Rotating shaft structure, centrifugal air compressor and vehicle

Abstract

The present invention relates to a rotating shaft structure, a centrifugal air compressor and a vehicle, wherein the rotating shaft structure comprises: a rotor, comprising a first shaft section and a second shaft section arranged in sequence in the axial direction; an impeller assembly, comprising at least one impeller, the impeller being sleeved on the first shaft section and / or the second shaft section; a thrust plate sleeved on the first shaft section of the rotor; a primary radial bearing sleeved on the first shaft section of the rotor; and a secondary radial bearing sleeved on the second shaft section of the rotor; wherein the length of the primary radial bearing is greater than the length of the secondary radial bearing, so that the force per unit area of ​​the primary radial bearing is equal to the force per unit area of ​​the secondary radial bearing. The above-mentioned rotating shaft structure, by increasing the length of the primary radial bearing, further reduces the force per unit area of ​​the radial support corrugated foil of the primary radial bearing, thereby preventing the rotor from tilting toward the side where the first shaft section is located, and ensuring the smooth operation of the centrifugal air compressor.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and in particular to a rotating shaft structure, a centrifugal air compressor and a vehicle. Background Art

[0002] Hydrogen fuel cells refer to devices that generate electricity through the chemical reaction of hydrogen with oxygen. Electric vehicles using hydrogen fuel cells are one of the current breakthroughs in new energy vehicles, with advantages such as high power performance, fast hydrogen refueling, and long driving range. As a component used to provide a high-pressure air source for the fuel cell system, air compressors play an important role in hydrogen fuel cell vehicles.

[0003] At present, common air compressors include centrifugal air compressors, screw air compressors and scroll air compressors. Compared with screw compressors and scroll compressors, centrifugal air compressors use impellers to drive gas to rotate at high speed, so that the gas generates centrifugal force. Due to the expansion pressure flow of the gas in the impeller, the flow rate and pressure of the gas after passing through the impeller are increased, and compressed air is continuously produced. Therefore, a higher pressure ratio gas source can be provided, which can significantly improve the power density and overall performance of the fuel cell stack. As one of the core components of centrifugal air compressors, hydrodynamic gas bearings have a series of advantages such as low friction loss, high speed, good high temperature stability, and no need for lubricating oil, and have a very broad application prospect.

[0004] The centrifugal air compressor includes a motor stator and a shaft structure. The shaft structure can rotate at high speed relative to the motor stator under the action of electromagnetic field force. The electronic rotor includes a rotor and two foil dynamic pressure gas radial bearings respectively mounted at both ends of the rotor. The foil dynamic pressure gas radial bearings achieve support based on the dynamic pressure effect. Figure 1 As shown, the foil dynamic pressure gas radial bearing 100 includes a bearing housing 120 and a bump foil 140 and a top foil 160 housed in the bearing housing 120, and the bump foil 140 is located between the bearing housing 120 and the top foil 160. Under the action of gravity, the rotor is eccentric relative to the foil dynamic pressure gas radial bearing 100, and then forms a wedge-shaped gap with the inner surface of the foil dynamic pressure gas radial bearing 100. When the rotor is rotating at a high speed, it continuously brings gas with a certain viscosity into the wedge-shaped gap, and the continuous entry of gas causes the gas film to generate a certain pressure. When the gas film force is sufficient to balance the load of the rotor, the rotor is completely separated from the foil dynamic pressure gas radial bearing 100. The process of generating the above-mentioned gas film is called the dynamic pressure effect.

[0005] From the above principles and bearing structure, it can be seen that when the foil dynamic pressure gas radial bearing is working, a high-pressure gas film is formed through the dynamic pressure effect, and the corrugated foil of the foil dynamic pressure gas radial bearing provides pressure for the gas film to support the rotor through deformation. The greater the load of the foil dynamic pressure gas radial bearing, the greater the deformation of the inner corrugated foil.

[0006] In the prior art, the structural strength of the foil is usually designed to meet the deformation range according to the load range of the foil dynamic pressure gas radial bearing when the air compressor is working, so that the rotor-bearing system works in a reasonable gap. When the air compressor works under high load, the bearing foil can achieve a certain degree of deformation, thereby providing greater bearing capacity to the rotor.

