JP6772136B2 - Non-contact annular seal and rotating machine equipped with it - Google Patents

Description

The present invention relates to a non-contact annular seal and a rotary machine including the same, and particularly reduces the amount of fluid leakage between an impeller or the like and a casing in a rotary machine that handles an incompressible fluid, and reduces vibration. The present invention relates to a non-contact annular seal exhibiting stable shaft sealing characteristics and a rotating machine provided with the non-contact annular seal.

Rotating machines that transfer liquids (hereinafter referred to as "pumps") are widely used in plants or equipment for the purpose of power generation, chemical processes, sewerage, water supply, and the like. The pump has a casing and a rotating shaft equipped with an impeller. The rotating shaft is arranged inside the casing and is rotatably supported by bearings. The liquid sucked from the suction port of the casing is boosted by the rotation of the impeller and discharged from the discharge port of the casing. That is, in the flow path inside the pump, a high pressure region and a low pressure region are formed, and the fluid flows from the high pressure region to the low pressure region. Here, if the fluid moves (leaks) from the high-pressure region to the low-pressure region through this gap in a slight gap between the casing (fixed portion) and the rotating shaft (rotating portion), the pump efficiency decreases. Therefore, the gap between the casing and the rotating shaft is sealed by the non-contact annular seal. This prevents the pressurized liquid from leaking to the low pressure side.

For example, in the typical multi-stage centrifugal pump shown in FIG. 1 (quoted from JIS Handbook Pump 1st Edition, page 74), the non-contact annular seal is used in the circled part in the figure. That is, it is used at the inlet of the impeller, between the impeller of the front stage and the impeller of the rear stage, between the outlet of the impeller at the last stage and the low pressure side (pump inlet pressure), and the like. In particular, since the differential pressure between the impeller outlet portion and the low pressure side is large and the fluid leakage is large, the fluid leakage in this portion has a large effect on the pump performance. For this reason, non-contact annular seals having various structures that can reduce the amount of fluid leakage are known.

A smooth seal is known as the most basic non-contact annular seal. A smooth seal is a seal formed by arranging double cylinders having a smooth surface. In order to reduce the amount of leakage of the non-contact annular seal such as the smooth seal, it is effective to reduce the radial gap between the rotating side and the stationary side of the non-contact annular seal. However, due to practical problems such as vibration and deflection of the rotating shaft, the radial gap cannot be made extremely small. Therefore, a non-contact annular seal that reduces the amount of leakage without reducing the radial gap is required. As such non-contact annular seals, parallel groove seals, damper seals, thread groove seals and the like are known. Hereinafter, an example of the conventional non-contact annular seal will be described.

FIG. 18 is a partial cross-sectional view of a conventional parallel groove seal. In FIG. 18, the fixed body 131 is shown in a cross-sectional view, and the rotating shaft 121 is shown in a side view. The parallel groove seal 111 has a rotating shaft 121 having a smooth outer peripheral surface, and a fixed body 131 having a plurality of concentric grooves 141 on the surface facing the rotating shaft 121. The parallel groove seal 111 includes energy loss due to a vortex generated when a fluid flowing in a gap between a rotating shaft 121 and a fixed body 131 passes through a groove 141, pressure loss generated due to rapid expansion and contraction of a flow path, and the like. Therefore, the amount of fluid leakage (movement amount) can be reduced.

19 and 20 are partial cross-sectional views of a conventional damper seal. FIG. 19 shows a damper seal that employs a honeycomb pattern as a damper structure. In FIG. 19, the fixed body 132 is shown in cross section, and the rotating shaft 122 is shown in side view. The damper seal 112 has a rotating shaft 122 having a smooth outer peripheral surface, and a fixed body 132 having a plurality of recesses 142 provided on a surface facing the rotating shaft 122. In the illustrated example, a hexagonal honeycomb pattern is used as the recess 142. The damper seal 112 can reduce the amount of fluid leakage due to the pressure loss of the fluid generated when the fluid flowing in the gap between the rotating shaft 122 and the fixed body 132 flows through the recess 142.

FIG. 20 shows a damper seal that employs a hole pattern as a damper structure. In FIG. 20, the fixed body 133 is shown in a cross-sectional view, and the rotating shaft 123 is shown in a side view. The damper seal 113 has a rotating shaft 123 having a smooth outer peripheral surface, and a fixed body 133 having a plurality of recesses 143 on the surface facing the rotating shaft 123. In the illustrated example, a circular concave hole pattern is used as the recess 143. The damper seal 113 can reduce the amount of fluid leakage due to the pressure loss of the fluid generated when the fluid flowing in the gap between the rotating shaft 123 and the fixed body 133 flows through the recess 143.

FIG. 21 is a partial cross-sectional view of a conventional thread groove seal. In FIG. 21, the fixed body 134 is shown in a cross-sectional view, and the rotating shaft 124 is shown in a side view. The thread groove seal 114 has a cylindrical fixed body 134 having a smooth inner peripheral surface, and a rotating shaft 124 having a thread groove 144 formed on a surface facing the fixed body 134. When the rotating shaft 124 rotates, the thread groove seal 114 has an effect of pushing the fluid back to the high pressure side by a pumping effect according to the rotation direction and reducing the amount of leakage. The screw groove 144 is a continuous groove from the seal inlet side (high pressure side) to the seal outlet side (low pressure side). When the pressure difference between the inlet side and the outlet side of the thread groove seal 114 is large, the leakage flow due to the pressure difference becomes large. Therefore, it is often possible to reduce the leakage amount by reducing the lead angle.

A non-contact annular seal used in a fluid machine such as a turbo molecular pump is disclosed in Japanese Patent Application Laid-Open No. 62-98798 (Patent Document 1) and the like.

