Variable vacuum capacitor

Abstract

The utility model discloses a variable vacuum capacitor, which comprises a shell, a moving electrode group movably arranged in the shell, a pull rod fixedly connected with the moving electrode group, a transmission mechanism in transmission connection with the pull rod, and a guide sleeve fixedly arranged on the shell, the transmission mechanism is used for driving the movable electrode group to do linear reciprocating motion through the pull rod under the driving of an external power device; the pull rod is coaxially inserted into the guide sleeve, a first ball set is arranged between the pull rod and the guide sleeve in the axial direction, and the first ball set makes rolling contact with the pull rod and the guide sleeve. According to the utility model, the friction between the pull rod and the guide sleeve is changed from sliding friction to rolling friction, so that the fit clearance and the contact area between the pull rod and the guide sleeve are reduced, thereby reducing the rotation torque and capacitance value repeatability deviation of the variable vacuum capacitor, improving the capacitance value adjusting speed and precision, and prolonging the service life of the variable vacuum capacitor. The purpose of rapidly and accurately adjusting the capacitance value of the variable vacuum capacitor is achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to capacitor technical field, especially a kind of variable vacuum capacitor. BACKGROUND

[0002] Vacuum capacitor is the capacitor with vacuum as dielectric. Because of the unique performance of vacuum dielectric, vacuum capacitor has the advantages of high voltage resistance, large current carrying capacity, low loss, self-healing after transient overload, etc. It is widely used in high-frequency and high-voltage equipment fields such as broadcast transmission, medical nuclear magnetic resonance, high-frequency heating, semiconductor etching and plasma cleaning. In these high-frequency and high-voltage equipment, vacuum capacitor and high-frequency inductor form a resonant circuit to complete high-frequency impedance matching and realize stable transmission of radio frequency power.

[0003] The variable vacuum capacitor is mainly composed of two groups of coaxial oxygen-free copper electrodes sealed in vacuum and ceramic insulation shell. The variable vacuum capacitor converts the rotary motion of the motor into the linear motion of the moving electrode through the metal bellows, the moving electrode guide system and the screw transmission system to change the electrode coupling area and realize the capacity adjustment.

[0004] Figure 1 As shown is a cross-sectional structure schematic diagram of the existing variable vacuum capacitor. The moving electrode group is fixedly connected with the pull rod one 15 in the guide sleeve one 16. The pull rod one 15 moves up and down in the guide sleeve one 16, and the two are in sliding fit. To ensure the free movement of the pull rod one 15, a certain gap is usually left between the pull rod one 15 and the guide sleeve one 16. The size of the gap has a great influence on the rotation torque of the capacitor and the capacity repeatability deviation. When the gap is large, the resistance between the pull rod one 15 and the guide sleeve one 16 is small, so the rotation torque of the product is small. However, a large gap will cause a large change in the electrode spacing during movement, resulting in a large capacity repeatability deviation. When the gap is small, the electrode spacing is stable during the movement of the pull rod one 15, and the capacity repeatability deviation is small. However, a small gap will increase the moving resistance of the pull rod one 15, thereby increasing the rotation torque. At the same time, the surface roughness of the guide parts will also affect the rotation torque and the mechanical life of the capacitor.

[0005] With the continuous improvement of the matching speed and matching accuracy of the impedance matching device of semiconductor manufacturing equipment, users require faster capacity adjustment speed of the variable vacuum capacitor, smaller rotation torque value of the variable vacuum capacitor, and smaller capacity repeatability deviation of the vacuum capacitor to realize fast and accurate matching of high-frequency impedance. Obviously, the existing variable vacuum capacitor cannot meet the requirements of users. Therefore, it is necessary to improve the existing technology to overcome the defects in the prior art. UTILITY MODEL CONTENTS

[0006] The utility model wants to solve the problem to provide a variable vacuum capacitor to overcome the defects that the present variable vacuum capacitor has large rotation torque value, large capacitance value repeatability deviation and cannot meet the requirement of fast and accurate matching of high frequency impedance.

