A CTC integrated system

Abstract

This application discloses a CTC integrated system. The system includes a battery pack, a vehicle chassis, and a heat dissipation structure. The battery pack includes N battery modules, which are bonded to the inner wall of an aluminum alloy longitudinal beam of the vehicle chassis. The N battery modules are arranged longitudinally along the vehicle chassis and bonded to the inner wall of the aluminum alloy longitudinal beam. Each battery module includes M square sodium cells. Longitudinal heat dissipation fins are provided on the outer surface of the aluminum alloy longitudinal beam of the vehicle chassis. The battery pack stores energy and provides high-power electricity to the drive motor. The vehicle chassis provides a platform for mounting and fixing all the battery cell modules and conducts heat generated by the square sodium cells during operation. The heat dissipation structure dissipates the heat conducted by the square sodium cells through the inner wall of the aluminum alloy longitudinal beam. This application can reduce the overall vehicle weight and production cost while ensuring effective battery heat dissipation and temperature control.

Description

Technical Field

[0001] This application relates to the field of thermal management technology for power batteries in new energy vehicles, specifically to a CTC integrated system. Background Technology

[0002] Currently, most vehicle power batteries use lithium iron phosphate batteries with an energy density of 180-200Wh / kg. Lithium iron phosphate batteries are the core energy storage component of the traditional Cell to Chassis (CTC) solution. Due to the poor thermal stability of lithium iron phosphate itself, the traditional CTC solution using this cell must be equipped with liquid cooling pipes, water pumps and coolant to achieve forced temperature control. The entire set of newly added liquid cooling components will simultaneously increase the vehicle's weight, the number of parts assembled, and the overall vehicle manufacturing cost. Summary of the Invention

[0003] Based on the above problems, this application provides a CTC integrated system that can reduce the weight of the vehicle and production costs while ensuring battery heat dissipation.

[0004] The embodiments of this application disclose the following technical solutions: A CTC integrated system includes a battery pack, a vehicle chassis, and a heat dissipation structure. The battery pack includes N battery modules, which are longitudinally arranged along the vehicle chassis and bonded to the inner wall of an aluminum alloy longitudinal beam of the vehicle chassis. Each battery module includes M square sodium battery cells. The heat dissipation structure is disposed on the outer surface of the aluminum alloy longitudinal beam of the vehicle chassis. N and M are both positive integers. The battery pack is used to store energy and provide high-power electricity to the drive motor; The vehicle chassis serves as a platform for installing and securing all the battery cell modules, and conducts the heat generated by the square sodium battery cells to the heat dissipation and heat exchange structure. The heat dissipation structure is used to dissipate the heat conducted by the square sodium battery cell through the inner wall of the aluminum alloy longitudinal beam.

[0005] In one possible implementation, the heat dissipation structure includes longitudinal heat dissipation fins or a high emissivity coating; the longitudinal heat dissipation fins are machined on the outer surface of the aluminum alloy longitudinal beams of the vehicle chassis; the high emissivity coating is applied to the outer surface of the aluminum alloy longitudinal beams of the vehicle chassis. The longitudinal heat dissipation fins are used to increase the contact area with the airflow under the vehicle, and quickly dissipate the battery heat through vehicle convection heat exchange to achieve passive heat dissipation without liquid cooling. The high emissivity coating is used to improve the thermal radiation efficiency of the outer surface of the aluminum alloy longitudinal beam in order to dissipate the heat accumulated in the square sodium battery cell. The high emissivity coating is a black chrome coating or a carbon nanotube coating with an emissivity greater than 0.95.

[0006] In one possible implementation, the system further includes multiple elastic pretensioners, which include multiple wave springs or multiple compressible foams; the wave springs or compressible foams are installed at both ends of each battery module. Wave springs or compressible foam are used to apply a constant preload pressure to the battery cell to compensate for the expansion deformation during the charging and discharging process.