Jikkai Sho 62-98798

By the way, in the non-contact annular seal, the fluid passing through the inside of the seal swirls around the outer circumference of the rotating shaft, so that unstable vibration (also called self-excited vibration) is generated in the rotating shaft, and an abnormal vibration state occurs in the rotating shaft. May occur. The difficulty of generating this unstable vibration is one of the important characteristics of the non-contact annular seal. It is known that this unstable vibration is more likely to occur as the swirling flow in the circumferential direction of the rotating shaft inside the seal is larger.

In the case of a thread groove seal, by providing an appropriate groove in the fixed body, it is possible to reduce the swirling flow of the fluid inside the seal due to the rotation of the rotating shaft. For this reason, a thread groove seal having a thread groove on the fixed body is often used as a means for suppressing unstable vibration. It was found that the effect of suppressing unstable vibration due to the screw groove provided on the fixed body becomes more remarkable as the lead angle of the screw groove becomes larger. However, as described above, when the lead angle of the screw groove is increased, the amount of leakage often increases, and it can be said that there is a trade-off relationship between the effect of suppressing unstable vibration and the effect of reducing the amount of leakage. Therefore, it has been difficult to achieve both reduction of leakage amount and suppression of unstable vibration at a high level.

The present invention has been made in view of the above-mentioned conventional problems, and one of the purposes thereof is to improve the effect of suppressing unstable vibration caused by a swirling flow in the circumferential direction of the rotating shaft, and to improve the inside of the seal. It is to suppress the increase in the amount of leakage of the fluid passing through.

Another object of the present invention is to reduce leakage of the fluid boosted by the impeller to the low pressure side in a rotary machine that rotates a rotating shaft to which an impeller is attached and transfers the fluid. This is to suppress unstable vibration caused by the fluid passing through the inside of the seal while increasing the efficiency.

As a result of diligent studies on the above problems, the present inventors have obtained the following findings. That is, in a thread groove seal having a relatively large lead angle of the thread groove, an action of suppressing unstable vibration on the high pressure side (seal inlet side) rather than an action of suppressing unstable vibration on the low pressure side (seal outlet side). Turned out to be large. Further, it was found that the thread groove seal having a relatively small lead angle of the thread groove has almost the same effect of reducing the amount of leakage on the low pressure side and the high pressure side.

The present invention has been made based on the above findings. According to one embodiment of the present invention, it has a rotating body provided in a rotating portion of a rotating machine and a fixed body provided in a fixed portion of the rotating machine, and flows through a gap between the rotating body and the fixed body. A non-contact annular seal configured to seal the fluid is provided. The non-contact annular seal has a screw groove provided on at least one of the surface of the rotating body and the surface of the fixed body forming the gap, and the screw groove is a plane orthogonal to the axial direction of the rotating body. The lead angle of the screw groove is defined with respect to the above, and the lead angle of the screw groove on the seal inlet side is larger than the lead angle of the screw groove on the seal outlet side. According to this, on the high pressure side (seal inlet side), which has a large effect of suppressing destabilizing vibration, the lead angle of the screw groove is relatively large, so that the effect of suppressing destabilizing vibration is improved. be able to. Further, on the low pressure side (seal outlet side), the lead angle of the screw groove is relatively small, so that an increase in the amount of fluid leaking through the seal can be suppressed. Therefore, according to one embodiment of the present invention, it is possible to achieve both the effect of suppressing unstable vibration of the non-contact annular seal and the high shaft sealing performance.

According to another aspect of the present invention, in one form of the non-contact annular seal, the thread groove is formed so that the lead angle of the thread groove gradually decreases from the seal inlet side to the seal outlet side. It is formed. According to this, the non-contact annular seal can be manufactured by joining a plurality of non-contact annular seals having screw grooves having different lead angles to each other. Therefore, the non-contact annular seal can be easily manufactured, for example, by using a conventional non-contact annular seal.

According to another aspect of the present invention, in one form of the non-contact annular seal, the thread groove has a lead angle of the thread groove continuously reduced from the seal inlet side to the seal outlet side. It is formed. According to this, the lead angle of the screw groove can be finely set to an appropriate angle according to the axial position. As a result, the effect of suppressing unstable vibration of the non-contact annular seal and the shaft sealing performance can be further improved.

According to another aspect of the present invention, in one form of the non-contact annular seal, the depth of the thread groove on the seal inlet side is larger than the depth of the thread groove on the seal outlet side. When the lead angle of the screw groove having a predetermined number of threads is increased in the non-contact annular seal, the width of the screw groove must be increased, and the total cross-sectional area of the screw groove becomes large. Further, when the lead angle of the screw groove having a predetermined width is increased, the number of threads must be increased, and the total cross-sectional area of the screw groove becomes large. The larger the sum of the cross-sectional areas of the threads, the easier it is for fluid to flow between the seals. According to one embodiment of the present invention, the total cross-sectional area of the threaded grooves of the non-contact annular seal can be reduced, so that the amount of fluid leaking between the seals can be further reduced.

According to another aspect of the present invention, in one form of the non-contact annular seal, the thread groove is formed at least on the surface of the fixed body. By forming the screw groove at least on the surface of the fixed body, it is possible to suppress an increase in the amount of leakage while improving the action of suppressing unstable vibration. By the way, when the rotating body of the non-contact annular seal is also provided with the screw groove, the pumping effect of pushing the fluid back to the high pressure side by the rotation of the rotating body increases. On the other hand, the rotation of the rotating body may cause the fluid around the rotating body to swirl and promote unstable vibration. Here, if the screw groove is formed on the surface of the fixed body, even if the screw groove is formed on the surface of the rotating body, the swirl of the fluid generated by the rotation of the rotating body is caused by the screw groove on the surface of the fixed body. It can be suppressed. Further, in this case, the amount of fluid leakage can be further reduced due to the pumping effect of the screw groove formed on the surface of the rotating body. Therefore, when the screw groove is formed on both the fixed body and the rotating body, the amount of leakage can be further suppressed while suppressing unstable vibration.