[0007] The utility model discloses to solve its technical problem adopts technical scheme: a variable vacuum capacitor, include: casing, the movable electrode group of activity in casing, the pull rod of fixed connection in movable electrode group, the transmission mechanism of transmission connection in pull rod and the guide bush of fixed mounting in casing, transmission mechanism is used for under the drive of external power device through pull rod drives movable electrode group and makes linear reciprocating motion, pull rod coaxially inserts in guide bush, and first ball group is established between pull rod with guide bush along the axial arrangement, first ball group with pull rod and guide bush all roll contact.

[0008] As a further improvement of the utility model, the outer wall of the pull rod and / or the inner wall of the guide sleeve is provided with a groove along the axial direction, and the first ball group is arranged in the groove along the axial direction.

[0009] As a further improvement of the utility model, the groove includes a first groove provided on the inner wall of the guide sleeve, the guide sleeve is provided with a stop step at one end of the first groove and a first ring groove at the other end, a first retainer ring is installed in the first ring groove, and the stop step and the first retainer ring are used to stop the first ball group in the first groove.

[0010] As a further improvement of the utility model, the groove further includes a second groove provided on the outer wall of the pull rod and opposite to the first groove, the first ball group is arranged in the first groove and the second groove, the pull rod is provided with a second ring groove at the upper end of the second groove, and a second retainer ring for stopping the first ball group is installed in the second ring groove.

[0011] As a further improvement of the utility model, the groove provided on the outer wall of the pull rod or the inner wall of the guide sleeve has at least three, and the at least three grooves are annularly and equally spaced, and each of the grooves contains the first ball group.

[0012] As a further improvement of the utility model, the transmission mechanism includes a rotating screw and an adjusting nut, the adjusting nut is sleeved on the rotating screw and fixedly connected to the pull rod, the outer wall of the rotating screw is provided with a first spiral groove, the inner wall of the adjusting nut is provided with a second spiral groove, and a second ball group is arranged between the first spiral groove and the second spiral groove.

[0013] As a further improvement of the utility model, the inside of the adjusting nut is equipped with a ball return hole, the ball return hole, the second spiral groove and the part opposite to the second spiral groove of the first spiral groove jointly constitute a ball circulation channel, and the second ball group circulates and rolls in the ball circulation channel.

[0014] As a further improvement of the utility model, the lower end of the rotating screw rod penetrates the adjusting nut and is fixed with an anti-dropping piece.

[0015] As a further improvement of the utility model, the upper end of the pull rod is equipped with a avoiding hole along the axis, the inner diameter of the upper section of the avoiding hole is expanded to form a stepped hole, the adjusting nut is fixed in the stepped hole, and the lower end of the rotating screw rod penetrates the adjusting nut and extends into the avoiding hole.

[0016] As a further improvement of the utility model, the top of the shell is fixed with a sleeve, the inside of the sleeve is equipped with a moving space for the linear reciprocating movement of the pull rod and the adjusting nut, the top of the sleeve is installed with a plane bearing, the upper end of the rotating screw rod penetrates the plane bearing and is fixedly connected with a motor joint.

[0017] The utility model has the advantages of:

[0018] 1. The variable vacuum capacitor is characterized in that the first ball group is arranged axially between the pull rod and the guide sleeve, the friction between the pull rod and the guide sleeve is changed from sliding friction to rolling friction, the matching gap and the contact area between the pull rod and the guide sleeve are reduced, the rotational torque and the capacitance repeatability deviation of the variable vacuum capacitor are reduced, the capacitance adjustment speed and the precision are improved, the purpose of quickly and accurately adjusting the capacitance of the variable vacuum capacitor is achieved, and the demand of quickly and accurately matching the high-frequency impedance in the semiconductor equipment is met.