[0007] In one possible implementation, the wave spring is made of 17-7 precipitation hardening stainless steel, and the free length of the wave spring is 5-8mm longer than the total length of the battery module. After assembly and compression, the wave spring outputs a preload of 0.8-1.2MPa. The compressible foam is made of silicone foam or melamine foam, and the thickness of the compressible foam is 5-10mm.

[0008] In one possible implementation, the flattest surface of the battery pack is bonded to the inner wall of the aluminum alloy longitudinal beam of the vehicle chassis using a highly thermally conductive structural adhesive.

[0009] In one possible implementation, the high thermal conductivity structural adhesive is incorporating microcapsule phase change material; the core material of the microcapsule phase change material is paraffin wax with a melting point of 45-48℃, and the shell material of the microcapsule phase change material is melamine-formaldehyde resin.

[0010] In one possible implementation, a thermal switch is provided on the inner wall of the aluminum alloy longitudinal beams of the vehicle chassis. The thermal switch is a shape memory alloy sheet with a phase transition temperature of 55°C. The thermal switch is used for: When the temperature of the aluminum alloy longitudinal beam is higher than the phase transition temperature, the thermal switch undergoes bending deformation to press the contact surfaces of each square sodium cell with the aluminum alloy longitudinal beam.

[0011] In one possible implementation, the system is configured with a battery management system (BMS); the BMS is used for: When the battery pack is in a low-temperature environment, the BMS sends a self-heating pulse to the battery pack to generate Joule heat from the internal resistance of the square sodium cells in the battery pack, thereby increasing the temperature of the square sodium cells. The self-heating pulse has a frequency of 1-2 Hz, a discharge rate of 0.3C, and a duration of 30-60 seconds for each pulse.

[0012] In one possible implementation, liquid cooling channels are pre-installed inside the aluminum alloy longitudinal beams of the vehicle chassis; the liquid cooling channels are used for: When a high temperature trigger condition is detected, the micro water pump is started to draw coolant from the storage tank, so that the coolant circulates in the liquid cooling channel. The high-temperature triggering conditions include the temperature of any square sodium battery cell exceeding a first temperature threshold, the vehicle being in a continuous uphill driving condition, or the ambient temperature exceeding a second temperature threshold.

[0013] In one possible implementation, the system further includes a flat heat pipe; the flat heat pipe is embedded between the N battery modules and the inner wall of the aluminum alloy longitudinal beam of the vehicle chassis; the flat heat pipe has an evaporation end and a condensation end, the evaporation end being in close contact with each square sodium battery cell, and the condensation end being embedded at the root of the longitudinal heat dissipation fins; the flat heat pipe is used for: The heat generated by each square sodium cell is absorbed at the evaporation end, and the heat is released to the root of the longitudinal heat dissipation fins through the condensation end.

[0014] Compared with the prior art, this application has the following beneficial effects: This application provides a CTC integrated system, which mainly includes a battery pack, a vehicle chassis, and a heat dissipation structure. The battery pack contains multiple battery modules arranged longitudinally along the chassis. All modules are directly bonded to the inner wall of the aluminum alloy longitudinal beams of the vehicle chassis. Each module is composed of several square sodium battery cells. The heat dissipation structure is integrally machined on the outer wall of the aluminum alloy longitudinal beams. The chassis serves as both the mounting base for supporting and fixing all the battery cell modules and for quickly dissipating the heat generated by the square sodium battery cells during operation. The battery pack stores electrical energy and delivers high-power electricity to the vehicle's drive motor. The heat transferred to the aluminum alloy longitudinal beams can be quickly dissipated through the heat dissipation structure. The entire structure achieves passive battery cooling without the need for liquid cooling components. This application replaces the lithium iron phosphate batteries used in traditional CTCs with square sodium cells. The battery module is attached and fixed to the inner wall of the aluminum alloy longitudinal beam of the chassis. The heat generated by the operation of the battery cell is transferred by the excellent thermal conductivity of the aluminum alloy material, and then dissipated through the heat exchange structure on the outside of the longitudinal beam. This eliminates all additional parts such as liquid cooling pipes, water pumps, and coolant, and completely solves the defects of traditional solutions such as increased vehicle weight, numerous parts, and high manufacturing costs caused by forced liquid cooling structure. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in this embodiment or the prior art, the drawings used in the description of the embodiment or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of a CTC integrated system provided in an embodiment of this application. Detailed Implementation