According to another embodiment of the present invention, a rotating machine is provided. This rotating machine includes an electric motor, a spindle connected to the electric motor and configured to be rotatable, an impeller fitted to the spindle and configured to be rotatable together with the spindle, and a casing accommodating the impeller. And a bearing that is attached to the casing and rotatably supports the spindle, the spindle has a rotating portion, the casing has a fixing portion, and the rotating portion and the fixing portion are described above. Has a non-contact annular seal.

According to one of the present inventions, it is possible to suppress an increase in the amount of fluid leaking through the inside of the seal while improving the effect of suppressing unstable vibration caused by a swirling flow in the circumferential direction of the rotating shaft.

Further, according to one of the present inventions, in a rotating machine that rotates a rotating shaft to which an impeller is attached and transfers a fluid, the fluid boosted by the impeller is reduced from leaking to the low pressure side to improve pump efficiency. While raising it, unstable vibration due to the fluid passing inside the seal can be suppressed.

A cross-sectional view of a high-pressure pump to which the non-contact annular seal according to the present embodiment can be applied is shown. It is an enlarged sectional view of the 1st stage impeller of the high pressure pump shown in FIG. It is a partial cross-sectional view which shows the non-contact annular seal of this embodiment applicable to the non-contact annular seal shown in FIG. It is a figure which shows another example of the cross-sectional shape of the screw groove formed in a fixed body. It is a figure which shows another example of the cross-sectional shape of the screw groove formed in a fixed body. It is a figure which shows another example of the cross-sectional shape of the screw groove formed in a fixed body. It is sectional drawing of the fixed body shown in FIG. 3 when cut in a plane including a central axis. FIG. 5 is a cross-sectional view showing another example of a fixed body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows still another example of the fixed body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows still another example of the fixed body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows still another example of the fixed body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows still another example of the fixed body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows still another example of the fixed body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows still another example of the fixed body used for the non-contact annular seal shown in FIG. FIG. 5 is a partial cross-sectional view showing a non-contact annular seal of another embodiment applicable to the non-contact annular seal shown in FIG. FIG. 5 is a partial cross-sectional view showing a non-contact annular seal of another embodiment applicable to the non-contact annular seal shown in FIG. FIG. 5 is a partial cross-sectional view showing a non-contact annular seal of another embodiment applicable to the non-contact annular seal shown in FIG. FIG. 5 is a partial cross-sectional view showing a non-contact annular seal of another embodiment applicable to the non-contact annular seal shown in FIG. It is a graph which shows the result of the evaluation test. It is a partial sectional view of the conventional parallel groove seal. It is a partial cross-sectional view of the conventional damper seal. It is a partial cross-sectional view of the conventional damper seal. It is a partial sectional view of the conventional screw groove seal.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings described below, the same or corresponding components are designated by the same reference numerals and duplicate description will be omitted. In the embodiments described below, a high-pressure pump will be described as an example of the rotary machine of the present invention.

FIG. 1 shows a cross-sectional view of a high-pressure pump (multistage centrifugal pump) to which the non-contact annular seal according to the present embodiment can be applied. The high-pressure pump 1 includes a spindle 11 that rotates by being connected to an electric motor (not shown), impellers 21a, 21b, 21c fitted to the spindle 11, a casing 31 that houses the impellers 21a, 21b, 21c, and a casing. The bearings 45a and 45b attached to the 31 are provided. The bearings 45a and 45b rotatably support the spindle 11. An electric motor (not shown) for rotationally driving the high-pressure pump 1 is connected to the spindle 11 via a coupling 13 fitted to the left end of the spindle 11.

The casing 31 has a suction port 33 for sucking an incompressible fluid such as water (hereinafter, simply referred to as a fluid) from the outside, and a discharge port 37 for discharging the sucked fluid. The first-stage impeller 21a fitted to the spindle 11 rotates with the rotation of the spindle 11, and sucks the fluid into the casing 31 from the suction port 33. The fluid sucked by the first-stage impeller 21a and boosted passes through the first flow path 35a and reaches the second-stage impeller 21b. The fluid boosted by the second stage impeller 21b passes through the second flow path 35b and reaches the third stage impeller 21c. The fluid is further boosted by the third stage impeller 21c, discharged from the discharge port 37, and transferred through a pipe (not shown). That is, the fluid is boosted by the first-stage impeller 21a, the second-stage impeller 21b, and the third-stage impeller 21c.

In the fluid, a pressure difference is generated between the suction side and the discharge side of each impeller 21a, 21b, 21c. That is, the suction side is the low pressure side, and the discharge side is the high pressure side. When this pressure difference occurs, a part of the fluid on the high pressure side leaks to the low pressure side through a slight gap. The non-contact annular seal of the present embodiment reduces its leakage. In the high-pressure pump 1 shown in FIG. 1, the non-contact annular seal of the present embodiment is provided at a portion surrounded by a circle. Since the high-pressure pump 1 shown in FIG. 1 is a multi-stage centrifugal pump, the pressure of the fluid is higher than that of the single-stage centrifugal pump, and the amount of fluid leakage is inevitably large. If the amount of leakage is large, the pump efficiency will decrease.

FIG. 2 is an enlarged cross-sectional view of the first stage impeller 21a of the high pressure pump 1 shown in FIG. As shown in the figure, the first-stage impeller 21a has a suction port 23 for sucking the fluid and a discharge port 25 for discharging the fluid. Here, the pressure of the fluid is low on the suction port 23 side and high on the discharge port 25 side. That is, the suction port 23 is the low pressure portion 36, and the discharge port 25 is the high pressure portion 38. Here, the fluid leakage points in the high-pressure pump 1 are mainly the facing portion X between the outer peripheral surface of the suction port 23 and the casing 31a, and the facing portion Y between the outer peripheral surface on the back surface of the impeller 21a and the casing 31b. The non-contact annular seals 41 and 43 according to the present embodiment are provided in the gaps formed in the opposing portions X and Y.

