JP2014231815A - Biaxial rotary pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxial rotary pump having a plurality of rotors in the axial direction of a rotation shaft, which can avoid influence of the sum of thermal expansion of the plurality of rotors, and thereby make a side clearance smaller to reduce generation of gas leak and thus improve the pump performance.SOLUTION: A unit pump structure 10 composed of a cylinder 50 and two rotors 30, 30 is provided in each of both ends of a rotation shaft 20 so that the two rotors 30, 30 are rotated in a non-contact manner therebetween and in non-contact with the inner face of the cylinder 50. Either of the unit pump structures 10, 10 is supported in a cantilever state via the rotation shafts 20, 20 by bearings 40, 40 arranged in one side in the axial direction of the rotation shafts 20, 20 between both of the unit pump structures 10, 10.

Description

  In the present invention, the two rotors are rotated without contact while maintaining a minute clearance, and the two rotors are rotated without contact while maintaining a minute clearance on the inner surface of the cylinder. The rotary shaft is provided with two rotary shafts supported by bearings, and sucks gas into the cylinder and exhausts compressed gas from the cylinder.

  As a biaxial rotary pump, there is a claw pump which is a non-contact type vacuum pump equipped with a claw rotor. For example, according to the claw pump exhaust structure and exhaust method previously proposed by the present applicant, the cylinder forming the pump chamber, one side plate that closes the end face of the cylinder, and the other side plate are parallel to each other in the cylinder. The two rotating shafts arranged to be positioned at each other and rotated in opposite directions, and integrally fixed to each of the two rotating shafts, are in contact with each other and inhaled gas Two rotors with hook-shaped claws formed so that they can be compressed, a rotary drive device, an intake port communicating with a portion of the pump chamber where the gas in the cylinder is not compressed, one side plate and the other side plate Both are provided with an exhaust port that opens to a portion of the pump chamber where the gas in the cylinder is compressed (see Patent Document 1). According to this, the pump performance of the claw pump can be improved by increasing the exhaust efficiency.

  When a multi-stage pump is used for such a biaxial rotary pump such as a claw pump, a rotary shaft having a plurality of rotors in the axial direction is conventionally supported at both ends so that the plurality of rotors are sandwiched between two bearings. (See Patent Document 2). According to this, although the compression ratio of the gas can be increased through the multi-stage cylinders by a plurality of (multi-stage) rotors, each stage cylinder generates heat by compressing the gas. Thermal expansion occurs. Since the multi-stage rotor is arranged on one rotating shaft, the side clearance, which is the clearance between the rotor and the end wall of the cylinder, is affected so that the thermal expansion of the plurality of rotors is added up. . That is, since it affects the thermal expansion of a plurality of rotors to be added together, it is difficult to reduce the side clearance and reduce the occurrence of gas leakage, and the pump performance cannot be improved. is there.

  Further, the claw pump has a compression step, and the exhaust efficiency is improved by compressing the suction gas (air). During the reaching operation of such a rotary pump, since there is no intake air amount, in principle, there is no pneumatic transport and compression of the pump, and work as a pump is zero. However, in reality, intake air exists due to leakage from a small gap even during ultimate operation, and the space (sealed space) immediately before the exhaust opening formed by the rotor and cylinder is externally (largely exhausted from the inside of the pump) through the exhaust port. When communicating with a space having air above the atmospheric pressure), the exhaust air above the atmospheric pressure flows back into the pump because the space just before the exhaust opening is negative. The backflowed air is recompressed and discharged to the outside again. Here, useless processes occur, and the power load and the pump internal temperature rise. The ultimate operation is the operation at the ultimate pressure, and the ultimate pressure is when the suction port of the vacuum pump, which is the maximum capacity for creating the vacuum of the pump, is closed (the exhaust flow rate becomes zero). Is the pressure that can be reached.

  That is, according to the exhaust air that flows back into the pump at the time of this reaching operation, the power load increases and the operation efficiency deteriorates. Further, the exhaust air flowing backward increases the internal temperature of the pump, so that deterioration of important parts such as rotor contact, oil seals and bearings due to thermal expansion tends to occur, and the reliability of the pump device is lowered. On the other hand, if the volume immediately before the exhaust opening is simply reduced so as to suppress the amount of backflow air, the air opening side when the exhaust flow rate is high (in the state where the pressure of the sucked air is close to the atmospheric pressure) Is overcompressed). Further, there arises a problem that the flow rate is reduced due to the reduction of the pump internal volume. As long as there is a volume immediately before the exhaust is released, backflow air is always generated, and it becomes a problem to rationally mitigate the above problems. Conventionally, this problem has been dealt with by restricting the operating conditions, and the operating efficiency has not been improved.