[0017] To facilitate understanding of the technical solutions provided in the embodiments of this application, the background technology involved in the embodiments of this application will be described below.

[0018] Currently, the mainstream power batteries used in automobiles are lithium iron phosphate batteries with an energy density of 180-200Wh / kg. As the core energy storage carrier of the traditional CTC battery integrated chassis solution, lithium iron phosphate batteries are limited by their thermal stability due to the large amount of heat generated during charging and discharging and the limited heat dissipation capacity. The traditional CTC solution can only rely on liquid cooling pipes, water pumps and coolant to build a forced liquid cooling system to complete the temperature control. The entire set of liquid cooling components not only increases the weight of the vehicle and the number of assembled parts, but also increases the overall vehicle manufacturing cost.

[0019] To address this issue, this application provides a CTC integrated system, comprising a battery pack, a vehicle chassis, and a heat dissipation structure. The battery pack contains multiple battery modules arranged longitudinally along the vehicle chassis. All battery modules are uniformly bonded and fixed to the inner wall of the aluminum alloy longitudinal beams of the vehicle chassis. Each battery module is equipped with several square sodium cells. The heat dissipation structure is integrally formed on the outer surface of the aluminum alloy longitudinal beams. During operation, the battery pack stores electrical energy and outputs high-power electrical energy to the vehicle's drive motor. The vehicle chassis serves as both a load-bearing structure for mounting and fixing all battery cell modules and for conducting the heat generated by the square sodium cells during operation. This heat is then quickly dissipated through the heat dissipation structure, achieving a passive cooling method that does not rely on liquid cooling equipment. This application uses sodium cells to replace lithium iron phosphate batteries to construct a liquid-free CTC integrated system, relying on the chassis's aluminum alloy structure for passive heat dissipation. While ensuring battery temperature control and operational safety, it eliminates the need for liquid cooling pipes, water pumps, and other supporting components, reducing overall vehicle weight and manufacturing costs.

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] See Figure 1 , Figure 1 This is a structural diagram of a CTC integrated system provided in an embodiment of this application.

[0022] like Figure 1The system shown comprises three core components: a battery pack, a vehicle chassis, and a heat dissipation and heat exchange structure. The battery pack, serving as the core for energy storage and output, contains N battery modules, where N ranges from 4 to 6. All battery modules are neatly arranged along the longitudinal direction of the vehicle chassis and are bonded to the inner wall of the aluminum alloy longitudinal beams of the chassis. Each battery module contains M square sodium cells, where M ranges from 16 to 20. Both N and M are positive integers. This cell configuration ensures that the battery pack outputs high-power electricity to meet the drive motor's requirements while balancing the system's energy storage capacity and installation compactness. The heat dissipation and heat exchange structure is correspondingly located on the outer surface of the aluminum alloy longitudinal beams of the vehicle chassis, forming an internal-external correspondence with the battery module installation position, facilitating heat conduction.

