Train heat dissipation brake disc adopting wing-shaped heat dissipation ribs

Abstract

The utility model relates to a train heat dissipation brake disc adopting wing-shaped heat dissipation ribs, which comprises a disc hub coaxially sleeved on an axle; the disc assembly comprises an inner disc and an outer disc which are coaxially and fixedly connected, round holes are formed in the centers of the inner disc and the outer disc, and the disc hub is sleeved with the disc assembly through the round holes; the radiating rib group comprises a plurality of first radiating ribs and a plurality of second radiating ribs and is arranged between the inner disc and the outer disc, the first radiating ribs and the second radiating ribs are annularly and alternately arranged along the periphery of the disc hub, the cross sections of the first radiating ribs and the second radiating ribs are wing-shaped, the wing-shaped bending directions of the first radiating ribs and the second radiating ribs are the same, and the wing-shaped bending directions of the first radiating ribs and the second radiating ribs are identical. A continuous arc-shaped heat dissipation channel is formed between every two adjacent heat dissipation ribs. The axial air inlet resistance can be effectively reduced, the air inlet amount in the channel is increased, the airflow speed in the channel is increased, the airflow in the channel is more stable and uniform, airflow separation is reduced, and then the heat dissipation efficiency is greatly improved.

Description

Technical Field

[0001] This utility model relates to the field of train braking device technology, and in particular to brakes, specifically to a train cooling brake disc using wing-shaped heat dissipation fins. Background Technology

[0002] The brake is a key component of high-speed trains. It uses a brake disc, coaxially fixed to the wheel and pressed against the brake pads, to brake and decelerate the train. During braking, the brake disc and brake pads absorb the train's kinetic energy through friction, converting it into heat. Some of this heat is conducted to the interior of the brake disc and brake pads, raising their temperature; the rest is transferred to the surrounding air primarily through thermal convection. Under emergency braking conditions, the heat load generated by friction on the brake disc causes its temperature to rise sharply. This reduces the coefficient of friction between the brake disc and brake pads and also causes thermal deformation and fatigue of the brake disc, directly affecting the braking performance and reliability of the braking system, thus hindering the safe and reliable operation of the train.

[0003] The heat exchange capacity between the brake disc and the surrounding air directly affects the release of the heat energy absorbed by the brake disc. To enhance the heat dissipation performance of the brake disc, ventilated disc brake discs are now widely used on high-speed trains. These discs have a complex internal heat dissipation fin structure. During train braking, the rotation of the brake disc introduces a large amount of air to the surface of the internal heat dissipation fin structure, enhancing the convective heat exchange capacity between the brake disc and the air. However, due to the turbulent airflow and low velocity in the train braking area, it can almost be considered that there is only natural convection between the heat dissipation fins and the introduced air. A large amount of heat energy remains unreleased, posing a significant safety hazard.

[0004] Therefore, there is an urgent need for a high-efficiency heat dissipation brake disc for trains that uses air-shaped heat dissipation fins. This disc can draw air into the disc body during rotation, thereby significantly increasing the airflow rate and enhancing the convective heat transfer capacity between the brake disc and the air, thus meeting the heat dissipation requirements of the brake disc. Utility Model Content

[0005] In view of the shortcomings of the prior art, the main purpose of this utility model is to provide a train heat dissipation brake disc with air fins to solve the problem of weak heat exchange capacity between the train brake disc and the air in the prior art, thereby meeting the high-efficiency heat dissipation requirements of the brake disc.

[0006] The technical solution of this utility model is as follows:

[0007] This utility model proposes a train cooling brake disc with airfoil-shaped heat dissipation ribs, comprising: a disc hub, coaxially sleeved on an axle; a disc assembly, including an inner disc and an outer disc coaxially fixedly connected, each of the inner and outer discs having a circular hole at its center, the disc assembly being sleeved on the disc hub through the circular hole; and a heat dissipation rib group, including multiple first heat dissipation ribs and multiple second heat dissipation ribs, disposed between the inner and outer discs, the first and second heat dissipation ribs being alternately arranged circumferentially along the outer periphery of the disc hub, and the cross-sections of the first and second heat dissipation ribs being airfoil-shaped, the airfoil bending directions of the first and second heat dissipation ribs being the same, and a continuous arc-shaped heat dissipation channel being formed between adjacent heat dissipation ribs.

