Thermal expansion compensation structure of electric spindle

Abstract

The invention provides a thermal expansion compensation structure of an electric spindle, and belongs to the technical field of machinery. The problem that an existing compensation structure affects the service life of an electric spindle is solved. The electric spindle comprises a cylindrical machine base and a spindle arranged in the machine base, the compensation structure comprises a positioning sleeve arranged outside the rear end of the spindle in a sleeving mode, the positioning sleeve is located in the machine base, the spindle and the positioning sleeve are rotationally matched through a first bearing, a gland is fixed to the rear end of the machine base, and an annular blocking shoulder is arranged on the inner wall of the front end of the positioning sleeve. The outer wall of the positioning sleeve is connected with the machine base through a connecting structure, and circumferential fixing and axial sliding are formed between the positioning sleeve and the machine base. A pressing ring is fixed at the rear end of the positioning sleeve; two ends of the outer ring of the first bearing are respectively pressed on the annular retaining shoulder and the pressing ring; an annular limiting base is formed on the inner wall of the machine base, the main shaft is sleeved with the limiting base, the limiting base is located on the front side of the positioning sleeve, and a spring enabling the positioning sleeve to have the backward moving tendency is arranged on the limiting base. The service life of the motorized spindle can be prolonged.

Description

Technical Field

[0001] This invention belongs to the field of mechanical technology and relates to an electric spindle, particularly an electric spindle thermal expansion compensation structure. Background Technology

[0002] An electric spindle is a type of machining spindle. The motor is usually installed inside the spindle housing. However, the high-speed rotation of the electric spindle during operation generates a lot of heat, and the motor also generates heat. This heat causes the spindle to expand thermally, which affects the machining accuracy.

[0003] To address the aforementioned issues, people have recognized the shortcomings and made improvements. For example, an ultrasonic electric spindle with a thermal expansion compensation structure (application number: 202020246399.2) disclosed in the Chinese Patent Database includes a spindle seat, a spindle, a front bearing assembly, and a rear bearing assembly. The spindle seat is hollow and open at both ends. The spindle passes through the spindle seat. The front bearing assembly is sleeved on the outside of the spindle and located at the front end of the spindle seat. The rear bearing assembly is sleeved on the outside of the spindle and located at the rear end of the spindle seat. The rear bearing assembly includes a rear bearing fixing seat, a rear bearing, and a bearing outer ring. The assembly includes a fixed ring, an inner bearing positioning sleeve, a first pressure ring, and a compensating spring. The rear bearing mounting seat is located at the rear end of the spindle seat. The rear bearing is sleeved outside the spindle and located inside the rear bearing mounting seat. The spindle has a first step. The inner bearing positioning sleeve abuts against the rear bearing and the first step. The compensating spring is located between the first pressure ring and the outer bearing limiting ring. The first pressure ring and the outer bearing limiting ring are sleeved outside the inner bearing positioning sleeve. The first pressure ring is fixedly installed on the rear bearing mounting seat, and the outer bearing limiting ring abuts against the rear bearing.

[0004] In the aforementioned electric spindle, the rear end of the spindle is directly rotatably mounted on the rear end bearing mounting seat via a rear end bearing. At this point, the outer ring of the rear end bearing and the rear end bearing mounting seat are in close contact, creating significant friction. In actual use, the rear end bearing mounting seat is fixed. As the spindle extends due to heat, it causes the rear end bearing to move backward synchronously. However, the aforementioned friction inhibits the thermal extension of the spindle, resulting in limited thermal extension and damage to both the spindle and the rear end bearing. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing an electric spindle thermal expansion compensation structure that can improve the lifespan and operational stability of the motor shaft.

