Combined angular contact ball bearing for compressor

Abstract

To provide a combined angular contact ball bearing for a compressor capable of preventing slippage between a ball and a raceway surface of an inner ring or outer ring even when subjected to abrupt load fluctuation and rotational fluctuation.SOLUTION: A combined angular contact ball bearing (1) for a compressor supports a rotational shaft of the compressor, and comprises: one or more first bearings (2) that receive a load in a first direction (D1) along an axial core direction while the compressor is operating; and one or more second bearings (3) that receive a load in a second direction (D2) opposite to the first direction (D1) when the compressor is stopped. A ball diameter (BD2) of the second bearing (3) is smaller than a ball diameter (BD1) of the first bearing (1).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a duplex angular contact ball bearing for a compressor, for example, used in a screw type compressor. [Background technology]

[0002] In applications where a bearing is subjected to both radial and axial loads in both directions, multiple rows of angular contact ball bearings may be used in combination. An example of such an application is supporting the screw shaft (rotor shaft) of a screw compressor. For example, Patent Document 1 discloses a bearing in which three rows of angular contact ball bearings are arranged as a bearing on the fixed side of the rotor shaft of a compressor. In the case of a three-row combination, an arrangement is used in which two rows of load side bearings are used to receive the axial load while the compressor is in operation, and one row of anti-load side bearings are used to receive the load in the opposite direction due to the reverse rotation of the rotor shaft immediately after the compressor is stopped. Generally, a multiple-row combination bearing is composed of bearings of the same size and type. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-139609 A Summary of the Invention [Problem to be solved by the invention]

[0004] Taking the application of supporting the screw shaft of a screw compressor as an example, in a conventional bearing structure, the load side bearing supports the axial load while the screw compressor is in operation, and the non-load side bearing rotates under a light load or no load. When the screw shaft is stopped, due to the characteristics of the compressor, the screw shaft rotates in the reverse direction due to the pressure difference with the high-pressure compression chamber. At this time, these bearings are subjected to an axial load in the opposite direction to that during operation. In other words, immediately after the device is stopped, an axial load acts on the non-load side bearing, and it goes from a light load (almost no load) state during operation to a state in which it is subjected to a load fluctuation (increase) and rotation fluctuation in the opposite direction.

[0005] In such a state where the bearing is subjected to sudden load and rotational fluctuations, slippage is likely to occur between the balls and the raceway surface of the inner or outer ring. As a result, the oil film between the balls and the raceway surface breaks, and even if an oil with relatively excellent lubricating properties is used for lubrication, there is a risk of surface damage such as smearing on the raceway surface and ball rolling surface of the bearing. In particular, in applications where starting and stopping are repeated frequently, damage may occur. This problem has a large impact on the non-load side bearing, which is exposed to a sudden increase in load immediately after driving is stopped.

[0006] Therefore, in order to solve the above-mentioned problems, the object of the present invention is to provide a duplex angular contact ball bearing for compressors (hereinafter sometimes simply referred to as a "duplex angular contact ball bearing") in which slippage is unlikely to occur between the balls and the raceway surfaces of the inner or outer ring even when subjected to sudden load fluctuations and rotation fluctuations. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a combined rolling bearing for a compressor, comprising: A combined angular contact ball bearing for supporting a rotating shaft of a compressor, The compressor includes one or more first bearings that receive a load in a first direction along the axial direction during operation of the compressor, and one or more second bearings that receive a load in a second direction opposite to the first direction when the compressor is stopped, The ball diameter of the second bearing is smaller than the ball diameter of the first bearing.

[0008] According to this configuration, by making the ball diameter of the second bearing smaller than that of the first bearing, the inertia (mass) of the balls of the second bearing is reduced and the contact surface pressure between the balls and the raceway surface is increased. This makes it easier for the balls of the second bearing to roll, suppressing ball slippage that may occur when a load such as a compressor is stopped, and thus suppressing surface damage such as smearing of the second bearing caused by this.

[0009] In one embodiment of the present invention, the ball diameter of the second bearing may be at least 25% smaller than the ball diameter of the first bearing. When the ball diameter of the steel ball used as the ball of the second bearing is reduced by, for example, 25%, the mass of the steel ball can be made equivalent to the mass of a ceramic ball having the original ball diameter, calculated based on the specific gravity of the bearing steel and ceramic. This allows the moment of inertia of the steel ball to be made equivalent to the moment of inertia of the ceramic ball. In this way, even in applications where the use of steel balls is preferable for strength reasons, it is possible to reduce the weight of the ball and suppress the slippage of the ball.

