A power battery system based on cylindrical cells

Abstract

The present invention discloses a power battery system based on cylindrical cells, comprising a lower tray (100); a plurality of battery modules (200) are placed on the top of the lower tray (100); each battery module (200) comprises two brackets (5) spaced apart from each other; each bracket (5) has a plurality of rows of cylindrical holes from top to bottom, and each cylindrical hole in each row of cylindrical holes contains a longitudinally distributed cylindrical cell (1); a serpentine tube (4) is provided between any two adjacent rows of cylindrical holes; the left and right ends of each bracket (5) respectively have vertically distributed, hollow end tubes (3); the left and right ends of each serpentine tube (4) are respectively connected to an end tube (3). The present invention can reliably and effectively perform reliable thermal management on the cylindrical battery system, timely cool and heat the battery cells, control the temperature difference between the battery cells, and ensure the temperature uniformity of the battery system.

Description

Technical Field

[0001] The present invention relates to the technical field of power batteries for new energy vehicles, and in particular to a power battery system based on cylindrical battery cells. Background Art

[0002] Currently, the primary energy source for new energy vehicles globally is batteries, particularly lithium batteries. The foundational technologies for various new electric vehicles remain the three-electric (electric, battery, and system) technologies, particularly lithium battery technology, encompassing both lithium battery cell technology and battery system technology. Cell types are broadly categorized into round, square, and pouch cells.

[0003] Compared with square or soft-pack battery systems, the main difficulty of cylindrical battery systems lies in the large number of battery cells and the heavy task of intelligent battery cell management. In particular, each battery cell requires thermal management, and each cylindrical battery cell module needs to integrate thermal management.

[0004] However, there is currently no technology that can reliably and effectively perform thermal management on cylindrical battery systems, timely cool and heat the battery cells, control the temperature difference between battery cells, and ensure the temperature uniformity of the battery system. Summary of the Invention

[0005] The purpose of the present invention is to provide a power battery system based on cylindrical battery cells in order to address the technical defects existing in the prior art.

[0006] To this end, the present invention provides a power battery system based on cylindrical cells, comprising a lower tray;

[0007] Multiple battery modules are placed on top of the lower tray;

[0008] Each battery module includes two brackets spaced apart in front and back;

[0009] Each bracket has multiple rows of cylindrical holes from top to bottom, and each cylindrical hole in each row of cylindrical holes contains a longitudinally distributed cylindrical battery cell;

[0010] A serpentine tube is provided between any two adjacent rows of cylindrical holes;

[0011] Each bracket has vertically distributed, hollow end tubes at the left and right ends respectively;

[0012] The left and right ends of each serpentine tube are respectively connected to an end tube.

[0013] The upper part or the lower part of each end pipe is connected to a joint.

[0014] The left and right ends of each serpentine tube are respectively connected to an end tube and welded.

[0015] The joint and the end pipe are interference-fitted.

[0016] The end pipe is composed of a main pipe, a main pipe head, a plug and a branch pipe head, wherein the plug is welded or bonded to the main pipe, the main pipe head is welded to the main pipe, and the branch pipe head is welded to the main pipe.

[0017] The serpentine tube includes a hollow middle branch tube, and the outside of the middle branch tube is wrapped with thermal conductive glue.

[0018] Among them, there is a main pipeline on the left and right sides of the bracket respectively;

[0019] The multiple joints located at the left and right ends of the bracket are respectively connected to the adjacent main pipelines.

[0020] Wherein, the lower tray includes a bottom plate as a whole composed of multiple bottom plates;

[0021] The rear end edge of the bottom plate is fixed with a transversely distributed main pipe beam;

[0022] A plurality of longitudinal beams are fixedly provided on the left and right edges of the bottom plate;

[0023] Crossbeams are fixedly arranged at the middle and front end of the bottom plate.

[0024] Among them, a heat management main joint is installed on the side of the main pipe beam at the rear end of the lower tray;

[0025] The thermal management main joint is connected to the main pipeline;

[0026] The thermal management main connector has two interfaces.

