Dry vacuum pump

Abstract

A dry vacuum pump (1) is provided with a sealing mechanism (18) that seals a shaft hole (71) that connects a pump chamber (2) and a gear chamber (4). In the sealing mechanism (18), sealing parts (21, 22) formed by sealing rings (31, 32) are arranged at intervals in the axial direction. Compared with a contact seal such as a lip seal, mechanical loss such as sliding loss can be reduced, and power reduction can be facilitated. A lubricating oil trapping groove (77) is formed between the sealing parts (21, 22), and lubricating oil passing through the sealing parts (21, 22) formed by the sealing rings (31, 32) is trapped by the lubricating oil trapping groove (77). The sealing performance required by the sealing mechanism (18) is ensured.

Description

Technical Field

[0001] The present invention relates to a dry vacuum pump such as a multi-stage Roots pump, and more particularly to a shaft seal portion that seals between a gear chamber that houses a gear train for rotating a pair of rotor shafts in synchronous manner in opposite directions and a pump chamber. Background Art

[0002] In a dry vacuum pump such as a multi-stage Roots pump, a motor for driving the pump is disposed on one side of the pump chamber, and a gear chamber is disposed on the other side to house a gear train for transmitting the rotation of the rotor shaft on the driving side to the rotor shaft on the driven side. Dry vacuum pumps do not use lubricating oil in the pump chamber to form a clean vacuum, but lubricating oil is supplied to the gear chamber for lubrication of the gears in the gear chamber, the bearings of the rotor shaft, and the like. The rotor shaft extends through an axial hole extending through the partition wall between the pump chamber and the gear chamber. A sealing mechanism consisting of a contact seal such as a lip seal is used to seal the inner circumference of the axial hole and the outer circumference of the rotor shaft, thereby preventing the lubricating oil from leaking into the pump chamber (Patent Documents 1 and 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2008 / 152713

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-39396 Summary of the Invention

[0007] Contact seals, such as lip seals, are commonly used as sealing mechanisms between the pump chamber and the gear chamber (mechanical chamber) of a dry vacuum pump. Contact seals, which generate sliding resistance, are detrimental to the low power consumption (energy saving) of dry vacuum pumps. To achieve this, non-contact seals are being considered in place of contact seals. However, non-contact seals generally have inferior sealing properties compared to contact seals and may not guarantee the required sealing properties for the shaft seal of a dry vacuum pump.

[0008] An object of the present invention is to provide a dry vacuum pump that can ensure the sealing performance required for a sealing mechanism between a pump chamber and a gear chamber and reduce mechanical loss caused by the sealing mechanism.

[0009] In order to solve the above-mentioned problems, the dry vacuum pump of the present invention is characterized by comprising:

[0010] a pump chamber and a gear chamber, which are separated by a partition wall;

[0011] an axial hole penetrating the partition wall and communicating with the pump chamber and the gear chamber;

[0012] a rotor shaft extending from the pump chamber through the shaft hole toward the gear chamber;

[0013] a bearing mounted in the shaft hole and supporting the rotor shaft so as to be rotatable relative to the partition wall; and

[0014] The sealing mechanism is arranged on the pump chamber side relative to the bearing and seals the shaft hole through which the shaft end of the rotor shaft passes.

[0015] The sealing mechanism has:

[0016] a plurality of sealing portions, each of which is arranged at different positions in the axial direction and is formed by one or more sealing rings; and

[0017] One or more lubricating oil catching grooves are located between the seal portions adjacent to each other in the axial direction and are formed on the inner peripheral surface of the shaft hole.

[0018] Regarding the sealing mechanism of the dry vacuum pump of the present invention, the sealing parts formed by the sealing rings are arranged at intervals in the axial direction. Compared with the case of using contact seals such as lip seals, it is possible to reduce mechanical losses caused by sliding resistance, etc., which is conducive to low power consumption. A lubricating oil capture groove is formed between a pair of adjacent sealing parts in the axial direction, and the lubricating oil passing through the sealing part formed by the sealing ring is captured by the lubricating oil capture groove. The sealing performance required by the sealing mechanism is ensured. In addition, by using sealing rings, the sealing mechanism can be constructed at a low cost compared to the case of providing a sealing part with a complex labyrinth structure.