[0019] 2. The utility model is characterized in that the first spiral groove is arranged on the outer wall of the rotating screw rod, the second spiral groove is arranged on the inner wall of the adjusting nut, and the second ball group is arranged between the first spiral groove and the second spiral groove, so that the friction between the rotating screw rod and the adjusting nut is changed from sliding friction to rolling friction, the matching gap and the contact area between the rotating screw rod and the adjusting nut are reduced, the rotational torque of the variable vacuum capacitor is greatly reduced, the capacitance precision is obviously improved, the purpose of quickly and accurately adjusting the capacitance of the variable vacuum capacitor is achieved, and the user can select a small-power driving motor due to the reduced rotational torque, which helps the user to reduce the volume and weight of the matcher and reduces the manufacturing cost of the semiconductor equipment. DRAWINGS

[0020] Figure 1It is a sectional view of the prior variable vacuum capacitor;

[0021] Figure 2 It is a perspective view of the variable vacuum capacitor of the utility model;

[0022] Figure 3 It is a sectional view of the variable vacuum capacitor of the utility model;

[0023] Figure 4 It is a half sectional perspective view of the pull rod and guide sleeve of the variable vacuum capacitor of the utility model;

[0024] Figure 5 It is a perspective view of the variable vacuum capacitor of the utility model Figure 4 It is an enlarged view of A part in the middle;

[0025] Figure 6 It is a sectional view of the transmission mechanism of the variable vacuum capacitor of the utility model.

[0026] The following description is made in conjunction with the drawings:

[0027] 1, shell; 101, porcelain tube; 102, upper base; 2, moving electrode group; 201, moving disc; 202, moving electrode; 3, pull rod; 301, second groove; 302, second ring groove; 303, second check ring; 304, avoidance hole; 305, stepped hole; 4, guide sleeve; 401, first groove; 402, stop step; 403, first ring groove; 404, first check ring; 5, first ball group; 6, rotating screw; 601, first helical groove; 7, adjusting nut; 701, second helical groove; 702, ball return hole; 703, ball guide joint; 8, second ball group; 9, anti-drop piece; 10, sleeve; 1001, active space; 11, plane bearing; 12, motor joint; 13, static electrode group; 1301, stator disc; 1302, static electrode; 14, corrugated pipe; 15, pull rod one; 16, guide sleeve one; 17, rotating screw one; 18, adjusting nut one. DETAILED DESCRIPTION

[0028] The preferred embodiment of the utility model is described in detail below in conjunction with the drawings.

[0029] Referring to Figures 2 to 6 , the utility model provides a variable vacuum capacitor, include: shell 1, moving electrode group 2, pull rod 3, guide sleeve 4, static electrode group 13 and transmission mechanism.

[0030] Among them, moving electrode group 2 includes moving disc 201 and the moving electrode 202 fixed on moving disc 201, static electrode group 13 includes stator disc 1301 and the static electrode 1302 fixed on stator disc 1301, and moving electrode 202 and static electrode 1302 are accommodated in the vacuum chamber of shell 1 with each other coupling.

[0031] In this embodiment, the shell 1 is specifically composed of a circular porcelain tube 101, an upper base 102 and a stator disk 1301 of the static electrode group 13. The upper base 102 and the stator disk 1301 of the static electrode group 13 are sealed and fixed to the upper and lower ends of the porcelain tube 101 respectively.

[0032] Furthermore, the moving electrode group 2 is movably arranged in the shell 1, and the top of the movable plate 201 of the moving electrode group 2 is sealed with the inner wall of the upper base 102 through the bellows 14 to ensure the vacuum environment inside the shell 1.

[0033] For ease of understanding, the axial direction described herein is defined as the central axis direction of the variable vacuum capacitor. A pull rod 3 is axially disposed within the housing 1, and the lower end of the pull rod 3 is fixedly connected to the movable disc 201 of the movable electrode assembly 2. A transmission mechanism is connected to the upper end of the pull rod 3. The transmission mechanism is used to drive the movable electrode assembly 2 in linear reciprocating motion via the pull rod 3 under the drive of an external power device, such as a motor, to change the coupling length between the movable electrode 202 and the static electrode 1302, thereby changing the coupling area between the two electrode groups, and thereby changing the capacitance of the vacuum capacitor, thereby achieving adjustment of the capacitance of the variable capacitor.

