JP2005171799A - Axial flow fluid machinery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial flow fluid machinery, for preventing contact of an outer member with an inner member in high speed rotation, while decreasing a flow rate of back-flow of gas by reducing clearance between the outer member and inner member. <P>SOLUTION: The axial flow fluid machinery comprises: the cylindrical outer member 2; the inner member 3 having an outer circumferential face 3a opposed to an inner circumferential side 2a of the outer member 2 through the clearance d; a screw part 4 at least one of the inner circumferential side and an outer circumferential side of the outer member 2. In the fluid machinery, fluid is sucked or discharged by rotating at least one of the outer member 2 and inner member 3. A fluid bearing part 5 is disposed between the inner circumferential face 2a of the outer member 2 and an outer circumferential member 3a of the inner member 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thread groove type axial flow type fluid machine including a cylindrical outer member, an inner member disposed therein, and a screw portion formed therebetween.

  Conventionally, as an axial flow type fluid machine for transferring fluid in the axial direction, a cylindrical outer member, an inner member having an outer peripheral surface opposed to an inner peripheral surface of the outer member via a gap, and an outer member Axial flow type fluid that includes a thread portion formed on at least one of the inner peripheral side and the outer peripheral side of the inner member and sucks or discharges the fluid by rotating at least one of the outer member and the inner member A machine is used.

  As such an axial flow type fluid machine, for example, as shown in FIG. 7, an outer member 101 that is a stator, an inner member 102 that is a rotor disposed on the inner peripheral side of the outer member 101, and a thread groove portion There is known a thread groove type vacuum pump 104 that includes a threaded portion 103 that is composed of 103a and a threaded portion 103b and is formed on the outer peripheral side of the inner member 102 (see, for example, Patent Document 1).

In the thread groove type vacuum pump 104, the screw portion 103 compresses gas by rotating the inner member 102 at a high speed, and exhausts air from the intake side 105 to the exhaust side 106. Here, the gap between the outer member 101 and the inner member 102 is normally set to several tens of μm to several hundreds of μm. For this reason, when exhausting a gas in the viscous flow region (vacuum degree: 1.0 × 10 ⁵ (= atmospheric pressure) to 1.0 × 10 ² Pa) from the intake side 105 toward the exhaust side 106, When a pressure difference between the side 105 and the exhaust side 106 occurs, a backflow of gas occurs from the exhaust side 106 to the intake side 105. By making the flow rate at which the screw portion 103 compresses and exhausts the gas larger than the reverse flow rate, the gas is exhausted from the intake side 105 to the exhaust side 106, and the degree of vacuum on the intake side 105 can be increased.
Japanese Unexamined Patent Publication No. 62-38898

  In the above-described thread groove type vacuum pump 104, in order to increase the compression ratio and increase the exhaust gas flow rate, it is necessary to reduce the gap between the outer member 101 and the inner member 102 as much as possible to reduce the gas back flow rate. However, in the above-described thread groove type vacuum pump 103, when the gap between the outer member 101 and the inner member 102 is reduced, the inner member 102 that rotates at high speed is affected by centrifugal force, thermal stress, vibration, etc. There is a risk of contact with the outer member 101.

  Therefore, an object of the present invention is to reduce the backflow flow rate of the gas by reducing the gap between the outer member and the inner member, while preventing contact between the outer member and the inner member during high speed rotation. It is to provide a fluid machine.

  In order to solve the above-described problems, in the present invention, a cylindrical outer member, an inner member having an outer peripheral surface disposed opposite to an inner peripheral surface of the outer member via a gap, and an inner periphery of the outer member And an axial flow type in which fluid is sucked or discharged by rotating at least one of the outer member and the inner member, and a thread portion formed on at least one of the outer member and the outer peripheral side of the inner member. In the fluid machine, a fluid bearing portion is provided between an inner peripheral surface of the outer member and an outer peripheral surface of the inner member.

  In the present invention, the hydrodynamic bearing portion is provided between the inner peripheral surface of the outer member and the outer peripheral surface of the inner member. Therefore, the outer member and the inner member can be kept in a non-contact state even during high-speed rotation. Further, the gap between the outer member and the inner member can be made as small as the bearing gap of the fluid bearing. That is, for example, when a gas is used as the fluid, the gap between the outer member and the inner member can be normally set to several tens of μm. As a result, the backflow can be kept small.

