JP2006518827A - Rotary piston pump - Google Patents

Abstract

A rotary piston pump having at least two rotors 8 with associated drive shafts 26 is disclosed. A bearing tube 28 protruding into the associated rotor 8, through which the associated drive shaft 26 extends, is associated with each rotor 8. The first gap 64 is provided between the inner surface 24 of each rotor 8 and the outer surface of the bearing tube 28. The first gap 64 contains coolant during operation and becomes part of the coolant circuit.

Description

  The present invention relates to a rotary piston pump having at least two rotors with associated drive shafts, each rotor extending into an associated rotor and associated bearings through which the associated drive shaft passes. The invention relates to a rotary piston pump in which a tube is provided and a first gap is provided between the inside of the rotor and the outside of the bearing tube.

  The invention particularly relates to a dry compression vacuum screw pump or a roots pump of this kind.

  In these vacuum pumps, a compressible medium having an absolute pressure of less than 1 millibar (mbar) is compressed to atmospheric pressure, in which case the mechanical space should be free of oil and wear.

  The parallel drive shafts are synchronized with each other, usually in a 1: 1 ratio, by the transmission device. The shaft rotation speeds all correspond to those of the motor or the motor rotation speed is increased by an additional spur gear pair. The non-contact meshing counter-rotating rotor forms a chamber that is carried from the suction side to the pressure side to exhibit a smaller volume, which is achieved by changing the rotor pitch.

  The resulting compression heat can be dissipated, for example, through the outer housing wall. It is also possible to cool the rotor from the inside. But it also involves considerable design effort. On the other hand, the thermal expansion of each part should be kept to a minimum, which can only be achieved by cooling, whereby a smaller gap between the rotors can be achieved, leading to a reduction in gap leakage. In addition, cooling can not only increase efficiency, but also provide a medium, such as a gas, that will reach temperatures in excess of 200 ° C. without cooling as a result of compression, at a much lower temperature than this temperature. it can. Finally, the lower temperature has a beneficial effect on the design and service life of the rotary piston pump part.

  As far as the mounting of the rotor is concerned, the general WO 97/01038 discloses the concept of providing a so-called protruding mounting. The invention relates to a rotary piston pump using such a protruding mounting of the rotor. The bearing tube of each rotor extends into the axial opening of the rotor. The bearing tube is usually mounted stationary at one end, preferably by coupling to a pump housing. An associated drive shaft having a drive end and an end connected to the rotor then extends through the bearing tube.

  General WO 97/01038 discloses a complex cooling scheme for a rotor in which the bearing tube itself is provided with a cooling passage through which coolant flows. It is also described that radiant heat is transferred from the rotor to the bearing tube through the gap between the rotor and the bearing tube. Sealing gas can also be introduced into the gap to protect the bearings and the drive area, and to protect them from the ingress of the medium pumped or contained in the pumped medium Provided to do.

  It is an object of the present invention to provide a rotary piston pump, in particular a vacuum screw pump, with a simple design and a design that requires less maintenance.

  In a rotary piston pump as described above, the purpose is that during operation the first gap contains coolant, i.e. the coolant is carried through the gap and is still part of the coolant circuit. It is realized by becoming. The first gap has a coolant inlet and a spatially independent or physically independent coolant outlet. In the rotary piston pump of the present invention, the cooling scheme through the first gap is much more effective because coolant is introduced into this gap that directly allows good heat dissipation in the rotor. This coolant is part of the coolant circuit, so a cooler liquid is always supplied to the rotor. With independent inlets and outlets, there is only one flow direction through the cooling gap where the coolant must flow back and forth, ie there is no dead space such as a blind hole.

  Thus, according to the prior art, cooling passages provided in the wall surface of the bearing tube or in the drive shaft can be omitted, thereby simplifying the manufacture and maintenance of the pump according to the invention. Other tubes, pockets, gaps, etc. inside the rotor can also be omitted.

  Preferably, a second gap that is part of the coolant circuit is provided between each inside of the bearing tube and the associated outside of the drive shaft. This means that the two gaps created very easily are flow-coupled to each other.

  In this regard, the coolant circuit is preferably designed such that the coolant flows first into the second radially inner gap and then into the first gap.

  The bearing tube has a stationary end and an opposed free end extending into the rotor.

  According to one aspect, the invention has a coolant inlet associated with the second gap at the fixedly attached end, and at the free end of the bearing tube at the axially opposite end. Providing a coolant outlet in flow communication with the coolant inlet of the first gap. In an upright bearing tube, this means that the coolant is pumped into the second gap to the free end of the bearing tube and then discharged radially outward into the first gap, Finally, it means that it flows downward along the inside of the rotor. A shear flow is created between the fixed bearing tube and the rotating rotor to ensure optimal transfer of heat from the rotor to the liquid.