[0006] The objective of this invention can be achieved through the following technical solution: an electric spindle thermal expansion compensation structure, wherein the electric spindle includes a cylindrical base and a spindle horizontally rotatably disposed within the base, the compensation structure includes a positioning sleeve fitted around the rear end of the spindle, the positioning sleeve being located within the base, and the spindle and the positioning sleeve being rotatably coupled via a first bearing, a pressure cap with a central hole being coaxially fixed at the rear end of the base, and an annular shoulder being provided on the inner wall of the front end of the positioning sleeve, characterized in that the outer wall of the positioning sleeve is connected to the base via a connecting structure, and under the action of the connecting structure, a circumferentially fixed and axially sliding relationship is formed between the positioning sleeve and the base; a pressure ring is coaxially fixed at the rear end of the positioning sleeve, and the two ends of the outer ring of the first bearing are respectively pressed against the annular shoulder and the pressure ring; a sliding gap exists between the pressure ring and the pressure cap in the axial direction of the spindle; an annular limiting seat is formed on the inner wall of the base, the limiting seat is fitted around the spindle and located in front of the positioning sleeve, and a spring is provided on the limiting seat to give the positioning sleeve a backward movement tendency.

[0007] When the electric spindle is running, the spindle extends backward due to heat, and moves the entire assembly consisting of the first bearing, positioning sleeve and pressure ring backward together, so that the pressure ring presses on the pressure cover, and is pressed by a spring to limit the positioning sleeve in the axial direction, ensuring stable operation of the spindle.

[0008] By setting the positioning sleeve to be circumferentially fixed and axially sliding with the machine base, the thermal elongation of the spindle can be effectively prevented by the positioning sleeve, and the damage to the spindle and the first bearing can be reduced, thereby improving the life, working stability and accuracy of the electric spindle.

[0009] In the aforementioned thermal expansion compensation structure for the electric spindle, a mounting groove coaxial with the limiting seat is provided on the rear end face of the limiting seat, and the mounting groove is positioned directly opposite the positioning sleeve. An annular block is axially slidably disposed within the mounting groove, forming a closed annular oil cavity between the front side of the annular block and the inner wall of the mounting groove. An oil hole is provided on the machine base to connect the annular oil cavity to the outside. Under the pressure of the oil within the annular oil cavity, the annular block can move backward and press against the positioning sleeve. The annular block, under the action of oil pressure, cooperates with the spring to support the positioning sleeve. Especially when the electric spindle is used vertically, this method can effectively increase the preload on the positioning sleeve, enhance the rigidity of the spindle during low-speed operation, and thus further improve the working stability and accuracy of the electric spindle.

[0010] In the aforementioned electric spindle thermal expansion compensation structure, the connecting structure includes a steel ball and a cylindrical retainer coaxially fixed within the machine base. The retainer has multiple ball-shaped pocket units evenly distributed circumferentially along its surface. Each ball-shaped pocket unit includes a pocket hole radially penetrating the side wall of the retainer and matching the steel ball. Each ball-shaped pocket unit includes multiple pocket holes evenly distributed axially along the retainer, and each pocket hole contains the aforementioned steel ball. A strip-shaped groove matching the steel ball is axially penetrating the outer wall of the positioning sleeve. The number of strip-shaped grooves and ball-shaped pocket units are the same, and their positions correspond one-to-one. One side of the steel ball presses against the inner wall of the machine base, and the other side extends into the corresponding strip-shaped groove and presses against its bottom wall. The rolling contact between the positioning sleeve and the machine base via the steel ball significantly reduces friction, further reducing the limitation on spindle thermal expansion and further improving the electric spindle's lifespan and operational stability.

[0011] In the above-mentioned electric spindle thermal expansion compensation structure, the cross-section of the strip groove is arc-shaped.

[0012] In the above-mentioned thermal expansion compensation structure of the electric spindle, a retaining ring is sleeved and fixed at the rear end of the spindle, and the rear end face of the inner ring of the first bearing presses against the retaining ring; an annular groove 1 coaxial with the retaining ring is opened on the front end face of the pressure ring, and an annular groove 2 coaxial with the retaining ring is opened on the rear end face of the retaining ring. Annular groove 1 and annular groove 2 are sleeved on each other and form a tortuous channel between them to form a labyrinth seal, which achieves a better waterproof effect and avoids water ingress damage to the bearing.