[0008] In this embodiment of the invention, the radial inner end of each heat dissipation fin extends to the circular hole, and the radial outer end extends to the outside of the disk assembly.

[0009] In the embodiments of this utility model, the curvature of the arc lines on both sides of the first heat dissipation rib is consistent, and the cross-sectional width of the first heat dissipation rib gradually increases along the radial direction of the inner or outer disc; and / or, the curvature of the arc lines on both sides of the second heat dissipation rib is consistent, and the cross-sectional width of the second heat dissipation rib gradually increases along the radial direction of the inner or outer disc.

[0010] In this embodiment of the invention, the inner radial end of the first heat dissipation fin is wingtip-shaped, and the outer radial end is arc-shaped; the edge lines of the inner radial end and the outer radial end are continuously connected to the curvature of the arc lines on both sides of the first heat dissipation fin.

[0011] In this embodiment of the invention, the inner radial end of the second heat dissipation fin is perforated, and the outer radial end is arc-shaped; the edge lines of the inner radial end and the outer radial end are continuously connected to the curvature of the arc lines on both sides of the second heat dissipation fin.

[0012] In this embodiment of the invention, a connecting hole is provided at the radial inner end of the second heat dissipation fin, and a bolt hole is provided at the corresponding position of the hub. The connecting hole and the bolt hole are connected by a fastening bolt.

[0013] In this embodiment of the invention, the arc of the bolt hole is tangent to the radial inner edge of the second heat dissipation fin.

[0014] In the embodiments of this utility model, the cross-sectional width of the arc-shaped heat dissipation channel remains consistent along the airflow direction, and the width difference between any two cross-sections does not exceed 5% of the width.

[0015] In this embodiment of the invention, a plurality of first heat dissipation fins and a plurality of second heat dissipation fins are integrally formed into a turbine-like structure.

[0016] In this embodiment of the invention, the train cooling brake disc further includes an annular baffle plate for sealing the gap between the outer disc and the axle.

[0017] The beneficial effects of this utility model compared to the prior art are as follows: This utility model proposes a train cooling brake disc using airfoil-shaped heat dissipation fins. This train cooling brake disc can effectively reduce the wind resistance of axial air intake and increase the air intake volume in the channel, increase the airflow velocity in the channel, make the airflow in the channel more stable and uniform, reduce airflow separation, and thus greatly improve the heat dissipation efficiency. More precisely, it has the following practical effects:

[0018] The cross-section of the heat dissipation fin of this invention is an airfoil shape based on the design of an aircraft wing. This shape allows airflow to flow smoothly along its surface, reducing the resistance of the gas passage. At the same time, it can reduce eddies in the heat dissipation channel, making the airflow entering the heat dissipation channel axially more stable and uniform, ensuring the uniformity of heat dissipation of the brake disc, and effectively avoiding thermal deformation and thermal fatigue of the brake disc caused by thermal stress due to uneven heat dissipation.

[0019] The heat dissipation fins of this invention form multiple continuous arc-shaped heat dissipation channels in a ring array around the outer periphery of the brake disc. When the brake disc rotates, the turbine-like structure formed by the heat dissipation fins can increase the air flow velocity in the heat dissipation channels and generate negative pressure, so that the outside air enters the heat dissipation channels from the leading edge of the heat dissipation fins at a certain speed along the axial direction of the brake disc. Since the curvature transition of the heat dissipation channels is uniform, it ensures that the air passes through the heat dissipation channels at high speed and evenly, thereby improving the convective heat transfer capacity of the brake disc.