[0007] However, since the foil is an elastic structure, when the air compressor is subjected to abnormal impact (such as shutdown due to failure, surge, sudden acceleration and deceleration of the car, etc.), the foil dynamic pressure gas radial bearing at one end of the rotor will be subjected to additional impact load, resulting in excessive deformation of the foil and a sudden increase in the bearing capacity of the top foil, which can easily damage the air film and cause direct friction between the motor shaft and the foil dynamic pressure gas radial bearing, or friction between the air compressor rotor and the stationary parts. Moreover, when the air compressor is at high speed, when the single load of the radial bearing foil of the foil dynamic pressure gas radial bearing at both ends of the rotor is unequal, it is easy to cause the rotor to tilt to one side, resulting in instability of the air film formed between the foil dynamic pressure gas radial bearing and the rotor, and collision between the rotor and the foil dynamic pressure gas radial bearing.

[0008] Therefore, in order to improve the operating reliability of the centrifugal air compressor, it is necessary to study a method for adjusting the center of gravity of the centrifugal air compressor rotor to ensure the smooth operation of the air compressor. Summary of the invention

[0009] In order to solve the problem that the rotor of an air compressor tilts to one side and collides with a bearing, the present invention provides a rotating shaft structure, a centrifugal air compressor and a vehicle. The rotating shaft structure, the centrifugal air compressor and the vehicle can achieve the technical effect of preventing the rotor from tilting to one side and colliding with the bearing.

[0010] According to one aspect of the present application, a rotating shaft structure is provided, comprising:

[0011] A rotor including a first shaft segment and a second shaft segment;

[0012] An impeller assembly, comprising at least one impeller, wherein the impeller is sleeved on the first shaft segment and / or the second shaft segment;

[0013] A thrust plate, sleeved on the first shaft section of the rotor;

[0014] a primary radial bearing, sleeved on the first shaft section of the rotor; and

[0015] A secondary radial bearing, sleeved on the second shaft section of the rotor;

[0016] Among them, the length of the first-level radial bearing is greater than the length of the second-level radial bearing, so that the force per unit area of ​​the first-level radial bearing is equal to the force per unit area of ​​the second-level radial bearing.

[0017] In one embodiment, the first-stage radial bearing and the second-stage radial bearing are both foil dynamic pressure gas radial bearings.

[0018] In one embodiment, the distance between the center of gravity of the side where the primary radial bearing of the shaft structure is located and the center of gravity of the shaft structure is defined as l1, the distance between the center of gravity of the side where the secondary radial bearing of the shaft structure is located and the center of gravity of the shaft structure is defined as l2, the length of the primary radial bearing is defined as L1, and the length of the secondary radial bearing is defined as L2;

[0019] The relationship among the l1, the l2, the L1 and the L2 satisfies: l1xL1=l2xL2.

[0020] In one embodiment, the relationship between L1 and L2 satisfies: L1=nL2, where 1.2 <n<1.7。

[0021] In one embodiment, the diameter of the primary radial bearing is equal to the diameter of the secondary radial bearing.

[0022] In one embodiment, the weight of the side of the rotating shaft structure where the primary radial bearing is located is defined as F1, the weight of the side of the rotating shaft structure where the secondary radial bearing is located is defined as F2, the distance between the center of gravity of the side of the rotating shaft structure where the primary radial bearing is located and the center of gravity of the rotating shaft structure is defined as l1, and the distance between the center of gravity of the side of the rotating shaft structure where the secondary radial bearing is located and the center of gravity of the rotating shaft structure is defined as l2;

[0023] A weight-reducing portion is provided in the first shaft section of the rotor so that the relationship among F1, F2, l1 and l2 satisfies: F1xl1=F2xl2.

[0024] In one embodiment, the first shaft segment of the rotor is provided with a first center hole, the second shaft segment of the rotor is provided with a second center hole, and the weight reduction portion is constructed as a groove provided in the hole wall of the first center hole.