[0019] Here, one or more sealing portions may be arranged on one side of the lubricating oil capturing groove in the axial direction. Similarly, one or more sealing portions may be arranged on the other side of the lubricating oil capturing groove in the axial direction. By arranging an appropriate number of sealing portions on both sides of the lubricating oil capturing groove, the required sealing performance of the sealing mechanism can be ensured.

[0020] Preferably, the sealing mechanism of the present invention includes a return hole for returning lubricating oil from the lubricating oil catching groove to the gear chamber. This maintains the lubricating oil catching ability of the lubricating oil catching groove and prevents or suppresses the lubricating oil from flowing out to the pump chamber.

[0021] Next, the sealing mechanism can be configured with a first oil slinger and a second oil slinger, mounted on the outer circumference of the shaft. In this case, the first oil slinger is preferably positioned axially between the pump chamber and the sealing portion closest to the pump chamber, while the second oil slinger is preferably positioned axially between the bearing and the sealing portion closest to the bearing. By placing the oil slingers on both axial sides of the multiple sealing portions formed by the sealing rings, the amount of lubricating oil flowing into the sealing portions can be reduced. This improves the sealing performance of the sealing mechanism.

[0022] In this case, a lubricating oil discharge hole is preferably provided on the inner circumference of the shaft hole surrounded by the second oil slinger located on the gear chamber side, so that the lubricating oil discharge hole communicates with the gear chamber directly or via the lubricating oil return hole. The centrifugal force of the second oil slinger squeezes lubricating oil flowing from the gear chamber side outward and returns it to the gear chamber side through the lubricating oil discharge hole. This reduces the amount of lubricating oil flowing into the seal ring, thereby achieving an effective sealing structure using this sealing mechanism.

[0023] The sealing mechanism of the present invention, for example, comprises: a cylindrical collar mounted on the outer circumferential surface of the rotor shaft end portion; and a plurality of seal ring mounting grooves formed on the outer circumferential surface of the cylindrical collar at intervals in the axial direction. In this case, the sealing portion comprises one or more seal rings mounted in the seal ring mounting grooves and contacting or facing the inner circumferential surface of the shaft hole with a predetermined gap therebetween. Alternatively, a first oil flinger ring may be integrally formed at the pump chamber-side end of the cylindrical collar, and a second oil flinger ring may be positioned between the gear chamber-side end of the cylindrical collar and the bearing.

[0024] Next, it is preferable that the outer diameter of the seal ring is smaller than the inner diameter of the bearing insertion hole formed in the shaft hole. This allows for efficient lubrication and cooling of the bearing.

[0025] Effects of the Invention

[0026] In the present invention, a seal ring is used as the sealing mechanism between the pump chamber and the gear chamber of a dry vacuum pump. Furthermore, a lubricating oil capture groove is disposed between the sealing portions formed by the seal ring. This provides a dry vacuum pump having a sealing mechanism that contributes to low power consumption while ensuring the required sealing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic cross-sectional view showing the structure of a dry vacuum pump to which the present invention is applied.

[0028] Figure 2 Therefore Figure 1 A schematic partial cross-sectional view showing the structure of a sealing mechanism for a rotor shaft on the drive side of a dry vacuum pump.

[0029] Figure 3 (A) and (B) are explanatory diagrams showing examples of arrangement of seal rings in the shaft sealing portion. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of a dry vacuum pump to which the present invention is applied will be described with reference to the accompanying drawings. Figure 11 is a cross-sectional view showing a schematic structure of a dry vacuum pump according to an embodiment. The dry vacuum pump 1 is, for example, a multi-stage Roots pump, and is used in a horizontal position with the pump center axis 1a being horizontal.