[0010] In one embodiment of the present invention, the second bearing may have a marking on the outer diameter surface or end surface of the outer ring to indicate that it is the second bearing. By providing a marking on the outer surface of the second bearing, the first bearing and the second bearing can be easily distinguished, and these bearings can be smoothly installed without being mixed up.

[0011] In one embodiment of the present invention, the duplex angular contact ball bearing may have a marking that allows the position of the second bearing to be identified. With this configuration, the first bearing and the second bearing can be smoothly installed in the device without making mistakes in their positions or orientations.

[0012] In one embodiment of the present invention, the duplex angular ball bearing may be used in a compressor that compresses hydrogen gas. The compressor may be a screw compressor. By employing the duplex angular ball bearing according to the present invention, even in a hydrogen gas compressor with a large driving force, where a sudden load change and rotation change occur due to reverse rotation of the rotor shaft immediately after the drive is stopped, slippage is unlikely to occur between the balls and the raceway surface of the inner or outer ring, and deterioration of the bearing can be suppressed.

[0013] In one embodiment of the present invention, the first bearing and the second bearing may have the same inner diameter and outer diameter. By making the inner diameter and outer diameter of the combined bearing the same in this way, it is possible to easily install the combined bearing by replacing the bearing of an existing compressor. Effect of the Invention

[0014] As described above, according to the combined angular contact ball bearing for a compressor of the present invention, it is possible to suppress slippage between the balls and the raceway surface of the inner ring or outer ring, even when subjected to sudden load fluctuations and rotation fluctuations. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic vertical cross-sectional view of a duplex angular contact ball bearing according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an enlarged vertical sectional view showing the dimensional relationship between balls in the duplex angular contact ball bearing of FIG. 1. [Diagram 3] 2 is a plan view showing the outer diameter surface of the duplex angular contact ball bearing of FIG. 1. [Figure 4] 1 is a schematic vertical sectional view showing a first application example in which a duplex angular contact ball bearing according to the present invention is applied to a screw compressor. [Diagram 5] FIG. 1 is a schematic vertical sectional view showing a second application example in which a duplex angular contact ball bearing according to the present invention is applied to a screw compressor. [Figure 6]1 is a schematic diagram showing a hydrogen station including a compressor using a duplex angular contact ball bearing according to the present invention.

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to this embodiment.

[0017] FIG. 1 shows a duplex angular ball bearing 10 for a compressor according to one embodiment of the present invention. The duplex angular ball bearing 10 of this embodiment is used, for example, to support a rotor shaft of a compressor that compresses gas. The axis A of the duplex angular ball bearing 10 coincides with the axis of the rotor shaft of the compressor. The duplex angular ball bearing 10 includes two first bearings 1 and one second bearing 2. However, the number of rows of the first and second bearings is not limited to this example. The first bearing 1 is a load-side bearing that receives a load in a first direction D1 along the axis of the rotor shaft during operation of the compressor. The second bearing 2 is a counter-load-side bearing that receives a load in a second direction D2 opposite to the first direction D1 due to the reverse rotation of the rotor shaft that occurs immediately after the device is stopped. The two first bearings 1, 1 are arranged in parallel combination, and the central first bearing 1 and the second bearing 2 adjacent to it on the left are arranged in face-to-face combination. Each first bearing 1 has a contact line S1 in a direction in which it receives a load in a first direction D1, and each second bearing 2 has a contact line S2 in a direction in which it receives a load in a second direction D2. However, the first bearing 1 and the second bearing 2 may be arranged in a back-to-back configuration.

[0018] Each of the first bearing 1 and the second bearing 2 includes an inner ring 4, an outer ring 5, balls 6, and a cage 7. In this embodiment, the balls 6 are steel balls. In this specification, when referring to the components of the first bearing 1, they may be referred to as the inner ring 4A, the outer ring 5A, the balls 6A, and the cage 7A, and when referring to the components of the second bearing 2, they may be referred to as the inner ring 4B, the outer ring 5B, the balls 6B, and the cage 7B.

[0019] 2, the ball diameter BD2 of the second bearing 2 is smaller than the ball diameter BD1 of the first bearing 1. More specifically, the ball diameter BD2 of the second bearing 2 is at least 25% smaller than the ball diameter BD1 of the first bearing 1. In this embodiment, the ball diameter BD2 of the second bearing 2 is approximately 40% smaller than the ball diameter BD1 of the first bearing 1.

