned near the bearing IV and used for detecting the working temperature of the bearing IV; the outer end face of the rear sleeve is of a flange plate structure, a rear sleeve displacement sensor is embedded in the flange plate of the outer end face of the rear sleeve, a probe of the rear sleeve displacement sensor penetrates through the flange plate and faces the end face, opposite to the flange plate, of the main shaft shell, and the axial displacement of the rear sleeve is monitored by measuring the distance change between the probe and the end face.
In the technical scheme, 6 set screws uniformly distributed around the axis of the main shaft are further arranged on the flange of the outer end face of the rear sleeve, the set screws penetrate through the flange of the outer end face of the rear sleeve, and the top ends of the set screws are used for propping up the end face, opposite to the flange, of the main shaft shell.
In the technical scheme, a circle of groove is formed in the outer wall of the spindle shell along the circumference of the outer wall of the spindle shell, and one end of the pretightening force adjusting bolt is exposed in the groove so as to adjust the screwing-in amount of the pretightening force adjusting bolt.
In the above technical scheme, the data acquisition and control system comprises a controller, an A/D converter and a D/A converter, wherein the force sensor, the spindle displacement sensor and the rear sleeve displacement sensor are respectively connected to the controller through the A/D converter, and the controller is sequentially connected with each piezoelectric actuator through the D/A converter and the voltage amplifier.
The invention can realize the monitoring and control of the pretightening force and pretightening displacement of a main shaft-bearing system by the pretightening displacement value measured by a main shaft displacement sensor and a rear sleeve displacement sensor and the pretightening force value measured by a force sensor and respectively controlling the voltages of three piezoelectric actuators according to the rotating speed of the main shaft and the temperature rise of a bearing, and the specific control method is as follows:
firstly, according to an optimal pre-tightening displacement (namely positioning pre-tightening) and pre-tightening force (namely constant pressure pre-tightening) database under the preset rotating speed and temperature rise determined based on the rotating speed and the temperature rise of a main shaft, respectively carrying out closed-loop control of the optimal pre-tightening displacement and closed-loop control of the optimal pre-tightening force under the working conditions of low speed and high speed of the main shaft: under the low-speed working condition (the rotating speed of the main shaft is less than 12000 rpm), the pre-tightening displacement voltage signal measured by the main shaft displacement sensor or the rear sleeve displacement sensor is converted into a pre-tightening displacement digital voltage signal through the A/D converter, the digital voltage signal is input into the controller and is compared with a set target pre-tightening displacement value (the value of the main shaft displacement sensor is theoretically half of that of the rear sleeve displacement sensor, the pre-tightening displacement value of the main shaft can be either the displacement value measured by the rear sleeve displacement sensor or the displacement value measured by the main shaft displacement sensor, and the pre-tightening displacement value measured by the rear sleeve displacement sensor is defined by a user; under a high-speed working condition (the rotating speed of the main shaft is larger than 12000rpm and smaller than 24000 rpm), the analog voltage signal of the pretightening force can be converted into the digital voltage signal of the pretightening force through the A/D converter by the pretightening force voltage signal measured by the force sensor, the digital voltage signal is input into the controller and is compared with a set target pretightening force value, the output signal of the controller converts the digital voltage signal into the analog voltage signal through the D/A converter, and the analog voltage signal is respectively output to each piezoelectric actuator by the voltage amplifier, so that the corresponding pretightening force is respectively output, and the closed-loop control of the optimal pretightening force under the high-speed working condition is realized.
The method for setting the initial pretightening force/initial pretightening displacement of the main shaft comprises the following steps:
after the assembly of the invention is completed, cooling liquid and oil gas are used for lubrication, and the initial pretightening force of the rotor is set according to the highest rotating speed of the main shaft and the cooling and lubricating conditions; the three pretightening force adjusting bolts are sequentially and circularly adjusted through the torque wrench, the pretightening force adjusting bolts push the piezoelectric actuator to slide towards one side of the rear sleeve in the unthreaded hole, so that the force sensor at the end part of the piezoelectric actuator loads axial pretightening force to the rear sleeve, after the rear sleeve is stressed, the rear sleeve sequentially drives the bearing and the lock nut to load the axial pretightening force to the spindle, the magnitude of the axial pretightening force to the spindle is measured through the force sensor in the loading process, the display values of the three force sensors are equal, the sum of the display values is equal to the initial pretightening force of the set spindle, and the pretightening displacement at the moment is defined as zero displacement.