[0031] The dry vacuum pump 1 includes a multi-stage pump chamber 2, a motor 3, and a gear chamber 4. The motor 3 is arranged on one side of the pump center axis 1a, i.e., in the axial direction, across the pump chamber 2, and the gear chamber 4 is arranged on the other side. The pump chamber 2 is formed by a pump housing 5 and a motor-side bearing housing 6 and a gear chamber-side bearing housing 7 mounted on both sides thereof. The gear chamber-side bearing housing 7 functions as a partition wall separating the pump chamber 2 and the gear chamber 4. The gear chamber 4 is formed inside a gear chamber housing 8 mounted on the gear chamber-side bearing housing 7. The pump chamber 2 is divided into a plurality of pump chambers in the direction of the pump center axis 1a. For example, it is divided into four stages of pump chambers 2a to 2d. The pump chamber 2a on the vacuum side is connected to the pump intake port 9, and the pump chamber 2d on the atmosphere side is connected to the pump exhaust port 10.

[0032] A pair of rotor shafts extend in parallel inside the multi-stage pump chamber 2. Figure 1 Only the rotor shaft 11 on the driving side is shown. The central axis of the rotor shaft 11 is the pump central axis 1a. The rotor shaft 11 extends through the multi-stage pump chambers 2 and is driven for rotation by the motor 3. Multiple pairs of rotors 3a-3d are mounted on the rotor shaft 11, positioned within each pump chamber 2a-2d. Similarly, multiple pairs of rotors are mounted on the other driven-side rotor shaft (not shown), positioned within each pump chamber 2a-2d.

[0033] The rotor shaft 11 is rotatably supported by a motor-side bearing 12 and a gear-chamber-side bearing 13. The motor-side bearing 12, serving as the free-side bearing, is, for example, a grease-filled bearing. The gear-chamber-side bearing 13, serving as the opposite, fixed-side bearing, is an oil-lubricated bearing lubricated by the lubricating oil stored in the gear chamber 4. The gear-chamber-side bearing 13 is mounted in a bearing insertion hole 72 formed in a portion of the gear chamber 4 side of the shaft hole 71 formed in the gear-chamber-side bearing housing 7, supporting a shaft end 111 at the distal end of the rotor shaft 11. Similarly, the other driven-side rotor shaft (not shown) is also rotatably supported by the motor-side and gear-chamber-side bearings (not shown).

[0034] The distal end portion 111 of the driving-side rotor shaft 11 protrudes from the gear-chamber-side bearing 13 into the gear chamber 4. As indicated by the imaginary line, a driving-side timing gear 14 is mounted to this distal end portion. Similarly, the distal end portion of the other, unillustrated, driven-side rotor shaft also protrudes into the gear chamber 4, and a driven-side timing gear (not shown) is mounted to this distal end portion. The driving-side timing gear 14 and the driven-side timing gear mesh with each other, and the driven-side rotor shaft rotates synchronously in the opposite direction to the rotation of the driving-side rotor shaft 11. The meshing portions and shaft portions of the timing gear 14 and other components are lubricated by lubricating oil from the gear chamber 4.

[0035] A seal mechanism 18 seals the gap between the shaft hole 71 formed in the gear chamber-side bearing housing 7 and the shaft end 111 of the driving-side rotor shaft 11 passing therethrough. The same seal applies to the other side of the driven-side rotor shaft (not shown). The seal mechanism 18 blocks the flow of lubricating oil through the shaft hole 71, preventing it from flowing into the pump chamber 2.

[0036] (Sealing mechanism)

[0037] Figure 2 This is a partial cross-sectional view showing the structure of the sealing mechanism 18 of the driving-side rotor shaft 11 of the dry vacuum pump 1. The sealing mechanism on the driven-side rotor shaft (not shown) is similarly configured, and therefore its description is omitted.

