Environmentally friendly rotary vane vacuum pump

Abstract

FIELD: vacuum pumps.SUBSTANCE: improved oil-lubricated rotary vane vacuum pump. Pump with at least one pump stage with a housing contains a rotor in a vane-rotor chamber. The inner wall of the vane-rotor chamber has a distance R0 to the center of the vane-rotor chamber. The inner wall of the vane-rotor chamber has at least one oil pocket. At least one oil pocket is formed with at least two sections. One or more oil pockets run along the circumference of the inner wall of the vane-rotor chamber. The sections differ in their cross-sectional area. At least one oil pocket has a total length d along the circumference of the inner wall of the vane-rotor chamber. The length d is made up of the length d1 of the first section and the length d2 of the second section. The ratio of d1 to d2 ranges from (1-2) to 1.EFFECT: reducing energy consumption at low suction pressures.16 cl, 4 dwg

Description

[0001] Field of invention

[0002] The invention relates to an improved oil-lubricated rotary vane vacuum pump with a rotor in a rotary vane chamber, wherein the inner wall of this rotary vane chamber contains at least one oil pocket with at least two oil pocket sections ("stepped oil pocket"), wherein one or more oil pockets extend along the circumference of the inner wall of the rotary vane chamber and wherein the oil pocket sections differ in their flow cross-section. In a preferred embodiment of the invention, the rotary vane chamber is cylindrical.

[0003] Rotary vane vacuum pumps comprise a pump stage with a casing in which a cylindrical rotor is eccentrically located in a preferably cylindrical vane-rotor chamber. In addition to the preferred circular cross-section, the vane-rotor chamber may also be oval, elliptical, or, in general, a continuous, symmetrical, numerically determined curve. Only the preferred shape (a cylindrical vane-rotor chamber) is described below; however, the invention is not limited thereto. The cylinder, together with the covers (of the cylinder), forms a casing into which the working medium enters, and is then compressed and expelled. The axis of the eccentrically located rotor runs parallel to and offset from the axis of the vane-rotor chamber. The rotor has one or more vanes. They are located in the rotor slots and are capable of sliding movement, wherein the slots are oriented approximately radially in cross-section.The vanes, driven by centrifugal force from the rotor's rotation, are pressed against the inner wall of the vane-rotor chamber. During vacuum pump operation, the rotor rotates radially offset from the central axis of the cylindrical vane-rotor chamber. This creates closed transport chambers, separated by vanes arranged radially offset, whose size changes per rotor revolution. This change in the size of the transport chambers during vacuum pump operation results in a pressure difference between the individual transport chambers and, consequently, between the inlet and outlet sides of the rotary positive displacement pump.

[0004] A typical rotary vane vacuum pump contains three vanes in three slots, creating three transport chambers. Rotary vane vacuum pumps with more or fewer vanes, slots, and transport chambers are also possible. For example, rotary vane vacuum pumps with two vanes, slots, and transport chambers are also possible.

[0005] Oil-lubricated rotary vane vacuum pumps are characterized by the fact that oil is introduced into the pump stage or, respectively, into the rotary vane chamber. This oil fills the gaps between the various components, particularly between the vanes and the walls of the rotary vane chamber. This prevents gas exchange between the various transport chambers. This allows higher vacuum levels to be achieved during operation than with dry rotary vane vacuum pumps.

[0006] The inner wall of the rotary vane chamber of rotary vane vacuum pumps typically contains one or more oil pockets. Preferably, the inner wall of the rotary vane chamber of large rotary vane vacuum pumps contains multiple oil pockets, while the inner wall of the rotary vane chamber of small pumps often has only one oil pocket.

[0007] Oil pockets are recesses in the inner wall of the vane-rotor chamber. These pockets allow theoretically separate transport chambers to communicate with each other, as the oil pockets create a channel between the transport chambers that uses gas to equalize pressure. The oil pockets extend along the circumference of the inner wall of the vane-rotor chamber and expand in the axial direction (their width). As the suction pressure decreases, more oil enters the pump stage or, respectively, the vane-rotor chamber due to the increasing pressure difference between the separator and the pump stage. The oil pockets create a volume into which oil can flow, preventing the vanes from attempting to compress the oil when suction pressures approach the final pressure, a process known as oil shock.This results in a reduction of the forces acting on the plate or plates and in minimizing pump noise.