The present applicant has previously proposed the following configuration for a rotary vacuum pump (vane pump) having a vane. The vacuum pump is provided with a gas exhaust hole, and the exhaust hole is provided with a first check valve. In addition, a pressure relief hole is provided to release the gas compressed above the atmospheric pressure in the vacuum pump into the outside air, and to reduce the power loss of the vacuum pump, and the pressure relief hole includes A second check valve is provided. The exhaust hole and the pressure relief hole constitute a gas exhaust port of the vacuum pump (see Patent Document 3).
According to this, the escape hole is provided in the peripheral wall part of the wall part which forms a cylinder, and it can suppress that the inside of the pump to be compressed becomes overcompressed and the temperature rises.

JP 2011-38476 A (first page) JP 2002-332963 A (FIG. 1) JP 2001-289167 A ([0020])

The problem to be solved with regard to the biaxial rotary pump is that when multiple rotors are provided in the axial direction of the rotary shaft, the thermal expansion of the multiple rotors is affected so that the side clearance is made smaller. It is difficult to reduce the occurrence of gas leakage, and the pump performance cannot be further improved.
Therefore, an object of the present invention is to provide a plurality of rotors in the axial direction of the rotating shaft, avoid the influence of the thermal expansion of the plurality of rotors being added together, reduce the side clearance, and prevent gas leakage. An object of the present invention is to provide a biaxial rotary pump capable of further improving pump performance by reducing generation.

The present invention has the following configuration in order to achieve the above object.
According to one mode of the biaxial rotary pump according to the present invention, the two rotors are rotated in a non-contact manner while maintaining a minute clearance, and the two rotors also maintain a minute clearance on the inner surface of the cylinder. In a biaxial rotary pump that is provided with two rotary shafts provided with the rotor supported by bearings so as to be rotated in a non-contact manner, and sucks gas into the cylinder and exhausts compressed gas from the cylinder A unit pump configuration constituted by the cylinder and the two rotors is provided at both ends of each of the rotary shafts, and in both of the unit pump configurations, the two rotors are connected to the rotary shafts of the two rotors. It is supported in a cantilever state via the rotary shaft by a bearing which is arranged on one side in the axial direction and arranged between both unit pump structures.

Further, according to one aspect of the biaxial rotary pump according to the present invention, at least one cylinder of the unit pump configuration at both ends of the rotary shaft, the end wall portion constituting both ends in the axial direction of the cylinder Of these, the end wall on the side of the cantilevered end face through which the rotating shaft is not inserted is provided with an escape hole that allows a part of the compressed gas to escape in the axial direction of the rotating shaft. can do.
Moreover, according to one form of the biaxial rotary pump which concerns on this invention, the said escape hole can be provided with two or more by the end wall part by the side of the said cantilever end surface.

Further, according to one embodiment of the biaxial rotary pump according to the present invention, the relief hole opens when the pressure in the cylinder is higher than a predetermined pressure, and lower than the predetermined pressure. Can be characterized by a check valve that is closed.
Moreover, according to one form of the biaxial rotary pump which concerns on this invention, the said non-return valve can be a reed valve.

  Moreover, according to one form of the biaxial rotary pump which concerns on this invention, the said rotor is a rotor of the claw pump provided with a hook-shaped claw part, The said cantilever end surface side of the said cylinder provided with the said relief hole An exhaust port for exhausting the compressed gas of the cylinder may be provided in the end wall portion.

  According to the biaxial rotary pump according to the present invention, when a plurality of rotors are provided in the axial direction of the rotary shaft, the influence of the thermal expansion of the plurality of rotors is avoided and the side clearance is further reduced. Thus, since the occurrence of gas leakage can be further reduced, the pump performance can be further improved.

It is sectional drawing which shows typically the example of a form of the biaxial rotary pump which concerns on this invention. It is a side view which shows the end wall part of the cylinder of the example of a form of FIG. It is a side view which shows the state which removed the relief valve of the end wall part of FIG. It is sectional drawing explaining the arrangement | positioning relationship between the two rotors of a form example of FIG. 1, and a some escape hole. It is sectional drawing explaining the change of the ratio of the compression state of the gas by the two rotors of the example of FIG. 1, and the opening by a some escape hole.