  A connection passage is provided between two gaps (gap) between the end face of the free end of each bearing tube and the adjacent wall surface of the rotor.

  The present invention provides several other advantages. In the prior art, all bearings should be expensive, sealed and permanently lubricated bearings, requiring expensive additional gaskets, whereas the present invention is the opposite. For example, at least one bearing is mounted between the drive shaft associated with each bearing tube through which the flow of coolant passes completely or partially so that the bearing is cooled and lubricated. Is done.

  Optionally or additionally, this can also be done in at least one bearing between the bearing tube and the associated rotor.

  Between the part adjacent to the bearing, one or more bypasses (side passages) for the coolant can be provided. If these bypasses increase the flow rate or the bearing should be sealed opposite to that described above, it will allow the passage of coolant near the corresponding bearing point.

  In terms of flow, the coolant circuit is preferably open to the cooling and lubricating fluid of the transmission device.

  A particular advantage of the present invention is that the cooling and lubricating liquid of the transmission device for driving the rotor also constitutes the rotor cooling liquid. Thus, the hermetic sealing performed in the prior art can be omitted and the overall pump is much simpler in design. That is, part of the transmission device filled with cooling and lubricating liquid constitutes part of the cooling liquid circuit.

  The simple design of the pump according to the invention is also evident by the fact that a coolant pump driven by the transmission device itself is housed in the transmission housing and that pump supplies coolant into the gap.

  According to the present invention, the drive shaft is designed without a cooling passage at least near the drive side end (transmission end), particularly along its entire length, thereby reducing manufacturing costs and improving stability.

  A coolant reservoir, such as a transmission housing containing cooling and lubricating fluid, is in flow communication with the first or second gap via a passage disposed outside the drive shaft.

  According to a preferred embodiment, the rotary piston pump according to the invention is designed without a sealing gas.

  Other features and advantages of the present invention can be understood from the following description and the accompanying drawings.

  FIG. 1 shows a dry compression rotary piston pump in the form of a vacuum screw pump, having a suction port 10 on the vacuum side and a discharge port 12 on the pressure side, where the suction port 10 and the discharge port 12 are both Both are connected to each other by a mechanism space 14. The mechanism space 14 accommodates two parallel rotors 8 having spirals 16 whose pitch gradually decreases downward. The rotors 8 mesh with each other and rotate in opposite directions to form a chamber 18 that is carried from the suction side to the pressure side during rotation of the rotor 8, i.e. with the pump stationary from top to bottom, so that The pump medium enclosed in the chamber is compressed toward the pressure side.

  The two rotors 8 have a hollow interior and are mounted protruding, and have the same geometry and the same structure within them with respect to their bearings, so that the description is simplified. Only the clockwise rotor 8 will be described together with its bearings.

  The rotor 8 has an axial through hole with a smaller diameter top 20 and a larger diameter adjacent portion defined by the inner side 24. The drive shaft 26 is press-fitted into the portion 20, and as a result, the rotor and the drive shaft 26 are connected to each other and rotate together. A bearing tube 28 extends into the larger diameter portion of the through-hole defined by the inner side 24, which is fixedly attached to the transmission housing 30, i.e. fixedly attached to the lower end 31 thereof. Is attached. Through this bearing tube 28, the drive shaft 26 extends into the interior 34 of the transmission housing 30. At the lower end, a bevel tooth bevel gear 38 is connected to the drive shaft 26, which meshes with the bevel bevel gear 40, which is securely attached to a shaft 42 that is rotated by a motor not shown. It has been. The two drive shafts 26 each have their own pair of bevel bevel gears 38 or bevel gears 40, which are mounted on a common shaft 42. The shaft 42 is further rotatably mounted in the transmission housing 30. The transmission method is a so-called vertical shaft method in which the shaft 42 is perpendicular to the parallel drive shaft 26. By this method, the rotational speed of the drive shaft 26 can be increased (the pitch circle of the curved bevel gear 40 is larger than that of the curved bevel small gear 38), but at the same time, the rotational direction of the drive shaft 26 is synchronized. .

  The peripheral speed of the gear connected to the drive shaft 26 is decisive for transmission noise. According to the prior art, by providing the bevel gear, the peripheral speed depends on the axial distance. This is not the case with the pump according to the invention. In this case, the peripheral speed of the bevel gear 40 and the bevel pinion 38 is not affected by the axial distance, and the diameter of the bevel pinion 38 is much smaller than the axial distance between the drive shafts 26. . Another advantage of the design of the present invention is that different axial distances can be achieved with the same gear when different rotors 8 are used.