[0008] In addition, the oil pockets also serve as oil collectors, thereby ensuring sufficient lubrication of the components in the pump stage.

[0009] The problem is that at suction pressures ≤ approximately 600 mbar, significant backflow losses due to oil pockets result, leading to increased energy consumption. When the exhaust valve is closed, the pressure in the front conveyor chamber is always higher than in the rear conveyor chamber. During compression, the gas uses the oil pocket to pass into the lower-pressure rear conveyor chamber. Once there, the gas is recompressed by the rotor's movement and passes again into the next rear conveyor chamber. The constant backflow increases losses, or, correspondingly, the vacuum pump's energy consumption in this suction pressure range. In other words, using long and deep oil pockets causes backflow of gas through the oil pocket itself in the low-suction-pressure region, as they form a channel between the chambers, leading to energy losses.

[0010] The object of the present invention is to reduce energy consumption at low suction pressures, in particular at suction pressures ≤ 600 mbar.

[0011] State of the art

[0012] The prior art solves this problem by shortening the oil pockets. While this optimizes energy consumption in the pressure range between the final pressure and 600 mbar, it also increases energy consumption at suction pressures above 600 mbar, as short and shallow oil pockets cause excessive compression at higher suction pressures. Since the oil pockets are typically connected to the outlet ports of the pump stage, at high suction pressures they determine the point at which gas escape is possible. Before the outlet ports are reached, the transport chamber already has excess pressure relative to atmospheric pressure, and the gas uses the oil pocket to flow into the front transport chamber and escape.If the oil pockets are shortened, the closed transport chamber reaches them later in the rotor revolution than with longer oil pockets. Until this point, the gas is compressed. This means that the gas has already reached the required relative atmospheric pressure before it reaches the oil pocket. However, since the gas cannot escape due to its geometry, it is overcompressed during further rotation, leading to energy losses. Therefore, shortening the oil pocket at suction pressures above 600 mbar also leads to significantly higher compression, known as overcompression.

[0013] Thus, another object of the invention is to optimize energy consumption over the entire range of suction pressures, i.e. pressures from the final pressure to atmospheric pressure.

[0014] In particular, the prior art discloses an oil-lubricated rotary vane vacuum pump, disclosed in JP 2006 097509 A, having at least one pump stage and including a housing with a rotor in a rotary vane chamber, wherein the inner wall of the rotary vane chamber is located at a certain distance from the center of the rotary vane chamber. The inner wall also has at least one oil pocket.

[0015] The well-known oil-lubricated rotary vane vacuum pump also suffers from all the previously mentioned drawbacks associated with gas backflow between the delivery chambers in the low-pressure range, as they form a channel that leads to energy loss. Shortening the oil pockets solves this problem only in the low-pressure range and leads to excessive compression above 600 mbar.

[0016] Therefore, the technical result can be seen in reducing the backflow of gas between the transport chambers in the rotary vane vacuum pump without reducing the efficiency at higher suction pressures due to over-compression.

[0017] Essence of the invention

[0018] The object of the invention is an oil-lubricated rotary vane vacuum pump 1 with at least one pump stage 2 with a housing 3 containing a rotor 4 in a rotary vane chamber 13, wherein the inner wall 5 of this rotary vane chamber has a distance R0 from the center of this rotary vane chamber, characterized in that the rotary vane chamber 13 contains on the inner wall 5 at least one oil pocket 9 with at least two sections 11 and 12 of the oil pocket, wherein one or more oil pockets 9 extend along the circumference of the inner wall 5 of the rotary vane chamber, and wherein the sections 11 and 12 of the oil pocket differ in their flow section. Preferably, the inner wall of the rotary vane chamber is cylindrical.