According to the invention, the fixed pressure pre-tightening mode under the preset pre-tightening force can be switched into the positioning pre-tightening mode through the rear sleeve displacement sensor and the set screw:
the method comprises the steps of pushing a force sensor by a piezoelectric actuator to apply target axial pretightening force to a main shaft (pushing the force sensor to apply expected pretightening force to the main shaft by three piezoelectric actuators simultaneously, enabling display values of the three force sensors to be equal and enabling sum of the display values to be equal to a set expected pretightening force value to the main shaft), sequentially and circularly adjusting six set screws through a torque wrench, sequentially and circularly discharging the axial pretightening force applied by the piezoelectric actuator, enabling the display values of the three force sensors to gradually tend to zero, enabling the main shaft-bearing system to reach an axial force balance state, and enabling a constant pressure pretightening mode under the preset pretightening force to be switched to a positioning pretightening mode.
In addition, at a certain rotation speed, the pretightening force of the bearing can be changed or adjusted by changing the temperature and the flow rate of the main shaft cooling liquid.
The invention has the advantages and beneficial effects that:
the high-speed precise spindle system based on the piezoelectric actuator for on-line monitoring and controlling the pre-tightening force and the pre-tightening displacement of the spindle-bearing system has the function of on-line monitoring and controlling the pre-tightening force and the pre-tightening displacement of the spindle-bearing system. The invention adopts the piezoelectric actuator assembly as a loading device of the spindle pretightening force, and has the advantages of high rigidity, high positioning accuracy and quick response. Through the structural design of the sleeve after the pressure sliding, two modes of positioning pre-tightening and constant pressure pre-tightening are realized by combining an electric actuator, a force sensor and a displacement sensor; meanwhile, closed-loop control based on pre-tightening displacement and closed-loop control based on pre-tightening force are realized. In addition, at a certain rotation speed, the pretightening force of the bearing can be changed or adjusted by changing the temperature and the flow rate of the main shaft cooling liquid. The dynamic characteristic and the thermal state characteristic of the high-speed precise main shaft are guaranteed to be globally excellent.
Drawings
FIG. 1 is a three-dimensional isometric view of the present invention;
FIG. 2 is a front view of the present invention;
FIG. 3 is a left side view of the present invention;
FIG. 4 is a cross-sectional view A-A of the present invention;
FIG. 5 is a schematic diagram of a data acquisition and control system according to the present invention;
fig. 6 is a flow chart of a control method of the present invention.
Reference numerals in the figures: 1. adjusting bolt, 2, pretension end cap, 3, piezoelectric actuator, 4, force sensor, 5, rear sleeve, 5-1, flange, 6, set screw, 7, rear sleeve displacement sensor, 8, rear end cap, 10, spindle, 11, ball cage guide bearing, 12, bearing IV, 13, bearing III, 14, bearing II, 15, bearing I, 16, first lock nut, 17, front end cap, 18, front sleeve, 19, positioning end cap, 20, spindle displacement sensor, 21, spindle housing, 22, second lock nut, 23, first cooling water channel, 24, second cooling water channel, 25, groove.
Detailed Description
For a further understanding of the invention, its features and advantages, reference is now made to the following examples, which are illustrated in the accompanying drawings in which:
referring to fig. 1 to 5, a high-speed precise spindle system for on-line monitoring and controlling the pretightening force and pretightening displacement of a spindle-bearing system based on a piezoelectric actuator comprises a spindle housing 21, a spindle 10, a front sleeve assembly, a rear sleeve assembly, the piezoelectric actuator assembly and a data acquisition and control system;
the main shaft shell 21 is of a cylinder structure with an installation cavity, and the installation cavity for installing a front sleeve assembly, a rear sleeve assembly and a main shaft is arranged in the main shaft shell 21;
the front sleeve assembly comprises a front sleeve 18, a positioning end cover 19 and a front end cover 17, wherein the front sleeve 18 is fixedly arranged in a main shaft shell 21 through bolts, the positioning end cover 19 is fixedly connected with the inner end of the front sleeve through bolts, and the front end cover 17 is fixedly connected with the outer end of the front sleeve through bolts and is used for compressing a bearing outer ring; a bearing I15 and a bearing II 14 are arranged in the front sleeve to mount the main shaft 10, and the bearing I and the bearing II are axially locked on the main shaft 10 through a first locking nut 16; a first cooling water channel 23 is provided on the outer cylinder wall of the front sleeve 18 along the circumference thereof; a bearing I temperature sensor (not shown) and a bearing II temperature sensor (not shown) are embedded in the front sleeve 4, a probe of the bearing I temperature sensor is positioned near the bearing I15 and used for detecting the working temperature of the bearing I, and a probe of the bearing II temperature sensor is positioned near the bearing II 14 and used for detecting the working temperature of the bearing II; a main shaft displacement sensor 20 is also arranged in the main shaft shell 21, the main shaft displacement sensor 20 is fixed on the inner wall of the main shaft shell 21 through a bracket, a probe of the main shaft displacement sensor 20 is aligned with a step surface of the main shaft, and the axial displacement of the main shaft is monitored by detecting the change of the distance from the probe to the step surface of the main shaft;