The non-contact annular seals 41, 43 have rotating bodies 41a, 43a provided on the impeller 21a, which is a rotating portion of the high-pressure pump 1, and fixed bodies 41b, 43b provided on casings 31a, 31b, which are fixing portions. .. In the illustrated example, the rotating bodies 41a and 43a are provided as members separate from the impeller 21a, but the rotating bodies 41a and 43a may be formed integrally with the impeller 21a. Similarly, in the illustrated example, the fixed bodies 41b and 43b are provided as members separate from the casings 31a and 31b, but the fixed bodies 41b and 43b may be integrally formed with the casings 31a and 31b.

FIG. 3 is a partial cross-sectional view showing the non-contact annular seal of the present embodiment applicable to the non-contact annular seals 41 and 43 shown in FIG. In FIG. 3, the fixed body 71 is shown in a cross-sectional view, and the rotating body 61 is shown in a side view.

As shown, the non-contact annular seal 51 of the present embodiment is attached to the rotating body 61 provided on the impeller 21a which is the rotating portion shown in FIG. 2 and the casings 31a and 31b which are the fixing portions shown in FIG. It is provided with a fixed body 71 provided. The rotating body 61 is configured to be rotatable together with the impeller 21a. The rotating body 61 rotates in a predetermined direction about the central axis 151. The central axis 151 coincides with, for example, the axial center of the main axis 11 shown in FIGS. 1 and 2.

Further, the fixed body 71 is provided with a screw groove 81 formed in a spiral shape on the inner surface thereof. That is, the non-contact annular seal 51 of this embodiment is a thread groove seal. The fixed body 71 is formed in a substantially cylindrical shape. The rotating body 61 is a substantially cylindrical member having an outer diameter smaller than the inner diameter of the fixed body 71. The rotating body 61 is arranged inside the fixed body 71 so as to have a predetermined gap with respect to the inner surface of the fixed body 71.

When the non-contact annular seal 51 is applied to the high pressure pump 1 shown in FIG. 1, the fluid makes a gap between the fixed body 71 and the rotating body 61 from the high pressure side 155 (seal inlet side) to the low pressure side 156 (seal outlet). It leaks toward the side), that is, toward the arrow A in the figure.

As shown in FIG. 3, the cross-sectional shape of the screw groove 81 formed in the fixed body 71 is substantially rectangular. However, the cross-sectional shape of the screw groove 81 may be substantially triangular as shown in FIG. 4A. Further, as shown in FIG. 4B, the cross-sectional shape of the screw groove 81 may be substantially U-shaped. Further, as shown in FIG. 4C, the cross-sectional shape of the screw groove 81 may be substantially semicircular. As the cross-sectional shape of the screw groove 81, any cross-sectional shape other than the cross-sectional shape shown in FIGS. 3 and 4A-4C can be adopted.

As described above, the present inventors have obtained the following findings through diligent studies. That is, in a thread groove seal having a relatively large lead angle of the thread groove, an action of suppressing unstable vibration on the high pressure side (seal inlet side) rather than an action of suppressing unstable vibration on the low pressure side (seal outlet side). Turned out to be large. Further, it was found that the thread groove seal having a relatively small lead angle of the thread groove has almost the same effect of reducing the amount of leakage on the low pressure side and the high pressure side.

Therefore, in the non-contact annular seal 51 according to the present embodiment shown in FIG. 3, the lead angle of the screw groove 81 on the high pressure side 155 (seal inlet side) is set to that of the screw groove 81 on the low pressure side 156 (seal outlet side). The thread groove 81 is formed so as to be larger than the lead angle. That is, in the non-contact annular seal 51 according to the present embodiment, the thread groove 81 on the high pressure side efficiently suppresses unstable vibration, and the screw groove 81 on the low pressure side reduces the amount of leakage. Therefore, the non-contact annular seal 51 according to the present embodiment can achieve both the effect of suppressing unstable vibration and high shaft sealing performance.

FIG. 5 is a cross-sectional view of the fixed body 71 shown in FIG. 3 when cut in a plane including the central axis 151. As shown in the figure, the fixed body 71 has a screw groove 81A located on the high pressure side 155 (seal inlet side), a screw groove 81C located on the low pressure side 156 (seal outlet side), and a screw groove 81A and a screw groove 81C. It has a screw groove 81B located between them. Here, the screw groove 81A, 81B, and 81C are collectively referred to as the screw groove 81. The screw grooves 81A, 81B, and 81C define lead angles θ1A, θ1B, and θ1C with respect to a plane orthogonal to the axial direction (axial direction of the central axis 151) of the rotating body 61 (see FIG. 3), respectively. Further, the screw grooves 81A, 81B, and 81C have widths W1A, W1B, and W1C, respectively. Here, the widths W1A, W1B, and W1C indicate the shortest distances in the width direction from arbitrary points on the side surfaces of the screw grooves 81A, 81B, and 81C. The depths of the screw grooves 81A, 81B, and 81C are all the same.

The thread groove 81 has boundaries 161, 162 in which the lead angle of the thread groove 81 changes. Specifically, the lead angle θ1A of the screw groove 81A changes to the lead angle θ1B of the screw groove 81B at the boundary portion 161. Further, the lead angle θ1B of the screw groove 81B changes to the lead angle θ1C of the screw groove 81C at the boundary portion 162. Since the boundaries 161, 162 do not have a substantial width, the threaded grooves 81 are continuously formed on the surface of the fixed body 71. In the present embodiment, the boundary portions 161, 162 are formed parallel to the plane orthogonal to the central axis 151. However, the boundary portions 161, 162 are not limited to the case where they are formed in a planar shape or a linear shape, and may have any shape. Further, as will be described later, the number of the boundary portions 161, 162 is not limited to two, and may be one or three or more (see FIGS. 10 and 11).

