Two-dimensional sensing grid suitable for monitoring bottom damage of battery pack of electric vehicle and electric vehicle

Abstract

The utility model provides a two-dimensional sensing grid suitable for monitoring damage to the bottom of a battery pack of an electric automobile and the electric automobile. The two-dimensional sensing grid comprises a first lead group, a second lead group and a third lead group, wherein the first lead group is attached to the bottom of a lower box body of the battery pack in an insulating manner in a first direction in a spraying manner; the second lead group is attached to the bottom of the lower box body of the battery pack in an insulating manner according to a second direction in a spraying manner; the first wire group and the second wire group are insulated and intersected in a plane where the bottom of the lower box body of the battery pack is located to form a wire grid; the wiring ends on the two sides of the first wire group and the second wire group are used for being electrically connected with an electric signal detection module, so that the monitoring unit can be suitable for battery packs with different actual structure surfaces, the material and construction cost of the monitoring unit is reduced, and the monitoring sensitivity and reliability are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to battery pack damage detection field especially relates to two -dimensional sensing grid suitable for electric automobile battery pack bottom damage monitoring and electric automobile. BACKGROUND

[0002] In the electric automobile spontaneous combustion fire accident, an important reason is that the power battery has the bottom knock (bottoming) accident, that is, the bottom damage caused by the automobile chassis rubbing the ground protrusions or other obstacles in the driving, and the bottoming situation can occur through the deceleration zone, the impact road edge, the uphill top, the pothole road and the pressure on the stone or brick on the road, and even the deformation, cracking and other conditions of the power battery shell or cooling flow passage position can be caused by the serious ones.

[0003] For the pure electric automobile, the bottom deformation of the battery pack caused by the bottoming can cause the stress extrusion of the part of the battery cell in the area, even damage the internal diaphragm structure, cause the internal positive and negative short circuit of the battery cell and aggravate the thermal runaway risk. In addition, the cooling liquid path is generally arranged at the bottom of the battery pack, and the bottoming can cause the deformation or blockage of the liquid path, thereby affecting the normal flow of the cooling liquid, the heat generated in the working process of the battery pack cannot be taken away in time, and the heat dissipation is uneven between different battery cells, affecting the service life and safety of the battery cell, such as causing the cracking of the battery pack box, which can also cause the decrease of the IP protection level of the battery pack, the entry of the liquid or water vapor in the battery pack, the influence on the insulation of the high-voltage system, and the safety hazard.

[0004] At present, most electric automobile manufacturers have their own after-sales battery pack bottom scraping detection standards. Different critical deformation amounts are set for battery packs of different material systems (such as LFP, NCM, etc.) and different parts of the battery pack (such as the bottom, the side wall, the flow passage area, etc.). The 4S store after-sales maintenance link of each brand requires the vehicle to enter the store, whether it is repaired or maintained, and the battery pack bottom scraping inspection must be carried out. If the battery pack bottom has scratches, deformation, cracking and other traces, and exceeds the specified value, the battery pack opening inspection will be forced to be carried out, and even the factory repair, replacement of new battery pack and the like, and the cost is often as high as ten thousand yuan. In addition, due to the interference of the vibration and bumping in the driving process, the damage caused by the bottoming is often not easy to detect, and it is difficult to identify the accident scene in the subsequent accident identification, resulting in the difficulty of insurance claim.

[0005] There is no mature vehicle-mounted power battery pack bottom monitoring and early warning scheme for real popularization and application. In the published patents, patent CN112406895A discloses a vehicle chassis bottom event monitoring method, monitoring device and server, but it cannot judge the position of the battery pack bottom; patent CN108802623A discloses a system and method for detecting loss of an electric vehicle battery pack shell, but it cannot judge the severity of the battery pack bottom. The above two patents indirectly obtain the battery pack bottom information, cannot accurately identify the bottom event, and cannot detect multiple bottom positions at the same time. The patent CN112652829A published mentions the use of resistance wire paving, which monitors the damage at the bottom by changes in resistance and current. This method requires additional resistance wire devices, which will increase the overall material cost and volume thickness. At the same time, during specific paving, problems such as the insulating property and adhesion of the resistance wire to the battery pack lower box (usually aluminum) will be encountered. In addition, for battery packs with complex flow channel designs at the bottom, the resistance wire cannot perfectly fit the concave-convex surface, and the detection of critical areas will have a missed report probability. For battery packs with a bottom protective coating (PVC), the application of resistance wire will also affect the normal progress of the bottom protective coating spraying process and the final coating adhesion.

