CN220628010U

CN220628010U - Battery pack

Info

Publication number: CN220628010U
Application number: CN202322198178.9U
Authority: CN
Inventors: 张永明; 沈全安; 温世标
Original assignee: Xinwangda Power Technology Co ltd
Current assignee: Xinwangda Power Technology Co ltd
Priority date: 2023-08-15
Filing date: 2023-08-15
Publication date: 2024-03-19
Anticipated expiration: 2033-08-15

Abstract

The application discloses a battery pack, belongs to the technical field of batteries, and comprises a battery box and a battery monomer, wherein the battery box comprises a bottom guard plate, side plates and side beams, and the side plates are connected with the periphery of the bottom guard plate and enclose to form an accommodating space which is used for accommodating a battery; the side beam is connected at the side that the curb plate deviates from with the battery, and the battery box has a first direction, and along first direction, the projection has on the backplate at least partially to the side beam. The battery box of this application is relative with end backplate through setting up at least part and the side roof beam, can be when the side roof beam receives the side to bump impact force and take place energy-absorbing deformation, the side roof beam warp and offset to end backplate through the part that is relative with end backplate, realizes bumping the power part with the side and to end backplate conduction to utilize end backplate to bump the power dispersion absorption with the part side, thereby improve the ability that the anti side of battery box bumped under the circumstances that does not increase side roof beam weight, improve the security.

Description

Battery pack

Technical Field

The application belongs to the technical field of batteries, and particularly relates to a battery pack.

Background

Most of battery packs in new energy automobiles are hoisted below the chassis of the automobile body, so that the battery packs are frequently subjected to external impact. At present, in order to cope with the side impact of the battery pack, the thickness of the reinforced side plate is often adopted to improve the side intrusion resistance of the battery pack, which not only leads to the increase of the weight of the battery pack, but also leads to the increase of the cost.

Disclosure of Invention

The utility model aims to: the embodiment of the application provides a battery pack, and aims to solve the problem that the weight energy density of the existing battery pack is sacrificed to improve the side intrusion resistance.

The technical scheme is as follows: the embodiment of the application a battery package, including battery box and battery monomer, the battery box includes:

a bottom guard board;

the side plates are connected with the periphery of the bottom guard plate and enclose to form an accommodating space, and the accommodating space is used for accommodating the battery cells;

the side beam is connected to one side of the side plate, which is opposite to the battery unit, the battery box is provided with a first direction, and at least part of the side beam is provided with a projection on the bottom guard plate along the first direction.

In some embodiments, at least one first buffer cavity is provided in the side rail.

In some embodiments, the first buffer chamber has a sidewall; along the first direction, at least one first buffer cavity is opposite to the bottom guard plate, the side wall is connected with a first reinforcing rib, and the first reinforcing rib inclines relative to the first direction and extends towards the bottom guard plate.

In some embodiments, the battery box further comprises a second stiffener connected to the side plate and the side rail.

In some embodiments, a first included angle alpha is formed between the side surface, away from the first buffer cavity, of the second reinforcing rib and the side plate, and alpha is more than or equal to 90 degrees.

In some embodiments, a second included angle beta is formed between the side surface, away from the first buffer cavity, of the first reinforcing rib and the side plate, wherein beta is less than or equal to 90 degrees.

In some embodiments, at least one second buffer cavity is disposed in the side plate, and along the first direction, the at least one second buffer cavity is opposite to one of the first buffer cavities.

In some embodiments, at least one third buffer chamber is disposed within the bottom guard plate, and along the first direction, the at least one third buffer chamber is opposite one of the first buffer chambers.

In some embodiments, a vertical rib is disposed in the third buffer chamber, the vertical rib extends along the first direction, and at least part of the first reinforcing rib is opposite to the vertical rib in the first direction.

In some embodiments, the side wall of the first buffer chamber opposite to the bottom guard plate is further provided with a force transmission rib, and a third included angle gamma is formed between the first reinforcing rib and the force transmission rib, and the third included angle gamma is an acute angle.