[0019] The invention will now be described based on a preferred embodiment of the oil-lubricated rotary vane vacuum pump according to the invention, in which the rotary vane chamber is cylindrical. However, the invention is not limited to this embodiment. As mentioned above, in addition to the preferred circular cross-section, the base of the rotary vane chamber may also have the shape of an oval, ellipse, or a generally continuous, symmetrical, numerically determined curve. In this case, the distance R0 of the inner wall of the rotary vane chamber from the center of the rotary vane chamber will vary (R01, R02, R03, etc.). In this case, it will also be clear to one skilled in the art that the distances of the individual sections of the oil pocket R1 and R2 from the center of the rotary vane chamber satisfy the conditions given below for the corresponding distance, i.e. R11>R21>R01 or, accordingly, R12>R22>R02, etc.

[0020] In a preferred embodiment of the invention, the oil pocket 9 comprises two oil pocket sections 11 and 12. The inner wall 14 of the first section 11 of the oil pocket preferably has a maximum distance R1 from the center of the vane-rotor chamber, and the inner wall 15 of the second section 12 of the oil pocket preferably has a distance R2 from the center of the vane-rotor chamber, wherein R1 is greater than R2 and R2 is greater than R0 (R1>R2>R0), wherein the first section 11 of the oil pocket transitions into the second section 12 of the oil pocket.

[0021] Since the oil pocket extends along the circumference of the inner wall 5 of the vane-rotor chamber, the term "length of the oil pocket section" refers to its arc size (see Fig. 3). In other words, the first section 11 of the oil pocket extends by the arc size d1, and the second section 12 of the oil pocket extends by the arc size d2.

[0022] The beginning and end of the oil pocket are respectively the point at which the distance to the center of the vane-rotor chamber deviates from R0.

[0023] Depending on the manufacturing method used for the oil pocket, i.e., either casting or milling, the inlet and / or outlet of the oil pocket is made flatter or flatter, i.e., the transition from R0 to R1 or R2 is shorter or longer. This also applies to the transition from one section of the oil pocket to another.

[0024] "Flow area" is the cross-sectional area of ​​an oil pocket section, i.e., the area used by gas and oil to pass from one transport chamber to another. The volumes of at least two oil pocket sections may be the same or different in size. If there are more than two oil pocket sections, they differ from each other in terms of flow area.

[0025] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, the volume of the oil pocket I with two oil pocket sections is 15-35 vol.%, preferably 20-30 vol.%, less than the volume of the traditional oil pocket II without two oil pocket sections in the traditional rotary vane vacuum pump with the same overall length and the same axial expansion of both oil pockets I and II. In this case, the first section of the oil pocket I and the oil pocket II, respectively, along their length have a distance R1 from the center of the rotary vane chamber, while the second section of the oil pocket I along its length has a distance R2 from the center of the rotary vane chamber, wherein R1>R2>R0.

[0026] It is also possible for the flow cross-section within individual sections of the oil pocket to vary continuously, i.e., without a stepped arrangement. However, both sections 11 and 12 of the oil pocket can still be clearly distinguished in their flow cross-sections through a variable stepped arrangement. Thus, their shape can be described using other mathematical forms, such as straight lines and splines.

[0027] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, the flow section in the oil pocket section 11 is larger than the flow section in the oil pocket section 12.

[0028] It is clear that the inner wall 5 of the vane-rotor chamber may also contain several such oil pockets 9, and individual or several oil pockets may be made either different or identical, respectively.

[0029] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, all of the provided oil pockets 9 have the same orientation, i.e., the oil pockets 9 are located next to each other on the inner wall 5 of the rotary vane chamber along a direction parallel to the circumferential direction. Such an arrangement of the oil pockets is shown, for example, in Fig. 4.

[0030] One or more oil pockets 9 may have a straight or curved shape along their length. In this context, "straight" means along a direction at a 90° angle to the rotor axis. "Curved" means that the oil pocket deviates from this direction along its length. It is also possible for straight and curved oil pockets to be present next to each other.

[0031] It is preferable that at least one oil pocket 9 is connected to an outlet channel 10. Preferably, the first portion 11 of the oil pocket is connected to the outlet channel 10. In another preferred embodiment of the invention, portion 11 of the oil pocket is connected to two outlet channels 10 and 10 1 .