[0027] Among them, the side of the main pipe beam at the rear end of the lower tray is also installed with high-voltage devices, total positive and negative connectors and communication connectors;

[0028] High voltage devices are conductively connected to the total positive and negative terminals;

[0029] The top of the battery module is equipped with series rows;

[0030] The exterior of the plurality of battery modules is covered with an upper cover;

[0031] A plurality of second lifting lugs are welded on the longitudinal beam at intervals;

[0032] A first lifting lug is welded to the left and right ends of the rear side surface of the main pipe beam.

[0033] It can be seen from the technical solution provided by the present invention above that, compared with the prior art, the power battery system based on cylindrical cells provided by the present invention can reliably and effectively perform reliable thermal management of the cylindrical battery system, timely cool and heat the battery cells, control the temperature difference between the battery cells, ensure the temperature uniformity of the battery system, can form industrial scale, is conducive to wide application, and has important production practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the overall structure of a power battery system based on cylindrical cells provided by the present invention.

[0035] Figure 2 This is a schematic diagram of the overall structure of a cylindrical cell-based power battery system provided by the present invention when the upper cover is not fastened.

[0036] Figure 3 A top view of a cylindrical cell-based power battery system provided by the present invention without the upper cover fastened.

[0037] Figure 4 This is a front view of the assembled battery module located at the front of a power battery system based on cylindrical batteries provided by the present invention.

[0038] Figure 5 This is a front view of the assembled battery module located in the middle of a power battery system based on cylindrical batteries provided by the present invention.

[0039] Figure 6 This is a front view of the assembled battery module located at the rear of a power battery system based on cylindrical batteries provided by the present invention.

[0040] Figure 7 This is a schematic assembly diagram of a thermal management structure of a battery module in a power battery system based on cylindrical batteries provided by the present invention.

[0041] Figure 8 A front view of an end tube in a power battery system based on cylindrical battery cells provided by the present invention.

[0042] Figure 9 A side view of an end tube in a power battery system based on cylindrical cells provided by the present invention.

[0043] Figure 10 A top view of an end tube in a power battery system based on cylindrical cells provided by the present invention.

[0044] Figure 11 This is an enlarged schematic diagram of a serpentine tube in a power battery system based on cylindrical batteries provided by the present invention.

[0045] Figure 12 This is a schematic diagram of the assembly of a thermal management structure in a power battery system based on cylindrical batteries provided by the present invention.

[0046] Figure 13 This is a schematic diagram of the assembly of a lower tray and lifting ears in a power battery system based on cylindrical batteries provided by the present invention. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and implementation methods.

[0048] See also Figures 1 to 13 , the present invention provides a power battery system based on cylindrical cells, comprising a lower tray 100;

[0049] A plurality of battery modules 200 are placed on top of the lower tray 100;

[0050] Each battery module 200 includes two brackets 5 spaced apart in front and back;

[0051] Each bracket 5 has multiple rows of cylindrical holes from top to bottom, and each cylindrical hole in each row of cylindrical holes contains a longitudinally distributed cylindrical battery cell 1;

[0052] A serpentine tube 4 is provided between any two adjacent rows of cylindrical holes.

[0053] Each bracket 5 has vertically distributed hollow end tubes 3 at the left and right ends respectively.

[0054] The left and right ends of each serpentine tube 4 are connected to an end tube 3 respectively.

[0055] In the present invention, in a specific implementation, the upper part or the lower part of each end pipe 3 is connected to a joint 2 .

[0056] It should be noted that, in practice, the left and right ends of each serpentine tube 4 are respectively plugged and welded to an end tube 3 to ensure a reliable seal between the serpentine tube 4 and the end tube 3. The joint 2 and the end tube 3 have an interference fit to maintain a reliable seal. Multiple serpentine tubes 4 are connected in parallel to form the module thermal management component.

[0057] In the present invention, the specific implementation is as follows: Figures 4 to 6 As shown, the battery module 200 may have Figures 4 to 6 Of course, there may be other structures, including different numbers of battery cells, not limited to the number shown in the figure.

[0058] exist Figures 4 to 6In the figure, the three structures of battery modules include 7 strings, 3 strings and 11 strings of battery cells respectively. In actual applications, they are located in the front, middle and rear of the system respectively. The internal structure of the module is the same. Each module is composed of a battery cell 1, a connector 2, an end tube 3, a serpentine tube 4 and a bracket 5. Each string is composed of multiple battery cells in parallel, and the protection range is not limited to the number of battery cells shown in the figure. Each module contains two connectors 2, two end tubes 3, two brackets 5 and multiple serpentine tubes 4. The number of serpentine tubes 4 is determined according to the system height space and battery cell size, and is not limited to the five serpentine tubes shown in the figure.