the rear sleeve assembly comprises a rear sleeve 5, a pre-tightening end cover 2 and a rear end cover 8, wherein the pre-tightening end cover 2 is fixedly connected with the inner end of the rear sleeve through bolts, and the rear end cover 8 is fixedly connected with the outer end of the rear sleeve through bolts and is used for compressing the bearing outer ring; the rear sleeve 5 is slidably mounted in the main shaft housing by means of a ball cage guide bearing 11 so that the rear sleeve assembly can slide along the axis of the main shaft 10; the rear sleeve 5 is internally provided with a bearing III 13 and a bearing IV 12 for installing the main shaft 10, and the bearing III and the bearing IV are axially locked on the main shaft through a second locking nut 22; a second cooling water channel 24 is arranged on the outer wall of the rear sleeve along the circumference of the rear sleeve; a bearing III temperature sensor (not shown) and a bearing IV temperature sensor (not shown) are embedded in the rear sleeve 5, a probe of the bearing III temperature sensor is positioned near a bearing III 13 and used for detecting the working temperature of the bearing III, and a probe of the bearing IV temperature sensor is positioned near a bearing IV 12 and used for detecting the working temperature of the bearing IV; the outer end face of the rear sleeve is of a flange plate 5-1 structure, a rear sleeve displacement sensor 7 is embedded in the flange plate 5-1 of the outer end face of the rear sleeve, a probe of the rear sleeve displacement sensor 7 penetrates through the flange plate 5-1 and faces the end face, opposite to the flange plate, of the main shaft shell, and the axial displacement of the rear sleeve 5 is monitored by measuring the change of the distance between the probe and the end face; the flange plate 5-1 of the outer end surface of the rear sleeve is also provided with 6 set screws 6 uniformly distributed around the axis of the main shaft, the set screws 6 are arranged on the flange plate 5-1 of the outer end surface of the rear sleeve in a penetrating way, and the top ends of the set screws 6 are used for propping against the end surface of the main shaft shell opposite to the flange plate;
three optical holes which are uniformly distributed around the axis of the spindle 10 and are parallel to the axis of the spindle are arranged in the spindle shell 2 at the rear sleeve and are used for installing the piezoelectric actuator assembly, and the piezoelectric actuator assembly is used for pushing the rear sleeve and applying axial load (namely axial pre-tightening force) to the rear sleeve; the piezoelectric actuator assembly comprises a piezoelectric actuator 3, a force sensor 4 and a pre-tightening force adjusting bolt 1, wherein the three piezoelectric actuators 3 are respectively arranged in three optical holes in a sliding way, the force sensor 4 is fixed at one end of each piezoelectric actuator, which is opposite to a flange 5-1 of a rear sleeve, the other end of each piezoelectric actuator 3 is connected with the pre-tightening force adjusting bolt 1 embedded on a spindle shell 21 (a circle of grooves 25 are formed in the outer wall of the spindle shell 21 along the circumference of each piezoelectric actuator, one end of each pre-tightening force adjusting bolt 1 is exposed in each groove 25 so as to adjust the screwing amount of each pre-tightening force adjusting bolt 1), the piezoelectric actuators 3 are pushed to slide towards one side of the rear sleeve 5 in the optical holes through the adjustment of the pre-tightening force adjusting bolts 1, so that the force sensor 4 at the end of each piezoelectric actuator 3 contacts the flange 5-1 of the rear sleeve, and the rear sleeve 5 is loaded with initial axial pre-tightening force (after the rear sleeve 5 is arranged on the spindle shell in a sliding way, the bearing III, the bearing IV 12 and the second locking nut 22 are sequentially driven to load the spindle with axial pre-tightening force through controlling the elongation of each piezoelectric actuator 3, and the axial pre-tightening force is further loaded on the spindle through the axial pre-tightening force measuring process of the axial force sensor 4 in the small axial pre-tightening force;
an encoder (not shown) for monitoring the rotation speed of the rotor is also arranged in the main shaft shell;
the data acquisition and control system comprises a controller, an A/D converter and a D/A converter. Referring to fig. 5, the force sensor 4, the spindle displacement sensor 20 and the rear sleeve displacement sensor 7 are respectively connected to a controller through an a/D converter, and the controller is connected to each piezoelectric actuator 3 through a D/a converter and a voltage amplifier in sequence.
