Battery liquid cooling plate as well as hot melting connection mold and hot melting connection method thereof
Through the hot-melt molding process, the runner plate of plastic or composite material and metal plates are combined with metal plates, which solves the problems of missing welding and low welding joint strength of the liquid-cooled plates in the brazing process of electric vehicle battery, and achieves higher heat exchange effect and lower production costs of the liquid-cooled plates, extending the service life of batteries and electric vehicles.
Patent Information
- Application Number
- CN202510078347.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-17
- Publication Date
- 2025-05-06
AI Technical Summary
During the brazing process, existing electric vehicle battery liquid-cooled plates have problems such as local welding leakage, risk of cooling medium leakage, and low strength of welding joints. At the same time, the liquid-cooled plates are heavy and have high production costs, which affects the safety and range of the battery pack.
The hot-melt molding process is adopted to combine the runner plate of plastic or non-metal composite material with the metal plate through hot-melt connection, and design a roundabout and coiled groove and cooling medium flow channel to improve connection reliability and heat exchange effect.
The rapid flow of cooling medium in the runner channel of the liquid-cooled plate is achieved, the connection reliability between the runner plate and the metal plate is enhanced, the weight and production cost of the liquid-cooled plate are reduced, and the working life of the battery and the range of the electric vehicle are extended.
Smart Images
Figure CN119944173A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of electric vehicle batteries, in particular to a battery liquid cooling plate of an electric vehicle, a hot-melt connection mold and a hot-melt connection method thereof. Background Art
[0002] The battery pack is the core component of the new energy electric vehicle drive system. Considering the range of electric vehicles, the OEM has put forward higher requirements for battery power and fast charging performance. In this case, how to quickly remove the heat generated by the battery, cool the battery pack, and ensure the safety performance of the battery is particularly important. At present, the mainstream cooling method for battery packs is liquid cooling, that is, the heat of the battery pack is achieved by the flow of cooling medium in the liquid cooling plate flow channel. Therefore, it is of great significance to reasonably design the flow channel of the liquid cooling plate and select the appropriate cold plate material to enhance the heat dissipation effect of the battery and extend the service life of the battery pack.
[0003] Brazing is a process method that uses a metal material with a lower melting point than the workpiece to be welded as a brazing material, heats the workpiece and the brazing material to a temperature higher than the melting point of the brazing material and lower than the melting point of the workpiece, and uses the liquid brazing material to wet the workpiece, fill the interface gap and achieve mutual diffusion of atoms with the workpiece, thereby achieving welding. The traditional electric vehicle battery liquid cooling plate is composed of two stamped metal plates combined into one by a brazing process. Due to the constraints of processing technology and material properties, the existing battery liquid cooling plate has the following two defects: First, during the brazing process, the workpiece needs to be wetted after the brazing material is melted, and there is a problem of local welding leakage due to insufficient wetting, which leads to the risk of cooling medium leakage; at the same time, because the brazing heating temperature is lower than the melting point of the workpiece, a corrosive brazing flux needs to be added to improve the welding effect. The residual brazing flux after brazing is difficult to be completely removed, thereby reducing the strength of the welded joint, causing corrosive defects at the welded joint, and increasing the risk of cooling medium leakage; in addition, the brazing smoke contains harmful substances such as tin, lead, rosin, and acid dust, which pollute the atmospheric environment. Second, the runner plate of the liquid cooling plate is usually made of metal materials such as aluminum or copper. The stamping process limits the thickness range of the plate and the minimum width of the runner, which increases the production cost and increases the weight of the liquid cooling plate, which has a negative impact on the vehicle's cruising range. Summary of the invention
[0004] The present invention provides a battery liquid cooling plate, a hot-melt connection mold and a hot-melt connection method thereof, aiming to achieve rapid flow of cooling medium in the liquid cooling plate flow channel, enhance reliability of connection between the flow plate and the metal plate, and reduce weight of the liquid cooling plate through optimized design of a flow channel plate structure of non-metallic materials and a hot-melt connection mold thereof, and to extend battery service life and electric vehicle range.