[0025] In one embodiment, the weight-reducing portion circumferentially surrounds the first center hole and extends from one axial end of the first center hole to the other axial end of the first center hole.

[0026] According to another aspect of the present application, a centrifugal air compressor is provided, comprising the above-mentioned rotating shaft structure.

[0027] According to another aspect of the present application, a vehicle is provided, comprising a fuel cell system and the above-mentioned centrifugal air compressor, wherein the centrifugal air compressor is used to provide a high-pressure air source for the fuel cell system.

[0028] The above-mentioned shaft structure increases the length of the first-stage radial bearing, thereby reducing the force per unit area of ​​the radial support corrugated foil of the first-stage radial bearing, thereby avoiding the rotor from tilting toward the side where the first shaft section is located, preventing the instability of the air film formed between the first-stage radial bearing and the rotor, eliminating the collision between the rotor and the radial bearing, and ultimately ensuring the smooth operation of the centrifugal air compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of the foil dynamic pressure gas radial bearing;

[0030] Figure 2 It is a structural schematic diagram of a centrifugal air compressor in one embodiment of the present invention;

[0031] Figure 3 It is a structural schematic diagram of a rotating shaft structure of a centrifugal air compressor in one embodiment of the present invention;

[0032] Figure 4 is a structural schematic diagram of a rotating shaft structure of a centrifugal air compressor in another embodiment of the present invention;

[0033] Description of Figure Numbers:

[0034] 200, centrifugal air compressor; 210, casing; 212, motor barrel; 214, first-stage volute; 216, second-stage volute; 220, shaft structure; 221, rotor; 2212, permanent magnet; 2214, first shaft section; 2214a, first center hole; 2216, second shaft section; 2216a, second center hole; 2218, mounting sleeve; 222, first-stage impeller; 223, second-stage impeller; 224, thrust plate; 225, first-stage locking nut; 226, second-stage locking nut; 227, first-stage radial bearing; 228, second-stage radial bearing; 230, motor stator; 240, first-stage diffuser; 250, second-stage diffuser; 260, bearing support; 270, comb teeth. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0036] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0038] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0040] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0041] See also Figures 2 to 4 , Figure 2 FIG. 1 shows a schematic structural diagram of a centrifugal air compressor in an embodiment of the present invention. Figure 3 A schematic structural diagram of a rotating shaft structure of a centrifugal air compressor in one embodiment of the present invention is shown; Figure 4 A schematic structural diagram of a rotating shaft structure of a centrifugal air compressor in another embodiment of the present invention is shown.

[0042] An embodiment of the present invention provides a centrifugal air compressor 200 , including a housing 210 , a rotating shaft structure 220 , a motor stator 230 , a first-stage diffuser 240 , a second-stage diffuser 250 , a bearing support 260 , and comb teeth 270 .

[0043] The housing 210 includes a motor barrel 212, a primary volute 214, and a secondary volute 216. The motor barrel 212 is a cylindrical structure with both ends open to form a motor accommodating chamber. The primary volute 214 and the secondary volute 216 are respectively arranged at opposite ends of the motor barrel 212 in the axial direction. The motor stator 230 is fixedly arranged in the motor accommodating chamber and forms a rotor mounting hole.

[0044] The rotating shaft structure 220 is rotatably disposed in the motor accommodating cavity and penetrates into the rotor mounting hole, and includes a rotor 221, an impeller assembly, a thrust plate 224, a primary locking nut 225, a secondary locking nut 226, a primary radial bearing 227 and a secondary radial bearing 228.

[0045] like Figure 2 and Figure 3As shown, the rotor 221 includes a permanent magnet 2212, a first shaft section 2214, a second shaft section 2216 and a mounting sleeve 2218. The permanent magnet 2212 is a solid columnar structure formed by magnetic steel. The first shaft section 2214 and the second shaft section 2216 are respectively arranged at opposite ends of the permanent magnet 2212 in the axial direction. The mounting sleeve 2218 is sleeved outside the first shaft section 2214, the permanent magnet 2212 and the second shaft section 2216, so that the first shaft section 2214, the permanent magnet 2212 and the second shaft section 2216 are fixedly connected to each other. The permanent magnet 2212 can generate a magnetic field, which is used to drive the rotating shaft structure 220 to rotate when the winding of the motor stator 230 is energized.