[0034] See Figure 3 The guide sleeve 4 is axially fixedly mounted on the upper base 102 of the housing 1, and the lower end of the guide sleeve 4 extends toward the interior of the housing 1. The pull rod 3 is coaxially inserted into the guide sleeve 4, and a first ball group 5 is axially arranged between the pull rod 3 and the guide sleeve 4. The first ball group 5 is in rolling contact with both the pull rod 3 and the guide sleeve 4, so that the friction between the pull rod 3 and the guide sleeve 4 is converted from sliding friction to rolling friction, reducing the fitting clearance and contact area between the pull rod 3 and the guide sleeve, thereby reducing the rotational torque and capacitance repeatability deviation of the variable vacuum capacitor, improving the capacitance adjustment speed and accuracy, achieving the purpose of rapid and precise capacitance adjustment of the variable vacuum capacitor, meeting the needs of rapid and precise matching of high-frequency impedance in semiconductor equipment, and reducing the manufacturing cost of semiconductor equipment.

[0035] To ensure axial movement of the first ball group 5 within the guide sleeve 4, the present invention provides axially disposed grooves on the outer wall of the tie rod 3 and / or the inner wall of the guide sleeve 4, with the first ball group 5 arranged axially within the grooves. In other words, the present invention can provide axially disposed grooves solely on the outer wall of the tie rod 3 to accommodate the first ball group 5, with at least a portion of the first ball group 5 protruding from the grooves to engage in rolling contact with the inner wall of the guide sleeve 4. Alternatively, the present invention can provide axially disposed grooves solely on the inner wall of the guide sleeve 4 to accommodate the first ball group 5, with at least a portion of the first ball group 5 protruding from the grooves to engage in rolling contact with the outer wall of the tie rod 3. Alternatively, the present invention can provide axially disposed grooves on both the outer wall of the tie rod 3 and the inner wall of the guide sleeve 4 to accommodate the first ball group 5.

[0036] Preferably, the embodiment simultaneously sets the grooves on the outer wall of the pull rod 3 and the inner wall of the guide sleeve 4 in the axial direction to accommodate the first ball group 5.

[0037] Specifically, the grooves include the first groove 401 provided on the inner wall of the guide sleeve 4 and the second groove 301 provided on the outer wall of the pull rod 3 and opposite to the first groove 401, both the first groove 401 and the second groove 301 are semicircular, and the first ball group 5 is simultaneously provided in the first groove 401 and the second groove 301.

[0038] Referring to Figure 4 and Figure 5 , the guide sleeve 4 is provided with a stop step 402 at the lower end of the first groove 401, and the guide sleeve 4 is provided with a first ring groove 403 at the upper end of the first groove 401, and the first ring groove 403 is provided with a first retainer ring 404, the stop step 402 and the first retainer ring 404 are used to stop the first ball group 5 in the first groove 401, to prevent the first ball group 5 from falling off the guide sleeve 4.

[0039] At the same time, the pull rod 3 is provided with a second ring groove 302 at the upper end of the second groove 301, and the second ring groove 302 is provided with a second retainer ring 303 for stopping the first ball group 5, further preventing the first ball group 5 from falling out of the groove.

[0040] As a preferred, the second groove 301 provided on the outer wall of the pull rod 3 and the first groove 401 provided on the inner wall of the guide sleeve 4 each have at least three. Exemplarily, four first grooves 401 and four second grooves 301 are provided, the four first grooves 401 and the four second grooves 301 are annularly and equally spaced and one-to-one corresponding, and each first groove 401 and second groove 301 accommodates a first ball group 5. The present application sets the first ball group 5 which is not limited to four rows distributed in the axial direction between the pull rod 3 and the guide sleeve 4, so that the pull rod 3 and the guide sleeve 4 are completely in rolling contact with the first ball group 5, the friction force is greatly reduced, and at the same time the stability of the reciprocating motion of the pull rod 3 in the guide sleeve 4 through the first ball group 5 can be ensured.