[0020] The heat dissipation fins of this utility model are designed to be used in combination with the first heat dissipation fins and the second heat dissipation fins. By relying on the mutual cooperation of the arcs of the two fins, the uniformity of the curvature transition of the heat dissipation channel is achieved. At the same time, the number of the two heat dissipation fins can be perfectly matched with the bolt holes, and they can be tightly connected to the hub by bolts, so as to improve the heat dissipation efficiency without affecting the original function.

[0021] It should be understood that the description in this utility model description section is not intended to limit the key or essential features of the embodiments of this utility model, nor is it intended to restrict the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Furthermore, implementation of any embodiment of this utility model does not imply the simultaneous possession or achievement of multiple or all of the aforementioned beneficial effects. Attached Figure Description

[0022] To more clearly illustrate the embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0023] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the implementation conditions of this utility model. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and purposes that this utility model can produce, should still fall within the scope of the technical content disclosed in this utility model.

[0024] Figure 1 This is a three-dimensional overall structural diagram of a train cooling brake disc according to some embodiments of the present invention;

[0025] Figure 2 This is a three-dimensional structural diagram of the disc hub according to some embodiments of the present invention;

[0026] Figure 3 This is a three-dimensional structural diagram of the heat dissipation fins according to some embodiments of the present invention;

[0027] Figure 4 This is a schematic diagram showing the connection between the heat dissipation fins and the hub in some embodiments of this utility model;

[0028] Figure 5 This is a three-dimensional structural diagram of the annular windbreak plate according to some embodiments of the present invention;

[0029] Figure 6 This is a schematic diagram of the brake disc velocity field in some embodiments of the present invention.

[0030] Marked in the image:

[0031] 1-Outer disc; 2-Inner disc; 3-First heat dissipation fin; 4-Second heat dissipation fin; 401-Connecting hole; 5-Disc hub; 501-Bolt hole; 6-Annular baffle; 7-Arc-shaped heat dissipation channel.

[0032] The same or corresponding marks in the diagram indicate the same or corresponding parts. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the embodiments of this utility model will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of this utility model and their descriptions are used to explain this utility model, but are not intended to limit this utility model.

[0034] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0035] It should be understood that the terms "comprising / including," "consisting of," or any other variations are intended to cover non-exclusive inclusion, such that a product, apparatus, process, or method that comprises a list of elements includes not only those elements but may also include, where necessary, other elements not expressly listed, or elements inherent to such a product, apparatus, process, or method. Without further limitation, an element defined by the phrases "comprising / including," "consisting of," does not exclude the presence of additional identical elements in the product, apparatus, process, or method that includes said element.

[0036] It should also be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device, component or structure referred to must have a specific orientation, be constructed or operated in a specific orientation, and should not be construed as a limitation on this utility model.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0038] The present invention will now be described in detail with reference to preferred embodiments.

[0039] like Figures 1 to 5As shown, this utility model proposes a train cooling brake disc using airfoil-shaped heat dissipation fins. The train cooling brake disc consists of a hub 5, a disc assembly, and a heat dissipation fin assembly. The hub 5 is coaxially mounted on the axle. The disc assembly includes an outer disc 1 and an inner disc 2, which are coaxial and fixed together by welding the heat dissipation fin assembly. Both the outer disc 1 and the inner disc 2 have a central hole, through which the disc assembly is fitted onto the outer periphery of the hub 5.

[0040] The heat dissipation fin assembly includes multiple first heat dissipation fins 3 and multiple second heat dissipation fins 4, which are disposed between the outer disk 1 and the inner disk 2. Both the first heat dissipation fins 3 and the second heat dissipation fins 4 can form heat dissipation channels with the disk assembly. The second heat dissipation fins 4 also serve to connect to the disk hub 5, and are fixed to the disk hub 5 with bolts. The multiple first heat dissipation fins 3 and the multiple second heat dissipation fins 4 are arranged alternately around the outer periphery of the disk hub 5, which avoids the flow inertia of a single structure and breaks the boundary layer limitation of heat transfer through differentiated disturbances.