The invention can realize the monitoring and control of the pretightening force and pretightening displacement of a main shaft-bearing system by the pretightening displacement value measured by the main shaft displacement sensor 20 and the rear sleeve displacement sensor 7 and the pretightening force value measured by the force sensor and respectively controlling the voltages of the three piezoelectric actuators according to the rotating speed of the main shaft and the temperature rise of the bearing, and the specific control method is as follows:
referring to fig. 5, first, according to a database of optimal pre-tightening displacement (i.e. positioning pre-tightening) and pre-tightening force (i.e. constant pressure pre-tightening) under a preset rotating speed and temperature rise determined based on the rotating speed and temperature rise of a main shaft, closed-loop control of the optimal pre-tightening displacement and closed-loop control of the optimal pre-tightening force under the working conditions of the main shaft at low speed and high speed are performed respectively: under the low-speed working condition (the rotating speed of the main shaft is less than 12000 rpm), the pre-tightening displacement voltage signal measured by the main shaft displacement sensor 20 or the rear sleeve displacement sensor 7 is converted into a pre-tightening displacement digital voltage signal through the A/D converter, the digital voltage signal is input into the controller and is compared with a set target pre-tightening displacement value (the value of the main shaft displacement sensor 20 is theoretically half of that of the rear sleeve displacement sensor 7, the pre-tightening displacement value of the main shaft can be the displacement value measured by the rear sleeve displacement sensor 7 or the displacement value measured by the main shaft displacement sensor 20, and the pre-tightening displacement value measured by the rear sleeve displacement sensor 7 is defined by a user, in the embodiment, the output voltage signal of the controller is converted into the analog voltage signal through the D/A converter, and the voltage amplifier is respectively output to each piezoelectric actuator to respectively output the corresponding displacement, so that the optimal pre-tightening displacement control under the low-speed working condition is realized; under a high-speed working condition (the rotating speed of the main shaft is larger than 12000rpm and smaller than 24000 rpm), the analog voltage signal of the pretightening force can be converted into the digital voltage signal of the pretightening force through the A/D converter by the pretightening force voltage signal measured by the force sensor, the digital voltage signal is input into the controller and is compared with a set target pretightening force value, the output signal of the controller converts the digital voltage signal into the analog voltage signal through the D/A converter, and the analog voltage signal is respectively output to each piezoelectric actuator by the voltage amplifier, so that the corresponding pretightening force is respectively output, and the closed-loop control of the optimal pretightening force under the high-speed working condition is realized.
The method for setting the initial pretightening force/initial pretightening displacement of the main shaft comprises the following steps:
after the assembly of the invention is completed, cooling liquid and oil gas are used for lubrication, and the initial pretightening force of the rotor is set according to the highest rotating speed of the main shaft and the cooling and lubricating conditions; the three pretightening force adjusting bolts are sequentially and circularly adjusted through the torque wrench, the pretightening force adjusting bolts push the piezoelectric actuator to slide towards one side of the rear sleeve in the unthreaded hole, so that the force sensor at the end part of the piezoelectric actuator loads axial pretightening force to the rear sleeve, after the rear sleeve is stressed, the rear sleeve sequentially drives the bearing and the lock nut to load the axial pretightening force to the spindle, the magnitude of the axial pretightening force to the spindle is measured through the force sensor in the loading process, the display values of the three force sensors are equal, the sum of the display values is equal to the initial pretightening force of the set spindle, and the pretightening displacement at the moment is defined as zero displacement.