[0005] In order to achieve the above object, the present invention adopts the following technical scheme: A battery liquid cooling plate comprises a flow channel plate and a flat plate; the flow channel plate is provided with a winding groove, and the flow channel plate is molded by plastic or non-metallic composite materials; the flat plate is provided with a liquid inlet and a liquid outlet, and the liquid inlet and the liquid outlet are respectively located at the two ends of the diagonal of the flat plate, and the flat plate is made of metal; the flow channel plate and the flat plate are integrated into one by a hot melt molding process, and a cooling medium guide channel connected to the liquid inlet and the liquid outlet is formed between the groove of the flow channel plate and the flat plate, and a plurality of groups of mounting holes for realizing the assembly of the battery liquid cooling plate and the battery shell are arranged in the non-cooling medium guide channel area.
[0006] The battery liquid cooling plate has a wall thickness of δ=0.8-2.5 mm, a transition fillet radius R between the bottom surface of the groove and the side wall of the flow channel plate of 1-10 mm, and a minimum width Wmin=3 mm of the cooling medium guide channel.
[0007] A battery liquid cooling plate hot melt connection mold is used to realize the hot melt molding operation of the flow channel plate and the flat plate in the above-mentioned battery liquid cooling plate, and it comprises an upper mold, a lower mold, an electric heating element and a temperature control system; the upper mold is provided with a flow channel plate accommodating groove cavity, and an avoidance groove matching the groove on the flow channel plate is arranged on the bottom surface of the flow channel plate accommodating groove cavity, and the depth of the avoidance groove is not less than the depth of the groove on the flow channel plate; the lower mold is provided with a flat plate accommodating groove cavity, and an electric heating element is arranged in the lower mold, and the working state of the electric heating element is controlled by the temperature control system of the mold; after the upper mold and the lower mold are buckled, a molding cavity is formed between the upper mold and the lower mold.
[0008] The above-mentioned battery liquid cooling plate hot melt connection mold is provided with several groups of positioning columns in the flat plate receiving groove cavity of the lower mold, and several groups of positioning holes are provided at the bottom of the flow channel plate receiving groove cavity of the upper mold; the positioning columns and positioning holes match the mounting holes on the battery liquid cooling plate.
[0009] A method for hot-melt connection of a battery liquid cooling plate, using the hot-melt connection mold to integrate the flow channel plate and the flat plate of the battery liquid cooling plate into one, the specific operation steps are as follows: a. Remove impurities and coatings from the surface of the flat plate, clean the surface of the flat plate, and then dry the cleaned flat plate; b. Place the workpiece: place the dried flat plate in the lower mold plate receiving groove cavity of the battery liquid cooling plate hot melt connection mold, and position it by matching the positioning column with the mounting hole opened on the flat plate, and then place the flow channel plate on the flat plate, so that the positioning column passes through the mounting hole opened on the flow channel plate; c. Clamp the mold, buckle the upper mold of the battery liquid cooling plate hot melt connection mold with the lower mold of the battery liquid cooling plate hot melt connection mold, and make the positioning column of the lower mold of the battery liquid cooling plate hot melt connection mold penetrate into the positioning hole of the upper mold of the battery liquid cooling plate hot melt connection mold; d. Heating: The temperature control system of the mold is connected by hot melting of the battery liquid cooling plate to raise the temperature of the metal plate to the set temperature range; e. Pressurize, apply pressure to the hot melt connection mold of the battery liquid cooling plate, and maintain the pressure for a certain period of time; f. Cooling: The temperature of the metal plate is reduced to the set temperature through the hot-melt connection of the battery liquid cooling plate to the temperature control system of the mold or the natural cooling process; g. Take out the workpiece and remove it after opening the mold to complete the hot melt molding operation of the battery liquid cooling plate.
[0010] The above-mentioned battery liquid cooling plate hot melt connection method, in step a, uses a laser cleaning device to clean the surface of the plate. In the above-mentioned hot-melt connection method for the battery liquid cooling plate, in the step d, the temperature of the metal plate is controlled between 155 and 250°C.
[0011] In the above-mentioned battery liquid cooling plate hot melt connection method, in the step e, a pressure of 8 to 12 MPa is applied to the battery liquid cooling plate hot melt connection mold, and the pressure is maintained for no less than 30 seconds.