[0013] In the above-mentioned electric spindle thermal expansion compensation structure, the front end of the gland forms a seal with the machine base through the sealing ring.

[0014] With the cooperation of the sealing ring and the aforementioned tortuous channel, this compensation structure can be placed in a relatively closed space, reducing external interference.

[0015] In the above-mentioned electric spindle thermal expansion compensation structure, a guide ring matching the inner hole of the rear end of the machine base is formed on the front end face of the pressure cover, and the guide ring is inserted into the rear end of the machine base; an annular positioning groove is opened on the outer side wall of the guide ring, the sealing ring is located in the positioning groove, and the outer side wall of the sealing ring contacts and seals with the inner wall of the machine base.

[0016] In the above-mentioned electric spindle thermal expansion compensation structure, the annular block includes an annular block, and the inner and outer walls of the block are sealed with the inner wall of the mounting groove through the sealing ring 2.

[0017] Compared with existing technologies, the thermal expansion compensation structure of this electric spindle has the following advantages: 1. By setting the positioning sleeve to be circumferentially fixed and axially sliding with the machine base, the thermal elongation of the spindle can be effectively prevented by the positioning sleeve, reducing damage to the spindle and the first bearing, thereby improving the life, working stability and accuracy of the electric spindle.

[0018] 2. The annular block, under hydraulic pressure, works with the spring to support the positioning sleeve. Especially when the electric spindle is used vertically, this method can effectively increase the preload on the positioning sleeve, enhance the rigidity of the spindle at low speeds, and thus further improve the working stability and accuracy of the electric spindle. Attached Figure Description

[0019] Figure 1 This is a three-dimensional schematic diagram of an electric spindle.

[0020] Figure 2 This is a cross-sectional schematic diagram of an electric spindle.

[0021] Figure 3 yes Figure 2 Enlarged diagram of point A in the middle.

[0022] In the diagram, 1. Machine base; 1a. Limit seat; 1b. Oil hole; 2. Main shaft; 3. Positioning sleeve; 3a. Annular shoulder; 3b. Strip groove; 4. First bearing; 5. Pressure cover; 5a. Guide ring; 6. Sealing ring one; 7. Pressure ring; 8. Spring; 9. Annular block; 9a. Sealing ring two; 10. Annular oil cavity; 11. Steel ball; 12. Cage; 12a. Pocket; 13. Retaining ring; 14. Twisted channel. Detailed Implementation

[0023] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0024] Example 1: As Figure 1 and Figure 2 As shown, in the electric spindle thermal expansion compensation structure, the electric spindle 2 includes a cylindrical base 1 and a spindle 2 horizontally rotatably disposed within the base 1. In the actual product, the spindle 2 is rotatably coupled to the base 1 via a second bearing.

[0025] This thermal expansion compensation structure is located at the rear end of the spindle 2 and within the machine base 1. Specifically, it includes a positioning sleeve 3 that is fitted around the rear end of the spindle 2. The positioning sleeve 3 is coaxial with the spindle 2 and is located within the machine base 1. The spindle 2 and the positioning sleeve 3 are rotatably connected via a first bearing 4. The first bearing 4 is a ball bearing, which includes an inner ring fixed to the spindle 2 and an outer ring fixed to the positioning sleeve 3. In the actual product, both the inner and outer rings of the first bearing 4 are fixed to the spindle 2 and the positioning sleeve 3 respectively by an interference fit.

[0026] like Figure 2 and Figure 3As shown, a pressure cap 5 with a central hole is coaxially fixed to the rear end of the base 1, and the front end of the pressure cap 5 forms a seal with the base 1 through a sealing ring 6. Specifically, the front end face of the pressure cap 5 presses against the rear end face of the base 1, and the pressure cap 5 is fixed to the base 1 by a ring of bolts, with the bolt axis extending front and rear. A guide ring 5a is formed on the front end face of the pressure cap 5, which matches the inner hole of the rear end of the base 1. The guide ring 5a and the pressure cap 5 are coaxially arranged and are an integral structure. The guide ring 5a is inserted into the rear end of the base 1, and an annular positioning groove is formed on the outer side wall of the guide ring 5a. The sealing ring 6 is located in the positioning groove, and the outer side wall of the sealing ring 6 contacts and seals the inner wall of the base 1.