[0059] In specific implementation, the two left and right connectors 2 are respectively the liquid inlet connector and the liquid outlet connector, and the positions of the two connectors can be Figures 4 to 6 The position shown, or diagonally from the end tube 3, is also possible. All serpentine tubes 4 are parallel pipes within the module, with either left-inlet and right-outlet or right-inlet and left-outlet. Heat exchange fluid flows through the serpentine tubes 4, exchanging heat with the outer cylindrical surface of the battery cell 1 through the tube walls. Each battery module has two brackets 5, each with two bolt holes on the left and right ends for securing the module to the beams on both sides of the lower tray 100.

[0060] It should be noted that, in the specific implementation of the power battery system of the present invention, three battery modules with different structures can be used, which are located at the front, middle and rear positions of the power battery system respectively, and liquid pipes are connected in parallel inside all modules.

[0061] In the present invention, the specific implementation is as follows: Figures 8 to 10 As shown, the end pipe 3 is composed of a main pipe 300, a main pipe head 301, a plug 302 and a branch pipe head 303, wherein the plug 302 is welded or bonded to the main pipe 300, the main pipe head 301 is welded to the main pipe 300, and the branch pipe head 303 is welded to the main pipe 300.

[0062] In the present invention, the specific implementation is as follows: Figure 11 As shown, the serpentine tube 4 includes a hollow middle branch tube 400 , and the outside of the middle branch tube 400 is wrapped with heat-conducting glue 401 .

[0063] It should be noted that the power battery system provided by the present invention adopts a cylindrical battery cell and three sizes of battery modules. The modules have the same structural form and are located at the front, middle and rear of the system respectively. Each module is equipped with a serpentine tube for battery cell thermal management. The thermal management pipelines inside all modules are connected in parallel to ensure fast, efficient and temperature uniformity of thermal management of all battery cells.

[0064] In the present invention, the specific implementation is as follows: Figures 4 to 6 As shown, for the present invention, when the battery module is assembled, the battery cell 1 is positioned in the cylindrical hole of the bracket 5, and the bracket 5 is usually made of insulating material (such as engineering plastic injection molding) and is used. Figures 9 to 10The branch head 303 shown is Figure 11 The intermediate branches 400 are connected and then welded together. Figure 7 The overall components of the thermal management structure of a battery module are shown.

[0065] Figure 4 The thermal management structure of the battery module shown is inserted as a whole between 4 and Figure 6 Between the cells 1 shown, Figure 1 Another bracket 5 (hidden in the figure) is buckled on the position along the perspective direction. Finally, on the outside of the bracket 5, traditional methods such as nickel sheets can be used to connect the cylindrical battery cells in series and parallel. Individual holes on the bracket 5 can be used to replace the battery cells with bolts to connect the brackets 5 on the front and rear sides of the battery cell 1. At this time, the assembly of a battery module is completed.

[0066] In the present invention, in a specific implementation, there is a main pipeline 6 on the left and right sides of the bracket 5 respectively;

[0067] The multiple joints 2 located at the left and right ends of the bracket 5 are respectively connected to the adjacent main pipelines 6.

[0068] In a specific implementation, the lower tray 100 includes a bottom plate as a whole composed of multiple bottom plates 16 (adjacent bottom plates 16 can be welded together, and the bottom plates 16 are fixedly connected by being welded to the cross beams and longitudinal beams respectively);

[0069] A transversely distributed main pipe beam 7 is fixedly provided (e.g., welded) on the rear end edge of the bottom plate as a whole;

[0070] A plurality of longitudinal beams 14 are fixedly provided on the left and right edges of the bottom plate;

[0071] A crossbeam 13 is fixedly provided at the middle and front end of the entire bottom plate.

[0072] Specifically, a heat management main joint 8 is installed on the side of the main pipe beam 7 at the rear end of the lower tray 100;

[0073] The thermal management main joint 8 is connected to the main pipeline 6.