  In this invention, it is preferable that the fluid bearing which comprises the said fluid bearing part is a fluid dynamic pressure bearing. In an axial flow type fluid machine, fluid is transferred in the axial direction by causing relative rotation between an outer member and an inner member. Therefore, by using the fluid dynamic bearing as the fluid dynamic bearing, the bearing portion can be configured using the relative rotation between the outer member and the inner member while using the fluid existing in the fluid bearing portion.

  In the present invention, it is preferable that the fluid bearing portion is provided at least between the inner peripheral surface of the outer member and the outer peripheral surface of the inner member at the fluid discharge side end. By providing the fluid bearing at the discharge side end, the backflow from the exhaust side can be effectively suppressed.

  In this invention, it is preferable that the said fluid bearing part is provided in the both sides of the said thread part in the rotating shaft direction. By comprising in this way, the both ends of the thread part which comprises the principal part in an axial flow type fluid machine can be supported, and the function sufficient as a bearing can be fulfill | performed.

  In the present invention, it is preferable that at least one of the inner peripheral surface of the outer member and the outer peripheral surface of the inner member is formed by a cylindrical sleeve fitted into a thread portion of the screw portion. That is, it is preferable that the hydrodynamic bearing portion is configured by using the inner peripheral surface or the outer peripheral surface of the cylindrical sleeve fitted into the thread portion. By comprising in this way, a fluid bearing part can be comprised, using the existing screw part.

  In the present invention, the axial flow type fluid machine may be a thread groove type vacuum pump for exhausting gas.

  In the present invention, the fluid bearing portion is provided between the inner peripheral surface of the outer member and the outer peripheral surface of the inner member constituting the axial flow type fluid machine. Therefore, contact between the outer member and the inner member during high-speed rotation can be prevented while reducing the gap between the outer member and the inner member to reduce the back flow rate of the gas. Therefore, with a simple configuration, the compression ratio of the axial flow type fluid machine can be increased or the suction / discharge flow rate can be increased. That is, as compared with the conventional axial flow type fluid machine, the suction / discharge flow rate can be increased if the compression ratio is the same. In addition, the compression ratio can be increased or the intake / exhaust flow rate can be increased even at a lower rotational speed than in the prior art.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

[Embodiment 1]
FIG. 1 is a longitudinal sectional side view showing an axial flow type fluid machine according to Embodiment 1 of the present invention. In FIG. 1, the side surface of the axial-flow type fluid machine with the outer member cut is shown.

(Outline configuration)
The axial flow type fluid machine according to the present embodiment includes a cylindrical outer member 2, an inner member 3 having an outer peripheral surface 3 a disposed opposite to an inner peripheral surface 2 a of the outer member 2 via a gap d, and an inner member 3. It is the thread groove type vacuum pump 1 provided with the thread part 4 formed in the outer peripheral side. The thread groove type vacuum pump 1 is configured to exhaust gas from the intake side 8 to the exhaust side 7 by rotating the inner member 3. Further, a gas bearing portion 5 as a fluid bearing portion is provided between the inner peripheral surface 2 a of the outer member 2 and the outer peripheral surface 3 a of the inner member 3.

  The inner member 3 includes a shaft 31 having a threaded portion 4 including a threaded groove portion 4a and a threaded portion 4b on the outer peripheral side, and a cylindrical sleeve 32. The lower end side of the shaft 31 is connected to a drive source such as a motor (not shown), and the shaft 31 is configured to rotate on the inner peripheral side of the outer member 2. In the present embodiment, the sleeve 32 has a thin cylindrical shape, and is fitted into the screw thread portion 4b while maintaining its airtightness with its inner peripheral surface being in close contact with the screw thread portion 4b by means such as press fitting. The outer peripheral surface of the sleeve 32 corresponds to the outer peripheral surface 3 a of the inner member 3. Further, the sleeve 32 is fitted into the screw thread portion 4b at two positions on both ends of the screw portion 4 in the rotation axis direction of the shaft 31, that is, on the upper and lower ends of the screw portion 4 in FIG. In addition, the clearance gap between the thread part 4b and the inner peripheral surface 2a of the outer member 2 is set to several tens μm to several hundreds μm.