In some embodiments, in the first direction, there is a gap between the side rail and the bottom shield.

The beneficial effects are that: compared with the prior art, the battery pack comprises a battery box and battery monomers, wherein the battery box comprises a bottom guard plate, side plates and side beams, and the side plates are connected with the periphery of the bottom guard plate and enclose to form an accommodating space which is used for accommodating the battery monomers; the side beam is connected at the side that curb plate and battery cell deviate from, and the battery box has first direction, and along first direction, the projection has on the backplate at least partially to the side beam. The battery box of this application is relative with end backplate through setting up at least part and the side roof beam, can be when the side roof beam receives the side to bump impact force and take place energy-absorbing deformation, the side roof beam warp and offset to end backplate through the part that is relative with end backplate, realizes bumping the power part with the side and to end backplate conduction to utilize end backplate to bump the power dispersion absorption with the part side, thereby improve the ability that the anti side of battery box bumped under the circumstances that does not increase side roof beam weight, improve the security.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic view of the overall structure of a battery pack of the present application;

FIG. 2 is a cross-sectional view of a bottom rail and side rail of one embodiment of a battery pack of the present application;

FIG. 3 is a cross-sectional view of a bottom guard plate and side rails of two embodiments of a battery pack of the present application;

fig. 4 is a schematic view of the force transmission direction of a battery pack according to the present application when the battery pack receives a side impact force.

Reference numerals:

1-bottom guard board, 11-third buffer cavity, 12-vertical rib, 2-side board, 21-second buffer cavity, 3-battery, 4-side beam, 41-first buffer cavity, 42-side wall, 421-first reinforcing rib, 422-second reinforcing rib, 423-force transmission rib, 5-gap, X first direction.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.

In the description of the present application, it should be understood that the terms "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate description of the present application and simplify the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more features. In the description of the present application, the meaning of "a plurality" is two or more, and at least one means may be one, two or more, unless explicitly defined otherwise. The term "parallel" in the present application includes not only the case of absolute parallelism but also the case of approximately parallelism as conventionally recognized in engineering, for example, "parallel" refers to a state in which straight lines form an angle of-1 ° to 1 ° with respect to straight lines, straight lines form an angle of plane with respect to plane, or plane with respect to plane; meanwhile, "vertical" includes not only the case of absolute vertical but also the case of substantially vertical as conventionally recognized in engineering, for example, vertical "refers to a state in which an angle formed by a straight line and a straight line, a straight line and a plane, or a plane and a plane is 89 ° to 91 °. The distances are equal or the angles are equal, not only the absolute equal condition is included, but also the general equal condition of the conventional cognition in engineering is included, and certain errors can exist, such as a state that the tolerance range is between-1% and 1%.

It should be further noted that, in the drawings of the present application, an arrow labeled X is used to indicate the first direction X, and the first direction X is introduced to facilitate description of the structural positional relationship of each component of the battery box, so as to facilitate understanding of the structure thereof. In this embodiment of the present application, the first direction X may correspond to a direction of the side impact force in actual application.

The applicant has noted that the side protection of the battery box is generally achieved by reinforcing the side beams of the box to increase the resistance to side intrusion of the box or by transmitting side impact forces to the beams to resist intrusion. However, the continuous reinforcement of the side beams inevitably leads to an increase in the weight of the battery box, resulting in an increase in cost and a decrease in weight energy density, while the beams can only exert resistance in a local position.

In view of this, this embodiment of the application provides a battery package, and the battery case in the battery package utilizes the structure that partial impact force warp and offset with end backplate 1 through side rail 4 when receiving the side force, transmits partial impact force to on backplate 1, realizes the dispersion absorption of side force, improves the anti side of battery case and bumps the ability, improves the security of battery package.

Referring to fig. 1, fig. 2, fig. 3 and fig. 4 together, fig. 1 is a schematic view of the overall structure of a battery pack according to the present application; FIG. 2 is a cross-sectional view of the bottom shield 1 and side rails 4 of one embodiment of a battery pack of the present application; FIG. 3 is a cross-sectional view of the bottom shield 1 and side rails 4 of two embodiments of a battery pack of the present application; fig. 4 is a schematic view of a force transmission direction when a battery pack receives a side impact force (the direction indicated by an arrow in the figure is the force transmission direction).