[0074] It should be noted that the thermal management main connector 8 has two interfaces, serving as a liquid inlet and a liquid outlet, for the flow of heat exchange liquid for heating or cooling. The heat exchange liquid can be a flame retardant coolant or other existing heat exchange liquid used in battery modules.

[0075] Specifically, the two interfaces of the thermal management main connector 8 can be connected to the liquid outlet and liquid inlet of a water pump through a hollow connecting pipe. The main pipe 6, the thermal management main connector 8, and the connecting pipe are pre-injected with heat exchange liquid. The function of the water pump is to provide circulation power to the coolant in the water pipe and the connecting pipe, thereby ensuring that the heat exchange liquid can flow through the main pipe 6, the thermal management main connector 8, and the connecting pipe, and to control the flow rate of the heat exchange liquid. Specifically, the water pump can be a conventional existing cooling pump, for example, the same cooling pump commonly used in ordinary automobiles.

[0076] Specifically, the side of the main pipe beam 7 at the rear end of the lower tray 100 is also equipped with a high-voltage device 17, a total positive and negative connector (i.e., a charging and discharging connector) 9, and a communication connector 10;

[0077] The high-voltage device 17 is electrically connected to the total positive and negative terminals 9 .

[0078] In a specific implementation, a series row 18 is installed on the top of the battery module 200 .

[0079] Figure 12 This is an assembly diagram of the thermal management structure of the power battery system provided by the present invention. The main pipeline 6 for the cooling liquid or heating liquid in and out of the power battery system is used to connect the liquid management systems of all modules in parallel. The various serpentine tubes 4 of the entire system are connected in parallel to the main pipeline 6 through various joints 2. The main pipeline 6 is connected to the main pipe beam 7. The liquid used for heat exchange circulates inside the main pipe beam 7, and there is an intermediate isolation at the thermal management main joint 8. The liquid enters and exits the thermal management main joint 8 to realize heat exchange between the Pack system and the entire vehicle.

[0080] Figure 13 This is an assembly diagram of the lower tray and lifting lugs of the power battery system of the present invention. Before the system is installed with modules, the lower tray 100 is assembled first. The assembly of the lower tray 100 is mainly welding (the joints are fixed with bolts). It is the main load-bearing member of the battery system and is mainly composed of a main pipe beam 7, a thermal management main joint 8, a total positive and negative joint (i.e., a charge and discharge joint) 9, a communication joint 10, a C-type first lifting lug 11, a Z-type second lifting lug 12, a cross beam 13, a longitudinal beam 14, connecting bolts 15 and a bottom plate 16.

[0081] Figure 2 and Figure 3 They are respectively an assembly diagram of the power battery system of the present invention and a top view of the system assembly. Figure 13On this basis, all battery modules and thermal management structures in the front, middle and rear positions are installed. As needed, high-voltage devices 17 are installed at the rear end of the system, and series rows 18 are installed above the modules. The total positive and negative of the batteries are connected to the high-voltage devices 17. The thermal management main connector 8, the total positive and negative output connectors 9 and the communication connector 10 are all installed at the rear end of the system according to the needs of the entire vehicle.

[0082] In the present invention, in a specific implementation, the exterior of the plurality of battery modules 200 is covered with an upper cover 19 .

[0083] In the present invention, in a specific implementation, a plurality of second lifting lugs 12 are welded to the longitudinal beam 14 at intervals;

[0084] A first lifting lug 11 is welded to the left and right ends of the rear side surface of the main pipe beam 7 respectively.

[0085] Figure 1 This is the overall assembly structure diagram of the power battery system mentioned in the present invention. Figure 7 and Figure 8 On the basis, buckle the upper cover 19, the entire battery system is mechanically connected to the chassis frame of the vehicle through the bolts 15 on the lifting ears, the thermal management main connector 8 is connected to the thermal management system of the new energy vehicle, and the battery thermal management control is realized through liquid heat exchange; the total positive and negative output connectors 9 are connected to the motor controller and charger of the new energy vehicle to realize battery discharge and charging; the communication connector 10 is connected to the vehicle controller of the new energy vehicle to realize CAN bus communication control.