Hereinafter, the form example of the biaxial rotary pump which concerns on this invention is demonstrated based on an accompanying drawing (FIGS. 1-5). In addition, about the code | symbol described in drawing, when there exist two or more structures of the same name, in order to identify the position where it has been arranged, A, B, C, and D are attached to the number, In the following text, when the configuration of the same name is generally described, only numerals with no A, B, C, and D added are described. For example, when describing the rotation axis as a whole, it is referred to as “rotation axis 20”, and when raising awareness about the arrangement of the two rotation axes, it is described as “two rotation axes 20A, 20B”. It is.
This embodiment is a positive displacement pump among the rotary pumps, and belongs to the biaxial rotary pump. Examples of the biaxial rotary pump include a claw pump that is a rotor non-contact type pump, a screw pump, and a roots pump. Such a rotary pump is driven by, for example, an electric motor and used as a pneumatic device such as a vacuum pump or a blower.

  In this embodiment, the two rotors 30 (each set of 30A and 30B, 30C and 30D) are rotated in a non-contact manner while maintaining a minute clearance, and the two rotors 30 and 30 are cylinders 50 (50A and 50B). The two rotary shafts 20 (20A and 20B) having the rotors 30 and 30 are rotated on the inner surfaces of the bearings 40 (40A and 40B, 40C and 40D) so that the inner surfaces of the rotors 30 and 30 are rotated without contact. And a biaxial rotary pump that sucks gas into the cylinder 50 and exhausts the compressed gas from the cylinder 50. The air is taken in through the air inlets 35A and 35B and is exhausted through the air outlets 55A and 55B.

The biaxial rotary pump of this embodiment is a claw pump, and the rotors 30 and 30 include a plurality of hook-shaped claw portions (see FIG. 4). In addition, since the claw pump can compress the gas to a high pressure, the temperature inside the pump tends to rise.
Further, in the claw pump of this embodiment, the unit pump configuration 10 (10A, 10B) including the cylinder 50 and the two rotors 30, 30 has a plurality of stages (two stages) in the axial direction of the two rotary shafts 20A, 20B. It is a multistage biaxial rotary pump provided.

In this embodiment, the unit pump configuration 10 (10A, 10B) configured by the cylinder 50 and the two rotors 30, 30 is provided at both ends of the rotary shaft 20, and either of the unit pump configurations 10A, 10B is provided. Also, the two rotors 30 and 30 are bearings 40 arranged on one side in the axial direction of the rotary shaft 20 (20A and 20B) in the two rotors 30 and 30 and between the two unit pump configurations 10A and 10B. (Each set of 40A and 40B, 40C and 40D) is supported in a cantilever state via the rotating shaft 20. In addition, as this bearing 40, an angular double row ball bearing can be used, for example.
In addition, by arranging the gears 21 and 22 between the two bearings 40A and 40B and the two bearings 40C and 40D, both ends of the gears 21 and 22 are supported. In addition, it is comprised so that the two rotating shafts 20A and 20B may rotate at the same speed in the opposite direction because the two gears 21 and 22 mesh.

  According to this, on the basis of the bearing 40 (40A, 40B, 40C, 40D), the rotors 30A, 30B are arranged on one side and the rotors 30C, 30D are arranged on the other side via the rotary shaft 20. It has become. For this reason, the thermal expansion is generated on both sides in the axial direction of the rotating shaft with respect to the bearing 40. Therefore, the influence of thermal expansion on the side clearance, which is the clearance between the rotor 30 and the end wall portion 52 in the axial direction of the cylinder, is distributed to one rotor 30A, 30B side and the other rotor 30C, 30D side. . For this reason, compared to the conventional multi-stage pump in which a rotary shaft having a plurality of rotors in the axial direction is supported at both ends so that the plurality of rotors are sandwiched between two bearings, the thermal expansion related to the side clearance is reduced. The impact will be small. Therefore, the side clearance can be made smaller, and the occurrence of gas leakage can be made smaller, and the pump performance can be improved.

  In this embodiment, both cylinders 50 (50A, 50B) of the unit pump configurations 10A, 10B at both ends of the rotary shaft 20 and end wall portions 52 (52A, 52B) constituting both ends of the cylinder 50 are used. , 52C, 52D), the end wall portion 52 (52A, 52D) on the side of the cantilevered end face through which the rotary shaft 20 is not inserted has an escape hole 70 through which a part of the compressed gas can escape. Open in the direction.