Here, the lead angle θ1A is larger than the lead angle θ1B. Further, the lead angle θ1B is larger than the lead angle θ1C. Therefore, the lead angle of the screw groove 81 is formed so as to gradually decrease from the high pressure side 155 to the low pressure side 156. That is, on the high-pressure side 155, which has a large effect of suppressing destabilizing vibration, the lead angle θ1A of the screw groove 81A is relatively large, so that the effect of suppressing destabilizing vibration can be improved. Further, on the low pressure side 156, the lead angle θ1B of the screw groove 81B and the lead angle θ1C of the screw groove 81C are relatively small, so that an increase in the amount of fluid leaking through the non-contact annular seal 51 can be suppressed. Can be done.

Further, since the thread groove 81 is formed so that the lead angle thereof gradually decreases from the high pressure side 155 to the low pressure side 156, the screw groove 81 can be easily machined in the fixed body 71. Specifically, the screw groove 81 can be formed by processing screw grooves 81A, 81B, and 81C having a constant width on the inner peripheral surface of the fixed body 71, respectively. Alternatively, for example, a fixed body having a screw groove 81A, a fixed body having a screw groove 81B, and a fixed body having a screw groove 81C are manufactured respectively, and the fixed body 71 can be easily manufactured by combining these fixed bodies. Can be done.

The number of threads of the screw groove 81A, the number of threads of the screw groove 81B, and the number of threads of the screw groove 81C are the same. When the number of threads of the thread groove 81 is constant, the width of the thread groove 81 decreases as the lead angle decreases. Therefore, the width W1A of the screw groove 81A on the high pressure side 155 of the boundary portion 161 is larger than the width W1B of the screw groove 81B on the low pressure side 156 of the boundary portion 161. Further, the width W1B of the screw groove 81B on the high pressure side 155 of the boundary portion 162 is larger than the width W1C of the screw groove 81C on the low pressure side 156 of the boundary portion 162. That is, the width of the screw groove 81 is formed so as to gradually decrease from the high pressure side 155 to the low pressure side 156. As will be described later, the number of threads of the screw groove 81A, the number of threads of the screw groove 81B, and the number of threads of the screw groove 81C may be different from each other (see FIG. 7). Further, as will be described later, the width W1A, the width W1B, and the width W1C may have the same size (see FIG. 7).

As shown in the figure, the cross-sectional area of the thread groove 81A on the high pressure side 155 at the boundary portion 161 is the same as the cross-sectional area of the thread groove 81B on the low pressure side 156. Similarly, at the boundary portion 162, the cross-sectional area of the thread groove 81B on the high pressure side 155 is the same as the cross-sectional area of the thread groove 81C on the low pressure side 156. As will be described later, the cross-sectional area of the thread groove 81 on the high pressure side 155 at the boundary portions 161, 162 may be different from the cross-sectional area of the screw groove 81 on the low pressure side 156 (see FIG. 7).

Further, as shown in the drawing, at the boundary portions 161, 162, the screw groove 81 on the high pressure side 155 is continuously formed in the screw groove 81 on the low pressure side 156. In other words, at the boundary portions 161, 162, the cross section of the thread groove 81 on the high pressure side 155 coincides with the cross section of the thread groove 81 on the low pressure side 156. Specifically, at the boundary portion 161, the cross section of the thread groove 81A on the high pressure side 155 coincides with the cross section of the thread groove 81B on the low pressure side 156. Further, at the boundary portion 162, the cross section of the thread groove 81B on the high pressure side 155 coincides with the cross section of the screw groove 81C on the low pressure side 156. As a result, it is possible to prevent the pumping effect from being hindered by the screw grooves 81 at the boundary portions 161, 162. As will be described later, at the boundary portions 161, 162, the screw groove 81 on the high pressure side 155 may be formed so as not to be continuous with the screw groove 81 on the low pressure side 156 (see FIGS. 6 and 7).

As described above, the non-contact annular seal 51 shown in FIG. 3 has a fixed body 71 in which the lead angle of the screw groove 81 on the high pressure side 155 is larger than the lead angle of the screw groove 81 on the low pressure side 156. The non-contact annular seal 51 may also include, for example, other fixtures as described below.

FIG. 6 is a cross-sectional view showing another example of the fixed body used for the non-contact annular seal 51 shown in FIG. FIG. 6 shows a cross-sectional view of a fixed body when cut in a plane including the central axis 151 shown in FIG. The fixed body 72 shown in FIG. 6 is different from the fixed body 71 shown in FIG. 5 in that the screw grooves 81 are discontinuous at the boundary portions 161, 162. Since the other parts of the fixed body 72 are the same as those of the fixed body 71 shown in FIG. 5 and their effects are also the same, detailed description thereof will be omitted.

As shown, at the boundary portions 161, 162, the cross section of the thread groove 81 on the high pressure side 155 is formed so as not to match the cross section of the thread groove 81 on the low pressure side 156. Specifically, at the boundary portion 161, the cross section of the thread groove 81A on the high pressure side 155 does not match the cross section of the thread groove 81B on the low pressure side 156. Further, at the boundary portion 162, the cross section of the thread groove 81B on the high pressure side 155 does not match the cross section of the screw groove 81C on the low pressure side 156.

FIG. 7 is a cross-sectional view showing still another example of the fixed body used for the non-contact annular seal 51 shown in FIG. FIG. 7 shows a cross-sectional view of the fixed body when cut in a plane including the central axis 151 shown in FIG. The fixed body 73 shown in FIG. 7 is different from the fixed body 71 shown in FIG. 5 in that the cross-sectional area of the screw groove 81 on the high pressure side 155 is different from that on the low pressure side 156, and the screw groove 81 at the boundary portions 161, 162. Is discontinuous, and the width of the thread groove 81 is constant.
Since the other parts of the fixed body 73 are the same as those of the fixed body 71 shown in FIG. 5 and their effects are also the same, detailed description thereof will be omitted.

As shown in the figure, the cross-sectional area of the thread groove 81A on the high pressure side 155 at the boundary portion 161 is different from the cross-sectional area of the thread groove 81B on the low pressure side 156. Further, at the boundary portion 162, the cross-sectional area of the screw groove 81B on the high pressure side 155 is different from the cross-sectional area of the screw groove 81C on the low pressure side 156. Since the screw groove 81 is formed so that the cross-sectional area of the screw groove 81 changes at the boundary portions 161, 162, the number of threads of the screw groove 81 can be changed before and after the boundary portions 161, 162. Therefore, the lead angles θ1A, θ1B, and θ1C of the screw grooves 81A, 81B, and 81C can be set more flexibly.

