CN113042764B - Bearing spacer ring for self-compensating machine tool spindle bearing heat-induced pretightening force and production method thereof - Google Patents

Abstract

The invention relates to a bearing space ring for self-compensating machine tool main shaft bearing heat-induced pretightening force and a production method thereof, the outer space ring of the bearing space ring is designed into a left half space ring and a right half space ring which are separated, the right end of the left half space ring is provided with a circle of outer arc surface, the left end of the right half space ring is provided with a circle of inner arc surface, the outer arc surface and the inner arc surface are smooth convex arc surfaces, when the left half space ring and the right half space ring are connected to form the outer space ring, the outer arc surface of the left half space ring is positioned in the inner arc surface of the right half space ring, the outer arc surface and the inner arc surface are plated with the multilayer film to improve the mechanical property, when the main shaft assembly of the machine tool is thermally expanded, the left half space ring and the right half space ring generate relative displacement along the axial direction through the dislocation of the arc surface to compensate the influence generated by the thermal induction pretightening force, and when the space rings are cooled, the left half space ring and the right half space ring can be automatically reset for next use.

Description

Bearing spacer ring for self-compensating machine tool spindle bearing heat-induced pretightening force and production method thereof

Technical Field

The invention relates to the technical field of thermal error control of a high-speed precision machine tool spindle unit, in particular to a bearing spacer ring for self-compensating thermal induced pretightening force of a machine tool spindle bearing and a production method thereof.

Background

The electric spindle unit has characteristics of high rotating speed, high angular velocity increase and decrease, quick stop and the like, so that the electric spindle unit is widely applied to the field of machining. The main shaft bearing is used as a core part of a main shaft unit of the high-speed precision machine tool, and the operating state of the main shaft bearing directly determines the working performance of the main shaft unit; the angular contact ball bearing is the most common type of a machine tool spindle bearing, the pretightening force is one of key factors influencing the running state of the bearing, and the pretightening force directly influences key performance indexes of the bearing, such as rolling element slippage, temperature rise, fatigue life and the like.

The bearing pre-tightening modes can be generally divided into three modes of positioning pre-tightening, constant-pressure pre-tightening and pressure-regulating pre-tightening. However, in the actual work of the spindle unit, because the rigidity of the spring used for constant-pressure pre-tightening is difficult to determine, the pressure-regulating pre-tightening structure is too complex, the operation is complicated and the like, and the two pre-tightening modes are hardly adopted. At present, a common bearing pre-tightening mode is that a bolt is used in combination with positioning pre-tightening, namely, the initial pre-tightening force is applied by adjusting the screwing length of the bolt; however, power loss is caused by friction of the bearing under the action of factors such as rotating speed, cutting force and initial pretightening force, so that the temperature of the main shaft unit assembly is greatly increased, the bearing generates larger heat-induced pretightening force, the temperature rise of the bearing is further increased, and meanwhile, the initial pretightening force applied by a pretightening mode in which the bolt is used in combination with positioning pretightening force is unknown, the actual pretightening force is difficult to regulate and control in the working of the main shaft unit, the generated heat-induced pretightening force is difficult to compensate, and the service characteristics of the main shaft unit are influenced.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a bearing space ring for self-compensating the thermal induced pretightening force of a main shaft bearing of a machine tool, which can reduce the uncertainty of the pretightening force regulation and control of the main shaft bearing caused by thermal expansion in the prior art; another purpose is to provide a production method of the bearing spacer ring, so that the spacer ring can automatically reset after being heated and expanded, and the problems can be better solved.

In order to achieve the purpose, the invention adopts the technical scheme that:

a bearing space ring for self-compensating the thermal induced pre-tightening force of a main shaft bearing of a machine tool comprises an inner space ring and an outer space ring, the outer space ring is designed to be a separated space ring and consists of a left half space ring and a right half space ring, the right end of the left half space ring is provided with an outer arc surface which extends from the right end surface to the outer wall in a transition mode, the left end of the right half space ring is provided with an inner arc surface which extends from the left end surface to the inner wall in a transition mode, the outer arc surface and the inner arc surface are smooth convex arc surfaces, when the left half space ring and the right half space ring are connected through arc surfaces, the outer arc surface of the left half space ring is located in the inner arc surface of the right half space ring, when a main shaft assembly of the machine tool is thermally expanded, the left half space ring and the right half space ring can generate relative displacement along the axial direction through the offset of the arc surfaces to compensate the influence generated by the thermal induced pre-tightening force, when the space ring is cooled, the left half space ring and the right half space ring can be automatically reset.