[0032] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, two or more oil pockets have the same "width," i.e., the same axial expansion. In a particularly preferred embodiment of the invention, the oil pockets connected to one or more outlet channels are wider than the oil pockets not connected to the outlet channel. In another embodiment of the invention, the width of the oil pockets not connected to the outlet channel decreases with increasing axial distance to the outlet channel.

[0033] In a preferred embodiment of the oil-lubricated rotary vane vacuum pump 1 according to the invention, two or more oil pockets have the same overall length d. In a particularly preferred embodiment of the invention, the oil pockets connected to the outlet channel have the same overall length d, while other possibly provided oil pockets not connected to the outlet channel may be shorter.

[0034] In another embodiment of the invention, the oil pockets connected to the outlet channel have the same overall length d, while other existing oil pockets not connected to the outlet channel have a greater length.

[0035] During operation of the rotary vane vacuum pump according to the invention, in particular the rotary vane vacuum pump according to Fig. 2 or Fig. 4, as the suction pressure decreases due to the increasing pressure difference between the separator and the pump stage, more and more oil enters the pump stage. The oil pockets according to the invention create a volume into which oil can flow, so as to prevent the vanes from attempting to compress the oil when the suction pressure approaches the final pressure, a process known as oil shock. This results in a reduction in the forces acting on the vane or vanes and a reduction in pump noise.At suction pressures <approximately 600 mbar, gas backflow through the oil pocket is still possible. However, due to the two sections of the oil pocket and their special stepped geometry, the backflow is reduced compared to rotary vane vacuum pumps with conventional oil pockets. This means that the flatter sections of the oil pockets impede the backflow of gas from the front to the rear transport chamber. This reduced backflow reduces energy consumption.

[0036] At suction pressures above 600 mbar, the gas reaches the required discharge pressure even before reaching the oil pocket. Because the gas can escape thanks to the inventive oil pocket geometry, energy consumption is also reduced compared to traditional rotary vane vacuum pumps.

[0037] Since the operation of the rotary vane vacuum pump according to the invention requires less energy than the operation of the traditional rotary vane vacuum pump, the rotary vane vacuum pump according to the invention is environmentally friendly.

[0038] Another advantage is the improvement of the noise characteristics when starting the pump, i.e. the pump according to the invention runs quieter when starting than a traditional rotary vane vacuum pump.

[0039] Other important features and advantages of the invention follow from the dependent claims of the invention, the drawings and the corresponding description of the figures based on the drawings.

[0040] It is understood that the above-mentioned and further explained below features can be used not only in the combination respectively given, but also in other combinations or separately, without going beyond the scope of the present invention.

[0041] Preferred embodiments of the invention are shown in the drawings and explained in more detail in the following description. The inner wall of the rotary vane chamber according to the invention is shown as an example on a rotary vane vacuum pump with a single pump stage, but can also be implemented in rotary vane vacuum pumps with two or more pump stages. In rotary vane vacuum pumps with more than two pump stages, the oil pockets can be located in only one pump stage, or in several or all of the pump stages.

[0042] The drawings show a preferred embodiment of an oil-lubricated rotary vane vacuum pump according to the invention with a cylindrical rotary vane chamber. However, the invention is not limited thereto.

[0043] Brief description of drawings

[0044] Fig. 1 shows a side view of a rotary vane vacuum pump according to the invention, without a view of the cylinder cover.

[0045] Fig. 2 shows a cross-section of a rotary vane vacuum pump according to the invention, with the arrow on the top pointing to the inlet and the arrow on the left pointing to the outlet.

[0046] Fig. 3 shows an enlarged image of fragment B from Fig. 2 (magnified three times).

[0047] Fig. 4 shows a section along line C-C in Fig. 1. Here, the parallel arrangement of the oil pockets next to each other, that is, along a direction parallel to the direction of the circumference, is clearly visible.

[0048] Preferred embodiments of the invention

[0049] In all figures, the same or functionally the same elements and devices, unless otherwise indicated, are designated by the same reference numbers.

[0050] Fig. 1 shows the design of a traditional pump stage of a vane-rotor vacuum pump, wherein the rotor 4 is located eccentrically in a cylindrical vane-rotor chamber 13 with an inner wall 5. Plates 6 / 6 I / 6 II are located in grooves that thus define the 8 / 8 transport chambers I / 8 II .