[0012] The present invention provides a battery liquid cooling plate, wherein the flow channel plate is made of a plastic plate or a composite material plate, and the flat plate is made of an aluminum alloy or other metal material. The two are combined into one by hot-melt connection, and the cooling medium guide channel is reasonably arranged, so that not only the liquid cooling plate has a better heat exchange effect, but also the good insulation properties of the composite material or plastic material are utilized to reduce the transfer of heat in the area that does not require cooling. The present invention also provides a battery liquid cooling plate hot-melt connection mold, which realizes the mass production of battery liquid cooling plates, and through the positioning column of the lower mold, the mounting hole on the workpiece and the positioning hole of the upper mold, the dimensional accuracy of the liquid cooling plate is guaranteed, and the work efficiency and product quality are improved. The battery liquid cooling plate hot-melt connection method of the present invention can realize the connection of different types of materials, has the advantages of high connection strength, simple process, etc., and reduces the production cost. In summary, the present invention achieves the purpose of ensuring the product quality of the liquid cooling plate, reducing production costs, and extending the battery service life and the cruising range of electric vehicles. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 It is a schematic diagram of the structure of the battery liquid cooling plate of the present invention; Figure 2 yes Figure 1 Explosion structure diagram of the liquid cooling plate of the middle battery; Figure 3 is a top view of the battery liquid cooling plate of the present invention; Figure 4 yes Figure 3 Schematic diagram of the AA section structure (enlarged); Figure 5This is an exploded structural diagram of the hot-melt connection mold for the battery liquid cooling plate of the present invention; Figure 6 yes Figure 5 Schematic diagram of the upper mold structure of the hot melt connection mold for the battery liquid cooling plate; Figure 7 This is a schematic diagram of the working state of the hot melt connection mold of the battery liquid cooling plate; Figure 8 yes Figure 7 Enlarged view of the structure at position Ⅰ in the middle.
[0014] Explanation of the symbols in the figure: 1 is the battery liquid cooling plate 1-1 is the flow channel plate, 1-1-1 is the groove, 1-2 is a flat plate, 1-2-1 is a liquid inlet, 1-2-2 is a liquid outlet, 1-3 are mounting holes. 1-4 is a cooling medium guide channel; 2 is the hot melt connection mold for the battery liquid cooling plate 2-1 is the upper mold, 2-1-1 is the flow channel plate accommodating groove cavity, 2-1-2 is the avoidance groove, 2-1-3 is the positioning hole, 2-2 is the lower mold, 2-2-1 is the flat plate receiving cavity, and 2-2-2 is the positioning column. DETAILED DESCRIPTION
[0015] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.
[0016] See Figure 1. Figure 2 , Figure 3 , Figure 4 The present invention provides a battery liquid cooling plate, the battery liquid cooling plate 1 comprises a flow channel plate 1-1 and a flat plate 1-2; the flow channel plate 1-1 is provided with a winding groove 1-1-1, and the flow channel plate 1-1 is molded by plastic or non-metal composite materials; the flat plate 1-2 is provided with a liquid inlet 1-2-1 and a liquid outlet 1-2-2, the liquid inlet 1-2-1 and the liquid outlet 1-2-2 are respectively located at the two ends of the diagonal of the flat plate, and the flat plate 1-2 is made of metal; the flow channel plate 1-1 and the flat plate 1-2 are integrated into one by a hot melt molding process, and a cooling medium guide channel 1-4 connected with the liquid inlet 1-2-1 and the liquid outlet 1-2-2 is formed between the groove 1-1-1 of the flow channel plate 1-1 and the flat plate 1-2, and a plurality of groups of mounting holes 1-3 for realizing the assembly of the battery liquid cooling plate 1 and the battery shell are arranged in the non-cooling medium guide channel area, and the mounting holes 1-3 pass through the flow channel plate 1-1 and the flat plate 1-2.
[0017] See also Figure 3 , Figure 4The battery liquid cooling plate of the present invention has a wall thickness of the flow channel plate 1-1 of δ=0.8~2.5mm, a transition fillet radius R=1~10mm between the bottom surface and the side wall of the groove 1-1-1 on the flow channel plate 1-1; and a minimum width Wmin=3mm of the cooling medium guide channel 1-4.