[0041] In this invention, the cross-sections of the first heat dissipation fin 3 and the second heat dissipation fin 4 are both airfoil shapes based on aircraft wing design. The airfoil cross-section reduces airflow separation and vortex formation through its streamlined profile, lowers rotational drag, and forms stable laminar flow, allowing gas to pass through the internal flow channels of the brake disc along the curved surface, significantly improving convective heat transfer efficiency.

[0042] The first heat dissipation fin 3 and the second heat dissipation fin 4 have the same airfoil bending direction, forming a continuous centrifugal acceleration flow field, reducing turbulent energy loss, and forming a continuous arc-shaped heat dissipation channel 7 between adjacent first heat dissipation fins 3 and second heat dissipation fins 4.

[0043] In this invention, the curvature of the arc-shaped heat dissipation channel is uniformly gradual. This uniform curvature transition reduces localized eddies and energy loss, ensuring the airflow remains in contact with the heat dissipation surface throughout its travel. The continuous curvature of the arc-shaped heat dissipation channel 7 guides the airflow smoothly along the surface of the heat dissipation fins, avoiding flow separation and eddies caused by right angles or abrupt structural changes, thus reducing kinetic energy loss. Simultaneously, the continuous change in curvature keeps the airflow in a turbulent state, enhancing the contact time between the airflow and the heat dissipation fins and improving heat exchange efficiency.

[0044] In this invention, multiple arc-shaped heat dissipation channels 7 form a continuous "centrifugal acceleration flow channel", which not only enhances the directional stripping and uniform heat dissipation, but also balances the flow resistance through the synergistic effect of alternating leading edges.

[0045] In some embodiments, the cross-sectional width of the arc-shaped heat dissipation channel 7 remains consistent along the airflow direction, and the width of any two cross-sections does not exceed 5% of that width. This consistent width avoids abrupt changes in airflow acceleration / deceleration caused by local expansion or contraction of the channel, maintains laminar flow stability, increases the airflow velocity within the channel, makes the airflow within the channel more stable and uniform, reduces airflow separation, and thus greatly improves heat dissipation efficiency.

[0046] See Figure 3 , Figure 4 The radially inner ends (leading edges) of the first heat dissipation fin 3 and the second heat dissipation fin 4 extend to the circular holes of the outer disk 1 and the inner disk 2. These extended leading edges guide the axial airflow smoothly into the arc-shaped heat dissipation channel. The radially outer ends (rear edges) of the first heat dissipation fin 3 and the second heat dissipation fin 4 extend beyond the disk assembly. These extended rear edges further optimize the continuity of the airflow path. More precisely, the radially outer ends of the first heat dissipation fin 3 and the second heat dissipation fin 4 slightly extend beyond the disk area.

[0047] It's easy to understand that the radial inner end refers to the end of the heat dissipation fin that is close to the center hole of the inner and outer plates, while the radial outer end refers to the end of the heat dissipation fin that is close to the outer edge of the inner and outer plates.

[0048] Continue to participate Figure 3 , Figure 4 The curvature of the arc lines on both sides of the first heat dissipation rib 3 is consistent, and the cross-sectional width of the first heat dissipation rib 3 gradually increases along the radial direction of the inner and outer plates. The curvature of the arc lines on both sides of the second heat dissipation rib 4 is consistent, and the cross-sectional width of the second heat dissipation rib 4 gradually increases along the radial direction of the inner and outer plates.

[0049] In this invention, the design of gradually increasing width of the heat dissipation fins along the radial direction matches the centrifugal force distribution law, which reduces stress concentration at the root and avoids gap imbalance caused by local thermal deformation.

[0050] In one specific embodiment, the maximum width of the first heat dissipation fin is 6.5 times the minimum width, and the maximum width of the second heat dissipation fin is 1.7 times the minimum width.