  In the vicinity of the lower end, the drive shaft 26 is positioned in the bearing tube 28 via a positioning bearing 50 that constitutes an open bearing, i.e. is not permanently lubricated and sealed, and the free upper end of the bearing tube 28. In the part, it is arranged via a bearing 42 floating in the axial direction and the radial direction. Therefore, the rotor 8 is also supported in the axial direction and the circumferential direction. Furthermore, the bearing 42 is not sealed and constitutes an open bearing.

  In order to cool each rotor 8, each rotor has its own coolant circuit, through which a cooling and lubricating liquid 60 provided inside the transmission housing 30 for lubricating and cooling the gears. Supplied. The cooling and lubricating liquid 60 in the transmission housing constitutes a reservoir for the cooling liquid of the rotor 8.

  Thus, the coolant circuit extends from the interior of the transmission housing 30 through an open positioning bearing 50 and / or a bypass 32 provided therein, ie a passage provided outside the drive shaft 26. A cylindrical annular gap extending to the bearing 42 is prepared between the drive shaft 26 and the bearing tube 28. Hereinafter, the gap 62 is referred to as a radially inner second gap. It is in flow communication with a first radially outer gap 64 formed between the inner side 24 of the rotor 8 and the outer side of the bearing tube 28. The flow connection between the gap 62 and the gap 64 is like an open floating bearing 42, an optional bypass 70, and a groove between the free end face of the bearing tube 28 and the adjacent end face wall of the rotor 8. This is done via a connecting passage or annular gap 80. The connecting passage 80 then reaches the coolant inlet 81 (upper end) of the first gap 64. The coolant outlet 83 of the first gap 64 is provided at its lower end, where a passage 90 leads to the collecting ring, from there into a sump not shown or to the interior 34 of the transmission device.

  At the liquid inlet at the lower end of the gap 62, the coolant thus flows into the gap and, if possible, after cooling and lubricating the bearing 50 and flows upward toward the bearing 42 and / or the bypass 70. To the liquid outlet and then reaches the gap 64 via the connecting passage 80, where it is pressed against the inner side 24 of the rotor by the existing centrifugal force, creating a shear flow. The rotor 8 heated during compression dissipates most of the heat to the coolant, which then flows to the coolant source where it is mixed with the cooled coolant 60.

  The illustrated pump also features a very simple seal. No sealing is necessary on the vacuum side. The seal 92 is only necessary between the lower end of the rotor 8 and the transmission device on the pressure side of the vacuum pump. However, because there is a connection with the pump outlet 12 and thus with the atmosphere, no pressure is applied to the seals 92, thereby improving their service life and their sealing performance. Sealing gas can be omitted.

  The embodiment shown in FIGS. 2 to 4 substantially corresponds to that shown in FIG. 1 and therefore only the differences are considered. It should also be emphasized that these characteristic features discussed below can be combined with each other as desired within the scope of the illustrated embodiment.

  In the embodiment shown in FIG. 2, in this case as a drive for an integrated coolant pump 110 which is housed in the interior 34 of the transmission device and still pumps the coolant 60 into each of the second gaps 62. Since the shaft extension portion 100 is provided, the left end portion of the shaft 42 is not attached in the transmission housing 30. The corresponding conduit is indicated at 120. A rib 130 of the transmission housing 30 extends between the bevel gear 40 and a shaft 42 is further mounted therein. A corresponding positioning bearing is shown at 132.

  The positioning bearings 132 between the bevel gears 40 are advantageous because they are supplied with heat and the shaft 42 can expand freely towards both shaft ends.

  In the embodiment shown in FIGS. 3 and 4, an open floating bearing 150 is again installed between the inner side 24 and the bearing tube 28 at the lower end of each rotor 8 so that the corresponding bearing of the rotor 8 is further at the lower end. Stabilize. The bearing 150 is preferably a plain bearing with a relatively simple design that bypasses a portion of the coolant through a bypass 160 in the form of a longitudinal groove in the bearing tube 28.

  The coolant is preferably oil.

  As an alternative to the vacuum screw pump shown, a design including a cooling circuit in the gaps 62, 64 can also be provided in the Roots pump.

  The pump of the present invention features a very simple structure that is free of complex passages inside the rotor, bearing tube, and drive shaft, and a very large surface that helps in the rapid transfer of heat to dissipate heat. To do.

  As shown, the housing 170 surrounding the rotor 8 can of course be provided with an additional cooling passage 180 containing coolant.

1 is a longitudinal section through a first embodiment of the rotary piston pump of the present invention designed as a vacuum screw pump. FIG. 3 is a longitudinal section through a second embodiment of the rotary piston pump of the present invention designed as a vacuum screw pump. It is a longitudinal cross-sectional view which passes along the bearing area | region of the rotor changed compared with the said Example. It is an enlarged view of the area | region X enclosed with the frame shown in FIG.