[0041] In the embodiment, the first ball group 5 is preferably steel balls, and the first ball group 5 and the groove accommodating the first ball group 5 can have a very smooth surface through grinding and polishing process, so the friction between the parts is small, the rotating torque of the variable vacuum capacitor is further reduced, and the mechanical life of the variable vacuum capacitor can be improved.

[0042] As Figure 1As shown, the transmission system of a conventional variable vacuum capacitor consists of a rotating screw 17 and an adjusting nut 18. The adjusting nut 18 is fixedly mounted in the inner bore of the pull rod 15 and threadedly connected to the rotating screw 17. The rotating screw 17 is connected to a motor, which drives the rotating screw 17 to rotate, thereby driving the pull rod 15 and the movable electrode up and down through the adjusting nut 18. To ensure smooth movement of the adjusting nut 18, a certain gap is left between the rotating screw 17 and the adjusting nut 18. Similarly, the size of this gap has a significant impact on the variable vacuum capacitor's torque and capacitance repeatability. Furthermore, the torque required for capacitance adjustment, capacitance change accuracy, capacitance adjustment speed, and mechanical life of the variable vacuum capacitor are all limited by the thread specifications, the material of the rotating parts, and their surface condition. Generally speaking, the torque of conventional variable vacuum capacitors is 0.15 N·m, the capacitance repeatability is 0.5%, and the adjustment speed, i.e., the motor speed, is typically less than 600 rpm.

[0043] To solve the above technical problems, see Figure 3 and Figure 6 The transmission mechanism of the present invention includes a rotating screw 6 and an adjusting nut 7. The adjusting nut 7 is sleeved on the rotating screw 6 and fixedly connected to the pull rod 3. The outer wall of the rotating screw 6 is provided with a first spiral groove 601, and the inner wall of the adjusting nut 7 is provided with a second spiral groove 701. A second ball group 8 is provided between the first spiral groove 601 and the second spiral groove 701. The second ball group 8 is in rolling contact with the rotating screw 6 and the adjusting nut 7, so that the friction between the rotating screw 6 and the adjusting nut 7 is changed from sliding friction to rolling friction, thereby reducing the matching friction between the rotating screw 6 and the adjusting nut 7. The gap and contact area are combined, thereby significantly reducing the rotational torque of the variable vacuum capacitor and significantly improving the capacitance accuracy. Specifically, the rotational torque can be less than 0.08N·m, the capacitance repeatability deviation can be less than 0.25%, the capacitance adjustment speed can reach 2000rpm, and the adjustment time is reduced from the previous 1min to 100ms. This not only achieves the purpose of fast and precise capacitance adjustment of the variable vacuum capacitor, but also, due to the reduced rotational torque, users can choose a low-power drive motor, helping users to reduce the size and weight of the matcher, reducing the manufacturing cost of semiconductor equipment.

[0044] Among them, the second ball group 8 is preferably steel balls, and the first spiral groove 601 and the second spiral groove 701 are also semicircular. The second ball group 8, the first spiral groove 601 and the second spiral groove 701 can obtain a very smooth surface through grinding and polishing processes, so the friction between the parts is small, which further reduces the rotational torque of the variable vacuum capacitor and at the same time can improve the mechanical life of the variable vacuum capacitor.

[0045] See Figure 6The interior of the adjusting nut 7 is provided with a ball return hole 702, the ball return hole 702, the second spiral groove 701 and the part opposite to the second spiral groove 701 jointly constitute a ball circulating channel, and the second ball group 8 circulates and rolls in the ball circulating channel, so as to ensure the reciprocating rotation of the second ball group 8 between the rotating screw 6 and the adjusting nut 7.