[0006] Therefore, there is a need for a technical solution suitable for electric vehicle battery pack bottom damage monitoring, which can be applied to battery packs with different structural surfaces, reduce the material and construction cost of the monitoring unit, and improve the sensitivity and reliability of the monitoring. Practical new type content

[0007] To solve the above technical problems, the utility model provides a two-dimensional sensing grid suitable for electric vehicle battery pack bottom damage monitoring, comprising:

[0008] a first conductor group is attached to the bottom of the battery pack lower box in the first direction by spraying;

[0009] a second conductor group is attached to the bottom of the battery pack lower box in the second direction by spraying;

[0010] Wherein, the first conductor group and the second conductor group are insulatedly intersected in the plane of the bottom of the battery pack lower box to form a conductor grid;

[0011] The two side connection ends of the first conductor group and the second conductor group are used for electrically connecting the electric signal detection module.

[0012] In a possible implementation, the first conductor group and the second conductor group extend from the bottom surface of the battery pack lower box to its side surface.

[0013] In a possible implementation, the first direction and the second direction are two directions orthogonal in a plane where the bottom of the battery pack lower case is located.

[0014] In a possible implementation, the first direction is a direction of a perpendicular line between a first pair of side faces of the battery pack lower case.

[0015] The second direction is a direction of a perpendicular line between a second pair of side faces of the battery pack lower case.

[0016] In a possible implementation, a position where the first wire group, the second wire group and the battery pack lower case are in contact is provided with an insulating layer, and a width of the insulating layer is at least not less than a width of the first conductive wire used for constructing the first wire group and a width of the second conductive wire used for constructing the second wire group.

[0017] In a possible implementation, the width of the insulating layer is 2-3 mm, and a thickness of the insulating layer is 20-100 μm.

[0018] In a possible implementation, the width of the first conductive wire and the second conductive wire is 1-2 mm, and a thickness of the first conductive wire and the second conductive wire is 20-100 μm.

[0019] In a possible implementation, the width of the insulating layer is 3 mm, and the thickness of the insulating layer is 50 μm.

[0020] The width of the first conductive wire and the second conductive wire is 2 mm, and the thickness of the first conductive wire and the second conductive wire is 50 μm.

[0021] In a possible implementation, a density of the wire grid at a position of the battery pack lower case where a cooling liquid flow channel is arranged is greater than a density of the wire grid at other positions of the battery pack lower case.

[0022] The utility model also provides a kind of electric vehicle, is provided with two-dimensional sensing grid and electric signal detection module as described above.

[0023] The technical scheme provided by the utility model has at least the following beneficial effects:

[0024] By being attached to the bottom of the battery pack lower case in the first direction and the second direction by spraying, the first wire group and the second wire group can be universally applied to different types of battery pack bottom structures, without additional assembly process and strong adhesion, sensitive to scratches, deformation and cracking defects on the battery pack bottom, fast and obvious response, high monitoring reliability, while effectively reducing the material cost when monitoring the damage of the battery pack bottom of electric vehicle in real time. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A two-dimensional sensing grid suitable for bottom damage monitoring of an electric vehicle battery pack provided by the embodiment of the present application is shown in the overall schematic view;

[0026] Figure 2 A cross-sectional view of the two-dimensional sensing grid suitable for bottom damage monitoring of an electric vehicle battery pack provided by the embodiment of the present application is shown in the overall schematic view;

[0027] In the drawings, 10, battery pack lower box; 11, first wire group; 12, second wire group; 13, insulation layer; 20, cooling liquid flow channel; 111, first conductive wire; 121, second conductive wire; 131, first insulation layer; 132, second insulation layer. DETAILED DESCRIPTION

[0028] In order to deepen the understanding of the present application, the present application will be further described in detail below in combination with the drawings and embodiments, which are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0029] Please refer to Figure 1 and Figure 2 The two-dimensional sensing grid suitable for bottom damage monitoring of an electric vehicle battery pack provided by the present application comprises:

[0030] The first wire group 11 is insulatively attached to the bottom of the battery pack lower box 10 in the first direction by spraying;

[0031] The second wire group 12 is insulatively attached to the bottom of the battery pack lower box 10 in the second direction by spraying;

[0032] The first wire group 11 and the second wire group 12 insulatively intersect in the plane where the bottom of the battery pack lower box 10 is located to form a wire grid;

[0033] The two sides of the first wire group 11 and the second wire group 12 are connected to the electrical signal detection module.