Further, the outer arc surface and the inner arc surface are both subjected to film coating treatment, and the coated film layer is CrN/W₂N multilayer film.

Further, the outer arc surface extends from a point on the right end surface of the left half space ring to the outer wall of the left half space ring, and the length of the outer arc surface in the axial direction of the bearing space ring is greater than the height of the outer arc surface in the radial direction of the bearing space ring; the inner arc surface extends from one point on the left end face of the right half space ring to the inner wall of the right half space ring, and the axial length of the inner arc surface of the right half space ring is larger than the radial height of the inner arc surface of the bearing space ring.

Further, the heights of the outer arc surface and the inner arc surface are different, and the lengths of the outer arc surface and the inner arc surface are different.

Furthermore, the right end face of the left half space ring and the left end face of the right half space ring form a step face after a part of outer wall is hollowed out, and the outer arc face or the inner arc face is arranged on the step adjacent to the inner wall of the space ring.

A production method of a bearing space ring for self-compensating thermal induced pretightening force of a machine tool spindle bearing comprises the following steps:

the method comprises the following steps: processing the blank raw material into a cylinder by adopting a lathe;

step two: hollowing out the middle of the cylinder by using a milling machine to form a left half space ring and a right half space ring which are circular;

step three: feeding the circular ring-shaped material into a numerical control machine tool, and carrying out accurate processing in the numerical control machine tool; the left half space ring takes one point on the axis of the circular ring as the center, selects a proper curvature radius, and processes a circle of convex spherical surface at the right end surface and the outer wall of the circular ring to form the outer arc surface; the right half space ring takes one point outside the circular ring as the center, selects a proper curvature radius, and processes a circle of convex spherical surface at the left end surface and the inner wall of the right half space ring to form the inner arc surface;

step four: and polishing the processed initial blank to obtain a bearing outer space ring sample.

Further, the production method also comprises a step of coating the outer arc surface and the inner arc surface, wherein a magnetron sputtering method is used for coating, a cleaned bearing outer spacer ring sample and a monocrystalline silicon wafer are placed on a sample table, then the distance between a target material and the sample table is adjusted, the introduced gas during sputtering is mixed gas of argon and nitrogen, a vacuum cavity is closed for sputtering coating, and the specific process is as follows:

(1) starting up the machine to preheat, introducing cooling water, starting up the mechanical pump to pump down to about 1Pa, starting up the molecular pump to pump up to 5X 10^-3Pa, while heating the vacuum chamber to 100 ℃;

(2) opening a gas cylinder valve and a flowmeter, introducing argon, and adjusting the air pressure to glow the target;

(3) bias the substrate to-500V with Ar⁺Sputtering the surface of the substrate for 30min to remove surface impurities;

(4) introducing nitrogen, and adjusting the working pressure to 0.4 Pa; adjusting the substrate bias voltage to-100V, and setting the substrate temperature to 100 ℃;

(5) depositing a transition layer of metal Cr to improve the binding force between the film and the substrate;

(6) adjusting the working air pressure to be 0.2Pa, setting the Cr target current to be 3A and the W target current to be 5A, sputtering the four targets for 2h together, simultaneously controlling the sample stage to rotate at a constant speed, and setting different rotating speeds to obtain CrN/W with different modulation periods₂N multilayer films;

(7) and after the film coating is finished, cooling, inflating and taking out the sample.