[0023] During system operation, the battery pack performs energy storage functions and continuously provides high-power electricity to the vehicle's drive motor to provide power support for vehicle movement; The vehicle chassis not only serves as a load-bearing structure, providing a stable platform for the installation and fixing of all battery modules and ensuring the structural stability of the battery modules during vehicle operation, but also utilizes the excellent thermal conductivity of aluminum alloy to efficiently conduct the heat generated by the square sodium battery cells during operation to the heat dissipation and heat exchange structure on the outer surface. The heat dissipation structure receives the heat generated by the battery cells through the aluminum alloy longitudinal beams and quickly dissipates the heat through corresponding heat dissipation methods, achieving efficient heat dissipation of the battery pack. This ensures that the square sodium battery cells are always within a suitable operating temperature range, avoiding the impact of heat accumulation on cell performance and lifespan. At the same time, this heat dissipation method does not require additional liquid cooling pipes, water pumps, and coolants, achieving passive heat dissipation without liquid cooling. This effectively solves the problems of increased vehicle weight, more parts, and higher costs caused by the traditional CTC solution with supporting liquid cooling components.

[0024] In one possible implementation, the heat dissipation structure of this application can take the form of either longitudinal heat dissipation fins or a high emissivity coating. Both are set on the outer surface of the aluminum alloy longitudinal beams of the vehicle chassis and can be flexibly selected according to the actual use scenario, together achieving the core goal of liquid-free passive heat dissipation.

[0025] The longitudinal heat dissipation fins are directly machined onto the outer surface of the aluminum alloy longitudinal beams. Their core function is to enhance the convective heat transfer effect during driving by increasing the contact area between the aluminum alloy longitudinal beams and the airflow under the vehicle. When the vehicle is driving normally, the rapid airflow generated under the vehicle can fully contact the longitudinal heat dissipation fins and quickly carry away the heat generated by the square sodium battery cells through the aluminum alloy longitudinal beams. This achieves efficient passive heat dissipation without liquid cooling and meets the heat dissipation requirements when the vehicle is driving normally.

[0026] The high emissivity coating is applied to the outer surface of the aluminum alloy longitudinal beam. Black chrome coating or carbon nanotube coating with an emissivity greater than 0.95 is selected. This type of coating can significantly improve the thermal radiation efficiency of the outer surface of the aluminum alloy longitudinal beam. Under conditions such as low vehicle speed, parking without strong convective airflow, and weak convective heat transfer effect at night or on cloudy days, the heat accumulated in the square sodium battery cells can be dissipated by thermal radiation. The radiative heat dissipation power can reach 100-200W / m², which effectively makes up for the deficiency of insufficient heat exchange capacity of longitudinal heat dissipation fins in scenarios with no airflow or low wind speed.

[0027] It should be noted that if a high emissivity coating is used alone as the heat dissipation structure, the longitudinal heat dissipation fins can be eliminated. However, this method has certain limitations in heat dissipation capacity and is only suitable for low-power, low-load application scenarios. It cannot meet the heat dissipation requirements of vehicles operating at high speeds and under high loads. Therefore, in practical applications, a single heat dissipation method or a combination of two methods can be flexibly selected according to the vehicle's operating conditions to ensure heat dissipation reliability in different scenarios. At the same time, there is no need to configure liquid cooling pipes, water pumps, and coolant, which fundamentally solves the problems of increased vehicle weight, more parts, and higher costs caused by the traditional CTC solution with liquid cooling components.

[0028] In one possible implementation, the system further includes multiple elastic pretensioners, which include multiple wave springs or multiple compressible foams; the wave springs or compressible foams are installed at both ends of each battery module. Wave springs or compressible foam are used to apply a constant preload pressure to the battery cell to compensate for the expansion deformation during charging and discharging. In one possible implementation, to further improve the system's structural stability and the battery cell's lifespan, the CTC integrated system of this application is also equipped with multiple elastic pretensioners. These elastic pretensioners can be either wave springs or compressible foam. The multiple elastic pretensioners are installed at both ends of each battery module, forming a cooperative structure with the battery module and the aluminum alloy longitudinal beam of the vehicle chassis to achieve stable protection and pressure compensation for the battery cells.