[0038] The gear chamber-side bearing housing 7, incorporating the sealing mechanism 18, comprises a housing body 73 with an annular hollow portion, and a cylindrical body 74 coaxially mounted to the housing body 73 from the gear chamber side. The gear chamber-side bearing housing 7 has a buffer chamber 75 formed within it. The shaft hole 71 is defined by the hollow portion of the cylindrical body 74 and a center hole 711 formed in the center of the end wall of the housing body 73 on the pump chamber side. The portion of the shaft hole 71 on the gear chamber 4 side forms a bearing insertion hole 72 with a slightly larger inner diameter, where the gear chamber-side bearing 13 is mounted from the gear chamber 4 side. The inner circumferential surface of the shaft hole 71 on the pump chamber side is divided by an annular gap 712, through which the shaft hole 71 communicates with the buffer chamber 75. The buffer chamber 75 communicates with the gear chamber 4 via a communication hole (equalizing hole) (not shown) formed in the housing body 73.

[0039] The sealing mechanism 18 includes a plurality of sealing portions, for example, two sealing portions 21 and 22, arranged at intervals in the axial direction. In this example, a cylindrical collar 40 is mounted on the shaft end 111 of the rotor shaft 11 while coaxially surrounding the outer peripheral surface portion of the gear chamber side bearing 13 on the pump chamber side. Two sealing ring mounting grooves 41 and 42 are formed on the circular outer peripheral surface of the cylindrical collar 40 at a predetermined interval in the axial direction. Each sealing ring mounting groove 41 and 42 is an annular groove having a rectangular cross-section that opens radially outward. One or more sealing rings 31 made of a material such as metal, resin, or rubber are mounted in the sealing ring mounting groove 41, and one or more sealing rings 32 made of a material such as metal, resin, or rubber are also mounted in the sealing ring mounting groove 42. Seal rings of the same structure are used as the sealing rings 31 and 32, but different structures may also be used. Each seal ring 31, 32 contacts the inner circumferential surface of the shaft hole 71 with a predetermined elastic force, and faces the outer circumferential surface of the rotor shaft 11 (the bottom surface of the seal ring mounting grooves 41, 42 of the cylindrical shaft ring 40) in a non-contact state with a slight gap therebetween. Seal rings 31, 32 may be formed by multiple wraps, for example, two wraps. Seal rings 31, 32 assembled in seal ring mounting grooves 41, 42 form sealing portions 21, 22. Furthermore, the outer diameter of seal rings 31, 32 is smaller than the inner diameter of bearing insertion hole 72 formed in shaft hole 71.

[0040] The sealing mechanism 18 also includes a lubricating oil catching groove 77 for capturing lubricating oil. The lubricating oil catching groove 77 is formed on the inner circumferential surface of the shaft hole 71 and is located between the axially adjacent sealing portions 21 and 22. The lubricating oil catching groove 77 is an annular groove with a rectangular cross-section that opens radially inward. It captures lubricating oil that flows axially along the shaft hole 71, past the sealing portions 21 and 22. For example, it captures lubricating oil that flows along the shaft hole 71 from the gear chamber 4 or the gear chamber-side bearing 13, past the sealing portion 22. Depending on the situation, the lubricating oil catching groove 77 may be omitted.

[0041] The lubricating oil return hole 78 communicates with the groove portion of the lubricating oil catching groove 77 located below the shaft end 111. The lubricating oil return hole 78 extends through the gear chamber-side bearing housing 7 and communicates with the gear chamber 4. The lubricating oil return hole 78 is located at a position higher than the oil level L of the lubricating oil stored in the gear chamber 4 so as to prevent the lubricating oil from flowing back from the gear chamber 4 to the lubricating oil catching groove 77.

[0042] The sealing mechanism 18 also includes a first oil slinger 51 and a second oil slinger 52 mounted on the outer circumferential surface of the shaft end 111 of the rotor shaft 11. The first oil slinger 51 is axially positioned between the seal portion 21 and the pump chamber 2, while the second oil slinger 52 is axially positioned between the seal portion 22 and the gear chamber-side bearing 13. In this example, the first oil slinger 51 is integrally formed with the pump chamber 2-side end of the cylindrical collar 40 mounted on the shaft end 111, with a radially outwardly protruding annular shape. In contrast, the second oil slinger 52 is a separate annular component from the cylindrical collar 40, positioned between the opposite end of the cylindrical collar 40 and the gear chamber-side bearing 13, and fixed to the outer circumferential surface of the shaft end 111 of the rotor shaft 11.