[0051] See Figure 3 , Figure 4 Multiple first cooling fins 3 and multiple second cooling fins 4 form a turbine-like structure. When the brake disc rotates, the turbine-like structure formed by the cooling fins can increase the airflow velocity in the cooling channel, generate negative pressure, and cause outside air to enter the cooling channel from the leading edge of the cooling fins along the axis of the brake disc at a certain speed. Since the curvature transition of the cooling channel is uniform, it ensures that the air passes through the cooling channel at high speed and evenly, thereby improving the convective heat transfer capacity of the brake disc.

[0052] In some embodiments, the radially inner end of the first heat dissipation fin 3 is wingtip-shaped, and the radially outer end of the first heat dissipation fin 3 is arc-shaped. The wingtip-shaped leading edge reduces airflow separation at the inlet of the arc-shaped heat dissipation channel 7 through its sharp or tapered profile, allowing the axial airflow to smoothly enter the arc-shaped heat dissipation channel 7, reducing frictional resistance, and improving the stability of airflow through the channel. The arc-shaped trailing edge not only disperses stress concentration points and inhibits crack initiation, but also reduces aerodynamic noise by weakening the amplitude of vortex shedding, further optimizing the continuity of the airflow path.

[0053] In some embodiments, the edge lines of the radial inner end and radial outer end of the first heat dissipation rib 3 are continuously connected to the curvature of the arc lines on both sides of the first heat dissipation rib 3. That is, the edge lines of the radial inner end and radial outer end of the first heat dissipation rib 3 transition evenly with the middle section of the first heat dissipation rib 3.

[0054] The radial inner end of the second heat dissipation fin 4 is perforated. (See also...) Figures 2 to 4 The second heat dissipation rib 4 has a connecting hole 401 at its radial inner end, and a bolt hole 501 is provided at the corresponding position of the hub 5. The second heat dissipation rib 4 is connected and fixed to the hub 5 by fastening bolts through the connecting hole 401 and the corresponding bolt hole 501. The radial outer end of the second heat dissipation rib 4 is arc-shaped. The arc-shaped design of the second heat dissipation rib 4 has the same effect as the arc-shaped design of the radial outer end of the first heat dissipation rib 3, and will not be repeated here.

[0055] In this invention, the perforated second heat dissipation fin 4 integrates the function of the hub hole through an integrated design. The hole shape and the thickness of the hub hole are consistent, which not only inherits the connection strength of the traditional hub hole, but also eliminates geometric abrupt changes through continuous arc transition, reducing flow separation and local stress concentration.

[0056] Preferably, the arc of the bolt hole 501 on the hub 5 is tangent to the radial inner outer edge of the second heat dissipation fin 4. More precisely, the radial inner outer edge of the second heat dissipation fin 4 coincides with the arc of the corresponding bolt hole 501. The curvature of the hub connection area matches the hole profile of the second heat dissipation fin 4, forming a continuous streamlined channel, reducing airflow resistance and improving the guiding efficiency of centrifugal flow.

[0057] In some embodiments, the edge lines of the inner and outer radial ends of the second heat dissipation rib 4 are continuously connected to the curvature of the arc lines on both sides of the second heat dissipation rib 4. That is, the edge lines of the inner and outer radial ends of the second heat dissipation rib 4 transition evenly with the middle section of the second heat dissipation rib 4.

[0058] In some embodiments, see Figure 1 , Figure 5 The train's cooling brake disc also includes an annular baffle 6. This annular baffle 6 is used to seal the gap between the outer disc 1 and the axle.

[0059] The train cooling brake disc of this invention solves the problem of weak heat exchange capacity between the original train brake disc and the air convection, and meets the high-efficiency heat dissipation requirements of the brake disc.

[0060] The applicant of this utility model conducted performance tests on a train cooling brake disc according to a specific embodiment of the present utility model. In this embodiment, a high-efficiency cooling brake disc with airfoil-shaped cooling fins designed according to the present utility model is mounted on the train axle. When the train is traveling at a speed of 300 km / h, the axial airflow is guided to the arc-shaped cooling channel inside the brake disc by the airflow guiding and centrifugal acceleration effect, significantly increasing the contact area and residence time between the airflow and the surface of the cooling fins.