Further, at the boundary portions 161, 162, the cross section of the thread groove 81 on the high pressure side 155 is formed so as not to match the cross section of the screw groove 81 on the low pressure side 156. Specifically, at the boundary portion 161, the cross section of the thread groove 81A on the high pressure side 155 does not match the cross section of the thread groove 81B on the low pressure side 156. Further, at the boundary portion 162, the cross section of the thread groove 81B on the high pressure side 155 does not match the cross section of the screw groove 81C on the low pressure side 156.

Further, as shown in the drawing, in the fixed body 73, the width W1A of the screw groove 81A on the high pressure side 155 of the boundary portion 161 is the same as the width W1B of the screw groove 81B on the low pressure side 156 of the boundary portion 161. Further, the width W1B of the screw groove 81B on the high pressure side 155 of the boundary portion 162 is the same as the width W1C of the screw groove 81C on the low pressure side 156 of the boundary portion 162. As a result, the number of threads of the screw groove 81A, the number of threads of the screw groove 81B, and the number of threads of the screw groove 81C are different. Specifically, the number of threads of the screw groove 81A is larger than the number of threads of the screw groove 81B, and the number of threads of the screw groove 81B is larger than the number of threads of the screw groove 81C.

FIG. 8 is a cross-sectional view showing still another example of the fixed body used for the non-contact annular seal 51 shown in FIG. FIG. 8 shows a cross-sectional view of the fixed body when cut in a plane including the central axis 151 shown in FIG. The fixed body 74 shown in FIG. 8 is different from the fixed body 71 shown in FIG. 5 in that the boundary portions 161, 162 have a predetermined width. Since the other parts of the fixed body 74 are the same as the fixed body 71 shown in FIG. 5 and the effects thereof are also the same, detailed description thereof will be omitted.

As shown in FIG. 8, the boundary portion 161 between the screw groove 81A and the screw groove 81B has a predetermined width. Further, the boundary portion 162 between the screw groove 81B and the screw groove 81C has a predetermined width. In other words, the thread groove 81 is intermittently formed on the surface of the fixed body 74. As described above, even if the screw groove 81 is intermittently formed on the surface of the fixed body 74, the same operation as that of the fixed body 71 shown in FIG. 5 can be obtained.

FIG. 9 is a cross-sectional view showing still another example of the fixed body used for the non-contact annular seal 51 shown in FIG. FIG. 9 shows a cross-sectional view of the fixed body when cut in a plane including the central axis 151 shown in FIG. The fixed body 75 shown in FIG. 9 is different from the fixed body 71 shown in FIG. 5 in that the depth of the screw groove 81 is formed so as to be gradually shallower. Since the other parts of the fixed body 75 are the same as the fixed body 71 shown in FIG. 5 and the effects thereof are also the same, detailed description thereof will be omitted.

As shown, the screw grooves 81A, 81B, 81C have depths D1A, D1B, D1C, respectively. The depth D1A of the screw groove 81A on the high pressure side 155 from the boundary portion 161 is larger than the depth D1B of the screw groove 81B on the low pressure side 156 from the boundary portion 161. Further, the depth D1B of the screw groove 81B on the high pressure side 155 from the boundary portion 162 is larger than the depth D1C of the screw groove 81C on the low pressure side 156 from the boundary portion 162.

Generally, in a non-contact annular seal, when the lead angle of a screw groove having a predetermined number of threads is increased, the width of the screw groove must be increased, and the total cross-sectional area of the screw groove becomes large. Further, when increasing the lead angle of a screw groove having a predetermined width, the number of threads must be increased, and the total cross-sectional area of the screw groove becomes large. The larger the sum of the cross-sectional areas of the threads, the easier it is for fluid to flow between the seals.

When the lead angle θ1A of the screw groove 81A is relatively large among the screw grooves 81 having a predetermined number of threads as in the fixed body 75 shown in FIG. 9, the width of the screw groove 81A becomes relatively large. The total cross-sectional area of the thread groove 81 becomes large. Therefore, as in the fixed body 75 shown in FIG. 9, the depth of the screw groove 81 is formed so as to be gradually shallower from the high pressure side 155 to the low pressure side 156, so that the cross-sectional area of the screw groove 81 is increased. The sum can be reduced. As a result, the amount of fluid leaking between the seals can be further reduced.

When the lead angle θ1A of the screw groove 81A is relatively large among the screw grooves 81 having a predetermined width as in the fixed body 73 shown in FIG. 7, the number of threads of the screw groove 81A is relatively large. More. Even in such a case, in order to further reduce the amount of fluid leaking between the seals, it is effective to form the screw groove 81 so that the depth of the screw groove 81 is gradually reduced. ..

FIG. 10 is a cross-sectional view showing still another example of the fixed body used for the non-contact annular seal 51 shown in FIG. FIG. 10 shows a cross-sectional view of a fixed body when cut in a plane including the central axis 151 shown in FIG. The fixed body 76 shown in FIG. 10 is different from the fixed body 71 shown in FIG. 5 in that the lead angle changes at more positions (boundaries). Since the other parts of the fixed body 76 are the same as those of the fixed body 71 shown in FIG. 5 and the effects thereof are also the same, detailed description thereof will be omitted.

As shown in FIG. 10, the fixed body 76 has a boundary portion 163 on the high pressure side 155 in addition to the boundary portions 161, 162. Therefore, the fixed body 76 has a screw groove 81D on the high pressure side in addition to the screw grooves 81A, 81B, 81C. The lead angle θ1D of the thread groove 81D is larger than the lead angle θ1A of the thread groove 81A. In this way, the boundary portions 161, 162, 163 change the lead angle of the screw groove 81 at more positions than that of the fixed body 71 shown in FIG. Therefore, the lead angle of the screw groove 81 can be finely set to an appropriate angle according to the axial position. As a result, the effect of suppressing unstable vibration of the non-contact annular seal 51 and the shaft sealing performance can be further improved. The number of boundary portions 161, 162, 163 is not limited to three, and may be four or more.