[0020] As shown in FIG. 3, the duplex angular ball bearing 10 has a marking 8 that allows the position of the second bearing 2 to be identified. In this embodiment, the marking 8 is a V-shaped thin linear groove provided from the outer diameter surface 5Aa of the first bearing 1 on the load side (right side of FIG. 3) through the outer diameter surface 5Aa of the adjacent first bearing 1 to the outer diameter surface 5Ba of the second bearing 2. Instead of or in addition to this configuration, a marking (not shown) indicating that it is the second bearing 2 may be provided on the outer diameter surface 5Ba of the outer ring 5B of the second bearing 2 or the end surface 5Bb of the outer ring 5B. This marking may be, for example, a recess or groove provided on the outer diameter surface 5Ba or the end surface 5Bb of the outer ring 5B. However, the shape of these markings is not limited to these examples and may be any shape.

[0021] <Action and effect> In order to suppress the slippage of the balls in the bearing, it is possible to reduce the inertia (mass) of the balls and to increase the contact surface pressure between the balls and the raceway surfaces of the inner and outer rings. According to the above-described duplex angular ball bearing 10, by making the ball diameter BD2 of the second bearing 2 in Fig. 2 smaller than the ball diameter BD1 of the first bearing 1, the inertia (mass) of the ball 6B of the second bearing 2 is reduced and the contact surface pressure between the ball 6B and the raceway surface is increased.

[0022] In order to reduce the inertia (mass) of the balls, it is considered that surface damage is less likely to occur by using, for example, ceramic balls instead of steel balls. However, depending on the application of the bearing, it may be desirable to use steel balls as rolling elements because the bearings are subjected to a large load. In particular, for bearings used in gas compressors, it is desirable to use steel balls as rolling elements. Therefore, in the present invention, the ball diameter BD2 of the steel balls used as the balls 6B of the second bearing 2 is made at least 25% smaller than the ball diameter BD1 of the first bearing 1. As a result, when calculated based on the specific gravity of the bearing steel and ceramic, the mass of the steel balls can be made equal to or smaller than the mass of the ceramic balls having the original ball diameter BD1. In addition, the moment of inertia of the steel balls can also be made equal to or smaller than the moment of inertia of the ceramic balls.

[0023] In this embodiment, as described above, the ball diameter BD2 of the second bearing 2 is approximately 40% smaller than the ball diameter BD1 of the first bearing 1. For example, when the ball diameter BD1 of the first bearing 1 is 13 / 16" (20.638 mm), by reducing the ball diameter BD2 of the second bearing 2 by 40%, the contact pressure of the ball 6B of the second bearing 2 can be increased while the mass can be reduced to approximately 1 / 5 and the moment of inertia to approximately 1 / 16, compared to a ball (steel ball) with a ball diameter BD1. In this way, it is possible to reduce the weight of the ball even in applications where it is preferable to use a steel ball for strength reasons. This makes it easier for the ball 6B of the second bearing 2 to roll, thereby suppressing ball slippage that may occur when a load such as a compressor is stopped, and suppressing surface damage such as smearing of the second bearing 2 caused by this.

[0024] Furthermore, with this configuration, the axial load in the first direction D1 is borne by the two first bearings 1, so that during operation of a device in which the duplex angular contact ball bearing 10 is used, the load-bearing performance of the duplex angular contact ball bearing 10 is improved and the duplex angular contact ball bearing 10 can withstand a larger axial load applied in the first direction D1. However, one or three or more first bearings 1 may be provided.

[0025] 3 on the outer diameter surfaces 5Aa, 5Ba of the first bearing 1 and the second bearing 2, which allows the position of the second bearing 2 to be identified, it is possible to smoothly install the first bearing 1 and the second bearing 2 in the device without making mistakes in their positions or orientations. Furthermore, if markings are provided on the outer surface of the second bearing 2, it is possible to easily distinguish between the first bearing 1 and the second bearing 2, which have the same inner diameter dimension I, outer diameter dimension O, width dimension W, and ball pitch diameter PCD, and it is possible to smoothly install these bearings without making mistakes.

[0026] <First application example to a screw compressor> The duplex angular contact ball bearing according to the present invention is mounted, for example, as follows: Fig. 4 shows an example in which the duplex angular contact ball bearing 10 according to the present invention is applied to a screw compressor 20. However, the compressor 20 is not limited to a screw compressor.