[0018] In the specific embodiment of the battery liquid cooling plate of the present invention, the flow channel plate 1-1 can be made of plastic or fiber-reinforced composite material, and the density of the plastic is 0.8-1g / cm 3 The density of the composite material is between 1.1 and 1.6 g / cm 3 The density of aluminum alloy is less than half; the strength of plastics and composite materials can reach 150MPa, which is equivalent to the strength of commonly used 3003-O aluminum plates. The thickness of the flow channel plate 1-1 in the battery liquid cooling plate 1 of the present invention can be controlled between 0.8 and 2.5 mm, and the size of the fillet is between 1 and 10 mm. The molding of plastics or composite materials can adopt a variety of processes, such as molding, blistering, etc. Plastics or composite materials have better formability than metal plates, providing more flexibility for the design of flow channels. The flow channel width can be narrower, and the minimum flow channel width can be 3mm, while the minimum flow channel width of aluminum alloy or metal plate is 6mm. Through reasonable flow channel arrangement, better heat exchange effect can be obtained. At the same time, composite plates or plastic plates have good thermal insulation properties, and their thermal conductivity is very low, which can play a heat insulation effect and reduce unnecessary heat transfer to areas that do not need cooling.
[0019] See also Figure 5 , Figure 6 , Figure 7 , Figure 8 The present invention also provides a battery liquid cooling plate hot melt connection mold, the battery liquid cooling plate hot melt connection mold 2 comprises an upper mold 2-1, a lower mold 2-2, an electric heating element and a temperature control system; the lower mold 2-2 is provided with a flat plate receiving groove cavity 2-2-1, an electric heating element is arranged in the lower mold 2-2, the working state of the electric heating element is controlled by the temperature control system of the mold, and a plurality of groups of positioning columns 2-2-2 are arranged in the flat plate receiving groove cavity 2-2-1 of the lower mold 2-2; the upper mold 2-1 is provided with a flow channel plate receiving groove cavity 2-1-1, and a bottom surface of the flow channel plate receiving groove cavity 2-1-1 is provided An avoidance groove 2-1-2 cooperates with the groove 1-1-1 on the flow channel plate 1-1, and the depth of the avoidance groove 2-1-2 is not less than the depth of the groove 1-1-1 on the flow channel plate 1-1. A plurality of groups of positioning holes 2-1-3 are arranged at the bottom of the flow channel plate accommodating groove cavity 2-1-1 of the upper mold 2-1; after the upper mold 2-1 and the lower mold 2-2 are buckled together, a molding cavity is formed between the upper mold 2-1 and the lower mold 2-2, and the positioning column 2-2-2 in the flat plate accommodating groove cavity 2-2-1 of the lower mold 2-2 penetrates into the positioning hole 2-1-3 at the corresponding position of the flow channel plate accommodating groove cavity 2-1-1 of the upper mold 2-1.
[0020] By adopting the battery liquid cooling plate hot-melt connection mold 2 of the present invention, mass production of the battery liquid cooling plate 1 is realized, and the reliable positioning of the flow channel plate 1-1 and the flat plate 1-2 in the battery liquid cooling plate 1 is ensured through the positioning column 2-2-2 of the lower mold 2-2, the mounting hole 1-3 on the battery liquid cooling plate 1 workpiece and the positioning hole 2-1-3 of the upper mold 2-1, thereby ensuring the dimensional accuracy of the battery liquid cooling plate 1 product and improving the work efficiency and product quality.
[0021] See also Figures 1 to 8 The present invention also provides a battery liquid cooling plate hot melt connection method, which integrates the flow channel plate 1-1 and the flat plate 1-2 of the battery liquid cooling plate 1 into one by using the battery liquid cooling plate hot melt connection mold 2. The specific operation steps are as follows: a. Remove impurities and coatings from the surface of the flat plate 1-2, use a laser cleaning device to clean the surface of the flat plate 1-2, and then dry the cleaned flat plate 1-2; b. Place the workpiece. Place the dried flat plate 1-2 in the flat plate receiving groove 2-2-1 of the lower mold 2-2 of the battery liquid cooling plate hot melt connection mold 2, and position it by matching the positioning column 2-2-2 with the mounting hole opened on the flat plate 1-2. Then place the flow channel plate 1-1 on the flat plate 1-2, and make the positioning column 2-2-2 pass through the mounting hole opened on the flow channel plate 1-1. c. Close the molds, and buckle the upper mold 2-1 of the battery liquid cooling plate hot melt connection mold 2 with the lower mold 2-2 of the battery liquid cooling plate hot melt connection mold 2, so that the positioning column 2-2-2 of the lower mold 2-2 of the battery liquid cooling plate hot melt connection mold 2 penetrates into the positioning hole 2-1-3 of the upper mold 2-1 of the battery liquid cooling plate hot melt connection mold 2; d. Heating: The temperature of the metal plate 1-2 is controlled between 155 and 250°C by hot-melting the battery liquid cooling plate to the temperature control system of the mold 2; e. Pressurize and apply pressure to the battery liquid cooling plate hot melt connection mold 2. The pressure range is controlled at 8 to 12 MPa, and the pressure holding time is not less than 30 seconds.