The invention can realize that the fixed pressure pre-tightening mode under the preset pre-tightening force is switched into the positioning pre-tightening mode through the rear sleeve displacement sensor 7 and the set screw 6:
the piezoelectric actuators are utilized to push the force sensors to apply target axial pretightening force to the main shaft (the three piezoelectric actuators are utilized to push the force sensors to apply expected pretightening force to the main shaft at the same time, so that the display values of the three force sensors are equal, the sum of the display values is equal to the set expected pretightening force value to the main shaft), then the six set screws 6 are sequentially and circularly regulated through the torque wrench, the axial pretightening force applied by the piezoelectric actuators is sequentially and circularly unloaded, the display values of the three force sensors gradually tend to zero, and therefore, the main shaft-bearing system reaches an axial force balance state, and the constant pressure pretightening mode under the preset pretightening force can be switched to a positioning pretightening mode.
In addition, at a certain rotation speed, the pretightening force of the bearing can be changed or adjusted by changing the temperature and the flow rate of the main shaft cooling liquid.
While the basic principles and main features of the present invention and advantages of the present invention have been described in the foregoing, it will be understood by those skilled in the art that the present invention is not limited by the foregoing embodiments and descriptions, which are merely illustrative of the principles of the present invention, various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims and their equivalents.
Claims (7)
1. A high-speed accurate main shaft system based on piezoelectric actuator on-line monitoring and control main shaft-bearing system pretightning force and pretightning displacement, its characterized in that: the device comprises a main shaft shell, a front sleeve assembly, a rear sleeve assembly, a piezoelectric actuator assembly and a main shaft;
the front sleeve assembly is fixedly arranged in the main shaft shell, the rear sleeve assembly is slidably arranged in the main shaft shell along the axis of the main shaft through a ball cage guide bearing, and the main shaft is coaxially and fixedly arranged in the front sleeve assembly and the rear sleeve assembly through bearings;
a plurality of piezoelectric actuator assemblies which are parallel to the main shaft and used for applying axial load to the rear sleeve are uniformly distributed on the main shaft shell along the circumference of the main shaft, each piezoelectric actuator assembly comprises a piezoelectric actuator, a force sensor and a pretightening force adjusting bolt, wherein the piezoelectric actuators are slidably arranged in light holes which are uniformly distributed around the axis of the main shaft and are parallel to the axis of the main shaft, the force sensor is fixed at one end of each piezoelectric actuator, which is opposite to a flange plate of the rear sleeve, and the other end of each piezoelectric actuator is connected with the pretightening force adjusting bolts embedded on the main shaft shell;
cooling water channels are arranged on the outer cylinder walls of the front sleeve and the rear sleeve along the circumferences of the front sleeve and the rear sleeve;
temperature sensors are embedded in the front sleeve and the rear sleeve and used for detecting the working temperature of the bearing;
an encoder for monitoring the rotating speed of the rotor is arranged in the main shaft shell;
a rear sleeve displacement sensor is arranged on the rear sleeve and is used for monitoring the axial displacement of the rear sleeve;
the front sleeve assembly comprises a front sleeve, a positioning end cover and a front end cover, wherein the front sleeve is fixedly arranged in the main shaft shell through bolts, the positioning end cover is fixedly connected with the inner end of the front sleeve through bolts, and the front end cover is fixedly connected with the outer end of the front sleeve through bolts and is used for compressing the bearing outer ring; the front sleeve is internally provided with a bearing I and a bearing II for installing a main shaft, and the bearing I and the bearing II are axially locked on the main shaft through a first locking nut;
the main shaft displacement sensor is fixed on the inner wall of the main shaft shell through a bracket, a probe of the main shaft displacement sensor is aligned with a stepped surface of the main shaft, and the axial displacement of the main shaft is monitored by detecting the change of the distance from the probe to the stepped surface of the main shaft.
2. The high-speed precision spindle system for on-line monitoring and controlling spindle-bearing system pretension and pretension displacement based on a piezoelectric actuator according to claim 1, wherein: the front sleeve is internally embedded with a bearing I temperature sensor and a bearing II temperature sensor, wherein a probe of the bearing I temperature sensor is positioned near the bearing I and used for detecting the working temperature of the bearing I, and a probe of the bearing II temperature sensor is positioned near the bearing II and used for detecting the working temperature of the bearing II.
3. The high-speed precision spindle system for on-line monitoring and controlling spindle-bearing system pretension and pretension displacement based on a piezoelectric actuator according to claim 1, wherein: the rear sleeve assembly comprises a rear sleeve, a pre-tightening end cover and a rear end cover, wherein the pre-tightening end cover is fixedly connected with the inner end of the rear sleeve through a bolt, and the rear end cover is fixedly connected with the outer end of the rear sleeve through a bolt and is used for compressing the bearing outer ring; the rear sleeve is internally provided with a bearing III and a bearing IV for installing the main shaft, and the bearing III and the bearing IV are axially locked on the main shaft through a second locking nut.