FIG. 11 is a cross-sectional view showing still another example of the fixed body used for the non-contact annular seal 51 shown in FIG. FIG. 11 shows a cross-sectional view of a fixed body when cut in a plane including the central axis 151 shown in FIG. The fixed body 77 shown in FIG. 11 is different from the fixed body 71 shown in FIG. 5 in that the change position (boundary portion) of the lead angle is small. Since the other parts of the fixed body 77 are the same as the fixed body 71 shown in FIG. 5 and the effects thereof are also the same, detailed description thereof will be omitted.

As shown in FIG. 11, the fixed body 77 has only the boundary portion 161. Therefore, the fixed body 77 does not have the screw groove 81C shown in FIG. 5, but has only the screw groove 81A and the screw groove 81B. As described above, if the fixed body 71 has at least one boundary portion 161 and has at least two screw grooves 81A and screw grooves 81B, the same operation as that of the fixed body 71 shown in FIG. 5 is obtained. obtain.

FIG. 12 is a cross-sectional view showing still another example of the fixed body used for the non-contact annular seal 51 shown in FIG. FIG. 12 shows a cross-sectional view of the fixed body when cut in a plane including the central axis 151 shown in FIG. The fixed body 78 shown in FIG. 12 is different from the fixed body 71 shown in FIG. 5 in that the lead angle θ1 of the screw groove 81 is continuously smaller.

As shown in FIG. 12, a screw groove 81 is formed in the fixed body 78 so that the lead angle θ1 continuously decreases from the high pressure side 155 to the low pressure side 156. Therefore, the fixed body 78 does not have a boundary portion in which the lead angle θ1 changes, such as the boundary portions 161, 162 shown in FIG.

In the fixed body 78 shown in FIG. 12, the number of threads of the screw grooves 81 does not change between the high pressure side 155 and the low pressure side 156, and the width of the screw grooves 81 increases from the high pressure side 155 to the low pressure side 156. The thread groove 81 is formed so as to be continuously reduced.

According to the fixed body 78 shown in FIG. 12, the lead angle θ1 of the screw groove 81 changes at more positions than the fixed body 71 shown in FIG. Therefore, the lead angle θ1 of the screw groove 81 can be finely set to an appropriate angle according to the axial position. As a result, the effect of suppressing unstable vibration of the non-contact annular seal 51 and the shaft sealing performance can be further improved. It is also possible to incorporate a portion where the lead angle changes continuously like the screw groove 81 shown in FIG. 12 into the fixed body shown in FIGS. 5 to 11.

The screw groove 81 described above has been described as being provided on the fixed body, but the present invention is not limited to this, and the screw groove 81 may be provided on the outer peripheral surface of the rotating body 62 shown in FIG. However, the thread groove 81 is preferably formed at least on the surface of the fixed body. By forming the screw groove 81 at least on the surface of the fixed body, it is possible to suppress an increase in the amount of leakage while improving the action of suppressing unstable vibration.

Next, an example of a non-contact annular seal different from the non-contact annular seal 51 shown in FIG. 3 will be described. FIG. 13 is a partial cross-sectional view showing a non-contact annular seal of another embodiment applicable to the non-contact annular seals 41 and 43 shown in FIG. The non-contact annular seal 52 shown in FIG. 13 has a different configuration of the rotating body 62 than the non-contact annular seal 51 shown in FIG. Since the other parts of the non-contact annular seal 52 are the same as those of the non-contact annular seal 51 shown in FIG. 3 and their effects are also the same, detailed description thereof will be omitted. The non-contact annular seal 52 shown in FIG. 13 has any of the fixed bodies 72, 73, 74, 75, 76, 77, 78 shown in FIGS. 6 to 12 instead of the fixed body 71. May be good.

The non-contact annular seal 52 has a rotating body 62 having thread grooves 91A, 91B, 91C formed on its surface. Here, the screw grooves 91A, 91B, and 91C are collectively referred to as the screw grooves 91. The screw grooves 91A, 91B, 91C have the same shape as the screw grooves 81A, 81B, 81C formed in the fixed body 71. That is, the screw groove 91 has boundary portions 164 and 165 in which the lead angle of the screw groove 91 changes, and the lead angle of the screw groove 91 is gradually reduced from the high pressure side 155 to the low pressure side 156. It is formed.

When the thread groove 91 is provided in the rotating body 62 of the non-contact annular seal 52, the pumping effect of pushing the fluid back to the high pressure side 155 by the rotation of the rotating body 62 increases. On the other hand, due to the rotation of the rotating body 62, the fluid around the rotating body 62 may swirl and unstable vibration may be promoted. However, since the screw groove 81 is formed on the surface of the fixed body 71, even if the screw groove 91 is formed on the surface of the rotating body 62, the swirling of the fluid generated by the rotation of the rotating body 62 is caused by the rotation of the fluid on the surface of the fixed body 71. It can be suppressed by the screw groove 91 of. Further, in this case, the amount of fluid leakage can be further reduced by the pumping effect of the screw groove 91 formed on the surface of the rotating body 62. Therefore, when the fixed body 71 and the rotating body 62 are formed with screw grooves 81 and 91 having a lead angle of 155 on the high pressure side larger than the lead angle of 156 on the low pressure side, respectively, leakage occurs while suppressing unstable vibration. The amount can be further suppressed.

Further, as shown in FIG. 14, the non-contact annular seal 52 may have a parallel groove 92 on the surface of the rotating body 62. Further, the non-contact annular seal 52 may have a damper seal 93 having a honeycomb pattern on the surface of the rotating body 62 as shown in FIG. 15, and as shown in FIG. 16, the non-contact annular seal 52 may have a damper seal 93 on the surface of the rotating body 62. It may have a damper seal 94 that employs a hole pattern.