[0027] The compressor 20 has a compression mechanism 21, two screw shafts 22, 22 connected to the compression mechanism 21, a duplex angular ball bearing 10, 10 provided on the screw shaft 22 as a fixed side bearing, and a housing 23 that covers the duplex angular ball bearing 10. In this application example, each duplex angular ball bearing 10 is composed of one first bearing 1 and one second bearing 2. However, the number of rows of the first and second bearings can be changed according to the output of the compressor. The input side (right side) of the screw shaft 22 is connected to a motor M as a driving machine, and an accumulator 24 is arranged on the output side (left side). The male rotor 25 and female rotor 26 of the compression mechanism 21 are driven and rotated by the motor M, thereby compressing gas in the compression mechanism 21. The input side (right side) of the screw shaft 22 is supported by a slide bearing, and the output side (left side) is supported by the housing 23 rotatably via the duplex angular ball bearing 10.

[0028] When the motor M of the compressor 20 is started, the screw shaft 22 is driven via the motor shaft of the motor M, and the male rotor 25 and the female rotor 26 of the compression mechanism 21 rotate around the central axis C1 and C2 of the screw shaft 22 in the directions indicated by the arrows R1 and R2 in FIG. 4. As the rotors 25 and 26 rotate, the gas sucked into the compression mechanism 21 is compressed by the meshing of the rotors 25 and 26 and pushed out in the second direction D2, and sent to the accumulator 24. At this time, the first bearing 1 of the duplex angular ball bearing 10 receives an axial load F1 in the first direction D1 due to the compression. On the other hand, the second bearing 2 rotates under a light load or no load. When the drive of the screw shaft 22 is stopped, the inside of the compression mechanism 21 remains at high pressure immediately after the drive is stopped, so the rotors 25 and 26 rotate in the opposite direction due to the pressure difference between the inside and outside of the compression mechanism 21, and the screw shaft 22 rotates in the opposite direction (the direction indicated by the arrows R2 and R1). The axial load F2 in the second direction D2 generated at this time is received by the second bearing 2.

[0029] When a sudden load change and rotational fluctuation occur due to the reverse rotation of the screw shaft 22 immediately after the drive is stopped, the load on the second bearing 2, which is the non-load side bearing, increases suddenly from a light load or no load state. If the lubrication state of the non-load side bearing is not good, slippage may occur between the balls of the non-load side bearing and the raceway surfaces of the inner and outer rings, or the lubricant film may be broken due to the slippage, which may cause surface damage such as smearing on the raceway surfaces of the inner and outer rings. By adopting the duplex angular ball bearing 10 according to the present invention, even if the above-mentioned load change and rotational fluctuation occur in the compressor 20, slippage is unlikely to occur between the balls 6B of the second bearing 2 and the raceway surfaces of the inner ring 4B or the outer ring 5B, so that it is possible to suppress deterioration of the bearing due to surface damage to the balls, raceway surfaces, etc.

[0030] <Second application example to screw compressor> FIG. 5 shows a second application example in which the duplex angular ball bearing 10 according to the present invention is applied to a screw compressor 30. In this example, the compressor 30 is a compressor that compresses hydrogen gas supplied from a storage tank at a hydrogen station, for example, to a high pressure for supplying the gas to an on-board tank. Typically, the pressure of the hydrogen gas supplied from the storage tank is 1 MPa or less, and the pressure of the hydrogen gas supplied to an automobile is about 80 MPa. The compressor 30 includes a compression mechanism 31 that rotates a rotor to compress the hydrogen gas, an input shaft 32 connected to the compression mechanism 31, a duplex angular ball bearing 10 provided on the input shaft 32 and rotatably supporting the input shaft 32, a housing 33 that covers the duplex angular ball bearing 10, and a motor M that drives the input shaft 32. The input shaft 32 is rotatably supported by the housing 33 via the duplex angular ball bearing 10. The duplex angular ball bearing 10 is composed of two first bearings 1 and one second bearing 2. The number of rows of the first and second bearings can be changed according to the output of the compressor. The inner ring 4 of the duplex angular contact ball bearing 10 is positioned on the input shaft 32 by a spacer 34, and the outer ring 5 is fixed to the housing 33.

[0031] When the motor M of the compressor 30 is started, the input shaft 32 is driven via the motor shaft 35 of the motor M, and the rotor (corresponding to 25 and 26 in FIG. 4) of the compression mechanism 31 rotates about its axis. As the rotor rotates, the hydrogen gas sucked into the compression mechanism 31 is compressed by the meshing of the rotors and pushed out in the second direction D2. At this time, the first bearing 1 of the duplex angular ball bearing 10 receives an axial load in the first direction D1. On the other hand, the second bearing 2 rotates under a light load or no load. When the input shaft 32 is stopped, the inside of the compression mechanism 31 remains at high pressure immediately after the drive is stopped, so the rotor rotates in the reverse direction due to the pressure difference between the inside and outside of the compression mechanism 31, and this causes the input shaft 32 to rotate in the reverse direction. The axial load in the second direction D2 generated at this time is received by the second bearing 2.