[0034] It needs to be explained that, since the battery pack is located at the bottom of the electric vehicle, it is easy to be contaminated by water, mud and the like during daily driving, which seriously affects the real-time monitoring and shooting of the traditional camera. At the same time, due to the large area of the bottom structure of the battery pack, the bottom structure has a concave-convex flow channel design, and the allowable critical deformation is small (in the range of several millimeters), so it is difficult to realize the coverage monitoring of the entire battery pack by using a single strain sensor. According to the specific application scene, the utility model designs and develops a two-dimensional sensing grid for use at the bottom of the battery pack, which can be integrated. When the electric vehicle encounters a bottom support condition, the box body 10 under the battery pack is scratched, deformed, or cracked, the two-dimensional sensing grid will convert the corresponding impact load into a corresponding electrical signal, and analyze and process the electrical signal through the electrical signal detection module to accurately locate and record the damage time, damage position and damage degree and other related data. Related data can be uploaded to the driving computer or the corresponding domain controller, and a safety warning can be sent to the driver in the form of an instrument fault light, and in an emergency, emergency measures such as limiting the maximum output power, remote contact emergency rescue and the like can be taken to ensure the safety of the vehicle and the driver. The electrical signal detection module can be powered by the battery pack, or a separate power supply can be provided, including a voltage detection unit and a current detection unit, which can be realized based on a single-chip microcomputer. By collecting voltage and current, the corresponding resistance can be calculated, and by changing voltage, resistance, current and the like, it can be judged which conductive line is broken, damaged or the like, so as to accurately locate and record the damage time, damage position and damage degree. The part of uploading related data to the driving computer or the corresponding domain controller and the subsequent operation is not within the scope of protection of the present application, but is used to improve the specific application scene, so that the technical solution of the present application can be better understood by those skilled in the art.

[0035] In specific implementation, considering the harsh working conditions of vehicle use, the two-dimensional sensing grid should have strong adhesion (anti-vibration), weather resistance (high and low temperature resistance, rain and snow salt spray resistance), long service life and other vehicle requirements, while meeting the monitoring accuracy and production process simple, low cost, insulation with the aluminum shell of the battery pack and a series of product application and promotion of strict requirements. The spraying method in the utility model adopts an integrated spraying process to integrally integrate the two-dimensional sensing grid and the box body 10 under the battery pack, which can accurately realize real-time monitoring of damage in different areas of the bottom of the battery pack. At the same time, the integrated spraying process can reduce the process steps and the number of parts, without affecting the appearance size of the battery pack, and can fully utilize the protection of the primer, prolong the service life of the two-dimensional sensing grid, and the spraying process can make the two-dimensional sensing grid well match the special shape of the bottom of the battery pack, such as the cooling flow channel, so as to effectively monitor the key area.

[0036] In this embodiment, the first wire group 11 and the second wire group 12 can be made of the same material, and the first wire group 11 and the second wire group 12 are not conductive to each other. The insulation of the first wire group 11 attached to the bottom of the battery pack lower box 10 can be understood as an insulating connection between the two, for example: if the battery pack lower box 10 itself is insulating, the first wire group 11 can be directly attached to the bottom of the battery pack lower box 10 by spraying; if the battery pack lower box 10 itself is conductive, an insulating layer needs to be provided between the first wire group 11 and the bottom of the battery pack lower box 10. The insulation of the second wire group 12 attached to the bottom of the battery pack lower box 10 can be understood as an insulating connection between the two, and the specific situation is similar to that of the first wire group 11.