  Since the gas bearing portion 5 is provided between the inner peripheral surface 2a of the outer member 2 and the outer peripheral surface 3a of the inner member 3, the inner peripheral surface 2a and the outer peripheral surface 3a, for example, the sleeve 32 is made of aluminum metal. On the other hand, the outer member 2 is made of a different metal material so as to be formed of stainless steel.

  The gas bearing which comprises the gas bearing part 5 is a gas dynamic pressure comprised so that the inner member 3 as a rotor may be supported in the non-contact state in the radial direction with respect to the outer member 2 as a stator at the time of the rotation. It is a bearing. In this embodiment, the gap d between the inner peripheral surface 2a of the outer member 2 and the outer peripheral surface 3a of the inner member 3 is set to tens of μm, and the inner peripheral surface 2a of the outer member 2 and the outer peripheral surface of the inner member 3 are set. A groove shape such as a herringbone is formed in at least one of 3a. As described above, since the sleeve 32 is fitted into the screw thread portion 4 b on the upper and lower ends of the screw portion 4 in FIG. 1, the gas bearing portion 5 is provided at two locations on both sides of the screw portion 4. It has been. Further, in this embodiment, the gas bearing portion 5 is provided between the inner peripheral surface 2 a of the outer member 2 and the outer peripheral surface 3 a of the inner member 3 at the exhaust side 7 end and the intake side 8 end. In addition, as a gas dynamic pressure bearing, what is called a perfect circle bearing which formed the cross section of the inner peripheral surface 2a of the outer side member 2 in the direction orthogonal to a rotating shaft and the outer peripheral surface 3a of the inner side member 3 in the substantially perfect circle, or the outer member 2 Various gas dynamic pressure bearings such as a bearing in which irregularities are formed on at least one of the inner peripheral surface 2a and the outer peripheral surface 3a of the inner member 3 can be used.

(Exhaust operation)
The exhaust operation when the gas in the viscous flow region is exhausted from the intake side 8 to the exhaust side 7 by the thread groove type vacuum pump 1 configured as described above will be described below.

  When exhausting gas from the intake side 8 to the exhaust side 7, the inner member 3 is rotated at a high speed. By rotating the inner member 3, the screw portion 4 is rotated, and the gas is pushed from the intake side 8 to the exhaust side 7. The gas pushed away from the intake side 8 to the exhaust side 7 mainly passes through the thread groove 4a. At this time, in the gas bearing portions 5 provided on both sides of the screw portion 4, dynamic pressure is generated in the radial direction by rotating the inner member 3 at a high speed, and the inner member 3 is not in contact with the outer member 2. Supported in state.

(Effect of this embodiment)
As described above, in the thread groove type vacuum pump 1 according to the present embodiment, the gas bearing portion 5 is provided between the inner peripheral surface 2 a of the outer member 2 and the outer peripheral surface 3 a of the inner member 3. For this reason, the closer the outer member 2 and the inner member 3 are to each other due to the influence of centrifugal force or vibration during the high speed rotation of the inner member 3, the greater the positive pressure between the members 2 and 3 in the gas bearing portion 5. Is generated, and a repulsive force acts in a direction in which both members 2 and 3 are moved away. Therefore, the outer member 2 and the inner member 3 can be kept in a non-contact state even when the inner member 3 rotates at a high speed. Further, when the inner member 3 is rotated at a high speed and gas is exhausted from the intake side 8 to the exhaust side 7, it is formed between the inner peripheral surface 2 a of the outer member 2 and the outer peripheral surface 3 a of the inner member 3. A back flow of the gas passing through the gap d, that is, the gap d in the gas bearing portion 5 occurs. However, as in the present embodiment, the gap d in the gas bearing portion 5 can be set as small as several tens of μm, so that the back flow rate of gas can be reduced. Therefore, the compression ratio of the thread groove type vacuum pump 1 can be increased and the exhaust flow rate can be increased. In addition, the rotational speed of the inner member 3 necessary for obtaining a compression ratio and exhaust flow rate comparable to those in the prior art can be reduced.