[0086] In the present invention, in terms of specific implementation, the present invention is a parallel thermal management system, which greatly improves the thermal management efficiency and helps to reduce the temperature difference of the battery cells. After simulation, the initial temperature of the battery system is 32°C, and it is charged at a rate of 0.5C. The liquid temperature at the inlet of each module is 25°C and the flow rate is 0.3m / s. The inlet diameter is 10mm, that is, under the initial conditions of module flow rate 1.4L / min and system flow rate 23.8L / min, after 18 minutes of simulation, the battery temperature dropped to about 26°C, the temperature difference of the battery cells in the module was controlled within 1°C, and the temperature difference of the whole system was controlled within 3°C. The initial temperature of the simulated battery is 32°C, and it is fast charged at a rate of 1C. Using the same liquid flow rate as mentioned above, after 20 minutes, the battery temperature dropped to about 26°C, the temperature difference of the battery cells in the module was controlled within 3°C, and the temperature difference of the whole system was controlled within 5°C. Both working conditions maintain the consistency of the working environment of the battery cells and extend the working life of the system.

[0087] In order to more clearly understand the technical solution of the present invention, it is described below with reference to specific embodiments.

[0088] like Figure 1 、 2As shown in Figure 3, this embodiment uses 4.5Ah-21700 cylindrical cells, and the entire system uses 23 parallel and 135 series, abbreviated as 23P135S. Figures 4 to 6 As shown, each string in the battery module has 25 cylindrical hole positions, 23 of which are used to connect 23 battery cells in parallel, and the other two positions are used to install built-in bolts for connecting the brackets 5 between the front and rear sides of the battery module.

[0089] exist Figure 1 and Figure 2 In the power battery system, three types of battery modules are arranged at the front, middle and rear, namely 23P7S modules (9 modules), 23P3S modules (2 modules), and 23P11S modules (6 modules). The battery modules are connected to the lower tray via bolts on the left and right sides of the bottom of the bracket 5. The two brackets on the front and back sides of each battery module have a total of eight bolt fixing holes reserved. The battery modules are electrically connected in series via the series row 18. The main pipes 6 for the heat exchange liquid in and out are located on the left and right sides of the power battery system and are connected to the connector 2 of each battery module, thus forming a thermal management system with parallel pipes for the entire system. The cooling or heating liquid (i.e., the heat exchange liquid) flows through each parallel serpentine tube 4. After simulation, the temperature difference of the entire system is within 3°C when charging at a 0.5C rate, and within 5°C when charging at a 1C rate.

[0090] In terms of specific implementation, the nominal voltage of a single cell is 3.65V, and the capacity is 4.5Ah. The total nominal voltage of the entire power battery system is 135*3.65=492.75V, the total nominal capacity is 4.5*23=103.5Ah, the total nominal energy is 492.75*103.5≈51kWh, the weight of the entire system is 359kg (excluding C-type and Z-type lifting ears), and the nominal energy density of the entire system is 51000 / 359=142Wh / kg.

[0091] In actual assembly, Figure 13 The base plate 16 can be friction stir welded with profiles, while the main pipe beam 7, longitudinal beams 14, and cross beams 13 can be welded with profiles to form the main load-bearing structure. First, the battery modules, thermal management structure, and series array are installed, followed by the high-voltage and BMS (battery management system) components. In this embodiment, these components are located at the rear end of the system. The specific interface installation locations can be adjusted based on the system's external requirements.

[0092] See also Figure 1 As shown, the upper cover 19 can be stamped from aluminum or formed from SMC, or molded from a carbon fiber mold to reduce weight. It is secured with traditional bolts and sealed to IP67. The C-shaped first lifting lug 11 and the Z-shaped second lifting lug 12 are cast or machined parts. Connecting bolts 15 allow the battery system to be hoisted underneath the chassis of a new energy vehicle.

[0093] For the present invention, the entire power battery system can adopt 4.5Ah 21700 power cells, combined with a full-module parallel thermal management system, because thermal management is more efficient, and the temperature difference control of the cell is easier, the spatial structure of the whole system is relatively regular, the thermal management main pipeline is located on the left and right, the actual manufacturing and space utilization are relatively reasonable, the spatial heat dissipation is relatively uniform, and the temperature difference of the whole system is controlled within 3°C when the charge and discharge rate is 0.5C (generally within 6°C), so that all cells can work in a more similar environment for a long time, and when the external low temperature is -20°C, the liquid in the parallel branch is quickly heated to ensure that each cell quickly works above 0°C. That is, the full-system parallel thermal management system provided by the present invention extends the battery life and ensures the safe operation of the vehicle for 10 years or 200,000 kilometers. See Table 1 below.