Claims (20)

A rotary piston pump,
Including at least two rotors (8) with associated drive shafts (26);
For each rotor (8) there is provided an associated bearing tube (28) that extends into this associated rotor (8) and through which the associated drive shaft (26) passes;
A first gap (64) is provided between the inside (24) of each rotor (8) and the outside of the bearing tube (28);
During operation, the first gap (64) contains coolant and becomes part of the coolant circuit and has a coolant inlet (81) and a spatially independent coolant outlet (83). A rotary piston pump.   The second gap (62), which is part of the coolant circuit, is provided between the inside of the bearing tube (28) and the outside of the drive shaft (26). The described rotary piston pump.   2. The coolant circuit according to claim 1, wherein the coolant circuit is formed such that coolant flows first into the second gap (62) and then into the first gap (64). 2. The rotary piston pump according to 2.   Each bearing pipe (28) extending into the rotor (8) has a fixed end and a free end, and the fixed end is provided with the second gap (62). ) With an associated coolant inlet and at the axially opposite end of the second gap, the coolant inlet of the first gap (64) at the free end of the bearing tube (28) 4. A rotary piston pump as claimed in claim 3, characterized in that it has a coolant outlet in flow connection.   At least one connection between the first gap (64) and the second gap (62) is provided between the end surface of the free end of each bearing tube (28) and the adjacent wall surface of the rotor (8). The rotary piston pump according to claim 4, characterized in that a passage (80) is formed.   The at least one bearing (42, 50) through which a coolant flow passes is provided between each bearing tube (28) and the associated drive shaft (26). A rotary piston pump according to any one of the above.   Each bearing tube (28) extending into the rotor (8) has a fixed end and a free end, and in the vicinity of the free end, a bearing (42) is connected to the bearing tube (28). The rotary piston pump according to claim 6, wherein the rotary piston pump is provided between the drive shaft and the associated drive shaft.   Any of the preceding claims, characterized in that between each bearing tube (28) and the associated rotor (8) there is arranged at least one bearing (150) through which the flow of coolant passes. Rotary piston pump as described in   Each bearing tube (28) extending into the rotor (8) has a fixedly attached end and a free end, in the vicinity of its own end associated with the fixedly attached end The rotary piston pump according to any of the preceding claims, characterized in that the rotor (8) is supported radially on the bearing tube (28) by a bearing (150).   On the one hand, between each bearing tube (28) and the associated drive shaft (26) and / or on the other hand, between each bearing tube (28) and the associated rotor (8), at least one Two bearings (42, 50, 150) and associated bypasses (32, 70, 160) are provided so that coolant passes past the bearings (42, 50, 150) and the bypass (32, 50, 150). 70, 160). Rotary piston pump according to any of the preceding claims, characterized in that it can flow through.   The said coolant circuit is not sealed against the transmission device connecting the rotor (8) and against the cooling and lubricating liquid contained in the rotor for the transmission device. A rotary piston pump according to any one of the above.   The rotor (8) is connected to each other via a transmission device housed in a transmission housing (30), and cooling and lubricating fluid (60) of the transmission device flows into the cooling fluid circuit. The rotary piston pump according to claim 11.   The rotor (8) is connected to each other via a transmission device housed in the transmission housing (30), and is driven by the transmission device in the transmission housing (30), and the gap (62, 40). A rotary piston pump according to any of the preceding claims, characterized in that it contains a coolant pump (110) for supplying coolant therein.   A rotary piston pump according to any of the preceding claims, characterized in that the rotary piston pump is a vacuum screw pump or a roots pump.   Bearings (42, 50, 150) for supporting the rotor (8) in the bearing tube (28) and / or the drive shaft (26) in the bearing tube (28) constitute an open bearing. A rotary piston pump according to any one of the preceding claims.   A rotary piston pump according to any of the preceding claims, characterized in that the bearing tube (28) is designed without a cooling passage in its wall surface.   Rotary shaft according to any of the preceding claims, characterized in that the drive shaft (26) forms a shaft without a cooling passage, at least in the vicinity of its drive end, preferably over its entire length. Piston pump.   A reservoir for cooling liquid is provided, and the cooling liquid reaches the gap (62, 40) via a passage (32) arranged outside the drive shaft (26). A rotary piston pump according to any one of the above.   A rotary piston pump according to any of the preceding claims, characterized in that the coolant inlet and outlet of the first gap (64) are provided near both ends of the bearing tube (28).   A rotary piston pump according to any of the preceding claims, characterized in that the rotary piston pump is designed without a sealing gas.

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