[0043] The lubricating oil flowing out from the gear chamber-side bearing 13 toward the second oil slinger 52 is squeezed radially outward by the centrifugal force of the second oil slinger 52, which rotates integrally with the rotor shaft 11. This prevents or suppresses the lubricating oil from flowing out in the axial direction toward the seal portion 22. Furthermore, the lubricating oil flowing out to the first oil slinger 51 is squeezed radially outward toward the buffer chamber 75 by the centrifugal force of the first oil slinger 51, which rotates integrally with the rotor shaft 11. This prevents or suppresses the lubricating oil from flowing into the pump chamber 2.

[0044] The upper end of the lubricating oil discharge hole 79 opens into the inner circumferential surface of the shaft hole 71, which surrounds the second oil slinger 52 located adjacent to the gear chamber-side bearing 13. The lubricating oil discharge hole 79 is formed below the shaft end 111 of the rotor shaft 11 of the gear chamber-side bearing housing 7, and its lower end merges midway with the lubricating oil return hole 78. Lubricating oil expelled radially outward by the second oil slinger 52 is returned from the lubricating oil discharge hole 79 to the gear chamber 4 via the lubricating oil return hole 78.

[0045] As described above, the sealing mechanism 18 of the dry vacuum pump 1 of this embodiment utilizes seal rings 31 and 32, with the seal portions 21 and 22 spaced apart in the axial direction. Compared to the use of contact seals such as lip seals, this reduces mechanical losses such as sliding loss, contributing to lower power consumption. The use of seal rings 31 and 32 allows for a more cost-effective sealing mechanism compared to the use of complex labyrinth-like seals.

[0046] Furthermore, a lubricating oil catching groove 77 is formed between the pair of axially adjacent seal portions 21 and 22. Lubricating oil passing through the seal portions 21 and 22 is captured by the lubricating oil catching groove 77. The lubricating oil captured by the lubricating oil catching groove 77 is returned to the gear chamber 4 through the lubricating oil return hole 78. This maintains the lubricating oil capture performance of the lubricating oil catching groove 77, and prevents or suppresses the lubricating oil from flowing toward the pump chamber 2.

[0047] Furthermore, first and second oil slingers 51 and 52 are disposed on either side of the sealing portions 21 and 22 formed by the seal rings 31 and 32. This reduces the amount of lubricating oil flowing into the sealing portions 21 and 22, ensuring the sealing performance of the sealing mechanism 18. Lubricating oil squeezed out by the second oil slinger 52 returns to the gear chamber 4 through the lubricating oil discharge hole 78. This reduces the amount of lubricating oil flowing into the seal ring 32, ensuring the sealing performance of the sealing mechanism 18.

[0048] On this basis, in this example, the outer diameters of the seal rings 31 and 32 are made smaller than the inner diameter of the bearing insertion hole 72 formed in the shaft hole 71. This allows the gear chamber side bearing 13 to be efficiently lubricated and cooled. That is, it is possible to ensure that lubricating oil actively flows into the gear chamber side bearing 13 assembled in the bearing insertion hole 72, and the oil that flows in accumulates in the gear chamber side bearing 13. As a result, the gear chamber side bearing 13 can be efficiently lubricated. On the other hand, the gear chamber side bearing 13 is cooled by the lubricating oil that is lifted up by the timing gear 14 and splashes onto the gear chamber side bearing 13 and other parts. The lubricating oil accumulated in the gear chamber side bearing 13 is constantly circulated, thereby improving the cooling efficiency of the gear chamber side bearing 13 and other parts.

[0049] (Arrangement example of seal portion)

[0050] Figure 3 (A) and (B) are explanatory diagrams showing an example of a sealing mechanism 18 including three or more sealing portions.