In an embodiment of the present application, a battery pack is provided, including a battery box and a battery unit 3, where the battery box includes a bottom guard plate 1, a side plate 2 and a side beam 4, and the side plate 2 is connected with a peripheral side of the bottom guard plate 1 and encloses to form an accommodating space, where the accommodating space is used for accommodating the battery unit 3; the side beam 4 is connected to a side of the side plate 2 facing away from the battery cell 3, the battery box has a first direction X, and along the first direction X, at least part of the side beam 4 has a projection on the bottom guard plate 1, specifically, at least part of the side beam 4 may be disposed opposite to the bottom guard plate 1.

Specifically, the side rail 4 of the present application is partially connected to the side plate 2 and is at least partially opposite to the bottom fender 1. The side rail 4 may or may not be in contact with the bottom shield 1 at this time. When the side impact force is impacted, the side impact force impacts the side edge beam 4 along the first direction, the side edge beam 4 deforms after being stressed, the side impact force absorbs energy, and then the side edge beam 4 correspondingly deforms towards the side plate 2 and the bottom guard plate 1 after being impacted, and partially abuts against the bottom guard plate 1, part of the impact force is transferred to the bottom guard plate 1 through the abutting part of the side edge beam 4 and the bottom guard plate 1, and the bottom guard plate 1 also bears part of the impact force. For traditional battery box only relies on the design that side beam 4 and crossbeam bear the side and bump the power, the battery box of this application has higher anti side and bumps the ability to end backplate 1 has covered the bottom of whole battery box, also can have stronger anti side and bump the ability in non-crossbeam region, has improved the security of battery box and even battery package.

In one embodiment of the present application, the first direction X is parallel to the plane of the bottom shielding plate 1. Specifically, the first direction X is parallel to the length direction or the width direction of the bottom guard plate 1, so that when the side beam 4 transmits force to the bottom guard plate 1, the bottom guard plate 1 can bear larger collision force, and the overall structural strength of the battery pack is improved.

Referring to fig. 2, 3 and 4, in some embodiments, at least one first buffer cavity 41 is provided in the side beam 4.

Specifically, at least one first buffer cavity 41 is arranged in the side beam 4, and when the side beam is impacted, the first buffer cavity 41 can be utilized to perform primary deformation energy absorption.

It should be noted that the first buffer chamber 41 may be one as shown in fig. 2, or may be plural as shown in fig. 3 and 4. The first buffer cavity 41 is utilized to provide a buffer deformation space, and the larger the space of the first buffer cavity 41 is, the larger the space corresponding to deformation energy absorption is.

Further, with continued reference to fig. 2, 3 and 4, in some embodiments, the first buffer chamber 41 has a sidewall 42; in the first direction, at least one first buffer chamber 41 is opposite to the bottom shield 1, and the side wall 42 is connected with first ribs 421, and the first ribs 421 are inclined with respect to the first direction and extend toward the bottom shield 1.

Specifically, in this embodiment, at least one first buffer cavity 41 is opposite to the bottom guard plate 1, so that after the first buffer cavity 41 receives the side impact force to absorb energy, the side wall 42 of the first buffer cavity 41 deforms towards the bottom guard plate 1 and finally abuts against the bottom guard plate 1, and the side wall 42 of the first buffer cavity 41 abuts against the bottom guard plate 1 to smoothly transfer part of the side impact force to the bottom guard plate 1, so that part of the impact force is received by the bottom guard plate 1.