  A gas bearing portion 5 is formed between the inner peripheral surface 2 a of the outer member 2 and the outer peripheral surface 3 a of the inner member 3. Therefore, it is not necessary to separately provide a bearing portion for the inner member 2, and the configuration of the thread groove type vacuum pump 1 is simplified. Further, since a gas bearing is employed as the bearing, there is no need for high-precision assembly using a tool such as a ball bearing or a magnetic bearing. Therefore, the assembly work can be performed relatively easily, and the efficiency of the assembly work of the thread groove type vacuum pump 1 is good.

  With this form, the gas bearing which comprises the gas bearing part 5 is a gas dynamic pressure bearing. Therefore, the bearing portion can be configured using the relative rotation between the outer member 2 and the inner member 3 while using the gas present in the gas bearing portion 5. That is, the gas bearing portion 5 can be configured with a simple configuration.

  In this embodiment, the gas bearing portion 5 is provided between the inner peripheral surface 2 a of the outer member 2 and the outer peripheral surface 3 a of the inner member 3 at least at the exhaust side 7 end. Therefore, the backflow of gas from the exhaust side 7 can be effectively prevented. That is, even if the gas bearing portion 5 is not formed between the inner peripheral surface 2a of the outer member 2 and the outer peripheral surface 3a of the inner member 3 at the end of the intake side 8 in FIG. Backflow can be prevented.

  In this embodiment, the gas bearing portion 5 is provided on both sides of the screw portion 4 in the rotation axis direction. Therefore, both ends of the screw part 4 constituting the main part of the thread groove type vacuum pump 1 can be supported, and a sufficient function as a bearing of the inner member 2 as a rotor can be achieved.

  In this embodiment, the outer peripheral surface 3a of the inner member 3 is formed by a thin cylindrical sleeve 32 fitted into the thread portion 4b. That is, the gas bearing portion 5 is configured using the outer peripheral surface of the sleeve 32. Therefore, the gas bearing part 5 can be comprised, without changing the screw part 4 used conventionally.

(Modification of this embodiment)
FIG. 2 is a longitudinal sectional side view showing a modification of the axial flow type fluid machine according to Embodiment 1 of the present invention. Also in FIG. 2, the side surface of the axial-flow type fluid machine in a state in which the outer member is cut is shown as in FIG.

  As shown in FIG. 2, a thin cylindrical sleeve 32 may be fitted over the entire length of the screw portion 4 in the rotation axis direction. Even if comprised in this way, the effect similar to Embodiment 1 can be acquired.

[Embodiment 2]
3A and 3B are a top view and a longitudinal sectional side view, respectively, showing an axial-flow type fluid machine according to Embodiment 2 of the present invention. FIG. 3B shows a side surface of the axial fluid machine with the outer member cut. Since the basic configuration of the axial flow type fluid machine according to the present embodiment is the same as that of the first embodiment, common portions are denoted by the same reference numerals and illustrated. Is omitted.

  As shown in FIG. 3, in the thread groove type vacuum pump 1 according to the present embodiment, the inner member 3 includes a shaft portion 33 in which a thread portion 4 including a thread groove portion 4 a and a screw thread portion 4 b is formed in part on the outer peripheral side. The shaft portion 33 and the boss portion 34 formed integrally with the shaft portion 33 are configured. The illustrated lower end side of the shaft portion 33 is connected to a driving source such as a motor (not shown), and the inner member 3 is configured to rotate on the inner peripheral side of the outer member 2.

  The boss part 34 has a larger diameter than the shaft part 33, and is formed at two locations on both ends of the screw part 4 formed on the shaft part 33. In this embodiment, the outer peripheral surface of the boss portion 34 corresponds to the outer peripheral surface 3 a of the inner member 3. A gas bearing portion 5 is provided between the outer peripheral surface 3 a and the inner peripheral surface 2 a of the outer member 2. The boss portion 34 is provided with a through hole 34a through which gas passes when the gas is exhausted from the intake side 8 to the exhaust side 7 in the axial direction. In this embodiment, eight through holes 34a are provided in an annular shape at intervals of 45 °.