Further, in this embodiment, a plurality of escape holes 70 are provided in the end wall portion 52 (52A, 52D) on the cantilever end surface side. Further, exhaust ports 55 (55A, 55B) for exhausting the compressed gas of the cylinders 50 (50A, 50B) are provided in the end wall portion 52 on the cantilever end surface side where the escape holes 70 are provided.
In addition, forms, such as a shape, a magnitude | size, a quantity, arrangement | positioning, etc. which concern on the escape hole 70 are not limited to this form example. For example, at least a part (plurality) of the large number of escape holes 70 is opened on the inner bottom surface of a groove-shaped recess formed and formed in a groove shape so as to be continuous with the inner surface of the cylinder 50 (50A, 50B). By doing so, the plurality of escape holes 70 may be integrated with each other on the inner surface side of the cylinder 50 so as to communicate with the band groove-shaped recess and function as one large hole. Even in this case, a check valve (reed valve 71), which will be described later, may be individually provided on the outer surface (exhaust side surface) of the cylinder 50 so as to correspond to each relief hole 70.

  According to the escape hole 70, over-compression on the air release side can be suppressed in a rotary pump such as a non-contact type vacuum pump equipped with a claw rotor. Since overcompression can be suppressed, it is possible to increase the compression ratio by reducing the exhaust ports (55A, 55B) so as to reduce the volume immediately before the exhaust is released. By reducing the volume immediately before the exhaust is released, the amount of exhaust air flowing back into the pump can be suppressed. By controlling the amount of air that flows back, energy can be saved by reducing the power load during the ultimate operation of the vacuum pump, and by suppressing the rise in the internal temperature of the pump during the ultimate operation, thermal expansion is suppressed and long life of important parts is achieved. Can be realized.

The relief hole 70 provided in the end wall portion 52 is formed so as to open in the axial direction of the rotary shaft 20, so that the depth thereof is short corresponding to the thickness of the end wall portion 52, and the relief hole 70 is provided. It has a form excellent in responsiveness as the hole 70. That is, the overcompressed gas can be exhausted sequentially with a short time lag. In addition, the escape hole 70 can be easily disposed at the optimum position on the surface of the end wall portion 52 and can be provided so as to optimally exert its function.
In addition, by providing a plurality of escape holes 70 in the end wall portion 52, the overcompressed gas can be exhausted in a timely manner in a well-balanced manner during the gas compression process, and its functionality can be further improved.

Further, in this embodiment, the rotation shafts 20A and 20B are not inserted through the end wall portions 52A and 52D arranged at both ends of the apparatus, so that the escape holes 70 are arranged on the surfaces of the end wall portions 52A and 52D. The relief hole 70 can be provided appropriately and easily, and the pump performance can be improved.
That is, in the case of a conventional both-end support structure in which the two rotating shafts 20A and 20B (shafts) pass through the side plate, the check valve 71 is optimal because the shaft interferes even if the relief hole 70 can be arranged. It is difficult to arrange at a position. On the other hand, when a cantilever structure in which the shaft does not pass through the side plates 11 and 13 (end wall portions 52A and 52D), the check valve 71 can be suitably arranged and configured without such restriction.
In addition, as shown with the virtual line (two-dot chain line) in FIG. 1, when the input shaft part 80 extended for the input of motive power about one rotating shaft 20A is provided, the input shaft part 80 is the side plate 11. However, the other rotating shaft 20B does not penetrate the side plate 11. Even in this case, there is an advantage that restrictions on the arrangement of the escape holes 70 are reduced.

  The relief hole 70 is provided with a check valve 71 that opens when the pressure in the cylinders 50A and 50B is higher than a predetermined pressure and closes when the pressure is lower than the predetermined pressure. The check valve 71 functions as a backflow suppression mechanism that suppresses exhaust gas that flows back from the escape hole 70 into the high vacuum cylinder. Since the backflow of the exhaust gas into the high vacuum can be prevented as much as possible, the pump efficiency can be improved.