[0032] In the second application example as well, even if the above-mentioned load fluctuations and rotation fluctuations occur in the compressor 30, slippage is unlikely to occur between the balls 6B of the second bearing 2 and the raceway surfaces of the inner ring 4B or outer ring 5B, so it is possible to suppress deterioration of the bearing due to surface damage to the balls, raceway surfaces, etc.

[0033] <Example of hydrogen station configuration> An example of a hydrogen station including a compressor using the duplex angular contact ball bearing according to the present invention will be described below. An outline of this hydrogen station is shown in FIG. 6. The hydrogen station 41 is a facility that supplies hydrogen gas, which is a fuel, to a fuel cell vehicle equipped with a fuel tank. The hydrogen station 41 includes a storage tank 42 for storing hydrogen gas, a hydrogen gas supply unit 43 for pressurizing the hydrogen gas from the storage tank 42 and supplying it to a pressure accumulator 44, an accumulator 44 for storing the high-pressure hydrogen gas supplied from the hydrogen gas supply unit 43, and a dispenser 45 for refilling the fuel cell vehicle with hydrogen gas from the pressure accumulator 44. The hydrogen station 41 further includes a gas inlet line 46 for transporting high-pressure hydrogen gas from the compressor 40 of the hydrogen gas supply unit 43 to the pressure accumulator 44, and a gas outlet line 47 for transporting hydrogen gas from the pressure accumulator 44 to the dispenser 45.

[0034] The hydrogen gas supply unit 43 has a receiving section 48 that receives hydrogen gas from the storage tank 42, and a compressor 40 that compresses the hydrogen gas to a predetermined high pressure. The compressor 40 is, for example, a screw type compressor. The compressor 40 internally pressurizes the hydrogen gas supplied from an inlet, and sends out the pressurized hydrogen gas from a discharge port of the compressor 40. The function and operation of the compressor 40 are similar to those of the compressors 20 and 30 of the above application example, and therefore a description thereof will be omitted. The compressor 40 is equipped with a duplex angular contact ball bearing according to the present invention, and provides the same effects as those obtained in the above application example.

[0035] As described above, the preferred embodiment of the present invention has been described with reference to the drawings, but various additions, modifications, and deletions can be made without departing from the spirit of the present invention. Therefore, such additions, modifications, and deletions are also included in the scope of the present invention. [Explanation of symbols]

[0036] 1...First bearing, 2...Second bearing, 4...Inner ring, 5...Outer ring, 6...Ball, 7...Cage, 8...Marking, 10...Double angular contact ball bearing, 20,30...Compressor, BD1...Ball diameter of first bearing, BD2...Ball diameter of second bearing, D1...First direction, D2...Second direction, I...Inner diameter, O...Outer diameter, PCD...Ball pitch diameter, W...Width

Claims

1. A combined angular contact ball bearing for supporting a rotating shaft of a compressor, one or more first bearings that receive a load in a first direction along an axial direction during operation of the compressor, and one or more second bearings that receive a load in a second direction opposite to the first direction when the compressor is stopped, a ball diameter of the second bearing being smaller than a ball diameter of the first bearing;

2. 2. The duplex angular contact ball bearing for a compressor according to claim 1, wherein the ball diameter of the second bearing is at least 25% smaller than the ball diameter of the first bearing.

3. 3. The duplex angular contact ball bearing for a compressor according to claim 1, wherein the second bearing has a marking on an outer diameter surface of the outer ring or an end surface of the outer ring indicating that it is the second bearing.

4. 3. The duplex angular contact ball bearing for a compressor according to claim 1, further comprising a marking that enables the position of the second bearing to be identified.

5. 3. The duplex angular contact ball bearing according to claim 1, wherein said duplex angular contact ball bearing is used in a compressor that compresses hydrogen gas.

6. 3. The duplex angular contact ball bearing for a compressor according to claim 1, wherein the compressor is a screw type compressor.

7. 3. The duplex angular ball bearing for a compressor according to claim 1, wherein the first bearing and the second bearing have the same inner diameter dimension and the same outer diameter dimension.

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