[0029] The core function of the wave springs or compressible foam is to apply a constant preload pressure to the prismatic sodium cells within the battery module. During charge-discharge cycles, the prismatic sodium cells undergo expansion and contraction deformation due to internal chemical reactions. Without effective pressure compensation, the cells are prone to pressure fluctuations, which can lead to electrical connection failures between cells, affecting the power supply stability of the battery pack. Uneven deformation can also cause structural damage to the cells, shortening their cycle life. By installing wave springs or compressible foam at both ends of each battery module, their elastic properties can continuously provide a uniform and constant preload force to the cells. When the cells expand during charge-discharge, the elastic preload compresses accordingly, absorbing the stress from the deformation and preventing damage from excessive local pressure. When the prismatic sodium cells contract, the elastic preload rebounds promptly, maintaining the preload pressure and ensuring a tight and reliable electrical connection between cells. This effectively prevents electrical connection failures and reduces wear and structural damage caused by deformation fluctuations, thereby extending the cycle life of the prismatic sodium cells.

[0030] In one possible implementation, the elastic preload is divided into two categories: wave springs and compressible foam, each with corresponding material, size, and mechanical parameter standards.

[0031] The wave spring is made of 17-7 precipitation hardening (PH) stainless steel. This material has high strength and excellent fatigue resistance. It can be repeatedly compressed and rebounded for a long time without easily failing. The free length of the wave spring is 5-8mm longer than the overall length of the battery module. After assembly, it will be compressed to fit the end face of the module and stably output a constant preload pressure in the range of 0.8-1.2MPa to continuously constrain the deformation of the battery cell.

[0032] Compressible foam is made of silicone foam or melamine foam. Both types of foam have uniform texture and stable compression and rebound performance. The thickness of a single sheet is uniformly set to 5-10mm. After being filled at both ends of the module, it can evenly distribute the pressure and complete the deformation compensation in conjunction with the expansion and contraction of the battery cell during charging and discharging, thus avoiding the problem of poor conductive contact caused by the sudden increase or decrease of pressure on the battery cell.

[0033] In one possible implementation, the battery pack is fixed to the inner wall of the aluminum alloy longitudinal beam of the vehicle chassis by relying on its maximum flat surface. The two are bonded and assembled by a high thermal conductivity structural adhesive. This bonding method can ensure that the battery module and the aluminum alloy longitudinal beam are tightly bonded, reduce the interface contact thermal resistance, and allow the heat generated by the square sodium battery cell to be quickly transferred to the heat dissipation and heat exchange structure on the outside of the chassis. At the same time, the structural adhesive can also play a role in buffering and shock absorption, insulation and sealing, and improve the overall structural rigidity.

[0034] The high thermal conductivity structural adhesive used is uniformly mixed with microencapsulated phase change material (MicroPCM). The microcapsules adopt a composite encapsulation structure. The inner core material is paraffin wax with a melting point in the range of 45-48℃, and the outer shell material is melamine-formaldehyde resin. The resin shell has good sealing performance and mechanical stability, which can prevent the paraffin wax from leaking or being lost during the phase change process, thus ensuring long-term performance.

[0035] Specifically, when a vehicle experiences rapid acceleration or other operating conditions, the square sodium battery cell discharges at a high current of 3C for a short period and heats up rapidly. Once the temperature of the battery cell conducted to the adhesive layer exceeds 45°C, the paraffin core material inside the microcapsule will undergo a solid-liquid phase transition. During the phase transition, it can absorb a large amount of latent heat of 150-200kJ / kg, quickly absorbing the excess heat generated by the battery cell in a short period of time, effectively suppressing the local temperature rise rate of the battery, avoiding a rapid increase in the temperature of the battery cell in a short period of time, alleviating the problem of instantaneous heat accumulation, and working in conjunction with the continuous heat dissipation of the aluminum alloy chassis and the external heat exchange structure.