  In the thread groove type vacuum pump 1 according to the present embodiment configured as described above, the inner member 3 is rotated at a high speed as in the first embodiment, and gas is exhausted from the intake side 8 to the exhaust side 7. . At this time, the gas pushed away from the intake side 8 to the exhaust side 7 mainly passes through the through hole 34 a on the intake side 8, the thread groove 4 a, and the through hole 34 a on the exhaust side 7.

  In the thread groove type vacuum pump 1 in this embodiment, the shaft portion 33 and the boss portion 34 are integrally formed to constitute the inner member 3, and the outer peripheral surface of the boss 34 portion, that is, the outer peripheral surface 3 a of the inner member 3 and the outer member 2. A gas bearing portion 5 is provided between the inner peripheral surface 2a of the first and second inner peripheral surfaces 2a. Therefore, as in the first embodiment, the gas bearing portion 5 cannot be configured without changing the conventionally used screw portion 4. However, since the shaft portion 33 and the boss portion 34 are integrally formed, processing becomes easy. Further, when the sleeve 32 is fitted into the thread portion 4 b, gas from between the thread portion 4 b and the inner peripheral surface of the sleeve 32 leaks out, and there is a risk of causing a back flow from the exhaust side 7 to the intake side 8. Therefore, it may be necessary to provide means for preventing gas leakage. However, if the configuration of this embodiment is adopted, it is not necessary to consider gas leakage.

[Other embodiments]
The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the screw part 4 is formed on the inner member 3 and the inner member 3 is rotated. However, the screw member 4 forming member and the inner member 3 and the outer member 2 can be rotated and fixed. The combinations shown in Table 1 below can be adopted as the patterns.

  That is, NO. Although the combination of 1 corresponds to Embodiments 1 and 2 described above, the inner member 3 may be fixed and the outer member 2 may be rotated as shown in FIG. 4 (NO. 2 in the table). In this case, since the screw part 4 does not rotate and the gas cannot be circulated, an impeller 10 for circulating the gas is provided at at least one end of the outer member 2 (see FIG. 4) or on the exhaust side 7 An auxiliary pump for roughing such as an oil rotary vacuum pump or a dry vacuum pump is provided. In addition, when using an auxiliary pump, it is not necessary to provide the impeller 10. Moreover, it is not restricted to rotating any one of the inner side member 3 and the outer side member 2, You may make it rotate both the members 3 and 2 (in the table | surface NO.3). In this case, the impeller 10 or the like is not necessary. The rotation directions at this time are preferably opposite to each other, but may be rotated in the same direction to provide a rotation speed difference.

  Moreover, as FIG. 5 shows, you may form the thread part 4 in the outer side member 2 (in the table | surface NO.4-6). In this case, when the member provided with the threaded portion 4 is fixed, the impeller 10 is provided on the rotating member (see FIG. 5), or an oil rotary vacuum pump, a dry vacuum pump, or the like is provided on the exhaust side 7. An auxiliary pump for roughing is provided (No. 4 in the table). When the screw part 4 is formed on the outer member 2, the inner peripheral surface 2a of the outer member 2 is formed by fitting a thin cylindrical sleeve 21 into the screw thread part 4b as shown in FIG. The gas bearing 5 may be provided. Or corresponding to said Embodiment 2, the inner peripheral surface 2a is formed and the gas bearing part 5 is provided by providing the outer member 2 with the thick part whose inner diameter is smaller than the screw thread part 4b. Anyway.

  Furthermore, as shown in FIG. 6, the screw portion 4 may be formed on both the inner member 3 and the outer member 2 (NO. 7 to 9 in the table). In this case, since the member provided with the screw portion 4 always rotates, it is not necessary to provide the impeller 10. In this case, the outer peripheral surface 3a of the inner member 3 is formed by fitting the sleeve 32 into the screw thread 4b of the inner member 3 (see FIG. 6) or by providing a boss portion on the inner member 3. An inner peripheral surface of the outer member 2 is provided by providing the outer member 2 with a thick portion 22 whose inner diameter is smaller than that of the screw thread portion 4b (see FIG. 6) or by fitting a sleeve into the screw thread portion 4b of the outer member 2. The gas bearing portion 5 may be provided by forming 2a.