[0046] The impeller assembly includes a primary impeller 222 and a secondary impeller 223. The primary impeller 222 is mounted on one end of the first shaft segment 2214 away from the permanent magnet 2212 in the axial direction through a primary locking nut 225, and is provided with a gap between the primary volute 214. The secondary impeller 223 is mounted on one end of the second shaft segment 2216 away from the permanent magnet 2212 in the axial direction through a secondary locking nut 226, and is provided with a gap between the secondary volute 216.

[0047] The primary radial bearing 227 is sleeved on the first shaft section 2214 and is located on the side of the primary impeller 222 close to the permanent magnet 2212, and the secondary radial bearing 228 is sleeved on the second shaft section 2216 and is located on the side of the secondary impeller 223 close to the permanent magnet 2212. In this way, the primary radial bearing 227 and the secondary radial bearing 228 are supporting points of the rotor 221, and are installed oppositely at opposite ends of the rotor 221. When the centrifugal air compressor 200 runs at high speed, an air film is formed between the rotor 221 and the primary radial bearing 227 and the secondary radial bearing 228, so that the rotor 221 is suspended in the air without being connected to the primary radial bearing 227 and the secondary radial bearing 228.

[0048] Furthermore, the first-stage radial bearing 227 and the second-stage radial bearing 228 are both foil dynamic pressure gas radial bearings, which include a bearing housing and a radial support wave foil and a radial top foil installed on the bearing housing, and the radial support wave foil is located between the radial bearing seat and the radial top foil.

[0049] The thrust plate 224 is sleeved on the first shaft section 2214 and is located between the first-stage impeller 222 and the first-stage radial bearing 227. The thrust plate 224 is interference fit with the first shaft section 2214. When the centrifugal air compressor 200 is running, the thrust plate 224 moves synchronously with the rotor 221, thereby preventing the rotor 221 from having a large axial movement.

[0050] The primary diffuser 240 is sleeved outside the thrust plate 224 and is in clearance with the thrust plate 224. The primary diffuser 240 is provided with comb teeth 270 for sealing in both the axial and radial directions. The secondary diffuser 250 is sleeved outside the secondary radial bearing 228 and is fixedly connected to the secondary radial bearing 228 by bolts and other fasteners.

[0051] The bearing support 260 is sleeved outside the primary radial bearing 227 and is fixedly connected to the motor barrel 212 and the primary radial bearing 227 by bolts and other fasteners, thereby supporting the primary radial bearing 227. The comb teeth 270 are sleeved on the second shaft section 2216 and located between the secondary radial bearing 228 and the secondary impeller 223. The comb teeth 270 are evenly distributed with grooves in the radial direction and the axial direction to play a sealing role.

[0052] As described in the background technology, in the above-mentioned centrifugal air compressor 200, since a thrust plate 224 is installed on the first shaft section 2214 of the rotor 221, the center of gravity of the entire rotating shaft structure 220 is biased toward the side where the first shaft section 2214 is located, and the first-stage radial bearing 227 is the only supporting point of the entire rotating shaft structure 220. When the axial force applied to it is too large, the rotor 221 will be tilted, causing the first-stage impeller 222 to collide with the first-stage volute 214, thereby reducing the reliability of the entire centrifugal air compressor 200.

[0053] In order to solve the above problems, in the rotor 221 structure of the present application, the diameters of the first-level radial bearing 227 and the second-level radial bearing 228 are equal, and the length of the first-level radial bearing 227 is greater than the length of the second-level radial bearing 228, so that the force per unit area of ​​the first-level radial bearing 227 is equal to the force per unit area of ​​the second-level radial bearing 228, that is, the force per unit area of ​​the radial support foil of the first-level radial bearing 227 is equal to the force per unit area of ​​the radial support foil of the second-level radial bearing 228.