[0022] f. Cooling: The temperature of the metal plate 1-2 is reduced to the set temperature through the temperature control system of the battery liquid cooling plate connected to the mold 2 or the natural cooling process; g. Take out the workpiece and remove it after opening the mold to complete the hot melt molding operation of the battery liquid cooling plate.
[0023] The present invention integrates the flow channel plate 1-1 and the flat plate 1-2 in the battery liquid cooling plate 1 into one by a hot melt connection process. In step a, the flat plate 1-2 made of an aluminum plate or other metal material is laser cleaned to remove surface impurities and coatings. The principle of laser cleaning is to use a high-energy laser beam to irradiate the surface of the workpiece, so that the dirt, rust or coating on the surface evaporates or peels off instantly, and the surface attachments or surface coatings of the cleaning object are removed quickly and effectively, thereby achieving the purpose of cleaning. Laser cleaning technology is a new technology based on the interaction effect between laser and matter. Unlike traditional mechanical cleaning methods, chemical cleaning methods and ultrasonic cleaning methods, laser cleaning does not require any CFC organic solvents that damage the ozone layer, is pollution-free, noise-free, harmless to the human body and the environment, and is a "green" cleaning technology. After laser cleaning the surface of the flat plate 1-2 made of an aluminum plate or other metal material, a microscopic concave-convex structure is formed on the surface of the flat plate 1-2 made of an aluminum plate or other metal material, and then the flat plate 1-2 made of an aluminum plate or other metal material is heated to a temperature above the melting point of the plastic or composite material substrate of the flow channel plate 1-1. At the same time, the hot-melt connection mold 2 of the battery liquid cooling plate is pressurized and maintained for 30 seconds. The substrate of the composite material melts and fuses with the flat plate 1-2 made of an aluminum plate or other metal material in terms of microstructure, so that the flow channel plate 1-1 and the flat plate 1-2 are tightly connected together with a high connection strength.
Claims
1. A battery liquid cooling plate, characterized in that: The battery liquid cooling plate (1) comprises a flow channel plate (1-1) and a flat plate (1-2); the flow channel plate (1-1) is provided with a winding groove (1-1-1), and the flow channel plate (1-1) is molded using plastic or non-metal composite materials; the flat plate (1-2) is provided with a liquid inlet (1-2-1) and a liquid outlet (1-2-2), the liquid inlet (1-2-1) and the liquid outlet (1-2-2) are respectively located at two ends of a diagonal line of the flat plate, and the flat plate (1-2 ) is made of metal; the flow channel plate (1-1) and the flat plate (1-2) are integrated into one body through a hot melt molding process, a cooling medium guide channel (1-4) connected to a liquid inlet (1-2-1) and a liquid outlet (1-2-2) is formed between the groove (1-1-1) of the flow channel plate (1-1) and the flat plate (1-2), and a plurality of groups of mounting holes (1-3) for assembling the battery liquid cooling plate (1) and the battery shell are arranged in a non-cooling medium guide channel area.
2. The battery liquid cooling plate according to claim 1, characterized in that: The wall thickness of the flow channel plate (1-1) is δ=0.8-2.5 mm, the transition fillet radius between the bottom surface and the side wall of the groove (1-1-1) on the flow channel plate (1-1) is R=1-10 mm; and the minimum width Wmin of the cooling medium guide channel (1-4) is 3 mm.