[0037] The spraying raw material of the first wire group 11 and the second wire group 12 can be a polymer solution (such as paint or colloid) containing conductive ions (such as Cu 2+ / Ag + or conductive particles (such as graphite / graphene, etc.), which is sprayed, dried (or naturally dried) on the battery pack lower box 10 to form several closely attached conductive wires (i.e. the first wire group 11 and the second wire group 12) with a width of several millimeters and a thickness of several tens of microns. In a specific implementation, the spraying raw material of the first wire group 11 and the second wire group 12 can be conductive paint containing Cu 2+ composite particles, with a volume resistance <6*10 -4 Ω·cm and an adhesion >=4B (3M600 tape), which is used after being dried for half an hour at 60°C. In the laboratory, the conductive wire sprayed on the PVC board has a width of about 2mm, a thickness of about 50um, and a length of 1m, and the actual resistance after drying is <100Ω.

[0038] As shown in Figure 1 , a two-dimensional sensing grid is formed on the battery pack lower box 10 by an integrated spraying and drying process. According to the monitoring accuracy requirements, a two-dimensional grid monitoring layer, i.e. a two-dimensional sensing grid (composed of the first wire group 11 in the X-axis direction and the second wire group 12 in the Y-axis direction) can be realized by multiple spraying in different directions (such as orthogonal X / Y-axis directions). By applying a low voltage (12V or 5V) to the conductive two-dimensional sensing grid (X-axis conductive wire bundle and Y-axis conductive wire bundle) through the electrical signal detection module, when the battery pack is externally damaged to cause scratching, deformation, cracking, etc., the conductive grid attached to the corresponding part of the two-dimensional sensing grid will be peeled off, stretched, broken, etc., and the collected electrical signals (such as resistance, voltage, etc.) will change, and after analysis and processing, the accurate damage location and damage degree can be obtained.

[0039] In a possible implementation, the first wire group 11 and the second wire group 12 extend from the bottom surface of the battery pack lower case 10 to the side surface thereof.

[0040] In this embodiment, the spraying area (spray head) of the first wire group 11 and the second wire group 12 covers the side surface of the bottom of the battery pack, so that the risk monitoring range can be increased. In a preferred solution, the spraying area (spray head) of the first wire group 11 and the second wire group 12 also covers the concave-convex surface of the cooling liquid flow channel 20 of the bottom of the battery pack, so as to further increase the risk monitoring range.

[0041] In a possible implementation, the first direction and the second direction are two directions orthogonal in the plane where the bottom of the battery pack lower case 10 is located.

[0042] In this embodiment, the first direction can be regarded as the X-axis direction in the XY plane, and the second direction can be regarded as the Y-axis direction in the XY plane. The two-dimensional sensing grid is an orthogonal grid in the X-axis direction and the Y-axis direction. The spraying of the first wire group 11 can be completed in the X-axis direction by composite spraying of insulating paint and conductive paint, and then the composite spraying of the second wire group 12 can be completed in the Y-axis direction. Alternatively, the spraying of the second wire group 12 can be completed in the Y-axis direction by composite spraying of insulating paint and conductive paint, and then the composite spraying of the first wire group 11 can be completed in the X-axis direction.

[0043] In a possible implementation, the first direction is the direction of the perpendicular line between the first pair of side surfaces of the battery pack lower case 10.

[0044] The second direction is the direction of the perpendicular line between the second pair of side surfaces of the battery pack lower case 10.

[0045] In this embodiment, the length direction of the battery pack lower case 10 can be regarded as the first direction, and the width direction can be regarded as the second direction.

[0046] In a possible implementation, the position where the first wire group 11, the second wire group 12 and the battery pack lower case 10 are in contact is provided with an insulating layer 13, and the width of the insulating layer 13 is at least not less than the width of the first conductive wire 111 used to construct the first wire group 11 and the second conductive wire 121 used to construct the second wire group 12.

[0047] In this embodiment, considering that most of the battery pack lower box 10 is made of aluminum profile splicing, the conductivity of the aluminum box will interfere with the collection and analysis of the signal on the two-dimensional sensing grid. In practical application, before the conductive wire is sprayed, a layer of insulating paint wire with the same width or slightly wider than the conductive wire and a thickness of tens of microns can be sprayed as part of the insulating layer 13, which can realize insulation and protection of the first conductive wire 111 and the second conductive wire 121. The first wire group 11 is constructed by a plurality of first conductive wires 111, and the second wire group 12 is constructed by a plurality of second conductive wires 121. The insulating layer 13 can use common acrylic system circuit board insulating paint, volume resistance > 1.0*10 14 Ω·cm, 30℃ half hour drying. After spraying, a transparent, tough protective film can be formed, and good electrical insulation performance is obtained. In order to better protect, insulating paint, conductive paint, and insulating paint can also be used in three-layer composite form, that is, the upper and lower surfaces of the first conductive wire 111 and the second conductive wire 121 are provided with insulating paint. In specific implementation, the thickness of the two-dimensional sensing grid is only tens to hundreds of microns, which has no effect on the size of the battery pack bottom and the vehicle ground clearance.