[0054] In this way, the present application increases the length of the first-stage radial bearing 227, thereby reducing the force per unit area of ​​the radial support foil of the first-stage radial bearing 227, thereby avoiding the rotor 221 from tilting toward the side where the first shaft section 2214 is located, preventing the instability of the air film formed between the first-stage radial bearing 227 and the rotor 221, eliminating the collision between the rotor 221 and the first-stage radial bearing 227, and ultimately ensuring the smooth operation of the centrifugal air compressor 200.

[0055] Specifically, define the weight of the rotating shaft structure 220 as G, the weight on the side where the first-stage radial bearing 227 is located as F1, the distance between the center of gravity of the side of the rotating shaft structure 220 where the first-stage radial bearing 227 is located and the center of gravity of the rotating shaft structure 220 as l1, the weight on the side where the second-stage radial bearing 228 is located as F2, the distance between the center of gravity of the side of the rotating shaft structure 220 where the second-stage radial bearing 228 is located and the center of gravity of the rotating shaft structure 220 as l2, the length of the first-stage radial bearing 227 as L1, and the length of the second-stage radial bearing 228 as L2. The relationship among l1, l2, L1, and L2 satisfies: l1×L1 = l2×L2.

[0056] Thus, approximately represent F = D×L, where (D is the diameter of the first-stage radial bearing 227 or the second-stage radial bearing 228, and L is the length of the first-stage radial bearing 227 or the second-stage radial bearing 228). Since the diameters of the first-stage radial bearing 227 and the second-stage radial bearing 228 are equal, it can be further obtained that the torques of the first-stage radial bearing 227 and the second-stage radial bearing 228 satisfy: F1×l1 = F2×l2. Since the torques of the first-stage radial bearing 227 and the second-stage radial bearing 228 satisfy the above formula, the stable operation of the rotor 221 structure is ensured. As a preferred embodiment, the relationship between L1 and L2 satisfies: L1 = nL2, where 1.2 < n < 1.7. It can be connected that the specific value of n is not limited to this and can be set as needed to meet different requirements.

[0057] It should be noted that the range of the side of the rotating shaft structure 220 where the first-stage radial bearing 227 is located is from the center point of the permanent magnet 2212 to the end face of the first shaft section 2214, and the range of the side of the rotating shaft structure 220 where the second-stage radial bearing 228 is located is from the center point of the permanent magnet 2212 to the end face of the second shaft section 2216.

[0058] As Figure 3 and Figure 4 shown, in some embodiments, in order to avoid the excessive length of the first-stage radial bearing 227, on the basis of increasing the length of the first-stage radial bearing 227, a weight-reducing portion can be provided in the first shaft section 2214 of the rotor 221 by means of removing materials to reduce the weight of the first shaft section 2214, so that the relationship among the weight F1 on the side of the rotating shaft structure 220 where the first-stage radial bearing 227 is located, the weight F2 on the side of the rotating shaft structure 220 where the second-stage radial bearing 228 is located, the distance l1 between the center of gravity of the side of the rotating shaft structure 220 where the first-stage radial bearing 227 is located and the center of gravity of the rotating shaft structure 220, and the distance l2 between the center of gravity of the side of the rotating shaft structure 220 where the second-stage radial bearing 228 is located satisfies: F1×l1 = F2×l2.

[0059] Specifically, in some embodiments, the first shaft section 2214 of the rotor 221 is provided with a first center hole 2214a, the second shaft section 2216 of the rotor 221 is provided with a second center hole 2216a, the weight reduction portion is constructed as a groove provided in the hole wall of the first center hole 2214a, and the weight reduction portion surrounds the first center hole 2214a in the circumferential direction and extends from one axial end of the first center hole 2214a to the other axial end of the first center hole 2214a. In this way, the weight of the first shaft section 2214 is reduced by removing material, thereby further ensuring that the center of gravity of the rotating shaft structure 220 is located at the center of the motor, solving the problem of unstable axial force when the centrifugal air compressor 200 is running.