  The check valve of this embodiment is configured by a reed valve 71. The reed valve 71 is formed in a semicircular strip plate shape at the front end, is held and fixed in a cantilever state at the rear end side, and the front end side is a free end so that the relief hole 70 can be opened and closed. Yes. The reed valve 71 is fixed by a check valve fixing bolt 72 that is screwed into the bolt hole 72a. The reed valve 71 is a check valve fixed to the exhaust side of the relief hole 70, and the differential pressure between the pressure on the exhaust side and the pressure in the compression space exceeds the spring force (elasticity) of the reed valve. Open when The check valve using the reed valve 71 has a simple structure, can be configured compactly and inexpensively, can be easily mounted, and can be easily maintained. Further, the check valve is not limited to the reed valve 71 as in the present embodiment, and for example, a check valve that uses an elastic body such as rubber or silicon, or a valve that opens and closes using a spring (spring) is used. Can do.

Further, 11 is one side plate, 12 is a pump body, and 13 is the other side plate. These components are connected in the axial direction of the rotary shaft 20 to provide an outer shell of the apparatus.
Reference numeral 15 denotes an oil bath portion, which constitutes an oil chamber in which a gear 21 fixed integrally to the rotary shaft 20A and a driven gear 22 fixed integrally to the rotary shaft 20B are built. The oil bath 15 is provided between one set of bearings (40A, 40B) and the other set of bearings (40C, 40D), and is configured to be properly lubricated. Reference numeral 43 denotes an oil seal.

  In the embodiment of FIG. 1, the power unit is not shown, but the biaxial rotary pump of this embodiment can be provided to be driven by transmitting power from an electric motor, for example. For example, a gear mechanism can be used as the driving force transmission means. As a driving force transmission means, when 20A is a driving side rotating shaft and 20B is a driven side rotating shaft, the driving shaft of the electric motor is arranged in series on the rotating shaft 20A and coupled by coupling. A known technique such as a form of connection may be appropriately used as appropriate.

  Moreover, about this embodiment, the unit pump configuration on one side (for example, the unit pump configuration 10B) can be a subsequent unit pump configuration that compresses gas to the highest pressure. In this way, when the unit pump configuration 10B is set to the subsequent stage, a connection air passage may be provided so as to connect the exhaust port 55A of the preceding unit pump configuration 10A and the intake port 35B of the subsequent unit pump configuration 10B. In that case, the rotors 30A and 30B of the front unit pump configuration 10A can be made wider and larger in mass because a large volume of gas is introduced into the front cylinder 50A. The rotors 30C and 30D of the rear unit pump configuration 10B can be made narrower and have a smaller mass because the gas is compressed and introduced into the rear cylinder 50B.

  According to the above-described two-sided cantilevered biaxial rotary pump according to the present invention, access to the rotor 30 is easy and the assembly and maintenance of the rotor requiring clearance adjustment are excellent. Furthermore, there is an advantage that a series with different flow rates can be easily manufactured only by changing the cylinder 50 and the rotor width on both sides, and the expandability of the series is high. In addition, the reed valves 71 can be mounted on both ends of the apparatus, and both unit pump configurations 10 can be manufactured easily and inexpensively while realizing high pump performance as described above. Further, since the basic configuration is the same on both sides, there is symmetry, and it is easy to balance the entire apparatus, and it is possible to more appropriately realize a structure that is suitable for downsizing and more reliable and economical. In addition, about the pump structure of both sides, it is also possible to comprise various application forms, without changing the essence of this invention, such as increasing the compression ratio of gas by multi-stage at least one side.

Next, based on FIG.4 and FIG.5, the example in the case of providing the some escape hole 70 is demonstrated in detail. 4 shows the configuration of the claw pump and the form of the exhaust state, FIG. 5 (a) shows the initial state of the gas compression process, and FIG. 5 (b) shows the exhaust port in the middle of the gas compression process. 55 shows a state in which the side surface of the rotor 30 is closed with a margin, and FIG. 5C shows a state immediately before the gas compression process ends. Moreover, the arrow described in FIG. 5 has shown the rotation direction of the rotor.
In the present embodiment, a plurality of cylinder walls 52 and 53 that constitute the cylinder 50, and a part of the compressed gas can be released to a portion of the wall that constitutes the compression space 51 in the gas compression step. A relief hole 70 is provided. The escape hole 70 of the present embodiment is provided in the end wall portion 52 so as to be opened in the axial direction of the rotary shaft 20.