[0051] Fig. 2 shows a cross-section of the pump stage of the vane-rotor vacuum pump according to the invention. As in Fig. 1, a rotor 4 is shown here, located in the cylindrical inner wall 5 of the vane-rotor chamber 13, with vanes 6 / 6 I / 6 II , grooves and transport chambers 8 / 8 I / 8 II . The oil pocket 9 is clearly shown with two sections 11 and 12 of the oil pocket, where one of the two sections 11 and 12 of the oil pocket is connected to both outlet channels 10 / 10 IIn this preferred embodiment, the deeper section 11 of the oil pocket is connected to the outlet channels.

[0052] The oil pockets 9 shown in Fig. 2, Fig. 3, and Fig. 4 have two oil pocket sections 11 and 12. Oil pockets with three or more oil pocket sections are also possible. Details regarding the location and shape of the oil pockets are shown in Fig. 4.

[0053] Fig. 4 shows a preferred embodiment of the inner wall of the vane-rotor chamber 13, which has eight oil pockets 9 I , 9 II , 9 III , 9 IV , 9 V , 9 VI , 9 VI1 and 9 VI11 straight shape. At the same time, oil pockets 9 III , 9 IV , 9 V and 9 VI connected to the exhaust. Preferably, these oil pockets 9 III , 9 IV , 9 V and 9 VI have an axial expansion b1. Additionally, four other oil pockets 9 are providedI , 9 II , 9 VI1 and 9 VI11 , which are not connected to the exhaust. Preferably, oil pockets 9 11 and 9 VI1 have axial expansion b2, and oil pockets 9 I and 9 VI11 have an axial expansion b3, where b1 is greater than b2 and b2 is greater than b3 (b1>b2>b3). In a particularly preferred embodiment of the invention, the ratio b1 to b2 to b3 = 6: 5: 4.

[0054] Oil pockets 9 I , 9 II , 9 III , 9 IV , 9 V , 9 VI , 9 VI1 and 9 VI11, as shown in Fig. 4, are located next to each other on the inner wall 5 of the vane-rotor chamber 13 along a direction parallel to the circumference direction, and preferably have the same overall length d, as well as the same arcuate dimension of the first and second sections 11 and 12 of the oil pockets. The ratio of the arcuate dimension d1 of the first section 11 of the oil pocket to the arcuate dimension d2 of the second section 12 of the oil pocket is preferably in the range of (1-2) to 1, particularly preferably in the range of (1.3-1.8) to 1, most preferably 1.5:1.

[0055] The figures show a cylindrical vane-rotor chamber with a cylindrical rotor. Thus, the vane-rotor chamber is based on a circular cross-section. However, instead of a circle, the vane-rotor chamber can be based on an oval, an ellipse, or, more generally, on a continuous, symmetrical, numerically determined curve.

[0056] Measurement of energy savings in oil-lubricated rotary vane vacuum pumps with staged oil pockets according to the invention

[0057] The measurement of energy savings due to changes in the geometry of oil pockets is carried out in two experiments on two rotary vane vacuum pumps with a nominal pumping speed of 100 m 3 / h, wherein one of said rotary vane vacuum pumps contains traditional oil pockets, and the other rotary vane vacuum pump contains oil pockets according to the invention.

[0058] Result: In a rotary vane vacuum pump, the stepped geometry of the oil pockets ensures a shorter vacuum process and lower energy consumption per cycle compared to a rotary vane vacuum pump with traditional oil pockets.