[0060] The above-mentioned rotating shaft structure 220 and centrifugal air compressor 200 adjust the length of the first-stage radial bearing 227 and the second-stage radial bearing 228 and remove the material in the first shaft section 2214 to make the force per unit area of ​​the radial support corrugated foil of the first-stage radial bearing 227 and the radial support corrugated foil of the second-stage radial bearing 228 equal, thereby effectively adjusting the center of gravity of the rotating shaft structure 220, avoiding the rotor 221 structure from tilting toward the side where the thrust plate 224 is located, and further eliminating the problem of the rotor 221 colliding due to the unstable air film formed between the first-stage radial bearing 227 and the rotor 221, avoiding the first-stage impeller 222 and the first-stage volute 214 from rubbing against each other, and ensuring the smooth operation of the centrifugal air compressor 200.

[0061] The present application also provides a vehicle, including a fuel cell system and the above-mentioned centrifugal air compressor 200, wherein the centrifugal air compressor 200 is used to provide a high-pressure air source for the fuel cell system.

[0062] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A rotating shaft structure, characterized in that: include: The rotor (221) comprises a first shaft segment (2214) and a second shaft segment (2216); An impeller assembly, comprising at least one impeller, wherein the impeller is sleeved on the first shaft segment (2214) and / or the second shaft segment (2216); A thrust plate (224) sleeved on the first shaft section (2214) of the rotor (221); a primary radial bearing (227), sleeved on the first shaft section (2214) of the rotor (221); and A secondary radial bearing (228), sleeved on the second shaft section (2216) of the rotor (221); Wherein, the first-stage radial bearing (227) and the second-stage radial bearing (228) are both foil dynamic pressure gas radial bearings, a weight reduction portion is provided in the first shaft section (2214), and the length of the first-stage radial bearing (227) is greater than the length of the second-stage radial bearing (228), so that the force per unit area of ​​the first-stage radial bearing (227) is equal to the force per unit area of ​​the second-stage radial bearing (228).

2. The rotating shaft structure according to claim 1, characterized in that: Define the distance between the center of gravity of the side where the primary radial bearing (227) of the rotating shaft structure is located and the center of gravity of the rotating shaft structure as l1, define the distance between the center of gravity of the side where the secondary radial bearing (228) of the rotating shaft structure is located and the center of gravity of the rotating shaft structure as l2, define the length of the primary radial bearing (227) as L1, and define the length of the secondary radial bearing (228) as L2; The relationship among the l1, the l2, the L1 and the L2 satisfies: l1xL1=l2xL2.

3. The rotating shaft structure according to claim 2, characterized in that: The relationship between L1 and L2 satisfies: L1=nL2, where 1.2 <n<1.7。 4. The rotating shaft structure according to claim 1, characterized in that: The diameter of the primary radial bearing (227) is equal to the diameter of the secondary radial bearing (228).

5. The rotating shaft structure according to claim 1, characterized in that: The weight of the side where the primary radial bearing (227) of the rotating shaft structure is located is defined as F1, the weight of the side where the secondary radial bearing (228) of the rotating shaft structure is located is defined as F2, the distance between the center of gravity of the side where the primary radial bearing (227) of the rotating shaft structure is located and the center of gravity of the rotating shaft structure is defined as l1, and the distance between the center of gravity of the side where the secondary radial bearing (228) of the rotating shaft structure is located and the center of gravity of the rotating shaft structure is defined as l2; The relationship between F1, F2, l1 and l2 satisfies: F1xl1=F2xl2.

6. The rotating shaft structure according to claim 5, characterized in that: The first shaft section (2214) of the rotor (221) is provided with a first center hole (2214a), the second shaft section (2216) of the rotor (221) is provided with a second center hole (2216a), and the weight reduction portion is constructed as a groove formed in the wall of the first center hole (2214a).

7. The rotating shaft structure according to claim 6, characterized in that: The weight-reducing portion surrounds the first center hole (2214a) in the circumferential direction and extends from one axial end of the first center hole (2214a) to the other axial end of the first center hole (2214a).

8. A centrifugal air compressor, characterized in that: It comprises the rotating shaft structure as claimed in any one of claims 1 to 7.

9. A vehicle, characterized in that: It comprises a fuel cell system and a centrifugal air compressor as claimed in claim 8, wherein the centrifugal air compressor is used to provide a high-pressure air source for the fuel cell system.

Images