[0036] In one possible implementation, a thermal switch is provided on the inner wall of the aluminum alloy longitudinal beams of the vehicle chassis. The thermal switch is a shape memory alloy sheet with a phase transition temperature of 55°C. The thermal switch is used for: When the temperature of the aluminum alloy longitudinal beam is higher than the phase transition temperature, the thermal switch undergoes bending deformation to press the contact surfaces of each square sodium cell with the aluminum alloy longitudinal beam, reducing the contact thermal resistance between the cell and the longitudinal beam from 1.0 cm². K / W decreased to 0.2 cm² K / W enhances heat transfer from the battery cell to the longitudinal beam, improving heat dissipation under high-temperature conditions.

[0037] In one possible implementation, the system is configured with a Battery Management System (BMS); the BMS can execute autonomous temperature control logic based on the real-time ambient temperature of the battery pack. When the ambient temperature of the battery pack is detected to be below -30°C, the BMS will output a self-heating pulse signal to the battery pack. The battery pack will generate Joule heat based on the internal resistance of the square sodium cells to complete the heating operation. The cell temperature can be raised to above -10°C. The entire heating process does not require the addition of external heating elements such as heating films or heating sheets, which simplifies the system structure and reduces the cost of parts and the weight of the vehicle.

[0038] Because sodium batteries have an internal resistance that is 30%-50% higher than that of lithium batteries, they have higher heating efficiency under the same pulse conditions. Therefore, square sodium cells are very suitable for pulse self-heating solutions.

[0039] The self-heating pulse parameters used have been matched and optimized. The pulse frequency is set at 1-2Hz, the discharge rate is 0.3C, and the duration of a single pulse is controlled at 30-60s. These parameters can ensure sufficient heating power to quickly improve the low-temperature charging and discharging performance, while avoiding excessive pulse current that could cause the cell to heat up too much and aggravate internal losses. This enables low-cost low-temperature preheating without an additional heat source in extremely cold environments.

[0040] In one possible implementation, the aluminum alloy longitudinal beams of the vehicle chassis have an integrated liquid cooling channel reserved inside, serving as a backup enhanced heat dissipation structure for the entire heat dissipation system, forming a graded temperature control system that adapts to high and low temperatures and light and heavy loads together with the external heat dissipation and heat exchange structure.

[0041] This liquid cooling channel is matched with a miniature water pump and a storage tank. When the BMS monitoring system determines that a high-temperature trigger condition has been entered, it will immediately drive the miniature water pump to draw coolant from the storage tank. The coolant will then circulate continuously along the liquid cooling channel inside the aluminum alloy longitudinal beam. With the help of the high specific heat capacity of the coolant, it will quickly remove the large amount of heat that has been conducted to the aluminum alloy longitudinal beam and continuously accumulated by the square sodium battery cells through the high thermal conductivity structural adhesive. This will strongly suppress the continuous rise in battery cell temperature and avoid safety hazards such as capacity decay and thermal runaway caused by high temperature.

[0042] The system's preset high-temperature trigger conditions include three types of judgment conditions. The liquid cooling cycle can be activated when any one of these conditions is met: First, the real-time temperature of any square sodium battery cell exceeds the first temperature threshold (e.g., 55℃); second, the vehicle is in a high-load output condition such as continuous uphill driving for a long time, and the continuous high-current discharge of the battery cell intensifies the heat generation; third, the ambient temperature of the vehicle exceeds the second temperature threshold (e.g., 45℃), and natural convection and radiation heat dissipation cannot balance the heat generation in time. At this time, the liquid cooling channel is activated for forced heat exchange, which can make up for the shortcomings of the pure passive heat dissipation structure in the heat dissipation capacity under extreme high temperature and high load scenarios, and take into account the advantages of lightweight without liquid cooling under normal conditions and the safety guarantee of forced cooling under extreme conditions.

[0043] In one possible implementation, the square sodium battery cell used in this application can be set to a size of 150mm×90mm×12mm, but is not limited to thinness and large planar area, which can fully fit the inner wall of the aluminum alloy longitudinal beam. Combined with a high thermal conductivity structural adhesive containing microcapsule phase change material, the interfacial thermal resistance is greatly reduced, and the heat can be efficiently transferred to the heat dissipation and heat exchange structure on the outside of the chassis.