[0061] Specifically, a simulation test was conducted on the heat dissipation capacity of a train cooling brake disc with wing-shaped heat dissipation fins designed according to this utility model: See [link to relevant documentation]. Figure 6 This heat dissipation capacity test used ANSYS Fluent software for fluid simulation, reflecting the average velocity within the disc. The results show that when air is blown through the center hole of the brake disc at a speed of 20 m / s, and the airflow passes evenly through the arc-shaped heat dissipation channel between the inner and outer discs, the average velocity within the disc, calculated by surface integration, is 59.5 m / s. Compared to the existing technology with an average velocity of 36.82 m / s, the airfoil-shaped heat dissipation fins of this design demonstrate superior airflow rectification and heat dissipation capabilities.

[0062] It will be readily understood by those skilled in the art that, without conflict, the above-mentioned preferred solutions can be freely combined and superimposed.

[0063] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A train cooling brake disc employing wing-shaped cooling fins, characterized in that, include: The hub is coaxially fitted onto the axle. The disk assembly includes an inner disk and an outer disk that are coaxially fixedly connected. Both the inner disk and the outer disk have a circular hole at their center. The disk assembly is fitted onto the disk hub through the circular hole. The heat dissipation fin assembly includes multiple first heat dissipation fins and multiple second heat dissipation fins, which are disposed between the inner and outer discs. The first and second heat dissipation fins are arranged alternately in the circumferential direction along the outer periphery of the disc hub, and the cross-sections of the first and second heat dissipation fins are both airfoil-shaped. The airfoil-shaped bending directions of the first and second heat dissipation fins are the same, and a continuous arc-shaped heat dissipation channel is formed between adjacent heat dissipation fins.

2. The train cooling brake disc according to claim 1, characterized in that, The radial inner end of each heat dissipation fin extends to the circular hole, and the radial outer end extends to the outside of the disk assembly.

3. The train cooling brake disc according to claim 1, characterized in that, The curvature of the arc lines on both sides of the first heat dissipation rib is consistent, and the cross-sectional width of the first heat dissipation rib gradually increases along the radial direction of the inner or outer disc; and / or, the curvature of the arc lines on both sides of the second heat dissipation rib is consistent, and the cross-sectional width of the second heat dissipation rib gradually increases along the radial direction of the inner or outer disc.

4. The train cooling brake disc according to claim 1, characterized in that, The inner radial end of the first heat dissipation fin is wingtip-shaped, and the outer radial end is arc-shaped; the edge lines of the inner radial end and the outer radial end are continuously connected to the curvature of the arc lines on both sides of the first heat dissipation fin.

5. The train cooling brake disc according to claim 1, characterized in that, The inner radial end of the second heat dissipation fin is perforated, and the outer radial end is arc-shaped; the edge lines of the inner radial end and the outer radial end are continuously connected to the curvature of the arc lines on both sides of the second heat dissipation fin.

6. The train cooling brake disc according to claim 1, characterized in that, The second heat dissipation fin has a connecting hole at its radial inner end, and the corresponding position of the hub has a bolt hole. The connecting hole and the bolt hole are connected by a fastening bolt.

7. The train cooling brake disc according to claim 6, characterized in that, The arc of the bolt hole is tangent to the radial inner edge of the second heat dissipation fin.

8. The train cooling brake disc according to claim 1, characterized in that, The cross-sectional width of the arc-shaped heat dissipation channel remains consistent along the airflow direction, and the difference in width between any two cross-sections does not exceed 5% of the width.

9. The train cooling brake disc according to claim 1, characterized in that, The multiple first heat dissipation fins and the multiple second heat dissipation fins together form a turbine-like structure.

10. The train cooling brake disc according to claim 1, characterized in that, The train's cooling brake disc also includes an annular baffle plate for sealing the gap between the outer disc and the axle.

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