[0027] Naturally, clamping the sealing ring 6 between the rear end face of the base 1 and the pressure plate 5 can also create a seal between the pressure plate 5 and the base 1.

[0028] like Figure 2 As shown, the inner wall of the front end of the positioning sleeve 3 has an annular shoulder 3a, which is coaxially arranged with the positioning sleeve 3 and forms an integral structure. The outer wall of the positioning sleeve 3 is connected to the machine base 1 through a connecting structure, and under the action of the connecting structure, the positioning sleeve 3 and the machine base 1 form a circumferential fixed and axial sliding relationship. The rear end of the positioning sleeve 3 is coaxially fixed with a pressure ring 7, and the two ends of the outer ring of the first bearing 4 are respectively pressed against the annular shoulder 3a and the pressure ring 7. There is a sliding gap between the pressure ring 7 and the pressure cover 5 in the axial direction of the main shaft 2. The inner wall of the machine base 1 is formed with an annular limiting seat 1a, which is coaxially arranged with the machine base 1. The limiting seat 1a is sleeved on the outside of the main shaft 2 and is located in front of the positioning sleeve 3. The limiting seat 1a is provided with a spring 8 that makes the positioning sleeve 3 have a backward movement tendency.

[0029] When the electric spindle 2 is running, the spindle 2 is heated and extends backward, which drives the whole assembly consisting of the first bearing 4, the positioning sleeve 3 and the pressure ring 7 to move backward together, so that the pressure ring 7 presses on the pressure cover 5 and is pressed by the spring 8 to limit the positioning sleeve 3 in the axial direction, so as to ensure the stable operation of the spindle 2.

[0030] By setting the positioning sleeve 3 to be circumferentially fixed and axially sliding with the base 1, the thermal elongation of the spindle 2 can be effectively prevented by the positioning sleeve 3, and the damage to the spindle 2 and the first bearing 4 can be reduced, thereby improving the life, working stability and accuracy of the electric spindle 2.

[0031] To further explain, a mounting groove coaxial with the positioning sleeve 3 is provided on the rear end face of the limiting seat 1a, and the mounting groove is positioned directly opposite the positioning sleeve 3. An annular block 9 is axially slidably disposed in the mounting groove, and a closed annular oil cavity 10 is formed between the front side of the annular block 9 and the inner wall of the mounting groove. The machine base 1 is provided with an oil hole 1b that connects the annular oil cavity 10 to the outside. In use, hydraulic oil is injected into the annular oil cavity 10 through the oil hole 1b. Under the push of the oil pressure in the annular oil cavity 10, the annular block 9 can move backward and press against the positioning sleeve 3. Under the action of oil pressure, the annular block 9 cooperates with the spring 8 to support the positioning sleeve 3. Especially when the electric spindle 2 is used vertically, this method can effectively increase the preload on the positioning sleeve 3, enhance the rigidity of the spindle 2 at low speeds, and thus further improve the working stability and accuracy of the electric spindle 2.

[0032] Preferably, the oil hole 1b is straight and its length extends radially along the base 1. The outer and inner openings of the oil hole 1b are respectively located on the outer side of the base 1 and the inner side of the annular oil cavity 10. In the actual product, an oil inlet connector is installed at the outer opening of the oil hole 1b.

[0033] In this embodiment, The spring 8 is installed as follows: A limiting groove matching the spring 8 is axially opened on the rear end face of the limiting seat 1a, and the limiting groove is located inside the mounting groove. There are at least two limiting grooves, which are evenly distributed along the circumference of the limiting seat 1a. Each limiting groove is equipped with the aforementioned spring 8, and the two ends of the spring 8 act on the annular shoulder 3a and the bottom surface of the corresponding limiting groove, respectively.