  Furthermore, in the embodiment described above, the axial flow type fluid machine is the thread groove type vacuum pump 1 that exhausts gas, but the axial flow type fluid machine in the present invention is not limited to this. That is, for example, the present invention may be applied to a compressor device that performs gas suction. Further, the present invention may be applied to an axial flow type fluid machine that handles an incompressible fluid such as water or oil other than gas.

  In the embodiment described above, the gas bearing constituting the gas bearing portion 5 is a gas dynamic pressure bearing, but the gas bearing may be a gas static pressure bearing. That is, for example, a gas bearing may be configured by supplying a gas having a predetermined pressure to the outer peripheral surface 3a of the inner member 3 in the gas bearing portion 5 in FIG.

  Furthermore, in the above-described embodiment, the outer member 2 has a cylindrical shape with a constant inner diameter of the inner peripheral surface 2a. However, the inner peripheral surface 2a of the outer member 2 has a tapered shape in which the inner diameter gradually changes in the axial direction. You may form in the cone shape which has. In the embodiment described above, the inner member 3 has a substantially cylindrical shape, but the inner member 3 may also be formed in a conical shape. In the above-described embodiment, the gas bearing portion 5 is provided at two locations on both ends of the screw portion 4, but may be provided at one location so that the screw portion 4 is sandwiched from both sides in the axial direction, for example. .

Furthermore, in the above-described embodiment, the gas in the viscous flow region is exhausted. However, since the reverse flow is caused by the pressure difference between the intake side and the exhaust side, not only the viscous fluid but also the intermediate flow region (vacuum degree) : 1.0 × 10 ^{2 to} 1.0 × 10 ⁻² Pa) gas may be exhausted. Furthermore, the gas in the molecular flow region (degree of vacuum:> 1.0 × 10 ⁻² Pa) may be exhausted.

It is a longitudinal cross-sectional side view which shows the axial flow type fluid machine which concerns on Embodiment 1 of this invention. FIG. 6 is a longitudinal sectional side view showing a modification of the axial flow type fluid machine according to the first embodiment. (A), (B) is the top view and longitudinal cross-sectional side view which respectively show the axial flow type fluid machine which concerns on Embodiment 2 of this invention. It is a longitudinal cross-sectional side view which shows the axial flow type fluid machine which concerns on other embodiment of this invention which the outer side member which does not have a thread part rotates. It is a longitudinal cross-sectional side view which shows the axial-flow type fluid machine which concerns on other embodiment of this invention which the inner member which does not have a thread part rotates. It is a longitudinal cross-sectional side view which shows the axial-flow type fluid machine which concerns on other embodiment of this invention in which an inner member and an outer member have a thread part. It is a side view which shows the conventional axial flow type fluid machine.

Explanation of symbols

1 Thread groove type vacuum pump (axial flow type fluid machine)
2 outer member 2a inner peripheral surface 3 inner member 3a outer peripheral surface 4 screw portion 4a screw groove portion 4b screw thread portion 5 gas bearing portion (fluid bearing portion)
21 sleeve 32 sleeve d gap

Claims (6)

At least one of a cylindrical outer member, an inner member having an outer peripheral surface opposed to the inner peripheral surface of the outer member via a gap, and an inner peripheral side of the outer member and an outer peripheral side of the inner member An axial flow type fluid machine that includes a threaded portion formed on the outer surface and rotates and / or sucks or discharges fluid by rotating at least one of the outer member and the inner member.
An axial flow type fluid machine, wherein a fluid bearing portion is provided between an inner peripheral surface of the outer member and an outer peripheral surface of the inner member. The axial flow type fluid machine according to claim 1, wherein the fluid bearing constituting the fluid bearing portion is a fluid dynamic pressure bearing. 2. The axial flow type fluid according to claim 1, wherein the fluid bearing portion is provided between an inner peripheral surface of the outer member and an outer peripheral surface of the inner member at least at a fluid discharge side end. machine. 2. The axial flow type fluid machine according to claim 1, wherein the fluid bearing portion is provided on both sides of the screw portion in the rotation axis direction. The at least one of the inner peripheral surface of the outer member and the outer peripheral surface of the inner member is formed by a cylindrical sleeve fitted into a thread portion of the screw portion. Axial flow type fluid machine. 2. The axial flow type fluid machine according to claim 1, wherein the axial flow type fluid machine is a thread groove type vacuum pump for exhausting gas.

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