[0044] In one possible implementation, the rated capacity of the square sodium cell can be set, but is not limited to, 35 Ah.

[0045] In one possible implementation, the system further includes a flat heat pipe as a highly efficient heat conduction transition component. The flat heat pipe is integrally embedded between each battery module and the inner wall of the aluminum alloy longitudinal beam of the vehicle chassis. The overall thickness of the heat pipe is controlled at 2-3mm, and the equivalent thermal conductivity is greater than 5000W / m. K features ultra-efficient axial heat conduction; the flat heat pipe is divided into two sections: an evaporation end and a condensation end. The layout adopts a partitioned bonding design. The evaporation end is closely bonded to the surface of each square sodium cell, which can capture the heat generated during the charging and discharging process of the cell at close range. The condensation end extends and is embedded at the root of the longitudinal heat dissipation fins, directly transferring heat to the convection heat transfer core area.

[0046] During operation, the flat heat pipe relies on the phase change of its internal working fluid to achieve rapid heat transfer. After absorbing the heat accumulated by the square sodium battery cell at the evaporation end, it is quickly conducted to the condensation end and released to the root of the longitudinal heat dissipation fins. This greatly reduces the thermal resistance caused by the multi-layer interface of the battery cell, structural adhesive, and aluminum alloy longitudinal beams, significantly improving the overall cross-interface thermal conductivity. On the one hand, the flat heat pipe can quickly equalize the temperature distribution of each battery cell within the same module, reduce the temperature difference between the cells, and avoid long-term overheating and accelerated degradation of local cells. On the other hand, it can concentrate the heat to the heat exchange core of the longitudinal heat dissipation fins, fully amplifying the heat exchange capacity of the chassis's passive convection cooling.

[0047] With the addition of this flat heat pipe, the upper limit of the entire passive heat dissipation system is greatly improved, which can stably support the continuous high-power discharge of the battery cell at 3-4C, making up for the shortcomings of insufficient heat dissipation in high-rate continuous discharge scenarios relying solely on structural adhesive for heat conduction and fin air cooling.

[0048] This application uses square sodium cells to replace lithium iron phosphate batteries, and directly attaches the battery module to the inner wall of the aluminum alloy longitudinal beam of the vehicle chassis. The heat generated by the square sodium cells is conducted by the aluminum alloy longitudinal beam, and the heat dissipation structure set on the outside of the longitudinal beam is used to achieve rapid heat dissipation. There is no need to configure additional liquid cooling pipes, water pumps and coolant-related components, thus eliminating the problems of high weight, number of parts and high production cost caused by the traditional solution with liquid cooling components from the source.

[0049] The CTC integrated system provided in this application has been described in detail above. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0050] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0051] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A CTC integrated system, characterized in that, The system includes a battery pack, a vehicle chassis, and a heat dissipation structure. The battery pack includes N battery modules, which are arranged longitudinally along the vehicle chassis and bonded to the inner wall of the aluminum alloy longitudinal beams of the vehicle chassis. Each battery module includes M square sodium cells. The heat dissipation structure is disposed on the outer surface of the aluminum alloy longitudinal beams of the vehicle chassis. Both N and M are positive integers; The battery pack is used to store energy and provide high-power electricity to the drive motor; The vehicle chassis is used to provide a platform for installing and fixing all the battery cell modules, and to conduct the heat generated by the square sodium battery cells to the heat dissipation and heat exchange structure. The heat dissipation structure is used to dissipate the heat conducted by the square sodium battery cell through the inner wall of the aluminum alloy longitudinal beam.