Further, a first rib 421 is attached to a side wall 42 of the first cushion chamber opposite to the bottom shield 1, and is inclined with respect to the first direction and extends toward the bottom shield 1. The arrangement of the structure can conduct side impact force by utilizing the first reinforcing ribs 421, the first reinforcing ribs 421 incline to extend to the bottom guard plate 1, and the side impact force can be correspondingly conducted to the bottom guard plate 1, so that more side impact force is conducted to the bottom guard plate 1, the side impact force born by the side edge beam 4 is further reduced, and the corresponding side impact resistance of the side edge beam 4 is improved. Of course, the first reinforcing ribs 421 are also supported between the side walls 42, which correspondingly improves the supporting strength of the side beams 4 and also correspondingly improves the side impact resistance of the side beams 4.

With continued reference to fig. 2, 3 and 4, in some embodiments, the battery compartment further includes a second stiffener 422, the second stiffener 422 being connected to the side panel 2 and the side rail 4.

Specifically, the second reinforcing ribs 422 connect the side plate 2 and the side beam 4, on one hand, the structural strength of connection between the side plate 2 and the side beam 4 is improved, on the other hand, the second reinforcing ribs 422 conduct partial side impact force from the side beam 4 to the side plate 2, and the side is utilized to further disperse and absorb partial side impact force, so that the impact resistance of the side beam 4 is further improved.

Please refer to fig. 3 and fig. 4 in combination, it should be noted that, this application is through setting up first strengthening rib 421 and second strengthening rib 422, on the one hand, improve the structural strength of side, improve the anti side of side roof beam 4 and bump the ability, on the other hand, when receiving the side to bump the power and strike, side roof beam 4 is at first through the body absorption part side to bump the power, then pass through first strengthening rib 421 and bump the power to backplate 1 partly, utilize second strengthening rib 422 to pass the side to bump the power to curb plate 2, side roof beam 4 still is connected with the crossbeam inside the battery box simultaneously, with the transmission of partly side to the crossbeam, thereby realize the large tracts of land dispersion of side to bump the power, make side roof beam 4, end backplate 1, curb plate 2, crossbeam all can bear the part impact force, realized the minimum injury to side roof beam 4, also realized the minimum injury to whole battery box, improve the security of whole battery box and battery package.

With continued reference to fig. 3 and 4, in some embodiments, a side of the second rib 422 facing away from the first buffer chamber 41 forms a first angle α with the side plate 2, and α is greater than or equal to 90 °.

Specifically, this application sets up that the slope of second strengthening rib 422 extends to curb plate 2, and is the obtuse angle between a side that the second strengthening rib 422 deviates from first buffer chamber 41 and the curb plate 2, can make the side that side roof beam 4 received bump the power along second strengthening rib 422 to curb plate 2 transmission, and the position of transmission is the position of keeping away from end backplate 1, so further realizes the scattered transmission of side bump power.

With continued reference to fig. 3 and 4, in some embodiments, a second angle β is formed between the side of the first rib 421 facing away from the first buffer chamber 41 and the side plate 2, and β is less than or equal to 90 °.

Specifically, the first reinforcing ribs 421 extend obliquely toward the bottom guard plate 1, and the side surface of the further first reinforcing ribs 421 facing away from the first buffer cavity 41 forms an acute angle with the side plate 2, so that the first reinforcing ribs 421 can smoothly disperse and transfer the side impact force to the bottom guard plate 1.

The second reinforcing ribs 422 are combined with the side plates 2 to form an obtuse angle and an acute angle is formed between the first reinforcing ribs 421 and the side plates 2, so that the extending directions of the first reinforcing ribs 421 and the second reinforcing ribs 422 are opposite, the side collision force is transmitted to opposite directions, the scattered transmission of the side collision force is further realized, the side collision force is prevented from being concentrated in the side beam 4 area, and the probability of local deformation and even breakage is reduced.

With continued reference to fig. 2, 3 and 4, in some embodiments, at least one second buffer chamber 21 is disposed in the side plate 2, and the at least one second buffer chamber 21 is opposite to one of the first buffer chambers 41 along the first direction.