3. A battery liquid cooling plate hot melt connection mold, used to realize the hot melt molding operation of the flow channel plate (1-1) and the flat plate (1-2) in the battery liquid cooling plate (1) as claimed in claim 1 or 2, characterized in that: The battery liquid cooling plate hot melt connection mold (2) comprises an upper mold (2-1), a lower mold (2-2), an electric heating element and a temperature control system; the upper mold (2-1) is provided with a flow channel plate accommodating groove cavity (2-1-1), and an avoidance groove (2-1-2) matching with the groove (1-1-1) on the flow channel plate (1-1) is provided on the bottom surface of the flow channel plate accommodating groove cavity (2-1-1), and the depth of the avoidance groove (2-1-2) is not less than the depth of the groove (1-1-1) on the flow channel plate (1-1); the lower mold (2-2) is provided with a flat plate accommodating groove cavity (2-2-1), and an electric heating element is provided in the lower mold (2-2), and the working state of the electric heating element is controlled by the temperature control system of the mold; after the upper mold (2-1) and the lower mold (2-2) are buckled together, a molding cavity is formed between the upper mold (2-1) and the lower mold (2-2).
4. The battery liquid cooling plate hot melt connection mold according to claim 3, characterized in that: A plurality of groups of positioning columns (2-2-2) are arranged in the flat plate receiving groove cavity (2-2-1) of the lower mold (2-2), and a plurality of groups of positioning holes (2-1-3) are arranged at the bottom of the flow channel plate receiving groove cavity (2-1-1) of the upper mold (2-1); the positioning columns (2-2-2) and the positioning holes (2-1-3) match the mounting holes (1-3) on the battery liquid cooling plate (1).
5. A method for hot-melt connection of a battery liquid cooling plate, characterized in that: The flow channel plate (1-1) and the flat plate (1-2) of the battery liquid cooling plate (1) according to claim 1 or 2 are integrated into one by using the battery liquid cooling plate hot melt connection mold (2) according to claim 3 or 4, and the specific operation steps are as follows: a. removing impurities and coatings from the surface of the plate (1-2), cleaning the surface of the plate (1-2), and then drying the cleaned plate (1-2); b. Placing the workpiece, placing the dried flat plate (1-2) in the flat plate receiving groove cavity (2-2-1) of the lower mold (2-2) of the battery liquid cooling plate hot melt connection mold (2), and positioning it by cooperating the positioning column (2-2-2) with the mounting hole opened on the flat plate (1-2), and then placing the flow channel plate (1-1) on the flat plate (1-2) so that the positioning column (2-2-2) passes through the mounting hole opened on the flow channel plate (1-1); c. Clamping the molds, buckling the upper mold (2-1) of the battery liquid cooling plate hot melt connection mold (2) with the lower mold (2-2) of the battery liquid cooling plate hot melt connection mold (2), so that the positioning column (2-2-2) of the lower mold (2-2) of the battery liquid cooling plate hot melt connection mold (2) penetrates into the positioning hole (2-1-3) of the upper mold (2-1) of the battery liquid cooling plate hot melt connection mold (2); d. Heating, by hot-melting the battery liquid cooling plate to connect the temperature control system of the mold (2), raising the temperature of the metal plate (1-2) to a set temperature range; e. Pressurizing: applying pressure to the battery liquid cooling plate hot melt connection mold (2) and maintaining the pressure for a certain period of time; f. Cooling, by hot-melting the battery liquid cooling plate to connect the temperature control system of the mold (2) or by a natural cooling process, so that the temperature of the metal plate (1-2) drops to a set temperature; g. Take out the workpiece and remove it after opening the mold to complete the hot melt molding operation of the battery liquid cooling plate.
6. The method for hot-melt connection of a battery liquid cooling plate according to claim 5, characterized in that: In the step a, a laser cleaning device is used to clean the surface of the flat plate (1-2).
7. The method for hot-melt connection of a battery liquid cooling plate according to claim 6, characterized in that: In the step d, the temperature of the metal plate (1-2) is controlled between 155 and 250°C.
8. The method for hot-melt connection of a battery liquid cooling plate according to claim 7, characterized in that: In the step e, a pressure of 8 to 12 MPa is applied to the battery liquid cooling plate hot melt connection mold (2), and the pressure is maintained for no less than 30 seconds.