[0059] List of reference positions

[0060] 1 Oil-lubricated rotary vane vacuum pump

[0061] 2 Pump stage

[0062] 3 Body

[0063] 4 Rotor

[0064] 5 Inner wall of vane-rotor chamber

[0065] 6, 6 I , 6 II plate

[0066] 7, 7I, 7 II Groove

[0067] 8, 8I, 8 II Transport chamber

[0068] 9I, 9 II , 9 III , 9 IV , 9 V , 9 VI , 9V 11 , 9 VI11 Oil pocket

[0069] 10, 10 I Exhaust channel

[0070] 11 First section of oil pocket

[0071] 12 Second section of oil pocket

[0072] 13 Vane-rotor chamber

[0073] 14 Inner wall of the first section of the oil pocket

[0074] 15 Inner wall of the second section of the oil pocket

Claims

1. An oil-lubricated vane-rotor vacuum pump (1) with at least one pump stage (2) with a housing (3) containing a rotor (4) in a vane-rotor chamber (13), wherein the inner wall (5) of the vane-rotor chamber has a distance R0 to the center of the vane-rotor chamber, wherein the inner wall (5) of the vane-rotor chamber has at least one oil pocket (9), characterized in that at least one oil pocket (9) is made with at least two sections (11) and (12) of the oil pocket, wherein the said one or more oil pockets (9) extend along the circumference of the inner wall (5) of the vane-rotor chamber (13), and wherein the sections (11) and (12) of the oil pockets differ in their flow section, wherein at least one oil pocket (9) has a total length d along the circumference of the inner walls of the plate-rotor chamber (13),wherein the length d is made up of the length d1 of the first section (11) of the oil pocket and the length d2 of the second section (12) of the oil pocket, and the ratio d1 to d2 is in the range from (1-2) to 1., 2. An oil-lubricated rotary vane vacuum pump (1) according to claim 1, characterized in that the ratio d1 to d2 is preferably in the range from (1.3-1.8) to 1 and most preferably is 1.5:

1.

3. An oil-lubricated rotary vane vacuum pump (1) according to claim 1 or 2, characterized in that the flow section of the section (11) of the oil pocket is larger than the flow section of the section (12) of the oil pocket.

4. An oil-lubricated rotary vane vacuum pump (1) according to one of paragraphs 1-3, characterized in that the inner wall (14) of the first section (11) of the oil pocket has a maximum distance R1 from the center of the rotary vane chamber, and the inner wall (15) of the second section (12) of the oil pocket has a maximum distance R2 from the center of the rotary vane chamber, wherein R1 is greater than R2, and R2 is greater than R0, and wherein the first section (11) of the oil pocket transitions into the second section (12) of the oil pocket.

5. An oil-lubricated vane-rotor vacuum pump (1) according to one of paragraphs 1-4, characterized in that the vane-rotor chamber is cylindrical.

6. An oil-lubricated rotary vane vacuum pump (1) according to one of paragraphs 1-5, characterized in that several oil pockets (9) are provided.

7. An oil-lubricated rotary vane vacuum pump (1) according to claim 6, characterized in that two or more oil pockets (9) have the same axial expansion.

8. An oil-lubricated rotary vane vacuum pump (1) according to one of paragraphs 6, 7, characterized in that two or more oil pockets (9) have the same total length d.

9. An oil-lubricated vane-rotor vacuum pump (1) according to one of paragraphs 6-8, characterized in that the oil pockets (9) are located next to each other on the inner wall (5) of the vane-rotor chamber (13) along a direction parallel to the direction of the circumference.

10. An oil-lubricated rotary vane vacuum pump (1) according to one of the preceding claims, characterized in that at least one oil pocket (9) is connected to at least one outlet channel (10).

11. An oil-lubricated rotary vane vacuum pump (1) according to claim 10, characterized in that the oil pocket (9) connected to the outlet channel (10) has a greater axial expansion than the oil pocket (9 I ), not connected to the outlet channel.

12. An oil-lubricated rotary vane vacuum pump (1) according to claim 6, characterized in that the axial expansion b of the oil pockets (9) decreases with increasing axial distance from the outlet channel.

13. An oil-lubricated rotary vane vacuum pump (1) according to claim 6 or 11, characterized in that the total length d of the oil pockets (9) decreases with increasing axial distance from the outlet channel.

14. An oil-lubricated rotary vane vacuum pump (1) according to one of paragraphs 10-13, characterized in that the first section (11) of the oil pocket of at least one oil pocket (9) is connected to the outlet channel (10).

15. An oil-lubricated rotary vane vacuum pump (1) according to one of paragraphs 10 or 12-14, characterized in that all available oil pockets (9) are connected to one or more outlet channels.

16. An oil-lubricated rotary vane vacuum pump (1) according to one of the preceding paragraphs, characterized in that the oil pockets (9) have a straight or curved shape.

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