[0094] Table 1: Performance parameters of the power battery system of the present invention in the embodiment.

[0095]

[0096] Therefore, in summary, compared with the existing technology, the present invention provides a power battery system based on cylindrical battery cells, which can reliably and effectively perform reliable thermal management of the cylindrical battery system, timely cool and heat the battery cells, control the temperature difference between the battery cells, ensure the temperature uniformity of the battery system, can form industrial scale, is conducive to wide application, and has important production practical significance.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A power battery system based on cylindrical cells, characterized in that: The invention comprises a lower tray (100); a plurality of battery modules (200) are placed on the top of the lower tray (100); each battery module (200) comprises two brackets (5) spaced apart from each other; a plurality of rows of cylindrical holes are opened from top to bottom in each bracket (5), and a longitudinally distributed cylindrical battery cell (1) is placed in each cylindrical hole in each row of cylindrical holes; a serpentine tube (4) is provided between any two adjacent rows of cylindrical holes, and a plurality of serpentine tubes (4) are connected in parallel to form a module thermal management component as a whole; a heat exchange liquid flows in the serpentine tube (4) and exchanges heat with the outer cylindrical surface of the battery cell (1) through the tube wall of the serpentine tube (4); the left and right ends of each bracket (5) are respectively provided with vertically distributed, hollow end tubes (3); the left and right ends of each serpentine tube (4) are respectively connected to an end tube (3); two bolt holes are left at the left and right ends of the bottom of each bracket (5) for fixing the battery module to the beams on both sides of the lower tray (100); the bracket (5) There is a main pipe (6) on each of the left and right sides, and a series row (18) is installed on the top of the battery module (200); the upper part or the lower part of each end pipe (3) is connected to a joint (2); a plurality of joints (2) located at the left and right ends of the bracket (5) are respectively connected to the adjacent main pipes (6); a heat management main joint (8) is installed on the side of the main pipe beam (7) located at the rear end of the lower tray (100); the heat management main joint (8) is connected to the main pipe (6); the heat management main joint (8) has two interfaces.

2. The power battery system based on cylindrical cells according to claim 1, characterized in that: The left and right ends of each serpentine tube (4) are respectively connected to an end tube (3) and welded.

3. The power battery system based on cylindrical cells according to claim 1, characterized in that: The joint (2) and the end pipe (3) are interference-fitted.

4. The power battery system based on cylindrical cells according to claim 1, characterized in that: The end pipe (3) is composed of a main pipe (300), a main pipe head (301), a plug (302) and a branch pipe head (303), wherein the plug (302) is welded or bonded to the main pipe (300), the main pipe head (301) is welded to the main pipe (300), and the branch pipe head (303) is welded to the main pipe (300).

5. The power battery system based on cylindrical cells according to claim 1, characterized in that: The serpentine tube (4) comprises a hollow middle branch tube (400), and the outside of the middle branch tube (400) is wrapped with heat-conducting glue (401).

6. The power battery system based on cylindrical cells according to claim 1, characterized in that: The lower tray (100) comprises a bottom plate unit composed of a plurality of bottom plates (16); a transversely distributed main pipe beam (7) is fixedly provided at the rear end edge of the bottom plate unit; a plurality of longitudinal beams (14) are fixedly provided at the left and right side edges of the bottom plate unit; and a cross beam (13) is fixedly provided at the middle and front end of the bottom plate unit.

7. The power battery system based on cylindrical cells according to claim 1, characterized in that: A high-voltage device (17), a total positive and negative connector (9), and a communication connector (10) are also installed on the side of the main pipe beam (7) located at the rear end of the lower tray (100); the high-voltage device (17) is conductively connected to the total positive and negative connector (9); the external cover of the multiple battery modules (200) has an upper cover (19); a plurality of second lifting lugs (12) are welded to the longitudinal beam (14) at intervals; and a first lifting lug (11) is welded to the left and right ends of the rear side of the main pipe beam (7).

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