Has the advantages that: 1. the bearing outer space ring is designed into a separated space ring, and the connecting part of the left half space ring and the right half space ring adopts the mutually matched arc surfaces, so that the left half space ring and the right half space ring form point contact at local parts and form line contact in the circumferential direction, so that when the main shaft part generates thermal expansion, the mutually contacted parts of the separated space rings are smooth, the mutually staggered movement of large displacement can be generated, the outer space ring resists the influence caused by the thermal expansion through the relative displacement, the thermal error is reduced, and a better heat-induced pre-tightening force compensation effect is obtained.

2. The invention further adds a surface coating on the arc surface, in particular to CrN/W₂The N multilayer films can reduce the internal stress of the arc surfaces, improve the toughness and improve the friction performance, when the bearing space ring is cooled, the friction force between the two arc surfaces is very small, and the separation type space ring can automatically reset due to the deformation caused by the temperature rise, so that the separation type space ring can take effect for many times.

Drawings

FIG. 1 is a schematic view of a bearing spacer of the present invention;

fig. 2 is an enlarged view of a point a in fig. 1.

Reference numerals: 1. the spindle box comprises a spindle box body, bearings 2 and 5, a left half space ring 3, a right half space ring 4, a right half space ring 6, a spindle, a 7 and an inner space ring.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.

As shown in fig. 1 and 2, a spindle 6 is arranged in a spindle box 1, bearings 2, 5 are arranged back to back, a spacer ring is arranged between the bearings, and a bearing spacer ring for self-compensating the thermal induced pre-tightening force of the spindle bearing of the machine tool comprises 7 inner spacer rings and outer spacer rings, wherein the outer spacer ring is designed as a separate spacer ring and consists of a left half spacer ring 3 and a right half spacer ring 4, the right end of the left half spacer ring 3 is provided with a circle of outer arc surface which extends from the right end to the outer wall in a transition manner, the left end of the right half spacer ring 4 is provided with a circle of inner arc surface which extends from the left end to the inner wall in a transition manner, the outer arc surface and the inner arc surface are smooth convex arc surfaces, when the left half spacer ring 3 and the right half spacer ring 4 are connected with each other arc surface to form the outer spacer ring, the inner arc surface of the left half spacer ring 3 is positioned in the inner arc surface of the right half spacer ring 4, when the spindle assembly is thermally expanded, the left half space ring 3 and the right half space ring 4 can generate relative displacement along the axial direction through the dislocation between the circular arc surfaces to compensate the influence generated by the thermal induction pretightening force, and when the space rings are cooled, the left half space ring 3 and the right half space ring 4 can be automatically reset.

In order to further improve the mechanical property of the arc surface on the spacer ring and enable the spacer ring to smoothly generate relative motion when being heated and expanded, the outer arc surface and the inner arc surface are both subjected to film coating treatment, and the coated film layer is CrN/W₂The N multi-layer film can reduce the internal stress of the arc surface, improve the toughness and improve the friction performance.

Specifically, the outer arc surface on the left half space ring 3 extends from a point on the right end surface of the left half space ring to the outer wall of the left half space ring, a circle of transition arc surface is formed at the external vertex angle of the left half space ring, and the length of the outer arc surface in the axial direction of the bearing space ring is greater than the height of the outer arc surface in the radial direction of the bearing space ring; the inner arc surface on the right half space ring 4 extends from a point on the left end face of the right half space ring to the inner wall of the right half space ring, a circle of transition arc surface is formed at the inner vertex angle of the right half space ring, and the axial length of the inner arc surface of the right half space ring is greater than the radial height of the inner arc surface of the bearing space ring.

Further, the heights and the lengths of the outer arc surface and the inner arc surface are different from each other, so that relative displacement can be better generated.

In order to provide a larger movement space for the mutual displacement of the left half space ring and the right half space ring, as shown in fig. 1, the right end surface of the left half space ring 3 and the left end surface of the right half space ring 4 are formed into a step surface by hollowing out a part of the outer wall, the outer arc surface or the inner arc surface is arranged on the step adjacent to the inner wall of the space ring, and the hollowed-out area provides a sufficient space for the mutual displacement of the two.