[0034] like Figure 2 and Figure 3 As shown, the connecting structure includes a steel ball 11 and a cylindrical retainer 12 coaxially fixed inside the base 1. The retainer 12 is sleeved outside the positioning sleeve 3. The retainer 12 is provided with a plurality of ball pocket units evenly distributed along the circumference of the retainer 12. Each ball pocket unit includes a pocket hole 12a that radially penetrates the side wall of the retainer 12 and matches the steel ball 11. Each ball pocket unit includes a plurality of pocket holes 12a evenly distributed along the axial direction of the retainer 12, and each pocket hole 12a contains the aforementioned steel ball 11. A strip groove 3b that matches the steel ball 11 is axially penetrated on the outer wall of the positioning sleeve 3. The number of strip grooves 3b and ball pocket units are the same and their positions correspond one-to-one. One side of the steel ball 11 is pressed against the inner wall of the base 1, and the other side of the steel ball 11 extends into the corresponding strip groove 3b and is pressed against the bottom wall of the strip groove 3b. The positioning sleeve 3 and the base 1 are in rolling contact via steel balls 11, which greatly reduces friction, further reducing the limitation on the thermal elongation of the spindle 2 and further improving the life and operational stability of the electric spindle 2. Preferably, the cross-section of the strip groove 3b is arc-shaped.

[0035] The structure of the annular block 9 is as follows: The annular block 9 includes an annular block, and both the inner and outer walls of the block are sealed to the inner wall of the mounting groove through sealing rings 9a. At this time, the block, the inner wall of the mounting groove, and the two sealing rings 9a together form the aforementioned annular oil cavity 10. Further, annular positioning grooves are provided on both the inner and outer walls of the block. The two sealing rings 9a are respectively located in the two positioning grooves. The outer wall of the outer sealing ring 9a contacts and seals with the inner wall of the mounting groove, while the inner wall of the inner sealing ring 9a contacts and seals with the inner wall of the mounting groove.

[0036] like Figure 2 and Figure 3 As shown, a retaining ring 13 is sleeved and fixed at the rear end of the main shaft 2, and the rear end face of the inner ring of the first bearing 4 presses against the retaining ring 13. Preferably, the retaining ring 13 is sealed and fixedly connected to the main shaft 2. An annular groove 1, coaxial with the pressure ring 7, is opened on the front end face of the pressure ring 7, and an annular groove 2, coaxial with the retaining ring 13, is opened on the rear end face of the retaining ring 13. The annular groove 1 and the annular groove 2 are sleeved on each other and the gap between them forms a tortuous channel 14 to form a labyrinth seal, which has a better waterproof effect and prevents water from entering and damaging the bearing. With the cooperation of the sealing ring 1 6 and the above-mentioned tortuous channel 14, this compensation structure can be placed in a relatively closed space, reducing external interference.

[0037] Example 2: The structure and principle of Example 2 are basically the same as those of Example 1. The difference is that the connection structure includes a ring of keyways formed on the inner wall of the rear end of the base 1a. The length of the keyways extends along the axial direction of the base 1a, and the rear end of the keyways is open. The outer wall of the positioning sleeve 3 is formed with key blocks that match the keyways. The number of key blocks is the same as the number of keyways and their positions correspond one-to-one. Each key block is inserted into the corresponding keyway.

[0038] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A thermal expansion compensation structure of an electric spindle, the electric spindle (2) comprising a cylindrical housing (1) and a spindle (2) horizontally rotatably arranged in the housing (1), the compensation structure comprising a locating sleeve (3) sleeved on the rear end of the spindle (2), the locating sleeve (3) being located in the housing (1) and the spindle (2) and the locating sleeve (3) being rotatably connected through a first bearing (4), a gland (5) with a central hole being coaxially fixed on the rear end of the housing (1), and the front end inner wall of the locating sleeve (3) having an annular shoulder (3a), characterized in that, The outer wall of the positioning sleeve (3) is connected with the base (1) through a connecting structure, and a circumferential fixing and axial sliding is formed between the positioning sleeve (3) and the base (1) under the action of the connecting structure; the rear end of the positioning sleeve (3) is coaxially fixed with a pressing ring (7), and the outer rings of the first bearing (4) are pressed on the annular shoulder (3a) and the pressing ring (7) respectively; a sliding gap exists between the pressing ring (7) and the pressing cover (5) in the axial direction of the main shaft (2), and a limiting seat (1a) in the form of a ring is formed on the inner wall of the base (1), the limiting seat (1a) is sleeved on the outer wall of the main shaft (2) and located on the front side of the positioning sleeve (3), and the limiting seat (1a) is provided with a spring (8) which makes the positioning sleeve (3) have a tendency to move backward.