[0051] about Figure 3 The sealing mechanism 18A shown in FIG. 7A has two seals 211 and 212 disposed on the pump chamber 2 side of the lubricating oil catching groove 77, and two seals 221 and 222 disposed on the gear chamber 4 side of the lubricating oil catching groove 77. Similar to the seals 21 and 22, these four seals 211 to 222 are constructed by mounting one or more seal rings 311, 312, 321, and 322 in seal ring mounting grooves 411, 412, 421, and 422, respectively. This allows for a symmetrical arrangement, with the same number of seals disposed on both sides of the lubricating oil catching groove 77.

[0052] about Figure 3In the sealing mechanism 18B shown in FIG (B), three sealing portions 211, 212, and 213 are arranged on the pump chamber 2 side of the lubricating oil catching groove 77, while only one sealing portion 22 is arranged on the gear chamber 4 side of the lubricating oil catching groove 77. Similar to the aforementioned sealing portions 21 and 22, these four sealing portions 211, 212, 213, and 22 are constructed by fitting one or more seal rings 311, 312, 313, and 32 into seal ring mounting grooves 411, 412, 413, and 42, respectively. In this manner, an asymmetric arrangement can also be employed, with different numbers of sealing portions arranged on either side of the lubricating oil catching groove 77.

Claims

1. A dry vacuum pump, characterized in that: The dry vacuum pump has: a pump chamber and a gear chamber, which are separated by a partition wall; an axial hole penetrating the partition wall and communicating with the pump chamber and the gear chamber; a rotor shaft extending from the pump chamber through the shaft hole toward the gear chamber; a bearing mounted in the shaft hole and supporting the rotor shaft so as to be rotatable relative to the partition wall; and a sealing mechanism disposed on the pump chamber side relative to the bearing and sealing the shaft hole through which the shaft end of the rotor shaft passes; The sealing mechanism comprises: a plurality of sealing portions, each of which is arranged at different positions in the axial direction and is formed by one or more sealing rings; and One or more lubricating oil capturing grooves are located between the seal portions adjacent to each other in the axial direction and are formed on the inner peripheral surface of the shaft hole.

2. The dry vacuum pump according to claim 1, characterized in that One or more seal portions are arranged on one side of the lubricating oil collecting groove in the axial direction. One or more seal portions are arranged on the other side of the lubricating oil capturing groove in the axial direction.

3. The dry vacuum pump according to claim 1, characterized in that The dry vacuum pump includes a lubricating oil return hole for returning the lubricating oil from the lubricating oil collecting groove to the gear chamber.

4. The dry vacuum pump according to claim 1, characterized in that The dry vacuum pump comprises a first oil slinger and a second oil slinger mounted on the outer peripheral surface of the shaft end portion of the rotor shaft. The first oil slinger is located between the pump chamber and the sealing portion located closest to the pump chamber in the axial direction. The second oil slinger is located between the bearing and the sealing portion located closest to the bearing in the axial direction.

5. The dry vacuum pump according to claim 4, characterized in that The dry vacuum pump includes: a lubricating oil discharge hole opened at a portion of the inner peripheral surface of the shaft hole surrounding the second oil slinger; The lubricating oil discharge hole is communicated with the gear chamber.

6. The dry vacuum pump according to claim 4, characterized in that The sealing mechanism comprises: a cylindrical collar mounted on an outer peripheral surface of an end portion of the rotor shaft; and A plurality of seal ring mounting grooves are formed on the outer peripheral surface of the cylindrical collar at intervals in the axial direction. The sealing portion is formed by one or more sealing rings respectively mounted in the sealing ring mounting groove and in contact with or facing the inner peripheral surface of the shaft hole with a predetermined gap therebetween. The first oil slinger is integrally formed at the end portion of the cylindrical collar on the pump chamber side. The second oil slinger is arranged between the end portion of the cylindrical collar on the gear chamber side and the bearing.

7. The dry vacuum pump according to claim 1, characterized in that The shaft hole has a bearing insertion hole for assembling the bearing. The outer diameter of the sealing ring is smaller than the inner diameter of the bearing insertion hole.

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