[0048] It should be noted that the material cost of the two-dimensional sensing grid in the utility model is low. For example: assuming that the bottom area of the battery pack lower box 10 is 2200mm*1500mm, if the wire grid density in the longitudinal and transverse directions is 1 minimum grid per 2cm, the wire width of the first conductive wire 111 and the second conductive wire 121 is 1mm, and the width of the insulating layer 13 is 2mm, the thickness is 50um, the total length of the sprayed conductive wire is about 333.7m, and the total volume of the conductive paint is only about 16.685cm 3 , and the total volume of the insulating paint is only 33.37cm 3 . It can be seen that the materials required for spraying the entire two-dimensional sensing grid on the bottom surface of the battery pack lower box 10 are not much, and the material cost is low.

[0049] In one possible implementation, the width of the insulating layer 13 is 2-3mm, and the thickness is 20-100um.

[0050] In this embodiment, in order to play the role of insulation and protection, the insulating layer 13 should have high resistance, strong adhesion, good temperature resistance, humidity resistance and corrosion resistance. One preferred scheme is that the volume resistance of the insulating layer 13 is >10 14 Ω·cm, the insulating layer 13 has an insulating line thickness of 20-100um (the thickness can be increased by repeated spraying), and the protection level is IP65 and above.

[0051] In one possible implementation, the width of the first conductive wire 111 and the second conductive wire 121 is 1-2mm, and the thickness is 20-100um.

[0052] In this embodiment, to maintain the accuracy and sensitivity of monitoring under low-pressure conditions, the two-dimensional conductive mesh possesses characteristics such as high conductivity, low resistance, and strong adhesion. A preferred embodiment is that the first conductive line 111 and the second conductive line 121 are identical conductive lines with a volume resistivity <10 Ω·cm. -4 Ω·cm, conductive wire thickness is 20~100μm (thickness can be increased by repeated spraying), adhesion strength >2H.

[0053] In one possible implementation, the insulating layer 13 has a width of 3 mm and a thickness of 50 μm;

[0054] The width of the first conductive line 111 and the thickness of the second conductive line 121 are 2 mm and 50 μm respectively.

[0055] In one possible implementation, the density of the wire mesh at the location where the coolant flow channel 20 is provided in the lower housing 10 of the battery pack is greater than the density of the wire mesh at other locations in the lower housing 10 of the battery pack.

[0056] In this embodiment, for critical areas, such as the cooling channel area (i.e., the area where each coolant channel 20 is located), the tolerance for damage (such as dents and deformation) is smaller, that is, the critical value is smaller. The density of the wire mesh can be increased (for example, by using a few nozzles to spray repeatedly or by increasing the nozzle density), thereby improving the accuracy of monitoring.

[0057] This utility model also provides an electric vehicle equipped with a two-dimensional sensing grid and an electrical signal detection module as described above.

[0058] In this embodiment, the two-dimensional conductive mesh sensing layer, i.e., the insulating layer 13 of the two-dimensional sensing mesh, is divided into a first insulating layer 131 in the X-axis direction and a second insulating layer 132 in the Y-axis direction. The fabrication process of the two-dimensional sensing mesh is as follows:

[0059] Step S100: First, clean and dry the battery pack lower housing 10 in the electric vehicle, including removing dust, oil, moisture (water film), etc.