4. The high-speed precision spindle system for on-line monitoring and controlling spindle-bearing system pretension and pretension displacement based on a piezoelectric actuator according to claim 3, wherein: the rear sleeve is internally embedded with a bearing III temperature sensor and a bearing IV temperature sensor, a probe of the bearing III temperature sensor is positioned near the bearing III and used for detecting the working temperature of the bearing III, and a probe of the bearing IV temperature sensor is positioned near the bearing IV and used for detecting the working temperature of the bearing IV; the outer end face of the rear sleeve is of a flange plate structure, a rear sleeve displacement sensor is embedded in the flange plate of the outer end face of the rear sleeve, a probe of the rear sleeve displacement sensor penetrates through the flange plate and faces the end face, opposite to the flange plate, of the main shaft shell, and the axial displacement of the rear sleeve is monitored by measuring the distance change between the probe and the end face.
5. The high-speed precision spindle system for on-line monitoring and controlling spindle-bearing system pretension and pretension displacement based on a piezoelectric actuator according to claim 1, wherein: the outer end face flange of the rear sleeve is further provided with 6 set screws uniformly distributed around the axis of the main shaft, the set screws penetrate through the outer end face flange of the rear sleeve, and the top ends of the set screws are used for propping up the end face, opposite to the flange, of the main shaft shell.
6. The high-speed precision spindle system for on-line monitoring and controlling spindle-bearing system pretension and pretension displacement based on a piezoelectric actuator according to claim 1, wherein: a circle of groove is formed in the outer wall of the spindle shell along the circumference of the spindle shell, and one end of the pretightening force adjusting bolt is exposed in the groove so as to adjust the screwing quantity of the pretightening force adjusting bolt.
7. The method for setting the initial pre-tightening force/initial pre-tightening displacement of the spindle based on the high-speed precise spindle system for on-line monitoring and controlling the pre-tightening force and pre-tightening displacement of the spindle-bearing system by the piezoelectric actuator according to one of claims 1 to 6, comprising the following steps:
setting initial pre-tightening force of a rotor according to the highest rotating speed of a main shaft and cooling and lubricating conditions; the three pretightening force adjusting bolts are sequentially and circularly adjusted through the torque wrench, the pretightening force adjusting bolts push the piezoelectric actuator to slide towards one side of the rear sleeve in the unthreaded hole, so that the force sensor at the end part of the piezoelectric actuator loads axial pretightening force to the rear sleeve, after the rear sleeve is stressed, the rear sleeve sequentially drives the bearing and the lock nut to load the axial pretightening force to the spindle, the magnitude of the axial pretightening force to the spindle is measured through the force sensor in the loading process, the display values of the three force sensors are equal, the sum of the display values is equal to the initial pretightening force of the set spindle, and the pretightening displacement at the moment is defined as zero displacement.
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| CN201610976385.4A CN106909177B (en) | 2016-11-07 | 2016-11-07 | High-speed precise spindle system based on piezoelectric actuator on-line monitoring and control of spindle-bearing system pretightening force and pretightening displacement |
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| CN201610976385.4A CN106909177B (en) | 2016-11-07 | 2016-11-07 | High-speed precise spindle system based on piezoelectric actuator on-line monitoring and control of spindle-bearing system pretightening force and pretightening displacement |
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| CN109883698B (en) * | 2017-12-05 | 2020-12-04 | 洛阳轴承研究所有限公司 | Method and device for measuring pre-tightening force of control moment gyro shafting and adjusting method |
| CN108856739B (en) * | 2018-07-23 | 2021-05-25 | 广州市昊志机电股份有限公司 | Control device, system, method and device for automatically adjusting pre-tightening force of main shaft system |
| CN110821958B (en) * | 2019-12-06 | 2024-05-14 | 中国工程物理研究院机械制造工艺研究所 | Axial dynamic-static pressure air floatation spindle |
| CN113803343A (en) * | 2021-08-25 | 2021-12-17 | 北京航空航天大学 | Intelligent bolt with real-time monitoring and active anti-loosening functions and system thereof |
| CN115355853B (en) * | 2022-05-20 | 2024-08-16 | 西安交通大学 | Development machine capable of monitoring axial play of main bearing on line and working method thereof |
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