  Then, as shown in FIG. 5, through the compression process inside the cylinder 50, the total number of the relief holes 70 opened with respect to the volume of the compression space 51 that decreases as the compression ratio of the compression process increases. The plurality of escape holes 70 are arranged so that the area ratio gradually increases. That is, the product of the compression ratio of the gas and the total area facing the cylinder where the escape holes are open gradually increases from the start of compression to the end of compression in the compression process, and reaches the maximum at the end of compression. A plurality of escape holes 70 are arranged so as to be.

  In order to arrange the plurality of escape holes 70 in this way, the area opened by the escape holes 70 in the range closer to the exhaust port 55 becomes larger than the area opened by the escape holes 70 in the range far from the exhaust port 55. It should be set as follows. Therefore, in the case where a plurality of escape holes 70 having the same size (same diameter) are arranged, it is preferable that the number of the escape holes 70 be larger in the portion closer to the exhaust port 55 of the end wall portion 52. . In other words, the closer to the exhaust port 55, the higher the density of the escape holes 70, the better. Furthermore, it is possible to satisfy the above condition by increasing the size of the escape hole 70 in a portion closer to the exhaust port 55 of the end wall portion 52.

In this embodiment, the total number of the plurality of escape holes 70 applied to the cylinder 50 is provided in the end wall portion 52 on the free end side of the cylinder. However, as long as the above-described conditions are satisfied, the present invention is not limited to this, and a part of the plurality of escape holes 70 is provided in at least one of the end wall portions 52 that constitute both ends of the cylinder 50. Form may be sufficient.
Furthermore, through the compression process inside the cylinder 50, the ratio of the total area in which the plurality of escape holes 70 are opened gradually increases with respect to the volume of the compression space 51 that decreases as the compression ratio of the compression process increases. A plurality of escape holes 70 may be provided in the peripheral wall portion 53 of the cylinder as long as the condition to do so is satisfied.

  The check valve 71 attached to the relief hole 70 is provided so as to open in a state in which the pressure inside the pump becomes positive before the exhaust port 55 is opened. Here, “positive pressure” means a pressure in which the pressure in the compression space exceeds the pressure on the exhaust side of the escape hole 70, and is not limited to a pressure higher than the atmospheric pressure. When the differential pressure between the pressure on the exhaust side and the pressure in the compression space exceeds the spring force (elasticity) of the check valve (reed valve 71), the reed valve 71 is opened. In the vacuum pump, the sucked negative pressure air is compressed by the claw-shaped rotor, the check valve 71 is opened by positive pressure (pressure at which the check valve 71 operates), and exhaust from the escape hole 70 is performed. Therefore, it is necessary to arrange the escape hole 70 at a position where the inside of the pump becomes a positive pressure in the compression process of the rotary track formed by the rotor shape. Since the compression process proceeds closer to the exhaust port and the inside is in a high pressure state, the check valve 71 is easier to operate, and the longer the compression process time is, the longer the operation time of the check valve 71 is. The over-compression suppressing effect on the open side is great. Further, in this embodiment, the check valve 71 is constituted by a reed valve, and the operating pressure can be changed / adjusted by changing its hardness / thickness.

As described above, by optimally setting the arrangement conditions of the relief holes 70 for suppressing overcompression on the atmosphere opening side, it is possible to maximize the effect of suppressing overcompression on the atmosphere opening side. .
Further, for the escape hole 70, the shape such as the number of holes, the hole diameter, and the chamfering of the holes may be selectively optimized as appropriate.

According to the present embodiment, a rotary pump such as a non-contact type vacuum pump equipped with a claw rotor is provided with a mechanism for suppressing overcompression by the escape hole 70. Regarding the effect of the escape hole 70, attention is paid to the chain of action. This will be described in detail below.
According to this overcompression suppressing mechanism (relief hole 70), it is possible to suppress overcompression on the atmosphere opening side where the exhaust gas flow rate is large (when operation is performed in a state where the pressure of the sucked air is close to atmospheric pressure). The entrance of exhaust gas that flows backward from the escape hole 70 into the vacuum cylinder can be suppressed by a backflow suppression mechanism using a check valve 71 that closes the escape hole 70.

  According to this, since over-compression can be suppressed as described above, it is possible to increase the compression ratio by reducing the exhaust port so as to reduce the volume immediately before the exhaust is opened. By reducing the volume immediately before the exhaust is released, the amount of exhaust gas flowing back into the pump can be suppressed. By suppressing the amount of gas that flows backward, it is possible to suppress an increase in the power load and the temperature inside the pump during the reaching operation of the vacuum pump.