2. The system according to claim 1, characterized in that, The heat dissipation structure includes longitudinal heat dissipation fins or a high emissivity coating; the longitudinal heat dissipation fins are machined on the outer surface of the aluminum alloy longitudinal beams of the vehicle chassis; the high emissivity coating is applied to the outer surface of the aluminum alloy longitudinal beams of the vehicle chassis. The longitudinal heat dissipation fins are used to increase the contact area with the airflow under the vehicle, and quickly dissipate the battery heat through vehicle convection heat exchange to achieve passive heat dissipation without liquid cooling. The high emissivity coating is used to improve the thermal radiation efficiency of the outer surface of the aluminum alloy longitudinal beam, so as to dissipate the heat accumulated in the square sodium battery cell. The high emissivity coating is a black chrome coating or a carbon nanotube coating with an emissivity greater than 0.

95.

3. The system according to claim 1, characterized in that, The system also includes multiple elastic pretensioners, which include multiple wave springs or multiple compressible foams; the wave springs or compressible foams are installed at both ends of each battery module. Wave springs or compressible foam are used to apply a constant preload pressure to the battery cell to compensate for the expansion deformation during the charging and discharging process.

4. The system according to claim 3, characterized in that, The wave spring is made of 17-7 precipitation hardening stainless steel. The free length of the wave spring is 5-8mm longer than the total length of the battery module. After assembly and compression, the wave spring outputs a preload of 0.8-1.2MPa. The compressible foam is made of silicone foam or melamine foam, and the thickness of the compressible foam is 5-10mm.

5. The system according to claim 1, characterized in that, The flattest surface of the battery pack is bonded to the inner wall of the aluminum alloy longitudinal beam of the vehicle chassis using a high thermal conductivity structural adhesive.

6. The system according to claim 5, characterized in that, The high thermal conductivity structural adhesive contains microcapsule phase change material; the core material of the microcapsule phase change material is paraffin wax with a melting point of 45-48℃, and the shell material of the microcapsule phase change material is melamine-formaldehyde resin.

7. The system according to claim 1, characterized in that, The inner wall of the aluminum alloy longitudinal beams of the vehicle chassis is equipped with a thermal switch, which is a shape memory alloy sheet with a phase transition temperature of 55°C; the thermal switch is used for: When the temperature of the aluminum alloy longitudinal beam is higher than the phase transition temperature, the thermal switch undergoes bending deformation to press the contact surfaces of each square sodium cell with the aluminum alloy longitudinal beam.

8. The system according to claim 1, characterized in that, The system is equipped with a battery management system (BMS); the BMS is used for: When the battery pack is in a low-temperature environment, the BMS sends a self-heating pulse to the battery pack to generate Joule heat from the internal resistance of the square sodium cells in the battery pack, thereby increasing the temperature of the square sodium cells. The self-heating pulse has a frequency of 1-2 Hz, a discharge rate of 0.3C, and a duration of 30-60 seconds for each pulse.

9. The system according to claim 1, characterized in that, The aluminum alloy longitudinal beams of the vehicle chassis have pre-reserved liquid cooling channels; the liquid cooling channels are used for: When a high temperature trigger condition is detected, the micro water pump is started to draw coolant from the storage tank, so that the coolant circulates in the liquid cooling channel. The high-temperature triggering conditions include the temperature of any square sodium battery cell exceeding a first temperature threshold, the vehicle being in a continuous uphill driving condition, or the ambient temperature exceeding a second temperature threshold.

10. The system according to claim 1, characterized in that, The system also includes a flat heat pipe; the flat heat pipe is embedded between the N battery modules and the inner wall of the aluminum alloy longitudinal beam of the vehicle chassis; the flat heat pipe has an evaporation end and a condensation end, the evaporation end being in close contact with each square sodium battery cell, and the condensation end being embedded in the root of the longitudinal heat dissipation fins; the flat heat pipe is used for: The heat generated by each square sodium cell is absorbed at the evaporation end, and the heat is released to the root of the longitudinal heat dissipation fins through the condensation end.

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