Specifically, since it is necessary to transmit a part of the side impact force to the side plate 2 and perform deformation energy absorption, the second buffer chamber 21 is provided correspondingly to the side plate 2, so that deformation energy absorption can be performed when the side impact force transmitted by the side sill 4 is received, and the impact resistance of the side plate 2 can be improved. And at least one second buffer cavity 21 is opposite to one of the first buffer cavities 41, so that the side plate 2 and the side beam 4 are partially connected, and the side beam 4 is ensured to transmit partial side collision force to the side plate 2; secondly, the side impact force in the first buffer cavity 41 is convenient to directly transfer to the second buffer cavity 21, the side impact force transferred by the first buffer cavity 41 can be absorbed through deformation by the outer side wall 42 corresponding to the second buffer cavity 21, and the second buffer cavity 21 can provide buffer space, so that the buffer space has better buffering energy absorption effect, meanwhile, the side wall 42 of the reinforcing rib or the directional side plate 2 is prevented from being directly opposite to the second buffer cavity 21, the larger deformation and even damage caused by larger impact force on the local part of the outer side wall 42 of the second buffer cavity 21 of the side plate 2 can be avoided, and the safety is improved.

With continued reference to fig. 2, 3 and 4, in some embodiments, at least one third buffer chamber 11 is provided in the backplate 1, and the at least one third buffer chamber 11 is opposite to one of the first buffer chambers 41 along the first direction. Further, a vertical rib 12 is disposed in the third buffer chamber 11, the vertical rib 12 extends along the first direction X, and at least part of the first reinforcing rib 421 is opposite to the vertical rib 12 in the first direction X.

Specifically, since part of the side impact force needs to be transferred to the bottom guard plate 1 and deformed and absorbed, the third buffer chambers 11 are correspondingly arranged in the bottom guard plate 1, and when the side impact force is transferred to the bottom guard plate 1, the corresponding third buffer chambers 11 deform and absorb the side impact force transferred to the bottom guard plate 1. Further, at least one third cushion chamber 11 is opposed to one of the first cushion chambers 41, and when the side beam 4 is deformed and the side wall 42 of the first cushion chamber 41 contacts the bottom guard plate 1, the side impact force can be uniformly transmitted to the bottom guard plate 1 by the first cushion chamber 41, so that the local impact to the bottom guard plate 1 can be reduced, and the safety can be improved. Meanwhile, the vertical ribs 12 are arranged in the third buffer cavity 11, the vertical ribs 12 are perpendicular to the first buffer cavity 41 along the first direction X, when the side wall of the first buffer cavity 41 is in contact with the bottom guard plate 1, the vertical ribs 12 can be used for supporting the third buffer cavity 11, the structural stability of the bottom guard plate 1 is improved, the force transmission and energy absorption effects can be achieved, and the buffer and energy absorption effects of the bottom guard plate 1 are improved.

With continued reference to fig. 2, 3 and 4, in some embodiments, the side wall 42 of the first cushion chamber 41 opposite to the bottom protection plate 1 further has a force transmission rib 423, and a third included angle γ is formed between the first reinforcing rib 421 and the force transmission rib 423, and the third included angle γ is an acute angle.

Specifically, the side wall 42 of the buffer cavity opposite to the bottom guard plate 1 is provided with the force transmission rib 423, an acute angle is defined between the first reinforcing rib 421 and the force transmission rib 423, meanwhile, the force transmission rib 423 extends obliquely to the direction of the bottom guard plate 1, and can transmit side impact force to the bottom guard plate 1 from the other side edge of the first buffer cavity 41, so that more side impact force is transmitted to the bottom guard plate 1, and as the bottom guard plate 1 covers the whole bottom of the battery box, the area of the bottom guard plate is larger, the corresponding side impact force can be absorbed, more side impact force is transmitted to the bottom guard plate 1, the side impact force can be absorbed better, and the safety of the battery box is improved.

Since the battery pack needs to take into account the occupation of the entire space, the side rail 4 is disposed to sag with respect to the side plate 2, but since the battery pack does not extend downward without limitation in consideration of the entire volume of the battery pack, only the first buffer chamber 41 on the outermost side of the side rail 4 is shown in the drawings to face the bottom guard plate 1, and at this time, the side rail 4 can transmit the side impact force to the bottom guard plate 1.