2. The thermal expansion compensation structure of the electric spindle according to claim 1, characterized in that, A mounting groove coaxial with the limiting seat (1a) is formed on the rear end face of the limiting seat (1a), and the mounting groove is arranged opposite to the positioning sleeve (3); an annular block (9) is axially slidably arranged in the mounting groove, a closed annular oil chamber (10) is formed between the front side of the annular block (9) and the inner wall of the mounting groove, and the base (1) is provided with an oil hole (1b) for connecting the annular oil chamber (10) with the outside, and the annular block (9) can move backward under the pushing of the oil pressure in the annular oil chamber (10) and abut against the positioning sleeve (3).

3. The thermal expansion compensation structure of an electric spindle according to claim 1 or 2, characterized in that, The connecting structure comprises a steel ball (11) and a cage (12) coaxially fixed in the base (1) and in the form of a cylinder, the cage (12) is provided with a plurality of ball pocket units uniformly distributed in the circumferential direction of the cage (12), each ball pocket unit comprises a pocket hole (12a) penetrating through the side wall of the cage (12) in the radial direction and matched with the steel ball (11), each ball pocket unit comprises a plurality of pocket holes (12a) uniformly distributed in the axial direction of the cage (12), and each pocket hole (12a) contains the steel ball (11); an axially penetrating strip-shaped groove (3b) matched with the steel ball (11) is formed in the outer wall of the positioning sleeve (3), the number of the strip-shaped grooves (3b) is the same as that of the ball pocket units and they are one-to-one corresponding, one side of the steel ball (11) is pressed against the inner wall of the base (1), and the other side of the steel ball (11) extends into the corresponding strip-shaped groove (3b) and is pressed against the bottom wall of the strip-shaped groove (3b).

4. The thermal expansion compensation structure of the electric spindle according to claim 3, characterized in that, The cross section of the strip-shaped groove (3b) is in the form of a circular arc.

5. The thermal expansion compensation structure of the electric spindle according to claim 1, characterized in that, The rear end of the main shaft (2) is sleeved and fixed with a stop ring (13), and the rear end face of the inner ring of the first bearing (4) abuts against the stop ring (13); an annular groove one coaxial with the pressing ring (7) is formed in the front end face of the pressing ring (7), an annular groove two coaxial with the stop ring (13) is formed in the rear end face of the stop ring (13), the annular groove one and the annular groove two are sleeved with each other and form a zigzag channel (14) therebetween.

6. The thermal expansion compensation structure of the electric spindle according to claim 5, characterized in that, The front end of the pressing cover (5) is sealed with the base (1) through a sealing ring one (6).

7. The thermal expansion compensation structure of the electric spindle according to claim 6, characterized in that, A guide ring (5a) matched with the rear end inner hole of the base (1) is formed on the front end face of the pressing cover (5) and inserted into the rear end of the base (1); a ring-shaped positioning groove is formed in the outer side wall of the guide ring (5a), the sealing ring one (6) is located in the positioning groove, and the outer side wall of the sealing ring one (6) is in contact with the inner wall of the base (1) for sealing.

8. The thermal expansion compensation structure of the electric spindle according to claim 2, characterized in that, The annular block (9) comprises an annular block body, and the inner side wall and the outer side wall of the block body are both sealed by the sealing ring two (9a) and the inner wall of the mounting groove.

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