[0046] The adjusting nut 7 is provided with a ball guide joint 703 at both ends of the ball return hole 702, the ball guide joint 703 is used for guiding the second ball group 8 to enter and exit the ball return hole 702, and can prevent the second ball group 8 from falling out of the ball circulating channel.

[0047] Referring to Figure 3 and Figure 4 The upper end of the pull rod 3 is provided with an avoiding hole 304 along the axis, and the upper section of the avoiding hole 304 is expanded in diameter to form a stepped hole 305, the adjusting nut 7 is fixed in the stepped hole 305, the lower end of the rotating screw 6 penetrates the adjusting nut 7 and extends into the avoiding hole 304, and the avoiding hole 304 is used for avoiding the rotating screw 6 when the pull rod 3 moves up and down.

[0048] The lower end of the rotating screw 6 penetrates the adjusting nut 7 and is fixed with an anti-falling part 9, the anti-falling part 9 can be but is not limited to a locking nut, the lower end of the rotating screw 6 is provided with an external thread, and the locking nut is threadedly fixed at the lower end of the rotating screw 6 and is used for forming a stop with the adjusting nut 7 to prevent the adjusting nut 7 from being separated from the rotating screw 6.

[0049] Referring to Figure 2 and Figure 3 The upper end of the guide sleeve 4 is provided with a flange part protruding from the top of the shell 1, and the flange part of the guide sleeve 4 is fixed with a sleeve 10, the interior of the sleeve 10 is provided with a moving space 1001 for the linear up-down reciprocating movement of the pull rod 3 and the adjusting nut 7. In addition, the top of the sleeve 10 is provided with a plane bearing 11, the upper end of the rotating screw 6 penetrates the plane bearing 11 and is fixedly connected with a motor joint 12 through a bolt. The utility model sets the bolt and the motor joint 12 at the upper end of the rotating screw 6, so as to limit the position of the rotating screw 6 and facilitate the connection of the rotating screw 6 with the motor. The shape of the motor joint 12 can be adjusted according to the connection mode of the user, and the motor joint 12 of the embodiment is a T-slot connection mode.

[0050] Therefore, the variable vacuum capacitor has the advantages that the friction between the pull rod 3 and the guide sleeve 4 is changed from sliding friction to rolling friction, the matching gap and the contact area between the pull rod 3 and the guide sleeve are reduced, the rotating torque and the capacitance repeatability deviation of the variable vacuum capacitor are reduced, the capacitance adjustment speed and the precision are improved, the purpose of quickly and accurately adjusting the capacitance of the variable vacuum capacitor is achieved, and the requirement of quickly and accurately matching the high-frequency impedance in the semiconductor equipment is met; meanwhile, the first helical groove 601 is arranged on the outer wall of the rotating screw 6, the second helical groove 701 is arranged on the inner wall of the adjusting nut 7, the second ball group 8 is arranged between the first helical groove 601 and the second helical groove 701, the friction between the rotating screw 6 and the adjusting nut 7 is changed from sliding friction to rolling friction, the matching gap and the contact area between the rotating screw 6 and the adjusting nut 7 are reduced, the rotating torque of the variable vacuum capacitor is greatly reduced, the capacitance precision is obviously improved, the purpose of quickly and accurately adjusting the capacitance of the variable vacuum capacitor is achieved, and the driving motor with small power can be selected due to the reduced rotating torque, the volume and the weight of the matching device are reduced, and the manufacturing cost of the semiconductor equipment is reduced.

[0051] In the foregoing description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the above descriptions are only preferred embodiments of the present application, and the present application can be implemented in many different ways from those described herein, so the present application is not limited to the above disclosed specific implementation. Meanwhile, any person skilled in the art can make many possible changes and modifications to the technical solutions of the present application, or modify equivalent embodiments, without departing from the scope of the technical solutions of the present application, by using the disclosed methods and technical contents. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, without departing from the scope of the technical solutions of the present application, are still within the protection scope of the technical solutions of the present application.