Next, the results of the evaluation test of the destabilizing force and the amount of leakage in the pump using the non-contact annular seal according to the present embodiment will be described. In this evaluation test, the destabilizing force (unstable vibration) when operating a pump (example) using the non-contact annular seal 51 shown in FIG. 3 and the amount of liquid leaking between the seals (leakage amount). Was evaluated. The conditions of the evaluation test are as follows. The minimum inner diameter of the fixed body 71 means the inner diameter of the fixed body 71 at the thread position.
Axial length of fixed body 71 / minimum inner diameter of fixed body 71: 0.817
Gap between the inner peripheral surface of the fixed body 71 and the outer peripheral surface of the rotating body 61 / Minimum inner diameter of the fixed body 71: 0.004
Number of threads: 8
Pump rotation speed: 3000 rpm
Differential pressure between the seal inlet side and the seal outlet side: 1.0 MPa

The screw groove 81A, the screw groove 81B, and the screw groove 81C have the same axial length. That is, the screw groove 81A is in the region of 1/3 of the high pressure side 155 of the inner peripheral surface of the fixed body 71, the screw groove 81C is in the region of 1/3 of the low pressure side 156, and the screw is in the intermediate region of the remaining 1/3. A groove 81B is formed. The relationship between the lead angle θ1A of the screw groove 81A of the fixed body 71, the lead angle θ1B of the screw groove 81B, and the lead angle θ1C of the screw groove 81C is as follows.
Lead angle θ1B = 1/2 x lead angle θ1A = 2 x lead angle θ1C

As a comparative example, the destabilizing force and the amount of leakage when the pump using the non-contact annular seal in which the lead angle of the thread groove 81 of the non-contact annular seal 51 shown in FIG. 3 was formed to be constant was evaluated were evaluated. Comparative Example 1 is a pump using a non-contact annular seal in which the lead angle of the thread groove 81 is a lead angle θ1B. Comparative Example 2 is a pump using a non-contact annular seal in which the lead angle of the thread groove 81 is a lead angle θ1A. Comparative Example 3 is a pump using a non-contact annular seal in which the lead angle of the thread groove 81 is a lead angle θ1C.

FIG. 17 is a graph showing the results of this evaluation test. In order to compare the results of this evaluation test, the destabilizing force and the leak amount of Comparative Example 1 are set to 100%, and the destabilizing force and the leak amount of Comparative Example 2, Comparative Example 3 and Example are shown.

As shown in FIG. 17, in Comparative Example 2 having a relatively large lead angle θ1A, the destabilizing force is suppressed to 31%, and unstable vibration is reduced as compared with Comparative Example 1, but leakage occurs. The amount has increased to 128%. Further, in Comparative Example 3 having a relatively small lead angle θ1C, the leakage amount was reduced to 92%, and the leakage amount was suppressed as compared with Comparative Example 1, but the destabilizing force was reduced to 200%. It can be seen that it is increasing.

On the other hand, in the examples, the destabilizing force is 42% and the leakage amount is 100%. That is, in the embodiment, it can be seen that while the unstable vibration is effectively suppressed, the increase in the amount of fluid leaking through the inside of the seal can also be suppressed.

Although the embodiments of the present invention have been described above, the above-described embodiments of the invention are for facilitating the understanding of the present invention and do not limit the present invention. The present invention can be modified and improved without departing from the spirit thereof, and it goes without saying that the present invention includes an equivalent thereof. In addition, any combination or omission of the claims and the components described in the specification is possible within the range in which at least a part of the above-mentioned problems can be solved or at least a part of the effect is exhibited. is there.

1 High-pressure pump 155 High-pressure side 156 Low-pressure side 161,162,163,164 Boundary 61,62 Rotating body 71,72,73,74,75,76,77,78 Fixed body 51,52 Non-contact annular seal 81,81A , 81B, 81C, 81D, 91, 91A Thread groove θ1, θ1A, θ1B, θ1C, θ1D Lead angle W1A, W1B, W1C Width D1A, D1B, D1C Depth 11 Main shaft 21a, 21b, 21c Impeller 31, 31, 31b Casing 45a, 45b bearing

Claims (6)

It has a rotating body provided in the rotating portion of the rotating machine and a fixed body provided in the fixed portion of the rotating machine, and is configured to seal the fluid flowing in the gap between the rotating body and the fixed body. It is a non-contact annular seal
It has screw grooves provided on at least one of the surface of the rotating body and the surface of the fixed body forming the gap.
The thread groove defines a lead angle of the thread groove with respect to a plane orthogonal to the axial direction of the rotating body.
A non-contact annular seal in which the lead angle of the thread groove on the seal inlet side is larger than the lead angle of the thread groove on the seal outlet side. In the non-contact annular seal according to claim 1,
The thread groove is a non-contact annular seal formed so that the lead angle of the thread groove gradually decreases from the seal inlet side to the seal outlet side. In the non-contact annular seal according to claim 1,
The thread groove is a non-contact annular seal formed so that the lead angle of the thread groove is continuously reduced from the seal inlet side to the seal outlet side. In the non-contact annular seal according to any one of claims 1 to 3.
A non-contact annular seal in which the depth of the thread groove on the seal inlet side is larger than the depth of the thread groove on the seal outlet side. In the non-contact annular seal according to any one of claims 1 to 4.
The thread groove is a non-contact annular seal formed at least on the surface of the fixed body. With an electric motor
A spindle that is connected to the electric motor and is rotatable
An impeller that is fitted to the spindle and is rotatable together with the spindle,
The casing that houses the impeller and
A bearing attached to the casing and rotatably supporting the spindle is provided.
The spindle has a rotating part and
The casing has a fixed portion and
A rotating machine having the rotating portion and the fixing portion having the non-contact annular seal according to any one of claims 1 to 5.

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