The invention also provides a production method of the bearing space ring, which generally comprises two steps of machining and coating, wherein the machining comprises the following steps:

step 1: processing the blank raw material into a cylinder by adopting a lathe;

step 2: hollowing out the middle of the cylinder of the milling machine to form a circular ring shape;

and step 3: feeding the circular ring-shaped material into a numerical control machine;

and 4, step 4: precisely machining in a numerical control machine tool, wherein the left half space ring takes one point on the outer end face of the ring as a coordinate origin, and selecting a proper circle center position and a proper curvature radius (for example, selecting the circle center position as x =1.767, y =0, z = -23.036, the curvature radius as 21.718mm, and the machining angle as 7 mm)^。38^’) Processing a circle of convex spherical surface at the outer vertex angle of the right end surface of the circular ring to form the outer arc surface; the right half space ring takes one point on the outer end surface of the ring as a coordinate origin, and selects a proper circle center position and a proper curvature radius (for example, the circle center position is selected as x =0.872, y =0, z = -26.318, the curvature radius is 27.912mm, and the machining angle is 6^。1^’) A circle of convex spherical surface is processed at the inner vertex angle (the left end surface and the inner wall) of the right half space ring to form the inner cambered surface;

and 5: and polishing the processed initial blank to obtain a separated outer space ring sample.

After the processing is finished, performing film coating treatment on the outer arc surface and the inner arc surface to further improve the mechanical property, performing film coating by adopting a magnetron sputtering method, placing a cleaned sample and a monocrystalline silicon wafer on a sample table, then adjusting the distance between a target and the sample table to be 15cm, introducing mixed gas of argon and nitrogen during sputtering, controlling the flow of the argon to be about 35sccm, controlling the flow of the nitrogen by an OEM (original manufacturer), closing a vacuum cavity, and performing sputtering film coating, wherein the process comprises the following steps:

(1) starting up the machine to preheat, introducing cooling water, starting up the mechanical pump to pump down to about 1Pa, starting up the molecular pump to pump up to 5X 10^-3Pa, while heating the vacuum chamber to 100 ℃;

(2) opening a gas cylinder valve and a flowmeter, introducing argon, and adjusting the air pressure to glow the target;

(3) bias the substrate to-500V with Ar⁺Sputtering the surface of the substrate for 30min to remove surface impurities;

(4) introducing nitrogen, and adjusting the working pressure to 0.4 Pa; adjusting the substrate bias voltage to-100V, and setting the substrate temperature to 100 ℃;

(5) depositing a transition layer of metal Cr to improve the binding force between the film and the substrate;

(6) adjusting the working air pressure to be 0.2Pa, setting the Cr target current to be 3A and the W target current to be 5A, sputtering the four targets for 2h together, simultaneously controlling the sample stage to rotate at a constant speed, and setting different rotating speeds to obtain CrN/W with different modulation periods₂N multilayer films;

(7) and after the film coating is finished, cooling, inflating and taking out the sample.

When the bearing space ring is applied to a machine tool main shaft, under the action of cutting force, rotating speed and initial pretightening force, a main shaft unit assembly generates thermal expansion, and because the contact part of the left half space ring and the right half space ring of the outer space ring is smooth, the left half space ring and the right half space ring generate relative displacement, the outer space ring deforms to compensate the influence caused by the thermally induced pretightening force, and when the space ring is cooled, the outer space ring can automatically reset for the next use.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (7)

1. A bearing space ring for self-compensating the thermal induced pre-tightening force of a main shaft bearing of a machine tool comprises an inner space ring and an outer space ring, and is characterized in that the outer space ring is designed to be a separated space ring and consists of a left half space ring and a right half space ring, the right end of the left half space ring is provided with a circle of outer arc surface which extends from the right end surface to the outer wall in a transition way, the left end of the right half space ring is provided with a circle of inner arc surface which extends from the left end surface to the inner wall in a transition way, the outer arc surface and the inner arc surface are both smooth convex arc surfaces, when the left half space ring and the right half space ring are connected by the arc surfaces, the outer arc surface of the left half space ring is positioned in the inner arc surface of the right half space ring, when the main shaft assembly of the machine tool is thermally expanded, the left half space ring and the right half space ring can generate relative displacement along the axial direction through the dislocation of the arc surfaces to compensate the influence generated by the thermal induced pre-tightening force, when the space ring is cooled, the left half space ring and the right half space ring can be automatically reset.