[0060] Step S200: Complete the spraying of the first insulating layer 131 and the first conductive wire layer (composed of several first conductive wires 111) in the X-axis direction (e.g., the length direction of the battery pack). First, the insulating paint is sprayed using a multi-nozzle fixture. Parameters such as the nozzle spray diameter, the distance between the nozzle and the lower casing 10 of the battery pack, and the nozzle routing speed are controlled to ultimately form an insulating paint layer with a width of approximately 3 mm and a thickness of approximately 50 μm. After drying at room temperature (25°C) for half an hour or with hot air (50°C) for 5 minutes, the first insulating layer 131 is sprayed. The first conductive wire layer covers the first insulating layer 131. The first insulating layer 131 is composed of several first insulating wires. Each first conductive wire 111 corresponds to one first insulating wire, and their center lines coincide, but the wires are slightly narrower (approximately 2 mm) to avoid short circuits from contact with the aluminum profile casing. After spraying, dry at 60℃-80℃ for half an hour (if the temperature is low, such as room temperature, the drying time should be extended to 24 hours) to ensure that the first conductive layer is completely dry.

[0061] Step S300: Using the same method as in step S200, complete the spraying of the second insulating layer 132 and the second conductive line layer (composed of several second conductive lines 121) in the Y-axis direction (e.g., the width direction of the battery pack). The final cross-sectional structure of the two-dimensional sensing grid is as follows. Figure 2 As shown;

[0062] Step S400: Two-dimensional sensor mesh inspection: For the wire mesh sprayed in the X / Y axis directions, the quality of the spraying can be judged by detecting the conductivity and resistance of each conductive wire, as well as the insulation between the conductive wires in the X / Y axis directions. Generally, each conductive wire has good conductivity, a resistance of tens to hundreds of ohms, and the resistance of each conductive wire in the X and Y axis directions is relatively stable. The insulation performance between the wires in the X and Y axis directions is good, and the insulation resistance should not be less than megohms.

[0063] Step S500: After the two-dimensional sensing grid is prepared, protect the terminals of each wire to facilitate subsequent wiring, and then spray a base coat (PVC) or lay a protective felt, etc.

[0064] The above embodiments should not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent conversion fall within the protection scope of the present invention.

Claims

1. A two-dimensional sensing grid suitable for monitoring damage at the bottom of electric vehicle battery packs, characterized in that, include: The first wire group is insulated and attached to the bottom of the lower casing of the battery pack by spraying in the first direction; The second wire group is insulated and attached to the bottom of the lower casing of the battery pack by spraying in the second direction; The first wire group and the second wire group intersect insulatedly in the plane at the bottom of the lower casing of the battery pack to form a wire grid. The terminals on both sides of the first and second wire groups are used for electrical connection to the electrical signal detection module.

2. The two-dimensional sensing grid according to claim 1, characterized in that, The first wire group and the second wire group extend from the bottom surface of the lower casing of the battery pack to its side surface.

3. The two-dimensional sensing grid according to claim 1, characterized in that, The first direction and the second direction are two orthogonal directions in the plane where the bottom of the lower casing of the battery pack is located.

4. The two-dimensional sensing grid according to claim 3, characterized in that, The first direction is the direction of the vertical line connecting the first pair of sides of the lower housing of the battery pack; The second direction is the direction of the vertical line connecting the second pair of sides of the lower housing of the battery pack.

5. The two-dimensional sensing grid according to claim 1, characterized in that, An insulating layer is provided at the contact points between the first conductor group, the second conductor group, and the lower casing of the battery pack. The width of the insulating layer is at least not less than the width of the first conductive line used to construct the first conductor group and the second conductive line used to construct the second conductor group.

6. The two-dimensional sensing grid according to claim 5, characterized in that, The insulating layer has a width of 2-3 mm and a thickness of 20-100 μm.

7. The two-dimensional sensing grid according to claim 6, characterized in that, The width of the first conductive line and the second conductive line is 1-2 mm, and the thickness is 20-100 μm.

8. The two-dimensional sensing grid according to claim 7, characterized in that, The insulating layer has a width of 3 mm and a thickness of 50 μm; The width of the first conductive line and the thickness of the second conductive line are 2 mm and 50 μm respectively.

9. The two-dimensional sensing grid according to claim 1, characterized in that, The density of the wire mesh at the location where the coolant flow channel is provided in the lower housing of the battery pack is greater than the density of the wire mesh at other locations in the lower housing of the battery pack.

10. An electric vehicle, characterized in that, It is equipped with a two-dimensional sensing grid and an electrical signal detection module as described in any one of claims 1-9.

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