  That is, according to the present embodiment, the volume of the backflow gas can be suppressed by reducing the volume immediately before the exhaust is released, the power load and the temperature increase can be suppressed, and the overcompression suppressing mechanism (relief hole 70) can be opened to the atmosphere. The inside of the cylinder, which is over-compressed on the side and is in a high vacuum, is controlled by the backflow suppression mechanism (check valve 71) to suppress the backflow gas from the escape hole 70, so that the flow rate is not reduced and A high-efficiency pump structure on the high vacuum pressure side that can use the full pressure range of a stage pump can be realized, and the effect can be maximized.

  In order to reduce the volume immediately before the exhaust is released, it is preferable to make the exhaust port small and provide the exhaust port at a position where the air inside the pump is compressed as much as possible. That is, the exhaust port is provided so as to increase the compression ratio. In order to suppress the amount of the exhaust gas flowing backward, there are other methods in which the exhaust from the front-stage pump is pulled by the rear-stage pump by a multistage structure and a check valve is attached to the exhaust port.

  Furthermore, to explain the above effects from the opposite viewpoint, by increasing the compression ratio in order to reduce the volume immediately before the exhaust is released, it is possible to suppress over-compression on the open side where the exhaust flow rate is high as a result. An escape hole 70 is provided as an over-compression suppressing mechanism. In addition, a check valve 71 is provided as a backflow suppressing mechanism that suppresses exhaust gas that flows back from the escape hole 70 to the inside of the cylinder in a high vacuum.

  As described above, the present invention has been described in various ways with preferred embodiments. However, the present invention is not limited to these embodiments, and many modifications can be made without departing from the spirit of the invention. That is.

DESCRIPTION OF SYMBOLS 10 Unit pump structure 10A Unit pump structure 10B Unit pump structure 11 One side plate 12 Pump main body 13 The other side plate 15 Oil bath part 20 Rotating shaft 20A Rotating shaft 20B Rotating shaft 21 Gear 22 Gear 30 Rotator 30A Rotor 30B Rotor 30C Rotor 30D Rotor 35A Intake port 35B Intake port 40 Bearing 40A One side bearing 40B One side bearing 40C The other side bearing 40D The other side bearing 43 Oil seal 50 Cylinder 50A Cylinder 50B Cylinder 51 Compression space 52 End wall 52A End wall 52B End wall portion 52C End wall portion 52D End wall portion 53 Peripheral wall portion 55 Exhaust port 55A Exhaust port 55B Exhaust port 70 Relief hole 71 Check valve (reed valve)
72 Check valve fixing bolt 72a Bolt hole

Claims (6)

Two rotors are provided with the rotor so that the two rotors are rotated without contact while maintaining a minute clearance, and the two rotors are rotated without contact with the inner surface of the cylinder while maintaining a minute clearance. In the biaxial rotary pump that is provided with a rotary shaft supported by a bearing, and that sucks gas into the cylinder and exhausts compressed gas from the cylinder,
A unit pump configuration constituted by the cylinder and the two rotors is provided at both ends of each of the rotation shafts, and in both of the unit pump configurations, the two rotors are the shafts of the rotation shafts in the two rotors. A biaxial rotary pump, characterized in that it is supported in a cantilevered manner via the rotary shaft by a bearing arranged on one side of the direction and between both unit pump configurations.   At least one cylinder of the unit pump configuration at both ends of the rotating shaft, and an end wall portion on the cantilever end surface side through which the rotating shaft is not inserted among end wall portions constituting both ends in the axial direction of the cylinder, 2. The biaxial rotary pump according to claim 1, wherein an escape hole through which a part of the compressed gas can escape is provided in the axial direction of the rotary shaft.   The biaxial rotary pump according to claim 2, wherein a plurality of the escape holes are provided in an end wall portion on the cantilever end face side.   The relief hole is provided with a check valve that opens when the pressure in the cylinder is higher than a predetermined pressure and closes when the pressure is lower than the predetermined pressure. Item 4. The biaxial rotary pump according to item 2 or 3.   The biaxial rotary pump according to claim 4, wherein the check valve is a reed valve.   The rotor is a rotor of a claw pump having a hook-shaped claw portion, and an exhaust port for exhausting the compressed gas of the cylinder to an end wall portion on the cantilever end face side of the cylinder provided with the escape hole. The biaxial rotary pump according to claim 2, wherein the biaxial rotary pump is provided.

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