2. The bearing spacer ring for self-compensating for thermally induced preload in a spindle bearing of a machine tool as claimed in claim 1, wherein said outer and inner arcuate surfaces are coated with a CrN/W coating₂N multilayer film.

3. The bearing spacer for self-compensating for the thermally induced preload of the spindle bearing of the machine tool as set forth in claim 1, wherein said outer arcuate surface extends from a point on the right end surface of the left half spacer to the outer wall of the left half spacer, and the length of the outer arcuate surface in the axial direction of the bearing spacer is greater than the height of said outer arcuate surface in the radial direction of the bearing spacer; the inner arc surface extends from one point on the left end face of the right half space ring to the inner wall of the right half space ring, and the axial length of the inner arc surface of the right half space ring is larger than the radial height of the inner arc surface of the bearing space ring.

4. The bearing spacer for self-compensating for thermally induced preload in a spindle bearing of a machine tool as claimed in claim 3, wherein said outer arcuate surface and said inner arcuate surface are of different heights and said outer arcuate surface and said inner arcuate surface are of different lengths.

5. The bearing spacer for self-compensating for thermally induced preload of a spindle bearing of a machine tool as claimed in claim 1, wherein said right end surface of said left spacer half and said left end surface of said right spacer half are each formed with a step surface by hollowing out a portion of the outer wall thereof, and said outer arc surface and said inner arc surface are each disposed on the step adjacent to the inner wall of the spacer.

6. The method for producing the bearing spacer ring for self-compensating the heat-induced preload of the main shaft bearing of the machine tool as claimed in claim 1, characterized by comprising the following steps:

the method comprises the following steps: processing the blank raw material into a cylinder by adopting a lathe;

step two: hollowing out the middle of the cylinder by using a milling machine to form a left half space ring and a right half space ring which are circular;

step three: feeding the circular ring-shaped material into a numerical control machine tool, and carrying out accurate processing in the numerical control machine tool; the left half space ring takes one point on the axis of the circular ring as the center, selects a proper curvature radius, and processes a circle of convex spherical surface at the right end surface and the outer wall of the circular ring to form the outer arc surface; the right half space ring takes one point outside the circular ring as the center, selects a proper curvature radius, and processes a circle of convex spherical surface at the left end surface and the inner wall of the right half space ring to form the inner arc surface;

step four: and polishing the processed initial blank to obtain a bearing outer space ring sample.

7. The production method according to claim 6, further comprising a step of coating the outer arc surface and the inner arc surface, wherein the step of coating is performed by a magnetron sputtering method, the cleaned sample of the outer spacer ring of the bearing and the monocrystalline silicon wafer are placed on a sample stage, then the distance between the target and the sample stage is adjusted, the gas introduced during sputtering is a mixed gas of argon and nitrogen, and the vacuum chamber is closed for sputtering coating, and the specific process is as follows:

(1) starting up the machine to preheat, introducing cooling water, starting up the mechanical pump to pump down to about 1Pa, starting up the molecular pump to pump up to 5X 10^{- 3}Pa, while heating the vacuum chamber to 100 ℃;

(2) opening a gas cylinder valve and a flowmeter, introducing argon, and adjusting the air pressure to glow the target;

(3) bias the substrate to-500V with Ar⁺Sputtering the surface of the substrate for 30min to remove surface impurities;

(4) introducing nitrogen, and adjusting the working pressure to 0.4 Pa; adjusting the substrate bias voltage to-100V, and setting the substrate temperature to 100 ℃;

(5) depositing a transition layer of metal Cr to improve the binding force between the film and the substrate;

(6) adjusting the working air pressure to be 0.2Pa, setting the Cr target current to be 3A and the W target current to be 5A, sputtering the four targets for 2h together, simultaneously controlling the sample stage to rotate at a constant speed, and setting different rotating speeds to obtain CrN/W with different modulation periods₂N multilayer films;

(7) and after the film coating is finished, cooling, inflating and taking out the sample.

Images