Claims

1. A variable vacuum capacitor, comprising a housing (1), a movable electrode group (2) movably arranged in the housing (1), a pull rod (3) fixedly connected to the movable electrode group (2), a transmission mechanism connected to the pull rod (3), and a guide sleeve (4) fixedly mounted on the housing (1), wherein the transmission mechanism is used to drive the movable electrode group (2) to perform linear reciprocating motion through the pull rod (3) under the drive of an external power device; and characterized in that: The pull rod (3) is coaxially inserted into the guide sleeve (4), and a first ball group (5) is axially arranged between the pull rod (3) and the guide sleeve (4), and the first ball group (5) is in rolling contact with both the pull rod (3) and the guide sleeve (4).

2. The variable vacuum capacitor according to claim 1, wherein: The outer wall of the pull rod (3) and / or the inner wall of the guide sleeve (4) are provided with grooves along the axial direction, and the first ball group (5) is arranged in the grooves along the axial direction.

3. The variable vacuum capacitor according to claim 2, wherein: The groove comprises a first groove (401) provided on the inner wall of the guide sleeve (4); the guide sleeve (4) is provided with a stop step (402) along one end of the first groove (401) and a first annular groove (403) at the other end; a first retaining ring (404) is installed in the first annular groove (403); the stop step (402) and the first retaining ring (404) are used to stop the first ball group (5) in the first groove (401).

4. The variable vacuum capacitor according to claim 3, wherein: The groove also includes a second groove (301) provided on the outer wall of the pull rod (3) and opposite to the first groove (401); the first ball group (5) is provided in both the first groove (401) and the second groove (301); the pull rod (3) is provided with a second annular groove (302) along the upper end of the second groove (301); a second retaining ring (303) for stopping the first ball group (5) is installed in the second annular groove (302).

5. The variable vacuum capacitor according to claim 2, wherein: There are at least three grooves provided on the outer wall of the pull rod (3) or the inner wall of the guide sleeve (4), the at least three grooves are distributed in an annular shape at equal intervals, and each groove accommodates the first ball group (5).

6. The variable vacuum capacitor according to claim 1, wherein: The transmission mechanism includes a rotating screw (6) and an adjusting nut (7), wherein the adjusting nut (7) is sleeved on the rotating screw (6) and fixedly connected to the pull rod (3), the outer wall of the rotating screw (6) is provided with a first spiral groove (601), the inner wall of the adjusting nut (7) is provided with a second spiral groove (701), and a second ball group (8) is provided between the first spiral groove (601) and the second spiral groove (701).

7. The variable vacuum capacitor according to claim 6, wherein: A ball return hole (702) is provided inside the adjusting nut (7), and the ball return hole (702), the second spiral groove (701) and the portion of the first spiral groove (601) opposite to the second spiral groove (701) together constitute a ball circulation channel, and the second ball group (8) circulates and rolls in the ball circulation channel; wherein, the adjusting nut (7) is provided with ball guide joints (703) at both ends of the ball return hole (702).

8. The variable vacuum capacitor according to claim 6, wherein: The lower end of the rotating screw (6) passes through the adjusting nut (7) and is fixed with an anti-slip component (9).

9. The variable vacuum capacitor according to claim 6, wherein: The upper end of the pull rod (3) is provided with an avoidance hole (304) along the axis, and the inner diameter of the upper section of the avoidance hole (304) is enlarged to form a stepped hole (305), the adjusting nut (7) is fixed in the stepped hole (305), and the lower end of the rotating screw (6) passes through the adjusting nut (7) and extends into the avoidance hole (304).

10. The variable vacuum capacitor according to claim 6, wherein: A sleeve (10) is fixed to the top of the housing (1), and a movable space (1001) is provided inside the sleeve (10) for the pull rod (3) and the adjusting nut (7) to perform linear reciprocating motion. A plane bearing (11) is installed on the top of the sleeve (10), and the upper end of the rotating screw (6) passes through the plane bearing (11) and is fixedly connected to the motor connector (12).

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