Referring again to fig. 2, 3 and 4, in some embodiments, in a first direction, there is a gap 5 between the side rail 4 and the bottom shield 1.

Since the side rail 4 is opposed to the bottom fender 1, the case where the side rail 4 is in contact with the bottom fender 1 and the case where the side rail 4 is not in contact with the bottom fender 1 are correspondingly included. When the side beam 4 contacts with the bottom guard plate 1, the side beam 4 directly transmits the side collision force to the bottom guard plate 1 when receiving the side collision force, and the side collision force is further absorbed by the bottom guard plate 1. In this embodiment, a gap 5 is further defined between the side beam 4 and the bottom guard plate 1, so that when the side beam 4 receives a side impact force, the side beam is deformed and then collides with the bottom guard plate 1, and the gap 5 corresponds to a semi-closed buffer cavity, so that a further buffering and energy absorbing effect can be achieved. In addition, the assembly is also convenient.

The battery pack in the embodiment of the application can be used for various electric equipment such as new energy automobiles, computers, energy storage power supply equipment and the like. It will be appreciated that the battery pack may include all of the technical features and advantages of the battery case described above, and will not be described in detail herein.

In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments.

The above describes a battery box and a battery pack provided in the embodiments of the present application in detail, and specific examples are applied to illustrate the principles and embodiments of the present application, where the above description of the embodiments is only for helping to understand the technical solution and core ideas of the present application; those of ordinary skill in the art will appreciate that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery pack, characterized by comprising a battery box and a battery cell (3); the battery box includes:

a bottom guard board (1);

the side plates (2) are connected with the periphery of the bottom guard plate (1) and enclose to form an accommodating space, and the accommodating space is used for accommodating the battery cells (3);

the side beam (4), the side beam (4) is connected the curb plate (2) with one side that the battery monomer (3) deviates from mutually, the battery box has first direction (X), follows first direction (X), at least part of side beam (4) is in have the projection on backplate (1).

2. Battery pack according to claim 1, characterized in that the side beams (4) are provided with at least one first buffer chamber (41) inside.

3. The battery pack according to claim 2, wherein the first buffer chamber (41) has a side wall (42); along the first direction (X), at least one first buffer cavity (41) is opposite to the bottom guard plate (1), a first reinforcing rib (421) is connected to the side wall (42), and the first reinforcing rib (421) inclines relative to the first direction (X) and extends towards the bottom guard plate (1).

4. The battery pack according to claim 2, wherein the battery case further includes a second reinforcing rib (422), the second reinforcing rib (422) being connected to the side plate (2) and the side rail (4).

5. The battery pack according to claim 4, wherein the side of the second reinforcing rib (422) facing away from the first buffer chamber (41) and the side plate (2) have a first angle α, α being equal to or greater than 90 °.

6. A battery pack according to claim 3, wherein the side of the first rib (421) facing away from the first buffer chamber (41) has a second angle β with respect to the side plate (2), β being equal to or less than 90 °.

7. Battery pack according to claim 2, characterized in that at least one second buffer chamber (21) is provided in the side plate (2), at least one second buffer chamber (21) being opposite one of the first buffer chambers (41) in the first direction (X).

8. A battery pack according to claim 3, wherein at least one third buffer chamber (11) is provided in the bottom protection plate (1), the at least one third buffer chamber (11) being opposite one of the first buffer chambers (41) along the first direction (X).

9. The battery pack according to claim 8, wherein a vertical rib (12) is provided in the third buffer chamber (11), the vertical rib (12) extends in the first direction (X), and at least part of the first reinforcing rib (421) is opposite to the vertical rib (12) in the first direction (X).

10. A battery pack according to claim 3, wherein the side wall (42) of the first buffer chamber (41) opposite the bottom guard plate (1) is further provided with a force transmission rib (423), and a third included angle γ is formed between the first reinforcing rib (421) and the force transmission rib (423), and the third included angle γ is an acute angle.

11. The battery pack according to claim 1, wherein a gap (5) is provided between the side rail (4) and the bottom protection plate (1) in the first direction (X).